We present an improved search for neutrinoless double-beta (0νββ) decay of ^{136}Xe in the KamLAND-Zen experiment. Owing to purification of the xenon-loaded liquid scintillator, we achieved a ...significant reduction of the ^{110m}Ag contaminant identified in previous searches. Combining the results from the first and second phase, we obtain a lower limit for the 0νββ decay half-life of T_{1/2}^{0ν}>1.07×10^{26} yr at 90% C.L., an almost sixfold improvement over previous limits. Using commonly adopted nuclear matrix element calculations, the corresponding upper limits on the effective Majorana neutrino mass are in the range 61-165 meV. For the most optimistic nuclear matrix elements, this limit reaches the bottom of the quasidegenerate neutrino mass region.
The KamLAND experiment has determined a precise value for the neutrino oscillation parameter Deltam21(2) and stringent constraints on theta12. The exposure to nuclear reactor antineutrinos is ...increased almost fourfold over previous results to 2.44 x 10(32) proton yr due to longer livetime and an enlarged fiducial volume. An undistorted reactor nuovere energy spectrum is now rejected at >5sigma. Analysis of the reactor spectrum above the inverse beta decay energy threshold, and including geoneutrinos, gives a best fit at Deltam21(2)=7.58(-0.13)(+0.14)(stat) -0.15+0.15(syst) x 10(-5) eV2 and tan2theta12=0.56(-0.07)+0.10(stat) -0.06+0.10(syst). Local Deltachi2 minima at higher and lower Deltam21(2) are disfavored at >4sigma. Combining with solar neutrino data, we obtain Deltam21(2)=7.59(-0.21)+0.21 x 10(-5) eV2 and tan2theta12=0.47(-0.05)+0.06.
We present the results of a search for extraterrestrial electron antineutrinos (v sub(e)'s) in the energy range 8.3 MeV < Ev sub(e) < 31.8 MeV using the KamLAND detector. In an exposure of 4.53 ...kton-year, we identify 25 candidate events. All of the candidate events can be attributed to background, most importantly neutral current atmospheric neutrino interactions, setting an upper limit on the probability of super(8)B solar converting into v sub(e)'s at 5.3 x 10 super(-5) (90% CL), if we assume an undistorted v sub(e) shape. This limit corresponds to a solar v sub(e) flux of 93 cm super(-2) s super(-1) or an event rate of 1.6 events (kton - year) super(-1) above the energy threshold Ev sub(e) > or =, slanted 8.3 MeV. The present data also allows us to set more stringent limits on the diffuse supernova neutrino flux and on the annihilation rates for light dark matter particles.
Particle dark matter could belong to a multiplet that includes an electrically charged state. WIMP dark matter (χ0) accompanied by a negatively charged excited state (χ−) with a small mass difference ...(e.g. < 20 MeV) can form a bound-state with a nucleus such as xenon. This bound-state formation is rare and the released energy is O(1−10) MeV depending on the nucleus, making large liquid scintillator detectors suitable for detection. We searched for bound-state formation events with xenon in two experimental phases of the KamLAND-Zen experiment, a xenon-doped liquid scintillator detector. No statistically significant events were observed. For a benchmark parameter set of WIMP mass mχ0=1 TeV and mass difference Δm=17 MeV, we set the most stringent upper limits on the recombination cross section times velocity 〈σv〉 and the decay-width of χ− to 9.2×10−30cm3/s and 8.7×10−14 GeV, respectively at 90% confidence level.
We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 nu (e) candidate events with energies above 3.4 MeV compared ...to 365.2+/-23.7 events expected in the absence of neutrino oscillation. Accounting for 17.8+/-7.3 expected background events, the statistical significance for reactor nu (e) disappearance is 99.998%. The observed energy spectrum disagrees with the expected spectral shape in the absence of neutrino oscillation at 99.6% significance and prefers the distortion expected from nu (e) oscillation effects. A two-neutrino oscillation analysis of the KamLAND data gives Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2). A global analysis of data from KamLAND and solar-neutrino experiments yields Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2) and tan((2)theta=0.40(+0.10)(-0.07), the most precise determination to date.
Aims
This study compared the bag‐mediated filtration system (BMFS) and standard WHO two‐phase separation methods for poliovirus (PV) environmental surveillance, examined factors impacting PV ...detection and monitored Sabin‐like (SL) PV type 2 presence with withdrawal of oral polio vaccine type 2 (OPV2) in April 2016.
Methods and Results
Environmental samples were collected in Nairobi, Kenya (Sept 2015–Feb 2017), concentrated via BMFS and two‐phase separation methods, then assayed using the WHO PV isolation algorithm and intratypic differentiation diagnostic screening kit. SL1, SL2 and SL3 were detected at higher rates in BMFS than two‐phase samples (P < 0·05). In BMFS samples, SL PV detection did not significantly differ with volume filtered, filtration time or filter shipment time (P > 0·05), while SL3 was detected less frequently with higher shipment temperatures (P = 0·027). SL2 was detected more frequently before OPV2 withdrawal in BMFS and two‐phase samples (P < 1 × 10−5).
Conclusions
Poliovirus was detected at higher rates with the BMFS, a method that includes a secondary concentration step, than using the standard WHO two‐phase method. SL2 disappearance from the environment was commensurate with OPV2 withdrawal.
Significance and Impact of the Study
The BMFS offers comparable or improved PV detection under the conditions in this study, relative to the two‐phase method.
We analyzed organophosphorus pesticide exposure in 218 farm worker households in agricultural communities in Washington State to investigate the take-home pathway of pesticide exposure and to ...establish baseline exposure levels for a community intervention project. House dust samples (n = 156) were collected from within the homes, and vehicle dust samples (n = 190) were collected from the vehicles used by the farm workers to commute to and from work. Urine samples were obtained from a farm worker (n = 213) and a young child (n = 211) in each household. Dust samples were analyzed for six pesticides, and urine samples were analyzed for five dialkylphosphate (DAP) metabolites. Azinphosmethyl was detected in higher concentrations (p < 0.0001) than the other pesticides: geometric mean concentrations of azinphosmethyl were 0.53 μg/g in house dust and 0.75 μg/g in vehicle dust. Dimethyl DAP metabolite concentrations were higher than diethyl DAP metabolite concentrations in both child and adult urine (p < 0.0001). Geometric mean dimethyl DAP concentrations were 0.13 μmol/L in adult urine and 0.09 μmol/L in child urine. Creatinine-adjusted geometric mean dimethyl DAP concentrations were 0.09 μmol/g in adult urine and 0.14 μmol/g in child urine. Azinphosmethyl concentrations in house dust and vehicle dust from the same household were significantly associated (r2=0.41, p < 0.0001). Dimethyl DAP levels in child and adult urine from the same household were also significantly associated (r2=0.18, p < 0.0001), and this association remained when the values were creatinine adjusted. The results of this work support the hypothesis that the take-home exposure pathway contributes to residential pesticide contamination in agricultural homes where young children are present.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Autoimmune diseases involve multiple genes. While functions of these genes are largely unknown, some may be related to an intrinsic hyperresponsiveness of B cells. B-cell responses are controlled by ...signaling thresholds through the B-cell antigen receptor (BCR) complex. The B1 isoform of type II IgG Fc receptors (FcgammaRIIB1) is exclusively expressed on B cells and serves as a negative regulator for inhibiting BCR-elicited activation. Thus, its allelic variants associated with functional deficits could be examined for possible associations with susceptibility to autoimmune diseases. We found that there are three types of polymorphisms in the reported FcgammaRIIB transcription regulatory regions in mouse strains. Compared to normal healthy mouse strains (group III), autoimmune disease-prone strains (group I) share three deletion sites: two in the promoter region and one in the third intron. Strains (group II) that per se are not autoimmune-prone, but have potentials to accelerate autoimmune diseases share two deletion sites in the third intron: one identical to that in group I and the other unique to group II. These polymorphisms correlated well with extents of down-regulation of FcgammaRIIB1 expression in germinal-center B cells upon stimulation with antigens and up-regulation of IgG antibody responses. Our data imply that these FcgammaRIIB polymorphisms are selected evolutionarily for natural defense against pathogens, and that such polymorphisms may, in turn, form the basis of one aspect of autoimmune susceptibility.
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