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arXiv2010

A modified porous titanium sheet prepared by plasma activated sintering for biomedical applications

This study aimed to develop a contamination free porous titanium scaffold by a plasma activated sintering within an originally developed TiN coated graphite mold. The surface of porous titanium sheet with or without a coated graphite mold was characterized. The cell adhesion property of porous titanium sheet was also evaluated in this study. The peak of TiC was detected on the titanium sheet processed with the graphite mold without a TiN coating. Since the titanium fiber elements were directly in contact with the carbon graphite mold during processing, surface contamination was unavoidable event in this condition. The TiC peak was not detectable on the titanium sheet processed within the TiN coated carbon graphite mold. This modified plasma activated sintering with the TiN coated graphite mold would be useful to fabricate a contamination free titanium sheet. The number of adherent cells on the modified titanium sheet was greater than that of the bare titanium plate. Stress fiber formation and the extension of the cells were observed on the titanium sheets. This modified titanium sheet is expected to be a new tissue engineering material in orthopedic bone repair.

q-bio.CB↗

arXiv2010

Bone regenerative potential of mesenchymal stem cells on a micro-structured titanium processed by wire-type electric discharge machining

A new strategy with bone tissue engineering by mesenchymal stem cell transplantation on titanium implant has been dawn attention. The surface scaffold properties of titanium surface play an important role in bone regenerative potential of cells. The surface topography and chemistry are postulated to be two major factors increasing the scaffold properties of titanium implants. This study aimed to evaluate the osteogenic gene expression of mesenchymal stem cells on titanium processed by wire-type electric discharge machining. Some amount of roughness and distinctive irregular features were observed on titanium processed by wire-type electric discharge machining. The thickness of suboxide layer was concomitantly grown during the processing. Since the thickness of oxide film and micro-topography allowed an improvement of mRNA expression of cells, titanium processed by wire-type electric discharge machining is a promising candidate for mesenchymal stem cell based functional restoration of implants.

q-bio.CB↗

arXiv2010

The Electron Capture Hypothesis - A Challenge to Neuroscientists

Lower speed impinging ions (with hydration shells) cannot transverse ion channels once internal charge goes positive. Yet neural pulse waveforms fail to show the expected risetime distortion beginning at zero voltage. Observed waveforms cannot be explained unless electron capture is considered.

q-bio.NC↗

arXiv2010

Perception of Surface Defects by Active Exploration with a Biomimetic Tactile Sensor

We investigate the transduction of tactile information during active exploration of finely textured surfaces using a novel tactile sensor mimicking the human fingertip. The sensor has been designed by integrating a linear array of 10 micro-force sensors in an elastomer layer. We measure the sensors' response to the passage of elementary topographical features in the form of a small hole on a flat substrate. The response is found to strongly depend on the relative location of the sensor with respect to the substrate/skin contact zone. This result can be quantitatively interpreted within the scope of a linear model of mechanical transduction, taking into account both the intrinsic response of individual sensors and the context-dependent interfacial stress field within the contact zone. Consequences on robotics of touch are briefly discussed.

cond-mat.soft↗

arXiv2010

Is it Possible to Extract Metabolic Pathway Information from In Vivo H Nuclear Magnetic Resonance Spectroscopy Data?

In vivo H nuclear magnetic resonance (NMR) spectroscopy is an important tool for performing non-invasive quantitative assessments of brain tumour glucose metabolism. Brain tumours are considered fast-growth tumours because of their high rate of proliferation. In addition, tumour cells exhibit profound genetic, biochemical and histological differences with respect to the original non-transformed cell types. Therefore, there is strong interest from the clinical investigator's point of view in understanding the role of brain metabolites under normal and pathological conditions and especially in the development of early tumour detection techniques. Unfortunately, current diagnosis techniques ignore the dynamic aspects of these signals. It is largely believed that temporal variations of NMR Spectra are simply due to noise or do not carry enough information to be exploited by any reliable diagnosis procedure. Thus, current diagnosis procedures are mainly based on empirical observations extracted from single averaged spectra. In this paper, firstly a machine learning framework for the analysis of NMR spectroscopy signals which can exploit both static and dynamic aspects of these signals is introduced. Secondly, the dynamics of the signals are further analyzed using elements from chaos theory in order to understand their underlying structure. Furthermore, we show that they exhibit rich chaotic dynamics suggesting the encoding of metabolic pathway information.

physics.bio-ph↗

arXiv2010

Gamma Radiation Measurements and Dose Rates in Commonly Used Building Materials in Cyprus

A first comprehensive study is presented on radioactivity concentrations and dose rates in 87 commonly used materials, manufactured or imported in Cyprus, for building purposes. The natural radioactivity of K-40, Th-232, U-238 and Ra-226 is determined using high-resolution gamma ray spectroscopy. The respective dose rates and the associated radiological effect indices are also calculated. A comparison of the measured specific activity values with the corresponding world average values shows that most of them are below the world average activity values. The annual indoor effective dose rates received by an individual from three measured imported granites and four measured imported ceramics are found to be higher than the world upper limit value of 1 mSv y-1. Hence, these materials should have a restricted use according to their corresponding calculated activity concentration index values and the related EC 1999 guidelines.

physics.med-ph↗

arXiv2010

Temporal and Spatial Independent Component Analysis for fMRI data sets embedded in a R package

For statistical analysis of functional Magnetic Resonance Imaging (fMRI) data sets, we propose a data-driven approach based on Independent Component Analysis (ICA) implemented in a new version of the AnalyzeFMRI R package. For fMRI data sets, spatial dimension being much greater than temporal dimension, spatial ICA is the tractable approach generally proposed. However, for some neuroscientific applications, temporal independence of source signals can be assumed and temporal ICA becomes then an attracting exploratory technique. In this work, we use a classical linear algebra result ensuring the tractability of temporal ICA. We report several experiments on synthetic data and real MRI data sets that demonstrate the potential interest of our R package.

stat.CO↗

arXiv2011

Site-specific Quantification of Bone Quality using Highly Nonlinear Solitary Waves

Osteoporosis is a well recognized problem affecting millions of individuals worldwide. Consequently, the need to effectively, efficiently, and affordably diagnose and identify those at risk is essential; moreover, site-specific assessment of bone quality is necessary, not only in the process of risk assessment, but may also be desirable for other applications. The present study evaluated a new one-dimensional granular crystal sensor, composed of a tightly packed chain of beads under Hertzian contact interaction, representing the most suitable fundamental component for solitary wave generation and propagation. First, the sensitivity of the novel sensor was tested using densities of rigid polyurethane foam, representing clinical bone quality ranging from healthy, to severely osteoporotic. Once the relationship between the signal response and known densities was established, the sensor was used to measure several sites located in the proximal femur of ten human cadaveric specimens. The accuracy of the model was then further investigated, using measurements of bone quality from the same cadaveric specimens, independently, using DEXA. The results indicate not only that the novel technique is capable of detecting differences in bone quality, but that the ability to measure site-specific properties without exposure to radiation, has the potential to be further developed for clinical applications.

physics.med-ph↗

arXiv2012

Can persistent Epstein-Barr virus infection induce Chronic Fatigue Syndrome as a Pavlov reflex of the immune response?

Chronic Fatigue Syndrome is a protracted illness condition (lasting even years) appearing with strong flu symptoms and systemic defiances by the immune system. Here, by means of statistical mechanics techniques, we study the most widely accepted picture for its genesis, namely a persistent acute mononucleosis infection, and we show how such infection may drive the immune system toward an out-of-equilibrium metastable state displaying chronic activation of both humoral and cellular responses (a state of full inflammation without a direct "causes-effect" reason). By exploiting a bridge with a neural scenario, we mirror killer lymphocytes $T_K$ and $B$ cells to neurons and helper lymphocytes $T_{H_1},T_{H_2}$ to synapses, hence showing that the immune system may experience the Pavlov conditional reflex phenomenon: if the exposition to a stimulus (EBV antigens) lasts for too long, strong internal correlations among $B,T_K,T_H$ may develop ultimately resulting in a persistent activation even though the stimulus itself is removed. These outcomes are corroborated by several experimental findings.

q-bio.CB↗

arXiv2011

A Comparison of Two Human Brain Tumor Segmentation Methods for MRI Data

The most common primary brain tumors are gliomas, evolving from the cerebral supportive cells. For clinical follow-up, the evaluation of the preoperative tumor volume is essential. Volumetric assessment of tumor volume with manual segmentation of its outlines is a time-consuming process that can be overcome with the help of computerized segmentation methods. In this contribution, two methods for World Health Organization (WHO) grade IV glioma segmentation in the human brain are compared using magnetic resonance imaging (MRI) patient data from the clinical routine. One method uses balloon inflation forces, and relies on detection of high intensity tumor boundaries that are coupled with the use of contrast agent gadolinium. The other method sets up a directed and weighted graph and performs a min-cut for optimal segmentation results. The ground truth of the tumor boundaries - for evaluating the methods on 27 cases - is manually extracted by neurosurgeons with several years of experience in the resection of gliomas. A comparison is performed using the Dice Similarity Coefficient (DSC), a measure for the spatial overlap of different segmentation results.

cs.CV↗

arXiv2013

Creation of high energy/intensity bremsstrahlung by a multitarget and focusing of the scattered electrons by small-angle backscatter at a cone wall and a magnetic field II - Enhancement of the outcome of linear accelerators in radiotherapy

The yield of bremsstrahlung from collisions of fast electrons (energy at least 6 MeV) with a Tungsten target can be significantly improved by exploitation of Tungsten wall scatter in a multi-layered target. A simplified version of a previously developed principle is also able to focus small angle scattered electrons by a Tungsten wall. It is necessary that the thickness of each Tungsten layer does not exceed 0.04 mm - a thickness of 0.03 mm is suitable for accelerators in medical physics. Further focusing of electrons results from suitable magnetic fields with field strength between 0.5 Tesla and 1.2 Tesla (if the cone with multi-layered targets is rather narrow). Linear accelerators in radiation therapy only need focusing by wall scatter without further magnetic fields (standard case: 31 plates with 0.03 mm thickness and 1 mm distance between the plates). We considered three cases with importance in medical physics: A very small cone with additional magnetic field for focusing (field diameter at 90 cm depth: 6cm), a medium cone with optional magnetic field (field diameter at 90 cm depth: 13 cm) and broad cone without magnetic field (field diameter at 90 cm depth: 30 cm). All these cases can be positioned in a carousel. Measurements have been performed in the existing carousel positioned in the plane of the flattening filter and scatter foils for electrons.

physics.med-ph↗

arXiv2011

On spatial and temporal multilevel dynamics and scaling effects in epileptic seizures

Epileptic seizures are one of the most well-known dysfunctions of the nervous system. During a seizure, a highly synchronized behavior of neural activity is observed that can cause symptoms ranging from mild sensual malfunctions to the complete loss of body control. In this paper, we aim to contribute towards a better understanding of the dynamical systems phenomena that cause seizures. Based on data analysis and modelling, seizure dynamics can be identified to possess multiple spatial scales and on each spatial scale also multiple time scales. At each scale, we reach several novel insights. On the smallest spatial scale we consider single model neurons and investigate early-warning signs of spiking. This introduces the theory of critical transitions to excitable systems. For clusters of neurons (or neuronal regions) we use patient data and find oscillatory behavior and new scaling laws near the seizure onset. These scalings lead to substantiate the conjecture obtained from mean-field models that a Hopf bifurcation could be involved near seizure onset. On the largest spatial scale we introduce a measure based on phase-locking intervals and wavelets into seizure modelling. It is used to resolve synchronization between different regions in the brain and identifies time-shifted scaling laws at different wavelet scales. We also compare our wavelet-based multiscale approach with maximum linear cross-correlation and mean-phase coherence measures.

q-bio.NC↗

arXiv2011

Abnormal effective connectivity in migraine with aura under photic stimulation

Migraine patients with aura show a peculiar pattern of visual reactivity compared with those of migraine patients without aura: an increased effective connectivity, connected to a reduced synchronization among EEG channels, for frequencies in the beta band. The effective connectivity is evaluated in terms of the Granger causality. This anomalous response to visual stimuli may play a crucial role in the progression of spreading depression and clinical evidences of aura symptoms.

q-bio.NC↗

arXiv2011

Deconvolution of a linear combination of Gaussian kernels by an inhomogeneous Fredholm integral equation of second kind and applications to image processing

Scatter processes of photons lead to blurring of images. Multiple scatter can usually be described by one Gaussian convolution kernel. This can be a crude approximation and we need a linear combination of 2/3 Gaussian kernels to account for tails.If image structures are recorded by appropriate measurements, these structures are always blurred. The ideal image (source function without any blurring) is subjected to Gaussian convolutions to yield a blurred image, which is recorded by a detector array. The inverse problem of this procedure is the determination of the ideal source image from really determined image. If the scatter parameters are known, we are able to calculate the idealistic source structure by a deconvolution. We shall extend it to linear combinations of two/three Gaussian convolution kernels in order to found applications to aforementioned image processing, where a single Gaussian kernel would be crude. In this communication, we shall derive a new deconvolution method for a linear combination of 2/3 Gaussian kernels with different rms values, namely the formulation of an inhomogeneous Fredholm integral equation of second kind and the related Liouville - Neumann series (LNS) to calculate solutions in every desired order. The LNS solution provides the source function rho in terms of the Fredholm kernel Kf. We can verify some advantages of LNS in image processing. Applications of the LNS solution are inverse problems (2 or 3 Gaussian kernels) of image processing in CBCT and IMRT detector arrays of portal imaging. A particular advantage of LNS is given, if the scatter functions depend on x,y,z. This fact implies that the scatter functions can be scaled according to the electron density provided by image reconstruction procedures.

physics.data-an↗

arXiv2011

Nanodiamond as a vector for siRNA delivery to Ewing sarcoma cells

We investigated the ability of diamond nanoparticles (nanodiamonds, NDs) to deliver small interfering RNA (siRNA) in Ewing sarcoma cells, in the perspective of in vivo anti-cancer nucleic acid drug delivery. siRNA was adsorbed onto NDs previously coated with cationic polymer. Cell uptake of NDs has been demonstrated by taking advantage of NDs intrinsic fluorescence coming from embedded color center defects. Cell toxicity of these coated NDs was shown to be low. Consistent with the internalization efficacy, we have shown a specific inhibition of EWS/Fli-1 gene expression at the mRNA and protein level by the ND vectorized siRNA in a serum containing medium.

q-bio.BM↗

arXiv2011

An Assessment of "What does photon energy tell us about cellphone safety" by Dr. William Bruno

Dr. William Bruno asserts the well-known fact that cell phones radiate microwaves in the classical regime. This, he says, means that the photon energy is not relevant to assessing safety. Citing optical tweezers as an example of biologically relevant non-thermal effects of electromagnetic radiation, Bruno concludes that all other reports of non-thermal effects from microwaves are likely valid. He seeks safety thresholds based upon requiring that cell phone energy density be less than kBT. This proposal and related ideas produce thresholds many orders of magnitude below present values. While Dr. Bruno is correct that cell phone microwave radiation is generally in the classical regime, he uses peculiar estimates (number of photons per cubic wavelength) that overstate the circumstance by more than 20 factors of ten. He misunderstands the operation of optical tweezers and ignores their significant thermal effects. He credulously accepts poorly supported claims of non-thermal effects. He mistakenly believes that kBT is the average thermal energy (per cubic wavelength or per cell) in materials. It is not. It is twice the average energy per molecule per degree of freedom in the material. The thermal energy density is (1/2)kBT X (average number of degrees of freedom of the molecules) X (Avogadro's number). (Avogadro's number is 6 X 1026 molecules/mole.) Thus, Bruno's proposed safety thresholds are more than 1025 too low. Using the correct value for the average thermal energy would place the thresholds close to today's standards. Throughout his analysis he neglects the index of refraction of living tissue, n \cong 9, or the absorption length, α \cong 1 cm-1, in the microwave region.

physics.bio-ph↗

arXiv2013

Tensile material properties of human rib cortical bone under quasi-static and dynamic failure loading and influence of the bone microstucture on failure characteristics

Finite element models of the thorax are under development to assist vehicle safety researchers with the design of countermeasures such as advanced restrain systems. Computational models have become more refined with increasing geometrical complexity as element size decreases. These finite element models can now capture small geometrical features with an attempt to predict fracture. However, the bone material properties currently available, and in particular the rate sensitivity, have been mainly determined from compression tests or tests on long bones. There is a need for a new set of material properties for the human rib cortical bone. With this objective, a new clamping technique was developed to test small bone coupons under tensile loading. Ten coupons were harvested from the cortical shell of the sixth and seventh left ribs from three cadavers. The coupons were tested to fracture under quasi-static (target strain rate of 0.07 %/s) and dynamic loading (target strain rate of 170 %/s). Prior to testing, each coupon was imaged with a computed micro-tomograph to document the bone microstructure. An optical method was used to determine the strain field in the coupon for the quasi-static tests. The rib bone coupons were found to be elastic, with brittle fracture. No plastic behavior was observed in this test series. The bone coupons were assumed isotropic, homogeneous and elastic linear, and the average Young's modulus for the quasi-static tests (13.5 GPa) and the failure stresses (quasi-static: 112 MPa, dynamic: 124.6 MPa) were in line with published data. Fracture however did not always occur in the gage area where the cross-sectional area was the smallest, which contradicted the assumption of isotropy and homogeneity. The comparison with material properties obtained for long bones suggests that the effective cross-section has an effect on the calculated material properties.

physics.bio-ph↗

arXiv2011

The physical condition from the perspective of complexity: Application of a physical activity program for Alzheimer's disease

Alzheimer's disease is a sickness that has been studied from various areas of knowledge (biomarkers, brain structure, behavior, cognitive impairment). Our aim was to develop and to apply a protocol of programmed physical activity according to a non-linear methodology to enhance or diminish the deterioration of cognitive and motor functions of adults with this disease, using concepts of complexity theory for planning and programing the program. We evaluated 18 patients (12 women and 6 men) diagnosed with mild and moderate grade. We worked in small groups (2 people/coach), a total of 16 weeks, 5 sessions per week and 60 minutes per session. We designed a protocol that integrated work balance, joint mobility, coordination, muscular strength and metabolic efficiency. The strong point of this intervention was how to design the planning of tasks for patients. The tasks were developed in parallel to processes of evocation and cognitive association individually designed and presented in order of complexity. In all subjects studied, we found an improvement in the results obtained in the Mini-Mental State Examination screening test, test of Cricthon, Set-Test of Isaacs, Clock Drawing Test and Trail Making Test, and the evaluation test of fitness. The physical activity program designed and the methodology used, has been an adecuated tool to improve quality of life and autonomy of subjects analyzed.

physics.med-ph↗