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The exact analytical solution of the electromagnetic field distribution produced by uniform electric currents excited on Cartesian half-planes and quadrants is presented. The total field is expressed in terms of geometrical optics (GO) and diffracted field contributions that remain valid for arbitrary observation points and frequency. The jump discontinuity of the GO field is exactly compensated by the diffracted field whose spatial distribution is described in terms of the incomplete Hankel functions and by means of a novel special function. The expression of the diffracted field includes contributions arising from the edges and the vertex of the considered Cartesian domain, illustrating the analytical behavior of the near-field singularities and providing insight into the physical mechanisms governing the field diffractive processes. The proposed solution yields a method to determine the physical optics (PO) response of flat metallic screens excited by uniform plane waves, as well as the fields produced by pulse-shaped basis functions used in the method-of-moments (MoM) solution of electromagnetic problems, showing the relevance of the exact analytical expressions of the GO and diffracted fields arising from edges and vertices of each rectangular pulse domain. Numerical examples validate the accuracy of the proposed field representation.

Using neutron diffraction, we have tracked the temperature dependence of structural properties for heavy water confined in the nanoporous silica matrix MCM-41-S. By observing the correlation peak corresponding to the pore-pore distance, which is determined by the scattering contrast between the silica and the water, we monitored the density of the confined water. Concurrently, we studied the prominent first diffraction peak of D(2)O at ≈ 1.8 Å(-1), which furnishes information on the microscopic arrangement of the water molecules. The data show the presence of a density maximum at ≈ 275 K (± 10 K), a property similar to bulk water, and the occurrence of a density minimum at ≈ 180 K (± 10 K). The prominent diffraction peak of D(2)O is found to shift and sharpen over a wide T range from 200 to 270 K, reflecting structural changes that are strongly correlated with the changes in density. We also observe the continuous formation of external ice, arising from water expelled from the pores while expansion takes place within the pores. An efficient method for monitoring the density of the confined D(2)O using a triple-axis spectrometer is demonstrated.

A representation of the surface current density particularly suited for the electrodynamic characterization of arbitrarily shaped discontinuities in monolithic microwave and millimeter-wave integrated circuits (MMICs) is presented. The spectral domain approach (SDA) is adopted to carry out the analysis. Some numerical results, obtained using the proposed current representation, are compared with those available in the literature. A fast and excellent numerical convergence for the scattering parameters is achieved.

A photoresponsive surfactant has been used as a means to control protein structure and dynamics with light illumination. This cationic azobenzene surfactant, azoTAB, which undergoes a reversible photoisomerization upon exposure to the appropriate wavelength of light, adopts a relatively hydrophobic, trans structure under visible light illumination and a relatively hydrophilic cis structure under UV light illumination. Small-angle neutron scattering (SANS) and neutron spin echo (NSE) spectroscopy were used to measure the tertiary structure and internal dynamics of lysozyme in the presence of the photosurfactant, respectively. The SANS-based in vitro structures indicate that under visible light the photosurfactant induces partial unfolding that principally occurs away from the active site near the hinge region connecting the α and β domains. Upon UV exposure, however, the protein refolds to a nativelike structure. At the same time, enhanced internal dynamics of lysozyme were detected with the surfactant in the trans form through NSE measurements of the Q-dependent effective diffusion coefficient (D(eff)) of the protein. In contrast, the D(eff) values of lysozyme in the presence of cis azoTAB largely agree with the rigid-body calculation as well as those measured for pure lysozyme, suggesting that the native protein is dormant on the nanosecond time and nanometer length scales. Lysozyme internal motions were modeled by assuming a protein of two (α and β domains) or three (α and β domains and the hinge region) domains connects by either soft linkers or rigid, freely rotating bonds. Protein dynamics were also tracked with Fourier transform infrared spectroscopy through hydrogen-deuterium exchange kinetics, which further demonstrated enhanced protein flexibility induced by the trans form of the surfactant relative to the native protein. Ensemble-averaged intramolecular fluorescent resonance energy transfer measurements similarly demonstrated the enhanced dynamics of lysozyme with the trans form of the photosurfactant. Previous results have shown a significant increase in protein activity in the presence of azoTAB in the trans conformation. Combined, these results provide insight into a unique light-based method of controlling protein structure, dynamics, and function and strongly support the relevance of large domain motions for the activity of proteins.

The introduction of new digital signals with spread spectrum modulation has generated the necessity to evaluate the behavior of the available traditional instruments, which are historically used to assess the field for human body exposure. For this reason, SAR probes have been tested, in order to evaluate the uncertainties introduced on their output in presence of a set of wideband signals. A proper experimental set-up has been designed and pre-characterized.

Aqueous solutions of lithium chloride are an excellent model system for studying the dynamics of water molecules down to low temperatures without freezing. The apparent dynamic crossover observed in an aqueous solution of LiCl at about 220 to 225 K [Mamontov, JPCB 2009, 113, 14073] is located practically at the same temperature as the crossover found for pure water confined in small hydrophilic pores. This finding suggests a strong similarity of water behavior in these two types of systems. At the same time, studies of solutions allow more effective explorations of the long-range diffusion dynamics, because the water molecules are not confined inside an impenetrable matrix. In contrast to the earlier incoherent quasielastic neutron scattering results obtained for the scattering momentum transfers of 0.3 A(-1) ≤ Q ≤ 0.9 A(-1), our present incoherent neutron spin-echo measurements at a lower Q of 0.1 A(-1) exhibit no apparent crossover in the relaxation times down to 200 K. At the same time, our present nuclear magnetic resonance measurements of the diffusion coefficients clearly show a deviation at the lower temperatures from the non-Arrhenius law obtained at the higher temperatures. Our results are consistent with a scenario in which more than one relaxational component may exist below the temperature of the dynamic crossover in water.

The thermal fluctuation and elasticity of dioleoyl-phosphocholine large unilamellar vesicle interacting with pore-forming peptide, melittin, were investigated by neutron spin-echo measurements. The relaxation behavior of the membrane fluctuation with different peptide to lipid molar ratio $P/L$ can be divided into three regions, resulting from characteristic changes of the effective bending modulus $\stackrel{\texttildelow{}}{\ensuremath{\kappa}}$ of the membrane which includes the effects of internal dissipation within the membrane. At low $P/L$, melittin is adsorbed parallel to the surface of membrane and $\stackrel{\texttildelow{}}{\ensuremath{\kappa}}$ decreases significantly due to perturbation of hydrocarbon chain packing. At a critical $P/L$, melittin forms pores in the membrane and $\stackrel{\texttildelow{}}{\ensuremath{\kappa}}$ starts to increase slightly due to high pore rigidity. At higher $P/L$ where the repulsive interpore interaction becomes significant, $\stackrel{\texttildelow{}}{\ensuremath{\kappa}}$ increases rapidly.

This review article describes our neutron scattering experiments made in the past four years for the understanding of the single-particle (hydrogen atom) dynamics of a protein and its hydration water and the strong coupling between them. We found that the key to this strong coupling is the existence of a fragile-to-strong dynamic crossover (FSC) phenomenon occurring at around T[subscript L] = 225±5 K in the hydration water. On lowering of the temperature toward FSC, the structure of hydration water makes a transition from predominantly the high density form (HDL), a more fluid state, to predominantly the low density form (LDL), a less fluid state, derived from the existence of a liquid–liquid critical point at an elevated pressure. We show experimentally that this sudden switch in the mobility of hydration water on Lysozyme, B-DNA and RNA triggers the dynamic transition, at a temperature T[subscript D] = 220 K, for these biopolymers. In the glassy state, below T[subscript D], the biopolymers lose their vital conformational flexibility resulting in a substantial diminishing of their biological functions. We also performed molecular dynamics (MD) simulations on a realistic model of hydrated lysozyme powder, which confirms the existence of the FSC and the hydration level dependence of the FSC temperature. Furthermore, we show a striking feature in the short time relaxation (β-relaxation) of protein dynamics, which is the logarithmic decay spanning 3 decades (from ps to ns). The long time α-relaxation shows instead a diffusive behavior, which supports the liquid-like motions of protein constituents. We then discuss our recent high-resolution X-ray inelastic scattering studies of globular proteins, Lysozyme and Bovine Serum Albumin. We were able to measure the dispersion relations of collective, intra-protein phonon-like excitations in these proteins for the first time. We found that the phonon energies show a marked softening and at the same time their population increases substantially in a certain wave vector range when temperature crosses over the T[subscript D]. Thus the increase of biological activities above T[subscript D] has positive correlation with activation of slower and large amplitude collective motions of a protein., United States. Dept. of Energy (Grant DE-FG02-90ER45429)

Primary intent of this study is development of realistic vascular structure and simulation of the blood perfusion in capillary. It is needed for precise thermal analysis using the modified bio-heat equation to provide better prediction of thermal response of tissues exposed to RF energy then in conventional Pennes model [1]. Particularly, motivation of this paper is to use previously presented modified bioheat equation [2–4] for heat exchange and temperature rise simulation on a realistic human head model.

The single particle dynamics of water confined in a hydrophobically modified MCM-41-S sample has been studied using three high resolution quasielastic neutron scattering spectrometers in the temperature range from 300 to 210 K. A careful modeling of the dynamics allowed us to obtain good agreement among the results obtained with the three instruments, which have very different energy resolutions. The picture arising from the data is that, because of the heterogenous environment experienced by the water molecules, the dynamics show a broad distribution of relaxation times. However, the Fickian diffusive behavior is retained. In the investigated temperature range we found no evidence of the dynamic crossover, from a non-Arrhenius to an Arrhenius behavior, which was detected for water confined in hydrophilic MCM-41-S. This finding is in agreement with what was reported by Chu et al. [Phys. Rev. E 76, 021505 (2007)] for water confined in other hydrophobic confining media that the dynamic crossover takes place at a much lower temperature. The results reported in the paper help clarify the role that the chemical interaction between the water molecules and the walls of the confining host plays in determining the characteristics of the water dynamics, as compared to purely geometric constraints such as the size and shape of the pores.

The low-temperature behavior of proteins under high pressure is not as extensively investigated as that at ambient pressure. In this paper, we study the dynamics of a hydrated protein under moderately high pressures at low temperatures using the quasielastic neutron scattering method. We show that when applying pressure to the protein−water system, the dynamics of the protein hydration water does not slow down but becomes faster instead. The degree of “softness” of the protein, which is intimately related to the enzymatic activity of the protein, shows the same trend as its hydration water as a function of temperature at different pressures. These two results taken together suggest that at lower temperatures, the protein remains soft and active under pressure.

The technique to improve performance of specific GPS antennas on portable handsets by means of controlling the radiation pattern is presented in this paper. Location-based applications for handheld wireless communication devices may represent a significant revenue stream for cellular operators and may therefore add value to global positioning system (GPS) enabled handsets. Location-enabled features may also be desirable or even required, for instance, in professional and public safety radios. In order for location-based applications to provide the required quality-of-service (QoS), as it may be defined from case to case depending on the type of application, it is critical to implement GPS systems capable of operating reliably in the envisioned use scenarios.

Location-based applications for handheld wireless communication devices may represent a significant revenue stream for cellular operators and may therefore add value to global positioning system (GPS) enabled handsets. Location-enabled features may also be desirable or even required in professional and public-safety radios. In order for location-based applications to provide the required quality-of-service (QoS) - as it may be defined from case to case depending on the type of application - it is critical to implement GPS systems capable of operating reliably in the envisioned use scenarios.

This paper presents the recent efforts to develop standards allowing numerical methods and techniques for accurate and representative simulations of human exposure to RF energy in automotive environments. The focus of this work is to standardize numerical and modeling procedures that produce repeatable results based on simulations of the human body exposure to RF energy emitted by mobile radios with vehicle- mount antennas. This activity is carried out in the framework of IEEE 1528.1 and IEEE 1528.2 standards development with the goal to provide a robust methodology for evaluating the compliance of vehicle-mount transmitters with respect to international exposure safety standards by means of numerical simulations.

An analytical formulation based on physical optics is employed to determine the field and the radiated power distribution by open-ended circular waveguides. Using the incomplete Hankel functions, the line integrals yielding the electromagnetic field are evaluated in closed analytical form along the waveguide axis. It is shown that cylindrical waves are generated by the surface currents flowing on the waveguide walls, while spherical waves are produced by the currents and charges excited at the waveguide truncation. Cylindrical and spherical waves are shown to be responsible for the field synthesis in terms of waveguide modes and scattered fields at the waveguide mouth. Numerical results concerning the spatial distribution of the electromagnetic field and associated power density are compared with previously published results, showing the advantage of the incomplete Hankel functions formulation. Finally, the uniform asymptotic representation of the incomplete Hankel function is shown to be suitable to compute the field distribution on the waveguide axis except for the TE 11 and TM 01 modes.

We have observed a Fragile‐to‐Strong Dynamic Crossover (FSC) phenomenon of the α‐relaxation time and self‐diffusion constant in confined supercooled water. The α‐relaxation time is measured by Quasielastic Neutron Scattering (QENS) experiments and the self‐diffusion constant by Nuclear Magnetic Resonance (NMR) experiments. Water is confined in 1‐d geometry in cylindrical pores of nanoscale silica materials, MCM‐41‐S and in Double‐Wall Carbon Nanotubes (DWNT). The crossover phenomenon can also be observed from appearance of a Boson peak in Incoherent Inelastic Neutron Scattering experiments. We observe a pronounced violation of the Stokes‐Einstein Relation at and below the crossover temperature at ambient pressure. Upon applying pressure to the confined water, the crossover temperature is shown to track closely the Widom line emanating from the existence of a liquid‐liquid critical point in an unattainable deeply supercooled state of bulk water. Relation of the dynamic crossover phenomenon to the existence of a density minimum in supercooled confined water is discussed. Finally, we discuss a role of the FSC of the hydration water in a biopolymer that controls the biofunctionality of the biopolymer.

The diffusion of wireless technology has caused concerns about interference in the hospital environment. Most hospitals have banned the use of cell phones on their premises although wireless technology can help in delivering time critical help to patients. We discuss some factors of radio frequency (RF) near field interference. These phenomena do not lend themselves easily to theoretical evaluation. It is possible to avert medical equipment interference by performing ad hoc tests. The method requires measurements of electromagnetic fields and the observation of interference events with increasing distance between equipment and RF transmitters. The results are applicable only to the specific testing environment. The ad hoc proposed method can be found in the draft document C63.18 of the American National Standard Institute.

The paper demonstrates a new way of overcoming the fundamental limit imposed on the fractional bandwidth of small antennas in relation to antenna volume by means of using a non-Foster (active) network. Unlike the techniques known in literature that use non-Foster matching circuits to broaden the operating bandwidth of electrically small antennas, the present approach utilizes the specific antenna structure with an additional port which is loaded by a non-Foster reactive element. The combination of properties of the specific two port antenna structures and the reactive loads produces an extremely wideband response not achievable with passive antennas of the same volume.

BACKGROUND Capsule enteroscopy is considered the gold standard for evaluating patients with obscure gastrointestinal bleeding. The costs of capsule enteroscopy examination, however, make it uncertain whether the clinically relevant diagnostic gain is also associated with cost savings. AIM To evaluate the incremental cost-effectiveness ratio of capsule enteroscopy in patients with obscure gastrointestinal bleeding. METHODS Retrospective study was carried out in nine Italian gastroenterology units from 2003 to 2005. Data on 369 consecutive patients with obscure gastrointestinal bleeding were collected. The diagnostic yield of capsule enteroscopy vs. other imaging procedures was evaluated as a measure of efficacy. The values of Diagnosis Related Group 175 (euro 1884.00 for obscure-occult bleeding and euro 2141.00 for obscure-overt bleeding) were calculated as measures of economic outcomes in the cost analysis. RESULTS Obscure and occult gastrointestinal bleeding was recorded in 177 patients (48%) with a mean duration of anemia history of 17.6+/-20.7 months. Among patients, 60.9% had had at least one hospital admission, 21.2% at least two, and 1.2% of obscure bleeders up to nine admissions. Overall, 58.4% of patients had positive findings with capsule enteroscopy compared with 28.0% with other imaging procedures (P

High-resolution quasielastic neutron scattering spectroscopy was used to measure H2O and D2O hydrated RNA samples. The contribution of scattering from RNA was subtracted out by taking the difference of the signals between the two samples. The measurements were made at a series of temperatures from 270 K down to 180 K. The relaxing-cage model was used to analyze the difference quasielastic spectra. We observed clear evidence of a fragile-to-strong dynamic crossover (FSC) at TL=220 K in RNA hydration water. We further show that the mean-square displacements of the hydrogen atoms in both RNA and its hydration water exhibit a sharp change in slope at approximately the same temperature 220 K. This latter fact suggests that the dynamic transition in RNA is triggered by the abrupt change of mobility of the hydration water at its FSC temperature.

An internal multi-band antenna for mobile phones featuring wide fractional bandwidth is presented. The antenna is realized by a flat conformal conductor above the ground plane, featuring a feed and ground connections to the PCB. A slot is cut in the flat conductor, which is open only in between the ground and feeding connections of the flat conductor, thus forming a slit. This structure is called enhanced bandwidth folded inverted conformal antenna (EB-FICA), with reference to its precursor FICA (Di Nallo and Faraone, 2005). The EB-FICA can be designed to be penta-band, covering the four GSM bands and the UMTS Rx band, and has been adopted in several Motorola products.

This paper proposes a different approach to non-Foster or active matching. An antenna structure with two ports is considered. One port is used to couple the signal, while the other one is connected to a non-Foster network. The advantage of this configuration is that the antenna can be designed to have real input impedance, as seen from the feeding port, fairly constant across a very broad band when the active load is applied. The input reactance compensation is essentially performed by the non-Foster network, typically behaving as a negative inductor.

Antenna systems that would enable seamless mobility using portable Software Definable Radios include a wide variety of technologies, ranging from multi-band, tunable, or active antennas, to multiple-input multiple output (MIMO) antenna systems. Depending on the specific SDR application and the expected spectrum coverage, some antenna technologies are more suitable to meet performance, size, complexity, and cost requirements. A number of antenna technologies suitable for enabling SDR on mobile phone and professional radio form factors are illustrated and comparatively analyzed. (6 pages)

The circuit model and the near-field behavior of a novel wide-band E-shaped microstrip patch antenna suitable for wireless communication devices are presented. A suitable locally conformal FDTD numerical procedure is employed to analyze the electromagnetic field excited by the radiator, and to derive a frequency-independent antenna equivalent circuit. Numerical results concerning the antenna parameters are in good agreement with experimental measurements. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 97–100, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22057

An overview of various analytical and computational methodologies for the assessment of the human exposure to radio-frequency (RF) sources is provided. Different methodologies find application in different exposure conditions, for instance in the near or far field of RF sources, or in indoor or outdoor environments. Exposure metrics can be the specific absorption rate (SAR), which is the basic restriction defined in international safety standards, or derived incident field levels. The thermal load produced by RF energy deposition is also addressed by referring to the numerical solution of the Pennes? bio-heat equation. Suitability of various methodologies to address different exposure conditions is discussed also in relation to present trends in safety and compliance standards.

Temperature rise evaluation in human body exposed to RF energy is becoming increasingly important topic related to the future development of the RF exposure safety standards. Therefore the validation of the existing methods like FDTD used in such complex multidisciplinary studies is very important. The accuracy of the FDTD solution of the bio-heat equation which is most often used in this type if studies have been analyzed based on the developed program package. The effect of stair case geometry representation in FDTD grid has been investigated by comparing the test case with analytical solution. In addition comparison was made with the published results. Preliminary data show that in case of constant temperature boundary conditions FDTD results slightly differ from the analytical solution during the transition state of the heat transfer process while there is a much better agreement in steady state regime. In case of convective boundary conditions the steady state temperature distribution at the convective boundary obtained by FDTD method also differ insignificantly from the FEM results reported in literature and temperature values inside the model are almost identical with that from FEM models. The results point to the conclusion that the error in FDTD simulations may be attributed to faster heat exchange which is due to the difference of surface area between the smooth and stair case boundaries of the modeled structures. These results are similar to those reported in T. Samaras et al. (2006). The impact on temperature inside the body far from the boundary is less than 1% while at the boundary is in the range of 4-7% for the models with 0.5 mm grid resolution and tissue like thermal properties

By means of a nuclear magnetic resonance experiment, we give evidence of the existence of a fragile-to-strong dynamic crossover transition (FST) in confined water at a temperature T(L)=223+/-2 K. We have studied the dynamics of water contained in 1D cylindrical nanoporous matrices (MCM-41-S) in the temperature range 190-280 K, where experiments on bulk water were so far hampered by crystallization. The FST is clearly inferred from the T dependence of the inverse of the self-diffusion coefficient of water (1D) as a crossover point from a non-Arrhenius to an Arrhenius behavior. The combination of the measured self-diffusion coefficient D and the average translational relaxation time tau(T), as measured by neutron scattering, shows the predicted breakdown of Stokes-Einstein relation in deeply supercooled water.

We report a set of dynamical data of confined water measured in a very deeply supercooled regime (290?190?K). Water is contained in silica matrices (MCM-41-S) which consist of 1D cylindrical pores with diameters d = 14,18 and 24??. When confined in these tubular pores, water does not crystallize, and can be supercooled well below 200?K. We use the NMR technique to obtain the characteristic proton relaxation time-constants (the spin?lattice relaxation time-constant T1 and the spin?spin relaxation time-constant T2) and a direct measurement of the self-diffusion coefficient in the whole temperature range. We give evidence of the existence of a fragile-to-strong dynamic crossover (FSC) at TL = 225?K from the temperature dependence of the self-diffusion coefficient. A combination of the NMR self-diffusion coefficient with the average translational relaxation time, as measured by quasi-elastic neutron scattering, shows a well defined decoupling of transport coefficients, i.e.? the breakdown of the Stokes?Einstein relation, on approaching the crossover temperature TL.

This paper presents an approach to estimate the main characteristics (specific absorption rate (SAR), total absorbed EM power and temperature rise) related to human exposure to EM energy. The assessment is done numerically using a proprietary software package, which is based on the finite difference time domain (FDTD) method and the method of auxiliary sources (MAS) (used here for partially homogeneous models). The general goal is to provide an efficient and sufficiently accurate method to assess human exposure to EM fields in a wide frequency range and for different types of exposure conditions: far field exposure (from cellular base stations) and near field exposure (from personal wireless communication devices). Dependence of exposure on different posture and EM field distribution inside the body is considered.

A full-wave FDTD analysis of a class of planar circular spiral inductors is presented. A locally conformal FDTD scheme is employed to analyze the circuital behavior and the spurious emission of inductors realized on a substrate of finite dimensions. Since the adopted model includes all the losses mechanisms taking place in the dielectric and metallic regions as well as the radiation phenomena due to the excitation of surface and volume waves it allows modeling accurately the relevant dynamic processes responsible for the structure behavior. The numerical results show that the circuital performances and the level of the radiated emission are significantly influenced by the inductor geometry as well as by the materials forming the structure.

At low temperatures proteins exist in a glassy state, a state which has no conformational flexibility and shows no biological functions. In a hydrated protein, at and above 220 K, this flexibility is restored and the protein is able to sample more conformational sub-states, thus becomes biologically functional. This 'dynamical' transition of protein is believed to be triggered by its strong coupling with the hydration water, which also shows a similar dynamic transition. Here we demonstrate experimentally that this sudden switch in dynamic behavior of the hydration water on lysozyme occurs precisely at 220 K and can be described as a Fragile-to-Strong dynamic crossover (FSC). At FSC, the structure of hydration water makes a transition from predominantly high-density (more fluid state) to low-density (less fluid state) forms derived from existence of the second critical point at an elevated pressure., Comment: 6 pages (Latex), 4 figures (Postscript)

By confining water in nanopores, so narrow that the liquid cannot freeze, it is possible to explore its properties well below its homogeneous nucleation temperature T H ≈ 235 K. In particular, the dynamical parameters of water can be measured down to 180 K, approaching the suggested glass transition temperature T g ≈ 165 K. Here we present experimental evidence, obtained from Nuclear Magnetic Resonance and Quasi-Elastic Neutron Scattering spectroscopies, of a well defined decoupling of transport properties (the self-diffusion coefficient and the average translational relaxation time), which implies the breakdown of the Stokes–Einstein relation. We further show that such a non-monotonic decoupling reflects the characteristics of the recently observed dynamic crossover, at ≈225 K, between the two dynamical behaviors known as fragile and strong, which is a consequence of a change in the hydrogen bond structure of liquid water.

The RF power absorption and specific absorption rate (SAR) distribution in a simplified three layer head phantom is investigated using a recently developed computational suit for electromagnetic and thermal analysis of biological objects exposed to RF energy. The simulations are based on FDTD methodology which is implemented in the code. The program is suitable for parametric analysis based on various thermal properties of the tissues including blood perfusion to study their influence on temperature change and its distribution associated with RF exposure. Various SAR averaging volumes are considered to find the one that is best correlated with temperature change distribution. The computations are performed at frequencies from 0.3 GHz to 3 GHz.

A multi-band internal antenna for mobile phones is realized by means of an elongated flat conductor featuring a closed slot, a ground leg, and a feed leg. A benchmark on a Motorola T192 handset is employed to illustrate the operation of this structure - called folded inverted conformal antenna (FICA) - showing that it provides significantly more radiating bandwidth that a conventional dual band PIFA under the same operating conditions. Because of its favorable performance, FICA is employed in several Motorola handsets in the consumer market.

The level and distribution of radiofrequency energy absorbed in a child's head during the use of a mobile phone compared to those in an adult head has been a controversial issue in recent years. It has been suggested that existing methods that are used to determine specific absorption rate (SAR) and assess compliance with exposure standards using an adult head model may not adequately account for potentially higher levels of exposure in children due to their smaller head size. The present study incorporates FDTD computations of locally averaged SAR in two different anatomically correct adult and child head models using the IEEE standard (Std. C95.3-2002) SAR averaging algorithm. The child head models were obtained by linear scaling of the adult head model to replicate the conditions of previous studies reported in the literature and also by transforming the different adult head models based on data on the external shapes of children's heads. The tissue properties of the adult and corresponding child head models were kept the same. In addition, modeling and experimental measurements were made using three spheres filled with a tissue-equivalent mixture to approximate heads of increasing size. Results show that the peak local average SAR over 1 g and 10 g of tissue and the electromagnetic energy penetration depths are about the same in all of the head models under the same exposure conditions. When making interlaboratory comparisons, the model and the SAR averaging algorithm used must be standardized to minimize controversy.

By confining water in nano-pores of silica glass, we can bypass the crystallization and study the pressure effect on the dynamical behavior in deeply supercooled state using neutron scattering. We observe a clear evidence of a cusp-like fragile-to-strong (F-S) dynamic transition. Here we show that the transition temperature decreases steadily with an increasing pressure, until it intersects the homogenous nucleation temperature line of bulk water at a pressure of 1600 bar. Above this pressure, it is no longer possible to discern the characteristic feature of the F-S transition. Identification of this end point with the possible second critical point is discussed., Comment: 4 pages, 3 figures

Prediction formulae for estimating the peak equivalent power density in the near-field of cellular base-station array antennas are demonstrated. Theoretical justification stemming from a uniform asymptotic expansion of the field radiated by collinear arrays is described, and verification is carried out by means of an extensive computational analysis of different classes of base station antennas. The formulae, which depend on a few, readily available parameters, can be conveniently employed for the estimation of compliance distances with respect to RF safety guidelines issued by the International Committee on Non-Ionizing Radiation Protection (ICNIRP), which have been adopted in many countries throughout the world, without requiring necessarily extensive and expensive nearfield measurements campaigns.

We report a set of viscoelastic measurements in concentrated aqueous solutions of a copolymer micellar system with short-range inter-micellar attractive interactions, a colloidal system characterized, in different regions of the composition–temperature phase diagram, by the existence of a percolation line (PT) and a kinetic glass transition (KGT). Both these transitions cause dramatic changes in the system viscoelasticity. Whereas the observed variations of the shear moduli at the PT are described in terms of percolation models, for the structural arrest at the KGT we investigate the frequency-dependent shear modulus behaviours by using a mode coupling theory (MCT) approach.

A novel class of special functions for electromagnetics is presented. Formed by the incomplete Hankel and modified Bessel functions, this class allows solving electromagnetics problems concerning truncated cylindrical structures. The differential and recurrence equations of these functions feature additional terms with respect to the classical theory of the Hankel and Bessel functions. The general properties, the most important analytical characteristics, and the large argument asymptotic approximations of the incomplete functions are derived using the steepest descent path (SDP) technique, showing that each special function splits into two terms. The first one has a discontinuous character and is linked to the saddle-point(s) contribution(s), while the second one, arising from the integral end-point contribution(s), compensates exactly the said discontinuity. In the solution of electromagnetic problems, the first term describes the geometrical optics (GO) field, the diffracted field being described by the second one. The general theory is employed to find the closed form analytical solution of the field radiated from a uniform line current source. Using the properties of the incomplete Hankel functions, it is demonstrated that this source excites cylindrical fields having optical character. Finally, the shape of the spatial regions where the GO solution cannot be applied is determined and discussed in details.

In this paper a design strategy to obtain low loss, small size dielectric antennas, by using very high dielectric constant materials is described. It is shown how by properly selecting the resonator shape and combining different resonant modes it is possible to design dielectric resonator antennas (DRA) with compact size and wide frequency coverage even at the cellular frequencies. Simple formulas are presented to illustrate the design procedure and allow a quick dimensioning of the antenna. Furthermore the paper describes techniques to enhance the response provided by the natural resonance frequencies of DRA, by adding parasitically coupled conducting strips, to enable multi-band operation. Results and examples are reported, showing the effectiveness of the proposed technique.

The radiation characteristics of a "folded patch antenna" (US Patent 6,121,932) are illustrated. This antenna features an omnidirectional radiation pattern, meaning that there is at least one strong linear component of the electromagnetic field that is radiated in any direction. Such a property, associated with the simplicity of construction, makes the folded patch attractive for applications where low antenna cost, size, and broad spherical coverage are important (e.g., GPS and Bluetooth).

SAR compliance tests of wireless products are performed measuring the electromagnetic energy deposition pattern in human-like shaped fiberglass shells filled with liquid tissue simulants. SAR measurements are performed by means of miniaturized electric field probes calibrated in the liquid. The overall uncertainty of SAR tests is strongly dependent on the isotropic response and the spatial resolution of dosimetric probes. We devised experimental procedures to determine these important quality parameters for miniaturized E-field probes immersed inside human tissue simulants. These procedures have been incorporated by the IEEE SCC-34/SC-2 in the upcoming IEEE recommended practice for assessing SAR compliance of hand-held wireless communication devices.

Quasielastic neutron scattering (QENS) has been used to investigate the single-particle dynamics of interfacial water in dicalcium silicate $({\mathrm{C}}_{2}\mathrm{S})/\mathrm{water}$ paste. Our previous neutron-scattering studies on interfacial water have focused attention on the translational dynamics of the center of mass of water molecules. In this paper, we have collected QENS data on a wider range of wave-vector transfer so that both translational and rotational motions of water molecules are detected. The data have been analyzed by models for translation and rotation we recently proposed for supercooled water. The evolution of the parameters describing the relaxational dynamics of water embedded in the ${\mathrm{C}}_{2}\mathrm{S}$ matrix is given at temperature $T=303 \mathrm{K}$ as a function of the curing time.

A space efficient, whole body microwave exposure system for unrestrained laboratory animals utilizing a flared parallel plate waveguide is described. The system comprises an Iridium wireless signal source, signal generator, power supply and amplifier (400 W), a coax to waveguide transition, an open ended, flared parallel plate waveguide, and animal exposure area with a dipole field sensing antenna. Across the waveguide aperture the system provides uniform exposure (±3 dB incident RF power density) for small animals (rats, mice or hamsters) in up to 18 standard cages for housing groups of animals. Overall system dimensions are 3.6 m (d)×2.4 m (w)×1.6 m (h). Operating at 1.62 GHz, the system provided average power density of 3.7 W/m2 in the cage area, resulting in a calculated whole body dose of 0.07 W/kg and a calculated average brain dose of 0.19 W/kg. Bioelectromagnetics 23:127–131, 2002. © 2002 Wiley-Liss, Inc.

We detect in a tri-block co-polymer micellar system an ergodic-to-nonergodic-to-ergodic transition, as a function of temperature, in a range of concentrations, by photon correlation measurements. The shear viscosity is also shown to jump two order of magnitude at these transition temperatures. Surprisingly, the structure factor as measured by small angle neutron scattering shows a marked narrowing at the structural arrest state. Rationalization of these results with the existence of an attractive branch in the phase diagram of an attractive colloid system predicted by mode coupling theory is made.

A model is proposed for the first-, second-, and third-order rotational correlation functions that are required for the computation of the rotational intermediate scattering function for the calculation of incoherent quasielastic neutron scattering (QENS) spectra from supercooled water. The model is tested against molecular-dynamics data generated from an extended-simple-point-charge model of water and is found to be satisfactory. The model can be used as a practical method for extracting rotational relaxation parameters from QENS spectra measured at large Q from supercooled bulk water or interfacial water in porous materials.

The topic dealt concerns with a study of the structural and dynamical properties of aqueous solutions of Poly(Ethylene Oxide) (PEO) by means different spectroscopic techniques. All the findings show that aggregation processes do not constitute an inherent property of the PEO-water system. In particular, the polymer-water interaction strength increases with the polymerization degree, indicating that the hydrophylic character of PEO weakens at low molecular weight and that the aggregative processes could be, eventually, activated by inhomogeneities in the system.