Free energy of colloidal particles at the surface of sessile drops

The influence of finite system size on the free energy of a spherical particle floating at the surface of a sessile droplet is studied both analytically and numerically. In the special case that the contact angle at the substrate equals $\pi/2$ a capillary analogue of the method of images is applied in order to calculate small deformations of the droplet shape if an external force is applied to the particle. The type of boundary conditions for the droplet shape at the substrate determines the sign of the capillary monopole associated with the image particle. Therefore, the free energy of the particle, which is proportional to the interaction energy of the original particle with its image, can be of either sign, too. The analytic solutions, given by the Green's function of the capillary equation, are constructed such that the condition of the forces acting on the droplet being balanced and of the volume constraint are fulfilled. Besides the known phenomena of attraction of a particle to a free contact line and repulsion from a pinned one, we observe a local free energy minimum for the particle being located at the drop apex or at an intermediate angle, respectively. This peculiarity can be traced back to a non-monotonic behavior of the Green's function, which reflects the interplay between the deformations of the droplet shape and the volume constraint.Comment: 24 pages, 19 figure

Greenhouse gas losses from peatland pipes: a major pathway for loss to the atmosphere?

Peatland pipes are large natural macropores which contribute significantly to streamflow and represent a potentially important transport pathway between terrestrial and aquatic/atmospheric systems. Our study aimed to estimate the contribution of pipeflow to catchment-scale greenhouse gas (GHG) losses (CO2, CH4 and N2O) in a UK peatland using a combination of fortnightly spot and continuous sensor measurements. Inter-pipe variability was high for all GHGs. Mean pipe water concentrations ranged from 0.70 to 6.51 mg C L-1, 0.90 to 897 μg C L-1, and 0.36 to 1.36 μg N L-1 for CO2, CH4 and N2O respectively. High-resolution CO2 data showed temporal changes in the connectivity between pipes and the surrounding peat, with connectivity greatest when water table was high and lowest at low water table depths when discharge was associated with deeper, CO2-enriched sources. Total downstream export from the eight studied pipes represented 3%, 38% and 3% of CO2, CH4 and N2O export at the catchment outlet, whilst contributing only ~2% of total catchment runoff. Direct degassing of CO2 and CH4 to the atmosphere was evident from an intensively monitored pipe outlet. Upscaling evasion estimates from the pipe outlets gave conservative catchment-scale emission rates of 7.08 g CO2-eq m-2 yr-1 and 50.2 g CO2-eq m-2 yr-1 for CO2 and CH4, respectively. Although the catchment-scale estimates contain significant uncertainty, they highlight the potential importance of pipes as a pathway for the release of terrestrially-produced GHGs to the atmosphere

Ocorrência de mastite bovina em fazendas produtoras de leite B no estado de São Paulo Occurrence of bovine mastitis in grade B milk farms in the state of São Paulo

Durante o período compreendido entre os meses de Março/1991 e Fevereiro /1992 foi realizado um experimento com o objetivo de avaliar a prevalência da mastite bovina em 07 fazendas produtoras de leite tipo B de diferentes regiões do estado de São Paulo. Foram analisadas 1683 vacas que deram origem a 7695 resultados do CMT e das quais foram coletadas 983 amostras de leite para realização do exame microbiológico. A análise do CMT indicou 47,0% de vacas com CMT negativo, 15,1% CMT + e 37,5% CMT ++/+ + + . Os escores do CMT foram distribuidos segundo o número de lactação (1ª lactação, 2ª lactação e 3ª ou + lactações) e segundo o estágio de lactação (1-30 dias de lactação, 31-90 dias, 91-250 dias e > 250 dias). A análise dos dados demonstrou que houve um efeito significativo (p < 0,0001) tanto do número quanto do estágio de lactação sobre a % de vacas CMT + + /+ + + Com relação ao perfil microbiológico das fazendas estudadas, foram encontradas 501 (50,97%) amostras positivas de um total de 983 amostras avaliadas. Das amostras positivas, destacou-se o Staphylococcus sp (44,6%) seguido por Corynebacterium sp (15,0%), Streptococcus sp (8,2%). Leveduras/Fungos (5,4%), Bacillus sp (4,4%), E.coli (3,2%) e Klebsiella sp (0,2%). Se considerarmos o isolamento tanto em cultura pura quanto em cultura mista, a ocorrência de Staphylococcus sp passa para 55,6%, a de Corynebacteríum sp para 18,6% e a Streptococcus sp para 15,0%.<br>From March/1991 to February/1992 1,683 cows from seven grade "B" milk producing dairy farms were used in a study on the prevalence of bovine mastitis. GMT tests (7,695) were 47.0% negative; 15.1% " +" and 37.5% "++/+ + +". CMT scores were grouped by number of lactation (1st, 2nd, 3rd or more) and by stage of lactation (1-30 days in milk; 31-90 days; 91-250 and > 250 days). Both stage of lactation and number of lactation had significant effect on % of cows CMT "++/+ + + ". Microbiological results from 983 milk samples were 50.97% positive. From the positive samples were isolated Staphylococcus sp (44.6%), Corynebacteríum sp (15.0%), Streptococcus sp (8.2%), Yeast/Fungi (5.4%). Bacillus sp (4.4%), E. coli (3.2%) and Klebsiella sp (0.2%). Considering both pure and mixed culture isolation, Staphylococcus sp represents 55.6%, Corynebacteríum sp, 18.6% and Streptococcus sp, 15.0%

A facile synthesis of 2-aryloxypyrimidine derivatives via a tandem reductive amination/intermolecular SNAr sequence*

A novel tandem reductive amination/intermolecular nucleophilic aromatic substitution (SNAr) sequence has been established for the synthesis of amine containing pyrimidine in formation of one carbon-oxygen and one carbon-nitrogen bonds in a one-pot fashion. Treatment of aldehyde with arylamine, 2-methanesulfonyl-4,6-dimethoxypyrimidine and sodium borohydride provides good overall yield. The p-toluenesulfonic acid (PTSA) can be used as activator and is generally needed in the reaction. Dioxane is the preferred reaction solvent, but reactions can also be carried out in tetrahydrofuran (THF), MeCN, toluene and dichloromethane. The procedure is carried out effectively in the presence of K2CO3. The reaction proceeds smoothly with aromatic aldehydes and arylamines possessing electron-donating or -withdrawing groups. This method can be applied to the synthesis of the oilseed rape herbicide and is superior to the classical one in several aspects: cutting out several purification steps, minimizing solvent use and chemical waste, and saving time. Its advantages such as operational convenience, high-efficient synthesis, and starting material availability make it a desirable method for preparing amines with molecular diversity and biological activity