Photoinduced anomalous current changes in some organometallic materials

Aloke Kumar Chakraborty,Biswanath Mallik 한국물리학회 2009 Current Applied Physics Vol.9 No.5

Photoinduced changes have been investigated by monitoring electrical measurements in some organometallic materials such as ferrocene derivatives, namely, ferrocenecarboxylic acid [Fc(COOH)], acetylferrocene [Fc(COCH3)], ferrocenecarbaldehyde [Fc(CHO)], hydroxymethylferrocene [Fc(CH2OH)]. The investigations were performed in dry nitrogen gas atmosphere at different constant temperatures. Powdery materials were used in sandwich type of cell configuration with constant d.c. bias voltage (27 V) and were exposed to polychromatic light source. Measurements performed in Fc(COCH3) and Fc(CH2OH) with a fixed intensity of exciting light source have shown a drastic change (usual to unusual) in the current vs. time profile. The similar measurement conditions in case of Fc(COOH) and Fc(CHO) showed the unusual/ anomalous current vs. time profiles in their entire temperature range of study. Anomalous changes that have been observed in the plot of the photocurrent vs. reciprocal of temperature for each material were completely absent in their corresponding dark current behaviour. The photoinduced changes were almost reversible along with some fluctuations/instabilities in equilibrium current measured after switching off the light source in a particular temperature range. The observed anomalous changes in photocurrent with time and cell temperature have been explained. The effects of various functional groups substituted into ferrocene-unit have been discussed. Photoinduced changes have been investigated by monitoring electrical measurements in some organometallic materials such as ferrocene derivatives, namely, ferrocenecarboxylic acid [Fc(COOH)], acetylferrocene [Fc(COCH3)], ferrocenecarbaldehyde [Fc(CHO)], hydroxymethylferrocene [Fc(CH2OH)]. The investigations were performed in dry nitrogen gas atmosphere at different constant temperatures. Powdery materials were used in sandwich type of cell configuration with constant d.c. bias voltage (27 V) and were exposed to polychromatic light source. Measurements performed in Fc(COCH3) and Fc(CH2OH) with a fixed intensity of exciting light source have shown a drastic change (usual to unusual) in the current vs. time profile. The similar measurement conditions in case of Fc(COOH) and Fc(CHO) showed the unusual/ anomalous current vs. time profiles in their entire temperature range of study. Anomalous changes that have been observed in the plot of the photocurrent vs. reciprocal of temperature for each material were completely absent in their corresponding dark current behaviour. The photoinduced changes were almost reversible along with some fluctuations/instabilities in equilibrium current measured after switching off the light source in a particular temperature range. The observed anomalous changes in photocurrent with time and cell temperature have been explained. The effects of various functional groups substituted into ferrocene-unit have been discussed.

Evaluation of isosorbide-5-mononitrate as a cervical ripening agent prior to induced abortion in contrast to misoprostol- a randomized controlled trial

De Aloke Kumar,Bhattacharyya Sanjoy Kumar,Chakraborty Aparna,Samanta Amrita 대한산부인과학회 2019 Obstetrics & Gynecology Science Vol.62 No.5

ObjectiveTo determine whether vaginal application of 40 mg isosorbide-5-mononitrate (ISMN) has a comparable cervicalripening efficacy to and lesser side effects than 400 μg misoprostol in women scheduled for the first trimester inducedabortion using a manual vacuum aspirator (MVA). MethodsWe conducted a prospective randomized open-label study in 70 women at 6–12 weeks of pregnancy at the R G KarMedical College and Hospital, Kolkata, India, over a period of two years from 2015 to 2017. Forty milligrams of ISMNand 400 μg misoprostol were vaginally applied for cervical priming. The primary outcome measure was the cervicalresponse assessed by the passage of the appropriate and largest sized MVA cannula through the internal os withoutresistance, at the beginning of the procedure. ResultsThe base line cervical dilatation was found to be significantly higher in the misoprostol group than in the ISMN group(7.65±1.38 vs. 6.9±1.26 mm; P=0.025, 95% confidence interval, −1.4046 to −0.953). However, when the women weresub-analyzed based on parity, there was no statistically significant difference in the same parameters among themultigravid women. The need for further cervical dilatation was significantly higher in the ISMN group when theprimigravid women were compared, although the multigravid women responded favorably to ISMN. ConclusionIn the primigravid women, misoprostol appears to exert a higher efficacy as a cervical ripening agent in contrast toISMN. However, ISMN can be used in multigravid women for the same purpose as in this group, misoprostol did notshow any significant improvement in efficacy over ISMN.

Hawking decay and thermodynamic transformation of a black hole: two examples

Sinha Aloke Kumar 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.80 No.4

The criterion for thermodynamic stability of rotating electrically charged quantum black holes was already derived by us. They appeared as a collection of inequalities connecting second-order derivatives of the black hole mass with respect to its horizon area, electric charge and angular momentum. We got similar results when this analysis was extended to black holes in arbitrary dimensional spacetime with any number of parameters that determine the mass of the black hole. Many black holes were shown to satisfy some of the stability criteria in certain regions of parameter space, but not all together. They are known as “Quasi Stable” black holes. Quasi stability restricts the accessibility of parameter space; hence, it creates bounds on various parameters of the quasi-stable black holes. They, although decaying under Hawking radiation, possess bounded fluctuations in certain regions of their accessibility for some of their parameters. We here consider Kerr–Newman and Kerr–Sen black holes as examples of two quasi-stable black holes. Their fluctuations are shown to be related to the bounds in parameter space. We also study the decay rate in various regions of their parameter spaces. We conclude that they transform to different kinds of black holes during their Hawking decay.

Subsecond melt processing for achieving SiGe layers

Matthias Voelskow,Aloke Kanjilal,Wolfgang Skorupa 한국물리학회 2010 Current Applied Physics Vol.10 No.5

Flash lamp annealing induced rapid melting of a near surface Ge enriched Si wafer and the subsequent formation of SiGe layers were demonstrated. The formation of an undesirable facetted liquid/solid interface, well known for pulse melting in the millisecond time regime, was found to decrease significantly due to the increasing melting temperature of Si with reducing Ge concentration at the SiGe/Si interface. A dislocation network and the existence of strain, which were evidenced by transmission electron microscopy and μ-Raman measurements, respectively, are expected to play an important role to form thin SiGe layers.

A Novel Adaptive Biasing Scheme for CMOS Op-Amps

Girish Kurkure,Aloke K. Dutta 대한전자공학회 2005 Journal of semiconductor technology and science Vol.5 No.3

In this paper, we present a new adaptive biasing scheme for CMOS op-amps. The designed circuit has been used in an Operational Transconductance Amplifier (OTA) with ±1 V power supply, and it has improved the positive and negative slew rates from 2.92 V/msec to 1242 V/msec and from 1.56 V/msec to 133 V/msec respectively, while maintaining all the smallsignal performance parameter values the same as that without adaptive biasing (as expected), however, there was a marginal decrease of the dynamic range. The most useful features of the proposed circuit are that it uses a very low number of components (thus not creating severe area penalty) and requires only 25 ㎻of extra stand-by power.

Remedies of Indian Universities Sports and higher level participation to improve the Global Human Recourses

( Sudarsan Biswas ),( Aloke Kumar Senguptta ) 한국체육학회 2015 국제스포츠과학 학술대회 Vol.2015 No.1

A Unified Analytical One-Dimensional Surface Potential Model for Partially Depleted (PD) and Fully Depleted (FD) SOI MOSFETs

RAHUL PANDEY,ALOKE K. DUTTA 대한전자공학회 2011 Journal of semiconductor technology and science Vol.11 No.4

In this work, we present a unified analytical surface potential model, valid for both PD and FD SOI MOSFETs. Our model is based on a simplified one dimensional and purely analytical approach, and builds upon an existing model, proposed by Yu et al. [4], which is one of the most recent compact analytical surface potential models for SOI MOSFETs available in the literature, to improve its accuracy and remove its inconsistencies, thereby adding to its robustness. The model given by Yu et al. [4] fails entirely in modeling the variation of the front surface potential with respect to the changes in the substrate voltage, which has been corrected in our modified model. Also, [4] produces self-inconsistent results due to misinterpretation of the operating mode of an SOI device. The source of this error has been traced in our work and a criterion has been postulated so as to avoid any such error in future. Additionally, a completely new expression relating the front and back surface potentials of an FD SOI film has been proposed in our model, which unlike other models in the literature, takes into account for the first time in analytical one dimensional modeling of SOI MOSFETs, the contribution of the increasing inversion charge concentration in the silicon film, with increasing gate voltage, in the strong inversion region. With this refinement, the maximum percent error of our model in the prediction of the back surface potential of the SOI film amounts to only 3.8% as compared to an error of about 10% produced by the model of Yu et al. [4], both with respect to MEDICI simulation results.

Adaptive Slicing with Curvature Considerations

Banerjee, Ashis Gopal,Kumar, Aloke,Tejavath, Shankar,Choudhury, Asimava Roy Society for Computational Design and Engineering 2003 International Journal of CAD/CAM Vol.3 No.1

In this paper, first order slice height calculation in Laminated Object Manufacturing (LOM) of free form surfaces is done with two different considerations: that a) the cutter trajectory is oriented in the direction of local absolute maximum more in number when compared to the case where the cutter trajectory is contained in the normal vertical section (NVS). However, it would help in achieving higher form accuracy of the final part because it would be a form of worst-case check. For the second proposed strategy, least number of slices results, thereby reducing overall build time drastically.

Evaluation of metal contamination and phytoremediation potential of aquatic macrophytes of East Kolkata Wetlands, India

Amina Khatun,Sandipan Pal,Aloke Kumar Mukherjee,Palas Samanta,Subinoy Mondal,Debraj Kole,Priyanka Chandra,Apurba Ratan Ghosh 환경독성보건학회 2016 환경독성보건학회지 Vol.31 No.-

Objectives The present study analyzes metal contamination in sediment of the East Kolkata Wetlands, a Ramsar site, which is receiving a huge amount of domestic and industrial wastewater from surrounding areas. The subsequent uptake and accumulation of metals in different macrophytes are also examined in regard to their phytoremediation potential. Methods Metals like cadmium (Cd), copper (Cu), manganese (Mn), and lead (Pb) were estimated in sediment, water and different parts of the macrophytes Colocasia esculenta and Scirpus articulatus. Results The concentration of metals in sediment were, from highest to lowest, Mn (205.0±65.5 mg/kg)>Cu (29.9±10.2 mg/kg)>Pb (22.7±10.3 mg/kg)>Cd (3.7±2.2 mg/kg). The phytoaccumulation tendency of these metals showed similar trends in both native aquatic macrophyte species. The rate of accumulation of metals in roots was higher than in shoots. There were strong positive correlations (p <0.001) between soil organic carbon (OC) percentage and Mn (r =0.771), and sediment OC percentage and Pb (r=0.832). Cation exchange capacity (CEC) also showed a positive correlation (p <0.001) with Cu (r=0.721), Mn (r=0.713), and Pb (r=0.788), while correlations between sediment OC percentage and Cu (r=0.628), sediment OC percentage and Cd (r=0.559), and CEC and Cd (r=0.625) were significant at the p <0.05 level. Conclusions Bioaccumulation factor and translocation factors of these two plants revealed that S. articulatus was comparatively more efficient for phytoremediation, whereas phytostabilization potential was higher in C. esculenta .

An optoelectrokinetic technique for programmable particle manipulation and bead-based biosignal enhancement.

Wang, Kuan-Chih,Kumar, Aloke,Williams, Stuart J,Green, Nicolas G,Kim, Kyung Chun,Chuang, Han-Sheng Royal Society of Chemistry 2014 Lab on a chip Vol.14 No.20

<P>Technologies that can enable concentration of low-abundance biomarkers are essential for early diagnosis of diseases. In this study, an optoelectrokinetic technique, termed Rapid Electrokinetic Patterning (REP), was used to enable dynamic particle manipulation in bead-based bioassays. Various manipulation capabilities, such as micro/nanoparticle aggregation, translation, sorting and patterning, were developed. The technique allows for versatile multi-parameter (voltage, light intensity and frequency) based modulation and dynamically addressable manipulation with simple device fabrication. Signal enhancement of a bead-based bioassay was demonstrated using dilute biotin-fluorescein isothiocyanate (FITC) solutions mixed with streptavidin-conjugated particles and rapidly concentrated with the technique. As compared with a conventional ELISA reader, the REP-enabled detection achieved a minimal readout of 3.87 nM, which was a 100-fold improvement in sensitivity. The multi-functional platform provides an effective measure to enhance detection levels in more bead-based bioassays.</P>