Determining conductivity and mobility values of individual components in multiphase composite Cu_(1.97)Ag_(0.03)Se

The intense interest in phase segregation in thermoelectrics as a means to reduce the lattice thermal conductivity and to modify the electronic properties from nanoscale size effects has not been met with a method for separately measuring the properties of each phase assuming a classical mixture. Here, we apply effective medium theory for measurements of the in-line and Hall resistivity of a multiphase composite, in this case Cu_(1.97) Ag_(0.03)Se. The behavior of these properties with magnetic field as analyzed by effective medium theory allows us to separate the conductivity and charge carrier mobility of each phase. This powerful technique can be used to determine the matrix properties in the presence of an unwanted impurity phase, to control each phase in an engineered composite, and to determine the maximum carrier concentration change by a given dopant, making it the first step toward a full optimization of a multiphase thermoelectric material and distinguishing nanoscale effects from those of a classical mixture

Trade and Related Climate Change Policies

Abstract: We empirically investigate the GHG emissions embodied in the bilateral trade between the United States and China and the United States and India and their countryspecific and global environmental impacts. In order to address the concerns of "levelplaying-field" and carbon leakage associated with domestic carbon pricing scheme, various border carbon adjustments have been proposed in recent U.S. climate change legislation. Employing GTAP-E model, this study examines how and to what extent the proposed carbon tariffs and export subsidies potentially affect bilateral trade flow, domestic production, and the GHG emissions. Results indicate that carbon tariff effectively alleviates the impact of domestic carbon tax on vulnerable domestic industries and slightly raises their output and GHG emissions. In addition, it is also evident that a combined or full border adjustment policy has bigger impacts than an individual policy

Enantioselective Intramolecular C-H Amination Catalyzed by Engineered Cytochrome P450 Enzymes In Vitro and In Vivo

Nitrogen activation: Though P450 enzymes are masters of oxygen activation and insertion into C-H bonds, their ability to use nitrogen for the same purpose has so far not been explored. Engineered variants of cytochrome P450_(BM3) have now been found to catalyze intramolecular C-H aminations in azide substrates. Mutations to two highly conserved residues significantly increased this activity

Enhanced thermoelectric performance in the very low thermal conductivity Ag_2Se_(0.5)Te_(0.5)

In this letter, we report the high-temperature thermoelectric properties of Ag_2Se_(0.5)Te_(0.5). We find that this particular composition displays very low thermal conductivity and competitive thermoelectric performance. Specifically, in the temperature region 520 K ≤ T ≤ 620 K, we observe non-hysteretic behavior between the heating and cooling curves and zT values ranging from 1.2 to 0.8. Higher zT values are observed at lower temperatures on cooling. Our results suggest that this alloy is conducive to high thermoelectric performance in the intermediate temperature range, and thus deserves further investigation

Engineered Bacterial Mimics of Human Drug Metabolizing Enzyme CYP2C9

Simple and universal methods for the preparation of human drug metabolites are required to produce quantities sufficient for their characterization and toxicity testing. Synthetic chemistry lacks general catalysts for selective oxidation of unactivated C[BOND]H bonds, a transformation that plays a key role in metabolism; bioconversions using P450 enzymes have emerged as a powerful alternative. Variants of P450BM3 from Bacillus megaterium act on diverse substrates, including drugs. Acidic substrates, such as the compounds metabolized by CYP2C9, which is one of three main hepatic human P450s, are not accepted by P450_(BM3) variants engineered to date. Herein, we report bacterial mimics of CYP2C9, which are active on two widely administered drugs, naproxen and ibuprofen, that are CYP2C9 substrates in vivo. These P450_(BM3) variants can also act on desmethylnaproxen, the human metabolite of naproxen, and convert it to the 1,4-naphthoquinone derivative. We analyzed the crystal structure of the heme domain of an early intermediate in the directed-evolution experiment. The active site mutation, L75R, which initially conferred activity on charged substrates, dramatically increased structural flexibility in the B′-helix. This increased flexibility, which was accompanied by a dramatic decrease in enzyme stability, may contribute to the variant’s ability to accept a broader range of substrates

FEV1 over time in patients with connective tissue disease-related bronchiolitis

SummaryBackgroundFibrosis or inflammation of the bronchioles is a well-known manifestation of connective tissue disease (CTD). However, the natural history of CTD-related bronchiolitis is largely unknown.MethodsWe analyzed consecutive patients evaluated at National Jewish Health (Denver, CO) from 1998 to 2008 with CTD and surgical lung biopsy-confirmed bronchiolitis. Linear mixed effects models were used to estimate the longitudinal postbronchodilator FEV1 %predicted (%pred) course and differences between subjects with or without constrictive bronchiolitis (CB).ResultsOf 28 subjects with a mean age of 53 ± 9 years, fourteen (50%) had CB. The most common CTD diagnosis was rheumatoid arthritis (n = 14; 50%). There were no significant differences in demographics, smoking status, underlying CTD diagnoses, 6-min walk distance, dyspnea score or drug therapy between subjects with CB and those with cellular bronchiolitis. Three subjects with CB (11%) and four with cellular bronchiolitis (14%) died. Compared with subjects with CB, those with cellular bronchiolitis had higher mean FEV1 %pred at all times. There were no significant differences in FEV1 %pred slope within- or between-groups (CB vs. cellular bronchiolitis) preceding surgical lung biopsy or afterward.ConclusionSubjects with CTD-related CB had lower FEV1 %pred values than those with CTD-related cellular bronchiolitis at all time points, but FEV1 %pred remained stable over time in both groups regardless of therapy received

Phase transition enhanced thermoelectric figure-of-merit in copper chalcogenides

While thermoelectric materials can be used for solid state cooling, waste heat recovery, and solar electricity generation, low values of the thermoelectric figure of merit, zT, have led to an efficiency too low for widespread use. Thermoelectric effects are characterized by the Seebeck coefficient or thermopower, which is related to the entropy associated with charge transport. For example, coupling spin entropy with the presence of charge carriers has enabled the enhancement of zT in cobalt oxides. We demonstrate that the coupling of a continuous phase transition to carrier transport in Cu 2Se over a broad (360–410 K) temperature range results in a dramatic peak in thermopower, an increase in phonon and electron scattering, and a corresponding doubling of zT (to 0.7 at 406 K), and a similar but larger increase over a wider temperature range in the zT of Cu 1.97 Ag .03Se (almost 1.0 at 400 K). The use of structural entropy for enhanced thermopower could lead to new engineering approaches for thermoelectric materials with high zT and new green applications for thermoelectrics