Naphtho[1,2‐c:5,6‐c′]bis[1,2,5]thiadiazole‐Containing π‐Conjugated Compound: Nonfullerene Electron Acceptor for Organic Photovoltaics

The development of nonfullerene acceptor materials applicable to organic photovoltaics (OPVs) has attracted considerable attention for the achievement of a high power conversion efficiency (PCE) in recent years. However, it is still challenging due to the insufficiency of both the variety of effective electron‐deficient units and certain guidelines for the design of such materials. This work focusses on naphtho[1,2‐c:5,6‐c′]bis[1,2,5]thiadiazole (NTz) as a key electron‐deficient unit. Therefore, a new electron‐accepting π‐conjugated compound (NTz‐Np), whose structure is based on the combination of NTz and the fluorene‐containing imide‐annelated terminal units (Np), is designed and synthesized. The NTz‐Np compound exhibits a narrow optical energy gap (1.73 eV), a proper energy level (?3.60 eV) of the lowest unoccupied molecular orbital, and moderate electron mobility (1.6 × 10^?5 cm² V^?1 s^?1), indicating that NTz‐Np has appropriate characteristics as an acceptor against poly(3‐hexylthiophene) (P3HT), a representative donor. OPV devices based on NTz‐Np under the blend with P3HT show high photovoltaic performance with a PCE of 2.81%, which is the highest class among the P3HT/nonfullerene‐based OPVs with the conventional device structure. This result indicates that NTz unit can be categorized as a potential electron‐deficient unit for the nonfullerene acceptors.     

Unsteady diffusional mass transfer at the sediment/water interface: Theory and significance for SOD measurement

Dissolved oxygen uptake at a sediment/water interface (SOD) is controlled by mass transport and/or biochemical reactions in two adjacent boundary layers: the diffusive boundary layer delta(D) in the water and the penetration depth delta in the sediment. Either one of those boundary layers or both can be controlling. The transition from sediment control to water control is a function of shear velocity at the sediment/water interface (U(*)) and biochemical activity rate (micro(0)) in the sediment. A model was developed for the unsteady response of SOD and DO profiles near the sediment/water interface. Michaelis-Menten kinetics were used initially, but zero order kinetics work just as well when the half saturation coefficient K(O(2)) is small as was suggested by field data. Beginning with zero DO in the sediments the times required to reach steady state DO profiles and SOD was on the order of minutes to hours, faster where biochemical activity is strong. The values of SOD estimated by the model were compared with experimental data to verify the reliability of the model. The model can reproduce observed penetration depths and diffusive boundary layer thickness. Values of SOD estimated by the model were of same magnitude as observed data. The unsteady DO uptake model can be used to provide guidance for field measurements of SOD. Placing a chamber (with a stirrer) into the sediments disturbs the DO equilibrium at the sediment/water interface. A new equilibrium will be reached within a time that can be measured in terms of cumulative DO consumption in the chamber (SOD exerted). Upper bounds for (SOD exerted) are larger when biochemical activity in the sediments is smaller. Values of SOD exerted are less than 0.1gm(-2) when micro(0) is less than 50mgl(-1)d(-1) and U(*)>0.1cm/s. In other words, steady state conditions are easier to reach for high SOD values. Actual times required to reach steady state can be from minutes to hours. If flow conditions in the chamber and at the natural sediment/water interface are much different, measured SOD values have to be adjusted. A procedure for the adjustments, which can be substantial, has been developed.     

In vivo rat subcutaneous tissue response of binder-free multi-walled carbon nanotube blocks cross-linked by de-fluorination

Binder-free multi-walled carbon nanotube (MWCNT) blocks from fluorinated MWCNTs were prepared using thermal heating and a compression method in vacuo. The resulting carbon nanotube blocks are lighter than graphite, can be machined and polished, possess average bending strengths of 102.2 MPa, a bending modulus of 15.4 GPa, and moderate wettability. The binder-free MWCNT blocks possess good biocompatibility when tested in the subcutaneous tissue of rats in vivo, which were covered by thin granulation tissue, 40-70 μm in thickness, comprising a few lymphocytes, cell with large cytoplasmic spaces like fibroblasts and foreign-body giant cells. That is indicative of a slight inflammatory response than MWCNT/resin blocks and poly(methyl methacrylate). This material can potentially be employed as an alternative artificial hard tissue or internal bone plate that makes use of the properties of CNTs.     

Rational design of minimal artificial Diels-Alderases based on the copper(II) cation-aromatic pi attractive interaction

We have designed a minimal artificial metalloenzyme that is prepared in situ from Cu(OTf) 2 or Cu(NTf 2) 2 (1.0 equiv) and L-DOPA-derived monopeptide (1.1 equiv) based on the cation-pi attractive interaction between copper(II) and the aromatic arm of the ligand, which is postulated on the basis of X-ray diffraction analysis and theoretical calculations. This catalyst (2-10 mol %) is highly effective for not only the enantioselective Diels-Alder reaction with alpha,beta-unsaturated 1-acyl-3,5-dimethylpyrazoles but also the enantioselective Mukaiyama-Michael reaction with these compounds. Products bearing a 3,5-dimethylpyrazolyl auxiliary may be transformed into a range of carboxylic acid derivatives, such as the corresponding carboxylic acids, esters, amides, alcohols, aldehydes, ketones, and beta-ketoesters, by known methods. The present results demonstrate that monopeptides are chirally economical and readily tunable ligands compared to bis(oxazoline)s, which have been reported to be notably useful ligands in various enantioselective reactions with bidentate electrophiles.     

Interspecific Variation of Floral Scent Composition in Glochidion and its Association with Host-specific Pollinating Seed Parasite (Epicephala)

Trees of the genus Glochidion (Phyllanthaceae) are pollinated by females of Epicephala moths (Gracillariidae) whose larvae consume the seeds of the flowers that they pollinate. Each Epicephala moth species is specific locally to a single host species, although two to four Glochidion hosts often cooccur. To investigate the role of olfactory signals in maintaining the plant−moth specificity, we analyzed floral scent composition of five Glochidion species by using gas chromatography–mass spectrometry (GC-MS) and conducted Y-tube olfactometer bioassays with Epicephala moths and their host flowers. The GC-MS analysis showed that the floral scents of the five Glochidion species are dominated by (R)-(−)- and (S)-(+)-linalool, and (E)- and (Z)-β-ocimene, and that each species produces 6–20 compounds. Transformation of scent profiles by using chord-normalized expected species shared distances and analysis of the data with nonmetric multidimensional scaling showed that floral volatiles of cooccurring Glochidion species can be distinguished by relative chemical composition, especially that of minor compounds. The bioassay with pollinators of Glochidion lanceolatum and Glochidion ruburm further indicated that Epicephala moths are capable of discriminating their hosts by using floral odor. The results suggest that the floral scent of Glochidion is one of the important key signals that mediate the encounters of the species-specific partners in the Glochidion–Epicephala mutualism.     

Ultralow-noise readout circuit with an avalanche photodiode: toward a photon-number-resolving detector

The charge-integration readout circuit was fabricated to achieve an ultralow-noise preamplifier for photoelectrons generated in an avalanche photodiode with linear mode operation at 77 K. To reduce the various kinds of noise, the capacitive transimpedance amplifier was used and consisted of low-capacitance circuit elements that were cooled with liquid nitrogen. As a result, the readout noise is equal to 3.0 electrons averaged for a period of 40 ms. We discuss the requirements for avalanche photodiodes to achieve photon-number-resolving detectors below this noise level.     

A large-area wireless power-transmission sheet using printed organic transistors and plastic MEMS switches

The electronics fields face serious problems associated with electric power; these include the development of ecologically friendly power-generation systems and ultralow-power-consuming circuits. Moreover, there is a demand for developing new power-transmission methods in the imminent era of ambient electronics, in which a multitude of electronic devices such as sensor networks will be used in our daily life to enhance security, safety and convenience. We constructed a sheet-type wireless power-transmission system by using state-of-the-art printing technologies using advanced electronic functional inks. This became possible owing to recent progress in organic semiconductor technologies; the diversity of chemical syntheses and processes on organic materials has led to a new class of organic semiconductors, dielectric layers and metals with excellent electronic functionalities. The new system directly drives electronic devices by transmitting power of the order of tens of watts without connectors, thereby providing an easy-to-use and reliable power source. As all of the components are manufactured on plastic films, it is easy to place the wireless power-transmission sheet over desks, floors, walls and any other location imaginable.     

What is a surrogate marker for optimal dialysis?

To find a surrogate marker to obtain optimal dialysis delivery from the viewpoint of nutrition, 180 maintenance hemodialysis patients (109 males/71 females) were enrolled between October 1999 and June 2006 at our kidney center. In the 449 hemodialysis treatments, ultrapure dialysis solutions and high-flux synthetic membranes were utilized. Parameters were measured by Kt/V(urea) and postdialysis urea rebound, Kc (the cellular membrane clearance for urea), urea clear space (CS), %creatinine generation rate, %lean body mass, total body water, and so on. We examined the correlation between dialysis delivery and nutritional parameters: Kt/V(urea) and postdialysis urea rebound were found to be strongly and negatively correlated with nutritional parameters. However, Kc and CS have shown positive and strong correlations with nutritional parameters such as %creatinine generation rate, %lean body mass, and total body water as well. In addition, the age factor was correlated with Kt/V(urea) positively, and it influenced Kc and CS negatively. As a conventional dialysis parameter, Kt/V(urea) did not reflect nutrition, but Kc was found to improve nutrition due to the increase of the dialysis delivery. Therefore, Kc might be a reliable surrogate marker for optimal dialysis.     

Physicochemical characterization of densely packed poly(ethylene glycol) layer for minimizing nonspecific protein adsorption

Modification of the surface with densely packed poly(ethylene glycol) (PEG) brush layer was studied to improve the protein repellent ability of the surface. A PEG-brushed layer was constructed on a gold substrate using a PEG possessing a mercapto group at the chain end. The density of the PEG brushed layer substantially increased with repetitive adsorption/rinse cycles of the PEG on the gold substrate, allowing dramatic reduction of nonspecific protein adsorption. Notably, formation of a short, filler layer of PEG (2 kDa) in the preconstructed longer PEG brushed layer (5 kDa) achieved high density brush and almost complete prevention of nonspecific protein adsorption. On the other hand, surface modification with only long PEG chain (5 kDa) showed lower PEG brush density regardless of repetitive immobilization. Detailed characterization of the PEGylated surface was done from the physicochemical (QCM, contact angle, and SPR) as well as the biological (protein adsorption) point of view to highlight the relation between the PEG brush density and the protein repellent ability. Densely packed PEG surface which showed great protein repellent ability, presented in this study, suggests promising utility as engineered biomaterials including high-throughput screening and clinical diagnostics.     

Optical Properties and Microstructure of Silver-Copper Nanoparticles Synthesized by Pulsed Laser Deposition

Utilizing a pulsed laser deposition (PLD) method, silver-copper (Ag-Cu) nanoparticles have been synthesized by changing the surface area ratio of the target (S _R = S _Cu/(S _Ag + S _Cu)) from 0 to 30%. The peak absorption attributed to surface plasmon resonance (SPR) increased when increasing S _R up to 15%, above which it decreased. The peak shifts seem to be induced by the changes in the conductivity and morphology of the Ag-Cu nanoparticles. Additionally, the interplanar spacings of the Ag-Cu nanoparticles prepared at S _R = 15% corresponded to the Ag {111}, {200}, {220}, and Cu {111} planes. However, since the interplanar spacings attributed to the Cu {200} and {220} planes were not detected, the Ag-Cu nanoparticles were believed to possess a lattice constant (a) close not to the Cu phase (a = 3.615 Å) but to the Ag phase (a = 4.086 Å). Moreover, confirming the presence of Cu atoms in the nanoparticles using energy dispersive X-ray (EDX) spectra, Ag-Cu nanoparticles may be a solid solution in which Cu atoms partially replace Ag atoms in the fcc structure.