基于结构方程模型的吴起县农业生态经济系统耦合关系

基于2008年吴起县农户调查资料,利用结构方程模型对吴起县农业生态经济系统耦合关系进行了分析.结果表明：具有相关关系的农业资源和产业态势对系统耦合有一定影响,其影响系数分别为0.14和1.00;农业资源与产业态势之间的相关系数为-0.11,说明吴起县的产业发展并非建立在对农业资源有效利用基础之上,农业资源对经济效益的变化没有直接作用;产业的发展主要建立在对农业资源之外的能量和物质的开发利用上,导致产业态势对经济效益的直接路径系数为-2.95,总的路径系数仅为0.23.从农业生态系统与经济系统的关系及其耦合的角度看,目前研究区农业系统建立在不稳定的、较少依赖于本系统资源的耦合态势下,即在农业生态经济系统良性耦合机制的建立与形成过程中潜伏了较大危机.为此,需要提高牧草等农业资源的利用率,发展林草及其相关产业.     

Numerical simulation of thermal bone necrosis during cementation of femoral prostheses

The implant of a femoral prosthesis is a critical process because of the relatively high temperature values reached at the bone/cement interface during the cementation of the infibulum. In fact, the cement is actually a polymer that polymerizes in situ generating heat. Moreover, the conversion of monomer into polymer is never 100%; this is dangerous because of the toxicity of the monomer. In this paper, we present a 3-D axisymmetric mathematical model capable of taking into account both the geometry of the implant and the chemical/physical properties of the cement. This model, together with its numerical simulation, thus represents a useful tool to set up the optimal conditions for the new materials developed in this orthopaedic field. The real complex geometry is assumed to be a bone/cement/metallic system having cylindrical symmetry, thus allowing the model to be reduced to two space variables. The cementation process is described by the Fourier heat equation coupled with a suitable polymerization kinetics. The numerical approximation is accomplished by semi-implicit finite differences in time and finite elements in space with numerical quadrature. The full discrete scheme amounts to solve linear positive definite symmetric systems preceded by an elementwise algebraic computation. We present various numerical simulations which confirm some critical aspects of this orthopaedic fixing technique such as thermal bone necrosis and the presence of unreacted residual monomer.This work was partially supported by MURST (Fondi per la Ricerca Scientifica 40%) and CNR (IAN, Contract 880032601, and Progetto Finalizzato Sistemi Informatici e Calcolo Parallelo, Sottoprogetto Calcolo Scientifico per Grandi Sistemi) of Italy     

Evaluation of Antibacterial Activity of Lavandulapedunculata subsp. atlantica (Braun‐Blanq.) Romo Essential Oil and Selected Terpenoids against Resistant Bacteria Strains–Structure–Activity Relationships

The genus Lavandula is known for its different uses in traditional medicine. This study is interested in the chemical composition of Lavandulapedunculata subsp.atlantica (Braun‐Blanq. ) Romo as well as evaluating its antibacterial potential against multi‐resistant strains. The analysis of Lavandulaatlantica essential oil (LAEO) allows the identification of 47 components representing 93.6 % of all identified. The main constituent of LAEO was camphor (50.4 %), followed by fenchone (14.1 %) and camphene (5.6 %). The antibacterial assays revealed that LAEO was active against all the studied bacteria. A preliminary study of the relationship between certain terpenoids and antibacterial activity was also carried out in order to note the compound(s) that are responsible for LAEO's antibacterial activity. This study showed that the activity of the essential oil may be due to the presence of certain minor compounds such as carvone, considering the presence of the synergistic effect between the essential oil.     

游荡型黄河滩涂植物群落多样性及种间联结性

黄河干流流量季节性变化和小浪底“调水调沙”形成了黄河河南段特殊的游荡型滩涂生态系统,为揭示游荡型黄河滩涂(嫩滩、二滩、高滩和大堤)群落组成和种间关系及群落稳定性规律,于2015年9月至2018年11月,采用典型样方法在郑州黄河湿地自然保护区游荡型黄河滩涂开展群落学调查,利用149个草本层样方分析群落物种组成、多样性、种间联结性和群落稳定性。结果表明：(1)研究区植物共有90科289属445种,其中被子植物87科286属440种,裸子植物2科2属3种;蕨类植物仅见1属2种。(2)不同滩涂生境优势种具有显著差异,且总体狗牙根(Cynodon dactylon)、芦苇(Phragmites australis)和小蓬草(Erigeron canadensis)为优势种,国家二级保护植物野大豆(Glycine soja)呈斑块聚集分布,且为嫩滩和二滩亚优势种。(3)大堤物种多样性各指标取值最大,嫩滩次之,二滩和高滩较小。(4)χ²检验、Jaccard指数、Pearson相关检验和Spearman秩相关检验表明,优势种种对种间联结性不强,各物种间相对独立。(5)二滩总体联结...     

Cyclic biphalin analogues with a novel linker lead to potent agonist activities at mu,delta, and kappa opioid receptors

In an effort to improve biphalin’s potency and efficacy at the µ-(MOR) and δ-opioid receptors (DOR), a series of cyclic biphalin analogues 1–5 with a cystamine or piperazine linker at the C-terminus were designed and synthesized by solution phase synthesis using Boc-chemistry. Interestingly, all of the analogues showed balanced opioid agonist activities at all opioid receptor subtypes due to enhanced κ-opioid receptor (KOR) activity. Our results indicate that C-terminal flexible linkers play an important role in KOR activity compared to that of the other cyclic biphalin analogues with a hydrazine linker. Among them, analogue 5 is a potent (Ki?=?0.27, 0.46, and 0.87?nM; EC₅₀?=?3.47, 1.45, and 13.5?nM at MOR, DOR, and KOR, respectively) opioid agonist with high efficacy. Based on the high potency and efficacy at the three opioid receptor subtypes, the ligand is expected to have a potential synergistic effect on relieving pain and further studies including in vivo tests are worthwhile.     

Hydration, structure, and molecular interactions in the headgroup region of dioleoylphosphatidylcholine bilayers: an electron spin resonance study

The relationship between bilayer hydration and the dynamic structure of headgroups and interbilayer water in multilamellar vesicles is investigated by electron spin resonance methods. Temperature variations of the order parameter of a headgroup spin label DPP-Tempo in DOPC in excess water and partially dehydrated (10 wt % water) show a cusp-like pattern around the main phase transition, Tc. This pattern is similar to those of temperature variations of the quadrupolar splitting of interbilayer D2O in PC and PE bilayers previously measured by 2H NMR, indicating that the ordering of the headgroup and the interbilayer water are correlated. The cusp-like pattern of these and other physical properties around Tc are suggestive of quasicritical fluctuations. Also, an increase (a decrease) in ordering of DPP-Tempo is correlated with water moving out of (into) interbilayer region into (from) the bulk water phase near the freezing point, Tf. Addition of cholesterol lowers Tf, which remains the point of increasing headgroup ordering. Using the small water-soluble spin probe 4-PT, it is shown that the ordering of interbilayer water increases with bilayer dehydration. It is suggested that increased ordering in the interbilayer region, implying a lowering of entropy, will itself lead to further dehydration of the interbilayer region until its lowered pressure resists further flow, i.e., an osmotic phenomenon.     

中国与北美苔藓植物区系关系的探讨

关于中国和北美间苔藓植物区系关系的研究是在20世纪90年代开始的。研究表明中国和北美苔类和藓类的种间关系疏远,这一事实说明两个大陆在第三纪后期分离后,由于地质、地理、气候等因素的差异致使苔藓植物区系成分也产生明显分异。虽然它们在科、属方面差异较小,但两个大陆已各自形成地区特有的苔类和藓类的属。已知的中国特有及东亚特有的苔类属有5个,藓类属有22个;而已知北美地区特有的苔类属有4个、藓类属有5个。北美东部和西部形成于不同地质时期,在苔藓植物方面与中国共同分布的科、属和种存在一定差异。从神农架藓类植物研究表明,从共同分布的种来看,北美东部与中国比北美西部与中国的相似性系数高约6％。从两地区间苔类和藓类植物的雌雄同株或雌雄异株及孢子直径大小而论,这两个因素似乎并不是影响苔藓植物在两大地区间分布的主要原因,但对苔藓植物的分布仍然十分重要。本文作者认为结合中国和北美的地史、地理条件及苔藓植物自身的特点,可以认为白令海峡不是阻碍中国和北美苔藓植物交流的绝对自然屏障;中国和北美苔藓植物区系关系目前的状况,是长期多次交流融合和分异的结果。     

N-Indolylglycosides bearing modifications at the glucose C6-position as sodium-dependent glucose co-transporter 2 inhibitors

Suppression of glucose reabsorption through the inhibition of sodium-dependent glucose co-transporter 2 (SGLT2) is a promising therapeutic approach for the treatment of type 2 diabetes. To investigate the effect of C6-substitution on inhibition of SGLT2 by N-indolylglucosides, a small library of 6-triazole, 6-amide, 6-urea, and 6-thiourea N-indolylglycosides were synthesized and tested. A detailed structure–activity relationship (SAR) study culminated in the identification of 6-amide derivatives 6a and 6o as potent SGLT2 inhibitors, which were further tested for inhibitory activity against SGLT1. The data obtained indicated that 6a and 6o are mildly to moderately selective for SGLT2 over SGLT1. Both compounds were also evaluated in a urinary glucose excretion test and pharmacokinetic study; 6a was found capable of inducing urinary glucose excretion in normal SD rats.     

Aromatic phosphonates inhibit the lysophospholipase D activity of autotaxin

Autotaxin (ATX) is an attractive target for the anticancer therapeutics that inhibits angiogenesis, invasion and migration. ATX is an extracellular lysophospholipase D that hydrolyzes lysophosphatidylcholine to form the bioactive lipid lysophosphatidic acid. The aromatic phosphonate S32826 was the first described nanomolar inhibitor of ATX. However, the tridecylamide substituent on aromatic ring contributed to its poor solubility and bioavailability, severely limiting its utility in vivo. c Log P calculations revealed that the lipophilicity of S32826 could be lowered by shortening its hydrophobic chain and by introducing substituents alpha to the phosphonate. Herein, we describe the synthesis of a small set of α-substituted phosphonate analogs of S32826, and we show that shortening the chain and adding α-halo or α-hydroxy substituents increased solubility; however, ATX inhibition was reduced by most substitutions. An optimal compound was identified for examination of biological effects of ATX inhibition in vivo.     

长喙毛茛泽泻的种群分布格局和群落内种间关联

长喙毛茛泽泻茶陵种群呈斑块分布,格局类型为聚集分布型,每个亚种群也呈聚集分布,但聚集强度不同。长喙毛茛泽泻与其几个主要伴生种的相关性经测定结果是：与莼菜及黄花狸藻之间的相关性不显著;与柳叶箬、双穗雀稗及石龙尾之间正相关显著;与疏勿蓼之间负相关显著,长喙毛茛泽泻种子近距离传播以及无性繁殖特性是造成其聚集分布的主要原因。柳叶箬、双穗雀稗和石龙尾对长喙毛茛泽泻具有极强的竞争作用。