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Proteins undergo unfolding when lowering the temperature by means of a process known as cold denaturation. Pure cold denaturation (without denaturants) is obtained at high pressures. In this paper, a recent proposal to explain the cold denaturation process based on the high density liquid state of water [Phys. Rev. Lett. 91, 138103 (2003)] is described in detail. The correct understanding of this process may be useful to artificially implement activation and inactivation of proteins at room temperatures with direct applications into the word of nanobiotechnology machinery.

The frequency dependence of the dielectric permitivity's maximum has been studied for poled and unpoled doped relaxor strontium barium niobate $Sr_{0.61}Ba_{0.39}Nb_{2}O_{6}:Cr^{3+}$ (SBN-61:Cr). In both cases the maximum found is broad and the frequency dispersion is strong. The present view of random fields compensation in the unpoled sample is not suitable for explaining this experimental result. We propose a new mechanism where the dispersion of quenched random electric fields, affecting the nanodomains, is minimized after poling. We test our proposal by numerical simulations on a random field Ising model. Results obtained are in agreement with the polarization's measurements presented by Granzow et al. [Phys. Rev. Lett {\bf 92}, 065701 (2004)]., Comment: 7 pages, 4 figures

Accurate Monte Carlo data from a set of isotherms near the critical point are analyzed using two RG based complementary representations, given respectively in terms of ℏ = h /|t |β δ and = t /h 1/β δ . Scaling plots for data on simple cubic Ising lattices are compared with plots of ML β ν vs. |t |L 1/ν for increasing L values and with high quality experimental data on CrBr 3 . Finite size effects and the equation of state are discussed.

The Ising model in a transverse field has been used for a long time to describe ferroelectric phase transitions. Quantum tunneling and zero point energy effects in double potential wells have been shown recently to give rise to analogous behavior at the phase transitions. In this work we show that Monte Carlo simulations of the temperature dependence of the order parameter, the susceptibility and the specific heat in Ising like systems with increasing zero point energy describe well the evolution of the phase transition in these systems from classical to quantum, reproducing the behavior of quantum paraelectrics at low temperature.

In this Letter, the optical forces on an electric dipole generated by a beam made up of two circularly polarized Hermite–Gaussian modes have been analyzed. When the intensity of the two modes is not the same, the mechanical action of the scattering force is completely different from the behavior of the Poynting vector. The dynamics of resonant metallic nanoparticles under this field have been calculated by means of Langevin molecular dynamic simulations. This configuration could be useful to experimentally verify how radiation pressure on a Rayleigh particle is due to the transfer of linear momentum coming solely from the orbital part of the Poynting vector.

5 pags. ; 5 figs. ; PACS number(s): 42.25.Dd, 78.67.Bf, 78.55.Qr, 78.66.Bz, The effect of spatial correlations on the Purcell effect in a bidimensional dispersion of resonant nanoparticles is analyzed. We perform extensive calculations on the fluorescence decay rate of a point emitter embedded in a system of nanoparticles statistically distributed according to a simple two-dimensional lattice-gas model near the critical point. For short-range correlations (high temperature thermalization) the Purcell factors present a long-tailed statistic which evolves towards a bimodal distribution when approaching the critical point where the spatial correlation length diverges. Our results suggest long-range correlations as a possible origin of the large fluctuations of experimental decay rates in disordered metal films. © 2014 American Physical Society., The authors acknowledge the funding from the Spanish Ministry of Economy and Competitiveness through grants “FUNCOAT” CONSOLIDER CSD2008- 00023, “MAPS” MAT2011-29194-C02-01, “NANOPLAS+” FIS2012-31070, and “MINIELPHO” FIS2012-36113-C03, and from the Comunidad de Madrid through grant “MICROSERES-CM” S2009/TIC- 1476 and “NANOBIOMAGNET” S2009/MAT-1726.

In the present article we analyze a vacuum microelectronics magnetic sensor based in a simple configuration with a double-gated wedge emitter with a split anode as current detector. The actuation of such device has been simulated using several numerical approaches including full determination of electrostatic potentials with accurate description of fields at the wedge region, electron beam propagation inside the device, and evaluation of the current density distributions at the anode detector screen. Calculated sensor sensitivities are larger than those found in conventional magnetic field sensors designed to detect similar magnetic field ranges. The focusing system provides a tuning mechanism able to change the sensor sensitivity and the magnetic field detection working range. The dependence of the sensitivity on geometrical parameters and control voltages is discussed.

Monte Carlo numerical simulations of Ising thin films have been used in an effort to characterize the dimensional crossover of the phase transitions in nanoscopic layered systems with a thickness of a few atoms. In particular, we have determined the behaviour of the critical temperature, of the effective critical exponents and of the crossover temperature. We have also compared our results with experimental data for FeCo using a proper extrapolation.

This is the peer reviewed version of the following article: Physica A: Statistical Mechanics and its Applications 284.1 (2000): 187-194, which has been published in final form at http://dx.doi.org/10.1016/S0378-4371(00)00228-4, The crossover of a pure (undiluted) Ising system (spin per site probability p = 1) to a diluted Ising system (spin per site probability p < 0.8) is studied by means of Monte Carlo calculations with p ranging between 1 and 0.8 at intervals of 0.025. The evolution of the self-averaging is analyzed by direct determination of the normalized square widths RM and RX as a function of p. We find a monotonous and smooth evolution from the pure to the randomly diluted universality class. The p-dependent transition is found to be indepent of size (L). This property is very convenient for extrapolation towards the randomly diluted universality class avoiding complications resulting from finite size effects, We acknowledge financial support from CGCyT through grant PB96-0037

Simple effective field arguments assuming an anisotropic layer of thickness Lc covering the ferroelectric bulk grain of perovskite ceramics are used to determine an expression for the transition temperature Tc(L) as a function of the grain linear size L. Experimental data for BaTiO3 ceramics as a function of grain size are described reasonably well by the expression of Tc(L) obtained this way. In order to show that the decrease of the transition temperature with the grain size of the sample is mainly due to surface effects, we have also performed Monte Carlo simulations of the critical temperature dependence with the grain size for finite Ising systems under free surface boundary conditions. We find that the behavior is comparable with the one previously reported experimentally for ferroelectric materials and that it can be described by a very similar expression.

The Monte Carlo (MC) approach is used to check the validity of the scaling relationship for the effective critical exponents in thin Ising films. We investigate this relationship not just in the critical region but throughout the crossover to the expected two-dimensional behavior. Our results indicate that this scaling relationship is very well-fulfilled throughout the entire crossover temperature region, as predicted by a previous renormalization group analysis. The two-dimensional universality class of Ising films is confirmed by means of data collapsing plots for plates with increasing L, up to L=100. The evolution of the maximum value of the effective critical exponents with film thickness is discussed.

Self-averaging of singular thermodynamic quantities at criticality for randomly and thermally diluted three dimensional Ising systems has been studied by the Monte Carlo approach. Substantially improved self-averaging is obtained for critically clustered (critically thermally diluted) vacancy distributions in comparison with the observed self-averaging for purely random diluted distributions. Critically thermal dilution, leading to maximum relative self-averaging, corresponds to the case when the characteristic vacancy ordering temperature is made equal to the magnetic critical temperature for the pure 3D Ising systems. For the case of a high ordering temperature, the self-averaging obtained is comparable to that in a randomly diluted system., 4 pages, 4figures, RevTex

In the present work, we analyze the operation of a pressure sensor based on an array of wedge emitters. The device comprises a silicon membrane acting as the anode of the device put in front of the emitter array. When the external pressure bends the membrane, there is a change in the separation tip membrane giving rise to a modification of the field emission current. An analytical solution has been used to calculate the deflection of the silicon diaphragm under different pressure conditions and a computer code was developed to compute the emission current from the array. The device shows high sensitivity allowing the determination of very small changes to the pressure at constant voltage working mode. Alternatively, broad ranges of pressure changes can be measured using a constant current mode.

Finite-size lattice Monte Carlo simulations of phase transitions in Ising systems (1⩽ d ⩽4) allow the determination of simple binomial scaling functions for T T c and T > T c , consistent with the asymptotic behavior for the critical isotherm, the spontaneous magnetization and the zero field susceptibility, which describe quite well the scaling behavior in an extended range of the scaling variable, 0.01⩽|( T − T c )/ T c | L 1/ ν ⩽20, for all four dimensionalities.

Laboratorio de Fi´sica de Sistemas Pequen˜os (CSIC-UAM), Universidad Auto´noma de Madrid,C-IX, Cantoblanco, E-28049-Madrid, Spain~Received 16 November 1995; revised manuscript received 4 October 1996!In this work we present experimental results concerning conductance quantization at room temperature inmetallic nanowires. The experiments are performed both at ambient presure and in ultrahigh vacuum usingscanning tunneling microscopy ~STM!-like devices. Both microscopic and macroscopic electrodes are used.The obtained results are independent of the electrode size, indicating that nanowires form at the last stages ofthe contact-breakage process, independently of the initial size and shape of the contact. In addition, we study~a! the stability of the nanowires, finding their lifetimes remarkably long, on the order of minutes; ~b! theI-V curves for different quantum channels; ~c! nanowires formed and visualized using a STM inside a scanningelectron microscope ~SEM!; ~d! the statistical behavior of the conductance, sampling tens of thousands ofconsecutive conductance experiments, showing clear quantized peaks up to five quanta of conductance; and~e!the length of the conductance plateaus, that might indicate the chaotic behavior of the quantum states formedat the nanowire. The statistical study of the conductance plateau lengths shows a broad Wigner-like distributionwith an average value of 0.13 nm for the first quantum channel. This is at variance with a constant length,predicted and experimentally observed, in the plateaus between force jumps. @S0163-1829~97!00207-5#I. INTRODUCTION

Scattering forces on small particles are proportional to the average value of the Poynting vector and to the curl of the spin angular momentum of the light field. In this paper we analyse the relevance of spin non-conservative forces in configurations where scattering forces are different from zero with a null Poynting vector or with a null average value of the Poynting vector.

In this paper we analyze the non-conservative forces on magneto-dielectric particles in special configurations where the scattering force is not proportional to the average value of the Poynting vector. Based on these results, we revisit the concept of electromagnetic momentum density.

A tapered dielectric waveguide that scans, at constant height, a sample containing a viral capsid is studied by combining a lattice gas model to simulate water meniscus formation and a finite difference time domain algorithm for light propagation through the media involved. Our results show different contrasts related to different water contents and different meniscus orientations. We propose this method as a way to study water content and evaporation process in nanocavities being either biological, like viral capsides, or nonbiological, like photonic crystals, This work has been funded through projects FIS2009-13403-C02-01 (MINECO), S2009-MAT-1467 (CAM), and CSD2010-00024 (MINECO)

Two-dimensional Ising models are used to explain the disorder effects in mixed solid solutions and doped relaxor systems. On ferro-ferro solutions like Pb(Zr1-xTix)O3 (PZT), the composition dependence of the Curie temperature TC(x) usually deviates from the averaged linear behavior known as the Vegard's law. This deviation is mimicked by a Hamiltonian model including interactions between different types of dipoles in a two dimensional lattice. Doping PZT with lanthanum (PLZT) results in a relaxor behavior that is explained by adding a new term to 2D Ising model that takes into account the interaction between dipoles and itinerant charges. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This work reviews several properties of liquid water, including the dielectric constant and the proton-spin lattice relaxation, and draws attention to a bilinear behaviour defining a crossover in the temperature range 50 ± 10°C between two possible states in liquid water. The existence of these two states in liquid water plays an important role in nanometric and biological systems. For example, the optical properties of metallic (gold and silver) nanoparticles dispersed in water, used as nanoprobes, and the emission properties of CdTe quantum dots (QDs), used for fluorescence bioimaging and tumour targeting, show a singular behaviour in this temperature range. In addition, the structural changes in liquid water may be associated with the behaviour of biological macromolecules in aqueous solutions and in particular with protein denaturation.

We analyze the forces on a small dipolar particle and the electromagnetic momentum density in a configuration consisting in two perpendicular circularly polarized stationary waves. The field distribution shows regions in which the electric and magnetic fields are parallel corresponding to a null Poynting vector. Although the average value of the momentum density, proportional to the Poynting vector, is zero in these regions, there are scattering forces acting on small particles due to light's spin force. The total scattering force suggests a new definition of the average value of the momentum density for free propagating electromagnetic fields.

Optical trapping and driving of small objects has become a topic of increasing interest in multidisciplinary sciences. We propose to use a chain made of metallic nanoparticles as a resonant light sail, attached by one end point to a transparent object and propelling it by the use of electromagnetic radiation. Driving forces exerted on the chain are theoretically studied as a function of radiation’s wavelength and chain’s alignments with respect to the direction of radiation. Interestingly, there is a window in the frequency spectrum in which null–torque equilibrium configuration, with minimum geometric cross section, corresponds to a maximum in the driving force.

The diffusion of silver nanoparticles in water at 298K inside an optical vortex lattice is analyzed in detail by numerical simulations. At power densities of the order of those used to trap nanoparticles with optical tweezers, the dynamic response shows three different regimes depending on the light wavelength. In the first one particles get trapped inside the light vortices following almost closed trajectories. In the second one, around the plasmon resonance, the diffusion constant is dramatically enhanced with respect to the Brownian motion. In the third one, at longer wavelengths, nanoparticles are confined during a few seconds in quasi-one-dimensional optical traps.

A microscopic relaxor model is described and its properties are studied by means of numerical simulations. No ‘a priori’ random interactions neither random fields are considered. The solely interaction of mobile charges with the dipoles of a highly polarizable medium is responsible for the appearance of typical relaxor properties such as a smeared transition, a glassy ground state with no macroscopic polarization, a external field frequency dependent dielectric constant and a field induced ferroelectric behavior.

Quantum paraelectrics are quasi critical systems with a high zero point energy that avoids ferroelectric order, and hence they do not undergo the corresponding phase transition. The quantum effective field approach, which substitutes the quantum oscillator for the classical one [1], turns out to be a very simple and useful way to explain the behavior of these materials [2,3], even when mixed in solid solutions with an isomorphous pure ferroelectric [4]. In this work we propose, using this approach, a little review of quantum paraelectrics from the point of view of the factors that influence their zero point energy.

The influence of coexisting correlated and noncorrelated impurities on the critical behavior of the three-dimensional Ising model is studied using Monte Carlo numerical simulations and finite-size scaling. The amount of correlated and noncorrelated vacancies is modified and controlled during the simulations. The long-range correlated (LRC) critical behavior is always found for any value of the concentration of correlated vacancies. The smaller the amount of correlated vacancies the larger the system size needed to detect the LRC universality class. This result explains why critical values measured in xerogel liquid-vapor experiments, where the concentration of correlated vacancies is marginal, seem to correspond to a short-range correlated disorder.

Light forces on small (Rayleigh) particles are usually described as the sum of two terms: the dipolar or gradient force and the scattering or radiation pressure force. The scattering force is traditionally considered proportional to the Poynting vector, which gives the direction and magnitude of the momentum flow. However, as we will show, there is an additional nonconservative contribution to the scattering force arising in a light field with nonuniform helicity. This force is shown to be proportional to the curl of the spin angular momentum of the light field. The relevance of the spin force is illustrated in the simple case of a 2D field geometry arising in the intersection region of two standing waves, This work was supported by the Spanish MEC through the Consolider NanoLight (CSD2007-00046), FIS2005-05137 and FIS2006-11170-C02-02 projects, Microseres-CM and by the Spanish-French PICASSO program (HF2007- 0068)

A high-pressure calorimetric experiment to test the validity of a water model's prediction, regarding the behavior of the heat capacity in the liquid-liquid critical point and singularity-free scenarios, is proposed in this paper. The response of the specific heat at high pressure is different depending on the existence, or not, of a second critical point. If the model presents a second critical point, there is a nondivergent maximum in the specific heat at a temperature $T\ensuremath{\sim}{T}_{c}$ for any pressure $Pg{P}_{c}$ (${T}_{c}$ and ${P}_{c}$ being the temperature and pressure of the model's second critical point). This maximum does not appear for the model with a singularity free scenario.

In a recent paper [PRL 91, 138103 (2003)] a new mechanism to explain the cold denaturation of proteins, based on the loss of local low-density water structure, has been proposed. In the present paper this mechanism is tested by means of full atom numerical simulations. In good agreement with this proposal, cold denaturation resulting in the unfolded state was found at the High Density Liquid (HDL) state of water, at which the amount of open tetragonal hydrogen bonds decreases at cooling., 5 pages, 5 figures

It has been known for a long time that the low temperature behavior shown by the dielectric constant of quantum paraelectric $SrTiO_{3}$ can not be fitted properly by Barrett's formula using a single zero point energy or saturation temperature ($T_{1}$). As it was originally shown [K. A. M\"{u}ller and H. Burkard, Phys. Rev. B {\bf 19}, 3593 (1979)] a crossover between two different saturation temperatures ($T_{1l}$=77.8K and $T_{1h}$=80K) at $T\sim10K$ is needed to explain the low and high temperature behavior of the dielectric constant. However, the physical reason for the crossover between these two particular values of the saturation temperature at $T\sim10K$ is unknown. In this work we show that the crossover between these two values of the saturation temperature at $T\sim10K$ can be taken as a direct consequence of (i) the quantum distribution of frequencies $g(\Omega)\propto\Omega^{2}$ associated with the complete set of low-lying modes and (ii) the existence of a definite maximum phonon frequency given by the structural transition critical temperature $T_{tr}$.

Several results have been reported so far as concerns magnetic sensors based on field emission arrays. In this paper, a new concept magnetic sensor is proposed and its operation is analysed using a numerical model. The sensor comprises an array of integrated electron emitters each one formed by a tip at voltage V/sub t/, and two deflection electrodes at potentials +V/2 and -V/2. The deflection of the beam due to the Lorentz force can be compensated by a suitable choice of the electric field formed between the electrodes. In this way, a correlation V(B) between the voltage V applied between two electrodes and the magnetic field B to be measured is obtained.

In this paper finite size scaling techniques are used to study the universality class of thermally diluted Ising systems, in which the realization of the disposition of magnetic atoms and vacancies is taken from the local distribution of spins in the pure original Ising model at criticality. The critical temperature, the critical exponents and therefore the universality class of these thermally diluted Ising systems depart markedly from the ones of short range correlated disordered systems. This result is in agreement with theoretical predictions previously made by Weinrib and Halperin for systems with long range correlated disorder.

We study cold denaturation of proteins at high pressures. Using multicanonical Monte Carlo simulations of a model protein in a water bath, we investigate the effect of water density fluctuations on protein stability. We find that above the pressure where water freezes to the dense ice phase ($\approx2$ kbar), the mechanism for cold denaturation with decreasing temperature is the loss of local low-density water structure. We find our results in agreement with data of bovine pancreatic ribonuclease A., Comment: 4 pages for double column and single space. 3 figures Added references Changed content

The equivalence between canonical and grand canonical constraints near a random fixed point in a critical disordered system is confirmed by means of Monte Carlo simulations. The slow approach to the asymptotic distribution for canonical averaging given by the L ( α / ν ) r a n d o m term is overcome by simulating long range correlated diluted Ising systems with (α/ν) r a n d o m = (a - d) for the particular values a = 2 (linear defects) and d = 3 (three dimensional systems).

Activated scaling is confirmed to hold in transverse field-induced phase transitions of randomly diluted Ising systems. Quantum Monte Carlo calculations have been made not just at the percolation threshold ${(p}_{c})$ but also well below and above it. We follow the evolution of the activated scaling at zero temperature in the phase transition from ferromagnetic to quantum Griffiths phase $(pg{p}_{c})$ at the phase boundary ${(p=p}_{c})$ and for transitions inside the nonferromagnetic quantum Griffiths phase $(pl{p}_{c}).$ A novel deactivation phenomenon inside the nonferromagnetic Griffiths-McCoy phase $(pl{p}_{c})$ is observed using a thermal (in contrast to random) dilution of the system.

We study a model for water with a tunable intra-molecular interaction $J_\sigma$, using mean field theory and off-lattice Monte Carlo simulations. For all $J_\sigma\geq 0$, the model displays a temperature of maximum density.For a finite intra-molecular interaction $J_\sigma > 0$,our calculations support the presence of a liquid-liquid phase transition with a possible liquid-liquid critical point for water, likely pre-empted by inevitable freezing. For J=0 the liquid-liquid critical point disappears at T=0., Comment: 8 pages, 4 figures

Monte Carlo calculations of Ising thin films with equal area (LXL) and different thickness (D) have been performed for D<

The universality class of thermally diluted Ising systems, in which the realization of the disposition of magnetic atoms and vacancies is taken from the local distribution of spins in the pure original Ising model at criticality, is investigated by finite size scaling techniques using the Monte Carlo method. We find that the critical temperature, the critical exponents and therefore the universality class of these thermally diluted Ising systems depart markedly from the ones of short range correlated disordered systems. Our results agree fairly well with theoretical predictions previously made by Weinrib and Halperin for systems with long range correlated disorder., 7 pages, 6 figures, RevTex

Monte Carlo simulations of some typical order-disorder ferroelectrics such as TGS, NaNO2 and DKDP nanocrystals were studied using a Transverse Ising Model Hamiltonian with four-spins interactions. The microscopic parameters corresponding to this Hamiltonian were adjusted to fit the experimental polarization-temperature curves for each one of the materials in the bulk phase. Then the dependences of the ferroelectric-paraelectric phase transition temperatures, Tc, on the sizes of those crystals were studied with Monte Carlo simulations of the order-disorder system. We report a weak dependence of Tc on the size of the crystal (d) for these materials above d∼6nm. The addition of surface effects showed that the expected lowtemperature shift of Tc due to size effects, can be reverted.

Recent investigations carried out in our group concerning the conductance quantization of metallic nanowires are reviewed. These include: i) The formation of metallic nanowires between macroscopic electrodes, including liquid metals, demonstrating that at the last stages of the contact breakage, a nanowire exists, independently of the initial contact size. ii) A statistical study of the conductance using thousands of consecutive contact breakage experiments, both at room and at liquid helium temperatures. These histograms, totally reproducible, present clear peaks close to integer values of the quantum of conductance G0=2e2/h for diamagnetic metals like Gold, Silver, Copper, Sodium, Platinum.... Ferromagnetic metals, Iron, Cobalt and Nickel, exhibit a flat conductance histogram. This effect is attributed to the combination of the lifting of the spin degeneracy in the ferromagnetic nanowires and the effect of geometry and disorder. The measured conductance histograms are basically independent of the temperature. iii) A discussion of the position and width of the observed peaks. Just geometrical effects can not explain the large conductance peak shifts observed experimentally, and disorder, behaving as a residual resistance, has to be invoked to explain them. iv) First realization of conductance quantization in Bi at 4K. Conductance plateaus lasting 20-100 nm electrode separation are presented; the histogram displays also clear peaks. v) A statistical study of the conductance plateau duration, demonstrating a broad distribution of this duration, 0.05-0.4 nm, with an average value that decreases as conductance increases. vi) A discussion of force and energy quantization within a resonant energy model of two reservoirs connected by a ballistic channel. vii) Experiments performed in ultra high vacuum, where we manage to stabilize the nanowires for hours and study switching and current voltage characteristics for different quantum conductance channels with remarkable accuracy. viii) Visualization inside scanning and transmission electron microscopes of the metallic contact between two macroscopic electrodes at the micron and nanometer scales. These experiments provide experimental evidence of the formation of a connective neck between the electrodes. ix) Experiments on light emission from breaking nanowires. A plausible explanation for this phenomenon is presented.

The relevance of the scanning near-field optical microscope (SNOM), for near-field characterization, is often shaded by the appearance of artifacts, especially when geometrical characterization is intended. Artifacts are related to many features such as the feedback system or the scanning mode. For non-vacuum environmental conditions, artifact sources may be related to tip geometry and the pollutants attached, either on the tip or on the studied surfaces, altering the optical image. As an environmental element, water vapor could be treated as a source for artifacts, but could also be used as a tool for chemical characterization of hydrophilic patches. Spontaneous meniscus formation between hydrophilic surfaces, such as the tip and the sample, may guide light from the tip to the sample, enhancing the transmitted signal. This study focuses on the effects that water condensation at the nanoscale has on the signals achieved by SNOM, combining two computational methods (Monte Carlo and finite difference time domain) in order to deal with light propagation through heterogeneous media and water condensation.

In this study we analyze a new vacuum microelectronics (VM) magnetic field sensor based on a simple configuration with a single-gated wedge emitter with a split anode current as detection system. The actuation of such a device has been simulated using different numerical approaches including a full determination of electrostatic potentials with an accurate description of the fields at the wedge-like emitter, the propagation of electrons inside the device, and the evaluation of the current density distributions at the anode detector screen. This device presents sensor sensitivities higher than those of conventional magnetic field sensors, and similar to other VM double-gated sensors. The dependence of the sensitivity on the geometric parameters and control voltages is discussed.

A new concept magnetic sensor is proposed and its operation is analyzed using a numerical model. The sensor comprises an array of integrated electron emitters, each one with the tip at potential Vt, and two deflection electrodes at potentials +Vd/2 and −Vd/2. The deflection of the beam due to the Lorentz force can be compensated by a suitable choice of the electric field formed between the electrodes. In this way, a correlation Vd(B) between the electron deflection compensating voltage Vd and the magnetic-field B to be measured is obtained. A linear relationship Vd(B) has been outlined, its slope depending on both the tip–anode difference of potential and the geometrical parameters of the system.

Connections between two macroscopic metallic (gold, copper, silver, platinum, and tungsten) wires have been investigated by transmission and scanning electron microscopy. The results show that metallic contacts exist but do not break cleanly. They are stretched into many filaments or threads of nanometer size leading to nanowire formation as time passes.