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Since the discovery of Perkinsus marinus as the cause of dermo disease in Crassostrea virginica, salinity and temperature have been identified as the main environmental drivers of parasite prevalence. However, little is known about how these variables affect the movement of the parasite from host to water column. In order to elucidate how environmental factors can influence the abundance of this parasite in the water column, we conducted a series of experiments testing the effects of time of day, temperature and salinity on the release of P. marinus cells from infected oysters. We found that P. marinus cells were released on a diurnal cycle, with most cells released during the hottest and brightest period of the day (12:00–18:00). Temperature also had a strong and immediate effect on the number of cells released, but salinity did not, only influencing the intensity of infection over the course of several months. Taken together, our results demonstrate that (1) the number of parasites in the water column fluctuates according to a diurnal cycle, (2) temperature and salinity act on different timescales to influence parasite abundance, and (3) live infected oysters may substantially contribute to the abundance of transmissive parasites in the water column under particular environmental conditions.
A set of graphs are called cospectral if their adjacency matrices have the same characteristic polynomial. In this paper we introduce a simple method for constructing infinite families of cospectral regular graphs. The construction is valid for special cases of a property introduced by Schwenk. For the case of cubic (3-regular) graphs, computational results are given which show that the construction generates a large proportion of the cubic graphs, which are cospectral with another cubic graph.
The vertical component of space occurs in two distinct fashions in natural environments. One kind of verticality is orthogonal-to-horizontal (as in climbing trees, operating in volumetric spaces such as water or air, or taking elevators in multilevel buildings). Another kind of verticality, which might be functionally distinct, comes from navigating on sloped terrain (as in traversing hills or ramps).
Multivitamin supplements are used by nearly half of middle-aged women in the USA. Despite this high prevalence of multivitamin use, little is known about the effects of multivitamins on health outcomes, including cancer risk. Our main objective was to determine the association between multivitamin use and the risk of breast cancer in women.
We conducted a population-based case–control study among 2968 incident breast cancer cases (aged 20–69 years), diagnosed between 2004 and 2007, and 2982 control women from Wisconsin, USA. All participants completed a structured telephone interview which ascertained supplement use prior to diagnosis, demographics and risk factor information. Odds ratios and 95 % confidence intervals were calculated using multivariable logistic regression.
Compared with never users of multivitamins, the OR for breast cancer was 1·02 (95 % CI 0·87, 1·19) for current users and 0·99 (95 % CI 0·74, 1·33) for former users. Further, neither duration of use (for ≥10 years: OR = 1·13, 95 % CI 0·93, 1·38, P for trend = 0·25) nor frequency (>7 times/week: OR = 1·00, 95 % CI 0·77, 1·28, P for trend = 0·97) was related to risk in current users. Stratification by menopausal status, family history of breast cancer, age, alcohol, tumour staging and postmenopausal hormone use did not significantly modify the association between multivitamin use and breast cancer.
The current study found no association between multivitamin supplement use and breast cancer risk in women.
The Arcminute Cosmology Bolometer Array Receiver (Acbar) is a multifrequency millimeter-wave receiver optimized for observations of the Cosmic Microwave Background (CMB) and the Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies. Acbar was installed on the 2.1 m Viper telescope at the South Pole in January 2001 and the results presented here incorporate data through July 2002. The power spectrum of the CMB at 150 GHz over the range ℓ = 150 — 3000 measured by Acbar is presented along with estimates for the values of the cosmological parameters within the context of ΛCDM models. The inclusion of ΩΛ greatly improves the fit to the power spectrum. Three-frequency images of the SZ decrement/increment are also presented for the galaxy cluster 1E0657–67.
We sampled blood from free-living spotted salamanders (Ambystoma maculatum) to test whether differences in the concentrations of a stress hormone (corticosterone) were associated with different qualities of breeding and migration habitat. Spotted salamanders are forest specialists that migrate to vernal pools to breed, and upland habitat degradation may have sub-lethal effects on animals that lead to population declines. An individual's level of physiological stress may function as a biomonitor for sub-lethal effects, and thus as a biomonitor for ecosystem quality. We compared unstressed (baseline) and stress-induced corticosterone concentrations in spotted salamanders: (1) at sites that differed in amount of forest loss; (2) during breeding migration across forest habitat versus pavement; (3) in microhabitats that varied in soil drainage and canopy cover. Removal of large amounts of terrestrial habitat surrounding a breeding pond was correlated with lower baseline (in males) and stress-induced corticosterone concentrations, which may indicate healthy individuals with a reduced ability to respond to additional stress or individuals experiencing chronic stress. Male salamanders migrating across pavement had elevated baseline corticosterone concentrations compared to animals migrating through a forest, consistent with an acute stress response. However, concentrations of corticosterone did not differ between individuals in microhabitats with canopy cover and well-drained soil versus those in microhabitats with no canopy cover and/or swampy soil. This endocrinological technique may be one useful measure of a population's health, helping to identify populations where further ecological study is recommended to evaluate conservation concerns.
We propose a new way of thinking conceptually and methodologically about drug use sequences. In terms of biopsychosocial views on drug use, such as Noble's (1996) theory on genetic variations that imply a genetically based differential rewarding effect of alcohol and drug use on the dopamine system, the effect of initial drug use on later drug use can be conceptualized as a sensitizing effect that influences the subsequent growth in use of other substances. Extensive use of a Gateway drug may serve to determine a higher initial level of use of a consequent drug or a faster trend of growth in use of the consequent drug across time. Additionally, a greater rate of growth across time in extent of use of the Gateway drug may itself serve to determine a faster trend of growth in extent of use of the consequent drug. This growth trajectory hypothesis for progression of drug use can be tested with a variant of structural equation modeling known as growth curve modeling. The more traditional cross-lag autoregressive model can be used to study lagged effects of one substance use on another. We compare these two ways of looking at drug use involvement in a sample of 679 African American and White high school youths assessed at three time points. In addition, we cross-validate our results on a previously published data set.
The effects of different growth parameters on the microstructure of the SiC films formed during simultaneous two-source molecular-beam-epitaxial (MBE) deposition have been investigated. Substrate temperatures as low as 750–900 °C have been used. The relationship between a number of different growth morphologies and deposition conditions has been established. The formation of single-crystal 3C films has been found to occur at low growth rates but within a limited Si: C adatom ratio. A combination of transmission electron microscopy (TEM) and atomic force microscopy (AFM) has been used to examine the different films, and the results of these investigations are described.
Fifty children with otitis media with effusion undergoing grommet insertion had into one ear a Minititanium grommet inserted and into the other ear a Mini-teflon grommet. Post-operative follow-up until after extrusion of the grommets demonstrated only a small difference between the extrusion times of the two grommets (a significant difference of 41 days) and no difference in the degree of tympanosclerosis seen with each grommet. We propose that the mass of a grommet appears to play less of a role than has previously been suggested in the pathogenesis of tympanosclerosis following grommet insertion and that duration of intubation may be the most significant factor.
Since the discovery of high critical temperature superconducting oxides, an important factor potentially limiting their technological application has been the typically low value of the critical current density that they can carry. Here are presented the results of a transmission electron microscopy study of sintered YBa2Cu3O7−x aimed primarily at the characterization of those elements of the microstructure responsible for the poor current-carrying capacity in the superconducting state. The observations are further discussed in relation both to the flux pinning characteristics required and to the prospect for controlling the microstructure in order to optimize the properties of this material for technological development.