242 research outputs found
SrKZnMnAs: a ferromagnetic semiconductor with colossal magnetoresistance
A bulk diluted magnetic semiconductor (Sr,K)(Zn,Mn)As was
synthesized with decoupled charge and spin doping. It has a hexagonal
CaAlSi-type structure with the (Zn,Mn)As layer forming
a honeycomb-like network. Magnetization measurements show that the sample
undergoes a ferromagnetic transition with a Curie temperature of 12 K and
\revision{magnetic moment reaches about 1.5 /Mn under = 5 T
and = 2 K}. Surprisingly, a colossal negative magnetoresistance, defined as
, up to 38\% under a low field of = 0.1
T and to 99.8\% under = 5 T, was observed at = 2 K. The
colossal magnetoresistance can be explained based on the Anderson localization
theory.Comment: Accepted for publication in EP
Improvement of Indoor Air Quality by MDF panels containing walnut shells
High levels of Volatile Organic Compounds (VOCs) and extremes of Relative Humidity (RH) commonly reduce indoor air quality with associated negative effects on human health and wellbeing. Interior materials are known to be one of the main contributors to poor indoor air quality. Notwithstanding, they can also act as a sink for airborne pollutants and excess moisture through adsorption. In this paper, we evaluate the ability of Medium Density Fibreboard (MDF) modified with walnut shell to regulate RH, toluene, limonene, dodecane and formaldehyde. The physicochemical properties, including molecular size/shape, vapour pressure, polarity and boiling point of VOCs allowed them to represent a range of pollutants. Adsorption and desorption behaviour of MDF containing up to 15% walnut shell was evaluated in 2-L environmental chambers under dynamic conditions at 23 °C and 50% RH. The porous microstructure of the MDF and walnut shell and their chemical composition were analysed using SEM, XRD and FTIR. Compared to a control panel, walnut shell additions showed an improved ability to remove VOCs and formaldehyde from the indoor air and buffer humidity. Of particular significance was the irreversible sink effect of formaldehyde and dodecane. This was attributed to the porous surface of walnut shell increasing the specific surface area of the panel and thus its adsorption capacity. The improved capacity of buffer humidity also increased the ability to adsorb water soluble VOCs such as formaldehyde. This research provides for the first time significant evidence that walnut shell modified MDF can improve indoor air quality
Lateral magnetic anisotropy superlattice out of a single (Ga,Mn)As layer
We use lithographically induced strain relaxation to periodically modulate
the magnetic anisotropy in a single (Ga,Mn)As layer. This results in a lateral
magnetoresistance device where two non-volatile magnetic states exist at zero
external magnetic field with resistances resulting from the orientation of two
lithographically defined regions in a single and contiguous layer.Comment: 5 pages, 7 figure
Testing the applicability of neural networks as a gap-filling method using CH4 flux data from high latitude wetlands
Peer reviewe
Improved weight management using genetic information to personalize a calorie controlled diet
Cold season emissions dominate the Arctic tundra methane budget
Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for >= 50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the "zero curtain" period, when subsurface soil temperatures are poised near 0 degrees C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 +/- 5 (95% confidence interval) Tg CH4 y(-1), similar to 25% of global emissions from extratropical wetlands, or similar to 6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.Peer reviewe
Indoor Air Quality
This is a report from the Air Quality Expert Group to the Department for Environment, Food and Rural Affairs; Scottish Government; Welsh Government; and Department of Agriculture, Environment and Rural Affairs in Northern Ireland, on indoor air quality in the UK. The information contained within this report represents a review of the understanding and evidence available at the time of writing
FLUXNET-CH<sub>4</sub> synthesis activity: objectives, observations, and future directions
We describe a new coordination activity and initial results for a global synthesis of eddy covariance CH4 flux measurements
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