Search results for: corneal curvature

Authors: Rita Emília Szabó, Róbert Polanek, Tünde Tőkés, Zoltán Szabó, Szabolcs Czifrus, Katalin Hideghéty

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Purpose: Several feature of zebrafish are making them amenable for investigation on therapeutic approaches such as ionizing radiation. The establishment of zebrafish model for comprehensive radiobiological research stands in the focus of our investigation, comparing the radiation effect curves of neutron and photon irradiation. Our final aim is to develop an appropriate vertebrate model in order to investigate the relative biological effectiveness of laser driven ionizing radiation. Methods and Materials: After careful dosimetry series of viable zebrafish embryos were exposed to a single fraction whole-body neutron-irradiation (1,25; 1,875; 2; 2,5 Gy) at the research reactor of the Technical University of Budapest and to conventional 6 MeV photon beam at 24 hour post-fertilization (hpf). The survival and morphologic abnormalities (pericardial edema, spine curvature) of each embryo were assessed for each experiment at 24-hour intervals from the point of fertilization up to 168 hpf (defining the dose lethal for 50% (LD50)). Results: In the zebrafish embryo model LD50 at 20 Gy dose level was defined and the same lethality were found at 2 Gy dose from the reactor neutron beam resulting RBE of 10. Dose-dependent organ perturbations were detected on macroscopic (shortening of the body length, spine curvature, microcephaly, micro-ophthalmia, micrognathia, pericardial edema, and inhibition of yolk sac resorption) and microscopic (marked cellular changes in skin, cardiac, gastrointestinal system) with the same magnitude of dose difference. Conclusion: In our observations, we found that zebrafish embryo model can be used for investigating the effects of different type of ionizing radiation and this system proved to be highly efficient vertebrate model for preclinical examinations.

Keywords: ionizing radiation, LD50, relative biological effectiveness, zebrafish embryo

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Authors: Anu S. Nair, V. Anantha Subramanian

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This paper presents a surface development and fairing technique combining the features of a modern computer-aided design tool namely the Non-Uniform Rational Basis Spline (NURBS) with an algorithm to obtain a rapidly faired hull form. Some of the older series based designs give sectional area distribution such as in the Wageningen-Lap Series. Others such as the FORMDATA give more comprehensive offset data points. Nevertheless, this basic data still requires fairing to obtain an acceptable faired hull form. This method uses the input of sectional area distribution as an example and arrives at the faired form. Characteristic section shapes define any general ship hull form in the entrance, parallel mid-body and run regions. The method defines a minimum of control points at each section and using the Golden search method or the bisection method; the section shape converges to the one with the prescribed sectional area with a minimized error in the area fit. The section shapes combine into evolving the faired surface by NURBS and typically takes 20 iterations. The advantage of the method is that it is fast, robust and evolves the faired hull form through minimal iterations. The curvature criterion check for the hull lines shows the evolution of the smooth faired surface. The method is applicable to hull form from any parent series and the evolved form can be evaluated for hydrodynamic performance as is done in more modern design practice. The method can handle complex shape such as that of the bulbous bow. Surface patches developed fit together at their common boundaries with curvature continuity and fairness check. The development is coded in MATLAB and the example illustrates the development of the method. The most important advantage is quick time, the rapid iterative fairing of the hull form.

Keywords: computer-aided design, methodical series, NURBS, ship design

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Authors: Samuele Viaro, Pierre Ricco

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Görtler instabilities generate in boundary layers from an unbalance between pressure and centrifugal forces caused by concave surfaces. Their spatial streamwise evolution influences transition to turbulence. It is therefore important to understand even the early stages where perturbations, still small, grow linearly and could be controlled more easily. This work presents a rigorous theoretical framework for compressible flows using the linearized unsteady boundary region equations, where only the streamwise pressure gradient and streamwise diffusion terms are neglected from the full governing equations of fluid motion. Boundary and initial conditions are imposed through an asymptotic analysis in order to account for the interaction of the boundary layer with free-stream turbulence. The resulting parabolic system is discretize with a second-order finite difference scheme. Realistic flow parameters are chosen from wind tunnel studies performed at supersonic and subsonic conditions. The Mach number ranges from 0.5 to 8, with two different radii of curvature, 5 m and 10 m, frequencies up to 2000 Hz, and vortex spanwise wavelengths from 5 mm to 20 mm. The evolution of the perturbation flow is shown through velocity, temperature, pressure profiles relatively close to the leading edge, where non-linear effects can still be neglected, and growth rate. Results show that a global stabilizing effect exists with the increase of Mach number, frequency, spanwise wavenumber and radius of curvature. In particular, at high Mach numbers curvature effects are less pronounced and thermal streaks become stronger than velocity streaks. This increase of temperature perturbations saturates at approximately Mach 4 flows, and is limited in the early stage of growth, near the leading edge. In general, Görtler vortices evolve closer to the surface with respect to a flat plate scenario but their location shifts toward the edge of the boundary layer as the Mach number increases. In fact, a jet-like behavior appears for steady vortices having small spanwise wavelengths (less than 10 mm) at Mach 8, creating a region of unperturbed flow close to the wall. A similar response is also found at the highest frequency considered for a Mach 3 flow. Larger vortices are found to have a higher growth rate but are less influenced by the Mach number. An eigenvalue approach is also employed to study the amplification of the perturbations sufficiently downstream from the leading edge. These eigenvalue results are compared with the ones obtained through the initial value approach with inhomogeneous free-stream boundary conditions. All of the parameters here studied have a significant influence on the evolution of the instabilities for the Görtler problem which is indeed highly dependent on initial conditions.

Keywords: compressible boundary layers, Görtler instabilities, receptivity, turbulence transition

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Authors: Julie V. Logan, Preston T. Webster, Kevin B. Woller, Christian P. Morath, Michael P. Short

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Semiconductors, as the base of critical electronic systems, are exposed to damaging radiation while operating in space, nuclear reactors, and particle accelerator environments. What innate property allows some semiconductors to sustain little damage while others accumulate defects rapidly with dose is, at present, poorly understood. This limits the extent to which radiation tolerance can be implemented as a design criterion. To address this problem of determining the driver of semiconductor radiation tolerance, the first step is to generate a dataset of the relative radiation tolerance of a large range of semiconductors (exposed to the same radiation damage and characterized in the same way). To accomplish this, Rutherford backscatter channeling experiments are used to compare the displaced lattice atom buildup in InAs, InP, GaP, GaN, ZnO, MgO, and Si as a function of step-wise alpha particle dose. With this experimental information on radiation-induced incorporation of interstitial defects in hand, hybrid density functional theory electron densities (and their derived quantities) are calculated, and their gradient and Laplacian are evaluated to obtain key fundamental information about the interactions in each material. It is shown that simple, undifferentiated values (which are typically used to describe bond strength) are insufficient to predict radiation tolerance. Instead, the curvature of the electron density at bond critical points provides a measure of radiation tolerance consistent with the experimental results obtained. This curvature and associated forces surrounding bond critical points disfavors localization of displaced lattice atoms at these points, favoring their diffusion toward perfect lattice positions. With this criterion to predict radiation tolerance, simple density functional theory simulations can be conducted on potential new materials to gain insight into how they may operate in demanding high radiation environments.

Keywords: density functional theory, GaN, GaP, InAs, InP, MgO, radiation tolerance, rutherford backscatter channeling

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Authors: Matt Collins, Bernadette O'Regan, Tom Cosgrove

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To determine the potential of a low cost Irish engineered timber product to replace high cost solid timber for use in bending active structures such as gridshells a single Irish engineered timber product in the form of orientated strand board (OSB) was selected. A comparative study of OSB and solid timber was carried out to determine the optimum properties that make a material suitable for use in gridshells. Three parameters were identified to be relevant in the selection of a material for gridshells. These three parameters are the strength to stiffness ratio, the flexural stiffness of commercially available sections, and the variability of material and section properties. It is shown that when comparing OSB against solid timber, OSB is a more suitable material for use in gridshells that are at the smaller end of the scale and that have tight radii of curvature. Typically, for solid timber materials, stiffness is used as an indicator for strength and engineered timber is no different. Thus, low flexural stiffness would mean low flexural strength. However, when it comes to bending active gridshells, OSB offers a significant advantage. By the addition of multiple layers, an increased section size is created, thus endowing the structure with higher stiffness and higher strength from initial low stiffness and low strength materials while still maintaining tight radii of curvature. This allows OSB to compete with solid timber on large scale gridshells. Additionally, a preliminary sustainability study using a set of sustainability indicators was carried out to determine the relative sustainability of building a large-scale gridshell in Ireland with a primary focus on economic viability but a mention is also given to social and environmental aspects. For this, the Savill garden gridshell in the UK was used as the functional unit with the sustainability of the structural roof skeleton constructed from UK larch solid timber being compared with the same structure using Irish OSB. Albeit that the advantages of using commercially available OSB in a bending active gridshell are marginal and limited to specific gridshell applications, further study into an optimised engineered timber product is merited.

Keywords: bending active gridshells, high end timber structures, low cost material, sustainability

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Authors: K. Doi, T. Nishimura, H. Fujimoto, T. Tanaka

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It has been known that visually impaired persons have some problems in getting visual information. Therefore, information accessibility for the visually impaired persons is very important in a current information society. Some application software with read-aloud function for using personal computer and smartphone are getting more and more popular among visually impaired persons in the world. On the other hand, it is also very important for being able to learn how to read and write characters such as Braille and Visual character. Braille typewriter has been widely used in learning Braille. And also raised-line drawing kits as writing material has been used for decades for especially acquired visually impaired persons. However, there are some drawbacks such as the drawn line cannot be erased. Moreover, visibility of drawing lines is not so good for visually impaired with low vision. We had significant number of requests for developing new writing material for especially acquired visually impaired persons instead of raised-line drawing kits. For conducting development research of novel writing material, we could receive a research grant from ministry of health, labor and welfare in Japanese government. In this research, we developed writing material typed pens and pencils with Beeswax-discharge instead of conventional raised-line drawing kits. This writing material was equipped with cartridge heater for melting beeswax and its heat controller. When this pen users held down the pen tip on the regular paper such as fine paper and so on, the melted beeswax could be discharged from pen tip with valve structure. The beeswax was discharged at 100 gf of holding down force based on results of our previous trial study. The shape of pen tip was semispherical for becoming low friction between pen tip and surface of paper. We conducted one basic experiment to evaluate influence of the curvature of pen tip on ease to write. Concretely, the conditions of curvature was 0.15, 0.35, 0.50, 1.00 mm. The following four interval scales were used as indexes of subjective assessment during writing such as feeling of smooth motion of pen, feeling of comfortable writing, sense of security and feeling of writing fatigue. Ten subjects were asked to participate in this experiment. The results reveal that subjects could draw easily when the radius of the pen tip was 1.00 mm, and lines drawn with beeswax-discharge writing material were easy to perceive.

Keywords: beeswax-discharge writing material, raised-line drawing kits, visually impaired persons, pen tip

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Authors: Prachi Abhishek Dave, Manisha Singh

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Purpose: The purpose is to study the microbiological profile, prognostic factors, and outcomes of surgery for microbial keratitis (MK) associated endophthalmitis. Methods: It is a retrospective analysis of 39 MK associated endophthalmitis cases which underwent combined PKP with VR surgery. Results: The majority (84.6%) of patients had a history of previous ocular surgery, cataract surgery being the most common (51.2%). Six patients had a history of trauma and 8 patients had corneal graft infection. The culture positivity rate was 92.3%. Organisms isolated were Streptococcal sp (20.5%), Pseudomonas (15.3%), Staphylococcal sp (12.8%) and Fungus (35.8%). Final visual acuities ranged from NPL to 20/120. Poor anatomic success was seen in 15(38.46%) eyes (9-phthisis, 6-eviscerated). Fungal cases had a poor success rate (P-0.02). Conclusion: MK associated endophthalmitis is a sight threatening ocular condition. Fungal etiology carries a poorer prognosis. Timely surgical intervention can achieve favourable anatomical and functional results.

Keywords: endophthalmitis, microbial keratitis, penetrating keratoplasty, vitreo retinal surgery

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Authors: Mohammad Ibrahim

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The study was conducted at Albasar international foundation ophthalmic hospitals in Sudan to study the burden and patterns of ophthalmic disorder in the sector. Review of the hospitals records revealed that the total number of patient examined in the hospitals and outreached camps conducted by the hospitals is 10,513,874, the total number of surgeries is 694,015 and the total number of pupils at school program is 230,382. The organization working with the highest management system and standards and quality result based planning. The study yielded that the ophthalmic problem in Sudan are of great percentage and the temporal blindness disorder are high since major cases and surgeries were Cataract (57.8%). Retinal problem (2.9%), Glaucoma (2.4%), Orbit and Occulo-plastic disorders (2.2%) other disorders are refractive errors, squint and strabismus, Corneal, Pediatrics and minor ophthalmic disorders.

Keywords: hospitals and outreach ophthalmic services, largest coverage of ophthalmic services, nonprofitable ophthalmic services, strong management system and standards

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Authors: Rongli Gai, Zhiyuan Chang

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At this stage, in view of various situations in the interpolation process, most researchers use self-adaptation to adjust the interpolation process, which is also one of the current and future research hotspots in the field of CNC machining. In the interpolation process, according to the overview of the spline curve interpolation algorithm, the adaptive analysis is carried out from the factors affecting the interpolation process. The adaptive operation is reflected in various aspects, such as speed, parameters, errors, nodes, feed rates, random Period, sensitive point, step size, curvature, adaptive segmentation, adaptive optimization, etc. This paper will analyze and summarize the research of adaptive imputation in the direction of the above factors affecting imputation.

Keywords: adaptive algorithm, CNC machining, interpolation constraints, spline curve interpolation

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Authors: Sarah Jacqueline Saram, Diya Baker, Jaishree Gandhewar

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Named after the Slovakian microbiologist, Miroslav Kocur, the Kocuria spp. are an emerging cause of significant human infections. Their predilection for immunocompromised states, such as malignancy and metabolic disorders, is highlighted in the literature. The coagulase-negative, gram-positive cocci are commensals found in the skin and oropharynx of humans, and their growing presence as responsible organisms in ocular infections cannot be ignored. The severe, rapid, and unrelenting disease course associated with Kocuria keratitis is underlined in the literature. However, the clinical features are variable, which may impede making a diagnosis. Here, we describe a first account of an initial misdiagnosis due to reliance on subjective analysis features on a confocal microscope, which ultimately led to a delay in commencing the correct treatment. In documenting this, we hope to underline to clinicians the difficulties in recognising a Kocuria Rhizophilia keratitis due to its similar clinical presentation to an Acanthamoeba Keratitis, thus emphasizing the need for early investigations such as corneal scrapes to secure the correct diagnosis and prevent further harm and vision loss for the patient.

Keywords: keratitis, cornea, infection, rare, Kocuria

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Authors: Aliouane Toufik, Hamdi Amine, Bouzid Djamel

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Aspheric optical components are an alternative to the use of conventional lenses in the implementation of imaging systems for the visible range. Spherical lenses are capable of producing aberrations. Therefore, they are not able to focus all the light into a single point. Instead, aspherical lenses correct aberrations and provide better resolution even with compact lenses incorporating a small number of lenses. Metrology of these components is very difficult especially when the resolution requirements increase and insufficient or complexity of conventional tools requires the development of specific approaches to characterization. This work is part of the problem existed because the objectives are the study and comparison of different methods used to measure surface rays hybrid aspherical lenses.

Keywords: manufacture of lenses, aspherical surface, precision molding, radius of curvature, roughness

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Authors: Abraham J. Domb

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Nearly every eye disorder and treatment of post operated eyes evolve around ocular drug delivery. Most ocular diseases are treated with repeated topical applications administered as eye drops. Various attempts have been made to improve drug bioavailability by increasing both the retention of the drug in the pre-corneal area and the penetration of the drug through the cornea. However, currently marketed products are associated with vision blurring, irritability, patient discomfort, toxicity, low drug bioavailability, manufacturing difficulties and inadequate aqueous stability. It has been suggested to use iontophoresis for the non-invasive delivery of drugs. The iontophoretic device is composed of a control panel, two electrodes, a cylindrical well for the insertion of a disposable hydrogel, and a disposable hydrogel pellet. The drug-loaded hydrogel is attached to a cylindrical well at the edge of the electrode of the device and placed onto the eye. The device applies a variable electrical current that can vary from 0.1 mA to 1.5 mA for pre-set periods from 10 seconds to 300 seconds. The iontophoretic device developed in the lab was found to be effective in the delivery of the drugs: gentamicin, water-soluble steroids, and various anticancer agents. When testing in rabbits for safety, the device was considered to be non-toxic and effective.

Keywords: iontophoresis, eye disorder, drug delivery, hydrogel

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Authors: Yanné Etienne

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The current climatic conditions necessarily impose the development and use of construction materials with low or no carbon footprint. The Far North Region of Cameroon has huge deposits of termite mounds. Various tests in this work have been carried out on these soils with the aim of using them as construction materials. They are mainly geotechnical tests, physical and mechanical tests. The different tests gave the following values: uniformity coefficient (4.95), curvature coefficient (1.80), plasticity index (12.85%), optimum moisture content (6.70%), maximum dry density (2.05 g.cm-³), friction angles (14.07°), and cohesion of 100.29 kN.m2. The results obtained show that termite mound soils, which are ecological materials, are plastic and water-stable can be used for the production of load-bearing elements in construction.

Keywords: termite mound soil, ecological materials, building materials, geotechnical tests, physical and mechanical tests

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Authors: Seydou Sinde

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The aims of this paper are to formulate mathematical expressions that can be used to estimate the standpipe pressure (SPP). The developed formulas take into account the main factors that, directly or indirectly, affect the behavior of SPP values. Fluid rheology and well hydraulics are some of these essential factors. Mud Plastic viscosity, yield point, flow power, consistency index, flow rate, drillstring, and annular geometries are represented by the frictional pressure (Pf), which is one of the input independent parameters and is calculated, in this paper, using Herschel-Bulkley rheological model. Other input independent parameters include the rate of penetration (ROP), applied load or weight on the bit (WOB), bit revolutions per minute (RPM), bit torque (TRQ), and hole inclination and direction coupled in the hole curvature or dogleg (DL). The technique of repeating parameters and Buckingham PI theorem are used to reduce the number of the input independent parameters into the dimensionless revolutions per minute (RPMd), the dimensionless torque (TRQd), and the dogleg, which is already in the dimensionless form of radians. Multivariable linear and polynomial regression technique using PTC Mathcad Prime 4.0 is used to analyze and determine the exact relationships between the dependent parameter, which is SPP, and the remaining three dimensionless groups. Three models proved sufficiently satisfactory to estimate the standpipe pressure: multivariable linear regression model 1 containing three regression coefficients for vertical wells; multivariable linear regression model 2 containing four regression coefficients for deviated wells; and multivariable polynomial quadratic regression model containing six regression coefficients for both vertical and deviated wells. Although that the linear regression model 2 (with four coefficients) is relatively more complex and contains an additional term over the linear regression model 1 (with three coefficients), the former did not really add significant improvements to the later except for some minor values. Thus, the effect of the hole curvature or dogleg is insignificant and can be omitted from the input independent parameters without significant losses of accuracy. The polynomial quadratic regression model is considered the most accurate model due to its relatively higher accuracy for most of the cases. Data of nine wells from the Middle East were used to run the developed models with satisfactory results provided by all of them, even if the multivariable polynomial quadratic regression model gave the best and most accurate results. Development of these models is useful not only to monitor and predict, with accuracy, the values of SPP but also to early control and check for the integrity of the well hydraulics as well as to take the corrective actions should any unexpected problems appear, such as pipe washouts, jet plugging, excessive mud losses, fluid gains, kicks, etc.

Keywords: standpipe, pressure, hydraulics, nondimensionalization, parameters, regression

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Authors: M. G. Murtaza, E. E. Tzirtzilakis, M. Ferdows

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The mixed convective flow of MHD incompressible, steady boundary layer in heat transfer over a curved stretching sheet due to temperature dependent thermal conductivity is studied. We use curvilinear coordinate system in order to describe the governing flow equations. Finite difference solutions with central differencing have been used to solve the transform governing equations. Numerical results for the flow velocity and temperature profiles are presented as a function of the non-dimensional curvature radius. Skin friction coefficient and local Nusselt number at the surface of the curved sheet are discussed as well.

Keywords: curved stretching sheet, finite difference method, MHD, variable thermal conductivity

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Authors: Lemonakis Panagiotis, Eliou Nikos, Karakasidis Theodoros, Botzoris George

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It is well known that trajectory along with speed are two of the most important contributing factors in road accidents. Trajectory is meant as the "line“, usually different from the center-line that a driver traverses through horizontal curves which depends on the characteristics of the road environment (especially the curvature), the vehicle and the driver himself. Drivers and especially riders, tend to broaden their paths in order to succeed greater path radiuses and hence, reduce the applied centrifugal force enhancing safety. The objective of the present research is to investigate riders’ path on horizontal curves. Within the context of the research, field measurements were conducted on a rural two lane highway, with the participation of eight riders and the use of an instrumented motorcycle. The research has shown that the trajectory of the riders is correlated to the radius and the length of the horizontal curve as well.

Keywords: trajectory, path, riders, horizontal curves

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Authors: Mousa Saleh Daoud

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Rickets is a condition that affects the development of bones in children. It causes soft bones, which can become bowed or curved, this bending and curvature is evident in the age of Walking. The most common cause of rickets is dietary deficiency of vitamin D or Lack of exposure to sunlight or both together. The link between vitamin D and rickets has been known for many years and is well understood by doctors and scientists. If a child does not get enough of the vitamin D, the bones cannot form hard outer shells. This is why they become soft and weak. This study was conducted on children who reviewed by our medical clinic between the years 2011-2013. The study included 400 children, aged between one and six years. 11 children had clear clinical manifestations of rickets of varying degrees and all of them due to lack of vitamin D except for one case of rickets resistant to vitamin D. 389 cases ranged between natural and deficiency in vitamin D without clinical manifestations of Rickets.

Keywords: rickts, bone metabolic diseases, vitamin D, child

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Authors: Jiangbo Li, Wenqian Huang

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Early detection of fungal infection in citrus fruit is one of the major problems in the postharvest commercialization process. The automatic and nondestructive detection of infected fruits is still a challenge for the citrus industry. At present, the visual inspection of rotten citrus fruits is commonly performed by workers through the ultraviolet induction fluorescence technology or manual sorting in citrus packinghouses to remove fruit subject with fungal infection. However, the former entails a number of problems because exposing people to this kind of lighting is potentially hazardous to human health, and the latter is very inefficient. Orange is used as a research object. This study would focus on this problem and proposed an effective method based on Vis-NIR hyperspectral imaging in the wavelength range of 400-1000 nm with a spectroscopic resolution of 2.8 nm. In this work, three normalization approaches are applied prior to analysis to reduce the effect of sample curvature on spectral profiles, and it is found that mean normalization was the most effective pretreatment for decreasing spectral variability due to curvature. Then, principal component analysis (PCA) was applied to a dataset composing of average spectra from decayed and normal tissue to reduce the dimensionality of data and observe the ability of Vis-NIR hyper-spectra to discriminate data from two classes. In this case, it was observed that normal and decayed spectra were separable along the resultant first principal component (PC1) axis. Subsequently, five wavelengths (band) centered at 577, 702, 751, 808, and 923 nm were selected as the characteristic wavelengths by analyzing the loadings of PC1. A multispectral combination image was generated based on five selected characteristic wavelength images. Based on the obtained multispectral combination image, the intensity slicing pseudocolor image processing method is used to generate a 2-D visual classification image that would enhance the contrast between normal and decayed tissue. Finally, an image segmentation algorithm for detection of decayed fruit was developed based on the pseudocolor image coupled with a simple thresholding method. For the investigated 238 independent set samples including infected fruits infected by Penicillium digitatum and normal fruits, the total success rate is 100% and 97.5%, respectively, and, the proposed algorithm also used to identify the orange infected by penicillium italicum with a 100% identification accuracy, indicating that the proposed multispectral algorithm here is an effective method and it is potential to be applied in citrus industry.

Keywords: citrus fruit, early rotten, fungal infection, hyperspectral imaging

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Authors: Cao Bin, Yuan Yi, Wang Qiang, Amor Abdelkader, Ali Reza Kamali, Diogo Montalvão

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The study of the electrodynamic behavior of non-ferrous particles in time-varying magnetic fields is a promising area of research with wide applications, including recycling of non-ferrous metals, mechanical transmission, and space debris. The key technology for recovering non-ferrous metals is eddy current separation (ECS), which utilizes the eddy current force and torque to separate non-ferrous metals. ECS has several advantages, such as low energy consumption, large processing capacity, and no secondary pollution, making it suitable for processing various mixtures like electronic scrap, auto shredder residue, aluminum scrap, and incineration bottom ash. Improving the separation efficiency of mixtures with different particle sizes in ECS can create significant social and economic benefits. Our previous study investigated the influence of particle size on separation efficiency by combining numerical simulations and separation experiments. Pearson correlation analysis found a strong correlation between the eddy current force in simulations and the repulsion distance in experiments, which confirmed the effectiveness of our simulation model. The interaction effects between particle size and material type, rotational speed, and magnetic pole arrangement were examined. It offer valuable insights for the design and optimization of eddy current separators. The underlying mechanism behind the effect of particle size on separation efficiency was discovered by analyzing eddy current and field gradient. The results showed that the magnitude and distribution heterogeneity of eddy current and magnetic field gradient increased with particle size in eddy current separation. Based on this, we further found that increasing the curvature of magnetic field lines within particles could also increase the eddy current force, providing a optimized method to improving the separation efficiency of fine particles. By combining the results of the studies, a more systematic and comprehensive set of optimization guidelines can be proposed for mixtures with different particle size ranges. The separation efficiency of fine particles could be improved by increasing the rotational speed, curvature of magnetic field lines, and electrical conductivity/density of materials, as well as utilizing the eddy current torque. When designing an ECS, the particle size range of the target mixture should be investigated in advance, and the suitable parameters for separating the mixture can be fixed accordingly. In summary, these results can guide the design and optimization of ECS, and also expand the application areas for ECS.

Keywords: eddy current separation, particle size, numerical simulation, metal recovery

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Authors: Kamel Hachour, Lydia Sadeg, Djamel Sersab, Tassadit Bellahcen

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The hydrostatic stress is, for polymers, a significant parameter which affects the yield behavior of these materials. In this work, we investigate the influence of this parameter on yield behavior of the high density polyethylene (hdpe). Some tests on specimens with diverse geometries are described in this paper. Uniaxial tests: tensile on notched round bar specimens with different curvature radii, compression on cylindrical specimens and simple shear on parallelepiped specimens were performed. Biaxial tests with various combinations of tensile/compressive and shear loading on butterfly specimens were also realized in order to determine the hydrostatic stress for different states of solicitation. The experimental results show that the yield stress is very affected by the hydrostatic stress developed in the material during solicitations.

Keywords: biaxial tests, hdpe, Hydrostatic stress, yield behavior

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Authors: Aymen Laadhari

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We present in this paper a fully implicit finite element method tailored for the numerical modeling of inextensible fluidic membranes in a surrounding Newtonian fluid. We consider a highly simplified version of the Canham-Helfrich model for phospholipid membranes, in which the bending force and spontaneous curvature are disregarded. The coupled problem is formulated in a fully Eulerian framework and the membrane motion is tracked using the level set method. The resulting nonlinear problem is solved by a Newton-Raphson strategy, featuring a quadratic convergence behavior. A monolithic solver is implemented, and we report several numerical experiments aimed at model validation and illustrating the accuracy of the proposed method. We show that stability is maintained for significantly larger time steps with respect to an explicit decoupling method.

Keywords: finite element method, level set, Newton, membrane

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Authors: Jim S. Meng, Mammo H. Yewondwossen

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As a part of routine oesophageal HDR brachytherapy procedure, treatment planning takes about 45 minutes while patients are under light sedation. Some patients may suffer gagging and/or spasms, and the treatment may need to be aborted. A pre-prepared plan generated before the patient’s sedation may reduce the brachytherapy procedure time by forty minutes. This paper reports the rationality and evidence of pre-prepared treatment plans. A retrospective study of 28 patients confirm that all of the pre-prepared plans would be acceptable. The rationality of pre-prepared HDR brachytherapy plans is further confirmed by a systemic study with a wide range of applicator curvature and treatment volume. Detailed comparison between CT based treatment plans and pre-prepared plans are discussed. This argument holds also for endobronchial HDR brachytherapy. With the above evidence, pre-prepared plans have been used for all oesophagus and bronchus HDR brachytherapy cases in our clinic.

Keywords: HDR brachytherapy, treatment planning, oesophageal carcinoma, pre-planning

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Authors: A. Hocine, A. Ghouaoula, S. M. Medjdoub, M. Cherifi

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The present paper proposed a meso–macro model describing the mechanical behaviour composite laminates of staking sequence [+θ/-θ]s under tensil loading. The behaviour of a layer is ex-pressed through elasticity coupled to damage. The elastic strain is due to the elasticity of the layer and can be modeled by using the classical laminate theory, and the laminate is considered as an orthotropic material. This means that no coupling effect between strain and curvature is considered. In the present work, the damage is associated to cracking of the matrix and parallel to the fibers and it being taken into account by the changes in the stiffness of the layers. The anisotropic damage is completely described by a single scalar variable and its evolution law is specified from the principle of maximum dissipation. The stress/strain relationship is investigated in plane stress loading.

Keywords: damage, behavior modeling, meso-macro model, composite laminate, membrane loading

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Authors: Khalil Khanafer

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The objective of this study is to determine if there is a correlation between the biological levels of matrix metalloproteinases and tissue inhibitor of matrix metalloproteinase (TIMP) and the elastic moduli of the ascending aortic wall in patients with ascending thoracic aortic aneurysms (ATAA). Methods: Circumferential specimens from twelve patients with ATAA were obtained from the greater curvature, and their tensile properties (maximum elastic modulus) were tested uniaxially. The levels of MMP2, 3, and 9, as well as TIMP1, were determined in these aortic wall specimens using MMP/TIMP antibodies array. Direct relations were found between MMP2 and the elastic modulus of the ascending aorta wall and between MMP9 and TIMP1.

Keywords: elastic modulus, MMPs/TIMPs levels, Ascending Thoracic Aortic Aneurysm

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Authors: Bader Alruwaili, Surajit Ray

Abstract:

Finite mixtures are a flexible and powerful tool that can be used for univariate and multivariate distributions, and a wide range of research analysis has been conducted based on the multivariate normal mixture and multivariate of a t-mixture. Determining the number of modes is an important activity that, in turn, allows one to determine the number of homogeneous groups in a population. Our work currently being carried out relates to the study of the modality of the skew normal distribution in the univariate and multivariate cases. For the skew normal distribution, the aims are associated with studying the modality of the skew normal distribution and providing the ridgeline, the ridgeline elevation function, the $\Pi$ function, and the curvature function, and this will be conducive to an exploration of the number and location of mode when mixing the two components of skew normal distribution. The subsequent objective is to apply these results to the application of real world data sets, such as flow cytometry data.

Keywords: mode, modality, multivariate skew normal, finite mixture, number of mode

Procedia PDF Downloads 478

Authors: Amir Hadi Ziaie, Mostafa Hashemi, Shahram Jalalzadeh

Abstract:

It is now known that the end state of the collapse process of a dense star under its own gravity is the formation of a spacetime singularity. This is the spacetime event where the energy density and spacetime curvature diverge, and the classical general relativity breaks down. As we know, a realistic star is composed of fermions so that their spin effects could alter the final fate of the collapse scenario. The underlying theory within which the inclusion of spin effects can be worked out is the Einstein-Cartan theory. In this theory, the spacetime torsion which is defined as a geometrical quantity, is related to an intrinsic angular momentum of fermions (spin). In this work, we study the collapse process of a homogeneous spin fluid in such a framework and show that taking into account the spin effects of the collapsing cloud could prevent the formation of spacetime singularity.

Keywords: gravitational collapse, einstein-cartan theory, spacetime singularity, black hole physics

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Authors: Hasan Mahmud Reza

Abstract:

Extensive studies of the human umbilical cord, both basic and translational, over the last three decades have unveiled a plethora of information. The cord lining harbors at least two phenotypically different multipotent stem cells: mesenchymal stem cells (MSCs) and cord lining epithelial stem cells (CLECs). These cells exhibit a mixed genetic profiling of both embryonic and adult stem cells, hence display a broader stem features than cells from other sources. We have observed that umbilical cord-derived cells are immunologically privileged and non-tumorigenic by animal study. These cells are ethically acceptable, thus provides a significant advantage over other stem cells. The high proliferative capacity, viability, differentiation potential, and superior harvest of these cells have made them better candidates in comparison to contemporary adult stem cells. Following 30 replication cycles, these cells have been observed to retain their stemness, with their phenotype and karyotype intact. Transplantation of bioengineered CLEC sheets in limbal stem cell-deficient rabbit eyes resulted in regeneration of clear cornea with phenotypic expression of the normal cornea-specific epithelial cytokeratin markers. The striking features of low immunogenicity protecting self along with co-transplanted allografts from rejection largely define the transplantation potential of umbilical cord-derived stem cells.

Keywords: cord lining epithelial stem cells, mesenchymal stem cell, regenerative medicine, umbilical cord

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Authors: E. L. Elghazy, A. M. Sanad, M. G. Ghoneim

Abstract:

Over the past two decades research has shown that fiber reinforced polymers can be efficiently, economically and safely used for strengthening and rehabilitation of reinforced concrete (RC) structures. Designing FRP confined concrete columns requires reliable analytical tools that predict the level of performance and ductility enhancement. A numerical procedure is developed aiming at determining the type and thickness of FRP jacket needed to achieve a certain level of ductility enhancement. The procedure starts with defining the stress strain curve, which is used to obtain moment curvature relationship then displacement ductility ratio of reinforced concrete cross-sections subjected to bending moment and axial force. Three sets of published experimental tests were used to validate the numerical procedure. Comparisons between predicted results obtained by using the proposed procedure and actual results of experimental tests proved the reliability of the proposed procedure.

Keywords: columns, confinement, ductility, FRP, numerical

Procedia PDF Downloads 438

Authors: Seyed Aliasghar Mosavi, Mostafa Naderi, Khosrow Jadidi, Amir Hashem Mohammadi

Abstract:

To study the measurement of intraocular pressure (IOP) before and after implantation of intrastromal corneal ring (MyoRing) in patients with keratoconus. Setting: Baqiyatallah University of Medical Sciences, Tehran, Iran. Methods: We compared the IOP of 13 eyes which underwent MyoRing implantation prior and six months post operation using Goldman applanation (as gold standard), Icare, and Corvis ST (uncorrected, corrected and corrected with cornea biomechanics). Results: The resulting intraocular pressure measurements prior to surgery, Icare, Corvis (corrected with cornea biomechanics) overestimated the IOP, however measurements by Corvis uncorrected underestimate the IOP. The resulting intraocular pressure measurements after surgery, Icare, Corvis (corrected with cornea biomechanics) overestimated the IOP but measurements by Corvis uncorrected underestimate the IOP. Conclusion: Consistent intraocular pressure measurements on eyes with Myoring in keratoconus can be obtained with the Goldman applanation tonometer as the gold standard measurement. We were not able to obtain consistent results when we measured the IOP by Icare and Corvis prior and after surgery.

Keywords: intraocular pressure, MyoRing, Keratoconus, Goldmann applanation, Icare, Corvis ST

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Authors: Ryan D. Hoult

Abstract:

The inherent assumption in the elementary theory of bending that plane sections remain plane is commonly used in the design of reinforced concrete members. However, in reality, a shear flow would develop in non-rectangular sections, where the longitudinal strains in between the web and flanges of the element would lag behind those at the boundary ends. This phenomenon, known as shear lag, can significantly reduce the expected moment capacity of non-rectangular reinforced concrete walls. This study focuses on shear lag effects in reinforced concrete U-shaped walls, which are commonly used as lateral load resisting elements in reinforced concrete buildings. An extensive number of finite element modelling analyses are conducted to estimate the vertical strain distributions across the web and flanges of a U-shaped wall with different axial load ratios and longitudinal reinforcement detailing. The results show that shear lag effects are prominent and sometimes significant in U-shaped walls, particularly for the wall sections perpendicular to the direction of loading.

Keywords: shear lag, walls, U-shaped, moment-curvature

Procedia PDF Downloads 191