Internal localized eigenmodes on spin discrete breathers in antiferromagnetic chains with on-site easy axis anisotropy

We investigate internal localized eigenmodes of the linearized equation around spin discrete breathers in 1D antiferromagnets with on-site easy axis anisotropy. The threshold of occurrence of the internal localized eigenmodes has a typical structure in parameter space depending on the frequency of the spin discrete breather. We also performed molecular dynamics simulation in order to show the validity of our linear analysis.Comment: 4 pages including 5 figure

Large pTp_T Hadroproduction of ZZ as a Probe of Gluon Distribution inside Proton

The transverse momentum distribution of single vector boson production at hadron colliders provides useful ways of testing the Standard Model and searching new physics beyond the Standard Model. We study large $p_{_T}$ hadroproduction of $Z$-boson as a probe of gluon distributions inside proton. We investigate how to get initial gluon-involving contributions, or how to subtract quark-quark (or -antiquark) contributions from total cross section. We also investigated the simultaneous measurement of the rapidity and the transverse momentum of the produced $Z$ boson, to obtain momentum fractions of initial partons. And we extracted relevant uncertainties involving in experimental and theoretical analyses. This large $p_{_T}$ hadroproduction of $Z$ can be used as constraints on analyses of global parton (gluon and quarks) distribution functions inside proton.Comment: (a) 13 pages(LaTeX) + 1 figure ps file(3 pages):compressed, uuencoded (b) accepted by Phys.Lett.B. (c) some figures are combined and one is omitted. (d) conclusion part is included into abstrac

Truncated moments of parton distributions

We derive evolution equations satisfied by moments of parton distributions when the integration over the Bjorken variable is restricted to a subset (x_0 <= x <= 1) of the allowed kinematical range 0<= x<= 1. The corresponding anomalous dimensions turn out to be given by a triangular matrix which couples the N--th truncated moment with all (N + K)--th truncated moments with integer K >= 0. We show that the series of couplings to higher moments is convergent and can be truncated to low orders while retaining excellent accuracy. We give an example of application to the determination of alpha_s from scaling violations.Comment: 11 pages, no figures, latex. Final version, to be published in Phys. Lett. B. A few typos corrected; derivation of eq.(9) improve

Beyond Symbolic Representation: A Comparison of the Electoral Pathways and Policy Priorities of Asian American and Latino Elected Officials

This is an exploratory study of the impact of Latino and Asian American elected officials on their respective groups\u27 political incorporation. The authors argue that Latino and Asian American elected officials\u27 paths to elected office do not always fit the biracial coalition model of political incorporation for minorities, and instead suggest a reconstructed model to explain the distinctive character of Latino and Asian American group efforts toward political representation. The results of this paper are based on information gathered from two nationwide mail surveys of Latino elected officials (LEOs) and Asian American elected officials (AAEOs). The 2000 National Asian American and Latino Elected Officials Survey was conducted in Fall 2000 with interviews of elected officials held in 2001. The 1999 National Asian American Elected Officials Survey was conducted in May 1999 with interviews of elected officials held throughout 2000. This paper focuses on analyzing the means by which Latinos and Asian Americans have achieved political power, their sources of community support, and the resources they needed to successfully win office. It also examines current Latinalo and Asian American office-holders and explores whether they direct policy benefits to their respective communities. The results of these surveys indicate that Latino and Asian American politicians are on average older, more financially secure, and better educated than their respective general populations. They also are more liberal ideologically than the general populations. The analysis further reveals that the percentage of ethnic population is a stronger determinant for the election of Latino politicians than for Asian American politicians. A significant number of LEOs aim their policies to benefit primarily the Latino community, whereas AAEOs focus on broader community issues due to their districts\u27 demographics. Ethnicity, however, can play a significant role for AAEOs, particularly in raising campaign contributions from their communities. This paper concludes that despite internal heterogeneity and structural barriers that have limited both groups\u27 political advancement, Latino and Asian American political activists are using a variety of methods to achieve political incorporation and policy responsiveness at the local and state levels

RowHammer: Reliability Analysis and Security Implications

As process technology scales down to smaller dimensions, DRAM chips become more vulnerable to disturbance, a phenomenon in which different DRAM cells interfere with each other's operation. For the first time in academic literature, our ISCA paper exposes the existence of disturbance errors in commodity DRAM chips that are sold and used today. We show that repeatedly reading from the same address could corrupt data in nearby addresses. More specifically: When a DRAM row is opened (i.e., activated) and closed (i.e., precharged) repeatedly (i.e., hammered), it can induce disturbance errors in adjacent DRAM rows. This failure mode is popularly called RowHammer. We tested 129 DRAM modules manufactured within the past six years (2008-2014) and found 110 of them to exhibit RowHammer disturbance errors, the earliest of which dates back to 2010. In particular, all modules from the past two years (2012-2013) were vulnerable, which implies that the errors are a recent phenomenon affecting more advanced generations of process technology. Importantly, disturbance errors pose an easily-exploitable security threat since they are a breach of memory protection, wherein accesses to one page (mapped to one row) modifies the data stored in another page (mapped to an adjacent row).Comment: This is the summary of the paper titled "Flipping Bits in Memory Without Accessing Them: An Experimental Study of DRAM Disturbance Errors" which appeared in ISCA in June 201

Trustworthy machine learning through the lens of privacy and security

Nowadays, machine learning (ML) becomes ubiquitous and it is transforming society. However, there are still many incidents caused by ML-based systems when ML is deployed in real-world scenarios. Therefore, to allow wide adoption of ML in the real world, especially in critical applications such as healthcare, finance, etc., it is crucial to develop ML models that are not only accurate but also trustworthy (e.g., explainable, privacy-preserving, secure, and robust). Achieving trustworthy ML with different machine learning paradigms (e.g., deep learning, centralized learning, federated learning, etc.), and application domains (e.g., computer vision, natural language, human study, malware systems, etc.) is challenging, given the complicated trade-off among utility, scalability, privacy, explainability, and security. To bring trustworthy ML to real-world adoption with the trust of communities, this study makes a contribution of introducing a series of novel privacy-preserving mechanisms in which the trade-off between model utility and trustworthiness is optimized in different application domains, including natural language models, federated learning with human and mobile sensing applications, image classification, and explainable AI. The proposed mechanisms reach deployment levels of commercialized systems in real-world trials while providing trustworthiness with marginal utility drops and rigorous theoretical guarantees. The developed solutions enable safe, efficient, and practical analyses of rich and diverse user-generated data in many application domains

A longitudinal analysis of physical activity and overweight/obesity in adolescents in Saskatoon

Overweight and obesity, one of the most common public health problems in affluent societies, have become epidemic not only in Canada but also throughout the world. Obesity is also a major contributor to the global burden of chronic disease and disability such as diabetes, hypertension, and cardiovascular disorders. Studies have demonstrated clearly that higher intake of cholesterol and saturated fats and generally higher intake of energy-dense food are a key determinant of increasing levels of obesity and overweight in children. Physical activity is also recognized as a major factor in preventing obesity among children. Environmental factors—by which we mean both social (such as social support, social networks) and physical environment (such as access to physical activity amenities, roads and trails, grocery stores)—in generally believed to have a powerful influence on either limiting or enhancing the effects of fundamental determinants (diet and physical activity) of obesity in children. This thesis focuses on one of the key determinants, physical activity, and in turn examines factors that are related to changing physical activity in children. This research was designed to examine two major questions: (1) How do physical activity and overweigh/obesity change over time in a cohort of adolescents in Saskatoon? Are there differences in the patterns of change in overweight/obesity and physical activity between boys and girls? (2) What are the effects of family/friends and physical environments on the changing patterns of physical activity in this sample? The data used in this study was taken from the in motion studies’ longitudinal data. Study participants include 837 adolescents from12-18 years of age from two high schools and five elementary schools from two diverse geographic areas in Saskatoon (low and high socioeconomic status). Physical activity patterns of adolescents were investigated over a five-month period (e.g., type, frequency, and duration). Participants were also asked to respond to questions on demographics, social support, perceived benefits and barriers of physical activity, and health practices. The results of this study indicated that overweight/obesity increased with age, while physical activity decreased with age for both boys and girls. Boys overall were more likely to be physically active than were girls. Adolescents who received greater direct support from family members were 21% more likely to sustain their physical activity levels (relative odds 1.21; 95% CI 1.17, 1.24); in contrast, the more the family’s indirect support the 5.4% less sustaining were the adolescents’ physical activity (relative odds 0.94; 95% CI 0.91, 0.98). Home environments which were ‘rich’ in resources relevant to physical activity had 4% greater influence on adolescents’ physical activity levels, and this relationship was stronger than that of the influence of living in certain neighbourhoods (relative odds 1.04; 95% CI 1.03, 1.05). This research shed some greater understanding of the impact of family’s support and physical environment factors on adolescents’ continued physical activity levels. The implications of results for further research, targeted programs, and social policy is discussed in the thesis