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Large Cavities (large + cavity)

Distribution by Scientific Domains
Chemistry46%
Medical Sciences26%
Life Sciences13%

Selected Abstracts

New Metal-Organic Frameworks with Large Cavities: Selective Sorption and Desorption of Solvent Molecules

CHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2007
Yan Wang
Abstract Five novel transition metal complexes [CdII3(tpba-2)2(SCN)6],6,THF,3,H2O (1), [CuII3(tpba-2)2(SCN)6],6,THF,3,H2O (2), [NiII3(tpba-2)2(SCN)6],6,THF,3,H2O (3), [CdII2(tpba-2)(SCN)3]ClO4 (4), [CuI3(SCN)6(H3tpba-2)] (5) [TPBA-2 = N,,N,,,N,,, -tris(pyrid-2-ylmethyl)-1,3,5-benzenetricarboxamide, THF=tetrahydrofuran] were obtained by reactions of the corresponding transition metal salts with TPBA-2 ligand in the presence of NH4SCN using layering or solvothermal method, respectively. The results of X-ray crystallographic analysis showed that complexes 1, 2 and 3 are isostructural and have the same 2D honeycomb network structure with Kagomé lattice, in which all the MII (M = Cd, Cu, Ni) atoms are six-coordinated, and the TPBA-2 ligands adopt cis,cis,cis conformation while the thiocyanate anions act as terminal ligands. Capsule-like motifs are found in 1, 2 and 3, in which six THF molecules are hosted, and the results of XPRD and solid-state 13C,NMR spectral measurements showed that the compound 1 can selectively desorb and adsorb THF molecules occurring along with the re-establishment of its crystallinity. In contrast to 1, 2 and 3, complex 4 has different 2D network structure, resulting from TPBA-2 ligands with cis,trans,trans conformation, thiocyanate anions serving as end-to-end bridging ligands, and the incomplete replacement of perchlorate anions, which further link the 2D layers into 3D framework by the hydrogen bonds. In complex 5, the CuII atoms are reduced to CuI during the process of solvothermal reaction, and the CuI atoms are connected by thiocyanate anions to form a 3D porous framework, in which the protonated TPBA-2 ligands are hosted in the cavities as templates. [source]

Osteoderm morphology in recent and fossil euphractine xenarthrans

ACTA ZOOLOGICA, Issue 4 2009
C. M. Krmpotic
Abstract The presence of osteoderms within the integument, forming a carapace, is one of the most distinctive features of armadillos with the external morphology of these elements forming the basis of most systematic schemes. This is especially true for fossil taxa, where these elements are most frequent in the palaeontological record. A detailed study of osteoderms from the cephalic shield and different regions of the dorsal armour of Chaetophractus villosus (Euphractinae, Xenarthra) was made and compared to those of the extant genus Dasypus (Dasypodinae, Xenarthra), and the extinct genus ,Eutatus. Three distinct histological zones were recognized: outer and inner zones are thin, formed by regular compact bone, the middle zone is thicker, with large cavities that contain mainly adipose tissue, hair follicles, and sweat and sebaceous glands. The internal structure of ,Eutatus (also a member of Euphractinae) osteoderms is close to that of C. villosus, consistent with the notion that these taxa are phylogenetically closely related. In contrast, Dasypus shows marked differences. Dasypus shows hair follicles associated with both gland types (sweat and sebaceous) and connected to foramina on the external surface. Although not observed in adult C. villosus, it has been documented during embryonic development, only to atrophy later in ontogeny. Furthermore, the presence of red bone marrow is rare in C. villosus, but widespread in Dasypus novemcinctus osteoderms. These results suggest an early split of both subfamilies and support the hypothesis that the Euphractinae are more derived than the Dasypodinae. [source]

Cathedral Cave, Wellington Caves, New South Wales, Australia.

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 14 2007
A multiphase, non-fluvial cave
Abstract Cathedral Cave is an outstanding example of a class of multiphase caves with largely non-fluvial origins. It contains large cavities such as cathedrals and cupolas, characteristic of excavation by convection currents in rising waters. Smaller-scale features such as rising half-tubes, pseudonotches, curved juts, projecting corners, blades and bridges indicate intersection and exhumation of older cavities during the formation of younger ones. It is possible to recognize at least ten significant phases of speleogenesis by morphostratigraphy, in addition to the four generations of cave-filling palaeokarst deposits intersected by the cave. The cave we see today results from the progressive integration of a number of previously disconnected or poorly connected solution cavities. Copyright © 2007 John Wiley & Sons, Ltd. [source]

In vitro evaluation of marginal and internal adaptation after occlusal stressing of indirect class II composite restorations with different resinous bases

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2003
Didier Dietschi
Composite inlays are indicated for large cavities, which frequently extend cervically into dentin. The purpose of this study was to compare in vitro the marginal and internal adaptation of class II fine hybrid composite inlays (Herculite, Kerr) made with or without composite bases, having different physical properties. Freshly extracted human molars were used for this study. The base extended up to the cervical margins on both sides and was made from Revolution (Kerr), Tetric flow (Vivadent), Dyract (Detrey-Dentsply) or Prodigy (Kerr), respectively. Before, during and after mechanical loading (1 million cycles, with a force varying from 50 to 100 N), the proximal margins of the inlay were assessed by scanning electron microscopy. Experimental data were analysed using non-parametric tests. The final percentages of marginal tooth fracture varied from 30.7% (no base) to 37.6% (Dyract). In dentin, percentages of marginal opening varied from 9.2% (Tetric Flow) to 30.1% (Prodigy), however, without significant difference between base products. Mean values of opened internal interface with dentin varied from 11.06% (Tetric Flow) to 28.15% (Prodigy). The present results regarding dentin adaptation confirmed that the physical properties of a base can influence composite inlay adaptation and that the medium-rigid flowable composite Tetric Flow is a potential material to displace, in a coronal position, proximal margins underneath composite inlays. [source]

DEFINITION OF INTERNAL MORPHOLOGY AND STRUCTURAL CHANGES DUE TO DEHYDRATION OF RADISH (RAPHANUS SATIVUS L. CV. SUPRELLA) USING MAGNETIC RESONANCE IMAGING SPECTROSCOPY

JOURNAL OF FOOD QUALITY, Issue 5-6 2005
ANNA SALERNO
ABSTRACT Magnetic resonance imaging (MRI) spectroscopy is a promising nondestructive analytical technique in food science. It offers the unique opportunity of studying vegetables, fruits and other foods in general, in their wholeness without any preparative manipulation of the sample. The aim of this study was to investigate the internal structure of radish and to monitor the variations induced by postharvest storage at low relative humidity. The MRI allowed for a clear definition of the internal structure of radishes with distinct visibility of xylematic and phloematic vessels distributed in a radial way. A decrease in water content, which results in the breakdown of tissues and the formation of large cavities with the detachment of the external cortex, is the main consequence of a few days' storage in low relative humidity. Both of these are factors that drastically decrease the quality of the radish's fleshy root. The MRI images give a novel insight into the internal organization of the hypocotyl, and this offers opportunities for further studies with regard to the structural differences related to the cultivars as well as the cultivation system. [source]

Ischial pressure sores: Reconstruction using the perforator-based reverse flow musculocutaneous 180° propeller flap

MICROSURGERY, Issue 8 2009
Rafael G. Jakubietz M.D.
The treatment of pressure sores requires soft tissue reconstruction with thick tissue to provide padding of bony prominences and obliterate dead space. Fasciocutaneous flaps may not provide adequate bulk. Propeller flaps (180°) based on perforators from the gluteal artery may be harvested as a reverse flow musculocutaneous flap including a muscle plug to reconstruct deep cavities. Three patients presenting with deep pressure sores required reconstruction of large cavities. In addition to a regular 180° propeller flap, a muscle plug based on a perforator found in the blade of the propeller was used to add bulk to the flap and obliterate the cavity with well-vascularized tissue. One flap required secondary closure of the donor site due to dehiscence, one hematoma required drainage. All flaps survived completely. No recurrence of osteomyelitis or pressure sores was seen. The 180° propeller flap can be harvested as a reverse flow musculocutaneous flap including a muscle plug in the distal blade. This adds volume which is required to adequately obliterate large cavities in cases of osteomyelitis. This new technique may be useful in other areas as well. © 2009 Wiley-Liss, Inc. Microsurgery 2009. [source]

The distal superficial femoral arterial branch to the sartorius muscle as a recipient vessel for soft tissue defects around the knee: Anatomic study and clinical applications

MICROSURGERY, Issue 6 2009
Fernando A. Herrera M.D.
Complex wounds surrounding the knee and proximal tibia pose a significant challenge for the reconstructive surgeon. Most of these defects can be managed using local or regional flaps alone. However, large defects with a wide zone of injury frequently require microvascular tissue transfers to aid in soft tissue coverage and closure of large cavities. We describe a unique recipient vessel for microvascular anastomosis for free flap reconstruction involving the knee and proximal tibia through anatomic and clinical studies. © 2009 Wiley-Liss, Inc. Microsurgery 2009. [source]

The disordered cluster compound CaMo5(Mo0.38Ti0.62)O10

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2008
P. Gougeon
The title compound, calcium pentamolybdenum titanium decaoxide, is isomorphous with the AMo5(Ti0.7Mo0.3)O10 (A = Sr and Eu) compounds. The smaller size of calcium induces a higher molybdenum content on the capping sites of the bioctahedral Mo10 clusters, leading to more Mo11 and Mo12 clusters in the crystal structure. The oxygen framework derives from the stacking of close-packed layers along the a direction in the ,ABAC, sequence. The Ca2+ ions occupy large cavities which result from the fusion of two cubooctahedra and are surrounded by ten O atoms. The Ti4+ ion is octahedrally coordinated by the O atoms. [source]

3-[5-(4-Bromo­phenyl)-1H -pyrazol-3-ylamino]-5,5-dimethyl­cyclo­hex-2-en-1-one,(Z)-3-(4-bromo­phenyl)-3-chloro­acrylonitrile (2/1): a stoichiometric cocrystal of a reaction product with one of its early precursors

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2006
Silvia Cruz
The title compound, 2C17H18BrN3O·C9H5BrClN, was crystallized from the reaction between 5,5-dimethyl­cyclo­hexane-1,3-dione, triethyl orthoformate and 5-amino-3-(4-bromo­phenyl)pyrazole, which had itself been prepared from the reaction between (Z)-3-(4-bromo­phenyl)-3-chloro­acrylo­nitrile and hydrazine. The compound is a stoichiometric 2:1 cocrystal of the reaction product 3-[5-(4-bromo­phenyl)-1H -pyrazol-3-ylamino]-5,5-dimethyl­cyclo­hex-2-en-1-one and the early reactant (Z)-3-(4-bromo­phenyl)-3-chloro­acrylonitrile. The two independent mol­ecules of cyclo­hex-2-en-1-one are linked by N,H,N and N,H,O hydrogen bonds into complex bilayers and the mol­ecules of acrylonitrile are trapped within large cavities in the substructure formed by the cyclo­hex-2-en-1-one mol­ecules. [source]

Rationally Designed, Polymeric, Extended Metal,Ciprofloxacin Complexes

CHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2005
Dong-Rong Xiao Dr.
Abstract Reactions of the antimicrobial fluoroquinolone ciprofloxacin (cfH) with metal salts in the presence of aromatic polycarboxylate ligands or under basic conditions produce fourteen new metal,cfH complexes, namely, [Ba2(cf)2(1,4-bdc)(H2O)2],H2O (1), [Sr6(cf)6(1,4-bdc)3(H2O)6],2,H2O (2), [M2(cfH)2(bptc)(H2O)2],8,H2O (M = Mn(3) and Cd(4)), [M(cfH)(1,3-bdc)] (M = Mn(5), Co(6), and Zn(7)), [Zn2(cfH)4(1,4-bdc)](1,4-bdc),13,H2O (8), [Ca(cfH)2(1,2-Hbdc)2],2,H2O (9) and [M(cf)2],2.5,H2O (M = Mn(10), Co(11), Zn(12), Cd(13), and Mg(14)) (1,4-bdc = 1,4-benzenedicarboxylate, bptc = 3,3,,4,4,-benzophenonetetracarboxylate, 1,3-bdc = 1,3-benzenedicarboxylate, 1,2-bdc = 1,2-benzenedicarboxylate). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric analyses. The structures of 1 and 2 consist of unique two-dimensional arm-shaped layers. Compounds 3 and 4 are isostructural and feature one-dimensional structures formed from the interconnection of [M2(cfH)2(H2O)2] dimers with bptc ligands. Compounds 5,7 are isostructural and contain double-chain-like ribbons constructed from [M2(cfH)2(CO2)2] dimers and 1,3-bdc. Compound 8 consists of a pair of [Zn(cfH)2]2+ fragments bridged by a 1,4-bdc into a dinuclear dumbbell structure. Compound 9 is a neutral monomeric complex. To the best of our knowledge, compounds 1,9 are the first examples of metal-quinolone complexes that contain aromatic polycarboxylate ligands. Compounds 10,14 are isostructural and exhibit interesting two-dimensional rhombic grids featuring large cavities with dimensions of 13.6×13.6 Å. Up to now, polymeric extended metal,cfH complexes have never been reported. [source]

Progress of Untreated Massive Cardiac Echinococcosis,Echocardiographic Follow-Up

ECHOCARDIOGRAPHY, Issue 9 2006
Serdar Soydinc M.D.
A 56-year-old man was admitted with chest pain and dyspnea. Echocardiographic evaluation revealed a giant cystic cardiac mass with multiple loculations at interventricular septum extended to inferoposterior region protruding inside the cavity. The patient refused surgical therapy. His complaints persisted without significant changes after 5 months. Second echocardiographic evaluation revealed conjugation of previous multiple cyst to gigantic intramyocardial cyst and minimal pericardial effusion. We intend to illustrate herein an unusual echocardiographic appearance and progress of an untreated massive "cardiac echinococcosis." If cardiac hydatid cyst is left untreated it may transform to large cavity with a high risk of rupture. [source]

Structures of the magnetoionic media around the Fanaroff,Riley Class I radio galaxies 3C 31 and Hydra A

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008
R. A. Laing
ABSTRACT We use high-quality Very Large Array (VLA) images of the Fanaroff,Riley Class I radio galaxy 3C 31 at six frequencies in the range 1365,8440 MHz to explore the spatial scale and origin of the rotation measure (RM) fluctuations on the line of sight to the radio source. We analyse the distribution of the degree of polarization to show that the large depolarization asymmetry between the north and south sides of the source seen in earlier work largely disappears as the resolution is increased. We show that the depolarization seen at low resolution results primarily from unresolved gradients in a Faraday screen in front of the synchrotron-emitting plasma. We establish that the residual degree of polarization in the short-wavelength limit should follow a Burn law and we fit such a law to our data to estimate the residual depolarization at high resolution. We discuss how to interpret the structure function of RM fluctuations in the presence of a finite observing beam and how to address the effects of incomplete sampling of RM distribution using a Monte Carlo approach. We infer that the observed RM variations over selected areas of 3C 31, and the small residual depolarization found at high resolution, are consistent with a power spectrum of magnetic fluctuations in front of 3C 31 whose power-law slope changes significantly on the scales sampled by our data. The power spectrum P(f) can only have the form expected for Kolmogorov turbulence [P(f) ,f,11/3] on scales ,5 kpc. On larger scales, we find . We briefly discuss the physical interpretation of these results. We also compare the global variations of RM across 3C 31 with the results of three-dimensional simulations of the magnetic-field fluctuations in the surrounding magnetoionic medium. We infer that the RM variation across 3C 31 is qualitatively as expected from relativistic-jet models of the brightness asymmetry wherein the apparently brighter jet is on the near side of the nucleus and is seen through less magnetoionic material than the fainter jet. We show that our data are inconsistent with observing 3C 31 through a spherically symmetric magnetoionic medium, but that they are consistent with a field distribution that favours the plane perpendicular to the jet axis , probably because the radio source has evacuated a large cavity in the surrounding medium. We also apply our analysis techniques to the case of Hydra A, where the shape and the size of the cavities produced by the source in the surrounding medium are known from X-ray data. We emphasize that it is essential to account for the potential exclusion of magnetoionic material from a large volume containing the radio source when using the RM variations to derive statistical properties of the fluctuations in the foreground magnetic field. [source]

A novel threefold-interpenetrating primitive cubic network based on a dinuclear Zn2 node

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2009
Yun-Peng Diao
In the mixed-ligand metal,organic polymeric compound poly[[,2 -1,4-bis(imidazol-1-yl)benzene](,2 -terephthalato)dizinc(II)], [Zn2(C8H4O4)2(C12H10N4)]n or [Zn2(bdc)2(bib)]n [H2bdc is terephthalic acid and bib is 1,4-bis(imidazol-1-yl)benzene], the asymmetric unit contains one ZnII ion, with two half bdc anions and one half bib molecule lying around inversion centers. The ZnII ion is in a slightly distorted tetrahedral environment, coordinated by three carboxylate O atoms from three different bdc anions and by one bib N atom. The crystal structure is constructed from the secondary building unit (SBU) [Zn2(CO2)2N2O2], in which the two metal centers are held together by two bdc linkers with bis(syn,syn -bridging bidentate) bonding modes. The SBU is connected by bdc bridges to form a two-dimensional grid-like (4,4)-layer, which is further pillared by the bib ligand. Topologically, the dinuclear SBU can be considered to be a six-connected node, and the extended structure exhibits an elongated primitive approximately cubic framework. The three-dimensional framework possesses a large cavity with dimensions of approximately 10 × 13 × 17,Å in cross-section. The potential porosity is filled with mutual interpenetration of two identical equivalent frameworks, generating a novel threefold interpenetrating network with an ,-polonium topology [Abrahams, Hoskins, Robson & Slizys (2002). CrystEngComm, 4, 478,482]. [source]

Structural and functional analysis of Rv0554 from Mycobacterium tuberculosis: testing a putative role in menaquinone biosynthesis

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2010
Jodie M. Johnston
Mycobacterium tuberculosis, the cause of tuberculosis, is a devastating human pathogen against which new drugs are urgently needed. Enzymes from the biosynthetic pathway for menaquinone are considered to be valid drug targets. The protein encoded by the open reading frame Rv0554 has been expressed, purified and subjected to structural and functional analysis to test for a putative role in menaquinone biosynthesis. The crystal structure of Rv0554 has been solved and refined in two different space groups at 2.35 and 1.9,Å resolution. The protein is dimeric, with an ,/,-hydrolase monomer fold. In each monomer, a large cavity adjacent to the catalytic triad is enclosed by a helical lid. Dimerization is mediated by the lid regions. Small-molecule additives used in crystallization bind in the active site, but no binding of ligands related to menaquinone biosynthesis could be detected and functional assays failed to support possible roles in menaquinone biosynthesis. [source]

Carbon Monoxide Mass Transfer for Syngas Fermentation in a Stirred Tank Reactor with Dual Impeller Configurations

BIOTECHNOLOGY PROGRESS, Issue 3 2007
Andrew J. Ungerman
This study compares the power demand and gas-liquid volumetric mass transfer coefficient, kLa, in a stirred tank reactor (STR) (T = 0.211 m) using different impeller designs and schemes in a carbon monoxide-water system, which is applicable to synthesis gas (syngas) fermentation. Eleven different impeller schemes were tested over a range of operating conditions typically associated with the "after large cavity" region (ALC) of a Rushton-type turbine (D/T = 0.35). It is found that the dual Rushton-type impeller scheme exhibits the highest volumetric mass transfer rates for all operating conditions; however, it also displays the lowest mass transfer performance (defined as the volumetric mass transfer coefficient per unit power input) for all conditions due to its high power consumption. Dual impeller schemes with an axial flow impeller as the top impeller show improved mass transfer rates without dramatic increases in power draw. At high gas flow rates, dual impeller schemes with a lower concave impeller have kLa values similar to those of the Rushton-type dual impeller schemes but show improved mass transfer performance. It is believed that the mass transfer performance can be further enhanced for the bottom concave impeller schemes by operating at conditions beyond the ALC region defined for Rushton-type impellers because the concave impeller can handle higher gas flow rates prior to flooding. [source]