A Samar - Academia.edu (original) (raw)

Papers by A Samar

AIP Conference Proceedings, 2001

The CMS experiment at CERN is setting up a Grid infrastructure required to fulfil the needs impos... more The CMS experiment at CERN is setting up a Grid infrastructure required to fulfil the needs imposed by Terabyte scale productions for the next few years. The goal is to automate the production and at the same time allow the users to interact with the system, if required, to make decisions which would optimise performance. We present the architecture, design and functionality of our first working Objectivity file replication prototype. The middle-ware of choice is the Globus toolkit that provides promising functionality. Our results prove the ability of the Globus toolkit to be used as an underlying technology for a worldwide Data Grid. The required data management functionality includes high speed file transfers, secure access to remote files, selection and synchronisation of replicas and managing the meta information. The whole system is expected to be flexible enough to incorporate site specific policies. The data management granularity is the file rather than the object level. The first prototype is currently in use for the High Level Trigger (HLT) production (autumn 2000). Owing to these efforts, CMS is one of the pioneers to use the Data Grid functionality in a running production system. The project can be viewed as an evaluator of different strategies, a test for the capabilities of middle-ware tools and a provider of basic Grid functionalities.

alexandria journal of veterinary sciences, 2012

Little information is available about Q. fever in Egypt, a zoonotic disease caused by Coxiellabur... more Little information is available about Q. fever in Egypt, a zoonotic disease caused by Coxiellaburnetii, transmitted from domestic ruminants. This study aimed to investigate the prevalence of IgG antibodies against C. burnetii phase II antigen in human serum of two different groups (healthy human population of a rural area and a population of an urban area suffering from respiratory complains), in other words determine the percentage of both symptomatic (urban) and asymptomatic (rural) Q. fever infections and also investigate about different risk factors. A total of 92 human serum samples (42 serum samples from patients with respiratory complains and 50 serum samples randomly collected from people free from respiratory complains) were collected. The detection of antibodies against C. burnetii was carried out by ELISA method. The obtained results in the current study revealed that 66 out of 92 (72%)humanserum samples were found to be ELISA positive for C. burnetii phase II IgG. 31seru...

International Journal of Molecular and Immuno Oncology, 2022

Objectives: We present real-world outcome with the use of palbociclib in patients with HR-positiv... more Objectives: We present real-world outcome with the use of palbociclib in patients with HR-positive Her2-negative breast cancer treated at single center in India. Material and Methods: We conducted a medical audit of consecutive patients with HR-positive Her2-negative metastatic breast cancer, who were treated with palbociclib at our center between November 2016 and May 2020. Palbociclib was commenced at a dose of 125 mg orally once daily and a schedule of 21 days on therapy followed by 7 days off therapy was followed. Survival analysis included the Kaplan–Meier method using Statistical Package for the Social Sciences software (Version 26). HRs were calculated using Cox proportional hazard regression models and 95% confidence intervals (CIs) for the incidence estimates. Results: A total of 67 female patients were commenced on treatment with palbociclib between November 2016 and May 2020. The median age was 55 years (range 29–78 years). A total of 51 (76%) of these patients were postm...

International Polymer Science and Technology, 2010

Egyptian Poultry Science Journal, 2019

The experiment was carried out to evaluate the response of broilers fed diet supplemented with an... more The experiment was carried out to evaluate the response of broilers fed diet supplemented with antibiotic alternatives, Probiotic (BioPlus 2B), Prebiotic (Techno MOs), Synbiotic and medicinal herbs (Mixture of Origanum majorana, Foeniculum vulgare and Carum carvi in ratio 1: 1: 1), on their performance and intestinal histology. A total of 125-day old chicks cobb (500) broiler chicks were randomly distributed into 5 treatments with five replicates of 5 chicks each and raised for 6 weeks. Chicks were kept in cleaned and fumigated cage of wire floored batteries. Experimental diets and water were offered ad-libitum over the experimental period starting from one day old. The experimental treatments received basal diets which were formulated to starter (1-21d) and grower-finisher (22-42d) broiler growth periods. During each growth period, birds received the control diet (un-supplemented), whereas the other groups fed diet contained either of tested feed additives (probiotic, prebiotic, synbiotic or medicinal plants mixture). The most important results obtained from this study could be summarized as follows:-a highly significant effect (p≤ 0.05) on live body weight at the end of experiment period was observed due to the effect of synbiotic treatment compared the other treatments. A highest body weight gain was recorded by the synbiotic treatment compared the control ones. Different feed additives improved feed conversion ratio compared to control (p≤0.001, for the whole experimental period. All supplements effect the intestinal histology compared to that of the control in duodenum and jejunum, intestine region but the effect is not significant. Also, feed additives led to significant improvement in villus height and crypt depth in ileum region. In conclusion, results show that synbiotic treatment was the superior in improving productive performance of broilers. Further research is still need to verify current results.

Grid Computing — GRID 2000, 2000

In this paper we report on preliminary work and architectural design carried out in the "Data Man... more In this paper we report on preliminary work and architectural design carried out in the "Data Management" work package in the International Data Grid project. Our aim within a time scale of three years is to provide Grid middleware services supporting the I/Ointensive worldwide distributed next generation experiments in High-Energy Physics, Earth Observation and Bioinformatics. The goal is to specify, develop, integrate and test tools and middleware infrastructure to coherently manage and share Petabyte-range information volumes in high-throughput production-quality Grid environments. The middleware will allow secure access to massive amounts of data in a universal namespace, to move and replicate data at high speed from one geographical site to another, and to manage synchronisation of remote copies. We put much attention on clearly specifying and categorising existing work on the Grid, especially in data management in Grid related projects. Challenging use cases are described and how they map to architectural decisions concerning data access, replication, meta data management, security and query optimisation. 1 CERN Regional Centre (RC) 1 RC 3 RC

Scientific Programming, 2002

The GDMP client-server software system is a generic file replication tool that replicates files s... more The GDMP client-server software system is a generic file replication tool that replicates files securely and efficiently from one site to another in a Data Grid environment using Globus Grid tools. In addition, it manages replica catalogue entries for file replicas and thus maintains a consistent view on names and locations of replicated files. Files to be transferred can be of any particular file format and GDMP treats them all in the same way. However, for Objectivity database files a particular plug-in exists. All files are assumed to be read-only.

IEEE 5th Control and System Graduate Research Colloquium (ICSGRC), 2014

Cloud computing is the realization for a long-held dream of computing as utility of establishment... more Cloud computing is the realization for a long-held dream of computing as utility of establishment of on-demand IT services. The considerable specifications of this emerging technology have attracted attentions of many users and enterprises in various industries. However, there are some considerable concerns that reduce reliability of cloud-based services. Managing user identities in clouds is one of the most challenging security issues that has led to many performed researches in this area. Hence, an agent-based user authentication model has been presented in this paper to enhance security of cloud computing environments. A unique extension has been provided in the proposed model is to identify the ownership of private individual devices and to establish a reasonable and logical dependency between cloud servers and clients. Furthermore, a provisional access permission algorithm has been presented for un-registered devices to investigate and verify authenticity and correctness of one-time access requests by a higher level of security in comparison with current models. The proposed model has been introduced and evaluated regarding to three main parameters: performance, security, and scalability. The analysis of user authentication agent shows that this model enhances the rate of security and reliability in cloud computing environments without affecting the rate of energy and time consumption, and scalability.

22nd International Symposium on Reliable Distributed Systems, 2003. Proceedings.

2008 IEEE International Symposium on Parallel and Distributed Processing, 2008

We present a novel protocol for restructuring a treebased overlay network in response to the work... more We present a novel protocol for restructuring a treebased overlay network in response to the workload of the application running over it. Through low-cost restructuring operations, our protocol incrementally adapts the tree so as to bring nodes that tend to communicate with one another closer together in the tree. It achieves this while respecting degree bounds on nodes so that, e.g., no node degenerates into a "hub" for the overlay. Moreover, it limits restructuring to those parts of the tree over which communication takes place, avoiding restructuring other parts of the tree unnecessarily. We show via experiments on PlanetLab that our protocol can significantly reduce communication latencies in workloads dominated by clusters of communicating nodes.

24th IEEE Symposium on Reliable Distributed Systems (SRDS'05)

We present an algorithm by which nodes arranged in a tree, with each node initially knowing only ... more We present an algorithm by which nodes arranged in a tree, with each node initially knowing only its parent and children, can construct a fault-tolerant communication structure (an expander graph) among themselves in a distributed and scalable way. The tree overlayed with this logical expander is a useful structure for distributed applications that require the intrinsic "treeness" from the topology but cannot afford any obstruction in communication due to failures. At the core of our construction is a novel distributed mechanism that samples nodes uniformly at random from the tree. In the event of node joins, node departures or node failures, the expander maintains its own fault tolerance and permits the reformation of the tree. We present simulation results to quantify the convergence of our algorithm to a fault tolerant network having both good vertex connectivity and expansion properties.

International Conference on Dependable Systems and Networks, 2004, 2004

A correctly working Domain Name System (DNS) is essential for the Internet. Due to its significan... more A correctly working Domain Name System (DNS) is essential for the Internet. Due to its significance and because of deficiencies in its current design, the DNS is vulnerable to a wide range of attacks. This paper presents the design and implementation of a secure distributed name service. Our service is able provide fault tolerance and security even in the presence of a fraction of corrupted servers, avoiding any single point of failure. It further solves the problem of storing zone secrets online in a way that does not leak them to a corrupted server, while still supporting secure dynamic updates. Our service uses state-machine replication and threshold cryptography. We present results from experiments performed using a prototype implementation on the Internet in realistic setups. The results show that our design achieves the required assurances while servicing most frequent requests in reasonable time.

... r hF s will lw ys e inde ted to himF h nks wike3 s would lso like to th nk ghenxi ng for ll t... more ... r hF s will lw ys e inde ted to himF h nks wike3 s would lso like to th nk ghenxi ng for ll the enlightening dis usE sions we h ve hd over the ye rsF wy st ytg rnegie wellon would not h ve een s ple sur le s it w sD hd it not een for friends like elin D plorin ... R histri uted p ultE oler nt rees ...

IEEE Transactions on Parallel and Distributed Systems, 2008

We present Quiver, a system that coordinates service proxies placed at the "edge" of the Internet... more We present Quiver, a system that coordinates service proxies placed at the "edge" of the Internet to serve distributed clients accessing a service involving mutable objects. Quiver enables these proxies to perform consistent accesses to shared objects by migrating the objects to proxies performing operations on those objects. These migrations dramatically improve performance when operations involving an object exhibit geographic locality, since migrating this object into the vicinity of proxies hosting these operations will benefit all such operations. Other workloads benefit from Quiver, dispersing the computation load across the proxies and saving the costs of sending operation parameters over the wide area when these are large. Quiver also supports optimizations for single-object reads that do not involve migrating the object. We detail the protocols for implementing object operations and for accommodating the addition, involuntary disconnection, and voluntary departure of proxies. We also evaluate Quiver through experiments on PlanetLab. Finally, we discuss the use of Quiver to build an e-commerce application and a distributed network traffic modeling service.

Echocardiography, 2013

Objectives: This study assessed the ability of live/real time three-dimensional transesophageal e... more Objectives: This study assessed the ability of live/real time three-dimensional transesophageal echocardiography (3DTEE) in measuring (1) atrial septal defect (ASD) maximum dimension, area, and adjacent rim size, (2) ASD occluder left and right atrial disk size, (3) length of contact between the left atrial (LA) disk and the aorta, and in (4) assessing device related complications such as residual shunt, device embolization, and device encroachment upon adjacent cardiac structures. Materials and Methods: 3DTEE images acquired during percutaneous ASD closure by the Amplatzer Septal Occluder in 15 adult patients were retrospectively analyzed. Offline analysis was done using both the Philips 5500 ultrasound system and Philips QLAB software. 3D color flow Doppler images were used to assess residual ASD shunting. Results: The Philips 5500 and Philips QLAB measurements correlated well for ASD maximum dimension and area measurements. The Philips QLAB 3DTEE disk size measurements also correlated well with the manufacturer obtained sizes. The aortic rim was deficient in 7 of the 15 patients, and the mean ASD occluder device size was 4 mm greater than the mean ASD maximum dimension. The LA occluder disk was in contact with the aorta throughout the cardiac cycle in 12 of the 15 patients, and the LA occluder disk size correlated significantly with the contact length with the aorta. Conclusion: Most of the patients demonstrated contact between the LA occluder disk and the aorta throughout the cardiac cycle. 3DTEE may be useful in identifying patients at greater risk for aortic erosion.

The American Journal of Geriatric Cardiology, 2006

Patent foramen ovale (PFO) is a well-recognized risk factor for ischemic strokes. The true preval... more Patent foramen ovale (PFO) is a well-recognized risk factor for ischemic strokes. The true prevalence of PFO among stroke patients is still under debate. Transesophageal echocardiography (TEE) is the "gold standard" in diagnosing PFO but the physiology requires right-to-left atrial shunting. In this report, we evaluate the prevalence of PFO in a diverse group of ischemic stroke patients studied by TEE. TEE of 1,663 ischemic stroke patients were reviewed for cardiac source of embolism, including PFO and atrial septal aneurysm (ASA). Agitated saline bubble injection was performed to look for right to left atrial shunting. Success of maneuvers to elevate right atrial pressure (RAP) was noted by looking at the atrial septal bulge. Among 1,435 ischemic stroke patients analyzed, the presence or absence of PFO could not be determined in 32.1% because bulging of the septum could not be demonstrated in patients with negative contrast study despite aggressive maneuvers to elevate RAP. Of the remaining 974 patients, 294 patients (30.2%) had a PFO. The mean age was 61.5 years in both groups, with a bimodal distribution of PFO and the highest prevalence occurring in…

Cluster Computing, Jul 1, 2002

Data replication is a key issue in a Data Grid and can be managed in different ways and at differ... more Data replication is a key issue in a Data Grid and can be managed in different ways and at different levels of granularity: for example, at the file level or object level. In the High Energy Physics community, Data Grids are being developed to support the distributed analysis of experimental data. We have produced a prototype data replication tool, the Grid Data Mirroring Package (GDMP) that is in production use in one physics experiment, with middleware provided by the Globus Toolkit used for authentication, data movement, and ...

AIP Conference Proceedings, 2001

The CMS experiment at CERN is setting up a Grid infrastructure required to fulfil the needs impos... more The CMS experiment at CERN is setting up a Grid infrastructure required to fulfil the needs imposed by Terabyte scale productions for the next few years. The goal is to automate the production and at the same time allow the users to interact with the system, if required, to make decisions which would optimise performance. We present the architecture, design and functionality of our first working Objectivity file replication prototype. The middle-ware of choice is the Globus toolkit that provides promising functionality. Our results prove the ability of the Globus toolkit to be used as an underlying technology for a worldwide Data Grid. The required data management functionality includes high speed file transfers, secure access to remote files, selection and synchronisation of replicas and managing the meta information. The whole system is expected to be flexible enough to incorporate site specific policies. The data management granularity is the file rather than the object level. The first prototype is currently in use for the High Level Trigger (HLT) production (autumn 2000). Owing to these efforts, CMS is one of the pioneers to use the Data Grid functionality in a running production system. The project can be viewed as an evaluator of different strategies, a test for the capabilities of middle-ware tools and a provider of basic Grid functionalities.

alexandria journal of veterinary sciences, 2012

Little information is available about Q. fever in Egypt, a zoonotic disease caused by Coxiellabur... more Little information is available about Q. fever in Egypt, a zoonotic disease caused by Coxiellaburnetii, transmitted from domestic ruminants. This study aimed to investigate the prevalence of IgG antibodies against C. burnetii phase II antigen in human serum of two different groups (healthy human population of a rural area and a population of an urban area suffering from respiratory complains), in other words determine the percentage of both symptomatic (urban) and asymptomatic (rural) Q. fever infections and also investigate about different risk factors. A total of 92 human serum samples (42 serum samples from patients with respiratory complains and 50 serum samples randomly collected from people free from respiratory complains) were collected. The detection of antibodies against C. burnetii was carried out by ELISA method. The obtained results in the current study revealed that 66 out of 92 (72%)humanserum samples were found to be ELISA positive for C. burnetii phase II IgG. 31seru...

International Journal of Molecular and Immuno Oncology, 2022

Objectives: We present real-world outcome with the use of palbociclib in patients with HR-positiv... more Objectives: We present real-world outcome with the use of palbociclib in patients with HR-positive Her2-negative breast cancer treated at single center in India. Material and Methods: We conducted a medical audit of consecutive patients with HR-positive Her2-negative metastatic breast cancer, who were treated with palbociclib at our center between November 2016 and May 2020. Palbociclib was commenced at a dose of 125 mg orally once daily and a schedule of 21 days on therapy followed by 7 days off therapy was followed. Survival analysis included the Kaplan–Meier method using Statistical Package for the Social Sciences software (Version 26). HRs were calculated using Cox proportional hazard regression models and 95% confidence intervals (CIs) for the incidence estimates. Results: A total of 67 female patients were commenced on treatment with palbociclib between November 2016 and May 2020. The median age was 55 years (range 29–78 years). A total of 51 (76%) of these patients were postm...

International Polymer Science and Technology, 2010

Egyptian Poultry Science Journal, 2019

The experiment was carried out to evaluate the response of broilers fed diet supplemented with an... more The experiment was carried out to evaluate the response of broilers fed diet supplemented with antibiotic alternatives, Probiotic (BioPlus 2B), Prebiotic (Techno MOs), Synbiotic and medicinal herbs (Mixture of Origanum majorana, Foeniculum vulgare and Carum carvi in ratio 1: 1: 1), on their performance and intestinal histology. A total of 125-day old chicks cobb (500) broiler chicks were randomly distributed into 5 treatments with five replicates of 5 chicks each and raised for 6 weeks. Chicks were kept in cleaned and fumigated cage of wire floored batteries. Experimental diets and water were offered ad-libitum over the experimental period starting from one day old. The experimental treatments received basal diets which were formulated to starter (1-21d) and grower-finisher (22-42d) broiler growth periods. During each growth period, birds received the control diet (un-supplemented), whereas the other groups fed diet contained either of tested feed additives (probiotic, prebiotic, synbiotic or medicinal plants mixture). The most important results obtained from this study could be summarized as follows:-a highly significant effect (p≤ 0.05) on live body weight at the end of experiment period was observed due to the effect of synbiotic treatment compared the other treatments. A highest body weight gain was recorded by the synbiotic treatment compared the control ones. Different feed additives improved feed conversion ratio compared to control (p≤0.001, for the whole experimental period. All supplements effect the intestinal histology compared to that of the control in duodenum and jejunum, intestine region but the effect is not significant. Also, feed additives led to significant improvement in villus height and crypt depth in ileum region. In conclusion, results show that synbiotic treatment was the superior in improving productive performance of broilers. Further research is still need to verify current results.

Grid Computing — GRID 2000, 2000

In this paper we report on preliminary work and architectural design carried out in the "Data Man... more In this paper we report on preliminary work and architectural design carried out in the "Data Management" work package in the International Data Grid project. Our aim within a time scale of three years is to provide Grid middleware services supporting the I/Ointensive worldwide distributed next generation experiments in High-Energy Physics, Earth Observation and Bioinformatics. The goal is to specify, develop, integrate and test tools and middleware infrastructure to coherently manage and share Petabyte-range information volumes in high-throughput production-quality Grid environments. The middleware will allow secure access to massive amounts of data in a universal namespace, to move and replicate data at high speed from one geographical site to another, and to manage synchronisation of remote copies. We put much attention on clearly specifying and categorising existing work on the Grid, especially in data management in Grid related projects. Challenging use cases are described and how they map to architectural decisions concerning data access, replication, meta data management, security and query optimisation. 1 CERN Regional Centre (RC) 1 RC 3 RC

Scientific Programming, 2002

The GDMP client-server software system is a generic file replication tool that replicates files s... more The GDMP client-server software system is a generic file replication tool that replicates files securely and efficiently from one site to another in a Data Grid environment using Globus Grid tools. In addition, it manages replica catalogue entries for file replicas and thus maintains a consistent view on names and locations of replicated files. Files to be transferred can be of any particular file format and GDMP treats them all in the same way. However, for Objectivity database files a particular plug-in exists. All files are assumed to be read-only.

IEEE 5th Control and System Graduate Research Colloquium (ICSGRC), 2014

Cloud computing is the realization for a long-held dream of computing as utility of establishment... more Cloud computing is the realization for a long-held dream of computing as utility of establishment of on-demand IT services. The considerable specifications of this emerging technology have attracted attentions of many users and enterprises in various industries. However, there are some considerable concerns that reduce reliability of cloud-based services. Managing user identities in clouds is one of the most challenging security issues that has led to many performed researches in this area. Hence, an agent-based user authentication model has been presented in this paper to enhance security of cloud computing environments. A unique extension has been provided in the proposed model is to identify the ownership of private individual devices and to establish a reasonable and logical dependency between cloud servers and clients. Furthermore, a provisional access permission algorithm has been presented for un-registered devices to investigate and verify authenticity and correctness of one-time access requests by a higher level of security in comparison with current models. The proposed model has been introduced and evaluated regarding to three main parameters: performance, security, and scalability. The analysis of user authentication agent shows that this model enhances the rate of security and reliability in cloud computing environments without affecting the rate of energy and time consumption, and scalability.

22nd International Symposium on Reliable Distributed Systems, 2003. Proceedings.

2008 IEEE International Symposium on Parallel and Distributed Processing, 2008

We present a novel protocol for restructuring a treebased overlay network in response to the work... more We present a novel protocol for restructuring a treebased overlay network in response to the workload of the application running over it. Through low-cost restructuring operations, our protocol incrementally adapts the tree so as to bring nodes that tend to communicate with one another closer together in the tree. It achieves this while respecting degree bounds on nodes so that, e.g., no node degenerates into a "hub" for the overlay. Moreover, it limits restructuring to those parts of the tree over which communication takes place, avoiding restructuring other parts of the tree unnecessarily. We show via experiments on PlanetLab that our protocol can significantly reduce communication latencies in workloads dominated by clusters of communicating nodes.

24th IEEE Symposium on Reliable Distributed Systems (SRDS'05)

We present an algorithm by which nodes arranged in a tree, with each node initially knowing only ... more We present an algorithm by which nodes arranged in a tree, with each node initially knowing only its parent and children, can construct a fault-tolerant communication structure (an expander graph) among themselves in a distributed and scalable way. The tree overlayed with this logical expander is a useful structure for distributed applications that require the intrinsic "treeness" from the topology but cannot afford any obstruction in communication due to failures. At the core of our construction is a novel distributed mechanism that samples nodes uniformly at random from the tree. In the event of node joins, node departures or node failures, the expander maintains its own fault tolerance and permits the reformation of the tree. We present simulation results to quantify the convergence of our algorithm to a fault tolerant network having both good vertex connectivity and expansion properties.

International Conference on Dependable Systems and Networks, 2004, 2004

A correctly working Domain Name System (DNS) is essential for the Internet. Due to its significan... more A correctly working Domain Name System (DNS) is essential for the Internet. Due to its significance and because of deficiencies in its current design, the DNS is vulnerable to a wide range of attacks. This paper presents the design and implementation of a secure distributed name service. Our service is able provide fault tolerance and security even in the presence of a fraction of corrupted servers, avoiding any single point of failure. It further solves the problem of storing zone secrets online in a way that does not leak them to a corrupted server, while still supporting secure dynamic updates. Our service uses state-machine replication and threshold cryptography. We present results from experiments performed using a prototype implementation on the Internet in realistic setups. The results show that our design achieves the required assurances while servicing most frequent requests in reasonable time.

... r hF s will lw ys e inde ted to himF h nks wike3 s would lso like to th nk ghenxi ng for ll t... more ... r hF s will lw ys e inde ted to himF h nks wike3 s would lso like to th nk ghenxi ng for ll the enlightening dis usE sions we h ve hd over the ye rsF wy st ytg rnegie wellon would not h ve een s ple sur le s it w sD hd it not een for friends like elin D plorin ... R histri uted p ultE oler nt rees ...

IEEE Transactions on Parallel and Distributed Systems, 2008

We present Quiver, a system that coordinates service proxies placed at the "edge" of the Internet... more We present Quiver, a system that coordinates service proxies placed at the "edge" of the Internet to serve distributed clients accessing a service involving mutable objects. Quiver enables these proxies to perform consistent accesses to shared objects by migrating the objects to proxies performing operations on those objects. These migrations dramatically improve performance when operations involving an object exhibit geographic locality, since migrating this object into the vicinity of proxies hosting these operations will benefit all such operations. Other workloads benefit from Quiver, dispersing the computation load across the proxies and saving the costs of sending operation parameters over the wide area when these are large. Quiver also supports optimizations for single-object reads that do not involve migrating the object. We detail the protocols for implementing object operations and for accommodating the addition, involuntary disconnection, and voluntary departure of proxies. We also evaluate Quiver through experiments on PlanetLab. Finally, we discuss the use of Quiver to build an e-commerce application and a distributed network traffic modeling service.

Echocardiography, 2013

Objectives: This study assessed the ability of live/real time three-dimensional transesophageal e... more Objectives: This study assessed the ability of live/real time three-dimensional transesophageal echocardiography (3DTEE) in measuring (1) atrial septal defect (ASD) maximum dimension, area, and adjacent rim size, (2) ASD occluder left and right atrial disk size, (3) length of contact between the left atrial (LA) disk and the aorta, and in (4) assessing device related complications such as residual shunt, device embolization, and device encroachment upon adjacent cardiac structures. Materials and Methods: 3DTEE images acquired during percutaneous ASD closure by the Amplatzer Septal Occluder in 15 adult patients were retrospectively analyzed. Offline analysis was done using both the Philips 5500 ultrasound system and Philips QLAB software. 3D color flow Doppler images were used to assess residual ASD shunting. Results: The Philips 5500 and Philips QLAB measurements correlated well for ASD maximum dimension and area measurements. The Philips QLAB 3DTEE disk size measurements also correlated well with the manufacturer obtained sizes. The aortic rim was deficient in 7 of the 15 patients, and the mean ASD occluder device size was 4 mm greater than the mean ASD maximum dimension. The LA occluder disk was in contact with the aorta throughout the cardiac cycle in 12 of the 15 patients, and the LA occluder disk size correlated significantly with the contact length with the aorta. Conclusion: Most of the patients demonstrated contact between the LA occluder disk and the aorta throughout the cardiac cycle. 3DTEE may be useful in identifying patients at greater risk for aortic erosion.

The American Journal of Geriatric Cardiology, 2006

Patent foramen ovale (PFO) is a well-recognized risk factor for ischemic strokes. The true preval... more Patent foramen ovale (PFO) is a well-recognized risk factor for ischemic strokes. The true prevalence of PFO among stroke patients is still under debate. Transesophageal echocardiography (TEE) is the "gold standard" in diagnosing PFO but the physiology requires right-to-left atrial shunting. In this report, we evaluate the prevalence of PFO in a diverse group of ischemic stroke patients studied by TEE. TEE of 1,663 ischemic stroke patients were reviewed for cardiac source of embolism, including PFO and atrial septal aneurysm (ASA). Agitated saline bubble injection was performed to look for right to left atrial shunting. Success of maneuvers to elevate right atrial pressure (RAP) was noted by looking at the atrial septal bulge. Among 1,435 ischemic stroke patients analyzed, the presence or absence of PFO could not be determined in 32.1% because bulging of the septum could not be demonstrated in patients with negative contrast study despite aggressive maneuvers to elevate RAP. Of the remaining 974 patients, 294 patients (30.2%) had a PFO. The mean age was 61.5 years in both groups, with a bimodal distribution of PFO and the highest prevalence occurring in…

Cluster Computing, Jul 1, 2002

Data replication is a key issue in a Data Grid and can be managed in different ways and at differ... more Data replication is a key issue in a Data Grid and can be managed in different ways and at different levels of granularity: for example, at the file level or object level. In the High Energy Physics community, Data Grids are being developed to support the distributed analysis of experimental data. We have produced a prototype data replication tool, the Grid Data Mirroring Package (GDMP) that is in production use in one physics experiment, with middleware provided by the Globus Toolkit used for authentication, data movement, and ...