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Statistical models for predicting number of involved nodes in breast cancer patients

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Health 2010年第7期2卷 641-651页

作者： alok kumar dwivedi Sada Nand dwivedi Suryanarayana Deo Rakesh Shukla Center for Biostatistical Services Department of Environmental Health College of Medicine University of Cincinnati Cincinnati USA.

Clinicians need to predict the number of involved nodes in breast cancer patients in order to ascertain severity, prognosis, and design subsequent treatment. The distribution of involved nodes often displays over-dispersion—a larger variability than expected. Until now, the negative binomial model has been used to describe this distribution assuming that over-dispersion is only due to unobserved heterogeneity. The distribution of involved nodes contains a large proportion of excess zeros (negative nodes), which can lead to over-dispersion. In this situation, alternative models may better account for over-dispersion due to excess zeros. This study examines data from 1152 patients who underwent axillary dissections in a tertiary hospital in India during January 1993-January 2005. We fit and compare various count models to test model abilities to predict the number of involved nodes. We also argue for using zero inflated models in such populations where all the excess zeros come from those who have at some risk of the outcome of interest. The negative binomial regression model fits the data better than the Poisson, zero hurdle/inflated Poisson regression models. However, zero hurdle/inflated negative binomial regression models predicted the number of involved nodes much more accurately than the negative binomial model. This suggests that the number of involved nodes displays excess variability not only due to unobserved heterogeneity but also due to excess negative nodes in the data set. In this analysis, only skin changes and primary site were associated with negative nodes whereas parity, skin changes, primary site and size of tumor were associated with a greater number of involved nodes. In case of near equal performances, the zero inflated negative binomial model should be preferred over the hurdle model in describing the nodal frequency because it provides an estimate of negative nodes that are at “high-risk” of nodal involvement.

关键词： Nodal Involvement Count Models Breast Cancer

An epidemiological study on delay in treatment initiation of cancer patients

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Health 2012年第2期4卷 66-79页

作者： alok kumar dwivedi Sada Nand dwivedi Suryanarayana Deo Rakesh Shukla Arvind Pandey Durgesh kumar dwivedi Center for Biostatistical Services Division of Biostatistics and Epidemiology Department of Environmental Health College of Medicine University of Cincinnati Cincinnati USA Department of Biostatistics All India Institute of Medical Sciences New Delhi India Department of NMR & MRI Facility All India Institute of Medical Sciences New Delhi India Department of Surgical Oncology All India Institute of Medical Sciences New Delhi India National Institute of Medical Statistics Indian Council of Medical Research New Delhi India

Early diagnosis and timely initiation of treatment of cancer patients may improve survival and quality of life. Various measures of delay can be made during diagnosis and treatment initiation. Most of the studies were based on single type of cancer with different definitions and measurements of delay in diagnosis and treatment. Thus, it has been difficult to synthesize results and generalize to other types of cancer. The study proposes to measure total duration between onsets of symptom to start of treatment into three components, namely primary, secondary and tertiary delays. Primary delay is defined as onset of symptoms to contacting the first medical person, secondary delay is from first medical contact to confirmed diagnosis, and tertiary delay is from confirmed diagnosis to treatment initiation. The aim of this study is to determine factors associated with primary, secondary and tertiary delays in cancer patients. This study was planned as a cross-sectional study. Data was collected from patients admitted to the surgical wards of Department of Surgical Oncology, Institute Rotary Cancer Hospital, New Delhi during 2006-2007. Gamma regression and quantile regressions at 25th, 50th and 75th percentile of each of the delays were used to determine related factors. A total of 403 patients were included in the analysis. The median tertiary delay was found almost two folds (59;Interquartile range: 26 - 101 days) than the primary and secondary delays. Extremity cancer patients had longest primary, secondary and tertiary delays. Shortest primary, secondary and tertiary delays were observed for gastrointestinal cancer, breast and genitourinary cancer respectively. There is an urgent need and scope to reduce delay at each level primary, secondary and tertiary delay. Intervention studies are needed through information, education and communication/screening programs to reduce the diagnostic and treatment delays in cancer patients.

关键词： Delay Cancer Log Gamma Regression Quantile Regression

Association of Obesity in Children with Pancreatitis in a Predominantly Hispanic Population at the US-Mexican Border: A Single Center Outpatient Study

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Health 2016年第15期8卷 1820-1829页

作者： Indu Pathak Diana Malbas Pukhraj Rai alok kumar dwivedi Department of Pediatrics Paul L. Foster School of Medicine Texas Tech University Health Sciences Center El Paso Texas USA El Paso Children’s Hospital El Paso Texas USA Division of Biostatistics & Epidemiology Department of Biomedical Sciences Paul L. Foster School of Medicine Texas Tech Univer-sity Health Sciences Center El Paso Texas USA

Importance: The incidence of pancreatitis has been increasing over the last decade. Limited data are available for pancreatitis in the Hispanic population. The clinical profile of pancreatitis and its association with obesity in a Mexican American population has not been well studied. Objective: To describe prevalence, the characteristics of pancreatitis cases, and determine its association with obesity. Design and Setting: Retrospective review of children from February 2012 to February 2015, at the Texas Tech University Health Sciences Center of El Paso (TTUHSC-El Paso) outpatient center. Case/non-case study was used to determine the association of overweight and obesity with pancreatitis. Participants: Children ages 2 - 18 years, only the newly diagnosed pancreatitis cases irrespective of its type excluding patients with traumatic and repeat visit for pancreatitis. Main Outcome and Measures: Pancreatitis and obesity. Results: The prevalence of pancreatitis was estimated as 20 cases in 21,444 patients seen in the outpatient clinic. In multivariable analysis, only obesity and ethnicity were significantly associated with pancreatitis. Obesity was found to be more than 7-fold likely with pancreatitis as compared to non-cases. Overweight was found to be more than 6-fold likely with pancreatitis as compared with non-cases. Our study demonstrates an association between obesity and pancreatitis in the study population. Conclusions and Relevance: Appropriate intervention for managing obesity may reduce the prevalence of pancreatitis and associated co-morbidities. A larger prospective study should be done to determine underlying causes of association between obesity and pancreatitis.

关键词： Pancreatitis Obesity Body Mass Index (BMI)

Moderate and Severe Blood Pressure Elevation Associated with Stroke in the Mexican Hispanic Population

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Health 2017年第6期9卷 951-963页

作者： Derek Senior Michael F. Osborn Katherene Tajnert Ahmed Badr alok kumar dwivedi Jun Zhang Department of Biomedical Sciences Texas Tech University Health Sciences Center El Paso USA

Background: Stroke is the fourth leading cause of death in US. Amongst other factors such as age, sex, race, genetics, obesity, diabetes etc., hypertension continues to be the leading contributing factor towards stroke. Studies regarding stroke in Hispanics are sparse and inconclusive. Objectives: The objective of the present study is to investigate the potential association between blood pressure elevation and risk of ischemic stroke among the Mexican Hispanic population. Methods: A retrospective data analysis was carried out for a planned case-control study with case-control ratios of 1:2. Mexican Hispanic cases were from the ElPasoStroke database with diagnosed hypertension that had sustained an ischemic stroke (n = 505) and Mexican Hispanics diagnosed with hypertension who were stroke-free as controls from the 2005-2010 NHANES databases (n = 1010). In this analysis, we included subjects who had data on systolic, diastolic or mean arterial blood pressures for cases (327) and controls (772). In cases, blood pressure was determined by the initial admission measurement, and in controls, the first measured blood pressure was used. The unadjusted and adjusted effects of continuous measurements of systolic, diastolic and mean arterial blood pressure on stroke were determined using logistic regression analyses. Subjects were further classified into groups based on prehypertension and hypertension ranges, as established by the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC7). Unadjusted and adjusted logistic regression models were also used to determine the effect of categorized blood pressures. Results: Our data indicate that per unit increase in systolic, diastolic or mean arterial blood pressure elevates the odds of stroke among the Mexican Hispanic population. Adjusted analysis of categorized blood pressures showed that mild or moderate/severe high blood pressure significantly associated with odds of stroke. M

关键词： Blood Pressure Risk Factors Ischemic Stroke Mexican Hispanic Epidemiology

Upper ocean high resolution regional modeling of the Arabian Sea and Bay of Bengal

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Acta Oceanologica Sinica 2019年第5期38卷 32-50页

作者： dwivedi Suneet Mishra alok kumar Srivastava Atul K Banerjee Centre of Atmospheric and Ocean Studies and M N Saha Centre of Space Studies University of Allahabad

In this paper, effort is made to demonstrate the quality of high-resolution regional ocean circulation model in realistically simulating the circulation and variability properties of the northern Indian Ocean(10°S–25°N,45°–100°E) covering the Arabian Sea(AS) and Bay of Bengal(BoB). The model run using the open boundary conditions is carried out at 10 km horizontal resolution and highest vertical resolution of 2 m in the upper *** surface and sub-surface structure of hydrographic variables(temperature and salinity) and currents is compared against the observations during 1998–2014(17 years). In particular, the seasonal variability of the sea surface temperature, sea surface salinity, and surface currents over the model domain is studied. The highresolution model's ability in correct estimation of the spatio-temporal mixed layer depth(MLD) variability of the AS and BoB is also shown. The lowest MLD values are observed during spring(March-April-May) and highest during winter(December-January-February) seasons. The maximum MLD in the AS(BoB) during December to February reaches 150 m (67 m). On the other hand, the minimum MLD in these regions during March-April-May becomes as low as 11–12 m. The influence of wind stress, net heat flux and freshwater flux on the seasonal variability of the MLD is discussed. The physical processes controlling the seasonal cycle of sea surface temperature are investigated by carrying out mixed layer heat budget analysis. It is found that air-sea fluxes play a dominant role in the seasonal evolution of sea surface temperature of the northern Indian Ocean and the contribution of horizontal advection, vertical entrainment and diffusion processes is small. The upper ocean zonal and meridional volume transport across different sections in the AS and BoB is also computed. The seasonal variability of the transports is studied in the context of monsoonal currents.

关键词： Indian Ocean modeling Arabian Sea and Bay of Bengal mixed layer depth transport

Biphasic reduction model for predicting the impacts of dye-bath constituents on the reduction of tris-azo dye Direct Green-1 by zero valent iron(Fe^0)

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Journal of Environmental Sciences 2017年第2期29卷 160-169页

作者： Raja kumar alok Sinha Department of Environmental Science&Engineering Indian School of MinesDhanbad 826004JharkhandIndia

Influence of common dye-bath additives, namely sodium chloride, ammonium sulphate,urea, acetic acid and citric acid, on the reductive decolouration of Direct Green 1 dye in the presence of Fe0 was investigated. Organic acids improved dye reduction by augmenting Fe0 corrosion, with acetic acid performing better than citric acid. Na Cl enhanced the reduction rate by its ‘salting out’ effect on the bulk solution and by Cl-anion-mediated pitting corrosion of iron surface.（NH4）2SO4induced ‘salting out’ effect accompanied by enhanced iron corrosion by SO42-anion and buffering effect of NH4＋ improved the reduction ***, at 2 g/L（NH4）2SO4concentration, complexating of SO42-with iron oxides decreased Fe0 reactivity. Urea severely compromised the reduction reaction, onus to its chaotropic and‘salting in’ effect in solution, and due to it masking the Fe0 surface. Decolouration obeyed biphasic reduction kinetics（R2〉 0.993 in all the cases） exhibiting an initial rapid phase,when more than 95% dye reduction was observed, preceding a tedious phase. Maximum rapid phase reduction rate of 0.955/min was observed at p H 2 in the co-presence of all dye-bath constituents. The developed biphasic model reckoned the influence of each dye-bath additive on decolouration and simulated well with the experimental data obtained at pH 2.

关键词： Biphasic kinetics/model Direct Green 1 Dye-bath additives Fe0

Powder mixed electrochemical discharge process for micro machining of C103 niobium alloy

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Defence Technology（防务技术） 2023年第8期26卷 84-101页

作者： Niladri Mandal Nitesh kumar alok kumar Das Defence Research&Development Laboratory(DRDL)-DRDO HyderabadIndia Department of Mechanical Engineering Indian Institute of Technology(ISM)DhanbadIndia

This work demonstrates the viability of the powder-mixed micro-electrochemical discharge machining(PMECDM) process to fabricate micro-holes on C103 niobium-based alloy for high temperature *** processes are involved simultaneously *** erosion,chemical etching,and abrasive grinding for removal of material while the classical electrochemical discharge machining process involves double actions *** erosion,and chemical *** powder-mixed electrolyte process resulted in rapid material removal along with a better surface finish as compared to the classical microelectrochemical discharge machining(MECDM).Further,the results are optimized through a multiobjective optimization approach and study of the surface topography of the hole wall surface obtained at optimized *** the selected range of experimental parameters,PMECDM shows a higher material removal rate(MRR) and lower surface roughness(R_(a))(MRR:2.8 mg/min and R_(a) of 0.61 μm) as compared to the MECDM process(MRR:2.01 mg/min and corresponding Raof 1.11 μm).A detailed analysis of the results is presented in this paper.

关键词： Micro-electrochemical discharge machining C103 niobium alloy Surface integrity Material removal rate Hybrid powder mixed ECDM

Study of damage behavior and repair effectiveness of patch repaired carbon fiber laminate under quasi-static indentation loading

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Defence Technology（防务技术） 2024年第4期34卷 29-41页

作者： alok kumar Chinmaya kumar Sahoo A.Arockiarajan Department of Applied Mechanics Indian Institute of Technology MadrasChennai 600036India

Damage caused due to low-velocity impacts in composites leads to substantial deterioration in their residual strength and eventually provokes structural *** work presents an experimental investigation on the effects of different patch and parent laminate stacking sequences on the enhancement of impact strength of Carbon Fiber Reinforced Polymers(CFRP)composites by utilising the adhesively bonded external patch repair *** evolution study is also performed with the aid of Acoustic Emission(AE).Two different quasi-isotropic configurations were selected for the parent laminate,viz.,[45°/45°/0°/0°]s and[45°/0°/45°/0°]*** Static Indentation(QSI)test was performed on both the pristine laminates,and damage areas were detected by using the C-scan inspection *** laminates were repaired by using a single-sided patch of two different configurations,viz.,[45°/45°/45°/45°]and[45°/0°/0°/45°],and employing a circular plug to fill the damaged *** different combinations of repaired laminates with two configurations of each parent and patch laminate were produced,which were further subjected to the QSI *** results reveal the effectiveness of the repair method,as all the repaired laminates show higher impact resistance compared to the respective pristine *** of[45°/0°/0°/45°]configuration when repaired by taking[45°/45°/0°/0°]s and[45°/0°/45°/0°]s as parents exhibited 68%and 73%higher peak loads,respectively,than the respective pristine ***,parent and patch of configuration[45°/0°/45°/0°]s and[45°/0°/0°/45°],respectively,attain the highest peak load,whereas[45°/45°/0°/0°]s and[45°/45°/45°/45°]combinations possess the most gradual decrease in the load.

关键词： Carbon fiber reinforced polymers(CFRP) Quasi-isotropic laminate Quasi static indentation(QSI) Acoustic emission(AE) Composite repair

Dual-Core Photonic Crystal Fiber Plasmonic Refractive Index Sensor: A Numerical Analysis

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Photonic Sensors 2019年第2期9卷 151-161页

作者： alok kumar PAUL Ajay Krishno SARKAR Department of Electrical & Electronic Engineering Rajshahi University of Engineering & Technology Rajshahi-6204 Bangladesh

A numerical analysis on dual core photonic crystal fiber (DC-PCF) based surface plasmon resonance (SPR) refractive index sensor is presented. The guiding parameters and required sensing performances are examined with finite element method (FEM) based software under MATLAB environment. According to simulation, it is warranted that the proposed refractive index sensor offers the maximum amplitude sensitivity of 554.9 refractive index unit (RIU-1) and 636.5 RIU 1 with the maximum wavelength sensitivity of 5800nm/RIU and 11 500nm/RIU, and the sensor resolutions of 1.72 ×10^-5RIU and 8.7× 10^-6 RIU, at analyte refractive index (RI) of 1.40 for x- and y-polarized modes, respectively. As the sensing performance in different wavelength ranges is quite high, the proposed sensor can be used in simultaneous detection for different wavelength ranges. Therefore, the proposed device is of a suitable platform for detecting biological, chemical, biochemical, and organic chemical analytes.

关键词： Photonic crystal fiber biosensor refractive index sensor finite element method plasmonic material