A nanoscale parametric feedback oscillator

We describe and demonstrate a new oscillator topology, the parametric feedback oscillator (PFO). The PFO paradigm is applicable to a wide variety of nanoscale devices and opens the possibility of new classes of oscillators employing innovative frequency-determining elements, such as nanoelectromechanical systems (NEMS), facilitating integration with circuitry and system-size reduction. We show that the PFO topology can also improve nanoscale oscillator performance by circumventing detrimental effects that are otherwise imposed by the strong device nonlinearity in this size regime.     

Pyridine‐Modified Polymer as a Non‐Covalent Compatibilizer for Multi‐Walled CNT/Poly[ethylene‐co‐(methacrylic acid)] Composites Fabricated by Direct Melt Mixing

Multi‐wall CNT/poly[ethylene‐co‐(methacrylic acid)] composites were prepared by melt mixing. To improve dispersion and promote polymer/nanotube interactions, a novel non‐covalent compatibilizer is synthesized by reacting the polymer with 4‐(aminomethyl)pyridine. The composite based on the pristine polymer shows electrical and rheological percolation thresholds at nanotube loadings of 1.85 and 1.4 wt%, respectively. When 5 wt% of the pyridine‐modified compatibilizer is added, the corresponding values are reduced to 1.44 and 0.8 wt%, respectively. The electrical resistivity decreases even further as 10 wt% of the novel dispersing agent is used. Microscopy and Raman spectroscopy confirm the improved dispersion and π‐interactions established during melt mixing.

     

HYDROFLUORIC ACID EXTRACTION BY TBP AND BY AMINES: I. A CRITICAL REVIEW OF THE HF-H2O-EXTRACTANT SYSTEM

Literature on HF extraction by amines and by tributyl phosphate is critically reviewed. The system amine-HF-H₂O shows an interesting feature concerning properties such as distribution curves compared to those for extraction of other acids, similarity to extraction by TBP, water extraction, selectivity, effect of amine type and dilution and diluent effect These properties sharply change (or even invert) when HF/amine molar ratio exceeds 2.     

Influence of partial charge on the material removal rate during chemical polishing

A partial charge-based chemical polishing model has been developed, which can serve as metric for describing the relative polishing material removal rate for different combinations of slurries and workpieces. A series of controlled polishing experiments utilizing a variety of colloidal polishing slurries (SiO₂, CeO₂, ZrO_2, MgO, Sb₂O₅) and optical materials [single crystals of Al₂O₃ (sapphire), SiC, Y₃Al₅O₁₂ (YAG), CaF₂, and LiB₃O₅ (LBO); a SiO₂-Al₂O₃-P₂O₅-Li₂O glass ceramic (Zerodur); and glasses of SiO₂:TiO₂ (ULE), SiO₂ (fused silica), and P₂O₅-Al₂O₃-K₂O-BaO (Phosphate)] was performed and its material removal rate was measured. As previously proposed by Cook (J Non-Cryst Solids. 1990;120:152), for many polishing systems, the removal rate is governed by a series of chemical reactions which include the formation of a surface hydroxide, followed by condensation of that hydroxyl moiety with the polishing particle, and a subsequent hydrolysis reaction. The rate of condensation can often be the rate limiting step, thus it can determine the polishing material removal rate. By largely keeping the numerous other factors that influence material removal rate fixed (such as due to particle size distributions, interface interactions, pad topography, kinematics, and applied pressure), the material removal rate is shown to scale exponentially with the partial charge difference (δ_wp-s) between the workpiece and polishing slurry particle for many of the slurry-workpiece combinations indicating that condensation rate is the rate limiting step. The partial charge (δ) describes the equilibrium distribution of electron density between chemically bonded atoms and is related to the electronegativity of the atoms chemically bonded to one another. This partial charge model also explains the age-old experimental finding of why cerium oxide is the most effective polishing slurry for chemical removal of many workpieces. Some of the slurry-workpiece combinations that did not follow the partial charge dependence offer insight to other removal mechanisms or rate limiting reaction pathways.     

HYDROFLUORIC ACID EXTRACTION BY TBP AND BY AMINES: MECHANISM,SPECIES FORMED AND UNIQUE PROPERTIES AT HIGH ACID TO AMINE MOLAR RATIOS

Analysis of data concerning HF extraction by amines reveals a change in extraction mechanism when HF/amine molar ratio in organic phase (Z) reaches 2. Up to this point extraction is by ion-pair formation and after it by H-bonding. As a result, the two HF molecules initially extracted differ in nature from subsequent ones. The change in mechanism explains why seemingly unrelated properties such as water co-extraction dilution and diluent effects, selectivity and viscosity - all change when amine bifluoride composition is attained. Similar change in extraction of other mono-basic acids occurs at Z=1. The system with Z>2 for HF is equivalent to that with Z>1 for other mono-basic acids and to that of extraction by TBP. It therefore provides a model for extraction from concentrated aqueous solutions.     

Vacancy chains and the degree of mobility in the housing market

Mobility among different states of the housing market (e.g., among tenure modes and price classes) not only generates liquidity but also carries a crucial effect on the price pattern in the market. Studying housing mobility may thus provide insights to the current developments in worldwide housing markets. We theoretically explore vacancy chains and mobility in the market where, among the various results, we show that, in comparing markets with different degrees of mobility, when the probability to transit from any given state to lower states is zero, the expected number of intra-state transitions (as opposed to inter-state transitions) is always smaller in the market that allows for the greater mobility. Also, we derive upper and lower bounds for the expected number of intra-state transitions in the market and specifically show that the “multiplier effect” of the vacancy chain represents a lower bound for this measure. Among the other results, we show that, for every given housing state i, the expected number of intra-state vacancy transitions is greater than the expected number of inter-state transitions for all states j ≠ i. Moreover, we find a condition under which we characterize a subgroup of markets whose expected number of intra-state transitions is greater than the expected number of inter-state transitions for each vacancy chain. Our analysis of mobility and vacancy chains, while specifically focusing on housing markets, may be generalized to other markets as well.     

Optimization of multi-layered metallic shield

We investigate the problem of optimization of multi-layered metallic shield whereby the goal is to determine the sequence of materials and the thicknesses of the layers that provide the maximum ballistic limit velocity of the shield. Optimization is performed under the following constraints: fixed areal density of the shield, the upper bound on the total thickness of the shield and the bounds on the thicknesses of the plates manufactured from every material. The problem is reduced to the problem of Geometric Programming which can be solved numerically using known methods. For the most interesting in practice cases of two-layered and three-layered shields the solution is obtained in the explicit analytical form.     

Small Molecule Receptor Binding Inhibitors with In Vivo Efficacy against Botulinum Neurotoxin Serotypes A and E

Botulinum neurotoxins (BoNTs) are the most poisonous substances in nature. Currently, the only therapy for botulism is antitoxin. This therapy suffers from several limitations and hence new therapeutic strategies are desired. One of the limitations in discovering BoNT inhibitors is the absence of an in vitro assay that correlates with toxin neutralization in vivo. In this work, a high-throughput screening assay for receptor-binding inhibitors against BoNT/A was developed. The assay is composed of two chimeric proteins: a receptor-simulating protein, consisting of the fourth luminal loop of synaptic vesicle protein 2C fused to glutathione-S-transferase, and a toxin-simulating protein, consisting of the receptor-binding domain of BoNT/A fused to beta-galactosidase. The assay was applied to screen the LOPAC1280 compound library. Seven selected compounds were evaluated in mice exposed to a lethal dose of BoNT/A. The compound aurintricarboxylic acid (ATA) conferred 92% protection, whereas significant delayed time to death (p < 0.005) was observed for three additional compounds. Remarkably, ATA was also fully protective in mice challenged with a lethal dose of BoNT/E, which also uses the SV2 receptor. This study demonstrates that receptor-binding inhibitors have the potential to serve as next generation therapeutics for botulism, and therefore the assay developed may facilitate discovery of new anti-BoNT countermeasures.     

Studying different dimensions of amylose–long chain fatty acid complexes: Molecular, nano and micro level characteristics

Recently amylose inclusion complexes, or V-amylose, have drawn much attention as a possible vehicle for the nanoencapsulation of unsaturated fatty acids. This study aimed to study three different structural strata of V-amylose, the molecular attributes using XRD, DSC and ¹³C CP/MAS NMR and the nanostructures using SAXS. Using these methods it was noted that decreased degree of fatty acid unsaturation induces the formation of more organized and well defined structures. Specifically, calculations based on SAXS data show that regardless of the crystallization temperature saturated SA yields the highest values for parameters like average crystalline lamellar thickness (φ = 0.26) and characteristic particle dimension (R_g = 9.6). SEM shows this trend extends even into the microscopic level. Overall, this study shows that in the case of long chain fatty acids, increased fatty acid unsaturation impairs the structure of amylose inclusion complexes.     

A 70 nm 16 Gb 16-Level-Cell NAND flash Memory

A 16 Gb 16-level-cell (16LC) NAND flash memory using 70 nm design rule has been developed . This 16LC NAND flash memory can store 4 bits in a cell which enabled double bit density comparing to 4-level-cell (4LC) NAND flash, and quadruple bit density comparing to single-bit (SLC) NAND flash memory with the same design rule. New programming method suppresses the floating gate coupling effect and enabled the narrow distribution for 16LC. The cache-program function can be achievable without any additional latches. Optimization of programming sequence achieves 0.62 MB/s programming throughput. This 16-level NAND flash memory technology reduces the cost per bit and improves the memory density even more.