Controlling the Frequency-Temperature Sensitivity of a Cryogenic Sapphire Maser Frequency Standard by Manipulating Fe3+ Spins in the Sapphire Lattice

To create a stable signal from a cryogenic sapphire maser frequency standard, the frequency-temperature dependence of the supporting Whispering Gallery mode must be annulled. We report the ability to control this dependence by manipulating the paramagnetic susceptibility of Fe3+ ions in the sapphire lattice. We show that the maser signal depends on other Whispering Gallery modes tuned to the pump signal near 31 GHz, and the annulment point can be controlled to exist between 5 to 10 K depending on the Fe3+ ion concentration and the frequency of the pump. This level of control has not been achieved previously, and will allow improvements in the stability of such devices.Comment: 17 pages, 10 figure

Antiradical, Antimetastatic and Antitumor Activity of Kaolin Preparation “Kremnevit”

The objective of the research was to determine antiradical, antimetastatic and antitumor activity of kaolin preparation “Kremnevit”.Material and methods. Experiments were carried out on 30 male C57BL mice inoculated with Lewis lung carcinoma (LLC) cells. The rate of superoxide radical generation in tumor cells as well as in animal organs was determined using 1-hydroxy-2,2,6,6-tetramethyl-4-oxopyrrolidin- hydrochloride spin traps and electron spin resonance (ESR) spectroscopy at room temperature.Results of the experiments showed that the preparation “Kremnevit” exhibits antitumor activity reducing the tumor mass by 24% in experimental animals compared to animals which did not receive the preparation. “Kremnevit” affects the rate of superoxide radical generation by intracellular (mitochondria) and extracellular sources (the NADPH oxidase of tumor-associated neutrophils (TANs). The superoxide-generating activity of TANs increased in mice treated with “Kremnevit” compared to animals which did not receive it.Conclusions. Non-toxic kaolin preparation “Kremnevit” has antitumor and antimetastatic activity regulating electron transport in hepatocyte mitochondria during superoxide radical generation by hepatocyte mitochondria and immunocompetent blood cells of mice inoculated with LLC cells.

Maser Oscillation in a Whispering-Gallery-Mode Microwave Resonator

We report the first observation of above-threshold maser oscillation in a whispering-gallery(WG)-mode resonator, whose quasi-transverse-magnetic, 17th azimuthal-order WG mode, at a frequency of approx. 12.038 GHz, with a loaded Q of several hundred million, is supported on a cylinder of mono-crystalline sapphire. An electron spin resonance (ESR) associated with Fe3+ ions, that are substitutively included within the sapphire at a concentration of a few parts per billion, coincides in frequency with that of the (considerably narrower) WG mode. By applying a c.w. `pump' to the resonator at a frequency of approx. 31.34 GHz, with no applied d.c. magnetic field, the WG (`signal') mode is energized through a three-level maser scheme. Preliminary measurements demonstrate a frequency stability (Allan deviation) of a few times 1e-14 for sampling intervals up to 100 s.Comment: REVTeX v.4, 3 pages, with a separate .bbl file and 3 .eps figure

Creating traveling waves from standing waves from the gyrotropic paramagnetic properties of Fe3+^{3+} ions in a high-Q whispering gallery mode sapphire resonator

We report observations of the gyrotropic change in magnetic susceptibility of the Fe$^{3+}$ electron paramagnetic resonance at 12.037GHz (between spin states $|1/2>$ and $|3/2>$) in sapphire with respect to applied magnetic field. Measurements were made by observing the response of the high-Q Whispering Gallery doublet (WGH$_{\pm17,0,0}$) in a Hemex sapphire resonator cooled to 5 K. The doublets initially existed as standing waves at zero field and were transformed to traveling waves due to the gyrotropic response.Comment: Accepted for publication in Phys. Rev.

Scale effects in tribological properties of solid-lubricating composites made of ultra-high molecular weight polyethylene filled with calcium stearate particles

Friction properties being influenced by scale effects are simulated in the paper by the example of polymer composite material made from Ultra High-Molecular Weight Polyethylenes (UHMWPE) filled by calcium stearate (C[36]H[70]CaO[4]). Of interest are the composites whose mechanical properties and tribotechnical characteristics do not depend monotonically on filler (inclusions) weight fraction. In order to describe the influence of scale effects onto frictional properties the model based on Reiss averaging (model of "weak phase") is employed. It is also suggested that when gradient elasticity theory is applicable the formal analogy between effective friction coefficient for surface heterogeneous structures and effective mechanical properties (compliances) for heterogeneous material can take place. Theoretical dependence to describe nonmonotonic change of effective friction coefficient versus filler concentration was obtained for the polymer composites under study. The suggested expressions might be useful for the sake of properties prognosis of antifriction polymeric materilas

Prevalence of cardiac arrhythmias among patients undergoing chronic hemodialysis

Aim. To evaluate the prevalence of arrhythmias in patients undergoing chronic hemodialysis, to characterize the arrhythmia types in relation to the dialysis procedure and to determine their relationship with clinical findings and echocardiographic characteristics.Material and methods. The study involved 152 patients with kidney failure undergoing chronic hemodialysis. All patients underwent an assessment of dialysis parameters, collection of clinical data, and 48-hour Holter monitoring. In addition, 93 patients underwent an echocardiography with an assessment of left ventricular (LV) mass index, LV ejection fraction, left atrial (LA) volume index, E/e’, cardiac output and preload, which was defined as increased LV filling pressure (E/e’ >12) and LA enlargement (LA volume index >30 ml/m2).Results. Among the 152 examined patients, premature supraventricular and ventricular contractions (PVCs) were observed in almost all patients, while 41% had paroxysmal supraventricular tachycardia. Clinically significant arrhythmias included persistent atrial fibrillation (AF) in 8,6% of patients, paroxysmal AF in 3,9%, nonsustained ventricular tachycardia in 19,7%, bradycardia in 4,6%, second-degree atrioventricular block in 1,3% and third-degree atrioventricular block among 2,6%. PVCs were more common on dialysis days, while tachyarrhythmias were more common during dialysis and in the immediate post- dialysis period. Older age (odds ratio (OR) 10 years older, 1,53; 95% confidence interval (CI): 1,15-2,03; P=0,003), lower cardiac output (OR 1 L/min more, 0,66; 95% CI: 0,44-1,00; P=0,05) were independently associated with clinically relevant arrhythmias.Conclusion. In patients on chronic hemodialysis, older age, increased preload and lower cardiac output are independently associated with clinically relevant arrhythmias. In addition, a positive association between increased LV mass index and AF episodes has been demonstrated. Lower cardiac output had positive correlation with AF and ventricular arrhythmias

Hybrid electron spin resonance and whispering gallery mode resonance spectroscopy of Fe3+ in sapphire

The development of a new era of quantum devices requires an understanding of how paramagnetic dopants or impurity spins behave in crystal hosts. Here, we describe a spectroscopic technique which uses traditional electron spin resonance (ESR) combined with the measurement of a large population of electromagnetic whispering gallery modes. This allows the characterization of the physical parameters of paramagnetic impurity ions in the crystal at low temperatures. We present measurements of two ultrahigh-purity sapphires cooled to 20 mK in temperature, and determine the concentration of Fe3 ions and their frequency sensitivity to a dc magnetic field. Our method is different from ESR in that it is possible to track the resonant frequency of the ion from zero applied magnetic field to any arbitrary value, allowing excellent measurement precision. This high precision reveals anisotropic behavior of the Zeeman splitting. In both crystals, each Zeeman component demonstrates a different g factor

Wear-Resistant Ultrahigh-Molecular-Weight Polyethylene-Based Nano- and Microcomposites for Implants

The influence of modification by hydroxyapatite (HA) nano- and microparticles on tribotechnical properties of ultrahigh-molecular-weight polyethylene (UHMWPE) was investigated to develop polymer implants for endoprosthesis. It was shown that modification of UHMWPE by hydroxyapatite nanoparticles within range of 0.1–0.5 wt.% results in increase of wear resistance at dry sliding by 3 times. On the other hand adding of 20 wt.% of micron size HA gives rise to the same effect. The effect of increasing wear resistance is not substantially changed at surface treatment of the nano- and microcomposites by N+ ion beams as compared with nonirradiated blends. Preliminary joint mechanical activation of UHMWPE powder and fillers results in more uniform distribution of nanofillers in the matrix and, as a result, formation of more ordered structure. Structure within bulk material and surface layers was studied by means of optical profilometry, scanning electron microscopy, infrared spectroscopy, and differential scanning calorimetry. It is shown that adding of hydroxyapatite nanoparticles and high-energy surface treatment of the composite by N+ ion implantation improve tribotechnical properties of UHMWPE due to formation of chemical bonds in the composite (crosslinking) and ordering of permolecular structure