Effect of age on markers of bone metabolism in renal hemodialysis patients

Bone metabolic markers were investigated in the male hemodialysis patients within and over 60 years old and the female hemodialysis patients within and over 50 years old. Our results indicated that bone metabolic markers were more increased in the lower values of serum estradiol in the male patients, but inversely were more enhanced in higher values of serum estradiol in the female patients.     

Oxygen stability in YBa2Cu3O7−x

The highT _c superconductor YBa₂Cu₃O_7?x has been found to lose appreciable amount of oxygen in a surprisingly low temperature range (～425–630 K), which drastically degrades the superconducting property. Accompanying this oxygen loss, the resistance behaviour has also been found to change from metallic to semiconducting.     

The influence of spatial separation on divided listening

If spatial attention acts like a "spotlight," focusing on one location and excluding others, it may be advantageous to have all targets of interest within the same spatial region. This hypothesis was explored using a task where listeners reported keywords from two simultaneous talkers. In Experiment 1, the two talkers were placed symmetrically about the frontal midline with various angular separations. While there was a small performance improvement for moderate separations, the improvement decreased for larger separations. However, the dependency of the relative talker intensities on spatial configuration accounted for these effects. Experiment 2 tested whether spatial separation improved the intelligibility of each source, an effect that could counteract any degradation in performance as sources fell outside the spatial spotlight of attention. In this experiment, intelligibility of individual sources was equalized across configurations by adding masking noise. Under these conditions, the cost of divided listening (the drop in performance when reporting both messages compared to reporting just one) was smaller when the spatial separation was small. These results suggest that spatial separation enhances the intelligibility of individual sources in a competing pair but increases the cost associated with having to process both sources simultaneously, consistent with the attentional spotlight hypothesis.     

Electrochemical microfluidic biosensor for the detection of nucleic acid sequences

A microfluidic biosensor with electrochemical detection for the quantification of nucleic acid sequences was developed. In contrast to most microbiosensors that are based on fluorescence for signal generation, it takes advantage of the simplicity and high sensitivity provided by an amperometric and coulorimetric detection system. An interdigitated ultramicroelectrode array (IDUA) was fabricated in a glass chip and integrated directly with microchannels made of poly(dimethylsiloxane) (PDMS). The assembly was packaged into a Plexiglas housing providing fluid and electrical connections. IDUAs were characterized amperometrically and using cyclic voltammetry with respect to static and dynamic responses for the presence of a reversible redox couple-potassium hexacyanoferrate (ii)/hexacyanoferrate (iii) (ferri/ferrocyanide). A combined concentration of 0.5 microM of ferro/ferricyanide was determined as lower limit of detection with a dynamic range of 5 orders of magnitude. Background signals were negligible and the IDUA responded in a highly reversible manner to the injection of various volumes and various concentrations of the electrochemical marker. For the detection of nucleic acid sequences, liposomes entrapping the electrochemical marker were tagged with a DNA probe, and superparamagnetic beads were coated with a second DNA probe. A single stranded DNA target sequence hybridized with both probes. The sandwich was captured in the microfluidic channel just upstream of the IDUA via a magnet located in the outside housing. Liposomes were lysed using a detergent and the amount of released ferro/ferricyanide was quantified while passing by the IDUA. Optimal location of the magnet with respect to the IDUA was investigated, the effect of dextran sulfate on the hybridization reaction was studied and the amount of magnetic beads used in the assay was optimized. A dose response curve using varying concentrations of target DNA molecules was carried out demonstrating a limit of detection at 1 fmol assay(-1) and a dynamic range between 1 and 50 fmol. The overall assay took 6 min to complete, plus 15-20 min of pre-incubation and required only a simple potentiostat for signal recording and interpretation.     

Optimization of DNA-tagged dye-encapsulating liposomes for lateral-flow assays based on sandwich hybridization

A novel protocol for the synthesis of dye-encapsulating liposomes tagged with DNA oligonucleotides at their outer surface was developed. These liposomes were optimized for use as signal enhancement agents in lateral-flow sandwich-hybridization assays for the detection of single-stranded RNA and DNA sequences. Liposomes were synthesized using the reverse-phase evaporation method and tagged with oligonucleotides by adding cholesteryl-modified DNA probes to the initial lipid mixture. This resulted in a greatly simplified protocol that provided excellent control of the probe coverage on the liposomes and cut the preparation time from 16 hours to just 6 hours. Liposomes were prepared using probe concentrations ranging from 0.00077 to 0.152 mol% of the total lipid, several hydrophobic and polyethylene glycol-based spacers between the cholesteryl anchor and the probe, and liposome diameters ranging from 208 nm to 365 nm. The liposomes were characterized by dynamic light scattering, visible spectroscopy, and fluorescence spectroscopy. Their signal enhancement functionality was compared by using them in lateral-flow optical biosensors for the detection of single-stranded DNA sequences. In these assays, an optimal reporter probe concentration of 0.013 mol%, liposome diameter of 315 nm, and liposome optical density of 0.4–0.6 at 532 nm were found. The spacer length between the cholesteryl anchor and the probe showed no significant effect on the signals in the lateral-flow assays. The results presented here provide important data for the general use of liposomes as labels in analytical assays, with specific emphasis on nucleic acid detection via lateral flow assays.     

Optimization of DNA-tagged liposomes for use in microtiter plate analyses

Dye-encapsulating unilamellar DNA oligonucleotide-tagged liposomes were prepared and characterized for use as signal-enhancing reagents in a microtiter plate sandwich-hybridization analyses of single-stranded RNA or DNA sequences. The liposomes were synthesized using the reversed-phase evaporation method and tagged with DNA oligonucleotides by adding cholesteryl-modified DNA reporter probes to the initial lipid mixture. Liposomes were prepared using probe coverages of 0.0013–0.103 mol% of the total lipid input, several hydrophobic and poly(ethylene glycol)-based spacers between the cholesteryl anchor and the probe, and liposome diameters ranging from 200 nm to 335 nm. Their signal enhancement functionality was compared by using them in microtiter plate sandwich-hybridization assays for the detection of single-stranded DNA sequences. In these assays, an optimal reporter probe concentration of 0.103 mol%, a liposome diameter of 274 nm, and a phospholipid concentration of 0.3 mM were found. The length between the cholesteryl anchor and the probe was optimal when a spacer composed of TEG+(CH₂O)₃ was used. Under optimal conditions, a detection limit of 0.5 nM for a truncated synthetic DNA sequence was found with a coefficient of variation of 4.4%. A 500-fold lower limit of detection using fluorescence was found using lysed dye-encapsulating liposomes versus a single fluorescein-labeled probe. Finally, when this method was applied to the detection of atxA RNA extracted from E.coli SG12036-pIu121 and amplified using NASBA, a minimum extracted concentration of RNA of 1.1×10⁻⁷ μg/μL was found.     

Study of Neutron-Rich Hypernuclei by the (π −, K +) Reaction at J-PARC

We are planning to perform an experiment at J-PARC and produce new neutron-rich Λ hypernuclei by using the (π ^?, K ⁺) reaction (J-PARC E10). As the first step, we are planning to produce ${^6_{\Lambda}{\rm H}}$ hypernuclei with a ⁶Li target. To conduct this experiment, we are developing new detectors, those are scintillating fiber tracker, and silicon strip detector, for high rate operation to aim at increasing beam intensity up to 10⁷/spill. As a result of beam test in Jun 2012, we are going to use high-rate beam at least 10⁷/spill.