195 research outputs found
Existence of global-in-time solutions to a generalized Dirac-Fock type evolution equation
We consider a generalized Dirac-Fock type evolution equation deduced from
no-photon Quantum Electrodynamics, which describes the self-consistent
time-evolution of relativistic electrons, the observable ones as well as those
filling up the Dirac sea. This equation has been originally introduced by Dirac
in 1934 in a simplified form. Since we work in a Hartree-Fock type
approximation, the elements describing the physical state of the electrons are
infinite rank projectors. Using the Bogoliubov-Dirac-Fock formalism, introduced
by Chaix-Iracane ({\it J. Phys. B.}, 22, 3791--3814, 1989), and recently
established by Hainzl-Lewin-Sere, we prove the existence of global-in-time
solutions of the considered evolution equation.Comment: 12 pages; more explanations added, some final (minor) corrections
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COPD classification models and mortality prediction capacity
Our aim was to assess the impact of comorbidities on existing COPD prognosis scores.
Patients and methods: A total of 543 patients with COPD (FEV1 < 80% and FEV1/ FVC <70%) were included between January 2003 and January 2004. Patients were stable for at least 6 weeks before inclusion and were followed for 5 years without any intervention by the research team. Comorbidities and causes of death were established from medical reports or information from primary care medical records. The GOLD system and the body mass index, obstruction, dyspnea and exercise (BODE) index were used for COPD classification. Patients were also classified into four clusters depending on the respiratory disease and comorbidities. Cluster analysis was performed by combining multiple correspondence analyses and automatic classification. Receiver operating characteristic curves and the area under the curve (AUC) were calculated for each model, and the DeLong test was used to evaluate differences between AUCs. Improvement in prediction ability was analyzed by the DeLong test, category-free net reclassification improvement and the integrated discrimination index.
Results: Among the 543 patients enrolled, 521 (96%) were male, with a mean age of 68 years, mean body mass index 28.3 and mean FEV1% 55%. A total of 167 patients died during the study follow-up. Comorbidities were prevalent in our cohort, with a mean Charlson index of 2.4. The most prevalent comorbidities were hypertension, diabetes mellitus and cardiovascular diseases. On comparing the BODE index, GOLDABCD, GOLD2017 and cluster analysis for pre-dicting mortality, cluster system was found to be superior compared with GOLD2017 (0.654 vs 0.722, P=0.006), without significant differences between other classification models. When cardiovascular comorbidities and chronic renal failure were added to the existing scores, their prognostic capacity was statistically superior (P<0.001).
Conclusion: Comorbidities should be taken into account in COPD management scores due to their prevalence and impact on mortalit
Chronic obstructive pulmonary disease subtypes. transitions over time
Background Although subtypes of chronic obstructive pulmonary disease are recognized, it is unknown what happens to these subtypes over time. Our objectives were to assess the stability of cluster-based subtypes in patients with stable disease and explore changes in clusters over 1 year. Methods Multiple correspondence and cluster analysis were used to evaluate data collected from 543 stable patients included consecutively from 5 respiratory outpatient clinics. Results Four subtypes were identified. Three of them, A, B, and C, had marked respiratory profiles with a continuum in severity of several variables, while the fourth, subtype D, had a more systemic profile with intermediate respiratory disease severity. Subtype A was associated with less dyspnea, better health-related quality of life and lower Charlson comorbidity scores, and subtype C with the most severe dyspnea, and poorer pulmonary function and quality of life, while subtype B was between subtypes A and C. Subtype D had higher rates of hospitalization the previous year, and comorbidities. After 1 year, all clusters remained stable. Generally, patients continued in the same subtype but 28% migrated to another cluster. Together with movement across clusters, patients showed changes in certain characteristics (especially exercise capacity, some variables of pulmonary function and physical activity) and changes in outcomes (quality of life, hospitalization and mortality) depending on the new cluster they belonged to Conclusions Chronic obstructive pulmonary disease clusters remained stable over 1 year. Most patients stayed in their initial subtype cluster, but some moved to another subtype and accordingly had different outcomes
P67 195. CirugÃa del tromboembolismo pulmonar masivo en el enfermo crÃtico
La extracción de los trombos pulmonares en el tromboembolismo pulmonar masivo antes de 1953 (operación de Trendelenburg) cosechó fracaso tras fracaso. Desde el advenimiento de la circulación extracorpórea (CEC) el porcentaje de éxito de esta operación mejoró notablemente, no habiendo dejado de aumentar hasta la actualidad, existiendo series que reflejan porcentajes de hasta el 94% de supervivencia inmediata, con 86 y 83% de supervivencia actuarial a 1 y 3años.Presentamos un caso de paciente varón de 35años sin enfermedad previa ni antecedentes familiares de enfermedad tromboembólica. Consulta por insuficiencia respiratoria, siendo diagnosticado por tomografÃa computarizada de tromboembolismo en AP izquierda, la cual ocluye. El ECO-Doppler de MMII descarta trombosis venosa profunda (TVP). Una nueva tomografÃa computarizada informa de persistencia de la obstrucción de AP izquierda y sus ramas, que parece haber aumentado. En ecocardiografÃa transtorácica (ETT) dilatación de cavidades derechas con función de ventrÃculo derecho (VD) normal y presión sistólica de la arteria pulmonar (PSAP) de 70 mmHg. Los estudios para investigar trombofilia fueron negativos.Tras unos dÃas empeora su situación, produciéndose dos paradas cardiorrespiratorias, de las que es reanimado y tratado inmediatamente con TNK. La tomografÃa computarizada muestra la existencia de nuevo episodio de tromboembolismo pulmonar que afecta a la AP derecha gravemente.Es intervenido quirúrgicamente bajo CEC sin parada circulatoria, extrayéndose molde trombótico de tronco y ambas ramas de la AP. La evolución postoperatoria fue favorable. En tomografÃa computarizada de control se observan limpios el tronco y las ramas de la AP, con cierto compromiso en ramas subsegmentarias de la AP izquierda.Se muestran imágenes de la intervención y tomografÃa computarizada pre y posquirúrgicas
Dynamic renormalization group study of a generalized continuum model of crystalline surfaces
We apply the Nozieres-Gallet dynamic renormalization group (RG) scheme to a
continuum equilibrium model of a d-dimensional surface relaxing by linear
surface tension and linear surface diffusion, and which is subject to a lattice
potential favoring discrete values of the height variable. The model thus
interpolates between the overdamped sine-Gordon model and a related continuum
model of crystalline tensionless surfaces. The RG flow predicts the existence
of an equilibrium roughening transition only for d = 2 dimensional surfaces,
between a flat low-temperature phase and a rough high-temperature phase in the
Edwards-Wilkinson (EW) universality class. The surface is always in the flat
phase for any other substrate dimensions d > 2. For any value of d, the linear
surface diffusion mechanism is an irrelevant perturbation of the linear surface
tension mechanism, but may induce long crossovers within which the scaling
properties of the linear molecular-beam epitaxy equation are observed, thus
increasing the value of the sine-Gordon roughening temperature. This phenomenon
originates in the non-linear lattice potential, and is seen to occur even in
the absence of a bare surface tension term. An important consequence of this is
that a crystalline tensionless surface is asymptotically described at high
temperatures by the EW universality class.Comment: 22 pages, 5 figures. Accepted for publication in Physical Review
. A trophic latitudinal gradient revealed in anchovy and sardine from the Western Mediterranean Sea using a multi-proxy approach
This work combines state-of-the-art methods (DNA metabarcoding) with classic approaches (visual stomach content characterization and stable isotope analyses of nitrogen (δ15N) and carbon (δ13C)) to investigate the trophic ecology of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) at high taxonomic and spatial resolution in the Western Mediterranean Sea. Gut contents observed are in accordance with the dietary plasticity generally described for anchovy and sardine, suggesting a diet related to the opportunistic ingestion of available prey in a certain area and/or time. Genetic tools also showed modest inter-specific differences regarding ingested species. However, inter-specific and intra-specific differences in ingested prey frequencies and prey biomass reflected a latitudinal signal that could indicate a more effective predation on large prey like krill by anchovy versus sardine, as well as a generalized higher large prey ingestion by both species southwards. In fact, both species presented lower δ15N in the northernmost area. This latitudinal gradient indicates changes in the trophic ecology of anchovy and sardine that coincide with previously described better biological conditions for fish in the southern part of the study area as well as higher landings of both species in recent years.En prensa2,92
Intraoperative radiotherapy electron boost followed by moderate doses of external beam radiotherapy in resected soft-tissue sarcoma of the extremities
To analyze the patterns of failure and the toxicity profile of
intraoperative electron beam radiotherapy (IOERT) after resection of soft tissue
sarcomas of the extremities (STS). PATIENTS AND METHODS: Forty-five patients with
extremity STS were treated with IOERT and moderate-dose postoperative
radiotherapy (45-50 Gy). Twenty-six patients were treated for primary disease
(PD) and 19 patients for an isolated recurrence (ILR). Tumor size was >5 cm
(maximum diameter) in 36 patients (80%), and high-grade histology in PD patients
was present in 14 patients (54%). In nine patients, IOERT was used alone, due to
previous irradiation or patient refusal. Chemotherapy (neoadjuvant and/or
adjuvant) was mainly given to high-grade tumors. RESULTS: Nine patients relapsed
in the extremity (20%), and 12 patients in distant sites (28%). Actuarial local
control at 5 years was 88% for patients with negative/close margins and 57% for
patients presenting positive margins (P=0.04). Five patients (11%) developed
neuropathy associated with the treatment. Extremity preservation was achieved in
40 patients (88%). With a median follow-up of 93 months (range: 27-143 months)
for the patients at risk, 25 patients remain alive (a 7-year actuarial survival
rate of 75% for PD and 47% for ILR; P=0.01). CONCLUSIONS: IOERT combined with
moderate doses of external beam irradiation yields high local control and
extremity preservation rates in resected extremity STS. Peripheral nerves in the
IOERT field are dose-limiting structures requiring a dose compromise in the IOERT
component to avoid severe neurological damage
Noise induced transitions in semiclassical cosmology
A semiclassical cosmological model is considered which consists of a closed
Friedmann-Robertson-Walker in the presence of a cosmological constant, which
mimics the effect of an inflaton field, and a massless, non-conformally coupled
quantum scalar field. We show that the back-reaction of the quantum field,
which consists basically of a non local term due to gravitational particle
creation and a noise term induced by the quantum fluctuations of the field, are
able to drive the cosmological scale factor over the barrier of the classical
potential so that if the universe starts near zero scale factor (initial
singularity) it can make the transition to an exponentially expanding de Sitter
phase. We compute the probability of this transition and it turns out to be
comparable with the probability that the universe tunnels from "nothing" into
an inflationary stage in quantum cosmology. This suggests that in the presence
of matter fields the back-reaction on the spacetime should not be neglected in
quantum cosmology.Comment: LaTex, 33.tex pages, no figure
Effects of dexmedetomidine on subthalamic local field potentials in parkinson's disease
Background: Dexmedetomidine is frequently used for sedation during deep brain stimulator implantation in patients with Parkinson's disease, but its effect on subthalamic nucleus activity is not well known. The aim of this study was to quantify the effect of increasing doses of dexmedetomidine in this population.
Methods: Controlled clinical trial assessing changes in subthalamic activity with increasing doses of dexmedetomidine (from 0.2 to 0.6 μg kg-1 h-1) in a non-operating theatre setting. We recorded local field potentials in 12 patients with Parkinson's disease with bilateral deep brain stimulators (24 nuclei) and compared basal activity in the nuclei of each patient and activity recorded with different doses. Plasma levels of dexmedetomidine were obtained and correlated with the dose administered.
Results: With dexmedetomidine infusion, patients became clinically sedated, and at higher doses (0.5-0.6 μg kg-1 h-1) a significant decrease in the characteristic Parkinsonian subthalamic activity was observed (P<0.05 in beta activity). All subjects awoke to external stimulus over a median of 1 (range: 0-9) min, showing full restoration of subthalamic activity. Dexmedetomidine dose administered and plasma levels showed a positive correlation (repeated measures correlation coefficient=0.504; P<0.001).
Conclusions: Patients needing some degree of sedation throughout subthalamic deep brain stimulator implantation for Parkinson's disease can probably receive dexmedetomidine up to 0.6 μg kg-1 h-1 without significant alteration of their characteristic subthalamic activity. If patients achieve a 'sedated' state, subthalamic activity decreases, but they can be easily awakened with a non-pharmacological external stimulus and recover baseline subthalamic activity patterns in less than 10 min
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