Analysis of Pesticides in Soil Using Dispersive Solid Phase Extraction Coupled to GC-MS

A multi-residue method using dispersive solid phase extraction and gas chromatography with mass spectrometric detection has been developed for determination of trace levels of 103 pesticides, including organophosphate, organochlorine, carbamate, and pyrethroid compounds in agricultural soil. Dispersive solid phase extraction using 10 mL of acetonitrile for 3 min of extraction time showed satisfactory extraction efficiency. Recoveries of pesticides from fortified agricultural soil samples ranged from 65% to 117% for three different fortified levels of 50, 100, and 500 μg/kg and relative standard deviations of the recoveries are below 19%. Detection and quantification limits ranged from 1 to 13 μg/kg and from 3 to 38 μg/kg, respectively. The proposed method was less time-consuming, safer, and easy to use for routine analysis.     

Radiation pressure on a biconcave human Red Blood Cell and the resulting deformation in a pair of parallel optical traps

We calculated the three‐dimensional optical stress distribution and the resulting deformation on a biconcave human red blood cell (RBC) in a pair of parallel optical trap. We assumed a Gaussian intensity distribution with a spherical wavefront for each trapping beam and calculated the optical stress from the momentum transfer associated with the reflection and refraction of the incident photons at each interface. The RBC was modelled as a biconcave thin elastic membrane with uniform elasticity and a uniform thickness of 0.25 μm. The resulting cell deformation was determined from the optical stress distribution by finite element software, Comsol Structure Mechanics Module, with Young's modulus (E) as a fitting parameter in order to fit the theoretical results for cell elongation to our experimental data. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effects of a nitrogen fixing plant Vigna radiata on growth,leaf stomatal gas exchange and hydraulic characteristics of the intercropping Juglans regia seedlings

采用砂培方法, 在温室内将一年生核桃(Juglans regia)嫁接苗木和绿豆(Vigna radiata)进行间作, 研究绿豆对核桃苗木生长、水分平衡和光合特性的影响。该研究设有5种处理, 即: 对照(核桃单作, 正常供应氮素); 核桃单作, 不添加氮素; 核桃绿豆间作, 不添加氮素; 核桃绿豆间作, 正常供应氮素; 绿豆单作, 不添加氮素。结果显示: 种植绿豆可以增加土壤氮含量和核桃茎内氮含量, 但对核桃叶和根系中的氮含量影响不明显。种植绿豆显著增加不施氮核桃的高生长和直径生长, 但降低了正常供氮核桃的生长。无论种植绿豆与否, 不供氮处理降低了核桃的总叶面积, 提高了根冠比。核桃叶片气孔气体交换对各处理的响应和生长有相同的趋势。缺氮显著降低了核桃叶柄在中午的导水率、提高了导水损失率; 种植绿豆显著提高不供氮核桃的导水率而且明显降低了其导水损失率。然而, 种植绿豆使正常供氮的核桃降低了导水率, 加剧了导水损失率。同时, 绿豆受到间作的竞争压力, 产量和生物量有所下降。由研究结果可知, 在贫瘠的土壤上, 固氮植物绿豆改善了间作的核桃的氮营养, 有益于核桃木质部发育、水分平衡以及光合代谢。但是在氮充足的土壤中, 种植绿豆反而降低了核桃的水分供应, 影响其气体交换和生长。     

血流感中的病原菌分布及耐药性分析

目的了解血流感染中的病原菌种类、分布及耐药性,为临床合理选用抗菌药物提供依据。方法按照无菌操作方法采集疑为血流感染患者的血液标本进行血培养,采用美国BD公司PHOENIX-100全自动细菌鉴定药敏系统进行细菌鉴定及药敏试验,并对结果进行统计分析。结果共检出1080株病原菌,其中革兰阴性杆菌630株（占58．3％）,革兰阳性球菌428株（占39．6％）,真菌22株（占2．1％）。药敏结果显示：革兰阳性球菌对万古霉素、利奈唑胺敏感率最高,对青霉素、红霉素、头孢菌素等耐药率较高。革兰阴性杆菌对碳青霉烯类、哌拉西林／他唑巴坦、头孢哌酮／舒巴坦敏感率较高,对青霉素类、头孢菌素类和喹诺酮类耐药率较高。结论引起血流感染的病原菌分布复杂,耐药率较高,临床应提高血培养送检率,根据药敏结果合理选用抗菌药物,以减少多重耐药菌的发生和传播。     

2011～2013年血液分离葡萄球菌的临床分布及耐药性分析

目的了解临床各科发热患者（怀疑细菌感染）血培养中葡萄球菌分布及耐药性,为临床治疗提供参考依据。方法血培养采用BaeT／Alert3D全自动血培养仪（梅里埃）培养5d,采用MicroScanWalk—Away-96plus全自动微生物鉴定和药敏分析系统（西门子）进行细菌鉴定和药敏试验。结果血培养共检出葡萄球菌185株,检出最多的科室是ICU,耐甲氧西林金黄色葡萄球菌（methicillin—resistant Staphylococcus aureus,MRSA）检出率为30．4％,而耐甲氧西林凝固酶阴性葡萄球菌（methicillin—resistant coagulase-negative Staphylococci,MRCNS）的检出率高达80．7％。还检出了1株万古霉素中介的凝固酶阴性葡萄球菌。结论通过血培养检出葡萄球菌的耐药性分析发现,凝固酶阴性葡萄球菌对苯唑西林、氨苄西林、青霉素、红霉素的耐药率在70％以上,而对氯霉素、利福平、四环素的耐药率在30％以下,因此这三种药物应为我院应对凝固酶阴性葡萄球菌血流感染的常用首选药物。     

Nutritional and ecological evaluation of dairy farming systems based on concentrate feeding regimes in semi-arid environments of Jordan

The objective of this study was to evaluate the nutritional and ecological aspects of feeding systems practiced under semi-arid environments in Jordan. Nine dairy farms representing the different dairy farming systems were selected for this study. Feed samples (n = 58), fecal samples (n = 108), and milk samples (n = 78) were collected from the farms and analysed for chemical composition. Feed samples were also analysed for metabolisable energy (ME) contents and in vitro organic matter digestibility according to Hohenheim-Feed-Test. Furthermore, fecal nitrogen concentration was determined to estimate in vivo organic matter digestibility. ME and nutrient intakes were calculated based on the farmer’s estimate of dry matter intake and the analysed composition of the feed ingredients. ME and nutrient intakes were compared to recommended standard values for adequate supply of ME, utilizable crude protein, rumen undegradable crude protein (RUCP), phosphorus (P), and calcium (Ca). Technology Impact Policy Impact Calculation model complemented with a partial life cycle assessment model was used to estimate greenhouse gas emissions of milk production at farm gate. The model predicts CH₄, N₂O and CO₂ gases emitted either directly or indirectly. Average daily energy corrected milk yield (ECM) was 19 kg and ranged between 11 and 27 kg. The mean of ME intake of all farms was 184 MJ/d with a range between 115 and 225 MJ/d. Intake of RUCP was lower than the standard requirements in six farms ranging between 19 and 137 g/d, was higher (32 and 93 g/d) in two farms, and matched the requirements in one farm. P intake was higher than the requirements in all farms (mean oversupply = 19 g/d) and ranged between 3 and 30 g/d. Ca intake was significantly below the requirements in small scale farms. Milk nitrogen efficiency N-_eff (milk N/intake N) varied between 19% and 28% and was mainly driven by the level of milk yield. Total CO₂ equivalent (CO₂ equ) emission ranged between 0.90 and 1.88 kg CO₂/kg ECM milk, where the enteric and manure CH₄ contributed to 52% of the total CO₂ equ emissions, followed by the indirect emissions of N₂O and the direct emissions of CO₂ gases which comprises 17% and 15%, respectively, from total CO₂ equ emissions. Emissions per kg of milk were significantly driven by the level of milk production (r² = 0.93) and of eDMI (r² = 0.88), while the total emissions were not influenced by diet composition. A difference of 16 kg ECM/d in milk yield, 9% in N-_eff and of 0.9 kg CO₂ equ/kg in ECM milk observed between low and high yielding animals. To improve the nutritional status of the animals, protein requirements have to be met. Furthermore, low price by-products with a low carbon credit should be included in the diets to replace the high proportion of imported concentrate feeds and consequently improve the economic situation of dairy farms and mitigate CO₂ equ emissions.     

Assessing the performance of the photo‐acoustic infrared gas monitor for measuring CO2, N2O,and CH4 fluxes in two major cereal rotations

Rapid, precise, and globally comparable methods for monitoring greenhouse gas (GHG) fluxes are required for accurate GHG inventories from different cropping systems and management practices. Manual gas sampling followed by gas chromatography (GC) is widely used for measuring GHG fluxes in agricultural fields, but is laborious and time‐consuming. The photo‐acoustic infrared gas monitoring system (PAS) with on‐line gas sampling is an attractive option, although it has not been evaluated for measuring GHG fluxes in cereals in general and rice in particular. We compared N₂O, CO_2, and CH₄ fluxes measured by GC and PAS from agricultural fields under the rice–wheat and maize–wheat systems during the wheat (winter), and maize/rice (monsoon) seasons in Haryana, India. All the PAS readings were corrected for baseline drifts over time and PAS‐CH₄ (PCH₄) readings in flooded rice were corrected for water vapor interferences. The PCH₄ readings in ambient air increased by 2.3 ppm for every 1000 mg cm^?3 increase in water vapor. The daily CO₂, N₂O, and CH₄ fluxes measured by GC and PAS from the same chamber were not different in 93–98% of all the measurements made but the PAS exhibited greater precision for estimates of CO₂ and N₂O fluxes in wheat and maize, and lower precision for CH₄ flux in rice, than GC. The seasonal GC‐ and PAS‐N₂O (PN₂O) fluxes in wheat and maize were not different but the PAS‐CO₂ (PCO₂) flux in wheat was 14–39% higher than that of GC. In flooded rice, the seasonal PCH₄ and PN₂O fluxes across N levels were higher than those of GC‐CH₄ and GC‐N₂O fluxes by about 2‐ and 4fold, respectively. The PAS (i) proved to be a suitable alternative to GC for N₂O and CO₂ flux measurements in wheat, and (ii) showed potential for obtaining accurate measurements of CH₄ fluxes in flooded rice after making correction for changes in humidity.     

Interactions Outside the Proteinase-binding Loop Contribute Significantly to the Inhibition of Activated Coagulation Factor XII by Its Canonical Inhibitor from Corn

Activated factor XII (FXIIa) is selectively inhibited by corn Hageman factor inhibitor (CHFI) among other plasma proteases. CHFI is considered a canonical serine protease inhibitor that interacts with FXIIa through its protease-binding loop. Here we examined whether the protease-binding loop alone is sufficient for the selective inhibition of serine proteases or whether other regions of a canonical inhibitor are involved. Six CHFI mutants lacking different N- and C-terminal portions were generated. CHFI-234, which lacks the first and fifth disulfide bonds and 11 and 19 amino acid residues at the N and C termini, respectively, exhibited no significant changes in FXIIa inhibition (K_i = 3.2 ± 0.4 nm). CHFI-123, which lacks 34 amino acid residues at the C terminus and the fourth and fifth disulfide bridges, inhibited FXIIa with a K_i of 116 ± 16 nm. To exclude interactions outside the FXIIa active site, a synthetic cyclic peptide was tested. The peptide contained residues 20–45 (Protein Data Bank code 1BEA), and a C29D substitution was included to avoid unwanted disulfide bond formation between unpaired cysteines. Surprisingly, the isolated protease-binding loop failed to inhibit FXIIa but retained partial inhibition of trypsin (K_i = 11.7 ± 1.2 μm) and activated factor XI (K_i = 94 ± 11 μm). Full-length CHFI inhibited trypsin with a K_i of 1.3 ± 0.2 nm and activated factor XI with a K_i of 5.4 ± 0.2 μm. Our results suggest that the protease-binding loop is not sufficient for the interaction between FXIIa and CHFI; other regions of the inhibitor also contribute to specific inhibition.     

Using Insect Electroantennogram Sensors on Autonomous Robots for Olfactory Searches

Robots designed to track chemical leaks in hazardous industrial facilities¹ or explosive traces in landmine fields² face the same problem as insects foraging for food or searching for mates³: the olfactory search is constrained by the physics of turbulent transport⁴. The concentration landscape of wind borne odors is discontinuous and consists of sporadically located patches. A pre-requisite to olfactory search is that intermittent odor patches are detected. Because of its high speed and sensitivity^5-6, the olfactory organ of insects provides a unique opportunity for detection. Insect antennae have been used in the past to detect not only sex pheromones⁷ but also chemicals that are relevant to humans, e.g., volatile compounds emanating from cancer cells⁸ or toxic and illicit substances^9-11. We describe here a protocol for using insect antennae on autonomous robots and present a proof of concept for tracking odor plumes to their source. The global response of olfactory neurons is recorded in situ in the form of electroantennograms (EAGs). Our experimental design, based on a whole insect preparation, allows stable recordings within a working day. In comparison, EAGs on excised antennae have a lifetime of 2 hr. A custom hardware/software interface was developed between the EAG electrodes and a robot. The measurement system resolves individual odor patches up to 10 Hz, which exceeds the time scale of artificial chemical sensors¹². The efficiency of EAG sensors for olfactory searches is further demonstrated in driving the robot toward a source of pheromone. By using identical olfactory stimuli and sensors as in real animals, our robotic platform provides a direct means for testing biological hypotheses about olfactory coding and search strategies¹³. It may also prove beneficial for detecting other odorants of interests by combining EAGs from different insect species in a bioelectronic nose configuration¹⁴ or using nanostructured gas sensors that mimic insect antennae¹⁵.     

Measurement of Greenhouse Gas Flux from Agricultural Soils Using Static Chambers

Measurement of greenhouse gas (GHG) fluxes between the soil and the atmosphere, in both managed and unmanaged ecosystems, is critical to understanding the biogeochemical drivers of climate change and to the development and evaluation of GHG mitigation strategies based on modulation of landscape management practices. The static chamber-based method described here is based on trapping gases emitted from the soil surface within a chamber and collecting samples from the chamber headspace at regular intervals for analysis by gas chromatography. Change in gas concentration over time is used to calculate flux. This method can be utilized to measure landscape-based flux of carbon dioxide, nitrous oxide, and methane, and to estimate differences between treatments or explore system dynamics over seasons or years. Infrastructure requirements are modest, but a comprehensive experimental design is essential. This method is easily deployed in the field, conforms to established guidelines, and produces data suitable to large-scale GHG emissions studies.