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L Poletto

Publications and source records attributed to L Poletto.

At least 19 recordsLinked to original sources
PubMed2006

Isolated single-cycle attosecond pulses.

We generated single-cycle isolated attosecond pulses around approximately 36 electron volts using phase-stabilized 5-femtosecond driving pulses with a modulated polarization state. Using a complete temporal characterization technique, we demonstrated the compression of the generated pulses for as low as 130 attoseconds, corresponding to less than 1.2 optical cycles. Numerical simulations of the generation process show that the carrier-envelope phase of the attosecond pulses is stable. The availability of single-cycle isolated attosecond pulses opens the way to a new regime in ultrafast physics, in which the strong-field electron dynamics in atoms and molecules is driven by the electric field of the attosecond pulses rather than by their intensity profile.

Journal Article↗
PubMed2006

Spectroscopic characterization of vacuum ultraviolet free electron laser pulses.

Because of the stochastic nature of self-amplified spontaneous emission (SASE), it is crucial to measure for single pulses the spectral characteristics of ultrashort pulses from the vacuum ultraviolet free electron laser (FLASH) at DESY, Germany. To meet this particular challenge, we have employed both photon and photoelectron spectroscopy. Each FEL pulse is composed of an intense and spectrally complex fundamental, centered at a photon energy of about 38.5 eV, with a bandwidth of 0.5% accompanied by higher harmonics, each carrying an intensity of typically 0.3 to 0.6% of that of the fundamental. The correlation between the harmonics and the fundamental is in remarkable agreement with a simple statistical model of SASE FEL radiation.

Journal Article↗
PubMed2006

Gratings in a conical diffraction mounting for an extreme-ultraviolet time-delay-compensated monochromator.

The conical diffraction mounting in which the direction of incident light belongs to a plane parallel to the direction of the grooves has the unique property of maintaining high diffraction efficiency, even in the extreme-ultraviolet (EUV) region. This property is useful for designing high-throughput time-delay-compensated monochromators for the spectral selection of ultrashort EUV pulses as the high-order harmonics generated by the interaction between an ultrashort laser pulse and a gas jet. The time compensation allows one to exploit the femtosecond scale duration of the harmonics both to have high intensity and to reach an unprecedented temporal resolution for pump and probe experiments. Because two gratings have to be used for time compensation, the high diffraction efficiency becomes an essential requirement, which can be fulfilled by the conical diffraction mounting. Measurements recently accomplished at the Bending Magnet for Emission Absorption and Reflectivity (BEAR) beam line (ELETTRA Synchrotron, Trieste, Italy) for three gratings in the 10-90 nm region are reported here that show a peak efficiency of as much as 0.7 in the first order. A model computing the electromagnetic propagation and the grating efficiency, implemented and tested with the experimental data, permits the study and design of rather complex systems operating in the conical mounting. Basic physical principles and mathematical aspects of the model are discussed here.

Journal Article↗
PubMed2005

Measurement of harmonic phase differences by interference of attosecond light pulses.

By using a self-referencing technique, we have experimentally measured the influence of the carrier-envelope phase of femtosecond light pulses on the phase of the electric field of the radiation produced by high-order harmonic generation. We show that, in particular experimental conditions, the temporal evolution of the electric field of the attosecond pulses, is directly controlled by the carrier-envelope phase of the driving pulses.

Journal Article↗
PubMed2004

Observation of carrier-envelope phase phenomena in the multi-optical-cycle regime.

So far the role of the carrier-envelope phase of a light pulse has been clearly experimentally evidenced only in the sub-6-fs temporal regime. Here we show, both experimentally and theoretically, the influence of the carrier-envelope phase of a multi-optical-cycle light pulse on high-order harmonic generation. For the first time, we demonstrate that the short and long electron quantum paths contributing to harmonic generation are influenced in a different way by the pulse carrier-envelope phase.

Journal Article↗
PubMed2002

High-brightness high-order harmonic generation by truncated bessel beams in the sub-10-fs regime.

Low-divergence, high-brightness harmonic emission has been generated by using a fundamental beam with a truncated Bessel intensity profile. Such a beam is directly obtained by using the hollow-fiber compression technique, which indeed allows one to optimize both temporal and spatial characteristics of the high-order harmonic generation process. This is particularly important for the applications of radiation, where extreme temporal resolution and high brightness are required.

Journal Article↗
PubMed2002

Morphological and demographic associations of biliary symptoms in subjects with gallstones: findings from a population-based survey in Rosario, Argentina.

BACKGROUND: Gallstone disease is a frequently encountered disorder in subjects living in Rosario. The reasons for the presence or absence of symptoms are unknown. AIMS: To determine associations between biliary symptoms and ultrasonographic features of gallbladder and gallstones. SUBJECTS: A random study was conducted on 1,173 subjects, inhabitants of 20 years and older, in the city of Rosario, Argentina. METHODS: High-resolution abdominal ultrasound examinations were performed. Biliary pain was defined based on previously published definitions. RESULTS: Gallstones were found in 149 subjects (101 female, 48 male) of whom 51% of females and 35% of males with cholelithiasis were symptomatic. Mean age was 53 years in symptomatic and 55 in asymptomatic subjects. Gallbladder size was normal in 97% of symptomatic and in 96% of the asymptomatic participants. There were no significant differences between the groups as far as concerns size and gallstone number. Impacted stones were observed in 10% of symptomatic and in none of the asymptomatic subjects (p<0.01). CONCLUSIONS: Subjects' age and gender, gallstones size and number, as well as ultrasonographic features of gallbladder and biliary tract did not differ significantly between symptomatic and asymptomatic subjects. Only impacted stones were significantly more frequent in symptomatic subjects.

Adult↗
PubMed2000

Spectral features and modeling of high-order harmonics generated by sub-10-fs pulses

Harmonic radiation generated in a neon gas jet by sub-10-fs laser pulses was investigated both experimentally and theoretically. The spectral profile of the harmonics with respect to the order, their intensity and relative spectral shifts were measured as a function of the position of the gas jet. The results point out spectral features typical of the quasi-single-cycle excitation regime. A nonadiabatic three-dimensional numerical model was developed, which provides harmonic spectra in remarkable agreement with the experiments.

Journal Article↗
PubMed2000

Epidemiology of gallstone disease in Argentina: prevalences in the general population and European descendants.

To assess gallstone disease prevalence in Argentina, a random sample of the Rosario City population was studied, considering already known associated factors, and analyzing ethnic groups living in the city. A total of 1,173 participants (69% response), both sexes, 20 years and older were studied. Each subject underwent an abdominal ultrasound examination, a blood test, and a standardized questionnaire. It was seen that gallstone disease prevalence (gallstones or cholecystectomy), overall was 20.5% (23.8% in women and 15.5% in men; (P = 0.0005), and was associated with age and body mass index in both sexes, and with pregnancy number and hypertriglyceridemia in women. As regards ancestors' nationalities, Italian and Spanish descendants presented higher prevalence rates for all age groups than those described in Italy and Spain. Thus far, in a subsample of 78% of nonparticipants submitted to a new home visit, presence of cholecystectomy or symptoms did not differ from participants, supporting the validity of our results.

Adult↗
PubMed2000

Tachycardia: an autosomal, monogenic, biallelic, recessive trait.

A brief commentary of the genetics of blood pressure is presented. The importance of the mechanisms of blood pressure regulation, among which heart rate is relevant, is emphasized. The analysis of a small population to test the quantitative model of the trait heart rate, considered as a metric character, is presented. The analysis of heart rate fitting to a qualitative model of inheritance is carried out. The results displayed might support the hypothesis that tachycardia could be an autosomal, monogenic, biallelic recessive trait.

Alleles↗
PubMed1999

Occupation and histopathology of lung cancer: A case-control study in Rosario, Argentina.

BACKGROUND: Male age-adjusted lung cancer mortality rate is high in Rosario City, Argentina (62.7 per 100,000). METHODS: Case-control study involving interviews with 367 male lung cancer patients and 576 controls. RESULTS: The histological distribution detected was: squamous cell 39%, adenocarcinoma 34%, small cell carcinoma 13%, and other or no specified cell type 14%. When comparing with the group unlikely to be exposed to occupational carcinogens, a 60% increase in risk was observed for the remaining occupations (P < 0.008). Risks were high for drivers (OR=1.9, CI: 1.1-4.0), construction (OR=2.5, CI: 1.0-5.9), and agricultural workers also (OR=1.8, CI: 1. 1-3.1). In regard to squamous cell carcinoma, increased risks were observed in the metal industry, particularly in welders (OR=2.9, CI: 1.0-10.1) and mechanics (OR=1.8, CI: 0.9-4.2). Smoking was not a substantial confounding effect. CONCLUSIONS: Occupational exposures partly account for the high lung cancer mortality rate among male residents of Rosario City.

Adenocarcinoma↗
PubMed1999

Irritable bowel syndrome: clinical and psychopathological correlations.

Irritable bowel syndrome is a common disorder in gastroenterology consultations. Our objectives were to assess patients' psychic functioning, the relationships between psychopathology and pain, the degree of psychopathology in constipated and diarrheic subgroups, and if previous abdominal surgery was related to pain intensity. Forty-five gastroenterological outpatients, both sexes, were studied. Patients were grouped as predominantly constipated, predominantly diarrheic, or alternating constipation and diarrhea. After diagnosis, patients had: Psychologist half-guided interviews, Bender Visuomotor Gestalt Test, Hammer Graphic Tests, and Rorschach Psychodiagnostic Tests. The last one showed that 78% suffered from distortion in reality perception; 100% thought away from reality and had a deficit in organizing capability, synthesis, and integration. Within psychological gnosiology, these patients would be diagnosed as borderline personalities and this would imply an overlapping of neurotic and psychotic functioning. Affective vulnerability and overadjustment to environment were found, and this finding is an original one to the best of our knowledge.

Adolescent↗
PubMed1998

Lerner's homeostasis and blood pressure.

Lerner's concept of developmental homeostasis, formerly elaborated with regard to the study of morphological traits, is proposed as a way of analysing the heritability of blood pressure. The important and controversial contribution of the autonomic nervous system to blood pressure regulation is also discussed with the aid of the hyperkinetic state, an entity described by Julius and Schork, and considered as an etiological factor in the occurrence of borderline hypertension. Experimental support through an analysis of a study performed on 87 pedigrees of normal healthy individuals is provided. The analysis calculates the heritabilities of systolic and diastolic blood pressure as well as heart rate. A classification in four categories, taking into account the hyperkinetic state, using the combined values of heart rate and mean arterial blood pressure is proposed, and its value regarding the categorization of normal individuals is emphasized and discussed simultaneously with the heritabilities calculated, in an attempt to explain the contribution of Lerner's theory to the inheritance of blood pressure.

Adult↗
PubMed1994

[Occupational exposure and lung cancer in smokers].

High male lung cancer incidence and mortality in Rosario city, Argentina, have been found in previous studies. A project was undertaken for the purpose of evaluating the life-time occupational history as well as the duration and intensity of cigarette smoking as determinants of histologic cell types in 211 male patients with primary lung cancer. Their histologic cell types were: squamous 39%, adenocarcinoma 29%, small cell 18%, and others and not specified 14%. An association was found between histologic cell types and occupations (p < 0.0001), adenocarcinoma being more prevalent in office personnel, teachers, accountants, lawyers, and squamous in the other, supposedly dirtier working environments, mainly in those men who had begun to work in farming and later transferred to mechanics and metallurgy. These latter ones were diagnosed at a younger age than those in other occupations, with a significant difference for squamous and small cell. No differences in the smoking intensity were found between the occupational groups. The mean age these patients began to smoke at was 15 years for those with squamous and small cell, and 17 years for those with adenocarcinoma (p < 0.001). An interesting finding was the difference at their mean-age at diagnosis, 58 years for smokers and 68 for ex-smokers (p < 0.0001). Studies are needed to elucidate the interplay of risk factors in the etiology of histologic subtypes of lung cancer.

Age Factors↗
PubMed1994

[Psychological differences between ulcer and non-ulcer dyspeptic patients].

The existence of differences in the psychological profile of 39 endoscopically evaluated patients with ulcer (U) and non ulcer (NU) dyspepsia were examined. There were 21 U and 18 NU subjects. Cigarette smoking, intake of alcohol, coffee, mate, aspirin and NSAID were recorded, but there were no significant differences between the two groups. Personality traits were determined by the Rorschach Test, considering psychological profile (introversive, extroversive, self-restrained), impulse and emotion control (do not allow their expression, impulsive, adequately conveyed) and level of social adaptation (low, normal, high). U and NU subjects experienced a similar number of potentially stressful life events. However, U patients perceived their events more negatively. Although no one type of "ulcer personality" was found consistently, ulcer patients tended to be more introversive and they had a better social adaptation than NU.

Adult↗
PubMed1993

Variation in smoking-related lung cancer risk factors by cell type among men in Argentina: a case-control study.

A high mortality rate for lung cancer (62.7 per 100,000) is found in Rosario, Argentina. To investigate the reasons for this high rate, a case-control study was carried out among 215 male cases with histologically confirmed lung cancer and 433 hospitalized controls for conditions unrelated to tobacco consumption. Odds ratios (OR) of squamous cell (SQ), adenocarcinoma (AD), and small cell (SM) carcinoma of the lung associated with different characteristics of the smoking habit were quantified. Ninety-eight percent of the cases had smoked regularly. Smokers were significantly younger at diagnosis than ex-smokers (P < 0.0001), a pattern consistent for all cell types. The ORs for the heaviest cf the lowest consumption categories were 15.3 for SQ, 11.6 for AD, and 11.6 for all lung cancer (P < 0.0001). Risks associated with the use of unfiltered cigarettes were three to five times higher than those for filtered cigarettes, depending on cell types. For ex-smokers, risks after 10 years of nonsmoking were about 12 times lower than those of current smokers (P < 0.001). To halt further increases in lung cancer, preventive measures in Argentina should be directed primarily towards smoking control.

Adenocarcinoma↗
PubMed1992

Blood lipid associations in 18 year-old men.

The association of cigarette smoking, physical activity at work, and social class with total cholesterol and with high and low density lipoprotein cholesterol were examined in a random sample of 238 males, of 18 years of age, of Rosario, Argentina. The mean (mg/dl) total serum cholesterol of the whole sample was 174.7, the high density lipoprotein cholesterol 52.8, and the low density lipoprotein cholesterol 121.5. Black tobacco consumers, evenly distributed by social class, had higher levels of total and low density lipoprotein cholesterol. Total cholesterol was higher in the high social class, differently from what smokers' distribution by social class, would lead one to expect. While a highly negative association was found between social class and physical activity at work, there were no significant differences in lipoprotein levels between manual and non-manual workers. It is possible that the nutritional differences by social class still prevail over the smoking habit in their influence on the lipoprotein levels in these subjects.

Adolescent↗