Sample Surface Research Articles

Assessment of microbial contamination in various processing rooms using culture-dependent and 16S rRNA methods in a commercial kitchen in eastern China

Commercial kitchens, frequently implicated in foodborne illness outbreaks, underscore the importance of studying bacterial communities in these settings. This study analyzed bacterial communities of two cooked food samples and 49 food contact surface samples in a commercial kitchen in eastern China, utilizing traditional bacterial cultivation methods and 16S rRNA sequencing. The cutting room exhibited the highest microbial contamination, with elevated bacterial colony counts on cutting boards and containers, suggesting it as the primary site for potential cross-contamination risks between different foods. Regarding bacterial communities, Coliform levels in refrigerators ranged from 1.0 to 3.0 log10 CFU/cm2, which is below sanitary standards. However, E. coli levels on food contact surfaces and cooked foods exceeded microbial limits set by GB1903 and GB 2726 in China. Proteobacteria were predominant at the phylum level across processing rooms, with Moraxellaceae notably prevalent and Pseudomonadaceae dominant in cooked foods at the family level. Source tracking identified food contact surfaces, including countertops, containers in the cutting room, and refrigerators in the cooking room, as primary sources of bacterial contamination in the final cooked foods, contributing 61.62% of contamination. These findings suggest that effective measures should be developed to control bacterial contamination on kitchen food contact surfaces to prevent cross-contamination among different cooked foods.

Characterization of internal defects in cylindrical components using laser ultrasonic method with a modified SAFT algorithm

The health monitoring of cylindrical elements is particularly important for the safe operation of industrial production, because cylinders bear a lot of support and transmission work. Normal non-destructive evaluation techniques need special designs to suit high curvature surfaces of cylinders. Laser ultrasonic (LU) method can provide a remote and non-destructive inspection solution to solid cylinders due to its flexible adaptability to complex structures and strong penetration depth. However, constrained by the common problems of optical detection systems, the detected ultrasonic signals will suffer low signal-to-noise ratio and bad resolution from poor sample surface quality. Thus, a modified synthetic aperture focusing technique (SAFT) optimized for cylindrical components is proposed to improve the detectability of LU on small and buried defects. Mode conversion wave signals obtained by multiple separate excitations are used in SAFT imaging for the reconstruction of the defects under surface profile correction. To reduce the influence of incident waves such as direct surface acoustic wave, besides common difference method, adjacent wave subtraction algorithm based on cross-correlation is used for signal preprocessing, suppressing the incident waves and exaggerating the mode conversion waves. In numerical simulation, internal defects with diameters from 0.6 to 0.2 mm with various buried depths are visualized and accurately located via the optimized SAFT algorithm using mode conversion waves. For validation, a circumferential scanning system is established in LU experiment and internal defects from 0.8 to 0.4 mm in diameter inside solid cylinders are successfully detected with precise location. The results elucidate the reliability of characterizing the location of small internal buried defects in solid cylinder structures through LU-SAFT imaging.

Fabrication of a cell irradiation technique by alpha-particles using allyl diglycol carbonate (ADC) detector and micro-capillary tubes.

To study the impact of micro-alpha irradiation collimator with a specific design to irradiate specific normal or up-normal cells using capillary tubes and nuclear track detector type CR-39. The in vitro experimental study was conducted at radiobiology Lab, of the Physics department, Salahaddin University, Erbil, Iraq from February to April 2022. Several alpha irradiation collimators were calibrated using allyl diglycol carbonate to fabricate a suitable blood cell irradiation technique. Time of irradiation and alpha particle energy were calibrated. Healthy blood samples of Albino rats and cancer blood samples were used to assess the applicability of the fabricated cell irradiation technique. The Rats were divided into intervention and control groups. Data was analysed using SPSS software version 28. Of the 15 healthy, male Albino rats having a mean weight of 230±12g each, there were 12(80%) in the intervention group and 3(20%) in the control group. Microcapillary tubes with suitable diameters had high stability for deposition of a sufficient density of alpha particles on the surface of allyl diglycol carbonate and blood samples. The optimum time of irradiation that had a significant (p<0.05) effect was 20 sec corresponding to alpha energy 4.5MeV. Low irradiation time had significant impact of alpha particles on the average percentage of lymphocyte and neutrophil cells.

Development of an Activity-Based Ratiometric Electrochemical Switch for Direct, Real-Time Sensing of Pantetheinase in Live Cells, Blood, and Urine Samples.

Pantetheinase is a key biomarker for the diagnosis of acute kidney injury and the monitoring of malaria progression. Currently, existing methods for sensing pantetheinase, also known as Vanin-1, show considerable potential but come with certain limitations, including their inability to directly sense analytes in turbid biofluid samples without tedious sample pretreatment. Here, we describe the first activity-based electrochemical probe, termed VaninLP, for convenient and specific direct targeting of pantetheinase activity in turbid liquid biopsy samples. The probe was designed such that cleavage of the pantetheinase amide linkage, triggered by a self-immolative reaction, simultaneously ejects an amino ferrocene reporter. Among the distinctive properties of the VaninLP probe for sensing pantetheinase are its high selectivity, sensitivity, and enzyme affinity, a wide linear concentration range (8-300 ng/mL), and low limit of detection (2.47 ng/mL). The designed probe precisely targeted pantetheinase and was free of interference by other electroactive biological species. We further successfully applied the VaninLP probe to monitor and quantify the activity of pantetheinase on the surfaces of HepG2 tumor cells, blood, and urine samples. Collectively, our findings indicate that VaninLP holds significant promise as a point-of-care tool for diagnosing early-stage kidney injury, as well as monitoring the progression of malaria.

Data-efficient fine-tuning of foundational models for first-principles quality sublimation enthalpies.

Calculating sublimation enthalpies of molecular crystal polymorphs is relevant to a wide range of technological applications. However, predicting these quantities at first-principles accuracy - even with the aid of machine learning potentials - is a challenge that requires sub-kJ mol-1 accuracy in the potential energy surface and finite-temperature sampling. We present an accurate and data-efficient protocol for training machine learning interatomic potentials by fine-tuning the foundational MACE-MP-0 model and showcase its capabilities on sublimation enthalpies and physical properties of ice polymorphs. Our approach requires only a few tens of training structures to achieve sub-kJ mol-1 accuracy in the sublimation enthalpies and sub-1% error in densities at finite temperature and pressure. Exploiting this data efficiency, we perform preliminary NPT simulations of hexagonal ice at the random phase approximation level and demonstrate a good agreement with experiments. Our results show promise for finite-temperature modelling of molecular crystals with the accuracy of correlated electronic structure theory methods.

Novel hybrid interference and atomic force microscopy

Abstract A novel hybrid microscope which combines an interference microscopic (IM) and an atomic force microscopic (AFM) measurement mode is introduced. It is realised by adding an AFM probe to an IM, where the AFM probe can be mechanically switched in or out of the beam path of the IM. When the AFM cantilever is out of the beam path, the system works in the IM measurement mode for noncontact and fast optical measurements. When the AFM cantilever is in the beam path, it works in the AFM measurement mode, where the AFM tip interacts with sample surfaces for measurements. The deformation of the AFM cantilever induced by the tip-sample interaction force is detected from interference fringes, which are formed by the interference of the light beam reflected from the backside of the AFM cantilever and a reference beam in the IM. This novel design has a high-level synergy of AFM and IM technologies and provides several promising application potentials. For instance, it can bring high-resolution AFM measurements whenever and wherever needed in IM measurements, thus, to complement the lateral resolution limits of IM; The AFM measurement mode can provide measurement results with higher topography fidelity, thus, to offer in-situ reference areal surface metrology for IM measurements. In the paper, design concept, realisation of a prototype instrument, and experimental results illustrating the performance of the prototype instrument are detailed. &amp;#xD;

Laser ultrasound wave pattern analysis for efficient defect detection in samples with curved surfaces

Many production processes involve curved sample surfaces, such as welding or additive manufacturing. These pose new challenges to characterization methods for quality inspection, which are usually optimized for flat extended sample geometries. In this paper, we present a laser ultrasound (LUS) method that can be used to efficiently detect defects (e.g., voids), without extensive scanning effort and without a prior knowledge of the defect location, in finite samples with curved surfaces. The developed method starts with generalized simulations of the LUS wave patterns in samples with varying radii of curvature and width as well as varying excitation size and mechanism (thermoelastic or ablative). Based on the wave pattern analysis, it is possible to predict how every point in the weld can be reached with only few excitation spots. In a second step, we assume a grid of finite size defects at locations at which such voids are most likely formed and perform a thorough simulation analysis that is based on B-Scans to find a few pairs of excitation–detection points most favorable for finding defects anywhere in the weld seam. These results are then compared to the wave pattern analysis, discussing similarities and deviations from the predictions. In a final step, the simulations are compared to experimental results, verifying the almost threefold increase in the detectability of defects by choosing the predicted optimal excitation–detection positions. It is expected that this method will significantly improve the reliability and time efficiency of detecting internal defects in samples with curved surfaces in potential industrial applications.

Risk investigation and diversity of microbial contamination during slaughter processing of yellow-feathered broiler

The cleanliness of slaughter process is very pivotal to ensure the safety of broiler products, and slaughter process is prone to cause microbial contamination since it involves a highly collaborative system including different operations. The procedures in slaughter processing are primary sources of bacterial contamination, and it is crucial for poultry industry to maximize product safety and quality by understanding the connection between bacterial diversity on chicken carcasses. The commercial yellow-feathered broiler plant was investigated to analysis the risk of microbial contamination. In this study, 16S rRNA sequencing was used to evaluate microbial diversity and microbial contamination was investigated by collecting 910 samples from different processing steps. Generally, total count of bacteria colonies ranged from 3.14 log CFU/cm2 to 5.68 log CFU/cm2, and the microbial load at yellow-feathered broiler carcass samples was significantly higher than that at environmental samples; moreover, the cutting areas were the high-risk areas of cross-contamination. In addition, the relative abundance of Actinobacteria (9.61%) at water samples was significantly higher than that at contact surfaces samples. This paper provides a valuable theoretical insight into the diversity and changes in the bacterial community during slaughter beneficial for enterprise managers further enhancing yellow-feathered chicken quality.

Storing liquid chromatographic separations on surface energy traps: decoupling the LC and the mass spectrometer.

We report a micro-fractionation device for high performance liquid chromatography-mass spectrometry to archive chromatographic separations on an array of optimized surface energy traps (SETs). The method has the potential to significantly alter nanoflow LC-MS workflow, decoupling separation and analysis. The wetting characteristics of the SETs cause the HPLC eluent stream to spontaneously split into droplet microfractions. The droplet mirofractions are then dried down to enable facile storage and transport of the archived separation. Discontinuously dewetting array parameters were explored to maximize array volume and resolution using a combination of SET design, shape, size, and spacing. Mass spectrometry analysis is performed utilizing a liquid micro-junction surface sampling probe to extract dried analytes from the surface of the SETs followed by electrospray ionisation. A reverse phase separation of pharmaceutical compounds is "recorded" using the micro-fractionation device followed by "reading" the chromatographic trace with a mass spectrometer 24 hours after the separation was performed/archived, demonstrating a true decoupling of LC, and MS. Additionally, we demonstrate the ability to collect microfractions with sub-one-second integration time, approaching the scan time of a mass spectrometer or UV-Vis detector. With further improvements to the device, sub-1-second micro-fractionation may enable seamless reconstruction of archived chromatograms indistinguishable from online LC-MS data, while also providing the benefits of easy storage and transport of archived separations.

An Effective Surface Passivation Assay for Single-Molecule Studies of Chromatin and Topoisomerase II.

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Novel electronic structures from anomalous stackings in NbS2 and MoS2

We show that in some transition metal dichalcogenides, minority regions of the cleaved sample surfaces show—unexpectedly and anomalously—a finite number of 2D electronic states instead of the expected 3D valence bands. In the case of NbS2, in addition to the typical spectrum associated with bulk 2Ha stacking, we also find minority regions with electronic structures consistent with few layers of 3R stacking. In MoS2, we find areas of both bulk 2Hc and 3R stackings, and regions exhibiting finite-layer quantization of both types. We further find evidence for a more exotic 4Ha stacking of MoS2, in which the valence band maximum is quasi-2D. The results highlight how variation of the interlayer stacking of van der Waals materials beyond the commonly reported bulk polytypes can yield novel electronic structures. Published by the American Physical Society 2024

Numerical Simulation on Lubrication and Experiment Study on Tribology Improvement of Slipper Pair at Low speeds

A mixed lubrication model for the slipper pair of an electric piston pump is proposed to solve problems such as inadequate lubrication, extreme friction, and wear at near-zero and low speeds. The lubrication characteristics of the slipper pair were numerically calculated and simulated, and the frictional characteristics in the low-speed range were analyzed. A self-lubricating and anti-wear slipper pair was developed to mitigate severe friction and wear at near-zero and low speeds. To improve the tribological properties of slippers, various concentrations of molybdenum disulfide (MoS2) powder mixed with epoxy resin (EP) were used as self-lubricating materials. The content of MoS2 ranged from 1 and 20 wt%. The optimal content of MoS2 was obtained by conducting frictional tests on the slipper pair samples as well as material examination and analysis of the slipper sample surfaces before and after the surface characterization tests. The lubrication mechanisms of the self-lubricating and antiwear slippers were determined. The EP/MoS2 composite lubricating materials exhibited excellent self-lubricating and anti-wear properties, providing a new direction for the optimized design of slipper pairs and other important friction pairs in piston pumps and promising research prospects.

Critical Resolved Shear Stress and Work Hardening Determination in HCP Metals: Application to Zr Single Crystals

Obtaining precise parameters of deformation modes remains a significant challenge in materials science research. Critical resolved shear stresses (CRSS) and work hardening, particularly in hexagonal metals, are crucial parameters for constitutive laws in crystal plasticity. This paper presents a novel approach to determine CRSS and specific hardening matrix coefficients for commercially pure zirconium (α-Zr) at room temperature. In situ methods are employed to measure displacement fields using grids applied to the sample surface, while a comprehensive characterization of the activated deformation systems is performed via SEM and TEM. The CRSS for prismatic ⟨a⟩, pyramidal ⟨a⟩, and 101¯2 and 112¯1 twinning systems, as well as the self-hardening for prismatic slip and several work-hardening coefficients (for prismatic/prismatic and prismatic/pyramidal interactions), are reported in Zr single crystals. Finally, the results are compared with findings from the literature and atomistic simulations.

Deuterium plasma induced preferential erosion in ultra-high temperature ceramics TiB2 and ZrB2*

Abstract Steady-state deuterium plasma exposures were performed on ultra-high temperature ceramics titanium diboride (TiB2) and zirconium diboride (ZrB2) using the PISCES-RF linear plasma device (LPD) as early screening for first wall, plasma-facing applications. Deuterium plasma exposures were performed using 40 eV ion energies at 240, 525, and 800 °C sample temperatures and 90 eV ion energies at 240 °C sample temperatures to analyze TiB2 and ZrB2 surface morphology and chemistry evolution behavior. Post-plasma exposure chemistry characterization of the near surface ( &lt; 50 nm) region of the samples all show transition metal enrichment, indicating boron preferential erosion. Transition metal to boron fractions vary with plasma exposure temperature under the 40 eV ion energy; metal enrichment is maximized at 800 °C and then minimized at 525 °C. SEM micrographs of all plasma exposed sample surfaces show no significant or noticeable plasma induced damage from cracking or blistering.

Rapid on-site nondestructive surface corrosion characterization of sintered nanocopper paste in power electronics packaging using hyperspectral imaging

Sintered nanocopper (nanoCu) paste, exhibiting excellent electrical, thermal, and mechanical performances, offers promise for interconnections in wide bandgap (WBG) semiconductors operating at higher temperatures. However, sintered nanoCu is prone to severe corrosion in environments containing H2S, with on-site characterization methods for the composition of corrosion products currently lacking. In this study, a novel method was proposed for the rapid characterization of corrosion products during the corrosion process based on hyperspectral imaging (HSI) technology. Sintered nanoCu samples were subjected to 336 h H2S gas corrosion tests with bulk Cu as the reference, followed by correlating the corrosion element content with hyperspectral characteristic parameters. Then, the morphology and composition of corrosion products were researched using focused ion beam scanning electron microscope (FIB-SEM) and transmission electron microscope (TEM) analysis. The results showed that (1) during the corrosion process, a linear relationship was established between the Cu, O elemental atomic contents on the sample surfaces and their hyperspectral characteristic parameters. (2) The elemental atomic content of S exhibited an exponential relationship with the characteristic parameter. (3) The change rate in the spectral characteristic parameters during the corrosion process reflected the severity of corrosion, which was confirmed by comparing the thickness of the corrosion products of the sintered nanoCu and bulk Cu. This study offers a foundation for the further investigation of rapid on-site characterization of sintered nanoCu corrosion involving H2S.

Assessing Mechanochemical Properties of Acrylonitrile Butadiene Styrene (ABS) Items in Cultural Heritage Through a Multimodal Spectroscopic Approach.

A multimodal spectroscopic approach is proposed to correlate the mechanical and chemical properties of plastic materials in art and design objects, at both surface and subsurface levels, to obtain information about their conservation state and to monitor their degradation. The approach was used to investigate the photo-oxidation of acrylonitrile butadiene styrene (ABS), a plastic commonly found in many artistic and design applications, using ABS-based LEGO bricks as model samples. The modifications of the chemical and viscoelastic properties of ABS during photoaging were monitored by correlative Brillouin and Raman microspectroscopy (BRaMS), combined with portable and noninvasive broad-range external reflection infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) relaxometry, directly applicable in museums. BRaMS enabled combined measurements of Brillouin light scattering and Raman spectroscopy in a microspectroscopic setup, providing for the coincident probe of the chemical and mechanical changes of ABS at the sample surface. NMR relaxometry allowed for noninvasive measurements of relaxation times and depth profiles which are directly related to the molecular mobility of the material. Complementary chemical information was acquired by external reflection IR spectroscopy. The simultaneous probe of the chemical and mechanical properties by this multimodal spectroscopic approach enabled us to define a decay model of ABS in terms of compositional changes and variation of stiffness and rigidity occurring with photodegradation. The knowledge acquired on LEGO samples has been used to rate the conservation state of ABS design objects noninvasively investigated by external reflection Fourier transform IR spectroscopy and NMR relaxometry offered by the MObile LABoratory (MOLAB) platform of the European Research Infrastructure of Heritage Science.

Changes in structure, physicochemical properties and in vitro digestibility of quinoa starch during heat moisture treatment with hydrogen-infused and plasma-activated waters

In this study, comparative effect of heat moisture treatment (HMT) with distilled, hydrogen-infused and plasma-activated waters on the structure, physicochemical properties and in vitro digestibility of quinoa starch (QS) was investigated. To our knowledge, this study is the first to apply hydrogen-infused water to starch modification. The surface of HMT-modified samples was much rougher than that of native QS. HMT did not change the typical “A”-type X-ray diffraction pattern of QS but it increased its relative crystallinity. Meanwhile, amylose content, gelatinization temperature and water absorption capacity of QS significantly increased, whereas viscosity and swelling power markedly decreased. The rapidly digestible starch level of HMT-treated samples was significantly lower than that of native QS, and the resistant starch content markedly increased. These alterations were dependent on treatment moisture level. Furthermore, compared to distilled water, the HMT with hydrogen-infused and plasma-activated waters induced much more extensive effect on above properties, and the sample treated with plasma-activated water had the highest extent due to the acidic or alkaline environment and reactive oxygen and nitrogen species. These results identified that the combination of HMT with hydrogen-infused or plasma-activated water was a novel strategy to improve the thermal stability and functionality of quinoa starch.

Microstructure and high temperature tribological behavior of nickel-based superalloy with addition of revert

The recycling of revert plays a crucial role in cost-efficiency and green manufacturing of superalloy. In this study, optical microscopy, scanning electron microscopy coupled with energy dispersive spectroscopy, tensile test, and tribological analysis were employed to investigate the microstructure, mechanical properties, and tribological behaviors of vacuum induction melted superalloys of 100% original material (Sample 1) and 40% original material + 60% revert (Sample 2). Dry sliding tests were conducted at 300 and 730 °C. The addition of revert promotes microstructure refinement, hardness increase, and carbide formation, at the cost of 18.5% ductility loss. During the high-temperature dry sliding process, abrasive, adhesive, and oxidative wear mechanisms were observed on the contact surfaces. Sample 2 exhibited a lower wear rate and coefficient of friction at both 300 and 730 °C. Additionally, a more continuous and wear-resistant tribolayer was formed on the wear track of Sample 2, effectively mitigating matrix oxidation compared to Sample 1. At 730 °C, a thick tribolayer developed on the wear surface of Sample 2, characterized by a hard and wear-resistant glaze layer on the outermost surface. The continuous sliding induced matrix heating, which facilitates recrystallization in the subsurface of Sample 2, induced by increased inclusions and carbides from the revert. The analysis of wear debris further illustrated the variations of wear mechanism at different temperatures. These findings are meaningful for understanding the high-temperature behavior of superalloys and optimizing alloy recycling process.

Triaxial creep test and damage model study of layered red sandstone under freeze-thaw cycles

To examine the creep behavior and degradation of stratified rock in cold areas, triaxial creep experiments and microscopic analyses were performed on layered red sandstone specimens under freeze-thaw (F-T) cycles. This study revealed the deterioration characteristics and damage mechanisms of red sandstone's creep behavior under the influence of F-T cycles and bedding inclination. The test results showed that: (1) The steady-state creep rates with bedding angles β=30°after 0, 40, 80, and 120F-T cycles were 0.0168 × 10−2·h−1, 0.0224 × 10−2·h−1, 0.0289 × 10−2·h−1, and 0.0368 × 10−2·h−1 respectively. The instantaneous deformation, creep deformation, and steady-state creep rates increased gradually with the increase of F-T cycles, while the long-term strength exhibited a decreasing trend. (2) After 40F-T cycles, the long-term strengths with bedding angles of 0°, 30°, 45°, 60° and 90° were 121.17 MPa, 65.47 MPa, 46.28 MPa, 77.64 MPa and 124.78 MPa, respectively. The bedding angle of 45° has the greatest influence on the triaxial creep properties of red sandstone, followed by the bedding angles of 30° and 60°, and the bedding angles of 0° and 90° have the least influence. (3) As the F-T cycles increases, the longitudinal wave velocity gradually decreases, and the pores and cracks on the sample surface continue to expand, leading to increased damage. The failure mode evolves from a single oblique shear plane to an “X”-shaped tensile splitting. Additionally, the bedding angle has a significant effect on the longitudinal wave velocity. As the bedding angle increases, the longitudinal wave velocity exhibits a “V”-shaped distribution, initially decreasing and then increasing. Based on the test results, a creep damage model of layered rock considering the influence of F-T cycles was established, and the rationality of the model was verified by test data. The research results can provide a scientific basis and technical reference for the long-term stability of layered rock engineering in cold regions.

Mechanism of Fatigue-Life Extension Due to Dynamic Strain Aging in Low-Carbon Steel at High Temperature.

An enhancement in fatigue life for ferrite-pearlite low-carbon steel (LCS) at high temperature (HT) has been discovered, where it increased from 190,873 cycles at room temperature (RT) to 10,000,000 cycles at 400 °C under the same stress conditions. To understand the mechanism behind this phenomenon, the evolution of microstructure and dislocation density during fatigue tests was comprehensively investigated. High-power X-ray diffraction (XRD) was employed to analyze the evolution of total dislocation density, while Electron Backscatter Diffraction (EBSD) and High-Resolution EBSD (HR-EBSD) were conducted to reveal the evolutions of kernel average misorientation (KAM), geometrically necessary dislocations (GND) and elastic strains. Results indicate that the enhancement was attributed to the dynamic strain aging (DSA) effect above the upper temperature limit, where serration and jerky flow disappeared but hindrance of dislocations persisted. Due to the DSA effect, periods of increase and decrease in the total dislocations were observed during HT fatigue tests, and the fraction of screw dislocations increased continuously, caused by viscous movement of the screw dislocations. Furthermore, the increased fraction of screw dislocations resulted in a lower energy configuration, reducing slip traces on sample surfaces and preventing fatigue-crack initiation.