A 4 bit highly energy and area efficient SC SAR ADC based on a combinational technique with reduced reset energy

A combinational method, based on hybrid and junction splitting techniques, is used to realize a 4 bit high energy efficient SC SAR ADC. The hybrid switching scheme is very energy efficient in which the first three comparison cycles do not consume any energy. In junction split technique, the total value of capacitors does not remain constant. Rather capacitors are appended as bits are being determined successively. The present method combines the features of these two methods to realize an even more energy efficient SC SAR ADC. Reset energy, in some cases, can seriously impact the overall efficiency of a SC SAR ADC. A study has been made about the normal reset energy and two step reset energy for the different cases. A table has been drawn to show the overall energy efficiency for normal conversion, conversion with single step reset and lastly conversion with two step reset for all the architectures.

     

Effect of tunneling current on the noise characteristics of a 4H-SiC Read Avalanche diode

Noise characteristics of a Read Avalanche diode are analyzed by incorporating the tunneling mechanism of the electron into the avalanche mechanism.Analytical expressions are presented for the mean square noise voltage and noise measure in MITATT(mixed tunneling and avalanche transit time) mode operation.A wide band gap semiconductor(4H-SiC) based MITATT diode is considered to study the effect of tunneling on the noise characteristics and negative conductance.While exhibiting enough potential for 4H-SiC to be used as a terahertz source of power in the MITATT mode,our results record a noise measure of 35.18 dB at a frequency of 1.5 THz.     

Prospects of gallium nitride double drift region mixed tunneling avalanche transit time diodes for operation in F, Y and THz bands

The potential of GaN as a wide band gap semiconductor is explored for application as double drift region mixed tunneling avalanche transit time (MITATT) diodes for operation at 120 GHz, 220 GHz and 0.35 THz using some computer simulation methods developed by our group. The salient features of our results have uncovered some peculiarities of the GaN based MITATT devices. An efficiency of more than 20% right up to a frequency of 0.35 THz (from the GaN MITATT diode) seems highly encouraging but a power output of only 0.76 W is indicative of its dismal fate. The existence of a noise measure minimum at the operating frequency of 0.35 THz is again exhilarating but the value of the minimum is miserably high i.e. more than 33 dB. Thus, although GaN is a wide band gap semiconductor, the disparate carrier velocities prevent its full potential from being exploited for application as MTATT diodes.     

Effects of Ir Substitution and Processing Conditions on Thermoelectric Performance of p-Type Zr0.5Hf0.5Co1?xIrxSb0.99Sn0.01 Half-Heusler Alloys

A series of samples with the composition Zr_0.5Hf_0.5Co_1−x Ir _x Sb_0.99Sn_0.01 (x = 0.0 to 0.7) were synthesized by high-temperature solid-state reaction at 1173 K. High-density pellets of the powders were obtained using hot press (HP) and spark plasma sintering (SPS) techniques. The thermoelectric properties of the pellets were measured from 300 K to 750 K. Independently of the pressing conditions, all Ir-containing samples (x > 0) showed p-type semiconducting behavior. At 300 K, the electrical conductivity and thermopower of Zr_0.5Hf_0.5Co_1−x Ir _x Sb_0.99Sn_0.01 materials surprisingly increased with increasing Ir concentration. The largest electrical conductivity and thermopower values of 150 S/cm and 140 μV/K, respectively, were observed at 300 K for x = 0.7. The thermal conductivity of the synthesized materials decreased with increasing Ir content, went through a minimum value (x = 0.3), and increased thereafter with further addition of Ir. Pellets fabricated by SPS showed smaller thermal conductivity than pellets of the same composition obtained from uniaxial hot pressing. A thermal conductivity value of ∼2.0 W/m K was observed at 300 K for an SPS pellet with the com- position Zr_0.5Hf_0.5Co_0.5Ir_0.5Sb_0.99Sn_0.01. The thermal conductivity of Zr_0.5Hf_0.5- Co_1−x Ir _x Sb_0.99Sn_0.01 decreased with rising temperature, and the smallest value of ∼1.5 W/m K was observed at 750 K for the SPS specimen with x = 0.5.     

Low Force Measurement Based on Impedance of a Piezo-resonator

Piezoelectric transducers have effectively been used for force measurement due to their inherently large stiffness. The primary transduction parameter of piezoelectric transducer is voltage which is used mostly for dynamic and sometimes for quasi-static force measurement. Other parameters of piezoelectric transducers such as resonant frequency, electrical impedance, etc. have also been used for force measurement. In the present work, precision measurement of conductance of a radial mode piezo-resonator has been carried out under different static loading and the resultant change in resonant conductance of the resonator have been evaluated as a function of loading force. This method based on resonant conductance measurement can prove to be effective in measuring forces between two interfaces which is an important requirement in many scientific and technical problems.     

Synthesis and Antitumor Activity of Ether Glycerophospholipids Bearing a Carbamate Moiety at the sn‐2 Position: Selective Sensitivity Against Prostate Cancer Cell Lines

Analogues of 1‐O‐hexadecyl‐sn‐3‐glycerophosphonocholine (compounds 1 – 4 ) or sn‐3‐glycerophosphocholine (compound 5 ) bearing a carbamate or dicarbamate moiety at the sn‐2 position were synthesized and evaluated for their antiproliferative activity against cancer cells derived from a variety of tissues. Although all of the compounds are antiproliferative, surprisingly the carbamates ( 1 and 2 ) are more effective against the hormone‐independent cell lines DU145 and PC3 than toward other cancer cell lines we examined. This selectivity was not observed with the dicarbamates ( 3 and 4 ). Phosphocholine carbamate analogue 5 is as effective against the prostate cancer cell lines as the corresponding phosphonocholine analogue 1 . Cell death induced by 2′‐(trimethylammonio)ethyl 4‐hexadecyloxy‐3(R)‐N‐methylcarbamoyl‐1‐butanephosphonate (carbamate analogue 2 ) appeared to be mediated by apoptosis, as assessed by caspase activation and loss of mitochondrial membrane potential. The in vivo activity of 2 was evaluated in a murine prostate cancer xenograft model. Oral and intravenous administration showed that 2 is effective in inhibiting the growth of PC3 tumors in Rag2M mice. Our studies show that the glycerolipid carbamates reported herein represent a class of prostate‐cancer‐selective cytotoxic agents.     

Computational and experimental studies on bed dynamics of a gas–solid fluidized bed using Geldart-A particle: A comparison

The bed dynamics of a two-dimensional gas–solid fluidized bed is studied experimentally and computationally using Geldart-A particles. Commercial software ANSYS FLUENT 13 is used for computational studies. Unsteady behavior of gas–solid fluidized bed is simulated by using the Eulerian–Eulerian model coupled with the kinetic theory of granular flow. The two-equation standard k?? model is used to describe the turbulent quantities. The simulation predictions are compared with experimentally observed data on volume fraction, bed pressure drop and bed expansion ratio. The results of simulations are found to be in close agreement with the experimental observations, implying that computational fluid dynamics (CFD) can be used for the design of an efficient bench-scale catalytic fluidized bed reactor.     

A semiautomatic approach for segmentation of carotid vasculature from patients’ CTA images

Segmentation of vasculature specific to the patients’ carotid vasculature is a complicated and challenging task because of its complex geometrical structure and interconnections. Accurate or approximate digital phantoms of the vasculature are extremely useful in quick analysis of the vascular geometry and the modelling of blood flow in the cerebrovasculature. All these analyses lead to effective diagnosis and detection/localization of the diseased arterial segment in the cerebrovasculature. In this work, we have proposed a semiautomatic geodesic path propagation algorithm based on fuzzy distance transform to generate digital cerebrovascular phantoms from the patients’ CT angiogram (CTA) images. We have also custom-developed a 2-D/3-D user interface for accurate placement of user-specified seeds on the input images. The proposed method effectively separates the artery/vein regions from the soft bones in the overlapping intensity regions using minimal human interaction. Qualitative results along with 3-D rendition of the segmented cerebrovasculature on eight patients’ CTA images are presented here.     

Structure–Activity Relationships of Glucosamine‐Derived Glycerolipids: the Role of the Anomeric Linkage,the Cationic Charge and the Glycero Moiety on the Antitumor Activity

The potent antitumor activity of 1‐O‐hexadecyl‐2‐O‐methyl‐3‐O‐(2′‐amino‐2′‐deoxy‐β‐D ‐glucopyranosyl)‐sn‐glycerol ( 1 ) was previously shown to arise through an apoptosis‐independent pathway. Here, a systematic structure–activity study in which the effects of the anomeric linkage, the cationic charge and the glycero moiety on the antitumor activity is described. Eight analogues of 1 were synthesized, and their antitumor activity against breast (JIMT1 and BT549), pancreas (MiaPaCa2) and prostate (DU145, PC3) cancer was determined. 1‐O‐Hexadecyl‐2‐O‐methyl‐3‐O‐(2′‐amino‐2′‐deoxy‐α‐D ‐glucopyranosyl)‐sn‐glycerol ( 2 ) consistently displayed the most potent activity against all five cell lines with CC₅₀ values in the range of 6–10 μM . However, replacement of the O‐glycosidic linkage by a thioglycosidic linkage or replacement of the amino group by an azide or guanidino group leads to a threefold or greater decrease in potency. The glycero moiety also contributes to the overall activity of 1 and 2 but its effects are of lesser importance. Investigation into the mode of action of this class of compounds revealed that, in agreement with previous findings, the cytotoxic effects arise through induction of large acid vacuoles.