期刊文献+
共找到200篇文章
< 1 2 10 >
每页显示 20 50 100
Provenance and depositional setting of the Late MiocenePleistocene clastic sediments in the eastern Arabian Peninsula and western Iraq using rare earth elements geochemistry 被引量:1
1
作者 Salih M.Awadh Zinah S.Al-Ankaz +1 位作者 Mohanad R.A.Al-Owaidi John S.Armstrong-Altrin 《Acta Geochimica》 EI CAS CSCD 2024年第2期399-410,共12页
The sandstones of the Late miocene–Pliocene Dibdibba Formation in the Najaf–Karbala Plateau and Basra were examined to determine their source rocks and origin. The rare earth elements(REE) and trace elements(Sc, Co,... The sandstones of the Late miocene–Pliocene Dibdibba Formation in the Najaf–Karbala Plateau and Basra were examined to determine their source rocks and origin. The rare earth elements(REE) and trace elements(Sc, Co, V, and Th) concentrations in these sandstones revealed that they likely derived from a single source. The steep light rare earth elements(LREE) and flat, heavy rare earth element(HREE) patterns, negative Eu anomaly, and high ΣREE contents in sandstones suggest its derivation from a suggests that a passive continental margin environment and originated from felsic source rocks. The average concentration of ΣREE is 93.5 ppm, which is lower than that of the average crustal compositions like Upper Continental Crust and Post Archean Australian Shale. The higher proportion of LREE compared to HREE implies that these sandstones were recycled and derived from a distal source. The Th/Co, Th/Sc, La/Sc, La/Co, Eu/Eu*and(La/Lu)cn elemental ratios indicated that these Late Miocene–Pliocene sandstones were derived from felsic rocks located in the marginal region of the Arabian Shield. 展开更多
关键词 REE Dibdibba formation Clastic sediments Passive continental margin
下载PDF
Highly divergent sympatric lineages of Leptotila verreauxi(Aves:Columbidae)suggest a secondary contact area in the Isthmus of Tehuantepec,Mexico
2
作者 Orlando J.Espinosa-Chávez Adolfo G.Navarro-Sigüenza +1 位作者 Hernando Rodríguez-Correa Luis A.Sánchez-González 《Avian Research》 SCIE CSCD 2024年第1期12-21,共10页
Due to a complex geological and biotic history,the Isthmus of Tehuantepec(IT),has been long recognized as a driver for the evolutionary divergence of numerous lowland and highland taxa.Widely distributed in the lowlan... Due to a complex geological and biotic history,the Isthmus of Tehuantepec(IT),has been long recognized as a driver for the evolutionary divergence of numerous lowland and highland taxa.Widely distributed in the lowlands of the American continent,the White-Tipped Dove(Leptotila verreauxi)is a polytypic species with 13 recognized subspecies.Four of these have been recorded in Mexico,and the distribution of three abuts at the IT,suggesting a contact zone.To estimate phylogenetic patterns,divergence times and genetic differentiation,we examined two mt DNA(ND2 and COI)and one n DNA(β-fibint 7)markers.We also used correlative ecological niche models(ENM)to assess whether ecological differences across the IT may have acted as a biogeographical boundary.We estimated paleodistributions during the Middle Holocene,Last Glacial Maximum and Last Interglacial,to evaluate the influence of climate changes on the distribution and demographic changes.Our results showed genetically distinct lineages that diverged approximately 2.5 million years ago.Climatic and ecological factors may have played a dual role in promoting differentiation,but also in the formation of a secondary contact zone in the southern IT.Our ecological niche comparisons indicated that the ecological niche of sympatric lineages at the IT are not identical,suggesting niches divergence;in addition,environmental niche models across the region indicated no abrupt biogeographic barriers,but the presence of regions with low suitability.These results suggest that genetic differentiation originated by a vicariant event probably related to environmental factors,favored the evolution of different ecological niches.Also,the absence of a biogeographic barrier but the presence of less suitable areas in the contact regions,suggest that secondary contact zones may be also maintained by climatic factors for the eastern group,but also by biotic interactions for the western group. 展开更多
关键词 Biogeographical boundary Humid and dry forests Isthmus of Tehuantepec PHYLOGEOGRAPHY Secondary contact
下载PDF
Multitemporal landslide inventory analysis of an intertropical mountain in west-central Mexico——Basis for hazard management 被引量:1
3
作者 Alejandro Cesar VALDES CARRERA Manuel E.MENDOZA +1 位作者 Teodoro CARLÓN ALLENDE Jose Luis MACIAS 《Journal of Mountain Science》 SCIE CSCD 2022年第6期1650-1669,共20页
Landslides in intertropical mountainous areas of Mexico are a natural hazard that could potentially generate a disaster. Despite this, many areas lack landslide inventories, making it difficult to monitor and efficien... Landslides in intertropical mountainous areas of Mexico are a natural hazard that could potentially generate a disaster. Despite this, many areas lack landslide inventories, making it difficult to monitor and efficiently manage the associated risks for local populations. For this reason, the aim of this research was to undertake a multitemporal landslide inventory and analyze its conditioning factors in the Pico de Tancítaro stratovolcano, which, in recent decades, has presented several high-risk geomorphological events with disastrous consequences for nearby localities. The spatial distribution of landslides and its conditioning factors were mapped at a 1:50,000 scale for the 1995-2020 period, through visual interpretation of orthophotos and satellite images(Landsat, SPOT, and SENTINEL). The conditioning factors that link the most to landslides were Quaternary andesite and basaltic andesite rocks;volcanic cones, mountain river valleys, and very steep to steep slopes(30° to >45°), oriented to the South, North, and East;Andosols and Leptosols;and the oyamel fir and mixed forests. 505 landslide events classified into slides and flows that occurred in 1995, 2004, 2010, and 2015 were identified. New scars generated by the reactivation of landslide processes were also observed. The landslides in the study area were triggered by torrential rains caused by hurricanes and tropical storms;such as hurricanes Alex and Patricia. The inventory and analysis of conditioning factors highlighted the distribution and dynamics of slides and flows in the study area. In addition, the most important factors for studies of landslide susceptibility, hazards, and risks in the Pico de Tancítaro stratovolcano were identified, contributing to the management of geomorphological risks in intertropical mountain areas. 展开更多
关键词 GEOMORPHOLOGY Mass wasting Natural hazards Pico de Tancítaro stratovolcano Risk management
下载PDF
Knowledge and preventive measures practiced by junior high school students from Mexico City regarding influenza A (H1N1) 被引量:1
4
作者 Veronica Cruz-Licea Fernando Gonzalez-Dominguez +2 位作者 Laura Vargas-Parada Monica Hernandez-Riquelme Ana Flisser 《Health》 2012年第10期995-999,共5页
Background: Influenza A (H1N1) is the most recent pandemic disease that has affected the human population. Objective: To evaluate knowledge and preventive measures related with this disease one year after the epidemic... Background: Influenza A (H1N1) is the most recent pandemic disease that has affected the human population. Objective: To evaluate knowledge and preventive measures related with this disease one year after the epidemic of Mexico- that took place in 2009. Material and methods: An epidemiologic survey regarding influenza A (H1N1) was conducted in June 2010 among 2541 students from the second grade of all public high schools in a borough in Mexico City. The questionnaire included items on the knowledge of the disease and practice of preventive measures. Results: Most students obtained the information from television, half of them from parents and only one fifth from teachers;72% of the participants had a favorable knowledge about the disease and the measures to avoid being infected. However, only 37% practiced such preventive measures. Conclusion: Knowledge has a positive influence on practices towards health. Parents and teachers have an important role in health education, thus efforts should be directed to involve them more intensely in health education. 展开更多
关键词 Alcohol Gel Epidemiologic Survey Hand Washing Health Behavior Influenza A (H1N1) Outbreak Mexico City
下载PDF
Phase equilibrium modelling of the amphibolite facies metamorphism in the Yelapa-Chimo Metamorphic Complex, Mexico
5
作者 Fabian Gutierrez-Aguilar Peter Schaaf +3 位作者 Gabriela Solís-Pichardo Gerardo F.Arrieta-García Teodoro Hernandez-Trevino Carlos Linares-Lopez 《Geoscience Frontiers》 SCIE CAS CSCD 2021年第1期293-312,共20页
The Yelapa-Chimo Metamorphic Complex forms part of the Jalisco Block in western Mexico and exposes a wide range of Early Cretaceous metamorphic rocks;such as paragneiss,orthogneiss,amphibolites,and migmatites.However,... The Yelapa-Chimo Metamorphic Complex forms part of the Jalisco Block in western Mexico and exposes a wide range of Early Cretaceous metamorphic rocks;such as paragneiss,orthogneiss,amphibolites,and migmatites.However,the pressure-temperature(P-T)conditions of metamorphism and partial melting remain poorly studied in the region.To elucidate metamorphic P-T conditions,phase equilibrium modelling was applied to two sillimanite-garnet paragneisses,one amphibole-orthogneiss,and one amphibolite.Sillimanite-garnet paragneisses exhibit a lepidoblastic texture with a biotite+sillimanite+kyanite+garnet+quartz+plagioclase+K-feldspar mineral assemblage.Amphibole-orthogneiss and amphibolite display a nematoblastic texture with an amphibole+(1)plagioclase+quartz+(1)titanite assemblage and an amphibole+(2)plagioclase+(2)titanite+ilmenite retrograde mineral assemblage.Pseudosections calculated for the two sillimanite-garnet paragneiss samples show P-T peak conditions at~6-7.5 kbar and~725-740℃.The results for amphibole-orthogneiss and the amphibolite yield P-T peak conditions at~8.5-10 kbar and~690-710℃.The mode models imply that metasedimentary and metaigneous units can produce up to~20 vol%and~10 vol%of melt,respectively.Modelling within a closed system during isobaric heating suggests that melt compositions of metasedimentary and metaigneous units are likely to have direct implications for the petrogenesis of the Puerto Vallarta Batholith.Our new data indicate that the Yelapa-Chimo Metamorphic Complex evolved through a metamorphic gradient between~23-33℃km^-1and the metamorphic rocks formed at depths between~22 km and~30 km with a burial rate of~2.0 km Ma^-1.Finally,the P-T data for both metasedimentary and metaigneous rocks provide new constraints on an accretionary framework,which is responsible for generating metamorphism and partial melting in the YelapaChimo Metamorphic Complex during the Early Cretaceous. 展开更多
关键词 Phase equilibrium modelling Yelapa-Chimo Metamorphic Complex Amphibolite facies Partial melting
下载PDF
A Remote Sensing Characterization of the Effects of Anastrepha striata & Anastrepha ludens on Guava Cultures in Mexico
6
作者 Eduardo Vazquez Roman Alvarezl 《Journal of Agricultural Science and Technology(A)》 2014年第8期663-678,共16页
Detection of the presence of Anastrepha striata and Anastrepha ludens in guava cultures is presently done in Mexico by actually catching the flies in strategically located traps. The objective of this study is to show... Detection of the presence of Anastrepha striata and Anastrepha ludens in guava cultures is presently done in Mexico by actually catching the flies in strategically located traps. The objective of this study is to show that it is possible to locate areas with the presence or absence of flies by remote sensing means, thereby simplifying the traditional way of detection of these plagues. In the field, groups of traps were selected where flies had been captured, as well as areas in which there was no capture in the traps. The radiometric signatures of whole trees and leaves were obtained, showing measurable differences between those specimens affected by the plague and those unaffected. Next we selected a SPOT5 image of 2007 corresponding to the study area in Calvillo, State of Aguascalientes, in Mexico, one of the major areas of guava cultures in the country. A supervised classification of the image allowed for the location of guava cultures in it. The guava culture areas obtained from this classification were validated comparing them to available maps of the cultured areas. Spectral signatures for the classes were derived from the image data. The separability of pairs of classes was also evaluated in order to maximize it. The IR/R (infrared to red ratio) ratio of the image bands was evaluated in 80 × 80 pixels around the locations of five traps where flies had been captured, and around five locations where the traps had not captured flies. Only the pixels where guava cultures were present were included in the analysis, other types of vegetation and soil coverage were rejected. We found that the index distributions with flies captured and those without flies captured cluster in two well-separated groups. We note that plotting the whole distribution of pixels around a trap yields a diagnostic view of the area, and individual index values do not provide such a view, since values with the flies' presence and without these overlap to some extent. Further analyses of other trap locations confirmed this separation and also revealed a third group of intermediate values between the two above, that are interpreted as locations in which the guava cultures are affected by the plague at an early stage of development, where the flies are not captured by the traps since they do not yet hatch. We concluded that it is possible to use remote sensing techniques to identify the presence ofAnastrepha striata and Anastrepha ludens in cultures of Psidium guajava L., even probably at early stages of development of the plague. 展开更多
关键词 Anastrepha striata guava cultures remote sensing plague detection.
下载PDF
Comparing the Adequacy of Some Non-Homogeneous Poisson Models to Estimate Ozone Exceedances in Mexico City
7
作者 Jorge A.Achcar Juan M.Barrios Eliane R.Rodrigues 《Journal of Environmental Protection》 2012年第9期1213-1227,共15页
We consider some non-homogeneous Poisson models to estimate the mean number of times that a given environmental threshold of interest is surpassed by a given pollutant. Seven different rate functions for the Poisson p... We consider some non-homogeneous Poisson models to estimate the mean number of times that a given environmental threshold of interest is surpassed by a given pollutant. Seven different rate functions for the Poisson processes describing the models are taken into account. The rate functions considered are the Weibull, exponentiated-Weibull, and their generalisation the Beta-Weibull rate function. We also use the Musa-Okumoto, the Goel-Okumoto, a generalised Goel- Okumoto and the Weibull-geometric rate functions. Whenever thought justifiable, the model allowing the presence of change-points is also going to be considered. The different models are applied to the daily maximum ozone measurements data provided by the monitoring network of the Metropolitan Area of Mexico City. The aim is to compare the adjustment of different rate functions to the data. Even though, some of the rate functions have been considered before, now we are applying them to the same data set. In previous works they were used in different data sets and therefore a comparison of the adequacy of those models were not possible. The measurements considered here were obtained after a series of environmental measures were implemented in Mexico City. Hence, the data present a different behaviour from that of earlier studies. 展开更多
关键词 MCMC Algorithms Non-Homogeneous Poisson Models Change-Points Ozone Air Pollution Mexico City
下载PDF
Essential Oils as an Alternative to Antibiotics to Reduce the Incidence and Severity of Necrotic Enteritis in Broiler Chickens: A Short Review
8
作者 Makenly E. Coles Brittany D. Graham +8 位作者 Juan D. Latorre Victor M. Petrone-Garcia Xochitl Hernandez-Velasco Inkar Castellanos-Huerta Xiaolun Sun Billy M. Hargis Saeed El-Ashram Awad A. Shehata Guillermo Tellez-Isaias 《Food and Nutrition Sciences》 CAS 2023年第3期233-257,共25页
Due to the removal of antibiotic growth promoters (AGPs) and consumer pressure for antibiotic-free (ABF) or no antibiotics ever (NAE) poultry production, there is a need for sustainable alternatives to prevent disease... Due to the removal of antibiotic growth promoters (AGPs) and consumer pressure for antibiotic-free (ABF) or no antibiotics ever (NAE) poultry production, there is a need for sustainable alternatives to prevent disease in commercial poultry operations. Without AGPs, there has been a rise in diseases that were traditionally controlled by subtherapeutic levels of antibiotics in the diet. This has impacted the health of commercial poultry and has been a significant cost to poultry producers. To mitigate this, the industry has started to investigate alternatives to antibiotics to treat these forthcoming health issues, such as necrotic enteritis (NE). NE is an enteric disease caused by an over proliferation of toxigenic Clostridium perfringens (CP) in the gastrointestinal tract. Although CP is a commensal in the avian intestinal tract, dysbiosis caused by inflammation and impaired intestinal integrity facilitates uncontrolled replication of CP. Infectious agents, such as Eimeria maxima, appear to be a predominant predisposing factor that promotes NE. However, non-infectious stressors, including dietary changes, have also been associated with NE to some degree. As a result of increased pressure to restrict the use of antibiotics, there is a need for research evaluating the efficacy of alternatives, such as plant-derived essential oils, as potential tools to mitigate NE in commercial poultry flocks. The aim of this study is to review the effects of essential oils as an alternative to antibiotics to reduce the incidence and severity of necrotic enteritis in broiler chickens. 展开更多
关键词 Necrotic Enteritis Essential Oils CHICKENS Clostridium perfringens Alternatives to Antibiotics
下载PDF
Hidden Quantum Effect in General Relativity
9
作者 Miguel Socolovsky 《Journal of High Energy Physics, Gravitation and Cosmology》 2023年第4期913-916,共4页
If the Planck length is chosen as the natural length scale of the Universe, the Penrose-Carter diagram associated with the classical gravitational collapse of a thin spherical shell of massless matter reveals, beyond ... If the Planck length is chosen as the natural length scale of the Universe, the Penrose-Carter diagram associated with the classical gravitational collapse of a thin spherical shell of massless matter reveals, beyond and in agreement with the claimed non locality of the horizon, a quantum nature of the whole process. 展开更多
关键词 Spherical Collapse Penrose-Carter Diagram Quantum Effect
下载PDF
Role of fecal microbiota transplant in management of hepatic encephalopathy: Current trends and future directions 被引量:1
10
作者 Yash R Shah Hassam Ali +11 位作者 Angad Tiwari David Guevara-Lazo Natalia Nombera-Aznaran Bhanu Siva Mohan Pinnam Manesh Kumar Gangwani Harishankar Gopakumar Amir H Sohail SriLakshmiDevi Kanumilli Ernesto Calderon-Martinez Geetha Krishnamoorthy Nimish Thakral Dushyant Singh Dahiya 《World Journal of Hepatology》 2024年第1期17-32,共16页
Fecal microbiota transplantation(FMT)offers a potential treatment avenue for hepatic encephalopathy(HE)by leveraging beneficial bacterial displacement to restore a balanced gut microbiome.The prevalence of HE varies w... Fecal microbiota transplantation(FMT)offers a potential treatment avenue for hepatic encephalopathy(HE)by leveraging beneficial bacterial displacement to restore a balanced gut microbiome.The prevalence of HE varies with liver disease severity and comorbidities.HE pathogenesis involves ammonia toxicity,gut-brain communication disruption,and inflammation.FMT aims to restore gut microbiota balance,addressing these factors.FMT's efficacy has been explored in various conditions,including HE.Studies suggest that FMT can modulate gut microbiota,reduce ammonia levels,and alleviate inflammation.FMT has shown promise in alcohol-associated,hepatitis B and C-associated,and non-alcoholic fatty liver disease.Benefits include improved liver function,cognitive function,and the slowing of disease progression.However,larger,controlled studies are needed to validate its effectiveness in these contexts.Studies have shown cognitive improvements through FMT,with potential benefits in cirrhotic patients.Notably,trials have demonstrated reduced serious adverse events and cognitive enhancements in FMT arms compared to the standard of care.Although evidence is promising,challenges remain:Limited patient numbers,varied dosages,administration routes,and donor profiles.Further large-scale,controlled trials are essential to establish standardized guidelines and ensure FMT's clinical applications and efficacy.While FMT holds potential for HE management,ongoing research is needed to address these challenges,optimize protocols,and expand its availability as a therapeutic option for diverse hepatic conditions. 展开更多
关键词 Hepatic encephalopathy Fecal microbiota transplant Cognitive impairment Liver cirrhosis Chronic liver disease
下载PDF
Impact of STAT-signaling pathway on cancer-associated fibroblasts in colorectal cancer and its role in immunosuppression
11
作者 Damián Sánchez-Ramírez Mónica G Mendoza-Rodríguez +7 位作者 Omar R Alemán Fernando A Candanedo-González Miriam Rodríguez-Sosa Juan JoséMontesinos-Montesinos Mauricio Salcedo Ismael Brito-Toledo Felipe Vaca-Paniagua Luis I Terrazas 《World Journal of Gastrointestinal Oncology》 SCIE 2024年第5期1705-1724,共20页
Colorectal cancer(CRC)remains one of the most commonly diagnosed and deadliest types of cancer worldwide.CRC displays a desmoplastic reaction(DR)that has been inversely associated with poor prognosis;less DR is associ... Colorectal cancer(CRC)remains one of the most commonly diagnosed and deadliest types of cancer worldwide.CRC displays a desmoplastic reaction(DR)that has been inversely associated with poor prognosis;less DR is associated with a better prognosis.This reaction generates excessive connective tissue,in which cancer-associated fibroblasts(CAFs)are critical cells that form a part of the tumor microenvironment.CAFs are directly involved in tumorigenesis through different mechanisms.However,their role in immunosuppression in CRC is not well understood,and the precise role of signal transducers and activators of transcription(STATs)in mediating CAF activity in CRC remains unclear.Among the myriad chemical and biological factors that affect CAFs,different cytokines mediate their function by activating STAT signaling pathways.Thus,the harmful effects of CAFs in favoring tumor growth and invasion may be modulated using STAT inhibitors.Here,we analyze the impact of different STATs on CAF activity and their immunoregulatory role. 展开更多
关键词 Cancer-associated fibroblasts Signal transducer and activator of transcription signaling Colorectal cancer IMMUNITY IMMUNOSUPPRESSION
下载PDF
Correlation between Intestinal Health and Coccidiosis Prevalence in Broilers during Different Seasons of the Year in Brazil from 2012 to 2018
12
作者 Fabio Luis Gazoni Gabriela Miotto Galli +5 位作者 Marcel Manente Boiago Lenita Moura Stefani Aline Zampar Marco A. Juárez-Estrada Guillermo Tellez-Isaias Aleksandro S. da Silva 《Food and Nutrition Sciences》 CAS 2024年第3期179-198,共20页
Coccidiosis is a disease caused by intracellular protozoan parasites, specifically belonging to the genus Eimeria. These parasites target the gastrointestinal tract in different types of hosts, causing sores in the in... Coccidiosis is a disease caused by intracellular protozoan parasites, specifically belonging to the genus Eimeria. These parasites target the gastrointestinal tract in different types of hosts, causing sores in the intestinal lining. The presence of these lesions reduces the animal’s ability to digest and absorb nutrients, significantly impacting their overall performance. The current study aimed to explore the potential correlation between seasonal variations and the incidence of Eimeria spp-induced lesions in broiler chickens’ gastrointestinal tracts in Brazil from 2012 to 2018. A total of 8,607 broiler chickens, aged 14 to 42 days, were sampled from 103 poultry integrated companies in Brazil to conduct intestinal health examinations. The sampling process involved selecting 3 to 6 chickens from each poultry house for examination. The assessment included various abnormalities such as shedding of intestinal cells and excessive fluid and mucus presence, thickening and tension of the intestines, food movement, roughened mucosal surface resembling a Turkish towel in the small intestine, tissue death, duodenal inflammation, intestinal inflammation, gizzard erosion, presence of worms and bedding material, and ingestion of mealworms. During the seasons, winter exhibited the highest average occurrence of Eimeria maxima microorganisms at 52.83%, with E. acervulina following closely at 26.42% in second place. In spring, E. maxima had an occurrence of 11.31%, while in fall, E. tenella had the lowest occurrence at 6.74%. When analyzing the seasonal occurrence of Eimeria, it was observed that E. maxima micro was more common during winter compared to summer (P = 0.0491). However, no discernible variation was observed in the occurrence of the remaining species across different seasons. Research findings suggest that subclinical coccidiosis is most prevalent during the winter season in Brazil. Likewise, clinical disease caused by E. acervulina is also prevalent during this time. In contrast, E. maxima is more likely to cause clinical disease in the spring, whereas E. tenella is more commonly associated with clinical disease in the fall. Lesions induced by Eimeria spp. are associated with factors influencing the overall health of broiler intestines. These findings allow for the utilization of seasonal metrics in disease management, thereby reducing economic losses associated with the condition. 展开更多
关键词 EIMERIA Epidemiology Intestinal Pathology Broiler Chickens Brazil
下载PDF
The role of the TrkB-T1 receptor in the neurotrophin-4/5 antagonism of brain-derived neurotrophic factor on corticostriatal synaptic transmission 被引量:2
13
作者 Elizabeth Hernandez-Echeagaray 《Neural Regeneration Research》 SCIE CAS CSCD 2020年第11期1973-1976,共4页
This manuscript reviews the function and fundamental characteristics of the neurotrophins and their receptors to introduce the reader to the differential effects exhibited by the neurotrophins;brain-derived neurotroph... This manuscript reviews the function and fundamental characteristics of the neurotrophins and their receptors to introduce the reader to the differential effects exhibited by the neurotrophins;brain-derived neurotrophic factor and neurotrophin 4/5 when acted together after sequential presentation.The neurotrophin 4/5 exhibits an inhibitory action on the modulatory effect of brain-derived neurotrophic factor in corticostriatal synapses when they are administered sequentially(brain-derived neurotrophic factor to neurotrophin 4/5).This inhibitory effect has not been previously documented and is relevant for these neurotrophins as both of them stimulate the TrkB receptor.The additive effect of these neurotrophins is also discussed and occurs when neurotrophin 4/5 exposure is followed by brain-derived neurotrophic factor in a mouse model of striatal degeneration.Occlusive and additive effects of both neurotrophins are accompanied by changes in the expression of the TrkB receptor isoforms,specifically TrkB-T1 and TrkB-FL,as well as differences in phosphorylation levels of the TrkB receptor.The results of the experiments described raise several questions to inquire about the role that TrkB-T1 receptor plays in striatal physiology,as well as the functional relevance of the interaction of brain-derived neurotrophic factor and neurotrophin 4/5 in the brain and more specifically at the striatal circuits in normal as well as pathological conditions. 展开更多
关键词 BRAIN-DERIVED NEUROTROPHIC factor NEUROTROPHIN 4/5 occlusive striatum synergic TrkB-FL TrkB-T1
下载PDF
Effective use of FibroTest to generate decision trees in hepatitis C 被引量:2
14
作者 Dana Lau-Corona Luís Alberto Pineda +10 位作者 Héctor Hugo Avilés Gabriela Gutiérrez-Reyes Blanca Eugenia Farfan-Labonne Rafael Núez-Nateras Alan Bonder Rosalinda Martínez-García Clara Corona-Lau Marco Antonio Olivera-Martínez Maria Concepción Gutiérrez-Ruiz Guillermo Robles-Díaz David Kershenobich 《World Journal of Gastroenterology》 SCIE CAS CSCD 2009年第21期2617-2622,共6页
AIM: To assess the usefulness of FibroTest to forecast scores by constructing decision trees in patients with chronic hepatitis C.METHODS: We used the C4.5 classification algorithm to construct decision trees with d... AIM: To assess the usefulness of FibroTest to forecast scores by constructing decision trees in patients with chronic hepatitis C.METHODS: We used the C4.5 classification algorithm to construct decision trees with data from 261 patients with chronic hepatitis C without a liver biopsy. The FibroTest attributes of age, gender, bilirubin, apolipoprotein, haptoglobin, α2 macroglobulin, and γ-glutamyl transpeptidase were used as predictors, and the FibroTest score as the target. For testing, a 10-fold cross validation was used.RESULTS: The overall classification error was 14.9% (accuracy 85.1%). FibroTest's cases with true scores of FO and F4 were classified with very high accuracy (18/20 for FO, 9/9 for FO-1 and 92/96 for F4) and the largest confusion centered on F3. The algorithm produced a set of compound rules out of the ten classification trees and was used to classify the 261 patients. The rules for the classification of patients in FO and F4 were effective in more than 75% of the cases in which they were tested.CONCLUSION: The recognition of clinical subgroups should help to enhance our ability to assess differences in fibrosis scores in clinical studies and improve our understanding of fibrosis progression, 展开更多
关键词 Hepatitis C FibroTest Decision trees C4.5algorithm Non-invasive biomarkers
下载PDF
Occult hepatitis B virus co-infection in human immunodeficiency virus-positive patients: A review of prevalence, diagnosis and clinical significance 被引量:2
15
作者 Angelica Maldonado-Rodriguez Ana Maria Cevallos +3 位作者 Othon Rojas-Montes Karina Enriquez-Navarro Ma Teresa Alvarez-Mu?oz Rosalia Lira 《World Journal of Hepatology》 CAS 2015年第2期253-260,共8页
The prevalence of human immunodeficiency virus(HIV) and hepatitis B virus(HBV) co-infection is high as they share similar mechanisms of transmission. The development and widespread use of highly sensitive tests for HB... The prevalence of human immunodeficiency virus(HIV) and hepatitis B virus(HBV) co-infection is high as they share similar mechanisms of transmission. The development and widespread use of highly sensitive tests for HBV diagnosis has demonstrated that a significant proportion of apparently healthy individuals with evidence of exposure to HBV continue to carry fully functional HBV DNA in their hepatocytes, a situation that predisposes them to the development of progressive liver disease and hepatocellular carcinoma. The presence of co-infections frequently influences the natural evolution of each of the participating infections present by either facilitating their virulence or competing for resources. Furthermore, the drugs used to treat these infections may also contribute to changes in the natural course of these infections, making the analysis of the impact of co-infection more difficult. The majority of studies has examined the impact of HIV on overt chronic hepatitis B, finding that co-infection carries an increased risk of progressive liver disease and the development of hepatocellular carcinoma. Although the effect of HIV on the natural history of occult hepatitis B infection(OBI) has not been fully assessed, all available data suggest a persisting risk of repeated flares of hepatitis and progressive liver disease. We describe studies regarding the diagnosis, prevalence and clinical significance of OBI in HIVpositive patients in this short review. Discrepancies in worldwide prevalence show the urgent need for the standardization of diagnostic criteria, as established by the Taormina statements. Ideally, standardized protocols for testing should be employed to enable the comparison of data from different groups. Additional studies are needed to define the differences in risk for OBI without HIV and in HIV-HBV co-infected patients with or without overt disease. 展开更多
关键词 Hepatitis B virus Occult hepatitis B virus infection Hepatitis C virus EGYPT Blood donors HEMODIALYSIS Hepatitis B virus reactivation
下载PDF
Condensed Extended Hyper-Wiener Index 被引量:2
16
作者 李新华 Abraham F.Jalbout 吉智 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 北大核心 2008年第9期1134-1140,共7页
According to the definitions of molecular connectivity and hyper-Wiener index, a novel set of hyper-Wiener indexes (Dn, ^mDn) were defined and named as condensed extended hyper-Wiener index, the potential usefulness... According to the definitions of molecular connectivity and hyper-Wiener index, a novel set of hyper-Wiener indexes (Dn, ^mDn) were defined and named as condensed extended hyper-Wiener index, the potential usefulness of which in QSAR/QSPR is evaluated by its correlation with a number of C3-C8 alkanes as well as by a favorable comparison with models based on molecular connectivity index and overall Wiener index. 展开更多
关键词 hyper-Wiener index (R) condensed extended hyper-Wiener index molecular connectivity index
下载PDF
Dipole and generalized oscillator strength derived electronic properties of an endohedral hydrogen atom embedded in a Debye-Huckel plasma 被引量:1
17
作者 C.Martínez-Flores R.Cabrera-Trujillo 《Matter and Radiation at Extremes》 SCIE EI CAS 2018年第5期227-242,共16页
We report electronic properties of a hydrogen atom encaged by an endohedral cavity under the influence of a weak plasma interaction. Weimplement a finite-difference approach to solve the Schrodinger equation for a hyd... We report electronic properties of a hydrogen atom encaged by an endohedral cavity under the influence of a weak plasma interaction. Weimplement a finite-difference approach to solve the Schrodinger equation for a hydrogen atom embedded in an endohedral cavity modeled by theWoods-Saxon potential with well depth V0, inner radius R0, thickness D, and smooth parameter g. The plasma interaction is described by aDebye-Hu¨ckel screening potential that characterizes the plasma in terms of a Debye screening length lD. The electronic properties of theendohedral hydrogen atom are reported for selected endohedral cavity well depths, V0, and screening lengths, lD, that emulate differentconfinement and plasma conditions. We find that for low screening lengths, the endohedral cavity potential dominates over the plasma interaction by confining the electron within the cavity. For large screening lengths, a competition between both interactions is observed. We assessand report the photo-ionization cross section, dipole polarizability, mean excitation energy, and electronic stopping cross section as function of lD and V0. We find a decrease of the Generalized Oscillator Strength (GOS) when the final excitation is to an s state as the plasma screeninglength decreases. For a final excitation into a p state, we find an increase in the GOS as the endohedral cavity well-depth increases. For the caseof the electronic stopping cross section, we find that the plasma screening and endohedral cavity effects are larger in the low-to-intermediateprojectile energies for all potential well depths considered. Our results agree well to available theoretical and experimental data and are afirst step towards the understanding of dipole and generalized oscillator strength dependent properties of an atom in extreme conditions encagedby an endohedral cavity immersed in a plasma medium. 展开更多
关键词 Oscillator strengths Debye-Huckel plasma CAVITIES Endohedral Energy loss Stopping power
下载PDF
How much has the Sun influenced Northern Hemisphere temperature trends?An ongoing debate 被引量:2
18
作者 Ronan Connolly Willie Soon +20 位作者 Michael Connolly Sallie Baliunas Johan Berglund C.John Butler Rodolfo Gustavo Cionco Ana G.Elias Valery M.Fedorov Hermann Harde Gregory W.Henry Douglas V.Hoyt Ole Humlum David R.Legates Sebastian Liming Nicola Scafetta Jan-Erik Solheim Laszlo Szarka Harry van Loon Victor M.Velasco Herrera Richard C.Willson Hong Yan Weijia Zhang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2021年第6期131-198,共68页
In order to evaluate how much Total Solar Irradiance(TSI)has influenced Northern Hemisphere surface air temperature trends,it is important to have reliable estimates of both quantities.Sixteen different estimates of t... In order to evaluate how much Total Solar Irradiance(TSI)has influenced Northern Hemisphere surface air temperature trends,it is important to have reliable estimates of both quantities.Sixteen different estimates of the changes in TSI since at least the 19th century were compiled from the literature.Half of these estimates are"low variability"and half are"high variability".Meanwhile,five largely-independent methods for estimating Northern Hemisphere temperature trends were evaluated using:1)only rural weather stations;2)all available stations whether urban or rural(the standard approach);3)only sea surface temperatures;4)tree-ring widths as temperature proxies;5)glacier length records as temperature proxies.The standard estimates which use urban as well as rural stations were somewhat anomalous as they implied a much greater warming in recent decades than the other estimates,suggesting that urbanization bias might still be a problem in current global temperature datasets-despite the conclusions of some earlier studies.Nonetheless,all five estimates confirm that it is currently warmer than the late 19th century,i.e.,there has been some"global warming"since the 19th century.For each of the five estimates of Northern Hemisphere temperatures,the contribution from direct solar forcing for all sixteen estimates of TSI was evaluated using simple linear least-squares fitting.The role of human activity on recent warming was then calculated by fitting the residuals to the UN IPCC’s recommended"anthropogenic forcings"time series.For all five Northern Hemisphere temperature series,different TSI estimates suggest everything from no role for the Sun in recent decades(implying that recent global warming is mostly human-caused)to most of the recent global warming being due to changes in solar activity(that is,that recent global warming is mostly natural).It appears that previous studies(including the most recent IPCC reports)which had prematurely concluded the former,had done so because they failed to adequately consider all the relevant estimates of TSI and/or to satisfactorily address the uncertainties still associated with Northern Hemisphere temperature trend estimates.Therefore,several recommendations on how the scientific community can more satisfactorily resolve these issues are provided. 展开更多
关键词 Sun:activity (Sun:)solar terrestrial relations (Sun:)sunspots Sun:faculae plages
下载PDF
Increased myo-inositol in the posterior cingulate cortex in first-episode major depressive patients 被引量:1
19
作者 Lily Magally Granados-Dominguez Enrique O.Flores-Gutierrez +3 位作者 Sarael Alcauter Juan Jose Cervantes Marina Torres-Alvarez Maria Corsi-Cabrera 《Advances in Bioscience and Biotechnology》 2013年第6期45-52,共8页
Major depressive disorder (MDD) is a severe, disabling pathology characterized, in addition to affective, cognitive and motor symptoms, by self-focused attention and rumination. During recursive self-focused processes... Major depressive disorder (MDD) is a severe, disabling pathology characterized, in addition to affective, cognitive and motor symptoms, by self-focused attention and rumination. During recursive self-focused processes and rumination, the posterior cingulate cortex (PCC) is activated. In vivo proton magnetic resonance spectroscopy (MRS) is a noninvasive imaging technique that can directly assess living biochemistry in localized brain regions. The aim of this study, therefore, was to use 1H-MRS as a means of analyzing brain metabolites in the PCC of a group of first-episode, unmedicated MDD patients. PCC metabolite levels were analyzed at 3-T in a single voxel located bilaterally over the PCC in 7 patients diagnosed for the first time with MDD and with no previous pharmacological treatment, as well as in 9 control subjects. Differences in metabolite levels between groups were compared using independent t-tests. Myo-inositol was significantly higher, and NAA + NAAG/Cr significantly lower, in MDD patients than in controls. The other brain metabolites showed no statistical differences. The present results suggest that alterations in PCC metabolite levels are likely involved in MDD pathophysiology, and may help to improve our understanding of MDD and the role of the PCC in some symptoms of depression. 展开更多
关键词 Major Depressive Disorder Posterior Cingulate Cortex METABOLITES ^(1)H-MRS MYO-INOSITOL N-Acetyl-Aspartate
下载PDF
IGCP 641 Project:Mechanisms,Monitoring and Modeling Earth Fissure Generation and Fault Activation due to Subsurface Fluid Exploitation
20
作者 YE Shujun Dora CARREoN-FREYRE +1 位作者 Pietro TEATINI Devin GALLOWAY 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2019年第S01期165-168,共4页
Ground ruptures(fractures,earth fissures and reactivation of pre-existing surface faults)caused by extraction of fluids from the subsurface have been observed in hundreds of sedimentary basins worldwide,mainly in semi... Ground ruptures(fractures,earth fissures and reactivation of pre-existing surface faults)caused by extraction of fluids from the subsurface have been observed in hundreds of sedimentary basins worldwide,mainly in semiarid to arid areas of the USA,Mexico,China,India,Libya,Iran,and Saudi Arabia. 展开更多
关键词 MECHANISMS monitoring modeling EARTH FISSURE SUBSURFACE FLUID EXPLOITATION
下载PDF
上一页 1 2 10 下一页 到第
使用帮助 返回顶部