Nonlinear Response of a Continuous Wave NMR Spectrometer for Samples with a Large Magnetization

We present a new insight in the response of a CW NMR spectrometer for highly magnetized samples above 100 MHz. The spectrometer is a bridge made of a magic T. The output of the bridge is proportional to the reflection coefficient, , of a resonant circuit, which is built with a coil containing the sample. The sensitivity of the reflection coefficient to the complex susceptibility of the sample, () = () – j(), depends on the quality factor, Q, of the circuit and filling factor, . When the condition Q 1 is not fulfilled, we show indeed that the use of a simple crystal detector, which is only sensitive to || gives rise to a strong nonlinear response of the spectrometer. Measurements of the complex value of by means of phase sensitive detection allow to recover a linear behavior. We discuss and illustrate those issues with a few circuits we designed for our measurements on liquid ³ He with spin polarizations up to 15 %. A method is described to build in a reproducible and predictable way resonant circuits matched to 50 in the frequency range 100 – 400 MHz with a quality factor as high as 1000 at 4 K.     

Absorption of Pulsed Terahertz and Optical Radiation in Earthworm Tissue and Its Heating Effect

Journal of Infrared, Millimeter, and Terahertz Waves - The transmission of THz, near-infrared (1030 nm), and green (515 nm) pulses through Eisenia andrei body wall is studied,...     

In situ HTXRD formation of magnesium titanates

Coprecipitated xerogel precursors of nanocrystalline magnesium titanates, with a Mg:Ti stoichiometric ratio of 2:1, were subjected to thermal treatment in air at constant temperature, from 100 to 1300°C, using a hot‐stage X‐ray powder diffractometer. The phase sequences, the kinetics of phase evolution and crystallite size were studied during the first hour of the process at different temperatures. Until 500°C no diffraction peaks were observed. Between 550 and 800°C the structure was a mixture of two cubic nanocrystalline coherent structures: qandilite‐like and periclase‐like forms. At 900 and 1000°C, after 15 minutes, geikielite and periclase appear in small amounts but the qandilite‐like phase remains predominant; at 1100°C and above, qandilite is formed again as a single phase. The diffraction lines were substantially broadened for all crystalline phases formed at low temperatures, becoming sharper with increasing temperature and time. The phase evolution is interpreted as a consequence of the decrease in the surface area to volume ratio with increasing temperature and time, thus decreasing the significance of the surface energy. Linear thermal expansion coefficients were derived for qandilite.     

Mining manufacturing databases to discover the effect of operation sequence on the product quality

Data mining techniques can be used for discovering interesting patterns in complicated manufacturing processes. These patterns are used to improve manufacturing quality. Classical representations of quality data mining problems usually refer to the operations settings and not to their sequence. This paper examines the effect of the operation sequence on the quality of the product using data mining techniques. For this purpose a novel decision tree framework for extracting sequence patterns is developed. The proposed method is capable to mine sequence patterns of any length with operations that are not necessarily immediate precedents. The core induction algorithmic framework consists of four main steps. In the first step, all manufacturing sequences are represented as string of tokens. In the second step a large set of regular expression-based patterns are induced by employing a sequence patterns. In the third step we use feature selection methods to filter out the initial set, and leave only the most useful patterns. In the last stage, we transform the quality problem into a classification problem and employ a decision tree induction algorithm. A comparative study performed on benchmark databases illustrates the capabilities of the proposed framework.     

Vibrational and NMR properties of polyynes

The bond-stretching phonon modes of linear polyynes with hydrogen atom termination at the both ends are calculated as a function of chain length within the density functional theory. The frequency of one of two particular Raman active phonon modes monotonically decreases with the increase of polyyne chain length while that of the other one shows an oscillating behavior, consistent with previous Raman measurements. The relative Raman intensity of the two phonon modes are evaluated by optimized geometries for ground states and excited states. We also present a nuclear magnetic resonance (NMR) calculation for spin–spin coupling constants as a function of distance between hydrogen and carbon-13 nuclei and, within carbon-13 nuclei, up to the polyyne center of symmetry. We compare the calculated results with recent NMR experiments.     

Vertical junction Si cells for concentrating photovoltaics

Vertical junction Si cell has shown a potential to operate at high concentrations, mainly the result of reduced series resistance losses due to its low‐current/high‐voltage design, but tests and analyses have so far only shown a modest efficiency of about 20%. We perform a comprehensive optimization study and show that the conversion efficiency of vertical multi‐junction (VMJ) cells can be significantly higher, close to 30% at concentrations of 1000 and higher. Reaching this efficiency requires junction dimensions that are significantly smaller than previous VMJ cells. This may require a different approach in the fabrication process, possibly by using a monolithic method rather than the wafer stacking approach. We also show that increased photoconductivity, which is usually negligible in conventional cells, produces a significant reduction in series resistance at high concentrations making it a significant contributor to the outstanding performance of the VMJ cell at high concentration. Copyright © 2011 John Wiley & Sons, Ltd.     

Studying the role of common membrane surface functionalities on adsorption and cleaning of organic foulants using QCM-D

Adsorption of organic foulants on nanofiltration (NF) and reverse osmosis (RO) membrane surfaces strongly affects subsequent fouling behavior by modifying the membrane surface. In this study, impact on organic foulant adsorption of specific chemistries including those in commercial thin-film composite membranes was investigated using self-assembled monolayers with seven different ending chemical functionalities (-CH(3), -O-phenyl, -NH(2), ethylene-glycol, -COOH, -CONH(2), and -OH). Adsorption and cleaning of protein (bovine serum albumin) and polysaccharide (sodium alginate) model foulants in two solution conditions were measured using quartz crystal microbalance with dissipation monitoring, and were found to strongly depend on surface functionality. Alginate adsorption correlated with surface hydrophobicity as measured by water contact angle in air; however, adsorption of BSA on hydrophilic -COOH, -NH(2), and -CONH(2) surfaces was high and dominated by hydrogen bond formation and electrostatic attraction. Adsorption of both BSA and alginate was the fastest on -COOH, and adsorption on -NH(2) and -CONH(2) was difficult to remove by surfactant cleaning. BSA adsorption kinetics was shown to be markedly faster than that of alginate, suggesting its importance in the formation of the conditioning layer. Surface modification to render -OH or ethylene-glycol functionalities are expected to reduce membrane fouling.     

Multi-objective evolutionary optimization for greywater reuse in municipal sewer systems

Sustainable design and implementation of greywater reuse (GWR) has to achieve an optimum compromise between costs and potable water demand reduction. Studies show that GWR is an efficient tool for reducing potable water demand. This study presents a multi-objective optimization model for estimating the optimal distribution of different types of GWR homes in an existing municipal sewer system. Six types of GWR homes were examined. The model constrains the momentary wastewater (WW) velocity in the sewer pipes (which is responsible for solids movement). The objective functions in the optimization model are the total WW flow at the outlet of the neighborhoods sewer system and the cost of the on-site GWR treatment system. The optimization routing was achieved by an evolutionary multi-objective optimization coupled with hydrodynamic simulations of a representative sewer system of a neighborhood located at the coast of Israel. The two non-dominated best solutions selected were the ones having either the smallest WW flow discharged at the outlet of the neighborhood sewer system or the lowest daily cost. In both solutions most of the GWR types chosen were the types resulting with the smallest water usage. This lead to only a small difference between the two best solutions, regarding the diurnal patterns of the WW flows at the outlet of the neighborhood sewer system. However, in the upstream link a substantial difference was depicted between the diurnal patterns. This difference occurred since to the upstream links only few homes, implementing the same type of GWR, discharge their WW, and in each solution a different type of GWR was implemented in these upstream homes. To the best of our knowledge this is the first multi-objective optimization model aimed at quantitatively trading off the cost of local/onsite GW spatially distributed reuse treatments, and the total amount of WW flow discharged into the municipal sewer system under unsteady flow conditions.     

The effect of traffic tickets on road traffic crashes

Road traffic crashes are globally a leading cause of death. The current study tests the effect of traffic tickets issued to drivers on subsequent crashes, using a unique dataset that overcomes some shortcomings of previous studies. The study takes advantage of a national longitudinal dataset at the individual level that merges Israeli census data with data on traffic tickets issued by the police and official data on involvement in road traffic crashes over seven years. The results show that the estimated probability of involvement in a subsequent fatal or severe crash was more than eleven times higher for drivers with six traffic tickets per year compared to those with one ticket per year, while controlling for various confounders. However, the majority of fatal and severe crashes involved the larger population of drivers who received up to one ticket on average per year. The current findings indicate that reducing traffic violations may contribute significantly to crash and injury reduction. In addition, mass random enforcement programs may be more effective in reducing fatal and severe crashes than targeting high-risk recidivist drivers.