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Search Results: 1 - 10 of 6240 matches for " Oscar Lao "
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GAGA: A New Algorithm for Genomic Inference of Geographic Ancestry Reveals Fine Level Population Substructure in Europeans
Oscar Lao ,Fan Liu,Andreas Wollstein,Manfred Kayser
PLOS Computational Biology , 2014, DOI: doi/10.1371/journal.pcbi.1003480
Abstract: Attempts to detect genetic population substructure in humans are troubled by the fact that the vast majority of the total amount of observed genetic variation is present within populations rather than between populations. Here we introduce a new algorithm for transforming a genetic distance matrix that reduces the within-population variation considerably. Extensive computer simulations revealed that the transformed matrix captured the genetic population differentiation better than the original one which was based on the T1 statistic. In an empirical genomic data set comprising 2,457 individuals from 23 different European subpopulations, the proportion of individuals that were determined as a genetic neighbour to another individual from the same sampling location increased from 25% with the original matrix to 52% with the transformed matrix. Similarly, the percentage of genetic variation explained between populations by means of Analysis of Molecular Variance (AMOVA) increased from 1.62% to 7.98%. Furthermore, the first two dimensions of a classical multidimensional scaling (MDS) using the transformed matrix explained 15% of the variance, compared to 0.7% obtained with the original matrix. Application of MDS with Mclust, SPA with Mclust, and GemTools algorithms to the same dataset also showed that the transformed matrix gave a better association of the genetic clusters with the sampling locations, and particularly so when it was used in the AMOVA framework with a genetic algorithm. Overall, the new matrix transformation introduced here substantially reduces the within population genetic differentiation, and can be broadly applied to methods such as AMOVA to enhance their sensitivity to reveal population substructure. We herewith provide a publically available (http://www.erasmusmc.nl/fmb/resources/GA?GA) model-free method for improved genetic population substructure detection that can be applied to human as well as any other species data in future studies relevant to evolutionary biology, behavioural ecology, medicine, and forensics.
Statistical analysis of post mortem DNA damage-derived miscoding lesions in Neandertal mitochondrial DNA
Sergi Vives, M Thomas Gilbert, Conchita Arenas, Elena Gigli, Oscar Lao, Carles Lalueza-Fox
BMC Research Notes , 2008, DOI: 10.1186/1756-0500-1-40
Abstract: The data indicates an extreme bias towards C→T over G→A miscoding lesions (observed ratio of 67:2 compared to an expected ratio of 7:2), implying that the mtDNA Light strand molecule suffers proportionally more damage-derived miscoding lesions than the Heavy strand.The clustering of Cs in the Light strand as opposed to the singleton pattern of Cs in the Heavy strand could explain the observed bias, a phenomenon that could be further tested with non-PCR based approaches. The characterization of the HVS1 hotspots will be of use to future Neandertal mtDNA studies, with specific regards to assessing the authenticity of new positions previously unknown to be polymorphic.The retrieval of DNA from extinct humans such as Neandertals is technically challenged by problems associated with post mortem damage of the original DNA [1]. The growing availability of Neandertal mitochondrial DNA (mtDNA) hypervariable (HVS) sequences (predominantly HVS1), generated with the polymerase chain reaction (PCR) provides a novel dataset to study miscoding lesions associated to DNA damage.The identification of true post mortem damage-derived miscoding lesions in ancient DNA studies, and their discrimination from other PCR artifacts, has been subject of much debate. Although the predominant cause was originally argued to be due to cytosine deamination, generating C→T and G→A miscoding lesions in the retrieved sequences [2,3], a number of studies that examined additional datasets suggested that damage may also include adenine to hypoxanthine modifications, thus resulting in A→G and T→C miscoding lesions [4,5]. The advent of 454/FLX sequencing technology, that allows the identification of which single DNA strand has been sequenced, has helped resolve this debate. In agreement with the original hypotheses [2,3], it is now generally accepted that cytosine deamination is the sole cause of damage-derived miscoding lesions, observed as C→T or G→A miscoding lesions [6-9].We have investigated the distri
Study on the Efficiency and Total Factor Productivity of China’s Securities Companies—Based on Hicks-Moorsteen TFP Index Method  [PDF]
Guohao Lao, Bin Mo
Technology and Investment (TI) , 2018, DOI: 10.4236/ti.2018.91004
Abstract: Along with the vigorous development of capital market, the number of security investors and security companies in number and scale has grown rapidly. Based on this, the paper focused on the national 15 large listed security companies as our research object. By using the ODonnell of Hicks-Moorsteen TFP index decomposition, we analyze the efficiency and total factor growth rate of the 15 listed security companies between 2010 and 2015. Research shows that: 1) the efficiency of the 15 listed security companies generally showed “V” shape; 2) the dis-economies of scope led to the decrease of the efficiency of the security companies; 3) in the sample period, the technical efficiency and scale efficiency of listed security companies did not fluctuate a lot.
Geographic stratification of linkage disequilibrium: a worldwide population study in a region of chromosome 22
Anna González-Neira, Francesc Calafell, Arcadi Navarro, Oscar Lao, Howard Cann, David Comas, Jaume Bertranpetit
Human Genomics , 2004, DOI: 10.1186/1479-7364-1-6-399
Abstract:
Recommendations for enhancing the quality of traditional Chinese medicine clinical research reporting
LAO Lixing
Zhong Xi Yi Jie He Xue Bao , 2004,
Abstract: Evidence-based medicine (EBM) has drawn the attention of the medical community around the world and is rapidly becoming the standard in medical research. EBM requires both rigorous clinical trial research design, including adequate randomization and appropriate control, and accurate and thorough reporting of the findings of trials. Despite China's active research program, the majority of traditional Chinese medicine (TCM) clinical research in the Chinese literature fails to meet world standards of clinical research reporting, largely due to insufficient and inadequate reporting. Because of rising world demand for information on TCM research, enhancing the quality of research reporting in Chinese journals is imperative. Quality of reporting is important in all aspects of a manuscript, including the introduction/background, materials and methods, results, and discussion/conclusion sections. TCM journal editors, who serve as gatekeepers of quality, must encourage higher quality clinical research reporting by setting and upholding publication standards
The Center for Integrative Medicine at the University of Maryland: the first complementary and alternative medicine center in a US medical school
Lixing LAO
Zhong Xi Yi Jie He Xue Bao , 2008,
Abstract: : The Center for Integrative Medicine at the University of Maryland was founded in 1991 and was the first center dedicated to evaluating complementary and alternative medicine at a US medical school. The center has been a National Institutes of Health center of excellence since 1995 focused on evaluating the efficacy, safety and mechanism of action of traditional Chinese medicine, acupuncture, and mind-body modalities including Qigong and mindfulness meditation. The Center functions as an interdisciplinary center in the university and is composed of four main areas—research, patient care, informatics, and education—that mutually enhance each other and create a cohesive unit. The Center has recently increased its international collaboration on acupuncture and traditional Chinese medicine research, particularly with universities in China such as Chinese University of Hong Kong, Shanghai University of Traditional Chinese Medicine (TCM) and other TCM universities.
Evaluating the effects of acupuncture on knee osteoarthritis: A stepwise approach to research, University of Maryland experience
Lixing Lao
Zhong Xi Yi Jie He Xue Bao , 2005,
Abstract: Conventional treatments for osteoarthritis (OA), the most common form of arthritis, are associated with unpleasant adverse effects and often ineffective. Acupuncture and traditional Chinese medicine (TCM) have been used for thousands of years to treat pain and other dysfunctions. However, the scientific evidence on the efficacy of acupuncture and TCM is equivocal, and adapting the Western biomedical model to assess them is a great challenge. By adopting a systematic, step-by-step approach, the research team at the University of Maryland has been carefully evaluating the effectiveness of acupuncture on knee OA over the past 10 years. Their successful experience may be a useful model for future acupuncture and TCM research.
Thermodynamic and Extrathermodynamic Studies of Enantioseparation of Imidazolinone Herbicides on Chiralcel OJ Column
Wenjian Lao
ISRN Chromatography , 2013, DOI: 10.1155/2013/460787
Abstract: A homologous series of chiral imidazolinone herbicide was previously resolved on Chiralcel OJ column in high performance liquid chromatography. However, the mechanism of the chiral separation remains unclear. In this study, chromatographic behaviors of five chiral imidazolinone herbicides were characterized by thermodynamic and extrathermodynamic methods in order to enhance the understanding of the chiral separation. Thermodynamic parameters of this study were derived from equilibrium constant ( ) that was estimated from the moment analysis of the chromatographic peak. Van't Hoff plots of ( versus ) were linear at a range of 15–50°C, only nonlinear at a range of 5–15?°C with n-hexane (0.1%, trifluoroacetic acid)-2-propanol 60/40 (v/v) mobile phase. The enantiomer retention on the chiral column was entropy-driven at a lower temperature (5°C) and enthalpy-driven at a higher temperature (10 to 50°C). Enantioseparations of four of the five imidazolinone herbicides were enthalpy-driven, only entropy-driven for imazaquin. Enantioseparation mechanisms were different in between 5–10°C and 15–50°C probably due to the conformational change of the OJ phase. Enthalpy-entropy compensation showed similar mechanisms in retention and chiral separation for the five or enantiomers. Several extrathermodynamic relationships were able to be extracted to address additivity of group contribution. 1. Introduction Chiral separation in high-performance liquid chromatography (HPLC) is keeping to be of great interest in diverse areas such as the agrochemicals and pharmaceutical industry [1]. To achieve better resolution and improve chiral stationary phase, enantioseparation mechanisms have been studied extensively using various methods [2–4]. A thermodynamic study is found to be especially valuable for providing information on the separation mechanism [5–7]. A link between chromatographic behavior and thermodynamic parameters such as enthalpy ( ), entropy ( ), and Gibbs free energy ( ) is distribution constant ( ) that describes the transfer of an analyte from mobile phase to stationary phase [8]. Moment analysis of elution peak based on a kinetic model provides an approach to estimate the value [9]. The present study is concerned with using the value to characterize retention and chiral separation, a case where there has been so far few works [10]. Extrathermodynamic relationships are empirical correlations of thermodynamic parameters with molecular structures, chromatographic conditions, and enthalpy-entropy compensation (EEC) and have been among the most important tools in
A network-dependent rewarding system: proof-of-mining
Joe Lao
Computer Science , 2014,
Abstract: A soft control of the network activity through varying reward in a proof-of-work (PoW) cryptocurrency is reported. Rewards are the necessity to incent the contributors activities (i.e., mining) in order to maintain the PoW network. Contrary to constant rewarding in a certain period implemented in most of cryptocurrency, such as bitcoin, we propose a network-dependent rewarding model system, primarily including two phases: 1) activities encouraging phase in which higher rewards are issued at higher network activities; and 2) discouraging further increase of activities by reducing rewards. The advantages of this system include 1) fair distribution of rewards among a variety of contributors, and 2) enforcing a limit to the network activity and hence the cost of maintaining the PoW network. This mechanism requires network contributors to show their participation in order to earn maximum rewards, i.e., proof-of-mining.
Recent human evolution has shaped geographical differences in susceptibility to disease
Urko M Marigorta, Oscar Lao, Ferran Casals, Francesc Calafell, Carlos Morcillo-Suárez, Rui Faria, Elena Bosch, Fran?ois Serra, Jaume Bertranpetit, Hernán Dopazo, Arcadi Navarro
BMC Genomics , 2011, DOI: 10.1186/1471-2164-12-55
Abstract: We report three main findings. First, contrary to previous results, genes associated to complex diseases present lower degrees of genetic differentiation among human populations than average genome-wide levels. Second, also contrary to previous results, the differences in replicability of disease associated-loci between Europeans and East Asians are highly correlated with genetic differentiation between these populations. Finally, highly replicated genes present increased levels of high-frequency derived alleles in European and Asian populations when compared to African populations.Our findings highlight the heterogeneous nature of the genetic etiology of complex disease, confirm the importance of the recent evolutionary history of our species in current patterns of disease susceptibility and could cast doubts on the status as false positives of some associations that have failed to replicate across populations.The discovery of genetic variants that increase susceptibility to disease represents one of the greatest challenges for epidemiology and genomics [1]. Detailed knowledge about the etiology of many diseases keeps accumulating and in the near future it will help to improve disease management [2]. After decades of research in genetic epidemiology, more than 51,000 different association studies for human diseases have been published and 11,501 genes have been described to be associated to disease, as recorded up to December 2010 in the HuGENet browser [3]. Moreover, thanks to last technological advances, we have recently escalated into a flurry of genome-wide association studies (GWAS) that simultaneously study hundreds of thousands of SNPs over the whole genome [3-5]. For instance, most GWAS recorded in the HuGENet browser have been published recently, from 2008 on (812 out of 935 by December 15th, 2010).In spite of their success, genetic association studies for common complex diseases usually suffer from a problem of lack of reproducibility of results. Only a v
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