Admission predictors for success in a mathematics graduate program

There are many factors that can influence the outcome for students in a mathematics PhD program: bachelor's GPA (BGPA), bachelor's major, GRE scores, gender, Under-Represented Minority (URM) status, institution tier, etc. Are these variables equally important predictors of a student's likelihood of succeeding in a math PhD program? In this paper, we present and analyze admission data of students from different groups entering a math PhD program at a southern California university. We observe that some factors correlate with success in the PhD program (defined as obtaining a PhD degree within a time-limit). According to our analysis, GRE scores correlate with success, but interestingly, the verbal part of the GRE score has a higher predictive power compared to the quantitative part. Further, we observe that undergraduate student GPA does not correlate with success (there is even a slight negative slope in the relationship between GPA and the probability of success). This counterintuitive observation is explained once undergraduate institutions are separated by tiers: students from "higher tiers" have undergone a more rigorous training program; they on average have a slightly lower GPA but run a slightly higher probability to succeed. Finally, a gender gap is observed in the probability to succeed with female students having a lower probability to finish with a PhD despite the same undergraduate performance, compared to males. This gap is reversed if we only consider foreign graduate students. It is our hope that this study will encourage other universities to perform similar analyses, in order to design better admission and retention strategies for Math PhD programs.Comment: 13 pages, 11 figures, 4 table

Polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAH) are a group of structurally related chemical compounds that are frequently produced during incomplete combustion of organic matter and are among the most widespread environmental pollutants. This chapter enumerates common sources of environmental PAH that contribute to human exposures including air and water pollution, residential soil and marine sediments, occupational exposures, and lifestyle sources such as cigarette smoking and diet. It summarizes toxic effects in humans, particularly carcinogenesis, along with recent developments in measurable biomarkers of exposure

A Stochastic Method for Solving Time-Fractional Differential Equations

We present a stochastic method for efficiently computing the solution of time-fractional partial differential equations (fPDEs) that model anomalous diffusion problems of the subdiffusive type. After discretizing the fPDE in space, the ensuing system of fractional linear equations is solved resorting to a Monte Carlo evaluation of the corresponding Mittag-Leffler matrix function. This is accomplished through the approximation of the expected value of a suitable multiplicative functional of a stochastic process, which consists of a Markov chain whose sojourn times in every state are Mittag-Leffler distributed. The resulting algorithm is able to calculate the solution at conveniently chosen points in the domain with high efficiency. In addition, we present how to generalize this algorithm in order to compute the complete solution. For several large-scale numerical problems, our method showed remarkable performance in both shared-memory and distributed-memory systems, achieving nearly perfect scalability up to 16,384 CPU cores.Comment: Submitted to the Journal of Computational Physic

A Fast Monte Carlo algorithm for evaluating matrix functions with application in complex networks

We propose a novel stochastic algorithm that randomly samples entire rows and columns of the matrix as a way to approximate an arbitrary matrix function. This contrasts with the "classical" Monte Carlo method which only works with one entry at a time, resulting in a significant better convergence rate than the "classical" approach. To assess the applicability of our method, we compute the subgraph centrality and total communicability of several large networks. In all benchmarks analyzed so far, the performance of our method was significantly superior to the competition, being able to scale up to 64 CPU cores with a remarkable efficiency.Comment: Submitted to the Journal of Scientific Computin

Common Neural Systems Associated with the Recognition of Famous Faces and Names: An Event-Related fMRI Study

Person recognition can be accomplished through several modalities (face, name, voice). Lesion, neurophysiology and neuroimaging studies have been conducted in an attempt to determine the similarities and differences in the neural networks associated with person identity via different modality inputs. The current study used event-related functional-MRI in 17 healthy participants to directly compare activation in response to randomly presented famous and non-famous names and faces (25 stimuli in each of the four categories). Findings indicated distinct areas of activation that differed for faces and names in regions typically associated with pre-semantic perceptual processes. In contrast, overlapping brain regions were activated in areas associated with the retrieval of biographical knowledge and associated social affective features. Specifically, activation for famous faces was primarily right lateralized and famous names were left-lateralized. However, for both stimuli, similar areas of bilateral activity were observed in the early phases of perceptual processing. Activation for fame, irrespective of stimulus modality, activated an extensive left hemisphere network, with bilateral activity observed in the hippocampi, posterior cingulate, and middle temporal gyri. Findings are discussed within the framework of recent proposals concerning the neural network of person identification

Semantic Memory Activation in Individuals at Risk for Developing Alzheimer Disease

Objective: To determine whether whole-brain, event-related fMRI can distinguish healthy older adults with known Alzheimer disease (AD) risk factors (family history, APOE ε4) from controls using a semantic memory task involving discrimination of famous from unfamiliar names. Methods: Sixty-nine cognitively asymptomatic adults were divided into 3 groups (n = 23 each) based on AD risk: 1) no family history, no ε4 allele (control [CON]); 2) family history, no ε4 allele (FH); and 3) family history and ε4 allele (FH+ε4). Separate hemodynamic response functions were extracted for famous and unfamiliar names using deconvolution analysis (correct trials only). Results: Cognitively intact older adults with AD risk factors (FH and FH+ε4) exhibited greater activation in recognizing famous relative to unfamiliar names than a group without risk factors (CON), especially in the bilateral posterior cingulate/precuneus, bilateral temporoparietal junction, and bilateral prefrontal cortex. The increased activation was more apparent in the FH+ε4 than in the FH group. Unlike the 2 at-risk groups, the control group demonstrated greater activation for unfamiliar than familiar names, predominately in the supplementary motor area, bilateral precentral, left inferior frontal, right insula, precuneus, and angular gyrus. These results could not be attributed to differences in demographic variables, cerebral atrophy, episodic memory performance, global cognitive functioning, activities of daily living, or depression. Conclusions: Results demonstrate that a low-effort, high-accuracy semantic memory activation task is sensitive to Alzheimer disease risk factors in a dose-related manner. This increased activation in at-risk individuals may reflect a compensatory brain response to support task performance in otherwise asymptomatic older adults

Semantic Knowledge for Famous Names in Mild Cognitive Impairment

Person identification represents a unique category of semantic knowledge that is commonly impaired in Alzheimer\u27s disease (AD), but has received relatively little investigation in patients with mild cognitive impairment (MCI). The current study examined the retrieval of semantic knowledge for famous names from three time epochs (recent, remote, and enduring) in two participant groups: 23 amnestic MCI (aMCI) patients and 23 healthy elderly controls. The aMCI group was less accurate and produced less semantic knowledge than controls for famous names. Names from the enduring period were recognized faster than both recent and remote names in both groups, and remote names were recognized more quickly than recent names. Episodic memory performance was correlated with greater semantic knowledge particularly for recent names. We suggest that the anterograde memory deficits in the aMCI group interferes with learning of recent famous names and as a result produces difficulties with updating and integrating new semantic information with previously stored information. The implications of these findings for characterizing semantic memory deficits in MCI are discussed. (JINS, 2009, 15, 9-18.

Eduarda Mansilla, periodismo y exaltación del ser nacional

It is difficult to talk about the journalistic writing of women in nineteenth century Argentina since not many voices that managed to be heard in that medium. Eduarda Mansilla de García (1834-1892) was one of the few women who managed to break this pattern, publishing on the front pages of multiple cultural newspapers and magazines in the city of Buenos Aires between 1879 and 1885. The presence of the author’s self reference in the Journalistic chronicles allows us to rediscover her life experiences such as her family history, her relationship with her parents, her experiences while living abroad and her interactions with other members of society. Through this autobiographical discursive construct, she relates an individual memory to a collective one in order to strengthen a sense of national identity. To corroborate this hypothesis, we propose to analyze two chronicles that have as their cores the events lived by the inhabitants of the city of Buenos Aires at the moment of repatriating the remains of the a man seen as “the father of Argentina”, the General Don José de San Martín. These works are «Accourez, accourez, multitudes» (1880) and «Collaboration. Let us remember “(1881), both aimed at reaffirming in readers the ideals and values supported by the literate culture in terms of the consolidation of a symbolic capital and a national imaginary that endorsed the principles established at the time of Argentine independence in 1816.Hablar de la escritura de mujeres en el periodismo decimonónico finisecular argentino es un desafío, ya que no fueron muchas las voces que lograron hacerse escuchar en ese medio. Eduarda Mansilla de García (1834-1892) fue una de las pocas mujeres que publicaba en la primera plana de diarios y revistas culturales de la ciudad de Buenos Aires, en especial, entre 1879 y 1885. La inscripción del «yo» autoral en las crónicas periodísticas permite recobrar sus propias experiencias de vida así como parte de la historia familiar que se remonta a su niñez, a la relación con sus padres, a las situaciones vividas en el extranjero y a la interacción con otros miembros de la sociedad. De esta manera, a través de una construcción discursiva autobiográfica, pone en relación su memoria individual con la memoria colectiva en aras de afianzar un sentimiento de identidad nacional. Para corroborarlo, nos proponemos analizar dos crónicas que tienen como eje los sucesos vividos por los habitantes de la ciudad de Buenos Aires al momento de repatriarse los restos del “padre de la Patria”, el General Don José de San Martín. Ellas son “Accourez,accourez, multitudes” (1880) y “Colaboracion. Recordémos” (1881), ambas destinadas a reafirmar en los lectores los ideales y valores sustentados por cultura letrada en cuanto a la consolidación de un capital simbólico y un imaginario nacional que refrendara los principios establecidos al momento de la Independencia argentina, en 1816