High-density Nano-scale N-channel Trench-gated MOSFETs Using the Self-aligned Technique

Identification of the microscopic structure of new hot carrier damage centers in short channel MOSFETs

A new application of metal oxide silicon field-effect transistor (MOSFET) devices is presented for solving the problem of drift in the characteristics of DC amplifiers under the effect of temperature variations in the range of 20-75°C. Expressions for the bias voltages and drain currents for operation at zero temperature coefficient for linear and nonlinear devices were derived. The validity of the derived expressions was checked experimentally for various samples of MOSFETs. These expressions were used to design the MOSFET stage to compensate for the drift of the DC amplifier. The amplifier has proved to be very reliable and can be adjusted for practically zero drift over a narrow band of temperatures. The drift was about 40 μV/°C over the range of 20-75°C and about 10 μV/°C over the range of 50-70°C. The 3-dB point in the frequency response is about 1.7 MHz. The overall gain is about 750 and the amplifier is capable of supplying a peak-to-peak output voltage of 3.0 V.

Chapter 2 - Power Semiconductors

A deep amorphization and solid phase epitaxial regrowth (AR) process to convert the initial crystal orientation has been investigated with the aim of co-integrating the (100) and the (110) Si surfaces on a buried oxide. P-channel metal oxide silicon field effect transistors(PMOSFETs) were fabricated on 20-nm-thick Si film silicon-on-insulator(SOI) wafers with and without the AR process. The electrical properties, such as the carrier mobility, transconductance, threshold voltage, and sub-threshold slope, were analyzed by comparing the AR-processed and the reference devices. The experimental results show that the AR process does not alter the original electrical properties of the material. Both (100)- and (110)- oriented Si films could be integrated on a continuous buried oxide.

In the brain, microglia are involved in immune responses and synaptic maturation. During early development, these cells invade the brain, proliferate, and morphologically mature to achieve coverage of the surrounding tissue with their fine processes. Their developmental proliferation overlaps with the postnatal development of neuronal circuits. Within the superior olivary complex (SOC), an auditory brainstem structure, microglia, and their early postnatal development have been documented. A quantification over the full developmental profile of the arrangement and morphological changes in single microglia cells is missing. Here, we used immunofluorescence labeling to quantify their distribution, morphological changes, and coverage during early and late postnatal development in the SOC of Mongolian gerbils. Microglia distributed rather homogenously within each nucleus with a bias to the nucleus borders at postnatal day (P) 5 and more centrally in the nucleus in mature stages. We found a nucleus-specific transient increase in microglia cell number and density reaching its peak at P17 with a subsequent decline to P55 values. Length and branching of microglia protrusions increased especially after P12. The stronger ramification together with the increase in cell density allows coverage of the surrounding tissue from P5 to mature stages, despite the large developmental increase in nucleus size. The transient increase in density during synaptic refinement in SOC nuclei suggests that microglia are important during the pruning period, compensating for developmental increase in tissue volume, and that in mature stages their main function appears tissue surveillance.

Effect of TCDD on the density of Langerhans cells in murine skin

This letter will present the n+–p junction characteristics in tantalum pentoxide gate dielectric (Ta2O5) and gate reoxidation ambient. The n+–p junctions in n-type metal–oxide–silicon field effect transistor fabricated with different gate dielectrics and post-thermal conditions were characterized by current–voltage measurements. The current–voltage measurements of junction leakage of Ta2O5 gate dielectric without gate reoxidation (MT1) show the hump characteristics due to the precipitates of oxide near the junction depletion regime. And their leakage mechanism is phonon-assisted tunneling, which facilitates the hopping of electrons from the valence band into the shallow attractive Coulomb center via the interface states in the precipitate, leaving holes in the valence band. However, the junction leakage currents of Ta2O5 dielectric with gate reoxidation in hydrogen rich ambient (MT2) are higher than those of thermal oxide samples and their leakage mechanism is Schottky barrier lowering due to the enhanced diffusion of oxygen into the junction depletion region.

The relationship between diffusion heterogeneity and microstructural changes in high-grade gliomas using Monte Carlo simulations

The amine precursor uptake and decarboxylase (APUD) cells in airways and small intestine of adult hamsters have been studied by quantitative, histochemical and immunocytochemical methods for the presence of argyrophilia, ACTH, hGH, calcitonin, bombesin and prolactin in control animals and following priming with two amine precursors: L-dopa and 5-hydroxytryptophane (5-HTP). APUD cells have been defined by the presence of intracytoplasmic argyrophilic granules. A method that related them to airway or gut perimeter length or total epithelial cell numbers has been applied. Calcitonin-like-immunoreactivity (CLIR) is present in epithelial cells in the tracheal epithelium and glands. The presence of ACTH, hGH, bombesin or prolactin is not detected. Priming with L-Dopa and 5-HTP results in up to 12 fold increases in densities of argyrophilic APUD cells in airways and ileum when ratios of APUD cells/100 nuclei are compared to those in control animals. Exposure to 5-HTP induces no significant changes in densities of cells with CLIR in the trachea but CLIR is not detected in animals exposed to L-DOPA. Ratios of APUD cells/100 epithelial cells appear to be more sensitive than those of APUD cells/mm in detecting significant changes in APUD cell densities. Priming with amine precursors is a valuable tool in quantitative studies of neuroendocrine cells.

Previously, we have showed that artificial epidermal permeability barrier disruption leads to an increase in epidermal Langerhans' cell (LC) density within 24 h. We now asked if this is accompanied by an enhancement of allergic contact dermatitis. Barrier disruption was induced by acetone on the upper arms in 6 volunteers with known sensitization to nickel, fragrance mix, or p-phenylenediamine. Twenty-four hours after this treatment the relevant allergen was applied without occlusion or with Finn chambers. Twenty-four hours after application of the allergen, clinical grading and transepidermal water loss (TEWL) measurements were performed and biopsies were taken. Immunohistochemical stainings for LCs (anti-CD1a, Leu6) and for epidermal proliferation (Ki-S3) were performed. Open applications of the allergens after acetone pretreatment resulted in strong allergic test reactions. TEWL, which showed a 70% recovery 24 h after acetone treatment, was increased again 4-fold by the allergic test reactions. LC density, which was increased by 80% 24 h after acetone-induced barrier disruption, was further enhanced 2.4-fold in total. Epidermal proliferation showed a 6-fold increase after open application of the allergens. Under patch test conditions after acetone pretreatment very strong bullous reactions were observed. We conclude that the increase in epidermal LC density induced by epidermal permeability barrier disruption is accompanied by an enhanced response in allergic contact dermatitis.

Computer models can be helpful tools to provide a better understanding of the mechanisms responsible for the complex movements of cyanobacteria resulting from changes in buoyancy and mixing of the water column in a lake. Kromkamp & Walsby (1990) developed a vertical migration model for Oscillatoria, that was based on the experimentally determined relationship between the rates of density change and photon irradiance in this cyanobacterium. To adapt this model to Microcystis, we determined related changes in carbohydrate content in cultures of Microcystis. Samples were incubated at various constant values of photon irradiance and then placed in the dark. The changes in carbohydrate content of the cells during these incubations were investigated. The relationship between the ratio of carbohydrate to protein and cell density in Microcystis was established to permit conversion of the rates of carbohydrate change to rates of density change. By plotting the calculated rates of density change against the values of photon irradiance experienced during the incubations, an irradiance-response curve of density change was established. The curve showed a distinct maximum at 278 mol photons m 2 s 1 . At higher values of photon irradiance, the rate of density change was strongly inhibited. A positive linear correlation was found between cell density and the rates of density decrease in the dark. The validity of the use of rate equations of density change, which are based on short-term incubations at constant values of photon irradiance, to predict density changes in Microcystis in fluctuating light regimes was tested. This was accomplished by measuring the time course of change in carbohydrate content of two continuous cultures of Microcystis, which were submitted to fluctuating light regimes, and comparing the results with the changes in the carbohydrate contents of these cultures predicted by the rate equations of carbohydrate change. The results showed good agreement: the rate equations of density change were therefore introduced into the model to simulate vertical migration of Microcystis .T he model predicts that the maximum migration depth of Microcystis will increase with colony size up to a maximum of 200 m radius. The effect of colony size on the net increase in cell density during the light period was also investigated with the model. It predicts that small colonies have a higher net increase in cell density than large colonies, but are inhibited at high photon irradiances at the surface.

Phenylethanolamine-N-methyltransferase-immunoreactive cells in developing rat superior cervical ganglion and the effect of hydrocortisone on their number

Background Intracerebroventricular streptozotocin injection at 3mg/kg of b/w causes phenotypes similar to that of sporadic Alzheimer’s disease (sAD) from 14th day post-injection. On the other hand, the body of evidence indicated that impairment in the sAD is the major contributor for cognitive decline. Taken together, we tested the adult neurogenesis hypothesis in streptozotocin model of sAD in female Wistar rats after extremely low magnetic stimulation (MF: 17.96, 50Hz, 2hr/day, 21days). Method 33 rats were randomly divided into three groups viz. Sham+MF, AD and AD+MF. Consequently, animals were first induced AD with stereotaxic manipulation and then they were exposed to low frequency magnetic field stimulation, followed by terminal cognitive behavioural tasks brain tissue being isolated for both biochemical and subcellular expression experiments (ethical no. 12/IAEC-1/2017). Results Showed reduction in latency to the goal quadrant (p= 0.002) and transfer latency (p= 0.045) in AD+MF group versus AD. Even, Dirichlet distribution of time spent in 4 quadrants indicated un-uniform in all the groups except AD group (p= 0.067, LRS= 7.35). Further, cell count in CA3 and DG exhibited increase in cell density in AD+MF group (p<0.05). However, we found significant reduction in SOD1 activity after MF treatment (p= 0.035) but no change in GSH level in hippocampus and frontal cortex. Interestingly, these changes in AD+MF animals are associated with increase in density of BrdU+/Nestin+ cells in granular layer (p= 0.002) and hilus region (p= 0.0005) of DG along with increase in expression of L-type Ca2+ channels as compared to AD group. Conclusion This experimental evidence suggests that non-invasive brain stimulation can promote adult neurogenesis by activating L-type ca2+ channels in the hilus, which intern helps in retention of long-term memory even after sAD.

The dependence of the cellular (biogenic) and frustule-associated (mineralized) silica content of the diatoms Navicula salinarum and Thalassiosira weissflogii on salinity and aluminium conditions was studied in order to make it possible to manipulate silicification in vitro and maximize it to levels required for physico-chemical frustule characterization by physisorption, X-ray scattering analysis and NMR, which is our ultimate objective. Enrichments with AlCl3 increased growth and the final cell density of the pennate N. salinarum, but not of the centric species T. weissflogii. Aluminium additions did not, however, result in a significant increase in the biogenic or mineralized silica content per cell and could not be detected in the silica matrix of the frustule. In contrast, lowering the salinity from 28 practical salinity units (PSU) to 20 and 15 resulted in a significant increase in the biogenic silica content per cell of both species, which is in line with an increase in density of the chemically derived silica under low salt conditions. The silica content per cell was variable during culture growth; increase in cell densities (during exponential growth) was accompanied by a decrease in contents of biogenic silica per cell. Electron microscopy and energy dispersive X-ray analysis (EDXA) support the chemical analyses and also suggest higher biogenic silica contents at lower salinities. The results indicate that besides silicate concentration and pH, the concentration of salts is an important inorganic factor that affects the silica polymerization inside the silica deposition vesicle of diatoms.

Literature assessing whether or not neurons (retinal ganglion cells and displaced amacrine cells) are lost from the retinal ganglion cell layer in mammals with age is still controversial, some studies finding a decrease in cell density and others not. To date there have been no studies estimating the total number of neurons in the retinal ganglion cell layer of humans throughout life. Recent studies have concentrated on the macular region and examined cell densities, which are reported to decrease during aging. In a study of the human retinal pigment epithelium (RPE), we showed that, while RPE cell number does not change, cell density increases significantly in central temporal retina (macular region) as the retina ages. We speculated that the increase in density represents a "drawing together" of the retinal sheet to maintain high cell densities, in this region of the neural retina, in the face of presumed cell loss from the ganglion cell layer due to aging. Here, therefore, we have sampled the entire ganglion cell layer of the human retina and estimated total neuron numbers in 12 retinae aged from 16 to 77 years. Human retinae, fixed in formalin, were obtained from the Queensland Eye Bank and whole-mounted, ganglion cell layer uppermost. The total number of neurons was lower in the older than younger retinae and neuronal density was lower in most retinal regions in older retinae. Retinal area increased with age and neuronal density fell throughout the retina with a mean reduction of 0.53% per year. However, the percentage reduction in density was much lower for the macular region, with a value of 0.29% per year. It is possible that this lesser reduction in cell density in the macula is a result of the drawing together of the retinal sheet in this region as we speculated from RPE data.