Quantitative evaluation of light-matter interaction parameters in organic single-crystal microcavities.

Investigation of physics on light-matter interaction and strong coupling formation in organic microcavities is important to characterize the device structure enabling efficient room-temperature polariton condensation. In this study, we evaluate quantitatively the light-matter interaction parameters for three types of organic single-crystal microcavities and discuss the effects of microcavity structures on the strong coupling formation. We found that improvement in cavity quality factor causes a reduction in the photon damping constant, which results in an increase in the Rabi splitting energy. Moreover, when we used a metal thin film as the cavity mirror, it was revealed that the exciton damping became 30 times stronger than that in a dielectric mirror cavity. These experimental findings are very intriguing to achieve low-threshold or electrically pumped organic polariton devices.

Full-Thickness Entire Nasal Alar Reconstruction Using a Forehead Flap in Asians: No Cartilaginous Infrastructural Lining Is Necessary.

Full-thickness defects of the entire nasal ala, including the rim, can be challenging to reconstruct. A forehead flap may provide a more imperceptible and natural-appearing reconstructed nasal ala. Previously, many authors have insisted adding cartilaginous infrastructural support for an entire, full-thickness defect to keep the postoperative alar structure symmetrical. They finally use a forehead flap after thinning of the distal covering portion subcutaneously, possibly for a Caucasian-type nasal ala. However, Asian skin has a thicker and more compact dermis than that of Caucasian skin, and the Asian ala is rounder and thicker. There may be another approach for an Asian-type nasal ala. The authors propose the possibility of nasal alar reconstruction for an entire, full-thickness defect in Asians using a forehead flap without structural support. Six patients with entire full-thickness nasal alar defects treated with full-thickness forehead flaps above the periosteum without structural support were reviewed. Five patients demonstrated esthetically good to excellent outcomes in color, texture, and symmetry. Their nasal linings were reconstructed using mucoperiosteal flaps or mucosal grafts. One patient treated with a nasal lining using a local flap showed a fair result esthetically. Asians forehead above the periosteum has adequate thickness and supportability to reconstruct the entire full-thickness nasal ala in Asians. No cartilage support is necessary.

Effectiveness of intraoperative indocyanine-green fluorescence angiography during inguinal lymph node dissection for skin cancer to prevent postoperative wound dehiscence.

PURPOSE: The incidence of postoperative wound dehiscence following inguinal lymph node dissection (ILND) is higher than that in other anatomic regions. To prevent wound dehiscence, intraoperative interventions, such as trimming off the ischemic part of the flap before wound closure based on indocyanine-green (ICG) fluorescence angiography, have been introduced in our institute. This report describes a retrospective clinical study of 17 cases, and the objective of the study was to evaluate the clinical efficacy of intraoperative intervention using ICG fluorescence angiography. METHOD: A total of 17 patients who underwent ILND for skin cancer between 2009 and 2013 at our institute were reviewed retrospectively, and the significance of variables, including intervention using ICG fluorescence angiography, was evaluated using Fisher's exact test. RESULTS: There were nine cases of wound dehiscence, and two of these cases required a secondary skin graft. Only one case of wound dehiscence developed in the eight patients who underwent intervention based on ICG fluorescence angiography. This procedure was a significant factor influencing the risk of wound dehiscence (p = 0.003) in our study. CONCLUSION: Although this was a small case series, intraoperative intervention based on ICG fluorescence angiography was effective for preventing postoperative wound dehiscence after ILND.

Exotic optoelectronic properties of organic semiconductors with super-controlled nanoscale sizes and molecular shapes.

We present several aspects of thiophene/phenylene co-oligomers (TPCOs). TPCOs are regarded as a newly occurring class of organic semiconductors. These materials are synthesized by hybridizing thiophene and phenylene rings at the molecular level with their various mutual arrangements. These materials are characterized by the super-controlled nanoscale sizes and molecular shapes. These produce peculiar crystallographic structures and high-performance optical and electronic properties. The crystals of TPCOs were obtained through both vapor phase and liquid phase. In the TPCO crystals, the molecules take upright configuration. These cause large carrier mobilities of field-effect transistors and laser oscillations under optical excitations. Spectrally-narrowed emissions (SNEs) were also achieved under weak optical excitation using a mercury lamp. The light-emitting field-effect transistors using these crystals for an active layer have shown the current-injected SNEs when the device was combined with an optical cavity and operated by an alternating-current gate-voltage method. Thus the TPCO materials will play an important role in the future in the fields of nanoscale technology and organic semiconductor materials as well as their optoelectronic device applications.

A case of pseudo-Kaposi sarcoma with chronic limb-threatening ischemia.

BACKGROUND: Pseudo-Kaposi sarcoma (PKS) is a rare vascular proliferative disease, caused by arteriovenous malformation (AVM) and chronic venous insufficiency. The lesions are characterized by purple or reddish-brownish papules, plaques, and nodules. Although benign, it is clinically similar to Kaposi's sarcoma (KS), a malignant disease, and must be differentiated by histopathological examination. We report a rare case of PKS with chronic limb-threatening ischemia (CLTI). CASE PRESENTATION: An 83-year-old man with diabetes mellitus (DM) presented to a local dermatology department with a complaint of a right second toe ulcer and was, thereby, referred to our department due to arterial bleeding during skin biopsy to exclude malignant diseases. Although the pulsation of dorsalis pedis artery of the affected limb was palpable, the skin perfusion pressure was only 20 and 30 mmHg on the dorsum and planter surface, respectively, indicating severe ischemia of toe and forefoot. Ultrasonography and computed tomography revealed an AVM around the right second metatarsophalangeal joint and occlusion of the right dorsalis pedis artery in the middle, indicating CLTI in the background. Pathological findings of the skin biopsy found capillary blood vessel proliferation, hemosiderin deposition, and extravascular red blood cell leakage in the dermal layer, which could be found in KS. However, CD34 was normally stained in the vascular endothelium, and human herpesvirus-8 staining was negative, resulting in the pathological diagnosis of PKS, a proliferative vascular lesion associated with AVM. The ulcer was spontaneously epithelialized, but 2 years later the ulcer recurred and infection developed, necessitating treatment for abnormal blood flow. Transarterial embolization using N-butyl 2-cyanoacrylate for the AVM controlled abnormal perfusion once; however, the procedure exacerbated perfusion of the toe, resulting in foot ulcer progression. Forefoot amputation with surgical excision of AVM was performed, and thereby, wound healing was achieved. CONCLUSION: This is a rare case of PKS with CLTI complicated with AVM. As there is currently no established consensus on the treatment of PKS, the approach to treatment strategy should be tailored to the specific condition of each patient.

Photogeneration of charge carrier correlated with amplified spontaneous emission in single crystals of a thiophene/phenylene co-oligomer.

Thiophene/phenylene co-oligomers have substantial promise for the use of not only organic electronics but also organic optical devices. However, considerably less is known about the correlation between their optical and optoelectronic properties. We have investigated the charge carrier generation in 1,4-bis(5-phenylthiophen-2-yl)benzene (AC5) single crystals by flash-photolysis time-resolved microwave conductivity (TRMC) and transient absorption spectroscopy (TAS). It was found that the dependence of photocarrier generation efficiency on excitation photon density differed from that of emission efficiency once amplified spontaneous emission (ASE) and resultant spectrally narrowed emission occur upon exposure to 355 nm. In contrast, the dependences of emission and photocarrier generation efficiencies were identical when ASE was not involved at a different excitation wavelength (193 nm). An approximated analytical solution of rate equation considering ASE or singlet-singlet annihilation was applied to the experiments, exhibiting good agreement. On the basis of TRMC, TAS, and extinction coefficient of radical cation assessed by pulse radiolysis, the minimum charge carrier mobility was estimated, without electrodes, to be 0.12 cm(2) V(-1) s(-1). The dynamics of charge carrier and triplet excited state is discussed, accompanying with examination by time-dependent density functional theory. The present work would open the way to a deeper understanding of the fate of excited state in optically robust organic semiconducting crystals.

Organic-crystal light-emitting field-effect transistors driven by square-wave gate voltages.

We have improved the operation method of organic light-emitting field-effect transistors by applying a square wave to the gate electrode. A thiophene/phenylene co-oligomer crystal was used as the organic layer. Compared with the sinusoidal wave gate bias application, the square-wave bias produces the emission intensity ten times as large as that of the former. The effective emissions take place through electrons injection from the source contact when the gate bias traverses 0 V so as to be positive. When asymmetric electrodes were used for the source and drain contacts, the resulting emission exhibited the narrowed spectral line at 491.5 nm with its FWHM approximately 1.1 nm. The line narrowing is expected to be a consequence of the emission intensity increment caused by the enhanced electrons injection from the Ag source contact. The location of the emission line is closely related to those of the multimodes due to the laser oscillation by cavity resonance.

Grating-assisted spectrally-narrowed emissions from an organic slab crystal excited with a mercury lamp.

We report spectrally-narrowed emissions that take place from an organic semiconductor slab crystal of 2,5-bis(4-biphenylyl)thiophene (BP1T) under a low excitation-intensity regime. These emissions are caused with a mercury lamp that operates on a household power supply with an electric current approximately 1 A. The BP1T slab crystal is equipped with a distributed Bragg reflector. To complete this structure the slab crystal is attached to a diffraction grating that is engraved on a surface of a quartz glass substrate. The diffraction gratings have precisely been formed using a focused ion beam with a nanometer-defined precision. The spectral narrowing accompanied by the emission intensity increment is related to the strong mode-coupling between the forward electromagnetic wave and the backward (i.e., reflected) wave within the grating zone. Using a laser we also carried out the emission measurements on the BP1T crystals under a high excitation-intensity regime. The emissions are characterized as the longitudinal multimode laser oscillation, enabling us to determine the group refractive index of 4.56 for the BP1T slab crystal. Under both the low and high excitation-intensity regimes excitons are dominant species of the emission. Their participation in the spectrally-narrowed emissions is briefly discussed.

A high optical-gain organic crystal comprising thiophene/phenylene co-oligomer nanomolecules.

We have estimated the optical gain for a crystal of a thiophene/phenylene co-oligomer, 1,4-bis(5-phenylthiophen-2-yl)benzene. We prepared the crystal by a vapor phase growth method and measured emission spectra by exciting it with a pulse laser and changing the pumped stripe lengths. With increasing the stripe lengths, the emission intensity was increased and the emission spectra were gain narrowed around 516 nm with its full width at half maximum down to approximately 6 nm. The optical gain spectrum was determined from the emission spectra that varied as a function of the pumped stripe lengths. The gain spectrum was peaked at 516 nm with the maximum net optical gain coefficient being 75 cm(-1). This peak location is in excellent agreement with the peak position of the gain narrowed emission spectra. The results indicate that the determination of the gain spectrum is important for laser applications of the material. The oligomer crystal in the present studies is a good candidate for them.

An field-effect transistor based upon thiophene/phenylene co-oligomer nanomolecules combined with a composite polymer gate insulator.

We have studied the FET device characteristics of the thiophene/phenylene co-oligomers chosen as organic semiconductors. The FET devices were made of two kinds of co-oligomer materials with different morphologies (i.e., the thin film and crystal). We show different device fabrication procedures depending upon the difference in the morphologies. The device characteristics were also investigated on various polymer gate insulators. The composite polymer gate insulators play an important role in achieving a good device performance. More specifically, the combination of poly(vinylphenol) and poly(methyl methacrylate) turned out very effective in attaining the pinch-off at larger drain voltages. This composite gate insulator is responsible for the steady device performance as well. A normal electrical feature is maintained under a reduced (or dry) pressure where conventional polymer gate FET devices did not function normally. The relevant results are evaluated and compared. The importance of the thiophene/phenylene co-oligomers as the nanomaterials (or nanomolecules) is briefly mentioned as well.

Improved device performance of organic crystal field-effect transistors fabricated on friction-transferred substrates.

We have improved performance of organic field-effect transistors (OFETs) composed of organic nanomolecular single crystals of a thiophene/phenylene co-oligomer. A poly(tetrafluoroethylene) thin layer was applied with friction-transfer technique to an insulator layer of silicon dioxide covering a silicon substrate. The crystals were grown in a liquid phase on the friction-transferred substrate such that the bottom-contact device was completed through depositing the crystals in firm contact with the premade metal electrodes. This technique ensures an excellent electrical contact between the crystal and the electrodes. The device shows the carrier mobility up to 0.26 cm2/Vs. The linear increase in the drain currents is clearly noted around the origin of the drain current-drain voltage action diagram. Thus we have achieved a high performance with the OFETs whose fabrication is based upon the friction-transfer technique.

Microcrystalline array structures induced by heat treatment of friction-transferred organic semiconductor films.

The correlation between molecular orientation and optoelectrical properties is most critical to the future design of molecular materials. We made highly-anisotropic microcrystalline array structures with an organic semiconductor, a methoxy-substituted thiophene/phenylene co-oligomer (TPCO), by depositing it on friction-transferred poly(tetrafluoroethylene) (PTFE) layers fabricated on substrates with several heat treatments. Polarising microscope observation, polarised emission and absorption spectra measurements indicated that the TPCO molecules aligned along the drawing direction of PTFE. Using these films, we fabricated two types of field-effect transistors (FETs) and compared them with those using non-heated TPCO films which provide aligned pleats structures. Ones had the channel length direction parallel to the drawing direction of PTFE and the others had the channel length direction perpendicular to that drawing direction. As for the microcrystalline array films, the mobility ratio of the former FET to that of the latter device was about 27 in the saturation region, while the emission polarisation ratio was 4.5. The heat treatment promoted the crystal growth to enhance the mobility while retaining the high anisotropy. The results demonstrate that the heat treatments of the TPCO films on the friction-transferred layers were useful for controlling crystallinity and orientation of the molecules.

Clarification of the Molecular Doping Mechanism in Organic Single-Crystalline Semiconductors and their Application in Color-Tunable Light-Emitting Devices.

Organic single-crystalline semiconductors with long-range periodic order have attracted much attention for potential applications in electronic and optoelectronic devices due to their high carrier mobility, highly thermal stability, and low impurity content. Molecular doping has been proposed as a valuable strategy for improving the performance of organic semiconductors and semiconductor-based devices. However, a fundamental understanding of the inherent doping mechanism is still a key challenge impeding its practical application. In this study, solid evidence for the "perfect" substitutional doping mechanism of the stacking mode between the guest and host molecules in organic single-crystalline semiconductors using polarized photoluminescence spectrum measurements and first-principles calculations is provided. The molecular host-guest doping is further exploited for efficient color-tunable and even white organic single-crystal-based light-emitting devices by controlling the doping concentration. The clarification of the molecular doping mechanism in organic single-crystalline semiconductor host-guest system paves the way for their practical application in high-performance electronic and optoelectronic devices.

A metal-lustrous porphyrin foil.

A metal-lustrous self-standing film, named "porphyrin foil", was formed from a glass-forming polymeric porphyrin. The amorphous glass nature of the porphyrin foil played a key role in spontaneously producing a smooth surface. Its sharp contrast in intense absorption and specular reflection of light at each wavelength provided a brilliant metallic lustre.

Spectrally-Narrowed Emissions from Organic Crystals Having a One-Dimensional Grating on Their Surface.

We have succeeded in directly engraving one-dimensional diffraction gratings on the surface of organic semiconducting oligomer crystals by using focused ion beam (FIB) lithography and laser ablation (LA) methods. The FIB method enabled us to shape the gratings with varying periods down to ~150 nm. With the LA method a large-area grating with a ~500-nm period was readily accessible. All the above crystals indicated spectrally-narrowed emission (SNE) lines even in the case of shallow groove depths ~2-4 nm. In particular, we definitively observed the SNE pertinent to the first-order diffraction with the crystal having the diffraction grating of a 148.3-nm average period. The present results indicate utility of the built-in gratings that can directly be fabricated on the surface of the crystals.

Synthesis and electrolytic polymerization of the ethylenedioxy-substituted terthiophene-fullerene dyad.

[reaction: see text] Two derivatives of ethylenedioxy-substituted terthiophene-fullerene dyads were newly synthesized as the precursors for polythiophene having fullerene side chains. By electrolytic oxidation of dyad 1, the charm-bracelet type polythiophene, poly-1, was obtained as a purple film, which showed electrochemical activity, electrochromism, and photoelectronic response.

Controlled release of granulocyte colony-stimulating factor enhances osteoconductive and biodegradable properties of Beta-tricalcium phosphate in a rat calvarial defect model.

Autologous bone grafts remain the gold standard for the treatment of congenital craniofacial disorders; however, there are potential problems including donor site morbidity and limitations to the amount of bone that can be harvested. Recent studies suggest that granulocyte colony-stimulating factor (G-CSF) promotes fracture healing or osteogenesis. The purpose of the present study was to investigate whether topically applied G-CSF can stimulate the osteoconductive properties of beta-tricalcium phosphate ( ß -TCP) in a rat calvarial defect model. A total of 27 calvarial defects 5 mm in diameter were randomly divided into nine groups, which were treated with various combinations of a ß -TCP disc and G-CSF in solution form or controlled release system using gelatin hydrogel. Histologic and histomorphometric analyses were performed at eight weeks postoperatively. The controlled release of low-dose (1 µ g and 5 µ g) G-CSF significantly enhanced new bone formation when combined with a ß -TCP disc. Moreover, administration of 5 µ g G-CSF using a controlled release system significantly promoted the biodegradable properties of ß -TCP. In conclusion, the controlled release of 5 µ g G-CSF significantly enhanced the osteoconductive and biodegradable properties of ß -TCP. The combination of G-CSF slow-release and ß -TCP is a novel and promising approach for treating pediatric craniofacial bone defects.

Light-emitting field-effect transistors having combined organic semiconductor and metal oxide layers.

A new organic light-emitting field-effect transistor characterized by a metal oxide layer inserted between the organic layer and the gate insulator is proposed. The metal oxide is indirectly connected with source and drain electrodes through the organic layer. Upon increasing the potential difference between the source and drain electrodes, the emission becomes exceedingly strong and the emission region encompasses the whole channel zone.

Sentinel lymph node biopsy using real-time fluorescence navigation with indocyanine green in cutaneous head and neck/lip mucosa melanomas.

BACKGROUND: The triple technique (lymphoscintigraphy, patent-blue staining, and a gamma probe) constitutes a reliable method for the sentinel lymph node (SLN) biopsy. However, in head and neck melanomas, a shine-through phenomenon, which occurs because these SLNs are close to the primary focus, is irreversibly problematic. To get around the shine-through phenomenon, this study uses the fluorescence navigation with indocyanine green (ICG) as well as the triple technique. METHODS: ICG is a green dye and can be used as a marker with infrared fluorescence. ICG solution is intradermally injected around the tumor. By using Photodynamic Eye (PDE) intraoperatively, it is possible to observe the injected ICG as SLNs in the fluorescence images. RESULTS: By use of the fluorescence imaging with ICG, clear identification of the SLN of the case became possible. CONCLUSIONS: We think the fluorescence navigation with ICG will be a useful option for the SLN biopsy in head and neck melanomas.

Current-confinement structure and extremely high current density in organic light-emitting transistors.

Extremely high current densities are realized in single-crystal ambipolar light-emitting transistors using an electron-injection buffer layer and a current-confinement structure via laser etching. Moreover, a linear increase in the luminance was observed at current densities of up to 1 kA cm(-2) , which is an efficiency-preservation improvement of three orders of magnitude over conventional organic light-emitting diodes (OLEDs) at high current densities.