The Relationship Between Low Back Pain and Sagittal Spinal Alignment and Back Muscle Mass in Korean Fishery Workers.

OBJECTIVE: To investigate the relationship between low back pain (LBP) and sagittal spino-pelvic parameters along with the relationship between LBP and back muscle mass in Korean male and female fishery workers. METHODS: This retrospective study included a total of 146 subjects who underwent Fishermen's health survey conducted between June 2018 and August 2020. LBP was evaluated through visual analogue scale (VAS) and Oswestry Disability Index (ODI). Sagittal spino-pelvic parameters were measured from whole spine standing X-rays. Back muscle cross-sectional areas were identified through lumbar spine magnetic resonance imaging and body composition was analyzed through bioelectrical impedance analysis. RESULTS: The study included 75 males and 71 females, with an average age of 58.33 years for males and 56.45 years for females. Female subjects exhibited higher VAS and ODI scores, larger pelvic tilt (PT) and trunk fat mass and smaller trunk muscle mass compared to males. In female, ODI positively correlated with sagittal vertical axis (SVA) and PT. No significant correlations were found between ODI scores and body composition in either sex. The high ODI group showed greater SVA, PT, and pelvic incidence-lumbar lordosis and higher trunk fat/muscle ratio. Psoas muscle mass, total and skeletal muscle mass and trunk muscle mass of that group were smaller than those of low ODI group. CONCLUSION: Spino-pelvic parameters and back muscle mass were associated with ODI and there were differences between Korean male and female fishery workers.

Maximization of a frequency splitting on continuous exceptional points in asymmetric optical microdisks.

We study a systematic formation of continuous exceptional points (EPs) in a fully-asymmetric optical microdisk. A parametric generation of chiral EP modes is investigated by analyzing asymmetricity-dependent coupling elements in an effective Hamiltonian. It is shown that given the external perturbation, the frequency splitting around EPs is scaled by the fundamental "strength" of EPs [J. Wiersig, Phys. Rev. Res.4, 023121 (2022)10.1103/PhysRevResearch.4.023121] multiplied by the extra responding strength of the newly added perturbation. Our finding demonstrates that the sensitivity of EP-based sensors can be maximized by carefully examining the continuous formation of EPs.

Far-Field Correlations Verifying Non-Hermitian Degeneracy of Optical Modes.

An experimental verification of an exceptional point (EP) in a stand-alone chaotic microcavity is a tough issue because as deformation parameters are fixed the traditional frequency analysis methods cannot be applied any more. Through numerical investigations with an asymmetric Reuleaux triangle microcavity (ARTM), we find that the eigenvalue difference of paired modes can approach near-zero regardless of nonorthogonality of the modes. In this case, for a definite verification of EPs in experiments, wave function coalescence should be confirmed. For this, we suggest the method of exploiting correlation of far-field patterns (FFPs), which is directly related to spatial mode patterns. In an ARTM, we demonstrate that the FFP correlation of paired modes can be used to confirm wave function coalescence when an eigenvalue difference approaches near zero.

Salient role of the non-Hermitian coupling for optimizing conditions in multiple maximizations of inter-cavity light transfer.

We reveal that non-Hermitian lossy couplings in an inter-cavity light transfer process are crucial for an optimum light transfer, unlike the prevailed belief. Our results turn out the fact that the light transfer can have multiple maxima following the increased inter-cavity distance. To validate this finding both in the weak and strong coupling regimes, we demonstrate our claim in the vicinity of the so-called exceptional point. We believe our results can contribute to realizing coupled-optical-cavity-based devices which is functional with an ultra-efficient light transfer, especially when the device scale is as small as the operation wavelength.

Rayleigh scatterer-induced steady exceptional points of stable-island modes in a deformed optical microdisk.

A formation of second-order non-Hermitian degeneracies, called exceptional points (EPs), in a chaotic oval-shaped dielectric microdisk is studied. Different symmetric optical modes localized on a stable period-3 orbit coalesce to form chiral EPs. Unlike a circular microdisk perturbed by two scatterers (CTS), our proposed system requires only one scatterer to build chiral EPs. The scatterer positions for counterpropagating EP modes are far distant from one another and almost steady against varying scatterer sizes in contrast to the CTS case. Our results can contribute to establishing a more solid platform for EP-based-device applications with flexibility and easy feasibility in obtaining EPs.

Lowest threshold lasing modes localized on marginally unstable periodic orbits in a semiconductor microcavity laser.

The lowest threshold lasing mode in a rounded D-shape microcavity is theoretically analyzed and experimentally demonstrated. To identify the lowest threshold lasing mode, we investigate threshold conditions of different periodic orbits by considering the linear gain condition due to the effective pumping region and total loss consisting of internal and scattering losses in ray dynamics. We compare the ray dynamical result with resonance mode analysis, including gain and loss. We find that the resonance modes localized on the pentagonal marginally unstable periodic orbit have the lowest threshold in our fabrication configuration. Our findings are verified by obtaining the path lengths and far-field patterns of lasing modes.

Effect of Vanadium Addition on the High-Temperature Friction Behavior in Nanostructured Al-Cr-V-N Films Prepared by UBMS.

In recent year, vanadium-doped tribological films have become available as possible candidates for self-lubrication at high temperatures. In this work, quaternary Al-Cr-V-N films were deposited onto silicon wafer and WC-Co substrates by an unbalanced magnetron sputtering using high purity (99.99%) CrAl2 and V targets with argon-nitrogen reactive gases. EPMA results revealed that vanadium atoms can incorporated from 0 to 13 at.% into the films. The maximum hardness value was ~32 GPa at vanadium content of 7.1 at.% in the Al-Cr-V-N films. The high-temperature tribometer was used to analysis the friction characteristics of the films with elevated temperature. As a result of the high temperature friction test after heating up to 700 °C, the average friction coefficient decreased from 0.62 to 0.35 with increasing of vanadium contents in the Al-Cr-V-N films. It is concluded that the reduction of the friction coefficient is attributed to the formation of V2O5, which is a Magnéli phase that acts as a lubrication at high temperature.

High Temperature Oxidation Behavior of Cr-Al-Si-N Nanocomposite Films Deposited by Filtered Arc Ion Plating Technique.

High temperature oxidation behavior of nanocomposite films is very important characteristics for application of machining and cutting tools. Quaternary Cr-Al-Si-N nanocomposite films with various compositions were deposited onto WC-Co and Si wafer substrates using a filtered arc ion plating technique. The composition of the films were controlled by different combinations of CrAl2 and Cr4Si composite target power in a reactive gas mixture of high purity Ar and N2 during depositions. The instrumental analyses revealed that the synthesized Cr-Al-Si-N films with Si content of 2.78 at.% were nanocomposites consisting of nano-sized crystallites (3-7 nm in dia.) and a thin layer of amorphous Si3N4 phases. The nanohardness of the Cr-Al-Si-N films exhibited the maximum values of ~42 GPa at a Si content of ~2.78 at.% due to the microstructural change to nanocomposite as well as solid-solution hardening. The Cr-Al-Si-N film shows superior result of oxidation resistance at 1050 °C for 30 min in air. Based on the XRD and GDOES analyses on the oxidized films, it could be revealed that the enrichment of Al (17.94 at.%) and Cr (26.24 at.%) elements in the film leads to form an Al2O3 and Cr2O3 layer on the Cr-Al-Si-N film surface. Therefore, in this study, the microstructural changes on the mechanical properties and oxidation behavior with various compositions in the Cr-Al-Si-N nanocomposite films were discussed and correlated with the deposition parameters.

When does spasticity in the upper limb develop after a first stroke? A nationwide observational study on 861 stroke patients.

This study investigated the time taken for upper extremity spasticity to develop and its regional difference after first-ever stroke onset in a nationwide multicenter study in South Korea. The retrospective observational study included 861 individuals with post-stroke spasticity in the upper limbs. Spasticity in the upper extremity joints was defined as a modified Ashworth Scale score ≥1. The median time to develop upper limb spasticity after stroke onset was 34 days. 12% of post-stroke spasticity cases developed between 2 months and 3 months and 13% developed after 3 months from onset. At the time of diagnosis of spasticity, most patients showed only a slight increase in muscle tone, which was observed most frequently in the elbow, followed by the wrist, and fingers. Younger stroke survivors were more spastic, and the severity of spasticity increased with time. Approximately half of the patients with post-stroke spasticity developed spasticity during the first month. However, post-stroke spasticity can develop more than 3 months after stroke onset. Therefore, it is important to assess spasticity, even in the chronic state.

Oxidation Behavior of Ti-Al-Si-N-O Nanocomposite Films Deposited by Filtered Arc Ion Plating Technique.

Oxidation behavior of nanocomposite films is very important characteristics for application of machining and cutting tools. In this study, Ti-Al-Si-N-O nanocomposite films were fabricated onto WC-Co and Si wafer substrates. The composition of the Ti-Al-Si-N-O films was analyzed by X-ray photo-electron spectroscope (XPS). Also X-ray diffactometer (XRD) analysis was conducted to investigate the crystallinity and phase transformation of the films. As a result of XRD, Ti-Al(18 at.%)-Si-N-O films showed the great oxidation resistance of 950 °C for 30 min in air. Based on glow discharge optical emission spectroscopy (GDOES) depth profiles, Ti-Al(18 at.%)- Si-N-O film annealed at 950 °C for 30 min shows formation of aluminum oxide layer on the film surface. On the other hand, Ti-Al(7.56 at.%)-Si-N-O film had a titanium oxide layer on the surface after annealing at 950 °C for 30 min.

Microstructure and Mechanical Properties of Functional Graded Ti-Al-Si-N-O Nanocomposite Films Deposited by Filtered Arc Ion Plating Technique.

Functional graded Ti-Al-Si-N-O nanocomposite films were deposited onto WC-Co substrate by a filtered arc ion plating system using TiAl and TiSi composite targets under N2/Ar atmosphere. XRD and XPS analyses revealed that the synthesized Ti-Al-Si-N-O films were nanocomposite consisting of nanosized (Ti, Al, Si)N crystallites embedded in an amorphous Si3N4/SiO2 matrix. The hardness of the Ti-Al-Si-N-O films exhibited the maximum hardness values of ~47 GPa at a Si content of ~5.63 at.% due to the microstructural change to a nanocomposite as well as the solid-solution hardening. Besides, Ti-Al-Si-N-O film with Si content of around 5.63 at.% also showed perfect adhesive strength value of 105.3 N. These excellent mechanical properties of Ti-Al-Si-N-O films could be help to improve the performance of machining tools and cutting tools with application of the film. A comparative study on microstructural characteristics among Ti-Al-Si-N-O films with various Si contents is reported in this paper.

Effects of resistance expiratory muscle strength training in elderly patients with dysphagic stroke.

BACKGROUND: Recently, resistance expiratory muscle strength training (EMST) has been reported as a remedial treatment for dysphagia. OBJECTIVE: To investigate the effect of resistance EMST on the swallowing function in stroke patients with oropharyngeal dysphagia. METHODS: Forty-two stroke patients with dysphagia were randomly assigned to two groups: an experimental group (n = 13) and a placebo group (n = 13). The experimental group performed EMST using a portable EMST device, while the placebo group performed EMST using a sham EMST device with no loading. The intervention was performed 5 days per week for 4weeks, in five sets of 5 breaths through the device for a total of 25 breaths per day. Both groups underwent conventional dysphagia treatment for 30 minutes/day, 5 days/week, for 4 weeks. Videofluoroscopic dysphagia scale (VDS) and penetration-aspiration scale (PAS) based on a videofluoroscopic swallowing study (VFSS) were assessed to analyze the oropharyngeal swallowing function. RESULTS: The experimental group showed more improvement in pharyngeal phase of the VDS (p = 0.018 and 0.006, respectively) and PAS compared to the placebo group (p = 0.014). CONCLUSIONS: We suggest that EMST could improve the effects of dysphagia observed in post-stroke elderly patients based on swallowing function.

Effects of Shaker exercise in stroke survivors with oropharyngeal dysphagia.

BACKGROUND: Dysphagia after stroke can cause a variety of complications, especially aspiration pneumonia, which can be life-threatening. Therefore, rehabilitation methods to reduce aspiration in patients with dysphagia are important. OBJECTIVE: In the present study, we aimed to investigate the effects of Shaker exercise on aspiration and oral diet level in stroke survivors with dysphagia. METHODS: Participants were randomly assigned to an experimental group (n = 16) or a control group (n = 16). Participants in the experimental group performed Shaker exercise and conventional dysphagia therapy, whereas those in the control group performed only conventional dysphagia therapy. All participants performed training 5 days a week for 4 weeks. Degree of aspiration was assessed using the Penetration-Aspiration Scale (PAS) based on videofluoroscopic swallowing study, while oral diet level was assessed using the Functional Oral Intake Scale (FOIS). RESULTS: The experimental group showed greater improvement on both the PAS (p < 0.05) and FOIS (p < 0.05) compared with the control group. CONCLUSIONS: The results of this study suggest that Shaker exercise is a effective exercise for recovery of swallowing function in stroke survivors with dysphagia.

Changes in Activation of Abdominal Muscles at Selected Angles During Trunk Exercise by Using Ultrasonography.

OBJECTIVE: To investigate the changes of activation of the abdominal muscles depending on exercise angles and whether the activation of rectus abdominis differs according to the location, during curl up and leg raise exercises, by measuring the thickness ratio of abdominal muscles using ultrasonography. METHODS: We examined 30 normal adults without musculoskeletal problems. Muscle thickness was measured in the upper rectus abdominis (URA), lower rectus abdominis (LRA), obliquus externus (EO), obliquus internus (IO), and transversus abdominis (TrA), at pre-determined angles (30°, 60°, 90°) and additionally at the resting angle (0°). Muscle thickness ratio was calculated by dividing the resting (0°) thickness for each angle, and was used as reflection of muscle activity. RESULTS: The muscle thickness ratio was significantly different depending on the angles in URA and LRA. For curl up-URA p=0 (30°<60°), p=0 (60°>90°), p=0.44 (30°<90°) and LRA p=0.01 (30°<60°), p=0 (60°>90°), p=0.44 (30°>90°), respectively, by one-way ANOVA test-and for leg raise-URA p=0 (30°<60°), p=0 (60°<90°), p=0 (30°<90°) and LRA p=0.01 (30°<60°), p=0 (60°<90°), p=0 (30°<90°), respectively, by one-way ANOVA test-exercises, but not in the lateral abdominal muscles (EO, IO, and TrA). Also, there was no significant difference in the muscle thickness ratio of URA and LRA during both exercises. In the aspect of muscle activity, there was significant difference in the activation of RA muscle by selected angles, but not according to location during both exercises. CONCLUSION: According to this study, exercise angle is thought to be an important contributing factor for strengthening of RA muscle; however, both the exercises are thought to have no property of strengthening RA muscle selectively based on the location.

Efficacy of kinesiology taping for recovery of dominant upper back pain in female sedentary worker having a rounded shoulder posture.

BACKGROUND: Sedentary workers are most prone to work-related musculoskeletal disorders. OBJECTIVE: We report the case of a female sedentary worker with rounded shoulder posture (RSP) whose dominant upper back pain decreased after correction of her RSP with kinesiology taping. METHODS: We applied kinesiology taping around the patient's upper back and shoulder for 1 month (six times per week, each session lasting approximately 16 h) without any other interventions. RESULTS: After kinesiology taping, the RSP decreased progressively and the dominant upper back pain gradually disappeared. The patient no longer complained of dominant upper back pain during desk work. CONCLUSION: We believe that kinesiology taping may be used to enable recovery from dominant upper back pain in female sedentary workers with RSP.

Effect of silane activation on shear bond strength of fiber-reinforced composite post to resin cement.

PURPOSE: Among the surface treatment methods suggested to enhance the adhesion of resin cement to fiber-reinforced composite posts, conflicting results have been obtained with silanization. In this study, the effects of silanization, heat activation after silanization, on the bond strength between fiber-reinforced composite post and resin cement were determined. MATERIALS AND METHODS: Six groups (n=7) were established to evaluate two types of fiber post (FRC Postec Plus, D.T. Light Post) and three surface treatments (no treatment; air drying; drying at 38℃). Every specimen were bonded with dual-curing resin cement (Variolink N) and stored in distilled water for 24 hours at 37℃. Shear-bond strength (MPa) between the fiber post and the resin cement were measured using universal testing device. The data were analyzed with 1-way ANOVA and by multiple comparisons according to Tukey's HSD (α=0.05). The effect of surface treatment, fiber post type, and the interactions between these two factors were analyzed using 2-way ANOVA and independent sample T-tests. RESULTS: Silanization of the FRC Postec Plus significantly increased bond strength compared with the respective non-treated control, whereas no effect was determined for the D.T. Light Post. Heat drying the silane coupling agent on to the fiber-reinforced post did not significantly improve bond strength compared to air-syringe drying. CONCLUSION: The bond strength between the fiber-reinforced post and the resin cement was significantly increased with silanization in regards to the FRC Postec Plus post. Bond strength was not significantly improved by heat activation of the silane coupling agent.

Melatonin plus exercise-based neurorehabilitative therapy for spinal cord injury.

Spinal cord injury (SCI) is damage to the spinal cord caused by the trauma or disease that results in compromised or loss of body function. Subsequent to SCI in humans, many individuals have residual motor and sensory deficits that impair functional performance and quality of life. The available treatments for SCI are rehabilitation therapy, activity-based therapies, and pharmacological treatment using antioxidants and their agonists. Among pharmacological treatments, the most efficient and commonly used antioxidant for experimental SCI treatment is melatonin, an indolamine secreted by pineal gland at night. Melatonin's receptor-independent free radical scavenging action and its broad-spectrum antioxidant activity makes it an ideal antioxidant to protect tissue from oxidative stress-induced secondary damage after SCI. Owing to the limitations of an activity-based therapy and antioxidant treatment singly on the functional recovery and oxidative stress-induced secondary damages after SCI, a melatonin plus exercise treatment may be a more effective therapy for SCI. As suggested herein, supplementation with melatonin in conjunction with exercise not only would improve the functional recovery by enhancing the beneficial effects of exercise but would reduce the secondary tissue damage simultaneously. Finally, melatonin may protect against exercise-induced fatigue and impairments. In this review, based on the documented evidence regarding the beneficial effects of melatonin, activity-based therapy and the combination of both on functional recovery, as well as reduction of secondary damage caused by oxidative stress after SCI, we suggest the melatonin combined with exercise would be a novel neurorehabilitative strategy for the faster recovery after SCI.