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Biomedical subjects

G Profeta

Publications and source records attributed to G Profeta.

At least 19 recordsLinked to original sources
PubMed2006

Superconductivity in lithium, potassium, and aluminum under extreme pressure: a first-principles study.

Extreme pressure strongly affects the superconducting properties of "simple" elemental metals, such as Li, K, and Al. Pressure induces superconductivity in Li (as high as 17 K) while suppressing it in Al. We report first-principles investigations of the superconducting properties of dense Li, K, and Al based on a recently proposed, parameter-free, method. Our results show an unprecedented agreement with experiments, assess the predictive power of the method over a wide range of densities and electron-phonon couplings, and provide predictions for K, where no experiments exist so far. More importantly, our results help uncover the physics of the different behaviors of Li and Al in terms of phonon softening and Fermi surface nesting in Li.

Journal Article↗
PubMed2005

Novel electronically driven surface phase predicted in C/Si(111).

We predict a novel electronically driven phase for the recently created C/Si(111) surface at 1/3 monolayer coverage. Whereas the isoelectronic surface Sn/Ge(111) is a 3 x 3 distorted metal and Si/SiC(0001) is an undistorted magnetic Mott insulator, the new phase combines both features. Two of three adatoms in C/Si(111) should form a distorted (3 x 3) honeycomb sublattice, the third an undistorted insulating and magnetic triangular sublattice. The generally conflicting elements, namely, band energy, favoring distortion, and strong electron correlations favoring a Mott state, actually conspire in this case. This kind of state represents the surface analog of the Fazekas-Tosatti state in the charge density wave compound 1T-TaS2.

Journal Article↗
PubMed2005

Superconducting properties of MgB2 from first principles.

Solid MgB(2) has rather interesting and technologically important properties, such as a very high superconducting transition temperature. Focusing on this compound, we report the first nontrivial application of a novel density-functional-type theory for superconductors, recently proposed by the authors. Without invoking any adjustable parameters, we obtain the transition temperature, the gaps, and the specific heat of MgB(2) in very good agreement with experiment. Moreover, our calculations show how the Coulomb interaction acts differently on sigma and pi states, thereby stabilizing the observed superconducting phase.

Journal Article↗
PubMed2002

Disproportionation phenomena on free and strained Sn/Ge(111) and Sn/Si(111) surfaces.

Distortions of the sqrt[3]x sqrt[3] Sn/Ge(111) and Sn/Si(111) surfaces are shown to reflect a disproportionation of an integer pseudocharge, Q, related to the surface band occupancy. A novel understanding of the (3 x 3)-1U ("1 up, 2 down") and 2U ("2 up, 1 down") distortions of Sn/Ge(111) is obtained by a theoretical study of the phase diagram under strain. Positive strain keeps the unstrained value Q=3 but removes distortions. Negative strain attracts pseudocharge from the valence band causing first a (3 x 3)-2U distortion (Q=4) on both Sn/Ge and Sn/Si, and eventually a (sqrt[3] x sqrt[3])-3U ("all up") state with Q=6. The possibility of a fluctuating phase in unstrained Sn/Si(111) is discussed.

Journal Article↗
PubMed2000

Preliminary experience with anterior cervical microdiscectomy and interbody titanium cage fusion (Novus CT-Ti) in patients with cervical disc disease.

BACKGROUND: Although the use of intervertebral fusion after anterior microdiscectomy in cervical disc disease remains controversial, a new surgical device is proposed for use in intervertebral fusion instead of bone graft. METHODS: This retrospective study at the Department of Neurosurgery, Cardarelli Hospital, Naples, from January 1993 to December 1998, compares the results of surgery on 58 patients with anterior microdiscectomy and intervertebral bone graft fusion (Group A) (ADIBG) with a group of 52 patients who underwent anterior microdiscectomy and intervertebral titanium cage fusion (Group B) (ADITC) in cervical radiculopathy and spondylotic myelopathy. In both groups a "radical discectomy" was performed under the operating microscope. In group A, interbody fusion was performed with autologous tricortical bone graft. In group B, a new type of titanium device (Novus CT-Ti) was used (Sofamor Danek Group). RESULTS: There was no collapse or extrusion of the device and no complications at the donor site (the bone fragments used to fill the cage were taken from osteophytes or vertebral body fragments). The use of this device provides immediate stabilization, reduces or eliminates pain, promotes bone fusion between the vertebrae adjacent to the cage by allowing bone growth through the cage, reestablishes and maintains the intervertebral space, reduces the average hospitalization time, and allows a quicker return to work. CONCLUSIONS: Patients who underwent ADITC did well and benefited from the surgery. Those who underwent ADITC did better than those who underwent ADIBG in regard to function, relief from pain, and complications. Early and good stability of the cervical spine seems to be the main advantage of using titanium cages.

Cervical Vertebrae↗
PubMed1998

[Reasons against lumbar puncture diagnosis with cerebrospinal fluid drainage in subarachnoid hemorrhage].

The necessity of cerebral angiography or angio-MRI was assessed in patients with thunderclap headache in whom subarachnoid haemorrhage had been ruled out on CT findings. In this cases the cerebrospinal fluid examination could be dangerous because could reduce the intracranial pressure with consequent risk of aneurysm rupture. CSF drainage, although, improves the clinical conditions and the symptoms of the patients, seems to not reduce the incidence of permanent neurological deficits caused by vasospasm; on the contrary, it increases the incidence of hydrocephalus requiring shunt procedures. We conclude that routine ventriculostomy with external ventricular drainage should be considered for all patients with altered sensorium and acute hyrocephalus following subarachnoid haemorrhage, with improvement in outcome.

Humans↗
PubMed1998

"Ultraearly" aneurysm surgery.

Three hundred and twenty-seven patients with intracranial aneurysm were managed at the Neurosurgical Division of Emergency Department of the Cardarelli Hospital of Naples. Of the 327 patient, 231 (70.6%), (I group), were operated on after 72 hours and 96 patients (29.4%), (II group), were operated on within 72 hours of subaracnoid hemorrhage. The patients operated on within 72 hours of hemorrhage (II group) were divided in two subgroups: 29 patients operated on within 72 hours formed the IIa group ("ultraearly" surgery) and 67 patients operated on between 24-72 hours formed the IIb group. Poor clinical grades (IV and V Hunt and Hess grades) were excluded from this study. Glasgow outcome scale (GOS), simplified in three grades was used to evaluate the results (GOS 1 good recovery; GOS 2 moderate or severe disability, and GOS 3 dead). The outcome was evaluated at the dimission and at 6 months. The best results seem to be for the patients in group IIb (24-72 hours), but if we consider that 31.2% of the patients operated on within 24 hours (IIa group) were in grade III of Hunt and Hess classification, also for these patients the surgical results seem to be good. The clinical presentation, treatment and outcome are discussed in this report.

Adult↗
PubMed1998

A new instrumentation for posterior stabilization of cervical traumatic instability.

BACKGROUND: Twenty-six patients underwent application of a new posterior plating system (CIDEF SYSTEM) for the alignment and the stabilization of C3-C7 cervical unstable fractures from January 1992 to December 1993. METHODS: The osteosynthesis apparatus employs posterior articular screw fixation and plate application. Indications for surgery were the presence of neurological damage and cervical column instability. Operative techniques included decompressive and exploratory laminectomy in 20 cases and an articular resection in six cases of posterior superior articular fractures. A one-stage operation with an anterior approach, designed to remove anterior compression from herniated discs, or bone fragments, was also performed in four cases. Three cervical motion segments were immobilized in 15 of the treated cases; four in nine; and five in two. All patients were studied pre- and postoperatively with plain radiographs and computed tomography. Pre- and postoperative examinations demonstrated no alteration in neurological status. RESULTS: At a mean follow-up period of 47 months, no evidence was found of infection, rejection of the materials used, or mechanical failure of the plates and screws; all patients with incomplete lesion showed improvement in neurological function. Four patients tetraplegic at admission expired from systemic complications (one from pulmonary embolism; one from Disseminated Intravascular Coagulopathy; one for sepsis; and one from myocardial infarction). All patients were immobilized for at least 4 months with a Philadelphia collar. No injury to the neural or vascular structures contiguous to the cervical spine has occurred. CONCLUSIONS: The authors' experience suggests that the new system offers ease and versatility of application, restoration of vertebral alignment, enhanced spinal stability and is useful in the treatment of urgent and rather complex traumatic lesions of the lower cervical spine.

Adult↗
PubMed1997

The postero-lateral approach in the treatment of post-traumatic canalar stenosis of the thoraco-lumbar spine.

METHODS: Twenty-four cases of unstable thoraco-lumbar fractures with significant canalar stenosis were operated in the Emergency Neurosurgical Unit of the Cardarelli Hospital from November 1989 to October 1991. The surgical technique was the combined transpedicular (TPA) and transarticular (TAA) postero-lateral approach, posterior osteosynthesis and arthrodesis. The average follow-up was 20 months. RESULTS: No evidence of implant breakage or pseudoarthrosis was detected. CONCLUSIONS: The authors affirm recalibration of the posterior wall by direct impaction, epidural hemostasis, removal of extruded disc fragments and dural repair are the advantages offered by this technique without compromise the contsrist stability. This approach represents an alternative to single posterior and combined anterior-posterior approaches in the management of the thoraco-lumbar fractures with severe canal stenosis.

Adolescent↗
PubMed1996

Surgical treatment of subdural empyema: a critical review.

Between 1990 and 1992 six cases of subdural empyema were surgically treated at the Neurosurgical Division of Emergency Department of Cardarelli Hospital in Naples. Three cases were associated with paranasal sinusitis and three cases with otitis media. Headache and fever were the presenting symptoms in all cases; in only two cases they were associated with seizures and altered mental status. CT scans showed convexity low density collections in five cases and multilocalized pus collection in one; concurrent paranasal or mastoid infections were visualized as well. The organisms responsible for the subdural empyema were Peptococcus in four cases, Streptococcus and anaerobius in the other two cases. In five cases surgical treatment consists in pus drainage by selective burr hole and placement of a subdural small silicon tube for local antibiotic therapy. In one case with a loculated diffuse empyema, craniotomy was performed in order to provide a better access to all the localizations. In all cases drainage of the wound and intravenous antibiotic therapy were used. Paranasal sinus drainage or mastoidectomy performed by the otolaryngologist when a localized collection of pus was present, grave a quicker regression of symptoms. A full recover of the original neurological status was achieved in all cases; a 20 months mean followup confirms the results.

Adolescent↗
PubMed1994

Directed movement of chromosome arms and fragments in mitotic newt lung cells using optical scissors and optical tweezers.

A pulsed-laser microbeam at 532 nm wavelength (optical scissors) and a laser-induced optical trap at 1064 nm wavelength (optical tweezers) have been successively combined to dissect and manipulate chromosomes in live newt lung epithelial cells. These preliminary experimental results demonstrated that chromosome fragments dissected by laser microbeam surgery, regardless of their size, could be easily pulled or rotated by optical forces when positioned at the periphery of the mitotic spindle. In addition, chromosome arms which were not subjected to laser microsurgery also could be moved with the optical tweezers at the spindle periphery. In our previous study on rat kangaroo kidney cells (PTK2), this degree of facilty in manipulating chromosome movement was not possible, most likely due to the close proximity of the intermediate filament "cage" to the spindle. It is concluded herein that optical scissors and tweezers can be used in combination to study the interaction of chromosomes with the mitotic spindle in cells where the peripheral regions of the spindle are unobstructed by intermediate filaments. This can be performed on newt cells, where the diameter of the cage can be substantially larger than the diameter of the spindle.

Animals↗
PubMed1994

Non invasive recording of CO2 cerebrovascular reactivity in normal subjects and patients with unilateral internal carotid artery stenosis.

CO2 cerebrovascular reactivity has been recorded in 12 healthy volunteers and 10 patients with unilateral > 70% extracranial internal carotid artery (ICA) stenosis, using non invasive techniques. The relative changes of middle cerebral artery blood flow velocity (VMCA) and velocity waveform pulsatility (PIMCA) after that hypocapnia was induced by spontaneous hyperventilation were recorded. 35.5% average VMCA reduction and 63% PIMCA increment of basal values was produced in healthy subjects after hyperventilation. The percentage variation of CO2 Reactivity Index (RI), expressed in terms of VMCA (V-RI) and PIMCA (PI-RI), per mmHg change in pCO2, presents a good right-left side correlation (r = 0.82 and r = 0.83 respectively) in healthy subjects, while a dissociation between V-RI and PI-RI was found in our patients. A significant reduction of PI-RI was also recorded in the group of patients on the side of ICA stenosis. From our data CO2 reactivity index recorded in terms of PI seems to allow a better separation between pathology and normality, without the need to assume a close relationship between velocity and blood flow under the condition considered. Furthermore, PI-RI seems to be a valid index in the evaluation of some attribute pertaining to the distal vascular bed.

Adult↗
PubMed1993

Lung cancer in patients with immunodeficiency syndrome.

We report adenocarcinoma of the lung in seven patients with human immunodeficiency virus (HIV) infection. We compared age, clinical findings and survival data with a sex-matched control group of HIV-negative patients with adenocarcinoma of the lung. Median age of HIV-infected patients with lung cancer was lower than in control patients with lung cancer. The HIV-infected patients had more systemic symptoms and abnormal physical findings than control subjects. Both groups had smoking histories. Laboratory data were similar but control subjects had lower blood oxygen tensions than did HIV patients; HIV patients had more abnormalities on chest roentgenograms and computed tomography scans than did control subjects. All HIV-infected patients were stage IV. Median survival was 4 weeks. For control patients, 50 percent had stage IV disease; median survival was 25.5 weeks. Thus, patients with HIV infection develop lung cancer at a younger age than sex-matched control subjects and undergo a more fulminant course with shortened survivals.

Acquired Immunodeficiency Syndrome↗
PubMed1992

A new instrumentation system for the reduction and posterior stabilization of unstable thoracolumbar fractures.

An innovative instrumentation and stabilization system was used for the treatment of unstable thoracolumbar fractures. The new osteosynthesis apparatus employs pedicle screw fixation, plate application, and a mechanical device for dynamic reduction in stable posterior fixation. Sixteen patients were treated with this operative technique that included a decompressive laminectomy, an arthropedunculectomy, and the removal of vertebral canal bone fragments. In most patients, three vertebral bodies, rather than four or five, were immobilized. All patients were studied pre- and postoperatively with plain radiographs and computed tomography. Pre- and postoperative examinations demonstrated no alteration in neurological status. All patients, however, with incomplete lesions showed improvement in neurological function at a mean follow-up period of 12 months. The authors' experience suggests that the new system offers ease and versatility of application, restoration of vertebral alignment through mechanical reduction, and enhanced spinal stability. The new system, moreover, enables the reduction of lateral dislocation.

Adolescent↗
PubMed1991

Laser-assisted versus mechanical recanalization of femoral arterial occlusions.

A randomized clinical trial was performed to test the hypothesis that a laser-heated probe is superior to standard techniques to reopen occluded femoral arteries. Twenty patients were treated with a standard guidewire and balloon dilation method. In a second group of 20 patients, the laser probe was initially used as a nonheated mechanical device. If the probe was unsuccessful in mechanically reopening the artery, an Argon laser was activated to heat the probe. The mean length of occlusion was 15.9 +/- 10.3 cm. The success rate for the laser probe was 15 of 20 (75%), which was not significantly different from the standard method, 19 of 20 (95%). Most of the success in the laser-probe group was due to the probe's mechanical properties. The laser probe was successful as a cold, mechanical device in 13 of 15 (87%) arteries. It was necessary to heat the probe in 5 patients. When heated, the laser probe assisted recanalization in 2 but perforated the artery in 3 cases. The results of this randomized trial do not support the hypotheses behind the use of the thermal laser probe. The laser probe functions primarily as a mechanical device. The thermal activation does not significantly improve the success rate without increasing the risk of perforation. This small additional benefit does not justify the large cost of current thermal laser devices. This controlled study also demonstrates a higher success rate in long occlusions than previous reports of mechanical balloon recanalization. This is due to a combination approach of retrograde and anterograde probing of the occluded segment.

Adult↗
PubMed1990

Laser assisted fixation of ear prostheses after stapedectomy.

Three different lasers (erbium:YAG, holmium:YAG, alexandrite) were used to drill a hole at the end of the long process of the incus in order to fix an ear prosthesis after stapedectomy or small fenestra stapedectomy. The energy was coupled into a 250-microns core diameter zirconium-fluoride fiber. The operations were carried out on human temporal bone models from cadavers. The fiber was guided to the incus under the stereoscopic surgical microscope. The tissue response was examined under the scanning electron microscope, and after decalcification, histologically. These studies suggest the feasibility of using the erbium:YAG laser to improve the anchorage of the prosthesis on the incus and to increase the stability in ossicular chain reconstruction.

Cochlear Implants↗
PubMed1989

Memory performances after anterior communicating artery aneurysm surgery.

10 patients operated on for anterior communicating artery aneurysm (ACoA) underwent to neuropsychological examination one year after surgery, in order to detect eventual behavioural and/or amnestic disorders, already described by others in a wide percentage of such patients. Even if after accurate neurological examination the therapeutic results were defined as "good", 60% circa of our patients present amnestic and/or behavioural disturbances. Possible correlations between neuropsychological tests finding and intraoperative occurrences (early aneurysm rupture, gyrectomy etc.) are considered and discussed.

Adult↗