Transmission electron microscope characterisation of molar-incisor-hypomineralisation

Molar-incisor-hypomineralisation (MIH), one of the major developmental defects in dental enamel, is presenting challenge to clinicians due, in part, to the limited understanding of microstructural changes in affected teeth. Difficulties in the preparation of site-specific transmission electron microscope (TEM) specimens are partly responsible for this deficit. In this study, a dual-beam field emission scanning electron microscope (FESEM)/focused ion beam (FIB) milling instrument was used to prepare electron transparent specimens of sound and hypomineralised enamel. Microstructural analysis revealed that the hypomineralised areas in enamel were associated with marked changes in microstructure; loosely packed apatite crystals within prisms and wider sheath regions were identified. Microstructural changes appear to occur during enamel maturation and may be responsible for the dramatic reduction in mechanical properties of the affected regions. An enhanced knowledge of the degradation of structural integrity in hypomineralised enamel could shed light on more appropriate management strategies for these developmental defects.     

Ureidosulfocoumarin Derivatives As Selective and Potent Carbonic Anhydrase IX and XII Inhibitors

Owing to severe allergic reactions (anaphylaxis) and resistance exhibited by sulfonamide-based carbonic anhydrase (CA) inhibitors, non-classical or non-sulfonamide CA inhibitors are gaining increased attention by medicinal chemists. In this context, we report the design and synthesis of 30 new non-sulfonamide sulfocoumarin derivatives as CA inhibitors. They were investigated against hCA I and II (cytosolic isozymes) as well as hCA IX and XII (transmembrane, tumor-associated enzymes). All compounds showed prominent selectivity for the tumor-associated isoenzymes hCA IX and XII over the cytosolic isoenzymes hCA I and II. Among all synthesized compounds, 1-(2,2-dioxidobenzo[e][1,2]oxathiin-6-yl)-3-(o-tolyl)urea( 5 j )and1-(3-fluorophenyl)-3-(8-methoxy-2,2-dioxidobenzo[e][1,2]oxathiin-6-yl)urea( 5 q )were found to be more potent and to have better inhibition constant values against hCA IX than the standard acetazolamide (AAZ), with K_i values of 23.6 and 23.3 nM, respectively. All other compounds were found to be active under K_i=920 nM against hCA IX and XII.This study provides a new perspective for the future development of non-sulfonamide derivatives as selective CA inhibitors.     

Effect of quantum interference on a three-level atom driven by two laser fields

Abstract

We study the effect of quantum interference on the population distribution and absorptive properties of a V-type three-level atom driven by two lasers of unequal intensities and different angular frequencies. Three coupling configurations of the lasers to the atom are analysed: (a) both lasers coupled to the same atomic transition, (b) each laser coupled to different atomic transition and (c) each laser coupled to both atomic transitions. Dressed states for the three coupling configurations are identified, and the population distribution and absorptive properties of the weaker field are interpreted in terms of transition dipole moments and transition frequencies among these dressed states. In particular, we find that in the first two cases there is no population inversion between the bare atomic states, but the population can be trapped in a superposition of the dressed states induced by quantum interference and the stronger field. We show, that the trapping of the population, which results from the cancellation of transition dipole moments, does not prevent the weaker field to be coupled to the cancelled (dark) transitions. As a result, the weaker field can be strongly amplified on transparent transitions. In the case of each laser coupled to both atomic transitions the population can be trapped in a linear superposition of the excited bare atomic states leaving the ground state unpopulated in the steady state. Moreover, we find that the absorption rate of the weaker field depends on the detuning of the strong field from the atomic resonances and the splitting between the atomic excited states. When the strong field is resonant to one of the atomic transitions a quasi-trapping effect appears in one of the dressed states. In the quasi-trapping situation all the transition dipole moments are different from zero, which allows the weaker field to be amplified on the inverted transitions. When the strong field is tuned halfway between the atomic excited states, the population is completely trapped in one of the dressed states and no amplification is found for the weaker field.     

Correlations of Bridgman-Grown Cd0.9Zn0.1Te Properties with Different Ampoule Rotation Schemes

A unique ampoule rotation system was developed at the Center for Materials Research at Washington State University for enhancing convection in the cadmium zinc telluride (CZT) melt by applying different ampoule rotation schemes (RS). Experiments were performed with different initial charge material concentrations and rotation parameters (acceleration, speed, rotation time, etc.). The applied speed and acceleration ranged from 30 rpm to 50 rpm and 30 rpm² to 200 rpm², respectively. Zinc (Zn) distribution profiles of radial and axial slices from the same regions in the grown ingot were determined by room-temperature photoluminescence mapping. The results demonstrate the effects of ampoule rotation on Zn segregation and growth interface evolution. The most stable interface propagation was obtained when 0.2 atomic percent (at.%) excess tellurium (Te) was used in the initial charge material along with a trapezoidal RS. Uniform radial Zn distribution was achieved using triangular RS, which is because of the interface flatness near the axis. Comparison of secondary phase (SP) generation for different RS and initial excess Te was performed. Closed-container CZT growth was performed using the trapezoidal RS, which resulted in high single-crystal yield with lower-diameter SP near the last-to-freeze region. High-resistivity (on the order of 10¹⁰ Ω-cm) crystals were obtained from all the RS. The mobility–lifetime product (μτ)_e of electrons for planar detectors was found to be on the order of 3 × 10^?3 cm²/V to 5 × 10^?3 cm²/V for all the RS with 3.5 at.% excess Te growths.     

Effect of aflatoxin,ochratoxin and their combination on protein and energy utilisation in white leghorn laying hens

The effect of dietary aflatoxin B₁ (AF) at levels of 0.5, 1 and 2 mg kg^?1, ochratoxin A (OA) at levels of 1, 2 and 4 mg kg^?1 and their corresponding combinations on protein and energy utilisation as well as energy partitioning was studied in white leghorn laying hens. Protein retention was adversely affected at all levels of AF and OA either singly or in combination, though the effect was more evident with OA and AF + OA. Minimum protein retention was recorded in hens fed the combination of toxins at their highest levels (2 mg kg^?1 AF + 4 mg kg^?1 OA). Aflatoxin at 1 and 2 mg kg^?1 and OA and AF + OA at all levels caused a significant reduction in metabolisable energy (ME) value of the diets. The minimum ME value was recorded for the diet containing both toxins at their highest levels (2 mg kg^?1 AF + 4 mg kg^?1 OA). A significant depression in egg energy deposition was observed with dietary inclusion of 1 and 2 mg kg^?1 AF, 2 and 4 mg kg^?1 OA and all levels of AF + OA in period I. In period II the reduction in egg energy deposition was significant at all levels of toxins either singly or in combination. Body energy deposition was adversely affected in hens fed the highest levels of AF (2 mg kg^?1) and OA (4 mg kg^?1) and all levels of AF + OA in period I. However, in period II a significant decrease in body energy deposition was observed at all levels of toxins except 1 mg kg^?1 OA. A significant increase in maintenance energy (ME_m/W^0.75 day^?1) requirement was recorded in hens fed 2 mg kg^?1 AF, 4 mg kg^?1 OA and all levels of AF + OA. It is suggested that AF and OA either singly or in combination affect not only protein and energy utilisation in laying hens but also energy partitioning i.e. egg and body energy deposition and maintenance energy requirement. However, the combination of toxins (AF + OA) has more severe adverse effects on all parameters than the individual toxins because of their synergistic toxicity effect. Copyright © 2007 Society of Chemical Industry     

Optical Double-resonance Spectra with Time-dependent Pulses

Abstract

The optical double-resonance spectrum for a three-level atom interacting with two monochromatic laser pulses with arbitrary temporal profiles is calculated by use of Light's perturbation theory. Unlike some earlier work, the theory is not restricted to exact resonance of the pump laser, or to pulse areas which are exact multiples of 2π. A variety of pulse profiles are investigated, and the spectra are found to depend strongly on the detuning of the pump laser.     

Synthesis and characterization of poly(acrylonitrile-co-methylmethacrylate) nanocomposites reinforced by functionalized multiwalled carbon nanotubes

Polyacrylonitrile-co-poly(methylmethacrylate)/multiwalled carbon nanotubes (PAN-co-PMMA/MWCNTs) nanocomposites were synthesized by an in situ emulsifier-free polymerization method with variable percentages of functionalized carbon nanotube (f-MWCNT). MWCNTs were functionalized with concentrated H₂SO₄ and HNO₃ with a continuous sonication process. Chemical interaction of f-MWCNT with the copolymer was studied by UV-visible spectroscopy. Fourier transform infrared spectroscopy proved the interaction of f-MWCNT with the PAN-co-PMMA copolymer matrix. The structural interaction of f-MWCNT with copolymer matrix was investigated by X-ray diffraction study. The dispersion and morphology of the f-MWCNT in the copolymer matrix were studied by scanning electron microscopy and high-resolution transmission electron microscopy. It was noticed that the f-MWCNTs were uniformly dispersed within the copolymer matrix. The thermal property of the PAN-co-PMMA/f-MWCNT nanocomposite was analyzed by thermogravimetric analysis. It was noticed that the thermal stability of the PAN-co-PMMA/f-MWCNT nanocomposite was more than that of the virgin copolymer matrix. When the electrical conductivity property of the synthesized nanocomposite was measured, it was noticed that the better dispersion of f-MWCNT in the non-conductive PAN-co-PMMA copolymer matrix made the PAN-co-PMMA/f-MWCNT nanocomposites conductive. From the measurement of gas barrier properties of synthesized nanocomposites, it was assumed that the well-dispersed f-MWCNT in the copolymer matrix creates the huddles for penetration of oxygen gas. It was noticed that the oxygen permeability of the PAN-co-PMMA/f-MWCNT nanocomposite was reduced by five times as compared to that of the neat PAN-co-PMMA copolymer matrix. The PAN-co-PMMA/f-MWCNT nanocomposites with higher thermal stability and reduced oxygen permeability properties may be suitable for application as conducting packaging materials.     

Effect of organoclays on the thermal,mechanical, and oxygen barrier properties of poly(methylmethacrylate‐co‐acrylonitrile)/clay nanocomposites

The nanostructured hybrid materials of poly(methylmethacrylate‐co‐acrylonitrile) copolymer were synthesized with incorporation of two organically modified clays, Cloisite® 30B and 93A by in situ intercalative emulsifier‐free emulsion polymerization method. The synthesized products were characterized by Fourier transform infrared spectroscopy to get evidence of copolymerization and formation of copolymer‐clay nanocomposite. X‐ray diffraction study and transmission electron microscopy analysis revealed that the clays were successfully intercalated and exfoliated into the copolymer matrix. Thermal properties of the nanocomposites were studied as a function of clay content of different clay types by thermogravimetric analysis. The results showed significant effect of both the clays in enhancing thermal resistance of the materials. Mechanical properties of the composites were also found to be improved at optimum clay loading. Oxygen barrier property of these materials was measured and it was found that the oxygen permeability was reduced almost by half due to incorporation of clays at 3% loading. Further, it was observed that Cloisite® 93A was more effective for improvement in properties when compared with Cloisite® 30B in the hybrid materials. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Tuning Conversion Efficiency in Metallo Endohedral Fullerene‐Based Organic Photovoltaic Devices

Here the influence that 1‐(3‐hexoxycarbonyl)propyl‐1‐phenyl‐[6,6]‐Lu₃N@C₈₁, Lu₃N@C₈₀–PCBH, a novel acceptor material, has on active layer morphology and the performance of organic photovoltaic (OPV) devices using this material is reported. Polymer/fullerene blend films with poly(3‐hexylthiophene), P3HT, donor material and Lu₃N@C₈₀–PCBH acceptor material are studied using absorption spectroscopy, grazing incident X‐ray diffraction and photocurrent spectra of photovoltaic devices. Due to a smaller molecular orbital offset the OPV devices built with Lu₃N@C₈₀–PCBH display increased open circuit voltage over empty cage fullerene acceptors. The photovoltaic performance of these metallo endohedral fullerene blend films is found to be highly impacted by the fullerene loading. The results indicate that the optimized blend ratio in a P3HT matrix differs from a molecular equivalent of an optimized P3HT/[6,6]‐phenyl‐C₆₁‐butyric methyl ester, C₆₀–PCBM, active layer, and this is related to the physical differences of the C₈₀ fullerene. The influence that active layer annealing has on the OPV performance is further evaluated. Through properly matching the film processing and the donor/acceptor ratio, devices with power conversion efficiency greater than 4% are demonstrated.     

Influence of Calcination Temperature on the Microstructure and Mechanical Properties of a Gel-Derived and Sintered 3 mol% Y-TZP Material

A pure coprecipitated 3 mol% Y-TZP powder was subjected to two calcination temperatures, 600° and 1000°C, prior to compaction and sintering. Significant differences in the initial sintering behavior were observed. The lower temperature calcined powder exhibited abnormal grain growth. The resultant mechanical properties mirrored the microstructure with the lower temperature calcined material having lower flexural strength. Hardness measurements of the two sintered bodies revealed significant differences in the two phases of the lower temperature calcined material. Differences in reactivity of the two powders after calcination are suggested as the basis for the difference in microstructure and resultant mechanical properties.