Design of a cold gas micro thruster

Keywords: Micro satellites, Micro propulsion, MEMS technologie

Modular Micro Propulsion System

The miniaturization of space applicable devices by means of MEMS technology is pursued by many research groups. MEMS devices are often designed as stand alone and require individual packaging which often makes them still quite large. Focusing on the integration of several MEMS components has the advantage of reducing size and mass much more. An integrated and miniaturized cold gas propulsion system for micro satellites is presented which consists of a valve, a particle filter, a pressure sensor, a nozzle and a gas tank. By selecting a convenient package first and adjusting the MEMS part to fit the package, costs are reduced and modularity is obtained. The baseline of the system is a glass tube bonded on a silicon disc which contains a valve seat as shown in Figure 1. The valve is normally closed by an embossed membrane which is stacked inside the glass tube. A piezo-disc is glued to the boss of the membrane to actuate the valve. The glass tube is functioning as hermetically sealed package as well as fluidic interconnect with the macro world. The pressure sensor and particle filter are suspended in the glass tube. This integrated system is connected to a pressurized N2 gas tank which is developed by TNO [1]. The tank contains 8 cold gas generators which makes it possible to reduce the working pressure to 3.4bar withoutcompromising on the amount of gas. During the symposium the technical development and results will be presented

Quantitative or qualitative development in decision making?

A key question in the developmental sciences is whether developmental differences are quantitative or qualitative. For example, does age increase the speed in processing a task (quantitative differences) or does age affect the way a task is processed (qualitative differences)? Until now, findings in the domain of decision making have been based on the assumption that developmental differences are either quantitative or qualitative. In the current study, we took a different approach in which we tested whether development is best described as being quantitative or qualitative. We administered a judgment version and a choice version of a decision-making task to a developmental sample (njudgment = 109 and nchoice = 137; Mage = 12.5 years, age range = 9–18). The task, the so-called Gambling Machine Task, required decisions between two options characterized by constant gains and probabilistic losses; these characteristics were known beforehand and thus did not need to be learned from experience. Data were analyzed by comparing the fit of quantitative and qualitative latent variable models, so-called multiple indicator multiple cause (MIMIC) models. Results indicated that individual differences in both judgment and choice tasks were quantitative and pertained to individual differences in “consideration of gains,” that is, to what extent decisions were guided by gains. These differences were affected by age in the judgment version, but not in the choice version, of the task. We discuss implications for theories of decision making and discuss potential limitations and extensions. We also argue that the MIMIC approach is useful in other domains, for example, to test quantitative versus qualitative development of categorization, reasoning, math, and memory

One-year follow-up effects of two obesity treatments on psychological well-being and weight.

Objectives. The effectiveness of a cognitive and a behavioural treatment for obese binge eaters and obese non-binge eaters was evaluated at I-year follow-up. Furthermore, we examined the role of weight changes on psychological well-being at I-year follow-up. Design and method. Participants were reassessed 6 months and I year after they had finished a group cognitive treatment or a group behavioural treatment. The outcome measures were; psychological well-being (concerns about shape, weight and eating, self-esteem and depression), binge eating, and weight. Results and conclusions. Analyses on the completers' sample revealed that both treatments had a markedly positive and lasting impact on shape concern, weight concern and eating concern, binge eating, self-esteem, and depression at 1-year followup. Cognitive treatment was not superior to behavioural treatment on most outcome measures. This might be due to selective drop-out, Analyses including non-responders showed that the cognitive treatment was superior on shape, weight and eating concern, and binge eating. The I-year follow-up results for weight-loss were disappointing. Between pre-treatment and 1-year follow-up participants in the behaviour treatment lost 3.0 kg, while participants in the cognitive treatment lost 0.3 kg. However, participants who gained weight were as successful on changes in psychological well-being changes as participants who lost weight

Bivalve nutrient cycling : nutrient turnover by suspended mussel communities in oligotrophic fjords

This study examined a range of eco-physiological processes (i.e filtration, growth, excretion, faeces production) and feedback mechanisms with the aim to investigate the contribution of suspended mussel Mytilus edulis communities to nutrient cycling in oligotrophic fjords. Previous work has shown that bivalves have the potential to play an important role in coastal nutrient cycling. Understanding bivalve nutrient dynamics is particularly essential in oligotrophic environments, where bivalve communities potentially have a higher influence as a consequence of low background nutrient levels. The eco-physiological response of individual mussels to oligotrophic conditions indicated that clearance and biodeposition rates were related to food/nutrient availability and were therefore respectively higher and lower compared to rates determined for eutrophic conditions. No specific responses to oligotrophic conditions were observed for excretion of inorganic metabolites or nutrient storage in tissue. However, in situ methods that determined nutrient dynamics along suspended communities (ropes) demonstrated that rates under field conditions may differ from what can be expected from extrapolation of rates measured in the laboratory for individual mussels. Clearance rates were lower for communities while nutrient regeneration was higher, specifically during periods with high fouling activity of ascidians. This study thereby highlights the need to consider community specific processes while evaluating bivalve-ecosystem interactions. Biodeposition is an important pathway in bivalve nutrient cycling and represented up to 47% of ingested nutrients under oligotrophic conditions. Nutrient releases from decomposing biodeposits were high for all nutrients (C-N-P-Si), and approximately 24% of carbon and 17% of nitrogen in the biodeposits were mineralized with enhanced temperatures resulting in faster decomposition (Q10=2-3). Combining mussel physiology with physical conditions of the systems showed that the fraction of ingested nutrients allocated to either nutrient regeneration (source) or nutrient removal (sink) was similar between oligotrophic fjords and eutrophic bays. Nutrient regeneration was imbalanced for each of the elements and differed from ratios observed in the ambient water. Mussel cultures thereby have the potential to influence phytoplankton community composition. However, positive and negative feedback estimates indicated that present mussel aquaculture in Norwegian fjord systems has low influence on nutrient cycling due to the low bivalve densities and physical characteristics of the fjords. This thesis provided insights in the pathways in which mussels interact with nutrient cycling, with special reference to oligotrophic conditions. The empirical data collected in this study can be applied to optimize models that simulate bivalve-ecosystem interactions, and thereby help to understand and predict the exploitation and management of coastal zones.</p

Multiplex PCR assay for immediate identification of the infecting species in patients with mycobacterial disease

Rapid identification of infecting mycobacterial species enables appropriate medical care decisions to be made. Our aim was to demonstrate the clinical usefulness of the multiplex PCR assay, a test based on PCR, which permits direct identification of 12 mycobacterial species in clinical specimens. A total of 259 specimens from 177 patients who had clinical symptoms of mycobacterial disease but for whom there were difficulties in diagnosis were tested. Specimens were analyzed within 48 h of receipt of the sample. Mycobacteria were identified in 102 specimens; 66 specimens contained nontuberculous mycobacteria, and 36 specimens contained Mycobacterium tuberculosis complex mycobacteria. The PCR assay identified the mycobacterial species in 43 (97.7%) of 44 microscopy- and culture-positive specimens and in 15 (93.8%) of 16 culture-positive, microscopy-negative specimens. It also permitted species identification in infections caused by more than one mycobacterial species. For 56 (96.5%) of the 58 specimens from patients with infections caused by opportunistic mycobacteria, the organisms were identified with the PCR assay. The test was useful also for the identification of fastidious mycobacteria, e.g., M. genavense, and those that cannot be cultured, e.g., M. leprae. After resolution of discrepant results, the sensitivity of the PCR assay was 97.9%, the specificity was 96.9%, the positive predictive value was 95.0%, and the negative predictive value was 98.7%. For culture these values were 60.8, 100, 100, and 81.0%, respectively. Thus, the multiplex PCR assay enables prompt diagnosis when rapid identification of infecting mycobacteria is necessary

Enantioselective Conjugate Addition of Diethylzinc to Chalcones Catalysed by Chiral Ni(II) Aminoalcohol Complexes

Conjugate addition of diethylzinc to chalcones is catalysed by complexes prepared in situ from Ni(acac)2 and cis-exo-N,N-dialkyl-3-aminoisoborneols or (+)-cis-endo-N,N-dimethyl-3-aminoborneol ((+)-DAB) (13b). The products are obtained with enantioselectivities up to 84 %. When scalemic (-)-cis-exo-N,N-dimethyl-3-aminoisoborneol ((-)-DAIB) (3c) was employed in the reaction a positive nonlinear relationship was found. Several factors which govern catalyst activity and enantioselectivity have been investigated

Mosselkweek in Noorse fjorden

Schelpdiercultuur is een groeiende sector in Noorwegen, al kent de ontwikkeling ook belemmeringen zoals logistieke beperkingen, sluiting van de oogst door giftige algen, hiaten in de kennis over kweekmethoden, beperkte financiële middelen en een gering ontwikkelingen van de Sector. Zowel de sector als de gerelateerde onderzoeksactiviteiten staan in Noorwegen in de kinderschoenen. Het Institute of Marine (IMR) heeft daarom samenwerking gezocht met Nederlandse, Frans en Canadese onderzoeksinstituten. Deze landen kennen een lange historie en goed gestructureerd onderzoeksveld én hebben een grote schelpdiersector. De samenwerking met IMARES is één van de voorbeelden van deze samenwerkingsverbanden. Aad Smaal en Henrice Jansen zijn vanuit IMARES betrokken bij een project naar de draagkracht voor mosselkweek in Noorse fjorden. Henrice verblijft voor een periode van vier jaar in Noorwegen om promotieonderzoek uit te voeren naar de nutriëntendynamiek in mosselkwekerijen