Elements and organic substances in epiretinal proliferative tissue excised during vitreous surgery: analysis by time-of-flight secondary-ion mass spectrometry

We examined with time-of-flight secondary-ion mass spectrometry (TOF-SIMS) various substances in vitreous proliferative tissues excised from patients with proliferative diabetic retinopathy or proliferative vitreoretinopathy. Amounts of elements, vitamins and fatty acids were measured with TOF-SIMS and then the average ratio of the count of spattered ions of each element and organic substance to the total count of spattered ions was calculated. The average ratios of Fe, Ca, Al, Zn and Cu ion counts to the total count of spattered ions were significantly larger in proliferative diabetic retinopathy than in proliferative vitreoretinopathy. The average ratios of each of vitamin A fragment-1 and palmitic acid ion counts to the total count of spattered ions were significantly larger in proliferative diabetic retinopathy than in proliferative vitreoretinopathy. The fact that diabetic and non-diabetic preretinal proliferative tissues contain organic substances suggests that these proliferative tissues are derived from the retina, especially the deep retina, probably the photoreceptor cell and/or retinal pigment epithelium. The presence of Zn and Cu also suggest the same process. Diabetic proliferative tissues rich in organic substances are thought to grow more than do non-diabetic tissues, because vitamins A and E, and fatty acids are necessary for the maintenance of cell structure and the proliferation of tissue. Analysis of biological specimens by TOF-SIMS is expected to provide valuable information.     

Preparation of highly active Cr-catalysts for ethylene polymerization

A Cr(CH₃COO)₃ · (CH₃CO)₂O/MgCl₂/AlEt₂Cl/2-EHA catalyst was prepared by modifying the Battelle catalyst with MgCl₂ in 2-ethyl-1-hexanol(2-EHA), and the polymerization of ethylene was carried out in toluene at 20–60°C. The rate of polymerization increased to reach an individual stationary value during the course of polymerization, and the stationary rate markedly increased with an increase in the molar ratio of Mg/Cr. The polyethylene obtained without MgCl₂ had a rather low molecular weight with a very broad polydispersity, whereas those obtained in the presence of MgCl₂ had extremely high molecular weights with narrow polydispersities.Polymerization of ethylene was subsequently performed under similar conditions using various types of metal chlorides in place of MgCl₂. A clear relation was found between the polymerization activity and the electronegativity X(M^x+) of metal ion in Mclx:metal chlorides having the electronegativities below X(Cr²⁺) accelerated the activity, whereas those above X(Cr²⁺) retarded it. A plausible mechanism for the enhancement of the activity by metal chlorides was proposed on the basis of these results.     

The constitutive creep equation for a eutectic Sn-Ag alloy using the modified theta-projection concept

Creep data for a eutectic tin-silver alloy at temperatures between 298 K and 398 K have been analyzed using the modified theta-projection concept, instead of the steady-state creep constitutive equation in the following formula: ɛ_cr=A {1−exp(−αt)}+B {exp(αt)−1}, where A, B, and α are constants to be experimentally determined. The equation describes well the creep curves of the eutectic tin-silver alloy up to the tertiary stage. All constants exhibited power law relationships with the applied stress. The rate constant, α, has a high stress exponent, which is attributed to dispersion strengthening. The rate constant a and the strain factor B only showed temperature dependence, while the strain factor A was independent of temperature. The activation energy for α was 65 kJ/mol at high stresses and 90 kJ/mol at low stresses. The energies suggest that the dislocation pipe diffusion and the lattice diffusion are predominant at high stresses and low stresses, respectively.     

Helix sense of copoly(ethyl-l-aspartate-benzyl-l-aspartate)

Copoly(ethyl-L-aspartate-benzyl-L-aspartate)s with various compositions were prepared by ethylation of poly (β-benzyl-L-aspartate). Helix sense of copolyaspartates in chloroform solution was examined by optical rotatory dispersion and circular dichroism methods as a function of a degree of ethylation and temperature. Copolyaspartates of ethylation less than 35% exhibited the same left handed helix as that of poly (β-benzyl-L-aspartate), while copolymer of ethylation more than 70% assumed the right handed α-helical conformation like poly (β-ethyl-L-aspartate). Copolymers with the intermediate ethyl content of 35–70% indicated the reversal in helix sense from a right handed to a left handed helix with increasing temperature from ?20° to 60°C. The transition of reversal was reversibly observed and transition temperature rose with the increase of ethylation. In these intermediate copolymers, the mechanism of the reversal in helix sense was examined by circular dichroism and dielectric measurements. Three possibilities were postulated here for the conformation which should arise at the transition temperature of the reversal; First is the random conformation, second is the equimolar mixture of left and right handed α-helices in a chain, and the third is the equimolar mixture of left and right handed α helix chains. No observational circular dichroism spectra characteristic to random coil conformation and no remarkable change in residue dipole moment strongly suggested the third possibility.     

A high background rejection method in a proportional counter using field-adjusting electrodes as guard cathodes

A single anode single large cell counter, with veto-counters around it, is described. To get uniform response of the pulse height and the energy resolution, the counter has field-adjusting electrodes at the end walls of the anode wire, and these electrodes are also used to reject the background events which are caused by cosmic rays passing through near the end walls of the anode.A rocket flight experiment showed that the combination of rise time discrimination and anti-coincidence method reduced the cosmic ray induced background events to a level of 1.2×10^?4 counts s^?1 cm^?2 keV^?1 in the energy range of 2–40 keV, which represented an overall background reduction of 98% in this energy range.     

Dynamic behavior of a solid particle bed in a liquid pool: SIMMER-III code verification

Dynamic behavior of solid particle beds in a liquid pool against pressure transients was investigated to model the mobility of core materials in a postulated disrupted core of a liquid metal fast reactor. A series of experiments was performed with a particle bed of different bed heights, comprising different monotype solid particles, where variable initial pressures of the originally pressurized nitrogen gas were adopted as the pressure sources. Computational simulations of the experiments were performed using SIMMER-III, a fast reactor safety analysis code. Comparisons between simulated and experimental results show that the physical model for multiphase flows used in the SIMMER-III code can reasonably represent the transient behaviors of pool multiphase flows with rich solid phases, as observed in the current experiments. This demonstrates the basic validity of the SIMMER-III code on simulating the dynamic behaviors induced by pressure transients in a low-energy disrupted core of a liquid metal fast reactor with rich solid phases.     

Improved thermal and mechanical properties of poly(butylene succinate) by polymer blending with a thermotropic liquid crystalline polyester

A novel polymer blending system consisting of poly(butylene succinate) (PBS) and a thermotropic liquid crystalline polyester [LCP: a poly(4‐hydroxybenzoate)‐based polymer] was investigated in the presence and absence of a polycarbodiimide (PCD) and/or 1,1′‐carbonyl biscaprolactam (CBC) as chain extenders. Although the LCP was immiscible with PBS, it formed elongated fibrous domains having an orientation in the flowing direction when an extensional flow was applied during the processing. Scanning electron micrograph (SEM) of the injection‐molded polymer blends supported the distribution of micro fibrils of LCP in the PBS matrix by which the efficient toughening was provided. These blend specimens showed highly improved mechanical properties along with retaining high dynamic storage‐moduli (E′) up to the melting temperature of PBS. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39952.     

Figure tolerance of a Wolter type I mirror for a soft-x-ray microscope

The demand for an x-ray microscope has received much attention because of the desire to study living cells at a high resolution and in a hydrated environment. A Wolter type I mirror used for soft-x-ray microscope optics has many advantages. From the mirror fabrication point of view, it is necessary to perform tolerance analysis, particularly with respect to figure errors that considerably degrade the image quality. The figure tolerance of a Wolter type I mirror for a biological application in terms of the image quality and the state-of-the-art fabrication technology is discussed. The figure errors rapidly destroyed the image quality, and the required slope error depended on the detector used in the soft-x-ray microscope.