4,763 research outputs found
Pairing and alpha-like quartet condensation in N=Z nuclei
We discuss the treatment of isovector pairing by an alpha-like quartet
condensate which conserves exactly the particle number, the spin and the
isospin. The results show that the quartet condensate describes accurately the
isovector pairing correlations in the ground state of systems with an equal
number of protons and neutronsComment: 4 pages, to appear in Journal of Physics: Conference Serie
Abnormal plasma DNA profiles in early ovarian cancer using a non-invasive prenatal testing platform: Implications for cancer screening
Background: Non-invasive prenatal testing (NIPT) identifies fetal aneuploidy by sequencing cell-free DNA in the maternal plasma. Pre-symptomatic maternal malignancies have been incidentally detected during NIPT based on abnormal genomic profiles. This low coverage sequencing approach could have potential for ovarian cancer screening in the non-pregnant population. Our objective was to investigate whether plasma DNA sequencing with a clinical whole genome NIPT platform can detect early- and late-stage high-grade serous ovarian carcinomas (HGSOC).
Methods: This is a case control study of prospectively-collected biobank samples comprising preoperative plasma from 32 women with HGSOC (16 âearly cancerâ (FIGO IâII) and 16 âadvanced cancerâ (FIGO IIIâIV)) and 32 benign controls. Plasma DNA from cases and controls were sequenced using a commercial NIPT platform and chromosome dosage measured. Sequencing data were blindly analyzed with two methods: (1) Subchromosomal changes were called using an open source algorithm WISECONDOR (WIthin-SamplE COpy Number aberration DetectOR). Genomic gains or losses â„ 15 Mb were prespecified as âscreen positiveâ calls, and mapped to recurrent copy number variations reported in an ovarian cancer genome atlas. (2) Selected whole chromosome gains or losses were reported using the routine NIPT pipeline for fetal aneuploidy.
Results: We detected 13/32 cancer cases using the subchromosomal analysis (sensitivity 40.6 %, 95 % CI, 23.7â59.4 %), including 6/16 early and 7/16 advanced HGSOC cases. Two of 32 benign controls had subchromosomal gains â„ 15 Mb (specificity 93.8 %, 95 % CI, 79.2â99.2 %). Twelve of the 13 true positive cancer cases exhibited specific recurrent changes reported in HGSOC tumors. The NIPT pipeline resulted in one âmonosomy 18â call from the cancer group, and two âmonosomy Xâ calls in the controls.
Conclusions: Low coverage plasma DNA sequencing used for prenatal testing detected 40.6 % of all HGSOC, including 38 % of early stage cases. Our findings demonstrate the potential of a high throughput sequencing platform to screen for early HGSOC in plasma based on characteristic multiple segmental chromosome gains and losses. The performance of this approach may be further improved by refining bioinformatics algorithms and targeting selected cancer copy number variations.
Abbreviations: CNV, copy number variation; HGSOC, high grade serous ovarian carcinoma; NIPT, non-invasive prenatal testing; WISECONDOR, within sample copy number aberration detecto
Synchronous Disease Kinetics in a Murine Model for Enterohemorrhagic E. coli Infection Using Food-Borne Inoculation
Upon colonization of the intestinal epithelium, the attaching and effacing (AE) pathogen Enterohemorrhagic Escherichia coli (EHEC) effaces microvilli and forms pedestal-like structures beneath the adherent bacterium. The production of one of its virulence factors, the phage-encoded Shiga toxin (Stx) results in systemic disease, including the development of renal failure. Although EHEC does not productively infect conventional mice, EHEC infection can be modeled in mice utilizing a derivative of the natural murine AE pathogen Citrobacter rodentium(CR). Gavage of mice with CR(ΊStx2dact), a C. rodentium lysogenized by a phage encoding an Stx variant with high potency in mice, features AE lesion formation on intestinal epithelium and Stx-mediated systemic disease, including renal damage. This model is somewhat limited by mouse-to-mouse variation in the course of disease, with the time to severe morbidity (and required euthanasia) varying by as many as 5 days, a feature that limits pathological analysis at defined stages of disease. In the current study, we altered and optimized the preparation, dose, and mode of delivery of CR(ΊStx2dact), using food-borne route of infection to generate highly synchronous disease model. We found that food-borne inoculation of as few as 3 x 104 CR(ΊStx2dact) resulted in productive colonization and severe systemic disease. Upon inoculation of 1 x 108 bacteria, the majority of infected animals suffered weight loss beginning 5 days post-infection and all required euthanasia on day 6 or 7. This enhanced murine model for EHEC infection should facilitate characterization of the pathology associated with specific phases of Stx-mediated disease
General pairing interactions and pair truncation approximations for fermions in a single-j shell
We investigate Hamiltonians with attractive interactions between pairs of
fermions coupled to angular momentum J. We show that pairs with spin J are
reasonable building blocks for the low-lying states. For systems with only a J
= Jmax pairing interaction, eigenvalues are found to be approximately integers
for a large array of states, in particular for those with total angular momenta
I le 2j. For I=0 eigenstates of four fermions in a single-j shell we show that
there is only one non-zero eigenvalue. We address these observations using the
nucleon pair approximation of the shell model and relate our results with a
number of currently interesting problems.Comment: a latex text file and 2 figures, to be publishe
Fiber-Cavity-Based Optomechanical Device
We describe an optomechanical device consisting of a fiber-based optical
cavity containing a silicon nitiride membrane. In comparison with typical
free-space cavities, the fiber-cavity's small mode size (10 {\mu}m waist, 80
{\mu}m length) allows the use of smaller, lighter membranes and increases the
cavity-membrane linear coupling to 3 GHz/nm and quadratic coupling to 20
GHz/nm^2. This device is also intrinsically fiber-coupled and uses glass
ferrules for passive alignment. These improvements will greatly simplify the
use of optomechanical systems, particularly in cryogenic settings. At room
temperature, we expect these devices to be able to detect the shot noise of
radiation pressure.Comment: 4 pages, 3 figures; the following article has been submitted to
Applied Physics Letter
Classification of states of single- fermions with -pairing interaction
In this paper we show that a system of three fermions is exactly solvable for
the case of a single- in the presence of an angular momentum- pairing
interaction. On the basis of the solutions for this system, we obtain new sum
rules for six- symbols. It is also found that the "non-integer" eigenvalues
of three fermions with angular momentum around the maximum appear as
"non-integer" eigenvalues of four fermions when is around (or larger than)
and the Hamiltonian contains only an interaction between pairs of
fermions coupled to spin . This pattern is also found in
five and six fermion systems. A boson system with spin exhibits a similar
pattern.Comment: to be published in Physical Review
Patterns of the ground states in the presence of random interactions: nucleon systems
We present our results on properties of ground states for nucleonic systems
in the presence of random two-body interactions. In particular we present
probability distributions for parity, seniority, spectroscopic (i.e., in the
laboratory framework) quadrupole moments and clustering in the ground
states. We find that the probability distribution for the parity of the ground
states obtained by a two-body random ensemble simulates that of realistic
nuclei: positive parity is dominant in the ground states of even-even nuclei
while for odd-odd nuclei and odd-mass nuclei we obtain with almost equal
probability ground states with positive and negative parity. In addition we
find that for the ground states, assuming pure random interactions, low
seniority is not favored, no dominance of positive values of spectroscopic
quadrupole deformation, and no sign of -cluster correlations, all in
sharp contrast to realistic nuclei. Considering a mixture of a random and a
realistic interaction, we observe a second order phase transition for the
-cluster correlation probability.Comment: 7 page
Neutrino Pair Bremsstrahlung in Neutron Star Crusts: a Reappraisal
We demonstrate that band-structure effects suppress bremsstrahlung of
neutrino pairs by electrons in the crusts of neutron stars at temperatures of
the order of and below. Taking this into account,
together with the fact that recent work indicates that the masses of neutron
star crusts are considerably smaller than previously estimated, we find
neutrino pair bremsstrahlung to be much less important for the thermal
evolution of neutron stars than earlier calculations suggested.Comment: 11 plain LaTeX pages, 3 figures available on request, NORDITA-93/72
A/S/
Discovery of the Acoustic Faraday Effect in Superfluid 3He-B
We report the discovery of the acoustic Faraday effect in superfluid 3He-B.
The observation of this effect provides the first direct evidence for
propagating transverse acoustic waves in liquid 3He, a mode first predicted by
Landau in 1957. The Faraday rotation is large and observable because of
spontaneously broken spin-orbit symmetry in 3He-B. We compare the experimental
observations with a simulation of the transverse acoustic impedance that
includes the field-induced circular birefringence of transverse waves.Comment: 4 pages in RevTex plus 3 postscript figures; new version includes:
minor corrections to the text and an updated of list of reference
Contribution of the massive photon decay channel to neutrino cooling of neutron stars
We consider massive photon decay reactions via intermediate states of
electron-electron-holes and proton-proton-holes into neutrino-antineutrino
pairs in the course of neutron star cooling. These reactions may become
operative in hot neutron stars in the region of proton pairing where the photon
due to the Higgs-Meissner effect acquires an effective mass that
is small compared to the corresponding plasma frequency. The contribution of
these reactions to neutrino emissivity is calculated; it varies with the
temperature and the photon mass as
for . Estimates show that these processes appear as extra
efficient cooling channels of neutron stars at temperatures K.Comment: accepted to publication in Zh. Eksp. Teor. Fiz. (JETP
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