Anomalously large capacitance of a plane capacitor with a two-dimensional electron gas

In electronic devices where a two-dimensional electron gas (2DEG) comprises one or both sides of a plane capacitor, the resulting capacitance $C$ can be larger than the "geometric capacitance" $C_g$ determined by the physical separation $d$ between electrodes. This larger capacitance is known to result from the Coulomb correlations between individual electrons within the low density 2DEG, which lead to a negative thermodynamic density of states (negative compressibility). Experiments on such systems generally operate in the regime where the average spacing between electrons $n^{-1/2}$ in the 2DEG is smaller than $d$, and these experiments observe $C > C_g$ by only a few percent. A recent experiment [1], however, has observed $C$ larger than $C_g$ by almost 40% while operating in the regime $nd^2 << 1$. In this paper we argue that at $nd^2 << 1$ correlations between the electronic charge of opposite electrodes become important. We develop a theory of the capacitance for the full range of $nd^2$. We show that, in the absence of disorder, the capacitance can be $4d/a$ times larger than the geometric value, where $a << d$ is the electron Bohr radius. Our results compare favorably with the experiment of Ref. [1] without the use of adjustable parameters.Comment: 8 pages, 6 figures; revised discussion of the zero density limit; some typos fixe

Changes in volatile compounds during ripening of Chorizo de Pamplona elaborated with Lactobacillus plantarum and Staphylococcus carnosus.

The ripening of chorizo de Pamplona was followed through the changes of the volatile compounds extracted by a simultaneous destilation-extraction with dichloromethane. An increase of the number and concentration of compounds was detected during the maturation, ranging from 63 compounds (10.26 mg dodecane/g dry matter) to 98 substances (223.16 mg of dodecane/g dry matter) identified in the mixing and in the final product, respectively. Acids showed the highest increase during the ripening, reaching 90% of the total amount of compounds at the end of the process, followed by esters and aldehydes. Short chain fatty acids, which contributed to the typical organoleptic charac teristics of dry fermented sausages, became apparent from the 21st day and accounted for only 1.3 mg of the total of acids in final product (202 mg dodecane/g dry matter). Sulphur compounds decreased slightly during the ripening, a result of the decrease in the content of the disulphide di- 2-propenyl, a compound originated from garlic

Potentials of Sludge from Drinking Water Treatment Plant for Use as Source of Soil Nutrients for Reclamation of Degraded Land

The residuals from Gubi drinking water treatment plant are usually discharged directly into the nearby streams without any form of treatment. The decomposition of the organic materials contained in the untreated sludge has caused the production of malodorous gases and unsightly condition in the area. The disposal of this sludge in an environmentally friendly manner is therefore not only desirable but necessary. The aim of this investigation was to assess the feasibility of utilizing the residuals from Gubi water treatment plant as a source of nutrients for reclamation of degraded lands especially those arising from mining activities. The study was carried out at Gubi water treatment plant located in the vicinity of Gubi Dam water reservoir.Ten sludge samples were collected from each of the three clerifiers. Important sludge properties that are known to aid nutrients status of soil were analyzed using standard laboratory procedures. The means of various soil quality parameters recorded in the WTRs were 6.8, 20.06g/kg, 34.90g/kg, 1.65g/kg, 2.30g/kg, 13.45mg/kg, 2.50Cmol/kg, 2.10Cmol/kg and 28Cmol/kg for pH, Organic C, Organic Matter, K, Total N, Olsen P, Ca, Mg and CEC respectively. The means of all the parameters analysed falls within the ranges considered good for vegetation growth. The heavy metals concentrations recorded in the residual were 1.8mg/kg, 0.1mg/kg, 2mg/kg, 29mg/kg, 66mg/kg, 15mg/kg, 8.7mg/kg, 6.2mg/kg and 0.03mg/kg for As, Cd, Pb, Cu, Zn, Ni, Co, Cr and Hg respectively. The concentrations of all the metals did not exceed the acceptable threshold limits recommended by regulatory authorities. Considering the enormous amount of plant nutrients and absence of excessive toxic metals in Gubi WTRs, it is safe to conclude that the residual can be use as a source of soil nutrients for reclamation of degraded land. Key words: Sludge, Soil Nutrients, Degraded Land, Reclamatio

Genotypic identification of coliforms isolated from cases of subclinical mastitis among pastoral herds in parts of Kaduna State, Nigeria

Background: Mastitis caused by Staphylococcus aureus was initially considered the major problem in dairy herds, but over the last few decades, the incidence of coliform mastitis has increased among the pastoral herds in Nigeria due to poor environmental and milking hygiene. Hence, this study was aimed at genotypic identification of coliform bacteria isolated from cases of bovine mastitis among pastoral herds in parts of Kaduna State, Nigeria.Methods: A cross-sectional survey of 30 herds of cows across 7 Local Government Areas of Kaduna State, Nigeria, was conducted. One hundred and forty seven cows were proportionately selected by purposive sampling technique. The milk samples were aseptically collected and bacteriologically screened for coliform bacteria following standard bacteriological techniques. Nine out of 12 coliforms identified phenotypically were selected for PCR amplification and sequencing of their 16S rRNA gene. The Basic Local Alignment Search Tool (BLAST) analysis of the sequences obtained was done on the National Centre for Biotechnology Information (NCBI) data base, and isolates confirmed based on similarity to 16S rDNA sequences in the Gen BankResults: Five of the 9 coliforms were confirmed to be Klebsiella pneumoniae (prevalence rate, 3.4%) and 4 were confirmed to be Escherichia coli (prevalence rate, 2.7%).Conclusion: This study shows that raw milk of mastitic cows can serve as a vehicle for the spread of pathogens such as K. pneumoniae and E. coli which, according to the Department of Health and Human Services of the United States Public Health Services, are potential threats to public health and safety of humans, animals and plant products.Keywords: pastoral herds, subclinical mastitis, cows, PCR, 16s rRNA, sequencin

Influence of the simultaneous addition of the protease flavourzyme and the lipase novozym 677BG on dry fermented sausage compounds extracted by SDE and analyzed by GC-MS

A dry fermented sausage (chorizo de Pamplona) was elaborated with the simultaneous addition of a lipase (Novozym 677BG) and a protease (Flavourzyme) and ripened during 21 days, in contrast to the control without enzymes and ripened during 35 days. Faster and more intense lipolytic and proteolytic activities were observed in the modified sausage, despite its shorter maturation time. At the end of the ripening, a determination of the profile of compounds extracted by simultaneous distillation-extraction with dichloromethane was carried out. The total amounts of extracted compounds (expressed in milligrams of dodecane per gram of dry matter) were 2.5 in the sausage with enzymes and 1.9 in the control. The chemical groups showing increments due to the use of enzymes were esters (103.5% increment) and acids (87% increment) in both cases due to the greater presence of long-chain fatty acid products. However, development of substances originated from further degradation process of amino acids and free fatty acids did not seem to have taken place

Analysis of volatile compounds by GC-MS of a dry fermented sausage: chorizo de Pamplona

The profile of volatile compounds of a typical Spanish dry fermented sausage, chorizo de Pamplona, has been analyzed by GC-MS, using a simultaneous distillation-extraction (SDE) system. Qualitative and quantitative differences were found in the volatile profiles obtained in the five analyzed commercial brands. One hundred and ninety three different substances were isolated, the group of acids being the most important from a quantitative point of view in all brands, accounting at least for the 60% of the total area. Aldehydes, basically from lipid oxidation, contributed between 7.72% and 13.97% to the total amount. Acids and aldehydes were the chemical families that showed the lowest variability among brands. In contrast, esters showed the highest coefficient of variation among brands (111%), followed by phenols (82%) and terpenes (76%). The variability observed in these three families could be attributed respectively to the different starter cultures, smoking process and spices employed in their production. Butylated hydroxytoluene (added as an antioxidant, E-321) was the third most abundant compound in 3 of the 5 brands

Efficacy of some bio-control agent formulations on scab of cowpea and groundnut late leaf spot in the Nigerian savanna

Field experiment on fungicidal efficacy of Trichoderma harzianum, Pseudomonas fluorescens and Bacillus cereus formulations against cowpea scab and groundnut late leaf spot was conducted. The trials were conducted in 2016 and 2017 rainy seasons on two farms of the Institute for Agricultural Research located at Samaru, Zaria (110 12′ N, 070 37′ E) in the Northern Guinea savanna and Minijbir, Kano (08031' E., l20 03' N) in the Sudan savanna. The formulations were applied as seed treatment, foliar spray and also incorporated into the soil by broadcasting the powdered formulations on the ridges. The experiment was laid in Randomized Complete Block Design replicated three times with five treatments which consisted of the three formulations, Funguforce (Mancozeb + Carbendazim) and control. Data were taken on plant emergence, pod yield, disease incidence and severity. Irrespective of the treatments, incidence of scab at both Samaru and Minjibir were at par. However, Funguforce application gave lowest mean scab severities of 10% and 8.5% at Minjibir and Samaru respectively in 2017. In 2016 at Samaru, P. fluorescens had the lowest incidence (50.57 %) while B. cereus had the lowest severity (14.40 %) of groundnut late leaf spot. At Minjibir however, T. harzianum recorded the lowest incidence (48.75 %) and severity (18.22 %). The incidence and severity of groundnut late leaf spot at Samaru in 2017 did not significantly vary while at Minjibir lowest incidence (9.77 %) and severity (9.73 %) were recorded on Funguforce. The microbial formulations recorded an average pod yield increase of 10 – 58 % which was comparable with that of Funguforce. The use of formulations of T. harzianum, P. fluorescens and B. cereus in the management of fungal diseases of cowpea and groundnut in the Nigerian savanna is therefore recommended.Keywords: Genetic-crosses, RILs, Polymorphisms, Genetic-Markers, EP

Detection of mycobacteria in raw cow milk sold in Bwari Area Council, Abuja FCT

Bovine tuberculosis (bTB) is an important zoonotic disease worldwide and hence it is of great public health significance. It is present in most developing countries where surveillance and control activities are often inadequate or unavailable. This study was designed to detect mycobacteria in raw milk of cows using ZN-stain, PCR, and cultural techniques to determine the prevalence of bTB in Bwari area council of FCT Abuja. Out of the 145 raw milk sampled, 6.89% tested positive by ZN-stain and culture while 1.3% were positive by PCR. The herd prevalence per satellite town based on ZN-stain technique was 8.89%, 10.0%, 3.33% and 5.00% for Bwari, Dei-Dei, Kubuwa and Ushafa respectively. While by cultural method, the prevalence was 2.22%, 10.00%, and 5.00% for Bwari, Dei-Dei, Kubuwa and Ushafa respectively. PCR revealed the prevalence of Mycobacterium species for Bwari and Dei-Dei as 2.22% and 3.33% respectively. Detection of Mycobacteria in raw (unpasteurized) pose a serious public health risk to raw milk consumers in Bwari area council.Keywords: Raw milk, bTB, ZN stain, PCR, Cultur

Structural Modification of Cellulosic Fabric via Esterification Using Balanites aegyptiaca Seed Oil

Cellulose fabrics were esterified by using varying volume of Balanites aegyptiaca seed oil. X-ray diffraction analysis was carried on the esterified fabrics and unesterified fabric. The crystallographs of all esterified fabrics gave almost the same profile different from that of control fabric. The control fabric gave a sharp single peak at 24.033º diffractometer angle. Esterified fabrics gave a slightly broad split peaks at lower diffractometer angles which ranged from 20.080 – 22.690º, suggesting that there was structural modification of cellulose. The inter-atomic distance (d-spacing) for control fabric was 3.7027 Å. There was increase in d-spacing which ranged from 3.9192 – 4.4216 Å for esterified fabric. The peak width increased from 1.5º (control) to range of 1.6 – 2.8º (esterified) fabrics. The peaks intensity increased from 5489 (control) to highest value (7798) for 30 cm3 of oil esterified fabric. The crystallite size reduced from 9.9 nm (control) to a maximum value (9.2 nm) for 40 cm3 and to minimum value (5.3 nm) for 10 cm3 oil esterified fabrics. The percentage crystallinity reduced from 65% (control) to a range of 62–63% for esterified fabrics. From the results obtained, it can be concluded that reduction in crystallite size, increase in d-spacing, intensity and peak width were due to the presence of a bulky ester group in the cellulose chain; this may also have led to the observed decrease in percentage crystallinity of the esterified fabrics. This structural modification is expected to have direct consequences on the physical and mechanical properties as well as the dyeing properties of the esterified fabrics

Ground-plane screening of Coulomb interactions in two-dimensional systems: How effectively can one two-dimensional system screen interactions in another?

The use of a nearby metallic ground-plane to limit the range of the Coulomb interactions between carriers is a useful approach in studying the physics of two-dimensional (2D) systems. This approach has been used to study Wigner crystallization of electrons on the surface of liquid helium, and most recently, the insulating and metallic states of semiconductor-based two-dimensional systems. In this paper, we perform calculations of the screening effect of one 2D system on another and show that a 2D system is at least as effective as a metal in screening Coulomb interactions. We also show that the recent observation of the reduced effect of the ground-plane when the 2D system is in the metallic regime is due to intralayer screening.Comment: 14 pages, 7 figures Accepted in PR