International Nuclear Information System (INIS)

Simulation irradiation experiments were carried out to investigate the formation processes and contribution to hardening of radiation-induced features in low alloy steels. Medium Cu (0.12 and 0.16%) and low Cu (0.03%) A533B steels were irradiated with 3 MeV Ni ions and 5 MeV electrons, and in KUR at 290degC. Irradiated steels were examined by three-dimensional atom probe, positron annihilation, high-resolution transmission electron microscopy and hardness measurements. Electron irradiation caused almost the same hardening as KUR irradiation in medium Cu steels under almost the same dose rate and dose conditions, whereas the formation of larger, denser and more Cu enriched clusters and smaller accumulation of single vacancies were confirmed for KUR irradiation. This indicated that cascade damage provides additional cluster nucleation sites to compensate for lower free point defect production. High dose rate Ni ion ...

Energy Technology Data Exchange (ETDEWEB)

Current advanced CMOS source/drain engineering involves the use of amorphizing implants with 3D geometry. Upon annealing, the induced transient enhanced diffusion (TED) can only be accurately predicted if the amorphized region is correctly modeled, as well as the formation and evolution of extended defects, particularly 3 1 1's and dislocation loops. In addition to the extended defects, already modeled in the atomistic kinetic Monte-Carlo simulator DADOS, we have developed a physically based modeling approach for the implant-induced damage build-up, amorphization and recrystallization, suitable to handle device-size process simulation. It is based on amorphous pockets (3D, irregular shape agglomerates of an arbitrary number of interstitials and vacancies, plus trapped impurities) with a size-dependent activation energy for recombination. The model is able to reproduce experimental aspects like the crystal-amorphous ...

Energy Technology Data Exchange (ETDEWEB)

In this paper, we report kinetic Monte Carlo study on the diffusion behavior of boron in silicon crystal, more particularly on the transient enhanced diffusion (TED) of boron in silicon during implantation and annealing. Firstly, the accuracy of our KMC code was verified by investigating the time evolutionary behavior of interstitial (I) and vacancy (V) when a silicon substrate is implanted with silicon dose with an energy of 10 keV and with a dose of 1 X 10{sup 14} ions/cm{sup 2}. To investigate the influence of native defects (I, V) on boron diffusion, a single and multi boron markers grown by MBE were employed. The simulation results revealed that the precursor of boron cluster (BI{sub 2}) is dominant at the initial stage of annealing, which explains the boron TED phenomenon in terms of the concentration of boron complexes and I, V clusters, respectively. The formation of {l_brace}311{r_brace} defects and dislocation ...

International Nuclear Information System (INIS)

Data on the recovery of Tsub(c) for several neutron irradiated A-15 compounds are presented. A model for the mechanism of recovery is suggested and has been applied to isothermal annealing data at 550"0C on a sample of Nb_3Ge and to isochronal annealing (200"0C-900"0C) data on V_3Si, Nb_3Ge and Nb_3Sn subjected to varying doses of fast neutrons and on Nb_3Al of various compositions subjected to the same dose. The recovery is assumed to take place by vacancy assisted reordering and occurs in several stages. The major low temperature stage is attributed to irradiation induced vacancies, while at high temperatures there are depleted and recovery is ascribed to the motion of thermal equilibrium vacancies. Activation energies deduced for these processes, approximately 1 eV for vacancy motion and approximately 1-2 eV for vacancy formation, are consistent with what is ...

International Nuclear Information System (INIS)

Point defect injection studies are performed to investigate how fluorine implantation influences the diffusion of boron marker layers in both the vacancy-rich and interstitial-rich regions of the fluorine damage profile. A 185 keV, 2.3x10"1"5 cm"-"2 F"+ implant is made into silicon samples containing multiple boron marker layers and rapid thermal annealing is performed at 1000 deg. C for times of 15-120 s. The boron and fluorine profiles are characterized by secondary ion mass spectroscopy and the defect structures by transmission electron microscopy (TEM). Fluorine implanted samples surprisingly show less boron diffusion under interstitial injection than those under inert anneal. This effect is particularly noticeable for boron marker layers located in the interstitial-rich region of the fluorine damage profile and for short anneal times (15 s). TEM images show a band of dislocation loops around the range of the fluorine implant and the ...

Energy Technology Data Exchange (ETDEWEB)

It has been observed that dislocation loops form and grow during annealing of silicon wafers implanted at doses above the amorphization threshold. Dislocation loops can act to store interstitials for prolonged periods of anneals, sustaining an interstitial super-saturation and thus causing substantial transient enhanced diffusion (TED). The authors have developed a comprehensive model which, in combination with a model and parameters for {l_brace}311{r_brace} defects from previous work, accounts for the formation and evolution of dislocation loops during ion implant annealing, as well as giving the correct TED behavior.

International Nuclear Information System (INIS)

Within the tight binding framework, a study is made of how the disorder affects the electronic properties of A-15 compounds. In particular it is shown that for compounds of two transition metals in the A-15 structure, the vacancy formation affects the density of states only in the low energy region or in the high energy region, in opposition with the isolated chain model of Labbe and Friedel. It is concluded that interchain interactions are important. (U.K.).

International Nuclear Information System (INIS)

Structural variations in 39-MeV alpha-particle irradiated (Tsub(irr) = 60 deg C) polycrystalline molybdenum during post-irradiation annealing were studied by X-ray and TEM methods. Despite the high density of irradiation induced defects in the structure of the specimen X-ray measurements showed zero relative lattice parameter change after an irradiation dose of 1.1 x 10"-_2 dpa. However, during the annealing #delta#a/a was changed in the positive range, exhibiting two peaks - at 100 and 300 deg C - whereas the damage structure detected by TEM indicated no changes. Analysis of the results leads to the conclusion that in the range 100 to 250 deg C migration of isolated vacancies and their annihilation at interstitial clusters as well as possible formation of new vacancy clusters occur. The second peak on the #delta#a/a temperature dependence curve is related to the transformation (probably, thermal disintegration) of ...

International Nuclear Information System (INIS)

Spectral-luminescent characteristics of Sr2Y8(SiO4)6O2: Eu powder crystal phosphor with the apatite structure and high-intensity luminescence of Eu3+ ions have been studied. The charge state of europium in the samples has been characterized by means of X-ray L3-adsorption spectroscopy. It was established that Eu3+ forms two types of optical centers. Besides, luminescence of Eu2+ions was found. Reduction Eu3+#->#Eu2+ was considered, which may be due to VSr|| vacancy formation in the 4f crystal lattice position and to negative charge transfer by this vacancy to two EuY3+ ions. Thus, in the silicate lattice there exist inhomogeneously distributed oxygen-deficient centers, which are responsible for nonradiative transfer of excitation energy to Eu3+ and Eu2+ ions. To study electron-vibrational interactions in the crystal phosphor samples, their IR and Raman spectra were examined. In the luminescence spectrum of Eu2+, a series ...

International Nuclear Information System (INIS)

The oxygen vacancies distribution in the rigid lattice and the thermally activated motion of oxygen atoms are studied in La1-xSrxGa1-xMgxO3-x (x=0.00; 0.05; 0.10; 0.15 and 0.20) compounds. For that 71Ga, 25Mg and 17O NMR was performed from 100 K up to 670 K, and ion conductivity measurements were carried out up to 1273 K. The comparison of the electric field gradients at the Ga- and Mg-sites evidences that oxygen vacancies appear exclusively near gallium cations as a species trapped below room temperature in local clusters, GaO5/2-#square#-GaO5/2. These clusters decay at higher temperature into mobile constituents of the structural octahedra Ga(O5/6#square#1/6)6/2. At the same time, the nearest octahedral oxygen environment of magnesium cations persists at different doping levels. The case of two adjacent vacant anion sites is found highly unlikely within the studied doping range. The thermally activated oxygen motion starts to develop above ...

International Nuclear Information System (INIS)

In this paper, we show that boron transient enhanced diffusion can be reduced to different extents by varying the distribution of nitrogen atoms in the junction. This is attributed to the relative location of nitrogen atoms with respect to boron profile and end-of-range defect band, affecting the interactions between dopants and defects upon annealing. In addition, variations in boron dopant activation and deactivation are also observed. Similar to fluorine co-implantation, it is proposed that nitrogen atoms react with vacancy point defects to form nitrogen-vacancy clusters that will trap the interstitials emitted from end-of-range defects. However, we report that the interstitial sink efficiency of nitrogen atoms is not as good as the co-implanted carbon atoms, which is noticed from the dopant deactivation curves. In terms of extended defect evolution, the results clearly indicate that end-of-range defects can be stabilized by choosing the ...

International Nuclear Information System (INIS)

A transient-enhanced diffusion has been observed during the furnace or rapid thermal annealing of ion-implanted silicon. We have studied this transient in detail and show that, for doses of Group V dopants sufficient to amorphize the silicon, it arises from the trapping of interstitials by dopant atoms during implantation. These are retained during solidphase-epitaxial (SPE) growth, but can be released by additional thermal processing to cause the observed transient and the formation of a band of extended defects. We have measured the enhanced diffusion coefficients and the duration of the transient for Sb-implanted Si by careful furnace annealing experiments. We obtain general expressions which predict the effects of the transient during any thermal processing based on SPE growth (furnace, CW laser, or rapid thermal annealing). We show that there is no analogous mechanism of vacancy trapping by Group III elements.

International Nuclear Information System (INIS)

The highest equilibrium free-carrier doping concentration possible in a given material is limited by the ''pinning energy'' which shows a remarkable universal alignment in each class of semiconductors. Our first-principles total energy calculations reveal that equilibrium n -type doping is ultimately limited by the spontaneous formation of close-shell acceptor defects: the 3- -charged cation vacancy in AlN, GaN, InP, and GaAs and the 1- -charged DX center in AlAs, AlP, and GaP. This explains the alignment of the pinning energies and predicts the maximum equilibrium doping levels in different materials. (c) 2000 The American Physical Society

Energy Technology Data Exchange (ETDEWEB)

Carbon capture and storage have been receiving increasing interest lately, mainly as an option to reduce CO{sub 2} emissions from the power sector. The concept could be adapted for production of H{sub 2} as well, which would provide a carbon free energy carrier that could be used for example as transportation fuel. In this doctoral thesis, the option to use chemical-looping technologies to produce H{sub 2} from fossil fuels with CO{sub 2} capture is explored. In chemical-looping combustion, direct contact between fuel and combustion air is avoided. Instead, a solid oxygen carrier performs the task of bringing oxygen from the air to the fuel. Thus, the resulting CO{sub 2} and H{sub 2}O are not diluted with N{sub 2}, and pure CO{sub 2} can easily be recovered by cooling and condensation. The heat of reaction is the same as for ordinary combustion. Chemical-looping reforming uses the same basic principles as ...

Energy Technology Data Exchange (ETDEWEB)

In this paper we have proposed a novel gas turbine cycle with hydrogen-fueled chemical-looping combustion, and the system study on two hydrogen-fueled power plants, the new gas turbine cycle and an advanced gas turbine cycle with H{sub 2}/O{sub 2} combustion, has been investigated with the aid of exergy principle (EUD methodology). The hydrogen fueled chemical-looping combustion in the new gas turbine cycle consists of two successive reactions: hydrogen fuel is reacted with metal oxide (reduction of metal oxide), and then instead of air or pure oxygen, the reduced metal is successively oxidized by the saturated air. As a result, the new hydrogen-fueled gas turbine cycle has a breakthrough performance, with at least about 12 percentage-point higher efficiency compared to the gas turbine cycle with H{sub 2}/O{sub 2} combustion, and will be environmentally superior due to complete elimination of NO{sub x} formation. The ...

Energy Technology Data Exchange (ETDEWEB)

Chemical-looping combustion is a promising technology for the combustion of gas or solid fuel with efficient use of energy and inherent separation of CO{sub 2}. Chemical-looping combustion of methane with calcium sulfate as a novel oxygen carrier was conducted in a laboratory scale fixed bed reactor. The effects of reaction temperature, gas flow rate, sample mass, and particle size on reduction reactions were investigated and an optimum operating condition was determined. The results show that this novel oxygen carrier has a high reduction reactivity and stability in a long-time reduction/oxidation test. The conversions of CH{sub 4} increased with a higher temperature, smaller gas flow rate, larger sample mass and smaller particle size. The suitable reaction temperature seems to be around 950 deg. C. Low temperatures lead to a low CH{sub 4} conversion, but a significant SO{sub 2} formation was observed at a higher ...

Energy Technology Data Exchange (ETDEWEB)

Results are presented of molecular dynamics (MD) studies of 1-10 keV displacement cascades in silicon. At these energies, the simulations couple directly to experimental observations of low energy implantation in silicon for shallow junction formation. The simulations are performed with the Stillinger-Weber potential for silicon in computational cells with up to 3.5x10{sup 5} atoms. The author employs periodic boundary conditions in the [100] and [010] directions and a free surface on the top (001) plane. The author discusses the results in terms of the structural evolution and the dynamics of the cascade zones. For sufficiently high energy recoils (>2 KeV), the cascades produce locally molten zones that result in the formation of amorphous silicon pockets upon recrystallization. Frenkel pairs are also produced during the cascade, although their number is very small (less than 10% of the binary collision predictions). Upon annealing of the ...

British Library Electronic Table of Contents (United Kingdom)

Bent specimens of A533B steel (0.16wt% Cu) were irradiated at 290degreeC to 1dpa with 6.4MeV Fe3+ ions. Calculated tensile stresses at the irradiated surface were set to 0, 250, 500 and 750MPa. The specimens were subjected to hardness measurements, transmission electron microscopy (TEM) observations and three-dimensional atom probe (3DAP) analysis. The radiation-induced hardening decreased with increasing stress to 500MPa which was near the yield strength. TEM and 3DAP results showed that well-defined dislocation loops and solute clusters were formed. The diameter of dislocation loops increased and the number density decreased when the stress was applied, whereas the diameter and number density of solute clusters decreased. The hardening was mainly attributed to solute cluster formation. A...

CERN Document Server

If two loops are isomorphic, then it is shown that their holomorphs are also isomorphic. Conversely, it is shown that if their holomorphs are isomorphic, then the loops are isotopic. It is shown that a loop is a Smarandache loop if and only if its holomorph is a Smarandache loop. This statement is also shown to be true for some weak Smarandache loops(inverse property, weak inverse property) but false for others(conjugacy closed, Bol, central, extra, Burn, A-, homogeneous) except if their holomorphs are nuclear or central. A necessary and sufficient condition for the Nuclear-holomorph of a Smarandache Bol loop to be a Smarandache Bruck loop is shown. Whence, it is found also to be a Smarandache Kikkawa loop if in addition the loop is a Smarandache A-loop with ...

International Nuclear Information System (INIS)

A set of equations describing a stress-mediated evolution of the nonequilibrium dopant-defect system has been derived and analyzed. Together with coupled diffusion of dopant atoms and point defects, we consider the drift of all mobile species in different charge states, namely vacancies, self-interstitials, and pairs 'dopant atom-point defect', in the field of stress. It has been shown that stresses may affect the diffusion of dopant atoms mainly in two ways: (1) directly, due to the drift of the pairs in the field of stress; (2) indirectly, by the formation of nonuniform defect distribution due to the drift of point defects. On this basis, various features of doping processes, such as phenomena of 'uphill' impurity diffusion near the surface (within the framework of the first or second mechanisms) and the peculiarities of high concentration phosphorus diffusion (due to the second mechanism), can be explained. Numerical computations of high ...

Energy Technology Data Exchange (ETDEWEB)

High concentrations of self-interstitials are trapped by dopant atoms during ion implantation into Si. For group V dopants, these complexes are sufficiently stable to survive solid-phase-epitaxial (SPE) growth but break up on subsequent thermal processing and cause a transient-enhanced diffusion. Dopant diffusion coefficients are enhanced by up to five orders of magnitude over tracer values and are characterized by an activation energy of approximately one half of the tracer values. In the case of group III dopants, any complexes formed during implantation do not survive SPE growth but a second source of self-interstitials becomes significant and leads to similar transient effects. This is the damaged layer underlying the original amorphous/crystalline interface. These observations provide direct evidence for long-range self-interstitial migration in Si, and we believe these are the first observations of the interstitialcy diffusion mechanism with no vacancy ...

Science.gov (United States)

The isomerization of neopentane has been investigated over the 0.76 wt% Pd/SiO{sub 2} catalyst. It is found that after high temperature reduction (HTR, at 873 K) the selectivity for isomerization is much higher than that after low temperature reduction (LTR, at 573 K). A variety of experiments, including kinetic, chemisorption (O{sub 2}, H{sub 2}, and CO), temperature-programmed desorption of H{sub 2}, and X-ray diffraction, showed that this selectivity enhancement cannot be interpreted in terms of H{sub 2} retention by catalyst. Instead, the formation of Pd-Si compound(s) (most probably Pd{sub 3}Si) during HTR seems immediately responsible for the catalytic behavior of HTR Pd/SiO{sub 2} catalysts. A mechanism is proposed for the Pd-SiO{sub 2} interaction in which Pd atoms (or ions) are incorporated into the silica support (via oxygen vacancies) and a new phase of palladium silicide is formed. Regeneration by an oxygen treatment of the HTR ...

International Nuclear Information System (INIS)

A unified physically based ion implantation damage model has been developed which successfully predicts both the impurity profiles and the damage profiles for a wide range of implant conditions for arsenic, phosphorus, BF_2, and boron implants into single-crystal silicon. In addition, the amorphous layer thicknesses predicted by this new damage model are also in excellent agreement with experimental measurements. This damage model is based on the physics of point defects in silicon, and explicitly simulates the defect production, diffusion, and their interactions which include interstitial-vacancy recombination, clustering of same type of defects, defect-impurity complex formation, emission of mobile defects from clusters, and surface effects for the first time. New computationally efficient algorithms have been developed to overcome the barrier of the excessive computational requirements. In addition, the new model has been incorporated in the ...

International Nuclear Information System (INIS)

Polycrystalline specimens of spinel (MgAl_2O_4) and alumina (Al_2O_3) were irradiated at room temperature and 650deg C with either dual- or triple-ion beams in order to investigate the effects of simultaneous displacement damage and helium implantation on cavity formation. The cavities in alumina were aligned along the direction of the c-axis, with diameters ranging from < 2 to 10 nm. The cavities in spinel were preferentially associated with dislocation loops and were of similar size as the cavities in alumina. Catastrophic amounts of cavitation were observed at the grain boundaries in spinel when the displacement damage level exceeded a critical value (#approx =# 20 dpa) in the presence of a fusion-relevant (#approx =# 60 appm/dpa) helium environment. (orig.).

International Nuclear Information System (INIS)

Results of an augmented-plane-wave calculation of the positron lifetime and the angular-correlation curves for aluminum, both in the vacancy-free crystal and in the crystal with a vacancy, are presented. The environment of the vacancy was simulated by a face-centered-cubic supercell with a volume 27 times that of the standard primitive unit cell of the Al lattice. The calculated positron-vacancy binding energy is 3.36 eV at room temperature. The temperature dependences of the trapping potential, the positron-vacancy binding energy, and the positron lifetime both in the Bloch state and in the vacancy-trapped state, associated only with the static thermal expansion of the lattice, have been calculated. It is found that the fractional increase in positron lifetime in the Bloch state is only approx.80% of the fractional increase in the volume of the lattice. The ...

Energy Technology Data Exchange (ETDEWEB)

Positron annihilation experiments on Fe-Cu model dilute alloys of nuclear reactor pressure vessel (RPV) steels have been performed after neutron irradiation in JMTR. Nanovoids whose inner surfaces were covered by Cu atoms were clearly observed. The nanovoids transformed to ultrafine Cu precipitates by dissociating their vacancies after annealing at around 400degC. The nanovoids and the ultrafine Cu precipitates are strongly suggested to be responsible for irradiation-induced embrittlement of RPV steels. Effects of Ni, Mn and P addition on the nanovoid and Cu precipitate formations were also studied. The nanovoid formation was enhanced by Ni and P, but suppressed by Mn. The Cu precipitates after annealing around 400degC were almost free from these doping elements and hence were pure Cu in the chemical composition. Furthermore the Fermi surface of the 'embedded' Cu precipitates with a body centered cubic ...

Energy Technology Data Exchange (ETDEWEB)

In order to develop modern two-stroke engines with low fuel consumption, respectively with low exhaust emissions, two alternative development areas -- the mixture formation and the scavenging system -- have been correlated. For a satisfying mixture formation without fuel losses by scavenging, the direct injection seems to be one of the best solution for the high speed two-stroke engine of the future. On the other hand the modern development of two-stroke scavenging systems shows a large field of application and improvement methods of cross and loop scavenging. Based on the specific optimization factors of the injection system, respectively of the scavenging system, the aim off this common work of the Universities of Pisa and Zwickau is to correlate both the optimization fields in an advantageous mixture formation process. The principal elements of this correlation are the design of the combustion ...

International Nuclear Information System (INIS)

General corrosion testing of Alloy 800 tube material by the General Electric Co. using out of pile loops with steam temperatures in the range 430 to 770 deg.C and 70 at. pressure with a surface heat flux of 55 W.cm"-"2 and flow velocities of 30 to 60 m.sec"-"1 showed after about 5000 h (a) a relatively moderate loss of metal at a fairly high corrosion rate, (b) a relatively high loss of oxide to the steam phase, and (c) the formation of a zone at the metal surface depleted in chromium by diffusion to the oxide film. It is important to establish whether these results for Alloy 800 were typical of those to be expected under heat transfer, and whether they could be used as a basis for extrapolation to the higher heat fluxes and longer exposure time relevant to superheat applications. Additional corrosion tests in superheated steam of 1000 h duration under isothermal conditions were therefore undertaken and an experimental loop ...

International Nuclear Information System (INIS)

In this letter, the effect of vacancies generated by preirradiated laser on dopant diffusion and activation in preamorphized silicon substrate has been studied. Laser-induced melting in silicon was used to generate excess vacancies near the maximum melt depth before silicon substrate amorphization and subsequent boron implantation. We demonstrate that by matching the preirradiated laser melt depth with the implant amorphize depth, it can effectively reduce the silicon self-interstitials released from the end-of-range defect band. The results show great suppression in boron transient enhanced diffusion and significant removal of end-of-range defects. This is attributed to the recombination of laser-generated excess vacancies with preamorphizing induced free silicon interstitials at the end-of-range region.

International Nuclear Information System (INIS)

Angular dependence from L_3-subshell to M-shell vacancy transfer probabilities for selected heavy elements from Au to U have been measured by using a Si(Li) detector coupled to a model 1024 computerized multi-channel analyzer. Because the angular dependence from L_3-subshell to M-shell vacancy transfer probabilities is not found in the literature, to the best of our knowledge there are no experimental values for worked elements. Therefore, the results for the elements obtained in the present study constitute the first experimental measurements; the comparison has been not made with other experimental and theoretical results. It has been observed that angular dependence from L_3-subshell to M-shell vacancy transfer probabilities increase with increasing cos #theta#.

Energy Technology Data Exchange (ETDEWEB)

Metals for potential use in the dissociator and the synthesizer reactors of a distributed solar receiver thermochemical transport loop utilizing SO/sub 3//SO/sub 2//O/sub 2/ molecular chemistry were tested in SO/sub 2//O/sub 2/ mixtures at 500/sup 0/C and 900/sup 0/C, respectively, for times of up to four weeks. They included titanium, aluminum and nickel, and iron-base, nickel-base and cobalt-base superalloys. Weight gain measurements determine the oxidation/sulfidation kinetics. Electron microprobe analysis identifies any possible penetration of oxygen and sulfur into the metal and the formation of internal oxides and sulfides. The most promising candidates as a result of these tests are the cobalt-base superalloys.

International Nuclear Information System (INIS)

Ion implantation is used at several critical stages of Si integrated circuit manufacturing. The authors show how #left brace#311#right brace# defects arising after implantation are responsible for both enhanced dopant diffusion during annealing, and stable dislocations post-anneal. They observe #left brace#311#right brace# defects in the earliest stages of an anneal. They subsequently undergo rapid Ostwald ripening and evaporation. At low implant doses evaporation dominates, and they can quantitatively relate the interstitials emitted from these defects to the transient enhancement in diffusivity of dopants such as B and P. At higher doses Ostwald ripening is significant, and they observe the defects to undergo a series of unfaulting reactions to form both Frank loops and perfect dislocations. They demonstrate the ability to control both diffusion and dislocations by the addition of small amounts of carbon impurities.

Energy Technology Data Exchange (ETDEWEB)

The diffusion of Sb and B markers has been studied in vacancy supersaturations produced by MeV Si implantation in float zone (FZ) silicon and bonded etch-back silicon-on-insulator (BESOI) substrates. MeV Si implantation produces a vacancy supersaturated near-surface region and an interstitial-rich region at the projected ion range. Transient enhanced diffusion (TED) of Sb in the near surface layer was observed as a result of a 2 MeV Si{sup +}, 1 {times} 10{sup 16}/cm{sup 2}, implant. A 4{times} larger TED of Sb was observed in BESOI than in FZ silicon, demonstrating that the vacancy supersaturation persists longer in BESOI than in FZ. B markers in samples with MeV Si implant showed a factor of 10{times} smaller diffusion relative to markers without the MeV Si{sup +} implant. This data demonstrates that a 2 MeV Si{sup +} implant injects vacancies into the near surface region.

CERN Document Server

We study the temporal evolution of coronal loops using data from the Solar X-ray Imager (SXI) on board of GOES-12. This instrument allows us to follow in detail the full lifetime of coronal loops. The observed light curves suggest three somewhat distinct evolutionary phases: rise, main, and decay. The durations and characteristic timescales of these phases are much longer than a cooling time and indicate that the loop-averaged heating rate increases slowly, reaches a maintenance level, and then decreases slowly. This suggests that a single heating mechanism operates for the entire lifetime of the loop. For monolithic loops, the loop-averaged heating rate is the intrinsic energy release rate of the heating mechanism. For loops that are bundles of impulsively heated strands, it is an indication of the frequency of occurrence of individual ...

Energy Technology Data Exchange (ETDEWEB)

Single crystals of trigonal Cr{sub 2}Te{sub 3}, monoclinic Cr{sub 5}Te{sub 8}, and trigonal Cr{sub 5}Te{sub 8} were prepared and the single crystal structures were determined. The structures are related to the NiAs structure type by successive removal of Cr in every second metal atom layer parallel to the c axis. The strong relationship between the structures is evidenced by their very similar X-ray powder patterns. In trigonal Cr{sub 2}Te{sub 3} excess Cr occupies only one of the two possible sites. In monoclinic Cr{sub 5}Te{sub 8} the Cr atoms occupy four different crystallographic sites. The resulting ordering of the vacancies is significantly different from the hitherto reported crystal structures of transition metal chalcogenides M{sub 5}X{sub 8}. A slight increase of the tellurium content leads to an order-disorder transition from the monoclinic to a trigonal phase. The Cr atoms are located on four crystallographically different sites leading to the ...

UK PubMed Central (United Kingdom)

A closed loop control process assures that a system performs within control limits. In closed loop control, the system's output feeds back directly to change the system's inputs. We describe an approach...Full Text Available

CERN Document Server

Two constructions due to Dr\\'apal produce a group by modifying exactly one quarter of the Cayley table of another group. We present these constructions in a compact way, and generalize them to Moufang loops, using loop extensions. Both constructions preserve associators, the associator subloop, and the nucleus. We conjecture that two Moufang 2-loops of finite order $n$ with equivalent associator can be connected by a series of constructions similar to ours, and offer empirical evidence that this is so for $n=16$, 24, 32; the only interesting cases with $n\\le 32$. We further investigate the way the constructions affect code loops and loops of type $M(G, 2)$. The paper closes with several conjectures and research questions concerning the distance of Moufang loops, classification of small Moufang loops, and generalizations of the two ...

Energy Technology Data Exchange (ETDEWEB)

We measure the transient enhanced diffusion of shallow molecular-beam-epitaxy grown marker layers of Sb and B due to deep MeV Si{sup +} ion implants at very high doses ({approx}10{sup 16}cm{sup {minus}2}). We expect the near-surface region of these implants to be vacancy rich, and we observe transient enhanced diffusion of Sb (the classic vacancy diffuser). The large enhancements imply a significant vacancy supersaturation ({approx}700 at 740{degree}C). Double implantation of the high-dose MeV Si followed by a shallow (40 keV) Si implant and annealing produces a greatly reduced number of {l_brace}311{r_brace} defects compared to a 40 keV implant into virgin Si, again consistent with a vacancy-rich region in the near-surface region of an MeV implant. However, the shallow B marker layers also show transient enhanced diffusion for the same MeV implant under similar annealing conditions, implying that an ...

Energy Technology Data Exchange (ETDEWEB)

This paper reports that the point defect model for steady-state passive films formed anodically on metal s in aqueous environments has been extended to include irreversible dissolution of the film and the irreversible generation and annihilation of cation and oxygen vacancies at the metal/film and film/solution interfaces. THe model yields a number of diagnostic criteria that can be used to identify the majority (vacancy) charge carrier and to characterize the kinetic nature of the interfacial vacancy generation and annihilation processes. We use these criteria to show that the steady-state passive film that forms on nickel in acidic phosphate buffer solutions is a cation conductor and that cation transport from the metal to the solution involves irreversible ejection of cations from the film. On the other hand, the passive film that forms on tungsten in the same environment under steady-state conditions is found to be an ...

Energy Technology Data Exchange (ETDEWEB)

The {delta} {yields} {alpha}{prime} martensitic transformation in Pu-1.9 at.% Ga occurs when the alloy is cooled below about -100 C. This transformation exhibits anomalous behavior, where the isothermal transformation proceeds atypically with double-C kinetics. Recent work has revealed that an ambient temperature isothermal hold (referred to as conditioning) prior to the transformation has different effects depending on whether transformation proceeds in the upper- or lower-C of the double-C: the amount of transformation is increased with conditioning in the upper-C, while the transformation in the lower-C seems to be engendered by conditioning. The mechanism by which conditioning affects the low-temperature {delta} {yields} {alpha}{prime} transformation is thus of great importance to understanding the transformation itself as well as the general circumstances that can affect a martensitic phase transformation. Using differential scanning calorimetry measurements, ...

Energy Technology Data Exchange (ETDEWEB)

Chemical looping combustion (CLC) of simulated coal-derived synthesis gas was conducted with NiO oxygen carriers supported on SiO2, ZrO2, TiO2, and sepiolite. The effect of H2S on the performance of these samples for the CLC process was also evaluated. Five-cycle thermogravimetric analysis (TGA) tests at 800 C indicated that all oxygen carriers had a stable performance at 800 C, except NiO/SiO2. Full reduction/oxidation reactions of the oxygen carrier were obtained during the five-cycle test. It was found that support had a significant effect on reaction performance of NiO both in reduction and oxidation rates. The reduction reaction was significantly faster than the oxidation reaction for all oxygen carriers, while the oxidation reaction is fairly slow due to oxygen diffusion on NiO layers. The reaction profile was greatly affected by the presence of H2S, but there was no effect on the capacity due to the presence of H2S in synthesis gas. The presence of H2S ...

CERN Document Server

A Smarandache quasigroup(loop) is shown to be universal if all its f,g-principal isotopes are Smarandache f,g-principal isotopes. Also, weak Smarandache loops of Bol-Moufang type such as Smarandache: left(right) Bol, Moufang and extra loops are shown to be universal if all their f,g-principal isotopes are Smarandache f,g-principal isotopes. Conversely, it is shown that if these weak Smarandache loops of Bol-Moufang type are universal, then some autotopisms are true in the weak Smarandache sub-loops of the weak Smarandache loops of Bol-Moufang type relative to some Smarandache elements. Futhermore, a Smarandache left(right) inverse property loop in which all its f,g-principal isotopes are Smarandache f,g-principal isotopes is shown to be universal if and only if it is a Smarandache left(right) Bol loop in which all its ...

International Nuclear Information System (INIS)

Generally, neutron, ion and electron Irradiations cause a substantial amount of hardening and significantly alter the deformation behavior of metals and alloys at relatively low irradiation temperatures. A radiation hardening is caused by the formation of microstructural defects such as dislocation loops, voids and precipitates under irradiation. Therefore, it is important to have a better knowledge of the irradiation induced microstructural defects under irradiation condition. As a part of the National mid- and long-term atomic energy R and D program, we are dealing with the radiation hardening behavior in Fe-Cr binary alloy. Fe-Cr binary alloy is a base alloy of Ferritic/Martensitic steel(F/M steel) planning to use for the Gen IV nuclear system. In this work, we investigated the radiation hardening and microstructural defect evolution in ion irradiated Fe-Cr alloys with irradiation temperature using nano-indentation measurement and ...

Energy Technology Data Exchange (ETDEWEB)

Metals for potential use in the dissociator and the synthesizer reactors of a distributed solar receiver thermochemical transport loop utilizing SO/sub 3//SO/sub 2//O/sub 2/ molecular chemistry includes stainless steels and iron-base, nickel-base and cobalt-base superalloys. We tested these alloys in SO/sub 2//O/sub 2/ mixtures and SO/sub 3/ gas at 500/sup 0/C and 900/sup 0/C, respectively, for times of up to four weeks. Weight gain measurements were used to determine the oxidation/sulfidation kinetics and electron microprobe analysis was used to measure penetration of oxygen and sulfur into the metal and to identify the formation of internal oxides and sulfides. Results of these tests showed that the most promising candidates are those containing sufficient quantities of both aluminum and chromium alloying additions to be alumina and chromia formers, such as Kanthal A-1, Nimonic 105 and Cabot 214.

International Nuclear Information System (INIS)

We present an atomistic simulation of the Ostwald ripening of extrinsic defects (clusters, #left brace#1 1 3#right brace#s and dislocation loops) which occurs during annealing of ion implanted silicon. The model describes the capture and emission of Si interstitial atoms to and from extrinsic defects of sizes up to thousands of atoms and includes a loss term due to the flux of interstitials to the recombining surface. Key input parameters of the simulation are the variations of the formation energy and of the capture efficiency with the size of the different defects. This model shows that the kinetics of the well-known dissolution of #left brace#1 1 3#right brace# defects is only driven by the recombination efficiency at the surface and the distance from the defects to the sample surface. We have subsequently used this model to study defect evolution in low and ultra low energy (ULE) B implanted Si during annealing. Defect dissolution occurs ...

Energy Technology Data Exchange (ETDEWEB)

This paper reports the development of a relay coordination package specially designed as a teaching aid. Fault studies required for relay coordination has been performed by using a newly developed loop impedance matrix. This new method of forming loop impedance matrix is particularly suitable for multiple fault studies environment as required in relay coordination. A simple topology searching technique has been used to find all loops of the network. This package simultaneously serves the purpose of teaching relay coordination, loop analysis technique and the method of topology searching.

Energy Technology Data Exchange (ETDEWEB)

The aim of this work is to account for the effects of the high temperature oxidation of metals on their microstructure and their mechanical properties. 'Model' materials like pure nickel, pure iron and the Ni-20Cr alloy are studied. Nickel foils have been oxidised at 1000 C on one side only in laboratory air, the other side being protected from oxidation by a reducing atmosphere. After the oxidation treatment, the unoxidized face was carefully examined by using an Atomic Force Microscope (AFM). Grain boundaries grooves were characterised and their depth were compared to the ones obtained on the same sample heat treated in the reducing atmosphere during the same time. They are found to be much deeper in the case of the single side oxidised samples. It is shown that this additional grooving is directly linked to the growth of the oxide scale on the opposite side and that it can be explained by the diffusion of the vacancies produced at the oxide ...

UK PubMed Central (United Kingdom)

A structurally conserved element, the trigger loop, has been suggested to play a key role in substrate selection and catalysis of RNA polymerase II (pol II) transcription elongation. Recently resolved...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

As evidence of its effectiveness rapidly accumulates, the Lomi process has most recently been used to decontaminate the recirculation loops and the reactor water clean-up unit of a BWR at Monticello in the United States. An average decontamination factor of 23 was achieved in the recirculation loops.

International Nuclear Information System (INIS)

Developed is a simple method alloing one to determine the k-loop coefficient of #beta# function in gauge theories provided the operator expansion is constructed in (k-1) loop for certain two-point functions. The calculation of the two-loop coefficient of the Gell-Mann-Low function becomes trival - it reduces to a few algebraic operations with expressions which are already known. As an example spinor, scalar and supersymmetric electrodynamics are considered. Although the corresponding results for #beta#"("2") are known in the literature, both the method of the calculations and some points referring to the construction of the operator expansion are novel.

Energy Technology Data Exchange (ETDEWEB)

ABO{sub 3} perovskite-type oxides having vacancies in the A-sites of their structure are interesting candidates for solid electrolytes when their A-sites are occupied by Li{sup +} ions having a high mobility. This is the case with the [Li{sub 3x}La{sub 2/3-x}]TiO{sub 3} solid solution compound which has a 10{sup -3} S cm{sup -1} ionic conductivity at ambient temperature. Electrochemical intercalation in this material is possible thanks to the presence of Ti{sup 4+} but the small amount of vacancies (0.33 maximum) leads to a low intercalation rate. In order to solve this problem, the LiLaNb{sub 2}O{sub 7} material which has a greater amount of vacancies has been studied and the results relative to the electrochemical intercalation of lithium in this perovskite are presented. The thermodynamical and kinetics properties of the lithium intercalation reaction have been studied by intermittent galvano-static discharges and ...

Energy Technology Data Exchange (ETDEWEB)

Presented are some preliminary studies made in preparation for the design of a solar powered loop for desalination by humidification - dehumidification process. The studies concentrated on the evaluation of different parameters affecting the performance of the combination of different components in such a loop in the hope of outlining the most decisive factors for the choice or design of solar collectors or heat source. The results presented relate to the performance of two of the most important components in a loop of such purpose, that is: the humidifying and the dehumidifying columns or stacks. 4 refs.

International Nuclear Information System (INIS)

The evolution of metallic substance atomic structure is studied on temperature variation including crystal heating up to melting points, a crystal- liquid phase transition and initiation of a high-density liquid specific structure. It is marked that heat induced changes of simple metal structure can be described as changes around a natural elementary cell which is common for both a crystal and a liquid and consists of a central atom and Z_1 atoms of the first coordination sphere. On this basis the vacancy model of melting is verified. Concentrations of melting vacancies are determined by coordination numbers in the form of Z_1/(1+Z_1)"2 which are the same for both a crystal and a natural elementary cell. The size of natural elementary cells is in an agreement with that of the coordination sphere featured in the liquid and phase transition statistical theory. Calculated data are given for a number of metals, Cs, Eu, Ni, V included

International Nuclear Information System (INIS)

Nowadays, diamond and the nitrogen-vacancy (NV) colour centres constitute the best solid-state system in view of quantum-computing applications. It has also been shown recently that single NV centres could be used as nanoscale magnetic sensors. Such applications require the creation of single NV centres with very high resolution and with a high efficiency. The nano-implanter at the university of Bochum provides low energy nitrogen ions which can be implanted through a hole pierced in the tip of an atomic force microscope. Ultrapure diamond samples have been implanted with spot sizes of 50nm and less. Stimulated Emission Depletion (STED) microscopy has been used to characterise and resolve the implanted spots.

International Nuclear Information System (INIS)

Nano indentation analysis and transmission electron microscopy observation were performed to investigate a microstructural evolution and its influence on the hardening behavior in Fe-Cr alloys after an irradiation with 8 MeV Fe4+ ions at room temperature. Nano indentation analysis shows that an irradiation induced hardening is generated more considerably in the Fe-15Cr alloy than in the Fe-5Cr alloy by the ion irradiation. TEM observation reveals a significant population of the a0 dislocation loops in the Fe-15Cr alloy and an agglomeration of the 1/2a0 dislocation loops in the Fe-5Cr alloy. The results indicate that the a0 dislocation loops will act as stronger obstacles to a dislocation motion than 1/2a0 dislocation loops.

International Nuclear Information System (INIS)

1 - Description of test facility: The LOBI facility is a 1/700 scale model of a four loop PWR and has two primary loops, the intact loop representing three loops and the broken loop representing one loop of a four-loop PWR. The reactor pressure vessel model contains an electrically heated rod-bundle with 64 rods and a heated length of 3.9 m. The nominal heating power is 5.3 MW. The downcomer is of annular shape. An upper head simulator is connected to the vessel. Each of the two primary loops contains a pump and a steam generator. The different mass flows in the loops are established by the pump speeds, since the two pumps are identical. Heat is removed from the steam generators by a secondary system. ECC water can be supplied from two accumulators, one for each loop. Cold or hot ...

Energy Technology Data Exchange (ETDEWEB)

Amorphization and a dual implant technique have been used to manipulate residual defects that persist following implantation and post-implant thermal treatments. Residual defects can often be attributed to ion-induced defect excesses. A defect is considered to be excess when it occurs in a localized region at a concentration greater than its complement. Sources of excess defects include spatially separated Frenkel pairs, excess interstitials resulting from the implanted atoms, and sputtering. Preamorphizing prior to dopant implantation has been proposed to eliminate dopant broadening due to ion channeling as well as dopant diffusion during subsequent annealing. However, transient-enhanced diffusion (TED) of implanted boron has been observed in pre-amorphized Si. The defects driving this enhanced boron diffusion are thought to be the extended interstitial-type defects that form below the amorphous-crystalline interface during implantation. A dual implantation process was applied in an ...

International Nuclear Information System (INIS)

M shell x-ray production cross sections in thick targets of Pb, Th and U by K x-rays of Rb, Nb and Mo respectively have been measured. As the incident K x-ray energies are above the L_3 edge but below L_2 edge energies of the respective target elements under reference, the M x-rays are produced not only due to direct interaction of incident photons with M shell electrons but also due to the shift of the L_3 subshell vacancies to the M shell. The experiment has been performed using a double reflection geometrical setup with a 1 Curie"2"4"1Am gamma ray source and a Si (Li) x-ray spectrometer. The measured values have been compared with those calculated using known values of M and L_3 subshell photoionisation cross sections and fluorescence yields etc., wherever possible. The component of the percentage contribution due to shift of L_3 subshell vacancies to M shell to the total M shell x-ray emission were evaluated and it is seen that the shift of ...

Energy Technology Data Exchange (ETDEWEB)

The adsorption equilibria of Kr, Xe and N{sub 2}, which are constituents of the off-gas from nuclear reprocessing processes, on representative adsorbents (Molecular Sieve 5A (MS5A) and activated charcoal) were studied. Adsorption experiments were conducted in the temperature range of 77 to 323 K using a packed bed column. The adsorption isotherms for the activated charcoal adsorbent were successfully correlated by the vacancy solution model. The adsorption isotherms for the MS5A adsorbent were properly correlated by the Langmuir model and the vacancy solution model. The adsorption experiments for the binary component systems (Kr-Xe, Kr-N{sub 2} systems) were also performed, and the results suggest that the coexistence of Xe greatly inhibits the adsorption of Kr. The coexistence of large amounts of N{sub 2} was also found to inhibit the adsorption of Kr. The experimental results for the adsorption equilibrium of binary component systems on the ...

International Nuclear Information System (INIS)

Three ternary austenitic alloys (Fe-15Cr-25Ni, Fe-15Cr-25Ni-0.04P, Fe-15Cr-45Ni in both annealed and cold worked conditions) were irradiated at 465 C to 0.15, 0.28, and 0.42 dpa at above core position in the Fast Flux Test Facility utilizing the Materials Open Test Assembly to study the separate and synergistic effects of He/dpa ratio, phosphorus addition, nickel content and cold work level on microstructural evolution and hardening. The helium/dpa ratio was varied by isotopic doping with "5"9Ni to enhance the production rate of helium. The helium production rate was evaluated to be 62 appm He/dpa in the "5"9Ni-doped specimens and 0.26 appm He/dpa in the undoped specimens. Transmission electron microscopic examinations revealed that alloy composition affected significantly the evolution of microstructure during irradiation. Phosphorus addition prevented the formation of Frank loops through the precipitation of phosphide. Nickel content ...

Energy Technology Data Exchange (ETDEWEB)

In order to study the two-phase natural circulation and flow termination during a small break loss of coolant accident in LWR, simulation experiments have been performed using two different thermal-hydraulic loops. The main focus of the experiment was the two-phase flow behavior in the hot-leg U-bend typical of BandW LWR systems. The first group of experiments was carried out in the nitrogen gas-water adiabatic simulation loop and the second in the Freon 113 boiling and condensation loop. Both of the loops have been designed as a flow visualization facility and built according to the two-phase flow scaling criteria developed under this program. The nitrogen gas-water system has been used to isolate key hydrodynamic phenomena such as the phase distribution, relative velocity between phases, two-phase flow regimes and flow termination mechanisms, whereas the Freon loop has been used ...

International Nuclear Information System (INIS)

In this paper, we propose a simple method for controlling an electromagnetic levitation (Mag lev) system. The model of the Mag lev system under consideration in this paper is third order, inherently nonlinear and unstable. For designing a controller to obtain a good disturbance rejection and being insensitive to parameter variations, we use an inner-loop and an outer-loop configuration. The configuration is the key to solve this problem. By using a nonlinear state transformation in the feedback path, a cascaded PI controller and a redefined input in the inner loop, we obtain a linear second order system. Furthermore, to achieve a stable system with a good disturbance rejection, we design a Pid controller cascaded with the inner loop system in the negative unity feedback configuration in the outer loop. We show that the closed-loop system is robustly stabilized ...

International Nuclear Information System (INIS)

We demonstrate reversible movement of (1/2)[110](110) dislocation loops generated from nanodisturbances in a #beta#-titanium alloy. High resolution transmission electron microscope observations during an in situ tensile test found three reversible deformation mechanisms, nanodisturbances, dislocation loops and martensitic transformation, that are triggered in turn with increasing applied stress. All three mechanisms contribute to the nonlinear elasticity of the alloy. The experiments also revealed the evolution of the dislocation loops to disclination dipoles that cause severe local lattice rotations.

International Nuclear Information System (INIS)

Compared with that of Daya Bay Nuclear Power Plant, the reactor power of QS-II Nuclear Power Plant is decreased and the primary coolant system is changed from three loops to two loops. Thereby the related systems were re-designed, and corresponding tests and engineering validation were carried out. Results of preliminary operation indicate that it is successful. The author describes the design modifications, features and corresponding tests of some systems, reflecting the successful incorporation of engineering and testing, and revealing the capability to develop nuclear power and design the large or medium sized commercial NPP on Self-Reliance in China

Science.gov (United States)

The spread spectrum acquisition and tracking performance for the Shuttle S-band and Ku-band communication links are analyzed and compared to test results. The S-band link requirements are more severe than those of the Ku-band links, hence, different despreader designs were developed for the two systems. The S-band despreader acquires pseudonoise code lock by examining all possible code phases in half chip steps while the Ku-band despreader acquires pseudonoise code lock by continuously sweeping a tau-jitter loop. Both despreaders employ a tau-jitter loop for code tracking. The code tracking performance is computed for the tau-jitter loop and compared to that of the more complex delay lock loop.

International Nuclear Information System (INIS)

Experiments have been performed with the PMK integral-type facility, a model of WWER-440 type PWRs, to investigate two-phase natural circulation behaviour. The phenomena to be expected in this reactor type are different from those in PWRs with vertical steam generators mainly due to the loop seal in the hot leg and the horizontal layout of the steam generator heat transfer tubes. The experiments showed that the system is repressurized when the water level drops to the hot leg elevation due to the effect of the loop seal. Opening of the loop seal can be smooth, but may lead to oscillations depending on the power and the mass inventory. Natural circulation recovers after the hot leg loop seal is opened, but then decreases with further mass inventory decrease. (orig.).

British Library Electronic Table of Contents (United Kingdom)

Background: Thyroid-stimulating autoantibodies (TSAb) bind to the thyrotropin receptor (TSHR) extracellular domain, or ectodomain (ECD), comprising a leucine-rich repeat domain (LRD) linked by a hinge region to the transmembrane domain (TMD). The LRD (residues 22???260; signal peptide 1???21) contains two disulfide-bonded loops at its N-terminus. In the crystal structure of the isolated LRD complexed with human TSAb monoclonal antibody (mAb) M22, N-terminal disulfide loop 1 (residues 22???30) could not be determined because of crystal disorder. Nevertheless, present crystal structure data are interpreted to exclude a role for the LRD N-terminal disulfide loops in the TSAb epitope(s), contradicting prior functional evidence of a role for these loops in TSAb function. Materials and Methods: ...

Science.gov (United States)

... of the loop filter based on ... algorithms, including delta-sigma approaches, routinely uses double-precision floating point number representations for ...

Energy Technology Data Exchange (ETDEWEB)

Predictions of the combination of our recent model for the formation of planetary nebulae (due to a diverging pulsational instability) together with nuclear-burning shell flashing, with regard to formation of multiple shells, are explored and discussed.

Energy Technology Data Exchange (ETDEWEB)

The relative contributions of interstitials and vacancies to diffusion of a dopant A in silicon are specified by the interstitial fraction of diffusivity, f{sub A}. Accurate knowledge of f{sub A} is required for predictive simulations of Si processing during which the point defect population is perturbed, such as transient enhanced diffusion. While experimental determination of f{sub A} is traditionally based on an underdetermined system of equations, we show here that it is actually possible to derive expressions that give meaningful bounds on f{sub A} without any further assumptions but that of local equilibrium. By employing a pair of dopants under the same point-defect perturbance, and by utilizing perturbances very far from equilibrium, we obtain experimentally f{sub Sb}{le}0.012 and f{sub B}{ge}0.98 at temperatures of {approximately}800{degree}C, which are the strictest bounds reported to date. Our results are in agreement with a theoretical expectation that ...

Energy Technology Data Exchange (ETDEWEB)

The structure of Bi/sub 1.8/Ce/sub 0.2/(MoO/sub 4/)/sub 3/ has been refined with powder neutron diffraction data by the Rietveld method. The structure can be derived by severely distorting the scheelite structure (AMO/sub 4/) and is perhaps better written A/sub (2/3)/phi/sub (1/3)/MO/sub 4/, where phi = cation vacancy. Of the two bismuth atom sites, cerium preferentially occupies the more symmetric of the two (Bi(2) in the structure) with some cerium found in the scheelite subcell vacancies also. This site preference is understood by examining the symmetries of the two Bi sites. Crystal data: monoclinic, space group P2/sub 1//c, Z = 4, a = 7.697(2), b = 11.535(3), c = 11.944(3), ..beta.. = 115.19.

International Nuclear Information System (INIS)

We demonstrate that the excess vacancies induced by a 1 MeV Si implant reduce the excess interstitials generated by a 40 keV Si implant during thermal annealing when these two implants are superimposed in silicon. It is shown that this previously observed reduction is dominated by vacancy annihilation and not by gettering to deeper interstitial-type extended defects. Interstitial supersaturations were measured using B doping superlattices (DSL) grown on a silicon-on-insulator (SOI) substrate. Implanting MeV and keV Si ions into the B DSL/SOI structure eliminated the B transient enhanced diffusion normally associated with the keV implant. The buried SiO_2 layer in the SOI substrate isolates the deep interstitials-type extended defects of the MeV implant, thereby eliminating the possibility that these defects getter the interstitial excess induced by the keV Si implant. copyright 1999 American Institute of Physics.

KoreaScience (Korea)

Full Text Available

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

International Nuclear Information System (INIS)

We have performed molecular dynamics simulations of radiation damage in fused silica. In this study, we discuss the role of successive cascade overlap on the saturation and self-healing of oxygen vacancy defects in the amorphous fused silica network. Furthermore, we present findings on the topological changes in fused silica due to repeated energetic recoil atoms. These topological network modifications consistent with experimental Raman spectroscopic observation on neutron and ion irradiated fused silica are indicators of permanent densification that has also been observed experimentally.

Energy Technology Data Exchange (ETDEWEB)

Self-consistent electronic structure calculations have been performed on two compositions of scandium sulfide ScS and Sc/sub 3/S/sub 4/. The results of the calculation of ScS are similar to those obtained for other transition metal chalcogenides and are in excellent agreement with heat capacity and reflectance measurements as well as UPS experiments. The calculation of the defect structure indicates the creation of sulfur p nonbonding states in metal-deficient ScS. The valency of the metal ions remains unchanged upon the creation of vacancies.

International Nuclear Information System (INIS)

The electronic structure of the clusters [V_3Si_4]"1"2"-, [Nb_3Sn_4]"1"2"-[Mo_3Ge_4]"1"5"- in crystalline V_3Si, Nb_3Sn, Mo_3Ge compounds is calculated by the Extended Hueckel method. The influence of different types of radiation induced defects on the density of states at the Fermi level (the anti-site defects, the displacement of atoms in linear chains, the vacancy-interstitial type defects) is considered. (author).

International Nuclear Information System (INIS)

For the purpose of optimizing the process of co-implantation of MeV Si ions to reduce boron transient enhanced diffusion and boron-enhanced diffusion in Si, multiple MeV implantations and annealing at different temperatures have been performed. A slight improvement on the suppression of B diffusion is observed by adding a low temperature annealing step after the MeV implantation. No differences in B diffusion are observed when the Si doses are increased from 1 x 10"1"5 to 1 x 10"1"6 cm"-"2. This dose independent behavior is speculated to be a quasi-steady state of vacancy cluster evaporation.

CERN Document Server

All-order spurion-corrected superpropagators and superfield Feynman rules are employed to systematically compute a two-loop corrected effective potential for the O'Raifeartaigh model, that realizes spontaneous supersymmetry breaking. Though the shifted superpropagators are rather nontrivial, superspace techniques may be suitably extended and confirm their efficacy in computing radiative corrections even when supersymmetry breakdown occurs.

Energy Technology Data Exchange (ETDEWEB)

We present a modification of the closed-loop state space model for AO control which allows delays that are a non-integer multiple of the system frame rate. We derive the new forms of the Predictive Fourier Control Kalman filters for arbitrary delays and show that they are linear combinations of the whole-frame delay terms. This structure of the controller is independent of the delay. System stability margins and residual error variance both transition gracefully between integer-frame delays.

Energy Technology Data Exchange (ETDEWEB)

The precipitation of excess silicon interstitials into dislocation loops is modeled. This situation occurs when an amorphous layer is created at the surface in order to avoid boron channeling and form shallow p junctions. The modeling of the nucleation of these extended defects is included into the process simulator IMPACT-4. Their density and mean radius are calculated for several annealing times and temperatures and they are compared with experimental characterizations. This is the first step towards a full modeling of the complex processes involved in the transient enhanced diffusion of boron.

British Library Electronic Table of Contents (United Kingdom)

A formula is obtained which describes the kinetics of low-temperature radiation hardening caused by creation of dislocation loops of interstitial type during irradiation. The radiation hardening of aluminum and vanadium is estimated using this formula and results of experiments on studying processes of nucleation and growth of interstitial dislocation loops in these materials by transparent electron microscopy. It is shown that the proposed formula is valid for description of the kinetics of low-temperature radiation hardening.

Energy Technology Data Exchange (ETDEWEB)

This talk is a brief review of gaugino condensation in superstring effective field theories and some related issues (such as renormalization of the gauge coupling in the effective supergravity theories and modular anomaly cancellation). As a specific example, we discuss a model containing perturbative (1-loop) corrections to the K{umlt a}hler potential and approximate S-duality symmetry.

CERN Document Server

A consistent combination of quantum geometry effects rules out a large class of models of loop quantum cosmology and their critical densities as they have been used in the recent literature. In particular, the critical density at which an isotropic universe filled with a free, massless scalar field would bounce must be well below the Planck density. In the presence of anisotropy, no model of the Schwarzschild black hole interior analyzed so far is consistent.

Science.gov (United States)

A description of LOOP covers the single point mooring (SPM) system; the offshore pipelines connecting each SPM to the pumping platform; the offshore platform complex, a pumping platform and a control platform; the onshore pipelines; and the Clovelly Dome storage terminal.

Energy Technology Data Exchange (ETDEWEB)

Fuel cell vehicles have been identified as the personal transportation technology of the future because of their high efficiency and very low emissions. To achieve the goal of road-ready fuel cell vehicles, great strides must be made in the development of fuel cells, hydrogen production and hydrogen storage technologies, that includes metal-H interaction studies and safety considerations. The interaction between two-hydrogen atoms and a {gamma}-Fe structure containing a vacancy has been studied using a cluster model and a theoretical method. For the study of the sequential absorption, the hydrogen atoms were positioned in their energy minima configurations, near the vacancy. The interactions mainly involve Fe 4s-H 1s atomic orbitals. The contribution of Fe 4p and Fe 3d orbitals is much less important. The Fe-Fe bond is weakened as new Fe-H-H and H-H pairs were formed. The effect of H atoms is limited to its first Fe neighbors. The Fe-Fe bond ...

Energy Technology Data Exchange (ETDEWEB)

Daylight responsive dimming systems have been used in few buildings to date because they require improvements to improve reliability. The key underlying factor contributing to poor performance is the variability of the ratio of the photosensor signal to daylight workplane illuminance in accordance with sun position, sky condition, and fenestration condition. Therefore, this paper describes the integrated systems between automated roller shade systems and daylight responsive dimming systems with an improved closed-loop proportional control algorithm, and the relative performance of the integrated systems and single systems. The concept of the improved closed-loop proportional control algorithm for the integrated systems is to predict the varying correlation of photosensor signal to daylight workplane illuminance according to roller shade height and sky conditions for improvement of the system accuracy. In this study, the performance of the ...

CERN Document Server

We re-examine the process of loop quantization for flat isotropic models in cosmology. In particular, we contrast different inequivalent `loop quantizations' of these simple models through their respective successes and limitations and assess whether they can lead to any viable physical description. We propose three simple requirements which any such admissible quantum model should satisfy: i) independence from any auxiliary structure, such as a fiducial interval/cell introduced to define the phase space when integrating over non-compact manifolds; ii) existence of a well defined classical limit and iii) provide a sensible "Planck scale" where quantum gravitational effects become manifest. We show that even when it may seem that one can have several possible loop quantizations, these physical requirements considerably narrow down the consistent choices. Apart for the so called improved dynamics of LQC, none of the other ...

International Nuclear Information System (INIS)

Small bowel obstructions can be distinguished into more simple and closed loop obstructions. The latter is a more severe condition which is often complicated by strangulation with vascular impairment, edema and intramural and mesenteric hemorrhage. Consequent arterial insufficiency rapidly leads to ischemia, infarction and necrosis. The radiologist plays a role in the early recognition of the closed loop obstruction and of any sign of strangulation. The role of CT in the diagnosis and workup of patients with suspected intestinal occlusion has been analyzed in the literature with reported 63% sensitivity, 78% specificity and 66% accuracy. CT is also capable of revealing the causes of occlusion in 73-95% of cases. The above CT signs allow to identify closed loop obstruction and also small bowel strangulation, thus supplying a valuable contribution to diagnosis and accurate preoperative evaluation. The conclusion is that CT ...

Science.gov (United States)

We have grown crack-free antiferroelectric (AFE) Pb{sub 0.92}La{sub 0.08}Zr{sub 0.95}Ti{sub 0.05}O{sub 3} (PLZT) films on nickel foils by chemical solution deposition. To eliminate the parasitic effect caused by the formation of a low-permittivity interfacial oxide, we applied a conductive buffer layer of lanthanum nickel oxide (LNO) on the nickel foil by chemical solution deposition prior to the PLZT deposition. Use of the LNO buffer allowed high-quality film-on-foil capacitors to be prepared at high temperatures in air. With the AFE PLZT deposited on LNO-buffered Ni foils, we observed field-induced phase transformations of AFE to ferroelectric (FE). The AFE-to-FE phase transition field, E{sub AF} = 260 kV cm{sup -1}, and the reverse phase transition field, E{sub FA} = 220 kV cm{sup -1}, were measured at room temperature on a {approx}1.15 {micro}m thick PLZT film grown on LNO-buffered Ni foils. The relative permittivities of the AFE and FE states were {approx}530 ...

CERN Document Server

Infinite loop space theory, both additive and multiplicative, arose largely from two basic motivations. One was to solve calculational questions in geometric topology. The other was to better understand algebraic K-theory. The Adams conjecture is intrinsic to the first motivation, and Quillen's proof of that led directly to his original, calculationally accessible, definition of algebraic K-theory. In turn, the infinite loop understanding of algebraic K-theory feeds back into the calculational questions in geometric topology. For example, use of infinite loop space theory leads to a method for determining the characteristic classes for topological bundles (at odd primes) in terms of the cohomology of finite groups. We explain just a little about how all that works, focusing on the central role played by E infinity ring spaces.

CERN Document Server

We complete the effective potential calculation of the two-loop, top/bottom Yukawa corrections to the Higgs boson masses in the Minimal Supersymmetric Standard Model, by computing the O(at^2 + at*ab + ab^2) contributions for arbitrary values of the bottom Yukawa coupling. We also compute the corrections to the minimization conditions of the effective potential at the same perturbative order. Our results extend the existing O(at^2) calculation, and are relevant in regions of the parameter space corresponding to tan(beta) >> 1. We extend to the Yukawa corrections a convenient renormalization scheme, previously proposed for the O(ab*as) corrections, that avoids unphysically large threshold effects associated with the bottom mass and absorbs the bulk of the corrections into the one-loop expression. For large values of tan(beta), the new contributions can account for a variation of several GeV in the lightest Higgs boson mass.

Energy Technology Data Exchange (ETDEWEB)

In order to apply chemical-looping combustion to a practical power plant, carbon deposition on the solid particle is one of the key problems to be overcome. Six kinds of solid particles were examined to clarify the kinetic behavior of carbon deposition. The effects of the solid composition, feed gas composition, and reaction temperature on carbon deposition were investigated by thermogravimetrical reactor on the basis of NiO/YSZ particle. From the viewpoints of both reactivity and resistance against carbon deposition, the particle of NiO mixed with YSZ (i.e., yttria-stabilized zirconia) was found to be a good candidate for chemical-looping combustion. It has been observed that carbon deposition could be completely avoided with very low concentration of water vapor. By means of a proposed model, the condition that carbon deposition would be avoided was identified. 12 refs., 8 figs., 2 tabs.

CERN Document Server

A fully consistent linear perturbation theory for cosmology is derived in the presence of quantum corrections as they are suggested by properties of inverse volume operators in loop quantum gravity. The underlying constraints present a consistent deformation of the classical system, which shows that the discreteness in loop quantum gravity can be implemented in effective equations without spoiling space-time covariance. Nevertheless, non-trivial quantum corrections do arise in the constraint algebra. Since correction terms must appear in tightly controlled forms to avoid anomalies, detailed insights for the correct implementation of constraint operators can be gained. The procedures of this article thus provide a clear link between fundamental quantum gravity and phenomenology.

Energy Technology Data Exchange (ETDEWEB)

Perturbative approach to two-dimensional gravity and supergravity is considered. One-loop renormalization of the central charge of SL(2,R) Kac-Moody algebra is calculated perturbatively by functional integration and by explicit calculations of the Feynman diagrams. Also the wavefunction renormalization and the anomalous dimensions in the presence of gravity are calculated.

Energy Technology Data Exchange (ETDEWEB)

In order to study the two-phase natural circulation and flow termination during a small break loss of coolant accident in LWR, simulation experiments have been performed. Based on the two-phase flow scaling criteria developed under this program, an adiabatic hot leg U-bend simulation loop using nitrogen gas and water and a Freon 113 boiling and condensation loop were built. The nitrogen-water system has been used to isolate key hydrodynamic phenomena from heat transfer problems, whereas the Freon loop has been used to study the effect of phase changes and fluid properties. Various tests were carried out to establish the basic mechanism of the flow termination and reestablishment as well as to obtain essential information on scale effects of parameters such as the loop frictional resistance, thermal center, U-bend curvature and inlet geometry. In addition to the above experimental study, a preliminary ...

International Nuclear Information System (INIS)

The authors present a state-of-the-art review of natural circulation heat transfer in loop type reactor plants. Most of the examples are taken from Fast Flux Test Facility (FFTF) design experience, drawing on the authors' familiarity and a developing base of available documentation. On-going studies related to the Clinch River Breeder Reactor (CRBR) and some foreign experience are also noted where available in the literature. The emphasis is on the role of natural circulation in decay heat removal; however, free convection during either operation at power or normal shutdown does influence some aspects of the design and these are reviewed. In treating decay heat removal the topics discussed include steady state loop performance and transient dynamics for conditions immediately after scram and for the longer term which involves different considerations. The review summarizes complex dynamics, specific to the FFTF design evaluation, which ...

Energy Technology Data Exchange (ETDEWEB)

Coal direct chemical looping (CDCL) substitutes the gasification process in syngas chemical looping (SCL), thus eliminating the need for higher oxygen consumption. In this study, operating conditions are assessed for CDCL and SCL, directed towards hydrogen production from coal. The main objective is to increase the overall H{sub 2}/CO{sub 2} ratio for a given amount of coal, based on the various conditions. The operating variables considered as part of a resource optimization analysis include: (i) inlet conditions to the primary reactors, (ii) minimum resource requirements (air, steam and iron oxide), (iii) hydrogen-to-component ratios, and (iv) effect of coal carrier gas. The results suggest that CDCL has a higher hydrogen-to-CO{sub 2} ratio than SCL along with advantages such as low overall resource requirements (steam and air) and fewer intermediate processes. The coal carrier gas affects the hydrogen production only in the SCL system by ...

Energy Technology Data Exchange (ETDEWEB)

In this paper the authors present some final results from a research project focused on introducing automatic control to the operation of cupola iron furnaces. The main aim of this research is to improve the operational efficiency and performance of the cupola furnace, an important foundry process used to melt iron. Previous papers have described the development of appropriate control system architectures for the cupola. In this paper experimental data is used to calibrate the model, which is taken as a first-order multivariable system with time delay. Then relative gain analysis is used to select loop pairings to be used in a multiloop controller. The resulting controller pairs melt rate with blast volume, iron temperature with oxygen addition, and carbon composition with metal-to-coke ratio. Special (nonlinear) filters are used to compute melt rate from actual scale readings of the amount of iron produced and to smooth the temperature measurement. The temperature ...

Energy Technology Data Exchange (ETDEWEB)

Results indicate that the probability of double-ended guillotine break (DEGB) in the reactor coolant loop piping of Westinghouse and Combustion Engineering plants is extremely low. It is recommended that the NRC seriously consider eliminating DEGB as a design basis event for reactor coolant loop piping in Westinghouse plants. Pipe whip restraints on reactor coolant loop piping could then be excluded or removed, and the requirement to design supports to withstand asymmetric blowdown loads could be eliminated. It is also recommended that the current requirement to couple safe shutdown earthquake (SSE) and DEGB be eliminated. Recognizing however that seismically induced support failure is the weak link in the DEGB evaluation, it is recommended that the strength of component supports, currently designed for the combination of SSE plus DEGB, not be reduced. The study indicates that the probability of DEGB in reactor coolant ...

International Nuclear Information System (INIS)

The Los Alamos FEL requires tight control of the amplitudes and phases of the fields in two linear accelerator tanks to obtain stable lasing. The accelerator control loops must establish constant, stable, repeatable amplitudes and phases of the rf fields and must have excellent bandwidth to control high-frequency noise components. A model of the feedback loops has been developed that agrees well with measurements and allows easy substitution of components and circuits, thus reducing breadboarding requirements. The model permits both frequency and time-domain analysis. This paper describes the accelerator control scheme and our model and discusses the control of noise in feedback loops, showing how low-frequency-noise components (errors) can be corrected, but high-frequency-noise components (errors) are actually amplified by the feedback circuit. Measurements of noise in both open- and closed-loop modes ...

UK PubMed Central (United Kingdom)

Hairpin oligonucleotides were synthesized with stems ending in a double-stranded structure, which can be ligated to double-strand breaks in DNA, and with loops that contain nucleotides modified by the...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

The theory and application of the optimal control of linear systems to stabilize or improve the system stability is well known. For an optimal linear regulator design, the arbitrariness involved in the parameters of the cost function always affects the final control law and the closed-loop system poles which decide the system dynamic characteristics. A new approach, 'The inverse problem approach' has been developed to overcome this difficulty. The system so designed will have preassigned closed-loop poles and the resulting closed-loop system performance can be ensured. In this paper the inverse problem approach for optimal regulator design is applied to the power system stabilizer (PSS) design for single-machine infinite-bus systems. The results show that, as far as the linearized model is concerned, systems designed by the inverse problem approach have better closed-loop performance ...

UK PubMed Central (United Kingdom)

Essential in mitosis, the human Kinesin-5 protein is a target for >80 classes of allosteric compounds that bind to a surface-exposed site formed by the L5 loop. Not established is why there...Full Text Available

UK PubMed Central (United Kingdom)

BackgroundThe MYC transcription factors are known to be involved in the biology of many human cancer types. But little is known about the Myc/microRNAs cooperation in the regulation...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

The structural integrity of the Fuel Test Loop(FTL) in a Korean experimental reactor is evaluated when the FTL, submerged in a water environment, is subjected to a postulated pipe rupture. The analyses are performed under static and dynamic conditions, imposing the thrust force history at each postulated pipe rupture section. Through analysis the following results are found: 1) A double ended guillotine can not be expected based on the toughness of the material, 2) the structural integrity of the chimney surrounding the FTL would not impede the structural integrity by the pipe whip. All analyses are performed by finite element methods.

Energy Technology Data Exchange (ETDEWEB)

Transient, greatly enhanced diffusion has been observed on annealing solid-phase-epitaxial (SPE) grown Si-Sb alloys. This is shown to be due to a high concentration of interstitials being trapped during SPE regrowth. The migration enthalpy, for diffusion of Sb by an interstitialcy mechanism was measured as 1.8 +/- 0.2 eV. The interstitials eventually condensed into loops, marking the end of the transient. In a SPE grown Si-Bi alloy a similar transient enhanced diffusion was observed, with an activation energy of 2.0 +/- 0.2 eV, but no loops formed. 8 figures, 7 references.

International Nuclear Information System (INIS)

The integrity of helium circulation loop flanged joints has been attracting recent attention as a design problem, in the development of high-temperature facilities incorporating helium loops (e.g., the VRG-50 pilot nuclear facility). Elevated temperatures and pressures, and the radiation environment, impose additional requirements on sealant materials. This applies first and foremost to rubber seals, which have found widespread favor on account of its excellent elasticity, its ability to spontaneously conform to possible changes in the clearance in the seal assembly, and the low compressive stresses developed in the flange joint assembly.

Science.gov (United States)

Eight years ago, corrosion and tube denting seriously threatened the reliability and design life of steam generators, especially for closed loop arrangements in pressurized water reactors (PWRs). Concentrated research by the Steam Generator Owners Group (SGOG) diagnosed the causes and produced effective solutions, notably guidelines for water chemistry control in the secondary loop. The guidelines recommend specific levels of water impurities and remedial actions to prevent cooling-water leaks in the condenser, prevent air leaks, limit corrosion product buildup, and remove some impurities while neutralizing others. Continued research in SGOB-II is investigating intergranular corrosion and stress corrosion cracking. 3 figures.

International Nuclear Information System (INIS)

We theoretically investigate the features of two-photon absorption in a coherently driven four-level atomic system with closed-loop configuration. It is found that two-photon absorption can be completely suppressed just by properly adjusting the relative phase of four coherent low-intensity driving fields and the atomic system becomes transparent against two-photon absorption. From a physical point of view, we explicitly explain these results in terms of quantum interference induced by two different two-photon excitation channels.

CERN Document Server

Big Bang nucleosynthesis requires a fine balance between equations of state for photons and relativistic fermions. Several corrections to equation of state parameters arise from classical and quantum physics, which are derived here from a canonical perspective. In particular, loop quantum gravity allows one to compute quantum gravity corrections for Maxwell and Dirac fields. Although the classical actions are very different, quantum corrections to the equation of state are remarkably similar. To lowest order, these corrections take the form of an overall expansion-dependent multiplicative factor in the total density. We use these results, along with the predictions of Big Bang nucleosynthesis, to place bounds on these corrections.

Energy Technology Data Exchange (ETDEWEB)

We perform a complete analytical reduction of general one-loop Feynman integrals with five and six external legs for tensors up to rank R=3 and 4, respectively. An elegant formalism with extensive use of signed minors is developed for the cancellation of inverse Gram determinants. The 6-point tensor functions of rank R are expressed in terms of 5-point tensor functions of rank R-1, and the latter are reduced to scalar four-, three-, and two-point functions. The resulting compact formulae allow both for a study of analytical properties and for efficient numerical programming. They are implemented in Fortran and Mathematica. (orig.)

International Nuclear Information System (INIS)

A disk formation model during collapse of the protosolar nebula, yielding a low-mass protoplanetary disk is presented. The following subject areas are covered: (1) circumstellar disks; (2) conditions for the formation of stars with disks; (3) early evolution of the protoplanetary disk; and (4) temperature conditions and the convection in the protoplanetary disk.

International Nuclear Information System (INIS)

Post-irradiation annealing was used to help identify the role of radiation-induced segregation (RIS) in irradiation-assisted stress corrosion cracking (IASCC) by preferentially removing dislocation loop damage from proton-irradiated austenitic stainless steels while leaving the RIS of major and minor alloying elements largely unchanged. The goal of this study is to better understand the underlying mechanisms of IASCC. Simulations of post-irradiation annealing of RIS and dislocation loop microstructure predicted that dislocation loops would be removed preferentially over RIS due to both thermodynamic and kinetic considerations. To verify the simulation predictions, a series of post-irradiation annealing experiments were performed. Both a high purity 304L (HP-304L) and a commercial purity 304 (CP-304) stainless steel alloy were irradiated with 3.2 MeV protons at 360 deg. C to doses of 1.0 and 2.5 dpa. Following irradiation, ...

International Nuclear Information System (INIS)

The effect of ion implantation on the aqueous corrosion resistance of Zr-4 in deaerated 1N H_2SO_4 was studied with the potentiokinetic technique. The Zr-4 alloy was bombarded with 5x10"1"4-2x10"1"6 Ar/cm"2 of 190 keV. It was found that the passive current density of Zr-4 decreases with increasing implantation dose. Photoelectrochemical results show that the ion implantation of Ar in Zr-4 raises the flatband potential of its passive film. AES was employed to analyze the surface of the passive film of Zr-4. The decrease in passive current density may be attributed to a thickening oxide layer on Zr-4 and a decrease in concentration of oxygen vacancies in its passive film. ((orig.)).

International Nuclear Information System (INIS)

We have studied L x-rays from 64 MeV iodine projectile in collision with various gas targets, Z_2 #18, do not arise from selective M subshell vacancy population, has been conclusively established by the observations by Datz et al (1971) and by Saha et al (1996) that the measured intensity ratio of the Ll and L#alpha# lines, which arise because of transitions from different M subshells into the same L, subshell, does not show any periodic behaviour with Z, but stays rather constant. Differences in the measured L#beta#_1/L#alpha# intensity ratio of iodine with 7"+ and 24"+ charge states impinging on Kr target established the minor role of the electrons in the N shell of the projectile in the x-ray production mechanism. (author)

Wastenet

...The RSPB: Great crested grebe A delightfully elegant waterbird with ornate head plumes which led to its being hunted for its feathers, almost leading to its extermination from the UK. E-mail to a friendE-newsletterContact us Home England Northern Ireland Scotland Wales About Overview Awards & recognition Contact us Facts and figures History How we are run Inspiring work Job vacancies Looking to the future Media centre Offices The RSPB view ...status: Green Listen Get Flash player Play sound 1 videoLatin name Podiceps cristatusFamily Grebes (Podicipedidae)Overview A delightfully elegant waterbird with ornate head plumes which led to its being hunted for its feathers, almost leading to its extermination from the UK. They dive to feed and also to escape, preferring this to flying. On land they are clumsy because their feet are placed so far back on their bodies. ...

Energy Technology Data Exchange (ETDEWEB)

One third of the microstructure of glassy carbon (GC) consists of closed pores. Density measurements indicate that the total pore volume depends only on the heat treatment temperature and not on the heat treatment time, a characteristic of coarsening. The kinetics of coarsening of these pores on heat treatment has been investigated by analyzing the changes in specific surface area of the pores as determined by the small angle X-ray scattering (SAXS) technique. A part of the surface area change is due to thermal expansion induced microcracking. Both the superposition method after correcting the thermal expansion induced surface area change and the curve fitting method give an activation energy of 64 +/- 10 kcal/mole. This value is compared with the activation energies of various rate processes in graphite. A model of coarsening of the pores based on a vacancy migration mechanism is proposed.

Energy Technology Data Exchange (ETDEWEB)

A model is presented to account for the effects of ion-induced defects during implantation processing of Si. It will be shown that processing is quite generally affected by the presence of defect excesses rather than the total number of defects. a defect is considered excess if it represents a surplus locally of one defect type over its compliment. Processing spanning a wide range of implantation conditions will be presented to demonstrate that the majority of the total defects played little or no role in the process. This is a direct result of the ease with which the spatially correlated Frenkel pairs recombine either dynamically or during a post-implantation annealing. Based upon this model, a method will be demonstrated for manipulating or engineering the excess defects to modify their effects. In particular high-energy, self-ions are shown to inject vacancies into a boron implanted region resulting in suppression of transient enhanced diffusion of the dopant.

Energy Technology Data Exchange (ETDEWEB)

Presently, most charge state distributions produced with highly charged ion sources are predicted with models that approximate the ionization process with the Lotz formula. The Lotz ionization cross sections decrease approximately geometrically with increasing charge state except for ions with very few vacancies, for ions with very few electrons, and for electron impact energies which barely exceed the ionization energy. The geometrical decrease causes these models to predict a maximum abundance for most of the charge states, which is only weakly dependent on the charge state. Experimental results, however, yield much higher abundances for ions with an empty M shell than ions with a partly filled M shell. This difference is explained with indirect ionization processes that are neglected by the Lotz approximation, and normally can be neglected for the ionization of the L shell, but can dominate the ionization of the M shell. (c) 2000 American Institute of Physics.

International Nuclear Information System (INIS)

We have investigated the diffusion of Sb in Si in the presence of defects injected by high-energy implantation of Si ions at room temperature. MeV ion implantation increases the concentrations of vacancies, which induce transient-enhanced diffusion of Sb deposited in Si. We observed a significant enhancement of Sb diffusion. Secondary ions mass spectroscopy has been performed on the implanted samples before and after annealing. Rutherford-backscattering spectrometry has been used to characterize the high-energy implantation damage. By fitting diffusion profiles to a linear diffusive model, information about atomic scale diffusion of Sb, i.e. the generation rate of mobile state Sb and its mean migration length were extracted.

International Nuclear Information System (INIS)

From self-consistent band structure calculations using the 'augmented plane wave'(APW) method, the density of states can be decomposed into local partial (according to azimuthal quantum number l) components, the l-character densities. Within the APW formalism the intensity of X-ray emission spectra is determined by radial transition probabilities and l-character densities of such valence states, which reside inside the same atomic sphere as the core vacancy and whose quantum number l differs by +-1 from the one corresponding to the core state. By taking into account lifetime broadening of the core and valence states and also the instrumental broadening the computed spectra (non-metal K-, vanadium K- and Lsub(III)-spectra) agree well with experiment. (orig.).

Science.gov (United States)

International Patenting Trends in Advanced Materials: Ceramics (June 18, 1999) This report is the ... manufacturing, biotechnology, and advanced materials. Hypertext Format Portable Document Format ...

Science.gov (United States)

Herpes simplex virus type-1 (HSV-1) entry into target cell is initiated by the ionic interactions between positively charged viral envelop glycoproteins and a negatively charged cell surface heparan sulfate (HS). This first step involves the induction of HS-rich filopodia-like structures on the cell surface that facilitate viral transport during cell entry. Targeting this initial first step in HSV-1 pathogenesis, we generated different zinc oxide (ZnO) micro-nano structures (MNSs) that were capped with multiple nanoscopic spikes mimicking cell induced filopodia. These MNSs were predicted to target the virus to compete for its binding to cellular HS through their partially negatively charged oxygen vacancies on their nanoscopic spikes, to affect viral entry and subsequent spread. Our results demonstrate that the partially negatively charged ZnO-MNSs efficiently trap the virions via a novel virostatic mechanism rendering them unable to enter into human corneal ...

KoreaScience (Korea)

Full Text Available

Czech Academy of Sciences Repository

Full Text Available

International Nuclear Information System (INIS)

... excessive. Due to the response being too weak, attempts to use Infrared

KoreaScience (Korea)

Full Text Available

KoreaScience (Korea)

Full Text Available

CERN Document Server

After presenting three ways of defining a bulge component in disc galaxies, we introduce the various types of bulges, namely the classical bulges, the boxy/peanut bulges and the disc-like bulges. We then discuss three specific topics linked to bulge formation and evolution, namely the coupled time evolution of the bar, buckling and peanut strengths; the effect of velocity anisotropy on peanut formation; and bulge formation via bar destruction.

International Nuclear Information System (INIS)

Published in summary form only.

International Nuclear Information System (INIS)

Published in summary form only.

KoreaScience (Korea)

Full Text Available

Science.gov (United States)

In vertebrates, the positioning of the internal organs relative to the midline is asymmetric and evolutionarily conserved. A number of molecules have been shown to play critical roles in left-right patterning. Using representational difference analysis to identify genes that are differentially expressed on the left and right sides of the chick embryo, we cloned chick Claudin-1, an integral component of epithelial tight junctions. Here, we demonstrate that retroviral overexpression of Claudin-1, but not Claudin-3, on the right side of the chick embryo between HH stages 4 and 7 randomizes the direction of heart looping. This effect was not observed when Claudin-1 was overexpressed on the left side of the embryo. A small, but reproducible, induction of Nodal expression in the perinodal region on the right side of the embryo was noted in embryos that were injected with Claudin-1 retroviral particles on their right sides. However, no changes in Lefty,Pitx2 or cSnR ...

Energy Technology Data Exchange (ETDEWEB)

The Coalspur Formation is a continental succession of interbedded mudstone, siltstone and fine grained sandstone with subordinate coarser grained sandstone layers and channel lag deposits. Chert-pebble conglomerate (the Entrance conglomerate) occurs at the base of the formation, and coal beds interbedded with coaly shale and numerous thin bentonites occur in the upper part of the formation. An economically significant amount of high-quality thermal coal occurs within the upper, Paleocene part of the formation named the Coalspur coal zone. Coal from this zone, also known as the Coal Valley coal zone is being exploited in the Coal Valley Mine. 17 refs., 4 figs.

CERN Document Server

We present an updated overview on the phenomenology of one-loop Higgs boson production at Linear Colliders within the general Two-Higgs-Doublet Model (2HDM). First we report on the Higgs boson pair production, and associated Higgs-Z boson production, at O(alpha^3_{ew}) from e+e- collisions. These channels furnish cross-sections in the range of 10-100 fb for Ecm=0.5 TeV and exhibit potentially large radiative corrections (of order 50%), whose origin can be traced back to the genuine enhancement capabilities of the triple Higgs boson self-interactions. Next we consider the loop-induced production of a single Higgs boson from direct gamma-gamma scattering. We single out sizable departures from the corresponding rates in the Standard Model, which are again correlated to trademark dynamical features of the 2HDM -- namely the balance of the non-standard Higgs/gauge, Higgs/fermion and Higgs self-interactions leading to sizable (destructive) ...

Science.gov (United States)

Chemical looping combustion (CLC) is a process in which an oxygen carrier is used for fuel combustion instead of air or pure oxygen as shown in the figure below. The combustion is split into air and fuel reactors where the oxidation of the oxygen carrier and the reduction of the oxidized metal occur respectively. The CLC system provides a sequestration-ready CO2 stream with no additional energy required for separation. This major advantage places combustion looping at the leading edge of a possible shift in strict control of CO2 emissions from power plants. Research in this novel technology has been focused in three distinct areas: techno-economic evaluations, integration of the system into power plant concepts, and experimental development of oxygen carrier metals such as Fe, Ni, Mn, Cu, and Ca. Our recent thorough literature review shows that multiphase fluid dynamics modeling for CLC is not available in the open literature. ...

Science.gov (United States)

This paper presents a semi-active vibration control of a scaled two-span bridge structure. Magneto-rheological fluid dampers are utilized as the semi-active energy absorbing deices and a bridge vibration control system is developed. Closed-loop control system based on fuzzy logic is used to suppress the bridge deck motion under random excitations. The sufficient condition for the closed-loop stability of the fuzzy control system is derived from the variable structure system theory. It is demonstrated that this stable fuzzy control system can significantly reduce the relative deck displacement using about 55 percent less power compared to passive-on state, while the absolute deck acceleration is relatively unaffected.

International Nuclear Information System (INIS)

We have computed the next-next-to-leading order QCD corrections to the Gross-Llewellyn Smith sum rule for deep inelastic neutrino-nucleon scattering and to the Bjorken sum rule for polarized electron-nucleon scattering. This involved the proper treatment of #gamma#_5 inside the loop integrals within dimensional regularization. We find that the difference between the two sum rules are entirely due to a class of six three-loop graphs and is of the order of 1% of the leading QCD term (O(#alpha#_s)). Hence the Q"2 behavior of both sum rules should be nearly the same if the physics is described adequately by the lower order terms of perturbative QCD. (orig.).

Energy Technology Data Exchange (ETDEWEB)

An explanation is given of what a loop heat pipe (LHP) is, and how it works. It is then shown that neutron imaging (both real time neutron radioscopy and single exposure neutron radiography) is an effective experimental tool for the study of LHPs. Specifically, neutron imaging has helped to identify and correct a cooling water distribution problem in the condenser, and has enabled visualization of two-phase flow (liquid and vapor) in various components of the LHP. In addition, partial wick dry-out, a phenomenon of great importance in the effective operation of LHPs, is potentially identifiable with neutron imaging. It is anticipated that neutron radioscopy and radiography will greatly contribute to our understanding of LHP operation, and will lead to improvement of LHP modeling and design.

International Nuclear Information System (INIS)

Object: To permit a valve operation test to be periodically made during plant operation without causing variations in plant power by detecting flow control valve defect on the basis of a valve aperture alteration instruction. Structure: Step signals which are equal in absolute value and opposite in sign are coupled to the input side of flow controllers provided on the recycling loops of two or more recycling flow control systems. With these inputs the aperture of the flow control valve on one side is increased (or reduced) while the aperture of the valve on the other side is reduced (or increased). As a result, the recycling flow rate in the loop on one side is increased (or reduced) while that on the other side is reduced (or increased). Whether the valve is normally operating or not is confirmed by checking the recycling flow rate and valve aperture. (Nakamura, S.).

Energy Technology Data Exchange (ETDEWEB)

A cold-leg small-break loss-of-coolant accident (SBLOCA) experiment was performed on the PACTEL facility to study the behavior of natural circulation in a VVER-440 reactor geometry. The facility is a volumetrically scaled (1:305) integral test loop simulating the VVER-440 reactors used in Finland. The test results were used to assess the computer codes RELAP5/MOD3.1 and APROS 3.0 for VVER reactors. The behavior of the horizontal steam generator and the effect of the hot-leg loop seal were of particular interest. The specific parameters to be compared included the primary pressure and the downcomer mass flow rate.

CERN Document Server

The full theory and the semiclassical description of loop quantum cosmology (LQC) have been studied in the Friedmann-Robertson-Walker and Bianchi I models. As an extension to include both anisotropy and intrinsic curvature, this paper investigates the cosmological model of Kantowski-Sachs spacetime with a free massless scalar field at the level of phenomenological dynamics with the LQC discreteness corrections. The LQC corrections are implemented in two different improved quantization schemes. In both schemes, the big bang and big crunch singularities of the classical solution are resolved and replaced by the big bounces when the area or volume scale factor approaches the critical values in the Planck regime measured by the reference of the scalar field momentum. Symmetries of scaling are also noted and suggest that the fundamental spatial scale (area gap) may give rise to a temporal scale. The bouncing scenarios are in an analogous fashion of the Bianchi I model, ...

International Nuclear Information System (INIS)

The present work summarizes efforts on the simulation of natural convection cooling within the IFMIF target and test cell. The simulations have been performed with the STAR-CD code using the k-#omega# high-Reynolds number turbulence model. A dedicated thermohydraulic model has been devised including Lithium loop components. Nuclear heat production has been calculated by the Monte-Carlo code McDeLicious for different parts of the target and test cell walls and was used as input for the STAR-CD simulations. Helium atmospheres at several pressures from 0.1 to 10"-"5 MPa have been investigated. In order to limit the maximum temperature of the concrete walls to 80 deg. C it was necessary to add thermal insulation layers to the hot Lithium loop surfaces and a conceptual system of two cooling layers in different depths of the concrete walls.

Energy Technology Data Exchange (ETDEWEB)

Many existing methods of identifying the optimum sites for installing power system stabilizers (PSSs) in multi-machine systems are restricted to the sequential PSS application, which considers the enhancement of damping of just one critical electromechanical mode at a time; the eigenstructure analysis of the open-loop system, which does not take the control matrix (i.e., the B matrix in the linearized model x = Ax + Bu for power systems) into consideration. This paper presents a method of identifying the optimum sites for installing power system stabilizers. The advantages of this method are: it can identify the optimum sites for installing PSSs so that several electrochemical modes are damped out simultaneously; it takes both the eigenstructure of the open-loop system and the control matrix into consideration.

CERN Document Server

A new mathematical framework is formulated to derive the effective equations of motion for the constrained quantum system which possesses an internal clock. In the realm close to classical behavior, the quantum evolution is approximated by a finite system of coupled but ordinary differential equations adhered to the weakly imposed Hamiltonian constraint. For the simplified version of loop quantum cosmology in the Bianchi I model with a free massless scalar filed, the resulting effective equations of motion affirm the bouncing scenario predicted by the previous studies: The big bang singularity is resolved and replaced by the big bounces, which take place up to three times, once in each diagonal direction, whenever the directional density approaches the critical value in the regime of Planckian density. It is also revealed that back-reaction arises from the quantum corrections and modifies the precise value of the directional density at the bouncing epoch. ...

British Library Electronic Table of Contents (United Kingdom)

This project is about the simulation design of an engine control unit (ECU) for an Otto cycle engine with electronic fuel injection (EFI). The simulation includes a model for the ECU as well as physical parameters of the engine, which allows closed-loop control and monitoring of various systems.This simulation has been realized using Simulink and Stateflow, which are components of Mathworks' MATLAB software.The program allows control of various parameters of the ECU, as well as the simulation of failures to verify that the designed ECU is fault-tolerant and can control the engine using an open loop control. The main function the ECU provides is fuel metering.Subsequently, this program could be used as a tool to quickly develop and test models of ECU in order to control an engine in laborat...

British Library Electronic Table of Contents (United Kingdom)

Phage display is effective in screening peptides that mimic venom's neutralizing epitopes. A phage display cyclized heptapeptide library (C7C library) was panned with purified divalent antivenin IgG, which neutralizes Naja naja atra venom (NAV) and Bungarus multicinctus venom (BMV). The selected heptapeptide sequences were aligned with known protein sequences of NAV and BMV in GenBank. One of the four consensus sequences, L/PKSSLL, mimicked the crucial epitope on Loop III of Taiwan cobra cardiotoxin that is associated with the venom's lethal potency. In dot blot analysis, several clones showed varying reactivities for NAV monovalent antivenin and lesser cross-reactions with BMV monovalent antivenin. The KSSLLRN-carrying phage occurred four times in selected clones and showed the strongest ...

International Nuclear Information System (INIS)

A chemical-looping process is proposed for the clean combustion of solid fuels for electric power or heat generation. The process is based on coal gasification with CO_2 to produce CO. The CO then reduces CaSO_4, which is used as an oxygen carrier, in a separate reactor to give CaS and CO_2. A portion of the CO_2 is recycled for the gasification stage and the rest can be sent for sequestration. The CaS is sent to another reactor for oxidation with air and to generate heat or power. The overall thermal effect is the same as direct combustion, but separation of CO_2 and other pollutants, such as sulphur, is achieved. In comparison with conventional chemical-looping combustion of natural gas, much less water is present in the CO_2 product, and hence the loss of heat energy and corrosion of the fuel-reactor system can be reduced.

CERN Document Server

In general relativity, the fields on a black hole horizon are obtained from those in the bulk by pullback and restriction. Similarly, in quantum gravity, the quantized horizon degrees of freedom should result from restricting, or pulling-back, the quantized bulk degrees of freedom. This is not yet fully realized in the - otherwise very successful - quantization of isolated horizons in loop quantum gravity. In this work we outline a setting in which the quantum horizon degrees of freedom are simply components of the quantized bulk degrees of freedom. There is no need to quantize them separately. We present evidence that for a horizon of sphere topology, the resulting horizon theory is remarkably similar to what has been found before.

International Nuclear Information System (INIS)

Oxide superconducting thin films were irradiated with X-rays and ultra-violet (UV) light, and induced radiation effects on electrical and chemical properties were examined by transport measurement, X-ray diffraction analysis (XRD), diamagnetization measurement and X-ray photoemission spectroscopy (XPS). After irradiation for ErBa_2Cu_3O_x films with X-rays emitted from a Rh tube for 100 hours, superconductivity was remarkably damaged, destroying the zero-resistance state. The UV-light irradiation for Bi_2Sr_2CaCu_2O_x films was performed in He gas of about 500 Pa with a low pressure mercury lamp. The superconductivity was gradually degraded with the UV irradiation time up to 70 minutes. In both cases, adequate oxygen-annealing treatments restored superconductivity. The X-ray photoemission spectra showed that the mean Cu valence of the films was decreased approximately from +2 to +1 by the irradiation. From these results we can find that irradiation with the X-ray and the UV-light ...

Energy Technology Data Exchange (ETDEWEB)

The influence of surface oxides of variable composition and nonstoichiometry formed at high temperatures in air on the general corrosion resistance of ferritic chromium steel type 08H17T (Fe-17Cr-1Ti) in weak sulfuric acid has been studied. Anodic passive films formed on steel with different pretreatments have also been examined. The surface oxide of nearly stoichiometric composition formed at 300 C provides for the passive state of steel in sulfuric acid despite its depletion by chromium when compared with that for nonstoichiometric Cr-enriched oxide formed at 600 C. The dissolution and transformation of nonstoichiometric thermal surface oxide in sulfuric acid appear to take place through defect sites, {minus}Fe{sup 2+} ions, and oxygen vacancies of the n-type conductor. The passive film formed on the nonstoichiometric oxide film, which had been produced at 600 C, was found to be more susceptible to open-circuit breakdown compared to the native oxide and to the ...

International Nuclear Information System (INIS)

Radio frequency (RF) plasma nitriding using different input plasma processing powers (250-600 W) improves the surface of titanium by forming hard phases of TiN, Ti_2N, and Ti (N) into the surface. The characteristics of the compound layer have been investigated by optical microscopy, microhardness measurements, and X-ray diffraction. The effect of plasma power on the sample temperature, electron temperature, and plasma density was studied using Langmuir double probe. The measured surface hardness value of the compound layer is 2190 HV 0.1 for treated sample at plasma power 500 W. The compound thickness continuously increases as the plasma power increases. The highest nitriding rate of 5.88 #mu#m"2/s was recorded when the input plasma power was adjusted at 550 W. This high nitriding rate of treated titanium samples is ascribed to the high concentration of active nitrogen species in the plasma atmosphere and the formed microcracks near to the surface of the sample during the plasma ...

Energy Technology Data Exchange (ETDEWEB)

It has been discovered that the presence of MoO/sub 3/ lowers the ..cap alpha..-..beta.. transition in Sb/sub 2/O/sub 4/ from 935 to 850/sup 0/C with concurrent dissolution of Mo in the high-temperature (..beta..) form. The structure of Mo-doped ..beta..-Sb/sub 2/O/sub 4/ has been investigated by powder neutron diffraction, extended X-ray absorption fine structure (EXAFS) and Raman spectroscopies, and scanning-electron microscopy (SEM). Cell parameters: a = 12.0571 (12) A, b = 4.8335 (1) A, c = 5.3838 (6) A, ..beta.. = 105.579 (5)/sup 0/, monoclinic, space group C2/c, Z = 4. Combining the results of these techniques leads to the hypothesis that Mo is located interstitially within channels of electron density in the Sb/sub 2/O/sub 4/ structure with concurrent vacancy of two Sb/sup III/ atoms. There is no apparent oxygen deficiency in the resulting structure. 25 references, 6 figures, 3 tables.

Energy Technology Data Exchange (ETDEWEB)

K beta X-ray lines from partially M-shell-ionized ions of titanium through nickel which are produced in vacuum-spark plasmas have been observed systematically for the first time, using a high-resolution curved-crystal spectrometer. Each K beta line is clearly separated into its corresponding charge state. As a result, it is possible to measure the K beta-type transition energies of the M-shell-ionized ions. The transition energies accurately determined are compared with those calculated for iron ions, and the agreement is excellent except for ions having some additional 3d outer-shell electrons or 3s inner-shell vacancies. The square root of the K beta transition frequency is expressed as a linear function of the nuclear charge for isoelectronic sequences. The effective nuclear charges have been also determined for each K beta transition. The 3p electrons do not affect the effective nuclear charges. 10 references.

British Library Electronic Table of Contents (United Kingdom)

The properties of ZnO films were investigated as functions of annealing temperatures in H2/Ar and vacuum. The resistivities and mobilities of ZnO films decreased with increase of annealing temperatures in vacuum and H2/Ar ambients. However, the carrier densities of ZnO films increased with increase of annealing temperatures in vacuum and H2/Ar ambients. The resistivities of ZnO2 films annealed at 300degreeC were 2186cm and 798cm in H2/Ar and vacuum ambients, respectively. The resistivities of ZnO films annealed in vacuum and H2/Ar ambients at 600degreeC were similar with 0.040cm and 0.035cm, respectively. The hydrogen donor was more dominant than the oxygen vacancy or Zn interstitial donor in ZnO films annealed in ambient H2/Ar at low temperatures. The average optical transmission was >82%...

International Nuclear Information System (INIS)

Semiconducting properties of passive films formed on AISI 304 stainless steel grade were investigated by capacitances measurements in chloride containing aqueous solutions for different surface finishes: BA (bright annealing in hydrogen containing atmospheres) and 2B (standard annealing in oxidising atmospheres followed by pickling in acid, then water rinsing). Mott-Schottky analysis shows that for high enough electrode potential, and whatever the surface finish, the films behave like n-type semiconductors. 2B passive film appears to be more donor-doped than BA one and the density of donor states increases with chloride concentration. The electron donor levels are assumed to be generated by negatively charged cations vacancies produced by the chloride ions reaction with the outer passive film. This reaction looks easier for 2B than BA condition, which explains why BA resists better than 2B to pit nucleation.

Energy Technology Data Exchange (ETDEWEB)

Radionuclides exhibiting in decaying a strong interaction between nucleus and electron shell (especially electron capture and internal conversion) are, in principle, sensitive to their chemical surroundings. Consequently, they can be used to yield chemical information after an appropriate labelling procedure. The information can be extracted from the decay rate variation as well as from their X-ray emission as a response to an inner-shell vacancy creation during nuclear deexcitation. As an example of the former method the relationship between the decay rate of /sup 99m/Tc and the chemical structures of pertechnetate and bis(meso-dimercapto-succinate)oxotechnetate(V) is considered. Lower expectations with respect to measuring techniques are associated with the observation of X-ray emission. For a number of elements (especially 3d transition elements) the K/sub ..cap alpha..//K/sub ..beta../ X-ray intensity ratio was found to be an indicator of the nearest neighbour ...

Energy Technology Data Exchange (ETDEWEB)

In support of Stockpile Stewardship activities, accelerated aging tests on a plutonium alloy enriched with 7.3 at.% of {sup 238}Pu is underway using dilatometry at 35, 50, and 65 deg. C and immersion density measurements of materials stored at 50 deg. C. Changes in density are expected from radiation damage in the lattice and helium in-growth. After 25 equivalent years of aging, the dilatometry data shows that the alloys at 35 deg. C have expanded in volume by 0.11-0.12% and have started to exhibit a near linear expansion behavior primarily caused by the helium accumulation. The average He-to-vacancy ratio from tested specimens was determined to be around 2.55. The model for the lattice damage and helium in-growth accurately represents the volume swelling at 35 deg. C. The density converted from the dilatometry corresponds well to the decreasing density trend of reference plutonium alloys as a function of time.

Energy Technology Data Exchange (ETDEWEB)

In support of Stockpile Stewardship activities, accelerated aging tests on a plutonium alloy enriched with 7.3 atomic percentage of {sup 238}Pu is underway using dilatometry at 35, 50, and 65 C and immersion density measurements of material stored at 50 C. Changes in density are expected from radiation damage in the lattice and helium in-growth. After twenty-five equivalent years of aging, the dilatometry data shows that the alloys at 35 C have expanded in volume by 0.11% to 0.12% and have started to exhibit a near linear expansion behavior primarily caused by the helium accumulation. The average He-to-vacancy ratio from tested specimens was determined to be around 2.3. The model for the lattice damage and helium in-growth accurately represents the volume swelling at 35 C. The density converted from the dilatometry corresponds well to the decreasing density trend of reference plutonium alloys as a function of time.

Science.gov (United States)

We present results of electronic structure calculations for the intermetallic perovskite Sc3InB with the full-potential KKR-LDA method. Sc3InB is a very promising candidate for a new superconductor (related to 8 K MgCNi3) and can be regarded as a boron-inserted cubic Sc3In, which is a high-pressure allotropic form of the hexagonal weak ferromagnet Sc3In. We predict that cubic Sc3In can also be magnetic, whereas Sc3InB having large DOS in the vicinity of E F exhibits non-magnetic ground state. Estimation of the electron-phonon coupling for Sc3InB gives 1. Furthermore, the effect of vacancies in Sc3InB1-x and antisite disorder in Sc3(In-B) on critical parameters is also discussed using the KKR-CPA method. All theoretical results support the possibility of the superconductivity onset in Sc3InB. Preliminary experimental measurements established the transition temperature close to 4.5 K, with a very abrupt change in susceptibility and a correlated drop of the ...

International Nuclear Information System (INIS)

A new atomistic approach to Si device process simulation is presented. It is based on a Monte Carlo diffusion code coupled to a binary collision program. Besides diffusion, the simulation includes recombination of vacancies and interstitials, clustering and re-emission from the clusters, and trapping of interstitials. We discuss the simulation of a typical room-temperature implant at 40 keV, 5x10"1"3 cm"-"2 Si into (001)Si, followed by a high temperature (815 degree C) anneal. The damage evolves into an excess of interstitials in the form of extended defects and with a total number close to the implanted dose. This result explains the success of the open-quote open-quote+1 close-quote close-quote model, used to simulate transient diffusion of dopants after ion implantation. It is also in agreement with recent transmission electron microscopy observations of the number of interstitials stored in (311) defects. copyright 1996 American Institute of Physics.

UK PubMed Central (United Kingdom)

Peri-prosthetic infections are notoriously difficult to treat as the biomaterial implant is ideal for bacterial adhesion and biofilm formation, resulting in decreased antibiotic sensitivity....Full Text Available

UK PubMed Central (United Kingdom)

In an earlier report, we used differential cloning to identify genes that might be critical in controlling arterial neointima formation (Giachelli, C., N. Bae, D. Lombardi, M. Majesky, and S. Schwartz....Full Text Available

Energy Technology Data Exchange (ETDEWEB)

The present invention relates to a method of acidizing a subterranean formation or well bore employing an acidic solution containing a corrosion inhibitor composition comprising an inhibiting effective amount of an acetylenic alcohol, a quaternary ammonium compound, an aromatic hydrocarbon and an antimony compound.

UK PubMed Central (United Kingdom)

External application of auxin and cytokinin is required for the formation of flower buds on thin-layer tissue explants of Nicotiana tabacum cv Samsun. Interaction between both plant...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

An analysis is made of the manner in which the process of primordial black-hole formation and the subsequent accretion of gas depend on the equation of state. On the assumption that the process is spherically symmetric, the problem is solved numerically.

UK PubMed Central (United Kingdom)

Explants from flower stalks of Nicotiana tabacum L. were cultured on different cytokinins to induce flower bud formation. All cytokinins tested except zeatin and zeatin-riboside induced...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

The wind unit working wheel has 4 radial rectangular frames arranged in two vertical planes which are perpendicular to each other. In the planes limited by the frames, on loop hinges with limiting supports, there are flat blades. When the working wheel rotates under the influence of wind pressure, the blades automatically occupy a vertical or horizontal (wind vane) position depending on the direction of blade motion and the direction of wind velocity.

Energy Technology Data Exchange (ETDEWEB)

We proposed a solid and a mercury target concepts through the preliminary conceptual design. To feasible these concepts, analysis and experimental works are being carried out. This paper introduces an outline of present status of target R and D such as heat transfer augmentation experiments for the solid target, mercury flow tests with a loop of maximum flow rate of 15L/min, flow pattern measurements for a cold source moderator etc. as well as preliminary conceptual design works. (author)

International Nuclear Information System (INIS)

The Cutkosky rules are generalized to include tachyons. A consequence is that Lorentz-invariant interacting theories which possess tachyons cannot obey even the weakest possible form of unitarity beyond the tree level. The problem (although not the cutting rules) is shown to extend to bosonic string theory. Thus unitarity cannot be used to determine the range of modular integration in bosonic string loop amplitudes.

International Nuclear Information System (INIS)

In the framework of the equivalence theorem the one-loop helicity amplitudes and cross section for the double Higgs production process #gamma##gamma##->#HH are calculated. It is shown that the cross section is measurable at TeV #gamma##gamma# colliders and is marginally sensitive to the triple-Higgs variation. (orig.).

Energy Technology Data Exchange (ETDEWEB)

The theoretical treatment of the relation between the critical angle of planar channeling and the characteristics of crystal lattice defects is carried out. The predictions are made about some typical forms of the critical angle dependence on the mean-square static displacement produced by defects, and then these predictions are detailed for the cases of homogeneous disordering, spherical clusters of point defects and dislocation loops. Analytical results are supported by the exact computer calculations for the defects in the intermetallic A-15 compounds.

International Nuclear Information System (INIS)

We investigate the scope of all relevant production modes of charged Higgs bosons in the MSSM, with mass larger than the one of the top quark, at future Linear Colliders operating in #gamma##gamma# mode at the TeV energy scale. Final states with one or two H"#+-# bosons are considered, as produced by both tree- and loop-level interactions. (orig.)

UK PubMed Central (United Kingdom)

The N¹-methyl-Adenosine (m¹A58) modification at the conserved nucleotide 58 in the TΨC loop is present in most eukaryotic tRNAs. In yeast, m¹A58 modification...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

Because of the chaotic nature of the corrosion process and the complexity of the electrochemical noise signals that are generated, there is no generally accepted method of measuring and interpreting these signals that allows the consistent detection and identification of sustained localized pitting (SLP) as compared to general corrosion. We have reexamined electrochemical noise analysis (ENA) of localized corrosion using different hardware, signal collection, and signal processing designs than those used in conventional ENA techniques. The new data acquisition system was designed to identify and monitor the progress of SLP by analyzing the power spectral density (PSD) of the trend of the corrosion current noise level (CNL) and potential noise level (PNL). Each CNL and PNL data point was calculated from the root-mean- square value of the ac components of current and potential fluctuation signals, which were measured simultaneously during a short time period. The PSD analysis results ...

CERN Document Server

If the soft supersymmetry (SUSY) breaking masses and couplings are complex and cancellations do take place in the SUSY induced contributions to the fermionic electric dipole moments, then the CP- violating soft phases can drastically modify much of the known phenomenological pattern of the minimal supersymmetric standard model. In particular, the squark loop content of the dominant Higgs production mechanism at the large hadron collider, the gluon-gluon fusion mode, could be responsible for large corrections to the known cross sections. (15 refs).

Energy Technology Data Exchange (ETDEWEB)

Qualifying corrosion inhibitors for use in high velocity multiphase flowlines in arctic or subsea environments is discussed. The tests include high velocity flow loop corrosion tests, pumpability through 0.125 (0.318 cm) inch capillary at low temperatures, compatibility with Nylon 11, emulsion tendency testing, and partitioning characteristics. Laboratory and field data show the importance for using the above criteria for inhibitor selection.

International Nuclear Information System (INIS)

Results on defect structure study and degree of molybdenum radiation hardening irradiated by fission neutrons and medium energy alpha-particles are presented. It is shown that molybdenum irradiation by alpha-particles and neutrons leads to different degree of material hardening for the same damage level. It is established that molybdenum radiation hardening is mainly defined by radiation defect clusters visible in electron microscope whose coefficient of rigidity depends on their size. 5 refs.; 6 figs.; 2 tabs. (author).

Energy Technology Data Exchange (ETDEWEB)

A lock out assembly for a circuit breaker which consists of a generally step-shaped unitary base with an aperture in the small portion of the step-shaped base and a roughly S shaped retaining pin which loops through the large portion of the step-shaped base. The lock out assembly is adapted to fit over a circuit breaker with the handle switch projecting through the aperture, and the retaining pin projecting into an opening of the handle switch, preventing removal.

International Nuclear Information System (INIS)

The quenched chiral logarithms are examined on a 163x28 lattice with Iwasaki gauge action and overlap fermions. The pion decay constant fpi is used to set the lattice spacing, a = 0.200(3) fm. With pion mass as low as #approx#180 MeV, we see the quenched chiral logarithms clearly in mpi2/m and fP, the pseudoscalar decay constant. The authors analyze the data to determine how low the pion mass needs to be in order for the quenched one-loop chiral perturbation theory (chiPT) to apply. With the constrained curve-fitting method, they are able to extract the quenched chiral logarithmic parameter delta together with other low-energy parameters. Only for mpi<=300 MeV do we obtain a consistent and stable fit with a constant delta which they determine to be 0.24(3)(4) (at the chiral scale Lambdachi = 0.8 GeV). By comparing to the 123x28 lattice, they estimate the finite volume effect to be about 2.7% for the smallest pion mass. They also fitted the pion mass to the form ...

Science.gov (United States)

imaging of the solar corona began in 1960 via a primitive pinhole camera on a ... IR wavelengths. Such data help us to study in detail the pre-eruptive ...... Schematic picture of flare loops, CME, and the current sheet between ..... As part of NASA's Living With a Star (LWS) program the planned Sentinel mission ...

UK PubMed Central (United Kingdom)

Yeast arginyl-tRNA synthetase recognizes the non-modified wild-type transcripts derived from both yeast tRNA(Arg) and tRNA(Asp) with equal efficiency. It discriminates its cognate natural substrate,...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

We discuss the determination of the infrared singularities of massive one-loop 5-point functions with Mellin-Barnes (MB) representations. Massless internal lines may lead to poles in the {epsilon} expansion of the Feynman diagram, while unresolved massless final state particles give endpoint singularities of the phase space integrals. MB integrals are an elegant tool for their common treatment. An evaluation by taking residues leads to inverse binomial sums. (orig.)

Science.gov (United States)

... The Effect of the Temperature to Which the Material is Heated on the Process of Formation of Intermetallic Compounds in Magnetic Pulse Welding,. ...

CERN Document Server

The nature of the first generation of stars in the Universe remains largely unknown. Observations imply the existence of massive primordial stars early in the history of the universe, and the standard theory for the growth of cosmic structure predicts that structures grow hierarchically through gravitational instability. We have developed an ab initio computer simulation of the formation of primordial stars that follows the relevant atomic and molecular processes in a primordial gas in an expanding universe. The results show that primeval density fluctuations left over from the Big Bang can drive the formation of a tiny protostar with a mass of just one percent that of the sun. The protostar is a seed for the subsequent formation of a massive primordial star.

Science.gov (United States)

... Admiral Olson mentions the requirement for a standing joint task force headquarters in USSOCOM in order to fulfill the command's charter as a ...

Energy Technology Data Exchange (ETDEWEB)

Stabilized formation temperatures were estimated at different depths in 40 wells from the Los Humeros geothermal field, Mexico, using the Horner and the spherical radial flow (SRF) methods. The results showed that the Horner method underestimates formation temperatures, while the SRF method gives temperatures that are closer to the true formation temperatures. This was supported by numerical simulation of a combined circulation and shut-in period in several wells, and results for well H-26 are presented. Numerical reproduction of logged temperature is more feasible if an initial temperature profile based on the SRF method is employed instead of using an initial temperature profile based on the Horner method. (Author)

Science.gov (United States)

PMID:21846114

Science.gov (United States)

Main purpose of mapping observations of the cloud is to make clear the mechanism of star formation and star evolution. Scientific objectives are summarized ...