Adhesive,Flexible, and Robust Polysaccharide Nanosheets Integrated for Tissue‐Defect Repair

Recent developments in nanotechnology have led to a method for producing free‐standing polymer nanosheets as a macromolecular organization. Compared with bulk films, the large aspect ratio of such nanosheets leads to unique physical properties, such as transparency, noncovalent adhesion, and high flexibility. Here, a biomedical application of polymer nanosheets consisting of biocompatible and biodegradable polysaccharides is reported. Micro‐scratch and bulge tests indicate that the nanosheets with a thickness of tens of nanometers have sufficient physical adhesiveness and mechanical strength for clinical use. A nanosheet of 75 nm thickness, a critical load of 9.1 × 10⁴ N m^?1, and an elastic modulus of 9.6 GPa is used for the minimally invasive repair of a visceral pleural defect in beagle dogs without any pleural adhesion caused by wound repair. For the first time, clinical benefits of sheet‐type nano‐biomaterials based on molecular organization are demonstrated, suggesting that novel therapeutic tools for overlapping tissue wounds will be possible without the need for conventional surgical interventions.     

Primary intracranial germ cell tumors: a clinical analysis of 153 histologically verified cases

The authors analyzed 153 cases of histologically verified intracranial germ cell tumors. The histological diagnosis was germinoma in 63 patients (41.2%), teratoma in 30 (19.6%), and other types of tumors in 60 patients (39.2%). The patients were treated by a consistent policy of surgical removal with histological verification followed by radiation therapy with or without chemotherapy. The 10- and 20-year survival rates of patients with pure germinoma were 92.7% and 80.6%, respectively. The 10-year survival rates of patients with mature teratoma and malignant teratoma were 92.9% and 70.7%, respectively. Patients with pure malignant germ cell tumors (embryonal carcinoma, yolk sac tumor, or choriocarcinoma) had a 3-year survival rate of 27.3%. The mixed tumors were divided into three subgroups: 1) mixed germinoma and teratoma; 2) mixed tumors whose predominant characteristics were germinoma or teratoma combined with some elements of pure malignant tumors; and 3) mixed tumors with predominantly pure malignant elements. The 3-year survival rates were 94.1% for the first group, 70% for the second group, and 9.3% for the third group, and the differences were statistically significant. Twenty-six patients with malignant tumors received chemotherapy that consisted of cisplatin and carboplatin combinations with or without radiation therapy. However, chemotherapy was not significantly more effective than radiation therapy alone. From these treatment results, the authors classified tumors into three groups with different prognoses and proposed a treatment guideline appropriate for the subgroups.     

Novel phase-tunable three-dimensional hollow waveguides with variable air core

We propose novel micromachined tunable waveguide devices based on hollow optical waveguides. The combination of hollow waveguides and mechanical movable elements gives us a large change in a propagation constant of guided waves in a hollow waveguides. We fabricated a three-dimensional (3-D) hollow waveguide and experimentally demonstrated the change of the propagation constant in the 3-D hollow waveguide with a variable air core. We observed the wavelength shift of 1.8 nm in a hollow waveguide resonator with a displacement of 6 /spl mu/m in an air core.     

Compact Radiation Shield for a Superconducting Array Molecule Detector

Recent development on large-scale superconducting array detectors requires a large through hole along the molecular flight path in a cryostat. The through hole causes degradation of detector performance due to the 300 K radiation and a short holding time at the cryostat base temperature. To realize a compact detector system, we designed and fabricated infrared radiation shields with a fine-honeycomb collimator and a micro-structured metal-mesh. The infrared flux through the honeycomb collimator located at 50 K was 300–500 μW. A test run in a cryostat showed a holding time of 8 hours. We fabricated a metal-mesh consisting of a self standing Cr/Cu film with an array of 2.0 μm holes having a pitch of 3.5 μm. The metal-mesh was supported by a Si reinforce structure. Spectral measurement indicates that the transmission of the 300 K radiation is less than 1%.      

Delayed hepatic signal recovery on ferucarbotran-enhanced magnetic resonance images: an experimental study in rat livers with gadolinium chloride-induced Kupffer cell damage

Objective

Hepatic signal recovery, rather than reduction, in ferucarbotran-enhanced magnetic resonance imaging (MRI) is a potential diagnostic marker of liver damage. We investigated hepatic signal recovery in rats with gadolinium chloride (GdCl₃)-induced Kupffer cell (KC) damage.

Materials and methods

Twelve rats received 8 μmol iron/kg of ferucarbotran 1 day after 0–7.5 mg/kg GdCl₃ injection (experiment A). Another 12 rats received ferucarbotran followed by GdCl₃ injection 6 h later (experiment B). In each experiment, three rats without GdCl₃ (“no injury group”) served as control. Another six rats received GdCl₃ alone without ferucarbotran. Hepatic signals were assessed on T ₂ ^* -weighted images for up to 29 days. Iron deposits were histologically examined on day 29.

Results

Hepatic signal recovery was delayed in a GdCl₃ dose-dependent manner in experiment A. Gadolinium chloride alone reduced hepatic signal 15 % during this experiment. Hepatic signal recovery was delayed only in rats that received 7.5 mg/kg GdCl₃ in experiment B. Hepatic signals negatively correlated with iron deposits in KCs and hepatocytes.

Conclusion

Hepatic signal recovery on ferucarbotran-enhanced MRI was delayed in the context of GdCl₃-induced KC damage due to increased hepatic iron deposits. Hepatic signal recovery may be used as a clinical marker of KC damage in liver disorders, including radiation-induced hepatitis.     

A replication process of metallic micro-mold by using parylene embossing and electroplating

This study demonstrated a replication process for metallic micro-mold that combines the parylene-C (poly-chloro-p-xylylene C) hot-embossing and electroplating techniques. A nickel original master was fabricated using the deep RIE silicon etching followed by the electroplating process. Then, the patterned fields composed of arrays of 25 μm-high, 10 μm-wide and 1 mm-long lines with 10 μm spacing in nickel molds were successfully replicated on the 60 μm-thick parylene-C films by the hot-emboss process. Under complete filling conditions, the deviation of the replicated micropattern was less than 2.4%. The electroplated copper successfully filled parylene-C replica master patterns with the aspect ratio of 2.5 without the void formation by both adding organic addictives and controlling the seed layer thickness. After electroplating, the copper micro-mold could be successfully separated from the parylene-C replica master.     

Microstructuring of SU-8 photoresist by UV-assisted thermal imprinting with non-transparent mold

In this study, we explored a rapid and low-cost process for patterning in a SU-8 photoresist by thermal imprinting with a non-transparent mold such as Ni mold. One of major obstacles in the process is that the extremely good formability of uncured SU-8 even near room temperature causes the collapse of imprinted patterns during and after de-molding because a sample cannot be exposed to UV light during imprinting owing to the non-transparency of a mold. To overcome this problem, un-cured SU-8 resists were pre-treated with UV light, heat, and O₂ plasma for controlling their formability, and applied to thermal imprint tests to be compared each other in terms of the replication fidelity. As a result, a SU-8 sample pre-treated with UV light for 8 s resulted in the best replication quality for given imprint conditions and mold dimensions, and we could successfully replicate micro patterns in SU-8 resist without a quartz mold. As compared with conventional UV-imprint processes, this process has potential merits such as a lower mold cost, an easier mold release and a less air-entrapment.     

Development of precursor ceramics using organic silicon polymer

This paper relates to the Bridge Building Award, which was presented to the author (Toshihiro Ishikawa) by the American Ceramic Society on 27 January 2020. We have developed many types of functional ceramics using polycarbosilane as a raw material. Since 1983, several grades of SiC-based fibers have been produced from polycarbosilane by Ube Industries, Ltd. Of these grades, we developed the highest heat-resistant SiC-polycrystalline fiber (Tyranno SA), which can withstand up to 2000°C, using an organic silicon polymer (poly-aluminocarbosilane) containing a small amount of aluminum as a precursor material. By employing curing (in air) and firing (in nitrogen atmosphere at 1300°C) processes using the precursor fiber, an amorphous fiber (Si-Al-C-O fiber) containing a small amount of aluminum was obtained; subsequent heat treatment at higher temperatures (~2000°C) in argon atmosphere led to carbothermal reduction (SiO₂ + 3C SiC + 2CO(g)) and a sintering process, producing the abovementioned SiC-polycrystalline fiber (Tyranno SA). In the same year, using the same raw precursor fiber (Si-Al-C-O fiber), we also developed a new type of tough, thermally conductive SiC composite (SA-Tyrannohex) with high strength up to 1600°C in air. This ceramic consists of a highly ordered, close-packed structure of very fine hexagonal columnar SiC-polycrystalline fibers with a thin interfacial carbon layer between them. Further, by using the polycarbosilane as a starting material, we successfully developed a strong photocatalytic fiber (TiO₂/SiO₂ fiber) with a gradient surface layer composed of TiO₂-nanocrystals, making the best use of controlled phase separation (bleed-out) of additives (titanium (IV) tert-butoxide) contained in polycarbosilane. In this paper, the story of the development of these materials and the subsequent progress will be described along with the historical background.