4,018 research outputs found
Large lepton asymmetry from Q-balls
We propose a scenario which can explain large lepton asymmetry and small
baryon asymmetry simultaneously. Large lepton asymmetry is generated through
Affleck-Dine (AD) mechanism and almost all the produced lepton numbers are
absorbed into Q-balls (L-balls). If the lifetime of the L-balls is longer than
the onset of electroweak phase transition but shorter than the epoch of big
bang nucleosynthesis (BBN), the large lepton asymmetry in the L-balls is
protected from sphaleron effects. On the other hand, small (negative) lepton
numbers are evaporated from the L-balls due to thermal effects, which are
converted into the observed small baryon asymmetry by virtue of sphaleron
effects. Large and positive lepton asymmetry of electron type is often
requested from BBN. In our scenario, choosing an appropriate flat direction in
the minimal supersymmetric standard model (MSSM), we can produce positive
lepton asymmetry of electron type but totally negative lepton asymmetry.Comment: 10 pages, 3 figures, ReVTeX
Impact of oxygen levels on human hematopoietic stem and progenitor cell expansion
Oxygen levels are an important variable during the in vitro culture of stem cells. There has been increasing interest in the use of low oxygen to maximize proliferation and, in some cases, effect differentiation of stem cell populations. It is generally assumed that the defined pO2 in the incubator reflects the pO2 to which the stem cells are being exposed. However, we demonstrate that the pO2 experienced by cells in static culture can change dramatically during the course of culture as cell numbers increase and as the oxygen utilization by cells exceeds the diffusion of oxygen through the media. Dynamic culture (whereby the cell culture plate is in constant motion) largely eliminates this effect, and a combination of low ambient oxygen and dynamic culture results in a fourfold increase in reconstituting capacity of human hematopoietic stem cells compared with those cultured in static culture at ambient oxygen tension. Cells cultured dynamically at 5% oxygen exhibited the best expansion: 30-fold increase by flow cytometry, 120-fold increase by colony assay, and 11% of human CD45 engraftment in the bone marrow of NOD/SCID mice. To our knowledge, this is the first study to compare individual and combined effects of oxygen and static or dynamic culture on hematopoietic ex vivo expansion. Understanding and controlling the effective oxygen tension experienced by cells may be important in clinical stem cell expansion systems, and these results may have relevance to the interpretation of low oxygen culture studies
Pre-recombinational energy release and narrow features in the CMB spectrum
Energy release in the early Universe (z<~ 2x10^6) should lead to some broad
spectral distortion of the cosmic microwave background (CMB) radiation field,
which can be characterized as y-type distortion when the injection process
started at redshifts z<~ 5x10^4. Here we demonstrate that if energy was
released before the beginning of cosmological hydrogen recombination (z~1400),
closed loops of bound-bound and free-bound transitions in HI and HeII lead to
the appearance of (i) characteristic multiple narrow spectral features at dm
and cm wavelengths, and (ii) a prominent sub-millimeter feature consisting of
absorption and emission parts in the far Wien tail of CMB spectrum. The
additional spectral features are generated in the pre-recombinational epoch of
HI (z>~1800) and HeII (z>~7000), and therefore differ from those arising due to
normal cosmological recombination in the undisturbed CMB blackbody radiation
field. We present the results of numerical computations including 25 atomic
shells for both HI and HeII, and discuss the contributions of several
individual transitions in detail. As examples, we consider the case of
instantaneous energy release (e.g. due to phase transitions) and exponential
energy release because of long-lived decaying particles. Our computations show
that due to possible pre-recombinational atomic transitions the variability of
the CMB spectral distortion increases when comparing with the distortions
arising in the normal recombination epoch. The existence of these narrow
spectral features would open an unique way to separate y-distortions due to
pre-recombinational ($1400<~ z <~5x10^4) energy release from those arising in
the post-recombinational era at redshifts z<~800. (abridged)Comment: 17 pages, 12 Figures, 1 Table, submitted to A&
WMAP 5-year constraints on lepton asymmetry and radiation energy density: Implications for Planck
In this paper we set bounds on the radiation content of the Universe and
neutrino properties by using the WMAP-5 year CMB measurements complemented with
most of the existing CMB and LSS data (WMAP5+All),imposing also self-consistent
BBN constraints on the primordial helium abundance. We consider lepton
asymmetric cosmological models parametrized by the neutrino degeneracy
parameter and the variation of the relativistic degrees of freedom, due to
possible other physical processes occurred between BBN and structure formation
epochs. We find that WMAP5+All data provides strong bounds on helium mass
fraction and neutrino degeneracy parameter that rivals the similar bounds
obtained from the conservative analysis of the present data on helium
abundance. We also find a strong correlation between the matter energy density
and the redshift of matter-radiation equality, z_re, showing that we observe
non-zero equivalent number of relativistic neutrinos mainly via the change of
the of z_re, rather than via neutrino anisotropic stress claimed by the WMAP
team. We forecast that the CMB temperature and polarization measurements
observed with high angular resolutions and sensitivities by the future Planck
satellite will reduce the errors on these parameters down to values fully
consistent with the BBN bounds
Human Neurobrucellosis with Intracerebral Granuloma Caused by a Marine Mammal Brucella spp.
We present the first report of community-acquired human infections with marine mammal–associated Brucella spp. and describe the identification of these strains in two patients with neurobrucellosis and intracerebral granulomas. The identification of these isolates as marine mammal strains was based on omp2a sequence and amplification of the region flanking bp26
High Burden of Impetigo and Scabies in a Tropical Country
Scabies and impetigo are often thought of as nuisance diseases, but have the potential to cause a great deal of morbidity and even mortality if infection becomes complicated. Accurate assessments of these diseases are lacking, particularly in tropical developing countries. We performed a series of studies in infants and primary school children in Fiji, a tropical developing country in the South Pacific. Impetigo was very common: more than a quarter of school-aged children and 12% of infants had active impetigo. Scabies was also very common affecting 18% of school children and 14% of infants. The group A streptococcus was the most common infective organism followed by Staphylococcus aureus. The size of the problem has been underestimated, particularly in the Pacific. It is time for more concerted public health efforts in controlling impetigo and scabies
The care of patients with Duchenne, Becker and other muscular dystrophies in the COVID-19 pandemic
The corona virus disease 2019 (COVID-19) pandemic has resulted in the reorganization of healthcare settings affecting clinical care delivery to patients with Duchenne and Becker muscular dystrophy (DBMD) as well as other inherited muscular dystrophies. The magnitude of the impact of this public health emergency on the care of patients with DBMD is unclear as they are suspected of having an increased risk for severe manifestations of COVID-19. In this paper, the authors discuss their consensus recommendations pertaining to care of these patients during the pandemic. We address issues surrounding corticosteroid and exon skipping treatments, cardiac medications, hydroxychloroquine use, emergency/respiratory care, rehabilitation management, and the conduct of clinical trials. We highlight the importance of collaborative treatment decisions between the patient, family, and health care provider, considering any geographic or institution-specific policies and precautions for COVID-19. We advocate for continuing multidisciplinary care for these patients using telehealth
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