Compact ambient pressure pyroelectric ion source for mass spectrometry

We present the construction and implementation of a compact, low-power ambient pressure pyroelectric ionization source. The source comprises a z-cut lithium niobate or lithium tantalate crystal with an attached resistive heater mounted in front of the atmospheric pressure inlet of an ion trap mass spectrometer. Positive and negative ion formation alternately results from thermally cycling the crystal over a narrow temperature range. Ionization of 1,1,1,3,3,3-hexafluoro-2-propanol or benzoic acid results in the observation of the singly deprotonated species and their clusters in the negative ion mass spectrum. Ionization of triethylamine or triphenylamine with the source results in observation of the corresponding singly protonated species of each in the positive ion mass spectrum. Although processes in which ion formation occurs directly on the highly charged crystal surface may contribute to the observed signal, ion formation appears to result mainly from electrical discharges occurring on the surface of the crystal, from one z face to another. This dielectric breakdown originates from the high electric fields generated at the surface of pyroelectric crystals when they are thermally cycled by as little as 30 K from ambient temperature. Ion formation is largely unaffected by contamination of the crystal faces. This robust source might prove particularly useful in applications where unattended operation in harsh environments, long service lifetimes, and durability are desirable characteristics.     

Application of the FLP/FRT system for conditional gene deletion in yeast Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae has proved to be an excellent model organism to study the function of proteins. One of the many advantages of yeast is the many genetic tools available to manipulate gene expression, but there are still limitations. To complement the many methods used to control gene expression in yeast, we have established a conditional gene deletion system by using the FLP/FRT system on yeast vectors to conditionally delete specific yeast genes. Expression of Flp recombinase, which is under the control of the GAL1 promoter, was induced by galactose, which in turn excised FRT sites flanked genes. The efficacy of this system was examined using the FRT site-flanked genes HSP104, URA3 and GFP. The pre-excision frequency of this system, which might be caused by the basal activity of the GAL1 promoter or by spontaneous recombination between FRT sites, was detected ca. 2% under the non-selecting condition. After inducing expression of Flp recombinase, the deletion efficiency achieved ca. 96% of cells in a population within 9 h. After conditional deletion of the specific gene, protein degradation and cell division then diluted out protein that was expressed from this gene prior to its excision. Most importantly, the specific protein to be deleted could be expressed under its own promoter, so that endogenous levels of protein expression were maintained prior to excision by the Flp recombinase. Therefore, this system provides a useful tool for the conditional deletion of genes in yeast.     

The Effect of Stretch Wrap Prestretch on Unitized Load Containment

There are three main factors affecting the stability of a palletized load that is unitized by a stretch wrapping mechanism – the type of unitized load, wrapping configuration and shipping method. The wrapping configuration is typically determined on the basis of the type of unitized load and shipping method. For this study, the aforementioned components were referred to as the package, the product and the distribution environment. This study was designed to observe and understand the interactions between each of the components of the stretch wrap system. Prior to stretch wrapping a pallet of product, the film is elongated or prestretched. The elastic nature of the stretch wrap forces the film to conform to the palletized load. It is hypothesized that the containment force that the stretch wrap applies to the palletized load contributes to improved load containment. Hence, the objective of this study was to determine the existence of a correlation between percentage prestretch to change in containment force and load containment. For the study, a range of prestretched unitized loads were subjected to International Safe Transit Association 3E distribution testing. Simultaneously, the containment force was monitored during the period of distribution testing. Subsequent to distribution testing, the load dispersion was quantified. The data obtained from this test suggested that there is no correlation between percentage prestretch and change in containment force or load containment. Copyright © 2014 John Wiley & Sons, Ltd.     

Processing additive suppresses phase separation in the active layer of organic photovoltaics based on naphthalene diimide

The development of non-fullerene electron acceptors for organic photovoltaics is gaining interest, as they offer the promise to overcome the light harvesting and energy tunability limitations of fullerenes. However, to fully take advantage of alternative acceptors, we must identify and achieve the needed morphologies within the active layer to maximize device performance. Here we demonstrate that the microstructure in the active layer of optimized poly(3-hexylthiophene)/naphthalene diimide devices resembles that of poly(3-hexylthiophene)/fullerene mixtures. Previously, we have reported on the synthesis of 2,6-dialkylaminonaphthalene diimides and found that the best performance was obtained with N,N′-di((thiophen-2-yl)methyl)-2,6-di(N-cyclohexylamino)-1,4,5,8-naphthalenetetracarboxydiimide (RF1). In this article, we show that suppressing the crystallization of both the donor and acceptor through the addition of 0.2% 1,8-diiodooctane (DIO) to the casting solution leads to finer morphologies in the active layer and a two-fold enhancement in the device efficiencies. Nevertheless, further increasing the DIO content of the casting solution leads to lower photocurrents and power conversion efficiencies, even though the morphology appears similar by energy-filtered TEM. We hypothesize that higher DIO content breaks up small RF1 aggregates, leading to suppression of charge separation. Continued development of novel non-fullerene acceptors must therefore take into consideration the balance between crystallization and aggregation of donors and acceptors for optimal performance.     

Changes in malt quality during production in two commercial malt houses

This investigation presents a holistic and comprehensive assessment of the stepwise changes in barley quality during the malting process for multiple batches of two Australian malting varieties (Buloke and Gairdner), in two modern, commercial scale pneumatic malthouses. The study sought to analyse and compare malting plant and variety with respect to basic changes in malt quality for protein (total protein and free amino nitrogen), fermentability (apparent attenuation limit and diastatic power), extract yield, along with filtration indicators (lautering efficiency, viscosity and β-glucan). Overall, comparing the two malt plants, it was observed that although malt batches and varieties followed different malting pathways, the finished and kilned malt  was of satisfactory quality in terms of FAN, viscosity, friability, fermentability and extract. © 2020 The Institute of Brewing & Distilling     

The Effects of Prodrug Size and a Carbonyl Linker on l-Type Amino Acid Transporter 1-Targeted Cellular and Brain Uptake

The l -type amino acid transporter 1 (LAT1, SLC7A5) imports dietary amino acids and amino acid drugs (e. g., l -DOPA) into the brain, and plays a role in cancer metabolism. Though there have been numerous reports of LAT1-targeted amino acid-drug conjugates (prodrugs), identifying the structural determinants to enhance substrate activity has been challenging. In this work, we investigated the position and orientation of a carbonyl group in linking hydrophobic moieties including the anti-inflammatory drug ketoprofen to l -tyrosine and l -phenylalanine. We found that esters of meta-carboxyl l -phenylalanine had better LAT1 transport rates than the corresponding acylated l -tyrosine analogues. However, as the size of the hydrophobic moiety increased, we observed a decrease in LAT1 transport rate with a concomitant increase in potency of inhibition. Our results have important implications for designing amino acid prodrugs that target LAT1 at the blood-brain barrier or on cancer cells.     

Candida Cell-Surface-Specific Monoclonal Antibodies Protect Mice against Candida auris Invasive Infection

Candida auris is a multidrug-resistant fungal pathogen that can cause disseminated bloodstream infections with up to 60% mortality in susceptible populations. Of the three major classes of antifungal drugs, most C. auris isolates show high resistance to azoles and polyenes, with some clinical isolates showing resistance to all three drug classes. We reported in this study a novel approach to treating C. auris disseminated infections through passive transfer of monoclonal antibodies (mAbs) targeting cell surface antigens with high homology in medically important Candida species. Using an established A/J mouse model of disseminated infection that mimics human candidiasis, we showed that C3.1, a mAb that targets β-1,2-mannotriose (β-Man₃), significantly extended survival and reduced fungal burdens in target organs, compared to control mice. We also demonstrated that two peptide-specific mAbs, 6H1 and 9F2, which target hyphal wall protein 1 (Hwp1) and phosphoglycerate kinase 1 (Pgk1), respectively, also provided significantly enhanced survival and reduction of fungal burdens. Finally, we showed that passive transfer of a 6H1+9F2 cocktail induced significantly enhanced protection, compared to treatment with either mAb individually. Our data demonstrate the utility of β-Man₃- and peptide-specific mAbs as an effective alternative to antifungals against medically important Candida species including multidrug-resistant C. auris.     

An improved correlation for dry pressure losses across static mixers at high Reynolds numbers

Corrugated (SMV-style) static mixers are industrially important for process intensification and can promote gas–liquid mass transfer in processes such as sour gas sweetening. Current correlations for pressure loss are limited to Reynolds numbers (Re) below 40 000, far below the ranges encountered in natural gas systems (10⁵ < Re < 10⁷). An experimental and numerical study of pressure drop across multiple corrugated mixers in the range of 10⁴ < Re <2 × 10⁵ encompassing different configurations (aligned, rotated), pipe diameters (1–4 in.), and sand grain surface roughness values (10–5000 μm) is reported here. Our previous correlation for pressure loss across a single corrugated element is shown to be extendable to multiple corrugated mixing elements. Through the inclusion of mixer tortuosity (τ), porosity (ε), and macro-scale (geometric) wall roughness (e), the correlation also matches historical pressure drop data (at different τ, ε) reported in literature, thereby demonstrating the utility of these variables as parameters that can help optimize mixer performance. Experiments and computational fluid dynamics (CFD) modelling revealed that the rotated configuration increased the residence time by up to 13% in comparison to the aligned configuration. This may have implications on the selective absorption of sour gas components that are based on fast kinetics. In addition, the role of wall roughness (both pipe housing and mixer) was demonstrated to be significant in this study (accounting for 55% of the pressure losses) and must be accurately accounted for when scaling laboratory measurements.