967 resultados para arid and semiarid region


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Salinization is a soil threat that adversely affects ecosystem services and diminishes soil functions in many arid and semi-arid regions. Soil salinity management depends on a range of factors, and can be complex expensive and time demanding. Besides taking no action, possible management strategies include amelioration and adaptation measures. The WOCAT Technologies Questionnaire is a standardized methodology for monitoring, evaluating and documenting sustainable land management practices through interaction with the stakeholders. Here we use WOCAT for the systematic analysis and evaluation of soil salinization amelioration measures, for the RECARE project Case Study in Greece, the Timpaki basin, a semi-arid region in south-central Crete where the main land use is horticulture in greenhouses irrigated by groundwater. Excessive groundwater abstractions have resulted in a drop of the groundwater level in the coastal part of the aquifer, thus leading to seawater intrusion and in turn to soil salinization due to irrigation with brackish water. Amelioration technologies that have already been applied in the case study by the stakeholders are examined and classified depending on the function they promote and/or improve. The documented technologies are evaluated for their impacts on ecosystem services, cost and input requirements. Preliminary results show that technologies which promote maintaining existing crop types while enhancing productivity and decreasing soil salinity such as composting, mulching, rain water harvesting and seed biopriming are preferred by the stakeholders. Further work will include result validation using qualitative approaches.

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Little is known about the aetiology of childhood brain tumours. We investigated anthropometric factors (birth weight, length, maternal age), birth characteristics (e.g. vacuum extraction, preterm delivery, birth order) and exposures during pregnancy (e.g. maternal: smoking, working, dietary supplement intake) in relation to risk of brain tumour diagnosis among 7-19 year olds. The multinational case-control study in Denmark, Sweden, Norway and Switzerland (CEFALO) included interviews with 352 (participation rate=83.2%) eligible cases and 646 (71.1%) population-based controls. Interview data were complemented with data from birth registries and validated by assessing agreement (Cohen's Kappa). We used conditional logistic regression models matched on age, sex and geographical region (adjusted for maternal age and parental education) to explore associations between birth factors and childhood brain tumour risk. Agreement between interview and birth registry data ranged from moderate (Kappa=0.54; worked during pregnancy) to almost perfect (Kappa=0.98; birth weight). Neither anthropogenic factors nor birth characteristics were associated with childhood brain tumour risk. Maternal vitamin intake during pregnancy was indicative of a protective effect (OR 0.75, 95%-CI: 0.56-1.01). No association was seen for maternal smoking during pregnancy or working during pregnancy. We found little evidence that the considered birth factors were related to brain tumour risk among children and adolescents.

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The sigma (σ) subunit of eubacterial RNA polymerase is required for recognition of and transcription initiation from promoter DNA sequences. One family of sigma factors includes those related to the primary sigma factor from E. coli, σ70. Members of the σ70 family have four highly conserved domains, of which regions 2 through 4 are present in all members. Region 1 can be subdivided into regions 1.1 and 1.2. Region 1.1 affects DNA binding by σ 70 alone, as well as transcription initiation by holoenzyme. Region 1.2, present and highly conserved in most sigma factors, has not yet been assigned a putative function, although previous work demonstrated that it is not required for either association with the core subunits of RNA polymerase or promoter specific binding by holoenzyme. This study primarily investigates the functional role of region 1.2 during transcription initiation. In vivo and in vitro characterization of thirty-two single amino acid substitutions targeted to region 1.2 of E. coli σ70 as well as a deletion of region 1.2, revealed that mutations in region 1.2 can affect promoter binding, open complex formation, initiated complex formation, and the transition from abortive transcription to elongation. The relative degree of solvent exposure of several positions in region 1.2 has been determined, with positions 116 and 122 likely to be located near the surface of σ70. ^ During the course of this study, the existence of two “wild type” variants of E. coli σ70 was discovered. The identity of amino acid 149 has been reported variably as either arginine or aspartic acid in published articles and in online databases. In vivo and in vitro characterization of the two reported variations of E. coli σ70 (N149 and D149) has determined that the two variants are functionally equivalent. However, in vivo and in vitro characterization of single amino acid substitutions and a region 1.2 deletion in the context of each variant background revealed that the behavior of some mutations are greatly affected by the identity of amino acid 149. ^

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Regional integration proposals often require agreements between countries that differ in geographic size, resource endowments, transportation assets, technologies, and product quality. In this asymmetric setting, questions arise about the potential for mutual gains and the distribution of benefits among industries and workers in each country. This paper examines how regional integration between a small landlocked country and a large neighboring country--with a unique port facility that both nations must use to export goods--affects the wage and location decisions of firms, the allocation of labor, the welfare of each country's workers and firms, and aggregate measures of economic welfare in each country and the region. A simulated spatial labor market model is used to explore the economic effects of various stages of regional integration. Beginning with autarky as a benchmark case, we consider two forms of regional integration: partial mobility (mobile labor with geographically restricted firms); and full mobility (mobile labor and firms) with convergence of production technologies and product quality.

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Background. The objective of this retrospective cohort study is to examine the presentation and outcomes for a contemporary series of cancer patients with anorectal infection. In addition, we seek to identify factors which are associated with surgical intervention. ^ Methods. The study cohort was identified from ICD-9 codes for diagnosis of infection of the anal and rectal region and patients who underwent a surgical oncology consultation between 1/2000 and 12/2006. Clinical presentation, treatment rendered, and outcomes were retrospectively recorded. ^ Results. Of the 100 patients evaluated by the surgical oncology service for anorectal infection, 42 were treated non-operatively and 58 underwent surgical intervention. Factors associated with surgical intervention based on logistic multivariable analysis included the diagnosis of an abscess (odds ratio [OR] 10.5; 95% confidence interval [CI] 2.9-38.5) and the documentation of erythema on physical examination (OR 3.1; 95% CI 1.1-8.4). Thrombocytopenia (platelets < 50,000) was associated with non-operative management (OR 0.3; 95% CI 0.1-0.7). Incision and drainage was the most common surgical procedure (79%) while a wide debridement for a necrotizing soft tissue infection was required in 2 patients. Infection-specific 90-day mortality was only 1% (N=1). However, the median overall survival for the entire cohort was only 14.4 months (95% CI 7.9-19.5). ^ Conclusions. Non-operative management is a reasonable treatment option for anorectal infection in patients with cancer. Identification of an abscess, erythema on physical exam, and thrombocytopenia were associated with management strategy. Although rare, necrotizing soft tissue infections are associated with significant mortality. ^

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Background. A few studies have reported gender differences along the colorectal cancer (CRC) continuum but none has done so longitudinally to compare a cancer and a non-cancer populations.^ Objectives and Methods. To examine gender differences in colorectal cancer screening (CRCS); to examine trends in gender differences in CRC screening among two groups of patients (Medicare beneficiaries with and without cancer); to examine gender differences in CRC incidence; and to examine for any differences over time. In Paper 1, the study population consisted of men and women, ages 67–89 years, with CRC (73,666) or without any cancer (39,006), residing in 12 U.S. Surveillance Epidemiology and End-Results (SEER) regions. Crude and age-adjusted percentages and odds ratios of receiving fecal occult blood test (FOBT), sigmoidoscopy (SIG), or colonoscopy (COL) were calculated. Multivariable logistic regression was used to assess gender on the odds of receiving CRC screening over time.^ In Paper 2, age-adjusted incidence rates and proportions over time were reported across race, CRC subsite, CRC stage and SEER region for 373,956 patients, ages 40+ years, residing in 9 SEER regions and diagnosed with malignant CRC. ^ Results. Overall, women had higher CRC screening rates than men and screening rates in general were higher in the SEER sample of persons with CRC diagnosis. Significant temporal divergence in FOBT screening was observed between men and women in both cohorts. Although the largest temporal increases in screening rates were found for COL, especially among the cohort with CRC, little change in the gender gap was observed over time. Receipt of FOBT was significantly associated with female gender especially in the period of full Medicare coverage. Receipt of COL was also significantly associated with male gender, especially in the period of limited Medicare coverage.^ Overall, approximately equal numbers of men (187,973) and women (185,983) were diagnosed with malignant CRC. Men had significantly higher age-adjusted CRC incidence rates than women across all categories of age, race, subsite, stage and SEER region even though rates declined in all categories over time. Significant moderate increases in rate difference occurred among 40-59 year olds; significant reductions occurred among patients age 70+, within subsite rectum, unstaged and distant stage CRC, and eastern and western SEER regions. ^ Conclusions. Persistent gender differences in CRC incidence across time may have implications for gender-based interventions that take age into consideration. A shift toward proximal cancer was observed over time for both genders, but the high proportion of men who develop rectal cancer suggests that a greater proportion of men may need to be targeted with newer screening methods such as fecal DNA or COL. Although previous reports have documented higher CRC screening among men, higher incidence of CRC observed among men suggests that higher risk categories of men are probably not being reached. FOBT utilization rates among women have increased over time and the gender gap has widened between 1998 and 2005. COL utilization is associated with male gender but the differences over time are small.^

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This study aims to address two research questions. First, ‘Can we identify factors that are determinants both of improved health outcomes and of reduced costs for hospitalized patients with one of six common diagnoses?’ Second, ‘Can we identify other factors that are determinants of improved health outcomes for such hospitalized patients but which are not associated with costs?’ The Healthcare Cost and Utilization Project (HCUP) Nationwide Inpatient Sample (NIS) database from 2003 to 2006 was employed in this study. The total study sample consisted of hospitals which had at least 30 patients each year for the given diagnosis: 954 hospitals for acute myocardial infarction (AMI), 1552 hospitals for congestive heart failure (CHF), 1120 hospitals for stroke (STR), 1283 hospitals for gastrointestinal hemorrhage (GIH), 979 hospitals for hip fracture (HIP), and 1716 hospitals for pneumonia (PNE). This study used simultaneous equations models to investigate the determinants of improvement in health outcomes and of cost reduction in hospital inpatient care for these six common diagnoses. In addition, the study used instrumental variables and two-stage least squares random effect model for unbalanced panel data estimation. The study concluded that a few factors were determinants of high quality and low cost. Specifically, high specialty was the determinant of high quality and low costs for CHF patients; small hospital size was the determinant of high quality and low costs for AMI patients. Furthermore, CHF patients who were treated in Midwest, South, and West region hospitals had better health outcomes and lower hospital costs than patients who were treated in Northeast region hospitals. Gastrointestinal hemorrhage and pneumonia patients who were treated in South region hospitals also had better health outcomes and lower hospital costs than patients who were treated in Northeast region hospitals. This study found that six non-cost factors were related to health outcomes for a few diagnoses: hospital volume, percentage emergency room admissions for a given diagnosis, hospital competition, specialty, bed size, and hospital region.^

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My dissertation focuses on developing methods for gene-gene/environment interactions and imprinting effect detections for human complex diseases and quantitative traits. It includes three sections: (1) generalizing the Natural and Orthogonal interaction (NOIA) model for the coding technique originally developed for gene-gene (GxG) interaction and also to reduced models; (2) developing a novel statistical approach that allows for modeling gene-environment (GxE) interactions influencing disease risk, and (3) developing a statistical approach for modeling genetic variants displaying parent-of-origin effects (POEs), such as imprinting. In the past decade, genetic researchers have identified a large number of causal variants for human genetic diseases and traits by single-locus analysis, and interaction has now become a hot topic in the effort to search for the complex network between multiple genes or environmental exposures contributing to the outcome. Epistasis, also known as gene-gene interaction is the departure from additive genetic effects from several genes to a trait, which means that the same alleles of one gene could display different genetic effects under different genetic backgrounds. In this study, we propose to implement the NOIA model for association studies along with interaction for human complex traits and diseases. We compare the performance of the new statistical models we developed and the usual functional model by both simulation study and real data analysis. Both simulation and real data analysis revealed higher power of the NOIA GxG interaction model for detecting both main genetic effects and interaction effects. Through application on a melanoma dataset, we confirmed the previously identified significant regions for melanoma risk at 15q13.1, 16q24.3 and 9p21.3. We also identified potential interactions with these significant regions that contribute to melanoma risk. Based on the NOIA model, we developed a novel statistical approach that allows us to model effects from a genetic factor and binary environmental exposure that are jointly influencing disease risk. Both simulation and real data analyses revealed higher power of the NOIA model for detecting both main genetic effects and interaction effects for both quantitative and binary traits. We also found that estimates of the parameters from logistic regression for binary traits are no longer statistically uncorrelated under the alternative model when there is an association. Applying our novel approach to a lung cancer dataset, we confirmed four SNPs in 5p15 and 15q25 region to be significantly associated with lung cancer risk in Caucasians population: rs2736100, rs402710, rs16969968 and rs8034191. We also validated that rs16969968 and rs8034191 in 15q25 region are significantly interacting with smoking in Caucasian population. Our approach identified the potential interactions of SNP rs2256543 in 6p21 with smoking on contributing to lung cancer risk. Genetic imprinting is the most well-known cause for parent-of-origin effect (POE) whereby a gene is differentially expressed depending on the parental origin of the same alleles. Genetic imprinting affects several human disorders, including diabetes, breast cancer, alcoholism, and obesity. This phenomenon has been shown to be important for normal embryonic development in mammals. Traditional association approaches ignore this important genetic phenomenon. In this study, we propose a NOIA framework for a single locus association study that estimates both main allelic effects and POEs. We develop statistical (Stat-POE) and functional (Func-POE) models, and demonstrate conditions for orthogonality of the Stat-POE model. We conducted simulations for both quantitative and qualitative traits to evaluate the performance of the statistical and functional models with different levels of POEs. Our results showed that the newly proposed Stat-POE model, which ensures orthogonality of variance components if Hardy-Weinberg Equilibrium (HWE) or equal minor and major allele frequencies is satisfied, had greater power for detecting the main allelic additive effect than a Func-POE model, which codes according to allelic substitutions, for both quantitative and qualitative traits. The power for detecting the POE was the same for the Stat-POE and Func-POE models under HWE for quantitative traits.

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Global and local climatic forcing, e.g. concentration of atmospheric CO2 or insolation, influence the distribution of C3 and C4 plants in southwest Africa. C4 plants dominate in more arid and warmer areas and are favoured by lower pCO2 levels. Several studies have assessed past and present continental vegetation by the analysis of terrestrial n-alkanes in near-coastal deep sea sediments using single samples or a small number of samples from a given climatic stage. The objectives of this study were to evaluate vegetation changes in southwest Africa with regard to climatic changes during the Late Pleistocene and the Holocene and to elucidate the potential of single sample simplifications. We analysed two sediment cores at high resolution, altogether ca. 240 samples, from the Southeast Atlantic Ocean (20°S and 12°S) covering the time spans of 18 to 1 ka and 56 to 2 ka, respectively. Our results for 20°S showed marginally decreasing C4 plant domination (of ca. 5%) during deglaciation based on average chain length (ACL27-33 values) and carbon isotopic composition of the C31 and C33 n-alkanes. Values for single samples from 18 ka and the Holocene overlap and, thus, are not significantly representative of the climatic stages they derive from. In contrast, at 12°S the n-alkane parameters show a clear difference of plant type for the Late Pleistocene (C4 plant domination, 66% C4 on average) and the Holocene (C3 plant domination, 40% C4 on average). During deglaciation vegetation change highly correlates with the increase in pCO2 (r² = 0.91). Short-term climatic events such as Heinrich Stadials or Antarctic warming periods are not reflected by vegetation changes in the catchment area. Instead, smaller vegetation fluctuations during the Late Pleistocene occur in accordance with local variations of insolation.

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The quantity, type, and maturity of organic matter of Quaternary and Tertiary sediments from the Philippine Sea (DSDP Leg 58; Sites 442-446) were determined. Hydrocarbons in lipid extracts were analyzed by capillary-column gas chromatography. Kerogen concentrates were investigated by microscopy for vitrinite reflectance values and maceral composition. In the Shikoku Basin sediments (Sites 442, 443, and 444), organic carbon values range between 0.03 and 0.44 per cent. The higher values in the younger sediments are interpreted as an indication of increasing deposition of eroded organic particles during the past 4 m.y. Microscopic analyses revealed a dominance of reworked organic matter. Primary material could not be distinguished readily; thus, no maturation trend could be established. Extract yields were low. TV-alkane distributions mostly show maxima at n-C29 and n-C31 and high odd-over-even predominances, typical of material which originated in terrigenous higher plants. The organic-carbon values of sediments of the Daito Ridge and Basin region (Sites 444 and 445) range from less than 0.01 to 0.05 per cent. TV-alkanes exhibit varying marine and terrigenous influences. Some carbonate-rich samples show a pronounced even-over-odd predominance. At least the older sediments contained less recycled organic matter than the Shikoku Basin samples. The maturity, where measurable, was low. None of the Philippine Sea samples indicates a significant hydrocarbon-generation potential.

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El objetivo principal de la presente tesis es la búsqueda de nuevos registros palinológicos para las formaciones del Grupo Salta, especialmente para aquellas que cuentan con poco o ningún registro de palinomorfos, tales como las Formaciones La Yesera, Las Curtiembres, Yacoraite y Olmedo. Los resultados palinológicos permitieron evaluar algunos aspectos geológicos como las relaciones estratigráficas, edad y ambientes de depósito. El muestreo se centró principalmente en el período comprendido entre el Neocomiano y Daniano, correspondiente a los subgrupos con mayor escasez de datos (Pirgua y Balbuena). 157 muestras palinológicas de la Cuenca del Grupo Salta y áreas relacionadas se trataron en laboratorio, 31 resultaron fértiles. Se brindan los primeros registros palinológicos de la Formación La Yesera (localidad valle de Pucará) que consisten en 35 especies. Las inferencias aleoambientales obtenidas a partir de la palinoflora apoyan las conclusiones que provienen de los datos sedimentológicos: presencia de un lago perenne al momento de la depositación del Miembro Brealito y sequías estacionales cuando se acumuló el Miembro Don Bartolo. La palinoflora indica un clima subtropical con presencia de cierta aridez. A partir de los rangos estratigráficos de algunas especies y de las dataciones radimétricas del Basalto de Isonza, se estima una edad entre el Albiano y el Cenomaniano. Para la Formación Las Curtiembres (Miembro Morales) se describen 19 especies provenientes de la quebrada de Palo Seco, que constituyen la primer asociación palinológica registrada. El predominio de Ephedraceae y Cheirolepidiaceae, junto a la escasa representación de pteridofitas, sugieren condiciones ambientales de aridez a semiaridez, en coincidencia con la sedimentología que indica que la sección superior del Miembro Morales es transicional con las capas rojas de la parte superior de la Formación Las Curtiembres. La asociación palinológica contiene representantes de amplia distribución espacial y temporal. Es relevante la presencia de Peninsulapollis gillii que indica una edad no mayor al Campaniano para la asociación estudiada. Sólo una muestra de la Formación Yacoraite en la localidad de Tres Cruces fue productiva en cuanto al contenido de palinomorfos. La asociación consta solamente de los géneros Leiosphaeridia y Pediastrum que se asocian a condiciones de agua dulce o mixtas. Para la Formación Olmedo se registran 34 especies de palinomorfos y 39 especies para la Formación Tunal (localidades de Garabatal y El Chorro respectivamente). Ambas formaciones comparten un 49 % de taxa. El marcado predominio de algas clorococales indica condiciones lacustres y un ambiente palustre se infiere por la presencia de Pandaniidites texus y Mtchedlishvilia saltenia. El elevado porcentaje de Verrustephanoporites simplex indica que la selva de ulmáceas, era la unidad fitogeográfica más ampliamente distribuida, comparable con la actual Selva de Transición de la Provincia de Yungas. La coincidencia de facies y contenido palinológico indicarían similares condiciones ambientales para las Formaciones Olmedo y Tunal. Mtchedlishvilia saltenia permiten circunscribir las Formaciones al Daniano. Los cambios climáticos acontecidos durante el desarrollo de la Cuenca del Grupo Salta quedaron evidenciados en la palinoflora. Durante el Cretácico Tardío, habrían prevalecido condiciones de aridez y a partir del Maastrichtiano, el clima se torna más húmedo. Las asociaciones del Daniano se caracterizan por una palinoflora de clima subtropical húmedo. Entre el Paleoceno Superior y hasta el Eoceno Inferior, continúa el registro de la flora de clima subtropical pero con una leve disminución en la humedad. Las especies Peninsulapollis gillii, Rhoipites sp. A, Rousea patagonica, Spinitricolpites jennerclarkei, Verrustephanoporites simplex y Azolla sp., pasan el límite Cretácio-Paleógeno registrándose en sedimentos pre- y post-danianos. Se requieren mayores estudios de detalle en aquellos niveles donde está contenido el límite para esclarecer los posibles cambios vegetacionales que hayan ocurrido.

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Hydrology, source region, and timing of precipitation are important controls on the climate of the Great Plains of North America and the composition of terrestrial ecosystems. Moisture delivered to the Great Plains varies seasonally and predominately derives from the Gulf of Mexico/Atlantic Ocean with minor contributions from the Pacific Ocean and Arctic region. For this work, we evaluate long-term relationships for the past ~ 35 million years between North American hydrology, climate, and floral change, using isotopic records and average carbon chain lengths of higher plant n-alkanes from Gulf of Mexico sediments (DSDP Site 94). We find that carbon isotope values (d13C) of n-alkanes, corrected for variations in the d13C value of atmospheric CO2, provide minor evidence for contributions of C4 plants prior to the Middle Miocene. A sharp spike in C4 input is identified during the Middle Miocene Climatic Optimum, and the influence of C4 plants steadily increased during the Late Miocene into the Pleistocene - consistent with other North American records. Chain-length distributions of n-alkanes, indicative of the composition of higher plant communities, remained remarkably constant from 33 to 4 Ma. However, a trend toward longer chain lengths occurred during the past 4 million years, concurrent with an increase in d13C values, indicating increased C4 plant influence and potentially aridity. The hydrogen isotope values (dD) of n-alkanes are relatively invariant between 33 and 9 Ma, and then become substantially more negative (75 per mil) from 9 to 2 Ma. Changes in the plant community and temperature of precipitation can solely account for the observed variations in dD from 33 to 5 Ma, but cannot account for Plio-Pleistocene dD variations and imply substantial changes in the source region of precipitation and seasonality of moisture delivery. We posit that hydrological changes were linked to tectonic and oceanographic processes including the shoaling and closure of the Panamanian Seaway, amplification of North Atlantic Deep Water Production and an associated increase of meridional winds. The southerly movement of the Intertropical Convergence Zone near 4 Ma allowed for the development of a near-modern pressure/storm track system, driving increased aridity and changes in seasonality within the North American interior.

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This study characterises the shape of the flow separation zone (FSZ) and wake region over large asymmetric bedforms under tidal flow conditions. High resolution bathymetry, flow velocity and turbulence data were measured along two parallel transects in a tidal channel covered with bedforms. The field data are used to verify the applicability of a numerical model for a systematic study using the Delft3D modelling system and test the model sensitivity to roughness length. Three experiments are then conducted to investigate how the FSZ size and wake extent vary depending on tidally-varying flow conditions, water levels and bathymetry. During the ebb, a large FSZ occurs over the steep lee side of each bedform. During the flood, no flow separation develops over the bedforms having a flat crest; however, a small FSZ is observed over the steepest part of the crest of some bedforms, where the slope is locally up to 15°. Over a given bedform morphology and constant water levels, no FSZ occurs for velocity magnitudes smaller than 0.1 m s**-1; as the flow accelerates, the FSZ reaches a stable size for velocity magnitudes greater than 0.4 m s**-1. The shape of the FSZ is not influenced by changes in water levels. On the other hand, variations in bed morphology, as recorded from the high-resolution bathymetry collected during the tidal cycle, influence the size and position of the FSZ: a FSZ develops only when the maximum lee side slope over a horizontal distance of 5 m is greater than 10°. The height and length of the wake region are related to the length of the FSZ. The total roughness along the transect lines is an order of magnitude larger during the ebb than during the flood due to flow direction in relation to bedform asymmetry: during the ebb, roughness is created by the large bedforms because a FSZ and wake develops over the steep lee side. The results add to the understanding of hydrodynamics of natural bedforms in a tidal environment and may be used to better parameterise small-scale processes in large-scale studies.

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Results of simultaneous determinations of chlorophyll "a" concentrations and primary production in the northeastern part of the Tropical Atlantic in spring 1977 are discussed. Primary production was low (250-350 mg C/m**2/day in the open parts of the ocean and high (600-1500 mg C/m**2/day) mainly in zones of current divergences and coastal region of the West Africa. Chlorophyll "a" concentration throughout the euphotic zone varied from 6 to 36 mg/m**3 and in the surface layer from 0.05 to 0.60 mg/m**3. Uneven distribution of primary production is due to physiological condition of phytoplankton.

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Fluid inclusions of protogenous halite, which were collected from two boreholes in the Charhan Salt Lake in the north part of the Qinghai-Xizang Plateau, werea nalyzed for their hydrogen and oxygen isotopes and for their Na, Mg etc. ions.On these grounds, the evolution of lake environment in this region during the last 50 000 years are discussed in this paper. The emphasis is to discuss the time range of extremely arid and cold climate at the last Glacial stage and the geological event of playa associated with such a climate.The guanidine hydrochloride method was used for measurement of hydrogen and oxygen stable isotopes. The measurement of Na, Mg etc. ions were achieved by determination of crystallization temperature of hydrohalite under microscope and then by calculation of chemical compositions of inclusion fluid using a thermodynamic model.The results obtained show that protogenous halite in the Charhan Lake area was formed in three different environment conditions: (1) In fluid inclusions of halite formed in the early period (50 000-30 000 a B. P. ), dD averages -14.9 per mil, d(18)O averages 8.37 per mil, and Mg(2+)ranges from 0.42 to 1.59 mol/L. Their plotting points fall on the right top part of the evaporation line of the present Charhan Lake area, indicating that the Lake water at that time had a higher concentration of brine, and the climate was hot and dry. (2) In fluid inclusions of halite formed in the middle period (30 000-15 000 a B. P.), SD average -66.0 per mil, d(18)O averages 1.00 pr mil, and Mg(2+) 1 mol/L. Their plotting points fall on the left low part of the evaporation line, indicating that the lake water at that time had a concentration of brine lower than that in the early period, and the environment was cold and dry. (3) In fluid inclusions of halite formed in the late period (15 000-present), dD averages 30.8 per mil, d(18)O averages 5.85 per mil, and Mg(2+) M 1 mol/L. Their plotting fall on the evaporation line, indicating that the climate environment at that time was warm and dry, almost the same as the present.The temperature variation of the last 50 000 years in the Charhan Lake area was calculated using the conversion equation proposed by Lorious et al. The time range of the Great ice age of the Last Glacial Stage is about 21 000-15 000 a B.P., which basically coincides with the time of a worldwide low sea level. The temperature in that period was below 0°C and 6-7°C lower than now. Because of lower temperatures, water supply to the lake area decreased rapidly and the concentration of lake water increased sharply. Therefore the Mg(2+) concentration in inclusion fluid reaches or closes to 2mol/L and the Mg/Na ratio varies within a very wide range. These show that the Charhan Lake at that time entered its playa stage. The Charhan Salt Lake is a typical one in the north part of the Qinghai-Xizang Plateau. It can be supposed that the extremely arid and cold climate of the Great Ice Age made most lakes in the north part of the Qinghai-Xizang Plateau enter their playa stage. This event is of importance for formation of salt resources.