Sub-picosecond snapshots of fast electrons from high intensity laser-matter interactions.

The interaction of a high-intensity short-pulse laser with thin solid targets produces electron jets that escape the target and positively charge it, leading to the formation of the electrostatic potential that in turn governs the ion acceleration. The typical timescale of such phenomena is on the sub-picosecond level. Here we show, for the first time, temporally-resolved measurements of the first released electrons that escaped from the target, so-called fast electrons. Their total charge, energy and temporal profile are provided by means of a diagnostics based on Electro-Optical Sampling with temporal resolution below 100 fs.

Enhanced proton acceleration by an ultrashort laser interaction with structured dynamic plasma targets.

We experimentally demonstrate a notably enhanced acceleration of protons to high energy by relatively modest ultrashort laser pulses and structured dynamical plasma targets. Realized by special deposition of snow targets on sapphire substrates and using carefully planned prepulses, high proton yields emitted in a narrow solid angle with energy above 21 MeV were detected from a 5 TW laser. Our simulations predict that using the proposed scheme protons can be accelerated to energies above 150 MeV by 100 TW laser systems.

5.5-7.5 MeV proton generation by a moderate-intensity ultrashort-pulse laser interaction with H2O nanowire targets.

We report on the first generation of 5.5-7.5 MeV protons by a moderate-intensity short-pulse laser (∼5×10(17) W/cm(2), 40 fsec) interacting with frozen H(2)O nanometer-size structure droplets (snow nanowires) deposited on a sapphire substrate. In this setup, the laser intensity is locally enhanced by the snow nanowire, leading to high spatial gradients. Accordingly, the nanoplasma is subject to enhanced ponderomotive potential, and confined charge separation is obtained. Electrostatic fields of extremely high intensities are produced over the short scale length, and protons are accelerated to MeV-level energies.

Ultrafast evolution of electric fields from high-intensity laser-matter interactions.

The interaction of high-power ultra-short lasers with materials offers fascinating wealth of transient phenomena which are in the core of novel scientific research. Deciphering its evolution is a complicated task that strongly depends on the details of the early phase of the interaction, which acts as complex initial conditions. The entire process, moreover, is difficult to probe since it develops close to target on the sub-picosecond timescale and ends after some picoseconds. Here we present experimental results related to the fields and charges generated by the interaction of an ultra-short high-intensity laser with metallic targets. The temporal evolution of the interaction is probed with a novel femtosecond resolution diagnostics that enables the differentiation of the contribution by the high-energy forerunner electrons and the radiated electromagnetic pulses generated by the currents of the remaining charges on the target surface. Our results provide a snapshot of huge pulses, up to 0.6 teravolt per meter, emitted with multi-megaelectronvolt electron bunches with sub-picosecond duration and are able to explore the processes involved in laser-matter interactions at the femtosecond timescale.

Femtosecond dynamics of energetic electrons in high intensity laser-matter interactions.

Highly energetic electrons are generated at the early phases of the interaction of short-pulse high-intensity lasers with solid targets. These escaping particles are identified as the essential core of picosecond-scale phenomena such as laser-based acceleration, surface manipulation, generation of intense magnetic fields and electromagnetic pulses. Increasing the number of the escaping electrons facilitate the late time processes in all cases. Up to now only indirect evidences of these important forerunners have been recorded, thus no detailed study of the governing mechanisms was possible. Here we report, for the first time, direct time-dependent measurements of energetic electrons ejected from solid targets by the interaction with a short-pulse high-intensity laser. We measured electron bunches up to 7 nanocoulombs charge, picosecond duration and 12 megaelectronvolts energy. Our 'snapshots' capture their evolution with an unprecedented temporal resolution, demonstrat- ing a significant boost in charge and energy of escaping electrons when increasing the geometrical target curvature. These results pave the way toward significant improvement in laser acceleration of ions using shaped targets allowing the future development of small scale laser-ion accelerators.

The prevalence of musculoskeletal pain and fibromyalgia in patients hospitalized on internal medicine wards.

OBJECTIVES: To estimate the prevalence of nonarticular pain complaints (chronic widespread pain, chronic localized pain, transient pain) and fibromyalgia in hospitalized patients and to study utilization patterns of health services associated with pain related problems. METHODS: Five hundred twenty-two patients hospitalized on internal medicine wards were enrolled. Data were collected with a questionnaire covering demographic background, information on pain and other symptoms, utilization of health services, and drug consumption. All subjects were classified into four pain groups: those with no pain, transient pain, chronic regional pain, and chronic widespread pain. Tenderness was assessed by thumb palpation, and patients were diagnosed as having fibromyalgia if they met the 1990 American College of Rheumatology criteria. RESULTS: Sixty-two percent of the patients reported pain; 36% reported chronic regional pain, 21% reported chronic widespread pain, and 5% reported transient pain. Fifteen percent of all patients had fibromyalgia, most of whom (91%) were women. The prevalence of chronic widespread pain and of fibromyalgia in women increased with age. Sleep problems, headache, and fatigue were highly prevalent, especially among those with chronic widespread pain. Patients with chronic widespread pain reported more visits to family physicians (6.2 visits per year) and more frequent use of drugs. They also were more frequently referred to rheumatologists, and they reported more hospitalizations. CONCLUSIONS: Pain syndromes and related symptoms are prevalent among hospitalized patients on the medicine wards. The internist taking care of these patients should be aware of the presence of these syndromes and realize that some of the reported symptoms are partly related to these (undiagnosed) pain syndromes rather than to the cause of hospitalization.

Increased non-articular tenderness in patients on steroid therapy.

Increased non-articular tenderness and tender shins have been suggested to be associated with steroid therapy in patients with lupus. The aim of the present study was to extend this observation in a different disease, inflammatory bowel disease (IBD), and to examine the relationship between tenderness, dosage and duration of steroid therapy. Eighty-seven patients with 11313, 23 of them on steroid therapy, were assessed for disease activity and nonarticular tenderness. A count of 18 tender points was conducted by thumb palpation, and tenderness thresholds were assessed by dolorimetry at four shin sites, nine tender point sites and four control point sites. Patients on steroids were significantly more tender than subjects not on steroids: their mean tender point counts were 13.3 and 6.7 (p < 0.001), respectively, and the dolorimetry thresholds at all three sites were significantly lower in the steroid group (p < 0.001). Increased tenderness was also associated with increased steroid dosage. However, tenderness was not related to duration of steroid therapy, to gender, or to previous steroid therapy being discontinued at least a year ago. Disease activity was neither related to tenderness nor to steroid treatment. The demonstration of increased tenderness in IBD patients on steroid therapy, in addition to earlier observations in lupus, may suggest that such a relationship is not disease specific. The recognition of this association is important to physicians treating patients with steroids and will prevent misinterpretations of complaints about tender shins and diffuse tenderness as part of the disease entity itself.

Human promyelocytic leukemia cells (HL-60): a new model to study the effects of chemopreventive agents on H2O2 production.

Tumor promoter-stimulated polymorphonuclear leukocytes (PMNs) produce excessive H2O2, which contributes to inflammation and carcinogenesis. A new model to study 12-O-tetradecanoylphorbol-13-acetate (TPA)-mediated H2O2 formation and its suppression by chemopreventive agents was developed using human promyelocytic leukemic HL-60 cells and validated by comparing results with those obtained using human PMNs. Equal H2O2 (20 to 25 nmol/ml) was generated by TPA-activated PMNs (2.5 x 10(5)/ml) and TPA-treated dimethylsulfoxide (DMSO)-differentiated HL-60 cells (5 x 10(5)/ml). The chemopreventive agent-mediated inhibition of TPA-induced H2O2 formation was also comparable in both cell types. These results suggest that HL-60 cells can become a useful in vitro system to screen rapidly for chemopreventive agents and to study their properties.