In most ferromagnets the magnetization rotates from one domain to the next with no preferred handedness. However, broken inversion symmetry can lift the chiral degeneracy, leading to topologically-rich spin textures such as spin-spirals 1,2 and skyrmions 3-5 via the Dzyaloshinskii-Moriya interaction (DMI)6 . Here we show that in ultrathin metallic ferromagnets sandwiched between a heavy metal and an oxide, the DMI stabilizes chiral domain walls (DWs) 2,7 whose spin texture enables extremely efficient current-driven motion [8][9][10][11] . We show that spin torque from the spin Hall effect [12][13][14][15] The Rashba field lacks the correct symmetry to drive DWs directly 16,26,27 , and the spin Hall effect (SHE) in the adjacent heavy metal has emerged as a possible alternative mechanism [12][13][14][15][16]27 . SHE-driven spin accumulation at the heavy-metal/ferromagnet interface generates a Slonczeswki-like torque 16,26,27 strong enough to switch uniformly-magnetized films [12][13][14][15]18 . However, the Bloch DWs expected in typical nanowire geometries [8][9][10][11]28 have their plane oriented perpendicular to the nanowire axis, in which case the Slonczewski-like torque vanishes 16 . This behavior was recently confirmed in asymmetric Pt/Co/Pt stacks in which the SHE-induced torques from the Pt layers did not cancel completely 15 . In that case, currentassisted DW depinning was observed when an applied field rotated the DW plane towards the current axis, but up-down and down-up DWs were driven in opposite directions and the current had no effect in the absence of the bias field. The SHE alone is therefore incapable of uniformly 3 driving trains of DWs in devices, and is insufficient to explain the high spin-torque efficiencies and DW velocities observed in Pt/Co/oxide 8-11 without applied fields.Here we characterize current-induced torques and DW dynamics in out-of-plane magnetized Pt/CoFe/MgO and Ta/CoFe/MgO stacks that are nominally identical except for the heavy-metal underlayers, whose spin Hall angles are large and of opposite sign [12][13][14] . By considering the symmetry of the measured current-induced torque along with the DW dynamics driven by this torque, we uniquely identify the DW configuration as Néel with a fixed chirality.Magnetostatics alone makes this configuration unstable and does not favor one chirality over the other, but the DMI has been theoretically shown to promote chiral Néel DWs 2,7 . By applying inplane magnetic fields, we verify that the DW magnetization aligns rigidly along the nanowire axis, and that the DW spin spiral exhibits a global chirality common to both Pt/CoFe/MgO and Ta/CoFe/MgO. Current-driven DW motion in heavy-metal/ferromagnet/oxide structures is naturally explained by the combination of the SHE, which produces the sole current-induced torque, and the DMI, which stabilizes chiral DWs whose symmetry permits uniform motion with very high efficiency.DW motion was characterized in 500-nm wide, 40-μm long nanowires overlaid with an orthogonal DW nucleation li...

Although chronic stress is known to be linked with memory and other neurological disorders, little is known about the relationship between chronic stress and the onset or development of Alzheimer's disease (AD). In this study, we investigated the effects of long-term stress on the onset and severity of cognitive deficits and pathological changes in APPV717I-CT100 mice overexpressing human APP-CT100 containing the London mutation (V717I) after exposure to immobilization stress. We found that chronic immobilization stress accelerated cognitive impairments, as accessed by the Passive avoidance and the Social Transfer of Food Preference (STFP) tests. Moreover, the numbers and densities of vascular and extracellular deposits containing amyloid beta peptide (Abeta) and carboxyl-terminal fragments of amyloid precursor protein (APP-CTFs), which are pathologic markers of AD, were significantly elevated in stressed animals, especially in the hippocampus. Moreover, stressed animals, also showed highly elevated levels of neurodegeneration and tau phosphorylation and increased intraneuronal Abeta and APP-CTFs immunoreactivities in the hippocampus and in the entorhinal and piriform cortex. This study provides the first evidence that chronic stress accelerates the onset and severity of cognitive deficits and that these are highly correlated with pathological changes, which thus indicates that chronic stress may be an important contributor to the onset and development of AD.

Despite the complexity and diversity of nature, there exists universality in the form of critical scaling laws among various dissimilar systems and processes such as stock markets, earthquakes, crackling noise, lung inflation and vortices in superconductors. This universality is mainly independent of the microscopic details, depending only on the symmetry and dimension of the system. Exploring how universality is affected by the system dimensions is an important unresolved problem. Here we demonstrate experimentally that universality persists even at a dimensionality crossover in ferromagnetic nanowires. As the wire width decreases, the magnetic domain wall dynamics changes from elastic creep in two dimensions to a particle-like stochastic behaviour in one dimension. Applying finite-size scaling, we find that all our experimental data in one and two dimensions (including the crossover regime) collapse onto a single curve, signalling universality at the criticality transition. The crossover to the one-dimensional regime occurs at a few hundred nanometres, corresponding to the integration scale for modern nanodevices.

A mathematical model was developed for a continuous reactor in which free radical polymerization of methyl methacrylate (MMA) occurred. Elementary reactions considered in this study were initiation, propagation, termination, and chain transfers to monomer and solvent. The reactor model took into account the density change of the reactor content and the gel effect. To measure the conversion and weight-average molecular weight on line, the on-line densitometer and viscometer were installed in such a way that the measured values of density were used to calculate the conversion and the viscosity measurement along with conversion data was used to determine the weight-average molecular weight. A control system was designed for a continuous reactor using an extended Kalman filter (EKF)-based nonlinear model predictive controller (NLMPC) to control both the conversion and the weight-average molecular weight of the polymer product. The control input variables were the jacket inlet temperature and the feed flow rate. For the purpose of validating the control strategy, an on-line digital control experiment was conducted with an on-line densitometer and viscometer installed. Despite the complex and nonlinear features of the polymerization reaction system, the EKF-based NLMPC performed quite satisfactorily for the property control of the continuous polymerization reactor.

Two distinct pinning mechanisms named as kinetic and static pinning of magnetic domain wall (DW) are experimentally resolved. Both the pinning situations are realized at an artificial notch on U-shaped Permalloy nanowires, depending on the initial DW states, moving or pinned. The kinetic depinning field—a critical field for a moving DW to be trapped at a notch—is revealed to be distinguishably smaller than the static depinning field—a critical field to depin a trapped DW at the notch. Based on one-dimensional collective model, the discrepancy is explained by the tilting angle of the moving DW.

We have found that the depinning field of domain walls (DWs) in permalloy (Ni(81)Fe(19)) nanowires can be experimentally controlled by interactions between magnetic stray fields and artificial constrictions. A pinning geometry that consists of a notch and a nanobar is considered, where a DW traveling in the nanowire is pinned by the notch with a nanobar vertical to it. We have found that the direction of magnetization of the nanobar affects the shape and local energy minimum of the potential landscape experienced by the DW; therefore, the pinning strength strongly depends on the interaction of the magnetic stray field from the nanobar with the external pinning force of the notch. The mechanism of this pinning behavior is applied for the instant and flexible control of the pinning strength with respect to various DW motions in DW-mediated magnetic memory devices.

Objectives: Urinary tract infection (UTI) is a common medical complication experienced by patients with neurologic diseases. In this study, we established the microbial etiologies of UTI, and resistances to antibiotics in UTI as well as determining which appropriate empirical antibiotics should be used to treat UTI in neurological patients. Designs and methods: We retrospectively reviewed microbial etiologies and antimicrobial resistance among patients experiencing UTI events in the neurology ward of Seoul National University Hospital from 2007 to 2016. Results: The total number of UTI events observed was 301, and Klebsiella pneumoniae was the most common pathogen observed in UTIs. But in catheter-associated UTI (CAUTI), Enterococcus species were the most prevalent pathogens. Susceptibility to commonly-prescribed antibiotics decreased over 10 years, indicating increased antibiotic resistance in pathogens associated with UTI. ESBL-producing K. pneumoniae increased significantly, while increases of MDR K. pneumoniae, ESBL-producing E. coli, and VRE were not observed. Conclusions: The worldwide trend of increasing drug-resistant pathogens should be considered, and further studies on antibiotics resistance in UTI are needed. These data will greatly assist physicians when they select antibiotics to treat UTIs in neurological patients.

BackgroundBed-ridden state, dysphagia, altered mental state, or respiratory muscle weakness are common in neurologic patients and increase the risk of pneumonia. The major causes of pneumonia in neurologic patients may differ from those in the general population, resulting in a different pathogen distribution. We investigated the trends of pathogen distribution in culture-positive pneumonia in hospitalized neurologic patients and the related antibiotic resistance in those with hospital-acquired pneumonia (HAP).MethodsA retrospective study was performed at Seoul National University Hospital, South Korea. Patients admitted to the Department of Neurology with a positive respiratory specimen culture between 2007 and 2016 were included. Pneumonia events in patients were screened by chronologically associating the date of respiratory specimen acquisition for culture studies and the date of antibiotics administration. Subgroup analyses regarding multidrug resistance in HAP were performed in different pneumonia categories, by presence of ≥1 risk factor and by time period (first half vs. second half of study period). Microbial resistance profiles of isolates from patients with pneumonia were analyzed.ResultsWe identified 351 pneumonia cases in 227 patients involving 36 different pathogens. 232 cases were HAP, of which 70 cases were intensive care unit (ICU)-HAP. The leading pathogens were Stapylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Streptococcus pneumoniae, and Enterobacter aerogenes, which were isolated in 133 (37.9%), 72 (20.5%), 55 (15.7%), 44 (12.5%), 33 (9.4%), and 27 (7.7%) cases, respectively. Cases with HAP showed a higher proportion of P. aeruginosa and a lower proportion of S. pneumoniae (both, p < 0.05) than those with non-HAP. ICU-HAP isolates showed a higher multidrug resistance (MDR) rate than non-ICU-HAP isolates (p < 0.005) in those with ≥1 MDR risk factor. Non-susceptibility to imipenem (p < 0.0005), piperacillin-tazobactam (p < 0.001), cefepime (p < 0.005), and trimethoprim-sulfamethoxazole (p < 0.05) in Gram-negative pathogens increased over time in both ICU and non-ICU settings.ConclusionsS. aureus, K. pneumoniae, A. baumannii, P. aeruginosa, S. pneumoniae, and E. aerogenes were the leading isolates in culture-positive pneumonia in hospitalized neurologic patients. Antimicrobial resistance of Gram-negative pathogens in neurologic patients with culture-positive HAP has recently increased.Electronic supplementary materialThe online version of this article (10.1186/s13756-019-0475-9) contains supplementary material, which is available to authorized users.