Grain-size Characteristics of Sediments Formed Since 8600 yr B.P. in Middle Reaches of Yarlung Zangbo River in Tibet and Their Paleoenvironmental Significance

Widespread aeolian sediments have been found in the middle reaches of the Yarlung Zangbo River, China, The grain-size characteristics of sediments from Cha＇er Section in the area were analyzed. The results show that the section include one stratum of paleo-mobile dunes, four strata of paleo-semi-fixed dunes, two strata of paleo-fixed dunes, one stratum of sandy immature soils. The paleo-mobile and paleo-semi-fixed dune sand in this section are similar to modem aeolian sand in either grain-size composition or Mz and c distribution. Compared the above types of dunes each other, the content of sand substance decreases, while the content of silt and clay increases for paleo-fixed dunes and sandy immature soils. Combined with age data for each stratum, the analysis shows that these strata are the products of climate changes and the evolution of aeolian landforms. The evolutionary sequence of the paleoclimate and of aeolian activities in the valley since 8600 yr B.P. reveals four stages： 8600-5700 yr B.P., when the paleoclimate was cold and dry, with strong winds, thereby activating dunes; 5700-3600 yr B.P., when it was warm and wet, with weak winds, causing dunes to undergo soil-forming processes; 3600-1900 yr B.P., when climate shifted from cold-dry with strong winds to warm-wet with weak winds, and activated dunes were fixed again; and 1900 yr B.P. -present, when the climate became fine, with weak winds, fixing dunes again.

The characteristics of grain size from the Kumtag Desert and its environmental significance

The Kumtag Desert is located in the arid northwestern portion of China,and is considered China’s sixth-largest desert.Grain-size analysis of the sand plays a very important role in differentiating sedimentary environments,determining the ways that sediments are transported,estimating hydrodynamic conditions,and analyzing grain-size trends.The analysis of the grain size of 20 sand samples that were taken from mid-northern,north margin,western,middle,southern,and southeast margins of the Kumtag Desert shows that grain sizes are vastly different.The grain-size parameters fall in the following range:the median diameter Mz = 1.55Φ-2.92Φ,the standard deviation σI= 0.41-1.11,the skewness SKI = ?0.11-0.31,kurtosis KG = 0.77-1.23.The frequency curves of grain size have characteristics with single peaks and multi-peaks,and most of the sand samples’ skewness appears close to asymmetric.The analytical results reveal that the sediments of the Kumtag Desert are complex and diverse,which affected by such forces as wind deposition,lacustrine sediment,and alluvial and proluvial river deposits.

Size Effect of Electromagnetic Constitutive Characteristics of Ultrathin Al Films

The ultrathin aluminum films with thickness in the range of 2～60 nm have been deposited by dc magnetron sputtering apparatus. Reflectance and transmittance of the obtained samples were measured with a WFZ-900-D4 UV/VIS spectrophotometer. The optical constant (n, k) and permittivity (ε', ε') were determined by applying Newton-Simpson recurrent substitution method. The results indicate that the electromagnetic constitutive characteristic of ultrathin aluminum films is a function of thickness and has obvious size effect.

Tumor size as a prognostic factor in patients with advanced gastric cancer in the lower third of the stomach

AIM: To explore the impact of tumor size on outcomes in patients with advanced gastric cancer in the lower third of the stomach. METHODS: We retrospectively analyzed the clinical records of 430 patients with advanced gastric cancer in the lower third of the stomach who underwent distal subtotal gastrectomy and D2 lymphadenectomy in our hospital from January 1998 to June 2004. Receiver-operating characteristic (ROC) curve analysis was used to determine the appropriate cutoff value for tumor size, which was measured as maximum tumor diameter. Based on this cutoff value, patients were divided into two groups: those with large-sized tumors (LSTs) and those with small-sized tumors (SSTs). The correlations between other clinicopathologic factors and tumor size were investigated, and the 5-year overall survival (OS) rate was compared between the two groups. Potential prognostic factors were evaluated by univariate KaplanMeier survival analysis and multivariate Cox's propor-tional hazard model analysis. The 5-year OS rates in the two groups were compared according to pT stage and pN stage. RESULTS: The 5-year OS rate in the 430 patients with advanced gastric cancer in the lower third of the stomach was 53.7%. The mean ± SD tumor size was 4.9 ± 1.9 cm, and the median tumor size was 5.0 cm. ROC analysis indicated that the sensitivity and specificity results for the appropriate tumor size cutoff value of 4.8 cm were 80.0% and 68.2%, respectively (AUC=0.795, 95%CI: 0.751-0.839, P=0.000). Using this cutoff value, 222 patients (51.6%) had LSTs (tumor size ≥ 4.8 cm) and 208 (48.4%) had SSTs (tumor size<4.8 cm). Tumor size was significantly correlated with histological type (P=0.039), Borrmann type (P=0.000), depth of tumor invasion (P=0.000), lymph node metastasis (P=0.000), tumor-nodes metastasis stage (P=0.000), mean number of metastatic lymph nodes (P=0.000) and metastatic lymph node ratio (P=0.000). Patients with LSTs had a significantly lower 5-year OS rate than those with SSTs (37.1% vs 63.3%, P=0.000). Univariate analysis showed that depth of tumor invasion (c 2=69.581, P=0.000), lymph node metastasis (c 2=138.815, P=0.000), tumor size (c 2=78.184, P=0.000) and metastatic lymph node ratio (c 2=139.034, P=0.000) were significantly associated with 5-year OS rate. Multivariate analysis revealed that depth of tumor invasion (P=0.000), lymph node metastasis (P=0.019) and tumor size (P=0.000) were independent prognostic factors. Gastric cancers were divided into 12 subgroups: pT2N0; pT2N1; pT2N2; pT2N3; pT3N0; pT3N1; pT3N2; pT3N3; pT4aN0; pT4aN1; pT4aN2; and pT4aN3. In patients with pT2-3N3 stage tumors and patients with pT4a stage tumors, 5-year OS rates were significantly lower for LSTs than for SSTs (P<0.05 each), but there were no significant differences in the 5-year OS rates in LST and SST patients with pT23N0-2 stage tumors (P > 0.05). CONCLUSION: Using a tumor size cutoff value of 4.8cm, tumor size is a prognostic factor in patients with pN3 stage or pT4a stage advanced gastric cancer located in the lower third of the stomach.

Morphodynamic response of an embayed beach to different typhoon events with varying intensities

Beach erosion has occurred globally in recent decades due to frequent and severe storms.Dongsha beach,located in Zhujiajian Island,Zhejiang Province,China,is a typical embayed sandy beach.This study focused on the morphodynamic response of Dongsha beach to typhoon events,based on beach topographies and surficial sediment characteristics acquired before and after four typhoon events with varying intensities.The four typhoons had different effects on the topography and sediment characteristics of Dongsha beach.Typhoons Ampil and Danas caused the largest(-51.72 m3/m)and the smallest erosion(-8.01 m3/m),respectively.Remarkable alongshore patterns of beach profile volumetric changes were found after the four typhoon events,with more erosion in the southern and central parts of the beach and few changes in the northern part.Grain size coarsening and poor sorting were the main sediment patterns on the beach influenced by different typhoons.Typhoons that occurred in the same year after another typhoon enhanced the effect of the previous typhoon on sediment coarsening and sorting variability,but this cumulative effect was not found between typhoons that occurred during different years.A comparison of the collected data revealed that the topographic state of the beach before the typhoon,typhoon characteristics,and tidal conditions were possible reasons for the difference in the responses of Dongsha beach to typhoon events.More severe beach erosion was caused by typhoons with higher intensity levels and longer durations,and high tide levels during typhoons can determine the upper limit of the beach profile erosion site.Taken together,these results can be used to improve beach management for storm prevention.

Particle size distribution and characteristics of heavy metals in road-deposited sediments from Beijing Olympic Park

Due to rapid urbanization and industrialization, heavy metals in road-deposited sediments（RDSs） of parks are emitted into the terrestrial, atmospheric, and water environment, and have a severe impact on residents＇ and tourists＇ health. To identify the distribution and characteristic of heavy metals in RDS and to assess the road environmental quality in Chinese parks, samples were collected from Beijing Olympic Park in the present study. The results indicated that particles with small grain size（〈150 μm） were the dominant fraction. The length of dry period was one of the main factors affecting the particle size distribution, as indicated by the variation of size fraction with the increase of dry days. The amount of heavy metal（i.e., Cu, Zn, Pb and Cd） content was the largest in particles with small size（〈150 μm） among all samples. Specifically, the percentage of Cu, Zn, Pb and Cd in these particles was 74.7%, 55.5%, 56.6% and 71.3%, respectively.Heavy metals adsorbed in sediments may mainly be contributed by road traffic emissions. The contamination levels of Pb and Cd were higher than Cu and Zn on the basis of the mean heavy metal contents. Specifically, the geoaccumulation index（I geo） decreased in the order：Cd〉Pb〉Cu〉Zn. This study analyzed the mobility of heavy metals in sediments using partial sequential extraction with the Tessier procedure. The results revealed that the apparent mobility and potential metal bioavailability of heavy metals in the sediments, based on the exchangeable and carbonate fractions, decreased in the order： Cd〉Zn≈Pb〉Cu.

Effects of an oasis protective system on aeolian sediment deposition:a case study from Gelintan oasis,southeastern edge of the Tengger Desert,China

Desert-oasis ecotones are boundary areas between oases and desert ecosystems.Large efforts to control sediment and stabilize these boundaries depend on understanding sedimentary processes,especially aeolian transport and deposition.Previous studies on aeolian sediment deposition have focused primarily on a single land surface type or a single engineering approach.Few studies have considered deposition in a multi-layer oasis protective system.A complete oasis protective system consists of an outer bare sand area,a sand barrier zone,a shrub and herbaceous plant zone,and a farmland shelter zone.This study used sedimentary analysis to quantify grain-size characteristics in samples from the four land surfaces under different types of weather conditions in the Gelintan oasis of the Tengger Desert,the fourth largest desert in China.The results showed that aeolian sediment deposition decreased from the outer bare sand area through the oasis protective system and into the interior.The four land surface types showed significant differences in deposition volume(P<0.05).Deposited sediment showed gradual decrease in dominant grain-size from sand to silt,but sediment deposited during dust weather contained a larger coarse-grained fraction.From the outer desert to the inner oasis,transport mechanisms shifted from saltation(sand)to suspension(silt and smaller)in non-dust weather.During dust weather,deposition primarily occurs from near-surface aeolian sand transport with saltation.Sediment sorting decreased from exterior to interior zones of the protective system while skewness and kurtosis showed no significant change(P<0.05).These results can help inform strategies for stabilizing and protecting desert-oasis ecotones in this region and other localities.

Preliminary evidence for 17 coastal terraces on Fildes Peninsula, King George Island, Antarctica

This study confirms the presence of 17 coastal terraces on Fildes Peninsula, Antarctica based on field observations and grain size analysis. The terraces formed by isostatic uplift during climate warming and glacier melting, and each level corresponds to a relatively stable period of climate. The grain size characteristics indicate an overlapping sedimentary origin for the sediments on the coastal terraces. The consistency of regional sea level rise, climate change, and glacial area suggest the presence of similar coastal terraces on King George Island since 18.0 ka.

Quantifying the characteristics of particulate matters captured by urban plants using an automatic approach

It is widely accepted that urban plant leaves can capture airborne particles. Previous studies on the particle capture capacity of plant leaves have mostly focused on particle mass and/or size distribution. Fewer studies, however, have examined the particle density, and the size and shape characteristics of particles, which may have important implications for evaluating the particle capture efficiency of plants, and identifying the particle sources. In addition, the role of different vegetation types is as yet unclear. Here, we chose three species of different vegetation types, and firstly applied an object-based classification approach to automatically identify the particles from scanning electron microscope（SEM）micrographs. We then quantified the particle capture efficiency, and the major sources of particles were identified. We found（1） Rosa xanthina Lindl（shrub species） had greater retention efficiency than Broussonetia papyrifera（broadleaf species） and Pinus bungeana Zucc.（coniferous species）, in terms of particle number and particle area cover.（2） 97.9% of the identified particles had diameter ≤10 μm, and 67.1% of them had diameter ≤2.5 μm. 89.8% of the particles had smooth boundaries, with 23.4% of them being nearly spherical.（3） 32.4%–74.1% of the particles were generated from bare soil and construction activities, and 15.5%–23.0% were mainly from vehicle exhaust and cooking fumes.

STRESS-STRAIN STATE OF ELASTOPLASTIC BODIES WITH CRACK

A physical cut model is used to describe the changes in the stress-strain state （SSS） in elastoplastic bodies weakened by cracks. The distance between the crack edges is considered to be finite in contrast to the mathematical cut. The interactive layer with a thickness limited by the possibility of using the hypothesis of continuity is distinguished on the physical cut extension, Distribution of stresses and strains over the layer thickness is constant and does not depend on the geometry of the boundary between the cut and the interactive layer. The relationship between stresses and strains is determined by the deformation plasticity theory. The problem of plane strain or plane stress state of an arbitrary finite body weakened by a physical cut is reduced to solving a system of two variational equations for displacement fields in the body parts adjacent to the interactive layer. The proposed approach eliminates the singularity in stress distribution in contrast to the mathematical cut model. Use of local strength criteria allows us to determine the time, point and direction of the fracture initiation. Possibilities of the proposed model are illustrated by solving the problems of determining the SSS of a rectangular body weakened by a physical cut under symmetric and antisymmetric loadings.