Hydrodynamic Limit of Brownian Particles Interacting with Short and Long Range Forces

We investigate the time evolution of a model system of interacting particles, moving in a $d$-dimensional torus. The microscopic dynamics are first order in time with velocities set equal to the negative gradient of a potential energy term $\Psi$ plus independent Brownian motions: $\Psi$ is the sum of pair potentials, $V(r)+\gamma^d J(\gamma r)$, the second term has the form of a Kac potential with inverse range $\gamma$. Using diffusive hydrodynamical scaling (spatial scale $\gamma^{-1}$, temporal scale $\gamma^{-2}$) we obtain, in the limit $\gamma\downarrow 0$, a diffusive type integro-differential equation describing the time evolution of the macroscopic density profile.Comment: 37 pages, in TeX (compile twice), to appear on J. Stat. Phys., e-mail addresses: [email protected], [email protected]

Linearity of Pulse Excited Coil-Less Fluxgate

In this paper, we study the open-loop linearity of pulse excited coil-less fluxgate. Narrow current pulses can be used instead of classical sinewave for the excitation of the coil-less fluxgate. This method has shown several advantages, mainly regarding reduction of power consumption, normally in order of tens of microwatts. The disadvantage is that traditional phase-sensitive detection cannot be used as it results in a very small sensitivity. Using pulse excitation, the output signal is obtained by integrating a part of the positive pulse and a part of the negative pulse, and then summing up the resulting voltages. This process was realized using two boxcar averagers SR 4153. The achieved open-loop linearity error is much higher than for sinewave excitation and it is not sufficient for precise applications. We show that the linearity strongly depends on the symmetry of the two integrating windows. In order to obtain precise timing, we realized an excitation board using PIC microcontrollers, which provides both the pulsing signals for excitation current and the gating signals for integration. Using this board and optimum position of the integrating window, we obtained a 0.6% maximum nonlinearity in plusmn100-muT range, which is sufficient for portable compass

Two-Domain Model for Orthogonal Fluxgate

In this paper a new model for orthogonal fluxgate is presented. A first attempt to explain the working principle of the orthogonal fluxgates was done in the 1970's. We show that this model does not work well on recently developed orthogonal fluxgate sensors with thin-film core on microwire. A new more accurate two-domain model based both on domain wall motion and magnetization rotation is proposed. We show that the new model better explains the observed properties of thin-film orthogonal fluxgate

Crossfield Sensitivity in AMR Sensors

We discuss the origin of the crossfield sensitivity of AMR sensors, the way how this error may influence the performance of an AMR compass and methods for its correction. Finally, we confirm the simple formulas experimentally. Crossfield may cause compass error up to 2.6 deg., depending on the compass orientation. The most effective way to suppress the crossfield error is using magnetic feedback, however this is not always possible. We suggest a method of processing of the SET/RESET sensor outputs which is more efficient than the usual averaging

Bi-Metallic Magnetic Wire With Insulating Layer as Core for Orthogonal Fluxgate

In this paper, we examine the problems related to orthogonal fluxgates realized using magnetic microwires as core. Starting from a description of orthogonal fluxgates evolution, we give a theoretical analysis of the problems involving the full saturation of the wire, necessary condition to obtain proper working conditions. Bi-metallic wires (magnetic layer on copper wire, carrying the excitation current) have been proposed to achieve full saturation using lower current. In this paper, we present a further improvement: we realized microwires with insulation layer between the copper wire and the magnetic layer. The current flows only into the copper, regardless of the working frequency. Using insulation layer, we achieve 20 mA saturation current at 10 kHz, which is 3 times smaller than for similar wires without insulation layer

Double Coil-Less Fluxgate in Bridge Configuration

In this paper, a new method for excitation of coil-less fluxgate is presented. The purpose of this method is to reduce the spurious component of the output voltage, allowing us to increase the amplification. The method is based on the employment of two coil-less fluxgates in a double bridge, which injects pulsing current in opposite direction in each wire. By taking the difference of the voltages on the two wires, we suppress the component of the voltages, which does not change under application of external measured field. The sensitive axes are in opposite direction, so the wire feels opposite field. As a result, we will obtain an output voltage with low peak value, including only the component of the voltage that changes when we apply external field. Finally, we propose an improved version of the double bridge to allow the employment of two sensing elements with difference characteristics. This is obtained by optimizing the suppression of the spurious voltages and, at the same time, setting independently chosen values of exciting current for each wire

Magnetic Microwires With Field-Induced Helical Anisotropy for Coil-Less Fluxgate

We present a new method for production of magnetic microwire with helical anisotropy. Coil-less fluxgate sensors are generally composed of a bimetallic wire excited by an alternating current; in order for the wire to work in coil-less fluxgate mode, the magnetic layer of the wire needs to have helical anisotropy. So far, we have achieved such anisotropy by mechanically twisting the wire. However, this method has some disadvantages for practical applications, mainly regarding the sensor stability. We propose a method that provides helical anisotropy by applying a helical field during the electrodeposition: this is achieved by the superposition of a longitudinal field generated by a Helmholtz coil and a circumferential field produced by a direct current flowing through the core of the wire during electrodeposition

Understanding the second wave of epidemics using the susceptible-infectious-recovered model

The world is currently reeling under the COVID-19 pandemic and secondary waves of the same are occurring in different countries. In the current paper, the authors try to explain the exact mathematical concept of a second wave based on their analysis of the popular SIR (susceptible-infectious-recovered) model in epidemiology. Effort is made to graphically and mathematically illustrate the natural infection curve, the necessity of austerity measures, the effects of such measures on the infection curve and the possible reasons for a second wave. The risk of quick mutation and need for effective vaccination is also discussed. It is believed that this analysis will be of immense help to scientists, doctors and policy-makers to devise proper strategies to urgently control the current COVID-19 pandemic, especially in countries where virus variants and secondary waves are occurring

Identification of Epigenetic Biomarkers in HPV-Related Carcinomas

Head and neck squamous cell carcinomas (HNSCC), especially those localised in the oropharynx and oral cavity, have increased significantly in recent decades, with persistent Human papillomavirus (HPV) infection identified as the main aetiological cause. Conventional clinical and pathological evaluation is often insufficient to accurately assess the risk of malignant transformation in precancerous lesions. This limitation often delays the diagnosis of oral cancer, contributing to unfavourable outcomes for many patients. Therefore, the need for correct patient risk stratification and appropriate patient triage has led to the search for new diagnostic and prognostic molecular biomarkers, specifically among the epigenetic modification of DNA methylation. In this context, the PreCursor-M+ kit (Fujirebio, Tokyo, Japan), designed to analyse hypermethylation of the two onco-suppressor genes FAM19A4 and miR124-2 in cervical samples from high-risk HPV-positive women, was used to assess the abnormal methylation level of 111 oral rinse samples. The samples were distinguished according to the histologically diagnosed lesion: oral squamous cell carcinoma (OSCC), potentially malignant lesions (OPMD) and benign lesions (BL). To these, a group of healthy individuals was added (NL). In each group, samples were selected to have approximately equal numbers of HPV-positive and HPV-negative samples. HPV detection was performed using INNO-LiPA® HPV Genotyping Extra II diagnostic kit (Fujirebio, Tokyo, Japan), which allows the identification of thirty-two distinct genotypes, distinguished into twelve low-risk HPVs and twenty high-risk HPVs. Analysis of the results showed how hypermethylation correlated with the severity of the diagnosis. A positive hypermethylation result, as indicated by the kit, was more common in OSCC (p<0.0001), while a negative result was more common in NL and BL (p= 0.0023 and p= 0.0162). HPV positivity was positively correlated with hypermethylation only in OSCCs (32.4%, p= 0.0006), although statistical significance was also maintained in HPV-negative patients (p= 0.0007). Among HPV-positive OSCC, those infected with HPV16 showed a higher methylation level. Furthermore, the methylation levels of the two targets taken individually increased from the NL group to the BL and OPMD groups and finally to OSCCs. This study has shown how assessing hypermethylation of two targets can help diagnose OSCC and identify those patients affected by OPMDs who could be at risk of developing cancer. The relatively small number of patients did not allow for the detection of statistically significant differences in the effect of HPV infection on target methylation levels. It is therefore imperative to increase the sample size to confirm these preliminary results and to outline new significant information