Signatures of resonantly driven laser-wakefield excitation by a pulse train generated by an optical delay mask.

Electron plasma waves can be efficiently excited by a resonant train of ultrashort pulses, spatially separated by a plasma wavelength. Generating a pulse train from a single amplified ultrashort pulse may be challenging when dealing with large beams. Here we discuss a pulse splitting technique using a simple delay mask that can be adapted to large diameter petawatt beams. We show via detailed numerical simulations that unique signatures of electrons accelerated by a resonantly excited wakefield can be obtained from realistic focused double-pulse trains obtained from a single-region delay mask.

Compact x-ray sources for mammographic applications: Monte Carlo simulations of image quality.

Thomson scattering x-ray sources can provide spectral distributions that are ideally suited for mammography with sufficient fluence rates. In this article, the authors investigate the effects of different spectral distributions on the image quality in simulated images of a breast mammographic phantom containing details of different compositions and thicknesses. They simulated monochromatic, quasimonochromatic, and polychromatic x-ray sources in order to define the energy for maximum figure of merit (signal-difference-to-noise ratio squared/mean glandular dose), the effect of an energy spread, and the effect of the presence of higher-order harmonics. The advantages of these sources with respect to conventional polychromatic sources as a function of phantom and detail thickness were also investigated. The results show that the energy for the figure of merit peak is between 16 and 27.4 keV, depending on the phantom thickness and detail composition and thickness. An energy spread of about 1 keV standard deviation, easily achievable with compact x-ray sources, does not appreciably affect the image quality.

Tracking propagation of ultrashort intense laser pulses in gases via probing of ionization.

We use optical interferometry to study the propagation of femtosecond laser pulses in gases. We show the measurements of propagation in a nitrogen gas jet and we compare the results with propagation in He under the same irradiation conditions. We find that in the case of nitrogen, the detailed temporal structure of the laser pulse can be tracked and visualized by measuring the phase and the resulting electron-density map. A dramatically different behavior occurs in He gas jets, where no details of the temporal structure of the laser pulse are visible. These observations are explained in terms of the ionization dynamics of nitrogen compared to helium. These circumstances make N2 gas sensitive to variations in the electric field and, therefore, allow the laser-pulse temporal and spatial structures to be visualized in detail.

Intense gamma-ray source in the giant-dipole-resonance range driven by 10-TW laser pulses.

A gamma-ray source with an intense component around the giant dipole resonance for photonuclear absorption has been obtained via bremsstrahlung of electron bunches driven by a 10-TW tabletop laser. 3D particle-in-cell simulation proves the achievement of a nonlinear regime leading to efficient acceleration of several sequential electron bunches per each laser pulse. The rate of the gamma-ray yield in the giant dipole resonance region (8

Femtosecond interferometry of propagation of a laminar ionization front in a gas.

We use optical interferometry to investigate ultrafast ionization induced by an intense, ultrashort laser pulse propagating in a helium gas. Besides standard phase shift information, our interferograms show a localized region of fringe visibility depletion (FVD) that moves along the laser propagation axis at luminal velocity. We find that such a loss of visibility can be quantitatively explained by the ultrafast change of refractive index due to the field ionization of the gas in the laser pulse width. We demonstrate that by combining the post facto phase shift distribution with the probe pulse transit effect in the ionizing region, the analysis of the observed FVD yields significant information on the ultrafast dynamics of propagation of the ionization front in the gas.

Predictors of high level of burden and distress in caregivers of demented patients: results of an Italian multicenter study.

BACKGROUND: Considerable suffering is experienced by carers of patients with dementia. Most existing studies do not consider the coexistence of subjective and objective aspects that cause, interacting to each other, this suffering. OBJECTIVES: In this study we: (1) define the high-risk group of caregivers on the bases of the scores obtained on the four scales evaluating burden, distress, depression and anxiety (BDDA) taken into account simultaneously and (2) evaluate risk factors related to the high level of BDDA. SUBJECTS AND METHODS: 419 elderly outpatients with dementia and their caregivers were enrolled. Patients were evaluated for their cognitive, neuropsychological and functional impairment and for comorbidity. Caregivers were evaluated with four scales for the assessment of burden, distress related to neuropsychological disturbances, depression and anxiety. Cluster analysis was used to identify the group with the High level of BDDA (HBDDA). RESULTS: By multiple logistic analysis, disability, specific behavioural disturbances of the patients as well as caregiver's age, type of relationship and living in the south of Italy were observed to be a major risk factor for HBDDA. CONCLUSION: The targeted use of scales specifically assessing BDDA of the caregiver and the identification of particular patient and caregiver characteristics are able to allow a precise and early definition of caregivers at high risk of burden and distress. This might be helpful in planning the correct social/clinical/rehabilitative approach.

Analyzing laser plasma interferograms with a continuous wavelet transform ridge extraction technique: the method.

Laser plasma interferograms are currently analyzed by extraction of the phase-shift map with fast Fourier transform (FFT) techniques [Appl. Opt. 18, 3101 (1985)]. This methodology works well when interferograms are only marginally affected by noise and reduction of fringe visibility, but it can fail to produce accurate phase-shift maps when low-quality images are dealt with. We present a novel procedure for a phase-shift map computation that makes extensive use of the ridge extraction in the continuous wavelet transform (CWT) framework. The CWT tool is flexible because of the wide adaptability of the analyzing basis, and it can be accurate because of the intrinsic noise reduction in the ridge extraction. A comparative analysis of the accuracy performances of the new tool and the FFT-based one shows that the CWT-based tool produces phase maps considerably less noisy and that it can better resolve local inhomogeneties.

[Prognostic value of ECG changes detected by Holter monitoring in silent ischemic heart disease in the aged]. / Significato prognostico delle alterazioni ECG-grafiche rilevate all'Holter nella cardiopatia ischemica silente dell'anziano.

Ischemic Cardiomiopathy (IC) is the main cause of morbidity and mortality in the elderly and its incidence increases progressively with age. Holter monitoring (HM) is used to study IC which reveals asymptomatic ischemic episodes identifiable with the depression of the ST tract. It has been demonstrated that these electric manifestations have the same unfavourable diagnostic value as those accompanied by pain. In order to evaluate the prevalence and prognostic significance of episodes of silent myocardial ischemia in the elderly patient, we examined 99 consecutive patients with stable clinical symptoms of myocardial ischemia and a positive ergometric test (ET). The patients were randomly divided according to age (< or = 65 years, >65 years) into two groups with homogeneous clinical feature, except for a higher prevalence of women in the second group. The HM analysis, carried out for 24 hours during common every day activities and after suspending anti-ischemic therapy, showed that 62 patients (63%) had 289 episodes of electric ischemia; 216 (75%) of these were asymptomatic, and, in the group of elderly there was a higher incidence of ST depression unaccompanied by pain (A vs B = 86 vs 132 episodes, p < 0.001). Comparing the patients with and without anamnestic evidence of myocardial infarction it was found that the first group presented a higher prevalence of ST depression both asymptomatic and symptomatic (147 vs 71 silent episodes, p < 0.001, and 49 vs 24 symptomatic episodes, p = 0.015 respectively), while no statistically significant differences were found between the two age groups. Electric alterations of the asymptomatic ischemic kind were more often found in subjects with stable angina, above all if elderly; this is important from a prognostic point of view as few elderly patients are capable of performing a maximal TE and it is thus significant of reduced coronary reserve. From our data we observed that in patients with stable angina, especially if elderly, Holter revealed asymptomatic ST depression analyzed considering both its length and magnitude, is able to give prognostic evidence of subsequent coronary events.

Long-term therapy of patients with heart failure. Drug therapy: from trial results to clinical practice.

Heart failure (HF) represents a major problem in Western countries due to its high prevalence, frequent need for hospitalization and extremely severe prognosis. There have been remarkable advances in long-term drug therapy. During the last decade, the use of vasodilatators, in particular of angiotensin-converting enzyme (ACE)-inhibitors, has been added to the traditional therapy based on diuretics and digitalis. There have been several controlled clinical trials demonstrating the long-term benefits of these drugs for survival. ACE-inhibitors have reduced the risk of mortality in HF, not only by their systemic vasodilatator action but also by their positive effects on ventricular remodelling. In fact, their use has led to a reduction in the incidence of sudden death, and progression of pump dysfunction. A reduction in the incidence of coronary events was also observed. ACE-inhibitors, in combination with diuretics and digitalis, have been rightfully introduced into long-term therapy of HF. At present, other pharmacological options, like flosequinan, some beta-blockers, and some calcium antagonists such as felodipine and amlodipine, hold promise, but further controlled trials are required before they can be introduced into the therapeutic repertoire of HF management.

[Ergometric test: prognostic significance in the pre-thrombolytic and thrombolytic period]. / Test ergometrico: significato prognostico nell'era pre-trombolitica e trombolitica.

In the pre-thrombolytic era exercise testing showed the ability to identify a low-risk population with a 1 year event rate < 1% and a moderate-high risk group with an event rate up to 17% within 1 year after acute myocardial infarction. The most significant parameters are the markers of compromised left ventricular contractility. Since the introduction of thrombolytic therapy the negative predictive ability of exercise testing has been questioned, due to the frequent occurrence of residual coronary stenosis with atherosclerotic plaque characterized by marked instability, to the point that the usefulness of exercise testing has been challenged. Nevertheless the available information, albeit sparse, seems to confirm that the negative predictive ability of exercise testing is still adequate (good), and certainly not inferior to that in pre-thrombolytic era.

Hemodynamic effects of cadralazine or chlorthalidone in verapamil-treated elderly hypertensives.

Fourteen hypertensives aged > 66-77 years, whose diastolic blood pressure (DBP) was > or = 95 mmHg at the end of 1-month treatment with verapamil 240 mg SR, took part in this clinical-hemodynamic study. Patients were randomized to add the long-acting hydralazine derivative, cadralazine, 10 mg once daily, or chlorthalidone 25 mg once daily for 1 month each, to their previous verapamil regimen, according to a double-blind crossover design. Echo-Doppler hemodynamics were performed before starting verapamil, 1 month after verapamil and then after each phase of the crossover study. A significant reduction in DBP both in supine and upright position was observed with both drugs, while the reduction in systolic blood pressure was not significant. Criteria for a satisfactory response were DBP < or = 90 mmHg or a DBP reduction > or = 10 mmHg; this goal was achieved in 9 patients with cadralazine, 9 patients with chlorthalidone, 5 patients with both. The hemodynamic study in responders showed that both cadralazine and chlorthalidone acted through a reduction of peripheral resistances without inducing reflex tachycardia. Thus, cadralazine and chlorthalidone represent a suitable second-step treatment in elderly hypertensives insufficiently controlled by verapamil monotherapy: both drugs act through a reduction in total peripheral resistance (TPR).

Impedance cardiography for repeated determination of stroke volume in elderly hypertensives: correlation with pulsed Doppler echocardiography.

In this double-blind, crossover study the authors have validated stroke volume determination by impedance cardiography against the pulsed Doppler echocardiographic method in elderly hypertensives. They found a good correlation between the stroke volume values obtained by the two methods over a range of values from 30 to 130 mL. The coefficient of linear regression was about .95 at each visit. The mean of the differences was -0.73 mL with a standard deviation of 8.46. Given that individual differences are normally distributed, the values corresponding to 2 standard deviations of the mean define a range covering 95% of the observed differences. From the distribution of the data around the mean plot it appears that, in comparison with pulsed Doppler, impedance cardiography tends to slightly underestimate stroke volumes of greater than 90 mL and to overestimate values of less than 50 mL. The results of this study indicate that impedance cardiography may represent a reliable alternative to pulsed Doppler echocardiography for the noninvasive estimation of cardiac output at rest in elderly patients.

Age-related antihypertensive and haemodynamic effects of verapamil SR: clinical results and effects on atrial natriuretic peptide.

The antihypertensive effect of the calcium-antagonist verapamil was investigated in two groups of patients, adult hypertensives (AH, less than 65 years of age) and elderly hypertensives (EH, greater than 65 years of age), who were treated with 240 mg p.o. sustained-release (SR) verapamil for 4 months. Arterial blood pressure was significantly reduced in both groups: the responders' rate was 65% in the AH group and 82% in the EG group. The heart rate was slightly but not significantly reduced. An improvement in cardiac haemodynamics was observed [cardiac index (CI), from 3.00 +/- 0.51 to 3.25 +/- 0.83 ml min-1 m-2 in AH and from 2.35 +/- 1.08 to 3.04 +/- 0.86 ml min-1 m-2 in EG]. We also evaluated the plasma concentrations of atrial natriuretic peptide (ANP) before and after treatment; ANP levels increased significantly only in the EH group. No serious side effects occurred. In conclusion, verapamil SR provided effective and well-tolerated antihypertensive treatment in both adult and elderly patients.