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

The meaning of different forms of structural myocardial injury, immune response and timing of infarct necrosis and cardiac repair

Although a decline in the all-cause and cardiac mortality rates following myocardial infarction (MI) during the past 3 decades has been reported, MI is a major cause of death and disability worldwide. From a pathological point of view MI consists in a particular myocardial cell death due to prolonged ischemia. After the onset of myocardial ischemia, cell death is not immediate, but takes a finite period of time to develop. Once complete myocytes’ necrosis has occurred, a process leading to a healed infarction takes place. In fact, MI is a dynamic process that begins with the transition from reversible to irreversible ischemic injury and culminates in the replacement of dead myocardium by a fibrous scar. The pathobiological mechanisms underlying this process are very complex, involving an inflammatory response by several pathways, and pose a major challenge to ability to improve our knowledge. An improved understanding of the pathobiology of cardiac repair after MI and further studies of its underlying mechanisms provide avenues for the development of future strategies directed toward the identification of novel therapies. The chronologic dating of MI is of great importance both to clinical and forensic investigation, that is, the ability to create a theoretical timeline upon which either clinicians or forensic pathologists may increase their ability to estimate the time of MI. Aging of MI has very important practical implications in clinical practice since, based on the chronological dating of MI, attractive alternatives to solve therapeutic strategies in the various phases of MI are developing

HSV-1 and endogenous retroviruses as risk factors in demyelination

Herpes simplex virus type 1 (HSV-1) is a neurotropic alphaherpesvirus that can infect the peripheral and central nervous systems, and it has been implicated in demyelinating and neurodegenerative processes. Transposable elements (TEs) are DNA sequences that can move from one genomic location to another. TEs have been linked to several diseases affecting the central nervous system (CNS), including multiple sclerosis (MS), a demyelinating disease of unknown etiology influenced by genetic and environmental factors. Exogenous viral transactivators may activate certain retrotransposons or class I TEs. In this context, several herpesviruses have been linked to MS, and one of them, HSV-1, might act as a risk factor by mediating processes such as molecular mimicry, remyelination, and activity of endogenous retroviruses (ERVs). Several herpesviruses have been involved in the regulation of human ERVs (HERVs), and HSV-1 in particular can modulate HERVs in cells involved in MS pathogenesis. This review exposes current knowledge about the relationship between HSV-1 and human ERVs, focusing on their contribution as a risk factor for MS

A newly discovered antler flint-knapping hammer and the question of their rarity in the Palaeolithic archaeological record: Reality or bias?

The use of soft (bone, antler, tooth and wood) hammers and retouchers is a key innovation in early stone tool technology, first appearing in the archaeological record with Lower Palaeolithic handaxe industries (e.g. Boxgrove, UK ~ 500 kya). Although organic knapping tools were undoubtedly a component of early human toolkits and are essential, for example, for the manufacture of finely-flaked handaxes, Mousterian scrapers and Upper Palaeolithic blades tools, such archaeological finds are exceptionally rare. In this study, we present qualitative and quantitative analyses (focus variation optical microscope, scanning electron microscope, micro-CT scanning and energy dispersive X-ray spectroscopy), to characterise use-damage on an antler base from Laugerie-Haute West (France). This specimen was originally identified as a waste-product from splinter manufacture, and the use-damage appears to have been missed. The new analysis shows that prior to being used as a flint-knapping percussor, the red deer antler had been further modified to reduce the length of its beam and to remove the tines. Although minimally used, characteristic use-damage includes attrition (pits and scores), compression of the antler matrix and flint chips embedded within some of the percussion features on the base of the burr. An AMS radiocarbon date of 12385 ± 55 BP (12647 ± 335 BC calibrated) confirms a Magdelanian context for the hammer. The fact that the Laugerie Haute knapping hammer went unrecognised in a well-studied and accessible collection for almost 200 years since its discovery, suggests that antler hammers may be more common than generally assumed. Only further re-examination of prehistoric antlers in museum collections will confirm whether the apparent rarity of antler hammers during the Lower and Middle Palaeolithic is real phenomenon or the result of analytical biases

Response of Broiler Birds to Choline Chloride in Semi Arid Sokoto, Nigeria

A study was carried out to evaluate growth performance and carcass characteristics of broiler birds fed with varying level of choline inclusion in their diets; T1 (control), T2 (10g/10kg) and T3 (20g/10kg). A total of 225 marshall broiler chicks were randomly divided into three (3) treatment group of 75 birds each. Each group was divided into five (5) replicates of fifteen (15) birds each laid in a completely randomized design. Feed and water was supplied ad-libitum and the experiment lasted for 49 days. The total feed intake (1316.75-14442.18) (24437.13-31999.76) for starter and finisher respectively, body weight gain (6227.30-8241.20) (10956.64-14182.96) for starter and finisher respectively, feed conversion ratio (1.73-2.26) (2.21-2.48) for starter and finisher respectively. Many (thigh, wings, back) of the carcass parameters measured were not significantly (p>0.05) affected by the treatments but significant difference (p<0.05) was observed in drum stick, breast and neck.  However, significant difference (p<0.05) was also observed in gizzard, liver and bile, heart, lungs, legs and head. There was significant difference (p<0.05) in primal cuts per live weight, primal cuts per dressed weight, organs per live weight and organs per dressed weight. In view of the results obtained, it can be concluded that treatment two (10g/10kg) performed better in terms of total body weight (TBW) and feed conversion ratio (FCR). Also in the carcass characteristics, treatment two performed better in terms of breast yield, drumstick, percentage of primal cuts from live weight (P/LW) and percentage of primal cuts from dressed weight

Characterisation of AMS H35 HV-CMOS monolithic active pixel sensor prototypes for HEP applications

Monolithic active pixel sensors produced in High Voltage CMOS (HV-CMOS) technology are being considered for High Energy Physics applications due to the ease of production and the reduced costs. Such technology is especially appealing when large areas to be covered and material budget are concerned. This is the case of the outermost pixel layers of the future ATLAS tracking detector for the HL-LHC. For experiments at hadron colliders, radiation hardness is a key requirement which is not fulfilled by standard CMOS sensor designs that collect charge by diffusion. This issue has been addressed by depleted active pixel sensors in which electronics are embedded into a large deep implantation ensuring uniform charge collection by drift. Very first small prototypes of hybrid depleted active pixel sensors have already shown a radiation hardness compatible with the ATLAS requirements. Nevertheless, to compete with the present hybrid solutions a further reduction in costs achievable by a fully monolithic design is desirable. The H35DEMO is a large electrode full reticle demonstrator chip produced in AMS 350 nm HV-CMOS technology by the collaboration of Karlsruher Institut f\"ur Technologie (KIT), Institut de F\'isica d'Altes Energies (IFAE), University of Liverpool and University of Geneva. It includes two large monolithic pixel matrices which can be operated standalone. One of these two matrices has been characterised at beam test before and after irradiation with protons and neutrons. Results demonstrated the feasibility of producing radiation hard large area fully monolithic pixel sensors in HV-CMOS technology. H35DEMO chips with a substrate resistivity of 200$\Omega$ cm irradiated with neutrons showed a radiation hardness up to a fluence of $10^{15}$n$_{eq}$cm$^{-2}$ with a hit efficiency of about 99% and a noise occupancy lower than $10^{-6}$ hits in a LHC bunch crossing of 25ns at 150V

Conversion of lignocellulose from palm (Elaeis guineensis) fruit fibre and physic (Jatropha curcas) nut shell into bio-oil

Harmful gases are released into the atmosphere through burning of residues which is commonly practiced in Nigeria and can be attributed to climate change issues. Agricultural residues have the potentials to be used as energy and chemical source and meet its deficit in the country. This paper focuses on utilization of lignocellulosic materials obtained from two agricultural residues through renewable technology to produce bio-energy and chemical feedstock. The lignocellulosic materials were extracted from palm fruit (Elaeis guineensis) fibre and physic nut (Jatropha curcas) shell, and pyrolyzed under low temperature and pressure at various particle sizes. The main properties of solid (lignocellulosic) materials were tested and the bio-oil produced was analyzed using GC-MS. Results show proximate analyses (volatile, ash and fixed carbon contents) and ultimate analysis (carbon, oxygen, nitrogen, magnesium, phosphorus and zinc). The pH value of the bio-oil from both residues increased with increase in temperatures. The density, viscosity and calorific value of the palm and physic residue oil are 831.99 and 947.5 kg/m3, 0.695 and 1.58 cPa at room temperature, 22.33 and 14.169 kJ/g, respectively. Aromatics and other compounds are major dominant compounds in the palm fruit fibre oil which is characterized for bio-fuel production. Physic nut shell oil contains aromatic ethers, cyclic ethers, secondary amides and organic halogen compound which are important chemical feedstock. Conversion of these residues to useful products will alleviate the energy supply deficit, improve social and economic development, promote clean and healthy atmosphere of the nation and significantly contribute to global climate change mitigation

Screening for diabetes mellitus in a Nigerian family practice population

Background Diabetes mellitus is a non-communicable disease with a rising prevalence worldwide. Most of the increase in prevalence is projected to be in the developing countries. As it is recognised that the onset of the disease and its complications predate the symptoms, it is expedient that screening procedures are undertaken to diagnose the disease in the individual as early as possible to minimise the risk of complications. Diabetes mellitus is a chronic disease necessitating life-long therapy, usually with drugs. This creates a life-long financial burden on the family, especially in low socio-economic communities in West Africa, where the majority of the population still lives on less than one dollar a day. This affects the wellbeing of the entire family, hence the need for early detection, prompt and adequate management of the disease and avoidance of its complications. Methods The study is an incidental screening to determine the prevalence of diabetes mellitus, its risk factors and the clinical characteristics of diabetics in a Nigerian family practice population. Four hundred and twenty subjects aged 15 years or older were recruited by systematic random sampling in a family practice in South West Nigeria over a three-month period. Data collected include the subjects\' socio-demographic data, family history of diabetes mellitus and hypertension, and history of tobacco and alcohol use. The subjects\' weight and height were measured and their body mass index (BMI) calculated. Each subject was examined for peripheral neuropathy, lens opacity and hypertension. Fasting blood glucose was measured using a glucometer and urine was tested for albumin. Those with a fasting blood glucose of greater than 6.1 had a fasting blood glucose determination by the standard spectrophotometric method. Results Ten (2.38%) subjects were known diabetics, while 57 (13.6%) were known hypertensives. Ten (2.38%) new diabetics were identified, and 7.5% of the females compared to 5.8% of the males were diabetic. Alcohol intake, obesity, age above 44 years and a positive parental history of diabetes were the significant risk factors (p < 0.01) for diabetes in the study. Proteinuria and peripheral neuropathy were the significant complications (p < 0.01). Conclusions It is concluded that diabetes is a common problem in our practice, with a prevalence of 4.76%, half of which was previously undiagnosed. Alcohol intake, obesity, positive parental history and age over 44 years were the identified risk factors. Peripheral neuropathy, proteinuria and high blood pressure were the identified complications. It is recommended that routine screening of people at high risk of diabetes mellitus in family practice be commenced. The glucometer, a relatively cheap item of equipment in the practice, is a highly useful, sensitive and specific tool for this purpose. South African Family Practice Vol. 49 (8) 2007: pp. 1

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

Heavy Metals Accumulation and Phytoremediation Ability of Onion (Allium cepa) and Garlic (Allium sativum) Grown on Contaminated Soils from Challawa Industrial Estate, Kano, Nigeria

This work was designed to assess and compare the heavy metals accumulation and phytoremediation ability of some allium species (Garlic; Allium sativum and Onion; Allium cepa) grown on two different soils (contaminated and Control soils) using standard methods. Heavy metals (of Cr, Fe, Mn, Ni, Pb, and Zn) Concentrations (mg/Kg) were determined using atomic absorption spectrophotometry (AAS Model: 210VGP). Plants growth and biomass production were assessed. Biological concentration factors (BCF) and translocation factors (TF) were calculated. The mean levels of elements obtained ranged widely from 0.55 mg/Kg Ni to 1830.64 mg/Kg Fe. The results showed that onion accumulated higher concentrations of all the heavy metals compared to garlic with exception of Zn. However, the differences in heavy metal concentrations where significant only in Cr and Mn. Phytoremediation efficiency indices (BCF and TF) showed a similar trend for both onion and garlic. The mean BCF values of Pb, Cr, Zn, Mn and Fe in onion were generally high &gt; 1. Ni and Pb had their mean TF values greater than 1. Thus, onion can be used as potential phytoextraction plant. The similarities in most of these metal accumulation trends, BCF and TF between onion and garlic might be due to their being similar species with similar physiological features and from the same family