FINITE ELEMENT MODEL FOR PREDICTING RESIDUAL STRESSES IN SHIELDED MANUAL METAL ARC WELDING OF MILD STEEL PLATES

 This paper investigates the prediction of residual stresses developed in shielded manual metal arc welding of mild steel plates through Finite Element Model simulation and experiments. The existence of residual stresses that cause fatigue and distortion in welded structures has been responsible for failure of machine parts in service. These stresses if not properly controlled can lead to loss of lives and property. The highlight is that various trial and error welding runs have to be carried out while hoping for the best performance during operation. This is wasteful of time, material and finance. Thus the need to incorporate Finite Element Analysis prediction of residual stresses by computational methods to first determine satisfactory welding conditions before actual production. The geometry of the butt welded Low Carbon (ASTM A36) steel plates was modeled and the residual stresses simulated using ANSYS Multiphysics V14. Three experimental samples of similar geometry were also produced using the shielded manual metal arc welding process to verify the result. Low carbon steel (ASTM A36) was used as the parent metal, E066 electrodes were used to complete the weld.  The generated residual stresses were measured using an X-Ray Diffractometer (XRD 6000). From the Finite Element Model Simulation, the transverse residual stress in the x-direction (σx) had a maximum value of 375MPa (tensile) and minimum value of -183MPa (compressive) while in the y-direction (σy), the maximum value of 172MPa (tensile) and minimum value of zero. The longitudinal stress in the x-direction (σx) indicated a maximum value of 355MPa (tensile) and a minimum value of -10MPa (compressive) while in the y-direction (σy), the maximum value was 167MPa and the minimum value of the residual stress was -375MPa. The experimental values as measured by the X-Ray diffractometer were of reasonable correlation as transverse residual stress (σx) along the weld line in the transverse x-direction varied from 353MPa (tensile) to -209MPa (compressive) while in the y-direction, stress (σy) along the weld line varied from 177MPa (tensile) to zero. The longitudinal stress measured by the X-Ray diffractometer in the x-direction (σx) varied from 339MPa (tensile) to zero (compressive) while in the y-direction (σy) varied from 171MPa (tensile) to -366MPa (compressive). These results shows that the residual stresses obtained by prediction from the finite element method are in fair agreement with the experimental results. Based on this, it can be concluded that Finite Element Model can be used to replicate and determine the expected residual stresses that would be generated before an actual welding process is carried out. http://dx.doi.org/10.4314/njt.v35i1.1

Improvement of 2-O-α-D-Glucopyranosyl-L-Ascorbic Acid Biosynthesis Using Ultrasonic Radiation

Purpose: To improve 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G) production using ultrasonic radiation (UR) treatment.Methods: The production of AA-2G using UR or ultrasonic radiation with shaking (URS) at 150 rpm, at varying power (100 − 500 W), temperature (30 – 65 °C), pH 4.0 −9.0, and time (2−24 h) was compared with that produced in a shaker water bath (SWB) in a reaction catalyzed by cyclodextrin glucanotransferase (CGTase) from Bacillus sp. SK13.002. The effect of URS on CGTase activity was also measured.Results: Maximum AA-2G production using UR at a power of 400 W, temperature of 37 oC, and pH 8.0 for 18 h was 5.69 ± 0.2 g/L, while URS at 500 W/150 rpm and 37 °C for 14 h yielded 7.05 ± 0.21 g/L of AA-2G. URS at 500 W/150 rpm, 55 °C, and pH 8.0 for 6 h yielded 6.6 ± 0.25 g/L of AA-2G. URS at 37 and 55 °C significantly increased CGTase activity. AA-2G yield using UR (400 W) was decreased by 9.7 % compared to that produced by SWB. However, the AA-2G yield using USS (500 W/150 rpm) at 37 and 55 °C increased by 11.9 and 4.8 %, respectively, with a reduction in process time of 41.7 and 75 %, respectively, compared to that previously produced by SWB.Conclusion: These results indicate that UR combined with shaking improves AA-2G production.Keywords: 2-O-α-D-glucopyranosyl-L-ascorbic acid, Ultrasonic radiation, Transglycosylation, Bacillus sp. SK13.00

Improving Natural Language Inference Using External Knowledge in the Science Questions Domain

Natural Language Inference (NLI) is fundamental to many Natural Language Processing (NLP) applications including semantic search and question answering. The NLI problem has gained significant attention thanks to the release of large scale, challenging datasets. Present approaches to the problem largely focus on learning-based methods that use only textual information in order to classify whether a given premise entails, contradicts, or is neutral with respect to a given hypothesis. Surprisingly, the use of methods based on structured knowledge -- a central topic in artificial intelligence -- has not received much attention vis-a-vis the NLI problem. While there are many open knowledge bases that contain various types of reasoning information, their use for NLI has not been well explored. To address this, we present a combination of techniques that harness knowledge graphs to improve performance on the NLI problem in the science questions domain. We present the results of applying our techniques on text, graph, and text-to-graph based models, and discuss implications for the use of external knowledge in solving the NLI problem. Our model achieves the new state-of-the-art performance on the NLI problem over the SciTail science questions dataset.Comment: 9 pages, 3 figures, 5 table

Investigations On The Carrier Rate Of Pasteurella Multocida In Black Rats (Rattus Rattus) In A Commercial Quail Farm

The aim was to investigate the level of Pasteurella Multocida infection from two anatomic sites of black rats (Rattus Rattus), popularly referred to as house or roof rats in a commercial quail farmhouse with recurrent fowl cholera outbreaks and also to evaluate the association between the Pasteurella Multocida found in rats co-habiting quail poultry houses and isolates from outbreaks of fowl cholera. Thus 100 pharyngeal and 100 rectum swabs samples taken from rats co-habiting farmhouse were obtained and evaluated bacteriologically for isolation of P. multocida; 54% of pharyngeal swabs and 62% of rectum swabs were positive for P. multocida. Extended phenotypic characterization of the isolates confirmed the presence of subspecies P. multocida multocida. Subspecies Pasteurella Multocida septica and gallicida were not encountered. Ramdom serotyping of 5 isolates each from the two sites confirmed serotypes A:4. Fowl cholera outbreaks were confirmed on the quail houses and carrier rats had the same Pasteurella Multocida subspecies and serotype as the infected quail. The public health significance of the finding is also discussed.African Journal of Clinical and Experimental Microbiology Vol. 10 (1) 2009: pp. 2-

Modelling the impact and cost-effectiveness of combination prevention amongst HIV serodiscordant couples in Nigeria

Objective: To estimate the impact and cost-effectiveness of treatment as prevention (TasP), pre-exposure prophylaxis (PrEP) and condom promotion for serodiscordant couples in Nigeria. / Design: Mathematical and cost modelling. / Methods: A deterministic model of HIV-1 transmission within a cohort of serodiscordant couples and to/from external partners was parameterized using data from Nigeria and other African settings. The impact and cost-effectiveness were estimated for condom promotion, PrEP and/or TasP, compared with a baseline where antiretroviral therapy (ART) was offered according to 2010 national guidelines (CD4+ <350 cells/μl) to all HIV-positive partners. The impact was additionally compared with a baseline of current ART coverage (35% of those with CD4+ <350 cells/μl). Full costs (in US $2012) of programme introduction and implementation were estimated from a provider perspective. / Results: Substantial benefits came from scaling up ART to all HIV-positive partners according to 2010 national guidelines, with additional smaller benefits of providing TasP, PrEP or condom promotion. Compared with a baseline of offering ART to all HIV-positive partners at the 2010 national guidelines, condom promotion was the most cost-effective strategy [US$1206/disability-adjusted-life-year (DALY)], the next most cost-effective intervention was to additionally give TasP to HIV-positive partners (incremental cost-effectiveness ratio US $1607/DALY), followed by additionally giving PrEP to HIV-negative partners until their HIV-positive partners initiate ART (US$7870/DALY). When impact was measured in terms of infections averted, PrEP with condom promotion prevented double the number of infections as condom promotion alone. / Conclusions: The first priority intervention for serodiscordant couples in Nigeria should be scaled up ART access for HIV-positive partners. Subsequent incremental benefits are greatest with condom promotion and TasP, followed by PrEP

BPIFB1 (LPLUNC1) is upregulated in cystic fibrosis lung disease

Although the biology the PLUNC (recently renamed BPI fold, BPIF) family of secreted proteins is poorly understood, multiple array based studies have suggested that some are differentially expressed in lung diseases. We have examined the expression of BPIFB1 (LPLUNC1), the prototypic two-domain containing family member, in lungs from CF patients and in mouse models of CF lung disease. BPIFB1 was localized in CF lung samples along with BPIFA1, MUC5AC, CD68 and NE and directly compared to histologically normal lung tissues and that of bacterial pneumonia. We generated novel antibodies to mouse BPIF proteins to conduct similar studies on ENaC transgenic (ENaC-Tg) mice, a model for CF-like lung disease. Small airways in CF demonstrated marked epithelial staining of BPIFB1 in goblet cells but staining was absent from alveolar regions. BPIFA1 and BPIFB1 were not co-localised in the diseased lungs. In ENaC-Tg mice there was strong staining of both proteins in the airways and luminal contents. This was most marked for BPIFB1 and was noted within 2 weeks of birth. The two proteins were present in distinct cells within epithelium. BPIFB1 was readily detected in BAL from ENaC-Tg mice but was absent from wild-type mice. Alterations in the expression of BPIF proteins is associated with CF lung disease in humans and mice. It is unclear if this elevation of protein production, which results from phenotypic alteration of the cells within the diseased epithelium, plays a role in the pathogenesis of the disease

The “Far-West” of Anopheles gambiae Molecular Forms

The main Afrotropical malaria vector, Anopheles gambiae sensu stricto, is undergoing a process of sympatric ecological diversification leading to at least two incipient species (the M and S molecular forms) showing heterogeneous levels of divergence across the genome. The physically unlinked centromeric regions on all three chromosomes of these closely related taxa contain fixed nucleotide differences which have been found in nearly complete linkage disequilibrium in geographic areas of no or low M-S hybridization. Assays diagnostic for SNP and structural differences between M and S forms in the three centromeric regions were applied in samples from the western extreme of their range of sympatry, the only area where high frequencies of putative M/S hybrids have been reported. The results reveal a level of admixture not observed in the rest of the range. In particular, we found: i) heterozygous genotypes at each marker, although at frequencies lower than expected under panmixia; ii) virtually all possible genotypic combinations between markers on different chromosomes, although genetic association was nevertheless detected; iii) discordant M and S genotypes at two X-linked markers near the centromere, suggestive of introgression and inter-locus recombination. These results could be indicative either of a secondary contact zone between M and S, or of the maintenance of ancestral polymorphisms. This issue and the perspectives opened by these results in the study of the M and S incipient speciation process are discussed

The evolving SARS-CoV-2 epidemic in Africa: insights from rapidly expanding genomic surveillance

Investment in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing in Africa over the past year has led to a major increase in the number of sequences that have been generated and used to track the pandemic on the continent, a number that now exceeds 100,000 genomes. Our results show an increase in the number of African countries that are able to sequence domestically and highlight that local sequencing enables faster turnaround times and more-regular routine surveillance. Despite limitations of low testing proportions, findings from this genomic surveillance study underscore the heterogeneous nature of the pandemic and illuminate the distinct dispersal dynamics of variants of concern—particularly Alpha, Beta, Delta, and Omicron—on the continent. Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve while the continent faces many emerging and reemerging infectious disease threats. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Sterol 14α-demethylase mutation leads to amphotericin B resistance in Leishmania mexicana

Amphotericin B has emerged as the therapy of choice for use against the leishmaniases. Administration of the drug in its liposomal formulation as a single injection is being promoted in a campaign to bring the leishmaniases under control. Understanding the risks and mechanisms of resistance is therefore of great importance. Here we select amphotericin B-resistant Leishmania mexicana parasites with relative ease. Metabolomic analysis demonstrated that ergosterol, the sterol known to bind the drug, is prevalent in wild-type cells, but diminished in the resistant line, where alternative sterols become prevalent. This indicates that the resistance phenotype is related to loss of drug binding. Comparing sequences of the parasites’ genomes revealed a plethora of single nucleotide polymorphisms that distinguish wild-type and resistant cells, but only one of these was found to be homozygous and associated with a gene encoding an enzyme in the sterol biosynthetic pathway, sterol 14α-demethylase (CYP51). The mutation, N176I, is found outside of the enzyme’s active site, consistent with the fact that the resistant line continues to produce the enzyme’s product. Expression of wild-type sterol 14α-demethylase in the resistant cells caused reversion to drug sensitivity and a restoration of ergosterol synthesis, showing that the mutation is indeed responsible for resistance. The amphotericin B resistant parasites become hypersensitive to pentamidine and also agents that induce oxidative stress. This work reveals the power of combining polyomics approaches, to discover the mechanism underlying drug resistance as well as offering novel insights into the selection of resistance to amphotericin B itself

Global, regional, and national burden of neurological disorders during 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015

Background Comparable data on the global and country-specific burden of neurological disorders and their trends are crucial for health-care planning and resource allocation. The Global Burden of Diseases, Injuries, and Risk Factors (GBD) Study provides such information but does not routinely aggregate results that are of interest to clinicians specialising in neurological conditions. In this systematic analysis, we quantified the global disease burden due to neurological disorders in 2015 and its relationship with country development level. Methods We estimated global and country-specific prevalence, mortality, disability-adjusted life-years (DALYs), years of life lost (YLLs), and years lived with disability (YLDs) for various neurological disorders that in the GBD classification have been previously spread across multiple disease groupings. The more inclusive grouping of neurological disorders included stroke, meningitis, encephalitis, tetanus, Alzheimer's disease and other dementias, Parkinson's disease, epilepsy, multiple sclerosis, motor neuron disease, migraine, tension-type headache, medication overuse headache, brain and nervous system cancers, and a residual category of other neurological disorders. We also analysed results based on the Socio-demographic Index (SDI), a compound measure of income per capita, education, and fertility, to identify patterns associated with development and how countries fare against expected outcomes relative to their level of development. Findings Neurological disorders ranked as the leading cause group of DALYs in 2015 (250·7 [95% uncertainty interval (UI) 229·1 to 274·7] million, comprising 10·2% of global DALYs) and the second-leading cause group of deaths (9·4 [9·1 to 9·7] million], comprising 16·8% of global deaths). The most prevalent neurological disorders were tension-type headache (1505·9 [UI 1337·3 to 1681·6 million cases]), migraine (958·8 [872·1 to 1055·6] million), medication overuse headache (58·5 [50·8 to 67·4 million]), and Alzheimer's disease and other dementias (46·0 [40·2 to 52·7 million]). Between 1990 and 2015, the number of deaths from neurological disorders increased by 36·7%, and the number of DALYs by 7·4%. These increases occurred despite decreases in age-standardised rates of death and DALYs of 26·1% and 29·7%, respectively; stroke and communicable neurological disorders were responsible for most of these decreases. Communicable neurological disorders were the largest cause of DALYs in countries with low SDI. Stroke rates were highest at middle levels of SDI and lowest at the highest SDI. Most of the changes in DALY rates of neurological disorders with development were driven by changes in YLLs. Interpretation Neurological disorders are an important cause of disability and death worldwide. Globally, the burden of neurological disorders has increased substantially over the past 25 years because of expanding population numbers and ageing, despite substantial decreases in mortality rates from stroke and communicable neurological disorders. The number of patients who will need care by clinicians with expertise in neurological conditions will continue to grow in coming decades. Policy makers and health-care providers should be aware of these trends to provide adequate services