Novel Thermoresponsive Biodegradable Nanocomposite Hydrogels for Dual Function in Biomedical Applications

Nanocomposite hydrogels were prepared through a blend solution of poly(lactic acid) and poly(N-isopropylacrylamide)-co-acrylamide via free radical polymerization. Plant extractions were used for the synthesis of Ag nanoparticles to study the antibacterial activity of the hydrogels. Similarly, 5-Fluorouracil drug was loaded through both in situ and ex situ methods to study thecontrolled release profiles. The nanocomposite hydrogels were characterized by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, Thermo gravimetric analysis - Differential scanning calorimetry (TGA-DSC), X-ray diffractometer, scanning electron microscopy, and transmission electron microscope. The dissolution and the agar diffusion test were performed to evaluate the drug release and antibacterial activity, respectively. The results suggested that the fabricated nanocomposite hydrogels can be used as a promising candidate for dual functions in biomedical applications.     

Graphene-ZnO nanocomposite for highly efficient photocatalytic degradation of methyl orange dye under solar light irradiation

A facile synthesis of graphene oxide-zinc oxide nanocomposite (GO-ZnO) was performed by using wet chemical method of graphene oxide and zinc acetate precursors. The nanocomposite was characterized and intercalated with Raman spectroscopy, FE-SEM, TEM, SAED and EDAX. The crystalline nature was studied from P-XRD, and surface area of the sample was analyzed by BET. The chemical composition was explained in the light of XPS phenomenon. The photo electron-excitation (PL) studies were conducted for understanding the photocatalytic mechanism, and photocatalytic degradation of methyl orange was studied by using UV-VIS spectrophotometer. We investigated the photocatalytic activity involving GO-ZnO nanocomposite besides checking the re-stability of the composite. Significant high-performance photocatalytic activity of GO-ZnO nanocomposite was exhibited on methyl orange degradation under solar light.     

Fabrication of bimetallic PtPd alloy nanospheres supported on rGO sheets for superior methanol electro-oxidation

Bimetallic PtPd nanospheres strongly fabricated on reduced graphene oxide (rGO) sheets (rGO-PtPd) by simple one pot wet reflux method for superior methanol electro-oxidation. There is no any other polymer or seed involved for preparation of nanocomposite. The as-synthesized materials structure and morphology was calibrated by Powdered X-ray diffraction (P-XRD), Raman, X-ray photo electron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The PtPd nanoparticles supported rGO sheets displays superior electro-catalytic activity and stability towards methanol electro-oxidation (MOR) because of their large electrochemical surface area (ECSA, which is 1.68 times greater than that of commercial Pt/C black) and synergistic effect of the bimetallic alloy. The rGO-PtPd showed enhanced electro-catalytic performances towards MOR in acidic media due to particle size and uniform distribution of particles, which rGO-Pt1Pd1 (Pt/Pd molar ratio 1/1) showed the more specific activity, mass activity and stability for MOR. Thus, as-synthesized rGO-PtPd catalyst could apply potential applications in direct methanol fuel cells (DMFCs) to lower their cost and advance their cycle ability, which make it promising for practical catalysis in energy conversion and storage.     

Preparation and characterization of nanoparticle-filled,mixed-matrix membranes for the pervaporation dehydration of isopropyl alcohol

Novel polymeric mixed-matrix membranes (MMMs) were prepared by the incorporation of different amounts of 13X zeolite into a sodium carboxymethylcellulose (NaCMC)/poly(vinyl alcohol) (PVA) blend matrix. The resulting MMMs were characterized by attenuated total reflectance–Fourier transform infrared spectroscopy to analyze the possible chemical reactions between NaCMC, PVA, zeolites, and glutaraldehyde. Scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and X-ray diffraction were used to analyze the surface morphology, thermal stability, and crystallinity, respectively, of the membranes. Swellings studies were performed at 35°C, and we found that membranes containing 20 wt % zeolite showed higher values (960 kg m⁻² h⁻¹) at 17.5 wt % water in an isopropyl alcohol (IPA)/water mixture. Pervaporation (PV) experiments were also performed to evaluate the membrane performance in different compositions of the IPA/water mixture at 35°C. The mechanical properties were also tested, and we found that the optimum mechanical strength and percentage elongation at break were 42.24 N/mm² and 3.38, respectively, for the membrane containing 15 wt % zeolite. The experimental results show that both the flux and selectivity increased with increasing zeolite content. The membrane containing 20 wt % zeolite showed the highest separation selectivity (5118) with a substantial flux of 0.121 kg m⁻² h⁻¹ at 35°C and with 10 wt % water in the feed; this suggested that the membranes could be used effectively to break the azeotropic point of the water–IPA mixture, so as to remove a small amount of water from IPA. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Use of a C-Band Ground-Based Scatterometer to Monitor Surface Roughness and Soil Moisture Changes

Eight experiments on remote sensing of soil moisture and surface roughness were carried out over bare fields with a microwave C-band scatterometer from 1998 until 2001. This device is able to provide backscattering coefficients in the range of +10 dB and –40 dB for incidence angles between 10° and 60°. The objective is to assess the conditions (of roughness and incidence angle) in which it is possible to separate the effects of roughness and soil moisture, thus allowing a reliable estimation of soil moisture from backscattering coefficients. In particular, starting with measurements carried out at different incidence angles, we experimented with an approach to normalize the backscattering coefficients to a reference angle with the principal aim of comparing data sets acquired in different conditions and putting in evidence the radar response to soil moisture variations. A sensitivity analysis, performed over the whole acquired data set, confirmed that the dependence of backscattering coefficients on the incidence angle is influenced more by surface roughness than by soil moisture, as indicated also by theoretical models and other similar data sets. A significant result is that a simple model for comparing data acquired with different incidence angles works better for rough surfaces: only in this case an acceptable correlation between backscattering coefficients and soil moisture is retained. In order to better understand this behavior, the experiments carried out in 2001 were designed to acquire radar measurements on a test site where soil moisture was controlled with artificial irrigation and constantly monitored during the dry-down phase. This allowed a direct estimation of the relationship between radar responses and soil moisture, a quantitative evaluation of the sensitivity of our device and a test for the model developed using the previous acquisitions.     

Grafting of Dispersants on MoS2 Nanoparticles in Base Oil Lubrication of Steel

Solid lubricant nanoparticles in suspension in oil are good lubricating options for practical machinery. In this article, we select a range of dispersants, based on their polar moieties, to suspend 50-nm molybdenum disulfide particles in an industrial base oil. The suspension is used to lubricate a steel on steel sliding contact. A nitrogen-based polymeric dispersant (aminopropyl trimethoxy silane) with a free amine group and an oxygen-based polymeric dispersant (sorbital monooleate) when grafted on the particle charge the particle negatively and yield an agglomerate size which is almost the same as that of the original particle. Lubrication of the contact by these suspensions gives a coefficient of friction in the ~0.03 range. The grafting of these surfactants on the particle is shown here to be of a chemical nature and strong as the grafts survive mechanical shear stress in tribology. Such grafts are superior to those of other silane-based test surfactants which have weak functional groups. In the latter case, the particles bereft of strong grafts agglomerate easily in the lubricant and give a coefficient of friction in the 0.08?C0.12 range. This article investigates the mechanism of frictional energy dissipation as influenced by the chemistry of the surfactant molecule.     

Mechanical Behavior of Commercial Purity Titanium Processed by Equal Channel Angular Pressing Followed by Cold Rolling

Equal channel angular pressing (ECAP) has been widely shown to be able to produce ultrafine grained microstructures in a variety of metals and alloys. In this study, the ECAP process has been used as an intermediate processing step prior to cold rolling to achieve superior mechanical properties. Commercial purity (CP) titanium was processed by ECAP at 400 °C and subsequently the ECAPed specimens were subjected to a post deformation process by conventional cold rolling. Microstructure and mechanical property characterization of CP titanium billets subjected to ECAP alone and ECAP plus cold rolling were carried out. 98 % reduction in thickness (from 15 to 0.2 mm thickness) was possible by cold rolling. Post-deformation by cold rolling significantly increased the strength of CP titanium while retaining considerable ductility. TEM images after ECAP show deformation induced dislocation networks and the disintegration of the initial coarse grained microstructure giving rise to lamellar structures 0.3–0.5 μm in width.     

Large-eddy simulations in mixed-flow pumps using an immersed-boundary method

Computations of turbulent and transitional flows in rotating machinery applications are very challenging due to complexity of the geometry, which usually consists of multiple rotating and stationary parts. The application of well-established, body-fitted methods frequently utilizes overset grids and different reference frames, which have an adverse impact on the overall accuracy and cost-efficiency of the method. In the present work we explore the feasibility of performing computations of such flows using a single reference frame and an immersed-boundary approach. In particular, we report one of the first large-eddy simulation in this class of flows, where a structured cylindrical coordinate solver with optimal conservation properties is utilized in conjunction with an immersed-boundary method. To evaluate the accuracy of the computations the results are compared to the experimental measurements in [1]. Results using the standard Smagorinsky model and the Filtered Structured Function model are presented. We demonstrate that the overall approach is well suited for the flow under consideration and the results with the more advanced subgrid scale model are in good agreement with the experiment. We also briefly discuss some of the features of the instantaneous flow dynamics, to provide a glimpse of the wealth of information that can be extracted from such computations.     

Inferring Vegetation Water Content From C- and L-Band SAR Images

This paper addresses the capability of synthetic aperture radar and optical images in combination with theoretical models to detect the vegetation water content (VWC) at field level. In this paper, a retrieval algorithm for the estimation of VWC from AirSAR acquired on vegetated fields during the SMEX'02 experiment is addressed. The aforementioned campaign has been chosen because, along with sensor observations, extensive ground truth measurements were acquired. The retrieval procedure, which is based on a Bayesian approach, has been initially developed for soil moisture extraction. It consists of two modules: one is pertinent to bare soils and the other one has been modified for vegetated fields. The last one uses the synergy with optical images to correct for the contribution of VWC. The VWC, a variable in the inversion procedure, as well as soil moisture can be estimated. The results indicate a good correlation with both ground measurements and VWC calculated from Landsat images through the use of normalized difference water index (NDWI). Furthermore, in the inversion procedure, the introduction of the dependence on roughness improves the estimates. This indicates that, even for dense vegetation, the contribution from bare soil greatly influences the radar signal. Three main levels of VWC are discriminated in the inversion procedure: values below 1 kg/m², values between 1 and 3 kg/m², and values greater than 3 kg/m².