Relationship of serum GDF11 levels with bone mineral density and bone turnover markers in postmenopausal Chinese women

Growth differentiation factor 11 （GDF11） is an important circulating factor that regulates aging. However, the role of GDF11 in bone metabolism remains unclear. The present study was undertaken to investigate the relationship between serum GDF11 level, bone mass, and bone turnover markers in postmenopausal Chinese women. Serum GDF11 level, bone turnover biochemical markers, and bone mineral density （BMD） were determined in 169 postmenopausal Chinese women （47-78 years old）. GDF11 serum levels increased with aging. There were negative correlations between GDF11 and BMD at the various skeletal sites. After adjusting for age and body mass index （BMI）, the correlations remained statistically significant. In the multiple linear stepwise regression analysis, age or years since menopause, BMI, GDF11, and estradiol were independent predictors of BMD. A significant negative correlation between GDF11 and bone alkaline phosphatase （BAP） was identified and remained significant after adjusting for age and BMI. No significant correlation was noted between cross-linked N-telopeptides of type I collagen （NTX） and GDF11. In conclusion, GDF11 is an independent negative predictor of BMD and correlates with a biomarker of bone formation, BAP, in postmenopausal Chinese women. GDF11 potentially exerts a negative effect on bone mass by regulating bone formation.

Relationship between the low density lipoprotein receptor gene polymorphism and serum lipid levels in the Guangxi Bai Ku Yao population

Objectives Bai Ku Yao(White-trousers Yaos)is a special branch of Yao minority in China.They are now living in both Lihu and Baxu villages,Nandan County, Guangxi,China.The population size is about 30,000.The special customs and culture of Bai Ku Yao,including their special clothing,intra-ethnic marriages and alcohol intake are still completely conserved to the present day.In previous epidemiologic studies,we found that the serum lipid levels and the prevalence of hyperlipidaemia were lower in Bai Ku Yao than in Han Chinese from the same region.This ethnic difference in serum lipid profiles is still not well known.We hypothesized that there may be significant differences in some genetic polymorphismsssociation of low density lipoprotein receptor (LDL-R) genepolymorphism and several environmental factors with serum lipid levels in the Guangxi Bai Ku Yao and Han populations.Methods A total of 1024 subjects of Bai Ku Yao and 792 participants of Han Chinese were stud- ied by a stratified randomized cluster sampling.Epidemiological survey was carried out using internationally standardized methods.Information on demographics,socioeconomic status, and lifestyle factors was collected with standardized questionnaires. The height,weight,waist circumference,blood pressure, and serum total cholesterol(TC),triglyceride(TG), high-density lipoprotein cholesterol(HDL-C),low-density lipoprotein cholesterol(LDL-C),apolipoprotein(Apo) A1, and ApoB were measured.Body massindex(BMI,kg/m2) was calculated.Genotyping of the LDL-RAvaⅡwas performed by polymerse chain reaction and restriction fragment length polymorphism combined with gel electrophoresis,and then confirmed by direct sequencing.Results(l)The height,weight,serum TC,HDL-C,LDL-C,ApoAl levels and the ratio of ApoAl to ApoB were lower in Bai Ku Yao than in Han Chinese(P【0.01 for all),whereas the percentage of subjects who consumed alcohol or smoked cigarettes was higher in Bai Ku Yao than in Han Chinese(P【0.01 for each).(2) The frequency of A+ allele in Bai Ku Yao was 34.5%,and the frequencies of A-A-,A-A+ and A+A + genotypes were 42.6%,45.9%and 11.5%;respectively. The frequency of A+ allele in Han Chinese was 19.3%(P【0.001),and the frequencies of A-A-,A-A + and A+A+ genotypes were 64.9%,31.6%and 3.5%(P【0.001);respectively. The frequencies of A-A-,A-A+ and A+A+ genotypes in Bai Ku Yao were significant difference between males and females,between normal TC and high TC subgroup, and between normal LDL-C and high LDL-C subgroup (P【0.05 for all),whereas the frequencies of A- and A+ ? alleles in Han Chinese were significant difference between males and females(P【0.05).(3) Serum LDL-C levels in Bai Ku Yao were significant difference among the A-A-, A-A+ and A+A+ genotypes(P【0.05),the A+ carriers had higher serum LDL-C levels.Serum HDL-C levels in Han Chiese were significant difference among the A-A-,A-A + and A+A+ genotypes(P【0.01),the A+ carriers had higher serum HDL-C levels.(4) After adjusting other factors,the prevalence of LDL-C abnormality was still higher in Han Chiese than in Bai Ku Yao.The prevalence of TC abnormality in Han Chinese was almost twice high as in Bai Ku Yao. The age and diet were common risk factor for TC abnormality. No effect of AvaⅡgenotype or alcohol consumption on the TC abnormality was found,but the combination of geno-type and alcohol consumption can increase the prevalence of TC abnormality[Exp(B) =(1.154)].Age was negatively cor- related with TG level.Conclusions Serum TC and LDL-C levels were lower in Bai Ku Yao than in Han Chinese.There were significant differences in the AvaⅡallele and genotype frequencies between the he A+ carriers in Bai Ku Yao had higher serum LDL-C levels,whereas the A+ carriers in Han had higher serum HDL-C levels.Interactions between alcohol consumption or cigarette smoking and the LDL-R AvaⅡgenotype were also observed.The differences in the serum lipid profiles between the two ethnic groups might partly result from different genotypic frequency of LDL-R AvaⅡpolymorphism or differentgene-enviromental interactions.Bai Ku Yao and Han population,the frequency of A + allele was higher in Bai Ku Yao than in Han.T between the two ethnic groups.Therefore,the aim of the present study was to detect the

Solubility study of hydrogen in direct coal liquefaction solvent based on quantitative structure–property relationships model

Direct coal liquefaction(DCL)is an important and effective method of converting coal into high-valueadded chemicals and fuel oil.In DCL,heating the direct coal liquefaction solvent(DCLS)from low to high temperature and pre-hydrogenation of the DCLS are critical steps.Therefore,studying the dissolution of hydrogen in DCLS under liquefaction conditions gains importance.However,it is difficult to precisely determine hydrogen solubility only by experiments,especially under the actual DCL conditions.To address this issue,we developed a prediction model of hydrogen solubility in a single solvent based on the machine-learning quantitative structure–property relationship(ML-QSPR)methods.The results showed that the squared correlation coefficient R^(2)=0.92 and root mean square error RMSE=0.095,indicating the model’s good statistical performance.The external validation of the model also reveals excellent accuracy and predictive ability.Molecular polarization(a)is the main factor affecting the dissolution of hydrogen in DCLS.The hydrogen solubility in acyclic alkanes increases with increasing carbon number.Whereas in polycyclic aromatics,it decreases with increasing ring number,and in hydrogenated aromatics,it increases with hydrogenation degree.This work provides a new reference for the selection and proportioning of DCLS,i.e.,a solvent with higher hydrogen solubility can be added to provide active hydrogen for the reaction and thus reduce the hydrogen pressure.Besides,it brings important insight into the theoretical significance and practical value of the DCL.

基于密度泛函理论研究聚醚类破乳剂的构效关系

油田采出液处理工艺中化学破乳剂的使用能够大大提升工作效率并且节约成本,其中聚醚类破乳剂的应用最为广泛,研究聚醚类破乳剂的构效关系对于新型破乳剂的研发及应用至关重要。本文首先对几种聚醚类破乳剂和反相破乳剂的破乳效果进行了评价和比较,然后根据沥青质分子的结构特点及现有聚醚类破乳剂和反相破乳剂的类型,选取了相应的模型分子,通过密度泛函理论(DFT)中B3LYP/6-31G基组得到其最优分子几何构型和静电势分布图,并利用泛函M062X/6-31G基组计算了聚醚类破乳剂模型分子分别与沥青质模型分子和水分子之间的相互作用能。结合聚醚类破乳剂和反相破乳剂的破乳性能评价结果,进而分析了聚醚类破乳剂的构效关系。结果表明,由理论化学计算结果所推测的破乳剂的破乳性能差异与其实际破乳效果相一致:具有支状结构、聚合度较高的聚醚类破乳剂的效果优于线型结构、聚合度较低的聚醚类破乳剂;酚醛树脂聚醚的破乳效果优于酚胺树脂聚醚,而反相破乳剂中则是多元醇聚醚类反相破乳剂的效果较优。该工作的开展表明采用密度泛函理论进行破乳剂的构效关系研究是可行的,能够为未来新型破乳剂的制备及选用奠定重要的理论基础和提供参考依据。

身体质量指数联合三酰甘油与高密度脂蛋白胆固醇比值预测2型糖尿病风险

目的利用体检指标中身体质量指数(BMI)和三酰甘油与高密度脂蛋白胆固醇比值(triglyceride to high-density lipoprotein cholesterol,TG/HDL-C)联合预测2型糖尿病(type 2 diabetes mellitus,T2DM)发病风险。方法基于瑞慈医疗集团2010—2016年体检人群的数据库,通过Cox比例风险模型观测不同BMI的人群基线TG/HDL-C对随访期间T2DM风险的影响,并分析TG/HDL-C与BMI是否存在交互作用。结果在随访期间,13685例研究对象中共有315例最终诊断为T2DM。以BMI=24 kg/m^(2)为界,将所有研究对象分成两个亚组。BMI<24 kg/m^(2)的亚组共有8238例研究对象,96例在随访结束时患T2DM,对潜在的混杂因素进行调整后,升高的TG/HDL-C导致T2DM事件的风险较高[HR 95%CI=1.47(1.23,1.74),P<0.001]。与最低五分位数(Q1)相比,升高的TG/HDL-C五分位数(Q2~Q5)T2DM发病率增加[HR 95%CI分别为:0.73(0.28,1.93)、2.75(1.29,5.85)、2.81(1.28,6.20)和3.91(1.51,10.11)]。BMI≥24 kg/m^(2)的亚组共有5447例研究对象,219例在随访结束时患T2DM。在两个亚组中,随着TG/HDL-C的增加,T2DM患病风险均呈非线性增加,这一变化在BMI<24 kg/m^(2)的亚组更为明显。绘制两个亚组TG/HDLC与3年和5年T2DM发病的ROC曲线,在BMI<24 kg/m^(2)的亚组中,ROC曲线下面积分别为0.72和0.77。在BMI≥24 kg/m^(2)的亚组中,ROC曲线下面积则分别为0.55和0.57。结论在BMI<24 kg/m^(2)的人群中,TG/HDL-C的升高提示T2DM患病风险显著增加。

Application of PCA and HCA to the Structure-Activity Relationship Study of Fluoroquinolones

Density functional theory （DFT） was used to calculate molecular descriptors （properties） for 12 fluoro-quinolone with anti-S.pneumoniae activity. Principal component analysis （PCA） and hierarchical cluster analysis （HCA） were employed to reduce dimensionality and investigate in which variables should be more effective for classifying fluoroquinolones according to their degree of an-S.pneumoniae activity. The PCA results showed that the variables ELUMO, Q3, Q5, QA, logP, MR, VOL and △EHL of these compounds were responsible for the anti-S.pneumoniae activity. The HCA results were similar to those obtained with PCA.The methodologies of PCA and HCA provide a reliable rule for classifying new fluoroquinolones with antiS.pneumoniae activity. By using the chemometric results, 6 synthetic compounds were analyzed through the PCA and HCA and two of them are proposed as active molecules with anti-S.pneumoniae, which is consistent with the results of clinic experiments.

基于AKNN异常检验与ADPC聚类的低压台区拓扑识别方法

低压台区拓扑信息的准确记录是进行台区线损分析、三相不平衡治理等工作的基础。针对目前拓扑档案排查成本高且效率低的问题,提出一种基于自适应k近邻(adaptive k nearest neighbor,AKNN)异常检验和自适应密度峰值(adaptive density peaks clustering,ADPC)聚类的低压台区拓扑识别方法。该方法利用动态时间弯曲(dynamic time warping,DTW)距离度量低压台区用户间电压序列的相似性,通过AKNN异常检验算法检验并校正异常的用户与变压器之间的关系(简称“户变关系”),在得到正确户变关系的基础上,采用ADPC聚类算法对台区内用户进行相位识别;最后,通过实际台区算例分析验证了该方法不需要人为设置参数,能有效实现低压台区的拓扑识别,具有较高的适用性与准确性。

外周血细胞与骨质疏松症的因果关系

背景:流行病学调查和一些实验表明,外周血细胞和骨质疏松症存在密切关系,但两者在遗传学层面上的因果关系尚不清楚。目的:运用孟德尔随机化探究外周血细胞和骨质疏松症的因果关系。方法:从BCX、MRC-IEU等数据库分别获取外周血细胞、不同年龄段全身骨密度、跟骨骨密度的GWAS数据集,将血细胞作为暴露数据,不同年龄段骨密度及跟骨骨密度作为结局数据,使用逆方差加权法、MR-Egger、加权中值法、加权中位数、简单中位数等方法进行孟德尔随机化分析,使用Cochran’s Q、MR-Egger回归、Leave-one-out法等检验对结果进行异质性、多效性和敏感性评估,用β值评估暴露与结局的因果关系。结果与结论:①因Cochran’s Q结果显示孟德尔随机化结果存在异质性,故研究结果以逆方差加权法结果为标准。逆方差加权结果显示:当不同年龄段骨密度作为结局时,白细胞计数与(45-60岁)全身骨密度呈负向因果关系(β=-0.07,95%CI:-0.13,-0.01,P=0.02),单核细胞计数与(45-60岁)全身骨密度呈正向因果关系(β=0.05,95%CI:0.00,0.10,P=0.037),白细胞计数、嗜碱性粒细胞计数与(>60岁)全身骨密度呈负向因果关系(β=-0.04,95%CI:-0.07,-0.01,P=0.005;β=-0.04,95%CI:-0.07,-0.00,P=0.038),血红蛋白浓度及红细胞压积与(>60岁)全身骨密度呈正向因果关系(β=0.04,95%CI:0.01,0.08,P=0.012;β=0.04,95%CI:0.00,0.07,P=0.039),白细胞计数与(未区分年龄段)全身骨密度呈负向因果关系(β=-0.10,95%CI:-0.16,-0.03,P=0.002);当跟骨骨密度作为结局时,白细胞计数与跟骨骨密度呈负向因果关系(β=-0.04,95%CI:-0.07,-0.01,P=0.016),血红蛋白浓度、红细胞压积与跟骨骨密度呈正向因果关系(β=0.05,95%CI:0.01,0.08,P=0.007;β=0.05,95%CI:0.01,0.08,P=0.004)。②为保证结果稳健性,将外周血细胞与不同年龄段全身骨密度、跟骨骨密度的孟德尔随机化结果进行Meta分析,结果提示对数变换后的白细胞计数每降低一个标准差,会使骨密度降低的风险减少5%(OR=0.95,95%CI:0.94,0.97,P<0.001);血红蛋白浓度、红细胞压积每增加一个标准差,会使骨密度降低风险减少4%(OR=1.04,95%CI:1.03,1.06,P<0.001)。③结果提示:外周血细胞中白细胞计数增加是骨密度的风险因素;红细胞压积、血红蛋白浓度增高是骨密度的保护因素。

他汀类药物与骨密度:一项药物靶向孟德尔随机化分析

背景:观察性研究表明他汀类药物可能对骨密度具有保护作用,这使其成为潜在的骨质疏松症治疗药物之一。目的:通过孟德尔随机化方法来评估药物靶点介导的脂质表型与骨密度之间的因果关系。方法:从IEU Open GWAS数据库获取了与他汀类药物相关的单核苷酸多态性以及骨密度相关数据。主要分析方法是逆方差加权法,同时也使用了加权中位数法、简单中位数法、加权中值方法和MR-Egger回归法。使用β值和95%CI来评估他汀类药物与骨密度之间的因果关系;另外,进行敏感性分析以验证结果的可靠性,使用Cochran’s Q检验来评估异质性,使用MR-Egger截距检验是否存在水平多效性。使用留一法分析确定是否有单个或多个单核苷酸多态性影响了结果。结果与结论:他汀类药物作用靶点——3-羟基-3-甲基戊二酰辅酶A还原酶介导的低密度脂蛋白胆固醇与足跟定量超声骨密度(β=-0.086,95%CI:-0.117至-0.055,P=5.42×10^(-8))和全身骨密度(β=-0.193,95%CI:-0.288至-0.098,P=7.35×10^(-5))呈显著相关。该研究结果支持了他汀类药物对骨密度的保护作用。这些发现不仅加深了对胆固醇相关基因和骨骼健康关系的理解,还揭示了改善骨密度的潜在治疗靶点。

炮口振动特性对自动炮射击精度的影响研究

为研究炮口振动特性对射击精度的影响,以某型自动炮为研究对象,对模型做出合理假设,分析自动炮系统各部件之间的约束关系,基于火炮发射多体动力学理论,考虑身管柔性、机构间隙等因素,建立了自动炮动力学仿真模型;通过火炮水平射击时后坐和复进的后坐力及后坐位移曲线,验证了仿真模型的准确性。对单发和连发射击时的自动炮动力学特性仿真模型进行仿真计算,得到了该自动炮单发及连发射击时的炮口动态特性。根据各发弹丸出炮口瞬间炮口振动特性,初步计算了千米立靶密集度。仿真结果及立靶密集度计算结果对火炮射击精度的提高和结构优化具有一定的参考价值。

锂/钠-氯二次电池的最新进展——从材料构建到性能评估

传统锂离子电池的能量密度已难以满足日益增长的更高能量密度的需求。开发新型高能量密度二次电池是最为有效的一个策略。近期,基于商用一次锂-亚硫酰氯锂电池衍生而来的锂/钠-氯二次电池因其高能量密度而备受关注,成为替代传统锂离子电池的有力竞争者。本文围绕锂/钠-氯二次电池的最新研究进展,综述了正极载体、负极及电解液等关键组分构建研究及其对电化学性能的影响。在正极载体方面,系统阐述了碳材料、共轭框架聚合物等载体设计对锂/钠-氯二次电池首次放电容量、可逆容量、倍率性能和温度的影响;在电解液方面,详细分析了针对反应机理、中间相产物和电解液腐蚀问题的解决策略;并简要介绍了适用于锂/钠-氯二次电池的新型合金负极。基于正极载体的理性设计与电解液系统优化,锂/钠-氯二次电池在新型二次电池领域已初现峥嵘,循环寿命可达500圈,尤其是在极端服役环境中表现优异(可在-80℃工作,电流密度最大可达16 A/g)。然而,氯物种转化动力学速率慢、活性氯物种利用率低以及氯物种对负极等的腐蚀难题仍然是限制其性能进一步提升的瓶颈,也是未来亟待解决的挑战所在。

沉水植物苦草根系功能性状对基质类型和种植密度的响应及其与个体表现关系

根系功能性状体现了植物细根的生长状况及其对外部环境的适应性,然而根系功能性状响应环境变化的时间稳定性如何仍不清楚。苦草(Vallisneria natans)是水体沉水植被修复的先锋种类,细根在其种群重建初期起着重要作用。该研究设计了草垫、草垫+沙子、草垫+黄泥及草垫+底泥4种生长基质和100株/m^(2)以及200株/m^(2)两种种植密度并将其两两组合,以模拟自然生境不同的基质和密度情况,并在不同时期对苦草功能性状指标进行取样测定,通过重复测量二元方差分析研究基质和密度对根系功能指标的影响,并通过线性拟合模型探讨个体水平的生长表现(生物量分配、营养吸收、个体定植)与具体的根系功能性状之间的关系对环境变化的响应。结果表明:所有测量指标均受到基质条件的显著影响,部分根系功能性状指标如根冠比(RSR)、根干重、比根长(SRL)、根比表面积(SRA)、根组织密度(RTD)、根系锚定力和根体积受密度的影响显著。苦草生物量的分配主要受基质条件的影响,对营养的吸收、运输及根系固着能力受基质和密度的共同影响。线性拟合模型表明SRA、RTD、根直径、根表面积以及根体积在个体水平上能一定程度地预测RSR对环境变化的响应,且RTD的预测效果最好;根冠比、SRA、生根数、总根长、根表面积以及根体积在个体水平上能一定程度地预测SRL对环境变化的响应,其中生根数的预测效果最好;SRA、根直径、根表面积以及根体积在个体水平上能一定程度地预测根系锚定力对环境变化的响应,并且SRA的预测效果最好。但是基质和密度在不同时期对苦草根系功能性状的影响方向会发生改变,当用根系功能性状预测植物个体表现时,需要考虑种群重建所处的时期。

糖尿病患者内脏脂肪面积、血清PTH、趋化素的变化及其与骨密度的关系

目的检测糖尿病患者内脏脂肪面积(VFA)、血清甲状旁腺激素(PTH)、趋化素(Chemerin)水平,并分析其与骨密度(BMD)的关系。方法前瞻性选取2021年10月至2023年10月驻马店市中心医院收治的101例糖尿病患者,根据BMD结果分为骨量正常组(n=36)、骨量减少组(n=33)和骨质疏松组(n=32),选取同期骨量正常的健康体检者为对照组(n=35)。比较四组受检者的基线资料、血清指标和不同部位骨骼的BMD,采用Pearson相关检验分析VFA、PTH、Chemerin与糖尿病患者L1~4BMD、股骨颈BMD、Wards三角BMD、全髋BMD的相关性。结果四组受检者在腰围、腰臀比、VFA、空腹血糖(FPG)、糖化血红蛋白(HbAlc)、胰岛素抵抗指数(HOMA-IR)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)、PTH、Chemerin方面比较差异均有统计学意义(P<0.05);四组受检者在L1~4BMD、股骨颈BMD、Wards三角BMD、全髋BMD方面比较差异均有统计学意义(P<0.05);Pearson相关检验分析结果显示,VFA、PTH、Chemerin与糖尿病患者L1~4BMD、股骨颈BMD、Wards三角BMD、全髋BMD均呈明显负相关(P<0.05)。结论糖尿病患者VFA明显增加,血清PTH、Chemerin水平明显上升,且VFA增加及血清PTH、Chemerin水平上升与糖尿病患者发生骨质疏松紧密相关。

社会网络视角下地质灾害应急处置合作关系

为探究我国地质灾害多部门应急协作关系,从某地质灾害多发省搜集省-市-县3级地质灾害应急管理预案。以参与地质灾害应急职能部门为研究对象,基于社会网络分析方法构建省-市-县3级地质灾害应急合作网络模型。运用中心性与迭代相关收敛法(CONCOR)迭代相关矩阵计算得到主题词块矩阵结构,以此划分各级职能部门间子群的结构层次。通过密度矩阵,研究子群内部之间关系模式,分析各级应急部门在地质灾害应急合作网络中的中心性、网络凝聚力及互动关系。结果表明:应急职能部门在地质灾害应急合作中具有不同的互依性和小团体性,合作模式存在协同不均、信息资源堵塞等问题。整个结构中省-市级应急合作关系相对密切,但县级应急合作网络的整体结构和关系模式相对孤立,部分组织结构间联系程度较低。因此,应进一步加强各职能部门之间的相互协同能力,完善县级政府在应急管理中组织结构建设。

肥胖和骨质疏松之间的关联:一项两样本双向孟德尔随机化分析

背景:多项临床研究观察表明肥胖与骨质疏松症之间存在密切关系,但肥胖与骨质疏松症之间是否存在遗传因果效应尚不清楚。目的:利用大规模全基因组关联研究的汇总数据,通过孟德尔随机化分析探究肥胖和骨质疏松之间的关联。方法:肥胖数据来自人体特征遗传调查(GIANT)和英国生物样本库(UKBB)的汇总统计数据。骨质疏松症的数据来自从骨质疏松症遗传因素联盟(GeFOS)获得的2种骨密度表型:全身骨密度和跟骨骨密度。逆方差加权法为主要分析方法,基于Egger回归的孟德尔随机化法(Mendelian randomization method based on Egger regression,MR-Egger)和加权中位数法作为补充方法来计算肥胖遗传变异与骨质疏松症之间的因果关联。采用敏感性分析来验证结果的可靠性,利用Cochran’s Q检验分析结果的异质性,利用MR-Egger截距检验分析结果的水平多效性,留一法评估合并的逆方差加权法估计值是否具有潜在影响的单核苷酸多态性。结果与结论:①肥胖对骨质疏松症的影响:除身体质量指数与前臂骨密度外,身体质量指数、腰臀比、经身体质量指数调整的腰臀比与全身骨密度、跟骨骨密度、前臂骨密度、腰椎骨密度及股骨颈骨密度两两之间呈正向因果关系;进一步Meta分析显示,肥胖会增加骨密度的风险(OR=1.08,95%CI:1.05-1.11,P<0.01);②骨质疏松症对肥胖的影响:除了前臂骨密度、腰椎骨密度作为暴露因素对肥胖有因果关系外,其他数据集均显示全身骨密度、跟骨骨密度、股骨颈骨密度与肥胖之间不呈现因果效应;进一步Meta分析显示,骨密度并不会增加肥胖的风险(OR=0.99,95%CI:0.98-1.01,P<0.01)。③结果证实:肥胖与骨质疏松之间存在因果关系,即肥胖可能是骨质疏松症的危险性因素,但未发现骨质疏松症对于肥胖的因果关联。

生态系统服务供需视角下高密度城区生态空间关键区识别与优化策略研究--以桂林市为例

生态系统服务综合管理是保障城市生态安全和优化国土空间格局的重要途径。城市中心城区生态空间稀缺、生态环境压力大、居民需求多样,面临着生态系统服务供需空间分异大、生态管控复杂的问题。因此,量化城市生态系统服务供给和需求,识别生态供给与居民需求的空间分布差异,是提升生态系统服务供给效率的重要途径,也是支撑城市用地空间进行科学规划管控的关键。以桂林市中心城区为例,利用生态系统服务供需比测度城市水源涵养、降温效益、雨洪调节、碳汇服务、土壤保持、生物多样性保护和游憩服务7项生态系统服务供需水平,并基于聚类分析识别了5类生态系统服务供需簇,耦合供需匹配与失衡区、生态保护区,划定三级生态保护与管控区和两类生态修复与功能提升区。依据分区的生态本底特点、分区内各类服务供需水平等,提出分级分类的管控指引和优化策略,以期为城市生态空间的规划与管理提供参考。

“00后”大学生宿舍人际关系影响因素研究--基于社会网络视角

宿舍人际关系质量影响着大学生的学习生活、身心健康和成长发展。采用社会网络分析的方法,分析“00后”大学生宿舍人际关系的状况及其影响因素。研究发现,“00后”大学生宿舍人际关系状况不太乐观,宿舍成员间的异质性、宿舍规模、性别是影响宿舍人际关系的主要因素。

基于联立方程模型的中国城市公园建设水平与人口密度互动关系分析

现阶段我国人口集聚显著,人绿矛盾尖锐,揭示公园建设水平与人口密度的互动关系对城市高密度化背景下协调二者发展具有重要意义。运用1996—2020年全国时间序列数据,构建联立方程模型,基于全国整体、不同密度类型城市的尺度,探究公园建设水平与人口密度的交互影响特征。研究结果表明:①二者具有非对称的良性互动关系,即人口密度对公园建设水平的促进作用更显著,其作用程度呈“人均公园面积>公园率>公园密度”的特征。②高密度城市二者互动关系显著,对公园建设水平具有较强推动作用;中低密度城市二者互动关系较弱,人均指标存在虚高现象。依据研究结果提出对策建议,以期为贯彻“公园城市”理念提供理论依据。

Effect of N-substituents on performance of thiourea collectors by density functional theory calculations

Using density functional methods,some properties were studied such as the energies and compositions of frontier molecular orbitals and the atomic charges,which are related to the reactive behavior of thioureas containing different N-substituent groupings.The calculation results indicate that the N-substituent groupings have significant effect on the flotation performance of thiourea collectors.The order of electron-donating ability is N-propyl-N'-benzyl-thiourea(PBZYTU)>N-propyl-N'-ethyl-thiourea (PETU)>N-propyl-N'-allyl-thiourea(PALTU)>>N-propyl-N'-acetyl-thiourea(PACTU)>N-propyl-N'-ethoxycarbonyl-thiourea (PECTU)>N-propyl-N'-benzoyl-thiourea(PBZOYTU),and the order of feedback-electron-accepting ability is PBZOYTU> PACTU>PECTU>>PALTU>PETU>PBZYTU.This implies that PBZOYTU,PACTU or PECTU can react with copper atoms having(t2g) 6 (eg) 3Cu(II)or t 6e 4Cu(I)configuration on the surfaces of copper sulfide minerals through normal covalent bond and back donation covalent bond,and exhibit excellently collecting performance for copper sulfide minerals.These are consistent with the experimental data reported in the literatures.

Linear QSAR Regression Models for the Prediction of Bioconcentration Factors of Chloroanilines in Fish by Density Functional Theory

Density functional theory（DFT）-B3LYP level with the 6-311G＊＊（d,p） basis set was used to calculate a set of molecular quantum chemical descriptors of 12 chloroanilines. Quantitative structure-activity relationship（QSAR） models of the bioconcentration factors（BCF） of the anilines in fish were established using some of the following calculated descriptors： EHOMO, ENHOMO, ELUMO, ENLUMO, ΔE1（= ELUMO- EHOMO）, ΔE2（= ENLUMO- ENHOMO）, dipole moment（μ）, molecular volume（V）, vibrational energy of 0 K（Ev）, thermodynamic energy（E）, heat capacity（Cv）, entropy（Sm） and the charge of benzene ring（Qph）. Using the variable selection and leaps-and-bounds regression, the quantum chemical descriptors derived directly from the molecular structures were employed to develop a linear QSAR model between the bioconcentration factors（BCF） and two descriptors（Sm, ENHOMO） of 12 chloroanilines. Statistically, the most significant one is a two-parameter linear equation with the correlation coefficient（R^2） of 0.981 and cross-validated correlation coefficient（Rcv^2） of 0.967. The established QSAR model has good stability and predictability based on the results from Rcv2 of leave-one-out cross-validation, AIC, FIT and tα/2. The quantum chemical analyses were performed from two aspects of frontier molecular orbital and entropy. The results show that two structural describers are crucial to the bioconcentration activity of chloroanilines.