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Biomedical subjects

G Carbone

Publications and source records attributed to G Carbone.

At least 19 recordsLinked to original sources
PubMed2005

Hot cracks in rubber: origin of the giant toughness of rubberlike materials.

We study crack propagation in rubberlike materials and show that the nonuniform temperature distribution which occurs in the vicinity of the crack tip has a profound influence on the crack propagation, and may strongly enhance the crack propagation energy G(v) for high crack velocities v. At very low crack-tip velocities, the heat produced at the crack tip can diffuse away, but already at moderate crack-tip velocities a very large temperature increase occurs close to the crack tip resulting in a "hot-crack" propagation regime. The transition between the low-speed regime and the hot-crack regime is very abrupt and may result in unstable crack motion, e.g., stick-slip motion or catastrophic failure.

Journal Article↗
PubMed2005

Crack motion in viscoelastic solids: the role of the flash temperature.

We present a simple theory of crack propagation in viscoelastic solids. We calculate the energy per unit area, G(v), to propagate a crack, as a function of the crack tip velocity v. Our study includes the non-uniform temperature distribution (flash temperature) in the vicinity of the crack tip, which has a profound influence on G(v). At very low crack tip velocities, the heat produced at the crack tip can diffuse away, resulting in very small temperature increase: in this "low-speed" regime the flash temperature effect is unimportant. However, because of the low heat conductivity of rubber-like materials, already at moderate crack tip velocities a very large temperature increase (of order of 1000 K) can occur close to the crack tip. We show that this will drastically affect the viscoelastic energy dissipation close to the crack tip, resulting in a "hot-crack" propagation regime. The transition between the low-speed regime and the hot-crack regime is very abrupt, which may result in unstable crack motion, e.g. stick-slip motion or catastrophic failure, as observed in some experiments. In addition, the high crack tip temperature may result in significant thermal decomposition within the heated region, resulting in a liquid-like region in the vicinity of the crack tip. This may explain the change in surface morphology (from rough to smooth surfaces) which is observed as the crack tip velocity is increased above the instability threshold.

Journal Article↗
PubMed2005

Atomic force microscope study of presmectic modulation in the nematic and isotropic phases of the liquid crystal octylcyanobiphenyl using piezoresistive force detection.

Using a temperature controlled atomic force microscope (AFM), we have studied surface induced pre-smectic order in the nematic and isotropic phases of 4-cyano- 4'-n -octylbiphenyl. A modified AFM head with piezoresitive cantilevers has been used to measure the structural force between a flat BK7 glass plate and a 10 microm glass sphere, both being treated to induce homeotropic alignment of the confined liquid crystal layer in between. We have observed surface-induced presmectic force not only in the isotropic, but also in the nematic phase. We have measured the temperature dependencies of the presmectic force, the smectic correlation length xi and the smectic order parameter psi at the surface. The correlation length xi(T) shows a power-law temperature dependence with a critical exponent of nu=0.67 +/- 0.03 and the bare correlation length of xi(0) = (0.39 +/- 0.08) nm, in good agreement with x-ray data. The smectic density at the surface is psi(2)(S) =0.4 in the nematic phase and decreases in the isotropic phase.

Journal Article↗
PubMed2005

Hydrophobic properties of a wavy rough substrate.

The wetting/non-wetting properties of a liquid drop in contact with a chemically hydrophobic rough surface (thermodynamic contact angle theta(e)>pi/2) are studied for the case of an extremely idealized rough profile: the liquid drop is considered to lie on a simple sinusoidal profile. Depending on surface geometry and pressure values, it is found that the Cassie and Wenzel states can coexist. But if the amplitude h of the substrate is sufficiently large the only possible stable state is the Cassie one, whereas if h is below a certain critical value hcr a transition to the Wenzel state occurs. Since in many potential applications of such super-hydrophobic surfaces, liquid drops often collide with the substrate (e.g. vehicle windscreens), in the paper the critical drop pressure pW is calculated at which the Cassie state is no longer stable and the liquid jumps into full contact with the substrate (Wenzel state). By analyzing the asymptotic behavior of the systems in the limiting case of a large substrate corrugation, a simple criterion is also proposed to calculate the minimum height asperity h necessary to prevent the Wenzel state from being formed, to preserve the super-hydrophobic properties of the substrate, and, hence, to design a robust super-hydrophobic surface.

Computer Simulation↗
PubMed2004

Dewetting at soft viscoelastic interfaces.

The dewetting transition of thin liquid films (approximately 100 nm) at soft viscoelastic interfaces is analyzed theoretically. It is shown that viscoelastic losses in the soft material can drastically increase the time to complete the dewetting. Thus, the influence of the thinning of the liquid film, due to the hydrodynamic drainage caused by the external applied pressure, has to be considered too. The squeezing pressure coupled with the hydrodynamic drainage may slow down the dewetting to almost zero growth rate of the dry zone; in this case a trapped rim of fluid should be observed.

Journal Article↗
PubMed2004

Is it possible to reduce job burnout of the health care staff working with demented patients?

The Maslach burnout inventory (MBI) was administered to the health care staff of a nursing home before implementing a therapeutic program of occupational therapy and cognitive rehabilitation for demented patients and one year later, while the patients continued the rehabilitative and occupational therapy. All the indices of the MBI showed a significant improvement at the staff's evaluation, when was appraised 12 months after the beginning of the therapeutic program. These treatments seem to have positive effects on both the patients, improving their performances, and the nursing staff, as an aid to reduce the job burnout.

Adult↗
PubMed1999

Acute respiratory failure in patients with severe community-acquired pneumonia. A prospective randomized evaluation of noninvasive ventilation.

In uncontrolled studies, noninvasive positive pressure ventilation (NPPV) was found useful in avoiding endotracheal intubation in patients with acute respiratory failure (ARF) caused by severe community-acquired pneumonia (CAP). We conducted a prospective, randomized study comparing standard treatment plus NPPV delivered through a face mask to standard treatment alone in patients with severe CAP and ARF. Patients fitting the American Thoracic Society criteria for severe CAP were included in presence of ARF (refractory hypoxemia and/or hypercapnia with acidosis). Exclusion criteria were: severe hemodynamic instability, requirement for emergent cardiopulmonary resuscitation, home mechanical ventilation or oxygen long-term supplementation, concomitant severe disease with a low expectation of life, inability to expectorate or contraindications to the use of the mask. Fifty-six consecutive patients (28 in each arm) were enrolled, and the two groups were similar at study entry. The use of NPPV was well tolerated, safe, and associated with a significant reduction in respiratory rate, need for endotracheal intubation (21% versus 50%; p = 0.03), and duration of intensive care unit (ICU) stay (1.8 +/- 0.7 d versus 6 +/- 1.8 d; p = 0.04). The two groups had a similar intensity of nursing care workload, time interval from study entry to endotracheal intubation, duration of hospitalization, and hospital mortality. Among patients with chronic obstructive pulmonary disease (COPD), those randomized to NPPV had a lower intensity of nursing care workload (p = 0.04) and improved 2-mo survival (88.9% versus 37.5%; p = 0.05). We conclude that in selected patients with ARF caused by severe CAP, NPPV was associated with a significant reduction in the rate of endotracheal intubation and duration of ICU stay. A 2-mo survival advantage was seen in patients with COPD.

Acute Disease↗
PubMed1999

[A rare case of gastric bleeding due to left-sided portal hypertension].

The authors report an uncommon gastric bleeding rate due to splenic hilum compression by a pancreatic cyst. The syndrome to be brought back to some sectorial portal hypertension form (left-sided portal hypertension) is difficult to diagnose because of absence of esophageal varices and other portal hypertension signs in an unchanged liver functionality patient. To put a correct diagnosis about gastric bottom bleeding varices without hepatic origin, the authors recommend to use arteriography and CT. Surgical treatment is proved to be the election one because of useless attempt of bleeding control through hepatic artery endoscopic sclerosis or embolization.

Diagnostic Errors↗
PubMed1999

[Renal oncocytoma: its differential diagnosis and the indications for surgical treatment].

The authors report an uncommon renal oncocytoma rate stressing difficulties that modern diagnostic modalities meet in a correct preoperative differential diagnosis with nephrocarcinoma. Oncocytoma is a low multifocal involvement. Surgical treatment is the primary choice, nephrectomy about localized monofocal lesions in advisable, with short and long term positive outcomes. In ambilateral involvement case without malignancy evident signs (scarce likelihood to infiltrate nephritic capsule, without lymphoadenopathy) conservative operations with partial resections are suggested with a five years survival from 84 to 96%.

Adenoma, Oxyphilic↗
PubMed1998

Intrahepatic bile duct loss in primary sclerosing cholangitis: a quantitative study.

AIMS: Intrahepatic bile duct volume density has been evaluated in four cases of primary sclerosing cholangitis (PSC) by applying a semiautomatic image analysis system to histological sections of surgical biopsies. Comparison was made between normal livers and cases of primary biliary cirrhosis. METHODS AND RESULTS: A marked decrease in both bile duct volume density in liver (up to 50% of normal value) and bile duct volume density in portal tracts (up to 21% of normal value) was found. The analysis of correlations between the portal tract size and the portal tract volume fraction constituted by bile ducts confirms that the destruction mainly affects small and medium-sized ducts. The ratio of bile duct to arterial component volume fractions in portal tracts turned out to be inverted with respect to that determined in normal liver, showing a decrease of up to 30% of normal value. CONCLUSIONS: The features observed in primary sclerosing cholangitis, as well as the extent of bile duct loss proved to be quite similar to what we had previously described in primary biliary cirrhosis. Thus, regardless of the causes and mechanisms leading to the bile duct loss, the quantification of ductopenia produced results which are alike for the two distinct cholestatic diseases.

Adult↗
PubMed1997

Naming deficit for non-living items: neuropsychological and PET study.

We report a patient with progressive left hemisphere atrophy who presented a lexical retrieval deficit more pronounced in naming non-living items than in naming living items. Word frequency and familiarity strongly influenced the performance, but the dissociation persisted when the items were controlled for these factors. In addition, the prevalent deficit for non-living items in respect to living items could be confirmed in tasks where other patients presented the opposite pattern. A PET study showed a significant hypometabolism in the left hemisphere regions suggesting that, at variance with living deficit which is observed in patients with bilateral lesions, non-living deficit is produced by unilateral left hemispheric lesions. This patient confirms that living and non-living categories may dissociate and that distinct neural systems subsume their knowledge.

Aged↗
PubMed1997

Role of reoperation in recurrence of adrenal cortical carcinoma: results from 188 cases collected in the Italian National Registry for Adrenal Cortical Carcinoma.

BACKGROUND: Recurrence of adrenal cortical carcinoma (ACC) after radical surgery is a common finding. Although successful reoperations have been reported with encouraging results, most published experiences are anecdotal and based on few cases. We report the results of surgical treatment for recurrent ACC in a multiinstitutional series. METHODS: One hundred eighty-eight cases of ACC were collected in a national registry. A complete follow-up was obtained in 179 cases. At initial diagnosis 92 patients had local disease (stage I or II). One hundred seventy patients underwent surgical treatment, considered radical in 140; in this group, recurrent disease was observed in 52 cases (37%) after a mean disease-free interval of 21.7 months. RESULTS: Adjuvant chemotherapy was ineffective in ameliorating the prognosis. The mean survival in 20 patients who underwent reoperation was significantly higher (15.85 +/- 14.9 months) than in nonreoperated cases (3.2 +/- 2.9 months). Five-year actuarial survival in reoperated patients is significantly better than in nonreoperated patients (49.7% versus 8.3%, respectively). CONCLUSIONS: Although the prognosis of this tumor is still poor, surgery is the only effective therapy; reoperation allows survival comparable to that observed in patients without recurrent disease. An aggressive strategy for recurrent ACC is advisable until prospective studies demonstrate a real effectiveness for chemotherapy.

Adolescent↗
PubMed1997

[Mechanical endarterectomy: review of the literature and description of an original device].

The Authors, after a Literature review on endovascular invasive procedures used for inferior limbs obstructive arteriopathy, describe the use of a new device for mechanical endarterectomy. Through the latest acquired experience the importance of dissecting progressively the single layers of the atheroma plaque without arriving to a complete denudation of the arterial wall, so avoiding the risk of myointimal hyperplasia reactions, is outlined. The possibility of using endoarterial stents in case of more indaginous recanalization is also stressed.

Angioplasty, Balloon↗
PubMed1997

[Surgical treatment of spontaneous rupture of the esophagus: case report].

Boerhaave's syndrome is a rare and severe syndrome, with a mortality rate around 40%. The Authors report a case recently observed and through a Literature review stress the importance of an early diagnosis and quick surgical treatment as far as quoad vitam prognosis is concerned.

Esophageal Diseases↗
PubMed1997

[Diagnostic and therapeutic approach to kidney injuries].

The Authors report a wide review of the literature on open and blunt renal traumas. All the problems related to this pathology as well as all the instrumental and laboratory tests currently available for the correct diagnosis are illustrated. Both conservative and surgical management are also discussed.

Humans↗
PubMed1994

Italian multicentric study on pain treatment with epidural spinal cord stimulation.

A multicentric study on the treatment of nonmalignant chronic pain with epidural spinal cord stimulation (SCS) has been carried out in 32 Italian centers devoted to pain therapy. Neurosurgical and anesthesiology units participated in this retrospective study. 410 of the eligible patients were enrolled in the protocol: 48% were male, 52% female. All patients underwent a screening test period (average 21 days) and 74% underwent the definitive implant. The diagnosis was failed back surgery syndrome in 45%, reflex sympathetic dystrophy in 15%, phantom limb pain in 14%, postherpetic neuralgia in 8%, peripheral nerve injury in 5%, others 13%. 84% received noninvasive unsuccessful treatment (10 tensor acupuncture). All had previous pharmacological therapy which was not always discontinued when SCS took place. Pain assessment had been done with the visual analog scale and verbal scale both subjectively and by the physician and nurses. Neuropsychological profile with minimal mental test or MMPI was obtained in 68% of the patients. These results were favorable (i.e. excellent or good; more than 50% reduction of pain) in 87% of the patients at the 3-month follow-up, 75% at the 6-month follow-up, 69% at the 1-year follow-up, and 58% at the 2-year follow-up. Complication rate was: dislocation of the electrocatheter 4%, technical problems 3%, infections of the system 2%. The results will be discussed in correlation with the different etiologies of the nonmalignant chronic pain syndrome.

Adolescent↗
PubMed1992

Involvement of somatically acquired ecotropic viruses in the immunogenicity of nude-transplanted NIH/3T3 transformed cell lines.

Immunogenic tumor variants were previously derived after transplantation in vivo into nude mice of NIH/3T3-transformed cell lines. Nude-passaged cell lines were rejected by immunocompetent H-2q NIH mice, were recognized by specific CTL clones, and expressed new retroviral Ag. The aim of the present work was to investigate whether somatically acquired proviral sequences were present in the genome of nude-passaged cells and to test directly for a causative relationship between murine leukemia virus (MuLV) expression and immunogenicity. Southern blot analysis of PstI-digested DNA indicated that in contrast to the parental NIH/3T3 transformed cell lines (pT, T12N/5a, NS-1) all the nude-passaged immunogenic variants (pT-nude, T12N/5a-nude, NS-1-nude) contained newly acquired ecotropic-related proviruses. Immediately after in vitro establishment, these tumors displayed multiple integration sites as assessed by analysis of 3' proviral-cellular junctions. Long term in vitro culture of one of the cell lines (pT-nude) resulted in a cell line (pT-nude/vitro) that was clonal or oligo-clonal with respect to viral integration. Northern blot analysis established that the new proviruses were actively transcribed in all the immunogenic variants. To assess whether the somatically acquired ecotropic proviral sequences encode for target structures recognized by specific CTL, obtained after immunization of NIH mice with pT-nude, the parental cell line pT was transfected with plasmids containing the entire AKV MuLV genome, the cloned AKV gag or env genes. Screening of transfectants for their ability to stimulate the production of TNF by anti-pT-nude effectors indicated that cells transfected with the entire ecotropic virus or with MuLV-env gene products could be recognized by an NIH anti-pT-nude CTL line and NIH anti-pT-nude Kq-restricted CTL clones as well as the immunizing target pT-nude.

3T3 Cells↗