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Background: Most surgeons are unaware that idiopathic neuropathy, which occurs independently of mechanical injury, can present as postoperative peripheral neuropathy. The aim of this study was to reveal the presence of postoperative neuropathy considered to be induced by surgical stress and to make surgeons aware that idiopathic neuropathy can occur postoperatively.Methods: We conducted a survey among orthopedic surgeons regarding patients with postoperative neuropathies of unknown cause. For each case, the type of neuropathy, preceding surgery and anesthesia, patient background, clinical findings, and clinical course were investigated.Results: Seven patients were identified. The mean time from surgery to the onset of neuropathy was 9.3 days (range 1-15 days). Five of the patients fully recovered spontaneously within 1 year, while the remaining two underwent neurolysis. One patient presented with hourglass-like constrictions in the radial nerve. No inflammatory cells were found in the epineurium of the affected nerve.Conclusions: Although it is rare, postoperative idiopathic neuropathy occurs in clinical practice, and it is crucial that surgeons recognize the existence of this neuropathy to elucidate its pathogenesis as well as to reduce the risk of litigation. [ABSTRACT FROM AUTHOR]

In this study, the formation of Ag–S bond was systematically elucidated by thickness‐dependent ultraviolet photoelectron spectroscopy (UPS) in order to understand the L‐cysteine interaction with silver surface. A clean Ag(111) as the model system for silver surface was used, and L‐cysteine films on silver substrate were formed by vacuum evaporation. The orbital configurations at the interface was estimated including work function, secondary electron cutoff (SECO), highest occupied molecular orbital (HOMO) onset, position of an interface state, charge injection barrier, and ionization energy. A clear spectral feature was appeared in between Fermi edge and HOMO of L‐cysteine, and the feature can be attributed to the formation of Ag–S bonding. In the case of SECO, the maximum shift was 0.46 eV to the higher binding energy side at the nominal thickness of 1 Å. However, from the nominal thickness of 2 Å, SECO started to shift to the lower binding energy side, and at 16 Å, the SECO shifted to a value of around 0.4 eV to the lower binding energy side to almost cancel the initial vacuum level shift. This behavior can be attributed to weakening of the silver‐sulfur bond with increasing of L‐cysteine coverage referring to the literature. The photoelectron yield spectroscopy (PYS) was also performed as an additional spectroscopic work, which exhibited that the work function of silver once decreased and then recovered at low coverage. This behavior can also be assigned to a weakening the interaction of L‐cysteine with silver by increasing of L‐cysteine coverage. [ABSTRACT FROM AUTHOR]

Theoretical simulations of the angle-resolved ultraviolet photoemission spectra (ARUPS) for the oligomer of poly(tetrafluoroethylene) [(CF2)n ; PTFE] were performed using the independent-atomic-center approximation combined with ab initio molecular orbital calculations. Previously observed normal-emission spectra for the end-on oriented sample (with long-chain axis perpendicular to the surface) showed the incident photon-energy (hv) dependence due to the intramolecular energy-band dispersion along the one-dimensional chain, and the present simulations successfully reproduced this hv dependence of the observed spectra. We employed the experimentally observed helical structure for PTFE oligomers for the simulations. We also calculated the density of states (DOS) for the planar zigzag structure, and examined the changes in the electronic structure due to the difference in the molecular structure by comparing the DOS for the helical and planar zigzag structures. Only a small change in the DOS was found between these structures, showing little change of the electronic structure between these conformations. We also evaluated the inner potential V0 , which is the parameter defining the energy origin of the free-electron-like final state, and checked the validity of the value of 10 Rev estimated in our previous study using the experimentally observed hv dependence of the peak intensity. The estimation of V0 was performed by pursuing the best agreement between the energy-band dispersion [E = E(k)] relation along the chain direction obtained from the simulated spectra and the experimentally deduced one. An excellent agreement in the topmost band was achieved when the assumed inner potential V0 was set at about zero. This value of V0 is much different from the value of V0 = -10 eV in the previous study, suggesting the invalidity of the previous assumption at the estimation of V0 from the peak intensity variation with hv. Using the presently obtained V0, we could derive more reliable E = E(k) dispersion relation from the observed ARUPS spectra. The comparison of this newly derived relation gave good agreement with theoretically calculated E = E(k) relations, in contrast to the poor agreement for the previous results with V0 = -10 eV. [ABSTRACT FROM AUTHOR]

Presents information on a study on the effect of the method used to clean indium-tin-oxide on its work function, using ultraviolet photoemission spectroscopy and x-ray photoemission spectroscopy. Experimental method; Results; Discussion; Conclusion.

Illumination stress (IS) and negative bias under illumination stress (NBIS) cause considerable device instability in thin-film transistors based on amorphous In–Ga–Zn–O (a-IGZO). Models using in-gap states are suggested to explain device instability. Therefore, to provide reliably their density of states (DOS), this study investigated the valence band, conduction band, and in-gap states of an a-IGZO thin film. The DOS of in-gap states was directly determined in a dynamic range of six orders of magnitude through constant final state yield spectroscopy (CFS-YS) using low-energy and low-flux photons. Furthermore, light irradiation irreversibly induced extra in-gap states near the Fermi level and shifted the Fermi level to the vacuum level side, which should be related to the device instability due to IS and NBIS. Hard x-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy using synchrotron radiation observed the large DOS of in-gap states near the Fermi level as in previous works. Here, we reveal that they are not intrinsic electronic states of undamaged a-IGZO, but induced by the intense measurement light of synchrotron radiation. This study demonstrates that CFS-YS is useful for determining the reliable DOS of the in-gap states for samples that are sensitive to light irradiation. The absorption spectrum measured through photothermal deflection spectroscopy is interpreted based on DOS directly determined via photoemission spectroscopies. This indicates that the line shape in the energy region below the region assigned to the Urbach tail in previous works actually roughly reflects the DOS of occupied in-gap states. [ABSTRACT FROM AUTHOR]

Trigger finger is a common hand disorder; however, its pathogenesis remains unknown. In this study, we aimed to investigate mast cells, fibroblast activators that synthesize collagen, in the tendon sheaths of trigger fingers. We investigated the presence of mast cells and their association with changes in the collagen content of the tendon sheath and clinical data. We performed a multicenter prospective study of 77 adult patients with trigger finger who had undergone resection of the first annular pulley between August 2012 and January 2020. The tendon sheath was immunostained with an anti-tryptase antibody to confirm mast cell presence. The percentage of collagen in the tendon sheath was determined by picrosirius red staining observed through a polarization microscope. The clinical data, including the duration from symptom onset to surgery, severity, pain numerical rating scale, and Hand20 scores, were evaluated. Tryptase-positive mast cells were recognized in 83.5% of all specimens. The mast cell presence group (Group P) had a significantly higher percentage of type-3 collagen in the tendon sheath than the non-mast cell presence group (Group N) (Group P, 15.6%; Group N, 12.7%; p = 0.03). Moreover, Group P had significantly higher pain numerical rating scale (Group P; 5, Group N; 3, p = 0.04) and Hand20 (Group P; 35.5, Group N; 13.0, p = 0.01) scores than Group N. These findings suggest that mast cell presence in the tendon sheath of the trigger finger is related to the pathology and clinical symptoms of trigger finger. [ABSTRACT FROM AUTHOR]

Abstract: Thin film of Alq3 and its interfaces with various metals (K, Li, Ca, Al)/Alq3 and the Al/LiF/Alq3 interface were investigated using NEXAFS spectroscopy. The assignments of structures in NEXAFS spectra at the C, N and O K-edges were performed using theoretical calculations taking account of the core-excitonic effect. The NEXAFS spectra at the three edges are well reproduced by the simulated results. The spectra at the N and O K-edges of Alq3 are similar to the partial density of unoccupied states (PDOUS) of the ground state, but the spectrum at the C K-edge is different from the PDOUS of ground state due to the core-excitonic effect. The present study is the first trial of the detailed analysis of the C K-edge spectrum of Alq3. The spectral changes at the metal/Alq3 and Al/LiF/Alq3 interface were found to depend on the metal. By the comparison with the theoretical simulations based on the 1:1 metal-Alq3 complex, we found that the electron transfer and orbital overlap occur at the interfaces of K/Alq3 and Li/Alq3, while the observed changes at the Ca/Alq3 and Al/Alq3 interfaces could not be understood by the simulated results. At the LiF/Alq3 interface, we observed the spectral changes which may result from some chemical interaction. Some of the spectral changes at Al/LiF/Alq3 interface differ from those of Al/Alq3 interface, indicating chemical interaction specific for the co-existence of Al, LiF, and Alq3. [Copyright &y& Elsevier]

Abstract: The adsorption of naphthalene molecules on a Si(100)-2×1 surface at room temperature is investigated using infrared reflection absorption spectroscopy in the multiple internal reflection geometry (MIR-IRAS). To determine the adsorption configurations on the surface in detail, IRAS spectra in the C–H stretching vibration region are analyzed in comparison with frequency calculations based on a density functional theory method (DFT). As a result, naphthalene molecules adsorb on the surface in different manners depending on the surface coverage of the molecule. At low coverage, a single configuration is favored, in which the 1,4,5,8 carbon atoms of the molecule are bound to the dangling bonds of two adjacent Si dimers to form Si–C σ bonds. At high coverage, it adsorbs in several different configurations. This exposure-dependence is discussed in relation to intermolecular interaction on the basis of the calculations for models in which two naphthalene molecules adsorb on a Si cluster. [Copyright &y& Elsevier]

The interface of the tris (8-hydroxyquinoline) aluminum (Alq[sub 3])/LiF/A1 system was investigated with ultraviolet photoelectron spectroscopy (UPS), metastable atom electron spectroscopy (MAES), and X-ray photoelectron spectroscopy (XPS). Strong chemical interaction was observed at Alq[sub 3] on Al interface. By inserting a LiF layer, this interaction is suppressed and interface energy level alignment is changed to reduce a barrier for electron injection. The enhancement of device efficiency is ascribed to these phenomena. The importance of the combined use of various techniques on the same interface is stressed. [ABSTRACT FROM AUTHOR]

Objective: Remote lung injury is induced by ischaemia/reperfusion (I/R) of the gastrointestinal tract and the liver following hypovolaemic shock. In the present study, the role of cytokine-induced neutrophil chemoattractant (CINC), a member of the interleukin (IL)-8 family, in neutrophil-mediated remote lung injury following intestinal I/R was investigated in anaesthetized rats. Methodology: The I/R group was subjected to 60 min of occlusion of the superior mesenteric artery with laparotomy, followed by 240 min of intestinal reperfusion. The sham-operated (sham) group was subjected to the same procedures with the exception of intestinal I/R. Results: In the I/R group, the permeability index of the lung, the neutrophil count in pulmonary vascular lavage fluid and bronchoalveolar lavage fluid (BALF), lung myeloperoxidase activity and neutrophil oxidative production were all significantly greater than those in the sham group. Cytokine-induced neutrophil chemoattractant-1 levels in blood and BALF were significantly increased at 240 min after intestinal reperfusion. There was a significant relationship between neutrophils in BALF and CINC-1 level in BALF. Conclusion: These findings suggest that intestinal reperfusion was associated with activation and accumulation of neutrophils in the lung and resulted in remote lung injury with increased microvascular permeability. Thus, CINC-1 in BALF may induce neutrophil migration from the pulmonary vessels to the interstitium and alveolar spaces in remote lung injury after intestinal I/R. [ABSTRACT FROM AUTHOR]

This paper reports an equivalent circuit model of self‐assembled electret (SAE) micro‐electro‐mechanical systems (MEMS) vibrational energy harvesters (VEHs). For the first time, a detailed equivalent circuit model of the SAE‐MEMS VEH has been implemented on a circuit simulator, considering the device energy diagram. The implemented equivalent circuit model allows analysis of the relationship between output current and SAE properties, device structures, and electrode materials. The validity of the model is confirmed by comparing the measurement and simulation results. Thus, the proposed model would be useful for the design of SAE‐MEMS VEHs. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Investigates the electronic structures of model interfaces of organic electroluminescent (EL) devices and porphyrin/metal interfaces by UV photoemission spectroscopy (UPS). Samples materials for the model interfaces of organic EL devices; Results and discussion of the experiments; Conclusions.

Photodiode‐type solar‐blind photodetectors (SBPDs) with the self‐powered feature hold great promise for applications in unattended secure communication, flame detection, and missile warning. However, the responsivity of SBPDs is usually limited due to the severe solar‐blind (SB) light extinction in substrates and charge transport layers. Herein, a spectrally selective hole extraction structure (SHE) is proposed for high‐efficiency perovskite SBPDs. The SHE consisting of a tandem Fabry–Perot cavity and energy‐level‐matched hole transport layer endows the device with narrowband absorption in the SB region and optimized charge extraction capability from the CsPbI2Br perovskite. The optimized SHE exhibits a peak transmittance of 27% at 255 nm and a half maximum at full width of 28 nm. Under SB light illumination, the champion device achieves a responsivity of 56.20 mA W−1 and a detectivity (D*) of 2.86 × 1013 Jones, which are the record values among the reported results. The approach demonstrated here paves the way for the optical and electrical design of perovskite photodetectors with spectrally selective detection. [ABSTRACT FROM AUTHOR]

The vibration-based electret generators (EGs) for energy harvesting have been extensively studied because they can obtain electrical energy from ambient vibrations. EGs exhibit a sandwich structure of electrodes surrounding an air gap and an electret, which is a dielectric material with a quasi-permanent electrical charge or dipole polarisation. Various charging processes have been developed because the surface charge density (σ) of the electret determines the output power of the device. However, such processes are considered to constitute a key productivity-limiting factor from the mass production viewpoint, making their simplification or elimination a highly desired objective. Herein, a model EG that does not require any charging process by utilising the spontaneous orientation polarisation of 1,3,5-tris(1-phenyl-1H-benzimidazole-2-yl)benzene (TPBi) is demonstrated. The surface potential (Vsp) of an evaporated TPBi film has reached 30.2 V at a film thickness of 500 nm without using a charging process. The estimated σ of 1.7 mC m−2 is comparable with that obtained using a conventional polymer-based electret after charging. Furthermore, Vsp is considerably stable in environmental conditions; thus, TPBi can be considered to be "self-assembled" electret (SAE). Application of SAE leads to developing an EG without requiring the charging process. [ABSTRACT FROM AUTHOR]

Ultraviolet photoelectron spectra were measured using synchrotron radiation for two kinds of π-conjugated polymers, poly(pyridine-2,5-diyl) (PPy) and poly(2,2′-bipyridine-5,5′-diyl) (PBPy) which exhibit n-type electrically conducting properties. The two compounds show similar spectra and they were analyzed with MO calculations and the comparison with the data of related molecules. The ionization threshold energies of PPy and PBPy were found to be 6.3 and 6.35 eV, respectively. These values are higher than those of π-conjugated conducting polymers capable of p doping. Upon potassium doping of PBPy, two new states appeared in the originally empty energy gap and the intensity of the state at 0.65 eV from EF grows as the doping proceeds. This finding and the change of optical absorption spectra upon doping indicate that bipolaron bands are formed in K-doped PBPy. While K-doped PPy also shows similar gap states, it requires higher dopant concentration to create bipolaron bands than in the case of K-doped PBPy. The difference of the dependence on dopant concentration between K-doped PPy and K-doped PBPy is discussed based on the conformational difference between these polymers. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The novel coronavirus (COVID-19) that emerged in 2019 and spread globally in 2020 has resulted in the imposition of lockdowns or a state of emergency in many cities worldwide. In Japan, a "new lifestyle" is being advocated. We hypothesize that the new lifestyle has changed people's use of their upper limbs during the COVID-19 pandemic. Therefore, through this questionnaire study, we aimed to determine the factors associated with exacerbation of symptoms during the pandemic and to investigate the current status of patients who require hand surgery. This study was a prospective multi-center questionnaire survey. This study was conducted in Japan from December 2020 to July 2021 at university and general hospitals in nine prefectures. A questionnaire was administered to patients who visited a hospital with symptoms of nerve entrapment syndrome, osteoarthritis, or tenosynovitis. A total of 502 patients with a mean age of 63.8 years responded. The 240 patients who experienced exacerbation (exacerbated and markedly exacerbated) were compared with other patients (unchanged, improved, and markedly improved). An increase in the time spent on personal computers and smartphones was associated with exacerbation of hand symptoms. Patients who wanted to undergo surgery but were postponed due to COVID-19 accounted for 23.5% of the outpatients. The mean scores for pain, jitteriness, and anxious depression in these patients were significantly higher than those of patients who did not want surgery. Our results suggest that an increase in the time spent on personal computers and smartphones is associated with exacerbation of hand symptoms during the COVID-19 pandemic. Patients who wanted to undergo surgery but were postponed by COVID-19 experienced greater pain, jitteriness, and anxious depression. [ABSTRACT FROM AUTHOR]

Spontaneous orientation polarization (SOP) of amorphous organic semiconducting films has attracted much attention because of its frequent observation in common organic light-emitting diodes (OLEDs) and potential influences on the device properties of OLEDs. On the other hand, the formation mechanism of SOP has been controversial for a long time, ever since its discovery in 2002. Recently, the formation mechanism of SOP was explained in terms of the surface equilibration mechanism of vapor-deposited glasses, and the understanding of SOP has progressed significantly. Based on the improved understanding, some active control methods of SOP have been demonstrated and further influences on the device performance of OLEDs were revealed, suggesting that higher efficiency can be achieved by managing SOP properly. Furthermore, some applications of SOP have also been proposed, such as a self-assembled electret and a tool for evaluating materials properties. In this paper, recent progress in the understanding of SOP and its applications to devices are reviewed. • Recent progress in understanding of spontaneous orientation polarization (SOP) in organic semiconducting films is reviewed. • Formation mechanism and active control methods of SOP are discussed. • Influences of SOP on the device performance of organic light-emitting diodes are discussed. • Applications of SOP are introduced. [ABSTRACT FROM AUTHOR]

Electret-based microelectromechanical system (MEMS) vibratory energy harvesting is a key technology for converting the mechanical energy of environmental vibrations into electricity. Unfortunately, conventional electret charging methods generally rely on high-voltage and high-temperature processes that present limitations to MEMS design and production. Here, we show a MEMS post-processed self-assembled electret (SAE) that enables the integration of electrets with MEMS vibratory devices via evaporation as a post-MEMS process. Owing to the spontaneous orientation of polar molecules, the surface potential of the SAE can build up at room temperature in a microscopic region without charging processes, which enhances the design and fabrication flexibility of electret-based MEMS energy harvesters. We develop a MEMS vibratory device followed by post-processing the SAE and confirm induced electrical currents caused by the electrical field of the SAE at the vibrational input. This SAE-based MEMS technology is a promising design guideline for highly integrated single-chip MEMS vibratory energy harvesters. [ABSTRACT FROM AUTHOR]

Abstract: We present an investigation of the interface between organic semiconductor films and metal substrates (organic/metal interface) using photoelectron yield spectroscopy (PYS) as the probing technique. PYS studies were conducted on the pentacene/Au, copper phthalocyanine (CuPc)/Au, and perfluorinated zinc phthalocyanine (F16ZnPc)/Au, and the results were compared with literature results obtained using conventional ultraviolet photoemission spectroscopy (UPS). PYS is advantageous for probing the electronic structure of the organic/metal interface because of the relatively long mean free path of photoexcited electrons with very low kinetic energy in PYS, which enables the detection of the photoelectrons from the metal substrate buried deep in the organic film. We demonstrate herein that the use of PYS reduces the significance of the final state effect of the electronic density surrounding the photohole at the organic molecule generated after the photoemission; this effect is known as the electric polarization effect. Although this effect has a significant influence on the results obtained using conventional UPS, the reduced influence of the final state effect in PYS makes it possible to construct an energy level diagram at the organic/metal interface with greater accuracy than can be achieved with UPS. In addition, a novel mechanism of the photoelectron detection for PYS enables us to apply PYS to very thick organic films, and therefore, PYS provides a reliable value of ionization energy for organic films without the influence of the substrate. Because the interface electronic structure has a significant influence on the carrier injection properties of organic devices, the increased reliability of the information obtained by PYS will render it very useful for the improvement of device performance as well for understanding their operation principles. [Copyright &y& Elsevier]

Abstract: Air-stable n-channel field-effect transistors based on thin films of the compound, N,N′-bis(4-trifluoromethylbenzyl)perylene-3,4,9,10-tetracarboxylic diimide (PTCDI-TFB), were fabricated, and the effects of surface treatment and substrate temperature at the film deposition on the electron mobility of the transistors were studied. The maximum mobility, 4.1×10−2 cm2 V−1 s−1 in the saturation region (1.7×10−2 cm2 V−1 s−1 in the linear region), was obtained in air for the film deposited at 95°C on the SiO2 surface modified with hexamethyldisilazane. The high electron affinity of PTCDI-TFB estimated at 4.8eV by photoelectron yield spectroscopy and UV–Vis absorption spectroscopy, which is ascribable to the trifluoromethylbenzyl groups, is likely to result in the observed stable transistor operation in air. [Copyright &y& Elsevier]

We investigated formation processes of a porous anodic alumina film on a p-type silicon (Si) substrate using infrared absorption spectroscopy in the multiple internal reflection geometry (MIR-IRAS). We observed drastic IR spectral changes when anodization took place near the interface between an aluminum (Al) layer and a Si substrate. The intensity of absorption peaks due to porous anodic alumina increased with a decrease in anodic current density and it decreased simultaneously with formation of silicon oxides (SiO2) at the interface between a porous anodic porous alumina film and a Si substrate after appearance of a spike of anodic current density which indicated changes of states of electric double layer at the interface between an electrolyte and an electrode due to contact between an electrolyte and a Si substrate. The results suggested that the formation of SiO2 nanodots on a Si substrate promoted penetration of electrolytes to peel the porous anodic alumina film from it. [Copyright &y& Elsevier]

Orientation of cations at the air/liquid interfaces of the salts of 1-butyl-3-methyl imidazolium with tetrafluoroborate and hexafluorophosphate is studied using infrared–visible sum frequency vibrational spectroscopy. For both salts, quantitative analyses show that the terminal methyl group of the butyl chain is polar-oriented with its symmetry axis aligned nearly vertical to the surface. [Copyright &y& Elsevier]

Recently, a spontaneous orientation polarization (SOP) has attracted much attention as an important factor improving the performance of organic light‐emitting devices. However, so far, SOP is reported only for films fabricated by vacuum vapor deposition, and no direct attempt is made to examine the existence of SOP for wet‐processed film. To examine this phenomenon, it is necessary to completely exclude light illumination in the sample system, as photocarriers can reduce or eliminate the surface potential caused by the SOP formation. Herein, the SOP of wet‐processed tris(8‐hydroxyquinolinato)aluminum (Alq3) film on an indium‐tin‐oxide substrate is investigated using a novel rotary Kelvin probe method. Film formation and surface potential measurement are conducted under completely dark condition. A surface potential shift of −0.33 V is observed for a 1 μm thick film of Alq3, indicating that the SOP of wet‐processed Alq3 film is negligible, in contrast to vacuum‐evaporated film. [ABSTRACT FROM AUTHOR]

Although the long-term stability of organic light-emitting diodes (OLEDs) under electrical operation made significant progress in recent years, the fundamental underlying mechanisms of the efficiency decrease during operation are not well understood. Hence, we present a comprehensive degradation study of an OLED structure comprising the well-known green phosphorescent emitter Ir(ppy)3. We use transient methods to analyze both electrical and optical changes during an accelerated aging protocol. Combining the results of displacement current measurements with time-resolved investigation of the excited states lifetimes of the emitter allows for a correlation of electrical (e.g., increase of the driving voltage due to trap formation) and optical (e.g., decrease of light-output) changes induced by degradation. Therewith, it is possible to identify two mechanisms resulting in the drop of the luminance: a decrease of the radiative quantum efficiency of the emitting system due to triplet-polaron-quenching at trapped charge carriers and a modified charge carrier injection and transport, as well as trap-assisted non-radiative recombination resulting in a deterioration of the charge carrier balance of the device. [ABSTRACT FROM AUTHOR]

Spontaneous orientation polarization (SOP) has been frequently observed in the evaporated films of organic light‐emitting diode materials. Because SOP modifies the charge injection and the accumulation properties of the device, understanding and controlling SOP is crucial in optimizing the performance of the device. In this study, we investigated the dominant factors for SOP formation by focusing on intermolecular interactions. We examined the giant surface potential characteristics of coevaporated films incorporating 1,3,5‐tris(1‐phenyl‐1H‐benzimidazol‐2‐yl)benzene (TPBi) that is a typical polar molecule exhibiting SOP. In the coevaporated films of TPBi and nonpolar molecules such as 4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl and 4,4′,4″‐tris (carbazol‐9‐yl)triphenylamine, the orientation degree of the permanent dipole moment (PDM) of TPBi is significantly enhanced with diluted TPBi density, though the enhancement is weak on the film with N,N′‐bis(1‐naphthyl)‐N,N′‐diphenyl‐1,1′‐biphenyl‐4,4′‐diamine. The results indicate that the PDM interaction between polar molecules results as a negative factor for SOP formation. Furthermore, we found that SOP formation is suppressed by the surface treatment of the self‐assembled monolayer on the gold substrate, indicating a positive effect of the van der Waals interaction between the molecule and the substrate surface. [ABSTRACT FROM AUTHOR]

Electron–hole pairs at the interface between electron‐donating and electron‐accepting molecules form charge‐transfer excitons (CTEs) via Coulomb attraction. Generally, the attraction energy of the CTE is weaker than that of the Frenkel exciton because of spatial separation of the charge pair; thus, the binding of the CTE is expected to be sensitive to an electric field. Here, the shielding of the binding energy of the CTEs by an internal electric field induced by spontaneous orientation polarization (SOP) of the solid‐state donor–acceptor blend film is reported. When the blend film forms a large SOP, the photogenerated CTEs spontaneously dissociate without an external electric field, resulting in carrier diffusion and carrier lifetimes that are in the milliseconds or longer. In the absence of a large SOP, the CTEs preferentially form exciplexes that quickly release their energy as light rather than dissociation. Hence, the control of SOP in the donor–acceptor blend films can provide new insights into exciton binding and facilitate the development of tailored high‐performance organic semiconductor devices. [ABSTRACT FROM AUTHOR]

Objectives: Muscle spindles are proprioceptive receptors in the skeletal muscle. Peripheral nerve injury results in a decreased number of muscle spindles and their morphologic deterioration. However, the muscle spindles recover when skeletal muscles are reinnervated with surgical procedures, such as nerve suture or nerve transfer. Morphological changes in muscle spindles by cell transplantation procedure have not been reported so far. Therefore, we hypothesized that transplantation of embryonic sensory neurons may improve sensory neurons in the skeletal muscle and reinnervate the muscle spindles. Materials and methods: We collected sensory neurons from dorsal root ganglions of 14‐day‐old rat embryos and prepared a rat model of peripheral nerve injury by performing sciatic nerve transection and allowing for a period of one week before which we performed the cell transplantations. Six months later, the morphological changes of muscle spindles in the cell transplantation group were compared with the naïve control and surgical control groups. Results: Our results demonstrated that transplantation of embryonic dorsal root ganglion cells induced regeneration of sensory nerve fibre and reinnervation of muscle spindles in the skeletal muscle. Moreover, calbindin D‐28k immunoreactivity in intrafusal muscle fibres was maintained for six months after denervation in the cell transplantation group, whereas it disappeared in the surgical control group. Conclusions: Cell transplantation therapies could serve as selective targets to modulate mechanosensory function in the skeletal muscle. [ABSTRACT FROM AUTHOR]

We investigate different parameters influencing the occurrence of s-shaped current voltage (j-V) characteristics in planar heterojunction organic solar cells. It is shown how substrate modification, purity of the active organic material as well as variation of the top contact can affect the shape of the j-V curves. The studies are performed on vacuum-evaporated planar heterojunction solar cells with diindenoperylene (DIP) as electron donor and fullerene C60 as acceptor. The focus is on the fill factor and forward current being the most direct indicators for s-shapes in j-V curves. We find that the main effect of substrate heating during film growth can be assigned to changes in energy barriers rather than to the modification of morphology and crystallinity, which is also influenced by elevated substrate temperatures. The decisive role of the barrier height between the anode work function and the HOMO (i.e., highest occupied molecular orbital) level of the donor is approved by comparing hole-injection layers with different work functions. By using donor materials of different purity we find a correlation between charge carrier mobilities and fill factors. Finally, it is demonstrated that an exciton blocking interlayer is essential to get high fill factors when aluminum is used as top contact, but is dispensable for samarium as cathode material. This finding can be ascribed to the protective effect of the interlayer from aluminum diffusion into the active semiconductor rather than to its role as exciton diffusion barrier. [ABSTRACT FROM AUTHOR]

2-amino-4,5-imidazoledicarbonitrile (AIDCN) has been considered as a promising material toward organic nonvolatile memory application. Aiming for achieving a deep understanding of the origins of the bistable electric behavior of the AIDCN-based memory devices and, in particular, of the reported drastic improvement of the device performance by replacement of the Al top-electrode material with Ag, we elucidated the electronic structures of the interfaces between AIDCN and electrode metals (Ag and Al), as well as the bulk of AIDCN, by photoemission spectroscopy (PES). Ionization energy of AIDCN was determined to be 6.6 eV that was also certified by photoelectron yield spectroscopy measurements. For the AIDCN/Ag interface, the highest occupied molecular orbital (HOMO)-derived peak was clearly resolved in the PES spectra even when the thickness of the AIDCN overlayers were below the monolayer. The peak position showed significant shifting (∼0.5 eV) to the higher binding energy side with formation of the multilayers. Probing angle dependent spectra revealed that the AIDCN monolayer on Ag shows different molecular orientation from that of the multilayers. These results strongly suggest that a sharp interface was formed between the Ag surface and AIDCN overlayers. In contrast, the PES spectra of the AIDCN/Al interface showed not a peak but a diffuse tailing structure in the HOMO region until the bulklike phase was formed. No angular dependent change appeared on the PES spectra in the low coverage region, which suggests the molecular orientation was random. The hole injection barriers, derived from energy offsets between the edges of the HOMO-derived spectral features and the Fermi level, of AIDCN/Ag and AIDCN/Al interfaces are estimated to be 2.0 eV and 1.0 eV, respectively. [ABSTRACT FROM AUTHOR]

The effect of atmospheric gases on the ionization energy (I) of titanyl phthalocyanine thin film was investigated by an apparatus of photoemission yield spectroscopy developed for the measurements of I for the same specimen both in vacuum and under gaseous atmosphere. It was found that the value of I is affected by the exposure to various ambient gases (i.e., air, nitrogen, and oxygen of 1 atm, and water vapor corresponding to 27% relative humidity at 300 K), and that the effect strongly depends on the gas. The ionization energies in vacuum could be determined as the onset I0 of the cube-root plot of the photoemission yield as a function of photon energy. When the sample was exposed to gases, the cube-root plot still gives an onset, but often a long tail at the low-energy side with another onset It was also observed. The first exposure to air did not affect both I0 and It much, while the following evacuation-exposure cycles caused mostly reversible decrease and increase of I0 and It by about 0.2 and 0.4 eV, respectively. Among the examined constituent gases of air, nitrogen was found to hardly affect both I0 and It except for the small temporal decrease by 0.06 eV at the first exposure. Similar trends of the change of I0 and It with those for air were found for oxygen, with the amplitudes of mostly reversible change being 0.1 eV for I0 and 0.2 eV for It. Overlapped with these changes, a slow decrease of both I0 and It, was also observed with a slope of 0.01 eV per day. For water, the trends were mostly similar with O2, except that (1) the first exposure to water vapor showed small and large changes in I0 (0.03 eV increase) and It (0.4 eV decrease) and (2) the amplitudes of the mostly reversible change of I0 (0.3 eV) and It (0.05 eV) were much larger and smaller than those for O2, respectively. A long-term decrease was also observed with a slope of 0.04 eV per day. These results indicate that the atmospheric effect by ambient air on I is mainly caused by water vapor, although oxygen also makes significant contribution. Since the observed trends are rather complex, there seem to be multiple factors affecting I, which is the energy difference between the vacuum level and the highest occupied molecular orbita. Possible microscopic mechanisms of the observed variation of I on these levels are also discussed in terms of the energy change in these levels. [ABSTRACT FROM AUTHOR]

We have investigated in situ the hybridization and denaturation of DNA in aqueous solution using infrared absorption spectroscopy (IRAS) in the multiple internal reflection (MIR) geometry. We demonstrate that conformational changes of DNA strands due to hybridization (binding of two complementary single-stranded DNAs) and denaturation (separation of double helix at elevated temperatures) are reflected in the infrared absorption spectra in the frequency region where vibrational modes of the bases of DNA appear. Comparison with results of ab initio cluster calculation shows that hybridization produces the specific C==O carbonyl stretching vibration modes in the hydrogen-bonded base pairs. The ratio of absorbance of the C==O stretching peak at 1690 cm-1 to the absorbance at 1660 cm-1 provides a definitive metric for determining DNA hybridization. We also reveal that the C==O stretching vibration modes of the bases of a single strand is strongly influenced by the surrounding water molecules that may interact with the C==O groups of the bases. The present results suggest that MIR-IRAS is applicable to label-free, high-sensitive biosensors that provide insight about the gene expression and a variety of biological interactions such as DNA-protein interactions. [ABSTRACT FROM AUTHOR]

We observed high and persistent spontaneous buildup of the surface potential (SP) upon vacuum deposition of tris(8-hydroxyquinolinato) aluminum(III) (Alq[sub 3]) on an Au substrate under dark conditions. SP determined by the Kelvin probe method reached 28 V at a thickness of 560 nm and the surface of the Alq[sub 3] film was positively charged. We propose a model in which preferential orientation of the dipole moments of Alq[sub 3] molecules is the origin of this buildup of the SP. The intensity of second-harmonic generation was also dramatically increased by the deposition of Alq[sub 3] under dark conditions, which supports the notion of a buildup of dipole layers. This giant surface potential was almost completely removed by irradiation of Alq[sub 3] molecules with visible light, and irradiation during deposition also prevented the buildup of SP. [ABSTRACT FROM AUTHOR]

The electronic structures of materials such as HOMO and LUMO are essential information to understand their functions. Photoemission spectroscopy, which is the most standard technique to examine the electronic structures of various materials, has been not well applied to biomolecules mostly due to sample charging and poor sensitivity. Very recently, we have developed high-sensitivity photoemission spectroscopy (HS-PES) using low photon energy. In this study, HS-PES has been successfully applied to a thermophilic rhodopsin (TR) film. The high sensitivity of our technique enabled to observe the HOMO region of retinal part in TR without any problem due to sample charging. This technique is expected to explore the electronic structures of various proteins. [ABSTRACT FROM AUTHOR]

In this paper we report on the angle-resolved ultraviolet photoelectron spectroscopy on ultrathin films of bis(1,2,5-thiadiazolo)-p-quinobis (1,3-dithiole) (BTQBT) deposited on a MoS2 surface with synchrotron radiation, and describe the quantitative analysis of the angular distribution of photoelectron from the highest occupied state. The observed angular distributions were better explained by those calculated with the single-scattering approximation combined with molecular orbital calculation considering intramolecularly scattered waves than the previously used independent-atomic-center approximation combined with molecular orbital calculation. Further, the low-energy-electron diffraction measurements were performed on the film. From the low-energy-electron diffraction, the two-dimensional lattice of the ultrathin films on the MoS2 was found to be MoS2(0001)-(13×13, R=±13.9°)-BTQBT, and from the analysis of the photoelectron angular distributions, it was found that at the lattice points the molecules lie flat with azimuthal orientations of 19° and 47° with respect to each surface crystal axis of MoS2. On the basis of these results, the full structure of the thin film, the two-dimensional lattice, and full molecular orientations at the lattice points, is proposed. © 1997 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents an ultraviolet photoemission spectroscopy study of electronic structures of organic molecular materials for organic electroluminescent devices. Details on organic electroluminescent devices; Details on methodology used to conduct study; Indication of findings; Discussion on results.

The molecular orientation in organic semiconductor films determines device performances. In particular, the spontaneous orientation of a permanent dipole moment (PDM) along the surface normal direction induces a polarization charge at the hetero-interfaces of stacked multilayer devices, and the interface charge dominates the charge accumulation and injection properties. Spontaneous orientation polarization (SOP) has been observed in the “randomly oriented” films of several organic semiconductor materials, and is potentially inherent in many common materials. Herein, we report that 11 additional molecules of organic light-emitting diode materials, including thermally activated delayed fluorescence emitters, and horizontally oriented emitters and electron transporters, exhibit SOP in their evaporated films. The experimental results clearly indicate that SOP frequently occurs in “horizontally oriented” films as well as “randomly oriented” films. The factors contributing to SOP formation are discussed in terms of the figure of merit per PDM. We found that strong intermolecular interactions tend to reduce the figure of merit. Moreover, we suggest the impact of SOP on device performances. [ABSTRACT FROM AUTHOR]

The structure of pn heterojunctions is an important subject in the field of organic semiconductor devices. In this work, the crystallinity of an epitaxial pn heterojunction of C 60 on single crystal pentacene is investigated by non-contact mode atomic force microscopy and high-resolution grazing incidence x-ray diffraction. Analysis shows that the C 60 molecules assemble into grains consisting of single crystallites on the pentacene single crystal surface. The in-plane mean crystallite size exceeds 0.1 µm, which is at least five time larger than the size of crystallites deposited onto polycrystalline pentacene thin films grown on SiO 2 . The results indicate that improvement in the crystal quality of the underlying molecular substrate leads to drastic promotion of the crystallinity at the organic semiconductor heterojunction. [ABSTRACT FROM AUTHOR]

Understanding of the electronic structures is indispensable for complete elucidation of the charge carrier behaviors in organic semiconductors. Although recent progress enabling accurate photoemission demonstrations of organic single crystals has greatly promoted such understanding, it had been achieved merely on partially oxidized surfaces by exposure to ambient conditions. In this study, we successfully prepared an oxide-free surface of the pentacene single crystal (PnSC) by cleavage in vacuum. X-ray and ultraviolet photoelectron spectroscopy measurements on the PnSC clean surface revealed improved energetic homogeneity of the C1s level and highest-occupied state in comparison to those of the partially oxidized surface. [ABSTRACT FROM AUTHOR]

No clinically applicable drug is currently available to enhance neurite elongation after nerve injury. To identify a clinically applicable drug, we screened pre-approved drugs for neurite elongation in the motor neuron-like NSC34 cells. We found that zonisamide, an anti-epileptic and anti-Parkinson’s disease drug, promoted neurite elongation in cultured primary motor neurons and NSC34 cells in a concentration-dependent manner. The neurite-scratch assay revealed that zonisamide enhanced neurite regeneration. Zonisamide was also protective against oxidative stress-induced cell death of primary motor neurons. Zonisamide induced mRNA expression of nerve growth factors (BDNF, NGF, and neurotrophin-4/5), and their receptors (tropomyosin receptor kinase A and B). In a mouse model of sciatic nerve autograft, intragastric administration of zonisamide for 1 week increased the size of axons distal to the transected site 3.9-fold. Zonisamide also improved the sciatic function index, a marker for motor function of hindlimbs after sciatic nerve autograft, from 6 weeks after surgery. At 8 weeks after surgery, zonisamide was protective against denervation-induced muscle degeneration in tibialis anterior, and increased gene expression of Chrne, Colq, and Rapsn, which are specifically expressed at the neuromuscular junction. We propose that zonisamide is a potential therapeutic agent for peripheral nerve injuries as well as for neuropathies due to other etiologies. [ABSTRACT FROM AUTHOR]

We report on the charge carrier dynamics and their degradation phenomena in an organic light-emitting diode (OLED) doped by a thermally activated delayed fluorescence emitter; (4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl) isophthalonitrile (4CzIPN). Displacement current measurement (DCM) data revealed the presence of negative interface charge originating from the spontaneous orientation polarization of the electron transport layer (ETL), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl) benzene. The negative interface charge acts as a hole reservoir and thus confines the recombination zone near the emission layer (EML); 4,4′-bis( N -carbazolyl)-1,1′-biphenyl (CBP):4CzIPN (5 wt%)/ETL interface. By keeping the recombination zone far from the hole transport layer, 4,4′-bis[ N -(1-naphthyl)- N -phenylamino]-biphenyl ( α -NPD), a better electroluminescence efficiency is expected because the Dexter energy transfer from the triplet state of 4CzIPN to that of α -NPD is suppressed. Moreover, we found an excellent linear relation between the accumulated hole amount and luminance losses owing to device aging. The results are consistent with hole traps originating at the degradation products of CBP as the main factor of device degradation. We suggest device architectures based on the charge carrier dynamics for better efficiency and lifetime. [ABSTRACT FROM AUTHOR]

The attenuation length (AL) of low energy photoelectrons inside a thin film of a π-conjugated organic semiconductor material, 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole), was investigated using ultraviolet photoelectron spectroscopy (UPS) and photoelectron yield spectroscopy (PYS) to discuss their probing depth in amorphous organic thin films. The present UPS results indicated that the AL is 2–3 nm in the electron energy range of 6.3–8.3 eV with respect to the Fermi level, while the PYS measurements which collected the excited electrons in a range of 4.5–6 eV exhibited a longer AL of 3.6 nm. Despite this still short AL in comparison to a typical thickness range of electronic devices that are a few tens of nm-thick, the photoemission signal penetrating through further thicker (18 nm) organic film was successfully detected by PYS. This fact suggests that the electronic structures of “buried interfaces” inside practical organic devices are accessible using this rather simple measurement technique. [ABSTRACT FROM AUTHOR]

The complete electronic structure inside a practical organic photovoltaic (OPV) device consisting of a trilayer structure of copper-phthalocyanine (CuPc), fullerene (C60), and bathocuproine (BCP) is demonstrated using low-energy ultraviolet photoelectron spectroscopy (LE-UPS) and photoelectron yield spectroscopy (PYS). The molecular orbital energy alignment and electrostatic potential distribution throughout the entire device is illustrated based on the LE-UPS results. A favorable potential gradient to carry the photogenerated holes and electrons is manifested to be built spontaneously in the CuPc and BCP layers, respectively. Furthermore, the ultrahigh sensitivity measurements of LE-UPS clearly unveil the distributions of faint density-of-states in the energy-gap region in the organic films. Substantially barrierless contacts to both electrodes are fulfilled by the existence of these gap states. The electronic structure under simulated sunlight illumination is examined for the purpose of elucidating the electronic structures inside the working devices in the open-circuit condition. These results indicate experimentally the electronic functionalities of each organic material, in particular of the BCP buffer layer, on the cell efficiency. [ABSTRACT FROM AUTHOR]

Highlights: [•] A modified technique of capacitance measurement for transistors was proposed. [•] The technique enables to observe the channel formation processes of transistors. [•] The channel formation processes of pentacene transistors were observed. [•] Validity of the gradual channel approximation in pentacene transistors was examined. [ABSTRACT FROM AUTHOR]

Highlights: [•] A well-defined overlayer of n-C44H90 (TTC) is formed onto the rubrene single crystal. [•] Commensurate growth of TTC to the rubrene surface is suggested by nc-AFM observation. [•] Uniform monolayer of TTC is obtained on rubrene upon annealing after RT deposition. [•] Photoemission measurements were conducted to probe the TTC–covered rubrene crystal. [•] Valence band width of rubrene is retained even in touch with the organic dielectric. [ABSTRACT FROM AUTHOR]

A tris(7-propyl-8-hydroxyquinolinato) aluminum [Al(7-Prq)3] film shows negative giant surface potential (GSP) because of spontaneous orientation polarization. The polarity of this film is opposite to those of tris-(8-hydroxyquinolate) aluminum films. In Al(7-Prq)3-based organic light-emitting diodes, negative GSP leads to the positive interface charge and governs the electron injection and accumulation properties. In addition, a high resistance to the electron injection at the Al(7-Prq)3/Ca interface is suggested possibly because of the negative polarization charge at the interface. These results show the importance of orientation polarization in controlling the charge injection and accumulation properties and potential profile of the resultant devices. [ABSTRACT FROM AUTHOR]

Abstract: Interface electronic structures of four-kinds of electron transporting or hole blocking organic materials (n-type) on a widely-used hole transporting material (p-type) in organic light emitting diodes (OLEDs), N,N′-bis (1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamin (NPB), were investigated by means of photoelectron spectroscopy (PES). 1,3-bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (OXD-7) and 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) overlayers show continuous energy shift of each overlayer-derived spectral components and the vacuum level proportional to the thickness. This energy shift is ascribed to a spontaneous building up of the electrostatic potential within the organic layers (giant surface potential; GSP). The energy shift of the overlayers induced by GSP as well as the interface vacuum level shift are adequately taken into account to determine the actual energy barrier heights of the hole conduction levels at the heterojunctions. 4,4′-bis(9-carbazolyl)biphenyl (CBP) and p-bis(triphenylsilyl) benzene (UGH2) induce band bending in the NPB film which presumably results from charge transfer (CT) to the n-type materials from NPB. Despite absence of a practical vacuum level shift and thickness dependent shift of the overlayer-derived electronic states, the CT-derived energy shift of NPB reduces the actual energy barrier height with respect to the nominal barrier height being simply interpreted from PES spectra of a thick overlayer of each material. The energy level diagrams across these ‘n-on-p’ organic–organic heterojunctions were finely determined based on the above interpretation of the PES spectra. [Copyright &y& Elsevier]

Abstract: Displacement current measurements (DCMs) were used to investigate transient carrier behavior during the carrier accumulation process in pentacene (Pn) metal–insulator–semiconductor structures [Au/Pn (100nm)/SiO2 (100nm)/p-type Si]. We propose a modified DCM technique that applies a combined voltage waveform of ramp and plateau parts to observe the transient carrier behavior. This allows to simultaneously detect both the effective capacitance of the device and the transient response which reflects the dynamic carrier behavior in the device. In addition, the long decay time during carrier spreading at the Pn/SiO2 interface agrees well with the inverse of the relaxation frequency, which was estimated by capacitance–frequency measurement. This result demonstrates that DCM is a powerful tool for investigating both the quasi-static and dynamic behavior of carriers in organic devices. [Copyright &y& Elsevier]

B Rotary Kelvin Probe Method b A new type of rotary Kelvin probe (KP) is developed to measure the spontaneous orientation polarization (SOP) of solution-processed films under completely dark conditions. Examination of Spontaneous Orientation Polarization in Wet-Processed Tris(8-hydroxyquinolinato)aluminum Film Measured by Rotary Kelvin Probe Method It is found that the SOP of solution-processed tris(8-hydroxyquinolinato)aluminum (Alq SB 3 sb ) film is negligible. [Extracted from the article]

The atmospheric effect on the ionization energy (I) of titanyl phthalocyanine (TiOPc) thin film was investigated by photoemission yield spectroscopy developed for the measurement of I for the same specimen both in vacuum and under gaseous atmosphere. The variation of I of TiOPc thin film induced by exposure to air was observed. [ABSTRACT FROM AUTHOR]

Abstract: In spite of recent extensive studies of organic field effect transistors (OFETs), the operation mechanism is not yet clear. Especially the origin of the carriers accumulated in channel of OFET should be clarified to discuss the performance of OFETs. We have to take care of impurity-induced-carriers as well as carriers injected from source and drain electrodes. The spread of the charge sheet at organic/dielectric interface is also critical to the PET performance. Thus an experimental technique to probe such behavior of carriers is highly required. In this study, we have proposed displacement current measurement (DCM) method as a tool to characterize OFETs. We found that this technique enables us to probe various properties in OFETs; the carrier injection from metal electrodes to organic materials, the effective area of charge sheet in the channel, and the amounts of carriers accumulated in the device. The results for pentacene and poly-3- hexylthiophene FETs are reported to discuss the relation between the carrier generation and FET performance. [Copyright &y& Elsevier]