IR study on hydrogen bonding in epoxy resin-silica nanocomposites

The chemical and physical interactions between ingredients in composites play an important role in the improvement of service properties. The nucleophilic addition between polymer and isophoron diisocyanate molecules was monitored by FT-IR technique. The intensity loss of isocyanate absorption band in conjunction with the intensity growth of carboxyl absorption band indicates the progress of reaction. FT-IR spectroscopy was also adopted to examine the intermolecular hydrogen bonding of epoxy resin with silica as well as intramolecular one within polymer matrix. The vibration frequency of carboxyl group (-C=O) and hydroxyl group (-OH) shift from 1736cm^-1to 1728 cm^-1and 3420 cm^-1to 3414 cm^-1 respectively, indicating the occurrence of hydrogen bonding between -C=O and -OH. The vibration frequency of Si-OH moves from 3435 cm^-1 to 3414 cm-1, suggesting the involvement of silica. Whereas the vibration frequency of pending –OH in polymer chain moves from 3435 cm^-1to 3420 cm^-1or 3414cm^-1, proposing this kind of interaction can also happen within polymer matrix.     

IR study on hydrogen bonding in epoxy resin–silica nanocomposites

The chemical and physical interactions between ingredients in composites play an important role in the improvement of service properties. The nucleophilic addition between polymer and isophoron diisocyanate molecules was monitored by FT-IR technique. The intensity loss of isocyanate absorption band in conjunction with the intensity growth of carboxyl absorption band indicates the progress of reaction. FT-IR spectroscopy was also adopted to examine the intermolecular hydrogen bonding of epoxy resin with silica as well as intramolecular one within polymer matrix. The vibration frequency of carboxyl group （-C=O） and hydroxyl group （-OH） shifts from 1736 to 1728 cm^-1and 3420 to 3414 cm^-1, respectively, indicating the occurrence of hydrogen bonding between -C=O and -OH. The vibration frequency of Si-OH moves from 3435 to 3414 cm^-1, suggesting the involvement of silica. Whereas the vibration frequency of pending -OH in polymer chain moves from 3435 to 3420 cm^-1 or 3414 cm^-1, proposing that this kind of interaction can also happen within polymer matrix.     

Structural,morphological, Raman,optical, magnetic,and antibacterial characteristics of CeO<Subscript>2</Subscript> nanostructures

In this study, CeO₂ nanostructures were synthesized by a soft chemical method. A hydrothermal treatment was observed to lead to an interesting morphological transformation of the nanoparticles into homogeneous microspheres composed of nanosheets with an average thickness of 40 nm. Structural analysis revealed the formation of a single-phase cubic fluorite structure of CeO₂ for both samples. A Raman spectroscopic study confirmed the XRD results and furthermore indicated the presence of a large number of oxygen vacancies in the nanosheets. These oxygen vacancies led to room-temperature ferromagnetism (RTFM) of the CeO₂ nanosheets with enhanced magnetic characteristics. Amazingly, the nanosheets exhibited substantially greater antibacterial activity than the nanoparticles. This greater antibacterial activity was attributed to greater exposure of high-surface-energy polar surfaces and to the presence of oxygen vacancies.     

Identification of hundreds of conserved and nonconserved human microRNAs

MicroRNAs are noncoding RNAs of approximately 22 nucleotides that suppress translation of target genes by binding to their mRNA and thus have a central role in gene regulation in health and disease. To date, 222 human microRNAs have been identified, 86 by random cloning and sequencing, 43 by computational approaches and the rest as putative microRNAs homologous to microRNAs in other species. To prove our hypothesis that the total number of microRNAs may be much larger and that several have emerged only in primates, we developed an integrative approach combining bioinformatic predictions with microarray analysis and sequence-directed cloning. Here we report the use of this approach to clone and sequence 89 new human microRNAs (nearly doubling the current number of sequenced human microRNAs), 53 of which are not conserved beyond primates. These findings suggest that the total number of human microRNAs is at least 800.     

Synthesis and characterization of conducting polyaniline nanocomposites containing ZnO nanorods

Polyaniline (PANI) based nanocomposites filled with ZnO nanorods were prepared by the chemical oxidative method of the aniline in acid medium with ammonium peroxydisulphate (APS) as an oxidant. The composition, morphology and structure of the polymer and the nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), UV–vis spectroscopy and electrical conductivity. The characteristic FTIR peaks of PANI were found to shift to higher or lower wave number in PANI–ZnO composites due to formation of H-bonding. Different amounts of ZnO nanorods were used to verify this effect on the characteristics of the synthesized materials. These observed effects have been attributed to interaction of ZnO nanorods with PANI molecular chains. XRD results revealed that the crystallinity of PANI was more pronounced after addition of nanorods, while the intensity of the peaks increased by addition of ZnO nanorods. Electrical conductivity of the PANI–ZnO nanocomposite film was found to be smaller than that of the PANI film. The decrease of electrical conductivity in PANI–ZnO films as compared to PANI was attributed to the interfaces formed between oxygen of ZnO nanorods and hydrogen of PANI. Also, TGA results showed that the decomposition of the nanocomposite was less than that of pure polyaniline which confirms the successful fabrication of products. These conductive polymers can be used in commercial paints as an additive.     

Climatic regionalization mapping of the Murrumbidgee Irrigation Area,Australia

In this study,spatial analysis techniques were used to generate climatic zoning maps of the East Murrumbidgee Irrigation Area (MIA),Australia.Long term climate data were used to analyze and assess regional climatic variation by cluster analysis in a GIS environment.Based on thermal and moisture factors,four variables were chosen to develop climate zones.These variables include annual average rainfalls,annual average ETc,annual average Growing Day Degree (GDD) and daily average temperature generated from daily climate data of 36 years (1971-2006) on 12 local weather stations as the fundamental elements of regional climate characteristics.GIS-based spatial analysis models are used to map climate sub-regions from sets of climatic parameters derived from regional climate data sources.Two climate zoning schemes are presented by integration of spatial interpolation,spatial cluster analysis and climate indices methods.One scheme comes with the two climate zones of the West and the East based on spatial cluster analysis according to selected climatic variables,and the other comes with the three comprehensive hydro-thermal zones and the six hydro-thermal balance zones.     

A single-step synthesis of nitrogen-doped graphene sheets decorated with cobalt hydroxide nanoflakes for the determination of dopamine

Nitrogen-doped reduced graphene oxide(NrGO)sheets decorated with Co(OH)_2nanoflakes were prepared by a single-step hydrothermal process.The morphological and structural characterizations of as synthesized Nr GO@Co(OH)_2nanoflakes were performed by field emission scanning electron microscopy(FESEM),EDX-mapping and X-ray diffraction(XRD).Nr GO@Co(OH)_2nanoflakes modified glassy carbon electrode(GCE)was used for electrochemical sensing of dopamine in neutral medium.The nanocomposite modified electrode showed enhanced electrochemical sensing ability for the detection of dopamine and the limit of detection(Lo D)was found to be 0.201μM with a sensitivity value of 0.0286±0.002 m A m M~(-1).Interference studies revealed that Nr GO@Co(OH)_2─GCE endow excellent selectivity for DA detection even in the presence of higher concentration of common co-existing physiological interfering analytes.Additionally,proposed sensor demonstrated excellent performance in urine samples with promising reproducibility and stability.     

Comparative studies of murine anionic and cationic arylsulfatase B

Summary Murine brain possesses an anionic form of arylsulfatase B which accounts for approximately 12–16% of nonmicrosomal arylsulfatase activity. This isozyme is antigenically similar to cationic arylsulfatase B, displays a similar developmental profile, and can be converted to a form resembling the cationic species by prior treatment with neuraminidase.This research was supported in part by National Institutes of Health Grant: GM 27707.     

Paths to understanding the genetic basis of autoimmune disease

Some people inherit an unfortunate combination of genetic sequences, such that exposure to an external trigger causes their immune response to turn on their own tissues. Although mutations in a single gene can cause autoimmunity, most autoimmune diseases are associated with several sequence variants. Marked advances in genetic resources and tools are now making it possible to identify the sequence variants that contribute to autoimmune diseases--promising a better understanding of how we normally remain tolerant of our own tissue components, and how this goes wrong in autoimmune disease.