Searching for better X-ray and γ-ray photodetectors: structure-composition properties of the TlPb2Br5-x I x quaternary system.

Developing X-ray and γ-ray detectors with stable operation at ambient temperature and high energy resolution is an open challenge. Here, we present an approach to search for new detector materials, combining binary photodetector compounds. More specifically, we explore quaternary TlPb2Br5-x I x compositions, relying on materials synergy between TlBr, TlI, and PbI2 photodetectors. We discover a broad solid solution in the TlPb2Br5-'TlPb2I5' section, which can be derived from a new quaternary compound, TlPb2BrI4, by partial substitution of Br by I atoms on the 4c site or by replacement of I by Br atoms on the 16l site. We carry out a thorough crystallographic analysis of the new TlPb2BrI4 compound and prepare a high-quality standardized structure file. We also complete the phase diagram of the TlPb2Br5-'TlPb2I5' section, based on 21 alloys. Furthermore, we synthesize a series of high quality centimeter-sized TlPb2Br5-x I x single crystals (x = 2, 2.5, 3, 3.5, 4, 4.5) by the Bridgman-Stockbarger method and study their structure and properties using a combination of experimental techniques (X-ray diffraction, X-ray photoelectron spectroscopy, and absorption spectroscopy) and theoretical calculations.

Concentration and excitation effects on the exciton dynamics of poly(3-hexylthiophene)/PbS quantum dot blend films.

The dynamics of photoexcitations in hybrid blends of poly(3-hexylthiophene) (P3HT) conjugated polymer donor and oleic-acid capped lead sulfide (PbS) quantum dot (QD) acceptors of different concentrations-for light harvesting applications-were investigated using time-resolved transmission and photoluminescence spectroscopies. Following excitation at 400 nm and probing in the 500-1000 nm region, we find that geminate excitation recombination in the blend of P3HT/PbS QDs dominates the transient decays at sub-ns times while intermaterial interactions such as charge transfer processes appear at longer times in the 1-50 ns regime. For the hybrid blend films with lower QD concentrations (<67% wt), polymer exciton recombination dominates the overall transient absorption signal. For higher QD contents, QD state relaxation effects become visible. Excitation density studies reveal the presence of linear exciton relaxation effects in the P3HT region while carrier decay for films with high PbS QD concentration is influenced by QD Auger recombination. Time-resolved luminescence shows that electron transfer from the P3HT/PbS QDs appears relatively inefficient in comparison to the geminate recombination, while hole transfer competes favorably to intrinsic QD recombination.

Treating acetaminophen overdose: thresholds, costs and uncertainties.

The United Kingdom's Medicines and Healthcare Products Regulatory Agency (MHRA) modified the indications for N-acetylcysteine therapy of acetaminophen (paracetamol) overdose in September 2012. The new treatment threshold line was lowered to 100 mg/L (662 µmol/L) for a 4 hours acetaminophen concentration from the previous 200 mg/L (1325 µmol/L). This decision has the potential to substantially increase overall costs associated with acetaminophen overdose with unclear benefits from a marginal increase in patients protected from hepatotoxicity, fulminant hepatic failure, death, or transplant. Changing the treatment threshold for acetaminophen overdose also implies that ingestion amounts previously thought not to require acetaminophen concentration measurements would need to be revised. As a result, more individuals will be sent to hospitals in order that everyone with a predicted 4 hours concentration above the 100 mg/L line will have concentrations measured and potentially be treated with N-acetylcysteine. Before others consider adopting this new treatment guideline, formal cost-effectiveness analyses need to be performed to define the appropriate thresholds for referral and treatment.

Effect of chronic antigen and beta 2 agonist exposure on airway remodeling in guinea pigs.

We recently reported that chronic exposure to fenoterol (FEN) in guinea pigs increases in vivo and in vitro airway responsiveness to a degree similar to that induced by chronic antigen (ovalbumin [OA]) exposure. We hypothesized that these changes were due to airway inflammation and airway remodeling. To trace newly recruited granulocytes as a marker of inflammation and to detect DNA replication in resident airway wall cells, the nucleotide 5'-bromo-2'-deoxyuridine (BrdU) was administered intermittently over the six-wk period of chronic FEN and/or OA exposure. Noncartilaginous airway dimensions were measured and the area fraction of BrdU-immunoreactive and total nuclei in adventitia, smooth muscle, and epithelium was determined by immunohistochemistry and point counting. The proliferation index was defined as the ratio of the two area fractions in each wall area. The adventitial areas of FEN- and OA-treated airways were respectively 62 and 88% greater than those of control airways (p < 0.05). The inner wall areas were not increased. The smooth muscle cell and epithelial cell proliferation index was increased after OA (smooth muscle index: control, 2.7 +/- 1.1% [SEM]; OA, 23.0 +/- 3.7%; p < 0.02) but not after FEN exposure, and there was an increased number of BrdU-immunoreactive granulocytes in the adventitia and epithelium after OA but not after FEN exposure. The increased in vivo airways responsiveness produced by chronic OA or FEN exposure may be attributable to adventitial thickening and increased in vitro muscle contractility, but the cellular mechanisms underlying these and other airway wall responses are different.(ABSTRACT TRUNCATED AT 250 WORDS)