Accelerated carbonation and leaching behavior of the slag from iron and steel making industry

Ground granulated blast furnace slag(GGBFS)and steelmaking slag have been used as a raw material for cement production or as an aggregate to make concrete,which contribute aluminum,calcium,iron,and silicon oxides.The suitability of the slag for a particular application depends on its reactivity,cost,availability,and its influence on the properties of the resulting concrete.For the interest of durability studying of concrete in the presence of slag,the accelerated carbonation products and leaching behavior of the slag and Portland cement(PC)were studied.The experimental results confirmed that the slag was more resistant to carbonation compared to PC.The carbonation degree of GGBFS reduced by 17.74%;and the carbonation degrees of steelmaking slags reduced by 9.51%-11.94%.Carbonation neutralized the alkaline nature of the hydrated pastes and gave rise to the redox potential of the leachate slightly(30-77 mV).The carbonation also increased the release of most of the elements presented,except for calcium,to the aqueous environment.It is concluded that blend cements(PC plus slag)have economical advantages and better durability compared to PC.     

Why large-scale climate indices seem to predict ecological processes better than local weather

Large-scale climatic indices such as the North Atlantic Oscillation are associated with population dynamics, variation in demographic rates and values of phenotypic traits in many species. Paradoxically, these large-scale indices can seem to be better predictors of ecological processes than local climate. Using detailed data from a population of Soay sheep, we show that high rainfall, high winds or low temperatures at any time during a 3-month period can cause mortality either immediately or lagged by a few days. Most measures of local climate used by ecologists fail to capture such complex associations between weather and ecological process, and this may help to explain why large-scale, seasonal indices of climate spanning several months can outperform local climatic factors. Furthermore, we show why an understanding of the mechanism by which climate influences population ecology is important. Through simulation we demonstrate that the timing of bad weather within a period of mortality can have an important modifying influence on intraspecific competition for food, revealing an interaction between climate and density dependence that the use of large-scale climatic indices or inappropriate local weather variables might obscure.     

Ice growth in supercooled solutions of antifreeze glycoprotein

Inhibition of ice growth in supercooled solution by certain proteins is vital to the survival of many living organisms. Some fish, native to both subzero northern and southern waters, have special proteins or glycoproteins in their blood serum that inhibit ice formation. Whereas these proteins have only a very small effect on the melting temperature of ice, the temperature of these fish can fall to nearly 1 K below the melting point before ice crystals grow. This phenomenon is called freezing hysteresis, in contrast to the normal colligative effect of solutes that depresses the equilibrium temperature, around which small changes lead to crystal growth or melting depending on sign. Some insects also exhibit a serum freezing hysteresis. We report the effects of different degrees of supercooling on the habit and rates of growth of ice crystals from solutions of these antifreeze glycoproteins (AFGPs). We find that the crystallization rate is up to five times greater than that in pure water.     

Early consolidation in human primary motor cortex.

Behavioural studies indicate that a newly acquired motor skill is rapidly consolidated from an initially unstable state to a more stable state, whereas neuroimaging studies demonstrate that the brain engages new regions for performance of the task as a result of this consolidation. However, it is not known where a new skill is retained and processed before it is firmly consolidated. Some early aspects of motor skill acquisition involve the primary motor cortex (M1), but the nature of that involvement is unclear. We tested the possibility that the human M1 is essential to early motor consolidation. We monitored changes in elementary motor behaviour while subjects practised fast finger movements that rapidly improved in movement acceleration and muscle force generation. Here we show that low-frequency, repetitive transcranial magnetic stimulation of M1 but not other brain areas specifically disrupted the retention of the behavioural improvement, but did not affect basal motor behaviour, task performance, motor learning by subsequent practice, or recall of the newly acquired motor skill. These findings indicate that the human M1 is specifically engaged during the early stage of motor consolidation.     

The relative metabolic demand of inhibition and excitation

By using the (14C)2-deoxyglucose method, inhibition has been shown to be a metabolically active process at the level of the synapse. This is supported by recent results from magnetic resonance spectroscopy that related the changes in neuroenergetics occurring with functional activation to neurotransmitter cycling. However, inhibitory synapses are less numerous and strategically better located than excitatory synapses, indicating that inhibition may be more efficient, and therefore less energy-consuming, than excitation. Here we test this hypothesis using event-related functional magnetic resonance imaging in volunteers whose motor cortex was inhibited during the no-go condition of a go/no-go task, as demonstrated by transcranial magnetic stimulation. Unlike excitation, inhibition evoked no measurable change in the blood-oxygenation-level-dependent signal in the motor cortex, indicating that inhibition is less metabolically demanding. Therefore, the 'activation' seen in functional imaging studies probably results from excitation rather than inhibition.     

The role of dietary fiber in dung size of bushy-tailed woodrats, Neotoma cinerea : its potential application to paleoclimatic interpretation

A laboratory study was conducted to examine causes underlying variation in woodrat dung size. Eight bushy-tailed woodrats, Neotoma cinerea , were captured and sequentially fed 2 diets of 46% and 63% neutral detergent fiber (NDF). Dung pellets were collected for 2 days following 7 days of acclimation to each diet. Length and width of oven-dried pellets ranged, respectively, from 8.3 to 10.2 mm and 3.2 to 4.9 mm for diet 1, and 8.9 to 12.4 mm and 3.6 to 4.7 mm for diet 2. Body weight ranged from 232.0 to 504.5 g and did not significantly affect dung size. A series of 2-factor analyses of variance with repeated measures and sequential Bonferroni tests was used to assess the effect of dietary fiber consumption on dung size. An increase in fiber intake led to a significant increase in dung length and dry dung weight but not dung width or body weight. Results suggest a relationship between dung length in prehistoric woodrat middens and changing climate, although the relationship is not clearly understood and needs further evaluation.     

Transcranial magnetic stimulation and the human brain

Transcranial magnetic stimulation (TMS) is rapidly developing as a powerful, non-invasive tool for studying the human brain. A pulsed magnetic field creates current flow in the brain and can temporarily excite or inhibit specific areas. TMS of motor cortex can produce a muscle twitch or block movement; TMS of occipital cortex can produce visual phosphenes or scotomas. TMS can also alter the functioning of the brain beyond the time of stimulation, offering potential for therapy.