Physical constraints on a class of two-Higgs doublet models with FCNC at tree level

We analyse the constraints and some of the phenomenological implications of a class of two Higgs doublet models where there are flavour-changing neutral currents (FCNC) at tree level but the potentially dangerous FCNC couplings are suppressed by small entries of the CKM matrix V. This class of models have the remarkable feature that, as a result of a discrete symmetry of the Lagrangian, the FCNC couplings are entirely fixed in the quark sector by V and the ratio v(2)/v(1) of the vevs of the neutral Higgs. The discrete symmetry is extended to the leptonic sector, so that there are FCNC in the leptonic sector with their flavour structure fixed by the leptonic mixing matrix. We analyse a large number of processes, including decays mediated by charged Higgs at tree level, processes involving FCNC at tree level, as well as loop induced processes. We show that in this class of models one has new physical scalars beyond the standard Higgs boson, with masses reachable at the next round of experiments

Temporary Closure of the Open Abdomen: A Systematic Review on Delayed Primary Fascial Closure in Patients with an Open Abdomen

Background This study was designed to systematically review the literature to assess which temporary abdominal closure (TAC) technique is associated with the highest delayed primary fascial closure (FC) rate. In some cases of abdominal trauma or infection, edema or packing precludes fascial closure after laparotomy. This "open abdomen'' must then be temporarily closed. However, the FC rate varies between techniques. Methods The Cochrane Register of Controlled Trials, MEDLINE, and EMBASE databases were searched until December 2007. References were checked for additional studies. Search criteria included (synonyms of) "open abdomen,'' "fascial closure,'' "vacuum,'' "reapproximation,'' and "ventral hernia.'' Open abdomen was defined as "the inability to close the abdominal fascia after laparotomy.'' Two reviewers independently extracted data from original articles by using a predefined checklist. Results The search identified 154 abstracts of which 96 were considered relevant. No comparative studies were identified. After reading them, 51 articles, including 57 case series were included. The techniques described were vacuum-assisted closure (VAC; 8 series), vacuum pack (15 series), artificial burr (4 series), Mesh/sheet (16 series), zipper (7 series), silo (3 series), skin closure (2 series), dynamic retention sutures (DRS), and loose packing (1 series each). The highest FC rates were seen in the artificial burr (90%), DRS (85%), and VAC (60%). The lowest mortality rates were seen in the artificial burr (17%), VAC (18%), and DRS (23%). Conclusions These results suggest that the artificial burr and the VAC are associated with the highest FC rates and the lowest mortality rate

Chapter 19. In vitro studies of phenol coupling enzymes involved in vancomycin biosynthesis

Oxidative phenol cross-linking reactions play a key role in the biosynthesis of glycopeptide antibiotics such as vancomycin. The vancomycin aglycone contains three cross-links between aromatic amino acid side-chains, which stabilize the folded backbone conformation required for binding to the target D-Ala-D-Ala dipeptide. At least the first cross-link is introduced into a peptide precursor whilst it is still bound as a thioester to a peptide carrier protein (PCP) domain (also called a thiolation domain) within the nonribosomal peptide synthetase. We described here methods for the solid-phase synthesis of peptides and their coupling to PCP domains, which may be useful for in vitro studies of cross-linking and related tailoring reactions during nonribosomal glycopeptide antibiotic biosynthesis

Bis-chlorination of a hexapeptide-PCP conjugate by the halogenase involved in vancomycin biosynthesis

Vancomycin is an important nosocomial antibiotic containing a glycosylated, cross-linked and doubly chlorinated heptapeptide backbone. During the biosynthesis of the vancomycin aglycone, two ß-hydroxytyrosine (Bht) residues are inserted at positions-2 and -6 into the heptapeptide backbone by a non-ribosomal peptide synthetase. A single flavin-dependent chlorinase (VhaA) is responsible for chlorinating both Bht residues at some ill-defined point in the assembly process. We show here using in vitro assays that VhaA is able to introduce a chlorine atom into each aromatic ring of both Bht residues at positions-2 and -6 of a peptide carrier protein-bound hexapeptide. The results suggest that VhaA can recognize and chlorinate two quite different sites within a linear hexapeptide intermediate during vancomycin biosynthesis

Imputation methods for addressing missing data in short-term monitoring of air pollutants

Monitoring of environmental contaminants is a critical part of exposure sciences research and public health practice. Missing data are often encountered when performing short-term monitoring (<24 h) of air pollutants with real-time monitors, especially in resource-limited areas. Approaches for handling consecutive periods of missing and incomplete data in this context remain unclear. Our aim is to evaluate existing imputation methods for handling missing data for real-time monitors operating for short durations. In a current field-study, realtime PM2.5 monitors were placed outside of 20 households and ran for 24-hours. Missing data was simulated in these households at four consecutive periods of missingness (20%, 40%, 60%, 80%). Univariate (Mean, Median, Last Observation Carried Forward, Kalman Filter, Random, Markov) and multivariate time-series (Predictive Mean Matching, Row Mean Method) methods were used to impute missing concentrations, and performance was evaluated using five error metrics (Absolute Bias, Percent Absolute Error in Means, R2 Coefficient of Determination, Root Mean Square Error, Mean Absolute Error). Univariate methods of Markov, random, and mean imputations were the best performingmethods that yielded 24-hour mean concentrations with the lowest error and highest R2 values across all levels of missingness. When evaluating error metrics minute-by-minute, Kalman filters, median, and Markov methods performed well at low levels of missingness (20-40%). However, at higher levels of missingness (60-80%), Markov, random, median, and mean imputation performed best on average. Multivariate methods were the worst performing imputation methods across all levels of missingness. Imputation using univariate methods may provide a reasonable solution to addressing missing data for short-term monitoring of air pollutants, especially in resource-limited areas. Further efforts are needed to evaluate imputation methods that are generalizable across a diverse range of study environments. (C) 2020 Elsevier B.V. All rights reserved.24 month embargo; published online: 3 May 2020This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]