Diatom evidence for autochthonous artifact deposition in the Valsequillo region, Puebla, Mexico during the Sangamonian (sensu lato = 80,000 to ca. 220,000 yr BP and Illinoian (220,000 to 430,000 yr BP))

Fossil diatoms in the Valsequillo area are important in supplying adequate paleoecological evidence for the in situ deposition (in the absence of strong water currents necessary for the displacement and redeposition) of artifacts as large as those at the Hueyatlaco Archaeological Site. The paleoecology of lacustrine diatom-bearing samples from four nearby localities in the Valsequillo region all correlated with numerous diatomaceous samples from the Hueyatlaco Site (Puebla, Mexico) and indicate an autochthonous deposition of the artifacts at that site. This correlative evidence is consistent with a deposition in Sangamonian to Illinoian time and is based on the relationships of percentages of taxa in categories of the current, pH, and halobian spectra in six lines of correlation of samples between the Hueyatlaco Site and the four localities.     

Simulation of marine boundary layer characteristics using a 1-D PBL model over the Bay of Bengal during BOBMEX-99

The characteristic features of the marine boundary layer (MBL) over the Bay of Bengal during the southwest monsoon and the factors influencing it are investigated. The Bay of Bengal and Monsoon Experiment (BOBMEX) carried out during July–August 1999 is the first observational experiment under the Indian Climate Research Programme (ICRP). A very high-resolution data in the vertical was obtained during this experiment, which was used to study the MBL characteristics off the east coast of India in the north and south Bay of Bengal. Spells of active and suppressed convection over the Bay were observed, of which, three representative convective episodes were considered for the study. For this purpose a one-dimensional multi-level PBL model with a TKE-ε closure scheme was used. The soundings, viz., the vertical profiles of temperature, humidity, zonal and meridional component of wind, obtained onboard ORV Sagar Kanya and from coastal stations along the east coast are used for the study. The temporal evolution of turbulent kinetic energy, marine boundary layer height (MBLH), sensible and latent heat fluxes and drag coefficient of momentum are simulated for different epochs of monsoon and monsoon depressions during BOBMEX-99.The model also generates the vertical profiles of potential temperature, specific humidity, zonal and meridional wind. These simulated values compared reasonably well with the observations available from BOBMEX.     

Alteration of hydrological processes and streamflow with juniper (Juniperus virginiana) encroachment in a mesic grassland catchment

To understand the effect of woody plant encroachment on hydrological processes of mesic grasslands, we quantified infiltration capacity in situ, the temporal changes in soil water storage, and streamflow of a grassland catchment and a catchment heavily encroached by juniper (Juniperus virginiana, eastern redcedar) in previously cultivated, non‐karst substrate grasslands in north‐central Oklahoma for 3 years. The initial and steady‐state infiltration rates under the juniper canopy were nearly triple to that of the grassland catchment and were intermediate in the intercanopy spaces within the encroached catchment. Soil water content and soil water storage on the encroached catchment were generally lower than on the grassland catchment, especially when preceding the seasons of peak rainfall in spring and fall. Frequency and magnitude of streamflow events were reduced in the encroached catchment. Annual runoff coefficients for the encroached catchment averaged 2.1%, in contrast to 10.6% for the grassland catchment. Annual streamflow duration ranged from 80 to 250 h for the encroached catchment compared with 600 to 800 h for the grassland catchment. Our results showed that the encroachment of juniper into previously cultivated mesic grasslands fundamentally alters catchment hydrological function. Rapid transformation of mesic grassland to a woodland state with juniper encroachment, if not confined, has the potential to drastically reduce soil water, streamflow and flow duration of ephemeral streams in the Southern Great Plains. Copyright © 2013 John Wiley & Sons, Ltd.     

Long‐term effects of revegetation on soil hydrological processes in vegetation‐stabilized desert ecosystems

Planting of sand‐binding vegetation in the Shapotou region on the southeastern edge of the Tengger Desert began in 1956. The revegetation programme successfully stabilized formerly mobile dunes in northern China, permitting the operation of the Baotou‐Lanzhou railway. Long‐term monitoring has shown that the revegetation programme produced various ecological changes, including the formation of biological soil crusts (BSCs). To gain insight into the role of BSCs in both past ecological change and current ecological evolution at the revegetation sites, we used field measurements and HYDRUS‐1D model simulations to investigate the effects of BSCs on soil hydrological processes at revegetated sites planted in 1956 and 1964 and at an unplanted mobile dune site. The results demonstrate that the formation of BSCs has altered patterns of soil water storage, increasing the moisture content near the surface (0–5 cm) while decreasing the moisture content in deeper layers (5–120 cm). Soil evaporation at BSC sites is elevated relative to unplanted sites during periods when canopy coverage is low. Rainfall infiltration was not affected by BSCs during the very dry period that was studied (30 April to 30 September 2005); during periods with higher rainfall intensity, differences in infiltration may be expected due to runoff at BSC sites. The simulated changes in soil moisture storage and hydrological processes are consistent with ongoing plant community succession at the revegetated sites, from deep‐rooted shrubs to more shallow‐rooted herbaceous species. Copyright © 2009 John Wiley & Sons, Ltd.     

Seasonal variation of the stable isotopic compositions of coastal marine plankton from Woods Hole,Massachusetts and Georges Bank

A study of the isotopic composition of plankton from Woods Hole Harbor was conducted to investigate seasonal variation in carbon and nitrogen stable isotopes in a shallow coastal environment. Stable isotopic ratios of carbon and nitrogen both showed temporal variation on the scale of weeks to months, with heaviest (most positive) values in summer to fall for both isotopes. Particulate organic matter (POM) δ¹³C values were highest (?19‰ to ?21‰) in August to November and lower (?21‰ to ?25‰) at other times of the year, while δ¹³N-POM values were highest (9.5‰ to 12‰) in March to September and lower (7.5‰ to 9.5‰) at other times of the year. Stable isotopic values were significantly correlated with temperature, DI¹³C, and C∶N ratios, but not with [DIC], [POC], [PN], [chlorophyll], or the taxonomic composition of the phytoplankton. There was no direct evidence of allochthonous inputs of carbon and nitrogen to the system. Woods Hole δ¹³C values were virtually identical to Georges Bank plankton values; similar POC: Chlorophyll and C∶N ratios in the two systems further suggest that Woods Hole Harbor is principally a marine system. The high δ¹³C values of net plankton (>20 μm) during summer and early fall are consistent with a smaller degree of photosynthetic isotopic fractionation at that time, related to temperature and/or [CO_2(aq)]. This pattern was not seen, however, in total POM. Plankton δ¹³N values were higher in Woods Hole Harbor than on Georges Bank, especially during warmer periods, possibly due to high rates of nitrification and organic matter recycling in Woods Hole waters. Relatively wide ranges of stable isotopic values from both Woods Hole Harbor and Georges Bank suggest that seasonality should be considered when attempting to establish endmember C and N isotopic values for temperate marine plankton. Preliminary results from size-fractionated samples suggest that cyanobacteria may fractionate carbon isotopes to a greater degree than net phytoplankton.     

用超速CT机检测99例无症状香港中国人降低钙指数

回顾分析Ｍａｔｉｌｄａ医院超速ＣＴ室筛选首批病人中９９例中国人资料，很明显从通常采用１３０－１００Ｈｏｕｎｓｆｉｅｌｄ单位作为检出冠状血管钙化的基数应用至中国人身上其阈值数目需要降低，同时，我们也发现如果病人年龄按每１０年范围分组（２１－３０，３０－４０，４１－５０，５１－６０）而计算其超速ＣＴ的钙化指数会较随机男女一起按平均计算更易区分其差异．进一步分析显示，男性中年时候超速ＣＴ指数已达最高值，而女性则晚１０年方达最高值，因此，为了更易探测冠脉循环内钙化倾向应作出超速ＣＴ检出钙化的指数数目．这些实践经验对动脉粥样硬化过程的预测或预防有实际意义．