The Experts below are selected from a list of 52692 Experts worldwide ranked by ideXlab platform
Derek Gordon - One of the best experts on this subject based on the ideXlab platform.
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Precision and type I error rate in the presence of genotype errors and missing parental data: a comparison between the Original Transmission disequilibrium test (TDT) and TDTae statistics.
BMC genetics, 2005Co-Authors: Sandra Barral, Chad Haynes, Mark A Levenstien, Derek GordonAbstract:Two factors impacting robustness of the Original Transmission disequilibrium test (TDT) are: i) missing parental genotypes and ii) undetected genotype errors. While it is known that independently these factors can inflate false-positive rates for the Original TDT, no study has considered either the joint impact of these factors on false-positive rates or the precision score of TDT statistics regarding these factors. By precision score, we mean the absolute difference between disease gene position and the position of markers whose TDT statistic exceeds some threshold. We apply our Transmission disequilibrium test allowing for errors (TDTae) and the Original TDT to phenotype and modified single-nucleotide polymorphism genotype simulation data from Genetic Analysis Workshop. We modify genotype data by randomly introducing genotype errors and removing a percentage of parental genotype data. We compute empirical distributions of each statistic's precision score for a chromosome harboring a simulated disease locus. We also consider inflation in type I error by studying markers on a chromosome harboring no disease locus. The TDTae shows median precision scores of approximately 13 cM, 2 cM, 0 cM, and 0 cM at the 5%, 1%, 0.1%, and 0.01% significance levels, respectively. By contrast, the Original TDT shows median precision scores of approximately 23 cM, 21 cM, 15 cM, and 7 cM at the corresponding significance levels, respectively. For null chromosomes, the Original TDT falsely rejects the null hypothesis for 28.8%, 14.8%, 5.4%, and 1.7% at the 5%, 1%, 0.1% and 0.01%, significance levels, respectively, while TDTae maintains the correct false-positive rate. Because missing parental genotypes and undetected genotype errors are unknown to the investigator, but are expected to be increasingly prevalent in multilocus datasets, we strongly recommend TDTae methods as a standard procedure, particularly where stricter significance levels are required.
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Precision and type I error rate in the presence of genotype errors and missing parental data: a comparison between the Original Transmission disequilibrium test (TDT) and TDTae statistics
BMC Genetics, 2005Co-Authors: Sandra Barral, Chad Haynes, Mark A Levenstien, Derek GordonAbstract:Abstract Background Two factors impacting robustness of the Original Transmission disequilibrium test (TDT) are: i) missing parental genotypes and ii) undetected genotype errors. While it is known that independently these factors can inflate false-positive rates for the Original TDT, no study has considered either the joint impact of these factors on false-positive rates or the precision score of TDT statistics regarding these factors. By precision score, we mean the absolute difference between disease gene position and the position of markers whose TDT statistic exceeds some threshold. Methods We apply our Transmission disequilibrium test allowing for errors (TDTae) and the Original TDT to phenotype and modified single-nucleotide polymorphism genotype simulation data from Genetic Analysis Workshop. We modify genotype data by randomly introducing genotype errors and removing a percentage of parental genotype data. We compute empirical distributions of each statistic's precision score for a chromosome harboring a simulated disease locus. We also consider inflation in type I error by studying markers on a chromosome harboring no disease locus. Results The TDTae shows median precision scores of approximately 13 cM, 2 cM, 0 cM, and 0 cM at the 5%, 1%, 0.1%, and 0.01% significance levels, respectively. By contrast, the Original TDT shows median precision scores of approximately 23 cM, 21 cM, 15 cM, and 7 cM at the corresponding significance levels, respectively. For null chromosomes, the Original TDT falsely rejects the null hypothesis for 28.8%, 14.8%, 5.4%, and 1.7% at the 5%, 1%, 0.1% and 0.01%, significance levels, respectively, while TDTae maintains the correct false-positive rate. Conclusion Because missing parental genotypes and undetected genotype errors are unknown to the investigator, but are expected to be increasingly prevalent in multilocus datasets, we strongly recommend TDTae methods as a standard procedure, particularly where stricter significance levels are required.
Pascale Massiani - One of the best experts on this subject based on the ideXlab platform.
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A comparative in situ TEM and UV–visible spectroscopic study of the thermal evolution of Ag species dispersed on Al2O3 and NaX zeolite supports
Catalysis Today, 2013Co-Authors: Elie Sayah, Dalil Brouri, Pascale MassianiAbstract:Abstract The oxidation states and dispersion of silver supported on alumina and faujasite were monitored by TEM, TPR and in situ UV–visible spectroscopy along the steps of thermal dehydration, then oxidation and finally reduction of the freshly prepared materials. An Original Transmission electron microscopy approach was conducted, based on the use of a pseudo-environmental TEM holder that provides direct observations, on given zones of the samples, of the formation (in the case of zeolite) or not (in the case of alumina) of reduced silver particles upon dehydration of the material in air. Besides, the question of the high propensity of the silver species supported on alumina to be reduced in hydrogen at temperatures as low as ambient temperature is addressed.
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A comparative in situ TEM and UV–visible spectroscopic study of the thermal evolution of Ag species dispersed on Al2O3 and NaX zeolite supports
Catalysis Today, 2013Co-Authors: Elie Sayah, Dalil Brouri, Pascale MassianiAbstract:International audienceThe oxidation states and dispersion of silver supported on alumina and faujasite were monitored by TEM, TPR and in situ UV-visible spectroscopy along the steps of thermal dehydration, then oxidation and finally reduction of the freshly prepared materials. An Original Transmission electron microscopy approach was conducted, based on the use of a pseudo-environmental TEM holder that provides direct observations, on given zones of the samples, of the formation (in the case of zeolite) or not (in the case of alumina) of reduced silver particles upon dehydration of the material in air. Besides, the question of the high propensity of the silver species supported on alumina to be reduced in hydrogen at temperatures as low as ambient temperature is addressed
Sandra Barral - One of the best experts on this subject based on the ideXlab platform.
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Precision and type I error rate in the presence of genotype errors and missing parental data: a comparison between the Original Transmission disequilibrium test (TDT) and TDTae statistics.
BMC genetics, 2005Co-Authors: Sandra Barral, Chad Haynes, Mark A Levenstien, Derek GordonAbstract:Two factors impacting robustness of the Original Transmission disequilibrium test (TDT) are: i) missing parental genotypes and ii) undetected genotype errors. While it is known that independently these factors can inflate false-positive rates for the Original TDT, no study has considered either the joint impact of these factors on false-positive rates or the precision score of TDT statistics regarding these factors. By precision score, we mean the absolute difference between disease gene position and the position of markers whose TDT statistic exceeds some threshold. We apply our Transmission disequilibrium test allowing for errors (TDTae) and the Original TDT to phenotype and modified single-nucleotide polymorphism genotype simulation data from Genetic Analysis Workshop. We modify genotype data by randomly introducing genotype errors and removing a percentage of parental genotype data. We compute empirical distributions of each statistic's precision score for a chromosome harboring a simulated disease locus. We also consider inflation in type I error by studying markers on a chromosome harboring no disease locus. The TDTae shows median precision scores of approximately 13 cM, 2 cM, 0 cM, and 0 cM at the 5%, 1%, 0.1%, and 0.01% significance levels, respectively. By contrast, the Original TDT shows median precision scores of approximately 23 cM, 21 cM, 15 cM, and 7 cM at the corresponding significance levels, respectively. For null chromosomes, the Original TDT falsely rejects the null hypothesis for 28.8%, 14.8%, 5.4%, and 1.7% at the 5%, 1%, 0.1% and 0.01%, significance levels, respectively, while TDTae maintains the correct false-positive rate. Because missing parental genotypes and undetected genotype errors are unknown to the investigator, but are expected to be increasingly prevalent in multilocus datasets, we strongly recommend TDTae methods as a standard procedure, particularly where stricter significance levels are required.
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Precision and type I error rate in the presence of genotype errors and missing parental data: a comparison between the Original Transmission disequilibrium test (TDT) and TDTae statistics
BMC Genetics, 2005Co-Authors: Sandra Barral, Chad Haynes, Mark A Levenstien, Derek GordonAbstract:Abstract Background Two factors impacting robustness of the Original Transmission disequilibrium test (TDT) are: i) missing parental genotypes and ii) undetected genotype errors. While it is known that independently these factors can inflate false-positive rates for the Original TDT, no study has considered either the joint impact of these factors on false-positive rates or the precision score of TDT statistics regarding these factors. By precision score, we mean the absolute difference between disease gene position and the position of markers whose TDT statistic exceeds some threshold. Methods We apply our Transmission disequilibrium test allowing for errors (TDTae) and the Original TDT to phenotype and modified single-nucleotide polymorphism genotype simulation data from Genetic Analysis Workshop. We modify genotype data by randomly introducing genotype errors and removing a percentage of parental genotype data. We compute empirical distributions of each statistic's precision score for a chromosome harboring a simulated disease locus. We also consider inflation in type I error by studying markers on a chromosome harboring no disease locus. Results The TDTae shows median precision scores of approximately 13 cM, 2 cM, 0 cM, and 0 cM at the 5%, 1%, 0.1%, and 0.01% significance levels, respectively. By contrast, the Original TDT shows median precision scores of approximately 23 cM, 21 cM, 15 cM, and 7 cM at the corresponding significance levels, respectively. For null chromosomes, the Original TDT falsely rejects the null hypothesis for 28.8%, 14.8%, 5.4%, and 1.7% at the 5%, 1%, 0.1% and 0.01%, significance levels, respectively, while TDTae maintains the correct false-positive rate. Conclusion Because missing parental genotypes and undetected genotype errors are unknown to the investigator, but are expected to be increasingly prevalent in multilocus datasets, we strongly recommend TDTae methods as a standard procedure, particularly where stricter significance levels are required.
Elie Sayah - One of the best experts on this subject based on the ideXlab platform.
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A comparative in situ TEM and UV–visible spectroscopic study of the thermal evolution of Ag species dispersed on Al2O3 and NaX zeolite supports
Catalysis Today, 2013Co-Authors: Elie Sayah, Dalil Brouri, Pascale MassianiAbstract:Abstract The oxidation states and dispersion of silver supported on alumina and faujasite were monitored by TEM, TPR and in situ UV–visible spectroscopy along the steps of thermal dehydration, then oxidation and finally reduction of the freshly prepared materials. An Original Transmission electron microscopy approach was conducted, based on the use of a pseudo-environmental TEM holder that provides direct observations, on given zones of the samples, of the formation (in the case of zeolite) or not (in the case of alumina) of reduced silver particles upon dehydration of the material in air. Besides, the question of the high propensity of the silver species supported on alumina to be reduced in hydrogen at temperatures as low as ambient temperature is addressed.
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A comparative in situ TEM and UV–visible spectroscopic study of the thermal evolution of Ag species dispersed on Al2O3 and NaX zeolite supports
Catalysis Today, 2013Co-Authors: Elie Sayah, Dalil Brouri, Pascale MassianiAbstract:International audienceThe oxidation states and dispersion of silver supported on alumina and faujasite were monitored by TEM, TPR and in situ UV-visible spectroscopy along the steps of thermal dehydration, then oxidation and finally reduction of the freshly prepared materials. An Original Transmission electron microscopy approach was conducted, based on the use of a pseudo-environmental TEM holder that provides direct observations, on given zones of the samples, of the formation (in the case of zeolite) or not (in the case of alumina) of reduced silver particles upon dehydration of the material in air. Besides, the question of the high propensity of the silver species supported on alumina to be reduced in hydrogen at temperatures as low as ambient temperature is addressed
James Gross - One of the best experts on this subject based on the ideXlab platform.
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channel coding versus cooperative arq reducing outage probability in ultra low latency wireless communications
Global Communications Conference, 2015Co-Authors: Martin Serror, Christian Dombrowski, Klaus Wehrle, James GrossAbstract:Nowadays wireless communications still lack the ability to provide high reliability and low latency, although mission-critical applications, such as found in industrial automation, rely on both requirements. The main challenge is that an improved reliability often comes at the price of an increased latency. It has been shown that cooperative schemes can effectively increase the reliability by leveraging spatial diversity. However, an important question remains how to integrate cooperative schemes when dealing with very short latency bounds and especially how much time should be reserved for potential reTransmissions. In this work, we propose and evaluate a centralized communication system that uses cooperative ARQ to achieve high reliability under the constraint of a strict latency bound of 1 ms. We evaluate this system analytically, using an outage-capacity model with average channel state information, by varying the reserved time for reTransmissions, where a shorter time for reTransmissions allows to apply stronger channel codes in the Original Transmission. As a baseline, we use a system without cooperation mechanism, thus applying the given time for stronger channel codes in the direct Transmission of a message. In case of cooperation, a third station may act as a relay if the Original Transmission failed. Our results reveal that an optimal size of the reserved reTransmission time exists around 15% to 30% of the total frame time, increasing the reliability by several orders of magnitude, even for a large number of Transmissions within a communication cycle.
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GLOBECOM Workshops - Channel Coding versus Cooperative ARQ: Reducing Outage Probability in Ultra-Low Latency Wireless Communications
2015 IEEE Globecom Workshops (GC Wkshps), 2015Co-Authors: Martin Serror, Christian Dombrowski, Klaus Wehrle, James GrossAbstract:Nowadays wireless communications still lack the ability to provide high reliability and low latency, although mission-critical applications, such as found in industrial automation, rely on both requirements. The main challenge is that an improved reliability often comes at the price of an increased latency. It has been shown that cooperative schemes can effectively increase the reliability by leveraging spatial diversity. However, an important question remains how to integrate cooperative schemes when dealing with very short latency bounds and especially how much time should be reserved for potential reTransmissions. In this work, we propose and evaluate a centralized communication system that uses cooperative ARQ to achieve high reliability under the constraint of a strict latency bound of 1 ms. We evaluate this system analytically, using an outage-capacity model with average channel state information, by varying the reserved time for reTransmissions, where a shorter time for reTransmissions allows to apply stronger channel codes in the Original Transmission. As a baseline, we use a system without cooperation mechanism, thus applying the given time for stronger channel codes in the direct Transmission of a message. In case of cooperation, a third station may act as a relay if the Original Transmission failed. Our results reveal that an optimal size of the reserved reTransmission time exists around 15% to 30% of the total frame time, increasing the reliability by several orders of magnitude, even for a large number of Transmissions within a communication cycle.