bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charpy Toughness and Tensile Properties of a Neutron-Irradiated Stainless Steel Submerged-Arc Weld Cladding Overlay
Authors: Corwin William R. , Berggren Reynold G. , Nanstad Randy K. 
Published: February 2018

The possibility of stainless steel cladding increasing the resistance of an operating nuclear reactor pressure vessel to extension of surface flaws is highly dependent upon the irradiated properties of the cladding. Therefore, weld overlay cladding irradiated at temperatures and fluences relevant to power reactor operation was examined. The cladding was applied to a pressure vessel steel plate by the submerged-arc, single-wire, oscillating electrode method. Three layers of cladding were applied to provide a cladding thickness adequate for fabrication of test specimens. The first layer was Type 309, and the upper two layers were Type 308 stainless steel. There was considerable dilution of the Type 309 in the first layer of cladding as a result of excessive melting of the base plate. Specimens for the irradiation study were taken from near the base plate/cladding interface and also from the upper layers of cladding. Charpy V-notch and tension specimens were irradiated at 288°C to neutron fluences of 2 × 1023 neutrons (n)/m2 (E &gt; 1 MeV).
When irradiated, both Types 308 and 309 cladding showed a 5 to 40% increase in yield strength accompanied by a slight increase in ductility in the temperature range from 25 to 288°C. All cladding exhibited ductile-to-brittle transition behavior during impact testing. The Type 308 cladding, microstructurally typical of that in reactor pressure vessels, showed very little degradation in either upper-shelf energy or transition temperature due to irradiation. Conversely, the impact properties of the specimens containing the highly diluted Type 309 cladding, microstructurally similar to that produced during some off-normal welding conditions in existing reactors, experienced significant increases in transition temperature and drops of up to 50% in upper-shelf energy. The impact energies of the Charpy specimens containing the Type 309 layer of cladding strongly reflected the amount of the Type 309 actually comprising the specimen, falling into two distinct high- and low-energy populations with the low-energy population corresponding to a higher fraction of Type 309 in the specimen.
Chemical Composition of Nuclear Reactor Vessel Welds
Authors: Moore Kenneth E. , Heller A. S. , Lowe Arthur L. 
Published: February 2018

The chemical compositions of Babcock & Wilcox Nuclear 177 fuel assembly (B&W 177 FA) reactor vessel beltline welds were characterized. Emphasis was placed on copper concentration and variability due to the effect of copper on the fracture and impact toughness properties of irradiated weld metals. Fourteen full section and surveillance program welds were examined. These welds (unique filler wire heats and flux lots) were made with 8 of the 13 heats of filler wire and a majority of the flux lots used in the B&W 177 FA reactor vessel beltline welds. The concentrations of 21 elements were measured using emission spectrographic analysis. A total of 290 through-weld-thickness analyses were performed on these welds that provided a measure of copper concentration and variation. The mean copper concentration of the 14 welds ranged from 0.18 to 0.42% by weight with standard deviation ranging from 0.005 to 0.07% by weight. The mean copper concentration of the 290 analyses was 0.29% by weight. Variability of the other 20 elements was found to be small within each weld.
Electron microprobe analysis was used to assess the micro-variations in copper concentration in a typical reactor vessel weldment. The measured degree of segregation was low.
Additional analyses were performed to determine the quantity of copper available on the weld filler wire that was transferred to the weld deposit during the weld process. The results of these analyses indicate copper concentration equivalence between the filler wire and the weld deposit.
Relationship of Yield Strength and Upper-Shelf Impact Energy Changes for Irradiated Reactor Vessel Steel
Authors: Byrne Stephen T. , Pirek Ronald C. 
Published: February 2018

Radiation-induced changes on the strength and toughness properties of reactor pressure vessel steels are known to be dependent on the chemical content and, to a lesser extent, on the product form. The precise relationship between key variables, however, is yet to be established. Emphasis is currently being placed on the development of mechanistic models to provide coherence between the variety of empirical observations presented to date.
Results are presented of an investigation of radiation damage trends exhibited by changes in the uniaxial tension and Charpy upper-shelf energy properties. Regression analysis techniques were used to determine trends based on chemistry and neutron fluence. These trends were evaluated in terms of proposed mechanistic models toward developing a broader understanding of radiation damage mechanisms.
Radiation-induced transition temperature shift in reactor vessel steels is known to be dependent on the copper and nickel content of the material. In this investigation, Charpy upper-shelf impact energy and ultimate tensile strength changes were found to exhibit similar dependencies on the copper content and neutron irradiation exposure, but neither property change was significantly influenced by nickel content. Based on the apparent difference in radiation behavior trends between transition temperature shift and shelf energy/tensile property changes, a multiple defect radiation damage model was postulated. The first defect type, dependent on copper content, increased the yield strength through a precipitation hardening mechanism. A second defect type, dependent on both copper and nickel content, affected the microcleavage fracture stress through a process such as grain boundary embrittlement. A third defect type, dependent on neutron irradiation only, affected the yield strength by a process such as vacancy hardening. This postulated model provides a reasonable basis for explaining observed differences in radiation behavior.
Analysis of Charpy V-Notch Impact Toughness of Irradiated A533-B Class 1 Plate and Four Submerged-Arc Welds
Authors: Berggren Reynold G. , Hawthorne J. Russell , Nanstad Randy K. 
Published: February 2018

Studies of the effects of neutron irradiation on Charpy V-notch impact properties of steels have, in general, included a minimum number of tests for each combination of material and irradiation parameters. The present study attempts to apply statistical analyses with multiple testing at selected temperatures to assess the accuracy and reliability of results.
Charpy V-notch impact test specimens were irradiated in the Bulk Shielding Reactor at Oak Ridge National Laboratory at 288°C to target neutron fluences of 2 × 1023 neutrons (n)/m2 (&gt;1 MeV). The materials were ASTM A533-B Class 1 plate (Heavy-Section Steel Technology Plate 02) and four submerged-arc welds representing current nuclear pressure vessel fabrication practice. Both unirradiated and irradiated specimens were tested by two separate groups and multiple tests were conducted at several selected temperatures. Statistical analyses permitted determination of material and test variability and an interlaboratory comparison.
Several Charpy curve-fitting methods were used and results are compared with predictions from several “trend curve” expressions.
A Transmission Electron Microscopy Study of the Structure and Annealing Behavior of Copper-Krypton Deposits
Authors: Evans John H. , Williamson Robert , Whitmell Derek S. 
Published: February 2018

A combined implantation and sputtering method has been developed at Harwell to entrap high (5%) atomic concentrations of krypton in a metal matrix. The work has been aimed at providing a safe and effective method for storing the active krypton-85 resulting from fuel reprocessing. In the present paper, the results of a transmission electron microscopy investigation into the structures of copper-krypton deposits will be presented together with the effects of annealing behavior. The overall impression of the as-deposited material is one of a very fine grain size, high dislocation density, and an extremely large concentration of small bubbles in the range 1.5 to 2.0 nm diameter. Taking into account additional results of macroscopic density and lattice parameter measurements, it is argued that the bubbles contain krypton at very high pressures; nevertheless, an appreciable fraction of krypton must be present in bubbles that are submicroscopic in size.
On annealing, large changes in bubble substructures became apparent at temperatures greater than half the melting point when the main effect was one of bubble coarsening as a result of coalescence and grain boundary bubble growth. These effects were reflected in the specimen surface structure as observed by scanning electron microscopy. The observations of the as-deposited material and its evolution with temperature should provide a useful background to the understanding of the material stability and high temperature gas release behavior.
Neural Determinants of Task Performance during Feature-Based Attention in Human Cortex
Authors: Jigo Michael , Gong Mengyuan , Liu Taosheng 
Published: February 2018

AbstractStudies of feature-based attention have associated activity in a dorsal frontoparietal network with putative attentional priority signals. Yet, how this neural activity mediates attentional selection and whether it guides behavior are fundamental questions that require investigation. We reasoned that endogenous fluctuations in the quality of attentional priority should influence task performance. Human subjects detected a speed increment while viewing clockwise (CW) or counterclockwise (CCW) motion (baseline task) or while attending to either direction amid distracters (attention task). In an fMRI experiment, direction-specific neural pattern similarity between the baseline task and the attention task revealed a higher level of similarity for correct than incorrect trials in frontoparietal regions. Using transcranial magnetic stimulation (TMS), we disrupted posterior parietal cortex (PPC) and found a selective deficit in the attention task, but not in the baseline task, demonstrating the necessity of this cortical area during feature-based attention. These results reveal that frontoparietal areas maintain attentional priority that facilitates successful behavioral selection.
Rescue of Learning and Memory Deficits in the Human Nonsyndromic Intellectual Disability Cereblon Knock-Out Mouse Model by Targeting the AMP-Activated Protein Kinase–mTORC1 Translational Pathway
Authors: Bavley Charlotte C. , Rice Richard C. , Fischer Delaney K. , Fakira Amanda K. , Byrne Maureen , Kosovsky Maria , Rizzo Bryant K. , Del Prete Dolores , Alaedini Armin , Morón Jose A. , Higgins Joseph J. , D'Adamio Luciano , Rajadhyaksha Anjali M. 
Published: February 2018

A homozygous nonsense mutation in the cereblon (CRBN) gene results in autosomal recessive, nonsyndromic intellectual disability that is devoid of other phenotypic features, suggesting a critical role of CRBN in mediating learning and memory. In this study, we demonstrate that adult maleCrbnknock-out (CrbnKO) mice exhibit deficits in hippocampal-dependent learning and memory tasks that are recapitulated by focal knock-out of Crbn in the adult dorsal hippocampus, with no changes in social or repetitive behavior. Cellular studies identify deficits in long-term potentiation at Schaffer collateral CA1 synapses. We further show thatCrbnis robustly expressed in the mouse hippocampus andCrbnKOmice exhibit hyperphosphorylated levels of AMPKα (Thr172). Examination of processes downstream of AMP-activated protein kinase (AMPK) finds thatCrbnKOmice have a selective impairment in mediators of the mTORC1 translation initiation pathway in parallel with lower protein levels of postsynaptic density glutamatergic proteins and higher levels of excitatory presynaptic markers in the hippocampus with no change in markers of the unfolded protein response or autophagy pathways. Acute pharmacological inhibition of AMPK activity in adultCrbnKOmice rescues learning and memory deficits and normalizes hippocampal mTORC1 activity and postsynaptic glutamatergic proteins without altering excitatory presynaptic markers. Thus, this study identifies that loss ofCrbnresults in learning, memory, and synaptic defects as a consequence of exaggerated AMPK activity, inhibition of mTORC1 signaling, and decreased glutamatergic synaptic proteins. Thus,CrbnKOmice serve as an ideal model of intellectual disability to further explore molecular mechanisms of learning and memory.SIGNIFICANCE STATEMENTIntellectual disability (ID) is one of the most common neurodevelopmental disorders. The cereblon (CRBN) gene has been linked to autosomal recessive, nonsyndromic ID, characterized by an intelligence quotient between 50 and 70 but devoid of other phenotypic features, making cereblon an ideal protein for the study of the fundamental aspects of learning and memory. Here, using the cereblon knock-out mouse model, we show that cereblon deficiency disrupts learning, memory, and synaptic function via AMP-activated protein kinase hyperactivity, downregulation of mTORC1, and dysregulation of excitatory synapses, with no changes in social or repetitive behaviors, consistent with findings in the human population. This establishes the cereblon knock-out mouse as a model of pure ID without the confounding behavioral phenotypes associated with other current models of ID.
The Effect of Locomotion on Early Visual Contrast Processing in Humans
Authors: Benjamin Alex V. , Wailes-Newson Kirstie , Ma-Wyatt Anna , Baker Daniel H. , Wade Alex R. 
Published: February 2018

Most of our knowledge about vision comes from experiments in which stimuli are presented to immobile human subjects or animals. In the case of human subjects, movement during psychophysical, electrophysiological, or neuroimaging experiments is considered to be a source of noise to be eliminated. Animals used in visual neuroscience experiments are typically restrained and, in many cases, anesthetized. In reality, however, vision is often used to guide the motion of awake, ambulating organisms. Recent work in mice has shown that locomotion elevates visual neuronal response amplitudes (Niell and Stryker, 2010; Erisken et al., 2014; Fu et al., 2014; Lee et al., 2014; Mineault et al., 2016) and reduces long-range gain control (Ayaz et al., 2013). Here, we used both psychophysics and steady-state electrophysiology to investigate whether similar effects of locomotion on early visual processing can be measured in humans. Our psychophysical results show that brisk walking has little effect on subjects' ability to detect briefly presented contrast changes and that co-oriented flankers are, if anything, more effective masks when subjects are walking. Our electrophysiological data were consistent with the psychophysics indicating no increase in stimulus-driven neuronal responses while walking and no reduction in surround suppression. In summary, we have found evidence that early contrast processing is altered by locomotion in humans but in a manner that differs from that reported in mice. The effects of locomotion on very low-level visual processing may differ on a species-by-species basis and may reflect important differences in the levels of arousal associated with locomotion.SIGNIFICANCE STATEMENTMice are the current model of choice for studying low-level visual processing. Recent studies have shown that mouse visual cortex is modulated by behavioral state: primary visual cortex neurons in locomoting mice tend to be more sensitive and less influenced by long-range gain control. Here, we tested these effects in humans by measuring psychophysical detection thresholds and electroencephalography (EEG) responses while subjects walked on a treadmill. We found no evidence of increased contrast sensitivity or reduced surround suppression in walking humans. Our data show that fundamental measurements of early visual processing differ between humans and mice and this has important implications for recent work on the links among arousal, behavior, and vision in these two species.
THE VOLUME OF THE CEREBELLUM IN THE SECOND SEMESTER OF GESTATION
Authors: Vulturar Damiana , Fărcăşanu Alexandru , Turcu Flaviu , Boitor Dan , Crivii Carmen 
Published: February 2018

Background and aims. The cerebellum (“little brain”), the largest part of hind brain, lies in the posterior cranial fossa, beneath the occipital lobe and dorsal to the brainstem. It develops over a long period: it is one of the first structures in the brain to begin to differentiate, but one of the last to mature. The use of ultrasonography has significantly improved the evaluation of fetal growth and development and has permitted prenatal diagnosis of a variety of congenital malformations.The aim of our study was to evaluate the cerebellar growth and development using 2 different measuring techniques: microMRI and ultrasound technique. The cerebellum measurements were related to gestational age.Methods. We used 14 human fetuses corresponding to 15-28 gestational weeks, immersed in a 9% formalin solution. Magnetic Resonance Imaging (MRI) was performed by employing a Bruker BioSpec 70/16USR scanner (Bruker BioSpin MRI GmbH, Ettlingen, Germany), operated at 7.04 Tesla for cerebellar volume measurement. Ultrasonographic measurements of the cerebellum diameter were performed on 14 pregnant women, 15 – 28 gestational weeks. Ultrasound scan used 5-10 MHZ for transvaginal approach. Taking into consideration the values of the cerebellum dimensions and considering the general shape of the cerebellum as a transverse ellipsoid, the volume of the cerebellum was calculated by a mathematical formula for ellipsoid volume.Results. The study correlates the measurements from the microMRI study with the ultrasounds data and the results are superposable. Both established the exponential volume growth after the 22-23 GW. We used the ellipsoid volume formula for the cerebellar volume using the half of the three diameters of the cerebellum determined by ultrasound measurements:Cerebellar Volume = Ellipsoid volume = r1 r2 r3Conclusion. There is a linear correlation between the microMRI measurements and ultrasound determinations. Based on all collected data we could apply an easy formula to calculate the volume of cerebellum, a useful criterion in the evaluation of the cerebellar development and the appreciation of the gestational age.
S-Substituted cysteine derivatives in production of flavour and colour
Authors: Velíšek J. , Kubec R. 
Published: February 2018

A brief review of our continuous investigations on S-substituted cysteine derivatives is presented herein. It comprises a summary on nonenzymatic (thermal) decomposition of these amino acids as well as on their role in the formation of blue and pink pigments during processing of garlic and onion, respectively. The emphasis is put on four most common derivatives, namely S-methyl-, S-allyl-, S-1-propenyl- and S-propylcysteine sulfoxides (methiin, alliin, isoalliin and propiin, respectively). Our results demonstrate that these sulfur-containing amino acids are the key primary precursors in the formation of both flavour and colour of alliaceous plants.
Antioxidation capacity of Maillard systems with carbonyl products of sugar fragmentation
Authors: Cejpek K. , Jarolímová L. , Velíšek J. 
Published: February 2018

A role of reactive C<sub>2</sub>-C<sub>5</sub> α-dicarbonyl and α-hydroxycarbonyl products of sugar fragmentation in the development of antioxidative activity (AOA) was investigated after heating in 0.5M binary aqueous mixtures with amino acids. Several kinetic and activity parameters related to the development of reducing power in the systems with different carbonyl fragments as well as glucose were evaluated and compared. The formation of electrochemically active compounds was correlated with colour development. To assess the antioxidation effects more properly, several different methods were used for AOA evaluation of the systems tested in addition to the HPLC-ECD method. Tests with scavenging of radicals or assays evaluating oxidation in different media (hydrophobic, hydrophilic, emulsions) were employed. Biacetyl was found as by far the most powerful precursor of reducing activity among the fragments tested. The major products possessing reducing power were isolated and characterized revealing dihydroxy dimethylbenzene structures. Based on the comparison of the same concentrations of BHA and a parent carbonyl compound, AOA found by different methods in the most powerful systems is fully comparable with BHA efficiency.
Synthesis of (Z,Z)-octadeca-10,12-dienoic acid
Authors: Kellersmann C. , Francke W. , Steinhart H. 
Published: February 2018

(Z,Z)-Octadeca-10,12-dienoic acid was synthesised by coupling (Z)-1-bromohept-1-ene with protected undec-10-yne-1-ol. Stereoselective hydrogenation of the triple bond of the obtained enyne-system followed by deprotection yielded (Z,ZZ)-octadeca-10,12-dienol. The latter can be easily oxidized to the corresponding acid.
Influence of phenolic compounds on sensory parameters of tea infusions
Authors: Košulič P. , Pokorný J. , Panovská Z. 
Published: February 2018

A set of 9 black teas and 10 green teas were analyzed. Sensory parameters of tea infusions were correlated with the content of total polyphenols (determined after Folin and Ciocalteu) and sensory parameters (determined after ISO standards). Total polyphenols affect both the astringency and the bitterness of green tea and black tea infusions. The relations are mainly semilogarithmic, but very close to linear. Sucrose decreased the astringency by 30–40%, and the bitterness was suppressed still more.
Peroxyl radical scavenging activity of soluble high molecular weight fraction from coffee brews
Authors: Delgado-Andrade C. , J Morales F. 
Published: February 2018

Roasting process of coffee beans affects the final composition of coffee brew. While the presence of some of its antioxidant compounds (phenolic acids) decrease throughout the treatment, melanoidins are formed during the thermal process. Recent research into nutritional, physiological and functional properties of melanoidins has suggested that they have antioxidant activity. Instant coffees produced from roasted coffee beans were obtained from a company coffee in three different roasting degrees: light (CTn 110), medium (CTn 85) and dark (CTn 60). Melanoidins of high molecular weight (&gt; 10 000 Da) were obtained from each coffee, as well as pure melanoidins by incubation in 2M ClNa and ultrafiltration. CGA contained in extractes of different melanoidins (1 mg/ml) was measured by HPLC. Peroxyl radical scavenging activity of melanoidins and pure melanoidins were tested using a procedure to inhibite the peroxidation of linoleic acid. Antioxidant efficiency (AE<sub>50</sub>, ml/min/mg) was calculated as the slope of the time of inhibition at 50% (min) against concentration (mg/ml). No significant differences were found between melanoidins and pure melanoidins in the different roasting degrees. Peroxyl radical scavenging activity of melanoidins from coffee brew is mainly due to the chelated compounds by ionic binds.