Skyrmion-(Anti)Vortex Coupling in a Chiral Magnet-Superconductor Heterostructure.

We report experimental coupling of chiral magnetism and superconductivity in [IrFeCoPt]/Nb heterostructures. The stray field of skyrmions with radius ≈50 nm is sufficient to nucleate antivortices in a 25 nm Nb film, with unique signatures in the magnetization, critical current, and flux dynamics, corroborated via simulations. We also detect a thermally tunable Rashba-Edelstein exchange coupling in the isolated skyrmion phase. This realization of a strongly interacting skyrmion-(anti)vortex system opens a path toward controllable topological hybrid materials, unattainable to date.

Spin-droplet state of an interacting 2D electron system.

We report thermodynamic magnetization measurements of two-dimensional electrons in several high-mobility Si metal-oxide-semiconductor field-effect transistors. We provide evidence for an easily polarizable electron state in a wide density range from insulating to deep into the metallic phase. The temperature and magnetic field dependence of the magnetization is consistent with the formation of large-spin droplets in the insulating phase. These droplets melt in the metallic phase with increasing density and temperature, though they survive up to large densities.

A magnetically focused molecular beam of ortho-water.

Like dihydrogen, water exists as two spin isomers, ortho and para, with the nuclear magnetic moments of the hydrogen atoms either parallel or antiparallel. The ratio of the two spin isomers and their physical properties play an important role in a wide variety of research fields, ranging from astrophysics to nuclear magnetic resonance (NMR). Unlike ortho and para H(2), however, the two water isomers remain challenging to separate, and as a consequence, very little is currently known about their different physical properties. Here, we report the formation of a magnetically focused molecular beam of ortho-water. The beam we formed also had a particular spin projection. Thus, in the presence of holding magnetic fields, the water molecules are hyperpolarized, laying the foundation for ultrasensitive NMR experiments in the future.

Detection of non-Gaussian fluctuations in a quantum point contact.

An experimental study of current fluctuations through a tunable transmission barrier, a quantum point contact, is reported. We measure the probability distribution function of transmitted charge with precision sufficient to extract the first three cumulants. To obtain the intrinsic quantities, corresponding to voltage-biased barrier, we employ a procedure that accounts for the response of the external circuit and the amplifier. The third cumulant, obtained with a high precision, is found to agree with the prediction for the statistics of transport in the non-Poissonian regime.

Measurement of counting statistics of electron transport in a tunnel junction.

We present measurements of the time-dependent fluctuations of electrical current in a voltage-biased tunnel junction. We were able to simultaneously extract the first three moments of the current counting statistics. Detailed comparison of the second and the third moments reveals that the statistics is accurately described as Poissonian, expected for spontaneous current fluctuations due to electron charge discreteness, realized in tunneling transport at negligible coupling to environment.

Cooling of electrons in a silicon inversion layer.

Low temperature cooling of two-dimensional electrons in silicon-metal-oxide semiconductor field effect transistors is studied experimentally and found to be more effective than expected from the bulk electron-phonon coupling in silicon. The extracted heat transfer rate to phonons depends cubically on electron temperature, suggesting that piezoelectric coupling, which is absent in bulk silicon, dominates over deformation potential. As a result, at 100 mK, electrons farther than approximately 100 microm from the contacts are mostly cooled by phonons. Using long devices and low excitation voltage we measure electron resistivity down to approximately 100 mK and find that some of the "metallic" curves turn insulating below approximately 300 mK.

Clinical utility of the polymerase chain reaction to diagnose Mycoplasma pneumoniae infection.

The diagnosis of Mycoplasma pneumoniae infection currently relies on serological methods which may be slow to produce diagnostic results and may be inconvenient for both the clinician and the patient. This study was designed to assess whether or not the polymerase chain reaction (PCR) is a useful additional diagnostic method. Comparison was therefore made with serology as it is routinely practiced. PCR was used to examine for the presence of M. pneumoniae DNA in throat swab specimens obtained from 99 hospitalized patients investigated for a range of respiratory pathogens including M. pneumoniae. PCR detected M. pneumoniae DNA in 24 adults and 25 children, which is significantly more than the 32 patients found to be antibody positive by the particle agglutination test (p = 0.001). M. pneumoniae DNA was not detected in any of the throat swabs from 32 apparently healthy volunteers. PCR inhibitors were not detected in any of the samples tested. Significantly more children (88%) than adults (38%) were found to be anti-mycoplasma antibody-positive (p < 0.0001). Routine clinical practice was reflected in the fact that 56 patients (57%) had indeterminate serological results because only single sera were obtained. The sensitivity and specificity of PCR were assessed to be 92% and 98% respectively, using a combination of serological and clinical data as the benchmark. PCR appears to have advantages over serological testing, both with respect to accuracy and convenience of single specimen testing. The poor performance of serological tests in adults makes PCR especially useful in this age group.

Comparison of nasopharyngeal aspirates and throat swab specimens in a polymerase chain reaction-based test for Mycoplasma pneumoniae.

Nasopharyngeal aspirates and throat swab specimens were compared in a polymerase chain reaction (PCR)-based test for Mycoplasma pneumoniae. The pathogen was detected in 50% and 45% of throat swab specimens and aspirates, respectively. However, in specimens negative for Mycoplasma pneumoniae by PCR, amplification inhibitors were detected in 0% and 36% of throat specimens and aspirates, respectively. Further investigations confirmed that no throat specimens, but one-quarter of aspirates, are likely to be rejected for containing inadequate respiratory material or excess amplification inhibitors. Because rejection of most of the unsuitable specimens is possible only after PCR, the use of aspirates is less cost-effective. This, and the reluctance to subject patients to aspiration, make the aspirate an inferior specimen for detection of Mycoplasma pneumoniae by PCR.

[Human diseases caused by leptospirae of the canicola serogroup in the Krasnodar Territory]. / Zabolevaniia cheloveka, vyzvannye leptospirami serogruppy canicola, v Krasnodarskom krae.

During the period of 34 years (1957-1990) diseases caused by leptospires of the serogroup canicola were confirmed in 2.7% of the total number of patients. The analysis revealed that in the presence of epidemic outbreaks Leptospira infection caused by bacteria of the serogroup canicola occurred 1.7 times more often than at the time when such outbreaks were absent. Periodic increases of leptospirosis caused by this serogroup were registered in individual towns and regions of the territory in different years. The analysis of 33 medical histories made it possible to state that the clinical manifestations of leptospirosis caused by bacteria of the serogroup canicola were characteristic of Leptospira infections caused not only by this serovar. As a rule, this kind of leptospirosis was registered in rural and urban areas as individual isolated cases.

The effects of RU 41.740, a glycoprotein immunomodulating agent derived from Klebsiella pneumoniae, on intra-abdominal abscess formation in mice.

The prophylactic and therapeutic efficacies of the immunomodulating agent RU 41.740 (a glycoprotein extract from Klebsiella pneumoniae) were studied in a murine model of intra-abdominal abscess formation with Bacteroides fragilis, Escherichia coli, and bran as an abscess-potentiating agent. Parenteral injection of RU 41.740, either before or after injection of an abscess-inducing mixture (AIM), was associated with significantly diminished incidence and size of abscesses. Abscess incidence and size were significantly decreased by oral administration of RU 41.740 after, but not before, AIM injection. Abscess formation and resolution are the results of complex interactions of host defence mechanisms with bacteria and potentiating agent, and RU 41.740 has been shown previously to activate both macrophage and neutrophil function. These results indicate that activation of non-specific defences may protect against abscess development in chronic sepsis.

[Identification of a protein product of a novel human gene SON and the biological effect upon administering a changed form of this gene into mammalian cells]. / Identifikatsiia belka-produkta novogo gena cheloveka SON i biologichekii éffekt pri vvedenii izmenennoi formy étogo gena v kletki mlekopitaiushchikh.

We have investigated the functional activity of human son gene, that possesses the homology to mos and myc genes. Specific antibodies (antiserum) were raised to synthetic peptide, that corresponds to son-protein 943-963 amino acid residues. With this antiserum the presence of son-protein was showed in lysates of cultured human cells transformed by adenovirus type 5, RAT 2 cells and primary human embryonic fibroblasts. son-Protein molecular weight (92 kDa) was determined by the method of electrophoresis in SDS-polyacrylamide gel. Thus, it was shown the presence of son gene protein in animal and human cells. To determine a possible son gene role in mammalian cells we have cloned the 3' part (2667 b.p.) of son cDNA in retroviral vector pPS-3-neo. Transformed cells of different lines were selected. A large portion of this cells changed their morphology. New protein product (120 k), that reacted with antiserum to son specific peptide, was found together with p92son in these clones.

The use of syngeneic cells producing human somatotropic hormone (hSTH) for immunization of mice and development of hybridomas.

We studied the possibility of syngeneic cells expressing heterologous protein being used for sensitization of mice and production of hybridomas. Recombinant retroviral vector containing cloned human somatotropic hormone (hSTH) gene was used to express hSTH in BALB/3T3 cells. BALB/c mice were injected intrasplenically (i/s) or combination of intraperitoneally (i/p) and intrasplenically with hSTH-producing cells. Sensitized splenocytes were fused with myeloma cell P3X63-AgB.653. Screening for anti-hSTH hybridomas was performed by enzyme-linked immunoassay. Both single i/s injection of producer cells as well as combined i/s and i/p injections were effective for sensitization of splenocytes. Combined injection was effective for production of IgG and IgM secreting hybridomas. Single i/s injection led to generation of only IgM producing hybridomas. The results proved that syngeneic cells expressing genes of heterologous proteins can be used for splenocyte sensitization and hybridoma preparation.

[Expression of human growth hormone in cultured mouse fibroblasts]. / Ekspressiia gormona rosta cheloveka v perevivaemykh fibroblastakh myshi.

The new system for the transfer and expression of foreign genes based on retroviral vectors pPS-neo, conferring neomycin resistance was constructed. The BALB/c mouse cell lines producing highly active human growth hormone (more than 7 micrograms/ml into culture medium) were constructed using these vectors. An antibody column was used to purify the growth hormone from cell culture medium. Possibilities of producers to be applied for gene therapy are discussed.

Response of a 'susceptible' Escherichia coli to metronidazole therapy: an investigation using experimental subcutaneous abscesses.

Earlier experiments under anaerobic conditions in vitro had indicated that Gram-negative facultative anaerobes were susceptible to therapeutically attainable concentrations of metronidazole. This prompted us to study the response of one such strain to metronidazole therapy. Mice with 3-day-old subcutaneous abscesses induced by 'susceptible' Escherichia coli (accompanied by potentiating agent and obligately anaerobic Bacteroides fragilis) were given metronidazole by mouth (250 mg/kg/dose 12 hourly) either as a two- or a four-dose course. This therapy reduced the viable numbers of E. coli/abscess by a mere 0.3 log10 and 0.7 log10, respectively. Assays showed that concentrations of metronidazole in abscess-contents compared favourably with those in the earlier in vitro experiments. But measurement of redox potentials in abscesses indicated that the conditions in these (-191 mV vs. Ag/AgCl) were not nearly as reduced as those in experiments in vitro (-650 mV). This, and the known dependence of metronidazole on low redox potentials for expression of its antimicrobial ability, appears to be the explanation for the poor anticoliform effect in the subcutaneous abscess model. Full assessment of the clinical implications of these observations must await the availability of data regarding redox potentials in clinical situations.

Effect of metronidazole on Escherichia coli in the presence of Bacteroides fragilis: an investigation in mice.

The observation that, in rats, metronidazole exhibited antimicrobial activity against resistant Escherichia coli (when this was accompanied by susceptible Bacteroides fragilis) prompted us to attempt to reproduce this phenomenon in another species and under other experimental conditions. In experiment 1, mice injected intraperitoneally with an E. coli/B. fragilis mixture were treated with metronidazole, 250 mg/kg given by mouth at 0 and 10 h, or left untreated. At 24 h, viable counts of bacteria in blood and peritoneal washings were determined. In experiment 2, mice with 5-day-old subcutaneous abscesses containing E. coli and B. fragilis were also either given metronidazole as above or left untreated. At 24 h, viable counts of bacteria in pus were determined. Metronidazole affected neither the frequency with which E. coli persisted at the three sites, nor the viability of E. coli at these sites. This was so despite the fact that, in each of the sites, a significant B. fragilis kill was registered. Thus, pending elucidation of the mechanism by which the phenomenon operates, its non-appearance in these experiments cautions against the extrapolation of the original observations beyond the circumstances under which they were first made.

Effect of Bacteroides fragilis on the peritoneal clearance of Escherichia coli in mice.

A report that Bacteroides fragilis inhibited the killing of facultative anaerobes by human leukocytes in vitro prompted us to look for such inhibition in the peritoneal cavities of mice. No evidence that this phenomenon was operative could be found.