Absolute calibration of Fujifilm BAS-TR image plate response to laser driven protons up to 40 MeV.

Image plates (IPs) are a popular detector in the field of laser driven ion acceleration, owing to their high dynamic range and reusability. An absolute calibration of these detectors to laser-driven protons in the routinely produced tens of MeV energy range is, therefore, essential. In this paper, the response of Fujifilm BAS-TR IPs to 1-40 MeV protons is calibrated by employing the detectors in high resolution Thomson parabola spectrometers in conjunction with a CR-39 nuclear track detector to determine absolute proton numbers. While CR-39 was placed in front of the image plate for lower energy protons, it was placed behind the image plate for energies above 10 MeV using suitable metal filters sandwiched between the image plate and CR-39 to select specific energies. The measured response agrees well with previously reported calibrations as well as standard models of IP response, providing, for the first time, an absolute calibration over a large range of proton energies of relevance to current experiments.

Biomechanical measures of clinician-defined unsteadiness during a forward stepdown task in individuals post-arthroscopy for femoroacetabular impingement syndrome.

BACKGROUND: Patients with femoroacetabular impingement syndrome can present with aberrant movement patterns including unsteady balance. Balance training is included in rehabilitation after hip arthroscopy and may improve quality of movement; however, specific biomechanical measures associated with clinician-defined balance impairments are unknown. We aimed to understand these associations as they may inform targeted rehabilitative interventions. METHODS: The forward stepdown is a clinical test used to evaluate movement quality, including balance. 23 individuals at least one-year post-arthroscopy for femoroacetabular impingement syndrome and 15 healthy comparisons performed the forward stepdown, recorded by 3-dimensional motion capture and 2-dimensional video. Three physical therapists graded the 2-dimensional video for steadiness. Two-way analyses of variance were used to evaluate the interaction of group (post-arthroscopy/healthy comparison) by steadiness (steady/unsteady), for center of pressure medial-lateral excursion, center of pressure path length, and lateral trunk, pelvis, and lower extremity joint excursions. FINDINGS: Six (26.1%) participants post-arthroscopy and five (33.3%) healthy comparisons were categorized as unsteady. The odds of being categorized as unsteady were not greater for participants post-arthroscopy (P = 0.72). There were no significant interactions; however, participants with clinician-defined unsteady balance, regardless of group, had significantly greater frontal plane trunk excursion, greater hip excursion, and greater center of pressure path length than those with steady balance (P ≤ 0.006). INTERPRETATION: The odds of being categorized as unsteady were not greater for individuals post-arthroscopy for femoroacetabular impingement syndrome. Clinician-defined unsteadiness was associated with greater frontal plane trunk and hip motion which may be rehabilitation targets to improve balance during a dynamic single-leg task.

Ground reaction force patterns in knees with and without radiographic osteoarthritis and pain: descriptive analyses of a large cohort (the Multicenter Osteoarthritis Study).

OBJECTIVE: To compare ground reaction force patterns (GRF) during walking among legs defined by presence or absence of knee pain and/or radiographic knee osteoarthritis (ROA). METHOD: Principal component analysis extracted major modes of variation (PCs) in GRF data from the Multicenter Osteoarthritis Study during self-paced walking. Legs were categorized as pain + ROA (n = 168), ROA only (n = 303), pain only (n = 476), or control (n = 1877). Relationships between group and GRF PCs were examined using Generalized Estimating Equations, adjusted for age, sex, body mass index, race, and clinic site with and without additional adjustment for gait speed. RESULTS: With or without speed adjustment, pain + ROA had flatter vertical GRF waveforms than control (speed adjusted PC2 difference [95%CI]: -66 [-113,-20]), pain + ROA and ROA only had higher lateral GRF at impact and greater mid-stance medial GRF than control (speed adjusted PC3 difference: 9 [3,16] and 6 [2,10], respectively), and ROA only had higher early vs late medial GRF than control (speed adjusted PC2 difference: 7 [2,13]). Pain only had flatter vertical GRF waveforms and a smaller difference between anterior and posterior GRF than control only without speed adjustment. CONCLUSION: In this large sample, sustained mid-stance loading and higher impact loads were identified in legs with ROA or ROA and pain, even when adjusting for differences in gait speed and other confounders. While it remains to be seen whether these features precede or result from ROA and pain, the presence of these patterns in the speed-adjusted models could have implications on gait interventions aimed to change joint loading.

Test-retest reliability and minimum detectable change for various frontal plane projection angles during dynamic tasks.

OBJECTIVE: Establish between-day test-retest reliability metrics for 2-dimensional frontal plane projection angles (FPPAs) during the lateral step-down (LSD), single-limb squat (SLS), single-limb landing (SLL), and drop vertical jump (DVJ). DESIGN: Test-retest reliability study. SETTING: University laboratory. PARTICIPANTS: 20 healthy adults (12 female, age = 23.60 ±â€¯1.93 years old, body mass index = 24.26 ±â€¯2.54 kg/m2) were tested on 2 separate occasions 7-14 days apart. MAIN OUTCOME MEASURES: Intraclass correlation coefficients (ICC), standard errors of the measurement (SEM), and minimal detectable change (MDC) values across the LSD, SLS, SLL, and DVJ for the following body region variables: trunk, trunk on pelvis, pelvis, hip, thigh to vertical, knee, and shank to vertical. RESULTS: There was moderate-to-substantial between-day test-retest reliability for nearly all body regions across all tasks (ICC = 0.65-0.96). SEM values varied across body regions and tasks (0.9-3.5°). MDCs were variable (2.3-9.8°). Of the body regions, MDCs were largest for the knee and hip. By task, MDCs were lowest for the LSD. CONCLUSIONS: This study identified between-day test-retest reliability metrics for 2-dimensional FPPAs across a variety of body regions during commonly assessed clinical tasks. These data allow clinicians and researchers to more confidently assess true change between assessments or over time.

Efficient post-acceleration of protons in helical coil targets driven by sub-ps laser pulses.

The characteristics of laser driven proton beams can be efficiently controlled and optimised by employing a recently developed helical coil technique, which exploits the transient self-charging of solid targets irradiated by intense laser pulses. Here we demonstrate a well collimated (<1° divergence) and narrow bandwidth (~10% energy spread) proton beamlet of ~107 particles at 10 ± 0.5 MeV obtained by irradiating helical coil targets with a few joules, sub-ps laser pulses at an intensity of ~2 × 1019 W cm-2. The experimental data are in good agreement with particle tracing simulations suggesting post-acceleration of protons inside the coil at a rate ~0.7 MeV/mm, which is comparable to the results obtained from a similar coil target irradiated by a fs class laser at an order of magnitude higher intensity, as reported in S. Kar et al., Nat. Commun, 7, 10792 (2016). The dynamics of hot electron escape from the laser irradiated target was studied numerically for these two irradiation regimes, which shows that the target self-charging can be optimised at a pulse duration of few hundreds of fs. This information is highly beneficial for maximising the post-acceleration gradient in future experiments.

An ultra-high gain and efficient amplifier based on Raman amplification in plasma.

Raman amplification arising from the excitation of a density echelon in plasma could lead to amplifiers that significantly exceed current power limits of conventional laser media. Here we show that 1-100 J pump pulses can amplify picojoule seed pulses to nearly joule level. The extremely high gain also leads to significant amplification of backscattered radiation from "noise", arising from stochastic plasma fluctuations that competes with externally injected seed pulses, which are amplified to similar levels at the highest pump energies. The pump energy is scattered into the seed at an oblique angle with 14 J sr-1, and net gains of more than eight orders of magnitude. The maximum gain coefficient, of 180 cm-1, exceeds high-power solid-state amplifying media by orders of magnitude. The observation of a minimum of 640 J sr-1 directly backscattered from noise, corresponding to ≈10% of the pump energy in the observation solid angle, implies potential overall efficiencies greater than 10%.

Experimental measurements of the collisional absorption of XUV radiation in warm dense aluminium.

The collisional (or free-free) absorption of soft x rays in warm dense aluminium remains an unsolved problem. Competing descriptions of the process exist, two of which we compare to our experimental data here. One of these is based on a weak scattering model, another uses a corrected classical approach. These two models show distinctly different behaviors with temperature. Here we describe experimental evidence for the absorption of 26-eV photons in solid density warm aluminium (T_{e}≈1 eV). Radiative x-ray heating from palladium-coated CH foils was used to create the warm dense aluminium samples and a laser-driven high-harmonic beam from an argon gas jet provided the probe. The results indicate little or no change in absorption upon heating. This behavior is in agreement with the prediction of the corrected classical approach, although there is not agreement in absolute absorption value. Verifying the correct absorption mechanism is decisive in providing a better understanding of the complex behavior of the warm dense state.

Picosecond metrology of laser-driven proton bursts.

Tracking primary radiation-induced processes in matter requires ultrafast sources and high precision timing. While compact laser-driven ion accelerators are seeding the development of novel high instantaneous flux applications, combining the ultrashort ion and laser pulse durations with their inherent synchronicity to trace the real-time evolution of initial damage events has yet to be realized. Here we report on the absolute measurement of proton bursts as short as 3.5±0.7 ps from laser solid target interactions for this purpose. Our results verify that laser-driven ion acceleration can deliver interaction times over a factor of hundred shorter than those of state-of-the-art accelerators optimized for high instantaneous flux. Furthermore, these observations draw ion interaction physics into the field of ultrafast science, opening the opportunity for quantitative comparison with both numerical modelling and the adjacent fields of ultrafast electron and photon interactions in matter.

Fast-electron refluxing effects on anisotropic hard-x-ray emission from intense laser-plasma interactions.

Fast-electron generation and dynamics, including electron refluxing, is at the core of understanding high-intensity laser-plasma interactions. This field is itself of strong relevance to fast ignition fusion and the development of new short-pulse, intense, x-ray, γ-ray, and particle sources. In this paper, we describe experiments that explicitly link fast-electron refluxing and anisotropy in hard-x-ray emission. We find the anisotropy in x-ray emission to be strongly correlated to the suppression of refluxing. In contrast to some previous work, the peak of emission is directly along the rear normal to the target rather than along either the incident laser direction or the specular reflection direction.

Characterisation of deuterium spectra from laser driven multi-species sources by employing differentially filtered image plate detectors in Thomson spectrometers.

A novel method for characterising the full spectrum of deuteron ions emitted by laser driven multi-species ion sources is discussed. The procedure is based on using differential filtering over the detector of a Thompson parabola ion spectrometer, which enables discrimination of deuterium ions from heavier ion species with the same charge-to-mass ratio (such as C(6+), O(8+), etc.). Commonly used Fuji Image plates were used as detectors in the spectrometer, whose absolute response to deuterium ions over a wide range of energies was calibrated by using slotted CR-39 nuclear track detectors. A typical deuterium ion spectrum diagnosed in a recent experimental campaign is presented, which was produced from a thin deuterated plastic foil target irradiated by a high power laser.

Electron refluxing and K-shell line emission from Ti foils irradiated with subpicosecond laser pulses at 527 nm.

We present data on emission of K-shell radiation from Ti foils irradiated with subpicosecond pulses of second harmonic radiation (527 nm) from the TARANIS laser system at intensities of up to 10(18) W cm(-2). The data are used to demonstrate that a resonance absorption type mechanism is responsible for absorption of the laser light and to estimate fast electron temperatures of 30-60 keV that are in broad agreement with expectation from models of absorption for a steep density gradient. Data taken with resin-backed targets are used to demonstrate clear evidence of electron refluxing even at the modest fast electron temperatures inferred.

Learning chronobiology by improving Wikipedia.

Although chronobiology is of growing interest to scientists, physicians, and the general public, access to recent discoveries and historical perspectives is limited. Wikipedia is an online, user-written encyclopedia that could enhance public access to current understanding in chronobiology. However, Wikipedia is lacking important information and is not universally trusted. Here, 46 students in a university course edited Wikipedia to enhance public access to important discoveries in chronobiology. Students worked for an average of 9 h each to evaluate the primary literature and available Wikipedia information, nominated sites for editing, and, after voting, edited the 15 Wikipedia pages they determined to be highest priorities. This assignment (http://www.nslc.wustl.edu/courses/Bio4030/wikipedia_project.html) was easy to implement, required relatively short time commitments from the professor and students, and had measurable impacts on Wikipedia and the students. Students created 3 new Wikipedia sites, edited 12 additional sites, and cited 347 peer-reviewed articles. The targeted sites all became top hits in online search engines. Because their writing was and will be read by a worldwide audience, students found the experience rewarding. Students reported significantly increased comfort with reading, critiquing, and summarizing primary literature and benefited from seeing their work edited by other scientists and editors of Wikipedia. We conclude that, in a short project, students can assist in making chronobiology widely accessible and learn from the editorial process.

Opacity measurements of a hot iron plasma using an x-ray laser.

The temporal evolution of the opacity of an iron plasma at high temperature (30-350 eV) and high density (0.001-0.2 g cm-3) has been measured using a nickel-like silver x-ray laser at 13.9 nm. The hot dense iron plasma was created in a thin (50 nm) iron layer buried 80 nm below the surface in a plastic target that was heated using a separate 80 ps pulse of 6-9 J, focused to a 100 microm diameter spot. The experimental opacities are compared with opacities evaluated from plasma conditions predicted using a fluid and atomic physics code.

Hip Abductor and Knee Extensor Muscle Strength of Children with and without Down Syndrome.

PURPOSE: The purposes of this study were to 1) determine test-retest reliability of hand-held dynamometer measurements of right hip abductor and knee extensor muscle strength in children with Down syndrome (DS), 2) identify differences in isometric muscle strength between children with DS and peers who are developing typically, and 3) determine the relationship between various anthropometric and demographic variables and isometric muscle strength. METHODS: Seventeen children with DS between the ages of seven and 15 years and a comparison group of 17 age- and gender-matched peers who were developing typically participated in the study. A hand-held dynamometer was used to measure peak force during maximal isometric right hip abduction and knee extension at two test sessions approximately one week apart. Peak torque values were calculated by multiplying peak force measurements by the appropriate segment lengths. Anthropometric measurements were obtained, and a questionnaire was used to measure habitual physical activity levels. RESULTS: Test-retest reliability was high, with intraclass correlation coefficients ranging from 0.89 to 0.95. Children with DS had significantly lower mean peak torque values for hip abduction and knee extension than children in the comparison group. Regression analyses indicated that weight, body mass index, height, activity level, and gender were significant predictors of peak torque production for the sample as a whole. CONCLUSIONS: Hand-held dynamometry can be used to obtain reliable measurements of isometric muscle strength in children with DS. Anthropometric characteristics and activity levels may play a role in peak torque production in children with and without DS.

Confidence of academic general internists and family physicians to teach ambulatory procedures.

OBJECTIVE: To evaluate and compare the readiness of academic general internal medicine physicians and academic family medicine physicians to perform and teach 13 common ambulatory procedures. DESIGN: Mailed survey. SETTING: Internal medicine and family medicine residency training programs associated with 35 medical schools in 9 eastern states. PARTICIPANTS: Convenience sample of full-time teaching faculty. MEASUREMENTS AND MAIN RESULTS: A total of 331 general internists and 271 family physicians returned completed questionnaires, with response rates of 57% and 65%, respectively. Academic generalists ranked most of the ambulatory procedures as important for primary care physicians to perform; however, they infrequently performed or taught many of the procedures. Overall, compared with family physicians, general internists performed and taught fewer procedures, received less training, and were less confident in their ability to teach these procedures. Physicians' confidence to teach a procedure was strongly associated with training to perform the procedure and performing or precepting a procedure at least 10 times per year. CONCLUSIONS: Many academic general internists do not perform or precept common adult ambulatory procedures. To ensure that residents have the opportunity to learn routine ambulatory procedures, training programs may need to recruit qualified faculty, train current faculty, or arrange for academic specialists or community physicians to teach these skills.

Confidence of graduating internal medicine residents to perform ambulatory procedures.

OBJECTIVE: To evaluate the training of graduating internal medicine residents to perform 13 common ambulatory procedures, 3 inpatient procedures, and 3 screening examinations. DESIGN: Self-administered descriptive survey. SETTING: Internal medicine training programs associated with 9 medical schools in the eastern United States. PARTICIPANTS: Graduating residents (N = 128); response rate, 60%. MEASUREMENTS AND MAIN RESULTS: The total number of procedures performed during residency, importance for primary care physicians to perform these procedures, confidence to perform these procedures, and helpfulness of rotations for learning procedures were assessed. The majority of residents performed only 2 of 13 outpatient procedures 10 or more times during residency: simple spirometry and minor wound suturing. For all other procedures, the median number performed was 5 or fewer. The percentage of residents attributing high importance to a procedure was significantly greater than the percentage reporting high confidence for 8 of 13 ambulatory procedures; for all inpatient procedures, residents reported significantly higher confidence than importance. Continuity clinic and block ambulatory rotations were not considered helpful for learning ambulatory procedures. CONCLUSIONS: Though residents in this sample considered most ambulatory procedures important for primary care physicians, they performed them infrequently, if at all, during residency and did not consider their continuity clinic experience helpful for learning these skills. Training programs need to address this deficiency by modifying the curriculum to ensure that these skills are taught to residents who anticipate a career in primary care medicine.

Patient preferences for care by general internists and specialists in the ambulatory setting.

OBJECTIVE: To investigate patients' preferences for care by general internists and specialists for common medical conditions. DESIGN: Telephone interview. SETTING: A convenience sample of general internal medicine practices at 10 eastern academic medical centers. PATIENT/PARTICIPANTS: A probability sample of 314 participants who had at least one visit with their primary care physician during the preceding 2 years. MEASUREMENTS AND MAIN RESULTS: Items addressed patients' attitudes concerning continuity of care, preferences for care by general internists or specialists for common medical problems, and perceptions about the competency of general internists and specialists to manage these problems. Continuity was important to participants, with 63% reporting they preferred having one doctor. Respondents were willing to wait 3 or 4 days to see their regular doctor (85%) and wanted their doctor to see them in the emergency department (77%) and monitor their care while in the hospital (94%). A majority (>60%) preferred care from their regular doctor for a variety of new conditions. Though respondents valued continuity, 84% felt it was important to be able to seek medical care from any type of physician without a referral, and 74% responded that if they needed to see a specialist, they were willing to pay out-of-pocket to do so. Although most participants (98%) thought their regular doctor was able to take care of usual medical problems, the majority thought that specialists were better able to care for allergies (79%) and better able to prescribe medications for depression (65%) and low-back pain (72%). CONCLUSIONS: Participants preferred to see their general internist despite their perceptions that specialists were more competent in caring for the conditions we examined. However, they wanted unrestricted access to specialists to supplement care provided by general internists.

The effect of suramin on the resorption of bovine nasal cartilage.

Suramin is an anti-neoplastic drug. Its actions include the inhibition of binding of urokinase-type plasminogen activator (uPA) to its receptor, an event which may prevent cartilage breakdown. The aim of this work was to determine the effect of suramin on cartilage resorption. Cartilage expiants, stimulated with interleukin-1alpha, tumour necrosis factor-alpha or retinoic acid were incubated with suramin. Release of incorporated (35)S-sulphate from pre-labelled expiants was used as a measure of proteoglycan breakdown and toluidine blue staining was used to visualise proteoglycan loss.Suramin inhibited the resorption of cytokine and retinoic acid-stimulated bovine nasal cartilage at concentrations between 100-1000 microM. These findings were confirmed by histochemistry. Though reversibility studies indicated that suramin toxicity could not be excluded above 100 muM, retention of suramin in the expiants may have contributed to this. There was no significant effect on lactate production up to 500 muM. The observed inhibition of cartilage resorption may reflect actions of suramin on the PA/plasmin system or on cytokine action.

Determination of (40)ca(+) in the presence of (40)ar(+): an illustration of the utility of time-gated detection in pulsed glow discharge mass spectrometry.

The glow discharge ionization source operated in the pulsed, or modulated, power mode affords a number of distinct advantages over its steady-state counterpart. It is well-known that pulsed plasma operation permits the application of higher instantaneous powers by allowing time for the sample to cool. This minimizes sample overheating while effecting higher sputtering yields and lower limits of detection. The presence of discrete time regimes affords the added advantage of temporal selectivity. Such selectivity allows the observation of analyte ions during a time regime in which their signal is at a maximum while that of electron ionized background species is declining. Significantly, time regimes are found when no background argon ion signals are observable but analyte ion signals remain. This means that discrimination against isobaric interferences arising from the discharge gas is possible. A prime example of the utility of this advantage arises in the determination of calcium with an argon glow discharge. Both the major argon and calcium isotopes are found at a nominal m/z of 40. Time-gated mass spectrometeric detection during the afterpeak time regime enables the ready determination of (40)Ca(+) in samples at the ppm level. A linear calibration curve is obtained that also demonstrates the elimination of the (40)Ar(+) signal from mass spectra obtained with either a dc or rf glow discharge ion source.