Dynamic Radio-Frequency Transverse Susceptibility in Magnetic Nanoparticle Systems

A novel resonant method based on a tunnel-diode oscillator (TDO) is used to study the dynamic transverse susceptibility in a Fe nanoparticle system. The magnetic system consists of an aggregate of nanometer-size core (Au)-shell (Fe) structure, synthesized by reverse micelle methods. Static and dynamic magnetization measurements carried out in order to characterize the system reveal a superparamagnetic behavior at high temperature. The field-dependent transverse susceptibility at radio-frequencies (RF), for different temperatures reveals distinct peak structure at characteristics fields (H_k, H_c) which changes with temperature. It is proposed that relaxation processes could explain the influence of the temperature on the field dependence of the transverse susceptibility on the MI.Comment: 3 pages, 2-column, 3 figures, To be published in J. Appl. Phys. 2000 (44th Annual MMM proceedings

Calorimetric Evidence of Strong-Coupling Multiband Superconductivity in Fe(Te0.57Se0.43) Single Crystal

We have investigated the specific heat of optimally-doped iron chalcogenide superconductor Fe(Te0.57Se0.43) with a high-quality single crystal sample. The electronic specific heat Ce of this sample has been successfully separated from the phonon contribution using the specific heat of a non-superconducting sample (Fe0.90Cu0.10)(Te0.57Se0.43) as a reference. The normal state Sommerfeld coefficient gamma_n of the superconducting sample is found to be ~ 26.6 mJ/mol K^2, indicating intermediate electronic correlation. The temperature dependence of Ce in the superconducting state can be best fitted using a double-gap model with 2Delta_s(0)/kBTc = 3.92 and 2Delta_l(0)/kBTc = 5.84. The large gap magnitudes derived from fitting, as well as the large specific heat jump of Delta_Ce(Tc)/gamma_n*Tc ~ 2.11, indicate strong-coupling superconductivity. Furthermore, the magnetic field dependence of specific heat shows strong evidence for multiband superconductivity

The temperature dependence of hysteretic processes in Co nanowires arrays

In this paper, the temperature dependence of the hysteretic processes of Co nanowires, squarelly ordered in an array prepared by electrodeposition in nanopores of alumina membranes was analyzed. Both the magnetostatic interactions induced in the nanowires arrays and the thermal stresses (radial, azimuthal and axial stresses), which appear during the cooling of the system (nanowire and alumina template) from room temperature to 3 K was evaluated. The analysis of thermal induced stresses provides useful informations concerning the magnetic anisotropy in the Co nanowires. The temperature dependence of the remanent magnetization and coercitive field as an effect of the induced thermal stresses and magnetostatic interactions between nanowires was studied

Searching for the reference point

Although reference dependence plays a central role in explaining behavior, little is known about the way that reference points are selected. This paper identifies empirically which reference point people use in decision under risk. We assume a comprehensive reference-dependent model that nests the main reference-dependent theories, including prospect theory, and that allows for isolating the reference point rule from other behavioral parameters. Our experiment involved high stakes with payoffs up to a week's salary. We used an optimal design to select the choices in the experiment and Bayesian hierarchical modeling for estimation. The most common reference points were the status quo and a security level (the maximum of the minimal outcomes of the prospects in a choice). We found little support for the use of expectations-based reference points

Pelvic floor disorders in gynecological malignancies. An overlooked problem?

Cervical, endometrial, ovarian, vulvar, and vaginal cancers affect women of a broad age spectrum. Many of these women are still sexually active when their cancer is diagnosed. Treatment options for gynecological malignancies, such as gynecological surgery, radiation, and chemotherapy, are proven risk factors for pelvic floor dysfunction. The prevalence of urinary incontinence, fecal incontinence, and sexual dysfunction before cancer treatment is still unclear. Hypotheses have been raised in the literature that these manifestations could represent early symptoms of pelvic cancers, but most remain overlooked even in cancer surviving patients. The primary focus of therapy is always cancer eradication, but as oncological and surgical treatment options become more successful, the number of cancer survivors increases. The quality of life of patients with gynecological cancers often remains an underrated subject. Pelvic floor disorders are not consistently reported by patients and are frequently overlooked by many clinicians. In this brief review we discuss the importance of pelvic floor dysfunction in patients with gynecological malignant tumors

Magnetic Properties of (γ-Fe₂O₃)₈₀Ag₂₀ Nanocomposites Prepared in Reverse Micelles

The magnetic properties of nanoparticles of gamma-Fe2O3 prepared by reverse micelles have been studied by dc magnetization, transverse ac susceptibility, and Mössbauer spectroscopy. The nanoparticles of gamma-Fe2O3 in the nanocomposite (gamma-Fe2O3)80Ag20 exhibit superparamagnetic behavior. The blocking temperatures determined by the three methods indicate the superparamagnetic nature of (gamma-Fe2O3)80Ag20 above 70-80 K and show correlation with measuring time. The average particle diameter obtained by transmission electron microscopy of the gamma-Fe2O3 particles is ~10 nm and that of the Ag particles is ~20 nm. The average particle size determined from the magnetic analyses for the gamma-Fe2O3 particles is ~12 nm. Mössbauer spectra obtained between 4.2 and 295 K clearly reveal the presence of superparamagnetic relaxation at temperatures above ~80 K. The Mössbauer spectra reveal at most 1% of paramagnetic Fe2+ ions in the 295-K spectrum