Effect of Vegetation Rehabilitation on Soil Carbon and Its Fractions in Mu Us Desert,Northwest China

Although vegetation rehabilitation on semi-arid and arid regions may enhance soil carbon sequestration, its effects on soil carbon fractions remain uncertain. We carried out a study after planting Artemisia ordosica (AO, 17 years), Astragalus mongolicum (AM, 5 years), and Salix psammophila (SP, 16 years) on shifting sand land (SL) in the Mu Us Desert, northwest China. We measured total soil carbon (TSC) and its components, soil inorganic carbon (SIC) and soil organic carbon (SOC), as well as the light and heavy fractions within soil organic carbon (LF-SOC and HF-SOC), under the SL and shrublands at depths of 100 cm. TSC stock under SL was 27.6 Mg ha^?1, and vegetation rehabilitation remarkably elevated it by 40.6 Mgha^?1, 4.5 Mgha^?1, and 14.1 Mgha^?1 under AO, AM and SP land, respectively. Among the newly formed TSC under the three shrublands, SIC, LF-SOC and HF-SOC accounted for 75.0%, 10.7% and 13.1% for AO, respectively; they made up 37.0%, 50.7% and 10.6% for AM, respectively; they occupied 68.6%, 18.8% and 10.0% for SP, respectively. The accumulation rates of TSC within 0–100 cm reached 238.6 g m^?2y^?1, 89.9 g m^?2y^?1 and 87.9 g m^?2y^?1 under AO, AM and SP land, respectively. The present study proved that the accumulation of SIC considerably contributed to soil carbon sequestration, and vegetation rehabilitation on shifting sand land has a great potential for soil carbon sequestration.     

Luminescence characteristics of Na3Ca2(SO4)3F: Ce3+ fluoride material

A new Na₃Ca₂(SO₄)₃F: Ce³⁺ phosphor synthesized by a solid state diffusion method is reported. The photoluminescence study showed a single high intensity emission peak at 307 nm wavelength when excited by UV light of wavelength 278 nm. An unresolved peak of comparatively less intensity was also observed at 357 nm along with the main peak. The characteristic emission of dopant Ce in Na₃Ca₂(SO₄)₃F phosphor clearly indicated that it resides in the host lattice in trivalent form. The emission peak can be attributed to 5d → 4f transition of rare earth Ce³⁺. The prepared sample is also characterized for its thermoluminescence properties. The TL glow curve of prepared sample showed a single broad peak at 147°C. The trapping parameters are also evaluated by Chen's method. The values of trap depth (E) and frequency factor (s) were found to be 0.64 ± 0.002 eV and 1.43 × 10⁷ s^–1 respectively. The study of PL and TL along with evaluation of trapping parameters has been undertaken and discussed for the first time. Copyright © 2014 John Wiley & Sons, Ltd.     

Mind the gap: non‐biological processes contributing to soil CO2 efflux

Widespread recognition of the importance of soil CO₂ efflux as a major source of CO₂ to the atmosphere has led to active research. A large soil respiration database and recent reviews have compiled data, methods, and current challenges. This study highlights some deficiencies for a proper understanding of soil CO₂ efflux focusing on processes of soil CO₂ production and transport that have not received enough attention in the current soil respiration literature. It has mostly been assumed that soil CO₂ efflux is the result of biological processes (i.e. soil respiration), but recent studies demonstrate that pedochemical and geological processes, such as geothermal and volcanic CO₂ degassing, are potentially important in some areas. Besides the microbial decomposition of litter, solar radiation is responsible for photodegradation or photochemical degradation of litter. Diffusion is considered to be the main mechanism of CO₂ transport in the soil, but changes in atmospheric pressure and thermal convection may also be important mechanisms driving soil CO₂ efflux greater than diffusion under certain conditions. Lateral fluxes of carbon as dissolved organic and inorganic carbon occur and may cause an underestimation of soil CO₂ efflux. Traditionally soil CO₂ efflux has been measured with accumulation chambers assuming that the main transport mechanism is diffusion. New techniques are available such as improved automated chambers, CO₂ concentration profiles and isotopic techniques that may help to elucidate the sources of carbon from soils. We need to develop specific and standardized methods for different CO₂ sources to quantify this flux on a global scale. Biogeochemical models should include biological and non‐biological CO₂ production processes before we can predict the response of soil CO₂ efflux to climate change. Improving our understanding of the processes involved in soil CO₂ efflux should be a research priority given the importance of this flux in the global carbon budget.     

Dual‐Confined Flexible Sulfur Cathodes Encapsulated in Nitrogen‐Doped Double‐Shelled Hollow Carbon Spheres and Wrapped with Graphene for Li–S Batteries

Batteries with high energy and power densities along with long cycle life and acceptable safety at an affordable cost are critical for large‐scale applications such as electric vehicles and smart grids, but is challenging. Lithium–sulfur (Li‐S) batteries are attractive in this regard due to their high energy density and the abundance of sulfur, but several hurdles such as poor cycle life and inferior sulfur utilization need to be overcome for them to be commercially viable. Li–S cells with high capacity and long cycle life with a dual‐confined flexible cathode configuration by encapsulating sulfur in nitrogen‐doped double‐shelled hollow carbon spheres followed by graphene wrapping are presented here. Sulfur/polysulfides are effectively immobilized in the cathode through physical confinement by the hollow spheres with porous shells and graphene wrapping as well as chemical binding between heteronitrogen atoms and polysulfides. This rationally designed free‐standing nanostructured sulfur cathode provides a well‐built 3D carbon conductive network without requiring binders, enabling a high initial discharge capacity of 1360 mA h g^?1 at a current rate of C/5, excellent rate capability of 600 mA h g^?1 at 2 C rate, and sustainable cycling stability for 200 cycles with nearly 100% Coulombic efficiency, suggesting its great promise for advanced Li–S batteries.     

口源性口臭指示菌的筛选

目的从口源性口臭(Oral Malodor)相关菌种中筛选主要代表菌,用以建立口臭细菌学(Oral Bacteri-ology)临床辅助诊断的指示菌(Indicator bacteria)。方法用感官检测(鼻闻法)(Organoleptic test)、气相色谱(Gas Chromatography)、硫化物检测仪(Halimeter)和硫化氢检测仪(Easicult S)等4种方法,在实验室检测常见的8种牙周及龋病致病菌,通过检测鼻闻臭味程度、硫化物(Volatile sulfur compounds,VSCs)、硫化氢(Hydrogen sulfide,H2S)及有异味的短链脂肪酸(Short Chain Fatlf acid)含量来确定指示菌。结果鼻闻:牙龈卟啉单胞菌(P.gingivalis,P.g)、中间普雷沃菌(P.intermedius,P.i)和具核梭杆菌具核梭亚种(F.subsp nucleatum,F.n)恶臭明显,其他菌有微臭或无味。气相色谱检测:P.g、P.i、F.n和伴放线聚生杆菌(Aggregatibscter actinomycetemcomitans,A.a)中有异味的丁酸(Butyric acid)含量在40%～66%,其他菌,其他产物含量较低。硫化物检测:P.g、P.i和F.n的VSCs量在1 000ppb以上,硫化氢检测:P.g、P.i和F.n的H2S在600 ppb以上,其他菌两项检测均在36 ppb以下。结论 P.g、P.i和F,n是主要产臭菌种,可作为临床口臭的细菌学辅助诊断的指示菌,供临床进一步研究。     

芥子气暴露的确证：家兔皮肤染毒后血红蛋白N端缬氨酸加合物的同位素稀释-NCI-GC/MS溯源性检测

素有＂毒剂之王＂之称的芥子气（HD）是目前危害最大的化学战剂之一,染毒后在体内可产生不同类型的特征性生物标志物,其对中毒诊断、溯源性分析以及毒理机制等研究有着重要的意义.本文首先采用同位素稀释-NCI-GC/MS分析方法监测和鉴定了HD体外全血染毒后产生的血红蛋白N端缬氨酸加合物（HETE-Val）;其次,研究了不同剂量HD（0.02～0.15LD50）经皮染毒家兔体内HETE-Val的时效、量效关系.结果表明,HETE-Val与家兔中毒剂量间有良好的量效关系,而时效关系表明染毒后15min内即可产生并检测到HETE-Val,一周内达到最大,随后逐渐下降,但至染毒后第103天仍可监测到该加合物.与血红蛋白N端缬氨酸加合反应的HD仅占HD染毒总量的～0.15‰,与家兔血液反应的HD约占HD染毒总量的～1%.表明HETE-Val是一种重要的生物标志物,并可应用于HD暴露的确证和化学武器核查的溯源性检测.     

Polymorphic Variants of Human Rhodanese Exhibit Differences in Thermal Stability and Sulfur Transfer Kinetics

Rhodanese is a component of the mitochondrial H₂S oxidation pathway. Rhodanese catalyzes the transfer of sulfane sulfur from glutathione persulfide (GSSH) to sulfite generating thiosulfate and from thiosulfate to cyanide generating thiocyanate. Two polymorphic variations have been identified in the rhodanese coding sequence in the French Caucasian population. The first, 306A→C, has an allelic frequency of 1% and results in an E102D substitution in the encoded protein. The second polymorphism, 853C→G, has an allelic frequency of 5% and leads to a P285A substitution. In this study, we have examined differences in the stability between wild-type rhodanese and the E102D and P285A variants and in the kinetics of the sulfur transfer reactions. The Asp-102 and Ala-285 variants are more stable than wild-type rhodanese and exhibit k_cat/K_m,CN values that are 17- and 1.6-fold higher, respectively. All three rhodanese forms preferentially catalyze sulfur transfer from GSSH to sulfite, generating thiosulfate and glutathione. The k_cat/K_m,sulfite values for the variants in the sulfur transfer reaction from GSSH to sulfite were 1.6- (Asp-102) and 4-fold (Ala-285) lower than for wild-type rhodanese, whereas the k_cat/K_m,GSSH values were similar for all three enzymes. Thiosulfate-dependent H₂S production in murine liver lysate is low, consistent with a role for rhodanese in sulfide oxidation. Our studies show that polymorphic variations that are distant from the active site differentially modulate the sulfurtransferase activity of human rhodanese to cyanide versus sulfite and might be important in differences in susceptibility to diseases where rhodanese dysfunction has been implicated, e.g. inflammatory bowel diseases.     

一株高含玫红品的红树林海洋紫色硫细菌分离鉴定及特性

摘要:【目的】挖掘我国海洋紫色硫细菌物种资源、深入理解紫色硫细菌在红树林生态系统中的作用。【方法】采用琼脂振荡稀释法、显微技术、紫外可见吸收光谱法、TLC、HPLC 和MS 法。【结果】从福建泉州洛阳桥红树林潮间带泥水样分离获得一株细胞内含多个硫粒的细菌菌株,光合内膜呈囊状、含细菌叶绿素a 和螺菌黄质系类胡萝卜素,结合16S rRNA 基因序列分析和系统发育分析,表明该菌株属于海洋着色菌属(Marichromatium)。该菌株细胞球杆状;最适pH 范围5.7－6.7;最适盐度范围2%－3.5%;温度范围20℃ －35℃;能耐受3.6 mmol/L 硫化物;主要积累玫红品类胡萝卜素,而不是螺菌黄质;3 种细菌叶绿素组分中,一种为BChl aP,另2 种未见报道;不需要生长因子;可光同化固定CO2、能很好利用多种有机酸盐、多价态氮化物和硫化物,尤其能利用柠檬酸、葡萄糖、蔗糖、果糖和丙醇;对氯霉素、头孢唑林、苯、对羟基联苯、恩诺沙星、啶虫脒、HgCl2 和CdCl2的IC50 值分别为70、100、20、20、3、170、5 mg /L和25 mg/L。【结论】该菌株是一株轻度耐酸、高含玫红品类胡萝卜素的紫色硫细菌,被鉴定为Marichromatium gracile 新菌株,编号YL28。该菌株具有广泛利用多种碳源、氮源和硫源物质的能力,对抗生素氯霉素和头孢唑啉、农药啶虫脒、重金属汞和镉具有较强耐受性,对抗生素恩诺沙星较敏感。