8,836 research outputs found
Influence of human pressures on large river structure and function
A large river study was conducted as part of the Cross Departmental Research Pool (CDRP) ecological integrity project to (i) provide an overview of the macroinvertebrate faunas of large rivers, including those in deep-water habitats, and (ii) to elucidate links between these faunas, river function and anthropogenic stressors. Eleven sites on 6th-order or 7th-order rivers were sampled; four in the South Island and seven in the North Island. We measured (i) macroinvertebrate communities colonising wood, riffles (where present), littoral habitats (1.5 m deep) (ii) ecosystem metabolism using a single-station open-channel approach based on natural changes in dissolved oxygen concentration over a 24-hour period, and (iii) wood and cellulose breakdown. Relationships were investigated between these response variables and reach-scale assessments of habitat quality, underlying upstream and segment environmental variables provided in the Freshwater Environments of New Zealand (FWENZ) database, and anthropogenic pressure variables provided by the Waters of National Importance (WONI) database
Bistable molecular conductors with a field-switchable dipole group
A class of bistable "stator-rotor" molecules is proposed, where a stationary
bridge (stator) connects the two electrodes and facilitates electron transport
between them. The rotor part, which has a large dipole moment, is attached to
an atom of the stator via a single sigma bond. Hydrogen bonds formed between
the rotor and stator make the symmetric orientation of the dipole unstable. The
rotor has two potential minima with equal energy for rotation about the sigma
bond. The dipole orientation, which determines the conduction state of the
molecule, can be switched by an external electric field that changes the
relative energy of the two potential minima. Both orientation of the rotor
correspond to asymmetric current-voltage characteristics that are the reverse
of each other, so they are distinguishable electrically. Such bistable
stator-rotor molecules could potentially be used as parts of molecular
electronic devices.Comment: 8 pages, 7 figure
Nucleosynthesis: Stellar and Solar Abundances and Atomic Data
Abundance observations indicate the presence of often surprisingly large
amounts of neutron capture (i.e., s- and r-process) elements in old Galactic
halo and globular cluster stars. These observations provide insight into the
nature of the earliest generations of stars in the Galaxy -- the progenitors of
the halo stars -- responsible for neutron-capture synthesis. Comparisons of
abundance trends can be used to understand the chemical evolution of the Galaxy
and the nature of heavy element nucleosynthesis. In addition age
determinations, based upon long-lived radioactive nuclei abundances, can now be
obtained. These stellar abundance determinations depend critically upon atomic
data. Improved laboratory transition probabilities have been recently obtained
for a number of elements. These new gf values have been used to greatly refine
the abundances of neutron-capture elemental abundances in the solar photosphere
and in very metal-poor Galactic halo stars. The newly determined stellar
abundances are surprisingly consistent with a (relative) Solar System r-process
pattern, and are also consistent with abundance predictions expected from such
neutron-capture nucleosynthesis.Comment: 8 pages, 2 figures, 1 table. To appear in the Proceedings of the NASA
Laboratory Astrophysics Workshop in Las Vegas, NV (February 2006
Heat Stress Effect on Immune Function in Dairy Cattle
This information was presented at the 2017 Cornell Nutrition Conference for Feed Manufacturers, organized by the Department of Animal Science In the College of Agriculture and Life Sciences at Cornell University. Softcover copies of the entire conference proceedings may be purchased at http://ansci.cals.cornell.edu/extension-outreach/adult-extension/dairy-management/order-proceedings-resources.This presentation will cover recent work examining the impact of heat stress in late gestation on the cow and the calf, during the dry period and subsequent lactation, including the effects on immune function. The presentation will also address the effects of heat stress on health and performance of lactating dairy cows, and use of an immune modulator to reduce the impacts of heat stress
Identification of Bacterial Pathogens of Bovine Mastitis by the Practicing Veterinarian
Culturing techniques are complicated and time consuming by many veterinarians. Control of mastitis is often attempted with out detection of subclinical cases which serve as reservoirs of infection for the entire herd. Effective control of bovine mastitis must necessarily be based upon the detection of every infected quarter in a herd. Identification of the etiologic agents avoids hit or miss methods, gives indications for specific therapy, aids in prognosis and furnishes information for a definite plan of control
Doppler-beaming in the Kepler light curve of LHS 6343 A
Context. Kepler observations revealed a brown dwarf eclipsing the M-type star
LHS 6343 A with a period of 12.71 days. In addition, an out-of-eclipse light
modulation with the same period and a relative semi-amplitude of 2 x 10^-4 was
observed showing an almost constant phase lag to the eclipses produced by the
brown dwarf. In a previous work, we concluded that this was due to the light
modulation induced by photospheric active regions in LHS 6343 A. Aims. In the
present work, we prove that most of the out-of-eclipse light modulation is
caused by the Doppler-beaming induced by the orbital motion of the primary
star. Methods. We introduce a model of the Doppler-beaming for an eccentric
orbit and also considered the ellipsoidal effect. The data were fitted using a
Bayesian approach implemented through a Monte Carlo Markov chain method. Model
residuals were analysed by searching for periodicities using a Lomb-Scargle
periodogram. Results. For the first seven quarters of Kepler observations and
the orbit previously derived from the radial velocity measurements, we show
that the light modulation of the system outside eclipses is dominated by the
Doppler-beaming effect. A period search performed on the residuals shows a
significant periodicity of 42.5 +- 3.2 days with a false-alarm probability of 5
x 10^-4, probably associated with the rotational modulation of the primary
component.Comment: 6 pages, 7 figure
Field Biology at Algona High School, Summer, 1960
The class was made up of seven junior and senior boys who had already successfully completed a regular one-year course in biology. The overall classroom time was 120 hours. Five hours were spent in the school and the remaining time was spent in the field. During the 5-week course, dove banding, wildlife survey of a section of land, gill-netting of fish, vegetation transect, and identification of birds, plants, fish, reptiles, amphibians, and mammals was carried on
The resilience of indigenous knowledge in small-scale African agriculture: key drivers
The successful use of indigenous knowledge (IK) in development practice in rural Africa over the last couple of decades has proved to be elusive and disappointing. Using empirical field data from northern Malawi, this study suggests that the two key drivers for farmers in this area are household food security and the maintenance of soil fertility. Indigenous ways of knowing underpin the agricultural system which has been developed, rather than the adoption of more modern, ‘scientific’ ways, to deliver against these drivers. Such IKs, however, are deeply embedded in the economic, social and cultural environments in which they operate
Force-Free Models of Magnetically Linked Star-Disk Systems
Disk accretion onto a magnetized star occurs in a variety of astrophysical
contexts, from young stars to X-ray pulsars. The magnetohydrodynamic
interaction between the stellar field and the accreting matter can have a
strong effect on the disk structure, the transfer of mass and angular momentum
between the disk and the star, and the production of bipolar outflows, e.g.,
plasma jets. We study a key element of this interaction - the time evolution of
the magnetic field configuration brought about by the relative rotation between
the disk and the star - using simplified, largely semianalytic, models. We
first discuss the rapid inflation and opening up of the magnetic field lines in
the corona above the accretion disk, which is caused by the differential
rotation twisting. Then we consider additional physical effects that tend to
limit this expansion, such as the effect of plasma inertia and the possibility
of reconnection in the disk's corona, the latter possibly leading to repeated
cycles in the evolution. We also derive the condition for the existence of a
steady state for a resistive disk and conclude that a steady state
configuration is not realistically possible. Finally, we generalize our
analysis of the opening of magnetic field lines by using a non-self-similar
numerical model that applies to an arbitrarily rotating (e.g. keplerian) disk.Comment: 75 pages, 22 figures, 2 tables. Submitted to Astrophysical Journa
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