Pretoria, South Africa
Pretoria, South Africa

Time filter

Source Type

Kaestner A.P.,Paul Scherrer Institute | Lehmann E.H.,Paul Scherrer Institute | Hovind J.,Paul Scherrer Institute | Radebe M.J.,Radiation Science | And 2 more authors.
Physics Procedia | Year: 2013

In an effort to provide a standardized method to quantify the imaging capabilities of neutron imaging beam-lines worldwide, we propose a set of test objects for neutron tomography. The test objects are designed to quantify spatial resolution and material contrast in tomograms. The resolution samples aim at detecting a thin film embedded in a different material. Two samples with complementary material compositions are proposed for this purpose. The contrast sample has several insets of different materials. The measurements are proposed to be done using both radiography and tomography. The image processing methods needed to evaluate the performance of the reconstructed data are presented. The methods are automated to avoid subjective decisions by persons who evaluate the data. Experimental data to demonstrate the test objects and their analysis methods were acquired with the cold neutron imaging beam-line, ICON, in comparison with data from the thermal neutron facility, NEUTRA at Paul Scherrer Institut, Switzerland. This is a first initiative and is open for discussion among the participants to further improve the evaluation procedure. © 2013 The Authors.

Fijal-Kirejczyk I.M.,National Center for Nuclear Research andrzeja Soltana | Milczarek J.J.,National Center for Nuclear Research andrzeja Soltana | Radebe M.J.,Radiation Science | de Beer F.C.,Radiation Science | And 2 more authors.
Drying Technology | Year: 2013

The application of modern digital neutron radiography in the study of the drying process in porous media is demonstrated with two simple examples of cylindrical and rectangular samples made of different materials. The statistical method of image analysis is presented and the standard deviation of grey scale values (referred to brightness) is shown to be a useful measure of receding drying front emergence. The motion of the drying front was analyzed and found neither linear nor proportional to the square root of time and was delineated with nonlinear functions different for each sample shape. © 2013 Copyright Taylor and Francis Group, LLC.

Smith A.,Ditsong National Museum of Cultural History | Botha H.,South African Institute for Objects Conservation | De Beer F.C.,Radiation Science | Ferg E.,Nelson Mandela Metropolitan University
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2011

The production techniques, corrosive deterioration, conservation and questions regarding authenticity of a small Egyptian bronze statuette of the Child Horus (in the collection of the Ditsong: National Museum of Cultural History in Pretoria) was scientifically examined and analysed. The statuette dates to Egypts 12th Dynasty. When the statuette was damaged, it was considered the appropriate time to obtain valuable information about its history and background through scientific research. Neutron tomography (NT), a relatively new non-destructive technique (NDT) to the South African R&D community to study museum objects, was applied to perform this research. The results from NT were supported by additional tests done through XRF and XRD analyses of samples taken from the damaged statuette. Results revealed that the lost-wax method was used in the manufacturing process. The extent of the restoration and materials used can be verified and as a result the deterioration of the object can now be monitored. This paper describes in detail the analytical techniques used in the study and how it contributed to the conservation of the statuette and its authenticity. © 2011 Elsevier B.V. All rights reserved.

Jacobson L.,McGregor Museum | Jacobson L.,Cape Peninsula University of Technology | De Beer F.C.,Radiation Science | Nshimirimana R.,Radiation Science
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2011

We demonstrate the use of both neutron- and X-ray imaging in two projects. The first project, using both the methods to view the temper in a ceramic sherd in order to model the effect the chemical composition of the temper has on the bulk chemical composition of the sherd showed that X-ray imaging is superior to neutron imaging for a ceramic. The second project, to establish whether apparent incised lines on stone slabs (dated to greater than 180,000 years ago) are natural or artificial, i.e., whether they were deliberately incised or natural, random striations showed conclusively that the incisions are in fact surface manifestations of natural internal fractures in the rock. © 2011 Elsevier B.V. All rights reserved.

Radebe M.J.,Radiation Science | De Beer F.C.,Radiation Science | Nshimirimana R.,Radiation Science
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2011

Qualitative measurements using digital neutron imaging has been the more explored aspect than accurate quantitative measurements. The reason for this bias is that quantitative measurements require correction for background and material scatter, and neutron spectral effects. Quantitative Neutron Imaging (QNI) software package has resulted from efforts at the Paul Scherrer Institute, Helmholtz Zentrum Berlin (HZB) and Necsa to correct for these effects, while the sample-detector distance (SDD) principle has previously been demonstrated as a measure to eliminate material scatter effect. This work evaluates the capabilities of the QNI software package to produce accurate quantitative results on specific characteristics of porous media, and its role to nondestructive quantification of material with and without calibration. The work further complements QNI abilities by the use of different SDDs. Studies of effective %porosity of mortar and attenuation coefficient of water using QNI and SDD principle are reported. © 2011 Elsevier B.V. All rights reserved.

Fijal-Kirejczyk I.M.,National Center for Nuclear Research | Milczarek J.J.,National Center for Nuclear Research | Zoladek-Nowak J.,National Center for Nuclear Research | De Beer F.C.,Radiation Science | And 2 more authors.
Acta Physica Polonica A | Year: 2012

The statistical approach to the thermal neutron radiography picture analysis is applied to evaluation of the experimental results obtained for drying of rectangular and cylindrical samples of granulated and rigid porous materials. We have shown that the time dependence of the standard deviation of image brightness reflects the appearance and motion of the drying front observed during second period of the drying process. The results are discussed within a simple two-region model of the drying sample image.

Viljoen J.,North West University South Africa | Campbell Q.P.,North West University South Africa | Le Roux M.,North West University South Africa | De Beer F.,Radiation Science
International Journal of Coal Preparation and Utilization | Year: 2015

The degradation of coal and the production of coal fines during handling and transport is a serious problem in processes that depend on closely sized large particles. To minimize the production of fines, a fundamental understanding of coal breakage is required, so, to clarify the complex nature of coal breakage, a series of experiments was conducted to determine the influence of the internal physical coal structures on compression breakage characteristics. The structures investigated are the cleat and layered structure of coal and the mineral inclusions. Samples of uniform size and shape were prepared from a large block of South African Waterberg coal. The samples were analyzed nondestructively using microfocus X-ray computed tomography then wrapped in cling film and mechanically compressed while the pressure applied was measured. The virtual three-dimensional volume tomograms of the initial sample and the progeny were compared and the changes qualitatively analyzed. Conclusions were drawn as to where the fatal cracks initialized and how the cracks propagated. Particle-size distributions were done to quantify the extent of breakage versus the breakage strength of the sample. It was found that, of all the internal structures, the inherent crack distribution has the biggest influence on breakage and breakage patterns of coal. © 2015 Taylor & Francis Group, LLC.

Birgander R.,Radiation science | Eklund A.,Umeå University
Acta Neurologica Scandinavica | Year: 2011

Objective - Cerebrospinal fluid (CSF) dynamics and long-term shunt survival of the Strata® CSF shunt were evaluated in patients with idiopathic normal pressure hydrocephalus (INPH). Subjects and methods - Seventy-two patients with INPH received a Strata® valve. A CSF infusion test, neuroimaging and video recording of gait were performed at baseline and at 6 months (n=68) after surgery. Long-term shunt survivals were obtained from patient records. Results - The shunt survival at 1year was 94% and at 3years 92.5%. Forty-nine patients (72%) had an improved gait. Two patients were improved despite non-functioning shunts, indicating a possible placebo response. Nineteen patients were not improved at the 6-month follow-up. The shunt tests revealed a functioning shunt in 12; thus, unnecessary shunt revisions could be avoided. Seventeen patients showed a siphoning effect. Shunt revisions were made in six patients. Eight hygromas/subdural hematomas were found. Conclusions - The long-term survival of the Strata® valves was good, and a concern of complications is not a reason to exclude elderly with INPH from shunt surgery. Studies are needed to evaluate pros and cons of the anti-siphon device. Using a CSF shunt test, unnecessary shunt revisions may be avoided. © 2010 John Wiley & Sons A/S.

De Beer F.C.,Radiation Science | Radebe M.J.,Radiation Science | Schillinger B.,TUM | Nshimirimana R.,Radiation Science | And 2 more authors.
Physics Procedia | Year: 2015

A common denominator of all neutron radiography (NRAD) facilities worldwide is that the perimeter of the experimental chamber of the facility is a radiation shielding structure which,in some cases, also includes flight tube and filter chamber structures. These chambers are normally both located on the beam port floor outside the biological shielding of the neutron source. The main function of the NRAD-shielding structure isto maintain a radiological safe working environment in the entire beam hall according to standards set by individual national radiological safety regulations. In addition, the shielding's integrity and capability should not allow, during NRAD operations, an increase in radiation levels in the beam port hall and thus negatively affectadjacent scientific facilities (e.g. neutron diffraction facilities).As a bonus, the shielding for the NRAD facility should also prevent radiation scattering towards the detector plane and doing so, thus increase thecapability of obtaining better quantitative results. This paper addresses Monte Carlo neutron-particletransport simulations to theoretically optimize the shielding capabilities of the biological barrierfor the SANRAD facility at the SAFARI-1 nuclear research reactor in South Africa. The experimental process to develop the shielding, based on the principles of the ANTARES facility, is described. After casting, the homogeneity distribution of these concrete mix materials is found to be near perfect and first order experimental radiation shielding characteristicsthrough film badge (TLD) exposure show acceptable values and trends in neutron- and gamma-ray attenuation. © 2015 The Authors.

PubMed | Radiation science
Type: Journal Article | Journal: Journal of clinical oncology : official journal of the American Society of Clinical Oncology | Year: 2016

9627 Background: This study was conducted to investigate if the previously described human gene LRIG1 is of interest in the malignant process of breast cancer. The gene is the human homologue of mouse Lig-1 and is located on chromosome band 3p14.3, a region frequently deleted in human cancers and previous studies of 3p have implicated that a tumour suppressor gene might be located in the area. This gene encodes a transmembrane cell surface protein with extracellular leucine-rich repeats and immunoglobulin-like regions. LRIG1 mRNA and protein has been detected in various tissues, with average levels in breast tissue.The present study was to characterize the expression of LRIG1 in breast cancer by FISH, CGH, quantitative RT-PCR, Western Blot and immunohistochemistry. Two subgroups were analysed; one group consists of randomly taken tumour samples from 19 patients collected 1987-1995 and the other group included consecutively samples of tumours from 9 patients with parallel sampled non-neoplastic breast tissues for comparison Results: Amplification of LRIG1 was found in 11 of 28 (39%) of tumours, resulting in an overexpression of mRNA and protein. The amplification correlated with increased levels of mRNA and protein by RT-PCR and Western blot.Amplification of LRIG1 in chromosome 3p14.3 is a novel observation indicating a role of LRIG1 in breast cancer. No significant financial relationships to disclose.

Loading Radiation Science collaborators
Loading Radiation Science collaborators