ISO Spectroscopy of Young Stellar Objects

Observations of gas-phase and solid-state species toward young stellar objects (YSOs) with the spectrometers on board the Infrared Space Observatory are reviewed. The excitation and abundances of the atoms and molecules are sensitive to the changing physical conditions during star-formation. In the cold outer envelopes around YSOs, interstellar ices contain a significant fraction of the heavy element abundances, in particular oxygen. Different ice phases can be distinguished, and evidence is found for heating and segregation of the ices in more evolved objects. The inner warm envelopes around YSOs are probed through absorption and emission of gas-phase molecules, including CO, CO_2, CH_4 and H_2O. An overview of the wealth of observations on gas-phase H_2O in star-forming regions is presented. Gas/solid ratios are determined, which provide information on the importance of gas-grain chemistry and high temperature gas-phase reactions. The line ratios of molecules such as H_2, CO and H_2O are powerful probes to constrain the physical parameters of the gas. Together with atomic and ionic lines such as [0 I] 63 µm, [S I] 25 µm and (Si II] 35 µm, they can also be used to distinguish between photon- and shock-heated gas. Finally, spectroscopic data on circumstellar disks around young stars are mentioned. The results are discussed in the context of the physical and chemical evolution of YSOs

Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF

The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described

Flow cytometry-assisted rapid isolation of recombinant Plasmodium berghei parasites exemplified by functional analysis of aquaglyceroporin

AbstractThe most critical bottleneck in the generation of recombinant Plasmodium berghei parasites is the mandatory in vivo cloning step following successful genetic manipulation. This study describes a new technique for rapid selection of recombinant P. berghei parasites. The method is based on flow cytometry to isolate isogenic parasite lines and represents a major advance for the field, in that it will speed the generation of recombinant parasites as well as cut down on animal use significantly. High expression of GFP during blood infection, a prerequisite for robust separation of transgenic lines by flow cytometry, was achieved. Isogenic recombinant parasite populations were isolated even in the presence of a 100-fold excess of wild-type (WT) parasites. Aquaglyceroporin (AQP) loss-of-function mutants and parasites expressing a tagged AQP were generated to validate this approach. aqp− parasites grow normally within the WT phenotypic range during blood infection of NMRI mice. Similarly, colonization of the insect vector and establishment of an infection after mosquito transmission were unaffected, indicating that AQP is dispensable for life cycle progression in vivo under physiological conditions, refuting its use as a suitable drug target. Tagged AQP localized to perinuclear structures and not the parasite plasma membrane. We suggest that flow-cytometric isolation of isogenic parasites overcomes the major roadblock towards a genome-scale repository of mutant and transgenic malaria parasite lines

Direct Voltage and Trapped Charge Effects on the Protective Characteristic of ZnO Surge Arresters

In AC power systems, under normal service conditions, surge arresters on isolated lines and cables can experience a direct voltage stress arising from trapped charges. If this is followed on reconnection by switching surges of reverse polarity, it can impose severe response requirements on the arresters. High-amplitude voltage reversal can also arise from restriking transients in circuit breakers. Direct voltage working stress with superimposed surges is also clearly present in HVDC systems. Despite this expected combination of direct voltage with superimposed surges, no analogous tests are specified in the relevant standards. New laboratory tests have been performed on ZnO surge arrester elements and arresters, where impulse voltages have been applied with and without the presence of pre-existing direct voltage or simulated trapped charge. These tests have been analysed to ascertain the effect of prestressing on the current growth and protective characteristic of the arrester. In the laboratory source, the line/cable system has been represented by an equivalent capacitance which has been previously charged from a direct voltage. A single-stage capacitor bank is triggered to provide a lightning impulse test current. For a given level of peak discharge current, a higher level of residual voltage is found to appear across an arrester when the polarity of the applied impulse opposes that of the trapped charge voltage. This effect is especially marked in the peak residual voltage under this combination. Initial results suggest that the effect increases with decreasing protection voltage leve