Specific features of unidirectional anisotropy in exchange-coupled DyCo/NiFe film structures

The dependence of the unidirectional anisotropy in a DyCo/NiFe bilayer system on the thickness of the magnetically soft layer has been studied using dynamic and static techniques. The magnitude of the exchange interaction between layers evaluated using the ferromagnetic resonance method is two times that determined from an analysis of the hysteresis loops. It is established that this difference is related to features of the magnetic microstructure of the DyCo layer.     

A dilatometric study of phase separation in sodium borosilicate glass with phosphorus and fluorine additions

The phase separation of sodium borosilicate glass with small additions of phosphorus and fluorine oxides has been investigated using dilatometry at a temperature of 550°C (the heat treatment time varies from 0.05 to 500 h). Two glass transition temperatures have been revealed in the dilatometric curves at heat treatment times of 65 h and more. The results indicate that the time of 65 h is enough to complete the phase separation in the glass at a temperature of 550°C.     

Bandwidth packing

We model a server that allocates varying amounts of bandwidth to “customers” during service. Customers could be computer jobs with demands for storage bandwidth or they could be calls with demands for transmission bandwidth on a network link. Service times are constants, each normalized to 1 time unit, and the system operates in discrete time, with packing (scheduling) decisions made only at integer times. Demands for bandwidths are for fractions of the total available and are limited to the discrete set {1/k, 2/k, …, 1} wherek is a given parameter. More than one customer can be served at a time, but the total bandwidth allocated to the customers in service must be at most the total available. Customers arrive ink flows and join a queue. Thejth flow has rate λ _j and contains just those customers with bandwidth demandsj/k. We study the performance of the two packing algorithms First Fit and Best Fit, both allocating bandwidth by a greedy rule, the first scanning the queue in arrival order and the second scanning the queue in decreasing order of bandwidth demand. We determine necessary and sufficient conditions for stability of the system under the two packing rules. The average total bandwidth demand of the arrivals in a time slot must be less than 1 for stability under any packing rule, i.e., the condition $$\rho {\text{ : = }}\sum\limits_i {\lambda i\left( {i/k} \right)} {\text{< 1}}$$ must hold. We prove that if the arrival rates λ₁, …, λ _k?1 are symmetric, i.e., λ _i =λ _k?i for alli, 1 ≤i ≤k ? 1, theρ<1 is also sufficient for stability under both rules. Our Best Fit result strengthens an earlier result confined to Poisson flows and equal rates λ₁=…=λ _{k ? 1}, and does so using a far simper proof. Our First Fit result is completely new. The work here extends earlier results on bandwidth packing in multimedia communication systems, on storage allocation in computer systems, and on message transmission along slotted communication channels. It is not surprising thatρ<1 is sufficient under Best Fit, since in a congested system, Best Fit tends to serve two complementary (matched) customers in each time slot, with bandwidth demands beingi/k and (k ? i)/k for somei, 1 ≤i ≤k ? 1. It is not so obvious, however, thatρ<1 is also sufficient under First Fit. Interestingly, when the system becomes congested, First Fit exhibits a “self-organizing” property whereby an ordering of the queue by time of arrival becomes approximately the same as an ordering by decreasing bandwidth demand.     

X-ray interference effects in thin equiatomic Co-Pt single crystal films

Thin single crystal films of an equiatomic Co₅₀Pt₅₀ alloy synthesized by magnetron sputtering on a MgO single crystal substrate were studied by X-ray diffractometry. Interference oscillations with a period depending on the Co-Pt alloy film thickness were observed in the region of (001) reflection, characterizing the L1₀ type ordering, and in the region of small diffraction angles (2Θ<10°).     

Collective Spin Glass State in Nanoscale Particles of Ferrihydrite

Semiconductors - Ferromagnetic resonance was used to study three types of ferrihydrite nanoparticles: nanoparticles formed as a result of the cultivation of microorganisms Klebsiella oxytoca;...     

Interactions of Chemically Synthesized Ferrihydrite Nanoparticles with Human Serum Transferrin: Insights from Fluorescence Spectroscopic Studies

Human serum transferrin (HST) is a glycoprotein involved in iron transport that may be a candidate for functionalized nanoparticles to bind and target cancer cells. In this study, the effects of the simple and doped with cobalt (Co) and copper (Cu) ferrihydrite nanoparticles (Fh-NPs, Cu-Fh-NPs, and Co-Fh-NPs) were studied by spectroscopic and molecular approaches. Fluorescence spectroscopy revealed a static quenching mechanism for all three types of Fh-NPs. All Fh-NPs interacted with HST with low affinity, and the binding was driven by hydrogen bonding and van der Waals forces for simple Fh-NPs and by hydrophobic interactions for Cu-Fh-NPs and Co-Fh-NPs binding, respectively. Of all samples, simple Fh-NPs bound the most to the HST binding site. Fluorescence resonance energy transfer (FRET) allowed the efficient determination of the energy transfer between HST and NPs and the distance at which the transfer takes place and confirmed the mechanism of quenching. The denaturation of the HST is an endothermic process, both in the case of apo HST and HST in the presence of the three types of Fh-NPs. Molecular docking studies revealed that Fh binds with a low affinity to HST (K_a = 9.17 × 10³ M⁻¹) in accord with the fluorescence results, where the interaction between simple Fh-NPs and HST was described by a binding constant of 9.54 × 10³ M⁻¹.     

Ion reduction in iron oxide and oxyhydroxide nanoparticles during ultrasonic treatment

The effect of ultrasonic treatment of iron oxide and iron oxyhydroxide nanoparticles (ferrihydrite nanoparticles synthesized by Klebsiella oxytoca microorganisms, ferrihydrite nanoparticles synthesized by a chemical method and hematite nanoparticles) is studied. Samples of nanoparticles were investigated using transmission electron microscopy, Mössbauer spectroscopy and X-ray diffraction methods. The formation of the α-Fe metal phase from nanoparticles of iron oxides and iron oxyhydroxides was detected. The metal phase is formed as a result of the reduction of iron ions during cavitation treatment. According to the experimental results, the presence of a protein or a polysaccharide component is necessary for the course of this reaction.     

Load characterization and anomaly detection for voice over IP traffic

We consider the problem of traffic anomaly detection in IP networks. Traffic anomalies typically arise when there is focused overload or when a network element fails and it is desired to infer these purely from the measured traffic. We derive new general formulae for the variance of the cumulative traffic over a fixed time interval and show how the derived analytical expression simplifies for the case of voice over IP traffic, the focus of this paper. To detect load anomalies, we show it is sufficient to consider cumulative traffic over relatively long intervals such as 5 min. We also propose simple anomaly detection tests including detection of over/underload. This approach substantially extends the current practice in IP network management where only the first-order statistics and fixed thresholds are used to identify abnormal behavior. We conclude with the application of the scheme to field data from an operational network.