Tensile and Tensile-Mode Fatigue Testing of Microscale Specimens in Constant Humidity Environment

A tensile and tensile-mode-fatigue tester has been developed for testing microscale specimens in high humidity environments in order to investigate the fracture mechanisms of microelectromechanical materials. A humidity control system was installed on a tensile-mode fatigue tester equipped with an electrostatic force grip. A specimen and a griping device were inserted into a small chamber and the humidity was controlled by air flow from a temperature and humidity chamber. The humidity stability was within ±2%RH for humidities in the range 25–90%RH for eight hours of testing. Fatigue tests were performed on single-crystal silicon (SCS) specimens in constant humidity environments and laboratory air for up to 10⁶ cycles. The gauge length, width, and thickness of the SCS specimens were 100 or 500 μm, 13.0 μm, and 3.3 μm, respectively. The average tensile strength was 3.68 GPa in laboratory air; this value decreased in high humidity environments. Fatigue failure was observed during cyclic loading at stresses lower than the average strength. A reduction in the fatigue strength was observed at high relative humidities. Different fracture origins and fracture behaviors were observed in tensile tests and fatigue tests, which indicates that the water vapor in air affects the fatigue properties of SCS specimens.     

One-dimensional regular isotropic heisenberg antiferromagnetism in an organic radical p-diethylaminophenyl nitronyl nitroxide [DEAPNN]: Observation of spin-flop at high field

The magnetic properties of the organic radical p-diethylaminophenyl nitronyl nitroxide (DEAPNN; 2-(4'-diethylaminophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxy-3-N-oxide) have been investigated. The magnetization isotherms of DEAPNN measured up to 20.5 T at 1.7 and 4.2 K show a spin-flop phenomenon characteristic of one-dimensional regular isotropic Heisenberg antiferromagnetism. The magnetic susceptibility of DEAPNN is well interpreted by the Heisenberg antiferromagnetism in the whole temperature range of 2–300 K. The exchange coupling constant is determined to be J/k = -2.45 K based on the spin Hamiltonian H = -2JΣS_iS_{i + 1}.     

Triangle contraction in six-membered-ring silicon clusters

We propose the “triangle contraction” as an important reconstruction mechanism of six-membered-ring silicon clusters on the basis of the force and virial analysis for Si₆, Si₁₀, Si₁₄, Si₁₈, Si₂₂, and Si₂₆ clusters. Forces acting on atoms have been calculated using the local-density-functional scheme with linear-combination-of-atomic-orbitals-Xα method. Calculated forces show that most of the (111)-surface equilateral triangles have tendency to contract, indicating the generality of the triangle-contraction mechanism.     

Neutral K1(890) and ρ0 meson production in e+e− annihilation at ;s=29GeV

The production of neutral K¹(890) and ρ⁰ mesons was studied in e⁺e^? annihilation at $\text{s}\text{=29}\text{GeV}$ using the High Resolution Spectrometer at PEP. Differential cross sections are presented as a function of the scaled energy variable z and compared to π⁰ and K⁰ production. The measured multiplicities are 0.84±0.08 ?⁰ mesons and $\text{0.57±0.09 K}{}^{10}\text{(890)}$ mesons per event for a meson momentum greater than 725 MeV/c. The ratios of vector meson to pseudoscalar meson production for (u,d), s and c quark are compared to predictions of the Lund model.     

siRNA-mediated Knockdown of the Heme Synthesis and Degradation Pathways: Modulation of Treatment Effect of 5-Aminolevulinic Acid-based Photodynamic Therapy in Urothelial Cancer Cell Lines

Photodynamic therapy mediated by 5-aminolevulinic acid (ALA-PDT) has been developed as a therapeutic modality for refractory superficial bladder cancers. Here, in experiments using urothelial cancer cell lines, we investigated the effects of siRNA modulating heme-synthetic and degradation pathways for ALA-PDT. Targeted knockdown of ferrochelatase (FECH) suppressed heme synthesis and significantly increased intracellular protoporphyrin IX (PpIX) accumulation, leading to enhanced phototoxicity in four of five cell lines. Heme oxygenase-1 (HO-1) is recognized as important for cytoprotection against oxidative stress such as PDT. Targeted knockdown of HO-1 leads to decreased intracellular PpIX accumulation, resulting in a failure to enhance ALA-PDT effect in four cell lines. Knockdown of HO-1 caused marked growth inhibition in UM-UC-2 overexpressing HO-1, whereas no inhibitory effect was observed in UM-UC-3 lacking HO-1 expression. Moreover, HO-1 protein levels and (GT) _n repeat polymorphism of the HO-1 gene promoter region were examined with the implication that the constitutive expressions of HO-1 protein were associated with a shorter (GT) _n repeat. Our results suggested that (1) FECH siRNA improved the phototoxicity of ALA-PDT, (2) overexpression of HO-1 was associated with shorter (GT) _n repeat of the promoter region, and (3) siRNA-mediated knockdown of HO-1 could suppress the growth of bladder cancer cells overexpressing HO-1.     

Capacitive micromachined ultrasonic transducers with novel membrane design

This paper presents a novel membrane design for capacitive micromachined ultrasonic transducers (cMUTs). The proposed design is composed of a thick membrane with reinforcing beams supported by a circumferential thin membrane to improve transducer sensitivity without degrading the membrane resonance frequency. Analytical formulation of sensitivity for the proposed design was newly derived and its validity was verified by finite element analysis (FEA). From the analysis, we confirmed that this thick membrane structure achieved three times higher sensitivity compared to the conventional design by decreasing 70 % of the mass of the thick membrane part with keeping the resonance frequency same.     

Magnetic phase transitions in transition-metal complexes with triazole derivatives

Three divalent transition-metal (Co, Ni and Cu) complexes with the organic anion, 1,2,4-triazolato (tr), as a ligand molecule were prepared by means of hydrothermal syntheses and their magnetic properties were investigated by SQUID magnetometry. The Co(tr)₂ and Cu(tr)₂ complexes exhibit long range ordering below 8 and 30 K, respectively, while the Ni(tr)₂ complex does not show any magnetic phase transition down to 1.8 K. The magnetization isotherms of Co(tr)₂ and Cu(tr)₂ measured at 2.0 K show hysteresis loops with the coercive fields of 0.5 and 4.7 kOe, respectively. At temperatures higher than about 50 K, the temperature dependence of the magnetic susceptibility of Co(tr)₂, Ni(tr)₂ and Cu(tr)₂ follows the Curie-Weiss law with the Curie constants of 2.95, 0.945 and 0.420 emu K mol⁻¹ and the Weiss temperatures of −62, −74 and −97 K, respectively. These results suggest that the magnetically ordered phases observed in Co(tr)₂ and Cu(tr)₂ at low temperatures come from antiferromagnetic interactions resulting in canted arrangements of magnetic moments of the transition-metal cations. We discuss here the magnetic interactions in these transition-metal complexes by referring the results of the magnetization measurements.     

Extension to velocity dependent gauge transformations

In previous papers it was shown that in phase space a generator of gauge transformations for a singular Lagrangian \(L(q,\dot q)\) is given byG[ε^α]=ε _k ^α φ _α ^k (q,p,t) where φ _α ^k are first class constraints andG is subjected to a stationarity condition. A non-trivial extension from velocity (or momentum) independent gauge transformations to velocity dependent ones is realized, by replacing gauge functions ε^α(t) with momentum dependent functions ε^α(q,p,t), as long asG satisfies the stationarity condition. Inversely, it is proved in a classical framework that, within velocity dependent gauge transformations, all generators of gauge transformations can be expressed in terms of the linear combinations of φ _α ^k .