Mathematical modeling of damage in unidirectional composites

A review of some approximate analytical models for damaged, fiber reinforced composite materials is presented. Using the classical shear lag stress displacement assumption, solutions are presented for a unidirectional laminate containing a notch, a rectangular cut-out, and a circular hole. The models account for longitudinal matrix yielding and splitting as well as transverse matrix yielding and fiber breakage. The constraining influence of a cover sheet on the unidirectional laminate is also modeled

Propagation of Light Elements in the Galaxy

The origin and evolution of isotopes of the lightest elements H2, He3, Li, Be, B in the universe is a key problem in such fields as astrophysics of CR, Galactic evolution, non-thermal nucleosynthesis, and cosmological studies. One of the major sources of these species is spallation by CR nuclei in the interstellar medium. On the other hand, it is the B/C ratio in CR and Be10 abundance which are used to fix the propagation parameters and thus the spallation rate. We study the production and Galactic propagation of isotopes of elements Z<6 using the numerical propagation code GALPROP and updated production cross sections.Comment: 4 pages, 6 ps-figures, tsukuba.sty, to appear in the Proc. 28th International Cosmic Ray Conference (Tsukuba, Japan 2003). More details can be found at http://www.gamma.mpe-garching.mpg.de/~aws/aws.htm

The Density Spike in Cosmic-Ray-Modified Shocks: Formation, Evolution, and Instability

We examine the formation and evolution of the density enhancement (density spike) that appears downstream of strong, cosmic-ray-modified shocks. This feature results from temporary overcompression of the flow by the combined cosmic-ray shock precursor/gas subshock. Formation of the density spike is expected whenever shock modification by cosmic-ray pressure increases strongly. That occurence may be anticipated for newly generated strong shocks or for cosmic-ray-modified shocks encountering a region of higher external density, for example. The predicted mass density within the spike increases with the shock Mach number and with shocks more dominated by cosmic-ray pressure. We find this spike to be linearly unstable under a modified Rayleigh-Taylor instability criterion at the early stage of its formation. We confirm this instability numerically using two independent codes based on the two-fluid model for cosmic-ray transport. These two-dimensional simulations show that the instability grows impulsively at early stages and then slows down as the gradients of total pressure and gas density decrease. Observational discovery of this unstable density spike behind shocks, possibly through radio emission enhanced by the amplified magnetic fields would provide evidence for the existence of strongly cosmic-ray modified shock structures.Comment: 26 pages in Latex and 6 figures. Accepted to Ap

Evaluation of enzyme immunoassays in the diagnosis of camel (Camelus dromedarius) trypanosomiasis:a preliminary investigation

Three enzyme immunoassays were used for the serodiagnosis of Trypanosoma evansi in camels in the Sudan in order to evaluate their ability to discriminate between infected and non-infected animals. Two assays were used for the detection of trypanosomal antibodies, one using specific anti-camel IgG conjugate and another using a non-specific Protein A conjugate. The third assay detected the presence of trypanosomal antigens using anti-T. evansi antibodies in a double antibody sandwich assay. Inspection of the frequency distribution of assay results suggested that the ELISA for circulating trypanosomal antibodies using specific antisera and the ELISA for circulating antigens can distinguish between non-infected camels and infected camels exhibiting patent infections or not. The ELISA using Protein A conjugate to bind non-specifically to camel immunoglobulin did not appear to discriminate between infected and non-infected animals

Evaluating an online self-help intervention for parents of children with food allergies

Background Parents of children with food allergies (CwFA) experience reduced quality of life (QoL) and may have reduced access to in-person interventions in the COVID-19 pandemic. This trial developed and evaluated an online, self-help, information provision website, aimed at improving QoL in parents of CwFA. Methods In a single-blinded, randomised controlled trial (RCT), participants were randomised to either receive access to the website or a waiting-list control. At baseline, post-intervention (week 4) and follow-up (week 8), measures of parental food allergy-related QoL, depression, anxiety, stress, intolerance of uncertainty (IU) and self-efficacy were obtained. Results A total of 205 participants were randomised; 97% were females, 91% white and 78% educated ≥ degree level, with a mean age of 38.95 years (SD = 6.89). 44.9% (n = 92) were retained at follow-up. The arms did not significantly differ on any outcome at any time point. For a sub-group of participants above the clinical cut-off for depression at baseline, the intervention may have improved QoL. Participants reported the website content as useful and accessible, but accessed it infrequently. In baseline data, IU and self-efficacy were significantly associated with QoL. Conclusion While the COVID-19 pandemic has encouraged greater provision of online interventions, our RCT suggests this particular website is not suitable for this population in general, although future research could examine its efficacy for depressed parents of CwFA, to increase confidence that the sub-group finding was not a Type 1 error. The baseline data suggest IU and self-efficacy remain potential proximal targets for intervention

Active and passive microwave measurements in Hurricane Allen

The NASA Langley Research Center analysis of the airborne microwave remote sensing measurements of Hurricane Allen obtained on August 5 and 8, 1980 is summarized. The instruments were the C-band stepped frequency microwave radiometer and the Ku-band airborne microwave scatterometer. They were carried aboard a NOAA aircraft making storm penetrations at an altitude of 3000 m and are sensitive to rain rate, surface wind speed, and surface wind vector. The wind speed is calculated from the increase in antenna brightness temperature above the estimated calm sea value. The rain rate is obtained from the difference between antenna temperature increases measured at two frequencies, and wind vector is determined from the sea surface normalized radar cross section measured at several azimuths. Comparison wind data were provided from the inertial navigation systems aboard both the C-130 aircraft at 3000 m and a second NOAA aircraft (a P-3) operating between 500 and 1500 m. Comparison rain rate data were obtained with a rain radar aboard the P-3. Evaluation of the surface winds obtained with the two microwave instruments was limited to comparisons with each other and with the flight level winds. Two important conclusions are drawn from these comparisons: (1) the radiometer is accurate when predicting flight level wind speeds and rain; and (2) the scatterometer produces well behaved and consistent wind vectors for the rain free periods

A bioassay for Heterodera spp. without counting cysts or larvae

RESP-469

Quantitative estimates of discrete harmonic measures

A theorem of Bourgain states that the harmonic measure for a domain in $\R^d$ is supported on a set of Hausdorff dimension strictly less than $d$ \cite{Bourgain}. We apply Bourgain's method to the discrete case, i.e., to the distribution of the first entrance point of a random walk into a subset of $\Z ^d$, $d\geq 2$. By refining the argument, we prove that for all \b>0 there exists \rho (d,\b)N(d,\b), any $x \in \Z^d$, and any $A\subset \{1,..., n\}^d$ | \{y\in\Z^d\colon \nu_{A,x}(y) \geq n^{-\b} \}| \leq n^{\rho(d,\b)}, where $\nu_{A,x} (y)$ denotes the probability that $y$ is the first entrance point of the simple random walk starting at $x$ into $A$. Furthermore, $\rho$ must converge to $d$ as \b \to \infty.Comment: 16 pages, 2 figures. Part (B) of the theorem is ne

Paediatric gastroesophageal reflux disease and parental mental health: Prevalence and predictors

Objective: The current study aimed to estimate the prevalence of common mental health difficulties in parents who have an infant with Gastroesophageal Reflux Disease (GORD), and to identify psychological predictors of parental anxiety, depression, and well-being, as a platform forsubsequent intervention development. Methods: Parents of infants with GORD (N= 309) completed online psychometric measures of potential predictors (self-compassion, illness appraisals, and illness uncertainty), potential confounders (sleep quality, relationship satisfaction, social support, and infant feeding satisfaction), and mental health outcomes (anxiety, depression, and wellbeing). The outcome measures were re-peated eight-weeks later (N= 103). Results: At the first time-point, 66% of participants exceed the clinical cut off for generalised anxiety disorder and 63% exceeded that for a depressive disorder. Both had significantly reduced eights-weeks later. Greater self-compassion predicted lower anxiety and depression, and better well-being, in both cross-sectional and longitudinal data, including when all confounders were controlled for. Illness uncertainty and illness appraisals were less consistent predictors. No robust differences were found between parents of infants with silent GORD and those with GORD with visible regurgitation. Conclusions: Parents of infants with GORD showed high rates of anxiety and depression, which were elevated compared to those that have been found in perinatal and general population samples. Self-compassion was a consistent predictor of better mental health and has promise as a proximal intervention target. Future research could benefit from examining the efficacy of a compassion-focussed intervention in this population