General techniques for analyzing DS/SSMA interference illustratedby evaluating a noncoherent system

A conditional probability density function of the multiple-access interference (MAI) in direct-sequence spread-spectrum multiple access (DS/SSMA) systems with complex modulation (e.g., M-ary and continuous phase) is derived from a geometric viewpoint. A method to efficiently calculate the two-dimensional (2-D) convolutions of a number of circularly symmetric densities is presented. The utility of these methods is then illustrated by evaluating a noncoherent DS/SSMA system     

Effect of pre-exposure on crack initiation life of a directionally solidified Ni-base superalloy

Blades and vanes are just two of several industrial gas turbine (IGT) components often subjected to long periods of elevated temperature before, during, and after high stress operating conditions. In these systems, cyclic loading is induced by repeated start-ups, firings, and shut-down ramps. Combinations of complex thermal and mechanical service conditions in the presence of aggressive reactants facilitate crack initiation via oxide spike formation. In the current study, the effect of pre-exposure on the oxide spiking damage mechanism and crack initiation life is characterized for a representative directionally solidified (DS) Ni-base superalloy, e.g. DS GTD-111. Comparisons of unexposed and pre-exposed samples reveal that 100 h of either creep pre-strain and/or thermal pre-exposure strongly influences the dominant damage mechanism that leads to crack initiation under subsequent fatigue cycling. A mechanistic model for crack initiation is modified to capture the influence of pre-exposure on life.     

Doctors and patients don't agree: cross sectional study of patients' and doctors' perceptions and assessments of disability in multiple sclerosis

OBJECTIVES: To compare the judgments of clinicians on which domains of health in the short form questionnaire (SF-36) would be most important to patients with multiple sclerosis with the opinions of patients themselves; to compare assessment of physical disability in multiple sclerosis by a clinician using Kurtzke's expanded disability status scale and a non-clinically qualified assistant using the Office of Population Census and Surveys' (OPCS) disability scale with self assessment of disability and other domains of health related quality of life by patients using the SF-36 and the EuroQol questionnaire; and to compare the scores of patients for each domain of the SF-36 with control data matched for age and sex. DESIGN: Cross sectional study. SETTING: Clinical department of neurology, Edinburgh. SUBJECTS: 42 consecutive patients with multiple sclerosis attending a neurology outpatient clinic for review or a neurology ward for rehabilitation. MAIN OUTCOME MEASURES: Scores on the SF-36; EuroQol; Kurtzke's expanded disability status scale; the OPCS disability scale. RESULTS: Patients and clinicians disagreed on which domains of health status were most important (chi 2 = 21, df = 7, P = 0.003). Patients' assessment of their physical disability using the physical functioning domain of the SF-36 was highly correlated with the clinicians' assessment (r = -0.87, P < 0.001) and the non-clinical assessment (r = -0.90, P < 0.001). However, none of the measures of physical disability correlated with overall health related quality of life measured with EuroQol, Quality of life correlated with vitality, general health, and mental health in the SF-36, each of which patients rated as more important than clinicians and for each of which patients scored lower than the controls. CONCLUSIONS: Patients with multiple sclerosis and possibly those with other chronic diseases are less concerned than their clinicians about physical disability in their illness. Clinical trials in multiple sclerosis should assess the effect of treatment on the other elements of health status that patients consider important, which are also affected by the disease process, are more closely related to overall health related quality of life, and may well be adversely affected by side effects of treatment.     

Reproductive effects of feeding gossypol and vitamin E to bulls

An experiment was conducted to determine the effects of long-term feeding of cottonseed meal on the reproductive traits of Holstein bulls. Holstein bulls approximately 6 mo of age were placed on the following treatments: 1) soybean meal + corn (CON); 2) cottonseed meal + corn (GOS); and 3) cottonseed meal + 4,000 IU vitamin E x bull(-1) x d(-1) (G+4E). The GOS and G+4E diets were formulated to supply 14 mg of free gossypol x kg(-1) BW x d(-1). These bulls had been in a previous experiment that evaluated the effects of feeding the same type of diets, but from 2 wk to 6 mo. of age. Percentage of motility, percentage of normal and live sperm, and daily sperm production were less (P<.05) in the GOS than in the other two treatments. Percentages of primary abnormalities and abnormal midpieces were greater (P<.05) in the GOS group than in the other two groups. At 12 and 16 mo. of age, bulls were given two assessments for sex drive traits. Bulls that received gossypol exhibited less sexual activity (P<.05) at the first test than bulls in other treatments. Vitamin E supplementation in bulls that received gossypol improved the number of mounts in the first test and the time to first service in the second test. There was a trend of gossypol to decrease and vitamin E to improve libido score. The results of the GOS first libido test may indicate lack of sexual maturity, which agrees with sperm production data. At the time of first test (12 mo. of age), none of GOS, two of CON, and six of G+4E bulls had reached puberty on the basis of experimental protocol. Long-term feeding of gossypol to Holstein bulls negatively affected some reproductive traits; however, vitamin E supplementation countered these adverse effects and even improved these traits.     

The use of a surface adhesion immunofluorescent (SAIF) method for the rapid detection of Yersinia enterocolitica serotype O:3 in meat

Defective trafficking of the cystic fibrosis transmembrane conductance regulator (CFTR) is the most common cause of cystic fibrosis. In chloride-secreting epithelia, it is well established that CFTR localizes to intracellular organelles and to apical membranes. However, it is controversial whether secretagogues regulate the trafficking of CFTR. To investigate whether acute hormonal stimulation of chloride secretion is coupled to the trafficking of CFTR, we used the intact shark rectal gland, a model tissue in which salt secretion is dynamically regulated and both chloride secretion and cellular CFTR immunofluorescence can be quantified in parallel. In rectal glands perfused under basal conditions without secretagogues, Cl- secretion was 151+/-65 microeq/h/g. Vasoactive intestinal peptide (VIP), forskolin, and genistein led to 10-, 6-, and 4-fold increases in Cl- secretion. In basal glands, quantitative confocal microscopy revealed CFTR immunofluorescence extending from the apical membrane deeply into the cell (7.28+/-0.35 micron). During stimulation with secretagogues, apical extension of CFTR immunofluorescence into the cell was reduced significantly to 3.24+/-0.08 micron by VIP, 4.08+/-0.13 by forskolin, and 3.19+/-0.1 by genistein (P < 0.001). Moreover, the peak intensity of CFTR fluorescence shifted towards the apical membrane (peak fluorescence 2.5+/-0.13 micron basal vs. 1.51+/-0.06, 1.77+/-0.1, and 1.38+/-0.05 for VIP, forskolin, and genistein; all P < 0.001). The increase in both Cl- secretion and apical CFTR trafficking reversed to basal values after removal of VIP. These data provide the first quantitative morphological evidence for acute hormonal regulation of CFTR trafficking in an intact epithelial tissue.     

Dual-phase continuous phase modulation for spread-spectrum multiple-access communication

A new class of direct-sequence spread-spectrum multiple-access (DS-SSMA) systems with continuous phase modulation (CPM) is defined. The signals are unique in that the spreading is done by adding an extra phase term to the information phase while maintaining phase continuity, constant envelope, and efficient bandwidth usage. The spreading phase is formed from the spreading code and is independent of the information phase, which allows despreading to be done separately before data detection, which, in turn, allows a simple CPM detector to be employed for data detection. The information phase is considered in the minimum-shift keying (MSK) format, and a serial-MSK-type spread-spectrum receiver is considered for performance analysis. Expressions for the signal-to-noise ratio, the power spectral density, and the probability of bit error are developed, along with methods for computing their values to an arbitrarily close approximation. Numerical results show that the proposed system is an attractive alternative to the conventional DS-SSMA systems.     

The chemical oxidation of catechins and other phenolics: A study of the formation of black tea pigments

The chemical oxidation of polyphenols has been used to produce black tea pigments. (+)-Catechin, (?)-epicatechin, (?)-epicatechin gallate and (?)-epigallocatechin gallate were isolated from convenient sources, their identity being confirmed by mass spectrometry and HPLC. The oxidation of a mixture of (?)-epicatechin gallate and gallic acid gave an oxidation product of (?)-epicatechin gallate in addition to epitheaflavic acid 3-gallate. The catechins were oxidised chemically and the products analysed by HPLC, the chromatograms being compared with a black tea chromatogram. The reactions gave both resolved and unresolved pigments, and many of the resolved pigments had HPLC retention times close to black tea pigments. Each catechin behaved differently, the chromatograms of the oxidation products from each starting material being clearly distinguishable. Resolved pigments were obtained by the chemical oxidation of other phenolic compounds. This work provides a convenient method for studying the formation of resolved and unresolved black tea pigments.     

A simple non-associated flow model for sand

 This paper proposes a simple non-associated plasticity model for sand. The yield surface is taken to be a member of a recently derived family of yield loci, requiring the specification of a single parameter in addition to the stress ratio at the peak value of deviatoric stress on the yield surface in deviatoric:mean effective stress space. This simple equation, can easily be fitted to given sand data. The flow rule also has a simple equation, such that the critical state is not at the top of the yield locus in stress space. The equation of the flow rule requires the specification of the critical state dissipation constant, plus one additional parameter. This permits realistic modelling of the undrained behaviour of sand in states looser and denser than critical. The parameter controlling the flow rule can, for convenience, be taken to be equal to the parameter governing the shape of the yield surface. However, since the two parameters are not required to be equal, the flow rule can easily be adjusted to model more accurately the rate of change of direction of the plastic strain increment vector with changing stress ratio around the yield surface. The model resembles more complex models based on the mathematical theory of envelopes, but the equations of the yield loci and flow rules are much simpler. The contribution in this paper is therefore to provide a model similar to those derived based on micro mechanical considerations, but which is more useful to geotechnical engineers, in that the number of parameters is kept to a minimum, the constitutive equations are simple, and the flow rule can easily be controlled. The model is easy to apply in geotechnical analysis, and would be easy to implement in a finite element program. Received: 11 January 2002