PubMed Health⌕ Search

Biomedical subjects

J Martí

Publications and source records attributed to J Martí.

At least 19 recordsLinked to original sources
PubMed2007

Tunable and reconfigurable photonic microwave filter based on stimulated Brillouin scattering.

A high Q-factor photonic microwave filter showing tuning and reshaping capabilities and based on stimulated Brillouin scattering is demonstrated. The filter bandpass can be continuously tuned, changing the microwave oscillator used to generate the pump power, and the filter shape can be modified by modulating the microwave tone. A single bandpass over the microwave spectrum can be obtained by using single-sideband suppressed carrier modulation. Experimental results demonstrate the wide tuning range of the filter, its reshaping capability, and Q factor of 670.

Journal Article↗
PubMed2006

Molecular dynamics simulation of liquid water confined inside graphite channels: dielectric and dynamical properties.

Electric and dielectric properties and microscopic dynamics of liquid water confined between graphite slabs are analyzed by means of molecular dynamics simulations for several graphite-graphite separations at ambient conditions. The electric potential across the interface shows oscillations due to water layering, and the overall potential drop is about -0.28 V. The total dielectric constant is larger than the corresponding value for the bulklike internal region of the system. This is mainly due to the preferential orientations of water nearest the graphite walls. Estimation of the capacitance of the system is reported, indicating large variations for the different adsorption layers. The main trend observed concerning water diffusion is 2-fold: on one hand, the overall diffusion of water is markedly smaller for the closest graphite-graphite separations, and on the other hand, water molecules diffuse in interfaces slightly slower than those in the bulklike internal areas. Molecular reorientational times are generally larger than those corresponding to those of unconstrained bulk water. The analysis of spectral densities revealed significant spectral shifts, compared to the bands in unconstrained water, in different frequency regions, and associated to confinement effects. These findings are important because of the scarce information available from experimental, theoretical, and computer simulation research into the dielectric and dynamical properties of confined water.

Journal Article↗
PubMed2005

All-optical flip-flop based on an active Mach-Zehnder interferometer with a feedback loop.

A novel architecture for an all-optical flip-flop is validated experimentally. The architecture comprises a single semiconductor optical amplifier-based Mach-Zehnder interferometer with an external feedback loop. The experimental results show optical bistable operation for a latching device with an on-off contrast ratio of 11 dB that employs set and reset pulses of less than 250 pJ, although the energy of these pulses could be greatly reduced by optical integration of the whole device.

Journal Article↗
PubMed2005

Structure of water nanoconfined between hydrophobic surfaces.

We report the results of a series of molecular-dynamics simulations of liquid water confined between two graphite plates with separations ranging from 7 to 15 A. Energies and free energies are provided, indicating also the corresponding stability density span of confined water phases. The structure of the different liquid layers is also discussed for all the considered systems. In particular, we studied atomic density profiles, two-dimensional radial distribution functions, hydrogen bonding, and angular orientations near the carbon plates.

Journal Article↗
PubMed2005

Antioxidant effect of virgin olive oil in patients with stable coronary heart disease: a randomized, crossover, controlled, clinical trial.

The Mediterranean diet, in which olive oil is the main source of fat, has been associated with a reduced incidence of coronary heart disease (CHD) and low blood pressure levels. Virgin olive oil (VOO), besides containing monounsaturated fat, is rich in phenolic compounds (PC) with antioxidant properties. The aim of this study was to examine the antioxidant and anti-hypertensive effect of two similar olive oils, but with differences in their PC (refined: 14.7 mg/kg versus virgin: 161.0 mg/kg), in 40 males with stable CHD. The study was a placebo controlled, crossover, randomized trial. A raw daily dose of 50 mL of VOO and refined olive oil (ROO) were sequentially administered over two periods of 3 weeks, preceded by 2-week washout periods in which ROO was used. Lower plasma oxidized LDL (p < 0.001) and lipid peroxide levels (p = 0.003), together with higher activities of glutathione peroxidase (p = 0.033), were observed after VOO intervention. Systolic blood pressure decreased after intake of VOO (p = 0.001) in hypertensive patients. No changes were observed in diastolic blood pressure, glucose, lipids, and antibodies against oxidized LDL. Consumption of VOO, rich in PC, could provide beneficial effects in CHD patients as an additional and complementary intervention to the pharmacological treatment.

Aged↗
PubMed2005

Percutaneous management of transplant ureteral fistulae is feasible in selected cases.

INTRODUCTION: Ureteral fistulae in renal transplants may develop as a consequence of compromised ureteral vascularity or from a technical factor related to the ureteroneocystostomy, the latter typically developing within the first 72 hours posttransplant. Recently, percutaneous nephrostomy drainage has been used with increasing frequency for the initial management. It alone can lead to resolution of the fistula in at least some patients. The aim of the study was the evaluation of endourological management of ureteral fistulae in renal transplants. MATERIAL AND METHODS: Between August 1981 and February 2004, 1000 adult recipients underwent renal transplantation. Sixteen out of 29 patients who developed ureteral fistulae were managed endourologically; 13, open surgery. The items recorded on these patients included the type of ureteroneocystostomy, the time to fistula diagnosis, the image technique, the type of ureteral stents, and the clinical evolution. RESULTS: The 13 patients who underwent open surgery did well. Endourological management of ureteral fistula was successfully performed in 10 of 16 cases. In all of them percutaneous nephrostomy drainage with stenting of the ureter with a double-J catheter did not prove any advantage to no stent (66.6% vs 57%). In 13 of these 16 patients in which the passage of contrast into the bladder was demonstrated, the fistula resolved in 10 cases (77%), while none of the three cases with no flow into the bladder were helped by this approach. CONCLUSION: Percutaneous techniques can provide definitive management for 62% of renal allograft patients who develop ureteral fistula beyond 72 hours after renal transplant.

Adult↗
PubMed2005

One thousand liver transplants: the hospital clinic experience.

OBJECTIVES: Our goal was to study a consecutive series of 1000 liver transplants performed in our institution to evaluate the changes over time in donors, recipients, and results. PATIENTS AND METHODS: With the aim to evaluate differences between transplantation in the first period and the present period, the first consecutive 100 liver transplants performed from June 1988 to June 1990 (first period) were compared with the last consecutive 200 liver transplants performed from January 2001 to June 2003 (second period). RESULTS: Increased donor age, change in donor cerebral death etiology, and increasing numbers of grafts from alternative methods using cadaveric donors were observed in the second period. Piggy-back technique and the biliary anastomosis without a t-tube was also started in the second period. One-year actuarial patient survival was higher in the second period (84% vs 91.3%). The need for retransplantation in the overall series was 95%. One-, 5-, and 10-year actuarial retransplant survival was 67.7%, 51.3%, and 39.4%, respectively. CONCLUSIONS: Technical innovations, better understanding of donor and recipient aspects, and global improvements were the reasons for time-related improved results of liver transplantation.

Adult↗
PubMed2005

Endourological management is better in early-onset ureteral stenosis in kidney transplantation.

INTRODUCTION: The incidence of ureteral stenosis in kidney transplant recipients is 3%-8%. The treatment of ureteral stenosis has been traditionally operative reconstruction, although such intervention is associated with high rates of serious complications, including graft loss and even perioperative mortality. More recently, endourological treatment has been proposed due to its low morbidity. OBJECTIVE: The objective of this study was to assess the usefulness of balloon percutaneous dilatation as a treatment technique for ureteral stenosis in kidney transplant recipients. PATIENTS AND METHODS: Among 1000 kidney transplantations performed between 1980 and 2004, the coexistence of high creatinine values and urinary tract dilatation in the postoperative period, after discarding concomitant causes, was managed with a percutaneous nephrostomy. Once renal function recovered, antegrade pyelography was performed to confirm the presence and determine the location of ureteral stenosis. Ureteral dilatation was performed using a 5-French balloon-fitted angioplasty catheter. RESULTS: Fifty-six patients were diagnosed with ureteral stenosis during follow-up, an incidence of 5.6%. Transluminal balloon dilatation was the first therapeutic option in 45 cases, whereas surgery was performed directly on 11 patients. Disappearance of the stenosis as well as maintenance of an improved creatinine level was verified in 45% of cases (20 patients). Two patients experienced graft loss. Both a short time to diagnosis after transplantation (P = .06) and the presence of a previous acute rejection episode (P < .05) were good prognosis factors for the endourologic solution of a ureteral stricture. CONCLUSIONS: Balloon dilatation may be considered the definitive procedure for treatment of ureteral stenosis in selected cases. Percutaneous nephrostomy should be used for initial diagnosis and improvement in the renal function before attempting an open procedure.

Adult↗
PubMed2004

Density and temperature effects on the orientational and dielectric properties of supercritical water.

The influence of temperature and density changes on the reorientational motions and dielectric properties of supercritical water is investigated by molecular dynamics simulations. A rigid simple point charged potential has been used to model water-water interactions. This model has revealed to be very satisfactory to reproduce thermodynamic, diffusive, and static dielectric properties of supercritical water. Reorientation times of water molecules have been computed along specific molecular directions and compared with available experimental data. The imaginary part of the frequency dependent dielectric constant, spectral densities of states, and residence times of water molecules in their first hydration shells are also evaluated.

Journal Article↗
PubMed2003

Right-sided endocarditis complicating an atrial septal defect.

We report the case of a 45-year-old male patient not addicted to narcotic who presented with an infective endocarditis on the pulmonary valve. He was found to have an uncomplicated secundum-type atrial septal defect. This association is an extremely rare event.

Echocardiography, Transesophageal↗
PubMed2002

[Parathyroid cyst. Report of one case].

Parathyroid cysts are rare in clinical practical. We report of 33 years old woman, with a cystic lesion in the right lobe of thyroid. The content of the cyst obtained through needle aspiration, showed a high PTH concentration (parathyroidhormone). The patient underwent surgery and the cyst was removed. The anatomopathological diagnosis was a parathyroid cyst.

Adult↗
PubMed2002

[Failure in the functioning of an implanted automatic defibrillator due to pneumothorax occurring during its implantation ].

A 67-year-old man with chronic bronchitis and coronary artery disease was scheduled to receive an implantable cardioverter defibrillator (ICD) after an episode of sustained monomorphic ventricular tachycardia. During implantation through the left subclavian vein, oxygen saturation decreased to slightly below baseline. Nevertheless, the procedure continued, given that the patient experienced neither breathing difficulties nor pain. When the ICD failed to reverse ventricular fibrillation induced to test the device, an external defibrillator was used. At that point, left-sided pneumothorax was observed by x-ray. Air in the pleural cavity caused an increase in the defibrillation threshold. After insertion of a thoracic drain, the ICD implantation procedure was completed successfully.

Aged↗
PubMed2001

Temperature effects on the static and dynamic properties of liquid water inside nanotubes.

We report a molecular dynamics simulation study of the behavior of liquid water adsorbed in carbon nanotubes under different thermodynamic conditions. A flexible simple point charged potential has been employed to model internal and intermolecular water interactions. Water-carbon forces are modeled with a Lennard-Jones-type potential. We have studied three types of tubes with effective radii ranging from 4.1 to 6.8 A and three temperatures, from 298 to 500 K for a fixed density of 1 g/cm(3). Structure of each thermodynamic state is analyzed through the characterization of the hydrogen-bond network. Time-dependent properties such as the diffusive behavior and molecular vibrational spectra are also considered. We observe the gradual destruction of the hydrogen-bond network together with faster diffusive regimes as temperature increases. A vibrational mode absent in bulk unconstrained water appears in the power spectra obtained from hydrogen velocity autocorrelation functions for all thermodynamic states. That frequency mode should be attributed to confinement effects.

Journal Article↗