Acceleration of electrons in the plasma wakefield of a proton bunch

High-energy particle accelerators have been crucial in providing a deeper understanding of fundamental particles and the forces that govern their interactions. To increase the energy of the particles or to reduce the size of the accelerator, new acceleration schemes need to be developed. Plasma wakefield acceleration^1–5, in which the electrons in a plasma are excited, leading to strong electric fields (so called ‘wakefields’), is one such promising acceleration technique. Experiments have shown that an intense laser pulse^6–9 or electron bunch^10,11 traversing a plasma can drive electric fields of tens of gigavolts per metre and above—well beyond those achieved in conventional radio-frequency accelerators (about 0.1 gigavolt per metre). However, the low stored energy of laser pulses and electron bunches means that multiple acceleration stages are needed to reach very high particle energies^5,12. The use of proton bunches is compelling because they have the potential to drive wakefields and to accelerate electrons to high energy in a single acceleration stage¹³. Long, thin proton bunches can be used because they undergo a process called self-modulation^14–16, a particle–plasma interaction that splits the bunch longitudinally into a series of high-density microbunches, which then act resonantly to create large wakefields. The Advanced Wakefield (AWAKE) experiment at CERN^17–19 uses high-intensity proton bunches—in which each proton has an energy of 400 gigaelectronvolts, resulting in a total bunch energy of 19 kilojoules—to drive a wakefield in a ten-metre-long plasma. Electron bunches are then injected into this wakefield. Here we present measurements of electrons accelerated up to two gigaelectronvolts at the AWAKE experiment, in a demonstration of proton-driven plasma wakefield acceleration. Measurements were conducted under various plasma conditions and the acceleration was found to be consistent and reliable. The potential for this scheme to produce very high-energy electron bunches in a single accelerating stage²⁰ means that our results are an important step towards the development of future high-energy particle accelerators^21,22.

Electron acceleration to very high energies is achieved in a single step by injecting electrons into a ‘wake’ of charge created in a 10-metre-long plasma by speeding long proton bunches.

Using risk of bias domains to identify opportunities for improvement in food- and nutrition-related research: An evaluation of research type and design, year of publication, and source of funding

PURPOSE

This retrospective cross-sectional study aimed to identify opportunities for improvement in food and nutrition research by examining risk of bias (ROB) domains.

METHODS

Ratings were extracted from critical appraisal records for 5675 studies used in systematic reviews conducted by three organizations. Variables were as follows: ROB domains defined by the Cochrane Collaboration (Selection, Performance, Detection, Attrition, and Reporting), publication year, research type (intervention or observation) and specific design, funder, and overall quality rating (positive, neutral, or negative). Appraisal instrument questions were mapped to ROB domains. The kappa statistic was used to determine consistency when multiple ROB ratings were available. Binary logistic regression and multinomial logistic regression were used to predict overall quality and ROB domains.

FINDINGS

Studies represented a wide variety of research topics (clinical nutrition, food safety, dietary patterns, and dietary supplements) among 15 different research designs with a balance of intervention (49%) and observation (51%) types, published between 1930 and 2015 (64% between 2000-2009). Duplicate ratings (10%) were consistent (κ = 0.86-0.94). Selection and Performance domain criteria were least likely to be met (57.9% to 60.1%). Selection, Detection, and Performance ROB ratings predicted neutral or negative quality compared to positive quality (p<0.001). Funder, year, and research design were significant predictors of ROB. Some sources of funding predicted increased ROB (p<0.001) for Selection (interventional: industry only and none/not reported; observational: other only and none/not reported) and Reporting (observational: university only and other only). Reduced ROB was predicted by combined and other-only funding for intervention research (p<0.005). Performance ROB domain ratings started significantly improving in 2000; others improved after 1990 (p<0.001). Research designs with higher ROB were nonrandomized intervention and time series designs compared to RCT and prospective cohort designs respectively (p<0.001).

CONCLUSIONS

Opportunities for improvement in food and nutrition research are in the Selection, Performance, and Detection ROB domains.

Phenotypic signatures and genetic determinants of oxacillin tolerance in a laboratory mutant of Staphylococcus aureus

Addition of β-lactam antibiotics to growing cultures of bacteria inhibit synthesis of the bacterial cell wall peptidoglycan accompanied by killing (loss of viable titer) and lysis (physical disintegration) of the cells. However, it has also been well established that these antibiotics are not effective in killing non-growing or slow-growing bacteria and the mechanism of this "antibiotic tolerance" is not well understood. In this study, we report on the genetic basis and phenotypic properties of an antibiotic tolerant derivative of the methicillin susceptible S. aureus strain 27s. Cultures were exposed to "pulses" of high concentrations of oxacillin followed by outgrowth of the surviving bacteria. This procedure quickly selected for antibiotic tolerant mutants with an increased ability to survive antibiotic treatment without increase in the MIC value for the antibiotic. Such mutants also exhibited longer lag phase, decreased lysis, virtually no change in antibiotic susceptibilities, cross tolerance to D-cycloserine and vancomycin, and increase in biofilm formation in the presence of high concentrations of oxacillin. Whole genome sequencing showed that these altered properties were linked to mutations in the atl and gdpP genes.

Abstract P2-03-10: Risk factors for upgrading and upstaging of pre-operative biopsies in ductal carcinoma in situ

Background: Ductal carcinoma in situ (DCIS), accounts for one fifth of all screen-detected neoplastic breast lesions. Contemporary research in DCIS focuses on separating lesions that need active treatment from those that can be safely left under surveillance. This, in turn, relies on accurate determination of invasive status and DCIS grade at time of initial biopsy. Most previous studies have examined factors associated with upstaging the diagnosis from DCIS to invasive breast cancer (IBC) following surgery, and few have evaluated factors associated with upgrading the diagnosis to a higher grade of DCIS. This is because upgrading has not traditionally influenced clinical management in the way that upstaging has done. However, recent interest in non-operative treatment for low-risk DCIS has meant that accurate determination of grade at time of initial biopsy has become more important. We aimed to compare risk factors for upgrading and upstaging of biopsies in DCIS.

Method: We undertook a cohort study of all women diagnosed with DCIS at a large specialist cancer centre between 2000–2014. Information from the clinical records was abstracted, including the pre-operative mammography (MMG) and pathology information from the initial biopsy. We also abstracted pathology information regarding the excised specimen in order to identify women whose diagnosis was subsequently upgraded or upstaged. We looked for factors that were predictive for upgrading or upstaging.

Result: A total of 641 women were diagnosed with DCIS at initial biopsy. Of these, 72 (11%) were upgraded: 26 (4%) from grade 1 to grade 2, 2 (0.3%) from grade 1 to grade 3 and 44 (7%) from grade 2 to grade 3. A further 115 (18%) were upstaged to IBC: 20 of these (3%) had grade 1 DCIS on initial biopsy, 47 (7%) had grade 2, 43 (7%) grade 3, and for 5 (1%) biopsy grade was not available. Necrosis on biopsy increased the risk of upgrading (with necrosis: 14% upgraded, without: 10% upgraded, p for difference 0.02) and also of upstaging (with necrosis: 23% upstaged, without: 15% upstaged, p for difference &lt;0.01). Lesions measuring ≥50 mm on MMG were more likely to be upgraded than smaller lesions (0-19 mm: 9% upgraded, 20-50 mm: 9% upgraded, ≥50 mm: 19% upgraded, p for heterogeneity &lt;0.01), while lesions measuring 20-50 mm and ≥50 mm were both more likely to be upstaged than lesions measuring 0-19 mm (0-19 mm: 9% upstaged, 20-50 mm: 23% upstaged and ≥50 mm: 21% upstaged, p for heterogeneity &lt;0.01). Fewer 9G vacuum-assisted biopsies than 14G core biopsies were upgraded (9G vacuum-assisted: 7% upgraded, 14G core: 15% upgraded, p for difference 0.01), while the effect of biopsy method on upstaging was not significant (9G vacuum-assisted: 12% upstaged, 14G core: 16% upstaged, p for difference 0.15). Presence of a palpable lump was not significantly associated with upgrading (palpable lump: 13% upgraded, no palpable lump: 10% upgraded, p for difference 0.19) but increased the risk of upstaging (palpable lump: 23% upstaged, no palpable lump: 16% upstaged, p for difference 0.02).

Conclusion: Our findings suggest that consideration of MMG lesion size and necrosis on biopsy may be helpful in selecting low-risk women for non-operative management of DCIS, as may use of the 9G vacuum-assisted method of biopsy.

Citation Format: Mannu GS, Groen E, Wang Z, Schaapveld M, Lips E, Chung M, Joore I, Leeuwen Fv, Teerstra J, Winter-Warnars GAO, Darby SC, Wesseling J. Risk factors for upgrading and upstaging of pre-operative biopsies in ductal carcinoma in situ [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-03-10.

Abstract P2-07-03: Systematic characterization of kinase inhibitors reveals heterogeneity in responses by class and cell line

Several publications have addressed concerns surrounding drug response screens by pointing out sources of variability and by presenting recommendations for better experimental methods and more robust analytical approaches. In the presented profiling effort, we integrated the latest advances in drug response measurement and focused on data diversity and quality rather than on breadth. We selected 32 breast cancer cell lines with a strong bias towards triple negative lines as well as 4 cell lines established from relevant patient-derived xenografts. We evaluated a panel of clinically relevant kinase inhibitors using a microscopy-based dose response assay to measure drug potency, and to quantify drug efficacy in terms of growth inhibition (GR metrics) and cell death. The use of the GR metrics to quantify drug sensitivity enabled us to identify and study differences between cytostatic and cytotoxic responses. This systematic dose response dataset is complemented by measurements of baseline transcript expression levels by mRNAseq, quantification of absolute abundance of ˜12,000 proteins, and relative phosphoprotein levels by shotgun mass spectrometry across all cell lines. Additionally, the baseline activity of transcription factors and kinases were inferred from the mRNA (using VIPER) and phosphoprotein (using kinase enrichment analysis) data, respectively. The complementarity of these multi-omics data has allowed us to address questions about the landscape of breast cancer cell lines such as: Where do the patient-derived lines lay relative to the conventional cell lines? How consistent are the landscapes defined by each dataset? How does integration across datasets provide mechanistic insight into signaling pathways that are active in each cancer subtypes? The measured and inferred baseline data were used to build predictors of the observed drug responses with the goal of identifying the biological processes responsible for the differences in sensitivity across drugs and cell lines. Overall the dataset that has been collected is a valuable resource for understanding drug response in triple negative breast cancer, and the molecular mechanisms that influence it.

Citation Format: Mills CE, Subramanian K, Hafner M, Chung M, Boswell SA, Everley RA, Juric D, Sorger PK. Systematic characterization of kinase inhibitors reveals heterogeneity in responses by class and cell line [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-07-03.

A Survey of Medical Social Services in Local Accident and Emergency Departments

This study is a structured questionnaire survey on all doctors and nurses working in 14 local Accident & Emergency Departments (EDs) on medical social services. The objectives of this study are to find out: (1) service provision and referral patterns in local EDs; (2) perceptions of doctors and nurses on the present service. In addition to routine referrals during office hours, nearly half of the respondents reported availability of on-site services per request, phone consults during office hours, and support during disaster activation. The most common social problems that doctors would refer to medical social service included child abuse, battered spouse, rape/sexual assault, deliberate self-harm and elderly patients with discharge problem. Over half of the doctors and nurses said the existing services were inadequate and the main shortcoming was no after office hours coverage. In cases of crisis intervention, 56% of doctors and 36% of nurses felt that medical social workers would only be helpful if they were available at short notice most time of the day. To improve the existing service, 62% of doctors and 43% of nurses thought that medical social workers should provide adequate feedback. Other areas for improvement included on-site service, 24-hour coverage and more experienced workers. (Hong Kong j.emerg.med. 2001;8:135–139)

Knowledge and Beliefs of Parents of Asthmatic Children Presenting to an Emergency Department

This is a survey on the knowledge and beliefs of 100 parents or guardians of asthmatic children presenting to the emergency department with an asthmatic attack and staying in the observation ward for treatment. The parents were asked to fill in a questionnaire on their knowledge and beliefs about asthma. Demographic data and data related to routine asthma care were also collected. The mean age of the children was 6.2± 3.2. The mean duration of asthma was 3.4 year (±2.6). In the preceding 6 months the mean attendance frequency at our accident and Energency department was 1.5±1.4. The majority of respondent (79%) agreed that asthma is caused by bronchoconstriction but only 42% understood that mucosal oedema is involved during an acute attack. Many people (82%) believed that asthma is just sensitive bronchus. Less than half (40%) believes asthma is a hereditary disease. It was a common belief that asthmatic attack can be precipitated by a change of weather (89%) and cold food/drink (77%). Over 75% agreed that carpet in the house is undesirable for an asthmatic child. The majority of parents (69%) disagreed that an asthmatic child should avoid physical exercise and only 13 would not allow the child to attend physical exercise class. Over half (54%) of the respondents believed that asthma could be cured. Only a minority (17%) believed that antibiotics are useful in shortening the attack. Thirty (30%) respondents also used alternative means of therapy for example crocodile meat. Parents' knowledge of preventive medication was inadequate. Understanding common beliefs among parents is beneficial in patient and parental education.

Perinatal outcomes and intrauterine complications following fetal intervention for congenital heart disease: systematic review and meta-analysis of observational studies

OBJECTIVE

To assess perinatal outcomes and intrauterine complications following fetal intervention for congenital heart disease (CHD).

METHODS

A systematic review and meta-analysis were performed following an electronic search of PubMed and Scopus databases (last searched August 2015). Perinatal outcomes that were assessed included fetal death, live birth, preterm delivery < 37 weeks' gestation and neonatal death. Intrauterine complications that were assessed included bradycardia requiring treatment and hemopericardium requiring drainage. Estimated proportions were reported as mean (95% CI). Inconsistency was assessed using the I² statistic.

RESULTS

An electronic search identified 2279 records, of which 29 studies (11 retrospective cohort and 18 case reports) were considered eligible for analysis. Fetal death after treatment of CHD by aortic valvuloplasty was reported in three studies, with a rate of 31% (95% CI, 9-60%), after pulmonary valvuloplasty in one study, with a rate of 25% (95% CI, 10-49%), after septoplasty in one study, with a rate of 14% (95% CI, 6-28%) and after pericardiocentesis and/or pericardioamniotic shunt placement in 24 studies, with a rate of 29% (95% CI, 18-41%). Bradycardia requiring treatment was reported after aortic valvuloplasty in two studies, with a rate of 52% (95% CI, 16-87%), after pulmonary valvuloplasty in one study, with a rate of 44% (95% CI, 23-67%), and after septoplasty in one study, with a rate of 27% (95% CI, 15-43%).

CONCLUSIONS

Current evidence on the effectiveness of prenatal intervention for CHD derives mostly from case reports and a few larger series; no study was randomized. Although the results of the meta-analysis are encouraging in terms of perinatal survival, they should be interpreted with caution when comparing with procedures performed after delivery. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Heterogeneous oxacillin-resistant phenotypes and production of PBP2A by oxacillin-susceptible/mecA-positive MRSA strains from Africa

OBJECTIVES

Recent surveillance of MRSA colonizing patients and healthcare workers in two African countries (Angola and São Tomé and Príncipe) reported the frequent recovery of oxacillin-susceptible MRSA (OS-MRSA): Staphylococcus aureus strains that gave positive results with the mecA DNA probe, but had low oxacillin MIC values characteristic of susceptible S. aureus. This apparent dissociation of the drug-resistant phenotype from mecA-the primary genetic determinant of resistance-prompted us to perform a more detailed analysis on nine of the African OS-MRSA strains.

METHODS

Oxacillin MIC values were determined by Etest and population analysis profiles with and without induction of the stringent stress response by mupirocin. Biochemical profiling using SDS-PAGE followed by western blotting was used for the detection of PBP2A protein produced.

RESULTS

Cultures of the African MRSA strains (ST88-IVa and ST8-V) showed heterogeneous oxacillin resistance in which the majority of cells exhibited low oxacillin MICs (≤0.75 mg/L), but highly resistant subpopulations were also present with oxacillin MIC values up to several hundred mg/L and with frequencies of 10(-4) to 10(-6). The same strains after induction of the stringent stress response by mupirocin 'converted' the heterogeneous phenotypes into a more homogeneous and higher level resistance. After induction by oxacillin and mupirocin, each of the nine African OS-MRSA strains produced PBP2A-the protein product of mecA.

CONCLUSIONS

The resistant phenotype of OS-MRSA resembles the phenotypes of historically early MRSA clones. The nature of genetic determinants responsible for the heterogeneous phenotypes of OS-MRSA remains to be determined.