Search for Boosted Dark Matter Interacting with Electrons in Super-Kamiokande.

A search for boosted dark matter using 161.9 kt yr of Super-Kamiokande IV data is presented. We search for an excess of elastically scattered electrons above the atmospheric neutrino background, with a visible energy between 100 MeV and 1 TeV, pointing back to the Galactic center or the Sun. No such excess is observed. Limits on boosted dark matter event rates in multiple angular cones around the Galactic center and Sun are calculated. Limits are also calculated for a baseline model of boosted dark matter produced from cold dark matter annihilation or decay. This is the first experimental search for boosted dark matter from the Galactic center or the Sun interacting in a terrestrial detector.

Search for Nucleon and Dinucleon Decays with an Invisible Particle and a Charged Lepton in the Final State at the Super-Kamiokande Experiment.

Search results for nucleon decays p→e^{+}X, p→µ^{+}X, n→νγ (where X is an invisible, massless particle) as well as dinucleon decays np→e^{+}ν, np→µ^{+}ν, and np→τ^{+}ν in the Super-Kamiokande experiment are presented. Using single-ring data from an exposure of 273.4 kton·yr, a search for these decays yields a result consistent with no signal. Accordingly, lower limits on the partial lifetimes of τ_{p→e^{+}X}>7.9×10^{32} yr, τ_{p→µ^{+}X}>4.1×10^{32} yr, τ_{n→νγ}>5.5×10^{32} yr, τ_{np→e^{+}ν}>2.6×10^{32} yr, τ_{np→µ^{+}ν}>2.2×10^{32} yr, and τ_{np→τ^{+}ν}>2.9×10^{31} yr at a 90% confidence level are obtained. Some of these searches are novel.

Search for neutrinos from annihilation of captured low-mass dark matter particles in the sun by super-kamiokande.

Super-Kamiokande (SK) can search for weakly interacting massive particles (WIMPs) by detecting neutrinos produced from WIMP annihilations occurring inside the Sun. In this analysis, we include neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock. Compared to the previous result, which used the upward-going muons only, the signal acceptances for light (few-GeV/c^{2}-200-GeV/c^{2}) WIMPs are significantly increased. We fit 3903 days of SK data to search for the contribution of neutrinos from WIMP annihilation in the Sun. We found no significant excess over expected atmospheric-neutrino background and the result is interpreted in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel. We set the current best limits on the spin-dependent WIMP-proton cross section for WIMP masses below 200 GeV/c^{2} (at 10 GeV/c^{2}, 1.49×10^{-39} cm^{2} for χχ→bb[over ¯] and 1.31×10^{-40} cm^{2} for χχ→τ^{+}τ^{-} annihilation channels), also ruling out some fraction of WIMP candidates with spin-independent coupling in the few-GeV/c^{2} mass range.

Search for trilepton nucleon decay via p→e+νν and p→µ+νν in the Super-Kamiokande experiment.

The trilepton nucleon decay modes p→e+νν and p→µ+νν violate |Δ(B-L)| by two units. Using data from a 273.4 kt yr exposure of Super-Kamiokande a search for these decays yields a fit consistent with no signal. Accordingly, lower limits on the partial lifetimes of τp→e+νν>1.7×10(32) years and τp→µ+νν>2.2×10(32) years at a 90% confidence level are obtained. These limits can constrain Grand Unified Theories which allow for such processes.

Search for nucleon decay via n→ν[over ¯]π0 and p→ν[over ¯]π+ in Super-Kamiokande.

We present the results of searches for nucleon decay via n→ν[over ¯]π0 and p→ν[over ¯]π+ using data from a combined 172.8 kt·yr exposure of Super-Kamiokande-I,-II, and-III. We set lower limits on the partial lifetime for each of these modes: τn→ν[over ¯]π0>1.1×10(33) years and τp→ν[over ¯]π+>3.9×10(32) years at a 90% confidence level.

First indication of terrestrial matter effects on solar neutrino oscillation.

We report an indication that the elastic scattering rate of solar B8 neutrinos with electrons in the Super-Kamiokande detector is larger when the neutrinos pass through Earth during nighttime. We determine the day-night asymmetry, defined as the difference of the average day rate and average night rate divided by the average of those two rates, to be [-3.2 ± 1.1(stat) ± 0.5(syst)]%, which deviates from zero by 2.7 σ. Since the elastic scattering process is mostly sensitive to electron-flavored solar neutrinos, a nonzero day-night asymmetry implies that the flavor oscillations of solar neutrinos are affected by the presence of matter within the neutrinos' flight path. Super-Kamiokande's day-night asymmetry is consistent with neutrino oscillations for 4 × 10(-5) eV(2) ≤ Δm 2(21) ≤ 7 × 10(-5) eV(2) and large mixing values of θ12, at the 68% C.L.

Search for dinucleon decay into kaons in Super-Kamiokande.

A search for the dinucleon decay pp → K+ K+ has been performed using 91.6 kton·yr data from Super-Kamiokande-I. This decay provides a sensitive probe of the R-parity-violating parameter λ112''. A boosted decision tree analysis found no signal candidates in the data. The expected background was 0.28±0.19 atmospheric neutrino induced events and the estimated signal detection efficiency was 12.6%±3.2%. A lower limit of 1.7×10(32) years has been placed on the partial lifetime of the decay O16 → C14K+ K+ at 90% C.L. A corresponding upper limit of 7.8×10(-9) has been placed on the parameter λ112''.

Evidence for the appearance of atmospheric tau neutrinos in super-Kamiokande.

Super-Kamiokande atmospheric neutrino data were fit with an unbinned maximum likelihood method to search for the appearance of tau leptons resulting from the interactions of oscillation-generated tau neutrinos in the detector. Relative to the expectation of unity, the tau normalization is found to be 1.42 ± 0.35(stat)(-0.12)(+0.14)(syst) excluding the no-tau-appearance hypothesis, for which the normalization would be zero, at the 3.8σ level. We estimate that 180.1 ± 44.3(stat)(-15.2)(+17.8) (syst) tau leptons were produced in the 22.5 kton fiducial volume of the detector by tau neutrinos during the 2806 day running period. In future analyses, this large sample of selected tau events will allow the study of charged current tau neutrino interaction physics with oscillation produced tau neutrinos.

Highest genetic diversity at the northern range limit of the rare orchid Isotria medeoloides.

Populations in previously glaciated regions are often genetically depauperate in comparison with populations at lower latitudes, due either to bottlenecks experienced in post-glacial colonization or to contemporary genetic drift in small, peripheral populations. Populations of the rare self-fertilizing North American orchid Isotria medeoloides are largest in the previously glaciated region near the northern range limit, allowing us to examine the role of historical versus contemporary processes in determining population genetic diversity and structure. If contemporary processes predominate, genetic diversity should increase with increasing census size. In contrast, if sequential bottlenecks associated with colonization are paramount, diversity should decrease with latitude and be relatively insensitive to census size. We genotyped 299 individuals from 20 populations at four variable microsatellite loci to contrast genetic diversity and structure for populations in previously glaciated regions versus previously unglaciated regions. Populations were highly inbred (F=0.95) and highly differentiated (R(ST)=0.485). Across all sampled populations, genetic diversity decreased and genetic differentiation increased with declining population size. Small southern populations were especially differentiated and genetically depauperate. In the glaciated part of the range, genetic diversity increased as populations approached the northern range limit, demonstrating the centrality of contemporary processes for this post-glacial colonist.

Search for differences in oscillation parameters for atmospheric neutrinos and antineutrinos at Super-Kamiokande.

We present a search for differences in the oscillations of antineutrinos and neutrinos in the Super-Kamiokande-I, -II, and -III atmospheric neutrino sample. Under a two-flavor disappearance model with separate mixing parameters between neutrinos and antineutrinos, we find no evidence for a difference in oscillation parameters. Best-fit antineutrino mixing is found to be at (Δm2,sin2 2θ)=(2.0×10(-3) eV2, 1.0) and is consistent with the overall Super-K measurement.

High-density SNP association study of the 17q21 chromosomal region linked to autism identifies CACNA1G as a novel candidate gene.

Chromosome 17q11-q21 is a region of the genome likely to harbor susceptibility to autism (MIM(209850)) based on earlier evidence of linkage to the disorder. This linkage is specific to multiplex pedigrees containing only male probands (MO) within the Autism Genetic Resource Exchange (AGRE). Earlier, Stone et al.(1) completed a high-density single nucleotide polymorphism association study of 13.7 Mb within this interval, but common variant association was not sufficient to account for the linkage signal. Here, we extend this single nucleotide polymorphism-based association study to complete the coverage of the two-LOD support interval around the chromosome 17q linkage peak by testing the majority of common alleles in 284 MO trios. Markers within an interval containing the gene, CACNA1G, were found to be associated with Autism Spectrum Disorder at a locally significant level (P=1.9 × 10(-5)). While establishing CACNA1G as a novel candidate gene for autism, these alleles do not contribute a sufficient genetic effect to explain the observed linkage, indicating that there is substantial genetic heterogeneity despite the clear linkage signal. The region thus likely harbors a combination of multiple common and rare alleles contributing to the genetic risk. These data, along with earlier studies of chromosomes 5 and 7q3, suggest few if any major common risk alleles account for Autism Spectrum Disorder risk under major linkage peaks in the AGRE sample. This provides important evidence for strategies to identify Autism Spectrum Disorder genes, suggesting that they should focus on identifying rare variants and common variants of small effect.

Genetic mosaics in strangler fig trees: implications for tropical conservation.

Single trees of six species of strangler figs (Ficus spp., Moraceae) in Panama were found to be made up of multiple genotypes, presumably formed by the fusion of different individuals. The phenomenon is frequent enough that strangler fig populations will contain considerably more genetic variation than would be expected from the number of trees. How this cryptic variation affects populations depends on the flowering phonology of composite trees. If the genetically different portions of trees flower asynchronously, populations of pollinating wasps may be more resistant to low host population sizes than previously thought. If different portions flower synchronously, attempts to infer mating-system parameters from the parentage of fruit crops will be misleading. The fruiting of figs, which are considered a keystone species in tropical forests, is important for maintaining biodiversity but is also particularly susceptible to failure at small population sizes. It is therefore important to know both the number of trees and the number of genotypes in a population.

Correlated conformational fluctuations during enzymatic catalysis: Implications for catalytic rate enhancement.

Correlated enzymatic conformational fluctuations are shown to contribute to the rate of enhancement achieved during catalysis. Cytidine deaminase serves as a model system. Crystallographic temperature factor data for this enzyme complexed with substrate analog, transition-state analog, and product are available, thereby establishing a measure of atomic scale conformational fluctuations along the (approximate) reaction coordinate. First, a neural network-based algorithm is used to visualize the decreased conformational fluctuations at the transition state. Second, a dynamic diffusion equation along the reaction coordinate is solved and shows that the flux velocity through the associated enzymatic conformation space is greatest at the transition state. These results suggest (1) that there are both dynamic and energetic restrictions to conformational fluctuations at the transition state, (2) that enzymatic catalysis occurs on a fluctuating potential energy surface, and (3) a form for the potential energy. The Michaelis-Menten equations are modified to describe catalysis on this fluctuating potential energy profile, leading to enhanced catalytic rates when fluctuations along the reaction coordinate are appropriately correlated. This represents a dynamic tuning of the enzyme for maximally effective transformation of the ES complex into EP.

Usefulness of different stimuli in visual evoked potentials.

The goal of this study was to determine the relative usefulness of the flash (FL), pattern reversal (PR) of 56', and PR of 28' in 62 patients (pts) with either MS (34) or non-MS (28) compared with normals (19). An abnormal visual evoked potential was found in 58%, 69%, and 81% of the eyes tested in possible, probable, and definite MS and in 88% of the non-MS group. The 28' PR produced the most abnormal responses, the greatest number with either greater than 3 standard deviations (SD) from the mean or greater than 2 SD in both MS and non-MS groups. The FL was second best at producing the most abnormal responses, but more often produced the only abnormality (29), compared with 28' PR (11). The 56' PR produced the only abnormality in none of the MS pts and in only one of the non-MS pts. In all categories (most abnormal, greater than 3 SD, greater than 2 SD, the only abnormality of greater than 3 SD or greater than 2 SD, and other peaks abnormal), the 28' PR was usually by far the best stimulus for definite (and probable) MS, but equally as effective was the FL in the possible MS pts Our data suggest the usefulness of 28' and not 56' PR, but the FL is especially useful in pts with possible MS.

Morphometric analysis of macular photoreceptors and ganglion cells in retinas with retinitis pigmentosa.

There have been a number of histopathologic studies of retinas that were taken post mortem from patients with retinitis pigmentosa (RP), but few have addressed the question of transneuronal degeneration of ganglion cells secondary to photoreceptor death. We studied sectioned maculae that were obtained from 41 patients with different genetic forms of RP: autosomal dominant (n = 11); X-linked (n = 9); and simplex (n = 21). We also studied sectioned maculae that were taken from 20 age-matched normal subjects. We counted cell bodies in the photoreceptor and ganglion cell layers at 100-microns (0.35 degrees) intervals from the foveola to 1500-microns eccentricity and compared the mean cell counts among each group with RP. Each RP type had significantly fewer (P < .05) photoreceptors than those of the control group at each 100-microns interval. At eccentricities of 700 to 1500 microns, the retinas with X-linked and autosomal dominant RP had significantly fewer (P < .05) ganglion cells than those of the control group; the simplex RP mean ganglion cell counts were significantly lower (P < .05) than those of the control group, from 1000 to 1500 microns. The mean photoreceptor and ganglion cell counts had a .43 correlation (P < .001) in the zone of 700 to 1500 microns, consistent with transneuronal ganglion cell degeneration. Current experimental attempts to restore vision in diseased retinas by simulating or replacing photoreceptors are based on the premise that ganglion cells are retained after photoreceptor death. Our findings support this assumption.

Proactive management of histopathology workloads: analysis of the UK Royal College of Pathologists' recommendations on specimens of limited or no clinical value on the workload of a teaching hospital gastrointestinal pathology service.

AIMS: To investigate the effect on the workload of a gastrointestinal pathology service of implementing the recommendations of the Royal College of Pathologists' (RCPath) working party on specimens of limited or no clinical value (LONCV). METHODS: All endoscopic gastrointestinal pathology reports for the first three months of 2001 at a large teaching hospital were reviewed against the RCPath recommendations. Specimens in the category of LONCV were recorded and the final histopathology diagnosis noted. RESULTS: The biopsies in the LONCV category were 30% of oesophageal, 61% of gastric, 0.5% of duodenal, and 7% of colorectal origin. CONCLUSIONS: Implementing the RCPath recommendations would reduce the number of requests for the examination of gastrointestinal endoscopic specimens by 3500 specimens each year in this department. None of the specimens in the LONCV category showed an abnormality that could not have been detected by a more efficient and less invasive method. In the UK, where there is a severe shortage of trained histopathologists, the implementation of these recommendations would ensure that these scarce resources are not misused.

One hundred consecutive cases of selective termination of an abnormal fetus in a multifetal gestation.

OBJECTIVE: To determine whether transabdominal selective termination of one or more abnormal fetuses in a multifetal pregnancy with dichorionic placentation is a safe and effective procedure. METHODS: One hundred consecutive selective termination procedures were performed by transabdominal injection of potassium chloride into the heart or umbilical vein of an anomalous fetus in a multifetal pregnancy. All of the abnormal fetuses were presumed to have dichorionic diamniotic placentas, based on an ultrasound evaluation before the procedure. Follow-up data were obtained for each patient regarding the development of postprocedural complications, laboratory or clinical evidence of a coagulopathy, maternal or neonatal morbidity, gestational age at delivery, and birth weight of the infants. RESULTS: Ninety-one sets of twins were reduced to singletons, six sets of triplets were reduced to twins, two sets of triplets were reduced to singletons, and one set of quadruplets was reduced to triplets. The anomalous fetus or fetuses were identified correctly and terminated in each case. Three patients spontaneously aborted, and one women electively terminated her pregnancy 2 weeks after the procedure. The mean gestational age at delivery of the 96 patients who delivered surviving infants was 36.8 weeks, and 85.4% delivered at 32 weeks or later. Three women developed laboratory evidence of a coagulopathy, but there were no cases of clinically evident disseminated intravascular coagulation. CONCLUSION: This procedure, performed at a single institution by a small number of operators using a common protocol, accomplished its objective in all cases, was accompanied by a low spontaneous loss rate, and resulted in the birth of healthy infants at or near term in the vast majority of cases. This series suggests that selective termination is a reasonable option to consider when one abnormal fetus is found in a multifetal pregnancy with dichorionic placentation.

Risk factors for severe preeclampsia.

OBJECTIVE: To identify risk factors associated with severe preeclampsia and to determine whether these factors are similar in nulliparous and multiparous patients. METHODS: Patients whose pregnancies were complicated by severe preeclampsia (n = 70) were compared retrospectively to 18,964 non-preeclamptic controls. Information on maternal demographic factors; medical, obstetric, and family histories; and neonatal outcome was retrieved and analyzed by univariate and multivariate analysis. RESULTS: By logistic regression, the only risk factors associated with the development of severe preeclampsia were severe obesity in all patients (adjusted odds ratio 3.5, 95% confidence interval [CI] 1.68-7.46) and a history of preeclampsia in multiparous patients (adjusted odds ratio 7.2, 95% CI 2.74-18.74). CONCLUSION: Severe obesity and a history of preeclampsia are the only maternal risk factors identified for the development of severe preeclampsia.

Keratoacanthoma in Kauai, Hawaii. The first documented incidence in a defined population.

BACKGROUND AND DESIGN: A prospective 5-year population-based incidence study was conducted on the island of Kauai, Hawaii, from 1983 through 1987 to investigate the frequency of keratoacanthoma in white residents. RESULTS: A total of 53 residents, 36 men and 17 women, were identified with an initial episode of keratoacanthoma during the 5-year study. The average annual incidence rate per 100,000 Kauai residents, standardized to the US white population, was 144 for men and 73 for women, with a combined rate of 104. The average patient age was 63.5 years. The limbs, particularly the hands and arms, were the most common anatomic site, with the trunk second. Only one patient developed a new subsequent keratoacanthoma, and no recurrent lesions were observed. Three patients had two keratoacanthomas when they first presented, and 13 patients had concurrent skin cancer. Sixty percent (32) of our patients developed skin cancer at one time or another. CONCLUSIONS: We report the first population-based keratoacanthoma incidence rates documented in the United States, which are almost equal to those of squamous cell carcinoma. Keratoacanthoma also shares many common epidemiological features with squamous cell carcinoma, such as increasing incidence in progressively older age groups.