Polymorphs and hydrates of Etoricoxib, a selective COX-2 inhibitor

The crystal structures of two polymorphs and two polymorphic hemihydrates of Etoricoxib are reported. Etoricoxib is a non-steroidal anti-inflammatory drug (NSAID) that is a selective inhibitor of COX-2. It is used in the treatment of various types of inflammation, pain and fever. Clas et al. have reported four polymorphs (labeled I through IV) and two solvates (hemi-and sesquihydrate) of the API in US patent 6,441,002 (Clas et al, US patent 6,441,002, 2002). However, no crystal structures have been reported for any of these forms. A comparison was made between the PXRD patterns reported in patent `002 and the powder spectra simulated from single crystal data. The two polymorphs characterized here correspond to form I and form IV of the patent. Form II of the patent could not be obtained by us with a variety of experimental conditions. Form III of the patent corresponds to hemihydrate II of this study. Form III is therefore not a polymorph of form I and form IV. What we have termed hemihydrate I in this study is obtained under a wide variety of conditions and it is also the only hemihydrate reported as such in the patent. Because the Etoricoxib molecule contains no conventional hydrogen bond donors, there cannot be any strong hydrogen bonds in the crystal structures of forms I and IV. The packing is accordingly characterized by weak hydrogen bonds of the C-H center dot center dot center dot O=S and C-H center dot center dot center dot N type. Thermal data were collected for form I, form IV and hemihydrate I to shed some light on relative stabilities. PXRD diffractograms show the transformation of form IV to form I at elevated temperature, indicating that form I is more stable than form IV. However, this transformation occurs only in samples of form IV that contain some form I; it does not occur in pure form IV. The formation of the two hemihydrates could follow from the known tendency of an acceptor-rich molecule to crystallize as a hydrate.

Calculation of Chemical Potentials and Occupancies in Clathrate Hydrates through Monte Carlo Molecular Simulations

The flexibility of the water lattice in clathrate hydrates and guest-guest interactions has been shown in previous studies to significantly affect the values of the thermodynamic properties, such as chemical potentials and free energies. Here we describe methods for computing occupancies, chemical potentials, and free energies that account for the flexibility of water lattice and guest-guest interactions in the hydrate phase. The methods are validated for a wide variety of guest molecules, such as methane, ethane, carbon dioxide, and tetrahydrodfuran by comparing the predicted occupancy values of guest molecules with those obtained from isothermal isobaric semigrand Monte Carlo simulations. The proposed methods extend the van der Waals and Platteuw theory for clathrate hydrates, and the Langmuir constant is calculated based on the structure of the empty hydrate lattice. These methods in combination with development of advanced molecular models for water and guest molecules should lead to a more thermodynamically consistent theory for clathrate hydrates.

Polymorphism and Phase Transformation Behavior of Solid Forms of 4-Amino-3,5-dinitrobenzamide

We report the preparation, analysis, and phase transformation behavior of polymorphs and the hydrate of 4-amino-3,5-dinitrobenzamide. The compound crystallizes in four different polymorphic forms, Form I (monoclinic, P2(1)/n), Form II (orthorhombic, Pbca), Form III (monoclinic, P2(1)/c), and Form IV (monoclinic, P2(1)/c). Interestingly, a hydrate (triclinic, P (1) over bar) of the compound is also discovered during the systematic identification of the polymorphs. Analysis of the polymorphs has been investigated using hot stage microscopy, differential scanning calorimetry, in situ variable-temperature powder X-ray diffraction, and single-crystal X-ray diffraction. On heating, all of the solid forms convert into Form I irreversibly, and on further heating, melting is observed. In situ single-crystal X-ray diffraction studies revealed that Form II transforms to Form I above 175 degrees C via single-crystal-to-single-crystal transformation. The hydrate, on heating, undergoes a double phase transition, first to Form III upon losing water in a single-crystal-to-single-crystal fashion and then to a more stable polymorph Form I on further heating. Thermal analysis leads to the conclusion that Form II appears to be the most stable phase at ambient conditions, whereas Form I is more stable at higher temperature.

Synthesis and antioxidant activity study of pyrazoline carrying an arylfuran/arylthiophene moiety

A novel series of N-acetyl-3-aryl-5-(5-(p/o-nitrophenyl)-2-furyl//thienyl)-substituted pyrazolines (3a-o) were synthesized by the reaction of 1-aryl-3-(5-(p/o-nitrophenyl)-2-furyl/thienyl)-2-propene-1-ones with hydrazine hydrate in acetic acid medium. The structures of the newly synthesized compounds were established by IR, H-1-NMR, mass spectra and a single-crystal X-ray study. The antioxidant activities of the synthesized compounds were determined using the DPPH scavenging assay. The compounds 3a, 3f, 3h and 3o showed moderate activity.

BIMODAL NANOINDENTATION RESPONSE OF THE (001) FACE IN CRYSTALLINE SODIUM SACCHARIN DIHYDRATE

The nanoindentation response of the (001) face of sodium saccharin dihydrate is examined. The structure can be demarcated into regular and irregular regions or domains. The regular domains have solid-like and the irregular ones have liquid-like characteristics. Therefore, these domains impart a microstructure to the crystal. The indent face (001) is prominently developed in this crystal and unambiguously presents the regular and irregular regions to nanoindention. Average values of elastic modulus and hardness show a distinct bimodal mechanical response. Such a response has been observed in the case of intergrown polymorphs of aspirin and felodipine. We examine two possible reasons as to why the responses could be for bimodal in this crystal. The first possibility could be that the two domains correspond to regions of the original dihydrate and a lower hydrate that is obtained by the loss of some water. The second possibility could be that these responses correspond to regular and irregular regions in the structure. Nanoindentation is a very useful technique in the characterization of molecular solids, as a complementary technique to X-ray crystallography, because it samples different length scales.

Yellow-red luminescence in ZnO nanoparticles synthesized from zinc acetylacetonate phenanthroline

ZnO powders/thin films/coatings when excited by a suitable excitation source, usually yield green luminescence in the visible wavelength range along with characteristic ultra-violet emission. We report yellow-red emission from ZnO nanoparticles synthesized within 5 min of microwave irradiation by using zinc acetylacetonate phenanthroline as the starting precursor material. The emission is strongly dependent on the typical structure of the starting precursor for ZnO synthesis, where one phenanthroline moiety is attached with zinc acetylacetonate hydrate complex. These ZnO nanoparticles could be potentially suitable phosphor for white light generation when excited by a blue laser. In contrast, the ZnO nanoparticles obtained from zinc acetylacetonate by similar method yield weak green emission. (C) 2015 Elsevier B.V. All rights reserved.

开采地层中的天然气水合物的数学模型

目前从天然气水合物中开采天然气的方法,主要有热激发法、化学试剂法和减压法.文章通过适当简化,从理论上推导出减压法开采天然气的数值模型和水合物分解前缘边界曲面离井筒距离表达式,并对推导出的偏微分方程经过线性简化和自相似原理,推导出多孔介质水合物地层中压力和温度的分布方程和天然气产量方程.通过实例,研究了多孔介质水合物地层中压力和温度的分布规律,即离井筒越近,压力和温度越小.进行了影响水合物分解前缘边界曲面离井筒距离各影响因素的敏感性分析,得到了减小井筒压力和增大地层温度可以使离井筒越远地方的水合物层分解释放出天然气,天然气的产量随着开采时间的增大而逐渐减小但最终趋于一稳定值的结论。

Submarine landslides : selected studies in the U.S. Exclusive Economic Zone

Submarine Landslides: An Introduction 1 By RIo Lee, W.C. Schwab, and J.S. Booth U.S. Atlantic Continental Slope Landslides: Their Distribution, General Anributes, and Implications 14 By J.S. Booth, D.W. O'Leary, Peter Popenoe, and W.W. Danforth Submarine Mass Movement, a Formative Process of Passive Continental Margins: The Munson-Nygren Landslide Complex and the Southeast New England Landslide Complex 23 By D.W. O'Leary The Cape Fear Landslide: Slope Failure Associated with Salt Diapirism and Gas Hydrate Decomposition 40 By Peter Popenoe, E.A. Schmuck, and W.P. Dillon Ancient Crustal Fractures Control the Location and Size of Collapsed Blocks at the Blake Escarpment, East of Florida 54 By W.P. Dillon, J.S. Risch, K.M. Scanlon, P.C. Valentine, and Q.J. Huggett Tectonic and Stratigraphic Control on a Giant Submarine Slope Failure: Puerto Rico Insular Slope 60 By W.C. Schwab, W.W. Danforth, and K.M. Scanlon Slope Failure of Carbonate Sediment on the West Florida Slope 69 By D.C. Twichell, P.C. Valentine, and L.M. Parson Slope Failures in an Area of High Sedimentation Rate: Offshore Mississippi River Delta 79 By J.M. Coleman, D.B. Prior, L.E. Garrison, and H.J. Lee Salt Tectonics and Slope Failure in an Area of Salt Domes in the Northwestern Gulf of Mexico 92 By B.A. McGregor, R.G. Rothwell, N.H. Kenyon, and D.C. Twichell Slope Stability in Regions 01 Sea-Floor Gas Hydrate: Beaufort Sea Continental Slope 97 By R.E. Kayen and H.J. Lee Mass Movement Related to Large Submarine Canyons Along the Beringian Margin, Alaska 104 By P.R. Carlson, H.A. Karl, B.D. Edwards, J.V. Gardner, and R. Hall Comparison of Tectonic and Stratigraphic Control of Submarine Landslides on the Kodiak Upper Continental Slope, Alaska 117 By M.A. Hampton Submarine Landslides That Had a Significant Impact on Man and His Activities: Seward and Valdez, Alaska 123 By M.A. Hampton, R.W. Lemke, and H.W. Coulter Processes Controlling the Style of Mass Movement in Glaciomarine Sediment: Northeastern Gulf of Alaska 135 By W.C. Schwab and H.J. Lee Contents V VI Contents Liquefaction of Continental Shelf Sediment: The Northern California Earthquake of 1980 143 By M.E. Field A Submarine Landslide Associated with Shallow Sea-Floor Gas and Gas Hydrates off Northern California 151 By M.E. Field and J.H. Barber, Jr. Sur Submarine Landslide, a Deep-Water Sediment Slope Failure 158 By C.E. Gutmacher and W.R. Normark Seismically Induced Mudflow in Santa Barbara Basin, California 167 By B.D. Edwards, H.J. Lee, and M.E. Field Submarine Landslides in a Basin and Ridge Setting, Southern California 176 By M.E. Field and B.D. Edwards Giant Volcano-Related Landslides and the Development of the Hawaiian Islands 184 By W.R. Normark, J.G. Moore, and M.E. Torresan Submarine Slope Failures Initiated by Hurricane Iwa, Kahe Point, Oahu, Hawaii 197 By W.R. Normark, Pat Wilde, J.F. Campbell, T.E. Chase, and Bruce Tsutsui (PDF contains 210 pages)

水合物沉积物力学性质的研究现状

天然气水合物(简称水合物)是一些具有相对较低分子质量的气体如甲烷,二氧化碳、氮气等在一定温度和压力条件下与水形成的内含笼形孔隙的冰状晶体.天然气水合物沉积物(简称水合物沉积物)是指蕴含水合物的砂、黏土以及混和土等土质的沉积物质.主要从现场调查、室内试验和理论模型分析3个方面对甲烷水合物沉积物力学性质的研究现状做了介绍.在现场调查方面着重介绍水合物沉积物原位和调查船上的物性试验,并对原位带孔压测量的圆锥静力触探试验在水合物沉积物力学性质现场调查中的应用前景进行了阐述;在室内试验方面主要介绍了原状和人工合成的水合物沉积物的三轴试验结果,测定弹性参数的声波测试试验结果,天然气和水的含量及沉积物特性对水合物沉积物强度影响的试验结果,以及与水合物开采有关的水合物分解对水合物沉积物强度影响的室内试验和结果:在理论模型方面着重介绍了目前经常采用的几个模型的特点及应用范围.最后提出了今后在水合物沉积物力学性质研究方面应开展的工作重点及发展方向.

水合物沉积物力学性质的实验装置和研究进展

天然气水合物是一种高效、洁净和储量巨大的新型能源,一般蕴含于砂岩、粘土以及其它土质的沉积物中.对水合物沉积物力学性质的实验研究,是水合物地层中基础稳定性分析和水合物开发评价重要的热点课题之一.本文首先介绍了水合物沉积物合成与分解实验、物性参数测量技术以及力学性质实验装置的主要组成部分和特点,然后介绍了目前国内外在水合物沉积物合成和分解及力学性质实验一体化装置和实验研究两个方面所取得的成果,最后指出在实验装置、测试技术和实验研究方面存在的问题以及今后研究的重点和方向.

Avaliação in vitro do efeito da incorporação de clorexidina nas propriedades físicas e na atividade antibacteriana de resinas acrílicas autopolimerizáveis

Objetivo. O objetivo do presente estudo foi avaliar o efeito da incorporação de diacetato de clorexidina (CDA), em diferentes concentrações e tempos de armazenamento, nas propriedades físicas e na atividade antibacteriana de resinas acrílicas, utilizadas na confecção de coroas e pontes provisórias. Métodos. Fase I: Foram confeccionados 150 corpos de prova retangulares (3,0 mm X 10 mm X 64 mm), de acordo com a norma ISO 1567 e 150 corpos de prova quadrados (10 mm X 10 mm X 2,0 mm), utilizando-se duas resinas acrílicas autopolimerizáveis, Duralay (Reliance Dental Mfg. Co.) e Dencor (Clássico). Os corpos de prova foram distribuídos em 30 grupos (n=10/grupo) de acordo com a concentração de CDA incorporada às resinas (p/p) (A) 0%, (B) 1%, (C) 2%, (D) 4%, (E) 5%, em função do tempo de armazenamento em água destilada, a 37C (T0 2h, T1 7 dias, T2 30 dias). Foram realizados os ensaios de microdureza Knoop, em microdurômetro Micromet 5104, Buehler (N), rugosidade superficial (Ra), em rugosímetro digital Mitutoyo Surftest SJ-201 (n=5) e resistência à flexão em três pontos (MPa), em uma máquina de ensaio universal EMIC MF 200 DL (n=5). Fase II: Adicionalmente, a atividade antibacteriana dos materiais sobre Streptococcus mutans foi determinada através da realização de testes de difusão em meio BHI, sendo para isso confeccionados 30 corpos de prova em forma de disco (12 mm X 3,0 mm) com as mesmas 5 concentrações (n=3/grupo). Os resultados foram tabulados e submetidos à análise estatística three-way ANOVA (Fase I) e two-way ANOVA (Fase II). Resultados. ANOVA mostrou que a adição de CDA não provocou alteração significativa na resistência à flexão dos materiais testados. A resistência à flexão é inversamente proporcional ao tempo para a resina Dencor e diretamente proporcional ao tempo para a resina Duralay. Houve aumento da microdureza com o acréscimo de CDA ao material Dencor com relação ao grupo controle, enquanto que no material Duralay a CDA não interferiu significativamente nesta propriedade. A rugosidade superficial aumentou significativamente (p<0,001) com o tempo e com o aumento da concentração de clorexidina na resina Dencor e não provocou alteração significativa em Duralay. Os testes de difusão em ágar demonstraram atividade antimicrobiana significativa (p<0,05) em todos os grupos, quando comparados ao grupo-controle. A inibição ao crescimento de Streptococcus mutans foi maior com o aumento da concentração desta substância. A resina Dencor apresentou maior halo de inibição do que a resina Duralay. Conclusões. Os resultados deste estudo sugerem que a incorporação de clorexidina aos materiais testados exibiu efeito antibacteriano contra S. mutans, sem contudo afetar de maneira crítica as propriedades físicas avaliadas.

法落海的化学成分及抗HIV活性

下载PDF阅读器利用多种柱层析方法,从法落海(Angelica apaensis)95%乙醇提取物中分离得到8个化合物.经IR、MS、NMR等波谱数据鉴定为氧化前胡素(oxypeucedanin,1)、氧化前胡素水合物(oxypeucedanin hydrate,2)、异欧芹属乙素(isoimperatorin,3)、白当归脑(byakangelicin,4)、白当归素(byakangelicol,5)、3'-O-acetylhamaudol (6)、(+)-9(Z),17-octadecadiene-12,14-diyne-1,11,16-triol(7)和9,17-octadecadiene-12,14-diyne-1,11,16-triol,1-acetate(8),其中,化合物6-8是首次从该植物中分离得到.我们对所有得到的8个化合物进行抗HIV活性分析,化合物1具有明显的抗HIV活性,其抑制合胞体形成的半数有效浓度(EC50)为1.6 ms/L,治疗指数(TI)为17.59.

Increased gas production from hydrates by combining depressurization with heating of the wellbore

To extract gas from hydrate reservoirs, it has to be dissociated in situ. This endothermic dissociation process absorbs heat energy from the formation and pore fluid. The heat transfer governs the dissociation rate, which is proportional to the difference between the actual temperature and the equilibrium temperature. This study compares three potential gas production schemes from hydrate-bearing soil, where the radial heat transfer is governing. Cylindrical samples with 40% pore-filling hydrate saturation were tested. The production tests were carried out over 90 min by dissociating the hydrate from a centered miniature wellbore, by either lowering the pressure to 6, 4, or 6 MPa with simultaneous heating of the wellbore to 288 K. All tests were replicated by a numerical simulation. With additional heating at the same wellbore pressure, the gas production from hydrates could, on average, be increased by 1.8 and 3.6 times in the simulation and experiments, respectively. If the heat influx from the outer boundary is limited, a simulation showed that the specific heat of the formation is rapidly used up when the wellbore is only depressurized and not heated. © 2012 American Chemical Society.

Thermogravimetric study on the hydration of reactive magnesia and silica mixture at room temperature

The synthesis of magnesium silicate hydrate (MSH), which has wide applications in both construction and environmental fields, has been studied for decades. However, it is known that the characteristics of magnesia (MgO) vary significantly depending on their calcination conditions, which is expected to affect their performance in the MgO-SiO2-H2O system. This paper investigated the effect of different MgO and silica sources on the formation of magnesium silicate hydrate (MSH) at room temperature. The hydration process was studied by mixing commercial reactive MgO and silica powders with water and curing for 1, 7 and 28 days. The hydration products were analysed with the help of X-ray diffraction (XRD) and thermogravimatric analysis (TGA). The results showed the continuous consumption of MgO and the existence of MSH and brucite and other minor phases such as magnesite and calcite. It is found that the Mg and Si sources have significant effect on the hydration process of MgO-SiO2-H2O system. The reaction degree is controlled by the availability of dissolved Mg and Si in the solution. The former is determined by the reactivity of MgO and the latter is related to the reactivity of the silica as well as the pH of the system. © 2013 Elsevier B.V. All rights reserved.

Strength and hydration products of reactive MgO-silica pastes

The reaction between MgO and microsilica has been studied by many researchers, who confirmed the formation of magnesium silicate hydrate. The blend was reported to have the potential as a novel material for construction and environment purposes. However, the characteristics of MgO vary significantly, e.g., reactivity and purity, which would have an effect on the hydration process of MgO-silica blend. This paper investigated the strength and hydration products of reactive MgO and silica blend at room temperature up to 90 days. The existence of magnesium silicate hydrate after 7 days' curing was confirmed with the help of infrared spectroscopy, thermogravimetric analysis and X-ray diffraction. The microstructural and elemental analysis of the resulting magnesium silicate hydrate was conducted using scanning electron microscopy and energy dispersive spectroscopy. In addition, the effect of characteristics of MgO on the hydration process was discussed. It was found that the synthesis of magnesium silicate hydrate was highly dependent on the reactivity of the precursors. MgO and silica with higher reactivity resulted in higher formation rate of magnesium silicate hydrate. In addition, the impurity in the MgO affects the pH value of the blends, which in turn determines the solubility of silica and the formation of magnesium silicate hydrate. © 2014 Elsevier Ltd. All rights reserved.