5,394 research outputs found
QCD analysis of neutrino charged current structure function F2 in deep inelastic scattering
An analytic expression for the neutrino charged current structure function F sub 2 (x, Q sup 2) in deep inelastic scattering, consistent with quantum chromodynamics, is proposed. The calculated results are in good agreement with experiment
The Odyssey Approach for Optimizing Federated SPARQL Queries
Answering queries over a federation of SPARQL endpoints requires combining
data from more than one data source. Optimizing queries in such scenarios is
particularly challenging not only because of (i) the large variety of possible
query execution plans that correctly answer the query but also because (ii)
there is only limited access to statistics about schema and instance data of
remote sources. To overcome these challenges, most federated query engines rely
on heuristics to reduce the space of possible query execution plans or on
dynamic programming strategies to produce optimal plans. Nevertheless, these
plans may still exhibit a high number of intermediate results or high execution
times because of heuristics and inaccurate cost estimations. In this paper, we
present Odyssey, an approach that uses statistics that allow for a more
accurate cost estimation for federated queries and therefore enables Odyssey to
produce better query execution plans. Our experimental results show that
Odyssey produces query execution plans that are better in terms of data
transfer and execution time than state-of-the-art optimizers. Our experiments
using the FedBench benchmark show execution time gains of at least 25 times on
average.Comment: 16 pages, 10 figure
A dual-mass resonant mems gyroscope design with electrostatic tuning for frequency mismatch compensation
The micro-electro-mechanical systems (MEMS)-based sensor technologies are considered to be the enabling factor for the future development of smart sensing applications, mainly due to their small size, low power consumption and relatively low cost. This paper presents a new structurally and thermally stable design of a resonant mode-matched electrostatic z-axis MEMS gyroscope considering the foundry constraints of relatively low cost and commercially available silicon-on-insulator multi-user MEMS processes (SOIMUMPs) microfabrication process. The novelty of the proposed MEMS gyroscope design lies in the implementation of two separate masses for the drive and sense axis using a unique mechanical spring configuration that allows minimizing the cross-axis coupling between the drive and sense modes. For frequency mismatch compensation between the drive and sense modes due to foundry process uncertainties and gyroscope operating temperature variations, a comb-drive-based electrostatic tuning is implemented in the proposed design. The performance of the MEMS gyroscope design is verified through a detailed coupled-field electric-structural-thermal finite element method (FEM)-based analysis
Germination of Themeda triandra (Kangaroo grass) as affected by different environmental conditions and storage periods
Low rainfall in range areas restricts germination, growth and development of majority of range grasses. However, germination and establishment potential of forage grasses vary and depends on environmental conditions. Themeda triandra is an excellent known grass to grow under different environmental conditions. T. triandra naturally grows over an extensive geographical range on many soil types. Germination of T. triandra is the key factor in its establishment or re-establishment because its germination varies widely which is also affected by storage periods of seed. Germination response of Themeda to storage period was conducted in the laboratory. Four storage periods (Fresh seed, 6, 12 and 18 months old) seeds were sown in laboratory in germination trays placed in growth chamber in completely randomized design. Germination was counted till 40 days after sowing and percentage calculated thereafter. The 12 month old seeds gave the maximum 84% germination. On the basis of laboratory experiment, 12 months seeds were sown at 3 diverse locations (Rawalpindi, Jhelum and Talagang) with 4 spacing treatments (20, 30, 40 and Broadcast) in completely randomized block design. Germination was recorded for 40 days after sowing (DAS) and the maximum germination was observed in 25 - 30 DAS depending on the environmental conditions of experimental sites. Closer plant spacing (20 cm) gave the maximum (79%) germination at high rainfall area (Rawalpindi) while the least (52%) was recorded for the wider plant spacing at low rain fall area (Talagang)
Cerebral fungal infection with mycotic aneurysm of basilar artery and subarachnoid haemorrhage
A 28-year-old Pakistani man was admitted with unresolved severe headaches for the past four weeks. Magnetic resonance (MR) imaging and MR angiography showed an enhancing mass in the sphenoid sinus, bilateral cerebellar infarcts and aneurysmal dilatation of the basilar artery. The differential diagnosis included fungal infection versus neoplastic lesion. The scrappings taken through the endoscope from the sphenoid sinus were initially negative for fungal infection. However, the second biopsy, done after putting him on antifungal, itraconazole 200 mg twice daily, revealed the presence of a fungal infection (aspergillosis). MR imaging revealed extension of the fungal infection from the sphenoid sinus into the clivus, and then intracranially. Imaging also revealed aneurysmal dilatation of the basilar artery and infarctions in the cerebellum and subarachnoid haemorrhage. Despite aggressive antifungal treatment, the Patient died after 29 days. This case report describes the probable mechanism of fungal mycotic aneurysmal vascular dilatation and growth. It also points to the need for a rapid diagnosis of potential cases and an aggressive treatment approach of confirmed cases of fungal infections of the central nervous system
Cytotoxic Effect of Ethanol Extract of Convolvulus arvensis L (Convolvulaceae) on Lymphoblastic Leukemia Jurkat Cells
Purpose: To evaluate the cytotoxic effect of ethanol extract of aerial parts of Convolvulus arvensis against lymphoblastic leukemia, Jurkat cells.Methods: The aerial parts of C. arvensis were collected, identified, powdered and soaked in ethanol. The extract was filtered and evaporated, and the residue assessed for cytotoxic activity in Jurkat cell line. The cells were exposed to different concentrations (10, 25, 50, 75 and 100 μg/mL) of the extract to determine cell viability, cell proliferation, apoptosis using Trypan blue exclusion assay, 3-(4,5- dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay and fluorescent activated cell sorter (FACS) analysis, respectively.Results: Trypan blue exclusion assay and MTS assay results indicate that the ethanol extract decreased the number of living cells in a concentration-dependent fashion. The results of FACS analysis showed that the lowest concentration of the extract (10 μg/mL) was most effective for the induction of apoptosis as it induced maximum apoptosis (85.34 %) and the highest concentration (100 μg/mL) was less effective as it induced less apoptosis (53.70 %) in Jurkat cells (p < 0.05).Conclusion: The ethanol extract of C. arvensis has significant cytotoxic activity against the selected cancer cell line. Furthermore, apoptotic effect was more prominent at lower doses and necrosis at higher doses of the extract.Keywords: Convolvulus arvensis; (MTS) 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4- sulfophenyl)-2H-tetrazolium assay; Trypan blue exclusion assay, Apoptosis, Necrosi
Conserved Quantities in Noncommutative Principal Chiral Model with Wess-Zumino Term
We construct noncommutative extension of U(N) principal chiral model with
Wess-Zumino term and obtain an infinite set of local and non-local conserved
quantities for the model using iterative procedure of Brezin {\it et.al}
\cite{BIZZ}. We also present the equivalent description as Lax formalism of the
model. We expand the fields perturbatively and derive zeroth- and first-order
equations of motion, zero-curvature condition, iteration method, Lax formalism,
local and non-local conserved quantities.Comment: 14 Page
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Abandoned Well Characterization: A Methodology to Evaluate Regional Hydraulic Controls on Flow From Hydrocarbon Reservoirs into Underground Sources of Drinking Water
Between 1859 and 1990, approximately 3.3 million wells for oil and gas exploration and production were drilled in the U.S., of which nearly 2.4 million have been shut-in, temporarily abandoned, or plugged and abandoned (World Oil, 1992). Several major petroleum basins in the country contain large populations of these wells. Because drilling, completion, and abandonment practices for wells have evolved over the years, older wells that were found to be unproductive (or dry), or which had to be permanently shut-in for mechanical problems or economic reasons, may not have been adequately plugged according to modern standards or regulations. In some instances, upward movement of saltwater in such abandoned wells may pose a risk of contamination to underground sources of drinking water (USDWs).
Three main conditions must exist for contamination of a USDW to occur by fluid migration from an oil and gas production zone or a waste disposal zone: (1) presence of a USDW overlying the zone; (2) presence of unplugged or inadequately plugged abandoned wells (or natural geologic pathways) that penetrate both a production or disposal zone and a USDW; and (3) an upward-directed hydraulic gradient between the zone of interest and the USDW. The first condition exists in many of the petroleum-producing areas in the U.S. However, the second and third conditions may or may not occur. In particular, the third condition depends in part upon the changes in pressure due to fluid withdrawal and injection associated with enhanced recovery or salt-water disposal (Class II wells).Bureau of Economic Geolog
Green and facile synthesis of cerium doped Ni3Fe electrocatalyst for efficient oxygen evolution reaction
Electrochemical water splitting is the most promising pathway to produce high-purity hydrogen to alleviate global energy crisis. This reaction demands inexpensive, efficient and robust electrocatalyst for its commercial use. Herein, we demonstrate an effective, facile and scalable method for the synthesis of cerium doped Ni3Fe nanostructures as an electrocatalyst for oxygen evolution reaction (OER) by following simple chemical bath deposition route. The different molar ratios (3, 6 and 12 mM) of cerium in the chemical bath were used to study its effect on the structural and the electrochemical properties of the Ni3Fe nanostructured films. Doping of cerium contents induced variations in the morphology of deposited Ni3Fe nanostructures. The optimized electrocatalyst Ni3Fe/Ce-6 yielded high surface area catalyst nanosheets uniformly deposited on three-dimensional conductive scaffold to ensure increase in the exposure of doped Ni3Fe catalytic sites with high electrical conductivity. As a result, this earth-abundant electrocatalyst affords high OER performance with a small overpotential of 310 mV versus reversible hydrogen electrode (RHE) at 10 mA cm-2 and retains good stability up to ~ 10 h in alkaline electrolyte. This scalable strategy has great potential in future advancement of efficient and low-cost electrocatalysts for their large-scale application in energy conversion systems.
KEY WORDS: Oxygen evolution, Electrocatalyst, Ni3Fe nanostructures, Cerium, Alkaline electrolyte
Bull. Chem. Soc. Ethiop. 2020, 34(2), 353-363
DOI: https://dx.doi.org/10.4314/bcse.v34i2.1
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