Large-scale parallel arrays of silicon nanowires via block copolymer directed self-assembly

Extending the resolution and spatial proximity of lithographic patterning below critical dimensions of 20 nm remains a key challenge with very-large-scale integration, especially if the persistent scaling of silicon electronic devices is sustained. One approach, which relies upon the directed self-assembly of block copolymers by chemical-epitaxy, is capable of achieving high density 1?:?1 patterning with critical dimensions approaching 5 nm. Herein, we outline an integration-favourable strategy for fabricating high areal density arrays of aligned silicon nanowires by directed self-assembly of a PS-b-PMMA block copolymer nanopatterns with a L(0) (pitch) of 42 nm, on chemically pre-patterned surfaces. Parallel arrays (5 × 10(6) wires per cm) of uni-directional and isolated silicon nanowires on insulator substrates with critical dimension ranging from 15 to 19 nm were fabricated by using precision plasma etch processes; with each stage monitored by electron microscopy. This step-by-step approach provides detailed information on interfacial oxide formation at the device silicon layer, the polystyrene profile during plasma etching, final critical dimension uniformity and line edge roughness variation nanowire during processing. The resulting silicon-nanowire array devices exhibit Schottky-type behaviour and a clear field-effect. The measured values for resistivity and specific contact resistance were ((2.6 ± 1.2) × 10(5)Ωcm) and ((240 ± 80) Ωcm(2)) respectively. These values are typical for intrinsic (un-doped) silicon when contacted by high work function metal albeit counterintuitive as the resistivity of the starting wafer (～10 Ωcm) is 4 orders of magnitude lower. In essence, the nanowires are so small and consist of so few atoms, that statistically, at the original doping level each nanowire contains less than a single dopant atom and consequently exhibits the electrical behaviour of the un-doped host material. Moreover this indicates that the processing successfully avoided unintentional doping. Therefore our approach permits tuning of the device steps to contact the nanowires functionality through careful selection of the initial bulk starting material and/or by means of post processing steps e.g. thermal annealing of metal contacts to produce high performance devices. We envision that such a controllable process, combined with the precision patterning of the aligned block copolymer nanopatterns, could prolong the scaling of nanoelectronics and potentially enable the fabrication of dense, parallel arrays of multi-gate field effect transistors.     

Refractory Alkali-Free Cristobalite Glass-Ceramics: Activated Reaction Sinter-Crystallization Synthesis and Properties

A new approach for the synthesis of chemically stabilized β-cristobalite-like glass-ceramic materials is developed. It is based on an activated reaction sinter-crystallization process of compacted powder mixtures at relatively low temperatures (1400–1450°C) and short heat treatment times. To facilitate homogeneous dopant distribution and thus the formation of a high content of β_x-cristobalite-like phases, possessing a very low thermal expansion coefficient, the batch components are introduced in a chemically, mechanically, or thermally preactivated form. In this way, the high-temperature glass premelting usually employed in the “classical” synthesis of glass-ceramics is avoided. Using different, mutually complementary techniques of analysis it is revealed that optimal refractory properties are achieved with glass-ceramics containing α_x- and β_x-cristobalite solid solutions with close values of the lattice parameters. In this case, the transformation between these two cristobalite-like solid solutions proceeds instead by a first-order displacive transition, by a process exhibiting features characteristic for both a suppressed first-order phase change and a second-order λ-type phase transitions. The refractory properties of the glass-ceramic materials thus synthesized and the possibility to use various forming techniques open many fields for their application.     

A switching system based on microcontroller for successive applying of MGT and CPT on MOSFETs

A new, low cost switching system based on PIC 18F4550 microcontroller (MCU), called APL-SM v1.0 system, which enables the successive measuring of both the electrical characteristics in midgap-subthreshold technique (MGT) and charge-pumping currents in charge-pumping technique (CPT) of metal–oxide–semiconductor field effect transistor (MOSFET), has been developed. The APL-SM v1.0 system, instead of expensive switching matrix which price is considerably higher, could be used for the switching from MGT to CPT and vice versa. Using the appropriate program, the system allows the monitoring of MOSFETs during long time periods, helping the performing of long lasting experiments. The good agreement in the electrical characteristics, as well as in the charge-pumping currents, obtained using ultra low current, high speed Keithley switching matrix (SM) and APL-SM system, was obtained.     

A CAD/CAE-integrated injection mold design system for plastic products

Mold design is a knowledge-intensive process. This paper describes a knowledge-based oriented, parametric, modular and feature-based integrated computer-aided design/computer-aided engineering (CAD/CAE) system for mold design. Development of CAx systems for numerical simulation of plastic injection molding and mold design has opened new possibilities of product analysis during the mold design. The proposed system integrates Pro/ENGINEER system with the specially developed module for the calculation of injection molding parameters, mold design, and selection of mold elements. The system interface uses parametric and CAD/CAE feature-based database to streamline the process of design, editing, and reviewing. Also presented are general structure and part of output results from the proposed CAD/CAE-integrated injection mold design system.     

IR-change and colour changes of long-oil air drying alkyd paints as a result of UV irradiation

In this study the formation of photo-oxidative species was studied by monitoring the changes in the FT-IR spectra and colour changes. To stabilize long-oil air drying alkyd paint, separate and synergistic influence of two stabilizers were used Uvasorb^®S28 as the UV-absorber and Uvasorb^®HA29 as the stabilizer which inhibits the degradation of some groups. In the presence of UV radiation (450 h, λ > 300 nm), the alkyd paint undergoes photodegradation with gradual change of its colour. The photochemical degradation of the alkyd paint is associated with an increase in the hydroxyl content and broadening of the absorption in the carbonyl region. Analysis of the colour changes in alkyd surface during photodegradation was carried out by measuring CIEL*a*b* colour components (L*, a*, b* and ΔE*). Overall, ΔE* colour change correlates well with photodegradation of alkyd paint by relative increase of the concentration of carbonyl and hydroxyl groups determinated by FT-IR measurements.     

The effect of lignin on the structure and characteristics of composite coatings electrodeposited on titanium

Composite coatings based on lignin, obtained by electrophoretic deposition (EPD) on titanium, were investigated. The aim of this work was to produce hydroxyapatite/lignin (HAP/Lig) coatings on titanium and to investigate the effect of the lignin concentration on microstructure, morphology, phase composition, thermal behavior and cytotoxicity of the HAP/Lig coatings. An organosolv lignin was used for the production of the composite coatings studied in this research. The properties of HAP/Lig coatings were characterized using X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FT-IR) and X-ray photoelectron spectroscopy (XPS), as well as the MTT test of cytotoxicity. The results showed that higher lignin concentrations protected the HAP lattice during sintering, thereby improving the stability of the HAP/Lig coatings. The cell survival of peripheral blood mononuclear cells (PBMC) after proliferation indicates that the HAP/Lig coating with 1 wt% Lig electrodeposited on titanium was non-toxic with significant promise as a potential bone-repair material.     

Effect of the Leaving Group and Solvent Combination on the LFER Reaction Constants

Fine effects that influence the variations of the reaction constants s(f) in LFER log k = s(f)(N(f) + E(f)) have been summarized here. Increasing solvent polarity in the series of binary mixtures increases the solvolysis rates for the same factor for all benzhydryl derivatives in which the solvation of the leaving group moiety in the transition state is substantial, i.e., log k vs. E(f) correlation lines are parallel (same s(f)). For the substrates in which the demand for solvation of the leaving groups moiety is reduced, (e.g., carbonates) s(f) parameters decrease as the fraction of the water in a given solvent/water mixture increases (log k vs. E(f) plots converge), due to decreasing solvation of the electrofuge moiety toward bigger electrofugality. The abscissa of the intersection of the converging plots might indicate the critical electrofugality above which the solvolysis rates should not depend of the water fraction. Larger reaction constant s(f) indicate later transition state for structurally related substrates only, while s(f) parameters for structurally different substrates cannot be compared likely due to different intrinsic barriers. Inversion in relative abilities of leaving groups is possible if they have similar reactivities and are characterized with different reaction constants.     

Antiproliferative and Proapoptotic Activities of Methanolic Extracts from Ligustrum vulgare L. as an Individual Treatment and in Combination with Palladium Complex

The aim of this study is to examine the growth inhibitory effects of methanolic leaf and fruit extracts of L. vulgare on HCT-116 cells over different time periods and their synergistic effect with a Pd(apox) complex. The antiproliferative activity of plant extracts alone or in combination with the Pd(apox) complex was determined using MTT cell viability assay, where the IC(50) value was used as a parameter of cytotoxicity. Results show that antiproliferative effects of L. vulgare extracts increase with extension of exposure time, with decreasing IC(50) values, except for 72 h where the IC(50) values for methanolic leaf extract were lower than for the fruit extract. The Pd(apox) complex alone had a weak antiproliferative effect, but combination with L. vulgare extracts caused stronger effects with lower IC(50) values than with L. vulgare extracts alone. The type of cell death was explored by fluorescence microscopy using the acridin orange/ethidium bromide method. Treatments with plant extracts caused typical apoptotic morphological changes in HCT-116 cells and co-treatments with Pd(apox) complex caused higher levels of apoptotic cells than treatment with plant extracts alone. The results indicate that L. vulgare is a considerable source of natural bioactive substances with antiproliferative activity on HCT-116 cells and which have a substantial synergistic effect with the Pd(apox) complex.     

Lipid peroxidative damage on Cisplatin exposure and alterations in antioxidant defense system in rat kidneys: a possible protective effect of selenium

Cisplatin (Cis-diamminedichloroplatinum II, CP) is an important chemotherapeutic agent, useful in the treatment of several cancers, but with several side effects such as nephrotoxicity. The present study investigated the possible protective effect of selenium (Se) against CP-induced oxidative stress in the rat kidneys. Male Wistar albino rats were injected with a single dose of cisplatin (7 mg CP/kg b.m., i.p.) and selenium (6 mg Se/kg b.m, as Na(2)SeO(3), i.p.), alone or in combination. The obtained results showed that CP increased lipid peroxidation (LPO) and decreased reduced glutathione (GSH) concentrations, suggesting the CP-induced oxidative stress, while Se treatment reversed this change to control values. Acute intoxication of rats with CP was followed by statistically significant decreased activity of antioxidant defense enzymes: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and glutathione-S-transferase (GST). Treatment with Se reversed CP-induced alterations of antioxidant defense enzyme activities and significantly prevented the CP-induced kidney damage.     

The A9 Core Sequence from NRPS Adenylation Domain Is Relevant for Thioester Formation

The adenylation (A) domain in nonribosomal peptide synthetases catalyses a two-step reaction in which an amino acid is activated and then transferred to the neighbouring thiolation (T) domain. In this study, we investigated the role of the conserved A9 core sequence of the A-domain of tyrocidine synthetase 1, by analysis of single amino acid mutations in the A9 region. Mutation of an absolutely conserved proline (P490G) significantly reduced the conformational stability of the protein, as evidenced by increased susceptibility to proteolytic cleavage and denaturation. All mutant A-domains were capable of amino acid activation, but the activity in the overall reaction was reduced. Surprisingly, the S491R mutant (mutation at the first residue following the A9 motif) showed elevated overall activity compared to the wild-type protein. Our results suggest that the A9 core sequence plays a role in the second reaction step, in which it could serve as a "clip" for the proper positioning of residues important for the interaction with the T-domain, and/or stabilisation of the thioester-forming conformation.