High-Power Infrared (8-Micrometer Wavelength) Superlattice Lasers

A quantum-cascade long-wavelength infrared laser based on superlattice active regions has been demonstrated. In this source, electrons injected by tunneling emit photons corresponding to the energy gap (minigap) between two superlattice conduction bands (minibands). A distinctive design feature is the high oscillator strength of the optical transition. Pulsed operation at a wavelength of about 8 micrometers with peak powers ranging from approximately 0.80 watt at 80 kelvin to 0.2 watt at 200 kelvin has been demonstrated in a superlattice with 1-nanometer-thick AlInAs barriers and 4.3-nanometer-thick GaInAs quantum wells grown by molecular beam epitaxy. These results demonstrate the potential of strongly coupled superlattices as infrared laser materials for high-power sources in which the wavelength can be tailored by design.     

Radar detection of the nucleus and coma of comet hyakutake

Radar observations of comet Hyakutake (C/1996 B2) made at the Goldstone Deep Space Communications Complex in California have detected echoes from the nucleus and from large grains in the inner coma. The nucleus of this bright comet was estimated to be only 2 to 3 kilometers in diameter. Models of the coma echo indicate backscatter from porous, centimeter-size grains ejected anisotropically at velocities of tens of meters per second. The radar observations suggest that a comet's activity may be a poor indicator of its size and provide evidence that large grains constitute an important component of the mass loss from a typical active comet.     

Effects of disease control by fungicides on greenhouse gas emissions by UK arable crop production

BACKGROUND: The UK government has published plans to reduce UK agriculture's greenhouse gas (GHG) emissions. At the same time, the goal of global food security requires an increase in arable crop yields. Foliar disease control measures such as fungicides have an important role in meeting both objectives. RESULTS: It is estimated that UK winter barley production is associated with GHG emissions of 2770 kg CO₂ eq. ha^?1 of crop and 355 kg CO₂ eq. t^?1 of grain. Foliar disease control by fungicides is associated with decreases in GHG emissions of 42–60 kg CO₂ eq. t^?1 in UK winter barley and 29–39 kg CO₂ eq. t^?1 in UK spring barley. The sensitivity of these results to the impact of disease control on yield and to variant GHG emissions assumptions is presented. Fungicide treatment of the major UK arable crops is estimated to have directly decreased UK GHG emissions by over 1.5 Mt CO₂ eq. in 2009. CONCLUSION: Crop disease control measures such as fungicide treatment reduce the GHG emissions associated with producing a tonne of grain. As national demand for food increases, greater yields as a result of disease control also decrease the need to convert land from non‐arable to arable use, which further mitigates GHG emissions. Copyright © 2011 Society of Chemical Industry     

An evaluation of anthelmintic properties,assessed using faecal nematode egg counts,of New Zealand native flax (Phormium tenax)

AIM: To investigate the anthelmintic properties of New Zealand native flax (Phormium tenax) for cattle, using a faecal egg count reduction test (FECRT).

METHODS: Twenty-six heifer calves with high (>300 epg) faecal nematode egg counts (FEC) were paired into two groups and fed either chopped flax leaves ad libitum, or barley straw at an equivalent dry matter (DM) rate, from Day 0–7; all were supplemented with 1.5 kg/head/day cereal feed supplement. On Days 8–10, all heifers were fed a common diet of 3.5 kg DM/ head/day barley straw and 1.5 kg/head/day cereal feed supplement. Heifers were weighed and faecal samples were collected on Days —6, 0, 7, and 10; samples were analysed in triplicate for FEC. The nutritive value of the flax and straw was analysed.

RESULTS: Both the flax and straw had low dry matter digestibility (DMD) and protein content. Although the flax-fed claves grew more than the controls, this may have been related to gut fill. Total daily faecal egg output was similar for flax and straw groups on Day 7 (14.7 vs 15.0 x 10⁶ eggs/day, respectively) and Day 10 (14.9 vs 15.1 x 10⁶ eggs/day, respectively). There was no difference in the change in FEC with time between the calves fed flax or straw diets.

CONCLUSION: Consumption of flax leaves did not reduce FEC in calves with a mixed nematode infection.     

Production, behaviour and fertility of Merino wethers, hemi-castrates with reduced testicular parenchyma and induced cryptorchids

Greasy wool production, body weight, behaviour and fertility of male, fine wool Merino sheep were studied from 10 to 21 months of age to assess their suitability for wool production. The males were either castrated (wethers), or were hemi-castrated with a vasectomy and reduction (either partially or in full) of the parenchyma of the retained testicle, or the testicles pushed up into the ingulnal canal and the scrotum shortened (induced cryptorchids). There were significant differences among all groups in body weight, with increases being associated with the larger amounts of testicular tissue present. Fertility was low in the induced cryptorchids at 19 months of age. The hemi-castrates with reduced testicular parenchyma were infertile. The hemi-castrates with reduced testicular parenchyma had significantly heavier greasy fleece weights than the wethers and induced cryptorchids, which had similar fleece weights. The wether group suffered a higher prevalence of posthitis in spring and autumn than the hemi-castrate or induced cryptorchid groups. Those hemi-castrates with the largest amount of testicular parenchyma retained and the induced cryptorchids exhibited masculine behaviour patterns and had an increased incidence of fly strike to the head. The principle of hemi-castration and reduction of the testicular parenchyma is shown to be applicable in wool producing flocks with the potential to increase greasy wool production while minimising the management and marketing limitations previously associated with induced cryptorchids.     

Effects of pH, sodium bicarbonate, cryoprotectants and foetal bovine serum on the cryopreservation of European eel sperm.

The main objective of the present study was to evaluate the influence of pH and bicarbonate concentration in the activation or inhibition of European eel (Anguilla anguilla) spermatozoa and to evaluate the effect of different cryoprotectants: dimethyl sulphoxide (DMSO), acetamide, ethylene glycol, propanol, glycerol and methanol (MeOH). The effect of these factors was evaluated comparing the percentage of motile cells, the percentage of alive cells (by Hoechst staining) and the spermatozoa morphometry pre- and post-cryopreservation (by computer-assisted morphology analysis). Based on the above findings, three cryoprotectants (DMSO, MeOH and glycerol) were chosen and evaluated in two media (P1 and P1 modified) with different concentrations of NaHCO(3) and in the presence or absence of foetal bovine serum (FBS). The effect of these factors was evaluated comparing the percentage of alive and motile cells post-cryopreservation. DMSO was the cryoprotectant showing better results in relation to the percentage of spermatic alive cells post-freezing and caused a smaller modification of the head spermatozoa morphology. The combination of P1-modified medium with DMSO and containing FBS increased slightly but significantly the percentage of motile spermatozoa post-cryopreservation.     

Lunar surface magnetic fields and their interaction with the solar wind: results from lunar prospector

The magnetometer and electron reflectometer experiment on the Lunar Prospector spacecraft has obtained maps of lunar crustal magnetic fields and observed the interaction between the solar wind and regions of strong crustal magnetic fields at high selenographic latitude (30 degreesS to 80 degreesS) and low ( approximately 100 kilometers) altitude. Electron reflection maps of the regions antipodal to the Imbrium and Serenitatis impact basins, extending to 80 degreesS latitude, show that crustal magnetic fields fill most of the antipodal zones of those basins. This finding provides further evidence for the hypothesis that basin-forming impacts result in magnetization of the lunar crust at their antipodes. The crustal magnetic fields of the Imbrium antipode region are strong enough to deflect the solar wind and form a miniature (100 to several hundred kilometers across) magnetosphere, magnetosheath, and bow shock system.