Observation of Skewed Electromagnetic Wakefields in an Asymmetric Structure Driven by Flat Electron Bunches.

Relativistic charged-particle beams that generate intense longitudinal fields in accelerating structures also inherently couple to transverse modes. The effects of this coupling may lead to beam breakup instability and thus must be countered to preserve beam quality in applications such as linear colliders. Beams with highly asymmetric transverse sizes (flat beams) have been shown to suppress the initial instability in slab-symmetric structures. However, as the coupling to transverse modes remains, this solution serves only to delay instability. In order to understand the hazards of transverse coupling in such a case, we describe here an experiment characterizing the transverse effects on a flat beam, traversing near a planar dielectric lined structure. The measurements reveal the emergence of a previously unobserved skew-quadrupolelike interaction when the beam is canted transversely, which is not present when the flat beam travels parallel to the dielectric surface. We deploy a multipole field fitting algorithm to reconstruct the projected transverse wakefields from the data. We generate the effective kick vector map using a simple two-particle theoretical model, with particle-in-cell simulations used to provide further insight for realistic particle distributions.

Friendship theory for public health research and practice: a critical realist review.

AIMS: To critically analyse theories of friendship through privileging research on the experience of friendship among those who have experienced mental ill-health. To inform public health approaches that aim to facilitate friendship and assist those experiencing mental ill-health. METHOD: A selective, iterative, purposive review of theoretical and empirical studies, within a critical realist epistemology, is undertaken to provide an analysis. RESULTS: Existing theories - exchange and equity, capital, identity, and attachment - all provide some insight into friendship when encountering mental ill-health. However, recognition theory is found to best capture and explain the experience. CONCLUSION: Recognition theory forms a substantial theoretical foundation for public health initiatives that address friendship and mental ill-health. Friendship can contribute to public mental health, and suggestions are made to give friendship itself recognition within public health frameworks.

Fabrication of THz corrugated wakefield structure and its high power test.

We present overall process for developing terahertz (THz) corrugated structure and its beam-based measurement results. 0.2-THz corrugated structures were fabricated by die stamping method as the first step demonstration towards GW THz radiation source and GV/m THz wakefield accelerator. 150-[Formula: see text]m thick disks were produced from an OFHC (C10100) foil by stamping. Two types of disks were stacked alternately to form 46 mm structure with [Formula: see text] 170 corrugations. Custom assembly was designed to provide diffusion bonding with a high precision alignment of disks. The compliance of the fabricated structure have been verified through beam-based wakefield measurement at Argonne Wakefield Accelerator Facility. Both measured longitudinal and transverse wakefield showed good agreement with simulated wakefields. Measured peak gradients, 9.4 MV/m/nC for a long single bunch and 35.4 MV/m/nC for a four bunch trains, showed good agreement with the simulation.

'... You feel like the one that got left behind': a narrative inquiry into the friendships of people who have endured mental health difficulties.

AIMS: To explore insights between friendship and mental health through a critical narrative inquiry. To conceptualise friendship and inform public health approaches to loneliness and mental health. METHOD: Seventeen interviews were conducted with middle-age people who had experienced mental health difficulties. Stories were subjected to a narrative analysis and interrogated further using critical theory. RESULTS: Compassion in friendship reduces alterity and loneliness, and results in mutual discovery of dignity in relation to distress and stage of life. This is not achievable in all friendship. CONCLUSION: The temporary encounter of friendship can provide new bases for authentically relating. Through dignity and authenticity, friendship can contribute to mental health and reduce loneliness. Suggestions are made to inform public health approaches to friendship.

A core outcome set for pre-eclampsia research: an international consensus development study.

OBJECTIVE: To develop a core outcome set for pre-eclampsia. DESIGN: Consensus development study. SETTING: International. POPULATION: Two hundred and eight-one healthcare professionals, 41 researchers and 110 patients, representing 56 countries, participated. METHODS: Modified Delphi method and Modified Nominal Group Technique. RESULTS: A long-list of 116 potential core outcomes was developed by combining the outcomes reported in 79 pre-eclampsia trials with those derived from thematic analysis of 30 in-depth interviews of women with lived experience of pre-eclampsia. Forty-seven consensus outcomes were identified from the Delphi process following which 14 maternal and eight offspring core outcomes were agreed at the consensus development meeting. Maternal core outcomes: death, eclampsia, stroke, cortical blindness, retinal detachment, pulmonary oedema, acute kidney injury, liver haematoma or rupture, abruption, postpartum haemorrhage, raised liver enzymes, low platelets, admission to intensive care required, and intubation and ventilation. Offspring core outcomes: stillbirth, gestational age at delivery, birthweight, small-for-gestational-age, neonatal mortality, seizures, admission to neonatal unit required and respiratory support. CONCLUSIONS: The core outcome set for pre-eclampsia should underpin future randomised trials and systematic reviews. Such implementation should ensure that future research holds the necessary reach and relevance to inform clinical practice, enhance women's care and improve the outcomes of pregnant women and their babies. TWEETABLE ABSTRACT: 281 healthcare professionals, 41 researchers and 110 women have developed #preeclampsia core outcomes @HOPEoutcomes @jamesmnduffy. [Correction added on 29 June 2020, after first online publication: the order has been corrected.].

Single Shot Characterization of High Transformer Ratio Wakefields in Nonlinear Plasma Acceleration.

Plasma wakefields can enable very high accelerating gradients for frontier high energy particle accelerators, in excess of 10 GeV/m. To overcome limits on single stage acceleration, specially shaped drive beams can be used in both linear and nonlinear plasma wakefield accelerators (PWFA), to increase the transformer ratio, implying that the drive beam deceleration is minimized relative to acceleration obtained in the wake. In this Letter, we report the results of a nonlinear PWFA, high transformer ratio experiment using high-charge, longitudinally asymmetric drive beams in a plasma cell. An emittance exchange process is used to generate variable drive current profiles, in conjunction with a long (multiple plasma wavelength) witness beam. The witness beam is energy modulated by the wakefield, yielding a response that contains detailed spectral information in a single-shot measurement. Using these methods, we generate a variety of beam profiles and characterize the wakefields, directly observing transformer ratios up to R=7.8. Furthermore, a spectrally based reconstruction technique, validated by 3D particle-in-cell simulations, is introduced to obtain the drive beam current profile from the decelerating wake data.

Observation of High Transformer Ratio of Shaped Bunch Generated by an Emittance-Exchange Beam Line.

Collinear wakefield acceleration has been long established as a method capable of generating ultrahigh acceleration gradients. Because of the success on this front, recently, more efforts have shifted towards developing methods to raise the transformer ratio (TR). This figure of merit is defined as the ratio of the peak acceleration field behind the drive bunch to the peak deceleration field inside the drive bunch. TR is always less than 2 for temporally symmetric drive bunch distributions and therefore recent efforts have focused on generating asymmetric distributions to overcome this limitation. In this Letter, we report on using the emittance-exchange method to generate a shaped drive bunch to experimentally demonstrate a TR≈5 in a dielectric wakefield accelerator.

Precision Control of the Electron Longitudinal Bunch Shape Using an Emittance-Exchange Beam Line.

We report on the experimental generation of relativistic electron bunches with a tunable longitudinal bunch shape. A longitudinal bunch-shaping (LBS) beam line, consisting of a transverse mask followed by a transverse-to-longitudinal emittance exchange (EEX) beam line, is used to tailor the longitudinal bunch shape (or current profile) of the electron bunch. The mask shapes the bunch's horizontal profile, and the EEX beam line converts it to a corresponding longitudinal profile. The Argonne wakefield accelerator rf photoinjector delivers electron bunches into a LBS beam line to generate a variety of longitudinal bunch shapes. The quality of the longitudinal bunch shape is limited by various perturbations in the exchange process. We develop a simple method, based on the incident slope of the bunch, to significantly suppress the perturbations.

The validity of commonly used adipose tissue body composition equations relative to dual energy X-ray absorptiometry (DXA) in gaelic games players.

Dual-energy X-ray absorptiometry (DXA) and adipose tissue percentage estimates (AT%) derived from regression based skinfold equations were compared. 35 Gaelic games players [20.9 ± 1.7 years; 78.1 ± 8.6 kg; 179.5 ± 5.7 cm] underwent whole body fan beam DXA scans following a standardised protocol and assessment of skinfold thickness at 8 sites. Adipose tissue% from the sum of skinfolds and/or via body density were calculated for general and athlete specific equations (SKf-AT %). The relationship, i. e., proportional bias, fixed bias and random error (SEE) between DXA-AT % and AT % derived from the 6 skinfold equations were determined using least squares regression analysis. Skinfold AT% estimates were underestimated relative to DXA-AT % across all skinfold equations except that of Durnin and Wormersley [9] (D&W-∑(4AT %)) (16.7 ± 3.4 vs. 16.6 ± 4.0 %). All equations demonstrated 95 % prediction intervals ranges exceeding ~10 %. Each equation failed to predict AT% relative to DXA within an accepted ± 3.5 % anthropometric error rate. It is recommended that the conversion of absolute skinfold thickness to an AT % is avoided and that the skinfold equations assessed herein are not utilised in Gaelic games players. Alternate 'sum of skinfold' approaches should be considered.

A 4 K cryogenic probe for use in magnetic resonance force microscopy experiments.

The detailed design of a mechanically detected nuclear magnetic resonance probe using the SPAM (Springiness Preservation by Aligning Magnetization) geometry, operating at 4 K, in vacuum, and a several-Tesla magnetic field is described. The probe head is vibration-isolated well enough from the environment by a three-spring suspension system that the cantilever achieves thermal equilibrium with the environment without the aid of eddy current damping. The probe uses an ultra-soft Si cantilever with a Ni sphere attached to its tip, and magnetic resonance is registered as a change in the resonant frequency of the driven cantilever. The RF system uses frequency sweeps for adiabatic rapid passage using a 500 µm diameter RF coil wound around a sapphire rod. The RF coil and optical fiber of the interferometer used to sense the cantilever's position are both located with respect to the cantilever using a Garbini micropositioner, and the sample stage is mounted on an Attocube nanopositioner.

NMR spectroscopy with force-gradient detection on a GaAs epitaxial layer.

We demonstrate nuclear magnetic resonance spectroscopy on 35 µm(3) of (69)Ga in a GaAs epitaxial layer in vacuum at 5K, and 5T yielding a linewidth on the order of 10 kHz. This was achieved by a force-gradient magnetic resonance detection scheme, using the interaction between the force-gradient of a Ni sphere-tipped single crystal Si cantilever and the nuclear spins to register changes in the spin state as a change in the driven cantilever's natural resonant frequency. The dichotomy between the background magnetic field (B0) homogeneity requirements imposed by NMR spectroscopy and the magnetic particle's large magnetic field gradient is resolved via sample shuttling during the NMR pulse encoding. A GaAs sample is polarized in a B0 of 5T for 3 T1. The sample is shuttled away from the magnetic particle to a region of negligible magnetic field inhomogeneity. A (π/2)x pulse rotates the polarization to the xy-plane, the magnetization is allowed to precess for 2-200 µs before a (π/2)x or (π/2)y pulse stores the remaining spin along the z-axis that represents a single point of the free induction decay (FID). The sample is shuttled back to the established tip-sample distance. An adiabatic rapid passage (ARP) sweep inverts the spins in a volume of interest, causing the cantilever's natural resonance frequency to shift an amount proportional to the spin polarization in the volume. By varying the delay between the first and second (π/2) pulses the entire FID is measured.

Effect of fat and CHO meals on intermittent exercise in soccer players.

Pre-exercise meals containing carbohydrates (CHO) are recommended to athletes, although there is evidence to suggest that a high fat meal prior to exercise increases utilisation of fats yet may not adversely affect performance. This study investigated the effect of a high fat and high CHO pre-exercise meal prior to high intensity intermittent exercise. Ten male recreational soccer players performed a soccer specific protocol followed by a 1 km time trial 3 ½ h after ingesting one of 2 test meals, high fat meal (HFM) or a high CHO meal (HCM). Blood glucose, fatty acids (FA), glycerol, ß-hydroxybutyrate, lactate and insulin were assessed prior to the meal, pre-exercise, half-time, and post-exercise, whilst rates of CHO and fat oxidation were determined at 4 time points during the exercise as well as heart rate (HR) and rating of perceived exertion (RPE). Significant increases in FA, glycerol, ß-hydroxybutyrate and fat oxidation after the HFM were observed, while CHO oxidation was significantly higher following the HCM (P<0.05). No performance effect was found for the 1 km time trial (HFM: 228.6+14.4 s; HCM: 229.4+26.5 s) (mean+SD). These findings suggest that the type of meal ingested prior to soccer simulated exercise has an impact on metabolism, but not on the subsequent performance as determined in the present study.

Effects of GI meals on intermittent exercise.

Pre-exercise meals or single foods containing low glycaemic index (LGI) carbohydrates (CHO) have been shown to enhance performance prior to prolonged steady state exercise compared to high glycaemic index (HGI) CHO. This study investigated the impact of HGI and LGI pre-exercise meals on intermittent high intensity exercise. Nine male recreational football players performed a football specific protocol followed by a 1 km time trial 3.5 h after ingesting 1 of 2 isoenergetic test meals (HGI: 870.3 kcal, LGI: 889.5 kcal), which were either HGI (GI: 80) or LGI (GI: 44). Blood glucose, fatty acids (FA), glycerol, ß-hydroxybutyrate, lactate and insulin were assessed before, during, and after the exercise bout, whilst rates of CHO and fat oxidation were determined at 4 time points during the protocol. No significant differences were found for the 1 km time trial (LGI: 210.2 ± 19.1 s: HGI: 215.8 ± 22.6 s) (mean ± SD), nor for any of the other variables measured (P>0.05) apart from a significant condition effect with FA and significant interaction effects observed for glucose, ß-hydroxybutyrate and lactate (P<0.05). These findings suggest that the type of CHO ingested in a pre-match meal has no significant impact on performance or metabolic responses during 90 min of intermittent high intensity exercise.

Single-shot nuclear magnetization recovery curves with force-gradient detection.

We measure the spin-lattice relaxation time as a function of sample temperature in GaAs in a real-time single-shot inversion recovery experiment using spin force gradients acting on a magnetic tipped cantilever. After inverting 69Ga spins localized near the magnet with a single 20 ms adiabatic rapid passage sweep, the spins' magnetization recovery was passively tracked by recording the cantilever's frequency change, which is proportional to the longitudinal component of the spins' magnetization. The cantilever's frequency was recorded for a time 3*T1 for sample temperatures ranging from 4.8 to 25 K. The temperature dependence was observed for the 69Ga quadrupolar relaxation interaction.

Effects of carbohydrate beverage ingestion on the salivary IgA response to intermittent exercise in the heat.

The purpose of this study was to establish if provision of CHO altered the mucosal immune and salivary cortisol responses to intermittent exercise in the heat. In a double-blind design, 10 males undertook soccer-specific intermittent exercise on a motorized treadmill on 2 occasions, each over 90 min and separated by 1 week. During CHO and placebo trials, subjects were given either a carbohydrate solution (3 ml · kg (-1) body weight) or placebo drink, 5 min before the commencement of exercise, at 15, 30 min, at half time, 60 and 75 min into exercise. Salivary flow rate increased throughout the placebo trial and decreased throughout the CHO treatment; the difference between conditions neared statistical significance (P=0.055). Neither s-IgA concentration nor s-IgA to osmolality ratio was affected by 2 conditions or differed at any time-point post-exercise (P>0.05). The s-IgA secretion rate increased, s-IgA to protein ratio decreased post-exercise and salivary cortisol decreased 24 h post-exercise (P<0.05) compared to pre-exercise. Carbohydrate supplementation whilst exercising in the heat, does not influence rating of perceived exertion, thermal sensation, salivary flow rate, s-IgA concentration, s-IgA secretion rate, s-IgA to osmolality ratio or s-IgA to protein ratio and salivary cortisol but heart rate was increased.

Prophylactic colectomy for hyperplastic polyposis.

BACKGROUND: Hyperplastic polyposis (HP) is important to recognise as it increases the risk of adenomata which may develop dysplastic change or frank adenocarcinoma. We present the case of a 58-year-old woman with HP. CASE: Following a diagnosis of HP in this patient, it was noted that the number of polyps were progressively increasing over time, becoming pancolic and extending into the rectum. Genetic testing for a familial polypotic syndrome was negative. Histological analysis demonstrated that the majority of polyps were hyperplastic, but there were also serrated and tubular adenomata with foci of low-grade dysplasia. Whilst there was no evidence of frank malignancy or high-grade dysplasia, following a risk-benefit discussion the patient underwent a laparoscopic total colectomy with an ileal pouch formation. CONCLUSION: This case highlights the complexity in the management of HP and that even in the absence of confirmed invasive disease, patients may elect to undergo prophylactic colonic resection.

The effect of a 9-week physical activity programme on bone and body composition of children aged 10-11 years: an exploratory trial.

A high-impact exercise and a lifestyle intervention were implemented over a 9-week period; changes in bone and body composition were compared to controls. Sixty-one children volunteered from three randomly selected schools. Each school was randomly assigned to either a structured exercise (STEX) intervention, a lifestyle intervention (PASS) or control (CONT). Bone mineral content (BMC) and density (BMD) of total body, femoral neck and lumbar spine were measured as well as fat and lean mass at baseline and post-intervention by dual-energy X-ray absorptiometry. The STEX intervention resulted in an additional mean increase in total body BMC of 63.3 g (p = 0.019) and an additional increase of 0.011 g . cm (-2) (p = 0.018) for BMD over increases observed by controls. Bone mineral increases observed for the PASS intervention were not significant compared to the control group (p > 0.05). Neither intervention produced significant increases in bone mineral at femoral neck or lumbar spine sites (p > 0.05) compared with the controls. No significant changes were found in fat mass index (p > 0.05), lean mass index (p > 0.05) or percent body fat (p = 0.09) in any groups. Structured impact exercise promoted significant and clinically relevant increases in bone measures, without significant changes to body composition. A larger, definitive randomised trial is needed to confirm the present results.

Effects of repeated bouts of soccer-specific intermittent exercise on salivary IgA.

Failure to recover fully between sessions has been suggested to cause immunodepression. Therefore, the cumulative effects of soccer-specific intermittent exercise undertaken on different days 48 h apart on salivary IgA, cortisol and total protein concentration were investigated. Nine male subjects completed two trials of soccer-specific intermittent exercise 48 h apart on a motorised treadmill. Timed unstimulated saliva samples were collected immediately before and after exercise, and 24 and 48 h post-exercise. Salivary IgA concentration (EX (1): 215 +/- 160 to 335 +/- 246 and EX (2): 144 +/- 93 to 271 +/- 185 mg . l (-1), p = 0.007), osmolality (p = 0.001) and total protein (p = 0.001) increased immediately following exercise in both trials and decreased 24 h afterwards, whereas saliva flow rate decreased significantly (p = 0.015) before returning to pre-exercise values 24 h postexercise. The IgA secretion rate, IgA to osmolality ratio, IgA to total protein, solute secretion rate, total protein secretion rate, and cortisol did not differ between the time-points. The results suggest that performing two bouts of moderate intensity soccer-specific intermittent exercise 48 h apart does not suppress resting salivary IgA concentration significantly although a small progressive reduction in salivary IgA was observed. These findings may not extend to successive competitive soccer games when vulnerable players might experience clinically relevant reductions in s-IgA.

Salivary IgA response to intermittent and continuous exercise.

Current evidence would support a view that intense exercise increases whereas moderate exercise reduces the susceptibility to illness, predominately upper respiratory tract infections. Concentrations of IgA and cortisol in saliva may be used to reflect changes in immune function. The aim of this study was to determine if the type of exercise (soccer-specific intermittent or continuous exercise at the same average work-rate and duration) affects salivary IgA (s-IgA) and cortisol responses. In a randomized, counterbalanced design, eight healthy males completed two trials one week apart at the same time of day on a motorized treadmill. One session entailed soccer-specific intermittent exercise, the other involved continuous exercise at the same overall work-rate. Diet and activity were standardized for 48 hours prior to and following each trial. Unstimulated saliva samples were collected via passive expectoration during the week prior to commencement of exercise, before, at half-time, immediately post-exercise, and 6 hours, 24 hours, and 48 hours post-exercise. No significant difference was observed in heart rate between the two exercise conditions (Intermittent: 142 +/- 14; Continuous: 141 +/- 16 beats x min (-1)). Average rating of perceived exertion was higher (p < 0.05) in intermittent exercise (11.9 +/- 0.8) than during continuous exercise (10.8 +/- 1.2). The pattern of change in salivary responses, including solute secretion rate, IgA concentration, IgA secretion rate, IgA to osmolality ratio, cortisol, and cortisol secretion rate did not differ between the two trials (p > 0.05). Concentrations of s-IgA for the intermittent and continuous protocols were 131.6 +/- 61.2 vs. 146.4 +/- 107.6 before, 148.4 +/- 82.5 vs. 229.2 +/- 159.6 after, and 125 +/- 78.7 vs. 131.1 +/- 80.7 48 h post-exercise, respectively. Saliva flow rate decreased and osmolality increased significantly across all time points (p < 0.05). In conclusion, soccer-specific intermittent exercise did not suppress the salivary IgA response or alter cortisol secretion compared to continuous exercise performed at the same overall work-rate.