A Design-Optimized Continuous-Time Delta–Sigma ADC for WLAN Applications

A third-order continuous-time delta-sigma (DeltaSigma) analog-to-digital converter (ADC) is presented for the conversion of an input signal bandwidth of 10 MHz. Design optimization towards minimal power consumption is demonstrated for the high-speed low-power building blocks of the DeltaSigma modulator. From this point of view, it is shown that GmC integrators are preferred over RC integrators in the low-pass filter of the modulator because they show a better tradeoff between power, speed, and accuracy. A new single-bit quantizer topology is presented that incorporates a local feedback path that improves stability using a switched-voltage technique. Finally, a design methodology for the single-bit digital-to-analog converter (DAC) in the feedback loop is proposed, focusing on the impact of high sampling rates on the stability of the converter. The presented continuous-time ADC achieves a simulated dynamic range of 72 dB and a signal-to-noise-and-distortion-ratio of 66 dB in a 10-MHz signal bandwidth. Therefore, it can be applied for WLAN broadband communication. The power consumption of the DeltaSigma modulator is limited to 7.5 mW. The chip is designed in a 0.18-mum triple-well CMOS technology     

Insights into nanofiltration of textile wastewaters for water reuse

Textile industry constitutes nowadays one the largest consumers of water, and consequently the wastewater reuse can be a profitable operation. In this study, the decontamination of pure dyes solutions (Remazol Turquoise Blue G, Remazol Yellow GR and Lanaset Blue 2R) and synthetic textile wastewaters was evaluated in a nanofiltration (NF) cross-flow cell, using polyamide NF membranes, NF90 and DK, with molecular weight cut-off between 200–400 Da and 150–300 Da, respectively. Permeate flux and the color reduction were evaluated for the different dye solutions under different temperature and pH conditions and, NaCl, wetting and dispersant concentrations. DK membrane showed the best results in terms of permeate flux for all the dye solutions tested. The highest permeate flux was achieved for higher temperatures under acidic to neutral pHs values, resulting in almost 100 % color removal for all situations.     

Divide and rule. The economic and legal implications of the proposed ownership unbundling of distribution and supply companies in the Dutch electricity sector

In Machiavelli's theory of power, the concept of ‘divide and rule’ forms the main theme: the ruler has absolute power and to maintain and increase such power all means are justified. When viewed against the background of this theory, the current debate in the Netherlands on the unbundling of energy (electricity, gas) companies can be observed as an example of ‘divide and rule’, in which the Dutch Minister of Economic Affairs plays a central role. Yet, contrary to Machiavelli in his time, the Dutch government does, in fact, aim principally at the greater welfare of the Dutch people. It is therefore noteworthy that, while important steps in the decision to unbundled have been taken, there is no evidence that the Dutch people will indeed benefit from the envisaged unbundling.     

Assessing the bioavailability of complex petroleum hydrocarbon mixtures in sediments

Several experimental methods have been developed to assess the bioavailability of individual organic compounds. So far none of them has however been applied to complex mixtures, such as oil (petroleum hydrocarbons), which is an ubiquitous pollutant. In the present study, we tested the potential of five of these experimental methods and that of a model approach to predict bioaccumulation of oil in the aquatic worm Lumbriculus variegatus exposed to 14 field-contaminated sediments. Actual and predicted bioaccumulation were compared in terms of both total bioaccumulative petroleum hydrocarbon concentrations and the relative distribution pattern of separate boiling point fractions (hydrocarbon blocks). None of the experimental methods was able to directly assess bioaccumulation in L. variegatus and correction factors were needed to match predicted and actual concentrations. These factors appeared concentration-dependent for solid phase micro extraction (SPME) and extractions with Tenax and cyclodextrin, most probably due to artifacts. Moreover, the hydrocarbon block pattern produced by these methods considerably differed from the pattern observed for worms; an additional reason for disqualification also applying to headspace-SPME. In contrast, the pattern produced by polyoxymethylene solid phase extraction (POM-SPE) closely mimicked the worm pattern and a sediment, hydrocarbon block, and concentration-independent correction factor (17) could be derived, based on which actual bioaccumulation could be predicted within a factor of 3. Finally, the model predicted bioaccumulation directly within a factor of 2. The accompanying hydrocarbon block pattern however deviated significantly more from the worm pattern than the POM-SPE pattern did. We therefore conclude that POM-SPE may be the overall best approach for predicting bioaccumulation of complex hydrocarbon mixtures in aquatic worms, all the more since an experimental approach will implicitly capture all factors determining bioavailability, which may prove difficult through a modeling approach.     

A review of salt marsh dynamics

Salt marshes have been the subject of extensive research over many years. As well as gaining the interest of biologists, physical processes within the marsh have been measured in some detail since at least the 1920s. There have been various attempts to develop a fuller understanding of the inter‐relationship between physical and biological processes within salt marshes. Advances often go in step changes. Over the last 10–20 years, there has been such a change with the ability to capture and manipulate spatial data in sufficient detail to be able to resolve not only surface topography but also variations in vegetation and a number of relevant physical properties. This review paper seeks to highlight the advances in the understanding of salt marsh dynamics and our ability to investigate the relationships between physical and biological properties. Some consideration is also given to the areas that would benefit from new or further research.     

The proximal ligand variant His93Tyr of horse heart myoglobin

The spectroscopic and structural properties of the His93Tyr variant of horse heart myoglobin have been studied to assess the effects of replacing the proximal His residue of this protein with a tyrosyl residue as occurs in catalases from various sources. The variant in the ferric form exhibits electronic spectra that are independent of pH between pH 7 and 10, and it exhibits changes in absorption maxima and intensity that are consistent with a five-coordinate heme iron center at the active site. The EPR spectrum of the variant is that of a high-spin, rhombic system similar to that reported for bovine liver catalase. The 1D 1H-NMR spectrum of the variant confirms the five-coordinate nature of the heme iron center and exhibits a broad resonance at 112.5 ppm that is attributable to the meta protons of the phenolate ligand. This result indicates that the new Tyr ligand flips at a significant rate in this protein. The thermal stability of the Fe(III) derivative is unchanged from that of the wild-type protein (pH 8) while the midpoint reduction potential [-208 mV vs SHE (pH 8.0, 25 degrees C)] is about 250 mV lower. The three-dimensional structure of the variant determined by X-ray diffraction analysis confirms the five-coordinate nature of the heme iron center and establishes that the introduction of a proximal Tyr ligand is accommodated by a shift of the F helix (residues 88-99) in which this residue resides away from the heme pocket. Additional effects of this change are small shifts in the positions of Leu29, a heme propionate, and a heme vinyl group that are accompanied by altered hydrogen bonding interactions with the heme prosthetic group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Transient local presence of nerve fibers at onset of secondary ossification in the rat knee joint

In view of recent evidence that nerves may be involved in bone formation, the present study examines the local occurrence of axons at the onset of secondary ossification center formation in the knee region of developing rats. Radiographic and histological examination showed that secondary ossification center formation commenced at day 10. At day 15 the epiphyseal ossification had reached a relatively mature state. As seen by light microscopy, cartilage canals first appeared at day 5, reaching the epiphyseal center by day 9. Axons exhibiting a neurofilament-like immunoreactivity emerged from the perichondrial plexa into the cartilage canals. Many calcitonin gene-related peptide (CGRP)-immunoreactive axons were found in the canals, as well as in the perichondrium. Axons with tyrosine hydroxylase-like immunoreactivity were not found in the canals, but such fibers occurred in relation to blood vessels at other sites. The canal-related axons disappeared between days 13 and 15, and the canals themselves did not persist beyond bone formation. As seen in the electron microscope, an individual canal contained 3-10 unmyelinated Schwann cell-enclosed axons with diameters of 0.1-2.0 microM. These observations show that putative sensory unmyelinated axons with CGRP-and SP-like immunoreactivity are transiently present during initiation of bone formation in developing epiphyses. Whether there is a causal relation between transient innervation and osteogenesis remains to be determined.     

Substituting Symbol Search for Coding on the WISC-III: Canadian normative tables for Performance and Full Scale IQ scores.

A. S. Kaufman (1994) recommends that the Symbol Search, an optional subtest to the WISC-III, be substituted for Coding in the calculation of WISC-III Performance and Full Scale IQ scores. Conversion tables have been published for use with American norms. The authors provide conversion tables for the Canadian-normed WISC-III. The standardization sample consisted of a representative group of 1,100 English-speaking Canadian children. The conversion tables are provided. These tables allow Canadian WISC-III examiners to substitute Symbol Search for Coding in the calculation of the Performance and Full Scale IQ scores. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maintaining range trees in secondary memory

Summary When storing and maintaining a data structure in secondary memory it is important to partition it into parts such that each query and update passes through a small number of parts. In this way the number of disk accesses and the amount of data transport required can be kept low. In Part I of this paper a number of partition schemes were given for partitioning range trees. In this paper we study lower bounds for partitions. In this way we prove that many of the partitions given in Part I are optimal.Supported by the Netherlands Organization for Scientific Research (NWO)