1,823 research outputs found
On the gravitational wave background from compact binary coalescences in the band of ground-based interferometers
This paper reports a comprehensive study on the gravitational wave (GW)
background from compact binary coalescences. We consider in our calculations
newly available observation-based neutron star and black hole mass
distributions and complete analytical waveforms that include post-Newtonian
amplitude corrections. Our results show that: (i) post-Newtonian effects cause
a small reduction in the GW background signal; (ii) below 100 Hz the background
depends primarily on the local coalescence rate and the average chirp
mass and is independent of the chirp mass distribution; (iii) the effects of
cosmic star formation rates and delay times between the formation and merger of
binaries are linear below 100 Hz and can be represented by a single parameter
within a factor of ~ 2; (iv) a simple power law model of the energy density
parameter up to 50-100 Hz is sufficient to be used
as a search template for ground-based interferometers. In terms of the
detection prospects of the background signal, we show that: (i) detection (a
signal-to-noise ratio of 3) within one year of observation by the Advanced LIGO
detectors (H1-L1) requires a coalescence rate of for binary neutron stars (binary black holes); (ii) this limit on
could be reduced 3-fold for two co-located detectors, whereas the
currently proposed worldwide network of advanced instruments gives only ~ 30%
improvement in detectability; (iii) the improved sensitivity of the planned
Einstein Telescope allows not only confident detection of the background but
also the high frequency components of the spectrum to be measured. Finally we
show that sub-threshold binary neutron star merger events produce a strong
foreground, which could be an issue for future terrestrial stochastic searches
of primordial GWs.Comment: A few typos corrected to match the published version in MNRA
Approximating electronically excited states with equation-of-motion linear coupled-cluster theory
A new perturbative approach to canonical equation-of-motion coupled-cluster
theory is presented using coupled-cluster perturbation theory. A second-order
M{\o}ller-Plesset partitioning of the Hamiltonian is used to obtain the well
known equation-of-motion many-body perturbation theory (EOM-MBPT(2)) equations
and two new equation-of-motion methods based on the linear coupled-cluster
doubles (EOM-LCCD) and linear coupled-cluster singles and doubles (EOM-LCCSD)
wavefunctions. This is achieved by performing a short-circuiting procedure on
the MBPT(2) similarity transformed Hamiltonian. These new methods are
benchmarked against very accurate theoretical and experimental spectra from 25
small organic molecules. It is found that the proposed methods have excellent
agreement with canonical EOM-CCSD state for state orderings and relative
excited state energies as well as acceptable quantitative agreement for
absolute excitation energies compared with the best estimate theory and
experimental spectra.Comment: 9 pages 3 figure
An effectual template bank for the detection of gravitational waves from inspiralling compact binaries with generic spins
We report the construction of a three-dimensional template bank for the
search for gravitational waves from inspiralling binaries consisting of
spinning compact objects. The parameter space consists of two dimensions
describing the mass parameters and one "reduced-spin" parameter, which
describes the secular (non-precessing) spin effects in the waveform. The
template placement is based on an efficient stochastic algorithm and makes use
of the semi-analytical computation of a metric in the parameter space. We
demonstrate that for "low-mass" () binaries,
this template bank achieves effective fitting factors --
towards signals from generic spinning binaries in the advanced detector era
over the entire parameter space of interest (including binary neutron stars,
binary black holes, and black hole-neutron star binaries). This provides a
powerful and viable method for searching for gravitational waves from generic
spinning low-mass compact binaries. Under the assumption that spin magnitudes
of black-holes [neutron-stars] are uniformly distributed between 0--0.98 [0 --
0.4] and spin angles are isotropically distributed, the expected improvement in
the average detection volume (at a fixed signal-to-noise-ratio threshold) of a
search using this reduced-spin bank is , as compared to a search
using a non-spinning bank.Comment: Minor changes, version appeared in Phys. Rev.
Kirurško liječenje stranog tijela u jednjaku minimalnoinvazivnom ezofagotomijom (MIOT) u indijske kornjače Flap-shell (Lissemys punctata) - prikaz slučaja
Accidental ingestion of fish hooks is common among turtles. Several techniques are available for retrieving fish hooks, ranging from simple non-invasive techniques to more complicated and invasive surgical procedures. The purpose of this case report is to document the successful surgical retrieval of an oesophageal foreign body (fish hook) using a minimally invasive oesophagotomy technique (MIOT) in an Indian Flap-shell turtle (Lissemys punctata). The adult male Indian Flap-shell turtle (Lissemys punctata) presented with a nylon thread protruding from its mouth. The dorsoventral radiographs confirmed the presence of a foreign body in the caudal oesophagus, just outside the coelomic cavity. After the induction of general anaesthesia, a sterile artificial insemination (AI) sheath was passed intraorally through the fishing line until it reached the hook. The fish hook was then retrieved by making a 5 mm incision at the point where the tip of the AI sheath was felt. The incision in the oesophagus and skin was closed in a routine manner. The turtle was kept in secure captivity for 20 days, following which it was released to its natural habitat. The oesophagotomy technique used in this case reduces the size of the incision considerably, thereby decreasing the possibility of postoperative complications.Slučajna ingestija udice među kornjačama je česta. Postoji nekoliko tehnika za uklanjanje udice, od neinvazivnih do složenijih i invazivnih kirurških zahvata. Ovaj prikaz slučaja govori o uspješnom kirurškom uklanjanju stranog tijela iz jednjaka (udice) primjenom minimalnoinvazivne ezofagotomije (MIOT) u indijske kornjače Flap-shell (Lissemys punctata). U odraslog mužjaka uočena je najlonska nit koja je virila iz usta. Dorzoventralna radiografija potvrdila je prisutnost stranog tijela u kaudalnom dijelu jednjaka, malo izvan celomične šupljine. Nakon opće anestezije, sterilni kateter za umjetno osjemenjivanje uveden je kroz usnu šupljinu uz najlonsku nit do udice. Udica je uklonjena kroz rez od 5 mm na mjestu gdje se mogao napipati vrh katetera. Rez na jednjaku i na koži zatvoren je na uobičajen način. Kornjača je 20 dana zadržana u sigurnom zatočeništvu, nakon čega je puštena u svoje prirodno stanište. Ovaj oblik ezofagotomije znatno je smanjio veličinu reza, što je smanjilo mogućnost poslijeoperacijskih komplikacija
Postoperative morbidity following Whipple’s procedure for periampullary carcinoma: a retrospective study spanning 5 years
Background: The morbidity rates for Whipple’s procedure has remained high even as mortality rates were coming down. This study was intended to assess postoperative morbidity rates in a tertiary care centre and to compare it with other centres.Methods: Data was collected from various registers and medical records for this retrospective cohort study. All Whipple’s procedures for 5 years were included in the study. Statistical analysis was done using R statistical software and the results were tabulated.Results: There were 48 patients and half of them developed morbidity. Surgical site infection was the most common complication (18.8%) followed by pulmonary complications (12.5%) and bile leak (6.25%). Half of the patients having pulmonary complications died while nobody with surgical site infection or bile leak died.Conclusions: In this study the morbidity rates were comparable to other centres. Hypoalbuminemia is a significant predictor of morbidity. Surgical site infection was the most common morbidity. Pulmonary complications were the most common cause for death. Morbidity rate is comparable to other centres and Whipple’s procedure is a safe surgery in the tertiary centre where the study was conducted
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