High-efficiency acceleration of an electron beam in a plasma wakefield accelerator.

High-efficiency acceleration of charged particle beams at high gradients of energy gain per unit length is necessary to achieve an affordable and compact high-energy collider. The plasma wakefield accelerator is one concept being developed for this purpose. In plasma wakefield acceleration, a charge-density wake with high accelerating fields is driven by the passage of an ultra-relativistic bunch of charged particles (the drive bunch) through a plasma. If a second bunch of relativistic electrons (the trailing bunch) with sufficient charge follows in the wake of the drive bunch at an appropriate distance, it can be efficiently accelerated to high energy. Previous experiments using just a single 42-gigaelectronvolt drive bunch have accelerated electrons with a continuous energy spectrum and a maximum energy of up to 85 gigaelectronvolts from the tail of the same bunch in less than a metre of plasma. However, the total charge of these accelerated electrons was insufficient to extract a substantial amount of energy from the wake. Here we report high-efficiency acceleration of a discrete trailing bunch of electrons that contains sufficient charge to extract a substantial amount of energy from the high-gradient, nonlinear plasma wakefield accelerator. Specifically, we show the acceleration of about 74 picocoulombs of charge contained in the core of the trailing bunch in an accelerating gradient of about 4.4 gigavolts per metre. These core particles gain about 1.6 gigaelectronvolts of energy per particle, with a final energy spread as low as 0.7 per cent (2.0 per cent on average), and an energy-transfer efficiency from the wake to the bunch that can exceed 30 per cent (17.7 per cent on average). This acceleration of a distinct bunch of electrons containing a substantial charge and having a small energy spread with both a high accelerating gradient and a high energy-transfer efficiency represents a milestone in the development of plasma wakefield acceleration into a compact and affordable accelerator technology.

Demonstration of electron acceleration in a laser-driven dielectric microstructure.

The enormous size and cost of current state-of-the-art accelerators based on conventional radio-frequency technology has spawned great interest in the development of new acceleration concepts that are more compact and economical. Micro-fabricated dielectric laser accelerators (DLAs) are an attractive approach, because such dielectric microstructures can support accelerating fields one to two orders of magnitude higher than can radio-frequency cavity-based accelerators. DLAs use commercial lasers as a power source, which are smaller and less expensive than the radio-frequency klystrons that power today's accelerators. In addition, DLAs are fabricated via low-cost, lithographic techniques that can be used for mass production. However, despite several DLA structures having been proposed recently, no successful demonstration of acceleration in these structures has so far been shown. Here we report high-gradient (beyond 250 MeV m(-1)) acceleration of electrons in a DLA. Relativistic (60-MeV) electrons are energy-modulated over 563 ± 104 optical periods of a fused silica grating structure, powered by a 800-nm-wavelength mode-locked Ti:sapphire laser. The observed results are in agreement with analytical models and electrodynamic simulations. By comparison, conventional modern linear accelerators operate at gradients of 10-30 MeV m(-1), and the first linear radio-frequency cavity accelerator was ten radio-frequency periods (one metre) long with a gradient of approximately 1.6 MeV m(-1) (ref. 5). Our results set the stage for the development of future multi-staged DLA devices composed of integrated on-chip systems. This would enable compact table-top accelerators on the MeV-GeV (10(6)-10(9) eV) scale for security scanners and medical therapy, university-scale X-ray light sources for biological and materials research, and portable medical imaging devices, and would substantially reduce the size and cost of a future collider on the multi-TeV (10(12) eV) scale.

Enhanced energy gain in a dielectric laser accelerator using a tilted pulse front laser.

Using an 800 nm, 45 fs pulse-front-tilted laser we demonstrate a record 315 keV energy gain in a dual grating dielectric laser accelerator (DLA) and average accelerating gradients of 560 MV/m over 0.5 mm. These results open a new regime in DLA characterized by significant evolution of the beam distribution in the longitudinal phase space, corresponding to > 1/4 of a synchrotron oscillation. By tilting the laser wavefront we control the resonant velocity of the DLA and observe a net energy gain, indicating that a tapered optical phase could be used to achieve very high energy gain.

Beam loading by distributed injection of electrons in a plasma wakefield accelerator.

We show through experiments and supporting simulations that propagation of a highly relativistic and dense electron bunch through a plasma can lead to distributed injection of electrons, which depletes the accelerating field, i.e., beam loads the wake. The source of the injected electrons is ionization of the second electron of rubidium (Rb II) within the wake. This injection of excess charge is large enough to severely beam load the wake, and thereby reduce the transformer ratio T. The reduction of the average T with increasing beam loading is quantified for the first time by measuring the ratio of peak energy gain and loss of electrons while changing the beam emittance. Simulations show that beam loading by Rb II electrons contributes to the reduction of the peak accelerating field from its weakly loaded value of 43 GV/m to a strongly loaded value of 26 GV/m.

High energy electron diffraction instrument with tunable camera length.

Ultrafast electron diffraction (UED) stands as a powerful technique for real-time observation of structural dynamics at the atomic level. In recent years, the use of MeV electrons from radio frequency guns has been widely adopted to take advantage of the relativistic suppression of the space charge effects that otherwise limit the temporal resolution of the technique. Nevertheless, there is not a clear choice for the optimal energy for a UED instrument. Scaling to beam energies higher than a few MeV does pose significant technical challenges, mainly related to the inherent increase in diffraction camera length associated with the smaller Bragg angles. In this study, we report a solution by using a compact post-sample magnetic optical system to magnify the diffraction pattern from a crystal Au sample illuminated by an 8.2 MeV electron beam. Our method employs, as one of the lenses of the optical system, a triplet of compact, high field gradients (>500 T/m), small-gap (3.5 mm) Halbach permanent magnet quadrupoles. Shifting the relative position of the quadrupoles, we demonstrate tuning the magnification by more than a factor of two, a 6× improvement in camera length, and reciprocal space resolution better than 0.1 Å-1 in agreement with beam transport simulations.

Revision parathyroid surgery - challenges and considerations in comparison to primary surgery.

OBJECTIVE: Revision parathyroidectomy is made necessary by recurrent or persistent parathyroid disease. This study aimed to identify challenges in revision surgery compared to primary parathyroid surgery. METHODS: All revision parathyroidectomies performed by one surgeon over a 17-year period were assessed for demographics, imaging, histology, biochemistry, cure rate, gland weight, gland location and gland ectopia, and compared to a series of 100 primary parathyroidectomies. RESULTS: Twenty-eight revision surgical procedures were identified. Sestamibi scanning for gland localisation was superior to ultrasound in both primary and revision surgery. Pre-operative calcium and gland weight were significantly higher in revision cases. There were no significant differences in post-operative calcium levels, pre- or post-operative parathyroid hormone levels, or gland location. 36 per cent of glands excised in revision surgery were ectopic, compared to 25 per cent in primary procedures. The cure rate was significantly lower in revision surgery. CONCLUSION: Revision parathyroidectomy patients present with higher pre-operative calcium and larger adenomas; the cure rate is significantly lower in these patients.

Patient outcomes following thyroid surgery for thyrotoxicosis.

OBJECTIVE: Total thyroidectomy can be used as a definitive treatment modality for thyrotoxicosis. This study assessed the outcomes of patients treated with surgery at a single secondary care site. METHOD: A retrospective cohort study was conducted analysing consecutive patients who underwent thyroid surgery for thyrotoxicosis between 24 November 2000 and 26 April 2019 (n = 595). RESULTS: Total thyroidectomy was performed in 95.4 per cent of patients. Two-thirds of patients had Graves' disease histology. Of patients, 22.8 per cent became transiently hypothyroid whilst on levothyroxine (thyroid hormone replacement therapy). Transient and persistent hypocalcaemia was present in 23.3 per cent and 2.8 per cent of patients respectively. Recurrent laryngeal nerve palsy was transient and persistent in 3.6 per cent and 0.3 per cent respectively. Of patients, 2.5 per cent developed post-operative haematomas that required surgical evacuation in the operating theatre. CONCLUSION: The overall complication rate for thyroid surgery is higher in thyrotoxic than in euthyroid patients. Compared to other treatment modalities, total thyroidectomy appears to be the most effective, definitive means of managing Graves' disease.

The effect of parathyroidectomy on neuropsychological symptoms and biochemical parameters in patients with asymptomatic primary hyperparathyroidism.

BACKGROUND: With increased biochemical screening, primary hyperparathyroidism (pHPT) is often discovered incidentally whilst patients are asymptomatic. OBJECTIVE: To assess the impact of parathyroidectomy on neuropsychological symptoms and biochemical parameters in people with asymptomatic pHPT, whilst controlling for the surgical procedure. PATIENTS/DESIGN/MEASUREMENTS: Twenty-four patients with asymptomatic pHPT requiring parathyroidectomy, in accordance with National Institutes for Health recommendations, were recruited prospectively. A control group of 23 subjects was recruited simultaneously from consecutive patients undergoing diagnostic hemithyroidectomy (HT) for benign thyroid nodules. Operations were performed by a single surgeon. Biochemical investigations and neuropsychological symptoms were measured preoperatively and 3 months after surgery. Neuropsychological symptoms were measured using the Hospital Anxiety (HAD-A) and Depression (HAD-D) scales and the Mood Rating Scale (MRS). RESULTS: Postoperatively, calcium and parathyroid hormone normalized in all patients in the pHPT group. Patients with pHPT showed a significant improvement in neuropsychological symptoms with a pre- and postoperative mean change of 2·45 ± 2·57 (P < 0·05) on HAD-A, 2·79 ± 3·85 (P < 0·05) on HAD-D, and 3·2 ± 4·57 (P < 0·05) on MRS, parameters that were unaltered in the HT group. The differences between the two groups remained statistically significant after adjustment for age and sex for HAD-D (mean change 2·8, 95% CI = 0·3, 5·3, P = 0·025) and MRS (mean difference 3·5, 95% CI = 0·4, 6·7, P = 0·027) but not for HAD-A (mean difference 1·5, 95% CI = -0·8, 3·8, P = 0·20). For all three mental health scores, there were no significant associations with either age or sex. CONCLUSIONS: Asymptomatic pHPT is associated with neuropsychological symptoms that improve after parathyroidectomy.

Intussusception as a presenting feature of Burkitt lymphoma: implications for management and outcome.

PURPOSE: Intussusception is a recognised but unusual presenting feature of Burkitt lymphoma. We sought to identify the clinical features associated with intussusception in this setting, and assess the outcome following protocol directed chemotherapy. METHODS: A retrospective case note review was performed on patients treated for Burkitt lymphoma at our institution between 1976 and 2010. Cases presenting with intussusception were identified from hospital records and oncology database. RESULTS: Fourteen of the 210 children seen with a diagnosis of Burkitt lymphoma during the study period (6.7%) developed intussusception. Median age was 6.1 years (range 2.5-10.9). Twelve patients presented with recurrent abdominal pain, and two patients with a jaw mass associated with endemic Burkitt lymphoma. Nine patients underwent a right hemicolectomy with ileo-colic anastomosis, and five had segmental small-bowel resections. Three patients had bone marrow involvement at diagnosis, two of whom died. All patients received chemotherapy. Median follow-up was 6.07 years (range 0.1-28.8). CONCLUSIONS: Small bowel lymphoma should be considered in children presenting with intussusception above the normal infantile peak age range. The presentation is often insidious, and complete obstruction may not be apparent. However, when surgically resected, the majority can achieve a good outcome with additional chemotherapy.

The utility of intraoperative PTH measurement in surgical parathyroidectomy after renal transplantation.

AIMS: Intraoperative PTH (ioPTH) monitoring is used widely to guide surgery in primary hyperparathyroidism, but its reliability in renal transplant recipients is largely unknown. The aim of this study was to examine the utility of ioPTH monitoring in predicting long-term effectiveness of parathyroid tissue excision in renal transplant recipients, and to investigate the effect of parathyroidectomy on transplant function. METHODS: Renal transplant recipients undergoing primary parathyroidectomy for persistent hyperparathyroidism were included. Intact PTH levels were measured at induction of anesthesia (PTH0), intra-operatively following removal of parathyroid tissue (PTH1) and 15 minutes after resection (PTH2). Serum PTH, calcium, phosphate and creatinine levels were measured up to 12 months postoperatively. RESULTS: 14 patients (9 male, mean age 55 ± 3 y) were included. PTH levels fell significantly from baseline (PTH0 237.4 ± 43.5 pg/ml) at both time points (PTH1 108.4 ± 38.3 pg/ml; PTH2 62.4 ± 31.3 pg/ml; p = 0.001). Three patients had a raised PTH level at 12 months post procedure. Analysis of these cases showed no difference in the fall of ioPTH, compared to patients in which the PTH level remained controlled. There was no significant change in renal function from baseline to 1 year post parathyroidectomy. CONCLUSION: Intra-operative and early postoperative measures of PTH may not be a reliable indicator of satisfactory parathyroid tissue excision in renal transplant recipients. Parathyroidectomy does not appear to be detrimental to long-term transplant function.

Percutaneous endoscopic, radiological and surgical gastrostomy tubes: a comparison study in head and neck cancer patients.

A gastrostomy feeding tube has become the most acceptable method for long-term feeding support in patients with head and neck cancer. The aim of this study was to compare the complications of percutaneous endoscopically inserted gastrostomy (PEG) tubes, radiologically inserted gastrostomy (RIG) tubes and surgically inserted gastrostomy (open/laparoscopic) (SUR) tubes in head and neck cancer patients and also to compare the mortality rates of these patients. Seventy-eight head and neck cancer patients underwent gastrostomy tube insertion (40 PEG, 28 RIG and 10 SUR) during the period February 2002 to February 2005. There were no significant demographic differences between the three groups. Thirty-six patients (46 per cent) developed complications, 32 minor and four major. All three groups were similar in their rate of minor complications, with the dislodgement and blockage rate being lowest in the PEG group (p > 0.05). The mortality rate was 4 per cent within 30 days of gastrostomy tube insertion. There were no deaths in the PEG group, two deaths in the RIG group and one in the SUR group. The PEG tube was considered superior to the RIG and SUR gastrostomy tubes, had fewer complications and was safer. Thus, PEG tube insertion is our first choice for head and neck cancer patients.

Is pharyngeal pouch stapling superior to open pharyngeal pouch repair? An analysis of a single institution's series.

BACKGROUND: Endoscopic stapling has become the primary procedure for pharyngeal pouch surgery because it is quick, less invasive and safe, but less is known about long-term outcomes. METHOD: Medical records were reviewed to compare rates of morbidity, operative failure, symptom control and revision surgery between open and closed procedures. RESULTS: A total of 120 pharyngeal pouch procedures, carried out on 97 patients from 2000 to 2014, were studied. These included 80 endoscopic stapling and 40 open procedures. Twelve patients had complications (15 per cent) and there was one mortality (1.2 per cent) in the endoscopic stapling group. Ten patients (25 per cent) developed complications in the open procedure group, with no mortalities. Symptom recurrence was significantly greater in the endoscopic stapling group (26 per cent) than in the open procedure group (7.5 per cent). Multiple surgical procedures were required for 22 endoscopically stapled patients (32 per cent); none were required in the open procedure group. Although the male-to-female ratio for pharyngeal pouch incidence was 2:1, the ratio for multiple surgical procedures was 10:1. CONCLUSION: Endoscopic stapling outcomes are not as good as those following an open approach on long-term follow up, and the early advantages are eliminated if pouch excision is avoided.

Thyroidectomy does not cause globus pattern symptoms.

Post-thyroidectomy patients often complain of globus pharyngeus type symptoms. One of the organic pathologies recognized as causing globus pattern symptoms is goitre. We conducted a prospective questionnaire-based study in the thyroid clinic at Hull Royal Infirmary to examine the relationship between goitre, thyroidectomy and globus pattern symptoms by using the Glasgow-Edinburgh Throat Scale. A questionnaire-based study in which 41 consecutive patients due to undergo thyroidectomy prospectively completed the questionnaire pre-operatively and 12 months post-operatively. A subset of 25 randomly selected patients also completed the questionnaire three months post-operatively. Globus symptoms were not worsened by thyroidectomy at three or 12 months. Indeed two of the questioned parameters were significantly improved at three months, and six at one year (p < 0.023). In conclusion, thyroidectomy does not exacerbate globus pharyngeus symptoms. Indeed, in the absence of other clinical causes, when a patient has a World Health Organization (WHO) 2 goitre or greater, thyroidectomy may improve them.

Parathyroid ectopia: development of a surgical algorithm based on operative findings.

OBJECTIVES: To study the incidence of ectopic parathyroid adenomata from a single surgical series, and to devise a surgical algorithm from the results to follow when an adenoma cannot initially be located. METHODS: A retrospective review was conducted of prospectively collected data. The study comprised all patients who underwent parathyroidectomy between June 2001 and February 2008 under the care of the senior author. A systematic surgical protocol was developed for locating ectopic superior and inferior parathyroid adenomata based on the order of incidence identified from the database. RESULTS: Parathyroid ectopia occurs in approximately 10 per cent of hyperparathyroidism cases. It is more common in superior than inferior parathyroid glands. The most common superior location is the right retroesophageal position and the most common inferior location is within the left thymic remnant. CONCLUSION: Prospective data collection and subsequent analysis can be used to develop a systematic surgical protocol to aid the localisation of ectopic enlarged parathyroid glands in the surgical management of hyperparathyroidism.

Conservative neck surgery in squamous cell carcinoma.

Squamous cell carcinoma of the upper aerodigestive tract metastasises to lymph nodes in the upper-deep cervical group. Control of these metastases is the single most important prognostic factor in the management of this disease. Traditionally, surgical control was achieved by the radical neck dissection, a mutilating procedure with significant morbidity. Contemporary research has led to an improved understanding of the patterns of nodal metastases. This has led to the evolution of more conservative techniques that still produce comparable results of control. This paper describes this evolutionary process, and the current management thinking.

Plasma electron fluid motion and wave breaking near a density transition.

Recently, Suk, Barov, and Rosenzweig [Phys. Rev. Lett. 86, 1011 (2001)] proposed a scheme for trapping background electrons in a plasma wake field using a sudden downward transition in the background ion density, where the density transition length is small compared to the plasma skin depth. In the present paper we present a fluid dynamical description of this mechanism that is self-consistent up to the point of wave breaking. A one-dimensional nonlinear relativistic second-order differential equation is derived for the electron fluid velocity in Lagrangian coordinates. Numerical integrations of this equation are used to map out the regions of parameter space in which wave breaking occurs and to determine the extent of the downstream region of plasma involved in wave breaking. Comparisons with one-dimensional particle-in-cell (PIC) simulations show that the onset of trapping occurs at the parameter values where wave breaking begins in the fluid analysis, but that the downstream extent of plasma involved in wave breaking is not a reliable predictor of the number of trapped particles. The PIC simulations also reveal that particles initially located on the upstream side of the density transition may become trapped, although these particles do not participate in wave breaking in the fluid description.

Nasal pH and saccharin clearance are unrelated in the physiologically normal nose.

A group of 56 asymptomatic non-smoking men was prospectively recruited to study the relationship between nasal mucosal pH and saccharin clearance rate. No significant relationship was found between the two variables (Pearson correlation coefficient = -.105, p = 0.44). This finding suggests that in vivo mucociliary flow rates are resistant to change within the pH range of the physiologically normal nose.

Primary hyperparathyroidism in pregnancy.

Primary hyperparathyroidism during pregnancy carries significant risks to both mother and fetus. Parathyroidectomy remains the only definitive treatment for the condition. The timing of surgery remains controversial, with ongoing debate regarding the safety of surgery during the third trimester. A case of symptomatic primary hyperparathyroidism treated by parathyroidectomy in the third trimester is described. The clinical features, investigations and treatment options are discussed.