Simple and comprehensive two-dimensional reversed-phase HPLC using monolithic silica columns

Simple and comprehensive two-dimensional (2D)-HPLC was studied in a reversed-phase mode using monolithic silica columns for second-dimension (2nd-D) separation. Every fraction from the first column, 15 cm long (4.6-mm i.d.), packed with fluoroalkylsilyl-bonded (FR) silica particles, was subjected to the separation in the 2nd-D using one or two octadecylsilylated (C(18)) monolithic silica columns (4.6-mm i.d., 3 cm). Monolithic silica columns in the 2nd-D were eluted at a flow rate of up to 10 mL/min with separation time of 30 s that meets the fractionation every 15-30 s at the first dimension (1st-D) operated at a flow rate of 0.4-0.8 mL/min. Three cases were studied. (1) In the simplest scheme of 2D-HPLC, effluent of the 1st-D was directly loaded into an injector loop of 2nd-D HPLC for 28 s, and 2 s was allowed for injection. (2) Two six-port valves each having a sample loop were used to hold the effluent of the 1st-D alternately for 30 s for one 2nd-D column to effect comprehensive 2D-HPLC without the loss of 1st-D effluent. (3) Two monolithic silica columns were used for 2nd-D by using a switching valve and two sets of 2nd-D chromatographs separating each fraction of the 1st-D effluent with the two 2nd-D columns alternately. In this case, two columns of the same stationary phase (C(18)) or different phases, C(18) and (pentabromobenzyloxy)propylsilyl-bonded (PBB), could be employed at the 2nd-D, although the latter needed two complementary runs. The systems produced peak capacity of approximately 1000 in approximately 60 min in cases 1 and 2 and in approximately 30 min in case 3. The three stationary phases, FR, C(18), and PBB, showed widely different selectivity from each other, making 2D separations possible. The simple and comprehensive 2D-HPLC utilizes the stability and high efficiency at high linear velocities of monolithic silica columns.     

Study on chemical structures of poly (tetrafluoroethylene-co-perfluoroalkylvinylether) by soft-EB irradiation in solid and molten state

Poly (tetrafluoroethylene-co-perfluoroalkylvinylether) (PFA) was irradiated by soft electron beam (soft-EB) under nitrogen gas atmosphere in solid-state and its molten state, respectively. The changes of thermal property and chemical structures of irradiated PFA in solid-state and molten state were studied by differential scanning calorimetric analysis (DSC) and solid-state ¹⁹F magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. By DSC analysis, the melting temperature shifted to lower temperatures, and crystallinity decreased with increasing soft-EB dose. By solid-state ¹⁹F MAS NMR spectroscopy, the new signals was observed and the detected new signals in irradiated PFA at 315 °C and at 30 °C were due to the tertiary carbon group with branching site (Y-type crosslinking site), perfluoro-propylene site and chain end methylene groups, respectively.Moreover, the molar ratio of perfluoroalkylvinylether (FAVE) structure to -CF₂- units decreased with increasing dose.     

Optimal periodic maintenance strategy under an intermittently used environment

In this paper, the optimal periodic replacement-like strategy with minimal repairs is considered under an intermittently used environment. Suppose that transactions or jobs with exponential service times arrive at a system according to a homogeneous Poisson process and the system is alternatively in either a busy or an idle period subject to demand for use. We derive approximately the optimal preventive maintenance schedule which minimizes the relevant expected cost criterion for the system which behaves intermittently on an M/M/1 queueing process, and compare it with the usual maintenance schedule for the continuously used system.     

Rapid sensing of trace ionic substances with the novel porous monolith type ion exchanger

Biological and chemical sensor with a rapid response in microlevel test is required for health and environmental monitor. A novel sensing due to porous ion exchanger with three-dimensional acceptor has been first attempted to develop a high-performance sensor. This porous monolith type ion exchanger has an open-cellular monolith structure with 5–50-μm diameter pores. The trace amount of inorganic ions dissolved in aqueous solutions can be quantitatively determined with the impedance given by the monolith, which attracts and adsorbs the ions rapidly. We have succeeded in detecting ions with a concentration as low as 10⁻⁷ mol. The porous ion exchanger has a potentiality as a high-performance device for biological and chemical sensing. POLYM. ENG. SCI., 47:1666–1670, 2007. © 2007 Society of Plastics Engineers     

Site‐Selective Iron(III) Chloride‐Catalyzed Arylation of 4‐Aryl‐4‐methoxy‐2,5‐cyclohexadienones for the Synthesis of Polyarylated Phenols

The iron(III) chloride‐catalyzed Friedel–Crafts arylation of 4‐aryl‐4‐methoxy‐2,5‐cyclohexadienones, which were easily prepared by the phenyliodine(III) diacetate (PIDA)‐mediated oxidation of 4‐arylphenols in methanol, proceeded site‐selectively to form meta‐terphenyl (2,4‐diarylphenol) derivatives in good yields. The subsequent PIDA‐mediated oxidation and iron(III) chloride‐catalyzed Friedel–Crafts arylation of the resulting products gave the corresponding 2,4,6‐triarylphenol derivatives. The present method provides useful highly substituted polyarylated compounds.

     

Development of an MRI-compatible needle insertion manipulator for stereotactic neurosurgery

At the University of California, San Francisco, 17 patients who met the following criteria-hepatic tumor unresectable because of location or inadequate liver reserve, no metastases, HBsAg negative, no tumor larger than 5 cm in diameter, and no more than three tumors--were enrolled prospectively in a protocol employing preoperative chemoembolization to assess whether orthotopic liver transplantation (OLT) could cure a majority of highly selected patients with hepatocellular carcinoma (HCC). Thirteen patients had biopsy-proven HCC, 2 had the fibrolamellar variant, and 2 had radiological findings of HCC but no biopsy confirmation. Fourteen had underlying liver disease. All arteriographically apparent lesions were chemoembolized using a mixture including Gelfoam powder, doxorubicin, mitomycin-c, and cisplatin. Eight patients with poor hepatic reserve were chemoembolized when a donor organ became available, whereas 9 patients were chemoembolized and then placed on the waiting list. The only complication of chemoembolization was a gangrenous gallbladder in 1 patient. Thirteen patients underwent liver transplantation (2 patients without prior histological confirmation of carcinoma had no identifiable tumor at OLT); 3 patients developed metastases between the time of enrollment and donor organ availability and subsequently died; and 1 patient underwent a trisegmentectomy. Ten of the 11 patients with biopsy-proven HCC who underwent transplantation remain free of recurrent cancer at a median of 40 months; 1 patient died at 6 months of lymphoproliferative disease with no cancer found at autopsy. Although the role of chemoembolization is uncertain, these data show that the majority of carefully selected patients with HCC may achieve long-term survival with OLT.     

An explicit application of partition of unity approach to XFEM approximation for precise reproduction of a priori knowledge of solution

The application of the XFEM to fracture mechanics is effective, because a crack can be modeled independently from the meshes and a complex remeshing procedure can be avoided. However, the classical XFEM has an essential problem in the approximation of partially enriched elements, that is, blending elements, which causes a lack of accuracy. For the weighted XFEM, although the numerical results show the effective improvements, it was found that the issue of blending elements still remains upon detailed examination. In the present paper, the PU‐XFEM is formulated as an explicit application of the partition of unity (PU) approach to the XFEM, in order to precisely reproduce a priori knowledge of the solution by enrichment. The PU‐XFEM is applied to two‐dimensional linear fracture mechanics, and its effectiveness is verified. It is consequently found out that the PU‐XFEM precisely reproduces a priori knowledge of the solution and is therefore effective to completely solve the problem of the blending elements. Copyright © 2013 John Wiley & Sons, Ltd.     

Optimization of antireflection coating for VO2-based energy efficient window

Vanadium dioxide (VO₂) films have been proposed as energy efficient window coatings for their thermochromism, with which the solar energy transmission in the IR region may be controlled passively. These coatings suffer from low visible (or luminous) transmission (380–760 nm in wavelength), which hinders their practical uses. We here consider an antireflection (AR) coating for the VO₂-based window. Optical calculation was first performed upon a basic structure for thermochromic window composed of a VO₂ layer on glass with an AR layer of refractive index n and thickness d. Optimization was carried out on n and d for a maximum integrated luminous transmittance (T_lum). The calculation demonstrates that the optimal n value changes with thickness of VO₂, and at n≈2.2 it gives the highest T_lum enhancement from 32% (without AR coating) to 55% for 50-nm VO₂. Experiment was done on a structure of 50-nm VO₂ on quartz glass using ZrO₂, of which n≈2.2 matching the best n value, as AR coating. Formation of an optimized structure, ZrO₂ (56 nm)/VO₂ (50 nm)/quartz, was done by sputtering, and its optical properties were characterized with spectrophotometry. An improvement of T_lum from 32.3% to 50.5% was confirmed for the semiconductor phase with similarity also for the metallic one. The IR switching properties were not much deteriorated.