Hemisphere Of Radius Research Articles

Comparison of the presence and non-presence states of magnetite nanoparticles in tissue-equivalent breast phantom via radiofrequency hyperthermia

Objective(s): Breast cancer is a fatal disease and the leading cause of mortality in women. Radiofrequency hyperthermia is an approach to the treatment of cancer cells through increasing their temperature. The present study aimed to investigate breast tumor ablation via radiofrequency hyperthermia in the presence and non-presence states of magnetite nanoparticles and assess the effects of magnetite nanoparticles on breast cancer treatment in hyperthermia.Materials and Methods: Radius hemisphere geometry (5 cm) was designed, which was similar to an actual breast based on the fat tissues, glandular tissues as a semi-oval embedded in the hemisphere, and a radius sphere (1 cm) as a tumor region inside. After utilization in a three-dimensional printer, each layer of the phantom was filled with a proper combination of oil-gelatin with similar dielectric and thermal properties to an actual breast. To evaluate the effects of the magnetite nanoparticles, three weights of the magnetite were added to the tumor region (0.01, 0.05, and 0.1 g). Finally, the phantom was placed in a radiofrequency device with the frequency of 13.56 MHz.Results: Temperature differences were measured at four different points of the phantom. The power and time in the treatment were estimated at 40 watts and five minutes, respectively. The temperature and specific absorption rate plots were obtained for all the states in several graphs for five minutes.The results showed that the heat generation with the utilization of the magnetite state was higher by approximately 2.5-7˚C compared to the state without magnetite. Furthermore, the temperature of 0.05 gram of magnetite indicated that without causing damage in the healthy tissues, the entire tumor region could attain adequate heat uniformly (6.1-6.4˚C). Conclusion: Therefore, it could be concluded that 0.05 gram of magnetite could cause ablation in the entire tumor region.

Physical Parameters Measurement of Breast Equivalent Phantom for Clinical Studies in Radiofrequency Hyperthermia

Purpose: Breast cancer is one of the fatal diseases which causes death in women. Microwave hyperthermia is one way to treat cancer cells by irradiating RF waves to the cells and increasing their temperature. In our study, we fabricated breast phantom. Then we placed it in an RF field with a frequency of 13.56 MHz. We measured the temperature difference in several parts of the phantom, eventually. Materials and Methods: We designed a 5cm radius hemisphere geometry which is similar to real breast considering as fat tissue, glandular tissue as a semi-oval embedded in the hemisphere and a 1cm radius sphere as a tumor region in it. Then, it is utilized in a three-dimensional printer. After that, each layer of the phantom was filled with a suitable mixture of oil-gelatin which had similar properties of a real breast. Finally, we placed it in a microwave device with a frequency of 13.56 MHz. Results: During exposing RF to the phantom, the temperature differences were measured in four different points of the phantom. Our power and time in this treatment were 40 watt and 5 minutes, respectively. Temperature and Specific Absorption Rate (SAR) plots were obtained in several graphs for 5 minutes. Conclusion: The results showed that the heat generation with this frequency is much enough to cause damage in tumor tissues while healthy tissues tolerate a lower amount of heat. The results have shown that this band of frequency can cause ablation in tumor tissues and can be used for breast cancer treatments.

Electrochemical ATR-SEIRAS Using Low-Cost, Micromachined Si Wafers

Thin, micromachined Si wafers, designed as internal reflection elements (IREs) for attenuated total reflectance infrared spectroscopy, are adapted to serve as substrates for electrochemical ATR surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). The 500 μm thick wafer IREs with groove angles of 35° are significantly more transparent at long mid-IR wavelengths as compared to conventional large Si hemisphere IREs. The appeal of greater transparency is mitigated by smaller optical throughput at larger grazing angles and steeper angles of incidence at the reflecting plane that reduce the enhancement factor. Through use of the potential dependent adsorption of 4-methoxypyridine (MOP) as a test system, the microgroove IRE is shown to provide relatively strong electrochemical ATR-SEIRAS responses when the angle of incident radiation is between 50 and 55°, corresponding to refracted angles through the crystal of ∼40°. The higher than expected enhancement is attributed to attenuation of the reflection loss of p-polarized light and multiple reflections within the wafer-based IRE. The micromachined IREs are shown to outperform a 25 mm radius hemisphere in terms of S/N at wavenumbers less than ca. 1400 cm-1 despite the weaker signal enhancement derived from the steeper angle incident on the IRE/sample interface. The high optical transparency of the new IREs allows the spectral observation of displaced water libration bands at ca. 730 cm-1 upon solvent replacement by adsorbed MOP. The results are highly encouraging for the further development of low-cost, Si wafer-based IREs for electrochemical ATR-SEIRAS applications.

A Tunable Dual-Band Miniaturized Monopole Antenna for Compact Wireless Devices

A technique for producing miniaturized tunable planar monopole antennas for wireless communication applications is introduced. Miniaturization is achieved by optimizing the geometry of a pixelated metallic patch surrounding the monopole antenna. Tuning of the antenna is implemented by varying the capacitance of a varactor diode loaded between the pixelated metallic patch and the ground plane. The result is an ultra-compact, dual band, folded monopole antenna that fits into a hemisphere of radius λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /20 at 2.1 GHz. Varying the capacitance of the varactor diode enables the two resonance frequencies to be tuned simultaneously, covering multiple frequency bands for different wireless applications. A prototype antenna has been fabricated and measured, confirming the feasibility of the proposed design.

Hybrid Reynolds-Averaged Navier-Stokes/Large-Eddy Simulation Investigating Control of Flow over a Turret

This investigation explores the flow over a turret atM1 0:4 and ReD 2:4 10 using both hybrid Reynoldsaveraged Navier–Stokes/implicit large-eddy simulation (RANS/ILES) and k-based unsteady Reynolds-averaged Navier–Stokes (URANS) simulations. Additional hybrid RANS/ILES simulations were performed to compare the effectiveness of two steady-suction flow control approaches. The hybrid RANS/ILES computations were obtained using awell-validated high-orderNavier–Stokes flow solver employing a fourth-order compact spatial discretization in conjunction with a sixth-order low-pass spatial filter. The URANS simulations were performed using a secondorder version of the flow solver and kturbulence model. The turret configuration consisted of a half-foot radius hemisphere atop a 4.5-in.-tall circular cylinder base. Both steady suction through a slot and a leeward porous turret shell were explored as forms of flow control. Time-mean hybrid RANS/ILES results, obtained on a 23 10-point mesh, compared reasonably well to experimental pressure coefficient and velocity profiles for the baseline flow. The separation angle was predicted to within 3 deg of experimental observations. The instantaneous hybrid RANS/ILES solutions display complex three-dimensional flow phenomena in the wake of the turret that the kURANS model was unable to resolve. Both steady-suction flow control approaches successfully attached the flow over most the turret dome and significantly reduced the size of the wake.

EMBEDDED DISC-TYPE SURFACES WITH LARGE CONSTANT MEAN CURVATURE AND FREE BOUNDARIES

Given Ω ⊂ ℝ3an open bounded set with smooth boundary ∂Ω and H ∈ ℝ, we prove the existence of embedded H-surfaces supported by ∂Ω, that is regular surfaces in ℝ3with constant mean curvature H at every point, contained in Ω and with boundary intersecting ∂Ω orthogonally. More precisely, we prove that if Q ∈ ∂Ω is a stable stationary point for the mean curvature of ∂Ω, then there exists a family of embedded [Formula: see text]-surfaces near Q, ε &gt; 0 small, which, once dilated by a factor [Formula: see text] and suitably translated, converges to a hemisphere of radius 1 as ε → 0.

Self-Consistent Calculations of the Current and Access Resistance in Open Ion Channels

The problem of calculating the current and access resistance in open ion channels is considered. A self-consistent analytic solution is introduced for an arbitrary number of species within the Poisson-Nernst-Planck (PNP) equations formalism. The model considered is a cylindrical channel of radius a in the protein which allows ions to cross a membrane that is bathed by two solutions of different concentration on its left and right-hand sides. Electro-diffusion in this system is described by the Poisson equation combined with the continuity equations for the mobile ions. The PNP equations are solved in the bulk in the Boltzmann approximation in 3D, assuming spherical symmetry, and in the pore in a 1D approximation. The boundary conditions (BCs) for the potential and concentration are set at infinity. The internal BCs for the current and the gradient of the potential are set at the surfaces of two hemispheres of radius a. The two solutions are matched together at the internal BCs using an iterative procedure in a self-consistent way. The method allows for calculation of the currents for an arbitrary number of ions species that have different diffusion constants in the channel and in the bulk. The sizes of the ions are taken into account by introducing a “filling factor” as an additional fitting parameter. The method is applied to model experimental I-V characteristics of the Gramicidin A channel for various concentrations, yielding qualitative good agreement.

Experimental Investigation of the Concept of a ‘Breathing Zone’ using a Mannequin Exposed to a Point Source of Inertial/Sedimenting Particles Emitted with Momentum

An inhaling mannequin, CALTOOL, was used in a specially ventilated room to compare the concentrations inhaled with those sampled by samplers mounted across the breathing zone. The CALTOOL is made from metal sheets and consists of a cylindrical torso (42 x 24 x 54 cm) with a circular cylinder as head. A circular nozzle simulates the mouth. This nozzle is part of a cassette that holds a filter. The inhalation rate is not periodic but kept constant at nominally 20 l min(-1). The CALTOOL was placed in a horizontal air stream ( approximately 10 cm s(-1)) either facing or back to the wind. In front of the lower chest of the CALTOOL, a particle source was mounted which emitted particles with a momentum directed upwards at an angle of 45 degrees towards the CALTOOL. Five monodisperse aluminium oxide powders were used as test aerosols. The mass median aerodynamic diameters of the test aerosols ranged approximately 10 to 95 mum. Six conically shaped aerosol samplers were mounted horizontally and over the breathing zone of the CALTOOL, one on each shoulder, three across the upper torso, and one at the lower torso centre. Four to six runs per test aerosol and CALTOOL orientation in the airflow were conducted. The samples were analysed gravimetrically. The concentration ratio aerosol sampler to the CALTOOL cassette was determined for the investigated mounting positions. The results showed that when the CALTOOL was exposed to particles emitted with momentum from a point source in front of the lower chest, the variation in concentration over the breathing zone was large. The ratio of the concentration sampled by an aerosol sampler mounted somewhere within the breathing zone to the CALTOOL cassette concentration, would, for specific particle sizes, easily differ by a factor of 3, but may extend up to 10-100, depending on the particular conditions. The basic concept of a breathing zone consisting of a hemisphere of radius 25-30 cm is therefore not well suited for workers handling a point source emitting large particles. For such sampling situations, it is suggested that the radius of the breathing zone is reduced to 10 cm, which may be achieved by a head-mounted sampler.

Bandwidth performance limits for finite antennas

Bounded bandwidth performance measures are defined for any finite antenna, either in free space or above a perfectly conducting ground plane. The measures are valid for any class of antenna, for example, for patch antennas, dielectric resonator antennas and so on, the radiating currents of which can be confined to the Chu sphere or hemisphere of radius a. The performance bounds are believed to be nearly achievable for electrically small antennas. Examples are given for a loop antenna and a patch dipole antenna, where the former is electrically small and the latter has dimensions comparable to a wavelength.

Kinematic Analysis and Optimization of a Novel Robot for Surgical Tool Manipulation

The size and limited dexterity of current surgical robotic systems are factors that limit their usefulness. To improve the level of assimilation of surgical robots in minimally invasive surgery (MIS), a compact, lightweight surgical robotic positioning mechanism with four degrees of freedom (DOFs) (three rotational DOFs and one translation DOF) is proposed in this paper. This spatial mechanism based on a bevel-gear wrist is remotely driven with three rotation axes intersecting at a remote rotation center (the MIS entry port). Forward and inverse kinematics are derived, and these are used for optimizing the mechanism structure given workspace requirements. By evaluating different spherical geared configurations with various link angles and pitch angles, an optimal design is achieved, which performs surgical tool positioning throughout the desired kinematic workspace while occupying a small space bounded by a hemisphere of radius 13.7cm. This optimized workspace conservatively accounts for collision avoidance between the patient and robot or internally between the robot links. This resultant mechanism is highly compact and yet has the dexterity to cover the extended workspace typically required in telesurgery. It can also be used for tool tracking and skills assessment. Due to the linear nature of the gearing relationships, it may also be well suited for implementing force feedback for telesurgery.

Infrared Microspectroscopic Imaging Using a Large Radius Germanium Internal Reflection Element and a Focal Plane Array Detector

Previously, we established the ability to collect infrared microspectroscopic images of large areas using a large radius hemisphere internal reflection element (IRE) with both a single point and a linear array detector. In this paper, preliminary work in applying this same method to a focal plane array (FPA) infrared imaging system is demonstrated. Mosaic tile imaging using a large radius germanium hemispherical IRE on a FPA Fourier transform infrared microscope imaging system can be used to image samples nearly 1.5 mm x 2 mm in size. A polymer film with a metal mask is imaged using this method for comparison to previous work. Images of hair and skin samples are presented, highlighting the complexity of this method. Comparisons are made between the linear array and FPA methods.

Scale Effects in the High Temperature Gas Pressure Forming of Electrodeposited Fine-Grained Copper Thin Sheet

Scale effects in the high temperature gas pressure forming of electrodeposited fine-grained copper thin sheets were investigated by a series of tests at various forming temperatures and die apertures. The average as-deposited copper grain size was 5 μm. The geometrical parameters of the bugling die system and the thickness of copper sheet varied in proportion. Different radius hemisphere parts from 0.5mm to 5mm were obtained at a strain rate of 5.0×10−4 s−1, which was controlled by pressure forces curves determined in terms of a finite element method (FEM) based on constitutive equation proposed by Backoften in 1964. The experimental relative bulging height (RBH) values were measured, and compared with that predicted by the same finite element method (FEM). It was found that the experimental values of large scale parts approach to simulated values, whereas the experimental values of small scale parts were quite different from simulated values. In order to explain these phenomena, a grain-rotation-weakened mechanism was proposed.

SU-DD-A1-04: Monte Carlo Validation of Clinical Brachytherapy Dosimetry Under Partial Scatter Conditions for Neutron-Emitting Sources

Purpose: Monte Carlo (MC) models were generated in support of a clinical trial on the effectiveness of neutron-based brachytherapy for a patient treated with a plaque containing Cf-252 sources. Because the AAPM brachytherapy dosimetry formalism does not replicate partial scatter conditions of superficial brachytherapy, MC simulations were performed to evaluate treatment time and dose distributions generated using conventional methods. Method and Materials: Clinical calculations employed the AAPM dosimetry formalism with modified parameters for the neutron dose component. MC simulations utilized MCNP5 and track length estimator tallies. Computations applied a rectilinear mesh to tabulate neutron transport, including induced photons, and primary photon transport in a 14×14×5 cm3 volume with 9 mm3 voxels. Patient surface was simulated using a 20 cm radius hemisphere of water, with a corresponding hemisphere of air. For comparison to the AAPM formalism, the air was replaced with water. An RBE of 6 converted results to cGy-eq for the neutron component. Results were normalized to 0.1 mg Cf-252 source strength. Results: At the 6 mm prescription depth, calculated dose rates were 186±2 and 205±2 cGy-eq h−1 at plaque center and 24 mm offset, respectively. The central 4×4 cm2 area received 227±32 cGy-eq h−1. For comparison, full-scatter simulations yielded 205±2 cGy-eq h−1 at plaque center and 244±32 cGy-eq h−1 over a 4×4 cm2 area; although, computation time increased by a factor of 6.6. Dose ratios of full- (4π) to partial-scatter (2π) environments increased from 1.07 to 1.10 as depth increased from 0.4 to 5 cm. Approximately 90% of the dose-equivalent was due to neutrons, while neutron physical dose was 68% and 57% of the total at 0.6 and 5.0 cm depths, respectively. Conclusion: Dose can be overestimated upto 10% by assuming full-scatter conditions for Cf-252 plaque brachytherapy. MC simulations are recommended to validate treatment plans generated using conventional methods.

How an antenna launches its input power into radiation: The pattern of the Poynting vector at and near an antenna

I address the question of whether the seat of the power radiated by an antenna made of conducting members is distributed over the arms of the antenna according to −J∙E, where J is the current density and E is the electric field produced by the source. Poynting’s theorem permits only a global identification of the total input power, usually from a localized generator, with the total power radiated to infinity, not a local correspondence of −J∙Ed3x with a specific radiated power, r2S∙r̂dΩ. I describe a model antenna consisting of two perfectly conducting hemispheres of radius a separated by a small equatorial gap across which occurs the driving oscillatory electric field. The fields and surface current are determined by solution of the boundary value problem. In contrast to the first approach (not a boundary value problem), the tangential electric field vanishes on the metallic surface. There is no radial Poynting vector at the surface. Numerical examples are shown to illustrate how the energy flows from the input region at the gap and is guided near the antenna by its arms until it is launched at larger r∕a into the radiation pattern determined by the value of ka.

Effect of Local Molecular Shape and Anisotropic Reactivity on the Rate of Diffusion-Controlled Reactions

The role of distance-dependent anisotropic reactivity and molecular geometry in the vicinity of localized reaction centers in influencing the rate of bimolecular diffusion-controlled reactions is analyzed in detail, both analytically and numerically. The effect of local molecular shape is considered within the model of reflective hemispheres of small radius l h on the surfaces of otherwise spherical molecules of radius R ( l h ≪ R) . The distance-dependent reactivity is modeled by reactive hemispheres of radius l r on top of the reflective hemispheres ( l r ≪ R) . It is shown that the presence of the reflective hemispheres leads to a markedly large increase of the reaction rate. The maximum effect is ∼ R/ l h ≫ 1 times, as described by the ratio of local to average molecular curvature. It is observed for l h ≈ R( l r /R) 1/2 ≫ l r. The effect of thickness of the reaction regions is described within the model of reactive cylinders of height l r and angular radius θ ≪ 1. It is shown that the characteristic parameter in the expansion of the reaction rate as a function of l r /R is l r /( Rθ 2 ) , and therefore, even for small relative thickness d = l r/ θ, its effect on the rate is very strong, i.e., the conventional model of reactive patches, which assumes zero thickness of the reaction region, may considerably underestimate the reaction rate.

The Soft X-Ray Properties of Nearby Low-Luminosity Active Galactic Nuclei and their Contribution to the Cosmic X-Ray Background

We have examined ROSAT soft X-ray observations of a complete, distance-limited sample of Seyfert and LINER galaxies. X-ray data are available for 46 out of 60 such objects which lie within a hemisphere of radius 18 Mpc. We have constructed radial profiles of the nuclear sources in order to characterize their spatial extent and, in some cases, to help constrain the amount of flux associated with a nuclear point source. PSPC data from ROSAT have been used to explore the spectral characteristics of the objects with sufficient numbers of detected counts. Based on the typical spectral parameters of these sources, we have estimated the luminosities of the weaker sources in the sample. We then explore the relationship between the soft X-ray and Hα luminosities of the observed objects; these quantities are correlated for higher luminosity AGNs. We find a weak correlation at low luminosities as well, and we have used this relationship to predict LX for the 14 objects in our sample that lack X-ray data. Using the results of the spatial and spectral analyses, we have compared the X-ray properties of Seyferts and LINERs, finding no striking differences between the two classes of objects. However, both types of objects often exhibit significant amounts of extended emission, which could minimize the appearance of differences in their nuclear properties. The soft X-ray characteristics of the type 1 and type 2 active galaxies in the sample are also discussed. We then compute the local X-ray volume emissivity of low-luminosity Seyferts and LINERs and investigate their contribution to the cosmic X-ray background. The 0.5–2.0 keV volume emissivity of 2.2 × 1038 ergs s-1 Mpc-3 we obtain for our sample suggests that low-luminosity AGNs produce at least 9% of the soft X-ray background.

Some Aspects of the Dynamic of V=H−H

We consider the evolution of a surface Γ(t) according to the equation V=H−H, where V is the normal velocity of Γ(t), H is the sum of the two principal curvatures and H is the average of H on Γ(t). We study the case where Γ(t) intersects orthogonally a fixed surface Σ and discuss some aspects of the dynamics of Γ(t) under the assumption that the volume of the region enclosed between Γ(t) and Σ is small. We show that, in this case, if Γ(0) is near a hemisphere, Γ(t) keeps its almost hemispherical shape and slides on Σ crawling approximately along orbits of the tangential gradient ∇HΣ of the sum HΣ of the two principal curvatures of Σ. We also show that, if p∈Σ is a nondegenerate zero of ∇HΣ and a>0 is sufficiently small, then there is a surface of constant mean curvature which is near a hemisphere of radius a with center near p and intersects Σ orthogonally.

On the derivation of boundary integral equations for scattering by an infinite two-dimensional rough surface

A plane acoustic wave is incident upon an infinite, rough, impenetrable surface S. The aim is to find the scattered field by deriving a boundary integral equation over S, using Green’s theorem and the free-space Green’s function. This requires careful consideration of certain integrals over a large hemisphere of radius r; it is known that these integrals vanish as r→∞ if the scattered field satisfies the Sommerfeld radiation condition, but that is not the case here—reflected plane waves must be present. It is shown that the well-known Helmholtz integral equation is not valid in all circumstances. For example, it is not valid when the scattered field includes plane waves propagating away from S along the axis of the hemisphere. In particular, it is not valid for the simplest possible problem of a plane wave at normal incidence to an infinite flat plane. Some suggestions for modified integral equations are discussed.

A multiwire hydrogen electrode for in vivo use

A multiwire surface electrode is described for measuring the partial pressure of hydrogen gas within extremely small volumes. The purpose was to record hydrogen clearance curves in vivo in order to analyse capillary blood flow. A method for improving the sensitivity and stability of the Clark-type polarographic sensor is presented. The in vitro and in vivo properties were investigated and are critically compared with the characteristics predicted from various models for the polarographic measurements of gases. The high stability and low drift of the electrode together with its small catchment volume (a hemisphere of radius 32 mu m) meant that it could be reliably used for accurate, reproducible local measurements of hydrogen clearance curves in vivo. The experiments also demonstrated that the electrode could be used most successfully for the measurement of capillary blood flow even in the heart and contracting skeletal muscle.

ChemInform Abstract: Ferroelectric Structure and Related Properties of Pb5W3O9F10.

AbstractThe new ferroelectric title material crystallizes in the tetragonal system (I4, Z=4).