Stratospheric feedback from continued increases in tropospheric methane

Tropospheric concentrations of methane have increased steadily over the past ten years at an average rate of 16.5 ppbv per year, to a value in January 1988 of 1.69 ppmv. Measurements of CH sub 4 concentrations in air bubbles trapped in ice cores have shown concentrations of about 0.7 ppmv 200 years ago, with little further change for thousands of years before that. Interpolation earlier into this century suggests a concentration of about 1.1 to 1.2 ppmv in the 1940's. The only important pathway believed to be important for transfer of air from the troposphere to the stratosphere in through the tropical tropopause which is cold enough to reduce the mixing ratio of H sub 2 O in that air to about 3 ppmv. The only other major pathway for the delivery of H to the stratosphere is through the simultaneous injection of gaseous CH sub 4 in the same rising air. The formation of clouds in the stratosphere is dependent upon very low temperatures, and generally upon the amount of water vapor available. The possibility of a positive feedback exists, especially in well-oxidized methane air, that clouds are easier to form than earlier. This could mean enhancement of PSCs in both Antarctic and Arctic locations. Additional H sub 2 O in the stratosphere can also add to some of the greenhouse calculations

Measurement of atmospheric HO by a chemical method

The parameters for a chemical technique can be outlined from the following set of desirable goals: (1) sufficient conversion of tracer species A to product B that B can be measured quantitatively in the presence of A and a great excess of air; (2) specificity of reaction such that A is converted to B only by reaction with HO; and (3) sufficient sensitivity for detection that the ambient concentration of HO is not seriously perturbed by the presence of A and B. This proposed study involves finding a chemical reaction specific enough for OH, and a measurement of the product formed. What one wants is a rate constant of about 10 to the -10th power cu cm/s, so that 0.1 percent of the OH will be converted in 100 s. Laboratory studies are needed to find a reaction which will fill this bill, yielding a product in quantity sufficient for precise measurement. This is an extremely fast constant and the search may be difficult. Again there is a question of perturbing the local environment, while still providing a sensitive measurement. Also the temperature and pressure dependence of the reaction rate is a complicated function for many of these species (that is, one must use a RRKM or Troe-based picture), and must be taken into account

Analogy of the slow dynamics between the supercooled liquid and the supercooled plastic crystal states of difluorotetrachloroethane

Slow dynamics of difluorotetrachloroethane in both supercooled plastic crystal and supercooled liquid states have been investigated from Molecular Dynamics simulations. The temperature and wave-vector dependence of collective dynamics in both states are probed using coherent dynamical scattering functions $S(Q,t)$. Our results confirm the strong analogy between molecular liquids and plastic crystals for which $\alpha$-relaxation times and non-ergodicity parameters are controlled by the non trivial static correlations $S(Q)$ as predicted by the Mode Coupling Theory. The use of infinitely thin needles distributed on a lattice as model of plastic crystals is discussed

Women at a Crossroads: Sudanese Women and Political Transformation

The ‘Arab Spring’ is a nuanced phenomenon of significance to African democracy and women’s rights in Sudan – north and south. Political transformation processes underway in postrevolution Arab states simultaneously give voice to human rights advocates and rise to Islamist political groups. The reverberating trend presents a risk of deepening Islamist governance in Sudan and reinforcing patriarchal patterns of kinship in South Sudan. It also offers opportunity, north and south, for Sudanese women to form a common agenda, engage politically, promote a vibrant civil society, challenge human rights violations and develop a voice through participation. Given the Islamist upsurge in the region, a review of literature highlights what women in post-revolution Arab states have reported back in terms of the effect the popular uprisings have had on their rights. In light of the outcomes, approaches are advanced that will strengthen Sudanese women’s movements and better position them to exploit opportunity for progress in the period of political transformation on the horizon in Sudan and South Sudan

The volatile acids produced by starters and by organisms isolated from them

The work done in various laboratories during the last few years has shown that starters, instead of being pure cultures of Skeptococcis lactis, as was at one time commonly supposed, contain two or more organisms, at least one of which produces considerable amounts of volatile acid. Good starters have regularly been found to yield a high and rather definite amount of volatile acidity but natural souring and sometimes poor starters also give a high volatile acidity, so that such an acidity is no guarantee as to the quality of a starter. This indicates that while the amount of volatile acid produced is important with a starter, the character of the volatile acids must also be considered and suggests the desirability of knowing what kinds of acids are produced in starters and in pure cultures of the starter organisms. The work herein reported represents an attempt to secure information along this line and also on the kinds of acids produced during prolonged natural souring such as occurs in old cream

Citric acid content of milk

The citric acid which is normally present in milk and cream can be fermented by a number of organisms commonly present in· dairy products. Some of these, such as the citric acid positive colon-aerogenes organisms, are always objectionable in milk and its derivatives, while others, Streptococcus citrovorus and S. paracitrovorus, which are frequently associated with S. lactis, are important in the development of flavor and aroma in starter and in butter, and undoubtedly in other materials

Behaviour of dairy cows on organic and non-organic farms

There is an increasing number of organic dairy farms in the UK. The aim of this study is to compare behaviour of dairy cows on organic and non-organic farms. Twenty organic and 20 non-organic farms throughout the UK were visited over two winters (2004/05 and 2005/06). Organic and non-organic farms were paired for housing type, herd size, milk production traits and location. The number of cows feeding was counted every fifteen minutes for 4.5 h after new feed was available post morning milking. Behaviour at the feed-face was recorded for 60 minutes and aggressive interactions between cows were quantified. Farm type had no effect on numbers of cows feeding. There were more interactions between cows feeding at open feed-faces compared to head-bale barriers. At open feed-faces, there were more interactions on organic farms than non-organic. It is possible that organic cows were hungrier than non-organic cows after the arrival of new feed