Collective optical Kerr effect exhibited by an integrated configuration of silicon quantum dots and gold nanoparticles embedded in ion-implanted silica.

The study of the third-order optical nonlinear response exhibited by a composite containing gold nanoparticles and silicon quantum dots nucleated by ion implantation in a high-purity silica matrix is presented. The nanocomposites were explored as an integrated configuration containing two different ion-implanted distributions. The time-resolved optical Kerr gate and z-scan techniques were conducted using 80 fs pulses at a 825 nm wavelength; while the nanosecond response was investigated by a vectorial two-wave mixing method at 532 nm with 1 ns pulses. An ultrafast purely electronic nonlinearity was associated to the optical Kerr effect for the femtosecond experiments, while a thermal effect was identified as the main mechanism responsible for the nonlinear optical refraction induced by nanosecond pulses. Comparative experimental tests for examining the contribution of the Au and Si distributions to the total third-order optical response were carried out. We consider that the additional defects generated by consecutive ion irradiations in the preparation of ion-implanted samples do not notably modify the off-resonance electronic optical nonlinearities; but they do result in an important change for near-resonant nanosecond third-order optical phenomena exhibited by the closely spaced nanoparticle distributions.

Modulation of the propagation speed of mechanical waves in silicon quantum dots embedded in a silicon-nitride film.

Using a vectorial picosecond self-diffraction method, we evaluate the modification of the speed of the sound in a silicon-nitride film containing silicon quantum dots prepared by remote plasma-enhanced chemical vapor deposition. Our non-contact technique is based on the stimulation of the electrostriction contribution to the nonlinearity of index exhibited by the sample in a multiwave mixing laser experiment. We identified the electronic birefringence using two of the incident beams to generate a self-diffraction signal, then, we modified the third order nonlinear response by means of the optical Kerr effect given by a phase-mismatched third beam which induced electrostriction. Our results indicated that the speed of the sound in a silicon-nitride film can be simultaneously tailored by an electronic nonlinear refractive index, and by an electrostriction effect, both resulting from silicon quantum dots doping.

Influence of colloidal silver nanoparticles on the novel flower-like titanium dioxide oxygen sensor performances.

Titanium dioxide (TiO2-anatase phase) thin films, consisting of agglomerated flower-like nanoparticles, have been synthesized using an ultrasonic spray pyrolysis (USP) method in combination with titanium (IV) oxide acetylacetonate [TiO(acac)2], and methanol at 550 degrees C. These thin films were subsequently thermally treated in air, at 950 degrees C for six hours, and the flower-like particles were transformed into smooth surfaces mainly formed by the TiO2-rutile phase. In order to prepare oxygen sensors of good performance, TiO2 thin films were deposited on interdigitated gold electrodes with contacted alumina substrates. The silver colloidal solution was impregnated on the TiO2 thin film. Since the solvent in which the silver nanoparticles are suspended evaporates at 200 degrees C, the thin films were then annealed at this temperature in air for one hour. The effect of colloidal silver nanoparticles on the response of the thin films TiO2 oxygen sensors has been studied, in a mixture with zero-grade air. The gas-sensing properties of TiO2 sensors in an atmosphere of 10(4) ppm of oxygen were measured between 25 and 500 degrees C. The experimental results obtained with colloidal silver nanoparticles as surface additive show that the sensitivity to an O2 concentration of 100 ppm in zero grade air at 300 degrees C reaches a stationary value of 0.40, and 0.03, for TiO2-anatase and -rutile phase films, respectively. This values are as high as those reported for oxygen sensors prepared by more expensive techniques.

Modification of the nonlinear optical absorption and optical Kerr response exhibited by nc-Si embedded in a silicon-nitride film.

We studied the absorptive and refractive nonlinearities at 532 nm and 26 ps pulses for silicon-nitride films containing silicon nanoclusters (nc-Si) prepared by remote plasma-enhanced chemical vapor deposition (RPECVD). Using a self-diffraction technique, we measured for the as-grown sample beta=7.7x10(-9)m/W, n(2)=1.8x10(-16)m(2)/W, and /chi(3)1111/ = 4.6x10(-10)esu; meanwhile, when the sample was exposed to an annealing process at 1000 degrees C during one hour in a nitrogen atmosphere, we obtained beta=-5x10(-10)m/W, n2=9x10(-17)m(2)/W, and /chi(3)1111/=1.1x10(-10)esu. A pure electronic nonlinear refraction was identified and a large threshold ablation of 41 J/cm(-2) was found for our films. By fitting nonlinear optical transmittance measurements, we were able to estimate that the annealed sample exhibits a response time close to 1 fs. We report an enhancement in the photoluminescence (PL) signal after the annealing process, as well as a red-shift due to an increment in size of the nc-Si during the thermal process.

Photoluminescence of as-grown silicon nanocrystals embedded in silicon nitride: influence of atomic hydrogen abundance.

Silicon nanocrystals embedded in silicon nitride films were grown by direct plasma enhanced chemical vapor deposition at 300 degrees C, using mixtures of SiH2Cl2/NH3/H2/Ar. The films composition and chemical stability was tested by Fourier Transform Infrared Spectroscopy and Rutherford Backscattering Spectroscopy. The influence of hydrogen abundance during the deposition process on the photoluminescence of as-grown samples was studied as a function of the radiofrequency power and hydrogen dilution flow rate. In situ Optical Emission Spectroscopy allowed the diagnostic of the species in the plasma region and their general trends as a function of the radiofrequency power. The changes in the hydrogen content and silicon incorporation to the film as a function of the radiofrequency power were discussed in terms of silicon nanocrystals formation and growth in the silicon nitride matrix. The photoluminescence emission from the as-grown samples was found to red-shift with increasing hydrogen abundance. This observation is consistent with the increase in silicon content associated to nc-Si of larger size. On the other hand, the photoluminescence intensity was observed to decrease for very high radiofrequency powers and hydrogen dilutions. High Resolution Transmission Electron Microscopy confirmed the presence of silicon nanocrystals embedded in the amorphous silicon nitride matrix and allowed the correlation between the nanocrystals size and the photoluminescence emission energy using the quantum confinement model.

Thermo-optic effect and optical third order nonlinearity in nc-Si embedded in a silicon-nitride film.

Using a self-diffraction experiment with 7ns pulses at 532nm we studied a silicon nitride film containing silicon nanoclusters (nc-Si) of 3.1+/-0.37 nm mean size. The sample was prepared by remote plasma-enhanced chemical vapor deposition (RPECVD), and we found that its nonlinearity consists of a combination of electronic and thermal contributions. By varying the repetition rate of the laser, we discriminated the responsible mechanisms for the nonlinear response. Using this procedure we determined a total /chi((3))1111/ = 3.3x10(-10)esu, n2 = 2.7x10(-16) m(2)/W, beta = 1x10(-9) m/W and dn/dT =1x10(-4) degrees C(-1) for our sample. We also show results for the optical Kerr effect using 80 fs pulses at 820 nm. The purely electronic nonlinearity measured is characterized by /chi((3))1111/=9.5 x10(-11) esu.

Factors related to the chronicity and evolution of hepatitis C infection in patients co-infected by the human immunodeficiency virus.

OBJECTIVES: This work analyses the influence of immune status, serum human immunodeficiency virus (HIV) load and hepatitis C virus (HCV) genotypes on the probability of resolution of HCV infection in HIV-co-infected patients, as well as the evolution of HCV viremia after antiretroviral therapy. PATIENTS AND METHODS: Forty-five patients with anti-HIV and anti-HCV antibodies were classified into two groups as a function of the positivity or persistent negativity of HCV RNA detection (active or recovered HCV infection, respectively). They were treated with highly active antiretroviral therapy (HAART). Serum HCV RNA was quantified by the reverse transcription-polymerase chain reaction. HCV genotypes were detected by line probe assay or by detection of type-specific antibodies. RESULTS: HCV RNA was detectable in 30 (66.6%) out of 45 HIV-infected patients. CD4+ T-cell counts, HIV viremia, or HCV genotypes were similar in patients with active or recovered HCV infection. Patients with active HCV infection had a non-significant decrease of HCV viremia during a follow-up of 12 months (from 6.15 +/- 6.32 to 5.96 +/- 6.05 log copies/mL). This was not influenced by baseline HCV or HIV viral load, HCV genotype, or CD4+ T-cell count. The non-significant decrease was present in patients with or without an immunological response to HAART. CONCLUSION: HCV genotypes, immune status, or serum HIV load did not influence the resolution or chronicity of HCV infection in HIV-co-infected individuals. A non-significant decrease of HCV viremia in these patients treated with combinations including antiproteases could be expected.

Community-based incidence rate of cardiovascular disease and mortality in 50-75 year old adults. / Incidencia poblacional de enfermedad cardiovascular y mortalidad en los adultos de 50-75 años.

BACKGROUNDS AND OBJECTIVES: Updated information on the incidence of the principal cardiovascular diseases (CVD) and cardiovascular mortality is not available in Spain. We have studied the incidence rate of new cases of myocardial infarction, heart failure, stroke and cardiovascular mortality in the adult population in Sanlúcar de Barrameda (Spain). MATERIAL AND METHODS: A community-based prospective follow-up study was conducted. The study enrolled 858 participants aged 50-75 years who were randomly selected from the population and followed-up for 5 years. Age and gender-adjusted incidence rates of cardiovascular disease and cardiovascular mortality were calculated, obtaining complete information for 855 participants. Prognostic risk factors of new cases of cardiovascular disease were obtained using Cox proportional hazard modeling. RESULTS: The community-based incidence rate of heart failure was 455/100.000 persons-year. The incidence of myocardial infarction, stroke and cardiovascular mortality (506, 216 and 225/100.000 persons-year, respectively) was also very elevated. Male gender, family history of early cardiovascular disease, diabetes, hypertension and sedentary life style were independent risk factors of cardiovascular disease. CONCLUSIONS: The community-based incidence rate of heart failure in Sanlúcar de Barrameda (Spain) is very high, and it is the first to be reported in Spain. The incidence of myocardial infarction is among the highest in Spain.

Community-based incidence rate of cardiovascular disease and mortality in 50-75 year old adults.

BACKGROUNDS AND OBJECTIVES: Updated information on the incidence of the principal cardiovascular diseases (CVD) and cardiovascular mortality is not available in Spain. We have studied the incidence rate of new cases of myocardial infarction, heart failure, stroke and cardiovascular mortality in the adult population in Sanlúcar de Barrameda (Spain). MATERIAL AND METHODS: A community-based prospective follow-up study was conducted. The study enrolled 858 participants aged 50-75 years who were randomly selected from the population and followed-up for 5 years. Age and gender-adjusted incidence rates of cardiovascular disease and cardiovascular mortality were calculated, obtaining complete information for 855 participants. Prognostic risk factors of new cases of cardiovascular disease were obtained using Cox proportional hazard modeling. RESULTS: The community-based incidence rate of heart failure was 455/100.000 persons-year. The incidence of myocardial infarction, stroke and cardiovascular mortality (506, 216 and 225/100.000 persons-year, respectively) was also very elevated. Male gender, family history of early cardiovascular disease, diabetes, hypertension and sedentary life style were independent risk factors of cardiovascular disease. CONCLUSIONS: The community-based incidence rate of heart failure in Sanlúcar de Barrameda (Spain) is very high, and it is the first to be reported in Spain. The incidence of myocardial infarction is among the highest in Spain.

Medication adherence in patients who undergo cardiac transplantation.

BACKGROUND: Heart transplant patients are required to take medication for life, both immunosuppressants to prevent rejection and any required for other illnesses. Treatment compliance can be measured quantitatively or qualitatively. Compliance measurement is not easy owing to different factors. The aim of this study was to assess the prevalence of therapeutic compliance in heart transplant patients. METHODS: We undertook a cross-sectional observational descriptive study. The sample comprised patients who received a heart transplant from 2001 to 2011. Of the 203 patients in total, we studied 99. We used the Morisky-Green test as an indirect method and recorded the immunosuppressant blood levels as a direct method. RESULTS: The mean age of the patients was 50 ± 12 years, and 84% were male. According to the Morisky-Green test, 33% of the patients were noncompliant, of whom 30% said they rarely forgot to take their medication. Patients took an average of 8 ± 3 drugs per day, but only 85% knew what the drugs were for; 24% of the patients had grade 3A rejection, and 65% had graft vessel disease. CONCLUSIONS: Transplanted patients in this study showed a high level of therapeutic adherence that did not differ from other transplant series, either cardiac or other organs, nor from other chronic diseases. The results for defaulters were higher than that expected from these patients. The defaulter results were expected to be lower, given the information that the patients were supposed to have, both before and after the transplantation, and with the strict medical monitoring. Therefore, we have to stress therapeutic compliance, both medical and dietary-hygiene measures, and seek new strategies to improve the results.

[Renal failure and insulin resistance: effect of the dialysis dose]. / Insuficiencia renal y resistencia insulínica: efecto de la dosis de diálisis.

BACKGROUND: The main cause of death in patients undergoing hemodialysis are cardiovascular events. We have analyzed the association between intradialysis fractional clearance of urea or Kt/V index in patients with chronic renal failure in hemodialysis as an indicator of adequate dialysis and the classical factors of cardiovascular risk. PATIENTS AND METHODS: A total of 47 patients with chronic renal failure on hemodialysis were included. Diabetes mellitus was considered an exclusion criteria. Optimization of dialysis was analyzed by Kt/v index in accordance with the Daugirdas formula. The cardiovascular risk factors evaluated were: insulin resistance, calculated according to the HOMA method, total cholesterol, LDL-cholesterol, triglycerides, arterial hypertension, obesity and metabolic syndrome. The relationship between cardiovascular risk factors and Kt/V index was analyzed with the variant and multivariant analysis. RESULTS: The HOMA median (interquartile range) of the patients was 1.16 (0.53-5.77). HOMA was correlated with triglycerides and HDL-cholesterol levels. HOMA was significantly greater in those who had less adapted dialysis (Kt/V < 1.4) (1.9 +/- 1.3 vs 1.0 +/- 0.3, p = 0.02). Furthermore, a negative correlation was found between HOMA and Kt/V. The multivariant analysis of the factors associated to HOMA demonstrated that the only associated parameters were Kt/V greater than 1.4, body mass index and age. CONCLUSIONS: In patients with chronic renal failure, adapted dialysis, determined by the Kt/V index, correlated negatively with insulin resistance. Based on these data, we suggest the need for longitudinal studies that consider this index as a predictive variable of cardiovascular events in this type of patients.

[Infection by Pseudomonas aeruginosa in patients with human immunodeficiency virus infection. Descriptive study of 35 cases]. / Infección por Pseudomonas aeruginosa en pacientes infectados por el virus de la inmunodeficiencia humana. Estudio descriptivo de 35 casos.

OBJECTIVE: Analysis of the spectrum of diseases attributed to Pseudomonas aeruginosa in patients with coinfection with the immunodeficiency virus (HIV). METHODS: Retrospective study of 35 cases of coinfection with P. aeruginosa-HIV, attended from 1985 until 1995. Analysis of putative factors implicated in mortality secondary to P. aeruginosa infection. RESULTS: The spectrum of infection due to P. aeruginosa was: ORL infection (4 cases), infection of upper respiratory tract (4 cases), pneumonia (21 cases), infected bronchiectasias (one case), endocarditis (2 cases) and primary bacteremia (3 cases). Most of these infections were community-acquired ones (30 cases [85.7%]). Degree of immunodepression was variable, with 12 cases (34.3%) affecting to patients with more than 200 CD4+lymphocytes x 10(-9)/l. Radiological pattern of pneumonias consisted in alveolar consolidation (18 cases [85.7%]), necrotizing pneumonia (2 cases [9.5%]) and interstitial pattern (one case [4.8%]). More than a 80% of isolates of P. aeruginosa was sensible to ceftazidime, ciprofloxacin, aminoglycosides, ureidopenicillins and imipenem. Recidives of the P. aeruginosa infection were detected in 7 cases (20%): 4 cases of ORL infection (100%) and 3 cases of lower respiratory tract infection (13.6%). Overall mortality was a 20% (7 cases), being directly attributed to P. aeruginosa infection in every one of the cases, all of them pneumonias. Secondary bacteremia was associated to a higher mortality (odds ratio [OR] 18.67; p = 0.0207). CONCLUSIONS: P. aeruginosa affect to the HIV-infected patients, independently of their immunodepression degree, affecting to different localizations. This bacteria continues to be sensible to conventional anti-Pseudmonas treatment. Pneumonia with secondary bacteremia is associated to a higher mortality.

Prognostic evaluation of bacteremia and fungemia in patients with acquired immunodeficiency syndrome.

The incidence of bacterial infections in general and of bacteremia in particular is high among patients with acquired immunodeficiency syndrome (AIDS). The factors influencing the prognosis of bacteremia in these patients are not well known. In order to better define those factors associated with a poor prognosis, all episodes of bacteremia or fungemia in patients with AIDS who were hospitalized in four general hospitals between 1 September 1987 and 31 December 1996 were studied prospectively. Among 1,390 patients diagnosed with AIDS, 238 (17.1%) developed 274 episodes of bacteremia or fungemia. Mortality related to bacteremia was 21.3%. Variables associated with high mortality were fungemia (odds ratio [OR], 6.19; 95% confidence interval [CI], 1.99 - 19.28), hypotension (OR, 19.65; 95%CI, 7.42 - 52.07), inappropriate antimicrobial treatment (OR, 16.94; 95%CI, 4.92 - 58.32), and unknown origin of bacteremia (OR, 3.93; 95%CI, 1.58 - 9.76). The mortality rate among patients with at least one of these factors was 46.7%, whereas in patients without any of these factors, the rate was 4.9% ( P < 0.001). Bacteremic episodes of unknown origin were significantly more frequently associated with community acquisition ( P = 0.001), inappropriate antimicrobial treatment ( P = 0.04), and etiology by gram-negative microorganisms or fungi ( P < 0.001) and were significantly less frequently associated with the presence of a previous intravenous catheter ( P = 0.004), resulting in peculiar etiologic and epidemiological profiles. The factors that influence the outcome of AIDS patients who develop bacteremia are sometimes avoidable or known during the first days after admission. Therefore, knowledge about these factors could improve the prognosis of bloodstream infections in this population.

Pneumocystis jiroveci isolates with dihydropteroate synthase mutations in patients with chronic bronchitis.

Since mutations in the dihydropteroate synthase (DHPS) gene possibly associated with sulfonamide resistance have been reported in patients with Pneumocystis jiroveci (previously carinii) pneumonia, and since P. jiroveci colonization has been recently demonstrated in patients with chronic pulmonary diseases, the present study aimed to investigate the possible occurrence of P. jiroveci DHPS mutations in patients with chronic bronchitis. P. jiroveci colonization was detected in 15 of 37 non-selected patients with chronic bronchitis by amplifying the large subunit of the mitochondrial gene of the ribosomal RNA using nested PCR. DHPS mutations were demonstrated using touchdown PCR and restriction enzyme analysis in two of eight patients with chronic bronchitis and in two of six patients from the same region who had AIDS-associated Pneumocystis pneumonia. In all cases, mutations were observed in subjects with no prior exposure to sulfonamides. These data could have important implications for public health, since (i) P. jiroveci colonization could speed the progression of chronic bronchitis, and (ii) these patients, who are customary sputum producers, could represent a reservoir for sulfonamide-resistant strains with the potential ability to transmit them to immunocompromised hosts susceptible to Pneumocystis pneumonia.

[A prospective study of meningitis diagnosed in a 3rd-level hospital during a 1-year period]. / Estudio prospectivo de las meningitis diagnosticadas en un hospital de tercer nivel durante un período de un año.

OBJECTIVE: One-year prospective observational study of meningitis diagnosed at a third level hospital. PATIENTS AND METHODS: All patients with a cerebrospinal fluid (CSF) specimen with cyto-biochemical characteristics and clinical picture consistent with meningitis were included in the study. They were followed from admission to hospital up to discharge or exitus. The epidemiologic characteristics of patients, etiology, related risk factors and predisposing situations, CSF characteristics, clinical manifestations, clinical course, and antibiotic susceptibility of the causative agents were analyzed. RESULTS: Ninety-five cases were included. Seventy-six (69.4%) were community acquired and 29 (30.5%) nosocomially acquired meningitis. Among community acquired meningitis, 31 (46.9%) were of bacterial origin (8 N. meningitidis, 3 H. influenzae, 2 S. pneumoniae, 1 Streptococcus group B, 1 Listeria monocytogenes, 1 Staphylococcus aureus, and 1 Brucella spp.); CSF culture was negative in 14 cases (41.2%). In most cases neither risk factor nor predisposing situations were detected. Patients with purulent meningitis and negative CSF culture had a significantly lower number of complications than patients with positive CSF culture. Among patients previously treated with beta-lactam antibiotics (8 cases) the probability of a negative CSF culture was greater than among not treated patients (OR 16.00, 95% CI 1.45-764.68; p = 0.011). The remaining cyto-biochemical characteristics were similar in both groups. Thirty-five cases (53.03%) of community acquisition were lymphocytic meningitis (31 viral, 3 tuberculous, and 1 luetic meningitis). Among nosocomial cases (29 cases, 30.5%), most were caused by gram-negative bacilli and microorganisms of the Staphylococcus genus. Fourteen cases (48.2%) were related to some type of neurosurgical procedure. Overall, only two exitus cases were recorded. CONCLUSIONS: The etiologic agents of community acquired meningitis are mainly N. meningitidis, S. pneumoniae and Haemophilus influenzae. The previous antibiotic therapy did not influence thy cyto-biochemical characteristics of CSF but it did influence the yielding of culture. Meningitis with negative CSF culture has a significantly lower number of complications. The availability of a Neurosurgery Department at a hospital confers a change in the epidemiologic spectrum of diagnosed meningitis, with a higher incidence of nosocomial meningitis. In our environment, a substantial proportion of cases due to Staphylococcus microorganisms was observed.

Incidencia poblacional de enfermedad cardiovascular y mortalidad en los adultos de 50-75 años / Community-based incidence rate of cardiovascular disease and mortality in 50-75 year old adults

Antecedentes y objetivos. En España no disponemos de una información actualizada sobre la incidencia poblacional de las principales enfermedades cardiovasculares (ECV) y de la mortalidad cardiovascular. Hemos determinado la densidad de incidencia de nuevos casos de infarto de miocardio, ictus, insuficiencia cardiaca y mortalidad cardiovascular en adultos de Sanlúcar de Barrameda. Material y métodos. Estudio poblacional prospectivo realizado sobre una cohorte de 858 adultos de 50-75 años seleccionados aleatoriamente y seguida durante 5 años. Se calculó la densidad de incidencia de enfermedad cardiovascular y de mortalidad cardiovascular ajustada a edad, sexo y a la población estándar europea, consiguiendo información completa de 855 participantes. Mediante el cálculo de riesgos proporcionales de Cox se obtuvieron los factores de riesgo pronósticos de nuevos casos de enfermedad cardiovascular. Resultados. La incidencia de insuficiencia cardiaca fue de 454/100.000 personas/año. Las incidencias de infarto de miocardio, ictus y mortalidad cardiovascular (506, 216 y 225/100.000 personas/año, respectivamente) también fueron muy elevadas. El sexo masculino, el antecedente familiar de ECV precoz, la diabetes, la hipertensión arterial y el sedentarismo fueron los factores pronósticos independientes de ECV. Conclusiones. La incidencia poblacional de la insuficiencia cardiaca en Sanlúcar de Barrameda es muy elevada, y es la primera que se comunica en España. La incidencia de infarto de miocardio es de las más elevadas de España(AU)

Backgrounds and objectives. Updated information on the incidence of the principal cardiovascular diseases (CVD) and cardiovascular mortality is not available in Spain. We have studied the incidence rate of new cases of myocardial infarction, heart failure, stroke and cardiovascular mortality in the adult population in Sanlúcar de Barrameda (Spain). Material and methods. A community-based prospective follow-up study was conducted. The study enrolled 858 participants aged 50-75 years who were randomly selected from the population and followed-up for 5 years. Age and gender-adjusted incidence rates of cardiovascular disease and cardiovascular mortality were calculated, obtaining complete information for 855 participants. Prognostic risk factors of new cases of cardiovascular disease were obtained using Cox proportional hazard modeling. Results. The community-based incidence rate of heart failure was 455/100.000 persons-year. The incidence of myocardial infarction, stroke and cardiovascular mortality (506, 216 and 225/100.000 persons-year, respectively) was also very elevated. Male gender, family history of early cardiovascular disease, diabetes, hypertension and sedentary life style were independent risk factors of cardiovascular disease. Conclusions. The community-based incidence rate of heart failure in Sanlúcar de Barrameda (Spain) is very high, and it is the first to be reported in Spain. The incidence of myocardial infarction is among the highest in Spain(AU)