North American Prairie Wetlands are Important Nonforested Land-Based Carbon Storage Sites

We evaluated the potential of prairie wetlands in North America as carbon sinks. Agricultural conversion has resulted in the average loss of 10.1 Mg ha- of soil organic carbon on over 16 million ha of wetlands in this region. Wetland restoration has potential to sequester 378 Tg of organic carbon over a 10-year period. Wetlands can sequester over twice the organic carbon as no-till cropland on only about 17% of the total land area in the region. We estimate that wetland restoration has potential to offset 2.4% of the annual fossil CO2 emission reported for North America in 1990

Mechanisms underlying a thalamocortical transformation during active tactile sensation

During active somatosensation, neural signals expected from movement of the sensors are suppressed in the cortex, whereas information related to touch is enhanced. This tactile suppression underlies low-noise encoding of relevant tactile features and the brain’s ability to make fine tactile discriminations. Layer (L) 4 excitatory neurons in the barrel cortex, the major target of the somatosensory thalamus (VPM), respond to touch, but have low spike rates and low sensitivity to the movement of whiskers. Most neurons in VPM respond to touch and also show an increase in spike rate with whisker movement. Therefore, signals related to self-movement are suppressed in L4. Fast-spiking (FS) interneurons in L4 show similar dynamics to VPM neurons. Stimulation of halorhodopsin in FS interneurons causes a reduction in FS neuron activity and an increase in L4 excitatory neuron activity. This decrease of activity of L4 FS neurons contradicts the "paradoxical effect" predicted in networks stabilized by inhibition and in strongly-coupled networks. To explain these observations, we constructed a model of the L4 circuit, with connectivity constrained by in vitro measurements. The model explores the various synaptic conductance strengths for which L4 FS neurons actively suppress baseline and movement-related activity in layer 4 excitatory neurons. Feedforward inhibition, in concert with recurrent intracortical circuitry, produces tactile suppression. Synaptic delays in feedforward inhibition allow transmission of temporally brief volleys of activity associated with touch. Our model provides a mechanistic explanation of a behavior-related computation implemented by the thalamocortical circuit

The Effect of Nitrogen on Martensite Formation in a Cr-Mn-Ni Stainless Steel

The influence of nitrogen (0 to 0.27 wt%) on martensite formation in an experimental low-nickel stainless-steel alloy (Fe-17Cr-7Mn-4Ni) has been investigated. The alloys containing 0.1 wt% or more nitrogen are fully austenitic at room temperature ; those containing less nitrogen consist of a mixture of austenite, martensite and δ-ferrite. The alloys containing less than 0.2 wt% nitrogen are metastable and undergo a transformation from austenite to martensite on deformation. Transmission electron microscopy investigations suggest that, within the nitrogen range considered in this investigation, the addition of nitrogen causes an increase in stacking fault energy which in turn inhibits the nucleation of martensite. As the low-nitrogen alloys (less than 0.2 wt% nitrogen) undergo deformation, α'-martensite (with the [-110]γ and [-13-10]ε zone axes parallel) is observed at the intersection of stacking faults. With increasing strain, the presence of α'-martensite is observed in conjunction with the ε-martensite, and only α'-martensite is observed at very high strains. Both the Nishiyama-Wasserman and Kurdjumov-Sachs orientation relationships are observed between austenite and α'-martensite. The transformation to martensite during deformation causes a significant variation in room-temperature mechanical properties, despite the overall narrow range in composition considered

Performance evaluation of aluminium Alloy 7075 for use in tool design for the plastics industry

The performance of a high-strength aluminium alloy AA7075 as a candidate injection mould material has been assessed. Particular attention has been focussed on the thermal and wear performance of the AA7075 alloy compared to a standard EN19 tool steel alloy. In view of the fact that aluminium often fails due to poor wear resistance, surface treatment of the aluminium alloy was implemented by hard anodising. The assessment was performed by manufacturing three mould insert sets of identical design from each of the materials, namely EN19 steel, AA7075 and AA7075 in the hard anodised state. Each insert set was subjected to 10 000 shots in an injection moulding machine. The core temperature of the inserts was measured during moulding and wear was assessed by comparing profile measurements of the mould cavities before and after moulding. The EN19 steel and uncoated AA7075 inserts did not show signs of wear whereas edge retention was impaired by hard anodising. The higher thermal conductivity of aluminium compared to conventional tool steel was not affected by hard anodising

Influence of temper condition on microstructure and mechanical properties of semisolide metal processed Al-Si-Mg alloy A356

The microstructures and mechanical properties of strontium modified semisolid metal high pressure die cast A356 alloy are presented. The alloy A356-F (as cast) has a globular primary grain structure containing a fine eutectic. Solution treatment results in spheroidisation of the eutectic silicon particles under the T4 and T6 temper conditions. The A356-T5 maintains the fibrous silicon morphology after artificial aging. A356-T4 has better ductility and impact strength than A356-T5 due to its spheroidised silicon morphology. The impact properties of semisolid metal high pressure die cast A356 are controlled mainly by the silicon morphology and alloy strength (hardness), whereas tensile strength is determined by the degree of solid solution coupled with precipitate formation during aging