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Molecular and stable sulfur isotopic (δ 34 S) analysis of petroleum recently discovered in the Bachu uplift of the Tarim Basin (China) was conducted to characterize the oil and assist future regional petroleum correlation studies. Sulfur-rich condensate from the Lower Ordovician – Upper Cambrian reservoir rock in the LS2 well showed abundant aromatic hydrocarbons and organic sulfur compounds. Extensive distributions of alkylated caged hydrocarbons (i.e., diamondoids) and caged sulfur compounds (thiadiamondoids), including many additional isomers not previously detected in petroleum, were resolved by GC × GC–MS analysis. The thiadiamondoid products and thioaromatics (i.e., benzothiophenes, dibenzothiophenes), also detected in LS2, products were attributed to a major thermochemical sulfate reduction (TSR) event, which resulted in elevated H 2 S (3.66%) and dry gas in the condensate. TSR might also have contributed to the generally heavier δ 34 S values of the benzothiophenes (+26 to +28‰) compared to dibenzothiophenes (+20 to +27‰). The LS2 reservoir has no sulfate evaporites and the temperature (144 °C) is relatively low for TSR, implying that it is a secondary reservoir for migrated TSR-derived gas, possibly derived from deeper and hotter (>200 °C) Cambrian strata.

The Kuqa fold–thrust belt (KFTB) has a complex thrust-system geometry and comprises basement-involved thrusts, decollement thrusts, triangle zones, strike-slip faults, transpressional faults, and pop-up structures. These structures, combined with the effects of Paleogene salt tectonics and Paleozoic basement uplift form a complex structural zone trending E–W. Interpretation and comprehensive analysis of recent high-quality seismic data, field observations, boreholes, and gravity data covering the KFTB has been performed to understand the characteristics and mechanisms of the deformation styles along strike. Regional sections, fold–thrust system maps of the surface and the sub-salt layer, salt and basement structure distribution maps have been created, and a comprehensive analysis of thrust systems performed. The results indicate that the thrust-fold system in Paleogene salt range can be divided into five segments from east to west: the Kela-3, Keshen, Dabei, Bozi, and Awate segments. In the easternmost and westernmost parts of the Paleogene salt range, strike-slip faulting and basement-involved thrusting are the dominant deformation styles, as basement uplift and the limits of the Cenozoic evaporite deposit are the main controls on deformation. Salt-core detachment fold–thrust systems coincide with areas of salt tectonics, and pop-up, imbricate, and duplex structures are associated with the main thrust faults in the sub-salt layer. Distribution maps of thrust systems, basement structures, and salt tectonics show that Paleozoic basement uplift controlled the Paleozoic foreland basin morphology and the distribution of Cenozoic salt in the KFTB, and thus had a strong influence on the segmented structural deformation and evolution of the fold–thrust belt. Three types of transfer zone are identified, based on the characteristics of the salt layer and basement uplift, and the effects of these zones on the fault systems are evaluated. Basement uplift and the boundary of the salt deposit generated strike-slip faults in the sub-salt layer and supra-salt layers at the basin boundary (Model A). When changes in the basement occurred within the salt basin, strike-slip faults controlled the deformation styles in the sub-salt layer and shear-zone dominated in the supra-salt layer (Model B). A homogeneous basement and discontinues salt layer formed different accommodation zones in the sub- and supra-salt layers (Model C). In the sub-salt layer the thrusts form imbricate structures on the basal decollement, whereas the supra-salt layer shows overlapping, discontinuous faults and folds with kinds of salt tectonics, and has greater structural variation than the sub-salt layer.

Based on the outcrop survey, 3D seismic data interpretation, drilling data analysis, the structural patterns and distribution of fault damage zones in carbonate strata of Tazhong Paleo-uplift were established to reveal the oil and gas enrichment law in the fault damage zones. The following findings were reached: (1) Through the filed survey, the fault damage zone system consists of fault core, damage zone with branch fault and fracture network. Affected by the active nature of the major faults, the fault damage zones differ in planar pattern and scale along the major faults. (2) 3D seismic profiles reveal that there are three types of fault damage zones in carbonate strata in Tazhong paleo-uplift, strike-slip fault damage zones, thrust fault damage zones and superimposed fault damage zones. Featuring 3 flowers and 3 root belts in vertical, the strike-slip fault damage zone can be subdivided into linear type, oblique type, feather type and horsetail type in plane. Thrust fault damage zones can be further divided into fault anticline type, anticline type and slope type. As the superimposition result of the above two kinds of fault damage zones, superimposed fault damage zones appear in three patterns, intersect type, encompassment type and penetrating type. (3) Cores from wells and geochemical data show oil and gas may migrate along the major fault and laterally. The feather type in strike-slip fault system, fault anticline type in thrust fault damage zone and intersect type in superimposed fault damage zone are possible sites for high production and efficiency wells. Key words: Tazhong Paleo-uplift, carbonate strata, fault damage zone, structural pattern, high production well area

The Kuqa foreland thrust belt is a recent hot topic of ultra-deep oil–gas exploration in China, and many natural gas fields with high and stable yields, have been found in subsalt clastic reservoirs with a buried depth of 6500–8000 m. In this paper, the well logging, core, and thin slice data are used to analyse the characteristics of the ultra-deep tight sandstone reservoir of the Bashijiqike Formation in the Kuqa foreland thrust belt and to discuss the relationship between tectonic stress and reservoir development. The results show that the sandstone reservoir of the Bashijiqike Formation can be vertically divided into 3 zones; from the top down, the surface porosity and the average pore aperture decrease, the rock density increase, and the permeability change. Such vertical differences are mainly affected by tectonic compression. Significant differences exist between the stress above and below the neutral plane in the same anticline. Above the neutral plane, the presence of local tensile stress and the dominant development of a large number of high-angle tension fractures with large apertures are conducive to dissolution; below the neutral plane, the presence of local compressional and torsional stress and the main development of reticulated shear cracks with small openings indicate the enhanced compaction of the reservoir. The variation of subsalt tectonic stress from the northern oblique to the southern transverse compression processes, development of pre-Mesozoic paleo-uplift, induction of the overlying salt body with low stress and arched extension of the underlying mudstone induced ultra-deep Cretaceous reservoir stress. A stratification model of the faulted anticline reservoir affected by the stress neutral plane is constructed and is significant for predicting a favourable reservoir in a compression basin.

Objective. Here, we aim to investigate the microRNA (miR) profiling in human gastric cancer (GC). Methods. Tumoral and matched peritumoral gastric specimens were collected from 12 GC patients who underwent routine surgery. A high-throughput miR sequencing method was applied to detect the aberrantly expressed miRs in a subset of 6 paired samples. The stem-loop quantitative real-time polymerase chain reaction (qRT-PCR) assay was subsequently performed to confirm the sequencing results in the remaining 6 paired samples. The profiling results were also validated in vitro in three human GC cell lines (BGC-823, MGC-803, and GTL-16) and a normal gastric epithelial cell line (GES-1). Results. The miR sequencing approach detected 5 differentially expressed miRs, hsa-miR-132-3p, hsa-miR-155-5p, hsa-miR-19b-3p, hsa-miR-204-5p, and hsa-miR-30a-3p, which were significantly downmodulated between the tumoral and peritumoral GC tissues. Most of the results were further confirmed by qRT-PCR, while no change was observed for hsa-miR-30a-3p. The in vitro finding also agreed with the results of both miR sequencing and qRT-PCR for hsa-miR-204-5p, hsa-miR-155-5p, and hsa-miR-132-3p. Conclusion. Together, our findings may serve to identify new molecular alterations as well as to enrich the miR profiling in human GC.

This study investigated the occurrence of tetracycline antibiotics in soils from different organic vegetable farms in Guangzhou, a subtropical city, South China and evaluated their ecological risk. Four tetracycline compounds (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) were extracted ultrasonically from soil samples (n = 69), with a solid-phase extraction cleanup, and were then measured by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results showed that four compounds were detected in all samples, with the concentrations of the individual compounds ranging from 0.04 to 184.8 μg/kg (dry weight). The concentrations of tetracycline compounds in the soils from different vegetable farms varied greatly, but their patterns of distribution were similar. Doxycycline was the predominant compound with a mean of 21.87 μg/kg, followed by chlortetracycline. The concentrations of doxycycline and chlortetracycline in 7.46 % of the samples were higher than the ecotoxic effect trigger value (100 μg/kg) set by the Steering Committee of Veterinary International Committee on Harmonization. Additionally, the concentrations of tetracyclines in greenhouse soils were significantly lower than those in open-field soils. Risk assessment based on single compound exposure showed that doxycycline could pose medium or high risks. Compared with other studies, the levels of tetracyclines in this study were relatively low. The hypothesis that antibiotic residues in the soil of organic farms fertilized with manure are higher than in the soils of conventional farms was not supported in the area studied due to the high levels of moisture, temperature, and microbial activity.

The Kuqa depression is associated with complex salt structures. Variation in fold geometries and subsalt fault activities were investigated using parallel cross-sections to reveal detailed along-strike variations within the Keshen 5 segment and their controlling factors. Along-strike variations were identified in both suprasalt and subsalt units. Linkages, such as the location of a transfer zone, were apparent, while the distribution of variations above and below the salt layer were decoupled. The results indicate that the pre-existing salt wall is the key factor driving along-strike variations because it acts as a weak zone that influences deformation propagation. Suprasalt structural variation results in different sediment depths, which have a significant impact on subsalt fault activity. In the eastern segment, fault activity decreases from the hinterland to the basin. In contrast, owing to the pre-existing salt wall and deep sedimentation near the hinterland in the western segment, the fault beneath the salt wall is characterized by maximum displacement. This study reveals the connection between suprasalt and subsalt deformation and the role of that a salt diapir plays in along-strike structural evolution variations for the Keshen 5 segment of the Kuqa depression. These findings are relevant for understanding along-strike deformation propagation and structural variation in other fold and thrust systems.

Regional crustal structure instabilities are potentially a significant cause of earthquakes, although current research focuses on other causes such as interactions between tectonic plates and the existence of fluids or faults. The Jiashi area, located at the junction of the Tarim block, the Tianshan orogenic belt, the West Kunlun orogenic belt, and the Pamir syntax, is subject to frequent earthquakes. Wide-angle reflections and refractions and near-vertical seismic reflection profiling data show that the crustal structure of the Jiashi area bears a special instability. The velocity distribution at subsurface depths above ~75 km suggests that the crust is structurally complex and hosts a number of high-and low-velocity blocks. Near-vertical seismic reflection profiles show detailed structural characteristics at a depth of 20 s two-way travel time. Sedimentary cover has well-layered reflections, and there is a stable zone highlighted by Reflectors C and D below the unstable zone of Reflectors A, B and E. A model of the crustal structure instability of the Jiashi area has been established, in which an unstable belt is formed by stacking a combination of high-and low-rigidity blocks that are correspondingly represented by high-and low-velocity blocks. They are hosted in the crust, within the stability belt of Reflectors C and D. The structural instability is aided by regional compression and deep crustal faults that intensify regional seismicity. Crustal structural instabilities also exist in the Japanese archipelago and Erdos Basin.

A continental condensate field, with the deepest burial depth (7084 m) so far in China, was recently discovered from the Cretaceous sandstone reservoir in the Bozi area of the Kuqa Depression, Tarim Basin. In this paper, we report general features of this field, including geochemistry of the condensates, their origin, and migration and accumulation. General geochemistry of the condensate reflects that it is an over pressured condensate reservoir. Analytical results by newly-developed high-resolution GC × GC–TOFMS method indicate that the condensate is rich in n -alkanes from nC 3 to nC 34 and in diamondoid hydrocarbons with a high content of adamantanes. The condensate has a high abundance of aromatic hydrocarbons. The gas δ 13 C 2 values in these are −23.3‰, which is characteristic of coal-derived gases. Compared with the contents of conventional condensate oils, the BZ1 well has a high content of aromatic hydrocarbons, suggesting that the condensate is in a stage of highly mature cracking. Analyses of oil biomarkers, carbon isotopes, gas compositions, etc., revealed that the condensate is dominantly sourced from the highly mature coals of the Jurassic Qiakemake Formation in the western Kuqa Depression. This set of coal source sequences has generated large quantities of condensate since 3 Ma, when the study area was subjected to a rapid subsidence with sediments over 2000 m and consequently attained at the condensate-generating stage. Such condensates then migrated vertically into the Cretaceous traps along faults. Therefore, the Bozi condensate field is a typical case of large-scale oil/gas field characterized by late-stage accumulation. Multiple elements favor the formation of this large-scale condensate field. The timing of trap formation accords with that of the condensate generation (since 3 Ma). The traps and source rocks are stacked vertically. Faults connect the source rock sequences and the reservoirs. The hydrocarbon charge is strong and efficient. Thick Paleogene gypsum beds act as an excellent cap rock, favoring the accumulation and preservation of the condensate.

The Tarim Basin, as the largest inland, oil-producing basin in China, is a large-scale composite basin, which formed from a Palaeozoic craton basin that was overprinted by a Mesozoic–Cenozoic foreland basin. Based on comprehensive analyses of gravitational data, aeromagnetic data and seismic data from the basin, 38 basement faults can be identified, demonstrating that the Tarim Basin has undergone several tectonic cycles. According to their distributional locations in the basin, basement faults can be divided into marginal and internal basin basement faults. Moreover, on the basis of the distribution characteristics in the plane and controlling effects on the basin, the basement faults can be divided into 20 primary basement faults and 18 secondary basement faults. Combined with the interpretations of seismic profiles, we can determine the relationship between the basement faults and sedimentary cover faults. Considering the section balance of seismic profiles, we find that some basement faults are syn-depositional with continuous long-term activity during the basin's evolution and control the deposition in the basin. By counting fault growth indexes of the main sections, it is obvious that different parts of the same fault have different growth indexes but show similar activity within the same geological period. The faults' stress states remain consistent with their geological history, although the growth indexes of different faults are inconsistent.

Late Cenozoic transtensional fault belt was discovered on Shajingzi fault belt, NW boundary of the Awati Sag in the northwestern Tarim Basin. And numerous Quaternary normal faults were discovered on Aqia and Tumuxiuke fault belts, SW boundary of Awati. This discovery reveals Quaternary normal fault activity in the Tarim Basin for the first time. It is also a new discovery in the southern flank of Tianshan Mountains. Shajingzi transtensional fault belt is made up of numerous, small normal faults. Horizontally, the normal faults are arranged in right-step, en echelon patterns along the preexisting Shajingzi basement fault, forming a sinistral transtensional normal fault belt. In profile, they cut through the Paleozoic to the mid-Quaternary and combine to form negative flower structures. The Late Cenozoic normal faults on the SW boundary of Awati Sag were distributed mainly in the uplift side of the preexisting Aqia and Tumuxiuke basement-involved faults, and combined to form small horst and graben structures in profile. Based on the intensive seismic interpretation, careful fault mapping, and growth index analysis, we conclude that the normal fault activity of Shajingzi transtensional fault belt began from Late Pliocene and ceased in Late Pleistocene (mid-Quaternary). And the normal faulting on the SW boundary of Awati Sag began from the very beginning of Quaternary and ceased in Pleistocene. The normal faulting on Awati’s SW boundary began a little later than those on the NW boundary. The origin of Shajingzi transtensional normal fault belt was due to the left-lateral strike-slip occurred in the southern flank of Tianshan, and then, due to the eastward escape of the Awati block, a tensional stress developed the normal faults on its SW boundary.

To understand the mechanism controlling cultivar differences in the accumulation of ciprofloxacin (CIP) in Chinese flowering cabbage (Brassica parachinensis L.), low-molecular-weight organic acids (LMWOAs) secreted from the roots of high- and low-CIP cultivars (Sijiu and Cutai, respectively) and their effects on the bioavailability of CIP in soil were investigated. Significant differences in the content of LMWOAs (especially maleic acid) between the two cultivars played a key role in the variation in CIP accumulation. Based on the Freundlich sorption coefficient (K f ) and distribution coefficient (K d ), the presence of LMWOAs reduced the CIP sorption onto soil particles, and higher concentrations of LMWOAs led to less CIP sorption onto soil. On the other hand, LMWOAs enhanced CIP desorption by lowering the solution pH, which changed the surface charge of soil particles and the degree of CIP ionization. LMWOAs promoted CIP desorption from soil by breaking cation bridges and dissolving metal cations, particularly Cu2+. These results implied that the LMWOAs (mainly maleic acid) secreted from Sijiu inhibited CIP sorption onto soil and improved CIP desorption from soil to a greater extent than those secreted from Cutai, resulting in higher bioavailability of CIP and more uptake and accumulation of CIP in the former.

Summary Background & aims Recent data suggest that current obesity diagnostic criterion based on body mass index (BMI) above 30 in Caucasians may not be appropriate for Asian populations. Our aim was to identify the usefulness of BMI, waist circumference (WC) and waist-to-hip ratio (WHR) in screening for obesity in an Asian population. Methods A cross-sectional sample of 1109 males and 879 females aged 20–45-yr were recruited. Height, weight, WC, hip circumference and percentage body fat (PBF) were measured in all subjects. Then receiver-operating characteristic analyses were used to evaluate the performances of the three anthropometric indices. Results BMI, WC and WHR showed strong positive correlation with PBF ( r = 0.47 – 0.75 ) in both males and females within both age groups. True-positive rates ranged from 82.4% to 94.1% and 68.8% to 86.3% in males and females, respectively. True-negative rates ranged from 64.1% to 84.7% and from 56.9% to 79.0%, respectively. The areas under the curves (AUCs) for WC and BMI were high (0.76–0.92) in both sexes and divided age groups (20–30-yr and 31–45-yr), and those for WHR were a little lower (0.74–0.88). Conclusions BMI and WC are two important predictors for obesity in Chinese, and WHR is an alternative.

A simple analytical model is developed to predict the average crack spacing and crack depth in highway pavements due to thermal loading. The pavement is modeled as a beam on a Winkler elastic foundation. The effect of cracks on the pavement is considered on the basis of compliance functions. A simple method is introduced to describe the behavior of the pavement material according to nonlinear fracture mechanics. It is shown that the material length in the fracture model should be defined by the total fracture energy, rather than the effective fracture energy. The effect of nonlinearity in the distribution of thermal stress across the pavement depth is also analyzed. The foundation of the pavement is found to have little importance. The theoretical predictions are shown to compare well with field observations on asphalt pavements.

In the preceding companion paper (Bažant and Li, 1995), the solution of an aging viscoelastic law was structure containing a cohesive crack with a rate-dependent stress-displacement softening law was reduced to a system of one-dimensional integro-differential equations involving compliance functions for points on the crack faces and the load point. An effective numerical algorithm for solving these equations, which dramatically reduces the computer time compared to the general two-dimensional finite element solution, is presented. The behavior of the model for various loading conditions is studied. It is shown that the model can closely reproduce the available experimental data from fracture tests with different loading rates spanning several orders of magnitude, and tests with sudden changes of the loading rate. Influence of the loading rate on the size effect and brittleness is also analyzed and is shown to agree with experiments.

The time dependence of fracture has two sources: (1) the viscoelasticity of material behavior in the bulk of the structure, and (2) the rate process of the breakage of bonds in the fracture process zone which causes the softening law for the crack opening to be rate-dependent. The objective of this study is to clarify the differences between these two influences and their role in the size effect on the nominal strength of stucture. Previously developed theories of time-dependent cohesive crack growth in a viscoelastic material with or without aging are extended to a general compliance formulation of the cohesive crack model applicable to structures such as concrete structures, in which the fracture process zone (cohesive zone) is large, i.e., cannot be neglected in comparison to the structure dimensions. To deal with a large process zone interacting with the structure boundaries, a boundary integral formulation of the cohesive crack model in terms of the compliance functions for loads applied anywhere on the crack surfaces is introduced. Since an unopened cohesive crack (crack of zero width) transmits stresses and is equivalent to no crack at all, it is assumed that at the outset there exists such a crack, extending along the entire future crack path (which must be known). Thus it is unnecessary to deal mathematically with a moving crack tip, which keeps the formulation simple because the compliance functions for the surface points of such an imagined preexisting unopened crack do not change as the actual front of the opened part of the cohesive crack advances. First the compliance formulation of the cohesive crack model is generalized for aging viscoelastic material behavior, using the elastic-viscoelastic analogy (correspondence principle). The formulation is then enriched by a rate-dependent softening law based on the activation energy theory for the rate process of bond ruptures on the atomic level, which was recently proposed and validated for concrete but is also applicable to polymers, rocks and ceramics, and can be applied to ice if the nonlinear creep of ice is approximated by linear viscoelasticity. Some implications for the characteristic length, scaling and size effect are also discussed. The problems of numerical algorithm, size effect, roles of the different sources of time dependence and rate effect, and experimental verification are left for a subsequent companion paper.

Organic fertilizer or manure containing antibiotics has been widely used in organic farms, but the distribution and potential impacts of antibiotics to the local environment are not well understood. In this study, four quinolone antibiotics in soil samples (n=69) from five organic vegetable farms in a subtropical city, Southern China, were analyzed using high performance liquid chromatography-tandem mass spectrometry. Our results indicated that quinolone compounds were ubiquitous in soil samples (detection frequency>97% for all compounds), and their concentrations ranged from not detectable to 42.0 μg/kg. Among the targets, enrofloxacin (ENR) was the dominant compound, followed by ciprofloxacin (CIP) and norfloxacin (NOR). The average total concentrations of four compounds in the soils were affected by vegetable types and species cultivated, decreasing in the order of fruit>rhizome>leaf vegetables. Moreover, the average concentrations of quinolone compounds (except ENR) in open-field soils were higher than those in greenhouse soils. The concentrations of quinolone antibiotics in this study were lower than the ecotoxic effect trigger value (100 μg/kg) proposed by the Veterinary Medicine International Coordination commission. Risk assessment based on the calculated risk quotients indicated that NOR, CIP, and ENR posed mainly medium to low risks to bacteria.

Sixteen typical antibiotics including four tetracyclines, four quinolones, and eight sulfonamides in vegetables from manure-amended farm were determined using the ultra high performance liquid chromatography-tandem mass spectrometry and their health risks to human via the diet pathway was assessed. Most antibiotics were frequently detected in vegetable samples, with the detection rate from 11% to 90%. Concentrations of a single compound were mainly less than 5 microg x kg(-1) (D. W.), with the maximum of 23.88 microg x kg(-1) and the average of 0.91 microg x kg(-1), respectively. Norfloxacin, ciprofloxacin, sulfamehtaoid and sulfadiazine were the dominant compounds. At least one antibiotic was detected in a single vegetable samples, and even up to ten antibiotics. The concentration of quinolones in underground parts was higher than those in aboveground parts. Intake dose of antibiotics via the consumption of the detected vegetables was lower than ADI, suggesting a lower health risk. But combination toxicity and resistance of antibiotics should not be ignored.

The preceding paper is extended to the analysis of size effect on strength and ductility of structures. For the case of geometrically similar structures of different sizes, the criterion of stability limit is transformed to an eigenvalue problem for a homogeneous Fredholm integral equation, with the structure size as the eigenvalue. Under the assumption of a linear softening stress-displacem ent relation for the cohesive crack, the eigenvalue problem is linear. The maximum load of structure under load control, as well as the maximum deflection under displacement control (which characterizes ductility of the structure), can be solved explicitly in terms of the eigenfunction of the aforementioned integral equation. crack model is a nonlinear theory of fracture me­ chanics in which the condition of stability limit is expressed in terms of the singularity condition of the second variation of the energy potential with respect to cohesive stresses or crack­ opening displacements. Although the criterion of stability limit can also be formulated in terms of energy variation with respect to the crack length, the resulting equation is not very useful, since the energy release rate in the cohesive crack model de­ pends on the cohesive stresses or crack-opening displacements. For a given structure, the criterion of stability limit leads to a highly nonlinear equation for crack length. However, when a class of geometrically similar structures of different sizes is considered and the relative crack length is given, the criterion of stability limit can be treated as an equation for the structure size at which the stability limit occurs at the given relative crack length. In this manner, the criterion of the stability limit is transformed into an eigenvalue problem, with the structure size as the eigenvalue. In the special case of linear softening, the eigenvalue problem is linear. It can be solved independently of the solution of the cohesive crack model. Furthermore, the corresponding maximum value of the load or loading parameter can be expressed explicitly in terms of the eigenfunction. In this way, the size effect curve can be obtained readily, without having to calculate the load-deflection curves for structures of various sizes.

The paper deals with a cohesive crack model in which the cohesive (crack-bridging) stress is a specified decreasing function of the crack-opening displacement. Under the assumption that no part of the crack undergoes unloading, the complementary energy and potential energy of an elastic structure which has a cohesive crack and is loaded by a flexible elastic frame is formulated using continuous influence functions representing compliances or stiffnesses relating various points along the crack. By variational analysis, in which the derivatives of the compliance or stiffness functions with respect to the crack length are related to the crack-tip stress intensity factors due to various unit loads, it is shown that the minimizing conditions reduce to the usual compatibility or equilibrium equations for the cohesive cracks. The variational equations obtained can be used as a basis for approximate solutions. Furthermore, the conditions of stability loss of a structure with a growing cohesive crack are obtained from the condition of vanishing of the second variation of the complementary energy or the potential energy. They have the form of a homogeneous Fredholm integral equation for the derivatives of the cohesive stresses or crack opening displacements with respect to the crack length. Loadings with displacement control, load control, or through a flexible loading frame are considered. Extension to the analysis of size effect on the maximum load or maximum displacement are left to a subsequent companion paper.

A simple method is proposed for determination of fracture energy of materials exhibiting quasi-brittle behavior during mode I cracking. A series of graphs showing the relationship between the nondimensional peak load and the nondimensional beam size are generated for a three-point beam configuration using a new and computationally efficient finite-element program. The method only requires the measurement of the peak load of a single-size beam specimen. It is preferred that the beam specimens have a small preexisting notch to ensure mode I cracking in a three-point bending test. The other required material properties for the use of nondimensionalized graphs include Young's modulus and tensile strength. Since the three-point bending test can be easily carried out in the laboratory, the proposed method offers a practical, yet expedient, way of characterizing the nonlinear fracture properties of materials that follow the linear stress-separation behavior in the process zone.

Previous studies have shown that two single-nucleotide polymorphisms (SNPs) in PSCA (rs2976392 and rs2294008) are associated with gastric cancer (GC), but the results are conflicting. Additionally, the prognostic value of PSCA gene polymorphisms for GC patients is unknown. We performed a meta-analysis using 9 eligible case-control studies to investigate the association between PSCA polymorphisms and GC risk, and additionally investigated the prognostic value of PSCA polymorphisms for GC patients with two eligible studies. The association was measured using random-effect or fixed-effect odds ratios (ORs) combined with 95% confidence intervals (CIs) according to the heterogeneity of the studies. We found that rs2294008 (dominant model: OR, 1.44; 95% CI, 1.16–1.79) and rs2976392 (dominant model: OR, 1.41; 95% CI, 0.98–2.04) polymorphisms were associated with increased risk of GC, although the association of rs2976392 was not statistically significant. For rs2294008, the associations were all consistently significant among the different subgroups stratified by ethnicity and tumor location, but not significant in intestinal or diffuse subtypes. For rs2976392, the associations were consistently significant for the intestinal, diffuse and non-cardia subtypes, but not significant for the cardia subtype. Furthermore, two eligible studies reported inverse results of PCSA in predicting the survival of GC patients (HR, 0.75; 95% CI, 0.59–0.96; and HR, 2.12; 95% CI, 1.22–3.69, respectively). In conclusion, PSCA gene polymorphisms are associated with increased risk of GC and are correlated with the prognosis of GC patients. Future studies are required to evaluate the molecular mechanisms of PSCA polymorphisms in GC and validate the prognostic value in a larger number of patients.

The problem of static penetration of an object through a sea ice plate is studied as a two‐dimensional fracture problem using linear elastic fracture mechanics. The ice sheet floating on water is modeled as a thin elastic plate resting on Winkler's elastic foundation. The equilibrium equations are established by minimizing the potential energy approximated by finite differences in terms of nodal deflections. The growth of radial cracks is analyzed using the plate bending theory. The fracture process zone is assumed to be a point in the plane of plate. The maximum load is found to occur when circumferential cracks begin to form, which is governed by a strength criterion. As a refinement and extension of a previous idea, a theory of initial crack spacing is proposed to estimate the number of radial cracks formed during penetration. This theory can also explain the change of the failure mechanism, from failure by formation of circumferential cracks to failure by a conic crack. Particular attention is paid to...