One-step selective chemistry for silicon-on-insulator sensor geometries

A one-step functionalization process has been developed for oxide-free channels of field effect transistor structures, enabling a self-selective grafting of receptor molecules on the device active area, while protecting the nonactive part from nonspecific attachment of target molecules. Characterization of the self-organized chemical process is performed on both Si(100) and SiO(2) surfaces by infrared and X-ray photoelectron spectroscopy, atomic force microscopy, and electrical measurements. This selective functionalization leads to structures with better chemical stability, reproducibility, and reliability than current SiO(2)-based devices using silane molecules.     

Fabrication optimization of a miniaturized array device for cell-free protein synthesis

Cell-free protein synthesis (CFPS) is an attractive alternative to cell-based protein expression systems because of its advantages including speed, simplicity, and adaptability to various formats. However, two major obstacles exist that have been preventing it from being widely used. One is high cost and the other is low protein synthesis yield. We report here a miniaturized CFPS device that addresses these challenges. The cost saving was achieved by miniaturization, which reduced the reagent consumption by two orders of magnitude. The protein synthesis yield was enhanced by prolonging CFPS reactions through continuous supply of reactants (e.g. nutrients and energy components). The reactants were contained in a feeding solution, which was replenished through a nanoporous membrane and microchannel. The design of the miniaturized device was optimized by running continuous-exchange CFPS in devices with a variation in the type of membrane, the size of the exchange interface, and the volume ratio of the reaction solution to the feeding solution. The effects of these design variations on the protein synthesis yield have been studied. Furthermore, the design was expanded into a 96-unit device that can produce a large number of proteins simultaneously, enabling high-throughput proteomics applications.     

Relaxation times of spin states of all ranks and orders of quadrupolar nuclei estimated from NMR z-spectra: Markov chain Monte Carlo analysis applied to 7Li+ and 23Na+ in stretched hydrogels

The NMR z-spectra of 7Li+ and 23Na+ in stretched hydrogels contain five minima, or critical values, with a sharp "dagger" on the central dip. The mathematical representation of such z-spectra from spin-3/2 nuclei contains nine distinct (the total is 15 but there is redundancy of the ±order-numbers) relaxation rate constants that are unique for each of the spin states, up to rank 3, order 3. We present an approach to multiple-parameter-value estimation that exploits the high level of separability of the effects of each of the relaxation rate constants on the features of the z-spectrum. The Markov chain Monte Carlo (MCMC) method is computationally demanding but it yielded statistically robust estimates (low coefficients of variation) of the parameter values. We describe the implementation of the MCMC analysis (in the present context) and posit that it can obviate the need for using multiple-quantum filtered RF-pulse sequences to estimate all relaxation rate constants/times under experimentally favorable, but readily achievable, circumstances.     

Enantioselective rhodium-catalysed addition of boronic acids using C2-symmetric aryl diphosphite ligands

The enantioselective rhodium-catalysed conjugate addition of aryl boronic acids to dehydroalanine derivatives has been successfully carried out in the presence of C₂-symmetric aryl diphosphite ligand (R,R,R-4) to prepare unnatural amino acid esters. The products have been obtained in up to 72% ee and with good isolated yield.     

Nonaxisymmetric anisotropy of solar wind turbulence

A key prediction of turbulence theories is frame-invariance, and in magnetohydrodynamic (MHD) turbulence, axisymmetry of fluctuations with respect to the background magnetic field. Paradoxically the power in fluctuations in the turbulent solar wind are observed to be ordered with respect to the bulk macroscopic flow as well as the background magnetic field. Here, nonaxisymmetry across the inertial and dissipation ranges is quantified using in situ observations from Cluster. The observed inertial range nonaxisymmetry is reproduced by a "fly through" sampling of a direct numerical simulation of MHD turbulence. Furthermore, fly through sampling of a linear superposition of transverse waves with axisymmetric fluctuations generates the trend in nonaxisymmetry with power spectral exponent. The observed nonaxisymmetric anisotropy may thus simply arise as a sampling effect related to Taylor's hypothesis and is not related to the plasma dynamics itself.     

Coefficients of Products of Powers of Eta Functions

We give an elementary proof of a conjecture of Cooper, Hirschhorn and Lewis concerning the coefficients of certain products of powers of Dedekind eta functions.