CuInP2S6 Room Temperature Layered Ferroelectric.

We explore ferroelectric properties of cleaved 2-D flakes of copper indium thiophosphate, CuInP2S6 (CITP), and probe size effects along with limits of ferroelectric phase stability, by ambient and ultra high vacuum scanning probe microscopy. CITP belongs to the only material family known to display ferroelectric polarization in a van der Waals, layered crystal at room temperature and above. Our measurements directly reveal stable, ferroelectric polarization as evidenced by domain structures, switchable polarization, and hysteresis loops. We found that at room temperature the domain structure of flakes thicker than 100 nm is similar to the cleaved bulk surfaces, whereas below 50 nm polarization disappears. We ascribe this behavior to a well-known instability of polarization due to depolarization field. Furthermore, polarization switching at high bias is also associated with ionic mobility, as evidenced both by macroscopic measurements and by formation of surface damage under the tip at a bias of 4 V-likely due to copper reduction. Mobile Cu ions may therefore also contribute to internal screening mechanisms. The existence of stable polarization in a van-der-Waals crystal naturally points toward new strategies for ultimate scaling of polar materials, quasi-2D, and single-layer materials with advanced and nonlinear dielectric properties that are presently not found in any members of the growing "graphene family".

Multicentre Study of the Prevalence and Clinical Value of Hospital-Acquired Infections in Emergency Hospitals of Russia: ERGINI Study Team.

BACKGROUND: Hospital-acquired infection (HAI) is a common problem in intensive care units (ICU) and other hospital units. The methodical system of surveillance of hospital-acquired infections (HAI) is not available in Russia and there is no reliable data about the prevalence or epidemiology of HAI. We aimed in this pioneer study to determine the prevalence, epidemiological and microbiological characteristics, risk factors, clinical value and outcomes of HAI in different units of emergency multifields hospitals of Russia. METHODS: This prospective multicentre 1-day prevalence study with 28-days follow-up was realized between January and May 2013. Thirty two emergency hospitals with more than 500-beds from 18 cities participated in this study. The study was conducted separately on 5 different days in ICU, therapeutic, surgical, urology and neurology units. All patients treated in the unit on the day of the study were examined for the presence of HAI according to CDC criterias. Risk factors of HAI, nosological and etiological structure, susceptibility of pathogens were also evaluated. RESULTS: Totally 3809 patients were included in the study during 5 days of investigation in ICU and therapeutic, surgical, urology and neurology units (respectively 449, 1281, 1431, 342 and 306 patients). The total number of registered HAI was 290 and the prevalence of HAI was 7.61% (95% CI 6.81%, 8.50%). The greatest rate of HAI was registered in ICU (26.28%) and neurological unit (13.73%); the rate was lower in therapeutic, surgical and urology units (4.76, 4.12 and 2.92%). The prevalence of HAI.was similar in adult and pediatric hospitals .(7.62 and 7.54%). The prevalence of community-acquired infections was 28.53%. The lower respiratory tract was the most common site of infection, accounting for 42.4%.of HAIs followed by the urinary tract (19.0%), skin and soft tissue (13.4%), abdomen (11.4%) and intravascular (4.8%). 311 pathogens were isolated: 58.8% of isolates were gram-negative, 32.8% gram-positive, and 8.4% Candida spp. The most common bacterial isolates were Klebsiella spp. (19.6%), E.coli (12.2%), S.aureus (11.3%), Acinetobacter spp. (10.9%), E.faecalis (7.4%) and P.aeruginosa (7.1%). The resistance rate of E.coli and Klebsiella spp. to 3rd generation of cephalosporins was 60.5 and 95.1%. Only 26.5% of Acinetobacter isolates and 59,1% of P.aeruginosa isolates were susceptible to imipenem. The MRSA rate was 48.6%; 17,4% of E.faecalis were resistant to ampicillin. The mortality rate was higher in patients with HAI (16.5%) than in patients without HAI (3.0%); the mean length of hospital stay was also higher in patients with HAI (24.6±11,4 vs. 16.2±15,3 days). CONCLUSION: The prevalence of HAI in Russian hospitals is high. According to the prevalence data the estimating annual number of HAI in Russia is approximately 2,300,000 cases. The multi-drug resistant microorganisms were dominated among causative agents of HAI.

[INDICATIONS FOR RESPIRATORY SUPPORT AT PATIENTS WITH STROKE AND NOSOCOMIAL PNEUMONIA.]

80 patients with cerebral stroke and nosocomial pneumonia ofwhich formed 2 groups of 40 patients each were included in the study. The groups were matched for severity at the beginning of the study. All patients received comprehensive treatment in the conditions of the neurological intensive care unit in 2011-2015 in the O.M Filatov clinical city hospital N2 15, Moscow. Patients from both groups were transferred on mechanical lung ventilation: group I - in the presence of severe clinical picture of respiratory distress and/or depression of consciousness, and group 2 -with deviations from the norm of acid-base status of blood parameters. The results of the study shows the first clinical and laboratory criteria for the transfer patients on mechanical lung ventilation, which are the changes of indicators in blood acid-base status (pH, lactate, glucose, pCO2, po2) and the degree of neurological deficit, not the clinical picture in the form of severe respiratory failure in patients with cerebral stroke.

[Performance evaluation of integrated cytoprotective therapy of different duration in patients with cerebral infarction].

The paper reviews the preliminary results of a multicenter randomized clinical research. The aim of the study was to determine the optimal duration of different types of energy-correction therapy. 99 case report forms of patients with cerebral infarction were reviewed with their prior envelope randomization into three groups. Patients in the first group (experimental group), consisting of 32 patients, as part of combined therapy received ascorbic acid (5% solution twice a day in a recommended dosage of 20 ml/day for 20 days); the second group (37 patients) received 10 ml of cytoflavin intravenously by drop infusion twice a day for 10 days; the third group received cytoflavin for 20 days (from day 1 to day 10 - 20 ml a day, from day 11 to day 20 - 10 ml a day). The average NIH scale score on admission was 14.9 ± 2.6. Prescription of cytoflavin came with average 1.7 - 1.8 time regression (p < 0.05) of the volumes of cerebral ischemia in the of cases of the 10- and 20-day courses of treatment, while there were no significant morphologic changes in the ascorbic acid group. These results correlated with the best dynamics and outcomes of the neurological and performance status of patients receiving cytoflavin. Despite the lack of significant general differences in the clinical and morphological data of the second and third groups, the patients with underlying grave medical condition in the 20-day cytoflavin group (with NIH score of 14-20 points on admission) tended to have improved neurologic status parameters in comparison with the experimental group and the 10-day cytoflavin group. These results attest to the advantages of personalized antioxidant energy-correction therapy.

Elastic coupling between nonferroelastic domain walls.

We reveal a strong elastic interaction between nonferroelastic domain walls in ferroelectric thin films. This interaction, having no analogue in bulk materials, is governed by elastic fields that are associated with the domain walls and extends to distances comparable to the film thickness. Such elastic widening of the nonferroelastic domain walls is shown to be particularly strong in common ferroelectric perovskites. The results are especially relevant for the control of domain wall propagation and the understanding of polarization dynamics.

Domain wall geometry controls conduction in ferroelectrics.

A new paradigm of domain wall nanoelectronics has emerged recently, in which the domain wall in a ferroic is itself an active device element. The ability to spatially modulate the ferroic order parameter within a single domain wall allows the physical properties to be tailored at will and hence opens vastly unexplored device possibilities. Here, we demonstrate via ambient and ultrahigh-vacuum (UHV) scanning probe microscopy (SPM) measurements in bismuth ferrite that the conductivity of the domain walls can be modulated by up to 500% in the spatial dimension as a function of domain wall curvature. Landau-Ginzburg-Devonshire calculations reveal the conduction is a result of carriers or vacancies migrating to neutralize the charge at the formed interface. Phase-field modeling indicates that anisotropic potential distributions can occur even for initially uncharged walls, from polarization dynamics mediated by elastic effects. These results are the first proof of concept for modulation of charge as a function of domain wall geometry by a proximal probe, thereby expanding potential applications for oxide ferroics in future nanoscale electronics.

Exploring mesoscopic physics of vacancy-ordered systems through atomic scale observations of topological defects.

Vacancy-ordered transition metal oxides have multiple similarities to classical ferroic systems including ferroelectrics and ferroelastics. The expansion coefficients for corresponding Ginzburg-Landau-type free energies are readily accessible from bulk phase diagrams. Here, we demonstrate that the gradient and interfacial terms can quantitatively be determined from the atomically resolved scanning transmission electron microscopy data of the topological defects and interfaces in model lanthanum-strontium cobaltite. With this knowledge, the interplay between ordering, chemical composition, and mechanical effects at domain walls, interfaces and structural defects can be analyzed.

Intrinsic single-domain switching in ferroelectric materials on a nearly ideal surface.

Ferroelectric domain nucleation and growth in multiferroic BiFeO(3) is studied on a single-domain level by using piezoresponse force spectroscopy. Variation of local electromechanical response with dc tip bias is used to determine the size of the domain formed below the conductive scanning probe tip. The domain parameters are calculated self-consistently from the decoupled Green function theory by using tip geometry determined from the domain wall profile. The critical parameters of the nucleating domain and the activation energy for nucleation are determined. The switching mechanism is modeled by using the phase-field method, and comparison with experimental results shows that the nucleation biases are within a factor of approximately 2 of the intrinsic thermodynamic limit. The role of atomic-scale defects and long-range elastic fields on nucleation bias lowering is discussed. These measurements open a pathway for quantitative studies of the role of a single defect on kinetics and thermodynamics of first order bias-induced phase transitions and electrochemical reactions.

Probing the temperature dependence of the mechanical properties of polymers at the nanoscale with band excitation thermal scanning probe microscopy.

Understanding local mechanisms for temperature-induced phase transitions in polymers requires quantitative measurements of the thermomechanical behavior, including glass transition and melting temperatures as well as temperature dependent elastic and loss modulus and thermal expansion coefficients in nanoscale volumes. Here, we demonstrate an approach for probing local thermal phase transitions based on the combination of thermal field confinement by a heated SPM probe and multi-frequency thermomechanical detection. The local measurement of the glass transition temperature is demonstrated and the detection limits are established.

Thermooptical evidence of carrier-stabilized ferroelectricity in ultrathin electrodeless films.

Ferroelectric films may lose polarization as their thicknesses decrease to a few nanometers because of the depolarizing field that opposes the polarization therein. The depolarizing field is minimized when electrons or ions in the electrodes or the surface/interface layers screen the polarization charge or when peculiar domain configuration is formed. Here, we demonstrate ferroelectric phase transitions using thermooptical studies in ∼5-nm-thick epitaxial Pb0.5Sr0.5TiO3 films grown on different insulating substrates. By comparing theoretical modeling and experimental observations, we show that ferroelectricity is stabilized through redistribution of charge carriers (electrons or holes) inside ultrathin films. The related high-density of screening carriers is confined within a few-nanometers-thick layer in the vicinity of the insulator, thus resembling a two-dimensional carrier gas.

[Difficulties in the diagnosis of stroke in pregnant women]. / Slozhnosti diagnostiki mozgovogo insul'ta u beremennykh.

AIM: To study the features of the clinical picture of stroke and results of laboratory/instrumental study in pregnant women. MATERIAL AND METHODS: A study included 44 women at different periods of gestation (mean age 33.4±9.7 years) with clinical symptoms of stroke hospitalized within 4-11h after stroke. Neuroimaging, clinical/instrumental and laboratory examinations were carried out in the first 40 min after admission. RESULTS: A routine screening examination during the management of pregnancy in women's consultation clinics does not always reduce the risk of life threatening events. The operative delivery can decrease the severity of the focal neurological deficit. Intensive treatment and dynamic management of patients with intracranial pathology in intensive care stroke unit improves outcome of stroke. CONCLUSION: A timely differential diagnosis of pathological conditions with different symptoms of stroke at the different stages of medical care of pregnant women helps to choose an optimal treatment plan and improve the outcome.

Ferroelectrics. Observation of a periodic array of flux-closure quadrants in strained ferroelectric PbTiO3 films.

Nanoscale ferroelectrics are expected to exhibit various exotic domain configurations, such as the full flux-closure pattern that is well known in ferromagnetic materials. Here we observe not only the atomic morphology of the flux-closure quadrant but also a periodic array of flux closures in ferroelectric PbTiO3 films, mediated by tensile strain on a GdScO3 substrate. Using aberration-corrected scanning transmission electron microscopy, we directly visualize an alternating array of clockwise and counterclockwise flux closures, whose periodicity depends on the PbTiO3 film thickness. In the vicinity of the core, the strain is sufficient to rupture the lattice, with strain gradients up to 10(9) per meter. Engineering strain at the nanoscale may facilitate the development of nanoscale ferroelectric devices.

[Biotransplants from the dura mater in the reconstruction of the aorta and arteries]. / Biotransplantaty iz tverdoi obolochki golovnogo mozga v rekonstruktsii aorty i arterii.

The authors have analyzed results of using dura mater as a plastic material in 1078 patients with occluding diseases of the aorta and major arteries. Immediate positive results were noted in 93.4% of the patients. Long-term results from 12 months to 19 years were studied in 683 patients.

Atomic-scale evolution of modulated phases at the ferroelectric-antiferroelectric morphotropic phase boundary controlled by flexoelectric interaction.

Physical and structural origins of morphotropic phase boundaries (MPBs) in ferroics remain elusive despite decades of study. The leading competing theories employ either low-symmetry bridging phases or adaptive phases with nanoscale textures to describe different subsets of the macroscopic data, while the decisive atomic-scale information has so far been missing. Here we report direct atomically resolved mapping of polarization and structure order parameter fields in a Sm-doped BiFeO(3) system and their evolution as the system approaches a MPB. We further show that both the experimental phase diagram and the observed phase evolution can be explained by taking into account the flexoelectric interaction, which renders the effective domain wall energy negative, thus stabilizing modulated phases in the vicinity of the MPB. Our study highlights the importance of local order-parameter mapping at the atomic scale and establishes a hitherto unobserved physical origin of spatially modulated phases existing in the vicinity of the MPB.

Nanoscale mapping of ion diffusion in a lithium-ion battery cathode.

The movement of lithium ions into and out of electrodes is central to the operation of lithium-ion batteries. Although this process has been extensively studied at the device level, it remains insufficiently characterized at the nanoscale level of grain clusters, single grains and defects. Here, we probe the spatial variation of lithium-ion diffusion times in the battery-cathode material LiCoO(2) at a resolution of ∼100 nm by using an atomic force microscope to both redistribute lithium ions and measure the resulting cathode deformation. The relationship between diffusion and single grains and grain boundaries is observed, revealing that the diffusion coefficient increases for certain grain orientations and single-grain boundaries. This knowledge provides feedback to improve understanding of the nanoscale mechanisms underpinning lithium-ion battery operation.

Probing the role of single defects on the thermodynamics of electric-field induced phase transitions.

The kinetics and thermodynamics of first order transitions are universally controlled by defects that act as nucleation sites and pinning centers. Here we demonstrate that defect-domain interactions during polarization reversal processes in ferroelectric materials result in a pronounced fine structure in electromechanical hysteresis loops. Spatially resolved imaging of a single defect center in multiferroic BiFeO3 thin film is achieved, and the defect size and built-in field are determined self-consistently from the single-point spectroscopic measurements and spatially resolved images. This methodology is universal and can be applied to other reversible bias-induced transitions including electrochemical reactions.