Search

A MICROMEGAS (MICRO Mesh GASeous) detector is developed to monitor neutrons with a continuous energy spectra generated by bombarding protons on a thick Be target at the MC-50 cyclotron of the Korea Institute of Radiological and Medical Sciences (KIRAMS). Two different neutron spectra are produced by protons of 20 and 40 MeV, and are detected by using the MICROMEGAS detector with a boron converter. Boron carbides (B4C) are deposited on the cathode of the detector and are used as a neutron-to-charged particle converter. α particles and 7Li nuclei produced by the 10B(n,α)7Li reaction are detected by using the MICROMEGAS detector. Monte Carlo simulations for the detector system are performed to compare the experimental data with the simulation results. For measuring the energies of the α particles and the 7Li nuclei, we vary the geometry of detector in both the simulations and the experiments to fully stop the α particles and the 7Li nuclei in the detector. The changes of the positions of the α and the 7Li peaks observed in the distribution of the deposited energy for different detector geometries agree more or less with those from the simulation results. The neutron conversion efficiency of the detector is studied.

Erigeron annuus (L.) Pers. (EAP), belonging to the Compositae (Asteraceas) family, has been used in traditional herbal medicine and has many pharmacological activities. Recently, EAP essential oil has been reported to have diverse biological activities. However, its physiological activity on skin remains to be investigated. In the present study, we extracted the essential oil from the EAP flower (EAPF), and determined the role of the EAPF essential oil on skin regeneration-associated responses, especially proliferation and migration, using human epidermal-keratinocytes (HaCats). The essential oil was obtained by steam distillation in 0.08 % yield and contained twelve constituents, as assessed in GC-MS analysis. The EAPF essential oil stimulated proliferation and migration in HaCats, and increased the phosphorylation of serine/threonine-specific protein kinase (AKT) and extracellular signal-regulated kinase (ERK) 1/2. In addition, the essential oil promoted sprout outgrowth in HaCats. From these fi...

Liquid crystal compounds are an important state of matter both scientifically and technologically. So we have prepared HSEO-n(n = 1,2,3,4) series shown below. In this study, in orde to acquire furt...

The latent tracks formed on CR-39 solid state track detector on exposure of alpha radiations emanating from a collimated 241 Am source were developed by a chemical etching method. Alpha track images were captured by an optical microscope and were processed by using Image Pro-Plus (6.0) software. GEANT4 simulations were carried out to obtain the angular and energy distribution profiles of the alpha particles. Apart from fluence, geometric parameters like aspect ratio (the ratio of the major to minor axis) and the depth profiles of etched tracks were measured experimentally and correlated with simulated angular and energy profile of incident radiations. Reasonable agreement was observed in the fluence and depth profile information obtained from experiments and simulations.

Recently, we reported n-type graphene can be achieved simply using H2 molecules. It was understood by the attachment of hydrogen atoms dissociated on the surface of graphene. However, the amount of attached hydrogen has not been yet investigated. Here, we show the possibility of the formation of C H bonds due to the H2 exposure theoretically and the mass of the attached hydrogen atoms on graphene experimentally. The amount of the attached hydrogen atoms has been measured by a quartz crystal microbalance (QCM). After exposure of a multilayer graphene (MLG) to 20 bar of H2 pressure at 353 K for 20 h, the resonance frequency (RF) of QCM decreased. It indicates that the mass of the MLG increases. On the basis of the RF variation, we concluded that the hydrogen atoms were bonded to 3.84% of carbon atoms in the MLG. In order to confirm the C H bonding of MLG, Raman spectroscopy was performed before and after exposure to H2 pressure. On exposure, the D peak developed and the peak for 2-D graphite in 2D band increased. The experimental results and theoretical calculation demonstrate that the H2 molecules on the surface of the graphene are dissociated and that some of dissociated H atoms are attached on graphene.

See paper for full list of authors; The Korea Rare Isotope Accelerator, currently referred to as KoRIA, is briefly presented. The KoRIA facility is aimed to enable cutting-edge sciences in a wide range of fields. It consists of a 70 kW isotope separator on-line (ISOL) facility driven by a 70 MeV, 1 mA proton cyclotron and a 400 kW in-flight fragmentation (IFF) facility. The ISOL facility uses a superconducting (SC) linac for post-acceleration of rare isotopes up to about 18 MeV/u, while the SC linac of IFF facility is capable of accelerating uranium beams up to 200 MeV/u, 8 pμA and proton beams up to 600 MeV, 660 μA. Overall features of the KoRIA facility are presented with a focus on the accelerator design.

International audience; In this article, we report the synthesis of ultra-long carbon nanotubes (CNTs) by thermal chemical vapour deposition method. Ultra-long, individual and aligned CNTs were directly grown on a flat silicon substrate. The orientation of the nanotubes was found parallel to the gas flow direction. The ultra-long CNTs were grown with different transition metallic salts, such as nickel chloride, iron (III) chloride, cobalt acetate and ruthenium acetate, as the catalysts. The influence of the growth conditions, such as growth temperature, reactive gas flow on the length and alignment of the CNTs was studied in detail. By using different catalysts, ultra-long single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) were successfully grown. These ultra-long CNTs were transferred to other substrates by two methods. (1) The first method is to use polydimethylsiloxane as a stamp. (2) The second method is to use KOH as an etching agent. The diameter and length of the CNTs were characterised by transmission electron microscope, scanning electron microscope, atomic force microscope and Raman spectroscopy. The results indicate that the length of the CNTs can reach up to 4 mm. The diameter of the SWCNTs is in the range of 0.7-2.1 nm and the diameter of the MWCNTs is approximately 150 nm.

In the present study, the chemical compositions and skin whitening-related antioxidant and anti-melanogenic effect of essential oils (EOs) extracted from Chrysanthemum borealeMakino (CBM) (CBMEOs) at vegetative, pre-flowering and full-flowering are investigated and contrasted among the three stages. The yields and components of the CBMEOs were different at each stage. The CBMEOs increased DPPH and ABTs scavenging activities and attenuated the α-melanocyte stimulating hormone (α-MSH)-induced tyrosinase activity and melanin synthesis in B16BL6 cells. Among CBMEO components, eugenol had the highest DPPH and ABTs scavenging activities and cuminaldehyde was the strongest inhibitor of α-MSH-induced tyrosinase activity and melanin synthesis. The CBMEOs in each stage showed the different levels of phosphorylation of extracellular signal-regulated kinase1/2 and p38 MAPK. These findings demonstrate that the CBMEOs have antioxidative and anti-melanogenic activities in all the CBM harvesting stages, resulting in skin-whitening biological activities and that the levels of their component contents and bioactivities differ among the CBM harvesting stages. The CBMEOs may have the potential for use in cosmetics and alternative medicine.

The photolithography process has generally been used for the making of catalyst layers used for the synthesis of CNTs due to its comparative ease. However, this method results in the formation of undesirable catalyst particles, which deteriorate the quality of the devices. Therefore, we tried to form a catalyst layer without using any lift-off or wet etching process, especially for the formation of carbon nanotube interconnects. After spin coating the samples, which were previously fabricated with several vias, with an iron-acetate solution, the catalyst layer was pulled down into the bottom of the holes through the force of gravity. We were able to remove the catalyst layer which was coated over undesirable areas, by TMAH (tetramethylammonium hydroxide, N(CH3)4OH) treatment. After the catalyst deposition process, we synthesized CNTs and observed them by scanning electron microscopy (SEM). © 2007 Published by Elsevier B.V.

The density-controlled carbon nanotubes (CNTs) were grown on the iron nanoparticles by using the freeze–dry method. The iron-acetate [Fe(II)(CH3COO)2] solution was used for the preparation of the catalytic iron nanoparticles. The density of CNTs was controlled in order to achieve the enhancement in the field emission process. Furthermore, the patterning of the iron nanoparticle catalyst layer for the fabrication of electronic devices was simply achieved by using an alkaline solution, TMAH (tetramethylammonium hydroxide). We applied this patterning process of catalyst layer to the formation of the electron emitter with under-gate type triode structure.

We studied the growth characteristics of carbon nanotubes which were grown from the uniformly dispersed iron nanoparticles prepared from iron acetate [Fe(II)(CH3COO)2]. The density of CNT was controlled from precursor concentrations. We also investigated the field emission properties of CNTs. We found that the optimization of CNT density is an important factor for field emission properties. Patterning process of iron acetate was achieved simply by alkaline solution.

The density controlled carbon nanotubes (CNTs) are grown on the iron acetate nanoparticles by using the freeze‐dry method. The iron‐acetate [Fe(||)(CH3COO)2] solution is used to prepare the catalytic iron nanoparticles. The density of CNTs is controlled in order to enhance the field emission process. Furthermore, the patterning of the iron nanoparticle catalyst‐layer for the fabrication of electronic devices is simply achieved by using alkaline solution, TMAH (tetramethylammonium hydroxide). We applied this patterning process of catalyst layer to form the electron emitter with under‐gate type triode structure.

For field emitters as a cathode of traveling wave tube–microwave power amplifiers (TWT–MPA), field-emission (FE) properties of in situ grown carbon nanotubes (CNTs) onto electrically conducting substrate were systematically characterized. CNTs grown on the Co/TiN coated Ta substrate with properly controlled process exhibited the best FE property. The maximum current density and corresponding total emission current were 3.5 mA/cm 2 and ∼1.7 mA at 21.6 V/μm, respectively. Details on the correlation between the FE properties and the morphological parameters will be discussed.

We investigated the effect of essential oil from the flower of Chrysanthemum boreale Makino (CBMEO) on growth of human keratinocytes (HaCaTs) and explored a possible mechanism for this response. CBMEO was extracted using the steam distillation method. CBMEO contained a total of 33 compounds. CBMEO stimulated HaCaT proliferation (EC50, 0.028 μg/mL) and also induced phosphorylation of Akt and ERK1/2 in HaCaTs (EC50, 0.007 and 0.005 μg/mL, for phosphorylated Akt and ERK1/2, respectively). Moreover, CBMEO promoted wound closure in the dorsal side skin of rat tail. This study demonstrated that CBMEO can stimulate growth of human skin keratinocytes, probably through the Akt and ERK1/2 pathways. Therefore, CBMEO may be helpful in skin regeneration and wound healing in human skin, and may also be a possible cosmetic material for skin beauty.

At room-temperature ambient, carbon nanotubes (CNTs) were selectively synthesized on each bridge of the microheater array (MHA) formed on a glass substrate. Both multiwalled (MW) and single-walled CNTs could be formed by controlling the MHA temperature, which was confirmed from Raman spectroscopy. By incorporating the selectively grown MW CNTs into the lateral-gated field-emitter arrays, high current density of electron emission was observed with low device leakage.

A proton cyclotron MC-50 in Korea Institute of Radiological & Medical Science (KIRAMS) is used to carry out neutron activation experiments with Y2 O3 targets irradiated with neutron beams of a continuous spectrum produced by proton beams on a thick beryllium target. Neutrons are generated by 9 Be (p, n) reaction with an incident proton intensity of 20 μA. The neutron spectra generated by proton beams of 30, 35, and 40 MeV are calculated by GEANT4 simulations. Nb powders are used for neutron flux monitoring by measuring the activities of 92m Nb through the reaction 93 Nb (n, 2n). By using a subtraction method, the average cross section of 89 Y(n,2n) and 89 Y(n,3n) reactions at the neutron energies of 29.8 ± 1.8 MeV and 34.8 ± 1.8 MeV are extracted and are found to be close to the existing cross sections from the EXFOR data and the evaluated nuclear data libraries such as TENDL-2015 or EAF-2010.

We measured 209 Bi(n, 4n) cross sections at neutron energies E n = 29.8 ± 1.8 MeV and E n = 34.8 ± 1.8 MeV. Bismuth oxide samples were irradiated with the neutrons produced by impinging 30, 35 and 40 MeV proton beams on a 1.05 cm thick beryllium target, where the proton beams were from the MC-50 Cyclotron of Korea Institute of Radiological Medical Sciences (KIRAMS). The neutron flux for each proton beam energy E p , Φ E p ( E n ), has a broad spectrum with respect to E n . By taking the difference in the neutron fluxes, the difference spectra, Φ 40 ( E n ) −Φ 35 ( E n ) and Φ 35 ( E n ) −Φ 30 ( E n ), are obatined and found to be peaked at E n = 29.8 and 34.8 MeV, respectively, with a width of about 3.6 MeV. By making use of this observation and employing the TENDL-2009 library we could extract the 209 Bi(n, 4n) 206 Bi cross sections at the aforementioned neutron energies.

Nano-objects would be of great interest for the development of new types of electronic circuits if one could combine their nanometer scale with original functionalities beyond the conventional transistor action. However, the associated circuit architectures will have to handle the increasing variability and defect rate intrinsic to the nanoscale. In this context, there is a very fast growing interest for memory devices, and in particular resistive memory devices, used as building blocks in reconfigurable circuits tolerant to defects and variability. It was recently shown that optically gated carbon nanotube field effect transistors (OG-CNTFETs) based on large assemblies of nanotubes covered by an organic photoconductive thin film can be operated as programmable resistors and thus used as artificial synapses in circuits with function-learning capabilities. Here, the potential of such approach is evaluated in terms of scalability by integrating and addressing several individually programmable resistances on a single carbon nanotube. In addition, the charge storage mechanism can be controlled at a length scale smaller than the device length allowing to also program the direction in which the current flows. It thus demonstrates that a single nanotube section can combine all-in-one the properties of an analog resistive memory and of a rectifying diode with tunable polarity.

Artemisia annua L. essential oil (AAEO) has diverse properties including antibacterial, antioxidant, antinociceptive, and antimicrobial activities. However, the effect of AAEO on obesity remains to be investigated. In this study, we analyzed the compounds of AAEO and explored the effect of AAEO on the differentiation of preadipocyte into adipocyte using preadipocyte cell line 3T3-L1. Total yield of AAEO from 20 kg A. annua leaf and flower was 0.5%, v/w. Gas chromatography-mass spectrometry analysis showed that AAEO contained 34 compounds. 3T3-L1 cells incubated in 3-isobutyl-1-methylxanthine / dexamethasone / insulin (MDI)-containing medium showed increased accumulation of lipid droplets. This increased response was suppressed by treatment with AAEO. Expressions of obesity-related proteins (PPARγ, C/EBPα, SREBP-1c, FAS, and ACC) were increased in 3T3-L1 cells cultured in MDI medium and these responses were decreased by treatment with AAEO. These findings demonstrate that AAEO may suppress 3T3-L1 cell differentiation by inhibiting adipogenesis and activation of lipid metabolism-related proteins.

Field emission properties of CNTs(carbon nanotubes) have been investigated in the various field, such as flat panel display and x-ray sources. Especially, the x-ray tube which fabricated using the CNTs can be operated with low power consumption compare with filament-based x-ray tubes. The cold cathode — CNTs- can be operated at the lower voltage and the electron which coming out from the CNTs can be controlled easilly by focus electrode. And for high emission current, the device should be stable at the high operate voltage. The gate electrode-mesh-type electrode- can be layered by using glass frit and firing process. At this point, the mesh structure can be controlled for the higher adhesion force which is for the emission stability at the high voltage. The glass frit could be act effectively between mesh electrode and insulating layer because of the designed mesh structure.

The triode-typed field emission (FE) devices using carbon nanotube (CNT) emitters for the x-ray application were fabricated. For the stability of the device, the leakage current between cathode and gate, and the emission current to the anode electrode should be controlled. We realized that the thickness of insulating layer-gap distance between cathode and gate- and the space between the gate electrodes-electron path from cathode and anode- should be controlled for the ratio of the current from cathode to anode (Ia) to the current from cathode to gate (Ig). The ratio of Ia to Ig can be represented the device efficiency. The rectangular-mesh electrode and screen printed insulating layer were controlled for Ia/Ig. When the size of gate hole was the 50 by 700 um — the electrode size is 25 by 700 um — and the thickness of insulator layer was 65 um, the maximum ratio of Ia/(Ia+Ig) was 0.63.

The flower of Pueraria thunbergiana BENTH (PTBF) contains isoflavonoids and essential oil components. It has many biological and pharmacological activities, including anti-diabetes, anti-oxidant, and weight loss. However, its effect on skin regeneration remains unknown. In the present study, we isolated the absolute from PTBF through solvent extraction and determined the role of the absolute on skin regeneration-associated responses in human epidermal-keratinocytes (HaCats). The PTBF absolute, which contained 10 compounds, stimulated migration and proliferation and increased the phosphorylation of serine/threonine-specific protein kinase and extracellular signal-regulated kinase1/2 in HaCats. It induced type I and IV collagen synthesis in HaCats. In addition, treatment with PTBF absolute resulted in increased sprout outgrowth in HaCats. These findings suggest that PTBF absolute may participate in skin regeneration, probably through promotion of migration, proliferation, and collagen synthesis.

A custom designed optical system is reported for tissue spectroscopy over four wavelengths of 677 nm, 780 nm, 830 nm, and 977 nm. A high speed laser driver is designed with a flat frequency response using pre-emphasis circuit. The driver is employed for high current in high power lasers. Phantom and intra-lipid experiments are performed to extract optical parameters of a turbid media. Broadband measurement is used to extract optical parameters of the phantom model simulating a breast tissue using forward scattering models. The optical parameters () are extracted with a very good accuracy.

Artemisia montana Pampan (Compositae) (AMP) contains various compounds, including phenolic acids, alkaloids, and essential oil. It has been widely used in oriental medicine due to a variety of biological effects. However, the biological activity of the essential oil from AMP (AMPEO) on skin has not been investigated. In the present study, AMPEO was evaluated for its composition and its effect on cellular events (migration and proliferation) related to skin regeneration using normal human keratinocytes (HaCats). AMPEO, which was extracted by steam distillation, contained 42 components. AMPEO increased proliferation in HaCats in a dose-dependent manner (EC 50, 8.5 ng/mL) and did not affect migration. AMPEO also enhanced the phosphorylation of Akt and ERK 1/2 and induced the synthesis of type IV collagen, but not type I collagen in HaCats. In addition, AMPEO promoted wound closure in the dorsal side skin of rat tail. These results demonstrated that AMPEO extracted by steam distillation induced proliferation and synthesis of type IV collagen in human skin keratinocytes, and may thereby exert positive effects on skin regeneration and wound healing in human skin.

For field emitters as an electron source of traveling wave tube microwave power amplifiers, field-emission properties of multiwalled carbon nanotubes (MWNTs) grown in situ onto an electrically conducting substrate were systematically characterized. MWNTs grown on a TiN-coated Ta substrate with NH3 plasma pre-treatment exhibited the best field-emission property. The maximum current density and corresponding total emission current were 9.4 mA/cm2 and ∼5 mA at 18.8 V/μm, respectively. These enhanced field-emission properties are caused by the highly conducting buffer layer (TiN), the optimum metal substrate (Ta) that produces high field-emission current, and the control of site density of MWNTs by NH3 plasma pre-etching. Details on the correlation between the field-emission properties and the morphological parameters will be discussed.