Annihilation characteristics of positrons in free-standing thin metal and polymer films

Annihilation characteristics of positrons and positronium (Ps) in thin metal and polymer films were studied. Monoenergetic positrons were implanted into free-standing thin W and Au films and the annihilation γ-rays of positron-electron pairs were measured as a function of the incident energy of positrons. At the front-side surfaces of the films, an emission of Ps into vacuum and a resultant self-annihilation of ortho-Ps (o-Ps) were observed. At the backside surfaces, the Ps emission was found to be enhanced by an increase in the numbers of epithermal positrons and/or secondary electrons introduced by the impact of energetic positrons. For thin polymer films (polyester and polystyrene), the emission rate of o-Ps from the backside surfaces was higher than that from the metal films, which was attributed to the out-diffusion of o-Ps formed in the films. Those results suggested that the emission rate of Ps into vacuum was sensitive to the Ps formation process in the bulk and at the surface.     

Study on the preparation and properties of novel block copolymeric materials based on structurally modified organometallic as well as organic polyamides and polydimethylsiloxane

Some novel ferrocene‐containing polyamide‐based block copolymer materials with telechelic polydimethylsiloxane oligomer and their organic analogues were prepared by solution‐phase polycondensation of ferrocene‐based organometallic and terephthaloyl‐ as well as isophthaloyl‐based organic acyl chlorides with a series of semi‐aromatic diamines having ether linkages together with variable aliphatic character. The corresponding polyamides of the synthesized materials, without polydimethylsiloxane segment, were also prepared for comparison of physicochemical properties. None of the synthesized organometallic and organic block copolymers along with their respective polyamides melted below 300 °C and their structural features were confirmed by their physical properties and spectroscopic studies. The weight‐average molecular weights and molecular parameters of all these materials were determined by the static laser light scattering technique. The materials were soluble in sulfuric acid and partially soluble in common organic solvents, and yet became readily soluble upon N‐trifluoroacetylation. The synthesized materials were further characterized by their water absorption characteristics, X‐ray diffraction studies and surface morphology (SEM and AFM) and thermal (DSC and TG) analyses, and their structure–property relationships were elucidated from these studies. The energies of pyrolysis for these materials were calculated by the Horowitz and Metzger method. © 2012 Society of Chemical Industry     

Thermodynamic and NMR investigations on the adsorption mechanism of puerarin with oligo‐β‐cyclodextrin‐coupled polystyrene‐based matrix

BACKGROUND: Adsorption of puerarin on native resin polystyrene (PS) and oligo‐β‐cyclodextrin‐coupled matrix (PS‐CDP) was studied for interactions between the adsorbents and the adsorbates. The sorption mechanism on PS‐CDP was investigated using the isosteric heat approach and nuclear magnetic resonance (NMR) spectroscopy. RESULTS: The equilibrium adsorption data of puerarin on the two matrices PS and PS‐CDP (polystyrene‐based matrix before and after coupling by oligo‐β‐cyclodextrin) in the temperature range 288–318 K were well fitted to the Freundlich adsorption isotherm model. The energetic heterogeneity of the media was observed based on the result that the values of isosteric enthalpy were quantitatively correlated with the fractional loading of puerarin adsorption. The more heterogeneous surface of PS‐CDP compared with PS was attributed to the complexation between puerarin and β‐cyclodextrin (β‐CD). NMR studies validated the formation of an inclusion complex puerarin/β‐CD. CONCLUSION: Thermodynamic and NMR studies confirmed that multi‐interaction cooperatively governed the isolation of puerarin from aqueous solution on PS‐CDP matrix. Copyright © 2009 Society of Chemical Industry     

Purification,surface modification of coal ash silica and its potential application in rubber composites

This article reports the purification and surface modification of coal ash silica and afterwards its utilization as reinforcing filler in solution‐styrene‐butadiene rubber/butadiene rubber (S‐SBR/BR). The coal ash silica free of unwanted metal ions/mineral oxides was obtained using phosphoric acid. The chemical composition of the purified coal ash silica in comparison to impure coal ash indicates the presence of characteristic hydroxyl functional group at 3440 cm^?1 and an increase in the oxygen content as determined with the help of Fourier Transform Infrared and x‐ray photoelectron spectroscopy, respectively. The contact angle analysis shows that after purification the polar part of the surface energy increased to 17.5 from 12 m Jm^?2. While the surface area increased to an order of magnitude, i.e., 11.6 to 110.5 m² g^?1. The modification of purified silica particles with bis(3‐triethoxysilylpropyl) tetrasulfane reveal the functionalization of hydroxyl to ‐Si‐O‐R groups as detected at 1560 cm^?1. As a consequence, the modified silica based S‐SBR/BR composite resulted in improved mechanical properties due to enhanced silica‐rubber interaction. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Morpho-anatomical characterization of some members of euglenophycota (algae) of north-east Punjab,Pakistan based on light microscopy (LM) and scanning electron microscopy (SEM)

The study was carried out in four districts, that is, Gujranwala, Gujarat, Narowal and Sialkot of Punjab, Pakistan. The sampling was carried out randomly in different seasons from the water bodies especially from wastewater. Twenty-one species belonging to Euglenophycota were identified using light microscopy and scanning electron microscopy from which 04 species belong to genus Phacus, 02 species belonging to Trachelomonas and Euglena based on light microscopy. It was observed that Euglena was the most diverse genus and it is supposed to be the indicator species of the polluted water. It was observed that E. oblonga was found in maximum pH range, that is, 7.0–11.0. Similarly, E. brevicaudatus was found in maximum EC, that is, 169 ± 1.5 ms/cm these outcomes indicated that for internal examination along with LM, SEM was necessary for correct identification of algal sample up to specie level.     

Pollen morphology and its taxonomic potential in some selected taxa of Caesalpiniaceae observed under light microscopy and scanning electron microscopy

Pollen micromorphology is not only used to check the functional and structural evolution in plants but also to solve the taxonomic problem related to the classification of plants. Therefore, keeping in view the significance of pollen traits, selected taxa of the subfamily Caesalpiniaceae was collected from different geographical regions of Pakistan. The species were then analyzed under both light microscopy and scanning electron microscopy techniques to investigate the importance of micromorphological characters of pollen in the identification and classification of species. Great variation was recorded in equatorial shape, surface ornamentation, tectum, polar diameter, equatorial diameter, and exine thickness. However, little variation was observed in pollen type, polar shape, and fertility of pollen. The equatorial shape of five types was observed: prolate, prolate-spheroidal, spheroidal-subprolate, subspheroidal-prolate, and subspheroidal. Four types of surface ornamentation, psilate, granulate, clavate, and perforate, were recorded. Tectum of five types, intactate, reticulate regulate, medium reticulate, tactate, and striate, was observed. Sexine was thicker than nexine in all studied species. The largest polar diameter was observed in Caesalpinia pulcherrima 64.1 μm while the smallest in Parkinsonia aculeata 26.1 μm. The largest equatorial diameter was found in C. pulcherrima of 70.25 μm whereas the smallest in P. aculeata 27.57 μm. All the pollens analyzed were tricolporate. All studied species have a fertility ratio of more than 90%. A taxonomic key was developed to show the variation in pollen features and delimit species for the correct identification. In conclusion, the pollen traits were found useful to define species boundaries at various taxonomic ranks and will strengthen the taxonomy of this subfamily. Besides, this study also explored the palynological traits and their implication in the taxonomy of the subfamily Caesalpiniaceae.     

Palyno-anatomical characters and their systematic significance in the family Apiaceae from Chitral,eastern Hindu Kush,Pakistan

The present study was performed to provide a detailed explanation of leaf epidermal anatomy and pollen micromorphological features of selected species of family Apiaceae from Chitral, eastern Hindu Kush region as the basis of forthcoming studies. In the present article pollen morphology of eight species and foliar epidermal of seven species of family Apiaceae have been examined through microscopic techniques. In results two types of pollen prolate (five species) and perprolate (three species) with three colpi have been recorded. The exine ornamentation was found to be regulate, striate, and cerebroid. Largest pollen was found in Heracleum leucocarpum with the polar diameter of 43.25 μm and equatorial diameter of 21.6 μm. Smallest pollen was observed in Elaeosticta chitralica with the polar diameter of 18.4 μm. The P/E ratio varied from 1.59 to 2.16. Regarding to foliar epidermal anatomy, three types of epidermal cells including rectangular, irregular, and polygonal with variation in anticlinal wall pattern were determined. In the selected species three kinds of stomata comprising anisocytic, anomocytic, and paracytic type were reported in the current research. The size of epidermal cells ranged from 106 × 42.50 μm in Bupleurum falcatum subsp. cernuum and 77.25 × 26.35 μm in Prangos pabularia in adaxial surface. Largest stomatal complex was found in Prangos pabularia both in adaxial 33.55 × 20.05 μm and abaxial 50.25 × 39.40 μm. All the observed quantitative and qualitative features of the species were proved to be useful in the delimitation of species at generic and species level.     

Comparison of eluted monomer from different indirect and direct resin composites

Indirect resin composites used in indirect restorations have been used as alternative methods to avoid the negative effects of a direct application. The composition and structure of these are similar to a direct composite. Several authors have discussed the elution monomer from resin composites because it is a crucial factor in optimizing the physical properties and biocompatibility of resin composites. The aim of this study was to compare the elution of monomers from different resin composites using high-performance liquid chromatography (HPLC). Indirect composites including Signum, Gradia, and Solidex, and direct composite Filtek Ultimate were used. The samples (2 x 5 mm) were prepared and polymerized for 20 seconds with a light-emitting diode unit. A secondary curing was then applied to the indirect resin composites. After fabrication, each sample was immediately immersed in a 75 wt% ethanol/water solution and analyzed by HPLC. The obtained data were analyzed with one-way ANOVA and Tukey HSD (p < 0.05). Residual monomers were eluted from indirect and direct resin composites and the amount of eluted monomers increased over time. The highest mean concentrations of residual Bis-GMA, UDMA, TEGDMA, and HEMA were detected with the Filtek Ultimate (2,342 µM), Solidex (7,908 µM), Signum (2.8 µM), and Filtek Ultimate (9.7 µM), respectively. The highest amount of eluted monomer concentrations detected was viewed as critical for toxic reactions in human cells.     

Suppression of TRPV1/TRPM8/P2Y Nociceptors by Withametelin via Downregulating MAPK Signaling in Mouse Model of Vincristine-Induced Neuropathic Pain

Vincristine (VCR) is a widely used chemotherapy drug that induced peripheral painful neuropathy. Yet, it still lacks an ideal therapeutic strategy. The transient receptor potential (TRP) channels, purinergic receptor (P2Y), and mitogen-activated protein kinase (MAPK) signaling play a crucial role in the pathogenesis of neuropathic pain. Withametelin (WMT), a potential Phytosteroid isolated from datura innoxa, exhibits remarkable neuroprotective properties. The present investigation was designed to explore the effect of withametelin on VCR-induced neuropathic pain and its underlying molecular mechanism. Initially, the neuroprotective potential of WMT was confirmed against hydrogen peroxide (H₂O₂)-induced PC12 cells. To develop potential candidates for neuropathic pain treatment, a VCR-induced neuropathic pain model was established. Vincristine (75 μg/kg) was administered intraperitoneally (i.p.) for 10 consecutive days (day 1–10) for the induction of neuropathic pain. Gabapentin (GBP) (60 mg/kg, i.p.) and withametelin (0.1 and 1 mg/kg i.p.) treatments were given after the completion of VCR injection on the 11th day up to 21 days. The results revealed that WMT significantly reduced VCR-induced pain hypersensitivity, including mechanical allodynia, cold allodynia, and thermal hyperalgesia. It reversed the VCR-induced histopathological changes in the brain, spinal cord, and sciatic nerve. It inhibited VCR-induced changes in the biochemical composition of the myelin sheath of the sciatic nerve. It markedly downregulated the expression levels of TRPV1 (transient receptor potential vanilloid 1); TRPM8 (Transient receptor potential melastatin 8); and P2Y nociceptors and MAPKs signaling, including ERK (Extracellular Signal-Regulated Kinase), JNK (c-Jun N-terminal kinase), and p-38 in the spinal cord. It suppressed apoptosis by regulating Bax (Bcl2-associated X-protein), Bcl-2 (B-cell-lymphoma-2), and Caspase-3 expression. It considerably attenuated inflammatory cytokines, oxidative stress, and genotoxicity. This study suggests that WMT treatment suppressed vincristine-induced neuropathic pain by targeting the TRPV1/TRPM8/P2Y nociceptors and MAPK signaling.