Influence of Bacillus subtilis on the growth of calcium oxalate

The influence of the bacteria Bacillus subtilis (B. subtilis) on the nucleation, growth and aggregation of calcium oxalate (CaOx) crystals in aqueous solution has been studied. The crystals obtained were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and X‐ray powder diffractometry. The results show that, in the presence of B. subtilis, quasi‐hexagonal calcium oxalate monohydrate (COM) crystals are obtained after 24 hours of reaction at a temperature of 30°C ± 1K. However, without the presence of the bacteria, irregular CaOx crystals were obtained which contain two crystal phases: COM and calcium oxalate dihydrate (COD). This suggests that B. subtilis may promote the crystallization of COM, the major component of urinary stone. The formation mechanism of CaOx crystals in the presence of B. subtilis is explored, indicating that the cell walls and extracellular proteins of the bacteria may act as templates to induce the nucleation, growth and aggregation of CaOx crystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

不同晶相草酸钙晶体的选区电子衍射和X射线衍射比较分析

在卵磷脂-水脂质体中制备了一水草酸钙(COM)、二水草酸钙(COD)和三水草酸钙(COT).并对它们分别进行了透射电镜(TEM)、选区电子衍射分析(SAED)和X射线衍射(XRD)分析.TEM结果表明,COM、COD和COT均为泡状,粒径约80～150nm.将SAED结果与XRD结果对比分析,发现将SAED图谱指标化后所得的衍射数据与XRD的特征峰值基本相符,但在相对强度上存在差别.本实验结果表明,将TEM、SAED和XRD技术联合分析纳米级草酸钙晶体,不但可以观察纳米级草酸钙的形貌,而且能对其晶相、单晶和多晶等进行深入的了解.     

A study of primary nucleation of calcium oxalate monohydrate: I‐Effect of supersaturation

There are various organic and inorganic constituents in kidney stones. Among them, calcium oxalate monohydrate (COM) is the primary inorganic constituent of kidney stones. However, the mechanisms of formation of kidney stones are not well understood. In this regard, a basic study is carried out for better understanding of nucleation, crystal growth and/or aggregation of formed COM crystals. The primary nucleation of calcium oxalate monohydrate is studied at the laboratory scale using turbidity measurements. Calcium chloride and potassium oxalate solutions are mixed and then added to a Turbidimeter tube for continuous recording of turbidity. Induction time (time to induce formation of detectable crystals) is estimated from time‐turbidity graphs. The effect of some urinary species, such as oxalate and calcium, on nucleation and crystallization characteristics of COM is determined by particle size distribution analysis, measuring weight of crystals and calculation of relative supersaturation. The classical nucleation theory is applied at high supersaturation ratios (SR) ranging from 1.6 to 2.2. The results indicate that nucleation rate increases with increasing supersaturation ratio from 0.81 × 10²⁸ nuclei/cm³.sec at 1.6 SR, to 18.02 × 10²⁸ nuclei/cm³.sec at 2.2 SR. On the other hand, free energy change and radius of critical nucleus are decreased as supersaturation ratio is increased. The nucleation rates are higher than those reported in literature. Such discrepancy is discussed on the bases of differences in experimental techniques. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A study of primary nucleation of calcium oxalate monohydrate: II. Effect of urinary species

Kidney stones consist of various organic and inorganic compounds. Calcium oxalate monohydrate (COM) is the main inorganic constituent of kidney stones. However, the mechanisms for the formation of calcium oxalate kidney stones are not well understood. In this regard, there are several hypotheses including nucleation, crystal growth and/or aggregation of formed COM crystals. The effect of some urinary species such as oxalate, calcium, citrate, and protein on nucleation and crystallization characteristics of COM is determined by measuring the weight of formed crystals and their size distributions under different chemical conditions, which simulate the urinary environment. Statistical experimental designs are used to determine the interaction effects among various factors. The data clearly show that oxalate and calcium promote nucleation and crystallization of COM. This is attributed to formation of a thermodynamically stable calcium oxalate monohydrate resulting from supersaturation. Citrate, however, inhibits nucleation and further crystal growth. These results are explained on the basis of the high affinity of citrate to combine with calcium to form soluble calcium citrate complexes. Thus, citrate competes with oxalate ion for binding to calcium cations. These conditions decrease the amount of free calcium ions available to form calcium oxalate crystals. In case of protein (mucin), however, the results suggest that no significant effect could be measured of mucin on nucleation and crystal growth. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth of calcium oxalate induced by the extracts of Semen Plantaginis and Folium Pyrrosiae

The crystallization of calcium oxalate (CaOxa) in aqueous solutions of the extracts of Semen Plantaginis and Folium Pyrrosiae has been investigated, focusing on the inhibition mechanism of some herbs on stone formation. It has been shown that in the presence of extracts of above two herbs, calcium oxalate dihydrate (COD) crystals with typical morphologies of tetragonal bipyramids were obtained. This suggests that the extracts of Semen Plantaginis and Folium Pyrrosiae can promote the formation of thermodynamically unstable COD, and inhibit the formation of calcium oxalate monohydrate (COM), a major component of urinary stone. The formation mechanism of COD crystals induced by Semen Plantaginis and Folium Pyrrosiae is also discussed, indicating that the bioorganic molecules in the extracts of the herbs can induce the nucleation and growth of COD crystals. This study can help us make clear the inhibition mechanism of some herbs on stone formation that is in favor of the prevention and treatment of urolithiasis. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Controlled deposition and transformation of amorphous calcium carbonate thin films

Controlled synthesis of amorphous calcium carbonate (ACC) films was realized by using the multiple templates, which are composed of a self‐assembled film (SAF, insoluble Poly (ε‐caprolactone) film) and a soluble modifier (poly allylamine), as modifiers. The formation of self‐assembled film was analyzed by monitoring the morphologies using atomic force microscopy. Even more noteworthy, using anhydrous ethanol as media, the ACC‐to‐vaterite‐to‐calcite transformation was also investigated, and the obtained products were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction. The results demonstrated that organic solvent has profound influence on transformation of amorphous calcium carbonate thin films. In the air of anhydrous ethanol, the controlled synthesis of calcium carbonate films with different morphologies, such as planar films with a few sporadic particles, symmetric rhombohedral crystals, novel crystals with symmetrical terraced convexity formation of calcite, was obtained by the fine‐tuning of induction time. It provides a new and simple method to prepare polymorphic CaCO₃ crystal films from the ACC films by controlling the crystallization process (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

柠檬酸钾对尿石患者和正常人尿液凝胶中草酸钙晶体生长的影响

采用扫描电子显微镜(SEM)和X射线衍射(XRD)方法,比较研究了防石药物柠檬酸钾(K3cit)在尿石患者尿液和正常人尿液制备的凝胶中对草酸钙(CaOxa)晶体生长的影响.没有加入K3cit时,CaOxa晶体均以一水草酸钙(COM)为主要晶相,加入K3cit后,不但COM晶体变得圆钝,比表面积减小,而且诱导了二水草酸钙(COD)生成.随着K3cit浓度从0.10增加到0.20 mol/L,在正常人尿液凝胶中COD晶体的百分含量从20;增加到45;,而在CaOxa结石患者尿液凝胶中,不但COD含量从10;增加到25;,而且K3cit可诱导草酸钙成核,从而产生大量的小尺寸草酸钙晶体,这有利于阻止草酸钙晶体变大形成尿石.本结果可为临床上治疗CaOxa结石提供启示.     

Influence of essential and non‐essential amino acids on calcium oxalate crystallization

The investigation on the mechanism of nucleation and growth of crystals at organic‐inorganic interfaces is crucial for understanding biological and physiological calcification processes such as the formation of urinary stones. The effects of five different amino acids on the crystallization of calcium oxalate have been investigated at pH 4.5 and 37 °C in aqueous solutions in the batch type crystallizer. The products were characterized by Scanning Electron Microscopy (SEM), Fourier Transfer Infrared Spectroscopy (FT/IR) and X‐Ray diffraction (XRD) analysis. Crystal size distribution (CSD) and filtration rate measurements were done. In order to determine the adsorption characteristics of amino acids on the calcium oxalate crystal surfaces, zeta potential measurements were also done and discussed. The results indicate that in the presence of all investigated amino acids, calcium oxalate monohydrate (COM) crystals were preferentially produced, but the crystal morphology varied with amino acid types and concentrations. Various crystal morphologies such as elongated hexagonal, coffin or platy habits were observed. In the presence of all investigated amino acids, the calcium oxalate crystallized in a monohydrate form. Electrostatic/ionic interaction, different adsorption properties and special functional effects of amino acids led to find different crystal morphology. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Precipitation of Alkaline-Earth Metal Oxalate Powders from Aqueous Solution. Crystal Numbers and Final Sizes

The precipitation magnesium oxalate dihydrate, calcium oxalate monohydrate, strontium oxalate monohydrate and barium oxalate hemihydrate was studied from equivalent solutions of concentrations from 0.001 M to 0.5 M, at pHs from 7 to 6, by optical microscopy and other methods. Crystal growth started after induction periods: the precipitations were heterogeneously nucleated at low supersaturations and homogeneously nucleated at medium to high supersaturations. The crystal form and numbers of the final precipitates depended on the type and number of the nuclei (and crystallites) formed during the induction periods. Crystal numbers at medium to high supersaturation, increased with increasing initial mean metal oxalate concentrations according to the relation, N = N₁c; β was 5 for calcium oxalate precipitations and β was 6 for the other metal oxalate precipitations. The N₁ values increased in the order MgC₂O₄ · 2 H₂O < BaC₂O₄ · 1/2 H₂O < SrC₂O₄ · H₂O < CaC₂O₄ · H₂O. The final crystal lengths, in this supersaturation range, then decreased (from maximum values) with increasing initial concentrations according to the relation, l_fin = l₁/C_MOx^β, where γ was 1.3 to 1.6. For precipitations from solution of any concentration at any pH, smaller crystals were obtained in the precipitates of the metal oxalate of lower solubility.     

Semi-Batch Precipitation of Calcium Oxalate Monohydrate

Calcium oxalate monohydrate (COM) formation on the semi-batch precipitation of CaCl₂ and Na₂C₂O₄ solutions in the stoichiometric ratio carried out at pH = 6 and 37 or 70°C, respectively, was studied. When a certain level of supersaturation in the system is reached, individual COM crystals of a rather uniform size are formed. These crystals then grown and form ‘loose’ agglomerates that later develop into compact and spherical particles. The particle size distribution (PSD) rapidly shifts during early stages of precipitation towards larger sizes as a result of crystal growth and agglomeration. Later the PSD reaches a shape and position on the size axis that remain virtually constant with progressing precipitation. COM agglomerates consisting of mainly intergrown crystals are formed by mechanism of primary and secondary agglomeration. The primary agglomeration can constitute an important factor in urolithiasis.     

海带硫酸多糖防止草酸钙结石形成的体外模拟

采用扫描电子显微镜、X射线衍射法和红外光谱在草酸钙(CaOxa)结石患者尿液中研究了从海带中提取的硫酸多糖(LSPS)的防石作用.结果表明,LSPS可以抑制一水草酸钙(COM)的成核和聚集,并诱导二水草酸钙(COD)晶体形成.随着ESPS浓度从0增加到0.005, 0.02和0.20 mg/ml,COD的百分含量从0分别增加到22;, 55;和100;.这些结果表明LSPS是抑制CaOxa结石形成的一种潜在药物.     

Growth of calcium oxalate monohydrate on uric acid crystals at sustained supersaturation

The effect of uric acid seeds on calcium oxalate formation was studied at pH 4.50 and 37 °C using a system providing constant supersaturation with respect to calcium oxalate and saturated in uric acid. In all cases the only solid‐phase forming was identified as calcium oxalate monohydrate (COM). Kinetic analysis of the initial rates showed that they were proportional with the relative supersaturation with respect to calcium oxalate monohydrate. The linear dependence of the rate of precipitation of COM on uric acid suggested that growth is mediated through a surface diffusion controlled mechanism. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of zinc oxide crystals with different shapes from zincate aqueous solutions stabilized with triethanolamine

ZnO crystals were synthesized from basic aqueous solutions including zincate ions stabilized with triethanolamine (N(C₂H₄OH)₃, teaH₃) by heating at 60°C. The influence of the basicity of the solutions on the morphology of the ZnO crystals was examined. The aqueous solutions were prepared using ZnSO₄·7H₂O, N(CH₃)₄OH (TMAOH), and teaH₃ as a zinc source, a base, and a stabilizer, respectively, at a zinc concentration of 0.2 M at a teaH₃ / Zn molar ratio of 4. Clear solutions were obtained at a molar ratio of TMAOH / Zn ≥ 3.0. When the clear solutions, in which glass or polyester substrates were placed, were heated at 60°C, agglomerates of ZnO crystals were deposited on the substrates in the TMAOH / Zn range from 3.0 to 3.6. With increasing the TMAOH / Zn ratio, the shape of the resulting ZnO crystals changed from a short asymmetric column with a hexagonal flat edge and a rounded one, through a rocket‐like shape formed by intergrowth, to a hexagonal rod. Although no films of ZnO were formed, ZnO crystals with different shapes were synthesized. When the glass substrates pre‐coated with a ZnO thin film by a sol‐gel method were used, highly oriented, dense ZnO films were formed. The films consisted of rod‐like crystals aligned normal to the substrate surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Some results of microscopic and X-ray investigations of calcium carbide

The structure of calcium carbide is investigated using thin sections and ground sections. Depending on chemical and other factors, calcium carbide occurs in three types of structure, which are interpreted as conversion products resulting from a high-temperature structure. The pavement-like structure containing CaC₂-I is present in industrial carbide with a low content of nitrogen. With increasing fraction of lignite high-temperature coke used for carbon supply as a substitute for coal coke in the production of carbide, the particle size decreases, and the micro hardness increases. The interlocked structure with CaC₂-II and higher contents of nitrogen, which has been detected in carbide produced in the laboratory, is extremely dense. No grain sizes can be given. This kind of carbide produced in the laboratory has a lower micro hardness than industrial carbide. The mixed crystal structure is typical of carbide with a high content of sulphur. CaC₂—CaS-I is present as a phase. In all three types, the respective carbide phases have a marked lamellar structure. No typical shapes of crystals can be detected. In consequence of poor crystal formation, the information obtained with a microscope about the phases contained in the material investigated is complemented by X-ray diffraction methods.     

Surface Chemistry of Polyacetylene: Adhesion to Silica,Derivatization With Nickel And Catalytic Activity

Adhesion of (CH)_x film prepared by the Luttinger method to glass can be improved by silylation in order to more closely match dispersive surface energies. Treatment of n-type (CH) films with NiBr₂/HMPA/THF affords (CH)_x -supported N° which shows selectivity in hydrogenation of phenyl acetylene.     

Calcium oxalate crystallization in the presence of amino acids,proteins and carboxylic acids

Reactive crystallization of calcium oxalate was investigated in the presence of amino acids, proteins and carboxylic acids at different pH and temperatures. Average particle size, filtration rates of calcium oxalate crystals obtained in the absence and presence of additives were determined. The influence of pH, temperatures and additives on crystal morphology of calcium oxalate were also investigated and discussed by SEM analysis. TG‐DTA, FT/IR and XRD analysis were carried out for all investigated conditions. Average particle size of calcium oxalate was affected significantly by the additive type and concentration. Variation of crystal morphology depending on type and concentration of the additives affected the filtration characteristics. Majority of calcium oxalate crystals occurred in the form of calcium oxalate monohydrate except those in the presence of tartaric acid. TG‐DTA, FT/IR and XRD analysis proved that calcium oxalate monohydrate and calcium oxalate dihydrate mixtures are formed in the presence of tartaric acid. The effect of all additives on scale formation was also investigated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the dimensions of species participating in the growth of ammonium oxalate monohydrate crystals from viscosity data of concentrated aqueous solutions

The experimental data of the temperature and concentration dependence of viscosity of concentrated aqueous ammonium oxalate solutions are analysed using the hole theory of liquids and Einstein's model of viscosity. Analysis of the data revealed that the dimensions of the species participating in the growth of ammonium oxalate monohydrate crystals are 3‐5 times larger than the dimensions of individual NH₄⁺ and C₂O₄^2‐ ions composing them. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electrochemical Cells Employing (Ch)x -Cathodes In A Nonaqueous Electrolyte

Polyacetylene films have been used as cathodes in electrochemical cells of the type A1/Li/LiC10₄(l…2M) - PC/ (CH)_X/Pt. Their performance characteristics have been measured. The results show that these cells can be cycled 10 to 15 times at deep discharges, over 300 times at shallow discharges and over 1000 times at very light discharges. Due to the instability of the oxidized (CH)_X the charge retention of the cells is poor.     

Effects of calcium salts on thermal characteristics of hydroxypropyl methylcellulose films

Cast films comprising hydroxypropyl methylcellulose (HPMC) and calcium chloride (CaCl₂) have higher flexibility than those with HPMC and calcium lactate pentahydrate (CLP). The aim of the present study was to investigate the relationship between the molecular behaviour and the film flexibility of HPMC cast films. In differential scanning calorimetry (DSC) measurements, the HPMC-only cast films exhibited a glass transition temperature (Tg) of 142.1-143.9 °C, which is similar that of HPMC/CLP cast films. In contrast, HPMC/CaCl₂ cast films exhibited Tg of 76.1-77.3 °C, which is lower than that of HPMC-only and HPMC/CLP films. Thermal mechanical analysis (TMA) results indicated that the HPMC-only and HPMC/CLP cast films contracted strongly around the Tg calculated using DSC. In contrast, the cast films comprising HPMC/CaCl₂ blends gradually contracted as the temperature increased; this behaviour is significantly different from that observed in the HPMC-only and HPMC/CLP films. The most probable mechanism for the film flexibility of HPMC/calcium salt blends was clarified through attenuated total reflection Fourier transform-infrared (ATR FT-IR) and thermogravimetric (TG) analysis. The analysis results suggest that the difference in the flexibility of the cast films in the presence of CaCl₂ or CLP depends on the difference affinity between calcium salts and water molecules.     

Growth aspects of barium oxalate monohydrate single crystals in gel medium

Single crystals of barium oxalate monohydrate (BaC₂O₄.H₂O, BOM) were grown in pure form by controlled diffusion of Ba²⁺ using the gel technique at different temperatures. Starting from aqueous Ba²⁺ chloride (BaCl₂) and acetic acid (C₂H₂O₄) in gel, this method offers a low‐cost and an easiest alternative to other preparation methods for the production of barium oxalate bulky single crystals. The optimal conditions for the growth of BOM crystals in silica gel were found by investigating different growth parameters such as gel pH, gel aging and crystallization temperature. Irrespective of all such crystallization environments, growth rate of the crystals were initially less and then exhibited supersaturation effect leading to non‐linearity. Gel aging and temperature has profound effect on nucleation density that resulted less number of crystals of maximum size in the gel matrix. Perfect single crystals were grown on gels of higher pH. The macropore morphology and porosity was controlled by changing age of the gel. It has been found that temperature has a fabulous effect in controlling the nucleation density by altering the supersaturation conditions for the formation of critical nuclei. The entire growth kinetics informed that the grown crystals were derived by the one dimensional diffusion controlled process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)