Shape transformation and self-alignment of Fe-based nanoparticles.

New types of functional material structures will emerge if the shape and properties are controlled in three-dimensional nanodevices. Possible applications of these would be nanoelectronics and medical systems. Magnetic nanoparticles (MNPs) are especially important in electronics such as magnetic storage, sensors, and spintronics. Also, in those that are used as magnetic resonance imaging contrasts, and tissue specific therapeutic agents, as well as in the labeling and sorting of cells, drug delivery, separation of biochemical products, and in other medical applications. Most of these applications require MNPs to be chemically stable, uniform in size, and controllable in terms of their magnetic properties and shape. In this paper three new functions of iron (Fe)-based nanoparticles are reported: shape transformation, oxidation prevention, and self-alignment. The shape of the Fe nanoparticles could be controlled by changing their oxidation states and properties by using a nanocarbon coating. Full field X-ray microscopy using synchrotron radiation revealed controllable magnetic properties of MNPs at the L3 edge which depended on the oxidation states. Then, inkjet printing was successfully performed to deposit a uniform layer of MNPs by the size.

Roll-to-Roll Production of Layer-Controlled Molybdenum Disulfide: A Platform for 2D Semiconductor-Based Industrial Applications.

A facile methodology for the large-scale production of layer-controlled MoS2 layers on an inexpensive substrate involving a simple coating of single source precursor with subsequent roll-to-roll-based thermal decomposition is developed. The resulting 50 cm long MoS2 layers synthesized on Ni foils possess excellent long-range uniformity and optimum stoichiometry. Moreover, this methodology is promising because it enables simple control of the number of MoS2 layers by simply adjusting the concentration of (NH4 )2 MoS4 . Additionally, the capability of the MoS2 for practical applications in electronic/optoelectronic devices and catalysts for hydrogen evolution reaction is verified. The MoS2 -based field effect transistors exhibit unipolar n-channel transistor behavior with electron mobility of 0.6 cm2 V-1 s-1 and an on-off ratio of ≈10³. The MoS2 -based visible-light photodetectors are fabricated in order to evaluate their photoelectrical properties, obtaining an 100% yield for active devices with significant photocurrents and extracted photoresponsivity of ≈22 mA W-1 . Moreover, the MoS2 layers on Ni foils exhibit applicable catalytic activity with observed overpotential of ≈165 mV and a Tafel slope of 133 mV dec-1 . Based on these results, it is envisaged that the cost-effective methodology will trigger actual industrial applications, as well as novel research related to 2D semiconductor-based multifaceted applications.

Two-Dimensional Excitonic Photoluminescence in Graphene on a Cu Surface.

Despite having outstanding electrical properties, graphene is unsuitable for optical devices because of its zero band gap. Here, we report two-dimensional excitonic photoluminescence (PL) from graphene grown on a Cu(111) surface, which shows an unexpected and remarkably sharp strong emission near 3.16 eV (full width at half-maximum ≤3 meV) and multiple emissions around 3.18 eV. As temperature increases, these emissions blue shift, displaying the characteristic negative thermal coefficient of graphene. The observed PL originates from the significantly suppressed dispersion of excited electrons in graphene caused by hybridization of graphene π and Cu d orbitals of the first and second Cu layers at a shifted saddle point 0.525(M+K) of the Brillouin zone. This finding provides a pathway to engineering optoelectronic graphene devices, while maintaining the outstanding electrical properties of graphene.

Clinical outcomes of subtotal cholecystectomy performed for difficult cholecystectomy.

PURPOSE: Laparoscopic subtotal cholecystectomy (LSC) can be an alternative surgical technique for difficult cholecystectomies. Surgeons performing LSC sometimes leave the posterior wall of the gallbladder (GB) to shorten the operation time and avoid liver injury. However, leaving the inflamed posterior GB wall is a major concern. In this study, we evaluated the clinical outcomes of standard laparoscopic cholecystectomy (SLC), LSC, and LSC removing only anterior wall of the GB (LSCA). METHODS: We retrospectively reviewed the medical records of laparoscopic cholecystectomies performed between January 2006 to December 2015 and analyzed the outcomes of SLC, LSC, and LSCA. RESULTS: A total of 1,037 patients underwent SLC. 22 patients underwent LSC; and 27 patients underwent LSCA. The mean operating times of SLC, LSC, and LSCA were 41, 74, and 68 minutes, respectively (P < 0.01). Blood loss was 5, 45, and 33 mL (P < 0.05). The mean lengths of postoperative hospitalization were 3.4, 5.4, and 5.8 days. Complications occurred in 24 SLC patients (2.3%), 2 LSC patients (9%), and 1 LSCA patient (3.7%). There was no mortality among the LSC and LSCA patients. CONCLUSION: LSC and LSCA are safe and feasible alternatives for difficult cholecystectomies. These procedures help surgeons avoid bile duct injury and conversion to laparotomy. LSCA has the benefits of shorter operation time and less bleeding compared to LSC.

Strain Relaxation of Graphene Layers by Cu Surface Roughening.

The surface morphology of copper (Cu) often changes after the synthesis of graphene by chemical vapor deposition (CVD) on a Cu foil, which affects the electrical properties of graphene, as the Cu step bunches induce the periodic ripples on graphene that significantly disturb electrical conduction. However, the origin of the Cu surface reconstruction has not been completely understood yet. Here, we show that the compressive strain on graphene induced by the mismatch of thermal expansion coefficient with Cu surface can be released by forming periodic Cu step bunching that depends on graphene layers. Atomic force microscopy (AFM) images and the Raman analysis show the noticeably longer and higher step bunching of Cu surface under multilayer graphene and the weaker biaxial compressive strain on multilayer graphene compared to monolayer. We found that the surface areas of Cu step bunches under multilayer and monolayer graphene are increased by ∼1.41% and ∼0.77% compared to a flat surface, respectively, indicating that the compressive strain on multilayer graphene can be more effectively released by forming the Cu step bunching with larger area and longer periodicity. We believe that our finding on the strain relaxation of graphene layers by Cu step bunching formation would provide a crucial idea to enhance the electrical performance of graphene electrodes by controlling the ripple density of graphene.

Triangular Black Phosphorus Atomic Layers by Liquid Exfoliation.

Few-layer black phosphorus (BP) is the most promising material among the two-dimensional materials due to its layered structure and the excellent semiconductor properties. Currently, thin BP atomic layers are obtained mostly by mechanical exfoliation of bulk BP, which limits applications in thin-film based electronics due to a scaling process. Here we report highly crystalline few-layer black phosphorus thin films produced by liquid exfoliation. We demonstrate that the liquid-exfoliated BP forms a triangular crystalline structure on SiO2/Si (001) and amorphous carbon. The highly crystalline BP layers are faceted with a preferred orientation of the (010) plane on the sharp edge, which is an energetically most favorable facet according to the density functional theory calculations. Our results can be useful in understanding the triangular BP structure for large-area applications in electronic devices using two-dimensional materials. The sensitivity and selectivity of liquid-exfoliated BP to gas vapor demonstrate great potential for practical applications as sensors.

Stable semiconductor black phosphorus (BP)@titanium dioxide (TiO2) hybrid photocatalysts.

Over the past few decades, two-dimensional (2D) and layered materials have emerged as new fields. Due to the zero-band-gap nature of graphene and the low photocatalytic performance of MoS2, more advanced semiconducting 2D materials have been prompted. As a result, semiconductor black phosphorus (BP) is a derived cutting-edge post-graphene contender for nanoelectrical application, because of its direct-band-gap nature. For the first time, we report on robust BP@TiO2 hybrid photocatalysts offering enhanced photocatalytic performance under light irradiation in environmental and biomedical fields, with negligible affected on temperature and pH conditions, as compared with MoS2@TiO2 prepared by the identical synthesis method. Remarkably, in contrast to pure few layered BP, which, due to its intrinsic sensitivity to oxygen and humidity was readily dissolved after just several uses, the BP@TiO2 hybrid photocatalysts showed a ~92% photocatalytic activity after 15 runs. Thus, metal-oxide-stabilized BP photocatalysts can be practically applied as a promising alternative to graphene and MoS2.

Innovative three-dimensional (3D) eco-TiO2 photocatalysts for practical environmental and bio-medical applications.

It is known that water purified by conventional TiO2 photocatalysts may not be safe enough for drinking, due to the toxicity by tiny existence of TiO2 nanoparticles after water treatment. We herein demonstrate a facile design of a three-dimensional (3D) TiO2 photocatalyst structure with which both the efficiency of purification and the safety level of the final purified water can be improved and ensured, respectively. The structure, consisting of 3D sulfur-doped TiO2 microtubes in nanotubes (eco-TiO2), is suitable for both environmental and bio-medical applications. Investigation of its formation mechanism reveals that anodic aluminum oxide (AAO), owing to a spatial constraint, causes a simple, nanoparticles-to-nanotubes structural rearrangement as a template for nanotube growth. It is found that eco-TiO2 can be activated under visible-light irradiation by non-metal (sulfur; S) doping, after which it shows visible-light photocatalytic activities over a range of solar energy. Importantly, an in vitro cytotoxicity test of well-purified water by eco-TiO2 confirms that eco-TiO2 satisfies the key human safety conditions.

Effect of growth pressure on the synthesis of vertically aligned carbon nanotubes and their growth termination.

When vertically aligned carbon nanotubes (VACNTs) are synthesized by thermal chemical vapor deposition (TCVD), their structural features such as height and density can be determined by TCVD growth conditions. In this study we investigated the effect of growth pressure on the structural features of VACNTs. Changes in growth pressure significantly affected the height, density, and crystalinity of synthesized VACNTs. In addition, we suggest that the growth termination of VACNTs could be due to the lack of carbon feedstock supply to the center of the VACNT film induced by the pressure-dependent adsorption of amorphous carbon at the edge of the VACNT film. In addition, the field emission characteristics of the VACNT film were carried out. The turn-on voltage of the VACNT film was 1.62 V/microm and the field enhancement factor (beta) was 2478. These results provide useful information for practical applications of VACNTs, such as field emission display and X-ray source.

Relationship between benign prostatic hyperplasia/lower urinary tract symptoms and total serum testosterone level in healthy middle-aged eugonadal men.

INTRODUCTION: Scant data are available concerning the relationship between lower urinary tract symptoms (LUTS)/benign prostatic hyperplasia (BPH) and total serum testosterone level (TT) in eugonadal state. AIM: We performed this study to evaluate the relationship between LUTS/BPH and TT in eugonadal men. METHODS: A cross-sectional study was conducted that included a total of 2,308 eugonadal (TT ≥ 3.0 ng/mL) male police officers aged 40-59 years who had participated in a health examination. LUTS/BPH were assessed by prostate-specific antigen level, international prostate symptom score (IPSS), total prostate volume (TPV), maximal flow rate (Qmax), postvoid residual urine volume (PVR), and a full metabolic workup. We then investigated their relationship using the Spearman correlation test, multiple linear regression, and logistic regression analyses. MAIN OUTCOME MEASURES: Associations of TT with IPSS, Qmax, and PVR. RESULTS: The median age and TT level were 49.0 years and 5.37 ng/mL, respectively. The TT level showed significant positive correlations with Qmax (r = 0.043, P = 0.048) and a significant negative correlation with PVR (r = -0.050, P = 0.022). No significant correlation was found between TT and TPV or IPSS. However, Qmax and PVR as well as TPV and IPSS did not significantly correlate with TT after adjusting for age and/or metabolic syndrome. On logistic regression, no significant difference was found in surrogate measures of LUTS/BPH (TPV > 30 mL, IPSS > 7, Qmax < 15 mL/second, and PVR > 50 mL) between the highest quartile TT group (median: 7.07 ng/mL) and the lowest quartile group (median: 3.92 ng/mL). CONCLUSION: In our study, TT was not clearly correlated with LUTS/BPH in middle-aged eugonadal men.

Immobilization of carbon nanotubes on functionalized graphene film grown by chemical vapor deposition and characterization of the hybrid material.

We report the surface functionalization of graphene films grown by chemical vapor deposition and fabrication of a hybrid material combining multi-walled carbon nanotubes and graphene (CNT-G). Amine-terminated self-assembled monolayers were prepared on graphene by the UV-modification of oxidized groups introduced onto the film surface. Amine-termination led to effective interaction with functionalized CNTs to assemble a CNT-G hybrid through covalent bonding. Characterization clearly showed no defects of the graphene film after the immobilization reaction with CNT. In addition, the hybrid graphene material revealed a distinctive CNT-G structure and p-n type electrical properties. The introduction of functional groups on the graphene film surface and fabrication of CNT-G hybrids with the present technique could provide an efficient, novel route to device fabrication.

Synthesis of graphene and carbon nanotubes hybrid nanostructures and their electrical properties.

The gapless semimetallic nature of graphene-based nanoelectronics is a major hurdle for the advancement of graphene-based field-effect transistors. Here graphene-carbon nanotubes hybrid nanostructures (Gr-CNTs HNSs) were formed by synthesizing single-walled carbon nanotubes (SWCNTs) with a bandgap on monolayer graphene by thermal chemical vapor deposition. We systematically established optimum conditions for the synthesis of Gr-CNTs HNSs by adjusting catalytic layer formation. The structural features of Gr-CNTs HNSs were investigated by scanning electron icroscopy and Raman spectroscopy. The surface morphologies and chemical states of the catlytic films used to optimize Gr-CNTs HNSs synthesis were explored by atomic force microscopy and X-ray photoelectron spectroscopy. In this process, graphene played a role as a barrier to prevent Fe nanoparticles from interdiffusing into Al2O3 layer. Based on these studies, we determined the catalytic structure (Fe/Graphene/Al2O3/SiO2) optimal for growing high-density SWCNTs on monolayer graphene. Electrical transport measurements revealed that Gr-CNTs HNSs exhibited p-type semiconducting behavior with combined properties of graphene and CNTs.

Effect of implant position, angulation, and attachment height on peri-implant bone stress associated with mandibular two-implant overdentures: a finite element analysis.

PURPOSE: The aim of this study was to analyze and compare the level and distribution of peri-implant bone stresses associated with mandibular two-implant overdentures with different implant positions. MATERIALS AND METHODS: Mathematical models of mandibles and overdentures were designed using finite element analysis software. Two intraosseous implants and ball attachment systems were placed in the interforaminal region. The overdenture, which was supported by the two implants, was designed to withstand bilateral and unilateral vertical masticatory loads (total 100 N). In all, eight types of models, which differed according to assigned implant positions, height of attachments, and angulation, were tested: MI (model with implants positioned in the lateral incisor sites), MC (implants in canine sites), MP (implants in premolar sites), MI-Hi (greater height of attachments), MC-M (canine implants placed with mesial inclination), MC-D (canine implants placed with distal inclination), MC-B (canine implants placed with buccal inclination), and MC-L (canine implants placed with lingual inclination). RESULTS: Peri-implant bone stress levels associated with overdentures retained by lateral incisor implants resulted in the lowest stress levels and the highest efficiency in distributing peri-implant stress. MI-Hi showed increased stress levels and decreased efficiency in stress distribution. As the implants were inclined, stress levels increased and the efficiency of stress distribution decreased. Among the inclined models, MC-B showed the lowest stress level and best efficiency in stress distribution. CONCLUSION: The lowest stress and the best stability of implants in mandibular two-implant overdentures were obtained when implants were inserted in lateral incisor areas with shorter attachments and were placed parallel to the long axes of the teeth.

Antipsychotic-induced sexual dysfunction and its management.

Sexual dysfunction is a common condition in patients taking antipsychotics, and is the most bothersome symptom and adverse drug effect, resulting in a negative effect on treatment compliance. It is known that hyperprolactinemia is a major cause of sexual dysfunction. Based on the blockade of dopamine D2 receptors, haloperidol, risperidone, and amisulpride are classed as prolactin-elevating antipsychotics, while olanzapine, clozapine, quetiapine, ziprasidone, and aripiprazole are classed as prolactin-sparing drugs. Risperidone and the other typical antipsychotics are associated with a high rate of sexual dysfunction as compared to olanzapine, clozapine, quetiapine, and aripiprazole. With regard to treatment in patients suffering from sexual dysfunction, sildenafil was associated with significantly more erections sufficient for penetration as compared to a placebo. Subsequent studies are needed in order to provide physicians with a better understanding of this problem, thereby leading toward efficacious and safe solutions.

Retirement plans for Korean dentists after the economic crisis in 1998.

OBJECTIVES: This study aims to investigate the economic hardships of dentists from the rapid reduction of incomes after the IMF crisis in Korea 1998, the retirement plan status of those dentists, and to provide the basic data to determine an economic retirement plan of dentists. METHODS: Among the 14,359 dentists in Korea, 855 dentists were surveyed. The surveys were from February 22, 2010 to April 22, 2010, and were carried out with 484 copies that were selected to be used for analysis. The collected data were analyzed with SPSS statistics program 15.0 (SPSS Inc., Chicago, IL, USA). RESULTS: The dentist group with a net monthly income of '2-2.5 million [corrected] won' showed the highest retirement planning (P < 0.001). The preparation period for an economic retirement was about 10 years (P < 0.001). Single and married dentists both showed 'private insurance' as the highest economic retirement plan (P < 0.05). CONCLUSIONS: A more systematic retirement plan for Korean dentists is required and the government needs to implement a training program for professional retirement planning.

Oral health behaviours according to demographic characteristics in Korean adolescents: a national representative sample.

OBJECTIVES: To provide information on how to teach correct oral health behaviour to youths and to develop programmes to that end, this study examined the oral health behaviour and demographic characteristics of adolescents. METHODS: The raw data of 'The Third 2007 Youth Health Behavior Online Survey' carried out by the Korea Center for Disease Control and Prevention were analysed. Independent t-test, one-way ANOVA, and chi-squared analyses were used to assess the relationships between oral health behaviours and demographic characteristics. RESULTS: The oral health behaviour of the adolescents who were investigated differed significantly depending on their demographic characteristics (P<0.001). Tooth brushing frequency differed significantly depending on gender and student grade (P<0.001) and the frequency of visits to a dental clinic differed depending on the gender, student grade, type of residential area (urban/rural), and type of school (middle or high) (P<0.001). School grade, type of residential area, and type of school also affected the likelihood of receiving preventive dental treatment (P<0.001). CONCLUSIONS: Adolescents who were in lower grades, female, and lived in large urban communities visited dental clinics more frequently and received more preventive dental treatment than adolescents who were in higher grades, male and resided in small urban and rural areas. These results highlight the need for the further development and dissemination of oral health programmes.