Hydroxyapatite containing superporous hydrogel composites: synthesis and in-vitro characterization

The synthesis of an acrylamide-based superporous hydrogel composite (SPHC) with hydroxyapatite (HA) was realized by solution polymerization technique. The characterization studies were performed by FTIR studies, determination of swelling kinetics, measurement of mechanical properties, SEM/EDAX studies and cytocompatibility tests. The FTIR and EDAX studies revealed the incorporation of HA in superporous hydrogel (SPH) structure. The results obtained from swelling experiments showed that, although the extent of swelling was decreased after incorporation of HA in SPH structure, the time to reach the equilibrium swelling was not affected for SPHC. This result indicated that, the presence of HA did not block the capillary channels and the interconnected pore structure was maintained which were consistent with the images obtained from SEM photographs. The results obtained from mechanical tests showed that, in the presence of HA, the compression strength of the hydrogel composite was improved significantly when compared to SPH structure. The compressive modulus for the SPHC increased to 6.59 ± 0.35 N/mm² whereas it was 0.63 ± 0.04 N/mm² for the SPH. The cytocompatibility test which was performed by using L929 fibroblasts showed that both the SPH and SPHC materials were cytocompatible towards fibroblasts. The synthesized superporous hydrogel composite possesses suitable properties especially for bone tissue engineering applications and shall be considered as a novel scaffold.     

High-κ dielectrics and advanced channel concepts for Si MOSFET

With scaling of the gate length downward to increase speed and density, the gate dielectric thickness must also be reduced. However, this practice which has been in effect for many decades has reached a fundamental limitation because gate dielectric thicknesses in the range of tunneling have been reached with the SiO₂ dielectric layer for MOSFETs. Consequently, the gate dielectrics with higher dielectric constants, dubbed the “high-κ”, which allow scaling with much larger thicknesses have become active research and development topics. In this review technological issues associated with the likely high-κ materials which are under consideration as well as challenges, and solution to them, they bring about in the fabrication of Si MOSFET are discussed. Moreover, in order to squeeze more speed out of CMOS, channels for both n- and p-type MOSFET enhanced with appropriate strain and the concepts behind them are discussed succinctly. Finally, the longer term approach of replacing Si with other channel materials such as GaAs (InGaAs) for n-channel and Ge for p-channel along with technological developments of their preparation on Si and likely gate oxide developments are treated in some detail.     

Single carbon nanotube transistor at GHz frequency

We report on microwave operation of top-gated single carbon nanotube transistors. From transmission measurements in the 0.1-1.6 GHz range, we deduce device transconductance gm and gate-nanotube capacitance Cg of micro- and nanometric devices. A large and frequency-independent gm approximately 20 microS is observed on short devices, which meets the best dc results. The capacitance per unit gate length of 60 aF/microm is typical of top gates on a conventional oxide with epsilon approximately 10. This value is a factor of 3-5 below the nanotube quantum capacitance which, according to recent simulations, favors high transit frequencies fT=gm/2piCg. For our smallest devices, we find a large fT approximately 50 GHz with no evidence of saturation in length dependence.     

Biofunctionalized lipid-polymer hybrid nanocontainers with controlled permeability

We have successfully developed, for the first time, a novel polymer-lipid hybrid nanocontainer with controlled permeability functionality. The nanocontainer is made by nanofabricating holes with desired dimensions in an impermeable polymer scaffold by focused ion beam drilling and sealing them with lipid bilayers containing remote-controlled pore-forming channel proteins. This system allows exchange of solutions only after channel activation at will to form temporary pores in the container. Potential applications are foreseen in bionanosensors, nanoreactors, nanomedicine, and triggered delivery.     

Zn(1-x)MnxTe diluted magnetic semiconductor nanowires grown by molecular beam epitaxy

It is shown that the growth of II-VI diluted magnetic semiconductor nanowires is possible by the catalytically enhanced molecular beam epitaxy (MBE). Zn(1-x)MnxTe NWs with manganese content up to x=0.60 were produced by this method. X-ray diffraction, Raman spectroscopy, and temperature dependent photoluminescence measurements confirm the incorporation of Mn(2+) ions in the cation substitutional sites of the ZnTe matrix of the NWs.     

Detection of single photoluminescent diamond nanoparticles in cells and study of the internalization pathway

Diamond nanoparticles are promising photoluminescent probes for tracking intracellular processes, due to embedded, perfectly photostable color centers. In this work, the spontaneous internalization of such nanoparticles (diameter 25 nm) in HeLa cancer cells is investigated by confocal microscopy and time-resolved techniques. Nanoparticles are observed inside the cell cytoplasm at the single-particle and single-color-center level, assessed by time-correlation intensity measurements. Improvement of the nanoparticle signal-to-noise ratio inside the cell is achieved using a pulsed-excitation laser and time-resolved detection taking advantage of the long radiative lifetime of the color-center excited state as compared to cell autofluorescence. The internalization pathways are also investigated, with endosomal marking and colocalization analyses. The low colocalization ratio observed proves that nanodiamonds are not trapped in endosomes, a promising result in prospect of drug delivery by these nanoparticles. Low cytotoxicity of these nanoparticles in this cell line is also shown.     

Nonlinear Observer-Based Feedback for Open-Channel Level Control

This paper is devoted to nonlinear observer and controller design for water level control of open-channel flow in irrigation canals or dam-river systems. A finite-dimensional model, previously developed by orthogonal collocation methods, based on Saint Venant equations and used for control design, is now further used for online flow rate and water infiltration estimation. This is done by a so-called state observer. In particular, the estimates obtained in this way can successfully be used in a controller previously proposed, resulting in a water level control law using only two level measurements along the canal (instead of the four measurements previously needed). The study is restricted to the case of a rectangular wetted section and subcritical flow. The results have been validated by simulations, on an implicit finite difference simulator based on a Preissmann scheme for various scenarios.     

Gender and education impact on brain aging: A general cognitive factor approach.

In cognitive aging research, the study of a general cognitive factor has been shown to have a substantial explanatory power over the study of isolated tests. The authors aimed at differentiating the impact of gender and education on global cognitive change with age from their differential impact on 4 psychometric tests using a new latent process approach, which intermediates between a single-factor longitudinal model for sum scores and an item-response theory approach for longitudinal data. The analysis was conducted on a sample of 2,228 subjects from PAQUID, a population-based cohort of older adults followed for 13 years with repeated measures of cognition. Adjusted for vascular factors, the analysis confirmed that women performed better in tests involving verbal components, while men performed better in tests involving visuospatial skills. In addition, the model suggested that women had a slightly steeper global cognitive decline with oldest age than men, even after excluding incident dementia or death. Subjects with higher education exhibited a better mean score for the 4 tests, but this difference tended to attenuate with age for tests involving a speed component. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reference Material for the Determination of Polychlorodibenzo-<Emphasis Type="Italic">p</Emphasis>-dioxins,Polychlorodibenzo-furans,and Polychlorinated Biphenyls in Fish: Production Process,Homogeneity, and Stability

The presence of dibenzo-p-dioxins, polychlorinated dibenzofurans, and polychlorinated biphenyls in food is an important consideration for food safety, especially in fish matrices that are susceptible to bioaccumulation of those compounds from marine environments. In this context, the production of a reference material (RM) for this analytical scope is of great importance for ensuring the reliability of the results generated by monitoring programs. A lyophilized material was produced by spiking tilapia fillets with 29 compounds, and the material was evaluated based on the potential for using it as a certified reference material (CRM) or in proficiency testing (PT) schemes. A pilot experiment was performed to evaluate the incorporation of the analytes in tilapia fillets using standards prepared in nonane and in fish oil. The process yield was approximately 16% for both conditions, but higher mean recoveries were achieved with fish oil. The tilapia fillets were processed, and a portion of this bulk was spiked and then homogenized. The spiked and unspiked portions were frozen prior to lyophilization. Each freeze-dried portion was homogenized and sieved, and then, the portions were mixed, packed, and stored under refrigeration. The material was considered homogeneous for all analytes based on the criteria established for PT. Of the tested analytes, 27 were found to be stable in the short-term design (p > 0.05) when the material was kept at 45 ± 2 °C for 9 days. Long-term stability was evaluated at 2, 4, 6, and 8 months, and 22 of the analytes were found to be stable through up to 4 months of storage based on the criteria defined in references related to both the production of CRM and PT. The contributions of the homogeneity and stability in the short- and long-term uncertainties were estimated and indicated the adequacy of the material for use as a reference for trueness experiments.     

Bioactive Sheath/Core nanofibers containing olive leaf extract

This study aimed at producing silk fibroin (SF)/hyaluronic acid (HA) and olive leaf extract (OLE) nanofibers with sheath/core morphology by coaxial electrospinning method, determining their antimicrobial properties, and examining release profiles of OLE from these coaxial nanofibers. Optimum electrospinning process and solution parameters were determined to obtain uniform and bead‐free coaxial nanofibers. Scanning electron microscopy and transmission electron microscopy (TEM) were used to characterize the morphology of the nanofibers. The antimicrobial activities of nanofibers were tested according to AATCC test method 100. Total phenolic content and total antioxidant activity were tested using in vitro batch release system. The quality and quantity of released components of OLE were determined by high‐performance liquid chromatography. The changes in nanofibers were examined by Fourier‐transform infrared spectroscopy. Uniform and bead‐free nanofibers were produced successfully. TEM images confirmed the coaxial structure. OLE‐loaded nanofibers demonstrated almost perfect antibacterial activities against both of gram‐negative and gram‐positive bacteria. Antifungal activity against C. albicans was rather poor. After a release period of 1 month, it was observed that ～70–95% of the OLE was released from nanofibers and it was still bioactive. Overall results indicate that the resultant shell/core nanofibers have a great potential to be used as biomaterials. Microsc. Res. Tech. 79:38–49, 2016. © 2015 Wiley Periodicals, Inc.