A New Dark Matter Candidate: Non-thermal Sterile Neutrinos

We propose a new and unique dark matter candidate: $\sim 100$ eV to $\sim 10$ keV sterile neutrinos produced via lepton number-driven resonant MSW (Mikheyev-Smirnov-Wolfenstein) conversion of active neutrinos. The requisite lepton number asymmetries in any of the active neutrino flavors range from 10$^{-3}$ to 10$^{-1}$ of the photon number - well within primordial nucleosynthesis bounds. The unique feature here is that the adiabaticity condition of the resonance strongly favors the production of lower energy sterile neutrinos. The resulting non-thermal (cold) energy spectrum can cause these sterile neutrinos to revert to non-relativistic kinematics at an early epoch, so that free-streaming lengths at or below the dwarf galaxy scale are possible. Therefore, the main problem associated with light neutrino dark matter candidates can be circumvented in our model.Comment: Latex 11 pages + 1 figur

Radiative Decay of a Long-Lived Particle and Big-Bang Nucleosynthesis

The effects of radiatively decaying, long-lived particles on big-bang nucleosynthesis (BBN) are discussed. If high-energy photons are emitted after BBN, they may change the abundances of the light elements through photodissociation processes, which may result in a significant discrepancy between the BBN theory and observation. We calculate the abundances of the light elements, including the effects of photodissociation induced by a radiatively decaying particle, but neglecting the hadronic branching ratio. Using these calculated abundances, we derive a constraint on such particles by comparing our theoretical results with observations. Taking into account the recent controversies regarding the observations of the light-element abundances, we derive constraints for various combinations of the measurements. We also discuss several models which predict such radiatively decaying particles, and we derive constraints on such models.Comment: Published version in Phys. Rev. D. Typos in figure captions correcte

Primordial Nucleosynthesis with a Decaying Tau Neutrino

A comprehensive study of the effect of an unstable tau neutrino on primordial nucleosynthesis is presented. The standard code for nucleosynthesis is modified to allow for a massive decaying tau neutrino whose daughter products include neutrinos, photons, $e^\pm$ pairs, and/or noninteracting (sterile) daughter products. Tau-neutrino decays influence primordial nucleosynthesis in three distinct ways: (i) the energy density of the decaying tau neutrino and its daughter products affect the expansion rate tending to increase $^4$He, D, and $^3$He production; (ii) electromagnetic (EM) decay products heat the EM plasma and dilute the baryon-to-photon ratio tending to decrease $^4$He production and increase D and $^3$He production; and (iii) electron neutrinos and antineutrinos produced by tau-neutrino decays increase the weak rates that govern the neutron-to-proton ratio, leading to decreased $^4$He production for short lifetimes (\la 30\sec) and masses less than about 10\MeV and increased $^4$He production for long lifetimes or large masses. The precise effect of a decaying tau neutrino on the yields of primordial nucleosynthesis and the mass-lifetime limits that follow depend crucially upon decay mode. We identify four generic decay modes that serve to bracket the wider range of possibilities:Comment: 27 pages, Latex, 12 Figures avaiable on request, FNAL--Pub--93/236-

It is time to reconsider the classification of dens fractures: an anatomical approach

A clinical study was performed to evaluate a new classification for odontoid process fractures. The external and internal anatomy of the axis has been studied. The files of 97 patients with a fracture of the odontoid process admitted to our institution were reviewed and classified according to the proposed new classification. The method was tested for reliability and validity. The patients were followed for a mean period of 14 years, in order to evaluate the outcome of these fractures and to correlate it to the fracture type. Intraobserver and interobserver agreement was excellent with intraclass correlation coefficients at levels of 0.98 and 0.85, respectively. Four types of odontoid process fractures are distinguished. Type B fractures are associated with high risk of pseudarthrosis. Existing classifications are inadequate and misleading since they do not include all types of odontoid process fractures, nor they consider the internal anatomy of the odontoid process. Classification of the odontoid process fractures has to be reconsidered as novel-imaging technology has shown new patterns of fractures. The analysis of the imaging data in the present study justifies the new classification

Type D fractures of the odontoid process

Type D fractures of the odontoid process are rare and usually occur in the elderly. The mechanism of fracture is unclear. Non-operative treatment is indicated provided that adequate immobilization using skull traction followed by either a collar or a halo vest can be achieved. The prognosis is usually favorable for this type of fractures. We present six patients with complex (type D) fractures of the odontoid process admitted and treated at our institution since 1970. There were five men and one woman with a mean age of 57.7 years (range, 16-81 years). Although there were concomitant injuries, no neurological deficits due to the odontoid process fracture was detected. All patients were treated non-operatively using skull traction or a halo vest for 8-12 weeks. One patient deceased 2 days after the injury. At the latest examination, all the remaining five patients had complete union of the odontoid process fracture; three of them had excellent range of motion and two had painful or restricted range of motion of the upper cervical spine

Translocation t(12;13)(p13;q14) in a patient with imatinib-sensitive MDS/MPD associated with resistance to treatment: Review of the literature

The category of myelodysplastic syndromes/myeloproliferative diseases (MDS/MPD) is a relatively new group of malignant hematologic diseases developed by the World Health Organization. These hematologic disorders lack the BCR/ABL fusion gene, although they can be associated with chromosomal translocations that involve genes encoding other protein kinases. Imatinib mesylate was recognized as a potent inhibitor of some of those kinases. We present a patient with a previously treated acute myeloid leukemia, who, after a 9-year-long remission, developed an MDS/MPD with normal karyotype, which initially responded to imatinib mesylate. Translocation t(12;13)(p12;q14) was detected after loss of response to imatinib treatment. Translocation t(12;13) is rare. It has been described in several hematologic malignancies including chronic myelomonocytic leukemia but not in MDS/MPD, previously described as Philadelphia-negative chronic myelogenous leukemia. Moreover, the correlation of this molecular abnormality with loss of efficacy of imatinib is unique in the literature. © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins