Long-term viable bioaerosol sampling using a temperature- and humidity-controlled filtration apparatus,a laboratory investigation using culturable E. coli.

Sampling for culturable (e.g., viable) aerosolized microbes (bioaerosols) is a useful means to provide information for public health monitoring and studies. However, it is challenging to maintain microbe culturability when sampling at high flow rates (>12 L/min) and extended periods of time (≥4 h). We developed a first-generation, viable bioaerosol collection system (VBCS) utilizing temperature (T) and relative humidity (RH)–conditioned filtration at a flow rate of 25 L/min. A two-stage system of tube-in-shell Nafion? exchange units provides cooling to ≤10°C and RH conditioning to 80–95%. Aerosol particles are collected on a polyurethane nanofiber filter providing a physical collection efficiency of >95% for sizes 0.06–10 µm. The T and RH conditions at the collection filter are maintained, despite changes to ambient conditions. The initial testing of the VBCS was done under indoor, laboratory conditions with aerosolized, vegetative E. coli. A scenario of a 30-min challenge of bioaerosol followed by continued sampling of clean air for various times was used to judge culturability maintenance under extended-term sampling. An initial loss of culturability upon collection onto the filter was observed; 23 ± 13% relative to 4-mm all-glass impinger. However once collected, 98% of culturability was maintained for an additional 4.5 h of sampling. An exponential decay in culturability was observed from 8 h to 15 h of sampling. Also, 24-h cold storage of the filters collected was studied. The VBCS is based on the use of dry filter cassettes, needs minimal maintenance, and preserves culturability of vegetative bacteria for >4 h.

© 2017 RTI International and Aerosol Dynamics Inc.     

Using a Fragment‐Based Approach To Target Protein–Protein Interactions

The ability to identify inhibitors of protein–protein interactions represents a major challenge in modern drug discovery and in the development of tools for chemical biology. In recent years, fragment‐based approaches have emerged as a new methodology in drug discovery; however, few examples of small molecules that are active against chemotherapeutic targets have been published. Herein, we describe the fragment‐based approach of targeting the interaction between the tumour suppressor BRCA2 and the recombination enzyme RAD51; it makes use of a screening pipeline of biophysical techniques that we expect to be more generally applicable to similar targets. Disruption of this interaction in vivo is hypothesised to give rise to cellular hypersensitivity to radiation and genotoxic drugs. We have used protein engineering to create a monomeric form of RAD51 by humanising a thermostable archaeal orthologue, RadA, and used this protein for fragment screening. The initial fragment hits were thoroughly validated biophysically by isothermal titration calorimetry (ITC) and NMR techniques and observed by X‐ray crystallography to bind in a shallow surface pocket that is occupied in the native complex by the side chain of a phenylalanine from the conserved FxxA interaction motif found in BRCA2. This represents the first report of fragments or any small molecule binding at this protein–protein interaction site.     

Plasma Processing of B4C–TiB2 Eutectic Composite Powders

The production of a composite powder of eutectic B₄C–TiB₂ is demonstrated via an atmospheric plasma processing method. Feedstock material is prepared for plasma processing by mixing and spray drying monolithic B₄C and TiB₂ to produce a flowable precursor powder. These powders are fed through a plasma torch, where they are melted and actively quenched in flight with argon gas. Plasma processed powders are composed of crystalline B₄C and TiB₂, with some additional B₂O₃ oxide phase. The plasma processing method results in the production of monolithic B₄C and TiB₂ nanoparticles, but some larger particles (generally ≥10 μm in diameter) are shown to contain the traditional lamellar eutectic microstructure. The eutectic interphase spacing ranges from 100 to 650 nm, and the composite microstructure is present through the entire thickness of the eutectic particles. Future work on plasma processing of eutectic powders should focus on methods utilizing passive in‐flight quenching to increase the average particle size.     

The depth profiling of TiO2 pigmented coil coatings using step scan phase modulation photoacoustic FTIR

The depth distribution of a TiO₂ pigment within the polyurethane (PU) coil coatings is investigated using step scan phase modulation photoacoustic (SS-PM-PA) FTIR. Coil coatings with different pigment contents were prepared and the modulation frequency (MF) of the SS-PM-PA FTIR varied to record the depth distribution of the pigment within the coating. The TiO₂ pigment was shown to contribute significantly to the SS-PM-PA FTIR signal. A TiO₂ aggregated region within the topcoat is found close to the topcoat-primer interface and further away from the topcoat surface. A deeper TiO₂ aggregated region can be identified when pigment content is relatively low. The SS-PM-PA FTIR signal shows a considerable contribution from the primer originated signal, provided the TiO₂ pigment content is sufficiently high and the modulation frequency applied is relatively low. SEM cross-section imaging results show a strong correlation of the TiO₂ depth distribution with SS-PM-PA FTIR results, which confirms the applicability of the SS-PM-PA FTIR technique to the depth profiling study of TiO₂ pigmented coil coatings.     

Assessing the reliability of ordered categorical scales using kappa-type statistics

Methods for the analysis of reliability of ordered categorical scales are discussed, focussing on the limitation of the single summary-weighted kappa coefficients. A symmetric matrix of kappa-type coefficients is suggested as an alternative. The method is proposed as being suitable for ordinal scale where there is no underlying continuum. Their application is illustrated using two data sets from reliability studies. If, instead, distances between categories can be specified, a weighted mean of the matrix terms can be used as a summary measure. This is equal to a weighted kappa coefficient with squared weights, provided distances between adjacent categories are equal. When a study design corresponds to a one-way random effects model, estimates of precision of kappa-type coefficient, including the coefficients described here, can be obtained using the delta-method, bootstrap resampling by subjects or jack-knifing by subjects. In the case of interobserver reliability studies, where there may be systematic differences between observers, the investigator may wish to generalise to a population of observers and subjects. In this case, jack-knifing by observer and subject is suggested. Empirical comparisons are made between standard error estimates based on the delta-method, on jack-knifing by subjects and a two-way jack-knife by subjects and observers. The results suggest that standard errors based on the delta-method or jack-knifing by subject alone may be overly precise.     

Simple N‐Heterocyclic Carbenes as Ligands in Ullmann‐Type Ether and Thioether Formations

A simple N‐heterocyclic carbene (NHC) derived from 1‐methyl‐3‐ethylimidazolium tetrafluoroborate was found to be an efficient ligand for a range of copper‐catalyzed cross‐coupling reactions, leading to the formation of aromatic ethers and thioethers.

     

Feather‐inspired carbon fiber reinforced polymers with nanofibrous fractal interlayer

Much work has been performed in improving carbon fiber‐reinforced polymer (CFRP) composites to prevent delamination, which is the major defect in laminated composites. Nevertheless, there is not much focus on improving conventional CFRP systems in terms of weight, especially when these are used in primary structures. This article explores whether lighter and at the same time stronger CFRP composites can be manufactured to replace conventional CFRP systems in major applications. Under this perspective, and having established the fundamentals for creating the next generation of light weight structural composites—the featherweight composites—this work introduces a feather‐inspired case which uses a controlled interlayer reinforcement in a fractal and reproducible manner at the macro‐, micro‐, and nano‐scales. By extensively describing the matrix system and the manufacturing processes and focusing on analytically and thermomechanically testing the CNT (Carbon Nanotubes) reinforced nanofiber interlayer system, it is shown that this feather‐inspired CFRP achieves significantly higher mechanical properties as well as potential weight savings. POLYM. COMPOS., 168–181, 2016. © 2014 Society of Plastics Engineers     

Thiol Redox and pKa Properties of Mycothiol,the Predominant Low‐Molecular‐Weight Thiol Cofactor in the Actinomycetes

The thiol pK_a and standard redox potential of mycothiol, the major low‐molecular‐weight thiol cofactor in the actinomycetes, are reported. The measured standard redox potential reveals substantial discrepancies in one or more of the other previously measured intracellular parameters that are relevant to mycothiol redox biochemistry.