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Abstract: Micro Proton Induced X-ray Emission (μ-PIXE) analysis has been employed herein in investigating and quantifying the distribution of a number of essential elements in thin human diseased articular cartilage sections affected by osteoarthritis (OA). Various cations Ca, P and Zn have been reported to play an important role both in the normal growth and remodelling of articular cartilage and subchondral bone as well as in the degenerative and inflammatory processes associated with the disease; they act as co-factors of a class of enzymes known as metalloproteinases which are believed to be active during the initiation, progress and remodelling processes associated with osteoarthritis. Other important enzymes such as alkaline phosphatase are associated with cartilage mineralization. Synchrotron radiation X-ray fluorescence (SR-XRF) for mapping of elemental distributions in bone and cartilage has also been employed by the present group and others. In the current investigations using the cSAXS beamline at the Swiss light source, Small-Angle X-ray Scattering (SAXS) was carried out on decalcified human articular cartilage to explore the structural and organizational changes of collagen networks in diseased articular cartilage. [Copyright &y& Elsevier]

Abstract: Clinical radiography has traditionally been based on contrast obtained from absorption when X-rays pass through the body. The contrast obtained from traditional radiography can be rather poor, particularly when it comes to soft tissue. A wide range of media of interest in materials science, biology and medicine exhibit very weak absorption contrast, but they nevertheless produce significant phase shifts with X-rays. The use of phase information for imaging purposes is therefore an attractive prospect. Some of the X-ray phase-contrast imaging methods require highly monochromatic plane wave radiation and sophisticated X-ray optics. However, the propagation-based phase-contrast imaging method adapted in this paper is a relatively simple method to implement, essentially requiring only a microfocal X-ray tube and electronic detection. In this paper, we present imaging results obtained from two different benchtop X-ray sources employing the free space propagation method. X-ray phase-contrast imaging provides higher contrast in many samples, including biological tissues that have negligible absorption contrast. [Copyright &y& Elsevier]

A dead-end filtration set-up with a vertically vibrated medium is used to study cake permeation. A key feature of these experiments is that a sudden increase in permeability at a certain critical vibration amplitude takes place, when the static loading is light. A theory to explain this phenomenon is put forward in terms of a relation to local fluidization near the medium, thus returning the clogged septum resistance to virtually its unclogged value. The fluidization is due to a particle stress induced by the vibration of the particle fluid mixture near the medium. This stress can be large enough to counteract the compressive stress that is caused by gravity and drag due to the fluid flow in the set-up.Estimates for the particle stresses are obtained; these are proportional to the amplitude decay inverse length λ. The latter is derived from the analysis of a vibrated particle–fluid mixture that is in a state of fluidization. It is argued that only in this state will the value of λ be large enough to generate the required particle stress. A much smaller value for λ is obtained when the particles in the medium make enduring contacts.The theory predicts a frequency dependence for the turnover point in the permeability according to the root of the applied frequency. This theoretical result is confirmed by the experiments. The theory also predicts that when the decay is too steep, so that the vibration amplitude vanishes at a distance of less than a particle diameter, no fluidization will occur. This is found to be true for larger cake masses. [Copyright &y& Elsevier]

Abstract: This paper discusses a method to determine the thickness of an absorber using the energy distribution of beta particles. An empirical relationship was obtained between the absorber thickness and the energy distribution of beta particles transmitted through. The thickness of a polyethylene radioactive source cover was determined by exploiting this relationship, which has largely been left unexploited allowing us to determine the in-situ cover thickness of beta sources in a fast, cheap and non-destructive way. [Copyright &y& Elsevier]

Abstract: The investigations reported herein link tissue structure and elemental presence with issues of environmental health and disease, exemplified by uptake and storage of potentially toxic elements in the body, the osteoarthritic condition and malignancy in the breast and other soft tissues. Focus is placed on application of state-of-the-art ionizing radiation techniques, including, micro-synchrotron X-ray fluorescence (μ-SXRF) and particle-induced X-ray emission/Rutherford backscattering mapping (μ-PIXE/RBS), coherent small-angle X-ray scattering (cSAXS) and X-ray phase-contrast imaging, providing information on elemental make-up, the large-scale organisation of collagen and anatomical features of moderate and low atomic number media. For the particular situations under investigation, use of such facilities is allowing information to be obtained at an unprecedented level of detail, yielding new understanding of the affected tissues and the progression of disease. [Copyright &y& Elsevier]

Abstract: There is a growing interest being shown in the changes occurring in elemental distribution at the bone–cartilage interface, the changes either being a result of mechanical damage or disease. In particular, such investigations have tended to concern the elemental alterations associated with the osteoarthritic wear and tear damage occurring to the cartilage and subchondral bone of synovial joints or that associated with disease processes such as rheumatic arthritis. Present studies examine sections of femoral head obtained from total hip replacement surgery, use being made of micro-proton-induced X-ray emission (μ-PIXE) and the Rutherford back scattering (RBS) techniques. Enhancements of Zn, Ca and P have been observed at the bone–cartilage interface. Further, the concentration of Zn in spongy bone underlying the subchondral surface of a section of the femoral head has been measured, obtaining 136μgg−1 bone, the presence of Ca and P at the same position being 0.235 and 0.0451gg−1 bone, respectively. These values are slightly different to figures recently published by other authors using similar techniques. [Copyright &y& Elsevier]

Abstract: The LB 1000-PW detector is mainly used for determining total alpha, beta and gamma activity of low activity natural sources such as water, soil, air filters and any other environmental sources. Detector efficiency needs to be known in order to measure the absolute activity of such samples. This paper presents results on the total gamma counting efficiency of a Phoswich detector from point and disk sources. The directions of photons emitted from the source were determined by Monte Carlo techniques and the true path lengths in the detector were determined by analytical equations depending on photon directions. Results are tabulated for various gamma energies. [Copyright &y& Elsevier]

Abstract: Since last decade, Pulsed Laser Ablation in Liquid (PLAL) has become an increasingly important technique for the production of the nanoparticles (NPs) since it usually provides high purity nanoparticle systems. This paper reports on the production and fragmentation of titanium oxide TiO2 nanoparticles by pulsed laser ablation of a titanium target immersed in Sodium Dodecyl Sulfate (SDS) solution using an ultrafast Ti:Sapphire laser. After the production of TiO2 nanoparticles for 30min of laser irradiation, second harmonics of the laser wavelength are re-applied for different energies (180,120, 60µJ) to SDS solution containing TiO2 colloids in order to fragment relatively large pieces to obtain smaller ones. It was found that size of nanoparticles after the treatment is independent of the initial characteristics of colloids, but depends strongly on laser parameters especially pulse energy and on the presence of chemically active species in the solution. It was reported that particle size and size distribution range can be decreased using second harmonics of Ti:Sapphire laser wavelengths by using different values of energy. Re-irradiation process at average energy value of 180μJ decreased average particle size from 185nm to 110nm. Characterization of the NPs was studied by applying various techniques such as UV–visible (UV–vis.), Transmission Electron Microscope (TEM), Dynamic Light Scattering (DLS) and Fourier Transform Infra-Red (FTIR). [Copyright &y& Elsevier]

Abstract: This paper reports the production of gold nanoparticles (NPs) with controlled morphology in an aqueous solution of sodium dodecyl sulfate (SDS) by Ti:Sapphire laser. When nanostructures were exposed to an additional laser irradiation/exposure at a particular wavelength corresponding to resonant excitation of surface plasmons or to an interband transition, a considerable size reduction of NPs from 78nm to 15nm has been achieved. This can simply be defined as size refining of NPs by a two-step laser ablation. The relationship between supercontinuum (SC) emission and absorption spectrum of gold NPs has been explored. Additionally the transformation of gold NPs into fractal-like structures has been examined. At longer exposure periods, it is observed that there is a tendency of assembling of NPs into one-dimensional (1d) nanostructures. [Copyright &y& Elsevier]

Abstract: This paper reports an experimental study of welding of dissimilar materials between transparent Polymethylmethacrylate (PMMA) and stainless steel 304 sheets using a pulsed mode Nd:YAG laser. The process was carried out for two cases; laser transmission joining (LTJ) and conduction joining (CJ). The former is achieved when the joint is irradiated from the polymer side and the latter when the joint is irradiated from the opposite side (metal side). The light and process parameters represented by the peak power (P p), pulse duration (τ), pulse repetition rate (PRR), scanning speed (ν) and pulse shape have a significant effect on the joint strength (F b), joint bead width (b), joint quality and appearance. The optimum parameters were determined according to joint quality, joint strength and bead width. The optimum results for the joint strength and bead width for both LTJ and CJ are 925N, 7.25mm and 495N, 8mm respectively using a rectangular pulse shape (RC). Further modeling studies were carried out based on two methods; one factor at a time method (OFM) and surface response methodology (RSM) method. RSM was used to determine optimum parameters for the experimental data building mathematical models for correlating parameters and responses (Fb and b) as well as to investigate how different parameters interact with each other and their effect on the weld quality. [Copyright &y& Elsevier]

Abstract: A Monte Carlo simulation study has been conducted of 60Co photons Compton scattered in concrete, illustrating the degraded energy spectra of gamma-ray radiation. Results are produced representing a NaI(Tl) detector model. We were able to analyse energy distributions of photons that reach the detector system after suffering several successive Compton scatterings in the target. The predicted decrease in intensity of single- and multiple-scattering peaks with increase in thickness of the target medium are in good agreement with experimental observations and findings reported by others. [Copyright &y& Elsevier]

Abstract: This paper reports a process by which two copper plates are welded together by using a millisecond pulse Nd:YAG laser with the addition of stellite 6 powder which increases the absorption of laser energy. It also reports an interesting application of Laser Induced Breakdown Spectroscopy (LIBS) in order to determine the elemental composition and diffusion of stellite 6 powder into the copper plates. The effects of laser peak power and pulse duration are examined to optimize the welding. The amount of stellite 6 powder is also optimized for a high quality welding. The tensile strength and hardness values are measured for different laser parameters. The EDX and SEM results show that the stellite 6 powder particles penetrate into the copper plates and increase the hardness. The elements in laser weld joints of copper plates were analyzed with LIBS, utilizing a high resolution multi-channel CCD spectrometer and a nanosecond pulse Nd:YAG laser, providing a depth profile of elemental composition of the penetrated region. [Copyright &y& Elsevier]

Abstract: Investigation is made on the energy spectrum of photons originating from interactions of 662keV primary gamma-ray photons emitted by a point source positioned at the centre of a water equivalent solid phantom of dimensions 19cm×19cm×24cm. Peaks resulting from total energy loss (photopeak) and multiple and back scattering have been observed using a 51mm×51mm NaI(Tl) detector; good agreement being found between the measured and simulated response functions. The energy spectrum of the gamma photons obtained through the Monte Carlo simulation reveals local maxima at about 100keV and 210keV, being also observed in the experimental response function. Such spectra can be used as a method of testing the water equivalence of solid phantom media before their use for dosimetry measurements. [Copyright &y& Elsevier]

Abstract: Alumina ceramics have found wide range of applications from semiconductors, communication technologies, medical devices, automotive to aerospace industries. Processing of alumina ceramics is rather difficult due to its high degree of brittleness, hardness, low thermal diffusivity and conductivity. Rapid improvements in laser technologies in recent years make the laser among the most convenient processing tools for difficult-to-machine materials such as hardened metals, ceramics and composites. This is particularly evident as lasers have become an inexpensive and controllable alternative to conventional hole drilling methods. This paper reports theoretical and experimental results of drilling the alumina ceramic with thicknesses of 5mm and 10.5mm using milisecond pulsed Nd:YAG laser. Effects of the laser peak power, pulse duration, repetition rate and focal plane position have been determined using optical and Scanning Electron Microscopy (SEM) images taken from cross-sections of the drilled alumina ceramic samples. In addition to dimensional analysis of the samples, microstructural investigations have also been examined. It has been observed that, the depth of the crater can be controlled as a function of the peak power and the pulse duration for a single laser pulse application without any defect. Crater depth can be increased by increasing the number of laser pulses with some defects. In addition to experimental work, conditions have been simulated using ANYS FLUENT package providing results, which are in good agreement with the experimental results. [Copyright &y& Elsevier]

Abstract: Synovial joints articulate in a lubricating environment, the system providing for smooth articulation. The articular cartilage overlying the bone consists of a network of collagen fibres. This network is essential to cartilage integrity, suffering damage in degenerative joint disease such as osteoarthritis. At Surrey and also in work conducted by this group at the Paul Scherrer Institute (PSI) synchrotron site we have been applying a number of techniques to study the bone–cartilage interface and of changes occurring in this with disease. One of the techniques attracting particular interest is X-ray phase contrast imaging, yielding information on anatomical features that manifest from the large scale organisation of collagen and the mineralised phase contained within the collagen fibres in the deep cartilage zone. This work briefly reviews some of the basic supporting physics of X-ray phase contrast imaging and then shows example images of the articular surface and subchondral bone and other supporting results obtained to-date. Present results have been obtained on sections of bone not displaying evidence of an osteoarthritic lesion and can be used as a baseline against which diseased bone can be compared. [Copyright &y& Elsevier]

Abstract: This paper presents results on the angular distribution of Compton scattering of 662keV gamma photons in both forward and backward hemispheres in copper medium. The number of scattered events graph has been determined for scattered gamma photons in both the forward and backward hemispheres and theoretical saturation thicknesses have been obtained using these results. Furthermore, response function of a 51×51mm NaI(Tl) detector at 60° angle with incoming photons scattered from a 10mm thick copper layer has been determined using Monte Carlo method. [Copyright &y& Elsevier]

Abstract: The main objective of the present study is to determine the type of environmental contamination in lichens in Gökçeada Island in the Northern Aegean Sea in Turkey. We used two different lichen species Cladonia foliacea and Ramalina pollinaria. In the first part of the investigation, the beta activities of lichens have been measured by using a TENNELEC LB 1000-PW detector. The range of beta activity values was between 607 ± 30 and 308 ± 12 Bq/kg for C. foliacea lichens collected from around Tuz Lake and values for R. pollinaria lichens were found to be 740 ± 25 and 541 ± 17 Bq/kg. The second part of the study was concerned with the gamma spectra of the lichen samples measured by using HpGe detector. 137Cs, 134Cs, 40K, 232Th, 226Ra radionuclides were found in C. foliacea collected from around Tepeköy and in R. pollinaria from around Tuz Lake. When these two types of lichens were compared, it was found that R. pollinaria contain more radionuclides. In order to compare and determine which of these lichens act as a better bioaccumulator, K, Mn, Zn, Rb, Sr, Ba and Pb metal content were determined by using Energy Dispersive X-ray fluorescence spectrometry. It was found that C. foliacea collected more Mn and Sr when compared to R. pollinaria. [Copyright &y& Elsevier]

Abstract: The mass energy absorption, the mass energy transfer and mass absorption coefficients have been widely used for problems and applications involving dose calculations. Direct measurements of the coefficients are difficult, and theoretical computations are usually employed. In this paper, analytical equations are presented for determining the mass energy transfer and mass absorption coefficients for gamma rays with an incident energy range between 0.4 and 10MeV in nitrogen, silicon, carbon, copper and sodium iodide. The mass absorption and mass energy transfer coefficients for gamma rays were calculated, and the results obtained were compared with the values reported in the literature. [Copyright &y& Elsevier]

Abstract: This paper presents results on the total gamma counting efficiency of a NaI(Tl) detector from point and disk sources. The directions of photons emitted from the source were determined by Monte-Carlo techniques and the photon path lengths in the detector were determined by analytic equations depending on photon directions. This is called the hybrid Monte-Carlo method where analytical expressions are incorporated into the Monte-Carlo simulations. A major advantage of this technique is the short computation time compared to other techniques on similar computational platforms. Another advantage is the flexibility for inputting detector-related parameters (such as source–detector distance, detector radius, source radius, detector linear attenuation coefficient) into the algorithm developed, thus making it an easy and flexible method to apply to other detector systems and configurations. The results of the total counting efficiency model put forward for point and disc sources were compared with the previous work reported in the literature. [Copyright &y& Elsevier]

Abstract: In this Letter, an expression is presented to calculate elastic scattering cross sections for incident electrons as a function of both energy and atomic number in the energy range between 1 keV and 1 MeV for materials with effective atomic number between 3 and 18. The expression we present has a rather simple analytical form which gives accurate results that are in very good agreement with the results calculated by a relativistic partial-wave expansion method. Hence, this equation can be employed accurately and efficiently in a continuous manner, without the need to go through rather large look-up tables, thus making the whole process quick, efficient and removing possible computational errors that may arise from the efforts of interpolation. [Copyright &y& Elsevier]