Standard Beam Research Articles

Beam Monitors for Tomorrow: The Challenges of Electron and Photon FLASH RT

The emergent FLASH RadioTherapy (RT) uses ultrahigh dose-rate irradiation (up to 107 Gy/s instantaneous dose-rate in each μs pulse) to deliver a single high dose of irradiation in a very short time (less than 200 milliseconds). Pre-clinical studies at ultrahigh dose-rates recently showed an increased ratio between tumoricidal effect and normal tissue toxicity (therapeutic index), compared to conventional RT at standard Gy/min dose-rates. If confirmed by biological in vivo validations, this could represent a breakthrough in cancer treatment. However, the reliability and the accuracy of experimental studies are nowadays limited by the lack of detectors able to measure online the beam fluence at FLASH dose-rates. The behaviour of standard beam monitors (gas-filled ionization chambers) is compromised by the volume recombination caused by the amount of charges created per unit volume and unit time, due to the large dose-rate. Moreover, due to the lack of proper monitoring devices and to the uncertainties of its future applications, very few facilities are able to deliver at present FLASH irradiations. In this contribution, we report about the physical and technological challenges of monitoring high and ultra-high dose-rates with electrons and photon beams, starting from the pre-clinical and clinical constraints for new devices. Based on the extensive experience in silicon detectors for monitoring applications in RT with external beams, the work then investigates silicon sensors as a possible option to tackle such extreme requirements and a rugged thin and large (e.g. 10×10 cm2) flat detector (silicon-based sensor + readout electronics) is therefore outlined. This study aims at presenting the FLASH-RT dosimetry problem and analysing the possibilities for a silicon sensor to be employed as sensing device for several FLASH scenarios, including some ideas on the readout part. However, more detailed simulations and studies are demanded to delineate more precisely the technical choices to be undertaken in order to tackle the clinical accuracy required on the beam fluence, typically a few %, during photon and electron high and ultra-high irradiations, the required minimal perturbation of the beam and the high level of radiation resistance.

Reactivity Index and Strength Development of High Strength Concrete with GGBFS Cement

The slag cement industry in Indonesia is growing in tandem with the smelter industry as a supplier of slag material. The use of slag cement instead of ordinary cement can reduce CO2 emissions. This research aimed to design the mixture composition of slag cement and ordinary cement for high-strength concrete. Standard concrete cylinders and concrete beams were tested to gain the compressive, tensile and flexural strength. The testing results indicate that generally, the concrete mixture compositions of low GGBFS (25%) gained their optimum strength at the age of 28 days while concrete with high composition of GGBFS (55%) achievedsimilar strength at the age of 90 days.A mixture using higher percentage replacement of GGBFS might attain its optimum strength at the longer ages. The use of Silica Fume (SF) in high-strength concrete mixtures with GGBFS found ineffective to increasethe concrete strength as the results indicate that concretes with SF have lower strength compared with non-SF concrete mixtures.

Systematic and quantitative comparison of lattice and Gaussian light-sheets

The axial resolving power of a light-sheet microscope is determined by the thickness of the illumination beam and the numerical aperture of its detection optics. Bessel-beam based optical lattices have generated significant interest owing to their reportedly narrow beam waist and propagation-invariant characteristics. Yet, despite their significant use in lattice light-sheet microscopy and recent incorporation into commercialized systems, there are very few quantitative reports on their physical properties and how they compare to standard Gaussian illumination beams. Here, we measure the beam properties in the transmission of dithered square lattices, which is the most commonly used variant of lattice light-sheet microscopy, and Gaussian-based light-sheets. After a systematic analysis, we find that square lattices are very similar to Gaussian-based light-sheets in terms of thickness, confocal parameter, propagation length and overall imaging performance.

Flexural response of composite beams made by Automated Fiber Placement process: Effect of fiber tow gaps

Automated Fiber Placement is one of the well-established composite fabrication techniques in both aerospace and automotive industries. However, new types of defects may be formed during the fiber steering due to replacing the prepreg sheets with the prepreg fiber tows. These defects can be a source of both intralaminar and interlaminar damages, which reduce the mechanical performance of the final products. Although the effect of these defects on the performance of the composite structure, especially the in-plane behavior can be found in the literature, there is still a lack of knowledge in the study of the mechanical performance of the composite structures with manufacturing induced defects. In the present study, the effect of automated manufacturing induced gaps on the mechanical response and failure of the Quasi-isotropic Carbon/Epoxy thin beams under out-of-plane loading is investigated. For this purpose, three-point bending tests are carried out on both short and standard beams to measure the interlaminar shear strength and flexural stiffness/strength of the composite beams with the gaps. The results are then compared with the results of the baseline sample (the one with no defect). Furthermore, Finite Element simulations are used to examine the stress distribution and also damage initiation and propagation of the composite beams under out-of-plane loading in the presence of the gaps. It is shown that the material scaling at the inhomogeneity area, which is widely used in the literature for Finite Element simulation of the composite structure with the gaps, is not sufficient for all scenarios of the loading and thickness scaling might also be applied to the models.

Analytical Modeling of the Postcracking Response Observed in Hybrid Steel/Polypropylene Fiber-Reinforced Concrete.

This study deals with the analytical modeling of hybrid fiber-reinforced concretes (HyFRCs) made with a blend of different types of fibers characterized by different geometries and/or constitutive materials. The presented analytical formulation is oriented towards predicting the postcracking behavior of HyFRC and is mainly based on the well-known “cracked-hinge” model originally employed for standard fiber-reinforced concrete beams. The proposed model is validated by considering the experimental results obtained in a previous study carried out on HyFRCs mixtures made with a blend of steel and polypropylene fibers. Theoretical results are presented to demonstrate the predictive capabilities of the model to simulate the observed experimental behavior. The model performance is in very good agreement with the experimental data. Therefore, it has the capability to forecast the postcracking behavior of a generic HyFRC of given fiber contents depending on the actual proportion of the fiber blend. Finally, the proposed formulation can be applied as a computational aid to the design of HyFRC mixtures for structural purposes.

Failure Propensity of GFRP Strengthen RC Beam

Fiber-reinforced polymer has eventually become a popular choice for retrofitting and strengthening of structural entities. Hence, a need arises to know the quantitative as well as qualitative effect of these techniques on the original integrity of the concerned structural entity. In the present study, the effect of change in width to depth ratio, percentage of steel and loading intensity in a simply supported reinforced concrete (RC) beam on the maximum deflection, stress, strain energy, natural frequencies and deflections of various modes of free vibration is obtained with the help of ANSYS Workbench 19.0 software till the failure of RC beam and a comparison is sought between the original beam and a failed beam retrofitted with one, two and three layers of GFRP sheets (Epoxy S-Glass UD). A standard beam of fixed dimensions and a two point loading was first simulated in the software while comparing the results with the manual calculations of maximum deflections to ascertain the most appropriate settings of the simulation in the three dimensional analysis environment of the software. Various beams were then analyzed altering the width to depth ratio, the percentage of tension steel and the loading intensity over the beam and the results of the static as well as modal (frequency) analysis were noted including the deflections, stresses, strains, strain energies, natural frequencies of first 5 modes of free vibrations and their respective displacements. The same beams were then retrofitted with layers of GFRP sheets with their principal axis inclined at an angle of 45° with the span of the beam. The same analysis was done on the beams and the results were noted. These results are compared, and a multivariate regression analysis is performed over the results to obtain equations to testify the observations and the trends. This whole process gives a conclusion that the effect of retrofitting is insignificant for single layer GFRP while the most effective results were obtained for the case of triple layer GFRP. Deflections, stress and strain energy with their relative change across various cases are accurately related to the varying parameters through regression analysis. Frequency is also accurately related but the relative change in frequency is not well established.

Proposal for the Promotion of Standardization of Precast Beams in Highway Concrete Bridges

Precast concrete beams for bridges are among the widely used applications of off-site construction with various standardized profiles and lengths being long used in different national contexts. The purpose of this paper is to highlight the important role of standardization in construction and promote the use of prefabrication in the design and construction of highway concrete bridges in countries with low construction industrialization. In this context, this research proposes a set of 45 standard precast extended – I beams, suitable for use in the majority of the common motorway bridge configurations. The selection of the proposed set of standard beams has emerged from data of 109 bridges (2,284 beams in total) constructed along the Egnatia Motorway and two of its perpendicular axes in Greece. Specifically, a database including the dimensions of the precast beams as built (length, depth, upper flange width (UFW), lower flange width (LFW) and web width (WW)), was first created. Following careful data review, 36 different combinations of depth, UFW and LFW and 64 different lengths were detected. Τhis, as well as further data analysis, demonstrated that in the project of Egnatia Motorway no attempt was made to globally standardize the beam configurations; as a result the efficiency benefits typifying standardization were not captured. Therefore, the dataset’s variables were subject to thorough statistical analysis, including multi-linear regression and correlation analysis, with the aim to determine a set of standard beam configurations. The resulting set of 45 beams represents 15 different lengths, coupled with 3 alternative depths each, in compliance to the regulatory requirements for the bridge’s effective width. Furthermore, this paper makes specific suggestions for a more effective procurement strategy which will be incorporating award criteria in favor of the use of off-site construction as well as the development of official guidelines enforcing the use of standard design elements. The important role of suitable contracts as well as the provision of training to the main stakeholders involved, are also highlighted. This proposal can help Greece, as well as other countries with non-well-established relevant standards, launch an effective strategy aimed at harnessing standardization’s efficiency benefits in bridge construction.

Adjustable ring mode and single beam fiber lasers: A performance comparison

The welding performance of adjustable ring mode (ARM) and standard single beam fiber lasers was analyzed from a steel welding perspective. The ARM laser has the capability of adjusting the distribution of laser power across beams. Thus, the ARM laser enabled an increase of penetration depth and minimized spatter formation. Furthermore, at the same total power, the ARM laser with higher power in the center than in the ring beam increased the depth of penetration in comparison with a standard fiber laser. However, applying more power in the ring beam than in the center beam noticeably reduced the accumulated spatter on the weld bead and surrounding area.

Experimentally Flexural Behaviour Study of Steel Beams with Corrugated Webs

The corrugated web girders had a wide applications because of its many favourable properties. Such as there is no need for intermediate stiffeners to avoid local buckling of the web and the reduction in web to produce by this technique. This study is an experimental investigation of flexural behaviour of I-section steel beams with corrugated webs and flat flange. The study involved testing six groups of steel beams. Each group consisted of two identical specimens and the average result was taken for compression. The first two groups consisted of standard and built-up I-section beams which served as a control beams. The other four groups content a corrugated web beams with different corrugation profiles (trapezoidal, rectangular, sinusoidal and zigzag). The experimental results showed that flexural contribution of the web does not exceed 7-11% from the total beam bending capacity for all configurations types. The rectangular corrugated web had the higher bending capacity and mid-span deflection among all the corrugation types.

Some characterization tests for an extrapolation chamber in CT standard beams in a specific chamber depth

The use of Computed Tomography (CT) for diagnostic images has been growing due to technological advances of this equipment. Therefore, there is a concern regarding the dose received by the patients undergoing this procedure, and this procedure needs to be performed with the highest precision and accuracy possible.The radiation detector used for CT beams is a pencil-type ionization chamber. However, there is no primary standard system for this kind of radiation beam. In this work a homemade extrapolation chamber was used to establish a CT primary standard [1]. This detector was tested for low-energy radiation beams and showing results within the internationally acceptable limits [2].This work had the objective to study the response stability of an extrapolation chamber, as well as obtaining the energy dependence and the angular dependence in standard CT beams of the Calibration Laboratory of IPEN (LCI).

Association between milk intake and childhood growth: results from a nationwide cross-sectional survey.

The literature is inconsistent regarding milk intake and physical growth. This study aims to evaluate the association of milk intake with body height and weight in a nationally representative sample of Chinese children. A total of 41,439 children ages 6-17 were recruited from 30 provinces in mainland China in 2013-2016 using a multistage stratified cluster sampling approach. Milk intake information was collected using a questionnaire aided with standard containers. Weight and height were measured using a standard physician beam scale with a height rod. Milk intake was categorized into no-, low-, and high-intake groups based on the intake rate, and weight status into normal, overweight, and obese groups based on the body-mass-index (BMI). Associations between height/weight status and milk intake were evaluated using multivariate weighted linear and logistic regression models. Chinese children had low milk intake: 1/5 of children did not drink milk, and those drinking milk had a median intake of 100 ml/month. The low- and high-intake groups were 0.83 cm (95% confidence interval: 0.00, 1.68 cm) and 1.26 cm (0.34, 2.19 cm) taller than the no-intake group for girls, respectively, after adjusting for confounding factors. Boys with high milk intake had lower BMI (-0.56, 95% CI: -1.00, -0.12 kg/m2) and risk of obesity (OR = 0.67, 95% CI: 0.46, 0.97) than those without milk intake. This study revealed the association of increased milk intake with increased body height and lowered obesity risk among Chinese children. Given the cross-sectional nature of the study and the possibility of residual confounding, further research is warranted to uncover the role of milk intake in promoting children's growth.

Super-resolution Imaging of the Protoplanetary Disk HD 142527 Using Sparse Modeling

Abstract With an emphasis on improving the fidelity even in super-resolution regimes, new imaging techniques have been intensively developed over the last several years, which may provide substantial improvements to the interferometric observation of protoplanetary disks. In this study, sparse modeling (SpM) is applied for the first time to observational data sets taken by the Atacama Large Millimeter/submillimeter Array (ALMA). The two data sets used in this study were taken independently using different array configurations at Band 7 (330 GHz), targeting the protoplanetary disk around HD 142527: one in the shorter-baseline array configuration (∼430 m), and the other in the longer-baseline array configuration (∼1570 m). The image resolutions reconstructed from the two data sets are different by a factor of ∼3. We confirm that the previously known disk structures appear on the images produced by both SpM and CLEAN at the standard beam size. The image reconstructed from the shorter-baseline data using the SpM matches that obtained with the longer-baseline data using the CLEAN, achieving a super-resolution image from which a structure finer than the beam size can be reproduced. Our results demonstrate that ongoing intensive development in the SpM imaging technique is beneficial to imaging with ALMA.

Phase I trial of nab-paclitaxel administered concurrently with radiotherapy in patients with locally advanced inoperable pancreatic adenocarcinoma (ART in LAP).

e16796 Background: Locally advanced pancreatic adenocarcinoma (LAPC) carries a poor prognosis with median overall survival of 12-18m. The optimal treatment is controversial. Nab-paclitaxel is active in advanced pancreatic cancer and has exhibited radio-sensitising anti-tumour efficacy. Methods: We conducted an investigator-initiated open-label, phase-I dose escalation trial of nab-paclitaxel with standard external beam radiotherapy (EBRT). All patients had biopsy-proven, untreated, localised, inoperable pancreatic adenocarcinoma; Patients received nab-paclitaxel on a weekly schedule for 6 weeks, concurrently with EBRT. A 3+3 cohort design was employed, with doses of nab-paclitaxel increasing from 25 mg/m2 (cohort 1), to 50 mg/m2 (cohort 2), 75 mg/m2 (cohort 3) and 100 mg/m2 (cohort 4). This principal objective of the trial was to establish the maximum tolerated dose (MTD) of nab-paclitaxel given concurrently with radiotherapy. Secondary objectives included safety and efficacy evaluation, including response rate, median PFS, median and 1- year OS. Results: Fourteen patients were recruited to the study, with a median age of 69 (range 40-86). 69% had a head or neck of pancreas tumour. Majority of patients had grade 1 or 2 toxicities with nausea (92%), fatigue (69%), diarrhoea (54%) and vomiting (54%) being the most common. Three patients were recruited in each of the first three cohorts, without any dose limiting toxicities (DLT). In cohort 4, DLT of febrile neutropenia and enterocolitis was observed in patient 1. The cohort was expanded with a subsequent DLT of febrile neutropenia and enterocolitis observed in patient 5. Both DLT events lead to death (grade 5). The MTD and recommended phase II study dose has been established as 75mg/ m2. The disease control (PR and SD) rate was 67%, median PFS 4.7 months (95% CI 2.5-27.5), 1 year OS 43% and median OS 11.4 months (95%CI 6.37-25.2). Conclusions: The combination of weekly nab-paclitaxel and fractionated radiation was generally well-tolerated at doses of nab-paclitaxel below 100 mg/m2. There were two treatment related DLTs leading to death in the nab-paclitaxel 100 mg/m2 cohort. The MTD and recommended phase II study dose for nab-paclitaxel combined with radiation therapy in the treatment of LAPC is 75mg/m2. Clinical trial information: ACTRN12613001013752 .

3D modeling of graphene oxide based nanoelectromechanical capacitive switch

The present work deals with 3D modeling of a novel configuration of a double clamped nanoelectromechanical (NEM) capacitive switch. In the proposed work, graphene oxide (GO) as a dielectric has been used as suspended beam material in NEM switch for the first time. Analysis of von Mises stress, pull-in, and pull-out voltages are investigated using COMSOL Multiphysics, for standard and perforated GO NEM switch structures. The actuation voltages of 5.4 V and 3.35 V are evaluated for standard and perforated beam structures respectively for the beam lengths of 1 µm and widths of 0.3 µm. The actuation voltage and von Mises stress value have reduced by making perforations in the beam. The von Mises stress comparative analysis of GO and graphene NEM switch exhibits that GO is a better choice for beam material as GO NEM switch withstand less von Mises stress than graphene NEM switch. The variation in capacitance including the fringing field capacitance is calculated as the beam is pulled down by the actuating electrode.

Analysis of Hybrid Vector Beams Generated with a Detuned Q-Plate

We use a tunable commercial liquid-crystal device tuned to a quarter-wave retardance to study the generation and dynamics of different types of hybrid vector beams. The standard situation where the q-plate is illuminated by a Gaussian beam is compared with other cases where the input beam is a vortex or a pure vector beam. As a result, standard hybrid vector beams but also petal-like hybrid vector beams are generated. These beams are analyzed in the near field and compared with the far field distribution, where their hybrid nature is observed as a transformation of the intensity and polarization patterns. Analytical calculations and numerical results confirm the experiments. We include an approach that provides an intuitive physical explanation of the polarization patterns in terms of mode superpositions and their transformation upon propagation based on their different Gouy phase. The tunable q-plate device presents worthy advantages, since it allows a compact and efficient generation of pure and hybrid vector beams to study these effects.

Mechanical Properties of Strengthened RC Beams using Steel Plates

The focus of this analysis is the review of steel plate strengthened RC beams using Single row and Stagger row bolt arrangements and to compare the bonding behaviour of different bolts arrangement under flexure. Also, to investigate the behaviour, load bearing capacity and the deflection for control and steel plate bonded beams. This research is constrained by FEM analysis utilizing ANSYS to the actions of standard RC Beam and RC beam steel plate associated.

Development of an Integrated Tool for Small-scale Maize Farming in Uganda

About 62% of the maize produced in developing countries is cultivated manually owing to limited access to appropriate technology. Available technologies perform a single operation, necessitating farmers to buy multiple implements, which is expensive. In this study, an ox-drawn tool integrating a plough, planter and cultivator for small-scale maize farming was developed and its performance evaluated. Planting and cultivating units were designed and fabricated for assembly onto an existing standard ox-plough beam. The integrated tool was tested in the field to assess the effectiveness and efficiency of cultivation and planting of maize. Results showed that the planting unit had an average seed rate of 35.4 kg ha-1 with a seed damage of 4% and an effective field capacity of 0.15 ha h-1 at a field efficiency of 87.3%. The cultivating unit had an effective field capacity of 0.1 ha h-1 and a weeding efficiency of 86%. The efficiency, effectiveness and reliability for field operations are superior to manual operations currently used by farmers and are comparable to single-unit prototypes developed in other countries. This demonstrates the technical feasibility of integrating planting and cultivation units onto an existing mouldboard plough instead of buying multiple tools.

Two-year outcomes of moderately hypofractionated 70 Gy in 28 fractions, intensity-modulated radiotherapy and volumetric modulated arc therapy for localised prostate cancer

AbstractIntroduction:Standard external beam radiotherapy is a treatment option for patients with localised prostate cancer and is used in patients with low-, intermediate- and high-risk disease with androgen deprivation according to the risk of the disease. In the last few years, hypofractionated radiotherapy has been demonstrated to be as safe as standard radiotherapy if given over a shorter time than standard radiotherapy with larger doses per fraction. External radiotherapy for localised prostate cancer typically delivers 37–42 fractions of 1·8–2·0 Gy per fraction given 5 days per week over 7·5–8·5 weeks. Hypofractionated radiotherapy delivers 20–28 fractions of 2·5–2·6 Gy per fraction given 5 days per week over 4–5·6 weeks.Methods:A retrospective analysis of assessment of 30 patients was undertaken from 2016 to 2018. The aim of this study was to evaluate the 2-year outcomes of 30 patients with prostate cancer treated with hypofractionated radiotherapy 70 Gy in 28 fractions.Results:Biochemical failure with hypofractionated radiotherapy was found in a total of 20% of patients. In the classification by risk groups, there were no biochemical failures in low-risk patients; in the low intermediate course, 3·3% of patients; in the high intermediate group, 3·3% patients; and in the high-risk group, the largest documented biochemical failure was in 13·3% of patients. For acute urinary toxicity, grade I was 56·6%; grade II, 6·6%. For acute rectal toxicity, grade I was 46·6%; grade II, 3·3%.Conclusion:This is one of the first studies of hypofractionated radiotherapy in prostate cancer in Latin America, and the results of this study demonstrated that the outcomes were similar to the standard regimen in all risk groups.

Radiation dose assessment of 64 Multi-Slices Computed Tomography scanner

This paper reports the performance and dose assessment of the X-ray generator and CT dosimetry of 64 Multi-Slices Computed Tomography (MSCT) scanners operating under the CT scanning condition during the axial mode. The dose was evaluated at various parameters (kV, mA, and exposure time) using a multi-function detector (Unfors) and nanoDot™ optically stimulated luminescence dosimeters (OSLDs). The measured values of the weighted CT Dose Index (CTDIw) were obtained using a 100 mm standard pencil beam ion chamber and nanoDot™ OSLDs operated on a cylindrical PMMA phantom of 160 mm long (160 mm-diameter head and 320 mm-diameter). The CTDIw values were specified either according to the central axis or 10 mm from the 4 outer edges of the phantom. The two sizes of the phantoms based on the measurements of the CTDIw of the CT scanner were recorded. The values of CTDIw were calculated to determine the performance of the CT X-ray generator. The deviation accuracy of the tube voltage was ±5 kV or ±5% (whichever is greater) whereas the accuracy of the tube potential (mA) was ±10%. The execution of the CT dosimetry steps was shown to ensure patient safety with reduced risk during the improper selection of the dose. It is established that the measured CTDIw values for the radiation dosage under exceptional CT scanning conditions in the axial mode may enable to meet the manufacturer's guidelines (<±20%).

A method for automated digital image‐based tracking of delamination fronts in translucent glass fibre‐laminated composite materials

AbstractA new automated digital image‐based method for tracking both the position and shape of the crack front of delaminations in translucent glass fibre‐laminated test specimens is proposed. The method is applicable to both fracture toughness tests and fatigue tests. The digital image‐based algorithm identifies the newly formed crack area by the change in reflected light and then extracts both the crack front shape and the position. The method is used in a standard double cantilevered beam specimen test setup with the addition of light sources and a camera. The method does not rely on subjective test operator interpretations or calibrations. A reference pattern on the specimen is used to correctly map between the camera coordinate system and the specimen coordinate system, which makes the method insensitive to the camera position and camera or specimen movement during the test. Experimental test examples are provided, which shows that the whole crack front can be tracked with significantly higher accuracy than possible with existing methods.