Current-induced transverse spin wave instability in a thin nanomagnet

We show that an unpolarized electric current incident perpendicular to the plane of a thin ferromagnet can excite a spin-wave instability transverse to the current direction if source and drain contacts are not symmetric. The instability, which is driven by the current-induced ``spin-transfer torque'', exists for one current direction only.Comment: 4 pages, 2 figure

Gender of offspring and long-term maternal breast cancer risk

Gender of offspring is influenced by maternal hormonal level during pregnancy, which is blieved to influence the subsequent maternal breast cancer risk. However, analysing national birth and cancer registrations in a cohort of 998 499 women, we found no association between gender of offspring and subsequent breast cancer risk. © 2000 Cancer Research Campaig

Current induced transverse spin-wave instability in thin ferromagnets: beyond linear stability analysis

A sufficiently large unpolarized current can cause a spin-wave instability in thin nanomagnets with asymmetric contacts. The dynamics beyond the instability is understood in the perturbative regime of small spin-wave amplitudes, as well as by numerically solving a discretized model. In the absence of an applied magnetic field, our numerical simulations reveal a hierarchy of instabilities, leading to chaotic magnetization dynamics for the largest current densities we consider.Comment: 14 pages, 10 figures; revtex

Gap-filling strategies for annual VOC flux data sets

Up to now the limited knowledge about the exchange of volatile organic compounds (VOCs) between the biosphere and the atmosphere is one of the factors which hinders more accurate climate predictions. Complete long-term flux data sets of several VOCs to quantify the annual exchange and validate recent VOC models are basically not available. In combination with long-term VOC flux measurements the application of gap-filling routines is inevitable in order to replace missing data and make an important step towards a better understanding of the VOC ecosystem–atmosphere exchange on longer timescales. <br><br> We performed VOC flux measurements above a mountain meadow in Austria during two complete growing seasons (from snowmelt in spring to snow reestablishment in late autumn) and used this data set to test the performance of four different gap-filling routines, mean diurnal variation (MDV), mean gliding window (MGW), look-up tables (LUT) and linear interpolation (LIP), in terms of their ability to replace missing flux data in order to obtain reliable VOC sums. According to our findings the MDV routine was outstanding with regard to the minimization of the gap-filling error for both years and all quantified VOCs. The other gap-filling routines, which performed gap-filling on 24 h average values, introduced considerably larger uncertainties. The error which was introduced by the application of the different filling routines increased linearly with the number of data gaps. Although average VOC fluxes measured during the winter period (complete snow coverage) were close to zero, these were highly variable and the filling of the winter period resulted in considerably higher uncertainties compared to the application of gap-filling during the measurement period. <br><br> The annual patterns of the overall cumulative fluxes for the quantified VOCs showed a completely different behaviour in 2009, which was an exceptional year due to the occurrence of a severe hailstorm, compared to 2011. Methanol was the compound which, at 381.5 mg C m^&minus;2 and 449.9 mg C m^&minus;2, contributed most to the cumulative VOC carbon emissions in 2009 and 2011, respectively. In contrast to methanol emissions, however, considerable amounts of monoterpenes (−327.3 mg C m^&minus;2) were deposited onto the mountain meadow during 2009 caused by a hailstorm. Other quantified VOCs had considerably lower influences on the annual patterns

Technical note: Novel estimates of the leaf relative uptake rate of carbonyl sulfide from optimality theory

In order to estimate the gross primary productivity (GPP) of terrestrial ecosystems from the canopy uptake of carbonyl sulfide (COS), the leaf relative uptake rate (LRU) of COS with respect to carbon dioxide needs to be known a priori. Currently, the variability of the LRU between plant species in different biomes of the world is poorly understood, making the choice of an appropriate LRU uncertain and hampering further progress towards developing COS as an alternative tracer of GPP. Here we propose a novel approach for estimating LRU based on plant optimality principles, validate it against in situ leaf gas exchange measurements and provide global monthly climatological estimates. The global vegetation season average simulated LRUs fall into the range of 0.5&ndash;1.4 and are thus lower than any other published global estimates. We advocate these LRU estimates to be adopted by global modellers in order to test to what degree these are compatible with our current understanding of the sources and sinks in the global COS budget.</p

Evidence for Magnetic Field Induced Changes of the Phase of Tunneling States: Spontaneous Echoes in (KBr)1−x_{1-x}(KCN)x_x in Magnetic Fields

Recently, it has been discovered that in contrast to expectations the low-temperature dielectric properties of some multi-component glasses depend strongly on magnetic fields. In particular, the low-frequency dielectric susceptibility and the amplitude of coherent polarization echoes show striking non-monotonic magnetic field dependencies. The low-temperature dielectric response of these materials is governed by atomic tunneling systems. We now have investigated the coherent properties of tunneling states in a crystalline host in magnetic fields up to 230$$mT. Two-pulse echo experiments have been performed on a KBr crystal containing about 7.5% CN$^-$. Like in glasses, but perhaps even more surprising in the case of a crystalline system, we observe a very strong magnetic field dependence of the echo amplitude. Moreover, for the first time we have direct evidence that magnetic fields change the phase of coherent tunneling systems in a well-defined way. We present the data and discuss the possible origin of this intriguing effect.Comment: 4 pages, 3 figures, submitted to PR

Replacement of soybean cake by Hermetia illucens meal in diets for layers

Insects will likely play an important role as protein sources for livestock in the future. Many insect species are able to convert materials not suitable for human nutrition – or even waste – into valuable protein with a favourable amino acid composition for poultry and other livestock. A feeding trial with partly de-fatted meal of dried Hermetia illucens larvae (Hermetia meal) reared on vegetarian by-products of the pasta and convenience food industry was carried out in small groups of Lohmann Selected Leghorn laying hens (four rounds, 10 hens/round). Experimental diets H12 and H24 contained 12 and 24 g/100 g Hermetia meal replacing 50 or 100% of soybean cake used in the control feed, respectively. After three weeks of feeding experimental diets, there were no significant differences between feeding groups with regard to performance (egg production, feed intake). There was a tendency (P=0.06) for lower albumen weight in the H24 group; yolk and shell weights did not differ. No mortality and no sign of health disorders occurred. Plumage as well as wound scores remained stable during the feeding period and did not differ between treatments. Dry matter of faeces increased with increasing proportions of Hermetia meal in the diet, with a significant difference between H24 and the control (P=0.03). An increase of black faecal pads was observed in the H12 and H24 groups. Overall, these results suggest Hermetia meal can be a valuable component of layer diets. However, insect meal production still has to become economically more viable through upscaling production and, especially, legislative issues have to be solved

Dielectric Susceptibility and Heat Capacity of Ultra-Cold Glasses in Magnetic Field

Recent experiments demonstrated unexpected, even intriguing properties of certain glassy materials in magnetic field at low temperatures. We have studied the magnetic field dependence of the static dielectric susceptibility and the heat capacity of glasses at low temperatures. We present a theory in which we consider the coupling of the tunnelling motion to nuclear quadrupoles in order to evaluate the static dielectric susceptibility. In the limit of weak magnetic field we find the resonant part of the susceptibility increasing like $B^2$ while for the large magnetic field it behaves as 1/B. In the same manner we consider the coupling of the tunnelling motion to nuclear quadrupoles and angular momentum of tunnelling particles in order to find the heat capacity. Our results show the Schotky peak for the angular momentum part, and $B^2$ dependence for nuclear quadrupoles part of heat capacity, respectively. We discuss whether or not this approach can provide a suitable explanation for such magnetic properties.Comment: 10 pages, 1 figur