Communications in Statistics Theory and Methods, Sep 2, 2006
An application of the pseudo maximum likelihood method to estimation of a multilevel linear model... more An application of the pseudo maximum likelihood method to estimation of a multilevel linear model fitted to the dependent observations coming from a finite population is demonstrated. The proposed approach provides a closed form solution for estimating of the model parameters. It is computationally simpler than the iterative procedures suggested in the literature (e.g., the iterative probability weighted least squares method of Pfeffermann et al. (Pfeffermann, D., Skinner, C.J., Holmes, D.J., Goldstein, H., Rasbash, J. (1998). Weighting for unequal selection probabilities in multilevel models. Journal of Royal Statistical Society B 60:23–40)). Issues related to model and sample design hierarchies and their impact on estimation are discussed. A problem of weighting at different levels is addressed. A small simulation study showed that the proposed procedure is efficient even for small within group sample sizes.
There has been little empirical documentation of the acute effects of bone marrow or stem cell tr... more There has been little empirical documentation of the acute effects of bone marrow or stem cell transplant (BMT) on children. In the present study, the responses of 153 children undergoing BMT were assessed in a prospective, longitudinal design. Children were assessed at the time of admission for transplant, then underwent weekly assessments to week +6, followed by monthly assessment to month +6. Data were obtained both by parent report and patient report (for patients age 5 and up) using the BASES scales. The major findings are: (1) children undergoing BMT enter the hospital with an already heightened level of distress (defined by high levels of somatic symptoms and mood disturbance, and low levels of activity) that increases dramatically following conditioning, reaching a peak approximately 1 week following transplant; (2) this increased distress is transient, declining rapidly back to admission levels by week +4 to week +5, followed by a further decline to presumed basal levels by months 4-6; and (3) the trajectories of distress depicted by both parent and child report are remarkably similar, each providing confirmatory support for the validity of the findings. These findings confirm a number of widely held clinical impressions that had not previously been documented empirically, and point to the need for new interventions or more intensive approaches to supportive care aimed at reducing levels of distress during the acute phase of transplant.
Advances in energy harvesting, low-power radios, and biometric sensing have enabled new applicati... more Advances in energy harvesting, low-power radios, and biometric sensing have enabled new applications in medical and scientific monitoring. In medicine, unobtrusive biosensors promise to wirelessly relay critical patient information including temperature, heart rate, or blood pressure. This paper describes key technologies needed to integrate complex, wirelessly-powered health monitors.
2006 IEEE International Conference on Reconfigurable Computing and FPGA's (ReConFig 2006), 2006
... 2. Compression Formats The FBI uses the wavelet scalar quantization (WSQ) method for encoding... more ... 2. Compression Formats The FBI uses the wavelet scalar quantization (WSQ) method for encoding/decoding fingerprint images [1]. Each image is firstnormalized with zero mean and pixel value range (-128,128). ...
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2009
Efficient, miniaturized wireless recording is critical for both existing and emerging health-moni... more Efficient, miniaturized wireless recording is critical for both existing and emerging health-monitoring applications. One important example of this is in the brain interface community, where new technologies allow improved observation and understanding of brain functions. This, in turn, drives the need for ever smaller, lower power, and higher performance circuitry for chronic recording. This paper describes circuit and system techniques for low power wireless brain interfaces. Active and passive architectures are described and compared, and measured in-vivo data from both are presented.
Many object-oriented metrics have been proposed, and at least fourteen empirical validations of t... more Many object-oriented metrics have been proposed, and at least fourteen empirical validations of thesemetrics have been performed. However, recently it was noted that without controlling for the effect ofclass size in a validation study, the impact of a metric may be exaggerated. It thus becomes necessaryto re-validate contemporary object-oriented metrics after controlling for size. In this paper we perform avalidation
Biomedical Engineering: Applications, Basis and Communications, 2015
Warfarin is a frequently used oral anticoagulant for long-term prevention and treatment of thromb... more Warfarin is a frequently used oral anticoagulant for long-term prevention and treatment of thromboembolic events. Due to its narrow therapeutic range and large inter-individual dose-response variability, it is highly desirable to personalize warfarin dosing. However, the complexity of the conventional kinetic-pharmacodynamic (K-PD) models hampers the development of the personalized dose management. To avert this challenge, we propose simplified PD models for warfarin dose-response relationship, which is motivated by ideas from control theory. The simplified models were further applied to longitudinal data of 37 patients undergoing anticoagulation treatment using the standard two-stage approach and then compared with the conventional K-PD models. Data analysis shows that all models have a similar predictive ability, but the simplified models are most parsimonious.
63rd Device Research Conference Digest, 2005. DRC '05., 2005
We describe novel AlGaN-GaN metal-oxide-semiconductor heterostructure field-effect transistors (M... more We describe novel AlGaN-GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) with record high power-voltage efficiencies (PVE = RF power/Drain bias), up to 0.43W/V-mm at 2 GHz. The RF powers of 15 W/mm at 35 V (PVE=0.43 W/V-mm) and 20 W/mm at 55 V (PVE= 0.36W/V-mm) were measured, which are approximately 50% higher than the previously reported values of PVE=0.25 W/V-mm (30
Post-traumatic stress disorder (PTSD) has been put forth as a model for understanding the adjustm... more Post-traumatic stress disorder (PTSD) has been put forth as a model for understanding the adjustment of children with cancer and their parents, but findings in the literature regarding the prevalence of post-traumatic stress symptoms (PTSS) have been mixed. This study examined PTSS levels in both patients and parents as a function of time elapsed from diagnosis, and by use of parent versus child reports for assessing patient PTSS. Four groups of patients (total N = 162) differing in time elapsed since diagnosis were assessed with standardized measures of PTSS. Patients reported on their own symptoms, while parents reported on their symptoms as well as symptoms in their child. Significant differences between groups were observed on all patient PTSS measures. Recently diagnosed patients obtained higher PTSS scores than survivors more than 5 years from diagnosis. Likewise, parents of recently diagnosed patients self-reported significantly higher levels of PTSS than parents of long-term survivors. Parent-child correlations were high and no differences were observed between parent and patient report of patient PTSS. Comparison with historical control data suggests that levels of PTSS in patients are very low. Concordance between parent and child reports of child PTSS suggests that data may be obtained with reasonable confidence from either if only one informant is available. Higher levels of PTSS in patients who are recently diagnosed (and their parents) in comparison to long-term survivors, suggest that the symptoms reported reflect primarily a concurrent response to ongoing acute stressors, rather than a post-traumatic re-experiencing of past traumas. This, in combination with the low levels of patient PTSS raise questions regarding the utility of PTSD as a model for understanding patient and parent adjustment to childhood cancer.
Parents (N = 151) of children undergoing bone marrow or stem cell transplantation (BMT) were asse... more Parents (N = 151) of children undergoing bone marrow or stem cell transplantation (BMT) were assessed in a prospective, longitudinal design with repeated measures of distress (mood disturbance, perceived stress, caregiver burden). Parents were assessed weekly from admission for BMT (week-1) through week +6 post-BMT, followed by monthly assessments through month +6. Concurrent measures of child distress (somatic distress, mood disturbance) were also obtained by parent and child report. Parents demonstrate modest, but significant elevations in distress, particularly during the early period from admission through week +3. Elevations in parental distress are transient, and appear to be largely resolved by 4-6 months post-BMT. Parental distress was unrelated to child age, gender, diagnosis, or type of transplant, but was significantly related to parental socioeconomic status (SES). Parents from lower SES backgrounds reported greater levels of distress throughout the BMT process. Moderate correlations were observed between measures of parent and child distress, and level of child distress at the time of admission for BMT was predictive parental distress trajectories across the acute phase of BMT. These findings point to appropriate targets for intervention to reduce transplant-related distress.
Communications in Statistics Theory and Methods, Sep 2, 2006
An application of the pseudo maximum likelihood method to estimation of a multilevel linear model... more An application of the pseudo maximum likelihood method to estimation of a multilevel linear model fitted to the dependent observations coming from a finite population is demonstrated. The proposed approach provides a closed form solution for estimating of the model parameters. It is computationally simpler than the iterative procedures suggested in the literature (e.g., the iterative probability weighted least squares method of Pfeffermann et al. (Pfeffermann, D., Skinner, C.J., Holmes, D.J., Goldstein, H., Rasbash, J. (1998). Weighting for unequal selection probabilities in multilevel models. Journal of Royal Statistical Society B 60:23–40)). Issues related to model and sample design hierarchies and their impact on estimation are discussed. A problem of weighting at different levels is addressed. A small simulation study showed that the proposed procedure is efficient even for small within group sample sizes.
There has been little empirical documentation of the acute effects of bone marrow or stem cell tr... more There has been little empirical documentation of the acute effects of bone marrow or stem cell transplant (BMT) on children. In the present study, the responses of 153 children undergoing BMT were assessed in a prospective, longitudinal design. Children were assessed at the time of admission for transplant, then underwent weekly assessments to week +6, followed by monthly assessment to month +6. Data were obtained both by parent report and patient report (for patients age 5 and up) using the BASES scales. The major findings are: (1) children undergoing BMT enter the hospital with an already heightened level of distress (defined by high levels of somatic symptoms and mood disturbance, and low levels of activity) that increases dramatically following conditioning, reaching a peak approximately 1 week following transplant; (2) this increased distress is transient, declining rapidly back to admission levels by week +4 to week +5, followed by a further decline to presumed basal levels by months 4-6; and (3) the trajectories of distress depicted by both parent and child report are remarkably similar, each providing confirmatory support for the validity of the findings. These findings confirm a number of widely held clinical impressions that had not previously been documented empirically, and point to the need for new interventions or more intensive approaches to supportive care aimed at reducing levels of distress during the acute phase of transplant.
Advances in energy harvesting, low-power radios, and biometric sensing have enabled new applicati... more Advances in energy harvesting, low-power radios, and biometric sensing have enabled new applications in medical and scientific monitoring. In medicine, unobtrusive biosensors promise to wirelessly relay critical patient information including temperature, heart rate, or blood pressure. This paper describes key technologies needed to integrate complex, wirelessly-powered health monitors.
2006 IEEE International Conference on Reconfigurable Computing and FPGA's (ReConFig 2006), 2006
... 2. Compression Formats The FBI uses the wavelet scalar quantization (WSQ) method for encoding... more ... 2. Compression Formats The FBI uses the wavelet scalar quantization (WSQ) method for encoding/decoding fingerprint images [1]. Each image is firstnormalized with zero mean and pixel value range (-128,128). ...
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2009
Efficient, miniaturized wireless recording is critical for both existing and emerging health-moni... more Efficient, miniaturized wireless recording is critical for both existing and emerging health-monitoring applications. One important example of this is in the brain interface community, where new technologies allow improved observation and understanding of brain functions. This, in turn, drives the need for ever smaller, lower power, and higher performance circuitry for chronic recording. This paper describes circuit and system techniques for low power wireless brain interfaces. Active and passive architectures are described and compared, and measured in-vivo data from both are presented.
Many object-oriented metrics have been proposed, and at least fourteen empirical validations of t... more Many object-oriented metrics have been proposed, and at least fourteen empirical validations of thesemetrics have been performed. However, recently it was noted that without controlling for the effect ofclass size in a validation study, the impact of a metric may be exaggerated. It thus becomes necessaryto re-validate contemporary object-oriented metrics after controlling for size. In this paper we perform avalidation
Biomedical Engineering: Applications, Basis and Communications, 2015
Warfarin is a frequently used oral anticoagulant for long-term prevention and treatment of thromb... more Warfarin is a frequently used oral anticoagulant for long-term prevention and treatment of thromboembolic events. Due to its narrow therapeutic range and large inter-individual dose-response variability, it is highly desirable to personalize warfarin dosing. However, the complexity of the conventional kinetic-pharmacodynamic (K-PD) models hampers the development of the personalized dose management. To avert this challenge, we propose simplified PD models for warfarin dose-response relationship, which is motivated by ideas from control theory. The simplified models were further applied to longitudinal data of 37 patients undergoing anticoagulation treatment using the standard two-stage approach and then compared with the conventional K-PD models. Data analysis shows that all models have a similar predictive ability, but the simplified models are most parsimonious.
63rd Device Research Conference Digest, 2005. DRC '05., 2005
We describe novel AlGaN-GaN metal-oxide-semiconductor heterostructure field-effect transistors (M... more We describe novel AlGaN-GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) with record high power-voltage efficiencies (PVE = RF power/Drain bias), up to 0.43W/V-mm at 2 GHz. The RF powers of 15 W/mm at 35 V (PVE=0.43 W/V-mm) and 20 W/mm at 55 V (PVE= 0.36W/V-mm) were measured, which are approximately 50% higher than the previously reported values of PVE=0.25 W/V-mm (30
Post-traumatic stress disorder (PTSD) has been put forth as a model for understanding the adjustm... more Post-traumatic stress disorder (PTSD) has been put forth as a model for understanding the adjustment of children with cancer and their parents, but findings in the literature regarding the prevalence of post-traumatic stress symptoms (PTSS) have been mixed. This study examined PTSS levels in both patients and parents as a function of time elapsed from diagnosis, and by use of parent versus child reports for assessing patient PTSS. Four groups of patients (total N = 162) differing in time elapsed since diagnosis were assessed with standardized measures of PTSS. Patients reported on their own symptoms, while parents reported on their symptoms as well as symptoms in their child. Significant differences between groups were observed on all patient PTSS measures. Recently diagnosed patients obtained higher PTSS scores than survivors more than 5 years from diagnosis. Likewise, parents of recently diagnosed patients self-reported significantly higher levels of PTSS than parents of long-term survivors. Parent-child correlations were high and no differences were observed between parent and patient report of patient PTSS. Comparison with historical control data suggests that levels of PTSS in patients are very low. Concordance between parent and child reports of child PTSS suggests that data may be obtained with reasonable confidence from either if only one informant is available. Higher levels of PTSS in patients who are recently diagnosed (and their parents) in comparison to long-term survivors, suggest that the symptoms reported reflect primarily a concurrent response to ongoing acute stressors, rather than a post-traumatic re-experiencing of past traumas. This, in combination with the low levels of patient PTSS raise questions regarding the utility of PTSD as a model for understanding patient and parent adjustment to childhood cancer.
Parents (N = 151) of children undergoing bone marrow or stem cell transplantation (BMT) were asse... more Parents (N = 151) of children undergoing bone marrow or stem cell transplantation (BMT) were assessed in a prospective, longitudinal design with repeated measures of distress (mood disturbance, perceived stress, caregiver burden). Parents were assessed weekly from admission for BMT (week-1) through week +6 post-BMT, followed by monthly assessments through month +6. Concurrent measures of child distress (somatic distress, mood disturbance) were also obtained by parent and child report. Parents demonstrate modest, but significant elevations in distress, particularly during the early period from admission through week +3. Elevations in parental distress are transient, and appear to be largely resolved by 4-6 months post-BMT. Parental distress was unrelated to child age, gender, diagnosis, or type of transplant, but was significantly related to parental socioeconomic status (SES). Parents from lower SES backgrounds reported greater levels of distress throughout the BMT process. Moderate correlations were observed between measures of parent and child distress, and level of child distress at the time of admission for BMT was predictive parental distress trajectories across the acute phase of BMT. These findings point to appropriate targets for intervention to reduce transplant-related distress.
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Papers by Shesh Rai