109 research outputs found
Craniofacial osteomas: From diagnosis to therapy
An osteoma is a benign bone lesion with no clear pathogenesis, almost exclusive to the craniofacial area. Osteomas show very slow continuous growth, even in adulthood, unlike other bony lesions. Since these lesions are frequently asymptomatic, the diagnosis is usually made by plain radiography or by a computed tomography (CT) scan performed for other reasons. Rarely, the extensive growth could determine aesthetic or functional problems that vary according to different locations. Radiographically, osteomas appear as radiopaque lesions similar to bone cortex, and may determine bone expansion. Cone beam CT is the optimal imaging modality for assessing the relationship between osteomas and adjacent structures, and for surgical planning. The differential diagnosis includes several inflammatory and tumoral pathologies, but the typical craniofacial location may aid in the diagnosis. Due to the benign nature of osteomas, surgical treatment is limited to symptomatic lesions. Radical surgical resection is the gold standard therapy; it is based on a minimally invasive surgical approach with the aim of achieving an optimal cosmetic result. Reconstructive surgery for an osteoma is quite infrequent and reserved for patients with large central osteomas, such as big mandibular or maxillary lesions. In this regard, computer-assisted surgery guarantees better outcomes, providing the possibility of preoperative simulation of demolitive and reconstructive surgery
Dynamical friction of massive objects in galactic centres
Dynamical friction leads to an orbital decay of massive objects like young
compact star clusters or Massive Black Holes in central regions of galaxies.
The dynamical friction force can be well approximated by Chandrasekhar's
standard formula, but recent investigations show, that corrections to the
Coulomb logarithm are necessary. With a large set of N-body simulations we show
that the improved formula for the Coulomb logarithm fits the orbital decay very
well for circular and eccentric orbits. The local scale-length of the
background density distribution serves as the maximum impact parameter for a
wide range of power-law indices of -1 ... -5. For each type of code the
numerical resolution must be compared to the effective minimum impact parameter
in order to determine the Coulomb logarithm. We also quantify the correction
factors by using self-consistent velocity distribution functions instead of the
standard Maxwellian often used. These factors enter directly the decay
timescale and cover a range of 0.5 ... 3 for typical orbits. The new Coulomb
logarithm combined with self-consistent velocity distribution functions in the
Chandrasekhar formula provides a significant improvement of orbital decay times
with correction up to one order of magnitude compared to the standard case. We
suggest the general use of the improved formula in parameter studies as well as
in special applications.Comment: 22 pages, 28 figures, accepted by MNRA
Analysis of factors influencing the ultrasonic fetal weight estimation
Objective: The aim of our study was the evaluation of sonographic fetal weight estimation taking into consideration 9 of the most important factors of influence on the precision of the estimation. Methods: We analyzed 820 singleton pregnancies from 22 to 42 weeks of gestational age. We evaluated 9 different factors that potentially influence the precision of sonographic weight estimation ( time interval between estimation and delivery, experts vs. less experienced investigator, fetal gender, gestational age, fetal weight, maternal BMI, amniotic fluid index, presentation of the fetus, location of the placenta). Finally, we compared the results of the fetal weight estimation of the fetuses with poor scanning conditions to those presenting good scanning conditions. Results: Of the 9 evaluated factors that may influence accuracy of fetal weight estimation, only a short interval between sonographic weight estimation and delivery (0-7 vs. 8-14 days) had a statistically significant impact. Conclusion: Of all known factors of influence, only a time interval of more than 7 days between estimation and delivery had a negative impact on the estimation
Precision measurement of the neutrino velocity with the ICARUS detector in the CNGS beam
During May 2012, the CERN-CNGS neutrino beam has been operated for two weeks
for a total of 1.8 10^17 pot in bunched mode, with a 3 ns narrow width proton
beam bunches, separated by 100 ns. This tightly bunched beam structure allows a
very accurate time of flight measurement of neutrinos from CERN to LNGS on an
event-by-event basis. Both the ICARUS-T600 PMT-DAQ and the CERN-LNGS timing
synchronization have been substantially improved for this campaign, taking
ad-vantage of additional independent GPS receivers, both at CERN and LNGS as
well as of the deployment of the "White Rabbit" protocol both at CERN and LNGS.
The ICARUS-T600 detector has collected 25 beam-associated events; the
corresponding time of flight has been accurately evaluated, using all different
time synchronization paths. The measured neutrino time of flight is compatible
with the arrival of all events with speed equivalent to the one of light: the
difference between the expected value based on the speed of light and the
measured value is tof_c - tof_nu = (0.10 \pm 0.67stat. \pm 2.39syst.) ns. This
result is in agreement with the value previously reported by the ICARUS
collaboration, tof_c - tof_nu = (0.3 \pm 4.9stat. \pm 9.0syst.) ns, but with
improved statistical and systematic errors.Comment: 21 pages, 13 figures, 1 tabl
The efficiency of the spiral-in of a black hole to the Galactic centre
We study the efficiency at which a black hole or dense star cluster
spirals-in to the Galactic centre. This process takes place on a dynamical
friction time scale, which depends on the value of the Coulomb logarithm ln(L).
We determine the accurate value of this parameter using the direct N-body
method, a tree algorithm and a particle-mesh technique with up to 2 million
plus one particles. The three different techniques are in excellent agreement.
Our result for the Coulomb logarithm appears to be independent of the number of
particles. We conclude that ln(L) = 6.6 +/- 0.6 for a massive point particle in
the inner few parsec of the Galactic bulge. For an extended object, like a
dense star cluster, ln(L) is smaller, with a value of the logarithm argument L
inversely proportional to the object size.Comment: 11 pages, 12 figures, MNRAS, in press revised version following
referee's comments, references updated, typos correcte
Measurement of CNGS muon neutrino speed with Borexino
We have measured the speed of muon neutrinos with the Borexino detector using
short-bunch CNGS beams. The final result for the difference in time-of-flight
between a =17 GeV muon neutrino and a particle moving at the speed of light
in vacuum is {\delta}t = 0.8 \pm 0.7stat \pm 2.9sys ns, well consistent with
zero.Comment: 6 pages, 5 figure
Disruption time scales of star clusters in different galaxies
The observed average lifetime of the population of star clusters in the Solar
Neighbourhood, the Small Magellanic Cloud and in selected regions of M51 and
M33 is compared with simple theoretical predictions and with the results of
N-body simulations. The empirically derived lifetimes (or disruption times) of
star clusters depend on their initial mass as t_dis ~ Mcl^0.60 in all four
galaxies. N-body simulations have shown that the predicted disruption time of
clusters in a tidal field scales as t_dis^pred ~ t_rh^0.75 t_cr^0.25, where
t_rh is the initial half-mass relaxation time and t_cr is the crossing time for
a cluster in equilibrium. We show that this can be approximated accurately by
t_dis^pred ~ M_cl^0.62 for clusters in the mass range of about 10^3 to 10^6
M_sun, in excellent agreement with the observations. Observations of clusters
in different extragalactic environments show that t_dis also depends on the
ambient density in the galaxies where the clusters reside. Linear analysis
predicts that the disruption time will depend on the ambient density of the
cluster environment as t_dis ~ rho_amb^-0.5. This relation is consistent with
N-body simulations.Comment: 7 pages, 4 figures. Accepted for publication in A&
Two-dimensional H_alpha kinematics of bulgeless disk galaxies
We present two-dimensional H_alpha velocity fields for 20 late-type,
disk-dominated spiral galaxies, the largest sample to date with high-resolution
H_alpha velocity fields for bulgeless disks. From these data we derive rotation
curves and the location of the kinematic centers. The galaxy sample was
selected to contain nucleated and non-nucleated galaxies, which allows us to
investigate what impact the gas kinematics in the host disk have on the
presence (or absence) of a nuclear star cluster. In general, we find that the
velocity fields span a broad range of morphologies. While some galaxies show
regular rotation, most have some degree of irregular gas motions. There appears
to be no systematic difference in the kinematics of nucleated and non-nucleated
disks. Due to the large fields of view of the integral field units we use, we
are able to observe the flattening of the rotation curve in almost all of our
sample galaxies. This makes modeling of the velocity fields relatively
straight-forward. Due to the complexities of the velocity fields, we obtain
reliable determinations of the kinematic center for only 6 of our 20 sample
galaxies. For all of these the locations of the nuclear star
cluster/photometric center and the kinematic center agree within the
uncertainties. If we disregard all kinematically irregular galaxies, our study
concludes that nuclear star clusters truly occupy the nuclei, or dynamical
centers, of their hosts. Our results are thus consistent with in-situ formation
of nuclear star clusters. Yet, many well-motivated formation scenarios for
nuclear clusters invoke off-center cluster formation and subsequent sinking of
clusters due to dynamical friction. In that case, our results imply that
dynamical friction in the centers of bulgeless galaxies must be very effective
in driving massive clusters to the kinematic center. (abridged)Comment: 16 pages, 7 figures(some in reduced quality); MNRAS in pres
Protocol for the immediate delivery versus expectant care of women with preterm prelabour rupture of the membranes close to term (PPROMT) Trial [ISRCTN44485060]
BACKGROUND: Preterm prelabour rupture of membranes (PPROM) complicates up to 2% of all pregnancies and is the cause of 40% of all preterm births. The optimal management of women with PPROM prior to 37 weeks, is not known. Furthermore, diversity in current clinical practice suggests uncertainty about the appropriate clinical management. There are two options for managing PPROM, expectant management (a wait and see approach) or early planned birth. Infection is the main risk for women in which management is expectant. This risk need to be balanced against the risk of iatrogenic prematurity if early delivery is planned. The different treatment options may also have different health care costs. Expectant management results in prolonged antenatal hospitalisation while planned early delivery may necessitate intensive care of the neonate for problems associated with prematurity. METHODS/DESIGN: We aim to evaluate the effectiveness of early planned birth compared with expectant management for women with PPROM between 34 weeks and 36(6 )weeks gestation, in a randomised controlled trial. A secondary aim is a cost analysis to establish the economic impact of the two treatment options and establish the treatment preferences of women with PPROM close to term. The early planned birth group will be delivered within 24 hours according to local management protocols. In the expectant management group birth will occur after spontaneous labour, at term or when the attending clinician feels that birth is indicated according to usual care. Approximately 1812 women with PPROM at 34–36(6 )weeks gestation will be recruited for the trial. The primary outcome of the study is neonatal sepsis. Secondary infant outcomes include respiratory distress, perinatal mortality, neonatal intensive care unit admission, assisted ventilation and early infant development. Secondary maternal outcomes include chorioamnionitis, postpartum infection treated with antibiotics, antepartum haemorrhage, induction of labour, mode of delivery, maternal satisfaction with care, duration of hospitalisation, and maternal wellbeing at four months postpartum. DISCUSSION: This trial will provide evidence on the optimal care for women with PPROM close to term (34–37 weeks gestation). Consideration of both the clinical and economic sequelae of the management of PPROM will enable informed decision making and guideline development
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