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1.
Neurol Sci ; 42(12): 5205-5211, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33821361

RESUMO

BACKGROUND AND RATIONALE: Histopathological studies revealed degeneration of the dorsal motor nucleus of the vagus nerve (VN) early in the course of idiopathic Parkinson's disease (IPD). Degeneration of VN axons should be detectable by high-resolution ultrasound (HRUS) as a thinning of the nerve trunk. In order to establish if the VN exhibits sonographic signs of atrophy in IPD, we examined patients with IPD compared with age-matched controls. MATERIAL AND METHODS: We measured the caliber (cross-sectional area, CSA) and perimeter of the VN in 20 outpatients with IPD (8 females and 12 males; mean age 73.0 + 8.6 years) and in age-matched controls using HRUS. Evaluation was performed by blinded raters using an Esaote MyLab Gamma device in conventional B-Mode with an 8-19 MHz probe. RESULTS: In both sides, the VN CSA was significantly smaller in IPD outpatients than in controls (right 2.37 + 0.91, left 1.87 + 1.35 mm2 versus 6.0 + 1.33, 5.6 + 1.26 mm2; p <0.001), as well as the perimeter (right 5.06 + 0.85, left 4.78 + 1.74 mm versus 8.87 + 0.86, 8.58 + 0.97 mm; p <0.001). There were no significant correlations between VN CSA and age, the Hoehn and Yahr scale, L-dopa therapy, and disease duration. CONCLUSION: Our findings provide evidence of atrophy of the VNs in IPD patients by HRUS. Moreover, HRUS of the VN represent a non-invasive easy imaging modality of screening in IPD patients independent of disease stage and duration and an interesting possible additional index of disease.


Assuntos
Doença de Parkinson , Idoso , Idoso de 80 Anos ou mais , Atrofia , Feminino , Humanos , Levodopa , Masculino , Pessoa de Meia-Idade , Doença de Parkinson/diagnóstico por imagem , Ultrassonografia , Nervo Vago/diagnóstico por imagem
2.
Phys Rev Lett ; 123(23): 234801, 2019 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-31868471

RESUMO

The transverse emittance of the electron beam is a fundamental parameter in linac-based x-ray free-electron lasers (FELs). We present results of emittance measurements carried out at SwissFEL, a compact x-ray FEL facility at the Paul Scherrer Institute in Switzerland, including a description of the novel high-resolution measurement techniques and the optimization procedure. We obtained slice emittance values at the undulator entrance down to 200 nm for an electron beam with a charge of 200 pC and an rms duration of 30-40 fs. Furthermore, we achieved slice emittances as low as 100 nm for 10 pC beams with few fs duration. These values set new standards for electron linear accelerators. The quality, verification, and control of our electron beams allowed us to generate high-power FEL radiation for a wavelength as short as 0.1 nm using an electron beam with an energy of only 6 GeV. The emittance values demonstrated at SwissFEL would allow producing hard x-ray FEL pulses with even lower-energy beams, thus paving the way for even more compact and cost-effective FEL facilities.

3.
Neurol Sci ; 38(11): 1985-1991, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28815313

RESUMO

Spontaneous dissection of cervical arteries (sCAD) is a major cause of ischemic stroke in young patients, with an incidence varying from 1.7 to 3/100,000/year for extracranial internal carotid artery (ICAD) and 1 to 1.9/100,000/year for extracranial vertebral artery (VAD). Reliable epidemiological data on stroke incidence related to sCAD are scarce in Italy. This study aims to evaluate the incidence, clinical features, and outcome of cerebrovascular events related to sCAD and spontaneous intracranial arteries dissections (sIAD) in the city of Pisa (Italy). We retrospectively analyzed consecutive patients admitted between December 1997 and June 2015 with a diagnosis of stroke, TIA, or Bernard-Horner syndrome due to acute cervical or intracranial artery dissection. Considering that our hospital collects presumptively all patients hospitalized with sCAD coming from the referral geographical area, data may provide a good approximation to real incidence of sCAD in our population. Clinical and radiological features, acute treatment and outcome were collected. Seventy-seven cases were included (mean age 48.1±10.4 years, range 23-77,72.7% males), 66 residents in the district of Pisa. Crude incidence rate of cerebrovascular events due to intra or extracranial dissection was 1.88/100,000/year. The incidence of ICAD was 0.80/100,000/year and 0.43/100,000/year for VAD. Stroke occurred in 76.6% of patients. VAD was more prone to cause ischemic stroke and present with cervical pain or focal signs (p < 0.01) than ICAD group, which had older age at onset. sIAD were more frequent in the posterior circle (p = 0.01) and more associated with ischemic lesions. A good outcome (mRS 0-2) was observed in 79% of patients. This is the first epidemiological attempt to investigate impact of sCAD and sIAD in Italy.


Assuntos
Dissecção Aórtica/epidemiologia , Transtornos Cerebrovasculares/epidemiologia , Adulto , Idade de Início , Idoso , Dissecção Aórtica/terapia , Transtornos Cerebrovasculares/terapia , Vértebras Cervicais , Cidades , Feminino , Humanos , Incidência , Itália/epidemiologia , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Adulto Jovem
4.
Rev Sci Instrum ; 95(1)2024 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-38236086

RESUMO

The bunch length in a linac driven Free Electron Laser (FEL) is a major parameter to be characterized to optimize the final accelerator performance. In linear machines, this observable is typically determined from the beam imaged on a screen located downstream of a Transverse Deflecting Structure (TDS) used to impinge a time dependent kick along the longitudinal coordinate of the beam. This measurement is typically performed during the machine setup and only sporadically to check the beam duration, but it cannot be continuously repeated because it is time consuming and invasive. A non-invasive method to determine the electron bunch length has already been presented in the past. This method is based on the analysis of the synchrotron radiation light spot emitted by the bunch passing through a magnetic chicane, provided that the energy chirp impinged on the bunch by the upstream radio frequency structures is known. In order to overcome a systematic discrepancy affecting the synchrotron radiation monitor based results compared to the absolute TDS based ones, we implemented and optimized a machine learning approach to predict the bunch length downstream of the two SwissFEL compression stages-from about 10 fs up to about 2 ps-as well as the beam longitudinal profile at the first one.

5.
Neurol Sci ; 34(10): 1871-3, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23703399

RESUMO

Acute basilar artery occlusion has a poor prognosis and best treatment has not been assessed yet; as for intra-arterial treatment, no "gold standard" exists. We evaluated a series of ten patients treated with intra-arterial combination of recombinant tissue plasminogen activator (rtPA) and abciximab. Partial/complete recanalisation was achieved in all patients and good outcome (1 month Modified Rankin Scale 0-2) in eight cases, while one patient had symptomatic intracranial haemorrhage and died. Such outcome appears significantly better if compared with the results of Basilar Artery International Cooperation Study, suggesting that intra-arterial administration of rtPA and abciximab may be a promising option in patients with acute basilar artery occlusion undergoing endovascular treatment.


Assuntos
Anticorpos Monoclonais/administração & dosagem , Fibrinolíticos/administração & dosagem , Fragmentos Fab das Imunoglobulinas/administração & dosagem , Inibidores da Agregação Plaquetária/administração & dosagem , Ativador de Plasminogênio Tecidual/administração & dosagem , Insuficiência Vertebrobasilar/tratamento farmacológico , Abciximab , Adulto , Idoso , Feminino , Seguimentos , Humanos , Injeções Intra-Arteriais , Masculino , Pessoa de Meia-Idade , Avaliação de Resultados em Cuidados de Saúde
6.
Cephalalgia ; 28(3): 300-1, 2008 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-18254899

RESUMO

Hemicrania continua (HC) is an indomethacin-responsive headache characterized by a chronic, strictly unilateral, side-locked without side-shifting, persistent headache. We report three cases of HC with atypical features in which an acute administration of indomethacin 50 mg IM (INDOTEST) was performed. In all three cases INDOTEST predicted chronic responsiveness to indomethacin. Thus, in cases of HC with atypical features, INDOTEST could help for a correct diagnosis and therapy.


Assuntos
Cefaleia/diagnóstico , Cefaleia/tratamento farmacológico , Indometacina/administração & dosagem , Adulto , Idoso , Doença Crônica , Método Duplo-Cego , Feminino , Humanos , Valor Preditivo dos Testes
7.
J Chem Phys ; 129(4): 044704, 2008 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-18681667

RESUMO

Terahertz transient conductivity measurements are performed on pentacene single crystals, which directly demonstrate a strong coupling of charge carriers to low frequency molecular motions with energies centered around 1.1 THz. We present evidence that the strong coupling to low frequency motions is the factor limiting the conductivity in these organic semiconductors. Our observations explain the apparent paradox of the "bandlike" temperature dependence of the conductivity beyond the validity limit of the band model.

8.
Talanta ; 186: 381-388, 2018 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-29784377

RESUMO

An electronic eye (EE) for fast and easy evaluation of grape phenolic ripening has been developed. For this purpose, berries of different grape varieties were collected at different harvest times from veraison to maturity, then an amount of the derived must was deposited on a white sheet of absorbent paper to obtain a sort of paper chromatography. Thus, RGB images of the must spots were collected using a flatbed scanner and converted into one-dimensional signals, named colourgrams, which codify the colour properties of the images. The dataset of colourgrams was used to build calibration models to relate the colour of the images with the phenolic composition of the samples - determined by reference analytical methods - and therefore to follow the ripening trend. Satisfactory calibration models were obtained for the prediction of the most important parameters related to phenolic ripening of grapes, such as colour index, tonality, total anthocyanins content, malvidin-3-O-glucoside and petunidin-3-O-glucoside.

9.
Eur J Cancer ; 42(10): 1501-6, 2006 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-16762541

RESUMO

Our aim was to determine the aneusomy level and the HER-2 gene copy numbers, by fluorescence in situ hybridization (FISH) and to analyze their impact on the amplification rate in breast carcinomas considered HER-2 weakly positive cases by immunohistochemistry. We evaluated 343 breast carcinomas using double colour FISH (LSI Her-2/neu gene and CEP 17). Monosomy and polysomy were demonstrated in 24.2% and 46.1% respectively and 101/343 (29.6%) of the specimens were amplified by FISH. A statistically significant difference was observed, when we compared the amplification percentage in polysomic and monosomic specimens (P<0.0001) and, among polysomic specimens, when tumours were compared with HER-2 gene signals number per cell between 3 and 10 and >10 respectively (P<0.0001). Logistic regression analysis showed that HER-2 signals >10 and polysomy absence were independently associated with amplification. Our results confirm that the majority of 2+ IHC cases express the HER-2 protein without gene amplification and highlight the effect of chromosome 17 aneusomy and the HER-2 gene copy number on amplification.


Assuntos
Neoplasias da Mama/genética , Aberrações Cromossômicas , Genes erbB-2 , Receptor ErbB-2/genética , Amplificação de Genes , Dosagem de Genes , Humanos , Imuno-Histoquímica , Ploidias , Análise de Regressão
10.
Phys Rev E ; 93(6): 062604, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27415317

RESUMO

Microfluidic separation of magnetic particles is based on their capture by magnetized microcollectors while the suspending fluid flows past the microcollectors inside a microchannel. Separation of nanoparticles is often challenging because of strong Brownian motion. Low capture efficiency of nanoparticles limits their applications in bioanalysis. However, at some conditions, magnetic nanoparticles may undergo field-induced aggregation that amplifies the magnetic attractive force proportionally to the aggregate volume and considerably increases nanoparticle capture efficiency. In this paper, we have demonstrated the role of such aggregation on an efficient capture of magnetic nanoparticles (about 80 nm in diameter) in a microfluidic channel equipped with a nickel micropillar array. This array was magnetized by an external uniform magnetic field, of intensity as low as 6-10 kA/m, and experiments were carried out at flow rates ranging between 0.3 and 30 µL/min. Nanoparticle capture is shown to be mostly governed by the Mason number Ma, while the dipolar coupling parameter α does not exhibit a clear effect in the studied range, 1.4 < α < 4.5. The capture efficiency Λ shows a strongly decreasing Mason number behavior, Λ∝Ma^{-1.78} within the range 32 ≤ Ma ≤ 3250. We have proposed a simple theoretical model which considers destructible nanoparticle chains and gives the scaling behavior, Λ∝Ma^{-1.7}, close to the experimental findings.

11.
Phys Med ; 32(12): 1659-1666, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27765457

RESUMO

PURPOSE: To predict patients who would benefit from adaptive radiotherapy (ART) and re-planning intervention based on machine learning from anatomical and dosimetric variations in a retrospective dataset. MATERIALS AND METHODS: 90 patients (pts) treated for head-neck cancer (H&N) formed a multicenter data-set. 41 H&N pts (45.6%) were considered for learning; 49 pts (54.4%) were used to test the tool. A homemade machine-learning classifier was developed to analyze volume and dose variations of parotid glands (PG). Using deformable image registration (DIR) and GPU, patients' conditions were analyzed automatically. Support Vector Machines (SVM) was used for time-series evaluation. "Inadequate" class identified patients that might benefit from replanning. Double-blind evaluation by two radiation oncologists (ROs) was carried out to validate day/week selected for re-planning by the classifier. RESULTS: The cohort was affected by PG mean reduction of 23.7±8.8%. During the first 3weeks, 86.7% cases show PG deformation aligned with predefined tolerance, thus not requiring re-planning. From 4th week, an increased number of pts would potentially benefit from re-planning: a mean of 58% of cases, with an inter-center variability of 8.3%, showed "inadequate" conditions. 11% of cases showed "bias" due to DIR and script failure; 6% showed "warning" output due to potential positioning issues. Comparing re-planning suggested by tool with recommended by ROs, the 4th week seems the most favorable time in 70% cases. CONCLUSIONS: SVM and decision-making tool was applied to overcome ART challenges. Pts would benefit from ART and ideal time for re-planning intervention was identified in this retrospective analysis.


Assuntos
Aprendizado de Máquina , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Assistida por Computador/métodos , Estudos de Coortes , Humanos , Reprodutibilidade dos Testes , Estudos Retrospectivos
12.
Brain Res Bull ; 65(4): 297-300, 2005 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-15811594

RESUMO

Rizatriptan represents a major advance in the treatment of migraine attack: inhibition of peripheral trigeminal nerve and constriction of intracranial extracerebral blood vessels have been proposed as its main antimigraine mechanisms of action. Although many studies may suggest that rizatriptan causes highly selective vasoconstriction within intracranial extracerebral vessels (i.e., meningeal arteries), no literature data are available to date on possible cerebral hemodynamic changes in humans after treatment with rizatriptan. The aim of this study was to evaluate the effect of rizatriptan on cerebral blood flow velocity performing transcranial Doppler during spontaneous attacks of migraine without aura. Fourteen patients suffering from migraine without aura were monitored to evaluate mean flow velocity changes on both middle cerebral arteries during migraine attack 30 min before and 120 min after oral administration of rizatriptan 10mg. Monitoring was repeated for 30 min during the pain-free period. All patients turned out to be drug responders and no significant mean flow velocity changes were observed between the pain-free period and pre-treatment phase; besides no significant difference in mean flow velocity value have been detected between the periods after the drug administration during the attack versus both pre-treatment period and pain-free phase. These findings indicate that the antimigraine action of rizatriptan is not associated with clear intracranial cerebral hemodynamic changes and may support its cerebrovascular safety.


Assuntos
Córtex Cerebral/efeitos dos fármacos , Transtornos de Enxaqueca/sangue , Fluxo Sanguíneo Regional/efeitos dos fármacos , Agonistas do Receptor de Serotonina/administração & dosagem , Triazóis/administração & dosagem , Adulto , Córtex Cerebral/fisiologia , Feminino , Lateralidade Funcional , Humanos , Fluxometria por Laser-Doppler/métodos , Masculino , Pessoa de Meia-Idade , Artéria Cerebral Média/efeitos dos fármacos , Artéria Cerebral Média/fisiopatologia , Transtornos de Enxaqueca/tratamento farmacológico , Fatores de Tempo , Triptaminas
13.
J Exp Clin Cancer Res ; 24(4): 633-8, 2005 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-16471327

RESUMO

Studies recently suggested that different genetic factors are involved in the development and progression of bladder cancer. In this study, 30 consecutive patients affected by bladder neoplasm were evaluated in order to analyze the frequency of c-erb-2 gene amplification and chromosome 7, 9, 17 aneusomy using fluorescence in situ hybridization (FISH) technique. C-erb-2 gene amplification, chromosome 17 gain and aneusomy were respectively observed in 3.7% (1/27), in 47% (12/27) and in 74% (20/27) of examined tumors. Moreover, chromosome 7 and 9 aneusomy were detected in 74% (20/27) and in 72% (16/27) of specimens. A statistically significant correlation was observed between chromosome 17 aneusomy and tumor stage and grade (r: 0.642, p = 0.0001; r: 0.385, p = 0.04, respectively). In conclusion, we observed a low incidence of C-erb-2 gene amplification, while chromosome 17 aneusomy was confirmed as a marker of advanced and aggressive bladder cancer.


Assuntos
Carcinoma de Células de Transição/genética , Aberrações Cromossômicas , Amplificação de Genes , Genes erbB-2 , Neoplasias da Bexiga Urinária/genética , Idoso , Idoso de 80 Anos ou mais , Carcinoma de Células de Transição/patologia , Humanos , Hibridização in Situ Fluorescente , Masculino , Pessoa de Meia-Idade , Neoplasias da Bexiga Urinária/patologia
14.
Arch Neurol ; 58(9): 1410-3, 2001 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11559312

RESUMO

BACKGROUND: Cerebral microembolism has often been documented by transcranial Doppler imaging during carotid angioplasty and stenting. However, few data are available about its characteristics during the 2 different kinds of procedure. OBJECTIVES: To compare the incidence of microemboli occurring during angioplasty alone with that during stenting in the different phases of the procedures and to relate it to periprocedural cerebrovascular complications. PATIENTS AND METHODS: Thirty-eight patients underwent 41 procedures (15 angioplasty alone and 26 stenting) for symptomatic carotid stenoses of 70% or more. Transcranial Doppler monitoring was performed to detect microemboli in the middle cerebral artery during 3 phases of the procedure: (1) guidewire crossing, (2) first dilatation in case of angioplasty alone or stent release with predilatation if performed, and (3) further dilatation. RESULTS: Microemboli occurred in all cases in phase 1 of the procedure but less frequently in the arteries treated with stenting when compared with those treated with angioplasty alone in phase 2 and particularly (P<.02) in phase 3. The mean number of microemboli was highest in phase 2, predominant (P<.05) during angioplasty alone, and particularly reduced (P<.02) in phase 3 during the stenting procedures. During 2 (5%) of the 41 procedures, cerebrovascular complications occurred in phase 1, with the number of microemboli being higher than mean values. CONCLUSIONS: Cerebral microembolism is a very common event, especially during guidewire crossing and angioplasty alone compared with stenting. Further studies concerning the prognostic significance of this are advisable.


Assuntos
Angioplastia com Balão/efeitos adversos , Estenose das Carótidas/terapia , Embolia Intracraniana/diagnóstico por imagem , Embolia Intracraniana/etiologia , Stents/efeitos adversos , Idoso , Feminino , Humanos , Incidência , Embolia Intracraniana/epidemiologia , Masculino , Pessoa de Meia-Idade , Ultrassonografia Doppler Transcraniana
15.
Brain Res ; 682(1-2): 101-15, 1995 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-7552300

RESUMO

We have recently reported that hypothyroidism increases immunoreactive (IR)-vasoactive intestinal polypeptide (VIP) and VIP mRNA content in both parvocellular and magnocellular neurons of the rat, hypothalamic paraventricular nucleus (PVN). As VIP can stimulate vasopressin (AVP) secretion, we conducted an anatomical investigation to determine whether VIP-containing neurons in other regions of the brain that are involved with homeostatic mechanisms of water and salt conservation are also affected by hypothyroidism. The distribution and intensity of VIP immunostaining in neurons and fibers of the magnocellular-neurohypophysial system, including the hypothalamic PVN, supraoptic nucleus (SON) and accessory magnocellular cell groups, circumventricular subfornical organ (SFO), preoptic and anterior hypothalamus, midline thalamus, subthalamic zona incerta and posterior septal nuclei were studied using a highly sensitive immunocytochemical technique and unbiased neuronal counting methods, based on the optical dissector principle. Hypothyroidism increased the intensity of VIP immunostaining and/or the number/section, percentage and numerical density of IR-VIP neurons in the PVN, SON, nucleus circularis, periventricular preoptic nucleus of the hypothalamus and SFO. In addition, IR-VIP perikarya and/or fibers in the hypothalamic medial preoptic area and anterior periventricular nucleus, nucleus reuniens of the thalamus and dorsal fornix-triangular septal nucleus complex were also apparent in the hypothyroid animals while no immunostaining was seen in these areas in control animals. No quantitative and/or qualitative modifications in IR-VIP neurons and fibers were noted in the anterior hypothalamic area, suprachiasmatic nucleus, thalamic paraventricular nucles an subthalamic zona incerta between hypothyroid and control animals. These findings suggest an inverse relationship between thyroid hormone and VIP content and/or distribution of IR-VIP neurons in specific forebrain regions involved in the control of AVP release, extracellular fluid volume, thirst, blood pressure and anterior pituitary secretion. This raises the possibility that changes in fluid homeostasis and cardiovascular function occurring in hypothyroidism may be mediated, at least in part, by VIP-producing neurons in diverse regions of the brain.


Assuntos
Hipotireoidismo/metabolismo , Neurônios/metabolismo , Neuro-Hipófise/metabolismo , Prosencéfalo/metabolismo , Peptídeo Intestinal Vasoativo/metabolismo , Animais , Antitireóideos/farmacologia , Peso Corporal , Hipotireoidismo/sangue , Hipotireoidismo/patologia , Imuno-Histoquímica , Masculino , Metimazol/farmacologia , Fibras Nervosas/metabolismo , Neuro-Hipófise/patologia , Prosencéfalo/patologia , Ratos , Ratos Sprague-Dawley , Hormônios Tireóideos/sangue
16.
J Heart Valve Dis ; 8(5): 488-94, 1999 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-10517388

RESUMO

BACKGROUND AND AIM OF THE STUDY: In asymptomatic prosthetic valve recipients, high-intensity transient signals (HITS) observed with transcranial Doppler (TCD) are a phenomenon of obscure clinical relevance which nature has not yet been elucidated convincingly. METHODS: Eighty-three patients without carotid disease, history of cerebrovascular accidents, and with negative preoperative TCD undergoing either valve replacement (mitral, n = 11; aortic, n = 56; mitral + aortic, n = 6; 40 mechanical prostheses, 29 biological prostheses, 10 homografts) or mitral repair (n = 10) were evaluated prospectively by means of TCD at discharge, three months and one year after surgery, to analyze the presence, incidence and characteristics of HITS. Furthermore, in 12 patients positive for HITS, TCD was repeated during a 30-min period of 100% O2 inhalation. RESULTS: Twenty-five patients (30%) were positive for HITS at all postoperative controls, although no neurological symptoms were observed. Mechanical prostheses showed a significantly higher incidence of HITS (85%) than biological prostheses (10%, p <0.001), repaired mitral valves (0%, p <0.001) and homografts (0%, p <0.001). At multivariate analysis the presence of a mechanical prosthesis was the only significant predictor of detection of HITS after valve replacement. During O2 inhalation, a significant decrease in the number of HITS per hour (55 +/- 79 versus 22 +/- 31, p = 0.002) occurred, which returned to initial values when room-air breathing was resumed. CONCLUSIONS: Prosthetic valve replacement, particularly when mechanical devices are used, is associated with the generation of HITS which persist throughout the follow up period, but remain clinically silent. The decrease of HITS during O2 inhalation strongly supports the hypothesis of the gaseous nature of such signals and confirms the validity of this method in helping to differentiate gaseous microemboli from solid microemboli in prosthetic valve recipients.


Assuntos
Embolia/diagnóstico por imagem , Implante de Prótese de Valva Cardíaca/efeitos adversos , Ultrassonografia Doppler Transcraniana , Adulto , Idoso , Idoso de 80 Anos ou mais , Valva Aórtica/cirurgia , Artérias Carótidas/diagnóstico por imagem , Embolia/etiologia , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Valva Mitral/cirurgia , Análise Multivariada , Estudos Prospectivos
17.
Phys Rev E Stat Nonlin Soft Matter Phys ; 69(4 Pt 2): 045502, 2004 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15169061

RESUMO

We show that the pulsed regimes observed in free-electron lasers (FELs) can be suppressed using feedback control. By applying tiny parameter perturbations, the feedback allows to keep the systems onto a stationary state that is naturally existing in phase space, but is usually inaccessible because of its unstable nature. We test this method numerically on a master equation derived from the classical iterative model. Then we present the experimental results obtained on the super-ACO FEL. This method is in principle directly applicable to the other free-electron lasers, whose instabilities have a dynamical (deterministic) origin.

18.
Phys Rev E Stat Nonlin Soft Matter Phys ; 63(5 Pt 2): 056501, 2001 May.
Artigo em Inglês | MEDLINE | ID: mdl-11415022

RESUMO

Measurements of coherent diffraction radiation from a slit of variable width generated by short electron bunches were performed in millimeter and submillimeter ranges. Experimental data are compared with the transition radiation case and theoretical predictions. A more realistic description than the conventional theory is necessary to account for the data correctly. No noticeable difference in the estimated bunch length was observed using diffraction radiation in a wide range of slit widths and transition radiation.

19.
Phys Rev E Stat Nonlin Soft Matter Phys ; 69(3 Pt 2): 036501, 2004 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15089421

RESUMO

We present a phenomenological treatment of free-electron laser storage ring saturation dynamics. The model includes longitudinal instabilities, Touschek intrabeam scattering, and nonzero off-energy-function contributions. The model predictions are compared with Super ACO experimental results and the agreement is shown to be satisfactory.

20.
IEEE Trans Neural Netw ; 4(1): 53-62, 1993.
Artigo em Inglês | MEDLINE | ID: mdl-18267703

RESUMO

Multilayer perceptrons (MLPs) with weight values restricted to powers of two or sums of powers of two are introduced. In a digital implementation, these neural networks do not need multipliers but only shift registers when computing in forward mode, thus saving chip area and computation time. A learning procedure, based on backpropagation, is presented for such neural networks. This learning procedure requires full real arithmetic and therefore must be performed offline. Some test cases are presented, concerning MLPs with hidden layers of different sizes, on pattern recognition problems. Such tests demonstrate the validity and the generalization capability of the method and give some insight into the behavior of the learning algorithm.

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