Ab initio predictions of structural and elastic properties of struvite: contribution to urinary stone research

In the present work, we carried out density functional calculations of struvite – the main component of the so-called infectious urinary stones – to study its structural and elastic properties. Using a local density approximation and a generalised gradient approximation, we calculated the equilibrium structural parameters and elastic constants C _ijkl . At present, there is no experimental data for these elastic constants C _ijkl for comparison. Besides the elastic constants, we also present the calculated macroscopic mechanical parameters, namely the bulk modulus (K), the shear modulus (G) and Young's modulus (E). The values of these moduli are found to be in good agreement with available experimental data. Our results imply that the mechanical stability of struvite is limited by the shear modulus, G. The study also explores the energy-band structure to understand the obtained values of the elastic constants.     

基于SRAP分析的梨授粉品种亲缘关系对砀山酥梨石细胞含量的影响

利用SRAP分子标记,从88对引物中筛选出34对引物组合,分析砀山酥梨母本与授粉品种之间的亲缘关系,探讨梨授粉品种亲缘关系对砀山酥梨石细胞含量的影响。结果表明:授粉品种紫酥、鸭梨和马蹄黄与砀山酥梨亲缘关系较远,授粉品种华山、幸水和圆黄与砀山酥梨亲缘关系较近;砀山酥梨自然授粉果实石细胞含量为0.61%;选用紫酥、鸭梨和马蹄黄作授粉树时,果实石细胞含量分别为0.34%、0.33%、0.36%,低于自然授粉的砀山酥梨;选用华山、幸水和圆黄作授粉树时,果实石细胞含量分别为0.84%、0.70%、0.66%,高于自然授粉的砀山酥梨。选用与砀山酥梨亲缘关系较远的梨品种作授粉树可减少砀山酥梨石细胞含量,改善口感     

不同基因型梨木质素代谢对石细胞含量和果实口感的影响

以五种基因型梨果实为材料,对石细胞团的大小、分布进行解剖学观察,并测定石细胞、木质素含量和木质素相关合成酶PAL、POD、PPO活性,探讨不同基因型梨果实木质素代谢对石细胞含量及口感的影响.结果表明,不同基因型梨木质素含量高时,石细胞含量也高,石细胞团相对较大,分布较密集,口感差.各基因型的梨木质素、石细胞含量和大小为...     

The influence of steam cleaning procedures on the surface roughness of commonly used type III dental stone for the fabrication of removable dentures

doi: 10.1111/j.1741‐2358.2012.00669.x The influence of steam cleaning procedures on the surface roughness of commonly used type III dental stone for the fabrication of removable dentures Objective: This study investigated the possible detrimental effects of steam treatment on the surface of type III dental stone, which is a common laboratory material used for the construction of removable dentures. Material and Methods: Forty dental stone specimens were prepared and divided into four groups (A, B, C and D), and group A was used as the control group. The other groups were treated with steam from a standard distance for varying durations (30, 60 and 120 s). Results: The duration of steam cleaning significantly increased Ra values (F = 63.150, p = 0.000). Similarly, the duration of steam application was directly correlated with the weight changes (F = 17.721, p = 0.000). A significant amount of dental stone can be removed from the surface while treating with steam. Conclusion: These studies demonstrated that expanded periods of steam cleaning cause weight loss and abrade the surface of type III dental stones; therefore, these devices should be used with caution during denture fabrication procedures.     

Importance of subaerial biofilms and airborne microflora in the deterioration of stonework: a molecular study

The study characterized the sessile microbial communities on mortar and stone in Milan University's Richini's Courtyard and investigated the relationship between airborne and surface-associated microbial communities. Active colonization was found in three locations: green and black patinas were present on mortar and black spots on stone. Confocal laser scanning microscopy, scanning electron microscopy and culture-independent molecular methods revealed that the biofilm causing deterioration was dominated by green algae and black fungi. The mortar used for restoration contained acrylic and siloxane resins that could be used by microorganisms as carbon and energy sources thereby causing proliferation of the biofilm. Epifluorescence microscopy and culture-based methods highlighted a variety of airborne microflora. Bacterial and fungal counts were quantitatively similar to those reported in other investigations of urban areas, the exception being fungi during summer (1–2 orders of magnitude higher). For the first time in the cultural heritage field, culture-independent molecular methods were used to resolve the structure of airborne communities near discoloured surfaces, and to investigate the relationship between such communities and surface-associated biofilms.     

The Paleolithic in the Nihewan Basin,China: Evolutionary history of an Early to Late Pleistocene record in Eastern Asia

The Nihewan Basin of China preserves one of the most important successions of Paleolithic archeological sites in Eurasia. Stratified archeological sites and mammalian fossils, first reported in the 1920s, continue to be recovered in large‐scale excavation projects. Here, we review key findings from archeological excavations in the Nihewan Basin ranging from ~1.66 Ma to 11.7 ka. We place particular emphasis on changes in stone tool technology over the long term. Though Pleistocene lithic industries from East Asia are often described as simple in character, re‐evaluation of the stone tool evidence from the Nihewan Basin demonstrates significant, though periodic, innovations and variability in manufacturing techniques through time, indicating adaptive and technological flexibility on the part of hominins. Synthesis of paleoenvironmental and archeological data indicate changes in hominin occupation frequency in the Nihewan Basin, with chronological gaps suggesting that continuous presence in high, seasonal latitudes was not possible prior to the Late Pleistocene.     

西沙石珊瑚共附生放线菌的分离培养及抗菌活性评价

【背景】珊瑚礁生态系统是海洋中一类极其重要的生态系统,健康珊瑚礁中丰富的共附生放线菌群体是珊瑚抵御各种致病菌的重要防线,因此,这类放线菌是寻找抗菌活性分子的重要资源,其药用潜力巨大。【目的】从西沙石珊瑚样品中分离共附生放线菌,并从中筛选具有良好抗菌活性的菌株。【方法】通过稀释涂布法分离珊瑚共附生放线菌,并根据16S rRNA基因序列构建系统发育树进行菌种鉴定;通过平板对峙法对放线菌进行抗菌活性筛选并确定目标菌株;将目标菌株涂布于不同氯化钠浓度的ISP2固体培养基上培养,测试其盐度耐受能力;通过平板对峙法对该菌株发酵产物的热稳定性和光稳定性进行测试;采用NanoPore和Illumina方法完成目标活性放线菌全基因组测序,并通过antiSMASH在线分析预测其次级代谢产物生物合成基因簇及其结构类型。【结果】从6份西沙石珊瑚样品中分离得到104株可培养放线菌,根据菌落形态和分离来源去重后对其中27株放线菌进行16S rRNA基因序列测序,通过序列比对和系统发育树分析将菌株初步鉴定为盐孢菌属(Salinispora)(25株)、链霉菌属(Streptomyces)(1株)和戈登菌属(Gord...     

植物乳酸杆菌对小鼠草酸钙结石的干预效果

【背景】草酸钙结石是一种临床常见且易复发的疾病,由于结石质地坚硬,只能通过外科手术的方法治疗,给患者带了很大的痛苦。已有研究证实,肠道菌群可影响草酸钙结石的形成,降低草酸钙结石的发病率。【目的】探究植物乳杆菌对小鼠草酸钙结石的干预效果。【方法】体外实验：在MRS培养基中加入0.02 mol/L草酸钠,制备菌株筛选培养基（MRS-OX）。接种200μL的3.48×10¹²CFU/L植物乳杆菌悬液至MRS-OX制备含菌培养基（B+MRS-OX）。将等体积MRS-OX和B+MRS-OX于37°C恒温培养2 d,测剩余草酸浓度。体内实验：以10周龄雄性昆明小鼠为实验动物,随机分为对照组、植物乳杆菌组、结石组和植物乳杆菌干预组,每组5只小鼠。通过乙醛酸诱导小鼠建立草酸钙结石模型,并给予200μL的3.48×10¹²CFU/L植物乳杆菌进行干预治疗以观察其预防小鼠草酸钙结石的效果。实验结束后,绘制各组小鼠平均体重变化趋势图并计算小鼠肾脏脏器指数,检测每只小鼠血液学指标和氧化应激指标总超氧化物歧化酶（superoxide dismutase,SOD）和丙二...     

河南淅川坑南遗址调查发现的石制品

河南淅川坑南遗址位于丹江口库区,丹江口库区是近年来旧石器考古发掘和研究的重点地区。2016年对坑南遗址发掘前,在周边调查发现旧石器时代石制品209件,石制品类型包括石核、石片、石叶和石器等。剥片方法有锤击法和砸击法。石器毛坯类型多为片状,少量为块状、砾石。石器修理方式以正向为主,其次为反向和复向。初步判断其时代最早能到旧石器时代中期。新发现对于探讨晚更新世南北旧石器过渡地带的特点,具有重要意义。     

库尔勒香梨果实石细胞发育及其对果实肉质影响初探

采用植物解剖学方法对库尔勒香梨果实石细胞形成过程和分布状况进行观察研究,结果表明,库尔勒香梨果实中石细胞从化后15d开始形成,随着时间的推移石细胞的直径和密度逐渐增大,花后110d左右直径达到最大值,花后50d左右密度达到高峰．之后随着果实的增大与成熟度的提高,石细胞团的密度表现下降的趋势。石细胞的分布特点是石细胞团以近果心和近果皮处分布密度高,直径大,中层果肉中石细胞团密度低,直径小。与其它品种相比,成熟库尔勒香梨的行细胞团密度最低,含有较大石细胞的含量相对较少,肉质较细。