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Biomedical subjects

P Santini

Publications and source records attributed to P Santini.

At least 19 recordsLinked to original sources
PubMed2006

Hidden order and low-energy excitations in NpO2.

We investigate the nature of the hidden order parameter in the ordered phase of NpO2, which had been identified with a staggered arrangement of Gamma5 magnetic multipoles. By analyzing the existing experimental data, we show that the most likely driving order parameter is not provided by octupoles, as usually assumed, but rather by the rank-5 triakontadipoles. Calculations of the coupled dynamics of spins, Gamma5 quadrupoles, and Gamma5 triakontadipoles in the ordered phase enable us to analyze the resulting structure of low-energy excitations. We show that the powder inelastic neutron scattering cross section should contain, in addition to the already-observed peak at 6.5 meV, a second weaker peak at about 14 meV.

Journal Article↗
PubMed2006

High-temperature slow relaxation of the magnetization in Ni10 magnetic molecules.

We investigate a family of molecular crystals containing noninteracting Ni10 magnetic molecules. We find slow relaxation of the magnetization below a temperature as high as 17 K and we show that this behavior is not associated with an anisotropy energy barrier. Ni10 has a characteristic magnetic energy spectrum structured in dense bands, the lowest of which makes the crystal opaque to phonons of energy below about 1 meV. We ascribe the nonequilibrium behavior to the resulting resonant trapping of these low-energy phonons. Trapping breaks up spin relaxation paths leading to a novel kind of slow magnetic dynamics which occurs in the lack of anisotropy, magnetic interactions and quenched disorder.

Journal Article↗
PubMed2005

Hypertension in early alcohol withdrawal in chronic alcoholics.

AIMS: Hypertension is an established risk factor in chronic alcoholics, but little is known about the relationship between blood pressure (BP), severity of their alcohol abuse, and severity of alcohol withdrawal syndrome (AWS). METHOD: BP was assessed daily for 18 days in a series of chronic alcoholics on early alcohol withdrawal (AW), while also assessing the severity of their AWS on the CIWA-Ar scale. RESULTS: A sharp and sustained decrease in BP was observed after AW; at T0, BP had increased in 55% of patients, and at T18 in 21%. The variation of BP is partially explained by years of at-risk drinking and AWS severity, but other factors may play a role in hypertension in alcoholics, as a large amount of BP variation was not explained by the alcohol-abuse-related parameters that we studied. BP values were not correlated with cigarette smoking, anxiety, or depression. Hypertension found in 'detoxified' alcoholics (approximately 20%) may be related to alcohol-independent hypertension or to a long-lasting alcohol-induced derangement of the BP regulating mechanisms. Further research is needed in these patients to elucidate the mechanisms of persistent hypertension and to set up a treatment protocol. At present, careful monitoring is advisable, as well as pharmacological treatment for moderate or severe hypertension; often a modification of life-style is needed which includes physical activity and possibly sodium (Na) restriction, since hypertension in detoxified alcoholics seems to be Na sensitive. CONCLUSION: Complete alcohol abstinence must be recommended to all hypertensive alcoholics, as AW-induced transient hypertension was found to be harmless in all our subjects, and abstinence leads to a complete recovery from hypertension in most cases.

Alcoholism↗
PubMed2005

Molecular engineering of antiferromagnetic rings for quantum computation.

The substitution of one metal ion in a Cr-based molecular ring with dominant antiferromagnetic couplings allows the engineering of its level structure and ground-state degeneracy. Here we characterize a Cr7Ni molecular ring by means of low-temperature specific-heat and torque-magnetometry measurements, thus determining the microscopic parameters of the corresponding spin Hamiltonian. The energy spectrum and the suppression of the leakage-inducing S mixing render the Cr7Ni molecule a suitable candidate for the qubit implementation, as further substantiated by our quantum-gate simulations.

Journal Article↗
PubMed2005

Intracranial pressure monitoring in children with single suture and complex craniosynostosis: a review.

INTRODUCTION: One third of patients with craniofacial dysostosis syndromes and about 15-20% of children with single suture craniostenosis have a documented increase in intracranial pressure (ICP). The early detection of intracranial hypertension is important in order to reduce the risks for brain development and visual function. However, in children with craniosynostosis, the clinical manifestations of abnormally increased ICP are difficult to detect, as the majority of patients may have neither warning signs nor symptoms for a long period of time. REVIEW: Moreover, data from the literature suggest that neither fundoscopic nor radiological findings are necessarily related to intracranial pressure recordings in this type of pathology. In this context prolonged ICP monitoring seems actually to be the most valuable diagnostic tool. Extradural, subdural, and intraparenchymal devices have been used, and different softwares have been employed for PC storage and analysis of the data obtained. Most recent series consider mean ICP combined with plateaux waves as the most sensitive indicators in the final evaluation of the results. CONCLUSIONS: The analysis of the literature demonstrates a significant difference in the prevalence of raised ICP preoperatively between non-syndromic and syndromic patients. Among the non-syndromic children, a direct relation between the number of sutures involved and raised ICP is documented. The analysis of plateaux waves seems to be particularly important in children with borderline mean ICP values. Persistent postoperative raised ICP has been described in 6-15% of patients with craniofacial dysostosis. It must be related to the multifactorial etiology of increased ICP in these patients, which includes cerebral venous congestion, upper airway obstruction, and hydrocephalus.

Cerebrospinal Fluid Shunts↗
PubMed2005

NMR as a probe of the relaxation of the magnetization in magnetic molecules.

We investigate the time autocorrelation of the molecular magnetization M(t) for three classes of magnetic molecules (antiferromagnetic rings, grids, and nanomagnets), in contact with the phonon heat bath. For all three classes, we find that the exponential decay of the fluctuations of M(t) is characterized by a single characteristic time tau(T,B) for not too high temperature T and field B. This is reflected in a nearly single-Lorentzian shape of the spectral density of the fluctuations. We show that such fluctuations are effectively probed by NMR, and that our theory explains the recent phenomenological observation by Baek et al. [Phys. Rev. B 70, 134434 (2004)] that the Larmor-frequency dependence of 1/T(1) data in a large number of AFM rings fits to a single-Lorentzian form.

Journal Article↗
PubMed2004

S mixing and quantum tunneling of the magnetization in molecular nanomagnets.

The role of S mixing in the quantum tunneling of the magnetization in nanomagnets has been investigated. We show that the effect on the tunneling frequency is huge and that the discrepancy (more than 3 orders of magnitude in the tunneling frequency) between spectroscopic and relaxation measurements in Fe(8) can be resolved if S mixing is taken into account.

Journal Article↗
PubMed2004

Quantum magneto-oscillations in a supramolecular Mn(II)-[3 x 3] grid.

The magnetic grid molecule Mn(II)-[3 x 3] has been studied by high-field torque magnetometry at 3He temperatures. At fields above 5 T, the torque versus field curves exhibit an unprecedented oscillatory behavior. A model is proposed which describes these magneto-oscillations well.

Journal Article↗
PubMed2004

Location of functioning metastases from differentiated thyroid carcinoma by simultaneous double isotope acquisition of I-131 whole body scan and bone scan.

In a young patient with differentiated thyroid carcinoma (DTC), previously submitted to total thyroidectomy and I-131 therapy for ablation of thyroid remnant, a follow-up 1-131 diagnostic whole body scan (WBS) demonstrated four small abnormal I-131 uptake areas. Two of these were projected over the thoracic region and corresponded to lung nodules, as later demonstrated by lung computerized tomography (CT)-scan. The remaining two areas were found in the lumbar-pelvic region, but their precise location could not be determined. Standard bone Rx examination and bone scan were negative. After I-131 therapy, we simultaneously acquired a I-131 WBS and a Tc-99m oxidronate bone scan by setting a dual window on the gamma camera. Comparing the I-131 and bone images we were able to identify the 4th lumbar vertebra and right ilium as the bone segments to be studied by a radiological approach. Eventually, the thin slice CT-scan demonstrated the presence of two small osteolytic lesions in these areas. In conclusion, the simultaneous acquisition of images both from I-131 and a bone-seeking agent may be useful to locate functioning bone metastases from DTC.

Adult↗
PubMed2003

Subdural hygroma: an unwanted result of Sylvian arachnoid cyst marsupialization.

INTRODUCTION: Subdural hygroma is a known complication of Sylvian fissure arachnoid cysts (SACs). However, most of the data in the literature refer to spontaneous or posttraumatic occurrence of subdural hygromas, regarded as either a favorable or an unfavorable event. Little is known about this phenomenon as a consequence of the surgical management of SACs. The present study was carried out to evaluate the significance of postoperative subdural hygromas in children with temporal arachnoid cysts, who have been treated with craniotomy and wide marsupialization of the cystic membrane. CLINICAL MATERIAL AND RESULTS: Between 1980 and March 2002, 104 children were operated on for a SAC at the Pediatric Neurosurgical Unit of the Catholic University Medical School in Rome. Six patients (5.8%; boys/girls=4/2; mean age 3.28 years) developed a subdural hygroma postoperatively, which required further treatment. According to Galassi's classification 4 children had a Type III cyst and 2 children a Type II cyst. All the patients had previously been submitted to open marsupialization of their arachnoid cyst and extensive removal of the cyst wall. In 5 patients (Type III cyst: 4 patients; Type II cyst: 1 patient), acute or subacute symptoms and signs of increased intracranial pressure (ICP) developed at a temporal distance, varying from 5 days to 1 month (mean interval: 14.3 days). All these children needed surgical treatment for the hygroma. A subduro-peritoneal (SDP) shunt was implanted as the first step in 3 patients (Type III cyst: 2 patients; Type II cyst: 1 patient). In the remaining 2 patients of this group (Type III cysts) medical therapy was initially attempted (acetazolamide: 24 mg/kg) without any improvement in clinical manifestations; on these grounds an external spinal subarachnoid drainage was implanted, but led only to the transient clearance of symptoms. The direct drainage of the subdural collection (SDP shunt in 1 patient and temporary external subdural drainage in the other), was followed by complete clinical recovery in both cases. The last patient in this series showed a pathologic increase in head circumference during the 1st month after surgery for his arachnoid cyst, followed by a subsequent stabilization. A CT scan documented a subdural hygroma, which first of all increased in size, but stabilized 2 months after surgery. No surgical treatment was performed in this case. At a mean follow-up of 2.38 years (minimum: 1 month; maximum: 5 years) all the patients are in excellent clinical conditions. Complete neuroradiological resolution of the hygroma was observed in 2 of the 4 shunted patients, who have both been submitted to shunt removal (2 and 3 years after the implant respectively). CONCLUSIONS: It is our opinion that a wide opening of the external membrane of SACs may predispose the CSF fluid to accumulate within the subdural space, where its absorption is insufficient. A ball mechanism created by CSF pulsation may further increase the subdural fluid accumulation. Secondary distortion and occlusion at the level of the basal cisterns may also contribute to the persistence of the subdural fluid collection. Clinical manifestations may be transient, but frequently have a progressive course and the drainage of the subdural collection is, though transient, required in most cases. On these grounds we suggest the selective opening of the basal cisterns associated with a limited resection of the outer cyst walls in order to limit CSF access to the subdural space.

Arachnoid Cysts↗
PubMed2003

[Symptoms experienced by people in vicinity of base stations: II/ Incidences of age, duration of exposure, location of subjects in relation to the antennas and other electromagnetic factors].

This is the 2nd part of a survey study conducted on 530 people (270 men, 260 women) living or not in vicinity of cellular phone base stations. Comparison of complaints frequencies for 16 Non Specific Health Symptoms was done with the CHI-Square test with Yates correction. Our results show significant increase (p < 0.05) in relation with age of subjects (elder subjects are more sensitive) and also, that the facing location is the worst position for some symptoms studied, especially for distances till 100 m from base stations. No significant difference is observed in the frequency of symptoms related to the duration of exposure (from < 1 year to > 5 years), excepted for irritability significantly increased after > 5 years. Other electromagnetic factors (electrical transformers, radio-television transmitters,...) have effects on the frequency of some symptoms reported by the subjects.

Adult↗
PubMed2003

[Prolonged ICP monitoring in children with sylvian fissure arachnoid cysts].

BACKGROUND: The decision making process for patients with sylvian fissure arachnoid cysts still represents a challenge for the neurosurgeon. A high proportion of the patients is indeed asymptomatic, in spite of neuroimaging signs of apparently increased intracranial pressure (ICP). The aim of the present study was to evaluate the usefulness of prolonged ICP recording in the preoperative work-out. METHODS: Twelve children (11 M/1 F) harboring temporal arachnoid cysts were investigated (men age 6.3 years). According to Galassi classification they were subdivided into 3 groups. Group I included 3 patients with Type I cysts; group II comprised 6 children with Type II cysts; group III consisted of 3 children with Type III cysts. An extensible silicone microprocessor (Codman ), developed for continuous ICP recording, was implanted intraparenchymally, adjacent to the major extension of the cyst. The collected information was cable unloaded to a PC and stored. All the patients underwent a minimum of 48 hours to a maximum of 72 hours ICP continuous check. Ten mmHg was arbitrarily chosen as the upper normal limit of ICP in resting conditions and the patients were classified according to the percentile distribution of their ICP daily and nightly pressure values. RESULTS: ICP recordings were in the normal range in all the 3 children with Type I cysts (49-86% <10 mmHg during the entire recording), in spite of the fact that 2 of them were apparently symptomatic. Three of the 6 children with a Type II temporal cyst had elevated ICP values (69-99% >10 mmHG), even though they had an incidental (1 case) or prenatal (2 cases) diagnosis. The remaining 3 patients had normal ICP values for more than 70% of the recording time period. Two of the 3 patients with type III temporal arachnoid cysts had almost constantly abnormal ICP values (95=99% >10 mmHg); conversely the third patient showed normal ICP values for more than 80% of the recording time period. Five patients were operated on; in 4 of them the surgical indication was based on ICP recordings (2 of the 3 children with a Type II cyst and increased ICP and the 2 patients with a Type III cyst and increased ICP). The last child, harboring a Type I cyst, was operated on under parents request, as a preventive measure. At a mean follow-up of 10.1 months all the patients operated on are in excellent clinical conditions; 1 of them (Type II cyst) initially submitted to craniotomy and cystic membrane excision needed a subdural-peritoneal shunt implant 3 months after surgery for the appearance of a symptomatic subdural hygroma on the side of the cyst. Postoperative CT showed signs of brain expansion in the 2 patients operated on for a Type III cyst, and in the patients operated on for a Type I cyst. CONCLUSIONS: With the limit of the relatively small series here presented, prolonged ICP recording appeared to be an important preoperative tool to rule out the necessity of operating on children with Type I cysts. Furthermore, it was particularly useful in the decision-making process for children with Type III cysts. In cases of Type II lesions, the investigation resulted less discriminating, though the ICP monitoring contributed to find out those patients in whom surgery was indicated in spite of the absence of symptoms.

Adolescent↗
PubMed2002

Triple-q(-->) octupolar ordering in NpO2.

We report the results of resonant x-ray scattering experiments performed at the Np M(4,5) edges in NpO2. Below T(0)=25 K, the development of long-range order of Np electric quadrupoles is revealed by the growth of superlattice Bragg peaks. The polarization and azimuthal dependence of the intensity of the resonant peaks are well reproduced assuming anisotropic tensor susceptibility scattering from a triple-q(-->) longitudinal antiferroquadrupolar structure. Electric-quadrupole order in NpO2 could be driven by the ordering at T0 of magnetic octupoles of Gamma(5) symmetry, splitting the Np ground state quartet and leading to a singlet ground state with zero dipole-magnetic moment.

Journal Article↗
PubMed2002

[Investigation on the health of people living near mobile telephone relay stations: I/Incidence according to distance and sex].

A survey study using questionnaire was conducted in 530 people (270 men, 260 women) living or not in vicinity of cellular phone base stations, on 18 Non Specific Health Symptoms. Comparisons of complaints frequencies (CHI-SQUARE test with Yates correction) in relation with distance from base station and sex, show significant (p < 0.05) increase as compared to people living > 300 m or not exposed to base station, till 300 m for tiredness, 200 m for headache, sleep disturbance, discomfort, etc. 100 m for irritability, depression, loss of memory, dizziness, libido decrease, etc. Women significantly more often than men (p < 0.05) complained of headache, nausea, loss of appetite, sleep disturbance, depression, discomfort and visual perturbations. This first study on symptoms experienced by people living in vicinity of base stations shows that, in view of radioprotection, minimal distance of people from cellular phone base stations should not be < 300 m.

Electromagnetic Fields↗
PubMed2001

Localized 4f states and dynamic Jahn-Teller effect in PrO2.

Neutron spectroscopic measurements of the magnetic excitations in PrO2 reveal (1) sharp peaks characteristic of transitions between levels of the 4f(1) configuration of Pr4+ split by the cubic crystal field, and (2) broad bands of scattering centered near 30 and 160 meV. We present a simple model based on a vibronic Hamiltonian that accounts for these contrasting features of the data. The analysis shows that 90%+/-10% of the Pr ions have a localized 4f(1) configuration and provides strong evidence for a dynamic Jahn-Teller effect in the gamma(8) electronic ground state.

Journal Article↗
PubMed2001

[Characterization and distribution of Citrobacter species in a university hospital].

OBJECTIVE: [corrected] a) To identify Citrobacter strains following the conventional biochemical reaction of Brenner and col; b) to evaluate the sensitivity and specificity of the O'Hara's method compared with Brenner's method, and c) to determine the rate and distribution of the strains in the clinical isolates. MATERIAL AND METHODS: One hundred and twenty two clinical isolates, characterized as Citrobacter spp. were collected between May of 1994 and August of 1997. Clinical isolates included inpatients and outpatients from Hospital de Clínicas. Strains were identified following the methods of Brenner and O'Hara. RESULTS: Methods of Brenner identified 111 of 122 strains: C. freundii 59 of 111; C. koseri 18 of 111; C. werkmanii 15 of 111; C. braakii 9 of 111; C. youngae 6 of 111 and C. amalonaticus 4 of 111. O'Hara's methods identified 104 of 111 strains (94%). C. freundii was recovered most frequently from urine and feces (p Fisher < 0.026 and 0.039 respectively), while C. koseri was isolated from urine principally (p Fisher < 0.0372). CONCLUSIONS: The genus Citrobacter is an important opportunistic pathogen that can be identified in clinical microbiology laboratories using O'Hara's method.

Bacteremia↗
PubMed2000

Magnetic-octupole order in neptunium dioxide?

The phase transition occurring at 25 K in NpO2, discovered almost 50 years ago, is the most long-lasting mystery in the physics of actinide compounds. Theories based on magnetic or electric-quadrupole order lead inevitably to fundamental, qualitative inconsistencies with observations. We show that the phenomenology of NpO2 can be understood if the order parameter is assumed to be a magnetic octupole of gamma(2) ( xyz) symmetry. NpO2 is the first compound for which indications of an octupolar phase transition have been found.

Journal Article↗