Observation of 2D-magnesium-intercalated gallium nitride superlattices.

Since the demonstration of p-type gallium nitride (GaN) through doping with substitutional magnesium (Mg) atoms1,2, rapid and comprehensive developments, such as blue light-emitting diodes, have considerably shaped our modern lives and contributed to a more carbon-neutral society3-5. However, the details of the interplay between GaN and Mg have remained largely unknown6-11. Here we observe that Mg-intercalated GaN superlattices can form spontaneously by annealing a metallic Mg film on GaN at atmospheric pressure. To our knowledge, this marks the first instance of a two-dimensional metal intercalated into a bulk semiconductor, with each Mg monolayer being intricately inserted between several monolayers of hexagonal GaN. Characterized as an interstitial intercalation, this process induces substantial uniaxial compressive strain perpendicular to the interstitial layers. Consequently, the GaN layers in the Mg-intercalated GaN superlattices exhibit an exceptional elastic strain exceeding -10% (equivalent to a stress of more than 20 GPa), among the highest recorded for thin-film materials12. The strain alters the electronic band structure and greatly enhances hole transport along the compression direction. Furthermore, the Mg sheets induce a unique periodic transition in GaN polarity, generating polarization-field-induced net charges. These characteristics offer fresh insights into semiconductor doping and conductivity enhancement, as well as into elastic strain engineering of nanomaterials and metal-semiconductor superlattices13.

Third harmonic generation due to free carrier in InSb using a terahertz free electron laser.

We report on the third harmonic generation (THG) in InSb semiconductor irradiated by a terahertz (THz) free electron laser (FEL). The conversion of 4 THz (wavelength 70 µm) FEL outputs into its third harmonic 12 THz was observed. We found that by tuning the sample temperature to 360 K, high conversion efficiency up to 1% can be obtained and is the highest in the THz and FIR regions below 10 THz. We also discuss the observed intensity dependence of the THG with the nonlinear order lower than 3 when the pumping intensity was high.

Near-infrared imaging via upconversion in Er3+:CaF2 crystal with dual wavelength excitation.

We propose a system for imaging 1510 nm near-infrared (NIR) wavelength via upconversion (UC) luminescence in an Er3+-doped CaF2 crystal. Er3+ ions are excited from the ground to the excited state levels by an 800-nm pre-excitation wavelength, followed by the promotion of these ions to a higher energy level by the NIR excitation wavelength. Relaxation of these excited ions gives rise to 540 nm UC luminescence in the visible region, enabling the detection of the 1510 nm NIR wavelength. Using this UC scheme, 1510 nm was successfully imaged. Our system enables imaging of NIR wavelengths using low-cost optics and readily available Si-based detectors that are sensitive only to visible wavelengths, opening new possibilities for detection and imaging of NIR wavelengths.

Timing of Initiation of Acute Stroke Rehabilitation and Management Corresponding to Complications at Primary Stroke Centers in Japan: A Nationwide Cross-Sectional Web-Based Questionnaire Survey.

INTRODUCTION: Many guidelines now recommend early rehabilitation for acute stroke patients. However, evidence remains lacking regarding the specific timings for initiation of various rehabilitation steps and management when complications are encountered in acute stroke rehabilitation. This survey aimed to investigate actual clinical situations in acute stroke rehabilitation in Japan and to improve the medical systems for rehabilitation and plan further studies. METHODS: This nationwide, cross-sectional, web-based questionnaire survey was administered between February 7, 2022, and April 21, 2022, targeting all primary stroke centers (PSCs) in Japan. Among several components of the survey, this paper focused on the timing of the initiation of three rehabilitation steps (passive bed exercise; head elevation; and out-of-bed mobilization), along with the management of rehabilitation (continued or suspended) in the event of complications during acute stroke rehabilitation. We also investigated the influence of facility features on these contents. RESULTS: Responses were obtained from 639 of the 959 PSCs surveyed (response rate: 66.6%). In cases of ischemic stroke and intracerebral hemorrhage, most PSCs initiated passive bed exercise on day 1, head elevation on day 1, and out-of-bed mobilization on day 2 (with day of admission defined as day 1). In cases with subarachnoid hemorrhage, rehabilitation steps were delayed compared to other stroke subtypes or showed wide variation depending on the facility. Passive bed exercise was accelerated by the presence of protocols for rehabilitation and weekend rehabilitation. Out-of-bed mobilization was accelerated by the presence of a stroke care unit. Facilities with board-certified rehabilitation doctors were cautious regarding the initiation of head elevation. Most PSCs suspended rehabilitation training in the event of symptomatic systemic/neurological complications. CONCLUSION: Our survey revealed the actual situation of acute stroke rehabilitation in Japan and indicated that some facility features appear to influence early increases in physical activity levels and early mobilization. Our survey provides fundamental data to improve the medical systems for acute stroke rehabilitation in the future.

Optimizing High-Resolution MR Angiography: The Synergistic Effects of 3D Wheel Sampling and Deep Learning-Based Reconstruction.

OBJECTIVE: The aim of this study was to assess the utility of the combined use of 3D wheel sampling and deep learning-based reconstruction (DLR) for intracranial high-resolution (HR)-time-of-flight (TOF)-magnetic resonance angiography (MRA) at 3 T. METHODS: This prospective study enrolled 20 patients who underwent head MRI at 3 T, including TOF-MRA. We used 3D wheel sampling called "fast 3D" and DLR for HR-TOF-MRA (spatial resolution, 0.39 × 0.59 × 0.5 mm3) in addition to conventional MRA (spatial resolution, 0.39 × 0.89 × 1 mm3). We compared contrast and contrast-to-noise ratio between the blood vessels (basilar artery and anterior cerebral artery) and brain parenchyma, full width at half maximum in the P3 segment of the posterior cerebral artery among 3 protocols. Two board-certified radiologists evaluated noise, contrast, sharpness, artifact, and overall image quality of 3 protocols. RESULTS: The contrast and contrast-to-noise ratio of fast 3D-HR-MRA with DLR are comparable or higher than those of conventional MRA and fast 3D-HR-MRA without DLR. The full width at half maximum was significantly lower in fast 3D-MRA with and without DLR than in conventional MRA (P = 0.006, P < 0.001). In qualitative evaluation, fast 3D-MRA with DLR had significantly higher sharpness and overall image quality than conventional MRA and fast 3D-MRA without DLR (sharpness: P = 0.021, P = 0.001; overall image quality: P = 0.029, P < 0.001). CONCLUSIONS: The combination of 3D wheel sampling and DLR can improve visualization of arteries in intracranial TOF-MRA.

A nationwide survey for the provision of acute stroke rehabilitation in Japan: initial dose and weekend/holiday rehabilitation.

OBJECTIVES: The early initiation of acute stroke rehabilitation with a sufficient dose, including at weekends/holidays, is important to improve functional outcome. We investigated the status of acute stroke rehabilitation in Japan by using a nationwide survey. MATERIALS AND METHODS: Facility features, rehabilitation dose provided in the first week in each stroke subtype, and weekend/holiday rehabilitation were investigated by using the results of a web-based survey among primary stroke centers. The relationships between facility features and weekend/holiday rehabilitation were also analyzed. RESULTS: A total of 639 stroke centers (66.6%) completed the questionnaire. The overall median dose was 2.0 (interquartile range, 1.7-3.0) U/day (1U = 20 min). After 7 days, the overall median dose increased to 4.0 (2.0-5.4) U/day. Almost 50% of facilities replied that they could not provide a sufficient dose of rehabilitation; the main reason was a lack of therapists (31%). For rehabilitation on long weekends, no rehabilitation was provided on 3-day weekends in 19% of facilities, and in 5% of facilities on ≥4-day weekends. The mean number of therapists was almost 50% less in the facilities that provided no rehabilitation on 3-day weekends compared to those that provided daily rehabilitation (19.4 vs. 36.2 therapists, respectively, p < 0.001). CONCLUSIONS: In this survey, the provision of acute stroke rehabilitation, including non-working days, was clarified. According to the results, prospective interventional or observational studies are needed to design more effective rehabilitation programs to improve outcome. In particular, it is important to determine the optimal dose and intensity of acute stroke rehabilitation.

Design and fabrication of a microcoil metamaterial absorber for the sub-terahertz region.

The development of electromagnetic wave absorbers operating in the sub-terahertz (sub-THz) region is necessary in 6G communications. We designed and fabricated a sub-THz metamaterial absorber based on metal microcoils embedded and periodically arranged in a dielectric substrate. The microcoil parameters were optimized by calculating the electromagnetic response of the metamaterial using finite element analysis. An actual metamaterial was then fabricated based on the optimized parameters and characterized using THz time-domain spectroscopy. Our microcoil absorber exhibits an absorptance of >80% and a high shielding performance at about 250 GHz. The resonance frequency can be precisely adjusted by modifying the microcoil array dimensions.

Enantioselective and Chemoselective Phosphine Oxide-catalyzed Aldol Reactions of N-Unprotected Cyclic Carboxyimides.

Asymmetric catalytic transformations of N-unprotected cyclic carboxyimides such as succinimides, hydantoins, oxazolidinediones, and glitazones, is a powerful way of directly accessing variety of biologically valuable chiral compounds. Herein, a bis(trichlorosilyl) nucleophilic intermediate formed from cyclic carboxyimides was reacted with aldehydes via (S)-SEGPHOS dioxide (SEGPHOSO), proceeding the aldol reaction in highly enantioselective fashion through a cyclic transition state. Furthermore, N-unprotected carboxyimides were chemoselectively activated, even in the presence of N-alkylated carboxyimides, to undergo stereoselective and chemoselective aldol reactions via in situ silicon tetrachloride activation. The functionalized cyclic carboxyimides is readily derived to the several synthetic units derivatization to various chiral building blocks without unnecessary protection/deprotection steps.

Porous Mn2+ Magnet with a Pt-Cl Framework: Correlation between Water Vapor Adsorption/Desorption and Slow Magnetic Relaxation.

We report the water adsorption/desorption behavior and dynamic magnetic properties of the Pt-Cl chain complex [{[Pt(en)2 ][PtCl2 (en)2 ]}3 ][{(MnCl5 )Cl3 }2 ] ⋅ 12H2 O (1). Upon heating 1 in a vacuum, we obtained the dehydrated form [{[Pt(en)2 ][PtCl2 (en)2 ]}3 ][{(MnCl5 )Cl3 }2 ] (1DH). The framework structures of 1 and 1DH are identical, and both complexes underwent slow magnetic relaxation. However, the magnetic relaxation times for 1DH were shorter than those for 1, meaning that the dynamic magnetic properties were controlled upon water vapor adsorption/desorption. From detailed analyses of the dynamic magnetic behavior, a phonon-bottleneck effect contributes to the magnetic relaxation processes. We discuss the mechanism for the changes in the magnetic relaxation processes upon dehydration in terms of the heat capacity and thermal conductivity.

Lithium Binaphtholate-Catalyzed Asymmetric Michael Reaction of Acrylamides.

Chiral lithium binaphtholates prepared from the corresponding binaphthols and lithium tert-butoxide effectively catalyze the asymmetric Michael additions of ketones to poorly reactive acrylamides. The lithium binaphtholate catalyst mediates ketone deprotonation and enantioselective carbon-carbon bond formation to the acrylamide to deliver the Michael adduct in good yield and enantioselectivity. A small excess of lithium tert-butoxide relative to the binaphthol successfully enolizes the ketone in the initial stage of the reaction to promote the Michael reaction. Computational analysis of the transition state suggested that the 3- and 3'-phenyl groups of the binaphtholate catalyst regulate the orientation of the lithium enolate and the subsequent approach of the acrylamide, leading to superior enantioselectivity.

Underdosed Direct Oral Anticoagulants in Atrial Fibrillation Patients Reduce Stroke Severity and Improve Outcome.

BACKGROUND AND PURPOSE: Anticoagulant drugs, including vitamin K antagonist (VKA) and direct oral anticoagulants (DOACs), can reduce stroke severity and are associated with good functional outcomes. Some patients are prescribed lower-than-recommended doses of DOACs; whether these have similar effects has not been clarified. METHODS: We retrospectively evaluated 1,139 consecutive ischemic stroke and transient ischemic attack patients with atrial fibrillation. Patients were divided into 5 groups according to their preceding anticoagulant drug therapies: no anticoagulant therapy (ACn), undercontrolling VKA doses (VKAuc), recommended, controlling VKA doses (VKArec), prescribed underdoses of DOAC (DOACud), and recommended doses of DOAC (DOACrec). We investigated the associations between these anticoagulant drug therapies and patients' initial stroke severity and 3-month outcomes. RESULTS: Median National Institutes of Health Stroke Scale scores at admission were as follows: ACn: 16, VKAuc: 15, VKArec: 9, DOACud: 5, and DOACrec: 7. When the ACn group was used as a reference, regression analysis showed that VKArec (odds ratio [OR] 1.49, 95% confidence interval [CI] 1.01-2.21), DOACud (OR 2.84, 95% CI: 1.47-5.66), and DOACrec (OR 1.83, 95% CI: 1.23-2.74) were associated with milder stroke severity, while VKAuc was not. Median 3-month modified Rankin Scale scores were 2 in the DOACud and DOACrec groups and 4 in all other groups. After adjusting for confounding factors, DOACud (OR 3.14, 95% CI: 1.50-6.57) and DOACrec (OR 1.67, 95% CI: 1.05-2.64) were associated with good 3-month outcomes while VKAuc and VKArec were not. CONCLUSIONS: In patients with atrial fibrillation, recommended doses and underdoses of DOACs reduced stroke severity on admission and were associated with good 3-month outcomes.

Tremor-like grasp phenomenon: case series study.

OBJECTIVE: Tremor-like movements in patients with the grasp phenomenon are reported rarely. METHODS: We clinically and neuroradiologically studied four patients with tremor-like movements related to the grasp phenomenon. RESULTS: All of the patients were women aged between 61 and 98 years. In the present cases, tremor-like movements were observed in the right arm and/or leg. The movements occurred suddenly in three of the patients and chronically in one. The movements were stereotypic, often rhythmical, tremor-like, and accompanied with groping or picking-like movements. All of the patients displayed the grasp phenomenon, including grasp reflex and/or instinctive grasping reaction ipsilateral to the movements. Two patients had a recent broad infarct ipsilateral to the movements. One patient had meningioma contralateral to the movements, which had been surgically resected. The other patient did not have any radiologically proven cerebral lesions, although she had a history of focal seizures contralateral to the movements. CONCLUSIONS: It was suggested that their abnormal movements were closely related to the grasp phenomenon. We concluded that their characteristic tremor-like movements, a "tremor-like grasp phenomenon," was a variation of the grasp phenomenon that was due to hyperexcitation of the frontal lobe contralateral to the movements.

Modified Rankin scale assessment by telephone using a simple questionnaire.

PURPOSE: The modified Rankin Scale (mRS) is widely used as a measure of post-stroke physical disability in clinical stroke trials; however, it is affected by inter-rater discrepancies. A Japanese version of the simplified mRS questionnaire (J-RASQ) has the potential to overcome the inter-rater discrepancies and might be feasible for clinical surveys. We aimed to determine the reliability of J-RASQ in a telephone survey administered by non-medical staff. METHODS: We recruited 103 patients (age = 73 ± 11 years; 57% males) with a history of ischemic stroke who visited the outpatient clinic of the department of neurology at our hospital between March and May, 2021. After obtaining informed consent for participation in the study, a stroke neurologist assessed the mRS score during the visit using the Japanese version of mRS. On the same day, a clerk telephoned the patient or his/her family members to administer the J-RASQ. The percentage of agreement between mRS and J-RASQ scores was evaluated using the kappa coefficient and weighted kappa coefficient. RESULTS: The median time for the telephone survey was 85 s (interquartile range = 70-135 s). The mRS and J-RASQ scores had an agreement of 63.1%, with a kappa statistic of 0.51 (95% confidence interval [CI] = 0.39-0.63). The weighted kappa statistic, which takes into account the extent of disagreement, was 0.81 (95% CI = 0.75-0.88). CONCLUSION: J-RASQ is easy to administer and reliable for assessment in telephone-based surveys performed by non-medical staff.

Subdiffraction focusing with a long focal length using a terahertz-wave super-oscillatory lens.

This Letter describes a super-oscillatory lens (SOL), with concentric ring-type metallic slits photolithographically fabricated on a glass substrate, that can function at subterahertz frequencies. The SOL has been investigated both experimentally and theoretically and demonstrates a spatial resolution of 1.5 mm (0.5λ), which is 0.45 times the diffraction limit, with a focal length of 75 mm (25λ) at 100 GHz (λ=3mm). Furthermore, the depth of focus of the lens was measured to be 47 mm, which is 10.8 times larger than that of a conventional lens. This type of SOL, with subdiffraction focusing, is thus highly effective for use in industrial inspections with millimeter and terahertz waves.

Ultrafast Control of Magnetic Anisotropy by Resonant Excitation of 4f Electrons and Phonons in Sm_{0.7}Er_{0.3}FeO_{3}.

We compare the ultrafast dynamics of the spin reorientation transition in the orthoferrite Sm_{0.7}Er_{0.3}FeO_{3} following two different pumping mechanisms. Intense few-cycle pulses in the midinfrared selectively excite either the f-f electronic transition of Sm^{3+} or optical phonons. With phonon pumping, a finite time delay exists for the spin reorientation, reflecting the energy transfer between the lattice and 4f system. In contrast, an instantaneous response is found for resonant f-f excitation. This suggests that 4f electronic pumping can directly alter the magnetic anisotropy due to the modification of 4f-3d exchange at femtosecond timescales, without involving lattice thermalization.

Clinical characteristics of patients with ischemic stroke after the 2016 Kumamoto earthquake, a multi-center study.

OBJECTIVE: To investigate the clinical characteristics of patients with ischemic stroke following the 2016 Kumamoto earthquake. METHODS: We retrospectively studied patients with ischemic stroke admitted to 5 stroke centers for 1 year after the earthquake. We compared clinical characteristics in these patients (the post-earthquake group) to those in the patients with ischemic stroke admitted during the same period from the previous 3 years (the pre-earthquake group). Additionally, we analyzed the trend of the incidence rate of stroke before and after the earthquake. RESULTS: A total of 1979 patients were admitted after the earthquake; 5670 (1,890/year on average) patients were admitted before the earthquake. A first-ever ischemic stroke (71 vs. 75%) and premorbid modified Rankin Scale > 1 (26 vs. 29%) were found significantly more frequently in patients after the earthquake. National Institutes of Health Stroke Scale score ≤ 2 at discharge (60 vs. 65%) was found more frequently in patients after the earthquake, although non-discharge to home (65 vs. 70%) was more frequent in patients after the earthquake. Trend analysis revealed a decrease of small vessel occlusion and large artery atherosclerosis in the month after the earthquake. CONCLUSIONS: The 2016 Kumamoto earthquake may have affected the characteristics of stroke during the early phase of the earthquake and increased the difficulty in returning home.

Aphasia Induced by Infratentorial Ischemic Stroke: Two Case Reports.

Aphasia induced by an infratentorial stroke has rarely been reported, and its mechanism has not been fully identified. We evaluated two individuals who had been admitted to Saiseikai Kumamoto Hospital in Kumamoto, Japan, due to acute ischemic stroke in order to determine whether their aphasia was induced by an infratentorial stroke. The first patient, a 59-year-old man with a history of left parietal embolic stroke with very mild sequelae of anomia, developed Wernicke's aphasia, nonfluent speech, and right limb ataxia as a result of the stroke. The second patient, a 76-year-old woman with a history of chronic renal failure, experienced transcortical sensory aphasia and right one-and-a-half syndrome as a result of the stroke. Both patients' recent ischemic lesions were limited to the right cerebellar hemisphere and the right medial portion of the midbrain. However, SPECT showed low-uptake lesions in both patients' left cerebral hemisphere that did not include the recent ischemic lesions but that had spread to an extent that was difficult to be explained by the old or recent ischemic lesions and that might be responsible for their recent aphasia. We believe that the aphasia experienced by these two patients may have been caused by crossed cerebello-cerebral diaschisis.

A Study of Terahertz-Wave Cylindrical Super-Oscillatory Lens for Industrial Applications.

This paper describes the design and development of a cylindrical super-oscillatory lens (CSOL) for applications in the sub-terahertz frequency range, which are especially ideal for industrial inspection of films using terahertz (THz) and millimeter waves. Product inspections require high resolution (same as inspection with visible light), long working distance, and long depth of focus (DOF). However, these are difficult to achieve using conventional THz components due to diffraction limits. Here, we present a numerical approach in designing a 100 mm × 100 mm CSOL with optimum properties and performance for 0.1 THz (wavelength λ = 3 mm). Simulations show that, at a focal length of 70 mm (23.3λ), the focused beam by the optimized CSOL is a thin line with a width of 2.5 mm (0.84λ), which is 0.79 times the diffraction limit. The DOF of 10 mm (3.3λ) is longer than that of conventional lenses. The results also indicate that the generation of thin line-shaped focal beam is dominantly influenced by the outer part of the lens.

Reliability of the Modified Rankin Scale Assessment Using a Simplified Questionnaire in Japanese.

OBJECTIVES: We developed a Japanese version of the simplified modified Rankin Scale questionnaire, of which the agreement between patients or their family members and neurologists was verified in a previous single-center study. In the present study, the reliability of the questionnaire was evaluated in another hospital. MATERIALS AND METHODS: The participants were prospectively-registered patients with acute ischemic stroke admitted to Saiseikai Kumamoto Hospital. The questionnaire was administered to the patients or their family members at discharge. At the same time, the attending physician assessed the Japanese version of a guidance scheme for the modified Rankin Scale. The agreement rate between the scores from both assessments was examined using the κ statistic and weighted κ statistic. We examined the factors related to disagreement between the modified Rankin Scale score by the attending physicians and the questionnaire score by patients/family members. RESULTS: A total of 146 patients (age 77 ± 12 years; 53% men) were included. Agreement between the raters was 39%; the κ statistic was 0.27, but the weighted κ statistic, taking into account the extent of disagreement, was 0.81. In multivariate analysis, the disagreement between the modified Rankin Scale score and the questionnaire score was negatively associated with a modified Rankin Scale score of 5 at discharge (odds ratio, 0.02 per score point; 95% confidence interval, 0.00-0.34). CONCLUSION: The questionnaire showed decent reliability and similarity to the modified Rankin Scale assessed by physicians. The questionnaire could be a reliable indicator for assessing stroke functional outcomes even when implemented by non-medical staff.

Pre-hospital Diagnosis of Large Vessel Occlusion in Patients Being Transported by Helicopter.

BACKGROUND: During the helicopter transportation of patients suspected of large vessel occlusion (LVO), an accurate and rapid decision-making process is required. AIMS: We attempted to create an algorithm for the pre-hospital diagnosis of the presence of LVO in patients suspected of stroke using data from patients transported urgently by helicopter. METHODS: One hundred and sixty-five patients transported by helicopter were divided into two subgroups: a training dataset and a validation dataset. We extracted clinical information obtained on site, the unadjusted score of the National Institutes of Health Stroke Scale, and previously reported pre-hospital scales as an LVO screen. On the basis of the analyses of these factors, an algorithm was devised to predict the presence of LVO and its predictive accuracy was evaluated using the validation dataset. RESULTS: Ischemic stroke with LVO was diagnosed in 36 out of 121 cases (29.8%) in the training dataset and in 10 out of 44 cases (22.7%) in the validation dataset. Combining five factors (conjugate deviation, upper limb paresis, atrial fibrillation, Japan Coma Scale ≥ 200, and systolic blood pressure ≥ 180), an algorithm was created to classify cases into six groups with different likelihoods of LVO presence. The algorithm predicted correctly 6 out of 10 cases in the validation dataset. Furthermore, it definitively ruled out 17 out of 34 cases in the validation dataset. CONCLUSIONS: Using the newly created algorithm, emergency staff could easily and accurately distinguish patients suitable for urgent endovascular thrombectomy from patients with non-LVO or stroke mimics.