21,063 research outputs found
Cold dark matter models with high baryon content
Recent results have suggested that the density of baryons in the Universe,
OmegaB, is much more uncertain than previously thought, and may be
significantly higher. We demonstrate that a higher OmegaB increases the
viability of critical-density cold dark matter (CDM) models. High baryon
fraction offers the twin benefits of boosting the first peak in the microwave
anisotropy power spectrum and of suppressing short-scale power in the matter
power spectrum. These enable viable CDM models to have a larger Hubble constant
than otherwise possible. We carry out a general exploration of high OmegaB CDM
models, varying the Hubble constant h and the spectral index n. We confront a
variety of observational constraints and discuss specific predictions. Although
some observational evidence may favour baryon fractions as high as 20 per cent,
we find that values around 10 to 15 per cent provide a reasonable fit to a wide
range of data. We suggest that models with OmegaB in this range, with h about
0.5 and n about 0.8, are currently the best critical-density CDM models.Comment: 14 pages, LaTeX, with 9 included figures, to appear in MNRAS. Revised
version includes updated references, some changes to section 4. Conclusions
unchange
Compactness of the space of causal curves
We prove that the space of causal curves between compact subsets of a
separable globally hyperbolic poset is itself compact in the Vietoris topology.
Although this result implies the usual result in general relativity, its proof
does not require the use of geometry or differentiable structure.Comment: 15 page
Transmission and Reflection of Bose-Einstein Condensates Incident on a Gaussian Potential Barrier
We investigate how Bose-Einstein condensates, whose initial state is either
irrotational or contains a single vortex, scatter off a one-dimensional
Gaussian potential barrier. We find that for low atom densities the vortex
structure within the condensate is maintained during scattering, whereas at
medium and high densities, multiple additional vortices can be created by the
scattering process, resulting in complex dynamics and disruption of the atom
cloud. This disruption originates from two different mechanisms associated
respectively with the initial rotation of the atom cloud and the interference
between the incident and reflected matter waves. We investigate how the
reflection probability depends on the vorticity of the initial state and on the
incident velocity of the Bose-Einstein condensate. To interpret our results, we
derive a general analytical expression for the reflection coefficient of a
rotating Bose-Einstein condensate that scatters off a spatially-varying
one-dimensional potential.Comment: 9 pages, 9 figure
Anomalous quantum reflection of Bose-Einstein condensates from a silicon surface: the role of dynamical excitations
We investigate the effect of inter-atomic interactions on the
quantum-mechanical reflection of Bose-Einstein condensates from regions of
rapid potential variation. The reflection process depends critically on the
density and incident velocity of the condensate. For low densities and high
velocities, the atom cloud has almost the same form before and after
reflection. Conversely, at high densities and low velocities, the reflection
process generates solitons and vortex rings that fragment the condensate. We
show that this fragmentation can explain the anomalously low reflection
probabilities recently measured for low-velocity condensates incident on a
silicon surface.Comment: 5 figures, 5 pages, references correcte
The connexin mimetic peptide Gap27 and Cx43-Knockdown reveal differential roles for Connexin43 in wound closure events in skin model systems
In the epidermis, remodelling of Connexin43 is a key event in wound closure. However, controversy between the role of connexin channel and non-channel functions exist. We compared the impact of SiRNA targeted to Connexin43 and the connexin mimetic peptide Gap27 on scrape wound closure rates and hemichannel signalling in adult keratinocytes (AK) and fibroblasts sourced from juvenile foreskin (JFF), human neonatal fibroblasts (HNDF) and adult dermal tissue (ADF). The impact of these agents, following 24 h exposure, on (encoding Connexin43), and gene expression, and Connexin43 and pSmad3 protein expression levels, were examined by qPCR and Western Blot respectively. In all cell types Gap27 (100-100 μM) attenuated hemichannel activity. In AK and JFF cells, Gap27 (100 nM-100 μM) enhanced scrape wound closure rates by ~50% but did not influence movement in HNDF or ADF cells. In both JF and AK cells, exposure to Gap27 for 24 h reduced the level of Cx43 protein expression but did not affect the level in ADF and HNDF cells. Connexin43-SiRNA enhanced scrape wound closure in all the cell types under investigation. In HDNF and ADF, Connexin43-SiRNA enhanced cell proliferation rates, with enhanced proliferation also observed following exposure of HDNF to Gap27. By contrast, in JFF and AK cells no changes in proliferation occurred. In JFF cells, Connexin43-SiRNA enhanced levels and in JFF and ADF cells both Connexin43-SiRNA and Gap27 enhanced pSmad3 protein expression levels. We conclude that Connexin43 signalling plays an important role in cell migration in keratinocytes and foreskin derived fibroblasts, however, different pathways are evoked and in dermal derived adult and neonatal fibroblasts, inhibition of Connexin43 signalling plays a more significant role in regulating cell proliferation than cell migration
Chemistry in isolation: High CCH/HCO+ line ratio in the AMIGA galaxy CIG 638
Multi-molecule observations towards an increasing variety of galaxies have
been showing that the relative molecular abundances are affected by the type of
activity. However, these studies are biased towards bright active galaxies,
which are typically in interaction. We study the molecular composition of one
of the most isolated galaxies in the local Universe where the physical and
chemical properties of their molecular clouds have been determined by intrinsic
mechanisms. We present 3 mm broad band observations of the galaxy CIG 638,
extracted from the AMIGA sample of isolated galaxies. The emission of the J=1-0
transitions of CCH, HCN, HCO+, and HNC are detected. Integrated intensity
ratios between these line are compared with similar observations from the
literature towards active galaxies including starburst galaxies (SB), active
galactic nuclei (AGN), luminous infrared galaxies (LIRG), and GMCs in M33. A
significantly high ratio of CCH with respect to HCN, HCO+, and HNC is found
towards CIG 638 when compared with all other galaxies where these species have
been detected. This points to either an overabundance of CCH or to a relative
lack of dense molecular gas as supported by the low HCN/CO ratio, or both. The
data suggest that the CIG 638 is naturally a less perturbed galaxy where a
lower fraction of dense molecular gas, as well as a more even distribution
could explain the measured ratios. In this scenario the dense gas tracers would
be naturally dimmer, while the UV enhanced CCH, would be overproduced in a less
shielded medium.Comment: Letter accepted for publication in A&
Carbon Free Boston: Transportation Technical Report
Part of a series of reports that includes:
Carbon Free Boston: Summary Report;
Carbon Free Boston: Social Equity Report;
Carbon Free Boston: Technical Summary;
Carbon Free Boston: Buildings Technical Report;
Carbon Free Boston: Waste Technical Report;
Carbon Free Boston: Energy Technical Report;
Carbon Free Boston: Offsets Technical ReportOVERVIEW:
Transportation connects Boston’s workers, residents and tourists to their livelihoods, health care, education,
recreation, culture, and other aspects of life quality. In cities, transit access is a critical factor determining
upward mobility. Yet many urban transportation systems, including Boston’s, underserve some populations
along one or more of those dimensions. Boston has the opportunity and means to expand mobility access to
all residents, and at the same time reduce GHG emissions from transportation. This requires the
transformation of the automobile-centric system that is fueled predominantly by gasoline and diesel fuel.
The near elimination of fossil fuels—combined with more transit, walking, and biking—will curtail air
pollution and crashes, and dramatically reduce the public health impact of transportation. The City embarks
on this transition from a position of strength. Boston is consistently ranked as one of the most walkable and
bikeable cities in the nation, and one in three commuters already take public transportation.
There are three general strategies to reaching a carbon-neutral transportation system:
• Shift trips out of automobiles to transit, biking, and walking;1
• Reduce automobile trips via land use planning that encourages denser development and affordable
housing in transit-rich neighborhoods;
• Shift most automobiles, trucks, buses, and trains to zero-GHG electricity.
Even with Boston’s strong transit foundation, a carbon-neutral transportation system requires a wholesale
change in Boston’s transportation culture. Success depends on the intelligent adoption of new technologies,
influencing behavior with strong, equitable, and clearly articulated planning and investment, and effective
collaboration with state and regional partners.Published versio
What have we already learned from the CMB?
The COBE satellite, and the DMR experiment in particular, was extraordinarily
successful. However, the DMR results were announced about 7 years ago, during
which time a great deal more has been learned about anisotropies in the Cosmic
Microwave Background (CMB). The CMB experiments currently being designed and
built, including long-duration balloons, interferometers, and two space
missions, promise to address several fundamental cosmological issues. We
present our evaluation of what we already know, what we are beginning to learn
now, and what the future may bring.Comment: 20 pages, 3 figures. Changes to match version accepted by PAS
Cognitive improvement following repair of a basal encephalocele.
We report the case of a 55-year-old woman presenting with progressive memory impairment secondary to a transsphenoidal encephalocele involving her dominant medial temporal lobe. Her clinical deterioration was accompanied by radiological progression in the encephalocele's size and associated encephalomalacia. Through a temporal craniotomy, her encephalocele was resected and the defect closed. Baseline neuropsychological assessment indicated global cognitive impairment, but post-operatively, she reported improved memory and concentration. Standardized assessment reflected an improvement in perceptual skills and an associated improved recall of a complex figure. This is the first case report to date of a patient's memory improving following treatment of a basal encephalocele
The influence of style and origin on mineral composition of beers retailing in the UK
Beer has high nutritional values in terms of energy and is also a dietary source of antioxidants, carbohydrates and minerals among others. In Europe, 53 Mt of beer are produced annually, and with an average supply of 68.2 kg capita‾¹ year‾¹ among adults. In this study, the mineral composition of 125 commercial beer samples retailing in the UK, but originating from ten countries, was determined; such detailed information is lacking in UK food composition tables. Beer composition data are reported for Al, As, Ba, Ca, Cd, Co, Cr, Cs, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Se, Sr, U, V and Zn, following analysis by inductively coupled plasma mass spectrometry. ANOVA results showed higher concentrations of Mo, Pb and Sr (0.160; 491.70 × 10‾⁵; 0.38 mg L‾¹, respectively) for stout/porter style and a significant higher amount of minerals such as Al (3.835 mg L−1), Cd (8.64 × 10−5 mg L‾¹), Mn (1.02 mg L‾¹) or Ni (0.312 mg L‾¹) among others for lambic beer. Regarding the country of origin, higher Se concentrations were reported from beer brewed in the USA (0.110 mg L‾¹). It is concluded that beer style was determined to have a greater effect on beer mineral composition than origin or container type
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