Micro milling cutters or micro mills are unique and important micro tools for fabricating miniaturised devices with sufficient geometrical and dimensional accuracy and machined surface integrity. ...Micro milling cutters, compared to conventional macro tools, have significantly different material removal mechanisms. They are also made of different raw materials and structures and exhibit distinctive machining characteristics and performances. Herein, we present the first comprehensive and up-to-date review of micro milling cutters in terms of their uniqueness, material removal mechanisms, materials and compositions, structures and design, fabrication techniques and machining performances, to provide adequate guidance for interested involvers. We also outline and discuss several possible future research directions to offer potential insights for the micro milling community and future researchers.
Display omitted
•Uniqueness of micro mills compared with ordinary macro tools are analyzed.•Material removal mechanisms of micro milling with emphasis on size effect are summarized.•Raw material types, structures, and design methodologies for micro mills are investigated.•Fabrication technologies, performances, and application of micro mills are discussed.•Possible future research or engineering directions are outlined.
The spreading powder layer plays a vital role in determining the quality of Laser powder bed fusion (LPBF) -manufactured samples. In this study, the effect of layer thickness is investigated ...numerically and experimentally. It was determined that the void fraction at a certain height is higher than that of the entire layer, especially for thicker layers, because of gravity. The former is consistent with the experimental result for powders of the same thickness. The void fraction of the sintered part was also measured to confirm their relationship. Furthermore, the dynamics of spreading particles on a particle bed were numerically studied to investigate whether support powders around the sintered part affect the powder-spreading process. The powder layer on a particle bed is denser than that on an adjacent solid bed, suggesting that support powders will affect the powder-spreading of the sintered part, especially its borders, and contribute to the surface topography.
Display omitted
•Layer height less than biggest D cannot achieve uniform particle distribution.•Increasing layer heights up to 2 × D significantly reduces void fraction.•Layer heights over 2 × D have diminishing returns, and may increase void fraction.•Adjacent support powders directly influence particle spread on solid substrates.
•A meta-analysis of the accuracy of metagenomic next-generation sequencing (mNGS) for pulmonary infections (PIs).•Specimen type in patients with PIs is bronchoalveolar lavage fluid.•We discovered ...that mNGS is more sensitive in patients with severe PIs.•We identified the great potential of mNGS to diagnose PIs.
Identifying pathogens in patients with pulmonary infection (PI) has always been a major challenge in medicine. Compared with sputum and throat swabs, bronchoalveolar lavage fluid (BALF) can better reflect the actual state of the lungs. However, there has not been a meta-analysis of the diagnostic efficacy of metagenomic next-generation sequencing (mNGS) in detecting pathogens in BALF from patients with PIs.
Data sources were PubMed, Web of Science, Embase, and the China National Knowledge Infrastructure. The pooled sensitivity and specificity were estimated using random-effects or fixed-effect models. Subgroup analysis was performed to reveal the effect of potential explanatory factors on the diagnostic performance measures.
The pooled sensitivity was 78% (95% confidence interval CI: 67-87%; I2 = 92%) and the pooled specificity was 77% (95% CI: 64-94%; I2 = 74%) for mNGS. Subgroup analyses for the sensitivity of mNGS revealed that patients with PIs who were severely ill or immunocompromised significantly affected heterogeneity (P < 0.001). The positive detection rate of mNGS for pathogens in BALF of severely or immunocompromised pulmonary-infected patients was 92% (95% CI: 78-100%).
mNGS has high diagnostic performance for BALF pathogens in patients with PIs, especially in critically ill or immunocompromised patients.
Due to the exceptional thermal conductivity and material hardness, CVD diamonds have been ideal materials for cutting tools; however, the specific properties of CVD diamonds vary with the grain size. ...An experimental study was carried out on chemical vapor deposition (CVD) diamonds with varying grain sizes in laser processing. This study aims to analyze the behavior of polycrystalline CVD diamonds under different thermal processing based on its thermal conductivity model. The pit formed under a single laser pulse on the material with a small grain size is shallow and tiny, because of its small thermal conductivity, a value calculated using the established model. The results show that for laser-machined surface, the material with a small grain size can obtain a better machined surface but a small material-removal depth; conversely, material with a large grain size provided opposite experimental results. Additionally, reasonable laser parameters achieved the desired material-removal depth of up to or even exceeding 180 μm and surface roughness Sa as low as 0.2 μm. Overall, both the grain sizes of polycrystalline CVD diamonds and laser parameters affect the machining result. However, there are considerable obstacles in simultaneously achieving a good surface and massive material removal. Hence, a tradeoff between the two aspects is essential in an actual machining process, and this study provides some useful guidance to practitioners and academicians.
Plant heat stress transcription factors (Hsfs) are the critical components involved in mediating responses to various environmental stressors. However, the detailed roles of many plant Hsfs are far ...from fully understood. In this study, an Hsf (SlHsfA3) was isolated from the cultivated tomato (Solanum lycopersicum, Sl) and functionally characterized at the genetic and developmental levels. The nucleus-localized SlHsfA3 was basally and ubiquitously expressed in different plant organs. The expression of SlHsfA3 was induced dramatically by heat stress, moderately by high salinity, and slightly by drought, but was not induced by abscisic acid (ABA). The ectopic overexpression of SlHsfA3 conferred increased thermotolerance and late flowering phenotype to transgenic Arabidopsis plants. Moreover, SlHsfA3 played a negative role in controlling seed germination under salt stress. RNA-sequencing data demonstrated that a number of heat shock proteins (Hsps) and stress-associated genes were induced in Arabidopsis plants overexpressing SlHsfA3. A gel shift experiment and transient expression assays in Nicotiana benthamiana leaves demonstrated that SlHsfA3 directly activates the expression of SlHsp26.1-P and SlHsp21.5-ER. Taken together, our results suggest that SlHsfA3 behaves as a typical Hsf to contribute to plant thermotolerance. The late flowering and seed germination phenotypes and the RNA-seq data derived from SlHsfA3 overexpression lines lend more credence to the hypothesis that plant Hsfs participate in diverse physiological and biochemical processes related to adverse conditions.
Severe α1-antitrypsin deficiency caused by the Z variant (Glu342Lys; ZZ-AT) is a well-known genetic cause for emphysema. Although severe lack of antiproteinase protection is the critical etiologic ...factor for ZZ-AT-associated chronic obstructive pulmonary disease (COPD), some reports have suggested enhanced lung inflammation as a factor in ZZ-AT homozygotes.
To provide molecular characterization of inflammation in ZZ-AT.
Inflammatory cell and cytokine profile (nuclear factor-κB, IL-6, tumor necrosis factor-α), intracellular polymerization of Z-AT, and endoplasmic reticulum (ER) stress markers (protein kinase RNA-like ER kinase, activator transcription factor 4) were assessed in transgenic mice and transfected cells in response to cigarette smoke, and in explanted lungs from ZZ and MM individuals with severe COPD.
Compared with M-AT, transgenic Z-AT mice lungs exposed to cigarette smoke had higher levels of pulmonary cytokines, neutrophils, and macrophages and an exaggerated ER stress. Similarly, the ER overload response was greater in lungs from ZZ-AT homozygotes with COPD, and was particularly found in pulmonary epithelial cells. Cigarette smoke increased intracellular Z-AT polymers, ER overload response, and proinflammatory cytokine release in Z-AT-expressing pulmonary epithelial cells, which could be prevented with an inhibitor of polymerization, an antioxidant, and an inhibitor of protein kinase RNA-like ER kinase.
We show here that aggregation of intracellular mutant Z-AT invokes a specific deleterious cellular inflammatory phenotype in COPD. Oxidant-induced intracellular polymerization of Z-AT in epithelial cells causes ER stress, and promotes excess cytokine and cellular inflammation. This pathway is likely to contribute to the development of COPD in ZZ-AT homozygotes, and therefore merits further investigation.
In plants, transcriptional regulation is the most important tool for modulating flavonoid biosynthesis. The basic helix-loop-helix transcription factors are only one example how then flavonoid ...pathway is regulated. There are other transcription factors as well. In this study, the codon-optimized VvbHLH1 gene from grape was chemically synthesized. Overexpression of VvbHLH1 significantly increased the accumulation of flavonoids and enhanced salt and drought tolerance in transgenic Arabidopsis thaliana plants. Real-time quantitative PCR analysis showed that overexpression of VvbHLH1 resulted in the up-regulation of genes involved in flavonoid biosynthesis, abscisic acid (ABA) signaling pathway, proline biosynthesis, stress responses and ROS scavenging under salt and drought stresses. Further analyses under salt and drought stresses showed significant increases of ABA and proline content, superoxide dismutase and peroxidase activities, as well as significant reduction of hydrogen peroxide (HâOâ) and malonaldehyde content. The results demonstrate the explicit role of VvbHLH1 in conferring salt and drought tolerance by increasing the accumulation of flavonoids and ABA signalling in transgenic A. thaliana. The VvbHLH1 gene has the potential to be used to increase the content of valuable flavonoids and improve the tolerance to abiotic stresses in A. thaliana and other plants.
Brucellosis is a severe public health problem in China. However, analysis on related infection events is lacking. We performed a systematic analysis of brucellosis laboratory infection and vaccine ...infection events from 2006 to 2019 in China based on the published literatures. Our analysis showed that most laboratoryBrucellainfections in hospitals were found in Southern China. The identification and handling of suspected samples ofBrucellainfection without following the recommended biosafety protection was the main risk factor. It is important to strengthen the preventive awareness of clinical laboratory staff and physicians, while highlighting the compulsory handling and identification of suspectedBrucella-infected samples in biosafety facilities and following biosafety practices. However, a severe Brucella infection accident at the Northeast Agricultural University, with 28 positive cases, showed that strengthening the management in teaching experiments of students in the veterinary-related profession is essential. However, cluster S2 vaccine strain infection events caused by vaccination and production were mainly observed in Northern China. Strengthening vaccination skills, personal protection, and improving the biosafety management of vaccine production and implementing regular risk surveillance is mandatory. Our analysis provides helpful clues for control of public health events involving brucellosis, as well as implementing intervention strategies is urgent.
ABSTRACT
The timing of high lake‐level stands during the Late Pleistocene in western China remains controversial. Here we report new results from Megalake Tengger based on a study of ...palaeo‐shorelines and a drill core from Baijian Lake in the northwestern Tengger Desert. Multiple dating methods, based on luminescence signals (quartz optically stimulated luminescence, K‐feldspar post infrared‐infrared stimulated luminescence) and electron spin resonance signals of quartz, were used to date beach sands from palaeo‐shoreline profiles at altitudes of ~1310 m (+20 m above lake level), ~1320 m (+30 m) and ~1350 m (+60 m), and from the top 20 m of sandy sediments from the drill core obtained from the modern beach of Baijian Lake. The dating results show that high lake‐level stands associated with the previously reported Megalake Tengger (~1310–1320 m) occurred during the late Early to Middle Pleistocene, which is much earlier than previously reported. In addition, no geomorphological evidence of shorelines and sedimentary evidence from the drill core profile were found to support the previously reported Late Pleistocene lake levels. Our results indicate that the exact age of the previously reported ‘high lake level event’ in a large part of northwestern China during the Late Pleistocene needs to be re‐evaluated.
PDF
