Accounting for the Attrition of African American Males in an Academic Support Setting

This dissertation addresses a continuing crisis in our nation\u27s education system. Historically African American students have underperformed academically. This achievement gap is particularly pronounced for African American males. AVID (Advancement Via Individual Determination), an academic support program for underachieving students, most recently created the African American Male Initiative (AAMI). The AAMI was designed specifically to respond to the needs of black males. Despite its efforts, the AAMI has had a difficult time attracting and retaining black male participants. The purpose of this study was to better understand why African American high school males are not choosing to participate in the AVID AAMI, or once enrolled, often drop out. This qualitative study examined the high school experiences of AAMI students, the factors that support and challenge their academic progress in general, and the factors that are more specifically influencing their retention in the AAMI program. Through an analysis of two AAMI pilot schools, this study used interviews with students, teachers, and coordinators, along with a survey and observational data of classes and AAMI meetings to construct an analysis of the individual, cultural, and structural factors that influence the educational experiences of these black males. One major finding from the study was that individual motivation and confidence influenced retention rates in the program. With regard to culture, a key finding was that the black males in this particular study did not view academic achievement as being only associated with white students or that trying to achieve academically in school was tantamount to acting white. In terms of structural arrangements, this study found that conducting pre-interviews with potential participants to gauge their buy-in would serve to bolster retention in the AAMI program. The implications of this research for the AVID AAMI, and for educators and policy makers focused on improving educational outcomes for African American male students in particular, are discussed

A Dynamic Politico-Economic Model of Intergenerational Contracts

This paper investigates the conditions for the emergence of implicit intergenerational contracts without assuming reputation mechanisms, commitment technology and altruism. We present a tractable dynamic politico-economic model in OLG environment where politicians play Markovian strategies in a probabilistic voting environment, setting multidimensional political agenda. Both backward and forward intergenerational transfers, respectively in the form of pension benefits and higher education investments, are simultaneously considered in an endogenous human capital setting with labor income taxation. On one hand, social security sustains investment in public education; on the other hand investment in education creates a dynamic linkage across periods through both human and physical capital driving the economy toward dierent Welfare State Regimes. Embedding a repeated-voting setup of electoral competition, we find that in a dynamic ecient economy both forward and backward intergenerational transfers simultaneously arise. The equilibrium allocation is education ecient, but, due to political overrepresentation of elderly agents, the electoral competition process induces overtaxation compared with a Benevolent Government solution with balanced welfare weights

Reactive mesogens for ultraviolet-transparent liquid crystal polymer networks

Transparency and stability to UV light are important and desirable properties for modern tunable optical elements and active soft robots. A library of novel reactive mesogens for liquid crystal polymer networks resilient and transparent to UV light has been synthetised and characterised. Phase behaviours of the reactive mesogens have been determined by polarised optical microscopy and differential scanning calorimetry. Liquid crystal polymer networks based on the combination of these novel reactive mesogens have been evaluated and compared to those based on common commercially available compounds. The results showed a twofold increase in transparency in a broad UV spectral region (200–400 nm) and importantly showed no degradation upon prolonged UV exposure contrary to the networks composed from commercial counterparts

Rapid Accurate Calculation of the s-Wave Scattering Length

Transformation of the conventional radial Schr\"odinger equation defined on the interval $\,r\in[0,\infty)$ into an equivalent form defined on the finite domain $\,y(r)\in [a,b]\,$ allows the s-wave scattering length $a_s$ to be exactly expressed in terms of a logarithmic derivative of the transformed wave function $\phi(y)$ at the outer boundary point $y=b$, which corresponds to $r=\infty$. In particular, for an arbitrary interaction potential that dies off as fast as $1/r^n$ for $n\geq 4$, the modified wave function $\phi(y)$ obtained by using the two-parameter mapping function $r(y;\bar{r},\beta) = \bar{r}[1+\frac{1}{\beta}\tan(\pi y/2)]$ has no singularities, and $$a_s=\bar{r}[1+\frac{2}{\pi\beta}\frac{1}{\phi(1)}\frac{d\phi(1)}{dy}].$$ For a well bound potential with equilibrium distance $r_e$, the optimal mapping parameters are $\,\bar{r}\approx r_e\,$ and $\,\beta\approx \frac{n}{2}-1$. An outward integration procedure based on Johnson's log-derivative algorithm [B.R.\ Johnson, J.\ Comp.\ Phys., \textbf{13}, 445 (1973)] combined with a Richardson extrapolation procedure is shown to readily yield high precision $a_s$-values both for model Lennard-Jones ($2n,n$) potentials and for realistic published potentials for the Xe--e$^-$, Cs_2(a\,^3\Sigma_u^+) and $^{3,4}$He_2(X\,^1\Sigma_g^+) systems. Use of this same transformed Schr{\"o}dinger equation was previously shown [V.V. Meshkov et al., Phys.\ Rev.\ A, {\bf 78}, 052510 (2008)] to ensure the efficient calculation of all bound levels supported by a potential, including those lying extremely close to dissociation.Comment: 12 pages, 9 figures, to appear in J. Chem. Phy

Entropy-driven cutoff phenomena

In this paper we present, in the context of Diaconis' paradigm, a general method to detect the cutoff phenomenon. We use this method to prove cutoff in a variety of models, some already known and others not yet appeared in literature, including a chain which is non-reversible w.r.t. its stationary measure. All the given examples clearly indicate that a drift towards the opportune quantiles of the stationary measure could be held responsible for this phenomenon. In the case of birth- and-death chains this mechanism is fairly well understood; our work is an effort to generalize this picture to more general systems, such as systems having stationary measure spread over the whole state space or systems in which the study of the cutoff may not be reduced to a one-dimensional problem. In those situations the drift may be looked for by means of a suitable partitioning of the state space into classes; using a statistical mechanics language it is then possible to set up a kind of energy-entropy competition between the weight and the size of the classes. Under the lens of this partitioning one can focus the mentioned drift and prove cutoff with relative ease.Comment: 40 pages, 1 figur

Reversible Charge Trapping in Bis-Carbazole-Diimide Redox Polymers with Complete Luminescence Quenching Enabling Nondestructive Read-Out by Resonance Raman Spectroscopy

The coupling of substituted carbazole compounds through carbon–carbon bond formation upon one-electron oxidation is shown to be a highly versatile approach to the formation of redox polymer films. Although the polymerization of single carbazole units has been proposed earlier, we show that by tethering pairs of carbazoles double sequential dimerization allows for facile formation of redox polymer films with fine control over film thickness. We show that the design of the monomers and in particular the bridging units is key to polymer formation, with the diaminobenzene motif proving advantageous, in terms of the matching to the redox potentials of the monomer and polymer film and thereby avoiding limitations in film thickness (autoinsulation), but introduces unacceptable instability due to the intrinsic redox activity of this moiety. The use of a diimide protecting group both avoids complications due to <i>p</i>-diamino-benzene redox chemistry and provides for a redox polymer in which the photoluminescence of the bis-carbazole moiety can be switched reversibly (on/off) with redox control. The monomer design approach is versatile enabling facile incorporation of additional functional units, such as naphthalene. Here we show that a multicomponent carbazole/naphthalene containing monomer (<b>APCNDI</b>) can form redox polymer films showing both p- and n- conductivity under ambient conditions and allows access to five distinct redox states, and a complex electrochromic response covering the whole of the UV/vis–NIR spectral region. The highly effective quenching of the photoluminescence of both components in poly-<b>APCNDI</b> enables detailed characterization of the redox polymer films. The poly-<b>APCNDI</b> films show extensive charge trapping, which can be read out spectroscopically in the case of films and is characterized as kinetic rather than chemical in origin on the basis of UV/vis–NIR absorption and resonance Raman spectroscopic analyses. The strong resonantly enhanced Raman scattering for the various oxidized and reduced states of <b>APCNDI</b> enables nondestructive “read-out” of the state of the polymer, including that in which charges are trapped kinetically at the surface, making poly-<b>APCNDI</b> highly suitable for application as a component in organic nonvolatile memory devices

Laser-driven electron beamlines generated by coupling laser-plasma sources with conventional transport systems

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Use of particle counter system for the optimization of sampling ,identification and decontamination procedures for biological aerosols dispersion in confined environment

Abstract In a CBRNe (Chemical, Biological, Radiological, Nuclear and explosive) scenario, biological agents hardly allow efficient detection/identification because of the incubation time that provides a lag in symptoms outbreak following their dissemination. The detection of atmospheric dispersion of biological agents (i.e.: toxins, viruses, bacteria and so on) is a key issue for the safety of people and security of environment. Another fundamental aspect is related to the efficiency of the sampling method, which leads to the identification of the agent released, in fact an effective sampling method is needed either to identify the contamination and to check for the decontamination procedure. Environmental monitoring is one of the ways to improve fast detection of biological agents; for instance, particle counters with the ability of discriminating between biological and non-biological particles are used for a first warning when the amount of biological particles exceeds a particular threshold. Nevertheless, these systems are not able to distinguish between pathogen and non-pathogen organisms, thus, classical “laboratory” assays are still required to unambiguously identify the particle which triggered the warning signal. In this work, a combination of commercially available equipment for detection and identification of the atmospheric dispersion of biological agents was evaluated in partnership between the Italian Army, the Department of Industrial Engineering and the School of Medicine and Surgery of the University of Rome “Tor Vergata”. The aim of this work, whose results are presented here, was to conduce preliminary studies on the dynamics of biological aerosols fallout after its dispersion, to improve detection, sampling and identification techniques. This will help minimizing the impact of the release of biological agents, guarantee environmental, and people safety and securit