Single-shot microscopic electron imaging of intense femtosecond laser-produced plasmas

A simple technique for single-shot microscopic electron imaging was demonstrated for the study of intense femtosecond laser-produced plasmas. Passed through a permanent magnet lens designed for 110-keV electrons, hot electrons emitted from the plasma produced by a single laser pulse of 0.8 mJ with intensity of 3 × 10(16) W/cm(2) were successfully imaged. Analyzing this image, we found that electrons were emitted from an area of 3 μm in diameter. At higher laser intensity of 10(18) W/cm(2), distinct structures were observed in and near the focal spot of the laser; that is, the electrons were emitted from several separate spots. These results show that laser-plasma electron imaging is promising for studying the interactions of femtosecond lasers with high-density plasmas.     

A DNA duplex with extremely enhanced thermal stability based on controlled immobilization on gold nanoparticles

The effect of DNA loadings on the thermal stability of DNA duplex immobilized on gold nanoparticles has been investigated. The modestly loaded duplexes on the gold nanoparticles showed enhanced thermal stability, as compared to that of the free duplex (without gold nanoparticles). However, the highly loaded duplex showed stability similar to that of free duplex. The stability could be controlled over a wide temperature range simply by varying the salt concentration (over 50 degrees C). Additionally, the gold nanoparticles with modestly loaded oligonucleotides could be used as nanoprobes for effective and fast strand exchange reactions, based on the increased thermal stability of the immobilized duplex. These results indicate that the interaction between the duplex and the nanoparticle surface plays an important role in determining the stability of the duplex.     

High-intensity laser-driven particle and electromagnetic wave sources for science, industry, and medicine

We simultaneously observed both the fast proton generation and terahertz (THz) radiation in the laser pulse interaction with a thin-foil target.The maximum proton energy of ～2.3 MeV and an intense THz radiation were observed at the pulse duration of ～30fs.We also measured the proton beam and UV harmonics from a thin-foil target by changing the laser pulse duration.In the case of the ～500 fs, peaks of UV harmonics up to fourth order appeared.This unique combination of the multiple beams will provide useful applications such as pump-probe experiments.     

Physicochemical state of the nanotopographic surface of commercially pure titanium following anodization-hydrothermal treatment reveals significantly improved hydrophilicity and surface energy profiles

A method of coating commercially pure titanium (cpTi) implants with a highly crystalline, thin hydroxyapatite (HA) layer using discharge anodic oxidation followed by hydrothermal treatment (Spark discharged Anodic oxidation treatment ; SA-treated cpTi) has been reported for use in clinical dentistry. We hypothesized that a thin HA layer with high crystallinity and nanostructured anodic titanium oxide film on such SA-treated cpTi implant surfaces might be a crucial function of their surface-specific potential energy. To test this, we analyzed anodic oxide (AO) cpTi and SA-treated cpTi disks by SEM and AFM. Contact angles and surface free energy of each disk surface was measured using FAMAS software. High-magnification SEM and AFM revealed the nanotopographic structure of the anodic titanium oxide film on SA-treated cpTi; however, this was not observed on the AO cpTi surface. The contact angle and surface free energy measurements were also significantly different between AO cpTi and SA-treated cpTi surfaces (Tukey's, P < 0.05). These data indicated that the change of physicochemical properties of an anodic titanium oxide film with HA crystals on an SA-treated cpTi surface may play a key role in the phenomenon of osteoconduction during the process of osseointegration.     

Progress and perspective of perfluorinated compound risk assessment and management in various countries and institutes

Perfluorooctane sulfonate (PFOS) and related compounds have recently been designated as target chemicals for regulation by the Stockholm Convention on Persistent Organic Pollutants (POPs). Many countries have investigated and tried to implement various countermeasures in response to this decision. In this article, we collect reports concerning regulations and risk evaluations of perfluorinated compounds (PFCs) and review the current PFC management practiced in various countries. The first part of this review contains a comprehensive collection of proposed standard PFC values, including provisional tolerable daily intakes (pTDI), drinking water guidelines, and predicted non-effect concentrations (PNEC). The pTDI values ranged from 0.1 to 0.3 μg/kg/day for PFOS, and there are wide margins of safety for adults. Health risks for plant workers exposed to PFCs and for infants are of particular concern. The application of these proposed values in controlling PFC pollution is one approach that may effectively control human health risk without unduly sacrificing the benefits from PFC use. The second part of this review contains a collection and review of a number of regulations and countermeasures, such as an EU directive, regulation in Canada, and the Significant New Use Rule (SNUR), including voluntary control (i.e., production phase-out by 3M, stewardship programs, regulation in the semiconductor industry). Most of these regulations are based principally on the precautionary principle. However, they may not be as effective in pollution reduction as intended because the chemicals in question are already widely distributed in the environment owing to their use and mobility in the environment. In addition, these types of regulations would be non-operative in developing countries because rapidly growing economies place great demand on high performance materials, including PFCs. Further development of risk assessment methods that allow the evaluation of the counter risks of PFC alternatives and the loss of benefits from the PFC ban is necessary because of the possible continuous use of PFCs, especially in developing countries.     

Capacity Fading Mechanism in All Solid‐State Lithium Polymer Secondary Batteries Using PEG‐Borate/Aluminate Ester as Plasticizer for Polymer Electrolytes

Solid‐state lithium polymer secondary batteries (LPB) are fabricated with a two‐electrode‐type cell construction of Li|solid‐state polymer electrolyte (SPE)|LiFePO₄. Plasticizers of poly(ethylene glycol) (PEG)‐borate ester (B‐PEG) or PEG‐aluminate ester (Al‐PEG) are added into lithium‐conducting SPEs in order to enhance their ionic conductivity, and lithium bis‐trifluoromethansulfonimide (LiTFSI) is used as the lithium salt. An improvement of the electrochemical properties is observed upon addition of the plasticizers at an operation temperature of 60 °C. However, a decrease of discharge capacities abruptly follows after tens of stable cycles. To understand the origin of the capacity fading, electrochemical impedance techniques, ex‐situ NMR and scanning electron microscopy (SEM)/energy dispersive X‐ray spectroscopy (EDS) techniques are adopted. Alternating current (AC) impedance measurements indicate that the decrease of capacity retention in the LPB is related to a severe increase of the interfacial resistance between the SPE and cathode. In addition, the bulk resistance of the SPE film is observed to accompany the capacity decay. Ex situ NMR studies combined with AC impedance measurements reveal a decrease of Li salt concentration in the SPE film after cycling. Ex situ SEM/EDS observations show an increase of concentration of anions on the electrode surface after cycling. Accordingly, the anions may decompose on the cathode surface, which leads to a reduction of the cycle life of the LPB. The present study suggests that a choice of Li salt and an increase of transference number is crucial for the realization of lithium polymer batteries.     

Occurrence of estrogenic compounds in and removal by a swine farm waste treatment plant

The total estrogenic activity of the wastewater from a swine farm in Japan was quantitatively characterized, and the compounds responsible for the estrogenic activity were identified and quantified. The wastewater treatment process consisted of a series of an up-flow anaerobic sludge blanket (UASB) and a trickling filter. Samples were collected at each treatment step, and the total estrogenic activity was determined by use of an in vitro gene expression assay (MVLN; MCF-7 human breast cancer cell stably transfected with the pVit-tk-LUC receptor plasmid). Individual estrogenic compounds were identified and quantified using liquid chromatography-mass spectrometry (LC/MS) and liquid chromatography-tandem mass spectrometry (LC/ MS/MS). To further identify the compounds contributing to the estrogenic activity in the wastewater, the sample extracts were fractionated into 12 fractions (fractions 1-12) by HPLC. The rate of removal of estrogenic activity between the effluent and the influent was greater than 97%. The trickling filter removed the majority of the estrogenic activity. The removal rates of specific estrogenic compounds ranged from 44 to 99%. Estrogenic activity was detected mainly in the fractions containing estrone (El), 17beta-estradiol (betaE2), 17alpha-estradiol (alpha E2), estriol (E3), bisphenol A (alphaPA), and equol (EQ0). The ratios of betaE2-EQc (betaE2 equivalents derived from chemical analysis) to betaE2-EQB (betaE2 equivalent derived from bioassay) in the 12 fractions collectively were contributed by El (17-30%), betaE2 (23-30%), acE2 (<1%), E3 (1-2%), BPA (<1%), and EQO (2-3%) in the influent and El (16-37%), PE2 (<1-7%), alphaE2 (<1%), E3 (<1-3%), BPA (<1%), and EQO (<1%) in the effluent. The compounds responsible for most of the estrogenic activity measured in the bioassay were natural estrogens such as El and betaE2.     

CONVECTIONAL MODE AND ELECTRICAL FIELD IN SILICON MELTS UNDER VERTICAL,HORIZONTAL, AND ROTATING MAGNETIC FIELDS

Numerical computations were carried out to study a convectional mode and an electrical field in silicon melts in a cylindrical container that is sufficiently long in an axial direction under various magnetic fields. Under both no and vertical magnetic fields, the fluid represented a rigid rotation. Under a horizontal magnetic field, flow in the circumferential direction was suppressed strongly. Under a rotating magnetic field, fluid rotated with the rotational rate of a magnetic field when the rotational rate of a magnetic field and that of a container were different. These flow patterns could be successfully explained by considering an electric field.