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Based on the uniaxial compression test, this study examined the effect of the dip angle of the rock formation on crack initiation, propagation, and penetration failure mechanism under the combined effects of freeze–thaw and load, utilizing the discrete element programmed. The results show that: The fracture area of fractured rock mass is mainly caused by fatigue damage caused by stress concentration at the end of fracture. The crack propagation path at the crack tip may be deflected due to the influence of freeze–thaw cycles. With the increase of the dip angle of the rock bridge, the failure mechanism of the rock sample gradually evolved from a single tension failure to a mixed tension-shear failure, and the fractal dimension of the crack increased first and then decreased. When the dip angle of the rock bridge is α < 60°, the relative displacement of the outer tip of the crack is shear dislocation, resulting in a low degree of stress. When the dip angle of the rock bridge is α ≥ 60°, the crack is separated and open, and the secondary inclined crack at the outer tip is transformed into a secondary coplanar crack, and the crack propagates from the loading direction to the crack direction. The deflection of the stress concentration area at the tip of the crack causes the deflection of the crack propagation direction, and the peak strength is inverted "spoon". [ABSTRACT FROM AUTHOR]

Research of thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP) materials is attractive owing to their extensive applications in various fields. However, achieving organic TADF and RTP materials, particularly those with stimulus‐responsiveness and tunability, is highly desirable but challenging and rarely reported. Herein, two easily synthesized organic molecules are reported with abnormal stimulus‐responsive switchable TADF and RTP effects, in which phenothiazine (PTZ) and benzo[b]phenothiazine (BPTZ) based donor−acceptor molecules PTZ‐DBQ and BPTZ‐DBQ show mechanical‐induced TADF in crystalline phase and photo‐responsive RTP in doping poly(methyl methacrylate) (PMMA) films. This is the first time tetracyclic BPTZ has been used as a donor in achieving TADF and RTP materials, and it is found that BPTZ‐DBQ exhibits remarkably better photophysical properties than PTZ‐DBQ. Systematic studies of experimental results and theoretical calculations indicate that the conformational heterogeneity plays an essential role in achieving mechanical‐induced TADF with mechanochromic luminescence (MCL) property. Embedding the organic phosphors into rigid polymer matrices effectively suppresses the molecular motion, thus turning on the RTP emission channel. The conversion of 3O2 to 1O2 under UV irradiation is mainly responsible for the photo‐induced process. These multifunctional luminescent materials have great potential applications in chemical sensors, information encryption, and anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

Two-stream convolution network (2SCN) is a classical method of action recognition. It is capable of extracting action information from two dimensions: spatial and temporal streams. However, the method of extracting motion features from a spatial stream is single-frame recognition, and there is still room for improvement in the perception ability of appearance coherence features. The classical two-stream convolution network structure is modified in this paper by utilizing the strong mining capabilities of the bidirectional gated recurrent unit (BiGRU) to allow the neural network to extract the appearance coherence features of actions. In addition, this paper introduces an attention mechanism (SimAM) based on neuroscience theory, which improves the accuracy and stability of neural networks. Experiments show that the method proposed in this paper (BS-2SCN, BiGRU-SimAM Two-stream convolution network) has high accuracy. The accuracy is improved by 2.6% on the UCF101 data set and 11.7% on the HMDB51 data set. [ABSTRACT FROM AUTHOR]

In tectonically active steep mountain belts, such as those in west Sichuan in China, frequent landslide disasters can occur during the rainy season. High-locality landslides often initiate with the failure of fractured rock masses or regolith near the ridge of a high and steep slope. Often, these events occur suddenly in the sense that people downslope are caught by surprise. High-locality landslides can be destructive owing to the large momentum and entrainment potential of the moving mass. Increasing attention has been given to these events since the 2008 Wenchuan earthquake. Indeed, slope ridges are particularly susceptible of topographic amplification of the seismic shaking, resulting in mechanical weakening that predisposes them to enhanced weathering and rain-triggered failures years or decades after the mainshock. Risk reduction in such cases must begin with a systematic surveying of the ridges to identify criticalities. Then, quantitative (numerical) approaches must be used to evaluate volumes and describe the movement. Risk assessments can then be produced, and mitigations suggested. Here, we describe the Tonghua landslide in Li County, which is currently in a creeping stage but threatens critical infrastructures and dwellings. We monitored the site for 3 years and identified additional potentially unstable areas before performing physically based modeling and hazard zonation. Our results could be useful in decision-making for risk reduction. [ABSTRACT FROM AUTHOR]

Poly‐p‐phenyleneterephthalamide (PPTA) is widely used in national defense, military industry, and aerospace. However, with weak compression resistance and twist resistance, development of PPTA is greatly impeded. In this work, a novel rigid rod polymer was synthesized by polycondensation of 2,6‐dihydroxyterephthalic acid with 2,3,5,6‐tetraminopyridine which have a large quantity of hydrogen bonds between these polymer chains which provide excellent thermal properties named poly [N‐(2,5‐diamino‐6‐[imino]‐3‐pyridyl)‐4‐formyl‐2,6‐dihydroxybenzamide] (PPDA). The structure of the polymers was characterized by X‐ray diffraction and Fourier transform infrared spectroscopy. The resulting showed that PPDA has good thermal stability and crystallinity, the maximum thermal decomposition temperature close to 900°C under the nitrogen atmosphere. At the same time, PPDA was insoluble in most organic solvents and exhibited good chemical stability. This indicated a superior performance over that of the poly(2,6‐diimidazo(4,5‐b:4′5′‐e)pyridinylene‐1,4(2,5‐dihydroxy)phenylene). In addition, we can foresee that PPDA will play an important role in prospective surgery and aramid areas. [ABSTRACT FROM AUTHOR]

This article used four types rock powder, including granite, gneiss, basalt and limestone, to replace 20% cement to prepare concrete with a water -to -binder of 0.47 or 0.32, and tested their workability and 3 ~1080 d strength, such as cube compressive strength and splitting tensile strength, when the fly ash concrete was selected as the reference sample. The testing results show that the rock powder will affect the concrete workability in different level, and the development model of concrete strength exhibit two-stage feature which contained the rapid development period at 3~180 d and the slow development period at 180 d to 1080 d. Compound exponential function can be used to accurately predict the strength development model of rock powder concrete. The compressive strength ratio of rock powder concrete and fly ash concrete was 0.7~0.9 while the splitting tensile strength ratio was 0.8~1.0. The relationship of compressive strength and splitting tensile strength of rock powder strength can be described by powder function. The 28~90d strength of rock powder concrete was 0.7~0.9 of long-age (1080 d) strength. [ABSTRACT FROM AUTHOR]

Dickeya zeae is a globally important bacterial pathogen that has been reported to cause severe soft rot diseases in several essential food crops, including bananas, rice, maize, and potatoes. Carvacrol, a hydrophobic terpene component, is found in aromatic plants of the Labiatae family and various essential oils. However, little work has been done on its antimicrobial potential against D. zeae. This study aimed to evaluate the antimicrobial activity and the functional mechanism of carvacrol against D. zeae. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of carvacrol against D. zeae were 0.1 mg/mL and 0.2 mg/mL, respectively. Carvacrol affected the cell membrane of D. zeae, as revealed by decreased intracellular ATP concentration, nucleic acid leakage, and decreased membrane potential. Scanning electron microscopy (SEM) micrographs confirmed that D. zeae cell membranes were damaged by carvacrol. Furthermore, a significant inhibition of D. zeae swimming motility and biofilm formation was observed following treatments with carvacrol at sub-inhibitory concentrations, indicating a significantly negative effect on these virulence factors. Accordingly, the tissue infection test revealed that carvacrol significantly reduced the pathogenicity of D. zeae. In a pot experiment, inoculated banana seedlings displayed remarkably lesser disease symptoms following treatment with carvacrol, and the control efficiency for banana soft rot was 32.0% at 14 days post-inoculation. To summarize, carvacrol exhibits strong antimicrobial activity against D. zeae and great potential applications in the control of D. zeae-associated crop diseases. [ABSTRACT FROM AUTHOR]

Photocatalysis with universality and feasibility has been widely applied to degrade pollutants that mainly exist in gas and liquid systems. However, the photocatalytic degradation of contaminants on solid surfaces is rarely reported. The investigation of the photocatalytic degradation mechanism of pesticide on a solid surface will provide a vital reference for removing pesticide residues on fruit surfaces. Here, we discovered that in situ photocatalytic degradation on solid surface (PDSS) is a moisture dependent process regulated by the interaction between TiO2 and H2O. The interaction mechanism between TiO2 and moisture was revealed by X-ray photoelectron spectroscopy and in situ FT-IR. Meanwhile, we investigated a water layer formed between TiO2 and water on the surface by density functional theory. The photocatalytic degradation process of imidacloprid on the solid surface is proposed. This work explores the H2O impact on photocatalysis in solid surfaces and provides a significant reference for removing pesticide residues in realistic environmental conditions. [ABSTRACT FROM AUTHOR]

A consequent slope, comprising weak planes in the same dip direction along the slope face, is the most dangerous type of rock slope. Herein, a consequent landslide that occurred on May 5, 2018, in Mabian County, Southwest China, was investigated. This landslide occurred in a region with a complex geological background and strong geological activity and is considered a typical consequent landslide. Field investigations and aerial photographic interpretations revealed that the rock mass slipped along the contact surface of the strongly and moderately weathered rock mass, triggered by continuous rainfall. A depth-integrated continuum method was used to study the dynamic process of the landslide. The applicability of the depth-integrated method was verified by comparing the moving boundary of the landslide extracted from a video with the simulation results. The results show that the velocity of the landslide first increased and then decreased from the top to the bottom of the landslide and reached a maximum of 21 m/s in the middle of the landslide. Based on this method, we predicted the potential danger zones and velocity distribution of unstable masses next to the Mabian landslide. On comparing the calculated results of a depth-integrated continuum method with the Scheidegger method, in the case of the Mabian landslide, a reduction factor λ was added to the Scheidegger formula to achieve a modified formula that determines the velocity of such consequent landslides relatively accurately. This work could provide reference for the study of landslide velocity and disaster prevention. [ABSTRACT FROM AUTHOR]

An online monitoring technology of Pu-239 aerosol based on aerosol direct introduction device, membrane desolvation nebuliser and ICP-MS was established for workplaces of reprocessing plants. Briefly, 0.8 l min−1 Pu-239 aerosol from the workplace was introduced into the aerosol direct introduction device where the air was replaced by Argon, and then the aerosol was introduced into the ICP-MS for measurement. To determine the activity of Pu-239 aerosol, 1.10E−3 Bq ml−1 Pu-242 standard solution generated by a membrane desolvation nebuliser was used. The introduction efficiency of the nebuliser was determined by sampling the aerosol generated from the nebuliser with Lead Standard Solution by glass fiber filter, which was (26.82 ± 3.33) %. The mass bias between Pu-239 and Pu-242 for the ICP-MS measurement was determined by Pu-239 and Pu-242 standard solutions generated by the nebuliser, and mass discrimination correction factor for Pu-239/Pu-242 was 0.972 ± 0.010. The limit of detection (LOD) and limit of quantification (LOQ) of this system were calculated according to the ISO 20 899:2018, which were 2.24E−05 Bq m−3 and 7.45E−05 Bq m−3 with 1 min measurement. The main interference which was from U-238 was determined by U-238 standard solution generated by the nebuliser, and the interferences of U-238 to 239 was (8.50 ± 1.05) E−05. According to the counts of U-238 from several workplaces of reprocessing plant where this system was tested, 239 counts rate from the interferences of U-238 of those workplaces were at the same level of the system background counts, which meant that the LOD above was suitable for those places. [ABSTRACT FROM AUTHOR]

Sterculia lanceolata, an important tropical woody plant, has high ornamental and medicinal value. To our knowledge, only brown root disease in this plant has been reported. In Nanning, Guangxi, China, an outbreak of leaf blight disease was observed on S. lanceolata in June 2019, with the leaf infection rate ranging from 80% to 100%. The disease seriously affected the leaves of trees and caused economic loss. Eight isolates were recovered from the infected leaves of different trees, and the pathogenicity was then determined by the methods of mycelial disc and conidial suspension, fulfilling Koch's postulates. According to the morphological and molecular biological characteristics of isolates, the pathogen causing leaf blight on S. lanceolata was identified as Colletotrichum siamense. Accurate identification of the pathogen provides a reliable basis for the control of the disease. [ABSTRACT FROM AUTHOR]

Perchlorate is a low molecular weight highly soluble anion. It occurs naturally in the environment, primarily near potash deposits and in arid regions. The determination of perchlorate in human milk is of interest in vulnerable populations such as infants and pregnant women. In this study, a sensitive and selective isotope dilution ion chromatography/tandem mass spectrometry (ID IC-MS/MS) method was developed and validated for the determination of perchlorate in human milk samples collected from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study. The limit of detection (LOD) was 0.27 µg·kg−1 for human milk. A total of 439 human milk samples were analysed with measurable levels of perchlorate in most of the milk samples, and the mean value was 7.62 ± 32.7 µg·kg−1. This project provided important information related to perchlorate levels in human milk collected across Canada and the extent to which pregnant women and their infants may be exposed to perchlorate. A dietary exposure assessment was also conducted in infants based on the measured values in human milk. The mean perchlorate probable daily intakes (PDIs) for infants consuming human milk were 0.31 ± 0.07 μg/kg bw/day for infants under 1 year and 0.17 ± 0.10 μg/kg bw/day for infants between 1 and 3 years old. None of the estimates exceeded the FAO/WHO provisional maximum tolerable daily intake (PMTDI) of 10 μg/kg bw/day. [ABSTRACT FROM AUTHOR]

The nicotinic acetylcholine receptor (nAChR) is one of the targets for developing drugs for the treatment of central nervous system (CNS) disorders and for control of agricultural pests. Pyrido[3,4‐b] homotropane (PHT) was originally designed and synthesized by Kanne and co‐workers and showed strong affinity binding to nAChR. PHT has a novel aza‐[4.2.1]nonane skeleton. Owing to its excellent biological activities and novel chemical structure, synthetic and medicinal chemists have been attracted by this molecule. Some PHT analogues with bridged aza‐[n.2.1] skeletons were also designed and synthesized via different strategies. Herein, we summarize the syntheses of PHT and its analogues. Their biological activity study is also briefly discussed. [ABSTRACT FROM AUTHOR]

The focus of this paper is on two large sequential landslides which formed a dam and the resulting lake that occurred along the Jinsha River on October 11 and November 3, 2018. About 24 and 9 × 106 m3 of material failed and rushed into the river, respectively. Both landslides totally blocked the river and induced hazard chains. Four multi-temporal unmanned aerial vehicle (UAV)-based high-resolution images and digital elevation models (DEMs) before and after the landslides were obtained and merged. The initial deformation of the two landslides can be clearly captured by optical remote-sensing images and interferometric synthetic aperture radar (InSAR) analysis. The depth-integrated continuum method was adopted to analyze the dynamic process of both landslides, using the same basal friction angle and cohesion. The computational results matched well with field measurements and observations. It is shown that the evaluation of potentially landslide-prone areas by the depth-integrated continuum method is feasible and is able to provide significant information before a possible event. [ABSTRACT FROM AUTHOR]

Bacterial soft rot caused by Dickeya zeae MS1 (Erwinia chrysanthemi) is one of the most devastating banana diseases worldwide. However, knowledge of the development and ecological interactions of D. zeae MS1 biofilm is limited. Here, we visualized the development and architecture of D. zeae MS1 biofilm using confocal laser scanning microscopy, and we evaluated the ability of D. zeae MS1 to form biofilms under different environmental conditions (carbon sources, temperatures, pH levels and mineral elements) using a microtiter plate assay. We found that the development of D. zeae MS1 biofilm could be categorized into four phases and that mature biofilm consisted of a highly organized architecture of both bacterial cells and a self-produced matrix of extracellular polysaccharides. Furthermore, sucrose was the most suitable carbon source for supporting the growth of biofilm cells and that 32 °C and pH 7.0 were the most favorable of the temperatures and pH levels examined. Meanwhile, the addition of Ca2+, Fe2+, K+ and Na+ enhanced the formation of biofilm in minimal medium cultures, whereas 2.5 mM Cu2+ and Mn2+ was inhibitory. A better understanding of biofilm formation under different environmental parameters will improve our knowledge of the growth kinetics of D. zeae MS1 biofilm. [ABSTRACT FROM AUTHOR]

In order to determine the baseline levels of perchlorate in major brands of baby food, 200 baby food products were collected from retail stores in Ottawa, Canada and analysed for perchlorate in 2010. The seven food groups tested were fruit, juices, vegetables, meat, yogurt, mixed (vegetable mixed with meat) and other (e.g. vegetable mixed with meat and cereal, cheese, egg,). Samples were extracted with a mixture of methanol and 1% acetic acid (4:1, v/v). Determination was conducted by stable isotope dilution ion chromatography tandem mass spectrometry (ID-IC-MS/MS). The complexity of different food matrices required additional method validation. The perchlorate levels in 46 samples were found to be lower than the quantification limit (0.2 ng g−1). The perchlorate levels in the other 154 baby food samples were also low; about 96.7% of the baby foods had perchlorate levels less than 10 ng g−1 (ranged from 0.2 to 22.4 ng g−1, median1.35 ng g−1); only 5 samples had perchlorate levels higher than 10 ng g−1. Dietary exposure to perchlorate from analysed baby food was conservatively estimated to range from 0.007 to 0.121 µg/kg bw/d based on the mean intake for children (1-5 years old). [ABSTRACT FROM AUTHOR]

Abstract: An efficient synthesis of (−)‐pyrido[3,4‐b]homotropane (PHT) as well as (±)‐PHT has been achieved in 7 steps from conveniently available starting materials. Key transformations involve an efficient construction of the core bridged 9‐aza‐[4.2.1]nonane skeleton via a Sc(OTf)3‐catalyzed intramolecular cross [3+2] cycloaddition (IMCC) followed by Krapcho decarboxylation and Barton reductive decarboxylation. The present work supplies a general and efficient strategy for synthesis of other bridged analogues. [ABSTRACT FROM AUTHOR]

A novel Lewis acid-catalyzed [3+2] intramolecular cross-cycloaddition (IMCC) between aziridine 2,2-diesters and conjugated dienes has been developed. This is the first regiospecific IMCC of intramolecular 1,3-dipolar cycloadditions of azomethine ylides with carbon=carbon double bonds, and supplies a general and efficient strategy for construction of structurally complex and diverse aza-[ n.2.1] skeletons. The [3+2]IMCC could be carried out under mild conditions and in gram scale. More importantly, 3-alkyl-substituted aziridines were also successful. The excellent structural diversity, the facile operation and the versatile post-modifications will support the applications of the [3+2]IMCC in natural products synthesis and drugs discovery. [ABSTRACT FROM AUTHOR]

Aiming to develop efficient and general strategies for construction of complex and diverse polycyclic skeletons, we have successfully developed [4+3]IMPC (intramolecular parallel cycloaddition) of cyclopropane 1,1-diesters with [3]dendralenes. With a combination of the [4+3]IMPC and subsequent [4+ n] cycloadditions, trans-[5.3.0]decane skeleton and its corresponding structurally complex and diverse polycyclic variants could be constructed efficiently. This novel [4+3] cycloaddition reaction mode of donor-acceptor cyclopropanes proceeds as a result of the ring-strain relief of a trans-[3.3.0]octane. We strongly believe that the developed methods will demonstrate potential applications in natural products synthesis and drug discovery. [ABSTRACT FROM AUTHOR]

In contast to the general [4+2] cycloaddition reactions of alkynylcyclopropane ketones reported in the literature, we report herein a Sc(OTf)3-catalyzed formal intermolecular [3+2] cycloaddition reaction of alkynylcyclopropane ketones with electron-rich aromatic aldehydes. 2,3,3,5-Tetrasubstituted tetrahydrofurans were obtained by this method, and the tetrahydrofuran skeleton was diastereoselectively constructed with a 2,5- trans configuration. This is also quite different to the 2,5- cis configuration usually obtained from typical [3+2] cycloaddition reactions of most donor-acceptor cyclopropanes. Additionally, the cycloadducts were subjected to a domino carbopalladation/C-H activation/C-C bond-formation process for the highly efficient construction of polycyclic skeletons. [ABSTRACT FROM AUTHOR]

Ion-pair chromatography coupled to inductively coupled plasma mass spectrometry (ICP-MS) was evaluated and validated for the determination of arsenic species in fruit juice and fruit drink products. A Phenomenex analytical column (Prodigy 3 μ ODS (3) 4 μm × 2.0 mm × 150 mm) and a mobile phase consisting of 5 mmol l malonic acid, 3 mmol l of tetrabutylammonium hydroxide solution and 5 % methanol were used to achieve arsenic speciation separation. The arsenic species were detected at m/ z 75 with an Agilent 7500cx ICP-MS. After demonstrating the method was sensitive, accurate and fit for purpose, and it was applied to analyze 96 fruit juice and fruit drink samples. Speciation analysis of the 96 fruit juice and fruit drink products revealed that inorganic arsenic was the major species found in the majority of juice products tested in the study. The concentration of inorganic arsenic (sum of As and As) ranged from

An acid-catalyzed domino Meinwald rearrangement of epoxides/intramolecular [3+2] cross-cycloaddition of cyclopropane 1,1-diesters was developed. This supplied a method for the construction of bridged oxa-[ n.2.1] ( n = 3, 4) skeletons. [ABSTRACT FROM AUTHOR]

Carbon bridges: The title reaction has been successfully developed, and applied to the total synthesis of the tetracyclic diterpenoids phyllocladanol and phyllocladene. The method provides an efficient, general, and conceptually new strategy for the construction of structurally complex and diverse [n.2.1] carbocyclic skeletons (see scheme). [ABSTRACT FROM AUTHOR]

Kohlenstoffbrücken: Die Titelreaktion wurde entwickelt und in der Totalsynthese der tetracyclischen Diterpenoide Phyllocladanol und Phyllocladen verwendet. Die Methode bietet eine effiziente, allgemeine und konzeptionell neue Strategie zum Aufbau strukturell komplexer [n.2.1]Carbocyclen (siehe Schema). [ABSTRACT FROM AUTHOR]

In this study, we compared a high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICP-MS) method and an isotope dilution gas chromatography mass spectrometry (ID-GC-MS) method for the analysis of methylmercury (MeHg) in fish samples. Using HPLC-ICP-MS, the limit of detection (LOD) was 2.0 ngHg · g for inorganic Hg and was 5.0 ngHg · g for MeHg. In comparison, the LOD for MeHg was 3.4 ngHg · g for using ID-GC-MS. Certified reference material (CRM) results agreed well with certified values for both methods. The mean recovery for analysis of CRM BCR 463 by HPLC-ICP-MS was 99 ± 2.1 % for MeHg and was 103 ± 2.1 % for total Hg. Two CRMs, BCR 463 and CRM DORM2, were analyzed by ID-GC-MS, the mean recovery of MeHg was 87 ± 1.9 % for BCR 463, and the mean recovery of MeHg was 102 ± 2.9 % for CRM DORM2. Matrix samples spiked with Hg or MeHg at various concentrations were analyzed by two methods. For HPLC-ICP-MS method, the mean recovery for MeHg spiked samples was 93 ± 4.2 %. For ID-GC-MS method, the mean recovery for MeHg spiked samples was 91 ± 5.2 %. A total of 19 predatory fish and 54 tuna fish samples were analyzed using both methods. No significant difference was observed between the MeHg data generated from both methods. The average relative standard deviation (RSD) between the two datasets for 19 predatory fish samples was 8.8 %. The average RSD between two datasets for 54 tuna fish samples was 4.4 %.The HPLC-ICP-MS method offers substantial advantages over the method of ID-GC-MS because the former method can determine the total mercury (Hg) and MeHg in a single chromatographic run and the analysis time is much shorter. The latter method is time consuming due to overnight digestion and having to conduct presample analysis for signal-matched isotope dilution spiking and requires more expensive isotope labeled reagents. [ABSTRACT FROM AUTHOR]

This article covers challenges and trends in the determination of some major food chemical contaminants and allergens, which-among others-are being monitored by Health Canada's Food Directorate and for which background levels in food and human exposure are being analyzed and calculated. Eleven different contaminants/contaminant groups and allergens have been selected for detailed discussion in this paper. They occur in foods as a result of: use as a food additive or ingredient; processing-induced reactions; food packaging migration; deliberate adulteration; and/or presence as a chemical contaminant or natural toxin in the environment. Examples include acrylamide as a food-processing-induced contaminant, bisphenol A as a food packaging-derived chemical, melamine and related compounds as food adulterants and persistent organic pollutants, and perchlorate as an environmental contaminant. Ochratoxin A, fumonisins, and paralytic shellfish poisoning toxins are examples of naturally occurring toxins whereas sulfites, peanuts, and milk exemplify common allergenic food additives/ingredients. To deal with the increasing number of sample matrices and analytes of interest, two analytical approaches have become increasingly prevalent. The first has been the development of rapid screening methods for a variety of analytes based on immunochemical techniques, utilizing ELISA or surface plasmon resonance technology. The second is the development of highly sophisticated multi-analyte methods based on liquid chromatography coupled with multiple-stage mass spectrometry for identification and simultaneous quantification of a wide range of contaminants, often with much less requirement for tedious cleanup procedures. Whereas rapid screening methods enable testing of large numbers of samples, the multi analyte mass spectrometric methods enable full quantification with confirmation of the analytes of interest. Both approaches are useful when gathering surveillance data to determine occurrence and background levels of both recognized and newly identified contaminants in foods in order to estimate human daily intake for health risk assessment. [ABSTRACT FROM AUTHOR]

We analyze the statistical properties of the urban public bus networks of two cities (Beijing and Chengdu) in China. To this end, we present a comprehensive survey of the degree distribution, average path length, and clustering of both networks. It is shown that both networks exhibit small world behavior and are hierarchically organized. We also discuss the differences between the statistical properties displayed by the two networks. In addition, we propose a weight distribution approach to study the passenger flow through the public bus networks we considered. A hierarchical structure is observed here also. [ABSTRACT FROM AUTHOR]

Two new cytochalasins, 18-deoxycytochalasin Q ( 1) and 21- O-deacetylcytochalasin Q ( 2), together with four known analogues, cytochalasin Q ( 3), 19,20-epoxycytochalasin Q ( 4), 21- O-deacetyl-19,20-epoxycytochalasin Q ( 5), and cytochalasin D ( 6), were isolated from the fungus Xylaria sp. SCSIO156 originated from the South China Sea marine sediment. The structures of 1 and 2 were elucidated by MS and 1D- and 2D-NMR data analyses, and comparison with known compounds. The known compounds 3- 6 were identified by comparison of their MS and NMR data with those reported in the literature. In the in vitro antitumor assay, compounds 2- 6 showed mild cytotoxicity against three tumor cell lines (MCF-7, SF-268, and NCI-H460). [ABSTRACT FROM AUTHOR]

A modified total synthesis of cystothiazole A is described. In this synthetic strategy, a one-step transformation of acylated oxazolidinone to β-ketoester has been successfully applied, thus making the synthetic route more efficient. This method may also be potentially applied in synthesis of other related β-substituted-β-methoxyl acrylates (bb-MOAs). [ABSTRACT FROM AUTHOR]