Search for light dark matter in XENON10 data

We report results of a search for light (≲10  GeV) particle dark matter with the XENON10 detector. The event trigger was sensitive to a single electron, with the analysis threshold of 5 electrons corresponding to 1.4 keV nuclear recoil energy. Considering spin-independent dark matter-nucleon scattering, we exclude cross sections σ(n)>7×10(-42)  cm(2), for a dark matter particle mass m(χ)=7  GeV. We find that our data strongly constrain recent elastic dark matter interpretations of excess low-energy events observed by CoGeNT and CRESST-II, as well as the DAMA annual modulation signal.

Limits on spin-dependent WIMP-nucleon cross sections from the XENON10 experiment

XENON10 is an experiment to directly detect weakly interacting massive particles (WIMPs), which may comprise the bulk of the nonbaryonic dark matter in our Universe. We report new results for spin-dependent WIMP-nucleon interactions with 129Xe and 131Xe from 58.6 live days of operation at the Laboratori Nazionali del Gran Sasso. Based on the nonobservation of a WIMP signal in 5.4 kg of fiducial liquid xenon mass, we exclude previously unexplored regions in the theoretically allowed parameter space for neutralinos. We also exclude a heavy Majorana neutrino with a mass in the range of approximately 10 GeV/c2-2 TeV/c2 as a dark matter candidate under standard assumptions for its density and distribution in the galactic halo.

First results from the XENON10 dark matter experiment at the Gran Sasso National Laboratory

The XENON10 experiment at the Gran Sasso National Laboratory uses a 15 kg xenon dual phase time projection chamber to search for dark matter weakly interacting massive particles (WIMPs). The detector measures simultaneously the scintillation and the ionization produced by radiation in pure liquid xenon to discriminate signal from background down to 4.5 keV nuclear-recoil energy. A blind analysis of 58.6 live days of data, acquired between October 6, 2006, and February 14, 2007, and using a fiducial mass of 5.4 kg, excludes previously unexplored parameter space, setting a new 90% C.L. upper limit for the WIMP-nucleon spin-independent cross section of 8.8x10(-44) cm2 for a WIMP mass of 100 GeV/c2, and 4.5x10(-44) cm2 for a WIMP mass of 30 GeV/c2. This result further constrains predictions of supersymmetric models.

Asplenism and systemic lupus erythematosus

Although functional hyposplenism, secondary to Fc-receptor blockage by circulating immune complexes saturation, has been described in systemic lupus erythematosus (SLE), only few cases of complete asplenism have been reported. We observed a 60-year-old woman with congenital asplenism who presented with active SLE. The course and the clinical characteristics of such patients are reviewed and the relationship between the asplenic state and initiation and severity of SLE are discussed. These patients are at high risk for fatal pneumococcemia and pneumococcal vaccine is recommended even if long term results are still conflicting.

The epidemiology of myopia

Many people have reduced unaided vision because of myopia, a spherical error of refraction. The biological theory of myopia views myopia as the result of genetically determined characteristics of eye tissues, whereas the use-abuse theory views myopia as the result of habitual use of the eye at a near focal length, near-work. The use-abuse theory implies that myopia is preventable whereas the biological theory does not. Myopia varies over age, gender, race, ethnicity, level of education, social class and degree of urbanization. The explanation of the epidemiology of myopia in the use-abuse theory is that some types of people do more near-work than others. Using data from the Health Examination Survey of 12 to 17-year-olds conducted by the US Public Health Service from 1966--1970, this paper finds that the use-abuse theory can explain at least some of the variance of myopia and much of the socially patterned variance. This finding raises the possibility that at least some of the myopia extant in a population is preventable.

A statistical analysis of the Biological Theory of spherical error of refraction

It is widely believed that Adolph Steiger proved in Die Entstehung der sphärischen Refraktionen des menschlichen Auges (The Origin of Spherical Refractions of the Human Eye) that the Biological Theory of spherical error of refraction statistically explains the entire distribution of such errors, hence excluding other theories such as the Use-Abuse Theory. Although Steiger's Biological Theory is a statistical argument, he never put it into formal notation. This paper puts a modernized version of the Biological Theory into formal statistical notation. It shows that the Biological Theory explains the dispersion of distributions of spherical error of refraction but not the location of their means. The Use-Abuse Theory is an explanation of mean spherical error in populations. Since a complete theory of spherical errors of refraction needs to explain both the mean and the dispersion of their distribution, the two theories are potentially complementary. No empirical evidence, however, is presented here for either theory.

Age, reading, and myopia

This paper tests whether the use-abuse theory or the biological theory of myopia explains the appearance and progression of myopia among 12--17 year olds in the United States. The use-abuse theory predicts that current amount of reading and cumulative exposure to reading, as indicated by years of schooling, explain myopia. The biological theory predicts that either age from birth or age from puberty explains any tendency for myopia to appear and progress among children or adolescents. Regression analysis shows that education explains all the tendency for myopia to appear and progress among 12--17-years-olds. When we control for education, age is not related to increased myopia. Myopia progresses, on the average, 0.22 D per academic year. However, education explains only a small fraction of the variance in myopia.