AN ANALYSIS OF PUERTO RICAN TESTIMONIOS OF OPPRESSION AND RESISTANCE IN POSTSECONDARY EDUCATION

College enrollment rates for Puerto Ricans in the United States and in the Commonwealth of Puerto Rico have been steadily increasing over the last twenty years; however, enrollment rates for 18- to 24-year-old Latinos remain low compared to whites of the same age groups. The rationale for this gap often portrays Latinos as deficient, using terms such as “academic underachievement” and “at-risk.” This framing—centered on the individual—shifts the focus away from systemic barriers, such as limited financial resources for Latinos, culturally relevant pedagogy, intergenerational transfer of disadvantage, and systemic racism, among other factors explored this this study. This study contributes to our collective understanding of the Puerto Rican educational experience (as the second-largest Latino subgroup) through Lightfoot’s portraiture methodology. In doing so, this study synthesizes the stories and other sources of data collected from four participants for the purpose of further analysis. These portraits seek to reconstruct in-depth lived-experience stories of Puerto Ricans who successfully navigated their educational journeys to the doctorate. As investigator, also a Puerto Rican earning a doctorate, I examine these portraits through the lens of Community Cultural Wealth (Yosso, 2005), which unpacks the forms of capital (aspirational, linguistic, familial, social, navigational, and resistant) each participant leveraged along their educational journeys. The portraits allow the investigator and the reader to ascertain a more nuanced understanding of the students’ educational journeys. For example, while participant portraits reflect highly varied backgrounds, participants experienced such barriers as poverty; access to books; and physical, emotional and/or sexual abuse. On the other hand, participants also experienced a number of factors that helped facilitate their educational journeys, such as community expectations; faculty member and/or advisor influence; and support from friends, peers, and loved ones. The portraits in this work shed light on the Puerto Rican experience through the doctorate, and contributes to limited literature regarding Puerto Rican doctoral degree attainment. The significance of this study highlights the need for more research on the educational experiences of Puerto Ricans, and the Latino diaspora more broadly. Recommendations for students, faculty, and administrators is also presented

Biomolecular imaging and electronic damage using X-ray free-electron lasers

Proposals to determine biomolecular structures from diffraction experiments using femtosecond X-ray free-electron laser (XFEL) pulses involve a conflict between the incident brightness required to achieve diffraction-limited atomic resolution and the electronic and structural damage induced by the illumination. Here we show that previous estimates of the conditions under which biomolecular structures may be obtained in this manner are unduly restrictive, because they are based on a coherent diffraction model that is not appropriate to the proposed interaction conditions. A more detailed imaging model derived from optical coherence theory and quantum electrodynamics is shown to be far more tolerant of electronic damage. The nuclear density is employed as the principal descriptor of molecular structure. The foundations of the approach may also be used to characterize electrodynamical processes by performing scattering experiments on complex molecules of known structure.Comment: 16 pages, 2 figure

Doses for Laboratory Animals based on Metabolic Rate

The differences in metabolic rates (M) of different mammals often make it difficult to estimate the dose of e.g. anaesthetics from one species to another. It is well known that the mammalian metabolic rate is correlated to the body weight (W), and the relationship between body weight and metabolic rate kan be expressed using the equation:(1) M = 3.8 x W-25Using the assumption, that the dose of e.g. an anaesthetic only depends on the metabolic rate of the animal, a simple mathematic equation can be used in scaling the dose from one species to another: As an example the equation is employed for the calculation of the doses of pentobarbital for a series of different mammals of different size. The calculated doses agree well with the doses reported in the literature. The equation may be of generel usefulness for a quick calculation of a suitable dose level, when the dose level of another species is known

Float zone experiments in space

The molten zone/freezing crystal interface system and all the mechanisms were examined. If Marangoni convection produces oscillatory flows in the float zone of semiconductor materials, such as silicon, then it is unlikely that superior quality crystals can be grown in space using this process. The major goals were: (1) to determine the conditions for the onset of Marangoni flows in molten tin, a model system for low Prandtl number molten semiconductor materials; (2) to determine whether the flows can be suppressed by a thin oxide layer; and (3) based on experimental and mathematical analysis, to predict whether oscillatory flows will occur in the float zone silicon geometry in space, and if so, could it be suppressed by thin oxide or nitride films. Techniques were developed to analyze molten tin surfaces in a UHV system in a disk float zone geometry to minimize buoyancy flows. The critical Marangoni number for onset of oscillatory flows was determined to be greater than 4300 on atomically clean molten tin surfaces

Interdependent Defense Games with Applications to Internet Security at the Level of Autonomous Systems

We propose interdependent defense (IDD) games, a computational game-theoretic framework to study aspects of the interdependence of risk and security in multi-agent systems under deliberate external attacks. Our model builds upon interdependent security (IDS) games, a model by Heal and Kunreuther that considers the source of the risk to be the result of a fixed randomized-strategy. We adapt IDS games to model the attacker’s deliberate behavior. We define the attacker’s pure-strategy space and utility function and derive appropriate cost functions for the defenders. We provide a complete characterization of mixed-strategy Nash equilibria (MSNE), and design a simple polynomial-time algorithm for computing all of them for an important subclass of IDD games. We also show that an efficient algorithm to determine whether some attacker’s strategy can be a part of an MSNE in an instance of IDD games is unlikely to exist. Yet, we provide a dynamic programming (DP) algorithm to compute an approximate MSNE when the graph/network structure of the game is a directed tree with a single source. We also show that the DP algorithm is a fully polynomial-time approximation scheme. In addition, we propose a generator of random instances of IDD games based on the real-world Internet-derived graph at the level of autonomous systems (≈27 K nodes and ≈100 K edges as measured in March 2010 by the DIMES project). We call such games Internet games. We introduce and empirically evaluate two heuristics from the literature on learning-in-games, best-response gradient dynamics (BRGD) and smooth best-response dynamics (SBRD), to compute an approximate MSNE in IDD games with arbitrary graph structures, such as randomly-generated instances of Internet games. In general, preliminary experiments applying our proposed heuristics are promising. Our experiments show that, while BRGD is a useful technique for the case of Internet games up to certain approximation level, SBRD is more efficient and provides better approximations than BRGD. Finally, we discuss several extensions, future work, and open problems

First quantized electron and photon model of QED and radiative processes

In this study we combine the classical models of the massive and massless spinning particles, derive the current-current interaction Lagrangian of the particles from the gauge transformations of the classical spinors, and discuss radiative processes in electrodynamics by using the solutions of the Dirac equation and the quantum wave equations of the photon. The longitudinal polarized photon states give a new idea about the vacuum concept in electrodynamics.Comment: LaTeX file, 20 pages, 7 figures. to appear in Canadian Journal of Physic

Anti-jamming performance of chaotic digital communication systems

Author name used in this publication: F. C. M. LauAuthor name used in this publication: C. K. TseAuthor name used in this publication: S. F. Hau2002-2003 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Effects of dopamine D4 receptor antagonist on spontaneous alternation in rats

<p>Abstract</p> <p>Background</p> <p>The present study was a component of a series of studies scrutinising the neuroreceptor substrate of behavioural flexibility in a rat model. Spontaneous alternation paradigms model the natural tendency of rodents to spontaneously and flexibly shift between alternative spatial responses. In the study it was tested for the first time if the neurochemical substrate mediating spontaneous alternation behaviour includes the dopamine D₄receptor.</p> <p>Methods</p> <p>The acute effects of the highly selective dopamine D₄receptor antagonist L-745,870 on rats' performance in a spontaneous alternation paradigm in a T-maze were examined. The paradigm was a food-rewarded continuous trial procedure performed for 20 trials.</p> <p>Results</p> <p>The spontaneous alternation rate was not affected by the doses of the drug administered (0.02 mg/kg; 0.2 mg/kg; 2 mg/kg), but the position bias of the group receiving the highest L-745,870 dose (2 mg/kg) was significantly increased compared to the group that received the lowest dose (0.02 mg/kg). No significant effects on position bias were found compared to saline. The drug did not increase response perseveration.</p> <p>Conclusion</p> <p>The results show that the neural substrate mediating the spatial distribution of responses in the spontaneous alternation paradigm includes the D₄receptor. However, the statistically significant effect of L-745,870 on position bias was found comparing a high drug dose with a low drug dose, and not comparing the drug doses with saline. For the tested doses of L-745,870 the effect on position bias was not large enough to affect the alternation rate.</p

Novelty Induces Behavioural And Glucocorticoid Responses In A Songbird Artificially Selected For Divergent Personalities

Stress physiology is thought to contribute to individual differences in behaviour. In part this reflects the fact that canonical personality measures consist of responses to challenges, including novel objects and environments. Exposure to novelty is typically assumed to induce a moderate increase in glucocorticoids (CORT), although this has rarely been tested. We tested this assumption using great tits, Parus major, selected for divergent personalities (bold-fast and shy-slow explorers), predicting that the shy birds would exhibit higher CORT following exposure to a novel object. We also scored behavioural responses to the novel object, predicting that bold birds would more frequently approach the novel object and exhibit more abnormal repetitive behaviours. We found that the presence of a novel object did induce a moderate CORT response, but selection lines did not differ in the magnitude of this response. Furthermore, although both selection lines showed a robust CORT elevation to a subsequent restraint stressor, the CORT response was stronger in bold birds and this effect was specific to novel object exposure. Shy birds showed a strong positive phenotypic correlation between CORT concentrations following the novel object exposure and the subsequent restraint stress. Behaviourally, the selection lines differed in their response during novel object exposure: as predicted, bold birds more frequently approached the novel object and shy birds more strongly decreased overall locomotion during the novel object trial, but birds from both selection lines showed significant and similar frequencies of abnormal repetitive behaviours during novel object exposure. Our findings support the hypothesis that personality emerges as a result of correlated selection on behaviour and underlying endocrine mechanisms and suggest that the relationship between endocrine stress physiology and personality is context dependent