Sub-optical resolution of single spins using magnetic resonance imaging at room temperature in diamond

There has been much recent interest in extending the technique of magnetic resonance imaging (MRI) down to the level of single spins with sub-optical wavelength resolution. However, the signal to noise ratio for images of individual spins is usually low and this necessitates long acquisition times and low temperatures to achieve high resolution. An exception to this is the nitrogen-vacancy (NV) color center in diamond whose spin state can be detected optically at room temperature. Here we apply MRI to magnetically equivalent NV spins in order to resolve them with resolution well below the optical wavelength of the readout light. In addition, using a microwave version of MRI we achieved a resolution that is 1/270 size of the coplanar striplines, which define the effective wavelength of the microwaves that were used to excite the transition. This technique can eventually be extended to imaging of large numbers of NVs in a confocal spot and possibly to image nearby dark spins via their mutual magnetic interaction with the NV spin.Comment: 10 pages, 8 figures, Journal of Luminescence (Article in Press

The effect of the skin-core structure of injection-molded isotactic polypropylene on the stress distribution in bending tests

We examine the effect of the skin-core structure of isotactic polypropylene (iPP) in bending tests. The depth-dependent material properties are determined in tensile tests and mapped to a finite element model. This enables the examination of internal stresses during bending numerically. In a bending test, one usually expects a monotonic stress distribution across the thickness, provided that the material is homogeneous and does not strain-soften. We found that the structural gradient of injection-molded iPP easily overcompensates the monotonic stress dependence, such that the maximal equivalent von Mises stress lies well below the surface in the so called shear layer. The latter is a result of the injection molding process

Experimental observation of laser-induced modification of Mössbauer spectra

The modification of Fe57 MÖssbauer spectra of a MgO single crystal under the action of laser radiation was observed. A possible interpretation of the observed effect is proposed

Coherent population trapping in ruby crystal at room temperature

Observation of coherent population trapping (CPT) at ground-state Zeeman sublevels of $Cr^{3+}$-ion in ruby is reported. The experiments are performed at room temperature by using both nanosecond optical pulses and nanosecond trains of ultrashort pulses. In both cases sharp drops in the resonantly induced fluorescence are detected as the external magnetic field is varied. Theoretical analysis of CPT in a transient regime due to pulsed action of optical pulses is presented.Comment: 4 pages, 4 figures, submitted to PR

Effects of optical radiation on the Mössbauer spectrum of 151Eu3+: CaF2

We study the changes in the shape of the Mössbauer spectrum for the 21.5 keV transition of 151Eu3+ nuclei in a CaF2 lattice, assuming that a population of the excited electronic state 5D0 is maintained by optical pumping. For a population of the excited state 5D0 of 10%, we determine the magnitude of the changes in the Mössbauer spectrum as 1.9% of the area of the unperturbed spectrum. © 2005 Taylor & Francis Group Ltd

Experimental observation of vibrations produced by pulsed laser beam in MgO:57Fe

We report the first observation of a laser-produced vibration with the aid of Mössbauer techniques. Thin platelets of MgO single crystals were doped by diffusion of 57Fe atoms. The illumination of the MgO: 57Fe sample with a pulsed Nd:YAG laser produced a significant broadening of the Mössbauer spectrum. In order to find out what caused these changes, we performed a series of time-domain experiments, in which the Mössbauer spectra were collected only during a 2.5 μs gate interval. This gate interval was swept from 5 μs to 190 μs over the time interval between the two laser pulses. After laser irradiation, the position of the Mössbauer line was found to be changing in time as a decaying oscillations of well-defined frequency, which can be due to the vibration of the sample induced by the laser pulse. © 2006 Springer Science+Business Media, Inc

Evaluation of oxidative stress status and antioxidant defense status of athletes after inclusion of a special product for sportive nutrition in their food ration

Objective: to evaluate the influence of special «product for sportive nutrition» on oxidative stress status and antioxidant defense status of athletes during physical loads. Materials and methods: 30 male swimmers of a student combined team (at the age of 23,0 ± 2,5 years) participated in the study. The sportsmen were divided into two groups: experimental and control. The sportsmen of experimental group additionally received the «product for sportive nutrition» in their food ration. The training process was the same in both groups; it was divided into three stages. First and third stages were characterized by systematic trainings; the intensity of physical loads was increased at second stage. The oxidative stress status and total antioxidant capacity (TAC) of serum were detected using reagent kit «PerOx (TOS/TOC) Kit» и «ImAnOx (TAS/TAC) Kit», firm «Immundiagnostik» (Germany). Serum cortisol was determined by immunoenzyme method with the use of reagent kit of joint-stock company «Vector-Best» (Russia). Results: intake of «product for sportive nutrition» during increased physical loads promoted a statistically significant decrease of oxidative stress level, tendency to a decrease of cortisol content and an increase of serum antioxidant capacity in comparison with control group. There was no correlation between cortisol value and oxidative stress level/total antioxidant capacity of serum. Conclusions: tested food product exerted a positive influence on system of free radical oxidation and cortisol. It can be recommended for further investigation in persons going in for sport

Biodegradable hydrogels based on chitosan and pectin for cisplatin delivery

Preparation of stable hydrogels using physically (electrostatically) interacting charge-complementary polyelectrolyte chains seems to be more attractive from a practical point of view than the use of organic crosslinking agents. In this work natural polyelectrolytes—chitosan and pectin—were used, due to their biocompatibility and biodegradability. The biodegradability of hydrogels is confirmed by experiments with hyaluronidase as an enzyme. It has been shown that the use of pectins with different molecular weights makes it possible to prepare hydrogels with different rheological characteristics and swelling kinetics. These polyelectrolyte hydrogels loaded with cytostatic cisplatin as a model drug provide an opportunity for its prolonged release, which is important for therapy. The drug release is regulated to a certain extent by the choice of hydrogel composition. The developed systems can potentially improve the effects of cancer treatment due to the prolonged release of cytostatic cisplatin