Thermally Controlled Construction of Fe-Nx Active Sites on the Edge of a Graphene Nanoribbon for an Electrocatalytic Oxygen Reduction Reaction.

Pyrolytically prepared iron and nitrogen codoped carbon (Fe/N/C) catalysts are promising nonprecious metal electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell applications. Fabrication of the Fe/N/C catalysts with Fe-Nx active sites having precise structures is now required. We developed a strategy for thermally controlled construction of the Fe-Nx structure in Fe/N/C catalysts by applying a bottom-up synthetic methodology based on a N-doped graphene nanoribbon (N-GNR). The preorganized aromatic rings within the precursors assist graphitization during generation of the N-GNR structure with iron-coordinating sites. The Fe/N/C catalyst prepared from the N-GNR precursor, iron ion, and the carbon support Vulcan XC-72R provides a high onset potential of 0.88 V (vs reversible hydrogen electrode (RHE)) and promotes efficient four-electron ORR. X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS) studies reveal that the N-GNR precursor induces the formation of iron-coordinating nitrogen species during pyrolysis. The details of the graphitization process of the precursor were further investigated by analyzing the precursors pyrolyzed at various temperatures using MgO particles as a sacrificial template, with the results indicating that the graphitized structure was obtained at 700 °C. The preorganized N-GNR precursors and its pyrolysis conditions for graphitization are found to be important factors for generation of the Fe-Nx active sites along with the N-GNR structure in high-performance Fe/N/C catalysts for the ORR.

Bimetallic M/N/C catalysts prepared from π-expanded metal salen precursors toward an efficient oxygen reduction reaction.

Nonprecious metal electrocatalysts are being explored as alternatives to platinum-group metal electrocatalysts for the oxygen reduction reaction (ORR) which is required for cathode materials in fuel cells. Herein, we describe a new method for preparing bimetallic nitrogen-containing carbon catalysts with high ORR activity using π-expanded M(salen) precursors. The M/N/C and bimetallic FeM/N/C ORR catalysts were obtained by pyrolysis of a mixture of a carbon support (Vulcan XC-72R) and the metal complex as a precursor. The bimetallic FeCu catalyst prepared from Fe and Cu complexes with the N,N'-bis(2-hydroxy-1-naphthylidene)-1,2-phenylenediamine ligand (2NAPD) is found to have an onset potential of 0.87 V, which is positively shifted by 50 mV from that of the catalyst prepared from the monometallic Fe(2NAPD) complex. The FeCu/N/C catalyst promotes efficient four-electron reduction in the ORR. High-resolution transmission electron microscopy studies reveal that both Fe and Cu metals together with pyridinic nitrogen species are highly dispersed within the carbonaceous structure in FeCu/2NAPD@VC, suggesting that the N-coordinated Fe and Cu sites promote efficient four-electron reduction of O2. This new methodology facilitates design of nonprecious bimetallic carbon catalysts with excellent ORR activity.

Immunoglobulin binding (B1) domain mediated antibody conjugation to quantum dots for in vitro and in vivo molecular imaging.

A facile method for the preparation of antibody-quantum dot (QD) conjugates using the immunoglobulin binding (B1) domain of protein G is presented. The utility of antibody-QD conjugates using the B1 domain is demonstrated for fluorescence imaging of breast tumor cells in vitro and in vivo.

The Impact of the Polymer Chain Length on the Catalytic Activity of Poly(N-vinyl-2-pyrrolidone)-supported Gold Nanoclusters.

Poly(N-vinyl-2-pyrrolidone) (PVP) of varying molecular weight (M w = 40-360 kDa) were employed to stabilize gold nanoclusters of varying size. The resulting Au:PVP clusters were subsequently used as catalysts for a kinetic study on the sized-dependent aerobic oxidation of 1-indanol, which was monitored by time-resolved in situ infrared spectroscopy. The obtained results suggest that the catalytic behaviour is intimately correlated to the size of the clusters, which in turn depends on the molecular weight of the PVPs. The highest catalytic activity was observed for clusters with a core size of ~7 nm, and the size of the cluster should increase with the molecular weight of the polymer in order to maintain optimal catalytic activity. Studies on the electronic and colloid structure of these clusters revealed that the negative charge density on the cluster surface also strongly depends on the molecular weight of the stabilizing polymers.

Decreased Defibrillation Threshold and Minimized Myocardial Damage With Left Axilla Implantable Cardioverter Defibrillator Implantation.

BACKGROUND: To reduce myocardial damage caused by implantable cardioverter defibrillator (ICD) shock, the left axilla was studied as an alternative pulse generator implantation site, and compared with the traditional implantation site, the left anterior chest. METHODS AND RESULTS: Computer simulation was used to study the defibrillation conduction pattern and estimate the simulated defibrillation threshold (DFT) and myocardial damage when pulse generators were placed in the left axilla and left anterior chest, respectively; pulse generators were also newly implanted in the left axilla (n=30) and anterior chest (n=40) to compare the corresponding DFT. On simulation, when ICD generators were implanted in the left axilla, compared with the left anterior chest, the whole heart may be defibrillated with a lower defibrillation energy (left axilla 6.4 J vs. left anterior chest 12.0 J) and thus the proportion of cardiac myocardial damage may be reduced (2.1 vs. 4.2%). Clinically, ventricular fibrillation was successfully terminated with a defibrillation output ≤5 J in 86.7% (26/30) of the left axillary group, and in 27.5% (11/40) of the left anterior group (P<0.001). CONCLUSIONS: Clinically and theoretically, the left axilla was shown to be an improved ICD implantation site that may reduce DFT and lessen myocardial damage due to shock. Lower DFT also facilitates less myocardial damage, as a result of the lower shock required.

Efficacy and Myocardial Injury With Subcutaneous Implantable Cardioverter Defibrillators　- Computer Simulation of Defibrillation Shock Conduction.

BACKGROUND: Subcutaneous implantable cardiac defibrillator (S-ICD) systems have a lower invasiveness than traditional ICD systems, and expand the indications of ICD implantations. The S-ICD standard defibrillation shock output energy, however, is approximately 4 times that of the traditional ICD system. This raises concern about the efficacy of the defibrillation and myocardial injury. In this study, we investigated the defibrillation efficacy and myocardial injury with S-ICD systems based on computer simulations. METHODS AND RESULTS: First, computer simulations were performed based on the S-ICD system configurations proposed in a previous study. Furthermore, simulations were performed by placing the lead at the left or right parasternal margin and the pulse generator in the superior and inferior positions (0-10 cm) of the recommended site. The simulated defibrillation threshold (DFT) for the 4 S-ICD system configurations were 30.1, 41.6, 40.6, and 32.8 J, which were generally similar to the corresponding clinical results of 33.5, 40.4, 40.1, and 34.3 J. CONCLUSIONS: The simulated DFT were generally similar to their clinical counterparts. In the simulation, the S-ICD system had a higher DFT but relatively less severe myocardial injury compared with the traditional ICD system. Further, the lead at the right parasternal margin may correspond to a lower DFT and cause less myocardial injury.

Evaluation of defibrillation safety and shock reduction in implantable cardioverter-defibrillator patients with increased time to detection: A randomized SANKS study.

BACKGROUND: The need for ways to minimize the number of implantable cardioverter-defibrillator (ICD) shocks is increasing owing to the risk of its adverse effects on life expectancy. Studies have shown that a longer detection time for ventricular tachyarrhythmia reduces the safety of therapies, in terms of syncope and mortality, but not substantially in terms of the success rate. We aimed to evaluate the effects of increased number of intervals to detect (NID) VF on the safety of ICD shock therapy and on the reduction of inappropriate shocks. METHODS: The present study was a prospective, multicenter, randomized, crossover study. Randomized VF induction testing with NID 18/24 or 30/40 was performed to compare the success rate of defibrillation with a 25-J shock and the time to detection. Inappropriate shock episodes were simulated retrospectively to evaluate a possibility of episodes avoidable at NID 24/32 and 30/40. RESULTS: Thirty-one consecutive patients implanted with an ICD or cardiac resynchronization therapy-defibrillator (CRT-D) were enrolled in this study. The success rate of defibrillation was 100% in both NID groups at the first shock. The time from VF induction to detection showed a significant increase in the NID 30/40 group (6.16±1.29 s vs. 9.00±1.31 s, p<0.001). Among the 120 patients implanted with an ICD or CRT-D, 10 experienced 32 inappropriate shock episodes. The inappropriate shock reduction rate was 53.1% and 62.5% with NID 24/32 and 30/40, respectively. CONCLUSIONS: The findings of this SANKS study suggest that VF NID 30/40 does not compromise the safety of ICD shock therapy, while decreasing the number of inappropriate shocks.

Simple observation of Streptococcus mutans biofilm by scanning electron microscopy using ionic liquids.

Scanning electron microscopy (SEM) has been successfully used to image biofilms because of its high resolution and magnification. However, conventional SEM requires dehydration and metal coating of biological samples before observation, and because biofilms consist mainly of water, sample dehydration may influence the biofilm structure. When coated with an ionic liquid, which is a kind of salt that exists in the liquid state at room temperature, biological samples for SEM observation do not require dehydration or metal coating because ionic liquids do not evaporate under vacuum conditions and are electrically conductive. This study investigates the ability of ionic liquids to allow SEM observation of Streptococcus mutans biofilms compared with conventional coating methods. Two hydrophilic and two hydrophobic ionic liquids, all of which are electronic conductors, are used. Compared with samples prepared by the conventional method, the ionic-liquid-treated samples do not exhibit a fibrous extracellular matrix structure and cracking on the biofilm surface. The hydrophilic ionic liquids give clearer images of the biofilm structure than those of the hydrophobic ionic liquids. This study finds that ionic liquids are useful for allowing the observation of biofilms by SEM without preparation by dehydration and metal coating.

Recombinant protein (EGFP-Protein G)-coated PbS quantum dots for in vitro and in vivo dual fluorescence (visible and second-NIR) imaging of breast tumors.

We report a one-step synthetic strategy for the preparation of recombinant protein (EGFP-Protein G)-coated PbS quantum dots for dual (visible and second-NIR) fluorescence imaging of breast tumors at the cellular and whole-body level.

Left axillary pacemaker generator implantation with a direct puncture of the left axillary vein.

BACKGROUND: Pacemaker generators are routinely implanted in the anterior chest. However, where to place the generator may need to be considered from the mental, functional, and cosmetic standpoints. METHODS: In this study, we performed the left axillary pacemaker generator implantation with a direct puncture of the left axillary vein in 40 consecutive patients, and evaluated the late safety and efficacy of this implantation. Complications, changes in the lead sensing, pacing threshold, and impedance were used as safety indexes for a mean follow-up of 3.4 years. In addition, the efficacy was also evaluated by comparing their questionnaire survey results to 119 patients in a control group of anterior chest implantation. RESULTS: Lead dislodgements were observed in two patients of the experiment group. There were no migrations of generators from the implantation site or abnormal variations in the pacing threshold, lead sensing, or impedance. In the left anterior chest and left axillary groups, 85% and 10% of the patients were worried about an external impact, 80% and 25% were worried about electromagnetic interference, and 68% and 0% answered that the pacemaker implantation site was noticeable, respectively. Apparently, more patients had a sense of security and cosmetic satisfaction with the left axillary implantation. CONCLUSION: The left axillary generator implantations may reduce the mental burden and cause no safety concerns, and may be performed if functional or cosmetic outcomes are required.

Ratiometric MRI sensors based on core-shell nanoparticles for quantitative pH imaging.

Ratiometric MRI sensors consist of paramagnetic cores and pH-sensitive polymer shells. The core-shell nanostructure enables the coexistence of two incompatible NMR relaxation properties in one particle. The sensors show pH sensitivity in transverse relaxivity (r2 ), but not in longitudinal relaxivity (r1 ). Quantitative pH imaging is achieved by measuring the r2 /r1 value with a clinical 3 T MRI scanner.

Aqueous synthesis of glutathione-coated PbS quantum dots with tunable emission for non-invasive fluorescence imaging in the second near-infrared biological window (1000-1400 nm).

Glutathione-coated PbS quantum dots with tunable emission were synthesized in the aqueous phase and used for non-invasive tissue imaging in the second near-infrared biological window.

Lorentzian-like image blur of gold nanoparticles on thick amorphous silicon films in ultra-high-voltage transmission electron microscopy.

We quantitatively analyzed the contrast degradation and blur of 20-nm gold nanoparticles adsorbed on the top of amorphous silicon films of thicknesses of 0.54, 1.09, 1.63 and 2.2 µm in bright-field transmission electron microscope (TEM) images taken at accelerating voltages of 0.5, 1, 2 and 3 MeV. The thickness dependence of the transmission was well explained and consistent with our calculations. The blur function, derived by assuming that the TEM image of a thick specimen can be reproduced by convolving the TEM image of a very thin specimen with it, was found to be expressed by a two-dimensional Lorentzian function. Considering the two characteristics of the Lorentzian function, a sharp peak around the center and a long tail, we concluded that, for TEM observations of thick specimens, the image contrast is degraded predominantly by inelastic scattering and the image is blurred predominantly by multiple elastic scattering.

Structural modifications of dentinal microcracks with human aging.

Several studies have reported the mechanism of crack propagation with aging. Although structural modifications of dentinal microcracks with aging have been evaluated by observing the cracked surface using scanning electron microscope (SEM), very few attempts have been made at sectional observation of the microcracks inside dentine using transmission electron microscopy (TEM). The objectives of this study were to: (1) examine the process of dentinal microcrack formation using TEM and (2) to morphologically evaluate the relation between dentinal microcrack propagation and human aging. Molars from 'young' (16-28 years) and 'aged' (62-76 years) subjects were evaluated. Dentine blocks were cracked with an indenter and sectioned using a diamond knife and ultramicrotome after embedding in epoxy resin. Microcracks were observed by TEM and ultra-high-voltage electron microscope tomography to determine the characteristics of crack propagation in the young and aged teeth. The results show that, in young teeth, crack propagation tended to pass through the dentinal tubules, while in aged teeth, it tended to deflect to the outer side of peritubular dentine (PTD), especially in coronal dentine. The advantage of this method is that it allows visualization and evaluation of the ultrastructural propagation of microcracks in dentine. The differences in crack propagation between young and aged dentine could be explained by differences in PTD thickness.

Cost effectiveness of radiofrequency catheter ablation vs. medical treatment for atrial fibrillation in Japan. -Cost performance for atrial fibrillation-.

BACKGROUND: Radiofrequency catheter ablation (RF) has recently become widely available for the treatment of atrial fibrillation (AF) and has broadened treatment options while confusing the selection of medication therapy or RF. METHODS AND RESULTS: Two drugs for the maintenance of sinus rhythm (Ry) and 2 drugs for control of the pulse rate (Ra) were selected and the costs of medication therapy were calculated. RF procedures were grouped into 2 groups each for persistent or paroxysmal AF (RF) and for chronic AF (RFChr), according to the cost of the devices used. The calculated cost of medication therapy was 5,270-23,560 yen per month. The calculated cost of RF procedures was 1,063,200-2,029,640 yen. The costs of RF corresponded to those of Ry for 3.8-14.3 years. The costs of RFChr corresponded to those of Ra for 16.6-63.9 years. The treatment of complications ranged from 360,000 to 1,241,500 yen. CONCLUSIONS: From the aspect of medical costs and complications, RF should be considered for the treatment of patients with AF detected early or early-stage AF, whereas treatment for its complications should be given priority in patients with chronic AF associated with reduced cardiac function.

Catalytic activity and regeneration property of a Pd nanoparticle encapsulated in a hollow porous carbon sphere for aerobic alcohol oxidation.

A core-shell composite consisting of a palladium (Pd) nanoparticle and a hollow carbon shell (Pd@hmC) was employed as a catalyst for aerobic oxidation of various alcohols. The core-shell structure was synthesized by consecutive coatings of Pd nanoparticles with siliceous and carbon layers followed by removal of the intermediate siliceous layer. Structural characterizations using TEM and N(2) adsorption-desorption measurements revealed that Pd@hmC thus-obtained was composed of a Pd nanoparticle core of 3-6 nm in diameter and a hollow carbon shell with well-developed mesopore (ca. 2.5 nm in diameter) and micropore (ca. 0.4-0.8 nm in diameter) systems. When compared to some Pd-supported carbons, Pd@hmC showed a high level of catalytic activity for oxidation of benzyl alcohol into benzaldehyde using atmospheric pressure of O(2) as an oxidant. The Pd@hmC composite also exhibited a high level of catalytic activity for aerobic oxidations of other primary benzylic and allylic alcohols into corresponding aldehydes. The presence of a well-developed pore system in the lateral carbon shell enabled efficient diffusion of both substrates and products to reach the central Pd nanoparticles, leading to such high catalytic activities. This core-shell structure also provided high thermal stability of Pd nanoparticles toward coalescence and/or aggregation due to the physical isolation of each Pd nanoparticle from neighboring particles by the carbon shell: this specific property of Pd@hmC resulted in possible regeneration of catalytic activity for these aerobic oxidations by a high-temperature heat treatment of the sample recovered after catalytic reactions.

Magnetic Cu-Ni (core-shell) nanoparticles in a one-pot reaction under microwave irradiation.

We successfully prepared face-centered cubic (fcc) Cu-Ni (core-shell) nanoparticles by intramolecular reduction of formate complexes of Cu(2+) and Ni(2+) with long-chain amine ligands in a one-pot reaction within an extremely short time realized only under microwave irradiation. Observation by an HAADF-STEM technique showed that the nanostructure in one particle consisted of a Ni-rich shell and a Cu-rich core. Cu(4)Ni(6) nanoparticles with an average size of 11.7 nm were comprised of a Cu core with a diameter of ca. 6.0 nm, a Ni shell ca. 1.6 nm thick and a 0.9 nm thick interlayer of mixed Cu-Ni alloy between the Cu core and the Ni shell. Both the oxidation characteristics and the magnetic properties were dramatically affected by the molar ratios of Cu : Ni in the Cu-Ni nanoparticles. The magnetization of Cu(3)Ni(7) and Cu(4)Ni(6) comprised of a diamagnetic Cu-rich core, ferromagnetic Ni-rich shell and antiferromagnetic NiO-rich layer on the particle surface showed an exchange bias (209 and 143 Oe, respectively).

Gender differences in patients referred for atrial fibrillation management to a tertiary center.

BACKGROUND: Atrial fibrillation (AF) ablation is less frequently performed in women than in men. Although the prevalence of AF is slightly higher in men, this does not fully account for the lower number of AF ablations performed in women. This study sought to examine the effect of gender on referral for AF and subsequent AF management. METHODS: Consecutive patients referred to our tertiary arrhythmia outpatient clinic for AF management were retrospectively analyzed. RESULTS: Of 264 patients referred, only 27% were women. Women were older than men (63 +/- 9 vs 58 +/- 11 years, P = 0.002), more often had paroxysmal AF (78% vs 63% in men, P = 0.022), and women more frequently complained about palpitations (71% vs 49%, P = 0.002). In addition, they had more often experienced amiodarone side effects than men (56% vs 36%, P = 0.046). In this referred population, there was no difference in the proportion of women and men undergoing AF ablation immediately following the initial evaluation (21% vs 25%, P = ns), at any time during the follow-up (38% vs 44%, P = ns), and there was no difference in the proportion of patients undergoing atrioventricular node ablation in both sexes (6% of women vs 3% of men, P = ns). CONCLUSIONS: There is an important difference in the proportion of men and women referred for management of AF in a specialized outpatient arrhythmia clinic, with women being referred three times less often than men. However, there is no gender-related difference in the subsequent treatment decisions. These findings emphasize the importance of focusing on management of symptomatic AF in women.

Behavior of fluorescent molecules bound to the interior of silica nanocapsules in various solvents.

Porous silica nanocapsules with 20% 3-aminopropyltrimethoxysilane (APS)-bound 6-carboxy-fluorescein (APS-fluorescein) and 80% APS molecules adsorbed on the surface of a 50-nm-diameter Au core were prepared by a modified core-shell method. Silica mesoporous nanocapsules were obtained after the Au cores were dissolved in sodium cyanide. The size of the pores in the silica shells corresponded to the area of the fluorescein (approximately 1.02 nm(2)) in each APS-fluorescein molecule, which was bound to the silica shell by coupling between the silanol groups of APS in the APS-fluorescein molecule and the silica shell. The amino group of APS bound to the silica inside the shell is also reactive. Dy485XL N-hydroxysuccinimide ester (NHS) molecules were then added to the mesoporous silica nanocapsules in the solution and bonded to the amino group of the interior. Thus, mesoporous (fluorescein and Dy485XL)-bound silica nanocapsules were obtained. The fluorescence of Dy485XL was only observed in the mesoporous (fluorescein and Dy485XL)-bound silica nanocapsules in aqueous solution after ultrafiltration. However, the fluorescence of fluorescein reappeared after the addition of acetonitrile. Furthermore, upon adding various solvents to the mesoporous (fluorescein and Dy485XL)-bound silica nanocapsules, their fluorescence varied with that of fluorescein or Dy485XL. In the case of a mixture of 6-carboxy-fluorescein-N-hydroxysuccinimide (FLUOS) and Dy485XL-NHS free molecules in aqueous solution, the fluorescence of FLUOS was observed. Such different fluorescence phenomena demonstrated that Dy485XL-NHS molecules can easily penetrate into the nanocapsule interior via the pores and that the interior of the silica nanocapsules can bind to Dy485XL molecules. These fluorescence behaviors are discussed in terms of fluorescence resonance energy transfer (FRET) and solvatochromism.

High sintering resistance of platinum nanoparticles embedded in a microporous hollow carbon shell fabricated through a photocatalytic reaction.

Platinum (Pt) nanoparticles encapsulated in microporous carbon with a hollow structure (nPt@hC) were fabricated on the basis of a titanium(IV) oxide (TiO2) photocatalytic reaction. From the tomogram of a sample studied by using a transmission electron microscope (TEM), the Pt nanoparticles were found to be embedded in the carbon shell and were physically separated from each other by the carbon matrix. Owing to this unique structure, the Pt particles showed high resistance to sintering when subjected to thermal treatment at temperatures up to 800 degrees C. As a result, hydrogenation reactions using various heat-treated nPt@hCs as catalysts indicated that loss of catalytic activity was minimized. Thus, the present system will be a promising system for optimizing catalyst nanostructures utilized in processes requiring rigorous conditions.