Process Parameter Optimization in Metal Laser-Based Powder Bed Fusion Using Image Processing and Statistical Analyses

The powder bed fusion additive manufacturing process has received widespread interest because of its capability to manufacture components with a complicated design and better surface finish compared to other additive techniques. Process optimization to obtain high quality parts is still a concern, which is impeding the full-scale production of materials. Therefore, it is of paramount importance to identify the best combination of process parameters that produces parts with the least defects and best features. This work focuses on gaining useful information about several features of the bead area, such as contact angle, porosity, voids, melt pool size and keyhole that were achieved using several combinations of laser power and scan speed to produce single scan lines. These features are identified and quantified using process learning, which is then used to conduct a comprehensive statistical analysis that allows to estimate the effect of the process parameters, such as laser power and scan speed on the output features. Both single and multi-response analyses are applied to analyze the response parameters, such as contact angle, porosity and melt pool size individually as well as in a collective manner. Laser power has been observed to have a more influential effect on all the features. A multi-response analysis showed that 150 W of laser power and 200 mm/s produced a bead with the best possible features.

Suppression of the Lycopene Cyclase Gene Causes Downregulation of Ascorbate Peroxidase Activity and Decreased Glutathione Pool Size, Leading to H2O2 Accumulation in Euglena gracilis

Carotenoids are photosynthetic pigments and hydrophobic antioxidants that are necessary for the survival of photosynthetic organisms, including the microalga Euglena gracilis. In the present study, we identified an uncharacterized gene encoding the E. gracilis β-carotene synthetic enzyme lycopene cyclase (EgLCY) and discovered a relationship between EgLCY-mediated carotenoid synthesis and the reactive oxygen species (ROS) scavenging system ascorbate-glutathione cycle. The EgLCY cDNA sequence was obtained via homology searching E. gracilis transcriptome data. An enzyme assay using Escherichia coli demonstrated that EgLCY converts lycopene to β-carotene. E. gracilis treated with EgLCY double-stranded RNA (dsRNA) produced colorless cells with hypertrophic appearance, inhibited growth, and marked decrease in carotenoid and chlorophyll content, suggesting that EgLCY is essential for the synthesis of β-carotene and downstream carotenoids, which are abundant and physiologically functional. In EgLCY dsRNA-treated cells, the ascorbate-glutathione cycle, composed of ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDAR), and glutathione reductase (GR), was unusually modulated; APX and GR activities significantly decreased, whereas DHAR and MDAR activities increased. Ascorbate content was significantly increased and glutathione content significantly decreased in EgLCY dsRNA-treated cells and was correlated with their recycling enzyme activities. Fluorescent imaging demonstrated that EgLCY dsRNA-treated cells accumulated higher levels of H2O2 compared to wild-type cells. Taken together, this study revealed that EgLCY-mediated synthesis of β-carotene and downstream carotenoid species upregulates APX activity and increases glutathione pool size for H2O2 scavenging. Our study suggests a possible relationship between carotenoid synthesis and the ascorbate-glutathione cycle for ROS scavenging in E. gracilis.

Negotiating Government-to-Government Food Importing Contracts: A Nash Bargaining Framework

Problem definition: Inspired by India’s challenges in importing pulses, we study the negotiation of government-to-government food importing contracts, with a focus on ad hoc and forward negotiations with multiple suppliers (henceforth referred to as multiple-sourcing negotiations). Academic/practical relevance: We are the first to comprehensively study ad hoc and forward multiple-sourcing negotiations for food importing. Such problems are widespread, especially in developing nations, and thus the research can be relevant to the wellbeing of large underprivileged populations. Methodology: We develop an analytical negotiation model in the Nash bargaining framework and adopt the Nash-in-Nash framework to analyze multiple-sourcing negotiations. Results: We find that while forward negotiations are not necessarily better than ad hoc negotiations for the buyer, it would be true with sufficiently many suppliers. When facing a supplier pool, we show that it may be optimal to mix forward and ad hoc suppliers. In general, fewer suppliers should be assigned as ad hoc as the pool size increases. We also find that adding a hybrid supplier (engaged in a forward negotiation with an ad hoc negotiation as the fallback option) may be better or worse than adding a forward supplier in the presence of other suppliers. Managerial implications: Our findings inform how a food importer should strategically utilize ad hoc and forward negotiations with its suppliers to improve the outcome. The work may help countries’ food importing policymaking and strategies and may improve the wellbeing of large underprivileged populations.

Evaluation of Sample Pooling for SARS-CoV-2 Detection in Nasopharyngeal Swab and Saliva Samples with the Idylla SARS-CoV-2 Test

To control outbreaks of coronavirus disease 2019 (COVID-19) and to avoid reagent shortages, testing strategies must be adapted and maintained for the foreseeable future. We analyzed the feasibility of pooling NPS and saliva samples for SARS-CoV-2 testing with the Idylla SARS-CoV-2 test, and we found that sensitivity was dependent on the pool size.

Loss of Atg2b and Gskip impairs the maintenance of the hematopoietic stem cell pool size

A germline copy number duplication of chromosome 14q32, which contains ATG2B and GSKIP , was identified in families with myeloproliferative neoplasm (MPN). Herein, we show that mice lacking both Atg2b and Gskip , but not either alone, exhibited decreased hematopoiesis, resulting in death in utero accompanied by anemia. In marked contrast to MPN patients with duplication of ATG2B and GSKIP , the number of hematopoietic stem cells (HSCs), in particular long-term HSCs, in double knockout fetal livers were significantly decreased due to increased cell death. Although the remaining HSCs still had the ability to differentiate into hematopoietic progenitor cells, the differentiation efficiency was quite low. Remarkably, mice with knockout of Atg2b or Gskip alone did not show any hematopoietic abnormality. Mechanistically, while loss of both genes had no effect on autophagy, it increased the expression of genes encoding enzymes involved in oxidative phosphorylation. Taken together, our results indicate that Atg2b and Gskip play a synergistic effect in maintaining the pool size of HSCs.

Rapid Review: Diagnostic Accuracy of Pooled Testing versus Individual Testing Using RT-PCR for SARS-CoV-2 for Screening and Surveillance of Individuals with Suspected COVID-19

Background. Pooled testing has been implemented on a limited scale, mainly for screening and surveillance in populations with a low prevalence of COVID-19 to save on limited resources. Objective. To determine the diagnostic accuracy of pooled compared with individual RT-PCR testing for SARS-CoV-2 in individuals suspected of COVID-19. Methods. We searched websites of living CPGs on COVID-19 (Australian COVID-19, COVID NMA, CEBM Oxford), Philippine DOH HTA, databases (PubMed, CENTRAL, medRXIV/bioRXIV), and Clinicaltrials.gov for studies that used pooled testing on individuals suspected of COVID-19. When appropriate, we pooled data for sensitivity and specificity and obtained the range and median of other data, such as positive predictive value and resource savings. We did a priori subgroup analysis for pool size, presence or absence of symptoms and use case, type of specimen, cutoff for positivity, type of kit, and post hoc subgroup analysis for method of pooling and timing of processing. Results. We included 21 studies: 6 diagnostic accuracy studies, and 15 clinical validation studies. Studies had varying populations, index test kit and performance characteristics, positivity rate (0.02 to 15%), and pool size (5 to 16). There was moderate pooled sensitivity, 81% (95% CI 72, 88; I2=73.6%; 6 studies, 776 pools) and high pooled specificity, 99% (95% CI, 98 to 100; I2=1.84%; 5 studies, 666 pools). Positive predictive value based on 21 studies ranged from 67% to 100%. Resource savings in the number of test kits used ranged from 49 to 89%. Identified harms of pooled testing were delayed turnaround time for positive samples and laboratory errors. Conclusion. There is moderate sensitivity and high specificity with pooled testing for the screening of individuals with suspected COVID-19. We recommend further studies to validate the utility based on community prevalence and other test variables.

Metabolic heritage mapping: heterogenous pools of cytoplasmic nucleotide sugars are selectively utilized by various glycosyltransferases

Biosynthesis of macromolecules requires precursors such as sugars or amino acids, originating from exogenous/dietary sources, reutilization/salvage of degraded molecules or de novo synthesis. Since these sources are assumed to contribute to one homogenous pool, their individual contributions are often overlooked. Protein glycosylation uses monosaccharides from all the above sources to produce nucleotide sugars required to assemble hundreds of distinct glycans. Here we demonstrate that cells identify the origin/heritage of the monosaccharide, fucose, for glycosylation. We measured the contribution of GDP-fucose from each of these sources for glycan synthesis and found that different fucosyltransferases, individual glycoproteins, and linkage-specific fucose residues identify and select different GDP-fucose pools dependent on their heritage. This supports the hypothesis that GDP-fucose exists in multiple, distinct pools, not as a single homogenous pool. The selection is tightly regulated since the overall pool size remains constant. We present novel perspectives on monosaccharide metabolism, which may have general applicability.

Metabolic evidence for distinct pyruvate pools inside plant mitochondria

The majority of the pyruvate inside plant mitochondria is either transported into the matrix from the cytosol via the mitochondria pyruvate carrier (MPC) or synthesised in the matrix by alanine aminotransferase (AlaAT) or NAD-malic enzyme (NAD-ME). Pyruvate from these origins could mix into a single pool in the matrix and contribute indistinguishably to respiration, or they could maintain a degree of independence in metabolic regulation. Here, we demonstrated that feeding isolated mitochondria with U-13C-pyruvate and unlabelled malate enables the assessment of pyruvate contribution from different sources to TCA cycle intermediate production. Imported pyruvate is the preferred source for citrate production even when the synthesis of NAD-ME-derived pyruvate was optimised. Genetic or pharmacological elimination of MPC activity removed this preference and allowed an equivalent amount of citrate to be generated from the pyruvate produced by NAD-ME. Increasing mitochondrial pyruvate pool size by exogenous addition only affected metabolites from pyruvate transported by MPC whereas depleting pyruvate pool size by transamination to alanine only affected metabolic products derived from NAD-ME. Together, these data reveal respiratory substrate supply in plants involves distinct pyruvate pools inside the matrix that can be flexibly mixed based on the rate of pyruvate transport from the cytosol. These pools are independently regulated and contribute differentially to organic acids export from plant mitochondria.