Soft x-ray Ar + 8 laser excited by low-voltage capillary discharge.

We demonstrated the operation of a 46.9-nm capillary discharge Ar + 8-laser excited by electrical pulses at a very low voltage (35 - 45 kV), which is approximately two times lower than previously reported. The decrease in pulse voltage not only allows for further reduction in the size of the laser's excitation part, but also a principal shift to the experimental methods, techniques, and technologies used in ordinary pulsed gas lasers operating in the ultraviolet, visible, and infrared regions of the spectra. In an argon-filled alumina capillary with an inner diameter of 3.1 mm and a length of 22 cm, laser pulses with an energy of 4 µJ and a duration of 1.6 ns were generated. The laser produces a beam with a Gaussian intensity distribution and an FWHM divergence of 1.9 mrad. The results could be particularly useful in the development of compact, practical soft x-ray capillary lasers for use in small laboratories at educational and research institutions.

Reflectivity and spectral shift from laser plasmas generated by high-contrast, high-intensity KrF laser pulses.

The energy and spectrum of the reflected 248 nm radiation are studied from solid targets up to 1.15 × 1018 W cm-2 intensity. The experiments used the 700 fs directly amplified pulses of the KrF system which was cleaned from prepulses with the new Fourier-filtering method providing 12 orders of magnitude temporal contrast. Increasing the intensity from 1015 W cm-2 results in increasing absorption up to more than 90% above 1018 W cm-2. This is accompanied by increasing x-ray conversion exhibiting a less steep power law dependence for low-Z matter than for gold. Strong blue shift of the reflected radiation from the backward propagating plasma was observed. It is shown that in the case of KrF laser pulses of highest contrast, vacuum heating can be one of the dominant absorption mechanisms. This article is part of a discussion meeting issue 'Prospects for high gain inertial fusion energy (part 1)'.

Short-pulse KrF amplifier using spatially tunable x-ray preionization.

The small saturation energy density of excimers requires amplifiers of large cross sections for amplification of short pulses of already medium power. Homogeneous excitation of large volumes of fluorine-based gas mixtures by discharge pumping is a critical interplay of the properties of both pumping and preionization, generally necessitating an intense spatially and temporally controlled x-ray preionization. In the present realization, the stringent intensity requirements of preionization are fulfilled by reducing the pulse duration of the x-ray flash to ∼16 ns and by positioning the x-ray source in the near vicinity of the active volume. It is proven both theoretically and experimentally that by proper choice of the positions of two cylindrical x-ray guns, the spatial distribution of preionization can be tuned to (and around) the optimum distribution. In this way, the spatial distribution of the discharge can also be controlled, giving a practical method to compensate for eventual inhomogenities of the E-field of excitation and to tune the discharge to the desired geometry. In this paper, design considerations and experimental realization of a KrF excimer amplifier of ∼5 × 4 cm2 cross section and a spatially tunable x-ray preionization are presented.

Resonant third harmonic generation of KrF laser in Ar gas.

Investigations of emission of harmonics from argon gas jet irradiated by 700 fs, 5 mJ pulses from a KrF laser are presented. Harmonics conversion was optimized by varying the experimental geometry and the nozzle size. For the collection of the harmonic radiation silicon and solar-blind diamond semiconductor detectors equipped with charge preamplifiers were applied. The possibility of using a single-crystal CVD diamond detector for separate measurement of the 3rd harmonic in the presence of a strong pumping radiation was explored. Our experiments show that the earlier suggested 0.7% conversion efficiency can really be obtained, but only in the case when phase matching is optimized with an elongated gas target length corresponding to the length of coherence.

Magnetoelectric confinement and stabilization of Z pinch in a soft-x-ray Ar(+8) laser.

Magnetoelectric confinement and stabilization of the plasma column in a soft-x-ray Ar(+8) laser, which is excited by a capillary Z pinch, via the combined magnetic and electric fields of the gliding surface discharge is experimentally demonstrated. Unlike soft-x-ray lasers excited by the conventional capillary Z pinches, the magnetoelectric confinement and stabilization of plasma do provide the laser operation without using any external preionization circuit.

One-lung ventilation does not result in cerebral desaturation during application of lung protective strategy if normocapnia is maintained.

BACKGROUND: Previously a report has suggested that administration of lung protective strategy for one-lung ventilation(OLV) results in oxygen desaturation of the brain parenchyma. The aim of our work was to confirm that the maintenance of normocapnia during protective OLV strategy results in alteration of cerebral blood fl ow and cerebral oxygen saturation as compared to double-lung ventilation. METHODS: Data were obtained from 24 patients undergoing thoracic surgery. Cerebral oxygen saturation (rSO2) was continuously monitored by INVOS 5100C Cerebral Oxymeter System along with measurement of cerebral blood fl ow velocity (MCAV) by transcranial Doppler sonography. Arterial blood samples were taken for blood gas analysis in the awake state, in the supine and lateral decubitus position during double-lung ventilation (DLV), and during OLV. RESULTS: When ventilation was changed from DLV to OLV, no significant change was observed in rSO2. A significant decrease of rSO2 was found compared to the value observed during DLV in lateral decubitus at the time point 60 minutes after the start of OLV. No clinically significant changes in the MCAV was observed throughout the course of the thoracic surgical procedure. CONCLUSIONS: OLV does not result in clinically relevant decreases in cerebral blood fl ow and cerebral oxygen saturation during application of lung protective ventilation if normocapnia is maintained.

Effects of different tidal volumes for one-lung ventilation on oxygenation with open chest condition and surgical manipulation: a randomised cross-over trial.

BACKGROUND: The ideal tidal volume (TV) during one-lung ventilation (OLV) remains controversial. High TVs may increase the incidence of postoperative lung injury after thoracic surgery. There is nonetheless little evidence that the use of low TV during OLV will fail to provide adequate arterial oxygenation. We evaluated the influence of low (5 mL/kg-1) and high (10 mL/kg-1) TV on arterial oxygenation during one-lung ventilation in clinical conditions. METHODS: A hundred patients scheduled for lung surgery were studied. Patients were randomly assigned to either 30 minutes of one-lung ventilation with a TV of 10 mL/kg-1 at a rate of 10 breaths/minute (Group 10, N.=50) or a TV of 5 mL/kg-1 with 5 cmH2O PEEP at a rate of 20 breaths/minute (Group 5, N.=50). According to the rules of crossover design during the subsequent 30 minutes, each patient received the alternative management. Arterial blood partial pressures, hemodynamic responses, and ventilatory parameters were recorded. Results are presented as means ± SDs; P<0.05 was considered statistically significant. RESULTS: PaO2 was unaffected by TV (10 mL/kg-1: 218±106 versus 5 mL/kg-1: 211±119 mmHg, P=0.29). Calculated intrapulmonary shunt fraction was also similar with each TV during OLV (5 mL/kg-1: 25±9% versus 10 mL/kg-1: 24±8%, p=0.14). In contrast, low TV significantly increased PaCO2 (10 mL/kg-1: 39±6 versus 5 mL/kg-1: 44±8 mmHg, P<0.001). There were significant differences both in peak (10 mL/kg-1: 27±6 versus 5 mL/kg-1: 21±5 cmH2O, P<0.001) and plateau airway pressure values (10 mL/kg-1: 22±6 versus 5 mL/kg-1: 18±5 cmH2O, P<0.001) during OLV. CONCLUSION: Low TV (5 mL/kg-1) accompanied by 5 cmH2O PEEP provides comparable arterial oxygenation and intrapulmonary shunt fraction during one-lung ventilation as higher TV (10 mL/kg-1) without PEEP.

Changes in DRIFT spectra of wood irradiated by lasers of different wavelength.

An exact wavelength separation of the spectrum cannot be accomplished when utilizing common ultraviolet (UV) light sources, so the dependence of photodegradation on wavelength cannot be done directly. The photodegradation of wood resulted in by laser irradiation on various wavelengths can be studied by comparing the changes in the DRIFT spectra of various wood materials. The analysis of the difference spectrum is a widely used method to investigate the changes in the infrared spectrum. As this procedure cannot be used to compare the changes quantitatively, a new indicator was introduced, termed Band Damage Index (BDI). The BDI and the results obtained by its analysis are going to be discussed.

Two-step preionization scheme for discharge pumped KrF excimer lasers.

The beam homogeneity and stored energy of discharge pumped KrF excimer amplifiers are critically dependent on the preionization level of the active medium and on the rise time of the electric excitation pulse. Here a scheme is presented to increase the effectiveness of the preionization and to improve the rise time of the pump pulse by the use of the auto-spark-gap UV preionization of increased gap separation. The modified charging circuit has been proven to enhance the discharge quality and the amplification properties of the excimer module. The increased temporal jitter of the preionization sparks of large gap separation is eliminated by an additional pre-preionization scheme. The circuit is especially well suited for short-pulse KrF amplifiers.

Factors influencing hemorrhagic transformation in ischemic stroke: a clinicopathological comparison.

As hemorrhagic transformation (HTr) is a frequent complication and can worsen the outcome of acute ischemic stroke, our aim was to assess the risk factors of HTr. Using the database of our neuropathological laboratory, 245 consecutive acute ischemic stroke patients were analyzed. An exploratory logistic regression procedure was carried out to find the best multiple model identifying the factors associated with HTr. The autopsy revealed ischemic infarct in 175 (71%) and ischemic infarct with HTr in 70 (29%) patients. Mean age was 71.5 +/- 11.4 years (mean +/- SD) and 74.8 +/- 10.2 years (mean +/- SD), respectively. The multiple model confirmed age in case of embolic stroke, and diabetes mellitus and infarct size as independent risk factors of HTr. It seems that not serum glucose level but diabetes mellitus in the case history is an independent predictor of HTr.

Vinpocetine for cognitive impairment and dementia.

BACKGROUND: Vinpocetine is a synthetic ethyl ester of apovincamine, a vinca alkaloid obtained from the leaves of the Lesser Periwinkle (Vinca minor) and discovered in the late 1960s. Although used in human treatment for over twenty years, it has not been approved by any regulatory body for the treatment of cognitive impairment. Basic sciences studies have been used to claim a variety of potentially important effects in the brain. However, despite these many proposed mechanisms and targets, the relevance of this basic science to clinical studies is unclear. OBJECTIVES: To assess the efficacy and safety of vinpocetine in the treatment of patients with cognitive impairment due to vascular disease, Alzheimer's disease, mixed (vascular and Alzheimer's disease) and other dementias. SEARCH STRATEGY: The Cochrane Dementia & Cognitive Improvement Group's Specialized Register was searched using the terms vinpocetin*, cavinton, kavinton, Rgh-4405, Tcv-3B, "ethyl apovincaminate", vinRx, periwinkle, "myrtle vincapervinc" and cezayirmeneksesi. The manufacturers of vinpocetine were asked for information on trials of vinpocetine for dementia. In addition we tried to collect articles not listed in MEDLINE or other sources on the Internet (e.g. articles in Hungarian and Romanian). SELECTION CRITERIA: All human, unconfounded, double-blind, randomized trials in which treatment with vinpocetine was administered for more than a day and compared to control in patients with vascular dementia, Alzheimer's dementia or mixed Alzheimer's and vascular dementia and other dementias. Non-randomized trials were excluded. DATA COLLECTION AND ANALYSIS: Data were independently extracted by the two reviewers (SzSz and PW) and cross-checked. Data from "washout" periods were not used for the analysis. For continuous or ordinal variables, such as cognitive test results, the main outcomes of interest were the change in score from baseline. The categorical outcome of global impression was transformed to binary data (improved or not improved) as was the occurrence of adverse effects; here the endpoint itself was of interest the Peto method of the "typical odds ratio" was used. A test for heterogeneity of treatment effects between the trials was made if appropriate. Data synthesis and analysis were performed using the Cochrane Review Manager software (RevMan version 4.1). MAIN RESULTS: All identified studies were performed before the 1990s and used various terms and criteria for cognitive decline and dementia. The three studies included in the review involved a total of 583 people with dementia treated with vinpocetine or placebo. The reports of these studies did not make possible any differentiation of effects for degenerative or vascular dementia. The results show benefit associated with treatment with vinpocetine 30mg/day and 60 mg/day compared with placebo, but the number of patients treated for 6 months or more was small. Only one study extended treatment to one year. Adverse effects were inconsistently reported and without regard for relationship to dose. The available data do not demonstrate many problems of adverse effects but intention-to-treat data were not available for any of the trials. REVIEWER'S CONCLUSIONS: Although the basic science is interesting, the evidence for beneficial effect of vinpocetine on patients with dementia is inconclusive and does not support clinical use. The drug seems to have few adverse effects at the doses used in the studies. Large studies evaluating the use of vinpocetine for people suffering from well defined types of cognitive impairment are needed to explore possible efficacy of this treatment.

The Mures-Uzhgorod-Debrecen study: a comparison of hospital stroke services in Central-Eastern Europe.

Stroke mortality is extremely high in Central-Eastern European countries. The high rate of risk factors and differences in health care services might be among the factors resulting in high stroke morbidity and mortality in this region. As only few prospectively collected information are available from this region, we decided to evaluate some characteristics of stroke services in neurological departments of a Romanian, a Ukrainian and a Hungarian city in the framework of the Mures-Uzhgorod-Debrecen comparative epidemiological study. We registered demographic data, the absence or presence of the most important risk factors, and clinical signs on admission and at discharge. We recorded the application of various diagnostic methods, stroke treatment and recommendations for secondary prevention. Follow-up is planned after 30 days and after 1 year. The paper summarizes the methodology of this prospective epidemiological study of stroke patients hospitalized in neurological departments in Târgu Mures, Uzhgorod and Debrecen, three Central-Eastern European cities in Romania, Ukraine and Hungary, respectively.

Screening of vascular cognitive impairment on a Hungarian cohort.

Cerebrovascular disease is a major public health problem in Eastern European countries. A Hungarian post-stroke population was examined to estimate the rate of dementia, the risk factors for cognitive impairment, and the applicability of a recently established Canadian diagnostic checklist in this cohort. Chronic cerebrovascular outpatients were screened for cognitive impairment with a combined checklist: the Diagnostic Checklist for Vascular Dementia established by the Consortium of Canadian Centres for Clinical Cognitive Research using the Mini Mental State Examination instead of the detailed neuropsychological part of the Checklist. Of the 247 consecutive patients at a cerebrovascular outpatient unit, 176 had cerebrovascular disorder diagnosed either by computed tomography (CT; n=126) or by the clinical signs. Of these, 15% were cognitively impaired and 5% fulfilled the criteria of dementia. The mean age of the patients with cognitive impairment was significantly higher than that of patients with normal cognition (68.2+/-10.2 and 60.5+/-10.5 years, P<0.001). The Barthel index was significantly lower in the cognitively affected group than in non-affected patients (92.4+/-16.0 and 97.1+/-8.7, P=0.027). Diabetes and more than two subcortical infarcts on CT or magnetic resonance imaging were more frequent in patients with cognitive loss (P=0.043 and P=0.013, respectively). Cognitive performance was also influenced by the level of education. Higher age, diabetes, motor deficits, and multiple subcortical infarcts are risk factors for cognitive impairment after stroke. The combined checklist appears to be a practical screening test for cognitive impairment in patients with chronic cerebrovascular diseases.

Optimization of the output beam homogeneity of short-pulse KrF amplifiers.

The output beam of short-pulse excimer amplifiers exhibits an inhomogeneous spatial intensity distribution caused by diffraction effects at laser windows and mirrors. Theoretical and experimental studies show that the amplification parameters of a KrF amplifier can be optimized with respect to the output beam homogeneity by proper choice of the energy density in the amplifier. The homogenized intensity distribution is obtained at the plane of the output window of the amplifier and can be transferred by optical imaging onto a target plane. It is shown that the amplification parameters for the best output homogeneity are close to the ones previously found for optimal energy extraction efficiency.

Group-velocity-dispersion-compensated propagation of short pulses in dispersive media.

An optical scheme based on a single angularly dispersive element is proposed for canceling group-velocity dispersion for pulse propagation in dispersive media. It is demonstrated experimentally that a pulse duration of 100 fs is preserved throughout the travel of a 248-nm-pulse through a 75-mm-long fused-silica slab.

Pulse compression and traveling wave excitation scheme using a single dispersive element.

A single dispersive element is shown to be sufficient for simultaneous pulse compression and tilting of the pulse front, and therefore well-suited for traveling-wave excitation of targets. It is shown that in all the previous arrangements used for traveling wave excitation, spatially dependent group velocity dispersion occurs along the target. A compensated arrangement is proposed that provides pulse compression at the target-plane and exact synchronism between the pump and the generated pulses for various targets.

Intensity-dependent loss properties of window materials at 248 nm.

Transmission of fused silica, CaF(2), LiF, and MgF(2) is measured using 450-fsec, 248-nm pulses in the range 10-120 GW/cm(2). Different loss mechanisms such as scattering of transmitted radiation, color-center formation, and multiphoton absorption were studied separately. For fused silica a two-photon absorption mechanism is found, while for CaF(2), LiF, and MgF(2) three-photon absorption and absorption due to color-center formation are found as dominant absorption mechanisms.