Eye Safety Related to Near Infrared Radiation Exposure to Biometric Devices

Biometrics has become an emerging field of technology due to its intrinsic security features concerning the identification of individuals by means of measurable biological characteristics. Two of the most promising biometric modalities are iris and retina recognition, which primarily use nonionizing radiation in the infrared region. Illumination of the eye is achieved by infrared light emitting diodes (LEDs). Even if few LED sources are capable of causing direct eye damage as they emit incoherent light, there is a growing concern about the possible use of LED arrays that might pose a potential threat. Exposure to intense coherent infrared radiation has been proven to have significant effects on living tissues. The purpose of this study is to explore the biological effects arising from exposing the eye to near infrared radiation with reference to international legislation

The Effects of 910-MHz Electromagnetic Field on Rat Cranial Arachnoid and Dura Mater Collagen. The Axial Periodicity of Collagen Fibrils

The axial periodicity of rat arachnoid and dura mater collagen fibrils exposed to 910 MHz for 2 h/day for 30 consecutive days was measured by means of image analysis of electron-optical data. Such measurements were compared with those from shamexposed animals. These measurements reveal that on exposure, the intermolecular interactions during collagen fibril assembly are affected. KEYWORDS: electromagnetic radiation, electron microscopy, electron-optical data, image analysis, collagen DOMAINS: microscopy, bioinformatics, protein databases, extracellular matrix, computational biology, biophysics INTRODUCTION It has been established that 900-MHz electromagnetic fields (EMF) induce various measurable biological effects When collagen fibrils are seen in the electron microscope, they exhibit a characteristic banded appearance MATERIALS AND METHODS Animals Male Wistar rats were housed in groups of four and were allowed to freely take solid diet and tap water. The breeding room was light (light period from 7:00 a.m. to 7:00 p.m.) and temperature (20 ± 1 o C) controlled. The experiments were started when the rats were either 5 or 16 months of age. For all experiments, 32 animals were used; 16 were 5 months old and the rest 16 months of age. Half of each age group were exposed to radiation and the rest were sham exposed and served as controls. Irradiation Setup Sixteen animals were exposed for 2 h/day for 30 consecutive days to radiation at 910 MHz. The irradiation setup used consisted of a CW electromagnetic generator with a maximum power output of 2.2 W and a dipole λ/2 antenna. Each time, four rats were exposed placed per two in two plexiglas cages. Rat cages were placed 5 mm away from the transmitting antenna from both sides in order to ensure a near field and equal exposure of the animals. Dositometric analyses were performed through SAR (specific absorption rates). SAR was calculated by the Finite Difference Time Domain (FDTD) analysis and the maximum value was found to be 0.42 W/Kg averaged over 10 g of tissue. More details for the irradiation setup are given in Tzaphlidou et al. Throughout the experiments, care was taken to minimize pain or discomfort. All studies were approved by the Ioannina University Institutional Animal Care and Use Committee. 71 Tzaphlidou/Fotiou: Effects of 910 MHz on Rat Brain Collagen TheScientificWorldJOURNAL (2004) 4(S2), 70-74 Tissue Preparation Rats were deeply anesthetized with ethyl ether. The head was cut with a big pair of scissors and the skull was opened with cutting forceps. Brain was removed with fine curved forceps and placed on a Petri dish on ice. Arachnoid and dura mater were gently teased from the surface of the brain and the internal surface of the skull. The isolated menigiel material was placed in Eppendorf tubes containing 2.5% glutaraldehyde buffered to a pH of 7.4 with 0.1 M sodium cacodylate. From the material studied, pieces of 1 mm 2 were obtained and immersed into the same fixative overnight at 4 o C. After this time, samples were washed in 0.1 M sodium cacodylate buffer and postosmicated for 2 h at 4 o C in 1% osmium tetroxide buffered in cacodylate, followed by washing in the same buffer and finally rinsed in distilled water. The specimens were then dehydrated in a graded alcohol series and impregnated overnight with a 1/1 mixture of propylene oxide and the resin used for embedding. Final embedding was performed in capsules with Agar resin. Polymerization was complete in 48 h at 60 o C. Ultrathin sections were positively stained with 2% aqueous solution of phosphotungstic acid (PTA), pH 3.3 (pH was adjusted with 0.1 N NaOH), for 1 h and then with 2% aqueous solution of uranyl acetate (UA), pH 4.3 (adjusted by 0.1 N NaOH), for 0.5 h, washing briefly in distilled water before and after UA staining. Electron Microscopy Electron microscopy was performed on a JEOL JEM-100 CX-II electron microscope and micrographs were taken at a constant magnification of ×53,000. Grating replicas were used for magnification calibration. Measurement of Axial Periodicity For our calculations, we developed a computer-aided procedure that was based on the periodic variations in intensity along the fibril For statistical analysis, the mean and standard deviation, as well as data from an unpaired t-test, were calculated with a laboratory computer according to Snedecor and Cochran[16] and Hays RESULTS 72 Tzaphlidou/Fotiou: Effects of 910 MHz on Rat Brain Collagen TheScientificWorldJOURNAL (2004) 4(S2), 70-74 DISCUSSION Under the present experimental conditions, the results show that 910-MHz electromagnetic radiation affects the axial periodicity of rat arachnoid and dura mater collagen fibrils. As noted earlier, D periodicity in collagen fibrils has its origins in the interactions that occur between the outwardly projecting side chains when two molecules come together in parallel juxtaposition. These intermolecular interactions, particularly those between the larger hydrophobic side chains and those between oppositely charged side chains, are greatest when the adjoining molecules are mutually displaced axially by D or integral multiples of D. As the axial periodicity is affected on exposure, we may conclude that the above interactions might be disturbed by the applied electromagnetic radiation and therefore they are not any more the maximum. Maximum hydrophobic interactions between apolar residues mean maximum hydrogen bonding between excluded water molecules, providing stability to the structure. Other data In conclusion, the axial periodicity of collagen fibrils is affected on exposure to 910-MHz electromagnetic radiation as demonstrated by image analysis of electron-optical data. It seems that this influence is restricted to hydrogen bonding between molecules. Providing that this information is coupled with that from other methods, collagen fibril periodicity measurement may serve as an additional marker for the determination of the factors responsible for collagen structural abnormalities brought about by the electromagnetic radiation. ACKNOWLEDGMENT

Skeletal Calcium/Phosphorus Ratio Measuring Techniques and Results. I. Microscopy and Microtomography

An approach to the problem of bone disorders is the measurement of the skeleton's static and dynamic strength, an estimate of which is bone mineral density. A decrease in the latter may be due to a decrease in either Ca or P, or to dissimilar decreases in both. Consequently, the determination of the Ca/P ratio may provide a sensitive measure of bone mineral changes and may add to our understanding of the changes occurring in bone diseases. This paper reviews techniques such as transmission electron microscopy (TEM) and micro-computed tomography (μu-CT), which have been developed for the in vitro assessment of the Ca,P content and the skeletal Ca/P ratio. Their main aspects are presented, as much as results regarding the referred values. The presentation of other in vitro or in vivo techniques, such as instrumental neutron activation analysis (INAA) or X-ray absorptiometry accordingly, would be the issue of another article. The authors argue that the choice of the best technique relies on its cost ad ease of applicability, its reliability, and precision

Mesenchymal Stem Cell Responses to Bone-Mimetic Electrospun Matrices Composed of Polycaprolactone, Collagen I and Nanoparticulate Hydroxyapatite

The performance of biomaterials designed for bone repair depends, in part, on the ability of the material to support the adhesion and survival of mesenchymal stem cells (MSCs). In this study, a nanofibrous bone-mimicking scaffold was electrospun from a mixture of polycaprolactone (PCL), collagen I, and hydroxyapatite (HA) nanoparticles with a dry weight ratio of 50/30/20 respectively (PCL/col/HA). The cytocompatibility of this tri-component scaffold was compared with three other scaffold formulations: 100% PCL (PCL), 100% collagen I (col), and a bi-component scaffold containing 80% PCL/20% HA (PCL/HA). Scanning electron microscopy, fluorescent live cell imaging, and MTS assays showed that MSCs adhered to the PCL, PCL/HA and PCL/col/HA scaffolds, however more rapid cell spreading and significantly greater cell proliferation was observed for MSCs on the tri-component bone-mimetic scaffolds. In contrast, the col scaffolds did not support cell spreading or survival, possibly due to the low tensile modulus of this material. PCL/col/HA scaffolds adsorbed a substantially greater quantity of the adhesive proteins, fibronectin and vitronectin, than PCL or PCL/HA following in vitro exposure to serum, or placement into rat tibiae, which may have contributed to the favorable cell responses to the tri-component substrates. In addition, cells seeded onto PCL/col/HA scaffolds showed markedly increased levels of phosphorylated FAK, a marker of integrin activation and a signaling molecule known to be important for directing cell survival and osteoblastic differentiation. Collectively these results suggest that electrospun bone-mimetic matrices serve as promising degradable substrates for bone regenerative applications

Diagenesis of archaeological bone and tooth

An understanding of the structural complexity of mineralised tissues is fundamental for exploration into the field of diagenesis. Here we review aspects of current and past research on bone and tooth diagenesis using the most comprehensive collection of literature on diagenesis to date. Environmental factors such as soil pH, soil hydrology and ambient temperature, which influence the preservation of skeletal tissues are assessed, while the different diagenetic pathways such as microbial degradation, loss of organics, mineral changes, and DNA degradation are surveyed. Fluctuating water levels in and around the bone is the most harmful for preservation and lead to rapid skeletal destruction. Diagenetic mechanisms are found to work in conjunction with each other, altering the biogenic composition of skeletal material. This illustrates that researchers must examine multiple diagenetic pathways to fully understand the post-mortem interactions of archaeological skeletal material and the burial environment