Long-term development of reservoir ecosystems - changes in pelagic food webs and their microbial component

Reservoirs differ from lakes mostly in three aspects: (i) water residence times usually are not longer than several months, (ii) horizontal heterogeneity induced by the inflowing river water is more pronounced, and (iii) they are historically much younger than lakes. As a consequence, seasonal and long-term dynamics of pelagic food webs reflect the changes in the catchment and hydrological variations more significantly than in lakes, and an ageing and "maturing" of the reservoir ecosystem might affect the pelagic biomass even several decades after filling. Using long-term data sets on pelagic biomass components from canyonshaped reservoirs of different residence time, the following topics are discussed: (1) changes of pelagic bacteria-phytoplankton - zooplankton abundances during ageing as well as longitudinal changes from the river inflow dowstream to the lacustrine part of a reservoir, (2) long-term changes of pelagic bacteria-phytoplankton-zooplankton abundances and seasonal changes of microbial loop in two reservoirs of different residence times. Periods with relative prevalence of bacterial above zooplankton biomass were detected, mostly coinciding with (or following after) the periods with low phytoplankton to zooplankton ratios.Los embalses difieren de los lagos principalmente en tres aspectos: (i) el tiempo de residencia del agua no suele ser superior a varios meses, (ii) la heterogeneidad horizontal inducida por la entrada de agua fluvial es más marcada, y (iii) son históricamente mucho más jóvenes que los lagos. Como consecuencia de todo ello, las dinámicas estacional y a largo plazo de las redes tróficas pelágicas reflejan los cambios en la cuenca y las variaciones hidrológicas más significativamente que en los lagos, y el envejecimiento y "madurez" del ecosistema del embalse podría afectar a la biomasa pelágica incluso varias décadas después de su llenado. Mediante el análisis de largas series de datos sobre la biomasa de componentes pelágicos en embalses con sección en forma de cañón y diferentes tiempos de residencia, se discuten los siguientes aspectos: (1) cambios en las abundancias de bacterias-fitoplancton-zooplancton pelágicos durante el envejecimiento del embalse, así como cambios longitudinales desde la entrada de los ríos hasta la zona lacustre del embalse, (2) cambios a largo plazo en las abundancias de bacterias-fitoplancton-zooplancton pelágicos y cambios estacionales del bucle microbiano en dos embalses con diferentes tiempos de residencia. Se detectaron períodos con un predominio relativo de la biomasa bacteriana sobre la biomasa de zooplancton, coincidiendo principalmente con (o justamente después de) los períodos con bajas relaciones fitoplancton / zooplancton

Complex gunshot injury to the heart as a consequence of suicide attempt in a schizophrenic patient

AbstractIntroductionSelf-inflicted gunshot injury to the heart is uncommon in Western Europe countries. However it is considered to have a high mortality through cardiac tamponade or exsanguination and concomitant chest or abdominal cavity injury.Case presentationWe present a 39-year-old schizophrenic woman who attempted suicide with the aid of a 6.35mm caliber handgun, after self-discontinuing of antipsychotic treatment. Lower third of sternum, right heart atrium and ventricle and inferior caval vein were hit by the bullet which consequently got lodged in the right paravertebral muscle mass at the lower thoracic vertebral level. As she was hemodynamically unstable due to hemopericardium and a huge right hemothorax, she underwent emergent surgery. Heart and inferior vena caval injuries were repaired on extracorporeal circulation. The postoperative course was uneventful and she was transferred to a psychiatric facility on the 7th postoperative day. One year after the surgery she is well, compliant to antipsychotic medications and on periodic follow-up by psychiatrists.ConclusionThis case represents management of complex self-inflicted gunshot cardiac injury in a schizophrenic patient who discontinued antipsychotic medication. Liaison between themedical rescue service and high level trauma center essentially reduced injury-to-surgery time. Complex heart injury was successfully repaired on extracorporeal circulation

Community structure, picoplankton grazing and zooplankton control of heterotrophic nanoflagellates in a eutrophic reservoir during the summer phytoplankton maximum

An intensive 5 wk study was conducted to investigate the role of protists, especially heterotrophic nanoflagellates (HNF), in microbial food webs during the summer phytoplankton bloom in the epilimnion and metalimnion of the eutrophic Rimov reservoir (South Bohemia, Czech Republic). On average, protists consumed similar to 90% of bacterial production in both layers. The community composition of HNF and the relative importance of different HNF groups as picoplankton consumers were determined. Small HNF (<8 mu m), as chrysomonads, bodonids and choanoflagellates, usually accounted for <30% of total HNF biomass but numerically dominated the community in both layers. They consumed most of (similar to 70 to 85 %) the bacterioplankton as well as autotrophic picoplankton (APP, exclusively cyanobacteria) production in the reservoir, with the rest consumed by ciliates. Both ciliates and HNF had higher clearance rates on APP than on bacteria and their grazing was likely responsible for a sharp decrease in APP abundance (from 3-4 x 10(5) to <2 x 10(3) ml(-1)) and a very constant size structure of bacterioplankton in which short rods in the size class of 0.4 to 0.8 mu m constituted 55 to 80 % of the total bacterial biomass in both layers. The proportion of HNF to total picoplankton biomass in the epilimnion indicated that the picoplankton biomass was sufficiently high to support HNF growth for most of the study. Uptake of picoplankton by less numerous, but larger, HNF (kathablepharids, Goniomonas sp., and Streptomonas sp.) was negligible, while their biomass, especially in the metalimnion, exceeded that of small HNF and the total biomass of picoplankton. This suggested that food items other than picoplankton were consumed to meet their carbon requirements. Analyzing potential bottom-up and top-down factors controlling HNF numbers and biomass, we did not find a tight relationship between HNF and the concentration of bacteria and chlorophyll. Variability of HNF abundance and biomass in the epilimnion could largely be explained by cladocerans or by pooled abundances of all potential crustacean consumers of HNF. In the metalimnion, the mean cell volume of HNF was positively linked to chlorophyll but negatively to the abundance of Cyclopidae and to the pooled abundances of Ceriodaphnia quadrangula and Diaphanosoma brachyurum

Investigation and Numerical Simulation of a High-Current AC Circuit Breaker

The article is devoted to the study of the high-current AC circuit breaker. The results of the study are presented for various configurations of the arc divider. The study includes methods of spectral diagnostics and high-speed camera shooting synchronized with the electrical characteristics of the circuit breaker (current, voltage) in time. The obtained results allow to determine the composition of the plasma and dynamics of changes in the composition of the discharge in time. Calculation of the plasma composition and properties is made according to the obtained data, which makes it possible to take into account the products of circuit breaker materials ablation in numerical simulation. Non-stationary two-dimensional mathematical model with a moving mesh is developed. The obtained results allow to correct and verify the developed mathematical model of the circuit breaker operation. The evaluation of the arc divider influence is presented in the article

Sensitivity And Specificity Of Hiv Rapid Tests Used For Research And Voluntary Counselling And Testing

Background: HIV rapid tests (RT) are a quick and non-technically demanding means to perform HIV voluntary counselling and testing (VCT) but understanding their limitations is vital to delivering quality VCT. Objective: To determine the sensitivity and specificity of HIV rapid tests used for research and voluntary counselling and testing at four sites in East Africa. Design: Cross-sectional study. Setting: Masaka District, Uganda; a sugar plantation in Kakira, Uganda; Coastal Villages in the Kilifi District of Kenya; and the Urban slum of Kangemi located West of Nairobi, Kenya. Subjects: Six thousands two hundred and fifty five consenting volunteers were enrolled into the study, and 675 prevalent HIV infections were identified. Results: The RT sensitivity tended to be high for all assays at all sites (97.63-100%) with the exception of the Uni-Gold assay (90.24% in Kangemi, 96.58% in Kilifi). Twenty four RT results were recorded as ‘weak positives\', 22 (92%) of which were negative by ELISA. There was a high rate of RT false positives in Uganda (positive predictive values ranging from 45.70% to 86.62%). Conclusions: The sensitivity and specificity of the RT varied significantly across sites. The rate of RT misclassification in Uganda suggests that a multiple test algorithm may be preferable to a single test as screener for HIV VCT. East African Medical Journal Vol. 85 (10) 2008: pp. 500-50

The yield of air fluorescence induced by electrons

The fluorescence yield for dry air and pure nitrogen excited by electrons is calculated using a combination of well-established molecular properties and experimental data of the involved cross sections. Particular attention has been paid to the role of secondary electrons from ionization processes. At high pressure and high energy, observed fluorescence turns out to be proportional to the ionization cross section which follows the Born-Bethe law. Predictions on fluorescence yields in a very wide interval of electron energies (eV - GeV) and pressures (1 and 1013 hPa) as expected from laboratory measurements are presented. Experimental results at energies over 1 MeV are in very good agreement with our calculations for pure nitrogen while discrepancies of about 20% are found for dry air, very likely associated to uncertainties in the available data on quenching cross sections. The relationship between fluorescence emission, stopping power and deposited energy is discussed.Comment: 27 pages, 12 figures, 64 references. Accepted in Astroparticle Physic

RESPOND – A patient-centred program to prevent secondary falls in older people presenting to the emergency department with a fall: Protocol for a multi-centre randomised controlled trial

Introduction: Participation in falls prevention activities by older people following presentation to the Emergency Department (ED) with a fall is suboptimal. This randomised controlled trial (RCT) will test the RESPOND program which is designed to improve older persons’ participation in falls prevention activities through delivery of patient-centred education and behaviour change strategies. Design and setting: An RCT at two tertiary referral EDs in Melbourne and Perth, Australia. Participants: Five-hundred and twenty eight community-dwelling people aged 60-90 years presenting to the ED with a fall and discharged home will be recruited. People who: require an interpreter or hands-on assistance to walk; live in residential aged care or >50 kilometres from the trial hospital; have terminal illness, cognitive impairment, documented aggressive behaviour or history of psychosis; are receiving palliative care; or are unable to use a telephone will be excluded. Methods: Participants will be randomly allocated to the RESPOND intervention or standard care control group. RESPOND incorporates: (1) home-based risk factor assessment; (2) education, coaching, goal setting, and follow-up telephone support for management of one or more of four risk factors with evidence of effective intervention; and (3) healthcare provider communication and community linkage delivered over six months. Primary outcomes are falls and fall injuries per-person-year. Discussion: RESPOND builds on prior falls prevention learnings and aims to help individuals make guided decisions about how they will manage their falls risk. Patient-centred models have been successfully trialled in chronic and cardiovascular disease however evidence to support this approach in falls prevention is limited. Trial registration. The protocol for this study is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12614000336684)

Preparative fractionation of a random copolymer (SAN) with respect to either chain length or chemical composition

The possibilities to fractionate copolymers with respect to their chemical composition on a preparative scale by means of the establishment of liquid/liquid phase equilibria were studied for random copolymers of styrene and acrylonitrile (san). Experiments with solutions of san in toluene have shown that fractionation does in this quasi-binary system, where demixing results from marginal solvent quality, take place with respect to the chain length of the polymer only. On the other hand, if phase separation is induced by a second, chemically different polymer one can find conditions under which fractionation with respect to composition becomes dominant. This opportunity is documented for the quasi-ternary system dmac/san/polystyrene, where the solvent dimethyl acetamide is completely miscible with both polymers. The theoretical reasons for the different fractionation mechanisms are discussed