Tunneling phenomenon in heterostructure devices

A theoretical formulation for carrier current across hetero-interface in heterostructure semiconductor devices is presented using tunneling as the phenomenon. An analytical expression for the transmission coefficient as a function of energy using the Airy\u27s function and exponential solutions to Schroedinger\u27s equation for a linear potential variation is used in the calculations. This thesis addresses two theoretical problems: physics and modeling of gate current dependance on gate voltage in a heterostructure insulated gated field effect transistor (HIGFET) and, oscillations in the current-voltage characteristics of a double heterostructure bipolar transistor (DHBT); For HIGFETs, two components of tunneling currents, one from the decay of the quasi-bound resonant states in the accumulation well and the other from the tunneling electrons with kinetic energy above the bulk energy level, were considered. Moreover, the possibility of hot electrons is addressed. The reason for the large discrepancies between the experimental values and the theoretical values reported in earlier literature is attributed mainly due to the exclusion of the hot electron mechanism and the neglect of the contribution to current from the decay of the resonant states in the accumulation well; The origin of oscillations in the collector saturation current of a DHBT (with a set back layer) is investigated theoretically. Energy band balance was performed at the base-set back layer and set back layer-collector junctions to determine the distribution of the output voltage, {dollar}V\sb{BC}{dollar}, at these junctions and the conduction band edge profile using degenerate statistics. Theoretical results are in excellent agreement with the experimental results with {dollar}V\sb{BC}{dollar}\u27s at which the first two peaks of the {dollar}I\sb{D,sat}{dollar} occur matching closely. (Abstract shortened by UMI.)

CONTROLLING OF AN INDUSTRIAL ROBOTIC ARM

Most of industrial robots are still programmed using the typical teaching process, through the use of the robot teach pendant. In this paper is proposed an accelerometer-based system to control an industrial robot using two low-cost and small 3-axis wireless accelerometers. These accelerometers are attached to the human arms, capturing its behavior (gestures and postures). An Artificial Neural Network (ANN) trained with a back-propagation algorithm was used to recognize arm gestures and postures, which then will be used as input in the control of the robot. The aim is that the robot starts the movement almost at the same time as the user starts to perform a gesture or posture (low response time). The results show that the system allows the control of an industrial robot in an intuitive way. However, the achieved recognition rate of gestures and postures (92%) should be improved in future, keeping the compromise with the system response time (160 milliseconds). Finally, the results of some tests performed with an industrial robot are presented and discussed

A Rare Presentation of Odontogenic Keratocyst Mimicking an Antral Polyp

Maxillary sinus harbours many pathological lesions. Many of those presents as a sinonasal mass and are rarely symptomatic. These masses are usually an antral polyp, mucoceles or mucous retention cysts. Odontogenic keratocyst, a benign odontogenic lesion presenting within the maxillary sinus is a rare entity. We present a case of odontogenic keratocyst of the maxillary sinus in a 35 years old female

Multiferroic Core-Shell Nanofibers, Assembly in a Magnetic field and Studies on MagnetoElectric Interactions

Ferromagnetic-ferroelectric nanocomposites are of interest for realizing strong strain mediated coupling between electric and magnetic subsystems due to high surface area-to-volume ratio. This report is on the synthesis of nickel ferrite (NFO) -barium titanate (BTO) core-shell nano-fibers, magnetic field assisted assembly into superstructures, and studies on magneto-electric (ME) interactions. Electrospinning techniques were used to prepare coaxial fibers of 0.5-1.5 micron in diameter. The core-shell structure of annealed fibers was confirmed by electron microscopy and scanning probe microscopy. The fibers were assembled into discs and films in a uniform magnetic field or a field gradient. Studies on ME coupling in the assembled films and discs were done by magnetic field H induced polarization, magneto-dielectric effects at low frequencies and at 16-24 GHz, and low frequency ME voltage coefficients (MEVC). We measured 2~ 2-7% change in remnant polarization and in the permittivity for H = 7 kOe, and a MEVC of 0.4 mV/cm Oe at 30 Hz. A model has been developed for low-frequency ME effects in an assembly of fibers and takes into account dipole-dipole interactions between the fibers and fiber discontinuity. Theoretical estimates for the low-frequency MEVC have been compared with the data. These results indicate strong ME coupling in superstructures of the core-shell fibers

Association of triglycerides/high density lipoprotein cholesterol ratio with insulin resistance in polycystic ovary syndrome

Background: Insulin resistance (IR) is frequently observed in women with polycystic ovary syndrome (PCOS). Recent studies advocated that triglyceride to high-density lipoprotein cholesterol ratio (TG/HDL-C) can be used as a simple clinical indicator of IR. Hence, the present study was performed to investigate the use of TG/HDL-C and its association with IR in PCOS.Methods: Forty-one patients with PCOS and 40 healthy age matched women were randomly enrolled. Demographic and clinical characteristics were obtained. Insulin resistance was defined by the homeostasis model assessment for insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI).Results: In PCOS group, the insulin, HOMA-IR and TG/HDL-C ratio were significantly higher (p=0.001) than controls while, QUICKI was lower (p=0.001). Insulin, HOMA-IR were positively correlated with TG/HDL-C (ρ=0.303, p=0.006 and ρ=0.312, p=0.005 respectively) while, QUICKI was negatively correlated (ρ=-0.698, p=0.001). In receiver operating characteristic (ROC) analysis, area under the curve (AUC) for model based on QUICKI levels was better 0.898 (95% CI: 0.811-0.955, p=0.001) than HOMA-IR 0.636 (95% CI: 0.522-0.740, p=0.03). A cut-off value 3.23 for TG/HDL-C is proposed from the model based on QUICKI with best combination of sensitivity 83.3% and specificity 86.7%.Conclusions: Results of present study support that TG/HDL-C ratio may be a simple indicator of IR in PCOS patients which helps clinicians to identify IR in small centers, where the assays for insulin measurement are not available

Kloniranje, ekspresija i karakterizacija paraflagelarnog gena Rod 2 bičaša Trypanosoma evansi

Paraflagellar rod is the major structural component of the trypanosomatid flagellum and is identified as a complex lattice of filaments which runs parallel to the axoneme throughout most of the flagellar length. The present study was carried out to investigate the existence of the paraflagellar rod (PFR 2) gene in Trypanosoma evansi infecting Indian cattle. Local isolates of T. evansi collected from naturally infected cow were multiplied in Wistar rats. Complementary DNA (cDNA) was synthesized from the RNA of host cell free T. evansi parasites by reverse transcription. The gel purified PCR product (PFR 2 gene of T. evansi) was cloned into the pTZ57R/T vector system. The nucleotide sequence of the PFR 2 gene of the T. evansi S.V.V.U. isolate (Accession No. KT277497) obtained in the present study revealed 100% homology with T. evansi China isolate and 99% homology with T. evansi Izatnagar and Bikaner isolates. The recombinant protein was sub-cloned into pET 32a and expressed in the BL21 (DE3) pLysS expression system. The PFR 2 gene of T. evansi S.V.V.U. isolate was further characterized by determination of its protein profile with SDS-PAGE and western blotting. Indirect ELISA was optimized for detection of the specific antibody titre against the recombinant protein of the PFR 2 gene of T. evansi. In the kinetoplastid species the PFR 2 gene is highly conserved. Therefore the PFR 2 gene was suggested as a vaccine candidate, as well as a diagnostic antigen.Paraflagelarni štapić glavna je strukturna komponenta tripanosomskog biča i dio je kompleksa filamenaza koji teku paralelno s aksonemom duž biča. Istraživanje je provedeno kako bi se ispitalo postojanje paraflagelarnog gena Rod 2 (PFR2) u bičaša Trypanosoma evansi koji invadira goveda u Indiji. Lokalni izolat T. evansi prikupljen od prirodno invadiranih krava umnožen je u Wistar štakora. Komplementarna DNA (cDNA) sintetizirana je iz RNA obrnutom transkripcijom iz stanica neinvadiranih nositelja T. evansi parazita. Pročišćeni PCR produkt (gen PFR2 bičaša T. evansi) kloniran je u vektorski sustav pTZ57R/T. Nukleotidna sekvencija gena PFR2 bičaša T. evansi, izolat S.V.V.U. (pristupni broj KT277497) dobivena u ovom istraživanju pokazala je 100 %-tnu sličnost s izolatom T. evansi China i 99 %-tnu s izolatom T. evansi Izatnagar i Bikaner. Rekombinantni protein ponovno je kloniran u sustavu pET 32a i prikazan u sustavu BL21 (DE3) pLysS. Gen PFR2 bičaša T. evansi, izolat S.V.V.U. dalje je karakteriziran određivanjem proteinskog profila metodama SDS-PAGE i Western blotting. Indirektni test ELISA optimiziran je za dokaz titra specifičnih protutijela za rekombinantni protein gena PFR2 bičaša T. evansi. U kinetoplastida gen PFR2 izrazito je očuvan. Stoga bi se gen PFR2 mogao upotrijebiti za cjepivo te kao dijagnostički antigen