1,838 research outputs found
Anisotropy of the Microwave Sky at 90 GHz: Results from Python II
We report on additional observations of degree scale anisotropy at 90~GHz
from the Amundsen-Scott South Pole Station in Antarctica. Observations during
the first season with the Python instrument yielded a statistically significant
sky signal; in this paper we report the confirmation of that signal with data
taken in the second year, and on results from an interleaving set of fields.Comment: 10 pages, plus 2 figures. Postscript and uufiles versions available
via anonymous ftp at ftp://astro.uchicago.edu/pub/astro/ruhl/pyI
Absorption of Ultrashort Laser Pulses in Strongly Overdense Targets
We report on the first absorption experiments of sub-10 fs high-contrast
Ti:Sa laser pulses incident on solid targets. The very good contrast of the
laser pulse assures the formation of a very small pre-plasma and the pulse
interacts with the matter close to solid density. Experimental results indicate
that p-polarized laser pulses are absorbed up to 80 percent at 80 degrees
incidence angle. The simulation results of PSC PIC code clearly confirm the
observations and show that the collisionless absorption works efficiently in
steep density profiles
Three-dimensional Gross-Pitaevskii solitary waves in optical lattices: stabilization using the artificial quartic kinetic energy induced by lattice shaking
In this Letter, we show that a three-dimensional Bose-Einstein solitary wave
can become stable if the dispersion law is changed from quadratic to quartic.
We suggest a way to realize the quartic dispersion, using shaken optical
lattices. Estimates show that the resulting solitary waves can occupy as little
as -th of the Brillouin zone in each of the three directions and
contain as many as atoms, thus representing a \textit{fully
mobile} macroscopic three-dimensional object.Comment: 8 pages, 1 figure, accepted in Phys. Lett.
Missing links in the study of solute and particle exchange between the sea floor and water column
Exchanges of solutes and solids between the sea floor and water column are a vital component of ecosystem functioning in marine habitats around the globe. This review explores particle and solute exchange processes, the different mechanisms through which they interact at the ecosystem level, as well as their interdependencies. Solute and particle exchange processes are highly dependent on the characteristics of the environment within which they takes place. Exchange is driven directly by a number of factors, such as currents, granulometry, nutrient, and matter inputs, as well as living organisms. In turn, the occurrence of exchanges can influence adjacent environments and organisms. Major gaps in the present knowledge include the temporal and spatial variation in many of the processes driving benthic/pelagic exchange processes and the variability in the relative importance of individual processes caused by this variation. Furthermore, the accurate assessment of some anthropogenic impacts is deemed questionable due to a lack of baseline data and long-term effects of anthropogenic actions are often unknown. It is suggested that future research should be transdisciplinary and at ecosystem level wherever possible and that baseline surveys should be implemented and long-term observatories established to fill the current knowledge gaps
Conservation and concealment in SpeciesBanking.com, USA: an analysis of neoliberal performance in the species offsetting industry
Market-based strategies are promoted as neoliberal
governance solutions to environmental problems, from
local to global scales. Tradable mitigation schemes
are proliferating. These include species banking, which
enables payments for the purchase of species credits
awarded to conserved areas to offset development
impacts on protected species elsewhere. An analysis of
species banks in the USA through a survey of data from
the website www.SpeciesBanking.com (established as
a ‘clearing house’ for species banking information)
was complemented by questionnaire material from
USA bank managers. The number of USA species
banks has increased rapidly, bank area ownership
and management is consolidated in a small number
of organizations, and public information on species
credit price is limited. In interrogating the case
material, the roles of specific economic policies
associated with neoliberalism are considered, focusing
on the extension of privatization, de- and re-regulation
and marketization into the arena of environmental
conservation, and commodification processes as
manifested in species banking. Problematic ecological
and distributive ‘concealments’ in species banking
include the ‘development-led’ nature of conservation
banking, tendencies towards net biodiversity loss,
and an emphasis on supporting conservation-related
wealth accumulation by larger landowners and
investors
The impact of Pinus halepensis mill. afforestation on mediterranean spontaneous vegetation: do soil treatment and canopy cover matter?
We investigated central Mediterranean Pinus halepensis plantations under semi-arid climate in order to evaluate the combined effect of soil treatment and afforestation practices on spontaneous plant species composition, richness and evenness, and on the trend and speed of vegetation dynamics. Phytosociological relevés of three different plot typologies, i.e. (1) soil-treatment and plantation, (2) only soil-treatment, (3) no soil-treatment and no plantation, were compared by (a) multivariate analysis and (b) with reference to species richness and evenness. Moreover, in order to compare vegetation dynamics within the plantations with those ones ongoing in semi-natural garrigue communities, we compared life form and syntaxonomic spectra between phytosociological relevés taken at 8 years of distance. DCA showed that floristic species composition and similarity are influenced by the canopy cover of Pine trees as well as by soil-treatment practices. Although species richness and evenness are not clearly related to neither soil treatment nor Pine afforestation, canopy cover clearly plays a major role: in fact, the highest Ph cover rates correspond to the lowest values of understory species richness. This is true also if only species of biogeographical/conservation interest are considered. Regarding vegetation dynamics, sites with dense Pine canopy cover evolve much slower than the adjacent garrigue communities. The same factors invoqued to explain the patterns of floristic composition and similarity (i.e. allelopathy and competition for light, water and nutrients) may also explain the lowering of diversity of therophytes and the strong decline of the cover perfomed by both therophytes and hemicryptophytes underneath the canopy of dense Ph plantations. Thus, in sites where Ph cover exceeds about 80%, thinning is recommended not only in order to accelerate succession, but also to give a natural ‘shape’ to afforestations
Focusing of Intense Subpicosecond Laser Pulses in Wedge Targets
Two dimensional particle-in-cell simulations characterizing the interaction
of ultraintense short pulse lasers in the range 10^{18} \leq I \leq 10^{20}
W/cm^{2} with converging target geometries are presented. Seeking to examine
intensity amplification in high-power laser systems, where focal spots are
typically non-diffraction limited, we describe key dynamical features as the
injected laser intensity and convergence angle of the target are systematically
varied. We find that laser pulses are focused down to a wavelength with the
peak intensity amplified by an order of magnitude beyond its vacuum value, and
develop a simple model for how the peak location moves back towards the
injection plane over time. This performance is sustained over hundreds of
femtoseconds and scales to laser intensities beyond 10^{20} W/cm^{2} at 1 \mu m
wavelength.Comment: 5 pages, 6 figures, accepted for publication in Physics of Plasma
Monitoring online biomass with a capacitance sensor during scale-up of industrially relevant CHO cell culture fed-batch processes in single-use bioreactors
In 2004, the FDA published a guideline to implement process analytical technologies (PAT) in biopharmaceutical processes for process monitoring to gain process understanding and for the control of important process parameters. Viable cell concentration (VCC) is one of the most important key performance indicator (KPI) during mammalian cell cultivation processes. Commonly, this is measured offline. In this work, we demonstrated the comparability and scalability of linear regression models derived from online capacitance measurements. The linear regressions were used to predict the VCC and other familiar offline biomass indicators, like the viable cell volume (VCV) and the wet cell weight (WCW), in two different industrially relevant CHO cell culture processes (Process A and Process B). Therefore, different single-use bioreactor scales (50–2000 L) were used to prove feasibility and scalability of the in-line sensor integration. Coefficient of determinations of 0.79 for Process A and 0.99 for Process B for the WCW were achieved. The VCV was described with high coefficients of determination of 0.96 (Process A) and 0.98 (Process B), respectively. In agreement with other work from the literature, the VCC was only described within the exponential growth phase, but resulting in excellent coefficients of determination of 0.99 (Process A) and 0.96 (Process B), respectively. Monitoring these KPIs online using linear regression models appeared to be scale-independent, enabled deeper process understanding (e.g. here demonstrated in monitoring, the feeding profile) and showed the potential of this method for process control. © 2019, The Author(s)
Spinfoams in the holomorphic representation
We study a holomorphic representation for spinfoams. The representation is
obtained via the Ashtekar-Lewandowski-Marolf-Mour\~ao-Thiemann coherent state
transform. We derive the expression of the 4d spinfoam vertex for Euclidean and
for Lorentzian gravity in the holomorphic representation. The advantage of this
representation rests on the fact that the variables used have a clear
interpretation in terms of a classical intrinsic and extrinsic geometry of
space. We show how the peakedness on the extrinsic geometry selects a single
exponential of the Regge action in the semiclassical large-scale asymptotics of
the spinfoam vertex.Comment: 10 pages, 1 figure, published versio
Long-term exposure to elevated pCO2 more than warming modifies juvenile shell growth patterns in a temperate gastropod
Co-occurring global change drivers, such as ocean warming and acidification, can have large impacts on the behaviour, physiology, and health of marine organisms. However, whilst early-life stages are thought to be most sensitive to these impacts, little is known about the individual level processes by which such impacts take place. Here, using mesocosm experiments simulating ocean warming (OW) and ocean acidification (OA) conditions expected for the NE Atlantic region by 2100 using a variety of treatments of elevated pCO2 and temperature. We investigated their impacts on bio-mineralization, microstructure, and ontogeny of Nucella lapillus (L.) juveniles, a common gastropod predator that exerts important top-down controls on biodiversity patterns in temperate rocky shores. The shell of juveniles hatched in mesocosms during a 14 month long experiment were analysed using micro-CT scanning, 3D geometric morphometrics, and scanning-electron microscopy. Elevated temperature and age determined shell density, length, width, thickness, elemental chemistry, shape, and shell surface damages. However, co-occurring elevated pCO2 modified the impacts of elevated temperature, in line with expected changes in carbonate chemistry driven by temperature. Young N. lapillus from acidified treatments had weaker shells and were therefore expected to be more vulnerable to predation and environmental pressures such as wave action. However, in some instances, the effects of both higher CO2 content and elevated temperature appeared to have reversed as the individuals aged. This study suggests that compensatory development may therefore occur, and that expected increases in juvenile mortality under OA and OW may be counteracted, to some degree, by high plasticity in shell formation in this species. This feature may prove advantageous for N. lapillus community dynamics in near-future conditions
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