Comparing fixed and auto adjusting continuous positive airway pressure (CPAP) amongst symptomatic Obstructive Sleep Apnoea patients - A randomised controlled trial.

INTRODUCTION: Continuous Positive Airway Pressure (CPAP) is required for obstructive sleep apnoea (OSA). Thisstudy compares the efficacy between Fixed Pressure CPAP (Fixed CPAP) and Auto-adjusting Pressure (APAP) based on Apnoea Hypopnoea Index (AHI), Epworth Sleepiness Score (ESS) among patients with symptomatic OSA and to ascertain their CPAP preference. METHODS: This is a prospective, randomised, crossover, single-blinded study conducted from February 2018 to February 2019 among adult subjects attending respiratory clinic Universiti Kebangsaan Malaysia Medical Centre (UKMMC). RESULTS: Forty-six subjects were recruited with 27 males (58.7%). The mean age was 54 (+11) year old. The baseline median Body Mass Index (BMI) was 34.2 kg/m2 (Interquartile Range IQR: 30.8 kg/m2 -41.7 kg/m2); baseline median AHI 28.8 /hour (IQR 21.2/hour-54.0/hour); andbaseline median ESS 15 (IQR 13-16). After intervention, the median AHI was 5.0 / hour (IQR 4.2/hour-6.0/hour) at fixed CPAP arm; APAP arm was 5.5/ hour (IQR 4.2/hour-6.3/hour); p<0.01. The median ESS at fixed CPAP arm was 2 (IQR 0-3); APAP arm was 2 (IQR 1-3); p < 0.01. Those who preferred APAP were 22 subjects (47.8%) and had median optimal CPAP pressure 13.0 cmH2O (IQR 12.0 cmH2O -13.5 cmH2O); 24 subjects (52.2%) who preferred Fixed CPAP had median optimal CPAP pressure 8.0 cmH2O (IQR 6.3 cmH2O -8.7 cmH2O); p<0.01. Median baseline BMI was 37.6 kg/m2 (IQR 30.8 kg/m2 -43.0 kg/m2) for those who preferred APAP and 32.3 kg/m2 (IQR 30.8 kg/m2 - 38.4 kg/m2) for subjects preferred Fixed CPAP; p=0.03. DISCUSSION: Fixed CPAP maybe considered as first line therapy for symptomatic moderate and severe OSA with titrated optimal CPAP pressure less than 8 cmH2O and BMI less than 32.3 kg/m2; based on subjects' preference. Baseline AHI and average daily CPAP usage was not statisticallysignificant in affecting patient preference between fixed and auto adjusting CPAP. This is the first study of its kind conducted in Malaysia.

Thermal behavior of spin-current generation in PtxCu1-x devices characterized through spin-torque ferromagnetic resonance.

High temperature studies of spin Hall effect have often been neglected despite its profound significance in real-world devices. In this work, high temperature spin torque ferromagnetic resonance measurement was performed to evaluate the effects of temperature on the Gilbert damping and spin Hall efficiency of PtxCu1-x. When the temperature was varied from 300 K to 407 K, the Gilbert damping was relatively stable with a change of 4% at composition x = 66%. Alloying Pt and Cu improved the spin Hall efficiency of Pt75Cu25/Co/Ta by 29% to a value of 0.31 ± 0.03 at 407 K. However, the critical switching current density is dependent on the ratio between the Gilbert damping and spin Hall efficiency and the smallest value was observed when x = 47%. It was found that at this concentration, the spin transparency was at its highest at 0.85 ± 0.09 hence indicating the importance of interfacial transparency for energy efficient devices at elevated temperature.

Author Correction: High velocity domain wall propagation using voltage controlled magnetic anisotropy.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Spin structure and spin Hall magnetoresistance of epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO3.

We report a combined study of imaging the antiferromagnetic (AFM) spin structure and measuring the spin Hall magnetoresistance (SMR) in epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO3. X-ray magnetic linear dichroism photoemission electron microscopy measurements reveal that the AFM spins of the SmFeO3(1 1 0) align in the plane of the film. Angularly dependent magnetoresistance measurements show that SmFeO3/Ta bilayers exhibit a positive SMR, in contrast to the negative SMR expected in previously studied collinear AFMs. The SMR amplitude increases linearly with increasing external magnetic field at higher magnetic fields, suggesting that field-induced canting of the AFM spins plays an important role. In contrast, around the coercive field, no detectable SMR signal is observed, indicating that the SMR of the AFM and canting magnetization components cancel out. Below 50 K, the SMR amplitude increases sizably by a factor of two as compared to room temperature, which likely correlates with the long-range ordering of the Sm ions. Our results show that the SMR is a sensitive technique for non-equilibrium spin systems of non-collinear AFMs.

High velocity domain wall propagation using voltage controlled magnetic anisotropy.

The use of voltage-controlled magnetic anisotropy (VCMA) via the creation of a sloped electric field has been hailed as an energy-efficient approach for domain wall (DW) propagation. However, this method suffers from a limitation of the nanowire length which the DW can propagate on. Here, we propose the use of multiplexed gate electrodes to propagate DWs on magnetic nanowires without having any length constraints. The multi-gate electrode configuration is demonstrated using micromagnetic simulations. This allows controllable voltages to be applied to neighboring gate electrodes, generating large strength of magnetic anisotropy gradients along the nanowire, and the results show that DW velocities higher than 300 m/s can be achieved. Analysis of the DW dynamics during propagation reveals that the tilt of the DW and the direction of slanted gate electrode greatly alters the steady state DW propagation. Our results show that chevron-shaped gate electrodes is an effective optimisation that leads to multi-DW propagation with high velocity. Moreover, a repeating series of high-medium-low magnetic anisotropy regions enables a deterministic VCMA-controlled high velocity DW propagation.

Efficient skyrmion transport mediated by a voltage controlled magnetic anisotropy gradient.

Despite the inefficiencies associated with current-induced spin torques, they remain the predominant mode of skyrmion propulsion. In this work, we demonstrate numerically that skyrmions can be transported much more efficiently with a voltage-controlled magnetic anisotropy (VCMA) gradient. An analytical model was developed to understand the underlying skyrmion dynamics on a track under the VCMA conditions. Our calculations reveal that the repulsive skyrmion-edge interaction not only prevents the skyrmion from annihilating but also generates most of the skyrmion propulsion. A multiplexed array of gate electrodes can be used to create discrete anisotropy gradients over a long distance, leading to the formation of a series of translatable skyrmion potential wells. Due to the strong confining potentials, skyrmions are transported at a 70% higher packing density. Finally, we demonstrated that this form of skyrmion propulsion can also be implemented on almost any 2D geometry, providing improved versatility over current-induced methods.

Role of RKKY torque on domain wall motion in synthetic antiferromagnetic nanowires with opposite spin Hall angles.

We experimentally show the effect of enhanced spin-orbit and RKKY induced torques on the current-induced motion of a pair of domain walls (DWs), which are coupled antiferromagnetically in synthetic antiferromagnetic (SAF) nanowires. The torque from the spin Hall effect (SHE) rotates the Néel DWs pair into the transverse direction, which is due to the fact that heavy metals of opposite spin Hall angles are deposited at the top and the bottom ferromagnetic interfaces. The rotation of both DWs in non-collinear fashion largely perturbs the antiferromagnetic coupling, which in turn stimulates an enhanced interlayer RKKY exchange torque that improved the DW velocity. The interplay between the SHE-induced torque and the RKKY exchange torque is validated via micromagnetic simulations. In addition, the DW velocity can be further improved by increasing the RKKY exchange strength.

Bi-directional high speed domain wall motion in perpendicular magnetic anisotropy Co/Pt double stack structures.

We report bi-directional domain wall (DW) motion along and against current flow direction in Co/Pt double stack wires with Ta capping. The bi-directionality is achieved by application of hard-axis magnetic field favoring and opposing the Dzyloshinskii-Moriya interaction (DMI), respectively. The speed obtained is enhanced when the hard-axis field favors the DMI and is along the current flow direction. Co/Pt double stack is a modification proposed for the high spin-orbit torque strength Pt/Co/Ta stack, to improve its thermal stability and perpendicular magnetic anisotropy (PMA). The velocity obtained reduces with increase in Pt spacer thickness due to reduction in DMI and enhances on increasing the Ta capping thickness due to higher SOT strength. The velocity obtained is as high as 530 m/s at a reasonable current density of 1 × 1012 A/m2 for device applications. The low anisotropy of the device coupled with the application of hard-axis field aids the velocity enhancement by preventing Walker breakdown.

Highly Efficient Domain Walls Injection in Perpendicular Magnetic Anisotropy Nanowire.

Electrical injection of magnetic domain walls in perpendicular magnetic anisotropy nanowire is crucial for data bit writing in domain wall-based magnetic memory and logic devices. Conventionally, the current pulse required to nucleate a domain wall is approximately ~10(12) A/m(2). Here, we demonstrate an energy efficient structure to inject domain walls. Under an applied electric potential, our proposed Π-shaped stripline generates a highly concentrated current distribution. This creates a highly localized magnetic field that quickly initiates the nucleation of a magnetic domain. The formation and motion of the resulting domain walls can then be electrically detected by means of Ta Hall bars across the nanowire. Our measurements show that the Π-shaped stripline can deterministically write a magnetic data bit in 15 ns even with a relatively low current density of 5.34 × 10(11) A/m(2). Micromagnetic simulations reveal the evolution of the domain nucleation - first, by the formation of a pair of magnetic bubbles, then followed by their rapid expansion into a single domain. Finally, we also demonstrate experimentally that our injection geometry can perform bit writing using only about 30% of the electrical energy as compared to a conventional injection line.

Guided current-induced skyrmion motion in 1D potential well.

Magnetic skyrmions are particle-like magnetization configurations which can be found in materials with broken inversion symmetry. Their topological nature allows them to circumvent around random pinning sites or impurities as they move within the magnetic layer, which makes them interesting as information carriers in memory devices. However, when the skyrmion is driven by a current, a Magnus force is generated which leads to the skyrmion moving away from the direction of the conduction electron flow. The deflection poses a serious problem to the realization of skyrmion-based devices, as it leads to skyrmion annihilation at the film edges. Here, we show that it is possible to guide the movement of the skyrmion and prevent it from annihilating by surrounding and compressing the skyrmion with strong local potential barriers. The compressed skyrmion receives higher contribution from the spin transfer torque, which results in the significant increase of the skyrmion speed.

Effect of an anterior-sloped brace joint on anterior tibial translation and axial tibial rotation: a motion analysis study.

BACKGROUND: Anterior tibial translation and axial tibial rotation are major biomechanical factors involved in anterior cruciate ligament injuries. This study sought to evaluate a brace prototype designed with an anterior-sloped joint, in terms of its efficacy in attenuating anterior tibial translation and axial tibial rotation during landing, using a motion analysis approach. METHODS: Ten healthy male subjects performed single-leg landing tasks from a 0.6-m height with and without the brace prototype. Ground reaction force and kinematics data were obtained using a motion-capture system and force-plates. Anterior tibial translation and axial tibial rotation were determined based on tibial and femoral marker reference frames. Vertical and anterior-posterior ground reaction forces, hip, knee and ankle joint range-of-motions and angular velocities, anterior tibial translation and axial tibial rotation were compared between unbraced and braced conditions using Wilcoxon signed-rank test. FINDINGS: We found no significant difference in peak vertical and anterior-posterior ground reaction forces (p=0.770 and p=0.332 respectively) between unbraced and braced conditions. Knee joint range-of-motion and angular velocity were lower (p=0.037 and p=0.038 respectively) for braced condition than unbraced condition. Anterior tibial translation and axial tibial rotation were reduced (p=0.027 and p=0.006 respectively) in braced condition, compared to unbraced condition. INTERPRETATION: The anterior-sloped brace joint helps to attenuate anterior tibial translation and axial tibial rotation present in the knee joint during landing. It is necessary to test the brace prototype in a sporting population with realistic sports landing situations in order to assess its effectiveness in lowering anterior cruciate ligament injury risk.