Resonators in Open-Loop Sigma–Delta Modulators

In this paper, we introduce the modulo resonator for use in analog-to-digital open-loop sigma-delta modulators (OLSDMs). The OLSDM presented in this paper is intended for use in high-accuracy (14-bit) high-speed analog-to-digital converters. The modulo resonator is used with a modulo notch filter to insert a zero in the noise transfer function at a nonzero frequency. The effect of finite gain in modulo integrators and resonators is described and verified through simulation. The modulo resonator and a previously published modulo integrator are used in a behavioral model of a switched-capacitor fifth-order OLSDM with more than 13-bit effective number of bits for an oversampling ratio of four. We prove for the N -order OLSDM that the number of bits in the quantizer (B) must be larger than N to ensure equivalence between open-loop sigma-delta modulation and sigma-delta modulation.     

Infrared Reflection Spectroscopy of Polycyanurate Thin Films on Solids-State of the Interphase

FTIR reflection spectroscopy was used to characterize thin films of a cyanurate prepolymer on evaporated aluminium and on silicon single crystal wafers. Both substrates are covered by their native oxides. The optical function of the prepolymer is derived from ATR measurements. The measured thin film reflectance spectra have to be interpreted in comparison with the corresponding bulk spectra obtained by simulation. All samples re-produce the bulk composition. The cyanate groups of the prepolymer are not involved in specific intermolecular interactions or in preferential orientation. This is also found for the triazine rings on Si. On Al, however, a considerable excess of triazine rings are oriented parallel to the interface. The vibration frequencies of the triazine groupings that are perpendicular to the Al substrate show a red shift to some 2-8 c^-1. This special interaction effect does not occur on Si. Both the preferential orientation and the specific inter-molecular interaction act at least 100 nm into the prepolymer layer.     

Management of uterine perforation following elective abortion

Experience is reported with 28 uterine perforations encountered from June 1, 1973, to June 1, 1976, among 20,000 first trimester abortion patients at Reproductive Health Services, St. Louis, Missouri. In order to prevent this complication, one must perform an exacting pelvic examination. The use of a sound is controversial. Dilators should be introduced only a short distance through the internal os, and as much of the products of conception as possible should be aspirated. A sharp curette should be diagnostically. Various questions should be asked before the operator constructs a scheme for managing perforation. The current policy for management used at this clinic is outlined.     

Satisfaction with processes of collecting student opinions about instruction: The student perspective.

This study used a 2?×?2?×?2 factorial experiment to examine student satisfaction with eight processes of collecting student ratings of instruction by varying (a) method (group interviews vs. individual standardized rating forms), (b) timing (midterm vs. end of course), and (c) amount of instructor reaction to student ratings (restricted vs. extended). Consistent with predictions drawn from reactance and social comparison theories, students were more satisfied with interview methods at midterm followed by extended instructor reaction than with traditional approaches for collecting student opinions about instruction (i.e., standardized rating forms administered at the end of a course). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

GRADIENT OF THE MECHANICAL MODULUS IN GLASS–EPOXY–METAL JOINTS AS MEASURED BY BRILLOUIN MICROSCOPY

The newly developed Brillouin microscopy is used for the first time to measure in situ the longitudinal elastic stiffness coefficient in the GHz-range inside of glass–epoxy–metal joints as a function of distance from the substrates. Interphases with a local variation of mechanical properties are quantitatively characterized. These interphases possess unexpected widths of tens to hundreds of microns. Inside the interphases, the spatial variation of the longitudinal stiffness coefficient depends on the type of substrate, on the curing conditions for the epoxy and probably on the distribution of internal stresses. The obtained spatial mechanical profiles provide valuable insight into the morphology-driven mechanics of the interphase, but additional information is needed for a full understanding of their physical and chemical origin. The presented results prove the sensitivity of the Brillouin microscopy; the elastic stiffness coefficients are detected with an accuracy in the subpercentage range. The spatial resolution is better than 10?µm.     

Comparator-based switched-capacitor pipelined analog-to-digital converter with comparator preset,and comparator delay compensation

We present a differential comparator-based switched-capacitor (CBSC) pipelined analog-to-digital converter (ADC) with comparator preset, and comparator delay compensation. Compensating for the comparator delay by digitally adjusting the comparator threshold improves the ADC resolution from 2.5-bit to 7.05-bit. The ADC is manufactured in a 90 nm CMOS technology, with a core area of 0.85 mm × 0.35 mm, a 1.2 V supply for the core and 1.8 V for the input switches. It has an effective number of bits (ENOB) of 7.05-bit, and a power dissipation of 8.5 mW at 60 MS/s.     

Matrix-limited fatigue properties in fibre composite materials

Cyclic stressing of fibre composites in the elastic-plastic region is discussed under the assumption of equal strains in the fibre and the matrix. Under conditions of alternating load, it is found that the strain decreases and the stress on the matrix increases with increasing number of cycles. Such a phenomenon appears to be a macroscopic version of the Orowan model of fatigue.Within certain stress-levels, it appears that the matrix may work-harden to its failure stress and the composite will fail by this mechanism. Equations are developed which relate the number of cycles to matrix failure to the composite stress. A characteristic of the equation is the existence of a matrix endurance limit, a stress below which the matrix will not fall by progressive work-hardening, but rather by conventional fatigue mechanisms.The analysis is applied to Ag-steel and Cu-W composites. It shows that, for stresses in excess of the endurance limit, the number of cycles to induce failure is rather limited. At high volume-fraction of fibres in these systems, the endurance limit is only a small fraction of the composite tensile strength.     

The int genes of bacteriophages P22 and lambda are regulated by different mechanisms

Bacteriophage P22 and lambda are related bacteriophages with similar gene organizations. In lambda the cll-dependent Pl promoter is responsible for lambda int gene expression. The only apparent counterpart to pl in P22 is oriented in the opposite direction, and cannot transcribe the P22 int gene. We show that this promoter, called P(al), is active both in vivo and in vitro, and is dependent upon the P22 cll-like gene, called c1. We have also determined the DNA sequence of a 3.3 kb segment that closes the gap between previously reported sequences to give a continuous sequence between the P22 pL promoter and the int gene. The newly determined sequence is densely packed with genes from the pL direction, and the proteins predicted by the sequence show excellent correlation with the proteins mapped by Youderian and Susskind in 1980. However, the sequence contains no apparent genes in the opposite (p(al)) direction, and no additional binding motifs for the P22 c1 protein. We conclude that int gene expression in P22 is regulated by a different mechanism than in lambda.