A generalized Damköhler number for classifying material processing in hydrological systems

Assessing the potential for transfer of pollutants and nutrients across catchments is of primary importance under changing land use and climate. Over the past decade the connectivity/disconnectivity dynamic of a catchment has been related to its potential to export material; however, we continue to use multiple definitions of connectivity, and most have focused strongly on physical (hydrological or hydraulic) connectivity. In contrast, this paper constantly focuses on the dynamic balance between transport and material transformation, and defines material connectivity as the effective transfer of material between elements of the hydrological cycle. The concept of exposure timescales is developed and used to define three distinct regimes: (i) which is hydrologically connected and transport is dominated by advection; (ii) which is hydrologically connected and transport is dominated by diffusion; and (iii) which is materially isolated. The ratio of exposure timescales to material processing timescales is presented as the non-dimensional number, NE, where NE is reaction-specific and allows estimation of relevant spatial scales over which the reactions of interest take place. Case studies within each regime provide examples of how NE can be used to characterise systems according to their sensitivity to shifts in hydrology and gain insight into the biogeochemical processes that are signficant under the specified conditions. Finally, we explore the implications of the NE framework for improved water management, and for our understanding of biodiversity, resilience and chemical competitiveness under specified conditions

Perfil de susceptibilidade a antimicrobianos em amostras de cocos Gram-positivos, catalase negativos, isoladas de mastite subclínica bubalina Profile of antimicrobial susceptibility in strains of Gram positive cocos, negative catalase, isolated from buffalo subclinical mastitis

Estudou-se o perfil de susceptibilidade a antimicrobianos em cocos Gram-positivos catalase negativos (21 amostras de Lactococcus garvieae e 6 de Enterococcus gallinarum), isoladas do leite de fêmeas com mastite subclínica e pertencentes a uma população composta por seis rebanhos bubalinos localizados no Estado do Rio de Janeiro. O teste utilizado foi o da difusão de discos em agar Müller Hinton, segundo recomendações do National Committee for Clinical Laboratory Standards - NCCLS, tendo sido testados discos com ampicilina (10mg), cefalotina (30mg), cefotaxima (30mg), cefoxitina (30mg), cloranfenicol (30mg), eritromicina (15mg), gentamicina (10mg), nitrofurantoína (300mg), norfloxacina (10mg), penicilina (10 UI), tetraciclina (30mg) e vancomicina (30mg). Os resultados evidenciaram que em se tratando de Lactococcus garvieae, o antimicrobiano mais eficiente foi o nitrofurantoína com 85,71% de sensibilidade, seguido da cefotaxima (61,90%), vancomicina (52,38%), norfloxacina (47,62%) e cefalotina (47,62%). A maior resistência foi desenvolvida frente a penicilina e ampicilina, com 95,24% de resistênciapara os dois antimicrobianos testados. O perfil de susceptibilidade desenvolvido pelas amostras de Enterococcus gallinarum, mostrou baixa sensibilidade frente aos antimicrobianos testados, onde os maiores índices foram observados frente eritromicina e gentamicina, com 33,34% de sensibilidade para ambos; quanto à resistência desenvolvida, foi possível observar 100% de resistência com relação a vancomicina e tetraciclina, seguindo-se cloranfenicol, penicilina, ampicilina, cefoxitina, cefalotina, cefotaxima, norfloxacina e nitrofurantoína, todas evidenciando uma resistência de 83,33% das amostras testadas.<br>The susceptibility of antimicrobials was studied in Gram positive and catalase negative cocci (21 samples of Lactococcus garvieae and 6 Enterococcus gallinarum), isolated from the milk of cows with subclinical mastitis, belonging to six buffalo herds in the State of Rio de Janeiro. The test used was diffusion of disks in agar Müller Hinton, according to recommendations of the National Committee for Clinical Laboratory Standards - NCCLS. There were tested disks with ampicillin (10mg), cefalotin (30mg), cefotaxime (30mg), cefoxitin (30mg), cloranfenicol (30mg), eritromycin (15mg), gentamycin (10mg), nitrofurantoin (300mg), norfloxacin (10mg), penicillin (10 IU), tetracyclin (30mg) and vancomycin (30mg). The results showed that with Lactococcus garvieae, the most efficient antimicrobial was nitrofurantoin, revealing 85.71% sensibility, followed by cefotaxime (61.90%), vancomycin (52.38%), norfloxacin (47.62&) and cefalotin (47.62%). The highest resistance was developed against penicillin and ampicillin, with 95.24% resistance for the two antimicrobials. The susceptibility profile developed by the strains of Enterococcus gallinarum showed low sensibility against the tested antimicrobials; the highest resistance observed was against eritromycin and gentamycin, with 33.34% sensibility for both. The antimicrobial evaluation showed 100% resistance against vancomycin and tetracyclin, followed by cloranfenicol, penicillin, ampicillin, cefoxitin, cefotaxim, norfloxacin and nitrofurantoin; all of them showed a resistance of 83.33% with the samples tested