37 research outputs found
Can we constrain the aftermath of binary neutron star mergers with short gamma-ray bursts?
The joint observation of GW170817 and GRB170817A proved that binary neutron
star (BNS) mergers are progenitors of short Gamma-ray Bursts (SGRB): this
established a direct link between the still unsettled SGRB central engine and
the outcome of BNS mergers, whose nature depends on the equation of state (EOS)
and on the masses of the NSs. We propose a novel method to probe the central
engine of SGRBs based on this link. We produce an extended catalog of BNS
mergers by combining recent theoretically predicted BNS merger rate as a
function of redshift and the NS mass distribution inferred from measurements of
Galactic BNSs. We use this catalog to predict the number of BNS systems ending
as magnetars (stable or Supramassive NS) or BHs (formed promptly or after the
collapse of a hypermassive NS) for different EOSs, and we compare these
outcomes with the observed rate of SGRBs. Despite the uncertainties mainly
related to the poor knowledge of the SGRB jet structure, we find that for most
EOSs the rate of magnetars produced after BNS mergers is sufficient to power
all the SGRBs, while scenarios with only BHs as possible central engine seems
to be disfavoured.Comment: Accepted for publication in MNRAS Letter
XX males SRY negative: a confirmed cause of infertility
BACKGROUND:
SOX9 is a widely expressed transcription factor playing several relevant functions during development and essential for testes differentiation. It is considered to be the direct target gene of the protein encoded by SRY and its overexpression in an XX murine gonad can lead to male development in the absence of Sry. Recently, a family was reported with a 178 kb duplication in the gene desert region ending about 500 kb upstream of SOX9 in which 46,XY duplicated persons were completely normal and fertile whereas the 46,XX ones were males who came to clinical attention because of infertility.
METHODS AND RESULTS:
We report a family with two azoospermic brothers, both 46,XX, SRY negative, having a 96 kb triplication 500 kb upstream of SOX9. Both subjects have been analyzed trough oligonucleotide array-CGH and the triplication was confirmed and characterised through qPCR, defining the minimal region of amplification upstream of SOX9 associated with 46,XX infertile males, SRY negative.
CONCLUSIONS:
Our results confirm that even in absence of SRY, complete male differentiation may occur, possibly driven by overexpression of SOX9 in the gonadal ridge, as a consequence of the amplification of a gene desert region. We hypothesize that this region contains gonadal specific long-range regulation elements whose alteration may impair the normal sex development. Our data show that normal XX males, with alteration in copy number or, possibly, in the critical sequence upstream to SOX9 are a new category of infertility inherited in a dominant way with expression limited to the XX background
The Blackholic energy and the canonical Gamma-Ray Burst IV: the "long", "genuine short" and "fake - disguised short" GRBs
(Shortened) [...] After recalling the basic features of the "fireshell
model", we emphasize the following novel results: 1) the interpretation of the
X-ray flares in GRB afterglows as due to the interaction of the optically thin
fireshell with isolated clouds in the CircumBurst Medium (CBM); 2) an
interpretation as "fake - disguised" short GRBs of the GRBs belonging to the
class identified by Norris & Bonnell [...] consistent with an origin from the
final coalescence of a binary system in the halo of their host galaxies with
particularly low CBM density [...]; 3) the first attempt to study a genuine
short GRB with the analysis of GRB 050509B, that reveals indeed still an open
question; 4) the interpretation of the GRB-SN association in the case of GRB
060218 via the "induced gravitational collapse" process; 5) a first attempt to
understand the nature of the "Amati relation", a phenomenological correlation
between the isotropic-equivalent radiated energy of the prompt emission E_{iso}
with the cosmological rest-frame \nu F_{\nu} spectrum peak energy E_{p,i}. In
addition, recent progress on the thermalization of the electron-positron plasma
close to their formation phase, as well as the structure of the electrodynamics
of Kerr-Newman Black Holes are presented. An outlook for possible explanation
of high-energy phenomena in GRBs to be expected from the AGILE and the Fermi
satellites are discussed. As an example of high energy process, the work by
Enrico Fermi dealing with ultrarelativistic collisions is examined. It is clear
that all the GRB physics points to the existence of overcritical
electrodynamical fields. In this sense we present some progresses on a unified
approach to heavy nuclei and neutron stars cores, which leads to the existence
of overcritical fields under the neutron star crust.Comment: 68 pages, 50 figures, in the Proceedings of the XIII Brazilian School
on Cosmology and Gravitation, M. Novello, S.E. Perez-Bergliaffa, editor
On Gamma-Ray Bursts
(Shortened) We show by example how the uncoding of Gamma-Ray Bursts (GRBs)
offers unprecedented possibilities to foster new knowledge in fundamental
physics and in astrophysics. After recalling some of the classic work on vacuum
polarization in uniform electric fields by Klein, Sauter, Heisenberg, Euler and
Schwinger, we summarize some of the efforts to observe these effects in heavy
ions and high energy ion collisions. We then turn to the theory of vacuum
polarization around a Kerr-Newman black hole, leading to the extraction of the
blackholic energy, to the concept of dyadosphere and dyadotorus, and to the
creation of an electron-positron-photon plasma. We then present a new
theoretical approach encompassing the physics of neutron stars and heavy
nuclei. It is shown that configurations of nuclear matter in bulk with global
charge neutrality can exist on macroscopic scales and with electric fields
close to the critical value near their surfaces. These configurations may
represent an initial condition for the process of gravitational collapse,
leading to the creation of an electron-positron-photon plasma: the basic
self-accelerating system explaining both the energetics and the high energy
Lorentz factor observed in GRBs. We then turn to recall the two basic
interpretational paradigms of our GRB model. [...] We then turn to the special
role of the baryon loading in discriminating between "genuine" short and long
or "fake" short GRBs [...] We finally turn to the GRB-Supernova Time Sequence
(GSTS) paradigm: the concept of induced gravitational collapse. [...] We then
present some general conclusions.Comment: 138 pages, 62 figures, to appear on the Proceedings of the Eleventh
Marcel Grossmann Meeting, Berlin (Germany), July 200
Case Report - Multinodular goiter in a patient with Congenital Hypothyroidism and Bannayan-Riley-Ruvalcaba syndrome: the possible synergic role of TPO and PTEN mutation
We report the case of a paediatric female patient affected by Bannayan-Riley-Ruvalcaba syndrome (BRRS) and congenital hypothyroidism (CH) with homozygous mutation of the TPO gene. She underwent total thyroidectomy at the age of seven years because of the development of a multinodular goiter. BRRS patients present an increased risk of benign and malignant thyroid disease since childhood because of inactivating mutation of PTEN, an onco-suppressor gene. Instead, homozygous mutations in the TPO gene can be associated with severe forms of hypothyroidism with goiter; previous studies have described cases of follicular and papillary thyroid cancer in CH patients with TPO mutation despite a perfectly controlled thyroid function with Levothyroxine therapy. To our knowledge, this is the first case that describes the possible synergic role of coexisting mutation of both TPO and PTEN in the development of multinodular goiter underlining the importance of a tailored surveillance program in these patients, especially during childhood
De Novo Unbalanced Translocations in Prader-Willi and Angelman Syndrome Might Be the Reciprocal Product of inv dup(15)s
The 15q11-q13 region is characterized by high instability, caused by the presence of several paralogous segmental duplications. Although most mechanisms dealing with cryptic deletions and amplifications have been at least partly characterized, little is known about the rare translocations involving this region. We characterized at the molecular level five unbalanced translocations, including a jumping one, having most of 15q transposed to the end of another chromosome, whereas the der(15)(pter->q11-q13) was missing. Imbalances were associated either with Prader-Willi or Angelman syndrome. Array-CGH demonstrated the absence of any copy number changes in the recipient chromosome in three cases, while one carried a cryptic terminal deletion and another a large terminal deletion, already diagnosed by classical cytogenetics. We cloned the breakpoint junctions in two cases, whereas cloning was impaired by complex regional genomic architecture and mosaicism in the others. Our results strongly indicate that some of our translocations originated through a prezygotic/postzygotic two-hit mechanism starting with the formation of an acentric 15qter->q1::q1->qter representing the reciprocal product of the inv dup(15) supernumerary marker chromosome. An embryo with such an acentric chromosome plus a normal chromosome 15 inherited from the other parent could survive only if partial trisomy 15 rescue would occur through elimination of part of the acentric chromosome, stabilization of the remaining portion with telomere capture, and formation of a derivative chromosome. All these events likely do not happen concurrently in a single cell but are rather the result of successive stabilization attempts occurring in different cells of which only the fittest will finally survive. Accordingly, jumping translocations might represent successful rescue attempts in different cells rather than transfer of the same 15q portion to different chromosomes. We also hypothesize that neocentromerization of the original acentric chromosome during early embryogenesis may be required to avoid its loss before cell survival is finally assured
Molecular Mechanisms Generating and Stabilizing Terminal 22q13 Deletions in 44 Subjects with Phelan/McDermid Syndrome
In this study, we used deletions at 22q13, which represent a substantial source of human pathology (Phelan/McDermid syndrome), as a model for investigating the molecular mechanisms of terminal deletions that are currently poorly understood. We characterized at the molecular level the genomic rearrangement in 44 unrelated patients with 22q13 monosomy resulting from simple terminal deletions (72%), ring chromosomes (14%), and unbalanced translocations (7%). We also discovered interstitial deletions between 17–74 kb in 9% of the patients. Haploinsufficiency of the SHANK3 gene, confirmed in all rearrangements, is very likely the cause of the major neurological features associated with PMS. SHANK3 mutations can also result in language and/or social interaction disabilities. We determined the breakpoint junctions in 29 cases, providing a realistic snapshot of the variety of mechanisms driving non-recurrent deletion and repair at chromosome ends. De novo telomere synthesis and telomere capture are used to repair terminal deletions; non-homologous end-joining or microhomology-mediated break-induced replication is probably involved in ring 22 formation and translocations; non-homologous end-joining and fork stalling and template switching prevail in cases with interstitial 22q13.3. For the first time, we also demonstrated that distinct stabilizing events of the same terminal deletion can occur in different early embryonic cells, proving that terminal deletions can be repaired by multistep healing events and supporting the recent hypothesis that rare pathogenic germline rearrangements may have mitotic origin. Finally, the progressive clinical deterioration observed throughout the longitudinal medical history of three subjects over forty years supports the hypothesis of a role for SHANK3 haploinsufficiency in neurological deterioration, in addition to its involvement in the neurobehavioral phenotype of PMS
GRB 090423 at redshift 8.1: A theoretical interpretation
GRB 090423 is the farthest gamma ray burst ever observed, with a redshift of about 8.1. We present within the fireshell scenario a complete analysis of this GRB.We model the prompt emission and the first rapid flux decay of the afterglow emission as being to the canonical emission of the interaction in the interval 0 ≤ t ≤ 440 s by using accelerated baryonic matter with the circumburst medium. After the data reduction of the Swift data in the BAT (15 - 150 keV) and XRT (0.2 - 10 keV) energy bands, we interpret the light curves and the spectral distribution in the context of the fireshell scenario. We also confirm in this source the existence of a second component, a plateau phase, as being responsible for the late emission in the X-ray light curve. This extra component originates from the fact that the ejecta have a range of the bulk Lorentz I' factor, which starts to interact each other ejecta at the start of the plateau phase