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A highly oriented cubic phase formed by lipids under shear
We demonstrate the formation of a macroscopically
oriented inverse bicontinuous cubic (QII) lipid
phase from a sponge (L3) phase by controlled hydration
during shear flow. The L3 phase was the monoolein/
butanediol/water system; the addition of water reduces
the butanediol concentration, inducing the formation of a
diamond (QIID) cubic phase, which is oriented by the shear
flow. The phenomenon was reproduced in both capillary
and Couette geometries, indicating that this represents a
robust general route for the production of highly aligned
bulkQII samples, with applications in nanomaterial templating and protein research
Modelling and Measurement of Charge Transfer in Multiple GEM Structures
Measurements and numerical simulations on the charge transfer in Gas Electron
Multiplier (GEM) foils are presented and their implications for the usage of
GEM foils in Time Projection Chambers are discussed. A small test chamber has
been constructed and operated with up to three GEM foils. The charge transfer
parameters derived from the electrical currents monitored during the
irradiation with an Fe-55 source are compared with numerical simulations. The
performance in magnetic fields up to 2 T is also investigated.Comment: 21 pages, 16 figures, submitted to NIM-
Charge Transfer and Charge Broadening of GEM Structures in High Magnetic Fields
We report on measurements of charge transfer in GEM structures in high
magnetic fields. These were performed in the framework of the R&D work for a
Time Projection Chamber at a future Linear Collider. A small test chamber has
been installed into the aperture of a superconducting magnet with the GEM
structures mounted perpendicular to the B field direction. The charge transfer
is derived from the electrical currents monitored during irradiation with an
Fe source. No severe loss of primary ionisation charge is observed,
but an improved ion feedback suppression is achieved for high magnetic fields.
Additionally, the width of the charge cloud released by individual Fe
photons is measured using a finely segmented strip readout after the triple GEM
structure. Charge widths between 0.3 and 0.5 mm RMS are observed, which
originate from the charge broadening inside the GEM readout. This charge
broadening is only partly suppressed at high magnetic fields.Comment: 11 pages, 9 figure
Creation of scalar and Dirac particles in the presence of a time varying electric field in an anisotropic Bianchi I universe
In this article we compute the density of scalar and Dirac particles created
by a cosmological anisotropic Bianchi type I universe in the presence of a time
varying electric field. We show that the particle distribution becomes thermal
when one neglects the electric interaction.Comment: 8 pages, REVTEX 3.0. to appear in Phys. Rev.
Adaption reveals a neural code for the visual location of orientation change
We apply an adaptation technique to explore the neural code for the visual location of textures defined by modulation of orientation over space. In showing that adaptation to textures modulated around one orientation shifts the perceived location of textures modulated around a different orientation, we demonstrate the existence of a neural code for the location of orientation change that generalises across orientation content. Using competitive adaptation, we characterise the neural processes underlying this code as single-opponent for orientation, that is with concentric excitatory/inhibitory receptive areas tuned to a single orientation.<br /
Classical and quantum radiation from a moving charge in an expanding universe
We investigate photon emission from a moving particle in an expanding
universe. This process is analogous to the radiation from an accelerated charge
in the classical electromagnetic theory. Using the framework of quantum field
theory in curved spacetime, we demonstrate that the Wentzel-Kramers-Brillouin
(WKB) approximation leads to the Larmor formula for the rate of the radiation
energy from a moving charge in an expanding universe. Using exactly solvable
models in a radiation-dominated universe and in a Milne universe, we examine
the validity of the WKB formula. It is shown that the quantum effect suppresses
the radiation energy in comparison with the WKB formula.Comment: 16 pages, JCAP in pres
N2O emissions from the global agricultural nitrogen cycle – current state and future scenarios
Reactive nitrogen (Nr) is not only an important nutrient for plant growth, thereby safeguarding human alimentation, but it also heavily disturbs natural systems. To mitigate air, land, aquatic, and atmospheric pollution caused by the excessive availability of Nr, it is crucial to understand the long-term development of the global agricultural Nr cycle.
For our analysis, we combine a material flow model with a land-use optimization model. In a first step we estimate the state of the Nr cycle in 1995. In a second step we create four scenarios for the 21st century in line with the SRES storylines.
Our results indicate that in 1995 only half of the Nr applied to croplands was incorporated into plant biomass. Moreover, less than 10 per cent of all Nr in cropland plant biomass and grazed pasture was consumed by humans. In our scenarios a strong surge of the Nr cycle occurs in the first half of the 21st century, even in the environmentally oriented scenarios. Nitrous oxide (N2O) emissions rise from 3 Tg N2O-N in 1995 to 7–9 in 2045 and 5–12 Tg in 2095. Reinforced Nr pollution mitigation efforts are therefore required
Drivers of sustainable intensification in Kenyan rural and peri-urban vegetable production
Sustainable intensification promotes environmentally sound and productive agriculture. However, use of sustainable intensification practices (SIPs) is low in many sub-Sharan African countries. This study examined the adoption of SIPs in Kenyan rural and peri-urban vegetable production to understand the scale of and underlying factors in the use of SIPs. A multistage sampling technique was employed to randomly select 685 rural and peri-urban vegetable farm households. Household data was then collected and anaylsed for four practices namely improved irrigation, integrated soil fertility, organic manure and crop diversification using a pre-tested structured questionnaire. A multivariate probit model was run to model simultaneous interdependent adoption decisions. Adoption of organic manure and African indigenous vegetables (AIV) diversification was high in both rural and peri-urban areas. However, adoption of improved irrigation systems and integrated soil fertility management was low, and even significantly lower in rural areas than in peri-urban areas (p < 0.041). Similarly, adoption intensity of SIPs was lower in rural areas than in peri-urban areas. Furthermore, the findings also show complementarities and substitutabilities between SIPs. Market integration, the farm location and household income were the major factors heavily influencing the adoption of most SIPs. Policies and programmes that seek to build household financial capital base and integrate farm households into effective and efficient vegetable markets need to be formulated and implemented in order to enhance adoption of SIPs in AIV production
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