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1.
Tijdschr Psychiatr ; 65(6): 383-387, 2023.
Article in Dutch | MEDLINE | ID: mdl-37434579

ABSTRACT

BACKGROUND: The effectiveness of mental health care is currently monitored through routine quantitative symptom-driven measurements in most clinical settings. These measurements seem inadequate, especially for target groups with complex, multi-faceted problems. There is as yet no alternative method. AIM: 1. To describe why quantitative symptom-driven measurements are inadequate for measuring healthcare effectiveness; and 2. to introduce a new data platform that adjusts for socioeconomic and environmental factors to monitor the effectiveness of healthcare. METHOD: Overview of developments based on literature and introduction of a unique data platform. RESULTS: In the case of complex, multi-faced problems, such as in children with mild intellectual disability and comorbid psychopathology, mental health problems cannot be quantified, isolated, and individualized, i.e., decontextualized. To evaluate care for external benchmarking and scientific research, a shift is advised from measuring clinical symptoms within the treatment period to measuring longer-term group-level social functioning across multiple life domains, with a focus on socio-demographic differences. The Extramuraal LUMC Academisch Netwerk Gezond & Gelukkig Den Haag (ELAN-GGDH ; in English: Extramural LUMC Academic Network Healthy & Happy The Hague) data platform accomplishes this by combining mental health data with Statistics Netherlands microdata. CONCLUSION: The data platform could add value to external benchmarking and scientific research at group level.


Subject(s)
Mental Health Services , Psychopathology , Child , Humans , Netherlands , Mental Health , Delivery of Health Care
2.
Environ Pollut ; 287: 117189, 2021 Oct 15.
Article in English | MEDLINE | ID: mdl-34023660

ABSTRACT

Micronized Cu (µ-Cu) is used as a wood preservative, replacing toxic chromated copper arsenate (CCA). Micronized Cu is malachite [Cu2CO3(OH)2] that has been milled to micron/submicron particles, with many particle diameters less than 100 nm, mixed with biocides and then used to treat wood. In addition to concerns about the fate of the Cu from µ-Cu, there is interest in the fate of the nano-Cu (n-Cu) constituents. We examined movement of Cu from µ-Cu-treated wood after placing treated-wood stakes into model wetland ecosystems. Release of Cu into surface and subsurface water was monitored. Surface water Cu reached maximum levels 3 days after stake installation and remained elevated if the systems remained inundated. Subsurface water Cu levels were 10% of surface water levels at day 3 and increased gradually thereafter. Sequential filtering indicated that a large portion of the Cu in solution was associating with soluble organics, but there was no evidence for n-Cu in solution. After 4 months, Cu in thin-sections of treated wood and adjacent soil were characterized with micro X-ray absorption fine structure spectroscopy (µ-XAFS). Localization and speciation of Cu in the wood and adjacent soil using µ-XAFS clearly indicated that Cu concentrations decreased over time in the treated wood and increased in the adjacent soil. However, n-Cu from the treated wood was not found in the adjacent soil or plant roots. The results of this study indicate that Cu in the µ-Cu-treated wood dissolves and migrates into adjacent soil and waters primarily in ionic form (i.e., Cu2+) and not as nano-sized Cu particles. A reduced form of Cu (Cu2S) was identified in deep soil proximal to the treated wood, indicating strong reducing conditions. The formation of the insoluble Cu2S effectively removes some portion of dissolved Cu from solution, reducing movement of Cu2+ to the water column and diminishing exposure.


Subject(s)
Soil Pollutants , Wood , Arsenates , Copper/analysis , Ecosystem , Soil , Soil Pollutants/analysis , Wetlands , Wood/chemistry
3.
Opt Express ; 26(23): 30435-30443, 2018 Nov 12.
Article in English | MEDLINE | ID: mdl-30469917

ABSTRACT

A new technique is presented to overcome beam size limitation in full field imaging at high brilliance synchrotron sources using specially designed refractive X-ray optics. These optics defocus the incoming beam in vertical direction and reshape the intensity distribution from a Gaussian to a more desirable top-hat-shaped profile at the same time. With these optics X-ray full-field imaging of extended objects becomes possible without having to stack several scans or applying a cone beam geometry in order to image the entire specimen. For in situ experiments in general and for diffraction limited sources in particular this gain in field of view and the optimization of the intensity distribution is going to be very beneficial.

4.
Ned Tijdschr Geneeskd ; 161: D1942, 2017.
Article in Dutch | MEDLINE | ID: mdl-29145907

ABSTRACT

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disease, with a global prevalence of 10 per 10,000. It is characterized by the formation of numerous cysts in both kidneys, and leads to renal function loss; the majority of patients will eventually need renal replacement therapy. It is possible to screen patients' presymptomatic family members from a young age, but this has not historically been recommended as until recently there were no treatment options. This year, the vasopressin V2 receptor antagonist tolvaptan was approved for prescription in ADPKD, to slow the rate of renal function decline. The availability of this new treatment option, along with other factors such as the possible use of IVF procedures with pre-implantation genetic diagnosis, imply that we have to rethink the issue of presymptomatic screening. Young adults at-risk should be screened, to give them the chance to opt for treatment.


Subject(s)
Genetic Testing , Polycystic Kidney, Autosomal Dominant/diagnosis , Polycystic Kidney, Autosomal Dominant/genetics , Adult , Antidiuretic Hormone Receptor Antagonists , Humans , Young Adult
5.
Opt Express ; 25(19): 22455-22466, 2017 Sep 18.
Article in English | MEDLINE | ID: mdl-29041555

ABSTRACT

We introduce the concept of a miniaturized compound refractive X-ray zoom lens consisting of SU-8 lenses fabricated by deep X-ray lithography. The focal length can be varied by changing the number of lens elements placed in the beam. We use suitable actuators to move single lens elements reversibly out of the beam. The X-ray zoom lens can accept different X-ray energies while keeping a fixed working distance, or vary the focal distance for a fixed energy. The latter is useful in tuning the magnification factor in full field microscopy.

6.
Int J Obes (Lond) ; 38(1): 132-9, 2014 Jan.
Article in English | MEDLINE | ID: mdl-23689359

ABSTRACT

OBJECTIVE: Induction of heme oxygenase-1 (HO-1) has been demonstrated to result in chronic weight loss in several rodent models of obesity. However, the specific contribution of the HO metabolite, carbon monoxide (CO) to this response remains unknown. In this study, we determined the effect of chronic low level administration of a specific CO donor on the progression of obesity and its effects on metabolism and adipocyte biology in mice fed a high-fat diet. DESIGN: Experiments were performed on C57BL/6J mice fed a high-fat diet (60%) from 4 weeks until 30 weeks of age. Mice were administered either the CO donor, carbon monoxide releasing molecules (CORM)-A1 (5 mg kg(-1), intraperitoneally every other day) or the inactive form of the drug (iCORM-A1). Body weights were measured weekly and fasted blood glucose, insulin as well as body composition were measured every 6 weeks. Food intake, O2 consumption, CO2 production, activity and body heat production were measured at 28 weeks after start of the experimental protocol. RESULTS: Chronic CORM-A1 attenuated the development of high fat induced obesity from 18 weeks until the end of the study. Chronic CORM-A1 treatment in mice fed a high-fat diet resulted in significant decreases in fasted blood glucose, insulin and body fat and increased O2 consumption and heat production as compared with mice treated with iCORM-A1. Chronic CORM-A1 treatment also resulted in a significant decrease in adipocyte size and an increase in adipocyte number and in NRF-1, PGC-1α and UCP1 protein levels in epidydmal fat. CONCLUSION: Our results demonstrate that chronic CO treatment prevents the development of high-fat diet induced obesity via stimulation of metabolism and remodeling of adipocytes.


Subject(s)
Adipocytes/drug effects , Boranes/pharmacology , Carbonates/pharmacology , Heme Oxygenase-1/pharmacology , Obesity/drug therapy , Weight Loss/drug effects , Adipocytes/metabolism , Animals , Blood Glucose/metabolism , Blotting, Western , Carbon Monoxide/pharmacology , Diet, High-Fat , Disease Models, Animal , Eating , Heme Oxygenase-1/metabolism , Male , Mice , Mice, Inbred C57BL , Obesity/metabolism , Up-Regulation
8.
Rev Sci Instrum ; 84(10): 106103, 2013 Oct.
Article in English | MEDLINE | ID: mdl-24182176

ABSTRACT

The Bragg angle, rocking curve, and reflection efficiency of a quartz crystal x-ray imager (Miller indices 234) were measured at photon energy of 15.6909 keV, corresponding to the K(α2) line of Zr, using the X15A beamline at the National Synchrotron Light Source at Brookhaven National Laboratory. One flat and three spherically curved samples were tested. The peak reflectivity of the best-performing crystal was determined to be (3.6 ± 0.7) × 10(-4) with a rocking-curve full width at half maximum of 0.09°. The Zr K(α2) emission was imaged from a hot Zr plasma generated by a 10-J multiterawatt laser.

9.
Neurocrit Care ; 19(3): 293-8, 2013 Dec.
Article in English | MEDLINE | ID: mdl-23860664

ABSTRACT

BACKGROUND: Recovery is common after subarachnoid hemorrhage (SAH), even in patients who are severely disabled at hospital discharge. Little is known about predictors of late recovery in such patients, even though such knowledge may influence treatment decisions. We hypothesized that cerebral infarction volume would be associated with 3 months outcomes in patients who are severely disabled at 14 days. METHODS: We prospectively identified consecutive aneurysmal SAH patients, documented the development of cerebral infarction, and ascertained the modified Rankin Scale (mRS) at 14 days and 3 months. We included patients with mRS 4 or 5 and NIH Stroke Scale (NIHSS) at least 8 on hospital day 14 (i.e., severe neurologic impairment) and calculated infarct volume in a semi-automated fashion using CT imaging. We explored outcome determinants with ordinal regression. RESULTS: At 14 days, 66 patients were severely disabled, 65 (98.5 %) of whom had mRS of 5; the median NIHSS was 21 [14-24]. At 3 months, 20 (32.8 %) of the 61 patients with known outcomes were independent. Larger infarction volumes were associated with death (20.4 vs. 0.85 mL, P = 0.02). In ordinal regression, increased infarct volume was associated with the worse mRS after correction for WFNS grade, age, and withdrawal of life support (OR 1.01 per mL of infarct, 95 % CI 1.01-1.03, P = 0.01). CONCLUSIONS: After SAH, even with severe neurological injury at 14 days, good recovery is frequent and is associated with lower infarction volume. These data may help clinicians inform surrogate decision makers as they plan the future care of such severely disabled patients.


Subject(s)
Cerebral Infarction/pathology , Cerebral Infarction/physiopathology , Recovery of Function/physiology , Subarachnoid Hemorrhage/pathology , Subarachnoid Hemorrhage/physiopathology , Tomography, X-Ray Computed/methods , Adult , Aged , Cerebral Infarction/etiology , Female , Humans , Male , Middle Aged , Patient Outcome Assessment , Predictive Value of Tests , Prognosis , Prospective Studies , Severity of Illness Index , Subarachnoid Hemorrhage/complications , Time Factors , Tomography, X-Ray Computed/instrumentation
10.
Phys Rev E Stat Nonlin Soft Matter Phys ; 86(2 Pt 2): 026404, 2012 Aug.
Article in English | MEDLINE | ID: mdl-23005866

ABSTRACT

We report on the measurement and computer simulation of the divergence of fast electrons generated in an ultraintense laser-plasma interaction (LPI) and the subsequent propagation in a nonrefluxing target. We show that, at Iλ(2) of 10(20) Wcm(-2)µm(2), the time-integrated electron beam full divergence angle is (60±5)°. However, our time-resolved 2D particle-in-cell simulations show the initial beam divergence to be much smaller (≤30°). Our simulations show the divergence to monotonically increase with time, reaching a final value of (68±7)° after the passage of the laser pulse, consistent with the experimental time-integrated measurements. By revealing the time-dependent nature of the LPI, we find that a substantial fraction of the laser energy (~7%) is transported up to 100 µm with a divergence of 32°.

11.
J Crit Care ; 27(5): 527.e7-11, 2012 Oct.
Article in English | MEDLINE | ID: mdl-22227077

ABSTRACT

PURPOSE: Reducing the incidence of hospital-acquired pneumonia (PNU) is important but depends on accurate assessment. We sought to determine the interrater reliability of diagnosis of PNU and its impact on resource utilization and functional outcomes in a high-risk population. MATERIALS AND METHODS: Patients admitted in 2007 with intracranial hemorrhage were prospectively identified. Pneumonia was prospectively diagnosed by Centers for Disease Control criteria by a neurointensivist and infection control. An independent retrospective determination was made by a fellow, an infectious disease attending physician, and a pulmonologist after review of the electronic medical records and radiographs. Interrater reliability was analyzed with κ statistics. One and 3-month outcomes were measured with the modified Rankin scale. RESULTS: Of 103 patients, the incidence of PNU ranged from 5% to 25%. Interrater reliability was poor (median κ = 0.30 [0.19-0.42]; P < .001). Any ascertainment of PNU was associated with longer intensive care unit length of stay, more fever and ventilator dependence, and worse functional outcomes. CONCLUSIONS: Pneumonia had poor interrater reliability despite highly trained reviewers and validated criteria. Although the clinical assessment of PNU is difficult, it was associated with greater resource use and worse outcomes. Diagnosis of clinical PNU may be suboptimal for measuring quality of intensive care.


Subject(s)
Cross Infection/diagnosis , Cross Infection/epidemiology , Intracranial Hemorrhages/epidemiology , Pneumonia/diagnosis , Pneumonia/epidemiology , Aged , Female , Humans , Incidence , Intensive Care Units , Length of Stay , Male , Middle Aged , Observer Variation , Prospective Studies , Respiration, Artificial , Sensitivity and Specificity
12.
Stroke ; 43(1): 67-71, 2012 Jan.
Article in English | MEDLINE | ID: mdl-21980211

ABSTRACT

BACKGROUND AND PURPOSE: Decreased diffusion (DD) consistent with acute ischemia may be detected on MRI after acute intracerebral hemorrhage (ICH), but its risk factors and impact on functional outcomes are not well-defined. We tested the hypotheses that DD after ICH is related to acute blood pressure (BP) reduction and lower hemoglobin and presages worse functional outcomes. METHODS: Patients who underwent MRI were prospectively evaluated for DD by certified neuroradiologists blinded to outcomes. Hemoglobin and BP data were obtained via electronic queries. Outcomes were obtained at 14 days and 3 months with the modified Rankin Scale, a functional scale scored from 0 (no symptoms) to 6 (dead). We used logistic regression for dependence or death (modified Rankin Scale score 4-6). RESULTS: DD distinct from the hematoma was found on MRI in 39 of 95 patients (41%). DD was associated with greater BP reductions from baseline and a higher risk of dependence or death at 3 months (odds ratio, 4.8; 95% confidence interval, 1.7-13.9; P=0.004) after correction for ICH score (1.8 per point; 95% confidence interval, 1.2-3.1; P=0.01). Lower hemoglobin was associated with worse ICH score, larger hematoma volume, and worse outcomes, but not DD. CONCLUSIONS: DD is common after ICH, associated with greater acute BP reductions, and associated with disability and death at 3 months in multivariate analysis. The potential benefits of acute BP reduction to reduce hematoma growth may be limited by DD. The prevention and treatment of cerebral ischemia manifested as DD are potential methods to improve outcomes.


Subject(s)
Blood Pressure/physiology , Cerebral Hemorrhage/physiopathology , Aged , Aged, 80 and over , Blood Pressure Determination , Cerebral Hemorrhage/mortality , Cerebral Hemorrhage/therapy , Diffusion Magnetic Resonance Imaging , Female , Humans , Male , Middle Aged , Prospective Studies , Risk Factors , Treatment Outcome
13.
Neurocrit Care ; 16(1): 82-7, 2012 Feb.
Article in English | MEDLINE | ID: mdl-21837536

ABSTRACT

BACKGROUND: In patients with acute intracerebral hemorrhage (ICH), reduced platelet activity on admission predicts hemorrhage growth and poor outcomes. We tested the hypotheses that platelet transfusion improves measured platelet activity. Further, we hypothesized that earlier treatment in patients at high risk for hemorrhage growth and poor outcome would reduce follow-up hemorrhage size and poor clinical outcomes. METHODS: We prospectively identified consecutive patients with ICH who had reduced platelet activity on admission and received a platelet transfusion. We defined high-risk patients as per a previous publication, reduced platelet activity, or known anti-platelet therapy (APT) and the diagnostic CT within 12 h of symptom onset. Platelet activity was measured with the VerifyNow-ASA (Accumetrics, CA), ICH volumes on CT with computerized quantitative techniques, and functional outcomes with the modified Rankin Scale (mRS) at 3 months. RESULTS: Forty-five patients received a platelet transfusion with an increase in platelet activity from 472 ± 50 (consistent with an aspirin effect) to 561 ± 92 aspirin reaction units (consistent with no aspirin effect, P < 0.001). For high-risk patients, platelet transfusion within 12 h of symptom onset, as opposed to >12 h, was associated with smaller follow-up hemorrhage size (8.4 [3-17.4] vs. 13.8 [12.3-62.5] ml, P = 0.04) and increased odds of independence (mRS < 4) at 3 months (11 of 20 vs. 0 of 7, P = 0.01). There were similar results for patients with known APT. CONCLUSIONS: In patients at high risk for hemorrhage growth and poor outcome, early platelet transfusion improved platelet activity assay results and was associated with smaller final hemorrhage size and more independence at 3 months.


Subject(s)
Cerebral Hemorrhage/therapy , Critical Illness/therapy , Platelet Activation/physiology , Platelet Transfusion/methods , Aged , Cerebral Hemorrhage/blood , Female , Humans , Male , Middle Aged , Platelet Transfusion/adverse effects , Prospective Studies , Risk , Severity of Illness Index , Treatment Outcome
14.
Phys Rev E Stat Nonlin Soft Matter Phys ; 86(6 Pt 2): 065402, 2012 Dec.
Article in English | MEDLINE | ID: mdl-23367996

ABSTRACT

Cu wires attached to Al cones are used to investigate the energy coupling efficiency of laser light to fast electrons through a cone into a dense plasma. We present experimental and simulation results demonstrating the effect on the energy coupling of effectively placing the cone in a surrounding high density plasma as well as the effect of a large preformed plasma inside the cone. Thick cone walls, simulating plasma surrounding the cone in fast ignition, reduce the energy coupling by a factor of up to 4. An increase in prepulse inside the cone by a factor of 50 further reduces coupling by a factor of 3. Simulations with the pic code lsp that include the laser plasma interaction and the preformed plasma from the flash code show that electron refluxing in thin cone-wall targets enhances coupling to the wire. The implications for full-scale cone-guided fast ignition are discussed.

15.
Rev Sci Instrum ; 82(12): 123503, 2011 Dec.
Article in English | MEDLINE | ID: mdl-22225215

ABSTRACT

We report on the development and characterization of a zirconium Kα imager for high energy density physics research. The imager consists of a spherically bent quartz crystal operating at 15.7 keV photon energy. We compare the performance of the imager in terms of integrated reflectivity (R(int)) and temperature dependent collection efficiency (η(Te)) to that of the widely used Cu Kα imager. Our collisional-radiative simulations show that the new imager can be reliably used up to 250 eV plasma temperature. Monte Carlo simulations show that for a 25 µm thick tracer layer of zirconium, the contribution to Kα production from photo-pumping is only 2%. We present, for the first time, 2D spatially resolved images of zirconium plasmas generated by a high intensity short pulse laser interacting with Zr solid targets.

16.
Neurocrit Care ; 13(3): 313-20, 2010 Dec.
Article in English | MEDLINE | ID: mdl-20717750

ABSTRACT

BACKGROUND AND PURPOSE: In patients with subarachnoid hemorrhage (SAH), higher hemoglobin (HGB) has been associated with better outcomes, but packed red blood cell (PRBC) transfusions with worse outcomes. We performed a prospective pilot trial of goal HGB after SAH. METHODS: Forty-four patients with SAH and high risk for vasospasm were randomized to goal HGB concentration of at least 10 or 11.5 g/dl. We obtained blinded clinical outcomes at 14 days (NIH Stroke Scale and modified Rankin Scale, mRS), 28 days (mRS), and 3 months (mRS), and blinded interpretation of brain MRI for cerebral infarction at 14 days. This trial is registered at www.stroketrials.org. RESULTS: Forty-four patients were randomized. Patients with goal HGB 11.5 g/dl received more PRBC units per transfusion [1 (1-2) vs. 1 (1-1), P < 0.001] and more total PRBC units [3 (2-4) vs. 2 (1-3), P = 0.045]. Prospectively defined safety endpoints were not different between groups. HGB concentration was different between study groups from day 4 onwards. The number of cerebral infarctions on MRI (6 of 20 vs. 9 of 22), NIH Stroke Scale scores at 14 days [1 (0-9.75) vs. 2 (0-16)], and rates of independence on the mRS at 14 days (65% vs. 44%) and 28 days (80% vs. 67%) were similar, but favored higher goal HGB (P > 0.1 for all). CONCLUSIONS: Higher goal hemoglobin in patients with SAH seems to be safe and feasible. A phase III trial of goal HGB after SAH is warranted.


Subject(s)
Anemia/blood , Anemia/therapy , Erythrocyte Transfusion , Hemoglobins/metabolism , Subarachnoid Hemorrhage/blood , Adult , Aged , Anemia/epidemiology , Cerebral Infarction/blood , Cerebral Infarction/epidemiology , Cerebral Infarction/pathology , Critical Care/methods , Critical Care/statistics & numerical data , Female , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Pilot Projects , Prospective Studies , Risk Factors , Subarachnoid Hemorrhage/epidemiology , Subarachnoid Hemorrhage/pathology , Treatment Outcome , Vasospasm, Intracranial/blood , Vasospasm, Intracranial/epidemiology , Vasospasm, Intracranial/pathology
17.
Neurocrit Care ; 13(1): 57-61, 2010 Aug.
Article in English | MEDLINE | ID: mdl-20568023

ABSTRACT

BACKGROUND: Hyponatremia is common in neurocritical care and is associated with poor outcome, but the optimal treatment is not known. We wished to test the hypothesis that for neurocritical care patients with severe hyponatremia (Na < 130 mmol/l) or hyponatremia (Na < 135 mmol/l) with depressed Glasgow Coma Scale (GCS) that conivaptan use would lead to increased serum sodium compared to usual care. METHODS: We prospectively screened 249 neurocritical care patients with hyponatremia for a prospective, randomized pilot (goal N = 20) trial. Study interventions were usual care, or usual care plus conivaptan 20 mg IV as a bolus followed by 20 mg IV over 24 h, the lower FDA-approved dose. Patients were prospectively followed for changes in serum and urine electrolytes and clinical examinations with a blinded examiner. This study is registered at www.clinicaltrials.gov (NCT00727090). RESULTS: Despite the prevalence of hyponatremia, recruitment was difficult, and the study was terminated after six patients were enrolled, three in each group. Most hyponatremia in screened but non-randomized patients was transient or not associated with depressed GCS. Conivaptan led to higher serum sodium compared to usual care. The change in serum sodium from baseline, the pre-specified endpoint, was significantly different between groups at six (7.0 +/- 1.7 vs. -0.6 +/- 2.1 mmol/l, P = 0.008), 24 (9.7 +/- 3.2 vs. 0 +/- 1.0 mmol/l), and 36 h (8.0 +/- 5.6 vs. -1.7 +/- 2.1 mmol/l, P = 0.05). There were no apparent differences in clinical examination as a result of treatment. Adverse events were similar, and all randomized patients completed the protocol. CONCLUSIONS: Despite an inclusive protocol, most patients were not candidates for conivaptan therapy for hyponatremia. The role of conivaptan in the Neuro-ICU remains to be defined.


Subject(s)
Antidiuretic Hormone Receptor Antagonists , Benzazepines/administration & dosage , Hyponatremia/drug therapy , Intensive Care Units , Adult , Aged , Benzazepines/adverse effects , Critical Illness/therapy , Dose-Response Relationship, Drug , Drug Administration Schedule , Female , Glasgow Coma Scale , Humans , Hyponatremia/physiopathology , Injections, Intravenous , Male , Middle Aged , Pilot Projects , Prospective Studies , Severity of Illness Index , Single-Blind Method , Sodium/blood , Time Factors , Young Adult
18.
Phys Rev E Stat Nonlin Soft Matter Phys ; 80(4 Pt 2): 045401, 2009 Oct.
Article in English | MEDLINE | ID: mdl-19905383

ABSTRACT

The energy transport in cone-guided low- Z targets has been studied for laser intensities on target of 2.5x10(20) W cm(-2). Extreme ultraviolet (XUV) imaging and transverse optical shadowgraphy of the rear surfaces of slab and cone-slab targets show that the cone geometry strongly influences the observed transport patterns. The XUV intensity showed an average spot size of 65+/-10 microm for slab targets. The cone slabs showed a reduced spot size of 44+/-10 microm. The shadowgraphy for the aforementioned shots demonstrate the same behavior. The transverse size of the expansion pattern was 357+/-32 microm for the slabs and reduced to 210+/-30 microm. A transport model was constructed which showed that the change in transport pattern is due to suppression of refluxing electrons in the material surrounding the cone.


Subject(s)
Energy Transfer/radiation effects , Gases/chemistry , Gases/radiation effects , Hot Temperature , Lasers , Models, Chemical , Computer Simulation
19.
Rev Sci Instrum ; 80(8): 083501, 2009 Aug.
Article in English | MEDLINE | ID: mdl-19725649

ABSTRACT

A dual-channel, curved-crystal spectrograph was designed to measure time-integrated x-ray spectra in the approximately 1.5 to 2 keV range (6.2-8.2 A wavelength) from small-mass, thin-foil targets irradiated by the VULCAN petawatt laser focused up to 4x10(20) W/cm(2). The spectrograph consists of two cylindrically curved potassium-acid-phthalate crystals bent in the meridional plane to increase the spectral range by a factor of approximately 10 compared to a flat crystal. The device acquires single-shot x-ray spectra with good signal-to-background ratios in the hard x-ray background environment of petawatt laser-plasma interactions. The peak spectral energies of the aluminum He(alpha) and Ly(alpha) resonance lines were approximately 1.8 and approximately 1.0 mJ/eV sr (approximately 0.4 and 0.25 J/A sr), respectively, for 220 J, 10 ps laser irradiation.

20.
Phys Rev E Stat Nonlin Soft Matter Phys ; 79(6 Pt 2): 066409, 2009 Jun.
Article in English | MEDLINE | ID: mdl-19658614

ABSTRACT

Expressions for the yield of electron-positron pairs, their energy spectra, and production rates have been obtained in the interaction of multi-kJ pulses of high-intensity laser light interacting with solid targets. The Bethe-Heitler conversion of hard x-ray bremsstrahlung [D. A. Gryaznykh, Y. Z. Kandiev, and V. A. Lykov, JETP Lett. 67, 257 (1998); K. Nakashima and H. Takabe, Phys. Plasmas 9, 1505 (2002)] is shown to dominate over direct production (trident process) [E. P. Liang, S. C. Wilks, and M. Tabak, Phys. Rev. Lett. 81, 4887 (1998)]. The yields and production rates have been optimized as a function of incident laser intensity by the choice of target material and dimensions, indicating that up to 5 x 10 (11) pairs can be produced on the OMEGA EP laser system [L. J. Waxer, Opt. Photonics News 16, 30 (2005)]. The corresponding production rates are high enough to make possible the creation of a pair plasma.

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