Heavy reliance of East Africa (EA) on rain-fed agriculture makes it vulnerable to drought-induced famine. Yet, most research on EA drought focuses on meteorological aspects with little attention paid ...on agricultural drought impacts. The inadequacy of in-situ rainfall data across EA has also hampered detailed agricultural drought impact analysis. Recently, however, there has been increased data availability from remote sensing (rainfall, vegetation condition index – VCI, terrestrial water storage – TWS), reanalysis (soil moisture and TWS), and land surface models (soil moisture). Here, these products were employed to characterise EA droughts between 1983 and 2013 in terms of severity, duration, and spatial extent. Furthermore, the capability of these products to capture agricultural drought impacts was assessed using maize and wheat production data. Our results show that while all products were similar in drought characterisation in dry areas, the similarity of CHIRPS and GPCC extended over the whole EA. CHIRPS and GPCC also identified the highest proportion of areas under drought followed closely by soil moisture products whereas VCI had the least coverage. Drought onset was marked first by a decline/lack of rainfall, followed by VCI/soil moisture, and then TWS. VCI indicated drought lag at 0–4 months following rainfall while soil moisture and TWS products had variable lags vis-à-vis rainfall. GLDAS mischaracterized the 2005–2006 drought vis-à-vis other soil moisture products. Based on the annual crop production variabilities explained, we identified CHIRPS, GPCC, FLDAS, and VCI as suitable for agricultural drought monitoring/characterization in the region for the study period. Finally, GLDAS explained the lowest percentages of the Kenyan and Ugandan annual crop production variances. These findings are important for the gauge data deficient EA region as they provide alternatives for monitoring agricultural drought.
•Characterized drought and assessed utility of drought indicators in East Africa (EA)•Order of drought detection is first rainfall, VCI/moisture then TWS.•VCI has 0–4months of lag in detecting drought cycle with respect to rainfall.•Suitable agricultural drought indicators for EA: CHIRP, GPCC, FLDAS, and VCI•The land surface models' products generally performed inconsistently over EA.
A search for dark matter using an underground single-phase liquid xenon detector was conducted at the Kamioka Observatory in Japan, particularly for Weakly Interacting Massive Particles (WIMPs). We ...have used 705.9 live days of data in a fiducial volume containing 97kg of liquid xenon at the center of the detector. The event rate in the fiducial volume after the data reduction was (4.2±0.2)×10−3day−1kg−1keVee−1 at 5keVee, with a signal efficiency of 20%. All the remaining events are consistent with our background evaluation, mostly of the “mis-reconstructed events” originated from 210Pb in the copper plates lining the detector's inner surface. The obtained upper limit on a spin-independent WIMP-nucleon cross section was 2.2×10−44cm2 for a WIMP mass of 60GeV/c2 at the 90% confidence level, which was the most stringent limit among results from single-phase liquid xenon detectors.
Burst Intensification by Singularity Emitting Radiation (BISER) is proposed. Singularities in multi-stream flows of emitting media cause constructive interference of emitted travelling waves, forming ...extremely localized sources of bright coherent emission. Here we for the first time demonstrate this extreme localization of BISER by direct observation of nano-scale coherent x-ray sources in a laser plasma. The energy emitted into the spectral range from 60 to 100 eV is up to ~100 nJ, corresponding to ~10
photons. Simulations reveal that these sources emit trains of attosecond x-ray pulses. Our findings establish a new class of bright laboratory sources of electromagnetic radiation. Furthermore, being applicable to travelling waves of any nature (e.g. electromagnetic, gravitational or acoustic), BISER provides a novel framework for creating new emitters and for interpreting observations in many fields of science.
Hidden photons and axion-like particles are candidates for cold dark matter if they were produced non-thermally in the early universe. We conducted a search for both of these bosons using 800 ...live-days of data from the XMASS detector with 327 kg of liquid xenon in the fiducial volume. No significant signal was observed, and thus we set constraints on the α′/α parameter related to kinetic mixing of hidden photons and the coupling constant gAe of axion-like particles in the mass range from 40 to 120 keV/c2, resulting in α′/α<6×10−26 and gAe<4×10−13. These limits are the most stringent over this mass range derived from both direct and indirect searches to date.
A search for dark matter (DM) with mass in the sub-GeV region (0.32–1 GeV) was conducted by looking for an annual modulation signal in XMASS, a single-phase liquid xenon detector. Inelastic nuclear ...scattering accompanied by bremsstrahlung emission was used to search down to an electron equivalent energy of 1 keV. The data used had a live time of 2.8 years (3.5 years in calendar time), resulting in a total exposure of 2.38 ton-years. No significant modulation signal was observed and 90% confidence level upper limits of 1.6×10−33 cm2 at 0.5 GeV was set for the DM-nucleon cross section. This is the first experimental result of a search for DM mediated by the bremsstrahlung effect. In addition, a search for DM with mass in the multi-GeV region (4–20 GeV) was conducted with a lower energy threshold than previous analysis of XMASS. Elastic nuclear scattering was used to search down to a nuclear recoil equivalent energy of 2.3 keV, and upper limits of 2.9 ×10−42 cm2 at 8 GeV was obtained.
We have searched for exotic neutrino-electron interactions that could be produced by a neutrino millicharge, by a neutrino magnetic moment, or by dark photons using solar neutrinos in the XMASS-I ...liquid xenon detector. We observed no significant signals in 711 days of data. We obtain an upper limit for neutrino millicharge of 5.4×10−12e at 90% confidence level assuming all three species of neutrino have common millicharge. We also set flavor-dependent limits assuming the respective neutrino flavor is the only one carrying a millicharge, 7.3×10−12e for νe, 1.1×10−11e for νμ, and 1.1×10−11e for ντ. These limits are the most stringent yet obtained from direct measurements. We also obtain an upper limit for the neutrino magnetic moment of 1.8×10−10 Bohr magnetons. In addition, we obtain upper limits for the coupling constant of dark photons in the U(1)B−L model of 1.3×10−6 if the dark photon mass is 1×10−3 MeV/c2, and 8.8×10−5 if it is 10 MeV/c2.
Graphene is known as an atomically thin, transparent, highly electrically and thermally conductive, light-weight, and the strongest 2D material. We investigate disruptive application of graphene as a ...target of laser-driven ion acceleration. We develop large-area suspended graphene (LSG) and by transferring graphene layer by layer we control the thickness with precision down to a single atomic layer. Direct irradiations of the LSG targets generate MeV protons and carbons from sub-relativistic to relativistic laser intensities from low contrast to high contrast conditions without plasma mirror, evidently showing the durability of graphene.
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