Joel Welling - Academia.edu (original) (raw)

Papers by Joel Welling

Research paper thumbnail of A Parallel Visualization Pipeline for Terascale Earthquake Simulations

Proceedings of the ACM/IEEE SC2004 Conference, 2004

This paper presents a parallel visualization pipeline implemented at the Pittsburgh Supercomputin... more This paper presents a parallel visualization pipeline implemented at the Pittsburgh Supercomputing Center (PSC) for studying the largest earthquake simulation ever performed. The simulation employs 100 million hexahedral cells to model 3D seismic wave propagation of the 1994 Northridge earthquake. The time-varying dataset produced by the simulation requires terabytes of storage space. Our solution for visualizing such terascale simulations is based on a parallel adaptive rendering algorithm coupled with a new parallel I/O strategy which effectively reduces interframe delay by dedicating some processors to I/O and preprocessing tasks. In addition, a 2D vector field visualization method and a 3D enhancement technique are incorporated into the parallel visualization framework to help scientists better understand the wave propagation both on and under the ground surface. Our test results on the HP/Compaq AlphaServer operated at the PSC show that we can completely remove the I/O bottlenecks commonly present in time-varying data visualization. The high-performance visualization solution we provide to the scientists allows them to explore their data in the temporal, spatial, and variable domains at high resolution. The new high-resolution explorability, likely not available to most computational science groups, will help lead to many new insights.

Research paper thumbnail of Landscaping the structures of GAVI country vaccine supply chains and testing the effects of radical redesign

Vaccine, 2015

Many of the world&amp... more Many of the world's vaccine supply chains do not adequately provide vaccines, prompting several questions: how are vaccine supply chains currently structured, are these structures closely tailored to individual countries, and should these supply chains be radically redesigned? We segmented the 57 GAVI-eligible countries' vaccine supply chains based on their structure/morphology, analyzed whether these segments correlated with differences in country characteristics, and then utilized HERMES to develop a detailed simulation model of three sample countries' supply chains and explore the cost and impact of various alternative structures. The majority of supply chains (34 of 57) consist of four levels, despite serving a wide diversity of geographical areas and population sizes. These four-level supply chains loosely fall into three clusters [(1) 18 countries relatively more bottom-heavy, i.e., many more storage locations lower in the supply chain, (2) seven with relatively more storage locations in both top and lower levels, and (3) nine comparatively more top-heavy] which do not correlate closely with any of the country characteristics considered. For all three cluster types, our HERMES modeling found that simplified systems (a central location shipping directly to immunization locations with a limited number of Hubs in between) resulted in lower operating costs. A standard four-tier design template may have been followed for most countries and raises the possibility that simpler and more tailored designs may be warranted.

Research paper thumbnail of Rotation of 3D volumes by Fourier-interpolated shears

Graphical Models, 2006

Algorithms for rotation of 2D images by multiple shearing transformations are well known; algorit... more Algorithms for rotation of 2D images by multiple shearing transformations are well known; algorithms which use as few as four shears to perform an arbitrary 3D rotation on a 3D volume have also been described. By using Fourier transform methods to implement these shears, rotations can be performed completely reversibly and without loss of information. This is of great utility

Research paper thumbnail of Augmenting Transport versus Increasing Cold Storage to Improve Vaccine Supply Chains

PLoS ONE, 2013

Background: When addressing the urgent task of improving vaccine supply chains, especially to acc... more Background: When addressing the urgent task of improving vaccine supply chains, especially to accommodate the introduction of new vaccines, there is often a heavy emphasis on stationary storage. Currently, donations to vaccine supply chains occur largely in the form of storage equipment.

Research paper thumbnail of How influenza vaccination policy may affect vaccine logistics

Vaccine, 2012

When policymakers make decision about the target populations and timing of influenza vaccination,... more When policymakers make decision about the target populations and timing of influenza vaccination, they may not consider the impact on the vaccine supply chains, which may in turn affect vaccine availability. Our goal is to explore the effects on the Thailand vaccine supply chain of introducing influenza vaccines and varying the target populations and immunization time-frames. We Utilized our custom-designed software HERMES (Highly Extensible Resource for Modeling Supply Chains), we developed a detailed, computational discrete-event simulation model of the Thailand's National Immunization Program (NIP) supply chain in Trang Province, Thailand. A suite of experiments simulated introducing influenza vaccines for different target populations and over different time-frames prior to and during the annual influenza season. Introducing influenza vaccines creates bottlenecks that reduce the availability of both influenza vaccines as well as the other NIP vaccines, with provincial to district transport capacity being the primary constraint. Even covering only 25% of the Advisory Committee on Immunization Practice-recommended population while administering the vaccine over six months hinders overall vaccine availability so that only 62% of arriving patients can receive vaccines. Increasing the target population from 25% to 100% progressively worsens these bottlenecks, while increasing influenza vaccination time-frame from 1 to 6 months decreases these bottlenecks. Since the choice of target populations for influenza vaccination and the time-frame to deliver this vaccine can substantially affect the flow of all vaccines, policy-makers may want to consider supply chain effects when choosing target populations for a vaccine.

Research paper thumbnail of The impact of making vaccines thermostable in Niger's vaccine supply chain

Vaccine, 2012

Objective: Determine the effects on the vaccine cold chain of making different types of World Hea... more Objective: Determine the effects on the vaccine cold chain of making different types of World Health Organization (WHO) Expanded Program on Immunizations (EPI) vaccines thermostable. Methods: Utilizing a detailed computational, discrete-event simulation model of the Niger vaccine supply chain, we simulated the impact of making different combinations of the six current EPI vaccines thermostable. Findings: Making any EPI vaccine thermostable relieved existing supply chain bottlenecks (especially at the lowest levels), increased vaccine availability of all EPI vaccines, and decreased cold storage and transport capacity utilization. By far, the most substantial impact came from making the pentavalent vaccine thermostable, increasing its own vaccine availability from 87% to 97% and the vaccine availabilities of all other remaining non-thermostable EPI vaccines to over 93%. By contrast, making each of the other vaccines thermostable had considerably less effect on the remaining vaccines, failing to increase the vaccine availabilities of other vaccines to more than 89%. Making tetanus toxoid vaccine along with the pentavalent thermostable further increased the vaccine availability of all EPI vaccines by at least 1-2%. Conclusion: Our study shows the potential benefits of making any of Niger's EPI vaccines thermostable and therefore supports further development of thermostable vaccines. Eliminating the need for refrigerators and freezers should not necessarily be the only benefit and goal of vaccine thermostability. Rather, making even a single vaccine (or some subset of the vaccines) thermostable could free up significant cold storage space for other vaccines, and thereby help alleviate supply chain bottlenecks that occur throughout the world.

Research paper thumbnail of Maintaining Vaccine Delivery Following the Introduction of the Rotavirus and Pneumococcal Vaccines in Thailand

PLoS ONE, 2011

Although the substantial burdens of rotavirus and pneumococcal disease have motivated many countr... more Although the substantial burdens of rotavirus and pneumococcal disease have motivated many countries to consider introducing the rotavirus vaccine (RV) and heptavalent pneumococcal conjugate vaccine (PCV-7) to their National Immunization Programs (EPIs), these new vaccines could affect the countries' vaccine supply chains (i.e., the series of steps required to get a vaccine from their manufacturers to patients). We developed detailed computational models of the Trang Province, Thailand, vaccine supply chain to simulate introducing various RV and PCV-7 vaccine presentations and their combinations. Our results showed that the volumes of these new vaccines in addition to current routine vaccines could meet and even exceed (1) the refrigerator space at the provincial district and sub-district levels and (2) the transport cold space at district and sub-district levels preventing other vaccines from being available to patients who arrive to be immunized. Besides the smallest RV presentation (17.

Research paper thumbnail of FUNCTIONAL BRAIN ABNORMALITIES ARE RELATED TO CLINICAL RECOVERY AND TIME TO RETURN-TO-PLAY IN ATHLETES

Neurosurgery, 2007

The relationship between athlete report of symptoms, neurophysiological activation and neuropsych... more The relationship between athlete report of symptoms, neurophysiological activation and neuropsychological functioning is investigated in a sample of high school athletes.

Research paper thumbnail of The Challenge of Functional Magnetic Resonance Imaging

Journal of Computational and Graphical Statistics, 1999

... Empirical evidence strongly suggests that this method provides a significant improvement inse... more ... Empirical evidence strongly suggests that this method provides a significant improvement insensitivity. ... particularly useful is a program for performing arithmetic (expressed in reverse Polish notation ... MS, Vevea, JM, Brady, TJ, and Rosen, BR (1991), "Functional Mapping of the ...

Research paper thumbnail of Statistical Issues in fMRI for Brain Imaging

International Statistical Review, 2001

Functional magnetic resonance imaging is a technique developed in the last decade and used in the... more Functional magnetic resonance imaging is a technique developed in the last decade and used in the fields of cognitive psychology and n e u d e n c e , among others, to study the processes underlying the working of the human brain. In this paper we examine some of the statistical issues in hnctional magnetic resonance imaging for brain researeh. We start by giving a brief introduction to the physics of magnetic resonance imaging. Using a psgchological experiment as a case study, we then describe questions of design and statisticat analysis. The data obtained from functional magnetic resonance imaging studies are of a highly complex nature, displaying both spatial and temporal correlation, as well as high levels of noise from different sources. Given this, the scope for statistics is vast, and is not limited to simple analysis of the data, once collected.

Research paper thumbnail of Distributed, on-demand, data-intensive and collaborative simulation analysis

Future Generation Computer Systems, 2003

Distributed, on-demand, data-intensive, and collaborative simulation analysis tools are being dev... more Distributed, on-demand, data-intensive, and collaborative simulation analysis tools are being developed by an international team to solve real problems such as bioinformatics applications. The project consists of three distinct focuses: compute, visualize, and collaborate. Each component utilizes software and hardware that performs across the International Grid. Computers in North America, Asia, and Europe are working on a common simulation programs. The results are visualized in a multi-way 3D visualization collaboration session where additional compute requests can be submitted in real-time. Navigation controls and data replication issues are addressed and solved with a scalable solution. Published by Elsevier B.V.

Research paper thumbnail of Pursuit and Saccadic Eye Movement Subregions in Human Frontal Eye Field: A High-resolution fMRI Investigation

Cerebral Cortex, 2002

Recent positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studie... more Recent positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies in humans have localized the frontal eye field (FEF) to the precentral sulcus (PCS). In macaque monkeys, low-threshold microstimulation and single unit recording studies have located a saccadic subregion of FEF in a restricted area along the anterior wall of the arcuate sulcus and a pursuit subregion located deeper in the sulcus close to the fundus. The functional organization and anatomical location of these two FEF subregions are still to be defined in humans. In the present study, we used fMRI with high spatial resolution image acquisition at 3.0 Tesla to map the saccade-and pursuit-related areas of FEF within the two walls of the PCS in 11 subjects. We localized the saccade-related area to the upper portion of the anterior wall of the precentral sulcus and the pursuit-related area to a deeper region along the anterior wall, extending in some subjects to the fundus or deep posterior wall. These findings localize distinct pursuit and saccadic subregions of FEF in humans and demonstrate a high degree of homology in the organization of these FEF subregions in the human and the macaque monkey.

Research paper thumbnail of Impact of changing the measles vaccine vial size on Niger's vaccine supply chain: a computational model

BMC Public Health, 2011

Background: Many countries, such as Niger, are considering changing their vaccine vial size prese... more Background: Many countries, such as Niger, are considering changing their vaccine vial size presentation and may want to evaluate the subsequent impact on their supply chains, the series of steps required to get vaccines from their manufacturers to patients. The measles vaccine is particularly important in Niger, a country prone to measles outbreaks. Methods: We developed a detailed discrete event simulation model of the vaccine supply chain representing every vaccine, storage location, refrigerator, freezer, and transport device (e.g., cold trucks, 4 × 4 trucks, and vaccine carriers) in the Niger Expanded Programme on Immunization (EPI). Experiments simulated the impact of replacing the 10-dose measles vial size with 5-dose, 2-dose and 1-dose vial sizes.

Research paper thumbnail of I/O strategies for parallel rendering of large time-varying volume data

visualization. This high-performance visualization solution we provide to the scientists allows t... more visualization. This high-performance visualization solution we provide to the scientists allows them to explore their data in the temporal, spatial, and visualization domains at high resolution. This new high-resolution explorability, likely not presently available to most computational science groups, will help lead to many new insights.

Research paper thumbnail of Impact of Introducing the Pneumococcal and Rotavirus Vaccines Into the Routine Immunization Program in Niger

American Journal of Public Health, 2012

Objectives-We investigated whether introducing the rotavirus and pneumococcal vaccines, which are... more Objectives-We investigated whether introducing the rotavirus and pneumococcal vaccines, which are greatly needed in West Africa, would overwhelm existing supply chains (i.e., the series of steps required to get a vaccine from the manufacturers to the target population) in Niger.

Research paper thumbnail of Replacing the measles ten-dose vaccine presentation with the single-dose presentation in Thailand

Vaccine, 2011

Introduced to minimize open vial wastage, single-dose vaccine vials require more storage space an... more Introduced to minimize open vial wastage, single-dose vaccine vials require more storage space and therefore may affect vaccine supply chains (i.e., the series of steps and processes entailed to deliver vaccines from manufacturers to patients). We developed a computational model of Thailand's Trang province vaccine supply chain to analyze the effects of switching from a tendose measles vaccine presentation to each of the following: a single-dose Measles-Mumps-Rubella vaccine (which Thailand is currently considering) and a single-dose measles vaccine. While the Trang province vaccine supply chain would generally have enough storage and transport capacity to accommodate the switches, the added volume could push some locations' storage and transport space utilization close to their limits. Single-dose vaccines would allow for more precise ordering and decrease open vial waste, but decrease reserves for unanticipated demand. Moreover, the added disposal and administration costs could far outweigh the costs saved from preventing open vial wastage.

Research paper thumbnail of A Parallel Visualization Pipeline for Terascale Earthquake Simulations

Proceedings of the ACM/IEEE SC2004 Conference, 2004

This paper presents a parallel visualization pipeline implemented at the Pittsburgh Supercomputin... more This paper presents a parallel visualization pipeline implemented at the Pittsburgh Supercomputing Center (PSC) for studying the largest earthquake simulation ever performed. The simulation employs 100 million hexahedral cells to model 3D seismic wave propagation of the 1994 Northridge earthquake. The time-varying dataset produced by the simulation requires terabytes of storage space. Our solution for visualizing such terascale simulations is based on a parallel adaptive rendering algorithm coupled with a new parallel I/O strategy which effectively reduces interframe delay by dedicating some processors to I/O and preprocessing tasks. In addition, a 2D vector field visualization method and a 3D enhancement technique are incorporated into the parallel visualization framework to help scientists better understand the wave propagation both on and under the ground surface. Our test results on the HP/Compaq AlphaServer operated at the PSC show that we can completely remove the I/O bottlenecks commonly present in time-varying data visualization. The high-performance visualization solution we provide to the scientists allows them to explore their data in the temporal, spatial, and variable domains at high resolution. The new high-resolution explorability, likely not available to most computational science groups, will help lead to many new insights.

Research paper thumbnail of Landscaping the structures of GAVI country vaccine supply chains and testing the effects of radical redesign

Vaccine, 2015

Many of the world&amp... more Many of the world's vaccine supply chains do not adequately provide vaccines, prompting several questions: how are vaccine supply chains currently structured, are these structures closely tailored to individual countries, and should these supply chains be radically redesigned? We segmented the 57 GAVI-eligible countries' vaccine supply chains based on their structure/morphology, analyzed whether these segments correlated with differences in country characteristics, and then utilized HERMES to develop a detailed simulation model of three sample countries' supply chains and explore the cost and impact of various alternative structures. The majority of supply chains (34 of 57) consist of four levels, despite serving a wide diversity of geographical areas and population sizes. These four-level supply chains loosely fall into three clusters [(1) 18 countries relatively more bottom-heavy, i.e., many more storage locations lower in the supply chain, (2) seven with relatively more storage locations in both top and lower levels, and (3) nine comparatively more top-heavy] which do not correlate closely with any of the country characteristics considered. For all three cluster types, our HERMES modeling found that simplified systems (a central location shipping directly to immunization locations with a limited number of Hubs in between) resulted in lower operating costs. A standard four-tier design template may have been followed for most countries and raises the possibility that simpler and more tailored designs may be warranted.

Research paper thumbnail of Rotation of 3D volumes by Fourier-interpolated shears

Graphical Models, 2006

Algorithms for rotation of 2D images by multiple shearing transformations are well known; algorit... more Algorithms for rotation of 2D images by multiple shearing transformations are well known; algorithms which use as few as four shears to perform an arbitrary 3D rotation on a 3D volume have also been described. By using Fourier transform methods to implement these shears, rotations can be performed completely reversibly and without loss of information. This is of great utility

Research paper thumbnail of Augmenting Transport versus Increasing Cold Storage to Improve Vaccine Supply Chains

PLoS ONE, 2013

Background: When addressing the urgent task of improving vaccine supply chains, especially to acc... more Background: When addressing the urgent task of improving vaccine supply chains, especially to accommodate the introduction of new vaccines, there is often a heavy emphasis on stationary storage. Currently, donations to vaccine supply chains occur largely in the form of storage equipment.

Research paper thumbnail of How influenza vaccination policy may affect vaccine logistics

Vaccine, 2012

When policymakers make decision about the target populations and timing of influenza vaccination,... more When policymakers make decision about the target populations and timing of influenza vaccination, they may not consider the impact on the vaccine supply chains, which may in turn affect vaccine availability. Our goal is to explore the effects on the Thailand vaccine supply chain of introducing influenza vaccines and varying the target populations and immunization time-frames. We Utilized our custom-designed software HERMES (Highly Extensible Resource for Modeling Supply Chains), we developed a detailed, computational discrete-event simulation model of the Thailand's National Immunization Program (NIP) supply chain in Trang Province, Thailand. A suite of experiments simulated introducing influenza vaccines for different target populations and over different time-frames prior to and during the annual influenza season. Introducing influenza vaccines creates bottlenecks that reduce the availability of both influenza vaccines as well as the other NIP vaccines, with provincial to district transport capacity being the primary constraint. Even covering only 25% of the Advisory Committee on Immunization Practice-recommended population while administering the vaccine over six months hinders overall vaccine availability so that only 62% of arriving patients can receive vaccines. Increasing the target population from 25% to 100% progressively worsens these bottlenecks, while increasing influenza vaccination time-frame from 1 to 6 months decreases these bottlenecks. Since the choice of target populations for influenza vaccination and the time-frame to deliver this vaccine can substantially affect the flow of all vaccines, policy-makers may want to consider supply chain effects when choosing target populations for a vaccine.

Research paper thumbnail of The impact of making vaccines thermostable in Niger's vaccine supply chain

Vaccine, 2012

Objective: Determine the effects on the vaccine cold chain of making different types of World Hea... more Objective: Determine the effects on the vaccine cold chain of making different types of World Health Organization (WHO) Expanded Program on Immunizations (EPI) vaccines thermostable. Methods: Utilizing a detailed computational, discrete-event simulation model of the Niger vaccine supply chain, we simulated the impact of making different combinations of the six current EPI vaccines thermostable. Findings: Making any EPI vaccine thermostable relieved existing supply chain bottlenecks (especially at the lowest levels), increased vaccine availability of all EPI vaccines, and decreased cold storage and transport capacity utilization. By far, the most substantial impact came from making the pentavalent vaccine thermostable, increasing its own vaccine availability from 87% to 97% and the vaccine availabilities of all other remaining non-thermostable EPI vaccines to over 93%. By contrast, making each of the other vaccines thermostable had considerably less effect on the remaining vaccines, failing to increase the vaccine availabilities of other vaccines to more than 89%. Making tetanus toxoid vaccine along with the pentavalent thermostable further increased the vaccine availability of all EPI vaccines by at least 1-2%. Conclusion: Our study shows the potential benefits of making any of Niger's EPI vaccines thermostable and therefore supports further development of thermostable vaccines. Eliminating the need for refrigerators and freezers should not necessarily be the only benefit and goal of vaccine thermostability. Rather, making even a single vaccine (or some subset of the vaccines) thermostable could free up significant cold storage space for other vaccines, and thereby help alleviate supply chain bottlenecks that occur throughout the world.

Research paper thumbnail of Maintaining Vaccine Delivery Following the Introduction of the Rotavirus and Pneumococcal Vaccines in Thailand

PLoS ONE, 2011

Although the substantial burdens of rotavirus and pneumococcal disease have motivated many countr... more Although the substantial burdens of rotavirus and pneumococcal disease have motivated many countries to consider introducing the rotavirus vaccine (RV) and heptavalent pneumococcal conjugate vaccine (PCV-7) to their National Immunization Programs (EPIs), these new vaccines could affect the countries' vaccine supply chains (i.e., the series of steps required to get a vaccine from their manufacturers to patients). We developed detailed computational models of the Trang Province, Thailand, vaccine supply chain to simulate introducing various RV and PCV-7 vaccine presentations and their combinations. Our results showed that the volumes of these new vaccines in addition to current routine vaccines could meet and even exceed (1) the refrigerator space at the provincial district and sub-district levels and (2) the transport cold space at district and sub-district levels preventing other vaccines from being available to patients who arrive to be immunized. Besides the smallest RV presentation (17.

Research paper thumbnail of FUNCTIONAL BRAIN ABNORMALITIES ARE RELATED TO CLINICAL RECOVERY AND TIME TO RETURN-TO-PLAY IN ATHLETES

Neurosurgery, 2007

The relationship between athlete report of symptoms, neurophysiological activation and neuropsych... more The relationship between athlete report of symptoms, neurophysiological activation and neuropsychological functioning is investigated in a sample of high school athletes.

Research paper thumbnail of The Challenge of Functional Magnetic Resonance Imaging

Journal of Computational and Graphical Statistics, 1999

... Empirical evidence strongly suggests that this method provides a significant improvement inse... more ... Empirical evidence strongly suggests that this method provides a significant improvement insensitivity. ... particularly useful is a program for performing arithmetic (expressed in reverse Polish notation ... MS, Vevea, JM, Brady, TJ, and Rosen, BR (1991), "Functional Mapping of the ...

Research paper thumbnail of Statistical Issues in fMRI for Brain Imaging

International Statistical Review, 2001

Functional magnetic resonance imaging is a technique developed in the last decade and used in the... more Functional magnetic resonance imaging is a technique developed in the last decade and used in the fields of cognitive psychology and n e u d e n c e , among others, to study the processes underlying the working of the human brain. In this paper we examine some of the statistical issues in hnctional magnetic resonance imaging for brain researeh. We start by giving a brief introduction to the physics of magnetic resonance imaging. Using a psgchological experiment as a case study, we then describe questions of design and statisticat analysis. The data obtained from functional magnetic resonance imaging studies are of a highly complex nature, displaying both spatial and temporal correlation, as well as high levels of noise from different sources. Given this, the scope for statistics is vast, and is not limited to simple analysis of the data, once collected.

Research paper thumbnail of Distributed, on-demand, data-intensive and collaborative simulation analysis

Future Generation Computer Systems, 2003

Distributed, on-demand, data-intensive, and collaborative simulation analysis tools are being dev... more Distributed, on-demand, data-intensive, and collaborative simulation analysis tools are being developed by an international team to solve real problems such as bioinformatics applications. The project consists of three distinct focuses: compute, visualize, and collaborate. Each component utilizes software and hardware that performs across the International Grid. Computers in North America, Asia, and Europe are working on a common simulation programs. The results are visualized in a multi-way 3D visualization collaboration session where additional compute requests can be submitted in real-time. Navigation controls and data replication issues are addressed and solved with a scalable solution. Published by Elsevier B.V.

Research paper thumbnail of Pursuit and Saccadic Eye Movement Subregions in Human Frontal Eye Field: A High-resolution fMRI Investigation

Cerebral Cortex, 2002

Recent positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studie... more Recent positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies in humans have localized the frontal eye field (FEF) to the precentral sulcus (PCS). In macaque monkeys, low-threshold microstimulation and single unit recording studies have located a saccadic subregion of FEF in a restricted area along the anterior wall of the arcuate sulcus and a pursuit subregion located deeper in the sulcus close to the fundus. The functional organization and anatomical location of these two FEF subregions are still to be defined in humans. In the present study, we used fMRI with high spatial resolution image acquisition at 3.0 Tesla to map the saccade-and pursuit-related areas of FEF within the two walls of the PCS in 11 subjects. We localized the saccade-related area to the upper portion of the anterior wall of the precentral sulcus and the pursuit-related area to a deeper region along the anterior wall, extending in some subjects to the fundus or deep posterior wall. These findings localize distinct pursuit and saccadic subregions of FEF in humans and demonstrate a high degree of homology in the organization of these FEF subregions in the human and the macaque monkey.

Research paper thumbnail of Impact of changing the measles vaccine vial size on Niger's vaccine supply chain: a computational model

BMC Public Health, 2011

Background: Many countries, such as Niger, are considering changing their vaccine vial size prese... more Background: Many countries, such as Niger, are considering changing their vaccine vial size presentation and may want to evaluate the subsequent impact on their supply chains, the series of steps required to get vaccines from their manufacturers to patients. The measles vaccine is particularly important in Niger, a country prone to measles outbreaks. Methods: We developed a detailed discrete event simulation model of the vaccine supply chain representing every vaccine, storage location, refrigerator, freezer, and transport device (e.g., cold trucks, 4 × 4 trucks, and vaccine carriers) in the Niger Expanded Programme on Immunization (EPI). Experiments simulated the impact of replacing the 10-dose measles vial size with 5-dose, 2-dose and 1-dose vial sizes.

Research paper thumbnail of I/O strategies for parallel rendering of large time-varying volume data

visualization. This high-performance visualization solution we provide to the scientists allows t... more visualization. This high-performance visualization solution we provide to the scientists allows them to explore their data in the temporal, spatial, and visualization domains at high resolution. This new high-resolution explorability, likely not presently available to most computational science groups, will help lead to many new insights.

Research paper thumbnail of Impact of Introducing the Pneumococcal and Rotavirus Vaccines Into the Routine Immunization Program in Niger

American Journal of Public Health, 2012

Objectives-We investigated whether introducing the rotavirus and pneumococcal vaccines, which are... more Objectives-We investigated whether introducing the rotavirus and pneumococcal vaccines, which are greatly needed in West Africa, would overwhelm existing supply chains (i.e., the series of steps required to get a vaccine from the manufacturers to the target population) in Niger.

Research paper thumbnail of Replacing the measles ten-dose vaccine presentation with the single-dose presentation in Thailand

Vaccine, 2011

Introduced to minimize open vial wastage, single-dose vaccine vials require more storage space an... more Introduced to minimize open vial wastage, single-dose vaccine vials require more storage space and therefore may affect vaccine supply chains (i.e., the series of steps and processes entailed to deliver vaccines from manufacturers to patients). We developed a computational model of Thailand's Trang province vaccine supply chain to analyze the effects of switching from a tendose measles vaccine presentation to each of the following: a single-dose Measles-Mumps-Rubella vaccine (which Thailand is currently considering) and a single-dose measles vaccine. While the Trang province vaccine supply chain would generally have enough storage and transport capacity to accommodate the switches, the added volume could push some locations' storage and transport space utilization close to their limits. Single-dose vaccines would allow for more precise ordering and decrease open vial waste, but decrease reserves for unanticipated demand. Moreover, the added disposal and administration costs could far outweigh the costs saved from preventing open vial wastage.