Abstract
The ANtarctic Impulsive Transient Antenna (ANITA) long-duration balloon
experiment is sensitive to interactions of ultrahigh-energy (E>10
18
eV)
neutrinos in the Antarctic ice sheet. The ...third flight of ANITA, lasting 22
days, began in December 2014. We develop a methodology to search for
energetic neutrinos spatially and temporally coincident with potential source
classes in ANITA data. This methodology is applied to several source classes:
the potential IceCube-identified neutrino sources TXS 0506+056 and NGC 1068, flaring high-energy blazars reported by the Fermi All-Sky Variability Analysis, gamma-ray bursts, and supernovae. Among
searches within the five source classes, one candidate was identified as associated
with SN 2015D, although not at a statistically significant level. We proceed to place upper limits on the source classes. We further
comment on potential application of this methodology to more
sensitive future instruments.
The balloon-borne HiCal radio-frequency (RF) transmitter, in concert with the ANITA radio-frequency receiver array, is designed to measure the Antarctic surface reflectivity in the RF wavelength ...regime. The amplitude of surface-reflected transmissions from HiCal, registered as triggered events by ANITA, can be compared with the direct transmissions preceding them by O(10) microseconds, to infer the surface power reflection coefficient R. The first HiCal mission (HiCal-1, Jan. 2015) yielded a sample of 100 such pairs, resulting in estimates of R at highly glancing angles (i.e., zenith angles approaching 90°), with measured reflectivity for those events which exceeded extant calculations P. W. Gorham et al., Journal of Astronomical Instrumentation, 1740002 (2017). The HiCal-2 experiment, flying from December 2016–January 2017, provided an improvement by nearly 2 orders of magnitude in our event statistics, allowing a considerably more precise mapping of the reflectivity over a wider range of incidence angles. We find general agreement between the HiCal-2 reflectivity results and those obtained with the earlier HiCal-1 mission, as well as estimates from Solar reflections in the radio-frequency regime D. Z. Besson et al., Radio Sci. 50, 1 (2015). In parallel, our calculations of expected reflectivity have matured; herein, we use a plane-wave expansion to estimate the reflectivity R from both a flat, smooth surface (and, in so doing, recover the Fresnel reflectivity equations) and also a curved surface. Multiplying our flat-smooth reflectivity by improved Earth curvature and surface roughness corrections now provides significantly better agreement between theory and the HiCal-2 measurements.
The application of nanoscale electrical and biological devices will benefit from the development of nanomanufacturing technologies that are high‐throughput, low‐cost, and flexible. Utilizing ...nanomaterials as building blocks and organizing them in a rational way constitutes an attractive approach towards this goal and has been pursued for the past few years. The optical near‐field nanoprocessing of nanoparticles for high‐throughput nanomanufacturing is reported. The method utilizes fluidically assembled microspheres as a near‐field optical confinement structure array for laser‐assisted nanosintering and nanoablation of nanoparticles. By taking advantage of the low processing temperature and reduced thermal diffusion in the nanoparticle film, a minimum feature size down to ≈100 nm is realized. In addition, smaller features (50 nm) are obtained by furnace annealing of laser‐sintered nanodots at 400 °C. The electrical conductivity of sintered nanolines is also studied. Using nanoline electrodes separated by a submicrometer gap, organic field‐effect transistors are subsequently fabricated with oxygen‐stable semiconducting polymer.
Fluidically assembled microspheres are used as near‐field optical lenses for the laser‐assisted nanosintering and nanoablation of solution‐deposited nanoparticles. The microsphere array can be selectively illuminated for arbitrary patterning. Organic field‐effect transistors with oxygen‐stable semiconducting polymer are fabricated with nanosintered electrodes.
The synthesis and characterization of platinum-containing conjugated polymers in which the platinum atom is attached to the conjugated backbone via a C∧N ligand is presented. The newly designed ...platinum-containing monomer can be polymerized under both Stille and Suzuki conditions. The polymers exhibit optical bandgaps between 2.1 and 1.65 eV depending on the choice of comonomer. Triplet exciton formation is detected indirectly by measuring photosensitized emission of singlet oxygen in both solution and in film. The ability of the materials to sensitize formation of singlet oxygen varies both with excitation wavelength and with the change from solution to solid state. This study provides design principles for developing conjugated polymers with significant triplet yields in the solid state. The photovoltaic performance of these polymers was also evaluated in preliminary experiments with power conversion efficiencies as high as 1.3% obtained for a bulk heterojunction cell with PCBM.
Neutron Monitor Response Functions Clem, John M; Dorman, Lev I
Space science reviews,
01/2000, Letnik:
93, Številka:
1-2
Journal Article
Recenzirano
The neutron monitor provides continuous ground-based recording of the hadronic component in atmospheric secondary radiation which is related to primary cosmic rays. Simpson (1948) discovered that the ...latitude variation of the secondary hadronic component was considerably larger than the muon component suggesting the response of a neutron monitor is more sensitive to lower energies in the primary spectrum. The different methods of determining the neutron monitor response function of primary cosmic rays are reviewed and discussed including early and recent results. The authors also provide results from a new calculation (Clem, 1999) including angle dependent yield functions for different neutron monitor types which are calculated using a simulation of cosmic ray air showers combined with a detection efficiency simulation for different secondary particle species. Results are shown for IGY and NM64 configurations using the standard ^sup 10^BF^sub 3^ detectors and the new ^sup 3^He detectors to be used in the Spaceship Earth Project (Bieber et al., 1995). The method of calculation is described in detail and the results are compared with measurements and previous calculations. A summary of future goals is discussed.PUBLICATION ABSTRACT
Neutron monitors are integral detectors of secondary cosmic rays. Since each of them has its own detection efficiency, energy spectra cannot readily be derived from their observations. To circumvent ...this problem, latitudinal surveys have been conducted for many years with mobile neutron monitors to derive such spectra. Another way, however, is to use the worldwide stationary neutron monitor network, but then the counting rates of these monitors must be normalized sufficiently accurately against one another. For this reason, two portable calibration neutron monitors were built at the Potchefstroom campus of the North‐West University, South Africa. When calibrations of an adequate number of the worldwide neutron monitors have been done, this paper demonstrates that the differential response functions derived from them will provide experimental data for modulation studies in the rigidity range of 1 to 15 GV. Several properties of these calibrators were investigated, in order to achieve sufficient calibration accuracy. The energy response over the cutoff rigidity range from the poles to the equator, as well as the instrumental temperature sensitivity, are described in this paper. The main conclusion is that the calibrator has a difference of almost 4% in its energy response over the cutoff rigidity range 0–16 GV in comparison with a standard 3NM64 neutron monitor. Furthermore, it is shown that not only the calibrator, but also the NM64 and IGY monitors, have fairly large instrumental temperature sensitivities. Correction coefficients for these effects are given.
We present nebular phase optical imaging and spectroscopy and near/mid-IR imaging of the Type II SN 2006bc. Observations reveal the central wavelength of the symmetric H alpha line profile to be ...redshifted with respect to the host galaxy H alpha emission by day 325. Such a phenomenon has been argued to result from an asymmetric explosion in the iron-peak elements resulting in a larger mass of super(56)Ni and higher excitation of hydrogen on the far side of the supernova (SN) explosion. We also observe a gradual blueshifting of this H alpha peak which is indicative of dust formation in the ejecta. Although showing a normal peak brightness, V ~ -17.2, for a core-collapse SN, 2006bc fades by ~6 mag during the first 400 days suggesting either a relatively low super(56)Ni yield, an increase in extinction due to new dust, or both. A short-duration flattening of the light curve is observed from day 416 to day 541 suggesting an optical light echo. Based on the narrow time window of this echo, we discuss implications on the location and geometry of the reflecting interstellar medium. With our radiative transfer models, we find an upper limit of 2 x 10 super(-3) M sub(middot in circle) of dust around SN 2006bc. In the event that all of this dust were formed during the SN explosion, this quantity of dust is still several orders of magnitude lower than that needed to explain the large quantities of dust observed in the early universe.
Two different baculovirus genes are known to be able to block apoptosis triggered upon infection of Spodoptera-frugiperda cells with p35 mutants of the insect baculovirus Autographa californica ...nuclear polyhedrosis virus (AcMNPV): p35 (P35-encoding gene) of AcMNPV (R.J. Clem, M. Fechheimer, and L.K. Miller, Science 254:1388-1390,1991) and iap (inhibitor of apoptosis gene) of Cydia pomonella granulosis virus (CPGV) (N.E. Crook. R.J. Clem, and L.K. Miller, J. Virol. 67:2168-2174, 1993). Using a genetic complementation assay to identify additional genes which inhibit apoptosis during infection with ap35 mutant, we have isolated a gene from Orgyia pseudotsugata NPV (Op-iap) that was able to functionally substitute for AcMNPV p35. The nucleotide sequence of this gene, Op-iap, predicted a 30-kDa polypeptide product with approximately 58% amino acid sequence identity to the product of CpGV iap, Cp-IAP. Like Cp-IAP, the predicted product of Op-iap has a carboxy-terminal C3HC4 zinc finger-like motif In addition, a pair of additional cysteine/histidine motifs were found in the N-terminal regions of both polypeptide sequences. Recombinant p35 mutant viruses carrying either Op-iap or Cp-iap appeared to have a normal phenotype in S. frugiperda cells. Thus, Cp-IAP and Op-IAP appear to be functionally analogous to P35 but are likely to block apoptosis by a different mechanism which may involve direct interaction with DNA
Crews of high-altitude aircraft are exposed to radiation from galactic cosmic rays (GCRs). To help determine such exposures, the Atmospheric Ionizing Radiation Project, an international collaboration ...of 15 laboratories, made simultaneous radiation measurements with 14 instruments on a NASA ER-2 high-altitude airplane. The primary instrument was a sensitive extended-energy multisphere neutron spectrometer. Its detector responses were calculated for energies up to 100 GeV using the radiation transport code MCNPX 2.5.d with improved nuclear models and including the effects of the airplane structure. New calculations of GCR-induced particle spectra in the atmosphere were used to correct for spectrometer counts produced by protons, pions and light nuclear ions. Neutron spectra were unfolded from the corrected measured count rates using the deconvolution code MAXED 3.1. The results for the measured cosmic-ray neutron spectrum (thermal to >10 GeV), total neutron fluence rate, and neutron dose equivalent and effective dose rates, and their dependence on altitude and geomagnetic cut-off agree well with results from recent calculations of GCR-induced neutron spectra.
PDF
