Optimal classification in sparse Gaussian graphic model

Consider a two-class classification problem where the number of features is much larger than the sample size. The features are masked by Gaussian noise with mean zero and covariance matrix $\Sigma$, where the precision matrix $\Omega=\Sigma^{-1}$ is unknown but is presumably sparse. The useful features, also unknown, are sparse and each contributes weakly (i.e., rare and weak) to the classification decision. By obtaining a reasonably good estimate of $\Omega$, we formulate the setting as a linear regression model. We propose a two-stage classification method where we first select features by the method of Innovated Thresholding (IT), and then use the retained features and Fisher's LDA for classification. In this approach, a crucial problem is how to set the threshold of IT. We approach this problem by adapting the recent innovation of Higher Criticism Thresholding (HCT). We find that when useful features are rare and weak, the limiting behavior of HCT is essentially just as good as the limiting behavior of ideal threshold, the threshold one would choose if the underlying distribution of the signals is known (if only). Somewhat surprisingly, when $\Omega$ is sufficiently sparse, its off-diagonal coordinates usually do not have a major influence over the classification decision. Compared to recent work in the case where $\Omega$ is the identity matrix [Proc. Natl. Acad. Sci. USA 105 (2008) 14790-14795; Philos. Trans. R. Soc. Lond. Ser. A Math. Phys. Eng. Sci. 367 (2009) 4449-4470], the current setting is much more general, which needs a new approach and much more sophisticated analysis. One key component of the analysis is the intimate relationship between HCT and Fisher's separation. Another key component is the tight large-deviation bounds for empirical processes for data with unconventional correlation structures, where graph theory on vertex coloring plays an important role.Comment: Published in at http://dx.doi.org/10.1214/13-AOS1163 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Smoothening creases on surfaces of strain-stiffening materials

When an elastic block (e.g., an elastomer or a soft tissue) is compressed to a critical strain, the smooth surface of the block forms creases, namely, localized regions of self-contact. Here we show how this instability behaves if the solid stiffens steeply. For a solid that stiffens steeply at large strains, as the compression increases, the surface is initially smooth, then forms creases, and finally becomes smooth again. For a solid that stiffens steeply at small strains, creases will never form and the surface remains smooth for all levels of compression. We also obtain the critical conditions for the formation and disappearance of wrinkles. When the surface does become unstable, we find that creases always set in at a lower compression than wrinkles. Our findings may shed light in developing crease-resistant materials.Engineering and Applied Science

Dcr-1 Maintains Drosophila Ovarian Stem Cells

SummaryMicroRNAs (miRNAs) regulate gene expression by controlling the turnover, translation, or both of specific mRNAs. In Drosophila, Dicer-1 (Dcr-1) is essential for generating mature miRNAs from their corresponding precursors. Because miRNAs are known to modulate developmental events, such as cell fate determination and maintenance in many species, we investigated whether a lack of Dcr-1 would affect the maintenance of stem cells (germline stem cells, GSCs; somatic stem cells, SSCs) in the Drosophila ovary by specifically removing its function from the stem cells. Our results show that dcr-1 mutant GSCs cannot be maintained and are lost rapidly from the niche without discernable features of cell death, indicating that Dcr-1 controls GSC self-renewal but not survival. bag of marbles (bam), the gene that encodes an important differentiating factor in the Drosophila germline, however, is not upregulated in dcr-1 mutant GSCs, and its removal does not slow down dcr-1 mutant GSC loss, suggesting that Dcr-1 controls GSC self-renewal by repressing a Bam-independent differentiation pathway. Furthermore, Dcr-1 is also essential for the maintenance of SSCs in the Drosophila ovary. Our data suggest that miRNAs produced by Dcr-1 are required for maintaining two types of stem cells in the Drosophila ovary

El análisis de las características de los grupos étnicos africanos en el suburbio de Foshan desde la perspectiva de la movilidad

La movilidad se ha convertido en un término popular en el siglo xxi, al mismo tiempo que el análisis de la formación y las características dinámicas de las comunidades étnicas ha ido cobrando una mayor importancia en las investigaciones recientes. En el presente estudio, se lleva a cabo una comparación entre el colectivo de africanos que residen en las ciudades de Guangzhou y Foshan. El trabajo se realiza desde la perspectiva de la movilidad y de sus comportamientos más destacados. En los contextos económico, social y político chinos, los suburbios étnicos han ido adquiriendo un mayor protagonismo, tanto por las pautas de movilidad que en ellos se desarrollan y en las que cobran una relevancia especial el espacio residencial, el tiempo de viaje y el medio de transporte, como por las características de la población inmigrante que en ellos reside, su identidad, las redes sociales que desarrollan, la fijación de sus establecimientos comerciales, etc. Estamos ante lugares cuya naturaleza es dinámica, compleja y está directamente relacionada con la situación de ilegalidad de los inmigrantes. A lo largo de este artículo, el trabajo de campo desarrollado y la aplicación de metodologías cuantitativas y cualitativas permitirán observar cómo, frente a los cambios que se producen en los contextos económico y político, las nuevas prácticas de movilidad de carácter transnacional y transregional de los migrantes pueden provocar la transformación de las comunidades étnicas tradicionales y el surgimiento de nuevos suburbios étnicos.La mobilitat s'ha convertit en un terme popular al segle xxi, alhora que l'anàlisi de la formació i les característiques dinàmiques de les comunitats ètniques ha anat adquirint més importància en les investigacions recents. En el present estudi, portem a terme una comparació entre el col·lectiu d'africans que resideixen a les ciutats de Guangzhou i Foshan. L'anàlisi es du a terme des de la perspectiva de la mobilitat i dels seus comportaments més destacats. En els contextos econòmic, social i polític xinès, els suburbis ètnics han anat adquirint més protagonisme, tant per les pautes de mobilitat que s'hi desenvolupen i en les quals cobra una rellevància especial l'espai residencial, el temps de viatge i el mitjà de transport, com per les característiques de la població immigrant que hi viu, les xarxes socials que s'hi desenvolupen, la fixació dels seus establiments comercials, etc. Estem davant de llocs que mostren una naturalesa dinàmica, complexa i directament relacionada amb la situació d'il·legalitat dels immigrants. Al llarg d'aquest article, el treball de camp desenvolupat i l'aplicació de les metodologies quantitatives i qualitatives permetran observar com, enfront dels canvis que es produeixen en el context econòmic i polític, les noves pràctiques de mobilitat de caràcter transnacional i transregional dels migrants poden provocar la transformació de les comunitats ètniques tradicionals i el sorgiment de nous suburbis ètnics.Au 21e siècle, le terme mobilité est devenu populaire et l'analyse de la formation et les caractéristiques dynamiques des communautés ethniques revêtent une grande importance dans les recherches récentes. Notre étude fait l'objet d'une comparaison entre le collectif d'Africains qui résident dans les villes de Guangzhou et Foshan. Le travail est fait dans une perspective de la mobilité et de ses comportements les plus remarquables. Du point de vue économique, social et politique chinois, les banlieues ethniques ont joué un rôle de plus en plus important que ce soit par les flux de mobilité qui s'y développent et où l'espace résidentiel, la durée de voyage et le moyen de transport sont primordiaux, que par les caractéristiques de la population immigrante résidente, son identité, les réseaux sociaux qu'ils développent, l'établissement des commerces, etc. Nous nous trouvons face à des lieux qui possèdent une nature dynamique et complexe et qui en rapport direct avec la situation d'illégalité des immigrants. Le travail sur le terrain et l'application de méthodologies quantitatives et qualitatives permettront de faire remarquer que, face aux changements en cours du point de vue économique et politique, les nouvelles expériences de mobilité à caractère transnationale et trans-régionale des migrants peuvent mener à la transformation des communautés ethniques et à l'apparition de nouvelles banlieues ethniques.Mobility has become a popular word and a powerful statement in the 21st century, while the analysis of the formation and dynamic characteristics of ethnic communities has become increasingly important in recent research. This study compares the group of Africans residing in the ethnic suburbs of Guangzhou and Foshan from the perspective of mobility and their prominent behaviours. In the Chinese economic, social and political context, ethnic suburbs have attracted increasing attention due to both the patterns of mobility developed in them, in which residential space, travel time and means of transport are of particular relevance, and the characteristics of the immigrant population living in them, their identity, the social networks they develop and the location of their commercial establishments, among other factors. These are spaces whose dynamic and complex nature is directly related to the illegal status of the immigrants. The fieldwork carried out and the application of quantitative and qualitative methodologies show how, in the face of changes occurring in the economic and political context, the new transnational and trans-regional mobility practices of migrants can transform traditional ethnic communities and favour the emergence of new ethnic suburbs

The Effectiveness of a Hybrid Cybersecurity Summer Camp for Teachers

Cybersecurity teacher education plays a vital role in narrowing the gap in the need for cybersecurity professionals in the workforce. In this paper, the authors examined the effectiveness of a hybrid cybersecurity summer camp for secondary education in-service teachers. The pre- and post-camp quizzes showed significant statistical difference, t(17) = -8.42, p \u3c .001, with a large effect size of 2.24. Focus group interviews with the teacher participants further suggested that the hybrid modality is not only viable but also a preferred format welcomed by the teachers

Biomarkers of Oxidative Stress and Endogenous Antioxidants for Patients with Chronic Subjective Dizziness

As a neurotologic disorder of persistent non-vertiginous dizziness, chronic subjective dizziness (CSD) arises unsteadily by psychological and physiological imbalance. The CSD is hypersensitivity reaction due to exposure to complex motions visual stimuli. However, the pathophysiological features and mechanism of the CSD still remains unclearly. The present study was purposed to establish possible endogenous contributors of the CSD using serum samples from patients with the CSD. A total 199 participants were gathered and divided into two groups; healthy (n = 152, male for 61, and female for 91) and CSD (n = 47, male for 5, female for 42), respectively. Oxidative stress parameters such as, hydrogen peroxide and reactive substances were significantly elevated (p < 0.01 or p < 0.001), whereas endogenous antioxidant components including total glutathione contents, and activities of catalase and superoxide dismutase were significantly deteriorated in the CSD group (p < 0.01 or p < 0.001) as comparing to the healthy group, respectively. Serum levels of tumor necrosis factor -α and interferon-γ were significantly increased in the CSD participants (p < 0.001). Additionally, emotional stress related hormones including cortisol, adrenaline, and serotonin were abnormally observed in the serum levels of the CSD group (p < 0.01 or p < 0.001). Our results confirmed that oxidative stress and antioxidants are a critical contributor of pathophysiology of the CSD, and that is first explored to establish features of redox system in the CSD subjects compared to a healthy population

Controlled formation and disappearance of creases

Soft, elastic materials are capable of large and reversible deformation, readily leading to various modes of instability that are often undesirable, but sometimes useful. For example, when a soft elastic material is compressed, its initially flat surface will suddenly form creases. While creases are commonly observed, and have been exploited to control chemical patterning, enzymatic activity, and adhesion of surfaces, the conditions for the formation and disappearance of creases have so far been poorly controlled. Here we show that a soft elastic bilayer can snap between the flat and creased states repeatedly, with hysteresis. The strains at which the creases form and disappear are highly reproducible, and are tunable over a large range, through variations in the level of pre-compression applied to the substrate and the relative thickness of the film. The introduction of bistable flat and creased states and hysteretic switching is an important step to enable applications of this type of instability.Engineering and Applied Science