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Due to the lack of basic information on water required by maize (Zea mays L.) in Brazil, the large amount of water applied usually exceeds crop requirements, wasting water and energy. In this study, we measured crop evapotranspiration (ETc) as evaporative heat flux from a centre pivot-irrigated maize plantation in Southern Brazil during winter and summer seasons, using the Bowen ratio method to evaluate how the degree of canopy-atmosphere coupling affects crop water needs and irrigation management. Irrigation requirements were determined by comparing ETc with reference evapotranspiration (ETo), derived from the Penman–Monteith equation and expressed as the ETc/ETo (Kc) ratio. In this study, the average Kc values obtained were 1.31 and 0.90 for the winter and summer, respectively. Using aerodynamic and canopy resistance measurements, the decoupling factor (Ω) was computed. Ω values tending to zero (0.09 and 0.20 for winter and summer, respectively) showed that strong coupling of maize plants to the atmosphere and sensitivity to high air temperatures, vapour pressure deficits and wind speed caused variations in Kc in relation to ETo ranges. During the experimental period, the Kc value ranged from 0.92 when the ETo exceeded 4 mm d−1 to 1.64 when the ETo was less than 2 mm d−1.
The use of roman numerals for stellar populations represents a classification approach to galaxy formation which is now well behind us. Nevertheless, the concept of a pristine generation of stars, followed by a protogalactic era, and finally the mainstream stellar population is a plausible starting point for testing our physical understanding of early star formation. This will be observationally driven as never before in the coming decade. In this paper, we search out observational tests of an idealised coeval and homogeneous distribution of population II stars. We examine the spatial distribution of quasars, globular clusters, and the integrated free electron density of the intergalactic medium, in order to test the assumption of homogeneity. Any real inhomogeneity implies a population II that is not coeval.
In the course of a long-term project investigating classical novae with large outburst amplitudes, we have performed multi-wavelength photometry and optical spectroscopy of several old nova candidates. We here introduce the aim of the project, the search for low mass-transfer novae with short orbital periods, and explain the method to recover these old novae via their colour characteristics. Finally we concentrate on first results for selected objects in our sample.
The study of extra solar planets represents a new exciting frontier for modern astronomy. Most of the results on extrasolar systems are obtained with Doppler surveys. Here we suggest a different approach aimed to study the polarimetric properties of the residual interplanetary dust. Dust can produce observable effects such as infrared emission excess (Beckwith & Sargent 1996; Spangler et al. 2001) and partial polarization of the star light via scattering (Mauron & Dole 1998; Yudin 2000), like in β Pictoris (Voshchinnikov & Krügel 1999). Some polarization could also be produced by a giant planet in a close orbit around the star (Saeger et al. 2000), but the resulting effect is too weak to be responsible for the polarizations actually observed.
Staphylococcus aureus is the most important causative agent of subclinical mastitis in cattle resulting in reduced milk production and quality. Methicillin-resistant S. aureus (MRSA) strains has a clear zoonotic relevance, especially in the case of occupational exposure. The aim of the study was to evaluate the prevalence of S. aureus and MRSA in bulk tank milk (BTM) from dairy cattle herds in the Lombardy Region (Northern Italy) and to identify the main MRSA circulating genotypes. MRSA strains were characterized by susceptibility testing, multi-locus sequence typing (MLST), spa typing and SCCmec typing. A total 844 BTM samples were analysed and S. aureus and MRSA were detected in 47·2% and 3·8% of dairy herds, respectively. MLST showed that the majority (28/32) of isolates belonged to the typical livestock-associated lineages: ST398, ST97 and ST1. Interestingly, in this study we report for the first time the new ST3211, a single locus variant of ST(CC)22, with the newly described 462 aroE allele. Our study indicates high diffusion of S. aureus mastitis and low, but not negligible, prevalence of MRSA in the considered area, suggesting the need for planning specific control programmes for bovine mastitis caused by S. aureus, especially when MRSA is implicated.
The small orbiting observatory MOUSE is described in its essential features. Insights in the optical solution (a 2 mirrors 3 reflections telescope using pure hyperbolical surfaces, no aspherics) are given which fit such type of optical layout to scientific requirements. An in-flight recentering of the photons collected by a solar-blind photon counter device will allow for an equivalent angular resolution of 2–3 arcsec over a field-of-view exceeding one square degree. The capabilities of the proposed satellite (imaging, low resolution grisms, polarizers) are described. The choice of the selected sky areas (the two Galactic Poles, the galactic equator and some Bulge Windows) is justified in terms of forefront astrophysical scientific objectives requiring imaging in UV over large fields. The science comprises UV analysis of a complete sample of QSOs, stellar population in galaxies, White Dwarfs, Globular and Open Clusters and OB Associations. In addition a plan for the early UV detection of Supernova events is described.
Although James Mill considered production and education to be two objectives of global welfare, he claimed that the former was not always consistent with the latter. On the one hand, production is necessary to provide humankind with the means of subsistence; on the other hand, if individuals allocate all their time to labor to the detriment of their own education, “neither intellect, virtue nor happiness can flourish upon the earth” (Mill  1825, p. 30). Mill argued that this problem might be solved by finding what he called “the precious middle point.” This point deserves special consideration: it acknowledges that there is a way in which education and production might be distributed in society in order to promote the greatest global welfare. The aim of this paper is to explain the relation between production and education through the working of the precious middle point.
New results presented include the oscillations of intervals between maxima of light oscillations, while in the case of GK Per the Orion system velocities oscillated with twice the light oscillation period.
About 16 old novae are accessible to IUE, but only five (RR Pic, V 603 Aql, HR Del, DQ Her, and GK Per) have been observed in the ultraviolet and studied in any detail. Considering that, because of selection effects, only few and the brightest objects have been observed, it not possible to draw general conclusions on the UV luminosity LUV and mass accretion rates Ṁacc of old novae. We plan to improve the rather poor statistic by observing in the near future all objects falling above the IUE detection limit of m(V) ≃ 15 (i.e. X Ser, DK Lac, DN Gem, and HR Lyr). In the following we present preliminary results for 7 old novae observed with the IUE satellite whitin our observing programmes or obtained from the IUE archive.
This communication gives some preliminary results of a spectroscopic survey of old novae presently carried out at Asiago Observatory. I have obtained image-tube spectra of 10 old novae in the spectral range 4000-7000 Å with dispersions from 60 to 180 Å/mm. The observed novae are: T Aur 1891, V 476 Cyg 1920, Q Cyg 1876, HR Del 1967, DN Gem 1912, DQ Her 1934, V 533 Her 1963, CP Lac 1936, V 841 Oph 1848 and GK Per 1901.
New spectroscopic observations of the old nova CP Pup suggest most probable orbital period of 0.061375 days. First systematic monitoring of the very old nova V841 Oph reveals orbital motion with a most probable period of about 0.6 days. A slightly eccentric solution at P = 0.3755 days is less probable.
The progenitors of cataclysmic variables (CVs) undergo a common envelope phase, during which their initial orbital period is reduced to a few hours. After this phase the radiative core of the secondary might rotate at a lower rate than the tidally coupled envelope. A shear is then generated at the core-envelope interface which can give rise to a boundary layer dynamo and, consequently, to the magnetic braking of the binary system. The temporal variation of the shear energy content can be obtained by comparing the rate of magnetic energy production with the input rate of orbital energy in the convective envelope. We assume for the flux tubes a filling factor, fV, owing to the expected size of the tubes and the fact that the dynamo action may be concentrated inside an equatorial belt of the boundary layer shell. We also assume that the production of toroidal field is efficient only inside the boundary layer, while the poloidal component of the field can be enhanced also across the outer convective envelope (see also Zangrilli & Bianchini 1995). We find that the decrease in the shear energy, caused by the continuous production of magnetic field and by the progressive reduction of the core moment of inertia, leads the core coupling with the envelope, thus switching off the dynamo at the core-envelope boundary. Further details of this core-envelope decoupling dynamo model will be given in a forthcoming paper (Zangrilli, Tout & Bianchini 1996).
Quiescent novae are more stable against mass transfer rate than dwarf novae. They may however show cyclical variations of their quiescent magnitudes on time scales of years, probably caused by solar–type cycles of activity of the secondary. The probability density function of the periods of the cycles observed in CVs is similar to that for single stars. Sometimes, periodic or quasi periodic light variations on time scales of tens to hundreds of days are also observed. Although the magnitudes of prenovae and postnovae are essentially the same, the definition of the magnitude of a quiescent nova is still uncertain. At present, the hibernation theory for old novae seems to be supported only by the observations of two very old novae.
The observed X-ray to IR continuum energy distribution of the old-nova GK Per, corrected for the contribution of the late-type secondary and for i.s. extinction,is found to be consistent with the model of an accreting magnetic white dwarf. Furthermore, we discuss plausible modifications of the standard disc structure caused by the presence of magnetic field lines threading the disc and evaluate the contribution to the observed radiation field from several physical mechanisms.
James Mill’s account of the decision process is part of his theory of the human mind, which in turn is the cornerstone of his theory of education. Mill believed the end of education was to produce happiness, and that this happiness required action by the individual. A problem, as Mill saw it, was that intemperance might interfere with the decision process, causing individuals to take actions that do not promote their greatest happiness. This paper provides an interpretation of this process from a formal perspective, in the light of Mill’s view on intemperance.
We investigate the effect of retirement on memory using the Survey on Health, Ageing and Retirement in Europe (SHARE). The availability of a panel data-set allows individual heterogeneity to be controlled for when estimating the effect of transitions into retirement on a commonly employed memory measure, word recall. We control for endogeneity of the retirement decision applying an instrumental variable technique to our fixed-effects transformation. Our main finding is that, conditional on the average non-linear memory age path of the typical individual, time spent in retirement has a positive effect on word recall.