Frequency Tunable Metamaterial Absorber Using Hygroscopicity of Nature Cork

Kenyu Ling,Minyeong Yoo,Sungjoon Lim IEEE 2015 IEEE antennas and wireless propagation letters Vol.14 No.-

<P>In this letter, a novel frequency tunable metamaterial absorber is proposed for wireless humidity sensor applications made with natural cork. Natural cork has excellent hygroscopicity and its electrical properties can be changed depending on the moisture content. In this work, the absorption ratio of the proposed absorber are simulated and measured in different moisture content ( M = 0%, 1.44%, 5.88%, 13.32%, 18.8%) of the cork substrate. The resonant frequency changed from 4.92 GHz in the dry ( M = 0%) state to 3.49 GHz in the wet ( M = 18.8%) state; the measured absorptivity is higher than 90% in all moisture content values. To the best of our knowledge, it is the first metamaterial absorber using natural cork.</P>

Flexible liquid metal-filled metamaterial absorber on polydimethylsiloxane (PDMS).

Ling, Kenyu,Kim, Kyeoungseob,Lim, Sungjoon Optical Society of America 2015 Optics express Vol.23 No.16

<P>In this paper, we propose a novel flexible metamaterial (MM) absorber. The conductive pattern consists of liquid metal eutectic gallium indium alloy (EGaIn) enclosed in elastomeric microfluidic channels. Polydimethylsiloxane (PDMS) material is used as a supporting substrate. The proposed MM absorber is flexible because of its liquid metal and PDMS substrate. Numerical simulations and experimental results are presented when the microfluidic channels are filled with liquid metal. In order to evaluate the proposed MM absorber's performance, the fabricated absorber prototype is tested with rectangular waveguides. Almost perfect absorptivity is achieved at a resonant frequency of 8.22 GHz.</P>

Neuropathic Pain in Elderly Patients with Chronic Low Back Painand Effects of Pregabalin: A Preliminary Study

Yoshihito Sakai,Kenyu Ito,Tetsuro Hida,Sadayuki Ito,Atsushi Harada 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.2

Study Design: Preliminary study. Purpose: To assess the association of neuropathic pain with chronic low back pain (LBP) and the effect of pregabalin on neuropathic pain in the elderly. Overview of Literature: Of those with chronic LBP, 37% were predominantly presenting with neuropathic pain in young adults. Pregabalin is effective for pain in patients with diabetic neuropathy and peripheral neuralgia. No study has reported on the effects of pregabalin for chronic LBP in elderly patients yet. Methods: Pregabalin was administered to 32 patients (age, ≥65 years) with chronic LBP for 4 weeks. Pain and activities of daily living were assessed using the Neuropathic Pain Screening Questionnaire (NePSQ), the pain DETECT questionnaire, visual analog scale, the Japanese Orthopedic Association score, the short form of the McGill Pain Questionnaire and the Roland Morris Disability Questionnaire. Modic change and spinal canal stenosis were investigated using magnetic resonance imaging. Results: Altogether, 43.3% of patients had neuropathic pain according to the NePSQ and 15.6% patients had pain according to the pain DETECT. The efficacy rate of pregabalin was 73.3%. A significant effect was observed in patients with neuropathic pain after 4 weeks of administration. Conclusions: Neuropathic pain was slightly less frequently associated with chronic LBP in the elderly. Pregabalin was effective in reducing pain in patients with chronic LBP accompanied with neuropathic pain. Lumbar spinal stenosis and lower limb symptoms were observed in patients with neuropathic pain. We recommend the use of pregabalin for patients after evaluating a screening score, clinical symptoms and magnetic resonance imaging studies.

Fabrication of polarization-insensitive, multi-resonant metamaterial absorber using wafer bonding of glass dielectric substrate

Lee, Duck-Hyun,Ling, Kenyu,Lim, Sungjoon,Baek, Chang-Wook Elsevier 2015 MICROELECTRONIC ENGINEERING Vol.136 No.-

<P><B>Abstract</B></P> <P>We present the design, fabrication and characterization of a terahertz multi-resonant metamaterial absorber showing polarization-insensitive characteristics. The proposed absorber uses Pyrex glass as a dielectric layer for higher absorption in a terahertz range and is wafer-level fabricated by thermo-compression bonding technique using gold films as intermediate layers. In addition, an array of comb-shaped hexagonal pattern is introduced as a multi-band LC resonator and symmetric geometry is used for polarization insensitivity. The fabricated absorber shows two absorption peaks at 0.98THz and 1.55THz with the absorptivity of 93% and 74%, respectively, and almost identical responses to the different polarization angles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> THz multi-resonant metamaterial absorber using glass wafer bonding is demonstrated. </LI> <LI> Pyrex glass wafer is used as a dielectric layer for high absorptivity in THz range. </LI> <LI> Hexagonal comb-shape resonator is used to realize polarization insensitivity. </LI> <LI> Fabricated absorber shows an absorptivity of 93% and 74%, at 0.98THz and 1.55THz. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Image Analysis of a Shadowgram Visualizing Surface Waves on a Falling Liquid Film

Takehiro Nosoko,Takashi Nagata,Takao Shinzato,Kenyu Oyakawa,Tsunehiro Ohmija,Minoru Nagai 대한기계학회 1993 International Symposium on Transport Phenomena in Vol.3 No.1

Efficacy of Anal Needle Electrodes for Intraoperative Spinal Cord Monitoring with Transcranial Muscle Action Potentials

Kazuyoshi Kobayashi,Kei Ando,Hideki Yagi,Kenyu Ito,Mikito Tsushima,Masayoshi Morozumi,Satoshi Tanaka,Masaaki Machino,Kyotaro Ota,Yukihiro Matsuyama,Naoki Ishiguro,Shiro Imagama 대한척추외과학회 2018 Asian Spine Journal Vol.12 No.4

Study Design: Retrospective study. Purpose: To examine the relationship between postoperative bowel bladder disorder (BBD) and the efficacy of needle electrodes for the external anal sphincter (EAS) in intraoperative spinal cord monitoring with transcranial muscle action potentials (Tc-MsEP). Overview of Literature: Spinal surgery for spina bifida, spinal cord tumor, and spinal tethered cord syndrome has a high rate of postoperative BBD. Monitoring of the EAS with Tc-MsEP is frequently performed during spinal surgery. We initially used plug-surface electrodes for this purpose, but have more recently switched to needle electrodes for the monitoring of the EAS. To date, there has been no comparison between the utility of these electrodes. Methods: Waveform derivation, exacerbation of postoperative BBD, and sensitivity and specificity for prediction of BBD by 70% amplitude reduction of EAS activity using needle and plug-surface electrodes were investigated in 239 spine surgeries. The cut-off for the % drop in amplitude for BBD prediction was determined for EAS monitoring using a needle electrode. Results: The overall rate of postoperative BBD aggravation was 7.1% (17/239 cases), with the individual rates using needle and plug-surface electrodes being 6.9% (8/116) and 7.3% (9/123), respectively. The waveform derivation rate was significantly higher using needle electrodes (91.3% [106/116] vs. 76.4% [94/123], p <0.01). In patients with baseline waveform detection, the sensitivity and specificity for postoperative BBD were similar in the two groups. With needle electrodes, a cutoff amplitude of Tc-MsEP for the EAS at the end of surgery of 25% of the baseline amplitude had a sensitivity of 89% and specificity of 82% for the prediction of postoperative BBD aggravation. Conclusions: The significantly higher waveform derivation rate using needle electrodes suggests that these electrodes are effective for monitoring the EAS in spinal surgery in cases with preoperative BBD.

Indirect Decompression Using Lateral Lumbar Interbody Fusion for Restenosis after an Initial Decompression Surgery

Nakashima Hiroaki,Kanemura Tokumi,Satake Kotaro,Ito Kenyu,Ishikawa Yoshimoto,Ouchida Jun,Segi Naoki,Yamaguchi Hidetoshi,Imagama Shiro 대한척추외과학회 2020 Asian Spine Journal Vol.14 No.3

Study Design: Retrospective comparative study.Purpose: We compared clinical and radiographical outcomes after lumbar decompression revision surgery for restenosis by lateral lumbar interbody fusion (LLIF) and posterior lumbar interbody fusion (PLIF).Overview of Literature: Indirect lumbar decompression with LLIF was used to treat degenerative lumbar diseases requiring neural decompression. However, only a few studies have focused on the effectiveness of this technique for restenosis after lumbar decompression.Methods: We retrospectively investigated 52 cases involving lumbar interbody fusions for restenosis with spondylolisthesis after lumbar decompressions; these cases consisted of 15 patients who underwent indirect decompression with LLIF and posterior fixation and 37 patients who underwent the same procedure with PLIF. We compared Japanese Orthopaedic Association (JOA) scores and perioperative complications between groups. The cross-sectional areas of the thecal sac on magnetic resonance imaging were measured before, immediately after, and 2 years after surgery. We conducted statistical analyses using unpaired t -test and Fisher’s exact tests, and a <i>p</i> -value <0.05 was considered statistically significant.Results: The operative time was significantly shorter in the LLIF group than in the PLIF group (115.3±33.6 min vs. 186.2±34.2 min, respectively; <i>p</i> <0.001). In addition, the intraoperative blood loss was significantly lower in the LLIF group than in the PLIF group (58.2±32.7 mL vs. 303.2±140.1 mL, respectively; <i>p</i> <0.001). We found two cases of transient lateral thigh weakness (13.3%) in the LLIF group and five cases of incidental durotomy, one case of deep infection, and one case of neurological deterioration in the PLIF group—resulting in a higher complication incidence (18.9%), although it did not reach (<i>p</i> =0.63). The JOA scores improved significantly in both groups.Conclusions: Indirect decompression using LLIF provided acceptable clinical and radiographical outcomes in patients with restenosis with spondylolisthesis after lumbar decompression; no revision-surgery-specific complications were found. Our results suggest that LLIF is a safe and minimally invasive procedure for revision surgery.

The Prevalence and Risk Factors for S2 Alar-Iliac Screw Loosening with a Minimum 2-Year Follow-up

Hiroaki Nakashima,Tokumi Kanemura,Kotaro Satake,Kenyu Ito,Yoshimoto Ishikawa,Jun Ouchida,Naoki Segi,Hidetoshi Yamaguchi,Shiro Imagama 대한척추외과학회 2020 Asian Spine Journal Vol.14 No.2

Study Design: A retrospective cohort study. Purpose: The purpose of this study was to investigate the prevalence and risk factors for S2 alar-iliac (SAI) screw loosening following lumbosacral fixation, with a minimum 2-year follow-up. Overview of Literature: Although SAI screws allow surgeons to perform lumbosacral fixation with a low profile and enhanced biomechanical strength, screw loosening following surgery can occur in some cases. However, few studies have investigated the prevalence and risk factors for SAI screw loosening. Methods: This retrospective study included 35 patients (mean age, 72.8±8.0 years; male, 10; female, 25) who underwent lumbosacral fixation using SAI screws with at least 2 years of follow-up. SAI screw loosening and L5–S bony fusion were assessed using computed tomography. The period for which the screws appeared loose and the risk factors for SAI screw loosening were investigated 2 years after surgery. Results: A total of 70 SAI screws and 70 S1 pedicle screws were inserted. Loosening was observed 0.5, 1, and 2 years after surgery in 17 (24.3%), 35 (50.0%), and 35 (50.0%) SAI screws, respectively. Bony fusion rate at L5–S was significantly lower in patients with SAI screw loosening than in those without screw loosening (65.0% vs. 93.3%, p=0.048). The score for SAI screw contact with the iliac cortical bone and the bony fusion rate at L5–S were significantly lower in the loosening group than in the non-loosening group (1.8±0.5 vs. 2.2±0.3, p<0.001, respectively). Postoperative pelvic incidence–lumbar lordosis was significantly higher in the loosening group than in the non-loosening group (7.9°±15.4° vs. 0.5°±8.7°, p=0.02, respectively). Conclusions: SAI screw loosening is closely correlated with pseudoarthrosis at L5–S. Appropriate screw insertion and optimal lumbar lordosis restoration are important to prevent postoperative complications related to SAI screws.

Perioperative Management of Patients with Hemophilia during Spinal Surgery

Kazuyoshi Kobayashi,Shiro Imagama,Kei Ando,Kenyu Ito,Mikito Tsushima,Masayoshi Morozumi,Satoshi Tanaka,Masaaki Machino,Kyotaro Ota,Yoshihiro Nishida,Naoki Ishiguro 대한척추외과학회 2018 Asian Spine Journal Vol.12 No.3

Study Design: Single-center retrospective study. Purpose: To optimize the perioperative management of patients with hemophilia who are undergoing spinal surgery. Overview of Literature: Hemophilia is a rare disease in which there is a tendency of bleeding because of a congenital deficiency in blood coagulation factor activity. There has been no previous report on spinal surgery in patients with hemophilia. Methods: The subjects were five patients (all males) with hemophilia who underwent spinal surgery at Nagoya University Hospital. Two patients had hemophilia A (deficiency of factor VIII) and three had hemophilia B (deficiency of factor IX). The mean age at the time of surgery was 63 years (range, 46–73 years). The following surgeries were performed: posterior lumbar interbody fusion (PLIF) in two patients, and lumbar fenestration, cervical laminoplasty and lumbar fenestration, and cervical laminoplasty and PLIF in one patient each. Results: Coagulation factor at a mean dose of 4.8 ×103 U (range, 3–6 ×103 U) was intravenously injected before surgery, and a mean dose of 5.2 ×103 U (rang, 4–6 ×103 U) was continuously administered for 24 hours after surgery. Factor activity was maintained at ≥80% until postoperative day 14 and at ≥50% thereafter. The average duration of surgery was 178 minutes (range, 133–233 minutes), the estimated blood loss was 661 mL (range, 272–1,344 mL), and a drain tube was left subfascially in place for 2 days in all patients. Reoperation due to postoperative surgical site infection was required in one patient, but there were no complications due to hemorrhagic diathesis. The total dose of coagulation factor administered during hospitalization was 102 ×103 U (range, 46–198 ×103 U). Conclusions: Coordination with a hematologist and dose adjustment of the coagulation factor preparation to maintain a target level of coagulation factor activity facilitated a smooth postoperative course with perioperative control of bleeding during spinal surgery for patients with hemophilia.

Variety of the Wave Change in Compound Muscle Action Potential in an Animal Model

Zenya Ito,Shiro Imagama,Kei Ando,Akio Muramoto,Kazuyoshi Kobayashi,Tetsuro Hida,Kenyu Ito,Yoshimoto Ishikawa,Mikito Tsushima,Akiyuki Matsumoto,Satoshi Tanaka,Masayoshi Morozumi,Yukihiro Matsuyama,Naok 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.6

Study Design: Animal study. Purpose: To review the present warning point criteria of the compound muscle action potential (CMAP) and investigate new criteria for spinal surgery safety using an animal model. Overview of Literature: Little is known about correlation palesis and amplitude of spinal cord monitoring. Methods: After laminectomy of the tenth thoracic spinal lamina, 2–140 g force was delivered to the spinal cord with a tension gage to create a bilateral contusion injury. The study morphology change of the CMAP wave and locomotor scale were evaluated for one month. Results: Four different types of wave morphology changes were observed: no change, amplitude decrease only, morphology change only, and amplitude and morphology change. Amplitude and morphology changed simultaneously and significantly as the injury force increased (p <0.05) Locomotor scale in the amplitude and morphology group worsened more than the other groups. Conclusions: Amplitude and morphology change of the CMAP wave exists and could be the key of the alarm point in CMAP.