38 research outputs found
Computer modeling and description of nonstoichiometric apatites Cd5-η/2(VO4)3I1-η and Cd5-η/2(PO4)3Br1-η as modified chimney-ladder structures with ladder-ladder and chimney-ladder coupling
No full textDiffraction patterns from apatite-structure compounds Cd5-η/2(TO4)3X1-η with T=P, V and X=Br, I show sheets of diffuse scattering normal to c* at incommensurate l=q (q=1.63 for Cd-V-I apatite and q=1.78 for Cd-P-Br apatite), because the c repeat of the average unit cell is shorter than two X diameters. The equilibrium X..X spacing along c defines the incommensurate periodicity c/q and stoichiometry (1-η)=q/2. The layers show a honeycomb texture for the Cd-V-I apatite, which is condensed into discrete spots for the Cd-P-Br compound. In both phases, X..X repulsions along 〈100〉 force neighboring rods of X atoms out of phase. In the Cd-P-Br phase, additional 〈210〉 attractions drive incipient formation of a rhombohedral superstructure. Average structure site occupancies and the observation of second-order diffuse layers at both l=2q and l=q+2 imply the existence of strong Cd..X in addition to X..X interactions. A three-dimensional computer model was used to produce finite-temperature structure simulations as a function of X..X interactions along 〈001〉, 〈100〉, and 〈210〉, and X..Cd interactions, from which diffraction patterns were calculated. The experimental patterns were fit and approximate values for the interaction energies obtained (hundreds to thousands of joules per mole). It was apparent that lock-in to commensurability caused by the X..Cd term and the formation of nonprimitive incommensurate modulated structures driven by X..X interactions were mutually antagonistic, and the actual structures are compromises between the two
Association between development of lower lip cancer and tobacco habits
No full textTobacco use is considered to increase the risk of tumor induction. The purpose of this case-controlled investigation was to assess the association of tobacco habits and development of squamous cell carcinoma of the lower lip. Sixty-one patients treated for lower lip cancer, aged between 42 and 90 years, were studied. Age- and sex-matched healthy controls showed a similar exposure to tobacco in years and a comparable distribution of tobacco habits. Although the mean exposure factor (duration times exposure) was greater in the tumor group, no intimate correlation between lip cancer and tobacco was demonstrated. However, an increased, although small, occurrence of herpes labialis lesions was found in cancer patients. The hypothesis is presented that smokers experiencing recurrent herpes simplex virus 1 (HSV-1) infections are more liable to tumor initiation, which issue will be subjected to a future study.</p
Dye-loaded particles
No full textAmorphous particles are provided comprising a homogeneous distribution of one or more dyes encapsulated by an amorphous, siliceous encapsulating agent, wherein the amorphous particle comprises from 3% to 20% dye, by wt. of the particle. [on SciFinder(R)]</p
The use of Zenker's solution in linear craniectomy for craniosynostosis: Technical modification and reappraisal
No full textOne-pot synthesis of well ordered mesoporous magnetic carriers
No full textThe facile preparation of a mesoporous magnetic carrier technology is demonstrated. The micron-sized spherical mesostructured particles are prepared using a newly-developed, one-step, combined emulsion and solvent evaporation (ESE) method. The surfactant-templated silica matrix display a well-ordered internal pore architecture. Very limited pore blocking, and only to a limited degree disordered- or worm-like structures are observed, induced by the iron oxide nanoparticles added to provide the superparamagnetic properties.The iron oxide content was precisely controlled, and themagnetic properties were well preserved during the process. Finally we demonstrate the applicability of the magnetically separable mesoporous material as an adsorbent for specific dissolved materials from dilute aqueous solutions.</p
"Repositioning of craniofacial tumorous bone after autoclaving"
No full textThirteen bone tumours that were invading the craniofacial skeleton were operated on by intracranial procedures. The resected tumorous bone was autoclaved and put back. Follow up of no less than one year included 122mTc scanning, computed tomography, radiography, bone biopsy and clinical examination. In every case, when rigidly fixed, most of the autoclaved bone was gradually revitalised by invading new and normal bone. We conclude that autoclaved bone will be replaced by normal bone, and that the present technique is justified for reconstruction of complicated structures or large areas of bone after operations for tumours invading the craniofacial skeleton
Modulating the anion ordering in apatites
No full textHydroxyapatite constitutes the main inorganic part of the skeleton, and since the beginning of the seventies, synthetic apatite has been used in implants. The physical properties of this crystalline material are directly dependent on its atomic arrangement. If a better understanding of apatite chemistry is sought, important for e.g. the development of new implant materials, it is absolutely crucial to know the detailed structural chemistry of the apatites. It is in this context that this thesis fits.X-ray and electron diffraction techniques in combination with high resolution transmission electron microscopy have been used for the characterisation of the new compounds and the combination of these techniques has been particularly useful.Common for the studies presented is that they focus on the anion ordering along the hexagonal axis within the apatite framework, this being responsible for the new structures discovered:The crystal structure of completely dehydrated hydroxyapatite, oxyapatite, has been elucidated from HREM images.Partially dehydrated hydroxyapatite is shown to be triclinic.The sulfo- and seleno analogues of oxyapatite have been prepared and their structures refined from X-ray diffraction data.A new commensurate modulation along c is found for iodo-oxyapatite.A new incommensurate modulation along c is found for cadmium-bromoapatite.As a consequence of the structural chemical investigations performed, the hypothesis arose that it might be possible to manipulate the hydroxide ion ordering in hydroxyapatite achieving a piezoelectric apatite. This hypothesis has recently been confirmed. This new apatite may find important applications in the development of new, biocompatible, implant materials.</p
Spray-drying process for the manufacture of dye-loaded particles
No full textAccording to a first aspect of the invention, a process is provided for the prepn. of amorphous particles comprising a homogeneous distribution of one or more dyes encapsulated by an amorphous, siliceous encapsulating agent, the process comprising: (a) providing a precursor of the encapsulating agent in liq. form; (b) providing the one or more dyes in liq. form; (c) mixing the liq. forms; (d) spraying the mixt. to form droplets comprising the one or more dyes and encapsulating agent; and (e) heating the droplets to form the particles comprising the one or more dyes encapsulated by the siliceous encapsulating agent; wherein at least one of the liq. forms provided is aq. and the or each aq. liq. form is acidic. According to a second aspect of the invention, encapsulated dyes made by the process of the first aspect of the invention are provided. [on SciFinder(R)]</p
Improved enzymatic activity of Thermomyces lanuginosus lipaseimmobilized in a hydrophobic particulate mesoporous carrier
No full textLipase from Thermomyces lanuginosus has been immobilized within particulate mesoporous silica carriers, with either hydrophilic or hydrophobic supporting surfaces, produced by the newly developed emulsion and solvent evaporation (ESE) method. The Michaelis-Menten model was used to calculate the parameters related to the enzymatic activity of lipase i.e. the turnover number, k(cat), and the specific activity. The specific activity was improved by immobilization of lipase onto the hydrophobic support, compared to lipase immobilized onto the hydrophilic support and lipase free in solution. The enhanced enzymatic activity of lipase onto a hydrophobic support was attributed to interfacial activation of the Thermomyces lanuginosus lipase when it is attached to a hydrophobic surface and a reduced denaturation. Confocal scanning laster microscopy (CLSM) studies, of fluorescently tagged lipase, showed that leakage of the lipase from the mesoporous particles was limited to all initial period of only a few hours. Both the rate and the amount of lipase leached were reduced when the lipase was immobilized onto the hydrophobic support.</p
