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Papers by amit sukul

Journal of Agricultural and Food Chemistry, Aug 17, 1997

Plasma membrane lipid composition of herbicide-resistant (R) and-susceptible (S) wild oat biotype... more Plasma membrane lipid composition of herbicide-resistant (R) and-susceptible (S) wild oat biotypes was analyzed to determine the basis for the differential effect of diclofop on the transmembrane electrogenic potential between the two biotypes and reduced herbicide uptake into protoplasts of the R biotype. In addition, lipoxygenase (LOX) activity was examined in herbicide-treated and untreated R and S plants to determine its involvement in herbicide action and resistance. Overall, no significant differences in lipid composition were found between the two biotypes. Glycolipids represented 41 and 36%, phospholipids 29 and 37%, and free sterols 30 and 27% of the total plasma membrane lipid in the R and S biotypes, respectively. No differences in LOX activity were observed between the herbicide-treated and untreated wild oat biotypes. It was concluded that differences in membrane transport of diclofop and its effect on plasma membrane potential in the R and S biotypes are not related to differences in membrane lipid composition or to differential effects of herbicides on LOX activity in the two biotypes.

Ash Annual Meeting Abstracts, Nov 16, 2008

Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disease characterised by elevated peri... more Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disease characterised by elevated peripheral platelet destruction and inadequate platelet production. Little published epidemiological data exists concerning the risk of thromboembolic events (TE) among adult patients with ITP. The objective of our investigation was to estimate the risk of TE among adult patients with and without ITP in the United Kingdom (UK) General Practice Research Database (GPRD), which contains patient data from 6.4 million patients from more than 480 representative medical practices across the UK. Using read [2871C] or Oxford Medical Information System (OXMIS) [D3130000, D313012, 42P2.11, D313.12] codes to define cases, incidence rates (IRs) per 10,000 patient-years of observation (PYO) with 95% confidence intervals (CIs) were estimated. Hazard ratios (HRs) of venous, arterial, and combined (venous and arterial) TE were modelled using Cox proportional hazards regression adjusting for history of prior TE, hypertension, splenectomy status, oral corticosteroids and intravenous immunoglobulin exposure. 840 adults (≥ 18 years) with codes for ITP first referenced between January 1, 1992 and September 30, 2005 and having at least one year pre-diagnosis and three months of post-diagnosis medical history were matched with 3,360 non-ITP patients by age, gender, primary care practice and pre-study follow-up time. Over a median 52 months of follow-up (range: 3–182 months), the cumulative incidence of TE among thromboembolic-free patients at baseline was higher within the ITP cohort [47 (6.7%) v. 172 (5.7%)]. As shown in the table below, the IRs of venous, arterial, and combined TE were additionally elevated among patients with ITP. Outcome Incidence Rate/10,000 PYO 95% CI Adult Patients with ITP Adult Patients without ITP Venous TE 70.83 (46.67–103.05) 47.53 (37.39–59.58) Arterial TE 82.02 (55.73–116.42) 71.50 (58.87–86.04) Combined TE 134.74 (99–179.18) 116.32 (99.59–135.06) Adjusted HRs of 1.58 (95% CI, 0.98–2.53), 1.02 (95% CI, 0.65–1.59), and 1.17 (95% CI, 0.82–1.66) were found for venous, arterial, and combined TE respectively. Further event categorisation revealed elevated HRs for each venous thromboembolic subtype [deep vein thrombosis 1.49 (95% CI, 0.62–3.61), pulmonary embolism 3.52 (95% CI, 1.23–10.04), and other TE 1.17 (95% CI, 0.64– 2.16)]. This study provides evidence of an increased risk in venous TE in adult patients with ITP relative to the general adult non-ITP population.

Vldb, 1997

In this paper, we reexamine the results of prior work on methods for computing ad hoc joins. We d... more In this paper, we reexamine the results of prior work on methods for computing ad hoc joins. We develop a detailed cost model for predicting join algorithm performance, and we use the model to develop cost formulas for the major ad hoc join methods found in the relational database literature. We show that various pieces of "common wisdom" about join algorithm performance fail to hold up when analyzed carefully, and we use our detailed cost model to derive optimal buffer allocation schemes for each of the join methods examined here. We show that optimizing their buffer allocations can lead to large performance improvements, e.g., as much as a 400% improvement in some cases. We also validate our cost model's predictions by measuring an actual implementation of each join algorithm considered. The results of this work should be directly useful to implementors of relational query optimizers and query processing systems.

Astronomy & Astrophysics, 2015

Context. In April 2013, the nearby TeV blazar, Mkn 421, showed one of the largest flares in X-ray... more Context. In April 2013, the nearby TeV blazar, Mkn 421, showed one of the largest flares in X-rays in the past decade. Aims. We study all multiwavelength data available during MJD 56 392 to 56 403, with special emphasis on X-ray data to understand the underlying particle energy distribution. Methods. We studied the correlations between the UV and gamma-ray bands with the X-ray band using the z-transformed discrete correlation function. We modelled the underlying particle energy spectrum with a single population of electrons emitting synchrotron radiation, and statistically fitted the simultaneous time-resolved data from Swift-XRT and NuSTAR. Results. The flux varied rapidly in the X-ray band, with a minimum doubling timescale of 1.69 ± 0.13 h. There were no corresponding flares in UV and gamma-ray bands. The variability in UV and gamma rays was relatively modest with ∼8% and ∼16%, respectively, and no significant correlation was found with the X-ray light curve. The observed X-ray spectrum shows a clear curvature that can be fit by a log parabolic spectral form. This is best explained as originating from a log parabolic electron spectrum. However, a broken power law or a power law with an exponentially falling electron distribution cannot be ruled out either. Moreover, the excellent broadband spectrum from 0.3-79 keV allows us to make predictions of the UV flux. We find that this prediction is compatible with the observed flux during the low state in X-rays. However, during the X-ray flares, depending on the adopted model, the predicted flux is a factor of 2-50 lower than the observed one. This suggests that the X-ray flares are probably caused by a separate population that does not contribute significantly to the radiation at lower energies. Alternatively, the underlying particle spectrum can be much more complex than those explored in this work.

Several AGNs of Blazar class, including Mkn421, Mkn501, 1ES2344+514, 1ES1218+304 and 3C454.3, hav... more Several AGNs of Blazar class, including Mkn421, Mkn501, 1ES2344+514, 1ES1218+304 and 3C454.3, have been observed at energies above 200 GeV with High Altitude GAmma Ray (HAGAR) telescope array located in Himalayas in India, over past two years. We had very long coverage of Mkn421 and have observed it in one of the brightest flaring episodes in February, 2010. HAGAR observations of this blazar during this flare have shown enhancement of flux level with a maximum flux of about 6 Crab units on 17th February. We present multi-waveband spectral energy distribution of this source during this flaring episode and investigate the correlation of variability in X-ray and gamma ray bands. Preliminary results on other blazars will also be presented.

A muffler is a part of the exhaust system on an automobile that plays a vital role. It needs to h... more A muffler is a part of the exhaust system on an automobile that plays a vital role. It needs to have modes that are located away from the frequencies that the engine operates at, whether the engine be idling or running at the maximum amount of revolutions per second. The purpose of the design project performed was to determine which modes are very high and may affect the automobile adversely while in operation. A muffler that affects an automobile in a negative way is one that causes noise or discomfort while the car engine is running. In order to determine the modes most at risk of adversely affecting an automobile, an impact test was conducted. Research was performed prior to the test to determine which frequencies to look for modes at. It was determined to conduct the experiment so data from 0 Hz to 1000 Hz could be collected. The force was caused manually by a hammer with a hard head. After collecting the data, the transfer functions were plotted using Matlab. To ensure correct analyzation, the transfer function equivalent graphs were also plotted. The data was put into an Excel table and analyzed. Six points on the muffler were chosen, after looking at the data, and determined to be under damped. Therefore, our design study suggests to increase the mass, increase the damping, or provide a negative stiffness to make the muffler more damped and to lower the modes of the transfer function. Once at least one of these tasks is performed, the damping will be lowered and there ought to be no more dangerous modes that could lead to excess noise and vibration.

Volume 1: 24th Conference on Mechanical Vibration and Noise, Parts A and B, 2012

The goal of this paper is to understand transient dynamics of an aero-structure under combined lo... more The goal of this paper is to understand transient dynamics of an aero-structure under combined loading. In this study, a nonlinear finite element model of a representative panel is used to evaluate the effect of combined thermal and mechanical loading on nonlinear response with specific focus on severe aerodynamic heating and fluctuating pressure. This results in nonlinear response behavior including thermal buckling, snap-through and snap-buckling. A snap-through boundary is presented in the space of combined loading parameters. Relationship between the frequency of snap-through and loading magnitude is also discussed. Some observations are presented on transient behavior as well as the asymmetric response. It is demonstrated that boundary conditions can be utilized to enhance the design of such structural panels.Copyright © 2012 by ASME

Kathmandu University medical journal (KUMJ)

Neurocysticercosis is the most common parasitic infection of the central nervous system. It is en... more Neurocysticercosis is the most common parasitic infection of the central nervous system. It is endemic in Central Europe, South Africa, South America and parts of Asia including Nepal. This study has been conducted with the objectives to know the diagnostic criteria for neurocysticercosis and the outcome of treated cases. This retrospective study was done at Nepalganj Medical College, Teaching Hospital, Kohalpur, by reviewing the record of the patients managed as case of neurocysticercosis in one financial year. All patients presented with seizure as a main symptom started in adult life. The mean age was 21 years; 80% were male and 20% female. The diagnosis seemed to be based on clinical presentation, CT scan findings and high index of suspicion. All were put on albendazole, steroids and anticonvulsant drugs; 93% was discharged when fits got controlled, one patient left against medical advice. Follow up record was not available to comment on resolution. Neurocysticercosis is difficu...

This paper presents analysis of a one degree of freedom human postural control model. The central... more This paper presents analysis of a one degree of freedom human postural control model. The central nervous system is captured in the model as an intermittent control law. Parametric and stability analysis of this single degree-of-freedom model are presented. The L2 Norm of the response is used as a measure of stability. This study shows that joint stiffness and associated time delay parameter are the most sensitive towards the response dynamics. In addition, a comparison of parametric linear stability boundary with the L2 Norm estimates is presented.Copyright © 2012 by ASME

The Astrophysical Journal, 2014

Since the detection of very high energy (VHE) γ-rays from Mrk 501, its broadband emission of radi... more Since the detection of very high energy (VHE) γ-rays from Mrk 501, its broadband emission of radiation was mostly and quite effectively modeled using the one zone emission scenario. However, broadband spectral and flux variability studies enabled by the multi-wavelength campaigns carried out during the recent years have revealed the rather complex behavior of Mrk 501. The observed emission from Mrk 501 could be due to a complex superposition of multiple emission zones. Moreover, new evidence of detection of very hard intrinsic γ-ray spectra obtained from Fermi-LAT observations has challenged the theories about the origin of VHE γ-rays. Our studies based on Fermi-LAT data indicate the existence of two separate components in the spectrum, one for low-energy γ-rays and the other for high-energy γ-rays. Using multi-waveband data from several ground-and space-based instruments, in addition to HAGAR data, the spectral energy distribution of Mrk 501 is obtained for various flux states observed during 2011. In the present work, this observed broadband spectral energy distribution is reproduced with a leptonic, multi-zone synchrotron self-Compton (SSC) model.

Design Engineering and Computers and Information in Engineering, Parts A and B, 2006

Accurate prediction of nonlinear response of a homogenous, buckled plate with clamped boundary co... more Accurate prediction of nonlinear response of a homogenous, buckled plate with clamped boundary conditions is essential in designing aircraft structures for long life and extreme combined loading. It is well known that the dynamic response becomes highly nonlinear for large response amplitudes of a buckled plate with clamped boundary condition. In this paper, a rectangular plate is experimentally studied for its nonlinear dynamic response. The results obtained are compared for the two buckling modes. Further, the numerical observations are conducted to differentiate the effect of amplitude of excitation on the nonlinear response, specifically characterizing the parametric regimes (amplitude and frequency) to differentiate between the small amplitude linear response and large amplitude snap-through response. It is desired to understand the parametric boundary separating these two qualitatively different response characteristics for its obvious impact on the fatigue life of the structure.Copyright © 2006 by ASME

Design Engineering, Parts A and B, 2005

Nonlinear active suspension systems are very popular in the automotive applications. They include... more Nonlinear active suspension systems are very popular in the automotive applications. They include nonlinear stiffness and nonlinear damping elements. One of the types of damping element is a magneto-rheological fluid based damper which is receiving increased attention in the applications to the automotive suspension systems. Latest trends in suspension systems also include electronically controlled systems which provide advanced system performance and integration with various processes to improve vehicle ride comfort, handling and stability. A control bifurcation of a nonlinear system typically occurs when its linear approximation loses stabilizability. These control bifurcations are different from the classical bifurcation where qualitative stability of the equilibrium point changes. Any nonlinear control system can also exhibit control bifurcations. In this paper, control bifurcations of the nonlinear active suspension system, modeled as a two degree of freedom system, are analyzed. It is shown that the system looses stability via Hopf bifurcation. Parametric control bifurcation analysis is conducted and results presented to highlight the significance of the design of control system for nonlinear active suspension system. A framework for the design of feedback using the parametric analysis for the control bifurcations is proposed and illustrated for the nonlinear active suspension system.Copyright © 2005 by ASME

ACM SIGMOD Record, 1998

Database researchers have made significant progress on several research issues related to multidi... more Database researchers have made significant progress on several research issues related to multidimensional data analysis, including the development of fast cubing algorithms, efficient schemes for creating and maintaining precomputed group-bys, and the design of efficient storage structures for multidimensional data. However, to date there has been little or no work on multidimensional query optimization. Recently, Microsoft has proposed “OLE DB for OLAP” as a standard multidimensional interface for databases. OLE DB for OLAP defines Multi-Dimensional Expressions (MDX), which have the interesting and challenging feature of allowing clients to ask several related dimensional queries in a single MDX expression. In this paper, we present three algorithms to optimize multiple related dimensional queries. Two of the algorithms focus on how to generate a global plan from several related local plans. The third algorithm focuses on generating a good global plan without first generating loca...

The spectral data ie eigenvalues (natural-frequencies) and eigenvectors (mode-shapes), characteri... more The spectral data ie eigenvalues (natural-frequencies) and eigenvectors (mode-shapes), characterizes the dynamics of the system. The dynamic analysis of physical systems leads to certain direct and inverse eigenvalue problems. The direct eigenvalue problem deals in evaluating the ...

International Journal of Drug Delivery, 2010

The rationale of this research was to prepare a gastroretentive drug delivery system of Ranitidin... more The rationale of this research was to prepare a gastroretentive drug delivery system of Ranitidine HCL. Floating Drug delivery system used to target drug release in the stomach or to the upper part of the intestine. The oral delivery of Ranitidine is tested by preparing a non-disintegrating floating dosage form, which increase its absorption in the stomach by increasing the drug's gastric residence time. The polymer PVC and Sodium bicarbonate was used as the gas-generating agents. Sodium bicarbonate causes the tablets to floats for more then 24hr. The prepared tablets were evaluated on their physicochemical properties and drug release characters. In-vitro release studies indicate that the Ranitidine release form the floating dosage form was uniform followed zero order release. A combination of sodium bicarbonate (70mg) and citric acid (15mg) was found to achieve Optimum in vitro buoyancy. The tablets with methocel K100 were found to float for longer duration of time as compared to formulations containing methocel K15M. The drug release from the tablets was sufficiently sustained.

The VLDB Journal The International Journal on Very Large Data Bases, 1997

The Astrophysical Journal, 2013

Variable γ-ray emission has been discovered in five Radio-loud Narrow Line Seyfert 1 (NLSy1) gala... more Variable γ-ray emission has been discovered in five Radio-loud Narrow Line Seyfert 1 (NLSy1) galaxies by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope. This has clearly demonstrated that these NLSy1 galaxies do have relativistic jets similar to two other cases of γ-ray emitting Active Galactic Nuclei (AGN), namely blazars and radio galaxies. We present here our results on the multi-band analysis of two γ-ray emitting NLSy1 galaxies namely PKS 1502+036 (z = 0.409) and PKS 2004−447 (z = 0.240) using archival data. We generate multi-band long term light curves of these sources, build their spectral energy distribution (SED) and model them using an one zone leptonic model. They resemble more to the SEDs of the flat spectrum radio quasar (FSRQ) class of AGN. We then compare the SEDs of these two sources with two other Fermi detected AGN along the traditional blazar sequence, namely the BL Lac Mrk 421 (z = 0.03) and the FSRQ 3C 454.3 (z = 0.86). The SEDs of both PKS 1502+036 and PKS 2004−447 are found to be intermediate to the SEDs of Mrk 421 and 3C 454.3. In the γ-ray spectral index v/s γ-ray luminosity plane, both these NLSy1 galaxies occupy a distinct position, wherein, they have luminosity between Mrk 421 and 3C 454.3, however steep γ-ray spectra similar to 3C 454.3. Their Compton dominance as well as their X-ray spectral slope also lie between Mrk 421 and 3C 454.3. We argue that the physical properties of both PKS 1502+036 and PKS 2004−447 are in general similar to blazars and intermediate between FSRQs and BL Lac objects and these sources thus could fit into the traditional blazar sequence.

Journal of Agricultural and Food Chemistry, 1997