Calculation of tunneling current across Trapezoidal potential barrier in a Scanning Tunneling Microscope

The Planar Model of the Electrode-Vacuum-Electrode configuration for STM in which electrode surfaces are assumed to be infinite parallel planes, with atomic size separation and vacuum between them, is used to calculate tunneling current densities for both low and high bias voltages. Non WKB, Airy function solutions for the Schr\"odinger Equation for the trapezoidal barrier in the tunneling region are used to calculate the tunneling probability. Pauli blocking effects are found to cancel in the calculation of the net (Forward-Reverse) current density. Temperature dependent Fermi Factors for each electrode are introduced and the calculation involves integration over the electron energies. Thus the energy of the tunneling electrons is not limited to the Fermi energy in this calculation. In order to convert the current densities obtained in the planar model to tunneling currents the tip and sample surfaces cannot be treated as infinite plane surfaces. Instead the tip and the sample surfaces are modelled as confocal hyperboloids, and the tip sample distance is replaced by the length of the line of force (field line). The current is found by integrating the current density over a finite area of the tip. The calculated tunnel currents for a few electrode pairs at room temperature are plotted for several values of bias voltage and tip sample distances. The effect of the curvature of the tip is also studied by repeating the calculations for various tip radii. The dependence of tunneling current on electrode temperatures is also studied. Some estimate of lateral resolution and its dependence on bias voltage and tip radius is also presented.Comment: 14 pages,19 figure

On the communication of well-being

The form that any communicatory exchange takes would depend on the extent to which the interests of the signaller and the recipient are at variance. Where such interests coincide, i.e. in cases of mutualism, the signals may be conspicuous when an immediate response is favoured, but rather subtle and variable otherwise. Over 80 % of the events of tactile communication that we have noted in our study of the social behaviour of free ranging groups of tame elephants appear to belong to this latter category. On Smith's standard classification, they can only be classified as 'associative', related to remaining in the company of another individual. However, such signals are commoner by a factor of 20-100 amongst elephant calves and their mothers and allomothers when compared to exchanges between adult cows. We suggest that the function of these signals is mutual monitoring of the state of well being amongst related individuals. The considerable degree of altruistic behaviour displayed in social groups, such as those of elephants is now believed to subserve the function of enhancing the inclusive fitness of the individuals concerned. We explore a mathematical model of exchange of social aid which suggests that animals in social groups may enhance their inclusive fitness further by adjusting the amount of social aid exchanged in relation to the state of well being of the donor as well as the recipient. Our model further suggests that optimal social aid depends on the state of well being in a complex fashion making it difficult for the recipient to deceive the donor so as to extract more aid. We therefore expect that by and large honest communication of the state of well being would be characteristic of the higher social animals. Such communication would be based on normal physiological changes consequent on a change in well being. Thus animals with a superior degree of well being would take postures conducive to greater activity, would be more receptive to sensory inputs and may also shift the balance of production of various metabolites. This monitoring of the well being has greatly advanced in the human species and may be at the base of the elaborate health care amongst human societies

Glycosylated fibronectin positivity in the spectrum of hypertensive disorders of pregnancy in relation to the severity and adverse outcomes

Background: The aim of the study was to estimate the levels of glycosylated fibronectin (GlyFn) in preeclampsia (PE), and hypertensive disorders of pregnancy (HDP) and to correlate with the severity of the disease, adverse outcomes and complications. The study included 77 cases of HDP that were managed in the Institute of Obstetrics and Gynaecology, Modern Government Maternity Hospital (MGMH), Osmania Medical College, Hyderabad.Methods: This study was a prospective non-interventional analytical investigative study. To ascertain the performance of this biomarker, GlyFn, we evaluated the LumellaTM GlyFn POC test.Results: GlyFn positivity percentage was found to be highest in eclampsia (78.57%), next in PE with severe features 74.07%, in HELLP syndrome and gestational hypertension (HTN) (71.42%). In PE without severe features (66.66%) and in chronic HTN with PE superimposed (55.55%). Maternal complications include: abruption 5 (6.57%), thrombocytopenia 3 (3.94%), acute kidney injury (AKI) 3 (3.94%), post-partum hemorrhage (PPH) 3 (3.94%), and ascites 3 (3.94%). Perinatal outcome in 77 cases include: fetal growth restriction in 18 (23.37%) and total perinatal mortality was 14 (18.18%).Conclusions: GlyFn positivity was found to be highest in eclampsia and the severe forms of PE. The positivity declined in the less severe disease. The birth weight in the severe forms of PE group was significantly lower (p<0.0006). The differences in the birth weight among the GlyFn positive and normal groups was not significant for this population size (p=0.38).

Oreocnide integrifolia Flavonoids Augment Reprogramming for Islet Neogenesis and β-Cell Regeneration in Pancreatectomized BALB/c Mice

Agents which can either trigger proliferation of β-cells or induce neogenesis of β-cells from precursors would be of pivotal role in reversing diabetic manifestations. We examined the role of flavonoid rich fraction (FRF) of Oreocnide integrifolia leaves using a mice model of experimental regeneration. BALB/c mice were subjected to ~70% pancreatectomy (Px) and supplemented with FRF for 7, 14, and 21 days after pancreatectomy. Px animals displayed increased blood glucose levels and decreased insulin titres which were ameliorated by FRF supplementation. FRF-treated mice demonstrated prominent newly formed islets budding off from ducts and depicting increased BrdU incorporation. Additionally, transcripts levels of Ins1/2, Reg-3α/γ, Ngn-3, and Pdx-1 were upregulated during the initial 1 week. The present study provides evidence of a nutraceutical contributing to islet neogenesis from ductal cells as the mode of β-cell regeneration and a potential therapeutic for clinical trials in management of diabetic manifestations

Nonintrusive TCP Connection Admission Control for Bandwidth Management of an Internet Access Link

We describe our approach to monitoring and managing the bandwidth of an Internet edge link with a view towards certain quality of service objectives for the services it carries. Such a link could be, for example, a campus&apos;s Internet access link, or a small ISP&apos;s backbone access link. We use SNMP polls and packet snooping to obtain traffic statistics, and TCP admission control for bandwidth management. Our implementation is completely nonintrusive: we use Ethernet packet capture in the promiscuous mode for traffic analysis, and use IP masquerading for blocking new TCP connections. This approach has been implemented by us in a software system for traffic management. We first justify our approach with a simple analytical model. We give an overview of our software implementation, and discuss some implementation issues. Then we provide measurement results that show the effectiveness of the techniques. Keywords: Internet bandwidth management; admission control; quality of service; TCP perfo..

Power Management in IEEE 802.11 WLAN using Proxy-Assisted WLAN Controller

Abstract-Hand-held devices consume significant amount of energy while downloading large files or while streaming multimedia over a WLAN. IEEE 802.11 for WLANs provides PSM mechanism to reduce the energy consumption of a wireless device by allowing the wireless interface to go into sleep mode whenever possible. It is found that as stations (STAs) share the wireless channel at the packet level, wireless devices do not get enough opportunity to enter into the &apos;doze&apos; state, making PSM ineffective. In this paper we present implementation and experimental evaluation of an energy saving scheme implemented over a home-grown centralised WLAN performance enhancing device, ADWISER, ( assisted by a proxy server. Our implementation is based on the time slicing approach discussed in [4]