Direct observation of the transition from spin waves to the magnon Bose condensate.

Bose-Einstein condensation occurs at an appropriate density of bosonic particles, depending on their mass and temperature. The transition from the semiclassical paradigm of spin waves to the magnon Bose-Einstein condensed state (mBEC) was obtained experimentally with increasing magnon density. We used the Faraday rotation effect to study the spatial distribution of the magnon density and phase far from their excitation region. A coherent magnetization precession was observed throughout the sample, which indicates the formation of a magnon BEC. It is shown that this result under experimental conditions goes beyond the applicability of the Landau-Lifshitz-Gilbert semiclassical theory.

Optical registration of a coherent magnon state outside of the excitation region.

Magnons have demonstrated enormous potential for the next generation of information technology and quantum computing. In particular, the coherent state of magnons resulting from their Bose-Einstein condensation (mBEC) is of great interest. Typically, mBEC is formed in the magnon excitation region. Here we demonstrate for the first time by optical methods the permanent existence of mBEC at large distances from the magnon excitation region. The homogeneity of the mBEC phase is also demonstrated. The experiments were carried out on films of yttrium iron garnet magnetized perpendicular to the surface and at room temperature. We use the method described in this article to develop coherent magnonics and quantum logic devices.

Magneto-optical imaging of coherent spin dynamics in ferrites.

The explosive development of quantum magnonics is associated with the possibility of its use as macroscopic quantum systems. In particular, they can find an application for quantum computing processors and other devices. The recently discovered phenomenon of magnon Bose-Einstein condensation and coherent precession of magnetization can be used for these purposes. Our letter describes a method for the optical observation of the coherently precessing magnetization in conditions when the concentration of magnons reaches the value necessary for their quantum condensation. The investigations were conducted in the out-of-plane magnetized yttrium iron garnet films. The required magnon density was achieved by magnetic resonance technique. The magneto-optical imaging method provides such important parameters of the coherent spin dynamics as the amplitude and phase distributed all over the sample. It should become an indispensable read-out tool for the upcoming quantum technologies based on the magnon Bose-Einstein condensation.

Quantum limits of position-sensitive photodiodes.

The split photodiode and the lateral effect photodiode are two popular detectors for measuring beam displacement. For small displacements of a Gaussian beam, which is the case of interest here, they are often seen as equivalent and used interchangeably, giving a signal proportional to the displacement. We show theoretically and experimentally that in the limit of low technical noise, where the signal to noise ratio is dominated by the shot noise of the light, the lateral effect photodiode produces a better signal to noise ratio than the split photodiode, owing to its optimum spatial detector response. This quantum advantage can be practically exploited in spite of the intrinsic thermal noise of the lateral effect photodiode.

[A comparative analysis of reproducibility of the jaws centric relation determined with the use of digital technologies]. / Sravnitel'nyi analiz vosproizvodimosti tsentral'nogo sootnosheniia cheliustei s ispol'zovaniem tsifrovykh tekhnologii.

AIM: To compare the precision of centric relation (CR) assessment by various methods using digital technologies. MATERIAL AND METHODS: Determination of the CR was carried out in the clinic of prosthetic dentistry on patients with intact dentition using methods of bilateral manipulation, anterior jig, leaf gauge and device for intraoral recording of the gothic arch angle. Optical jaw impressions were obtained using the intraoral 3D scanner Trios (3Shape) and the CR registers were scanned using the laboratory scanner Prime (DOF). To evaluate the reproducibility of the CR, the computer program of 3D modeling Avantis (Russia) was used, which integrated the obtained optical impressions and digital copies of the CR registers. RESULTS: None of the methods showed 100% accuracy in CR assessment. The most stable reproducibility of the position of the mandible in the CR relative to the first registration was determined by the method using an anterior jig (of our own design) and amounted to 0.119±0.012 mm, which is significantly less than using the methods of bilateral manipulation (0.225±0.028, p≤0.05) and a leaf gauge (0.207±0.02, p≤0.05). We observed a similar mean values of the reproduction accuracy when determining the CR by recording the Gothic arch angle (0,120±0,013, p≤0.05), which also has a significantly lower value (p≤0.05) compared to other methods for CR determining.

[The precision of central jaw relationship estimation in restorative dentistry]. / Analiz pretsizionnosti opredeleniia tsentral'nogo sootnosheniia cheliustei v klinike ortopedicheskoi stomatologii.

The aim of the study was to investigate accuracy of the most frequently used methods of obtaining centric relation in clinical practice. Finding of CR was carried out in clinic of prosthodontic dentistry on a 5 patients with intact dentition using four methods that are most often used, including: bimanual manipulation, leaf gauge, using an anterior deprogrammind device, the technique of determining CR with intraoral devices recording the gothic angle. To assess the accuracy of each technique there were performed 10 registrations of the central relation by one operator (200 CR registrations), with 30 minutes' intervals between the CA determination. Analysis of the contacts in CR were carried out using a photometric method of investigation. The graphic images were downloaded in Adobe Photoshop for calculation, metric data translated into digital values. The studies above showed that the accuracy of finding CR in all methods were not ideal. It can be noted that the smallest deviation of the position of the first contact in the CR was observed with use of the anterior deprogrammind device and with the intoral gothic angle recording device. The deviation along the VO axis was 0.039±0.002 mm and 0.084±0.004 mm respectively, along the MD axis 0.043±0.002 mm and 0.054±0.001 mm, respectively. The greatest error of recording the CR was shown by bimanual manipulation Dawson technique, the deviation along the axis of the VO and MD was 0.634±0.04 mm and 0.388±0.04 mm, respectively.

Coherent evolution of singlet spin states in PHOTO-PHIP and M2S experiments.

A consistent theoretical description of the spin dynamics underlying photo-PHIP (para-hydrogen induced polarization) experiments is given and validated experimentally: spectra from zero-quantum coherence (ZQC) "in-phase" and "out-of-phase" were obtained and evolution of ZQCs and the population of singlet spin state was tracked and modeled. Data from recent literature [O. Torres et al., J. Am. Chem. Soc., 2014] are reinterpreted. Advantages of using M2S sequences such as APSOC for detecting photo-PHIP are demonstrated. A sequence for 2D ZQ spectroscopy based on APSOC is proposed and the fundamental principles of ZQ spectroscopy are formulated. This investigation opens a new way to obtain information on the sign of J-couplings using ZQ spectroscopy. The proposed method is also useful to track the redistribution of the singlet spin population in various PHIP related experiments, which is essential for efficient polarization transfer to target nuclei.

Application of magnetic methods for assessment of soil restoration in the vicinity of metallurgical copper-processing plant in Bulgaria.

Copper ore mining and processing are among the most harmful anthropogenic influences for the environment and they are a subject of international and national law regulations. Recultivation of areas influenced by mining and processing industry is commonly applied and monitored in order to restore as much as possible the natural environment. In this study, environmental magnetic methods are applied in order to assess the degree of soil restoration in terms of soil development, after remediation of waste dump from Cu-processing plant. Soils developed under birch forest stands of different age (5, 15, and 25 years) as well as raw waste material were sampled along depth down to 20-30 cm. Variations in magnetic parameters and ratios obtained (magnetic susceptibility, frequency-dependent magnetic susceptibility, anhysteretic remanence (ARM), isothermal remanence (IRM), ARM/IRM100mT) suggest the presence of magnetic enhancement in the upper 0-15 cm, the thickness of this layer varying depending on the age of the forest stand. Magnetic mineral responsible for this enhancement is of magnetite type, while waste material contains a large amount of hematite, as evidenced by coercivity analysis of IRM acquisition curves and thermal demagnetization of composite IRM. Magnetic grain-sized proxy parameters suggest that magnetite particles are coarser, magnetically stable, while no or minor amount of superparamagnetic grains were detected at room temperature. A well-defined linear regression between the topsoil magnetic susceptibility and the approximate age of the forest stand provides an indication that the magnetic enhancement is of pedogenic origin. It is concluded that the observed magnetic enhancement of recultivated soils studied is linked to a combined effect of pedogenic contribution and possible additions of industrial ashes as a liming agent for soil restoration.

Optimization of Eva Green real-time mPCR for differentiating C. jejuni/coli directly from feces.

OBJECTIVE: To develop and optimize a rapid molecular method for diagnosing campylobacteriosis directly from a clinical fecal sample and at the same time for determining the most common causing agents - C. jejuni/coli. MATERIALS AND METHODS: 38 clinical fecal samples from hospitalized patients with diarrheal syndrome were tested using a rapid immunochromatographic test. All positive samples were tested for confirmation by culturing in a microaerophilic atmosphere. The Eva Green real-time mPCR reaction of a direct fecal sample was conducted using the "IQ5TM Real-Time PCR System" apparatus. RESULTS: Out of 38 clinical fecal samples which were ICT positive, 18 strains were isolated by culture, namely, 17 of C. jejuni and 1 of C. coli. The Eva Green real-time mPCR reaction also reported 18 positive samples for Campylobacter, out of which 17 were of C. jejuni and only one of C.coli. CONCLUSION: We developed and optimized the Eva Green real-time mPCR for the detection and species differentiation of C. jejuni/coli directly from a clinical fecal sample. The molecular analysis we described has a 100% sensitivity and specificity when comparing the results obtained by it to those of the culture method, which is currently the "gold standard" in the diagnosis of campylobacteriosis (Tab. 2, Fig. 1, Ref. 6).

Synthesis of magnetic silica nanomarkers with controlled physicochemical properties.

Magnetic markers which can be detected with an extremely high sensitivity with the method of magnetic particle quantification (MPQ) were synthesized. Using a controlled Stober reaction, a set of magnetic silica markers of different sizes and zeta potentials was obtained. The use of a carboxymethyl dextran polymer to stabilize the magnetite particles during the synthesis made it possible to substantially reduce the detection limit of the obtained construct, which opens up new opportunities for creating effective diagnostic nanoagents.

Clostridium perfringensα-toxin interaction with red cells and model membranes.

The effects of Clostridium perfringensα-toxin on host cells have previously been studied extensively but the biophysical processes associated with toxicity are poorly understood. The work reported here shows that the initial interaction between the toxin and lipid membrane leads to measurable changes in the physical properties and morphology of the membrane. A Langmuir monolayer technique was used to assess the response of different lipid species to toxin. Sphingomyelin and unsaturated phosphatidylcholine showed the highest susceptibility to toxin lypolitic action, with a two stage response to the toxin (an initial, rapid hydrolysis stage followed by the insertion and/or reorganisation of material in the monolayer). Fluorescence confocal microscopy on unsaturated phosphatidylcholine vesicles shows that the toxin initially aggregates at discrete sites followed by the formation of localised "droplets" accumulating the hydrolysis products. This process is accompanied by local increases in the membrane dipole potential by about 50 (±42) mV. In contrast, red blood cells incubated with the toxin suffered a decrease of the membrane dipole potential by 50 (±40) mV in areas of high toxin activity (equivalent to a change in electric field strength of 10(7) V m(-1)) which is sufficient to affect the functioning of the cell membrane. Changes in erythrocyte morphology caused by the toxin are presented, and the early stages of interaction between toxin and membrane are characterised using thermal shape fluctuation analysis of red cells which revealed two distinct regimes of membrane-toxin interaction.

The effect of oxidative stress on the membrane dipole potential of human red blood cells.

The membrane dipole potential (ψ(d)) is an important biophysical determinant of membrane function and a sensitive indicator of lipid organisation. In this study we have used the environmentally sensitive probe di-8-anepps to explore the effects of oxidative stress on the membrane dipole potential of human erythrocytes. Cells suspended in 0.15mM phosphate buffered saline containing 0.1mg/ml albumin maintained a mean value for ψ(d) of 270 (±20) mV over the course of 1hour. In the presence of 0.4mM cumene hydroperoxide there was an increase in ψ(d) of 14 (±7)%, accompanied by a decrease in cell diameter of ~14 (±2)%. Exposure of the cells to 0.4mM hydrogen peroxide caused ψ(d) to decrease by 13 (±8)% at the centre of the cell and 8 (±5)% at the edge whilst the diameter remained constant. In both cases the changes were equivalent to a change in transmembrane electric field of a magnitude of ~10MVm(-1), sufficient to influence membrane function. Raman microspectrometry supported the conclusion that cumene exerts its effect primarily on membrane lipids whilst hydrogen peroxide causes the formation of spectrin-haemoglobin complexes which stiffen the membrane.

Spectroscopic ellipsometry as an optical probe of strain evolution in ferroelectric thin films.

Heteroepitaxial strain in ferroelectric thin films is known to have a significant impact on both their low and high frequency dielectric properties. In this paper, we use ex-situ spectroscopic ellipsometry to study the strain evolution with film thickness, and strain relaxation in ferroelectric Ba0.5Sr0.5

Systemic and extraintestinal forms of human infection due to non-typhoid salmonellae in Bulgaria, 2005-2010.

The purpose of this investigation was to review the clinical cases diagnosed as systemic or extraintestinal salmonellosis between 2005 and 2010 in Bulgaria, to determine the antimicrobial resistance of the causative salmonellae, and to analyze the pulsed field gel electrophoresis (PFGE) profiles of extraintestinal Salmonella Corvallis isolates. Culture, biochemical tests, and serotyping were performed. Resistance to 12 antimicrobial agents was studied with the Bauer-Kirby disk diffusion method. The double-disk synergy method was used for the screening of the presence of extended-spectrum beta-lactamases (ESBLs). PFGE typing and analysis of the dendrogram was performed for the comparative investigation of Salmonella Corvallis isolates. Between 2005 and 2010, 2,227 human non-typhoid Salmonella isolates were investigated at the National Reference Laboratory of Enteric Pathogens, Sofia, Bulgaria. Thirty-three strains (1.48 %) from nine national regions were isolated from patients with systemic and extraintestinal forms of salmonellosis. The serotype distribution was as follows: S. enteritidis (n = 21), S. choleraesuis (diphasic n = 3; monophasic n = 3), S. typhimurium (n = 2), Salmonella Corvallis (n = 2), Salmonella Montevideo (n = 1), and S. javiana (n = 1). Eight patients developed severe forms of infections: sepsis (n = 2), septic shock (n = 1 with fatal outcome), meningitis (n = 3), and acute renal failure (n = 2). Twenty-two percent of isolates were resistant to ampicillin and gentamicin, 17.64 % to tetracycline, 14.28 % to nalidixic acid, and 10 % to chloramphenicol. All isolates were susceptible to ciprofloxacin. One Salmonella Corvallis isolate recovered from a patient with chronic hemolytic anemia produced an ESBL and its PFGE profile demonstrated less than 96 % similarity to fecal and wound Salmonella Corvallis with susceptible phenotypes. S. enteritidis was the most common cause of systemic and extraintestinal forms of human salmonellosis in Bulgaria. Resistance to ampicillin and gentamicin were the predominant profiles, although one Salmonella Corvallis isolate produced an ESBL. The ESBL-producing Salmonella Corvallis isolate clustered separately from the susceptible Salmonella Corvallis isolates.

Motion and mixing for multiple ferromagnetic microswimmers.

This paper concerns the interaction of several ferromagnetic microswimmers, their motion and the resulting fluid mixing. Each swimmer consists of two ferromagnetic beads joined by an elastic link, and is driven by an external, time-dependent magnetic field. The external field provides a torque on a swimmer and, together with the varying attraction between the magnetic beads, generates a time-irreversible motion leading to persistent swimming in a low Reynolds number environment. The aim of the present paper is to consider the interactions between several swimmers. A regime is considered in which identical swimmers move in the same overall direction, and their motion is synchronised because of driving by the external field. It is found that two swimmers tend to encircle one another while three undergo more complicated motion that may involve the braiding of swimmer trajectories. By means of approximations it is established that the interaction between pairs of swimmers gives circulatory motion which falls off with an inverse square law and is linked to their overall speed of motion through the fluid. As groups of two or more swimmers move through the fluid they process fluid, leaving behind a trail of fluid that has undergone mixing: this is investigated by following streak lines numerically.

Coupling between internal spin dynamics and external degrees of freedom in the presence of colored noise.

We observe asymmetric transition rates between Zeeman levels (spin flips) of magnetically trapped atoms. The asymmetry strongly depends on the spectral shape of an applied noise. This effect follows from the interplay between the internal states of the atoms and their external degrees of freedom, where different trapped levels experience different potentials. Such insight may prove useful for controlling atomic states by the introduction of noise, as well as provide a better understanding of the effect of noise on the coherent operation of quantum systems.

Campylobacteriosis and other bacterial gastrointestinal diseases in Sofia, Bulgaria for the period 1987-2008.

Campylobacter is the most commonly reported enteric bacterial pathogen in humans. We still do not have any systematic data concerning campylobacteriosis in Bulgaria. For that reason, we present data of the thermophilic Campylobacter jejuni and Campylobacter coli in the aetiology of diarrhoeal diseases in Sofia, for the period from 1987 to 2008. The study included patients from 0 to over 65 years-old. A total of 51,607 faecal specimens were screened for Campylobacter. C. jejuni and C. coli were detected in 3.58% (1,847) of the strains, with the highest percentage in 1988 (7.5%) and the lowest in 2006 (0.3%). Campylobacteriosis occurred most frequently in the wet months of March, April, May and June, with 105, 102, 124 and 141 cases, respectively, and was rare in January with 25 cases. The most affected groups were children between 0 and 4 years of age (52%) and between five and 14 years of age (30%). Campylobacter infection occurred in 22% of all bacterial gastrointestinal diseases in the city of Sofia during the study period. Salmonella was the most frequently identified pathogen with 32%, followed by Shigella (30%), Campylobacter (22%) and diarrhoeagenic Escherichia coli (16%). The study shows that Campylobacter plays an important role as a bacterial cause of enterocolitis in Sofia, Bulgaria.

Contribution of glia cells specifically astrocytes in the pathology of depression: immunohistochemical study in different brain areas.

BACKGROUND: The contribution of glial cells to the pathophysiology of depression is an emerging research purpose. This study investigated the deficits in glial cells, specifically astrocytes in various brain regions, after the development of depression and then after voluntary running in depressed rats. MATERIALS AND METHODS: Forty-five adult male Wistar rats aged 8-10 weeks were used in the study. A depression model was generated through a forced swimming programme; voluntary running was allowed on rat running wheels; and brain sections were taken from the hippocampus, dentate gyrus (DG), medial prefrontal cortex (mPFC) and cerebellar cortex. After immunostaining with specific antibodies immuno-stain, the astrocytes, oligodendroglia and microglial cells were counted, and certain indices relating astrocytes to other glial cells were calculated. Astrocytic morphology was studied, and the optical density (OD) of glial fibrillary acidic protein (GFAP) immuno-expression was measured in different groups. RESULTS: Compared to the control group, animals in the depression group exhibited significant decreases in the mean astrocyte count in all studied brain areas, significant decreases in GFAP OD values in all areas and significantly reduced values for all glial astrocyte indices in the hippocampus, DG and mPFC. Compared to the rats in the depression group, those in the depression/exercise group exhibited significantly elevated mean astrocyte and oligodendroglia counts in all studied areas, significantly elevated GFAP OD values in all studied areas, and non-significant differences in glial astrocyte indices in the hippocampus, mPFC and cerebellar cortex. CONCLUSION: Astrocytes, rather than other glia, constitute a basis for the development and/or relief of depression.

Occurrence and characterization of Salmonella enterica subspecies enterica serovar 9,12:l,v:- strains from Bulgaria, Denmark, and the United States.

In 2006, Salmonella enterica serovar I 9,12:l,v:- emerged in Bulgaria. The aim of this study was to characterize Salmonella serovar I 9,12:l,v:- isolates from Bulgaria, Denmark, and the United States. We compared isolates of Salmonella I 9,12:l,v:- and diphasic serovars with similar antigenic formulas by pulsed-field gel electrophoresis (PFGE) and antimicrobial susceptibility. The phase 2 flagellin gene (fljB) was also sequenced for selected isolates. By PFGE, the Salmonella I 9,12:l,v:- isolates from Bulgaria were indistinguishable from the isolate from the United States and distinct from isolates from Denmark; furthermore, several Salmonella I 9,12:l,v:- were indistinguishable from an isolate of Salmonella serovar Goettingen. Sequence analysis showed 100% sequence identity with known H:e,n,z15 sequences of Salmonella Goettingen, which has the antigenic formula I 9,12:l,v:e,n,z15. The study indicated that Salmonella I 9,12:l,v:- is a monophasic variant of Salmonella Goettingen and is present in different countries and on different continents.

Salmonellosis cases caused by a rare Salmonella Enteritidis PT6c associated with travel to Bulgaria, June-July 2008.

In June 2008 an outbreak of gastroenteritis was registered in Sunny Beach resort situated on the Black Sea coast in Bulgaria, affecting 14 employees of a hotel, five of whom tested positive for Salmonella Enteritidis. During June-July 2008 four sporadic S. Enteritidis cases were also reported and two of them were foreign tourists. In the same period S. Enteritidis cases connected with travel to Bulgaria were reported to the European Centre for Disease Prevention and Control (ECDC) from Finland, United Kingdom, Sweden, Germany and Norway. We describe a study performed to find out relatedness between Bulgarian and Finnish S. Enteritidis isolates using phage typing (PT) and pulse-field gel electrophoresis (PFGE). Fifteen S. Enteritidis isolates from Bulgaria and 195 from Finland (including 28 from travellers to Bulgaria) were phage typed. Within Bulgarian isolates four different PTs were found and PT6c with eight strains was predominant. Nineteen out of 28 strains isolated from the Finns visiting Bulgaria belonged also to PT6c. PFGE typing (with one enzyme) of all S. Enteritidis PT6c strains (8 Bulgarian and 19 Finnish isolates) showed indistinguishable PFGE profile. The typing results thus demonstrated a link between Bulgarian and Finnish S. Enteritidis isolates. We conclude that S. Enteritidis PT6c was the cause of salmonella outbreak in Sunny Beach and was exported to Finland, and likely to the United Kingdom, Norway, Sweden and Germany.