123 research outputs found

    Undocumented Immigrants: Myths and Reality

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    In this article, six common myths about immigrants are debunked

    Civic Contributions: Taxes Paid by Immigrants in the Washington, DC, Metropolitan Area

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    This report estimates the taxes paid by immigrants in the Washington, D.C., area in 1999-2000 and documents their demographics, household composition, income, and dispersal across jurisdictions in the region. The findings in this report are based mostly on analysis of 2000 U.S. Census data, because the census provides the most recent comprehensive data that allow disaggregation by country of origin groups and by many of the region's local jurisdictions. The demographic data in the report are updated through 2004 using the U.S. Current Population Survey. We calculate taxes at both the individual level (e.g., income and payroll taxes) and the household level (e.g., property taxes), but aggregate them up to the household level. Throughout the report we refer to households headed by immigrants (whether citizens, legal immigrants, or unauthorized migrants) as "immigrant households" and compare their incomes and tax payments to households headed by native-born U.S. citizens

    The New Neighbors: A User's Guide to Data on Immigrants in U.S. Communities

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    Provides a guide for identifying characteristics, contributions, and needs of immigrant populations. Discusses national immigration trends, and addresses public policy questions. Includes a profile of the immigrant population in Providence, Rhode Island

    Public Perceptions of Gender Bias in the Decisions of Female State Court Judges

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    How are women on the bench, and their decisions, perceived by the public? Many scholars find that gender influences the voting behavior of judges and the assessment of judges by state judicial systems and the American Bar Association. However, few scholars have examined how judge gender affects the way in which the public responds to judicial outcomes. Does the public perceive the decisions of female state court judges as being biased by their gender identity, particularly in cases involving reproductive rights/family law? Also, does the public view female judges on state courts as more likely to rely on ideology when ruling in cases? Using a survey experiment that varies judge gender in a state child custody case, we examine whether respondents exhibit less support for judicial decisions authored by female state court judges. Additionally, we test whether respondents are more likely to perceive the decisions of female state court judges as ideologically biased or as a product of gender influences (as compared to male judges). Finally, we assess whether these effects are conditional on or exacerbated by respondent characteristics such as gender, race, and religiosity. The influence of gender on public response to state court decisions has important implications for our understanding of why certain court decisions find public support and acceptance

    The Health and Well-Being of Young Children of Immigrants

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    Provides an overview of immigration trends and their effects on the composition of the young child population. Looks at poverty, family structure, parental work patterns, immigrant parents' education, health status, and health insurance coverage

    Parallel depth first vs. work stealing schedulers on CMP architectures

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    In chip multiprocessors (CMPs), limiting the number of off-chip cache misses is crucial for good performance. Many multithreaded programs provide opportunities for constructive cache sharing, in which concurrently scheduled threads share a largely overlapping working set. In this brief announcement, we highlight our ongoing study [4] comparing the performance of two schedulers designed for fine-grained multithreaded programs: Parallel Depth First (PDF) [2], which is designed for constructive sharing, and Work Stealing (WS) [3], which takes a more traditional approach.Overview of schedulers. In PDF, processing cores are allocated ready-to-execute program tasks such that higher scheduling priority is given to those tasks the sequential program would have executed earlier. As a result, PDF tends to co-schedule threads in a way that tracks the sequential execution. Hence, the aggregate working set is (provably) not much larger than the single thread working set [1]. In WS, each processing core maintains a local work queue of readyto-execute threads. Whenever its local queue is empty, the core steals a thread from the bottom of the first non-empty queue it finds. WS is an attractive scheduling policy because when there is plenty of parallelism, stealing is quite rare. However, WS is not designed for constructive cache sharing, because the cores tend to have disjoint working sets.CMP configurations studied. We evaluated the performance of PDF and WS across a range of simulated CMP configurations. We focused on designs that have fixed-size private L1 caches and a shared L2 cache on chip. For a fixed die size (240 mm2), we varied the number of cores from 1 to 32. For a given number of cores, we used a (default) configuration based on current CMPs and realistic projections of future CMPs, as process technologies decrease from 90nm to 32nm.Summary of findings. We studied a variety of benchmark programs to show the following findings.For several application classes, PDF enables significant constructive sharing between threads, leading to better utilization of the on-chip caches and reducing off-chip traffic compared to WS. In particular, bandwidth-limited irregular programs and parallel divide-and-conquer programs present a relative speedup of 1.3-1.6X over WS, observing a 13- 41% reduction in off-chip traffic. An example is shown in Figure 1, for parallel merge sort. For each schedule, the number of L2 misses (i.e., the off-chip traffic) is shown on the left and the speed-up over running on one core is shown on the right, for 1 to 32 cores. Note that reducing the offchip traffic has the additional benefit of reducing the power consumption. Moreover, PDF's smaller working sets provide opportunities to power down segments of the cache without increasing the running time. Furthermore, when multiple programs are active concurrently, the PDF version is also less of a cache hog and its smaller working set is more likely to remain in the cache across context switches.For several other applications classes, PDF and WS have roughly the same execution times, either because there is only limited data reuse that can be exploited or because the programs are not limited by off-chip bandwidth. In the latter case, the constructive sharing PDF enables does provide the power and multiprogramming benefits discussed above.Finally, most parallel benchmarks to date, written for SMPs, use such a coarse-grained threading that they cannot exploit the constructive cache behavior inherent in PDF.We find that mechanisms to finely grain multithreaded applications are crucial to achieving good performance on CMPs

    Scheduling threads for constructive cache sharing on CMPs

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    In chip multiprocessors (CMPs), limiting the number of offchip cache misses is crucial for good performance. Many multithreaded programs provide opportunities for constructive cache sharing, in which concurrently scheduled threads share a largely overlapping working set. In this paper, we compare the performance of two state-of-the-art schedulers proposed for fine-grained multithreaded programs: Parallel Depth First (PDF), which is specifically designed for constructive cache sharing, and Work Stealing (WS), which is a more traditional design. Our experimental results indicate that PDF scheduling yields a 1.3 - 1.6X performance improvement relative to WS for several fine- grain parallel benchmarks on projected future CMP configurations; we also report several issues that may limit the advantage of PDF in certain applications. These results also indicate that PDF more effectively utilizes off-chip bandwidth, making it possible to trade-off on-chip cache for a larger number of cores. Moreover, we find that task granularity plays a key role in cache performance. Therefore, we present an automatic approach for selecting effective grain sizes, based on a new working set profiling algorithm that is an order of magnitude faster than previous approaches. This is the first paper demonstrating the effectiveness of PDF on real benchmarks, providing a direct comparison between PDF and WS, revealing the limiting factors for PDF in practice, and presenting an approach for overcoming these factors. Copyright 2007 ACM

    Shugoshin Prevents Dissociation of Cohesin from Centromeres During Mitosis in Vertebrate Cells

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    Cohesion between sister chromatids is essential for their bi-orientation on mitotic spindles. It is mediated by a multisubunit complex called cohesin. In yeast, proteolytic cleavage of cohesin's α kleisin subunit at the onset of anaphase removes cohesin from both centromeres and chromosome arms and thus triggers sister chromatid separation. In animal cells, most cohesin is removed from chromosome arms during prophase via a separase-independent pathway involving phosphorylation of its Scc3-SA1/2 subunits. Cohesin at centromeres is refractory to this process and persists until metaphase, whereupon its α kleisin subunit is cleaved by separase, which is thought to trigger anaphase. What protects centromeric cohesin from the prophase pathway? Potential candidates are proteins, known as shugoshins, that are homologous to Drosophila MEI-S332 and yeast Sgo1 proteins, which prevent removal of meiotic cohesin complexes from centromeres at the first meiotic division. A vertebrate shugoshin-like protein associates with centromeres during prophase and disappears at the onset of anaphase. Its depletion by RNA interference causes HeLa cells to arrest in mitosis. Most chromosomes bi-orient on a metaphase plate, but precocious loss of centromeric cohesin from chromosomes is accompanied by loss of all sister chromatid cohesion, the departure of individual chromatids from the metaphase plate, and a permanent cell cycle arrest, presumably due to activation of the spindle checkpoint. Remarkably, expression of a version of Scc3-SA2 whose mitotic phosphorylation sites have been mutated to alanine alleviates the precocious loss of sister chromatid cohesion and the mitotic arrest of cells lacking shugoshin. These data suggest that shugoshin prevents phosphorylation of cohesin's Scc3-SA2 subunit at centromeres during mitosis. This ensures that cohesin persists at centromeres until activation of separase causes cleavage of its α kleisin subunit. Centromeric cohesion is one of the hallmarks of mitotic chromosomes. Our results imply that it is not an intrinsically stable property, because it can easily be destroyed by mitotic kinases, which are kept in check by shugoshin

    A Mathematical Model of Mitotic Exit in Budding Yeast: The Role of Polo Kinase

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    Cell cycle progression in eukaryotes is regulated by periodic activation and inactivation of a family of cyclin–dependent kinases (Cdk's). Entry into mitosis requires phosphorylation of many proteins targeted by mitotic Cdk, and exit from mitosis requires proteolysis of mitotic cyclins and dephosphorylation of their targeted proteins. Mitotic exit in budding yeast is known to involve the interplay of mitotic kinases (Cdk and Polo kinases) and phosphatases (Cdc55/PP2A and Cdc14), as well as the action of the anaphase promoting complex (APC) in degrading specific proteins in anaphase and telophase. To understand the intricacies of this mechanism, we propose a mathematical model for the molecular events during mitotic exit in budding yeast. The model captures the dynamics of this network in wild-type yeast cells and 110 mutant strains. The model clarifies the roles of Polo-like kinase (Cdc5) in the Cdc14 early anaphase release pathway and in the G-protein regulated mitotic exit network
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