Transient heating of Pd nanoparticles studied by x-ray diffraction with time of arrival photon detection.

Pulsed laser heating of an ensemble of Pd nanoparticles, supported by a MgO substrate, is studied by x-ray diffraction. By time-resolved Bragg peak shift measurements due to thermal lattice expansion, the transient temperature of the Pd nanoparticles is determined, which quickly rises by at least 100 K upon laser excitation and then decays within 90 ns. The diffraction experiments were carried out using a Cu x-ray tube, giving continuous radiation, and the hybrid pixel detector Timepix3 operating with single photon counting in a time-of-arrival mode. This type of detection scheme does not require time-consuming scanning of the pump-probe delay. The experimental time resolution is estimated at 15 ± 5 ns, which is very close to the detector's limit and matches with the 7 ns laser pulse duration. Compared to bulk metal single crystals, it is discussed that the maximum temperature reached by the Pd nanoparticles is higher and their cooling rate is lower. These effects are explained by the oxide support having a lower heat conductivity.

Dataset on the tested and simulated response of thick cold-formed circular hollow sections under cyclic loading.

This article describes a dataset used to calibrate a finite element model of a thick circular hollow section (CHS) with varying d/t (diameter to thickness) ratio under cyclic loading which may be used as a computational model validation benchmark by researchers working on similar problems in structural and mechanical engineering. The test data consists of seven cold-formed S335J2H steel CHS tube specimens tested to buckling failure in low-cycle fatigue under a three-point bending arrangement, instrumented with discrete strain gauges, displacement transducers and string potentiometers together with continuous surface deformation fields obtained by two pairs of digital image correlation (DIC) cameras. 'Half-cycle' material data from the uniaxial tensile testing of dog-bone coupons is also provided. Comparisons between measured and simulated entities such as midspan forces, moments, displacements and mean curvatures can be obtained with MATLAB processing scripts. Complete ABAQUS model input files are also provided to aid in benchmarking.

Evaluation of a Sample-to-Result POCKIT Central SARS-CoV-2 PCR System.

The emergence of COVID-19 has caused unprecedented impacts on global public health and many other aspects. Meanwhile, many types of methods have been developed to detect the causative agent, SARS-CoV-2; this has greatly advanced the technologies in the diagnostic field. Here, we describe the development and validation of a sample-in-result-out POCKIT Central SARS-CoV-2 PCR system for detecting SARS-CoV-2 in comparison with a commercial reference real-time RT-PCR assay (TaqPath COVID-19 Combo Kit). Both assays were specific and did not cross-react with non-SARS-CoV-2 agents. Both assays were able to detect various SARS-CoV-2 strains including some variants. Based on testing serial dilutions of SARS-CoV-2 USA-WA1/2020 isolate, the limit of detection was 0.8 TCID50/mL (1.87 × 103 genomic copies/mL) for POCKIT Central SARS-CoV-2 PCR and 0.16 TCID50/mL (3.75 × 102 genomic copies/mL) for the reference PCR. Subsequently, 183 clinical samples were tested by both assays and the diagnostic sensitivity, specificity, and agreement of the POCKIT Central SARS-CoV-2 PCR were 91.7%, 100%, and 94.0%, respectively, when compared to the reference PCR. The compact sample-to-result POCKIT Central SARS-CoV-2 PCR system is a simplified and efficient point-of-care tool for SARS-CoV-2 detection. In addition, this platform can be readily adapted to detect other human and animal viruses.

Power Generation by a Limestone-Contained Putty.

A novel contact-separation triboelectric generator concept is proposed in this paper, which consists of a limestone-based mounting putty and a metallized polyester (PET/Al) sheet. This is an attempt to explore tacky materials for power generation and extend the operational frequency bandwidth compared to existing TriboElectric NanoGenerators (TENGs). Moreover, the proposed design is very cost-effective and easy to build. Unlike traditional TENGs, which generate power solely due to a charge developing on the surface, the putty also replies on charge developed inside the material. Parametric study was conducted to determine the optimal putty thickness in a shaker test at 40 Hz. It was found that a putty layer at 0.6 mm thick yielded maximum power generation. During the separation phase, the electrical breakdown between triboelectric layers allows most existing electrons to flow back from the ground due to rapid charge removal at the interface. We are able to achieve a peak power of 16 mW in a shaker test at 40 Hz with an electrical load of 8 MΩ, which corresponds to a power density of 25.6 W/m2. A peak power of 120 mW in a manual prototype generator is achieved, which operates at approximately 2 Hz. Since putty material has less tackiness than double-sided tape, we are able to expand the frequency bandwidth up to 80 Hz, which is significantly higher than a TENG (typically <10 Hz). The mounting putty material contains limestone with approximate 31 nm of mean grain size mixed with synthetic rubber materials. Elasticity from rubber and the nanohardness of calcite crystallites allow us to operate a putty generator repeatedly without the concern of grain fracture. Also, a durability test was conducted with up to 250,000 contact-separation cycles. In summary, comparable performance is achieved in the proposed putty generator to benefit energy harvesting and sensor applications.

Power Generation by a Double-Sided Tape.

A novel contact-separation triboelectric generator concept is proposed in this study, which is composed of a double-sided tape with acrylic adhesive material and a metalized polyester (PET/Al) film (an aluminum layer coating on one side). The proposed concept is very cost-effective and easy to fabricate compared to existing triboelectric nanogenerators (TENGs), which require special equipment and sophisticated procedure to build. The strong bonding nature of acrylic adhesive on the tape induces a significant charge when contacting. The peak power generation depends on the induced pressure at the impact. During the separation phase, the air breakdown between triboelectric layers allows most existing electrons to flow back from the ground due to rapid charge removal at the interface. A higher voltage can be generated when the PET is interfaced with the double-sided tape compared to the Al-acrylic configuration because of the effect of triboelectric series and a Schottky barrier formation for electrons at the tape-Al interface during contact. A double-electrode configuration with an assembly of Al/PET-tape-PET/Al significantly improved the performance, in which a 21.2 mW peak power is achieved compared to 7.6 mW in the single-electrode design with tape-PET/Al assembly when excited at 20 Hz in a shaker test. This double-electrode triboelectric generator can power 476 LEDs with an active area of 38 mm × 25 mm. Moreover, a direct power of a 650 nm laser diode was demonstrated. In summary, the proposed triboelectric generator concept using tacky materials shows the potential for higher-energy harvesting via triboelectrification and advances the state of the art by offering low cost and easy fabrication options. It is expected that such newly proposed triboelectric generators are able to meet power requirements in many engineering applications.

Operando reaction cell for high energy surface sensitive x-ray diffraction and reflectometry.

A proof of concept is shown for the design of a high pressure heterogeneous catalysis reaction cell suitable for surface sensitive x-ray diffraction and x-ray reflectometry over planar samples using high energy synchrotron radiation in combination with mass spectrometry. This design enables measurements in a pressure range from several tens to hundreds of bars for surface investigations under realistic industrial conditions in heterogeneous catalysis or gaseous corrosion studies.

Adsorption of oleic acid on magnetite facets.

The microscopic understanding of the atomic structure and interaction at carboxylic acid/oxide interfaces is an important step towards tailoring the mechanical properties of nanocomposite materials assembled from metal oxide nanoparticles functionalized by organic molecules. We have studied the adsorption of oleic acid (C17H33COOH) on the most prominent magnetite (001) and (111) crystal facets at room temperature using low energy electron diffraction, surface X-ray diffraction and infrared vibrational spectroscopy complemented with molecular dynamics simulations used to infer specific hydrogen bonding motifs between oleic acid and oleate. Our experimental and theoretical results give evidence that oleic acid adsorbs dissociatively on both facets at lower coverages. At higher coverages, the more pronounced molecular adsorption causes hydrogen bond formation between the carboxylic groups, leading to a more upright orientation of the molecules on the (111) facet in conjunction with the formation of a denser layer, as compared to the (001) facet. This is evidenced by the C=O double bond infrared line shape, in depth molecular dynamics bond angle orientation and hydrogen bond analysis, as well as X-ray reflectivity layer electron density profile determination. Such a higher density can explain the higher mechanical strength of nanocomposite materials based on magnetite nanoparticles with larger (111) facets.

Epitaxy and Shape Heterogeneity of a Nanoparticle Ensemble during Redox Cycles.

The role of metal-support epitaxy on shape and size heterogeneity of nanoparticles and their response to gas atmospheres is not very well explored. Here we show that an ensemble of Pd nanoparticles, grown on MgO(001) by deposition under ultrahigh vacuum, mostly consists of two distinctly epitaxially oriented particles, each having a different structural response to redox cycles. X-ray reciprocal space patterns were acquired in situ under oxidizing and reducing environments. Each type of nanoparticle has a truncated octahedral shape, whereby the majority grows with a cube-on-cube epitaxy on the substrate. Less frequently occurring and larger particles have their principal crystal axes rotated ±3.7° with respect to the substrate's. Upon oxidation, the top (001) facets of both types of particles shrink. The relative change of the rotated particles' top facets is much more pronounced. This finding indicates that a larger mass transfer is involved for the rotated particles and that a larger portion of high-index facets forms. On the main facets of the cube-on-cube particles, the oxidation process results in a considerable strain, as concluded from the evolution to largely asymmetric facet scattering signals. The shape and strain responses are reversible upon reduction, either by annealing to 973 K in vacuum or by reducing with hydrogen. The presented results are important for unraveling different elements of heterogeneity and their effect on the performance of real polycrystalline catalysts. It is shown that a correlation can exist between the particle-support epitaxy and redox-cycling-induced shape changes.

Metastability of palladium carbide nanoparticles during hydrogen release from liquid organic hydrogen carriers.

Efficient hydrogen release from liquid organic hydrogen carriers (LOHCs) requires a high level of control over the catalytic properties of supported noble metal nanoparticles. Here, the formation of carbon-containing phases under operation conditions has a direct influence on the activity and selectivity of the catalyst. We studied the formation and stability of carbide phases using well-defined Pd/α-Al2O3(0001) model catalysts during dehydrogenation of a model LOHC, methylcyclohexane, in a flow reactor by in situ high-energy grazing incidence X-ray diffraction. The phase composition of supported Pd nanoparticles was investigated as a function of particle size and reaction conditions. Under operating conditions, we detected the formation of a PdxC phase followed by its conversion to Pd6C. The dynamic stability of the Pd6C phase results from the balance between uptake and release of carbon by the supported Pd nanoparticles in combination with the thermodynamically favorable growth of carbon deposits in the form of graphene. For small Pd nanoparticles (6 nm), the Pd6C phase is dynamically stable under low flow rate of reactants. At the high reactant flow, the Pd6C phase decomposes shortly after its formation due to the growth of graphene. Structural analysis of larger Pd nanoparticles (15 nm) reveals the formation and simultaneous presence of two types of carbides, PdxC and Pd6C. Formation and decomposition of Pd6C proceeds via a PdxC phase. After an incubation period, growth of graphene triggers the decomposition of carbides. The process is accompanied by segregation of carbon from the bulk of the nanoparticles to the graphene phase. Notably, nucleation of graphene is more favorable on bigger Pd nanoparticles. Our studies demonstrate that metastability of palladium carbides associated with dynamic formation and decomposition of the Pd6C and PdxC phases is an intrinsic phenomenon in LOHC dehydrogenation on Pd-based catalysts and strongly depends on particle size and reaction conditions.

Studying the urine microbiome in superficial bladder cancer: samples obtained by midstream voiding versus cystoscopy.

BACKGROUND: Preliminary data suggest that the urinary microbiome may play a role in bladder cancer. Information regarding the most suitable method of collecting urine specimens is needed for the large population studies needed to address this. To compare microbiome metrics resulting from 16S ribosomal RNA gene sequencing between midstream, voided specimens and those obtained at cystoscopy. METHODS: Adults, with a history of superficial urothelial cell carcinoma (non-muscle invasive bladder cancer) being followed with periodic surveillance cystoscopy had a urine sample collected by a mid-stream, voided technique and then from the bladder at cystoscopy. Urine samples underwent 16S ribosomal RNA gene sequencing on the Illumina MiSeq platform. RESULTS: 22 subjects (8 female, 14 male) were included. There was no significant difference in beta diversity (diversity between samples) in all samples between collection methods. However, analysis by sex revealed a difference between voided and cystoscopy samples from the same individual in males (p = 0.006, Adonis test) but not in females (p = 0.317, Adonis test). No differences were seen by collection method in any alpha diversity (diversity within a sample) measurement or differential abundance of taxa. CONCLUSIONS: Beta diversity of the urine microbiome did differ by collection method for males only. This suggests that the urinary microbiomes of the two collection methods are not equivalent to each other, at least in males, which is the sex that bladder cancer occurs most frequently in. Therefore, the same collection method within a given study should be used.

A field-deployable insulated isothermal RT-PCR assay for identification of influenza A (H7N9) shows good performance in the laboratory.

BACKGROUND: Avian influenza A (H7N9) remains circulating in China. For countries at risk of introduction of H7N9, such as Vietnam, early detection of H7N9 virus is essential for the early containment of the virus. Insulated isothermal reverse transcriptase PCR (iiRT-PCR) is a portable PCR system that can be deployed under field conditions to identify pathogens at the sampling site. Applying PCR at the sampling site will greatly reduce the time to obtain a diagnostic result which allows the veterinary authority to take immediate action to contain disease spreading. OBJECTIVE: To determine analytical and diagnostic sensitivity and specificity of the portable iiRT-PCR for H7N9 virus detection. METHODS: A panel of 59 virus isolates, including H7N9, avian influenza viruses of subtype H1 to H13, swine and human influenza viruses, Newcastle disease virus, and infectious bursal disease virus, were tested by H7 and N9 iiRT-PCR reagents, using probes and primers specific to H7 or N9, in comparison with laboratory-based real-time RT-PCR assays to determine analytical sensitivity and specificity. Fifty oropharyngeal samples from experimentally infected chicken and ducks with H7N9 and 50 non-infected control swabs were tested by the H7 iiRT-PCR to determine diagnostic sensitivity and specificity. RESULTS: The H7 and N9 iiRT-PCR reagents yielded comparable levels of analytical sensitivity and specificity with real-time RT-PCR for the detection of H7N9 virus. Diagnostic sensitivity and specificity of H7 iiRT-PCR were 98% and 100%, respectively. CONCLUSION: The observed high sensitivity and specificity of iiRT-PCR for H7N9 detection show its potential for early detection of H7N9 in risk-based surveillance.

A fully automated sample-to-answer PCR system for easy and sensitive detection of dengue virus in human serum and mosquitos.

BACKGROUND: The insulated isothermal PCR (iiPCR) technology enables consistent PCR amplification and detection in a simple heating device. A pan-dengue virus (DENV) RT-iiPCR, targeting the 5' untranslated region, was validated previously on the semi-automated POCKIT combo system (involving separate devices for nucleic acid extraction and PCR amplification/detection) to offer performance comparable to a laboratory real-time PCR. Working on the same technologies, a compact automated sample-in-answer-out system (POCKIT Central Nucleic Acid Analyser) has been available commercially for iiPCR, minimizing human error risks and allowing easy molecular bio-detection near points of need. Here, we evaluated the analytical and clinical performance of the pan-DENV RT-iiPCR on the fully automated system by comparison to those on the semi-automated system. METHODOLOGY/PRINCIPAL FINDINGS: Testing sera containing serial diluted DENV-1, -2, -3, or -4 cell culture stock, the pan-DENV RT-iiPCR system had similar 100% detection endpoints on the two systems; i.e. at 1, 10, 1 and 10 PFU/ml, respectively, on the fully automated system, and at 10, 1, 10 and 10 PFU/ml, respectively, on the semi-automated system. Furthermore, both fully automated and semi-automated PCR system can detect all four DENV serotypes in mosquitos. Clinical performance of the reagent on the two systems was evaluated by testing 60 human serum samples. Both systems detected the same 40 samples (ten DENV-1, -2, -3, and -4 positive each) and did not detect the other 20; 100% agreement (κ = 1) was found between the two systems. CONCLUSIONS/SIGNIFICANCE: With performance comparable to a previously validated system, the fully-automated PCR system allows applications of the pan-DENV reagent as a useful tool near points of need to facilitate easy, fast and effective detection of dengue virus and help mitigate versatile public health challenges in the control and management of dengue disease.

Pinwheel motifs: formation of unusual homo- and hetero-nuclear aggregates via bridging thiolates.

The homohexanuclear complexes [Ni2[Ni(L1)]4](BF4)4 x MeCN, 1, [Pd2(Pd(L2)]4](BF4)4, 2, and the heteropentanuclear aggregate [Cu2[Ni(L3)]3](PF6)2, 3, all adopt a 'pinwheel' type structural motif via thiolate bridging between square-planar Ni(II) or Pd(II) and between trigonal planar Cu(I) centres, respectively.