Due to their importance in representing, explaining, and analyzing phenomena, statistical lifetim... more Due to their importance in representing, explaining, and analyzing phenomena, statistical lifetime distributions are widely used in science. As a result, this paper discusses a modern lifetime model called Birnbaum–Saunders logistic distribution. This distribution extends the Birnbaum–Saunders distribution, as it has proven to be characterized by great flexibility in data modeling in practice. Different features of this distribution have been discussed. The parameters of the model are estimated using the maximum likelihood and modified moment estimation methods. To evaluate the performance of the methods, a simulation study with data contamination scenarios is presented. Finally, the new model’s flexibility is tested using real datasets.
Background: Nephrotic syndrome is the predominant glomeurular disease in childhood. Mutations in ... more Background: Nephrotic syndrome is the predominant glomeurular disease in childhood. Mutations in numerous genes are known to be the reason for steroid-resistant nephrotic syndrome; however, the presence of these mutations seems to be effected by race sociocultural differences and interethnic group. Mutations in NPHS2 and WT1 genes record for nearly 20% and 5% of all children cases with steroid-resistant nephrotic syndrome, respectively. By contrast, mutations are absent from children with either steroid-dependent nephrotic syndrome or frequently-relapse nephrotic syndrome. Methods: Mutation analysis was accomplished by direct sequencing of the complete 8 exons of NPHS2 and exons 8 and 9 of WT1 in 20 patients with steroid-resistant nephrotic syndrome, 25 with steroid-dependent nephrotic syndrome, and 13 with frequently-relapse nephrotic syndrome. Results: Three pathogenic mutations in NPHS2 were detected within steroid-resistant nephrotic syndrome patients. One as a nonsense mutation...
Background: Nephrotic syndrome is the predominant glomeurular disease in childhood. Mutations in ... more Background: Nephrotic syndrome is the predominant glomeurular disease in childhood. Mutations in numerous genes are known to be the reason for steroid-resistant nephrotic syndrome; however, the presence of these mutations seems to be effected by race sociocultural differences and interethnic group. Mutations in NPHS2 and WT1 genes record for nearly 20% and 5% of all children cases with steroid-resistant nephrotic syndrome, respectively. By contrast, mutations are absent from children with either steroid-dependent nephrotic syndrome or frequently-relapse nephrotic syndrome. Methods: Mutation analysis was accomplished by direct sequencing of the complete 8 exons of NPHS2 and exons 8 and 9 of WT1 in 20 patients with steroid-resistant nephrotic syndrome, 25 with steroid-dependent nephrotic syndrome, and 13 with frequently-relapse nephrotic syndrome. Results: Three pathogenic mutations in NPHS2 were detected within steroid-resistant nephrotic syndrome patients. One as a non-sense mutatio...
Ciências Exatas e da Terra 104 homogêneo em diferentes suportes, tanto orgânicos quanto inorgânic... more Ciências Exatas e da Terra 104 homogêneo em diferentes suportes, tanto orgânicos quanto inorgânicos. Iniciamos um estudo de imobilização do complexo Fe(acac) 3 em sílica através do processo sol-gel, o qual é uma ferramenta poderosa para a imobilização de catalisadores de metais de transição. A química desse método está baseada na polimerização de precursores moleculares e envolve a formação de uma rede inorgânica a partir de uma solução. Esse processo torna-se interessante devido, ainda, às propriedades físicas e químicas que os materiais exibem e às possibilidades de processamento oferecidas pelo estado coloidal. Inicialmente, foi obtido um novo precursor orgânico contendo grupos oxigenados quelantes, o acetilacetonatopropiltrimetilsiloxano (acacSIL). Esse precursor foi policondensado com tetraetilortosilicato (TEOS) para obter um novo polímero híbrido, xerogel, contendo grupos acetilacetonatos ancorados (sílica/acac). O híbrido preparado será complexado com metais de transição conhecidos como ativos na reação de epoxidação aeróbica de olefinas (Fe 3+ , Co 2+ , Ni 2+ , etc). Os materiais obtidos serão caracterizados através das técnicas de espectroscopia na região do infravermelho, análise elementar (C, H e Metal), microscopia eletrônica, isotermas de adsorção de N 2 , área superficial, etc.
Abstract The hazard (failure) rate is a fundamental statistical indicator commonly used in both r... more Abstract The hazard (failure) rate is a fundamental statistical indicator commonly used in both reliability and survival analyses. In practice, the hazard curve might exhibit a non-monotonic unimodal behavior. Thus, determining the highest point of the peak of a non-monotonic hazard function is indeed a point of interest in lifetime analysis. This study discusses the shape of the hazard function of the logistic Birnbaum-Saunders distribution and associate estimation. This model belongs to the generalized Birnbaum-Saunders family of positively skewed models with lighter and heavier tails than the conventional two-parameter Birnbaum-Saunders distribution. The latter model originated from a problem related to material fatigue, a phenomenon of interest in material sciences. In this paper, we establish that the hazard rate of the logistic Birnbaum-Saunders distribution is either unimodal or decreasing depending on the value of the shape parameter. We also estimate the critical value of the hazard rate, which is the highest point of the peak of the hazard function, using moment estimators. We perform extensive Monte Carlo simulations to examine estimation efficiency numerically; moreover, we analyze a data set for the sake of illustration.
Due to their importance in representing, explaining, and analyzing phenomena, statistical lifetim... more Due to their importance in representing, explaining, and analyzing phenomena, statistical lifetime distributions are widely used in science. As a result, this paper discusses a modern lifetime model called Birnbaum–Saunders logistic distribution. This distribution extends the Birnbaum–Saunders distribution, as it has proven to be characterized by great flexibility in data modeling in practice. Different features of this distribution have been discussed. The parameters of the model are estimated using the maximum likelihood and modified moment estimation methods. To evaluate the performance of the methods, a simulation study with data contamination scenarios is presented. Finally, the new model’s flexibility is tested using real datasets.
Background: Nephrotic syndrome is the predominant glomeurular disease in childhood. Mutations in ... more Background: Nephrotic syndrome is the predominant glomeurular disease in childhood. Mutations in numerous genes are known to be the reason for steroid-resistant nephrotic syndrome; however, the presence of these mutations seems to be effected by race sociocultural differences and interethnic group. Mutations in NPHS2 and WT1 genes record for nearly 20% and 5% of all children cases with steroid-resistant nephrotic syndrome, respectively. By contrast, mutations are absent from children with either steroid-dependent nephrotic syndrome or frequently-relapse nephrotic syndrome. Methods: Mutation analysis was accomplished by direct sequencing of the complete 8 exons of NPHS2 and exons 8 and 9 of WT1 in 20 patients with steroid-resistant nephrotic syndrome, 25 with steroid-dependent nephrotic syndrome, and 13 with frequently-relapse nephrotic syndrome. Results: Three pathogenic mutations in NPHS2 were detected within steroid-resistant nephrotic syndrome patients. One as a nonsense mutation...
Background: Nephrotic syndrome is the predominant glomeurular disease in childhood. Mutations in ... more Background: Nephrotic syndrome is the predominant glomeurular disease in childhood. Mutations in numerous genes are known to be the reason for steroid-resistant nephrotic syndrome; however, the presence of these mutations seems to be effected by race sociocultural differences and interethnic group. Mutations in NPHS2 and WT1 genes record for nearly 20% and 5% of all children cases with steroid-resistant nephrotic syndrome, respectively. By contrast, mutations are absent from children with either steroid-dependent nephrotic syndrome or frequently-relapse nephrotic syndrome. Methods: Mutation analysis was accomplished by direct sequencing of the complete 8 exons of NPHS2 and exons 8 and 9 of WT1 in 20 patients with steroid-resistant nephrotic syndrome, 25 with steroid-dependent nephrotic syndrome, and 13 with frequently-relapse nephrotic syndrome. Results: Three pathogenic mutations in NPHS2 were detected within steroid-resistant nephrotic syndrome patients. One as a non-sense mutatio...
Ciências Exatas e da Terra 104 homogêneo em diferentes suportes, tanto orgânicos quanto inorgânic... more Ciências Exatas e da Terra 104 homogêneo em diferentes suportes, tanto orgânicos quanto inorgânicos. Iniciamos um estudo de imobilização do complexo Fe(acac) 3 em sílica através do processo sol-gel, o qual é uma ferramenta poderosa para a imobilização de catalisadores de metais de transição. A química desse método está baseada na polimerização de precursores moleculares e envolve a formação de uma rede inorgânica a partir de uma solução. Esse processo torna-se interessante devido, ainda, às propriedades físicas e químicas que os materiais exibem e às possibilidades de processamento oferecidas pelo estado coloidal. Inicialmente, foi obtido um novo precursor orgânico contendo grupos oxigenados quelantes, o acetilacetonatopropiltrimetilsiloxano (acacSIL). Esse precursor foi policondensado com tetraetilortosilicato (TEOS) para obter um novo polímero híbrido, xerogel, contendo grupos acetilacetonatos ancorados (sílica/acac). O híbrido preparado será complexado com metais de transição conhecidos como ativos na reação de epoxidação aeróbica de olefinas (Fe 3+ , Co 2+ , Ni 2+ , etc). Os materiais obtidos serão caracterizados através das técnicas de espectroscopia na região do infravermelho, análise elementar (C, H e Metal), microscopia eletrônica, isotermas de adsorção de N 2 , área superficial, etc.
Abstract The hazard (failure) rate is a fundamental statistical indicator commonly used in both r... more Abstract The hazard (failure) rate is a fundamental statistical indicator commonly used in both reliability and survival analyses. In practice, the hazard curve might exhibit a non-monotonic unimodal behavior. Thus, determining the highest point of the peak of a non-monotonic hazard function is indeed a point of interest in lifetime analysis. This study discusses the shape of the hazard function of the logistic Birnbaum-Saunders distribution and associate estimation. This model belongs to the generalized Birnbaum-Saunders family of positively skewed models with lighter and heavier tails than the conventional two-parameter Birnbaum-Saunders distribution. The latter model originated from a problem related to material fatigue, a phenomenon of interest in material sciences. In this paper, we establish that the hazard rate of the logistic Birnbaum-Saunders distribution is either unimodal or decreasing depending on the value of the shape parameter. We also estimate the critical value of the hazard rate, which is the highest point of the peak of the hazard function, using moment estimators. We perform extensive Monte Carlo simulations to examine estimation efficiency numerically; moreover, we analyze a data set for the sake of illustration.
Uploads
Papers by Abeer Almalki