http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Spectral Flux of the p-^7Li(C) Q-M Neutron Source Measured by Proton Recoil Telescope
J. Novak,P. Bem,M. Gotz,M. Honusek,E. Simeckova,M. Stefanik,U. Fischer,S. P. Simakov 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The cyclotron-based fast neutron source at NPI produces mono-energetic neutron fields up to 35 MeV neutron energy using the p+^7Li(carbon backing) reactions. To be applied for activation cross-section measurements, not only the intensity of neutron peak, but also the contribution of low-energy continuum in the spectra must be well determined. Simulations of the spectral flux from present source at a position of irradiated samples were performed using CYRIC TOF-data validated in the present work against LA150h by calculations with the transport Monte Carlo code MCNPX. Simulated spectra were tested by absolute measurements using a proton-recoil telescope technique. The recoil-proton spectrometer consisted of a shielded scattering chamber with polyethylene and carbon radiators and the ΔE_1-ΔE_2-E telescope of silicon-surface detectors located to the neutron beam axis at 45˚ in the laboratory system. Si-detectors were handled by usual data acquisition system. Dead-time - and pulse-overlap losses of events were determined from the count rate of pulse generator registered during duty cycle of accelerator operation. The proton beam charge and data were taken in the list mode for later replay and analysis. The calculations for ^7Li(p,n) and ^(12)C(p,n) reactions reasonably reproduce CYRIC TOF neutron source spectra. The influence of neutron source set-up (proton beam dimensions, ^7Li-foil, carbon stopper, cooling medium, target support/chamber and the geometry-arrangement of irradiated sample) on the spectral flux is discussed in details.
Sapper, Eva,Novak, Nikola,Jo, Wook,Granzow, Torsten,Rö,del, Jü,rgen American Institute of Physics 2014 JOURNAL OF APPLIED PHYSICS - Vol.115 No.19
The electric-field-temperature phase diagram for the lead-free relaxor material (1 - x)(Bi1/2Na1/2) TiO3 - xBaTiO(3) (x = 0.03, 0.06, and 0.09) doped with 0.5 mol% Mn (BNT-100xBT:Mn) was established. Transition lines between ergodic or nonergodic relaxor states and the field-induced ferroelectric state were determined at constant temperatures with electric-field-dependent measurements of the polarization as well as of the piezoelectric coefficient and permittivity. Near the depolarization temperature T-d, the switching between two ferroelectric poling directions occurs in two steps via an intermediate relaxor state. This effect is closely related to the pinching of the ferroelectric hysteresis loop. (C) 2014 AIP Publishing LLC.
Acosta, M.,Novak, N.,Jo, W.,Rodel, J. Elsevier Science 2014 Acta materialia Vol.80 No.-
The Ba(Zr<SUB>0.2</SUB>Ti<SUB>0.8</SUB>)O<SUB>3</SUB>-x(Ba<SUB>0.7</SUB>Ca<SUB>0.3</SUB>)TiO<SUB>3</SUB> system was synthesized in a wide compositional range in order to study the relationship between its phase diagram and electromechanical properties. Phase transitions were marked using peaks in temperature-dependent permittivity, providing up to three transitions from the rhombohedral phase to an orthorhombic, tetragonal and finally cubic phase, which meet in a region that is termed the phase convergence region in this work. In situ small and large signal electromechanical properties were studied as a function of temperature with specific emphasis on these transitions. A small signal piezoelectric coefficient, d<SUB>33</SUB>, presents maximized values at the transition from the orthorhombic to the tetragonal phase, while a large signal piezoelectric coefficient, d<SUB>33</SUB><SUP>*</SUP>, does so at both rhombohedral to orthorhombic and to tetragonal phase transitions. Maximum polarization P<SUB>max</SUB> was the only quantity determined that had a clear maximum at the phase convergence region.
Kim, Sang K.,J.Woodcroft, Kimberley,Oh, Soo Jin,A.Abdelmegeed, Mohamed,F.Novak, Raymond 충남대학교 형질전환복제돼지연구센터 2007 논문집 Vol. No.10
Mechanical stress is known to activate signaling cascades, including mitogen-activated protein kinase (MAPK) pathways. Although mechanical stress has been implicated in hepatic cirrhosis and liver regeneration following hepatectomy, the signaling pathway(s) that may be activated in hepatocytes in response to mechanical stress have not been determined, Using primary cultured rat hepatocytes to examine cellular signaling in response to mechanical stress associated with medium change, we observed that the phosphorylation status of extracellular signal-regulated kinase 1/2 (ERK1/2), Jun N-terminal kinase and p38 MAPK, but not Akt, was altered. MAPK activation, especially ERK 1/2, was rapidly increased within 5 min, followed by a subsequent decrease to below basal levels between 30 min and 1 h following medium change. MAPK/ERK kinase (MEK1/2) phosphorylation followed the same pattern, The phosphorylation of Raf-l in response to medium change was also consistent with Raf-l serving as an upstream regulator of MEK 1/2-ERK1/2 signaling. Phosphorylation of ERK1/2 was increased by mechanical stress alone, suggesting that mechanical stress may be primarily responsible for ERK1/2 activation in response to medium change. Medium change produced a marked decline in oxidized glutathione and malondialdehyde levels, and the antioxidant N-acetyl-L-cysteine decreased basal ERK1/2 phosphorylation. suggesting a role for oxidative stress in maintaining basal ERK1/2 phosphorylation in cultured hepatocytes, These data suggest that medium change results in immediate activation of the MAPK signaling pathway due to mechanical stress, followed by a subsequent inactivation of MAPK signaling due to a reduction in oxidative stress levels. These processes may be associated with alteration of hepatic hemodynamic circulation observed in hepatic diseases and in liver transplantation.
UV photoinitiated changes of humic fluorophores, influence of metal ions
Klementova, S.,Kriz, D.,Kopacek, J.,Novak, F.,Porcal, P. Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.5
Fluorophore types and their photochemical stability have been tested in two samples of humic acids (HA) and four types of fulvic acids (FA) extracted from upper soil horizons (O and A horizons) in Norway spruce forest mountain ecosystems. Only one type of fluorophore occurred in all samples, with an excitation maximum at 310 nm for both HA and FA samples and emission maxima between 420-435 and 440-450 for HA and FA, respectively. HA weak native fluorescence increased significantly during irradiation in the first 12 h. Fluorophores in FA were uniformly degraded from the beginning of irradiation. Addition of metal (aluminium or ferric) ions did not affect the positions of fluorescence maxima in any of the studied samples; mild effects on fluorescence intensities were observed.
POLARIMETRY OF DG TAU AT 350 μm
Krejny, M.,Matthews, T. G.,Novak, G.,Cho, J.,Li, H.,Shinnaga, H.,Vaillancourt, J. E. IOP Publishing 2009 The Astrophysical journal Vol.705 No.1
<P>We present the first 350 mu m polarization measurement for the disk of the T Tauri star (TTS) DG Tau. The data were obtained using the SHARP polarimeter at the Caltech Submillimeter Observatory. We measured normalized Stokes parameters q = -0.0086 +/- 0.0060 and u = -0.0012 +/- 0.0061, which gives a 2 sigma upper limit for the percent polarization of 1.7%. We obtain information about the polarization spectrum by comparing our 350 mu m measurement with an 850 mu m polarization detection previously published for this source. Comparing the two measurements in Stokes space ( not in percent polarization) shows that the two data points are not consistent, i.e., either the degree of polarization or the angle of polarization (or both) must change significantly as one moves from 850 mu m to 350 mu m. This conclusion concerning the polarization spectrum disagrees with the predictions of a recent model for TTS disk polarization. We show that this discrepancy can be explained by optical depth effects. Specifically, we demonstrate that if one were to add more mass to the model disk, one would expect to obtain a model polarization spectrum in which the polarization degree falls sharply with increasing frequency, consistent with the observations at the two wavelengths. We suggest that multiwavelength polarimetry of TTS disk emission may provide a promising method for probing the opacity of TTS disks.</P>
The Measurement of Neutron Activation Cross Section of ^(59)Co Below 36 MeV
E. Simeckov,P. Bem,V. Burjan,M. Gotz,M. Honusek,V. Kroha,J. Novak,U. Fischer,S. P. Simakov,R. A. Forrest 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
An accurate knowledge of the cross section for neutron-induced reactions on ^(59)Co is of importance due to use of cobalt as a structural material in fission and fusion reactors, its applicability in neutron dosimetry and for testing theoretical models as well. The thin Co foils (0.25 mm thickness, 99.9% purity, Goodfellow product) were irradiated in the quasi-momoenergetic p-Li neutron field. For the production of the neutron fields, the proton beam from the NPI energy-variable cyclotron U120M at proton energies 19.8, 25.1, 27.6, 30.1, 32.7, 35.0, and 37.4 MeV and thin ^7Li target with carbon stopper were used. The reaction ^7Li(p,n) produces the high-energy quasi-monoenergetic neutrons with tail to lower energies. The flux density and neutron spectra were evaluated by MCNPX code using ^7Li(p,n) cross section measurement of other authors and including correction to the NPI target layout. The time profile of the neutron source strength during the irradiation was monitored by the proton beam current on the neutron-source target, recorded by a calibrated current-to-frequency converter on a PC. Au foils were used as additional monitors. The foil activity determination was performed by the nuclear spectrometry method employing two calibrated HPGe detectors of 23 and 50% efficiency and of FWHM (Full Width Half Maximum) 1.8 keV at 1.3 MeV for gamma-ray measurement. The reaction rates for ^(59)Co(n,p)^(59)Fe, ^(59)Co(n,α)^(56)Mn, ^(59)Co(n,2nα)^(54)Mn, ^(59)Co(n,3n)^(57)Co, ^(59)Co(n,2n)^(58m)Co, and ^(59)Co(n,2n)^(58g)Co were obtained. Integral activation cross sections were estimated. The preliminary results are discussed.