8,613 research outputs found
Usefulness of 3D transperineal ultrasound in severe stenosis of the anal canal : preliminary experience in four cases
Background Organic or functional anal canal stenoses are uncommon conditions that occur in the majority of cases as a consequence of anal diseases. A proper assessment is fundamental for decision making; however, proctological examination and endoanal ultrasound are often unfeasible or very difficult to perform even under local or general anesthesia. We therefore began to use 3D transperineal ultrasound to assess patients. The aim of this study was to compare the results of evacuation proctography and 3D transperineal ultrasound in patients with severe anal canal stenosis. Methods Four consecutive patients with high-grade anal canal stenosis were evaluated using both proctography and 3D transperineal ultrasound with a micro-convex transducer between March and June 2011.Results In all cases, 3D transperineal ultrasound provided detailed information on the length and level of stenosis and on the integrity of the anal sphincters. Conclusions Our preliminary experience suggests that 3D transperineal ultrasound makes it possible to plan optimal surgical treatment
Valence-bond states in dynamical Jahn-Teller molecular systems
We discuss a hopping model of electrons between idealized molecular sites
with local orbital degeneracy and dynamical Jahn-Teller effect, for crystal
field environments of sufficiently high symmetry. For the Mott-insulating case
(one electron per site and large Coulomb repulsions), in the simplest two-fold
degenerate situation, we are led to consider a particular exchange hamiltonian,
describing two isotropic spin-1/2 Heisenberg problems coupled by a quartic term
on equivalent bonds. This twin-exchange hamiltonian applies to a physical
regime in which the inter-orbital singlet is the lowest-energy intermediate
state available for hopping. This regime is favored by a relatively strong
electron-phonon coupling. Using variational arguments, a large-N limit, and
exact diagonalization data, we find that the ground state, in the one
dimensional case, is a solid valence bond state. The situation in the two
dimensional case is less clear. Finally, the behavior of the system upon hole
doping is studied in one dimension.Comment: 11 pages, 5 figure
Epigenetic Engineering of Ribosomal RNA Genes Enhances Protein Production
Selection of mammalian high-producer cell lines remains a major challenge for the biopharmaceutical manufacturing industry. Ribosomal RNA (rRNA) genes encode the major component of the ribosome but many rRNA gene copies are not transcribed [1]–[5] due to epigenetic silencing by the nucleolar remodelling complex (NoRC) [6], which may limit the cell's full production capacity. Here we show that the knockdown of TIP5, a subunit of NoRC, decreases the number of silent rRNA genes, upregulates rRNA transcription, enhances ribosome synthesis and increases production of recombinant proteins. However, general enhancement of rRNA transcription rate did not stimulate protein synthesis. Our data demonstrates that the number of transcriptionally competent rRNA genes limits efficient ribosome synthesis. Epigenetic engineering of ribosomal RNA genes offers new possibilities for improving biopharmaceutical manufacturing and provides novel insights into the complex regulatory network which governs the translation machinery in normal cellular processes as well as in pathological conditions like cancer
Quantization of multidimensional cat maps
In this work we study cat maps with many degrees of freedom. Classical cat
maps are classified using the Cayley parametrization of symplectic matrices and
the closely associated center and chord generating functions. Particular
attention is dedicated to loxodromic behavior, which is a new feature of
two-dimensional maps. The maps are then quantized using a recently developed
Weyl representation on the torus and the general condition on the Floquet
angles is derived for a particular map to be quantizable. The semiclassical
approximation is exact, regardless of the dimensionality or of the nature of
the fixed points.Comment: 33 pages, latex, 6 figures, Submitted to Nonlinearit
Hard X-ray Bursts from Collapse of the Super Massive Stars
The very first stars in the Universe can be very massive, up to
. They would leave behind massive black holes that could act as
seeds for growing super massive black holes of active galactic nuclei. Given
the anticipated fast rotation such stars would end their live as super massive
collapsars and drive powerful magnetically-dominated jets. In this paper we
investigate the possibility of observing the bursts of high-energy emission
similar to the Long Gamma Ray Bursts associated with normal collapsars. We show
that during the collapse of supercollapsars, the Blandford-Znajek mechanism can
produce jets as powerful as fewerg/s and release up to
erg of the black hole rotational energy. Due to the higher intrinsic
time scale and higher redshift the initial bright phase of the burst can last
for about seconds whereas the central engine would remain active for
about 10 days. Due to the high redshift the burst spectrum is expected to be
soft, with the spectral energy distribution peaking at around 60keV. The peak
total flux density is relatively low, few,
but not prohibitive. The such events should be rear 0.03 year, the
observations needs long term program and could be done in future.Comment: 4 pages, 2 figures. proceedings of workshop "Many faces of GRB
phenomena - optics vs high energy", SAO Russia, October 12-16, 2009
A rare case of posterior fossa tumor and central precocious puberty: Case presentation and review of the literature
Central precocious puberty (CPP) is a condition that causes early gonadotropin-dependent sexual development; CPP is idiopathic in girls in most cases, whereas more than 50% of boys have an identifiable etiology. We conducted a qualitative systematic review following the ENTREQ (enhancing transparency in reporting the synthesis of qualitative research) framework. A search was made in MEDLINE/Pubmed and MeSH Database using the terms “precocious puberty” AND “brain tumor” OR “posterior fossa tumor” OR “cerebellar tumor” OR “infratentorial tumor”, iden-tifying five cases of pediatric patients with infratentorial tumors and CPP and a case of cerebellar ganglioglioma without hypothalamic−pituitary−gonadal axis involvement and/or intracranial hypertension. Our work highlights the importance of a multidisciplinary approach and extensive central nervous system imaging for patients presenting with CPP in order to detect possible tumor association. Moreover, we believe that this manuscript could contribute to stimulate other research because the exact mechanism of CPP in infratentorial brain lesions has not been understood yet
Dynamical charge susceptibility in layered cuprates: the influence of screened inter-site Coulomb repulsion
The analytical expression for dynamical charge susceptibility in layered
cuprates has been derived in the frame of singlet-correlated band model beyond
random-phase-approximation (RPA) scheme. Our calculations performed near
optimal doping regime show that there is a peak in real part of the charge
susceptibility at {\bf Q} = (, ) at strong
enough inter-site Coulomb repulsion. Together with the strong maximum in the Im
at 15 meV it confirms the formation of low-energetic
plasmons or charge fluctuations. This provides a jsutification that these
excitations are important and together with a spin flcutuations can contribute
to the Cooper pairing in layered cuprates. Analysing the charge susceptibilitiy
with respect to an instability we obtain a new plasmon branch, , along the Brillouin Zone. In particular, we have found that it goes to
zero near {\bf Q}
Optimization by Quantum Annealing: Lessons from hard 3-SAT cases
The Path Integral Monte Carlo simulated Quantum Annealing algorithm is
applied to the optimization of a large hard instance of the Random 3-SAT
Problem (N=10000). The dynamical behavior of the quantum and the classical
annealing are compared, showing important qualitative differences in the way of
exploring the complex energy landscape of the combinatorial optimization
problem. At variance with the results obtained for the Ising spin glass and for
the Traveling Salesman Problem, in the present case the linear-schedule Quantum
Annealing performance is definitely worse than Classical Annealing.
Nevertheless, a quantum cooling protocol based on field-cycling and able to
outperform standard classical simulated annealing over short time scales is
introduced.Comment: 10 pages, 6 figures, submitted to PR
Development of fluorescent thermoresponsive nanoparticles for temperature monitoring on membrane surfaces
In this work, tris(phenantroline)ruthenium(II) chloride (Ru(phen)3) was immobilized in silica nanoparticles prepared according to the Stöber method. Efforts were devoted on the optimization of the nano-thermometer in terms of size, polydispersity, intensity of the emission and temperature sensitivity. In particular, the immobilization of the luminophore in an external thin shell made of silica grown in a second step on bare silica nanoparticles allowed producing fluorescent monodisperse silica nanoparticles (420 ± 20 nm). A systematic study was addressed to maximize the intensity of the emission of the fluorescent nanoparticles by adjusting the concentration of Ru(phen)32+ in the shell from 0.2 to 24 wt.%, whereas the thickness of the shell is affected by the amount of silica precursor employed. The luminescent activity of the doped nanoparticles was found to be sensitive to the temperature. In fact, the intensity of the emission linearly decreased by increasing the temperature from 20 °C to 65 °C. The thermoresponsive nanoparticles were functionalized with long aliphatic chains in order to obtain hydrophobic nanoparticles. The developed nanoparticles were immobilized via dip-coating procedure on the surface of hydrophobic porous membranes, such as Polyvinylidene fluoride (PVDF) prepared via Non-Solvent Induced Phase Separation (NIPS), providing local information about the membrane surface temperature
Use of Transversus Abdominis Plane and Intercostal Blocks in Bitches Undergoing Laparoscopic Ovariectomy: A Randomized Controlled Trial
In humans and dogs, loco-regional anesthesia is associated with lower peri-operative opioid consumption and less related side effects. The combination of transversus abdominis plane (TAP) and intercostal blocks can be used to desensitize the entire abdominal wall in dogs. The aim of this study was to evaluate the effectiveness of TAP and intercostal blocks in bitches undergoing laparoscopic ovariectomy. Twenty client-owned bitches were enrolled in this double-blinded randomized controlled trial. After premedication with dexmedetomidine, methadone and ketamine, the animals were randomized into two groups. Dogs in the TAP group received intercostal blocks from T8 to T10 and a TAP block with ropivacaine. Dogs in the FEN group received a fentanyl bolus and a constant rate infusion for the entire duration of the procedure. Intra-operative cardiovascular stability, post-operative pain scores, rescue opioid requirement, dysphoria during recovery, time to attain sternal recumbency and interest in food at 6 h post-extubation were compared. Bitches in the TAP group received a statistically significant lower amount of rescue fentanyl intra-operatively and methadone post-operatively. Pain scores were lower in the TAP group until 6 h post-extubation. No difference was found for dysphoric recoveries, time to attain sternal recumbency and appetite at 6 h post-extubation. No adverse event was recorded for any of the dogs. The combination of TAP and intercostal blocks can be part of an effective multi-modal analgesic strategy in bitches undergoing laparoscopic ovariectomy
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