Holes in the walls: primordial black holes as a solution to the cosmological domain wall problem

We propose a scenario in which the cosmological domain wall and monopole problems are solved without any fine tuning of the initial conditions or parameters in the Lagrangian of an underlying filed theory. In this scenario domain walls sweep out (unwind) the monopoles from the early universe, then the fast primordial black holes perforate the domain walls, change their topology and destroy them. We find further that the (old vacuum) energy density released from the domain walls could alleviate but not solve the cosmological flatness problem.Comment: References added; Published in Phys. Rev.

MACHOs, White Dwarfs, and the Age of the Universe

(Abridged Abstract) A favored interpretation of recent microlensing measurements towards the Large Magellanic Cloud implies that a large fraction (i.e. 10--50%) of the mass of the galactic halo is composed of white dwarfs. We compare model white dwarf luminosity functions to the data from the observational surveys in order to determine a lower bound on the age of any substantial white dwarf halo population (and hence possibly on the age of the Universe). We compare various theoretical white dwarf luminosity functions, in which we vary hese three parameters, with the abovementioned survey results. From this comparison, we conclude that if white dwarfs do indeed constitute more than 10% of the local halo mass density, then the Universe must be at least 10 Gyr old for our most extreme allowed values of the parameters. When we use cooling curves that account for chemical fractionation and more likely values of the IMF and the bolometric correction, we find tighter limits: a white dwarf MACHO fraction of 10% (30%) requires a minimum age of 14 Gyr (15.5 Gyr). Our analysis also indicates that the halo white dwarfs almost certainly have helium-dominated atmospheres.Comment: Final version accepted for publication, straight TeX formate, 6 figs, 22 page

Evolutionary conservation of excision repair in Schizosaccharomyces pombe: Evidence for a family of sequences related to the Saccharomyces cerevisiae RAD2 gene

Cells mutated at the rad13 locus in the fission yeast, Schizosaccharomyces pombe are deficient in excision-repair of UV damage. We have cloned the S.pombe rad13 gene by its ability to complement the UV sensitivity of a rad13 mutant. The gene is not essential for cell proliferation. Sequence analysis of the cloned gene revealed an open reading-frame of 1113 amino acids with structural homology to the RAD2 gene of the distantly related Saccharomyces cerevisiae. The sequence similarity is confined to three domains, two close to the N-terminus of the encoded protein, the third being close to the C-terminus. The central region of about 500 amino acids shows little similarity between the two organisms. The first and third domains are also found in a related yet distinct pair of homologous S.pombe/S.cerevisiae DNA repair genes (rad2/YKL510), which have only a very short region between these two conserved domains. Using the polymerase chain reaction with degenerate primers, we have isolated fragments from a gene homologous to rad13/RAD2 from Aspergillus nidulans. These findings define new functional domains involved in excision-repair, as well as identifying a conserved family of genes related to RAD2

Effect of Primordial Black Holes on the Cosmic Microwave Background and Cosmological Parameter Estimates

We investigate the effect of non-evaporating primordial black holes (PBHs) on the ionization and thermal history of the universe. X-rays emitted by gas accretion onto PBHs modify the cosmic recombination history, producing measurable effects on the spectrum and anisotropies of the Cosmic Microwave Background (CMB). Using the third-year WMAP data and FIRAS data we improve existing upper limits on the abundance of PBHs with masses >0.1 Msun by several orders of magnitude. Fitting WMAP3 data with cosmological models that do not allow for non-standard recombination histories, as produced by PBHs or other early energy sources, may lead to an underestimate of the best-fit values of the amplitude of linear density fluctuations (sigma_8) and the scalar spectral index (n_s). Cosmological parameter estimates are affected because models with PBHs allow for larger values of the Thomson scattering optical depth, whose correlation with other parameters may not be correctly taken into account when PBHs are ignored. Values of tau_e=0.2, n_s=1 and sigma_8=0.9 are allowed at 95% CF. This result that may relieve recent tension between WMAP3 data and clusters data on the value of sigma_8. PBHs may increase the primordial molecular hydrogen abundance by up to two orders of magnitude, this promoting cooling and star formation. The suppression of galaxy formation due to X-ray heating is negligible for models consistent with the CMB data. Thus, the formation rate of the first galaxies and stars would be enhanced by a population of PBHs.Comment: 17 pages (Apj style), 9 figures, submitted to Ap

Rapid Depletion of Target Proteins Allows Identification of Coincident Physiological Responses

Targeted protein degradation is a powerful tool that can be used to create unique physiologies depleted of important factors. Current strategies involve modifying a gene of interest such that a degradation peptide is added to an expressed target protein and then conditionally activating proteolysis, either by expressing adapters, unmasking cryptic recognition determinants, or regulating protease affinities using small molecules. For each target, substantial optimization may be required to achieve a practical depletion, in that the target remains present at a normal level prior to induction and is then rapidly depleted to levels low enough to manifest a physiological response. Here, we describe a simplified targeted degradation system that rapidly depletes targets and that can be applied to a wide variety of proteins without optimizing target protease affinities. The depletion of the target is rapid enough that a primary physiological response manifests that is related to the function of the target. Using ribosomal protein Si as an example, we show that the rapid depletion of this essential translation factor invokes concomitant changes to the levels of several mRNAs, even before appreciable cell division has occurred

Growth of structure seeded by primordial black holes

We discuss the possibilities for primordial black holes (PBHs) to grow via the accretion of dark matter. In agreement with previous works, we find that accretion during the radiation-dominated era does not lead to a significant mass increase. However, during matter-domination, PBHs may grow by up to two orders of magnitude in mass through the acquisition of large dark matter halos. We discuss the possibility of PBHs being an important component in dark matter halos of galaxies as well as their potential to explain the ultra-luminous x-ray sources (ULXs) observed in nearby galactic disks. We point out that although PBHs are ruled out as the dominant component of dark matter, there is still a great deal of parameter space open to them playing a role in the modern-day universe. For example, a primordial halo population of PBHs each at $10^{2.5} M_\odot$ making up 0.1% of the dark matter grow to $10^{4.5} M_\odot$ via the accumulation of dark matter halos to account for $\sim 10$ of the dark matter mass by a redshift of $z \approx 30$. These intermediate mass black holes may then ``light up'' when passing through molecular clouds, becoming visible as ULXs at the present day, or they may form the seeds for supermassive black holes at the centers of galaxies.Comment: 10 pages, 5 figures. Submitted to Ap

Anomalous metamagnetism in the low carrier density Kondo lattice YbRh3Si7

We report complex metamagnetic transitions in single crystals of the new low carrier Kondo antiferromagnet YbRh3Si7. Electrical transport, magnetization, and specific heat measurements reveal antiferromagnetic order at T_N = 7.5 K. Neutron diffraction measurements show that the magnetic ground state of YbRh3Si7 is a collinear antiferromagnet where the moments are aligned in the ab plane. With such an ordered state, no metamagnetic transitions are expected when a magnetic field is applied along the c axis. It is therefore surprising that high field magnetization, torque, and resistivity measurements with H||c reveal two metamagnetic transitions at mu_0H_1 = 6.7 T and mu_0H_2 = 21 T. When the field is tilted away from the c axis, towards the ab plane, both metamagnetic transitions are shifted to higher fields. The first metamagnetic transition leads to an abrupt increase in the electrical resistivity, while the second transition is accompanied by a dramatic reduction in the electrical resistivity. Thus, the magnetic and electronic degrees of freedom in YbRh3Si7 are strongly coupled. We discuss the origin of the anomalous metamagnetism and conclude that it is related to competition between crystal electric field anisotropy and anisotropic exchange interactions.Comment: 23 pages and 4 figures in the main text. 7 pages and 5 figures in the supplementary materia

Constraints on dark matter particles charged under a hidden gauge group from primordial black holes

In order to accommodate increasingly tighter observational constraints on dark matter, several models have been proposed recently in which dark matter particles are charged under some hidden gauge group. Hidden gauge charges are invisible for the standard model particles, hence such scenarios are very difficult to constrain directly. However black holes are sensitive to all gauge charges, whether they belong to the standard model or not. Here, we examine the constraints on the possible values of the dark matter particle mass and hidden gauge charge from the evolution of primordial black holes. We find that the existence of the primordial black holes with reasonable mass is incompatible with dark matter particles whose charge to mass ratio is of the order of one. For dark matter particles whose charge to mass ratio is much less than one, we are able to exclude only heavy dark matter in the mass range of 10^(11) GeV - 10^(16) GeV. Finally, for dark matter particles whose charge to mass ratio is much greater than one, there are no useful limits coming from primordial black holes.Comment: accepted for publication in JCA

Nasopharyngeal carriage of pneumococcus in children in England up to 10 years after 13-valent pneumococcal conjugate vaccine introduction: persistence of serotypes 3 and 19A and emergence of 7C

Background: Monitoring changes in pharyngeal carriage of pneumococcus in children following 13-valent pneumococcal conjugate vaccine (PCV13) introduction in the United Kingdom in 2010 informs understanding of patterns of invasive pneumococcal disease (IPD) incidence. Methods: Nasopharyngeal swabs from healthy children vaccinated with PCV13 according to schedule (2, 4, and 12 months) were cultured and serotyped. Results for children aged 13–48 months were compared between 2014–2015 and 2017–2019 and with children aged 6–12 months (2017–2020). Blood was obtained from a subset of children for pneumococcal serotype-specific immunoglobulin G (IgG). Results: Total pneumococcal carriage at 13–48 months was 47.9% (473/988) in 2014–2015 and 51.8% (412/795) in 2017–2019 (P = .10); at age 6–12 months this value was 44.6% (274/615). In 2017–2019, 2.9% (95% confidence interval, 1.8%–4.3%) of children aged 13–48 months carried PCV13 serotypes (mainly 3 [1.5%] and 19A [0.8%]) and >20% carried the additional 20-valent PCV (PCV20) serotypes. Similar proportions of children had IgG ≥0.35 IU/mL for each serotype in 2014–2015 and 2017–2019. Serotype 7C carriage increased significantly (P < .01) between 2014–2015 and 2017–2019. Carriage of PCV20 serotypes 8 and 12F, both major causes of IPD, was rare. Conclusions: Introduction of PCV20, if licensed for children, could significantly change the composition of pneumococcal serotypes carried in the pharynx of UK children. Clinical Trials Registration: NCT03102840

Transcriptional Profiling of Bacillus anthracis Sterne (34F2) during Iron Starvation

Lack of available iron is one of many environmental challenges that a bacterium encounters during infection and adaptation to iron starvation is important for the pathogen to efficiently replicate within the host. Here we define the transcriptional response of B. anthracis Sterne (34F2) to iron depleted conditions. Genome-wide transcript analysis showed that B. anthracis undergoes considerable changes in gene expression during growth in iron-depleted media, including the regulation of known and candidate virulence factors. Two genes encoding putative internalin proteins were chosen for further study. Deletion of either gene (GBAA0552 or GBAA1340) resulted in attenuation in a murine model of infection. This attenuation was amplified in a double mutant strain. These data define the transcriptional changes induced during growth in low iron conditions and illustrate the potential of this dataset in the identification of putative virulence determinants for future study