Search

The design and optimization of laser-Compton x-ray systems based on compact distributed charge accelerator structures can enable micron-scale imaging of disease and the concomitant production of beams of Very High Energy Electrons (VHEEs) capable of producing FLASH-relevant dose rates. The physics of laser-Compton x-ray scattering ensures that the scattered x-rays follow exactly the trajectory of the incident electrons, thus providing a route to image-guided, VHEE FLASH radiotherapy. The keys to a compact architecture capable of producing both laser-Compton x-rays and VHEEs are the use of X-band RF accelerator structures which have been demonstrated to operate with over 100 MeV/m acceleration gradients. The operation of these structures in a distributed charge mode in which each radiofrequency (RF) cycle of the drive RF pulse is filled with a low-charge, high-brightness electron bunch is enabled by the illumination of a high-brightness photogun with a train of UV laser pulses synchronized to the frequency of the underlying accelerator system. The UV pulse trains are created by a patented pulse synthesis approach which utilizes the RF clock of the accelerator to phase and amplitude modulate a narrow band continuous wave (CW) seed laser. In this way it is possible to produce up to 10 μA of average beam current from the accelerator. Such high current from a compact accelerator enables production of sufficient x-rays via laser-Compton scattering for clinical imaging and does so from a machine of "clinical" footprint. At the same time, the production of 1000 or greater individual micro-bunches per RF pulse enables > 10 nC of charge to be produced in a macrobunch of < 100 ns. The design, construction, and test of the 100-MeV class prototype system in Irvine, CA is also presented., Competing Interests: CONFLICT OF INTEREST STATEMENT CPJB, JMA, AJA, JCRB, SMB, MMC, RADLL, DAD, HHE, RF, AG, KJG, ASG, FVH, YH, GI, MJ, CAJ, KWK, AL, RJL, MWM, EM, CLN, HJN, KRP, ZRP, MEQ, FR, TR, JS, MES, MWLS, JYY, CBZ, LEZ, and EJZ declare that they have stock-related financial interest in Lumitron Technologies, Inc. CPJB holds patents related to the underlying research presented in this work.

Investing in adolescents in Africa holds great promise for the development of the continent. The steps involved in identifying factors linked to interventions that may accelerate the attainment of multiple SDGs for adolescents in Nigeria are described. Data from a survey to investigate the well-being of 1800 adolescents aged 10-19 years in Southwest Nigeria was analysed. A four-step process was employed: 1) Mapping of variables deemed as suitable proxies for SDG targets; 2) Mapping hypothesised protective factors (accelerators) from the study instruments. Consequently, SDG targets related to elimination of hunger, good health, gender equality and peace; and seven accelerators (safe schools, parenting support, good mental health, no survival work, food security, stable childhood, and regular physical activity) were identified; 3) evaluating associations using bivariate analysis and multivariable logistic regression, 4) calculating adjusted probabilities. The mean age of the adolescents was 15.02 ± 2.27 years (48.6% female). Good mental health, not doing survival work, safe schools, stable childhood and parental support were significantly associated with at least two SDG targets. For example, food security was significantly associated with the highest number of SDG outcomes: one SDG target related to child survival (no substance use: x 2  = 3.39, p = <0.001); three SDG targets related to educational outcomes (school progression: x 2  = 5.68, p  = 0.017, ability to concentrate in school: x 2  = 26.92, p = <0.001, and school attendance: x 2  = 25.89, p = <0.001); and four SDG targets related to child protection (no risky sexual behaviours: x 2  = 16.14, p = <0.001, no perpetration of violence: x 2  = 15.74, p = <0.001, no community violence: x 2  = 39.06, p =<0.001, and no sexual abuse: x 2  = 7.66, p  = 0.006). Interventions centred around good mental health, not doing survival work, safe schools, small family size, stable childhood and parental support are potential accelerators for the attainment of SDG outcomes by adolescents living in Nigeria.

The multiple domains of development covered by the Sustainable Development Goals (SDGs) present a practical challenge for governments. This is particularly acute in highly resource-constrained settings which use a sector-by-sector approach to structure financing and prioritization. One potentially under-prioritized solution is to implement interventions with the potential to simultaneously improve multiple outcomes across sectors, what United Nations Development Programme refer to as development 'accelerators'. An increasing number of accelerators are being identified in the literature. There are, however, challenges associated with the evaluation and implementation of accelerators. First, as accelerators have multiple benefits, possibly in different sectors, they will be undervalued if the priority setting is conducted sector-by-sector. Second, even if their value is recognized, accelerators may not be adopted if doing so clashes with any of the multiple competing interests policymakers consider, of which efficiency/social desirability is but one. To illustrate the first challenge, and outline a possible solution, we conduct a cost-effectiveness analysis comparing the implementation of three sector-specific interventions to an accelerator, first using a sector-by-sector planning perspective, then a whole of government approach. The case study demonstrates how evaluating the cost-effectiveness of interventions sector-by-sector can lead to suboptimal efficiency rankings and overlook interventions that are efficient from a whole of government perspective. We then examine why recommendations based on a whole of government approach to evaluation are unlikely to be heeded. To overcome this second challenge, we outline a menu of existing and novel financing mechanisms that aim to address the mismatch between political incentives and logistical constraints in the priority setting and the economic evaluation evidence for cost-effective accelerators. These approaches to financing accelerators have the potential to improve efficiency, and in doing so, progress towards the SDGs, by aligning political incentives more closely with recommendations based on efficiency rankings., (© The Author(s) 2023. Published by Oxford University Press in association with The London School of Hygiene and Tropical Medicine.)

Incubators and accelerators catalyze the launch of life science startups and have evolved from simple facilities to vibrant ecosystems offering research infrastructure, programs, and funding. Analysis of financing activities indicates the outperformance of incubator companies relative to accelerators in fundraising, mergers and acquisitions (M&As), and initial public offerings (IPOs), attributed to extended interactions with investors and peers., Competing Interests: Declaration of interests W.M., R.S., and R.C. are co-founders of BEVC Management, LLC, a venture capital investment firm focused on early-stage companies. D.V.S. is executive director of QB3, an inventor on numerous patents related to gene delivery and stem cell technologies, and co-founder of 4D Molecular Therapeutics and Axent Biosciences., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Systolic arrays are an integral part of many modern machine learning (ML) accelerators due to their efficiency in performing matrix multiplication that is a key primitive in modern ML models. Current state-of-the-art in systolic array-based accelerators mainly target area and delay optimizations with power optimization being considered as a secondary target. Very few accelerator designs directly target power optimizations and that too using very complex algorithmic modifications that in turn result in a compromise in the area or delay performance. We present a novel Power-Intent Systolic Array (PI-SA) that is based on the fine-grained power gating of the multiplication and accumulation (MAC) block multiplier inside the processing element of the systolic array, which reduces the design power consumption quite significantly, but with an additional delay cost. To offset the delay cost, we introduce a modified decomposition multiplier to obtain smaller reduction tree and to further improve area and delay, we also replace the carry propagation adder with a carry save adder inside each sub-multiplier. Comparison of the proposed design with the baseline Gemmini naive systolic array design and its variant, i.e., a conventional systolic array design, exhibits a delay reduction of up to 6%, an area improvement of up to 32% and a power reduction of up to 57% for varying accumulator bit-widths.

To maximize the performance and energy efficiency of Spiking Neural Network (SNN) processing on resource-constrained embedded systems, specialized hardware accelerators/chips are employed. However, these SNN chips may suffer from permanent faults which can affect the functionality of weight memory and neuron behavior, thereby causing potentially significant accuracy degradation and system malfunctioning. Such permanent faults may come from manufacturing defects during the fabrication process, and/or from device/transistor damages (e.g., due to wear out) during the run-time operation. However, the impact of permanent faults in SNN chips and the respective mitigation techniques have not been thoroughly investigated yet. Toward this, we propose RescueSNN, a novel methodology to mitigate permanent faults in the compute engine of SNN chips without requiring additional retraining, thereby significantly cutting down the design time and retraining costs, while maintaining the throughput and quality. The key ideas of our RescueSNN methodology are (1) analyzing the characteristics of SNN under permanent faults; (2) leveraging this analysis to improve the SNN fault-tolerance through effective fault-aware mapping (FAM); and (3) devising lightweight hardware enhancements to support FAM. Our FAM technique leverages the fault map of SNN compute engine for (i) minimizing weight corruption when mapping weight bits on the faulty memory cells, and (ii) selectively employing faulty neurons that do not cause significant accuracy degradation to maintain accuracy and throughput, while considering the SNN operations and processing dataflow. The experimental results show that our RescueSNN improves accuracy by up to 80% while maintaining the throughput reduction below 25% in high fault rate (e.g., 0.5 of the potential fault locations), as compared to running SNNs on the faulty chip without mitigation. In this manner, the embedded systems that employ RescueSNN-enhanced chips can efficiently ensure reliable executions against permanent faults during their operational lifetime., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Putra, Hanif and Shafique.)

Reducing cement CO 2 footprint is a societal need. This is being achieved mainly by replacing an increasing amount of Portland clinker by supplementary cementitious materials. However, this comes at a price: lower mechanical strengths at early ages due to slow pozzolanic reaction(s). This is being addressed by using accelerator admixtures. In this context, calcium silicate hydrate nucleation seeding seems to have a promising future, as it can accelerate cement and pozzolanic reactions at early ages, optimising their microstructures, without compromising late strength and durability performances. In fact, these features could even be improved. Moreover, other uses are low temperature concreting, precasting, shotconcrete, etc. Here, we focus on reviewing recent reports on calcium silicate hydrate seeding using commercially available admixtures. Current knowledge on the consequences of nucleation seeding on hydration reactions and on early and late mechanical strengths is discussed. It is noted that other features, in addition to the classic alite hydration acceleration, are covered here including the enhanced ettringite precipitation and the very efficient porosity refinement, which take place in the seeded binders. Finally, because the seeded binders seem to be denser, durability properties could also be enhanced although this remains to be properly established.

Processing large-scale graphs is challenging due to the nature of the computation that causes irregular memory access patterns. Managing such irregular accesses may cause significant performance degradation on both CPUs and GPUs. Thus, recent research trends propose graph processing acceleration with Field-Programmable Gate Arrays (FPGA). FPGAs are programmable hardware devices that can be fully customised to perform specific tasks in a highly parallel and efficient manner. However, FPGAs have a limited amount of on-chip memory that cannot fit the entire graph. Due to the limited device memory size, data needs to be repeatedly transferred to and from the FPGA on-chip memory, which makes data transfer time dominate over the computation time. A possible way to overcome the FPGA accelerators' resource limitation is to engage a multi-FPGA distributed architecture and use an efficient partitioning scheme. Such a scheme aims to increase data locality and minimise communication between different partitions. This work proposes an FPGA processing engine that overlaps, hides and customises all data transfers so that the FPGA accelerator is fully utilised. This engine is integrated into a framework for using FPGA clusters and is able to use an offline partitioning method to facilitate the distribution of large-scale graphs. The proposed framework uses Hadoop at a higher level to map a graph to the underlying hardware platform. The higher layer of computation is responsible for gathering the blocks of data that have been pre-processed and stored on the host's file system and distribute to a lower layer of computation made of FPGAs. We show how graph partitioning combined with an FPGA architecture will lead to high performance, even when the graph has Millions of vertices and Billions of edges. In the case of the PageRank algorithm, widely used for ranking the importance of nodes in a graph, compared to state-of-the-art CPU and GPU solutions, our implementation is the fastest, achieving a speedup of 13 compared to 8 and 3 respectively. Moreover, in the case of the large-scale graphs, the GPU solution fails due to memory limitations while the CPU solution achieves a speedup of 12 compared to the 26x achieved by our FPGA solution. Other state-of-the-art FPGA solutions are 28 times slower than our proposed solution. When the size of a graph limits the performance of a single FPGA device, our performance model shows that using multi-FPGAs in a distributed system can further improve the performance by about 12x. This highlights our implementation efficiency for large datasets not fitting in the on-chip memory of a hardware device., Competing Interests: Competing interestsThe authors declare that they have no competing interests., (© The Author(s) 2023.)

Proton minibeam radiation therapy (pMBRT) is a novel therapeutic strategy that combines the normal tissue sparing of sub-millimetric, spatially fractionated beams with the improved ballistics of protons. This may allow a safe dose escalation in the tumour and has already proven to provide a remarkable increase of the therapeutic index for high-grade gliomas in animal experiments. One of the main challenges in pMBRT concerns the generation of minibeams and the implementation in a clinical environment. This article reviews the different approaches for generating minibeams, using mechanical collimators and focussing magnets, and discusses the technical aspects of the implementation and delivery of pMBRT., (Copyright © 2022 Associazione Italiana di Fisica Medica e Sanitaria. Published by Elsevier Ltd. All rights reserved.)

The acceleration of very early age cement hydration by C-S-H seeding is getting attention from scholars and field applications because the enhanced early age features do not compromise later age performances. This acceleration could be beneficial for several low-CO 2 cements as a general drawback is usually the low very early age mechanical strengths. However, the mechanistic understanding of this acceleration in commercial cements is not complete. Reported here is a contribution to this understanding from the study of the effects of C-S-H gel seeding in one Portland cement and two belite cements at two widely studied water-cement ratios, 0.50 and 0.40. Two commercially available C-S-H nano-seed-based admixtures, i.e., Master X-Seed 130 and Master X-Seed STE-53, were investigated. A multi-technique approach was adopted by employing calorimetry, thermal analysis, powder diffraction (data analysed by the Rietveld method), mercury intrusion porosimetry, and mechanical strength determination. For instance, the compressive strength at 1 day for the PC ( w / c = 0.50) sample increased from 15 MPa for the unseeded mortar to 24 and 22 MPs for the mortars seeded with the XS130 and STE53, respectively. The evolution of the amorphous contents was determined by adding an internal standard before recording the powder patterns. In summary, alite and belite phase hydrations, from the crystalline phase content evolutions, are not significantly accelerated by C-S-H seedings at the studied ages of 1 and 28 d for these cements. Conversely, the hydration rates of tetracalcium alumino-ferrate and tricalcium aluminate were significantly enhanced. It is noted that the degrees of reaction of C 4 AF for the PC paste ( w / c = 0.40) were 10, 30, and 40% at 1, 7, and 28 days. After C-S-H seeding, the values increased to 20, 45, and 60%, respectively. This resulted in larger ettringite contents at very early ages but not at 28 days. At 28 days of hydration, larger amounts of carbonate-containing AFm-type phases were determined. Finally, and importantly, the admixtures yielded larger amounts of amorphous components in the pastes at later hydration ages. This is justified, in part, by the higher content of amorphous iron siliceous hydrogarnet from the enhanced C 4 AF reactivity.

Background: This study aimed to identify possible entry points for interventions that can act as development accelerators for children and adolescents in South Africa and Malawi., Methods: This study was a secondary data analysis. Data were sourced from the Child Community Care longitudinal study which tracked child well-being outcomes among 989 children (4-13 years) and their caregivers affected by HIV and enrolled in community-based organizations in South Africa and Malawi. We examined associations between five hypothesized accelerating services/household provisions-measured as access at baseline and follow-up and 12 child outcomes that relate to indicators within the Sustainable Development Goals (SDGs) framework. We calculated the adjusted probabilities of experiencing each SDG aligned outcome conditional on receipt of single, combined or all identified accelerators., Results: The results show household food security is associated with positive child education and cognitive development outcomes. Cash grants were positively associated with nutrition and cognitive development outcomes. Living in a safe community was positively associated with all mental health outcomes. Experiencing a combination of two factors was associated with higher probability of positive child outcomes. However, experiencing all three accelerators was associated with better child outcomes, compared with any of the individual factors by themselves with substantial improvements noted in child education outcomes., Conclusions: Combined delivery of specific interventions or services may yield greater improvements in child outcomes across different developmental domains. It is recommended that multiple support avenues in combination like improving food security and safe communities, as well as social protection grants, should be provided for vulnerable children to maximize the impact., (© 2021 John Wiley & Sons Ltd.)

The application of vacuum materials with low secondary electron yield (SEY) is one of the effective methods to mitigate the electron cloud (EC). In this study, the Ti-Hf-V-Zr non-evaporable getter (NEG) film was deposited on open-cell copper foams with different pore sizes for the suppression of electron multipacting effects. Besides, the influence of the film thickness on the secondary electron emission (SEE) characteristics of Ti-Hf-V-Zr NEG film-coated open-cell copper foam substrates was investigated for the first time. The results highlighted that all uncoated and NEG-coated foamed porous copper substrates achieved a low SEY (<1.2), which reduced at least 40% compared to the traditional copper plates, and the foamed porous coppers with 1.34-μm-thick NEG coating had the lowest SEY. Moreover, the surface chemistry and the morphological and structural properties of foamed porous coppers of different pore sizes with and without Ti-Hf-V-Zr NEG films were systematically analyzed.

Objectives: We examined associations between accelerators (interventions impacting ≥2 SDG targets) and SDG-aligned well-being indicators among adolescents 16-24 years old in Zambia. Methods: We surveyed adults from 1,800 randomly sampled households receiving social cash transfers. We examined associations between accelerators (social cash transfers, life-long learning, mobile phone access) and seven well-being indicators among adolescents using multivariate logistic regressions. Results: The sample comprised 1,725 adolescents, 881 (51.1%) girls. Mobile phone access was associated with no poverty (adjusted Odds Ratio [aOR] 2.08, p < 0.001), informal cash transfers (aOR 1.82, p = 0.004), and seeking mental health support (aOR 1.61, p = 0.020). Social cash transfers were associated with no disability-related health restrictions (aOR 2.56, p = 0.004) and lesser odds of seeking mental health support (aOR 0.53, p = 0.029). Life-long learning was associated with informal cash transfers (aOR 3.49, p < 0.001) and lower school enrollment (aOR 0.70, p = 0.004). Adolescents with disabled head-of-household reported worse poverty, good health but less suicidal ideation. Conclusions: Social cash transfers, life-long learning, and mobile phone access were positively associated with well-being indicators. Adolescents living with disabled head-of-household benefited less. Governments should implement policies to correct disability-related inequalities., Competing Interests: CM and GT were employed by Palm Associates Limited. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Chipanta, Estill, Stöckl, Hertzog, Toska, Chanda, Mwanza, Kaila, Matome, Tembo, Keiser and Cluver.)

Since the adoption of the sustainable development goals (SDGs) by the United Nations (UN), the search has been on to identify interventions that have effects on multiple SDG-targets simultaneously. Like other developing countries, Ghana has a youthful population and would require creative, urgent, youth-focused interventions to be able to attain the SDGs by 2030. This paper describes the application of the accelerator model on data from a sample of Ghanaian adolescents to identify potential accelerators towards selected SDG targets involving youth. The data for 944 adolescents, 10-19 years (mean age 12.31 ± 3.51 years), extracted from two cross-sectional surveys on children and adolescents aged 6-19 years in Kumasi, Ghana, were analysed in this paper. Variables considered suitable proxies for SDG targets and potential accelerators were identified from the study instruments. Consequently, four aligned SDG targets (good mental health, access to ICT, school completion and no open defaecation) and five accelerators (cognitive stimulation, no relative poverty, low student-teacher ratio, high caregiver education and safe water) were extracted. Associations between accelerators and SDG targets were assessed using multivariable logistic regression adjusting for sociodemographic covariates and multiple testing. Cumulative effects were tested by marginal effects modelling. The three hypothesised accelerators identified were cognitive stimulation, low student-teacher ratio, and no relative poverty. A combination of all three accelerators was associated with a higher likelihood of adolescents having access to Information and Communication Technology (ICT) by +73% (CI 0.72-0.74), no open defecation by +44% (CI 0.43-0.46), school completion by +27% (CI 0.26-0.27) and good mental health by +9% (CI 0.08-0.10). Three hypothesized accelerators showed association across all four SDG aligned targets. The accelerator model has been further validated in this dataset from Ghana. Robust interventions designed around these accelerators may represent an opportunity for achieving the SDGs in Ghana.

The preparation of ultra-high-performance concrete (UHPC) with both high-early-strength and good workability contributes to further promotion of its development and application. This study investigated the effects of different accelerators (SM, alkaline powder accelerator; SF, alkaline powder accelerator containing fluorine; and AF, alkali-free liquid accelerator containing fluorine) on the workability and strength properties of UHPC. The microstructure of UHPC was also characterized by using XRD and SEM. Several dosage levels of accelerators (2%, 4%, 6%, and 8% by mass) were selected. The results indicate that the setting time and fluidity of UHPC are gradually decreased with an increase in accelerators dosage. Compared with fluorine-containing SF/AF, fluorine-free SM evidently facilitates UHPC early strength gain speed. However, the fluorine-containing accelerators have a higher 28 d strength ratio, especially AF. The maximum compressive and flexural strength ratios are obtained at a dosage of 6%, which are 95.5% and 98.3%, respectively. XRD and SEM tests further reveal the effect of different accelerators on the macroscopic properties of UHPC from the micro level.

The physical and clinical benefits of charged particle therapy (CPT) are well recognized. However, the availability of CPT and complete exploitation of dosimetric advantages are still limited by high facility costs and technological challenges. There are extensive ongoing efforts to improve upon these, which will lead to greater accessibility, superior delivery, and therefore better treatment outcomes. Yet, the issue of cost remains a primary hurdle as utility of CPT is largely driven by the affordability, complexity and performance of current technology. Modern delivery techniques are necessary but limited by extended treatment times. Several of these aspects can be addressed by developments in the beam delivery system (BDS) which determines the overall shaping and timing capabilities enabling high quality treatments. The energy layer switching time (ELST) is a limiting constraint of the BDS and a determinant of the beam delivery time (BDT), along with the accelerator and other factors. This review evaluates the delivery process in detail, presenting the limitations and developments for the BDS and related accelerator technology, toward decreasing the BDT. As extended BDT impacts motion and has dosimetric implications for treatment, we discuss avenues to minimize the ELST and overview the clinical benefits and feasibility of a large energy acceptance BDS. These developments support the possibility of advanced modalities and faster delivery for a greater range of treatment indications which could also further reduce costs. Further work to realize methodologies such as volumetric rescanning, FLASH, arc, multi-ion and online image guided therapies are discussed. In this review we examine how increased treatment efficiency and efficacy could be achieved with improvements in beam delivery and how this could lead to faster and higher quality treatments for the future of CPT., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Yap, De Franco and Sheehy.)

A nested neutron spectrometer was used to measure the stray neutron fluence and ambient dose equivalent produced by protons from a 4 MV tandem accelerator on various target materials at the Reactor Materials Testing Laboratory (RMTL), Queen's University, Kingston, Ontario. The nested neutron spectrometer utilizes a Helium-3 proportional counter and measures the thermal neutron count rate as a function of moderator shell-thickness. Using custom unfolding software, neutron spectra and neutron dosimetric quantities were derived at various locations within the RMTL. The nested neutron spectrometer can be operated in both a pulse mode and current mode allowing for measurements over a wide range of accelerator beam currents. All measurements conducted at the facility were within the main accelerator chamber and experimental target rooms. Target room measurements were conducted with a variety of target materials representative of those to be used for research planned at the RMTL., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: Adolescents experience a multitude of vulnerabilities which need to be addressed in order to achieve the Sustainable Development Goals (SDGs). In sub-Saharan Africa, adolescents experience high burden of HIV, violence exposure, poverty, and poor mental and physical health. This study aimed to identify interventions and circumstances associated with three or more targets ("accelerators") within multiple SDGs relating to HIV-affected adolescents and examine cumulative effects on outcomes., Methods: Prospective longitudinal data from 3401 adolescents from randomly selected census enumeration areas in two provinces with > 30% HIV prevalence carried out in 2010/11 and 2011/12 were used to examine six hypothesized accelerators (positive parenting, parental monitoring, free schooling, teacher support, food sufficiency and HIV-negative/asymptomatic caregiver) targeting twelve outcomes across four SDGs, using a multivariate (multiple outcome) path model with correlated outcomes controlling for outcome at baseline and socio-demographics. The study corrected for multiple-hypothesis testing and tested measurement invariance across sex. Percentage predicted probabilities of occurrence of the outcome in the presence of the significant accelerators were also calculated., Results: Sample mean age was 13.7 years at baseline, 56.6% were female. Positive parenting, parental monitoring, food sufficiency and AIDS-free caregiver were variously associated with reductions on ten outcomes. The model was gender invariant. AIDS-free caregiver was associated with the largest reductions. Combinations of accelerators resulted in a percentage reduction of risk of up to 40%., Conclusion: Positive parenting, parental monitoring, food sufficiency and AIDS-free caregivers by themselves and in combination improve adolescent outcomes across ten SDG targets. These could translate to the corresponding real-world interventions parenting programmes, cash transfers and universal access to antiretroviral treatment, which when provided together, may help governments in sub-Saharan Africa more economically to reach their SDG targets., (© 2021. The Author(s).)

The development of innovative approaches that would reduce the sensitivity of healthy tissues to irradiation while maintaining the efficacy of the treatment on the tumor is of crucial importance for the progress of the efficacy of radiotherapy. Recent methodological developments and innovations, such as scanned beams, ultra-high dose rates, and very high-energy electrons, which may be simultaneously available on new accelerators, would allow for possible radiobiological advantages of very short pulses of ultra-high dose rate (FLASH) therapy for radiation therapy to be considered. In particular, very high-energy electron (VHEE) radiotherapy, in the energy range of 100 to 250 MeV, first proposed in the 2000s, would be particularly interesting both from a ballistic and biological point of view for the establishment of this new type of irradiation technique. In this review, we examine and summarize the current knowledge on VHEE radiotherapy and provide a synthesis of the studies that have been published on various experimental and simulation works. We will also consider the potential for VHEE therapy to be translated into clinical contexts.

Nuclear Magnetic Resonance (NMR) relaxometry is a valuable tool for investigating cement-based materials. It allows monitoring of pore evolution and water consumption even during the hydration process. The approach relies on the proportionality between the relaxation time and the pore size. Note, however, that this approach inherently assumes that the pores are saturated with water during the hydration process. In the present work, this assumption is eliminated, and the pore evolution is discussed on a more general basis. The new approach is implemented here to extract information on surface evolution of capillary pores in a simple cement paste and a cement paste containing calcium nitrate as accelerator. The experiments revealed an increase of the pore surface even during the dormant stage for both samples with a faster evolution in the presence of the accelerator. Moreover, water consumption arises from the beginning of the hydration process for the sample containing the accelerator while no water is consumed during dormant stage in the case of simple cement paste. It was also observed that the pore volume fractal dimension is higher in the case of cement paste containing the accelerator.

The pair of copper radionuclides 64 Cu/ 67 Cu (T 1/2 = 12. 7 h/61.8 h) allows, respectively, PET imaging and targeted beta therapy. An analysis of the different production routes of 67 Cu with charged particles was performed and the reaction 70 Zn(d,x) route was identified as a promising one. It may allow the production of 67 Cu without 64 Cu. The production cross section has been measured up to 28.7 MeV. Measurements were done using the well-known stacked-foils technique using 97.5% enriched 70 Zn homemade electroplated targets. These measurements complement at higher incident energies the only set of data available in nuclear databases. The results show that using a 26 MeV deuteron beam and a highly enriched 70 Zn target, it is possible to produce high purity 67 Cu comparable to that obtained using photoproduction. This production route can be of interest for future linear accelerators under development where mA deuteron beams can be available if adequate targetry is developed., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Nigron, Guertin, Haddad and Sounalet.)

In the last decade, the development of more compact and lightweight radiation detection systems led to their application in handheld and small unmanned systems, particularly air-based platforms. Examples of improvements are: the use of silicon photomultiplier-based scintillators, new scintillating crystals, compact dual-mode detectors (gamma/neutron), data fusion, mobile sensor networks, cooperative detection and search. Gamma cameras and dual-particle cameras are increasingly being used for source location. This study reviews and discusses the research advancements in the field of gamma-ray and neutron measurements using mobile radiation detection systems since the Fukushima nuclear accident. Four scenarios are considered: radiological and nuclear accidents and emergencies; illicit traffic of special nuclear materials and radioactive materials; nuclear, accelerator, targets, and irradiation facilities; and naturally occurring radioactive materials monitoring-related activities. The work presented in this paper aims to: compile and review information on the radiation detection systems, contextual sensors and platforms used for each scenario; assess their advantages and limitations, looking prospectively to new research and challenges in the field; and support the decision making of national radioprotection agencies and response teams in respect to adequate detection system for each scenario. For that, an extensive literature review was conducted.

Secondary electron emission (SEE) inhibition and vacuum instability are two important issues in accelerators that may induce multiple effects in accelerators, such as power loss and beam lifetime reduction. In order to mitigate SEE and maintain high vacuum simultaneously, open-cell copper metal foam (OCMF) substrates with Ti-Zr-V-Hf non-evaporable getter (NEG) coatings are first proposed, and the properties of surface morphology, surface chemistry and secondary electron yield (SEY) were analyzed for the first time. According to the experimental results tested at 25 °C, the maximum SEY (δmax) of OCMF before and after Ti-Zr-V-Hf NEG film deposition were 1.25 and 1.22, respectively. The XPS spectra indicated chemical state changes of the metal elements (Ti, Zr, V and Hf) of the Ti-Zr-V-Hf NEG films after heating, suggesting that the NEG films can be activated after heating and used as getter pumps.

Biomedical applications at high-energy particle accelerators have always been an important section of the applied nuclear physics research. Several new facilities are now under constructions or undergoing major upgrades. While the main goal of these facilities is often basic research in nuclear physics, they acknowledge the importance of including biomedical research programs and of interacting with other medical accelerator facilities providing patient treatments. To harmonize the programs, avoid duplications, and foster collaboration and synergism, the International Biophysics Collaboration is providing a platform to several accelerator centers with interest in biomedical research. In this paper, we summarize the programs of various facilities in the running, upgrade, or construction phase., Competing Interests: Conflict of Interest: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

In radiotherapy treatments utilizing accelerator gantry rotation, gantry-mounted kilovoltage (kV) imaging systems have become integral to treatment verification. The accuracy of such verification depends on the stability of the imaging components during gantry rotation. In this study, a simple measurement method and accurate algorithm are introduced for investigation of the kV panel and source movement during gantry rotation. The method is based on images of a ball-bearing phantom combined with a Winston-Lutz phantom, and determines the movements of all the mechanical parameters of the kV imaging system relative to the reference at zero gantry angle. Analysis was performed on different linear accelerators and both gantry rotation directions. The precision of the method was tested and was less than 0.04 mm. This method is suitable to be included in the quality assurance testing of linacs to monitor the kV imaging system performance and provides additional mechanical information that previous tests cannot., (© 2020 IOP Publishing Ltd.)

Versatile product protective coatings that deliver faster drying times and shorter minimum overcoat intervals that enable curing at faster line speeds and though lower energy consumption are often desired by coating manufacturers. Product protective coatings, based on silsesquioxane-modified diglycidyl ether of bisphenol-A (DGEBA) epoxy resin, are prepared through a glycidyl ring-opening polymerization using dicyandiamide (DICY) as a curing agent. As silsesquioxane modifier serves the octaglycidyl-polyhedral oligomeric silsesquioxane (GlyPOSS). To decrease the operational temperature of the curing processes, three different accelerators for crosslinking are tested, i.e., N,N -benzyl dimethylamine, 2-methylimidazole, and commercial Curezol 2MZ-A. Differential scanning calorimetry, temperature-dependent FT-IR spectroscopy, and rheology allow differentiation among accelerators' effectiveness according to their structure. The former only contributed to epoxy ring-opening, while the latter two, besides participate in crosslinking. The surface roughness of the protective coatings on aluminum alloy substrate decreases when the accelerators are applied. The scanning electron microscopy (SEM) confirms that coatings with accelerators are more homogeneous. The protective efficiency is tested with a potentiodynamic polarization technique in 0.5 M NaCl electrolyte. All coatings containing GlyPOSS, either without or with accelerators, reveal superior protective efficiency compared to neat DGEBA/DICY coating., Competing Interests: The authors declare no conflict of interest.

Deep neural networks (DNNs) have proliferated in most of the application domains that involve data processing, predictive analysis and knowledge inference. Alongside the need for developing highly performance-efficient DNN accelerators, there is an utmost need to improve the yield of the manufacturing process in order to reduce the per unit cost of the DNN accelerators. To this end, we present 'SalvageDNN', a methodology to enable reliable execution of DNNs on the hardware accelerators with permanent faults (typically due to imperfect manufacturing processes). It employs a fault-aware mapping of different parts of a given DNN on the hardware accelerator (subjected to faults) by leveraging the saliency of the DNN parameters and the fault map of the underlying processing hardware. We also present novel modifications in a systolic array design to further improve the yield of the accelerators while ensuring reliable DNN execution using 'SalvageDNN' and negligible overheads in terms of area, power/energy and performance. This article is part of the theme issue 'Harmonizing energy-autonomous computing and intelligence'.

The goal of this thesis is to estimate the physical radiation doses for two victims who were accidently exposed to an industrial electron beam at an industrial accelerator facility on 7 July 7 2016 in Tianjin, China. On the basis of the radiation source parameters, irradiation situation and irradiation time, physical dose reconstruction was carried out at the accident site by using a Bottle-Manikin-Absorption (BOMAB) phantom and an Alderson Radiation Therapy (ART) phantom. With thermoluminscent dosimeters (TLDs), skin estimation was conducted for the feet, calves, upper arms, left side of the body and neck, and the mean dose was estimated to be 14.1 ± 5.6 Gy. The foot and leg skin received the highest dose, which was >16.3 Gy. In addition, the mean dose estimated for the eye lens was 0.18 ± 0.07 Gy. The organ effective dose estimated and the total organs effective dose estimated were 0.46-4.94 mSv and 0.21 Sv, respectively. In the course of the accident, the damage caused by the electron radiation field to the exposed person was mainly to the skin, and the contributions to other radiation-sensitive organs were small. The damage to the organs other than the skin was mainly caused by the X-rays generated by the bremsstrahlung of the electron beam from the environment or the human body., (© The Author(s) 2019. Published by Oxford University Press on behalf of The Japanese Radiation Research Society and Japanese Society for Radiation Oncology.)

A linear electron-positron collider operating at TeV-scale energies will provide high precision measurements and allow, for example, precision studies of the Higgs boson as well as searches for physics beyond the standard model. A future linear collider should produce collisions at high energy, with high luminosity and with a good wall plug to beam power transfer efficiency. The luminosity per power consumed is a key metric that can be used to compare linear collider concepts. The plasma wakefield accelerator has demonstrated high-gradient, high-efficiency acceleration of an electron beam and is therefore a promising technology for a future linear collider. We will go through the opportunities of using plasma wakefield acceleration technology for a collider, as well as a few of the collider-specific challenges that must be addressed in order for a high-energy, high luminosity-per-power plasma wakefield collider to become a reality. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'.

Beam-driven plasma wakefield acceleration (PWFA) has demonstrated significant progress during the past two decades of research. The new Facility for Advanced Accelerator Experimental Tests (FACET) II, currently under construction, will provide 10 GeV electron beams with unprecedented parameters for the next generation of PWFA experiments. In the context of the FACET II facility, we present simulation results on expected betatron radiation and its potential application to diagnose emittance preservation and hosing instability in the upcoming PWFA experiments. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'.

This paper discusses the properties of electron beams formed in plasma wakefield accelerators through ionization injection. In particular, the potential for generating a beam composed of co-located multi-colour beamlets is demonstrated in the case where the ionization is initiated by the evolving charge field of the drive beam itself. The physics of the processes of ionization and injection are explored through OSIRIS simulations. Experimental evidence showing similar features are presented from the data obtained in the E217 experiment at the FACET facility of the SLAC National Laboratory. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'.

Charged particle therapy is the most advanced radiotherapy method in oncology. The favorable depth-dose distribution and the biological properties of charged particles have potentially a great benefit for reducing toxicity and increasing the local control. While the number of proton centers is exponentially growing worldwide, the therapy remains controversial due to the high cost and lack of level-I evidence of superior effectiveness compared to conventional X-rays. Here we will discuss the advantages and the challenges in both physics and biology to fully exploit the potential of ion therapy in medicine. The challenges include reducing the footprint and costs of accelerators, reducing range uncertainty, exploitation of the biological advantages such as the high effectiveness against hypoxic tumors, and to select patients with biology-driven personalized approaches. International collaboration in the field is likely to bring definite answers to these ongoing problems., (Copyright © 2019 Elsevier Inc. All rights reserved.)

In this study, the setting property and mechanical strength of cement pastes containing accelerators (CPCA) with or without superabsorbent polymers (SAPs) were first studied. The early microstructure evolution and water distribution at 7 and 28 days were probed by 1D ( T ₂) and 2D ( T ₁- T ₂ maps) H¹ nuclear magnetic resonance (NMR) relaxometry, and the microstructure was systematically investigated by using mercury intrusion porosimetry (MIP), back-scattered electron (BSE) image and energy-dispersive X-ray spectroscopy (EDX) analysis. Results showed that the SAPs in the cement paste containing accelerators had various influences on setting time and compressive strength depending on the type of accelerators. The presence of SAPs in the cement paste containing alkaline free accelerators could alleviate the decrease of internal relative humidity, promote hydration and help to modify the pore structure. Moreover, it was observed that the SAP cavities could be nicely filled with calcium hydroxide (CH) in the cement paste with alkaline free accelerators.

Objective: This study compares the effect of the white mineral trioxide aggregate (WMTA) accelerators, including disodium hydrogen orthophosphate (Na2HPO4; 2.5 wt%), calcium chloride (CaCl2; 5 and 10 wt%), and KY jelly, on the push-out bond strength of WMTA. The null hypothesis was that the WMTA accelerators would not affect the push-out bond strength of WMTA., Materials and Methods: Slices (2-mm-thick) were obtained from 75 human mandibular molar distal roots. The slices were enlarged up to size 6 Gates-Glidden burs to obtain a 1.5-mm canal diameter. The slices were randomly divided into 4 experimental groups and a control group (n = 15 in each group). Freshly prepared WMTA mixture was placed into the root slices and stored at 37°C in a 100% humidified atmosphere for 60 days. The force required to dislodge the WMTA cement from the root slice was determined using a universal testing machine. The push-out bond strength was calculated., Results: Push- out bond strength of 5- and 10-wt% CaCl2, and 2.5-wt% Na2HPO4 WMTA groups was significantly lower than in the KY-jelly and control groups (p < 0.05). The mean push-out bond strength of KY jelly was lower than in the control group but not statistically significant., Conclusion: The addition of KY jelly to WMTA did not have an adverse effect on the push-out bond strength of WMTA, in contrast to the other accelerators, including Na2HPO4 and CaCl2, which reduced the push-out bond strength., (© 2018 The Author(s) Published by S. Karger AG, Basel.)

Wire and nonparallel plate electrode-type electrostatic air accelerators have attracted significant interest. The physical process involved in using accelerators is complicated. Moreover, mechanisms are unclear, especially for accelerators with double- and multiwire electrodes. In this study, the two-dimensional (2D) model of a wire-nonparallel plate-type accelerator validated by experiments is established with a finite element method. Onset voltage, average current, and outlet average velocity are analyzed with respect to different parameters. Onset voltage is derived by the proposed quadratic regression extrapolation method. Moreover, current is affected by interference and discharge effects, while velocity is also influenced by the suction effect. For the single-wire electrode, high wind speed can be obtained by either increasing channel slope or placing the wire near the entry section. For the double-wire electrode, velocity can be further increased when one of the wires is placed near the inlet and the distance between the two wires is widened. Comparatively, the velocity of the three-wire electrode is higher with larger gaps between wires and stronger discharge effect. The highest velocity is obtained by the four-wire electrode. Comparisons indicate that higher velocity can be obtained with weaker interference effect, stronger suction effect, and intensified discharge effect. Optimum parameter combinations are considered by the Taguchi method. Consequently, velocity can be enhanced by more than 39% after optimization compared with the reference design.

Aim: To investigate the effect of accelerated-set mineral trioxide aggregate (MTA) on the proliferation and odontoblastic differentiation of human dental pulp cell niches (DPSC)., Methodology: ProRoot White MTA (WMTA; Dentsply Tulsa Dental, Johnson City, TN, USA) was mixed with various additives, which included distilled water, 2.5% disodium hydrogen phosphate (Na 2 HPO 4 ; Merck, Darmstadt, Germany) and 5% calcium chloride (CaCl 2 ; Merck). DPSC niches extracted from third molars were cultured directly on MTA in the culture medium. Cell viability was evaluated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4- sulphophenyl)-2H-tetrazolium (MTS) assay. Cell growth and expression of odontoblastic differentiation markers (dentine sialophosphoprotein (DSPP) and collagen type 1 (COL1)) were determined using Real-Time Polymerase Chain Reaction analysis. Osteo-/odontogenic differentiation of DPSC niches was evaluated by measurement of alkaline phosphatase activity (ALP). Calcium deposition was assessed using von Kossa staining. The results were analysed statistically using Mann-Whitney tests and Kruskal-Wallis tests., Results: MTA mixed with 5% CaCl 2 and 2.5% Na 2 HPO 4 exhibited optimal cell viability (P < 0.05) compared to MTA mixed with distilled water. MTA mixed with 5% CaCl 2 and 2.5% Na 2 HPO 4 significantly increased ALP activity (P < 0.05), significantly promoted mineralization nodule formation (P < 0.05) and significantly enhanced the mRNA expression level of the osteogenic/odontogenic markers (P < 0.05; DSPP and COL1) compared with MTA mixed with distilled water., Conclusions: MTA mixed with 5% CaCl 2 and 2.5% Na 2 HPO 4 was biocompatible with dental pulp stem cell niches. Accelerated-set MTA promoted better differentiation in DPSC niches than conventional MTA. The accelerators could provide an alternative to MTA mixed with distilled water., (© 2017 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

A personal recollection of events leading up to the construction and commissioning of NSRL, including reference to precursor facilities and the development of the NASA Space Radiation Program., (Copyright © 2016 The Committee on Space Research (COSPAR). Published by Elsevier Ltd. All rights reserved.)

The aim of this study was to evaluate the effects of several additives on the setting time and cytotoxicity of accelerated-set mineral trioxide aggregate (MTA) on stem cells of human dental pulp. ProRoot white MTA (WMTA) (Dentsply Tulsa Dental, Johnson City, TN) was mixed with various additives including distilled water, 2.5% disodium hydrogen phosphate (Na2HPO4) (Merck, Darmstadt, Germany), K-Y Jelly (Johnson & Johnson, Markham, ON, Canada), and 5% and 10% calcium chloride (CaCl2) (Merck). The setting times were evaluated using a Vicat apparatus (Alsa Lab, Istanbul, Turkey). Human dental pulp stem cells were isolated and seeded into 48-well plates at 2 × 10(3) cells per well and incubated with MTA samples for 24 hours, 3 days, and 7 days. Cell viability was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay. MTA mixed with 10% CaCl2 showed the lowest setting time (P < .05). According to the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium results on the 1st, 3rd, and 7th days, a statistically significant difference was found (P < .05) between MTA groups and the control group. MTA mixed with K-Y Jelly in all groups showed the lowest cell viability at all time points (P < .05). The cell viability of MTA mixed with distilled water, 5% CaCl2, 10% CaCl2, and Na2HPO4 increased significantly through time (P < .05). This in vitro study found MTA mixed with 5% and 10% CaCl2 and Na2HPO4 is biocompatible with dental pulp stem cells in terms of cell viability. Further in vitro and in vivo investigations are required to prove the clinical applications of MTA mixed with various additives., (Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

State-of-the-art techniques derived from particle accelerators, detectors, and physics computing are routinely used in clinical practice and medical research centers: from imaging technologies to dedicated accelerators for cancer therapy and nuclear medicine, simulations, and data analytics. Principles of particle physics themselves are the foundation of a cutting edge radiotherapy technique for cancer treatment: hadron therapy. This article is an overview of the involvement of CERN, the European Organization for Nuclear Research, in medical applications, with specific focus on hadron therapy. It also presents the history, achievements, and future scientific goals of the European Network for Light Ion Hadron Therapy, whose co-ordination office is at CERN.

The first BNCT trials took place in the USA in the early 1960's, yet BNCT is still far from mainstream medicine. Nonetheless, in recent years, reported results in the treatment of head and neck cancer and recurrent glioma, coupled with the progress in developing linear accelerators specifically for BNCT applications, have given some optimism to the future of BNCT. This article provides a brief reminder on the ups and downs of the history of BNCT and supports the view that controlled and prospective clinical trials with a modern design will make BNCT an evidence-based treatment modality within the coming decade., (© 2013 Elsevier Ltd. All rights reserved.)

Aim: To evaluate and compare the influence of various accelerators, 15% disodium hydrogen phosphate (Na2HPO4), 10% calcium chloride (CaCl2) and 23.1 wt% calcium lactate gluconate (CLG), on the immediate (after 72 h) and delayed (after 2 months) sealing ability of white ProRoot mineral trioxide aggregate (WMTA) when it is used as an apical plug., Materials and Methods: Eighty, single-rooted mandibular premolars were instrumented and standardized artificial open apices were created. The samples were then randomly assigned into four experimental groups and two control groups. WMTA was mixed with the respective accelerators and an apical plug of 4-mm thickness was fabricated. The remaining canal spaces were then backfilled. The samples were stored for the stipulated time periods and then immersed in 0.2% Rhodamine B solution for 72 h. Dye leakage was analyzed using a stereomicroscope., Results: Mean microleakage values of all experimental groups revealed that MTA + 23.1 wt% CLG showed the least leakage, followed by MTA + 15% Na2HPO4 and MTA + 10% CaCl2 with MTA + deionized water showing the maximum leakage at both the time intervals (P < 0.001). All the samples stored for a period of 2 months showed less leakage as compared with the samples stored for 72 h (P < 0.05)., Conclusions: It was found that all three accelerators significantly accelerated the set of WMTA, of which 23.1 wt% CLG showed the best results, followed by 15% Na2HPO4 and 10% CaCl2. The sealing ability of all the experimental groups was significantly superior after 2 months as compared with that after 72 h.

This chapter outlines terminology and its origins. It traces the development of physics ideas from Thales of Miletus, via Isaac Newton, to the nuclear physics investigations at the beginning of the twentieth century. It also outlines the evolving technology required to make the discoveries that would form the basis of radiosurgery. Up to the 1920s, all experiments on atomic structure and radioactivity had involved the use of vacuum tubes and naturally occurring radioactive substances. There was a need to make useable subatomic particles to obtain better understanding of the interior structure of atoms. Because of this, machines that could make atoms move at high speed were invented, known as particle accelerators. A new era had dawned. There is a brief mention of the effect of radiation on living tissue and of the units used to measure it.

The knowledge of ambient and peak radiation levels prevailing inside the bunkers of the accelerator facilities is essential in assessing the accidental human exposure inside the bunkers and in protecting sensitive electronic equipments by minimizing the exposure to high intensity mixed radiation fields. Radiation field mapping dynamically, inside bunkers are rare, though generally dose-rate data are available in every particle accelerator facilities at specific locations. Taking into account of the fact that the existing neutron fields with a spread of energy from thermal up to the energy of the accelerated charged projectiles, prompt photons and other particles prevailing during cyclotron operation inside the bunkers, neutron and gamma survey meters with extended energy ranges attached to a robotic carrier have been used. The robotic carrier movement was controlled remotely from the control room with the help of multiple visible range optical cameras provided inside the bunkers and the wireless and wired protocols of communication helped its movement and data acquisition from the survey meters. Variable Energy Cyclotron Centre, Kolkata has positive ion accelerating facilities such as K-130 room Temperature Cyclotron, K-500 Super Conducting Cyclotron and a forthcoming 30 MeV Proton Medical Cyclotron with high beam current. The dose rates data for K-130 Room Temperature Cyclotron, VECC were collected for various energies of alpha and proton beams losing their total energy at different stages on different materials at various strategic locations of radiological importance inside the bunkers. The measurements established that radiation levels inside the machine bunker dynamically change depending upon the beam type, beam energy, machine operation parameters, deflector condition, slit placement and central region beam tuning. The obtained inference from the association of dose rates with the parameters like beam intensity, type and energy of projectiles, helped in improving the primary beam transmission and minimizing the ambient radiation fields inside the bunkers., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Structural Shielding Design and Evaluation for Megavoltage X- and Gamma-Ray Radiotherapy Facilities NCRP Report No. 151, 2005, 246 pp. (Hardcover $100). National Council on Radiation Protection and Measurements, 7910 Woodmont Avenue, Suite 400, Bethesda, MD 20814-3095. ISBN-10 0-0929600-87-8; http://www.NCRPonline.org., (© 2006 American Association of Physicists in Medicine.)

Earlier studies of the infrared spectra of natural rubber and some vulcanizates of rubber have been extended into the 650 to 33 cm -1 far infrared region. Some of the absorption bands originating in the crystalline portion of unvulcanized rubber have been studied by using polarized radiation and samples oriented by stretching. Vulcanization of rubber with sulfur alone produces a general weakening of all absorption bands and no new absorptions. Vulcanization with sulfur and an accelerator also results in a reduction in intensity of the rubber absorptions, but is accompanied by the appearance of new bands. When the accelerator is tetramethylthiuram disulfide (TMTD) the new bands are probably indicative of a thiocarbamate structure. When zinc dibutyldithiocarbamate is used as an accelerator a band probably due to zinc sulfide occurs. Vulcanization with TMTD alone produces only slight changes in the far infrared spectrum. However, when TMTD is used in the presence of zinc oxide a reaction occurs in which zinc dimethyldithiocarbamate (ZnDMDC) is formed. After vulcanization for a short period of time strong TMTD bands remain, but after long vulcanization the TMTD bands are replaced by ZnDMDC bands.