639 research outputs found
Entanglement between a qubit and the environment in the spin-boson model
The quantitative description of the quantum entanglement between a qubit and
its environment is considered. Specifically, for the ground state of the
spin-boson model, the entropy of entanglement of the spin is calculated as a
function of , the strength of the ohmic coupling to the environment,
and , the level asymmetry. This is done by a numerical
renormalization group treatment of the related anisotropic Kondo model. For
, the entanglement increases monotonically with , until it
becomes maximal for . For fixed , the entanglement
is a maximum as a function of for a value, .Comment: 4 pages, 3 figures. Shortened version restricted to groundstate
entanglemen
Magnetotransport through a strongly interacting quantum dot
We study the effect of a magnetic field on the conductance through a strongly
interacting quantum dot by using the finite temperature extension of Wilson's
numerical renormalization group method to dynamical quantities. The quantum dot
has one active level for transport and is modelled by an Anderson impurity
attached to left and right electron reservoirs. Detailed predictions are made
for the linear conductance and the spin-resolved conductance as a function of
gate voltage, temperature and magnetic field strength. A strongly coupled
quantum dot in a magnetic field acts as a spin filter which can be tuned by
varying the gate voltage. The largest spin-filtering effect is found in the
range of gate voltages corresponding to the mixed valence regime of the
Anderson impurity model.Comment: Revised version, to appear in PRB, 4 pages, 4 figure
Real-Time-RG Analysis of the Dynamics of the Spin-Boson Model
Using a real-time renormalization group method we determine the complete
dynamics of the spin-boson model with ohmic dissipation for coupling strengths
. We calculate the relaxation and dephasing time, the
static susceptibility and correlation functions. Our results are consistent
with quantum Monte Carlo simulations and the Shiba relation. We present for the
first time reliable results for finite cutoff and finite bias in a regime where
perturbation theory in or in tunneling breaks down. Furthermore, an
unambigious comparism to results from the Kondo model is achieved.Comment: 4 pages, 5 figures, 1 tabl
Evaluating the expression of urokinase and tissue leukocyte being in benign and malignant breast disease
Introduction: Our objectives is to show that the expression of uPA leukocyte could be considered, in the future, as a marker of
the expression of uPA in the malignant tissue and therefore a potential indicator of prognosis.
Methods: We examined the expression of uPa in leukocytes and tissues of three groups of women: with breast cancer; with
benign breast lesion and healthy women (control group). We used RT Real Time PCR assay. The expression of urokinase is
significantly higher in malignant breast lumps compared to benign lesions. However, in women with carcinoma of the breast,
malignant tissue expresses higher amounts of uPA than the healthy counterpart. There are no statistically significant differences in
the expression of uPA, between tissues taken from women with benign lesions. The lymphocytes taken from healthy volunteers
show a level of expression of uPA significantly lower than the other tested samples Lymphocytes extracted from cancer patients
express higher amounts of uPA compared to lymphocytes belonging to women with benign breast lesions. The expression of uPA
was compared with the clinical and biological parameters commonly used in clinical practice for the definition of the prognosis.
The only exception found, concerns those tumors characterized by the simultaneous negativity for estrogen receptors,
progesterone and HER2 (state of triple negative), in which the expression of uPA is very high.
Results and conclusions: Our data show that uPA expressed by leukocytes of each individual patient is the mirror image of the
one expressed by malignant nodular uPA.Introduction: Our objectives is to show that the expression of uPA leukocyte could be considered, in the future, as a marker of
the expression of uPA in the malignant tissue and therefore a potential indicator of prognosis.
Methods: We examined the expression of uPa in leukocytes and tissues of three groups of women: with breast cancer; with
benign breast lesion and healthy women (control group). We used RT Real Time PCR assay. The expression of urokinase is
significantly higher in malignant breast lumps compared to benign lesions. However, in women with carcinoma of the breast,
malignant tissue expresses higher amounts of uPA than the healthy counterpart. There are no statistically significant differences in
the expression of uPA, between tissues taken from women with benign lesions. The lymphocytes taken from healthy volunteers
show a level of expression of uPA significantly lower than the other tested samples Lymphocytes extracted from cancer patients
express higher amounts of uPA compared to lymphocytes belonging to women with benign breast lesions. The expression of uPA
was compared with the clinical and biological parameters commonly used in clinical practice for the definition of the prognosis.
The only exception found, concerns those tumors characterized by the simultaneous negativity for estrogen receptors,
progesterone and HER2 (state of triple negative), in which the expression of uPA is very high.
Results and conclusions: Our data show that uPA expressed by leukocytes of each individual patient is the mirror image of the
one expressed by malignant nodular uPA
Recent advancement in the search of innovative antiprotozoal agents targeting trypanothione metabolism
Leishmania and Trypanosoma parasites are responsible for the challenging neglected tropical diseases leishmaniases, Chagas disease, and human African trypanosomiasis, which account for up to 40,000 deaths annually mainly in developing countries. Current chemotherapy relies on drugs with significant limitations in efficacy and safety, prompting the urgent need to explore innovative approaches to improve the drug discovery pipeline. The unique trypanothione-based redox pathway, which is absent in human hosts, is vital for all trypanosomatids and offers valuable opportunities to guide the rational development of specific, broad-spectrum and innovative anti-trypanosomatid agents. Major efforts focused on the key metabolic enzymes trypanothione synthetase-amidase and trypanothione reductase, whose inhibition should affect the entire pathway and, finally, parasite survival. Herein, we will report and comment on the most recent studies in the search for enzyme inhibitors, underlining the promising opportunities that have emerged so far to drive the exploration of future successful therapeutic approaches
Rehabilitation of COPD patients: which training modality?
Non pharmacological therapy has been gaining more interest and has been evolving rapidly over the last decade as an essential part of therapy for COPD patients. Pulmonary Rehabilitation (PR), the most important non pharmacological treatment in patients with COPD, has a primary goal: to achieve the highest possible level of individual exercise tolerance, thus reducing the primary and/or secondary health care utilisation. The aim of the present review is to focus the role of exercise training in these patients as well as to address the question on which training methods are the most beneficial. We have therefore undertaken a MEDLINE-based search including the terms: pulmonary rehabilitation, exercise, lung disease/obstructive. Several strategies based on endurance or strength training are nowadays implemented during PR programmes in order to maximise the benefits for each patient. The impaired function of ambulation muscles causing breathlessness as one of the more frequent symptoms in many COPD, suggests that training the lower extremities is the most important goal to achieve during pulmonary rehabilitation of these patients. On the other hand, as muscle strength appears to be an independent contributor to survival and utilisation of health care resources, it seems largely justified also to include this further modality in the PR program of these patients. In conclusion, both modalities are effective and useful for COPD patients. However, whether resistance training should be administered to all COPD and which is the optimal length of strength training still needs to be elucidated
The numerical renormalization group method for quantum impurity systems
In the beginning of the 1970's, Wilson developed the concept of a fully
non-perturbative renormalization group transformation. Applied to the Kondo
problem, this numerical renormalization group method (NRG) gave for the first
time the full crossover from the high-temperature phase of a free spin to the
low-temperature phase of a completely screened spin. The NRG has been later
generalized to a variety of quantum impurity problems. The purpose of this
review is to give a brief introduction to the NRG method including some
guidelines of how to calculate physical quantities, and to survey the
development of the NRG method and its various applications over the last 30
years. These applications include variants of the original Kondo problem such
as the non-Fermi liquid behavior in the two-channel Kondo model, dissipative
quantum systems such as the spin-boson model, and lattice systems in the
framework of the dynamical mean field theory.Comment: 55 pages, 27 figures, submitted to Rev. Mod. Phy
Scaling and universality in the anisotropic Kondo model and the dissipative two-state system
Scaling and universality in the Ohmic two-state system is investigated by
exploiting the equivalence of this model to the anisotropic Kondo model. For
the Ohmic two-state system, we find universal scaling functions for the
specific heat, , static susceptibility, , and
spin relaxation function depending on the reduced
temperature (frequency ), with
the renormalized tunneling frequency, and uniquely specified by the dissipation
strength (). The scaling functions can be used to extract
and in experimental realizations.Comment: 5 pages (LaTeX), 4 EPS figures. Minor changes, typos corrected,
journal reference adde
Commencing rehabilitation in the ICU.
Rehabilitation is an integral part of the management of patients inIntensive Care Units (ICUs).The most important aim in this area isto enhance the patient's overall functional capacity and to restorehis/her respiratory and physical independence, thus decreasing the risks of bed-rest and associated complications.The evidence for applying a weaning protocol and physiotherapytechniques (postures, percussion/vibration, limb exercise, and active mobilization) in these patients has proved to be effective according to the application rationale of each process. However, todate, there are only strong recommendations concerning the evidence-based strategies to speed weaning from mechanical ventilation.Early physiotherapy may be effective in the ICU: nonetheless,most techniques need to be further studied in a wider population.In particular, evidence supporting physiotherapy interventionsis limited as there are no studies examining the specific effectsof interventions on long-term outcomes
Assisted hopping and interaction effects in impurity models
We study, using Numerical Renormalization Group methods, the generalization
of the Anderson impurity model where the hopping depends on the filling of the
impurity. We show that the model, for sufficiently large values of the assisted
hopping term, shows a regime where local pairing correlations are enhanced.
These correlations involve pairs fluctuating between on site and nearest
neighbor positions
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