MELCOR/CONTAIN LMR Implementation Report. FY14 Progress

DOE Office of Scientific and Technical Information (OSTI.GOV)

Humphries, Larry L; Louie, David L.Y.

2014-10-01

This report describes the preliminary implementation of the sodium thermophysical properties and the design documentation for the sodium models of CONTAIN-LMR to be implemented into MELCOR 2.1. In the past year, the implementation included two separate sodium properties from two different sources. The first source is based on the previous work done by Idaho National Laboratory by modifying MELCOR to include liquid lithium equation of state as a working fluid to model the nuclear fusion safety research. To minimize the impact to MELCOR, the implementation of the fusion safety database (FSD) was done by utilizing the detection of the datamore » input file as a way to invoking the FSD. The FSD methodology has been adapted currently for this work, but it may subject modification as the project continues. The second source uses properties generated for the SIMMER code. Preliminary testing and results from this implementation of sodium properties are given. In this year, the design document for the CONTAIN-LMR sodium models, such as the two condensable option, sodium spray fire, and sodium pool fire is being developed. This design document is intended to serve as a guide for the MELCOR implementation. In addition, CONTAIN-LMR code used was based on the earlier version of CONTAIN code. Many physical models that were developed since this early version of CONTAIN may not be captured by the code. Although CONTAIN 2, which represents the latest development of CONTAIN, contains some sodium specific models, which are not complete, the utilizing CONTAIN 2 with all sodium models implemented from CONTAIN-LMR as a comparison code for MELCOR should be done. This implementation should be completed in early next year, while sodium models from CONTAIN-LMR are being integrated into MELCOR. For testing, CONTAIN decks have been developed for verification and validation use.« less

Structure of the transcriptional regulator LmrR and its mechanism of multidrug recognition.

PubMed

Madoori, Pramod Kumar; Agustiandari, Herfita; Driessen, Arnold J M; Thunnissen, Andy-Mark W H

2009-01-21

LmrR is a PadR-related transcriptional repressor that regulates the production of LmrCD, a major multidrug ABC transporter in Lactococcus lactis. Transcriptional regulation is presumed to follow a drug-sensitive induction mechanism involving the direct binding of transporter ligands to LmrR. Here, we present crystal structures of LmrR in an apo state and in two drug-bound states complexed with Hoechst 33342 and daunomycin. LmrR shows a common topology containing a typical beta-winged helix-turn-helix domain with an additional C-terminal helix involved in dimerization. Its dimeric organization is highly unusual with a flat-shaped hydrophobic pore at the dimer centre serving as a multidrug-binding site. The drugs bind in a similar manner with their aromatic rings sandwiched in between the indole groups of two dimer-related tryptophan residues. Multidrug recognition is facilitated by conformational plasticity and the absence of drug-specific hydrogen bonds. Combined analyses using site-directed mutagenesis, fluorescence-based drug binding and protein-DNA gel shift assays reveal an allosteric coupling between the multidrug- and DNA-binding sites of LmrR that most likely has a function in the induction mechanism.

Deep Chandra Observations of Abell 586: A Remarkably Relaxed Non-Cool-Core Cluster

NASA Astrophysics Data System (ADS)

Richstein, Hannah; Su, Yuanyuan

2018-01-01

The dichotomy between cool-core and non-cool-core clusters has been a lasting perplexity in extragalactic astronomy. Nascent cores in non-cool-core clusters may have been disrupted by major mergers, yet the dichotomy cannot be reproduced in cosmology simulations. We present deep Chandra observations of the massive galaxy cluster Abell 586, which resides at z=0.17, thus allowing its gas properties to be measured out to its virial radius. Abell 586 appears remarkably relaxed with a nearly spherical X-ray surface brightness distribution and without any offset between its X-ray and optical centroids. We measure that its temperature profile does not decrease towards the cluster center and its central entropy stays above 100 keV cm2. A non-cool-core emerges in Abell 586 in the absence of any disruptions on the large scale. Our study demonstrates that non-cool-core clusters can be formed without major mergers. The origins of some non-cool-core clusters may be related to conduction, AGN feedback, or preheating.The SAO REU program is funded by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant AST-1659473, and by the Smithsonian Institution.

Reactor core isolation cooling system

DOEpatents

Cooke, F.E.

1992-12-08

A reactor core isolation cooling system includes a reactor pressure vessel containing a reactor core, a drywell vessel, a containment vessel, and an isolation pool containing an isolation condenser. A turbine is operatively joined to the pressure vessel outlet steamline and powers a pump operatively joined to the pressure vessel feedwater line. In operation, steam from the pressure vessel powers the turbine which in turn powers the pump to pump makeup water from a pool to the feedwater line into the pressure vessel for maintaining water level over the reactor core. Steam discharged from the turbine is channeled to the isolation condenser and is condensed therein. The resulting heat is discharged into the isolation pool and vented to the atmosphere outside the containment vessel for removing heat therefrom. 1 figure.

Reactor core isolation cooling system

DOEpatents

Cooke, Franklin E.

1992-01-01

A reactor core isolation cooling system includes a reactor pressure vessel containing a reactor core, a drywell vessel, a containment vessel, and an isolation pool containing an isolation condenser. A turbine is operatively joined to the pressure vessel outlet steamline and powers a pump operatively joined to the pressure vessel feedwater line. In operation, steam from the pressure vessel powers the turbine which in turn powers the pump to pump makeup water from a pool to the feedwater line into the pressure vessel for maintaining water level over the reactor core. Steam discharged from the turbine is channeled to the isolation condenser and is condensed therein. The resulting heat is discharged into the isolation pool and vented to the atmosphere outside the containment vessel for removing heat therefrom.

Isolated core vs. superficial cooling effects on virtual maze navigation.

PubMed

Payne, Jennifer; Cheung, Stephen S

2007-07-01

Cold impairs cognitive performance and is a common occurrence in many survival situations. Altered behavior patterns due to impaired navigation abilities in cold environments are potential problems in lost-person situations. We investigated the separate effects of low core temperature and superficial cooling on a spatially demanding virtual navigation task. There were 12 healthy men who were passively cooled via 15 degrees C water immersion to a core temperature of 36.0 degrees C, then transferred to a warm (40 degrees C) water bath to eliminate superficial shivering while completing a series of 20 virtual computer mazes. In a control condition, subjects rested in a thermoneutral (approximately 35 degrees C) bath for a time-matched period before being transferred to a warm bath for testing. Superficial cooling and distraction were achieved by whole-body immersion in 35 degree water for a time-matched period, followed by lower leg immersion in 10 degree C water for the duration of the navigational tests. Mean completion time and mean error scores for the mazes were not significantly different (p > 0.05) across the core cooling (16.59 +/- 11.54 s, 0.91 +/- 1.86 errors), control (15.40 +/- 8.85 s, 0.82 +/- 1.76 errors), and superficial cooling (15.19 +/- 7.80 s, 0.77 +/- 1.40 errors) conditions. Separately reducing core temperature or increasing cold sensation in the lower extremities did not influence performance on virtual computer mazes, suggesting that navigation is more resistive to cooling than other, simpler cognitive tasks. Further research is warranted to explore navigational ability at progressively lower core and skin temperatures, and in different populations.

MELCOR/CONTAIN LMR Implementation Report-Progress FY15

DOE Office of Scientific and Technical Information (OSTI.GOV)

Humphries, Larry L.; Louie, David L.Y.

2016-01-01

This report describes the progress of the CONTAIN-LMR sodium physics and chemistry models to be implemented in to MELCOR 2.1. It also describes the progress to implement these models into CONT AIN 2 as well. In the past two years, the implementation included the addition of sodium equations of state and sodium properties from two different sources. The first source is based on the previous work done by Idaho National Laborat ory by modifying MELCOR to include liquid lithium equation of state as a working fluid to mode l the nuclear fusion safety research. The second source uses properties generatedmore » for the SIMMER code. Testing and results from this implementation of sodium pr operties are given. In addition, the CONTAIN-LMR code was derived from an early version of C ONTAIN code. Many physical models that were developed sin ce this early version of CONTAIN are not captured by this early code version. Therefore, CONTAIN 2 is being updated with the sodium models in CONTAIN-LMR in or der to facilitate verification of these models with the MELCOR code. Although CONTAIN 2, which represents the latest development of CONTAIN, now contains ma ny of the sodium specific models, this work is not complete due to challenges from the lower cell architecture in CONTAIN 2, which is different from CONTAIN- LMR. This implementation should be completed in the coming year, while sodi um models from C ONTAIN-LMR are being integrated into MELCOR. For testing, CONTAIN decks have been developed for verification and validation use. In terms of implementing the sodium m odels into MELCOR, a separate sodium model branch was created for this document . Because of massive development in the main stream MELCOR 2.1 code and the require ment to merge the latest code version into this branch, the integration of the s odium models were re-directed to implement the sodium chemistry models first. This change led to delays of the actual implementation. For aid in the future implementation of

Testing the Large-scale Environments of Cool-core and Non-cool-core Clusters with Clustering Bias

NASA Astrophysics Data System (ADS)

Medezinski, Elinor; Battaglia, Nicholas; Coupon, Jean; Cen, Renyue; Gaspari, Massimo; Strauss, Michael A.; Spergel, David N.

2017-02-01

There are well-observed differences between cool-core (CC) and non-cool-core (NCC) clusters, but the origin of this distinction is still largely unknown. Competing theories can be divided into internal (inside-out), in which internal physical processes transform or maintain the NCC phase, and external (outside-in), in which the cluster type is determined by its initial conditions, which in turn leads to different formation histories (I.e., assembly bias). We propose a new method that uses the relative assembly bias of CC to NCC clusters, as determined via the two-point cluster-galaxy cross-correlation function (CCF), to test whether formation history plays a role in determining their nature. We apply our method to 48 ACCEPT clusters, which have well resolved central entropies, and cross-correlate with the SDSS-III/BOSS LOWZ galaxy catalog. We find that the relative bias of NCC over CC clusters is b = 1.42 ± 0.35 (1.6σ different from unity). Our measurement is limited by the small number of clusters with core entropy information within the BOSS footprint, 14 CC and 34 NCC clusters. Future compilations of X-ray cluster samples, combined with deep all-sky redshift surveys, will be able to better constrain the relative assembly bias of CC and NCC clusters and determine the origin of the bimodality.

Testing the Large-scale Environments of Cool-core and Non-cool-core Clusters with Clustering Bias

DOE Office of Scientific and Technical Information (OSTI.GOV)

Medezinski, Elinor; Battaglia, Nicholas; Cen, Renyue

2017-02-10

There are well-observed differences between cool-core (CC) and non-cool-core (NCC) clusters, but the origin of this distinction is still largely unknown. Competing theories can be divided into internal (inside-out), in which internal physical processes transform or maintain the NCC phase, and external (outside-in), in which the cluster type is determined by its initial conditions, which in turn leads to different formation histories (i.e., assembly bias). We propose a new method that uses the relative assembly bias of CC to NCC clusters, as determined via the two-point cluster-galaxy cross-correlation function (CCF), to test whether formation history plays a role in determiningmore » their nature. We apply our method to 48 ACCEPT clusters, which have well resolved central entropies, and cross-correlate with the SDSS-III/BOSS LOWZ galaxy catalog. We find that the relative bias of NCC over CC clusters is b = 1.42 ± 0.35 (1.6 σ different from unity). Our measurement is limited by the small number of clusters with core entropy information within the BOSS footprint, 14 CC and 34 NCC clusters. Future compilations of X-ray cluster samples, combined with deep all-sky redshift surveys, will be able to better constrain the relative assembly bias of CC and NCC clusters and determine the origin of the bimodality.« less

Evaluation of advanced cooling therapy's esophageal cooling device for core temperature control.

PubMed

Naiman, Melissa; Shanley, Patrick; Garrett, Frank; Kulstad, Erik

2016-05-01

Managing core temperature is critical to patient outcomes in a wide range of clinical scenarios. Previous devices designed to perform temperature management required a trade-off between invasiveness and temperature modulation efficiency. The Esophageal Cooling Device, made by Advanced Cooling Therapy (Chicago, IL), was developed to optimize warming and cooling efficiency through an easy and low risk procedure that leverages heat transfer through convection and conduction. Clinical data from cardiac arrest, fever, and critical burn patients indicate that the Esophageal Cooling Device performs very well both in terms of temperature modulation (cooling rates of approximately 1.3°C/hour, warming of up to 0.5°C/hour) and maintaining temperature stability (variation around goal temperature ± 0.3°C). Physicians have reported that device performance is comparable to the performance of intravascular temperature management techniques and superior to the performance of surface devices, while avoiding the downsides associated with both.

The first high resolution image of coronal gas in a starbursting cool core cluster

NASA Astrophysics Data System (ADS)

Johnson, Sean

2017-08-01

Galaxy clusters represent a unique laboratory for directly observing gas cooling and feedback due to their high masses and correspondingly high gas densities and temperatures. Cooling of X-ray gas observed in 1/3 of clusters, known as cool-core clusters, should fuel star formation at prodigious rates, but such high levels of star formation are rarely observed. Feedback from active galactic nuclei (AGN) is a leading explanation for the lack of star formation in most cool clusters, and AGN power is sufficient to offset gas cooling on average. Nevertheless, some cool core clusters exhibit massive starbursts indicating that our understanding of cooling and feedback is incomplete. Observations of 10^5 K coronal gas in cool core clusters through OVI emission offers a sensitive means of testing our understanding of cooling and feedback because OVI emission is a dominant coolant and sensitive tracer of shocked gas. Recently, Hayes et al. 2016 demonstrated that synthetic narrow-band imaging of OVI emission is possible through subtraction of long-pass filters with the ACS+SBC for targets at z=0.23-0.29. Here, we propose to use this exciting new technique to directly image coronal OVI emitting gas at high resolution in Abell 1835, a prototypical starbursting cool-core cluster at z=0.252. Abell 1835 hosts a strong cooling core, massive starburst, radio AGN, and at z=0.252, it offers a unique opportunity to directly image OVI at hi-res in the UV with ACS+SBC. With just 15 orbits of ACS+SBC imaging, the proposed observations will complete the existing rich multi-wavelength dataset available for Abell 1835 to provide new insights into cooling and feedback in clusters.

78 FR 63516 - Initial Test Program of Emergency Core Cooling Systems for New Boiling-Water Reactors

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-24

... NUCLEAR REGULATORY COMMISSION [NRC-2012-0134] Initial Test Program of Emergency Core Cooling....79.1, ``Initial Test Program of Emergency Core Cooling Systems for New Boiling-Water Reactors.'' This... emergency core cooling systems (ECCSs) for boiling- water reactors (BWRs) whose licenses are issued after...

Fuel Breeding and Core Behavior Analyses on In Core Fuel Management of Water Cooled Thorium Reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Permana, Sidik; Department of Physics, Bandung Institute of Technology, Gedung Fisika, Jl. Ganesha 10, Bandung 40132; Sekimoto, Hiroshi

2010-12-23

Thorium fuel cycle with recycled U-233 has been widely recognized having some contributions to improve the water-cooled breeder reactor program which has been shown by a feasible area of breeding and negative void reactivity which confirms that fissile of 233U contributes to better fuel breeding and effective for obtaining negative void reactivity coefficient as the main fissile material. The present study has the objective to estimate the effect of whole core configuration as well as burnup effects to the reactor core profile by adopting two dimensional model of fuel core management. About more than 40 months of cycle period hasmore » been employed for one cycle fuel irradiation of three batches fuel system for large water cooled thorium reactors. All position of fuel arrangement contributes to the total core conversion ratio which gives conversion ratio less than unity of at the BOC and it contributes to higher than unity (1.01) at the EOC after some irradiation process. Inner part and central part give the important part of breeding contribution with increasing burnup process, while criticality is reduced with increasing the irradiation time. Feasibility of breeding capability of water-cooled thorium reactors for whole core fuel arrangement has confirmed from the obtained conversion ratio which shows higher than unity. Whole core analysis on evaluating reactivity change which is caused by the change of voided condition has been employed for conservative assumption that 100% coolant and moderator are voided. It obtained always a negative void reactivity coefficient during reactor operation which shows relatively more negative void coefficient at BOC (fresh fuel composition), and it becomes less negative void coefficient with increasing the operation time. Negative value of void reactivity coefficient shows the reactor has good safety properties in relation to the reactivity profile which is the main parameter in term of criticality safety analysis. Therefore

Luminorefrigeration: vibrational cooling of NaCs.

PubMed

Wakim, A; Zabawa, P; Haruza, M; Bigelow, N P

2012-07-02

We demonstrate the use of optical pumping of kinetically ultracold NaCs to cool an initial vibrational distribution of electronic ground state molecules X(1)Σ(+)(v ≥ 4) into the vibrational ground state X(1)Σ(+)(v=0). Our approach is based on the use of simple, commercially available multimode diode lasers selected to optically pump population into X(1)Σ(+)(v=0). We investigate the impact of the cooling process on the rotational state distribution of the vibrational ground state, and observe that an initial distribution, J(initial)=0-2 is only moderately affected resulting in J(final)=0-4. This method provides an inexpensive approach to creation of vibrational ground state ultracold polar molecules.

77 FR 36014 - Initial Test Program of Emergency Core Cooling Systems for Boiling-Water Reactors

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-15

... NUCLEAR REGULATORY COMMISSION [NRC-2012-0134] Initial Test Program of Emergency Core Cooling... for public comment draft regulatory guide (DG), DG-1277, ``Initial Test Program of Emergency Core... acceptable to implement with regard to initial testing features of emergency core cooling systems (ECCSs) for...

Deep Chandra study of the truncated cool core of the Ophiuchus cluster

NASA Astrophysics Data System (ADS)

Werner, N.; Zhuravleva, I.; Canning, R. E. A.; Allen, S. W.; King, A. L.; Sanders, J. S.; Simionescu, A.; Taylor, G. B.; Morris, R. G.; Fabian, A. C.

2016-08-01

We present the results of a deep Chandra observation of the Ophiuchus cluster, the second brightest galaxy cluster in the X-ray sky. The cluster hosts a truncated cool core, with a temperature increasing from kT ˜ 1 keV in the core to kT ˜ 9 keV at r ˜ 30 kpc. Beyond r ˜ 30 kpc, the intracluster medium (ICM) appears remarkably isothermal. The core is dynamically disturbed with multiple sloshing-induced cold fronts, with indications for both Rayleigh-Taylor and Kelvin-Helmholtz instabilities. The residual image reveals a likely subcluster south of the core at the projected distance of r ˜ 280 kpc. The cluster also harbours a likely radio phoenix, a source revived by adiabatic compression by gas motions in the ICM. Even though the Ophiuchus cluster is strongly dynamically active, the amplitude of density fluctuations outside of the cooling core is low, indicating velocities smaller than ˜100 km s-1. The density fluctuations might be damped by thermal conduction in the hot and remarkably isothermal ICM, resulting in our underestimate of gas velocities. We find a surprising, sharp surface brightness discontinuity, that is curved away from the core, at r ˜ 120 kpc to the south-east of the cluster centre. We conclude that this feature is most likely due to gas dynamics associated with a merger. The cooling core lacks any observable X-ray cavities and the active galactic nucleus (AGN) only displays weak, point-like radio emission, lacking lobes or jets. The lack of strong AGN activity may be due to the bulk of the cooling taking place offset from the central supermassive black hole.

Implementation of the TDCR liquid scintillation method at CNEA-LMR, Argentina.

PubMed

Arenillas, Pablo; Cassette, Philippe

2006-01-01

During the last two years, a triple-to-double coincidence ratio (TDCR) system was assembled and adjusted at the CNEA-LMR, Argentina. The new counting system will add complementary capabilities to the absolute measurements section of the CNEA-LMR. This work describes its implementation and validation. Several checks and a set of beta-emitting standard solutions were used in order to perform the validation experiments. In preliminary measurements, a 3H LNHB solution with reference activity concentration of (119.7+/-0.9) kBq/g on 11 November 2003 was used. The CNEA-LMR TDCR counter gave, at the same reference date, an activity concentration of (120+/-1) kBq/g. Results and improvements are presented in detail. Concerning the asymmetry of the system, the quantum efficiency of the three photomultiplier tubes was studied for different operating conditions of the focusing voltage. The counter also includes an automatic system to change the efficiency by defocusing the photomultipliers and on the other hand, it was coupled to a HPGe detector to also measure beta-gamma coincidences.

REVIEWS OF TOPICAL PROBLEMS: Cooling of neutron stars and superfluidity in their cores

NASA Astrophysics Data System (ADS)

Yakovlev, Dmitrii G.; Levenfish, Kseniya P.; Shibanov, Yurii A.

1999-08-01

We study the heat capacity and neutrino emission reactions (direct and modified Urca processes, nucleon-nucleon bremsstrahlung, Cooper pairing of nucleons) in the supranuclear density matter of neutron star cores with superfluid neutrons and protons. Various superfluidity types are analysed (singlet-state pairing and two types of triplet-state pairing, without and with gap nodes at the nucleon Fermi surface). The results are used for cooling simulations of isolated neutron stars. Both the standard cooling and the cooling enhanced by the direct Urca process are strongly affected by nucleon superfluidity. Comparison of the cooling theory of isolated neutron stars with observations of their thermal radiation may give stringent constraints on the critical temperatures of the neutron and proton superfluidities in the neutron star cores.

A Massive, Cooling-Flow-Induced Starburst in the Core of a Highly Luminous Galaxy Cluster

NASA Technical Reports Server (NTRS)

McDonald, M.; Bayliss, M.; Benson, B. A.; Foley, R. J.; Ruel, J.; Sullivan, P.; Veilleux, S.; Aird, K. A.; Ashby, M. L. N.; Bautz, M.;

Basic Residues R260 and K357 Affect the Conformational Dynamics of the Major Facilitator Superfamily Multidrug Transporter LmrP

PubMed Central

Wang, Wei; van Veen, Hendrik W.

2012-01-01

Secondary-active multidrug transporters can confer resistance on cells to pharmaceuticals by mediating their extrusion away from intracellular targets via substrate/H+(Na+) antiport. While the interactions of catalytic carboxylates in these transporters with coupling ions and substrates (drugs) have been studied in some detail, the functional importance of basic residues has received much less attention. The only two basic residues R260 and K357 in transmembrane helices in the Major Facilitator Superfamily transporter LmrP from Lactococcus lactis are present on the outer surface of the protein, where they are exposed to the phospholipid head group region of the outer leaflet (R260) and inner leaflet (K357) of the cytoplasmic membrane. Although our observations on the proton-motive force dependence and kinetics of substrate transport, and substrate-dependent proton transport demonstrate that K357A and R260A mutants are affected in ethidium-proton and benzalkonium-proton antiport compared to wildtype LmrP, our findings suggest that R260 and K357 are not directly involved in the binding of substrates or the translocation of protons. Secondary-active multidrug transporters are thought to operate by a mechanism in which binding sites for substrates are alternately exposed to each face of the membrane. Disulfide crosslinking experiments were performed with a double cysteine mutant of LmrP that reports the substrate-stimulated transition from the outward-facing state to the inward-facing state with high substrate-binding affinity. In the experiments, the R260A and K357A mutations were found to influence the dynamics of these major protein conformations in the transport cycle, potentially by removing the interactions of R260 and K357 with phospholipids and/or other residues in LmrP. The R260A and K357A mutations therefore modify the maximum rate at which the transport cycle can operate and, as the transitions between conformational states are differently affected by

Spiral Flows in Cool-core Galaxy Clusters

NASA Astrophysics Data System (ADS)

Keshet, Uri

2012-07-01

We argue that bulk spiral flows are ubiquitous in the cool cores (CCs) of clusters and groups of galaxies. Such flows are gauged by spiral features in the thermal and chemical properties of the intracluster medium, by the multiphase properties of CCs, and by X-ray edges known as cold fronts. We analytically show that observations of piecewise-spiral fronts impose strong constraints on the CC, implying the presence of a cold, fast flow, which propagates below a hot, slow inflow, separated by a slowly rotating, trailing, quasi-spiral, tangential discontinuity surface. This leads to the nearly logarithmic spiral pattern, two-phase plasma, ρ ~ r -1 density (or T ~ r 0.4 temperature) radial profile, and ~100 kpc size, characteristic of CCs. By advecting heat and mixing the gas, such flows can eliminate the cooling problem, provided that a feedback mechanism regulates the flow. In particular, we present a quasi-steady-state model for an accretion-quenched, composite flow, in which the fast phase is an outflow, regulated by active galactic nucleus bubbles, reproducing the observed low star formation rates and explaining some features of bubbles such as their Rb vpropr size. The simplest two-component model reproduces several key properties of CCs, so we propose that all such cores harbor a spiral flow. Our results can be tested directly in the next few years, for example by ASTRO-H.

Inactivation of a putative efflux pump (LmrB) in Streptococcus mutans results in altered biofilm structure and increased exopolysaccharide synthesis: implications for biofilm resistance.

PubMed

Liu, Jia; Zhang, Jianying; Guo, Lihong; Zhao, Wei; Hu, Xiaoli; Wei, Xi

2017-07-01

Efflux pumps are a mechanism associated with biofilm formation and resistance. There is limited information regarding efflux pumps in Streptococcus mutans, a major pathogen in dental caries. The aim of this study was to investigate potential roles of a putative efflux pump (LmrB) in S. mutans biofilm formation and susceptibility. Upon lmrB inactivation and antimicrobial exposure, the biofilm structure and expression of other efflux pumps were examined using confocal laser scanning microscopy (CLSM) and qRT-PCR. lmrB inactivation resulted in biofilm structural changes, increased EPS formation and EPS-related gene transcription (p < 0.05), but no improvement in susceptibility was observed. The expression of most efflux pump genes increased upon lmrB inactivation when exposed to antimicrobials (p < 0.05), suggesting a feedback mechanism that activated the transcription of other efflux pumps to compensate for the loss of lmrB. These observations imply that sole inactivation of lmrB is not an effective solution to control biofilms.

Preliminary engineering design of sodium-cooled CANDLE core

NASA Astrophysics Data System (ADS)

Takaki, Naoyuki; Namekawa, Azuma; Yoda, Tomoyuki; Mizutani, Akihiko; Sekimoto, Hiroshi

2012-06-01

The CANDLE burning process is characterized by the autonomous shifting of burning region with constant reactivity and constant spacial power distribution. Evaluations of such critical burning process by using widely used neutron diffusion and burning codes under some realistic engineering constraints are valuable to confirm the technical feasibility of the CANDLE concept and to put the idea into concrete core design. In the first part of this paper, it is discussed that whether the sustainable and stable CANDLE burning process can be reproduced even by using conventional core analysis tools such as SLAROM and CITATION-FBR. As a result, it is certainly possible to demonstrate it if the proper core configuration and initial fuel composition required as CANDLE core are applied to the analysis. In the latter part, an example of a concrete image of sodium cooled, metal fuel, 2000MWt rating CANDLE core has been presented by assuming an emerging inevitable technology of recladding. The core satisfies engineering design criteria including cladding temperature, pressure drop, linear heat rate, and cumulative damage fraction (CDF) of cladding, fast neutron fluence and sodium void reactivity which are defined in the Japanese FBR design project. It can be concluded that it is feasible to design CADLE core by using conventional codes while satisfying some realistic engineering design constraints assuming that recladding at certain time interval is technically feasible.

A 100-kWt NaK-Cooled Space Reactor Concept for an Early-Flight Mission

NASA Astrophysics Data System (ADS)

Poston, David I.

2003-01-01

A stainless-steel (SS) sodium-potassium (NaK) cooled reactor could potentially be the first step in utilizing fission technology in space. The sum of all system-level experience for liquid-metal-cooled space reactors has been with NaK, including the SNAP-10a, the only reactor ever launched by the US. This paper describes a 100-kWt NaK reactor, the NaK-100, which is designed to be developed with minimal technical risk. In additional to NaK technology heritage, the NaK-100 uses a proven fuel-form (SS/UO2) and is designed for simplified system integration and testing. The pins are placed within a solid SS prism, and the NaK flows in an annulus between the pins and the prism. The nuclear and thermal-hydraulic performance of the NaK-100 is presented, as well as the major differences between the NaK-100 and SNAP-10a.

Shivering heat production and body fat protect the core from cooling during body immersion, but not during head submersion: a structural equation model.

PubMed

Pretorius, Thea; Lix, Lisa; Giesbrecht, Gordon

2011-03-01

Previous studies showed that core cooling rates are similar when only the head or only the body is cooled. Structural equation modeling was used on data from two cold water studies involving body-only, or whole body (including head) cooling. Exposure of both the body and head increased core cooling, while only body cooling elicited shivering. Body fat attenuates shivering and core cooling. It is postulated that this protection occurs mainly during body cooling where fat acts as insulation against cold. This explains why head cooling increases surface heat loss with only 11% while increasing core cooling by 39%. Copyright © 2011 Elsevier Ltd. All rights reserved.

Cleaning residual NaK in the fast flux test facility fuel storage cooling system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burke, T.M.; Church, W.R.; Hodgson, K.M.

2008-01-15

The Fast Flux Test Facility (FFTF), located on the U.S. Department of Energy's Hanford Reservation, is a liquid metal-cooled test reactor. The FFTF was constructed to support the U.S. Liquid Metal Fast Breeder Reactor Program. The bulk of the alkali metal (sodium and NaK) has been drained and will be stored onsite prior to final disposition. Residual NaK needed to be removed from the pipes, pumps, heat exchangers, tanks, and vessels in the Fuel Storage Facility (FSF) cooling system. The cooling system was drained in 2004 leaving residual NaK in the pipes and equipment. The estimated residual NaK volume wasmore » 76 liters in the storage tank, 1.9 liters in the expansion tank, and 19-39 liters in the heat transfer loop. The residual NaK volume in the remainder of the system was expected to be very small, consisting of films, droplets, and very small pools. The NaK in the FSF Cooling System was not radiologically contaminated. The portions of the cooling system to be cleaned were divided into four groups: 1. The storage tank, filter, pump, and associated piping; 2. The heat exchanger, expansion tank, and associated piping; 3. Argon supply piping; 4. In-vessel heat transfer loop. The cleaning was contracted to Creative Engineers, Inc. (CEI) and they used their superheated steam process to clean the cooling system. It has been concluded that during the modification activities (prior to CEI coming onsite) to prepare the NaK Cooling System for cleaning, tank T-914 was pressurized relative to the In-Vessel NaK Cooler and NaK was pushed from the tank back into the Cooler and that on November 6, 2005, when the gas purge through the In-Vessel NaK Cooler was increased from 141.6 slm to 283.2 slm, NaK was forced from the In-Vessel NaK Cooler and it contacted water in the vent line and/or scrubber. The gases from the reaction then traveled back through the vent line coating the internal surface of the vent line with NaK and NaK reaction products. The hot gases also exited the

First evidence of diffuse ultra-steep-spectrum radio emission surrounding the cool core of a cluster

NASA Astrophysics Data System (ADS)

Savini, F.; Bonafede, A.; Brüggen, M.; van Weeren, R.; Brunetti, G.; Intema, H.; Botteon, A.; Shimwell, T.; Wilber, A.; Rafferty, D.; Giacintucci, S.; Cassano, R.; Cuciti, V.; de Gasperin, F.; Röttgering, H.; Hoeft, M.; White, G.

2018-05-01

Diffuse synchrotron radio emission from cosmic-ray electrons is observed at the center of a number of galaxy clusters. These sources can be classified either as giant radio halos, which occur in merging clusters, or as mini halos, which are found only in cool-core clusters. In this paper, we present the first discovery of a cool-core cluster with an associated mini halo that also shows ultra-steep-spectrum emission extending well beyond the core that resembles radio halo emission. The large-scale component is discovered thanks to LOFAR observations at 144 MHz. We also analyse GMRT observations at 610 MHz to characterise the spectrum of the radio emission. An X-ray analysis reveals that the cluster is slightly disturbed, and we suggest that the steep-spectrum radio emission outside the core could be produced by a minor merger that powers electron re-acceleration without disrupting the cool core. This discovery suggests that, under particular circumstances, both a mini and giant halo could co-exist in a single cluster, opening new perspectives for particle acceleration mechanisms in galaxy clusters.

Rhapsody-G simulations I: the cool cores, hot gas and stellar content of massive galaxy clusters

DOE PAGES

Hahn, Oliver; Martizzi, Davide; Wu, Hao -Yi; ...

2017-01-25

We present the rhapsody-g suite of cosmological hydrodynamic zoom simulations of 10 massive galaxy clusters at the M vir ~10 15 M ⊙ scale. These simulations include cooling and subresolution models for star formation and stellar and supermassive black hole feedback. The sample is selected to capture the whole gamut of assembly histories that produce clusters of similar final mass. We present an overview of the successes and shortcomings of such simulations in reproducing both the stellar properties of galaxies as well as properties of the hot plasma in clusters. In our simulations, a long-lived cool-core/non-cool-core dichotomy arises naturally, andmore » the emergence of non-cool cores is related to low angular momentum major mergers. Nevertheless, the cool-core clusters exhibit a low central entropy compared to observations, which cannot be alleviated by thermal active galactic nuclei feedback. For cluster scaling relations, we find that the simulations match well the M 500–Y 500 scaling of Planck Sunyaev–Zeldovich clusters but deviate somewhat from the observed X-ray luminosity and temperature scaling relations in the sense of being slightly too bright and too cool at fixed mass, respectively. Stars are produced at an efficiency consistent with abundance-matching constraints and central galaxies have star formation rates consistent with recent observations. In conclusion, while our simulations thus match various key properties remarkably well, we conclude that the shortcomings strongly suggest an important role for non-thermal processes (through feedback or otherwise) or thermal conduction in shaping the intracluster medium.« less

rhapsody-g simulations - I. The cool cores, hot gas and stellar content of massive galaxy clusters

NASA Astrophysics Data System (ADS)

Hahn, Oliver; Martizzi, Davide; Wu, Hao-Yi; Evrard, August E.; Teyssier, Romain; Wechsler, Risa H.

2017-09-01

We present the rhapsody-g suite of cosmological hydrodynamic zoom simulations of 10 massive galaxy clusters at the Mvir ˜ 1015 M⊙ scale. These simulations include cooling and subresolution models for star formation and stellar and supermassive black hole feedback. The sample is selected to capture the whole gamut of assembly histories that produce clusters of similar final mass. We present an overview of the successes and shortcomings of such simulations in reproducing both the stellar properties of galaxies as well as properties of the hot plasma in clusters. In our simulations, a long-lived cool-core/non-cool-core dichotomy arises naturally, and the emergence of non-cool cores is related to low angular momentum major mergers. Nevertheless, the cool-core clusters exhibit a low central entropy compared to observations, which cannot be alleviated by thermal active galactic nuclei feedback. For cluster scaling relations, we find that the simulations match well the M500-Y500 scaling of Planck Sunyaev-Zeldovich clusters but deviate somewhat from the observed X-ray luminosity and temperature scaling relations in the sense of being slightly too bright and too cool at fixed mass, respectively. Stars are produced at an efficiency consistent with abundance-matching constraints and central galaxies have star formation rates consistent with recent observations. While our simulations thus match various key properties remarkably well, we conclude that the shortcomings strongly suggest an important role for non-thermal processes (through feedback or otherwise) or thermal conduction in shaping the intracluster medium.

Enhanced upconversion emission in colloidal (NaYF4:Er(3+))/NaYF4 core/shell nanoparticles excited at 1523 nm.

PubMed

Shao, Wei; Chen, Guanying; Damasco, Jossana; Wang, Xianliang; Kachynski, Aliaksandr; Ohulchanskyy, Tymish Y; Yang, Chunhui; Ågren, Hans; Prasad, Paras N

2014-03-15

In this work, we report on efficient visible and near-IR upconversion emissions in colloidal hexagonal-phase core/shell NaYF4:Er(3+)/NaYF4 nanoparticles (∼38  nm) under IR laser excitation at 1523 nm. Varying amounts of Er(3+) dopants were introduced into the core NaYF4:Er(3+) nanoparticles, revealing an optimized Er(3+) concentration of 10% for the highest luminescent efficiency. An inert epitaxial shell layer of NaYF4 grown onto the core of the NaYF4:Er(3+) 10% nanoparticle increased its upconversion emission intensity fivefold due to suppression of surface-related quenching mechanisms, yielding the absolute upconversion efficiency to be as high as ∼3.9±0.3% under an excitation density of 18  W/cm(2). The dependence of the intensity of upconversion emission peaks on laser excitation density in the core/shell nanoparticle displayed "saturation effects" at low excitation density in the range of 1.5-18  W/cm(2), which again demonstrates high upconversion efficiency.

System Study: Reactor Core Isolation Cooling 1998-2014

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroeder, John Alton

2015-12-01

This report presents an unreliability evaluation of the reactor core isolation cooling (RCIC) system at 31 U.S. commercial boiling water reactors. Demand, run hours, and failure data from fiscal year 1998 through 2014 for selected components were obtained from the Institute of Nuclear Power Operations (INPO) Consolidated Events Database (ICES). The unreliability results are trended for the most recent 10 year period, while yearly estimates for system unreliability are provided for the entire active period. No statistically significant trends were identified in the RCIC results.

Shivering heat production and core cooling during head-in and head-out immersion in 17 degrees C water.

PubMed

Pretorius, Thea; Cahill, Farrell; Kocay, Sheila; Giesbrecht, Gordon G

2008-05-01

Many cold-water scenarios cause the head to be partially or fully immersed (e.g., ship wreck survival, scuba diving, cold-water adventure swim racing, cold-water drowning, etc.). However, the specific effects of head cold exposure are minimally understood. This study isolated the effect of whole-head submersion in cold water on surface heat loss and body core cooling when the protective shivering mechanism was intact. Eight healthy men were studied in 17 degrees C water under four conditions: the body was either insulated or exposed, with the head either out of the water or completely submersed under the water within each insulated/exposed subcondition. Submersion of the head (7% of the body surface area) in the body-exposed condition increased total heat loss by 11% (P < 0.05). After 45 min, head-submersion increased core cooling by 343% in the body-insulated subcondition (head-out: 0.13 +/- 0.2 degree C, head-in: 0.47 +/- 0.3 degree C; P < 0.05) and by 56% in the body-exposed subcondition (head-out: 0.40 +/- 0.3 degree C and head-in: 0.73 +/- 0.6 degree C; P < 0.05). In both body-exposed and body-insulated subconditions, head submersion increased the rate of core cooling disproportionally more than the relative increase in total heat loss. This exaggerated core-cooling effect is consistent with a head cooling induced reduction of the thermal core, which could be stimulated by cooling of thermosensitive and/or trigeminal receptors in the scalp, neck, and face. These cooling effects of head submersion are not prevented by shivering heat production.

Core cooling under accident conditions at the high-flux beam reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tichler, P.; Cheng, L.; Fauske, H.

The High-Flux Beam Reactor (HFBR) at Brookhaven National Laboratory (BNL) is cooled and moderated by heavy water and contains {sup 235}U in the form of narrow-channel, parallel-plate-type fuel elements. During normal operation, the flow direction is downward through the core. This flow direction is maintained at a reduced flow rate during routine shutdown and on loss of commercial power by means of redundant pumps and power supplies. However, in certain accident scenarios, e.g. loss-of-coolant accidents (LOCAs), all forced-flow cooling is lost. Although there was experimental evidence during the reactor design period (1958-1963) that the heat removal capacity in the fullymore » developed natural circulation cooling mode was relatively high, it was not possible to make a confident prediction of the heat removal capacity during the transition from downflow to natural circulation. Accordingly, a test program was initiated using an electrically heated section to simulate the fuel channel and a cooling loop to simulate the balance of the primary cooling system.« less

Study on core radius minimization for long life Pb-Bi cooled CANDLE burnup scheme based fast reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afifah, Maryam, E-mail: maryam.afifah210692@gmail.com; Su’ud, Zaki; Miura, Ryosuke

2015-09-30

Fast Breeder Reactor had been interested to be developed over the world because it inexhaustible source energy, one of those is CANDLE reactor which is have strategy in burn-up scheme, need not control roads for control burn-up, have a constant core characteristics during energy production and don’t need fuel shuffling. The calculation was made by basic reactor analysis which use Sodium coolant geometry core parameter as a reference core to study on minimum core reactor radius of CANDLE for long life Pb-Bi cooled, also want to perform pure coolant effect comparison between LBE and sodium in a same geometry design.more » The result show that the minimum core radius of Lead Bismuth cooled CANDLE is 100 cm and 500 MWth thermal output. Lead-Bismuth coolant for CANDLE reactor enable to reduce much reactor size and have a better void coefficient than Sodium cooled as the most coolant for FBR, then we will have a good point in safety analysis.« less

Abell 1763: A Giant Gas Sloshing Spiral But No Cool Core

NASA Astrophysics Data System (ADS)

Douglass, Edmund

2017-09-01

We propose a 76 ksec observation of the z=0.23 galaxy cluster Abell 1763. Previous Chandra data reveals the system as host to a large 950 kpc gas sloshing spiral. Atypical of spiral-hosting clusters, an intact cool core is not detected. Its absence suggests the interaction has led to significant disruption since the onset of core sloshing. The primary cluster is accompanied by two X-ray emitting subsystems. Given the orientation of the spiral, both systems are strong candidates for being the perturber responsible for its formation. Abell 1763 provides us with the rare opportunity to examine an infall event (primary + perturber) resulting in sloshing to the point of core disintegration. Detailed analysis will be performed on the disrupted core, the spiral, and the perturber candidates.

Pd-Ag chronometry of IVA iron meteorites and the crystallization and cooling of a protoplanetary core

DOE PAGES

Matthes, M.; Fischer-Godde, M.; Kruijer, T. S.; ...

2017-09-07

To constrain the timescales and processes involved in the crystallization and cooling of protoplanetary cores, we examined the Pd-Ag isotope systematics of the IVA iron meteorites Muonionalusta and Gibeon. A Pd-Ag isochron for Muonionalusta provides an initial 107Pd/ 108Pd = (2.57 ± 0.07) × 10 -5. The three metal samples analyzed from Gibeon plot below the Muonionalusta isochron, but these samples also show significant effects of cosmic ray-induced neutron capture reactions, as is evident from 196Pt excesses in the Gibeon samples. After correction for neutron capture effects on Ag isotopes, the Gibeon samples plot on the Muonionalusta isochron, indicating thatmore » these two IVA irons have indistinguishable initial 107Pd/ 108Pd. Collectively, the Pd-Ag data indicate cooling of the IVA core below Pd-Ag closure between 2.9 ± 0.4 Ma and 8.9 ± 0.6 Ma after CAI formation, where this age range reflects uncertainties in the initial 107Pd/ 108Pd ratios of the solar system, which in turn result from uncertainties in the Pb-Pb age of Muonionalusta. The Ag isotopic data indicate that the IVA core initially evolved with a modestly elevated Pd/Ag, but the low Ag concentrations measured for some metal samples indicate derivation from a source with much lower Ag contents and, hence, higher Pd/Ag. These contrasting observations can be reconciled if the IVA irons crystallized from an initially more Ag-rich core, followed by extraction of Fe-S melts during compaction of the nearly solidified core. Owing to its strong tendency to partition into Fe-S melts, Ag was removed from the IVA core during compaction, leading to the very low Ag concentration observed in metal samples of IVA irons. Alternatively, Ag was lost by evaporation from a still molten metallic body just prior to the onset of crystallization. The Pd-Ag isotopic data indicate that Muonionalusta cooled at >500 K/Ma through the Pd-Ag closure temperature of ~900 K, consistent with the rapid cooling inferred from

Pd-Ag chronometry of IVA iron meteorites and the crystallization and cooling of a protoplanetary core

NASA Astrophysics Data System (ADS)

Matthes, M.; Fischer-Gödde, M.; Kruijer, T. S.; Kleine, T.

2018-01-01

To constrain the timescales and processes involved in the crystallization and cooling of protoplanetary cores, we examined the Pd-Ag isotope systematics of the IVA iron meteorites Muonionalusta and Gibeon. A Pd-Ag isochron for Muonionalusta provides an initial 107Pd/108Pd = (2.57 ± 0.07) × 10-5. The three metal samples analyzed from Gibeon plot below the Muonionalusta isochron, but these samples also show significant effects of cosmic ray-induced neutron capture reactions, as is evident from 196Pt excesses in the Gibeon samples. After correction for neutron capture effects on Ag isotopes, the Gibeon samples plot on the Muonionalusta isochron, indicating that these two IVA irons have indistinguishable initial 107Pd/108Pd. Collectively, the Pd-Ag data indicate cooling of the IVA core below Pd-Ag closure between 2.9 ± 0.4 Ma and 8.9 ± 0.6 Ma after CAI formation, where this age range reflects uncertainties in the initial 107Pd/108Pd ratios of the solar system, which in turn result from uncertainties in the Pb-Pb age of Muonionalusta. The Ag isotopic data indicate that the IVA core initially evolved with a modestly elevated Pd/Ag, but the low Ag concentrations measured for some metal samples indicate derivation from a source with much lower Ag contents and, hence, higher Pd/Ag. These contrasting observations can be reconciled if the IVA irons crystallized from an initially more Ag-rich core, followed by extraction of Fe-S melts during compaction of the nearly solidified core. Owing to its strong tendency to partition into Fe-S melts, Ag was removed from the IVA core during compaction, leading to the very low Ag concentration observed in metal samples of IVA irons. Alternatively, Ag was lost by evaporation from a still molten metallic body just prior to the onset of crystallization. The Pd-Ag isotopic data indicate that Muonionalusta cooled at >500 K/Ma through the Pd-Ag closure temperature of ∼900 K, consistent with the rapid cooling inferred from metallographic

Pd-Ag chronometry of IVA iron meteorites and the crystallization and cooling of a protoplanetary core

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthes, M.; Fischer-Godde, M.; Kruijer, T. S.

To constrain the timescales and processes involved in the crystallization and cooling of protoplanetary cores, we examined the Pd-Ag isotope systematics of the IVA iron meteorites Muonionalusta and Gibeon. A Pd-Ag isochron for Muonionalusta provides an initial 107Pd/ 108Pd = (2.57 ± 0.07) × 10 -5. The three metal samples analyzed from Gibeon plot below the Muonionalusta isochron, but these samples also show significant effects of cosmic ray-induced neutron capture reactions, as is evident from 196Pt excesses in the Gibeon samples. After correction for neutron capture effects on Ag isotopes, the Gibeon samples plot on the Muonionalusta isochron, indicating thatmore » these two IVA irons have indistinguishable initial 107Pd/ 108Pd. Collectively, the Pd-Ag data indicate cooling of the IVA core below Pd-Ag closure between 2.9 ± 0.4 Ma and 8.9 ± 0.6 Ma after CAI formation, where this age range reflects uncertainties in the initial 107Pd/ 108Pd ratios of the solar system, which in turn result from uncertainties in the Pb-Pb age of Muonionalusta. The Ag isotopic data indicate that the IVA core initially evolved with a modestly elevated Pd/Ag, but the low Ag concentrations measured for some metal samples indicate derivation from a source with much lower Ag contents and, hence, higher Pd/Ag. These contrasting observations can be reconciled if the IVA irons crystallized from an initially more Ag-rich core, followed by extraction of Fe-S melts during compaction of the nearly solidified core. Owing to its strong tendency to partition into Fe-S melts, Ag was removed from the IVA core during compaction, leading to the very low Ag concentration observed in metal samples of IVA irons. Alternatively, Ag was lost by evaporation from a still molten metallic body just prior to the onset of crystallization. The Pd-Ag isotopic data indicate that Muonionalusta cooled at >500 K/Ma through the Pd-Ag closure temperature of ~900 K, consistent with the rapid cooling inferred from

Gamma ray heating and neutrino cooling rates due to weak interaction processes on sd-shell nuclei in stellar cores

NASA Astrophysics Data System (ADS)

Fayaz, Muhammad; Nabi, Jameel-Un; Majid, Muhammad

2017-07-01

Gamma ray heating and neutrino cooling rates, due to weak interaction processes, on sd-shell nuclei in stellar core are calculated using the proton neutron quasiparticle random phase approximation theory. The recent extensive experimental mass compilation of Wang et al. (Chin. Phys. C 36:1603, 2012), other improved model input parameters including nuclear quadrupole deformation (Raman et al. in At. Data Nucl. Data Tables 78(1):1-128, 2001; Möller et al. in At. Data Nucl. Data Tables 109:1-204, 2016) and physical constants are taken into account in the current calculation. The purpose of this work is two fold, one is to improve the earlier calculation of weak rates performed by Nabi and Klapdor-Kleingrothaus (At. Data Nucl. Data Tables 71:149, 1999a) using the same theory. We further compare our results with previous calculations. The selected sd-shell nuclei, considered in this work, are of special interest for the evolution of O-Ne-Mg core in 8-10 M_{⊙} stars due to competitive gamma ray heating rates and cooling by URCA processes. The outcome of these competitions is to determine, whether the stars end up as a white dwarf (Nabi in Phys. Rev. C 78(4):045801, 2008b), an electron-capture supernova (Jones et al. in Astrophys. J. 772(2):150, 2013) or Fe core-collapse supernova (Suzuki et al. in Astrophys. J. 817(2):163, 2016). The selected sd-shell nuclei for calculation of associated weak-interaction rates include ^{20,23}O, ^{20,23}F, ^{20,23,24}Ne, {}^{20,23-25}Na, and {}^{23-25}Mg. The cooling and heating rates are calculated for density range (10 ≤ ρ (g cm^{-3}) ≤ 10^{11}) and temperature range (0.01× 109≤ T(K)≤ 30× 109). The calculated gamma heating rates are orders of magnitude bigger than the shell model rates (except for ^{25}Mg at low densities). At high temperatures the gamma heating rates are in reasonable agreement. The calculated cooling rates are up to an order of magnitude bigger for odd-A nuclei.

NaF-loaded core-shell PAN-PMMA nanofibers as reinforcements for Bis-GMA/TEGDMA restorative resins.

PubMed

Cheng, Liyuan; Zhou, Xuegang; Zhong, Hong; Deng, Xuliang; Cai, Qing; Yang, Xiaoping

2014-01-01

A kind of core-shell nanofibers containing sodium fluoride (NaF) was produced and used as reinforcing materials for dimethacrylate-based dental restorative resins in this study. The core-shell nanofibers were prepared by coaxial-electrospinning with polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) solutions as core and shell fluids, respectively. The produced PAN-PMMA nanofibers varied in fiber diameter and the thickness of PMMA shell depending on electrospinning parameters. NaF-loaded nanofibers were obtained by incorporating NaF nanocrystals into the core fluid at two loadings (0.8 or 1.0wt.%). Embedment of NaF nanocrystals into the PAN core did not damage the core-shell structure. The addition of PAN-PMMA nanofibers into Bis-GMA/TEGDMA clearly showed the reinforcement due to the good interfacial adhesion between fibers and resin. The flexural strength (Fs) and flexural modulus (Ey) of the composites decreased slightly as the thickness of PMMA shell increasing. Sustained fluoride releases with minor initial burst release were achieved from NaF-loaded core-shell nanofibers and the corresponding composites, which was quite different from the case of embedding NaF nanocrystals into the dental resin directly. The study demonstrated that NaF-loaded PAN-PMMA core-shell nanofibers were not only able to improve the mechanical properties of restorative resin, but also able to provide sustained fluoride release to help in preventing secondary caries. © 2013.

Core design of a direct-cycle, supercritical-water-cooled fast breeder reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jevremovic, T.; Oka, Yoshiaki; Koshizuka, Seiichi

1994-10-01

The conceptual design of a direct-cycle fast breeder reactor (FBR) core cooled by supercritical water is carried out as a step toward a low-cost FBR plant. The supercritical water does not exhibit change of phase. The turbines are directly driven by the core outlet coolant. In comparison with a boiling water reactor (BWR), the recirculation systems, steam separators, and dryers are eliminated. The reactor system is much simpler than the conventional steam-cooled FBRs, which adopted Loeffler boilers and complicated coolant loops for generating steam and separating it from water. Negative complete and partial coolant void reactivity are provided without muchmore » deterioration in the breeding performances by inserting thin zirconium-hydride layers between the seeds and blankets in a radially heterogeneous core. The net electric power is 1245 MW (electric). The estimated compound system doubling time is 25 yr. The discharge burnup is 77.7 GWd/t, and the refueling period is 15 months with a 73% load factor. The thermal efficiency is high (41.5%), an improvement of 24% relative to a BWR's. The pressure vessel is not thick at 30.3 cm.« less

Application of reliability-centered maintenance to boiling water reactor emergency core cooling systems fault-tree analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Y.A.; Feltus, M.A.

1995-07-01

Reliability-centered maintenance (RCM) methods are applied to boiling water reactor plant-specific emergency core cooling system probabilistic risk assessment (PRA) fault trees. The RCM is a technique that is system function-based, for improving a preventive maintenance (PM) program, which is applied on a component basis. Many PM programs are based on time-directed maintenance tasks, while RCM methods focus on component condition-directed maintenance tasks. Stroke time test data for motor-operated valves (MOVs) are used to address three aspects concerning RCM: (a) to determine if MOV stroke time testing was useful as a condition-directed PM task; (b) to determine and compare the plant-specificmore » MOV failure data from a broad RCM philosophy time period compared with a PM period and, also, compared with generic industry MOV failure data; and (c) to determine the effects and impact of the plant-specific MOV failure data on core damage frequency (CDF) and system unavailabilities for these emergency systems. The MOV stroke time test data from four emergency core cooling systems [i.e., high-pressure coolant injection (HPCI), reactor core isolation cooling (RCIC), low-pressure core spray (LPCS), and residual heat removal/low-pressure coolant injection (RHR/LPCI)] were gathered from Philadelphia Electric Company`s Peach Bottom Atomic Power Station Units 2 and 3 between 1980 and 1992. The analyses showed that MOV stroke time testing was not a predictor for eminent failure and should be considered as a go/no-go test. The failure data from the broad RCM philosophy showed an improvement compared with the PM-period failure rates in the emergency core cooling system MOVs. Also, the plant-specific MOV failure rates for both maintenance philosophies were shown to be lower than the generic industry estimates.« less

Stainless Steel NaK-Cooled Circuit (SNaKC) Fabrication and Assembly

NASA Technical Reports Server (NTRS)

Godfroy, Thomas J.

2007-01-01

An actively pumped Stainless Steel NaK Circuit (SNaKC) has been designed and fabricated by the Early Flight Fission Test Facility (EFF-TF) team at NASA's Marshall Space Flight Center. This circuit uses the eutectic mixture of sodium and potassium (NaK) as the working fluid building upon the experience and accomplishments of the SNAP reactor program from the late 1960's The SNaKC enables valuable experience and liquid metal test capability to be gained toward the goal of designing and building an affordable surface power reactor. The basic circuit components include a simulated reactor core a NaK to gas heat exchanger, an electromagnetic (EM) liquid metal pump, a liquid metal flow meter, an expansion reservoir and a drain/fill reservoir To maintain an oxygen free environment in the presence of NaK, an argon system is utilized. A helium and nitrogen system are utilized for core, pump, and heat exchanger operation. An additional rest section is available to enable special component testing m an elevated temperature actively pumped liquid metal environment. This paper summarizes the physical build of the SNaKC the gas and pressurization systems, vacuum systems, as well as instrumentation and control methods.

FFTF Passive Safety Test Data for Benchmarks for New LMR Designs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wootan, David W.; Casella, Andrew M.

Liquid Metal Reactors (LMRs) continue to be considered as an attractive concept for advanced reactor design. Software packages such as SASSYS are being used to im-prove new LMR designs and operating characteristics. Significant cost and safety im-provements can be realized in advanced liquid metal reactor designs by emphasizing inherent or passive safety through crediting the beneficial reactivity feedbacks associ-ated with core and structural movement. This passive safety approach was adopted for the Fast Flux Test Facility (FFTF), and an experimental program was conducted to characterize the structural reactivity feedback. The FFTF passive safety testing pro-gram was developed to examine howmore » specific design elements influenced dynamic re-activity feedback in response to a reactivity input and to demonstrate the scalability of reactivity feedback results to reactors of current interest. The U.S. Department of En-ergy, Office of Nuclear Energy Advanced Reactor Technology program is in the pro-cess of preserving, protecting, securing, and placing in electronic format information and data from the FFTF, including the core configurations and data collected during the passive safety tests. Benchmarks based on empirical data gathered during operation of the Fast Flux Test Facility (FFTF) as well as design documents and post-irradiation examination will aid in the validation of these software packages and the models and calculations they produce. Evaluation of these actual test data could provide insight to improve analytical methods which may be used to support future licensing applications for LMRs« less

Annular core liquid-salt cooled reactor with multiple fuel and blanket zones

DOEpatents

Peterson, Per F.

2013-05-14

A liquid fluoride salt cooled, high temperature reactor having a reactor vessel with a pebble-bed reactor core. The reactor core comprises a pebble injection inlet located at a bottom end of the reactor core and a pebble defueling outlet located at a top end of the reactor core, an inner reflector, outer reflector, and an annular pebble-bed region disposed in between the inner reflector and outer reflector. The annular pebble-bed region comprises an annular channel configured for receiving pebble fuel at the pebble injection inlet, the pebble fuel comprising a combination of seed and blanket pebbles having a density lower than the coolant such that the pebbles have positive buoyancy and migrate upward in said annular pebble-bed region toward the defueling outlet. The annular pebble-bed region comprises alternating radial layers of seed pebbles and blanket pebbles.

Coupled CaAl-NaSi diffusion in plagioclase feldspar: Experiments and applications to cooling rate speedometry

NASA Astrophysics Data System (ADS)

Grove, Timothy L.; Baker, Michael B.; Kinzler, Rosamond J.

1984-10-01

The rate of CaAl-NaSi interdiffusion in plagioclase feldspar was determined under 1 atm anhydrous conditions over the temperature range 1400° to 1000°C in calcic plagioclase (An 80-81) by homogenizing coherent exsolution lamellae. The dependence of the average interdiffusion coefficient on temperature is given by the expression: D˜ = 10.99 ( cm 2/sec) exp (-123.4( kcal/mol)/RT), (T in °K). This value is for diffusion perpendicular to the (03 1¯) interface of the lamellae. CaAl-NaSi interdiffusion is 4 to 5 orders of magnitude slower than oxygen diffusion in the temperature range 1400° to 1200°C and possibly 10 orders of magnitude slower at subsolidus temperatures. The large differences in diffusion rates explain the apparent contradiction posed by the plagioclases of large layered intrusions ( e.g., the Skaergaard), which retain delicate Ca, Na compositional zoning profiles on the micron scale, but have undergone complete oxygen isotopic exchange with heated meteoric groundwater from the surrounding wall rocks. CaAl-NaSi diffusion is slow, the closure temperature is high (within the solidus-liquidus interval), and Ca-Na zoning is preserved. Oxygen diffusion is faster, the closure temperature is lower (350°-400°C) and the feldspars exchange oxygen with the low-temperature hydrothermal fluids. The complex micron-scale oscillatory zones in plagioclase can also be used as cooling rate speedometers for volcanic and plutonic plagioclase. Cooling histories typical of large mafic intrusions ( e.g. the Stillwater) are slow, begin at high initial temperatures (1200°C) and result in homogenization of oscillatory zones on the scale of 10 microns. The oscillatory zones found in the plagioclase of granodioritic plutons are preserved because cooling is initiated at a lower temperature (1000°C) limiting diffusion to submicron length scales despite the slow cooling rate of the intrusion.

Study of NaI(Tl) scintillator cooled down to liquid nitrogen temperature

NASA Astrophysics Data System (ADS)

Sibczyński, P.; Moszyński, M.; Szczęśniak, T.; Czarnacki, W.

2012-11-01

Since early 50's NaI(Tl) scintillators have been commonly used in many branches of physics and industry due to their relatively low price, high light output and fair energy resolution. Through this period of time, both spectroscopic and luminescence properties of NaI(Tl) were measured at room temperature. In this work, the gamma spectrometry and the luminescence properties of the NaI(Tl) at LN2 temperature were studied. The gamma spectrometry was carried out with the light readout by avalanche photodiodes cooled down together with the crystal in the cryostat. It was observed that non-proportionality measured at LN2 temperature is significantly better than that at room temperature. The energy resolution of the NaI(Tl) at 662 keV measured at LN2 temperature was estimated to be 6.57%, comparable to that measured commonly at RT with photomultipliers. A decay time measurement of the NaI(Tl) at LN2 showed a slower decay of 736±10 ns.

Development concept for a small, split-core, heat-pipe-cooled nuclear reactor

NASA Technical Reports Server (NTRS)

Lantz, E.; Breitwieser, R.; Niederauer, G. F.

1974-01-01

There have been two main deterrents to the development of semiportable nuclear reactors. One is the high development costs; the other is the inability to satisfy with assurance the questions of operational safety. This report shows how a split-core, heat-pipe cooled reactor could conceptually eliminate these deterrents, and examines and summarizes recent work on split-core, heat-pipe reactors. A concept for a small reactor that could be developed at a comparatively low cost is presented. The concept would extend the technology of subcritical radioisotope thermoelectric generators using 238 PuO2 to the evolution of critical space power reactors using 239 PuO2.

Effects of pre-cooling procedures on intermittent-sprint exercise performance in warm conditions.

PubMed

Duffield, Rob; Marino, Frank E

2007-08-01

The aim of this study was to determine whether pre-cooling procedures improve both maximal sprint and sub-maximal work during intermittent-sprint exercise. Nine male rugby players performed a familiarisation session and three testing sessions of a 2 x 30-min intermittent sprint protocol, which consisted of a 15-m sprint every min separated by free-paced hard-running, jogging and walking in 32 degrees C and 30% humidity. The three sessions included a control condition, Ice-vest condition and Ice-bath/Ice-vest condition, with respective cooling interventions imposed for 15-min pre-exercise and 10-min at half-time. Performance measures of sprint time and % decline and distance covered during sub-maximal exercise were recorded, while physiological measures of core temperature (T (core)), mean skin temperature (T (skin)), heart rate, heat storage, nude mass, rate of perceived exertion, rate of thermal comfort and capillary blood measures of lactate [La(-)], pH, Sodium (Na(+)) and Potassium (K(+)) were recorded. Results for exercise performance indicated no significant differences between conditions for the time or % decline in 15-m sprint efforts or the distance covered during sub-maximal work bouts; however, large effect size data indicated a greater distance covered during hard running following Ice-bath cooling. Further, lowered T (core), T (skin), heart rate, sweat loss and thermal comfort following Ice-bath cooling than Ice-vest or Control conditions were present, with no differences present in capillary blood measures of [La(-)], pH, K(+) or Na(+). As such, the ergogenic benefits of effective pre-cooling procedures in warm conditions for team-sports may be predominantly evident during sub-maximal bouts of exercise.

Core cooling under accident conditions at the high flux beam reactor (HFBR)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tichler, P.; Cheng, L.; Fauske, H.

In certain accident scenarios, e.g. loss of coolant accidents (LOCA) all forced flow cooling is lost. Decay heating causes a temperature increase in the core coolant and the resulting thermal buoyancy causes a reversal of the flow direction to a natural circulation mode. Although there was experimental evidence during the reactor design period (1958--1963) that the heat removal capacity in the fully developed natural circulation cooling mode was relatively high, it was not possible to make a confident prediction of the heat removal capacity during the transition from downflow to natural circulation. In a LOCA scenario where even limited fuelmore » damage occurs and natural circulation is established, fission product gases could be carried from the damaged fuel by steam into areas where operator access is required to maintain the core in a coolable configuration. This would force evacuation of the building and lead to extensive core damage. As a result the HFBR was shut down by the Department of Energy (DOE) and an extensive review of the HFBR was initiated. In an effort to address this issue BNL developed a model designed to predict the heat removal limit during flow reversal that was found to be in good agreement with the test results. Currently a thermal-hydraulic test program is being developed to provide a more realistic and defensible estimate of the flow reversal heat removal limit so that the reactor power level can be increased.« less

Effect of Cooling Rate on SCC Susceptibility of β-Processed Ti-6Al-4V Alloy in 0.6M NaCl Solution

NASA Astrophysics Data System (ADS)

Ahn, Soojin; Park, Jiho; Jeong, Daeho; Sung, Hyokyung; Kwon, Yongnam; Kim, Sangshik

2018-03-01

The effects of cooling rate on the stress corrosion cracking (SCC) susceptibility of β-processed Ti-6Al-4V (Ti64) alloy, including BA/S specimen with furnace cooling and BQ/S specimen with water quenching, were investigated in 0.6M NaCl solution under various applied potentials using a slow strain rate test technique. It was found that the SCC susceptibility of β-processed Ti64 alloy in aqueous NaCl solution decreased with fast cooling rate, which was particularly substantial under an anodic applied potential. The micrographic and fractographic analyses suggested that the enhancement with fast cooling rate was related to the random orientation of acicular α platelets in BQ/S specimen. Based on the experimental results, the effect of cooling rate on the SCC behavior of β-processed Ti64 alloy in aqueous NaCl solution was discussed.

Passive containment cooling system

DOEpatents

Conway, Lawrence E.; Stewart, William A.

1991-01-01

A containment cooling system utilizes a naturally induced air flow and a gravity flow of water over the containment shell which encloses a reactor core to cool reactor core decay heat in two stages. When core decay heat is greatest, the water and air flow combine to provide adequate evaporative cooling as heat from within the containment is transferred to the water flowing over the same. The water is heated by heat transfer and then evaporated and removed by the air flow. After an initial period of about three to four days when core decay heat is greatest, air flow alone is sufficient to cool the containment.

78 FR 64027 - Preoperational Testing of Emergency Core Cooling Systems for Pressurized-Water Reactors

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-25

...The U.S. Nuclear Regulatory Commission (NRC) is issuing a revision to regulatory guide (RG), 1.79, ``Preoperational Testing of Emergency Core Cooling Systems for Pressurized-Water Reactors.'' This RG is being revised to incorporate guidance for preoperational testing of new pressurized water reactor (PWR) designs.

Design, Fabrication and Integration of a NaK-Cooled Circuit

NASA Technical Reports Server (NTRS)

Garber, Anne; Godfroy, Thomas

2006-01-01

The Early Flight Fission Test Facilities (EFF-TF) team has been tasked by the NASA Marshall Space Flight Center Nuclear Systems Office to design, fabricate, and test an actively pumped alkali metal flow circuit. The system, which was originally designed for use with a eutectic mixture of sodium potassium (NaK), was redesigned to for use with lithium. Due to a shi$ in focus, it is once again being prepared for use with NaK. Changes made to the actively pumped, high temperature circuit include the replacement of the expansion reservoir, addition of remotely operated valves, and modification of the support table. Basic circuit components include: reactor segment, NaK to gas heat exchanger, electromagnetic (EM) liquid metal pump, load/drain reservoir, expansion reservoir, instrumentation, and a spill reservoir. A 37-pin partial-array core (pin and flow path dimensions are the same as those in a fill design) was selected for fabrication and test. This paper summarizes the integration and preparations for the fill of the pumped liquid metal NaK flow circuit.

a Dosimetry Assessment for the Core Restraint of AN Advanced Gas Cooled Reactor

NASA Astrophysics Data System (ADS)

Thornton, D. A.; Allen, D. A.; Tyrrell, R. J.; Meese, T. C.; Huggon, A. P.; Whiley, G. S.; Mossop, J. R.

2009-08-01

This paper describes calculations of neutron damage rates within the core restraint structures of Advanced Gas Cooled Reactors (AGRs). Using advanced features of the Monte Carlo radiation transport code MCBEND, and neutron source data from core follow calculations performed with the reactor physics code PANTHER, a detailed model of the reactor cores of two of British Energy's AGR power plants has been developed for this purpose. Because there are no relevant neutron fluence measurements directly supporting this assessment, results of benchmark comparisons and successful validation of MCBEND for Magnox reactors have been used to estimate systematic and random uncertainties on the predictions. In particular, it has been necessary to address the known under-prediction of lower energy fast neutron responses associated with the penetration of large thicknesses of graphite.

The Role of Cerenkov Radiation in the Pressure Balance of Cool Core Clusters of Galaxies

NASA Astrophysics Data System (ADS)

Lieu, Richard

2017-03-01

Despite the substantial progress made recently in understanding the role of AGN feedback and associated non-thermal effects, the precise mechanism that prevents the core of some clusters of galaxies from collapsing catastrophically by radiative cooling remains unidentified. In this Letter, we demonstrate that the evolution of a cluster's cooling core, in terms of its density, temperature, and magnetic field strength, inevitably enables the plasma electrons there to quickly become Cerenkov loss dominated, with emission at the radio frequency of ≲350 Hz, and with a rate considerably exceeding free-free continuum and line emission. However, the same does not apply to the plasmas at the cluster's outskirts, which lacks such radiation. Owing to its low frequency, the radiation cannot escape, but because over the relevant scale size of a Cerenkov wavelength the energy of an electron in the gas cannot follow the Boltzmann distribution to the requisite precision to ensure reabsorption always occurs faster than stimulated emission, the emitting gas cools before it reheats. This leaves behind the radiation itself, trapped by the overlying reflective plasma, yet providing enough pressure to maintain quasi-hydrostatic equilibrium. The mass condensation then happens by Rayleigh-Taylor instability, at a rate determined by the outermost radius where Cerenkov radiation can occur. In this way, it is possible to estimate the rate at ≈2 M ⊙ year-1, consistent with observational inference. Thus, the process appears to provide a natural solution to the longstanding problem of “cooling flow” in clusters; at least it offers another line of defense against cooling and collapse should gas heating by AGN feedback be inadequate in some clusters.

The Role of Cerenkov Radiation in the Pressure Balance of Cool Core Clusters of Galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lieu, Richard

2017-03-20

Despite the substantial progress made recently in understanding the role of AGN feedback and associated non-thermal effects, the precise mechanism that prevents the core of some clusters of galaxies from collapsing catastrophically by radiative cooling remains unidentified. In this Letter, we demonstrate that the evolution of a cluster's cooling core, in terms of its density, temperature, and magnetic field strength, inevitably enables the plasma electrons there to quickly become Cerenkov loss dominated, with emission at the radio frequency of ≲350 Hz, and with a rate considerably exceeding free–free continuum and line emission. However, the same does not apply to themore » plasmas at the cluster's outskirts, which lacks such radiation. Owing to its low frequency, the radiation cannot escape, but because over the relevant scale size of a Cerenkov wavelength the energy of an electron in the gas cannot follow the Boltzmann distribution to the requisite precision to ensure reabsorption always occurs faster than stimulated emission, the emitting gas cools before it reheats. This leaves behind the radiation itself, trapped by the overlying reflective plasma, yet providing enough pressure to maintain quasi-hydrostatic equilibrium. The mass condensation then happens by Rayleigh–Taylor instability, at a rate determined by the outermost radius where Cerenkov radiation can occur. In this way, it is possible to estimate the rate at ≈2 M {sub ⊙} year{sup −1}, consistent with observational inference. Thus, the process appears to provide a natural solution to the longstanding problem of “cooling flow” in clusters; at least it offers another line of defense against cooling and collapse should gas heating by AGN feedback be inadequate in some clusters.« less

Liquid metal cooled nuclear reactors with passive cooling system

DOEpatents

Hunsbedt, Anstein; Fanning, Alan W.

1991-01-01

A liquid metal cooled nuclear reactor having a passive cooling system for removing residual heat resulting from fuel decay during reactor shutdown. The passive cooling system comprises a plurality of cooling medium flow circuits which cooperate to remove and carry heat away from the fuel core upon loss of the normal cooling flow circuit to areas external thereto.

Synthesis of Multicolor Core/Shell NaLuF4:Yb3+/Ln3+@CaF2 Upconversion Nanocrystals

PubMed Central

Li, Hui; Hao, Shuwei; Yang, Chunhui; Chen, Guanying

2017-01-01

The ability to synthesize high-quality hierarchical core/shell nanocrystals from an efficient host lattice is important to realize efficacious photon upconversion for applications ranging from bioimaging to solar cells. Here, we describe a strategy to fabricate multicolor core @ shell α-NaLuF4:Yb3+/Ln3+@CaF2 (Ln = Er, Ho, Tm) upconversion nanocrystals (UCNCs) based on the newly established host lattice of sodium lutetium fluoride (NaLuF4). We exploited the liquid-solid-solution method to synthesize the NaLuF4 core of pure cubic phase and the thermal decomposition approach to expitaxially grow the calcium fluoride (CaF2) shell onto the core UCNCs, yielding cubic core/shell nanocrystals with a size of 15.6 ± 1.2 nm (the core ~9 ± 0.9 nm, the shell ~3.3 ± 0.3 nm). We showed that those core/shell UCNCs could emit activator-defined multicolor emissions up to about 772 times more efficient than the core nanocrystals due to effective suppression of surface-related quenching effects. Our results provide a new paradigm on heterogeneous core/shell structure for enhanced multicolor upconversion photoluminescence from colloidal nanocrystals. PMID:28336867

Convection Destroys the Core/Mantle Structure in Hybrid C/O/Ne White Dwarfs

NASA Astrophysics Data System (ADS)

Brooks, Jared; Schwab, Josiah; Bildsten, Lars; Quataert, Eliot; Paxton, Bill

2017-01-01

A hybrid C/O/Ne white dwarf (WD)—an unburned C/O core surrounded by an O/Ne/Na mantle—can be formed if the carbon flame is quenched in a super-AGB star or white dwarf merger remnant. We show that this segregated hybrid structure becomes unstable to rapid mixing within 2000 years of the onset of WD cooling. Carbon burning includes a weak reaction that removes electrons, resulting in a lower electron-to-baryon ratio ({Y}{{e}}) in the regions processed by carbon burning compared to the unburned C/O core, making the O/Ne mantle denser than the C/O core as the WD cools. This is unstable to efficient mixing. We use the results of {\\mathtt{MESA}} models with different size C/O cores to quantify the rate at which the cores mix with the mantle as they cool. In all cases, we find that the WDs undergo significant core/mantle mixing on timescales shorter than the time available to grow the WD to the Chandrasekhar mass (MCh) by accretion. As a result, hybrid WDs that reach MCh due to later accretion will have lower central carbon fractions than assumed thus far. We briefly discuss the implications of these results for the possibility of SNe Ia from hybrid WDs.

Effect of a Cooling Vest on Core Temperature in Athletes With and Without Spinal Cord Injury

PubMed Central

Trbovich, Michelle

2014-01-01

Background: It is well accepted that persons with spinal cord injury (SCI) have impaired ability to regulate core temperature due to impaired vasomotor and sudomotor activity below their level of injury. Impaired heat dissipation puts SCI athletes at great risk of exercise-induced hyperthermia (EIH) (>37.8°C). There is minimal evidence for efficacy of any specific cooling method in SCI athletes in a thermoneutral sport-specific setting. Objective: To evaluate the extent of EIH in persons with and without SCI and subsequently examine the effect of a cooling vest to attenuate rise in core body temperature (Tc). Methods: SCI (n = 17) and able-bodied (AB; n = 19) athletes participated in a 60-minute intermittent sprinting exercise in a thermoneutral (21.1°C-23.9°C) environment. Participants were separated according to their level of injury: tetraplegia defined as above T1 (TP; n = 6), high paraplegia defined as T5 through T1 (HP; n = 5), low paraplegia defined as T6 and below (LP; n = 6), and AB (n = 19). Tc was recorded at 15-minute intervals using an ingestible thermometer pill. This protocol was completed with a cooling vest (V) and without a cooling vest (NV). Results: All SCI and most AB athletes experienced EIH. After 60 minutes, Tc of TP athletes was significantly increased compared to HP (P = .03) and AB athletes (P = .007). There was no significant effect of the vest on Tc over time for any group. Conclusions: TP athletes have the highest risk of exercise-induced hyperthermia. The cooling vest does not significantly attenuate rise in Tc in SCI or AB athletes. PMID:24574824

Effect of a cooling vest on core temperature in athletes with and without spinal cord injury.

PubMed

Trbovich, Michelle; Ortega, Catherine; Schroeder, James; Fredrickson, Mark

2014-01-01

It is well accepted that persons with spinal cord injury (SCI) have impaired ability to regulate core temperature due to impaired vasomotor and sudomotor activity below their level of injury. Impaired heat dissipation puts SCI athletes at great risk of exercise-induced hyperthermia (EIH) (>37.8°C). There is minimal evidence for efficacy of any specific cooling method in SCI athletes in a thermoneutral sport-specific setting. To evaluate the extent of EIH in persons with and without SCI and subsequently examine the effect of a cooling vest to attenuate rise in core body temperature (Tc). SCI (n = 17) and able-bodied (AB; n = 19) athletes participated in a 60-minute intermittent sprinting exercise in a thermoneutral (21.1°C-23.9°C) environment. Participants were separated according to their level of injury: tetraplegia defined as above T1 (TP; n = 6), high paraplegia defined as T5 through T1 (HP; n = 5), low paraplegia defined as T6 and below (LP; n = 6), and AB (n = 19). Tc was recorded at 15-minute intervals using an ingestible thermometer pill. This protocol was completed with a cooling vest (V) and without a cooling vest (NV). All SCI and most AB athletes experienced EIH. After 60 minutes, Tc of TP athletes was significantly increased compared to HP (P = .03) and AB athletes (P = .007). There was no significant effect of the vest on Tc over time for any group. TP athletes have the highest risk of exercise-induced hyperthermia. The cooling vest does not significantly attenuate rise in Tc in SCI or AB athletes.

Core--strategy leading to high reversible hydrogen storage capacity for NaBH4.

PubMed

Christian, Meganne L; Aguey-Zinsou, Kondo-François

2012-09-25

Owing to its high storage capacity (10.8 mass %), sodium borohydride (NaBH(4)) is a promising hydrogen storage material. However, the temperature for hydrogen release is high (>500 °C), and reversibility of the release is unachievable under reasonable conditions. Herein, we demonstrate the potential of a novel strategy leading to high and stable hydrogen absorption/desorption cycling for NaBH(4) under mild pressure conditions (4 MPa). By an antisolvent precipitation method, the size of NaBH(4) particles was restricted to a few nanometers (<30 nm), resulting in a decrease of the melting point and an initial release of hydrogen at 400 °C. Further encapsulation of these nanoparticles upon reaction of nickel chloride at their surface allowed the synthesis of a core--shell nanostructure, NaBH(4)@Ni, and this provided a route for (a) the effective nanoconfinement of the melted NaBH(4) core and its dehydrogenation products, and (b) reversibility and fast kinetics owing to short diffusion lengths, the unstable nature of nickel borohydride, and possible modification of reaction paths. Hence at 350 °C, a reversible and steady hydrogen capacity of 5 mass % was achieved for NaBH(4)@Ni; 80% of the hydrogen could be desorbed or absorbed in less than 60 min, and full capacity was reached within 5 h. To the best of our knowledge, this is the first time that such performances have been achieved with NaBH(4). This demonstrates the potential of the strategy in leading to major advancements in the design of effective hydrogen storage materials from pristine borohydrides.

Dual functional NaYF4:Yb3+, Er3+@NaYF4:Yb3+, Nd3+ core-shell nanoparticles for cell temperature sensing and imaging

NASA Astrophysics Data System (ADS)

Shi, Zengliang; Duan, Yue; Zhu, Xingjun; Wang, Qiwei; Li, DongDong; Hu, Ke; Feng, Wei; Li, Fuyou; Xu, Chunxiang

2018-03-01

Lanthanide-doped up-conversion nanoparticles (UCNPs) provide a remote temperature sensing approach to monitoring biological microenvironments. In this research, the UCNPs of NaYF4:Yb3+, Er3+@NaYF4:Yb3+, Nd3+ with hexagonal (β)-phase were synthesized and applied in cell temperature sensing as well as imaging after surface modification with meso-2, 3-dimercaptosuccinic acid. In the core-shell UCNPs, Yb3+ ions were introduced as energy transfer media between sensitizers of Nd3+ and activators of Er3+ to improve Er3+emission and prevent their quenching behavior due to multiple energy levels of Nd3+. Under the excitations of 808 nm and 980 nm lasers, the NaYF4:Yb3+, Er3+@NaYF4:Yb3+, Nd3+ nanoparticles exhibited an efficient green band with two emission peaks at 525 nm and 545 nm, respectively, which originated from the transitions of 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 for Er3+ ions. We demonstrate that an occurrence of good logarithmic linearity exists between the intensity ratio of these two emission peaks and the reciprocal of the inside or outside temperature of NIH-3T3 cells. A better thermal stability is proved through temperature-dependent spectra with a heating-cooling cycle. The obtained viability of NIH-3T3 cells is greater than 90% after incubations of about 12 and 24 (h), and they possess a lower cytotoxicity of UCNPs. This work provides a method for monitoring the cell temperature and its living state from multiple dimensions including temperature response, cell images and visual up-conversion fluorescent color.

Synthesis and functionalization of NaGdF4:Yb,Er@NaGdF4 core-shell nanoparticles for possible application as multimodal contrast agents.

PubMed

Baziulyte-Paulaviciene, Dovile; Karabanovas, Vitalijus; Stasys, Marius; Jarockyte, Greta; Poderys, Vilius; Sakirzanovas, Simas; Rotomskis, Ricardas

2017-01-01

Upconverting nanoparticles (UCNPs) are promising, new imaging probes capable of serving as multimodal contrast agents. In this study, monodisperse and ultrasmall core and core-shell UCNPs were synthesized via a thermal decomposition method. Furthermore, it was shown that the epitaxial growth of a NaGdF 4 optical inert layer covering the NaGdF 4 :Yb,Er core effectively minimizes surface quenching due to the spatial isolation of the core from the surroundings. The mean diameter of the synthesized core and core-shell nanoparticles was ≈8 and ≈16 nm, respectively. Hydrophobic UCNPs were converted into hydrophilic ones using a nonionic surfactant Tween 80. The successful coating of the UCNPs by Tween 80 has been confirmed by Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy (SEM), powder X-ray diffraction (XRD), photoluminescence (PL) spectra and magnetic resonance (MR) T1 relaxation measurements were used to characterize the size, crystal structure, optical and magnetic properties of the core and core-shell nanoparticles. Moreover, Tween 80-coated core-shell nanoparticles presented enhanced optical and MR signal intensity, good colloidal stability, low cytotoxicity and nonspecific internalization into two different breast cancer cell lines, which indicates that these nanoparticles could be applied as an efficient, dual-modal contrast probe for in vivo bioimaging.

Recent advances on the understanding of structural and composition evolution of LMR cathodes for Li-ion batteries

DOE PAGES

Yan, Pengfei; Zheng, Jianming; Xiao, Jie; ...

2015-06-08

Lithium-rich, magnesium-rich (LMR) cathode materials have been regarded as one of the very promising cathodes for Li-ion battery applications. However, their practical application is still limited by several challenges, especially by their limited electrochemical stability rate capability. In this work, we present recent progresses on the understanding of the structural and composition evolution of LMR cathode materials with emphasis being placed on the correlation between structural/chemical evolution and electrochemical properties. In particular, using Li [Li 0.2Ni 0.2Mn 0.6O 2 as a typical example, we clearly illustrate the structural characteristics of the pristine materials and their dependence on the materials processingmore » history, cycling induced structural degradation/chemical partition and their correlation with degradation of electrochemical performance. The fundamental understanding obtained in this work may also guide the design and preparation of new cathode materials based on ternary system of transitional metal oxide.« less

Core-melt source reduction system

DOEpatents

Forsberg, Charles W.; Beahm, Edward C.; Parker, George W.

1995-01-01

A core-melt source reduction system for ending the progression of a molten core during a core-melt accident and resulting in a stable solid cool matrix. The system includes alternating layers of a core debris absorbing material and a barrier material. The core debris absorbing material serves to react with and absorb the molten core such that containment overpressurization and/or failure does not occur. The barrier material slows the progression of the molten core debris through the system such that the molten core has sufficient time to react with the core absorbing material. The system includes a provision for cooling the glass/molten core mass after the reaction such that a stable solid cool matrix results.

New Detections of Radio Minihalos in Cool Cores of Galaxy Clusters

NASA Technical Reports Server (NTRS)

Giacintucci, Simona; Markevitch, Maxim; Venturi, Tiziana; Clarke, Tracy E.; Cassano, Rossella; Mazzotta, Pasquale

2013-01-01

Cool cores of some galaxy clusters exhibit faint radio minihalos. Their origin is unclear, and their study has been limited by their small number. We undertook a systematic search for minihalos in a large sample of X-ray luminous clusters with high-quality radio data. In this article, we report four new minihalos (A 478, ZwCl 3146,RXJ 1532.9+3021, and A 2204) and five candidates found in the reanalyzed archival Very Large Array observations.The radio luminosities of our minihalos and candidates are in the range of 102325 W Hz1 at 1.4 GHz, which is consistent with these types of radio sources. Their sizes (40160 kpc in radius) are somewhat smaller than those of previously known minihalos. We combine our new detections with previously known minihalos, obtaining a total sample of 21 objects, and briefly compare the cluster radio properties to the average X-ray temperature and the total masses estimated from Planck.We find that nearly all clusters hosting minihalos are hot and massive. Beyond that, there is no clear correlation between the minihalo radio power and cluster temperature or mass (in contrast with the giant radio halos found in cluster mergers, whose radio luminosity correlates with the cluster mass). Chandra X-ray images indicate gas sloshing in the cool cores of most of our clusters, with minihalos contained within the sloshing regions in many of them. This supports the hypothesis that radio-emitting electrons are reaccelerated by sloshing. Advection of relativistic electrons by the sloshing gas may also play a role in the formation of the less extended minihalos.

Self powered neutron detectors as in-core detectors for Sodium-cooled Fast Reactors

NASA Astrophysics Data System (ADS)

Verma, V.; Barbot, L.; Filliatre, P.; Hellesen, C.; Jammes, C.; Svärd, S. Jacobsson

2017-07-01

Neutron flux monitoring system forms an integral part of the design of a Generation IV sodium cooled fast reactor. Diverse possibilities of detector system installation must be studied for various locations in the reactor vessel in order to detect any perturbations in the core. Results from a previous paper indicated that it is possible to detect changes in neutron source distribution initiated by an inadvertent withdrawal of outer control rod with in-vessel fission chambers located azimuthally around the core. It is, however, not possible to follow inner control rod withdrawal and precisely know the location of the perturbation in the core. Hence the use of complimentary in-core detectors coupled with the peripheral fission chambers is proposed to enable robust core monitoring across the radial direction. In this paper, we assess the feasibility of using self-powered neutron detectors (SPNDs) as in-core detectors in fast reactors for detecting local changes in the power distribution when the reactor is operated at nominal power. We study the neutron and gamma contributions to the total output current of the detector modelled with Platinum as the emitter material. It is shown that this SPND placed in an SFR-like environment would give a sufficiently measurable prompt neutron induced current of the order of 600 nA/m. The corresponding induced current in the connecting cable is two orders of magnitude lower and can be neglected. This means that the SPND can follow in-core power fluctuations. This validates the operability of an SPND in an SFR-like environment.

Core-melt source reduction system

DOEpatents

Forsberg, C.W.; Beahm, E.C.; Parker, G.W.

1995-04-25

A core-melt source reduction system for ending the progression of a molten core during a core-melt accident and resulting in a stable solid cool matrix. The system includes alternating layers of a core debris absorbing material and a barrier material. The core debris absorbing material serves to react with and absorb the molten core such that containment overpressurization and/or failure does not occur. The barrier material slows the progression of the molten core debris through the system such that the molten core has sufficient time to react with the core absorbing material. The system includes a provision for cooling the glass/molten core mass after the reaction such that a stable solid cool matrix results. 4 figs.

Core-shell-shell heterostructures of α-NaLuF4:Yb/Er@NaLuF4:Yb@MF2 (M = Ca, Sr, Ba) with remarkably enhanced upconversion luminescence.

PubMed

Su, Yue; Liu, Xiuling; Lei, Pengpeng; Xu, Xia; Dong, Lile; Guo, Xianmin; Yan, Xingxu; Wang, Peng; Song, Shuyan; Feng, Jing; Zhang, Hongjie

2016-07-05

Core-shell-shell heterostructures of α-NaLuF4:Yb/Er@NaLuF4:Yb@MF2 (M = Ca, Sr, Ba) have been successfully fabricated via the thermal decomposition method. Upconversion nanoparticles (UCNPs) were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), upconversion luminescence (UCL) spectroscopy, etc. Under 980 nm excitation, the emission intensities of the UCNPs are remarkably enhanced after coating the MF2 (M = Ca, Sr, and Ba) shell. Among these samples, CaF2 coated UCNPs show the strongest overall emission, while BaF2 coated UCNPs exhibit the longest lifetime. These results demonstrate that alkaline earth metal fluorides are ideal materials to improve the UCL properties. Meanwhile, although the lattice mismatch between the ternary NaREF4 core and the binary MF2 (M = Sr and Ba) shell is relatively large, the successfully synthesized NaLuF4:Yb/Er@NaLuF4:Yb@MF2 indicates a new outlook on the fabrication of heterostructural core-shell UCNPs.

Gas-cooled nuclear reactor

DOEpatents

Peinado, Charles O.; Koutz, Stanley L.

1985-01-01

A gas-cooled nuclear reactor includes a central core located in the lower portion of a prestressed concrete reactor vessel. Primary coolant gas flows upward through the core and into four overlying heat-exchangers wherein stream is generated. During normal operation, the return flow of coolant is between the core and the vessel sidewall to a pair of motor-driven circulators located at about the bottom of the concrete pressure vessel. The circulators repressurize the gas coolant and return it back to the core through passageways in the underlying core structure. If during emergency conditions the primary circulators are no longer functioning, the decay heat is effectively removed from the core by means of natural convection circulation. The hot gas rising through the core exits the top of the shroud of the heat-exchangers and flows radially outward to the sidewall of the concrete pressure vessel. A metal liner covers the entire inside concrete surfaces of the concrete pressure vessel, and cooling tubes are welded to the exterior or concrete side of the metal liner. The gas coolant is in direct contact with the interior surface of the metal liner and transfers its heat through the metal liner to the liquid coolant flowing through the cooling tubes. The cooler gas is more dense and creates a downward convection flow in the region between the core and the sidewall until it reaches the bottom of the concrete pressure vessel when it flows radially inward and up into the core for another pass. Water is forced to flow through the cooling tubes to absorb heat from the core at a sufficient rate to remove enough of the decay heat created in the core to prevent overheating of the core or the vessel.

Real-time LMR control parameter generation using advanced adaptive synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

King, R.W.; Mott, J.E.

1990-01-01

The reactor delta T'', the difference between the average core inlet and outlet temperatures, for the liquid-sodium-cooled Experimental Breeder Reactor 2 is empirically synthesized in real time from, a multitude of examples of past reactor operation. The real-time empirical synthesis is based on reactor operation. The real-time empirical synthesis is based on system state analysis (SSA) technology embodied in software on the EBR 2 data acquisition computer. Before the real-time system is put into operation, a selection of reactor plant measurements is made which is predictable over long periods encompassing plant shutdowns, core reconfigurations, core load changes, and plant startups.more » A serial data link to a personal computer containing SSA software allows the rapid verification of the predictability of these plant measurements via graphical means. After the selection is made, the real-time synthesis provides a fault-tolerant estimate of the reactor delta T accurate to {plus}/{minus}1{percent}. 5 refs., 7 figs.« less

Globally synchronous ice core volcanic tracers and abrupt cooling during the last glacial period

USGS Publications Warehouse

Bay, R.C.; Bramall, N.E.; Price, P.B.; Clow, G.D.; Hawley, R.L.; Udisti, R.; Castellano, E.

2006-01-01

We perform a Monte Carlo pattern recognition analysis of the coincidence between three regional volcanic histories from ice coring of Greenland and Antarctica over the period 2 to 45 ka, using SO4 anomalies in Greenland and East Antarctica determined by continuous core chemistry, together with West Antarctic volcanic ash layers determined by remote optical borehole logging and core assays. We find that the Antarctic record of volcanism correlates with Glacial abrupt climate change at a 95% to >99.8% (???3??) significance level and that volcanic depositions at the three locations match at levels exceeding 3??, likely indicating that many common horizons represent single eruptive events which dispersed material world wide. These globally coincident volcanics were associated with abrupt cooling, often simultaneous with onsets or sudden intensifications of millennial cold periods. The striking agreement between sites implies that the consistency of current timescales obtained by isotopic and glaciological dating methods is better than estimated. Copyright 2006 by the American Geogphysical Union.

Cooling system for a nuclear reactor

DOEpatents

Amtmann, Hans H.

1982-01-01

A cooling system for a gas-cooled nuclear reactor is disclosed which includes at least one primary cooling loop adapted to pass coolant gas from the reactor core and an associated steam generator through a duct system having a main circulator therein, and at least one auxiliary cooling loop having communication with the reactor core and adapted to selectively pass coolant gas through an auxiliary heat exchanger and circulator. The main and auxiliary circulators are installed in a common vertical cavity in the reactor vessel, and a common return duct communicates with the reactor core and intersects the common cavity at a junction at which is located a flow diverter valve operative to effect coolant flow through either the primary or auxiliary cooling loops.

Gold decorated NaYF4:Yb,Er/NaYF4/silica (core/shell/shell) upconversion nanoparticles for photothermal destruction of BE(2)-C neuroblastoma cells

NASA Astrophysics Data System (ADS)

Qian, Li Peng; Zhou, Li Han; Too, Heng-Phon; Chow, Gan-Moog

2011-02-01

Gold decorated NaYF4:Yb,Er/NaYF4/silica (core/shell/shell) upconversion (UC) nanoparticles ( 70-80 nm) were synthesized using tetraethyl orthosilicate and chloroauric acid in a one-step reverse microemulsion method. Gold nanoparticles ( 6 nm) were deposited on the surface of silica shell of these core/shell/shell nanoparticles. The total upconversion emission intensity (green, red, and blue) of the core/shell/shell nanoparticles decreased by 31% after Au was deposited on the surface of silica shell. The upconverted green light was coupled with the surface plasmon of Au leading to rapid heat conversion. These UC/silica/Au nanoparticles were very efficient to destroy BE(2)-C cancer cells and showed strong potential in photothermal therapy.

SEARCHING FOR COOLING SIGNATURES IN STRONG LENSING GALAXY CLUSTERS: EVIDENCE AGAINST BARYONS SHAPING THE MATTER DISTRIBUTION IN CLUSTER CORES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blanchard, Peter K.; Bayliss, Matthew B.; McDonald, Michael

2013-07-20

The process by which the mass density profile of certain galaxy clusters becomes centrally concentrated enough to produce high strong lensing (SL) cross-sections is not well understood. It has been suggested that the baryonic condensation of the intracluster medium (ICM) due to cooling may drag dark matter to the cores and thus steepen the profile. In this work, we search for evidence of ongoing ICM cooling in the first large, well-defined sample of SL selected galaxy clusters in the range 0.1 < z < 0.6. Based on known correlations between the ICM cooling rate and both optical emission line luminositymore » and star formation, we measure, for a sample of 89 SL clusters, the fraction of clusters that have [O II]{lambda}{lambda}3727 emission in their brightest cluster galaxy (BCG). We find that the fraction of line-emitting BCGs is constant as a function of redshift for z > 0.2 and shows no statistically significant deviation from the total cluster population. Specific star formation rates, as traced by the strength of the 4000 A break, D{sub 4000}, are also consistent with the general cluster population. Finally, we use optical imaging of the SL clusters to measure the angular separation, R{sub arc}, between the arc and the center of mass of each lensing cluster in our sample and test for evidence of changing [O II] emission and D{sub 4000} as a function of R{sub arc}, a proxy observable for SL cross-sections. D{sub 4000} is constant with all values of R{sub arc}, and the [O II] emission fractions show no dependence on R{sub arc} for R{sub arc} > 10'' and only very marginal evidence of increased weak [O II] emission for systems with R{sub arc} < 10''. These results argue against the ability of baryonic cooling associated with cool core activity in the cores of galaxy clusters to strongly modify the underlying dark matter potential, leading to an increase in SL cross-sections.« less

EFFECT OF ACTIVE COOLING AND α-2 ADRENOCEPTOR ANTAGONISM ON CORE TEMPERATURE IN ANESTHETIZED BROWN BEARS (URSUS ARCTOS).

PubMed

Ozeki, Larissa Mourad; Caulkett, Nigel; Stenhouse, Gordon; Arnemo, Jon M; Fahlman, Åsa

2015-06-01

Hyperthermia is a common complication during anesthesia of bears, and it can be life threatening. The objective of this study was to evaluate the effectiveness of active cooling on core body temperature for treatment of hyperthermia in anesthetized brown bears (Ursus arctos). In addition, body temperature after reversal with atipamezole was also evaluated. Twenty-five adult and subadult brown bears were captured with a combination of zolazepam-tiletamine and xylazine or medetomidine. A core temperature capsule was inserted into the bears' stomach or 15 cm into their rectum or a combination of both. In six bears with gastric temperatures≥40.0°C, an active cooling protocol was performed, and the temperature change over 30 min was analyzed. The cooling protocol consisted of enemas with 2 L of water at approximately 5°C/100 kg of body weight every 10 min, 1 L of intravenous fluids at ambient temperature, water or snow on the paws or the inguinal area, intranasal oxygen supplementation, and removing the bear from direct sunlight or providing shade. Nine bears with body temperature>39.0°C that were not cooled served as control for the treated animals. Their body temperatures were recorded for 30 min, prior to administration of reversal. At the end of the anesthetic procedure, all bears received an intramuscular dose of atipamezole. In 10 bears, deep rectal temperature change over 30 min after administration of atipamezole was evaluated. The active cooling protocol used in hyperthermic bears significantly decreased their body temperatures within 10 min, and it produced a significantly greater decrease in their temperature than that recorded in the control group.

HEDL FACILITIES CATALOG 400 AREA

DOE Office of Scientific and Technical Information (OSTI.GOV)

MAYANCSIK BA

1987-03-01

The purpose of this project is to provide a sodium-cooled fast flux test reactor designed specifically for irradiation testing of fuels and materials and for long-term testing and evaluation of plant components and systems for the Liquid Metal Reactor (LMR) Program. The FFTF includes the reactor, heat removal equipment and structures, containment, core component handling and examination, instrumentation and control, and utilities and other essential services. The complex array of buildings and equipment are arranged around the Reactor Containment Building.

HIGH-REDSHIFT X-RAY COOLING-CORE CLUSTER ASSOCIATED WITH THE LUMINOUS RADIO-LOUD QUASAR 3C 186

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siemiginowska, Aneta; Burke, D. J.; Aldcroft, Thomas L.

2010-10-10

We present the first results from a new, deep (200 ks) Chandra observation of the X-ray luminous galaxy cluster surrounding the powerful (L {approx} 10{sup 47} erg s{sup -1}), high-redshift (z = 1.067), compact-steep-spectrum radio-loud quasar 3C 186. The diffuse X-ray emission from the cluster has a roughly ellipsoidal shape and extends out to radii of at least {approx}60 arcsec ({approx}500 kpc). The centroid of the diffuse X-ray emission is offset by 0.68 {+-} 0.''11 ({approx}5.5 {+-} 0.9 kpc) from the position of the quasar. We measure a cluster mass within the radius at which the mean enclosed density ismore » 2500 times the critical density, r{sub 2500} = 283{sup +18}{sub -13} kpc, of 1.02{sup +0.21}{sub -0.14} x 10{sup 14} M{sub sun}. The gas-mass fraction within this radius is f{sub gas} = 0.129{sup +0.015}{sub -0.016}. This value is consistent with measurements at lower redshifts and implies minimal evolution in the f{sub gas}(z) relation for hot, massive clusters at 0 < z < 1.1. The measured metal abundance of 0.42{sup +0.08}{sub -0.07} Solar is consistent with the abundance observed in other massive, high-redshift clusters. The spatially resolved temperature profile for the cluster shows a drop in temperature, from kT {approx} 8 keV to kT {approx} 3 keV, in its central regions that is characteristic of cooling-core clusters. This is the first spectroscopic identification of a cooling-core cluster at z>1. We measure cooling times for the X-ray emitting gas at radii of 50 kpc and 25 kpc of 1.7 {+-} 0.2 x 10{sup 9} years and 7.5 {+-} 2.6 x 10{sup 8} years, as well as a nominal cooling rate (in the absence of heating) of 400 {+-} 190 M{sub sun} year{sup -1} within the central 100 kpc. In principle, the cooling gas can supply enough fuel to support the growth of the supermassive black hole and to power the luminous quasar. The radiative power of the quasar exceeds by a factor of 10 the kinematic power of the central radio source, suggesting that radiative

THR-TH: a high-temperature gas-cooled nuclear reactor core thermal hydraulics code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vondy, D.R.

1984-07-01

The ORNL version of PEBBLE, the (RZ) pebble bed thermal hydraulics code, has been extended for application to a prismatic gas cooled reactor core. The supplemental treatment is of one-dimensional coolant flow in up to a three-dimensional core description. Power density data from a neutronics and exposure calculation are used as the basic information for the thermal hydraulics calculation of heat removal. Two-dimensional neutronics results may be expanded for a three-dimensional hydraulics calculation. The geometric description for the hydraulics problem is the same as used by the neutronics code. A two-dimensional thermal cell model is used to predict temperatures inmore » the fuel channel. The capability is available in the local BOLD VENTURE computation system for reactor core analysis with capability to account for the effect of temperature feedback by nuclear cross section correlation. Some enhancements have also been added to the original code to add pebble bed modeling flexibility and to generate useful auxiliary results. For example, an estimate is made of the distribution of fuel temperatures based on average and extreme conditions regularly calculated at a number of locations.« less

Cooling of Accretion-Heated Neutron Stars

NASA Astrophysics Data System (ADS)

Wijnands, Rudy; Degenaar, Nathalie; Page, Dany

2017-09-01

We present a brief, observational review about the study of the cooling behaviour of accretion-heated neutron stars and the inferences about the neutron-star crust and core that have been obtained from these studies. Accretion of matter during outbursts can heat the crust out of thermal equilibrium with the core and after the accretion episodes are over, the crust will cool down until crust-core equilibrium is restored. We discuss the observed properties of the crust cooling sources and what has been learned about the physics of neutron-star crusts. We also briefly discuss those systems that have been observed long after their outbursts were over, i.e, during times when the crust and core are expected to be in thermal equilibrium. The surface temperature is then a direct probe for the core temperature. By comparing the expected temperatures based on estimates of the accretion history of the targets with the observed ones, the physics of neutron-star cores can be investigated. Finally, we discuss similar studies performed for strongly magnetized neutron stars in which the magnetic field might play an important role in the heating and cooling of the neutron stars.

Synthesis and Characterization of Monodisperse Core-shell Lanthanide Upconversion Nanoparticles NaYF4: Yb,Tm/SiO2

NASA Astrophysics Data System (ADS)

Manurung, R. V.; Wiranto, G.; Hermida, I. D. P.

2018-05-01

Lanthanide up-converting luminescent nanoparticles (UCNPs) are exciting and promising materials for optical bioimaging, biosensor and theranostic due to their unique and advantageous optical and chemical properties. The UCNPs absorb low energy near-infrared (NIR) light and emit high-energy shorter wavelength photons (visible light). Their unique features allow them to overcome various problems associated with conventional imaging probes such as photostability, lack of toxicity, and to provide versatility for creating nanoplatforms with both imaging and therapeutic modalities. This paper reports synthesis and characterization of core-shell structured of NaYF4:Yb,Tm/SiO2 microspheres. The synthesis of lanthanide upconversion nanoparticles NaYF4:Yb,Tm was prepared by thermal decomposition process which involves dissolving organic precursors in high-boiling-point solvents oleic acid (OA) and octadecene (ODE). After that, the NaYF4:Yb,Tm phosphors was coated by silica via reverse microemulsion process to obtain core-shell structured NaYF4:Yb,Tm/SiO2. Scanning electron microscopy, transmission electron microscopy, specific area electron diffraction, and photoluminescence were applied to characterize these samples. The obtained core-shell structured NaYF4:Yb,Tm/SiO2 phosphors exhibit a perfect cubic morphology with narrow size distribution and smooth surface. Upon IR excitation at 980 nm, the NaYF4:Yb,Tm/SiO2 samples exhibit whitish blue upconversion (UC) luminescence, respectively. These phosphors show potential applications in the displaying on biological fields and biosensing.

Experimental and numerical CHT-investigations of cooling structures formed by lost cores in cast housings for optimal heat transfer

NASA Astrophysics Data System (ADS)

Kohlstädt, S.; Vynnycky, M.; Gebauer-Teichmann, A.

2018-05-01

This paper investigates the cooling performance of six different lost core designs for automotive cast houses with regard to their cooling efficiency. For this purpose, the conjugate heat transfer (CHT) solver, chtMultiregion, of the freely available CFD-toolbox OpenFOAM in its implementation of version 2.3.1 is used. The turbulence contribution to the Navier-Stokes equations is accounted for by using the RANS Menter SST k - ω model. The results are validated for one of the geometries by comparing with experimental data. Of the six investigated cooling structures, the one that forces the fluid flow to change its direction the most produces the lowest temperatures on the surface of the cast housing. This good cooling performance comes at the price of the highest pressure loss in the cooling fluid and hence increased pump power. It is also found that the relationship between performance and pressure drop is by no means generally linear. Slight changes in the design can lead to a structure which cools almost as well, but at much decreased pressure loss. Regarding the absolute values, the simulations showed that the designed cooling structures are suitable for handling the cooling requirements in the particular applications and that the maximum temperature stays below the critical limits of the electronic components.

Comparative study between single core model and detail core model of CFD modelling on reactor core cooling behaviour

NASA Astrophysics Data System (ADS)

Darmawan, R.

2018-01-01

Nuclear power industry is facing uncertainties since the occurrence of the unfortunate accident at Fukushima Daiichi Nuclear Power Plant. The issue of nuclear power plant safety becomes the major hindrance in the planning of nuclear power program for new build countries. Thus, the understanding of the behaviour of reactor system is very important to ensure the continuous development and improvement on reactor safety. Throughout the development of nuclear reactor technology, investigation and analysis on reactor safety have gone through several phases. In the early days, analytical and experimental methods were employed. For the last four decades 1D system level codes were widely used. The continuous development of nuclear reactor technology has brought about more complex system and processes of nuclear reactor operation. More detailed dimensional simulation codes are needed to assess these new reactors. Recently, 2D and 3D system level codes such as CFD are being explored. This paper discusses a comparative study on two different approaches of CFD modelling on reactor core cooling behaviour.

Effect of Bath Temperature on Cooling Performance of Molten Eutectic NaNO3-KNO3 Quench Medium for Martempering of Steels

NASA Astrophysics Data System (ADS)

Pranesh Rao, K. M.; Narayan Prabhu, K.

2017-10-01

Martempering is an industrial heat treatment process that requires a quench bath that can operate without undergoing degradation in the temperature range of 423 K to 873 K (150 °C to 600 °C). The quench bath is expected to cool the steel part from the austenizing temperature to quench bath temperature rapidly and uniformly. Molten eutectic NaNO3-KNO3 mixture has been widely used in industry to martemper steel parts. In the present work, the effect of quench bath temperature on the cooling performance of a molten eutectic NaNO3-KNO3 mixture has been studied. An Inconel ASTM D-6200 probe was heated to 1133 K (860 °C) and subsequently quenched in the quench bath maintained at different temperatures. Spatially dependent transient heat flux at the metal-quenchant interface for each bath temperature was calculated using inverse heat conduction technique. Heat transfer occurred only in two stages, namely, nucleate boiling and convective cooling. The mean peak heat flux ( q max) decreased with increase in quench bath temperature, whereas the mean surface temperature corresponding to q max and mean surface temperature at the start of convective cooling stage increased with increase in quench bath temperature. The variation in normalized cooling parameter t 85 along the length of the probe increased with increase in quench bath temperature.

Geminga: A cooling superfluid neutron star

NASA Technical Reports Server (NTRS)

Page, Dany

1994-01-01

We compare the recent temperature estimate for Geminga with neutron star cooling models. Because of its age (approximately 3.4 x 10(exp 5) yr), Geminga is in the photon cooling era. We show that its surface temperature (approximately 5.2 x 10(exp 5) K) can be understood by both types of neutrino cooling scenarios, i.e., slow neutrino cooling by the modified Urca process or fast neutrino cooling by the direct Urca process or by some exotic matter, and thus does not allow us to discriminate between these two competing schemes. However, for both types of scenarios, agreement with the observed temperature can only be obtained if baryon pairing is present in most, if not all, of the core of the star. Within the slow neutrino cooling scenario, early neutrino cooling is not sufficient to explain the observed low temperature, and extensive pairing in the core is necessary to reduce the specific heat and increase the cooling rate in the present photon cooling era. Within all the fast neutrino cooling scenarios, pairing is necessary throughout the whole core to control the enormous early neutrino emission which, without pairing suppression, would result in a surface temperature at the present time much lower than observed. We also comment on the recent temperature estimates for PSR 0656+14 and PSR 1055-52, which pertain to the same photon cooling era. If one assumes that all neutron stars undergo fast neutrino cooling, then these two objects also provide evidence for extensive baryon pairing in their core; but observational uncertainties also permit a more conservative interpretation, with slow neutrino emission and no pairing at all. We argue though that observational evidence for the slow neutrino cooling model (the 'standard' model) is in fact very dim and that the interpretation of the surface temperature of all neutron stars could be done with a reasonable theoretical a priori within the fast neutrino cooling scenarios only. In this case, Geminga, PSR 0656+14, and PSR

Unravelling the core microbiome of biofilms in cooling tower systems.

PubMed

Di Gregorio, L; Tandoi, V; Congestri, R; Rossetti, S; Di Pippo, F

2017-11-01

In this study, next generation sequencing and catalyzed reporter deposition fluorescence in situ hybridization, combined with confocal microscopy, were used to provide insights into the biodiversity and structure of biofilms collected from four full-scale European cooling systems. Water samples were also analyzed to evaluate the impact of suspended microbes on biofilm formation. A common core microbiome, containing members of the families Sphingomonadaceae, Comamonadaceae and Hyphomicrobiaceae, was found in all four biofilms, despite the water of each coming from different sources (river and groundwater). This suggests that selection of the pioneer community was influenced by abiotic factors (temperature, pH) and tolerances to biocides. Members of the Sphingomonadaceae were assumed to play a key role in initial biofilm formation. Subsequent biofilm development was driven primarily by light availability, since biofilms were dominated by phototrophs in the two studied 'open' systems. Their interactions with other microbial populations then shaped the structure of the mature biofilm communities analyzed.

Magnetic suspension using high temperature superconducting cores

NASA Technical Reports Server (NTRS)

Scurlock, R. G.

1992-01-01

The development of YBCO high temperature superconductors, in wire and tape forms, is rapidly approaching the point where the bulk transport current density j vs magnetic field H characteristics with liquid nitrogen cooling will enable its use in model cores. On the other hand, BSCCO high temperature superconductor in wire form has poor j-H characteristics at 77 K today, although with liquid helium or hydrogen cooling, it appears to be superior to NbTi superconductor. Since liquid nitrogen cooling is approx. 100 times cheaper than liquid helium cooling, the use of YBCO is very attractive for use in magnetic suspension. The design is discussed of a model core to accommodate lift and drag loads up to 6000 and 3000 N respectively. A comparison is made between the design performance of a liquid helium cooled NbTi (or BSCCO) superconducting core and a liquid nitrogen cooled YBCO superconducting core.

RADIO AND DEEP CHANDRA OBSERVATIONS OF THE DISTURBED COOL CORE CLUSTER ABELL 133

DOE Office of Scientific and Technical Information (OSTI.GOV)

Randall, S. W.; Nulsen, P. E. J.; Forman, W. R.

2010-10-10

We present results based on new Chandra and multi-frequency radio observations of the disturbed cool core cluster Abell 133. The diffuse gas has a complex bird-like morphology, with a plume of emission extending from two symmetric wing-like features. The plume is capped with a filamentary radio structure that has been previously classified as a radio relic. X-ray spectral fits in the region of the relic indicate the presence of either high-temperature gas or non-thermal emission, although the measured photon index is flatter than would be expected if the non-thermal emission is from inverse Compton scattering of the cosmic microwave backgroundmore » by the radio-emitting particles. We find evidence for a weak elliptical X-ray surface brightness edge surrounding the core, which we show is consistent with a sloshing cold front. The plume is consistent with having formed due to uplift by a buoyantly rising radio bubble, now seen as the radio relic, and has properties consistent with buoyantly lifted plumes seen in other systems (e.g., M87). Alternatively, the plume may be a gas sloshing spiral viewed edge-on. Results from spectral analysis of the wing-like features are inconsistent with the previous suggestion that the wings formed due to the passage of a weak shock through the cool core. We instead conclude that the wings are due to X-ray cavities formed by displacement of X-ray gas by the radio relic. The central cD galaxy contains two small-scale cold gas clumps that are slightly offset from their optical and UV counterparts, suggestive of a galaxy-galaxy merger event. On larger scales, there is evidence for cluster substructure in both optical observations and the X-ray temperature map. We suggest that the Abell 133 cluster has recently undergone a merger event with an interloping subgroup, initialing gas sloshing in the core. The torus of sloshed gas is seen close to edge-on, leading to the somewhat ragged appearance of the elliptical surface brightness edge

Reversing cooling flows with AGN jets: shock waves, rarefaction waves and trailing outflows

NASA Astrophysics Data System (ADS)

Guo, Fulai; Duan, Xiaodong; Yuan, Ye-Fei

2018-01-01

The cooling flow problem is one of the central problems in galaxy clusters, and active galactic nucleus (AGN) feedback is considered to play a key role in offsetting cooling. However, how AGN jets heat and suppress cooling flows remains highly debated. Using an idealized simulation of a cool-core cluster, we study the development of central cooling catastrophe and how a subsequent powerful AGN jet event averts cooling flows, with a focus on complex gasdynamical processes involved. We find that the jet drives a bow shock, which reverses cooling inflows and overheats inner cool-core regions. The shocked gas moves outward in a rarefaction wave, which rarefies the dense core and adiabatically transports a significant fraction of heated energy to outer regions. As the rarefaction wave propagates away, inflows resume in the cluster core, but a trailing outflow is uplifted by the AGN bubble, preventing gas accumulation and catastrophic cooling in central regions. Inflows and trailing outflows constitute meridional circulations in the cluster core. At later times, trailing outflows fall back to the cluster centre, triggering central cooling catastrophe and potentially a new generation of AGN feedback. We thus envisage a picture of cool cluster cores going through cycles of cooling-induced contraction and AGN-induced expansion. This picture naturally predicts an anti-correlation between the gas fraction (or X-ray luminosity) of cool cores and the central gas entropy, which may be tested by X-ray observations.

To cool, but not too cool: that is the question--immersion cooling for hyperthermia.

PubMed

Taylor, Nigel A S; Caldwell, Joanne N; Van den Heuvel, Anne M J; Patterson, Mark J

2008-11-01

Patient cooling time can impact upon the prognosis of heat illness. Although ice-cold-water immersion will rapidly extract heat, access to ice or cold water may be limited in hot climates. Indeed, some have concerns regarding the sudden cold-water immersion of hyperthermic individuals, whereas others believe that cutaneous vasoconstriction may reduce convective heat transfer from the core. It was hypothesized that warmer immersion temperatures, which induce less powerful vasoconstriction, may still facilitate rapid cooling in hyperthermic individuals. Eight males participated in three trials and were heated to an esophageal temperature of 39.5 degrees C by exercising in the heat (36 degrees C, 50% relative humidity) while wearing a water-perfusion garment (40 degrees C). Subjects were cooled using each of the following methods: air (20-22 degrees C), cold-water immersion (14 degrees C), and temperate-water immersion (26 degrees C). The time to reach an esophageal temperature of 37.5 degrees C averaged 22.81 min (air), 2.16 min (cold), and 2.91 min (temperate). Whereas each of the between-trial comparisons was statistically significant (P < 0.05), cooling in temperate water took only marginally longer than that in cold water, and one cannot imagine that the 45-s cooling time difference would have any meaningful physiological or clinical implications. It is assumed that this rapid heat loss was due to a less powerful peripheral vasoconstrictor response, with central heat being more rapidly transported to the skin surface for dissipation. Although the core-to-water thermal gradient was much smaller with temperate-water cooling, greater skin and deeper tissue blood flows would support a superior convective heat delivery. Thus, a sustained physiological mechanism (blood flow) appears to have countered a less powerful thermal gradient, resulting in clinically insignificant differences in heat extraction between the cold and temperate cooling trials.

Self-regulated cooling flows in elliptical galaxies and in cluster cores - Is exclusively low mass star formation really necessary?

NASA Technical Reports Server (NTRS)

Silk, J.; Djorgovski, S.; Wyse, R. F. G.; Bruzual A., G.

1986-01-01

A self-consistent treatment of the heating by supernovae associated with star formation in a spherically symmetric cooling flow in a cluster core or elliptical galaxy is presented. An initial stellar mass function similar to that in the solar neighborhood is adopted. Inferred star-formation rates, within the cooling region - typically the inner 100 kpc around dominant galaxies at the centers of cooling flows in XD clusters - are reduced by about a factor of 2, relative to rates inferred when the heat input from star formation is ignored. Truncated initial mass functions (IMFs) are also considered, in which massive star formation is suppressed in accordance with previous treatments, and colors are predicted for star formation in cooling flows associated with central dominant elliptical galaxies and with isolated elliptical galaxies surrounded by gaseous coronae. The low inferred cooling-flow rates around isolated elliptical galaxies are found to be insensitive to the upper mass cutoff in the IMF, provided that the upper mass cutoff exceeds 2 M solar mass. Comparison with observed colors favors a cutoff in the IMF above 1 M solar mass in at least two well-studied cluster cooling flows, but a normal IMF cannot be excluded definitively. Models for NGC 1275 support a young (less than about 3 Gyr) cooling flow. As for the isolated elliptical galaxies, the spread in colors is consistent with a normal IMF. A definitive test of the IMF arising via star formation in cooling flows requires either UV spectral data or supernova searches in the cooling-flow-centered galaxies.

Mission planning for large microwave radiometers

NASA Technical Reports Server (NTRS)

Schartel, W. A.

1984-01-01

Earth orbiting, remote sensing platforms that use microwave radiometers as sensors are susceptible to data interpretation difficulties. The capability of the large microwave radiometer (LMR) was augmented with the inclusion of auxillary sensors that expand and enhance the LMR capability. The final system configuration demonstrates a holistic approach in the design of future orbiting remote sensing platforms that use a LMR as the core instrument.

Life jacket design affects dorsal head and chest exposure, core cooling, and cognition in 10 degrees C water.

PubMed

Lockhart, Tamara L; Jamieson, Christopher P; Steinman, Alan M; Giesbrecht, Gordon G

2005-10-01

Personal floatation devices (PFDs) differ in whether they maintain the head out of the water or allow the dorsum of the head to be immersed. Partial head submersion may hasten systemic cooling, incapacitation, and death in cold water. Six healthy male volunteers (mean age = 26.8 yr; height = 184 cm; weight = 81 kg; body fat = 20%) were immersed in 10 degrees C water for 65 min, or until core temperature = 34 degrees C, under three conditions: PFD#1 maintained the head and upper chest out of the water; PFD#2 allowed the dorsal head and whole body to be immersed; and an insulated drysuit (control) allowed the dorsal head to be immersed. Mental performance tests included: logic reasoning test; Stroop word-color test; digit symbol coding; backward digit span; and paced auditory serial addition test (PASAT). Core cooling was significantly faster for PFD#2 (2.8 +/- 1.6 degrees C x h(-1)) than for PFD#1 (1.5 +/- 0.7 degrees C x h(-1)) or for the drysuit (0.4 +/- 0.2 degrees C x h(-1)). Although no statistically significant effects on cognitive performance were noted for the individual PFDs and drysuit, when analyzed as a group, four of the tests of cognitive performance (Stroop word-color, digit symbol coding, backward digit span, and PASAT) showed significant correlations between decreasing core temperature to 34 degrees C and diminished cognitive performance. Performance in more complicated mental tasks was adversely affected as core temperature decreased to 34 degrees C. The PFD that kept the head and upper chest out of the water preserved body heat and mental performance better than the PFD that produced horizontal flotation.

Interim MELCOR Simulation of the Fukushima Daiichi Unit 2 Accident Reactor Core Isolation Cooling Operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, Kyle W.; Gauntt, Randall O.; Cardoni, Jeffrey N.

2013-11-01

Data, a brief description of key boundary conditions, and results of Sandia National Laboratories’ ongoing MELCOR analysis of the Fukushima Unit 2 accident are given for the reactor core isolation cooling (RCIC) system. Important assumptions and related boundary conditions in the current analysis additional to or different than what was assumed/imposed in the work of SAND2012-6173 are identified. This work is for the U.S. Department of Energy’s Nuclear Energy University Programs fiscal year 2014 Reactor Safety Technologies Research and Development Program RC-7: RCIC Performance under Severe Accident Conditions.

Core/Shell NaGdF4:Nd3+/NaGdF4 Nanocrystals with Efficient Near-Infrared to Near-Infrared Downconversion Photoluminescence for Bioimaging Applications

PubMed Central

Chen, Guanying; Ohulchanskyy, Tymish Y.; Liu, Sha; Law, Wing-Cheung; Wu, Fang; Swihart, Mark T.; Ågren, Hans; Prasad, Paras N.

2012-01-01

We have synthesized core/shell NaGdF4:Nd3+/NaGdF4 nanocrystals with an average size of 15 nm and exceptionally high photoluminescence (PL) quantum yield. When excited at 740 nm, the nanocrystals manifest spectrally distinguished, near infrared to near infrared (NIR-to-NIR) downconversion PL peaked at ~900, ~1050, and ~1300 nm. The absolute quantum yield of NIR-to-NIR PL reached 40% for core-shell nanoparticles dispersed in hexane. Time-resolved PL measurements revealed that this high quantum yield was achieved through suppression of nonradiative recombination originating from surface states and cross relaxations between dopants. NaGdF4:Nd3+/NaGdF4 nanocrystals, synthesized in organic media, were further converted to be water-dispersible by eliminating the capping ligand of oleic acid. NIR-to-NIR PL bioimaging was demonstrated both in vitro and in vivo through visualization of the NIR-to-NIR PL at ~900 nm under incoherent lamp light excitation. The fact that both excitation and the PL of these nanocrystals are in the biological window of optical transparency, combined with their high quantum efficiency, spectral sharpness and photostability, makes these nanocrystals extremely promising as optical biomaging probes. PMID:22401578

AGN-driven perturbations in the intracluster medium of the cool-core cluster ZwCl 2701

NASA Astrophysics Data System (ADS)

Vagshette, Nilkanth D.; Sonkamble, Satish S.; Naik, Sachindra; Patil, Madhav K.

2016-09-01

We present the results obtained from a total of 123 ks X-ray (Chandra) and 8 h of 1.4 GHz radio (Giant Metrewave Radio Telescope - GMRT) observations of the cool-core cluster ZwCl 2701 (z = 0.214). These observations of ZwCl 2701 showed the presence of an extensive pair of ellipsoidal cavities along the east and west directions within the central region < 20 kpc. Detection of bright rims around the cavities suggested that the radio lobes displaced X-ray-emitting hot gas forming shell-like structures. The total cavity power (mechanical power) that directly heated the surrounding gas and cooling luminosity of the cluster were estimated to be ˜2.27 × 1045 erg s-1 and 3.5 × 1044 erg s-1 , respectively. Comparable values of cavity power and cooling luminosity of ZwCl 2701 suggested that the mechanical power of the active galactic nuclei (AGN) outburst is large enough to balance the radiative cooling in the system. The star formation rate derived from the Hα luminosity was found to be ˜0.60 M⊙ yr-1, which is about three orders of magnitude lower than the cooling rate of ˜196 M⊙ yr-1. Detection of the floor in entropy profile of ZwCl 2701 suggested the presence of an alternative heating mechanism at the centre of the cluster. Lower value of the ratio (˜10-2) between black hole mass accretion rate and Eddington mass accretion rate suggested that launching of jet from the super massive black hole is efficient in ZwCl 2701. However, higher value of ratio (˜103) between black hole mass accretion rate and Bondi accretion rate indicated that the accretion rate required to create cavities is well above the Bondi accretion rate.

Advanced Na-NiCl2 Battery Using Nickel-Coated Graphite with Core-Shell Microarchitecture.

PubMed

Chang, Hee-Jung; Canfield, Nathan L; Jung, Keeyoung; Sprenkle, Vincent L; Li, Guosheng

2017-04-05

Stationary electric energy storage devices (rechargeable batteries) have gained increasing prominence due to great market needs, such as smoothing the fluctuation of renewable energy resources and supporting the reliability of the electric grid. With regard to raw materials availability, sodium-based batteries are better positioned than lithium batteries due to the abundant resource of sodium in Earth's crust. However, the sodium-nickel chloride (Na-NiCl 2 ) battery, one of the most attractive stationary battery technologies, is hindered from further market penetration by its high material cost (Ni cost) and fast material degradation at its high operating temperature. Here, we demonstrate the design of a core-shell microarchitecture, nickel-coated graphite, with a graphite core to maintain electrochemically active surface area and structural integrity of the electron percolation pathway while using 40% less Ni than conventional Na-NiCl 2 batteries. An initial energy density of 133 Wh/kg (at ∼C/4) and energy efficiency of 94% are achieved at an intermediate temperature of 190 °C.

Core assembly storage structure

DOEpatents

Jones, Jr., Charles E.; Brunings, Jay E.

1988-01-01

A structure for the storage of core assemblies from a liquid metal-cooled nuclear reactor. The structure comprises an enclosed housing having a substantially flat horizontal top plate, a bottom plate and substantially vertical wall members extending therebetween. A plurality of thimble members extend downwardly through the top plate. Each thimble member is closed at its bottom end and has an open end adjacent said top plate. Each thimble member has a length and diameter greater than that of the core assembly to be stored therein. The housing is provided with an inlet duct for the admission of cooling air and an exhaust duct for the discharge of air therefrom, such that when hot core assemblies are placed in the thimbles, the heat generated will by convection cause air to flow from the inlet duct around the thimbles and out the exhaust duct maintaining the core assemblies at a safe temperature without the necessity of auxiliary powered cooling equipment.

REMOVING COOL CORES AND CENTRAL METALLICITY PEAKS IN GALAXY CLUSTERS WITH POWERFUL ACTIVE GALACTIC NUCLEUS OUTBURSTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo Fulai; Mathews, William G., E-mail: fulai@ucolick.or

2010-07-10

Recent X-ray observations of galaxy clusters suggest that cluster populations are bimodally distributed according to central gas entropy and are separated into two distinct classes: cool core (CC) and non-cool core (NCC) clusters. While it is widely accepted that active galactic nucleus (AGN) feedback plays a key role in offsetting radiative losses and maintaining many clusters in the CC state, the origin of NCC clusters is much less clear. At the same time, a handful of extremely powerful AGN outbursts have recently been detected in clusters, with a total energy {approx}10{sup 61}-10{sup 62} erg. Using two-dimensional hydrodynamic simulations, we showmore » that if a large fraction of this energy is deposited near the centers of CC clusters, which is likely common due to dense cores, these AGN outbursts can completely remove CCs, transforming them to NCC clusters. Our model also has interesting implications for cluster abundance profiles, which usually show a central peak in CC systems. Our calculations indicate that during the CC to NCC transformation, AGN outbursts efficiently mix metals in cluster central regions and may even remove central abundance peaks if they are not broad enough. For CC clusters with broad central abundance peaks, AGN outbursts decrease peak abundances, but cannot effectively destroy the peaks. Our model may simultaneously explain the contradictory (possibly bimodal) results of abundance profiles in NCC clusters, some of which are nearly flat, while others have strong central peaks similar to those in CC clusters. A statistical analysis of the sizes of central abundance peaks and their redshift evolution may shed interesting insights on the origin of both types of NCC clusters and the evolution history of thermodynamics and AGN activity in clusters.« less

Therapeutic hypothermia for out-of-hospital ventricular fibrillation survivors: a feasibility study comparing time to achieve target core temperature using conventional conductive cooling versus combined conductive plus pericranial convective cooling.

PubMed

Wass, C Thomas; White, Roger D; Schroeder, Darrell R; Mirzoyev, Sultan A; Warfield, Karen T

2013-04-01

Mild to moderate therapeutic hypothermia (TH) has been shown to improve survival and neurologic outcome, as well as to reduce healthcare costs in patients resuscitated from out-of-hospital cardiac arrest (OHCA) with ventricular fibrillation. Accordingly, the American Heart Association has categorized this as a Class IB intervention. The therapeutic window for initiating TH is narrow, and thus, achieving target temperature expeditiously is of paramount importance to improve postresuscitative neurologic outcome. The present investigation is a feasibility study designed to assess the practicality and efficacy of including pericranial cooling in our postresuscitative TH protocol. Specifically, we compared time required to achieve target temperature (33°C) using our present standard of TH care (ie, conductive body cooling, conventional TH group) versus combined conductive body cooling plus convective (forced-air) head and neck cooling (combined TH group). Adult patients who experienced OHCA were included in the study provided TH could be initiated within 4 hours of resuscitation from ventricular fibrillation. Patients enrolled in both groups were cooled using the servo-controlled Arctic Sun conductive cooling system (Medivance, Inc, Louisville, CO). However, patients enrolled in the combined TH group also received forced-air pericranial cooling with an ambient temperature of approximately 13°C. In all cases, the target core (bladder) temperature was 33°C. The primary endpoint (ie, time required to achieve a core temperature of 33°C) was analyzed as a continuous variable and compared between groups using the rank sum test, whereas categorical variables were compared between groups using the chi-square test. Cardiac intensive care unit at a major tertiary care teaching center in Rochester, MN. Adult patients who experienced OHCA were included in the study. Patients enrolled in both groups were cooled using the servo-controlled Arctic Sun conductive cooling system

Superficial cooling does not decrease core body temperature before, during, or after exercise in an American football uniform.

PubMed

Lopez, Rebecca M; Eberman, Lindsey E; Cleary, Michelle A

2012-12-01

The purpose of this study was to identify the effects of superficial cooling on thermoregulatory responses while exercising in a hot humid environment while wearing an American football uniform. Nine male and female subjects wore a superficial cooling garment while in a cooling (CS) experimental condition or a no cooling (NCS) control condition during an exercise task consisting of warm-up (WU), exercise (EX), and recovery (R). The exercise task simulated an American football conditioning session with subjects wearing a full American football uniform and performing anaerobic and aerobic exercises in a hot humid environment. Subjects were allowed to drink water ad libitum during rest breaks. During the WU, EX, and R periods, core body temperature (T(c)) was measured to assess the effect of the cooling garment. Neither baseline resting before warm-up T(c) nor after warm-up T(c) was significantly different between trials. No significant differences in exercise T(c) between conditions were found. Time to return to baseline T(c) revealed no significant differences between the experimental and control conditions. The authors found that the volume of fluid consumed was 34% less in the experimental condition (711.1 ± 188.0 ml) compared with the control condition (1,077.8 ± 204.8 ml). The findings indicate that the cooling garment was not effective in blunting the rise in T(c) during warm-up, attenuating a rise in T(c) during intermittent exercise, or in increasing a return to baseline T(c) during a resting recovery period in a hot humid environment while wearing an American football uniform.

The cooling history and the depth of detachment faulting at the Atlantis Massif oceanic core complex

NASA Astrophysics Data System (ADS)

Schoolmeesters, Nicole; Cheadle, Michael J.; John, Barbara E.; Reiners, Peter W.; Gee, Jeffrey; Grimes, Craig B.

2012-10-01

Oceanic core complexes (OCCs) are domal exposures of oceanic crust and mantle interpreted to be denuded to the seafloor by large slip oceanic detachment faults. We combine previously reported U-Pb zircon crystallization ages with (U-Th)/He zircon thermochronometry and multicomponent magnetic remanence data to determine the cooling history of the footwall to the Atlantis Massif OCC (30°N, MAR) and help establish cooling rates, as well as depths of detachment faulting and gabbro emplacement. We present nine new (U-Th)/He zircon ages for samples from IODP Hole U1309D ranging from 40 to 1415 m below seafloor. These data paired with U-Pb zircon ages and magnetic remanence data constrain cooling rates of gabbroic rocks from the upper 800 m of the central dome at Atlantis Massif as 2895 (+1276/-1162) °C Myr-1 (from ˜780°C to ˜250°C); the lower 600 m of the borehole cooled more slowly at mean rates of ˜500 (+125/-102) °C Myr-1(from ˜780°C to present-day temperatures). Rocks from the uppermost part of the hole also reveal a brief period of slow cooling at rates of ˜300°C Myr-1, possibly due to hydrothermal circulation to ˜4 km depth through the detachment fault zone. Assuming a fault slip rate of 20 mm/yr (from U-Pb zircon ages of surface samples) and a rolling hinge model for the sub-surface fault geometry, we predict that the 780°C isotherm lies at ˜7 km below the axial valley floor, likely corresponding both to the depth at which the semi-brittle detachment fault roots and the probable upper limit of significant gabbro emplacement.

IBS FOR ION DISTRIBUTION UNDER ELECTRON COOLING.

DOE Office of Scientific and Technical Information (OSTI.GOV)

FEDOTOV,A.V.; BEN-ZVI,I.; EIDELMAN, YU.

Standard models of the intra-beam scattering (IBS) are based on the growth of the rms beam parameters for a Gaussian distribution. As a result of electron cooling, the core of beam distribution is cooled much faster than the tails, producing a denser core. In this paper, we compare various approaches to IBS treatment for such distribution. Its impact on the luminosity is also discussed.

Shocks and Cool Cores: An ALMA View of Massive Galaxy Cluster Formation at High Redshifts

NASA Astrophysics Data System (ADS)

Basu, Kaustuv

2017-07-01

These slides present some recent results on the Sunyaev-Zel'dovich (SZ) effect imaging of galaxy cluster substructures. The advantage of SZ imaging at high redshifts or in the low density cluster outskirts is already well-known. Now with ALMA a combination of superior angular resolution and high sensitivity is available. One example is the first ALMA measurement of a merger shock at z=0.9 in the famous El Gordo galaxy cluster. Here comparison between SZ, X-ray and radio data enabled us to put constraints on the shock Mach number and magnetic field strength for a high-z radio relic. Second example is the ALMA SZ imaging of the core region of z=1.4 galaxy cluster XMMU J2235.2-2557. Here ALMA data provide an accurate measurement of the thermal pressure near the cluster center, and from a joint SZ/X-ray analysis we find clear evidence for a reduced core temperature. This result indicate that a cool core establishes itself early enough in the cluster formation history while the gas accumulation is still continuing. The above two ALMA measurements are among several other recent SZ results that shed light on the formation process of massive clusters at high redshifts.

Space power reactor in-core thermionic multicell evolutionary (S-prime) design

NASA Astrophysics Data System (ADS)

Determan, William R.; Van Hagan, Tom H.

1993-01-01

A 5- to 40-kWe moderated in-core thermionic space nuclear power system (TI-SNPS) concept was developed to address the TI-SNPS program requirements. The 40-kWe baseline design uses multicell Thermionic Fuel Elements (TFEs) in a zirconium hydride moderated reactor to achieve a specific mass of 18.2 We/kg and a net end-of-mission (EOM) efficiency of 8.2%. The reactor is cooled with a single NaK-78 pumped loop, which rejects the heat through a 24 m2 heat pipe space radiator.

Cooling of core debris and the impact on containment pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, J.W.

1981-07-01

An evaluation of the core debris/water interactions associated with a postulated meltdown of a PWR and its impact on the containment pressure is presented. In the event of a complete core meltdown in a PWR, the interaction of molten debris with water in the bottom head of the reactor vessel could result in complete evaporation of water and breach of the vessel wall. In the reactor cavity, the debris-water interaction may lead to a rapid generation of steam, which could lead to pressures beyond the containment building limit. Previous analysis of the debris-water interactions with the MARCH code was basedmore » on the single-sphere model, in which the internal and surface heat transfer are the controlling mechanisms. In this study, the potential in-vessel and ex-vessel debris-water interactions are analyzed in terms of porous debris bed models. The debris cooling and steam generation are controlled by the hydrodynamics of the two-phase flow. The porous models developed by Dhir-Catton and by Lipinski were examined and used to test their impact on containment dynamics. The tests include several particle sizes from 1 mm to 50 mm. Detailed transient data on the pressure, temperature, and mass of steam in the containment building was obtained for all cases. Bands of pressure variation which represents the possible pressure rise under accident conditions were obtained for the Dhir-Catton model and for the Lipinski model. The results show that, for the case of a wet cavity, the magnitude of the predicted pressure rises is not strongly affected by the different models. The occurrence of the peak pressure, however, is considerably delayed by using the debris bed model. For the case of a dry cavity, a large reduction of the peak pressure is obtained by using the debris bed model.« less

Attenuated noradrenergic sensitivity during local cooling in aged human skin

PubMed Central

Thompson, Caitlin S; Holowatz, Lacy A; Kenney, W. Larry

2005-01-01

Reflex-mediated cutaneous vasoconstriction (VC) is impaired in older humans; however, it is unclear whether this blunted VC also occurs during local cooling, which mediates VC through different mechanisms. We tested the hypothesis that the sensitization of cutaneous vessels to noradrenaline (NA) during direct skin cooling seen in young skin is blunted in aged skin. In 11 young (18–30 years) and 11 older (62–76 years) men and women, skin blood flow was monitored at two forearm sites with laser Doppler (LD) flowmetry while local skin temperature was cooled and clamped at 24°C. Cutaneous vascular conductance (CVC; LD flux/mean arterial pressure) was expressed as percentage change from baseline (%ΔCVCbase). At one site, five doses of NA (10−10–10−2m) were sequentially infused via intradermal microdialysis during cooling while the other 24°C site served as control (Ringer solution + cooling). At control sites, VC due to cooling alone was similar in young versus older (−54 ± 5 versus −56 ± 3%ΔCVCbase, P= 0.46). In young, NA infusions induced additional dose-dependent VC (10−8, 10−6, 10−4 and 10−2m: −70 ± 2, −72 ± 3, −78 ± 3 and −79 ± 4%ΔCVCbase; P < 0.05 versus control). In older subjects, further VC did not occur until the highest infused dose of NA (10−2m: −70 ± 5%ΔCVCbase; P < 0.05 versus control). When cutaneous arterioles are sensitized to NA by direct cooling, young skin exhibits the capacity to further constrict to NA in a dose-dependent manner. However, older skin does not display enhanced VC capacity until treated with saturating doses of NA, possibly due to age-associated decrements in Ca2+ availability or α2C-adrenoceptor function. PMID:15705648

Cool DZ white dwarfs II: compositions and evolution of old remnant planetary systems

NASA Astrophysics Data System (ADS)

Hollands, M. A.; Gänsicke, B. T.; Koester, D.

2018-06-01

In a previous study, we analysed the spectra of 230 cool (Teff < 9000 K) white dwarfs exhibiting strong metal contamination, measuring abundances for Ca, Mg, Fe and in some cases Na, Cr, Ti, or Ni. Here, we interpret these abundances in terms of the accretion of debris from extrasolar planetesimals, and infer parent body compositions ranging from crust-like (rich in Ca and Ti) to core-like (rich in Fe and Ni). In particular, two white dwarfs, SDSS J0823+0546 and SDSS J0741+3146, which show log [Fe/Ca] > 1.9 dex, and Fe to Ni ratios similar to the bulk Earth, have accreted by far the most core-like exoplanetesimals discovered to date. With cooling ages in the range 1-8 Gyr, these white dwarfs are among the oldest stellar remnants in the Milky Way, making it possible to probe the long-term evolution of their ancient planetary systems. From the decrease in maximum abundances as a function of cooling age, we find evidence that the arrival rate of material on to the white dwarfs decreases by three orders of magnitude over a ≃ 6.5 Gyr span in white dwarf cooling ages, indicating that the mass-reservoirs of post-main sequence planetary systems are depleted on a ≃ 1 Gyr e-folding time-scale. Finally, we find that two white dwarfs in our sample are members of wide binaries, and both exhibit atypically high abundances, thus providing strong evidence that distant binary companions can dynamically perturb white dwarf planetary systems.

Safety margins in zircaloy oxidation and embrittlement criteria for emergency core cooling system acceptance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williford, R.E.

1986-09-01

Current emergency core cooling system acceptance criteria for light water reactors specify that, under loss-of-coolant accident (LOCA) conditions, the Baker-Just (BJ) correlation must be used to calculate Zircaloy-steam oxidation, calculated peak cladding temperatures (PCT) must not exceed 1204/sup 0/C, and calculated oxidation must not exceed 17% equivalent cladding reacted (ECR). An appropriately defined minimum margin of safety was estimated for each of these criteria. The currently required BJ oxidation correlation provides margins only over the 1100 to 1500/sup 0/C temperature range at the 95% confidence level. The PCT margins for thermal shock and handling failures are adequate at oxidation temperaturesmore » above 1204/sup 0/C for up to 210 and 160 s, respectively, at the 95% confidence level. The ECR thermal shock and handling margins at the 50 and 95% confidence levels, respectively, range between 2 and 7% ECR for the BJ correlation, but vanish at temperatures above 1100 to 1160/sup 0/C for the best-estimate Cathcart-Pawel correlation. However, use of the Cathcart Pawel correlation for ''design basis'' LOCA calculations can be justified at the 85 to 88% confidence level if cooling rate effects can be neglected.« less

Water immersion for post incident cooling of firefighters; a review of practical fire ground cooling modalities.

PubMed

Brearley, Matt; Walker, Anthony

2015-01-01

Rapidly cooling firefighters post emergency response is likely to increase the operational effectiveness of fire services during prolonged incidents. A variety of techniques have therefore been examined to return firefighters core body temperature to safe levels prior to fire scene re-entry or redeployment. The recommendation of forearm immersion (HFI) in cold water by the National Fire and Protection Association preceded implementation of this active cooling modality by a number of fire services in North America, South East Asia and Australia. The vascularity of the hands and forearms may expedite body heat removal, however, immersion of the torso, pelvis and/or lower body, otherwise known as multi-segment immersion (MSI), exposes a greater proportion of the body surface to water than HFI, potentially increasing the rates of cooling conferred. Therefore, this review sought to establish the efficacy of HFI and MSI to rapidly reduce firefighters core body temperature to safe working levels during rest periods. A total of 38 studies with 55 treatments (43 MSI, 12 HFI) were reviewed. The core body temperature cooling rates conferred by MSI were generally classified as ideal (n = 23) with a range of ~0.01 to 0.35 °C min(-1). In contrast, all HFI treatments resulted in unacceptably slow core body temperature cooling rates (~0.01 to 0.05 °C min(-1)). Based upon the extensive field of research supporting immersion of large body surface areas and comparable logistics of establishing HFI or MSI, it is recommended that fire and rescue management reassess their approach to fireground rehabilitation of responders. Specifically, we question the use of HFI to rapidly lower firefighter core body temperature during rest periods. By utilising MSI to restore firefighter Tc to safe working levels, fire and rescue services would adopt an evidence based approach to maintaining operational capability during arduous, sustained responses. While the optimal MSI protocol will be

AIR COOLED NEUTRONIC REACTOR

DOEpatents

Fermi, E.; Szilard, L.

1958-05-27

A nuclear reactor of the air-cooled, graphite moderated type is described. The active core consists of a cubicle mass of graphite, approximately 25 feet in each dimension, having horizontal channels of square cross section extending between two of the opposite faces, a plurality of cylindrical uranium slugs disposed in end to end abutting relationship within said channels providing a space in the channels through which air may be circulated, and a cadmium control rod extending within a channel provided in the moderator. Suitable shielding is provlded around the core, as are also provided a fuel element loading and discharge means, and a means to circulate air through the coolant channels through the fuel charels to cool the reactor.

Apparatus for controlling nuclear core debris

DOEpatents

Jones, Robert D.

1978-01-01

Nuclear reactor apparatus for containing, cooling, and dispersing reactor debris assumed to flow from the core area in the unlikely event of an accident causing core meltdown. The apparatus includes a plurality of horizontally disposed vertically spaced plates, having depressions to contain debris in controlled amounts, and a plurality of holes therein which provide natural circulation cooling and a path for debris to continue flowing downward to the plate beneath. The uppermost plates may also include generally vertical sections which form annular-like flow areas which assist the natural circulation cooling.

NaYF{sub 4}:Er,Yb/Bi{sub 2}MoO{sub 6} core/shell nanocomposite: A highly efficient visible-light-driven photocatalyst utilizing upconversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yuanyuan; Wang, Wenzhong, E-mail: wzwang@mail.sic.ac.cn; Sun, Songmei

2014-04-01

Highlights: • Design and synthesis of NaYF{sub 4}:Er,Yb/Bi{sub 2}MoO{sub 6} based on upconversion. • NaYF{sub 4}:Er,Yb/Bi{sub 2}MoO{sub 6} nanocomposite was prepared for the first time. • Core–shell structure benefits the properties. • Upconversion contributed to the enhanced photocatalytic activity. • Helps to understand the functionality of new type photocatalysts. - Abstract: NaYF{sub 4}:Er,Yb/Bi{sub 2}MoO{sub 6} core/shell nanocomposite was designed and prepared for the first time based on upconversion. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution TEM (HRTEM), energy dispersive X-ray spectroscopy (EDS) and diffuse reflectance spectra (DRS). The results revealed that the as-synthesizedmore » NaYF{sub 4}:Er,Yb/Bi{sub 2}MoO{sub 6} consisted of spheres with a core diameter of about 26 nm and a shell diameter of around 6 nm. The core was upconversion illuminant NaYF{sub 4}:Er,Yb and the shell was Bi{sub 2}MoO{sub 6} around the core, which was confirmed by EDS. The NaYF{sub 4}:Er,Yb/Bi{sub 2}MoO{sub 6} exhibited higher photocatalytic activity for the photodecomposition of Rhodamine B (RhB) under the irradiation of Xe lamp and green light emitting diode (g-LED). The mechanism of the high photocatalytic activity was discussed by photoluminescence spectra (PL), which is mainly attributed to upconversion of NaYF{sub 4}:Er,Yb in the NaYF{sub 4}:Er,Yb/Bi{sub 2}MoO{sub 6} nanocomposite and the core–shell structure.« less

Temperature profiles of different cooling methods in porcine pancreas procurement.

PubMed

Weegman, Bradley P; Suszynski, Thomas M; Scott, William E; Ferrer Fábrega, Joana; Avgoustiniatos, Efstathios S; Anazawa, Takayuki; O'Brien, Timothy D; Rizzari, Michael D; Karatzas, Theodore; Jie, Tun; Sutherland, David E R; Hering, Bernhard J; Papas, Klearchos K

2014-01-01

Porcine islet xenotransplantation is a promising alternative to human islet allotransplantation. Porcine pancreas cooling needs to be optimized to reduce the warm ischemia time (WIT) following donation after cardiac death, which is associated with poorer islet isolation outcomes. This study examines the effect of four different cooling Methods on core porcine pancreas temperature (n = 24) and histopathology (n = 16). All Methods involved surface cooling with crushed ice and chilled irrigation. Method A, which is the standard for porcine pancreas procurement, used only surface cooling. Method B involved an intravascular flush with cold solution through the pancreas arterial system. Method C involved an intraductal infusion with cold solution through the major pancreatic duct, and Method D combined all three cooling Methods. Surface cooling alone (Method A) gradually decreased core pancreas temperature to <10 °C after 30 min. Using an intravascular flush (Method B) improved cooling during the entire duration of procurement, but incorporating an intraductal infusion (Method C) rapidly reduced core temperature 15-20 °C within the first 2 min of cooling. Combining all methods (Method D) was the most effective at rapidly reducing temperature and providing sustained cooling throughout the duration of procurement, although the recorded WIT was not different between Methods (P = 0.36). Histological scores were different between the cooling Methods (P = 0.02) and the worst with Method A. There were differences in histological scores between Methods A and C (P = 0.02) and Methods A and D (P = 0.02), but not between Methods C and D (P = 0.95), which may highlight the importance of early cooling using an intraductal infusion. In conclusion, surface cooling alone cannot rapidly cool large (porcine or human) pancreata. Additional cooling with an intravascular flush and intraductal infusion results in improved core porcine pancreas temperature profiles during procurement and

Temperature Profiles of Different Cooling Methods in Porcine Pancreas Procurement

PubMed Central

Weegman, Brad P.; Suszynski, Thomas M.; Scott, William E.; Ferrer, Joana; Avgoustiniatos, Efstathios S.; Anazawa, Takayuki; O’Brien, Timothy D.; Rizzari, Michael D.; Karatzas, Theodore; Jie, Tun; Sutherland, David ER.; Hering, Bernhard J.; Papas, Klearchos K.

2014-01-01

Background Porcine islet xenotransplantation is a promising alternative to human islet allotransplantation. Porcine pancreas cooling needs to be optimized to reduce the warm ischemia time (WIT) following donation after cardiac death, which is associated with poorer islet isolation outcomes. Methods This study examines the effect of 4 different cooling Methods on core porcine pancreas temperature (n=24) and histopathology (n=16). All Methods involved surface cooling with crushed ice and chilled irrigation. Method A, which is the standard for porcine pancreas procurement, used only surface cooling. Method B involved an intravascular flush with cold solution through the pancreas arterial system. Method C involved an intraductal infusion with cold solution through the major pancreatic duct, and Method D combined all 3 cooling Methods. Results Surface cooling alone (Method A) gradually decreased core pancreas temperature to < 10 °C after 30 minutes. Using an intravascular flush (Method B) improved cooling during the entire duration of procurement, but incorporating an intraductal infusion (Method C) rapidly reduced core temperature 15–20 °C within the first 2 minutes of cooling. Combining all methods (Method D) was the most effective at rapidly reducing temperature and providing sustained cooling throughout the duration of procurement, although the recorded WIT was not different between Methods (p=0.36). Histological scores were different between the cooling Methods (p=0.02) and the worst with Method A. There were differences in histological scores between Methods A and C (p=0.02) and Methods A and D (p=0.02), but not between Methods C and D (p=0.95), which may highlight the importance of early cooling using an intraductal infusion. Conclusions In conclusion, surface cooling alone cannot rapidly cool large (porcine or human) pancreata. Additional cooling with an intravascular flush and intraductal infusion results in improved core porcine pancreas temperature

The Merging Galaxy Cluster A520 - A Broken-Up Cool Core, A Dark Subcluster, and an X-Ray Channel

NASA Technical Reports Server (NTRS)

Wang, Qian H.S.; Markevitch, Maxim; Giacintucci, Simona

2016-01-01

We present results from a deep Chandra X-ray observation of a merging galaxy cluster A520. A high-resolution gas temperature map reveals a long trail of dense, cool clumpsapparently the fragments of a cool core that has been stripped from the infalling subcluster by ram pressure. The clumps should still be connected by the stretched magnetic field lines. The observed temperature variations imply that thermal conductivity is suppressed by a factor greater than 100 across the presumed direction of the magnetic field (as found in other clusters), and is also suppressed along the field lines by a factor of several. Two massive clumps in the periphery of A520, visible in the weak-lensing mass map and the X-ray image, have apparently been completely stripped of gas during the merger, but then re-accreted the surrounding high-entropy gas upon exit from the cluster. The mass clump that hosted the stripped cool core is also re-accreting hotter gas. An X-ray hydrostatic mass estimate for the clump that has the simplest geometry agrees with the lensing mass. Its current gas mass to total mass ratio is very low, 1.5 percent to 3 percent, which makes it a "dark subcluster." We also found a curious low X-ray brightness channel (likely a low-density sheet in projection) going across the cluster along the direction of an apparent secondary merger. The channel may be caused by plasma depletion in a region of an amplified magnetic field (with plasma Beta approximately equal to 10-20). The shock in A520 will be studied in a separate paper.

Inner Core Rotation from Geomagnetic Westward Drift and a Stationary Spherical Vortex in Earth's Core

NASA Technical Reports Server (NTRS)

Voorhies, Coerte V.

1998-01-01

The idea that geomagnetic westward drift indicates convective leveling of the planetary momentum gradient within Earth's core is pursued in search of a differentially rotating mean state, upon which various oscillations and secular effects might be superimposed. The desired state conforms to roughly spherical boundary conditions, minimizes dissipative interference with convective cooling in the bulk of the core, yet may aid core cooling by depositing heat in the uppermost core and lower mantle. The variational calculus of stationary dissipation applied to a spherical vortex within the core yields an interesting differential rotation profile, akin to spherical Couette flow bounded by thin Hartmann layers. Four boundary conditions are required. To concentrate shear induced dissipation near the core-mantle boundary, these are taken to be: (i) no-slip at the core-mantle interface; (ii) geomagnetically estimated bulk westward flow at the base of the core-mantle boundary layer; (iii) no-slip at the inner-outer core interface; and, to describe magnetic locking of the inner core to the deep outer core; (iv) hydrodynamically stress-free at the inner-outer core boundary. By boldly assuming the axial core angular momentum anomaly to be zero, the super-rotation of the inner core relative to the mantle is calculated to be at most 1.5 deg./yr.

Inner Core Rotation from Geomagnetic Westward Drift and a Stationary Spherical Vortex in Earth's Core

NASA Technical Reports Server (NTRS)

Voorhies, C. V.

1999-01-01

The idea that geomagnetic westward drift indicates convective leveling of the planetary momentum gradient within Earth's core is pursued in search of a differentially rotating mean state, upon which various oscillations and secular effects might be superimposed. The desired state conforms to roughly spherical boundary conditions, minimizes dissipative interference with convective cooling in the bulk of the core, yet may aide core cooling by depositing heat in the uppermost core and lower mantle. The variational calculus of stationary dissipation applied to a spherical vortex within the core yields an interesting differential rotation profile akin to spherical Couette flow bounded by thin Hartmann layers. Four boundary conditions are required. To concentrate shear induced dissipation near the core-mantle boundary, these are taken to be: (i) no-slip at the core-mantle interface; (ii) geomagnetically estimated bulk westward flow at the base of the core-mantle boundary layer; (iii) no-slip at the inner-outer core interface; and, to describe magnetic locking of the inner core to the deep outer core, (iv) hydrodynamically stress-free at the inner-outer core boundary. By boldly assuming the axial core angular momentum anomaly to be zero, the super-rotation of the inner core is calculated to be at most 1.5 degrees per year.

Heating and Cooling Rates With an Esophageal Heat Exchange System.

PubMed

Kalasbail, Prathima; Makarova, Natalya; Garrett, Frank; Sessler, Daniel I

2018-04-01

The Esophageal Cooling Device circulates warm or cool water through an esophageal heat exchanger, but warming and cooling efficacy in patients remains unknown. We therefore determined heat exchange rates during warming and cooling. Nineteen patients completed the trial. All had general endotracheal anesthesia for nonthoracic surgery. Intraoperative heat transfer was measured during cooling (exchanger fluid at 7°C) and warming (fluid at 42°C). Each was evaluated for 30 minutes, with the initial condition determined randomly, starting at least 40 minutes after induction of anesthesia. Heat transfer rate was estimated from fluid flow through the esophageal heat exchanger and inflow and outflow temperatures. Core temperature was estimated from a zero-heat-flux thermometer positioned on the forehead. Mean heat transfer rate during warming was 18 (95% confidence interval, 16-20) W, which increased core temperature at a rate of 0.5°C/h ± 0.6°C/h (mean ± standard deviation). During cooling, mean heat transfer rate was -53 (-59 to -48) W, which decreased core temperature at a rate of 0.9°C/h ± 0.9°C/h. Esophageal warming transferred 18 W which is considerably less than the 80 W reported with lower or upper body forced-air covers. However, esophageal warming can be used to supplement surface warming or provide warming in cases not amenable to surface warming. Esophageal cooling transferred more than twice as much heat as warming, consequent to the much larger difference between core and circulating fluid temperature with cooling (29°C) than warming (6°C). Esophageal cooling extracts less heat than endovascular catheters but can be used to supplement catheter-based cooling or possibly replace them in appropriate patients.

Effects of Cooling During Exercise on Thermoregulatory Responses of Men With Paraplegia.

PubMed

Bongers, Coen C W G; Eijsvogels, Thijs M H; van Nes, Ilse J W; Hopman, Maria T E; Thijssen, Dick H J

2016-05-01

People with spinal cord injury (SCI) have an altered afferent input to the thermoregulatory center, resulting in a reduced efferent response (vasomotor control and sweating capacity) below the level of the lesion. Consequently, core body temperature rises more rapidly during exercise in individuals with SCI compared with people who are able-bodied. Cooling strategies may reduce the thermophysiological strain in SCI. The aim of this study was to examine the effects of a cooling vest on the core body temperature response of people with a thoracic SCI during submaximal exercise. Ten men (mean age=44 years, SD=11) with a thoracic lesion (T4-T5 or below) participated in this randomized crossover study. Participants performed two 45-minute exercise bouts at 50% maximal workload (ambient temperature 25°C), with participants randomized to a group wearing a cooling vest or a group wearing no vest (separate days). Core body temperature and skin temperature were continuously measured, and thermal sensation was assessed every 3 minutes. Exercise resulted in an increased core body temperature, skin temperature, and thermal sensation, whereas cooling did not affect core body temperature. The cooling vest effectively decreased skin temperature, increased the core-to-trunk skin temperature gradient, and tended to lower thermal sensation compared with the control condition. The lack of differences in core body temperature among conditions may be a result of the relative moderate ambient temperature in which the exercise was performed. Despite effectively lowering skin temperature and increasing the core-to-trunk skin temperature gradient, there was no impact of the cooling vest on the exercise-induced increase in core body temperature in men with low thoracic SCI. © 2016 American Physical Therapy Association.

COOLED NEUTRONIC REACTOR

DOEpatents

Binner, C.R.; Wilkie, C.B.

1958-03-18

This patent relates to a design for a reactor of the type in which a fluid coolant is flowed through the active portion of the reactor. This design provides for the cooling of the shielding material as well as the reactor core by the same fluid coolant. The core structure is a solid moderator having coolant channels in which are disposed the fuel elements in rod or slug form. The coolant fluid enters the chamber in the shield, in which the core is located, passes over the inner surface of said chamber, enters the core structure at the center, passes through the coolant channels over the fuel elements and out through exhaust ducts.

Internally Cooled Monolithic Silicon Nitride Aerospace Components

NASA Technical Reports Server (NTRS)

Best, Jonathan E.; Cawley, James D.; Bhatt, Ramakrishna T.; Fox, Dennis S.; Lang, Jerry (Technical Monitor)

2000-01-01

A set of rapid prototyping (RP) processes have been combined with gelcasting to make ceramic aerospace components that contain internal cooling geometry. A mold and core combination is made using a MM6Pro (Sanders Prototyping, Inc.) and SLA-250/40 (3Dsystems, Inc.). The MM6Pro produces cores from ProtoBuild (trademarked) wax that are dissolved in room temperature ethanol following gelcasting. The SLA-250/40 yields epoxy/acrylate reusable molds. Parts produced by this method include two types of specimens containing a high density of thin long cooling channels, thin-walled cylinders and plates, as well as a model hollow airfoil shape that can be used for burner rig evaluation of coatings. Both uncoated and mullite-coated hollow airfoils has been tested in a Mach 0.3 burner rig with cooling air demonstrating internal cooling and confirming the effectiveness of mullite coatings.

Apparatus for controlling molten core debris

DOEpatents

Golden, Martin P. [Trafford, PA; Tilbrook, Roger W. [Monroeville, PA; Heylmun, Neal F. [Pittsburgh, PA

1977-07-19

Apparatus for containing, cooling, diluting, dispersing and maintaining subcritical the molten core debris assumed to melt through the bottom of a nuclear reactor pressure vessel in the unlikely event of a core meltdown. The apparatus is basically a sacrificial bed system which includes an inverted conical funnel, a core debris receptacle including a spherical dome, a spherically layered bed of primarily magnesia bricks, a cooling system of zig-zag piping in graphite blocks about and below the bed and a cylindrical liner surrounding the graphite blocks including a steel shell surrounded by firebrick. Tantalum absorber rods are used in the receptacle and bed.

Direct cooled power electronics substrate

DOEpatents

Wiles, Randy H [Powell, TN; Wereszczak, Andrew A [Oak Ridge, TN; Ayers, Curtis W [Kingston, TN; Lowe, Kirk T [Knoxville, TN

2010-09-14

The disclosure describes directly cooling a three-dimensional, direct metallization (DM) layer in a power electronics device. To enable sufficient cooling, coolant flow channels are formed within the ceramic substrate. The direct metallization layer (typically copper) may be bonded to the ceramic substrate, and semiconductor chips (such as IGBT and diodes) may be soldered or sintered onto the direct metallization layer to form a power electronics module. Multiple modules may be attached to cooling headers that provide in-flow and out-flow of coolant through the channels in the ceramic substrate. The modules and cooling header assembly are preferably sized to fit inside the core of a toroidal shaped capacitor.

Method of detecting leakage of reactor core components of liquid metal cooled fast reactors

DOEpatents

Holt, Fred E.; Cash, Robert J.; Schenter, Robert E.

1977-01-01

A method of detecting the failure of a sealed non-fueled core component of a liquid-metal cooled fast reactor having an inert cover gas. A gas mixture is incorporated in the component which includes Xenon-124; under neutron irradiation, Xenon-124 is converted to radioactive Xenon-125. The cover gas is scanned by a radiation detector. The occurrence of 188 Kev gamma radiation and/or other identifying gamma radiation-energy level indicates the presence of Xenon-125 and therefore leakage of a component. Similarly, Xe-126, which transmutes to Xe-127 and Kr-84, which produces Kr-85.sup.m can be used for detection of leakage. Different components are charged with mixtures including different ratios of isotopes other than Xenon-124. On detection of the identifying radiation, the cover gas is subjected to mass spectroscopic analysis to locate the leaking component.

Mid-Cretaceous oblique rifting of West Antarctica: Emplacement and rapid cooling of the Fosdick Mountains migmatite-cored gneiss dome

USGS Publications Warehouse

McFadden, Rory; Teyssier, Christian; Siddoway, Christine; Cosca, Michael A.; Fanning, C. Mark

2015-01-01

In Marie Byrd Land, West Antarctica, the Fosdick Mountains migmatite-cored gneiss dome was exhumed from mid- to lower middle crustal depths during the incipient stage of the West Antarctic Rift system in the mid-Cretaceous. Prior to and during exhumation, major crustal melting and deformation included transfer and emplacement of voluminous granitic material and numerous intrusions of mantle-derived diorite in dikes. A succession of melt- and magma-related structures formed at temperatures in excess of 665 ± 50 °C based on Ti-in-zircon thermometry. These record a transition from wrench to oblique extensional deformation that culminated in the development of the oblique South Fosdick Detachment zone. Solid-state fabrics within the detachment zone and overprinting brittle structures record translation of the detachment zone and dome to shallow levels.To determine the duration of exhumation and cooling, we sampled granite and gneisses at high spatial resolution for U–Pb zircon geochronology and 40Ar/39Ar hornblende and biotite thermochronology. U–Pb zircon crystallization ages for the youngest granites are 102 Ma. Three hornblende ages are 103 to 100 Ma and 12 biotite ages are 101 to 99 Ma. All overlap within uncertainty. The coincidence of zircon crystallization ages with 40Ar/39Ar cooling ages indicates cooling rates > 100 °C/m.y. that, when considered together with overprinting structures, indicates rapid exhumation of granite and migmatite from deep to shallow crustal levels within a transcurrent setting. Orientations of structures and age-constrained crosscutting relationships indicate counterclockwise rotation of stretching axes from oblique extension into nearly orthogonal extension with respect to the Marie Byrd Land margin. The rotation may be a result of localized extension arising from unroofing and arching of the Fosdick dome, extensional opening within a pull-apart zone, or changes in plate boundary configuration.The rapid tectonic and

Optical properties of core-shell and multi-shell nanorods

NASA Astrophysics Data System (ADS)

Mokkath, Junais Habeeb; Shehata, Nader

2018-05-01

We report a first-principles time dependent density functional theory study of the optical response modulations in bimetallic core-shell (Na@Al and Al@Na) and multi-shell (Al@Na@Al@Na and Na@Al@Na@Al: concentric shells of Al and Na alternate) nanorods. All of the core-shell and multi-shell configurations display highly enhanced absorption intensity with respect to the pure Al and Na nanorods, showing sensitivity to both composition and chemical ordering. Remarkably large spectral intensity enhancements were found in a couple of core-shell configurations, indicative that optical response averaging based on the individual components can not be considered as true as always in the case of bimetallic core-shell nanorods. We believe that our theoretical results would be useful in promising applications depending on Aluminum-based plasmonic materials such as solar cells and sensors.

James Webb Space Telescope Core 2 Test - Cryogenic Thermal Balance Test of the Observatorys Core Area Thermal Control Hardware

NASA Technical Reports Server (NTRS)

Cleveland, Paul; Parrish, Keith; Thomson, Shaun; Marsh, James; Comber, Brian

2016-01-01

The James Webb Space Telescope (JWST), successor to the Hubble Space Telescope, will be the largest astronomical telescope ever sent into space. To observe the very first light of the early universe, JWST requires a large deployed 6.5-meter primary mirror cryogenically cooled to less than 50 Kelvin. Three scientific instruments are further cooled via a large radiator system to less than 40 Kelvin. A fourth scientific instrument is cooled to less than 7 Kelvin using a combination pulse-tube Joule-Thomson mechanical cooler. Passive cryogenic cooling enables the large scale of the telescope which must be highly folded for launch on an Ariane 5 launch vehicle and deployed once on orbit during its journey to the second Earth-Sun Lagrange point. Passive cooling of the observatory is enabled by the deployment of a large tennis court sized five layer Sunshield combined with the use of a network of high efficiency radiators. A high purity aluminum heat strap system connects the three instrument's detector systems to the radiator systems to dissipate less than a single watt of parasitic and instrument dissipated heat. JWST's large scale features, while enabling passive cooling, also prevent the typical flight configuration fully-deployed thermal balance test that is the keystone of most space missions' thermal verification plans. This paper describes the JWST Core 2 Test, which is a cryogenic thermal balance test of a full size, high fidelity engineering model of the Observatory's 'Core' area thermal control hardware. The 'Core' area is the key mechanical and cryogenic interface area between all Observatory elements. The 'Core' area thermal control hardware allows for temperature transition of 300K to approximately 50 K by attenuating heat from the room temperature IEC (instrument electronics) and the Spacecraft Bus. Since the flight hardware is not available for test, the Core 2 test uses high fidelity and flight-like reproductions.

Strategy for thermometry via Tm³⁺-doped NaYF₄ core-shell nanoparticles.

PubMed

Zhou, Shaoshuai; Jiang, Guicheng; Li, Xinyue; Jiang, Sha; Wei, Xiantao; Chen, Yonghu; Yin, Min; Duan, Changkui

2014-12-01

Optical thermometers usually make use of the fluorescence intensity ratio of two thermally coupled energy levels, with the relative sensitivity constrained by the limited energy gap. Here we develop a strategy by using the upconversion (UC) emissions originating from two multiplets with opposite temperature dependences to achieve higher relative temperature sensitivity. We show that the intensity ratio of the two UC emissions, ³F(2,3) and ¹G₄, of Tm³⁺ in β-NaYF₄:20%Yb³⁺, 0.5%Tm³⁺/NaYF₄:1%Pr³⁺ core-shell nanoparticles under 980 nm laser excitation exhibits high relative temperature sensitivity between 350 and 510 K, with a maximum of 1.53%  K⁻¹ at 417 K. This demonstrates the validity of the strategy, and that the studied material has the potential for high-performance optical thermometry.

Emergency cooling analysis for the loss of coolant malfunction

NASA Technical Reports Server (NTRS)

Peoples, J. A.

1972-01-01

This report examines the dynamic response of a conceptual space power fast-spectrum lithium cooled reactor to the loss of coolant malfunction and several emergency cooling concepts. The results show that, following the loss of primary coolant, the peak temperatures of the center most 73 fuel elements can range from 2556 K to the region of the fuel melting point of 3122 K within 3600 seconds after the start of the accident. Two types of emergency aftercooling concepts were examined: (1) full core open loop cooling and (2) partial core closed loop cooling. The full core open loop concept is a one pass method of supplying lithium to the 247 fuel pins. This method can maintain fuel temperature below the 1611 K transient damage limit but requires a sizable 22,680-kilogram auxiliary lithium supply. The second concept utilizes a redundant internal closed loop to supply lithium to only the central area of each hexagonal fuel array. By using this method and supplying lithium to only the triflute region, fuel temperatures can be held well below the transient damage limit.

Postexercise Cooling Rates in 2 Cooling Jackets

PubMed Central

Brade, Carly; Dawson, Brian; Wallman, Karen; Polglaze, Ted

2010-01-01

Abstract Context: Cooling jackets are a common method for removing stored heat accumulated during exercise. To date, the efficiency and practicality of different types of cooling jackets have received minimal investigation. Objective: To examine whether a cooling jacket containing a phase-change material (PC17) results in more rapid postexercise cooling than a gel cooling jacket and a no-jacket (control) condition. Design: Randomized, counterbalanced design with 3 experimental conditions. Setting: Participants exercised at 75% V̇o2max workload in a hot climate chamber (temperature  =  35.0 ± 1.4°C, relative humidity  =  52 ± 4%) for 30 minutes, followed by postexercise cooling for 30 minutes in cool laboratory conditions (ambient temperature  =  24.9 ± 1.8°C, relative humidity  =  39% ± 10%). Patients or Other Participants: Twelve physically active men (age  =  21.3 ± 1.1 years, height  =  182.7 ± 7.1 cm, body mass  =  76.2 ± 9.5 kg, sum of 6 skinfolds  =  50.5 ± 6.9 mm, body surface area  =  1.98 ± 0.14 m2, V̇o2max  =  49.0 ± 7.0 mL·kg−1·min−1) participated. Intervention(s): Three experimental conditions, consisting of a PC17 jacket, a gel jacket, and no jacket. Main Outcome Measure(s): Core temperature (TC), mean skin temperature (TSk), and TC cooling rate (°C/min). Results: Mean peak TC postexercise was 38.49 ± 0.42°C, 38.57 ± 0.41°C, and 38.55 ± 0.40°C for the PC17 jacket, gel jacket, and control conditions, respectively. No differences were observed in peak TC cooling rates among the PC17 jacket (0.038 ± 0.007°C/min), gel jacket (0.040 ± 0.009°C/min), and control (0.034 ± 0.010°C/min, P > .05) conditions. Between trials, no differences were calculated for mean TSk cooling. Conclusions: Similar cooling rates for all 3 conditions indicate that there is no benefit associated with wearing the PC17 or gel jacket. PMID:20210620

Cooling interventions for athletes: An overview of effectiveness, physiological mechanisms, and practical considerations

PubMed Central

Bongers, Coen C. W. G.; Hopman, Maria T. E.; Eijsvogels, Thijs M. H.

2017-01-01

ABSTRACT Exercise-induced increases in core body temperature could negative impact performance and may lead to development of heat-related illnesses. The use of cooling techniques prior (pre-cooling), during (per-cooling) or directly after (post-cooling) exercise may limit the increase in core body temperature and therefore improve exercise performance. The aim of the present review is to provide a comprehensive overview of current scientific knowledge in the field of pre-cooling, per-cooling and post-cooling. Based on existing studies, we will discuss 1) the effectiveness of cooling interventions, 2) the underlying physiological mechanisms and 3) practical considerations regarding the use of different cooling techniques. Furthermore, we tried to identify the optimal cooling technique and compared whether cooling-induced performance benefits are different between cool, moderate and hot ambient conditions. This article provides researchers, physicians, athletes and coaches with important information regarding the implementation of cooling techniques to maintain exercise performance and to successfully compete in thermally stressful conditions. PMID:28349095

THE COOLING REQUIREMENTS AND PROCESS SYSTEMS OF THE SOUTH AFRICAN RESEARCH REACTOR, SAFARI 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colley, J.R.

1962-12-01

The SAFARI 1 research reactor is cooled and moderated by light water. There are three process systems, a primary water system which cools the reactor core and surroundings, a pool water system, and a secondary water system which removes the heat from the primary and pool systems. The cooling requirements for the reactor core and experimental facilities are outlined, and the cooling and purification functions of the three process systems are described. (auth)

Late-time Cooling of Neutron Star Transients and the Physics of the Inner Crust

NASA Astrophysics Data System (ADS)

Deibel, Alex; Cumming, Andrew; Brown, Edward F.; Reddy, Sanjay

2017-04-01

An accretion outburst onto a neutron star transient heats the neutron star’s crust out of thermal equilibrium with the core. After the outburst, the crust thermally relaxes toward equilibrium with the neutron star core, and the surface thermal emission powers the quiescent X-ray light curve. Crust cooling models predict that thermal equilibrium of the crust will be established ≈ 1000 {days} into quiescence. Recent observations of the cooling neutron star transient MXB 1659-29, however, suggest that the crust did not reach thermal equilibrium with the core on the predicted timescale and continued to cool after ≈ 2500 {days} into quiescence. Because the quiescent light curve reveals successively deeper layers of the crust, the observed late-time cooling of MXB 1659-29 depends on the thermal transport in the inner crust. In particular, the observed late-time cooling is consistent with a low thermal conductivity layer near the depth predicted for nuclear pasta that maintains a temperature gradient between the neutron star’s inner crust and core for thousands of days into quiescence. As a result, the temperature near the crust-core boundary remains above the critical temperature for neutron superfluidity, and a layer of normal neutrons forms in the inner crust. We find that the late-time cooling of MXB 1659-29 is consistent with heat release from a normal neutron layer near the crust-core boundary with a long thermal time. We also investigate the effect of inner crust physics on the predicted cooling curves of the accreting transient KS 1731-260 and the magnetar SGR 1627-41.

Simulation of cracking cores when molding piston components

NASA Astrophysics Data System (ADS)

Petrenko, Alena; Soukup, Josef

2014-08-01

The article deals with pistons casting made from aluminum alloy. Pistons are casting at steel mold with steel core. The casting is provided by gravity casting machine. The each machine is equipped by two metal molds, which are preheated above temperature 160 °C before use. The steel core is also preheated by flame. The metal molds and cores are heated up within the casting process. The temperature of the metal mold raise up to 200 °C and temperature of core is higher. The surface of the core is treated by nitration. The mold and core are cooled down by water during casting process. The core is overheated and its top part is finally cracked despite its intensive water-cooling. The life time cycle of the core is decreased to approximately 5 to 15 thousands casting, which is only 15 % of life time cycle of core for production of other pistons. The article presents the temperature analysis of the core.

Experimental studies on metallic fuel relocation in a single-pin core structure of a sodium-cooled fast reactor

DOE PAGES

Kim, Taeil; Harbaruk, Dzmitry; Gerardi, Craig; ...

2017-07-10

Experiments dropping molten uranium into test sections of single fuel pin geometry filled with sodium were conducted to investigate relocation behavior of metallic fuel in the core structures of sodium-cooled fast reactors during a hypothetical core disruptive accident. Metallic uranium was used as a fuel material and HT-9M was used as a fuel cladding material in the experiment in order to accurately mock-up the thermo-physical behavior of the relocation. The fuel cladding failed due to eutectic formation between the uranium and HT-9M for all experiments. The extent of the eutectic formation increased with increasing molten uranium temperature. Voids in themore » relocated fuel were observed for all experiments and were likely formed by sodium boiling in contact with the fuel. In one experiment, numerous fragments of the relocated fuel were found. In conclusion, it could be concluded that the injected metallic uranium fuel was fragmented and dispersed in the narrow coolant channel by sodium boiling« less

Experimental studies on metallic fuel relocation in a single-pin core structure of a sodium-cooled fast reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Taeil; Harbaruk, Dzmitry; Gerardi, Craig

Experiments dropping molten uranium into test sections of single fuel pin geometry filled with sodium were conducted to investigate relocation behavior of metallic fuel in the core structures of sodium-cooled fast reactors during a hypothetical core disruptive accident. Metallic uranium was used as a fuel material and HT-9M was used as a fuel cladding material in the experiment in order to accurately mock-up the thermo-physical behavior of the relocation. The fuel cladding failed due to eutectic formation between the uranium and HT-9M for all experiments. The extent of the eutectic formation increased with increasing molten uranium temperature. Voids in themore » relocated fuel were observed for all experiments and were likely formed by sodium boiling in contact with the fuel. In one experiment, numerous fragments of the relocated fuel were found. In conclusion, it could be concluded that the injected metallic uranium fuel was fragmented and dispersed in the narrow coolant channel by sodium boiling« less

Lanthanide-doped NaGdF4 core-shell nanoparticles for non-contact self-referencing temperature sensors.

PubMed

Zheng, Shuhong; Chen, Weibo; Tan, Dezhi; Zhou, Jiajia; Guo, Qiangbing; Jiang, Wei; Xu, Cheng; Liu, Xiaofeng; Qiu, Jianrong

2014-06-07

We report that non-contact self-referencing temperature sensors can be realized with the use of core-shell nanostructures. These lanthanide-based nanothermometers (NaGdF4:Yb(3+)/Tm(3+)@Tb(3+)/Eu(3+)) exhibit higher sensitivity in a wide range from 125 to 300 K based on two emissions of Tb(3+) at 545 nm and Eu(3+) at 615 nm under near-infrared laser excitation.

Demonstration of passively cooled high-power Yb fiber amplifier

NASA Astrophysics Data System (ADS)

Bradford, Joshua; Cook, Justin; Antonio-Lopez, Jose Enrique; Shah, Larry; Amezcua Correa, Rodrigo; Richardson, Martin

2018-02-01

This work investigates the feasibility of passive cooling in high-power Yb amplifiers. Experimentally, an all-glass airclad step-index (ACSI) amplifier is diode-pumped with 400W and provides 200W power levels. With only natural convection to extract heat, core temperatures are estimated near 130°C with no degradation of performance relative to cooled architectures. Further, advanced analysis techniques allow for core temperature determination using thermal interferometry without the need for complicated stabilization or calibration.

GAS COOLED NUCLEAR REACTORS

DOEpatents

Long, E.; Rodwell, W.

1958-06-10

A gas-cooled nuclear reactor consisting of a graphite reacting core and reflector structure supported in a containing vessel is described. A gas sealing means is included for sealing between the walls of the graphite structure and containing vessel to prevent the gas coolant by-passing the reacting core. The reacting core is a multi-sided right prismatic structure having a pair of parallel slots around its periphery. The containing vessel is cylindrical and has a rib on its internal surface which supports two continuous ring shaped flexible web members with their radially innermost ends in sealing engagement within the radially outermost portion of the slots. The core structure is supported on ball bearings. This design permits thermal expansion of the core stracture and vessel while maintainirg a peripheral seal between the tvo elements.

Prognostic meaning of neutrophil to lymphocyte ratio (NLR) and lymphocyte to monocyte ration (LMR) in newly diagnosed Hodgkin lymphoma patients treated upfront with a PET-2 based strategy.

PubMed

Romano, Alessandra; Parrinello, Nunziatina Laura; Vetro, Calogero; Chiarenza, Annalisa; Cerchione, Claudio; Ippolito, Massimo; Palumbo, Giuseppe Alberto; Di Raimondo, Francesco

2018-06-01

Recent reports identify NLR (the ratio between absolute neutrophils counts, ANC, and absolute lymphocyte count, ALC), as predictor of progression-free survival (PFS) and overall survival (OS) in cancer patients. We retrospectively tested NLR and LMR (the ratio between absolute lymphocyte and monocyte counts) in newly diagnosed Hodgkin lymphoma (HL) patients treated upfront with a PET-2 risk-adapted strategy. NLR and LMR were calculated using records obtained from the complete blood count (CBC) from 180 newly diagnosed HL patients. PFS was evaluated accordingly to Kaplan-Meier method. Higher NLR was associated to advanced stage, increased absolute counts of neutrophils and reduced count of lymphocytes, and markers of systemic inflammation. After a median follow-up of 68 months, PFS at 60 months was 86.6% versus 70.1%, respectively, in patients with NLR ≥ 6 or NLR < 6. Predictors of PFS at 60 months were PET-2 scan (p < 0.0001), NLR ≥ 6.0 (p = 0.02), LMR < 2 (p = 0.048), and ANC (p = 0.0059) in univariate analysis, but only PET-2 was an independent predictor of PFS in multivariate analysis. Advanced-stage patients (N = 119) were treated according to a PET-2 risk-adapted protocol, with an early switch to BEACOPP regimen in case of PET-2 positivity. Despite this strategy, patients with positive PET-2 still had an inferior outcome, with PFS at 60 months of 84.7% versus 40.1% (negative and positive PET-2 patients, respectively, p < 0.0001). Independent predictors of PFS by multivariate analysis were PET-2 status and to a lesser extend NLR in advanced stage, while LMR maintained its significance in early stage. By focusing on PET-2 negative patients, we found that patients with NLR ≥ 6.0 or LMR < 2 had an inferior outcome compared to patients with both ratios above the cutoff (78.7 versus 91.9 months, p = 0.01). We confirm NLR as predictor of PFS in HL patients independently from stage at diagnosis

Cooling rates of group IVA iron meteorites

NASA Technical Reports Server (NTRS)

Willis, J.; Wasson, J. T.

1978-01-01

Cooling rates of six group IVA iron meteorites were estimated by a taenite central Ni concentration-taenite half-width method. Calculated cooling rates range from 13 to 25 C/Myr, with an average of 20 C/Myr. No correlation between cooling rate and bulk Ni content is observed, and the data appear to be consistent with a uniform cooling rate as expected from an igneous core origin. This result differs from previous studies reporting a wide range in cooling rates that were strongly correlated with bulk Ni content. The differences result mainly from differences in the phase diagram and the selected diffusion coefficients. Cooling rates inferred from taenite Ni concentrations at the interface with kamacite are consistent with those based on taenite central Ni content.

Gfr Core Neutronics Studies at CEA

NASA Astrophysics Data System (ADS)

Bosq, J. C.; Brun-Magaud, V.; Rimpault, G.; Tommasi, J.; Conti, A.; Garnier, J. C.

2006-04-01

The Gas cooled Fast Reactor (GFR) is a high priority in the CEA R&D program on Future Nuclear Energy Systems. After preliminary neutronics and thermo-aerolic studies, a first He-cooled 2400MWth core design based on a series of carbide CERCER plates arranged in an hexagonal wrapper were selected. Although GFR subassembly and core design studies are still at an early stage of development, it is nonetheless possible to identify a number of nuclear data needs that could have some impact on the actual design: new materials, decay heat contributors….

Apparatus for controlling molten core debris. [LMFBR

DOEpatents

Golden, M.P.; Tilbrook, R.W.; Heylmun, N.F.

1977-07-19

Disclosed is an apparatus for containing, cooling, diluting, dispersing and maintaining subcritical the molten core debris assumed to melt through the bottom of a nuclear reactor pressure vessel in the unlikely event of a core meltdown. The apparatus is basically a sacrificial bed system which includes an inverted conical funnel, a core debris receptacle including a spherical dome, a spherically layered bed of primarily magnesia bricks, a cooling system of zig-zag piping in graphite blocks about and below the bed and a cylindrical liner surrounding the graphite blocks including a steel shell surrounded by firebrick. Tantalum absorber rods are used in the receptacle and bed. 9 claims, 22 figures.

Dynamics of core accretion

DOE PAGES

Nelson, Andrew F.; Ruffert, Maximilian

2012-12-21

In this paper, we perform three-dimensional hydrodynamic simulations of gas flowing around a planetary core of mass M pl = 10M ⊕ embedded in a near Keplerian background flow, using a modified shearing box approximation. We assume an ideal gas behaviour following an equation of state with a fixed ratio of the specific heats, γ = 1.42, consistent with the conditions of a moderate-temperature background disc with solar composition. No radiative heating or cooling is included in the models. We employ a nested grid hydrodynamic code implementing the ‘Piecewise Parabolic Method’ with as many as six fixed nested grids, providingmore » spatial resolution on the finest grid comparable to the present-day diameters of Neptune and Uranus. We find that a strongly dynamically active flow develops such that no static envelope can form. The activity is not sensitive to plausible variations in the rotation curve of the underlying disc. It is sensitive to the thermodynamic treatment of the gas, as modelled by prescribed equations of state (either ‘locally isothermal’ or ‘locally isentropic’) and the temperature of the background disc material. The activity is also sensitive to the shape and depth of the core's gravitational potential, through its mass and gravitational softening coefficient. Each of these factors influences the magnitude and character of hydrodynamic feedback of the small-scale flow on the background, and we conclude that accurate modelling of such feedback is critical to a complete understanding of the core accretion process. The varying flow pattern gives rise to large, irregular eruptions of matter from the region around the core which return matter to the background flow: mass in the envelope at one time may not be found in the envelope at any later time. No net mass accretion into the envelope is observed over the course of the simulation and none is expected, due to our neglect of cooling. Except in cases of very rapid cooling however, as

Dynamics of core accretion

NASA Astrophysics Data System (ADS)

Nelson, Andrew F.; Ruffert, Maximilian

2013-02-01

We perform three-dimensional hydrodynamic simulations of gas flowing around a planetary core of mass Mpl = 10M⊕ embedded in a near Keplerian background flow, using a modified shearing box approximation. We assume an ideal gas behaviour following an equation of state with a fixed ratio of the specific heats, γ = 1.42, consistent with the conditions of a moderate-temperature background disc with solar composition. No radiative heating or cooling is included in the models. We employ a nested grid hydrodynamic code implementing the `Piecewise Parabolic Method' with as many as six fixed nested grids, providing spatial resolution on the finest grid comparable to the present-day diameters of Neptune and Uranus. We find that a strongly dynamically active flow develops such that no static envelope can form. The activity is not sensitive to plausible variations in the rotation curve of the underlying disc. It is sensitive to the thermodynamic treatment of the gas, as modelled by prescribed equations of state (either `locally isothermal' or `locally isentropic') and the temperature of the background disc material. The activity is also sensitive to the shape and depth of the core's gravitational potential, through its mass and gravitational softening coefficient. Each of these factors influences the magnitude and character of hydrodynamic feedback of the small-scale flow on the background, and we conclude that accurate modelling of such feedback is critical to a complete understanding of the core accretion process. The varying flow pattern gives rise to large, irregular eruptions of matter from the region around the core which return matter to the background flow: mass in the envelope at one time may not be found in the envelope at any later time. No net mass accretion into the envelope is observed over the course of the simulation and none is expected, due to our neglect of cooling. Except in cases of very rapid cooling however, as defined by locally isothermal or

Limits on turbulent propagation of energy in cool-core clusters of galaxies

NASA Astrophysics Data System (ADS)

Bambic, C. J.; Pinto, C.; Fabian, A. C.; Sanders, J.; Reynolds, C. S.

2018-04-01

We place constraints on the propagation velocity of bulk turbulence within the intracluster medium of three clusters and an elliptical galaxy. Using Reflection Grating Spectrometer measurements of turbulent line broadening, we show that for these clusters, the 90% upper limit on turbulent velocities when accounting for instrumental broadening is too low to propagate energy radially to the cooling radius of the clusters within the required cooling time. In this way, we extend previous Hitomi-based analysis on the Perseus cluster to more clusters, with the intention of applying these results to a future, more extensive catalog. These results constrain models of turbulent heating in AGN feedback by requiring a mechanism which can not only provide sufficient energy to offset radiative cooling, but resupply that energy rapidly enough to balance cooling at each cluster radius.

Casting core for a cooling arrangement for a gas turbine component

DOEpatents

Lee, Ching-Pang; Heneveld, Benjamin E

2015-01-20

A ceramic casting core, including: a plurality of rows (162, 166, 168) of gaps (164), each gap (164) defining an airfoil shape; interstitial core material (172) that defines and separates adjacent gaps (164) in each row (162, 166, 168); and connecting core material (178) that connects adjacent rows (170, 174, 176) of interstitial core material (172). Ends of interstitial core material (172) in one row (170, 174, 176) align with ends of interstitial core material (172) in an adjacent row (170, 174, 176) to form a plurality of continuous and serpentine shaped structures each including interstitial core material (172) from at least two adjacent rows (170, 174, 176) and connecting core material (178).

Apparatus and method for controlling the temperature of the core of a super-conducting transformer

DOEpatents

Golner, Thomas; Pleva, Edward; Mehta, Shirish

2006-10-10

An apparatus for controlling the temperature of a core of a transformer is provided that includes a core, a shield surrounding the core, a cast formed between the core and the shield, and tubing positioned on the shield. The cast directs heat from the core to the shield and cooling fluid is directed through the tubing to cool the shield.

Ion-neutral-atom sympathetic cooling in a hybrid linear rf Paul and magneto-optical trap

NASA Astrophysics Data System (ADS)

Goodman, D. S.; Sivarajah, I.; Wells, J. E.; Narducci, F. A.; Smith, W. W.

2012-09-01

Long-range polarization forces between ions and neutral atoms result in large elastic scattering cross sections (e.g., ˜106a.u. for Na-Na+ or Na-Ca+ at cold and ultracold temperatures). This suggests that a hybrid ion-neutral trap should offer a general means for significant sympathetic cooling of atomic or molecular ions. We present simion 7.0 simulation results concerning the advantages and limitations of sympathetic cooling within a hybrid trap apparatus consisting of a linear rf Paul trap concentric with a Na magneto-optical trap (MOT). This paper explores the impact of various heating mechanisms on the hybrid system and how parameters related to the MOT, Paul trap, number of ions, and ion species affect the efficiency of the sympathetic cooling.

ACUTE CARDIOVASCULAR EFFECTS OF FIREFIGHTING AND ACTIVE COOLING DURING REHABILITATION

PubMed Central

Burgess, Jefferey L.; Duncan, Michael D.; Hu, Chengcheng; Littau, Sally R.; Caseman, Delayne; Kurzius-Spencer, Margaret; Davis-Gorman, Grace; McDonagh, Paul F.

2012-01-01

Objectives To determine the cardiovascular and hemostatic effects of fire suppression and post-exposure active cooling. Methods Forty-four firefighters were evaluated prior to and after a 12 minute live-fire drill. Next, 50 firefighters undergoing the same drill were randomized to post-fire forearm immersion in 10°C water or standard rehabilitation. Results In the first study, heart rate and core body temperature increased and serum C-reactive protein decreased but there were no significant changes in fibrinogen, sE-selectin or sL-selectin. The second study demonstrated an increase in blood coagulability, leukocyte count, factors VIII and X, cortisol and glucose, and a decrease in plasminogen and sP-selectin. Active cooling reduced mean core temperature, heart rate and leukocyte count. Conclusions Live-fire exposure increased core temperature, heart rate, coagulability and leukocyte count; all except coagulability were reduced by active cooling. PMID:23090161

Multicompartment Liquid-Cooling/Warming Protective Garments

NASA Technical Reports Server (NTRS)

Koscheyev, Victor S.; Leon, Gloria R.; Dancisak, Michael J.

2005-01-01

Shortened, multicompartment liquid-cooling / warming garments (LCWGs) for protecting astronauts, firefighters, and others at risk of exposure to extremes of temperature are undergoing development. Unlike prior liquid-circulation thermal-protection suits that provide either cooling or warming but not both, an LCWG as envisioned would provide cooling at some body locations and/or heating at other locations, as needed: For example, sometimes there is a need to cool the body core and to heat the extremities simultaneously. An LCWG garment of the type to be developed is said to be shortened because the liquid-cooling and - heating zones would not cover the whole body and, instead, would cover reduced areas selected for maximum heating and cooling effectiveness. Physiological research is under way to provide a rational basis for selection of the liquid-cooling and -heating areas. In addition to enabling better (relative to prior liquid-circulation garments) balancing of heat among different body regions, the use of selective heating and cooling in zones would contribute to a reduction in the amount of energy needed to operate a thermal-protection suit.

Cooling Performance Analysis of ThePrimary Cooling System ReactorTRIGA-2000Bandung

NASA Astrophysics Data System (ADS)

Irianto, I. D.; Dibyo, S.; Bakhri, S.; Sunaryo, G. R.

2018-02-01

The conversion of reactor fuel type will affect the heat transfer process resulting from the reactor core to the cooling system. This conversion resulted in changes to the cooling system performance and parameters of operation and design of key components of the reactor coolant system, especially the primary cooling system. The calculation of the operating parameters of the primary cooling system of the reactor TRIGA 2000 Bandung is done using ChemCad Package 6.1.4. The calculation of the operating parameters of the cooling system is based on mass and energy balance in each coolant flow path and unit components. Output calculation is the temperature, pressure and flow rate of the coolant used in the cooling process. The results of a simulation of the performance of the primary cooling system indicate that if the primary cooling system operates with a single pump or coolant mass flow rate of 60 kg/s, it will obtain the reactor inlet and outlet temperature respectively 32.2 °C and 40.2 °C. But if it operates with two pumps with a capacity of 75% or coolant mass flow rate of 90 kg/s, the obtained reactor inlet, and outlet temperature respectively 32.9 °C and 38.2 °C. Both models are qualified as a primary coolant for the primary coolant temperature is still below the permitted limit is 49.0 °C.

Limits on turbulent propagation of energy in cool-core clusters of galaxies

NASA Astrophysics Data System (ADS)

Bambic, C. J.; Pinto, C.; Fabian, A. C.; Sanders, J.; Reynolds, C. S.

2018-07-01

We place constraints on the propagation velocity of bulk turbulence within the intracluster medium of three clusters and an elliptical galaxy. Using Reflection Grating Spectrometer measurements of turbulent line broadening, we show that for these clusters, the 90 per cent upper limit on turbulent velocities when accounting for instrumental broadening is too low to propagate energy radially to the cooling radius of the clusters within the required cooling time. In this way, we extend previous Hitomi-based analysis on the Perseus cluster to more clusters, with the intention of applying these results to a future, more extensive catalogue. These results constrain models of turbulent heating in active galactic nucleus feedback by requiring a mechanism which can not only provide sufficient energy to offset radiative cooling but also resupply that energy rapidly enough to balance cooling at each cluster radius.

RF cavity using liquid dielectric for tuning and cooling

DOEpatents

Popovic, Milorad [Warrenville, IL; Johnson, Rolland P [Newport News, VA

2012-04-17

A system for accelerating particles includes an RF cavity that contains a ferrite core and a liquid dielectric. Characteristics of the ferrite core and the liquid dielectric, among other factors, determine the resonant frequency of the RF cavity. The liquid dielectric is circulated to cool the ferrite core during the operation of the system.

Effect of Impacts on the Cooling Rates of Differentiated Planetesimals

NASA Astrophysics Data System (ADS)

Lyons, R. J.; Bowling, T. J.; Ciesla, F. J.; Davison, T. M.; Collins, G. S.

2018-05-01

I have modeled planetismal impacts in the early solar system, following their formation, differentiation, and cooling. I found that small collisions can expose the core, resulting in more than an order of magnitude increase in the cooling rates.

Cooling of neutron stars

NASA Technical Reports Server (NTRS)

Pethick, C. J.

1992-01-01

It is at present impossible to predict the interior constitution of neutron stars based on theory and results from laboratory studies. It has been proposed that it is possible to obtain information on neutron star interiors by studying thermal radiation from their surfaces, because neutrino emission rates, and hence the temperature of the central part of a neutron star, depend on the properties of dense matter. The theory predicts that neutron stars cool relatively slowly if their cores are made up of nucleons, and cool faster if the matter is in an exotic state, such as a pion condensate, a kaon condensate, or quark matter. This view has recently been questioned by the discovery of a number of other processes that could lead to copious neutrino emission and rapid cooling.

Fabrication of cooled radial turbine rotor

NASA Technical Reports Server (NTRS)

Hammer, A. N.; Aigret, G. G.; Psichogios, T. P.; Rodgers, C.

1986-01-01

A design and fabrication program was conducted to evaluate a unique concept for constructing a cooled, high temperature radial turbine rotor. This concept, called split blade fabrication was developed as an alternative to internal ceramic coring. In this technique, the internal cooling cavity is created without flow dividers or any other detail by a solid (and therefore stronger) ceramic plate which can be more firmly anchored within the casting shell mold than can conventional detailed ceramic cores. Casting is conducted in the conventional manner, except that the finished product, instead of having finished internal cooling passages, is now a split blade. The internal details of the blade are created separately together with a carrier sheet. The inserts are superalloy. Both are produced by essentially the same software such that they are a net fit. The carrier assemblies are loaded into the split blade and the edges sealed by welding. The entire wheel is Hot Isostatic Pressed (HIPed), braze bonding the internal details to the inside of the blades. During this program, two wheels were successfully produced by the split blade fabrication technique.

Two-Phase Flow in High-Heat-Flux Micro-Channel Heat Sink for Refrigeration Cooling Applications. Part 2: Low Temperature Hybrid Micro-Channel/Micro-Jet Impingement Cooling

DTIC Science & Technology

2008-09-01

TWO-PHASE FLOW IN HIGH-HEAT-FLUX MICRO-CHANNEL HEAT SINK FOR REFRIGERATION COOLING APPLICATIONS (Contract No. N00014-05-1-0408) by Issam Mudawar ...Refrigeration Cooling Applications 5b. GRANT NUMBER N00014-04-1-0408 5c. PROGRAM ELEMENT NUMBER NA 6. AUTHOR(S) 5d. PROJECT NUMBER Mudawar , Issam NA...ABSTRACT OF Mudawar , Issam PAGES U U U UU 465 19b. TELEPHONE NUMBER (Include area code) 765-494-5705 Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std

Decrement in manual arm performance during whole body cooling.

PubMed

Giesbrecht, G G; Bristow, G K

1992-12-01

Six subjects performed three manual arm tasks: 1) prior to immersion in 8 degrees C water; 2) soon after immersion to the neck, but prior to any decrease in core temperature; and 3) every 15 min until core temperatures decreased 2-4.5 degrees C. The tasks were speed of flexion and extension of the fingers, handgrip strength and manual dexterity. There was no immediate effect of cold immersion; however, all scores decreased significantly after core temperature decreased 0.5 degrees C. Further decrease in core temperature was associated with a progressive impairment of performance, although at a slower rate than during the first 0.5 degrees C decrease. Flexion and extension of the fingers was affected relatively more than handgrip strength or manual dexterity. Decrement in performance is a result of peripheral cooling on sensorimotor function with a probable additional effect of central cooling on cerebral function.

Industry Application Emergency Core Cooling System Cladding Acceptance Criteria Early Demonstration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szilard, Ronaldo H.; Youngblood, Robert W.; Zhang, Hongbin

2015-09-01

The U. S. NRC is currently proposing rulemaking designated as “10 CFR 50.46c” to revise the loss-of-coolant-accident (LOCA)/emergency core cooling system (ECCS) acceptance criteria to include the effects of higher burnup on cladding performance as well as to address other technical issues. The NRC is also currently resolving the public comments with the final rule expected to be issued in April 2016. The impact of the final 50.46c rule on the industry may involve updating of fuel vendor LOCA evaluation models, NRC review and approval, and licensee submittal of new LOCA evaluations or re-analyses and associated technical specification revisions formore » NRC review and approval. The rule implementation process, both industry and NRC activities, is expected to take 4-6 years following the rule effective date. As motivated by the new rule, the need to use advanced cladding designs may be a result. A loss of operational margin may result due to the more restrictive cladding embrittlement criteria. Initial and future compliance with the rule may significantly increase vendor workload and licensee cost as a spectrum of fuel rod initial burnup states may need to be analyzed to demonstrate compliance. Consequently, there will be an increased focus on licensee decision making related to LOCA analysis to minimize cost and impact, and to manage margin. The proposed rule would apply to a light water reactor and to all cladding types.« less

Industry Application ECCS / LOCA Integrated Cladding/Emergency Core Cooling System Performance: Demonstration of LOTUS-Baseline Coupled Analysis of the South Texas Plant Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Hongbin; Szilard, Ronaldo; Epiney, Aaron

Under the auspices of the DOE LWRS Program RISMC Industry Application ECCS/LOCA, INL has engaged staff from both South Texas Project (STP) and the Texas A&M University (TAMU) to produce a generic pressurized water reactor (PWR) model including reactor core, clad/fuel design and systems thermal hydraulics based on the South Texas Project (STP) nuclear power plant, a 4-Loop Westinghouse PWR. A RISMC toolkit, named LOCA Toolkit for the U.S. (LOTUS), has been developed for use in this generic PWR plant model to assess safety margins for the proposed NRC 10 CFR 50.46c rule, Emergency Core Cooling System (ECCS) performance duringmore » LOCA. This demonstration includes coupled analysis of core design, fuel design, thermalhydraulics and systems analysis, using advanced risk analysis tools and methods to investigate a wide range of results. Within this context, a multi-physics best estimate plus uncertainty (MPBEPU) methodology framework is proposed.« less

Cooling System to Treat Exercise-Induced Hyperthermia

DTIC Science & Technology

2016-06-01

temperatures . Additionally, individual variations in sweat rates, ventilation rates, fitness levels, and oxygen consumption were not...gastrointestinal MHR maximum heart rate NASA National Aeronautics and Space Administration Tc core temperature UCHS uncompensated heat stress VO2peak peak oxygen consumption ...the effectiveness of a cooling pump based patient thermal management system supplied by Aspen Systems on lowering core body temperature

Optical temperature sensing of NaYbF4: Tm3+@SiO2 core-shell micro-particles induced by infrared excitation.

PubMed

Wang, Xiangfu; Zheng, Jin; Xuan, Yan; Yan, Xiaohong

2013-09-09

NaYbF(4):Tm3+@SiO(2) core-shell micro-particles were synthesized by a hydrothermal method and subsequent ultrasonic coating process. Optical temperature sensing has been observed in NaYbF4: Tm(3+)@SiO(2)core-shell micro-particles with a 980 nm infrared laser as excitation source.The fluorescence intensity ratios, optical temperature sensitivity, and temperature dependent population re-distribution ability from the thermally coupled (1)D(2)/(1)G(4) and (3)F(2) /(3)H(4) levels of the Tm(3+) ion have been analyzed as a function of temperature in the range of 100~700 K in order to check its availability as a optical temperature sensor. A better behavior as a lowtemperature sensor has been obtained with a minimum sensitivity of 5.4 × 10(-4) K(-1) at 430 K. It exhibits temperature induced population re-distribution from (1)D(2) /(1)G(4) thermally coupled levels at higher temperature range.

Intelligent Engine Systems: Thermal Management and Advanced Cooling

NASA Technical Reports Server (NTRS)

Bergholz, Robert

2008-01-01

The objective of the Advanced Turbine Cooling and Thermal Management program is to develop intelligent control and distribution methods for turbine cooling, while achieving a reduction in total cooling flow and assuring acceptable turbine component safety and reliability. The program also will develop embedded sensor technologies and cooling system models for real-time engine diagnostics and health management. Both active and passive control strategies will be investigated that include the capability of intelligent modulation of flow quantities, pressures, and temperatures both within the supply system and at the turbine component level. Thermal management system concepts were studied, with a goal of reducing HPT blade cooling air supply temperature. An assessment will be made of the use of this air by the active clearance control system as well. Turbine component cooling designs incorporating advanced, high-effectiveness cooling features, will be evaluated. Turbine cooling flow control concepts will be studied at the cooling system level and the component level. Specific cooling features or sub-elements of an advanced HPT blade cooling design will be downselected for core fabrication and casting demonstrations.

An Experimental Test Facility to Support Development of the Fluoride Salt Cooled High Temperature Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoder Jr, Graydon L; Aaron, Adam M; Cunningham, Richard Burns

2014-01-01

The need for high-temperature (greater than 600 C) energy exchange and delivery systems is significantly increasing as the world strives to improve energy efficiency and develop alternatives to petroleum-based fuels. Liquid fluoride salts are one of the few energy transport fluids that have the capability of operating at high temperatures in combination with low system pressures. The Fluoride Salt-Cooled High-Temperature Reactor design uses fluoride salt to remove core heat and interface with a power conversion system. Although a significant amount of experimentation has been performed with these salts, specific aspects of this reactor concept will require experimental confirmation during themore » development process. The experimental facility described here has been constructed to support the development of the Fluoride Salt Cooled High Temperature Reactor concept. The facility is capable of operating at up to 700 C and incorporates a centrifugal pump to circulate FLiNaK salt through a removable test section. A unique inductive heating technique is used to apply heat to the test section, allowing heat transfer testing to be performed. An air-cooled heat exchanger removes added heat. Supporting loop infrastructure includes a pressure control system; trace heating system; and a complement of instrumentation to measure salt flow, temperatures, and pressures around the loop. The initial experiment is aimed at measuring fluoride salt heat transfer inside a heated pebble bed similar to that used for the core of the pebble bed advanced high-temperature reactor. This document describes the details of the loop design, auxiliary systems used to support the facility, the inductive heating system, and facility capabilities.« less

Monte Carlo Analysis of the Battery-Type High Temperature Gas Cooled Reactor

NASA Astrophysics Data System (ADS)

Grodzki, Marcin; Darnowski, Piotr; Niewiński, Grzegorz

2017-12-01

The paper presents a neutronic analysis of the battery-type 20 MWth high-temperature gas cooled reactor. The developed reactor model is based on the publicly available data being an `early design' variant of the U-battery. The investigated core is a battery type small modular reactor, graphite moderated, uranium fueled, prismatic, helium cooled high-temperature gas cooled reactor with graphite reflector. The two core alternative designs were investigated. The first has a central reflector and 30×4 prismatic fuel blocks and the second has no central reflector and 37×4 blocks. The SERPENT Monte Carlo reactor physics computer code, with ENDF and JEFF nuclear data libraries, was applied. Several nuclear design static criticality calculations were performed and compared with available reference results. The analysis covered the single assembly models and full core simulations for two geometry models: homogenous and heterogenous (explicit). A sensitivity analysis of the reflector graphite density was performed. An acceptable agreement between calculations and reference design was obtained. All calculations were performed for the fresh core state.

Assessment of Effectiveness of Cool Coat in Reducing Heat Strain among Workers in Steel Industry.

PubMed

Parameswarappa, S B; Narayana, J

2017-01-01

A research study was conducted to assess the effectiveness of cool coat in reducing heat strain among workers exposed to heat in a steel plant located in south India. The study consists of assessing heat strain of workers exposed to heat in a steel plant by measuring physiological reactions of workers such as pulse rate and core body temperature with and without cool coat. The coal coat taken for this study was procured from M/s Yamuna Industries, Noida. Out of 140 employees exposed to heat hazard, 101 employees were examined in this study. Study was done in important production units in steel plant having heat hazard. Workers were interviewed and examined and information regarding thermal comfort was collected. First, the heat strain was assessed when the workers were not using cool coats. The air temperature was measured at all hot zone workplaces and found in the range of 34 0 C to 39.4 0 C (Mean: 36.54 0 C & S.D: 1.54). Physiological response such as core body temperature, pulse rate and blood pressure of workers exposed to heat hazard were measured before & after work to know the heat strain sustained by workers when they were working. Maximum core body temperature after work was found to be 39.3 0 C (Mean; 38.52 & S.D; 0.7). Maximum pulse rate of workers after work was found to be 120 beats/minute (Mean; 94.96 beats/minute, S.D: 13.11). The study indicate core body temperature of workers was found more than the permissible exposure limit prescribed by ACGIH, indicating the heat strain sustained by workers is significant, whereas the pulse rate and blood pressure was found normal & not exceeded the limits. Second, with cool coat, the heat strain was assessed among 10 workers selected from the 101 employees. Core body temperature was measured before and soon after work, The core body temperature recorded soon after work was in the range of 35.5 - 37.20C (Mean 36.36, SD= 0.52), indicating a drop in the core body temperature. In this study, a core body

Assessment of Effectiveness of Cool Coat in Reducing Heat Strain among Workers in Steel Industry

PubMed Central

Parameswarappa, S. B.; Narayana, J.

2017-01-01

A research study was conducted to assess the effectiveness of cool coat in reducing heat strain among workers exposed to heat in a steel plant located in south India. The study consists of assessing heat strain of workers exposed to heat in a steel plant by measuring physiological reactions of workers such as pulse rate and core body temperature with and without cool coat. The coal coat taken for this study was procured from M/s Yamuna Industries, Noida. Out of 140 employees exposed to heat hazard, 101 employees were examined in this study. Study was done in important production units in steel plant having heat hazard. Workers were interviewed and examined and information regarding thermal comfort was collected. First, the heat strain was assessed when the workers were not using cool coats. The air temperature was measured at all hot zone workplaces and found in the range of 34 0 C to 39.4 0 C (Mean: 36.54 0 C & S.D: 1.54). Physiological response such as core body temperature, pulse rate and blood pressure of workers exposed to heat hazard were measured before & after work to know the heat strain sustained by workers when they were working. Maximum core body temperature after work was found to be 39.3 0 C (Mean; 38.52 & S.D; 0.7). Maximum pulse rate of workers after work was found to be 120 beats/minute (Mean; 94.96 beats/minute, S.D: 13.11). The study indicate core body temperature of workers was found more than the permissible exposure limit prescribed by ACGIH, indicating the heat strain sustained by workers is significant, whereas the pulse rate and blood pressure was found normal & not exceeded the limits. Second, with cool coat, the heat strain was assessed among 10 workers selected from the 101 employees. Core body temperature was measured before and soon after work, The core body temperature recorded soon after work was in the range of 35.5 - 37.20C (Mean 36.36, SD= 0.52), indicating a drop in the core body temperature. In this study, a core body

A ventilation cooling shirt worn during office work in a hot climate: cool or not?

PubMed

Zhao, Mengmeng; Kuklane, Kalev; Lundgren, Karin; Gao, Chuansi; Wang, Faming

2015-01-01

The aim of the study was to identify whether a ventilation cooling shirt was effective in reducing heat strain in a hot climate. Eight female volunteers were exposed to heat (38 °C, 45% relative humidity) for 2 h with simulated office work. In the first hour they were in normal summer clothes (total thermal insulation 0.8 clo); in the second hour a ventilation cooling shirt was worn on top. After the shirt was introduced for 1 h, the skin temperatures at the scapula and the chest were significantly reduced (p < 0.05). The mean skin and core temperatures were not reduced. The subjects felt cooler and more comfortable by wearing the shirt, but the cooling effect was most conspicuous only during the initial 10 min. The cooling efficiency of the ventilation shirt was not very effective under the low physical activity in this hot climate.

Keep the brain cool--endovascular cooling in patients with severe traumatic brain injury: a case series study.

PubMed

Fischer, Marlene; Lackner, Peter; Beer, Ronny; Helbok, Raimund; Klien, Stephanie; Ulmer, Hanno; Pfausler, Bettina; Schmutzhard, Erich; Broessner, Gregor

2011-04-01

As brain temperature is reported to be extensively higher than core body temperature in traumatic brain injury (TBI) patients, posttraumatic hyperthermia is of particular relevance in the injured brain. To study the influence of prophylactic normothermia on brain temperature and the temperature gradient between brain and core body in patients with severe TBI using an intravascular cooling system and to assess the relationship between brain temperature and intracranial pressure (ICP) under endovascular temperature control. Prospective case series study conducted in the neurologic intensive care unit of a tertiary care university hospital. Seven patients with severe TBI with a Glasgow Coma Scale score of 8 or less were consecutively enrolled. Prophylactic normothermia, defined as a target temperature of 36.5°C, was maintained using an intravascular cooling system. Simultaneous measurements of brain and urinary bladder temperature and ICP were taken over a 72-hour period. The mean bladder temperature in normothermic patients was 36.3 ± 0.4°C, and the mean brain temperature was determined as 36.4 ± 0.5°C. The mean temperature difference between brain and bladder was 0.1°C. We found a significant direct correlation between brain and bladder temperature (r = 0.95). In 52.4% of all measurements, brain temperature was higher than core body temperature. The mean ICP was 18 ± 8 mm Hg. Intravascular temperature management stabilizes both brain and body core temperature; prophylactic normothermia reduces the otherwise extreme increase of intracerebral temperature in patients with severe TBI. The intravascular cooling management proved to be an efficacious and feasible method to control brain temperature and to avoid hyperthermia in the injured brain. We could not find a statistically significant correlation between brain temperature and ICP.

Neutron star cooling and pion condensation

NASA Technical Reports Server (NTRS)

Umeda, Hideyuki; Nomoto, Ken'ichi; Tsuruta, Sachiko; Muto, Takumi; Tatsumi, Toshitaka

1994-01-01

The nonstandard cooling of a neutron star with the central pion core is explored. By adopting the latest results from the pion condensation theory, neutrino emissivity is calulated for both pure charged pions and a mixture of charged and neutral pions, and the equations of state are constructed for the pion condensate. The effect of superfluidity on cooling is investigated, adopting methods more realistic than in previous studies. Our theoretical models are compared with the currently updated observational data, and possible implications are explored.

Developing core-shell upconversion nanoparticles for optical encoding

NASA Astrophysics Data System (ADS)

Huang, Kai

Lanthanide-doped upconversion nanoparticles (UCNPs) are an emerging class of luminescent materials that emit UV or visible light under near infra-red (NIR) excitations, thereby possessing a large anti-Stokes shift property. Also considering their sharp emission bands, excellent photo- and chemical stability, and almost zero auto-fluorescence of their NIR excitation, UCNPs are advantageous for optical encoding. Fabricating core-shell structured UCNPs provides a promising strategy to tune and enhance their upconverting luminescence. However, the energy transfer between core and shell had been rarely studied. Moreover, this strategy had been limited by the difficulty of coating thick shells onto the large cores of UCNPs. To overcome these constraints, the overall aim of this project is to study the inter-layers energy transfer in core-shell UCNPs and to develop an approach for coating thicker shell onto the core UCNPs, in order to fabricate UCNPs with enhanced and tunable luminescence for optical encoding. The strategy for encapsulating UCNPs into hydrogel droplet to fabricate multi-color bead barcodes has also been developed. Firstly, to study the inter-layers energy transfer between the core and shell of coreshell UCNPs, the activator and sensitizer ions were separately doped in the core or shell by fabricating NaYF4:Er NaYF4:Yb and NaYF4:Yb NaYF4:Er UCNPs. This eliminated the intra-layer energy transfer, resulting in a luminescence that is solely based on the energy transfer between layers, which facilitated the study of inter-layers energy transfer. The results demonstrated that the NaYF4:Yb NaYF4:Er structure, with sensitizer ions doped in the core, was preferable because of the strong luminescence, through minimizing the cross relaxations between Er3+ and Yb3+ and the surface quenching. Based on these information, a strategy of enhancing and tuning upconversion luminescence of core-shell UCNPs by accumulating sensitizer in the core has been developed. Next, a

Comparison of active cooling devices to passive cooling for rehabilitation of firefighters performing exercise in thermal protective clothing: A report from the Fireground Rehab Evaluation (FIRE) trial

PubMed Central

Hostler, David; Reis, Steven E; Bednez, James C; Kerin, Sarah; Suyama, Joe

2010-01-01

Background Thermal protective clothing (TPC) worn by firefighters provides considerable protection from the external environment during structural fire suppression. However, TPC is associated with physiological derangements that may have adverse cardiovascular consequences. These derangements should be treated during on-scene rehabilitation periods. Objective The present study examined heart rate and core temperature responses during the application of four active cooling devices, currently being marketed to the fire service for on-scene rehab, and compared them to passive cooling in a moderate temperature (approximately 24°C) and to an infusion of cold (4°C) saline. Methods Subjects exercised in TPC in a heated room. Following an initial exercise period (BOUT 1) the subjects exited the room, removed TPC, and for 20 minutes cooled passively at room temperature, received an infusion of cold normal saline, or were cooled by one of four devices (fan, forearm immersion in water, hand cooling, water perfused cooling vest). After cooling, subjects donned TPC and entered the heated room for another 50-minute exercise period (BOUT 2). Results Subjects were not able to fully recover core temperature during a 20-minute rehab period when provided rehydration and the opportunity to completely remove TPC. Exercise duration was shorter during BOUT 2 when compared to BOUT 1 but did not differ by cooling intervention. The overall magnitude and rate of cooling and heart rate recovery did not differ by intervention. Conclusions No clear advantage was identified when active cooling devices and cold intravenous saline were compared to passive cooling in a moderate temperature after treadmill exercise in TPC. PMID:20397868

A scaling and experimental approach for investigating in-vessel cooling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henry, R.E.

1997-02-01

The TMI-2 accident experienced the relocation of a large quantity of core material to the lower plenum. The TMI-2 vessel investigation project concluded that approximately 20 metric tonnes of once molten fuel material drained into the RPV lower head. As a result, the lower head wall experienced a thermal transient that has been characterized as reaching temperatures as high as 1100{degrees}C, then a cooling transient with a rate of 10 to 100{degrees}C/min. Two mechanisms have been proposed as possible explanations for this cooling behavior. One is the ingression of water through core material as a result of interconnected cracks inmore » the frozen debris and/or water ingression around the crust which is formed on internal structures (core supports and in-core instrumentation) in the lower head. The second focuses on the lack of adhesion of oxidic core debris to the RPV wall when the debris contacts the wall. Furthermore, the potential for strain of the RPV lower head when the wall is overheated could provide for a significant cooling path for water to ingress between the RPV and the frozen core material next to the wall. To examine these proposed mechanisms, a set of scaled experiments have been developed to examine the potential for cooling. These are performed in a scaled system in which the high temperature molten material is iron termite and the RPV wall is carbon steel. A termite mass of 40 kg is used and the simulated reactor vessels have water in the lower head at pressures up to 2.2 MPa. Furthermore, two different thicknesses of the vessel wall are examined with the thicker vessel having virtually no potential for material creep during the experiment and the thinner wall having the potential for substantial creep. Moreover, the experiment includes the option of having molten iron as the first material to drain into the RPV lower head or molten aluminum oxide being the only material that drains into the test configuration.« less

Powering Earth's dynamo with magnesium precipitation from the core.

PubMed

O'Rourke, Joseph G; Stevenson, David J

2016-01-21

Earth's global magnetic field arises from vigorous convection within the liquid outer core. Palaeomagnetic evidence reveals that the geodynamo has operated for at least 3.4 billion years, which places constraints on Earth's formation and evolution. Available power sources in standard models include compositional convection (driven by the solidifying inner core's expulsion of light elements), thermal convection (from slow cooling), and perhaps heat from the decay of radioactive isotopes. However, recent first-principles calculations and diamond-anvil cell experiments indicate that the thermal conductivity of iron is two or three times larger than typically assumed in these models. This presents a problem: a large increase in the conductive heat flux along the adiabat (due to the higher conductivity of iron) implies that the inner core is young (less than one billion years old), but thermal convection and radiogenic heating alone may not have been able to sustain the geodynamo during earlier epochs. Here we show that the precipitation of magnesium-bearing minerals from the core could have served as an alternative power source. Equilibration at high temperatures in the aftermath of giant impacts allows a small amount of magnesium (one or two weight per cent) to partition into the core while still producing the observed abundances of siderophile elements in the mantle and avoiding an excess of silicon and oxygen in the core. The transport of magnesium as oxide or silicate from the cooling core to underneath the mantle is an order of magnitude more efficient per unit mass as a source of buoyancy than inner-core growth. We therefore conclude that Earth's dynamo would survive throughout geologic time (from at least 3.4 billion years ago to the present) even if core radiogenic heating were minimal and core cooling were slow.

The effects of passive heating and head-cooling on perception of exercise in the heat.

PubMed

Simmons, Shona E; Mündel, Toby; Jones, David A

2008-09-01

The capacity to perform exercise is reduced in a hot environment when compared to cooler conditions. A limiting factor appears to be a higher core body temperature (T (core)) and it has been suggested that an elevated T (core) reduces the drive to exercise, this being reflected in higher ratings of perceived exertion (RPE). The purpose of the present study was to determine whether passive heating to increase T (core) would have a detrimental effect on RPE and thermal comfort during subsequent exercise in the heat and whether head-cooling during passive heating would attenuate these unpleasant sensations of an elevated T (core) during subsequent exercise in the heat. Nine physically-active, non-heat-acclimated volunteers [6 males, 3 females; age: 21 +/- 1 year, VO(2max) 50 +/- 9 ml kg(-1).min(-1), peak power output: 286 +/- 43 W (mean +/- SD)] performed two 12-minute constant-load cycling tests at 70% VO(2max) in a warm-dry environment (34 +/- 1 degrees C, relative humidity <30%) separated by a period of passive heating in a sauna (68 +/- 3 degrees C) to increase T (core). In one trial, subjects had their head and face cooled continually in the sauna (HC), the other trial was a control (CON). Passive heating increased T (core) by 1.22 +/- 0.03 degrees C in the CON and by 0.75 +/- 0.07 degrees C in the HC trial (P < 0.01). Passive heating increased weighted mean skin temperature (T (msk)) in both the CON and HC trials (P < 0.01), however, head-cooling lowered T (msk) during passive heating (P < 0.05). Exercise time following passive heating was reduced in both the CON and HC trials (P < 0.05). Passive heating increased RPE (P < 0.01), however, RPE was lower following passive heating with head-cooling (P < 0.05). There was a significant correlation between T (core) and RPE (r = 0.82, P < 0.001). In conclusion, our results suggest increased RPE during exercise in the heat is primarily due to the increase in T (core). Furthermore, head-cooling attenuates the rise in T

Cause and Effect of Feedback: Multiphase Gas in Cluster Cores Heated by AGN Jets

NASA Astrophysics Data System (ADS)

Gaspari, M.; Ruszkowski, M.; Sharma, P.

2012-02-01

Multiwavelength data indicate that the X-ray-emitting plasma in the cores of galaxy clusters is not cooling catastrophically. To a large extent, cooling is offset by heating due to active galactic nuclei (AGNs) via jets. The cool-core clusters, with cooler/denser plasmas, show multiphase gas and signs of some cooling in their cores. These observations suggest that the cool core is locally thermally unstable while maintaining global thermal equilibrium. Using high-resolution, three-dimensional simulations we study the formation of multiphase gas in cluster cores heated by collimated bipolar AGN jets. Our key conclusion is that spatially extended multiphase filaments form only when the instantaneous ratio of the thermal instability and free-fall timescales (t TI/t ff) falls below a critical threshold of ≈10. When this happens, dense cold gas decouples from the hot intracluster medium (ICM) phase and generates inhomogeneous and spatially extended Hα filaments. These cold gas clumps and filaments "rain" down onto the central regions of the core, forming a cold rotating torus and in part feeding the supermassive black hole. Consequently, the self-regulated feedback enhances AGN heating and the core returns to a higher entropy level with t TI/t ff > 10. Eventually, the core reaches quasi-stable global thermal equilibrium, and cold filaments condense out of the hot ICM whenever t TI/t ff <~ 10. This occurs despite the fact that the energy from AGN jets is supplied to the core in a highly anisotropic fashion. The effective spatial redistribution of heat is enabled in part by the turbulent motions in the wake of freely falling cold filaments. Increased AGN activity can locally reverse the cold gas flow, launching cold filamentary gas away from the cluster center. Our criterion for the condensation of spatially extended cold gas is in agreement with observations and previous idealized simulations.

Potassium-bearing Iron-Nickel Sulfides in Nature and High-Pressure Experiments: Geochemical Consequences of Potassium in the Earth's Core

NASA Technical Reports Server (NTRS)

Keshav, S.; Corgne, A.; McDonough, W. F.; Fei, Y.

2005-01-01

Introduction: Potassium (K) as a large ion lithophile element has dominantly been concentrated in the Earth s crust and the mantle through differentiation, and in the form of K-40 contributes to the planet s heat budget. However, whether or not K also enters core-forming phases, has been debated for over three decades. Arguments favoring entry of K in the core are based on: (1) K-sulfide (with Fe, Ni, Cu, Na, and Cl; djerfisherite) found in highly reduced enstatite chondrites (or aubrites, enstatite achondrites); (2) demonstration that K, owing to an s-d electronic switch at high-pressure, exhibits transition- element like character, (3) solubility of measurable K in Fe-Ni-S liquids at high pressure, temperature conditions, and (4) models of cooling of the core that seem to require, besides convection, some form of radioactivity, and thus lending support to the experimental work. In this contribution, we assess the effect of sequestering K in the core, as it is perhaps an element that is a key to reconciling geochemistry, paleomagnetism, accretion, and thermal evolution models for the planet.

Stacking with stochastic cooling

NASA Astrophysics Data System (ADS)

Caspers, Fritz; Möhl, Dieter

2004-10-01

Accumulation of large stacks of antiprotons or ions with the aid of stochastic cooling is more delicate than cooling a constant intensity beam. Basically the difficulty stems from the fact that the optimized gain and the cooling rate are inversely proportional to the number of particles 'seen' by the cooling system. Therefore, to maintain fast stacking, the newly injected batch has to be strongly 'protected' from the Schottky noise of the stack. Vice versa the stack has to be efficiently 'shielded' against the high gain cooling system for the injected beam. In the antiproton accumulators with stacking ratios up to 105 the problem is solved by radial separation of the injection and the stack orbits in a region of large dispersion. An array of several tapered cooling systems with a matched gain profile provides a continuous particle flux towards the high-density stack core. Shielding of the different systems from each other is obtained both through the spatial separation and via the revolution frequencies (filters). In the 'old AA', where the antiproton collection and stacking was done in one single ring, the injected beam was further shielded during cooling by means of a movable shutter. The complexity of these systems is very high. For more modest stacking ratios, one might use azimuthal rather than radial separation of stack and injected beam. Schematically half of the circumference would be used to accept and cool new beam and the remainder to house the stack. Fast gating is then required between the high gain cooling of the injected beam and the low gain stack cooling. RF-gymnastics are used to merge the pre-cooled batch with the stack, to re-create free space for the next injection, and to capture the new batch. This scheme is less demanding for the storage ring lattice, but at the expense of some reduction in stacking rate. The talk reviews the 'radial' separation schemes and also gives some considerations to the 'azimuthal' schemes.

Turbofan Engine Core Compartment Vent Aerodynamic Configuration Development Methodology

NASA Technical Reports Server (NTRS)

Hebert, Leonard J.

2006-01-01

This paper presents an overview of the design methodology used in the development of the aerodynamic configuration of the nacelle core compartment vent for a typical Boeing commercial airplane together with design challenges for future design efforts. Core compartment vents exhaust engine subsystem flows from the space contained between the engine case and the nacelle of an airplane propulsion system. These subsystem flows typically consist of precooler, oil cooler, turbine case cooling, compartment cooling and nacelle leakage air. The design of core compartment vents is challenging due to stringent design requirements, mass flow sensitivity of the system to small changes in vent exit pressure ratio, and the need to maximize overall exhaust system performance at cruise conditions.

Microstructure and microchemistry of flash sintered K 0.5Na 0.5NbO 3

DOE PAGES

Corapcioglu, Gulcan; Gulgun, Mehmet Ali; Kisslinger, Kim; ...

2016-04-30

In this paper, flash sintering experiments were performed, for the first time, on sodium potassium niobate (KNN) ceramics. A theoretical density of 94% was achieved in 30 s under 250 V/cm electric-field at 990°C. These conditions are ~100°C lower and faster than the conventional sintering conditions. Grains tended to grow after 30 s. flash sintering duration under constant electric-field. Detailed microstructural and chemical investigations of the sample showed that there was inhomogenous Na, K distribution and it resembles a core–shell structure where K is more in the shell and Na is more in the core region. The inhomogenous distribution ofmore » Na and K was correlated with the doubling of the unit cell within the grain along 002 direction. Compositional equilibrium is achieved after a heat treatment at 1000°C for 4 h. Finally, the compositional variations appeared to have been linked to grain boundary melting during flash and consequent recrystallization as the sample cooled.« less

Decay Heat Removal from a GFR Core by Natural Convection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, Wesley C.; Hejzlar, Pavel; Driscoll, Michael J.

2004-07-01

One of the primary challenges for Gas-cooled Fast Reactors (GFR) is decay heat removal after a loss of coolant accident (LOCA). Due to the fact that thermal gas cooled reactors currently under design rely on passive mechanisms to dissipate decay heat, there is a strong motivation to accomplish GFR core cooling through natural phenomena. This work investigates the potential of post-LOCA decay heat removal from a GFR core to a heat sink using an external convection loop. A model was developed in the form of the LOCA-COLA (Loss of Coolant Accident - Convection Loop Analysis) computer code as a meansmore » for 1D steady state convective heat transfer loop analysis. The results show that decay heat removal by means of gas cooled natural circulation is feasible under elevated post-LOCA containment pressure conditions. (authors)« less

NEUTRONIC REACTOR CORE

DOEpatents

Thomson, W.B.; Corbin, A. Jr.

1961-07-18

An improved core for a gas-cooled power reactor which admits gas coolant at high temperatures while affording strong integral supporting structure and efficient moderation of neutrons is described. The multiplicities of fuel elements constituting the critical amassment of fissionable material are supported and confined by a matrix of metallic structure which is interspersed therebetween. Thermal insulation is interposed between substantially all of the metallic matrix and the fuel elements; the insulation then defines the principal conduit system for conducting the coolant gas in heat-transfer relationship with the fuel elements. The metallic matrix itseif comprises a system of ducts through which an externally-cooled hydrogeneous liquid, such as water, is circulated to serve as the principal neutron moderant for the core and conjointly as the principal coolant for the insulated metallic structure. In this way, use of substantially neutron transparent metals, such as aluminum, becomes possible for the supporting structure, despite the high temperatures of the proximate gas. The Aircraft Nuclear Propulsion program's "R-1" reactor design is a preferred embodiment.

Microchip transponder thermometry for monitoring core body temperature of antelope during capture.

PubMed

Rey, Benjamin; Fuller, Andrea; Hetem, Robyn S; Lease, Hilary M; Mitchell, Duncan; Meyer, Leith C R

2016-01-01

Hyperthermia is described as the major cause of morbidity and mortality associated with capture, immobilization and restraint of wild animals. Therefore, accurately determining the core body temperature of wild animals during capture is crucial for monitoring hyperthermia and the efficacy of cooling procedures. We investigated if microchip thermometry can accurately reflect core body temperature changes during capture and cooling interventions in the springbok (Antidorcas marsupialis), a medium-sized antelope. Subcutaneous temperature measured with a temperature-sensitive microchip was a weak predictor of core body temperature measured by temperature-sensitive data loggers in the abdominal cavity (R(2)=0.32, bias >2 °C). Temperature-sensitive microchips in the gluteus muscle, however, provided an accurate estimate of core body temperature (R(2)=0.76, bias=0.012 °C). Microchips inserted into muscle therefore provide a convenient and accurate method to measure body temperature continuously in captured antelope, allowing detection of hyperthermia and the efficacy of cooling procedures. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of a New Cooling Technology on Physical Performance in US Air Force Military Personnel.

PubMed

O'Hara, Reginald; Vojta, Christopher; Henry, Amy; Caldwell, Lydia; Wade, Molly; Swanton, Stacie; Linderman, Jon K; Ordway, Jason

2016-01-01

Heat-related illness is a critical factor for military personnel operating in hyperthermic environments. Heat illness can alter cognitive and physical performance during sustained operations missions. Therefore, the primary purpose of this investigation was to determine the effects of a novel cooling shirt on core body temperature in highly trained US Air Force personnel. Twelve trained (at least 80th percentile for aerobic fitness according to the American College of Sports Medicine, at least 90% on the US Air Force fitness test), male Air Force participants (mean values: age, 25 ± 2.8 years; height, 178 ± 7.9cm; body weight 78 ± 9.6kg; maximal oxygen uptake, 57 ± 1.9mL/kg/ min; and body fat, 10% ± 0.03%) completed this study. Subjects performed a 70-minute weighted treadmill walking test and 10-minute, 22.7kg sandbag shuttle test under two conditions: (1) "loaded" (shirt with cooling inserts) and (2) "unloaded" (shirt with no cooling inserts). Core body temperature, exercise heart rate, capillary blood lactate, and ratings of perceived exertion were recorded. Core body temperature was lower (ρ = .001) during the 70-minute treadmill walking test in the loaded condition. Peak core temperature during the 70-minute walking test was also significantly lower (ρ = .038) in the loaded condition. This lightweight (471g), passive cooling technology offers multiple hours of sustained cooling and reduced core and peak body temperature during a 70-minute, 22.7kg weighted-vest walking test. 2016.

Cryogenic performance of a cryocooler-cooled superconducting undulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fuerst, J. D.; Doose, C.; Hasse, Q.

2014-01-29

A cryocooler-cooled superconducting undulator has been installed and operated with beam at the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). The device consists of a dual-core 42-pole magnet structure that is cooled to 4.2 K with a system of four cryocoolers operating in a zero-boil-off configuration. This effort represents the culmination of a development program to establish concept feasibility and evaluate cryostat design and cryocooler-based refrigeration. Cryostat performance is described including cool-down/warm-up, steady-state operation, cooling margin, and the impact of beam during operation in the APS storage ring. Plans for future devices with longer magnets, which will incorporatemore » lessons learned from the development program, are also discussed.« less

Generator stator core vent duct spacer posts

DOEpatents

Griffith, John Wesley; Tong, Wei

2003-06-24

Generator stator cores are constructed by stacking many layers of magnetic laminations. Ventilation ducts may be inserted between these layers by inserting spacers into the core stack. The ventilation ducts allow for the passage of cooling gas through the core during operation. The spacers or spacer posts are positioned between groups of the magnetic laminations to define the ventilation ducts. The spacer posts are secured with longitudinal axes thereof substantially parallel to the core axis. With this structure, core tightness can be assured while maximizing ventilation duct cross section for gas flow and minimizing magnetic loss in the spacers.

Formation of Si grains from a NaSi melt prepared by reaction of SiO2 and Na

NASA Astrophysics Data System (ADS)

Yamane, Hisanori; Morito, Haruhiko; Uchikoshi, Masahito

2013-08-01

A mixture of Na2SiO3 and NaSi was found to be formed by reaction of SiO2 and Na at 650 °C as follows: 5Na+3SiO2→2Na2SiO3+NaSi. Single crystals of NaSi were grown by cooling the mixture of Na2SiO3 and NaSi with an excess amount of Na from 850 °C, and polycrystalline Si was obtained by vaporization of Na from the crystals. Coarse grains of Si were also crystallized by Na evaporation after the formation of Na2SiO3 and Si-dissolved liquid Na at 830 °C. The Si grains were collected by washing the product with water. The yield of the Si grains was 85% of the ideal amount expected from the reaction.

A Global Model for Circumgalactic and Cluster-core Precipitation

NASA Astrophysics Data System (ADS)

Voit, G. Mark; Meece, Greg; Li, Yuan; O'Shea, Brian W.; Bryan, Greg L.; Donahue, Megan

2017-08-01

We provide an analytic framework for interpreting observations of multiphase circumgalactic gas that is heavily informed by recent numerical simulations of thermal instability and precipitation in cool-core galaxy clusters. We start by considering the local conditions required for the formation of multiphase gas via two different modes: (1) uplift of ambient gas by galactic outflows, and (2) condensation in a stratified stationary medium in which thermal balance is explicitly maintained. Analytic exploration of these two modes provides insights into the relationships between the local ratio of the cooling and freefall timescales (I.e., {t}{cool}/{t}{ff}), the large-scale gradient of specific entropy, and the development of precipitation and multiphase media in circumgalactic gas. We then use these analytic findings to interpret recent simulations of circumgalactic gas in which global thermal balance is maintained. We show that long-lasting configurations of gas with 5≲ \\min ({t}{cool}/{t}{ff})≲ 20 and radial entropy profiles similar to observations of cool cores in galaxy clusters are a natural outcome of precipitation-regulated feedback. We conclude with some observational predictions that follow from these models. This work focuses primarily on precipitation and AGN feedback in galaxy-cluster cores, because that is where the observations of multiphase gas around galaxies are most complete. However, many of the physical principles that govern condensation in those environments apply to circumgalactic gas around galaxies of all masses.

A STRONGLY COUPLED REACTOR CORE ISOLATION COOLING SYSTEM MODEL FOR EXTENDED STATION BLACK-OUT ANALYSES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Haihua; Zhang, Hongbin; Zou, Ling

2015-03-01

The reactor core isolation cooling (RCIC) system in a boiling water reactor (BWR) provides makeup cooling water to the reactor pressure vessel (RPV) when the main steam lines are isolated and the normal supply of water to the reactor vessel is lost. The RCIC system operates independently of AC power, service air, or external cooling water systems. The only required external energy source is from the battery to maintain the logic circuits to control the opening and/or closure of valves in the RCIC systems in order to control the RPV water level by shutting down the RCIC pump to avoidmore » overfilling the RPV and flooding the steam line to the RCIC turbine. It is generally considered in almost all the existing station black-out accidents (SBO) analyses that loss of the DC power would result in overfilling the steam line and allowing liquid water to flow into the RCIC turbine, where it is assumed that the turbine would then be disabled. This behavior, however, was not observed in the Fukushima Daiichi accidents, where the Unit 2 RCIC functioned without DC power for nearly three days. Therefore, more detailed mechanistic models for RCIC system components are needed to understand the extended SBO for BWRs. As part of the effort to develop the next generation reactor system safety analysis code RELAP-7, we have developed a strongly coupled RCIC system model, which consists of a turbine model, a pump model, a check valve model, a wet well model, and their coupling models. Unlike the traditional SBO simulations where mass flow rates are typically given in the input file through time dependent functions, the real mass flow rates through the turbine and the pump loops in our model are dynamically calculated according to conservation laws and turbine/pump operation curves. A simplified SBO demonstration RELAP-7 model with this RCIC model has been successfully developed. The demonstration model includes the major components for the primary system of a BWR, as well as the

Enzyme immobilization in novel alginate-chitosan core-shell microcapsules.

PubMed

Taqieddin, Ehab; Amiji, Mansoor

2004-05-01

Alginate-chitosan core-shell microcapsules were prepared in order to develop a biocompatible matrix for enzyme immobilization, where the protein is retained either in a liquid or solid core and the shell allows permeability control over substrates and products. The permeability coefficients of different molecular weight compounds (vitamin B2, vitamin B12, and myoglobin) were determined through sodium tripolyphosphate (Na-TPP)-crosslinked chitosan membrane. The microcapsule core was formed by crosslinking sodium alginate with either calcium or barium ions. The crosslinked alginate core was uniformly coated with a chitosan layer and crosslinked with Na-TPP. In the case of calcium alginate, the phosphate ions of Na-TPP were able to extract the calcium ions from alginate and liquefy the core. A model enzyme, beta-galactosidase, was immobilized in the alginate core and the catalytic activity was measured with o-nitrophenyl-beta-D-galactopyranoside (ONPG). Change in the activity of free and immobilized enzyme was determined at three different temperatures. Na-TPP crosslinked chitosan membranes were found to be permeable to solutes of up to 17,000Da molecular weight. The enzyme loading efficiency was higher in the barium alginate core (100%) as compared to the calcium alginate core (60%). The rate of ONPG conversion to o-nitrophenol was faster in the case of calcium alginate-chitosan microcapsules as compared to barium alginate-chitosan microcapsules. Barium alginate-chitosan microcapsules, however, did improve the stability of the enzyme at 37 degrees C relative to calcium alginate-chitosan microcapsules or free enzyme. This study illustrates a new method of enzyme immobilization for biotechnology applications using liquid or solid core and shell microcapsule technology.

Mass Distribution in Galaxy Cluster Cores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hogan, M. T.; McNamara, B. R.; Pulido, F.

Many processes within galaxy clusters, such as those believed to govern the onset of thermally unstable cooling and active galactic nucleus feedback, are dependent upon local dynamical timescales. However, accurate mapping of the mass distribution within individual clusters is challenging, particularly toward cluster centers where the total mass budget has substantial radially dependent contributions from the stellar ( M {sub *}), gas ( M {sub gas}), and dark matter ( M {sub DM}) components. In this paper we use a small sample of galaxy clusters with deep Chandra observations and good ancillary tracers of their gravitating mass at both largemore » and small radii to develop a method for determining mass profiles that span a wide radial range and extend down into the central galaxy. We also consider potential observational pitfalls in understanding cooling in hot cluster atmospheres, and find tentative evidence for a relationship between the radial extent of cooling X-ray gas and nebular H α emission in cool-core clusters. At large radii the entropy profiles of our clusters agree with the baseline power law of K ∝ r {sup 1.1} expected from gravity alone. At smaller radii our entropy profiles become shallower but continue with a power law of the form K ∝ r {sup 0.67} down to our resolution limit. Among this small sample of cool-core clusters we therefore find no support for the existence of a central flat “entropy floor.”.« less

Design of a Mechanical NaK Pump for Fission Space Power Systems

NASA Technical Reports Server (NTRS)

Mireles, Omar R.; Bradley, David; Godfroy, Thomas

2010-01-01

Alkali liquid metal cooled fission reactor concepts are under development for mid-range spaceflight power requirements. One such concept utilizes a sodium-potassium eutectic (NaK) as the primary loop working fluid. Traditionally, linear induction pumps have been used to provide the required flow and head conditions for liquid metal systems but can be limited in performance. This paper details the design, build, and check-out test of a mechanical NaK pump. The pump was designed to meet reactor cooling requirements using commercially available components modified for high temperature NaK service.

Nonpharmacologic approach to minimizing shivering during surface cooling: a proof of principle study.

PubMed

Shah, Nirav G; Cowan, Mark J; Pickering, Edward; Sareh, Houtan; Afshar, Majid; Fox, Dawn; Marron, Jennifer; Davis, Jennifer; Herold, Keith; Shanholtz, Carl B; Hasday, Jeffrey D

2012-12-01

This study had 2 objectives: (1) to quantify the metabolic response to physical cooling in febrile patients with systemic inflammatory response syndrome (SIRS) and (2) to provide proof for the hypothesis that the efficiency of external cooling and the subsequent shivering response are influenced by site and temperature of surface cooling pads. To quantify shivering thermogenesis during surface cooling for fever, we monitored oxygen consumption (VO(2)) in 6 febrile patients with SIRS during conventional cooling with cooling blankets and ice packs. To begin to determine how location and temperature of surface cooling influence shivering, we compared 5 cooling protocols for inducing mild hypothermia in 6 healthy volunteers. In the patients with SIRS, core temperature decreased 0.67 °C per hour, all patients shivered, VO(2) increased 57.6%, and blood pressure increased 15% during cooling. In healthy subjects, cooling with the 10 °C vest was most comfortable and removed heat most efficiently without shivering or VO(2) increase. Cooling with combined vest and thigh pads stimulated the most shivering and highest VO(2) and increased core temperature. Reducing vest temperature from 10 °C to 5 °C failed to increase heat removal secondary to cutaneous vasoconstriction. Capsaicin, an agonist for the transient receptor potential cation channel subfamily V member 1 (TRPV1) warm-sensing channels, partially reversed this effect in 5 subjects. Our results identify the hazards of surface cooling in febrile critically ill patients and support the concept that optimization of cooling pad temperature and position may improve cooling efficiency and reduce shivering. Copyright © 2012 Elsevier Inc. All rights reserved.

Cooling Rates of Humans in Air and in Water: An Experiment

NASA Astrophysics Data System (ADS)

Bohren, Craig F.

2012-12-01

In a previous article I analyzed in detail the physical factors resulting in greater cooling rates of objects in still water than in still air, emphasizing cooling of the human body. By cooling rate I mean the rate of decrease of core temperature uncompensated by metabolism. I concluded that the "correct ratio for humans is closer to 2 than to 10." To support this assertion I subsequently did experiments, which I report following a digression on hypothermia.

Intracluster medium cooling, AGN feedback, and brightest cluster galaxy properties of galaxy groups. Five properties where groups differ from clusters

NASA Astrophysics Data System (ADS)

Bharadwaj, V.; Reiprich, T. H.; Schellenberger, G.; Eckmiller, H. J.; Mittal, R.; Israel, H.

2014-12-01

Aims: We aim to investigate cool-core and non-cool-core properties of galaxy groups through X-ray data and compare them to the AGN radio output to understand the network of intracluster medium (ICM) cooling and feedback by supermassive black holes. We also aim to investigate the brightest cluster galaxies (BCGs) to see how they are affected by cooling and heating processes, and compare the properties of groups to those of clusters. Methods: Using Chandra data for a sample of 26 galaxy groups, we constrained the central cooling times (CCTs) of the ICM and classified the groups as strong cool-core (SCC), weak cool-core (WCC), and non-cool-core (NCC) based on their CCTs. The total radio luminosity of the BCG was obtained using radio catalogue data and/or literature, which in turn was compared to the cooling time of the ICM to understand the link between gas cooling and radio output. We determined K-band luminosities of the BCG with 2MASS data, and used a scaling relation to constrain the masses of the supermassive black holes, which were then compared to the radio output. We also tested for correlations between the BCG luminosity and the overall X-ray luminosity and mass of the group. The results obtained for the group sample were also compared to previous results for clusters. Results: The observed cool-core/non-cool-core fractions for groups are comparable to those of clusters. However, notable differences are seen: 1) for clusters, all SCCs have a central temperature drop, but for groups this is not the case as some have centrally rising temperature profiles despite very short cooling times; 2) while for the cluster sample, all SCC clusters have a central radio source as opposed to only 45% of the NCCs, for the group sample, all NCC groups have a central radio source as opposed to 77% of the SCC groups; 3) for clusters, there are indications of an anticorrelation trend between radio luminosity and CCT. However, for groups this trend is absent; 4) the indication of

Nonpharmacologic Approach to Minimizing Shivering During Surface Cooling: A Proof of Principle Study1

PubMed Central

Shah, Nirav G.; Cowan, Mark J.; Pickering, Edward; Sareh, Houtan; Afshar, Majid; Fox, Dawn; Marron, Jennifer; Davis, Jennifer; Herold, Keith; Shanholtz, Carl B.; Hasday, Jeffrey D.

2012-01-01

Purpose This study had two objectives: (1) to quantify the metabolic response to physical cooling in febrile patients with Systemic Inflammatory Response Syndrome (SIRS); and (2) to provide proof for the hypothesis that the efficiency of external cooling and the subsequent shivering response are influenced by site and temperature of surface cooling pads. Methods To quantify shivering thermogenesis during surface cooling for fever, we monitored oxygen consumption (VO2) in six febrile patients with SIRS during conventional cooling with cooling blankets and ice packs. To begin to determine how location and temperature of surface cooling influences shivering, we compared 5 cooling protocols for inducing mild hypothermia in six healthy volunteers. Results In the SIRS patients, core temperature decreased 0.67°C per hour, all patients shivered, VO2 increased 57.6% and blood pressure increased 15% during cooling. In healthy subjects, cooling with the 10°C vest was most comfortable and removed heat most efficiently without shivering or VO2 increase. Cooling with combined vest and thigh pads stimulated the most shivering and highest VO2, and increased core temperature. Reducing vest temperature from 10°C to 5°C failed to increase heat removal secondary to cutaneous vasoconstriction. Capsaicin, an agonist for TRPV1 warm-sensing channels, partially reversed this effect in 5 subjects. Conclusions Our results identify the hazards of surface cooling in febrile critically ill patients and support the concept that optimization of cooling pad temperature and position may improve cooling efficiency and reduce shivering. PMID:22762936

Potential Application of a Thermoelectric Generator in Passive Cooling System of Nuclear Power Plants

NASA Astrophysics Data System (ADS)

Wang, Dongqing; Liu, Yu; Jiang, Jin; Pang, Wei; Lau, Woon Ming; Mei, Jun

2017-05-01

In the design of nuclear power plants, various natural circulation passive cooling systems are considered to remove residual heat from the reactor core in the event of a power loss and maintain the plant's safety. These passive systems rely on gravity differences of fluids, resulting from density differentials, rather than using an external power-driven system. Unfortunately, a major drawback of such systems is their weak driving force, which can negatively impact safety. In such systems, there is a temperature difference between the heat source and the heat sink, which potentially offers a natural platform for thermoelectric generator (TEG) applications. While a previous study designed and analyzed a TEG-based passive core cooling system, this paper considers TEG applications in other passive cooling systems of nuclear power plants, after which the concept of a TEG-based passive cooling system is proposed. In such a system, electricity is produced using the system's temperature differences through the TEG, and this electricity is used to further enhance the cooling process.

Physiologic and Functional Responses of MS Patients to Body Cooling Using Commercially Available Cooling Garments

NASA Technical Reports Server (NTRS)

Ku, Yu-Tsuan E.; Montgomery, Leslie D.; Lee, Hank C.; Luna, Bernadette; Webbon, Bruce W.; Mead, Susan C. (Technical Monitor)

1999-01-01

Personal cooling systems are widely used in industrial and aerospace environments to alleviate thermal stress. Increasingly they are also used by heat sensitive multiple sclerosis (HSMS) patients to relieve symptoms and improve quality of life. There are a variety of cooling systems commercially available to the MS community. However, little information is available regarding the comparative physiological changes produced by routine operation of these various systems. The objective of this study was to document and compare the patient response to two passive cooling vests and one active cooling garment. The Life Enhancement Technology, Inc. (LET) lightweight active cooling vest with cap, the MicroClimate Systems (MCS) Change of Phase garment, and the Steele Vest were each used to cool 13 male and 13 female MS subjects (31 to 67 yr.) in this study. The subjects, seated in an upright position at normal room temperature (approximately 22 C), were tested with one of the cooling garments. Oral, fight and left ear temperatures were logged manually every 5 min. An-n, leg, chest and rectal temperatures; heart rate; and respiration were recorded continuously on a U.F.I., Inc. Biolog ambulatory monitor. Each subject was given a series of subjective and objective evaluation tests before and after cooling. The LET and Steele vests test groups had similar, significant (P less than 0.01) cooling effects on oral and ear canal temperature, which decreased approximately 0.4 C, and 0.3 C, respectively. Core temperature increased (N.S.) with all three vests during cooling. The LET vest produced the coldest (P less than 0.01) skin temperature. Overall, the LET vest provided the most improvement on subjective and objective performance measures. These results show that the garment configurations tested do not elicit a similar thermal response in all MS patients. Cooling with the LET active garment configuration resulted in the lowest body temperatures for the MS subjects; cooling with

77 FR 19740 - Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant Accident

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-02

... NUCLEAR REGULATORY COMMISSION [NRC-2010-0249] Water Sources for Long-Term Recirculation Cooling... Regulatory Guide (RG) 1.82, ``Water Sources for Long-Term Recirculation Cooling Following a Loss-of-Coolant... regarding the sumps and suppression pools that provide water sources for emergency core cooling, containment...

Radial metal abundance profiles in the intra-cluster medium of cool-core galaxy clusters, groups, and ellipticals

NASA Astrophysics Data System (ADS)

Mernier, F.; de Plaa, J.; Kaastra, J. S.; Zhang, Y.-Y.; Akamatsu, H.; Gu, L.; Kosec, P.; Mao, J.; Pinto, C.; Reiprich, T. H.; Sanders, J. S.; Simionescu, A.; Werner, N.

2017-07-01

The hot intra-cluster medium (ICM) permeating galaxy clusters and groups is not pristine, as it has been continuously enriched by metals synthesised in Type Ia (SNIa) and core-collapse (SNcc) supernovae since the major epoch of star formation (z ≃ 2-3). The cluster/group enrichment history and mechanisms responsible for releasing and mixing the metals can be probed via the radial distribution of SNIa and SNcc products within the ICM. In this paper, we use deep XMM-Newton/EPIC observations from a sample of 44 nearby cool-core galaxy clusters, groups, and ellipticals (CHEERS) to constrain the average radial O, Mg, Si, S, Ar, Ca, Fe, and Ni abundance profiles. The radial distributions of all these elements, averaged over a large sample for the first time, represent the best constrained profiles available currently. Specific attention is devoted to a proper modelling of the EPIC spectral components, and to other systematic uncertainties that may affect our results. We find an overall decrease of the Fe abundance with radius out to 0.9 r500 and 0.6 r500 for clusters and groups, respectively, in good agreement with predictions from the most recent hydrodynamical simulations. The average radial profiles of all the other elements (X) are also centrally peaked and, when rescaled to their average central X/Fe ratios, follow well the Fe profile out to at least 0.5 r500. As predicted by recent simulations, we find that the relative contribution of SNIa (SNcc) to the total ICM enrichment is consistent with being uniform at all radii, both for clusters and groups using two sets of SNIa and SNcc yield models that reproduce the X/Fe abundance pattern in the core well. In addition to implying that the central metal peak is balanced between SNIa and SNcc, our results suggest that the enriching SNIa and SNcc products must share the same origin and that the delay between the bulk of the SNIa and SNcc explosions must be shorter than the timescale necessary to diffuse out the metals

Moving core beam energy absorber and converter

DOEpatents

Degtiarenko, Pavel V.

2012-12-18

A method and apparatus for the prevention of overheating of laser or particle beam impact zones through the use of a moving-in-the-coolant-flow arrangement for the energy absorbing core of the device. Moving of the core spreads the energy deposition in it in 1, 2, or 3 dimensions, thus increasing the effective cooling area of the device.

Design of a Mechanical NaK Pump for Fission Space Power

NASA Technical Reports Server (NTRS)

Mireles, Omar R.; Bradley, David E.; Godfroy, Thomas

2011-01-01

Alkali liquid metal cooled fission reactor concepts are under development for spaceflight power requirements. One such concept utilizes a sodium-potassium eutectic (NaK) as the primary loop working fluid, which has specific pumping requirements. Traditionally, electromagnetic linear induction pumps have been used to provide the required flow and pressure head conditions for NaK systems but they can be limited in performance, efficiency, and number of available vendors. The objective of the project was to develop a mechanical NaK centrifugal pump that takes advantages of technology advances not available in previous liquid metal mechanical pump designs. This paper details the design, build, and performance test of a mechanical NaK pump developed at NASA Marshall Space Flight Center. The pump was designed to meet reactor cooling requirements using commercially available components modified for high temperature NaK service.

Na2Ti6O13@TiO2 core-shell nanorods with controllable mesoporous shells and their enhanced photocatalytic performance

NASA Astrophysics Data System (ADS)

Zhou, Xuefan; Zhong, Donglin; Luo, Hang; Pan, Jun; Zhang, Dou

2018-01-01

In this study, dispersive and free-standing Na2Ti6O13 nanorods with diameter of about 500 nm and length of about 10 μm were synthesized by the molten salt method. The Na2Ti6O13@TiO2 (denoted as TTO) core-shell nanorods were fabricated by a versatile kinetics controlled coating method. The TiO2 shells were uniform and mesoporous with exposed {101} facets. The thickness of TiO2 shells can be well controlled by the content of Ti(OC4H9)4, ranging from 0 nm, 15 nm, 60 nm to 70 nm corresponding to Na2Ti6O13, 0.25-TTO, 0.50-TTO and 0.75-TTO nanorods respectively. The crystalline phases, microstructure, porosity, photoabsorption and photocatalytic performance of all the samples were investigated systematically. The nanoscale heterojunction structure between Na2Ti6O13 and TiO2, reductive TiO2 {101} facets and high aspect ratio Na2Ti6O13 nanorods resulted in the enhanced photocatalytic performance of TTO nanorods. The optimized thickness of TiO2 shells were about 60 nm for 0.50-TTO nanorods, which possessed superior BET surface area, optical absorption and photocatalytic performance.

Using Firn Air for Facility Cooling at the WAIS Divide Site

DTIC Science & Technology

2014-09-17

reduce logistics costs at remote field camps where it is critical to maintain proper temperatures to preserve sensitive deep ice cores. We assessed the...feasibility of using firn air for cooling at the West Antarc- tic Ice Sheet (WAIS) Divide ice core drilling site as a means to adequately and...efficiently refrigerate ice cores during storage and processing. We used estimates of mean annual temperature, temperature variations, and firn

Mpc-scale diffuse radio emission in two massive cool-core clusters of galaxies

NASA Astrophysics Data System (ADS)

Sommer, Martin W.; Basu, Kaustuv; Intema, Huib; Pacaud, Florian; Bonafede, Annalisa; Babul, Arif; Bertoldi, Frank

2017-04-01

Radio haloes are diffuse synchrotron sources on scales of ˜1 Mpc that are found in merging clusters of galaxies, and are believed to be powered by electrons re-accelerated by merger-driven turbulence. We present measurements of extended radio emission on similarly large scales in two clusters of galaxies hosting cool cores: Abell 2390 and Abell 2261. The analysis is based on interferometric imaging with the Karl G. Jansky Very Large Array, Very Large Array and Giant Metrewave Radio Telescope. We present detailed radio images of the targets, subtract the compact emission components and measure the spectral indices for the diffuse components. The radio emission in A2390 extends beyond a known sloshing-like brightness discontinuity, and has a very steep in-band spectral slope at 1.5 GHz that is similar to some known ultrasteep spectrum radio haloes. The diffuse signal in A2261 is more extended than in A2390 but has lower luminosity. X-ray morphological indicators, derived from XMM-Newton X-ray data, place these clusters in the category of relaxed or regular systems, although some asymmetric features that can indicate past minor mergers are seen in the X-ray brightness images. If these two Mpc-scale radio sources are categorized as giant radio haloes, they question the common assumption of radio haloes occurring exclusively in clusters undergoing violent merging activity, in addition to commonly used criteria for distinguishing between radio haloes and minihaloes.

Synthesis and characterization of Na(Gd0.5Lu0.5)F4: Nd3+,a core-shell free multifunctional contrast agent.

PubMed

Mimun, L Christopher; Ajithkumar, G; Rightsell, Chris; Langloss, Brian W; Therien, Michael J; Sardar, Dhiraj K

2017-02-25

Compared to conventional core-shell structures, core-shell free nanoparticles with multiple functionalities offer several advantages such as minimal synthetic complexity and low production cost. In this paper, we present the synthesis and characterization of Nd 3+ doped Na(Gd 0.5 Lu 0.5 )F 4 as a core-shell free nanoparticle system with three functionalities. Nanocrystals with 20 nm diameter, high crystallinity and a narrow particle size distributions were synthesized by the solvothermal method and characterized by various analytical techniques to understand their phase and morphology. Fluorescence characteristics under near infrared (NIR) excitation at 808 nm as well as X-ray excitation were studied to explore their potential in NIR optical and X-ray imaging. At 1.0 mol% Nd concentration, we observed a quantum yield of 25% at 1064 nm emission with 13 W/cm 2 excitation power density which is sufficiently enough for imaging applications. Under 130 kVp (5 mA) power of X-ray excitation, Nd 3+ doped Na(Gd 0.5 Lu 0.5 )F 4 shows the characteristic emission bands of Gd 3+ and Nd 3+ with the strongest emission peak at 1064 nm due to Nd 3+ . Furthermore, magnetization measurements show that the nanocrystals are paramagnetic in nature with a calculated magnetic moment per particle of ~570 μB at 2T. These preliminary results support the suitability of the present nanophosphor as a multimodal contrast agent with three imaging features viz. optical, magnetic and X-ray.

Revisiting the Cooling Flow Problem in Galaxies, Groups, and Clusters of Galaxies

NASA Astrophysics Data System (ADS)

McDonald, M.; Gaspari, M.; McNamara, B. R.; Tremblay, G. R.

2018-05-01

We present a study of 107 galaxies, groups, and clusters spanning ∼3 orders of magnitude in mass, ∼5 orders of magnitude in central galaxy star formation rate (SFR), ∼4 orders of magnitude in the classical cooling rate ({\\dot{M}}cool}\\equiv {M}gas}(r< {r}cool})/{t}cool}) of the intracluster medium (ICM), and ∼5 orders of magnitude in the central black hole accretion rate. For each system in this sample, we measure the ICM cooling rate, {\\dot{M}}cool}, using archival Chandra X-ray data and acquire the SFR and systematic uncertainty in the SFR by combining over 330 estimates from dozens of literature sources. With these data, we estimate the efficiency with which the ICM cools and forms stars, finding {ε }cool}\\equiv {SFR}/{\\dot{M}}cool}=1.4 % +/- 0.4% for systems with {\\dot{M}}cool}> 30 M ⊙ yr‑1. For these systems, we measure a slope in the SFR–{\\dot{M}}cool} relation greater than unity, suggesting that the systems with the strongest cool cores are also cooling more efficiently. We propose that this may be related to, on average, higher black hole accretion rates in the strongest cool cores, which could influence the total amount (saturating near the Eddington rate) and dominant mode (mechanical versus radiative) of feedback. For systems with {\\dot{M}}cool}< 30 M ⊙ yr‑1, we find that the SFR and {\\dot{M}}cool} are uncorrelated and show that this is consistent with star formation being fueled at a low (but dominant) level by recycled ISM gas in these systems. We find an intrinsic log-normal scatter in SFR at a fixed {\\dot{M}}cool} of 0.52 ± 0.06 dex (1σ rms), suggesting that cooling is tightly self-regulated over very long timescales but can vary dramatically on short timescales. There is weak evidence that this scatter may be related to the feedback mechanism, with the scatter being minimized (∼0.4 dex) for systems for which the mechanical feedback power is within a factor of two of the cooling luminosity.

Group IVA irons: New constraints on the crystallization and cooling history of an asteroidal core with a complex history

NASA Astrophysics Data System (ADS)

McCoy, T. J.; Walker, R. J.; Goldstein, J. I.; Yang, J.; McDonough, W. F.; Rumble, D.; Chabot, N. L.; Ash, R. D.; Corrigan, C. M.; Michael, J. R.; Kotula, P. G.

2011-11-01

We report analyses of 14 group IVA iron meteorites, and the ungrouped but possibly related, Elephant Moraine (EET) 83230, for siderophile elements by laser ablation ICP-MS and isotope dilution. EET was also analyzed for oxygen isotopic composition and metallographic structure, and Fuzzy Creek, currently the IVA with the highest Ni concentration, was analyzed for metallographic structure. Highly siderophile elements (HSE) Re, Os and Ir concentrations vary by nearly three orders of magnitude over the entire range of IVA irons, while Ru, Pt and Pd vary by less than factors of five. Chondrite normalized abundances of HSE form nested patterns consistent with progressive crystal-liquid fractionation. Attempts to collectively model the HSE abundances resulting from fractional crystallization achieved best results for 3 wt.% S, compared to 0.5 or 9 wt.% S. Consistent with prior studies, concentrations of HSE and other refractory siderophile elements estimated for the bulk IVA core and its parent body are in generally chondritic proportions. Projected abundances of Pd and Au, relative to more refractory HSE, are slightly elevated and modestly differ from L/LL chondrites, which some have linked with group IVA, based on oxygen isotope similarities. Abundance trends for the moderately volatile and siderophile element Ga cannot be adequately modeled for any S concentration, the cause of which remains enigmatic. Further, concentrations of some moderately volatile and siderophile elements indicate marked, progressive depletions in the IVA system. However, if the IVA core began crystallization with ˜3 wt.% S, depletions of more volatile elements cannot be explained as a result of prior volatilization/condensation processes. The initial IVA core had an approximately chondritic Ni/Co ratio, but a fractionated Fe/Ni ratio of ˜10, indicates an Fe-depleted core. This composition is most easily accounted for by assuming that the surrounding silicate shell was enriched in iron

Revealing Thermal Instabilities in the Core of the Phoenix Cluster

NASA Astrophysics Data System (ADS)

McDonald, Michael

2017-08-01

The Phoenix cluster is the most relaxed cluster known, and hosts the strongest cool core of any cluster yet discovered. At the center of this cluster is a massive starburst galaxy, with a SFR of 500-1000 Msun/yr, seemingly satisfying the early cooling flow predictions, despite the presence of strong AGN feedback from the central supermassive black hole. Here we propose deep narrow-band imaging of the central 120 kpc of the cluster, to map the warm (10^4K) ionized gas via the [O II] emission line. In low-z clusters, such as Perseus and Abell 1795, the warm, ionized phase is of critical importance to map out thermal instabilities in the hot gas, and maps of Halpha and [O II] have been used for decades to understand how (and how not) cooling proceeds in the intracluster medium. The data proposed for here, combined with deep ALMA data, a recently-approved Large Chandra Program, and recently-approved multi-frequency JVLA data, will allow us to probe the cooling ICM, the cool, filamentary gas, the cold molecular gas, the star-forming population, and the AGN jets all on scales of <10 kpc. This multi-observatory campaign, focusing on the most extreme cooling cluster, will lead to a more complete understanding of how and why thermal instabilities develop in the hot ICM of cool core clusters.

Computer Simulation To Assess The Feasibility Of Coring Magma

NASA Astrophysics Data System (ADS)

Su, J.; Eichelberger, J. C.

2017-12-01

Lava lakes on Kilauea Volcano, Hawaii have been successfully cored many times, often with nearly complete recovery and at temperatures exceeding 1100oC. Water exiting nozzles on the diamond core bit face quenches melt to glass just ahead of the advancing bit. The bit readily cuts a clean annulus and the core, fully quenched lava, passes smoothly into the core barrel. The core remains intact after recovery, even when there are comparable amounts of glass and crystals with different coefficients of thermal expansion. The unique resulting data reveal the rate and sequence of crystal growth in cooling basaltic lava and the continuous liquid line of descent as a function of temperature from basalt to rhyolite. Now that magma bodies, rather than lava pooled at the surface, have been penetrated by geothermal drilling, the question arises as to whether similar coring could be conducted at depth, providing fundamentally new insights into behavior of magma. This situation is considerably more complex because the coring would be conducted at depths exceeding 2 km and drilling fluid pressures of 20 MPa or more. Criteria that must be satisfied include: 1) melt is quenched ahead of the bit and the core itself must be quenched before it enters the barrel; 2) circulating drilling fluid must keep the temperature of the coring assembling cooled to within operational limits; 3) the drilling fluid column must nowhere exceed the local boiling point. A fluid flow simulation was conducted to estimate the process parameters necessary to maintain workable temperatures during the coring operation. SolidWorks Flow Simulation was used to estimate the effect of process parameters on the temperature distribution of the magma immediately surrounding the borehole and of drilling fluid within the bottom-hole assembly (BHA). A solid model of the BHA was created in SolidWorks to capture the flow behavior around the BHA components. Process parameters used in the model include the fluid properties and

Constraints on The Coupled Thermal Evolution of the Earth's Core and Mantle, The Age of The Inner Core, And The Origin of the 186Os/188Os Core(?) Signal in Plume-Derived Lavas

NASA Astrophysics Data System (ADS)

Lassiter, J. C.

2005-12-01

Thermal and chemical interaction between the core and mantle has played a critical role in the thermal and chemical evolution of the Earth's interior. Outer core convection is driven by core cooling and inner core crystallization. Core/mantle heat transfer also buffers mantle potential temperature, resulting in slower rates of mantle cooling (~50-100 K/Ga) than would be predicted from the discrepancy between current rates of surface heat loss (~44 TW) and internal radioactive heat production (~20 TW). Core/mantle heat transfer may also generate thermal mantle plumes responsible for ocean island volcanic chains such as the Hawaiian Islands. Several studies suggest that mantle plumes, in addition to transporting heat from the core/mantle boundary, also carry a chemical signature of core/mantle interaction. Elevated 186Os/188Os ratios in lavas from Hawaii, Gorgona, and in the 2.8 Ga Kostomuksha komatiites have been interpreted as reflecting incorporation of an outer core component with high time-integrated Pt/Os and Re/Os ( Brandon et al., 1999, 2003; Puchtel et al., 2005). Preferential partitioning of Os relative to Re and Pt into the inner core during inner core growth may generate elevated Re/Os and Pt/Os ratios in the residual outer core. Because of the long half-life of 190Pt (the parent of 186Os, t1/2 = 489 Ga), an elevated 186Os/188Os outer core signature in plume lavas requires that inner core crystallization began early in Earth history, most likely prior to 3.5 Ga. This in turn requires low time-averaged core/mantle heat flow (<~2.5 TW) or large quantities of heat-producing elements in the core. Core/mantle heat flow may be estimated using boundary-layer theory, by measuring the heat transported in mantle plumes, by estimating the heat transported along the outer core adiabat, or by comparing the rates of heat production, surface heat loss, and secular cooling of the mantle. All of these independent methods suggest time-averaged core/mantle heat flow of ~5

Hemodynamic and thermal responses to head and neck cooling in men and women

NASA Technical Reports Server (NTRS)

Ku, Y. T.; Montgomery, L. D.; Webbon, B. W.

1996-01-01

Personal cooling systems are used to alleviate symptoms of multiple sclerosis and to prevent increased core temperature during daily activities. The objective of this study was to determine the operating characteristics and the physiologic changes produced by short term use of one commercially available thermal control system. A Life Support Systems, Inc. Mark VII portable cooling system and a liquid cooling helmet were used to cool the head and neck regions of 12 female and 12 male subjects (25-55 yr) in this study. The healthy subjects, seated in an upright position at normal room temperature (approximately 21 degrees C), were tested for 30 min with the liquid cooling garment operated at its maximum cooling capacity. Electrocardiograms and scalp and intracranial blood flows were recorded periodically during each test sequence. Scalp, right and left ear, and oral temperatures and cooling system parameters were logged every 5 min. Scalp, right and left ear canal, and oral temperatures were all significantly (P <0.05) reduced by 30 min of head and neck cooling. Oral temperatures decreased approximately 0.2-0.6 degrees C after 30 min and continued to decrease further (approximately 0.1-0.2 degrees C) for a period of approximately 10 min after removal of the cooling helmet. Intracranial blood flow decreased significantly (P < 0.05) during the first 10 min of the cooling period. Both right and left ear temperatures in the women were significantly lower than those of the men during the cooling period. These data indicate that head and neck cooling may be used to reduce core temperature to that needed for symptomatic relief of both male and female multiple sclerosis patients. This study quantifies the operating characteristics of one liquid cooling garment as an example of the information needed to compare the efficiency of other garments operated under different test conditions.

Development of a fuel-rod simulator and small-diameter thermocouples for high-temperature, high-heat-flux tests in the Gas-Cooled Fast Reactor Core Flow Test Loop

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCulloch, R.W.; MacPherson, R.E.

1983-03-01

The Core Flow Test Loop was constructed to perform many of the safety, core design, and mechanical interaction tests in support of the Gas-Cooled Fast Reactor (GCFR) using electrically heated fuel rod simulators (FRSs). Operation includes many off-normal or postulated accident sequences including transient, high-power, and high-temperature operation. The FRS was developed to survive: (1) hundreds of hours of operation at 200 W/cm/sup 2/, 1000/sup 0/C cladding temperature, and (2) 40 h at 40 W/cm/sup 2/, 1200/sup 0/C cladding temperature. Six 0.5-mm type K sheathed thermocouples were placed inside the FRS cladding to measure steady-state and transient temperatures through cladmore » melting at 1370/sup 0/C.« less

Rapid endovascular catheter core cooling combined with cold saline as an adjunct to percutaneous coronary intervention for the treatment of acute myocardial infarction. The CHILL-MI trial: a randomized controlled study of the use of central venous catheter core cooling combined with cold saline as an adjunct to percutaneous coronary intervention for the treatment of acute myocardial infarction.

PubMed

Erlinge, David; Götberg, Matthias; Lang, Irene; Holzer, Michael; Noc, Marko; Clemmensen, Peter; Jensen, Ulf; Metzler, Bernhard; James, Stefan; Bötker, Hans Erik; Omerovic, Elmir; Engblom, Henrik; Carlsson, Marcus; Arheden, Håkan; Ostlund, Ollie; Wallentin, Lars; Harnek, Jan; Olivecrona, Göran K

2014-05-13

The aim of this study was to confirm the cardioprotective effects of hypothermia using a combination of cold saline and endovascular cooling. Hypothermia has been reported to reduce infarct size (IS) in patients with ST-segment elevation myocardial infarctions. In a multicenter study, 120 patients with ST-segment elevation myocardial infarctions (<6 h) scheduled to undergo percutaneous coronary intervention were randomized to hypothermia induced by the rapid infusion of 600 to 2,000 ml cold saline and endovascular cooling or standard of care. Hypothermia was initiated before percutaneous coronary intervention and continued for 1 h after reperfusion. The primary end point was IS as a percent of myocardium at risk (MaR), assessed by cardiac magnetic resonance imaging at 4 ± 2 days. Mean times from symptom onset to randomization were 129 ± 56 min in patients receiving hypothermia and 132 ± 64 min in controls. Patients randomized to hypothermia achieved a core body temperature of 34.7°C before reperfusion, with a 9-min longer door-to-balloon time. Median IS/MaR was not significantly reduced (hypothermia: 40.5% [interquartile range: 29.3% to 57.8%; control: 46.6% [interquartile range: 37.8% to 63.4%]; relative reduction 13%; p = 0.15). The incidence of heart failure was lower with hypothermia at 45 ± 15 days (3% vs. 14%, p < 0.05), with no mortality. Exploratory analysis of early anterior infarctions (0 to 4 h) found a reduction in IS/MaR of 33% (p < 0.05) and an absolute reduction of IS/left ventricular volume of 6.2% (p = 0.15). Hypothermia induced by cold saline and endovascular cooling was feasible and safe, and it rapidly reduced core temperature with minor reperfusion delay. The primary end point of IS/MaR was not significantly reduced. Lower incidence of heart failure and a possible effect in patients with early anterior ST-segment elevation myocardial infarctions need confirmation. (Efficacy of Endovascular Catheter Cooling Combined With Cold

Core Design Characteristics of the Fluoride Salt-Cooled High Temperature Demonstration Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Nicholas R; Qualls, A L; Betzler, Benjamin R

2016-01-01

Fluoride salt-cooled high temperature reactors (FHRs) are a promising reactor technology option with significant knowledge gaps to implementation. One potential approach to address those technology gaps is via a small-scale demonstration reactor with the goal of increasing the technology readiness level (TRL) of the overall system for the longer term. The objective of this paper is to outline a notional concept for such a system, and to address how the proposed concept would advance the TRL of FHR concepts. Development of the proposed FHR Demonstration Reactor (DR) will enable commercial FHR deployment through disruptive and rapid technology development and demonstration.more » The FHR DR will close remaining gaps to commercial viability. Lower risk technologies are included in the initial FHR DR design to ensure that the reactor can be built, licensed, and operated within an acceptable budget and schedule. Important capabilities that will be demonstrated by building and operating the FHR DR include core design methodologies; fabrication and operation of high temperature reactors; salt procurement, handling, maintenance, and ultimate disposal; salt chemistry control to maximize vessel life; tritium management; heat exchanger performance; pump performance; and reactivity control. The FHR DR is considered part of a broader set of FHR technology development and demonstration efforts, some of which are already underway. Nonreactor test efforts (e.g., heated salt loops or loops using simulant fluids) can demonstrate many technologies necessary for commercial deployment of FHRs. The FHR DR, however, fulfills a crucial role in FHR technology development by advancing the technical maturity and readiness level of the system as a whole.« less

Na-KATPase activity and intracellular ion concentrations in the lactating guinea pig mammary gland. Studies on Na-K activated adenosine triphosphatase, XXXVI.

PubMed

Vreeswijk, J H; de Pont, J J; Bonting, S L

1975-01-01

The intracellular sodium, potassium and chloride concentrations in slices of lactating guinea pig mammary gland have been determined by chemical analysis and the use of appropriate values for extracellular space. These ion concentrations after 1 hr incubation at 37 degrees C in a Krebs-Ringer bicarbonate solution are 45mM Na+, 138 mM K+ and 44 mM Cl-, which values are in agreement with those found in fresh mammary gland slices. Inhibition of the NaK activated ATPase cation pump system of the tissue by 10(-4)M ouabain, anoxia or cooling to 0 degrees C Causes a gain of Na+ and an equimolar loss of K+ without a significant change in chloride concentration. The effect of cooling (0 degrees C) is reversible by reincubation at 37 degrees C. Water content of the tissue (76.5% of wet weight) and extracellular space (40.5%) do not change under these conditions. The results permit the conclusion that the NaK activated ATPase system is responsible for the maintenance of the intracellular Na+ and K+ concentrations, but do not support the presence of a chloride pump.

Application of formal optimization techniques in thermal/structural design of a heat-pipe-cooled panel for a hypersonic vehicle

NASA Technical Reports Server (NTRS)

Camarda, Charles J.; Riley, Michael F.

1987-01-01

Nonlinear mathematical programming methods are used to design a radiantly cooled and heat-pipe-cooled panel for a Mach 6.7 transport. The cooled portion of the panel is a hybrid heat-pipe/actively cooled design which uses heat pipes to transport the absorbed heat to the ends of the panel where it is removed by active cooling. The panels are optimized for minimum mass and to satisfy a set of heat-pipe, structural, geometric, and minimum-gage constraints. Two panel concepts are investigated: cylindrical heat pipes embedded in a honeycomb core and an integrated design which uses a web-core heat-pipe sandwich concept. The latter was lighter and resulted in a design which was less than 10 percent heavier than an all actively cooled concept. The heat-pipe concept, however, is redundant and can sustain a single-point failure, whereas the actively cooled concept cannot. An additional study was performed to determine the optimum number of coolant manifolds per panel for a minimum-mass design.

NUCLEAR REACTOR CORE DESIGN

DOEpatents

Mahlmeister, J.E.; Peck, W.S.; Haberer, W.V.; Williams, A.C.

1960-03-22

An improved core design for a sodium-cooled, graphitemoderated nuclear reactor is described. The improved reactor core comprises a number of blocks of moderator material, each block being in the shape of a regular prism. A number of channels, extending the length of each block, are disposed around the periphery. When several blocks are placed in contact to form the reactor core, the channels in adjacent blocks correspond with each other to form closed conduits extending the length of the core. Fuel element clusters are disposed in these closed conduits, and liquid coolant is forced through the annulus between the fuel cluster and the inner surface of the conduit. In a preferred embodiment of the invention, the moderator blocks are in the form of hexagonal prisms with longitudinal channels cut into the corners of the hexagon. The main advantage of an "edge-loaded" moderator block is that fewer thermal neutrons are absorbed by the moderator cladding, as compared with a conventional centrally loaded moderator block.

Does the diurnal increase in central temperature interact with pre-cooling or passive warm-up of the leg?

PubMed

Racinais, Sébastien; Blonc, Stephen; Oksa, Juha; Hue, Olivier

2009-01-01

Seven male subjects volunteered to participate in an investigation of whether the diurnal increase in core temperature influences the effects of pre-cooling or passive warm-up on muscular power. Morning (07:00-09:00h) and afternoon (17:00-19:00h) evaluation of maximal power output during a cycling sprint was performed on different days in a control condition (room at 21.8 degrees C, 69% rh), after 30min of pre-cooling in a cold bath (16 degrees C), or after 30min of passive warm-up in a hot bath (38 degrees C). Despite an equivalent increase from morning to afternoon in core temperature in all conditions (+0.4 degrees C, P<0.05), power output displayed a diurnal increase in control condition only. A local cooling or heating of the leg in a neutral environment blunted the diurnal variation in muscular power. Because pre-cooling decreases muscle power, force and velocity irrespective of time-of-day, athletes should strictly avoid any cooling before a sprint exercise. In summary, diurnal variation in muscle power output seems to be more influenced by muscle rather than core temperature.

A non cool-core 4.6-keV cluster around the bright nearby radio galaxy PKS B1416-493

NASA Astrophysics Data System (ADS)

Worrall, D. M.; Birkinshaw, M.

2017-05-01

We present new X-ray (Chandra) and radio (ATCA) observations of the z = 0.09 radio galaxy PKS B1416-493, a member of the southern equivalent of the 3CRR sample. We find the source to be embedded in a previously unrecognized bright kT = 4.6-keV non cool-core cluster. The discovery of new clusters of such high temperature and luminosity within z = 0.1 is rare. The radio source was chosen for observation based on its intermediate FR I/II morphology. We identify a cavity coincident with the northeast lobe, and excess counts associated with the southwest lobe that we interpret as inverse-Compton X-ray emission. The jet power, at 5.3 × 1044 erg s-1, when weighted by radio source density, supports suggestions that radio sources of intermediate morphology and radio power may dominate radio-galaxy heating in the local Universe.

Compaction-Driven Evolution of Pluto's Rocky Core: Implications for Water-Rock Interactions

NASA Astrophysics Data System (ADS)

Gabasova, L. R.; Tobie, G.; Choblet, G.

2018-05-01

We model the compaction of Pluto's rocky core after accretion and explore the potential for hydrothermal circulation within the porous layer, as well as examine its effect on core cooling and the persistence of a liquid internal ocean.

Performance potential of gas-core and fusion rockets - A mission applications survey.

NASA Technical Reports Server (NTRS)

Fishbach, L. H.; Willis, E. A., Jr.

1971-01-01

This paper reports an evaluation of the performance potential of five nuclear rocket engines for four mission classes. These engines are: the regeneratively cooled gas-core nuclear rocket; the light bulb gas-core nuclear rocket; the space-radiator cooled gas-core nuclear rocket; the fusion rocket; and an advanced solid-core nuclear rocket which is included for comparison. The missions considered are: earth-to-orbit launch; near-earth space missions; close interplanetary missions; and distant interplanetary missions. For each of these missions, the capabilities of each rocket engine type are compared in terms of payload ratio for the earth launch mission or by the initial vehicle mass in earth orbit for space missions (a measure of initial cost). Other factors which might determine the engine choice are discussed. It is shown that a 60 day manned round trip to Mars is conceivable.-

Transient Response to Rapid Cooling of a Stainless Steel Sodium Heat Pipe

NASA Technical Reports Server (NTRS)

Mireles, Omar R.; Houts, Michael G.

2011-01-01

Compact fission power systems are under consideration for use in long duration space exploration missions. Power demands on the order of 500 W, to 5 kW, will be required for up to 15 years of continuous service. One such small reactor design consists of a fast spectrum reactor cooled with an array of in-core alkali metal heat pipes coupled to thermoelectric or Stirling power conversion systems. Heat pipes advantageous attributes include a simplistic design, lack of moving parts, and well understood behavior. Concerns over reactor transients induced by heat pipe instability as a function of extreme thermal transients require experimental investigations. One particular concern is rapid cooling of the heat pipe condenser that would propagate to cool the evaporator. Rapid cooling of the reactor core beyond acceptable design limits could possibly induce unintended reactor control issues. This paper discusses a series of experimental demonstrations where a heat pipe operating at near prototypic conditions experienced rapid cooling of the condenser. The condenser section of a stainless steel sodium heat pipe was enclosed within a heat exchanger. The heat pipe - heat exchanger assembly was housed within a vacuum chamber held at a pressure of 50 Torr of helium. The heat pipe was brought to steady state operating conditions using graphite resistance heaters then cooled by a high flow of gaseous nitrogen through the heat exchanger. Subsequent thermal transient behavior was characterized by performing an energy balance using temperature, pressure and flow rate data obtained throughout the tests. Results indicate the degree of temperature change that results from a rapid cooling scenario will not significantly influence thermal stability of an operating heat pipe, even under extreme condenser cooling conditions.

Mold with improved core for metal casting operation

DOEpatents

Gritzner, Verne B.; Hackett, Donald W.

1977-01-01

The present invention is directed to a mold containing an improved core for use in casting hollow, metallic articles. The core is formed of, or covered with, a layer of cellular material which possesses sufficient strength to maintain its structural integrity during casting, but will crush to alleviate the internal stresses that build up if the normal contraction during solidification and cooling is restricted.

Superconducting HTS coil made from round cable cooled by liquid nitrogen flow

NASA Astrophysics Data System (ADS)

Šouc, J.; Gömöry, F.; Vojenčiak, M.; Solovyov, M.; Seiler, E.; Kováč, J.; Frolek, L.

2017-10-01

The concept of simple cooling arrangement for superconducting coil made from a round cable based on high-temperature superconductor tapes is demonstrated. The cable architecture is similar to the Conductor on Round Core (CORC®) concept: it consists of eight superconducting tapes wound in two layers on a copper tube core in a helical manner. Such a Conductor on Round Tube hand-made cable 4 m long was used to wind the coil with eight turns on 14 cm diameter. Layers of commercial aerogel and polyurethane foam were applied to the coil to provide vacuum-less thermal insulation at its cooling by the flow of liquid nitrogen (LN) in the cable tube. The temperature of superconducting tapes was around 1 K above the coolant temperature in these conditions, causing about 16% reduction of the critical current compared to the LN bath cooling. Electromagnetic performance of the coil was calculated by the model based on the finite element method and the results compared with experimental observations.

The effect of starting or stopping skin cooling on the thermoregulatory responses during leg exercise in humans.

PubMed

Demachi, K; Yoshida, T; Kume, M; Tsuneoka, H

2012-07-01

To assess the effects of starting or stopping leg cooling on the thermoregulatory responses during exercise, 60 min of cycling exercise at 30% of maximal oxygen uptake was performed under 4 conditions using tube trouser perfused with water at 10 °C; no leg cooling (NC), starting of leg cooling after 30 min of exercise (delayed cooling, DC), continuous leg cooling (CC), and stopping of continuous leg cooling after 30 min of exercise (SC) at an environmental temperature of 28.5 °C. During exercise under the DC conditions, an instantaneous increase in the esophageal temperature (Tes), a suppression of the cutaneous vascular conductance at the forearm (%CVC), and a decrease in the mean skin temperature (Tsk) were observed after leg cooling. The total sweat loss (Δm sw,tot) was lower under the DC than the NC condition. In the SC study, however, the Tes remained constant, while the %CVC increased gradually after leg cooling was stopped, and the Δm sw,tot was greater than that under the CC condition. These results suggest that during exercise, rapid skin cooling of the leg may cause an increase in core temperature, while also enhancing thermal stress. However, stopping skin cooling did not significantly affect the core temperature long-term, because the skin blood flow and sweat rate subsequently increased. © Georg Thieme Verlag KG Stuttgart · New York.

Thermionic nuclear reactor with internal heat distribution and multiple duct cooling

DOEpatents

Fisher, C.R.; Perry, L.W. Jr.

1975-11-01

A Thermionic Nuclear Reactor is described having multiple ribbon-like coolant ducts passing through the core, intertwined among the thermionic fuel elements to provide independent cooling paths. Heat pipes are disposed in the core between and adjacent to the thermionic fuel elements and the ribbon ducting, for the purpose of more uniformly distributing the heat of fission among the thermionic fuel elements and the ducts.

How cores grow by pebble accretion. I. Direct core growth

NASA Astrophysics Data System (ADS)

Brouwers, M. G.; Vazan, A.; Ormel, C. W.

2018-03-01

directly form rocky cores up to only 0.6 M⊕, and is unable to form similarly sized icy cores. Subsequent core growth can proceed indirectly when the planet cools, provided it is able to retain its high-Z material.

Cooling hyperthermic firefighters by immersing forearms and hands in 10 degrees C and 20 degrees C water.

PubMed

Giesbrecht, Gordon G; Jamieson, Christopher; Cahill, Farrell

2007-06-01

Firefighters experience significant heat stress while working with heavy gear in a hot, humid environment. This study compared the cooling effectiveness of immersing the forearms and hands in 10 and 20 degrees C water. Six men (33 +/- 10 yr; 180 +/- 4 cm; 78 +/- 9 kg; 19 +/- 5% body fat) wore firefighter 'turn-out gear' (heavy clothing and breathing apparatus weighing 27 kg) in a protocol including three 20-min exercise bouts (step test, 78 W, 40 degrees C air, 40% RH) each followed by a 20-min rest/cooling (21 degrees C air); i.e., 60 min of exercise, 60 min of cooling. Turn-out gear was removed during rest/cooling periods and subjects either rested (Control), immersed their hands in 10 or 20 degrees C water (H-10, H-20), or immersed their hands and forearms in 10 or 20 degrees C water (HF-10, HF-20). In 20 degrees C water, hand immersion did not reduce core temperature compared with Control; however, including forearm immersion decreased core temperature below Control values after both the second and final exercise periods (p < 0.001). In 10 degrees C water, adding forearm with hand immersion produced a lower core temperature (0.8 degrees C above baseline) than all other conditions (1.1 to 1.4 degrees C above baseline) after the final exercise period (p < 0.001). Sweat loss during Control (1458 g) was greater than all active cooling protocols (1146 g) (p < 0.001), which were not different from each other. Hand and forearm immersion in cool water is simple, reduces heat strain, and may increase work performance in a hot, humid environment. With 20 degrees C water, forearms should be immersed with the hands to be effective. At lower water temperatures, forearm and/or hand immersion will be effective, although forearm immersion will decrease core temperature further.

Whole planet coupling between climate, mantle, and core: Implications for rocky planet evolution

NASA Astrophysics Data System (ADS)

Foley, Bradford J.; Driscoll, Peter E.

2016-05-01

Earth's climate, mantle, and core interact over geologic time scales. Climate influences whether plate tectonics can take place on a planet, with cool climates being favorable for plate tectonics because they enhance stresses in the lithosphere, suppress plate boundary annealing, and promote hydration and weakening of the lithosphere. Plate tectonics plays a vital role in the long-term carbon cycle, which helps to maintain a temperate climate. Plate tectonics provides long-term cooling of the core, which is vital for generating a magnetic field, and the magnetic field is capable of shielding atmospheric volatiles from the solar wind. Coupling between climate, mantle, and core can potentially explain the divergent evolution of Earth and Venus. As Venus lies too close to the sun for liquid water to exist, there is no long-term carbon cycle and thus an extremely hot climate. Therefore, plate tectonics cannot operate and a long-lived core dynamo cannot be sustained due to insufficient core cooling. On planets within the habitable zone where liquid water is possible, a wide range of evolutionary scenarios can take place depending on initial atmospheric composition, bulk volatile content, or the timing of when plate tectonics initiates, among other factors. Many of these evolutionary trajectories would render the planet uninhabitable. However, there is still significant uncertainty over the nature of the coupling between climate, mantle, and core. Future work is needed to constrain potential evolutionary scenarios and the likelihood of an Earth-like evolution.

Core-powered mass-loss and the radius distribution of small exoplanets

NASA Astrophysics Data System (ADS)

Ginzburg, Sivan; Schlichting, Hilke E.; Sari, Re'em

2018-05-01

Recent observations identify a valley in the radius distribution of small exoplanets, with planets in the range 1.5-2.0 R⊕ significantly less common than somewhat smaller or larger planets. This valley may suggest a bimodal population of rocky planets that are either engulfed by massive gas envelopes that significantly enlarge their radius, or do not have detectable atmospheres at all. One explanation of such a bimodal distribution is atmospheric erosion by high-energy stellar photons. We investigate an alternative mechanism: the luminosity of the cooling rocky core, which can completely erode light envelopes while preserving heavy ones, produces a deficit of intermediate sized planets. We evolve planetary populations that are derived from observations using a simple analytical prescription, accounting self-consistently for envelope accretion, cooling and mass-loss, and demonstrate that core-powered mass-loss naturally reproduces the observed radius distribution, regardless of the high-energy incident flux. Observations of planets around different stellar types may distinguish between photoevaporation, which is powered by the high-energy tail of the stellar radiation, and core-powered mass-loss, which depends on the bolometric flux through the planet's equilibrium temperature that sets both its cooling and mass-loss rates.

MODULAR CORE UNITS FOR A NEUTRONIC REACTOR

DOEpatents

Gage, J.F. Jr.; Sherer, D.B.

1964-04-01

A modular core unit for use in a nuclear reactor is described. Many identical core modules can be placed next to each other to make up a complete core. Such a module includes a cylinder of moderator material surrounding a fuel- containing re-entrant coolant channel. The re-entrant channel provides for the circulation of coolant such as liquid sodium from one end of the core unit, through the fuel region, and back out through the same end as it entered. Thermal insulation surrounds the moderator exterior wall inducing heat to travel inwardly to the coolant channel. Spaces between units may be used to accommodate control rods and support structure, which may be cooled by a secondary gas coolant, independently of the main coolant. (AEC)

Hemodynamic and Thermal Responses to Head and Neck Cooling in Men and Women

NASA Technical Reports Server (NTRS)

Ku, Yu-Tsuan E.; Montgomery, Leslie D.; Carbo, Jorge E.; Webbon, Bruce W.

1995-01-01

Personal cooling systems are used to alleviate symptoms of multiple sclerosis and to prevent increased core temperature during daily activities. Configurations of these systems include passive ice vests and circulating liquid cooling garments (LCGs) in the forms of vests, cooling caps and combined head and neck cooling systems. However, little information is available oil the amount or heat that can be extracted from the body with these systems or the physiologic changes produced by routine operation of these systems. The objective of this study was to determine the operating characteristics and the physiologic change, produced by short term use of one commercially available thermal control system.

Revealing the core-shell interactions of a giant strain relaxor ferroelectric 0.75Bi1/2Na1/2TiO3-0.25SrTiO3.

PubMed

Liu, Na; Acosta, Matias; Wang, Shuai; Xu, Bai-Xiang; Stark, Robert W; Dietz, Christian

2016-11-14

Lead-free relaxor ferroelectrics that feature a core-shell microstructure provide an excellent electromechanical response. They even have the potential to replace the environmentally hazardous lead-zirconia-titanate (PZT) in large strain actuation applications. Although the dielectric properties of core-shell ceramics have been extensively investigated, their piezoelectric properties are not yet well understood. To unravel the interfacial core-shell interaction, we studied the relaxation behaviour of field-induced ferroelectric domains in 0.75Bi 1/2 Na 1/2 TiO 3 -0.25SrTiO 3 (BNT-25ST), as a typical core-shell bulk material, using a piezoresponse force microscope. We found that after poling, lateral domains emerged at the core-shell interface and propagated to the shell region. Phase field simulations showed that the increased electrical potential beneath the core is responsible for the in-plane domain evolution. Our results imply that the field-induced domains act as pivotal points at the coherent heterophase core-shell interface, reinforcing the phase transition in the non-polar shell and thus promoting the giant strain.

Cooling of a Bose-Einstein Condensate by Spin Distillation.

PubMed

Naylor, B; Maréchal, E; Huckans, J; Gorceix, O; Pedri, P; Vernac, L; Laburthe-Tolra, B

2015-12-11

We propose and experimentally demonstrate a new cooling mechanism leading to purification of a Bose-Einstein condensate (BEC). Our scheme starts with a BEC polarized in the lowest energy spin state. Spin excited states are thermally populated by lowering the single particle energy gap set by the magnetic field. Then, these spin-excited thermal components are filtered out, which leads to an increase of the BEC fraction. We experimentally demonstrate such cooling for a spin 3 ^{52}Cr dipolar BEC. Our scheme should be applicable to Na or Rb, with the perspective to reach temperatures below 1 nK.

GRACKLE: a chemistry and cooling library for astrophysics

NASA Astrophysics Data System (ADS)

Smith, Britton D.; Bryan, Greg L.; Glover, Simon C. O.; Goldbaum, Nathan J.; Turk, Matthew J.; Regan, John; Wise, John H.; Schive, Hsi-Yu; Abel, Tom; Emerick, Andrew; O'Shea, Brian W.; Anninos, Peter; Hummels, Cameron B.; Khochfar, Sadegh

2017-04-01

We present the GRACKLE chemistry and cooling library for astrophysical simulations and models. GRACKLE provides a treatment of non-equilibrium primordial chemistry and cooling for H, D and He species, including H2 formation on dust grains; tabulated primordial and metal cooling; multiple ultraviolet background models; and support for radiation transfer and arbitrary heat sources. The library has an easily implementable interface for simulation codes written in C, C++ and FORTRAN as well as a PYTHON interface with added convenience functions for semi-analytical models. As an open-source project, GRACKLE provides a community resource for accessing and disseminating astrochemical data and numerical methods. We present the full details of the core functionality, the simulation and PYTHON interfaces, testing infrastructure, performance and range of applicability. GRACKLE is a fully open-source project and new contributions are welcome.

Enhancement of the sulfur capture capacity of limestones by the addition of Na2CO3 and NaCl.

PubMed

Laursen, K; Grace, J R; Lim, C J

2001-11-01

The ability of Na2CO3 and NaCl to enhance the sulfur capture capacity of three limestones was evaluated via fixed-bed calcination and sulfation experiments. The tested limestones represent three different sulfation morphologies: unreacted-core, network, and uniformly sulfated. Treatment with aqueous or powdered Na2CO3 significantly increased the Ca-utilization for two stones which normally sulfate in an unreacted-core pattern (20% to 45%) and network pattern (33% to 49%). The increase was lower for the uniformly sulfated stone (44% to 48%). Na2CO3 treatment increased the number of macropores leading to uniform sulfation of all particles, nearly eliminating the normal strong dependence of utilization on limestone type and particle size. The effect of Na2CO3 is believed to be associated with formation of a eutectic melt which enhances ionic diffusion and accelerates molecular rearrangement of the CaO. Treatment with aqueous NaCl solution caused a decrease in utilization, probably due to formation of large grains and plugging of pores caused by formation of a large amount of eutectic melt. The effect of Na2CO3 is less sensitive than that of NaCl to the amount added and the combustion environment (temperature and gas composition). In addition, Na2CO3 neither promotes corrosion nor forms chlorinated byproducts, which are main concerns associated with NaCl. Thus, Na2CO3 appears to have significant advantages over NaCl for enhancement of limestone sulfur capture capacity in fluidized-bed combustors.

Wave propagation simulation in the upper core of sodium-cooled fast reactors using a spectral-element method for heterogeneous media

NASA Astrophysics Data System (ADS)

Nagaso, Masaru; Komatitsch, Dimitri; Moysan, Joseph; Lhuillier, Christian

2018-01-01

ASTRID project, French sodium cooled nuclear reactor of 4th generation, is under development at the moment by Alternative Energies and Atomic Energy Commission (CEA). In this project, development of monitoring techniques for a nuclear reactor during operation are identified as a measure issue for enlarging the plant safety. Use of ultrasonic measurement techniques (e.g. thermometry, visualization of internal objects) are regarded as powerful inspection tools of sodium cooled fast reactors (SFR) including ASTRID due to opacity of liquid sodium. In side of a sodium cooling circuit, heterogeneity of medium occurs because of complex flow state especially in its operation and then the effects of this heterogeneity on an acoustic propagation is not negligible. Thus, it is necessary to carry out verification experiments for developments of component technologies, while such kind of experiments using liquid sodium may be relatively large-scale experiments. This is why numerical simulation methods are essential for preceding real experiments or filling up the limited number of experimental results. Though various numerical methods have been applied for a wave propagation in liquid sodium, we still do not have a method for verifying on three-dimensional heterogeneity. Moreover, in side of a reactor core being a complex acousto-elastic coupled region, it has also been difficult to simulate such problems with conventional methods. The objective of this study is to solve these 2 points by applying three-dimensional spectral element method. In this paper, our initial results on three-dimensional simulation study on heterogeneous medium (the first point) are shown. For heterogeneity of liquid sodium to be considered, four-dimensional temperature field (three spatial and one temporal dimension) calculated by computational fluid dynamics (CFD) with Large-Eddy Simulation was applied instead of using conventional method (i.e. Gaussian Random field). This three-dimensional numerical

CHAP-2 heat-transfer analysis of the Fort St. Vrain reactor core

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kotas, J.F.; Stroh, K.R.

1983-01-01

The Los Alamos National Laboratory is developing the Composite High-Temperature Gas-Cooled Reactor Analysis Program (CHAP) to provide advanced best-estimate predictions of postulated accidents in gas-cooled reactor plants. The CHAP-2 reactor-core model uses the finite-element method to initialize a two-dimensional temperature map of the Fort St. Vrain (FSV) core and its top and bottom reflectors. The code generates a finite-element mesh, initializes noding and boundary conditions, and solves the nonlinear Laplace heat equation using temperature-dependent thermal conductivities, variable coolant-channel-convection heat-transfer coefficients, and specified internal fuel and moderator heat-generation rates. This paper discusses this method and analyzes an FSV reactor-core accident thatmore » simulates a control-rod withdrawal at full power.« less

Exchange biased Co3O4 nanowires: A new insight into its magnetic core-shell nature

NASA Astrophysics Data System (ADS)

Thomas, S.; Jose, A.; Thanveer, T.; Anantharaman, M. R.

2017-06-01

We investigated interfacial exchange coupling effect in nano casted Co3O4 nanowires. Magnetometry measurements indicated that the magnetic response of the wires has two contributions. First one from the core of the wire which has characteristics of a 2D-DAFF(two-dimensional diluted antiferromagnet in a field). The second one is from uncompensated surface spins which get magnetically ordered towards the field direction once field cooled below 25 K. Below 25 K, the net magnetization of the core of the wire gets exchange coupled with the uncompensated surface spins giving rise to exchange bias effect. The unique 2D-DAFF/spin-glass core/shell heterostructure showed a pronounced training effect in the first field cycling itself. The magnitude of exchange bias field showed a maximum at intermediate cooling fields and for the higher cooling field, exchange bias got reduced.

Hypothalamic, rectal, and muscle temperatures in exercising dogs - Effect of cooling

NASA Technical Reports Server (NTRS)

Kruk, B.; Kaciuba-Uscilko, H.; Nazar, K.; Greenleaf, J. E.; Kozlowski, S.

1985-01-01

An experimental investigation of the mechanisms of performance prolongation during exercise is presented. Measurements were obtained of the rectal, muscle, and hypothalamic temperature of dogs during treadmill exercise at an ambient temperature of 22 + or - 1 C, with and without cooling by use of ice packs. In comparison with exercise without cooling, exercise with cooling was found to: (1) increase exercise duration from 90 + or - 14 to 145 + or - 15 min; (2) attenuate increases in hypothalamic, rectal and muscle temperature; (3) decrease respiratory and heart rates; and (4) lower blood lactic acid content. It is shown that although significant differences were found between the brain, core, and muscle temperatures during exercise with and without cooling, an inverse relation was observed between muscle temperature and the total duration of exercise. It is suggested that sustained muscle hyperthermia may have contributed to the limitation of working ability in exercise with and without cooling.

Effect of pre-cooling, with and without thigh cooling, on strain and endurance exercise performance in the heat.

PubMed

Cotter, J D; Sleivert, G G; Roberts, W S; Febbraio, M A

2001-04-01

Body cooling before exercise (i.e. pre-cooling) reduces physiological strain in humans during endurance exercise in temperate and warm environments, usually improving performance. This study examined the effectiveness of pre-cooling humans by ice-vest and cold (3 degrees C) air, with (LC) and without (LW) leg cooling, in reducing heat strain and improving endurance performance in the heat (35 degrees C, 60% RH). Nine habitually-active males completed three trials, involving pre-cooling (LC and LW) or no pre-cooling (CON: 34 degrees C air) before 35-min cycle exercise: 20 min at approximately 65% VO2peak then a 15-min work-performance trial. At exercise onset, mean core (Tc, from oesophagus and rectum) and skin temperatures, forearm blood flow (FBF), heart rate (HR), and ratings of exertion, body temperature and thermal discomfort were lower in LW and LC than CON (P<0.05). They remained lower at 20 min [e.g. Tc: CON 38.4+/-0.2 (+/-S.E.), LW 37.9+/-0.1, and LC 37.8+/-0.1 degrees C; HR: 177+/-3, 163+/-3 and 167+/-3 b.p.m.), except that FBF was equivalent (P=0.10) between CON (15.5+/-1.6) and LW (13.6+/-1.0 ml.100 ml tissue(-1) x min(-1)). Subsequent power output was higher in LW (2.95+/-0.24) and LC (2.91+/-0.25) than in CON (2.52+/-0.28 W kg(-1), P=0.00, N=8), yet final Tc remained lower. Pre-cooling by ice-vest and cold air effectively reduced physiological and psychophysical strain and improved endurance performance in the heat, irrespective of whether thighs were warmed or cooled.

DYNAMICS AND MAGNETIZATION IN GALAXY CLUSTER CORES TRACED BY X-RAY COLD FRONTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keshet, Uri; Markevitch, Maxim; Birnboim, Yuval

2010-08-10

Cold fronts (CFs)-density and temperature plasma discontinuities-are ubiquitous in cool cores of galaxy clusters, where they appear as X-ray brightness edges in the intracluster medium, nearly concentric with the cluster center. We analyze the thermodynamic profiles deprojected across core CFs found in the literature. While the pressure appears continuous across these CFs, we find that all of them require significant centripetal acceleration beneath the front. This is naturally explained by a tangential, nearly sonic bulk flow just below the CF, and a tangential shear flow involving a fair fraction of the plasma beneath the front. Such shear should generate near-equipartitionmore » magnetic fields on scales {approx}<50pc from the front and could magnetize the entire core. Such fields would explain the apparent stability of cool core CFs and the recently reported CF-radio minihalo association.« less

Pm-1 Reactor Core Final Design Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagley, R. O.; Cox, F. H.; Carnasale, A.

1962-01-01

The PM-1 water cooled and moderated core contains 741 highly enriched stainless steel cermet tubular fuel elements and 90 lumped B stainless steel burnable poison elements, and it is controlled by 6 Y-shaped europium titanate movable control rods. The core has a lifetime of 1.95 years when operated at its design power level of 9.37 mw of thermal energy. The control of the core is designed so that there is a positive shutdown margin at all times with either one rod stuck completely out or the core or with two rods stuck in the operating condition. The core power ismore » removed by 2125 gpm of pressurized water at an average temperature of 463 deg F and pressure of 1300 psia. In reactors of this type, the core is stable with a negative temperature coefficient of approximately 2.5 x 10/sup -4/ DELTA K/K/ deg F.« less

A Gas-Cooled-Reactor Closed-Brayton-Cycle Demonstration with Nuclear Heating

NASA Astrophysics Data System (ADS)

Lipinski, Ronald J.; Wright, Steven A.; Dorsey, Daniel J.; Peters, Curtis D.; Brown, Nicholas; Williamson, Joshua; Jablonski, Jennifer

2005-02-01

A gas-cooled reactor may be coupled directly to turbomachinery to form a closed-Brayton-cycle (CBC) system in which the CBC working fluid serves as the reactor coolant. Such a system has the potential to be a very simple and robust space-reactor power system. Gas-cooled reactors have been built and operated in the past, but very few have been coupled directly to the turbomachinery in this fashion. In this paper we describe the option for testing such a system with a small reactor and turbomachinery at Sandia National Laboratories. Sandia currently operates the Annular Core Research Reactor (ACRR) at steady-state powers up to 4 MW and has an adjacent facility with heavy shielding in which another reactor recently operated. Sandia also has a closed-Brayton-Cycle test bed with a converted commercial turbomachinery unit that is rated for up to 30 kWe of power. It is proposed to construct a small experimental gas-cooled reactor core and attach this via ducting to the CBC turbomachinery for cooling and electricity production. Calculations suggest that such a unit could produce about 20 kWe, which would be a good power level for initial surface power units on the Moon or Mars. The intent of this experiment is to demonstrate the stable start-up and operation of such a system. Of particular interest is the effect of a negative temperature power coefficient as the initially cold Brayton gas passes through the core during startup or power changes. Sandia's dynamic model for such a system would be compared with the performance data. This paper describes the neutronics, heat transfer, and cycle dynamics of this proposed system. Safety and radiation issues are presented. The views expressed in this document are those of the author and do not necessarily reflect agreement by the government.

Modifying the size and uniformity of upconversion Yb/Er:NaGdF4 nanocrystals through alkaline-earth doping.

PubMed

Lei, Lei; Chen, Daqin; Huang, Ping; Xu, Ju; Zhang, Rui; Wang, Yuansheng

2013-11-21

NaGdF4 is regarded as an ideal upconversion (UC) host material for lanthanide (Ln(3+)) activators because of its unique crystal structure, high Ln(3+) solubility, low phonon energy and high photochemical stability, and Ln(3+)-doped NaGdF4 UC nanocrystals (NCs) have been widely investigated as bio-imaging and magnetic resonance imaging agents recently. To realize their practical applications, controlling the size and uniformity of the monodisperse Ln(3+)-doped NaGdF4 UC NCs is highly desired. Unlike the routine routes by finely adjusting the multiple experimental parameters, herein we provide a facile and straightforward strategy to modify the size and uniformity of NaGdF4 NCs via alkaline-earth doping for the first time. With the increase of alkaline-earth doping content, the size of NaGdF4 NCs increases gradually, while the size-uniformity is still retained. We attribute this "focusing" of size distribution to the diffusion controlled growth of NaGdF4 NCs induced by alkaline-earth doping. Importantly, adopting the Ca(2+)-doped Yb/Er:NaGdF4 NCs as cores, the complete Ca/Yb/Er:NaGdF4@NaYF4 core-shell particles with excellent size-uniformity can be easily achieved. However, when taking the Yb/Er:NaGdF4 NCs without Ca(2+) doping as cores, they could not be perfectly covered by NaYF4 shells, and the obtained products are non-uniform in size. As a result, the UC emission intensity of the complete core-shell NCs increases by about 30 times in comparison with that of the cores, owing to the effective surface passivation of the Ca(2+)-doped cores and therefore protection of Er(3+) in the cores from the non-radiative decay caused by surface defects, whereas the UC intensity of the incomplete core-shell NCs is enhanced by only 3 times.

Heat Transfer in Pebble-Bed Nuclear Reactor Cores Cooled by Fluoride Salts

NASA Astrophysics Data System (ADS)

Huddar, Lakshana Ravindranath

With electricity demand predicted to rise by more than 50% within the next 20 years and a burgeoning world population requiring reliable emissions-free base-load electricity, can we design advanced nuclear reactors to help meet this challenge? At the University of California, Berkeley (UCB) Fluoride-salt-cooled High Temperature Reactors (FHR) are currently being investigated. FHRs are designed with better safety and economic characteristics than conventional light water reactors (LWR) currently in operation. These reactors operate at high temperature and low pressure making them more efficient and safer than LWRs. The pebble-bed FHR (PB-FHR) variant includes an annular nuclear reactor core that is filled with randomly packed pebble fuel. It is crucial to characterize the heat transfer within this unique geometry as this informs the safety limits of the reactor. The work presented in this dissertation focused on furthering the understanding of heat transfer in pebble-bed nuclear reactor cores using fluoride salts as a coolant. This was done through experimental, analytical and computational techniques. A complex nuclear system with a coolant that has never previously been in commercial use requires experimental data that can directly inform aspects of its design. It is important to isolate heat transfer phenomena in order to understand the underlying physics in the context of the PB-FHR, as well as to make decisions about further experimental work that needs to be done in support of developing the PB-FHR. Certain organic oils can simulate the heat transfer behaviour of the fluoride salt if relevant non-dimensional parameters are matched. The advantage of this method is that experiments can be done at a much lower temperature and at a smaller geometric scale compared to FHRs, thereby lowering costs. In this dissertation, experiments were designed and performed to collect data demonstrating similitude. The limitations of these experiments were also elucidated by

A practical cooling strategy for reducing the physiological strain associated with firefighting activity in the heat.

PubMed

Barr, D; Gregson, W; Sutton, L; Reilly, T

2009-04-01

The aim of this study was to establish whether a practical cooling strategy reduces the physiological strain during simulated firefighting activity in the heat. On two separate occasions under high ambient temperatures (49.6 +/- 1.8 degrees C, relative humidity (RH) 13 +/- 2%), nine male firefighters wearing protective clothing completed two 20-min bouts of treadmill walking (5 km/h, 7.5% gradient) separated by a 15-min recovery period, during which firefighters were either cooled (cool) via application of an ice vest and hand and forearm water immersion ( approximately 19 degrees C) or remained seated without cooling (control). There was no significant difference between trials in any of the dependent variables during the first bout of exercise. Core body temperature (37.72 +/- 0.34 vs. 38.21 +/- 0.17 degrees C), heart rate (HR) (81 +/- 9 vs. 96 +/- 17 beats/min) and mean skin temperature (31.22 +/- 1.04 degrees C vs. 33.31 +/- 1 degrees C) were significantly lower following the recovery period in cool compared with control (p < 0.05). Core body temperature remained consistently lower (0.49 +/- 0.02 degrees C; p < 0.01) throughout the second bout of activity in cool compared to control. Mean skin temperature, HR and thermal sensation were significantly lower during bout 2 in cool compared with control (p < 0.05). It is concluded that this practical cooling strategy is effective at reducing the physiological strain associated with demanding firefighting activity under high ambient temperatures.

Cutaneous vascular and core temperature responses to sustained cold exposure in hypoxia.

PubMed

Simmons, Grant H; Barrett-O'Keefe, Zachary; Minson, Christopher T; Halliwill, John R

2011-10-01

We tested the effect of hypoxia on cutaneous vascular regulation and defense of core temperature during cold exposure. Twelve subjects had two microdialysis fibres placed in the ventral forearm and were immersed to the sternum in a bathtub on parallel study days (normoxia and poikilocapnic hypoxia with an arterial O(2) saturation of 80%). One fibre served as the control (1 mM propranolol) and the other received 5 mM yohimbine (plus 1 mM propranolol) to block adrenergic receptors. Skin blood flow was assessed at each site (laser Doppler flowmetry), divided by mean arterial pressure to calculate cutaneous vascular conductance (CVC), and scaled to baseline. Cold exposure was first induced by a progressive reduction in water temperature from 36 to 23°C over 30 min to assess cutaneous vascular regulation, then by clamping the water temperature at 10°C for 45 min to test defense of core temperature. During normoxia, cold stress reduced CVC in control (-44 ± 4%) and yohimbine sites (-13 ± 7%; both P < 0.05 versus precooling). Hypoxia caused vasodilatation prior to cooling but resulted in greater reductions in CVC in control (-67 ± 7%) and yohimbine sites (-35 ± 11%) during cooling (both P < 0.05 versus precooling; both P < 0.05 versus normoxia). Core cooling rate during the second phase of cold exposure was unaffected by hypoxia (-1.81 ± 0.23°C h(-1) in normoxia versus -1.97 ± 0.33°C h(-1) in hypoxia; P > 0.05). We conclude that hypoxia increases cutaneous (non-noradrenergic) vasoconstriction during prolonged cold exposure, while core cooling rate is not consistently affected.

Magnetism and Mössbauer study of formation of multi-core γ -Fe2O3 nanoparticles

NASA Astrophysics Data System (ADS)

Kamali, Saeed; Bringas, Eugenio; Hah, Hien-Yoong; Bates, Brian; Johnson, Jacqueline A.; Johnson, Charles E.; Stroeve, Pieter

2018-04-01

A systematic investigation of magnetic nanoparticles and the formation of a core-shell structure, consisting of multiple maghemite (γ -Fe2O3) nanoparticles as the core and silica as the shell, has been performed using various techniques. High-resolution transmission electron microscopy clearly shows isolated maghemite nanoparticles with an average diameter of 13 nm and the formation of a core-shell structure. Low temperature Mössbauer spectroscopy reveals the presence of pure maghemite nanoparticles with all vacancies at the B-sites. Isothermal magnetization and zero-field-cooled and field-cooled measurements are used for investigating the magnetic properties of the nanoparticles. The magnetization results are in good accordance with the contents of the magnetic core and the non-magnetic shell. The multiple-core γ -Fe2O3 nanoparticles show similar behavior to isolated particles of the same size.

The inner core thermodynamics of the tropical cyclone boundary layer

NASA Astrophysics Data System (ADS)

Williams, Gabriel J.

2016-10-01

Although considerable progress has been made in understanding the inner-core dynamics of the tropical cyclone boundary layer (TCBL), our knowledge of the inner-core thermodynamics of the TCBL remains limited. In this study, the inner-core budgets of potential temperature (θ), specific humidity ( q), and reversible equivalent potential temperature (θ _e) are examined using a high-resolution multilevel boundary layer model. The potential temperature budgets show that the heat energy is dominated by latent heat release in the eyewall, evaporative cooling along the outer edge of the eyewall, and upward surface fluxes of sensible and latent heat from the underlying warm ocean. It is shown that the vertical θ advection overcompensates the sum of radial advective warming from the boundary layer outflow jet and latent heating for the development of cooling in the eyewall within the TCBL. The moisture budgets show the dominant upward transport of moisture in the eyewall updrafts, partly by the boundary-layer outflow jet from the bottom eye region, so that the eyewall remains nearly saturated. The θ _e budgets reveal that the TCBL is maintained thermodynamically by the upward surface flux of higher-θ _e air from the underlying warm ocean, the radial transport of low-θ _e air from the outer regions of the TCBL, and the dry adiabatic cooling associated by eyewall updrafts. These results underscore the significance of vertical motion and the location of the boundary layer outflow jet in maintaining the inner core thermal structure of the TCBL.

Transpulmonary hypothermia: a novel method of rapid brain cooling through augmented heat extraction from the lungs.

PubMed

Kumar, Matthew M; Goldberg, Andrew D; Kashiouris, Markos; Keenan, Lawrence R; Rabinstein, Alejandro A; Afessa, Bekele; Johnson, Larry D; Atkinson, John L D; Nayagam, Vedha

2014-10-01

Delay in instituting neuroprotective measures after cardiac arrest increases death and decreases neuronal recovery. Current hypothermia methods are slow, ineffective, unreliable, or highly invasive. We report the feasibility of rapid hypothermia induction in swine through augmented heat extraction from the lungs. Twenty-four domestic crossbred pigs (weight, 50-55kg) were ventilated with room air. Intraparenchymal brain temperature and core temperatures from pulmonary artery, lower esophagus, bladder, rectum, nasopharynx, and tympanum were recorded. In eight animals, ventilation was switched to cooled helium-oxygen mixture (heliox) and perfluorocarbon (PFC) aerosol and continued for 90min or until target brain temperature of 32°C was reached. Eight animals received body-surface cooling with water-circulating blankets; eight control animals continued to be ventilated with room air. Brain and core temperatures declined rapidly with cooled heliox-PFC ventilation. The brain reached target temperature within the study period (mean [SD], 66 [7.6]min) in only the transpulmonary cooling group. Cardiopulmonary functions and poststudy histopathological examination of the lungs were normal. Transpulmonary cooling is novel, rapid, minimally invasive, and an effective technique to induce therapeutic hypothermia. High thermal conductivity of helium and vaporization of PFC produces rapid cooling of alveolar gases. The thinness and large surface area of alveolar membrane facilitate rapid cooling of the pulmonary circulation. Because of differences in thermogenesis, blood flow, insulation, and exposure to the external environment, the brain cools at a different rate than other organs. Transpulmonary hypothermia was significantly faster than body surface cooling in reaching target brain temperature. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Luminosity and cooling of highly magnetized white dwarfs: suppression of luminosity by strong magnetic fields

NASA Astrophysics Data System (ADS)

Bhattacharya, Mukul; Mukhopadhyay, Banibrata; Mukerjee, Subroto

2018-06-01

We investigate the luminosity and cooling of highly magnetized white dwarfs with electron-degenerate cores and non-degenerate surface layers where cooling occurs by diffusion of photons. We find the temperature and density profiles in the surface layers or envelope of white dwarfs by solving the magnetostatic equilibrium and photon diffusion equations in a Newtonian framework. We also obtain the properties of white dwarfs at the core-envelope interface, when the core is assumed to be practically isothermal. With the increase in magnetic field, the interface temperature increases whereas the interface radius decreases. For a given age of the white dwarf and for fixed interface radius or interface temperature, we find that the luminosity decreases significantly from about 10-6 to 10-9 L⊙ as the magnetic field strength increases from about 109 to 1012 G at the interface and hence the envelope. This is remarkable because it argues that magnetized white dwarfs are fainter and can be practically hidden in an observed Hertzsprung-Russell diagram. We also find the cooling rates corresponding to these luminosities. Interestingly, the decrease in temperature with time, for the fields under consideration, is not found to be appreciable.

Time-dependent heat transfer in the spherical Earth: Implications on the power and thermal evolution of the core

NASA Astrophysics Data System (ADS)

Hofmeister, A. M.; Criss, R. E.

2015-12-01

We quantitatively investigate the time-dependence of heat conduction for a post-core, spherical Earth that is not convecting, due to compositional layering, based on hundreds of measurements of thermal diffusivity (D) for insulators and metals. Consistency of our solutions for widely ranging input parameters indicates how additional heat transfer mechanisms (mantle magmatism and convection) affect thermal evolution of the core. We consider 1) interior starting temperatures (T) of 273-5000 K, which represent variations in primordial heat, 2) different distributions and decay of long-lived radioactive isotopes, 3) additional heat sources in the core (primordial or latent heat), and 4) variable depth-T dependence of D. Our new analytical solution for cooling of a constant D sphere validates our numerical results. The bottom line is that the thermally insulating nature of minerals, combined with constraints of spherical geometry, limits steep thermal gradients to the upper mantle, consistent with the short length scale (x ~700 km) of cooling over t = 4.5 Ga indicated by dimensional analysis [x2 ~ 4Dt], and with plate tectonics. Consequently, interior temperatures vary little so the core has remained hot and is possibly warming. Findings include: 1) Constant vs. variable D affects thermal profiles only in detail, with D for the metallic core being inconsequential. 2) The hottest zone in Earth may lie in the uppermost lower mantle; 3) Most radiogenic heat is released in Earth's outermost 1000 km thereby driving an active outer shell; 4) Earth's core is essentially isothermal and is thus best described by the liquid-solid phase boundary; 5) Deeply sequestered radioactivity or other heat will melt the core rather than by run the dynamo (note that the heat needed to have melted the outer core is 10% of radiogenic heat generated over Earth's history); 6) Inefficient cooling of an Earth-sized mass means that heat essentially remains where it is generated, until it is removed

Observation of Feshbach resonances between ultracold Na and Rb atoms

NASA Astrophysics Data System (ADS)

Wang, Fudong; Xiong, Dezhi; Li, Xiaoke; Wang, Dajun

2013-03-01

Absolute ground-state 23Na87Rb molecule has a large electric dipole moment of 3.3 Debye and its two body exchange chemical reaction is energetically forbidden at ultracold temperatures. It is thus a nice candidate for studying quantum gases with dipolar interactions. We have built an experiment setup to investigate ultracold collisions between Na and Rb atoms as a first step toward the production of ground state molecular samples. Ultracold mixtures are first obtained by evaporative cooling of Rb and sympathetic cooling of Na. They are then transferred to a crossed dipole trap and prepared in different spin combinations for Feshbach resonance study. Several resonances below 1000 G are observed with both atoms prepared in either | F = 1,mF = 1 > or | F = 1,mF = - 1 > hyperfine states. Most of them are within 30 G of predicted values§ based on potentials obtained by high quality molecular spectroscopy studies. This work is supported by RGC Hong Kong. § E. Tiemann, private communications

Turbine airfoil cooling system with cooling systems using high and low pressure cooling fluids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marsh, Jan H.; Messmann, Stephen John; Scribner, Carmen Andrew

A turbine airfoil cooling system including a low pressure cooling system and a high pressure cooling system for a turbine airfoil of a gas turbine engine is disclosed. In at least one embodiment, the low pressure cooling system may be an ambient air cooling system, and the high pressure cooling system may be a compressor bleed air cooling system. In at least one embodiment, the compressor bleed air cooling system in communication with a high pressure subsystem that may be a snubber cooling system positioned within a snubber. A delivery system including a movable air supply tube may be usedmore » to separate the low and high pressure cooling subsystems. The delivery system may enable high pressure cooling air to be passed to the snubber cooling system separate from low pressure cooling fluid supplied by the low pressure cooling system to other portions of the turbine airfoil cooling system.« less

Decay Heat Removal in GEN IV Gas-Cooled Fast Reactors

DOE PAGES

Cheng, Lap-Yan; Wei, Thomas Y. C.

2009-01-01

The safety goal of the current designs of advanced high-temperature thermal gas-cooled reactors (HTRs) is that no core meltdown would occur in a depressurization event with a combination of concurrent safety system failures. This study focused on the analysis of passive decay heat removal (DHR) in a GEN IV direct-cycle gas-cooled fast reactor (GFR) which is based on the technology developments of the HTRs. Given the different criteria and design characteristics of the GFR, an approach different from that taken for the HTRs for passive DHR would have to be explored. Different design options based on maintaining core flow weremore » evaluated by performing transient analysis of a depressurization accident using the system code RELAP5-3D. The study also reviewed the conceptual design of autonomous systems for shutdown decay heat removal and recommends that future work in this area should be focused on the potential for Brayton cycle DHRs.« less

Dynamical onset of superconductivity and retention of magnetic fields in cooling neutron stars

NASA Astrophysics Data System (ADS)

Ho, Wynn C. G.; Andersson, Nils; Graber, Vanessa

2017-12-01

A superconductor of paired protons is thought to form in the core of neutron stars soon after their birth. Minimum energy conditions suggest magnetic flux is expelled from the superconducting region due to the Meissner effect, such that the neutron star core is largely devoid of magnetic fields for some nuclear equation of state and proton pairing models. We show via neutron star cooling simulations that the superconducting region expands faster than flux is expected to be expelled because cooling timescales are much shorter than timescales of magnetic field diffusion. Thus magnetic fields remain in the bulk of the neutron star core for at least 106-107yr . We estimate the size of flux free regions at 107yr to be ≲100 m for a magnetic field of 1011G and possibly smaller for stronger field strengths. For proton pairing models that are narrow, magnetic flux may be completely expelled from a thin shell of approximately the above size after 105yr . This shell may insulate lower conductivity outer layers, where magnetic fields can diffuse and decay faster, from fields maintained in the highly conducting deep core.

The white-dwarf cooling sequence of NGC 6791: a unique tool for stellar evolution

NASA Astrophysics Data System (ADS)

García-Berro, E.; Torres, S.; Renedo, I.; Camacho, J.; Althaus, L. G.; Córsico, A. H.; Salaris, M.; Isern, J.

2011-09-01

Context. NGC 6791 is a well-studied, metal-rich open cluster that is so close to us that it can be imaged down to luminosities fainter than that of the termination of its white-dwarf cooling sequence, thus allowing for an in-depth study of its white dwarf population. Aims: White dwarfs carry important information about the history of the cluster. We use observations of the white-dwarf cooling sequence to constrain important properties of the cluster stellar population, such as the existence of a putative population of massive helium-core white dwarfs, and the properties of a large population of unresolved binary white dwarfs. We also investigate the use of white dwarfs to disclose the presence of cluster subpopulations with a different initial chemical composition, and we obtain an upper bound to the fraction of hydrogen-deficient white dwarfs. Methods: We use a Monte Carlo simulator that employs up-to-date evolutionary cooling sequences for white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres, with carbon-oxygen and helium cores. The cooling sequences for carbon-oxygen cores account for the delays introduced by both 22Ne sedimentation in the liquid phase and by carbon-oxygen phase separation upon crystallization. Results: We do not find evidence for a substantial fraction of helium-core white dwarfs, and hence our results support the suggestion that the origin of the bright peak of the white-dwarf luminosity function can only be attributed to a population of unresolved binary white dwarfs. Moreover, our results indicate that if this hypothesis is at the origin of the bright peak, the number distribution of secondary masses of the population of unresolved binaries has to increase with increasing mass ratio between the secondary and primary components of the progenitor system. We also find that the observed cooling sequence appears to be able to constrain the presence of progenitor subpopulations with different chemical compositions and the fraction of

The effect of a 48 h fast on the thermoregulatory responses to graded cooling in man.

PubMed

Macdonald, I A; Bennett, T; Sainsbury, R

1984-10-01

The thermoregulatory responses to graded cooling were measured in 11 healthy male subjects after a 12 h fast and after a 48 h fast. The cooling stimulus was produced by changing the temperature of the skin of the trunk and legs with a water-perfused suit. Five levels of skin temperature from 35.5 to 24 degrees C were applied on each occasion. After a 12 h fast, core temperature was maintained during cooling. This maintenance of core temperature was associated with an increase in metabolic rate and a reduction in blood flow to the hand and to the forearm. After 48 h of fasting, the subjects could not maintain core temperature during cooling, and a decrease of 0.36 +/- 0.05 degrees C occurred as the suit temperature was reduced from 35.9 to 24 degrees C. Metabolic rate was slightly higher after the 48 h fast than after the 12 h fast, but similar increases in metabolic rate were observed during cooling. Vasoconstriction in the hand was initially less after a 48 h fast than after a 12 h fast, but at the lowest suit temperature, hand blood flow was similar, and low, on both occasions. After 48 h of fasting, forearm blood flow was elevated at all suit temperatures, being approximately twice the level recorded after the 12 h fast. Venous plasma noradrenaline levels did not change during cooling after the 12 h fast, whilst after 48 h of fasting a significant increase in noradrenaline level was observed at the lowest suit temperature. The results of this study provide further evidence that fasting induces an impairment of autonomic reflex mechanisms, but it is not clear whether this is due to a suppression of sympathetic nervous activity.

The Onset of Thermally Unstable Cooling from the Hot Atmospheres of Giant Galaxies in Clusters: Constraints on Feedback Models

NASA Astrophysics Data System (ADS)

Hogan, M. T.; McNamara, B. R.; Pulido, F. A.; Nulsen, P. E. J.; Vantyghem, A. N.; Russell, H. R.; Edge, A. C.; Babyk, Iu.; Main, R. A.; McDonald, M.

2017-12-01

We present accurate mass and thermodynamic profiles for 57 galaxy clusters observed with the Chandra X-ray Observatory. We investigate the effects of local gravitational acceleration in central cluster galaxies, and explore the role of the local free-fall time ({t}{ff}) in thermally unstable cooling. We find that the radially averaged cooling time ({t}{cool}) is as effective an indicator of cold gas, traced through its nebular emission, as the ratio {t}{cool}/{t}{ff}. Therefore, {t}{cool} primarily governs the onset of thermally unstable cooling in hot atmospheres. The location of the minimum {t}{cool}/{t}{ff}, a thermodynamic parameter that many simulations suggest is key in driving thermal instability, is unresolved in most systems. Consequently, selection effects bias the value and reduce the observed range in measured {t}{cool}/{t}{ff} minima. The entropy profiles of cool-core clusters are characterized by broken power laws down to our resolution limit, with no indication of isentropic cores. We show, for the first time, that mass isothermality and the K\\propto {r}2/3 entropy profile slope imply a floor in {t}{cool}/{t}{ff} profiles within central galaxies. No significant departures of {t}{cool}/{t}{ff} below 10 are found. This is inconsistent with models that assume thermally unstable cooling ensues from linear perturbations at or near this threshold. We find that the inner cooling times of cluster atmospheres are resilient to active galactic nucleus (AGN)-driven change, suggesting gentle coupling between radio jets and atmospheric gas. Our analysis is consistent with models in which nonlinear perturbations, perhaps seeded by AGN-driven uplift of partially cooled material, lead to cold gas condensation.

Optimize out-of-core thermionic energy conversion for nuclear electric propulsion

NASA Technical Reports Server (NTRS)

Morris, J. F.

1977-01-01

Current designs for out of core thermionic energy conversion (TEC) to power nuclear electric propulsion (NEP) were evaluated. Approaches to improve out of core TEC are emphasized and probabilities for success are indicated. TEC gains are available with higher emitter temperatures and greater power densities. Good potentialities for accommodating external high temperature, high power density TEC with heat pipe cooled reactors exist.

Thermal history of a metamorphic core complex

NASA Astrophysics Data System (ADS)

Dokka, R. K.; Mahaffie, M. J.; Snoke, A. W.

Fission track (FT) thermochronology studies of lower plate rocks of the Ruby Mountains-East Humbolt Range metamorphic core complex provide important constraints on the timing an nature of major middle Tertiary extension of northeast Nevada. Rocks analyzed include several varieties of mylonitic orthogneiss as well as amphibolitic orthognesses from the non-mylonitic infrastructural core. Oligocene-age porphyritic biotite granodiorite of the Harrison Pass pluton was also studied. The minerals dated include apatite, zircon, and sphene and were obtained from the same rocks that have been previously studied. FT ages are concordant and range in age from 26.4 Ma to 23.8 Ma, with all showing overlap at 1 sigma between 25.4 to 23.4 Ma. Concordancy of all FT ages from all structural levels indicates that the lower plate cooled rapidly from temperatures above approx. 285 C (assumed sphene closure temperature (2)) to below approx. 150 C (assumed apatite closure temperature) near the beginning of the Miocene. This suggests that the lower plate cooled at a rate of at least approx. 36 deg C/Ma during this event. Rapid cooling of the region is considered to reflect large-scale tectonic denudation (intracrustal thinning), the vertical complement to intense crustal extension. FT data firmly establish the upper limit on the timing of mylonitization during detachment faulting and also coincide with the age of extensive landscape disruption.

Thermal history of a metamorphic core complex

NASA Technical Reports Server (NTRS)

Dokka, R. K.; Mahaffie, M. J.; Snoke, A. W.

1985-01-01

Fission track (FT) thermochronology studies of lower plate rocks of the Ruby Mountains-East Humbolt Range metamorphic core complex provide important constraints on the timing an nature of major middle Tertiary extension of northeast Nevada. Rocks analyzed include several varieties of mylonitic orthogneiss as well as amphibolitic orthognesses from the non-mylonitic infrastructural core. Oligocene-age porphyritic biotite granodiorite of the Harrison Pass pluton was also studied. The minerals dated include apatite, zircon, and sphene and were obtained from the same rocks that have been previously studied. FT ages are concordant and range in age from 26.4 Ma to 23.8 Ma, with all showing overlap at 1 sigma between 25.4 to 23.4 Ma. Concordancy of all FT ages from all structural levels indicates that the lower plate cooled rapidly from temperatures above approx. 285 C (assumed sphene closure temperature (2)) to below approx. 150 C (assumed apatite closure temperature) near the beginning of the Miocene. This suggests that the lower plate cooled at a rate of at least approx. 36 deg C/Ma during this event. Rapid cooling of the region is considered to reflect large-scale tectonic denudation (intracrustal thinning), the vertical complement to intense crustal extension. FT data firmly establish the upper limit on the timing of mylonitization during detachment faulting and also coincide with the age of extensive landscape disruption.

Reduction of HAuCl 4 by Na 2S revisited: The case for Au nanoparticle aggregates and against Au 2S/Au core/shell particles

DOE PAGES

Schwartzberg, A. M.; Grant, C. D.; van Buuren, Tony; ...

2007-03-10

The reaction of sodium sulfide with chloroauric acid has been surrounded by a controversy over the structure of the resulting product. The original report proposed a Au 2S/Au core/shell structure based on strong near-IR resonance and limited transmission electron microscopy. Subsequent reports used the same model without further attempts to determine the structure of the products. With a significant body of experimental work compiled over a period of several years, we have shown that the major product of this reaction is aggregated spherical nanoparticles of gold with a minority component consisting of triangular and rod-like structures. This is in contradictionmore » to the core/shell structures as originally proposed. Recently, there have been additional reports that again suggest a Au 2S/Au core/shell structure or irregularly shaped Au nanoparticles as an explanation for the near-IR resonance. To help resolve this issue, we have carried out further experiments to determine how the reaction products may depend on experimental conditions such as concentration and aging of the reactants, particularly Na 2S. It has been determined that sodium thiosulfate is the likely product from Na 2S aging. In addition, persistent spectral hole burning experiments have been conducted on gold nanoparticle aggregate (GNA) samples at excitation intensities that are lower than that required to melt the nanostructures. We have observed a decrease in optical absorption on resonance with the excitation laser wavelength, with simultaneous increases in absorption to the blue and red of this wavelength region. However, in the presence of the stabilizer poly(vinyl pyrrolidone) (PVP), no increase in absorbance was observed but rather a blue shifting and decrease in intensity of the near-IR plasmon resonance. These results imply that the non-stabilized GNAs are able to break apart and reform into off resonant aggregate structures. In contrast, this behavior is suppressed in PVP stabilized

Cooling vests with phase change materials: the effects of melting temperature on heat strain alleviation in an extremely hot environment.

PubMed

Gao, Chuansi; Kuklane, Kalev; Holmér, Ingvar

2011-06-01

A previous study by the authors using a heated thermal manikin showed that the cooling rates of phase change material (PCM) are dependent on temperature gradient, mass, and covering area. The objective of this study was to investigate if the cooling effects of the temperature gradient observed on a thermal manikin could be validated on human subjects in extreme heat. The subjects wore cooling vests with PCMs at two melting temperatures (24 and 28°C) and fire-fighting clothing and equipment, thus forming three test groups (vest24, vest28 and control group without the vest). They walked on a treadmill at a speed of 5 km/h in a climatic chamber (air temperature = 55°C, relative humidity = 30%, vapour pressure = 4,725 Pa, and air velocity = 0.4 m/s). The results showed that the PCM vest with a lower melting temperature (24°C) has a stronger cooling effect on the torso and mean skin temperatures than that with a higher melting temperature (28°C). Both PCM vests mitigate peak core temperature increase during the resting recovery period. The two PCM vests tested, however, had no significant effect on the alleviation of core temperature increase during exercise in the heat. To study the possibility of effective cooling of core temperature, cooling garments with PCMs at even lower melting temperatures (e.g. 15°C) and a larger covering area should be investigated.

Crustal Cooling in the Neutron Star Low-Mass X-Ray Binary KS 1731-260

NASA Astrophysics Data System (ADS)

Merritt, Rachael L.

Neutron stars in binary systems can undergo periods of accretion (outburst), where in- falling material heats the crust of the star out of thermal equilibrium with the core. When accretion stops (quiescence), we can directly observe the thermal relaxation of the crust. Crustal cooling of accretion-heated neutron stars provides insight into the stellar interior of neutron stars. The neutron star X-ray transient, KS 1731-260, was in outburst for 12.5 years before returning to quiescence in 2001. Here, we present a 150 ks Chandra observation of KS 1731-260 taken in August 2015, about 14.5 years into quiescence. We find that the neutron star surface temperature is consistent with the previous observation, suggesting the crust has reached thermal equilibrium with the core. Using a theoretical thermal evolution code, we fit the observed cooling curves and constrain the core temperature, composition, and the required level of extra shallow heating.

Monitoring system for a liquid-cooled nuclear fission reactor. [PWR

DOEpatents

DeVolpi, A.

1984-07-20

The invention provides improved means for detecting the water levels in various regions of a water-cooled nuclear power reactor, viz., in the downcomer, in the core, in the inlet and outlet plenums, at the head, and elsewhere; and also for detecting the density of the water in these regions. The invention utilizes a plurality of exterior gamma radiation detectors and a collimator technique operable to sense separate regions of the reactor vessel to give respectively, unique signals for these regions, whereby comparative analysis of these signals can be used to advise of the presence and density of cooling water in the vessel.

Safety and core design of large liquid-metal cooled fast breeder reactors

NASA Astrophysics Data System (ADS)

Qvist, Staffan Alexander

In light of the scientific evidence for changes in the climate caused by greenhouse-gas emissions from human activities, the world is in ever more desperate need of new, inexhaustible, safe and clean primary energy sources. A viable solution to this problem is the widespread adoption of nuclear breeder reactor technology. Innovative breeder reactor concepts using liquid-metal coolants such as sodium or lead will be able to utilize the waste produced by the current light water reactor fuel cycle to power the entire world for several centuries to come. Breed & burn (B&B) type fast reactor cores can unlock the energy potential of readily available fertile material such as depleted uranium without the need for chemical reprocessing. Using B&B technology, nuclear waste generation, uranium mining needs and proliferation concerns can be greatly reduced, and after a transitional period, enrichment facilities may no longer be needed. In this dissertation, new passively operating safety systems for fast reactors cores are presented. New analysis and optimization methods for B&B core design have been developed, along with a comprehensive computer code that couples neutronics, thermal-hydraulics and structural mechanics and enables a completely automated and optimized fast reactor core design process. In addition, an experiment that expands the knowledge-base of corrosion issues of lead-based coolants in nuclear reactors was designed and built. The motivation behind the work presented in this thesis is to help facilitate the widespread adoption of safe and efficient fast reactor technology.

A white dwarf cooling age of 8 Gyr for NGC 6791 from physical separation processes.

PubMed

García-Berro, Enrique; Torres, Santiago; Althaus, Leandro G; Renedo, Isabel; Lorén-Aguilar, Pablo; Córsico, Alejandro H; Rohrmann, René D; Salaris, Maurizio; Isern, Jordi

2010-05-13

NGC 6791 is a well studied open cluster that it is so close to us that can be imaged down to very faint luminosities. The main-sequence turn-off age ( approximately 8 Gyr) and the age derived from the termination of the white dwarf cooling sequence ( approximately 6 Gyr) are very different. One possible explanation is that as white dwarfs cool, one of the ashes of helium burning, (22)Ne, sinks in the deep interior of these stars. At lower temperatures, white dwarfs are expected to crystallize and phase separation of the main constituents of the core of a typical white dwarf ((12)C and (16)O) is expected to occur. This sequence of events is expected to introduce long delays in the cooling times, but has not hitherto been proven. Here we report that, as theoretically anticipated, physical separation processes occur in the cores of white dwarfs, resolving the age discrepancy for NGC 6791.

Ab initio study of the neutral and anionic alkali and alkaline earth hydroxides: Electronic structure and prospects for sympathetic cooling of OH−

PubMed Central

2017-01-01

We have performed a systematic ab initio study on alkali and alkaline earth hydroxide neutral (MOH) and anionic (MOH−) species where M = Li, Na, K, Rb, Cs or Be, Mg, Ca, Sr, Ba. The CCSD(T) method with extended basis sets and Dirac-Fock relativistic effective core potentials for the heavier atoms has been used to study their equilibrium geometries, interaction energies, electron affinities, electric dipole moment, and potential energy surfaces. All neutral and anionic species exhibit a linear shape with the exception of BeOH, BeOH−, and MgOH−, for which the equilibrium structure is found to be bent. Our analysis shows that the alkaline earth hydroxide anions are valence-bound whereas the alkali hydroxide anions are dipole bound. In the context of sympathetic cooling of OH− by collision with ultracold alkali and alkaline earth atoms, we investigate the 2D MOH− potential energy surfaces and the associative detachment reaction M + OH→− MOH + e−, which is the only energetically allowed reactive channel in the cold regime. We discuss the implication for the sympathetic cooling of OH− and conclude that Li and K are the best candidates for an ultracold buffer gas. PMID:28527437

[Effects of hot-NaOH pretreatment on Jerusalem artichoke stalk composition and subsequent enzymatic hydrolysis].

PubMed

Wang, Qing; Qiu, Jingwen; Li, Yang; Shen, Fei

2015-10-01

In order to explore the possibility of Jerusalem artichoke stalk for bioenergy conversion, we analyzed the main composition of whole stalk, pitch, and core of the stalk. Meanwhile, these parts were pretreated with different NaOH concentrations at 121 degrees C. Afterwards, enzymatic hydrolysis was performed to evaluate the pretreatment efficiency. Jerusalem artichoke stalk was characterized by relatively high lignin content (32.0%) compared with traditional crop stalks. The total carbohydrate content was close to that of crop stalks, but with higher cellulose content (40.5%) and lower hemicellulose (19.6%) than those of traditional crop stalks. After pretreatment, the lignin content in the whole stalk, pitch, and core decreased by 13.1%-13.4%, 8.3%-13.5%, and 19.9%-27.2%, respectively, compared with the unpretreated substrates. The hemicellulose content in the whole stalk, pitch, and core decreased 87.8%-96.9%, 87.6%-95.0%, and 74.0%-90.2%, respectively. Correspondingly, the cellulose content in the pretreated whole stalk, pitch, and core increased by 56.5%-60.2%, 52.2%-55.4%, and 62.7%-73.2%, respectively. Moreover, increase of NaOH concentration for pretreatment could improve the enzymatic hydrolysis of the whole stalk and pitch by 2.3-2.6 folds and 10.3-18.5 folds, respectively. The hydrolysis of pretreated stalk core decreased significantly as 2.0 mol/L NaOH was employed, although the increased NaOH concentration can also improve its hydrolysis performance. Based on these results, hot-NaOH can be regarded as an option for Jerusalem artichoke stalk pretreatment. Increasing NaOH concentration was beneficial to hemicellulose and lignin removal, and consequently improved sugar conversion. However, the potential decrease of sugar conversion of the pretreated core by higher NaOH concentration suggested further optimization on the pretreatment conditions should be performed.

Metallographic cooling rates of L-group ordinary chondrites

NASA Technical Reports Server (NTRS)

Bennett, Marvin E.; Mcsween, Harry Y., Jr.

1993-01-01

Shock metamorphism appears to be a ubiquitous feature in L-group ordinary chondrites. Brecciation and heterogeneous melting obscure much of the early history of this meteorite group and have caused confusion as to whether L chondrites have undergone thermal metamorphism within onion-shell or rubble-pile parent bodies. Employing the most recent shock criteria, we have examined 55 Antarctic and 24 non-Antarctic L chondrites in order to identify those which have been least affected by post-accretional shock. Six low-shock samples (those with shock grade less than S4) of petrographic types L3-L5 were selected from both populations and metallographic cooling rates were obtained following the technique of Willis and Goldstein. All non-Antarctic L6 chondrites inspected were too heavily shocked to be included in this group. However, 4 shocked L6 chondrites were analyzed in order to determine what effects shock may impose on metallographic cooling rates. Metallographic cooling rates were derived by analyzing the cores of taenite grains and then measuring the distance to the nearest grain edge. Taenites were identified using backscatter imaging on a Cameca SX-50 electron microprobe. Using backscatter we were able to locate homogeneous, rust-free, nearly spherical grains. M-shaped profiles taken from grain traverses were also used to help locate the central portions of selected grains. All points which contained phosphorus above detection limits were discarded. Plots of cooling-rate data are summarized and data from the high-shock samples are presented. The lack of coherency of cooling rates for individual samples is indicative of heterogeneous cooling following shock. The data confirms the statement expressed by numerous workers that extreme care must be taken when selecting samples of L chondrites for cooling-rate studies. Data for the 6 non-Antarctic low-shock samples are also presented. The samples display a general trend in cooling rates. The lowest metamorphic grade

The use of mixed-method, part-body pre-cooling procedures for team-sport athletes training in the heat.

PubMed

Duffield, Rob; Steinbacher, Geoff; Fairchild, Timothy J

2009-12-01

The current study investigated the effects of a pre-cooling intervention on physiological and performance responses to team-sport training in the heat. Seven male lacrosse players performed a familiarization session and 2 randomized, counterbalanced sessions consisting of a 30-minute intermittent-sprint conditioning session. Prior to the sessions, players performed a 20-minute mixed-method, part-body cooling intervention (consisting of cooling vests, cold towels to the neck, and ice packs to the quadriceps) or no cooling intervention. Performance was determined from collection of 1 Hz global positioning system (GPS) data and analyzed for distance and speed. Prior to, during, and following the sessions, core temperature, heart rate, rating of perceived exertion (RPE), and thermal sensation scale (TSS) were measured; additionally, a venous blood sample was collected before and after each session for measurement of interleukin-6 (IL-6), insulin-like growth factor (IGF-1) and insulin-like growth factor-binding protein3 (IGF-BP3). Results indicated that a greater distance was covered during the pre-cooling condition (3.35 +/- 0.20 vs. 3.11 +/- 0.13 km; p = 0.05). Further, most of this improvement was evident from a greater distance covered during moderate intensities of 7 to 14 km/h (2.28 +/- 0.18 vs. 2.00 +/- 0.24 km; p = 0.05). Peak speeds and very-high-intensity efforts (20 km/h +/-) were not different between conditions (p > 0.05). The increase in core temperature was blunted following cooling, with a lower core temperature throughout the cooling session (38.8 +/- 0.3 vs. 39.3 +/- 0.4 degrees C; p < 0.05). However, there were no differences in heart rate, RPE, TSS, IL-6, IGF-1, or IGF-BP3 between conditions (p > 0.05). Accordingly, the use of a mixed-method, part-body cooling intervention prior to an intermittent-sprint training session in the heat can assist in reducing thermoregulatory load and improve aspects of training performance for team sports.

Effects of processing parameters on immersion vacuum cooling time and physico-chemical properties of pork hams.

PubMed

Feng, Chao-Hui; Drummond, Liana; Zhang, Zhi-Hang; Sun, Da-Wen

2013-10-01

The effects of agitation (1002 rpm), different pressure reduction rates (60 and 100 mbar/min), as well as employing cold water with different initial temperatures (IWT: 7 and 20°C) on immersion vacuum cooling (IVC) of cooked pork hams were experimentally investigated. Final pork ham core temperature, cooling time, cooling loss, texture properties, colour and chemical composition were evaluated. The application for the first time of agitation during IVC substantially reduced the cooling time (47.39%) to 4.6°C, compared to IVC without agitation. For the different pressure drop rates, there was a trend that shorter IVC cooling times were achieved with lower cooling rate, although results were not statistically significant (P>0.05). For both IWTs tested, the same trend was observed: shorter cooling time and lower cooling loss were obtained under lower linear pressure drop rate of 60 mbar/min (not statistically significant, P>0.05). Compared to the reference cooling method (air blast cooling), IVC achieved higher cooling rates and better meat quality. Copyright © 2013 Elsevier Ltd. All rights reserved.

Comprehensive Evaluation of Biological Growth Control by Chlorine-Based Biocides in Power Plant Cooling Systems Using Tertiary Effluent

PubMed Central

Chien, Shih-Hsiang; Dzombak, David A.; Vidic, Radisav D.

2013-01-01

Abstract Recent studies have shown that treated municipal wastewater can be a reliable cooling water alternative to fresh water. However, elevated nutrient concentration and microbial population in wastewater lead to aggressive biological proliferation in the cooling system. Three chlorine-based biocides were evaluated for the control of biological growth in cooling systems using tertiary treated wastewater as makeup, based on their biocidal efficiency and cost-effectiveness. Optimal chemical regimens for achieving successful biological growth control were elucidated based on batch-, bench-, and pilot-scale experiments. Biocide usage and biological activity in planktonic and sessile phases were carefully monitored to understand biological growth potential and biocidal efficiency of the three disinfectants in this particular environment. Water parameters, such as temperature, cycles of concentration, and ammonia concentration in recirculating water, critically affected the biocide performance in recirculating cooling systems. Bench-scale recirculating tests were shown to adequately predict the biocide residual required for a pilot-scale cooling system. Optimal residuals needed for proper biological growth control were 1, 2–3, and 0.5–1 mg/L as Cl2 for NaOCl, preformed NH2Cl, and ClO2, respectively. Pilot-scale tests also revealed that Legionella pneumophila was absent from these cooling systems when using the disinfectants evaluated in this study. Cost analysis showed that NaOCl is the most cost-effective for controlling biological growth in power plant recirculating cooling systems using tertiary-treated wastewater as makeup. PMID:23781129

Comprehensive Evaluation of Biological Growth Control by Chlorine-Based Biocides in Power Plant Cooling Systems Using Tertiary Effluent.

PubMed

Chien, Shih-Hsiang; Dzombak, David A; Vidic, Radisav D

2013-06-01

Recent studies have shown that treated municipal wastewater can be a reliable cooling water alternative to fresh water. However, elevated nutrient concentration and microbial population in wastewater lead to aggressive biological proliferation in the cooling system. Three chlorine-based biocides were evaluated for the control of biological growth in cooling systems using tertiary treated wastewater as makeup, based on their biocidal efficiency and cost-effectiveness. Optimal chemical regimens for achieving successful biological growth control were elucidated based on batch-, bench-, and pilot-scale experiments. Biocide usage and biological activity in planktonic and sessile phases were carefully monitored to understand biological growth potential and biocidal efficiency of the three disinfectants in this particular environment. Water parameters, such as temperature, cycles of concentration, and ammonia concentration in recirculating water, critically affected the biocide performance in recirculating cooling systems. Bench-scale recirculating tests were shown to adequately predict the biocide residual required for a pilot-scale cooling system. Optimal residuals needed for proper biological growth control were 1, 2-3, and 0.5-1 mg/L as Cl 2 for NaOCl, preformed NH 2 Cl, and ClO 2 , respectively. Pilot-scale tests also revealed that Legionella pneumophila was absent from these cooling systems when using the disinfectants evaluated in this study. Cost analysis showed that NaOCl is the most cost-effective for controlling biological growth in power plant recirculating cooling systems using tertiary-treated wastewater as makeup.

High-resolution molecular-beam spectroscopy of NaCN and Na 13CN

NASA Astrophysics Data System (ADS)

van Vaals, J. J.; Meerts, W. Leo; Dymanus, A.

The sodium cyanide molecule was studied by molecular-beam electric-resonance spectroscopy in the microwave region. We used the seeded-beam technique to produce a supersonic beam with strong translational, rotational and vibrational cooling. In the frequency range 9.5-40 GHz we observed and identified for NaCN 186 and for Na 13CN 107 hyperfine transitions in 20 and 16 rotational transitions, respectively, all in the ground vibrational state. The rotational, the five quartic and three sextic centrifugal distortion constants of NaCN are: A″ = 57921.954(7) MHz; B″ = 8369.312(2) MHz, C″ = 7272.712(2) MHz. All quadrupole and several spin-rotation coupling constants for the hyperfine interaction were evaluated. The quadrupole coupling constants (in MHz) for NaCN are: eQq12(Na) = -5.344(5), eQq12 = 2.397(7). eQq12(N) = 2.148(4), eQq12(N) = -4.142(5). From these constants and those of Na 13CN we have determined the principal components of the quadrupole coupling tensor for potassium and nitrogen. The structure of sodium cyanide evaluated from the rotational constants of NaCN and Na 13CN was found to be T shaped, similar to the structure of KCN but completely different from the linear isocyanide configuration of LiNC. The effective structural parameters for sodium cyanide in the ground vibrational state are: rCN = 1.170(4) Å, rNaC = 2.379(15) Å, rN12N = 2.233(15) Å, in gratifying agreement with ab initio calculations. Both the geometrical structure and the hyperfine coupling justify the conclusion that the CN group in gaseous sodium cyanide approximately can be considered as a free CN - ion.

Prototype CoolCup cryolipolysis applicator with over 40% reduced treatment time demonstrates equivalent safety and efficacy with greater patient preference.

PubMed

Kilmer, Suzanne L

2017-01-01

Cryolipolysis is a safe, effective non-surgical procedure to reduce fat. For most cryolipolysis treatments, tissue is pulled between parallel cooling plates with a treatment duration of 60 minutes. A novel contoured cup, medium-sized applicator was developed to increase tissue contact with reduced skin tension and reduced treatment time. This prototype contoured cup was investigated with a standard cryolipolysis applicator to evaluate safety, efficacy, and patient preference. A prototype CoolCup medium-sized vacuum applicator (CoolSculpting System, ZELTIQ Aesthetics) was used to treat n = 19 subjects in the flanks. Randomly assigned, one flank received standard treatment with the CoolCore applicator (-10°C for 60 minutes). The contralateral flank received treatment from the CoolCup (-11°C for 35 minutes). The clinical study primary efficacy endpoint was 70% correct identification of baseline photographs by independent physician review. Incidence of adverse device effects was monitored. Fat layer reduction was measured by ultrasound and subject surveys were administered 12 weeks post-treatment. Equivalent efficacy was demonstrated between the CoolCore standard treatment and the prototype CoolCup. Independent review from three blinded physicians found 81% correct identification of baseline photographs for the standard treatment and 79% for the CoolCup. Ultrasound measurements indicated mean fat layer reduction of 4.38 mm for the standard treatment and 4.40 mm for the CoolCup; no statistically significant difference was found when comparing treatment efficacy of the two applicators (P = 0.96). Patient questionnaires revealed 85% preferred CoolCup because of shorter treatment duration and greater comfort. Procedural assessments revealed 45% lower pain scores for CoolCup. Immediate post-treatment clinical assessments revealed 82% less bruising. Typical side effects, such as numbness and erythema, were similar. There were no adverse events. This clinical

An improved heat transfer configuration for a solid-core nuclear thermal rocket engine

NASA Technical Reports Server (NTRS)

Clark, John S.; Walton, James T.; Mcguire, Melissa L.

1992-01-01

Interrupted flow, impingement cooling, and axial power distribution are employed to enhance the heat-transfer configuration of a solid-core nuclear thermal rocket engine. Impingement cooling is introduced to increase the local heat-transfer coefficients between the reactor material and the coolants. Increased fuel loading is used at the inlet end of the reactor to enhance heat-transfer capability where the temperature differences are the greatest. A thermal-hydraulics computer program for an unfueled NERVA reactor core is employed to analyze the proposed configuration with attention given to uniform fuel loading, number of channels through the impingement wafers, fuel-element length, mass-flow rate, and wafer gap. The impingement wafer concept (IWC) is shown to have heat-transfer characteristics that are better than those of the NERVA-derived reactor at 2500 K. The IWC concept is argued to be an effective heat-transfer configuration for solid-core nuclear thermal rocket engines.

Chandra Observations of MS0440.5+0204 & MS0839.9+2938: Cooling Flow Clusters in Formation?

NASA Astrophysics Data System (ADS)

McNamara, Brian

2000-09-01

We propose to observe two redshift z~0.2 clusters, MS0839.9+2938 and MS0440+0204, discovered as bright X-ray sources in the Einstein Medium Sensitivity Survey. The cluster cores are structured in the X-ray and optical bands, and they harbor large cooling flows. Their central cluster galaxies contain luminous nebular emission systems, active star formation, and strong radio sources. Using the Chandra data, we will determine whether the large discrepancies between the X-ray cooling rates and optical star formation rates can be reconciled, and we will test the hypothesis that cooling flows form as cool, dense groups accrete into massive clusters.

Macro-channel cooled high power fiber coupled diode lasers exceeding 1.2kW of output power

NASA Astrophysics Data System (ADS)

Koenning, Tobias; Alegria, Kim; Wang, Zuolan; Segref, Armin; Stapleton, Dean; Faßbender, Wilhelm; Flament, Marco; Rotter, Karsten; Noeske, Axel; Biesenbach, Jens

2011-03-01

We report on a new series of fiber coupled diode laser modules exceeding 1.2kW of single wavelength optical power from a 400um / 0.2NA fiber. The units are constructed from passively cooled laser bars as opposed to other comparably powered, commercially available modules that use micro-channel heat-sinks. Micro-channel heat sinks require cooling water to meet demanding specifications and are therefore prone to failures due to contamination and increase the overall cost to operate and maintain the laser. Dilas' new series of high power fiber coupled diode lasers are designed to eliminate micro channel coolers and their associated failure mechanisms. Low-smile soldering processes were developed to maximize the brightness available from each diode laser bar. The diode laser brightness is optimally conserved using Dilas' recently developed propriety laser bar stacking geometry and optics. A total of 24 bars are coupled into a single fiber core using a polarization multiplexing scheme. The modular design permits further power scaling through wavelength multiplexing. Other customer critical features such as industrial grade fibers, pilot beams, fiber interlocks and power monitoring are standard features on these modules. The optical design and the beam parameter calculations will be presented to explain the inherit design trade offs. Results for single and dual wavelengths modules will be presented.

Thermal Evolution of Earht's Core during Accretion: a Preliminary Solid Inner Core at the End of Accrfetion.

NASA Astrophysics Data System (ADS)

Arkani-Hamed, J.

2015-12-01

Growth of an inner core has conventionally been related to core cooling blow the liquidus of iron. It is however possible that the core of the proto-Earth solidifies upon pressure increase during accretion. The lithostatic pressure in the proto-Earth increases immediately after merging each impactor, and the pressure-dependent liquidus of iron may supersede the temperature near the center resulting in a solid inner core. Assuming that Earth is formed by accreting a few dozen Moon to Mars size planetary embryos, the thermal evolution of the proto-Earth's core is investigated during accretion. The collision of an embryo heats the Earth differentially and the rotating low-viscosity, differentially heated core stratifies, creating a spherically symmetric stable and radially increasing temperature distribution. Convection occurs in the outer core while heat transfers by conduction in deeper parts. It is assumed that the iron core of an embryo pools at the bottom of partially molten mantle and thermally equilibrates with surroundings. It then descends as an iron diapir in the solid silicate mantle, while releasing its gravitational energy. Depending on its temperature when arrives at the core mantle boundary, it may spread on the core creating a hot layer or plunge into the core and descend to a neutrally buoyant level while further releasing its gravitational energy. A few dozen thermal evolution models of the core are investigates to examine effects of major parameters such as: total number of impacting embryos; partitioning of the gravitational energy released during the descent of the diaper in the mantle (between the silicate mantle and the iron diaper), and in the core (between the proto-Earth's core and that of the embryo); and gravitational energy and latent heat released due to the core solidification. All of the models predict a large solid inner core, about 1500 to 2000 km in radius, at the end of accretion.

Composite casting/bonding construction of an air-cooled, high temperature radial turbine wheel

NASA Technical Reports Server (NTRS)

Hammer, A. N.; Aigret, G.; Rodgers, C.; Metcalfe, A. G.

1983-01-01

A composite casting/bonding technique has been developed for the fabrication of a unique air-cooled, high temperature radial inflow turbine wheel design applicable to auxilliary power units with small rotor diameters and blade entry heights. The 'split blade' manufacturing procedure employed is an alternative to complex internal ceramic coring. Attention is given to both aerothermodynamic and structural design, of which the latter made advantageous use of the exploration of alternative cooling passage configurations through CAD/CAM system software modification.

Cooled spool piston compressor

NASA Technical Reports Server (NTRS)

Morris, Brian G. (Inventor)

1993-01-01

A hydraulically powered gas compressor receives low pressure gas and outputs a high pressure gas. The housing of the compressor defines a cylinder with a center chamber having a cross-sectional area less than the cross-sectional area of a left end chamber and a right end chamber, and a spool-type piston assembly is movable within the cylinder and includes a left end closure, a right end closure, and a center body that are in sealing engagement with the respective cylinder walls as the piston reciprocates. First and second annual compression chambers are provided between the piston enclosures and center housing portion of the compressor, thereby minimizing the spacing between the core gas and a cooled surface of the compressor. Restricted flow passageways are provided in the piston closure members and a path is provided in the central body of the piston assembly, such that hydraulic fluid flows through the piston assembly to cool the piston assembly during its operation. The compressor of the present invention may be easily adapted for a particular application, and is capable of generating high gas pressures while maintaining both the compressed gas and the compressor components within acceptable temperature limits.

Field-Based Pre-Cooling for On-Court Tennis Conditioning Training in the Heat

PubMed Central

Duffield, Rob; Bird, Stephen P.; Ballard, Robert J.

2011-01-01

The present study investigated the effects of pre-cooling for on- court, tennis-specific conditioning training in the heat. Eight highly-trained tennis players performed two on-court conditioning sessions in 35°C, 55% Relative Humidity. Sessions were randomised, involved either a pre-cooling or control session, and consisted of 30-min of court- based, tennis movement drills. Pre-cooling involved 20-min of an ice-vest and cold towels to the head/neck and legs, followed by warm-up in a cold compression garment. On-court movement distance was recorded by 1Hz Global Positioning Satellite (GPS) devices, while core temperature, heart rate and perceptual exertion and thermal stress were also recorded throughout the session. Additionally, mass and lower-body peak power during repeated counter-movement jumps were measured before and after each session. No significant performance differences were evident between conditions, although a moderate-large effect (d = 0.7-1.0; p > 0.05) was evident for total (2989 ± 256 v 2870 ± 159m) and high-intensity (805 ± 340 v 629 ± 265m) distance covered following pre-cooling. Further, no significant differences were evident between conditions for rise in core temperature (1.9 ± 0.4 v 2. 2 ± 0.4°C; d > 0.9; p > 0.05), although a significantly smaller change in mass (0.9 ± 0.3 v 1. 3 ± 0.3kg; p < 0.05) was present following pre-cooling. Perceived thermal stress and exertion were significantly lower (d > 1.0; p < 0.05) during the cooling session. Finally, lower-body peak power did not differ between conditions before or after training (d < 0.3; p > 0.05). Conclusions: Despite trends for lowered physiological load and increased distances covered following cooling, the observed responses were not significantly different or as explicit as previously reported laboratory-based pre-cooling research. Key points Pre-cooling did not significantly enhance training performance or reduce physiological load for tennis training in the heat

Multi channel thermal hydraulic analysis of gas cooled fast reactor using genetic algorithm

NASA Astrophysics Data System (ADS)

Drajat, R. Z.; Su'ud, Z.; Soewono, E.; Gunawan, A. Y.

2012-05-01

There are three analyzes to be done in the design process of nuclear reactor i.e. neutronic analysis, thermal hydraulic analysis and thermodynamic analysis. The focus in this article is the thermal hydraulic analysis, which has a very important role in terms of system efficiency and the selection of the optimal design. This analysis is performed in a type of Gas Cooled Fast Reactor (GFR) using cooling Helium (He). The heat from nuclear fission reactions in nuclear reactors will be distributed through the process of conduction in fuel elements. Furthermore, the heat is delivered through a process of heat convection in the fluid flow in cooling channel. Temperature changes that occur in the coolant channels cause a decrease in pressure at the top of the reactor core. The governing equations in each channel consist of mass balance, momentum balance, energy balance, mass conservation and ideal gas equation. The problem is reduced to finding flow rates in each channel such that the pressure drops at the top of the reactor core are all equal. The problem is solved numerically with the genetic algorithm method. Flow rates and temperature distribution in each channel are obtained here.

A long-lived lunar core dynamo.

PubMed

Shea, Erin K; Weiss, Benjamin P; Cassata, William S; Shuster, David L; Tikoo, Sonia M; Gattacceca, Jérôme; Grove, Timothy L; Fuller, Michael D

2012-01-27

Paleomagnetic measurements indicate that a core dynamo probably existed on the Moon 4.2 billion years ago. However, the subsequent history of the lunar core dynamo is unknown. Here we report paleomagnetic, petrologic, and (40)Ar/(39)Ar thermochronometry measurements on the 3.7-billion-year-old mare basalt sample 10020. This sample contains a high-coercivity magnetization acquired in a stable field of at least ~12 microteslas. These data extend the known lifetime of the lunar dynamo by 500 million years. Such a long-lived lunar dynamo probably required a power source other than thermochemical convection from secular cooling of the lunar interior. The inferred strong intensity of the lunar paleofield presents a challenge to current dynamo theory.

AGN Feedback and Cooling Flows: Problems with Simple Hydrodynamic Models

NASA Astrophysics Data System (ADS)

Vernaleo, John C.; Reynolds, Christopher S.

2006-07-01

In recent years it has become increasingly clear that active galactic nuclei, and radio galaxies in particular, have an impact on large-scale structure and galaxy formation. In principle, radio galaxies are energetic enough to halt the cooling of the virialized intracluster medium (ICM) in the inner regions of galaxy clusters, solving the cooling flow problem and explaining the high-mass truncation of the galaxy luminosity function. We explore this process through a series of high-resolution, three-dimensional hydrodynamic simulations of jetted active galaxies that act in response to cooling-mediated accretion of an ICM atmosphere. We find that our models are incapable of producing a long-term balance of heating and cooling; catastrophic cooling can be delayed by the jet action but inevitably takes hold. At the heart of the failure of these models is the formation of a low-density channel through which the jet can freely flow, carrying its energy out of the cooling core. It is possible that this failure is due to an oversimplified treatment of the fast jet (which may underestimate the ``dentist drill'' effect). However, it seems likely that additional complexity (large-angle jet precession or ICM turbulence) or additional physics (magnetohydrodynamic effects and plasma transport processes) is required to produce a spatial distribution of jet heating that can prevent catastrophic cooling. This work also underscores the importance of including jet dynamics in any feedback model, as opposed to the isotropically inflated bubble approach taken in some previous works.

Chondritic Mn/Na ratio and limited post-nebular volatile loss of the Earth

NASA Astrophysics Data System (ADS)

Siebert, Julien; Sossi, Paolo A.; Blanchard, Ingrid; Mahan, Brandon; Badro, James; Moynier, Frédéric

2018-03-01

The depletion pattern of volatile elements on Earth and other differentiated terrestrial bodies provides a unique insight as to the nature and origin of planetary building blocks. The processes responsible for the depletion of volatile elements range from the early incomplete condensation in the solar nebula to the late de-volatilization induced by heating and impacting during planetary accretion after the dispersion of the H2-rich nebular gas. Furthermore, as many volatile elements are also siderophile (metal-loving), it is often difficult to deconvolve the effect of volatility from core formation. With the notable exception of the Earth, all the differentiated terrestrial bodies for which we have samples have non-chondritic Mn/Na ratios, taken as a signature of post-nebular volatilization. The bulk silicate Earth (BSE) is unique in that its Mn/Na ratio is chondritic, which points to a nebular origin for the depletion; unless the Mn/Na in the BSE is not that of the bulk Earth (BE), and has been affected by core formation through the partitioning of Mn in Earth's core. Here we quantify the metal-silicate partitioning behavior of Mn at deep magma ocean pressure and temperature conditions directly applicable to core formation. The experiments show that Mn becomes more siderophile with increasing pressure and temperature. Modeling the partitioning of Mn during core formation by combining our results with previous data at lower P-T conditions, we show that the core likely contains a significant fraction (20 to 35%) of Earth's Mn budget. However, we show that the derived Mn/Na value of the bulk Earth still lies on the volatile-depleted end of a trend defined by chondritic meteorites in a Mn/Na vs Mn/Mg plot, which tend to higher Mn/Na with increasing volatile depletion. This suggests that the material that formed the Earth recorded similar chemical fractionation processes for moderately volatile elements as chondrites in the solar nebula, and experienced limited post

Cooling During Exercise: An Overlooked Strategy for Enhancing Endurance Performance in the Heat.

PubMed

Stevens, Christopher J; Taylor, Lee; Dascombe, Ben J

2017-05-01

It is well established that endurance performance is negatively affected by environmental heat stress due to a complex interaction of physical, physiological and psychological alterations. Numerous scientific investigations have attempted to improve performance in the heat with pre-cooling (cooling prior to an exercise test), and as such this has become a well-established ergogenic practice for endurance athletes. However, the use of mid-cooling (cooling during an exercise test) has received considerably less research attention in comparison, despite recent evidence to suggest that the advantage gained from mid-cooling may outweigh that of pre-cooling. A range of mid-cooling strategies are beneficial for endurance performance in the heat, including the ingestion of cold fluids and ice slurry, both with and without menthol, as well as cooling of the neck and face region via a cooling collar or water poured on the head and face. The combination of pre-cooling and mid-cooling has also been effective, but few comparisons exist between the timing and type of such interventions. Therefore, athletes should experiment with a range of suitable mid-cooling strategies for their event during mock competition scenarios, with the aim to determine their individual tolerable limits and performance benefits. Based on current evidence, the effect of mid-cooling on core temperature appears largely irrelevant to any subsequent performance improvements, while cardiovascular, skin temperature, central nervous system function and psychophysiological factors are likely involved. Research is lacking on elite athletes, and as such it is currently unclear how this population may benefit from mid-cooling.

Depletion of potassium and sodium in mantles of Mars, Moon and Vesta by core formation.

PubMed

Steenstra, E S; Agmon, N; Berndt, J; Klemme, S; Matveev, S; van Westrenen, W

2018-05-04

The depletions of potassium (K) and sodium (Na) in samples from planetary interiors have long been considered as primary evidence for their volatile behavior during planetary formation processes. Here, we use high-pressure experiments combined with laser ablation analyses to measure the sulfide-silicate and metal-silicate partitioning of K and Na at high pressure (P) - temperature (T) and find that their partitioning into metal strongly increases with temperature. Results indicate that the observed Vestan and Martian mantle K and Na depletions can reflect sequestration into their sulfur-rich cores in addition to their volatility during formation of Mars and Vesta. This suggests that alkali depletions are not affected solely by incomplete condensation or partial volatilization during planetary formation and differentiation, but additionally or even primarily reflect the thermal and chemical conditions during core formation. Core sequestration is also significant for the Moon, but lunar mantle depletions of K and Na cannot be reconciled by core formation only. This supports the hypothesis that measured isotopic fractionations of K in lunar samples represent incomplete condensation or extensive volatile loss during the Moon-forming giant impact.

Microbial analysis of meatballs cooled with vacuum and conventional cooling.

PubMed

Ozturk, Hande Mutlu; Ozturk, Harun Kemal; Koçar, Gunnur

2017-08-01

Vacuum cooling is a rapid evaporative cooling technique and can be used for pre-cooling of leafy vegetables, mushroom, bakery, fishery, sauces, cooked food, meat and particulate foods. The aim of this study was to apply the vacuum cooling and the conventional cooling techniques for the cooling of the meatball and to show the vacuum pressure effect on the cooling time, the temperature decrease and microbial growth rate. The results of the vacuum cooling and the conventional cooling (cooling in the refrigerator) were compared with each other for different temperatures. The study shows that the conventional cooling was much slower than the vacuum cooling. Moreover, the microbial growth rate of the vacuum cooling was extremely low compared with the conventional cooling. Thus, the lowest microbial growth occurred at 0.7 kPa and the highest microbial growth was observed at 1.5 kPa for the vacuum cooling. The mass loss ratio for the conventional cooling and vacuum cooling was about 5 and 9% respectively.

High-dose diazepam facilitates core cooling during cold saline infusion in healthy volunteers.

PubMed

Hostler, David; Northington, William E; Callaway, Clifton W

2009-08-01

Studies have suggested that inducing mild hypothermia improves neurologic outcomes after traumatic brain injury, major stroke, cardiac arrest, or exertional heat illness. While infusion of cold normal saline is a simple and inexpensive method for reducing core temperature, human cold-defense mechanisms potentially make this route stressful or ineffective. We hypothesized that intravenous administration of diazepam during a rapid infusion of 30 mL.kg-1 of cold (4 degrees C) 0.9% saline to healthy subjects would be more comfortable and reduce core body temperature more than the administration of cold saline alone. Fifteen subjects received rapidly infused cold (4 degrees C) 0.9% saline. Subjects were randomly assigned to receive, intravenously, 20 mg diazepam (HIGH), 10 mg diazepam (LOW), or placebo (CON). Main outcomes were core temperature, skin temperature, and oxygen consumption. Data for the main outcomes were analyzed with generalized estimating equations to identify differences in group, time, or a group x time interaction. Core temperature decreased in all groups (CON, 1.0 +/- 0.2 degrees C; LOW, 1.4 +/- 0.2 degrees C; HIGH, 1.5 +/- 0.2 degrees C), while skin temperature was unchanged. Mean (95% CI) oxygen consumption was 315.3 (253.8, 376.9) mL.kg-1.min-1 in the CON group, 317.9 (275.5, 360.3) in the LOW group, and 226.1 (216.4, 235.9) in the HIGH group. Significant time and group x time interaction was observed for core temperature and oxygen consumption (p < 0.001). Administration of high-dose diazepam resulted in decreased oxygen consumption during cold saline infusion, suggesting that 20 mg of intravenous diazepam may reduce the shivering threshold without compromising respiratory or cardiovascular function.

PARTICLE IMAGE VELOCIMETRY MEASUREMENTS IN A REPRESENTATIVE GAS-COOLED PRISMATIC REACTOR CORE MODEL: FLOW IN THE COOLANT CHANNELS AND INTERSTITIAL BYPASS GAPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas E. Conder; Richard Skifton; Ralph Budwig

Core bypass flow is one of the key issues with the prismatic Gas Turbine-Modular Helium Reactor, and it refers to the coolant that navigates through the interstitial, non-cooling passages between the graphite fuel blocks instead of traveling through the designated coolant channels. To determine the bypass flow, a double scale representative model was manufactured and installed in the Matched Index-of-Refraction flow facility; after which, stereo Particle Image Velocimetry (PIV) was employed to measure the flow field within. PIV images were analyzed to produce vector maps, and flow rates were calculated by numerically integrating over the velocity field. It was foundmore » that the bypass flow varied between 6.9-15.8% for channel Reynolds numbers of 1,746 and 4,618. The results were compared to computational fluid dynamic (CFD) pre-test simulations. When compared to these pretest calculations, the CFD analysis appeared to under predict the flow through the gap.« less

Nuclear reactor spacer grid and ductless core component

DOEpatents

Christiansen, David W.; Karnesky, Richard A.

1989-01-01

The invention relates to a nuclear reactor spacer grid member for use in a liquid cooled nuclear reactor and to a ductless core component employing a plurality of these spacer grid members. The spacer grid member is of the egg-shell type and is constructed so that the walls of the cell members of the grid member are formed of a single thickness of metal to avoid tolerance problems. Within each cell member is a hydraulic spring which laterally constrains the nuclear material bearing rod which passes through each cell member against a hardstop in response to coolant flow through the cell member. This hydraulic spring is also suitable for use in a water cooled nuclear reactor. A core component constructed of, among other components, a plurality of these spacer grid members, avoids the use of a full length duct by providing spacer sleeves about the sodium tubes passing through the spacer grid members at locations between the grid members, thereby maintaining a predetermined space between adjacent grid members.

Combined cooling and purification system for nuclear reactor spent fuel pit, refueling cavity, and refueling water storage tank

DOEpatents

Corletti, Michael M.; Lau, Louis K.; Schulz, Terry L.

1993-01-01

The spent fuel pit of a pressured water reactor (PWR) nuclear power plant has sufficient coolant capacity that a safety rated cooling system is not required. A non-safety rated combined cooling and purification system with redundant branches selectively provides simultaneously cooling and purification for the spent fuel pit, the refueling cavity, and the refueling water storage tank, and transfers coolant from the refueling water storage tank to the refueling cavity without it passing through the reactor core. Skimmers on the suction piping of the combined cooling and purification system eliminate the need for separate skimmer circuits with dedicated pumps.

Combined cooling and purification system for nuclear reactor spent fuel pit, refueling cavity, and refueling water storage tank

DOEpatents

Corletti, M.M.; Lau, L.K.; Schulz, T.L.

1993-12-14

The spent fuel pit of a pressured water reactor (PWR) nuclear power plant has sufficient coolant capacity that a safety rated cooling system is not required. A non-safety rated combined cooling and purification system with redundant branches selectively provides simultaneously cooling and purification for the spent fuel pit, the refueling cavity, and the refueling water storage tank, and transfers coolant from the refueling water storage tank to the refueling cavity without it passing through the reactor core. Skimmers on the suction piping of the combined cooling and purification system eliminate the need for separate skimmer circuits with dedicated pumps. 1 figures.

Rapid Neutrino Cooling in the Neutron Star MXB 1659-29.

PubMed

Brown, Edward F; Cumming, Andrew; Fattoyev, Farrukh J; Horowitz, C J; Page, Dany; Reddy, Sanjay

2018-05-04

We show that the neutron star in the transient system MXB 1659-29 has a core neutrino luminosity that substantially exceeds that of the modified Urca reactions (i.e., n+n→n+p+e^{-}+ν[over ¯]_{e} and inverse) and is consistent with the direct Urca (n→p+e^{-}+ν[over ¯]_{e} and inverse) reaction occurring in a small fraction of the core. Observations of the thermal relaxation of the neutron star crust following 2.5 yr of accretion allow us to measure the energy deposited into the core during accretion, which is then reradiated as neutrinos, and infer the core temperature. For a nucleonic core, this requires that the nucleons are unpaired and that the proton fraction exceeds a critical value to allow the direct Urca reaction to proceed. The neutron star in MXB 1659-29 is the first with a firmly detected thermal component in its x-ray spectrum that needs a fast neutrino-cooling process. Measurements of the temperature variation of the neutron star core during quiescence would place an upper limit on the core specific heat and serve as a check on the fraction of the neutron star core in which nucleons are unpaired.

Rapid Neutrino Cooling in the Neutron Star MXB 1659-29

NASA Astrophysics Data System (ADS)

Brown, Edward F.; Cumming, Andrew; Fattoyev, Farrukh J.; Horowitz, C. J.; Page, Dany; Reddy, Sanjay

2018-05-01

We show that the neutron star in the transient system MXB 1659-29 has a core neutrino luminosity that substantially exceeds that of the modified Urca reactions (i.e., n +n →n +p +e-+ν¯ e and inverse) and is consistent with the direct Urca (n →p +e-+ν¯e and inverse) reaction occurring in a small fraction of the core. Observations of the thermal relaxation of the neutron star crust following 2.5 yr of accretion allow us to measure the energy deposited into the core during accretion, which is then reradiated as neutrinos, and infer the core temperature. For a nucleonic core, this requires that the nucleons are unpaired and that the proton fraction exceeds a critical value to allow the direct Urca reaction to proceed. The neutron star in MXB 1659-29 is the first with a firmly detected thermal component in its x-ray spectrum that needs a fast neutrino-cooling process. Measurements of the temperature variation of the neutron star core during quiescence would place an upper limit on the core specific heat and serve as a check on the fraction of the neutron star core in which nucleons are unpaired.

Effect of Different Cooling Rates on the Corrosion Behavior of High-Carbon Pearlitic Steel

NASA Astrophysics Data System (ADS)

Katiyar, Prvan Kumar; Misra, Sudhir; Mondal, K.

2018-03-01

The present work discusses the effect of pearlitic morphology on the corrosion behavior of high-carbon fully pearlitic steel in 3.5% NaCl solution. Four different types of pearlitic steels (furnace-cooled, as-received, air-cooled and forced-air-cooled) consisting of coarse, medium, fine and very fine microstructures, respectively, were tested. Electrochemical behavior of these steels was studied with the help of dynamic and linear polarization and AC impedance spectroscopic tests. The corrosion resistance improved with fineness of the microstructure in general. However, with further reduction in interlamellar spacing beyond a limit, the corrosion resistance reduced slightly. Formation of homogeneous distribution of microgalvanic cells between cementite and ferrite lamellae of fine pearlitic steel improved the corrosion resistance. However, entanglement of the lamellae of pearlite in very fine pearlitic structure as well as breaking of cementite lamellae due to finer pearlitic colonies was attributed to the higher corrosion of the forced-air-cooled steel as compared to the air-cooled steel.

A comparison of 2 evaporative cooling systems on a commercial dairy farm in Saudi Arabia.

PubMed

Ortiz, X A; Smith, J F; Villar, F; Hall, L; Allen, J; Oddy, A; Al-Haddad, A; Lyle, P; Collier, R J

2015-12-01

Efficacy of 2 cooling systems (Korral Kool, KK, Korral Kool Inc., Mesa, AZ; FlipFan dairy system, FF, Schaefer Ventilation Equipment LLC, Sauk Rapids, MN) was estimated utilizing 400 multiparous Holstein dairy cows randomly assigned to 1 of 4 cooled California-style shade pens (2 shade pens per cooling system). Each shaded pen contained 100 cows (days in milk=58±39, milk production=56±18 kg/d, and lactation=3±1). Production data (milk yield and reproductive performance) were collected during 3mo (June-August, 2013) and physiological responses (core body temperature, respiration rates, surface temperatures, and resting time) were measured in June and July to estimate responses of cows to the 2 different cooling systems. Water and electricity consumption were recorded for each system. Cows in the KK system displayed slightly lower respiration rates in the month of June and lower surface temperatures in June and July. However, no differences were observed in the core body temperature of cows, resting time, feed intake, milk yield, services/cow, and conception rate between systems. The FF system used less water and electricity during this study. In conclusion, both cooling systems (KK and FF) were effective in mitigating the negative effects of heat stress on cows housed in arid environments, whereas the FF system consumed less water and electricity and did not require use of curtains on the shade structure. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Heat-bath algorithmic cooling with correlated qubit-environment interactions

NASA Astrophysics Data System (ADS)

Rodríguez-Briones, Nayeli A.; Li, Jun; Peng, Xinhua; Mor, Tal; Weinstein, Yossi; Laflamme, Raymond

2017-11-01

Cooling techniques are essential to understand fundamental thermodynamic questions of the low-energy states of physical systems, furthermore they are at the core of practical applications of quantum information science. In quantum computing, this controlled preparation of highly pure quantum states is required from the state initialization of most quantum algorithms to a reliable supply of ancilla qubits that satisfy the fault-tolerance threshold for quantum error correction. Heat-bath algorithmic cooling has been shown to purify qubits by controlled redistribution of entropy and multiple contact with a bath, not only for ensemble implementations but also for technologies with strong but imperfect measurements. In this paper, we show that correlated relaxation processes between the system and environment during rethermalization when we reset hot ancilla qubits, can be exploited to enhance purification. We show that a long standing upper bound on the limits of algorithmic cooling Schulman et al (2005 Phys. Rev. Lett. 94, 120501) can be broken by exploiting these correlations. We introduce a new tool for cooling algorithms, which we call ‘state-reset’, obtained when the coupling to the environment is generalized from individual-qubits relaxation to correlated-qubit relaxation. Furthermore, we present explicit improved cooling algorithms which lead to an increase of purity beyond all the previous work, and relate our results to the Nuclear Overhauser Effect.

Evolution of oceanic core complex domes and corrugations

NASA Astrophysics Data System (ADS)

Cann, J.; Escartin, J.; Smith, D.; Schouten, H.

2007-12-01

In regions of the oceans where detachment faulting is developed widely, individual core complex domes (elevated massifs capped by corrugated detachment surfaces) show a consistent morphology. At their outward sides, most core complex domes are attached to a planar slope, interpreted (Smith et al., 2006) as an originally steep inward-facing normal fault that has been rotated to shallower angles. We suggest that the break in slope where the originally steep normal fault meets the domal corrugated surface marks the trace of the brittle-ductile transition at the base of the original normal fault. The steep faults originate within a short distance of the spreading axis. This means that the arcuate shape of the intersection of the steep fault with the dome must indicate the shape of the brittle-ductile transition very close to the spreading axis. The transition must be very shallow close to the summit of the dome and deeper on each flank. Evidence from drilling of some core complexes (McCaig et al, 2007) shows that while the domal detachment faults are active they may channel hydrothermal flow at black smoker temperatures and may be simultaneously injected by magma from below. This indicates a close link between igneous activity, hydrothermal flow and deformation while a core complex is forming. Once the shape of the core complex dome is established, it persists as the ductile footwall mantle rising from below is shaped by the overlying brittle hanging wall that has been cooled by the hydrothermal circulation. The corrugations in the footwall must be moulded into it by irregularities in the brittle hanging wall, as suggested by Spencer (1999). The along-axis arched shape of the hanging wall helps to stabilise the domal shape of the footwall as it rises and cools.

Combination pipe rupture mitigator and in-vessel core catcher

DOEpatents

Tilbrook, Roger W.; Markowski, Franz J.

1983-01-01

A device which mitigates against the effects of a failed coolant loop in a nuclear reactor by restricting the outflow of coolant from the reactor through the failed loop and by retaining any particulated debris from a molten core which may result from coolant loss or other cause. The device reduces the reverse pressure drop through the failed loop by limiting the access of coolant in the reactor to the inlet of the failed loop. The device also spreads any particulated core debris over a large area to promote cooling.

Candidate molten salt investigation for an accelerator driven subcritical core

NASA Astrophysics Data System (ADS)

Sooby, E.; Baty, A.; Beneš, O.; McIntyre, P.; Pogue, N.; Salanne, M.; Sattarov, A.

2013-09-01

We report a design for accelerator-driven subcritical fission in a molten salt core (ADSMS) that utilizes a fuel salt composed of NaCl and transuranic (TRU) chlorides. The ADSMS core is designed for fast neutronics (28% of neutrons >1 MeV) to optimize TRU destruction. The choice of a NaCl-based salt offers benefits for corrosion, operating temperature, and actinide solubility as compared with LiF-based fuel salts. A molecular dynamics (MD) code has been used to estimate properties of the molten salt system which are important for ADSMS design but have never been measured experimentally. Results from the MD studies are reported. Experimental measurements of fuel salt properties and studies of corrosion and radiation damage on candidate metals for the core vessel are anticipated. A special thanks is due to Prof. Paul Madden for introducing the ADSMS group to the concept of using the molten salt as the spallation target, rather than a conventional heavy metal spallation target. This feature helps to optimize this core as a Pu/TRU burner.

Forced convective head cooling device reduces human cross-sectional brain temperature measured by magnetic resonance: a non-randomized healthy volunteer pilot study.

PubMed

Harris, B A; Andrews, P J D; Marshall, I; Robinson, T M; Murray, G D

2008-03-01

This pilot study in five healthy adult humans forms the pre-clinical assessment of the effect of a forced convective head cooling device on intracranial temperature, measured non-invasively by magnetic resonance spectroscopy (MRS). After a 10 min baseline with no cooling, subjects received 30 min of head cooling followed by 30 min of head and neck cooling via a hood and neck collar delivering 14.5 degrees C air at 42.5 litre s(-1). Over baseline and at the end of both cooling periods, MRS was performed, using chemical shift imaging, to measure brain temperature simultaneously across a single slice of brain at the level of the basal ganglia. Oesophageal temperature was measured continuously using a fluoroptic thermometer. MRS brain temperature was calculated for baseline and the last 10 min of each cooling period. The net brain temperature reduction with head cooling was 0.45 degrees C (SD 0.23 degrees C, P=0.01, 95% CI 0.17-0.74 degrees C) and with head and neck cooling was 0.37 degrees C (SD 0.30 degrees C, P=0.049, 95% CI 0.00-0.74 degrees C). The equivalent net reductions in oesophageal temperature were 0.16 degrees C (SD 0.04 degrees C) and 0.36 degrees C (SD 0.12 degrees C). Baseline-corrected brain temperature gradients from outer through intermediate to core voxels were not significant for either head cooling (P=0.43) or head and neck cooling (P=0.07), indicating that there was not a significant reduction in cooling with progressive depth into the brain. Convective head cooling reduced MRS brain temperature and core brain was cooled.

Direct Correlation of Excitonics with Efficiency in a Core-Shell Quantum Dot Solar Cell.

PubMed

Dana, Jayanta; Maiti, Sourav; Tripathi, Vaidehi S; Ghosh, Hirendra N

2018-02-16

Shell thickness dependent band-gap engineering of quasi type II core-shell material with higher carrier cooling time, lower interfacial defect states, and longer charge carrier recombination time can be a promising candidate for both photocatalysis and solar cell. In the present investigation, colloidal CdSe@CdS core-shells with different shell thickness (2, 4 and 6 monolayer CdS) were synthesized through hot injection method and have been characterized by high resolution transmission electron microscope (HRTEM) followed by steady state absorption and luminescence techniques. Ultrafast transient absorption (TA) studies suggest longer carrier cooling, lower interfacial surface states, and slower carrier recombination time in CdSe@CdS core-shell with increasing shell thickness. By TA spectroscopy, the role of CdS shell in power conversion efficiency (PCE) has been explained in detail. The measured PCE was found to initially increase and then decrease with increasing shell thickness. Shell thickness has been optimized to maximize the efficiency after correlating the shell controlled carrier cooling and recombination with PCE values and a maximum PCE of 3.88 % was obtained with 4 monolayers of CdS shell, which is found to be 57 % higher than compared to bare CdSe QDs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Why Do Some Cores Remain Starless?

NASA Astrophysics Data System (ADS)

Anathpindika, S.

2016-08-01

Prestellar cores, by definition, are gravitationally bound but starless pockets of dense gas. Physical conditions that could render a core starless (in the local Universe) is the subject of investigation in this work. To this end, we studied the evolution of four starless cores, B68, L694-2, L1517B, L1689, and L1521F, a VeLLO. We demonstrate: (i) cores contracted in quasistatic manner over a timescale on the order of ~ 105 yr. Those that remained starless briefly acquired a centrally concentrated density configuration that mimicked the profile of a unstable BonnorEbert sphere before rebounding, (ii) three cores viz. L694-2, L1689-SMM16, and L1521F remained starless despite becoming thermally super-critical. By contrast, B68 and L1517B remained sub-critical; L1521F collapsed to become a VeLLO only when gas-cooling was enhanced by increasing the size of dust-grains. This result is robust, for other starless cores viz. B68, L694-2, L1517B, and L1689 could also be similarly induced to collapse. The temperature-profile of starless cores and those that collapsed was found to be radically different. While in the former type, only very close to the centre of a core was there any evidence of decline in gas temperature, by contrast, a core of the latter type developed a more uniformly cold interior. Our principle conclusions are: (a) thermal super-criticality of a core is insufficient to ensure it will become protostellar, (b) potential star-forming cores (the VeLLO L1521F here), could be experiencing dust-coagulation that must enhance gasdust coupling and in turn lower gas temperature, thereby assisting collapse. This also suggests, mere gravitational/virial boundedness of a core is insufficient to ensure it will form stars.

Effect of Na2O on Crystallisation Behaviour and Heat Transfer of Fluorine-Free Mould Fluxes

NASA Astrophysics Data System (ADS)

Yang, Jian; Zhang, Jianqiang; Sasaki, Yasushi; Ostrovski, Oleg; Zhang, Chen; Cai, Dexiang; Kashiwaya, Yoshiaki

Most of the commercial mould fluxes contain fluorides which bring about serious environmental problems. The major challenge in the application of fluorine-free mould fluxes is to control the heat transfer from the strand to copper mould which is closely related to crystallisation behaviour. In this study, the effects of Na2O on the crystallisation behaviour and heat transfer of CaO-SiO2-Na2O-B2O3-TiO2-Al2O3-MgO-Li2O mould fluxes were investigated using single /double hot thermocouple technique (SHTT/DHTT) and infrared emitter technique (IET), respectively. Continuous cooling transformation (CCT) and time-temperature transformation (TTT) diagrams constructed using SHTT showed that the increase of Na2O concentration led to higher critical cooling rate and shorter incubation time. The crystallisation behaviour in a thermal gradient was examined using DHTT. The heat flux measured by IET showed that the increase of Na2O concentration decreased the heat flux when Na2O was lower than 9 mass% but the further increase of Na2O raised the heat flux. The relationship between flux crystallisation and heat transfer was also discussed.

Enhanced Upconversion Luminescence in Yb3+/Tm3+-Codoped Fluoride Active Core/Active Shell/Inert Shell Nanoparticles through Directed Energy Migration

PubMed Central

Qiu, Hailong; Yang, Chunhui; Shao, Wei; Damasco, Jossana; Wang, Xianliang; Ågren, Hans; Prasad, Paras N.; Chen, Guanying

2014-01-01

The luminescence efficiency of lanthanide-doped upconversion nanoparticles is of particular importance for their embodiment in biophotonic and photonic applications. Here, we show that the upconversion luminescence of typically used NaYF4:Yb3+30%/Tm3+0.5% nanoparticles can be enhanced by ~240 times through a hierarchical active core/active shell/inert shell (NaYF4:Yb3+30%/Tm3+0.5%)/NaYbF4/NaYF4 design, which involves the use of directed energy migration in the second active shell layer. The resulting active core/active shell/inert shell nanoparticles are determined to be about 11 times brighter than that of well-investigated (NaYF4:Yb3+30%/Tm3+0.5%)/NaYF4 active core/inert shell nanoparticles when excited at ~980 nm. The strategy for enhanced upconversion in Yb3+/Tm3+-codoped NaYF4 nanoparticles through directed energy migration might have implications for other types of lanthanide-doped upconversion nanoparticles. PMID:28348285

Enhanced Upconversion Luminescence in Yb3+/Tm3+-Codoped Fluoride Active Core/Active Shell/Inert Shell Nanoparticles through Directed Energy Migration.

PubMed

Qiu, Hailong; Yang, Chunhui; Shao, Wei; Damasco, Jossana; Wang, Xianliang; Ågren, Hans; Prasad, Paras N; Chen, Guanying

2014-01-03

The luminescence efficiency of lanthanide-doped upconversion nanoparticles is of particular importance for their embodiment in biophotonic and photonic applications. Here, we show that the upconversion luminescence of typically used NaYF₄:Yb 3+ 30%/Tm 3+ 0.5% nanoparticles can be enhanced by ~240 times through a hierarchical active core/active shell/inert shell (NaYF₄:Yb 3+ 30%/Tm 3+ 0.5%)/NaYbF₄/NaYF₄ design, which involves the use of directed energy migration in the second active shell layer. The resulting active core/active shell/inert shell nanoparticles are determined to be about 11 times brighter than that of well-investigated (NaYF₄:Yb 3+ 30%/Tm 3+ 0.5%)/NaYF₄ active core/inert shell nanoparticles when excited at ~980 nm. The strategy for enhanced upconversion in Yb 3+ /Tm 3+ -codoped NaYF₄ nanoparticles through directed energy migration might have implications for other types of lanthanide-doped upconversion nanoparticles.

Core thermal response and hydrogen generation of the N Reactor hydrogen mitigation design basis accident

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, M.D.; Lombardo, N.J.; Heard, F.J.

1988-04-01

Calculations were performed to determine core heatup, core damage, and subsequent hydrogen production of a hypothetical loss-of-cooling accident at the Department of Energy's N Reactor. The thermal transient response of the reactor core was solved using the TRUMP-BD computer program. Estimates of whole-core thermal damage and hydrogen production were made by weighting the results of multiple half-length pressure tube simulations at various power levels. The Baker-Just and Wilson parabolic rate equations for the metal-water chemical reactions modeled the key phenomena of chemical energy and hydrogen evolution. Unlimited steam was assumed available for continuous oxidation of exposed Zircaloy-2 surfaces and formore » uranium metal with fuel cladding beyond the failure temperature (1038 C). Intact fuel geometry was modeled. Maximum fuel temperatures (1181 C) in the cooled central regions of the core were predicted to occur one-half hour into the accident scenario. Maximum fuel temperatures of 1447 C occurred in the core GSCS-regions at the end of the 10-h transient. After 10-h 26% of the fuel inventory was predicted to have failed. Peak hydrogen evolution equaled 42 g/s, while 10-h integrated hydrogen evolution equaled 167 kg. 12 refs., 12 figs., 2 tabs.« less

Warming by immersion or exercise affects initial cooling rate during subsequent cold water immersion.

PubMed

Scott, Chris G; Ducharme, Michel B; Haman, François; Kenny, Glen P

2004-11-01

We examined the effect of prior heating, by exercise and warm-water immersion, on core cooling rates in individuals rendered mildly hypothermic by immersion in cold water. There were seven male subjects who were randomly assigned to one of three groups: 1) seated rest for 15 min (control); 2) cycling ergometry for 15 min at 70% Vo2 peak (active warming); or 3) immersion in a circulated bath at 40 degrees C to an esophageal temperature (Tes) similar to that at the end of exercise (passive warming). Subjects were then immersed in 7 degrees C water to a Tes of 34.5 degrees C. Initial Tes cooling rates (initial approximately 6 min cooling) differed significantly among the treatment conditions (0.074 +/- 0.045, 0.129 +/- 0.076, and 0.348 +/- 0.117 degrees C x min(-1) for control, active, and passive warming conditions, respectively); however, secondary cooling rates (rates following initial approximately 6 min cooling to the end of immersion) were not different between treatments (average of 0.102 +/- 0.085 degrees C x min(-1)). Overall Tes cooling rates during the full immersion period differed significantly and were 0.067 +/- 0.047, 0.085 +/- 0.045, and 0.209 +/- 0.131 degrees C x min(-1) for control, active, and passive warming, respectively. These results suggest that prior warming by both active and, to a greater extent, passive warming, may predispose a person to greater heat loss and to experience a larger decline in core temperature when subsequently exposed to cold water. Thus, functional time and possibly survival time could be reduced when cold water immersion is preceded by whole-body passive warming, and to a lesser degree by active warming.

The thermal evolution of Mercury's Fe-Si core

NASA Astrophysics Data System (ADS)

Knibbe, Jurriën Sebastiaan; van Westrenen, Wim

2018-01-01

We have studied the thermal and magnetic field evolution of planet Mercury with a core of Fe-Si alloy to assess whether an Fe-Si core matches its present-day partially molten state, Mercury's magnetic field strength, and the observed ancient crustal magnetization. The main advantages of an Fe-Si core, opposed to a previously assumed Fe-S core, are that a Si-bearing core is consistent with the highly reduced nature of Mercury and that no compositional convection is generated upon core solidification, in agreement with magnetic field indications of a stable layer at the top of Mercury's core. This study also present the first implementation of a conductive temperature profile in the core where heat fluxes are sub-adiabatic in a global thermal evolution model. We show that heat migrates from the deep core to the outer part of the core as soon as heat fluxes at the outer core become sub-adiabatic. As a result, the deep core cools throughout Mercury's evolution independent of the temperature evolution at the core-mantle boundary, causing an early start of inner core solidification and magnetic field generation. The conductive layer at the outer core suppresses the rate of core growth after temperature differences between the deep and shallow core are relaxed, such that a magnetic field can be generated until the present. Also, the outer core and mantle operate at higher temperatures than previously thought, which prolongs mantle melting and mantle convection. The results indicate that S is not a necessary ingredient of Mercury's core, bringing bulk compositional models of Mercury more in line with reduced meteorite analogues.

Preparation of Al-La Master Alloy by Thermite Reaction in NaF-NaCl-KCl Molten Salt

NASA Astrophysics Data System (ADS)

Jang, Poknam; Li, Hyonmo; Kim, Wenjae; Wang, Zhaowen; Liu, Fengguo

2015-05-01

A NaF-NaCl-KCl ternary system containing La2O3 was investigated for the preparation of Al-La master alloy by the thermite reaction method. The solubility of La2O3 in NaF-NaCl-KCl molten salt was determined by the method of isothermal solution saturation. Inductively coupled plasma-optical emission spectroscopy and x-ray diffraction (XRD) analyses were used to consider the content of La2O3 in molten salt and the supernatant composition of molten salt after dissolution of La2O3, respectively. The results showed that the content of NaF had a positive influence on the solubility of La2O3 in NaF-NaCl-KCl molten salts, and the solubility of La2O3 could reach 8.71 wt.% in molten salts of 50 wt.%NaF-50 wt.% (44 wt.%NaCl + 56 wt.%KCl). The XRD pattern of cooling molten salt indicated the formation of LaOF in molten salt, which was probably obtained by the reaction between NaF and La2O3. The kinetic study showed that the thermite reaction was in accord with a first-order reaction model. The main influence factors on La content in the Al-La master alloy product, including molten salt composition, amount of Al, concentration of La2O3, stirring, reduction time and temperature, were investigated by single-factor experimentation. The content of La in the Al-La master alloy could be reached to 10.1 wt.%.

Thermoregulatory, cardiovascular, and perceptual responses to intermittent cooling during exercise in a hot, humid outdoor environment.

PubMed

Cleary, Michelle A; Toy, Michelle G; Lopez, Rebecca M

2014-03-01

Decreasing core body temperature during exercise may improve exercise tolerance, facilitate acclimatization, and prevent heat illness during summer training. We sought to evaluate the effectiveness of intermittent superficial cooling on thermoregulatory, cardiovascular, and perceptual responses during exercise in a hot humid environment. We used a randomized, counterbalanced, repeated measures investigation with 2 conditions (control and cooling) during exercise and recovery outdoors on artificial turf in a hot, humid tropical climate in the sun (wet bulb globe temperature outdoors [WBGTo], 27.0 ± 0.8° C; range, 25.8-28.1° C) and in the shade (WBGTo, 25.4 ± 0.9° C; range, 24.3-26.8° C). Participants were 10 healthy males (age, 22.6 ± 1.6 years; height, 176.0 ± 6.9 cm; mass, 76.5 ± 7.8 kg; body fat, 15.6 ± 5.4%) who wore shorts and T-shirt (control) or "phase change cooling" vest (cooling) during 5-minute rest breaks during 60 minutes of intense American football training and conditioning exercises in the heat and 30 minutes of recovery in the shade. Throughout, we measured core (Tgi) and skin (Tchest) temperature, heart rate (HR), thermal and thirst sensations, and rating of perceived exertion. We found significant (p ≤ 0.001) hypohydration (-2.1%); for Tgi, we found no significant differences between conditions (p = 0.674) during exercise and progressive decreases during recovery (p < 0.001). For [INCREMENT]Tg,i we found no significant (p = 0.090) differences. For Tchest, we found significantly (p < 0.001) decreased skin temperature in the cooling condition (Tchest, 31.85 ± 0.43° C) compared with the control condition (Tchest, 34.38 ± 0.43° C) during exercise and significantly (p < 0.001) lower skin temperature in the cooling condition (Tchest, 31.24 ± 0.47° C) compared with the control condition (Tchest, 33.48 ± 0.47° C) during recovery. For HR, we found no significant difference (p = 0.586) between the conditions during exercise; however, we

Meta-analysis of the effects of microclimate cooling systems on human performance under thermal stressful environments: potential applications to occupational workers.

PubMed

Chan, Albert P C; Song, Wenfang; Yang, Yang

2015-01-01

This study aims to determine the appropriate microclimate cooling systems (MCSs) to reduce heat stress and improve human performance of occupational workers and their practicality in the occupational field. Meta-analysis was employed to summarize, analyze, and compare the effects of various MCSs on human performance with corresponding physiological and psychological responses, thereby providing solid suggestions for selecting suitable MCSs for occupational workers. Wearing MCSs significantly attenuated the increases in core temperature (-0.34 °C/h) and sweating rate (-0.30 L/h), and significantly improved human performance (+29.9%, effect size [EFS] = 1.1) compared with no cooling condition (CON). Cold air-cooled garments (ACG-Cs; +106.2%, EFS = 2.32) exhibited greater effects on improving human performance among various microclimate cooling garments (MCGs), followed by liquid cooling garments (LCGs; +68.1%, EFS = 1.86) and hybrid cooling garment combining air and liquid cooling (HBCG-AL; +59.1%, EFS=3.38), natural air-cooled garments (ACG-Ns; +39.9%, EFS = 1.12), and phase change material cooling garments (PCMCGs; +19.5%, EFS = 1.2). Performance improvement was observed to be positively and linearly correlated to the differences of core temperature increase rate (r = 0.65, p < 0.01) and sweating rate (r = 0.80, p < 0.001) between MCSs and CON. Considering their application in industrial settings, ACG-Cs, LCGs, and HBCG-AL are practical for work, in which workers do not move frequently, whereas ACG-Ns and PCMCGs are more applicable for the majority of occupational workers. Further enhancement of the cooling efficiency of these two cooling strategies should be initiated. Copyright © 2015 Elsevier Ltd. All rights reserved.

Preconceptual design of a fluoride high temperature salt-cooled engineering demonstration reactor: Motivation and overview

DOE PAGES

Qualls, A. Louis; Betzler, Benjamin R.; Brown, Nicholas R.; ...

2016-12-21

Engineering demonstration reactors are nuclear reactors built to establish proof of concept for technology options that have never been built. Examples of engineering demonstration reactors include Peach Bottom 1 for high temperature gas-cooled reactors (HTGRs) and Experimental Breeder Reactor-II (EBR-II) for sodium-cooled fast reactors. Historically, engineering demonstrations have played a vital role in advancing the technology readiness level of reactor technologies. Our paper details a preconceptual design for a fluoride salt-cooled engineering demonstration reactor. The fluoride salt-cooled high-temperature reactor (FHR) demonstration reactor (DR) is a concept for a salt-cooled reactor with 100 megawatts of thermal output (MWt). It would usemore » tristructural-isotropic (TRISO) particle fuel within prismatic graphite blocks. FLiBe (2 7LiF-BeF2) is the reference primary coolant. The FHR DR is designed to be small, simple, and affordable. Development of the FHR DR is a necessary intermediate step to enable near-term commercial FHRs. The design philosophy of the FHR DR was focused on safety, near-term deployment, and flexibility. Lower risk technologies are purposely included in the initial FHR DR design to ensure that the reactor can be built, licensed, and operated as an engineering demonstration with minimal risk and cost. These technologies include TRISO particle fuel, replaceable core structures, and consistent structural material selection for core structures and the primary and intermediate loops, and tube-and-shell primary-to-intermediate heat exchangers. Important capabilities to be demonstrated by building and operating the FHR DR include fabrication and operation of high temperature reactors; heat exchanger performance (including passive decay heat removal); pump performance; and reactivity control; salt chemistry control to maximize vessel life; tritium management; core design methodologies; salt procurement, handling, maintenance and ultimate

Preconceptual design of a fluoride high temperature salt-cooled engineering demonstration reactor: Motivation and overview

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qualls, A. Louis; Betzler, Benjamin R.; Brown, Nicholas R.

Engineering demonstration reactors are nuclear reactors built to establish proof of concept for technology options that have never been built. Examples of engineering demonstration reactors include Peach Bottom 1 for high temperature gas-cooled reactors (HTGRs) and Experimental Breeder Reactor-II (EBR-II) for sodium-cooled fast reactors. Historically, engineering demonstrations have played a vital role in advancing the technology readiness level of reactor technologies. Our paper details a preconceptual design for a fluoride salt-cooled engineering demonstration reactor. The fluoride salt-cooled high-temperature reactor (FHR) demonstration reactor (DR) is a concept for a salt-cooled reactor with 100 megawatts of thermal output (MWt). It would usemore » tristructural-isotropic (TRISO) particle fuel within prismatic graphite blocks. FLiBe (2 7LiF-BeF2) is the reference primary coolant. The FHR DR is designed to be small, simple, and affordable. Development of the FHR DR is a necessary intermediate step to enable near-term commercial FHRs. The design philosophy of the FHR DR was focused on safety, near-term deployment, and flexibility. Lower risk technologies are purposely included in the initial FHR DR design to ensure that the reactor can be built, licensed, and operated as an engineering demonstration with minimal risk and cost. These technologies include TRISO particle fuel, replaceable core structures, and consistent structural material selection for core structures and the primary and intermediate loops, and tube-and-shell primary-to-intermediate heat exchangers. Important capabilities to be demonstrated by building and operating the FHR DR include fabrication and operation of high temperature reactors; heat exchanger performance (including passive decay heat removal); pump performance; and reactivity control; salt chemistry control to maximize vessel life; tritium management; core design methodologies; salt procurement, handling, maintenance and ultimate

The deep Earth may not be cooling down

NASA Astrophysics Data System (ADS)

Andrault, Denis; Monteux, Julien; Le Bars, Michael; Samuel, Henri

2016-06-01

The Earth is a thermal engine generating the fundamental processes of geomagnetic field, plate tectonics and volcanism. Large amounts of heat are permanently lost at the surface yielding the classic view of the deep Earth continuously cooling down. Contrary to this conventional depiction, we propose that the temperature profile in the deep Earth has remained almost constant for the last ∼4.3 billion years. The core-mantle boundary (CMB) has reached a temperature of ∼4400 K in probably less than 1 million years after the Moon-forming impact, regardless the initial core temperature. This temperature corresponds to an abrupt increase in mantle viscosity atop the CMB, when ∼60% of partial crystallization was achieved, accompanied with a major decrease in heat flow at the CMB. Then, the deep Earth underwent a very slow cooling until it reached ∼4100 K today. This temperature at, or just below, the mantle solidus is suggested by seismological evidence of ultra-low velocity zones in the D;-layer. Such a steady thermal state of the CMB temperature excludes thermal buoyancy from being the predominant mechanism to power the geodynamo over geological time. An alternative mechanism to sustain the geodynamo is mechanical forcing by tidal distortion and planetary precession. Motions in the outer core are generated by the conversion of gravitational and rotational energies of the Earth-Moon-Sun system. Mechanical forcing remains efficient to drive the geodynamo even for a sub-adiabatic temperature gradient in the outer core. Our thermal model of the deep Earth is compatible with an average CMB heat flow of 3.0 to 4.7 TW. Furthermore, the regime of core instabilities and/or secular changes in the astronomical forces could have supplied the lowermost mantle with a heat source of variable intensity through geological time. Episodic release of large amounts of heat could have remelted the lowermost mantle, thereby inducing the dramatic volcanic events that occurred during the

Design of energy efficient building with radiant slab cooling

NASA Astrophysics Data System (ADS)

Tian, Zhen

2007-12-01

Air-conditioning comprises a substantial fraction of commercial building energy use because of compressor-driven refrigeration and fan-driven air circulation. Core regions of large buildings require year-round cooling due to heat gains from people, lights and equipment. Negative environmental impacts include CO2 emissions from electric generation and leakage of ozone-depleting refrigerants. Some argue that radiant cooling simultaneously improves building efficiency and occupant thermal comfort, and that current thermal comfort models fail to reflect occupant experience with radiant thermal control systems. There is little field evidence to test these claims. The University of Calgary's Information and Communications Technology (ICT) Building, is a pioneering radiant slab cooling installation in North America. Thermal comfort and energy performance were evaluated. Measurements included: (1) heating and cooling energy use, (2) electrical energy use for lighting and equipment, and (3) indoor temperatures. Accuracy of a whole building energy simulation model was evaluated with these data. Simulation was then used to compare the radiant slab design with a conventional (variable air volume) system. The radiant system energy performance was found to be poorer mainly due to: (1) simultaneous cooling by the slab and heating by other systems, (2) omission of low-exergy (e.g., groundwater) cooling possible with the high cooling water temperatures possible with radiant slabs and (3) excessive solar gain and conductive heat loss due to the wall and fenestration design. Occupant thermal comfort was evaluated through questionnaires and concurrent measurement of workstation comfort parameters. Analysis of 116 sets of data from 82 occupants showed that occupant assessment was consistent with estimates based on current thermal comfort models. The main thermal comfort improvements were reductions in (1) local discomfort from draft and (2) vertical air temperature stratification. The

Analysing neutron star in HESS J1731-347 from thermal emission and cooling theory

NASA Astrophysics Data System (ADS)

Ofengeim, D. D.; Kaminker, A. D.; Klochkov, D.; Suleimanov, V.; Yakovlev, D. G.

2015-12-01

The central compact object in the supernova remnant HESS J1731-347 appears to be the hottest observed isolated cooling neutron star. The cooling theory of neutron stars enables one to explain observations of this star by assuming the presence of strong proton superfluidity in the stellar core and the existence of the surface heat blanketing envelope which almost fully consists of carbon. The cooling model of this star is elaborated to take proper account of the neutrino emission due to neutron-neutron collisions which is not suppressed by proton superfluidity. Using the results of spectral fits of observed thermal spectra for the distance of 3.2 kpc and the cooling theory for the neutron star of age 27 kyr, new constraints on the stellar mass and radius are obtained which are more stringent than those derived from the spectral fits alone.

Early Wuchiapingian cooling linked to Emeishan basaltic weathering?

NASA Astrophysics Data System (ADS)

Yang, Jianghai; Cawood, Peter A.; Du, Yuansheng; Condon, Daniel J.; Yan, Jiaxin; Liu, Jianzhong; Huang, Yan; Yuan, Dongxun

2018-06-01

The last glaciation during the late Paleozoic ice age commenced at around the Guadalupian-Lopingian (G-L) boundary and is synchronous with the emplacement of the Emeishan large igneous province. Using CA-TIMS zircon U-Pb dating, we obtained an age of 259.51 ± 0.21 Ma for the uppermost tuff from the Puan volcanic sequence in the eastern Emeishan large igneous province, constraining the timing of Emeishan volcanism and providing another candidate age for the G-L boundary. In addition, we determined an age of 259.69 ± 0.72 Ma for a basal claystone in the immediately overlying Longtan Formation from a drill core section in southwest South China. These ages, along with source weathering trends of mudstones from the lower Longtan Formation, and compiled paleotemperature records, indicate an earliest Wuchiapingian cooling coinciding with the onset of the last Permian glaciation. This global cooling is associated with positive shifts in both organic and carbonate carbon isotopic records and likely a decrease in atmospheric pCO2. A hypothesised causal linkage is proposed in which the rapid post-eruptive basaltic weathering of the Emeishan province in an equatorial humid belt may accelerate the atmospheric CO2 consumption and lead to climate cooling. Our work supports the long-term climate cooling effects of large igneous provinces.

Testing of an Integrated Reactor Core Simulator and Power Conversion System with Simulated Reactivity Feedback

NASA Technical Reports Server (NTRS)

Bragg-Sitton, Shannon M.; Hervol, David S.; Godfroy, Thomas J.

2009-01-01

A Direct Drive Gas-Cooled (DDG) reactor core simulator has been coupled to a Brayton Power Conversion Unit (BPCU) for integrated system testing at NASA Glenn Research Center (GRC) in Cleveland, OH. This is a closed-cycle system that incorporates an electrically heated reactor core module, turbo alternator, recuperator, and gas cooler. Nuclear fuel elements in the gas-cooled reactor design are replaced with electric resistance heaters to simulate the heat from nuclear fuel in the corresponding fast spectrum nuclear reactor. The thermodynamic transient behavior of the integrated system was the focus of this test series. In order to better mimic the integrated response of the nuclear-fueled system, a simulated reactivity feedback control loop was implemented. Core power was controlled by a point kinetics model in which the reactivity feedback was based on core temperature measurements; the neutron generation time and the temperature feedback coefficient are provided as model inputs. These dynamic system response tests demonstrate the overall capability of a non-nuclear test facility in assessing system integration issues and characterizing integrated system response times and response characteristics.

Testing of an Integrated Reactor Core Simulator and Power Conversion System with Simulated Reactivity Feedback

NASA Technical Reports Server (NTRS)

Bragg-Sitton, Shannon M.; Hervol, David S.; Godfroy, Thomas J.

2010-01-01

A Direct Drive Gas-Cooled (DDG) reactor core simulator has been coupled to a Brayton Power Conversion Unit (BPCU) for integrated system testing at NASA Glenn Research Center (GRC) in Cleveland, Ohio. This is a closed-cycle system that incorporates an electrically heated reactor core module, turboalternator, recuperator, and gas cooler. Nuclear fuel elements in the gas-cooled reactor design are replaced with electric resistance heaters to simulate the heat from nuclear fuel in the corresponding fast spectrum nuclear reactor. The thermodynamic transient behavior of the integrated system was the focus of this test series. In order to better mimic the integrated response of the nuclear-fueled system, a simulated reactivity feedback control loop was implemented. Core power was controlled by a point kinetics model in which the reactivity feedback was based on core temperature measurements; the neutron generation time and the temperature feedback coefficient are provided as model inputs. These dynamic system response tests demonstrate the overall capability of a non-nuclear test facility in assessing system integration issues and characterizing integrated system response times and response characteristics.

ACHILLES: Heat Transfer in PWR Core During LOCA Reflood Phase

DOE Office of Scientific and Technical Information (OSTI.GOV)

2013-11-01

1. NAME AND TITLE OF DATA LIBRARY ACHILLES -Heat Transfer in PWR Core During LOCA Reflood Phase. 2. NAME AND TITLE OF DATA RETRIEVAL PROGRAMS N/A 3. CONTRIBUTOR AEA Technology, Winfrith Technology Centre, Dorchester DT2 8DH United Kingdom through the OECD Nuclear Energy Agency Data Bank, Issy-les-Moulineaux, France. 4. DESCRIPTION OF TEST FACILITY The most important features of the Achilles rig were the shroud vessel, which contained the test section, and the downcomer. These may be thought of as representing the core barrel and the annular downcomer in the reactor pressure vessel. The test section comprises a cluster of 69more » rods in a square array within a circular shroud vessel. The rod diameter and pitch (9.5 mm and 12.6 mm) were typical of PWR dimensions. The internal diameter of the shroud vessel was 128 mm. Each rod was electrically heated over a length of 3.66 m, which is typical of the nuclear heated length in a PWR fuel rod, and each contained 6 internal thermocouples. These were arranged in one of 8 groupings which concentrated the thermocouples in different axial zones. The spacer grids were at prototypic PWR locations. Each grid had two thermocouples attached to its trailing edge at radial locations. The axial power profile along the rods was an 11 step approximation to a "chopped cosine". The shroud vessel had 5 heating zones whose power could be independently controlled. 5. DESCRIPTION OF TESTS The Achilles experiments investigated the heat transfer in the core of a Pressurized Water Reactor during the re-flood phase of a postulated large break loss of coolant accident. The results provided data to validate codes and to improve modeling. Different types of experiments were carried out which included single phase cooling, re-flood under low flow conditions, level swell and re-flood under high flow conditions. Three series of experiments were performed. The first and the third used the same test section but the second used another test section

Comparing Social Stories™ to Cool versus Not Cool

ERIC Educational Resources Information Center

Leaf, Justin B.; Mitchell, Erin; Townley-Cochran, Donna; McEachin, John; Taubman, Mitchell; Leaf, Ronald

2016-01-01

In this study we compared the cool versus not cool procedure to Social Stories™ for teaching various social behaviors to one individual diagnosed with autism spectrum disorder. The researchers randomly assigned three social skills to the cool versus not cool procedure and three social skills to the Social Stories™ procedure. Naturalistic probes…

Antarctic and Southern Ocean influences on Late Pliocene global cooling

USGS Publications Warehouse

McKay, Robert; Naish, Tim; Carter, Lionel; Riesselman, Christina; Dunbar, Robert; Sjunneskog, Charlotte; Winter, Diane; Sangiorgi, Francesca; Warren, Courtney; Pagani, Mark; Schouten, Stefan; Willmott, Veronica; Levy, Richard; DeConto, Robert; Powell, Ross D.

2012-01-01

The influence of Antarctica and the Southern Ocean on Late Pliocene global climate reconstructions has remained ambiguous due to a lack of well-dated Antarctic-proximal, paleoenvironmental records. Here we present ice sheet, sea-surface temperature, and sea ice reconstructions from the ANDRILL AND-1B sediment core recovered from beneath the Ross Ice Shelf. We provide evidence for a major expansion of an ice sheet in the Ross Sea that began at ~3.3 Ma, followed by a coastal sea surface temperature cooling of ~2.5 °C, a stepwise expansion of sea ice, and polynya-style deep mixing in the Ross Sea between 3.3 and 2.5 Ma. The intensification of Antarctic cooling resulted in strengthened westerly winds and invigorated ocean circulation. The associated northward migration of Southern Ocean fronts has been linked with reduced Atlantic Meridional Overturning Circulation by restricting surface water connectivity between the ocean basins, with implications for heat transport to the high latitudes of the North Atlantic. While our results do not exclude low-latitude mechanisms as drivers for Pliocene cooling, they indicate an additional role played by southern high-latitude cooling during development of the bipolar world.

Interim status report on lead-cooled fast reactor (LFR) research and development.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tzanos, C. P.; Sienicki, J. J.; Moisseytsev, A.

2008-03-31

This report discusses the status of Lead-Cooled Fast Reactor (LFR) research and development carried out during the first half of FY 2008 under the U.S. Department of Energy Generation IV Nuclear Energy Systems Initiative. Lead-Cooled Fast Reactor research and development has recently been transferred from Generation IV to the Reactor Campaign of the Global Nuclear Energy Partnership (GNEP). Another status report shall be issued at the end of FY 2008 covering all of the LFR activities carried out in FY 2008 for both Generation IV and GNEP. The focus of research and development in FY 2008 is an initial investigationmore » of a concept for a LFR Advanced Recycling Reactor (ARR) Technology Pilot Plant (TPP)/demonstration test reactor (demo) incorporating features and operating conditions of the European Lead-cooled SYstem (ELSY) {approx} 600 MWe lead (Pb)-cooled LFR preconceptual design for the transmutation of waste and central station power generation, and which would enable irradiation testing of advanced fuels and structural materials. Initial scoping core concept development analyses have been carried out for a 100 MWt core composed of sixteen open-lattice 20 by 20 fuel assemblies largely similar to those of the ELSY preconceptual fuel assembly design incorporating fuel pins with mixed oxide (MOX) fuel, central control rods in each fuel assembly, and cooled with Pb coolant. For a cycle length of three years, the core is calculated to have a conversion ratio of 0.79, an average discharge burnup of 108 MWd/kg of heavy metal, and a burnup reactivity swing of about 13 dollars. With a control rod in each fuel assembly, the reactivity worth of an individual rod would need to be significantly greater than one dollar which is undesirable for postulated rod withdrawal reactivity insertion events. A peak neutron fast flux of 2.0 x 10{sup 15} (n/cm{sup 2}-s) is calculated. For comparison, the 400 MWt Fast Flux Test Facility (FFTF) achieved a peak neutron fast flux of 7.2 x

Metallographic Cooling Rates of IAB Iron Meteorites

NASA Astrophysics Data System (ADS)

Meibom, A.; Haack, H.; Jensen, S. K.; Ulff-Moller, F.; Rasmussen, K. L.

1995-09-01

Non-metals can play an important role for the diffusion-controlled growth of the Widmanstatten structure in iron meteorites. The presence of P significantly changes the diffusivity and equilibrium concentration of Ni in kamacite and taenite [1,2], and the effects of P have therefore been included in metallographic cooling rate calculations for many years. The presence of C probably increases the diffusivity of Ni in taenite up to a factor of two, which is considerably smaller than the effect of P that increases the Ni diffusivity by up to a factor of 10 [3,1]. On the other hand, C partitions strongly into taenite leaving kamacite essentially C-free (<10 micrograms/g [4]) and significantly reduces the equilibrium Ni-concentration in taenite [5]. Therefore, the effect of C should be included in metallographic cooling rate calculations of C-rich iron meteorites [6]. IAB iron meteorites have much higher bulk C-concentrations than most other iron meteorites and the metallic phases of the IAB irons were probably saturated with C soon after kamacite nucleation commenced. Since C is expected to decrease the solubility of P in taenite [7] we have based our cooling rate estimate of Toluca (IAB) on the Fe-Ni-C system rather than the Fe-Ni-P system. Previous metallographic cooling rates determined for IAB irons, including the effect of P, are low (1-10 degrees C/My [8] and 30-70 degrees C/My [9]). Fractional crystallization of S-rich cores [10, 11] and impact generated melt pools [12] have been proposed as origins of the IAB iron meteorites. Since we expect melt pools near the surface to have cooled significantly faster than the core of a differentiated parent body, the metallographic cooling rates may be used to discriminate between the two models. We have performed thermodynamic calculations on the C-saturated Fe-Ni-C-system at temperatures above 400 degrees C [13]. The results agree with earlier experimental work [5] and indicate that C, to the same degree as P, reduces the

Induction simulation of gas core nuclear engine

NASA Technical Reports Server (NTRS)

Poole, J. W.; Vogel, C. E.

1973-01-01

The design, construction and operation of an induction heated plasma device known as a combined principles simulator is discussed. This device incorporates the major design features of the gas core nuclear rocket engine such as solid feed, propellant seeding, propellant injection through the walls, and a transpiration cooled, choked flow nozzle. Both argon and nitrogen were used as propellant simulating material, and sodium was used for fuel simulating material. In addition, a number of experiments were conducted utilizing depleted uranium as the fuel. The test program revealed that satisfactory operation of this device can be accomplished over a range of operating conditions and provided additional data to confirm the validity of the gas core concept.

An ancient core dynamo in asteroid Vesta.

PubMed

Fu, Roger R; Weiss, Benjamin P; Shuster, David L; Gattacceca, Jérôme; Grove, Timothy L; Suavet, Clément; Lima, Eduardo A; Li, Luyao; Kuan, Aaron T

2012-10-12

The asteroid Vesta is the smallest known planetary body that has experienced large-scale igneous differentiation. However, it has been previously uncertain whether Vesta and similarly sized planetesimals formed advecting metallic cores and dynamo magnetic fields. Here we show that remanent magnetization in the eucrite meteorite Allan Hills A81001 formed during cooling on Vesta 3.69 billion years ago in a surface magnetic field of at least 2 microteslas. This field most likely originated from crustal remanence produced by an earlier dynamo, suggesting that Vesta formed an advecting liquid metallic core. Furthermore, the inferred present-day crustal fields can account for the lack of solar wind ion-generated space weathering effects on Vesta.

Regulation of the X-ray luminosity of clusters of galaxies by cooling and supernova feedback.

PubMed

Voit, G M; Bryan, G L

2001-11-22

Clusters of galaxies are thought to contain about ten times as much dark matter as baryonic matter. The dark component therefore dominates the gravitational potential of a cluster, and the baryons confined by this potential radiate X-rays with a luminosity that depends mainly on the gas density in the cluster's core. Predictions of the X-rays' properties based on models of cluster formation do not, however, agree with the observations. If the models ignore the condensation of cooling gas into stars and feedback from the associated supernovae, they overestimate the X-ray luminosity because the density of the core gas is too high. An early episode of uniformly distributed supernova feedback could rectify this by heating the uncondensed gas and therefore making it harder to compress into the core, but such a process seems to require an implausibly large number of supernovae. Here we show how radiative cooling of intergalactic gas and subsequent supernova heating conspire to eliminate highly compressible low-entropy gas from the intracluster medium. This brings the core entropy and X-ray luminosities of clusters into agreement with the observations, in a way that depends little on the efficiency of supernova heating in the early Universe.

Film cooling for a closed loop cooled airfoil

DOEpatents

Burdgick, Steven Sebastian; Yu, Yufeng Phillip; Itzel, Gary Michael

2003-01-01

Turbine stator vane segments have radially inner and outer walls with vanes extending therebetween. The inner and outer walls are compartmentalized and have impingement plates. Steam flowing into the outer wall plenum passes through the impingement plate for impingement cooling of the outer wall upper surface. The spent impingement steam flows into cavities of the vane having inserts for impingement cooling the walls of the vane. The steam passes into the inner wall and through the impingement plate for impingement cooling of the inner wall surface and for return through return cavities having inserts for impingement cooling of the vane surfaces. At least one film cooling hole is defined through a wall of at least one of the cavities for flow communication between an interior of the cavity and an exterior of the vane. The film cooling hole(s) are defined adjacent a potential low LCF life region, so that cooling medium that bleeds out through the film cooling hole(s) reduces a thermal gradient in a vicinity thereof, thereby the increase the LCF life of that region.

Melting and solidification behavior of Cu/Al and Ti/Al bimetallic core/shell nanoparticles during additive manufacturing by molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Rahmani, Farzin; Jeon, Jungmin; Jiang, Shan; Nouranian, Sasan

2018-05-01

Molecular dynamics (MD) simulations were performed to investigate the role of core volume fraction and number of fusing nanoparticles (NPs) on the melting and solidification of Cu/Al and Ti/Al bimetallic core/shell NPs during a superfast heating and slow cooling process, roughly mimicking the conditions of selective laser melting (SLM). One recent trend in the SLM process is the rapid prototyping of nanoscopically heterogeneous alloys, wherein the precious core metal maintains its particulate nature in the final manufactured part. With this potential application in focus, the current work reveals the fundamental role of the interface in the two-stage melting of the core/shell alloy NPs. For a two-NP system, the melting zone gets broader as the core volume fraction increases. This effect is more pronounced for the Ti/Al system than the Cu/Al system because of a larger difference between the melting temperatures of the shell and core metals in the former than the latter. In a larger six-NP system (more nanoscopically heterogeneous), the melting and solidification temperatures of the shell Al roughly coincide, irrespective of the heating or cooling rate, implying that in the SLM process, the part manufacturing time can be reduced due to solidification taking place at higher temperatures. The nanostructure evolution during the cooling of six-NP systems is further investigated. [Figure not available: see fulltext.

Infrared spectrum of an extremely cool white-dwarf star

PubMed

Hodgkin; Oppenheimer; Hambly; Jameson; Smartt; Steele

2000-01-06

White dwarfs are the remnant cores of stars that initially had masses of less than 8 solar masses. They cool gradually over billions of years, and have been suggested to make up much of the 'dark matter' in the halo of the Milky Way. But extremely cool white dwarfs have proved difficult to detect, owing to both their faintness and their anticipated similarity in colour to other classes of dwarf stars. Recent improved models indicate that white dwarfs are much more blue than previously supposed, suggesting that the earlier searches may have been looking for the wrong kinds of objects. Here we report an infrared spectrum of an extremely cool white dwarf that is consistent with the new models. We determine the star's temperature to be 3,500 +/- 200 K, making it the coolest known white dwarf. The kinematics of this star indicate that it is in the halo of the Milky Way, and the density of such objects implied by the serendipitous discovery of this star is consistent with white dwarfs dominating the dark matter in the halo.

How to get cool in the heat: comparing analytic models of hot, cold, and cooling gas in haloes and galaxies with EAGLE

NASA Astrophysics Data System (ADS)

Stevens, Adam R. H.; Lagos, Claudia del P.; Contreras, Sergio; Croton, Darren J.; Padilla, Nelson D.; Schaller, Matthieu; Schaye, Joop; Theuns, Tom

2017-05-01

We use the hydrodynamic, cosmological EAGLE simulations to investigate how the hot gas in haloes condenses to form and grow galaxies. We select haloes from the simulations that are actively cooling and study the temperature, distribution and metallicity of their hot, cold and transitioning 'cooling' gas, placing these in the context of semi-analytic models. Our selection criteria lead us to focus on Milky Way-like haloes. We find that the hot-gas density profiles of the haloes form a progressively stronger core over time, the nature of which can be captured by a β profile that has a simple dependence on redshift. In contrast, the hot gas that will cool over a time-step is broadly consistent with a singular isothermal sphere. We find that cooling gas carries a few times the specific angular momentum of the halo and is offset in spin direction from the rest of the hot gas. The gas loses ˜60 per cent of its specific angular momentum during the cooling process, generally remaining greater than that of the halo, and it precesses to become aligned with the cold gas already in the disc. We find tentative evidence that angular-momentum losses are slightly larger when gas cools on to dispersion-supported galaxies. We show that an exponential surface density profile for gas arriving on a disc remains a reasonable approximation, but a cusp containing ˜20 per cent of the mass is always present, and disc scale radii are larger than predicted by a vanilla Fall & Efstathiou model. These scale radii are still closely correlated with the halo spin parameter, for which we suggest an updated prescription for galaxy formation models.

Feasibility Study of Venus Surfuce Cooling Using Chemical Reactions with the Atmosphere

NASA Technical Reports Server (NTRS)

Evans, Christopher

2013-01-01

A literature search and theoretical analysis were conducted to investigate the feasibility of cooling a craft on Venus through chemical reformation of materials from the atmosphere. The core concept was to take carbon dioxide (CO2) from the Venus atmosphere and chemically reform it into simpler compounds such as carbon, oxygen, and carbon monoxide. This process is endothermic, taking energy from the surroundings to produce a cooling effect. A literature search was performed to document possible routes for achieving the desired reactions. Analyses indicated that on Venus, this concept could theoretically be used to produce cooling, but would not perform as well as a conventional heat pump. For environments other than Venus, the low theoretical performance limits general applicability of this concept, however this approach to cooling may be useful in niche applications. Analysis indicated that environments with particular atmospheric compositions and temperatures could allow a similar cooling system to operate with very good performance. This approach to cooling may also be useful where the products of reaction are also desirable, or for missions where design simplicity is valued. Conceptual designs for Venus cooling systems were developed using a modified concept, in which an expendable reactant supply would be used to promote more energetically favorable reactions with the ambient CO2, providing cooling for a more limited duration. This approach does not have the same performance issues, but the use of expendable supplies increases the mass requirements and limits the operating lifetime. This paper summarizes the findings of the literature search and corresponding analyses of the various cooling options

Feasibility Study of Venus Surface Cooling Using Chemical Reactions with the Atmosphere

NASA Technical Reports Server (NTRS)

Evans, Christopher

2013-01-01

A literature search and theoretical analysis were conducted to investigate the feasibility of cooling a craft on Venus through chemical reformation of materials from the atmosphere. The core concept was to take carbon dioxide (CO2) from the Venus atmosphere and chemically reform it into simpler compounds such as carbon, oxygen, and carbon monoxide. This process is endothermic, taking energy from the surroundings to produce a cooling effect. A literature search was performed to document possible routes for achieving the desired reactions. Analyses indicated that on Venus, this concept could theoretically be used to produce cooling, but would not perform as well as a conventional heat pump. For environments other than Venus, the low theoretical performance limits general applicability of this concept, however this approach to cooling may be useful in niche applications. Analysis indicated that environments with particular atmospheric compositions and temperatures could allow a similar cooling system to operate with very good performance. This approach to cooling may also be useful where the products of reaction are also desirable, or for missions where design simplicity is valued. Conceptual designs for Venus cooling systems were developed using a modified concept, in which an expendable reactant supply would be used to promote more energetically favorable reactions with the ambient CO2, providing cooling for a more limited duration. This approach does not have the same performance issues, but the use of expendable supplies increases the mass requirements and limits the operating lifetime. This paper summarizes the findings of the literature search and corresponding analyses of the various cooling options.

Pebble Fuel Handling and Reactivity Control for Salt-Cooled High Temperature Reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peterson, Per; Greenspan, Ehud

2015-02-09

This report documents the work completed on the X-PREX facility under NEUP Project 11- 3172. This project seeks to demonstrate the viability of pebble fuel handling and reactivity control for fluoride salt-cooled high-temperature reactors (FHRs). The research results also improve the understanding of pebble motion in helium-cooled reactors, as well as the general, fundamental understanding of low-velocity granular flows. Successful use of pebble fuels in with salt coolants would bring major benefits for high-temperature reactor technology. Pebble fuels enable on-line refueling and operation with low excess reactivity, and thus simpler reactivity control and improved fuel utilization. If fixed fuel designsmore » are used, the power density of salt- cooled reactors is limited to 10 MW/m 3 to obtain adequate duration between refueling, but pebble fuels allow power densities in the range of 20 to 30 MW/m 3. This can be compared to the typical modular helium reactor power density of 5 MW/m3. Pebble fuels also permit radial zoning in annular cores and use of thorium or graphite pebble blankets to reduce neutron fluences to outer radial reflectors and increase total power production. Combined with high power conversion efficiency, compact low-pressure primary and containment systems, and unique safety characteristics including very large thermal margins (>500°C) to fuel damage during transients and accidents, salt-cooled pebble fuel cores offer the potential to meet the major goals of the Advanced Reactor Concepts Development program to provide electricity at lower cost than light water reactors with improved safety and system performance.This report presents the facility description, experimental results, and supporting simulation methods of the new X-Ray Pebble Recirculation Experiment (X-PREX), which is now operational and being used to collect data on the behavior of slow dense granular flows relevant to pebble bed reactor core designs. The X-PREX facility uses

Cooling circuit for steam and air-cooled turbine nozzle stage

DOEpatents

Itzel, Gary Michael; Yu, Yufeng

2002-01-01

The turbine vane segment includes inner and outer walls with a vane extending therebetween. The vane includes leading and trailing edge cavities and intermediate cavities. An impingement plate is spaced from the outer wall to impingement-cool the outer wall. Post-impingement cooling air flows through holes in the outer wall to form a thin air-cooling film along the outer wall. Cooling air is supplied an insert sleeve with openings in the leading edge cavity for impingement-cooling the leading edge. Holes through the leading edge afford thin-film cooling about the leading edge. Cooling air is provided the trailing edge cavity and passes through holes in the side walls of the vane for thin-film cooling of the trailing edge. Steam flows through a pair of intermediate cavities for impingement-cooling of the side walls. Post-impingement steam flows to the inner wall for impingement-cooling of the inner wall and returns the post-impingement cooling steam through inserts in other intermediate cavities for impingement-cooling the side walls of the vane.

Structural and Magnetic Response in Bimetallic Core/Shell Magnetic Nanoparticles

PubMed Central

Nairan, Adeela; Khan, Usman; Iqbal, Munawar; Khan, Maaz; Javed, Khalid; Riaz, Saira; Naseem, Shahzad; Han, Xiufeng

2016-01-01

Bimagnetic monodisperse CoFe2O4/Fe3O4 core/shell nanoparticles have been prepared by solution evaporation route. To demonstrate preferential coating of iron oxide onto the surface of ferrite nanoparticles X-ray diffraction (XRD), High resolution transmission electron microscope (HR-TEM) and Raman spectroscopy have been performed. XRD analysis using Rietveld refinement technique confirms single phase nanoparticles with average seed size of about 18 nm and thickness of shell is 3 nm, which corroborates with transmission electron microscopy (TEM) analysis. Low temperature magnetic hysteresis loops showed interesting behavior. We have observed large coercivity 15.8 kOe at T = 5 K, whereas maximum saturation magnetization (125 emu/g) is attained at T = 100 K for CoFe2O4/Fe3O4 core/shell nanoparticles. Saturation magnetization decreases due to structural distortions at the surface of shell below 100 K. Zero field cooled (ZFC) and Field cooled (FC) plots show that synthesized nanoparticles are ferromagnetic till room temperature and it has been noticed that core/shell sample possess high blocking temperature than Cobalt Ferrite. Results indicate that presence of iron oxide shell significantly increases magnetic parameters as compared to the simple cobalt ferrite. PMID:28335200

Effect of a Cooling Step Treatment on a High-Voltage GaN LED During ICP Dry Etching

NASA Astrophysics Data System (ADS)

Lin, Yen-Sheng; Hsiao, Sheng-Yu; Tseng, Chun-Lung; Shen, Ching-Hsing; Chiang, Jung-Sheng

2017-02-01

In this study, a lower dislocation density for a GaN surface and a reduced current path are observed at the interface of a SiO2 isolation sidewall, using high-resolution transmission electron microscopy. This is grown using a 3-min cooling step treatment during inductivity coupled plasma dry etching. The lower forward voltage is measured, the leakage current decreases from 53nA to 32nA, and the maximum output power increases from 354.8 W to 357.2 W for an input current of 30 mA. The microstructure and the optoelectronic properties of high-voltage light-emitting-diodes is proven to be affected by the cooling step treatment, which allows enough time to release the thermal energy of the SiO2 isolation well.

Multifrequency VLA observations of PKS 0745 - 191 - The archetypal 'cooling flow' radio source?

NASA Technical Reports Server (NTRS)

Baum, S. A.; O'Dea, C. P.

1991-01-01

Ninety-, 20-, 6- and 2-cm VLA observations of the high-radio-luminosity cooling-flow radio source PKS 0745 - 191 are presented. The radio source was found to have a core with a very steep spectrum (alpha is approximately -1.5) and diffuse emission with an even steeper spectrum (alpha is approximately -1.5 to -2.3) without clear indications of the jets, hotspots, or double lobes found in the other radio sources of comparable luminosity. It is inferred that the energy to power the radio source comes from the central engine, but the source's structure may be heavily influenced by the past history of the galaxy and the inflowing intracluster medium. It is shown that, while the radio source is energetically unimportant for the cluster as a whole, it is important on the scale of the cooling flow. The mere existence of cosmic rays and magnetic fields within a substantial fraction of the volume inside the cooling radius has important consequences for cooling-flow models.

Combination pipe-rupture mitigator and in-vessel core catcher. [LMFBR

DOEpatents

Tilbrook, R.W.; Markowski, F.J.

1982-03-09

A device is described which mitigates against the effects of a failed coolant loop in a nuclear reactor by restricting the outflow of coolant from the reactor through the failed loop and by retaining any particulated debris from a molten core which may result from coolant loss or other cause. The device reduces the reverse pressure drop through the failed loop by limiting the access of coolant in the reactor to the inlet of the failed loop. The device also spreads any particulated core debris over a large area to promote cooling.

Emergency cooling system and method

DOEpatents

Oosterkamp, W.J.; Cheung, Y.K.

1994-01-04

An improved emergency cooling system and method are disclosed that may be adapted for incorporation into or use with a nuclear BWR wherein a reactor pressure vessel (RPV) containing a nuclear core and a heat transfer fluid for circulation in a heat transfer relationship with the core is housed within an annular sealed drywell and is fluid communicable therewith for passage thereto in an emergency situation the heat transfer fluid in a gaseous phase and any noncondensibles present in the RPV, an annular sealed wetwell houses the drywell, and a pressure suppression pool of liquid is disposed in the wetwell and is connected to the drywell by submerged vents. The improved emergency cooling system and method has a containment condenser for receiving condensible heat transfer fluid in a gaseous phase and noncondensibles for condensing at least a portion of the heat transfer fluid. The containment condenser has an inlet in fluid communication with the drywell for receiving heat transfer fluid and noncondensibles, a first outlet in fluid communication with the RPV for the return to the RPV of the condensed portion of the heat transfer fluid and a second outlet in fluid communication with the drywell for passage of the noncondensed balance of the heat transfer fluid and the noncondensibles. The noncondensed balance of the heat transfer fluid and the noncondensibles passed to the drywell from the containment condenser are mixed with the heat transfer fluid and the noncondensibles from the RPV for passage into the containment condenser. A water pool is provided in heat transfer relationship with the containment condenser and is thermally communicable in an emergency situation with an environment outside of the drywell and the wetwell for conducting heat transferred from the containment condenser away from the wetwell and the drywell. 5 figs.

Convective cooling in a pool-type research reactor

NASA Astrophysics Data System (ADS)

Sipaun, Susan; Usman, Shoaib

2016-01-01

A reactor produces heat arising from fission reactions in the nuclear core. In the Missouri University of Science and Technology research reactor (MSTR), this heat is removed by natural convection where the coolant/moderator is demineralised water. Heat energy is transferred from the core into the coolant, and the heated water eventually evaporates from the open pool surface. A secondary cooling system was installed to actively remove excess heat arising from prolonged reactor operations. The nuclear core consists of uranium silicide aluminium dispersion fuel (U3Si2Al) in the form of rectangular plates. Gaps between the plates allow coolant to pass through and carry away heat. A study was carried out to map out heat flow as well as to predict the system's performance via STAR-CCM+ simulation. The core was approximated as porous media with porosity of 0.7027. The reactor is rated 200kW and total heat density is approximately 1.07+E7 Wm-3. An MSTR model consisting of 20% of MSTR's nuclear core in a third of the reactor pool was developed. At 35% pump capacity, the simulation results for the MSTR model showed that water is drawn out of the pool at a rate 1.28 kg s-1 from the 4" pipe, and predicted pool surface temperature not exceeding 30°C.

Antarctic Glaciation during the Tertiary Recorded in Sub-Antarctic Deep-Sea Cores.

PubMed

Margolis, S V; Kennett, J P

1970-12-04

Study of 18 Cenozoic South Pacific deep-sea cores indicates an association of glacially derived ice-rafted sands and relatively low planktonic foraminiferal diversity with cooling of the Southern Ocean during the Lower Eocene, upper Middle Eocene, and Oligocene. Increased species diversity and reduction or absence of ice-rafted sands in Lower and Middle Miocene cores indicate a warming trend that ended in the Upper Miocene. Antarctic continental glaciation appears to have prevailed throughout much of the Cenozoic.

Material Issues of Blanket Systems for Fusion Reactors - Compatibility with Cooling Water -

NASA Astrophysics Data System (ADS)

Miwa, Yukio; Tsukada, Takashi; Jitsukawa, Shiro

Environmental assisted cracking (EAC) is one of the material issues for the reactor core components of light water power reactors(LWRs). Much experience and knowledge have been obtained about the EAC in the LWR field. They will be useful to prevent the EAC of water-cooled blanket systems of fusion reactors. For the austenitic stainless steels and the reduced-activation ferritic/martensitic steels, they clarifies that the EAC in a water-cooled blanket does not seem to be acritical issue. However, some uncertainties about influences on water temperatures, water chemistries and stress conditions may affect on the EAC. Considerations and further investigations elucidating the uncertainties are discussed.

Thermoregulatory influence of a cooling vest on hyperthermic athletes.

PubMed

Lopez, Rebecca M; Cleary, Michelle A; Jones, Leon C; Zuri, Ron E

2008-01-01

Athletic trainers must have sound evidence for the best practices in treating and preventing heat-related emergencies and potentially catastrophic events. To examine the effectiveness of a superficial cooling vest on core body temperature (T(c)) and skin temperature (T(sk)) in hypohydrated hyperthermic male participants. A randomized control design with 2 experimental groups. Participants exercised by completing the heat-stress trial in a hot, humid environment (ambient temperature = 33.1 +/- 3.1 degrees C, relative humidity = 55.1 +/- 8.9%, wind speed = 2.1 +/- 1.1 km/hr) until a T(c) of 38.7 +/- 0.3 degrees C and a body mass loss of 3.27 +/- 0.1% were achieved. Ten healthy males (age = 25.6 +/- 1.6 years, mass = 80.3 +/- 13.7 kg). Recovery in a thermoneutral environment wearing a cooling vest or without wearing a cooling vest until T(c) returned to baseline. Rectal T(c), arm T(sk), time to return to baseline T(c), and cooling rate. During the heat-stress trial, T(c) significantly increased (3.6%) and, at 30 minutes of recovery, T(c) had decreased significantly (2.6%) for both groups. Although not significant, the time for return to baseline T(c) was 22.6% faster for the vest group (43.8 +/- 15.1 minutes) than for the no-vest group (56.6 +/- 18.0 minutes), and the cooling rate for the vest group (0.0298 +/- 0.0072 degrees C/min) was not significantly different from the cooling rate for the no-vest group (0.0280 +/- 0.0074 degrees C/min). The T(sk) during recovery was significantly higher (2.1%) in the vest group than in the no-vest group and was significantly lower (7.1%) at 30 minutes than at 0 minutes for both groups. We do not recommend using the cooling vest to rapidly reduce elevated T(c). Ice-water immersion should remain the standard of care for rapidly cooling severely hyperthermic individuals.

Plasmon enhanced upconversion luminescence of NaYF4:Yb,Er@SiO2@Ag core-shell nanocomposites for cell imaging

NASA Astrophysics Data System (ADS)

Yuan, Peiyan; Lee, Yih Hong; Gnanasammandhan, Muthu Kumara; Guan, Zhenping; Zhang, Yong; Xu, Qing-Hua

2012-07-01

NaYF4:Yb,Er@SiO2@Ag core-shell nanocomposites were prepared to investigate metal-enhanced upconversion luminescence. Two sizes (15 and 30 nm) of Ag nanoparticles were used. The emission intensity of the upconversion nanocrystals was found to be strongly modulated by the presence of Ag nanoparticles (NPs) on the outer shell layer of the nanocomposites. The extent of modulation depended on the separation distance between Ag NPs and upconversion nanocrystals. The optimum upconversion luminescence enhancement was observed at a separation distance of 10 nm for Ag NPs with two different sizes (15 and 30 nm). A maximum upconversion luminescence enhancement of 14.4-fold was observed when 15 nm Ag nanoparticles were used and 10.8-fold was observed when 30 nm Ag NPs were used. The separation distance dependent emission intensity is ascribed to the competition between energy transfer and enhanced radiative decay rates. The biocompatibility of the nanocomposites was significantly improved by surface modification with DNA. The biological imaging capabilities of these nanocomposites were demonstrated using B16F0 cells.NaYF4:Yb,Er@SiO2@Ag core-shell nanocomposites were prepared to investigate metal-enhanced upconversion luminescence. Two sizes (15 and 30 nm) of Ag nanoparticles were used. The emission intensity of the upconversion nanocrystals was found to be strongly modulated by the presence of Ag nanoparticles (NPs) on the outer shell layer of the nanocomposites. The extent of modulation depended on the separation distance between Ag NPs and upconversion nanocrystals. The optimum upconversion luminescence enhancement was observed at a separation distance of 10 nm for Ag NPs with two different sizes (15 and 30 nm). A maximum upconversion luminescence enhancement of 14.4-fold was observed when 15 nm Ag nanoparticles were used and 10.8-fold was observed when 30 nm Ag NPs were used. The separation distance dependent emission intensity is ascribed to the competition between energy

Modified rod-in-tube for high-NA tellurite glass fiber fabrication: materials and technologies.

PubMed

Chen, Qiuling; Wang, Hui; Wang, Qingwei; Chen, Qiuping; Hao, Yinlei

2015-02-01

In this paper, we report the whole fabrication process for high-numerical aperture (NA) tellurite glass fibers from material preparation to preform fabrication, and eventually, fiber drawing. A tellurite-based high-NA (0.9) magneto-optical glass fiber was drawn successfully and characterized. First, matchable core and cladding glasses were fabricated and matched in terms of physical properties. Second, a uniform bubble-free preform was fabricated by means of a modified rod-in-tube technique. Finally, the fiber drawing process was studied and optimized. The high-NA fibers (∅(core), 40-50 μm and ∅(cladding), 120-130 μm) so obtained were characterized for their geometrical and optical properties.

Evaporation Loss of Light Elements as a Function of Cooling Rate: Logarithmic Law

NASA Technical Reports Server (NTRS)

Xiong, Yong-Liang; Hewins, Roger H.

2003-01-01

Knowledge about the evaporation loss of light elements is important to our understanding of chondrule formation processes. The evaporative loss of light elements (such as B and Li) as a function of cooling rate is of special interest because recent investigations of the distribution of Li, Be and B in meteoritic chondrules have revealed that Li varies by 25 times, and B and Be varies by about 10 times. Therefore, if we can extrapolate and interpolate with confidence the evaporation loss of B and Li (and other light elements such as K, Na) at a wide range of cooling rates of interest based upon limited experimental data, we would be able to assess the full range of scenarios relating to chondrule formation processes. Here, we propose that evaporation loss of light elements as a function of cooling rate should obey the logarithmic law.

The end of the iron-core age.

NASA Technical Reports Server (NTRS)

Lyttleton, R. A.

1973-01-01

The terrestrial planets aggregated essentially from small particles, to begin as solid cool bodies with the same general compositions, and there is no possibility of an iron-core developing within any of them at any stage. Their differing internal and surface properties receive ready explanation from their different masses which determine whether the pressures within are sufficient to bring about phase-changes. The claim that the terrestrial core can be identified by means of shock-wave data as nickel-iron is based on theoretical misconception, whereas the actual seismic data establish an uncompressed-density value much lower than any such mixture could have. The onset of the Ramsey phase-change in the earth takes the form of a rapid initial collapse to produce a large core in metallic state which thereafter continues to grow secularly as a result of radioactive heating and leads to reduction of surface-area at long last adequate to account for folded and thrusted mountain-building.

A Technology Demonstration Experiment for Laser Cooled Atomic Clocks in Space

NASA Technical Reports Server (NTRS)

Klipstein, W. M.; Kohel, J.; Seidel, D. J.; Thompson, R. J.; Maleki, L.; Gibble, K.

2000-01-01

We have been developing a laser-cooling apparatus for flight on the International Space Station (ISS), with the intention of demonstrating linewidths on the cesium clock transition narrower than can be realized on the ground. GLACE (the Glovebox Laser- cooled Atomic Clock Experiment) is scheduled for launch on Utilization Flight 3 (UF3) in 2002, and will be mounted in one of the ISS Glovebox platforms for an anticipated 2-3 week run. Separate flight definition projects funded at NIST and Yale by the Micro- gravity Research Division of NASA as a part of its Laser Cooling and Atomic Physics (LCAP) program will follow GLACE. Core technologies for these and other LCAP missions are being developed at JPL, with the current emphasis on developing components such as the laser and optics subsystem, and non-magnetic vacuum-compatible mechanical shutters. Significant technical challenges in developing a space qualifiable laser cooling apparatus include reducing the volume, mass, and power requirements, while increasing the ruggedness and reliability in order to both withstand typical launch conditions and achieve several months of unattended operation. This work was performed at the Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration.

Seismic Wave Velocity in Earth's Shallow Core

NASA Astrophysics Data System (ADS)

Alexandrakis, C.; Eaton, D. W.

2008-12-01

Studies of the outer core indicate that it is composed of liquid Fe and Ni alloyed with a ~10% fraction of light elements such as O, S or Si. Recently, unusual features, such as sediment accumulation, immiscible fluid layers or stagnant convection, have been predicted in the shallow core region. Secular cooling and compositional buoyancy drive vigorous convection that sustains the geodynamo, although critical details of light-element composition and thermal regime remain uncertain. Seismic velocity models can provide important constraints on the light element composition, however global reference models, such as Preliminary Reference Earth Model (PREM), IASP91 and AK135 vary significantly in the 200 km below the core-mantle boundary. Past studies of the outermost core velocity structure have been hampered by traveltime uncertainties due to lowermost mantle heterogeneities. The recently published Empirical Transfer Function (ETF) method has been shown to reduce the uncertainty using a waveform stacking approach to improve global observations of SmKS teleseismic waves. Here, we apply the ETF method to achieve a precise top-of-core velocity measurement of 8.05 ± 0.03 km/s. This new model accords well with PREM. Since PREM is based on the adiabatic form of the Adams-Williamson equation, it assumes a well mixed (i.e. homogeneous) composition. This result suggests a lack of heterogeneity in the outermost core due to layering or stagnant convection.

Prognostic significance of the lymphocyte-to-monocyte ratio in patients with metastatic colorectal cancer.

PubMed

Shibutani, Masatsune; Maeda, Kiyoshi; Nagahara, Hisashi; Ohtani, Hiroshi; Sakurai, Katsunobu; Yamazoe, Sadaaki; Kimura, Kenjiro; Toyokawa, Takahiro; Amano, Ryosuke; Tanaka, Hiroaki; Muguruma, Kazuya; Hirakawa, Kosei

2015-09-14

To evaluate the prognostic significance of the lymphocyte to monocyte ratio (LMR) in patients with unresectable metastatic colorectal cancer who received palliative chemotherapy. A total of 104 patients with unresectable metastatic colorectal cancer who underwent palliative chemotherapy were enrolled. The LMR was calculated from blood samples by dividing the absolute lymphocyte count by the absolute monocyte count. Pre-treatment LMR values were measured within one week before the initiation of chemotherapy, while post-treatment LMR values were measured eight weeks after the initiation of chemotherapy. The median pre-treatment LMR was 4.16 (range: 0.58-14.06). We set 3.38 as the cut-off level based on the receiver operating characteristic curve. Based on the cut-off level of 3.38, 66 patients were classified into the high pre-treatment LMR group and 38 patients were classified into the low pre-treatment LMR group. The low pre-treatment LMR group had a significantly worse overall survival rate (P = 0.0011). Moreover, patients who demonstrated low pre-treatment LMR and normalization after treatment exhibited a better overall survival rate than the patients with low pre-treatment and post-treatment LMR values. The lymphocyte to monocyte ratio is a useful prognostic marker in patients with unresectable metastatic colorectal cancer who receive palliative chemotherapy.

Earth's inner core nucleation paradox

NASA Astrophysics Data System (ADS)

Huguet, Ludovic; Van Orman, James A.; Hauck, Steven A.; Willard, Matthew A.

2018-04-01

The conventional view of Earth's inner core is that it began to crystallize at Earth's center when the temperature dropped below the melting point of the iron alloy and has grown steadily since that time as the core continued to cool. However, this model neglects the energy barrier to the formation of the first stable crystal nucleus, which is commonly represented in terms of the critical supercooling required to overcome the barrier. Using constraints from experiments, simulations, and theory, we show that spontaneous crystallization in a homogeneous liquid iron alloy at Earth's core pressures requires a critical supercooling of order 1000 K, which is too large to be a plausible mechanism for the origin of Earth's inner core. We consider mechanisms that can lower the nucleation barrier substantially. Each has caveats, yet the inner core exists: this is the nucleation paradox. Heterogeneous nucleation on a solid metallic substrate tends to have a low energy barrier and offers the most straightforward solution to the paradox, but solid metal would probably have to be delivered from the mantle and such events are unlikely to have been common. A delay in nucleation, whether due to a substantial nucleation energy barrier, or late introduction of a low energy substrate, would lead to an initial phase of rapid inner core growth from a supercooled state. Such rapid growth may lead to distinctive crystallization texturing that might be observable seismically. It would also generate a spike in chemical and thermal buoyancy that could affect the geomagnetic field significantly. Solid metal introduced to Earth's center before it reached saturation could also provide a nucleation substrate, if large enough to escape complete dissolution. Inner core growth, in this case, could begin earlier and start more slowly than standard thermal models predict.

Core/coil assembly for use in superconducting magnets and method for assembling the same

DOEpatents

Kassner, David A.

1979-01-01

A core/coil assembly for use in a superconducting magnet of the focusing or bending type used in syncronous particle accelerators comprising a coil assembly contained within an axial bore of the stacked, washer type, carbon steel laminations which comprise the magnet core assembly, and forming an interference fit with said laminations at the operating temperature of said magnet. Also a method for making such core/coil assemblies comprising the steps of cooling the coil assembly to cryogenic temperatures and drawing it rapidly upwards into the bore of said stacked laminations.

Antarctic and Southern Ocean influences on Late Pliocene global cooling

PubMed Central

McKay, Robert; Naish, Tim; Carter, Lionel; Riesselman, Christina; Dunbar, Robert; Sjunneskog, Charlotte; Winter, Diane; Sangiorgi, Francesca; Warren, Courtney; Pagani, Mark; Schouten, Stefan; Willmott, Veronica; Levy, Richard; DeConto, Robert; Powell, Ross D.

2012-01-01

The influence of Antarctica and the Southern Ocean on Late Pliocene global climate reconstructions has remained ambiguous due to a lack of well-dated Antarctic-proximal, paleoenvironmental records. Here we present ice sheet, sea-surface temperature, and sea ice reconstructions from the ANDRILL AND-1B sediment core recovered from beneath the Ross Ice Shelf. We provide evidence for a major expansion of an ice sheet in the Ross Sea that began at ∼3.3 Ma, followed by a coastal sea surface temperature cooling of ∼2.5 °C, a stepwise expansion of sea ice, and polynya-style deep mixing in the Ross Sea between 3.3 and 2.5 Ma. The intensification of Antarctic cooling resulted in strengthened westerly winds and invigorated ocean circulation. The associated northward migration of Southern Ocean fronts has been linked with reduced Atlantic Meridional Overturning Circulation by restricting surface water connectivity between the ocean basins, with implications for heat transport to the high latitudes of the North Atlantic. While our results do not exclude low-latitude mechanisms as drivers for Pliocene cooling, they indicate an additional role played by southern high-latitude cooling during development of the bipolar world. PMID:22496594

Li- and Mn-Rich Cathode Materials: Challenges to Commercialization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Jianming; Myeong, Seungjun; Cho, Woongrae

2016-12-14

The lithium- and manganese-rich (LMR) layered structure cathode exhibit one of the highest specific energy (~900 Wh kg-1) among all the cathode materials. However, the practical applications of LMR cathodes are still hindered by several significant challenges including voltage fade, large initial capacity loss, poor rate capability and limited cycle life. Herein, we review the recent progresses and understandings on the application of LMR cathode materials from practical point of view. Several key parameters of LMR cathodes that affect the LMR/graphite full cell operation are systematically analysed. These factors include the first cycle capacity loss, voltage fade, powder tap density,more » electrode density of LMR based cathode etc. New approaches to minimize the detrimental effect of these factors are highlighted in this work. We also provided the perspectives for the future research on LMR cathode materials, focusing on addressing the fundamental problems of LMR cathodes while always keeping practical considerations in mind.« less

Positron cooling of antiprotons: precursor of recombination

NASA Astrophysics Data System (ADS)

Tan, J. N.; Estrada, J.; Yesley, P.; Bowden, N.; Oxley, P.; Storry, C.; Wessels, M.; Tan, J.; Gabrielse, G.; Oelert, W.; Scheppers, G.; Gronzonka, D.; Sefsick, T.; Fermann, H.; Zmeskal, H.; Breunlich, W.; Kalinowsky, H.; Wesdorp, C.

2001-05-01

The quest for cold antihydrogen, interrupted with the shut-down of LEAR, resumed with the operation of the newest antiproton decelerator (AD) at CERN.[See G.Gabrielse,Adv. in AMO Physics,vol.45,pp.1-38(2001).] Antiprotons injected into the AD with 2.75 GeV of kinetic energy slow to 5.31 MeV before extraction into the ATRAP apparatus, built for antihydrogen recombination experiments. Antiprotons extracted from the AD and positrons emitted from a 112 mCi ^22Na source are simultaneously accumulated in the ultra-high vacuum and 6 T field of a prototype Penning trap incorporating a miniature rotatable electrode. Preloaded electrons are used to thermalize ~ 10^5 antiprotons with the LHe-cooled trap (4.2K). Over 10^6 positrons/hr can be loaded with a new mechanism involving Rydberg positronium. After accumulation, the positrons are moved through the rotatable electrode into close proximity with the antiprotons to study their interactions. We report the first observation of positron cooling of antiprotons in a nested trap configuration suited for three-body recombination and other mechanisms.

Iron snow in the Martian core?

NASA Astrophysics Data System (ADS)

Davies, Christopher J.; Pommier, Anne

2018-01-01

The decline of Mars' global magnetic field some 3.8-4.1 billion years ago is thought to reflect the demise of the dynamo that operated in its liquid core. The dynamo was probably powered by planetary cooling and so its termination is intimately tied to the thermochemical evolution and present-day physical state of the Martian core. Bottom-up growth of a solid inner core, the crystallization regime for Earth's core, has been found to produce a long-lived dynamo leading to the suggestion that the Martian core remains entirely liquid to this day. Motivated by the experimentally-determined increase in the Fe-S liquidus temperature with decreasing pressure at Martian core conditions, we investigate whether Mars' core could crystallize from the top down. We focus on the "iron snow" regime, where newly-formed solid consists of pure Fe and is therefore heavier than the liquid. We derive global energy and entropy equations that describe the long-timescale thermal and magnetic history of the core from a general theory for two-phase, two-component liquid mixtures, assuming that the snow zone is in phase equilibrium and that all solid falls out of the layer and remelts at each timestep. Formation of snow zones occurs for a wide range of interior and thermal properties and depends critically on the initial sulfur concentration, ξ0. Release of gravitational energy and latent heat during growth of the snow zone do not generate sufficient entropy to restart the dynamo unless the snow zone occupies at least 400 km of the core. Snow zones can be 1.5-2 Gyrs old, though thermal stratification of the uppermost core, not included in our model, likely delays onset. Models that match the available magnetic and geodetic constraints have ξ0 ≈ 10% and snow zones that occupy approximately the top 100 km of the present-day Martian core.

Mixed-method pre-cooling reduces physiological demand without improving performance of medium-fast bowling in the heat.

PubMed

Minett, Geoffrey M; Duffield, Rob; Kellett, Aaron; Portus, Marc

2012-05-01

This study examined physiological and performance effects of pre-cooling on medium-fast bowling in the heat. Ten, medium-fast bowlers completed two randomised trials involving either cooling (mixed-methods) or control (no cooling) interventions before a 6-over bowling spell in 31.9±2.1°C and 63.5±9.3% relative humidity. Measures included bowling performance (ball speed, accuracy and run-up speeds), physical characteristics (global positioning system monitoring and counter-movement jump height), physiological (heart rate, core temperature, skin temperature and sweat loss), biochemical (serum concentrations of damage, stress and inflammation) and perceptual variables (perceived exertion and thermal sensation). Mean ball speed (114.5±7.1 vs. 114.1±7.2 km · h(-1); P = 0.63; d = 0.09), accuracy (43.1±10.6 vs. 44.2±12.5 AU; P = 0.76; d = 0.14) and total run-up speed (19.1±4.1 vs. 19.3±3.8 km · h(-1); P = 0.66; d = 0.06) did not differ between pre-cooling and control respectively; however 20-m sprint speed between overs was 5.9±7.3% greater at Over 4 after pre-cooling (P = 0.03; d = 0.75). Pre-cooling reduced skin temperature after the intervention period (P = 0.006; d = 2.28), core temperature and pre-over heart rates throughout (P = 0.01-0.04; d = 0.96-1.74) and sweat loss by 0.4±0.3 kg (P = 0.01; d = 0.34). Mean rating of perceived exertion and thermal sensation were lower during pre-cooling trials (P = 0.004-0.03; d = 0.77-3.13). Despite no observed improvement in bowling performance, pre-cooling maintained between-over sprint speeds and blunted physiological and perceptual demands to ease the thermoregulatory demands of medium-fast bowling in hot conditions.

NPF MECHANICAL CELL NaK DISPOSAL AND FUME ABATEMENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rey, G.

Some of the fuels originally scheduled for processing in the nonproduction fuel (NPF) processing program incorporated sodium or sodium- potassium alloy (NaK) as the bonding material between stainless-steel cladding and the uranium or uranium-molybdenum alloy core. Because of the special hazards involved in handling NaK, studies were made to determine safe methods for processing NaK-containing fuels. An underwater NaK dispensing system was installed, and tests were made to determine the characteristics of the NaK-water reaction. The equipment consisted of a dispenser, reaction pan, and off-gas scrubber. After initinl studies, a prototype test was made wherein U-Mo canned slugs containing NaKmore » reservoirs were hack sawed underwater. The studies demonstrated that the NaK reservoirs can be safely deactivated by hack sawing under a submerged hood in a shallow water bath. (W.L.H.)« less

Cooling Flows

NASA Astrophysics Data System (ADS)

Fabian, A.; Murdin, P.

2000-11-01

A subsonic cooling flow occurs when the hot gaseous atmosphere of a galaxy, group or cluster of galaxies cools slowly. Such atmospheres occur as a result of gas having fallen into the DARK MATTER well of the object and heated by gravitational energy release. A dominant cooling process is the emission of radiation by the gas. As cooling proceeds the gas sinks further in the potential well, giving ...

Global Cooling Drive Tectonic Scale Aridification of Asian Interior since Miocene

NASA Astrophysics Data System (ADS)

Jiang, F.; Zhu, X.

2017-12-01

Global cooling and the uplift of Tibetan Plateau are two potential mechanisms for tectonic scale aridification of Asian interior since Miocene. However, their relative importance is still controversial due to lack of continuous paleoclimate record. Here, using a 164 m long sediment core from Site U1438 in the Amami Sankaku Basin (ASB) in the NW Pacific, we show that the tectonic scale aridification of Asian interior is linked to global cooling rather than the uplift of the Tibetan Plateau. We analyzed the characteristics and variations of clastic mineral (e.g. quartz), clay minerals, radiogenic strontium (Sr) and neodymium (Nd) isotopes of the fine pelagic mud intervals from the sediment core. These new evidences indicate a continuous input of Asian dust from Asian interior to ASB since Miocene. We found that Asian dust in the ASB overall increased starting from ca.15.0 Myr (mid-Miocene), and ca. 3.5 Myr (Late Pliocene). The variations of Asian dust transport and accumulation closely responds to known times of enhanced Asian aridification and prevailing westerlies. The overall and gradual increase of Asian dust since mid-Miocene and Late Pliocene are in agreement with the formation and development of the polar ice caps, and are coupled with the gradual decrease of the global temperature recorded by the δ18O ratio of forams, but lag behind the tectonic uplift of the Tibetan Plateau. We argue that global cooling drove the aridification of the Asian interior and resulted in the increase of Asian dust deposition in the ASB.

Open loop increase in trunk temperature produced by face cooling in working humans.

PubMed Central

Cabanac, M; Caputa, M

1979-01-01

1. Five human subjects pedalled on a bicyle ergometer for at least two 74 min periods at 10 degrees C ambient temperature. During the first period the subjects cycled for 42 min with face fanning, followed by 32 min with the head thermally insulated. In the second period, this procedure was reversed. Oesophageal (tes), tympanic (Tty), forehead and hand skin temperatures were recorded. In addition, heart rate (H.R.) was counted throughout the experiments, and the technique of perceptual rating of cool and warm stimuli was used in order to appreciate whether the subjects were hypo-, normo-, or hyperthermic. 2. Face fanning resulted in decreased Tty, decreased H.R., mild skin vasoconstriction but increased Tes. 3. Head covering resulted in increased Tty and H.R., while Tes decreased slightly, due to peripheral vasodilatation. 4. When their faces were being fanned so that Tty was low and Tes was high, the subjects gave slightly hypothermic ratings. Ratings were clearly hyperthermic when their heads were covered and Tty was high and Tes was low. 5. The close correlation between vasomotor response and H.R. on the one hand and Tty on the other confirms that this variable is a better approximation of regulated core temperature than Tes. 6. Increase in Tes during face fanning and decrease in Tes during face insulation is new evidence for the possibility of the human brian being cooled during exercise by cool blood returning from the face. 7. We suggest that this selective brain cooling determines the apparent upper resetting of core temperature during exercise while brain temperature remains precisely regulated and constant. PMID:458648

Structure determination in 55-atom Li-Na and Na-K nanoalloys.

PubMed

Aguado, Andrés; López, José M

2010-09-07

The structure of 55-atom Li-Na and Na-K nanoalloys is determined through combined empirical potential (EP) and density functional theory (DFT) calculations. The potential energy surface generated by the EP model is extensively sampled by using the basin hopping technique, and a wide diversity of structural motifs is reoptimized at the DFT level. A composition comparison technique is applied at the DFT level in order to make a final refinement of the global minimum structures. For dilute concentrations of one of the alkali atoms, the structure of the pure metal cluster, namely, a perfect Mackay icosahedron, remains stable, with the minority component atoms entering the host cluster as substitutional impurities. At intermediate concentrations, the nanoalloys adopt instead a core-shell polyicosahedral (p-Ih) packing, where the element with smaller atomic size and larger cohesive energy segregates to the cluster core. The p-Ih structures show a marked prolate deformation, in agreement with the predictions of jelliumlike models. The electronic preference for a prolate cluster shape, which is frustrated in the 55-atom pure clusters due to the icosahedral geometrical shell closing, is therefore realized only in the 55-atom nanoalloys. An analysis of the electronic densities of states suggests that photoelectron spectroscopy would be a sufficiently sensitive technique to assess the structures of nanoalloys with fixed size and varying compositions.

Cooling of hypernuclear compact stars

NASA Astrophysics Data System (ADS)

Raduta, Adriana R.; Sedrakian, Armen; Weber, Fridolin

2018-04-01

We study the thermal evolution of hypernuclear compact stars constructed from covariant density functional theory of hypernuclear matter and parametrizations which produce sequences of stars containing two-solar-mass objects. For the input in the simulations, we solve the Bardeen-Cooper-Schrieffer gap equations in the hyperonic sector and obtain the gaps in the spectra of Λ, Ξ0, and Ξ- hyperons. For the models with masses M/M⊙ ≥ 1.5 the neutrino cooling is dominated by hyperonic direct Urca processes in general. In the low-mass stars the (Λp) plus leptons channel is the dominant direct Urca process, whereas for more massive stars the purely hyperonic channels (Σ-Λ) and (Ξ-Λ) are dominant. Hyperonic pairing strongly suppresses the processes on Ξ-s and to a lesser degree on Λs. We find that intermediate-mass 1.5 ≤ M/M⊙ ≤ 1.8 models have surface temperatures which lie within the range inferred from thermally emitting neutron stars, if the hyperonic pairing is taken into account. Most massive models with M/M⊙ ≃ 2 may cool very fast via the direct Urca process through the (Λp) channel because they develop inner cores where the S-wave pairing of Λs and proton is absent.

Convective cooling in a pool-type research reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sipaun, Susan, E-mail: susan@nm.gov.my; Usman, Shoaib, E-mail: usmans@mst.edu

2016-01-22

A reactor produces heat arising from fission reactions in the nuclear core. In the Missouri University of Science and Technology research reactor (MSTR), this heat is removed by natural convection where the coolant/moderator is demineralised water. Heat energy is transferred from the core into the coolant, and the heated water eventually evaporates from the open pool surface. A secondary cooling system was installed to actively remove excess heat arising from prolonged reactor operations. The nuclear core consists of uranium silicide aluminium dispersion fuel (U{sub 3}Si{sub 2}Al) in the form of rectangular plates. Gaps between the plates allow coolant to passmore » through and carry away heat. A study was carried out to map out heat flow as well as to predict the system’s performance via STAR-CCM+ simulation. The core was approximated as porous media with porosity of 0.7027. The reactor is rated 200kW and total heat density is approximately 1.07+E7 Wm{sup −3}. An MSTR model consisting of 20% of MSTR’s nuclear core in a third of the reactor pool was developed. At 35% pump capacity, the simulation results for the MSTR model showed that water is drawn out of the pool at a rate 1.28 kg s{sup −1} from the 4” pipe, and predicted pool surface temperature not exceeding 30°C.« less

Rapid hydrothermal cooling above the axial melt lens at fast-spreading mid-ocean ridge

NASA Astrophysics Data System (ADS)

Zhang, Chao; Koepke, Juergen; Kirchner, Clemens; Götze, Niko; Behrens, Harald

2014-09-01

Axial melt lenses sandwiched between the lower oceanic crust and the sheeted dike sequences at fast-spreading mid-ocean ridges are assumed to be the major magma source of oceanic crust accretion. According to the widely discussed ``gabbro glacier'' model, the formation of the lower oceanic crust requires efficient cooling of the axial melt lens, leading to partial crystallization and crystal-melt mush subsiding down to lower crust. These processes are believed to be controlled by periodical magma replenishment and hydrothermal circulation above the melt lens. Here we quantify the cooling rate above melt lens using chemical zoning of plagioclase from hornfelsic recrystallized sheeted dikes drilled from the East Pacific at the Integrated Ocean Drilling Program Hole 1256D. We estimate the cooling rate using a forward modelling approach based on CaAl-NaSi interdiffusion in plagioclase. The results show that cooling from the peak thermal overprint at 1000-1050°C to 600°C are yielded within about 10-30 years as a result of hydrothermal circulation above melt lens during magma starvation. The estimated rapid hydrothermal cooling explains how the effective heat extraction from melt lens is achieved at fast-spreading mid-ocean ridges.

Prognostic significance of the lymphocyte-to-monocyte ratio in patients with metastatic colorectal cancer

PubMed Central

Shibutani, Masatsune; Maeda, Kiyoshi; Nagahara, Hisashi; Ohtani, Hiroshi; Sakurai, Katsunobu; Yamazoe, Sadaaki; Kimura, Kenjiro; Toyokawa, Takahiro; Amano, Ryosuke; Tanaka, Hiroaki; Muguruma, Kazuya; Hirakawa, Kosei

2015-01-01

AIM: To evaluate the prognostic significance of the lymphocyte to monocyte ratio (LMR) in patients with unresectable metastatic colorectal cancer who received palliative chemotherapy. METHODS: A total of 104 patients with unresectable metastatic colorectal cancer who underwent palliative chemotherapy were enrolled. The LMR was calculated from blood samples by dividing the absolute lymphocyte count by the absolute monocyte count. Pre-treatment LMR values were measured within one week before the initiation of chemotherapy, while post-treatment LMR values were measured eight weeks after the initiation of chemotherapy. RESULTS: The median pre-treatment LMR was 4.16 (range: 0.58-14.06). We set 3.38 as the cut-off level based on the receiver operating characteristic curve. Based on the cut-off level of 3.38, 66 patients were classified into the high pre-treatment LMR group and 38 patients were classified into the low pre-treatment LMR group. The low pre-treatment LMR group had a significantly worse overall survival rate (P = 0.0011). Moreover, patients who demonstrated low pre-treatment LMR and normalization after treatment exhibited a better overall survival rate than the patients with low pre-treatment and post-treatment LMR values. CONCLUSION: The lymphocyte to monocyte ratio is a useful prognostic marker in patients with unresectable metastatic colorectal cancer who receive palliative chemotherapy. PMID:26379401

Dynamical Core in Atmospheric Model Does Matter in the Simulation of Arctic Climate

NASA Astrophysics Data System (ADS)

Jun, Sang-Yoon; Choi, Suk-Jin; Kim, Baek-Min

2018-03-01

Climate models using different dynamical cores can simulate significantly different winter Arctic climates even if equipped with virtually the same physics schemes. Current climate simulated by the global climate model using cubed-sphere grid with spectral element method (SE core) exhibited significantly warmer Arctic surface air temperature compared to that using latitude-longitude grid with finite volume method core. Compared to the finite volume method core, SE core simulated additional adiabatic warming in the Arctic lower atmosphere, and this was consistent with the eddy-forced secondary circulation. Downward longwave radiation further enhanced Arctic near-surface warming with a higher surface air temperature of about 1.9 K. Furthermore, in the atmospheric response to the reduced sea ice conditions with the same physical settings, only the SE core showed a robust cooling response over North America. We emphasize that special attention is needed in selecting the dynamical core of climate models in the simulation of the Arctic climate and associated teleconnection patterns.

Graphene Oxide in Lossy Mode Resonance-Based Optical Fiber Sensors for Ethanol Detection.

PubMed

Hernaez, Miguel; Mayes, Andrew G; Melendi-Espina, Sonia

2017-12-27

The influence of graphene oxide (GO) over the features of an optical fiber ethanol sensor based on lossy mode resonances (LMR) has been studied in this work. Four different sensors were built with this aim, each comprising a multimode optical fiber core fragment coated with a SnO₂ thin film. Layer by layer (LbL) coatings made of 1, 2 and 4 bilayers of polyethyleneimine (PEI) and graphene oxide were deposited onto three of these devices and their behavior as aqueous ethanol sensors was characterized and compared with the sensor without GO. The sensors with GO showed much better performance with a maximum sensitivity enhancement of 176% with respect to the sensor without GO. To our knowledge, this is the first time that GO has been used to make an optical fiber sensor based on LMR.

Research on The Removal of Scale Ions from Circulating Cooling Wastewater by Chemical Coagulation Process

NASA Astrophysics Data System (ADS)

Du, Song; Jin, Wenbiao; Duan, Feng

2018-06-01

In this paper, the circulating cooling wastewater was treated by chemical coagulation process through adding NaOH/Na2CO3.The effect of NaOH and Na2CO3 dose on removal of scale ions, such as Ca2+, Mg2+, Ba2+, Sr2+, SiO2, was studied and the removal mechanism was discussed. The results showed that the increase of NaOH dose was beneficial to the removal of above-mentioned scale ions. When NaOH was only added, the removal efficiency of Ca2+, Mg2+, Ba2+, Sr2+, SiO2 was 86.3%, 91.6%, 86.5%, 58.1%, 84.2%, respectively. When 680 mg/L of NaOH and 300 mg/L of Na2CO3 were added, and the effluent pH was above 11.2, the removal efficiency of Ca2+, Mg2+ was 95.8% and 89.4%, respectively, and the concentration of Ca2+and Mg2+ was below 20 mg/L, which met the target of wastewater treatment. Finally the possible removal mechanism of Ca2+, Mg2+, Ba2+, Sr2+and SiO2 was discussed.

Thermally induced fracture for core-veneered dental ceramic structures.

PubMed

Zhang, Zhongpu; Guazzato, Massimiliano; Sornsuwan, Tanapon; Scherrer, Susanne S; Rungsiyakull, Chaiy; Li, Wei; Swain, Michael V; Li, Qing

2013-09-01

Effective and reliable clinical uses of dental ceramics necessitate an insightful analysis of the fracture behaviour under critical conditions. To better understand failure characteristics of porcelain veneered to zirconia core ceramic structures, thermally induced cracking during the cooling phase of fabrication is studied here by using the extended finite element method (XFEM). In this study, a transient thermal analysis of cooling is conducted first to determine the temperature distributions. The time-dependent temperature field is then imported to the XFEM model for viscoelastic thermomechanical analysis, which predicts thermally induced damage and cracking at different time steps. Temperature-dependent material properties are used in both transient thermal and thermomechanical analyses. Three typical ceramic structures are considered in this paper, namely bi-layered spheres, squat cylinders and dental crowns with thickness ratios of either 1:2 or 1:1. The XFEM fracture patterns exhibit good agreement with clinical observation and the in vitro experimental results obtained from scanning electron microscopy characterization. The study reveals that fast cooling can lead to thermal fracture of these different bi-layered ceramic structures, and cooling rate (in terms of heat transfer coefficient) plays a critical role in crack initiation and propagation. By exploring different cooling rates, the heat transfer coefficient thresholds of fracture are determined for different structures, which are of clear clinical implication. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Widespread Miocene deep-sea hiatuses: coincidence with periods of global cooling.

USGS Publications Warehouse

Barron, J.A.; Keller, G.

1982-01-01

High-resolution biostratigraphic analyses of Miocene deep-sea cores reveal eight intervals of widespread hiatuses in the world ocean. In complete sections these hiatuses correspond to intervals of cool faunal and floral assemblages, rapid enrichment of delta 18O, and sea-level regressions. These factors suggest that Miocene deep-sea hiatuses result from an increased intensity of circulation and corrosiveness of bottom currents during periods of increased polar refrigeration.-Authors

Industrial Cooling Tower Disinfection Treatment to Prevent Legionella spp.

PubMed

Iervolino, Matteo; Mancini, Benedetta; Cristino, Sandra

2017-09-26

The contamination of industrial cooling towers has been identified as one cause of legionellosis, but the real risk has been underestimated. Two different disinfection treatments were tested on Legionella colonization in an industrial Cooling Tower System (CTS). Environmental monitoring of Legionella , P. aeruginosa , and a heterotrophic plate count (HPC) at 36 °C was performed from June to October 2016. The disinfection procedures adopted were based on hydrogen peroxide (H₂O₂) and silver salts (Ag⁺), in addition to an anti-algal treatment, then using hyperclorination as a shock, and then continuous treatment by sodium hypochlorite (NaClO). L . pneumophila serogroup 8 was found at a concentration of 5.06 Log cfu/L after the CTS filling; a shock treatment performed by H₂O₂/Ag⁺ produced a rapid increase in contamination up to 6.14 Log cfu/L. The CTS activity was stopped and two subsequent shock treatments were performed using NaClO, followed by continuous hyperclorination. These procedures showed a significant decrease ( p < 0.05) in Legionella concentration (1.77 Log cfu/L). The same trend was observed for P . aeruginosa (0.55 Log cfu/100 mL) and HPC (1.95 Log cfu/mL) at 36 °C. Environmental monitoring and the adoption of maintenance procedures, including anti-scale treatment, and physical, chemical, and microbiological control, ensure the good performance of a CTS, reducing the Legionella risk for public health.