Dendritic effects on the ordered assembly and the interfacial one-electron oxidation of redox-active dendron-functionalized gold nanoparticles

A higher generation dendron with a long-alkyl chain thiol (DA2-SH) induced the formation of nanoparticles with a small core with quite a narrow size distribution (1.5 +/- 0.1 nm), the self-assembly of one-dimensional arrays of these gold nanoparticles (DA2-Au), and the stabilization for the formation of the radical cation of the phenothiazine of DA2-Au nanoparticles from the interfacial one-electron oxidation of the nanoparticles with NOBF4.     

Adaptive echolocation sounds of insectivorous bats, Pipistrellus abramus, during foraging flights in the field

Echolocation pulses emitted by wild Pipistrellus abramus were investigated while foraging for insects in the field. Similar to other European pipistrelles, the frequency structure during foraging varied. During the search phase, the bats emitted long shallow frequency-modulated pulses 9-11 ms in duration, whereas the maximum pulse duration of the bats approaching a large target wall in the laboratory was 3 ms. No significant difference was observed between decreases in the interpulse interval during these two approach flights. It is concluded that the bats use a long quasi-constant frequency pulse to find a weak echo from a small prey target.     

On the Upper Bound of Some Geometric Constants of Absolute Normalized Norms on $${\mathbb{R}^2}$$

This is a continuation of the paper (Mizuguchi and Saito, Ann Funct Anal 2:22–33, 2011). We consider the Banach space \({X=(\mathbb{R}^2, \|\cdot\|)}\) with a normalized, absolute norm. We treat three geometric constants; the von Neumann–Jordan constant C _NJ(X), the modified von Neumann–Jordan constant \({C^{\prime}_{\rm NJ}(X)}\) and the Zb?ganu constant C _Z (X). We consider the conditions in which these constants coincide with their upper bound.     

Estimation of dye configuration from conventional chiroptical spectra of porphyrin integrates: combination of exciton theory with Monte Carlo molecular structural simulation

Dye integrates (arrays and aggregates) are the subject of current interest in photochemical devices. However, they are in general not suitable for X-ray crystallography because of their poor crystallinity. Here, we improved a simple method of estimating dye configurations in porphyrin integrates from their visible absorption (AB) and circular dichroism (CD) spectra. For this purpose, we calculate the dipolar and optical rotatory strengths of an integrate on the basis of the exciton theory for a given porphyrin configuration, generate the theoretical AB and CD spectra of the dye integrate using a phenomenological line shape function, a Voigt function with an adjustable line width, and optimize the configuration by minimizing the square sum (S) of the difference between the observed and calculated spectra. We adopted two optimization methods to achieve a least-squares fit between the calculated and observed spectra: the Metropolis Monte Carlo (MC) method, which incorporates S into the molecular force-field energy as a constraint, and the quasi-Newton (QN) method, which numerically minimizes S and uses no molecular force field. To check the feasibility of these methods, we simulated the AB and CD spectra of Tr?ger's base and meso-meso-linked porphyrins using the QN program, then compared the dye configurations with their X-ray structures. The calculated dye configuration of Tr?ger's base porphyrin is sufficiently in agreement with that of the X-ray structure (RMSD=0.21 A for the ZnS4 center), whereas that of meso-meso-linked porphyrin was not. These results were discussed in terms of charge transfer between two porphyrins. Finally, we applied the QN and MC methods to the structural estimation of a newly prepared peptide-linked bis(porphyrin) Boc-(PorZn,S)2-OBut. The best configurations estimated by these two methods were sufficiently in agreement with each other.     

Echo-intensity compensation in echolocating bats (Pipistrellus abramus) during flight measured by a telemetry microphone

An onboard microphone (Telemike) was developed to examine changes in the basic characteristics of echolocation sounds of small frequency-modulated echolocating bats, Pipistrellus abramus. Using a dual high-speed video camera system, spatiotemporal observations of echolocation characteristics were conducted on bats during a landing flight task in the laboratory. The Telemike allowed us to observe emitted pulses and returning echoes to which the flying bats listened during flight, and the acoustic parameters could be precisely measured without traditional problems such as the directional properties of the recording microphone and the emitted pulse, or traveling loss of the sound in the air. Pulse intensity in bats intending to land exhibited a marked decrease by 30 dB within 2 m of the target wall, and the reduction rate was approximately 6.5 dB per halving of distance. The intensity of echoes returning from the target wall indicated a nearly constant intensity (-42.6 +/- 5.5 dB weaker than the pulse emitted in search phase) within a target distance of 2 m. These findings provide direct evidence that bats adjust pulse intensity to compensate for changes in echo intensity to maintain a constant intensity of the echo returned from the approaching target at an optimal range.     

A protocol for searching the most probable phase‐retrieved maps in coherent X‐ray diffraction imaging by exploiting the relationship between convergence of the retrieved phase and success of calculation

Coherent X‐ray diffraction imaging (CXDI) is a technique for visualizing the structures of non‐crystalline particles with size in the submicrometer to micrometer range in material sciences and biology. In the structural analysis of CXDI, the electron density map of a specimen particle projected along the direction of the incident X‐rays can be reconstructed only from the diffraction pattern by using phase‐retrieval (PR) algorithms. However, in practice, the reconstruction, relying entirely on the computational procedure, sometimes fails because diffraction patterns miss the data in small‐angle regions owing to the beam stop and saturation of the detector pixels, and are modified by Poisson noise in X‐ray detection. To date, X‐ray free‐electron lasers have allowed us to collect a large number of diffraction patterns within a short period of time. Therefore, the reconstruction of correct electron density maps is the bottleneck for efficiently conducting structure analyses of non‐crystalline particles. To automatically address the correctness of retrieved electron density maps, a data analysis protocol to extract the most probable electron density maps from a set of maps retrieved from 1000 different random seeds for a single diffraction pattern is proposed. Through monitoring the variations of the phase values during PR calculations, the tendency for the PR calculations to succeed when the retrieved phase sets converged on a certain value was found. On the other hand, if the phase set was in persistent variation, the PR calculation tended to fail to yield the correct electron density map. To quantify this tendency, here a figure of merit for the variation of the phase values during PR calculation is introduced. In addition, a PR protocol to evaluate the similarity between a map of the highest figure of merit and other independently reconstructed maps is proposed. The protocol is implemented and practically examined in the structure analyses for diffraction patterns from aggregates of gold colloidal particles. Furthermore, the feasibility of the protocol in the structure analysis of organelles from biological cells is examined.     

Magnetic properties and domain structures of FeSiB thin films

Smooth Fe₇₈Si₁₀B₁₂ thin films were prepared by r.f. sputtering with the very slow deposition rate of 0.59 nm/min. The as-deposited films were not fully amorphous, instead α-Fe(Si) nanocrystallites were found to be embedded in the amorphous matrix. The saturation magnetostriction λ_s of the as-deposited film is about 6.5 × 10⁻⁶. After annealing at 540 °C for 1 h in an ultrahigh vacuum (4.5 × 10⁻⁵ Pa), the fraction of α-Fe(Si) crystalline phase largely increased, and correspondingly the λ_s decreased to 4.5 × 10⁻⁷. Ripple domain structures were observed in the as-deposited film, while dense stripe domains were observed in the annealed sample, characterized by a very narrow domain width of 80 nm. (1 1 0) texture and island-like configuration of α-Fe(Si) nanocrystallites formed by the annealing treatment are responsible for the perpendicular anisotropy. For the as-deposited film, the magnetization curves increased linearly with the increase of the magnetic field, and showed the very small hysteresis. On the other hand, the annealed sample clearly showed a very steep jump near the origin, which is due to the switch process of the dense stripe domain.     

Visible-Light-Induced Synthesis of 1,2,3,4-Tetrahydroquinolines through Formal [4+2] Cycloaddition of Acyclic α,β-Unsaturated Amides and Imides with N,N-Dialkylanilines

1,2,3,4-Tetrahydroquinolines should be applicable to the development of new pharmaceutical agents. A facile synthesis of 1,2,3,4-tetrahydroquinolines that is achieved by a photoinduced formal [4+2] cycloaddition reaction of acyclic α,β-unsaturated amides and imides with N,N-dialkylanilines under visible-light irradiation, in which a new Ir^III complex photosensitizer, a thiourea, and an oxidant act cooperatively in promoting the reaction, is reported. The photoreaction enables the synthesis of a wide variety of 1,2,3,4-tetrahydroquinolines, while controlling the trans/cis diastereoselectivity (>99:1) and constructing contiguous stereogenic centers. A chemoselective cleavage of an acyclic imide auxiliary is demonstrated.