Thermisch harden van glas

A review with 9 refs. The background of thermal hardening is discussed. Thermal prestressing is the most important method available for increasing the strength of flat glass. The topics include: introduction; phys. description of thermal prestressing of glass; effect of glass properties and process parameters on prestressing; practical aspects; and conclusions. [on SciFinder (R)

Planaire optische versterkers

Langs een glasfiber kan in de vorm van optische pulsjes verschrikkelijk veel informatie worden verzonden: de fiber heeft een zeer hoge transmissiecapaciteit. Wanneer echter voor het schakelen van de informatiestroom, of voor het regenereren van de pulsjes, de informatiestroom naar het elektrische domein omgezet moet worden en vice versa, geeft dit een enorme verlaging van deze capaciteit. Door drie Nederlandse groepen, wordt gedeeltelijk onder de paraplu van het IOP onderzoek gedaan aan een speciale klasse van planaire versterkers: nl die waarin de versterking berust op eigenschappen van zeldzame aard ionen zoals het Erbium-ion. En over dit onderzoek gaat dit artikel

Thermal behaviour of glass batch on batch heating

The heating process of a Ba-Sr glass batch was studied in a 40 L pot furnace, using a multiple thermocouple assembly. The effect of several batch parameters on the heating process was measured, including layer thickness, cullet fraction, water content, and pellets. The results were evaluated using a heat penetration batch model. In the model 2 heating stages, below and above a certain batch transition temp., ns, typically 800 to 900 Deg, are distinguished. Values for the temp.-dependent thermal diffusivity of the batch were derived from exptl. temp. distributions in the batch during heating. Below ns, the thermal diffusivity has an almost const. value of 0.4 * 10-6 m2/s for a std. (powder) batch blanket; for n > ns, the net thermal diffusivity strongly increases with temp., due to the formation of primary melt phases. For ns <n <1100 Deg, the av. value is about 1.4 * 10-6 m2/s. A 100% cullet layer has a 50% higher thermal diffusivity for n <ns; pelletizing the batch has little influence on the virtual thermal diffusivity and (extra) wetting has a retarding effect on batch heating due to extra heat absorption. As for the furnace temp., it appears that increasing the temp. of the glass melt is more effective for improving the batch heating rate than increasing the temp. of the combustion chamber. Practical recommendations are given for batch prepn., charging, and heating in industrial glass tanks. [on SciFinder (R)

The effect of parenteral nnutrition with lipovenous or intralipid on the fatty acid composition of plasma and erythrocyte membrane lipids in very-low-birthweight infants

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The role of alkalinity generation in controlling the fluxes of CO₂ during exposure and inundation on tidal flats

Dissolved inorganic carbon (DIC), gaseous CO2 and alkalinity fluxes from intertidal sediments were investigated during periods of exposure and inundation, using laboratory core incubations, previously published field data and reactive transport model simulations. In the incubations and previous field data, it was found that during periods of alkalinity production (attributed to the accumulation of reduced sulfur species within the sediment), the flux of DIC out of the sediment was greater during inundation than the gaseous CO2 flux during exposure by a factor of up to 1.8. This finding was supported by computational simulations which indicated that large amounts of sulfate reduction and reduced sulfur burial (FeS) induce an alkalinity flux from the sediment during high tide conditions. Model simulations also found that the amount of reactive Fe in the sediment was a major driver of net alkalinity production. Our finding that CO2 fluxes can be significantly lower than total metabolism during exposure has implications for how total metabolism is quantified on tidal flats

Political innovation as ideal and strategy: the case of aleatoric democracy in the City of Utrecht

Political innovations aim to strengthen democracy but few connect well to the institutionalized democratic context. This paper explores how political innovations can be successfully embedded in existing democratic systems. It builds upon both the literature on political innovation and on new democratic arrangements and studies a practice of aleatoric democracy – using the lottery instead of elections to select representatives – in the Dutch City of Utrecht. The case study shows how the idealist logic of improving democracy and the realist logic of realizing specific political goals intertwine to get the political innovation accepted by the institutionalized democratic system

Modified gravity without dark matter

On an empirical level, the most successful alternative to dark matter in bound gravitational systems is the modified Newtonian dynamics, or MOND, proposed by Milgrom. Here I discuss the attempts to formulate MOND as a modification of General Relativity. I begin with a summary of the phenomenological successes of MOND and then discuss the various covariant theories that have been proposed as a basis for the idea. I show why these proposals have led inevitably to a multi-field theory. I describe in some detail TeVeS, the tensor-vector-scalar theory proposed by Bekenstein, and discuss its successes and shortcomings. This lecture is primarily pedagogical and directed to those with some, but not a deep, background in General RelativityComment: 28 pages, 10 figures, lecture given at Third Aegean Summer School, The Invisible Universe: Dark Matter and Dark Energy, minor errors corrected, references update

Observational Constraints on Chaplygin Quartessence: Background Results

We derive the constraints set by several experiments on the quartessence Chaplygin model (QCM). In this scenario, a single fluid component drives the Universe from a nonrelativistic matter-dominated phase to an accelerated expansion phase behaving, first, like dark matter and in a more recent epoch like dark energy. We consider current data from SNIa experiments, statistics of gravitational lensing, FR IIb radio galaxies, and x-ray gas mass fraction in galaxy clusters. We investigate the constraints from this data set on flat Chaplygin quartessence cosmologies. The observables considered here are dependent essentially on the background geometry, and not on the specific form of the QCM fluctuations. We obtain the confidence region on the two parameters of the model from a combined analysis of all the above tests. We find that the best-fit occurs close to the $\Lambda$CDM limit ($\alpha=0$). The standard Chaplygin quartessence ($\alpha=1$) is also allowed by the data, but only at the $\sim2\sigma$ level.Comment: Replaced to match the published version, references update

Effect of enzyme therapy and prognostic factors in 69 adults with Pompe disease: An open-label single-center study

Abstract. Background: Enzyme replacement therapy (ERT) in adults with Pompe disease, a progressive neuromuscular disorder, is of promising but variable efficacy. We investigated whether it alters the course of disease, and also identified potential prognostic factors. Methods. Patients in this open-label single-center study were treated biweekly with 20 mg/kg alglucosidase alfa. Muscle strength, muscle function, and pulmonary function were assessed every 3-6 months and analyzed using repeated-measures ANOVA. Results: Sixty-nine patients (median age 52.1 years) were followed for a median of 23 months. Muscle strength increased after start of ERT (manual muscle testing 1.4 percentage points per year (pp/y); hand-held dynamometry 4.0 pp/y; both p < 0.001). Forced vital capacity (FVC) remained stable when measured in upright, but declined in supine position (-1.1 pp/y; p = 0.03). Muscle function did not improve in all patients (quick motor function test 0.7 pp/y; p = 0.14), but increased significantly in wheelchair-independent patients and those with mild and moderate muscle weakness.Relative to the pre-treatment period (49 patients with 14 months pre-ERT and 22 months ERT median follow-up), ERT affected muscle strength positively (man