Time delay for one-dimensional quantum systems with steplike potentials

This paper concerns time-dependent scattering theory and in particular the concept of time delay for a class of one-dimensional anisotropic quantum systems. These systems are described by a Schr\"{o}dinger Hamiltonian $H = -\Delta + V$ with a potential $V(x)$ converging to different limits $V_{\ell}$ and $V_{r}$ as $x \to -\infty$ and $x \to +\infty$ respectively. Due to the anisotropy they exhibit a two-channel structure. We first establish the existence and properties of the channel wave and scattering operators by using the modern Mourre approach. We then use scattering theory to show the identity of two apparently different representations of time delay. The first one is defined in terms of sojourn times while the second one is given by the Eisenbud-Wigner operator. The identity of these representations is well known for systems where $V(x)$ vanishes as $|x| \to \infty$ ($V_\ell = V_r$). We show that it remains true in the anisotropic case $V_\ell \not = V_r$, i.e. we prove the existence of the time-dependent representation of time delay and its equality with the time-independent Eisenbud-Wigner representation. Finally we use this identity to give a time-dependent interpretation of the Eisenbud-Wigner expression which is commonly used for time delay in the literature.Comment: 48 pages, 1 figur

On the exit statistics theorem of many particle quantum scattering

We review the foundations of the scattering formalism for one particle potential scattering and discuss the generalization to the simplest case of many non interacting particles. We point out that the "straight path motion" of the particles, which is achieved in the scattering regime, is at the heart of the crossing statistics of surfaces, which should be thought of as detector surfaces. We sketch a proof of the relevant version of the many particle flux across surfaces theorem and discuss what needs to be proven for the foundations of scattering theory in this context.Comment: 15 pages, 4 figures; to appear in the proceedings of the conference "Multiscale methods in Quantum Mechanics", Accademia dei Lincei, Rome, December 16-20, 200

Engano no primeiro, segundo e terceiro grau: as respostas dos professores às avaliações com conseqüências graves

Educators are under tremendous pressure to ensure that their students perform well on tests. Unfortunately, this pressure has caused some educators to cheat. The purpose of this study was to investigate the types of, and degrees to which, a sample of teachers in Arizona were aware of, or had themselves engaged in test-related cheating practices as a function of the high-stakes testing policies of No Child Left Behind. A near census sample of teachers was surveyed, with valid responses obtained from about 5 percent, totaling just over 3,000 teachers. In addition, one small convenience sample of teachers was interviewed, and another participated in a focus group. Data revealed that cheating occurs and that educators can be quite clever when doing so. But how one defines cheating makes it difficult to quantify the frequency with which educators engage in such practices. Our analysis thus required us to think about a taxonomy of cheating based on the definitions of 1st, 2nd, and 3rd degree offenses in the field of law. These categories were analyzed to help educators better define, and be more aware of others' and their own cheating practices, in an attempt to inform local testing policies and procedures.Los educadores estn siendo fuertemente presionados para asegurar que sus estudiantes obtengan buenos resultados en las pruebas de rendimiento. Desafortunadamente, esas presiones hacen que algunos educadores hagan trampas. El objetivo de este estudio fue investigar los tipos y grados de conocimiento que educadores en el estado de Arizona tenan sobre o que haban participado directamente en prcticas fraudulentas en relacin a las polticas de evaluacin de desempeo relacionadas con la ley No Child Left Behind. Una muestra cuasi-censal de profesores con un total de 5% de respuestas vlidas y poco ms de 3.000 profesores fue investigada. Adems, un grupo pequeo (muestra de conveniencia) de los profesores fue entrevistado, mientras que otro grupo participo en un grupo focal. Los datos revelan que existe el fraude y los educadores actan de manera muy inteligente cuando los resultados. Sin embargo como uno define el fraude dificulta medir cuantitativamente la frecuencia con la cual los profesores tienen este comportamiento. Por esa razn, nuestro anlisis requiere pensar en una taxonoma de falsificacin basada en las definiciones de 1, 2 e 3 niveles de infracciones legales. Estas categoras se analizaron para ayudar a los educadores a definir con ms precisin y ser ms conscientes de los casos de fraude cometidos por otros maestros y por s mismos, en un intento de reflexionar sobre las polticas y procesos de evaluacin.Educadores esto sob presso para garantir que seus alunos obtenham timos resultados nos testes de desempenho. Infelizmente, tal presso abre precedentes para que educadores falsifiquem os resultados. O objetivo deste estudo foi investigar os tipos, alm das variaes, de uma amostra de professores do estado do Arizona que percebiam ou que estiveram envolvidos em prticas fraudulentas em funo das polticas de avaliao de desempenho do programa No Child Left Behind. Uma amostra dos professores foi investigada, com as respostas vlidas obtidas a partir de cerca de 5%, totalizando pouco mais de 3.000 professores. Alm disso, uma pequena amostra de convenincia de professores foi entrevistada, enquanto outra amostra participou de um grupo focal. Os dados revelaram que as fraudes ocorrem e que os educadores agem de forma inteligente quando falsificam os resultados. Porm, a maneira como cada um define fraude dificulta a possibilidade de mensurar a freqncia com que educadores se envolvem em tais prticas. Nossa anlise, portanto, exige pensar sobre uma classificao de falsificao baseada nas definies de 1, 2 e 3 graus de infraes nos domnios da lei. Tais categorias foram analisadas para ajudar os educadores a definir de forma mais precisa e estar mais conscientes das prticas de fraude realizadas por outros professores e por eles mesmos, em uma tentativa de informar as polticas e procedimentos de avaliao local

Exploring the integration of evidence-based medicine, quality of life considerations and health economics for rare diseases

This thesis is expected to contribute to the practice of treatment of rare diseases by integrating the three perspectives Evidence Based Medicine (EBM), Quality of Life (QoL) and Health Economics (HE) considerations into a comprehensive framework. Rare diseases have low prevalence but combined affect approximately up to 10% of the overall population, posing unique challenges across all three perspectives. Multiple stakeholders exert influence and drive decisions based on different and sometimes conflicting criteria and objectives, resulting in controversies and real or perceived suboptimal outcomes and deployment of resources which affect the well-being of patients. EBM, QoL and HE are not directly linked with one another and most often not considered together in all relevant decisions. Agency theory is utilized as an underlying theoretical framework. Both previous research and current empirical evidence have identified some gaps which are consistents with the double agency theory framework and, in addition, with the missed opportunity to fully integrate the three perspectives. This thesis aims to confirm and possibly close some of these gaps, broaden the scope and applicability of the theory, attempting to offer an integrated approach that mitigates the current empirical observation that each approach is taken independently forces on the other stakeholders’ suboptimal results. A deductive research method was selected and both qualitative and quantitave research was pursued. This thesis reports on research that focuses on Hereditary Angioedema (HAE) as an example for rare diseases, using a combination of a broad survey with treating physicians, a search on social media and a metaanalysis of scientific articles and research on the condition and its relevant aspects. The chosen methodology allowed for a broad scope of sources and perspectives, consistent findings and strong conclusions, and the identification of potential gaps and misalignments. The research confirmed patients, the physicians and the payers as the most important stakeholders. It also provided insights on the variables leading to diagnosis and treatment decisions, which included specific aspects of the condition, behaviors by patients, caregivers and physicians, alternative treatment options and objectives, with their corresponding implications on clinical outcomes, QoL and costs. The different components of the research mapped into the themes identified in the literature search, reinforcing the application of the theoretical framework and extending its application into the area of rare diseases. While answering the RQs and substantiating the application of the double agency theory as an underlying theoretical framework, the thesis was able to prove the interrelation of the different variables, possibly setting the groundwork to develop an algorithm or a formula which would allow to optimize the outcome of the treatment and the funding decisions. However, current constraints such as high variability and lack of sufficient data would probably cause such an algorithm to be cumbersome and of limited use in real life. On the other hand, the prioritization and quantification of the variables, may be instrumental and could contribute to building bridges across the stakeholders patients, physicians and payers, enabling the sharing of knowledge and augmenting its impact through the integrated approach, offering a more robust instrument to enhance the impact of their action

Recovery of scandium from acidic waste solutions by means of polymer inclusion membranes

Scandium is a raw material with properties that promise considerable potential for application in alloys to enable aviation fuel savings and as dopants for use in sustainable energy production using solid oxide fuel cells. Despite these attractive properties, scandium is rarely used due to its scarcity and unreliable supply. Therefore, new strategies for scandium recovery are of economic priority. In this study, polymer inclusion membranes (PIMs) consisting of PVDF-HFP, 2-NPOE and DEHPA, were optimised for selective scandium separation from real TiO2 production waste. With the optimised system, >60% of the scandium was recovered with high selectivity, resulting in scandium mole fraction at more than two orders of magnitude higher in the receiving phase than in the original waste. This suggests PIMs may be an effective way to recover scandium from bulk waste, thus easing the scarcity and insecurity that currently limit its bulk application

The Impact of High-Stakes Tests on Student Academic Performance

This study looked at data from 28 states where high-stakes testing programs are already in place and found no systemic evidence of improved achievement after states implemented high-stakes testing programs. Report and Appendix total 236 pages in two sections. The report is available here at epicpolicy.org

An Analysis of Some Unintended and Negative Consequences of High-Stakes Testing

This study examined the unintended consequences of high-stakes tests in 16 states that have implemented high-stakes graduation exams. In those states the authors found increased dropout rates, decreased graduation rates, and higher rates of younger people taking the GED equivalency exams. Report and appendix total 138 pages in two sections

The various power decays of the survival probability at long times for free quantum particle

The long time behaviour of the survival probability of initial state and its dependence on the initial states are considered, for the one dimensional free quantum particle. We derive the asymptotic expansion of the time evolution operator at long times, in terms of the integral operators. This enables us to obtain the asymptotic formula for the survival probability of the initial state $\psi (x)$, which is assumed to decrease sufficiently rapidly at large $|x|$. We then show that the behaviour of the survival probability at long times is determined by that of the initial state $\psi$ at zero momentum $k=0$. Indeed, it is proved that the survival probability can exhibit the various power-decays like $t^{-2m-1}$ for an arbitrary non-negative integers $m$ as $t \to \infty$, corresponding to the initial states with the condition $\hat{\psi} (k) = O(k^m)$ as $k\to 0$.Comment: 15 pages, to appear in J. Phys.