Preparation for Nursing Mentorship

Preparation for Nursing Mentorship Name: W. Effah Domain 2 of the NMC (2008) Standards for learning and assessment in practice asks mentors to ‘Facilitate learning for a range of students, within a particular area of practice where appropriate, encouraging self-management of learning opportunities and providing support to maximise individual potential.’ Supervision and supporting the learning of student nurses in clinical placement has been the professional obligation and central constituent of Nursing and Midwifery Council (NMC) registered nurses. In this essay many issues are broached, due to the limitations of space and are treated comprehensively. It is anticipated that the reader will appreciate the magnitude of the effort of NMC registered nurses to facilitate the learning of a range of students in clinical practice. The brief of the essay will use the critical and systematic approach to consider how mentors facilitate the learning of a range of students in clinical practice in selecting appropriate learning opportunities to meet individual needs. In addition, it will consider how students can be supported to critically reflect upon their learning experiences in order to enhance future learning. With the relevant literature, it will appraise the learning needs of students and the provision of a wide range of support to maximize the individual potential. The challenges of mentoring students in clinical environment will be also analysed. Finally, all the relevant evidences will be compared and contrasted and own suggestions made with examples in practice where appropriate. The NMC (2008) describes a mentor as a facilitator, an assessor and a supervisor of students in clinical practice. To Stenfors-Hayes T. et al(2011), a mentor is anyone who shares what it means to be a nurse, who can answer questions and give advice and finally one who listens and stimulates reflection. However, from a review of Chandan and Watts(2012) a mentor goes far beyond the description above and not only advises and assesses, but in addition guides and ultimately acts as role model. Due to the wide range of students and the level of knowledge, mentors play an important role in supporting students to learn from the experiences they meet during their clinical placement. Consequently, it is for mentors to select the appropriate learning opportunities that are available and can be utilised by a range of students.(NMC2008) According to Levett-Jones and Bourgeois(2012) it is significant for mentors to know what level the student is early on in the placement to enable them know their level of competence. Hence, Clarke at al( 2002) suggested that, students should be allowed and encouraged to self-evaluate their competence prior to placement. Walsh(2010) added that regardless of the stage or year a student is, they may vary extremely in their levels of competence. In practice there were two students, one straight out of school and another student with care work experience. It is noted that the level of understanding in clinical practice was different. In order to enhance their knowledge two different approaches are needed to mentor them. This was stressed by Walsh(2010)that, the understanding of the students’ level of competence is more vital as they advance in the course of their training as mentors can allocate them to perform more tasks. An important skill for students is self-confidence and students who lack self-confidences as learners hardly discover success. The lack of self-confidence may be due to the lack the opportunities to develop self-direction. (Myers and Anderson,2012). Cash(2011) added that some students are over confident and have flight idea regarding their own levels of competence and a mentor should be wary of that. The role of the mentor is to Garvey et al(2009), the facilitating learners to develop their self confidence, independence and maturity. This is supported by Rogers’ 10 principles of adult learning (1983) cited in Jaques and Salmon(2007), that mentors can facilitate in the learning when they let students participate responsibly in the learning process actively thereby enabling them to build self-confidence. In addition self-initiated learning, independence, creativity, self-reliance, self-criticism and self-evaluation are very important in facilitating the learning of the students. NMC(2008) stated that a conducive learning environment with the appropriate professional and inter professionals, can be valued in a practical way to enhance and support the learning outcomes for students. From the classic surveys in the 1980’s, a dominant factor of the learning environment is the qualified staff as well as the role of a ward manager. Not only do they provide a good learning structure and have an important effect on learning environment but can serve as role-models for clinical practice.(Quinn, 2007) However, Stuart(2007) stated that due to the frequent interactions and activities, the clinical environment is regularly noisy which makes the clinical environment unpredictable and unstable. Stuart(2013) added that most learners will perceive the clinical area as a fear-provoking area which may limit their learning. A study by Phillips(2007) stated that the term â€Å"scary†, â€Å"frightening†, â€Å"terrified† and â€Å"anxious† were used to describe their early days in practice placement. Wilkes (2006) argued that, the abilities, qualities and attitudes of individual mentors are more essential than the learning environment whilst, Quinn (2007) emphasised that students are responsible for their own learning outcomes from an environment and they are not there just to observe. Finally, learners learn in different ways. Individuals will have a dominant learning style, either visual, auditory or kinesthetic. In addition to the dominant learning style, there is often a preferred mix of different learning styles. Research shows that an average of 60-72% of adults are visual learners, 12-18% are auditory learners 18-30% kinaesthetic. It is therefore the role of the mentors to identify the dominant learning style of the students. (Britton , 2010). As 60% of adult learners have preference for visual learning, it means that mentors can support them with flip charts and things they can see. In order to enhance future learning of students in clinical practice, the NMC (2008) standards for learning and assessment require mentors to support students to reflect upon their learning experiences. Howatson-Jones(2013), stressed that it is important for the novice practitioner to develop an understanding of their role and support the learning of new skills by reflection. To do so reflection can occur within the experience or by looking back at the experience. In addition OCarrol and Park(2007), mentioned that, nurses as well students can reflect in different ways at different times. When working with a service user, students can reflect to their mentors on what is happening between them (reflection-in-action). It is also possible to reflect on the same interaction after what has happened (reflection-on-action). For the Gibbs(1988) reflective cycle is to describe what happened, feelings, evaluation, description and action plan. On 5 cue questions, John (1995) cycle enables students to break down their practice and critically reflect on the process and outcomes.(Driscoll,2007) Driscoll’s â€Å"What? model (2000) structured reflection describes the event, an analysis of the event, proposed actions following the event, actioning the new learning from that experience in clinical practice and experience practice environment.(Driscoll,2007) For Walsh(2010), it is important for nurses to adopt the â€Å"action research model† that was originally developed by Kurst Lewin(1946). It is cycle of activities with ongoing evaluation and improvement. The key stages are for nurses to reflect upon what is happening, explain what is happening, carry out a literature research, plan a change, implement it, observe, evaluate its results, amend the plan and repeat the cycle. Hinchliff et al(2008) emphasised that, the core of professional nursing practice is reflection and is a skill that may develop with experience like clinical skills, which needs to be practised and learned. To them critical reflection is looking at the individual clinical practice. It considers how the individual will act in an event and evaluate his performance against what the real situation would have been. Johns(2000) added that the practitioner can see critical reflection as a window where he can focus on his lived experience which can help him to deal with, identify and work to resolve the contradictions in his practice involving what is desirable and actual clinical practice. White et al(2006) is of the view that critical reflection is a process by which practitioners identify the assumptions central to their practice, locate the historical and cultural source of these assumptions, question the meaning of the assumptions and develop alternative ways of acting. On the other hand Hinchliff et al(2008), is of the view that, critical reflection is cognitive, emotional and experiential of assumptions embedded in actions or experience. It is a review and re-evaluation of events and reworking of concepts and practice, based on this evaluation. Subsequently, Driscoll(2007) reinforces this, by emphasising that, critical reflection provides a mechanism for mentors to support and guide students and gives the opportunity to stimulate new ideas and thinking. Therefore the role of the mentor is to provide support for the students to reflect on their practice and to give constructive feed back.(Howatson-Jones, 2013). As advocated by Levett–Jones et al(2009) students on clinical placement are encouraged by the writer and other professionals to critically reflect on their experiences. Students are supported to critically reflect on their practice using any of the reflective models that best suits them and provided with a constructive feedback on their performance. This enhances their personal and clinical development in the delivery of high quality care. According to Walsh(2010), mentors that implement reflection in their practice will be a source of inspiration for student nurses. Furthermore, feedback is part of a valuable learning and is so essential not only for students in practice but also other professionals. It helps the students by offering them a comprehensible direction on how to improve their practice.(Howatson-Jones, 2013) Hinchliff et al(2008) argued that a challenge to critical reflection is that, it is always difficult to analyse ones own event and would benefit from another’s expertise or viewpoint. So it is important for nurses to support students on placement and to critically reflect. OCarrol and Park(2007), is of the view that listening, empathy, assertiveness and managing change are additional skills that are essential for reflection. One of the disadvantages of reflection according to Walsh(2010) is the doubling of staff time and that mentors and students may reflect differently since they are not one and the same person. Furthermore, as mentors assume the role of the expert in demonstrating skills, there is a risk of feeling uncomfortable, thinking their weaknesses may be exposed. However, Howatson-Jones(2013 ), without critical reflection, nurses cannot not deliver high quality care and is a source of inspiration for students in their future clinical practice. Furthermore, when reflection takes place it enables not only the development of knowledge by the student nurses beginning clinical practice but also its articulation by qualified nurses.(Elder et al, 2011) As set by the NMC(2008) code of conduct nurses have a professional duty to facilitate students and others to develop their competence. However, Stuart(2013) stressed that clinical practice assessment is challenging and time consuming and carries with and the burden of responsibility and answerable. In addition, they face the demand of the day-to-day clinical workload with the additional role and obligation as a mentor. Furthermore, some mentors feel not recognised and rewarded for taking additional roles. (Bray and Nettleton, 2007). In Walsh(2010) opinion, mentoring is by no means a one-way-traffic. It brings with it increased professional role, being updated by and learning from the student, developing teaching skills, adding to personal profile and increased self-esteem. Mentors are hesitant to fail students due to the fear of more documentation, the university overturning the fail and dealing with disputes.(Stuart, 2013). Abbot(2009) emphasised that the relationship formed between the mentor and the student may affect the ability to conduct an objective assessment and fail a student. Kinnell and Hughes(2010) added that, the relationship between the student and the mentor to be successful depends on each respecting and understanding the other. For Casey and Clark(2011) the relationship should be a professional one and that there should be clear boundaries from the start of the placement. Mentors, for this purpose, should distinguish their association from that of a friend. By doing this, there would be balance which would give the mentor the opportunity to carry out appropriate evaluation and feedback. Furthermore, mentors should be given support by ward managers and other professionals in mentoring students.(O’Driscoll et al, 2010). This essay has attempted to explore how mentors can facilitate the learning for a range of students, within the writers practice area. In doing so, it is realised that the benefits of mentoring for the mentor, the mentee and the NHS organisation in offering an exceptional opportunities for nurses to influence and build up the practitioners of the future cannot be overemphasized. It is also established that the learning environment is crucial in maximizing the learning of students. Additionally, it is important that students reflect upon their learning experiences in other to recognise their strengths and any areas that need further development. The writer is of the view that the relationship that develops between the mentor in facilitating the learning of a range of students can sometimes become complex. From the writers own experience, it is therefore necessary that the mentor by offering support should set out the ground rules initially and should be objective and disciplined. Ultimately, mentors should exercise caution when establishing relationship with students otherwise the final assessment can be subjective. Word count 2167 Reference: Abbott H. (2009) The experiences and challenges of mentorship in clinical practice in pre-registration education, Technic: The Journal of Operating Department Practice, 5 pp.9-13. Bray, L. and Nettleton, P. (2007) ‘Assessor or mentor? Role confusion in professional education’. Nurse Education Today 27(8), pp. 848–855. Britton, J. J. (2010) Effective group coaching: Tried and tested tools and resources for optimum couching results. Ontario: John Wily Sons. 4. Burton, R., Ormrod, G. and Holland, K. (2011) Nursing: transition to professional practice. Oxford: Oxford University Press. Casey, D. C. and Clark, L. (2011) ‘Roles and responsibilities of the student nurse mentor: an update’ British Journal of Nursing 20 (15) pp.933-937 6. Cash, R. M. (2011) Advancing differentiation: Thinking and learning for the 21st Century. 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Garvey, R., Stokes, P. and Megginson, D.(2009) Coaching and mentoring: theory and practice. London: Sage Publications. Jaques, D. and Salmon, G.(2007). Learning in groups: A handbook for face-to-face and online environments. 4th edn. Oxon: Routledge Kinnell, D. and Hughes, P.( 2010) Mentoring nursing and healthcare students. London: Sage Publications. Levett-Jones, T. and Lathlean, J.(2009)†The Ascent to Competence Conceptual Framework: an outcome of a study of belongingness†. Journal of Clinical Nursing 18. pp. 2870–2879. Levett-Jones, T., and Bourgeois, S.(2009) The clinical placement: A nursing survival guide. 2nd edn. Oxford: Balliere Tindal Publishers. McKenzie, K. (2004) Mentoring: it’s a two-way street. RCM-Midwives Journal. 7 (12), 526-528. Midgley, K. (2006) Pre-registration student nurses’ perception of the hospital learning environment during clinical placements. Nurse Education Today, 26 (4), 338-345. Moscaritolo, L.M. (2009) Interventional strategies to decrease nursing student anxiety in the clinical learning environment. The Journal of Nursing Education. 48 (1). pp.17-23. Myers, S. and Anderson, C.(2012) Dimensions in mentoring: A continuum of practice from beginning teachers to teacher leaders. Rotterdam: Sense Publishers Nursing and Midwifery Council (2008) Standards to support learning and assessment in practice: NMC Standards for mentors, practice teachers and teachers. 2nd edn. London: Nursing and Midwifery Council. O’Driscoll, M.F., Allan, H.T. and Smith, P.A. (2010) ‘Still looking for leadership – Who is responsible for student nurses’ learning in practice?’ Nurse Education Today 30 pp. 212–217. Ousey, K. (2009) ‘Socialization of student nurses: the role of the mentor’, Learning in Health and Social Care, 8, pp.175-184. Phillips, B. (2007) Nursing care and understanding the experiences of others: a Gadamerian perspective. Nursing Inquiry 2007 14(1), 89–94 Price, B. (2007) Developing skills for practice. (Course study guide). Milton Keynes :The Open University Quinn F. M., and Hughes, S. J. (2007) Quinns principles and practice of nurse education: 5th edn. Andover: Nelson Thornes Limited. Rogers, C.(1983), (cited in Jaques, D. and Salmon, G., 2007) Freedom to learn for the 80. New York: Merrill Wright Stenfors-Hayes, T., Hult, H., and Dahlgren, L. O.(2011) â€Å"What does it mean to be a mentor in medical education?† Medical Teacher 2011, Vol. 33, No. 8 , pp. e423-e428 Stuart, C. C.(2013) Mentoring, learning and assessment in clinical Practice. 3rd edn. London: Churchill Livingstone Stuart, C.C. (2007) Assessment, supervision and support in clinical practice: A guide for nurses, midwives and other health professionals. 2nd edn. London: Churchill Livingstone. 31. Walsh, D. (2010) The nurse mentors handbook: supporting students in clinical practice. Maidenhead: Open University Press Wilkes, Z. (2006)The student-mentor relationship: a review of the literature. Nursing Stand 20 (37): 42–7

Novel Eu3+-doped Garnet-tpye Tellurate Red-emitting Phosphor

Novel Eu3+-doped Garnet-tpye Tellurate Red-emitting Phosphor A novel Eu3+-doped garnet-tpye tellurate red-emitting phosphor with high thermal stability and color purity Introduction The garnet-related family Li3Ln3Te2O12(Ln=Y, Pr, Nd, Sm-Lu) have been extensively studied as promising solid electrolytes for application in solid state rechargeable lithium-ion batteries for the last few decades [1-4]. In 2006, OCallaghan et al. developed garnet-type Li3Ln3Te2O12 (Ln = Y, Pr, Nd, Sm-Lu) to investigate the relationship between Li site occupation and Li ion conductivity [1]. The lattice constant increases with increasing Ln ionic radius in Li3Ln3Te2O12. These Li3Ln3Te2O12 garnets have exhibited a fairly low ionic conductivity of ∠¼10−5 S cm−1 at 600  °C with a high activation energy (>1 eV) [3]. In 2014, the crystal structures and conductivity data for the most of perspective Li-ion solid electrolytes based on garnet-type metal oxides have been recently reviewed by Thangadurai et al. [4]. Garnet host lattices are of considerable interest due to their wide applications as laser hosts and as phosphors for white light emitting diodes [5]. For example, trivalent rare earth doped Y3Al5O12 (YAG) is one of the widely used systems of compounds for solid state lighting applications. Meanwhile, some new garnet-type compound can be constructed based on the garnet structural model, such as the green-emitting Ca3Sc2Si3O12:Ce3+, the orange-emitting Lu2CaMg2(Si, Ge)3O12:Ce3+, and the green-emitting Ca2LaZr2Ga3O12:Ce3+phosphors [6]. Therefore, the development of phosphors based on garnet-type materials is of great interest. As an important activator, the europium ion is one of the most studied lanthanide activators because of its singular luminescence properties, exhibiting pure red emission transitions with a series of sharp lines arising from the excited state 5D0 to the lower energy state 7F0-6. Eu3+ ions exhibit pure magnetic and electric dipole transitions which make it a very s ensitive probe for the rare earth ion site structure/symmetry. 5D0→7F2 electric dipole (ED) transitions around 610 nm are highly hypersensitive, which is highly sensitive to the symmetry of the Eu3+ sites in the lattices; however, the magnetic dipole transitions (5D0→7F1) are not affected by the environment, and their emission intensities are often used as an internal standard [7]. However, luminescence properties of Eu3+-doped garnet-type Li3Gd3Te2O12 have not been studied yet. In this work, red emitting phosphors Li3Gd3(1-x)Eu3xTe2O12(x = 0.01-0.30) were synthesized by the conventional solid-state reaction. The structure, composition and photoluminescence properties of Li3Gd3Te2O12:Eu3+ phosphors were investigated. In addition, the luminescence quenching of Eu3+ doping concentration and CIE on the photoluminescence spectra were demonstrated in detail. 2. Experimental Procedure    The synthesis of Li3Gd3Te2O12 phosphors doped with Eu3+ ions was carried out via a high-temperature solid-state reaction method. Li2CO3 (99.99%), Gd2O3 (99.99%), TeO2 (99.9%), and Eu2O3 (99.99%) as raw materials, they were purchased from Sigma-Aldrich without further purification and thoroughly mixed in an agate mortar. The mixtures were sintered in air at 900 °C for 10 h. when the reaction was end at 900 °C, the products were cooled down to room temperature without cooling devices. Finally, white powers were obtained by grinding. The relevant reaction formulas are as follows: 3Li2CO3+3(1-x)Gd2O3 + 4TeO2 + 3xEu2O3 + 2O2 = 2Li3Gd3(1-x)Eu3xTe2O12+ 3CO2 The crystal structure of phosphors were characterized for phase formation by using powder X-ray diffraction (XRD) analysis with a Philips XPert MPD (Philips, Netherlands) with Cu KÃŽ ± radiation (ÃŽ » = 1.5418 Ã…). The diffraction patterns were scanned within angular range of 10-70ËÅ ¡(2ÃŽ ¸). The morphology and size of the phosphors were measured using a scanning electron microscope (SEM, JEOL JSM-6490). The photoluminescence (PL) and photoluminescence excitation (PLE) spectra of the samples were analyzed using a Hitachi F-4600 spectrophotometer at room temperature. The temperature-dependent PL spectra of the phosphor were recorded in air on an Edinburgh FLS 920 spectrometer equipped with a 450 W Xe lamp. Results and discussion Li3Gd3Te2O12 belongs to the cubic crystal system, space group of Iad (No.230), in the structure of Li3Gd3Te2O12, Gd3+ and Te6+ cations occupy the 8- and 6-fold sites, and Li+ ions are located exclusively in the tetrahedral (24d) sites, respectively. As shown in Fig. 1, this structure can be considered to be formed from two interpenetrating, body-centered lattices composed of edge-shared distorted [GdO8] cubes [8, 9]. One of these frameworks composed of Gd (black sphere) and O (red sphere) is shown in Fig.1(b) along with selected polyhedra to illustrate the linkages between the [GdO8] units. Tellurium in the [TeO6] polyhedra is accommodated in an octahedral site that shares edges with an edge-linked [GdO8] dimer.   Fig. 2 shows the observed, calculated, and patterns of the Li3Gd2.55Te2O12:0.15Eu3+phosphors, confirmed from Rietveld analysis using GSAS software. The final refinement converged with weighted profile of χ2 = 1.086, Rp = 24.4à ¯Ã‚ ¼Ã¢â‚¬ ¦, and Rwp = 33.9à ¯Ã‚ ¼Ã¢â‚¬ ¦ for Li3Gd2.55Te2O12:0.15Eu3+. It is clear that all the diffraction peaks of these samples are in good agreement with the pure Li3Gd3Te2O12 (JCPDS 22-0683) and no second phase can be found, indicating that each sample is purity phase and that the substitution of Gd3+ by Eu3+ do not significantly influence the crystal structure. Li3Gd3Te2O12 belongs to the cubic system, and the lattice parameters are calculated to be a = b = c = 12.41 Ã…, V = 1911.24 Ã…3, which are consistent with the literature [1]. As the similarity of valence and the ionic radii of Eu3+(r = 0.95 Ã…, CN = 8) is the closest to that of Gd3+(r = 0.94 Ã…, CN = 8), the doped Eu3+ is supposed to substitute for the Gd3+ sites [10].   SEM analysis was carried out to investigate the surface morphology and particle sizes of the synthesized phosphor powder. Fig. 3 shows the representative SEM images of two different concentrations of Li3Gd3Te2O12:xEu3+(a, x = 0.05; b, x = 0.20). It seemed as if these small spherical particles combined together to form big crystallites. The size of particles is found to be in micrometer dimension. Meanwhile, the result indicated that doping content of Eu3+ content in Li3Gd3Te2O12:xEu3+from 0.05 to 0.20 mol did not alter the particle size and agglomeration. The grain size of phosphors is important for their applications in commercial WLEDs. In general, for practical bepowdering applications, the phosphors with micron particles can feed well the commercial demand for WLEDs. Therefore, a long ball-milling step is required to break up the agglomerations and improve the quality of the phosphor powder. Figure 4 shows the excitation spectra of Li3Gd2.55Te2O12:0.15Eu3+ monitored at 613 nm emission (5D0→7F2) at room temperature. The broad band of 200-300 nm (No.1) centered at around 275 nm is called as charge transfer (CT) band which is ascribed to the charge-transfer state (CTS) transition of O2−→Eu3+ ions. The position of this band mightily relies on the host lattice. A sequence of sharp excitation bands(Nos.2-11)between 300 and 500 nm was attributable to the intra-configurational 4f-4f transitions of Eu3+ in the matrix, namely,7F0 to 5FJ, 5H6, 5H3, 5D4, 5L8, 5G3, 5G2, 5L6, 5D3, and 5D2at wavelengths300, 314, 321, 364, 368, 381, 386, 396, 419 and 466 nm respectively [11]. The strongest absorption band located at approximately 396 nm occurred from the 7F0→5L6 transition of Eu3+ ions. A suitable red-emitting ultraviolet light-emitting diode (UV-LED) phosphor should exhibit an absorption of around 400 nm (LED excitation wavelength). Obviously, the Li3Gd3Te2O1 2:Eu3+phosphor has a potential value for white lighting device. Upon 396 nm excitation, the PL emission spectrum of the Li3Gd3Te2O12:Eu3+phosphors was measured as presented in Fig. 5. Clearly, the PL emission spectrum was dominated by a strong red emission with a center of about 613 nm due to the 5D0 →7F2 transition. Meanwhile, there also existed some relatively weak excitation peaks at 570, 596, 655 and 709 nm which are attributed to the 4f-4f transitions of Eu3+ ions from the excited state of 5D0 to 7F0, 7F1, 7F3 and 7F4, respectively. Generally, the local symmetry of Eu3+ site in the crystal lattice can be mostly reflected by Eu3+ emission profile. When Eu3+ ion occupies a crystallographic site with inversion symmetry, its magnetic-dipole 5D0→7F1 orange emission is dominant, while the electric dipole 5D0 →7F2 red emission dominates when possessing the non-centrosymmetrical site [12]. Thus, the I0-2/I0-1 emission ratio can be used in lanthanide-based systems as a probe for the local surroundings of a cation. As shown in Fig . 5, in comparison with that of the 5D0→7F1transition, the emission intensity of the 5D0→7F2 transition was much stronger, and the I0-2/I0-1 ratio was about 4.84. They demonstrated that the Eu3+ ions occupied the low symmetry sites with non-inversion centers in Li3Gd3Te2O12 host lattice. This ratio value is larger in comparison with those of the other Eu3+-doped phosphors. This larger ratio is favorable to improve the red color purity. The intensity of luminescence in phosphors is usually affected by the variation in concentration of activators. Dependence of PL emission intensity of Li3Gd3Te2O12:Eu3+ phosphors on dopant concentration can be seen in Fig. 6. None of wavelength shift or peak was observed for a new site at high Eu3+ concentrations. The emission intensity of the phosphor initially increases up to 15 mol%. The maximum intensity is observed at 15 mol% and after this it starts decreasing. The decrease in the emission intensity is due to concentration quenching effect. The concentration quenching of luminescence is observed when the energy transfer from one activator to another. Blasse has pointed out that if the activator is introduced solely on Z ion sites, xc is the critical concentration, N is the number of Z ions in the unit cell and V is the volume of the unit cell, then there is on the average one activator ion per V/xcN [13]. The critical transfer distance (Rc) is approximately equal to twice the radius of a sphere with this volume: The critical transfer distance of the centerEu3+ in Li3Gd3Te2O12:Eu3+ phosphor by taking the appropriate values of V, N, and xc (1911.24 Ã…3, 8, and 0.15, respectively) is 14 Ã…. The intensity of multipolar interaction can be determined from the change in the emission intensity. The emission intensity is related to the emitting level which has the multipolar interaction. The emission intensity (I) per activator ion is given by the formula [14]: where χ is the activator concentration; Q is a constant of multipolar interaction and equals 3, 6, 8, or 10 for the nearest-neighbor ions, dipole-dipole, dipole-quadrupole or quadrupole-quadrupole interaction, respectively; and K and ÃŽ ² are constants under the same excitation condition for the given host crystal [14, 15]. Then we use this equation to fit the experimental results of the relationship between integrated emission intensity and Eu3+ concentration. The curve of lgI/x vs. lgx in Li3Gd3Te2O12: Eu3+ phosphor based on Fig. 6 is shown in Fig. 7. The figure clearly shows that the relation between lgI/x and lgx is approximately linear and the slope is about -1.0. The Q value calculated based on the linear fitting using Eq. (2) is 3.0. This finding indicates that the concentration quenching of the Eu3+-site emission centers is caused by the energy transfer around the nearest-neighbor ions in the Li3Gd3Te2O12:Eu3+ phosphor. The similar phenomenon has been reported in the Sr1. 7Zn0.3CeO4: Eu3+ phosphor [16]. Both the maintenance of the chromaticity and brightness of white light output are favored by a lower-temperature quenching in the solid-state lighting application. Figure 8 represents the temperature-dependent PL spectra of Li3Gd3Te2O12: Eu3+ excited at 396 nm from 300 K to 460 K. The PL intensity almost unchanged with increase of temperature from 300 K to 460 K. The temperature dependence of the integrated emission intensities normalized at the 300 K value. The sample remained at about 82% of the intensity measured at room temperature, even the sample was heated to 420 K (the temperature at which LEDs typically operate). The thermal quenching temperature T50, the temperature at the 50% emission intensity, was above 500 K for Li3Gd3Te2O12:Eu3+. The Eu3+-activated Li3Ba2Gd3(MoO4)8 red phosphor shows lower quenching temperature and only remain 60% of the room temperature emission intensity at 200  °C. The good thermal quenching performance is similar with K2Ba5Si12O30:Eu2+, BaTiF6:Mn 4+, Sr3Lu0.2(PO4)3:0.8Eu3+phosphor [18-20]. Furthermore, the emission wavelengths showed no shift with increasing temperature. The small decrease in the emission intensity and good color purity stability at higher temperature indicates that the phosphor Li3Gd3Te2O12:Eu3+ has good thermal stability and can serve a potential red emitting phosphor for white LEDs. In order to clarify the thermal quenching behavior and to calculate the activation energy, the Arrhenius equation is fitted to the thermal quenching data of Li3Gd3Te2O12:Eu3+ [21]: Where I0 means the initial intensity at room temperature, I(T) means the intensity at   temperature T, c is a constant, k is Boltzmanns constant (8.62 10−5eV/K), and Eais the activation energy for the thermal quenching process fitted with the thermal quenching data. The inset in Figure 9 plots ln[(I0/I)−1] versus 1/T for Li3Gd3Te2O12:Eu3+. Linear regression showed that the thermal activation energy Ea for quenching was calculated to be ~ 0.22 eV. The thermal quenching of the emission intensity of Eu3+-activated phosphors was due to the excited electrons easily jumping into the CTS band after absorbing thermal energy at high temperatures, which the probability of non-radiative transition may increase. Thus, the emission intensity of Eu3+-activated phosphors decreased with increased temperature [22, 23].    The emission spectra of Li3Gd3Te2O12:0.15Eu3+ and commercial Y2O3:Eu3+ excited at 396 nm were then compared in Fig. 10. Remarkably, the integral emission intensity of Li3Gd3Te2O12:0.15Eu3+ was 3.03 times than that of Y2O3:Eu3+. The CIE chromaticity coordinates of the phosphors were calculated to be (0.642, 0.332) for Li3Gd3Te2O12:0.15Eu3+ according to its PL spectra, which are shown in the CIE 1931 chromaticity diagram in the insets of Fig. 10. It was found that the CIE coordinates of the present red phosphor are more close to those of the NTSC standard CIE chromaticity coordinate values for red (0.67, 0.33) standard value, which is better than those of the commercial red phosphors Y2O3:Eu3+ (0.49, 0.32) [24] and Y2O2S:Eu3+ (0.65, 0.36) [25]. Furthermore, to better understand the red emission of the Eu3+-activated Li3Gd3Te2O12 phosphors, the color purity was calculated according to the following expression described by Fred Schubert [26]: where (x, y) denotes the CIE coordinate of the synthesized compounds, (xi, yi) presents the color coordinate of the white illumination and the (xd, yd) is the color coordinates of the dominant wavelength. The dominant wavelength point can be calculated from the intersection of the connecting line between the equal energy point and the sample point. The color purity of Li3Gd3Te2O12:0.15Eu3+ (0.642, 0.332) phosphors is determined to be around 92.6%. This indicates high color purity and excellent chromaticity coordinate characteristics. The inset image in Fig. 10 shows that strong red emission was observed with the naked eyes when Li3Gd3Te2O12:0.15Eu3+is under a 365 nm UV lamp. Conclusion A novel garnet-type red-emitting phosphor Li3Gd3Te2O12:Eu3+ was prepared by the convenient solid-state reaction. The excitation and emission spectra and the dependence of luminescence on temperature were studied. The excitation spectra indicate that this phosphor can be effectively excited by near-UV light, which matches the emission wavelength of near-UV-LED chips well. The phosphor shows intense red emission, which has a high quenching temperature and can keep a stable color purity with elevated temperature. The optimum dopant concentration of Eu3+ ions in Li3Gd3Te2O12:Eu3+ was around 15 mol%, and the critical transfer distance of Eu3+ was calculated to be 14 Ã…. The concentration quenching is probably caused by the energy transfer among the nearest-neighbor ions in the Li3Gd3Te2O12:Eu3+ phosphor. Because of its good excitation profile and stable luminescence properties at high temperature, Eu3+-doped Li3Gd3Te2O12 phosphors are a potential red phosphors for NUV chip-based WLEDs and display devices.

Walt Disney the American Hero Essays -- essays research papers

Walt Disney the American Hero Walt Disney; When that name is spoken faces of children and adults alike light up with looks of sheer joy. When debating what to see at the movies the newest Disney flick is almost always decided upon over the others. With Disney people are 100 percent sure to walk out of the theater happy and smiling. From the catchy theme songs to the thrilling theme parks Disney has built the fantasy empire. Although he built the fantasy world Disney was not a man who walked around with his head in the clouds. He used his animation and film making skills to not only make fantastic movies but to also bring joy into times of war, fun into times of education, and excitement into times of vacation making him, Walt Disney, the epitome of an American hero. At the young age of sixteen Walt Disney was not the typical teenager. He was not obsessed with how he looked, or who did or didn't like him. His concerns were of the world and the fate of his country. In 1918, Walt signed up to defend his country in the military, but because of his young age he was turned away(www.tudlp.org Walt Disney Biography). Rejection was no discouragement to Walt, in fact, it was quite the opposite it was an encouragement to join the American Red Cross. With the Red Cross Walt was immediately shipped over seas to be a chauffeur and ambulance driver(www.tudlp.org Walt Disney Biography). Even in times of war Disney could bring smiles. Disney risked being captured, by covering his ambulance not with usual war time camouflage but with bright lively Disney cartoons(www.tudlp.org Walt Disney Biography). Again, unlike most other teenagers, who were more concerned with getting the job witch paid the most money and entailed the least amount of physical labor, Disn ey volunteered out of his own free will to risk his life for his country with his only reward being the moments of happiness he had brought to a country plagued with war. As part of his down to earth optimistic nature Disney had always put the advancement of education at the top of his priorities. He was a man who knew that education should be fun and wanted to do everything possible to make it that way. As Disney got older he realized that along with fame comes influence. He used his influence to build a school, a college of the cr... ...rf sized Oscars(Great Events from History. Disney releases Snow White and the Seven Dwarfs). Walt Disney created the American fantasy from thoughts pulled out of the far reaches of his imagination. He was a man who had never let go of his inner child. By simply reaching for that inner child he created every child's dream in the form of a simple talking mouse. That mouse became his trademark. Mickey was a trade mark to be used to his advantage though. With his fame and money gained from Mickey he could go on to do heroic things like build schools, work to aid his country during war, build family friendly theme parks, and make unforgettable movies. Walt Disney once said "The way to get started is to quit talking and start doing(ww2.netnitco.net Walt Disney's Great Quotes)." That is exactly what Disney has done and what all Americans should strive to do. Throughout his life Disney taught the world that "It's kind of fun to do the impossible(ww2.netnitco.net Walt Disney's Great Quotes)." If all of America strove to do the impossible everyday then every A merican would soon fit in beside Walt Disney under the category of an American hero.

Summary and Analysis of The Summoners Tale :: Canterbury Tales The Summoners Tale Essays

Summary and Analysis of The Summoner's Tale (The Canterbury Tales) Prologue to the Summoner's Tale: The Summoner was enraged by the tale that the Friar told. He claims in response to the Friar that friars and fiends are one and the same. He tells that a friar once was brought to hell by an angel and remarked that he saw no friars there. However, Satan lifted his tail and thousands of friars came out from his ass and swarmed around hell. Analysis The Summoner becomes insane with anger upon hearing the Friar's Tale, which, although it was told with great vitriol against summoners, had a measured manner and refrained from personal attacks. Where the Friar was intensely contemptuous yet civil, the Summoner becomes a brutish and ill-tempered barbarian. Rather than combating the image that Friar's Tale had given of his profession, the Summoner confirms the worst about the low qualities of his kind. The Summoner's Tale: A friar went to preach and beg in a marshy region of Yorkshire called Holderness. In his sermons he begged for donations for the church and afterward he begged for charity from the local residents. He went to the house of Thomas, a local resident who normally indulged him, and found him ill. The friar speaks of the sermon he gave and essentially orders a meal from Thomas's wife. She tells the friar that her child died not more than two weeks before. The friar claimed that he had a revelation that her child had died and entered heaven. He claims that his fellow friars had a similar vision, for they are more privy to God's messages than laymen, who live richly on earth, as compared to richly spiritually. He speaks about how, among the clergy, only friars remain impoverished and thus close to God, and tells Thomas that his illness persists because he has given so little to the church. When Thomas remarks that his wife is angry, the friar launches into a tirade about the ill effects of i re in men of high degree. He tells the tale of an angry king who sentenced a knight to death because he returned without his partner and automatically assumed that he had murdered him. When a third knight lead the condemned knight to his death, they found the knight that he had supposedly murdered. When the third knight returned to the king to have the sentenced reversed, the king sentenced all three to death: the first because he had originally declared it so, the second because he was the cause of the first's death, and the third because he did not obey the king.

Affirmative Action Essay -- Affirmative Action Essays

Affirmative action is meant to be an attempt at equality throughout society. It supposedly proposes that each person receives equal opportunities in the classroom as well as the work force. Not only would this apply to minorities but to women as well. Every sector in America would be equal and unprejudiced - or so proponents say. On the other hand, adopting affirmative action would force many employers to replace hard-working employees with those of less qualification simply due to their gender or ethnic background. Many people feel that affirmative action would be very beneficial to our society. They have many thought-inspiring arguments. Some claim that we owe blacks for what we took from them in the past. We gave them a setback in our economic system, and affirmative action would be our way of reimbursing them for time and opportunities they lost out on (Norman 50). But where should the line be drawn; how much do we do to repay people - in this case blacks - for past wrongs? Is it enough to give them equal rights, or will we give them extra opportunities to make up for those we took away? It has been argued that the black sector in America, in general, is lower in class due to their environment prior to the Civil War, but the black people of today are not those who lived then. Each person today - no matter their gender,   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   2 origin, race, belief, or whatever difference has the same opportunities as everyone else. In my opinion no one needs any special favors to get ahead. In this paper I will discuss some of the problems with affirmative action. These include disgruntled employees, reverse discrimination, and the negative effect on our economic status. People who are for affirmative action have many possible positive outcomes as a result of this law passing, some of which have already been implicated. The first subject I will discuss is diversity in the work place, including women and minorities.   Ã‚  Ã‚  Ã‚  Ã‚  Proponents of affirmative action attempt to show that diversity in the work force has brought w... ...urface affirmative action sounds and looks good. How could giving people an opportunity to work and learn to get along be a bad   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   6 idea? But after looking deeper into this concept, it seems that the scale of benefits are still not evenly spread amongst the community. After looking at all the negative outcomes, the choice should be clear. This is obviously not the right plan to help our social and economic system and we should stop using it until we can find a better choice. Works Cited Abner, Lacy. Discrimination behind a mask. Lighthouse publishing co. Boston, 1996 Carlton, Melinda. Affirmative Action and Affirming Diversity. Public Management. Florida, 1997. Norman, Jim. Politics of the nineties: Americas Verdict on Affirmative Action is Decidedly Mixed. USA Today. June/July 1997: 49-52. Internet website. www.washingtonpost.com

Celta – Focus on the Learner

This case study is based on Patricia, a Spanish national in her twenties who is in her last year studying an Economics degree course. She is also a student on the Elementary course at the British Language Centre. Patricia’s started learning English at the bi-lingual school she attended. She learnt English for 3 years but did not take any official examinations, but sees this as a possibility for the future. At school she learnt English because it was obligatory. The only other language she speaks is Spanish. She started attending the British Language Centre (which she still attends) to help her find a job in an international company and to prepare her for her visit to Eastbourne, East Sussex (UK) in July. She will be staying with a house family for one month and hopes to improve her English and use all of the language she has been learning to date. Her reasons for learning English are a combination of extrinsic and intrinsic ones. The main reason she is motivated to learn English is because she believes it will help her find a good job and earn loads of money, she also reads a lot about English culture and customs and watches films in English with subtitles for her own enjoyment. This can also be related to her learning styles. The results of her â€Å"multiple intelligences† questionnaire indicates that her learning style preferences are linguistic, spatial and interpersonal. Her conversations in English refer to things that she has read or heard, she enjoys solving mazes and other visual puzzles and considers herself to be a leader. Problems and Possible solutions with Grammar The student enjoys English grammar, and generally finds it much easier than Spanish grammar. An example of this is the verb formations. She normally uses the correct tense when speaking in English but sometimes uses the infinitive form instead of the progressive. â€Å"I read† instead of â€Å"I’m reading†. Spanish often use an infinitive where English would use a progressive; this can be attributed to language interference. To resolve this problem more tasks relating to real situations could be set along with reading and listening exercises that incorporate and contrast the infinitive nd progressive forms. When asked about the aspect of English she finds most difficult, she said ‘phrasal verbs’. Her problems include understanding the meaning of phrasal verbs, especially when the meaning can vary according to context, and choosing the correct particle to accompany the verb. For example â€Å"to break up† I broke up with my girlfriend last night, the main cause is likely to be comprehension issues as a result of conflict with meanings she already knows. Solutions to such problems would be dictionary analysis and sentencing restructuring exercises. Another problem she has is with the structuring of sentences. A classic example of this would be using the adjective after the noun â€Å"shoes big† instead of â€Å"big shoes†. This can also be attributed to language interference. Solutions to this problem would include drills (oral and written); practice would include guided dialogues, language games, parallel writing, dictations etc. 3 Problems and Possible Solutions with Vocabulary A common problem can be irregular plurals. (Refer to Appendix – example 1). In Spanish irregular plurals are not formed the same as in English. The common rule is that a â€Å"s† is added to the singular i. e. hombre = hombres. A solution to this problem is getting the student to record a list of all irregular verbs as they come up (recycling the vocabulary in future classes) and correct their mistakes in reading and writing exercises. Another problem is that many words are used in different contexts but with a connection to their original meaning. (Refer to Appendix – example 2). This forms a problem for Spanish speakers as the word flood â€Å"inundar† is only used in 1 context. Solutions and practice can be given through activities where the student has to use the word in different contexts and apply the alternatives. There are several different expressions where â€Å"bother† can be used. (Refer to Appendix – example 3). The meaning changes slightly from expression to expression. In Spanish this word is not used in the same way. A solution and practice to this would be to present all of the words to the student within a real context, through a reading or writing exercise. 2 Problems and Possible Solutions with Pronunciation. Morphemes that have more than one pronunciation present a problem relating to the sound of words. (Refer to Appendix – example 4). Both problems relate to rhythm when speaking, Spanish rhythm is syllable timed, whereas, English rhythm is stressed timed. (Spanish also has a narrower pitch range than English). Both problems can be directly related to language interference. Solutions include instant and planned remedial. The best procedure in addressing these problems is to draw attention to the problematic sound or pattern. Get them to pronounce it in isolation and explain how the pattern or sound is formed, and drill the student ensuring they have a record. The learner skills strengths and weaknesses: Speaking: The student is very comfortable speaking on a one to one basis and has no qualms about making mistakes. She articulates and forms her sentences well. Her main problem in fluency speaking is hesitation, something that she is fully aware of. She takes time to work things out in her mind before speaking, and this pause is evident in class, for example, when a teacher asks her a question. The more complicated the question or response, the longer the pause. She has very few opportunities to speak English outside the classroom, and this lack of practice contributes to her hesitation. Reading: The student seems to get the general gist of reading as long as she has some guidance and visuals. She is not afraid to ask questions if necessary and hardly ever uses her dictionary in class. Areas she could improve on are her vocabulary range to help her understand texts better and additional reading outside of the class. Listening: The student understands most of the instructions given out in lass and regularly helps her peers when they do not understand something. Her main weaknesses include not being able to follow a native person’s conversation; she has already established learning habits in the classroom that will not be effective when speaking to a native person. She also has poor vocabulary, which will limit her understanding relating to words she does not know. Wri ting: Reader – When I left university I wanted to do exactly the same things as you: find a job working for an international company which would allow me to travel around the world and buy a house. Writing teacher – Overall you did a very good job, things you need to consider next time are using shorter sentences to give more impact and tenses. Language expert: A good attempt at the set task, you need to think more about the structure of sentences and using the right vocabulary. Also review definite/indefinite articles and propositions. In order to improve your language skills and learn a new language many different sub skills are required. It is a good idea to learn techniques such as skimming and scanning to abstract relevant information more quickly. Distinguishing sounds of the different vowels in English is also very important along with determining the stress and intonations in sentences. Listening and reading stimuli or input is very important in producing more effective language, and it is a good idea to put yourself in situations where you are only able to converse in English, as this will force you to use the language more and help increase your confidence levels.

Chemistry Extended Essay Essay

To investigate the effect of 2-bromo-2-methyl propane concentration and temperature of the system on the rate of reaction of solvolysis of 2-bromo-2-methyl propane in 90% ethyl alcohol Done by: Habib Iscandar Hinn Friend’s Boy’s School June 22, 2007 To investigate the effect of 2-bromo-2-methyl propane concentration and temperature of the system on the rate of reaction of solvolysis of 2-bromo-2-methyl propane in 90% ethyl alcohol Introduction: The major product of the solvolysis of t -butyl chloride in 70 % water – 30 % acetone is t-butyl alcohol, with a small amount of isobutylene being formed as a by product And this is with accordance of first order kinetic and suggests a two step mechanism in which the rate determining step consists of the ionization of t-butyl chloride, and in this mechanism a carbonium ion is formed as inter- mediate and this bonds immediately to near by nucleophile (in this case nucleophile is a neutral molecule) the initial product is t-butyl carbonium ion. â€Å"Note1: if the nucleophile is neutral the product will be charged since the leaving group takes both bonding electrons away with it† So chemists have proposed to general types of mechanism: 1- Nucleophilic substitution Sn1 The ionization step in a Sn1 reaction is endothermic and much slower than the exothermic neutralization of carbonium ion by a nucleophile. And so the rate determining step being the unimolecular ionization of the t-butyl chloride equation 4, and as a result, the overall rate of reaction is not affected by changes in the concentration or kinds of nucleophilic reagents present. â€Å"Note2: the factor which determines the mechanisms employed is typically the nature of the substrate it self and not the particular nucleophile† â€Å"Note3: if the sum of the energy of the product is lower than the energy of the reactant the reaction is exothermic, and if the product have higher energy than the reactant the reaction is endothermic.† 2- Elimination E1 (elimination unimolecular) And because t-butyl chloride acts as a Lewis acid (an electrophile) and combines with a nucleophile to give a substitution product, so the major product of the solvolysis of t-butyl chloride in water-acetone solvent is t-butyl alcohol. (â€Å"Note4†: electrophile: an electron deficient atom, ion or molecule that as affinity for an electron pair, and will bond to a base or nucleophile.) (â€Å"Note5 â€Å": nucleophile: and atom, ion , or molecule that has an electron pair that may be donated in forming covalent bond to an electerophile.) Evaluating the mechanism: The only reactant that is undergoing change in the rate determining step is t-butyl chloride and so such reactions is a unimolecular and follow a first order equation (Sn1, E1). â€Å"This means that the rate of the reaction varies directly with the concentration of t- butyl chloride†. And since nucleophilic only participate in the fast second step, so their relative molar concentrations rather than their nucleiophilities are the primary product – determining factor, and by using nucleophilic solvent like water, so its high concentration will assure that alcohols are the major product, and because water have a high dielectric constant (e=81) so water molecule tend to orient them-selves in such a way as to decrease the electrostatic forces between ions. And an important factor is the salvations which refer to water molecules ability stabilize ions by encasing them in a sheath of weakly bonded solvent molecules: 1- Anions are solvated by hydrogen – bonding, 2- Cations are solvated by nucleophilic sites on water molecule (oxygen). And in this case of t-butyl carbonium ion the nucleophiles form strong covalent bond to carbon and converting the intermediate to a substitution product. The reaction mechanism is a sequential account of each transition state and intermediate in a total reaction, the over all rate of reaction is determined by the transition state of highest energy in the sequence, so the rate determining step is the rate determining step for both the Sn1 and E1 for t – butyl chloride. (â€Å"Note 6†: the water soluble organic solvent acetone is used to keep a reasonable concentration of t-butyl chloride in solution) The balance equation for t-butyl chloride solvolysis in water-acetone solvent is: The effect of concentration on the solvolysis of t-butyl chloride in 70 %water – 30 %acetone solvent. As the reaction proceeds the solution becomes increasingly acidic until all of the t -butyl chloride has reacted and all HCl that can form has formed. So we will monitor the reaction by allowing HCl formed to neutralize a predetermined amount of NaOH. An indicator dye (bromo-phenol blue) will change color when the NaOH has been neutralized, and clocking of the reaction should begin at the instant. So according to kinetic measurements: Rate of reaction = K [t – butyl chloride] Where K is the specific rate constant in S -1 and [t – butyl chloride] is the concentration of t-butyl chloride in M. Our kinetic measurement will depend on the determination of the amount of HCl produced by the reaction, so by monitoring the color change of the acid – base indicator, we will determine the time required for 10% of t-butyl chloride to hydrolyze by having 10 % as much NaOH present as T-butyl chloride. Rate = – d [Rcl] dt ; Where Rcl = -dt [Rcl] = K [Rcl] dt Rearranging, d [Rcl] = -K dt [Rcl] And integrating for t=0 to t=t will give; = Ln [Rcl] t – Ln [Rcl] 0 = – Kt – 2.303 Log [Rcl] 0 = – Kt [Rcl] t 2.303 Log [Rcl] 0 = Kt [Rcl] t Where [Rcl] 0: is the molar concentration at time t = 0 [Rcl] t: is the molar concentration at time t = t Two methods to calculate K 1- since the equation Kt = 2.303 Log [Rcl] 0 [Rcl] t Is an equation of a straight line (y=mx+b) with slope k. and intercept =0, a plot of 2.303 log [Rcl] 0 / [Rcl] t versus t should yield a straight line with slope k. 2- if the solvolysis reaction run to 10% completion Then, [Rcl] = 0.90 [Rcl] 0 Kt = 2.303 Log [Rcl] 0 = 2.303 log (1.11) 0.90 [Rcl] 0 And therefore, K = 0.104 T So by finding the value of K and compensate it in the rate of reaction equation â€Å"Rate = K[Rcl]† where the concentration of Rcl is known we can calculate the value of the rate of reaction and we will see it’s effect on the solvolysis of t – butyl chloride in 70% water – 30 % acetone solution. The effect of temperature on the solvolysis of t -butyl chloride in 70%water – 30%acetone solvent. In nearly every instance an increase in temperature causes an increase in the rate of reaction, â€Å"because the total fraction of all of the t – butyl chloride 1molecules having energies equal to or greater than activation energy (Ea) Corresponds to the shaded portion of the area under the curve increases by increasing the temperature† and by comparing the area for two different temperature, we see that the total fraction of t- butyl chloride molecules with sufficient kinetic energy to undergo reaction increases with increasing temperature and consequently, so does the reaction rate. â€Å"Note7: changing the concentration affects the rate of reaction changing the temperature affects the rate constant as well as the rate.† By finding the values of reaction rate constant K for different concentration of t-butyl chloride and different reaction temperature, we will find the effect of temperature on the solvolysis of t-butyl chloride in water acetone solvent. Quantitatively, K (s-1) is related to Ea and T by the equation K1 = Ae-Ea/RT1 †¦Ã¢â‚¬ ¦1 Ea is the activation energy, in joule / mole. (Jmol-1) A is a proportionality constant, in s-1 R is the gas constant = 8.314 Jmol-1K-1 e is the base of the natural logarithms. T is temperature in Kelvin. This relation ship is known as Arrhenius equation We measure Ea by taking the natural logarithm of eq.1 Ln K = ln A – Ea RT Thus, a plot of ln k versus 1/T gives a straight line whose slope is equal to -Ea/R and whose intercept with coordinate is ln A â€Å"Note8: Ea is the activation energy, a constant characteristic of the reaction† We can calculate the rate constant at some specific temperature if Ea and K at some other temperature are known. For any temp. T1 (known), Ea (known), K1 (known) K1 = A e -Ea/RT1 For any other T2 (known); (K2 unknown) K2 = A e -Ea/RT2 By dividing K1 over K2 K1 = A e -Ea/RT1 K2 A e -Ea/RT2 Taking natural logarithm of both sides, we get Ln K1 = Ea (1/T2 – 1/T1). K2 R Or in common logarithms (base 10 logarithms) gives: Log K1 = Ea (1/T2 – 1/T1) K2 2.303 R And by finding the value of K2 we will be able to find the rate of reaction at T2 and we will find the effect of temperature on the rate of solvolysis of t – butyl chloride in 70 % water – 30 % acetone solution. By finding the values of reaction rate constant K for different concentration of t-butyl chloride and different reaction temperature, we will find the effect of concentration and temperature on the solvolysis of t-butyl chloride in water acetone solvent. Procedure: Part A: the effect of concentration on the rate of solvolysis of t – butyl chloride in 70%water – 30%acetone solvent. a- Experimental procedure: to measure the time necessary for 10 % solvolysis of t – butyl chloride (0.1 M concentration) in 70 % water – 30% acetone solvent at room temperature. A, a, I:- 1- Prepare 500 ml of 0.1 M t- butyl chloride in acetone only and put it in an Erlenmeyer flask and label it #1. 2- Prepare 100 ml of 0.1 M NaOH solutions (in water) and put it in an Erlenmeyer and label it #2. 3- Using a burette take 30 ml of the solution in flask #1 and put it in another Erlenmeyer and label it #3. 4- By a graduated pipette take 3 ml of sodium hydroxide 0.1 M in an Erlenmeyer flask and label it #4. 5- Using a graduated cylinder measure 67 ml of distilled water added to an Erlenmeyer flask #4. 6- Add two drops of Bromo-phenol blue indicator to flask #4. A, a, II:- 1- Add quickly the solution in Erlenmeyer flask #4 to solution in flask #3 and start the stop watch to count for time in seconds. 2- Swirl the mixture and after one or two seconds immediately pour the combined solutions back into Erlenmeyer flask #4 to minimize the errors in the results. 3- The color of the mixed solutions is blue, so continue swirling the solution in Erlenmeyer flask #4 till the instant color of the solution start changing to yellow, then we stop the stopwatch and record the time. 4- Repeat the procedure at least three times and calculate the average. 5- Tabulate the results in record A. b- Experimental procedure: to measure the time necessary for 10 % solvolysis of t – butyl chloride (0.2 M concentration) in 70 % water – 30% acetone solvent at room temperature. A, b, I:- 1- Prepare 500 ml of 0.2 M t- butyl chloride in acetone only and put it in an Erlenmeyer flask and label it #1. 2- Prepare 100 ml of 0.1 M NaOH solutions (in water) and put it in an Erlenmeyer flask and label it #2. 3- Using a burette take 30 ml of the solution in Erlenmeyer flask #1 and put it in another Erlenmeyer flask and label it #3. 4- By a graduated pipette take 3 ml of sodium hydroxide 0.1 M in an Erlenmeyer flask and label it #4. 5- Using a graduated cylinder measure 67 ml of distilled water added to an Erlenmeyer flask #4. 6- Add two drops of bromo-phenol blue indicator to Erlenmeyer flask #4. A, b, II:- 1- Add quickly the solution in an Erlenmeyer flask #4 to solution in flask #3 and start the stop watch to count for time in seconds. 2- Swirl the mixture and after one or two seconds immediately pour the combined solutions back into an Erlenmeyer flask #4 to minimize the errors in the results. 3- The color of the mixed solutions is blue, so continue swirling the solution in Erlenmeyer flask #4 till the instant color of the solution start changing to yellow, then we stop the stopwatch and record the time. 4- Repeat the procedure at least three times and calculate the average. 5- Tabulate the results in record A. Part B: the effect of temperature on the rate of solvolysis of t – butyl chloride in 70%water – 30%acetone solvent. a- Experimental procedure: to measure the time necessary for 10 % solvolysis of t – butyl chloride (0.1 M concentration) in 70 % water – 30% acetone solvent at zero Celsius degree. B, a, I:- 1- Prepare 500 ml of 0.1 M t- butyl chloride in acetone only and put it in an Erlenmeyer flask and label it #1. 2- Prepare 100 ml of 0.1 M NaOH solutions (in water) and put it in an Erlenmeyer flask and label it #2. 3- Using a burette take 30 ml of the solution in Erlenmeyer flask #1and put it in an Erlenmeyer flask and label it #3. 4- By a graduated pipette take 3 ml of sodium hydroxide 0.1 M in an Erlenmeyer flask and label it #4. 5- Using a graduated cylinder measure 67 ml of distilled water added to Erlenmeyer flask #4. 6- Add two drops of bromo-phenol blue indicator to Erlenmeyer flask #4. B, a, II:- 1- Suspend the Erlenmeyer flasks in a water bath full with ice and water, allowing the temperature of the Erlenmeyer flasks and their contents to equilibrate for ten minutes. 2- Adding quickly the solution in Erlenmeyer flask #4 to solution in Erlenmeyer flask #3 and start the stop watch to count for time in seconds. 3- Swirl the mixture and after one or two seconds immediately pour the combined solutions back into Erlenmeyer flask #4 to minimize the errors in the results. 4- The color of the solution after that will become blue, so continue swirling the solution in Erlenmeyer flask #4 till the instant color of the solution start changing to yellow we stop the stop watch and record the time 5- Repeat the procedure at least three times and calculate the average. 6- Tabulate the results in record B. b- Experimental procedure: to measure the time necessary for 10 % solvolysis of t – butyl chloride (0.1 M concentration) in 70 % water – 30% acetone solvent at a temperature greater than room temperature by ten degrees. B, b, I:- 1- Prepare 500 ml of 0.1 M t- butyl chloride in acetone only and put it in an Erlenmeyer flask and label it #1. 2- Prepare 100 ml of 0.1 M NaOH solutions (in water) and put it in an Erlenmeyer flask and label it #2. 3- Using a burette take 30 ml of the solution in Erlenmeyer flask #1 and put it in an Erlenmeyer flask and label it #3. 4- By a graduated pipette put 3 ml of sodium hydroxide 0.1 M in an Erlenmeyer flask and label it #4. 5- Using a graduated cylinder measure 67 ml of distilled water added to Erlenmeyer flask #4. 7- Add two drops of bromo-phenol blue indicator to flask #4. B, b, II:- 1- Suspend the flasks #3 and #4 in a water bath full with ice and water, allowing the temperature of the flasks and their contents to equilibrate for ten minutes.(to reach the temperature of the water bath) 2- Adding quickly the solution in flask #4 to solution in flask #3 and start the stop watch to count for time in seconds. 3- Swirl the mixture and after one or two seconds immediately pour the combined solutions back into flask #4 to minimize the errors in the results. 4- The color of the mixed solutions is blue, so continue swirling the solution in flask #4 till the instant color of the solution start changing to yellow we stop the stopwatch and record the time 5- Repeat the procedure at least three times and calculate the average. 6- Tabulate the results in record B. Record A Run number Temperature Time of 10 % reaction Average time / seconds Record B Run number Temperature Time required for 10% reaction Average time/seconds Average time/ seconds References; * E. Brady, James. E. Humiston, Gerard., General Chemistry Principles and Structure, second edition, SI version, john Willy and sons, Inc. * Brewester, Vaderwerf and McEwen. â€Å"Unitized Experiments in Organic Chemistry†, 3rd Ed. * Streitwieser, Andrew. H. Heathcock, Clayton. Introduction to Organic Chemistry. * H. Reusch, William. An Introduction to Organic Chemistry. * J. Laidler, Keith. Chemical kinetics. 2nd ed. * Search engines that where used: o www.google.com o www.yahoo.com * Goldwhite, Harold. R. Spielman, John. College Chemistry, 1984