Basic sites on mixed nitrided galloaluminophosphates “AlGaPON”: infrared studies of SO2 and CDCl3 adsorption

The basic properties of nitrided galloaluminophosphate “AlGaPON” are documented by FTIR of sulphur dioxide and deuterated chloroform. To evidence the increase in the number of basic sites with nitrogen enrichment, we compared the spectra recorded after adsorption of CDCl₃ on the phosphate precursor “AlGaPO” and on four oxynitrides with increasing nitrogen contents. On the oxide, adsorption arises from CDCl₃ interacting with surface hydroxyl groups, on the oxynitrides basic sites are shown to be M–NH₂ groups. This interpretation is confirmed by FTIR of adsorbed SO₂. This revised version was published online in July 2006 with corrections to the Cover Date.     

Extreme catalysts from low-temperature environments

Cold-loving or psychrophilic organisms are widely distributed in nature as a large part of the earth's surface is at temperatures around 0 degrees C. To maintain metabolic rates and to prosper in cold environments, these extremophilic organisms have developed a vast array of adaptations. One main adaptive strategy developed in order to cope with the reduction of chemical reaction rates induced by low temperatures is the synthesis of cold-adapted or psychrophilic enzymes. These enzymes are characterized by a high catalytic activity at low temperatures associated with a low thermal stability. A study of protein adaptation strategies suggests that the high activity of psychrophilic enzymes could be achieved by the destabilization of the active site, allowing the catalytic center to be more flexible at low temperatures, whereas other protein regions may be destabilized or as rigid as their mesophilic counterparts. Due to these particular properties, psychrophilic enzymes offer a high potential not only for fundamental research but also for biotechnological applications.     

Enthalpies of formation of some solid hafnium nickel compounds and of the Ni-Rich HfNi liquid by direct reaction calorimetry

In the course of a systematic study of binary transition metal alloys, the enthalpies of formation of five Hf-Ni compounds were measured by direct reaction calorimetry: Hf_0.17Ni_0.83(l/6HfNi₅): Δ_fH(1323 K) = − 37,000 J/mole of atoms (±3200) Hf_0.22Ni_0.781/9Hf₂Ni₇): Δ_f(1623 K) = −50,700 J/mole of atoms (±2000) Hf_0.45Ni_0.55(l/2OHf₉Ni₁₁): Δ_fH(1473 K) = −54,500 J/mole of atoms (±2200) Hf_0.50Ni_0.50(l/2HfNi): Δ_fH(1573 K) = −47,900 J/mole of atoms (±1800) Hf_0.67Ni_0.33(l/3Hf₂Ni): ΔH(1423 K) = −36,700 J/mole of atoms (±1300) with reference to pure metals in their equilibrium states at the reaction temperatures. The Ni-rich Hf-Ni liquid was also studied by the dissolution of Hf in the liquid alloy of variable composition at 1743 and 1633 K. Results show that the enthalpy of formation of the liquid at a given composition depends strongly on temperature, and this point suggests the existence of associations in the liquid. The melting temperature of Hf_0.22Ni_0.78(Hf₂Ni₇) which was found (1705 K) is slightly lower than the one (1743 K) given in the literature. Formerly Senior Research Student with the Laboratoire de Thermodynamique Métallurgique, Université de Nancy Un, France     

Immunohistochemical Evaluation of Periodontal Regeneration Using a Porous Collagen Scaffold

(1) Aim: To immunohistochemically evaluate the effect of a volume-stable collagen scaffold (VCMX) on periodontal regeneration. (2) Methods: In eight beagle dogs, acute two-wall intrabony defects were treated with open flap debridement either with VCMX (test) or without (control). After 12 weeks, eight defects out of four animals were processed for paraffin histology and immunohistochemistry. (3) Results: All defects (four test + four control) revealed periodontal regeneration with cementum and bone formation. VCMX remnants were integrated in bone, periodontal ligament (PDL), and cementum. No differences in immunohistochemical labeling patterns were observed between test and control sites. New bone and cementum were labeled for bone sialoprotein, while the regenerated PDL was labeled for periostin and collagen type 1. Cytokeratin-positive epithelial cell rests of Malassez were detected in 50% of the defects. The regenerated PDL demonstrated a larger blood vessel area at the test (14.48% ± 3.52%) than at control sites (8.04% ± 1.85%, p = 0.0007). The number of blood vessels was higher in the regenerated PDL (test + control) compared to the pristine one (p = 0.012). The cell proliferative index was not statistically significantly different in pristine and regenerated PDL. (4) Conclusions: The data suggest a positive effect of VCMX on angiogenesis and an equally high cell turnover in the regenerated and pristine PDL. This VCMX supported periodontal regeneration in intrabony defects.     

Structural stability of intermetallic phases in the Sn–Ti system

The total energies of intermetallic compounds in the Sn–Ti system are calculated employing electronic density-functional theory (DFT) using pseudopotentials constructed by the projector augmented waves (PAW) method in the generalized gradient (GGA) approximation for the exchange and correlation energy. The calculations are performed for the experimentally observed compounds at their ideal stoichiometry as well as for structures which are stable in systems of early transition metals or rare earth elements with p-elements of columns IIIB, IVB, and VB. The calculated formation enthalpy of the hexagonal Sn₅Ti₆ compound is slightly less exothermic than the value obtained by direct reaction calorimetry. For the stable intermetallic compounds, the calculated zero-temperature lattice parameters agree well with those obtained experimentally at ambient temperature. More, for stable phases with unit cell-internal degree(s) of freedom, the results of ab initio calculations show good agreement when compared with data obtained by structural analysis of X-ray diffraction. The composition dependence of the enthalpies of formation is slightly asymmetric. The electronic densities of state of the D8₈- Sn₃Ti₅ compound have been computed; the curve shows the hybridization of Sn 5p states with Ti 3d states. The stability of the intermetallic compounds in the Ti–Sn system is due to this hybridization.     

Short-range synthetic aperture imaging at 633 nm by digital holography

We present an active optical synthetic aperture-imaging system. A phase-step digital holographic setup is used as a wavefront sensor in the far field. The overlap of the holograms enables the estimation and compensation of their relative positions and phase with a speckle cross-correlation algorithm. Experimental results on a short-range synthetic aperture setup at 633 nm are presented that are based on 128 x 128 holograms. The synthesis is executed in one direction by means of rotation of the object. Test images show a significant gain of resolution in the synthesis direction. Processing errors are estimated through experiment. Random processing errors of a synthetic pupil composed of 33 merged holograms are negligible, but biases induced by unknown optical aberrations ofthe reference wave induce defocusing and astigmatism.     

Reduction of the correlation sensitivity to the changes of the input illumination by a post processing based on the correlation statistics

Linear-correlation amplitude changes when the intensity level of the input image is modified. As recognition is often based on the correlation-peak level, a change of the input illumination may result in a false recognition. We propose an illumination-change compensation by a post processing of the correlation distribution that is based on statistical measures of the correlation histograms. The theoretical background and simulation results are provided in the frame of an actual application in biology.     

Author Index,Volume 8 (2002)

Authors Index

Author Index, Volume 8 (2002)