1,961 research outputs found
Caudate lobe resections: a single-center experience and evaluation of factors predictive of outcomes
BACKGROUND: Despite the increasing frequency of liver resection for multiple types of disease, caudate lobe resection remains a rare surgical event. The goal of this study is to review our experience and evaluate possible predictors of adverse outcomes in patients undergoing caudate lobectomy. METHODS: We reviewed a 1,900-patient prospective hepato-pancreatico-biliary database from January 2000 to December 2011, identifying 36 hepatectomy patients undergoing caudate lobe resection. Clinicopathologic characteristic and outcome data were compared using chi-square, T-test, ANOVA, Kaplan-Meier, and Cox regression analysis. Primary endpoints were the incidence and severity of complications, and secondary endpoints were blood loss, hospital stay, and transfusion requirements. Patients were also divided in two groups with group A being patients operated on before December 2007 and group B after 2007. We compared the demographics, risk factors, complication rates, and operative details between the two groups. RESULTS: Thirty-six patients underwent caudate lobe resection for cholangiocarcinoma (47.2%), metastatic colorectal cancer (36.1%), hepatocellular carcinoma (8.3%), or benign disease (8.3%). Nine patients (29%) had additional liver resection. Median overall survival (OS) was 21 months. Complications occurred in 52.7% (19/36) of patients with a median grade of 2. Tobacco abuse was associated with an increased risk of operative complications (73.3% vs. 38.9%, p = 0.03). Prior history of cardiac disease was associated with a higher complication rate (87% vs. 42%, p = 0.03). Neoadjuvant chemotherapy, biliary procedures, hepatitis, and prior major abdominal surgery were not predictive of complications. Major complication was also predicted by the volume of RBC transfusion (2.7 vs. 4.1 units, p = 0.003). In our subgroup analysis of the patients undergoing surgery before and after 2007, the two groups were well matched based on age, comorbidities, and risk factors. The complication rates and rates of high-grade complications were similar, but blood loss (600 ml vs. 400 ml, p = 0.03), inflow occlusion time (Pringle time 12.6 vs. 6, p = 0.00), and hospital stay (9.5 vs. 7 days, p = 0.01) were significantly lower in group B. CONCLUSIONS: With appropriate patient selection, caudate lobe resection is an effective component of surgery for hepatic disease. Tobacco use and prior cardiac history increase the risk of complications
L\'evy Distribution of Single Molecule Line Shape Cumulants in Low Temperature Glass
We investigate the distribution of single molecule line shape cumulants,
, in low temperature glasses based on the sudden jump,
standard tunneling model. We find that the cumulants are described by L\'evy
stable laws, thus generalized central limit theorem is applicable for this
problem.Comment: 5 pages, 3 figure
On the Evolution of and High-Energy Emission from GHz-Peaked-Spectrum Sources
Here we discuss evolution and broad-band emission of compact (< kpc) lobes in
young radio sources. We propose a simple dynamical description for these
objects, consisting of a relativistic jet propagating into a uniform gaseous
medium in the central parts of an elliptical host. In the framework of the
proposed model, we follow the evolution of ultrarelativistic electrons injected
from a terminal hotspot of a jet to expanding lobes, taking into account their
adiabatic energy losses as well as radiative cooling. This allows us to discuss
the broad-band lobe emission of young radio sources. In particular, we argue
that the observed spectral turnover in the radio synchrotron spectra of these
objects cannot originate from the synchrotron self-absorption process but is
most likely due to free-free absorption effects connected with neutral clouds
of interstellar medium engulfed by the expanding lobes and photoionized by
active centers. We also find a relatively strong and complex high-energy
emission component produced by inverse-Compton up-scattering of various
surrounding photon fields by the lobes' electrons. We argue that such high
energy radiation is strong enough to account for several observed properties of
GHz-peaked-spectrum (GPS) radio galaxies at UV and X-ray frequencies. In
addition, this emission is expected to extend up to GeV (or possibly even TeV)
photon energies and can thus be probed by several modern gamma-ray instruments.
In particular, we suggest that GPS radio galaxies should constitute a
relatively numerous class of extragalactic sources detected by GLAST.Comment: 32 pages, 3 figures included. Revised version, accepted for
publication in Ap
Quantum catastrophe of slow light
Catastrophes are at the heart of many fascinating optical phenomena. The
rainbow, for example, is a ray catastrophe where light rays become infinitely
intense. The wave nature of light resolves the infinities of ray catastrophes
while drawing delicate interference patterns such as the supernumerary arcs of
the rainbow. Black holes cause wave singularities. Waves oscillate with
infinitely small wave lengths at the event horizon where time stands still. The
quantum nature of light avoids this higher level of catastrophic behaviour
while producing a quantum phenomenon known as Hawking radiation. As this letter
describes, light brought to a standstill in laboratory experiments can suffer a
similar wave singularity caused by a parabolic profile of the group velocity.
In turn, the quantum vacuum is forced to create photon pairs with a
characteristic spectrum. The idea may initiate a theory of quantum
catastrophes, in addition to classical catastrophe theory, and the proposed
experiment may lead to the first direct observation of a phenomenon related to
Hawking radiation.Comment: Published as "A laboratory analogue of the event horizon using slow
light in an atomic medium
Time resolution of the plastic scintillator strips with matrix photomultiplier readout for J-PET tomograph
Recent tests of a single module of the Jagiellonian Positron Emission
Tomography system (J-PET) consisting of 30 cm long plastic scintillator strips
have proven its applicability for the detection of annihilation quanta (0.511
MeV) with a coincidence resolving time (CRT) of 0.266 ns. The achieved
resolution is almost by a factor of two better with respect to the current
TOF-PET detectors and it can still be improved since, as it is shown in this
article, the intrinsic limit of time resolution for the determination of time
of the interaction of 0.511 MeV gamma quanta in plastic scintillators is much
lower. As the major point of the article, a method allowing to record
timestamps of several photons, at two ends of the scintillator strip, by means
of matrix of silicon photomultipliers (SiPM) is introduced. As a result of
simulations, conducted with the number of SiPM varying from 4 to 42, it is
shown that the improvement of timing resolution saturates with the growing
number of photomultipliers, and that the 2 x 5 configuration at two ends
allowing to read twenty timestamps, constitutes an optimal solution. The
conducted simulations accounted for the emission time distribution, photon
transport and absorption inside the scintillator, as well as quantum efficiency
and transit time spread of photosensors, and were checked based on the
experimental results. Application of the 2 x 5 matrix of SiPM allows for
achieving the coincidence resolving time in positron emission tomography of
0.170 ns for 15 cm axial field-of-view (AFOV) and 0.365 ns
for 100 cm AFOV. The results open perspectives for construction of a
cost-effective TOF-PET scanner with significantly better TOF resolution and
larger AFOV with respect to the current TOF-PET modalities.Comment: To be published in Phys. Med. Biol. (26 pages, 17 figures
Object Relations in the Museum: A Psychosocial Perspective
This article theorises museum engagement from a psychosocial perspective. With the aid of selected concepts from object relations theory, it explains how the museum visitor can establish a personal relation to museum objects, making use of them as an ‘aesthetic third’ to symbolise experience. Since such objects are at the same time cultural resources, interacting with them helps the individual to feel part of a shared culture. The article elaborates an example drawn from a research project that aimed to make museum collections available to people with physical and mental health problems. It draws on the work of the British psychoanalysts Donald Winnicott and Wilfred Bion to explain the salience of the concepts of object use, potential space, containment and reverie within a museum context. It also refers to the work of the contemporary psychoanalyst Christopher Bollas on how objects can become evocative for individuals both by virtue of their intrinsic qualities and by the way they are used to express personal idiom
Phase diagram of the metal-insulator transition in 2D electronic systems
We investigated the interdependence of the effects of disorder and carrier
correlations on the metal-insulator transition in two-dimensional electronic
systems. We present a quantitative metal-insulator phase diagram. Depending on
the carrier density we find two different types of metal-insulator transition -
a continuous localization for rs=<8 and a discontinuous transition at higher
rs. The critical level of disorder at the transition decreases with decreasing
carrier density. At very low carrier densities we find that the system is
always insulating. The value of the conductivity at the transition is
consistent with recent experimental measurements. The self-consistent method
which we have developed includes the effects of both disorder and correlations
on the transition, using a density relaxation theory with the Coulomb
correlations determined from numerical simulation data.Comment: 4 pages, RevTeX + epsf, 5 figures. New comments on conducting phase
and on the conductivity. References updated and correcte
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