7,602 research outputs found
Consumptie verplicht : een kleine sociologie van consumeren tussen vreten en geweten
Consumptie verplicht biedt een beknopt overzicht van hedendaags sociologisch denken over consumptie, met de nadruk op voedselconsumptie. ‘Consumptie verplicht’ krijgt een drievoudige interpretatie. Ten eerste als een verplicht onderdeel van de sociologie van vandaag. Ten tweede in termen van de karakterisering van steeds méér consumeren als plicht. Ten derde in de betekenis van de samenhang van consumptie met normatieve verplichtingen
The Vector Meson Form Factor Analysis in Light-Front Dynamics
We study the form factors of vector mesons using a covariant fermion field
theory model in dimensions. Performing a light-front calculation in the
frame in parallel with a manifestly covariant calculation, we note the
existence of a nonvanishing zero-mode contribution to the light-front current
and find a way of avoiding the zero-mode in the form factor calculations.
Upon choosing the light-front gauge (\ep^+_{h=\pm}=0) with circular
polarization and with spin projection , only the
helicity zero to zero matrix element of the plus current receives zero-mode
contributions. Therefore, one can obtain the exact light-front solution of the
form factors using only the valence contribution if only the helicity
components, , and , are used. We also compare our
results obtained from the light-front gauge in the light-front helicity basis
(i.e. ) with those obtained from the non-LF gauge in the instant form
linear polarization basis (i.e. ) where the zero-mode contributions to
the form factors are unavoidable.Comment: 33 pages; typo in Eq.(15) is corrected; comment on Ref.[9] is
corrected; version to appear in Phys. Rev.
Neutrophil gelatinase-associated lipocalin as an early indicator for mortality in adult critically ill patients with acute kidney injury
Duurzaam consumeren : maatschappelijke context en mogelijkheden voor beleid
Deze studie schetst vanuit een omgevingsperspectief een state of the art van het debat over duurzame consumptie en vergelijkt twee actuele onderzoekstrajecten (CONTRAST en CAPABILITY) waarin op verschillende wijze wordt getracht kennis te ontwikkelen die de bevordering van duurzame consumptie kan ondersteunen. Vergelijking van de onderzoekstrajecten laat zien dat deze sterke en zwakke punten hebben die goeddeels met elkaar contrasteren. Verder blijken CONTRAST en CAPABILITY interessante overeenkomsten te hebben en zijn er mogelijke aansluitingspunten. Zo komt een aantal consumptiedomeinen binnen het CONTRAST-project nagenoeg naadloos overeen met domeinen van capabilities en hulpbronnen die voor een CAPABILITY-index worden geïdentificeerd. Beide benaderingen pleiten ook voor de ontwikkeling van beleidsgerichte indicatorensets. De conclusie is dat de uitdaging moet worden aangegaan deze twee onderzoeksbenaderingen te combineren. Op deze manier kan een rijker geheel van beleidsondersteunende kennis worden gerealiseerd om duurzame consumptie te bevorderen. Trefwoorden: Duurzaamheid, duurzame consumptie, consumptiesociologie, kritische theorie, indicatoren, kwantitatieve methoden, kwalitatieve methoden
Measuring very negative water potentials with polymer tensiometers: principles, performance and applications
In recent years, a polymer tensiometer (POT) was developed and tested to directly measure matric potentials in dry soils. By extending the measurement range to wilting point (a 20-fold increase compared to conventional, water-filled tensiometers), a myriad of previously unapproachable research questions are now open to experimental exploration. Furthermore, the instrument may well allow the development of more water-efficient irrigation strategies by recording water potential rather than soil water content. The principle of the sensor is to fill it with a polymer solution instead of water, thereby building up osmotic pressure inside the sensor. A high-quality ceramic allows the exchange of water with the soil while retaining the polymer. The ceramic has pores sufficiently small to remain saturated even under very negative matric potentials. Installing the sensor in an unsaturated soil causes the high pressure of the polymer solution to drop as the water potentials in the soil and in the POT equilibrate. As long as the pressure inside the polymer chamber remains sufficiently large to prevent cavitation, the sensor will function properly. If the osmotic potential in the polymer chamber can produce a pressure of approximately 2.0 MPa when the sensor is placed in water, proper readings down to wilting point are secured. Various tests in disturbed soil, including an experiment with root water uptake, demonstrate the operation and performance of the new polymer tensiometer and illustrate how processes such as root water uptake can be studied in more detail than before. The paper discusses the available data and explores the long term perspectives offered by the instrument
Transition Form Factors between Pseudoscalar and Vector Mesons in Light-Front Dynamics
We study the transition form factors between pseudoscalar and vector mesons
using a covariant fermion field theory model in dimensions. Performing
the light-front calculation in the frame in parallel with the
manifestly covariant calculation, we note that the suspected nonvanishing
zero-mode contribution to the light-front current does not exist in our
analysis of transition form factors. We also perform the light-front
calculation in a purely longitudinal frame and confirm that the form
factors obtained directly from the timelike region are identical to the ones
obtained by the analytic continuation from the spacelike region. Our results
for the decay process satisfy the constraints on the
heavy-to-heavy semileptonic decays imposed by the flavor independence in the
heavy quark limit.Comment: 20 pages, 14 figure
Neutrophil gelatinase-associated lipocalin as an early indicator for postoperative renal failure
Public exhibit for demonstrating the quantum of electrical conductance
We present a new robust setup that explains and demonstrates the quantum of
electrical conductance for a general audience and which is continuously
available in a public space. The setup allows users to manually thin a gold
wire of several atoms in diameter while monitoring its conductance in real
time. During the experiment, a characteristic step-like conductance decrease
due to rearrangements of atoms in the cross-section of the wire is observed.
Just before the wire breaks, a contact consisting of a single atom with a
characteristic conductance close to the quantum of conductance can be
maintained up to several seconds. The setup is operated full-time, needs
practically no maintenance and is used on different educational levels
New Polymer Tensiometers: Measuring Matric Pressures Down to the Wilting Point
Tensiometers are commonly used for measuring soil water matric pressures. Unfortunately, the water-filled reservoir of conventional tensiometers limits their applicability to soil water matric pressures above approximately –0.085 MPa. Tensiometers filled with a polymer solution instead of water are able to measure a larger range of soil water matric pressures. We designed and constructed six prototype polymer tensiometers (previously called osmotic tensiometers) consisting of a wide-range pressure transducer with a temperature sensor, a stainless steel casing, and a ceramic plate with a membrane preventing polymer leakage. A polymer chamber (0.1–2.2 cm3) was located between the pressure transducer and the plate. We tested the polymer tensiometers for long-term operation, the effects of temperature, response times, and performance in a repacked sandy loam under laboratory conditions. Several months of continuous operation caused a gradual drop in the osmotic pressure, for which we developed a suitable correction. The osmotic potential of polymer solutions is temperature dependent, and requires calibration before installation. The response times to sudden and gradual changes in ambient temperature were found to be affected by polymer chamber height and polymer type. Practically useful response times (<0.2 d) are feasible, particularly for chambers shorter than 0.20 cm. We demonstrated the ability of the instrument to measure the range of soil water pressures in which plant roots are able to take up water (from 0 to –1.6 MPa), to regain pressure without user interference and to function properly for time periods of up to 1 yr
- …