Contrasting sensitivities to toxicants of the freshwater amphipods Gammarus pulex and G. fossarum

Amphipods are an important component of freshwater ecosystems. They are very often used in ecotoxicology, particularly the freshwater amphipod Gammarus pulex. However, there is scarce information on the sensitivity to toxicants of other species within the genus Gammarus. The present study aims to: (1) to compare sensitivities to ivermectin and cadmium between two species of freshwater amphipods (G. pulex and G. fossarum); (2) to compare sensitivities to these toxicants between juveniles and adults within each species; and (3) to assess whether the sensitivity to toxicants of these co-generic species is related with the wideness of their natural distribution area. Eight independent short-term bioassays (96 h) were conducted to assess sensitivity for ivermectin and cadmium for juvenile and adult life stages for each species. The LC50 (mortality) and EC50 (mortality plus immobility) were calculated to 48 and 96 h of continuous exposure. Our results showed that G. pulex was less tolerant to ivermectin than G. fossarum, the reverse being true for cadmium. In general, juveniles of both species were less tolerant to cadmium than adults. In the case of ivermectin, only for G. fossarum EC50 values were different between life stages. These results suggest that the risk assessment of toxicants to freshwater amphipods should include bioassays with the most sensitive species and life stag

Economic development for an exploding population

A journal article on economic development for an expanding population.I could use this occasion to come up with lots of facts and figures on population explosion and economic development. Alternatively, I could expand on the nature and use of mathematical computer models of population or socioeconomic development, which is my field of research. I am not going to do either of these. What I am going to do is to look at the development needs and problems of a country faced with an exploding population from my personal point of view, and on the assumption that Rhodesia, or if you prefer Zimbabwe, will emerge from its present political problems with a stable government, whatever its political flavour might be. I do believe that this symposium was organised in the spirit of this assumption, and with this hope, for where there is no hope there is no way

The hydrodynamics of the southern basin of Tauranga Harbour

The circulation of the southern basin of Tauranga Harbour was simulated using a 3-D hydrodynamic model ELCOM. A 9-day field campaign in 1999 provided data on current velocity, temperature and salinity profiles at three stations within the main basin. The tidal wave changed most in amplitude and speed in the constricted entrances to channels, for example the M2 tide attenuated by 10% over 500 m at the main entrance, and only an additional 17% over the 15 km to the top of the southern basin. The modelled temperature was sensitive to wind mixing, particularly in tidal flat regions. Residence times ranged from 3 to 8 days, with higher residence times occurring in sub-estuaries with constricted mouths. The typical annual storm events were predicted to reduce the residence times by 24%–39% depending on season. Model scenarios of storm discharge events in the Wairoa River varying from 41.69 m3/s to 175.9 m3/s show that these events can cause salinity gradients across the harbour of up to 4 PSU

The conduction pathway of potassium channels is water free under physiological conditions.

Ion conduction through potassium channels is a fundamental process of life. On the basis of crystallographic data, it was originally proposed that potassium ions and water molecules are transported through the selectivity filter in an alternating arrangement, suggesting a "water-mediated" knock-on mechanism. Later on, this view was challenged by results from molecular dynamics simulations that revealed a "direct" knock-on mechanism where ions are in direct contact. Using solid-state nuclear magnetic resonance techniques tailored to characterize the interaction between water molecules and the ion channel, we show here that the selectivity filter of a potassium channel is free of water under physiological conditions. Our results are fully consistent with the direct knock-on mechanism of ion conduction but contradict the previously proposed water-mediated knock-on mechanism

De schijnwerkelijkheid van gezamenlijke besluitvorming

Het nemen van besluiten lijkt inherent te zijn aan ziek zijn. Steeds vaker wordt er van de patiënt verwacht dat hij zelf gaat kiezen en eigen regie voert. De patiënt weet immers zelf wat het beste voor hem is, is de gedachte. Gezamenlijke besluitvorming lijkt hierin een welkom concept om te komen tot goede zorg. Maar is dit wel het geval? Door middel van zorgethisch onderzoek is er inzicht verworven in de ervaringen van twee patiënten, en diens naasten, waar besluiten worden gevormd omtrent behandeling op het moment dat er sprake is van ziekte. Er zijn twee fenomenologische casestudies uitgevoerd om antwoord te kunnen geven op de hoofdvraag: Hoe ervaren mensen met uitgezaaide, ongeneeslijke kanker de besluitvorming omtrent behandeling en wat is voor hen daarin goede zorg? Vanuit de verworven data worden vijf thema’s gedestilleerd: vervreemding van het vertrouwde, ervaring van chaos, hoop, gezien worden en samen ziek zijn. Te zien is dat deze thema’s samen een membraan vormen waarin de patiënt terecht komt. Binnen dit membraan worden geen rationele keuzes gemaakt, iets wat het concept van gezamenlijke besluitvorming binnen de dominante literatuur wel verondersteld. De vooronderstelde werkelijkheid sluit niet aan bij de echte werkelijkheid met een schijnwerkelijkheid tot gevolg. De dominante opvatting van gezamenlijke besluitvorming sluit dan ook niet aan bij de wereld van de patiënten en laat patiënten juist alleen in deze onvertrouwde en onveilige situatie. Dit onderzoek laat zien dat goed zorgen meer is dan kiezen en het nemen van besluiten. Er zal vanuit een relationeel mensbeeld aansluiting moeten worden gevonden bij de aspecten van afhankelijkheid en kwetsbaarheid die inherent zijn aan het menselijk bestaan, juist ook op het moment van ziekte. Die kwetsbaarheid en afhankelijkheid spelen een belangrijke rol in de vorming van besluiten en de strubbelingen en opgaven waar patiënten voor komen te staan

Bootstrap tomography of high-precision pulses for quantum control

Long-time dynamical decoupling and quantum control of qubits require high-precision control pulses. Full characterization (quantum tomography) of imperfect pulses presents a bootstrap problem: tomography requires initial states of a qubit which can not be prepared without imperfect pulses. We present a protocol for pulse error analysis, specifically tailored for a wide range of the single solid-state electron spins. Using a single electron spin of a nitrogen-vacancy (NV) center in diamond, we experimentally verify the correctness of the protocol, and demonstrate its usefulness for quantum control tasks

Stratospheric isotopic water profiles from a single submillimeter limb scan by TELIS

Around 490 GHz relatively strong HDO and H<sub>2</sub><sup>18</sup>O emission lines can be found in the submillimeter thermal-emission spectrum of the Earth's atmosphere, along with lines of the principal isotopologue of water vapour. These can be used for remote sensing of the rare/principal isotope ratio in the stratosphere. A sensitivity study has been performed for retrieval simulations of water isotopologues from balloon-borne measurements by the limb sounder TELIS (TErahertz and submillimeter LImb Sounder). The study demonstrates the capability of TELIS to determine, from a single limb scan, the profiles for H<sub>2</sub><sup>18</sup>O and HDO between 20 km and 37 km with a retrieval error of ≈3 and a spatial resolution of 1.5 km, as determined by the width of the averaging kernel. In addition HDO can be retrieved in the range of 10–20 km, albeit with a strongly deteriorated retrieval error. Expected uncertainties in instrumental parameters have only limited impact on the retrieval results