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Biomedical subjects

A Arnau

Publications and source records attributed to A Arnau.

At least 19 recordsLinked to original sources
PubMed2006

Self-assembly of heterogeneous supramolecular structures with uniaxial anisotropy.

Uniaxial anisotropy in two-dimensional self-assembled supramolecular structures is achieved by the coadsorption of two different linear molecules with complementary amine and imide functionalization. The two-dimensional monolayer is defined by a one-dimensional stack of binary chains, which can be forced to line up along steps in vicinal surfaces. The competing driving forces in the self-organization process are discussed in light of the structures observed during single molecule adsorption and coadsorption on flat and vicinal surfaces and the corresponding theoretical calculations.

Molecular Structure↗
PubMed2006

[Smoking among adolescents: population study on parental and school influences].

OBJECTIVE: Smoking represents a public health problem, one which begins during adolescence. The main objective of this study was to analyze the association between smoking and parental and school factors. SUBJECTS AND METHODS: The study sample consisted of the students from the 20 secondary schools in the region of Osona, Barcelona, Spain. A self-report questionnaire was used to obtain information on the following variables: smoking habit, age of initiation, frequency, type of school (state school or private-subsidized), sex, age, persons living in the home, town, whether the student had lunch at school, whether the student often had lunch or dinner alone at home. RESULTS: A total of 2280 students participated in the study (91%). Mean age was 15.5 years. Of the participants, 20% said they were smokers; 5%, ex-smokers; 34% had tried smoking at least once, and 41% had never smoked. Factors significantly associated with smoking in the multivariate analysis were age, rural town, state school, single parent family, eating alone, and not lunching at school. CONCLUSIONS: Smoking prevalence is high among adolescents in our society and there is no gender difference. Our results show that family structure and dynamics can influence smoking in adolescents. Smoking is less prevalent among adolescents who have lunch at school.

Adolescent↗
PubMed2005

Role of elastic scattering in electron dynamics at ordered alkali overlayers on Cu(111).

Scanning tunneling spectroscopy of p(2 x 2) Cs and Na ordered overlayers on Cu(111) reveals similar line widths of quasi-two-dimensional quantum well states despite largely different binding energies. Detailed calculations show that 50% of the line widths are due to electron-phonon scattering while inelastic electron-electron scattering is negligible. The mechanism of enhanced elastic scattering due to Brillouin zone backfolding contributes the remaining width.

Journal Article↗
PubMed2004

Contrast reversal and shape changes of atomic adsorbates measured with scanning tunneling microscopy.

Systematic, quantitative comparisons between scanning tunneling microscopy (STM) experiments and first principles simulations of O(2 x 2)/Ru(0001) have been performed. The shape of the atomic adsorbates in the images depends strongly on the tunneling resistance and changes reversibly from circular (high resistance) to triangular (low resistance). In addition, after adsorption of oxygen on the STM tip we observe a contrast reversal on the surface, confirmed by extensive numerical simulations.

Journal Article↗
PubMed2001

A new method for continuous monitoring of series resonance frequency and simple determination of motional impedance parameters for loaded quartz-crystal resonators.

A new electronic design for continuous motional series resonant frequency monitoring of loaded quartz crystal resonators is presented. Using this circuit, a low-cost method for a simple determination of equivalent circuit parameters of quartz crystal resonators is described. Measurements made with the proposed system on typical AT cut quartz crystals are in good agreement with those of an Impedance Analyzer.

Letter↗
PubMed2001

An extended Butterworth-Van Dyke model for quartz crystal microbalance applications in viscoelastic fluid media.

An extended Butterworth-Van Dyke (EBVD) model with frequency-independent parameters for the characterization of a resonant compound formed by a quartz crystal in contact with a finite viscoelastic layer contacting a semi-infinite viscoelastic medium is extracted by analysis of the lumped element model. The formulation of the EBVD model is compared with the complete expression of the electrical admittance of the loaded quartz derived from the transmission line model (TLM). Relative deviations between them do not exceed 3% around 1% bandwidth near resonance. An extended Martin & Granstaff's model and an explicit expression for the frequency shift that supposes an extension of Kanazawa's model for viscoelastic media are obtained. An analysis of the errors associated with the extraction of shear parameters of the coating for different materials prove that, to obtain an error less than 5% in the shear parameters determination, the viscoelastic contribution, defined as the relative error in the thickness computed from the frequency shift by Sauerbrey equation, must be greater than a limit that depends on Q, which is defined as the ratio of the shear storage modulus (G') to shear loss modulus (G"). In the materials studied, polymers in the transition range or in the rubbery state with Q = 1 and 10, the viscoelastic contribution must be higher than 15% and 50%, respectively, for a 5% limit error in the shear parameters extraction. A criterion for a practical determination of the appropriate viscoelastic regimes is indicated.

Journal Article↗
PubMed2000

Unexpected behavior of the stopping of slow ions in ionic crystals

The energy loss of slow ions during grazing scattering from a LiF(100) surface as a function of the projectile atomic number Z1 is observed to show oscillations similar to those occurring in metals. A model of stopping of ions in an electron gas where screening is calculated from density functional theory reproduces well the experimental data. The same model gives good agreement with the energy loss obtained in transmission experiments performed with H and He projectiles. Analysis of these results allows us to gain new insights in the stopping of slow ions in ionic crystals.

Journal Article↗
PubMed2000

[Hyoid fracture and traumatic subcutaneous cervical emphysema from an attempted hanging. Apropos a case].

We describe a patient with a history of psychiatric disorder who was brought to our hospital after attempted suicide by hanging. Severe subcutaneous facial, palpebral and cervical emphysema was present, with dysphonia, dysphagia and slight respiratory difficulty. Fiberoptic bronchoscopy revealed upper airway obstruction due to edema in an intact airway. Successive CAT scans gave evidence of hyoid fracture and laryngocele, in addition to the corresponding emphysema of the subcutaneous area and pneumomediastinum. Given the persistence of dysphagia, we ordered esophageal tests, which showed functional alteration of the upper esophageal sphincter. Suprasternal cervicotomy to drain the pneumomediastinum and laryngeal microsurgery to treat the laryngocele resolved the problem.

Alcoholism↗
PubMed2000

[Pneumothorax as the clinical presentation of bronchogenic carcinoma. A report of 3 cases].

The association of pneumothorax and lung cancer is rare and diagnosis is complex in such cases. Clinical suspicion of cancer must be based on radiological findings and the existence of risk factors. We discuss the mechanisms involved in the development of pneumothorax in patients with lung cancer, the clinical significance of the association, and the recommended diagnostic approach and therapeutic guidelines.

Adenocarcinoma↗
PubMed2000

Epidermal growth factor secreted from submandibular salivary glands interferes with the lipolytic effect of adrenaline in mice.

We had described that epidermal growth factor (EGF) interfered with the lipolytic effect of catecholamines in isolated adipocytes. Since catecholamines stimulate the release of EGF from submandibular salivary glands to blood plasma in male mice, we studied whether EGF affected also the lipolytic response to adrenaline in whole animals. We studied the effect of adrenaline in sialoadenectomized and sham-operated mice receiving or not a high dose of EGF following adrenaline injection. There was no difference in plasma EGF concentration between sham-operated and sialoadenectomized animals receiving saline. After adrenaline administration plasma EGF increased by 20-fold in sham-operated but did not increase in sialoadenectomized mice. Indeed, the increase was much higher (more than 100-fold) in mice receiving exogenous EGF. The effect of adrenaline on plasma concentration of both glycerol and nonesterified fatty acids was higher as lower was plasma EGF concentration. Isolated adipocytes obtained from sham-operated or sialoadenectomized mice had identical lipolytic response to adrenaline. The lipolytic response of adipocytes to isoproterenol was decreased by addition of EGF. To study whether the interference with the in vivo lipolytic effect of adrenaline had further metabolic consequences, we measured plasma beta-hydroxybutyrate concentration in plasma. There was no difference in the response to adrenaline between sham-operated and sialoadenectomized mice in spite of the difference in plasma nonsterified fatty acid concentration. Studies in isolated hepatocytes indicated that ketogenesis run at near maximal rate in this range of substrate concentration. These results suggest that EGF in the physiological range decreases the lipolytic effect of adrenaline but does not compromise further metabolic events like the enhancement of ketogenesis.

3-Hydroxybutyric Acid↗
PubMed2000

Immobilization stress induces c-Fos accumulation in liver.

Acute stress-induced injury in tissues has been revealed by both biochemical markers in plasma and microscopy. However, little is known of the mechanisms by which tissue integrity is restored. Recently, induction of early response genes such as c-fos has been reported in the heart and stomach of immobilized animals. Herein, we show that immobilization stress in mice increased plasma alanine aminotransferase activity, a marker of liver damage. c-Fos protein accumulation in liver was induced by stress after 20 minutes of immobilization and persisted for 3 hours. Immobilization also induced the release of epidermal growth factor (EGF) from submandibular salivary glands and a transient increase in EGF concentration in plasma. Although EGF administration induced a 2.5-fold increase in c-Fos mass in the liver of anesthetized mice, sialoadenectomy (which abolished the effect of immobilization on plasma EGF) did not affect the stress-induced rise in plasma alanine aminotransferase activity or liver c-Fos accumulation. Therefore, we conclude that immobilization stress induces c-Fos accumulation in liver and that this effect is not triggered by the increase in plasma EGF concentration.

Alanine Transaminase↗
PubMed1998

[Bronchial carcinoid tumors: a prospective study].

We report the results of a study performed in the thoracic surgery department of Hospital General Universitario of Valencia from October 1989 to December 1996. Of the 621 patients diagnosed of lung cancer during this period, 320 underwent the usual surgical excision, 18 were confirmed histologically as bronchial carcinoid tumors, indicating an incidence of 5.6% of all pulmonary neoplasms resected in our department. The symptoms most often reported were recurring infection (44.5%) and chest pain (33.3%). Only one patient presented carcinoid syndrome. The most common radiologic presentation was solitary pulmonary nodule (50%). The tumor was visible by fiberoptic bronchoscopy in 9 cases. Diagnosis was by bronchial biopsy in four cases. Confirmation was by immunohistochemical analysis of the specimen in all cases. Electron microscopy and immunohistochemical techniques using neuroendocrine panmarkers is considered fundamental for differentiating between neuroendocrine neoplasms and typical and atypical carcinoid tumors. Thirteen (72.2%) of the 18 patients studied were diagnosed of typical carcinoids and 5 (27.8%) of atypical carcinoids. Neuroendocrine marking showed neurospecific enolase in 15 patients and chromogranin positivity in 10.

Adolescent↗
PubMed1997

[Pneumoreduction in the treatment of emphysema: preliminary results].

The results of the first three pulmonary reduction operations performed at our hospital for the palliative treatment of pulmonary emphysema are described. The upper third of the upper right lobe and part of the middle lobe were resected in two patients. An upper right lobectomy was performed on the third. Goretex coated autosutures were used and pleurosis was performed with talcum on the upper third of the hemithorax. Drains with -5 cmH2O suction were inserted. We emphasize the advance stage of disease of the three patients and the good outcomes observed in terms of survival, hospital stay and improvement in lung function and symptoms. We discuss the functional improvement resulting from lung reduction in cancer patients if the resected area is emphysematous.

Aged↗