Selected results for LDEF thermal control coatings

NASA Technical Reports Server (NTRS)

Golden, Johnny L.

1993-01-01

Several different thermal control coatings were analyzed as part of the Long Duration Exposure Facility (LDEF) Materials Special Investigation Group activity and as part of the Space Environment Effects on Spacecraft Materials Experiment M0003. A brief discussion of the results obtained for these materials is presented.

Antinociceptive effects of long-acting nalbuphine decanoate after intramuscular administration to Hispaniolan Amazon parrots (Amazona ventralis).

PubMed

Sanchez-Migallon Guzman, David; Braun, Jana M; Steagall, Paulo V M; Keuler, Nicholas S; Heath, Timothy D; Krugner-Higby, Lisa A; Brown, Carolyn S; Paul-Murphy, Joanne R

2013-02-01

To evaluate the thermal antinociceptive effects and duration of action of nalbuphine decanoate after IM administration to Hispaniolan Amazon parrots (Amazona ventralis). 10 healthy adult Hispaniolan Amazon parrots of unknown sex. Nalbuphine decanoate (33.7 mg/kg) or saline (0.9% NaCl) solution was administered IM in a randomized complete crossover experimental design (periods 1 and 2). Foot withdrawal threshold to a noxious thermal stimulus was used to evaluate responses. Baseline thermal withdrawal threshold was recorded 1 hour before drug or saline solution administration, and thermal foot withdrawal threshold measurements were repeated 1, 2, 3, 6, 12, 24, 48, and 72 hours after drug administration. Nalbuphine decanoate administered IM at a dose of 33.7 mg/kg significantly increased thermal foot withdrawal threshold, compared with results after administration of saline solution during period 2, and also caused a significant change in withdrawal threshold for up to 12 hours, compared with baseline values. Nalbuphine decanoate increased the foot withdrawal threshold to a noxious thermal stimulus in Hispaniolan Amazon parrots for up to 12 hours and provided a longer duration of action than has been reported for other nalbuphine formulations. Further studies with other types of nociceptive stimulation, dosages, and dosing intervals as well as clinical trials are needed to fully evaluate the analgesic effects of nalbuphine decanoate in psittacine birds.

The effect of load on heat production, thermal effects and expenditure of time during implant site preparation - an experimental ex vivo comparison between piezosurgery and conventional drilling.

PubMed

Stelzle, Florian; Frenkel, Carsten; Riemann, Max; Knipfer, Christian; Stockmann, Philipp; Nkenke, Emeka

2014-02-01

Piezoelectric surgery (PS) is meant to be a gentle osteotomy method. The aim of this study was to compare piezosurgical vs. conventional drilling methods for implant site preparation (ISP) - focusing on load-dependent thermal effect on hard tissue and the expenditure of ISP time. Three hundred and sixty ISP were performed on ex vivo pig heads using piezosurgery, spiral burs (SB) and trephine burs (TB). The load applied was increased from 0 to 1000 g in 100-g intervals. Temperature within the bone was measured with a thermocouple, and duration was recorded with a stop watch. Thermal effects were histomorphometrically analysed. Twelve ISPs per technique were performed at the lateral wall of the maxillary sinus. PS yields the highest mean temperatures (48.6 ± 3.4°C) and thermal effects (200.7 ± 44.4 μm), both at 900-1000 g. Duration is reduced with a plus of load and significantly longer in either case for PS (P < 0.05). There is a correlation of the applied load with all other examined factors for PS and TB. Temperature and histological effects decrease for SB beyond 500 g. PS yields significantly higher temperatures and thermal tissue alterations on load levels higher than 500 g and is significantly slower for ISP compared to SB and TB. For ISP with PS, a maximum load of 400 g should be maintained. © 2012 John Wiley & Sons A/S.

Space environmental effects on spacecraft: LEO materials selection guide, part 2

NASA Astrophysics Data System (ADS)

Silverman, Edward M.

1995-08-01

This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 2 covers thermal control systems, power systems, optical components, electronic systems, and applications.

Space environmental effects on spacecraft: LEO materials selection guide, part 2

NASA Technical Reports Server (NTRS)

Silverman, Edward M.

1995-01-01

This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 2 covers thermal control systems, power systems, optical components, electronic systems, and applications.

Potential impact of thermal effects during ultrasonic neurostimulation: retrospective numerical estimation of temperature elevation in seven rodent setups

NASA Astrophysics Data System (ADS)

Constans, Charlotte; Mateo, Philippe; Tanter, Mickaël; Aubry, Jean-François

2018-01-01

In the past decade, a handful but growing number of groups have reported worldwide successful low intensity focused ultrasound induced neurostimulation trials on rodents. Its effects range from movement elicitations to reduction of anesthesia time or reduction of the duration of drug induced seizures. The mechanisms underlying ultrasonic neuromodulation are still not fully understood. Given the low intensities used in most of the studies, a mechanical effect is more likely to be responsible for the neuromodulation effect, but a clear description of the thermal and mechanical effects is necessary to optimize clinical applications. Based on five studies settings, we calculated the temperature rise and thermal doses in order to evaluate its implication in the neuromodulation phenomenon. Our retrospective analysis shows thermal rise ranging from 0.002 °C to 0.8 °C in the brain for all setups, except for one setup for which the temperature increase is estimated to be as high as 7 °C. We estimate that in the latter case, temperature rise cannot be neglected as a possible cause of neuromodulation. Simulations results were supported by temperature measurements on a mouse with two different sets of parameters. Although the calculated temperature is compatible with the absence of visible thermal lesions on the skin, it is high enough to impact brain circuits. Our study highlights the usefulness of performing thermal simulations prior to experiment in order to fully take into account not only the impact of the peak intensity but also pulse duration and pulse repetition.

Experimental investigation on the vascular thermal response to near-infrared laser pulses.

PubMed

Li, Dong; Chen, Bin; Wu, Wenjuan; Ying, Zhaoxia

2017-12-01

Port wine stains (PWS) are congenital vascular malformations that progressively darken and thicken with age. To improve the effect of laser therapy in clinical practice, thermal response of blood vessel to a 1064 nm Nd:YAG laser with controlled energy doses and pulse durations was evaluated using the dorsal skin chamber model. A total of 137 vessels with 30-300 μm diameters were selected from the dorsal skin of the mouse to match those capillaries in port wine stains. Experimental results showed that the thermal response of blood vessels to 1064 nm laser irradiation can be classified as follows: vessel dilation, coagulation, constriction with decreased diameter, complete constriction, hemorrhage, and collagen damage with increasing laser radiant exposure. In most cases, that is, 83 of 137 blood vessels (60.6%), Nd:YAG laser irradiation was characterized by complete constriction (immediate blood vessel disappearance). To reveal the possible damage mechanisms and evaluate blood vessel photocoagulation patterns, theoretical investigation using bioheat transfer equation was conducted in mouse skin with a depth of 1000 μm. Complete constriction as the dominant thermal response as evidenced by uniform blood heating within the vessel lumen was noted in both experimental observation and theoretical investigation. To achieve the ideal clinical effect using the Nd:YAG laser treatment, the radiant exposure should not only be high enough to induce complete constriction of the blood vessels but also controlled carefully to avoid surrounding collagen damage. The short pulse duration of 1-3 ms is better than long pulse durations because hemorrhaging of small capillaries is occasionally observed postirradiation with pulse durations longer than 10 ms.

The Effect of Load Position on Biomechanical and Physiological Measures during a Short Duration March

DTIC Science & Technology

2001-05-01

completed subjective evaluations of the load location after each loaded trial. The questionnaire asked about overall acceptability, balance, thermal comfort , load... thermal comfort when marching Results The results of this study are summarized in Table 2. Oxygen consumption levels across load distributions were not...acceptable in 7 out of 8 categories that were examined. The alternate configuration ranked most acceptable in all categories except thermal comfort , where

Thermal degradation of wood fibers during hot-pressing of MDF composites. Part I, Relative effects and benefits of thermal exposure

Treesearch

Jerrold E. Winandy; Andrzej M. Krzysik

2007-01-01

This research evaluated the potential of wood fiber to chemically decompose during hot-pressing. We evaluated changes in carbohydrate composition and structure as a function of multiple press temperatures (180°, 200°, and 220°C) and an array of hot-pressing durations from 180 to 2500 s. Results show how this thermal degradation in chemical composition directly results...

Long duration exposure facility post-flight thermal analysis, part 1

NASA Technical Reports Server (NTRS)

Berrios, William M.; Sampair, Thomas R.

1992-01-01

Results of the post-flight thermal analysis of the Long Duration Exposure Facility (LDEF) mission are presented. The LDEF mission thermal analysis was verified by comparing the thermal model results to flight data from the LDEF Thermal Measurements System (THERM). Post-flight calculated temperature uncertainties have been reduced to under +/- 18 F from the pre-flight uncertainties of +/- 40 F. The THERM consisted of eight temperature sensors, a shared tape recorder, a standard LDEF flight battery, and an electronics control box. The temperatures were measured at selected locations on the LDEF structure interior during the first 390 days of flight and recorded for post-flight analysis. After the LDEF retrieval from Space on 12 Jan. 1990, the tape recorder was recovered from the spacecraft and the data reduced for comparison to the LDEF predicted temperatures. The LDEF mission temperatures were calculated prior to the LDEF deployment on 7 Apr. 1980, and updated after the LDEF retrieval with the following actual flight parameter data: including thermal fluxes, spacecraft attitudes, thermal coatings degradation, and contamination effects. All updated data used for the calculation of post-flight temperatures is also presented in this document.

FEM modeling and histological analyses on thermal damage induced in facial skin resurfacing procedure with different CO2 laser pulse duration

NASA Astrophysics Data System (ADS)

Rossi, Francesca; Zingoni, Tiziano; Di Cicco, Emiliano; Manetti, Leonardo; Pini, Roberto; Fortuna, Damiano

2011-07-01

Laser light is nowadays routinely used in the aesthetic treatments of facial skin, such as in laser rejuvenation, scar removal etc. The induced thermal damage may be varied by setting different laser parameters, in order to obtain a particular aesthetic result. In this work, it is proposed a theoretical study on the induced thermal damage in the deep tissue, by considering different laser pulse duration. The study is based on the Finite Element Method (FEM): a bidimensional model of the facial skin is depicted in axial symmetry, considering the different skin structures and their different optical and thermal parameters; the conversion of laser light into thermal energy is modeled by the bio-heat equation. The light source is a CO2 laser, with different pulse durations. The model enabled to study the thermal damage induced into the skin, by calculating the Arrhenius integral. The post-processing results enabled to study in space and time the temperature dynamics induced in the facial skin, to study the eventual cumulative effects of subsequent laser pulses and to optimize the procedure for applications in dermatological surgery. The calculated data where then validated in an experimental measurement session, performed in a sheep animal model. Histological analyses were performed on the treated tissues, evidencing the spatial distribution and the entity of the thermal damage in the collageneous tissue. Modeling and experimental results were in good agreement, and they were used to design a new optimized laser based skin resurfacing procedure.

Long duration exposure facility post-flight thermal analysis: Orbital/thermal environment data package

NASA Technical Reports Server (NTRS)

Berrios, William M.

1990-01-01

A post flight mission thermal environment for the Long Duration Exposure Facility was created as part of the thermal analysis data reduction effort. The data included herein is the thermal parameter data used in the calculation of boundary temperatures. This boundary temperature data is to be released in the near future for use by the LDEF principal investigators in the final analysis of their particular experiment temperatures. Also included is the flight temperature data as recorded by the LDEF Thermal Measurements System (THERM) for the first 90 days of flight.

Applicability of Long Duration Exposure Facility environmental effects data to the design of Space Station Freedom electrical power system

NASA Technical Reports Server (NTRS)

Christie, Robert J.; Lu, Cheng-Yi; Aronoff, Irene

1992-01-01

Data defining space environmental effects on the Long Duration Exposure Facility (LDEF) are examined in terms of the design of the electrical power system (EPS) of the Space Station Freedom (SSF). The significant effects of long-term exposure to space are identified with respect to the performance of the LDEF's materials, components, and systems. A total of 57 experiments were conducted on the LDEF yielding information regarding coatings, thermal systems, electronics, optics, and power systems. The resulting database is analyzed in terms of the specifications of the SSF EPS materials and subsystems and is found to be valuable in the design of control and protection features. Specific applications are listed for findings regarding the thermal environment, atomic oxygen, UV and ionizing radiation, debris, and contamination. The LDEF data are shown to have a considerable number of applications to the design and planning of the SSF and its EPS.

Infrared skin damage thresholds from 1319-nm continuous-wave laser exposures

NASA Astrophysics Data System (ADS)

Oliver, Jeffrey W.; Vincelette, Rebecca; Noojin, Gary D.; Clark, Clifton D.; Harbert, Corey A.; Schuster, Kurt J.; Shingledecker, Aurora D.; Kumru, Semih S.; Maughan, Justin; Kitzis, Naomi; Buffington, Gavin D.; Stolarski, David J.; Thomas, Robert J.

2013-12-01

A series of experiments were conducted in vivo using Yucatan miniature pigs (Sus scrofa domestica) to determine thermal damage thresholds to the skin from 1319-nm continuous-wave Nd:YAG laser irradiation. Experiments employed exposure durations of 0.25, 1.0, 2.5, and 10 s and beam diameters of ˜0.6 and 1 cm. Thermal imagery data provided a time-dependent surface temperature response from the laser. A damage endpoint of fifty percent probability of a minimally visible effect was used to determine threshold for damage at 1 and 24 h postexposure. Predicted thermal response and damage thresholds are compared with a numerical model of optical-thermal interaction. Resultant trends with respect to exposure duration and beam diameter are compared with current standardized exposure limits for laser safety. Mathematical modeling agreed well with experimental data, predicting that though laser safety standards are sufficient for exposures <10 s, they may become less safe for very long exposures.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Gas-dynamic effects in the interaction of a motionless optical pulsating discharge with gas

NASA Astrophysics Data System (ADS)

Tishchenko, V. N.; Grachev, G. N.; Pavlov, A. A.; Smirnov, A. L.; Pavlov, A. A.; Golubev, M. P.

2008-01-01

The effect of energy removal from the combustion zone of a motionless optical pulsating discharge in the horizontal direction along the axis of a repetitively pulsed laser beam producing the discharge is discovered. The directivity diagram of a hot gas flow is formed during the action of hundreds of pulses. The effect is observed for short pulse durations, when the discharge efficiently generates shock waves. For long pulse durations, the heated gas propagates upward, as in a thermal source.

Thermal effects in laser-assisted pre-embryo zona drilling

NASA Astrophysics Data System (ADS)

Douglas-Hamilton, Diarmaid H.; Conia, Jerome D.

2001-04-01

Diode lasers ((lambda) equals 1480 nm) are used with in vitro fertilization to dissect the zone pellucida (shell) of pre- embryos. A focused laser beam is applied in vitro to form a channel or trench in the zona pellucida. The procedure is used to facilitate biopsy or as a promoter of embryo hatching. We present examples and measurements of zona pellucida ablation using animal models. In using the laser it is vital not to damage pre-embryo cells, e.g., by overheating. In order to define safe regimes we have derived some thermal side effects of zona pellucida removal. The temperature profile in the beam and vicinity is predicted as function of laser pulse duration and power. In a crossed- beam experiment a HeNe laser probe is used to detect the temperature-induced change in the refractive index of an aqueous solution, and estimate local thermal gradient. We find that the diode laser beam produces superheated water approaching 200 degree(s)C on the beam axis. Thermal histories during and following the laser pulse are given for regions in the neighborhood of the beam. We conclude that an optimum regime exists with pulse duration

Optimization of conditions for thermal smoothing GaAs surfaces

NASA Astrophysics Data System (ADS)

Akhundov, I. O.; Kazantsev, D. M.; Kozhuhov, A. S.; Alperovich, V. L.

2018-03-01

GaAs thermal smoothing by annealing in conditions which are close to equilibrium between the surface and vapors of As and Ga was earlier proved to be effective for the step-terraced surface formation on epi-ready substrates with a small root-mean-square roughness (Rq ≤ 0.15 nm). In the present study, this technique is further developed in order to reduce the annealing duration and to smooth GaAs samples with a larger initial roughness. To this end, we proposed a two-stage anneal with the first high-temperature stage aimed at smoothing "coarse" relief features and the second stage focused on "fine" smoothing at a lower temperature. The optimal temperatures and durations of two-stage annealing are found by Monte Carlo simulations and adjusted after experimentation. It is proved that the temperature and duration of the first high-temperature stage are restricted by the surface roughening, which occurs due to deviations from equilibrium conditions.

Differences between young adults and elderly in thermal comfort, productivity, and thermal physiology in response to a moderate temperature drift and a steady-state condition.

PubMed

Schellen, L; van Marken Lichtenbelt, W D; Loomans, M G L C; Toftum, J; de Wit, M H

2010-08-01

Results from naturally ventilated buildings show that allowing the indoor temperature to drift does not necessarily result in thermal discomfort and may allow for a reduction in energy use. However, for stationary conditions, several studies indicate that the thermal neutral temperature and optimum thermal condition differ between young adults and elderly. There is a lack of studies that describe the effect of aging on thermal comfort and productivity during a moderate temperature drift. In this study, the effect of a moderate temperature drift on physiological responses, thermal comfort, and productivity of eight young adults (age 22-25 year) and eight older subjects (age 67-73 year) was investigated. They were exposed to two different conditions: S1-a control condition; constant temperature of 21.5 degrees C; duration: 8 h; and S2-a transient condition; temperature range: 17-25 degrees C, duration: 8 h, temperature drift: first 4 h: +2 K/h, last 4 h: -2 K/h. The results indicate that thermal sensation of the elderly was, in general, 0.5 scale units lower in comparison with their younger counterparts. Furthermore, the elderly showed more distal vasoconstriction during both conditions. Nevertheless, TS of the elderly was related to air temperature only, while TS of the younger adults also was related to skin temperature. During the constant temperature session, the elderly preferred a higher temperature in comparison with the young adults. Because the stock of fossil fuels is limited, energy savings play an important role. Thermal comfort is one of the most important performance indicators to successfully apply measures to reduce the energy need in buildings. Allowing drifts in indoor temperature is one of the options to reduce the energy demand. This study contributes to the knowledge concerning the effects of a moderate temperature drift and the age of the inhabitants on their thermal comfort.

Female upper body and breast skin temperature and thermal comfort following exercise.

PubMed

Ayres, B; White, J; Hedger, W; Scurr, J

2013-01-01

Breast support reduces breast pain and movement during exercise, however, an extra layer of clothing may affect thermoregulation. This preliminary study investigated female upper body and breast skin temperature and thermal comfort following short-duration exercise. Eight female participants with C-cup breasts had thermal images (infra-red camera, FLIR systems) of the bare breasts, the breasts in two sports bras (composite and polyester) and the abdomen, taken before and after 20 min of exercise at 28(o)C. Following exercise, bare-breast, bra and abdomen temperatures reduced by 0.61(o)C, 0.92(o)C and 2.06(o)C, respectively. The polyester sports bra demonstrated greater thermal comfort and enabled a greater change in skin temperature than the composite sports bra. It is concluded that following short-duration exercise, sports bras reduced the cooling ability of the breast. Material properties of the bras affect thermal comfort and post-exercise skin temperature; this should be an important consideration for sports bra manufacturers. This study investigates the effect of sports bras on thermal regulation of the breast following exercise. Sports bras negatively affected the cooling ability of the skin on the breast, with the material properties of the bra affecting thermal comfort following exercise. These results present important considerations for sports bra manufacturers.

Thermal control surfaces experiment: Initial flight data analysis

NASA Technical Reports Server (NTRS)

Wilkes, Donald R.; Hummer, Leigh L.

1991-01-01

The behavior of materials in the space environment continues to be a limiting technology for spacecraft and experiments. The thermal control surfaces experiment (TCSE) aboard the Long Duration Exposure Facility (LDEF) is the most comprehensive experiment flown to study the effects of the space environment on thermal control surfaces. Selected thermal control surfaces were exposed to the LDEF orbital environment and the effects of this exposure were measured. The TCSE combined in-space orbital measurements with pre and post-flight analyses of flight materials to determine the effects of long term space exposure. The TCSE experiment objective, method, and measurements are described along with the results of the initial materials analysis. The TCSE flight system and its excellent performance on the LDEF mission is described. A few operational anomalies were encountered and are discussed.

Thermal expansion behavior of LDEF metal matrix composites

NASA Technical Reports Server (NTRS)

Le, T. D.; Steckel, G. L.

1992-01-01

The effects of the space environment on the thermal expansion stability of metal matrix composites (graphite/Al and graphite/Mg) will be presented. A sample from each category of metal matrix composites mounted on the leading and trailing edge was chosen for analysis of the temperature-time-thermal strain histories. Typical thermal expansion curves over the same range of temperature were selected at the beginning, mid, and end of the recording duration. The thermal expansion of selected post-flight LDEF samples were measured over the same range of temperature in the laboratory using a Michelson laser interferometer. The thermal strains were monitored concurrently with a laser interferometer and a mounted strain gage.

Evaluation of the efficacy of lambda-cyhalothrin applied as ultra-low volume and thermal fog for emergency control of Aedes aegypti in Honduras.

PubMed

Perich, M J; Sherman, C; Burge, R; Gill, E; Quintana, M; Wirtz, R A

2001-12-01

An extended-duration formulation of lambda-cyhalothrin (Demand CS) applied as either an ultra-low volume (ULV) or thermal fog spray from a new handheld sprayer (Terrier) against Aedes aegypti was evaluated in Honduras. Spray applications were made at the front door for 1 min or to each room for 15 sec, both for the ULV and thermal fog applications to houses in separate blocks for each treatment. The efficacy and duration of effectiveness of the spray was determined from sentinel caged mosquito mortality and collection of mosquitoes within houses with a backpack power aspirator. Sentinel caged mosquito mortality in both open and sequestered locations was 97-100% for all spray treatments, with control mortality less than 2%. Both ULV applications (front door and each room) provided 4 wk of significant control (P < 0.01) based on adult Ae. aegypti house collections.

Space environmental effects on spacecraft: LEO materials selection guide, part 1

NASA Astrophysics Data System (ADS)

Silverman, Edward M.

1995-08-01

This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 1 covers spacecraft design considerations for the space environment; advanced composites; polymers; adhesives; metals; ceramics; protective coatings; and lubricants, greases, and seals.

Space environmental effects on spacecraft: LEO materials selection guide, part 1

NASA Technical Reports Server (NTRS)

Silverman, Edward M.

1995-01-01

This document provides performance properties on major spacecraft materials and subsystems that have been exposed to the low-Earth orbit (LEO) space environment. Spacecraft materials include metals, polymers, composites, white and black paints, thermal-control blankets, adhesives, and lubricants. Spacecraft subsystems include optical components, solar cells, and electronics. Information has been compiled from LEO short-term spaceflight experiments (e.g., space shuttle) and from retrieved satellites of longer mission durations (e.g., Long Duration Exposure Facility). Major space environment effects include atomic oxygen (AO), ultraviolet radiation, micrometeoroids and debris, contamination, and particle radiation. The main objective of this document is to provide a decision tool to designers for designing spacecraft and structures. This document identifies the space environments that will affect the performance of materials and components, e.g., thermal-optical property changes of paints due to UV exposures, AO-induced surface erosion of composites, dimensional changes due to thermal cycling, vacuum-induced moisture outgassing, and surface optical changes due to AO/UV exposures. Where appropriate, relationships between the space environment and the attendant material/system effects are identified. Part 1 covers spacecraft design considerations for the space environment; advanced composites; polymers; adhesives; metals; ceramics; protective coatings; and lubricants, greases, and seals.

Evaluation of non-thermal plasma-induced anticancer effects on human colon cancer cells

PubMed Central

Choi, Jae-Sun; Kim, Jeongho; Hong, Young-Jun; Bae, Woom-Yee; Choi, Eun Ha; Jeong, Joo-Won; Park, Hun-Kuk

2017-01-01

Non-thermal atmospheric-pressure plasma has been introduced in various applications such as sterilization, wound healing, blood coagulation, and other biomedical applications. The most attractive application of non-thermal atmospheric-pressure plasma is in cancer treatment, where the plasma is used to produce reactive oxygen species (ROS) to facilitate cell apoptosis. We investigate the effects of different durations of exposure to dielectric-barrier discharge (DBD) plasma on colon cancer cells using measurement of cell viability and ROS levels, western blot, immunocytochemistry, and Raman spectroscopy. Our results suggest that different kinds of plasma-treated cells can be differentiated from control cells using the Raman data. PMID:28663896

Effect of Thermal Aging and Test Temperatures on Fracture Toughness of SS 316(N) Welds

NASA Astrophysics Data System (ADS)

Dutt, B. Shashank; Babu, M. Nani; Shanthi, G.; Moitra, A.; Sasikala, G.

2018-03-01

The effect of thermal aging and test temperatures on fracture toughness (J 0.2) of SS 316(N) weld material has been studied based on J-R curve evaluations. The aging of the welds was carried out at temperatures 370, 475 and 550 °C and for durations varying from 1000 to 20,000 h. The fracture toughness (J-R curve) tests were carried out at 380 and 550 °C for specimens after all aging conditions, including as-weld condition. The initiation fracture toughness (J 0.2) of the SS 316(N) weld material has shown degradation after 20,000-h aging durations and is reflected in all the test temperatures and aging temperatures. The fracture toughness after different aging conditions and test temperatures, including as-weld condition, was higher than the minimum specified value for this class of welds.

Effect of thermal cycling on ZrO2-Y2O3 thermal barrier coatings

NASA Technical Reports Server (NTRS)

Mcdonald, G.; Hendricks, R. C.

1980-01-01

The paper studies the comparative life of plasma-sprayed ZrO2-Y2O3 thermal barrier coatings on NiCrAlY bond coats on Rene 41 in short (4 min) and long (57 min) thermal cycles at 1040 C in a 0.3-Mach flame. Attention is given to determining the effect of short- and long-duration cycles on ZrO2-Y2O3 coatings, the cause of any cycle frequency effects, and methods to improve tolerance to thermal stress. Short cycles greatly reduced the life of the ceramic coating in terms of time at temperatures as compared to longer cycles, the failed coating indicating compressive failure. The experiments and stress calculations show that repeatedly subjecting a ceramic coating to high rates of initial heating has a more destructive influence on the coating than sustained operation at temperature. The effect of such thermal compressive stresses might be minimized through coating deposition and thickness control and by turbine cycle measurement to keep starting heating rates below critical values.

Duration of shoot elongation in Scots pine varies within the crown and between years.

PubMed

Schiestl-Aalto, Pauliina; Nikinmaa, Eero; Mäkelä, Annikki

2013-10-01

Shoot elongation in boreal and temperate trees typically follows a sigmoid pattern where the onset and cessation of growth are related to accumulated effective temperature (thermal time). Previous studies on leader shoots suggest that while the maximum daily growth rate depends on the availability of resources to the shoot, the duration of the growth period may be an adaptation to long-term temperature conditions. However, other results indicate that the growth period may be longer in faster growing lateral shoots with higher availability of resources. This study investigates the interactions between the rate of elongation and the duration of the growth period in units of thermal time in lateral shoots of Scots pine (Pinus sylvestris). Length development of 202 lateral shoots were measured approximately three times per week during seven growing seasons in 2-5 trees per year in a mature stand and in three trees during one growing season in a sapling stand. A dynamic shoot growth model was adapted for the analysis to determine (1) the maximum growth rate and (2) the thermal time reached at growth completion. The relationship between those two parameters and its variation between trees and years was analysed using linear mixed models. The shoots with higher maximum growth rate within a crown continued to grow for a longer period in any one year. Higher July-August temperature of the previous summer implied a higher requirement of thermal time for growth completion. The results provide evidence that the requirement of thermal time for completion of lateral shoot extension in Scots pine may interact with resource availability to the shoot both from year to year and among shoots in a crown each year. If growing season temperatures rise in the future, this will affect not only the rate of shoot growth but its duration also.

The effects of metals and inhibitors on thermal oxidative degradation reactions of unbranched perfluoroalkyl ethers

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.; Paciorek, K. J. L.; Harris, D. H.; Smythe, M. E.; Nakahara, J. H.; Kratzer, R. H.

1985-01-01

Thermal oxidative degradation studies were performed on unbranched perfluoroalkylethers at 288 C in oxygen. Metals and alloys studied included Ti, Al, and Ti (4 Al, 4 Mn). The mechanism of degradation was by chain scission. Ti and Al promoted less degradation than Ti (4 Al, 4 Mn). The two inhibitors investigated (a perfluorophenyl phosphine and a phosphatriazine) reduced degradation rates by several orders of magnitude. Both inhibitors were effective for the same duration (75 to 100 hours). The phosphatriazine appeared to provide more surface protection.

Effects of thermal processing by nanofluids on vitamin C, total phenolics and total soluble solids of tomato juice.

PubMed

Jafari, S M; Jabari, S S; Dehnad, D; Shahidi, S A

2017-03-01

In this research, our main idea was to apply thermal processing by nanofluids instead of conventional pasteurization processes, to shorten duration of thermal procedure and improve nutritional contents of fruit juices. Three different variables of temperature (70, 80 and 90 °C), nanofluid concentration (0, 2 and 4%) and time (30, 60 and 90 s) were selected for thermal processing of tomato juices by a shell and tube heat exchanger. The results demonstrated that 4% nanofluid concentration, at 30 °C for 30 s could result in 66% vitamin C retention of fresh juice while it was about 56% for the minimum nanofluid concentration and maximum temperature and time. Higher nanoparticle concentrations made tomato juices that require lowered thermal durations, because of better heat transfer to the product, and total phenolic compounds dwindle less severely; In fact, after 30 s thermal processing at 70 °C with 0 and 4% nanoparticles, total phenolic compounds were maintained by 71.9 and 73.6%, respectively. The range of total soluble solids for processed tomato juices was 5.4-5.6, meaning that nanofluid thermal processing could preserve the natural condition of tomato juices successfully. Based on the indices considered, a nanofluid thermal processing with 4% nanoparticle concentration at the temperature of 70 °C for 30 s will result in the best nutritional contents of final tomato juices.

Effect of low thermal budget annealing on surface passivation of silicon by ALD based aluminum oxide films.

PubMed

Vandana; Batra, Neha; Gope, Jhuma; Singh, Rajbir; Panigrahi, Jagannath; Tyagi, Sanjay; Pathi, P; Srivastava, S K; Rauthan, C M S; Singh, P K

2014-10-21

Thermal ALD deposited Al2O3 films on silicon show a marked difference in surface passivation quality as a function of annealing time (using a rapid thermal process). An effective and quality passivation is realized in short anneal duration (∼100 s) in nitrogen ambient which is reflected in the low surface recombination velocity (SRV <10 cm s(-1)). The deduced values are close to the best reported SRV obtained by the high thermal budget process (with annealing time between 10-30 min), conventionally used for improved surface passivation. Both as-deposited and low thermal budget annealed films show the presence of positive fixed charges and this is never been reported in the literature before. The role of field and chemical passivation is investigated in terms of fixed charge and interface defect densities. Further, the importance of the annealing step sequence in the MIS structure fabrication protocol is also investigated from the view point of its effect on the nature of fixed charges.

Effect of local cooling on short-term, intense exercise.

PubMed

Kwon, Young S; Robergs, Robert A; Schneider, Suzanne M

2013-07-01

The widespread belief that local cooling impairs short-term, strenuous exercise performance is controversial. Eighteen original investigations involving cooling before and intermittent cooling during short-term, intensive exercise are summarized in this review. Previous literature examining short-term intensive exercise and local cooling primarily has been limited to the effects on muscle performance immediately or within minutes following cold application. Most previous cooling studies used equal and longer than 10 minutes of pre-cooling, and found that cooling reduced strength, performance and endurance. Because short duration, high intensity exercise requires adequate warm-up to prepare for optimal performance, prolonged pre-cooling is not an effective method to prepare for this type of exercise. The literature related to the effect of acute local cooling immediately before short duration, high intensity isotonic exercise such as weight lifting is limited. However, local intermittent cooling during short-term, high intense exercise may provide possible beneficial effects; first, by pain reduction, caused by an "irritation effect" from hand thermal receptors which block pain sensation, or second, by a cooling effect, whereby stimulation of hand thermal receptors or a slight lowering of blood temperature might alter central fatigue.

Effects of low Earth orbit environment on the Long Duration Exposure Facility thermal control coatings

NASA Technical Reports Server (NTRS)

Sampair, Thomas R.; Berrios, William M.

1992-01-01

One of the benefits of the Long Duration Exposure Facility (LDEF) was the opportunity to study the before and after effects of low earth orbit space environment on the spacecraft thermal control coatings. Since the LDEF's thermal control was totally passive by design, the selection of the external surface absorptivity to emissivity ratio (alpha/epsilon) and the ability for the coating to retain the alpha/epsilon over time was an important consideration in the thermal design of the LDEF. The primary surface coating chosen for the LDEF structure was clear chromic anodized aluminum with an average design alpha/epsilon of 0.32/0.16. External surface absorptivity (alpha) and emissivity (epsilon) were measured on all intercostals, longerons, tray mounting flanges, thermal control panels, and a limited number of experiment surface coatings after the experiment trays were removed from the LDEF structure. All surface alpha/epsilon measurements were made using portable hand held infrared and solar spectrum reflectometers. The absorptivity measurements were taken with a Devices and Services SSR-ER version 5.0 solar spectra reflectometer which has a stated uncertainty of +/- 0.01, and all normal emissivity measurements were made using the Gier Dunkle DB-100 infrared reflectometer also with a stated uncertainty of +/- 0.01. Both instruments were calibrated in the laboratory by LaRC instrumentation personnel before being used in the field at KSC. A combined total of 733 measurements were taken on the anodized aluminum hardware which included the structure (intercostals, longerons, and center ring), earth and space end thermal control panels, and experiment tray mounting flanges. The facility thermal control coatings measured in this survey cover 33 percent of the total exposed LDEF surface area. To correlate low earth orbit environmental effects on the anodized coatings, measurements were taken in both exposed and unexposed surfaces and compared to quality assurance (QA) measurements taken on the new surfaces at the time of hardware fabrication in 1978. The results of investigation are presented.

Thermal effects in laser-assisted embryo hatching

NASA Astrophysics Data System (ADS)

Douglas-Hamilton, Diarmaid H.; Conia, Jerome D.

2000-08-01

Diode lasers [(lambda) equals 1480 nm] are used with in-vitro fertilization [IVF] as a promoter of embryo hatching. A focused laser beam is applied in vitro to form a channel in the zona pellucida (shell) of the pre-embryo. After transfer into the uterus, the embryo hatches: it extrudes itself through the channel and implants into the uterine wall. Laser-assisted hatching can result in improving implantation and pregnancy success rates. We present examples of zone pellucida ablation using animal models. In using the laser it is vital not to damage pre-embryo cells, e.g. by overheating. In order to define safe regimes we have derived some thermal side-effects of zona pellucida removal. The temperature profile in the beam and vicinity is predicted as function of laser pulse duration and power. In a crossed-beam experiment a HeNe laser probe detects the temperature-induced change in refractive index. We find that the diode laser beam produces superheated water approaching 200 C on the beam axis. Thermal histories during and following the laser pulse are given for regions in the neighborhood of the beam. We conclude that an optimum regime exists with pulse duration

Fabrication of lanthanum-doped thorium dioxide by high-energy ball milling and spark plasma sintering

NASA Astrophysics Data System (ADS)

Scott, Spencer M.; Yao, Tiankai; Lu, Fengyuan; Xin, Guoqing; Zhu, Weiguang; Lian, Jie

2017-03-01

High-energy ball milling was used to synthesize Th1-xLaxO2-0.5x (x = 0.09, 0.23) solid solutions, as well as improve the sinterability of ThO2 powders. Dense La-doped ThO2 pellets with theoretical density above 94% were consolidated by spark plasma sintering at temperatures above 1400 °C for 20 min, and the densification behavior and the non-equilibrium effects on phase and structure were investigated. A lattice contraction of the SPS-densified pellets occurred with increasing ball milling duration, and a secondary phase with increased La-content was observed in La-doped pellets. A dependence on the La-content and sintering duration for the onset of localized phase segregation has been proposed. The effects of high-energy ball milling, La-content, and phase formation on the thermal diffusivity were also studied for La-doped ThO2 pellets by laser flash measurement. Increasing La-content and high energy ball milling time decreases thermal diffusivity; while the sintering peak temperature and holding time beyond 1600 °C dramatically altered the temperature dependence of the thermal diffusivity beyond 600 °C.

Thermal expansion behavior of LDEF metal matrix composites

NASA Technical Reports Server (NTRS)

Le, Tuyen D.; Steckel, Gary L.

1993-01-01

The thermal expansion behavior of Long Duration Exposure Facility (LDEF) metal matrix composite materials was studied by (1) analyzing the flight data that was recorded on orbit to determine the effects of orbital time and heating/cooling rates on the performance of the composite materials, and (2) characterizing and comparing the thermal expansion behavior of post-flight LDEF and lab-control samples. The flight data revealed that structures in space are subjected to nonuniform temperature distributions, and thermal conductivity of a material is an important factor in establishing a uniform temperature distribution and avoiding thermal distortion. The flight and laboratory data showed that both Gr/Al and Gr/Mg composites were stabilized after prolonged thermal cycling on orbit. However, Gr/Al composites showed more stable thermal expansion behavior than Gr/Mg composites and offer advantages for space structures particularly where very tight thermal stability requirements in addition to high material performance must be met.

An active thermal control surfaces experiment. [spacecraft temperature determination

NASA Technical Reports Server (NTRS)

Wilkes, D. R.; Brown, M. J.

1979-01-01

An active flight experiment is described that has the objectives to determine the effects of the low earth natural environment and the Shuttle induced environment on selected thermal control and optical surfaces. The optical and thermal properties of test samples will be measured in-situ using an integrating sphere reflectrometer and using calorimetric methods. This experiment has been selected for the Long Duration Exposure Facility (LDEF) flight which will be carried to orbit by the NASA Space Shuttle. The LDEF will remain in orbit to be picked up by a later Shuttle mission and returned for postflight evaluation.

Investigation the effect of modification with nanopowders on crystallization process and microstructure of some alloys

NASA Astrophysics Data System (ADS)

Kuzmanov, P. M.; Popov, S. I.; Yovkov, L. V.; Dimitrova, R. N.; Cherepanov, A. N.; Manolov, V. K.

2017-10-01

Modified with nano-powders (NP), AlSi7Mg aluminum alloy, P265GH steel and GG25 gray cast iron, have been investigated. Thermal and metallographic analyses have been made. For modified AlSi7Mg alloy, reduction of overcooling and duration of crystallization at the initial crystallization and their increase at eutectic crystallization have been found. For cast iron GG25, reduction of overcooling at crystallization was established and for P265GH steel, overcooling was not recorded, only a change in the slope of the temperature dependence. The thermal effects obtained in the crystallization correspond to the refinement of micro- and macrostructures. A mathematical model for crystallization of samples for thermal analysis has been developed and solved.

Space environmental effects on silvered Teflon thermal control surfaces

NASA Technical Reports Server (NTRS)

Hemminger, C. S.; Stuckey, W. K.; Uht, J. C.

1991-01-01

Cumulative space environment effects on Ag/fluorinated ethylene propylene (FEP) were a function of exposure orientation. Samples from nineteen silvered Teflon (Ag/FEP) thermal control surfaces recovered from the Long Duration Exposure Facility (LDEF) were analyzed to determine changes in this material as a function of position on the spacecraft. Although solar absorptance and infrared emittance of measured thermal blanket specimens are relatively unchanged from control specimen values, significant changes in surface morphology, composition and chemistry were observed. Researchers hypothesize that the FEP surfaces on LDEF were degraded by ultraviolet radiation exposure at all orientations, but that the damaged material had been removed by erosion from the blankets exposed to atomic oxygen flux and that contamination is masking the damage on trays flanking the trailing edge.

A new sealed RF-excited CO2 laser for enamel ablation operating at 9.4-μm with a pulse duration of 26-μs

PubMed Central

Chan, Kenneth H.; Jew, Jamison M.; Fried, Daniel

2016-01-01

Several studies over the past 20 years have shown that carbon dioxide lasers operating at wavelengths between 9.3 and 9.6-μm with pulse durations near 20-μs are ideal for hard tissue ablation. Those wavelengths are coincident with the peak absorption of the mineral phase. The pulse duration is close to the thermal relaxation time of the deposited energy of a few microseconds which is short enough to minimize peripheral thermal damage and long enough to minimize plasma shielding effects to allow efficient ablation at practical rates. The desired pulse duration near 20-μs has been difficult to achieve since it is too long for transverse excited atmospheric pressure (TEA) lasers and too short for radio-frequency (RF) excited lasers for efficient operation. Recently, Coherent Inc. (Santa Clara, CA) developed the Diamond J5-V laser for microvia drilling which can produce laser pulses greater than 100-mJ in energy at 9.4-μm with a pulse duration of 26-μs and it can achieve pulse repetition rates of 3 KHz. We report the first results using this laser to ablate dental enamel. Efficient ablation of dental enamel is possible at rates exceeding 50-μm per pulse. This laser is ideally suited for the selective ablation of carious lesions. PMID:27006521

Effect of thermal annealing on the thermoluminescent properties of nano-calcium fluoride and its dose-response characteristics.

PubMed

Mundupuzhakal, J K; Biswas, R H; Chauhan, S; Varma, V; Acharya, Y B; Chakrabarty, B S

2015-12-01

Nano-CaF2, prepared by the co-precipitation method, was annealed under different annealing conditions to improve its thermoluminescence (TL) characteristics. Different annealing parameters, such as temperature (400-700°C), duration (1-4 h) and environment (vacuum and air), were explored. The effect on TL sensitivity, peak position (Tm) and full-width at half-maximum (FWHM) with respect to the different annealing conditions are discussed as they are the measure of crystallinity of the material. Annealing temperature of 500°C with annealing duration of two and a half hours in vacuum provided the highest luminescence response (i.e. maximum sensitivity, minimum peak temperature and FWHM). Wide detectable dose range (5 mGy to 2 kGy), absence of thermal quenching and sufficient activation energy (1.04 eV) of this phosphor make it suitable for dosimetric applications. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Revisiting a pre-inflationary radiation era and its effect on the CMB power spectrum

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

Das, Suratna; Goswami, Gaurav; Rangarajan, Raghavan

2015-06-01

We revisit the scenario where inflation is preceded by a radiation era by considering that the inflaton too could have been in thermal equilibrium early in the radiation era. Hence we take into account not only the effect of a pre-inflationary era on the inflaton mode functions but also that of a frozen thermal distribution of inflaton quanta. We initially discuss in detail the issues relevant to our scenario of a pre-inflationary radiation dominated era and then obtain the scalar power spectrum for this scenario. We find that the power spectrum is free from infrared divergences. We then use themore » WMAP and Planck data to determine the constraints on the inflaton comoving 'temperature' and on the duration of inflation. We find that the best fit value of the duration of inflation is less than 1 e-folding more than what is required to solve cosmological problems, while only an upper bound on the inflaton temperature can be obtained.« less

Laser effects in the manipulation of human eggs and embryos for in vitro fertilization.

PubMed

Tadir, Yona; Douglas-Hamilton, Diarmaid H

2007-01-01

Gamete manipulations using laser micro beams were introduced in 1991 and testing its application for assisted hatching occurred shortly thereafter. This procedure has now become an accepted modality of penetrating or reducing the thickness of the zona pellucida in human in vitro fertilization (IVF). Lasers used in earlier work are summarized. Although the earliest lasers used pulses as long as 15 ms, the simplest and safest laser presently used in this application is the high-power 1480-nm In GaAsP diode, used in pulses with duration typically < 1 ms. Since prevention of damage to the blastomeres is essential, we specifically discuss this system with particular attention to safety considerations. The laser operates by its thermal effect on the zona pellucida, and the implications for embryo safety are discussed in detail. A thermal model is derived using numerical analysis and the effect on the embryo of laser beam power and pulse duration is indicated. Typical recommended protocols and operating values for various applications in the human IVF laboratory are given.

Compensatory escape mechanism at low Reynolds number

PubMed Central

Gemmell, Brad J.; Sheng, Jian; Buskey, Edward J.

2013-01-01

Despite high predation pressure, planktonic copepods remain one of the most abundant groups on the planet. Their escape response provides one of most effective mechanisms to maximize evolutionary fitness. Owing to their small size (100 µm) compared with their predators (>1 mm), increasing viscosity is believed to have detrimental effects on copepods’ fitness at lower temperature. Using high-speed digital holography we acquire 3D kinematics of the nauplius escape including both location and detailed appendage motion. By independently varying temperature and viscosity we demonstrate that at natural thermal extremes, contrary to conventional views, nauplii achieve equivalent escape distance while maintaining optimal velocity. Using experimental results and kinematic simulations from a resistive force theory propulsion model, we demonstrate that a shift in appendage timing creates an increase in power stroke duration relative to recovery stroke duration. This change allows the nauplius to limit losses in velocity and maintain distance during escapes at the lower bound of its natural thermal range. The shift in power stroke duration relative to recovery stroke duration is found to be regulated by the temperature dependence of swimming appendage muscle groups, not a dynamic response to viscosity change. These results show that copepod nauplii have natural adaptive mechanisms to compensate for viscosity variations with temperature but not in situations in which viscosity varies independent of temperature, such as in some phytoplankton blooms. Understanding the robustness of escapes in the wake of environmental changes such as temperature and viscosity has implications in assessing the future health of performance compensation. PMID:23487740

Thermal latency adds to lesion depth after application of high-power short-duration radiofrequency energy: Results of a computer-modeling study.

PubMed

Irastorza, Ramiro M; d'Avila, Andre; Berjano, Enrique

2018-02-01

The use of ultra-short RF pulses could achieve greater lesion depth immediately after the application of the pulse due to thermal latency. A computer model of irrigated-catheter RF ablation was built to study the impact of thermal latency on the lesion depth. The results showed that the shorter the RF pulse duration (keeping energy constant), the greater the lesion depth during the cooling phase. For instance, after a 10-second pulse, lesion depth grew from 2.05 mm at the end of the pulse to 2.39 mm (17%), while after an ultra-short RF pulse of only 1 second the extra growth was 37% (from 2.22 to 3.05 mm). Importantly, short applications resulted in deeper lesions than long applications (3.05 mm vs. 2.39 mm, for 1- and 10-second pulse, respectively). While shortening the pulse duration produced deeper lesions, the associated increase in applied voltage caused overheating in the tissue: temperatures around 100 °C were reached at a depth of 1 mm in the case of 1- and 5-second pulses. However, since the lesion depth increased during the cooling period, lower values of applied voltage could be applied in short durations in order to obtain lesion depths similar to those in longer durations while avoiding overheating. The thermal latency phenomenon seems to be the cause of significantly greater lesion depth after short-duration high-power RF pulses. Balancing the applied total energy when the voltage and duration are changed is not the optimal strategy since short pulses can also cause overheating. © 2017 Wiley Periodicals, Inc.

Effect of coating thickness on microstructure and low temperature cyclic thermal fatigue behavior of thermal barrier coating (Al2O3)

NASA Astrophysics Data System (ADS)

Verma, Vijay; Patel, Sachin; Swarnkar, Vikas; K, Rajput S.

2018-03-01

Effect of coating thickness on low temperature cyclic thermal fatigue behaviour of Al2O3 thermal barrier coating (TBC) was concluded through the cyclic furnace thermal fatigue test (CFTF). Detonation gun (Thermal Spray) process was used for bond coating of NiCr and top coating of Al2O3 on Aluminium Alloy 6061 substrate. Top coating was done at two level of thickness to investigate the effect of coating thickness on low temperature cyclic thermal fatigue. The top coat of thickness 100μm-150μm was considered as thin TBC while the top coat of thickness 250μm-300μm was considered as thick TBC. The thickness of bond coat was taken as 120μm constant for both level of Al2O3 top coating. During CFTF test appearance of any crack on coated surface was adapted as main criterion of coating failure. Crack initiation was observed at edges and corner of thin thermal barrier coating after 60 number of thermal fatigue cycles while in case of thick thermal barrier coating these crack initiation was observed after 72 cycles of cyclic thermal fatigue test. During the study, it was observed that thick thermal barrier coating survived for long duration in comparison of thin TBC. Hence it can be concluded that application of thick TBC is more favourable to improve thermal durability of any component.

Photochemical mechanisms of ocular photic injury (Abstract Only)

NASA Astrophysics Data System (ADS)

Stuck, Bruce E.; Lund, David J.; Zuclich, Joseph A.

2000-03-01

Mechanisms of photic injury to the eye can be categorized as photochemical, photothermal or photodistruptive. Exposure wavelength, exposure duration, ocular tissue characteristics and response criteria are key factors in the delineation of the ocular injury mechanisms. Depending on the exposure condition, one or all of the laser-tissue interaction mechanisms can be involved. Although photic injury to the eye was initially assumed to involve thermal mechanisms, more recent research has demonstrated that ocular effects can be produced by light exposure without a significant retinal temperature rise. Photochemical mechanisms are also implicated in UV photic injury to the cornea and lens. Exposure of the retina to short visible wavelengths for prolonged durations results in photochemical retinal damage with negligible localized retinal temperature elevation. For exposure conditions where photochemical mechanisms are dominate, the reciprocity of irradiance and exposure duration is apparent. The latency until observation of a photochemical lesion is often 24-48 hours whereas a thermal lesion is observed immediately or within a few hours after the exposure. Action spectra for photochemical injury to the eye are discussed in the context of ocular injury thresholds and current permissible exposure limits.

Optimization of the generator settings for endobiliary radiofrequency ablation.

PubMed

Barret, Maximilien; Leblanc, Sarah; Vienne, Ariane; Rouquette, Alexandre; Beuvon, Frederic; Chaussade, Stanislas; Prat, Frederic

2015-11-10

To determine the optimal generator settings for endobiliary radiofrequency ablation. Endobiliary radiofrequency ablation was performed in live swine on the ampulla of Vater, the common bile duct and in the hepatic parenchyma. Radiofrequency ablation time, "effect", and power were allowed to vary. The animals were sacrificed two hours after the procedure. Histopathological assessment of the depth of the thermal lesions was performed. Twenty-five radiofrequency bursts were applied in three swine. In the ampulla of Vater (n = 3), necrosis of the duodenal wall was observed starting with an effect set at 8, power output set at 10 W, and a 30 s shot duration, whereas superficial mucosal damage of up to 350 μm in depth was recorded for an effect set at 8, power output set at 6 W and a 30 s shot duration. In the common bile duct (n = 4), a 1070 μm, safe and efficient ablation was obtained for an effect set at 8, a power output of 8 W, and an ablation time of 30 s. Within the hepatic parenchyma (n = 18), the depth of tissue damage varied from 1620 μm (effect = 8, power = 10 W, ablation time = 15 s) to 4480 μm (effect = 8, power = 8 W, ablation time = 90 s). The duration of the catheter application appeared to be the most important parameter influencing the depth of the thermal injury during endobiliary radiofrequency ablation. In healthy swine, the currently recommended settings of the generator may induce severe, supratherapeutic tissue damage in the biliary tree, especially in the high-risk area of the ampulla of Vater.

Pharmacological action of choline and aspirin coadministration on acute inflammatory pain.

PubMed

Yong-Ping, Shi; Jin-Da, Wang; Ru-Huan, Wang; Xiang-Di, Zhao; Hai-Tao, Yu; Hai, Wang

2011-09-01

Non-steroidal anti-inflammatory drugs (NSAIDs) are effective for relieving pain but undesirable side effects limit their clinical usefulness. Choline is a α7 nicotinic receptor agonist that has antinociceptive effects in a variety of pain models. Drug combination is a strategy in the management of pain to reduce side effects. The aim of the study was to evaluate the nature of the interaction between choline and aspirin in two distinct inflammatory pain models. The analgesic mechanism of choline was also investigated. In the writhing test, intravenous administration of choline or aspirin showed dose-dependent antinociceptive activity, and isobolographic analysis revealed a synergistic nature of the interaction between choline and aspirin. More importantly, coadministration choline with aspirin could significantly shorten the antinociceptive latency of aspirin and prolong the antinociceptive duration of aspirin in the writhing test. In the carrageenan test, single administration of choline or aspirin significantly attenuated carrageenan-induced thermal hyperalgesia in a dose-dependent relationship. Coadministration of non-analgesic doses of aspirin with choline significantly suppressed the thermal hyperalgesia, with a longer duration efficacy. Furthermore, we found that α7 nicotinic, muscarinic, and opioid-receptors are involved in the antinociceptive effect of choline in the writhing test and the antinociceptive effect produced by systemically administered choline may be via a peripheral mechanism. In conclusion, coadministration of choline and aspirin holds promise for development as a safe analgesic drug combination for inflammatory pain, with a higher potency and longer duration than either aspirin or choline alone. Copyright © 2011 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.

An analysis of LDEF-exposed silvered FEP teflon thermal blanket material

NASA Technical Reports Server (NTRS)

Young, Philip R.; Slemp, Wayne S.

1991-01-01

The characterization of selected silvered fluorinated ethylene propylene (FEP) teflon thermal blanket material which received 5 years and 9 months of exposure to the LEO environment on the Long Duration Exposure Facility is reported. X-ray photoelectron spectroscopy, infrared, and thermal analyses did not detect a significant change at the molecular level as the result of this exposure. However, various microscopic analyses revealed a roughening of the coating surface due to atomic oxygen erosion which resulted in some materials changing from specular reflectors of visible radiation to diffuse reflectors. The potential effect of silicon-containing molecular contamination on these materials is addressed.

Generalizing the flash technique in the front-face configuration to measure the thermal diffusivity of semitransparent solids

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

Pech-May, Nelson Wilbur; Department of Applied Physics, CINVESTAV Unidad Mérida, carretera Antigua a Progreso km6, A.P. 73 Cordemex, Mérida Yucatán 97310, México; Mendioroz, Arantza

2014-10-15

In this work, we have extended the front-face flash method to retrieve simultaneously the thermal diffusivity and the optical absorption coefficient of semitransparent plates. A complete theoretical model that allows calculating the front surface temperature rise of the sample has been developed. It takes into consideration additional effects, such as multiple reflections of the heating light beam inside the sample, heat losses by convection and radiation, transparency of the sample to infrared wavelengths, and heating pulse duration. Measurements performed on calibrated solids, covering a wide range of absorption coefficients (from transparent to opaque) and thermal diffusivities, validate the proposed method.

Seasonal acclimatization of the cardiac potassium currents (IK1 and IKr) in an arctic marine teleost, the navaga cod (Eleginus navaga).

PubMed

Abramochkin, Denis V; Vornanen, Matti

2015-12-01

Several freshwater fishes of north-temperate latitudes exhibit marked seasonal changes in cardiac action potential (AP) waveform as an outcome of temperature-dependent changes in the density of delayed rectifiers (IKr, IKs) and inward rectifier (IK1) potassium currents. Thus far, ionic mechanisms of cardiac excitability in arctic marine fishes have not been examined. To this end we examined ventricular AP and the role of two major potassium currents (IK1, IKr) in repolarization of cardiac AP in winter-acclimatized (WA, caught in March) and summer-acclimatized (SA, caught in September) navaga cod (Eleginus navaga) of the White Sea. The duration of ventricular AP of WA navaga at 3 °C (APD50 = 659.5 ± 32.8 ms) was similar to the AP duration of SA navaga at 12 °C (APD50 = 543.9 ± 14.6 ms) (p > 0.05) indicating complete thermal compensation of AP duration. This acclimation effect was associated with strong up-regulation of the cardiac potassium currents in winter. Densities of ventricular IK1 (at -120 mV) and IKr (at +50 mV) of the WA navaga at 3 °C were 2.9 times and 2.8 times, respectively, higher than those of the SA navaga at 12 °C, thus indicating marked thermal overcompensation. Qualitatively similar results were obtained from atrial myocytes. Seasonal changes in IK1 and IKr are more than sufficient to explain the complete thermal compensation of ventricular AP duration. The excellent acclimation capacity of cardiac excitability of the navaga cod is probably needed to maintain high cardiac performance at subzero temperatures in winter and to increase thermal resilience of cardiac function under seasonally variable arctic temperature conditions.

Lasers in Ophthalmology

PubMed Central

Rock, William

1986-01-01

Lasers provide a convenient source of focused light energy that can be delivered to a target and, specifically, can do one of two things in the eye. Lasers can create a thermal lesion, that is, a burn, in the same way that light from the sun that is focused with a magnifying glass will burn paper. This thermal lesion can create a scar or hole in the target tissue. In photocoagulation techniques depend on the thermal effect, i.e., the absorption characteristics of the tissues to be coagulated indicate the wavelength to be chosen. The three important ocular light absorbers are melanin, hemoglobin and xanthophyll. For anterior segment work, melanin in the iris and trabecular meshwork is the most important absorber and hemoglobin in blood is the second most important. In retinal work, hemoglobin and xanthophyll absorption are the most important absorbers. The second type of laser effect is achieved with very short duration, high-powered lasers such as the Q-switched neodymium YAG. Non-thermal effects cause disruption of any target tissue either transparent or opaque. PMID:21267103

Analysis of systems hardware flown on LDEF. Results of the systems special investigation group

NASA Technical Reports Server (NTRS)

Dursch, Harry W.; Spear, W. Steve; Miller, Emmett A.; Bohnhoff-Hlavacek, Gail L.; Edelman, Joel

1992-01-01

The Long Duration Exposure Facility (LDEF) was retrieved after spending 69 months in low Earth orbit (LEO). LDEF carried a remarkable variety of mechanical, electrical, thermal, and optical systems, subsystems, and components. The Systems Special Investigation Group (Systems SIG) was formed to investigate the effects of the long duration exposure to LEO on systems related hardware and to coordinate and collate all systems analysis of LDEF hardware. Discussed here is the status of the LDEF Systems SIG investigation through the end of 1991.

Analysis of systems hardware flown on LDEF. Results of the systems special investigation group

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

Dursch, H.W.; Spear, W.S.; Miller, E.A.

1992-04-01

The Long Duration Exposure Facility (LDEF) was retrieved after spending 69 months in low Earth orbit (LEO). LDEF carried a remarkable variety of mechanical, electrical, thermal, and optical systems, subsystems, and components. The Systems Special Investigation Group (Systems SIG) was formed to investigate the effects of the long duration exposure to LEO on systems related hardware and to coordinate and collate all systems analysis of LDEF hardware. Discussed here is the status of the LDEF Systems SIG investigation through the end of 1991.

Coronal Seismology of Flare-Excited Standing Slow-Mode Waves Observed by SDO/AIA

NASA Astrophysics Data System (ADS)

Wang, Tongjiang; Ofman, Leon; Davila, Joseph M.

2016-05-01

Flare-excited longitudinal intensity oscillations in hot flaring loops have been recently detected by SDO/AIA in 94 and 131 Å bandpasses. Based on the interpretation in terms of a slow-mode wave, quantitative evidence of thermal conduction suppression in hot (>9 MK) loops has been obtained for the first time from measurements of the polytropic index and phase shift between the temperature and density perturbations (Wang et al. 2015, ApJL, 811, L13). This result has significant implications in two aspects. One is that the thermal conduction suppression suggests the need of greatly enhanced compressive viscosity to interpret the observed strong wave damping. The other is that the conduction suppression provides a reasonable mechanism for explaining the long-duration events where the thermal plasma is sustained well beyond the duration of impulsive hard X-ray bursts in many flares, for a time much longer than expected by the classical Spitzer conductive cooling. In this study, we model the observed standing slow-mode wave in Wang et al. (2015) using a 1D nonlinear MHD code. With the seismology-derived transport coefficients for thermal conduction and compressive viscosity, we successfully simulate the oscillation period and damping time of the observed waves. Based on the parametric study of the effect of thermal conduction suppression and viscosity enhancement on the observables, we discuss the inversion scheme for determining the energy transport coefficients by coronal seismology.

Stability of blood potassium: effects of duration, temperature and transport during 10 hours storage of human whole blood in serum and plasma.

PubMed

Dromigny, Jacques-Albert; Robert, Emmanuel

2017-08-01

To comply with the pre-analytical requirements of ISO EN 15189, we investigated the stability of potassium, a very critical and sensitive analyte. We took into count effects of duration, temperature and transport after 10 hours storage of human whole blood in serum and plasma. Blood of 12 healthy subjects was analyzed after 4, 6, 8 and 10 hours of storage. Three study groups were designed: samples stored in laboratory at room temperature, transported by car during 4 hours at a temperature of 21±1̊C, with or without previous thermal shock (20 min at 4±1 ̊C) before transportation. Variations in concentration were expressed as mean bias from baseline using the analytical change limit (ACL) and the reference change value (RCV). Using RCV, we considered that potassium was biologically stable during 10 hours whatever our study groups. Considering ACL, potassium in serum was not stable after the thermal shock. We conclude that whole blood in lithium-heparin tubes may be used for routine potassium analysis even if long car transportation and previous thermal shock is involved. It confirms that potassium analysis can be still performed in locations distant from a medical laboratory.

Space environmental effects on silvered Teflon thermal control surfaces

NASA Technical Reports Server (NTRS)

Hemminger, C. S.; Stuckey, W. K.; Uht, J. C.

1992-01-01

Cumulative space environmental effects on silver/fluorinated ethylene propylene (Ag/FEP) were a function of exposure orientation. Samples from nineteen silvered Teflon (Ag/FEP) thermal control surfaces recovered from the Long Duration Exposure Facility (LDEF) were analyzed to determine changes in this material as a function of position on the spacecraft. Although solar absorptance and infrared emittance of measured thermal blanket specimens are relatively unchanged from control specimen values, significant changes in surface morphology, composition, and chemistry were observed. We hypothesize that the FEP surfaces on the LDEF are degraded by UV radiation at all orientations, but that the damaged material has been removed by erosion from the blankets exposed to atomic oxygen flux and that contamination is masking the damage in some areas on the trays flanking the trailing edge.

Effects of electrocautery on transvenous lead insulation materials.

PubMed

Lim, Kiam-Khiang; Reddy, Shantanu; Desai, Shrojal; Smelley, Matthew; Kim, Susan S; Beshai, John F; Lin, Albert C; Burke, Martin C; Knight, Bradley P

2009-04-01

Insulation defects are a leading cause of transvenous lead failure. The purpose of this study was to determine the effects of electrocautery on transvenous lead insulation materials. A preparation was done to simulate dissection of a transvenous lead from tissues. Radiofrequency energy was delivered using a standard cautery blade at outputs of 10, 20, and 30 W, for 3 and 6 seconds, using parallel and perpendicular blade orientations on leads with outermost insulations of silicone rubber, polyurethane, and silicone-polyurethane copolymer. Damage to each lead segment was classified after visual and microscopic analysis. Significant insulation damage occurred to almost all polyurethane leads. Full insulation breaches were observed with 30 W regardless of application duration with a parallel direction and with all power outputs with a perpendicular direction. Thermal insulation damage to copolymer insulation was similar to that of the polyurethane leads. In contrast, there was no thermal damage to silicone leads, regardless of the power output and duration of power delivery. However, mechanical insulation damage was observed to all silicone leads when at least 20 W was applied in a direction perpendicular to the lead. Polyurethane (PU55D) and copolymer materials have low thermal stability and are highly susceptible to thermal damage during cautery. Implanting physicians should be aware of the lead insulation materials being used during implant procedures and their properties. The use of direct contact cautery on transvenous leads should be minimized to avoid damage to the lead, especially on leads with polyurethane or copolymer outer insulations.

Evaluation of the parameters affecting bone temperature during drilling using a three-dimensional dynamic elastoplastic finite element model.

PubMed

Chen, Yung-Chuan; Tu, Yuan-Kun; Zhuang, Jun-Yan; Tsai, Yi-Jung; Yen, Cheng-Yo; Hsiao, Chih-Kun

2017-11-01

A three-dimensional dynamic elastoplastic finite element model was constructed and experimentally validated and was used to investigate the parameters which influence bone temperature during drilling, including the drill speed, feeding force, drill bit diameter, and bone density. Results showed the proposed three-dimensional dynamic elastoplastic finite element model can effectively simulate the temperature elevation during bone drilling. The bone temperature rise decreased with an increase in feeding force and drill speed, however, increased with the diameter of drill bit or bone density. The temperature distribution is significantly affected by the drilling duration; a lower drilling speed reduced the exposure duration, decreases the region of the thermally affected zone. The constructed model could be applied for analyzing the influence parameters during bone drilling to reduce the risk of thermal necrosis. It may provide important information for the design of drill bits and surgical drilling powers.

Shift in room-temperature photoluminescence of low-fluence Si+-implanted SiO2 films subjected to rapid thermal annealing.

PubMed

Fu, Ming-Yue; Tsai, Jen-Hwan; Yang, Cheng-Fu; Liao, Chih-Hsiung

2008-12-01

We experimentally demonstrate the effect of the rapid thermal annealing (RTA) in nitrogen flow on photoluminescence (PL) of SiO 2 films implanted by different doses of Si + ions. Room-temperature PL from 400-nm-thick SiO 2 films implanted to a dose of 3×10 16 cm -2 shifted from 2.1 to 1.7 eV upon increasing RTA temperature (950-1150 °C) and duration (5-20 s). The reported approach of implanting silicon into SiO 2 films followed by RTA may be effective for tuning Si-based photonic devices.

Shift in room-temperature photoluminescence of low-fluence Si+-implanted SiO2 films subjected to rapid thermal annealing

PubMed Central

Fu, Ming-Yue; Tsai, Jen-Hwan; Yang, Cheng-Fu; Liao, Chih-Hsiung

2008-01-01

We experimentally demonstrate the effect of the rapid thermal annealing (RTA) in nitrogen flow on photoluminescence (PL) of SiO2 films implanted by different doses of Si+ ions. Room-temperature PL from 400-nm-thick SiO2 films implanted to a dose of 3×1016 cm−2 shifted from 2.1 to 1.7 eV upon increasing RTA temperature (950–1150 °C) and duration (5–20 s). The reported approach of implanting silicon into SiO2 films followed by RTA may be effective for tuning Si-based photonic devices. PMID:27878029

Preliminary findings of the LDEF Materials Special Investigation Group

NASA Technical Reports Server (NTRS)

Stein, Bland A.; Pippin, H. Gary

1992-01-01

The retrieval of NASA's LDEF from low Earth orbit provided an opportunity for the study of long duration space environmental effects on materials. The five year, nine month flight of the LDEF greatly enhanced the potential value of most LDEF materials. NASA recognized this potential by forming the LDEF Space Environmental Effects on Materials Special Investigation Group (MSIG). Its goal is to explore the expanded materials analysis opportunities available in the LDEF structure and on experiment trays. The charter and scope of MSIG activities is presented, followed by an overview of the preliminary MSIG observations. These observations of low Earth orbit environmental effects on materials were made in-space during LDEF retrieval and during LDEF tray disintegration. Also presented are initial findings of lab analyses of LDEF materials. Included are effects of individual environmental parameters: atomic oxygen, ultraviolet radiation, meteoroid and debris impacts, thermal cycling, vacuum, and contamination, plus combined effects of these parameters. Materials considered include anodized aluminum, polymer matrix composites, polymer films, silvered Teflon thermal blankets, and a white thermal control paint.

LDEF's contribution to the selection of thermal control coatings for the Space Station

NASA Technical Reports Server (NTRS)

Babel, Henry W.

1995-01-01

The design of the Space Station presented new challenges in the selection and qualification of thermal control materials that would survive in low Earth orbit for a duration of up to 30 years. Prior to LDEF, flight data were obtained from Orbiting Solar Observatory (OSO) satellites, a number of Orbiter flights, and limited ground tests. The excellent data obtained from the OSO satellites were based on calorimetry and temperature measurements which were transmitted to Earth; these satellites were not recovered. For some of these flight experiments it was difficult to distinguish between changes due to contamination, atomic oxygen (AO), ultraviolet radiation (UV), particle radiation and the synergistic effects between them. The data from Shuttle flights were primarily focused on developing a better understanding of atomic oxygen (AO) effects. Although UV and AO were present, the relatively short duration of the Orbiter flights, about one week, was viewed as too short to show the effects from UV or possible synergistic interactions with AO and contamination. At the beginning of the program in 1989 there was no established design data base for AO resistant thermal control coatings for the Space Station. Then came the Long Duration Exposure Facility (LDEF). It provided the first long life data for materials exposed and recovered from space with a characterized environment. Post flight analysis proved data on the effects of contamination on optical properties in the ram (velocity) and wake directions and the erosion of Teflon and multilayer insulation (MLI) covers. The results from LDEF confirmed and, in some cases, modified the approach used for the Space Station, as well as helped to focus our development activities. These development activities resulted in a number of new technical solutions which are applicable to many spacecraft surfaces and missions. LDEF also showed the detrimental effects that could occur from silicone contamination, an issue that has not been completely resolved. An investigation was initiated in 1993 on the effects of silicone contamination and was continuing at the time this paper was prepared.

Simulated Space Environment Effects on a Candidate Solar Sail Material

NASA Technical Reports Server (NTRS)

Kang, Jin Ho; Bryant, Robert G.; Wilkie, W. Keats; Wadsworth, Heather M.; Craven, Paul D.; Nehls, Mary K.; Vaughn, Jason A.

2017-01-01

For long duration missions of solar sails, the sail material needs to survive harsh space environments and the degradation of the sail material controls operational lifetime. Therefore, understanding the effects of the space environment on the sail membrane is essential for mission success. In this study, we investigated the effect of simulated space environment effects of ionizing radiation, thermal aging and simulated potential damage on mechanical, thermal and optical properties of a commercial off the shelf (COTS) polyester solar sail membrane to assess the degradation mechanisms on a feasible solar sail. The solar sail membrane was exposed to high energy electrons (about 70 keV and 10 nA/cm2), and the physical properties were characterized. After about 8.3 Grad dose, the tensile modulus, tensile strength and failure strain of the sail membrane decreased by about 20 95%. The aluminum reflective layer was damaged and partially delaminated but it did not show any significant change in solar absorbance or thermal emittance. The effect on mechanical properties of a pre-cracked sample, simulating potential impact damage of the sail membrane, as well as thermal aging effects on metallized PEN (polyethylene naphthalate) film will be discussed.

Predictive modeling of infrared radiative heating in tomato dry-peeling process: Part I. Model development

USDA-ARS?s Scientific Manuscript database

Infrared (IR) dry-peeling has emerged as an effective non-chemical alternative to conventional lye and steam methods of peeling tomatoes. Successful peel separation induced by IR radiation requires the delivery of a sufficient amount of thermal energy onto tomato surface in a very short duration. Th...

Long Duration Life Test of Propylene Glycol Water Based Thermal Fluid Within Thermal Control Loop

NASA Technical Reports Server (NTRS)

Le, Hung; Hill, Charles; Stephan, Ryan A.

2010-01-01

Evaluations of thermal properties and resistance to microbial growth concluded that 50% Propylene Glycol (PG)-based fluid and 50% de-ionized water mixture was desirable for use as a fluid within a vehicle s thermal control loop. However, previous testing with a commercial mixture of PG and water containing phosphate corrosion inhibitors resulted in corrosion of aluminum within the test system and instability of the test fluid. This paper describes a follow-on long duration testing and analysis of 50% Propylene Glycol (PG)-based fluid and 50% de-ionized water mixture with inorganic corrosion inhibitors used in place of phosphates. The test evaluates the long-term fluid stability and resistance to microbial and chemical changes

Plant response to environmental conditions: assessing potential production, water demand, and negative effects of water deficit

PubMed Central

Tardieu, François

2013-01-01

This paper reviews methods for analyzing plant performance and its genetic variability under a range of environmental conditions. Biomass accumulation is linked every day to available light in the photosynthetically active radiation (PAR) domain, multiplied by the proportion of light intercepted by plants and by the radiation use efficiency. Total biomass is cumulated over the duration of the considered phase (e.g., plant cycle or vegetative phase). These durations are essentially constant for a given genotype provided that time is corrected for temperature (thermal time). Several ways of expressing thermal time are reviewed. Two alternative equations are presented, based either on the effect of transpiration, or on yield components. Their comparative interests and drawbacks are discussed. The genetic variability of each term of considered equations affects yield under water deficit, via mechanisms at different scales of plant organization and time. The effect of any physiological mechanism on yield of stressed plants acts via one of these terms, although the link is not always straightforward. Finally, I propose practical ways to compare the productivity of genotypes in field environments, and a “minimum dataset” of environmental data and traits that should be recorded for that. PMID:23423357

Disinfection effect of non-thermal atmospheric pressure plasma for foodborne bacteria

NASA Astrophysics Data System (ADS)

Pervez, Mohammad Rasel; Inomata, Takanori; Ishijima, Tatsuo; Kakikawa, Makiko; Uesugi, Yoshihiko; Tanaka, Yasunori; Yano, Toshihiro; Miwa, Shoji; Noguchi, Akinori

2015-09-01

Non-thermal atmospheric pressure plasma (NAPP) exposure can be a suitable alternative for bacteria inactivation in food processing industry. Specimen placed in the enclosure are exposed to various reactive radicals produced within the discharge chamber. It is also exposed to the periodic variation of the electric field strength in the chamber. Dielectric barrier discharge is produced by high voltage pulse (Vpp = 18 kV, pulse width 20 μs, repetition frequency 10 kHz) in a polypropylene box (volume = 350 cm3) using helium as main feed gas. Inactivation efficiency of NAPP depends on the duration of NAPP exposure, applied voltage pulse strength and type, pulse duration, electrode separation and feed gas composition. In this study we have investigated inactivation of Bacillus lichenformis spore as an example of food borne bacteria. Keeping applied voltage, electrode configuration and total gas flow rate constant, spores are exposed to direct NAPP for different time duration while O2 concentration in the feed gas composition is varied. 10 minutes NAPP exposure resulted in ~ 3 log reduction of Bacillus lichenformis spores for 1% O2concentration (initial concentration ~ 106 / specimen). This work is supported by research and development promotion grant provided by the Hokuriku Industrial Advancement Center.

Analysis of Silverized Teflon Thermal Control Material Flown on the Long Duration Exposure Facility

NASA Technical Reports Server (NTRS)

Pippin, H. Gary

1995-01-01

Silver backed teflon (Ag/FEP) material used for thermal control on the Long Duration Exposure Facility (LDEF) has been examined in detail. Optical, mechanical, and chemical properties were characterized for specimens exposed to a variety of space environmental conditions. Recession rates were determined for this material. Samples were obtained from virtually every LDEF location except the Earth-end. Atomic oxygen exposed regions changed from specular to diffusely reflective.

Time-dependence of the holographic spectral function: diverse routes to thermalisation

DOE PAGES

Banerjee, Souvik; Ishii, Takaaki; Joshi, Lata Kh; ...

2016-08-08

Here, we develop a new method for computing the holographic retarded propagator in generic (non-) equilibrium states using the state/geometry map. We check that our method reproduces the thermal spectral function given by the Son-Starinets prescription. The time-dependence of the spectral function of a relevant scalar operator is studied in a class of non-equilibrium states. The latter are represented by AdS-Vaidya geometries with an arbitrary parameter characterising the timescale for the dual state to transit from an initial thermal equilibrium to another due to a homogeneous quench. For long quench duration, the spectral function indeed follows the thermal form atmore » the instantaneous effective temperature adiabatically, although with a slight initial time delay and a bit premature thermalisation. At shorter quench durations, several new non-adiabatic features appear: (i) time-dependence of the spectral function is seen much before than that in the effective temperature (advanced time-dependence), (ii) a big transfer of spectral weight to frequencies greater than the initial temperature occurs at an intermediate time (kink formation) and (iii) new peaks with decreasing amplitudes but in greater numbers appear even after the effective temperature has stabilised (persistent oscillations). We find four broad routes to thermalisation for lower values of spatial momenta. At higher values of spatial momenta, kink formations and persistent oscillations are suppressed, and thermalisation time decreases. The general thermalisation pattern is globally top-down, but a closer look reveals complexities.« less

Analysis of Solar-Heated Thermal Wadis to Support Extended-Duration Lunar Exploration

NASA Technical Reports Server (NTRS)

Balasubramaniam, R.; Wegeng, R. S.; Gokoglu, S. A.; Suzuki, N. H.; Sacksteder, K. R.

2010-01-01

The realization of the renewed exploration of the Moon presents many technical challenges; among them is the survival of lunar surface assets during periods of darkness when the lunar environment is very cold. Thermal wadis are engineered sources of stored solar energy using modified lunar regolith as a thermal storage mass that can enable the operation of lightweight robotic rovers or other assets in cold, dark environments without incurring potential mass, cost, and risk penalties associated with various onboard sources of thermal energy. Thermal wadi-assisted lunar rovers can conduct a variety of long-duration missions including exploration site surveys; teleoperated, crew-directed, or autonomous scientific expeditions; and logistics support for crewed exploration. This paper describes a thermal analysis of thermal wadi performance based on the known solar illumination of the moon and estimates of producible thermal properties of modified lunar regolith. Analysis was performed for the lunar equatorial region and for a potential Outpost location near the lunar south pole. The results are presented in some detail in the paper and indicate that thermal wadis can provide the desired thermal energy reserve, with significant margin, for the survival of rovers or other equipment during periods of darkness.

Effects of temperature, thermal exposure, and fatigue on an alumina/aluminum composite

NASA Technical Reports Server (NTRS)

Olsen, G. C.

1980-01-01

An experimental investigation of the mechanical properties and microstructure of an aluminum matrix/polycrystalline alumina fiber composite material is discussed. The effects of fabrication, isothermal exposure (up to 10,000 hours at 590 K), thermal cycling (6000 cycles between 200 K and 590 K), fatigue (1,000,000 tension-tension cycles) were determined by mechanical testing and metallurgical analysis. The fabrication process severely degraded the fiber strength by reducing the alumina to a nonstoichiometric form and quenching in the resultant vacancies and stress fields. However, isothermal exposure, thermal cycling, and fatigue cycling all restored the fiber strength by enhancing vacancy annihilation. Comparison of the as-fabricated material with other aerospace materials shows that it is an attractive candidate for select applications. Long duration isothermal exposure weakened the matrix by overaging and through the diffusional loss of lithium to a surface reaction forming lithium carbonate. Thermal cycling initiated cracks in the matrix and fibers. Tension-tension fatigue cycling caused no apparent damage to the as-fabricated material but in fact, strengthened it to the rule-of-mixtures value. Fatigue cycling after thermal exposure did have a cumulative damage effect.

Simulated Space Environment Effects on a Candidate Solar Sail Material

NASA Technical Reports Server (NTRS)

Kang, Jin Ho; Bryant, Robert G.; Wilkie, W. Keats; Wadsworth, Heather M.; Craven, Paul D.; Nehls, Mary K.; Vaughn, Jason A.

2017-01-01

For long duration missions of solar sail vehicles, the sail material needs to survive the harsh space environment as the degradation of the sail material determines its operational lifetime. Therefore, understanding the effects of the space environment on the sail membrane is essential for mission success. In this study, the effect of simulated space environments of ionizing radiation and thermal aging were investigated. In order to assess some of the potential damage effects on the mechanical, thermal and optical properties of a commercial off the shelf (COTS) polyester solar sail membrane. The solar sail membrane was exposed to high energy electrons [about 70 keV and 10 nA/cm(exp. 2)], and the physical properties were characterized. After about 8.3 Grad dose, the tensile modulus, tensile strength and failure strain of the sail membrane decreased by 20 to 95%. The aluminum reflective layer was damaged and partially delaminated but it did not show any significant change in solar absorbance or thermal emittance. The mechanical properties of a precracked sample, simulating potential impact damage of the sail membrane, as well as thermal aging effects on metallized PEN (polyethylene naphthalate) film, will be discussed.

Pulse thermal processing of functional materials using directed plasma arc

DOEpatents

Ott, Ronald D [Knoxville, TN; Blue, Craig A [Knoxville, TN; Dudney, Nancy J [Knoxville, TN; Harper, David C [Kingston, TN

2007-05-22

A method of thermally processing a material includes exposing the material to at least one pulse of infrared light emitted from a directed plasma arc to thermally process the material, the pulse having a duration of no more than 10 s.

Optimization of the generator settings for endobiliary radiofrequency ablation

PubMed Central

Barret, Maximilien; Leblanc, Sarah; Vienne, Ariane; Rouquette, Alexandre; Beuvon, Frederic; Chaussade, Stanislas; Prat, Frederic

2015-01-01

AIM: To determine the optimal generator settings for endobiliary radiofrequency ablation. METHODS: Endobiliary radiofrequency ablation was performed in live swine on the ampulla of Vater, the common bile duct and in the hepatic parenchyma. Radiofrequency ablation time, “effect”, and power were allowed to vary. The animals were sacrificed two hours after the procedure. Histopathological assessment of the depth of the thermal lesions was performed. RESULTS: Twenty-five radiofrequency bursts were applied in three swine. In the ampulla of Vater (n = 3), necrosis of the duodenal wall was observed starting with an effect set at 8, power output set at 10 W, and a 30 s shot duration, whereas superficial mucosal damage of up to 350 μm in depth was recorded for an effect set at 8, power output set at 6 W and a 30 s shot duration. In the common bile duct (n = 4), a 1070 μm, safe and efficient ablation was obtained for an effect set at 8, a power output of 8 W, and an ablation time of 30 s. Within the hepatic parenchyma (n = 18), the depth of tissue damage varied from 1620 μm (effect = 8, power = 10 W, ablation time = 15 s) to 4480 μm (effect = 8, power = 8 W, ablation time = 90 s). CONCLUSION: The duration of the catheter application appeared to be the most important parameter influencing the depth of the thermal injury during endobiliary radiofrequency ablation. In healthy swine, the currently recommended settings of the generator may induce severe, supratherapeutic tissue damage in the biliary tree, especially in the high-risk area of the ampulla of Vater. PMID:26566429

Comparison of the effect of land-sea thermal contrast on interdecadal variations in winter and summer blockings

NASA Astrophysics Data System (ADS)

He, Yongli; Huang, Jianping; Li, Dongdong; Xie, Yongkun; Zhang, Guolong; Qi, Yulei; Wang, Shanshan; Totz, Sonja

2017-11-01

The influence of winter and summer land-sea surface thermal contrast on blocking for 1948-2013 is investigated using observations and the coupled model intercomparison project outputs. The land-sea index (LSI) is defined to measure the changes of zonal asymmetric thermal forcing under global warming. The summer LSI shows a slower increasing trend than winter during this period. For the positive of summer LSI, the EP flux convergence induced by the land-sea thermal forcing in the high latitude becomes weaker than normal, which induces positive anomaly of zonal-mean westerly and double-jet structure. Based on the quasiresonance amplification mechanism, the narrow and reduced westerly tunnel between two jet centers provides a favor environment for more frequent blocking. Composite analysis demonstrates that summer blocking shows an increasing trend of event numbers and a decreasing trend of durations. The numbers of the short-lived blocking persisting for 5-9 days significantly increases and the numbers of the long-lived blocking persisting for longer than 10 days has a weak increase than that in negative phase of summer LSI. The increasing transient wave activities induced by summer LSI is responsible for the decreasing duration of blockings. The increasing blocking due to summer LSI can further strengthen the continent warming and increase the summer LSI, which forms a positive feedback. The opposite dynamical effect of LSI on summer and winter blocking are discussed and found that the LSI-blocking negative feedback partially reduces the influence of the above positive feedback and induce the weak summer warming rate.

Effect of viscoplasticity on ignition sensitivity of an HMX based PBX

NASA Astrophysics Data System (ADS)

Hardin, D. Barrett; Zhou, Min

2017-01-01

The effect of viscoplastic deformation of the energetic component (HMX) on the mechanical, thermal, and ignition responses of a two-phase (HMX and Estane) PBX is analyzed. PBX microstructures are subjected to impact loading from a constant velocity piston traveling at a rate of 50 to 200 m/s. The analysis uses a 2D cohesive finite element framework, the focus of which is to evaluate the relative ignition sensitivity of the materials to determine the effect of the viscoplasticity of HMX on the responses. To delineate this effect, two sets of calculations are carried out; one set assumes the HMX grains are fully hyperelastic, and the other set assumes the HMX grains are elastic-viscoplastic. Results show that PBX specimens with elastic-viscoplastic HMX grains experience lower average and peak temperature rises, and as a result, show lower numbers of hotspots. An ignition criterion based on a criticality threshold obtained from chemical kinetics is used to quantify the ignition behavior of the materials. The criterion focuses on hotspot size and temperature to determine if a hotspot will undergo thermal runaway. It is found that the viscoplasticity of HMX increases the minimum load duration, mean load duration, threshold loading velocity, and total input energy required for ignition.

Long Duration Exposure Facility (LDEF). Mission 1 Experiments

NASA Technical Reports Server (NTRS)

Clark, L. G. (Editor); Kinard, W. H. (Editor); Carter, D. L., Jr. (Editor); Jones, J. L., Jr. (Editor)

1984-01-01

Spaceborne experiments using the space shuttle payload known as the Long Duration Exposure Facility are described. Experiments in the fields of materials, coatings, thermal systems, power and propulsion, electronic, and optics are discussed.

HISTORICAL SNOW AMOUNTS IN THE LAKE EFFECT REGION OF LAKE SUPERIOR: EVIDENCE OF CLIMATE CHANGE IN THE GREAT LAKES

EPA Science Inventory

Recent studies (Levitus et al., .2000) suggest a warming of the world ocean over the past 50 years. This could be occurring in the Great Lakes also but thermal measurements are lacking. Historical trends in natural phenomena, such as the duration of ice cover on lakes, provide in...

Neurofeedback and biofeedback with 37 migraineurs: a clinical outcome study

PubMed Central

2010-01-01

Background Traditional peripheral biofeedback has grade A evidence for effectively treating migraines. Two newer forms of neurobiofeedback, EEG biofeedback and hemoencephalography biofeedback were combined with thermal handwarming biofeedback to treat 37 migraineurs in a clinical outpatient setting. Methods 37 migraine patients underwent an average of 40 neurofeedback sessions combined with thermal biofeedback in an outpatient biofeedback clinic. All patients were on at least one type of medication for migraine; preventive, abortive or rescue. Patients kept daily headache diaries a minimum of two weeks prior to treatment and throughout treatment showing symptom frequency, severity, duration and medications used. Treatments were conducted an average of three times weekly over an average span of 6 months. Headache diaries were examined after treatment and a formal interview was conducted. After an average of 14.5 months following treatment, a formal interview was conducted in order to ascertain duration of treatment effects. Results Of the 37 migraine patients treated, 26 patients or 70% experienced at least a 50% reduction in the frequency of their headaches which was sustained on average 14.5 months after treatments were discontinued. Conclusions All combined neuro and biofeedback interventions were effective in reducing the frequency of migraines with clients using medication resulting in a more favorable outcome (70% experiencing at least a 50% reduction in headaches) than just medications alone (50% experience a 50% reduction) and that the effect size of our study involving three different types of biofeedback for migraine (1.09) was more robust than effect size of combined studies on thermal biofeedback alone for migraine (.5). These non-invasive interventions may show promise for treating treatment-refractory migraine and for preventing the progression from episodic to chronic migraine. PMID:20205867

The utilization of nonthermal blue (405-425 nm) and near infrared (850-890 nm) light in aesthetic dermatology and surgery-a multicenter study.

PubMed

Lask, Gary; Fournier, Nathalie; Trelles, Mario; Elman, Monica; Scheflan, Michael; Slatkine, Michael; Naimark, Jenny; Harth, Yoram

2005-12-01

A major cause of skin aging is a chronic micro-inflammation triggered by UV radiation and external pollutants. It has been demonstrated that blue light diminishes inflammatory conditions and near infrared light enhances circulation. To assess the effectiveness of a non thermal dual wavelength -- blue (405 - 420 nm) and near infrared (850 - 900 nm) -- light source in skin rejuvenation, in the reduction of the duration of post skin resurfacing erythema and in the acceleration of healing of post surgical conditions (face lift and breast augmentation). We have utilized a non contact, hand free dual wavelength light source (iClearXL and Clear100XL, Curelight Ltd) to treat over 60 patients and perform three controlled studies in four centers. Follow up duration was three months. Control group for photo-rejuvenation consisted of patients treated with Glycolic peeling and daily appliance of vitamin C Control group for post skin resurfacing erythema duration consisted of patients untreated by the light source and control group for post surgical healing consisted of patients untreated by the light source or treated by the light source on one side only. Post skin resurfacing erythema duration is reduced by 90%. The healing of post surgical conditions is substantially accelerated and discomfort is reduced. The anti aging effect of the light source includes: reduction of pore size in 90% of patients with stable results at three months follow up, enhanced skin radiance in 90% of patients with stable results at three months follow up and smoothing of fine wrinkles in 45% of patients with stable results at three months follow up. The control group showed poor results which were stable for a duration of less than one month. A non thermal, non contact / hand free light source emitting at 405-420 nm and 850-900 nm considerably enhances aesthetic and surgical aesthetic procedures without consuming user time.

Effects of long duration exposure to simulated space environment on nonmetallic materials properties

NASA Technical Reports Server (NTRS)

Peacock, C. L., Jr.; Whitaker, A. F.

1983-01-01

Nonmetallic materials specimens from the Viking program were tested in situ invacuo after continuous thermal vacuum exposure from 1971/1972 to the present. Eleven tests were done on appropriate specimens of 30 materials; however, no single material received all the tests. Some specimens also were exposed to 1 or 2.5 MeV electrons at differing fluences before testing. Baseline exposure data is reported for graphite/epoxy specimens that were exposed to vacuum since 1974. These materials were transferred to the thermal vacuum storage facility for future in situ testing and irradiation. Thin G/E specimens were tensile tested after thermal-vacuum cycling exposure. Photomicrographic examinations and SEM analyses were done on the failed specimens.

Effect of oxygen plasma and thermal oxidation on shallow nitrogen-vacancy centers in diamond

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

Kim, M.; Rugar, D., E-mail: rugar@us.ibm.com; Center for Probing the Nanoscale, Stanford University, Stanford, California 94305

2014-07-28

We investigate the effect of two different surface treatments on shallow nitrogen-vacancy (NV) centers in diamond. Short duration oxygen plasma exposure is found to damage near-surface NV centers, resulting in their disappearance in fluorescence images. Subsequent annealing creates large numbers of new NV centers, attributed to plasma-induced vacancy creation. By tracking individual NV centers during thermal oxidation, we show that oxidation at 550 °C results in modest improvement of spin coherence. Higher temperature oxidations correlate with gradual decline in spin coherence and eventual instability of NV centers before ultimate disappearance. This is indicative of a reduction of the NV-to-surface distance duemore » to oxidative etching. Thermal oxidation can offer controlled access to near-surface NV spins at the nanometer scale, an important requirement for many applications of NV-based nanomagnetometry.« less

Influences of thermal decontamination on mercury removal, soil properties, and repartitioning of coexisting heavy metals.

PubMed

Huang, Yu-Tuan; Hseu, Zeng-Yei; Hsi, Hsing-Cheng

2011-08-01

Thermal treatment is a useful tool to remove Hg from contaminated soils. However, thermal treatment may greatly alter the soil properties and cause the coexisting contaminants, especially trace metals, to transform and repartition. The metal repartitioning may increase the difficulty in the subsequent process of a treatment train approach. In this study, three Hg-contaminated soils were thermally treated to evaluate the effects of treating temperature and duration on Hg removal. Thermogravimetric analysis was performed to project the suitable heating parameters for subsequent bench-scale fixed-bed operation. Results showed that thermal decontamination at temperature>400°C successfully lowered the Hg content to<20 mg kg(-1). The organic carbon content decreased by 0.06-0.11% and the change in soil particle size was less significant, even when the soils were thermally treated to 550°C. Soil clay minerals such as kaolinite were shown to be decomposed. Aggregates were observed on the surface of soil particles after the treatment. The heavy metals tended to transform into acid-extractable, organic-matter bound, and residual forms from the Fe/Mn oxide bound form. These results suggest that thermal treatment may markedly influence the effectiveness of subsequent decontamination methods, such as acid washing or solvent extraction. Copyright © 2011 Elsevier Ltd. All rights reserved.

Prediction of In-Space Durability of Protected Polymers Based on Ground Laboratory Thermal Energy Atomic Oxygen

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; deGroh, Kim K.; Rutledge, Sharon; DiFilippo, Frank J.

1996-01-01

The probability of atomic oxygen reacting with polymeric materials is orders of magnitude lower at thermal energies (greater than O.1 eV) than at orbital impact energies (4.5 eV). As a result, absolute atomic oxygen fluxes at thermal energies must be orders of magnitude higher than orbital energy fluxes, to produce the same effective fluxes (or same oxidation rates) for polymers. These differences can cause highly pessimistic durability predictions for protected polymers and polymers which develop protective metal oxide surfaces as a result of oxidation if one does not make suitable calibrations. A comparison was conducted of undercut cavities below defect sites in protected polyimide Kapton samples flown on the Long Duration Exposure Facility (LDEF) with similar samples exposed in thermal energy oxygen plasma. The results of this comparison were used to quantify predicted material loss in space based on material loss in ground laboratory thermal energy plasma testing. A microindent hardness comparison of surface oxidation of a silicone flown on the Environmental Oxygen Interaction with Materials-III (EOIM-III) experiment with samples exposed in thermal energy plasmas was similarly used to calibrate the rate of oxidation of silicone in space relative to samples in thermal energy plasmas exposed to polyimide Kapton effective fluences.

Comprehensive stabilization mechanism of electron-beam irradiated polyacrylonitrile fibers to shorten the conventional thermal treatment

PubMed Central

Park, Sejoon; Yoo, Seung Hwa; Kang, Ha Ri; Jo, Seong Mu; Joh, Han-Ik; Lee, Sungho

2016-01-01

An electron beam was irradiated on polyacrylonitrile (PAN) fibers prior to thermal stabilization. The electron-beam irradiation effectively shortened the thermal stabilization process by one fourth compared with the conventional thermal stabilization process. A comprehensive mechanistic study was conducted regarding this shortening of the thermal stabilization by electron-beam irradiation. Various species of chain radicals were produced in PAN fibers by electron-beam irradiation and existed for a relatively long duration, as observed by electron spin resonance spectroscopy. Subsequently, these radicals were gradually oxidized to peroxy radicals in the presence of oxygen under storage or heating. We found that these peroxy radicals (CO) enabled such an effective shortcut of thermal stabilization by acting as intermolecular cross-linking and partial aromatization points in the low temperature range (100–130 °C) and as earlier initiation seeds of successive cyclization reactions in the next temperature range (>130–140 °C) of thermal stabilization. Finally, even at a low irradiation dose (200 kGy), followed by a short heat treatment (230 °C for 30 min), the PAN fibers were sufficiently stabilized to produce carbon fibers with tensile strength and modulus of 2.3 and 216 GPa, respectively, after carbonization. PMID:27349719

Temperature measurements during laser skin welding

NASA Astrophysics Data System (ADS)

Fried, Nathaniel M.; Choi, Bernard; Welch, Ashley J.; Walsh, Joseph T., Jr.

1999-06-01

A thermal camera was used to measure surface temperatures during laser skin welding to provide feedback for optimization of the laser parameters. Two-cm-long, full- thickness incisions were made in guinea pig skin. India ink was used as an absorber. Continuous-wave, 1.06-μm, Nd:YAG laser radiation was scanned over the incisions, producing a pulse duration of approximately 100 ms. Cooling durations between scans of 1.6, 4.0, and 8.0 s were studied with total operation times of 3, 5, and 10 min, respectively. A laser spot diameter of 5 mm was used with the power constant at 10 W. Thermal images were obtained at 30 frames per second with a thermal camera detecting 3.5 micrometers radiation. Surface temperatures were recorded at 0, 1, and 6 mm from the center line of the incision. Cooling durations between scans of 1.6 s and 4.0 s in vitro resulted in temperatures at the weld site remaining above ~65°C for prolonged periods of time. Cooling durations between scans as long as 8.0 s were sufficient both in vitro and in vivo to prevent a significant rise in baseline temperatures at the weld site over time.

Repeatability Measurements of Apparent Thermal Conductivity of Multilayer Insulation (MLI)

NASA Astrophysics Data System (ADS)

Vanderlaan, M.; Stubbs, D.; Ledeboer, K.; Ross, J.; Van Sciver, S.; Guo, W.

2017-12-01

This report presents and discusses the results of repeatability experiments gathered from the multi-layer insulation thermal conductivity experiment (MIKE) for the measurement of the apparent thermal conductivity of multi-layer insulation (MLI) at variable boundary temperatures. Our apparatus uses a calibrated thermal link between the lower temperature shield of a concentric cylinder insulation assembly and the cold head of a cryocooler to measure the heat leak. In addition, thermocouple readings are taken in-between the MLI layers. These measurements are part of a multi-phase NASA-Yetispace-FSU collaboration to better understand the repeatability of thermal conductivity measurements of MLI. NASA provided five 25 layer coupons and requested boundary temperatures of 20 K and 300 K. Yetispace provided ten 12-layer coupons and requested boundary temperatures of 77 K and 293 K. Test conditions must be met for a duration of four hours at a steady state variance of less than 0.1 K/hr on both cylinders. Temperatures from three Cernox® temperature sensors on each of the two cylinders are averaged to determine the boundary temperatures. A high vacuum, less than 10-5 torr, is maintained for the duration of testing. Layer density varied from 17.98 - 26.36 layers/cm for Yetispace coupons and 13.05 - 17.45 layers/cm for the NASA coupons. The average measured heat load for the Yetispace coupons was 2.40 W for phase-one and 2.92 W for phase-two. The average measured heat load for the NASA coupons was 1.10 W. This suggests there is still unknown variance of MLI performance. It has been concluded, variations in the insulation installation heavy effect the apparent thermal conductivity and are not solely dependent on layer density.

Thermal shock effect on Mechanical and Physical properties of pre-moisture treated GRE composite

NASA Astrophysics Data System (ADS)

Chakraverty, A. P.; Panda, A. B.; Mohanty, U. K.; Mishra, S. C.; Biswal, B. B.

2018-03-01

Many practical situations may be encountered under which a GFRP (Glass fibre reinforced polymer) composite, during its service life, is exposed to the severities of sudden temperature fluctuations. Moisture absorption of GRE (Glass fibre reinforced epoxy) composites followed by various gradients of temperature fluctuations may cause thermo- mechanical degradation. It is on this context, the hand layed GRE composite samples are exposed to up-thermal shock (-40°C to +50°C) and down-thermal shock (+50°C to -40°C) for various time interval after several periods of moisture (hydrothermal/hygrothermal) conditioning. The thermally shocked GRE specimens are put to 3-point bend test to divulge inter laminar shear strength (ILSS). Least ILSS values are recorded for the samples with maximum period of moisture treatments under with both up-thermal and down-thermal shock conditions. Lower glass transition temperature (Tg) values, as revealed through the low temperature DSC test, are exhibited at maximum durations of both up-thermal and down-thermal shock for the samples with higher periods of hygrothermal/hydrothermal treatments. SEM fractographs of representative GRE specimens after optimum period of moisture treatments and thermal shock show the various modes of failures.

The performance of thermal control coatings on LDEF and implications to future spacecraft

NASA Technical Reports Server (NTRS)

Wilkes, Donald R.; Miller, Edgar R.; Mell, Richard J.; Lemaster, Paul S.; Zwiener, James M.

1993-01-01

The stability of thermal control coatings over the lifetime of a satellite or space platform is crucial to the success of the mission. With the increasing size, complexity, and duration of future missions, the stability of these materials becomes even more important. The Long Duration Exposure Facility (LDEF) offered an excellent testbed to study the stability and interaction of thermal control coatings in the low-Earth orbit (LEO) space environment. Several experiments on LDEF exposed thermal control coatings to the space environment. This paper provides an overview of the different materials flown and their stability during the extended LDEF mission. The exposure conditions, exposure environment, and measurements of materials properties (both in-space and postflight) are described. The relevance of the results and the implications to the design and operation of future space vehicles are also discussed.

Advanced extravehicular protective systems study, volume 1

NASA Technical Reports Server (NTRS)

Sutton, J. G.; Heimlich, P. F.; Tepper, E. H.

1972-01-01

An appraisal was made of advanced portable and emergency life support systems concepts for space station, space shuttle, lunar base, and Mars EVA missions. Specifications are given, and the methodology is described. Subsystem studies and systems integration efforts are summarized. Among the conclusions are the following: (1) For long duration missions, a configuration incorporating a regenerable CO2 control subsystem and a thermal control subsystem utilizing a minimum of expendables decreases the vehicle penalty of present configurations. (2) For shorter duration missions, a configuration incorporating an expendable water thermal control subsystem is the most competitive subsystem; regenerable CO2 control subsystems if properly developed are competitive with nonregenerable counterparts. (3) The CO2 reduction and oxygen reclamation withing the parent vehicle is only competitive when there are three or more parent vehicle resupply periods. (4) For long duration emergency systems of one hour or more, inherent redundancy within the primary configuration to provide emergency thermal control is the most competitive approach.

Pulsed lasers in dentistry: sense or nonsense?

NASA Astrophysics Data System (ADS)

Koort, Hans J.; Frentzen, Matthias

1991-05-01

The great interest in the field of laser applications in dentistry provokes the question, if all these new techniques may really fulfill advantages, which are expected after initial in-vitro studies. Whereas laser surgery of soft oral tissues has been developed to a standard method, laser treatment of dental hard tissues and the bone are attended with many unsolved problems. Different laser types, especially pulsed lasers in a wide spectrum of wavelengths have been proofed for dental use. Today neither the excimer lasers, emitting in the far uv-range from 193 to 351 nm, nor the mid-infrared lasers like Nd:YAG (1,064 μm), Ho:YAG (2,1 μm) and Er:YAG (2,96 μm) or the C02-laser (10,6 μm) show mechanism of interaction more carefully and faster than a preparation of teeth with diamond drillers. The laser type with the most precise and considerate treatment effects in the moment is the short pulsed (15 ns) ArF-excimer laser with a wavelength of 193 nm. However this laser type has not yet the effectivity of mechanical instruments and it needs a mirror system to deliver the radiation. Histological results point out, that this laser shows no significant pathological alterations in the adjacent tissues. Another interesting excimer laser, filled with XeCI and emitting at a wavelength of 308 nm has the advantage to be good to deliver through quartz fibers. A little more thermal influence is to be seen according to the longer wavelength. Yet the energy density, necessary to cut dental hard tissues will not be reached with the laser systems available now. Both the pulsed Er:YAG- (2,94 μm, pulse duration 250 s) and the Ho:YAG -laser (2,1 μm, pulse duration 250 μs) have an effective coupling of the laser energy to hydrogeneous tissues, but they do not work sufficient on healthy enamel and dentine. The influence to adjacent healthy tissue is not tolerable, especially in regard of the thermal damage dentine and pulp tissues. Moreover, like the 193 nm ArF-excimer laser radiation the Er:YAG-laser radiation could also only be delivered via mirror systems, while the radiation of the Ho:YAG-Laser can be well transmitted through quartz fibers. The energy of the well known and in other medical disciplines often used Nd:YAG - laser (1,064 μm, pulse duration 150 us) laser can be transmitted through fiber systems without problems, but this laser has not the effectivity to work sufficient on healthy hard dental tissues due to the high transmission in mineralized dental tissues. The thermal injuries of this laser type are not tolerable. The short pulsed TEA-C02-laser (9,6 and 10,6 μm, pulse duration 200-300 ns), which has an excellent coupling not only to the hydrogeneous tissues but also to the mineralized tissues could be an alternative system to prepare dental tissues. The greatest disadvantage of this system is the noneffective delivery of the light energy through flexible fiber systems, which are still in development. Another good chance perhaps will have the q-switched Neodym, Erbium and Holmium:- YAG lasers with pulse durations of about some hundred ns. Both, possible thermal influences and possible disruptive effects should be small enough to let the adjacent tissues undamaged.

Long Duration Exposure Facility (LDEF)

NASA Technical Reports Server (NTRS)

1984-01-01

The Long Duration Exposure Facility (LDEF) was designed by the Marshall Space Flight Center (MSFC) to test the performance of spacecraft materials, components, and systems that have been exposed to the environment of micrometeoroids and space debris for an extended period of time. The LDEF proved invaluable to the development of future spacecraft and the International Space Station (ISS). The LDEF carried 57 science and technology experiments, the work of more than 200 investigators. MSFC`s experiments included: Trapped Proton Energy Determination to determine protons trapped in the Earth's magnetic field and the impact of radiation particles; Linear Energy Transfer Spectrum Measurement Experiment which measures the linear energy transfer spectrum behind different shielding configurations; Atomic oxygen-Simulated Out-gassing, an experiment that exposes thermal control surfaces to atomic oxygen to measure the damaging out-gassed products; Thermal Control Surfaces Experiment to determine the effects of the near-Earth orbital environment and the shuttle induced environment on spacecraft thermal control surfaces; Transverse Flat-Plate Heat Pipe Experiment, to evaluate the zero-gravity performance of a number of transverse flat plate heat pipe modules and their ability to transport large quantities of heat; Solar Array Materials Passive LDEF Experiment to examine the effects of space on mechanical, electrical, and optical properties of lightweight solar array materials; and the Effects of Solar Radiation on Glasses. Launched aboard the Space Shuttle Orbiter Challenger's STS-41C mission April 6, 1984, the LDEF remained in orbit for five years until January 1990 when it was retrieved by the Space Shuttle Orbiter Columbia STS-32 mission and brought back to Earth for close examination and analysis.

Broad spectrum infrared thermal desorption of wipe-based explosive and narcotic samples for trace mass spectrometric detection.

PubMed

Forbes, Thomas P; Staymates, Matthew; Sisco, Edward

2017-08-07

Wipe collected analytes were thermally desorbed using broad spectrum near infrared heating for mass spectrometric detection. Employing a twin tube filament-based infrared emitter, rapid and efficiently powered thermal desorption and detection of nanogram levels of explosives and narcotics was demonstrated. The infrared thermal desorption (IRTD) platform developed here used multi-mode heating (direct radiation and secondary conduction from substrate and subsequent convection from air) and a temperature ramp to efficiently desorb analytes with vapor pressures across eight orders of magnitude. The wipe substrate experienced heating rates up to (85 ± 2) °C s -1 with a time constant of (3.9 ± 0.2) s for 100% power emission. The detection of trace analytes was also demonstrated from complex mixtures, including plastic-bonded explosives and exogenous narcotics, explosives, and metabolites from collected artificial latent fingerprints. Manipulation of the emission power and duration directly controlled the heating rate and maximum temperature, enabling differential thermal desorption and a level of upstream separation for enhanced specificity. Transitioning from 100% power and 5 s emission duration to 25% power and 30 s emission enabled an order of magnitude increase in the temporal separation (single seconds to tens of seconds) of the desorption of volatile and semi-volatile species within a collected fingerprint. This mode of operation reduced local gas-phase concentrations, reducing matrix effects experienced with high concentration mixtures. IRTD provides a unique platform for the desorption of trace analytes from wipe collections, an area of importance to the security sector, transportation agencies, and customs and border protection.

Modeling of hydrogen-air diffusion flame

NASA Technical Reports Server (NTRS)

Isaac, K. M.

1988-01-01

Work performed during the first six months of the project duration for NASA Grant (NAG-1-861) is reported. An analytical and computational study of opposed jet diffusion flame for the purpose of understanding the effects of contaminants in the reactants and thermal diffusion of light species on extinction and reignition of diffusion flames is in progress. The methodologies attempted so far are described.

Design of a Resistively Heated Thermal Hydraulic Simulator for Nuclear Rocket Reactor Cores

NASA Technical Reports Server (NTRS)

Litchford, Ron J.; Foote, John P.; Ramachandran, Narayanan; Wang, Ten-See; Anghaie, Samim

2007-01-01

A preliminary design study is presented for a non-nuclear test facility which uses ohmic heating to replicate the thermal hydraulic characteristics of solid core nuclear reactor fuel element passages. The basis for this testing capability is a recently commissioned nuclear thermal rocket environments simulator, which uses a high-power, multi-gas, wall-stabilized constricted arc-heater to produce high-temperature pressurized hydrogen flows representative of reactor core environments, excepting radiation effects. Initially, the baseline test fixture for this non-nuclear environments simulator was configured for long duration hot hydrogen exposure of small cylindrical material specimens as a low cost means of evaluating material compatibility. It became evident, however, that additional functionality enhancements were needed to permit a critical examination of thermal hydraulic effects in fuel element passages. Thus, a design configuration was conceived whereby a short tubular material specimen, representing a fuel element passage segment, is surrounded by a backside resistive tungsten heater element and mounted within a self-contained module that inserts directly into the baseline test fixture assembly. With this configuration, it becomes possible to create an inward directed radial thermal gradient within the tubular material specimen such that the wall-to-gas heat flux characteristics of a typical fuel element passage are effectively simulated. The results of a preliminary engineering study for this innovative concept are fully summarized, including high-fidelity multi-physics thermal hydraulic simulations and detailed design features.

Planktonic events may cause polymictic-dimictic regime shifts in temperate lakes

PubMed Central

Shatwell, Tom; Adrian, Rita; Kirillin, Georgiy

2016-01-01

Water transparency affects the thermal structure of lakes, and within certain lake depth ranges, it can determine whether a lake mixes regularly (polymictic regime) or stratifies continuously (dimictic regime) from spring through summer. Phytoplankton biomass can influence transparency but the effect of its seasonal pattern on stratification is unknown. Therefore we analysed long term field data from two lakes of similar depth, transparency and climate but one polymictic and one dimictic, and simulated a conceptual lake with a hydrodynamic model. Transparency in the study lakes was typically low during spring and summer blooms and high in between during the clear water phase (CWP), caused when zooplankton graze the spring bloom. The effect of variability of transparency on thermal structure was stronger at intermediate transparency and stronger during a critical window in spring when the rate of lake warming is highest. Whereas the spring bloom strengthened stratification in spring, the CWP weakened it in summer. The presence or absence of the CWP influenced stratification duration and under some conditions determined the mixing regime. Therefore seasonal plankton dynamics, including biotic interactions that suppress the CWP, can influence lake temperatures, stratification duration, and potentially also the mixing regime. PMID:27074883

Remediation of hydrocarbon-contaminated soils by ex situ microwave treatment: technical, energy and economic considerations.

PubMed

Falciglia, P P; Vagliasindi, F G A

2014-01-01

In this study, the remediation of diesel-polluted soils was investigated by simulating an ex situ microwave (MW) heating treatment under different conditions, including soil moisture, operating power and heating duration. Based on experimental data, a technical, energy and economic assessment for the optimization of full-scale remediation activities was carried out. Main results show that the operating power applied significantly influences the contaminant removal kinetics and the moisture content in soil has a major effect on the final temperature reachable during MW heating. The first-order kinetic model showed an excellent correlation (r2 > 0.976) with the experimental data for residual concentration at all operating powers and for all soil moistures tested. Excellent contaminant removal values up to 94.8% were observed for wet soils at power higher than 600 W for heating duration longer than 30 min. The use of MW heating with respect to a conventional ex situ thermal desorption treatment could significantly decrease the energy consumption needed for the removal of hydrocarbon contaminants from soils. Therefore, the MW treatment could represent a suitable cost-effective alternative to the conventional thermal treatment for the remediation of hydrocarbon-polluted soil.

Planktonic events may cause polymictic-dimictic regime shifts in temperate lakes.

PubMed

Shatwell, Tom; Adrian, Rita; Kirillin, Georgiy

2016-04-14

Water transparency affects the thermal structure of lakes, and within certain lake depth ranges, it can determine whether a lake mixes regularly (polymictic regime) or stratifies continuously (dimictic regime) from spring through summer. Phytoplankton biomass can influence transparency but the effect of its seasonal pattern on stratification is unknown. Therefore we analysed long term field data from two lakes of similar depth, transparency and climate but one polymictic and one dimictic, and simulated a conceptual lake with a hydrodynamic model. Transparency in the study lakes was typically low during spring and summer blooms and high in between during the clear water phase (CWP), caused when zooplankton graze the spring bloom. The effect of variability of transparency on thermal structure was stronger at intermediate transparency and stronger during a critical window in spring when the rate of lake warming is highest. Whereas the spring bloom strengthened stratification in spring, the CWP weakened it in summer. The presence or absence of the CWP influenced stratification duration and under some conditions determined the mixing regime. Therefore seasonal plankton dynamics, including biotic interactions that suppress the CWP, can influence lake temperatures, stratification duration, and potentially also the mixing regime.

Rapid screening of pharmaceutical drugs using thermal desorption - SALDI mass spectrometry

NASA Astrophysics Data System (ADS)

Grechnikov, A. A.; Kubasov, A. E.; Georgieva, V. B.; Borodkov, A. S.; Nikiforov, S. M.; Simanovsky, Ya O.; Alimpiev, S. S.

2012-12-01

A novel approach to the rapid screening of pharmaceutical drugs by surface assisted laser desorption-ionization (SALDI) mass spectrometry with the rotating ball interface coupled with temperature programmed thermal desorption has been developed. Analytes were thermally desorbed and deposited onto the surface of amorphous silicon substrate attached to the rotating ball. The ball was rotated and the deposited analytes were analyzed using SALDI. The effectiveness of coupling SALDI mass spectrometry with thermal desorption was evaluated by the direct and rapid analysis of tablets containing lidocaine, diphenhydramine and propranolol without any sample pretreatment. The overall duration of the screening procedure was 30÷40 sec. Real urine samples were studied for drug analysis. It is shown that with simple preparation steps, urine samples can be quantitatively analyzed using the proposed technique with the detection limits in the range of 0.2÷0.5 ng/ml.

Experimental study and modelling of deuterium thermal release from Be-D co-deposited layers

NASA Astrophysics Data System (ADS)

Baldwin, M. J.; Schwarz-Selinger, T.; Doerner, R. P.

2014-07-01

A study of the thermal desorption of deuterium from 1 µm thick co-deposited Be-(0.1)D layers formed at 330 K by a magnetron sputtering technique is reported. A range of thermal desorption rates 0 ⩽ β ⩽ 1.0 K s-1 are explored with a view to studying the effectiveness of the proposed ITER wall and divertor bake procedure (β = 0 K s-1) to be carried out at 513 and 623 K. Fixed temperature bake durations up to 24 h are examined. The experimental thermal release data are used to validate a model input into the Tritium Migration and Analysis Program (TMAP-7). Good agreement with experiment is observed for a TMAP-7 model incorporating trap populations of activation energies for D release of 0.80 and 0.98 eV, and a dynamically computed surface D atomic to molecular recombination rate.

Using the shuttlebox experimental design to determine temperature preference for juvenile Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi)

PubMed Central

Kovachik, Colin; Charles, Colin; Enders, Eva C

2018-01-01

Abstract Temperature preference for various fishes has often been used as a proxy of optimal temperature for growth and metabolism due to the ease of obtaining preferred temperature zones in laboratory experiments. Several laboratory designs and methods have been proposed to examine preferred temperature zones, however, differences between them (i.e. thermal gradients vs. static temperatures in chambers and duration of acclimation/experimental periods) have led to varying measurements, precluding comparisons between experiments, species and/or life-stages. Juvenile Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi), a species listed as threatened in Alberta and of special concern in British Columbia, were tested in an automated shuttlebox experimental design (Loligo® Systems) to determine average and ranges of temperature preference (Tpref) and occupied temperatures. Previous lab studies suggested that Westslope Cutthroat Trout (WCT) prefer temperatures around 15°C, however, we found that average daytime Tpref for lab-reared juvenile WCT was substantially higher at 18.6°C, with occupied temperatures ranging between 11.9°C and 26.0°C throughout the duration of trials. This seems to indicate that despite constant lab-rearing conditions of 12°C, juvenile WCT may tolerate and even prefer warmer water temperatures. The duration of the acclimation period (1h, 12 h and 24 h) did not have an effect on Tpref, however, Tpref differed significantly for variable trial durations (12 h, 24 h and 36 h). A closer look at thermal trends throughout trials revealed that photoperiod significantly influenced Tpref, as nighttime temperature preference reached consistently 26°C. Collectively, these results suggest that shuttlebox experiments on WCT need to take into account the photoperiod, as behaviour may drive Tpref more so than the duration of acclimation periods. PMID:29692899

Thermal plasticity of diving behavior, aquatic respiration, and locomotor performance in the Mary River turtle Elusor macrurus.

PubMed

Clark, Natalie J; Gordos, Matthew A; Franklin, Craig E

2008-01-01

Locomotion is a common measure of performance used in studies of thermal acclimation because of its correlation with predator escape and prey capture. However, for sedentary animals such as freshwater turtles, we propose that diving behavior may be a more ecologically relevant measure of performance. Increasing dive duration in hatchling turtles reduces predator exposure and therefore functions as an ecological benefit. Diving behavior is thermally dependent, and in some species of freshwater turtles, it is also reliant on aquatic respiration. This study examined the influence of thermal acclimation on diving behavior, aquatic respiration, and locomotor performance in the endangered, bimodally respiring Mary River turtle Elusor macrurus. Diving behavior was found to partially acclimate at 17 degrees C, with turtles acclimated to a cold temperature (17 degrees C) having a significantly longer dive duration than hatchlings acclimated to a warm temperature (28 degrees C). This increase in dive duration at 17 degrees C was not a result of physiological alterations in metabolic rate but was due instead to an increase in aquatic oxygen consumption. Increasing aquatic oxygen consumption permitted cold-acclimated hatchlings to remain submerged for significantly longer periods, with one turtle undertaking a dive of over 2.5 d. When burst-swimming speed was used as the measure of performance, thermal acclimation was not detected. Overall, E. macrurus demonstrated a partial ability to acclimate to changes in environmental temperature.

Stream bed temperature profiles as indicators of percolation characteristics beneath arroyos in the middle Rio Grande Basin, USA

USGS Publications Warehouse

Constantz, J.; Thomas, C.L.

1997-01-01

Stream bed temperature profiles were monitored continuously during water year 1990 and 1991 (WY90 and 91) in two New Mexico arroyos, similar in their meteorological features and dissimilar in their hydrological features. Stream bed temperature profiles between depths of 30 and 300 cm were examined to determine whether temporal changes in temperature profiles represent accurate indicators of the timing, depth and duration of percolation in each stream bed. These results were compared with stream flow, air temperature, and precipitation records for WY90 and 91, to evaluate the effect of changing surface conditions on temperature profiles. Temperature profiles indicate a persistently high thermal gradient with depth beneath Grantline Arroyo, except during a semi-annual thermal reversal in spring and autumn. This typifies the thermal response of dry sediments with low thermal conductivities. High thermal gradients were disrupted only during infrequent stream flows, followed by rapid re-establishment of high gradients. The stream bed temperature at 300 cm was unresponsive to individual precipitation or stream flow during WY90 and 91. This thermal pattern provides strong evidence that most seepage into Grantline Arroyo failed to percolate at a sufficient rate to reach 300 cm before being returned to the atmosphere. A distinctly different thermal pattern was recorded beneath Tijeras Arroyo. Low thermal gradients between 30 and 300 cm and large diurnal variations in temperature, suggest that stream flow created continuous, advection-dominated heat transport for over 300 days, annually. Beneath Tijeras Arroyo, low thermal gradients were interrupted only briefly during periodic, dry summer conditions. Comparisons of stream flow records for WY90 and 91 with stream bed temperature profiles indicate that independent analysis of thermal patterns provides accurate estimates of the timing, depth and duration of percolation beneath both arroyos. Stream flow loss estimates indicate that seepage rates were 15 times greater for Tijeras Arroyo than for Grantline Arroyo, which supports qualitative conclusions derived from analysis of stream bed temperature responses to surface conditions. ?? 1997 John Wiley & Sons, Ltd.

Two-Phase Thermal Switching System for a Small, Extended Duration Lunar Science Platform

NASA Technical Reports Server (NTRS)

Bugby, D.; Farmer, J.; OConnor, B.; Wirzburger, M.; Abel, E.; Stouffer, C.

2010-01-01

Issue: extended duration lunar science platforms, using solar/battery or radioisotope power, require thermal switching systems that: a) Provide efficient cooling during the 15-earth-day 390 K lunar day; b) Consume minimal power during the 15-earth-day 100 K lunar night. Objective: carry out an analytical study of thermal switching systems that can meet the thermal requirements of: a) International Lunar Network (ILN) anchor node mission - primary focus; b) Other missions such as polar crater landers. ILN Anchor Nodes: network of geophysical science platforms to better understand the interior structure/composition of the moon: a) Rationale: no data since Apollo seismic stations ceased operation in 1977; b) Anchor Nodes: small, low-power, long-life (6-yr) landers with seismographic and a few other science instruments (see next chart); c) WEB: warm electronics box houses ILN anchor node electronics/batteries. Technology Need: thermal switching system that will keep the WEB cool during the lunar day and warm during the lunar night.

Solar Thermal Propulsion Concept

NASA Technical Reports Server (NTRS)

2004-01-01

Harnessing the Sun's energy through Solar Thermal Propulsion will propel vehicles through space by significantly reducing weight, complexity, and cost while boosting performance over current conventional upper stages. Another solar powered system, solar electric propulsion, demonstrates ion propulsion is suitable for long duration missions. Pictured is an artist's concept of space flight using solar thermal propulsion.

Optical and thermal properties in ultrafast laser surface nanostructuring on biodegradable polymer

NASA Astrophysics Data System (ADS)

Yada, Shuhei; Terakawa, Mitsuhiro

2015-03-01

We investigate the effect of optical and thermal properties in laser-induced periodic surface structures (LIPSS) formation on a poly-L-lactic acid (PLLA), a biodegradable polymer. Surface properties of biomaterials are known to be one of the key factors in tissue engineering. Methods to process biomaterial surfaces have been studied widely to enhance cell adhesive and anisotropic properties. LIPSS formation has advantages in a dry processing which is able to process complex-shaped surfaces without using a toxic chemical component. LIPSS, however, was difficult to be formed on PLLA due to its thermal and optical properties compared to other polymers. To obtain new perspectives in effect of these properties above, LIPSS formation dependences on wavelength, pulse duration and repetition rate have been studied. At 800 nm of incident wavelength, high-spatial frequency LIPSS (HSFL) was formed after applying 10000 femtosecond pulses at 1.0 J/cm2 in laser fluence. At 400 nm of the wavelength, HSFL was formed at fluences higher than 0.20 J/cm2 with more than 3000 pulses. Since LIPSS was less formed with lower repetition rate, certain heat accumulation may be required for LIPSS formation. With the pulse duration of 2.0 ps, higher laser fluence as well as number of pulses compared to the case of 120 fs was necessary. This indicates that multiphoton absorption process is essential for LIPSS formation. Study on biodegradation modification was also performed.

Analysis of thermal damage in vocal cords for the prevention of collateral laser treatment effects

NASA Astrophysics Data System (ADS)

Fanjul Vélez, Félix; Luis Arce-Diego, José; del Barrio Fernández, Ángela; Borragán Torre, Alfonso

2007-05-01

The importance of vocal cords for the interaction with the world around is obviously known. Vocal cords disorders can be divided mainly into three categories: difficulty of movement of one or both vocal folds, lesion formation on them, and difficulty or lack of mucosal wave movement. In this last case, a laser heating treatment can be useful in order to improve tissue vibration. However, thermal damage should be considered to adjust laser parameters and so to prevent irreversible harmful effects to the patient. in this work, an analysis of thermal damage in vocal folds is proposed. Firstly thermo-optical laser-tissue interaction is studied, by means of a RTT (Radiation Transfer Theory) model solved with a Monte Carlo approach for the optical propagation of radiation, and a bio-heat equation, with a finite difference numerical method based solution, taking into account blood perfusion and boundary effects, for the thermal distribution. The spatial-temporal temperature distributions are obtained for two widely used lasers, Nd:YAG (1064 nm) and KTP (532 nm). From these data, an Arrhenius thermal damage analysis allows a prediction of possible laser treatment harmful effects on vocal cords that could cause scar formation or tissue burn. Different source powers and exposition times are considered, in such a way that an approximation of adequate wavelength, power and duration is achieved, in order to implement an efficient and safe laser treatment.

Laser-driven short-duration heating angioplasty: dilatation performance in cadaver atherosclerotic femoral arteries

NASA Astrophysics Data System (ADS)

Shimazaki, Natsumi; Naruse, Sho; Arai, Tsunenori; Imanishi, Nobuaki; Aiso, Sadakazu

2013-03-01

The purpose of this study was to investigate the artery dilatation performance of the short-duration heating balloon catheter in cadaver stenotic arteries. We designed a prototype short-duration heating balloon catheter that can heat artery media to around 60 °C in 15-25 s by a combination of laser-driven heat generation and continuous fluid irrigation in the balloon. We performed ex vivo short-duration heating dilatation in the cadaver atherosclerotic femoral arteries (initial percent diameter stenosis was 36-98%), with the maximum balloon temperature of 65+/-5 °C, laser irradiation duration of 25 s, and balloon dilatation pressure of 3.5 atm. The artery lumen configurations before and after the dilatations were assessed with a commercial IVUS system. After the short-duration heating dilatations, the percent diameter stenosis was reduced below 30% without any artery tears or dissections. We estimated that the artery media temperature was raised to around 60 °C in which plaque thickness was below 0.8 mm by a thermal conduction calculation. The estimated maximum temperature in artery adventitia and surrounding tissue was up to 45 °C. We found that the short-duration heating balloon could sufficiently dilate the cadaver stenotic arteries, without thermal injury in artery adventitia and surroundings.

An Extension of Analysis of Solar-Heated Thermal Wadis to Support Extended-Duration Lunar Exploration

NASA Technical Reports Server (NTRS)

Balasubramaniam, R.; Gokoglu, S. A.; Sacksteder, K. R.; Wegeng, R. S.; Suzuki, N. H.

2010-01-01

The realization of the renewed exploration of the Moon presents many technical challenges; among them is the survival of lunar surface assets during periods of darkness when the lunar environment is very cold. Thermal wadis are engineered sources of stored solar energy using modified lunar regolith as a thermal storage mass that can supply energy to protect lightweight robotic rovers or other assets during the lunar night. This paper describes an extension of an earlier analysis of performance of thermal wadis based on the known solar illumination of the Moon and estimates of producible thermal properties of modified lunar regolith. The current analysis has been performed for the lunar equatorial region and validates the formerly used 1-D model by comparison of predictions to those obtained from 2-D and 3-D computations. It includes the effects of a thin dust layer covering the surface of the wadi, and incorporating either water as a phase-change material or aluminum stakes as a high thermal conductivity material into the regolith. The calculations indicate that thermal wadis can provide the desired thermal energy and temperature control for the survival of rovers or other equipment during periods of darkness.

Pivotal issues on relativistic electrons in ITER

NASA Astrophysics Data System (ADS)

Boozer, Allen H.

2018-03-01

The transfer of the plasma current from thermal to relativistic electrons is a threat to ITER achieving its mission. This danger is significantly greater in the nuclear than in the non-nuclear phase of ITER operations. Two issues are pivotal. The first is the extent and duration of magnetic surface breaking in conjunction with the thermal quenches. The second is the exponential sensitivity of the current transfer to three quantities: (1) the poloidal flux change required to e-fold the number of relativistic electrons, (2) the time τa after the beginning of the thermal quench before the accelerating electric field exceeds the Connor-Hastie field for runaway, and (3) the duration of the period τ_op in which magnetic surfaces remain open. Adequate knowledge does not exist to devise a reliable strategy for the protection of ITER. Uncertainties are sufficiently large that a transfer of neither a negligible nor the full plasma current to relativistic electrons can be ruled out during the non-nuclear phase of ITER. Tritium decay can provide a sufficiently strong seed for a dangerous relativistic-electron current even if τa and τ_op are sufficiently long to avoid relativistic electrons during non-nuclear operations. The breakup of magnetic surfaces that is associated with thermal quenches occurs on a time scale associated with fast magnetic reconnection, which means reconnection at an Alfvénic rather than a resistive rate. Alfvénic reconnection is well beyond the capabilities of existing computational tools for tokamaks, but its effects can be studied using its property of conserving magnetic helicity. Although the dangers to ITER from relativistic electrons have been known for twenty years, the critical issues have not been defined with sufficient precision to formulate an effective research program. Studies are particularly needed on plasma behavior in existing tokamaks during thermal quenches, behavior which could be clarified using methods developed here.

Investigation of Teflon FEP Embrittlement on Spacecraft in Low-Earth Orbit

NASA Technical Reports Server (NTRS)

deGroh, Kim K.; Banks, Bruce A.

1997-01-01

Teflon fluorinated ethylene propylene (FEP) (DuPont) is commonly used on exterior spacecraft surfaces for thermal control in the low-Earth orbit environment. Silverized or aluminized Teflon FEP is used for the outer layers of the thermal control blanket because of its high reflectance, low solar absorptance, and high thermal emittance. Teflon FEP is also desirable because, compared with other spacecraft polymers (such as Kapton), it has relatively high resistance to atomic oxygen erosion. Because of its comparably low atomic oxygen erosion yield, Teflon FEP has been used unprotected in the space environment. Samples of Teflon FEP from the Long Duration Exposure Facility (LDEF) and the Hubble Space Telescope (retrieved during its first servicing mission) were evaluated for solar-induced embrittlement and for synergistic effects of solar degradation and atomic oxygen.

Thermal modelling of various thermal barrier coatings in a high heat flux rocket engine

NASA Technical Reports Server (NTRS)

Nesbitt, James A.

1989-01-01

Traditional Air Plasma Sprayed (APS) ZrO2-Y2O3 Thermal Barrier Coatings (TBC's) and Low Pressure Plasma Sprayed (LPPS) ZrO2-Y2O3/Ni-Cr-Al-Y cermet coatings were tested in a H2/O2 rocked engine. The traditional ZrO2-Y2O3 (TBC's) showed considerable metal temperature reductions during testing in the hydrogen-rich environment. A thermal model was developed to predict the thermal response of the tubes with the various coatings. Good agreement was observed between predicted temperatures and measured temperatures at the inner wall of the tube and in the metal near the coating/metal interface. The thermal model was also used to examine the effect of the differences in the reported values of the thermal conductivity of plasma sprayed ZrO2-Y2O3 ceramic coatings, the effect of 100 micron (0.004 in.) thick metallic bond coat, the effect of tangential heat transfer around the tube, and the effect or radiation from the surface of the ceramic coating. It was shown that for the short duration testing in the rocket engine, the most important of these considerations was the effect of the uncertainty in the thermal conductivity of temperatures (greater than 100 C) predicted in the tube. The thermal model was also used to predict the thermal response of the coated rod in order to quantify the difference in the metal temperatures between the two substrate geometries and to explain the previously-observed increased life of coatings on rods over that on tubes. A thermal model was also developed to predict heat transfer to the leading edge of High Pressure Fuel Turbopump (HPFTP) blades during start-up of the space shuttle main engines. The ability of various TBC's to reduce metal temperatures during the two thermal excursions occurring on start-up was predicted. Temperature reductions of 150 to 470 C were predicted for 165 micron (0.0065 in.) coatings for the greater of the two thermal excursions.

Analgesic effect of piracetam on peripheral neuropathic pain induced by chronic constriction injury of sciatic nerve in rats.

PubMed

Mehta, Ashish K; Bhati, Yogendra; Tripathi, Chakra D; Sharma, Krishna K

2014-08-01

Despite immense advances in the treatment strategies, management of neuropathic pain remains unsatisfactory. Piracetam is a prototype of nootropic drugs, used to improve cognitive impairment. The present study was designed to investigate the effect of piracetam on peripheral neuropathic pain in rats. Neuropathic pain was induced by the chronic constriction injury of the sciatic nerve. Following this, piracetam was intraperitoneally administered for 2 weeks in doses of 50, 100 and 200 mg/kg, and pain was assessed by employing the behavioural tests for thermal hyperalgesia (hot plate and tail flick tests) and cold allodynia (acetone test). After the induction of neuropathic pain, significant development of thermal hyperalgesia and cold allodynia was observed. The administration of piracetam (50 mg/kg) did not have any significant effect on all the behavioural tests. Further, piracetam (100 mg/kg) also had no effect on the hot plate and tail flick tests; however it significantly decreased the paw withdrawal duration in the acetone test. Piracetam in a dose of 200 mg/kg significantly modulated neuropathic pain as observed from the increased hot plate and tail flick latencies, and decreased paw withdrawal duration (in acetone test). Therefore, the present study suggests the potential use of piracetam in the treatment of neuropathic pain, which merits further clinical investigation.

Reliability of High Power Laser Diode Arrays Operating in Long Pulse Mode

NASA Technical Reports Server (NTRS)

Amzajerdian, Farzin; Meadows, Byron L.; Barnes, Bruce W.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.; Baker, Nathaniel R.

2006-01-01

Reliability and lifetime of quasi-CW laser diode arrays are greatly influenced by their thermal characteristics. This paper examines the thermal properties of laser diode arrays operating in long pulse duration regime.

Thermal Control System for a Small, Extended Duration Lunar Surface Science Platform

NASA Technical Reports Server (NTRS)

Bugby, D.; Farmer, J.; OConnor, B.; Wirzburger, M.; Abel, E.; Stouffer, C.

2010-01-01

The presentation slides include: Introduction: lunar mission definition, Problem: requirements/methodology, Concept: thermal switching options, Analysis: system evaluation, Plans: dual-radiator LHP (loop heat pipe) test bed, and Conclusions: from this study.

Post flight system analysis of FRECOPA (AO 138)

NASA Technical Reports Server (NTRS)

Durin, Christian

1991-01-01

The unexpected duration for the flight of the Long Duration Exposure Facility (LDEF) conducted CNES to create a special investigation group in order to analyze all the materials and systems which compose the French Cooperative Payload (FRECOPA) except the experiments especially prepared for the flight. The FRECOPA tray was on the trailing face (V-) of the LDEF and protected from the atomic oxygen flux during all the flight. However, the solar irradiation was very important with solar flux quite perpendicular to the experiment once an orbit. There was also a good vacuum environment. The objectives are to test the effects of the combined space environment on materials and components like: structure, thermal control coatings and blankets, electronic unit, motors, and mechanical fixtures. When the LDEF returned to Kennedy Space Center, a visual inspection showed the very good behavior of the materials used and it was noted that the three mechanisms to open and close the experiment canisters worked completely. Many impacts of micrometeoroids or space debris on the structure and on the thermal protections were observed. After FRECOPA was brought back to Toulouse, many tests were performed and include: working order tests, mechanical tests (tension), optical and electronic microscopy (SEM), surface analysis (ESCA, SIMS, RBS, AUGER, etc.), thermal analysis, pressure measurements, and gas analysis (outgassing tests). The results of these experiments are discussed.

Temperature peaks affect fire-induced soil water repellency, infiltration and erosion risk of Mediterranean shrublands. Implications for water and sediment connectivity

NASA Astrophysics Data System (ADS)

Jordán, Antonio; Zavala, Lorena M.; Gordillo-Rivero, Ángel J.; Miriam, Miriam; Keesstra, Saskia; Cerdà, Artemi

2017-04-01

We know that the impact of fire on soil water repellency varies largely with the availability of water and physical and chemical soil properties, as well as the intensity of pre-existing hydrophobicity. However, there are few studies that relate the intensity of post-fire soil hydrophobicity and its persistence to the intensity and duration of thermal peaks occurring during fire. Fundamentally, this is due to the difficulty of quantifying these factors in situ, so that experimental fires are an extremely useful tool. The objective of this work was to study the impact of the intensity and duration of the thermal peaks observed during an experimental fire in the hydrophobicity of previously wet or slightly hydrophobic soils and the consequences of these changes on infiltration, runoff and soil loss (through rainfall simulation) in the immediate (30 days) and medium-term (1 year) post-fire period. In general, soil water repellency increased in all cases, although high temperatures and residence times of moderate thermal peaks caused the greatest impact. Although infiltration rates determined by mini-disk infiltrometer with water generally declined, no significant changes were observed in the same measurement with ethanol (which negates the effect of hydrophobicity).

Results of the examination of LDEF polyurethane thermal control coatings

NASA Technical Reports Server (NTRS)

Golden, Johnny L.

1994-01-01

This report summarizes the condition of polyurethane thermal control coatings subjected to 69 months of low earth orbit (LEO) exposure on the Long Duration Exposure Facility (LDEF) mission. Specimens representing all environmental aspects obtainable by LDEF were analyzed. Widely varying changes in the thermo-optical and mechanical properties of these materials were observed, depending on atomic oxygen and ultraviolet radiation fluences. High atomic oxygen fluences, regardless of ultraviolet radiation exposure levels, resulted in near original optical properties for these coatings but with a degradation in their mechanical condition. A trend in solar absorptance increase with ultraviolet radiation fluence was observed. Contamination, though observed, exhibited minimal effects.

Plasma Membrane Permeabilization by 60- and 600-ns Electric Pulses Is Determined by the Absorbed Dose

PubMed Central

Ibey, Bennett L.; Xiao, Shu; Schoenbach, Karl H.; Murphy, Michael R.; Pakhomov, Andrei G.

2008-01-01

We explored how the effect of plasma membrane permeabilization by nanosecond-duration electric pulses (nsEP) depends on the physical characteristics of exposure. The resting membrane resistance (Rm) and membrane potential (MP) were measured in cultured GH3 and CHO cells by conventional whole-cell patch-clamp technique. Intact cells were exposed to a single nsEP (60 or 600 ns duration, 0-22 kV/cm), followed by patch-clamp measurements after a 2-3 min delay. Consistent with earlier findings, nsEP caused long-lasting Rm decrease, accompanied by the loss of MP. The threshold for these effects was about 6 kV/cm for 60 ns pulses, and about 1 kV/cm for 600 ns pulses. Further analysis established that it was neither pulse duration nor the E-field amplitude per se, but the absorbed dose that determined the magnitude of the biological effect. In other words, exposure to nsEP at either pulse duration caused equal effects if the absorbed doses were equal. The threshold absorbed dose to produce plasma membrane effects in either GH3 or CHO cells at either pulse duration was found to be at or below 10 mJ/g. Despite being determined by the dose, the nsEP effect clearly is not thermal, as the maximum heating at the threshold dose is less than 0.01 °C. The use of the absorbed dose as a universal exposure metric may help to compare and quantify nsEP sensitivity of different cell types and of cells in different physiological conditions. The absorbed dose may also prove to be a more useful metric than the incident E-field in determining safety limits for high peak, lowaverage power EMF emissions. PMID:18839412

Multilayer Insulation Material Guidelines

NASA Technical Reports Server (NTRS)

Finckenor, M. M.; Dooling, D.

1999-01-01

Multilayer Insulation Material Guidelines provides data on multilayer insulation materials used by previous spacecraft such as Spacelab and the Long-Duration Exposure Facility and outlines other concerns. The data presented in the document are presented for information only. They can be used as guidelines for multilayer insulation design for future spacecraft provided the thermal requirements of each new design and the environmental effects on these materials are taken into account.

Genetic variation reveals influence of landscape connectivity on population dynamics and resiliency of western trout in disturbance-prone habitats

Treesearch

Helen M. Neville; R. E. Gresswell; J. B. Dunham

2012-01-01

Salmonid fishes have evolved and persisted in dynamic ecosystems (Waples and others 2008) where disturbance events vary in frequency, magnitude, timing, and duration (Gresswell 1999; Dale and others 2001), as well as the specific nature of associated effects (e.g., changes in thermal or flow regimes, geomorphology, or water chemistry; Reeves and others 1995; Benda and...

The LDEF benefits. [planned experiments

NASA Technical Reports Server (NTRS)

Kinard, W. H.

1982-01-01

The Long Duration Exposure Facility (LDEF) is described, and experiments planned for the first LDEF mission are discussed. Four of the eight involve scientific studies of interstellar gas, micrometeoroids, cosmic rays, and crystal growth in zero gravity, and four involve technology studies of the space environmental effects on solar cells, composite materials, thermal coatings, fiber optics, and electronic instruments. For each experiment, the objectives and methods are discussed.

Wavelength dependence of laser-induced retinal injury

NASA Astrophysics Data System (ADS)

Lund, David J.; Edsall, Peter; Stuck, Bruce E.

2005-04-01

The threshold for laser-induced retinal damage is dependent primarily upon the laser wavelength and the exposure duration. The study of the wavelength dependence of the retinal damage threshold has been greatly enhanced by the availability of tunable lasers. The Optical Parametric Oscillator (OPO), capable of providing useful pulse energy throughout a tuning range from 400 nm to 2200 nm, made it possible to determine the wavelength dependence of laser-induced retinal damage thresholds for q-switched pulses throughout the visible and NIR spectrum. Studies using the a tunable TI:Saph laser and several fixed-wavelength lasers yielded threshold values for 0.1 s exposures from 440 nm to 1060 nm. Laser-induced retinal damage for these exposure durations results from thermal conversion of the incident laser irradiation and an action spectrum for thermal retinal damage was developed based on the wavelength dependent transmission and absorption of ocular tissue and chromatic aberration of the eye optics. Long (1-1000s) duration exposures to visible laser demonstrated the existence of non-thermal laser-induced retinal damage mechanisms having a different action spectrum. This paper will present the available data for the wavelength dependence of laser-induced thermal retinal damage and compare this data to the maximum permissible exposure levels (MPEs) provided by the current guidelines for the safe use of lasers.

Arrhenius analysis of the relationship between hyperthermia and Hsp70 promoter activation: a comparison between ex vivo and in vivo data.

PubMed

Deckers, Roel; Debeissat, Christelle; Fortin, Pierre-Yves; Moonen, Chrit T W; Couillaud, Franck

2012-01-01

Tight regulation of gene expression in the region where therapy is necessary and for the duration required to achieve a therapeutic effect and to minimise systemic toxicity is very important for clinical applications of gene therapy. Hyperthermia in combination with a temperature sensitive heat shock protein (Hsp70) promoter presents a unique approach allowing non-invasive spatio-temporal control of transgene expression. In this study we investigated the in vivo and ex vivo relationship between temperature and duration of thermal stress with respect to the resulting gene expression using an Arrhenius analysis. A transgenic mouse expressing the luciferase reporter gene under the transcriptional control of a thermosensitive promoter was used to assure identical genotype for in vivo (mouse leg) and ex vivo (bone marrow mononuclear and embryonic fibroblast cells) studies. The mouse leg and cells were heated at different temperatures and different exposure times. Bioluminescence imaging and in vitro enzymatic assay were used to measure the resulting transgene expression. We showed that temperature-induced Hsp70 promoter activation was modulated by both temperature as well as duration of hyperthermia. The relationship between temperature and duration of hyperthermia and the resulting reporter gene expression can be modelled by an Arrhenius analysis for both in vivo as well as ex vivo. However, the increase in reporter gene expression after elevating the temperature of the thermal stress with 1°C is not comparable for in vivo and ex vivo situations. This information may be valuable for optimising clinical gene therapy protocols.

Vibration waveform effects on dynamic stabilization of ablative Rayleigh-Taylor instability

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

Piriz, A. R.; Lucchio, L. Di; Rodriguez Prieto, G.

2011-08-15

An analysis of dynamic stabilization of Rayleigh-Taylor instability in an ablation front is performed by considering a general square wave for modulating the vertical acceleration of the front. Such a kind of modulation allows for clarifying the role of thermal conduction in the mechanism of dynamic stabilization. In addition, the study of the effect of different modulations by varying the duration and amplitude of the square wave in each half-period provides insight on the optimum performance of dynamic stabilization.

Design and testing of a liquid cooled garment for hot environments.

PubMed

Guo, Tinghui; Shang, Bofeng; Duan, Bin; Luo, Xiaobing

2015-01-01

Liquid cooled garments (LCGs) are considered a viable method to protect individuals from hyperthermia and heat-related illness when working in thermally stressful environments. While the concept of LCGs was proposed over 50 years ago, the design and testing of these systems is undeveloped and stands in need of further study. In this study, a detailed heat transfer model of LCG in a hot environment was built to analyze the effects of different factors on the LCG performance, and to identify the main limitations to achieve maximum performance. An LCG prototype was designed and fabricated. Series of tests were done by a modified thermal manikin method to validate the heat transfer model and to evaluate the thermal properties. Both experimental and predicted results show that the heat flux components match the heat balance equation with an error of less than 10% at different flowrate. Thermal resistance analysis also manifests that the thermal resistance between the cooling water and the ambient (R2) is more sensitive to the flowrate than to the one between the skin surface and the cooling water (R1). When the flowrate increased from 225 to 544 mL/min, R2 decreased from 0.5 to 0.3 °C m(2)/W while R1 almost remained constant. A specific duration time was proposed to assess the durability and an optimized value of 1.68 h/kg was found according to the heat transfer model. The present heat transfer model and specific duration time concept could be used to optimize and evaluate this kind of LCG respectively. Copyright © 2015 Elsevier Ltd. All rights reserved.

Research on EHN additive on the diesel engine combustion characteristics in plateau environment

NASA Astrophysics Data System (ADS)

Sun, Zhixin; Li, Ruoting; Wang, Xiancheng; Hu, Chuan

2017-03-01

Aiming at the combustion deterioration problem of diesel engine in plateau environment, a bench test was carried out for the effects of EHN additive on combustion characteristics of the diesel engine with intake pressure of 0.68 kPa. Test results showed that with the full load working condition of 1 400 r/min: Cylinder pressure and pressure uprising rate decreased with EHN additive added in, mechanical load on the engine could be relieved; peak value of the heat release rate decreased and its occurrence advanced, ignition delay and combustion duration were shortened; cylinder temperature and exhaust gas temperature declined, thermal load on the engine could be relieved, output torque increased while specific oil consumption decreased, and effective thermal efficiency of diesel engine increased.

Electrical parameter changes in silicon solar cells induced by thermal donor formation

NASA Astrophysics Data System (ADS)

Ruiz, J. M.; Cid, M.

Statistical results of 450 C annealing experiments of variable duration, performed on n(+)pp(+), 10-ohm-cm Czochralski silicon (Cz silicon), bifacial solar cells are presented. The specific temperature used is known to favor the nucleation of interstitial oxygen, creating the thermal donors, with important effects on the electrical properties of Cz silicon. Two distinct behaviors are observed with solar cells. The annealing during moderate time (below 4-5 h) leads, on the average, to an improvement of the photovoltaic performances. Longer heat treatments (mainly above 8 h) induce an effective inversion of the base polarity (from p type to n type), with the net result of partially losing the precedent benefits. Both phenomena have been found to be permanent, provided further processes at higher temperatures are avoided.

Spectroscopic determination of thermal impulse in sub-second heating events using lanthanide-doped oxide precursors and phenomenological modeling

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

Anderson, Benjamin R., E-mail: branderson@wsu.edu; Gunawidjaja, Ray; Price, Patrick

2016-08-28

Using a mixture of crystalline-Ho:ZrO{sub 2}, precursor-Dy:Y{sub 2}O{sub 3}, and precursor-Eu:ZrO{sub 2} nanoparticles we develop thermal impulse sensors capable of measuring equivalent isothermal temperatures and durations during a heating event, with response times of <100 ms, and a temperature range of at least 673 K to 1173 K. In order to determine the temperature and duration from the sensors after the heating event we measure the sensors' fluorescence spectrum, which is then compared with lab based calibration data. By using two precursor materials with different reaction kinetics we are able to extract both temperature and duration. Based on blind sample testing we findmore » that the sensors and calculation method are accurate for measuring temperature and duration, but currently suffer a lack of precision due to difficulties in producing homogeneously heated samples.« less

Thermal Modelling of Various Thermal Barrier Coatings in a High Flux Rocket Engine

NASA Technical Reports Server (NTRS)

Nesbitt, James A.

1998-01-01

A thermal model was developed to predict the thermal response of coated and uncoated tubes tested in a H2/O2 rocket engine. Temperatures were predicted for traditional APS ZrO2-Y2O3 thermal barrier coatings, as well as APS and LPPS ZrO2-Y2O3/NiCrAlY cermet coatings. Good agreement was observed between predicted and measured metal temperatures at locations near the tube surface or at the inner tube wall. The thermal model was also used to quantitatively examine the effect of various coating system parameters on the temperatures in the substrate and coating. Accordingly, the effect of the presence a metallic bond coat and the effect of radiation from the surface of the ceramic layer were examined. In addition, the effect of a variation in the values of the thermal conductivity of the ceramic layer was also investigated. It was shown that a variation in the thermal conductivity of the ceramic layer, on the order of that reported in the literature for plasma sprayed ZrO2-Y2O3 coatings, can result in temperature differences in the substrate greater than 100 C, a much greater effect than that due to the presence of a bond coat or radiation from the ceramic layer. The thermal model was also used to predict the thermal response of a coated rod in order to quantify the difference in the metal temperatures between the two substrate geometries in order to explain the previously-observed increased life of coatings on rods over that on tubes. It was shown that for the short duration testing in the rocket engine, the temperature in a tube could exceed that in a rod by more than 100 C. Lastly, a two-dimensional model was developed to evaluate the effect of tangential heat transfer around the tube and its impact on reducing the stagnation point temperature. It was also shown that tangential heat transfer does not significantly reduce the stagnation point temperature, thus allowing application of a simpler, one-dimensional model for comparing measured and predicted stagnation point temperatures.

Estimation of optimal hologram recording modes on photothermal materials

NASA Astrophysics Data System (ADS)

Dzhamankyzov, Nasipbek Kurmanalievich; Ismanov, Yusupzhan Khakimzhanovich; Zhumaliev, Kubanychbek Myrzabekovich; Alymkulov, Samsaly Amanovich

2018-01-01

A theoretical analysis of the hologram recording process on photothermal media to estimate the required laser radiation power for the information recording as the function of the spatial frequency and radiation exposure duration is considered. Results of the analysis showed that materials with a low thermal diffusivity are necessary to increase the recording density in these media and the recording should be performed with short pulses to minimize the thermal diffusion length. A solution for the heat conduction equation for photothermal materials heated by an interference laser field was found. The solution obtained allows one to determine the required value of the recording temperature for given spatial frequencies, depending on the thermal physical parameters of the medium and on the power and duration of the heating radiation.

TRPV1 channels in the nucleus of the solitary tract mediate thermal prolongation of the LCR in decerebrate piglets

PubMed Central

Xia, Luxi; Bartlett, Donald; Leiter, J.C.

2011-01-01

Elevating body temperature or just the temperature of the dorsal medulla by approximately 2 °C prolongs the laryngeal chemoreflex (LCR) in decerebrate neonatal piglets. We tested the hypothesis that transient receptor potential vanilloid 1 (TRPV1) receptors in the nucleus of the solitary tract (NTS) mediate thermal prolongation of the LCR. We studied the effect of a selective TRPV1 receptor antagonist on thermal prolongation of the LCR, and we tested the effect of a TRPV1 agonist on the duration of the LCR under normothermic conditions. We studied 37 decerebrate neonatal piglets between the ages of post-natal days 4 and 7. The TRPV1 receptor antagonist, 5−iodoresiniferatoxin (65 microM/L in 100 nL), blocked thermal prolongation of the LCR when injected bilaterally into the region of the NTS. The TRPV1 agonist, resiniferatoxin (0.65-1.0 mM/L in 100 nL), prolonged the LCR after bilateral injection into the NTS even when the body temperature of each piglet was normal. The effect of the TRPV1 agonists could be blocked by treatment with the GABAA receptor antagonist, bicuculline, whether given intravenously (0.3 mg/kg) or focally injected bilaterally into the NTS (10 mM in 100nL). We conclude that TRPV1 receptors in the NTS mediate thermal prolongation of the LCR. PMID:21276877

Hall Thruster Thermal Modeling and Test Data Correlation

NASA Technical Reports Server (NTRS)

Myers, James; Kamhawi, Hani; Yim, John; Clayman, Lauren

2016-01-01

The life of Hall Effect thrusters are primarily limited by plasma erosion and thermal related failures. NASA Glenn Research Center (GRC) in cooperation with the Jet Propulsion Laboratory (JPL) have recently completed development of a Hall thruster with specific emphasis to mitigate these limitations. Extending the operational life of Hall thursters makes them more suitable for some of NASA's longer duration interplanetary missions. This paper documents the thermal model development, refinement and correlation of results with thruster test data. Correlation was achieved by minimizing uncertainties in model input and recognizing the relevant parameters for effective model tuning. Throughout the thruster design phase the model was used to evaluate design options and systematically reduce component temperatures. Hall thrusters are inherently complex assemblies of high temperature components relying on internal conduction and external radiation for heat dispersion and rejection. System solutions are necessary in most cases to fully assess the benefits and/or consequences of any potential design change. Thermal model correlation is critical since thruster operational parameters can push some components/materials beyond their temperature limits. This thruster incorporates a state-of-the-art magnetic shielding system to reduce plasma erosion and to a lesser extend power/heat deposition. Additionally a comprehensive thermal design strategy was employed to reduce temperatures of critical thruster components (primarily the magnet coils and the discharge channel). Long term wear testing is currently underway to assess the effectiveness of these systems and consequently thruster longevity.

Mobile phone and my health

NASA Astrophysics Data System (ADS)

Surducan, Aneta; Dabala, Dana; Neamtu, Camelia; Surducan, Vasile; Surducan, Emanoil

2013-11-01

The interaction of the microwave radiation emitted by mobile phones with the user's body is analyzed from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) recommendations perspective as a correlation between the specific absorption ratio (SAR) of the mobile phone and the call duration. The relative position of the cell phone to the user's body, the dielectric properties of the exposed body parts, the SAR value and the call duration are considered in the local body temperature rise due to the microwave heating effect. The recommended local temperature rise limit in the human body is evaluated according to standards. The aim of this study is to disseminate information to young people, especially high school students, about the microwave thermal effects on the human body, to make them aware of the environmental electromagnetic pollution and to offer them a simple method of biological self protection.

Analysis of systems hardware flown on LDEF: New findings and comparison to other retrieved spacecraft hardware

NASA Technical Reports Server (NTRS)

Dursch, Harry; Bohnhoff-Hlavacek, Gail; Blue, Donald; Hansen, Patricia

1995-01-01

The Long Duration Exposure Facility (LDEF) was retrieved in 1990 after spending 69 months in low-earth-orbit (LEO). A wide variety of mechanical, electrical, thermal, and optical systems, subsystems, and components were flown on LDEF. The Systems Special Investigation Group (Systems SIG) was formed by NASA to investigate the effects of the 69 month exposure on systems related hardware and to coordinate and collate all systems analysis of LDEF hardware. This report is the Systems SIG final report which updates earlier findings and compares LDEF systems findings to results from other retrieved spacecraft hardware such as Hubble Space Telescope. Also included are sections titled (1) Effects of Long Duration Space Exposure on Optical Scatter, (2) Contamination Survey of LDEF, and (3) Degradation of Optical Materials in Space.

Analysis of systems hardware flown on LDEF: New findings and comparison to other retrieved spacecraft hardware

NASA Astrophysics Data System (ADS)

Dursch, Harry; Bohnhoff-Hlavacek, Gail; Blue, Donald; Hansen, Patricia

1995-09-01

The Long Duration Exposure Facility (LDEF) was retrieved in 1990 after spending 69 months in low-earth-orbit (LEO). A wide variety of mechanical, electrical, thermal, and optical systems, subsystems, and components were flown on LDEF. The Systems Special Investigation Group (Systems SIG) was formed by NASA to investigate the effects of the 69 month exposure on systems related hardware and to coordinate and collate all systems analysis of LDEF hardware. This report is the Systems SIG final report which updates earlier findings and compares LDEF systems findings to results from other retrieved spacecraft hardware such as Hubble Space Telescope. Also included are sections titled (1) Effects of Long Duration Space Exposure on Optical Scatter, (2) Contamination Survey of LDEF, and (3) Degradation of Optical Materials in Space.

Thermal antinociception after dexmedetomidine administration in cats: a comparison between intramuscular and oral transmucosal administration.

PubMed

Slingsby, Louisa S; Taylor, Polly M; Monroe, Taylor

2009-10-01

Dexmedetomidine 40microg/kg was administered either intramuscularly (IM) or oral transmucosally (OTM) to 12 cats in a randomised cross-over study. Thermal nociceptive thresholds and visual analogue scale (VAS) sedation scores were obtained before and at regular intervals up to 24h after test drug administration. The summary measures of overall mean threshold, overall mean VAS sedation plus onset, offset and duration of analgesia were investigated using a univariate general linear model. There were no significant differences between treatment groups. Data are presented as mean+/-standard deviation: delta T mean increase over time (IM 6 degrees C+/-3 degrees C, OTM 6 degrees C+/-2 degrees C); overall mean VAS (IM 43+/-9 OTM 39+/-1); onset (IM 35+/-32 and OTM 30+/-40min); offset (IM 96+/-56 and OTM 138+/-135min); duration (IM 61+/-47 OTM 99+/-124min). Dexmedetomidine is well absorbed through the oral mucosa in cats since OTM and IM administration of dexmedetomidine 40microg/kg produced similar overall sedative and antinociceptive effects.

Hyperthermal Environments Simulator for Nuclear Rocket Engine Development

NASA Technical Reports Server (NTRS)

Litchford, Ron J.; Foote, John P.; Clifton, W. B.; Hickman, Robert R.; Wang, Ten-See; Dobson, Christopher C.

2011-01-01

An arc-heater driven hyperthermal convective environments simulator was recently developed and commissioned for long duration hot hydrogen exposure of nuclear thermal rocket materials. This newly established non-nuclear testing capability uses a high-power, multi-gas, wall-stabilized constricted arc-heater to produce hightemperature pressurized hydrogen flows representative of nuclear reactor core environments, excepting radiation effects, and is intended to serve as a low-cost facility for supporting non-nuclear developmental testing of hightemperature fissile fuels and structural materials. The resulting reactor environments simulator represents a valuable addition to the available inventory of non-nuclear test facilities and is uniquely capable of investigating and characterizing candidate fuel/structural materials, improving associated processing/fabrication techniques, and simulating reactor thermal hydraulics. This paper summarizes facility design and engineering development efforts and reports baseline operational characteristics as determined from a series of performance mapping and long duration capability demonstration tests. Potential follow-on developmental strategies are also suggested in view of the technical and policy challenges ahead. Keywords: Nuclear Rocket Engine, Reactor Environments, Non-Nuclear Testing, Fissile Fuel Development.

Experimental research of kinetic and dynamic characteristics of temperature movements of machines

NASA Astrophysics Data System (ADS)

Parfenov, I. V.; Polyakov, A. N.

2018-03-01

Nowadays, the urgency of informational support of machines at different stages of their life cycle is increasing in the form of various experimental characteristics that determine the criteria for working capacity. The effectiveness of forming the base of experimental characteristics of machines is related directly to the duration of their field tests. In this research, the authors consider a new technique that allows reducing the duration of full-scale testing of machines by 30%. To this end, three new indicator coefficients were calculated in real time to determine the moments corresponding to the characteristic points. In the work, new terms for thermal characteristics of machine tools are introduced: kinetic and dynamic characteristics of the temperature movements of the machine. This allow taking into account not only the experimental values for the temperature displacements of the elements of the carrier system of the machine, but also their derivatives up to the third order, inclusively. The work is based on experimental data obtained in the course of full-scale thermal tests of a drilling-milling and boring CNC machine.

Predicted and observed directional dependence of meteoroid/debris impacts on LDEF thermal blankets

NASA Astrophysics Data System (ADS)

Drolshagen, Gerhard

1992-06-01

The number of impacts from meteoroids and space debris particles to the various Long Duration Exposure Facility (LDEF) rows is calculated using ESABASE/DEBRIS, a 3-D numerical analysis tool. It is based on the latest environment flux models and includes geometrical and directional effects. A detailed comparison of model predictions and actual observations is made for impacts on the thermal blankets which covered the USCR experiment. Impact features on these blankets were studied intensively in European laboratories and hypervelocity impacts for calibration were performed. The thermal blankets were located on all LDEF rows, except 3, 9, and 12. Because of their uniform composition and thickness, these blankets allow a direct analysis of the directional dependence of impacts and provide a unique test case for the latest meteoroid and debris flux models.

Thermal imaging diagnostics of high-current electron beams.

PubMed

Pushkarev, A; Kholodnaya, G; Sazonov, R; Ponomarev, D

2012-10-01

The thermal imaging diagnostics of measuring pulsed electron beam energy density is presented. It provides control of the electron energy spectrum and a measure of the density distribution of the electron beam cross section, the spatial distribution of electrons with energies in the selected range, and the total energy of the electron beam. The diagnostics is based on the thermal imager registration of the imaging electron beam thermal print in a material with low bulk density and low thermal conductivity. Testing of the thermal imaging diagnostics has been conducted on a pulsed electron accelerator TEU-500. The energy of the electrons was 300-500 keV, the density of the electron current was 0.1-0.4 kA/cm(2), the duration of the pulse (at half-height) was 60 ns, and the energy in the pulse was up to 100 J. To register the thermal print, a thermal imager Fluke-Ti10 was used. Testing showed that the sensitivity of a typical thermal imager provides the registration of a pulsed electron beam heat pattern within one pulse with energy density over 0.1 J/cm(2) (or with current density over 10 A/cm(2), pulse duration of 60 ns and electron energy of 400 keV) with the spatial resolution of 0.9-1 mm. In contrast to the method of using radiosensitive (dosimetric) materials, thermal imaging diagnostics does not require either expensive consumables, or plenty of processing time.

Thermal, physiological and perceptual strain mediate alterations in match-play tennis under heat stress.

PubMed

Périard, Julien D; Racinais, Sébastien; Knez, Wade L; Herrera, Christopher P; Christian, Ryan J; Girard, Olivier

2014-04-01

This study compared the thermal, physiological and perceptual responses associated with match-play tennis in HOT (∼34°C wet-bulb-globe temperature (WBGT)) and COOL (∼19°C WBGT) conditions, along with the accompanying alterations in match characteristics. 12 male tennis players undertook two matches for an effective playing time (ie, ball in play) of 20 min, corresponding to ∼119 and ∼102 min of play in HOT and COOL conditions, respectively. Rectal and skin temperatures, heart rate, subjective ratings of thermal comfort, thermal sensation and perceived exertion were recorded, along with match characteristics. End-match rectal temperature increased to a greater extent in the HOT (∼39.4°C) compared with the COOL (∼38.7°C) condition (p<0.05). Thigh skin temperature was higher throughout the HOT match (p<0.001). Heart rate, thermal comfort, thermal sensation and perceived exertion were also higher during the HOT match (p<0.001). Total playing time was longer in the HOT compared with the COOL match (p<0.05). Point duration (∼7.1 s) was similar between conditions, while the time between points was ∼10 s longer in the HOT relative to the COOL match (p<0.05). This led to a ∼3.4% lower effective playing percentage in the heat (p<0.05). Although several thermal, physiological and perceptual variables were individually correlated to the adjustments in time between points and effective playing percentage, thermal sensation was the only predictor variable associated with both adjustments (p<0.005). These adjustments in match-play tennis characteristics under severe heat stress appear to represent a behavioural strategy adopted to minimise or offset the sensation of environmental conditions being rated as difficult.

Diurnal and Seasonal Variations of Thermal Stratification and Vertical Mixing in a Shallow Fresh Water Lake

NASA Astrophysics Data System (ADS)

Yang, Yichen; Wang, Yongwei; Zhang, Zhen; Wang, Wei; Ren, Xia; Gao, Yaqi; Liu, Shoudong; Lee, Xuhui

2018-04-01

Among several influential factors, the geographical position and depth of a lake determine its thermal structure. In temperate zones, shallow lakes show significant differences in thermal stratification compared to deep lakes. Here, the variation in thermal stratification in Lake Taihu, a shallow fresh water lake, is studied systematically. Lake Taihu is a warm polymictic lake whose thermal stratification varies in short cycles of one day to a few days. The thermal stratification in Lake Taihu has shallow depths in the upper region and a large amplitude in the temperature gradient, the maximum of which exceeds 5°C m-1. The water temperature in the entire layer changes in a relatively consistent manner. Therefore, compared to a deep lake at similar latitude, the thermal stratification in Lake Taihu exhibits small seasonal differences, but the wide variation in the short term becomes important. Shallow polymictic lakes share the characteristic of diurnal mixing. Prominent differences on the duration and frequency of long-lasting thermal stratification are found in these lakes, which may result from the differences of local climate, lake depth, and fetch. A prominent response of thermal stratification to weather conditions is found, being controlled by the stratifying effect of solar radiation and the mixing effect of wind disturbance. Other than the diurnal stratification and convection, the representative responses of thermal stratification to these two factors with contrary effects are also discussed. When solar radiation increases, stronger wind is required to prevent the lake from becoming stratified. A daily average wind speed greater than 6 m s-1 can maintain the mixed state in Lake Taihu. Moreover, wind-induced convection is detected during thermal stratification. Due to lack of solar radiation, convection occurs more easily in nighttime than in daytime. Convection occurs frequently in fall and winter, whereas long-lasting and stable stratification causes less convection in summer.

Phototoxicity to the retina: mechanisms of damage.

PubMed

Glickman, Randolph D

2002-01-01

Light damage to the retina occurs through three general mechanisms involving thermal, mechanical, or photochemical effects. The particular mechanism activated depends on the wavelength and exposure duration of the injuring light. The transitions between the various light damage mechanism may overlap to some extent. Energy confinement is a key concept in understanding or predicting the type of damage mechanism produced by a given light exposure. As light energy (either from a laser or an incoherent source) is deposited in the retina, its penetration through, and its absorption in, various tissue compartments is determined by its wavelength. Strongly absorbing tissue components will tend to "concentrate" the light energy. The effect of absorbed light energy largely depends on the rate of energy deposition, which is correlated with the exposure duration. If the rate of energy deposition is too low to produce an appreciable temperature increase in the tissue, then any resulting tissue damage necessarily occurs because of chemical (oxidative) reactions induced by absorption of energetic photons (photochemical damage). If the rate of energy deposition is faster than the rate of thermal diffusion (thermal confinement), then the temperature of the exposed tissue rises. If a critical temperature is reached (typically about 10 degrees C above basal), then thermal damage occurs. If the light energy is deposited faster than mechanical relaxation can occur (stress confinement), then a thermoelastic pressure wave is produced, and tissue is disrupted by shear forces or by cavitation-nonlinear effects. Very recent evidence suggests that ultrashort laser pulses can produce tissue damage through nonlinear and photochemical mechanisms; the latter because of two-photon excitation of cellular chromophores. In addition to tissue damage caused directly by light absorption, light toxicity can be produced by the presence of photosensitizing agents. Drugs excited to reactive states by ultraviolet (UV) or visible light produce damage by type I (free radical) and type II (oxygen dependent) mechanisms. Some commonly used drugs, such as certain antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs), and psychotherapeutic agents, as well as some popular herbal medicines, can produce ocular phototoxicity. Specific cellular effects and damage end points characteristic of light damage mechanisms are described.

Studying the Transient Thermal Contact Conductance Between the Exhaust Valve and Its Seat Using the Inverse Method

NASA Astrophysics Data System (ADS)

Nezhad, Mohsen Motahari; Shojaeefard, Mohammad Hassan; Shahraki, Saeid

2016-02-01

In this study, the experiments aimed at analyzing thermally the exhaust valve in an air-cooled internal combustion engine and estimating the thermal contact conductance in fixed and periodic contacts. Due to the nature of internal combustion engines, the duration of contact between the valve and its seat is too short, and much time is needed to reach the quasi-steady state in the periodic contact between the exhaust valve and its seat. Using the methods of linear extrapolation and the inverse solution, the surface contact temperatures and the fixed and periodic thermal contact conductance were calculated. The results of linear extrapolation and inverse methods have similar trends, and based on the error analysis, they are accurate enough to estimate the thermal contact conductance. Moreover, due to the error analysis, a linear extrapolation method using inverse ratio is preferred. The effects of pressure, contact frequency, heat flux, and cooling air speed on thermal contact conductance have been investigated. The results show that by increasing the contact pressure the thermal contact conductance increases substantially. In addition, by increasing the engine speed the thermal contact conductance decreases. On the other hand, by boosting the air speed the thermal contact conductance increases, and by raising the heat flux the thermal contact conductance reduces. The average calculated error equals to 12.9 %.

Thermal Effects on Microstructural Heterogeneity of Inconel 718 Materials Fabricated by Electron Beam Melting

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

Sames, William J.; Unocic, Kinga A.; Dehoff, Ryan R.

2014-07-28

Additive manufacturing (AM) technologies, also known as 3D printing, have demonstrated the potential to fabricate complex geometrical components, but the resulting microstructures and mechanical properties of these materials are not well understood due to unique and complex thermal cycles observed during processing. The electron beam melting (EBM) process is unique because the powder bed temperature can be elevated and maintained at temperatures over 1000 °C for the duration of the process. This results in three specific stages of microstructural phase evolution: (a) rapid cool down from the melting temperature to the process temperature, (b) extended hold at the process temperature,more » and (c) slow cool down to the room temperature. In this work, the mechanisms for reported microstructural differences in EBM are rationalized for Inconel 718 based on measured thermal cycles, preliminary thermal modeling, and computational thermodynamics models. The relationship between processing parameters, solidification microstructure, interdendritic segregation, and phase precipitation (δ, γ´, and γ´´) are discussed.« less

Lamb Wave Assessment of Fatigue and Thermal Damage in Composites

NASA Technical Reports Server (NTRS)

Seale, Michael D.; Smith, Barry T.; Prosser, W. H.

2004-01-01

Among the various techniques available, ultrasonic Lamb waves offer a convenient method of evaluating composite materials. Since the Lamb wave velocity depends on the elastic properties of a structure, an effective tool exists to monitor damage in composites by measuring the velocity of these waves. Lamb wave measurements can propagate over long distances and are sensitive to the desired in-plane elastic properties of the material. This paper describes two studies which monitor fatigue damage and two studies which monitor thermal damage in composites using Lamb waves. In the fatigue studies, the Lamb wave velocity is compared to modulus measurements obtained using strain gage measurements in the first experiment and the velocity is monitored along with the crack density in the second. In the thermal damage studies, one examines samples which were exposed to varying temperatures for a three minute duration and the second includes rapid thermal damage in composites by intense laser beams. In all studies, the Lamb wave velocity is demonstrated to be an excellent method to monitor damage in composites.

Thermal Electrons in Gamma-Ray Burst Afterglows

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

Ressler, Sean M.; Laskar, Tanmoy

2017-08-20

To date, nearly all multi-wavelength modeling of long-duration γ -ray bursts has ignored synchrotron radiation from the significant population of electrons expected to pass the shock without acceleration into a power-law distribution. We investigate the effect of including the contribution of thermal, non-accelerated electrons to synchrotron absorption and emission in the standard afterglow model, and show that these thermal electrons provide an additional source of opacity to synchrotron self-absorption, and yield an additional emission component at higher energies. The extra opacity results in an increase in the synchrotron self-absorption frequency by factors of 10–100 for fiducial parameters. The nature ofmore » the additional emission depends on the details of the thermal population, but is generally observed to yield a spectral peak in the optical brighter than radiation from the nonthermal population by similar factors a few seconds after the burst, remaining detectable at millimeter and radio frequencies several days later.« less

Enabling Long-Duration Lunar Equatorial Operations With Thermal Wadi Infrastructure

NASA Technical Reports Server (NTRS)

Jones, Heather L.; Thornton, John P.; Balasubramaniam, Ramaswamy; Gokoglu, Suleyman, A.; Sacksteder, Kurt R.; Whittaker, William L.

2011-01-01

Long duration missions on the Moon s equator must survive lunar nights. With 350 hr of cryogenic temperatures, lunar nights present a challenge to robotic survival. Insulation is imperfect, so it is not possible to passively contain enough heat to stay warm through the night. Components that enable mobility, environmental sensing and solar power generation must be exposed, and they leak heat. Small, lightweight rovers cannot store enough energy to warm components throughout the night without some external source of heat or power. Thermal wadis, however, can act as external heat sources to keep robots warm through the lunar night. Electrical power can also be provided to rovers during the night from batteries stored in the ground beside wadis. Buried batteries can be warmed by the wadi s heat. Results from analysis of the interaction between a rover and a wadi are presented. A detailed three-dimensional (3D) thermal model and an easily configurable two-dimensional (2D) thermal model are used for analysis.

Thermal shock removal of defective glass-enamel coating from cast-iron products

NASA Astrophysics Data System (ADS)

Aleutdinov, A. D.; Ghyngazov, S. A.; Mylnikova, T. S.; Luchnikov, P. A.

2015-04-01

A setup for light beam exposure has been developed. The setup was used to consider the technology of thermal shock destruction of the coating by pulsed-periodic exposure to powerful focused light from the xenon arc lamp DKsShRB-10000. It is shown that this type of exposure can effectively remove the glass-enamel coating from iron products. The optimal mode of setup operation to efficiently remove the defective glass-enamel coating is found: the diameter of the focused light beams is 2.5-3.5 cm; the lamp arc pulse current is 350-450 A; pulse duration is (0.5-1) s and pulse repetition frequency is (0.15-0.5) s-1.

Lattice parameter evolution in Pt nanoparticles during photo-thermally induced sintering and grain growth

DOE PAGES

Kelly, B.G.; Loether, A.; DiChiara, A. D.; ...

2017-04-20

An in-situ optical pump/x-ray probe technique has been used to study the size dependent lattice parameter of Pt nanoparticles subjected to picosecond duration optical laser pulses. The as-prepared Pt nanoparticles exhibited a contracted lattice parameter consistent with the response of an isolated elastic sphere to a compressive surface stress. During photo-thermally induced sintering and grain growth, however, the Pt lattice parameter did not evolve with the inverse particle size dependence predicted by simple surface stress models. Lastly, the observed behavior could be attributed to the combined effects of a compressive surface/interface stress and a tensile stress arising from intergranular material.

Lattice parameter evolution in Pt nanoparticles during photo-thermally induced sintering and grain growth

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

Kelly, B.G.; Loether, A.; DiChiara, A. D.

An in-situ optical pump/x-ray probe technique has been used to study the size dependent lattice parameter of Pt nanoparticles subjected to picosecond duration optical laser pulses. The as-prepared Pt nanoparticles exhibited a contracted lattice parameter consistent with the response of an isolated elastic sphere to a compressive surface stress. During photo-thermally induced sintering and grain growth, however, the Pt lattice parameter did not evolve with the inverse particle size dependence predicted by simple surface stress models. Lastly, the observed behavior could be attributed to the combined effects of a compressive surface/interface stress and a tensile stress arising from intergranular material.

Cryogenic Fluid Management Technology Development for Nuclear Thermal Propulsion

NASA Technical Reports Server (NTRS)

Taylor, B. D.; Caffrey, J.; Hedayat, A.; Stephens, J.; Polsgrove, R.

2015-01-01

Cryogenic fluid management technology is critical to the success of future nuclear thermal propulsion powered vehicles and long duration missions. This paper discusses current capabilities in key technologies and their development path. The thermal environment, complicated from the radiation escaping a reactor of a nuclear thermal propulsion system, is examined and analysis presented. The technology development path required for maintaining cryogenic propellants in this environment is reviewed. This paper is intended to encourage and bring attention to the cryogenic fluid management technologies needed to enable nuclear thermal propulsion powered deep space missions.

Influence of age, body temperature, GABAA receptor inhibition and caffeine on the Hering-Breuer inflation reflex in unanesthetized rat pups

PubMed Central

Arnal, Ashley V.; Gore, Julie L.; Rudkin, Alison; Bartlett, Donald; Leiter, J.C.

2013-01-01

We measured the duration of apnea induced by sustained end-inspiratory lung inflation (the Hering Breuer Reflex; HBR) in unanesthetized infant rat pups aged 4 days (P4) to P20 at body temperatures of 32°C and 36°C. The expiratory prolongation elicited by the HBR lasted longer in the younger pups and lasted longer at the higher body temperature. Blockade of adenosine receptors by caffeine following injection into the cisterna magna (ICM) significantly blunted the thermal prolongation of the HBR. Blockade of gama-amino-butyric acid A (GABAA) receptors by pre-treatment with ICM bicuculline had no effect on the HBR duration at either body temperature. To test the hypothesis that developmental maturation of GABAergic inhibition of breathing was modifying the response to bicuculline, we pretreated rat pups with systemically administered bumetanide to lower the intracellular chloride concentration, and repeated the bicuculline studies. Bicuculline still did not alter the HBR at either temperature after bumetanide treatment. We administered PSB-36, a selective adenosine A1 receptor antagonist, and this drug treatment did not modify the HBR. We conclude that caffeine blunts the thermal prolongation of the HBR, probably by blocking adenosine A2a receptors. The thermally-sensitive adenosinergic prolongation of the HBR in these intact animals does not seem to depend on GABAA receptors PMID:23318703

Rapid and repeatable fabrication of high A/R silk fibroin microneedles using thermally-drawn micromolds.

PubMed

Lee, JiYong; Park, Seung Hyun; Seo, Il Ho; Lee, Kang Ju; Ryu, WonHyoung

2015-08-01

Thermal drawing is a versatile rapid prototyping method that can freely form microneedle (MN) structures with ultra-high aspect ratio without relying on any complex and expensive process. However, it is still challenging to repeatedly produce MNs with identical shapes using this thermal drawing due to small fluctuations in processing conditions such as temperatures, drawing speeds, drawing heights, or parallelism in the drawing setup. In addition, thermal drawing is only applicable to thermoplastic materials and most natural biomaterials are incompatible with this method. Thus, we propose use of thermal drawing to fabricate master molds with high aspect ratios and replicate the shape by micromolding. In this work, high A/R MNs with various body profiles were fabricated by thermal drawing and replicated to silk fibroin (SF) MNs multiple times using micromolding. The original MN shape was precisely copied to the SF MNs. Methanol treatment enhanced the mechanical strength of SF MNs up to about 113% more depending on the treatment duration. We also demonstrated that methanol exposure time could effectively control drug release rates from SF MNs. Copyright © 2015 Elsevier B.V. All rights reserved.

Descriptors of natural thermal regimes in streams and their responsiveness to change in the Pacific Northwest of North America

USGS Publications Warehouse

Arismendi, Ivan; Johnson, Sherri L.; Dunham, Jason B.; Haggerty, Roy

2013-01-01

1. Temperature is a major driver of ecological processes in stream ecosystems, yet the dynamics of thermal regimes remain poorly described. Most work has focused on relatively simple descriptors that fail to capture the full range of conditions that characterise thermal regimes of streams across seasons or throughout the year. 2. To more completely describe thermal regimes, we developed several descriptors of magnitude, variability, frequency, duration and timing of thermal events throughout a year. We evaluated how these descriptors change over time using long-term (1979–2009), continuous temperature data from five relatively undisturbed cold-water streams in western Oregon, U.S.A. In addition to trends for each descriptor, we evaluated similarities among them, as well as patterns of spatial coherence, and temporal synchrony. 3. Using different groups of descriptors, we were able to more fully capture distinct aspects of the full range of variability in thermal regimes across space and time. A subset of descriptors showed both higher coherence and synchrony and, thus, an appropriate level of responsiveness to examine evidence of regional climatic influences on thermal regimes. Most notably, daily minimum values during winter–spring were the most responsive descriptors to potential climatic influences. 4. Overall, thermal regimes in streams we studied showed high frequency and low variability of cold temperatures during the cold-water period in winter and spring, and high frequency and high variability of warm temperatures during the warm-water period in summer and autumn. The cold and warm periods differed in the distribution of events with a higher frequency and longer duration of warm events in summer than cold events in winter. The cold period exhibited lower variability in the duration of events, but showed more variability in timing. 5. In conclusion, our results highlight the importance of a year-round perspective in identifying the most responsive characteristics or descriptors of thermal regimes in streams. The descriptors we provide herein can be applied across hydro-ecological regions to evaluate spatial and temporal patterns in thermal regimes. Evaluation of coherence and synchrony of different components of thermal regimes can facilitate identification of impacts of regional climate variability or local human or natural influences.

Prevalence of distal diabetic polyneuropathy using quantitative sensory methods in a population with diabetes of more than 10 years' disease duration.

PubMed

Miralles-García, José M; de Pablos-Velasco, Pedro; Cabrerizo, Lucio; Pérez, María; López-Gómez, Vanessa

2010-11-01

Results of studies on the prevalence of distal diabetic polyneuropathy (DPN) are contradictory. Conventional methods used for the diagnosis of DPN in clinical practice have limited effectiveness. The present study aimed to assess the prevalence of DPN in a population with long-standing diabetes (more than 10 years disease duration) by measuring vibratory, thermal and tactile sensitivities with quantitative sensory devices, as well as their relationship with associated clinical risk factors. A total of 1011 diabetic patients were evaluated in a multicenter, cross-sectional, observational study. The three sensitivities were assessed by ultrabiothesiometer, aesthesiometer and thermoskin devices, respectively. The prevalence of neuropathic pain was validated by the DN4 questionnaire. Of the 1011 cases included, 400 (39.6%) met the diagnostic criteria of DPN, while no DPN was found in the remaining 611 (60.4%). Of the 400 patients with DPN, 253 (63.2%) showed clinical manifestations, while 147 (36.8%) were diagnosed as subclinical DPN. The prevalence of DPN increased with disease duration. There was a progressive loss of the three sensitivities with increased disease duration, particularly thermal and vibratory sensitivities. This loss was statistically significant for the latter two sensitivities. Among patients with clinical DPN, 84.2% had painful neuropathic symptoms. The prevalence of DPN was positively related to micro- and macroangiopathic complications and with dyslipidemia. This study reveals a high degree of underdiagnosis of DPN, most likely due to the asymptomatic nature of the disease in a considerable proportion of patients. Our observations provide evidence of the usefulness of specific equipment for quantitative and objective assessment of polyneuropathy. Copyright © 2010 SEEN. Published by Elsevier Espana. All rights reserved.

The Effect of a Non-Gaussian Random Loading on High-Cycle Fatigue of a Thermally Post-Buckled Structure

NASA Technical Reports Server (NTRS)

Rizzi, Stephen A.; Behnke, marlana N.; Przekop, Adam

2010-01-01

High-cycle fatigue of an elastic-plastic beam structure under the combined action of thermal and high-intensity non-Gaussian acoustic loadings is considered. Such loadings can be highly damaging when snap-through motion occurs between thermally post-buckled equilibria. The simulated non-Gaussian loadings investigated have a range of skewness and kurtosis typical of turbulent boundary layer pressure fluctuations in the vicinity of forward facing steps. Further, the duration and steadiness of high excursion peaks is comparable to that found in such turbulent boundary layer data. Response and fatigue life estimates are found to be insensitive to the loading distribution, with the minor exception of cases involving plastic deformation. In contrast, the fatigue life estimate was found to be highly affected by a different type of non-Gaussian loading having bursts of high excursion peaks.

Aqueously Dispersed Silver Nanoparticle-Decorated Boron Nitride Nanosheets for Reusable, Thermal Oxidation-Resistant Surface Enhanced Raman Spectroscopy (SERS) Devices

NASA Technical Reports Server (NTRS)

Lin, Yi; Bunker, Christopher E.; Fernandos, K. A. Shiral; Connell, John W.

2012-01-01

The impurity-free aqueous dispersions of boron nitride nanosheets (BNNS) allowed the facile preparation of silver (Ag) nanoparticle-decorated BNNS by chemical reduction of an Ag salt with hydrazine in the presence of BNNS. The resultant Ag-BNNS nanohybrids remained dispersed in water, allowing convenient subsequent solution processing. By using substrate transfer techniques, Ag-BNNS nanohybrid thin film coatings on quartz substrates were prepared and evaluated as reusable surface enhanced Raman spectroscopy (SERS) sensors that were robust against repeated solvent washing. In addition, because of the unique thermal oxidation-resistant properties of the BNNS, the sensor devices may be readily recycled by short-duration high temperature air oxidation to remove residual analyte molecules in repeated runs. The limiting factor associated with the thermal oxidation recycling process was the Ostwald ripening effect of Ag nanostructures.

Heating of solid targets with laser pulses

NASA Technical Reports Server (NTRS)

Bechtel, J. H.

1975-01-01

Analytical and numerical solutions to the heat-conduction equation are obtained for the heating of absorbing media with pulsed lasers. The spatial and temporal form of the temperature is determined using several different models of the laser irradiance. Both surface and volume generation of heat are discussed. It is found that if the depth of thermal diffusion for the laser-pulse duration is large compared to the optical-attenuation depth, the surface- and volume-generation models give nearly identical results. However, if the thermal-diffusion depth for the laser-pulse duration is comparable to or less than the optical-attenuation depth, the surface-generation model can give significantly different results compared to the volume-generation model. Specific numerical results are given for a tungsten target irradiated by pulses of different temporal durations and the implications of the results are discussed with respect to the heating of metals by picosecond laser pulses.

Mobile phone and my health

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

Surducan, Aneta; Dabala, Dana; Neamtu, Camelia, E-mail: emanoil.surducan@itim-cj.ro

The interaction of the microwave radiation emitted by mobile phones with the user's body is analyzed from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) recommendations perspective as a correlation between the specific absorption ratio (SAR) of the mobile phone and the call duration. The relative position of the cell phone to the user's body, the dielectric properties of the exposed body parts, the SAR value and the call duration are considered in the local body temperature rise due to the microwave heating effect. The recommended local temperature rise limit in the human body is evaluated according to standards. Themore » aim of this study is to disseminate information to young people, especially high school students, about the microwave thermal effects on the human body, to make them aware of the environmental electromagnetic pollution and to offer them a simple method of biological self protection.« less

Comparison of the Thermal Spread of Three Different Electrosurgical Generators on Rat Uterus: A Preliminary Experimental Study.

PubMed

Karacan, Tolga; Usta, Taner; Ozkaynak, Aysel; Onur Cakir, Omer; Kahraman, Aslı; Ozyurek, Eser

2018-05-23

The objective of this study was to compare the depth and width of thermal spread caused on rat uterine tissue after application of 3 different electrosurgical generators. Alsa Excell 350 MCDSe (Unit A), Meditom DT-400P (Unit M), and ERBE Erbotom VIO 300 D (Unit E) electrosurgical units (ESUs) were used. The number of Wistar Hannover rats required to obtain valid results was 10. The primary objective of the study was to compare the 3 ESUs using the same instrument and the same waveform. The secondary objective of the study was to compare the differences between monopolar and bipolar systems of each ESU separately using the same waveform. The thermal spread caused by each ESU using monopolar instruments with continuous and interrupted waveforms was significantly different. Among the 3 devices, Unit A caused the largest thermal uterine tissue spread. On the other hand, Unit E caused the most superficial thermal tissue spread, and the smallest thermal spread among all ESUs. Surgeons should note that different ESUs used with the same power output might create different thermal effects especially in the monopolar configuration within the same waveform, for the same duration, and with the same instrument. © 2018 S. Karger AG, Basel.

Research Technology

NASA Image and Video Library

2004-04-15

Harnessing the Sun's energy through Solar Thermal Propulsion will propel vehicles through space by significantly reducing weight, complexity, and cost while boosting performance over current conventional upper stages. Another solar powered system, solar electric propulsion, demonstrates ion propulsion is suitable for long duration missions. Pictured is an artist's concept of space flight using solar thermal propulsion.

Effects of local climate and hydrological conditions on the thermal regime of a reservoir at Tropic of Cancer, in southern China.

PubMed

Wang, Sheng; Qian, Xin; Han, Bo-Ping; Luo, Lian-Cong; Hamilton, David P

2012-05-15

Thermal regime is strongly associated with hydrodynamics in water, and it plays an important role in the dynamics of water quality and ecosystem succession of stratified reservoirs. Changes in both climate and hydrological conditions can modify thermal regimes. Liuxihe Reservoir (23°45'50″N; 113°46'52″E) is a large, stratified and deep reservoir in Guangdong Province, located at the Tropic of Cancer of southern China. The reservoir is a warm monomictic water body with a long period of summer stratification and a short period of mixing in winter. The vertical distribution of suspended particulate material and nutrients are influenced strongly by the thermal structure and the associated flow fields. The hypolimnion becomes anoxic in the stratified period, increasing the release of nutrients from the bottom sediments. Fifty-one years of climate and reservoir operational observations are used here to show the marked changes in local climate and reservoir operational schemes. The data show increasing air temperature and more violent oscillations in inflow volumes in the last decade, while the inter-annual water level fluctuations tend to be more moderate. To quantify the effects of changes in climate and hydrological conditions on thermal structure, we used a numerical simulation model to create scenarios incorporating different air temperatures, inflow volumes, and water levels. The simulations indicate that water column stability, the duration of the mixing period, and surface and outflow temperatures are influenced by both natural factors and by anthropogenic factors such as climate change and reservoir operation schemes. Under continuous warming and more stable storage in recent years, the simulations indicate greater water column stability and increased duration of stratification, while irregular large discharge events may reduce stability and lead to early mixing in autumn. Our results strongly suggest that more attention should be focused on water quality in years of extreme climate variation and hydrological conditions, and selective withdrawal of deep water may provide an efficient means to reduce internal loading in warm years. Copyright © 2012 Elsevier Ltd. All rights reserved.

Space environment durability of beta cloth in LDEF thermal blankets

NASA Technical Reports Server (NTRS)

Linton, Roger C.; Whitaker, Ann F.; Finckenor, Miria M.

1993-01-01

Beta cloth performance for use on long-term space vehicles such as Space Station Freedom (S.S. Freedom) requires resistance to the degrading effects of the space environment. The major issues are retention of thermal insulating properties through maintaining optical properties, preserving mechanical integrity, and generating minimal particulates for contamination-sensitive spacecraft surfaces and payloads. The longest in-flight test of beta cloth's durability was on the Long Duration Exposure Facility (LDEF), where it was exposed to the space environment for 68 months. The LDEF contained 57 experiments which further defined the space environment and its effects on spacecraft materials. It was deployed into low-Earth orbit (LEO) in Apr. 1984 and retrieved Jan. 1990 by the space shuttle. Among the 10,000 plus material constituents and samples onboard were thermal control blankets of multilayer insulation with a beta cloth outer cover and Velcro attachments. These blankets were exposed to hard vacuum, thermal cycling, charged particles, meteoroid/debris impacts, ultraviolet (UV) radiation, and atomic oxygen (AO). Of these space environmental exposure elements, AO appears to have had the greatest effect on the beta cloth. The beta cloth analyzed in this report came from the MSFC Experiment S1005 (Transverse Flat-Plate Heat Pipe) tray oriented approximately 22 deg from the leading edge vector of the LDEF satellite. The location of the tray on LDEF and the placement of the beta cloth thermal blankets are shown. The specific space environment exposure conditions for this material are listed.

TRPV1 channels in the nucleus of the solitary tract mediate thermal prolongation of the LCR in decerebrate piglets.

PubMed

Xia, Luxi; Bartlett, Donald; Leiter, J C

2011-04-30

Elevating body temperature or just the temperature of the dorsal medulla by approximately 2°C prolongs the laryngeal chemoreflex (LCR) in decerebrate neonatal piglets. We tested the hypothesis that transient receptor potential vanilloid 1 (TRPV1) receptors in the nucleus of the solitary tract (NTS) mediate thermal prolongation of the LCR. We studied the effect of a selective TRPV1 receptor antagonist on thermal prolongation of the LCR, and we tested the effect of a TRPV1 agonist on the duration of the LCR under normothermic conditions. We studied 37 decerebrate neonatal piglets between the ages of post-natal days 4 and 7. The TRPV1 receptor antagonist, 5'-iodoresiniferatoxin (65μM/L in 100nL), blocked thermal prolongation of the LCR when injected bilaterally into the region of the NTS. The TRPV1 agonist, resiniferatoxin (0.65-1.0mM/L in 100nL), prolonged the LCR after bilateral injection into the NTS even when the body temperature of each piglet was normal. The effect of the TRPV1 agonists could be blocked by treatment with the GABA(A) receptor antagonist, bicuculline, whether given intravenously (0.3mg/kg) or focally injected bilaterally into the NTS (10mM in 100nL). We conclude that TRPV1 receptors in the NTS mediate thermal prolongation of the LCR. Copyright © 2011 Elsevier B.V. All rights reserved.

Intracranial inertial cavitation threshold and thermal ablation lesion creation using MRI-guided 220-kHz focused ultrasound surgery: preclinical investigation.

PubMed

Xu, Zhiyuan; Carlson, Carissa; Snell, John; Eames, Matt; Hananel, Arik; Lopes, M Beatriz; Raghavan, Prashant; Lee, Cheng-Chia; Yen, Chun-Po; Schlesinger, David; Kassell, Neal F; Aubry, Jean-Francois; Sheehan, Jason

2015-01-01

In biological tissues, it is known that the creation of gas bubbles (cavitation) during ultrasound exposure is more likely to occur at lower rather than higher frequencies. Upon collapsing, such bubbles can induce hemorrhage. Thus, acoustic inertial cavitation secondary to a 220-kHz MRI-guided focused ultrasound (MRgFUS) surgery is a serious safety issue, and animal studies are mandatory for laying the groundwork for the use of low-frequency systems in future clinical trials. The authors investigate here the in vivo potential thresholds of MRgFUS-induced inertial cavitation and MRgFUS-induced thermal coagulation using MRI, acoustic spectroscopy, and histology. Ten female piglets that had undergone a craniectomy were sonicated using a 220-kHz transcranial MRgFUS system over an acoustic energy range of 5600-14,000 J. For each piglet, a long-duration sonication (40-second duration) was performed on the right thalamus, and a short sonication (20-second duration) was performed on the left thalamus. An acoustic power range of 140-300 W was used for long-duration sonications and 300-700 W for short-duration sonications. Signals collected by 2 passive cavitation detectors were stored in memory during each sonication, and any subsequent cavitation activity was integrated within the bandwidth of the detectors. Real-time 2D MR thermometry was performed during the sonications. T1-weighted, T2-weighted, gradient-recalled echo, and diffusion-weighted imaging MRI was performed after treatment to assess the lesions. The piglets were killed immediately after the last series of posttreatment MR images were obtained. Their brains were harvested, and histological examinations were then performed to further evaluate the lesions. Two types of lesions were induced: thermal ablation lesions, as evidenced by an acute ischemic infarction on MRI and histology, and hemorrhagic lesions, associated with inertial cavitation. Passive cavitation signals exhibited 3 main patterns identified as follows: no cavitation, stable cavitation, and inertial cavitation. Low-power and longer sonications induced only thermal lesions, with a peak temperature threshold for lesioning of 53°C. Hemorrhagic lesions occurred only with high-power and shorter sonications. The sizes of the hemorrhages measured on macroscopic histological examinations correlated with the intensity of the cavitation activity (R2 = 0.74). The acoustic cavitation activity detected by the passive cavitation detectors exhibited a threshold of 0.09 V·Hz for the occurrence of hemorrhages. This work demonstrates that 220-kHz ultrasound is capable of inducing a thermal lesion in the brain of living swines without hemorrhage. Although the same acoustic energy can induce either a hemorrhage or a thermal lesion, it seems that low-power, long-duration sonication is less likely to cause hemorrhage and may be safer. Although further study is needed to decrease the likelihood of ischemic infarction associated with the 220-kHz ultrasound, the threshold established in this work may allow for the detection and prevention of deleterious cavitations.

Reactive simulation of the chemistry behind the condensed-phase ignition of RDX from hot spots.

PubMed

Joshi, Kaushik L; Chaudhuri, Santanu

2015-07-28

Chemical events that lead to thermal initiation and spontaneous ignition of the high-pressure phase of RDX are presented using reactive molecular dynamics simulations. In order to initiate the chemistry behind thermal ignition, approximately 5% of RDX crystal is subjected to a constant temperature thermal pulse for various time durations to create a hot spot. After application of the thermal pulse, the ensuing chemical evolution of the system is monitored using reactive molecular dynamics under adiabatic conditions. Thermal pulses lasting longer than certain time durations lead to the spontaneous ignition of RDX after an incubation period. For cases where the ignition is observed, the incubation period is dominated by intermolecular and intramolecular hydrogen transfer reactions. Contrary to the widely accepted unimolecular models of initiation chemistry, N-N bond dissociations that produce NO2 species are suppressed in the condensed phase. The gradual temperature and pressure increase in the incubation period is accompanied by the accumulation of short-lived, heavier polyradicals. The polyradicals contain intact triazine rings from the RDX molecules. At certain temperatures and pressures, the polyradicals undergo ring-opening reactions, which fuel a series of rapid exothermic chemical reactions leading to a thermal runaway regime with stable gas-products such as N2, H2O and CO2. The evolution of the RDX crystal throughout the thermal initiation, incubation and thermal runaway phases observed in the reactive simulations contains a rich diversity of condensed-phase chemistry of nitramines under high-temperature/pressure conditions.

Response of rainy season duration over Asian monsoon region to astronomical forcing under glacial and interglacial conditions

NASA Astrophysics Data System (ADS)

Shi, Z.

2017-12-01

The responses of Asian summer monsoon and associated precipitation to astronomical forcing have beenintensively explored during the past decades, but debate still exists regarding whether or not the Asianmonsoon is controlled by northern or southern summer insolation. Various modeling studies have been conducted that support the potential roles played by the insolation in bothhemispheres. Among these previous studies, however, the main emphasis has been on the Asianmonsoon intensity, with the response of monsoon duration having received little consideration. In thepresent study, the response of the rainy season duration over different monsoon areas to astronomical forcingand its contribution to total annual precipitation are evaluated using an atmospheric general circulationmodel. The results show that the durations of the rainy seasons, especially their withdrawal, in northernEast Asia and the India-Bay of Bengal region, are sensitive to precession change under interglacial-likeconditions. Compared to those during stronger boreal summer insolation, the Asian monsoon associatedrainy seasons at weaker insolation last longer, although the peak intensity is smaller. Thislonger duration of rainfall, which results from the change in land-ocean thermal contrast associated withatmospheric diabatic heating, can counterbalance the weakened intensity in certain places and induce anopposite response of total annual precipitation. However, the duration effect of Asian monsoon is limitedunder glacial-like conditions. Nevertheless, monsoon duration is a factor that can dominate the astronomical-scalevariability of Asian monsoon, alongside the intensity, and it should therefore receive greaterattention when attempting to explain astronomical-scale monsoon change.

Non-thermal plasma instabilities induced by deformation of the electron energy distribution function

NASA Astrophysics Data System (ADS)

Dyatko, N. A.; Kochetov, I. V.; Napartovich, A. P.

2014-08-01

Non-thermal plasma is a key component in gas lasers, microelectronics, medical applications, waste gas cleaners, ozone generators, plasma igniters, flame holders, flow control in high-speed aerodynamics and others. A specific feature of non-thermal plasma is its high sensitivity to variations in governing parameters (gas composition, pressure, pulse duration, E/N parameter). This sensitivity is due to complex deformations of the electron energy distribution function (EEDF) shape induced by variations in electric field strength, electron and ion number densities and gas excitation degree. Particular attention in this article is paid to mechanisms of instabilities based on non-linearity of plasma properties for specific conditions: gas composition, steady-state and decaying plasma produced by the electron beam, or by an electric current pulse. The following effects are analyzed: the negative differential electron conductivity; the absolute negative electron mobility; the stepwise changes of plasma properties induced by the EEDF bi-stability; thermo-current instability and the constriction of the glow discharge column in rare gases. Some of these effects were observed experimentally and some of them were theoretically predicted and still wait for experimental confirmation.

Improving oxidation resistance and thermal insulation of thermal barrier coatings by intense pulsed electron beam irradiation

NASA Astrophysics Data System (ADS)

Mei, Xianxiu; Liu, Xiaofei; Wang, Cunxia; Wang, Younian; Dong, Chuang

2012-12-01

In this paper, intense pulsed electron beam was used for the irradiation treatment of 6-8% Y2O3-stablized ZrO2 thermal barrier coating prepared by electron beam-physical vapor deposition to achieve the "sealing" of columnar crystals, thus improving their thermal insulation properties and high temperature oxidation resistance. The electron beam parameters used were: pulse duration 200 μs, electron voltage 15 kV, energy density 3, 5, 8, 15, 20 J/cm2, and pulsed numbers 30. 1050 °C cyclic oxidation and static oxidation experiments were used for the research on oxidation resistance of the coatings. When the energy density of the electron beam was larger than 8 J/cm2, ZrO2 ceramic coating surface was fully re-melted and became smooth, dense and shiny. The coating changed into a smooth polycrystalline structure, thus achieving the "sealing" effect of the columnar crystals. After irradiations with the energy density of 8-15 J/cm2, the thermally grown oxide coating thickness decreased significantly in comparison with non-irradiated coatings, showing that the re-melted coating improved the oxidation resistance of the coatings. The results of thermal diffusivity test by laser flash method showed that the thermal diffusion rate of the irradiated coating was lower than that of the coating without irradiation treatment, and the thermal insulation performance of irradiated coating was improved.

Maternal influences on early development: preferred temperature prior to oviposition hastens embryogenesis and enhances offspring traits in the Children's python, Antaresia childreni.

PubMed

Lorioux, Sophie; DeNardo, Dale F; Gorelick, Root; Lourdais, Olivier

2012-04-15

Embryonic life is particularly sensitive to its surroundings, and the developmental environment can have long-lasting effects on offspring. In oviparous species, the impacts of the developmental environment on offspring traits are mostly examined during development within the egg. However, as more than 25% of the development of squamate reptiles can occur prior to oviposition, we explored the effect of thermal conditions on development prior to oviposition in an oviparous snake species, the Children's python (Antaresia childreni). We housed gravid female pythons under three thermal cycles: an optimal regime that reflected maternal preference in a non-constrained environment (constant preferred body temperature of gravid females, T(set)=31.5°C) and two mildly suboptimal regimes that shared the same mean temperature of 27.7°C, but differed in the duration at T(set). In one of the constraining regimes, females had access to T(set) for 4 h daily whereas in the other regime, females never reached T(set) (maximal temperature of 29.0°C). Thermal treatments were maintained throughout gravidity in all three groups, but, after oviposition, all eggs were incubated at T(set) until hatching. Compared with the optimal regime, the two suboptimal regimes had a longer duration of gravidity, which resulted in delayed hatching. Between the two suboptimal regimes, gravidity was significantly shorter in the treatment that included time at T(set). Furthermore, suboptimal regimes influenced offspring traits at hatching, including body morphology, antipredator behavior, strength and metabolism. However, partial access to maternal T(set) significantly enhanced several offspring traits, including performance. Our results demonstrate the importance of time at T(set) on early development and suggest an adaptive significance of maternal thermoregulation prior to oviposition.

Biologically-Derived Photonic Materials for Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Johnson, Sylvia M.; Squire, Thomas H.; Lawson, John W.; Gusman, Michael; Lau, K.-H.; Sanjurjo, Angel

2014-01-01

Space vehicles entering a planetary atmosphere at high velocity can be subject to substantial radiative heating from the shock layer in addition to the convective heating caused by the flow of hot gas past the vehicle surface. The radiative component can be very high but of a short duration. Approaches to combat this effect include investigation of various materials to reflect the radiation. Photonic materials can be used to reflect radiation. The wavelengths reflected depend on the length scale of the ordered microstructure. Fabricating photonic structures, such as layers, can be time consuming and expensive. We have used a biologically-derived material as the template for forming a high temperature photonic material that could be incorporated into a heatshield thermal protection material.

Use of Liposomal Bupivacaine for Postoperative Analgesia in an Incisional Pain Model in Rats (Rattus norvegicus)

PubMed Central

Kang, Stacey C; Jampachaisri, Katechan; Seymour, Travis L; Felt, Stephen A; Pacharinsak, Cholawat

2017-01-01

The local anesthetic bupivacaine is valuable for perioperative analgesia, but its use in the postoperative period is limited by its short duration of action. Here, we evaluated the application of a slow-release liposomal formulation of bupivacaine for postoperative analgesia. The aim was to assess whether liposomal bupivacaine effectively attenuates postoperative mechanical and thermal hypersensitivity in a rat model of incisional pain. Rats (n = 36) were randomly assigned to 1 of 5 treatment groups: saline, 1 mL/kg SC every 12 h for 2 d; buprenorphine HCl, 0.05 mg/kg SC every 12 h for 2 d (Bup HCl); 0.5% bupivacaine, 2 mg/kg SC local infiltration once (Bupi); liposomal bupivacaine, 1 mg/kg SC local infiltration once (Exp1); and liposomal bupivacaine, 6 mg/kg SC local infiltration once (Exp6). Mechanical and thermal hypersensitivity were evaluated daily on days –1, 0, 1, 2, 3, and 4. The saline group exhibited both hypersensitivities through all 4 evaluated postoperative days. Bup HCl attenuated mechanical hypersensitivity for 2 d and thermal hypersensitivity for 1 d. Bupi attenuated only thermal hypersensitivity for 4 d. Rats in the Exp1 group showed attenuation of both mechanical and thermal hypersensitivity for 4 d, and those in the Exp6 group had attenuation of mechanical hypersensitivity on day 0 and thermal hypersensitivity for 4 d. These data suggest that a single local infiltration of liposomal bupivacaine at a dose of 1 mg/kg SC effectively attenuates postoperative mechanical and thermal hypersensitivity for 4 d in a rat model of incisional pain. PMID:28905717

Use of Liposomal Bupivacaine for Postoperative Analgesia in an Incisional Pain Model in Rats (Rattus norvegicus).

PubMed

Kang, Stacey C; Jampachaisri, Katechan; Seymour, Travis L; Felt, Stephen A; Pacharinsak, Cholawat

2017-01-01

The local anesthetic bupivacaine is valuable for perioperative analgesia, but its use in the postoperative period is limited by its short duration of action. Here, we evaluated the application of a slow-release liposomal formulation of bupivacaine for postoperative analgesia. The aim was to assess whether liposomal bupivacaine effectively attenuates postoperative mechanical and thermal hypersensitivity in a rat model of incisional pain. Rats (n = 36) were randomly assigned to 1 of 5 treatment groups: saline, 1 mL/kg SC every 12 h for 2 d; buprenorphine HCl, 0.05 mg/kg SC every 12 h for 2 d (Bup HCl); 0.5% bupivacaine, 2 mg/kg SC local infiltration once (Bupi); liposomal bupivacaine, 1 mg/kg SC local infiltration once (Exp1); and liposomal bupivacaine, 6 mg/kg SC local infiltration once (Exp6). Mechanical and thermal hypersensitivity were evaluated daily on days -1, 0, 1, 2, 3, and 4. The saline group exhibited both hypersensitivities through all 4 evaluated postoperative days. Bup HCl attenuated mechanical hypersensitivity for 2 d and thermal hypersensitivity for 1 d. Bupi attenuated only thermal hypersensitivity for 4 d. Rats in the Exp1 group showed attenuation of both mechanical and thermal hypersensitivity for 4 d, and those in the Exp6 group had attenuation of mechanical hypersensitivity on day 0 and thermal hypersensitivity for 4 d. These data suggest that a single local infiltration of liposomal bupivacaine at a dose of 1 mg/kg SC effectively attenuates postoperative mechanical and thermal hypersensitivity for 4 d in a rat model of incisional pain.

Ultrashort pulse high repetition rate laser system for biological tissue processing

DOEpatents

Neev, Joseph; Da Silva, Luiz B.; Matthews, Dennis L.; Glinsky, Michael E.; Stuart, Brent C.; Perry, Michael D.; Feit, Michael D.; Rubenchik, Alexander M.

1998-01-01

A method and apparatus is disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates. The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place. The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates. The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width. The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications. The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment.

Validity of reciprocity rule on mouse skin thermal damage due to CO2 laser irradiation

NASA Astrophysics Data System (ADS)

Parvin, P.; Dehghanpour, H. R.; Moghadam, M. S.; Daneshafrooz, V.

2013-07-01

CO2 laser (10.6 μm) is a well-known infrared coherent light source as a tool in surgery. At this wavelength there is a high absorbance coefficient (860 cm-1), because of vibration mode resonance of H2O molecules. Therefore, the majority of the irradiation energy is absorbed in the tissue and the temperature of the tissue rises as a function of power density and laser exposure duration. In this work, the tissue damage caused by CO2 laser (1-10 W, ˜40-400 W cm-2, 0.1-6 s) was measured using 30 mouse skin samples. Skin damage assessment was based on measurements of the depth of cut, mean diameter of the crater and the carbonized layer. The results show that tissue damage as assessed above parameters increased with laser fluence and saturated at 1000 J cm-2. Moreover, the damage effect due to high power density at short duration was not equivalent to that with low power density at longer irradiation time even though the energy delivered was identical. These results indicate the lack of validity of reciprocity (Bunsen-Roscoe) rule for the thermal damage.

Properties of nanostructured undoped ZrO{sub 2} thin film electrolytes by plasma enhanced atomic layer deposition for thin film solid oxide fuel cells

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

Cho, Gu Young; Noh, Seungtak; Lee, Yoon Ho

2016-01-15

Nanostructured ZrO{sub 2} thin films were prepared by thermal atomic layer deposition (ALD) and by plasma-enhanced atomic layer deposition (PEALD). The effects of the deposition conditions of temperature, reactant, plasma power, and duration upon the physical and chemical properties of ZrO{sub 2} films were investigated. The ZrO{sub 2} films by PEALD were polycrystalline and had low contamination, rough surfaces, and relatively large grains. Increasing the plasma power and duration led to a clear polycrystalline structure with relatively large grains due to the additional energy imparted by the plasma. After characterization, the films were incorporated as electrolytes in thin film solidmore » oxide fuel cells, and the performance was measured at 500 °C. Despite similar structure and cathode morphology of the cells studied, the thin film solid oxide fuel cell with the ZrO{sub 2} thin film electrolyte by the thermal ALD at 250 °C exhibited the highest power density (38 mW/cm{sup 2}) because of the lowest average grain size at cathode/electrolyte interface.« less

Ultrashort pulse high repetition rate laser system for biological tissue processing

DOEpatents

Neev, J.; Da Silva, L.B.; Matthews, D.L.; Glinsky, M.E.; Stuart, B.C.; Perry, M.D.; Feit, M.D.; Rubenchik, A.M.

1998-02-24

A method and apparatus are disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates. The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place. The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates. The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width. The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications. The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment. 8 figs.

Protection of Electrical Systems from EM Hazards - Design Guide.

DTIC Science & Technology

1981-09-01

cm) Surface flashover Voltage (KV/cm) This criterion should be met for lighting voltage stresses of either polarity applied at up to 1000 KV/v sec rate...suppressor devices can be predicted. The part failure rate models in the handbook include the effects of part electrical stress , thermal stress , operating... stress . This test series contained over one million device hours of operation at temperatures uF to 145°C. The average duration of testing ranges from

Nonlinear Raman forward scattering of a short laser pulse in a collisional transversely magnetized plasma

NASA Astrophysics Data System (ADS)

Paknezhad, Alireza

2013-01-01

Nonlinear Raman forward scattering (NRFS) of an intense short laser pulse with a duration shorter than the plasma period through a homogenous collisional transversely magnetized plasma is investigated theoretically when ponderomotive, relativistic and collioninal nonlinearities are taken into account. The plasma is embedded in a uniform magnetic field perpendicular to both, the direction of propagation and electric vector of the radiation field. Nonlinear wave equation is set up and Fourier transformation method is used to solve the coupled equations describing NRFS instability. Finally, the growth rate of this instability is obtained. Thermal effects of plasma electrons and effect of the electron-ion collisions are examined. It is found that the growth rate of Raman forward scattering first decreases on increasing electron thermal velocity, minimizes at an optimum value, and then increases. Our results also show that the growth rate increases by increasing the electron-ion collisions.

Radiation and Thermal Effects on Used Nuclear Fuel and Nuclear Waste Forms

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

Weber, William J.; Zhang, Yanwen

This is the final report of the NEUP project “Radiation and Thermal Effects on Used Nuclear Fuel and Nuclear Waste Forms.” This project started on July 1, 2012 and was successfully completed on June 30, 2016. This report provides an overview of the main achievements, results and findings through the duration of the project. Additional details can be found in the main body of this report and in the individual Quarterly Reports and associated Deliverables of this project, which have been uploaded in PICS-NE. The objective of this research was to advance understanding and develop validated models on the effectsmore » of self-radiation from beta and alpha decay on the response of used nuclear fuel and nuclear waste forms during high-temperature interim storage and long-term permanent disposition. To achieve this objective, model used-fuel materials and model waste form materials were identified, fabricated, and studied.« less

High power, diffraction limited picosecond oscillator based on Nd:GdVO₄ bulk crystal with σ polarized in-band pumping.

PubMed

Lin, Hua; Guo, Jie; Gao, Peng; Yu, Hai; Liang, Xiaoyan

2016-06-27

We report on a high power passively mode-locked picosecond oscillator based on Nd:GdVO₄ crystal with σ polarized in-band pumping. Thermal gradient and thermal aberration was greatly decreased with proposed configuration. Maximum output power of 37 W at 81 MHz repetition rate with 19.3 ps pulse duration was achieved directly from Nd:GdVO₄ oscillator, corresponding to 51% optical efficiency. The oscillator maintained diffraction limited beam quality of M² < 1.05 at different output coupling with pulse duration between 11.2 ps to 19.3 ps.

Finite element model of thermal processes in retinal photocoagulation

NASA Astrophysics Data System (ADS)

Sramek, Christopher; Paulus, Yannis M.; Nomoto, Hiroyuki; Huie, Phil; Palanker, Daniel

2009-02-01

Short duration (< 20 ms) pulses are desirable in patterned scanning laser photocoagulation to confine thermal damage to the photoreceptor layer, decrease overall treatment time and reduce pain. However, short exposures have a smaller therapeutic window (defined as the ratio of rupture threshold power to that of light coagulation). We have constructed a finite-element computational model of retinal photocoagulation to predict spatial damage and improve the therapeutic window. Model parameters were inferred from experimentally measured absorption characteristics of ocular tissues, as well as the thresholds of vaporization, coagulation, and retinal pigment epithelial (RPE) damage. Calculated lesion diameters showed good agreement with histological measurements over a wide range of pulse durations and powers.

High-energy long duration frequency-doubled Nd:YAG laser and application to venous occlusion

NASA Astrophysics Data System (ADS)

Zhang, Laiming; Yang, Guilong; Li, Dianjun; Lu, Qipeng; Gu, Huadong; Zhu, Linlin; Zhao, Zhenwu; Li, Xin; Tang, Yuguo; Guo, Jin

2005-01-01

Laser treatment represents an attractive option to other methods of vessel diseases especially varicose veins. A long pulse (30~50ms) 532nm laser (Fig.1) is used in our experiments with the pulse duration matching the thermal relaxation time of the vessels and the green laser matching the absorption spectrum peak of the blood. Laser irradiates nude vein vessels directly or exterior skin to finish operation faster and to acquire the practical data for upper enteron varicose vein treatment in several animal experiments performed in vivo. The 5J-energy pulse allows us to finely occlude rabbit or dog"s vein vessels up to 2 mm in diameter when irradiating them off external skin (Fig.2). Blood vessels are occluded at once and later biopsy specimens show the immediate and long-term lasting occlusion effect. While irradiating vessels directly (Fig.3), the vessels are usually irradiated to perforate, detailed causes are still under investigation. Animal experiments show long pulse green laser therapy is a safe and effective solution to the vein"s occlusion, which promises such laser with high energy of each pulse and 30~50 ms duration is an ideal candidate for vessel diseases treatment.

Effects of warming rate, acclimation temperature and ontogeny on the critical thermal maximum of temperate marine fish larvae

PubMed Central

Candebat, Caroline; Ruhbaum, Yannick; Álvarez-Fernández, Santiago; Claireaux, Guy; Zambonino-Infante, José-Luis; Peck, Myron A.

2017-01-01

Most of the thermal tolerance studies on fish have been performed on juveniles and adults, whereas limited information is available for larvae, a stage which may have a particularly narrow range in tolerable temperatures. Moreover, previous studies on thermal limits for marine and freshwater fish larvae (53 studies reviewed here) applied a wide range of methodologies (e.g. the static or dynamic method, different exposure times), making it challenging to compare across taxa. We measured the Critical Thermal Maximum (CTmax) of Atlantic herring (Clupea harengus) and European seabass (Dicentrarchus labrax) larvae using the dynamic method (ramping assay) and assessed the effect of warming rate (0.5 to 9°C h-1) and acclimation temperature. The larvae of herring had a lower CTmax (lowest and highest values among 222 individual larvae, 13.1–27.0°C) than seabass (lowest and highest values among 90 individual larvae, 24.2–34.3°C). At faster rates of warming, larval CTmax significantly increased in herring, whereas no effect was observed in seabass. Higher acclimation temperatures led to higher CTmax in herring larvae (2.7 ± 0.9°C increase) with increases more pronounced at lower warming rates. Pre-trials testing the effects of warming rate are recommended. Our results for these two temperate marine fishes suggest using a warming rate of 3–6°C h-1: CTmax is highest in trials of relatively short duration, as has been suggested for larger fish. Additionally, time-dependent thermal tolerance was observed in herring larvae, where a difference of up to 8°C was observed in the upper thermal limit between a 0.5- or 24-h exposure to temperatures >18°C. The present study constitutes a first step towards a standard protocol for measuring thermal tolerance in larval fish. PMID:28749960

Dynamic modeling of photothermal interactions for laser-induced interstitial thermotherapy: parameter sensitivity analysis.

PubMed

Jiang, S C; Zhang, X X

2005-12-01

A two-dimensional model was developed to model the effects of dynamic changes in the physical properties on tissue temperature and damage to simulate laser-induced interstitial thermotherapy (LITT) treatment procedures with temperature monitoring. A modified Monte Carlo method was used to simulate photon transport in the tissue in the non-uniform optical property field with the finite volume method used to solve the Pennes bioheat equation to calculate the temperature distribution and the Arrhenius equation used to predict the thermal damage extent. The laser light transport and the heat transfer as well as the damage accumulation were calculated iteratively at each time step. The influences of different laser sources, different applicator sizes, and different irradiation modes on the final damage volume were analyzed to optimize the LITT treatment. The numerical results showed that damage volume was the smallest for the 1,064-nm laser, with much larger, similar damage volumes for the 980- and 850-nm lasers at normal blood perfusion rates. The damage volume was the largest for the 1,064-nm laser with significantly smaller, similar damage volumes for the 980- and 850-nm lasers with temporally interrupted blood perfusion. The numerical results also showed that the variations in applicator sizes, laser powers, heating durations and temperature monitoring ranges significantly affected the shapes and sizes of the thermal damage zones. The shapes and sizes of the thermal damage zones can be optimized by selecting different applicator sizes, laser powers, heating duration times, temperature monitoring ranges, etc.

The effect of three different (-135°C) whole body cryotherapy exposure durations on elite rugby league players.

PubMed

Selfe, James; Alexander, Jill; Costello, Joseph T; May, Karen; Garratt, Nigel; Atkins, Stephen; Dillon, Stephanie; Hurst, Howard; Davison, Matthew; Przybyla, Daria; Coley, Andrew; Bitcon, Mark; Littler, Greg; Richards, Jim

2014-01-01

Whole body cryotherapy (WBC) is the therapeutic application of extreme cold air for a short duration. Minimal evidence is available for determining optimal exposure time. To explore whether the length of WBC exposure induces differential changes in inflammatory markers, tissue oxygenation, skin and core temperature, thermal sensation and comfort. This study was a randomised cross over design with participants acting as their own control. Fourteen male professional first team super league rugby players were exposed to 1, 2, and 3 minutes of WBC at -135°C. Testing took place the day after a competitive league fixture, each exposure separated by seven days. No significant changes were found in the inflammatory cytokine interleukin six. Significant reductions (p<0.05) in deoxyhaemoglobin for gastrocnemius and vastus lateralis were found. In vastus lateralis significant reductions (p<0.05) in oxyhaemoglobin and tissue oxygenation index (p<0.05) were demonstrated. Significant reductions (p<0.05) in skin temperature were recorded. No significant changes were recorded in core temperature. Significant reductions (p<0.05) in thermal sensation and comfort were recorded. Three brief exposures to WBC separated by 1 week are not sufficient to induce physiological changes in IL-6 or core temperature. There are however significant changes in tissue oxyhaemoglobin, deoxyhaemoglobin, tissue oxygenation index, skin temperature and thermal sensation. We conclude that a 2 minute WBC exposure was the optimum exposure length at temperatures of -135°C and could be applied as the basis for future studies.

Influence of age, body temperature, GABAA receptor inhibition and caffeine on the Hering-Breuer inflation reflex in unanesthetized rat pups.

PubMed

Arnal, Ashley V; Gore, Julie L; Rudkin, Alison; Bartlett, Donald; Leiter, J C

2013-03-01

We measured the duration of apnea induced by sustained end-inspiratory lung inflation (the Hering Breuer Reflex, HBR) in unanesthetized infant rat pups aged 4 days (P4) to P20 at body temperatures of 32°C and 36°C. The expiratory prolongation elicited by the HBR lasted longer in the younger pups and lasted longer at the higher body temperature. Blockade of adenosine receptors by caffeine following injection into the cisterna magna (ICM) significantly blunted the thermal prolongation of the HBR. Blockade of gama-amino-butyric acid A (GABAA) receptors by pre-treatment with ICM bicuculline had no effect on the HBR duration at either body temperature. To test the hypothesis that developmental maturation of GABAergic inhibition of breathing was modifying the response to bicuculline, we pretreated rat pups with systemically administered bumetanide to lower the intracellular chloride concentration, and repeated the bicuculline studies. Bicuculline still did not alter the HBR at either temperature after bumetanide treatment. We administered PSB-36, a selective adenosine A1 receptor antagonist, and this drug treatment did not modify the HBR. We conclude that caffeine blunts the thermal prolongation of the HBR, probably by blocking adenosine A2a receptors. The thermally sensitive adenosinergic prolongation of the HBR in these intact animals does not seem to depend on GABAA receptors. Copyright © 2013 Elsevier B.V. All rights reserved.

Thermal reaction norms and the scale of temperature variation: latitudinal vulnerability of intertidal nacellid limpets to climate change.

PubMed

Morley, Simon A; Martin, Stephanie M; Day, Robert W; Ericson, Jess; Lai, Chien-Houng; Lamare, Miles; Tan, Koh-Siang; Thorne, Michael A S; Peck, Lloyd S

2012-01-01

The thermal reaction norms of 4 closely related intertidal Nacellid limpets, Antarctic (Nacella concinna), New Zealand (Cellana ornata), Australia (C. tramoserica) and Singapore (C. radiata), were compared across environments with different temperature magnitude, variability and predictability, to test their relative vulnerability to different scales of climate warming. Lethal limits were measured alongside a newly developed metric of "duration tenacity", which was tested at different temperatures to calculate the thermal reaction norm of limpet adductor muscle fatigue. Except in C. tramoserica which had a wide optimum range with two break points, duration tenacity did not follow a typical aerobic capacity curve but was best described by a single break point at an optimum temperature. Thermal reaction norms were shifted to warmer temperatures in warmer environments; the optimum temperature for tenacity (T(opt)) increased from 1.0°C (N. concinna) to 14.3°C (C. ornata) to 18.0°C (an average for the optimum range of C. tramoserica) to 27.6°C (C. radiata). The temperature limits for duration tenacity of the 4 species were most consistently correlated with both maximum sea surface temperature and summer maximum in situ habitat logger temperature. Tropical C. radiata, which lives in the least variable and most predictable environment, generally had the lowest warming tolerance and thermal safety margin (WT and TSM; respectively the thermal buffer of CT(max) and T(opt) over habitat temperature). However, the two temperate species, C. ornata and C. tramoserica, which live in a variable and seasonally unpredictable microhabitat, had the lowest TSM relative to in situ logger temperature. N. concinna which lives in the most variable, but seasonally predictable microhabitat, generally had the highest TSMs. Intertidal animals live at the highly variable interface between terrestrial and marine biomes and even small changes in the magnitude and predictability of their environment could markedly influence their future distributions.

Thermal Reaction Norms and the Scale of Temperature Variation: Latitudinal Vulnerability of Intertidal Nacellid Limpets to Climate Change

PubMed Central

Morley, Simon A.; Martin, Stephanie M.; Day, Robert W.; Ericson, Jess; Lai, Chien-Houng; Lamare, Miles; Tan, Koh-Siang; Thorne, Michael A. S.; Peck, Lloyd S.

2012-01-01

The thermal reaction norms of 4 closely related intertidal Nacellid limpets, Antarctic (Nacella concinna), New Zealand (Cellana ornata), Australia (C. tramoserica) and Singapore (C. radiata), were compared across environments with different temperature magnitude, variability and predictability, to test their relative vulnerability to different scales of climate warming. Lethal limits were measured alongside a newly developed metric of “duration tenacity”, which was tested at different temperatures to calculate the thermal reaction norm of limpet adductor muscle fatigue. Except in C. tramoserica which had a wide optimum range with two break points, duration tenacity did not follow a typical aerobic capacity curve but was best described by a single break point at an optimum temperature. Thermal reaction norms were shifted to warmer temperatures in warmer environments; the optimum temperature for tenacity (Topt) increased from 1.0°C (N. concinna) to 14.3°C (C. ornata) to 18.0°C (an average for the optimum range of C. tramoserica) to 27.6°C (C. radiata). The temperature limits for duration tenacity of the 4 species were most consistently correlated with both maximum sea surface temperature and summer maximum in situ habitat logger temperature. Tropical C. radiata, which lives in the least variable and most predictable environment, generally had the lowest warming tolerance and thermal safety margin (WT and TSM; respectively the thermal buffer of CTmax and Topt over habitat temperature). However, the two temperate species, C. ornata and C. tramoserica, which live in a variable and seasonally unpredictable microhabitat, had the lowest TSM relative to in situ logger temperature. N. concinna which lives in the most variable, but seasonally predictable microhabitat, generally had the highest TSMs. Intertidal animals live at the highly variable interface between terrestrial and marine biomes and even small changes in the magnitude and predictability of their environment could markedly influence their future distributions. PMID:23285194

Antinociceptive effects after oral administration of tramadol hydrochloride in Hispaniolan Amazon parrots (Amazona ventralis).

PubMed

Sanchez-Migallon Guzman, David; Souza, Marcy J; Braun, Jana M; Cox, Sherry K; Keuler, Nicholas S; Paul-Murphy, Joanne R

2012-08-01

To evaluate antinociceptive effects on thermal thresholds after oral administration of tramadol hydrochloride to Hispaniolan Amazon parrots (Amazona ventralis). Animals-15 healthy adult Hispaniolan Amazon parrots. 2 crossover experiments were conducted. In the first experiment, 15 parrots received 3 treatments (tramadol at 2 doses [10 and 20 mg/kg] and a control suspension) administered orally. In the second experiment, 11 parrots received 2 treatments (tramadol hydrochloride [30 mg/kg] and a control suspension) administered orally. Baseline thermal foot withdrawal threshold was measured 1 hour before drug or control suspension administration; thermal foot withdrawal threshold was measured after administration at 0.5, 1.5, 3, and 6 hours (both experiments) and also at 9 hours (second experiment only). For the first experiment, there were no overall effects of treatment, hour, period, or any interactions. For the second experiment, there was an overall effect of treatment, with a significant difference between tramadol hydrochloride and control suspension (mean change from baseline, 2.00° and -0.09°C, respectively). There also was a significant change from baseline for tramadol hydrochloride at 0.5, 1.5, and 6 hours after administration but not at 3 or 9 hours after administration. Tramadol at a dose of 30 mg/kg, PO, induced thermal antinociception in Hispaniolan Amazon parrots. This dose was necessary for induction of significant and sustained analgesic effects, with duration of action up to 6 hours. Further studies with other types of noxious stimulation, dosages, and intervals are needed to fully evaluate the analgesic effects of tramadol hydrochloride in psittacines.

An airborne robotic platform for mapping thermal structure in surface water bodies

NASA Astrophysics Data System (ADS)

Thompson, S. E.; Chung, M.; Detweiler, C.; Ore, J. P.

2015-12-01

The significance of thermal heterogeneities in small surface water bodies as drivers of mixing and for habitat provision is increasingly recognized, yet obtaining three-dimensionally resolved observations of the thermal structure of lakes and rivers remains challenging. For relatively shallow water bodies, observations of water temperature from aerial platforms are attractive: they do not require shoreline access, they can be quickly and easily deployed and redeployed, facilitating repeated sampling, and they can rapidly move between measurement locations, allowing multiple measurements to be made during single flights. However, they are also subject to well-known limitations including payload, flight duration and operability, and their effectiveness as a mobile platform for thermal sensing is still poorly characterized. In this talk, I will introduce an aerial thermal sensing platform that enables water temperature measurements to be made and spatially located throughout a water column, and present preliminary results from initial field experiments comparing in-situ temperature observations to those made from the UAS platform. The results highlight the potential scalability of the platform to provide high-resolution 3D thermal mapping of a ~1 ha lake in 2-3 flights (circa 1 hour), sufficient to resolve diurnal variations. Operability constraints and key needs for further development are also identified.

Thermal relationships and exercise physiology in anuran amphibians: integration and evolutionary implications.

PubMed

Navas, Carlos A; Gomes, Fernando R; Carvalho, José Eduardo

2008-11-01

Thermal and water balance are coupled in anurans, and species with particularly permeable skin avoid overheating more effectively than minimizing variance of body temperature. In turn, temperature affects muscle performance in several ways, so documenting the mean and variance of body temperature of active frogs can help explain variation in behavioral performance. The two types of activities studied in most detail, jumping and calling, differ markedly in duration and intensity, and there are distinct differences in the metabolic profile and fiber type of the supporting muscles. Characteristics of jumping and calling also vary significantly among species, and these differences have a number of implications that we discuss in some detail throughout this paper. One question that emerges from this topic is whether anuran species exhibit activity temperatures that match the temperature range over which they perform best. Although this seems the case, thermal preferences are variable and may not necessarily reflect typical activity temperatures. The performance versus temperature curves and the thermal limits for anuran activity reflect the thermal ecology of species more than their systematic position. Anuran thermal physiology, therefore, seems to be phenotypically plastic and susceptible to adaptive evolution. Although generalizations regarding the mechanistic basis of such adjustments are not yet possible, recent attempts have been made to reveal the mechanistic basis of acclimation and acclimatization.

Treatment for meibomian gland dysfunction and dry eye symptoms with a single-dose vectored thermal pulsation: a review.

PubMed

Blackie, Caroline A; Carlson, Alan N; Korb, Donald R

2015-07-01

Meibomian gland dysfunction (MGD) is understood to be a highly prevalent, chronic progressive disease and the leading cause of dry eye. All available published peer-reviewed results of the novel vectored thermal pulsation therapy for patients with MGD are investigated. The PubMed and meeting abstract search revealed a total of 31 peer-reviewed reports on vectored thermal pulsation therapy at the time of the search (eight manuscripts and 23 meeting abstracts). All manuscripts evidence a significant increase in meibomian gland function (∼3×) and symptom improvement post a single 12-min treatment. Additional reported objective measures such as osmolarity, tear break-up time, or lipid layer thickness also increased as a result of the therapy; however, not all findings were statistically significant. The randomized controlled studies evidence sustained gland function and symptom relief lasting out to 12 months. The uncontrolled case series evidence significantly longer duration of effect. A single 12 minute vectored thermal pulsation treatment allows for reducing dry eye symptoms, improving meibomian gland function and other correlates of the ocular surface health.

A model of freezing foods with liquid nitrogen using special functions

NASA Astrophysics Data System (ADS)

Rodríguez Vega, Martín.

2014-05-01

A food freezing model is analyzed analytically. The model is based on the heat diffusion equation in the case of cylindrical shaped food frozen by liquid nitrogen; and assuming that the thermal conductivity of the cylindrical food is radially modulated. The model is solved using the Laplace transform method, the Bromwich theorem, and the residue theorem. The temperature profile in the cylindrical food is presented as an infinite series of special functions. All the required computations are performed with computer algebra software, specifically Maple. Using the numeric values of the thermal and geometric parameters for the cylindrical food, as well as the thermal parameters of the liquid nitrogen freezing system, the temporal evolution of the temperature in different regions in the interior of the cylindrical food is presented both analytically and graphically. The duration of the liquid nitrogen freezing process to achieve the specified effect on the cylindrical food is computed. The analytical results are expected to be of importance in food engineering and cooking engineering. As a future research line, the formulation and solution of freezing models with thermal memory is proposed.

Thermal, physiological and perceptual strain mediate alterations in match-play tennis under heat stress

PubMed Central

Périard, Julien D; Racinais, Sébastien; Knez, Wade L; Herrera, Christopher P; Christian, Ryan J; Girard, Olivier

2014-01-01

Objectives This study compared the thermal, physiological and perceptual responses associated with match-play tennis in HOT (∼34°C wet-bulb-globe temperature (WBGT)) and COOL (∼19°C WBGT) conditions, along with the accompanying alterations in match characteristics. Methods 12 male tennis players undertook two matches for an effective playing time (ie, ball in play) of 20 min, corresponding to ∼119 and ∼102 min of play in HOT and COOL conditions, respectively. Rectal and skin temperatures, heart rate, subjective ratings of thermal comfort, thermal sensation and perceived exertion were recorded, along with match characteristics. Results End-match rectal temperature increased to a greater extent in the HOT (∼39.4°C) compared with the COOL (∼38.7°C) condition (p<0.05). Thigh skin temperature was higher throughout the HOT match (p<0.001). Heart rate, thermal comfort, thermal sensation and perceived exertion were also higher during the HOT match (p<0.001). Total playing time was longer in the HOT compared with the COOL match (p<0.05). Point duration (∼7.1 s) was similar between conditions, while the time between points was ∼10 s longer in the HOT relative to the COOL match (p<0.05). This led to a ∼3.4% lower effective playing percentage in the heat (p<0.05). Although several thermal, physiological and perceptual variables were individually correlated to the adjustments in time between points and effective playing percentage, thermal sensation was the only predictor variable associated with both adjustments (p<0.005). Conclusions These adjustments in match-play tennis characteristics under severe heat stress appear to represent a behavioural strategy adopted to minimise or offset the sensation of environmental conditions being rated as difficult. PMID:24668377

Special Course on Aerothermodynamics of Hypersonic Vehicles

DTIC Science & Technology

1989-06-01

8, No. 3, 1970, pp. 511-518. 36. Kutler P. and Lomax, H., "Shock- Capturing Finite Difference Approach to Supersonic Flows," Journal of Spacecraft and...layer. These were termed *sandwich’ gages. (2) heat may be captured within a thermal mass which acts as a calorimeter and whose transient temperature...within the test duration, the backface thermal sensor is not responsive and the gage becomes one in which the thermal pulse is ’ captured ’ within the

An electrical method for the measurement of the thermal and electrical conductivity of reduced graphene oxide nanostructures.

PubMed

Schwamb, Timo; Burg, Brian R; Schirmer, Niklas C; Poulikakos, Dimos

2009-10-07

This paper introduces an electrical four-point measurement method enabling thermal and electrical conductivity measurements of nanoscale materials. The method was applied to determine the thermal and electrical conductivity of reduced graphene oxide flakes. The dielectrophoretically deposited samples exhibited thermal conductivities in the range of 0.14-2.87 W m(-1) K(-1) and electrical conductivities in the range of 6.2 x 10(2)-6.2 x 10(3) Omega(-1) m(-1). The measured properties of each flake were found to be dependent on the duration of the thermal reduction and are in this sense controllable.

The effects of intrathecal morphine encapsulated in L- and D-dipalmitoylphosphatidyl choline liposomes on acute nociception in rats.

PubMed

Nishiyama, T; Ho, R J; Shen, D D; Yaksh, T L

2000-08-01

Liposomes can serve as a sustained-release carrier system, permitting the spinal delivery of large opioid doses restricting the dose for acute systemic uptake. We evaluated the antinociceptive effects of morphine encapsulated in liposomes of two isomeric phospholipids, L-dipalmitoylphosphatidyl choline (L-DPPC) and D-dipalmitoylphosphatidyl choline (D-DPPC), in comparison with morphine in saline. Sprague-Dawley rats with chronic lumbar intrathecal catheters were tested for their acute nociceptive response using a hindpaw thermal escape test. Their general behavior, motor function, pinna reflex, and corneal reflex were also examined. The duration of antinociception was longer in both liposomal morphine groups than in the free morphine group. The peak antinociceptive effects were observed within 30 min after intrathecal morphine, L-DPPC or D-DPPC morphine injection. The rank order of the area under the effect-time curve for antinociception was L-DPPC morphine > D-DPPC morphine > morphine. The 50% effective dose was: 2.7 microg (morphine), 4.6 microg (L-DPPC morphine), and 6.4 microg (D-DPPC morphine). D-DPPC morphine had less side effects for a given antinociceptive AUC than morphine. In conclusion, L-DPPC and D-DPPC liposome encapsulation of morphine prolonged the antinociceptive effect on acute thermal stimulation and could decrease side effects, compared with morphine alone. Two isomers of liposome (L-dipalmitoylphosphatidyl choline and D-dipalmitoylphosphatidyl choline) encapsulation of morphine prolonged the analgesic effect on acute thermal-induced pain when administered intrathecally and could decrease side effects, compared with morphine alone.

Effect of ND:YAG laser irradiation and root planing on the root surface: structural and thermal effects.

PubMed

Wilder-Smith, P; Arrastia, A M; Schell, M J; Liaw, L H; Grill, G; Berns, M W

1995-12-01

Effects of ND:YAG laser irradiation on untreated and root planed tooth roots were investigated to determine whether a cleaning effect and/or removal of smear layer could be achieved without concomitant microstructural or thermal damage. Sixty (60) healthy extracted teeth were either untreated, irradiated only, root planed only, or irradiated and root planed. Intra-pulpal and surface temperatures were monitored during irradiation, then SEM was performed. Smear layer elimination was achieved without inducing hard tissue microstructural damage at 5W, using pulse durations and intervals of 0.1 s, a fluence of 0.77 J/cm2, and a total energy density of approximately 700 J/cm2. However, these results were not consistent in all samples. At these parameters, intra-pulpal temperature increases of 9 to 22 degrees C and surface temperature increases of 18 to 36 degrees C were recorded. Thus, despite their effectiveness for smear layer removal, these parameters may not be appropriate for clinical use as an adjunct to conventional periodontal therapy.

Design, fabrication and test of Load Bearing multilayer insulation to support a broad area cooled shield

NASA Astrophysics Data System (ADS)

Dye, S. A.; Johnson, W. L.; Plachta, D. W.; Mills, G. L.; Buchanan, L.; Kopelove, A. B.

2014-11-01

Improvements in cryogenic propellant storage are needed to achieve reduced or Zero Boil Off of cryopropellants, critical for long duration missions. Techniques for reducing heat leak into cryotanks include using passive multi-layer insulation (MLI) and vapor cooled or actively cooled thermal shields. Large scale shields cannot be supported by tank structural supports without heat leak through the supports. Traditional MLI also cannot support shield structural loads, and separate shield support mechanisms add significant heat leak. Quest Thermal Group and Ball Aerospace, with NASA SBIR support, have developed a novel Load Bearing multi-layer insulation (LBMLI) capable of self-supporting thermal shields and providing high thermal performance. We report on the development of LBMLI, including design, modeling and analysis, structural testing via vibe and acoustic loading, calorimeter thermal testing, and Reduced Boil-Off (RBO) testing on NASA large scale cryotanks. LBMLI uses the strength of discrete polymer spacers to control interlayer spacing and support the external load of an actively cooled shield and external MLI. Structural testing at NASA Marshall was performed to beyond maximum launch profiles without failure. LBMLI coupons were thermally tested on calorimeters, with superior performance to traditional MLI on a per layer basis. Thermal and structural tests were performed with LBMLI supporting an actively cooled shield, and comparisons are made to the performance of traditional MLI and thermal shield supports. LBMLI provided a 51% reduction in heat leak per layer over a previously tested traditional MLI with tank standoffs, a 38% reduction in mass, and was advanced to TRL5. Active thermal control using LBMLI and a broad area cooled shield offers significant advantages in total system heat flux, mass and structural robustness for future Reduced Boil-Off and Zero Boil-Off cryogenic missions with durations over a few weeks.

Prototype Aerogel Insulation for Melamine-Foam Substitute: Critical Space Station Express Rack Technology

NASA Technical Reports Server (NTRS)

Noever, David A.; Sibille, Laurent; Smith, David; Cronise, Raymond

1998-01-01

There is a current lack of environmentally acceptable foams to insulate Long-Duration Human Spaceflight Missions, including the experimental Express Rack for the Space Station. A recent 60-day manned test in a sealed chamber at Johnson Space Center (JSC) was nearly aborted, because of persistently high formaldehyde concentrations in the chamber. Subsequent investigation showed that the source was melamine foam (used extensively for acoustic insulation). The thermal and acoustic potential for melamine-foam substitutes is evaluated for scale-up to a silica-based foam and aerogel, which is environmentally benign for long duration space flight. These features will be discussed in reference to an aerogel prototype to: 1) assemble material strength data for various formulated aerogels, both silica and organic carbon aerogels; 2) assemble the aerogel into panels of mylar/vacuum-encapsulated rigid boards which can be molded in various shapes and rigidities; and 3) describe a process for space applications for formaldehyde-free, long duration thermal and acoustic insulators.

Variations in leaf growth parameters within the tree structure of adult Coffea arabica in relation to seasonal growth, water availability and air carbon dioxide concentration.

PubMed

Rakocevic, Miroslava; Matsunaga, Fabio Takeshi

2018-04-05

Dynamics in branch and leaf growth parameters, such as the phyllochron, duration of leaf expansion, leaf life span and bud mortality, determine tree architecture and canopy foliage distribution. We aimed to estimate leaf growth parameters in adult Arabica coffee plants based on leaf supporter axis order and position along the vertical profile, considering their modifications related to seasonal growth, air [CO2] and water availability. Growth and mortality of leaves and terminal buds of adult Arabica coffee trees were followed in two independent field experiments in two sub-tropical climate regions of Brazil, Londrina-PR (Cfa) and Jaguariúna-SP (Cwa). In the Cwa climate, coffee trees were grown under a FACE (free air CO2 enrichment) facility, where half of those had been irrigated. Plants were observed at a 15-30 d frequency for 1 year. Leaf growth parameters were estimated on five axes orders and expressed as functions of accumulated thermal time (°Cd per leaf). The phyllochron and duration of leaf expansion increased with axis order, from the seond to the fourth. The phyllochron and life span during the reduced vegetative seasonal growth were greater than during active growth. It took more thermal time for leaves from the first- to fourth-order axes to expand their blades under irrigation compared with rainfed conditions. The compensation effects of high [CO2] for low water availability were observed on leaf retention on the second and third axes orders, and duration of leaf expansion on the first- and fourth-order axes. The second-degree polynomials modelled leaf growth parameter distribution in the vertical tree profile, and linear regressions modelled the proportion of terminal bud mortality. Leaf growth parameters in coffee plants were determined by axis order. The duration of leaf expansion contributed to phyllochron determination. Leaf growth parameters varied according the position of the axis supporter along the vertical profile, suggesting an effect of axes age and micro-environmental light modulations.

Characterization of selected LDEF polymer matrix resin composite materials

NASA Technical Reports Server (NTRS)

Young, Philip R.; Slemp, Wayne S.; Witte, William G., Jr.; Shen, James Y.

1991-01-01

The characterization of selected graphite fiber reinforced epoxy (934 and 5208) and polysulfone (P1700) matrix resin composite materials which received 5 years and 10 months of exposure to the LEO environment on the Long Duration Exposure Facility is reported. Resin loss and a decrease in mechanical performance as well as dramatic visual effects were observed. However, chemical characterization including infrared, thermal, and selected solution property measurements showed that the molecular structure of the polymeric matrix had not changed significantly in response to this exposure. The potential effect of a silicon-containing molecular contamination of these specimens is addressed.

Hazards To The Eye From UV

NASA Astrophysics Data System (ADS)

Zuclich, Joseph A.

1980-10-01

Ocular effects of ultraviolet radiation, 200-400 nm, are reviewed. Depending upon the exposure parameter involved, UV radiation may be harmful to the cornea, lens and/or retina. Ranges of exposure parameters (wavelength, exposure duration, etc.) for which each of the tissues is susceptible are specified and the nature of the tissue is described. Present understanding of the thermal and photochemical damage mechanism operative for various conditions of exposure are discussed Ocular damage thresholds for wide ranges of exposure parameters are summarized and compared to existing safety standards.

Effects of remediation train sequence on decontamination of heavy metal-contaminated soil containing mercury.

PubMed

Hseu, Zeng-Yei; Huang, Yu-Tuan; Hsi, Hsing-Cheng

2014-09-01

When a contaminated site contains pollutants including both nonvolatile metals and Hg, one single remediation technology may not satisfactorily remove all contaminants. Therefore, in this study, chemical extraction and thermal treatment were combined as a remediation train to remove heavy metals, including Hg, from contaminated soil. A 0.2 M solution of ethylenediamine tetraacetic acid (EDTA) was shown to be the most effective reagent for extraction of considerable amounts of Cu, Pb, and Zn (> 50%). Hg removal was ineffective using 0.2 M EDTA, but thermogravimetric analysis suggested that heating to 550 degrees C with a heating rate of 5 degrees C/min for a duration of 1 hr appeared to be an effective approach for Hg removal. With the employment of thermal treatment, up to 99% of Hg could be removed. However executing thermal treatment prior to chemical extraction reduced the effectiveness of the subsequent EDTA extraction because nonvolatile heavy metals were immobilized in soil aggregates after the 550 degrees C treatment. The remediation train of chemical extraction followed by thermal treatment appears to remediate soils that have been contaminated by many nonvolatile heavy metals and Hg. Implications: A remediation train conjoining two or more techniques has been initialized to remove multiple metals. Better understandings of the impacts of treatment sequences, namely, which technique should be employed first on the soil properties and the decontamination efficiency, are in high demand. This study provides a strategy to remove multiple heavy metals including Hg from a contaminated soil. The interactions between thermal treatment and chemical extraction on repartitioning of heavy metals was revealed. The obtained results could offer an integrating strategy to remediate the soil contaminated with both heavy metals and volatile contaminants.

Exceptional summer warming leads to contrasting outcomes for methane cycling in small Arctic lakes of Greenland

NASA Astrophysics Data System (ADS)

Cadieux, Sarah B.; White, Jeffrey R.; Pratt, Lisa M.

2017-02-01

In thermally stratified lakes, the greatest annual methane emissions typically occur during thermal overturn events. In July of 2012, Greenland experienced significant warming that resulted in substantial melting of the Greenland Ice Sheet and enhanced runoff events. This unusual climate phenomenon provided an opportunity to examine the effects of short-term natural heating on lake thermal structure and methane dynamics and compare these observations with those from the following year, when temperatures were normal. Here, we focus on methane concentrations within the water column of five adjacent small lakes on the ice-free margin of southwestern Greenland under open-water and ice-covered conditions from 2012-2014. Enhanced warming of the epilimnion in the lakes under open-water conditions in 2012 led to strong thermal stability and the development of anoxic hypolimnia in each of the lakes. As a result, during open-water conditions, mean dissolved methane concentrations in the water column were significantly (p < 0.0001) greater in 2012 than in 2013. In all of the lakes, mean methane concentrations under ice-covered conditions were significantly (p < 0.0001) greater than under open-water conditions, suggesting spring overturn is currently the largest annual methane flux to the atmosphere. As the climate continues to warm, shorter ice cover durations are expected, which may reduce the winter inventory of methane and lead to a decrease in total methane flux during ice melt. Under open-water conditions, greater heat income and warming of lake surface waters will lead to increased thermal stratification and hypolimnetic anoxia, which will consequently result in increased water column inventories of methane. This stored methane will be susceptible to emissions during fall overturn, which may result in a shift in greatest annual efflux of methane from spring melt to fall overturn. The results of this study suggest that interannual variation in ground-level air temperatures may be the primary driver of changes in methane dynamics because it controls both the duration of ice cover and the strength of thermal stratification.

On the physics of laser-induced selective photothermolysis of hair follicles: Influence of wavelength, pulse duration, and epidermal cooling.

PubMed

Svaasand, Lars O; Nelson, J Stuart

2004-01-01

The physical basis for optimization of wavelength, pulse duration, and cooling for laser-induced selective photothermolysis of hair follicles in human skin is discussed. The results indicate that the most important optimization parameter is the cooling efficiency of the technique utilized for epidermal protection. The optical penetration is approximately the same for lasers at 694, 755, and 800 nm. The penetration of radiation from Nd:yttrium-aluminum-garnet lasers at 1064 nm is, however, somewhat larger. Photothermal damage to the follicle is shown to be almost independent of laser pulse duration up to 100 ms. The results reveal that epidermal cooling by a 30-80-ms-long cryogen spurt immediately before laser exposure is the only efficient technique for laser pulse durations less than 10 ms. For longer pulse durations in the 30-100 ms range, protection can be done efficiently by skin cooling during laser exposure. For laser pulses of 100 ms, an extended precooling period, e.g., by bringing a cold object into good thermal contact with the skin for about 1 s, can be of value. Thermal quenching of laser induced epidermal temperature rise after pulsed exposure can most efficiently be done with a 20 ms cryogen spurt applied immediately after irradiation. (c) 2004 Society of Photo-Optical Instrumentation Engineers.

Thermal-vacuum response of polymer matrix composites in space

NASA Technical Reports Server (NTRS)

Tennyson, R. C.; Matthews, R.

1993-01-01

This report describes a thermal-vacuum outgassing model and test protocol for predicting outgassing times and dimensional changes for polymer matrix composites. Experimental results derived from 'control' samples are used to provide the basis for analytical predictions to compare with the outgassing response of Long Duration Exposure Facility (LDEF) flight samples. Coefficient of thermal expansion (CTE) data are also presented. In addition, an example is given illustrating the dimensional change of a 'zero' CTE laminate due to moisture outgassing.

Thermal modeling for pulsed radiofrequency ablation: analytical study based on hyperbolic heat conduction.

PubMed

López Molina, Juan A; Rivera, María J; Trujillo, Macarena; Berjano, Enrique J

2009-04-01

The objectives of this study were to model the temperature progress of a pulsed radiofrequency (RF) power during RF heating of biological tissue, and to employ the hyperbolic heat transfer equation (HHTE), which takes the thermal wave behavior into account, and compare the results to those obtained using the heat transfer equation based on Fourier theory (FHTE). A theoretical model was built based on an active spherical electrode completely embedded in the biological tissue, after which HHTE and FHTE were analytically solved. We found three typical waveforms for the temperature progress depending on the relations between the dimensionless duration of the RF pulse delta(a) and the expression square root of lambda(rho-1), with lambda as the dimensionless thermal relaxation time of the tissue and rho as the dimensionless position. In the case of a unique RF pulse, the temperature at any location was the result of the overlapping of two different heat sources delayed for a duration delta(a) (each heat source being produced by a RF pulse of limitless duration). The most remarkable feature in the HHTE analytical solution was the presence of temperature peaks traveling through the medium at a finite speed. These peaks not only occurred during the RF power switch-on period but also during switch off. Finally, a physical explanation for these temperature peaks is proposed based on the interaction of forward and reverse thermal waves. All-purpose analytical solutions for FHTE and HHTE were obtained during pulsed RF heating of biological tissues, which could be used for any value of pulsing frequency and duty cycle.

Effects of seasonal and climate variations on calves' thermal comfort and behaviour.

PubMed

Tripon, Iulian; Cziszter, Ludovic Toma; Bura, Marian; Sossidou, Evangelia N

2014-09-01

The aim of this study was to measure the effect of season and climate variations on thermal comfort and behaviour of 6-month-old dairy calves housed in a semi-opened shelter to develop animal-based indicators for assessing animal thermal comfort. The ultimate purpose was to further exploit the use of those indicators to prevent thermal stress by providing appropriate care to the animals. Measurements were taken for winter and summer seasons. Results showed that season significantly influenced (P ≤ 0.01) the lying down behaviour of calves by reducing the time spent lying, from 679.9 min in winter to 554.1 min in summer. Moreover, season had a significant influence (P ≤ 0.01) on feeding behaviour. In detail, the total length of feeding periods was shorter in winter, 442.1 min in comparison to 543.5 min in summer. Time spent drinking increased significantly (P ≤ 0.001), from 11.9 min in winter to 26.9 min in summer. Furthermore, season had a significant influence (P ≤ 0.001) on self grooming behaviour which was 5.5 times longer in duration in winter than in summer (1,336 s vs 244 s). It was concluded that calves' thermal comfort is affected by seasonal and climate variations and that this can be assessed by measuring behaviour with animal-based indicators, such as lying down, resting, standing up, feeding, rumination, drinking and self grooming. The indicators developed may be a useful tool to prevent animal thermal stress by providing appropriate housing and handling to calves under seasonal and climate challenge.

Computational model of retinal photocoagulation and rupture

NASA Astrophysics Data System (ADS)

Sramek, Christopher; Paulus, Yannis M.; Nomoto, Hiroyuki; Huie, Phil; Palanker, Daniel

2009-02-01

In patterned scanning laser photocoagulation, shorter duration (< 20 ms) pulses help reduce thermal damage beyond the photoreceptor layer, decrease treatment time and minimize pain. However, safe therapeutic window (defined as the ratio of rupture threshold power to that of light coagulation) decreases for shorter exposures. To quantify the extent of thermal damage in the retina, and maximize the therapeutic window, we developed a computational model of retinal photocoagulation and rupture. Model parameters were adjusted to match measured thresholds of vaporization, coagulation, and retinal pigment epithelial (RPE) damage. Computed lesion width agreed with histological measurements in a wide range of pulse durations and power. Application of ring-shaped beam profile was predicted to double the therapeutic window width for exposures in the range of 1 - 10 ms.

Nonlinear side effects of fs pulses inside corneal tissue during photodisruption

NASA Astrophysics Data System (ADS)

Heisterkamp, A.; Ripken, T.; Mamom, T.; Drommer, W.; Welling, H.; Ertmer, W.; Lubatschowski, H.

In order to evaluate the potential for refractive surgery, fs laser pulses of 150-fs pulse duration were used to process corneal tissue of dead and living animal eyes. By focusing the laser radiation down to spot sizes of several microns, very precise cuts could be achieved inside the treated cornea, accompanied with minimum collateral damage to the tissue by thermal or mechanical effects. During histo-pathological analysis by light and transmission electron microscopy considerable side effects of fs photodisruption were found. Due to the high intensities at the focal region several nonlinear effects occurred. Self-focusing, photodissociation, UV-light production were observed, leading to streak formation inside the cornea.

Study on indoor thermal environment in winter for rural residences in Yulin region

NASA Astrophysics Data System (ADS)

Yanjun, Li; Weixiao, Han

2018-02-01

Yulin region is located in the northern part of Shaanxi Province, China. The winter here is very cold and it has a long duration. In this paper, a rural residence which was located in Yulin region was taken as a study object. Indoor thermal environment of the rural residence were tested, including indoor air temperature and air relative humidity. Then, test data were analyzed. It was summarized that indoor thermal environment of test room can not fully meet human thermal comfort needs, and some tactics of regulation building thermal environment were proposed. This research contributes to improvement of indoor thermal environment for local rural residences and it provides reference for rural residences in other cold regions.

Anodized aluminum on LDEF

NASA Technical Reports Server (NTRS)

Golden, Johnny L.

1993-01-01

A compilation of reported analyses and results obtained for anodized aluminum flown on the Long Duration Exposure Facility (LDEF) was prepared. Chromic acid, sulfuric acid, and dyed sulfuric acid anodized surfaces were exposed to the space environment. The vast majority of the anodized surface on LDEF was chromic acid anodize because of its selection as a thermal control coating for use on the spacecraft primary structure, trays, tray clamps, and space end thermal covers. Reports indicate that the chromic acid anodize was stable in solar absorptance and thermal emittance, but that contamination effects caused increases in absorptance on surfaces exposed to low atomic oxygen fluences. There were some discrepancies, however, in that some chromic acid anodized specimens exhibited significant increases in absorptance. Sulfuric acid anodized surfaces also appeared stable, although very little surface area was available for evaluation. One type of dyed sulfuric acid anodize was assessed as an optical baffle coating and was observed to have improved infrared absorptance characteristics with exposure on LDEF.

Shielding Development for Nuclear Thermal Propulsion

NASA Technical Reports Server (NTRS)

Caffrey, Jarvis A.; Gomez, Carlos F.; Scharber, Luke L.

2015-01-01

Radiation shielding analysis and development for the Nuclear Cryogenic Propulsion Stage (NCPS) effort is currently in progress and preliminary results have enabled consideration for critical interfaces in the reactor and propulsion stage systems. Early analyses have highlighted a number of engineering constraints, challenges, and possible mitigating solutions. Performance constraints include permissible crew dose rates (shared with expected cosmic ray dose), radiation heating flux into cryogenic propellant, and material radiation damage in critical components. Design strategies in staging can serve to reduce radiation scatter and enhance the effectiveness of inherent shielding within the spacecraft while minimizing the required mass of shielding in the reactor system. Within the reactor system, shield design is further constrained by the need for active cooling with minimal radiation streaming through flow channels. Material selection and thermal design must maximize the reliability of the shield to survive the extreme environment through a long duration mission with multiple engine restarts. A discussion of these challenges and relevant design strategies are provided for the mitigation of radiation in nuclear thermal propulsion.

Performance of silvered Teflon thermal control blankets on spacecraft

NASA Astrophysics Data System (ADS)

Pippin, G.; Stuckey, W. K.; Hemminger, C. S.

1993-03-01

Silver-backed fluorinated ethylene propylene Teflon (Ag/FEP) thin film material was used for thermal control in many locations on the Long Duration Exposure Facility (LDEF). The Ag/FEP registered the effects of atomic oxygen, solar ultraviolet radiation, meteoroid and debris impacts, thermal cycling, and contamination. This report summarizes the post-flight condition of the Ag/FEP, compares the results with performance on other spacecraft, and presents lifetime estimates for use under a variety of environmental exposures. Measurements of optical property and mechanical property and surface chemistry changes with exposure conditions, and their significance for design considerations and expected performance lifetimes, are reported for material flown on LDEF. The LDEF based data provides detailed information performance of Ag/FEP under relatively long term exposure in low Earth orbit. Comparison of this data with results from short term shuttle flights, Solar Max, SCATHA, other satellites, and ground based measurements is made to present a comprehensive summary of the use of this material for spacecraft applications.

Repeat work bouts increase thermal strain for Australian firefighters working in the heat.

PubMed

Walker, Anthony; Argus, Christos; Driller, Matthew; Rattray, Ben

2015-01-01

Firefighters regularly re-enter fire scenes during long duration emergency events with limited rest between work bouts. It is unclear whether this practice is impacting on the safety of firefighters. To evaluate the effects of multiple work bouts on firefighter physiology, strength, and cognitive performance when working in the heat. Seventy-seven urban firefighters completed two 20-minute simulated search and rescue tasks in a heat chamber (105 ± 5°C), separated by a 10-minute passive recovery. Core and skin temperature, rate of perceived exertion (RPE), thermal sensation (TS), grip strength, and cognitive changes between simulations were evaluated. Significant increases in core temperature and perceptual responses along with declines in strength were observed following the second simulation. No differences for other measures were observed. A significant increase in thermal strain was observed when firefighters re-entered a hot working environment. We recommend that longer recovery periods or active cooling methods be employed prior to re-entry.

Repeat work bouts increase thermal strain for Australian firefighters working in the heat

PubMed Central

Walker, Anthony; Argus, Christos; Driller, Matthew; Rattray, Ben

2015-01-01

Background: Firefighters regularly re-enter fire scenes during long duration emergency events with limited rest between work bouts. It is unclear whether this practice is impacting on the safety of firefighters. Objectives:To evaluate the effects of multiple work bouts on firefighter physiology, strength, and cognitive performance when working in the heat. Methods: Seventy-seven urban firefighters completed two 20-minute simulated search and rescue tasks in a heat chamber (105 ± 5°C), separated by a 10-minute passive recovery. Core and skin temperature, rate of perceived exertion (RPE), thermal sensation (TS), grip strength, and cognitive changes between simulations were evaluated. Results: Significant increases in core temperature and perceptual responses along with declines in strength were observed following the second simulation. No differences for other measures were observed. Conclusions: A significant increase in thermal strain was observed when firefighters re-entered a hot working environment. We recommend that longer recovery periods or active cooling methods be employed prior to re-entry. PMID:25849044

Thermal Evolution and Radiative Output of Solar Flares Observed by the EUV Variability Experiment (EVE)

NASA Technical Reports Server (NTRS)

Chamberlin, P. C.; Milligan, R. O.; Woods, T. N.

2012-01-01

This paper describes the methods used to obtain the thermal evolution and radiative output during solar flares as observed by the Extreme u ltraviolet Variability Experiment (EVE) onboard the Solar Dynamics Ob servatory (SDO). Presented and discussed in detail are how EVE measur ements, due to its temporal cadence, spectral resolution and spectral range, can be used to determine how the thermal plasma radiates at v arious temperatures throughout the impulsive and gradual phase of fla res. EVE can very accurately determine the radiative output of flares due to pre- and in-flight calibrations. Events are presented that sh ow the total radiated output of flares depends more on the flare duration than the typical GOES X-ray peak magnitude classification. With S DO observing every flare throughout its entire duration and over a la rge temperature range, new insights into flare heating and cooling as well as the radiative energy release in EUV wavelengths support exis ting research into understanding the evolution of solar flares.

SRB thermal protection systems materials test results in an arc-heated nitrogen environment

NASA Technical Reports Server (NTRS)

Wojciechowski, C. J.

1979-01-01

The external surface of the Solid Rocket Booster (SRB) will experience imposed thermal and shear environments due to aerodynamic heating and radiation heating during launch, staging and reentry. This report is concerned with the performance of the various TPS materials during the staging maneuver. During staging, the wash from the Space Shuttle Main Engine (SSME) exhust plumes impose severe, short duration, thermal environments on the SRB. Five different SRB TPS materials were tested in the 1 MW Arc Plasma Generator (APG) facility. The maximum simulated heating rate obtained in the APG facility was 248 Btu/sq ft./sec, however, the test duration was such that the total heat was more than simulated. Similarly, some local high shear stress levels of 0.04 psia were not simulated. Most of the SSME plume impingement area on the SRB experiences shear stress levels of 0.02 psia and lower. The shear stress levels on the test specimens were between 0.021 and 0.008 psia. The SSME plume stagnation conditions were also simulated.

Predicting eruptions from precursory activity using remote sensing data hybridization

NASA Astrophysics Data System (ADS)

Reath, K. A.; Ramsey, M. S.; Dehn, J.; Webley, P. W.

2016-07-01

Many volcanoes produce some level of precursory activity prior to an eruption. This activity may or may not be detected depending on the available monitoring technology. In certain cases, precursors such as thermal output can be interpreted to make forecasts about the time and magnitude of the impending eruption. Kamchatka (Russia) provides an ideal natural laboratory to study a wide variety of eruption styles and precursory activity prior to an eruption. At Bezymianny volcano for example, a clear increase in thermal activity commonly occurs before an eruption, which has allowed predictions to be made months ahead of time. Conversely, the eruption of Tolbachik volcano in 2012 produced no discernable thermal precursors before the large scale effusive eruption. However, most volcanoes fall between the extremes of consistently behaved and completely undetectable, which is the case with neighboring Kliuchevskoi volcano. This study tests the effectiveness of using thermal infrared (TIR) remote sensing to track volcanic thermal precursors using data from both the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Advanced Very High Resolution Radiometer (AVHRR) sensors. It focuses on three large eruptions that produced different levels and durations of effusive and explosive behavior at Kliuchevskoi. Before each of these eruptions, TIR spaceborne sensors detected thermal anomalies (i.e., pixels with brightness temperatures > 2 °C above the background temperature). High-temporal, low-spatial resolution (i.e., hours and 1 km) AVHRR data are ideal for detecting large thermal events occurring over shorter time scales, such as the hot material ejected following strombolian eruptions. In contrast, high-spatial, low-temporal resolution (i.e., days to weeks and 90 m) ASTER data enables the detection of much lower thermal activity; however, activity with a shorter duration will commonly be missed. ASTER and AVHRR data are combined to track low-level anomalies months prior to an eruption and higher-energy events prior to large eruptions to develop a monitoring approach for this eruption style. Results show that strombolian eruptions produce enough energy in the pre-eruptive phase to trigger an AVHRR detection. Paired with ASTER data, the results can be extended back in time to develop a precursory timeline, which captures subtle changes in volcanic activity that would commonly go unnoticed in a single data set. Although these precursors may be volcano and eruption specific, the now sixteen-year-old database from ASTER allows this methodology to be repeatable at other volcanoes to establish a quantitative precursory baseline, which would be an improvement over current eruption classifications.

Corneal thermal damage threshold dependence on the exposure duration for near-infrared laser radiation at 1319 nm

NASA Astrophysics Data System (ADS)

Wang, Jiarui; Jiao, Luguang; Chen, Hongxia; Yang, Zaifu; Hu, Xiangjun

2016-01-01

The corneal damage effects induced by 1319-nm transitional near-infrared laser have been investigated for years. However, the damage threshold dependence on exposure duration has not been revealed. The in vivo corneal damage thresholds (ED50s) were determined in New Zealand rabbits for 1319-nm laser radiation for exposure durations from 75 ms to 10 s. An additional corneal ED50 was determined at 1338 nm for a 5-ms exposure. The incident corneal irradiance diameter was fixed at 2 mm for all exposure conditions to avoid the influence of spot size on threshold. The ED50s given in terms of the corneal radiant exposure for exposure durations of 5 ms, 75 ms, 0.35 s, 2 s, and 10 s were 39.4, 51.5, 87.2, 156.3, and 311.1 J/cm2, respectively. The 39.4 J/cm2 was derived from the ED50 for 1338 nm (27.0 J/cm2). The ED50s for exposure durations of 75 ms to 10 s were correlated by a power law equation, ED50=128.9t0.36 in J/cm2, where t was the input in the unit of second, with correlation coefficient (R) of 0.997. Enough safe margins existed between the ED50s and the maximum permitted exposures from current laser safety standard.

Space transportation system options for extended duration and power

NASA Technical Reports Server (NTRS)

Loftus, J. P., Jr.

1979-01-01

A modification kit for the Space Transportation System (STS) Orbiter is proposed to provide more power and mission duration for payloads. The power extension package (PEP) - a flexible-substrate solar array deployed on the Space Shuttle Orbiter remote manipulator system - can provide as much as 29 kW total power for durations of 10 to 48 days. The kit is installed only for those flights which require enhanced power or duration. Modifications to the Orbiter thermal control and life support systems to improve heat balance and to reduce consumables are proposed. The changes consist of repositioning the Orbiter forward radiators and replacing the lithium hydroxide scrubber with a regenerable solid amine.

Laser desorption of explosives as a way to create an effective non-contact sampling device

NASA Astrophysics Data System (ADS)

Akmalov, Artem E.; Chistyakov, Alexander A.; Kotkovskii, Gennadii E.

2015-10-01

Comparison of desorption effectiveness of Nd3+:YAG nanosecond laser sources (λ=266, 354, 532 nm) has been carried out to investigate a possibility of creating a non-contact sampling device for detectors of explosives based on principles of ion mobility spectrometry (IMS) and field asymmetric ion mobility spectrometry (FAIMS). The results of mass spectrometric study of laser desorption of nitroamine, nitrate ester and nitroaromatic compounds from a quartz substrate are presented. It is shown that irradiation of adsorbed layers of studied samples by a single pulse of non-resonant laser radiation (λ=532 nm) leads to efficient desorption at laser intensity 107 W/cm2 and above. Excitation of the first singlet state of nitro compounds by resonant radiation (λ=354 nm) provides heating of adsorbed layers and thermal desorption. A strongly non-equilibrium (non-thermal) dissociation process is developed when the second singlet state of nitroaromatic molecules is excited by radiation at λ=266 nm, along with thermal desorption. It is shown that Nd3+: YAG laser with wavelength λ=266 nm, pulse duration 5-10 ns, intensity 107-109 W/cm2 is the most effective source for creation a non-contact sampling device based on desorption of explosives from surfaces.

PICARD payload thermal control system and general impact of the space environment on astronomical observations

NASA Astrophysics Data System (ADS)

Meftah, M.; Irbah, A.; Hauchecorne, A.; Hochedez, J.-F.

2013-05-01

PICARD is a spacecraft dedicated to the simultaneous measurement of the absolute total and spectral solar irradiance, the diameter, the solar shape, and to probing the Sun's interior by the helioseismology method. The mission has two scientific objectives, which are the study of the origin of the solar variability, and the study of the relations between the Sun and the Earth's climate. The spacecraft was successfully launched, on June 15, 2010 on a DNEPR-1 launcher. PICARD spacecraft uses the MYRIADE family platform, developed by CNES to use as much as possible common equipment units. This platform was designed for a total mass of about 130 kg at launch. This paper focuses on the design and testing of the TCS (Thermal Control System) and in-orbit performance of the payload, which mainly consists in two absolute radiometers measuring the total solar irradiance, a photometer measuring the spectral solar irradiance, a bolometer, and an imaging telescope to determine the solar diameter and asphericity. Thermal control of the payload is fundamental. The telescope of the PICARD mission is the most critical instrument. To provide a stable measurement of the solar diameter over three years duration of mission, telescope mechanical stability has to be excellent intrinsically, and thermally controlled. Current and future space telescope missions require ever-more dimensionally stable structures. The main scientific performance related difficulty was to ensure the thermal stability of the instruments. Space is a harsh environment for optics with many physical interactions leading to potentially severe degradation of optical performance. Thermal control surfaces, and payload optics are exposed to space environmental effects including contamination, atomic oxygen, ultraviolet radiation, and vacuum temperature cycling. Environmental effects on the performance of the payload will be discussed. Telescopes are placed on spacecraft to avoid the effects of the Earth atmosphere on astronomical observations (turbulence, extinction, ...). Atmospheric effects, however, may subsist when spacecraft are launched into low orbits, with mean altitudes of the order of 735 km.

Numerical Modeling of Thermal-Hydrology in the Near Field of a Generic High-Level Waste Repository

NASA Astrophysics Data System (ADS)

Matteo, E. N.; Hadgu, T.; Park, H.

2016-12-01

Disposal in a deep geologic repository is one of the preferred option for long term isolation of high-level nuclear waste. Coupled thermal-hydrologic processes induced by decay heat from the radioactive waste may impact fluid flow and the associated migration of radionuclides. This study looked at the effects of those processes in simulations of thermal-hydrology for the emplacement of U. S. Department of Energy managed high-level waste and spent nuclear fuel. Most of the high-level waste sources have lower thermal output which would reduce the impact of thermal propagation. In order to quantify the thermal limits this study concentrated on the higher thermal output sources and on spent nuclear fuel. The study assumed a generic nuclear waste repository at 500 m depth. For the modeling a representative domain was selected representing a portion of the repository layout in order to conduct a detailed thermal analysis. A highly refined unstructured mesh was utilized with refinements near heat sources and at intersections of different materials. Simulations looked at different values for properties of components of the engineered barrier system (i.e. buffer, disturbed rock zone and the host rock). The simulations also looked at the effects of different durations of surface aging of the waste to reduce thermal perturbations. The PFLOTRAN code (Hammond et al., 2014) was used for the simulations. Modeling results for the different options are reported and include temperature and fluid flow profiles in the near field at different simulation times. References:G. E. Hammond, P.C. Lichtner and R.T. Mills, "Evaluating the Performance of Parallel Subsurface Simulators: An Illustrative Example with PFLOTRAN", Water Resources Research, 50, doi:10.1002/2012WR013483 (2014). Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2016-7510 A

Temperature extremes reduce seagrass growth and induce mortality.

PubMed

Collier, C J; Waycott, M

2014-06-30

Extreme heating (up to 43 °C measured from five-year temperature records) occurs in shallow coastal seagrass meadows of the Great Barrier Reef at low tide. We measured effective quantum yield (ϕPSII), growth, senescence and mortality in four tropical seagrasses to experimental short-duration (2.5h) spikes in water temperature to 35 °C, 40 °C and 43 °C, for 6 days followed by one day at ambient temperature. Increasing temperature to 35 °C had positive effects on ϕPSII (the magnitude varied between days and was highly correlated with PPFD), with no effects on growth or mortality. 40 °C represented a critical threshold as there were strong species differences and there was a large impact on growth and mortality. At 43 °C there was complete mortality after 2-3 days. These findings indicate that increasing duration (more days in a row) of thermal events above 40 °C is likely to affect the ecological function of tropical seagrass meadows. Copyright © 2014 Elsevier Ltd. All rights reserved.

SU-F-J-215: Non-Thermal Pulsed High Intensity Focused Ultrasound Therapy Combined with 5-Aminolevulinic Acid: An in Vivo Pilot Study

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

Wang, B; He, W; Cvetkovic, D

Purpose: It has recently been shown that non-thermal pulsed high intensity focused ultrasound (pHIFU) has a cell-killing effect. The purpose of the study is to investigate the sonosensitizing effect of 5-Aminolevulinic Acid (5-ALA) in non-thermal pHIFU cancer therapy. Methods: FaDu human head and neck squamous cell carcinoma cells were injected subcutaneously in the flanks of nude mice. After one to two weeks, the tumors reached the volume of 112 ± 8 mm3 and were assigned randomly into a non-thermal pHIFU group (n=9) and a non-thermal sonodynamic therapy (pHIFU after 5-ALA administration) group (n=7). The pHIFU treatments (parameters: 1 MHz frequency;more » 25 W acoustic power; 0.1 duty cycle; 60 seconds duration) were delivered using an InSightec ExAblate 2000 system with a GE Signa 1.5T MR scanner. The mice in the non-thermal sonodynamic group received 5-ALA tail-vein injection 4 hours prior to the pHIFU treatment. The tumor growth was monitored using the CT scanner on a Sofie-Biosciences G8 PET/CT system. Results: The tumors in this study grew very aggressively and about 60% of the tumors in this study developed ulcerations at various stages. Tumor growth delay after treatments was observed by comparing the treated (n=9 in pHIFU group; n=7 in sonodynamic group) and untreated tumors (n=17). However, no statistically significant differences were found between the non-thermal pHIFU and non-thermal sonodynamic group. The mean normalized tumor volume of the untreated tumors on Day 7 after their first CT scans was 7.05 ± 0.54, while the normalized volume of the treated tumors on Day 7 after treatment was 5.89 ± 0.79 and 6.27 ± 0.47 for the sonodynamic group and pHIFU group, respectively. Conclusion: In this study, no significant sonosensitizing effects of 5-ALA were obtained on aggressive FaDu tumors despite apparent tumor growth delay in some mice treated with non-thermal sonodynamic therapy.« less

Self-Shielding of Thermal Radiation by Chicxulub Ejecta: Firestorm or Fizzle?

NASA Astrophysics Data System (ADS)

Goldin, T. J.; Melosh, H. J.

2008-12-01

The discovery of soot within the Chicxulub ejecta sequence and the observed survival patterns of terrestrial organisms across the K/Pg boundary led to the hypothesis that thermal radiation from the atmospheric reentry of hypervelocity impact ejecta was sufficient to ignite global wildfires and cause biological catastrophe. Using a two-dimensional, two-phase fluid flow code, KFIX-LPL, we model the atmospheric reentry of distal Chicxulub ejecta and calculate the fluxes of thermal radiation throughout the atmosphere. The model treatment includes optical opacity, allowing us to examine the effects that greenhouse gases and the spherules themselves have on the transfer of thermal radiation to the ground. We model a simple Chicxulub scenario where 250-µm spherules reenter the atmosphere for an hour with maximum inflow after 10 minutes. Our models predict a pulse of thermal radiation at the ground peaking at ~6 kW/m2, analogous to an oven set on 'broil'. Previous calculations, which did not consider spherule opacity, yielded >10 kW/ m2 sustained over an hour or more and such an extended pulse of high fluxes is thought to be required for wildfire ignition. However, our model suggests a half-hour in which fluxes exceed the solar norm and only a few minutes >5 kW/m2. Large fluxes are not sustained in our models due to the increasingly opaque cloud of settling spherules, which increasingly blocks the transmission of thermal radiation from the decelerating spherules above. Hence, the spherules themselves limit the magnitude and duration of thermal radiation at the ground. Such self-shielding may have prevented the ignition of global wildfires following Chicxulub and limited other environmental effects. Keeping the impact wildfire hypothesis will require a mechanism to override this effect. A nonuniform distribution of spherule reentry may produce gaps in the opaque spherule layer through which the downward thermal radiation may be concentrated. Additionally, an opaque cloud of dust, injected into the upper atmosphere from the impact plume, would act to reflect some of the space-bound thermal radiation downwards.

Impact of thermal time shift on wheat phenology and yield under warming climate in the Huang-Huai-Hai Plain, China

NASA Astrophysics Data System (ADS)

Xiao, Dengpan; Qi, Yongqing; Li, Zhiqiang; Wang, Rende; Moiwo, Juana P.; Liu, Fengshan

2017-03-01

Given climate change can potentially influence crop phenology and subsequent yield, an investigation of relevant adaptation measures could increase the understanding and mitigation of these responses in the future. In this study, field observations at 10 stations in the Huang-Huai-Hai Plain of China (HHHP) are used in combination with the Agricultural Production Systems Simulator (APSIM)-Wheat model to determine the effect of thermal time shift on the phenology and potential yield of wheat from 1981-2009. Warming climate speeds up winter wheat development and thereby decreases the duration of the wheat growth period. However, APSIM-Wheat model simulation suggests prolongation of the period from flowering to maturity (Gr) of winter wheat by 0.2-0.8 d•10yr-1 as the number of days by which maturity advances, which is less than that by which flowering advances. Based on computed thermal time of the two critical growth phases of wheat, total thermal time from floral initiation to flowering (TT_floral_initiation) increasesd in seven out of the 10 investigated stations. Alternatively, total thermal time from the start of grainfilling to maturity (TT_start_ grain_fill) increased in all investigated stations, except Laiyang. It is thus concluded that thermal time shift during the past three decades (1981-2009) prolongs Gr by 0.2-3.0 d•10yr-1 in the study area. This suggests that an increase in thermal time (TT) of the wheat growth period is critical for mitigating the effect of growth period reduction due to warming climatic condition. Furthermore, climate change reduces potential yield of winter wheat in 80% of the stations by 2.3-58.8 kg•yr-1. However, thermal time shift (TTS) increases potential yield of winter wheat in most of the stations by 3.0-51.0 kg•yr-1. It is concluded that wheat cultivars with longer growth periods and higher thermal requirements could mitigate the negative effects of warming climate on crop production in the study area.

Direct formation of InN-codoped p-ZnO/n-GaN heterojunction diode by solgel spin-coating scheme.

PubMed

Huang, Chun-Ying; Lee, Ya-Ju; Lin, Tai-Yuan; Chang, Shao-Lun; Lian, Jan-Tian; Lin, Hsiu-Mei; Chen, Nie-Chuan; Yang, Ying-Jay

2014-02-15

In this work p-ZnO/n-GaN heterojunction diodes were directly formed on the Si substrate by a combination of cost-effective solgel spin-coating and thermal annealing treatment. Spin-coated n-ZnO films on InN/GaN/Si wafers were converted to p-type polarity after thermal treatment of proper annealing durations. X-ray diffraction (XRD) analysis reveals that InN-codoped ZnO films have grown as the standard hexagonal wurtzite structure with a preferential orientation in the (002) direction. The intensity of the (002) peak decreases for a further extended annealing duration, indicating the greater incorporation of dopants, also confirmed by x-ray photoelectron spectroscopy and low-temperature photoluminescence. Hall and resistivity measurements validate that our p-type ZnO film has a high carrier concentration of 3.73×10¹⁷ cm⁻³, a high mobility of 210 cm²/Vs, and a low resistivity of 0.079 Ωcm. As a result, the proposed p-ZnO/n-GaN heterojunction diode displays a well-behaving current rectification of a typical p-n junction, and the measured current versus voltage (I-V) characteristic is hence well described by the modified Shockley equation. The research on the fabrication of p-ZnO/n-GaN heterojunctions shown here generates useful advances in the production of cost-effective ZnO-based optoelectronic devices.

Effect of dual laser beam on dissimilar welding-brazing of aluminum to galvanized steel

NASA Astrophysics Data System (ADS)

Mohammadpour, Masoud; Yazdian, Nima; Yang, Guang; Wang, Hui-Ping; Carlson, Blair; Kovacevic, Radovan

2018-01-01

In this investigation, the joining of two types of galvanized steel and Al6022 aluminum alloy in a coach peel configuration was carried out using a laser welding-brazing process in dual-beam mode. The feasibility of this method to obtain a sound and uniform brazed bead with high surface quality at a high welding speed was investigated by employing AlSi12 as a consumable material. The effects of alloying elements on the thickness of intermetallic compound (IMC) produced at the interface of steel and aluminum, surface roughness, edge straightness and the tensile strength of the resultant joint were studied. The comprehensive study was conducted on the microstructure of joints by means of a scanning electron microscopy and EDS. Results showed that a dual-beam laser shape and high scanning speed could control the thickness of IMC as thin as 3 μm and alter the failure location from the steel-brazed interface toward the Al-brazed interface. The numerical simulation of thermal regime was conducted by the Finite Element Method (FEM), and simulation results were validated through comparative experimental data. FEM thermal modeling evidenced that the peak temperatures at the Al-steel interface were around the critical temperature range of 700-900 °C that is required for the highest growth rate of IMC. However, the time duration that the molten pool was placed inside this temperature range was less than 1 s, and this duration was too short for diffusion-control based IMC growth.

Seasonal changes in the behaviour and respiration physiology of the freshwater duck mussel, Anodonta anatina.

PubMed

Lurman, Glenn; Walter, Johanna; Hoppeler, Hans H

2014-01-15

For low-energy organisms such as bivalves, the costs of thermal compensation of biological rates (synonymous with acclimation or acclimatization) may be higher than the benefits. We therefore conducted two experiments to examine the effect of seasonal temperature changes on behaviour and oxygen consumption. In the first experiment, we examined the effects of seasonal temperature changes on the freshwater bivalve Anodonta anatina, taking measurements each month for a year at the corresponding temperature for that time of year. There was no evidence for compensation of burrowing valve closure duration or frequency, or locomotory speed. In the second experiment, we compared A. anatina at summer and winter temperatures (24 and 4°C, respectively) and found no evidence for compensation of the burrowing rate, valve closure duration or frequency, or oxygen consumption rates during burrowing, immediately after valve closure or at rest. Within the experimental limits of this study, the evidence suggests that thermal compensation of biological rates is not a strategy employed by A. anatina. We argue that this is due to either a lack of evolutionary pressure to acclimatize, or evolutionary pressure to not acclimatize. Firstly, there is little incentive to increase metabolic rate to enhance predatory ability given that these are filter feeders. Secondly, maintained low energetic demand, enhanced at winter temperatures, is essential for predator avoidance, i.e. valve closure. Thus, we suggest that the costs of acclimatization outweigh the benefits in A. anatina.

BLAST BIOLOGY. Technical Progress Report

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

White, C.S.; Richmond, D.R.

1959-09-18

Experimental data regarding the biologic consequences of exposure to several environmental variations associated with actual and simulated explosive detonations were reviewed. Blast biology is discussed relative to primary, secondary, tentiary, and miscellaneous blast effects as those attributable, respectively, to variations in environmental pressure, trauma from blast-produced missiles (both penetrating and nonpenetrating), the consequences of physical displacement of biological targets by blast-produced winds, and hazards due to ground shock, dust, and thermal phenomena not caused by thermal radiation per se. Primary blast effects were considered, noting physical-biophysical factors contributing to the observed pathophysiology. A simple hydrostatic model was utilized diagrammatically inmore » pointing out possible etiologic mechanisms. The gross biologic response to single. "fast"-rising overpressures were described as was the tolerance of mice, rats, guinea pigs. and rabbits to "long"-duration pressure pulses rising "rapidly" in single and double steps. Data regarding biological response to "slowly" rising over-pressures of "long" duration are discussed. Attention was called to the similarities under certain circumstances between thoracic trauma from nonpenetrating missiles and that noted from air blast. The association between air emboli, increase in lung weight (hemorrhage and edema), and mortality was discussed. Data relevant to the clinical symptoms and therapy of blast injury are presented. The relation of blast hazards to nuclear explosions was assessed and one approach to predicting the maximal potential casualties from blast phenomena is presented making use of arbitrary and tentative criteria. (auth)« less

Thermal sensations and comfort investigations in transient conditions in tropical office.

PubMed

Dahlan, Nur Dalilah; Gital, Yakubu Yau

2016-05-01

The study was done to identify affective and sensory responses observed as a result of hysteresis effects in transient thermal conditions consisting of warm-neutral and neutral - warm performed in a quasi-experiment setting. Air-conditioned building interiors in hot-humid areas have resulted in thermal discomfort and health risks for people moving into and out of buildings. Reports have shown that the instantaneous change in air temperature can cause abrupt thermoregulation responses. Thermal sensation vote (TSV) and thermal comfort vote (TCV) assessments as a consequence of moving through spaces with distinct thermal conditions were conducted in an existing single-story office in a hot-humid microclimate, maintained at an air temperature 24 °C (± 0.5), relative humidity 51% (± 7), air velocity 0.5 m/s (± 0.5), and mean radiant temperature (MRT) 26.6 °C (± 1.2). The measured office is connected to a veranda that showed the following semi-outdoor temperatures: air temperature 35 °C (± 2.1), relative humidity 43% (± 7), air velocity 0.4 m/s (± 0.4), and MRT 36.4 °C (± 2.9). Subjective assessments from 36 college-aged participants consisting of thermal sensations, preferences and comfort votes were correlated against a steady state predicted mean vote (PMV) model. Local skin temperatures on the forehead and dorsal left hand were included to observe physiological responses due to thermal transition. TSV for veranda-office transition showed that no significant means difference with TSV office-veranda transition were found. However, TCV collected from warm-neutral (-0.24, ± 1.2) and neutral-warm (-0.72, ± 1.3) conditions revealed statistically significant mean differences (p < 0.05). Sensory and affective responses as a consequence of thermal transition after travel from warm-neutral-warm conditions did not replicate the hysteresis effects of brief, slightly cool, thermal sensations found in previous laboratory experiments. These findings also indicate that PMV is an acceptable alternative to predict thermal sensation immediately after a down-step thermal transition (≤ 1 min exposure duration) for people living in a hot-humid climate country. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Impact of thermal effects induced by ultrasound on viability of rat C6 glioma cells.

PubMed

Kujawska, T; Secomski, W; Bilmin, K; Nowicki, A; Grieb, P

2014-07-01

In order to have consistent and repeatable effects of sonodynamic therapy (SDT) on various cancer cells or tissue lesions we should be able to control a delivered ultrasound energy and thermal effects induced. The objective of this study was to investigate viability of rat C6 glioma cells in vitro depending on the intensity of ultrasound in the region of cells and to determine the exposure time inducing temperature rise above 43 °C, which is known to be toxic for cells. For measurements a planar piezoelectric transducer with a diameter of 20 mm and a resonance frequency of 1.06 MHz was used. The transducer generated tone bursts with 94 μs duration, 0.4 duty-cycle and initial intensity ISATA (spatial averaged, temporal averaged) varied from 0.33 W/cm(2) to 8 W/cm(2) (average acoustic power varied from 1 W to 24 W). The rat C6 glioma cells were cultured on a bottom of wells in 12-well plates, incubated for 24h and then exposed to ultrasound with measured acoustic properties, inducing or causing no thermal effects leading to cell death. Cell viability rate was determined by MTT assay (a standard colorimetric assay for assessing cell viability) as the ratio of the optical densities of the group treated by ultrasound to the control group. Structural cellular changes and apoptosis estimation were observed under a microscope. Quantitative analysis of the obtained results allowed to determine the maximal exposure time that does not lead to the thermal effects above 43 °C in the region of cells for each initial intensity of the tone bursts used as well as the threshold intensity causing cell death after 3 min exposure to ultrasound due to thermal effects. The averaged threshold intensity was found to be about 5.7 W/cm(2). Copyright © 2014 Elsevier B.V. All rights reserved.

Correlating measured transient temperature rises with damage rate processes in cultured cells

NASA Astrophysics Data System (ADS)

Denton, Michael L.; Tijerina, Amanda J.; Gonzalez, Cherry C.; Gamboa, B. Giovana; Noojin, Gary D.; Ahmed, Elharith M.; Rickman, John M.; Dyer, Phillip H.; Rockwell, Benjamin A.

2017-02-01

Thermal damage rate processes in biological tissues are usually characterized by a kinetics approach. This stems from experimental data that show how the transformation of a specified biological property of cells or biomolecule (plating efficiency for viability, change in birefringence, tensile strength, etc.) is dependent upon both time and temperature. Here, two disparate approaches were used to study thermal damage rate processes in cultured retinal pigment epithelial cells. Laser exposure (photothermal) parameters included 2-μm laser exposure of non-pigmented cells and 532-nm exposures of cells possessing a variety of melanosome particle densities. Photothermal experiments used a mid-IR camera to record temperature histories with spatial resolution of about 8 μm, while fluorescence microscopy of the cell monolayers identified threshold damage at the boundary between live and dead cells. Photothermal exposure durations ranged from 0.05-20 s, and the effects of varying ambient temperature were investigated. Temperature during heat transfer using a water-jacketed cuvette was recorded with a fast microthermister, while damage and viability of the suspended cells were determined as percentages. Exposure durations for the heat transfer experiments ranged from 50- 60 s. Empirically-determined kinetic parameters for the two heating methods were compared with each other, and with values found in the literature.

Sintering of highly porous silica-particle samples: analogues of early Solar-System aggregates

NASA Astrophysics Data System (ADS)

Poppe, T.

2003-07-01

I describe a new method to make particle layers which consist of SiO 2 spheres with 0.78 μm radius. The layers were produced by sedimentation of aggregates which had grown in ballistic particle collisions, and the layers had a porosity of 0.95. They were used for experiments on sintering, i.e., the samples were heated in an oven at varying temperatures and heating durations, and the samples were analyzed by scanning electron microscopy. Based on the change of particle diameter, surface diffusion sintering and viscous flow are identified as important transformation mechanisms. The first effect dominated at the start of restructuring and the latter at higher temperatures. The neck growth of adjacent particles was fitted to a surface diffusion sintering model and predicts neck radii as a heating temperature and duration function. Between the temperature range of neck formation and of melting, further restructuring occurred which lead to dissolution of particulate structure and to densification and which resulted in a porous object consisting of straight elongated substructures which connected kinks of higher material density. The thermal transformation is important for the change of strength, collisional behavior, light-scattering properties, and thermal conductivity with relevance to dust aggregates, planetesimals, comets, interplanetary dust particles, and regolith-covered celestial bodies.

The Effect of Three Different (-135°C) Whole Body Cryotherapy Exposure Durations on Elite Rugby League Players

PubMed Central

Selfe, James; Alexander, Jill; Costello, Joseph T.; May, Karen; Garratt, Nigel; Atkins, Stephen; Dillon, Stephanie; Hurst, Howard; Davison, Matthew; Przybyla, Daria; Coley, Andrew; Bitcon, Mark; Littler, Greg; Richards, Jim

2014-01-01

Background Whole body cryotherapy (WBC) is the therapeutic application of extreme cold air for a short duration. Minimal evidence is available for determining optimal exposure time. Purpose To explore whether the length of WBC exposure induces differential changes in inflammatory markers, tissue oxygenation, skin and core temperature, thermal sensation and comfort. Method This study was a randomised cross over design with participants acting as their own control. Fourteen male professional first team super league rugby players were exposed to 1, 2, and 3 minutes of WBC at −135°C. Testing took place the day after a competitive league fixture, each exposure separated by seven days. Results No significant changes were found in the inflammatory cytokine interleukin six. Significant reductions (p<0.05) in deoxyhaemoglobin for gastrocnemius and vastus lateralis were found. In vastus lateralis significant reductions (p<0.05) in oxyhaemoglobin and tissue oxygenation index (p<0.05) were demonstrated. Significant reductions (p<0.05) in skin temperature were recorded. No significant changes were recorded in core temperature. Significant reductions (p<0.05) in thermal sensation and comfort were recorded. Conclusion Three brief exposures to WBC separated by 1 week are not sufficient to induce physiological changes in IL-6 or core temperature. There are however significant changes in tissue oxyhaemoglobin, deoxyhaemoglobin, tissue oxygenation index, skin temperature and thermal sensation. We conclude that a 2 minute WBC exposure was the optimum exposure length at temperatures of −135°C and could be applied as the basis for future studies. PMID:24489726

Thermal bleaching in single fluorescent molecules under two-photon excitation regime

NASA Astrophysics Data System (ADS)

Chirico, Giuseppe; Cannone, Fabio; Baldini, Giancarlo; Diaspro, Alberto

2003-07-01

Single molecule spectroscopy often requires the immobilization of the molecules onto solid or quasi-solid substrates and the use of relatively high excitation intensity We have studied the fluorescence emission of four common dyes used for bio-imaging studies, rhodamine 6G, fluorescein, pyrene and indo-1 at the single molecule level under two-photon excitation regime. We focus on two-photon excitation thermal effects on the stability of the single molecules, influencing the internal photo-dynamics and the total duration of the fluorescent emission. Single dye molecules, spread on a glass substrate by spin coating, show a constant fluorescence output till a sudden transition to a dark state very close to the background. The bleaching time that is found to vary in the series pyrene, Indo-1, fluorescein and rhodamine 6G from the fastest to the slowest one respectively, has a Gaussian distribution suggesting that bleaching is not due to photo-bleaching. Moreover it shows a correlation to the amount of absorbed power not re-irradiated as fluorescence and to the complexity of the molecule. These observations are interpreted as thermal bleaching where the temperature increase is induced by the two-photon excitation process. This study should be extended to different trapping media of interest in single molecule basic research and applications, such as silica and polyacrylamide gels or nanosctructured polyelectrolyte matrices. We think that the observed behavior and the correlations found to the molecular chemical and physical parameters, may be of some help for the design of molecules with switching on-off behavior of longer duration.

A randomized controlled clinical and histopathological trial comparing excisional biopsies of oral fibrous hyperplasias using CO2 and Er:YAG laser.

PubMed

Suter, Valerie G A; Altermatt, Hans Jörg; Bornstein, Michael M

2017-04-01

This study was conducted in order to compare clinical and histopathological outcomes for excisional biopsies when using pulsed CO 2 laser versus Er:YAG laser. Patients (n = 32) with a fibrous hyperplasia in the buccal mucosa were randomly allocated to the CO 2 (140 Hz, 400 μs, 33 mJ) or the Er:YAG laser (35 Hz, 297 μs, 200 mJ) group. The duration of excision, intraoperative bleeding and methods to stop the bleeding, postoperative pain (VAS; ranging 0-100), the use of analgesics, and the width of the thermal damage zone (μm) were recorded and compared between the two groups. The median duration of the intervention was 209 s, and there was no significant difference between the two methods. Intraoperative bleeding occurred in 100% of the excisions with Er:YAG and 56% with CO 2 laser (p = 0.007). The median thermal damage zone was 74.9 μm for CO 2 and 34.0 μm for Er:YAG laser (p < 0.0001). The median VAS score on the evening after surgery was 5 for the CO 2 laser and 3 for the Er:YAG group. To excise oral soft tissue lesions, CO 2 and Er:YAG lasers are both valuable tools with a short time of intervention and postoperative low pain. More bleeding occurs with the Er:YAG than CO 2 laser, but the lower thermal effect of Er:YAG laser seems advantageous for histopathological evaluation.

Patterns of developmental plasticity in response to incubation temperature in reptiles.

PubMed

While, Geoffrey M; Noble, Daniel W A; Uller, Tobias; Warner, Daniel A; Riley, Julia L; Du, Wei-Guo; Schwanz, Lisa E

2018-05-28

Early life environments shape phenotypic development in important ways that can lead to long-lasting effects on phenotype and fitness. In reptiles, one aspect of the early environment that impacts development is temperature (termed 'thermal developmental plasticity'). Indeed, the thermal environment during incubation is known to influence morphological, physiological, and behavioral traits, some of which have important consequences for many ecological and evolutionary processes. Despite this, few studies have attempted to synthesize and collate data from this expansive and important body of research. Here, we systematically review research into thermal developmental plasticity across reptiles, structured around the key papers and findings that have shaped the field over the past 50 years. From these papers, we introduce a large database (the 'Reptile Development Database') consisting of 9,773 trait means across 300 studies examining thermal developmental plasticity. This dataset encompasses data on a range of phenotypes, including morphological, physiological, behavioral, and performance traits along with growth rate, incubation duration, sex ratio, and survival (e.g., hatching success) across all major reptile clades. Finally, from our literature synthesis and data exploration, we identify key research themes associated with thermal developmental plasticity, important gaps in empirical research, and demonstrate how future progress can be made through targeted empirical, meta-analytic, and comparative work. © 2018 Wiley Periodicals, Inc.

Modeling the effect of heatsink performance in high-peak-power laser-diode-bar pump sources for solid-state lasers 011 011

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

Honea, E.C., LLNL

We derive approximate expressions for transient output power and wavelength chirp of high- peak-power laser-diode bars assuming one-dimensional heat flow and linear temperature dependences for chirp and efficiency. The model is derived for pulse durations, 10 < {tau} < 1000 ps, typically used for diode-pumped solid-state lasers and is in good agreement with experimental data for Si heatsink mounted 940 nm laser-diode bars operating at 100 W/cm. The analytic expressions are more flexible and easily used than the results of operating point dependent numerical modeling. In addition, the analytic expressions used here can be integrated to describe the energy permore » unit wavelength for a given pulse duration, initial emission bandwidth and heatsink material. We find that the figure-of-merit for a heatsink material in this application is ({rho}C{sub p}K) where {rho}C{sub p} is the volumetric heat capacity and K is the thermal conductivity. As an example of the utility of the derived expressions, we determine an effective absorption coefficient as a function of pump pulse duration for a diode-pumped solid-state laser utilizing Yb:Sr{sub 5}(PO{sub 4}){sub 3}F (Yb:S-FAP) as the gain medium.« less

Low-Earth orbit effects on organic composite materials flown on LDEF

NASA Technical Reports Server (NTRS)

George, Pete E.; Dursch, Harry W.

1993-01-01

Over 35 different types of organic matrix composites were flown as part of 11 different experiments onboard the NASA Long Duration Exposure Facility (LDEF) satellite. This materials and systems experiment satellite flew in low-earth orbit (LEO) for 69 months. For that period, the experiments were subjected to the LEO environment including atomic oxygen (AO), ultraviolet (UV) radiation, thermal cycling, microvacuum, meteoroid and space debris (M&D), and particle radiation. Since retrieval of the satellite in January of 1990, the principal experiment investigators have been deintegrating, examining, and testing the materials specimens flown. The most detrimental environmental effect on all organic matrix composites was material loss due to AO erosion. AO erosion of uncoated organic matrix composites (OMC) facing the satellite ram direction was responsible for significant mechanical property degradations. Also, thermal cycling-induced microcracking was observed in some nonunidirectional reinforced OMC's. Thermal cycling and outgassing caused significant but predictable dimensional changes as measured in situ on one experiment. Some metal and metal oxide-based coatings were found to be very effective at preventing AO erosion of OMC's. However, M&D impacts and coating fractures which compromised these coatings allowed AO erosion of the underlying OMC substrates. The findings for organic matrix composites flown on the LDEF are summarized and the LEO environmental factors, their effects, and the influence on space hardware design factors for LEO applications are identified.

Space tug thermal control. [design criteria and specifications

NASA Technical Reports Server (NTRS)

1974-01-01

It was determined that space tug will require the capability to perform its mission within a broad range of thermal environments with currently planned mission durations of up to seven days, so an investigation was conducted to define a thermal design for the forward and intertank compartments and fuel cell heat rejection system that satisfies tug requirements for low inclination geosynchronous deploy and retrieve missions. Passive concepts were demonstrated analytically for both the forward and intertank compartments, and a worst case external heating environment was determined for use during the study. The thermal control system specifications and designs which resulted from the research are shown.

A nonventing cooling system for space environment extravehicular activity, using radiation and regenerable thermal storage

NASA Technical Reports Server (NTRS)

Bayes, Stephen A.; Trevino, Luis A.; Dinsmore, Craig E.

1988-01-01

This paper outlines the selection, design, and testing of a prototype nonventing regenerable astronaut cooling system for extravehicular activity space suit applications, for mission durations of four hours or greater. The selected system consists of the following key elements: a radiator assembly which serves as the exterior shell of the portable life support subsystem backpack; a layer of phase change thermal storage material, n-hexadecane paraffin, which acts as a regenerable thermal capacitor; a thermoelectric heat pump; and an automatic temperature control system. The capability for regeneration of thermal storage capacity with and without the aid of electric power is provided.

Micrometeoroid/space debris effects on materials

NASA Technical Reports Server (NTRS)

Zwiener, James M.; Finckenor, Miria M.

1993-01-01

The Long Duration Exposure Facility (LDEF) micrometeoroid/space debris impact data has been reduced in terms that are convenient for evaluating the overall quantitative effect on material properties. Impact crater flux has been evaluated as a function of angle from velocity vector and as a function of crater size. This data is combined with spall data from flight and ground testing to calculate effective solar absorption and emittance values versus time. Results indicate that the surface damage from micrometeoroid/space debris does not significantly affect the overall surface optical thermal physical properties. Of course the local damage around impact craters radically alter optical properties. Damage to composites and solar cells on an overall basis was minimal.

Cryogenic Fluid Management Technology Development for Nuclear Thermal Propulsion

NASA Technical Reports Server (NTRS)

Taylor, Brian; Caffrey, Jarvis; Hedayat, Ali; Stephens, Jonathan; Polsgrove, Robert

2015-01-01

The purpose of this paper is to investigate, facilitate a discussion and determine a path forward for technology development of cryogenic fluid management technology that is necessary for long duration deep space missions utilizing nuclear thermal propulsion systems. There are a number of challenges in managing cryogenic liquids that must be addressed before long durations missions into deep space, such as a trip to Mars can be successful. The leakage rate of hydrogen from pressure vessels, seals, lines and valves is a critical factor that must be controlled and minimized. For long duration missions, hydrogen leakage amounts to large increases in hydrogen and therefore vehicle mass. The size of a deep space vehicle, such as a mars transfer vehicle, must be kept small to control cost and the logistics of a multi launch, assembled in orbit vehicle. The boil off control of the cryogenic fluid is an additional obstacle to long duration missions. The boil off caused by heat absorption results in the growth of the propellant needs of the vehicle and therefore vehicle mass. This is a significant problem for a vehicle using nuclear (fission) propulsion systems. Radiation from the engines deposits large quantities of heat into the cryogenic fluid, greatly increasing boil off beyond that caused by environmental heat leakage. Addressing and resolving these challenges is critical to successful long duration space exploration. This paper discusses the state of the technology needed to address these challenges and discuss the path forward needed in technology development.

Aerogel Insulation Applications for Liquid Hydrogen Launch Vehicle Tanks

NASA Technical Reports Server (NTRS)

Fesmire, J. E.; Sass, J.

2007-01-01

Aerogel based insulation systems for ambient pressure environments were developed for liquid hydrogen (LH2) tank applications. Solutions to thermal insulation problems were demonstrated for the Space Shuttle External Tank (ET) through extensive testing at the Cryogenics Test Laboratory. Demonstration testing was performed using a 1/10th scale ET LH2 intertank unit and liquid helium as the coolant to provide the 20 K cold boundary temperature. Cryopumping tests in the range of 20K were performed using both constant mass and constant pressure methods. Long-duration tests (up to 10 hours) showed that the nitrogen mass taken up inside the intertank is reduced by a factor of nearly three for the aerogel insulated case as compared to the un-insulated (bare metal flight configuration) case. Test results including thermal stabilization, heat transfer effectiveness, and cryopumping confirm that the aerogel system eliminates free liquid nitrogen within the intertank. Physisorption (or adsorption) of liquid nitrogen within the fine pore structure of aerogel materials was also investigated. Results of a mass uptake method show that the sorption ratio (liquid nitrogen to aerogel beads) is about 62 percent by volume. A novel liquid nitrogen production method of testing the liquid nitrogen physical adsorption capacity of aerogel beads was also performed to more closely approximate the actual launch vehicle cooldown and thermal stabilization effects within the aerogel material. The extraordinary insulating effectiveness of the aerogel material shows that cryopumping is not an open-cell mass transport issue but is strictly driven by thermal communication between warm and cold surfaces. The new aerogel insulation technology is useful to solve heat transfer problem areas and to augment existing thermal protection systems on launch vehicles. Examples are given and potential benefits for producing launch systems that are more reliable, robust, reusable, and efficient are outlined.

The technology for creating of decorative plywood with low formaldehyde emission

NASA Astrophysics Data System (ADS)

Safin, R. R.; Khasanshin, R. R.; Shaikhutdinova, A. R.; Ziatdinov, R. R.

2015-10-01

The development of new technologies of processing of industrial art products to improve their functional, ergonomic and aesthetic properties is one of the important directions of improvement of product design. The article presents the technology of preliminary contact thermal modification of sheets of veneer in the production of low-toxic decorative plywood and laminated products, which lets significantly improve their water resistance. It has been established that thermal modification of wood material causes a decrease in density with increasing temperature and duration of treatment. A mathematical model describing the process of heat treatment of wood veneer and allowing predicting the degree of thermal modification of wood material depending on the modes of modification has been developed. Several studies to determine the basic properties of plywood made on the basis of heat-treated veneer were conducted in the work. Studies have shown that the thermal effect on veneer in the manufacture of plywood provides improves water-repellent properties of it, while not increasing its toxicity. It has also been found that the alternating of layers of wood with varying degrees of heat treatment when creating laminated products greatly enhances the decorative features of the products.

Space stable thermal control coatings

NASA Technical Reports Server (NTRS)

Harada, Y.

1982-01-01

A specification quality zinc orthotitanate coating was developed. This silicate-bonded Zn2TiO4 coating is discussed. The effects of precursor chemistry, precursor mixing procedures, stoichiometry variations, and of different heat treatments on the physical and optical properties of Zn2TiO4 are investigated. Inorganic silicates are compared to organic silicone binder systems. The effects of pigment to binder ratio, water content, and of different curing procedures on the optical and physical properties of Zn2TiO4 potassium silicate coatings are also studied. Environmental tests were conducted to determine the UV vacuum stability of coatings for durations up to 5000 equivalent Sun hours.

Effect of vitro preservation on mechanical properties of brain tissue

NASA Astrophysics Data System (ADS)

Zhang, Wei; Liu, Yi-fan; Liu, Li-fu; Niu, Ying; Ma, Jian-li; Wu, Cheng-wei

2017-05-01

To develop the protective devices for preventing traumatic brain injuries, it requires the accurate characterization of the mechanical properties of brain tissue. For this, it necessary to elucidate the effect of vitro preservation on the mechanical performance of brain tissue as usually the measurements are carried out in vitro. In this paper, the thermal behavior of brain tissue preserved for various period of time was first investigated and the mechanical properties were also measured. Both reveals the deterioration with prolonged preservation duration. The observations of brain tissue slices indicates the brain tissue experiences karyorrhexis and karyorrhexis in sequence, which accounts for the deterioration phenomena.

Effect of thermal stress and water deprivation on the acetylcholinesterase activity of the pig brain and hypophyses

NASA Astrophysics Data System (ADS)

Adejumo, D. O.; Egbunike, G. N.

1988-06-01

The effects of direct exposure of boars to thermal stress for 1 h daily for 5 days and to acute water deprivation for 24 or 48 h were studied on the acetylcholinesterase (AChE) activity of porcine brain and hypophysial regions. Mean ambient temperatures, respiratory rates and rectal temperatures in the open were significantly higher than inside the pen. Heat stress induced a rise in AChE activities in the pons, cerebellum, amygdala, hippocampus, hypothalamus, mid-brain and medulla oblongata. However, no significant changes were observed in the cerebral cortex, adenohypophysis and neurohypophysis. Water deprivation significantly ( P<0.05) depressed AChE activity to varying extents depending on the duration of water restriction. Thus AChE activity in the amygdala was depressed by water deprivation for 24 h but partially restored at 48 h. The pons and medulla oblongata were comparable to the amygdala in this respect. The adenohypophysis and neurohypophysis were relatively unaffected.

Melt layer formation in stainless steel under transient thermal loads

NASA Astrophysics Data System (ADS)

Steudel, I.; Klimov, N. S.; Linke, J.; Loewenhoff, Th.; Pintsuk, G.; Pitts, R. A.; Wirtz, M.

2015-08-01

To investigate the performance of stainless steel under transient thermal events, such as photon pulses caused by disruptions mitigated by massive gas injection (MGI), the material has been exposed to electron beam loads with ITER relevant power densities slightly above the melting threshold (245 MW/m2) and a pulse duration of 3 ms (Sugihara et al., 2012; Klimov et al., 2013; Pitts et al., 2013). The samples were manufactured from different steel grades with slightly modified chemical composition. To investigate the effect of repetitive surface heat loads on the melting process and the melt motion, identical heat pulses in the range of 100-3000 were applied. All tested materials showed intense melt-induced surface roughening, driven by repeated shallow surface melting up to several ten micrometre and fast re-solidification with epitaxial grain growth. During the liquid phase, melt motion induced by cohesive forces results in the formation of a wavy surface structure with apexes. Further experiments have been performed to study the effects of non-perpendicular surfaces or leading edges.

Purification of Carbon Nanotubes: Alternative Methods

NASA Technical Reports Server (NTRS)

Files, Bradley; Scott, Carl; Gorelik, Olga; Nikolaev, Pasha; Hulse, Lou; Arepalli, Sivaram

2000-01-01

Traditional carbon nanotube purification process involves nitric acid refluxing and cross flow filtration using surfactant TritonX. This is believed to result in damage to nanotubes and surfactant residue on nanotube surface. Alternative purification procedures involving solvent extraction, thermal zone refining and nitric acid refiuxing are used in the current study. The effect of duration and type of solvent to dissolve impurities including fullerenes and P ACs (polyaromatic compounds) are monitored by nuclear magnetic reasonance, high performance liquid chromatography, and thermogravimetric analysis. Thermal zone refining yielded sample areas rich in nanotubes as seen by scanning electric microscopy. Refluxing in boiling nitric acid seem to improve the nanotube content. Different procedural steps are needed to purify samples produced by laser process compared to arc process. These alternative methods of nanotube purification will be presented along with results from supporting analytical techniques.

Cracking of coated materials under transient thermal stresses

NASA Technical Reports Server (NTRS)

Rizk, A. A.; Erdogan, Fazil

1988-01-01

The crack problem for a relatively thin layer bonded to a very thick substrate under thermal shock conditions is considered. The effect of surface cooling rate is studied by assuming the temperature boundary condition to be a ramp function. Among the crack geometries considered are the edge crack in the coating layer, the broken layer, the edge crack going through the interface, the undercoat crack in the substrate and the embedded crack crossing the interface. The primary calculated quantity is the stress intensity factor at various singular points and the main variables are the relative sizes and locations of cracks, the time, and the duration of the cooling ramp. The problem is solved and rather extensive results are given for two material pairs, namely a stainless steel layer welded on a ferritic medium and a ceramic coating on a steel substrate.

Cracking of coated materials under transient thermal stresses

NASA Technical Reports Server (NTRS)

Rizk, A. A.; Erdogan, F.

1989-01-01

The crack problem for a relatively thin layer bonded to a very thick substrate under thermal shock conditions is considered. The effect of surface cooling rate is studied by assuming the temperature boundary condition to be a ramp function. Among the crack geometries considered are the edge crack in the coating layer, the broken layer, the edge crack going through the interface, the undercoat crack in the substrate and the embedded crack crossing the interface. The primary calculated quantity is the stress intensity factor at various singular points and the main variables are the relative sizes and locations of cracks, the time, and the duration of the cooling ramp. The problem is solved and rather extensive results are given for two material pairs, namely a stainless steel layer welded on a ferritic medium and a ceramic coating on a steel substrate.

Summary of solar cell data from the Long Duration Exposure Facility (LDEF)

NASA Technical Reports Server (NTRS)

Hill, David C.; Rose, M. Frank

1994-01-01

The contractor has obtained and reviewed data relating solar cells assemblies (SCA's) flown as part of the following LDEF experiments: the Advanced Photovoltaic Experiment (S0014); the Solar Array Materials Passive LDEF Experiment (A0171); the Advanced Solar Cell and Coverglass Analysis Experiment (M0003-4); the LDEF Heat Pipe Experiment (S1001); the Evaluation of Thermal Control Coatings Y Solar Cells Experiment (S1002); and the Space Plasma-High Voltage Drainage Experiment (A0054). Where possible, electrical data have been tabulated and correlated with various environmental effects, including meteoroid and debris impacts, radiation exposure, atomic oxygen exposure, contamination, UV radiation exposure, and thermal cycling. The type, configuration, and location of all SCA's are documented here. By gathering all data and results together, a comparison of the survivability of the various types and configurations can be made.

Thermal-environmental testing of a 30-cm engineering model thruster

NASA Technical Reports Server (NTRS)

Mirtich, M. J.

1976-01-01

An experimental test program was carried out to document all 30-cm electron bombardment Hg ion bombardment thruster functions and characteristics over the thermal environment of several proposed missions. An engineering model thruster was placed in a thermal test facility equipped with -196 C walls and solar simulation. The thruster was cold soaked and exposed to simulated eclipses lasting in duration from 17 to 72 minutes. The thruster was operated at quarter, to full beam power in various thermal configurations which simulated multiple thruster operation, and was also exposed to 1 and 2 suns solar simulation. Thruster control characteristics and constraints; performance, including thrust magnitude and direction; and structural integrity were evaluated over the range of thermal environments tested.

Space tug thermal control

NASA Technical Reports Server (NTRS)

Ward, T. L.

1975-01-01

The future development of full capability Space Tug will impose strict requirements upon the thermal design. While requiring a reliable and reusable design, Space Tug must be capable of steady-state and transient thermal operation during any given mission for mission durations of up to seven days and potentially longer periods of time. Maximum flexibility and adaptability of Space Tug to the mission model requires that the vehicle operate within attitude constraints throughout any specific mission. These requirements were translated into a preliminary design study for a geostationary deploy and retrieve mission definition for Space Tug to determine the thermal control design requirements. Results of the study are discussed with emphasis given to some of the unique avenues pursued during the study, as well as the recommended thermal design configuration.

Thermal-environment testing of a 30-cm engineering model thruster

NASA Technical Reports Server (NTRS)

Mirtich, M. J.

1976-01-01

An experimental test program was carried out to document all 30-cm electron bombardment Hg ion bombardment thruster functions and characteristics over the thermal environment of several proposed missions. An engineering model thruster was placed in a thermal test facility equipped with -196 C walls and solar simulation. The thruster was cold soaked and exposed to simulated eclipses lasting in duration from 17 to 72 minutes. The thruster was operated at quarter, to full beam power in various thermal configurations which simulated multiple thruster operation, and was also exposed to 1 and 2 suns solar simulation. Thruster control characteristics and constraints; performance, including thrust magnitude and direction; and structural integrity were evaluated over the range of thermal environments tested.

The Long Duration Exposure Facility (LDEF) photographic survey special publication

NASA Technical Reports Server (NTRS)

Oneal, Robert L.; Levine, Arlene S.; Kiser, Carol C.

1995-01-01

During the construction, integration, launch, retrieval and deintegration of the Long Duration Exposure Facility (LDEF), photographic surveys were made. Approximately 10,000 photographs were taken during the various phases of the LDEF project. These surveys are of technical and scientific importance because they revealed the pre and post flight conditions of the experiment trays as well as the spacecraft. Visual inspection of the photographs reveal valuable data such as space environment's effects and the earth atmosphere's effects post-retrieval. Careful files and records have been kept of these photographs. Each photograph has a Kennedy Space Center photo number or a Johnson Spaceflight Center photo number as well as a Langley Research Center photo number. The tray number, row number, and experiment number are also noted. Out of the 10,000 photographs taken, approximately 700 selected photographs were chosen for publication in a NASA Special Publication (SP) because they reveal the effects of space exposure to the viewer. These photographs will give researchers and spacecraft designers visual images of the effects of the space environment on specific materials, systems and spacecraft in general. One can visually see the degradation of thermal blankets, meteoroid craters, outgassing discoloration, atomic oxygen erosion, etc.

Ecological traps in shallow coastal waters-Potential effect of heat-waves in tropical and temperate organisms.

PubMed

Vinagre, Catarina; Mendonça, Vanessa; Cereja, Rui; Abreu-Afonso, Francisca; Dias, Marta; Mizrahi, Damián; Flores, Augusto A V

2018-01-01

Mortality of fish has been reported in tide pools during warm days. That means that tide pools are potential ecological traps for coastal organisms, which happen when environmental changes cause maladaptive habitat selection. Heat-waves are predicted to increase in intensity, duration and frequency, making it relevant to investigate the role of tide pools as traps for coastal organisms. However, heat waves can also lead to acclimatization. If organisms undergo acclimatization prior to being trapped in tide pools, their survival chances may increase. Common tide pool species (46 species in total) were collected at a tropical and a temperate area and their upper thermal limits estimated. They were maintained for 10 days at their mean summer sea surface temperature +3°C, mimicking a heat-wave. Their upper thermal limits were estimated again, after this acclimation period, to calculate each species' acclimation response. The upper thermal limits of the organisms were compared to the temperatures attained by tide pool waters to investigate if 1) tide pools could be considered ecological traps and 2) if the increase in upper thermal limits elicited by the acclimation period could make the organisms less vulnerable to this threat. Tropical tide pools were found to be ecological traps for an important number of common coastal species, given that they can attain temperatures higher than the upper thermal limits of most of those species. Tide pools are not ecological traps in temperate zones. Tropical species have higher thermal limits than temperate species, but lower acclimation response, that does not allow them to survive the maximum habitat temperature of tropical tide pools. This way, tropical coastal organisms seem to be, not only more vulnerable to climate warming per se, but also to an increase in the ecological trap effect of tide pools.

Atomic oxygen exposure of LDEF experiment trays

NASA Technical Reports Server (NTRS)

Bourassa, R. J.; Gillis, J. R.

1992-01-01

Atomic oxygen exposures were determined analytically for rows, longerons, and end bays of the Long Duration Exposure Facility (LDEF). The calculations are based on an analytical model that accounts for the effects of thermal molecular velocity, atmospheric temperature, number density, spacecraft velocity, incidence angle, and atmospheric rotation on atomic oxygen flux. Results incorporate variations in solar activity, geomagnetic index, and orbital parameters occurring over the 6-year flight of the spacecraft. To facilitate use of the data, both detailed tabulations and summary charts for atomic oxygen fluences are presented.

Characterization of Engine Control Authority on HCCI Combustion as the High Load Limit is Approached

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

Szybist, James P; Edwards, Kevin Dean; Foster, Matthew

2013-01-01

While the potential emissions and efficiency benefits of homogeneous charge compression ignition (HCCI) combustion are well known, realizing the potentials on a production intent engine presents numerous challenges. In this study we focus on characterizing the authority of the available engine controls as the high load limit of HCCI combustion is approached. The experimental work is performed on a boosted single-cylinder research engine equipped with direct injection (DI) fueling, cooled external exhaust gas recirculation (EGR), and a hydraulic valve actuation (HVA) valve train to enable the negative valve overlap (NVO) breathing strategy. Valve lift and duration are held constant whilemore » phasing is varied in an effort to make the results as relevant as possible to production intent cam-based variable valve actuation (VVA) systems on multi-cylinder engines. Results presented include engine loads from 350 to 650 kPa IMEPnet and manifold pressure from 98 to 190 kPaa at 2000 rpm. It is found that in order to increase engine load to 650 kPa IMEPnet, it is necessary to increase manifold pressure and external EGR while reducing the NVO duration. Both NVO duration and fuel injection timing are effective means of controlling combustion phasing, with NVO duration being a coarse control and fuel injection timing being a fine control. NOX emissions are low throughout the study, with emissions below 0.1 g/kW-h at all boosted HCCI conditions, while good combustion efficiency is maintained (>96.5%). Net indicated thermal efficiency increases with load up to 600 kPa IMEPnet, where a peak efficiency of 41% is achieved. Results of independent parametric investigations are presented on the effect of external EGR, intake effect of manifold pressure, and the effect of NVO duration. It is found that increasing EGR at a constant manifold pressure and increasing manifold pressure at a constant EGR rate both have the effect of retarding combustion phasing. It is also found that combustion phasing becomes increasingly sensitive to NVO duration as engine load increases. Finally, comparisons are made between three commonly used noise metrics (AVL noise meter, ringing intensity (RI), and maximum pressure rise rate (MPRR)). It is found that compared to the AVL noise meter, RI significantly underestimates combustion noise under boosted conditions.« less

Controlled dipole-dipole interactions between K Rydberg atoms in a laser-chopped effusive beam

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

Kutteruf, M. R.; Jones, R. R.

2010-12-15

We explore pulsed-field control of resonant dipole-dipole interactions between K Rydberg atoms. A laser-based atomic beam chopper is used to reduce the relative velocities of Rydberg atoms excited from an effusive thermal source. Resonant energy transfer (RET) between pairs of atoms is controlled via Stark tuning of the relevant Rydberg energy levels. Resonance line shapes in the electric field dependence of the RET probability are used to determine the effective temperature of the sample. We demonstrate that the relative atom velocities can be reduced to the point where the duration of the electric-field tuning pulses, and not the motion ofmore » neighboring atoms, defines the interaction time for each pair within the ensemble. Coherent, transform-limited broadening of the resonance line shape is observed as the tuning pulse duration is reduced below the natural time scale for collisions.« less

Follow-up on the effects of the space environment on UHCRE thermal blankets

NASA Technical Reports Server (NTRS)

Levadou, Francois; Vaneesbeek, Marc

1993-01-01

An overview of the effects of the space environment on the thermal blanket of the UHCRE experiment is presented with an emphasis on atomic oxygen (AO) erosion. A more accurate value for FEP Teflon reaction efficiency is given and corresponds, at normal incidence, to 3.24 10(exp -25) cu cm/atomic, therefore, the FEP Teflon erosion corresponding to the Long Duration Exposure Facility (LDEF) total mission is 29.5 microns. A power 1.44 of the cosine of the incident angle of the oxygen atoms is found. It is shown that this value is not far from the power found using Fergusson's relationship between efficiency and energy of the O-atoms. An hypothesis concerning the effect of oxygen ions (O(+)) is also presented. The presence of oxygen ions may explain the different results obtained from different flights and from laboratory tests. Finally an XPS analysis of Chemglaze Z306(tm) black paint demonstrates the presence of silicone in the paint which may explain part of the contamination found on LDEF.

Fin-and-tube heat exchanger material and inlet velocity effect under frosting conditions

NASA Astrophysics Data System (ADS)

Keryakos, Elie; Toubassy, Joseph; Danlos, Amélie; Clodic, Denis; Descombes, Georges

2017-02-01

The frosting fin-and-tube heat exchanger used in this study is implemented in the dehydration process of a biogas upgrading pilot. Water is separated from the biogas by frosting it at very low temperatures on the cold surfaces of the fin-and-tube heat exchanger. Once frosted, a defrosting system is used to remove water from the process. The main interest of this study is the frosting system. The effects of the biogas velocity, fin material, tube material and frost layer thickness on the performance of the fin-and-tube heat exchanger are investigated. Increasing the biogas velocity tends to increase the frosting layer thickness and the external pressure drop. This will lead to decrease the heat exchanger performance and the frosting cycle duration. The thermal conductivity of the fins and tubes has a major effect on the performance of the heat exchanger. Higher thermal conductivity decreases the heat exchanged surface. A numerical model has been developed, then numerical and experimental results extracted from a biogas upgrading pilot are compared.

Contamination Examples and Lessons from Low Earth Orbit Experiments and Operational Hardware

NASA Technical Reports Server (NTRS)

Pippin, Gary; Finckenor, Miria M.

2009-01-01

Flight experiments flown on the Space Shuttle, the International Space Station, Mir, Skylab, and free flyers such as the Long Duration Exposure Facility, the European Retrievable Carrier, and the EFFU, provide multiple opportunities for the investigation of molecular contamination effects. Retrieved hardware from the Solar Maximum Mission satellite, Mir, and the Hubble Space Telescope has also provided the means gaining insight into contamination processes. Images from the above mentioned hardware show contamination effects due to materials processing, hardware storage, pre-flight cleaning, as well as on-orbit events such as outgassing, mechanical failure of hardware in close proximity, impacts from man-made debris, and changes due to natural environment factors.. Contamination effects include significant changes to thermal and electrical properties of thermal control surfaces, optics, and power systems. Data from several flights has been used to develop a rudimentary estimate of asymptotic values for absorptance changes due to long-term solar exposure (4000-6000 Equivalent Sun Hours) of silicone-based molecular contamination deposits of varying thickness. Recommendations and suggestions for processing changes and constraints based on the on-orbit observed results will be presented.

Analysis of Depth of Ablation,Thermal Damage, Wound Healing, and Wound Contraction With Erbium YAG Laser in a Yorkshire Pig Model.

PubMed

Alsaad, Salman M S; Ross, E Victor; Smith, Wiley J; DeRienzo, Damian P

2015-11-01

The erbium YAG laser is commonly used for skin resurfacing. It is known that varying the pulse duration can influence residual thermal damage and wound healing. Our study used a porcine model to evaluate a broad range of settings in a comparison of depth of ablation, depth of residual thermal damage (RTD), and wound contraction employing both a full coverage and fractional hand piece with an erbium YAG laser. The laser delivered an ablative pulse followed by a heating pulse of variable duration using either the full coverage or fractional hand piece. Pulse durations for specific coagulation depths were selected based on existing heat transfer models. The bilateral flanks of a single Yorkshire pig were irradiated. There were 14 treatment groups. 3 sites were treated per group for a total of 42 sites. Two of the 3 sites were for observational assessments and the 3rd site served as a reservoir for biopsies. Biopsy specimens were collected on days 0, 1, 3, 7, 14, and 28. Bleeding, erythema, wound healing, and wound contraction (in the fractional hand piece groups) were assessed. Wound healing is faster for fractional laser skin resurfacing compared with traditional contiguous resurfacing as demonstrated by textural changes and degree of erythema. The laser operator can be confident that the depth of ablation displayed on this system accurately reflects what is occurring in vivo for both confluent and fractional modes. Likewise, the measured degree of coagulation was consistent with panel display settings for the confluent mode. However, the degree of coagulation, as measured by the thickness of residual thermal damage, did not vary significantly between the fractional groups. In other words, the pulse duration of the second (heating) pulse did not impact the degree of coagulation in the fractional mode. There was a 2.3% wound contraction between some groups and a 6.5% wound contraction between other groups. A two way analysis of variance found a statistically significant difference in wound contraction based on ablation depth ( P = 0.012) but the degree of coagulation did not prove to be statistically significant for wound contraction (P = 0.66).

Experimental and modeling study of thermal exposure of a self-contained breathing apparatus (SCBA).

PubMed

Donnelly, Michelle K; Yang, Jiann C

2015-08-01

An experimental apparatus designed to study firefighter safety equipment exposed to a thermal environment was developed. The apparatus consisted of an elevated temperature flow loop with the ability to heat the air stream up to 200°C. The thermal and flow conditions at the test section were characterized using thermocouples and bi-directional probes. The safety equipment examined in this study was a self-contained breathing apparatus (SCBA), including a facepiece and an air cylinder. The SCBA facepiece was placed on a mannequin headform and coupled to a breathing simulator that was programmed with a prescribed breathing pattern. The entire SCBA assembly was placed in the test section of the flow loop for these thermal exposure experiments. Three air stream temperatures, 100°C, 150°C, and 200°C, were used with the average air speed at the test section set at 1.4m/s and thermal exposure durations up to 1200 s. Measurements were made using type-K bare-bead thermocouples located in the mannequin's mouth and on the outer surface of the SCBA cylinder. The experimental results indicated that increasing the thermal exposure severity and duration increased the breathing air temperatures supplied by the SCBA. Temperatures of breathing air from the SCBA cylinder in excess of 60°C were observed over the course of the thermal exposure conditions used in most of the experiments. A mathematical model for transient heat transfer was developed to complement the thermal exposure experimental study. The model took into consideration forced convective heat transfer, quasi-steady heat conduction through the composite layers of the SCBA cylinder wall, the breathing pattern and action of the breathing simulator, and predicted air temperatures from the thermally exposed SCBA cylinder and temperatures at the outer surface of the SCBA cylinder. Model predictions agreed reasonably well with the experimental measurements. Published by Elsevier Ltd.

Thermal design and test results for SUNLITE ultra-stable reference cavity

NASA Technical Reports Server (NTRS)

Amundsen, Ruth M.

1991-01-01

SUNLITE (Stanford University-NASA Laser In-Space Technology Experiment) is a space-based experiment which uses a reference cavity to provide a stable frequency reference for a terahertz laser oscillator. Thermal stability of the cavity is a key factor in attaining a stable narrow-linewidth laser beam. The mount which is used to support and align the cavity will provide thermal isolation from the environment. The baseline requirement for thermal stability of the cavity is 0.025 C/min, but the design is directed toward achieving stability well beyond this requirement to improve the science data gained. A prototype of the cavity mount was fabricated and tested to characterize the thermal performance. The thermal vacuum test involved stable high-resolution temperature measurements and stable baseplate temperature control over long durations. Based on test data, the cavity mount design satisfies the severe requirement for the cavity thermal stability.

Analysis of Solar-Heated Thermal Wadis to Support Extended-Duration Lunar Exploration

NASA Technical Reports Server (NTRS)

Balasubramaniam, R.; Gokoglu, S.; Sacksteder, K.; Wegeng, R.; Suzuki, N.

2011-01-01

The realization of the renewed exploration of the moon presents many technical challenges; among them is the survival of lunar-surface assets during periods of darkness when the lunar environment is very cold. Thermal wadis are engineered sources of stored solar energy using modified lunar regolith as a thermal storage mass that can supply energy to protect lightweight robotic rovers or other assets during the lunar night. This paper describes an analysis of the performance of thermal wadis based on the known solar illumination of the moon and estimates of producible thermal properties of modified lunar regolith. Analysis has been performed for the lunar equatorial region and for a potential outpost location near the lunar south pole. The calculations indicate that thermal wadis can provide the desired thermal energy and temperature control for the survival of rovers or other equipment during periods of darkness.

Analysis of Solar-Heated Thermal Wadis to Support Extended-Duration Lunar Exploration

NASA Technical Reports Server (NTRS)

Balasubramaniam, R.; Gokoglu, S. A.; Sacksteder, K. R.; Wegeng, R.; Suzuki, N.

2011-01-01

The realization of the renewed exploration of the Moon presents many technical challenges; among them is the survival of lunar-surface assets during periods of darkness when the lunar environment is very cold. Thermal wadis are engineered sources of stored solar energy using modified lunar regolith as a thermal storage mass that can supply energy to protect lightweight robotic rovers or other assets during the lunar night. This paper describes an analysis of the performance of thermal wadis based on the known solar illumination of the Moon and estimates of producible thermal properties of modified lunar regolith. Analysis has been performed for the lunar equatorial region and for a potential outpost location near the Lunar South Pole. The calculations indicate that thermal wadis can provide the desired thermal energy and temperature control for the survival of rovers or other equipment during periods of darkness.

An Adaptive Multiscale Finite Element Method for Large Scale Simulations

DTIC Science & Technology

2015-09-28

Illinois at Urbana-Champaign Abstract Hypersonic vehicles are subjected to extreme acoustic, thermal and mechanical loading with strong spatial and temporal...07/15/2012 Reporting Period End Date 07/14/2015 Abstract Hypersonic vehicles are subjected to extreme acoustic, thermal and mechanical loading with...gradients and for extended periods of time. Long duration, 3-D simulations of non-linear response of these vehicles , is prohibitively expensive using

Thermal Optimization of an On-Orbit Long Duration Cryogenic Propellant Depot

NASA Technical Reports Server (NTRS)

Honour, Ryan; Kwas, Robert; O'Neil, Gary; Kutter, Gary

2012-01-01

A Cryogenic Propellant Depot (CPD) operating in Low Earth Orbit (LEO) could provide many near term benefits to NASA's space exploration efforts. These benefits include elongation/extension of spacecraft missions and requirement reduction of launch vehicle up-mass. Some of the challenges include controlling cryogenic propellant evaporation and managing the high costs and long schedules associated with the new development of spacecraft hardware. This paper describes a conceptual CPD design that is thermally optimized to achieve extremely low propellant boil-off rates. The CPD design is based on existing launch vehicle architecture, and its thermal optimization is achieved using current passive thermal control technology. Results from an integrated thermal model are presented showing that this conceptual CPD design can achieve propellant boil-off rates well under 0.05% per day, even when subjected to the LEO thermal environment.

Thermal Optimization and Assessment of a Long Duration Cryogenic Propellant Depot

NASA Technical Reports Server (NTRS)

Honour, Ryan; Kwas, Robert; O'Neil, Gary; Kutter, Bernard

2012-01-01

A Cryogenic Propellant Depot (CPD) operating in Low Earth Orbit (LEO) could provide many near term benefits to NASA space exploration efforts. These benefits include elongation/extension of spacecraft missions and reduction of launch vehicle up-mass requirements. Some of the challenges include controlling cryogenic propellant evaporation and managing the high costs and long schedules associated with new spacecraft hardware development. This paper describes a conceptual CPD design that is thermally optimized to achieve extremely low propellant boil-off rates. The CPD design is based on existing launch vehicle architecture, and its thermal optimization is achieved using current passive thermal control technology. Results from an integrated thermal model are presented showing that this conceptual CPD design can achieve propellant boil-off rates well under 0.05% per day, even when subjected to the LEO thermal environment.

MNASA as a Test for Carbon Fiber Thermal Barrier Development

NASA Technical Reports Server (NTRS)

Bauer, Paul; McCool, Alex (Technical Monitor)

2001-01-01

A carbon fiber rope thermal barrier is being evaluated as a replacement for the conventional room temperature vulcanizing (RTV) thermal barrier that is currently used to protect o-rings in Reusable Solid Rocket Motor (RSRM) nozzle joints. Performance requirements include its ability to cool any incoming, hot propellant gases that fill and pressurize the nozzle joints, filter slag and particulates, and to perform adequately in various joint assembly conditions as well as dynamic flight motion. Modified National Aeronautics and Space Administration (MNASA) motors, with their inherent and unique ability to replicate select RSRM internal environment features, were an integral step in the development path leading to full scale RSRM static test demonstration of the carbon fiber rope (CFR) joint concept. These 1/4 scale RSRM motors serve to bridge the gap between the other classes of subscale test motors (extremely small and moderate duration, or small scale and short duration) and the critical asset RSRM static test motors. A series of MNASA tests have been used to demonstrate carbon fiber rope performance and have provided rationale for implementation into a full-scale static motor and flight qualification.

Thermal Performance of Low Layer Density Multilayer Insu1ation Using Liquid Nitrogen

NASA Technical Reports Server (NTRS)

Johnson, Wesley L.; Fesmire, James E.

2011-01-01

In order to support long duration cryogenic propellant storage, the Cryogenic Fluid Management (CFM) Project of the Exploration Technology Development Program (ETDP) is investigating the long duration storage propertie$ of liquid methane on the lunar surface. The Methane Lunar Surface Thermal Control (MLSTC) testing is using a tank of the approximate dimensions of the Altair ascent tanks inside of a vacuum chamber to simulate the environment in low earth orbit and on the lunar surface. The thermal performance testing of multilayer insulation (MLI) coupons that are fabricated identically to the tank applied insulation is necessary to understand the performance of the blankets and to be able to predict the performance of the insulation prior to testing. This coupon testing was completed in Cryostat-100 at the Cryogenics Test Laboratory. The results showed the properties of the insulation as a function of layer density, number of layers, and warm boundary temperature. These results aid in the understanding of the performance parameters o fMLI and help to complete the body of literature on the topic.

Automated coronal hole identification via multi-thermal intensity segmentation

NASA Astrophysics Data System (ADS)

Garton, Tadhg M.; Gallagher, Peter T.; Murray, Sophie A.

2018-01-01

Coronal holes (CH) are regions of open magnetic fields that appear as dark areas in the solar corona due to their low density and temperature compared to the surrounding quiet corona. To date, accurate identification and segmentation of CHs has been a difficult task due to their comparable intensity to local quiet Sun regions. Current segmentation methods typically rely on the use of single Extreme Ultra-Violet passband and magnetogram images to extract CH information. Here, the coronal hole identification via multi-thermal emission recognition algorithm (CHIMERA) is described, which analyses multi-thermal images from the atmospheric image assembly (AIA) onboard the solar dynamics observatory (SDO) to segment coronal hole boundaries by their intensity ratio across three passbands (171 Å, 193 Å, and 211 Å). The algorithm allows accurate extraction of CH boundaries and many of their properties, such as area, position, latitudinal and longitudinal width, and magnetic polarity of segmented CHs. From these properties, a clear linear relationship was identified between the duration of geomagnetic storms and coronal hole areas. CHIMERA can therefore form the basis of more accurate forecasting of the start and duration of geomagnetic storms.

Nanoscale Ex-Situ Thermal Impulse Sensors for Structural Fire Forensics.

PubMed

Anderson, Benjamin R; Gese, Natalie; Gunawidjaja, Ray; Eilers, Hergen

2017-01-01

We develop nanoscale ex situ thermal impulse (i.e., the temperature and duration of a heating event) sensors for structural fire forensics using a mixture of two lanthanide-doped oxide precursors (precursor Eu:ZrO 2 and precursor Dy:Y 2 O 3 ) that undergo irreversible phase changes when heated. These changes are probed using photoluminescence (PL) spectroscopy with the PL spectra being dependent on the thermal impulse (TI) experienced by the sensors. By correlating the PL spectra to different in-lab TIs, we are able to produce a spectroscopic calibration for our sensors. This calibration allows us to determine an unknown TI of a heating event using only the PL spectrum of the heated TI sensors. In this study, we report on the calibration of these sensors for isothermal heating durations up to 600 s and isothermal temperatures up to 1273 K. Using this calibration, we also demonstrate their ability to determine an unknown TI and demonstrate their functionality when dispersed into paint, which is heated in the presence of drywall.

Reaction-space analysis of homogeneous charge compression ignition combustion with varying levels of fuel stratification under positive and negative valve overlap conditions

DOE PAGES

Kodavasal, Janardhan; Lavoie, George A.; Assanis, Dennis N.; ...

2015-10-26

Full-cycle computational fluid dynamics simulations with gasoline chemical kinetics were performed to determine the impact of breathing and fuel injection strategies on thermal and compositional stratification, combustion and emissions during homogeneous charge compression ignition combustion. The simulations examined positive valve overlap and negative valve overlap strategies, along with fueling by port fuel injection and direct injection. The resulting charge mass distributions were analyzed prior to ignition using ignition delay as a reactivity metric. The reactivity stratification arising from differences in the distributions of fuel–oxygen equivalence ratio (Φ FO), oxygen molar fraction (χ O2) and temperature (T) was determined for threemore » parametric studies. In the first study, the reactivity stratification and burn duration for positive valve overlap valve events with port fuel injection and early direct injection were nearly identical and were dominated by wall-driven thermal stratification. nitrogen oxide (NO) and carbon monoxide (CO) emissions were negligible for both injection strategies. In the second study, which examined negative valve overlap valve events with direct injection and port fuel injection, reactivity stratification increased for direct injection as the Φ FO and T distributions associated with direct fuel injection into the hot residual gas were positively correlated; however, the latent heat absorbed from the hot residual gas by the evaporating direct injection fuel jet reduced the overall thermal and reactivity stratification. These stratification effects were offsetting, resulting in similar reactivity stratification and burn durations for the two injection strategies. The higher local burned gas temperatures with direct injection resulted in an order of magnitude increase in NO, while incomplete combustion of locally over-lean regions led to a sevenfold increase in CO emissions compared to port fuel injection. The final study evaluated positive valve overlap and negative valve overlap valve events with direct injection. Furthermore, relative to positive valve overlap, the negative valve overlap condition had a wider reactivity stratification, a longer burn duration and higher NO and CO emissions associated with reduced fuel–air mixing.« less

Action spectrum for retinal thermal injury

NASA Astrophysics Data System (ADS)

Lund, David J.; Edsall, Peter R.

1999-06-01

The action spectrum for light-induced damage to the retina results from the wavelength dependence transmission of the preretinal ocular media, wavelength dependent absorption in retinal chromophores and chromatic aberration of the eye optics. While various light/tissue interaction mechanisms have been implicated, thermal mechanisms dominate in the red and near-infrared for all exposure durations and in the visible for exposures shorter than a few seconds. A number of investigators have measured the transmission of the eye and the spectra of retinal absorbers, and thermal models based on these data predict the broad features of the action spectrum. Dose/response studies with lasers and incoherent light sources, conducted over the past 10 years mainly validate the thermal models.

Burn Propagation in a PBX 9501 Thermal Explosion

NASA Astrophysics Data System (ADS)

Henson, B. F.; Smilowitz, L.; Romero, J. J.; Sandstrom, M. M.; Asay, B. W.; Schwartz, C.; Saunders, A.; Merrill, F.; Morris, C.; Murray, M. M.; McNeil, W. V.; Marr-Lyon, M.; Rightley, P. M.

2007-12-01

We have applied proton radiography to study the conversion of solid density to gaseous combustion products subsequent to ignition of a thermal explosion in PBX 9501. We apply a thermal boundary condition to the cylindrical walls of the case, ending with an induction period at 205 C. We then introduce a laser pulse that accelerates the thermal ignition and synchronizes the explosion with the proton accelerator. We then obtain fast, synchronized images of the evolution of density loss with few microsecond resolution during the approximately 100 microsecond duration of the explosion. We present images of the solid explosive during the explosion and discuss measured rates and assumed mechanisms of burning the role of pressure in this internal burning.

Solar thermal propulsion for planetary spacecraft

NASA Technical Reports Server (NTRS)

Sercel, J. C.

1985-01-01

Previous studies have shown that many desirable planetary exploration missions require large injection delta-V. Solar Thermal Rocket (STR) propulsion, under study for orbit-raising applications may enhance or enable such high-energy missions. The required technology of thermal control for liquid hydrogen propellant is available for the required storage duration. Self-deploying, inflatable solar concentrators are under study. The mass penalty for passive cryogenic thermal control, liquid hydrogen tanks and solar concentrators does not compromise the specific impulse advantage afforded by the STR as compared to chemical propulsion systems. An STR injection module is characterized and performance is evaluated by comparison to electric propulsion options for the Saturn Orbiter Titan Probe (SOTP) and Uranus Flyby Uranus Probe (UFUP) missions.

New experiments selected for 1980 operational shuttle flight

NASA Technical Reports Server (NTRS)

1978-01-01

Experiments selected for NASA's Long Duration Exposure Facility mission are described. Technical areas represented by the experiments include materials, thermal control coatings, detectors, power, micrometeoroids, electronics, lubrication, optics, and space debris detection.

Duration of mineralization and fluid-flow history of the Upper Mississippi Valley zinc-lead district

USGS Publications Warehouse

Rowan, E.L.; Goldhaber, M.B.

1995-01-01

Studies of fluid inclusions in sphalerite and biomarkers from the Upper Mississippi Valley zinc district show homogenization temperatures to be primarily between 90 and 150??C, yet show relatively low levels of thermal maturity. Numerical calculations are used to simulate fluid and heat flow through fracture-controlled ore zones and heat transfer to the adjacent rocks. Combining a best-fit path through fluid-inclusion data with measured thermal alteration of biomarkers, the time interval during which mineralizing fluids circulated through the Upper Mississippi Valley district was calculated to be on the order of 200 ka. Cambrian and Ordovician aquifers underlying the district, principally the St. Peter and Mt. Simon Sandstones, were the source of the mineralizing fluid. The duration of mineralization thus reflects the fluid-flow history of these regional aquifers. -from Authors

Surface temperature and thermal penetration depth of Nd:YAG laser applied to enamel and dentin

NASA Astrophysics Data System (ADS)

White, Joel M.; Neev, Joseph; Goodis, Harold E.; Berns, Michael W.

1992-06-01

The determination of the thermal effects of Nd:YAG laser energy on enamel and dentin is critical in understanding the clinical applications of caries removal and surface modification. Recently extracted non-carious third molars were sterilized with gamma irradiation. Calculus and cementum were removed using scaling instruments and 600 grit sand paper. The smear layer produced by sanding was removed with a solution of 0.5 M EDTA (pH 7.4) for two minutes. Enamel and dentin surfaces were exposed to a pulsed Nd:YAG laser with 150 microsecond(s) pulse duration. Laser energy was delivered to the teeth with a 320 micrometers diameter fiberoptic delivery system, for exposure times of 1, 10 and 30 seconds. Laser parameters varied from 0.3 to 3.0 W, 10 to 30 Hz and 30 to 150 mJ/pulse. Other conditions included applications of hot coffee, carbide bur in a dental air-cooled turbine drill and soldering iron. Infrared thermography was used to measure the maximum surface temperature on, and thermal penetration distance into enamel and dentin. Thermographic data were analyzed with a video image processor to determine the diameter of maximum surface temperature and thermal penetration distance of each treatment. Between/within statistical analysis of variance (p

Management of refractory trigeminal neuralgia using extended duration pulsed radiofrequency application.

PubMed

Thapa, Deepak; Ahuja, Vanita; Dass, Christopher; Verma, Parul

2015-01-01

Trigeminal neuralgia (TN) produces incapacitating facial pain that reduces quality of life in patients. Thermal radiofrequency (RF) ablation of gasserian ganglion (GG) is associated with masseter weakness and unpleasant sensations along the distribution of the ablated nerve. Pulsed radiofrequency (PRF) of GG has minimal side effects but literature is inconclusive regarding its benefit in refractory TN. Increasing the duration of PRF application to 6 minutes in TN produced encouraging results. PRF application to the saphenous nerve for 8 minutes reported improved pain relief and patient satisfaction. We report successful management of two patients of classic TN, which were refractory to medical management and interventional nerve blocks. The lesion site were confirmed with motor and sensory stimulation through a 22 G, 10 cm RF needle with 5 mm active tip. Both the patients received four cycles of PRF at 42 °C with each cycle of 120 seconds (8 minutes). The visual analogue scale (VAS) in case 1 reduced from pre-block score of 80 to score 10 post-block, while in case 2 the VAS reduced from pre-block score of 85 to score 15 post-block. During follow up both the patients are now pain free with minimal dose of carbamazepine at 12 and 6 months respectively. We used PRF for longer duration (8 minutes) in these patients, which resulted in improved VAS and WHOQOL-BREF score in these patients. PRF of mandibular division of GG for extended duration provided long-term effective pain relief and quality of life in patients of refractory classic TN.

Failure modes of vacuum plasma spray tungsten coating created on carbon fibre composites under thermal loads

NASA Astrophysics Data System (ADS)

Hirai, T.; Bekris, N.; Coad, J. P.; Grisolia, C.; Linke, J.; Maier, H.; Matthews, G. F.; Philipps, V.; Wessel, E.

2009-07-01

Vacuum plasma spray tungsten (VPS-W) coating created on a carbon fibre reinforced composite (CFC) was tested under two thermal load schemes in the electron beam facility to examine the operation limits and failure modes. In cyclic ELM-like short transient thermal loads, the VPS-W coating was destroyed sub-layer by sub-layer at 0.33 GW/m 2 for 1 ms pulse duration. At longer single pulses, simulating steady-state thermal loads, the coating was destroyed at surface temperatures above 2700 °C by melting of the rhenium containing multilayer at the interface between VPS-W and CFC. The operation limits and failure modes of the VPS-W coating in the thermal load schemes are discussed in detail.

Computer assisted thermal-vacuum testing

NASA Technical Reports Server (NTRS)

Petrie, W.; Mikk, G.

1977-01-01

In testing complex systems and components under dynamic thermal-vacuum environments, it is desirable to optimize the environment control sequence in order to reduce test duration and cost. This paper describes an approach where a computer is utilized as part of the test control operation. Real time test data is made available to the computer through time-sharing terminals at appropriate time intervals. A mathematical model of the test article and environmental control equipment is then operated on using the real time data to yield current thermal status, temperature analysis, trend prediction and recommended thermal control setting changes to arrive at the required thermal condition. The data acquisition interface and the time-sharing hook-up to an IBM-370 computer is described along with a typical control program and data demonstrating its use.

Mars Propellant Liquefaction and Storage Performance Modeling using Thermal Desktop with an Integrated Cryocooler Model

NASA Technical Reports Server (NTRS)

Desai, Pooja; Hauser, Dan; Sutherlin, Steven

2017-01-01

NASAs current Mars architectures are assuming the production and storage of 23 tons of liquid oxygen on the surface of Mars over a duration of 500+ days. In order to do this in a mass efficient manner, an energy efficient refrigeration system will be required. Based on previous analysis NASA has decided to do all liquefaction in the propulsion vehicle storage tanks. In order to allow for transient Martian environmental effects, a propellant liquefaction and storage system for a Mars Ascent Vehicle (MAV) was modeled using Thermal Desktop. The model consisted of a propellant tank containing a broad area cooling loop heat exchanger integrated with a reverse turbo Brayton cryocooler. Cryocooler sizing and performance modeling was conducted using MAV diurnal heat loads and radiator rejection temperatures predicted from a previous thermal model of the MAV. A system was also sized and modeled using an alternative heat rejection system that relies on a forced convection heat exchanger. Cryocooler mass, input power, and heat rejection for both systems were estimated and compared against sizing based on non-transient sizing estimates.

Mars Propellant Liquefaction Modeling in Thermal Desktop

NASA Technical Reports Server (NTRS)

Desai, Pooja; Hauser, Dan; Sutherlin, Steven

2017-01-01

NASAs current Mars architectures are assuming the production and storage of 23 tons of liquid oxygen on the surface of Mars over a duration of 500+ days. In order to do this in a mass efficient manner, an energy efficient refrigeration system will be required. Based on previous analysis NASA has decided to do all liquefaction in the propulsion vehicle storage tanks. In order to allow for transient Martian environmental effects, a propellant liquefaction and storage system for a Mars Ascent Vehicle (MAV) was modeled using Thermal Desktop. The model consisted of a propellant tank containing a broad area cooling loop heat exchanger integrated with a reverse turbo Brayton cryocooler. Cryocooler sizing and performance modeling was conducted using MAV diurnal heat loads and radiator rejection temperatures predicted from a previous thermal model of the MAV. A system was also sized and modeled using an alternative heat rejection system that relies on a forced convection heat exchanger. Cryocooler mass, input power, and heat rejection for both systems were estimated and compared against sizing based on non-transient sizing estimates.

Mechanical properties and thermal shock performance of W-Y2O3 composite prepared by high-energy-rate forging

NASA Astrophysics Data System (ADS)

Lian, Youyun; Liu, Xiang; Feng, Fan; Song, Jiupeng; Yan, Binyou; Wang, Yingmin; Wang, Jianbao; Chen, Jiming

2017-12-01

The effects of the addition of Y2O3 and hot-deformation on the mechanical properties of tungsten (W) have been studied. The processing route comprises a doping technique for the distribution of Y2O3 particles in a tungsten matrix, conventional sintering in a hydrogen environment, and high-energy-rate forging (HERF). The microstructure of the composite was characterized by using transmission electron microscopy and electron backscattering diffraction imaging technique, and its mechanical properties were studied by means of tensile testing. The thermal shock response of the HERF processed W-Y2O3 was evaluated by applying edge-localized mode-like loads (100 pulses) with a pulse duration of 1 ms and an absorbed power density of up to 1 GW m-2 at various temperatures between room temperature and 200 °C. HERF processing has produced elongated W grains with preferred orientations and a high density of structure defects in the composite. The composite material exhibits high tensile strength and good ductility, and a thermal shock cracking threshold lower than 100 °C.

Thermal and metabolic responses of military divers during a 6-hour static dive in cold water.

PubMed

Riera, Florence; Horr, Reed; Xu, Xiaojiang; Melin, Bruno; Regnard, Jacques; Bourdon, Lionel

2014-05-01

Human thermal responses during prolonged whole-body immersion in cold water are of interest for the military, especially French SEALS. This study aims at describing the thermo-physiological responses. There were 10 male military divers who were randomly assigned to a full immersion in neutral (34 degrees C), moderately cold (18 degrees C), and cold (10 degrees C) water wearing their operational protective devices (5.5 mm wetsuit with 3.0 mm thick underwear) for 6 h in a static position. Rectal temperature (T(re)) and 14 skin temperatures (T(sk)), blood analysis (stress biomarkers, metabolic substrates), and oxygen consumption (Vo2) were collected. At 34 degrees C, there were no significant modifications of the thermo-physiological responses over time. The most interesting result was that rates of rectal temperature decrease (0.15 +/- 0.02 degrees C x min(-1)) were the same between the two cold stress experimental conditions (at 18 degrees C and 10 degrees C). At the final experiment, rectal temperature was not significantly different between the two cold stress experimental conditions. Mean T(sk) decreased significantly during the first 3 h of immersion and then stabilized at a lower level at 10 degrees C (25.6 +/- 0.8 degrees C) than at 18 degrees C (29.3 +/- 0.9 degrees C). Other results demonstrate that the well-trained subjects developed effective physiological reactions. However, these reactions are consistently too low to counterbalance the heat losses induced by cold temperature conditions and long-duration immersion. This study shows that providing divers with thermal protection is efficient for a long-duration immersion from a medical point of view, but not from an operational one when skin extremities were taken into account.

Climate Change Expands the Spatial Extent and Duration of Preferred Thermal Habitat for Lake Superior Fishes

PubMed Central

Cline, Timothy J.; Bennington, Val; Kitchell, James F.

2013-01-01

Climate change is expected to alter species distributions and habitat suitability across the globe. Understanding these shifting distributions is critical for adaptive resource management. The role of temperature in fish habitat and energetics is well established and can be used to evaluate climate change effects on habitat distributions and food web interactions. Lake Superior water temperatures are rising rapidly in response to climate change and this is likely influencing species distributions and interactions. We use a three-dimensional hydrodynamic model that captures temperature changes in Lake Superior over the last 3 decades to investigate shifts in habitat size and duration of preferred temperatures for four different fishes. We evaluated habitat changes in two native lake trout (Salvelinus namaycush) ecotypes, siscowet and lean lake trout, Chinook salmon (Oncorhynchus tshawytscha), and walleye (Sander vitreus). Between 1979 and 2006, days with available preferred thermal habitat increased at a mean rate of 6, 7, and 5 days per decade for lean lake trout, Chinook salmon, and walleye, respectively. Siscowet lake trout lost 3 days per decade. Consequently, preferred habitat spatial extents increased at a rate of 579, 495 and 419 km2 per year for the lean lake trout, Chinook salmon, and walleye while siscowet lost 161 km2 per year during the modeled period. Habitat increases could lead to increased growth and production for three of the four fishes. Consequently, greater habitat overlap may intensify interguild competition and food web interactions. Loss of cold-water habitat for siscowet, having the coldest thermal preference, could forecast potential changes from continued warming. Additionally, continued warming may render more suitable conditions for some invasive species. PMID:23638023

Performance of silvered Teflon (trademark) thermal control blankets on spacecraft

NASA Technical Reports Server (NTRS)

Pippin, Gary; Stuckey, Wayne; Hemminger, Carol

1993-01-01

Silverized Teflon (Ag/FEP) is a widely used passive thermal control material for space applications. The material has a very low alpha/e ratio (less than 0.1) for low operating temperatures and is fabricated with various FEP thicknesses (as the Teflon thickness increases, the emittance increases). It is low outgassing and, because of its flexibility, can be applied around complex, curved shapes. Ag/FEP has achieved multiyear lifetimes under a variety of exposure conditions. This has been demonstrated by the Long Duration Exposure Facility (LDEF), Solar Max, Spacecraft Charging at High Altitudes (SCATHA), and other flight experiments. Ag/FEP material has been held in place on spacecraft by a variety of methods: mechanical clamping, direct adhesive bonding of tapes and sheets, and by Velcro(TM) tape adhesively bonded to back surfaces. On LDEF, for example, 5-mil blankets held by Velcro(TM) and clamping were used for thermal control over 3- by 4-ft areas on each of 17 trays. Adhesively bonded 2- and 5-mil sheets were used on other LDEF experiments, both for thermal control and as tape to hold other thermal control blankets in place. Performance data over extended time periods are available from a number of flights. The observed effects on optical properties, mechanical properties, and surface chemistry will be summarized in this paper. This leads to a discussion of performance life estimates and other design lessons for Ag/FEP thermal control material.

Research on Protective Coating on Inner Surface of Alloy Tube

NASA Astrophysics Data System (ADS)

Zhang, Y. C.; Liu, Y. H.; Zhou, Z. J.; Zheng, M. M.; Kong, S. Y.; Xia, H. H.; Li, H. L.

2017-09-01

Materials are one of the most important factors which limit reactor development. Molten salt not only used as the coolant but used as application in which fissile materials and fission products are dissolved in Molten Salt Reactors (MSRs). Therefore the corrosion resistance of structure materials is the one of most important aspects for application in MSRs. Compatibility and chemical stability with the molten salt should be considered for some common structural alloys such as Incoloy-800H. In this research, the pure nickel coating was obtained by electroplating on the inner surface of nickel alloy to improve the corrosion resistance. However, there are some problems for plating on the inner surface of tube. For example the current is shielded and the anode is easy to passivate. The inner anode was used for solving these problems in this study. Pure nickel coating was obtain and the microstructure and properties of coating were analysed using this method. The thickness, hardness and microstructure of coating were observed by metallographic microscope, micro hardness tester and field emission scanning electron microscope, and the influence of deposition duration and annealing treatment duration on properties were analysed. Thermal shock performance was investigated as well. The results showed that the coating thickness increased linearly with the increasing of plating durations and the size of grain increased with the durations as well, the surface of coating became inhomogeneous correspondingly. The hardness of coating changed as the change of durations of annealing treatment. The thermal shock test showed that bonding strength of coating with substrate was good.

Correlation of p63 immunohistochemistry with histology and contrast enhanced MRI in characteristic lesions induced by minimally invasive thermal treatments in a dog prostate

NASA Astrophysics Data System (ADS)

Pascal, A.; Butts-Pauly, K.; Plata, J.; Sommer, G.; Daniel, B.; Bouley, D. M.

2017-03-01

Thermal ablation techniques are important tools to treat low grade tumors in the prostate gland. The use of Magnetic Resonance Imaging (MRI) has been an excellent tool to visualize and assess the thermally ablated areas in real time. In this study slides from dog prostates previously treated with cryoablation or High Intensity Focal Ultrasound (HIFU) were immunohistochemically stained with the biomarker p63, in order to determine if this marker would be helpful for differentiatiating between viable, sub lethally damaged and normal glands. Digitized slides were analyzed using Sedeen Viewer software, and compared with corresponding representative H&E slides and MR images. p63 staining in the cryoablated acute duration prostates was negative in the coagulation necrosis zone (region of interest subjected to the coldest temperatures). In acute duration HIFU treated prostates, the central heat-fixed zone (region of interest subjected to the hottest temperatures) still displayed + p63 staining. Cryoablated or HIFU subacute duration treated prostates were very hemorrhagic, but presented the same stain pattern in the treated areas as the acute duration prostates, and in chronic duration prostates, whether treated with cryo or HIFU, glands displayed robust p63 staining most prevalent in the outer edges of the lesion where there was extensive glandular regeneration. In conclusion, this study demonstrates the value of p63 IHC and its usefulness in detecting viable prostate basal cells in normal dog prostates following either cryoablation of HIFU. Our results suggest that the portions of the lesion with complete loss of p63 staining correspond well to the non-enhancing region in cryoablated prostates, as viewed with MRI. However, p63 staining in the heat-fixed zone in acute harvested HIFU treated prostates remains positive, suggesting either inadequate heat to destroy basal cells, or heat-fixation of the p63 antigen and false positive staining. Therefore p63 staining does not appear to be beneficial in determining cell viability in HIFU-treated tissues, and would not aid in predicting if unwanted tumor cells in a similarly treated area could regenerate.

High-temperature annealing of proton irradiated beryllium – A dilatometry-based study

DOE PAGES

Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong; ...

2016-04-07

S—200 F grade beryllium has been irradiated with 160 MeV protons up to 1.2 10 20 cm –2 peak fluence and irradiation temperatures in the range of 100–200 °C. To address the effect of proton irradiation on dimensional stability, an important parameter in its consideration in fusion reactor applications, and to simulate high temperature irradiation conditions, multi-stage annealing using high precision dilatometry to temperatures up to 740 °C were conducted in air. X-ray diffraction studies were also performed to compliment the macroscopic thermal study and offer a microscopic view of the irradiation effects on the crystal lattice. The primary objectivemore » was to qualify the competing dimensional change processes occurring at elevated temperatures namely manufacturing defect annealing, lattice parameter recovery, transmutation 4He and 3H diffusion and swelling and oxidation kinetics. Further, quantification of the effect of irradiation dose and annealing temperature and duration on dimensional changes is sought. Here, the study revealed the presence of manufacturing porosity in the beryllium grade, the oxidation acceleration effect of irradiation including the discontinuous character of oxidation advancement, the effect of annealing duration on the recovery of lattice parameters recovery and the triggering temperature for transmutation gas diffusion leading to swelling.« less

Controlled destruction and temperature distributions in biological tissues subjected to monoactive electrocoagulation.

PubMed

Erez, A; Shitzer, A

1980-02-01

An analysis of the temperature fields developed in a biological tissue undergoing a monoactive electrical coagulating process is presented, including thermal recovery following prolonged heating. The analysis is performed for the passage of alternating current and assumes a homogeneous and isotropic tissue model which is uniformly perfused by blood at arterial temperature. Solution for the one-dimensional spherical geometry is obtained by a Laplace transform and numerical integrations. Results obtained indicate the major role which blood perfusion plays in determining the effects of the coagulating process; tissue temperatures and depth of destruction are drastically reduced as blood perfusion increases. Metabolic heat generation rate is found to have negligible effects on tissue temperatures whereas electrode thermal inertia affects temperature levels appreciably. However, electrodes employed in practice would have a low thermal inertia which might be regarded as zero for all practical purposes. It is also found that the depth of tissue destruction is almost directly proportional to the electrical power and duration of application. To avoid excessively high temperatures and charring, it would be advantageous to reduce power and increase the time of application. Results of this study should be regarded as a first approximation to the rather complex phenomena associated with electrocoagulation. They may, nevertheless, serve as preliminary guidelines to practicing surgeons applying this technique.

The Impact of Greenspace on Thermal Comfort in a Residential Quarter of Beijing, China.

PubMed

Wu, Zhifeng; Kong, Fanhua; Wang, Yening; Sun, Ranhao; Chen, Liding

2016-12-08

With the process of urbanization, a large number of residential quarters, which is the main dwelling form in the urban area of Beijing, have been developed in last three decades to accommodate the rising population. In the context of intensification of urban heat island (UHI), the potential degradation of the thermal environment of residential quarters can give rise to a variety of problems affecting inhabitants' health. This paper reports the results of a numerical study of the thermal conditions of a residential quarter on a typical summertime day under four greening modification scenarios, characterized by different leaf area density (LAD) profiles. The modelling results demonstrated that vegetation could evidently reduce near-surface air temperature, with the combination of grass and mature trees achieving as much as 1.5 °C of air temperature decrease compared with the non-green scenario. Vegetation can also lead to smaller air temperature fluctuations, which contribute to a more stable microclimate. The Universal Thermal Climate Index (UTCI) was then calculated to represent the variation of thermal environment of the study area. While grass is helpful in improving outdoor thermal comfort, trees are more effective in reducing the duration and expansion of suffering from severe heat stress. The results of this study showed that proper maintenance of vegetation, especially trees, is significant to improving the outdoor thermal environment in the summer season. In consideration of the deficiency of the current code in the management of greenspace in residential areas, we hope the results reported here will help promote the improvement of the code and related regulations for greenspace management.

The Impact of Greenspace on Thermal Comfort in a Residential Quarter of Beijing, China

PubMed Central

Wu, Zhifeng; Kong, Fanhua; Wang, Yening; Sun, Ranhao; Chen, Liding

2016-01-01

With the process of urbanization, a large number of residential quarters, which is the main dwelling form in the urban area of Beijing, have been developed in last three decades to accommodate the rising population. In the context of intensification of urban heat island (UHI), the potential degradation of the thermal environment of residential quarters can give rise to a variety of problems affecting inhabitants’ health. This paper reports the results of a numerical study of the thermal conditions of a residential quarter on a typical summertime day under four greening modification scenarios, characterized by different leaf area density (LAD) profiles. The modelling results demonstrated that vegetation could evidently reduce near-surface air temperature, with the combination of grass and mature trees achieving as much as 1.5 °C of air temperature decrease compared with the non-green scenario. Vegetation can also lead to smaller air temperature fluctuations, which contribute to a more stable microclimate. The Universal Thermal Climate Index (UTCI) was then calculated to represent the variation of thermal environment of the study area. While grass is helpful in improving outdoor thermal comfort, trees are more effective in reducing the duration and expansion of suffering from severe heat stress. The results of this study showed that proper maintenance of vegetation, especially trees, is significant to improving the outdoor thermal environment in the summer season. In consideration of the deficiency of the current code in the management of greenspace in residential areas, we hope the results reported here will help promote the improvement of the code and related regulations for greenspace management. PMID:27941659

Tissue effects of Ho:YAG laser with varying fluences and pulse widths

NASA Astrophysics Data System (ADS)

Vari, Sandor G.; van der Veen, Maurits J.; Pergadia, Vani R.; Shi, Wei-Qiang; Duffy, J. T.; Weiss, Andrew B.; Fishbein, Michael C.; Grundfest, Warren S.

1994-02-01

We investigated the effect of varying fluence and pulse width on the ablation rate and consequent thermal damage of the Ho:YAG (2.130 micrometers ) laser. The rate of ablation on fresh bovine knee joint tissues, fibrous cartilage, hyaline cartilage, and bone in saline was determined after varying the fluence (160 - 640 J/cm2) and pulse width (150, 250, 450 microsecond(s) ec, FWHM) at a repetition rate of 2 Hz. A 400/440 micrometers fiber was used. The ablation rate increased linearly with the fluence. In fibrocartilage, different pulse durations generated significant changes in the ablation rates, but showed minor effects on hyaline cartilage and bone. The heat of ablation for all three tissue types decreased after lengthening the pulse.

Thermal and Nonthermal Effects of Discontinuous Microwave Exposure (2.45 Gigahertz) on the Cell Membrane of Escherichia coli

PubMed Central

Rougier, Carole; Chazal, Philippe; Leveque, Philippe; Leprat, Patrick

2014-01-01

The aim of this study was to investigate the effects on the cell membranes of Escherichia coli of 2.45-GHz microwave (MW) treatment under various conditions with an average temperature of the cell suspension maintained at 37°C in order to examine the possible thermal versus nonthermal effects of short-duration MW exposure. To this purpose, microwave irradiation of bacteria was performed under carefully defined and controlled parameters, resulting in a discontinuous MW exposure in order to maintain the average temperature of the bacterial cell suspensions at 37°C. Escherichia coli cells were exposed to 200- to 2,000-W discontinuous microwave (DW) treatments for different periods of time. For each experiment, conventional heating (CH) in a water bath at 37°C was performed as a control. The effects of DW exposure on cell membranes was investigated using flow cytometry (FCM), after propidium iodide (PI) staining of cells, in addition to the assessment of intracellular protein release in bacterial suspensions. No effect was detected when bacteria were exposed to conventional heating or 200 W, whereas cell membrane integrity was slightly altered when cell suspensions were subjected to powers ranging from 400 to 2,000 W. Thermal characterization suggested that the temperature reached by the microwave-exposed samples for the contact time studied was not high enough to explain the measured modifications of cell membrane integrity. Because the results indicated that the cell response is power dependent, the hypothesis of a specific electromagnetic threshold effect, probably related to the temperature increase, can be advanced. PMID:24907330

The separated electric and magnetic field responses of luminescent bacteria exposed to pulsed microwave irradiation

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

Williams, Catrin F., E-mail: williamscf@cardiff.ac.uk; School of Biosciences, Cardiff University, Main Building, Cathays Park, Cardiff, CF10 3AT Wales; Geroni, Gilles M.

Electromagnetic fields (EMFs) are ubiquitous in the digital world we inhabit, with microwave and millimetre wave sources of non-ionizing radiation employed extensively in electronics and communications, e.g., in mobile phones and Wi-Fi. Indeed, the advent of 5G systems and the “internet of things” is likely to lead to massive densification of wireless networks. Whilst the thermal effects of EMFs on biological systems are well characterised, their putative non-thermal effects remain a controversial subject. Here, we use the bioluminescent marine bacterium, Vibrio fischeri, to monitor the effects of pulsed microwave electromagnetic fields, of nominal frequency 2.5 GHz, on light emission. Separatedmore » electric and magnetic field effects were investigated using a resonant microwave cavity, within which the maxima of each field are separated. For pulsed electric field exposure, the bacteria gave reproducible responses and recovery in light emission. At the lowest pulsed duty cycle (1.25%) and after short durations (100 ms) of exposure to the electric field at power levels of 4.5 W rms, we observed an initial stimulation of bioluminescence, whereas successive microwave pulses became inhibitory. Much of this behaviour is due to thermal effects, as the bacterial light output is very sensitive to the local temperature. Conversely, magnetic field exposure gave no measurable short-term responses even at the highest power levels of 32 W rms. Thus, we were able to detect, de-convolute, and evaluate independently the effects of separated electric and magnetic fields on exposure of a luminescent biological system to microwave irradiation.« less

The separated electric and magnetic field responses of luminescent bacteria exposed to pulsed microwave irradiation

NASA Astrophysics Data System (ADS)

Williams, Catrin F.; Geroni, Gilles M.; Pirog, Antoine; Lloyd, David; Lees, Jonathan; Porch, Adrian

2016-08-01

Electromagnetic fields (EMFs) are ubiquitous in the digital world we inhabit, with microwave and millimetre wave sources of non-ionizing radiation employed extensively in electronics and communications, e.g., in mobile phones and Wi-Fi. Indeed, the advent of 5G systems and the "internet of things" is likely to lead to massive densification of wireless networks. Whilst the thermal effects of EMFs on biological systems are well characterised, their putative non-thermal effects remain a controversial subject. Here, we use the bioluminescent marine bacterium, Vibrio fischeri, to monitor the effects of pulsed microwave electromagnetic fields, of nominal frequency 2.5 GHz, on light emission. Separated electric and magnetic field effects were investigated using a resonant microwave cavity, within which the maxima of each field are separated. For pulsed electric field exposure, the bacteria gave reproducible responses and recovery in light emission. At the lowest pulsed duty cycle (1.25%) and after short durations (100 ms) of exposure to the electric field at power levels of 4.5 W rms, we observed an initial stimulation of bioluminescence, whereas successive microwave pulses became inhibitory. Much of this behaviour is due to thermal effects, as the bacterial light output is very sensitive to the local temperature. Conversely, magnetic field exposure gave no measurable short-term responses even at the highest power levels of 32 W rms. Thus, we were able to detect, de-convolute, and evaluate independently the effects of separated electric and magnetic fields on exposure of a luminescent biological system to microwave irradiation.

A Thermal Runaway Failure Model for Low-Voltage BME Ceramic Capacitors with Defects

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2017-01-01

Reliability of base metal electrode (BME) multilayer ceramic capacitors (MLCCs) that until recently were used mostly in commercial applications, have been improved substantially by using new materials and processes. Currently, the inception of intrinsic wear-out failures in high quality capacitors became much greater than the mission duration in most high-reliability applications. However, in capacitors with defects degradation processes might accelerate substantially and cause infant mortality failures. In this work, a physical model that relates the presence of defects to reduction of breakdown voltages and decreasing times to failure has been suggested. The effect of the defect size has been analyzed using a thermal runaway model of failures. Adequacy of highly accelerated life testing (HALT) to predict reliability at normal operating conditions and limitations of voltage acceleration are considered. The applicability of the model to BME capacitors with cracks is discussed and validated experimentally.

Failure mechanisms of thermal barrier coatings exposed to elevated temperatures

NASA Technical Reports Server (NTRS)

Miller, R. A.; Lowell, C. E.

1982-01-01

The failure of a ZrO2-8%Y2O3/Ni-14% Al-0.1% Zr coating system on Rene 41 in Mach 0.3 burner rig tests was characterized. High flame and metal temperatures were employed in order to accelerate coating failure. Failure by delamination was shown to precede surface cracking or spalling. This type of failure could be duplicated by cooling down the specimen after a single long duration isothermal high temperature cycle in a burner rig or a furnace, but only if the atmosphere was oxidizing. Stresses due to thermal expansion mismatch on cooling coupled with the effects of plastic deformation of the bond coat and oxidation of the irregular bond coat are the probable life limiting factors. Heat up stresses alone could not fail the coating in the burner rig tests. Spalling eventually occurs on heat up but only after the coating has already failed through delamination.

Night ventilation control strategies in office buildings

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

Wang, Zhaojun; Yi, Lingli; Gao, Fusheng

2009-10-15

In moderate climates night ventilation is an effective and energy-efficient approach to improve the indoor thermal environment for office buildings during the summer months, especially for heavyweight construction. However, is night ventilation a suitable strategy for office buildings with lightweight construction located in cold climates? In order to answer this question, the whole energy-consumption analysis software EnergyPlus was used to simulate the indoor thermal environment and energy consumption in typical office buildings with night mechanical ventilation in three cities in northern China. The summer outdoor climate data was analyzed, and three typical design days were chosen. The most important factorsmore » influencing night ventilation performance such as ventilation rates, ventilation duration, building mass and climatic conditions were evaluated. When night ventilation operation time is closer to active cooling time, the efficiency of night ventilation is higher. With night ventilation rate of 10 ach, the mean radiant temperature of the indoor surface decreased by up to 3.9 C. The longer the duration of operation, the more efficient the night ventilation strategy becomes. The control strategies for three locations are given in the paper. Based on the optimized strategies, the operation consumption and fees are calculated. The results show that more energy is saved in office buildings cooled by a night ventilation system in northern China than ones that do not employ this strategy. (author)« less

Effects of Fuel Temperature on Injection Process and Combustion of Dimethyl Ether Engine.

PubMed

Guangxin, Gao; Zhulin, Yuan; Apeng, Zhou; Shenghua, Liu; Yanju, Wei

2013-12-01

To investigate the effects of fuel temperature on the injection process in the fuel-injection pipe and the combustion characteristics of compression ignition (CI) engine, tests on a four stroke, direct injection dimethyl ether (DME) engine were conducted. Experimental results show that as the fuel temperature increases from 20 to 40 °C, the sound speed is decreased by 12.2%, the peak line pressure at pump and nozzle sides are decreased by 7.2% and 5.6%, respectively. Meanwhile, the injection timing is retarded by 2.2 °CA and the injection duration is extended by 0.8 °CA. Accordingly, the ignition delay and the combustion duration are extended by 0.7 °CA and 4.0 °CA, respectively. The cylinder peak pressure is decreased by 5.4%. As a result, the effective thermal efficiency is decreased, especially for temperature above 40 °C. Before beginning an experiment, the fuel properties of DME, including the density, the bulk modulus, and the sound speed were calculated by "ThermoData." The calculated result of sound speed is consistent with the experimental results.

Physicochemical characterization and mechanisms of release of theophylline from melt-extruded dosage forms based on a methacrylic acid copolymer.

PubMed

Young, Christopher R; Dietzsch, Caroline; Cerea, Matteo; Farrell, Thomas; Fegely, Kurt A; Rajabi-Siahboomi, Ali; McGinity, James W

2005-09-14

The purpose of the current study was to investigate the physicochemical properties of melt-extruded dosage forms based on Acryl-EZE and to determine the influence of gelling agents on the mechanisms and kinetics of drug release from thermally processed matrices. Acryl-EZE is a pre-mixed excipient blend based on a methacrylic acid copolymer that is optimized for film-coating applications. Powder blends containing theophylline, Acryl-EZE, triethyl citrate and an optional gelling agent, Methocel K4M Premium (hydroxypropyl methylcellulose, HPMC, hypromellose 2208) or Carbopol 974P (carbomer), were thermally processed using a Randcastle single-screw extruder. The physical and chemical stability of materials during processing was determined using thermal gravimetric analysis and HPLC. The mechanism of drug release was determined using the Korsmeyer-Peppas model and the hydration and erosion of tablets during the dissolution studies were investigated. The excipient blends were physically and chemically stable during processing, and the resulting dosage forms exhibited pH-dependent dissolution properties. Extrusion of blends containing HPMC or carbomer changed the mechanism and kinetics of drug release from the thermally processed dosage forms. At concentrations of 5% or below, carbomer was more effective than HPMC at extending the duration of theophylline release from matrix tablets. Furthermore, carbomer containing tablets were stable upon storage for 3 months at 40 degrees C/75% RH. Thus, hot-melt extrusion was an effective process for the preparation of controlled release matrix systems based on Acryl-EZE.

First Stage Solid Propellant Multiply Debris Thermal Analysis

NASA Technical Reports Server (NTRS)

Toleman, Benjamin M.

2011-01-01

Destruction of a solid rocket stage of a launch vehicle can create a thermal radiation hazard for an aborting crew module. This hazard was assessed for the Constellation Program (Cx) crew and launch vehicle concept. For this concept, if an abort was initiated in first stage flight, the Crew Module (CM) will separate and be pulled away from the malfunctioning launch vehicle via a Launch Abort System (LAS). Having aborted the mission, the launch vehicle will likely be destroyed via a Flight Termination System (FTS) in order to prevent it from errantly traversing back over land and posing a risk to the public. The resulting launch vehicle debris field, composed primarily of first stage solid propellant, poses a threat to the CM. The harsh radiative thermal environment, caused by surrounding burning propellant debris, may lead to CM parachute failure. A methodology, detailed herein, has been developed to address this concern and to quantify the risk of first stage propellant debris leading to the thermal demise of the CM parachutes. Utilizing basic thermal radiation principles, a software program was developed to calculate parachute temperature as a function of time for a given abort trajectory and debris piece trajectory set. Two test cases, considered worst case aborts with regard to launch vehicle debris environments, were analyzed using the simulation: an abort declared at Mach 1 and an abort declared at maximum dynamic pressure (Max Q). For both cases, the resulting temperature profiles indicated that thermal limits for the parachutes were not exceeded. However, short duration close encounters by single debris pieces did have a significant effect on parachute temperature. Therefore while these two test cases did not indicate exceedance of thermal limits, in order to quantify the risk of parachute failure due to radiative effects from the abort environment, a more thorough probability-based analysis using the methodology demonstrated herein must be performed.

Assessment of thermal load on transported goats administered with ascorbic acid during the hot-dry conditions

NASA Astrophysics Data System (ADS)

Minka, N. S.; Ayo, J. O.

2012-03-01

The major factor in the induction of physiological stress during road transportation of livestock is the complex fluctuations of the thermal transport microenvironment, encountered when animals are transported across different ecological zones. Recommended guidelines on optimum "on-board" conditions in which goats should be transported are lacking, and there are no acceptable ranges and limits for the thermal loads to which goats may be subjected during long-distance road transportation in hot-dry conditions. Panting score (PS), rectal temperature (RT), heart rate (HR) and respiratory rate (RR) were employed as reliable stress indices to assess the effects of different thermal loads, measured as temperature humidity index (THI), encountered in the vehicle during 12 h of road transportation of 40 goats, and to suggest the administration of 100 mg/kg body weight of ascorbic acid (AA) as an ameliorating agent. The results obtained showed that the PS, RT, HR and RR rose above normal reference values with increase in the THI and journey duration. The rise in PS value, which is a visual indicator of the severity of thermal load, was the most pronounced. The results suggest that values of THI in the vehicle up to 94.6 constitute no risk, while at of 100 it presents a moderate risk and above 100 may result in severe stress. The relationships between the thermal load and the physiological variables were positive and significant ( P < 0.05). They reflect the degree of stress imposed by each THI value during the transportation, and may be used as recommended ranges and limit thermal load values in transported goats. The results demonstrated that administration of 100 mg/kg body weight of AA before road transportation mitigated the risk of adverse effects of high THI values and other stress factors due to road transportation in goats.

SU-E-T-558: An Exploratory RF Pulse Sequence Technique Used to Induce Differential Heating in Tissues Containing Iron Oxide Nanoparticles for a Possible Hyperthermic Adjuvant Effect to Radiotherapy

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

Yee, S; Ionascu, D; Wilson, G

2014-06-01

Purpose: In pre-clinical trials of cancer thermotherapy, hyperthermia can be induced by exposing localized super-paramagnetic iron oxide nanoparticles (SPION) to external alternating magnetic fields generated by a solenoid electrical circuit (Zhao et al., Theranostics 2012). Alternatively, an RF pulse technique implemented in a regular MRI system is explored as a possible hyperthermia induction technique . Methods: A new thermal RF pulse sequence was developed using the Philips pulse programming tool for the 3T Ingenia MRI system to provide a sinusoidal magnetic field alternating at the frequency of 1.43 kHz (multiples of sine waves of 0.7 ms period) before each excitationmore » RF pulse for imaging. The duration of each thermal RF pulse routine was approximately 3 min, and the thermal pulse was applied multiple times to a phantom that contains different concentrations (high, medium and low) of SPION samples. After applying the thermal pulse each time, the temperature change was estimated by measuring the phase changes in the T1-weighted inversion-prepared multi-shot turbo field echo (TFE) sequence (TR=5.5 ms, TE=2.7 ms, inversion time=200 ms). Results: The phase values and relative differences among them changed as the number of applied thermal RF pulses increased. After the 5th application of the thermal RF pulse, the relative phase differences increased significantly, suggesting the thermal activation of the SPION. The increase of the phase difference was approximately linear with the SPION concentration. Conclusion: A sinusoidal RF pulse from the MRI system may be utilized to selectively thermally activate tissues containing super-paramagnetic iron oxide nanoparticles.« less

A study of processing parameters in thermal-sprayed alumina and zircon mixtures

NASA Astrophysics Data System (ADS)

Li, Y.; Khor, K. A.

2002-06-01

A method of plasma spraying of alumina and zircon mixtures to form ZrO2-mullite composites has been proposed and developed. The feedstock is prepared by a combination of mechanical alloying, which allows formation of fine-grained, homogeneous solid-solution mixtures, followed by plasma spheroidization that yields rapid solidified microstructures and enhanced compositional homogeneity. The effects of ball-milling duration and milling media were studied. It was found that zirconia is a more efficient milling media and that increasing milling duration enhanced the dissociation of zircon. Flame spray and plasma spray processes were used to spheroidize the spray-dried powders. The temperature of the flame spray was found to be insufficient to melt the powders completely. The processing parameters of the plasma spray played an important role in zircon decomposition and mullite formation. Increasing the arc current or reducing secondary gas pressure caused more zircon to decompose and more mullite to form after heat treatment at 1200 °C for 3 h. Dissociation of zircon and the amount of mullite for med can be enhanced significantly when using the more efficient, computerized plasma-spraying system and increasing the ball-milling duration from 4 to 8 h.

Considerations for theoretical modeling of thermal ablation with catheter-based ultrasonic sources: implications for treatment planning, monitoring and control

PubMed Central

Prakash, Punit; Diederich, Chris J.

2012-01-01

Purpose To determine the impact of including dynamic changes in tissue physical properties during heating on feedback controlled thermal ablation with catheter-based ultrasound. Additionally, we compared impact several indicators of thermal damage on predicted extents of ablation zones for planning and monitoring ablations with this modality. Methods A 3D model of ultrasound ablation with interstitial and transurethral applicators incorporating temperature based feedback control was used to simulate thermal ablations in prostate and liver tissue. We investigated five coupled models of heat dependent changes in tissue acoustic attenuation/absorption and blood perfusion of varying degrees of complexity.. Dimensions of the ablation zone were computed using temperature, thermal dose, and Arrhenius thermal damage indicators of coagulative necrosis. A comparison of the predictions by each of these models was illustrated on a patient-specific anatomy in the treatment planning setting. Results Models including dynamic changes in blood perfusion and acoustic attenuation as a function of thermal dose/damage predicted near-identical ablation zone volumes (maximum variation < 2.5%). Accounting for dynamic acoustic attenuation appeared to play a critical role in estimating ablation zone size, as models using constant values for acoustic attenuation predicted ablation zone volumes up to 50% larger or 47% smaller in liver and prostate tissue, respectively. Thermal dose (t43 ≥ 240min) and thermal damage (Ω ≥ 4.6) thresholds for coagulative necrosis are in good agreement for all heating durations, temperature thresholds in the range of 54 °C for short (< 5 min) duration ablations and 50 °C for long (15 min) ablations may serve as surrogates for determination of the outer treatment boundary. Conclusions Accounting for dynamic changes in acoustic attenuation/absorption appeared to play a critical role in predicted extents of ablation zones. For typical 5—15 min ablations with this modality, thermal dose and Arrhenius damage measures of ablation zone dimensions are in good agreement, while appropriately selected temperature thresholds provide a computationally cheaper surrogate. PMID:22235787

[Biological characteristics of the egg phase of citrus root weevils].

PubMed

Guedes, Jerson V C; Parra, José R P

2007-01-01

The goal of this work was to study some characteristics of the egg phase of three species of citrus root weevils. The insects were collected from citrus plants in Itapetininga, SP, and brought to the Laboratório de Biologia de Insetos of ESALQ/USP, in Piracicaba, SP, where the species Naupactus cervinus (Boheman), Naupactus versatilis (Hustache) and Parapantomorus fluctuosus (Boheman) were kept. Duration and viability of the egg phase were evaluated, and the lower temperature threshold and thermal constant (K) were calculated for these species. The species of citrus root weevils showed different duration of egg phases. The egg phase ranged from 40.4 to 13.8 N. cervinus, from 38.7 to 20.0 days for N. versatilis, and from 35.0 to 13.8 days for P. fluctuosus, depending upon temperature. The temperature thresholds of this stage were 8.1, 8.3, and 9.9 masculineC at thermal constant was 385.7, 397.7 and 294.1 degree-days, for N. cervinus, N. versatilis and P. fluctuosus respectively. The duration of the egg phases of N. cervinus and N. versatilis were similar at the same temperatures and P. fluctuosus had a faster development than Naupactus spp. in all temperatures tested.

Estimation of the base temperature and growth phase duration in terms of thermal time for four grapevine cultivars

NASA Astrophysics Data System (ADS)

Zapata, D.; Salazar, M.; Chaves, B.; Keller, M.; Hoogenboom, G.

2015-12-01

Thermal time models have been used to predict the development of many different species, including grapevine ( Vitis vinifera L.). These models normally assume that there is a linear relationship between temperature and plant development. The goal of this study was to estimate the base temperature and duration in terms of thermal time for predicting veraison for four grapevine cultivars. Historical phenological data for four cultivars that were collected in the Pacific Northwest were used to develop the thermal time model. Base temperatures ( T b) of 0 and 10 °C and the best estimated T b using three different methods were evaluated for predicting veraison in grapevine. Thermal time requirements for each individual cultivar were evaluated through analysis of variance, and means were compared using the Fisher's test. The methods that were applied to estimate T b for the development of wine grapes included the least standard deviation in heat units, the regression coefficient, and the development rate method. The estimated T b varied among methods and cultivars. The development rate method provided the lowest T b values for all cultivars. For the three methods, Chardonnay had the lowest T b ranging from 8.7 to 10.7 °C, while the highest T b values were obtained for Riesling and Cabernet Sauvignon with 11.8 and 12.8 °C, respectively. Thermal time also differed among cultivars, when either the fixed or estimated T b was used. Predictions of the beginning of ripening with the estimated temperature resulted in the lowest variation in real days when compared with predictions using T b = 0 or 10 °C, regardless of the method that was used to estimate the T b.

The thermal comfort and its changes in the 31 provincial capital cities of mainland China in the past 30 years

NASA Astrophysics Data System (ADS)

Chi, Xiaoli; Li, Rui; Cubasch, Ulrich; Cao, Wenting

2018-04-01

The thermal comfort and its changes in the 31 provincial capital cities of mainland China in the past 30 years were comprehensively evaluated using the Physiologically Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI) indicators. The PET and UTCI values were highly correlated with each other and presented similar thermal comfort pattern, although their sensitivities might differ slightly. The results showed that these cities covered, respectively, 4-8 and 6-8 thermal comfort classes of the PET and UTCI scale. On the whole, the annual cumulative number of pleasant days was more than 160 days/year. In terms of seasonal variations in thermal comfort conditions, the 31 provincial capital cities in mainland China can be classified into 5 types, which are, respectively, characterized by pleasant summer and severe cold winter (type-I); pleasant spring, autumn, winter, and severe hot summer (type-II); pleasant spring and autumn, slightly pleasant summer, and cold winter (type-III); pleasant spring and autumn, hot stress summer, and slightly cold winter (type-IV); and pleasant spring, summer, autumn, and cool winter (type-V). Type-II cities are rare winter resorts, while type-I cities are natural summer resorts. Type-V cities are the year round pleasant resorts. In the past three decades, the cities in mainland China had experienced increasing pleasant duration in late winter and early spring and intensifying heat stress in summer. The reduction in annual cumulative number of cold stress days in higher latitude/altitude cities outweighed the increase in duration of heat stress in subtropical cities. These may provide some references for urban planning and administration in mainland China.

Thermal Considerations for Reducing the Cooldown and Warmup Duration of the James Webb Space Telescope OTIS Cryo-Vacuum Test

NASA Technical Reports Server (NTRS)

Yang, Kan; Glazer, Stuart; Ousley, Wes; Burt, William

2017-01-01

The James Webb Space Telescope (JWST), set to launch in 2018, is NASAs next-generation flagship telescope. The Optical Telescope Element (OTE) and Integrated Science Instrument Module (ISIM) contain all of the optical surfaces and instruments to capture and analyze the telescopes infrared targets. The integrated OTE and ISIM are denoted as OTIS, and will be tested as a single unit in a critical thermal-vacuum test in mid-2017 at NASA Johnson Space Centers Chamber A facility. The payload will be evaluated for workmanship and functionality in a 20K simulated flight environment during this thermal-vacuum test. However, the sheer thermal mass of the OTIS payload as well as the restrictive gradient, rate, and contamination-related constraints placed on test components precludes rapid cooldown or warmup to its steady-state cryo-balance condition. Hardware safety considerations precludes injection of helium gas for free molecular heat transfer. Initial thermal analysis predicted that transient radiative cooldown from ambient temperatures, while meeting all limits and constraints, would take 33.3 days; warmup similarly would take 28.4 days. This paper discusses methods used to reduce transition times from the original predictions through modulation of boundary temperatures and environmental conditions. By optimizing helium shroud transition rates and heater usage, as well as rigorously re-examining previously imposed constraints, savings of up to three days on cooldown and up to a week on warmup can be achieved. The efficiencies gained through these methods allow the JWST thermal test team to create faster cooldown and warmup profiles, thus reducing the overall test duration and cost, while keeping all of the required test operations.

Influence of thermal stimulation during the late phase of incubation on hatching results and post-hatch broiler performance under commercial conditions.

PubMed

Elmehdawi, A S; Hall, M A; Skewes, P A; Wicker, D L; Maurice, D V

2016-12-01

Two experiments, which differed in breeder age, strain and season, were conducted to study the influence of low-intensity, short-duration thermal stimuli during the late phase of incubation on hatchability and performance. The first experiment conducted in April-June used eggs from Cobb × Ross broiler breeders at 35-41 weeks of age and the second experiment performed in February-April used eggs from Hubbard × Cobb broiler breeders at 49-53 weeks of age. Eggs in the test group had the same physical environment as eggs in the control group except that incubation temperature was increased by 1˚C for 2 h/d above the control group from 18 to 20 d of incubation (DI). The results demonstrated that thermal stimulation of 1˚C for 2 h/d above control incubation temperature during 18-21DI did not have any adverse effects on hatch and post-hatch performance of broilers. In both experiments, treatment did not significantly alter the secondary sex ratio in hatched chickens, but hatch residue showed that the proportion of unhatched male embryos was significantly lower in the test groups than in the control groups. In the first experiment, thermal stimulation improved feed conversion by 1.82% compared with the control.

Solar electric thermal hydronic (SETH) product development project

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

Stickney, B.L.; Sindelar, A.

Positive Energy, Inc. received a second Technology Maturation and Commercialization Project Subcontract during the 1999 round of awards. This Subcontract is for the purpose of further aiding Positive Energy, Inc. in preparing its Solar Electric Thermal Hydronic (SETH) control and distribution package for market introduction. All items of this subcontracted project have been successfully completed. This Project Report contains a summary of the progress made during the SETH Development Project (the Project) over the duration of the 1999 Subcontract. It includes a description of the effort performed and the results obtained in the pursuit of intellectual property protection and developmentmore » of product documentation for the end users. This report also summarizes additional efforts taken by and for the SETH project outside of the Subcontract. It presents a chronology of activities over the duration of the Subcontract, and includes a few selected sample copies of documents offered as evidence of their success.« less

Thermal energy storage for the Stirling engine powered automobile

NASA Technical Reports Server (NTRS)

Morgan, D. T. (Editor)

1979-01-01

A thermal energy storage (TES) system developed for use with the Stirling engine as an automotive power system has gravimetric and volumetric storage densities which are competitive with electric battery storage systems, meets all operational requirements for a practical vehicle, and can be packaged in compact sized automobiles with minimum impact on passenger and freight volume. The TES/Stirling system is the only storage approach for direct use of combustion heat from fuel sources not suitable for direct transport and use on the vehicle. The particular concept described is also useful for a dual mode TES/liquid fuel system in which the TES (recharged from an external energy source) is used for short duration trips (approximately 10 miles or less) and liquid fuel carried on board the vehicle used for long duration trips. The dual mode approach offers the potential of 50 percent savings in the consumption of premium liquid fuels for automotive propulsion in the United States.

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

Kuzmina, M S; Khazanov, E A

The problem on laser radiation propagation in a birefringent medium is solved with the allowance made for thermally induced linear birefringence under the conditions of cubic nonlinearity. It is shown that at high average and peak radiation powers the degree of isolation in a Faraday isolator noticeably reduces due to the cubic nonlinearity: by more than an order of magnitude when the B-integral is equal to unity. This effect is substantial for pulses with the energy of 0.2 – 3 J, duration of 10 ps to 4 ns and pulse repetition rate of 0.2 – 40 kHz. (components of lasermore » devices)« less

Effects of atomic oxygen and ultraviolet radiation on candidate elastomeric materials for long duration missions. Test series no.1

NASA Technical Reports Server (NTRS)

Linton, R. C.; Finckenor, M. M.; Kamenetzky, R. R.; Gray, P.

1993-01-01

Research was conducted at MSFC on the behavior of elastomeric materials after exposure to simulated space environment. Silicone S383 and Viton V747 samples were exposed to thermal vacuum, ultraviolet radiation, and atomic oxygen and then evaluated for changes in material properties. Characterization of the elastomeric materials included weight, hardness, optical inspection under normal and black light, spectrofluorescence, solar absorptance and emittance, Fourier transform infrared spectroscopy, and permeability. These results indicate a degree of sensitivity to exposure and provided some evidence of UV and atomic oxygen synergism.

Investigation of Teflon FEP Embrittlement on Spacecraft in Low Earth Orbit

NASA Technical Reports Server (NTRS)

deGroh, Kim K.; Smith, Daniela C.

1997-01-01

Teflon(registered trademark) FEP (fluorinated ethylene-propylene) is commonly used on exterior spacecraft surfaces in the low Earth orbit (LEO) environment for thermal control. Silverized or aluminized FEP is used for the outer layer of thermal control blankets because of its low solar absorptance and high thermal emittance. FEP is also preferred over other spacecraft polymers because of its relatively high resistance to atomic oxygen erosion. Because of its low atomic oxygen erosion yield, FEP has not been protected in the space environment. Recent, long term space exposures such as on the Long Duration Exposure Facility (LDEF, 5.8 years in space), and the Hubble Space Telescope (HST, after 3.6 years in space) have provided evidence of LEO environmental degradation of FEP. These exposures provide unique opportunities for studying environmental degradation because of the long durations and the different conditions (such as differences in altitude) of the exposures. Samples of FEP from LDEF and from HST (retrieved during its first servicing mission) have been evaluated for solar induced embrittlement and for synergistic effects of solar degradation and atomic oxygen. Micro-indenter results indicate that the surface hardness increased as the ratio of atomic oxygen fluence to solar fluence decreased for the LDEF samples. FEP multilayer insulation (MLI) retrieved from HST provided evidence of severe embrittlement on solar facing surfaces. Micro-indenter measurements indicated higher surface hardness values for these samples than LDEF samples, but the solar exposures were higher. Cracks induced during bend testing were significantly deeper for the HST samples with the highest solar exposure than for LDEF samples with similar atomic oxygen fluence to solar fluence ratios. If solar fluences are compared, the LDEF samples appear as damaged as HST samples, except that HST had deeper induced cracks. The results illustrate difficulties in comparing LEO exposed materials from different missions. Because the HST FEP appears more damaged than LDEF FEP based on depth of embrittlement, other causes for FEP embrittlement in addition to atomic oxygen and ultraviolet (UV) radiation, such as thermal effects and the possible role of soft x-ray radiation, need to be considered. FEP that was exposed to soft x-rays in a ground test facility, showed embrittlement similar to that witnessed in LEO, which indicates that the observed differences between LDEF and HST FEP might be attributed to the different soft x-ray fluences during these two missions.

Development of an inflatable radiator system. [for space shuttles

NASA Technical Reports Server (NTRS)

Leach, J. W.

1976-01-01

Conceptual designs of an inflatable radiator system developed for supplying short duration supplementary cooling of space vehicles are described along with parametric trade studies, materials evaluation/selection studies, thermal and structural analyses, and numerous element tests. Fabrication techniques developed in constructing the engineering models and performance data from the model thermal vacuum tests are included. Application of these data to refining the designs of the flight articles and to constructing a full scale prototype radiator is discussed.

Dynamics of laser-induced channel formation in water and influence of pulse duration on the ablation of biotissue under water with pulsed erbium-laser radiation

NASA Astrophysics Data System (ADS)

Ith, M.; Pratisto, H.; Altermatt, H. J.; Frenz, M.; Weber, H. P.

1994-12-01

The ability to use fiber-delivered erbium-laser radiation for non-contact arthroscopic meniscectomy in a liquid environment was studied. The laser radiation is transmitted through a water-vapor channel created by the leading part of the laser pulse. The dynamics of the channel formation around a submerged fiber tip was investigated with time-resolved flash photography. Strong pressure transients with amplitudes up to a few hundreds of bars measured with a needle hydrophone were found to accompany the channel formation process. Additional pressure transients in the range of kbars were observed after the laser pulse associated with the collapse of the vapor channel. Transmission measurements revealed that the duration the laser-induced channel stays open, and therefore the energy transmittable through it, is substantially determined by the laser pulse duration. The optimum pulse duration was found to be in the range between 250 and 350 µS. This was confirmed by histological evaluations of the laser incisions in meniscus: Increasing the pulse duration from 300 to 800 µs leads to a decrease in the crater depth from 1600 to 300 µm. A comparison of the histological examination after laser treatment through air and through water gave information on the influence of the vapor channel on the ablation efficiency, the cutting quality and the induced thermal damage in the adjacent tissue. The study shows that the erbium laser combined with an adequate fiber delivery system represents an effective surgical instrument liable to become increasingly accepted in orthopedic surgery.

Diving through the thermal window: implications for a warming world

PubMed Central

Campbell, Hamish A.; Dwyer, Ross G.; Gordos, Matthew; Franklin, Craig E.

2010-01-01

Population decline and a shift in the geographical distribution of some ectothermic animals have been attributed to climatic warming. Here, we show that rises in water temperature of a few degrees, while within the thermal window for locomotor performance, may be detrimental to diving behaviour in air-breathing ectotherms (turtles, crocodilians, marine iguanas, amphibians, snakes and lizards). Submergence times and internal and external body temperature were remotely recorded from freshwater crocodiles (Crocodylus johnstoni) while they free-ranged throughout their natural habitat in summer and winter. During summer, the crocodiles' mean body temperature was 5.2 ± 0.1°C higher than in winter and the largest proportion of total dive time was composed of dive durations approximately 15 min less than in winter. Diving beyond 40 min during summer required the crocodiles to exponentially increase the time they spent on the surface after the dive, presumably to clear anaerobic debt. The relationship was not as significant in winter, even though a greater proportion of dives were of a longer duration, suggesting that diving lactate threshold (DLT) was reduced in summer compared with winter. Additional evidence for a reduced DLT in summer was derived from the stronger influence body mass exerted upon dive duration, compared to winter. The results demonstrate that the higher summer body temperature increased oxygen demand during the dive, implying that thermal acclimatization of the diving metabolic rate was inadequate. If the study findings are common among air-breathing diving ectotherms, then long-term warming of the aquatic environment may be detrimental to behavioural function and survivorship. PMID:20610433

Determinants and clinical impact of pressure drift in manoscan anorectal high resolution manometry system.

PubMed

Parthasarathy, G; McMaster, J; Feuerhak, K; Zinsmeister, A R; Bharucha, A E

2016-09-01

Pressure drift (PD), resulting from differences between room and body temperature, reduces the accuracy of pressure measurements with the Manoscan high resolution manometry (HRM) system. Our aims were to assess PD during anorectal HRM. Defined as the residual pressure measured immediately after the catheter was removed, PD was calculated for each sensor and averaged across all 12 sensors in 454 anorectal consecutive studies recorded with 3 HRM catheters. The relationship between PD and study duration, number of prior uses of a catheter, and peak and average pressure exposure during a study were evaluated. The correction of PD with a software algorithm (thermal compensation) was evaluated in 76 studies where the most distal sensor was outside the body. The PD varied among sensors and across catheters. The average PD (7.3 ± 0.2 mmHg) was significantly greater for newer catheters, during longer studies, or when sensors were exposed to higher pressures. Together, these factors explained 81% of the variance in overall PD. After thermal compensation, the uncorrected median PD for the most distal sensor was 2.5-5 mmHg over the study duration. Correcting this changed the interpretation (e.g., as abnormal instead of normal) of at least 1 anorectal parameter in eight of 76 studies. During anorectal HRM, PD declines with catheter use and is greater for newer catheters, when sensors are exposed to higher pressures, and for studies of longer duration. While PD is partially corrected with thermal compensation algorithms, the impact on interpretation is modest. © 2016 John Wiley & Sons Ltd.

Review: Weak radiofrequency radiation exposure from mobile phone radiation on plants.

PubMed

Halgamuge, Malka N

2017-01-01

The aim of this article was to explore the hypothesis that non-thermal, weak, radiofrequency electromagnetic fields (RF-EMF) have an effect on living plants. In this study, we performed an analysis of the data extracted from the 45 peer-reviewed scientific publications (1996-2016) describing 169 experimental observations to detect the physiological and morphological changes in plants due to the non-thermal RF-EMF effects from mobile phone radiation. Twenty-nine different species of plants were considered in this work. Our analysis demonstrates that the data from a substantial amount of the studies on RF-EMFs from mobile phones show physiological and/or morphological effects (89.9%, p < 0.001). Additionally, our analysis of the results from these reported studies demonstrates that the maize, roselle, pea, fenugreek, duckweeds, tomato, onions and mungbean plants seem to be very sensitive to RF-EMFs. Our findings also suggest that plants seem to be more responsive to certain frequencies, especially the frequencies between (i) 800 and 1500 MHz (p < 0.0001), (ii) 1500 and 2400 MHz (p < 0.0001) and (iii) 3500 and 8000 MHz (p = 0.0161). The available literature on the effect of RF-EMFs on plants to date observed the significant trend of radiofrequency radiation influence on plants. Hence, this study provides new evidence supporting our hypothesis. Nonetheless, this endorses the need for more experiments to observe the effects of RF-EMFs, especially for the longer exposure durations, using the whole organisms. The above observation agrees with our earlier study, in that it supported that it is not a well-grounded method to characterize biological effects without considering the exposure duration. Nevertheless, none of these findings can be directly associated with human; however, on the other hand, this cannot be excluded, as it can impact the human welfare and health, either directly or indirectly, due to their complexity and varied effects (calcium metabolism, stress proteins, etc.). This study should be useful as a reference for researchers conducting epidemiological studies and the long-term experiments, using whole organisms, to observe the effects of RF-EMFs.

Effects of annealing on arrays of Ge nanocolumns formed by glancing angle deposition

NASA Astrophysics Data System (ADS)

Khare, C.; Gerlach, J. W.; Höche, T.; Fuhrmann, B.; Leipner, H. S.; Rauschenbach, B.

2012-10-01

Post-deposition thermal annealing of glancing angle deposited Ge nanocolumn arrays was carried out in a continuous Ar-flow at temperatures ranging from TA = 300 to 800 °C for different annealing durations. Morphological alterations and the recrystallization process induced by the thermal annealing treatment were investigated for the Ge nanocolumns deposited on planar and pre-patterned Si substrates. From X-ray diffraction (XRD) measurements, the films annealed at TA ≥ 500 °C were found to be polycrystalline. On planar Si substrates, at TA = 600 °C nanocolumns exhibited strong coarsening and merging, while a complete disintegration of the nanocolumns was detected at TA = 700 °C. The morphology of nanostructures deposited on pre-patterned substrates differs substantially, where the merging or column-disintegration effect was absent at elevated annealing temperatures. The two-arm-chevron nanostructures grown on pre-patterned substrates retained their complex shape and morphology, after extended annealing intervals. Investigations by transmission electron microscopy revealed nanocrystalline domains of the order of 5-30 nm (in diameter) present within the chevron structures after the annealing treatment.

Direct measurement of the lethal isotherm for radiofrequency ablation of myocardial tissue.

PubMed

Wood, Mark; Goldberg, Scott; Lau, Melissa; Goel, Aneesh; Alexander, Daniel; Han, Frederick; Feinstein, Shawn

2011-06-01

The lethal isotherm for radiofrequency catheter ablation of cardiac myocardium is widely accepted to be 50°C, but this has not been directly measured. The purpose of this study was to directly measure the tissue temperature at the edge of radiofrequency lesions in real time using infrared thermal imaging. Fifteen radiofrequency lesions of 6 to 240 seconds in duration were applied to the left ventricular surface of isolated perfused pig hearts. At the end of radiofrequency delivery, a thermal image of the tissue surface was acquired with an infrared camera. The lesion was then stained and an optical image of the lesion was obtained. The thermal and optical images were electronically merged to allow determination of the tissue temperature at the edge of the lesion at the end of radiofrequency delivery. By adjusting the temperature overlay display to conform with the edge of the radiofrequency lesion, the lethal isotherm was measured to be 60.6°C (interquartile ranges, 59.7° to 62.4°C; range, 58.1° to 64.2°C). The areas encompassed by the lesion border in the optical image and the lethal isotherm in the thermal image were statistically similar and highly correlated (Spearman ρ=0.99, P<0.001). The lethal isotherm temperature was not related to the duration of radiofrequency delivery or to lesion size (both P>0.64). The areas circumscribed by 50°C isotherms were significantly larger than the areas of the lesions on optical imaging (P=0.002). By direct measurement, the lethal isotherm for cardiac myocardium is near 61°C for radiofrequency energy deliveries <240 seconds in duration. A 50°C isotherm overestimates lesion size. Accurate knowledge of the lethal isotherm for radiofrequency ablation is important to clinical practice as well as mathematical modeling of radiofrequency lesions.

Surface contamination detection by means of near-infrared stimulation of thermal luminescence

NASA Astrophysics Data System (ADS)

Carrieri, Arthur H.; Roese, Erik S.

2006-02-01

A method for remotely detecting liquid chemical contamination on terrestrial surfaces is presented. Concurrent to irradiation by an absorbing near-infrared beam, the subject soil medium liberates radiance called thermal luminescence (TL) comprising middle-infrared energies (numir) that is scanned interferometrically in beam duration tau. Cyclic states of absorption and emission by the contaminant surrogate are rendered from a sequential differential-spectrum measurement [deltaS(numir,tau)] of the scanned TL. Detection of chemical warfare agent simulant wetting soil is performed in this manner, for example, through pattern recognition of its unique, thermally dynamic, molecular vibration resonance bands on display in the deltaS(numir,tau) metric.

Sleep Deprivation and Recovery Sleep Prior to a Noxious Inflammatory Insult Influence Characteristics and Duration of Pain

PubMed Central

Vanini, Giancarlo

2016-01-01

Study Objectives: Insufficient sleep and chronic pain are public health epidemics. Sleep loss worsens pain and predicts the development of chronic pain. Whether previous, acute sleep loss and recovery sleep determine pain levels and duration remains poorly understood. This study tested whether acute sleep deprivation and recovery sleep prior to formalin injection alter post-injection pain levels and duration. Methods: Male Sprague-Dawley rats (n = 48) underwent sleep deprivation or ad libitum sleep for 9 hours. Thereafter, rats received a subcutaneous injection of formalin or saline into a hind paw. In the recovery sleep group, rats were allowed 24 h between sleep deprivation and the injection of formalin. Mechanical and thermal nociception were assessed using the von Frey test and Hargreaves' method. Nociceptive measures were performed at 1, 3, 7, 10, 14, 17 and 21 days post-injection. Results: Formalin caused bilateral mechanical hypersensitivity (allodynia) that persisted for up to 21 days post-injection. Sleep deprivation significantly enhanced bilateral allodynia. There was a synergistic interaction when sleep deprivation preceded a formalin injection. Rats allowed a recovery sleep period prior to formalin injection developed allodynia only in the injected limb, with higher mechanical thresholds (less allodynia) and a shorter recovery period. There were no persistent changes in thermal nociception. Conclusion: The data suggest that acute sleep loss preceding an inflammatory insult enhances pain and can contribute to chronic pain. The results encourage studies in a model of surgical pain to test whether enhancing sleep reduces pain levels and duration. Citation: Vanini G. Sleep deprivation and recovery sleep prior to a noxious inflammatory insult influence characteristics and duration of pain. SLEEP 2016;39(1):133–142. PMID:26237772

Focused ultrasound thermal therapy system with ultrasound image guidance and temperature measurement feedback.

PubMed

Lin, Kao-Han; Young, Sun-Yi; Hsu, Ming-Chuan; Chan, Hsu; Chen, Yung-Yaw; Lin, Win-Li

2008-01-01

In this study, we developed a focused ultrasound (FUS) thermal therapy system with ultrasound image guidance and thermocouple temperature measurement feedback. Hydraulic position devices and computer-controlled servo motors were used to move the FUS transducer to the desired location with the measurement of actual movement by linear scale. The entire system integrated automatic position devices, FUS transducer, power amplifier, ultrasound image system, and thermocouple temperature measurement into a graphical user interface. For the treatment procedure, a thermocouple was implanted into a targeted treatment region in a tissue-mimicking phantom under ultrasound image guidance, and then the acoustic interference pattern formed by image ultrasound beam and low-power FUS beam was employed as image guidance to move the FUS transducer to have its focal zone coincident with the thermocouple tip. The thermocouple temperature rise was used to determine the sonication duration for a suitable thermal lesion as a high power was turned on and ultrasound image was used to capture the thermal lesion formation. For a multiple lesion formation, the FUS transducer was moved under the acoustic interference guidance to a new location and then it sonicated with the same power level and duration. This system was evaluated and the results showed that it could perform two-dimensional motion control to do a two-dimensional thermal therapy with a small localization error 0.5 mm. Through the user interface, the FUS transducer could be moved to heat the target region with the guidance of ultrasound image and acoustic interference pattern. The preliminary phantom experimental results demonstrated that the system could achieve the desired treatment plan satisfactorily.

Temperature-associated population diversity in salmon confers benefits to mobile consumers

USGS Publications Warehouse

Ruff, Casey P.; Schindle, Daniel E.; Armstrong, Jonathan B.; Bentle, Kale T.; Brooks, Gabriel T.; Holtgrieve, Gordon W.; McGlauflin, Molly T.; Torgersen, Christian E.; Seeb, James E.

2011-01-01

Habitat heterogeneity can generate intraspecific diversity through local adaptation of populations. While it is becoming increasingly clear that population diversity can increase stability in species abundance, less is known about how population diversity can benefit consumers that can integrate across population diversity in their prey. Here we demonstrate cascading effects of thermal heterogeneity on trout–salmon interactions in streams where rainbow trout rely heavily on the seasonal availability of anadromous salmon eggs. Water temperature in an Alaskan stream varied spatially from 5°C to 17.5°C, and spawning sockeye salmon showed population differentiation associated with this thermal heterogeneity. Individuals that spawned early in cool regions of the 5 km long stream were genetically differentiated from those spawning in warmer regions later in the season. Sockeye salmon spawning generates a pulsed resource subsidy that supports the majority of seasonal growth in stream-dwelling rainbow trout. The spatial and temporal structuring of sockeye salmon spawn timing in our focal stream extended the duration of the pulsed subsidy compared to a thermally homogeneous stream with a single population of salmon. Further, rainbow trout adopted movement strategies that exploited the multiple pulses of egg subsidies in the thermally heterogeneous stream. Fish that moved to track the resource pulse grew at rates about 2.5 times higher than those that remained stationary or trout in the reference stream with a single seasonal pulse of eggs. Our results demonstrate that habitat heterogeneity can have important effects on the population diversity of dominant species, and in turn, influence their value to species that prey upon them. Therefore, habitat homogenization may have farther-reaching ecological effects than previously considered.

Optical stimulation of the hearing and deaf cochlea under thermal and stress confinement condition

NASA Astrophysics Data System (ADS)

Schultz, M.; Baumhoff, P.; Kallweit, N.; Sato, M.; Krüger, A.; Ripken, T.; Lenarz, T.; Kral, A.

2014-03-01

There is a controversy, to which extend cochlear stimulation with near infrared laser pulses at a wavelength of 1860 nm is based on optoacoustic stimulation of intact hair cells or -in contrast- is based on direct stimulation of the nerve cells in absence of functional hair cells. Thermal and stress confinement conditions apply, because of the pulse duration range (5 ns, 10 μs-20 ms) of the two lasers used. The dependency of the signal characteristics on pulse peak power and pulse duration was investigated in this study. The compound action potential (CAP) was measured during stimulation of the cochlea of four anaesthetized guinea pigs, which were hearing at first and afterwards acutely deafened using intracochlear neomycin-rinsing. For comparison hydrophone measurements in a water tank were performed to investigate the optoacoustic signals at different laser interaction regimes. With rising pulse peak power CAPs of the hearing animals showed first a threshold, then a positively correlated and finally a saturating dependency. CAPs also showed distinct responses at laser onset and offset separated with the pulse duration. At pulse durations shorter than physiological response times the signals merged. Basically the same signal characteristics were observed in the optoacoustic hydrophone measurements, scaled with the sensitivity and response time of the hydrophone. Taking together the qualitative correspondence in the signal response and the absence of any CAPs in deafened animals our results speak in favor of an optoacoustic stimulation of intact hair cells rather than a direct stimulation of nerve cells.

Conodont color and surface textural alteration in the Muschelkalk (Triassic) of the Silesian-Cracow Zn-Pb district, Poland

USGS Publications Warehouse

Repetski, J.E.; Narkiewicz, M.

1996-01-01

Limestone and dolostone samples were collected from sites within and adjacent to ore zones in the Trzebionka mine, Silesia-Cracow zinc-lead mining district, southern Poland, to assess the level of thermal alteration of the enclosed conodonts, via the color alteration index (CAI) technique, and to study any surface alteration effects on these microfossils. Additional conodont sampling from stratigraphic levels correlative with the horizons being mined in the Trzebionka mine was accomplished at four surface and two borehole localities in the district, to compare the CAI and surface alteration effects at these, commercially non-mineralized, localities with those effects in the mine. Data show that: 1. The overall background thermal level of the Triassic strata studied, presumably due to only shallow burial, is very low: CAI = 1; in the range of 50 to 80??C. 2. CAI values in the ore zones in the Trzebionka mine are slightly higher than this regional background: 1+ to 1.5 (in the range ???50 to 90??C minimum heating over geologic time of about 0.1 to more than 1 m. y.). This implies that heating "events" of higher temperatures affecting the conodonts, including the passage of the local ore-bearing solutions, were of rather short duration(s), on the order of about 1,000 to 50,000 years. CAI data from the Trzebionka Mine is consistent with temperature data from fluid inclusions, indicating ore-bearing fluid temperatures in the 100 to 138??C range, and the scenario that these fluids were resident in these strata for a geologically short period. 3. Conodonts from both surface and subsurface samples rarely show surface corrosion effects, but tend to show apatite overgrowths. These overgrowths vary in degree of development, but are consistent for each morphological type of conodont element, and qualitatively are consistent in each sample observed. 4. Ichthyoliths (fish teeth, spines, and scales), found in most of the samples, do not exhibit either mineral overgrowths or apparent corrosion effects to the extent seen in the conodont elements. 5. Ichthyoliths show color alteration effects that are consistent within-sample but which are very different from the CAI values of conodonts in the same sample. The color alteration of the fish teeth might be of value as a thermal maturation index in the future, if and when calibrated through controlled laboratory experimental testing, but at present cannot and should not be used as equivalent to conodont CAI.

Lamb Wave Stiffness Characterization of Composites Undergoing Thermal-Mechanical Aging

NASA Technical Reports Server (NTRS)

Seale, Michael D.; Madaras, Eric I.

2004-01-01

The introduction of new, advanced composite materials into aviation systems requires a thorough understanding of the long term effects of combined thermal and mechanical loading upon those materials. Analytical methods investigating the effects of intense thermal heating combined with mechanical loading have been investigated. The damage mechanisms and fatigue lives were dependent on test parameters as well as stress levels. Castelli, et al. identified matrix dominated failure modes for out-of-phase cycling and fiber dominated damage modes for in-phase cycling. In recent years, ultrasonic methods have been developed that can measure the mechanical stiffness of composites. To help evaluate the effect of aging, a suitably designed Lamb wave measurement system is being used to obtain bending and out-of-plane stiffness coefficients of composite laminates undergoing thermal-mechanical loading. The system works by exciting an antisymmetric Lamb wave and calculating the velocity at each frequency from the known transducer separation and the measured time-of-flight. The same peak in the waveforms received at various distances is used to measure the time difference between the signals. The velocity measurements are accurate and repeatable to within 1% resulting in reconstructed stiffness values repeatable to within 4%. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. A mechanical scanner is used to move the sensors over the surface to map the time-of-flight, velocity, or stiffnesses of the entire specimen. Access to only one side of the material is required and no immersion or couplants are required because the sensors are dry coupled to the surface of the plate. In this study, the elastic stiffnesses D(sub 11), D(sub 22), A(sub 44), and A(sub 55) as well as time-of-flight measurements for composite samples that have undergone combined thermal and mechanical aging for a duration of 10,000 hours are reported.

Photo-thermal characteristics of water-based Fe3O4@SiO2 nanofluid for solar-thermal applications

NASA Astrophysics Data System (ADS)

Khashan, Saud; Dagher, Sawsan; Omari, Salahaddin Al; Tit, Nacir; Elnajjar, Emad; Mathew, Bobby; Hilal-Alnaqbi, Ali

2017-05-01

This work proposes and demonstrates the novel idea of using Fe3O4@SiO2 core/shell structure nanoparticles (NPs) to improve the solar thermal conversion efficiency. Magnetite (Fe3O4) NPs are synthesized by controlled co-precipitation method. Fe3O4@SiO2 NPs are prepared based on sol-gel approach, then characterized. Water-based Fe3O4@SiO2 nanofluid is prepared and usedto illustrate the photo-thermal conversion characteristics of a solar collector under solar simulator. The temperature rise characteristics of the nanofluids are investigated at different heights of the solar collector, for duration of 300 min, under a solar intensity of 1000 W m-2. The experimental results show that Fe3O4@SiO2 NPs have a core/shell structure with spherical morphology and size of about 400 nm. Fe3O4@SiO2/H2O nanofluid enhances the photo-thermal conversion efficiency compared with base fluid and Fe3O4/H2O nanofluid, since the silica coating improves both the thermodynamic stability of the nanofluid and the light absorption effectiveness of the NPs. At a concentration of 1 mg/1 ml of Fe3O4@SiO2/H2O, and with the utilization of kerosene into the solar collector, and exposure for radiation for 5 min, the photo-thermal conversion efficiency has shown an enhancement at the bottom of the collector of about 32.9% compared to the base fluid.

Hotter nests produce hatchling lizards with lower thermal tolerance.

PubMed

Dayananda, Buddhi; Murray, Brad R; Webb, Jonathan K

2017-06-15

In many regions, the frequency and duration of summer heatwaves is predicted to increase in future. Hotter summers could result in higher temperatures inside lizard nests, potentially exposing embryos to thermally stressful conditions during development. Potentially, developmentally plastic shifts in thermal tolerance could allow lizards to adapt to climate warming. To determine how higher nest temperatures affect the thermal tolerance of hatchling geckos, we incubated eggs of the rock-dwelling velvet gecko, Amalosia lesueurii , at two fluctuating temperature regimes to mimic current nest temperatures (mean 23.2°C, range 10-33°C, 'cold') and future nest temperatures (mean 27.0°C, range 14-37°C, 'hot'). Hatchlings from the hot incubation group hatched 27 days earlier and had a lower critical thermal maximum (CT max 38.7°C) and a higher critical thermal minimum (CT min 6.2°C) than hatchlings from cold incubation group (40.2 and 5.7°C, respectively). In the field, hatchlings typically settle under rocks near communal nests. During the hatching period, rock temperatures ranged from 13 to 59°C, and regularly exceeded the CT max of both hot- and cold-incubated hatchlings. Because rock temperatures were so high, the heat tolerance of lizards had little effect on their ability to exploit rocks as retreat sites. Instead, the timing of hatching dictated whether lizards could exploit rocks as retreat sites; that is, cold-incubated lizards that hatched later encountered less thermally stressful environments than earlier hatching hot-incubated lizards. In conclusion, we found no evidence that CT max can shift upwards in response to higher incubation temperatures, suggesting that hotter summers may increase the vulnerability of lizards to climate warming. © 2017. Published by The Company of Biologists Ltd.

Thermal History and Mantle Dynamics of Venus

NASA Technical Reports Server (NTRS)

Hsui, Albert T.

1997-01-01

One objective of this research proposal is to develop a 3-D thermal history model for Venus. The basis of our study is a finite-element computer model to simulate thermal convection of fluids with highly temperature- and pressure-dependent viscosities in a three-dimensional spherical shell. A three-dimensional model for thermal history studies is necessary for the following reasons. To study planetary thermal evolution, one needs to consider global heat budgets of a planet throughout its evolution history. Hence, three-dimensional models are necessary. This is in contrasts to studies of some local phenomena or local structures where models of lower dimensions may be sufficient. There are different approaches to treat three-dimensional thermal convection problems. Each approach has its own advantages and disadvantages. Therefore, the choice of the various approaches is subjective and dependent on the problem addressed. In our case, we are interested in the effects of viscosities that are highly temperature dependent and that their magnitudes within the computing domain can vary over many orders of magnitude. In order to resolve the rapid change of viscosities, small grid spacings are often necessary. To optimize the amount of computing, variable grids become desirable. Thus, the finite-element numerical approach is chosen for its ability to place grid elements of different sizes over the complete computational domain. For this research proposal, we did not start from scratch and develop the finite element codes from the beginning. Instead, we adopted a finite-element model developed by Baumgardner, a collaborator of this research proposal, for three-dimensional thermal convection with constant viscosity. Over the duration supported by this research proposal, a significant amount of advancements have been accomplished.

A new setup for studying thermal microcracking through acoustic emission monitoring

NASA Astrophysics Data System (ADS)

Griffiths, Luke; Heap, Michael; Baud, Patrick; Schmittbuhl, Jean

2016-04-01

Thermal stressing is common in geothermal environments and has been shown in the laboratory to induce changes in the physical and mechanical properties of rocks. These changes are generally considered to be a consequence of the generation of thermal microcracks and debilitating chemical reactions. Thermal microcracks form as a result of the build-up of internal stresses due to: (1) the thermal expansion mismatch between the different phases present in the material, (2) thermal expansion anisotropy within individual minerals, and (3) thermal gradients. The generation of cracks during thermal stressing has been monitored in previous studies using the output of acoustic emissions (AE), a common proxy for microcrack damage, and through microstructural observations. Here we present a new experimental setup which is optimised to record AE from a rock sample at high temperatures and under a servo-controlled uniaxial stress. The design is such that the AE transducer is embedded in the top of the piston, which acts as a continuous wave guide to the sample. In this way, we simplify the ray path geometry whilst minimising the number of interfaces between the microcrack and the transducer, maximising the quality of the signal. This allows for an in-depth study of waveform attributes such as energy, amplitude, counts and duration. Furthermore, the capability of this device to apply a servo-controlled load on the sample, whilst measuring strain in real time, leads to a spectrum of possible tests combining mechanical and thermal stress. It is also an essential feature to eliminate the build-up of stresses through thermal expansion of the pistons and the sample. We plan a systematic experimental study of the AE of thermally stressed rock during heating and cooling cycles. We present results from pilot tests performed on Darley Dale sandstone and Westerly granite. Understanding the effects of thermal stressing in rock is of particular interest at a geothermal site, where circulating fluids influence the temperature field in the surrounding rock mass. These stresses can, for example, provoke thermal borehole breakouts due to cooling-induced tensile microcracking or may be actively used to enhance the injectivity of geothermal wells.

The influence of laser pulse duration and energy on ICP-MS signal intensity, elemental fractionation, and particle size distribution in NIR fs-LA-ICP-MS

PubMed Central

Diwakar, Prasoon K.; Harilal, Sivanandan S.; LaHaye, Nicole L.; Hassanein, Ahmed; Kulkarni, Pramod

2015-01-01

Laser parameters, typically wavelength, pulse width, irradiance, repetition rate, and pulse energy, are critical parameters which influence the laser ablation process and thereby influence the LA-ICP-MS signal. In recent times, femtosecond laser ablation has gained popularity owing to the reduction in fractionation related issues and improved analytical performance which can provide matrix-independent sampling. The advantage offered by fs-LA is due to shorter pulse duration of the laser as compared to the phonon relaxation time and heat diffusion time. Hence the thermal effects are minimized in fs-LA. Recently, fs-LA-ICP-MS demonstrated improved analytical performance as compared to ns-LA-ICP-MS, but detailed mechanisms and processes are still not clearly understood. Improvement of fs-LA-ICP-MS over ns-LA-ICP-MS elucidates the importance of laser pulse duration and related effects on the ablation process. In this study, we have investigated the influence of laser pulse width (40 fs to 0.3 ns) and energy on LA-ICP-MS signal intensity and repeatability using a brass sample. Experiments were performed in single spot ablation mode as well as rastering ablation mode to monitor the Cu/Zn ratio. The recorded ICP-MS signal was correlated with total particle counts generated during laser ablation as well as particle size distribution. Our results show the importance of pulse width effects in the fs regime that becomes more pronounced when moving from femtosecond to picosecond and nanosecond regimes. PMID:26664120

Thermal diffusivity of alpha-mercuric iodide

NASA Astrophysics Data System (ADS)

Burger, A.; Morgan, S. H.; Henderson, D. O.; Silberman, E.; Nason, D.

1991-01-01

The thermal diffusivity and its anisotropy is measured along the principal axes of tetragonal alpha-HgI2 semiconductor single crystals grown from vapor. The experiments are carried out using the flash pulse method. The results show that alpha(100-line-type) = 0.00370 sq cm/s + or - 3 percent and alpha(001-line-type = 0.00103 sq cm/s + or - 10 percent. Necessary corrections are made for the experimental variables of heat losses and finite pulse duration in the data analysis.

Long duration exposure facility solar illumination data package

NASA Technical Reports Server (NTRS)

Berrios, William M.; Sampair, Thomas

1990-01-01

A post flight solar illumination data package was created by the LDEF thermal analysis data group in support of the LDEF science office data group. The data presented was prepared with the Thermal Radiation Analysis System (TRASYS) program. Ground tracking data was used to calculate daily orbital beta angles for the calculation of resultant fluxes. This data package will be useful in calculation of solar illumination fluent for a variety of beta angle orbital conditions encountered during the LDEF mission.

Life testing of reflowed and reworked advanced CCGA surface mount packages in harsh thermal environments

NASA Astrophysics Data System (ADS)

Ramesham, Rajeshuni

2013-03-01

Life testing/qualification of reflowed (1st reflow) and reworked (1st reflow, 1st removal, and then 1st rework) advanced ceramic column grid array (CCGA) surface mount interconnect electronic packaging technologies for future flight projects has been studied to enhance the mission assurance of JPL-NASA projects. The reliability of reworked/reflowed surface mount technology (SMT) packages is very important for short-duration and long-duration deep space harsh extreme thermal environmental missions. The life testing of CCGA electronic packages under extreme thermal environments (for example: -185°C to +125°C) has been performed with reference to various JPL/NASA project requirements which encompass the temperature range studied. The test boards of reflowed and reworked CCGA packages (717 Xilinx package, 624, 1152, and 1272 column Actel Packages) were selected for the study to survive three times the total number of expected temperature cycles resulting from all environmental and operational exposures occurring over the life of the flight hardware including all relevant manufacturing, ground operations, and mission phases or cycles to failure to assess the life of the hardware. Qualification/life testing was performed by subjecting test boards to the environmental harsh temperature extremes and assessing any structural failures, mechanical failures or degradation in electrical performance solder-joint failures due to either overstress or thermal cycle fatigue. The large, high density, high input/output (I/O) electronic interconnect SMT packages such as CCGA have increased usage in avionics hardware of NASA projects during the last two decades. The test boards built with CCGA packages are expensive and often require a rework to replace a reflowed, reprogrammed, failed, redesigned, etc., CCGA packages. Theoretically speaking, a good rework process should have similar temperature-time profile as that used for the original manufacturing process of solder reflow. A multiple rework processes may be implemented with CCGA packaging technology to understand the effect of number of reworks on the reliability of this technology for harsh thermal environments. In general, reliability of the assembled electronic packages reduces as a function of number of reworks and the extent is not known yet. A CCGA rework process has been tried and implemented to design a daisy-chain test board consists of 624 and 717 packages. Reworked CCGA interconnect electronic packages of printed wiring polyimide boards have been assembled and inspected using non-destructive x-ray imaging and optical microscope techniques. The assembled boards after 1st rework and 1st reflow were subjected to extreme temperature thermal atmospheric cycling to assess their reliability for future deep space JPL/NASA for moderate to harsh thermal mission environments. The resistance of daisy-chained interconnect sections were monitored continuously during thermal cycling to determine intermittent failures. This paper provides the experimental reliability test results to failure of assemblies for the first time of reflowed and reworked CCGA packages under extreme harsh thermal environments.

Efficacy of ketanserin in the therapy of Raynaud's phenomenon: thermometric data.

PubMed

Arosio, E; Montesi, G; Zannoni, M; Perbellini, L; Paluani, F; Lechi, A

1991-05-01

After a two-week washout (WO) period with placebo 1 capsule/bid, 12 patients suffering from stable Raynaud's phenomenon were treated with ketanserin (K) 40 mg/bid for fifteen days. Blood pressure, heart rate, and laboratory parameters were evaluated at the end of each period. Patients used diary cards to record the number, duration, and intensity of attacks. Computerized thermometry of the fingers was evaluated at basal temperature after acclimatization, 23 degrees C for thirty minutes; after cold test, 10 degrees C for five minutes; and after thermal recovery, 23 degrees C for eighteen minutes. Results were analyzed statistically by use of Student's t-test for paired data (p less than 0.05). No marked changes were observed in the symptoms of the attacks, but K proved effective in significantly reducing the number and duration of daily attacks and in promoting their spontaneous regression. Thermometry revealed a parallel increase in temperatures, particularly basal and recovery values. The data suggest increased flow and decreased vasospasm following 5-HT2 receptor blockade.

The effect of temperature and thermal acclimation on the sustainable performance of swimming scup.

PubMed

Rome, Lawrence C

2007-11-29

There is a significant reduction in overall maximum power output of muscle at low temperatures due to reduced steady-state (i.e. maximum activation) power-generating capabilities of muscle. However, during cyclical locomotion, a further reduction in power is due to the interplay between non-steady-state contractile properties of muscle (i.e. rates of activation and relaxation) and the stimulation and the length-change pattern muscle undergoes in vivo. In particular, even though the relaxation rate of scup red muscle is slowed greatly at cold temperatures (10 degrees C), warm-acclimated scup swim with the same stimulus duty cycles at cold as they do at warm temperature, not affording slow-relaxing muscle any additional time to relax. Hence, at 10 degrees C, red muscle generates extremely low or negative work in most parts of the body, at all but the slowest swimming speeds. Do scup shorten their stimulation duration and increase muscle relaxation rate during cold acclimation? At 10 degrees C, electromyography (EMG) duty cycles were 18% shorter in cold-acclimated scup than in warm-acclimated scup. But contrary to the expectations, the red muscle did not have a faster relaxation rate, rather, cold-acclimated muscle had an approximately 50% faster activation rate. By driving cold- and warm-acclimated muscle through cold- and warm-acclimated conditions, we found a very large increase in red muscle power during swimming at 10 degrees C. As expected, reducing stimulation duration markedly increased power output. However, the increased rate of activation alone produced an even greater effect. Hence, to fully understand thermal acclimation, it is necessary to examine the whole system under realistic physiological conditions.

Evaluation of the analgesic effects of oral and subcutaneous tramadol administration in red-eared slider turtles

PubMed Central

Baker, Bridget B.; Sladky, Kurt K.; Johnson, Stephen M.

2011-01-01

Objective To determine the dose- and time-dependent changes in analgesia and respiration caused by tramadol administration in red-eared slider turtles (Trachemys scripta). Design Crossover study. Animals 30 adult male and female red-eared slider turtles. Procedures 11 turtles received tramadol at various doses (1, 5, 10, or 25 mg/kg [0.45, 2.27, 4.54, or 11.36 mg/lb], PO; 10 or 25 mg/kg, SC) or a control treatment administered similarly. Degree of analgesia was assessed through measurement of hind limb thermal withdrawal latencies (TWDLs) at 0, 3, 6, 12, 24, 48, 72, and 96 hours after tramadol administration. Nineteen other freely swimming turtles received tramadol PO (5, 10, or 25 mg/kg), and ventilation (VE), breath frequency, tidal volume (VT and expiratory breath duration were measured. Results The highest tramadol doses (10 and 25 mg/kg, PO) yielded greater mean TWDLs 6 to 96 hours after administration than the control treatment did, whereas tramadol administered at 5 mg/kg, PO, yielded greater mean TWDLs at 12 and 24 hours. The lowest tramadol dose (1 mg/kg, PO) failed to result in analgesia. Tramadol administered SC resulted in lower TWDLs, slower onset, and shorter duration of action, compared with PO administration. Tramadol at 10 and 25 mg/kg, PO, reduced the VE at 12 hours by 51% and 67%, respectively, and at 24 through 72 hours by 55% to 62% and 61% to 70%, respectively. However, tramadol at 5 mg/kg, PO, had no effect on the VE. Conclusions and Clinical Relevance Tramadol administered PO at 5 to 10 mg/kg provided thermal analgesia with less respiratory depression than that reported for morphine in red-eared slider turtles. PMID:21235376

Optoacoustic monitoring of cutting efficiency and thermal damage during laser ablation.

PubMed

Bay, Erwin; Douplik, Alexandre; Razansky, Daniel

2014-05-01

Successful laser surgery is characterized by a precise cut and effective hemostasis with minimal collateral thermal damage to the adjacent tissues. Consequently, the surgeon needs to control several parameters, such as power, pulse repetition rate, and velocity of movements. In this study we propose utilizing optoacoustics for providing the necessary real-time feedback of cutting efficiency and collateral thermal damage. Laser ablation was performed on a bovine meat slab using a Q-switched Nd-YAG laser (532 nm, 4 kHz, 18 W). Due to the short pulse duration of 7.6 ns, the same laser has also been used for generation of optoacoustic signals. Both the shockwaves, generated due to tissue removal, as well as the normal optoacoustic responses from the surrounding tissue were detected using a single broadband piezoelectric transducer. It has been observed that the rapid reduction in the shockwave amplitude occurs as more material is being removed, indicating decrease in cutting efficiency, whereas gradual decrease in the optoacoustic signal likely corresponds to coagulation around the ablation crater. Further heating of the surrounding tissue leads to carbonization accompanied by a significant shift in the optoacoustic spectra. Our results hold promise for real-time monitoring of cutting efficiency and collateral thermal damage during laser surgery. In practice, this could eventually facilitate development of automatic cut-off mechanisms that will guarantee an optimal tradeoff between cutting and heating while avoiding severe thermal damage to the surrounding tissues.

A randomized trial of prewarming on patient satisfaction and thermal comfort in outpatient surgery.

PubMed

Akhtar, Zohaib; Hesler, Brian D; Fiffick, Alexa N; Mascha, Edward J; Sessler, Daniel I; Kurz, Andrea; Ayad, Sabry; Saager, Leif

2016-09-01

To test the primary hypothesis that forced-air prewarming improves patient satisfaction after outpatient surgery and to evaluate the effect on core temperature and thermal comfort. Prospective randomized controlled trial. Preoperative area, operating room, and postanesthesia care unit. A total of 115 patients aged 18 to 75 years with American Society of Anesthesiologists status <4 and body mass index of 15 to 36kg/m(2) who were undergoing outpatient surgery (duration <4 hours). Patients were randomized to active prewarming with a Mistral-Air warming system initially set to 43°C or no active prewarming. All patients were warmed intraoperatively. Demographic and morphometric characteristics, perioperative core temperature, ambient temperature, EVAN-G satisfaction score, thermal comfort via visual analog scales. Data from 102 patients were included in the final analysis. Prewarming did not significantly reduce redistribution hypothermia, with prewarmed minus not prewarmed core temperature differing by only 0.18°C (95% confidence interval [CI], -0.001 to 0.37) during the initial hour of anesthesia (P=.052). Prewarming increased the mean EVAN-G satisfaction score, although not significantly, with an overall difference (prewarmed minus not prewarmed) of 5.6 (95% CI, -0.9 to 12.2; P=.09). Prewarming increased thermal comfort, with an overall difference of 6.6 mm (95% CI, 1.0-12.9; P=.02). Active prewarming increased thermal comfort but did not significantly reduce redistribution hypothermia or improve postoperative patient satisfaction. Copyright © 2016 Elsevier Inc. All rights reserved.

Second LDEF Post-Retrieval Symposium interim results of experiment A0034

NASA Technical Reports Server (NTRS)

Linton, Roger C.; Kamenetzky, Rachel R.

1993-01-01

Thermal control coatings and contaminant collector mirrors were exposed on the leading and trailing edge modules of Long Duration Exposure Facility (LDEF) experiment A0034 to provide a basis of comparison for investigating the role of atomic oxygen in the stimulation of volatile outgassing products. The exposure of identical thermal coatings on both the leading and trailing edges of the LDEF and the additional modified exposure of identical coatings under glass windows and metallic covers in each of the flight modules provided multiple combinations of space environmental exposure to the coatings and the contaminant collector mirrors. Investigations were made to evaluate the effects of the natural space and the induced environments on the thermal coatings and the collector mirrors to differentiate the sources of observed material degradation. Two identical flight units were fabricated for the LDEF mission, each of which included twenty-five thermal control coatings mounted in isolated compartments, each with an adjacent contaminant collector mirror mounted on the wall. The covers of the flight units included apertures for each compartment, exposing the thermal coatings directly to the space environment. Six of these compartments were sealed with ultraviolet-grade transmitting quartz windows and four other compartments were sealed with aluminum covers. One module of this passive LDEF experiment, occupying one-sixth of a full tray, was mounted in Tray C9 (leading edge), while the other identical module was mounted in Tray C3 (trailing edge).

Thick thermal barrier coatings for diesel components

NASA Technical Reports Server (NTRS)

Yonushonis, T. M.

1991-01-01

An engineered thick thermal barrier coating consisting of multiple layers of zirconia and CoCrAlY with a zirconia top layer and having a system thermal conductance less than 410 w/m(exp 2)K exceeded the 100 hour engine durability goals set forth in this program. The thermal barrier coatings were intact at the test conclusion. Back to back single cylinder research engine tests were conducted with watercooled, metal hardware and oil-cooled, thermal barrier coating insulated hardware to determine apparent heat release and fuel economy. Apparent heat release data revealed that the insulated engine had a shorter ignition delay and a longer combustion duration than the metal engine. The insulated engine fuel economy was approximately two percent worse on average for this series of tests. There was no attempt to optimize engine efficiency of the insulated engine by modifying the engine timing, coating, or other techniques.

The effects of poly-unsaturated fatty acids on the physiology of hibernation in a South American marsupial, Dromiciops gliroides.

PubMed

Contreras, Carolina; Franco, Marcela; Place, Ned J; Nespolo, Roberto F

2014-11-01

Many mammals hibernate, which is a profound lethargic state of several weeks or months during winter, that represents a transitory episode of hetherothermy. As with other cases of dormancy, the main benefit of hibernation seems to be energy saving. However, the depth and duration of torpor can be experimentally modified by the composition of food, especially by fattyacid composition. In eutherians, diets rich in unsaturated fatty acids (i.e., fatty acids with at least one double bond) lengthen torpor, reduce metabolism and permit hibernation at lower temperatures. Here we studied whether diets varying in fatty acid composition have an effect on the physiology of hibernation in a South American marsupial, Dromiciops gliroides. We designed a factorial experiment where thermal acclimation (two levels: natural versus constant temperature) was combined with diet acclimation: saturated (i.e., diets with high concentration of saturated fatty acids) versus unsaturated (i.e., diets with high concentration of unsaturated fatty acids). We measured energy metabolism in active and torpid individuals, as well as torpor duration, and a suite of 12 blood biochemical parameters. After a cafeteria test, we found that D. gliroides did not show any preference for a given diet. Also, we did not find effects of diet on body temperature during torpor, or its duration. However, saturated diets, combined with high temperatures provoked a disproportionate increase in fat utilization, leading to body mass reduction. Those animals were more active, and metabolized more fats than those fed with a high proportion of unsaturated fatty acids (="unsaturated diets"). These results contrast with previous studies, which showed a significant effect of fatty acid composition of diets on food preferences and torpor patterns in mammals. Copyright © 2014 Elsevier Inc. All rights reserved.

First Stage Solid Propellant Multi Debris Thermal Analysis

NASA Technical Reports Server (NTRS)

Toleman, Benjamin M.

2011-01-01

The crew launch vehicle considered for the Constellation (Cx) Program utilizes a first stage solid rocket motor. If an abort is initiated in first stage flight the Crew Module (CM) will separate and be pulled away from the launch vehicle via a Launch Abort System (LAS) in order to safely and quickly carry the crew away from the malfunction launch vehicle. Having aborted the mission, the launch vehicle will likely be destroyed via a Flight Termination System (FTS) in order to prevent it from errantly traversing back over land and posing a risk to the public. The resulting launch vehicle debris field, composed primarily of first stage solid propellant, poses a threat to the CM. The harsh radiative thermal environment induced by surrounding burning propellant debris may lead to CM parachute failure. A methodology, detailed herein, has been developed to address this concern and quantify the risk of first stage propellant debris leading to radiative thermal demise of the CM parachutes. Utilizing basic thermal radiation principles, a software program was developed to calculate parachute temperature as a function of time for a given abort trajectory and debris piece trajectory set. Two test cases, considered worst-case aborts with regard to launch vehicle debris environments, were analyzed using the simulation: an abort declared at Mach 1 and an abort declared at maximum dynamic pressure (Max Q). For both cases, the resulting temperature profiles indicated that thermal limits for the parachutes were not exceeded. However, short duration close encounters by single debris pieces did have a significant effect on parachute temperature, with magnitudes on the order of 10 s of degrees Fahrenheit. Therefore while these two test cases did not indicate exceedance of thermal limits, in order to quantify the risk of parachute failure due to radiative effects from the abort environment, a more thorough probability-based analysis using the methodology demonstrated herein must be performed.

Ecological traps in shallow coastal waters—Potential effect of heat-waves in tropical and temperate organisms

PubMed Central

Mendonça, Vanessa; Cereja, Rui; Abreu-Afonso, Francisca; Dias, Marta; Mizrahi, Damián; Flores, Augusto A. V.

2018-01-01

Mortality of fish has been reported in tide pools during warm days. That means that tide pools are potential ecological traps for coastal organisms, which happen when environmental changes cause maladaptive habitat selection. Heat-waves are predicted to increase in intensity, duration and frequency, making it relevant to investigate the role of tide pools as traps for coastal organisms. However, heat waves can also lead to acclimatization. If organisms undergo acclimatization prior to being trapped in tide pools, their survival chances may increase. Common tide pool species (46 species in total) were collected at a tropical and a temperate area and their upper thermal limits estimated. They were maintained for 10 days at their mean summer sea surface temperature +3°C, mimicking a heat-wave. Their upper thermal limits were estimated again, after this acclimation period, to calculate each species’ acclimation response. The upper thermal limits of the organisms were compared to the temperatures attained by tide pool waters to investigate if 1) tide pools could be considered ecological traps and 2) if the increase in upper thermal limits elicited by the acclimation period could make the organisms less vulnerable to this threat. Tropical tide pools were found to be ecological traps for an important number of common coastal species, given that they can attain temperatures higher than the upper thermal limits of most of those species. Tide pools are not ecological traps in temperate zones. Tropical species have higher thermal limits than temperate species, but lower acclimation response, that does not allow them to survive the maximum habitat temperature of tropical tide pools. This way, tropical coastal organisms seem to be, not only more vulnerable to climate warming per se, but also to an increase in the ecological trap effect of tide pools. PMID:29420657

Long Duration Exposure Facility (LDEF) preliminary findings: LEO space effects on the space plasma-voltage drainage experiment

NASA Technical Reports Server (NTRS)

Blakkolb, Brian K.; Yaung, James Y.; Henderson, Kelly A.; Taylor, William W.; Ryan, Lorraine E.

1992-01-01

The Space Plasma-High Voltage Drainage Experiment (SP-HVDE) provided a unique opportunity to study long term space environmental effects on materials because it was comprised of two identical experimental trays; one tray located on the ram facing side (D-10), and the other on the wake facing side (B-4) of the LDEF. This configuration allows for the comparison of identical materials exposed to two distinctly different environments. The purpose of this work is to document an assessment of the effects of five and three quarters years of low Earth orbital space exposure on materials comprising the SP-HVDE (experiment no. A0054). The findings of the materials investigation reported focus on atomic oxygen effects, micrometeor and debris impact site documentation, thermal property measurements, and environmentally induced contamination.

Cracking of a layered medium on an elastic foundation under thermal shock

NASA Technical Reports Server (NTRS)

Rizk, Abd El-Fattah A.; Erdogan, Fazil

1988-01-01

The cladded pressure vessel under thermal shock conditions which is simulated by using two simpler models was studied. The first model (Model 1) assumes that, if the crack size is very small compared to the vessel thickness, the problem can be treated as a semi-infinite elastic medium bonded to a very thin layer of different material. However, if the crack size is of the same order as the vessel thickness, the curvature effects may not be negligible. In this case it is assumed that the relatively thin walled hollow cylinder with cladding can be treated as a composite beam on an elastic foundation (Model 2). In both models, the effect of surface cooling rate is studied by assuming the temperature boundary condition to be a ramp function. The calculated results include the transient temperature, thermal stresses in the uncracked medium and stress intensity factors which are presented as a function of time, and the duration of cooling ramp. The stress intensity factors are also presented as a function of the size and the location of the crack. The problem is solved for two bonded materials of different thermal and mechanical properties. The mathematical formulation results in two singular integral equations which are solved numerically. The results are given for two material pairs, namely an austenitic steel layer welded on a ferritic steel substrate, and a ceramic coating on ferritic steel. In the case of the yielded clad, the stress intensity factors for a crack under the clad are determined by using a plastic strip model and are compared with elastic clad results.

Studies of the influence of nonequilibrium plasma thermal exposure on the characteristics of the capillary-porous polymer material

NASA Astrophysics Data System (ADS)

Makhotkina, L. Yu; Khristoliubova, V. I.

2017-01-01

Capillary-porous materials, which include natural macromolecular tanning material, are exposed to a number of factors during the treatment by a nonequilibrium plasma. Plasma particles exchange the charge and energy with the atoms of the material during the interaction of the plasma with the surface. The results of treatment are desorption of atoms and molecules from the body surface, sputtering and evaporation of material’s particles, changes of the structure and phase state. In real terms during the modification of solids by nonequilibrium low-temperature plasma thermal effect influences the process. The energy supplied from the discharge during the process with low pressure, which is converted into heat, is significantly less than during the atmospheric pressure, but the thermal stability of high-molecular compounds used in the manufacture of materials and products of the tanning industry, is very limited and depends on the duration of the effect of temperature. Even short heating of hydrophilic polymers (proteins) (100-180 °C) causes a change in their properties. It decreases the collagen ability to absorb water vapor, to swell in water, acids, alkalis, and thus decreases their durability. Prolonged heating leads to a deterioration of the physical and mechanical properties. Higher heating temperatures it leads to the polymer degradation. The natural leather temperature during plasma exposure does not rise to a temperature of collagen degradation and does not result in changes of physical phase of the dermis. However, the thermal plasma exposure must be considered, since the high temperatures influence on physical and mechanical properties.

Modified Johnson-Cook model incorporated with electroplasticity for uniaxial tension under a pulsed electric current

NASA Astrophysics Data System (ADS)

Kim, Moon-Jo; Jeong, Hye-Jin; Park, Ju-Won; Hong, Sung-Tae; Han, Heung Nam

2018-01-01

An empirical expression describing the electroplastic deformation behavior is suggested based on the Johnson-Cook (JC) model by adding several functions to consider both thermal and athermal electric current effects. Tensile deformation behaviors are carried out for an AZ31 magnesium alloy and an Al-Mg-Si alloy under pulsed electric current at various current densities with a fixed duration of electric current. To describe the flow curves under electric current, a modified JC model is proposed to take the electric current effect into account. Phenomenological descriptions of the adopted parameters in the equation are made. The modified JC model suggested in the present study is capable of describing the tensile deformation behaviors under pulsed electric current reasonably well.

The effect of insulated combustion chamber surfaces on direct-injected diesel engine performance, emissions, and combustion

NASA Technical Reports Server (NTRS)

Dickey, Daniel W.; Vinyard, Shannon; Keribar, Rifat

1988-01-01

The combustion chamber of a single-cylinder, direct-injected diesel engine was insulated with ceramic coatings to determine the effect of low heat rejection (LHR) operation on engine performance, emissions, and combustion. In comparison to the baseline cooled engine, the LHR engine had lower thermal efficiency, with higher smoke, particulate, and full load carbon monoxide emissions. The unburned hydrocarbon emissions were reduced across the load range. The nitrous oxide emissions increased at some part-load conditions and were reduced slightly at full loads. The poor LHR engine performance was attributed to degraded combustion characterized by less premixed burning, lower heat release rates, and longer combustion duration compared to the baseline cooled engine.

Temperature measurement by thermal strain imaging with diagnostic power ultrasound, with potential for thermal index determination.

PubMed

Liang, Hai-Dong; Zhou, Li-Xia; Wells, Peter N T; Halliwell, Michael

2009-05-01

Over the years, there has been a substantial increase in acoustic exposure in diagnostic ultrasound as new imaging modalities with higher intensities and frame rates have been introduced; and more electronic components have been packed into the probe head, so that there is a tendency for it to become hotter. With respect to potential thermal effects, including those which may be hazardous occurring during ultrasound scanning, there is a correspondingly growing need for in vivo techniques to guide the operator as to the actual temperature rise occurring in the examined tissues. Therefore, an in vivo temperature estimator would be of considerable practical value. The commonly-used method of tissue thermal index (TI) measurement with a hydrophone in water could underestimate the actual value of TI (in one report by as much as 2.9 times). To obtain meaningful results, it is necessary to map the temperature elevation in 2-D (or 3-D) space. We present methodology, results and validation of a 2-D spatial and temporal thermal strain ultrasound temperature estimation technique in phantoms, and its apparently novel application in tracking the evolution of heat deposition at diagnostic exposure levels. The same ultrasound probe is used for both transmission and reception. The displacement and thermal strain estimation methods are similar to those used in high-intensity focused ultrasound thermal monitoring. The use of radiofrequency signals permits the application of cross correlation as a similarity measurement for tracking feature displacement. The displacement is used to calculate the thermal strain directly related to the temperature rise. Good agreement was observed between the temperature rise and the ultrasound power and scan duration. Thermal strain up to 1.4% was observed during 4000-s scan. Based on the results obtained for the temperature range studied in this work, the technique demonstrates potential for applicability in phantom (and possibly in vivo tissue) temperature measurement for the determination of TI.

Acute thermal stressor increases glucocorticoid response but minimizes testosterone and locomotor performance in the cane toad (Rhinella marina).

PubMed

Narayan, Edward J; Hero, Jean-Marc

2014-01-01

Climatic warming is a global problem and acute thermal stressor in particular could be considered as a major stressor for wildlife. Cane toads (Rhinella marina) have expanded their range into warmer regions of Australia and they provide a suitable model species to study the sub-lethal impacts of thermal stressor on the endocrine physiology of amphibians. Presently, there is no information to show that exposure to an acute thermal stressor could initiate a physiological stress (glucocorticoid) response and secondly, the possible effects on reproductive hormones and performance. Answering these questions is important for understanding the impacts of extreme temperature on amphibians. In this study, we experimented on cane toads from Queensland, Australia by acclimating them to mildly warm temperature (25°C) and then exposing to acute temperature treatments of 30°, 35° or 40°C (hypothetical acute thermal stressors). We measured acute changes in the stress hormone corticosterone and the reproductive hormone testosterone using standard capture and handling protocol and quantified the metabolites of both hormones non-invasively using urinary enzyme-immunoassays. Furthermore, we measured performance trait (i.e. righting response score) in the control acclimated and the three treatment groups. Corticosterone stress responses increased in all toads during exposure to an acute thermal stressor. Furthermore, exposure to a thermal stressor also decreased testosterone levels in all toads. The duration of the righting response (seconds) was longer for toads that were exposed to 40°C than to 30°, 35° or 25°C. The increased corticosterone stress response with increased intensity of the acute thermal stressor suggests that the toads perceived this treatment as a stressor. Furthermore, the results also highlight a potential trade-off with performance and reproductive hormones. Ultimately, exposure acute thermal stressors due to climatic variability could impact amphibians at multiple eco-physiological levels through impacts on endocrine physiology, performance and potentially fitness traits (e.g. reproductive output).

Acute Thermal Stressor Increases Glucocorticoid Response but Minimizes Testosterone and Locomotor Performance in the Cane Toad (Rhinella marina)

PubMed Central

Narayan, Edward J.; Hero, Jean-Marc

2014-01-01

Climatic warming is a global problem and acute thermal stressor in particular could be considered as a major stressor for wildlife. Cane toads (Rhinella marina) have expanded their range into warmer regions of Australia and they provide a suitable model species to study the sub-lethal impacts of thermal stressor on the endocrine physiology of amphibians. Presently, there is no information to show that exposure to an acute thermal stressor could initiate a physiological stress (glucocorticoid) response and secondly, the possible effects on reproductive hormones and performance. Answering these questions is important for understanding the impacts of extreme temperature on amphibians. In this study, we experimented on cane toads from Queensland, Australia by acclimating them to mildly warm temperature (25°C) and then exposing to acute temperature treatments of 30°, 35° or 40°C (hypothetical acute thermal stressors). We measured acute changes in the stress hormone corticosterone and the reproductive hormone testosterone using standard capture and handling protocol and quantified the metabolites of both hormones non-invasively using urinary enzyme-immunoassays. Furthermore, we measured performance trait (i.e. righting response score) in the control acclimated and the three treatment groups. Corticosterone stress responses increased in all toads during exposure to an acute thermal stressor. Furthermore, exposure to a thermal stressor also decreased testosterone levels in all toads. The duration of the righting response (seconds) was longer for toads that were exposed to 40°C than to 30°, 35° or 25°C. The increased corticosterone stress response with increased intensity of the acute thermal stressor suggests that the toads perceived this treatment as a stressor. Furthermore, the results also highlight a potential trade-off with performance and reproductive hormones. Ultimately, exposure acute thermal stressors due to climatic variability could impact amphibians at multiple eco-physiological levels through impacts on endocrine physiology, performance and potentially fitness traits (e.g. reproductive output). PMID:24643017

Direct thermal effects of the Hadean bombardment did not limit early subsurface habitability

NASA Astrophysics Data System (ADS)

Grimm, R. E.; Marchi, S.

2018-03-01

Intense bombardment is considered characteristic of the Hadean and early Archean eons, yet some detrital zircons indicate that near-surface water was present and thus at least intervals of clement conditions may have existed. We investigate the habitability of the top few kilometers of the subsurface by updating a prior approach to thermal evolution of the crust due to impact heating, using a revised bombardment history, a more accurate thermal model, and treatment of melt sheets from large projectiles (>100 km diameter). We find that subsurface habitable volume grows nearly continuously throughout the Hadean and early Archean (4.5-3.5 Ga) because impact heat is dissipated rapidly compared to the total duration and waning strength of the bombardment. Global sterilization was only achieved using an order of magnitude more projectiles in 1/10 the time. Melt sheets from large projectiles can completely resurface the Earth several times prior to ∼4.2 Ga but at most once since then. Even in the Hadean, melt sheets have little effect on habitability because cooling times are short compared to resurfacing intervals, allowing subsurface biospheres to be locally re-established by groundwater infiltration between major impacts. Therefore the subsurface is always habitable somewhere, and production of global steam or silicate-vapor atmospheres are the only remaining avenues to early surface sterilization by bombardment.

Squeezed states and graviton-entropy production in the early universe

NASA Technical Reports Server (NTRS)

Giovannini, Massimo

1994-01-01

Squeezed states are a very useful framework for the quantum treatment of tensor perturbations (i.e. gravitons production) in the early universe. In particular, the non equilibrium entropy growth in a cosmological process of pair production is completely determined by the associated squeezing parameter and is insensitive to the number of particles in the initial state. The total produced entropy may represent a significant fraction of the entropy stored today in the cosmic blackbody radiation, provided pair production originates from a change in the background metric at a curvature scale of the Planck order. Within the formalism of squeezed thermal states it is also possible to discuss the stimulated emission of gravitons from an initial thermal bath, under the action of the cosmic gravitational background field. We find that at low energy the graviton production is enhanced, if compared with spontaneous creation from the vacuum; as a consequence, the inflation scale must be lowered, in order not to exceed the observed CMB quadrupole anisotropy. This effect is important, in particular, for models based on a symmetry-breaking transition which require, as initial condition, a state of thermal equilibrium at temperatures higher than the inflation scale and in which inflation has a minimal duration.

Thermal Vacuum Facility for Testing Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Daryabeigi, Kamran; Knutson, Jeffrey R.; Sikora, Joseph G.

2002-01-01

A thermal vacuum facility for testing launch vehicle thermal protection systems by subjecting them to transient thermal conditions simulating re-entry aerodynamic heating is described. Re-entry heating is simulated by controlling the test specimen surface temperature and the environmental pressure in the chamber. Design requirements for simulating re-entry conditions are briefly described. A description of the thermal vacuum facility, the quartz lamp array and the control system is provided. The facility was evaluated by subjecting an 18 by 36 in. Inconel honeycomb panel to a typical re-entry pressure and surface temperature profile. For most of the test duration, the average difference between the measured and desired pressures was 1.6% of reading with a standard deviation of +/- 7.4%, while the average difference between measured and desired temperatures was 7.6% of reading with a standard deviation of +/- 6.5%. The temperature non-uniformity across the panel was 12% during the initial heating phase (t less than 500 sec.), and less than 2% during the remainder of the test.

Evaporative cooling by a pulsed jet spray of binary ethanol-water mixture

NASA Astrophysics Data System (ADS)

Karpov, P. N.; Nazarov, A. D.; Serov, A. F.; Terekhov, V. I.

2015-07-01

We have experimentally studied the heat transfer under conditions of pulsed multinozzle jet spray impact onto a vertical surface. The working coolant fluid was aqueous ethanol solution in a range of concentrations K 1 = 0-96%. The duration of spray pulses was τ = 2, 4, and 10 ms at a repetition frequency of 10 Hz. The maximum heat transfer coefficient was achieved at an ethanol solution concentration within 50-60%. The thermal efficiency of pulsed spray cooling grows with increasing ethanol concentration and decreasing jet spray pulse duration.

Thermal Infrared Anomalies of Several Strong Earthquakes

PubMed Central

Wei, Congxin; Guo, Xiao; Qin, Manzhong

2013-01-01

In the history of earthquake thermal infrared research, it is undeniable that before and after strong earthquakes there are significant thermal infrared anomalies which have been interpreted as preseismic precursor in earthquake prediction and forecasting. In this paper, we studied the characteristics of thermal radiation observed before and after the 8 great earthquakes with magnitude up to Ms7.0 by using the satellite infrared remote sensing information. We used new types of data and method to extract the useful anomaly information. Based on the analyses of 8 earthquakes, we got the results as follows. (1) There are significant thermal radiation anomalies before and after earthquakes for all cases. The overall performance of anomalies includes two main stages: expanding first and narrowing later. We easily extracted and identified such seismic anomalies by method of “time-frequency relative power spectrum.” (2) There exist evident and different characteristic periods and magnitudes of thermal abnormal radiation for each case. (3) Thermal radiation anomalies are closely related to the geological structure. (4) Thermal radiation has obvious characteristics in abnormal duration, range, and morphology. In summary, we should be sure that earthquake thermal infrared anomalies as useful earthquake precursor can be used in earthquake prediction and forecasting. PMID:24222728

Thermal infrared anomalies of several strong earthquakes.

PubMed

Wei, Congxin; Zhang, Yuansheng; Guo, Xiao; Hui, Shaoxing; Qin, Manzhong; Zhang, Ying

2013-01-01

In the history of earthquake thermal infrared research, it is undeniable that before and after strong earthquakes there are significant thermal infrared anomalies which have been interpreted as preseismic precursor in earthquake prediction and forecasting. In this paper, we studied the characteristics of thermal radiation observed before and after the 8 great earthquakes with magnitude up to Ms7.0 by using the satellite infrared remote sensing information. We used new types of data and method to extract the useful anomaly information. Based on the analyses of 8 earthquakes, we got the results as follows. (1) There are significant thermal radiation anomalies before and after earthquakes for all cases. The overall performance of anomalies includes two main stages: expanding first and narrowing later. We easily extracted and identified such seismic anomalies by method of "time-frequency relative power spectrum." (2) There exist evident and different characteristic periods and magnitudes of thermal abnormal radiation for each case. (3) Thermal radiation anomalies are closely related to the geological structure. (4) Thermal radiation has obvious characteristics in abnormal duration, range, and morphology. In summary, we should be sure that earthquake thermal infrared anomalies as useful earthquake precursor can be used in earthquake prediction and forecasting.

Die Attachment for -120 C to +20 C Thermal Cycling of Microelectronics for Future Mars Rovers: An Overview

NASA Technical Reports Server (NTRS)

Kirschman, Randall K.; Sokolowski, Witold M.; Kolawa, Elizabeth A.

1999-01-01

Active thermal control for electronics on Mars Rovers imposes a serious penalty in weight, volume, power consumption, and reliability. Thus, we propose that thermal control be eliminated for future Rovers. From a functional standpoint there is no reason that the electronics could not operate over the entire temperature range of the Martian environment, which can vary from a low of approximately equal -90 C to a high of approximately equal +20 C during the Martian night and day. The upper end of this range is well within that for conventional electronics. Although the lower end is considerably below that for which conventional--even high-reliability electronics is designed or tested, it is well established that electronic devices can operate to such low temperatures. The primary concern is reliability of the overall electronic system, especially in regard to the numerous daily temperature cycles that it would experience over the duration of a mission on Mars. Accordingly, key reliability issues have been identified for elimination of thermal control on future Mars Rovers. One of these is attachment of semiconductor die onto substrates and into packages. Die attachment is critical since it forms a mechanical, thermal and electrical interface between the electronic device and the substrate or package. This paper summarizes our initial investigation of existing information related to this issue, in order to form an opinion whether die attachment techniques exist, or could be developed with reasonable effort, to withstand the Mars thermal environment for a mission duration of approximately I year. Our conclusion, from a review of literature and personal contacts. is that die attachment can be made sufficiently reliable to satisfy the requirements of future Mars Rovers. Moreover, it appears that there are several possible techniques from which to choose and that the requirements could be met by judicious selection from existing methods using hard solders, soft solders, or organic adhesives. Thus from the standpoint of die attachment. it appears feasible to eliminate thermal control for Rover electronics. We recommend that this be further investigated and verified for the specific hardware and thermal conditions appropriate to Mars Rovers.

Can temperate insects take the heat? A case study of the physiological and behavioural responses in a common ant, Iridomyrmex purpureus (Formicidae), with potential climate change.

PubMed

Andrew, Nigel R; Hart, Robert A; Jung, Myung-Pyo; Hemmings, Zac; Terblanche, John S

2013-09-01

Insects in temperate regions are predicted to be at low risk of climate change relative to tropical species. However, these assumptions have generally been poorly examined in all regions, and such forecasting fails to account for microclimatic variation and behavioural optimisation. Here, we test how a population of the dominant ant species, Iridomyrmex purpureus, from temperate Australia responds to thermal stress. We show that ants regularly forage for short periods (minutes) at soil temperatures well above their upper thermal limits (upper lethal temperature = 45.8 ± 1.3°C; CT(max) = 46.1°C) determined over slightly longer periods (hours) and do not show any signs of a classic thermal performance curve in voluntary locomotion across soil surface temperatures of 18.6-57°C (equating to a body temperature of 24.5-43.1°C). Although ants were present all year round, and dynamically altered several aspects of their thermal biology to cope with low temperatures and seasonal variation, temperature-dependence of running speed remained invariant and ants were unable to elevate high temperature tolerance using plastic responses. Measurements of microclimate temperature were higher than ant body temperatures during the hottest part of the day, but exhibited a stronger relationship with each other than air temperatures from the closest weather station. Generally close associations of ant activity and performance with microclimatic conditions, possibly to maximise foraging times, suggest I. purpureus displays highly opportunistic thermal responses and readily adjusts behaviour to cope with high trail temperatures. Increasing frequency or duration of high temperatures is therefore likely to result in an immediate reduction in foraging efficiency. In summary, these results suggest that (1) soil-dwelling temperate insect populations may be at higher risks of thermal stress with increased frequency or duration of high temperatures resulting from climate change than previously thought, however, behavioural cues may be able to compensate to some extent; and (2) indices of climate change-related thermal stress, warming tolerance and thermal safety margin, are strongly influenced by the scale of climate metrics employed. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effect of Random Thermal Spikes on Stirling Convertor Heater Head Reliability

NASA Technical Reports Server (NTRS)

Shah, Ashwin R.; Korovaichuk, Igor; Halford, Gary R.

2004-01-01

Onboard radioisotope power systems being developed to support future NASA exploration missions require reliable design lifetimes of up to 14 yr and beyond. The structurally critical heater head of the high-efficiency developmental Stirling power convertor has undergone extensive computational analysis of operating temperatures (up to 650 C), stresses, and creep resistance of the thin-walled Inconel 718 bill of material. Additionally, assessment of the effect of uncertainties in the creep behavior of the thin-walled heater head, the variation in the manufactured thickness, variation in control temperature, and variation in pressure on the durability and reliability were performed. However, it is possible for the heater head to experience rare incidences of random temperature spikes (excursions) of short duration. These incidences could occur randomly with random magnitude and duration during the desired mission life. These rare incidences could affect the creep strain rate and therefore the life. The paper accounts for these uncertainties and includes the effect of such rare incidences, random in nature, on the reliability. The sensitivities of variables affecting the reliability are quantified and guidelines developed to improve the reliability are outlined. Furthermore, the quantified reliability is being verified with test data from the accelerated benchmark tests being conducted at the NASA Glenn Research Center.

Fast round-trip Mars trajectories

NASA Technical Reports Server (NTRS)

Wilson, Sam

1990-01-01

This paper is concerned with the effect of limiting the overall duration or else the one-way flight time of a round trip to Mars, as reflected in the sum of impulsive velocity increments required of the spacecraft propulsion system. Ignition-to-burnout mass ratios for a hypothetical single stage spacecraft, obtained from the rocket equation by combining these delta-V sums with appropriate values of specific impulse, are used to evaluate the relative effectiveness of four high-thrust propulsion alternatives. If the flight crew goes to the surface of Mars and stays there for the duration of their stopover, it is much cheaper (in terms of delta-V) to minimize their zero-g exposure by limiting the interplanetary transit time of a conjunction-class mission (round trip time = 800-1000 days, Mars stopover = 450-700 days) than to impose the same limit on an opposition-class mission (round trip time less than 600 days, stopover = 40 days). Using solid-core nuclear thermal propulsion to fly a conjunction-class mission, for a moderate mass penalty the interplanetary transit time (each way) probably could be limited to something in the range of 4 to 6 months, depending on the launch year.

An ultra-stable single-chain insulin analog resists thermal inactivation and exhibits biological signaling duration equivalent to the native protein.

PubMed

Glidden, Michael D; Aldabbagh, Khadijah; Phillips, Nelson B; Carr, Kelley; Chen, Yen-Shan; Whittaker, Jonathan; Phillips, Manijeh; Wickramasinghe, Nalinda P; Rege, Nischay; Swain, Mamuni; Peng, Yi; Yang, Yanwu; Lawrence, Michael C; Yee, Vivien C; Ismail-Beigi, Faramarz; Weiss, Michael A

2018-01-05

Thermal degradation of insulin complicates its delivery and use. Previous efforts to engineer ultra-stable analogs were confounded by prolonged cellular signaling in vivo , of unclear safety and complicating mealtime therapy. We therefore sought an ultra-stable analog whose potency and duration of action on intravenous bolus injection in diabetic rats are indistinguishable from wild-type (WT) insulin. Here, we describe the structure, function, and stability of such an analog, a 57-residue single-chain insulin (SCI) with multiple acidic substitutions. Cell-based studies revealed native-like signaling properties with negligible mitogenic activity. Its crystal structure, determined as a novel zinc-free hexamer at 2.8 Å, revealed a native insulin fold with incomplete or absent electron density in the C domain; complementary NMR studies are described in the accompanying article. The stability of the analog (Δ G U 5.0(±0.1) kcal/mol at 25 °C) was greater than that of WT insulin (3.3(±0.1) kcal/mol). On gentle agitation, the SCI retained full activity for >140 days at 45 °C and >48 h at 75 °C. These findings indicate that marked resistance to thermal inactivation in vitro is compatible with native duration of activity in vivo Further, whereas WT insulin forms large and heterogeneous aggregates above the standard 0.6 mm pharmaceutical strength, perturbing the pharmacokinetic properties of concentrated formulations, dynamic light scattering, and size-exclusion chromatography revealed only limited SCI self-assembly and aggregation in the concentration range 1-7 mm Such a combination of favorable biophysical and biological properties suggests that SCIs could provide a global therapeutic platform without a cold chain. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Low Earth orbit thermal control coatings exposure flight tests: A comparison of U.S. and Russian results

NASA Technical Reports Server (NTRS)

Tribble, A. C.; Lukins, R.; Watts, E.; Naumov, S. F.; Sergeev, V. K.

1995-01-01

Both the United States (US) and Russia have conducted a variety of space environment effects on materials (SEEM) flight experiments in recent years. A prime US example was the Long Duration Exposure Facility (LDEF), which spent 5 years and 9 months in low Earth orbit (LEO) from April 1984 to January 1990. A key Russian experiment was the Removable Cassette Container experiment, (RCC-1), flown on the Mir Orbital Station from 11 January 1990 to 26 April 1991. This paper evaluates the thermal control coating materials data generated by these two missions by comparing: environmental exposure conditions, functionality and chemistry of thermal control coating materials, and pre- and post-flight analysis of absorptance, emittance, and mass loss due to atomic oxygen erosion. It will be seen that there are noticeable differences in the US and Russian space environment measurements and models, which complicates comparisons of environments. The results of both flight experiments confirm that zinc oxide and zinc oxide orthotitanate white thermal control paints in metasilicate binders (Z93, YB71, TP-co-2, TP-co-11, and TP-co-12), are the most stable upon exposure to the space environment. It is also seen that Russian flight materials experience broadens to the use of silicone and acrylic resin binders while the US relies more heavily on polyurethane.

RP-2 Thermal Stability and Heat Transfer Investigation for Hydrocarbon Boost Engines

NASA Technical Reports Server (NTRS)

VanNoord, J. L.; Stiegemeier, B. R.

2010-01-01

A series of electrically heated tube tests were performed at the NASA Glenn Research Center s Heated Tube Facility to investigate the use of RP-2 as a fuel for next generation regeneratively cooled hydrocarbon boost engines. The effect that test duration, operating condition and test piece material have on the overall thermal stability and materials compatibility characteristics of RP-2 were evaluated using copper and 304 stainless steel test sections. The copper tests were run at 1000 psia, heat flux up to 6.0 Btu/in.2-sec, and wall temperatures up to 1180 F. Preliminary results, using measured wall temperature as an indirect indicator of the carbon deposition process, show that in copper test pieces above approximately 850 F, RP-2 begins to undergo thermal decomposition resulting in local carbon deposits. Wall temperature traces show significant local temperature increases followed by near instantaneous drops which have been attributed to the carbon deposition/shedding process in previous investigations. Data reduction is currently underway for the stainless steel test sections and carbon deposition measurements will be performed in the future for all test sections used in this investigation. In conjunction with the existing thermal stability database, these findings give insight into the feasibility of cooling a long life, high performance, high-pressure liquid rocket combustor and nozzle with RP-2.

Prior stress exposure increases pain behaviors in a rat model of full thickness thermal injury.

PubMed

Nyland, Jennifer E; McLean, Samuel A; Averitt, Dayna L

2015-12-01

Thermal burns among individuals working in highly stressful environments, such as firefighters and military Service Members, are common. Evidence suggests that pre-injury stress may exaggerate pain following thermal injury; however current animal models of burn have not evaluated the potential influence of pre-burn stress. This sham-controlled study evaluated the influence of prior stress exposure on post-burn thermal and mechanical sensitivity in male Sprague-Dawley rats. Rats were exposed to 20 min of inescapable swim stress or sham stress once per day for three days. Exposure to inescapable swim stress (1) increased the intensity and duration of thermal hyperalgesia after subsequent burn and (2) accelerated the onset of thermal hyperalgesia and mechanical allodynia after subsequent burn. This stress-induced exacerbation of pain sensitivity was reversed by pretreatment and concurrent treatment with the serotonin-norepinephrine reuptake inhibitor (SNRI) duloxetine. These data suggest a better understanding of mechanisms by which prior stress augments pain after thermal burn may lead to improved pain treatments for burn survivors. Copyright © 2015 Elsevier Ltd and ISBI. All rights reserved.

Elements for the modeling of the thermal process in heating furnaces for steel forming

NASA Astrophysics Data System (ADS)

Constantinescu, D.; Carlan, A. B.

2017-02-01

In the present paper, by “modelling of thermal process” will be understood the thermal techniques modelling, applied to the heating of steel billets in a large scale, in view of processing by forming. These technologies are correlated with the particularities of the thermal aggregates, having as main objective the reducing of energy consumptions and the optimizing of the aggregate design. When heating the steel billets in view of processing by forming, the duration and the quality of heating are influenced by the modality that the billets are receiving the thermal flow. The reception of the thermal flow depends on the heated surface exposed to the thermal radiation in compliance with their position on the hearth of the heating aggregate. The present paper intends to establish some parameters in view of optimizing the heating process. A basic point of the work is also the determination of some components of a mathematical model for the proposed heating technology. The authors have in view the complexity of the technical evolutions of the furnaces.

LDEF: A bibliography with abstracts

NASA Technical Reports Server (NTRS)

Gouger, H. Garland (Editor)

1992-01-01

The Long Duration Exposure Facility (LDEF) was a free-flying cylindrical structure that housed self-contained experiments in trays mounted on the exterior of the structure. Launched into orbit from the Space Shuttle Challenger in 1984, the LDEF spent almost six years in space before being recovered in 1990. The 57 experiments investigated the effects of the low earth orbit environment on materials, coatings, electronics, thermal systems, seeds, and optics. It also carried experiments that measured crystals growth, cosmic radiation, and micrometeoroids. This bibliography contains 435 selected records from the NASA aerospace database covering the years 1973 through June of 1992. The citations are arranged within subject categories by author and date of publication.

Scanning Tunneling Microscopy analysis of space-exposed polymer films

NASA Technical Reports Server (NTRS)

Kalil, Carol R.; Young, Philip R.

1993-01-01

The characterization of the surface of selected space-exposed polymer films by Scanning Tunneling Microscopy (STM) is reported. Principles of STM, an emerging new technique for materials analysis, are reviewed. The analysis of several films which received up to 5.8 years of low Earth orbital (LEO) exposure onboard the NASA Long Duration Exposure Facility (LDEF) is discussed. Specimens included FEP Teflon thermal blanket material, Kapton film, and several experimental polymer films. Ultraviolet and atomic oxygen-induced crazing and erosion are described. The intent of this paper is to demonstrate how STM is enhancing the understanding of LEO space environmental effects on polymer films.

Effect of preliminary thermal treatment on decomposition kinetics of austenite in low-alloyed pipe steel in intercritical temperature interval

NASA Astrophysics Data System (ADS)

Makovetskii, A. N.; Tabatchikova, T. I.; Yakovleva, I. L.; Tereshchenko, N. A.; Mirzaev, D. A.

2013-06-01

The decomposition kinetics of austenite that appears in the 13KhFA low-alloyed pipe steel upon heating the samples in an intercritical temperature interval (ICI) and exposure for 5 or 30 min has been studied by the method of high-speed dilatometry. The results of dilatometry are supplemented by the microstructure analysis. Thermokinetic diagrams of the decomposition of the γ phase are represented. The conclusion has been drawn that an increase in the duration of exposure in the intercritical interval leads to a significant increase in the stability of the γ phase.

Thermal effects of diagnostic ultrasound in an anthropomorphic skull model.

PubMed

Vyskocil, E; Pfaffenberger, S; Kollmann, C; Gleiss, A; Nawratil, G; Kastl, S; Unger, E; Aumayr, K; Schuhfried, O; Huber, K; Wojta, J; Gottsauner-Wolf, M

2012-12-01

Exposure to diagnostic ultrasound (US) can significantly heat biological tissue although conventional routine examinations are regarded as safe. The risk of unwanted thermal effects increases with a high absorption coefficient and extended insonation time. Certain applications of transcranial diagnostic US (TC-US) require prolonged exposure. An anthropomorphic skull model (ASM) was developed to evaluate thermal effects induced by TC-US of different modalities. The objective was to determine whether prolonged continuous TC-US application results in potentially harmful temperature increases. The ASM consists of a human skull with tissue mimicking material and exhibits acoustic and anatomical characteristics of the human skull and brain. Experiments are performed with a diagnostic US device testing four different US modalities: Duplex PW (pulsed wave) Doppler, PW Doppler, color flow Doppler and B-mode. Temperature changes are recorded during 180 minutes of insonation. All measurements revealed significant temperature increases during insonation independent of the US modality. The maximum temperature elevation of + 5.25° C (p < 0.001) was observed on the surface of the skull exposed to duplex PW Doppler. At the bone-brain border a maximum temperature increae of + 2.01 °C (p < 0.001) was noted. Temperature increases within the brain were < 1.23 °C (p = 0.001). The highest values were registered using the duplex PW Doppler modality. TC-US induces significant local heating effects in an ASM. An application duration that extends routine clinical periods causes potentially harmful heating especially in tissue close to bone. TC-US elevates the temperature in the brain mimicking tissue but is not capable of producing harmful temperature increases during routine examinations. However, the risk of thermal injury in brain tissue increases significantly after an exposure time of > 2 hours. © Georg Thieme Verlag KG Stuttgart · New York.

Accelerated Thermal-Aging-Induced Degradation of Organometal Triiodide Perovskite on ZnO Nanostructures and Its Effect on Hybrid Photovoltaic Devices.

PubMed

Kumar, S; Dhar, A

2016-07-20

Organometal halide perovskite materials are presently some of the pacesetters for light harvesting in hybrid photovoltaic devices because of their excellent inherent electrical and optical properties. However, long-term durability of such perovskite materials remains a major bottleneck for their commercialization especially in countries with hot and humid climatic conditions, thus violating the international standards for photovoltaic technology. Albeit, TiO2 as an electron-transport layer has been well investigated for perovskite solar cells; the high-temperature processing makes it unsuitable for low-cost and large-scale roll-to-roll production of flexible photovoltaic devices. Herein, we have chosen low-temperature (<150 °C)-processable nanostructured ZnO as the electron-selective layer and used a two-step method for sensitizing ZnO nanorods with methylammonium lead iodide (MAPbI3) perovskite, which is viable for flexible photovoltaic devices. We have also elaborately addressed the effect of the annealing duration on the conversion of a precursor solution into the required perovskite phase on ZnO nanostructures. The investigations show that the presence of ZnO nanostructures accelerates the rate of degradation of MAPbI3 films under ambient annealing and thus requires proper optimization. The role of ZnO in enhancing the degradation kinetics of the perovskite layer has been investigated by X-ray photoelectron spectroscopy and a buffer layer passivation technique. The effect of the annealing duration of the MAPbI3 perovskite on the optical, morphological, and compositional behavior has been closely studied and correlated with the photovoltaic efficiency. The study captures the degradation behavior of the commercially interesting MAPbI3 perovskite on a ZnO electron-transport layer and thus can provide insight for developing alternative families of perovskite material with better thermal and environmental stability for application in low-cost flexible photovoltaic technology.

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

Nuccitelli, Richard, E-mail: rich@bioelectromed.com; Tran, Kevin; Athos, Brian

Highlights: Black-Right-Pointing-Pointer Nanoelectroablation is a new, non-thermal therapy that triggers apoptosis in tumors. Black-Right-Pointing-Pointer Low energy, ultrashort, high voltage pulses ablate the tumor with little or no scar. Black-Right-Pointing-Pointer Nanoelectroablation eliminates 99.8% of the BCC but may leave a few remnants behind. Black-Right-Pointing-Pointer Pilot clinical trials on human BCCs are ongoing and leave no remnants in most cases. -- Abstract: When skin tumors are exposed to non-thermal, low energy, nanosecond pulsed electric fields (nsPEF), apoptosis is initiated both in vitro and in vivo. This nanoelectroablation therapy has already been proven effective in treating subdermal murine allograft tumors. We wanted tomore » determine if this therapy would be equally effective in the treatment of autochthonous BCC tumors in Ptch1{sup +/-}K14-Cre-ER p53 fl/fl mice. These tumors are similar to human BCCs in histology and in response to drug therapy . We have treated 27 BCCs across 8 mice with either 300 pulses of 300 ns duration or 2700 pulses of 100 ns duration, all at 30 kV/cm and 5-7 pulses per second. Every nsPEF-treated BCC began to shrink within a day after treatment and their initial mean volume of 36 {+-} 5 (SEM) mm{sup 3} shrunk by 76 {+-} 3% over the ensuing two weeks. After four weeks, they were 99.8% ablated if the size of the treatment electrode matched the tumor size. If the tumor was larger than the 4 mm wide electrode, multiple treatments were needed for complete ablation. Treated tumors were harvested for histological analysis at various times after treatment and exhibited apoptosis markers. Specifically, pyknosis of nuclei was evident as soon as 2 days after nsPEF treatment, and DNA fragmentation as detected via TUNEL staining was also evident post treatment. Nanoelectroablation is effective in triggering apoptosis and remission of radiation-induced BCCs with a single 6 min-long treatment of 2700 pulses.« less

Photothermal inactivation of bacteria on plasmonic nanostructures

NASA Astrophysics Data System (ADS)

Santos, Greggy M.; Ibañez de Santi Ferrara, Felipe; Zhao, Fusheng; Rodrigues, Debora F.; Shih, Wei-Chuan

2016-03-01

Hospital-acquired bacterial infections are frequently associated with the pathogenic biofilms on surfaces of devices and instruments used in medical procedures. The utilization of thermal plasmonic agents is an innovative approach for sterilizing hospital equipment and for in vivo therapeutic treatment of bacterial infection. A photothermal inactivation technique via array of nanoporous gold disks (NPGDs) has been developed by irradiating near infrared (NIR) light onto deposited bacterial cells (Escherichia coli, Bacillus subtilis, Exiguobacterium AT1B) on the surface of metal nanostructure. The physical and photothermal properties of the NPGD substrate were investigated using topographical scanning electron microscopy (SEM) and thermographic infrared imaging. Bacterial viability studies on NPGD substrates irradiated with and without NIR light were evaluated using a fluorescence-based two-component stain assay. The results show that the heat generated from the NPGD substrate promotes high cell death counts (~100%) at short exposure durations (<25 s) even for thermally-resistant bacterial strains. The photothermal effects on NPGD substrate can lead to point-of-care applications.

On the Prediction of Solar Cell Degradation in Space

NASA Astrophysics Data System (ADS)

Bourgoin, J. C.; Boizot, B.; Khirouni, K.; Khorenko, V.

2014-08-01

We discuss the validity of the procedure which is used to predict End Of Life performances of a solar cell in space. This procedure consists to measure the performances of the cell after it has been irradiated at the EOL fluence during a time ti very short compared to the duration tm of the mission in space, i.e. with a considerably larger flux. We show that this procedure is valid only when the defects created by the irradiation do not anneal (thermally or by carrier injection) with a time constant shorter than tm or larger than ti. This can be a common situation since annealing of irradiation induced defects occurs in all type of cells, at least in specific conditions (temperature, intensity of illumination, flux and nature of irradiating particles). Using modeling, we illustrate the effect of injection or thermal annealing on EOL prediction in the case GaInP, material at the heart of modern high efficiency space solar cells.

Fabrication and properties of aluminum silicate fibrous materials with in situ synthesized K2Ti6O13 whiskers

NASA Astrophysics Data System (ADS)

Liu, Hao; Wei, Nan; Wang, Zhou-fu; Wang, Xi-tang; Ma, Yan

2017-11-01

To improve their mechanical and thermal insulation properties, aluminum silicate fibrous materials with in situ synthesized K2Ti6O13 whiskers were prepared by firing a mixture of short aluminum silicate fibers and gel powders obtained from a sol-gel process. During the preparation process, the fiber surface was coated with K2Ti6O13 whiskers after the fibers were subjected to a heat treatment carried out at various temperatures. The effects of process parameters on the microstructure, compressive strength, and thermal conductivity were analyzed systematically. The results show that higher treatment temperatures and longer treatment durations promoted the development of K2Ti6O13 whiskers on the surface of aluminum silicate fibers; in addition, the intersection structure between whiskers modulated the morphology and volume of the multi-aperture structure among fibers, substantially increasing the fibers' compressive strength and reducing their heat conduction and convective heat transfer at high temperatures.

Liquid-cooled clothing for hot mine rescue work

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

Not Available

1979-04-01

To prevent exhaustion caused by thermal stress, a rescuer can wear a liquid-cooled hood and vest which absorbs heat, thereby reducing the heat-induced strain on the rescuer's heart and circulatory system. Liquid coolant is continuously circulated through a self-contained system in which the coolant is chilled by a heat sink on the wearer's belt. Cooling duration is approximately 40 minutes when both the hood and vest are worn. Tests were conducted at NASA's Ames Research Center to evaluate the effectiveness of this system. When using the hood and vest with a refrigerated water supply, thermal strain on the wearer wasmore » cut in half and the heart rate was reduced by 30 to 50 beats per minute. Body temperature was significantly lowered, about 0.65/sup 0/C. This system can increase safety for rescue workers who must work in a hot environment, especially when they are not acclimated to high temperaures. Laboratory tests also were conducted using members of a mine rescue team.« less

Environmental Durability Issues for Solar Power Systems in Low Earth Orbit

NASA Technical Reports Server (NTRS)

Degroh, Kim K.; Banks, Bruce A.; Smith, Daniela C.

1994-01-01

Space solar power systems for use in the low Earth orbit (LEO) environment experience a variety of harsh environmental conditions. Materials used for solar power generation in LEO need to be durable to environmental threats such as atomic oxygen, ultraviolet (UV) radiation, thermal cycling, and micrometeoroid and debris impact. Another threat to LEO solar power performance is due to contamination from other spacecraft components. This paper gives an overview of these LEO environmental issues as they relate to space solar power system materials. Issues addressed include atomic oxygen erosion of organic materials, atomic oxygen undercutting of protective coatings, UV darkening of ceramics, UV embrittlement of Teflon, effects of thermal cycling on organic composites, and contamination due to silicone and organic materials. Specific examples of samples from the Long Duration Exposure Facility (LDEF) and materials returned from the first servicing mission of the Hubble Space Telescope (HST) are presented. Issues concerning ground laboratory facilities which simulate the LEO environment are discussed along with ground-to-space correlation issues.

Impact of nursing care on temperature environment in preterm newborns nursed in closed convective incubators.

PubMed

Deguines, C; Dégrugilliers, L; Ghyselen, L; Chardon, K; Bach, V; Tourneux, P

2013-03-01

Very-low-birth-weight (VLBW) neonates require regular nursing procedures with frequent opening of the incubator resulting in a decrease in incubator air temperature. This study was designed to assess changes in the thermal status of VLBW neonates according to the type of nursing care and incubator openings. Thirty-one VLBW neonates (mean gestational age: 28.7 ± 0.3 weeks of gestation) were included. Over a 10-day period, each opening of the incubator was recorded together with details about caregiving. Body temperature was recorded continuously, and door opening and closing events were recorded by a video camera. This study analysed 1,798 caregiving procedures with mean durations ranging from 6.2 ± 2.1 to 88.5 ± 33.4 min. Abdominal skin temperature decreased by up to 1.08°C/h for procedures such as tracheal intubation (p < 0.01). The temperature decrease was strongly correlated with the type of procedure (p < 0.01), incubator opening (p < 0.01) and procedure duration (p < 0.01). The procedure duration accounted for only 10% of the abdominal skin temperature change (p < 0.01). For VLBW neonates nursed in skin temperature servo-control incubators, the decrease in abdominal skin temperature during caregiving was correlated with the type of procedure, incubator opening modalities and procedure duration. These parameters should be considered to optimize the thermal management of VLBW neonates. ©2012 The Author(s)/Acta Paediatrica ©2012 Foundation Acta Paediatrica.

Sleep Deprivation and Recovery Sleep Prior to a Noxious Inflammatory Insult Influence Characteristics and Duration of Pain.

PubMed

Vanini, Giancarlo

2016-01-01

Insufficient sleep and chronic pain are public health epidemics. Sleep loss worsens pain and predicts the development of chronic pain. Whether previous, acute sleep loss and recovery sleep determine pain levels and duration remains poorly understood. This study tested whether acute sleep deprivation and recovery sleep prior to formalin injection alter post-injection pain levels and duration. Male Sprague-Dawley rats (n = 48) underwent sleep deprivation or ad libitum sleep for 9 hours. Thereafter, rats received a subcutaneous injection of formalin or saline into a hind paw. In the recovery sleep group, rats were allowed 24 h between sleep deprivation and the injection of formalin. Mechanical and thermal nociception were assessed using the von Frey test and Hargreaves' method. Nociceptive measures were performed at 1, 3, 7, 10, 14, 17 and 21 days post-injection. Formalin caused bilateral mechanical hypersensitivity (allodynia) that persisted for up to 21 days post-injection. Sleep deprivation significantly enhanced bilateral allodynia. There was a synergistic interaction when sleep deprivation preceded a formalin injection. Rats allowed a recovery sleep period prior to formalin injection developed allodynia only in the injected limb, with higher mechanical thresholds (less allodynia) and a shorter recovery period. There were no persistent changes in thermal nociception. The data suggest that acute sleep loss preceding an inflammatory insult enhances pain and can contribute to chronic pain. The results encourage studies in a model of surgical pain to test whether enhancing sleep reduces pain levels and duration. © 2016 Associated Professional Sleep Societies, LLC.

The influence of episodic shallow magma degassing on heat and chemical transport in volcanic hydrothermal systems

USGS Publications Warehouse

Chen, Kewei; Zhan, Hongbin; Burns, Erick; Ingebritsen, Steven E.; Agrinier, Pierre

2018-01-01

Springs at La Soufrière of Guadeloupe have been monitored for nearly four decades since the phreatic eruption and associated seismic activity in 1976. We conceptualize degassing vapor/gas mixtures as square‐wave sources of chloride and heat and apply a new semianalytic solution to demonstrate that chloride and heat pulses with the same timing and duration result in good matches between measured and simulated spring temperatures and concentrations. While the concentration of chloride pulses is variable, the local boiling temperature of 96°C was assigned to all thermal pulses. Because chloride is a conservative tracer, chloride breakthrough is only affected by one‐dimensional advection and dispersion. The thermal tracer is damped and lagged relative to chloride due to conductive heat exchange with the overlying and underlying strata. Joint analysis of temperature and chloride allows estimation of the onset and duration of degassing pulses, refining the chronology of recent magmatic intrusion.

The Influence of Episodic Shallow Magma Degassing on Heat and Chemical Transport in Volcanic Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Chen, Kewei; Zhan, Hongbin; Burns, Erick R.; Ingebritsen, Steven E.; Agrinier, Pierre

2018-04-01

Springs at La Soufrière of Guadeloupe have been monitored for nearly four decades since the phreatic eruption and associated seismic activity in 1976. We conceptualize degassing vapor/gas mixtures as square-wave sources of chloride and heat and apply a new semianalytic solution to demonstrate that chloride and heat pulses with the same timing and duration result in good matches between measured and simulated spring temperatures and concentrations. While the concentration of chloride pulses is variable, the local boiling temperature of 96°C was assigned to all thermal pulses. Because chloride is a conservative tracer, chloride breakthrough is only affected by one-dimensional advection and dispersion. The thermal tracer is damped and lagged relative to chloride due to conductive heat exchange with the overlying and underlying strata. Joint analysis of temperature and chloride allows estimation of the onset and duration of degassing pulses, refining the chronology of recent magmatic intrusion.

Laser heating and ablation at high repetition rate in thermal confinement regime

NASA Astrophysics Data System (ADS)

Brygo, François; Semerok, A.; Oltra, R.; Weulersse, J.-M.; Fomichev, S.

2006-09-01

Laser heating and ablation of materials with low absorption and thermal conductivity (paint and cement) were under experimental and theoretical investigations. The experiments were made with a high repetition rate Q-switched Nd:YAG laser (10 kHz, 90 ns pulse duration and λ = 532 nm). High repetition rate laser heating resulted in pulse per pulse heat accumulation. A theoretical model of laser heating was developed and demonstrated a good agreement between the experimental temperatures measured with the infrared pyrometer and the calculated ones. With the fixed wavelength and laser pulse duration, the ablation threshold fluence of paint was found to depend on the repetition rate and the number of applied pulses. With a high repetition rate, the threshold fluence decreased significantly when the number of applied pulses was increasing. The experimentally obtained thresholds were well described by the developed theoretical model. Some specific features of paint heating and ablation with high repetition rate lasers are discussed.

Thermal Fatigue Study on the Divertor Plate Materials

NASA Astrophysics Data System (ADS)

Wu, Ji-hong; Zhang, Fu; Xu, Zeng-yu; Yan, Jian-cheng

2002-10-01

Thermal fatigue property of the divertor plate is one of the key issues that governs the lifetime of the divertor plate. Taking tungsten as surface material, a small-mock-up divertor plate was made by hot isostatic press welding (HIP). A thermal cycling experiment for divertor mock-up was carried out in the vacuum, where a high-heat-flux electronic gun was used as the thermal source. A cyclic heat flux of 9 MW/m2 was loaded onto the mock-up, a heating duration of 20 s was selected, the cooling water flow rate was 80 ml/s. After 1000 cycles, the surface and the W/Cu joint of the mock-up did not show any damage. The SEM was used to analyze the microstructure of the welding joint, where no cracks were found also.

Micrometeorite dynamic pyrometamorphism: Nonstoichiometric clinoenstatite (CLEN)

NASA Technical Reports Server (NTRS)

Rietmeijer, Frans J. M.

1993-01-01

Polymorphs of enstatite are common phases in many meteorites. They contain clues on their formation and the thermal evolution of their host rock which includes shock metamorphism. Rare, micron-sized, CLEN whiskers and thin platelets in chondritic porous micrometeorites were interpreted as solar nebula condensates that remained unaffected during atmospheric entry flash-heating. This CLEN formed by protoenstatite (PEN) inversion whereby the surface energy of the micron-sized PEN crystals aided the OREN-CLEN transformation or by metastable growth. Ca-poor, Mg,Fe-pyroxene with unequilibrated, intraparticle, Mg/(Mg+Fe) distributions occur in most chondritic micrometeorites. These distributions are a parent body signature that survived dynamic pyrometamorphism because the duration of the thermal spike during atmospheric entry is too short but this conclusion does not consider the ultrafine grain size of micrometeorites. The maximum temperature and duration of the heating event will depend on the kinetic energy and entry angle of the incoming micrometeorite. But lacking detailed petrological data for an individual particle, its thermal profile during atmospheric entry can not be deduced from its mass alone as a function of entry angle. In order to constrain dynamic pyrometamorphism in unmelted micrometeorites, I determined the petrological composition and silicate mineralogy in non-chondritic micrometeorites L2005T13, L2005E40, and L2006A28.

Thin Aerogel as a Spacer in Multilayer Insulation

NASA Technical Reports Server (NTRS)

Moroz, Nancy

2015-01-01

Cryogenic fluid management is a critical technical area that is needed for future space exploration. A key challenge is the storability of liquid hydrogen (LH2), liquid methane (LCH4), and liquid oxygen (LOX) propellants for long-duration missions. The storage tanks must be well-insulated to prevent over-pressurization and venting, which can lead to unacceptable propellant losses for long-duration missions to Mars and beyond. Aspen Aerogels had validated the key process step to enable the fabrication of thin, low-density aerogel materials. The multilayer aerogel insulation (MLAI) system prototypes were prepared using sheets of aerogel materials with superior thermal performance exceeding current state-of-the-art insulation for space applications. The exceptional properties of this system include a new breakthrough in high-vacuum cryogenic thermal insulation, providing a durable material with excellent thermal performance at a reduced cost when compared to longstanding state-of-the-art multilayer insulation systems. During the Phase II project, further refinement and qualification/system-level testing of the MLAI system will be performed for use in cryogenic storage applications. Aspen has been in discussions with United Launch Alliance, LLC; NASA's Kennedy Space Center; and Yetispace, Inc., to test the MLAI system on real-world tanks such as Vibro-Acoustic Test Article (VATA) or the Cryogenic Orbital Testbed (CRYOTE).

Thin Aerogel as a Spacer in Multilayer Insulation

NASA Technical Reports Server (NTRS)

Moroz, Nancy

2015-01-01

Cryogenic fluid management is a critical technical area that is needed for future space exploration. A key challenge is the storability of liquid hydrogen (LH2), liquid methane (LCH4), and liquid oxygen (LOX) propellants for long-duration missions. The storage tanks must be well-insulated to prevent over-pressurization and venting, which can lead to unacceptable propellant losses for long-duration missions to Mars and beyond. Aspen Aerogels had validated the key process step to enable the fabrication of thin, low-density aerogel materials. The multilayer aerogel insulation (MLAI) system prototypes were prepared using sheets of aerogel materials with superior thermal performance exceeding current state-of-the-art insulation for space applications. The exceptional properties of this system include a new breakthrough in high-vacuum cryogenic thermal insulation, providing a durable material with excellent thermal performance at a reduced cost when compared to longstanding state-of-the-art multilayer insulation systems. During the Phase II project, further refinement and qualification/system-level testing of the MLAI system will be performed for use in cryogenic storage applications. Aspen has been in discussions with United Launch Alliance, LLC; NASA's Kennedy Space Center; and Yetispace, Inc., to test the MLAI system on rea-lworld tanks such as Vibro-Acoustic Test Article (VATA) or the Cryogenic Orbital Testbed (CRYOTE).

Thermal measurements of short-duration CO2 laser resurfacing

NASA Astrophysics Data System (ADS)

Harris, David M.; Fried, Daniel; Reinisch, Lou; Bell, Thomas; Lyver, Rex

1997-05-01

The thermal consequences of a 100 microsecond carbon-dioxide laser used for skin resurfacing were examined with infrared radiometry. Human skin was evaluated in a cosmetic surgery clinic and extirpated rodent skin was measured in a research laboratory. Thermal relaxation following single pulses of in vivo human and ex vivo animal skin were quantitatively similar in the 30 - 1000 msec range. The thermal emission from the area of the irradiated tissue increased monotonically with increasing incident laser fluence. Extremely high peak temperatures during the 100 microsecond pulse are attributed to plume incandescence. Ejecta thermal emission may also contribute to our measurements during the first several msecs. The data are combined into a thermal relaxation model. Given known coefficients, and adjusting tissue absorption to reflect a 50% water content, and thermal conductivity of 2.3 times that of water, the measured (both animal back and human forearm) and calculated values coincide. The high thermal conductance suggests preferential thermal conduction along the protein matrix. The clinical observation of a resurfacing procedure clearly shows thermal overlap and build-up is a result of sequential, adjacent pulses. A decrease of 4 - 6 degrees Celsius in surface temperature at the treatment site that appeared immediately post-Tx and gradually diminished over several days is possibly a sign of dermal convective and/or evaporative cooling.

Current Issues in Human Spacecraft Thermal Control Technology

NASA Technical Reports Server (NTRS)

Ungar, Eugene K.

2008-01-01

Efficient thermal management of Earth-orbiting human spacecraft, lunar transit spacecraft and landers, as well as a lunar habitat will require advanced thermal technology. These future spacecraft will require more sophisticated thermal control systems that can dissipate or reject greater heat loads at higher input heat fluxes while using fewer of the limited spacecraft mass, volume and power resources. The thermal control designs also must accommodate the harsh environments associated with these missions including dust and high sink temperatures. The lunar environment presents several challenges to the design and operation of active thermal control systems. During the Apollo program, landings were located and timed to occur at lunar twilight, resulting in a benign thermal environment. The long duration polar lunar bases that are foreseen in 15 years will see extremely cold thermal environments. Long sojourns remote from low-Earth orbit will require lightweight, but robust and reliable systems. Innovative thermal management components and systems are needed to accomplish the rejection of heat from lunar bases. Advances are required in the general areas of radiators, thermal control loops and equipment. Radiators on the Moon's poles must operate and survive in very cold environments. Also, the dusty environment of an active lunar base may require dust mitigation and removal techniques to maintain radiator performance over the long term.

LDEF polymeric materials: A summary of Langley characterization

NASA Technical Reports Server (NTRS)

Young, Philip R.; Slemp, Wayne S.; Whitley, Karen S.; Kalil, Carol R.; Siochi, Emilie J.; Shen, James Y.; Chang, A. C.

1995-01-01

The NASA Long Duration Exposure Facility (LDEF) enabled the exposure of a wide variety of materials to the low earth orbit (LEO) environment. This paper provides a summary of research conducted at the Langley Research Center into the response of selected LDEF polymers to this environment. Materials examined include graphite fiber reinforced epoxy, polysulfone, and additional polyimide matrix composites, films of FEP Teflon, Kapton, several experimental high performance polyimides, and films of more traditional polymers such as poly(vinyl toluene) and polystyrene. Exposure duration was either 10 months or 5.8 years. Flight and control specimens were characterized by a number of analytical techniques including ultraviolet-visible and infrared spectroscopy, thermal analysis, scanning electron and scanning tunneling microscopy, x-ray photoelectron spectroscopy, and, in some instances, selected solution property measurements. Characterized effects were found to be primarily surface phenomena. These effects included atomic oxygen-induced erosion of unprotected surfaces and ultraviolet-induced discoloration and changes in selected molecular level parameters. No gross changes in molecular structure or glass transition temperature were noted. The intent of this characterization is to increase our fundamental knowledge of space environmental effects as an aid in developing new and improved polymers for space application. A secondary objective is to develop benchmarks to enhance our methodology for the ground-based simulation of environmental effects so that polymer performance in space can be more reliably predicted.

Low-temperature crystallization of anodized TiO2 nanotubes at the solid-gas interface and their photoelectrochemical properties

NASA Astrophysics Data System (ADS)

Liu, Jing; Liu, Zhaoyue; Zhang, Tierui; Zhai, Jin; Jiang, Lei

2013-06-01

TiO2 nanotubular arrays formed by electrochemical anodization have attracted significant attention for photoelectrochemical applications that utilize solar energy. However, the as-anodized TiO2 nanotubes are amorphous, and need to be crystallized by high-temperature thermal annealing. Herein, we describe a low-temperature hydrothermal solid-gas route to crystallize TiO2 nanotubes. In this process, the as-anodized TiO2 hydroxo nanotubes are dehydrated to yield anatase phase via solid-gas interface reaction in an autoclave at a temperature of less than 180 °C. The solid-gas interface reaction alleviates the collapse of as-anodized TiO2 nanotubes during hydrothermal process efficiently. Compared with the common thermal annealing at the same temperature but at atmospheric pressure, the hydrothermal route improves the photocurrent density of TiO2 nanotubes by ~10 times in KOH electrolyte. The duration of the hydrothermal reaction has a substantial effect on the photoelectrochemical properties of TiO2 nanotubes, which is ascribed to the synergetic effect between the crystallization and structural evolution. Electron donors can further suppress the charge recombination in the low-temperature crystallized TiO2 nanotubes and boost the photocurrent density by ~120%.TiO2 nanotubular arrays formed by electrochemical anodization have attracted significant attention for photoelectrochemical applications that utilize solar energy. However, the as-anodized TiO2 nanotubes are amorphous, and need to be crystallized by high-temperature thermal annealing. Herein, we describe a low-temperature hydrothermal solid-gas route to crystallize TiO2 nanotubes. In this process, the as-anodized TiO2 hydroxo nanotubes are dehydrated to yield anatase phase via solid-gas interface reaction in an autoclave at a temperature of less than 180 °C. The solid-gas interface reaction alleviates the collapse of as-anodized TiO2 nanotubes during hydrothermal process efficiently. Compared with the common thermal annealing at the same temperature but at atmospheric pressure, the hydrothermal route improves the photocurrent density of TiO2 nanotubes by ~10 times in KOH electrolyte. The duration of the hydrothermal reaction has a substantial effect on the photoelectrochemical properties of TiO2 nanotubes, which is ascribed to the synergetic effect between the crystallization and structural evolution. Electron donors can further suppress the charge recombination in the low-temperature crystallized TiO2 nanotubes and boost the photocurrent density by ~120%. Electronic supplementary information (ESI) available: Morphology images of TiO2 nanotubular arrays crystallized by hydrothermal solid-liquid reaction at 130 °C, 160 °C and 180 °C for 4 h. Cross-sectional image of TiO2 nanotubular arrays prepared by anodizing Ti foil at 20 V for 20 min in 0.5 wt% HF solution followed by drying in air at 100 °C for 1 h; Photocurrent density-potential curves of TiO2 nanotubular arrays crystallized by thermal annealing at 450 °C and atmospheric pressure for 4 h. See DOI: 10.1039/c3nr01286g

Feasibility of Using Ultrasonic Nakagami Imaging for Monitoring Microwave-Induced Thermal Lesion in Ex Vivo Porcine Liver.

PubMed

Zhang, Siyuan; Han, Yuqiang; Zhu, Xingguang; Shang, Shaoqiang; Huang, Guojing; Zhang, Lei; Niu, Gang; Wang, Supin; He, Xijing; Wan, Mingxi

2017-02-01

The feasibility of using ultrasonic Nakagami imaging to evaluate thermal lesions induced by microwave ablation (MWA) in ex vivo porcine liver was explored. Dynamic changes in echo amplitudes and Nakagami parameters in the region of the MWA-induced thermal lesion, as well as the contrast-to-noise ratio (CNR) between the MWA-induced thermal lesion and the surrounding normal tissue, were calculated simultaneously during the MWA procedure. After MWA exposure, a bright hyper-echoic region appeared in ultrasonic B-mode and Nakagami parameter images as an indicator of the thermal lesion. Mean values of the Nakagami parameter in the thermal lesion region increased to 0.58, 0.71 and 0.91 after 1, 3 and 5 min of MVA. There were no significant differences in envelope amplitudes in the thermal lesion region among ultrasonic B-mode images obtained after different durations of MWA. Unlike ultrasonic B-mode images, Nakagami images were less affected by the shadow effect in monitoring of MWA exposure, and a fairly complete hyper-echoic region was observed in the Nakagami image. The mean value of the Nakagami parameter increased from approximately 0.47 to 0.82 during MWA exposure. At the end of the postablation stage, the mean value of the Nakagami parameter decreased to 0.55 and was higher than that before MWA exposure. CNR values calculated for Nakagami parameter images increased from 0.13 to approximately 0.61 during MWA and then decreased to 0.26 at the end of the post-ablation stage. The corresponding CNR values calculated for ultrasonic B-mode images were 0.24, 0.42 and 0.17. This preliminary study on ex vivo porcine liver suggested that Nakagami imaging have potential use in evaluating the formation of MWA-induced thermal lesions. Further in vivo studies are needed to evaluate the potential application. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Effects of Various Wavelength Ranges of Vacuum Ultraviolet Radiation on Teflon FEP Film Investigated

NASA Technical Reports Server (NTRS)

Dever, Joyce A.; McCracken, Cara A.

2004-01-01

Teflon Fluorinated Ethylene Propylene (FTP) films (DuPont) have been widely used for spacecraft thermal control and have been observed to become embrittled and cracked upon exposure to the space environment. This degradation has been attributed to a synergistic combination of radiation and thermal effects. A research study was undertaken at the NASA Glenn Research Center to examine the effects of different wavelength ranges of vacuum ultraviolet (VUV) radiation on the degradation of the mechanical properties of FEP. This will contribute to an overall understanding of space radiation effects on Teflon FEP, and will provide information necessary to determine appropriate techniques for using laboratory tests to estimate space VUV degradation. Research was conducted using inhouse facilities at Glenn and was carried out, in part, through a grant with the Cleveland State University. Samples of Teflon FEP film of 50.8 microns thickness were exposed to radiation from a VUV lamp from beneath different cover windows to provide different exposure wavelength ranges: MgF2 (115 to 400 nm), crystalline quartz (140 to 400 nm), and fused silica (FS, 155 to 400 nm). Following exposure, FEP film specimens were tensile tested to determine the ultimate tensile strength and elongation at failure as a function of the exposure duration for each wavelength range. The graphs show the effect of ultraviolet exposure on the mechanical properties of the FEP samples.

SU-E-T-112: Experimental Characterization of a Novel Thermal Reservoir for Consistent and Accurate Annealing of High-Sensitivity TLDs.

PubMed

Donahue, W; Bongiorni, P; Hearn, R; Rodgers, J; Nath, R; Chen, Z

2012-06-01

To develop and characterize a novel thermal reservoir for consistent and accurate annealing of high-sensitivity thermoluminescence dosimeters (TLD-100H) for dosimetry of brachytherapy sources. The sensitivity of TLD-100H is about 18 times that of TLD-100 which has clear advantages in for interstitial brachytherapy sources. However, the TLD-100H requires a short high temperature annealing cycle (15 min.) and opening and closing the oven door causes significant temperature fluctuations leading to unreliable measurements. A new thermal reservoir made of aluminum alloy was developed to provide stable temperature environment in a standard hot air oven. The thermal reservoir consisted of a 20 cm × 20 cm × 8 cm Al block with a machine-milled chamber in the middle to house the aluminum TLD holding tray. The thermal reservoir was placed inside the oven until it reaches thermal equilibrium with oven chamber. The temperatures of the oven chamber, heat reservoir, and TLD holding tray were monitored by two independent thermo-couples which interfaced digitally to a control computer. A LabView interface was written for monitoring and recording the temperatures in TLD holding tray, the thermal reservoir, and oven chamber. The temperature profiles were measured as a function of oven-door open duration. The settings for oven chamber temperature and oven door open-close duration were optimized to achieve a stable temperature of 240 0C in the TLD holding tray. Complete temperature profiles of the TLD annealing tray over the entire annealing process were obtained. A LabView interface was written for monitoring and recording the temperatures in TLD holding The use of the thermal reservoir has significantly reduced the temperature fluctuations caused by the opening of oven door when inserting the TLD holding tray into the oven chamber. It has enabled consistent annealing of high-sensitivity TLDs. A comprehensive characterization of a custom-built novel thermal reservoir for annealing high-sensitivity TLD has been carried out. It enabled consistent and accurate annealing of high- sensitivity TLDs which could significantly improve the efficiency of brachytherapy source characterizations. Supported in part by NIH grant R01-CA134627. © 2012 American Association of Physicists in Medicine.

Effect of contrast water therapy duration on recovery of cycling performance: a dose-response study.

PubMed

Versey, Nathan; Halson, Shona; Dawson, Brian

2011-01-01

This study investigated whether contrast water therapy (CWT) has a dose-response effect on recovery from high-intensity cycling. Eleven trained male cyclists completed four trials, each commencing with a 75-min cycling protocol containing six sets of five 15-s sprints and three 5-min time-trials in thermoneutral conditions. Ten minutes post-exercise, participants performed one of four recovery protocols: CWT for 6 min (CWT6), 12 min (CWT12), or 18 min (CWT18) duration, or a seated rest control trial. The CWT commenced in hot water (38.4 ± 0.6°C) and alternated between hot and cold water (14.6 ± 0.3°C) every minute with a 5-s changeover. The cycling protocol was repeated 2 h after completion of exercise bout one. Prior to exercise bout two, core temperature was lower in CWT12 (-0.19 ± 0.14°C, mean ± 90% CL) and CWT18 (-0.21 ± 0.10°C) than control. Compared with control, CWT6 substantially improved time-trial (1.5 ± 2.1%) and sprint performance (3.0 ± 3.1%), and CWT12 substantially improved sprint total work (4.3 ± 3.4%) and peak power (2.7 ± 3.8%) in exercise bout two. All CWT conditions generally improved thermal sensation, whole body fatigue and muscle soreness compared with control, but no differences existed between conditions in heart rate or rating of perceived exertion. In conclusion, CWT duration did not have a dose-response effect on recovery from high-intensity cycling; however, CWT for up to 12 min assisted recovery of cycling performance.

Comparative study of cryogen spray cooling with R-134a and R-404a: implications for laser treatment of dark human skin

NASA Astrophysics Data System (ADS)

Dai, Tianhong; Yaseen, Mohammad A.; Diagaradjane, Parmeswaran; Chang, David W.; Anvari, Bahman

2006-07-01

Cutaneous laser treatment in dark skin patients is challenging due to significant light absorption by the melanin at the basal layer of epidermis, which can result in irreversible nonspecific thermal injury to the epidermis. Cryogen spray cooling (CSC) with R-134a (boiling point ≈ -26.2°C at 1 atm), which is currently used during cutaneous laser treatment, has shown poor efficacy in protecting dark human skin. We investigated the potential of CSC with R-404a (boiling point ≈ -46.5°C at 1 atm), which has a lower boiling point than R-134a, for improved therapeutic outcome in dark human skin at three levels: in vitro (epoxy resin skin phantom), ex vivo (normal dark human skin sample), and in vivo (skin of the rabbit external ear). The skin phantom was used to acquire the surface and internal temperature profiles in response to CSC with R-134a or R-404a at various spurt durations, based upon which CSC-induced heat removal from the skin phantom was estimated using an algorithm that solved a one-dimensional inverse heat conduction problem. CSC with R-404a increased the temperature reductions within the phantom and subsequently the amount of heat removal from the phantom in comparison to that with R-134a. Normal ex vivo Fitzpatrick types V-VI human skin samples were used to investigate the thermal response of dark human skin epidermis to CSC (R-134a or R-404a) at various spurt durations in conjunction with 595-nm pulsed dye laser irradiation at various radiant exposures. Cryogen R-404a increased the threshold radiant exposures for irreversible thermal injury to the epidermis in dark pigmentation skin. No obvious CSC-induced morphological changes to human skin was observed when sprayed with R404-a spurts using durations up to 300 ms. In vivo rabbit ear vasculature was used as a model of cutaneous anomalies to assess the influences of CSC (with R-134a or R-404a) on the photothermolysis of dermal blood vessels. CSC (R-134a or R-404a) with the spurt durations of 100 to 300 ms increased the most superficial depth of thermally damaged dermal blood vessel compared with the sites without CSC, implying possible nonspecific cooling of superficial dermal blood vessels by the cryogen spurts with the settings applied.

Space Shuttle Projects

NASA Image and Video Library

1984-04-01

The Long Duration Exposure Facility (LDEF) was designed by the Marshall Space Flight Center (MSFC) to test the performance of spacecraft materials, components, and systems that have been exposed to the environment of micrometeoroids and space debris for an extended period of time. The LDEF proved invaluable to the development of future spacecraft and the International Space Station (ISS). The LDEF carried 57 science and technology experiments, the work of more than 200 investigators. MSFC`s experiments included: Trapped Proton Energy Determination to determine protons trapped in the Earth's magnetic field and the impact of radiation particles; Linear Energy Transfer Spectrum Measurement Experiment which measures the linear energy transfer spectrum behind different shielding configurations; Atomic oxygen-Simulated Out-gassing, an experiment that exposes thermal control surfaces to atomic oxygen to measure the damaging out-gassed products; Thermal Control Surfaces Experiment to determine the effects of the near-Earth orbital environment and the shuttle induced environment on spacecraft thermal control surfaces; Transverse Flat-Plate Heat Pipe Experiment, to evaluate the zero-gravity performance of a number of transverse flat plate heat pipe modules and their ability to transport large quantities of heat; Solar Array Materials Passive LDEF Experiment to examine the effects of space on mechanical, electrical, and optical properties of lightweight solar array materials; and the Effects of Solar Radiation on Glasses. Launched aboard the Space Shuttle Orbiter Challenger's STS-41C mission April 6, 1984, the LDEF remained in orbit for five years until January 1990 when it was retrieved by the Space Shuttle Orbiter Columbia STS-32 mission and brought back to Earth for close examination and analysis.

Three-Dimensional Effects of Artificial Mixing in a Shallow Drinking-Water Reservoir

NASA Astrophysics Data System (ADS)

Chen, Shengyang; Little, John C.; Carey, Cayelan C.; McClure, Ryan P.; Lofton, Mary E.; Lei, Chengwang

2018-01-01

Studies that examine the effects of artificial mixing for water-quality mitigation in lakes and reservoirs often view a water column with a one-dimensional (1-D) perspective (e.g., homogenized epilimnetic and hypolimnetic layers). Artificial mixing in natural water bodies, however, is inherently three dimensional (3-D). Using a 3-D approach experimentally and numerically, the present study visualizes thermal structure and analyzes constituent transport under the influence of artificial mixing in a shallow drinking-water reservoir. The purpose is to improve the understanding of artificial mixing, which may help to better design and operate mixing systems. In this reservoir, a side-stream supersaturation (SSS) hypolimnetic oxygenation system and an epilimnetic bubble-plume mixing (EM) system were concurrently deployed in the deep region. The present study found that, while the mixing induced by the SSS system does not have a distinct 3-D effect on the thermal structure, epilimnetic mixing by the EM system causes 3-D heterogeneity. In the experiments, epilimnetic mixing deepened the lower metalimnetic boundary near the diffuser by about 1 m, with 55% reduction of the deepening rate at 120 m upstream of the diffuser. In a tracer study using a 3-D hydrodynamic model, the operational flow rate of the EM system is found to be an important short-term driver of constituent transport in the reservoir, whereas the duration of the EM system operation is the dominant long-term driver. The results suggest that artificial mixing substantially alters both 3-D thermal structure and constituent transport, and thus needs to be taken into account for reservoir management.

Thermal modelling of stepwise anatexis in a thrust-thickened sialic crust

USGS Publications Warehouse

Zen, E.-A.

1988-01-01

One-dimensional modelling of the thermal history of a sialic crust thickened by multiple overstack thrusting of upper crustal material shows that anatexis is likely. both the uplift rate and the length of the incubation period between end of tectonism and start of uplift are important controls on the amount and temperature of the melt. Heat of fusion does not significantly affect the long-term thermal structure of the crust if the melt is not extracted because only a small fraction of conductive heat is converted to latent heat, though short-term thermal effects of latent heat can be locally important. Model results show that commonly <15% of mantle heat flux is converted to latent heat; even during peak melting in the most productive models, less than half of incremental mantle flux is converted. The results have obvious implications on the acceptability of proposed heat sources for crustal anatexis. Fusion could retard crustal temperature rise by nearly 100??C, but the system would recover except for situations of very rapid uplift. Understanding of the thermal evolution of a burial-uplift system requires knowledge not only of the timing of anatexis but of the pooling and movement of the magma, as well as the duration and nature of the incubation period; we are poorly equipped to measure these events. The model predicts that the characteristic time for anatexis is a thickened sialic crust is several tens of millions of years, comparable to the time lapse between orogenies; in making geological interpretations of magmatism, this time lag must be considered. -Author

Thermal shock induced oxidation of beryllium

NASA Astrophysics Data System (ADS)

Spilker, B.; Linke, J.; Pintsuk, G.; Wirtz, M.

2017-12-01

Beryllium has been chosen as a plasma facing material for the first wall of the experimental fusion reactor ITER, mainly because of its low atomic number and oxygen getter capabilities, which are favorable for a high plasma performance. While the steady state operational temperature of 250 °C has no deteriorating effect on the beryllium surface, transient plasma events can deposit power densities of up to 1 GW m-2 on the beryllium armor tiles. Previous research has shown that the oxidation of beryllium can occur under these thermal shock events. In the present study, S-65 grade beryllium specimens were exposed to 100 thermal shocks with an absorbed power density of 0.6 GW m-2 and a pulse duration of 1 ms, leading to a peak surface temperature of ˜800 °C. The induced surface morphology changes were compared to a steady state heated specimen at the same surface temperature with a holding time of 150 s. As a result, a pitting structure with an average pit diameter of ˜0.45 μm was observed on the thermal shock loaded surface, which was caused by beryllium oxide grain nucleation and subsequent erosion of the weakly bound beryllium oxide particles. In contrast, the steady state heated surface exhibited a more homogeneous beryllium oxide layer featuring small pits with diameters of tens of nm and showed the beryllium oxide grain nucleation in a beginning stage. The experiment demonstrated that thermal shock loading conditions can significantly accelerate the beryllium oxide grain nucleation. The resulting surface morphology change can potentially alter the fusion application relevant erosion, absorption, and retention characteristics of beryllium.

Effect of multi-layer thermal insulation thickness and location on the hypervelocity impact response of dual-wall structures

NASA Astrophysics Data System (ADS)

Schonberg, William P.

Traditional perforation-resistant wall design for long-duration spacecraft consists of a "bumper" that is placed a small distance away from the main "pressure wall" of a spacecraft compartment or module. This concept has been studied extensively as a means of reducing the perforation threat of hypervelocity projectiles such as meteoroids and orbital debris. If a dual-wall system is employed on an earth-orbiting spacecraft, then a blanket of multi-layer insulation (MLI) will typically be included within the dual-wall system for thermal protection purposes. This paper presents the results of an experimental study in which aluminum dual-wall structures were tested under a variety of high-speed impact conditions to study the effect of MLI thickness and location on perforation resistance. The results presented consist of test-by-test comparisons of the damage sustained by similar dual-wall systems with blanket MLI of various thicknesses and at various locations within the dual-wall systems under similar impact loading conditions. The analyses performed revealed that the placement of the MLI had a significant effect on the ballistic limit of the dual-wall structures considered while reducing the thickness of the MLI by as much as 1/3 did not.

Evaluation of effectiveness of Er,Cr:YSGG laser for root canal disinfection: theoretical simulation of temperature elevations in root dentin.

PubMed

Zhu, L; Tolba, M; Arola, D; Salloum, M; Meza, F

2009-07-01

Erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) lasers are currently being investigated for disinfecting the root canal system. Prior to using laser therapy, it is important to understand the temperature distribution and to assess thermal damage to the surrounding tissue. In this study, a theoretical simulation using the Pennes bioheat equation is conducted to evaluate how heat spreads from the canal surface using an Er,Cr:YSGG laser. Results of the investigation show that some of the proposed treatment protocols for killing bacteria in the deep dentin are ineffective, even for long heating durations. Based on the simulation, an alternative treatment protocol is identified that has improved effectiveness and is less likely to introduce collateral damage to the surrounding tissue. The alternative protocol uses 350 mW laser power with repeating laser tip movement to achieve bacterial disinfection in the deep dentin (800 microm lateral from the canal surface), while avoiding thermal damage to the surrounding tissue (T<47 degrees C). The alternative treatment protocol has the potential to not only achieve bacterial disinfection of deep dentin but also shorten the treatment time, thereby minimizing potential patient discomfort during laser procedures.

Unravelling the switching mechanisms in electric field induced insulator-metal transitions in VO2 nanobeams

NASA Astrophysics Data System (ADS)

Rathi, Servin; Park, Jin-Hyung; Lee, In-yeal; Baik, Jeong Min; Yi, Kyung Soo; Kim, Gil-Ho

2014-07-01

We studied insulator-metal transitions in VO2 nanobeams for both abrupt and gradual changes in applied electric fields. Based on the observations, the Poole-Frenkel effect explained the abrupt transition, while the gradual case is found to be dominated by the Joule heating phenomenon. We also carried out power model and finite element method based simulations which supported the Joule heating phenomena for gradual transition. An in-principle demonstration of the Poole-Frenkel effect, performed using a square voltage pulse of 1 µs duration, further confirms the proposed insulator-metal transition mechanism with a switching time in the order of 100 ns. Finally, conductivity variations introduced via rapid thermal annealing at various temperatures validate the roles of both Joule heating and Poole-Frenkel mechanisms in the transitions.

High-Performing, Low-Temperature-Operating, Long-Lifetime Aerospace Lubricants

NASA Technical Reports Server (NTRS)

Joshi, Prakash

2015-01-01

Long-duration space exploration will require spacecraft systems that can operate effectively over several years with minimal or no maintenance. Aerospace lubricants are key components of spacecraft systems. Physical Sciences Inc., has synthesized and characterized novel ionic liquids for use in aerospace lubricants that contribute to decreased viscosity, friction, and wear in aerospace systems. The resulting formulations offer low vapor pressure and outgassing properties and thermal stability up to 250 C. They are effective for use at temperatures as low as -70 C and provide long-term operational stability in aerospace systems. In Phase II, the company scaled several new ionic liquids and evaluated a novel formulation in a NASA testbed. The resulting lubricant compounds will offer lower volatility, decreased corrosion, and better tribological characteristics than standard liquid lubricants, particularly at lower temperatures.

Mixed-Initiative Constraint-Based Activity Planning for Mars Exploration Rovers

NASA Technical Reports Server (NTRS)

Bresina, John; Jonsson, Ari K.; Morris, Paul H.; Rajan, Kanna

2004-01-01

In January, 2004, two NASA rovers, named Spirit and Opportunity, successfully landed on Mars, starting an unprecedented exploration of the Martian surface. Power and thermal concerns constrained the duration of this mission, leading to an aggressive plan for commanding both rovers every day. As part of the process for generating these command loads, the MAPGEN tool provides engineers and scientists an intelligent activity planning tool that allows them to more effectively generate complex plans that maximize the science return each day. The key to'the effectiveness of the MAPGEN tool is an underlying artificial intelligence plan and constraint reasoning engine. In this paper we outline the design and functionality of the MAEPGEN tool and focus on some of the key capabilities it offers to the MER mission engineers.

RP-1 Thermal Stability and Copper Based Materials Compatibility Study

NASA Technical Reports Server (NTRS)

Stiegemeier, B. R.; Meyer, M. L.; Driscoll, E.

2005-01-01

A series of electrically heated tube tests was performed at the NASA Glenn Research Center s Heated Tube Facility to investigate the effect that sulfur content, test duration, and tube material play in the overall thermal stability and materials compatibility characteristics of RP-1. Scanning-electron microscopic (SEM) analysis in conjunction with energy dispersive spectroscopy (EDS) were used to characterize the condition of the tube inner wall surface and any carbon deposition or corrosion formed during these runs. Results of the parametric study indicate that tests with standard RP-1 (total sulfur -23 ppm) and pure copper tubing are characterized by a depostion/deposit shedding process producing local wall temperature swings as high as 500 F. The effect of this shedding is to keep total carbon deposition levels relatively constant for run times from 20 minutes up to 5 hours, though increasing tube pressure drops were observed in all runs. Reduction in the total sulfur content of the fuel from 23 ppm to less than 0.1 ppm resulted in the elimination of deposit shedding, local wall temperature variation, and the tube pressure drop increases that were observed in standard sulfur level RP-1 tests. The copper alloy GRCop-84, a copper alloy developed specifically for high heat flux applications, was found to exhibit higher carbon deposition levels compared to identical tests performed in pure copper tubes. Results of the study are consistent with previously published heated tube data which indicates that small changes in fuel total sulfur content can lead to significant differences in the thermal stability of kerosene type fuels and their compatibility with copper based materials. In conjunction with the existing thermal stability database, these findings give insight into the feasibility of cooling a long life, high performance, high-pressure liquid rocket combustor and nozzle with RP-1.

Evaluation of the effect of balneotherapy in patients with osteoarthritis of the hands: a randomized controlled single-blind follow-up study.

PubMed

Horváth, Katalin; Kulisch, Ágota; Németh, András; Bender, Tamás

2012-05-01

To evaluate the effectiveness of thermal mineral water compared with magnetotherapy without balneotherapy as control, in the treatment of hand osteoarthritis. Randomized controlled single-blind follow-up study. Rheumatology specialist clinic of Gunaras Health Spa. Patients between 50 and 70 years of age with hand osteoarthritis, randomly assigned into three groups. The subjects in the first two groups bathed in thermal mineral water of two different temperatures (36°C and 38°C) for three weeks five times a week for 20 minutes a day and received magnetotherapy to their hands three times weekly. The third group received only magnetotherapy. Visual analogue scale scores, handgrip strength, pinchgrip strength, the number of swollen and tender joints of the hand, the duration of morning joint stiffness, Health Assessment Questionnaire, and Short Form-36 questionnaire. The study parameters were administered at baseline, immediately after treatment and after 13 weeks. The study included 63 patients. Statistically significant improvement was observed in several studied parameters after the treatment and during the follow-up study in the thermal water groups versus the control group. The 38°C thermal water treatment significantly improved the pinch strength of the right hand (0.6 (95% confidence interval (CI) 0.2 to 1.1) vs. 0.03 (95% CI -0.3 to 0.4), P < 0.05) and the Health Assessment Questionnaire parameters (-0.4 (95% CI -0.6 to -0.2) vs. -0.1 (95% CI -0.2 to 0.1), P < 0.01) even in the long term. Balneotherapy combined with magnetotherapy improved the pain and function as well as the quality of life in patients with hand osteoarthritis.

Effects of seasonal acclimatization on temperature dependence of cardiac excitability in the roach, Rutilus rutilus.

PubMed

Badr, A; El-Sayed, M F; Vornanen, M

2016-05-15

Temperature sensitivity of electrical excitability is a potential limiting factor for performance level and thermal tolerance of excitable tissues in ectothermic animals. To test whether the rate and rhythm of the heart acclimatize to seasonal temperature changes, thermal sensitivity of cardiac excitation in a eurythermal teleost, the roach (Rutilus rutilus), was examined. Excitability of the heart was determined from in vivo electrocardiograms and in vitro microelectrode recordings of action potentials (APs) from winter and summer roach acclimatized to 4 and 18°C, respectively. Under heat ramps (3°C h(-1)), starting from the acclimatization temperatures of the fish, heart rate increased to maximum values of 78±5 beats min(-1) (at 19.8±0.5°C) and 150±7 beats min(-1) (at 28.1±0.5°C) for winter and summer roach, respectively, and then declined in both groups. Below 20°C, heart rate was significantly higher in winter than in summer roach (P<0.05), indicating positive thermal compensation. Cardiac arrhythmias appeared with rising temperature as missing QRS complexes, increase in variability of heart rate, episodes of atrial tachycardia, ventricular bradycardia and complete cessation of the heartbeat (asystole) in both winter and summer roach. Unlike winter roach, atrial APs of summer roach had a distinct early repolarization phase, which appeared as shorter durations of atrial AP at 10% and 20% repolarization levels in comparison to winter roach (P<0.05). In contrast, seasonal acclimatization had only subtle effects on ventricular AP characteristics. Plasticity of cardiac excitation appears to be necessary for seasonal improvements in performance level and thermal resilience of the roach heart. © 2016. Published by The Company of Biologists Ltd.

Thermal Fatigue Study of W/cu Joint

NASA Astrophysics Data System (ADS)

Zhang, Fu; Wu, Jihong; Xu, Zengyu; Xu, Ying

2003-06-01

HHFC mock-ups with a structure of W/Cu/SS were developed by hot isostatic pressing (HIP). The performance of the W/Cu joint under high heat loads was tested using an electron beam. The size of specimens for heat load tests was 25×25 mm and the size of beam spot on the specimen surface was 22 mm in diameter. During heat load test, the specimens were water-cooled. Thermal fatigue test were conducted at power density of 8.7 MW/m2 with pulse duration of 20 seconds and interval of 20 seconds. After 1000 cycles of tests, no cracks and failure were found in the W/Cu joint. The thermal performance was also investigated in the range of 1 ~ 9 MW/m2.

Guidance and Control of an Autonomous Soaring UAV

NASA Technical Reports Server (NTRS)

Allen, Michael J.; Lin, Victor

2007-01-01

Thermals caused by convection in the lower atmosphere are commonly used by birds and glider pilots to extend flight duration, increase cross-country speed, improve range, or simply to conserve energy. Uninhabited Aerial Vehicles (UAVs) can also increase performance and reduce energy consumption by exploiting atmospheric convection. An autonomous soaring research project was conducted at the NASA Dryden Flight Research Center to evaluate the concept through flight test of an electric-powered motorglider with a wingspan of 4.27 m (14 ft). The UAV's commercial autopilot software was modified to include outer-loop soaring guidance and control. The aircraft total energy state was used to detect and soar within thermals. Estimated thermal size and position were used to calculate guidance commands for soaring flight. Results from a total of 23 thermal encounters show good performance of the guidance and control algorithms to autonomously detect and exploit thermals. The UAV had an average climb of 172 m (567 ft) during these encounters.

Guidance and Control of an Autonomous Soaring UAV

NASA Technical Reports Server (NTRS)

Allen, Michael J.

2007-01-01

Thermals caused by convection in the lower atmosphere are commonly used by birds and glider pilots to extend flight duration, increase cross-country speed, improve range, or simply to conserve energy. Uninhabited Aerial Vehicles (UAVs) can also increase performance and reduce energy consumption by exploiting atmospheric convection. An autonomous soaring research project was conducted at the NASA Dryden Flight Research Center to evaluate the concept through flight test of an electric-powered motor-glider with a wingspan of 4.27 m (14 ft). The UAV's commercial autopilot software was modified to include outer-loop soaring guidance and control. The aircraft total energy state was used to detect and soar within thermals. Estimated thermal size and position were used to calculate guidance commands for soaring flight. Results from a total of 23 thermal encounters show good performance of the guidance and control algorithms to autonomously detect and exploit thermals. The UAV had an average climb of 172 m (567 ft) during these encounters.

Development of cryogenic thermal control heat pipes. [of stainless steels

NASA Technical Reports Server (NTRS)

1978-01-01

The development of thermal control heat pipes that are applicable to the low temperature to cryogenic range was investigated. A previous effort demonstrated that stainless steel axially grooved tubing which met performance requirements could be fabricated. Three heat pipe designs utilizing stainless steel axially grooved tubing were fabricated and tested. One is a liquid trap diode heat pipe which conforms to the configuration and performance requirements of the Heat Pipe Experiment Package (HEPP). The HEPP is scheduled for flight aboard the Long Duration Flight Exposure Facility (LDEF). Another is a thermal switch heat pipe which is designed to permit energy transfer at the cooler of the two identical legs. The third thermal component is a hybrid variable conductance heat pipe (VCHP). The design incorporates both a conventional VCHP system and a liquid trap diode. The design, fabrication and thermal testing of these heat pipes is described. The demonstrated heat pipe behavior including start-up, forward mode transport, recovery after evaporator dry-out, diode performance and variable conductance control are discussed.

Macro-fiber composites under thermal cycles for space applications

NASA Astrophysics Data System (ADS)

Acosta, Krystal L.; Hobeck, Jared D.; Owen, Robert B.; Inman, Daniel J.

2017-04-01

Macro-Fiber Composites (MFCs) are a piezoelectric material typically employed in applications ranging from vibration damping to actuation to structural health monitoring. These composites have flown in space but only with thermal protection and for a short duration. They have not been significantly tested under thermally cyclic conditions similar to those they would experience in Low-Earth Orbit (LEO) without shielding. Research has shown that the performance of MFCs varies when the MFC undergoes a thermal cycle. This paper outlines an autonomous experiment that will be able to run impedance measurements and actuate MFCs, further testing their performance in a space environment where thermal cycles are common. This will be installed on a CubeSat and flown to LEO where it will collect data and downlink it back for study. Details of the layout of the experiments and electronic systems being used on the CubeSat for the payload are presented alongside future steps that need to be taken to ensure a successful flight.

Thermal-field propagation in an exocontact zone of a magmatic body and its impact on radiogenic isotope concentrations in minerals.

PubMed

Brandt, I S; Rasskazov, S V; Brandt, S B; Ivanov, A V

2002-03-01

In application of radioactive isotope systems (K-Ar, Rb-Sr etc.) during the last decades, experience was gained not only on their geochronometrical uses, but also on estimations of some important parameters of geological processes, especially temperatures and durations of superimposed thermal events. In this paper, the formation of an exocontact thermal field of a magmatic intrusion is considered as a spreading of a thermal source delta-function. Appropriate solutions of the heat-transfer equation are deduced and correlated with diffusion parameters of the radiogenic argon, coupling radioactive, thermal and kinetic parameters in an exocontant zone of a magmatic body. These solutions were used for quantitative reinterpretations of data taken from Hart's classical paper [The petrology and isotopic mineral age relations of a contact zone in the Front Range, Colorado. J. Geol., 1964, v. 72, pp. 493-525]. Theoretic and measured radiogenic argon and strontium concentrations within exocontact aureoles are found to be in good concordance.

Diurnal variations of summer precipitation over the regions east to Tibetan Plateau

NASA Astrophysics Data System (ADS)

Wu, Yang; Huang, Anning; Huang, Danqing; Chen, Fei; Yang, Ben; Zhou, Yang; Fang, Dexian; Zhang, Lujun; Wen, Lijuan

2017-12-01

Based on the hourly gauge-satellite merged precipitation product with the horizontal resolution of 0.1° latitude/longitude during 2008-2014, diurnal variations of the summer precipitation amount (PA), frequency (PF), and intensity (PI) with different duration time over the regions east to Tibetan Plateau have been systematically revealed in this study. Results indicate that the eight typical precipitation diurnal patterns identified by the cluster analysis display pronounced regional features among the plateaus, basins, plains, hilly and coastal areas. The precipitation diurnal cycles are significantly affected by the sub-grid terrain fluctuations. The PA, PF and PI of the total rainfall show much more pronounced double diurnal peaks with the sub-grid topography standard deviation (SD) decreased. Meanwhile, the diurnal peaks of PA and PF (PI) strengthen (weaken) with the sub-grid topography SD enhanced. Over the elevated mountain ranges, southeastern hilly and coastal regions, the PA and PF diurnal patterns of the total rainfall generally show predominant late-afternoon peaks, which are closely associated with the short-duration (≤slant 3 h) rainfall. Along the Tibetan Plateau to its downstream, the diurnal peaks of PA, PF and PI for the total rainfall all exhibit obvious eastward phase time delay mainly due to the diurnal evolutions of long-duration (> 6 h) rainfall. However, the 4-6 h rainfall leads to the eastward phase time delay of the total rainfall along the Taihang Mountains to its downstream. Further mechanism analysis suggests that the midnight to morning diurnal evolution of the long-duration rainfall is closely associated with the diurnal variations of the upward branches of thermally driven mountain-plain solenoids and the water vapor transport associated with the accelerated nocturnal southwesterly winds. The late-afternoon peak of the short-duration PA over the southeastern hilly and coastal regions is ascribed to the strong local thermal convections due to the solar heating in afternoon, while the early-evening peak of the short-duration PA over the elevated mountain ranges is significantly contributed by the upward warm-moist wind from the surrounding low-lying basins or plains.

Work duration does not affect cortisol output in experienced firefighters performing live burn drills.

PubMed

Rosalky, Deena S; Hostler, David; Webb, Heather E

2017-01-01

Work duration may affect firefighters' stress responses. Forty-two firefighters (38 males) performed either 2 (SWD) or 3 (LWD) bouts of simulated fire suppression activity. Salivary cortisol, self-reported fear and anxiety, and perceptual thermal responses were measured. Cortisol was evaluated using area-under-the-curve calculations (Pruessner et al., 2003). Affective responses between the two conditions were compared using T-tests. Pearson product moment correlations were used to analyze the relationships between affect and change in thermal load perception. Cortisol decreased across the protocol in both groups, and no difference was found in cortisol or affect between the groups. Cortisol decreased (F4,36 = 3.43, p < 0.05) in the SWD group from a mean concentration of 40.93 ± 11.41 nmol/L to 25.07 ± 9.88 nmol/L at the end of the protocol. In the LWD group, the mean cortisol concentration decreased from 42.89 ± 11.83 to 25.07 ± 8.82 at the end of the protocol (F5,50 = 14.77, p < 0.01). Anxiety increased in the LWD (F4,72 = 5.11, p = 0.001) but not the SWD group. Fear increased in the SWD (F3,48 = 14.15, p < 0.001) and LWD group (F4,60 = 4.47, p < 0.01). The present findings suggests a moderate fear load with firefighting, which appears not to be associated with duration of work bout. Examination of more varied work bout lengths may reveal an association between anxiety and work duration. However, the work bout durations investigated in the current study comprise the range of what is practical from an occupational standpoint and the physiological capabilities of the firefighters. Copyright © 2016 Elsevier Ltd. All rights reserved.

An investigation of the spatial selectivity of the duration after-effect.

PubMed

Maarseveen, Jim; Hogendoorn, Hinze; Verstraten, Frans A J; Paffen, Chris L E

2017-01-01

Adaptation to the duration of a visual stimulus causes the perceived duration of a subsequently presented stimulus with a slightly different duration to be skewed away from the adapted duration. This pattern of repulsion following adaptation is similar to that observed for other visual properties, such as orientation, and is considered evidence for the involvement of duration-selective mechanisms in duration encoding. Here, we investigated whether the encoding of duration - by duration-selective mechanisms - occurs early on in the visual processing hierarchy. To this end, we investigated the spatial specificity of the duration after-effect in two experiments. We measured the duration after-effect at adapter-test distances ranging between 0 and 15° of visual angle and for within- and between-hemifield presentations. We replicated the duration after-effect: the test stimulus was perceived to have a longer duration following adaptation to a shorter duration, and a shorter duration following adaptation to a longer duration. Importantly, this duration after-effect occurred at all measured distances, with no evidence for a decrease in the magnitude of the after-effect at larger distances or across hemifields. This shows that adaptation to duration does not result from adaptation occurring early on in the visual processing hierarchy. Instead, it seems likely that duration information is a high-level stimulus property that is encoded later on in the visual processing hierarchy. Copyright © 2016 Elsevier Ltd. All rights reserved.

Analytical estimation of ultrasound properties, thermal diffusivity, and perfusion using magnetic resonance-guided focused ultrasound temperature data

PubMed Central

Dillon, C R; Borasi, G; Payne, A

2016-01-01

For thermal modeling to play a significant role in treatment planning, monitoring, and control of magnetic resonance-guided focused ultrasound (MRgFUS) thermal therapies, accurate knowledge of ultrasound and thermal properties is essential. This study develops a new analytical solution for the temperature change observed in MRgFUS which can be used with experimental MR temperature data to provide estimates of the ultrasound initial heating rate, Gaussian beam variance, tissue thermal diffusivity, and Pennes perfusion parameter. Simulations demonstrate that this technique provides accurate and robust property estimates that are independent of the beam size, thermal diffusivity, and perfusion levels in the presence of realistic MR noise. The technique is also demonstrated in vivo using MRgFUS heating data in rabbit back muscle. Errors in property estimates are kept less than 5% by applying a third order Taylor series approximation of the perfusion term and ensuring the ratio of the fitting time (the duration of experimental data utilized for optimization) to the perfusion time constant remains less than one. PMID:26741344

Temperature and heat flux measurements: Challenges for high temperature aerospace application

NASA Technical Reports Server (NTRS)

Neumann, Richard D.

1992-01-01

The measurement of high temperatures and the influence of heat transfer data is not strictly a problem of either the high temperatures involved or the level of the heating rates to be measured at those high temperatures. It is a problem of duration during which measurements are made and the nature of the materials in which the measurements are made. Thermal measurement techniques for each application must respect and work with the unique features of that application. Six challenges in the development of measurement technology are discussed: (1) to capture the character and localized peak values within highly nonuniform heating regions; (2) to manage large volumes of thermal instrumentation in order to efficiently derive critical information; (3) to accommodate thermal sensors into practical flight structures; (4) to broaden the capabilities of thermal survey techniques to replace discrete gages in flight and on the ground; (5) to provide supporting instrumentation conduits which connect the measurement points to the thermally controlled data acquisition system; and (6) to develop a class of 'vehicle tending' thermal sensors to assure the integrity of flight vehicles in an efficient manner.

Space station thermal control surfaces. Volume 1: Interim report

NASA Technical Reports Server (NTRS)

Maag, C. R.; Millard, J. M.

1978-01-01

The U.S. space program goals for long-duration manned missions place particular demands on thermal-control systems. The objective of this program is to develop plans which are based on the present thermal-control technology, and which will keep pace with the other space program elements. The program tasks are as follows: (1) requirements analysis, with the objectives to define the thermal-control-surface requirements for both space station and 25 kW power module, to analyze the missions, and to determine the thermal-control-surface technology needed to satisfy both sets of requirements; (2) technology assessment, with the objectives to perform a literature/industry survey on thermal-control surfaces, to compare current technology with the requirements developed in the first task, and to determine what technology advancements are required for both the space station and the 25 kW power module; and (3) program planning that defines new initiative and/or program augmentation for development and testing areas required to provide the proper environment control for the space station and the 25 kW power module.

Analysis of airborne pesticides from different chemical classes adsorbed on Radiello® Tenax® passive tubes by thermal-desorption-GC/MS.

PubMed

Raeppel, Caroline; Fabritius, Marie; Nief, Marie; Appenzeller, Brice M R; Briand, Olivier; Tuduri, Ludovic; Millet, Maurice

2015-02-01

An analytical methodology using automatic thermal desorption (ATD) and GC/MS was developed for the determination of 28 pesticides of different chemical classes (dichlobenil, carbofuran, trifluralin, clopyralid, carbaryl, flazasulfuron, mecoprop-P, dicamba, 2,4-MCPA, dichlorprop, 2,4-D, triclopyr, cyprodinil, bromoxynil, fluroxypyr, oxadiazon, myclobutanil, buprofezin, picloram, trinexapac-p-ethyl, ioxynil, diflufenican, tebuconazole, bifenthrin, isoxaben, alphacypermethrin, fenoxaprop and tau-fluvalinate) commonly used in nonagricultural areas in atmospheric samples. This methodology was developed to evaluate the indoor and outdoor atmospheric contamination by nonagricultural pesticides. Pesticides were sampled passive sampling tubes containing Tenax® adsorbent. Since most of these pesticides are polar (clopyralid, mecoprop-P, dicamba, 2,4-MCPA, dichlorprop, 2,4-D, triclopyr, bromoxynil, fluroxypyr, picloram, trinexapac-p-ethyl and ioxynil), a derivatisation step is required. For this purpose, a silylation step using N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide (MtBSTFA) was added before thermal desorption. This agent was chosen since it delivers very specific ions on electronic impact (m/z = M-57). This method was established with special consideration for optimal thermal desorption conditions (desorption temperature, desorb flow and duration; trap heating duration and flow; outlet split), linear ranges, limits of quantification and detection which varied from 0.005 to 10 ng and from 0.001 to 2.5 ng, respectively, for an uncertainty varied from 8 to 30 %. The method was applied in situ to the analysis of passive tubes exposed during herbicide application to an industrial site in east of France.

Nociception and inflammatory hyperalgesia evaluated in rodents using infrared laser stimulation after Trpv1 gene knockout or resiniferatoxin lesion.

PubMed

Mitchell, Kendall; Lebovitz, Evan E; Keller, Jason M; Mannes, Andrew J; Nemenov, Michael I; Iadarola, Michael J

2014-04-01

TRPV1 is expressed in a subpopulation of myelinated Aδ and unmyelinated C-fibers. TRPV1+ fibers are essential for the transmission of nociceptive thermal stimuli and for the establishment and maintenance of inflammatory hyperalgesia. We have previously shown that high-power, short-duration pulses from an infrared diode laser are capable of predominantly activating cutaneous TRPV1+ Aδ-fibers. Here we show that stimulating either subtype of TRPV1+ fiber in the paw during carrageenan-induced inflammation or following hind-paw incision elicits pronounced hyperalgesic responses, including prolonged paw guarding. The ultrapotent TRPV1 agonist resiniferatoxin (RTX) dose-dependently deactivates TRPV1+ fibers and blocks thermal nociceptive responses in baseline or inflamed conditions. Injecting sufficient doses of RTX peripherally renders animals unresponsive to laser stimulation even at the point of acute thermal skin damage. In contrast, Trpv1-/- mice, which are generally unresponsive to noxious thermal stimuli at lower power settings, exhibit withdrawal responses and inflammation-induced sensitization using high-power, short duration Aδ stimuli. In rats, systemic morphine suppresses paw withdrawal, inflammatory guarding, and hyperalgesia in a dose-dependent fashion using the same Aδ stimuli. The qualitative intensity of Aδ responses, the leftward shift of the stimulus-response curve, the increased guarding behaviors during carrageenan inflammation or after incision, and the reduction of Aδ responses with morphine suggest multiple roles for TRPV1+ Aδ fibers in nociceptive processes and their modulation of pathological pain conditions. Copyright © 2014. Published by Elsevier B.V.

Thermal stress cycling of GaAs solar cells

NASA Technical Reports Server (NTRS)

Janousek, B. K.; Francis, R. W.; Wendt, J. P.

1985-01-01

A thermal cycling experiment was performed on GaAs solar cells to establish the electrical and structural integrity of these cells under the temperature conditions of a simulated low-Earth orbit of 3-year duration. Thirty single junction GaAs cells were obtained and tests were performed to establish the beginning-of-life characteristics of these cells. The tests consisted of cell I-V power output curves, from which were obtained short-circuit current, open circuit voltage, fill factor, and cell efficiency, and optical micrographs, spectral response, and ion microprobe mass analysis (IMMA) depth profiles on both the front surfaces and the front metallic contacts of the cells. Following 5,000 thermal cycles, the performance of the cells was reexamined in addition to any factors which might contribute to performance degradation. It is established that, after 5,000 thermal cycles, the cells retain their power output with no loss of structural integrity or change in physical appearance.

Modelling of thermal shock experiments of carbon based materials in JUDITH

NASA Astrophysics Data System (ADS)

Ogorodnikova, O. V.; Pestchanyi, S.; Koza, Y.; Linke, J.

2005-03-01

The interaction of hot plasma with material in fusion devices can result in material erosion and irreversible damage. Carbon based materials are proposed for ITER divertor armour. To simulate carbon erosion under high heat fluxes, electron beam heating in the JUDITH facility has been used. In this paper, carbon erosion under energetic electron impact is modeled by the 3D thermomechanics code 'PEGASUS-3D'. The code is based on a crack generation induced by thermal stress. The particle emission observed in thermal shock experiments is a result of breaking bonds between grains caused by thermal stress. The comparison of calculations with experimental data from JUDITH shows good agreement for various incident power densities and pulse durations. A realistic mean failure stress has been found. Pre-heating of test specimens results in earlier onset of brittle destruction and enhanced particle loss in agreement with experiments.

Silicic magma differentiation in ascent conduits. Experimental constraints

NASA Astrophysics Data System (ADS)

Rodríguez, Carmen; Castro, Antonio

2017-02-01

Crystallization of water-bearing silicic magmas in a dynamic thermal boundary layer is reproduced experimentally by using the intrinsic thermal gradient of piston-cylinder assemblies. The standard AGV2 andesite under water-undersaturated conditions is set to crystallize in a dynamic thermal gradient of about 35 °C/mm in 10 mm length capsules. In the hotter area of the capsule, the temperature is initially set at 1200 °C and decreases by programmed cooling at two distinct rates of 0.6 and 9.6 °C/h. Experiments are conducted in horizontally arranged assemblies in a piston cylinder apparatus to avoid any effect of gravity settling and compaction of crystals in long duration runs. The results are conclusive about the effect of water-rich fluids that are expelled out the crystal-rich zone (mush), where water saturation is reached by second boiling in the interstitial liquid. Expelled fluids migrate to the magma ahead of the solidification front contributing to a progressive enrichment in the fluxed components SiO2, K2O and H2O. The composition of water-rich fluids is modelled by mass balance using the chemical composition of glasses (quenched melt). The results are the basis for a model of granite magma differentiation in thermally-zoned conduits with application of in-situ crystallization equations. The intriguing textural and compositional features of the typical autoliths, accompanying granodiorite-tonalite batholiths, can be explained following the results of this study, by critical phenomena leading to splitting of an initially homogeneous magma into two magma systems with sharp boundaries. Magma splitting in thermal boundary layers, formed at the margins of ascent conduits, may operate for several km distances during magma transport from deep sources at the lower crust or upper mantle. Accordingly, conduits may work as chromatographic columns contributing to increase the silica content of ascending magmas and, at the same time, leave behind residual mushes that eventually are dragged as enclaves or autoliths.

Long Duration Exposure Facility M0003-5 thermal control coatings on DoD flight experiment

NASA Technical Reports Server (NTRS)

Hurley, Charles J.; Lehn, William L.

1992-01-01

The M0003-5 thermal control coatings and materials orbited on the LDEF M0003 Space Environment Effects on Spacecraft Materials were a part of a Wright Laboratories Materials Directorate larger experiment. They were selected from new materials which emerged from development programs during the 1978-1982 time frame. Included were materials described in the technical literature which were being considered or had been applied to satellites. Materials that had been exposed on previous satellite materials experiments were also included to provide data correlation with earlier space flight experiments. The objective was to determine the effect of the LDEF environment on the physical and optical properties of thermal control coatings and materials. One hundred and two specimens of various pigmented organic and inorganic coatings, metallized polymer thin films, optical solar reflectors, and mirrors were orbited on LDEF. The materials were exposed in four separate locations on the vehicle. The first set was exposed on the direct leading edge of the satellite. The second set was exposed on the direct trailing edge of the vehicle. The third and fourth sets were exposed in environmental exposure control canisters (EECC) located 30 degrees off normal to the leading and trailing edges. The purpose of the experiment was to understand the changes in the properties of materials before and after exposure to the space environment and to compare the changes with predictions based on laboratory experiments. The basic approach was to measure the optical and physical properties of materials before and after long-term exposure to a low earth orbital environment comprised of UV, VUV, electrons, protons, atomic oxygen, thermal cycling, vacuum, debris, and micrometeoroids. Due to the unanticipated extended orbital flight of LDEF, the thermal control coatings and materials in the direct leading and trailing edge were exposed for a full five years and ten months to the space environment and the canister materials were exposed for approximately one year to the full environment.

Optimization and Analysis of Thermoelectric Properties of Unfilled Co(1-x-y)Ni(x)Fe(y)Sb3 Synthesized via a Rapid Hydrothermal Procedure.

PubMed

Gharleghi, Ahmad; Chu, Yu-Hsien; Lin, Fei-Hung; Yang, Zong-Ren; Pai, Yi-Hsuan; Liu, Chia-Jyi

2016-03-02

A series of nanostructured co-doped Co(1-x-y)Ni(x)Fe(y)Sb3 were fabricated using a rapid hydrothermal method at 170 °C for a duration of 12 h, followed by evacuated-and-encapsulated heating at 580 °C for a short period of 5 h. The resulting samples were characterized using powder X-ray diffraction, field emission scanning electron microscopy, bulk density, electronic and thermal transport measurements. The power factor of Co(1-x-y)Ni(x)Fe(y)Sb3 is significantly enhanced in the high-temperature region due to significant enhancement of the electrical conductivity and absolute value of thermopower. The latter arises from the onset of bipolar effect being shifted to higher temperatures as compared with the non-doped CoSb3. The room temperature thermal conductivity falls in the range between 1.22 and 1.67 W m(-1) K(-1) for Co(1-x-y)Ni(x)Fe(y)Sb3. The thermal conductivity of both the (x,y) = (0.14,10) and (0.14,12) samples is measured up to 600 K and found to decrease with increasing temperature. The thermal conductivity of the (0.14,10) sample goes down to ∼1.02 W m(-1) K(-1). As a result, zT = 0.68 is attained at 600 K. The lattice thermal conductivity is analyzed to gain insight into the contribution of various scattering processes that suppress the heat transfer through the phonons in Co(1-x-y)Ni(x)Fe(y)Sb3. The effect of the simultaneous presence of Co, Ni, and Fe elements on the electronic structure and transport properties of Co(1-x-y)Ni(x)Fe(y)Sb3 is described using the quantum mechanical tunneling theory of electron transmission among the potential barriers.

Experimental investigation on IXV TPS interface effects in Plasmatron

NASA Astrophysics Data System (ADS)

Ceglia, Giuseppe; Trifoni, Eduardo; Gouriet, Jean-Baptiste; Chazot, Olivier; Mareschi, Vincenzo; Rufolo, Giuseppe; Tumino, Giorgio

2016-06-01

An experimental investigation related to the thermal protection system (TPS) interfaces of the intermediate experimental vehicle has been carried out in the Plasmatron facility at the von Karman Institute for fluid dynamics. The objective of this test campaign is to qualify the thermal behaviours of two different TPS interfaces under flight representative conditions in terms of heat flux and integral heat load ( 180 kW/m2 for 700 s). Three test samples are tested in off-stagnation configuration installed on an available flat plate holder under the same test conditions. The first junction is composed of an upstream ceramic matrix composite (CMC) plate and an ablative P50 cork composite block separated by a gap of 2 mm. The second one is made of an upstream P50 block and a downstream ablative SV2A silicon elastomer block with silicon-based filler in between. A sample composed of P50 material is tested in order to obtain reference results without TPS interface effect. The overheating at the CMC-P50 interface due to the jump of the catalytic properties of the materials, and the recession/swelling behaviour of the P50-SV2A interface are under investigation. All the test samples withstand relatively well the imposed heat flux for the test duration. As expected, both the ablative materials undergo a thermal degradation. The P50 exhibits the formation of a porous char layer and its recession; on the other hand, the SV2A swells and forms a fragile char layer.

Improved photoacoustic dosimetry for retinal laser surgery

NASA Astrophysics Data System (ADS)

Dufour, Suzie; Brown, Robert B.; Gallant, Pascal; Mermut, Ozzy

2018-02-01

Lasers are employed for numerous medical interventions by exploiting ablative, disruptive or thermal effects. In ocular procedures, lasers have been used for decades to treat diseases such as diabetic retinopathy, macular edema and aged related macular degeneration via photocoagulation of retinal tissues. Although laser photocoagulation is well established in today's practice, efforts to improve clinical outcomes by reducing the collateral damage from thermal diffusion is leading to novel treatments using shorter (μs) laser pulses (e.g. selective retinal therapy) which result in physical rather than thermal damage. However, for these new techniques to be widely utilized, a method is required to ensure safe but sufficient dosage has been applied, since no visible effects can be seen by ophthalmoscopy directly post treatment. Photoacoustic feedback presents an attractive solution, as the signal is dependent directly on absorbed dosage. Here, we present a method that takes advantage of temporal pulse formatting technology to minimize variation in absorbed dose in ophthalmic laser treatment and provide intelligent dosimetry feedback based on photoacoustic (PA) response. This method tailors the pulse to match the frequency response of the sample and/or detection chain. Depending on the system, this may include the absorbing particle size, the laser beam diameter, the laser pulse duration, tissue acoustic properties and the acoustic detector frequency response. A significant improvement (<7x) of photoacoustic signal-to-noise ratio over equivalent traditional pulse formats have been achieved, while spectral analysis of the detected signal provides indications of cavitation events and other sample properties.

Effect of conditions of modification on thermal and rheological properties of phosphorylated pumpkin starch.

PubMed

Przetaczek-Rożnowska, Izabela; Fortuna, Teresa

2017-11-01

This study aimed at analyzing the effect of conditions of modification process on thermal and rheological properties of phosphorylated pumpkin starch. The esterification process was conducted at 115°C and 145°C for 1, 2, and 3h. The thermodynamic properties of samples were determined using differential scanning calorimetry (DSC), flow curves were plotted and the resulting curves were described the Herschel-Bulkley model, textural properties were evaluated with the TPA method. The data proved that the chemical modification of starch affected its rheological and thermal characteristics, but the direction and extent of the changes were found to depend on both temperature and duration of phoshorylation. The results demonstrated that temperatures of gelatinization of the samples modified at 145°C were higher by 1.4-8.5°C than those of the samples obtained at 115°C. Prolongation of starch modification at 115°C caused reduction of shear stress (from 2.10Pa to 0.86Pa), and higher temperature of esterification also reduced the value of this parameter. The hardness of the samples heated at 145°C was higher by 45-59N than that of heated at 115°C. Adjustment of phosphorylation process caused an increase in gumminess by 1.8-37.9N, wherein higher temperature and process prolongation resulted in the highest gumminess. Copyright © 2017 Elsevier B.V. All rights reserved.

Metastability of a-SiOx:H thin films for c-Si surface passivation

NASA Astrophysics Data System (ADS)

Serenelli, L.; Martini, L.; Imbimbo, L.; Asquini, R.; Menchini, F.; Izzi, M.; Tucci, M.

2017-01-01

The adoption of a-SiOx:H films obtained by PECVD in heterojunction solar cells is a key to further increase their efficiency, because of its transparency in the UV with respect to the commonly used a-Si:H. At the same time this layer must guarantee high surface passivation of the c-Si to be suitable in high efficiency solar cell manufacturing. On the other hand the application of amorphous materials like a-Si:H and SiNx on the cell frontside expose them to the mostly energetic part of the sun spectrum, leading to a metastability of their passivation properties. Moreover as for amorphous silicon, thermal annealing procedures are considered as valuable steps to enhance and stabilize thin film properties, when performed at opportune temperature. In this work we explored the reliability of a-SiOx:H thin film layers surface passivation on c-Si substrates under UV exposition, in combination with thermal annealing steps. Both p- and n-type doped c-Si substrates were considered. To understand the effect of UV light soaking we monitored the minority carriers lifetime and Sisbnd H and Sisbnd O bonding, by FTIR spectra, after different exposure times to light coming from a deuterium lamp, filtered to UV-A region, and focused on the sample to obtain a power density of 50 μW/cm2. We found a certain lifetime decrease after UV light soaking in both p- and n-type c-Si passivated wafers according to a a-SiOx:H/c-Si/a-SiOx:H structure. The role of a thermal annealing, which usually enhances the as-deposited SiOx passivation properties, was furthermore considered. In particular we monitored the UV light soaking effect on c-Si wafers after a-SiOx:H coating by PECVD and after a thermal annealing treatment at 300 °C for 30 min, having selected these conditions on the basis of the study of the effect due to different temperatures and durations. We correlated the lifetime evolution and the metastability effect of thermal annealing to the a-SiOx:H/c-Si interface considering the evolution of hydrogen in the film revealed by FTIR spectra, and we developed a model for the effect of both treatments on the Sisbnd H bonding and the metastability shown in the lifetime of a-SiOx:H/c-Si/a-SiOx:H structure. We found that, after UV exposure, thermal annealing steps can be used as a tool for the c-Si passivation recovery and enhancement.

Thermal durations and heating behaviour for the Barrovian metamorphism, Scotland

NASA Astrophysics Data System (ADS)

Viete, D. R.; Lister, G. S.; Hermann, J.; Forster, M. A.; Oliver, G. J.

2008-12-01

Published U/Pb ages for the syn-metamorphic gabbros and granites of the Grampian Terrane, Scotland, that provided heat for the classical Barrovian metamorphism, suggests that they were emplaced between 473.5 and 470 Ma. New SHRIMP U/Pb ages of 472.2 ± 5.8 Ma and 470.4 ± 6.1 Ma for peak metamorphism in the highest-grade units of the Barrovian metamorphic series are consistent with a 473.5 to 470 Ma heating episode in the highest-grade units. U/Pb-calibrated 40Ar/39Ar ages for white mica from the Barrovian metamorphic series vary from c. 465 Ma for the biotite zone to c. 461 Ma for the sillimanite zone and suggest that the Barrovian thermal episode lasted less than 8.5 million years in the biotite zone and less than 12.5 million years in the sillimanite zone. The lowest-grade units of the Barrovian metamorphic series retain detrital ages in white mica 40Ar/39Ar step-heating spectra, while units metamorphosed to temperatures of 475°C or more yield Grampian 40Ar/39Ar plateau ages. Forward modelling of Ar diffusion from white mica grains was carried out for different grain sizes and thermal histories to match the position of the across-metamorphic-grade transition from detrital 40Ar/39Ar patterns to Grampian 40Ar/39Ar plateau ages. The results of Ar diffusion modelling are consistent with thermal durations of between one and 4.5 million years for the Barrovian metamorphism of the biotite zone. Microstructural observations suggest that peak metamorphism and cooling occurred earliest in the lowest-grade units of the Barrovian metamorphic series and metamorphism in the higher-grade units continued for longer. We propose metamorphic durations of between 3.5 and eight million years for the Barrovian metamorphism of the sillimanite zone. Geochemical textures preserved within high-grade garnets from the Barrovian metamorphic series record evidence of Mn diffusion over c. 1000 μm lengthscales during the Barrovian metamorphism. In addition, sillimanite-grade garnets from the Barrovian metamorphic series preserve c. 100 μm diffusion textures between sillimanite-grade rim domains and lower-grade cores. Timescales for Fickian diffusion processes increase with the square of the diffusion lengthscale. Lengthscales of diffusion are considered within the context of 3.5- to eight-million-year duration for the Barrovian thermal event. Heat associated with regional metamorphism appears to have accumulated within the metamorphosed units following numerous, short- timescale (tens of thousands of year) heating events. Shear zones that occur in the highest-grade parts of the Barrovian metamorphic series provide a suitably narrow heating region for regional metamorphism over a several million years and, with episodic movement histories, can account for self-similar heating behaviour (by mechanical work and/or the introduction of magmas and hot fluids).

Effects of elevated core temperature and normoxic 30% nitrous oxide on human ventilation during short duration, high intensity exercise.

PubMed

Yogev, A; Hall, A M; Jay, O; White, M D

2015-01-15

It was hypothesized that normoxic 30% nitrous oxide (N2O) would suppress and hyperthermia would increase exercise ventilation during short duration, high intensity exercise. Thirteen males (24.2±0.8y; mean±SE), of normal physique (BMI, 23.8±1.0kgm(-2)), performed 4 separate 30s Wingate tests on a cycle ergometer. Exercise ventilation and its components, as well as mean skin and esophageal temperature (TES), were assessed in 2 way experimental design with factors of Thermal State (Normothermia or Hyperthermia) and Gas Type (Air or 30% Normomoxic N2O). In the 2 hyperthermic tests TES was elevated to ∼38.5°C in a 40°C bath. The main results indicated a significant interaction (F=7.14, P=0.02) between Gas Type and Thermal state for the exercise-induced increase in ventilation (ΔV˙E). During both the normothermia and hyperthermia conditions with AIR breathing, the exercise ΔV˙E was ∼80Lmin(-1) and it was significantly decreased to 73.1±24.1Lmin(-1) in the normothermia condition with N2O breathing relative to that of 92.0±25.0Lmin(-1) in the hyperthermia condition with N2O breathing. In conclusion, normoxic N2O breathing suppressed high intensity exercise ventilation during normothermia relative to that during hyperthermia on account of decreases in the tidal volume and this led CO2 retention. Copyright © 2014 Elsevier B.V. All rights reserved.

Repetitive pulses and laser-induced retinal injury thresholds

NASA Astrophysics Data System (ADS)

Lund, David J.

2007-02-01

Experimental studies with repetitively pulsed lasers show that the ED 50, expressed as energy per pulse, varies as the inverse fourth power of the number of pulses in the exposure, relatively independently of the wavelength, pulse duration, or pulse repetition frequency of the laser. Models based on a thermal damage mechanism cannot readily explain this result. Menendez et al. proposed a probability-summation model for predicting the threshold for a train of pulses based on the probit statistics for a single pulse. The model assumed that each pulse is an independent trial, unaffected by any other pulse in the train of pulses and assumes that the probability of damage for a single pulse is adequately described by the logistic curve. The requirement that the effect of each pulse in the pulse train be unaffected by the effects of other pulses in the train is a showstopper when the end effect is viewed as a thermal effect with each pulse in the train contributing to the end temperature of the target tissue. There is evidence that the induction of cell death by microcavitation bubbles around melanin granules heated by incident laser irradiation can satisfy the condition of pulse independence as required by the probability summation model. This paper will summarize the experimental data and discuss the relevance of the probability summation model given microcavitation as a damage mechanism.

Heat-balling wasps by honeybees

NASA Astrophysics Data System (ADS)

Ken, Tan; Hepburn, H. R.; Radloff, S. E.; Yusheng, Yu; Yiqiu, Liu; Danyin, Zhou; Neumann, P.

2005-10-01

Defensiveness of honeybee colonies of Apis cerana and Apis mellifera (actively balling the wasps but reduction of foraging) against predatory wasps, Vespa velutina, and false wasps was assessed. There were significantly more worker bees in balls of the former than latter. Core temperatures in a ball around a live wasp of A. cerana were significantly higher than those of A. mellifera, and also significantly more when exposed to false wasps. Core temperatures of bee balls exposed to false wasps were significantly lower than those exposed to V. velutina for both A. cerana and for A. mellifera. The lethal thermal limits for V. velutina, A. cerana and A. mellifera were significantly different, so that both species of honeybees have a thermal safety factor in heat-killing such wasp predators. During wasps attacks at the hives measured at 3, 6 and 12 min, the numbers of Apis cerana cerana and Apis cerana indica bees continuing to forage were significantly reduced with increased wasp attack time. Tropical lowland A. c. indica reduced foraging rates significantly more than the highland A. c. cerana bees; but, there was no significant effect on foraging by A. mellifera. The latency to recovery of honeybee foraging was significantly greater the longer the duration of wasp attacks. The results show remarkable thermal fine-tuning in a co-evolving predator prey relationship.

Controlled tissue emulsification produced by high intensity focused ultrasound shock waves and millisecond boiling

PubMed Central

Khokhlova, Tatiana D.; Canney, Michael S.; Khokhlova, Vera A.; Sapozhnikov, Oleg A.; Crum, Lawrence A.; Bailey, Michael R.

2011-01-01

In high intensity focused ultrasound (HIFU) applications, tissue may be thermally necrosed by heating, emulsified by cavitation, or, as was recently discovered, emulsified using repetitive millisecond boiling caused by shock wave heating. Here, this last approach was further investigated. Experiments were performed in transparent gels and ex vivo bovine heart tissue using 1, 2, and 3 MHz focused transducers and different pulsing schemes in which the pressure, duty factor, and pulse duration were varied. A previously developed derating procedure to determine in situ shock amplitudes and the time-to-boil was refined. Treatments were monitored using B-mode ultrasound. Both inertial cavitation and boiling were observed during exposures, but emulsification occurred only when shocks and boiling were present. Emulsified lesions without thermal denaturation were produced with shock amplitudes sufficient to induce boiling in less than 20 ms, duty factors of less than 0.02, and pulse lengths shorter than 30 ms. Higher duty factors or longer pulses produced varying degrees of thermal denaturation combined with mechanical emulsification. Larger lesions were obtained using lower ultrasound frequencies. The results show that shock wave heating and millisecond boiling is an effective and reliable way to emulsify tissue while monitoring the treatment with ultrasound. PMID:22088025

Dentin surface treatment using a non-thermal argon plasma brush for interfacial bonding improvement in composite restoration

PubMed Central

Ritts, Andy Charles; Li, Hao; Yu, Qingsong; Xu, Changqi; Yao, Xiaomei; Hong, Liang; Wang, Yong

2010-01-01

The objective of this study is to investigate the treatment effects of non-thermal atmospheric gas plasmas on dentin surfaces for composite restoration. Extracted unerupted human third molars were used by removing the crowns and etching the exposed dentin surfaces with 35% phosphoric acid gel. The dentin surfaces were treated by using a non-thermal atmospheric argon plasma brush for various durations. The molecular changes of the dentin surfaces were analyzed using FTIR/ATR and an increase in carbonyl groups on dentin surfaces was detected with plasma treated dentin. Adper Single Bond Plus adhesive and Filtek Z250 dental composite were applied as directed. To evaluate the dentin/composite interfacial bonding, the teeth thus prepared were sectioned into micro-bars as the specimens for tensile test. Student Newman Keuls tests showed that the bonding strength of the composite restoration to peripheral dentin was significantly increased (by 64%) after 30 s plasma treatment. However, the bonding strength to plasma treated inner dentin did not show any improvement. It was found that plasma treatment of peripheral dentin surface up to 100 s gave an increase in interfacial bonding strength, while a prolong plasma treatment of dentin surfaces, e.g., 5 min treatments, showed a decrease in interfacial bonding strength. PMID:20831586

Optimization-based sale transactions and hydrothermal scheduling

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

Prasannan, B.; Luh, P.B.; Yan, H.

1995-12-31

Selling and purchasing power are important activities for utilities because of potential savings. When a selling utility presents an offer including prices, power levels and durations, a purchasing utility selects power levels and durations within the offered range subject to relevant constraints. The decisionmaking process is complicated because transactions are coupled with system demand and reserve, therefore decisions have to be made in conjunction with the commitment and dispatching of units. Furthermore, transaction decisions have to be made in almost real time in view of the competitiveness of the power market caused by deregulation. In this paper, transactions are analyzedmore » from a selling utility`s viewpoint for a system consisting of thermal, hydro and pumped-storage units. To effectively solve the problem, linear sale revenues are approximated by nonlinear functions, and non-profitable options are identified and eliminated from consideration. The multipliers are then updated at the high level by using a modified subgradient method to obtain near optimal solutions quickly. Testing results show that the algorithm produces good sale offers efficiently.« less

Optimization-based sale transactions and hydrothermal scheduling

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

Prasannan, B.; Luh, P.B.; Yan, H.

1996-05-01

Selling and purchasing power are important activities for utilities because of potential savings. When a selling utility presents an offer including prices, power levels and durations, a purchasing utility selects power levels and durations within the offered range subject to relevant constraints. The decisionmaking process is complicated because transactions are coupled with system demand and reserve, therefore decisions have to be made in conjunction with the commitment and dispatching of units. Furthermore, transaction decisions have to be made in almost real time in view of the competitiveness of the power market caused by deregulation. In this paper, transactions are analyzedmore » from a selling utility`s viewpoint for a system consisting of thermal, hydro and pumped-storage units. To effectively solve the problem, linear sale revenues are approximated by nonlinear functions, and non-profitable options are identified and eliminated from consideration. The multipliers are then updated at the high level by using a modified subgradient method to obtain near optimal solutions quickly. Testing results show that the algorithm produces good sale offers efficiently.« less

Tank Pressure Control Experiment on the Space Shuttle

NASA Technical Reports Server (NTRS)

1989-01-01

The tank pressure control experiment is a demonstration of NASA intent to develop new technology for low-gravity management of the cryogenic fluids that will be required for future space systems. The experiment will use freon as the test fluid to measure the effects of jet-induced fluid mixing on storage tank pressure and will produce data on low-gravity mixing processes critical to the design of on-orbit cryogenic storage and resupply systems. Basic data on fluid motion and thermodynamics in low gravity is limited, but such data is critical to the development of space transfer vehicles and spacecraft resupply facilities. An in-space experiment is needed to obtain reliable data on fluid mixing and pressure control because none of the available microgravity test facilities provide a low enough gravity level for a sufficient duration to duplicate in-space flow patterns and thermal processes. Normal gravity tests do not represent the fluid behavior properly; drop-tower tests are limited in length of time available; aircraft low-gravity tests cannot provide the steady near-zero gravity level and long duration needed to study the subtle processes expected in space.

Past primary sex-ratio estimates of 4 populations of Loggerhead sea turtle based on TSP durations.

NASA Astrophysics Data System (ADS)

Monsinjon, Jonathan; Kaska, Yakup; Tucker, Tony; LeBlanc, Anne Marie; Williams, Kristina; Rostal, David; Girondot, Marc

2016-04-01

Ectothermic species are supposed to be strongly affected by climate change and particularly those that exhibit temperature-dependent sex-determination (TSD). Actually, predicting the embryonic response of such organism to incubation-temperature variations in natural conditions remains challenging. In order to assess the vulnerability of sea turtles, primary sex-ratio estimates should be produced at pertinent ecological time and spatial scales. Although information on this important demographic parameter is one of the priorities for conservation purpose, accurate methodology to produce such an estimate is still lacking. The most commonly used method invocates incubation duration as a proxy for sex-ratio. This method is inappropriate because temperature influences incubation duration during all development whereas sex is influenced by temperature during only part of development. The thermosensitive period of development for sex determination (TSP) lies in the middle third of development. A model of embryonic growth must be used to define precisely the position of the TSP at non-constant incubation temperatures. The thermal reaction norm for embryonic growth rate have been estimated for 4 distinct populations of the globally distributed and threatened marine turtle Caretta caretta. A thermal reaction norm describes the pattern of phenotypic expression of a single genotype across a range of temperatures. Moreover, incubation temperatures have been reconstructed for the last 35 years using a multi-correlative model with climate temperature. After development of embryos have been modelled, we estimated the primary sex-ratio based on the duration of the TSP. Our results suggests that Loggerhead sea turtles nesting phenology is linked with the period within which both sexes can be produced in variable proportions. Several hypotheses will be discussed to explain why Caretta caretta could be more resilient to climate change than generally thought for sex determination.

NASA's Plans for Developing Life Support and Environmental Monitoring and Control Systems

NASA Technical Reports Server (NTRS)

Lawson, B. Michael; Jan, Darrell

2006-01-01

Life Support and Monitoring have recently been reworked in response to the Vision for Space Exploration. The Exploration Life Support (ELS) Project has replaced the former Advanced Life Support Element of the Human Systems Research and Technology Office. Major differences between the two efforts include: the separation of thermal systems into a new stand alone thermal project, deferral of all work in the plant biological systems, relocation of food systems to another organization, an addition of a new project called habitation systems, and overall reduction in the number of technology options due to lower funding. The Advanced Environmental Monitoring and Control (AEMC) Element is retaining its name but changing its focus. The work planned in the ELS and AEMC projects is organized around the three major phases of the Exploration Program. The first phase is the Crew Exploration Vehicle (CEV). The ELS and AEMC projects will develop hardware for this short duration orbital and trans-lunar vehicle. The second phase is sortie landings on the moon. Life support hardware for lunar surface access vehicles including upgrades of the CEV equipment and technologies which could not be pursued in the first phase due to limited time and budget will be developed. Monitoring needs will address lunar dust issues, not applicable to orbital needs. The ELS and AEMC equipment is of short duration, but has different environmental considerations. The third phase will be a longer duration lunar outpost. This will consist of a new set of hardware developments better suited for long duration life support and associated monitoring needs on the lunar surface. The presentation will show the planned activities and technologies that are expected to be developed by the ELS and AEMC projects for these program phases.

Quantitative calibration of remote mountain lake sediments as climatic recorders of ice-cover duration

NASA Astrophysics Data System (ADS)

Thompson, R.; Price, D.

2003-04-01

Using a thermal degree modelling approach ice cover duration on European mountain lakes is found to be very sensitive to temperature change. For example our thermal degree model (which incorporates a weather generator) predicts a 100 day shortening in ice-cover duration for a 3 degree Centigrade temperature rise for north facing catchments at elevations of 1200m in the southern Alps, and 1500m in the Pyrenees. 30% higher sensitivities (130d/3oC) are found for the more maritime lakes of Scotland, while lakes in NW Finland, in a more continental setting, have only half the sensitivity (50d/3oC). A pan European data set of the species abundance of 252 diatom taxa in 462 mountain and sub Arctic lakes has been compiled. Taxonomic harmonisation is based on a team effort carried out as an integral part of the AL:PE, CHILL and EMERGE projects. Transfer functions have been created relating ice-cover duration to diatom species composition based on a weighted averaging - partial least squares (WA-PLS) approach. Cross validation was used to test the transfer functions. The pan European data set yields an R-squared of 0.73, an R-squared(jack) of 0.58, and an RMSEP error of 23 days. A regional, northern Scandinavian transect, (151 lakes, 122 taxa) yields an R-squared(jack) of 0.50, and an RMSEP of 9 days. The pan European database displays greatest skill when reconstructing winter or spring temperatures. This contrasts with the summer temperatures normally studied when using local elevation gradients. The northern Scandinavian transect has a remarkably low winter RMSEP of 0.73 oC.

What's All the Talc About? Air Entrainment in Dilute Pyroclastic Density Currents

NASA Astrophysics Data System (ADS)

Marshall, B. J.; Andrews, B. J.; Fauria, K.

2015-12-01

A quantitative understanding of air entrainment is critical to predicting the behaviors of dilute Pyroclastic Density Currents (PDCs), including runout distance, liftoff, and mass fractionation into co-PDC plumes. We performed experiments in an 8.5x6x2.6 meter tank using 20 micron talc powder over a range of conditions to describe air entrainment as a function of temperature, duration and mass flux. The experiments are reproducible and are scaled with respect to the densimetric and thermal Richardson numbers (Ri and RiT), Froude number, thermal to kinetic energy density ratio (TEb/KE), Stokes number, and Settling number, such that they are dynamically similar to natural dilute PDCs. Experiments are illuminated with a swept laser sheet and imaged at 1000 Hz to create 3D reconstructions of the currents, with ~1-2 cm resolution, at up to 1.5 Hz. An array of 30 high-frequency thermocouples record the precise temperature in the currents at 3 Hz. Bulk entrainment rates are calculated based on measured current volumes, surface areas, temperatures and velocities. Entrainment rates vary from ~0-0.9 and do not show simple variation with TEb/KE, Ri, or RiT. Entrainment does, however, increase with decreasing eruption duration and increasing mass flux. Our results suggest that current heads entrain air more efficiently than current bodies (>0.5 compared to ~0.1). Because shorter duration currents have proportionally larger heads, their bulk entrainment rates are controlled by those heads, whereas longer duration currents are dominated by their bodies. Our experiments demonstrate that air entrainment, which exerts a fundamental control on PDC runout and liftoff, varies spatially and temporally within PDCs.

HALT to qualify electronic packages: a proof of concept

NASA Astrophysics Data System (ADS)

Ramesham, Rajeshuni

2014-03-01

A proof of concept of the Highly Accelerated Life Testing (HALT) technique was explored to assess and optimize electronic packaging designs for long duration deep space missions in a wide temperature range (-150°C to +125°C). HALT is a custom hybrid package suite of testing techniques using environments such as extreme temperatures and dynamic shock step processing from 0g up to 50g of acceleration. HALT testing used in this study implemented repetitive shock on the test vehicle components at various temperatures to precipitate workmanship and/or manufacturing defects to show the weak links of the designs. The purpose is to reduce the product development cycle time for improvements to the packaging design qualification. A test article was built using advanced electronic package designs and surface mount technology processes, which are considered useful for a variety of JPL and NASA projects, i.e. (surface mount packages such as ball grid arrays (BGA), plastic ball grid arrays (PBGA), very thin chip array ball grid array (CVBGA), quad flat-pack (QFP), micro-lead-frame (MLF) packages, several passive components, etc.). These packages were daisy-chained and independently monitored during the HALT test. The HALT technique was then implemented to predict reliability and assess survivability of these advanced packaging techniques for long duration deep space missions in much shorter test durations. Test articles were built using advanced electronic package designs that are considered useful in various NASA projects. All the advanced electronic packages were daisychained independently to monitor the continuity of the individual electronic packages. Continuity of the daisy chain packages was monitored during the HALT testing using a data logging system. We were able to test the boards up to 40g to 50g shock levels at temperatures ranging from +125°C to -150°C. The HALT system can deliver 50g shock levels at room temperature. Several tests were performed by subjecting the test boards to various g levels ranging from 5g to 50g, test durations of 10 minutes to 60 minutes, hot temperatures of up to +125°C and cold temperatures down to -150°C. During the HALT test, electrical continuity measurements of the PBGA package showed an open-circuit, whereas the BGA, MLF, and QFPs showed signs of small variations of electrical continuity measurements. The electrical continuity anomaly of the PBGA occurred in the test board within 12 hours of commencing the accelerated test. Similar test boards were assembled, thermal cycled independently from -150°C to +125°C and monitored for electrical continuity through each package design. The PBGA package on the test board showed an anomalous electrical continuity behavior after 959 thermal cycles. Each thermal cycle took around 2.33 hours, so that a total test time to failure of the PBGA was 2,237 hours (or ~3.1 months) due to thermal cycling alone. The accelerated technique (thermal cycling + shock) required only 12 hours to cause a failure in the PBGA electronic package. Compared to the thermal cycle only test, this was an acceleration of ~186 times (more than 2 orders of magnitude). This acceleration process can save significant time and resources for predicting the life of a package component in a given environment, assuming the failure mechanisms are similar in both the tests. Further studies are in progress to make systematic evaluations of the HALT technique on various other advanced electronic packaging components on the test board. With this information one will be able to estimate the number of mission thermal cycles to failure with a much shorter test program. Further studies are in progress to make systematic study of various components, constant temperature range for both the tests. Therefore, one can estimate the number of hours to fail in a given thermal and shock levels for a given test board physical properties.

Space Shuttle power extension package

NASA Technical Reports Server (NTRS)

Loftus, J. P., Jr.; Craig, J. W.

1980-01-01

A modification kit for the Space Transportation System (STS) Orbiter is proposed to provide more power and mission duration for payloads. The power extension package (PEP), a flexible-substrate solar array deployed on the Space Shuttle Orbiter remote manipulator system, can provide as much as 29 kW total power for durations of 10 to 48 days. The kit is installed only for those flights which require enhanced power or duration. The PEP is made possible by development of the flexible-substrate array technology and, in itself, contributes to the technology base for the use of large area solar cells. Modifications to the Orbiter thermal control and life support systems to improve heat balance and to reduce consumables are proposed. The changes consist of repositioning the Orbiter forward radiators and replacing the lithium hydroxide scrubber with a regenerable solid amine.

Ocular hazards of light

NASA Technical Reports Server (NTRS)

Sliney, David H.

1994-01-01

The eye is protected against bright light by the natural aversion response to viewing bright light sources. The aversion response normally protects the eye against injury from viewing bright light sources such as the sun, arc lamps and welding arcs, since this aversion limits the duration of exposure to a fraction of a second (about 0.25 s). The principal retinal hazard resulting from viewing bright light sources is photoretinitis, e.g., solar retinitis with an accompanying scotoma which results from staring at the sun. Solar retinitis was once referred to as 'eclipse blindness' and associated 'retinal burn'. Only in recent years has it become clear that photoretinitis results from a photochemical injury mechanism following exposure of the retina to shorter wavelengths in the visible spectrum, i.e., violet and blue light. Prior to conclusive animal experiments at that time, it was thought to be a thermal injury mechanism. However, it has been shown conclusively that an intense exposure to short-wavelength light (hereafter referred to as 'blue light') can cause retinal injury. The product of the dose-rate and the exposure duration always must result in the same exposure dose (in joules-per-square centimeter at the retina) to produce a threshold injury. Blue-light retinal injury (photoretinitis) can result from viewing either an extremely bright light for a short time, or a less bright light for longer exposure periods. This characteristic of photochemical injury mechanisms is termed reciprocity and helps to distinguish these effects from thermal burns, where heat conduction requires a very intense exposure within seconds to cause a retinal coagulation otherwise, surrounding tissue conducts the heat away from the retinal image. Injury thresholds for acute injury in experimental animals for both corneal and retinal effects have been corroborated for the human eye from accident data. Occupational safety limits for exposure to UVR and bright light are based upon this knowledge. As with any photochemical injury mechanism must consider the action spectrum, which describes the relative effectiveness of different wavelengths in causing a photobiological effect. The action spectrum for photochemical retinal injury peaks at approximately 440 nm.

Application of a liquid crystal spatial light modulator to laser marking.

PubMed

Parry, Jonathan P; Beck, Rainer J; Shephard, Jonathan D; Hand, Duncan P

2011-04-20

Laser marking is demonstrated using a nanosecond (ns) pulse duration laser in combination with a liquid crystal spatial light modulator to generate two-dimensional patterns directly onto thin films and bulk metal surfaces. Previous demonstrations of laser marking with such devices have been limited to low average power lasers. Application in the ns regime enables more complex, larger scale marks to be generated with more widely available and industrially proven laser systems. The dynamic nature of the device is utilized to improve mark quality by reducing the impact of the inherently speckled intensity distribution across the generated image and reduce thermal effects in the marked surface. © 2011 Optical Society of America

Generation of 1-J bursts with picosecond pulses from Perla B thin-disk laser system

NASA Astrophysics Data System (ADS)

Chyla, Michal; Nagisetty, Siva S.; Severova, Patricie; Zhou, Huang; Smrz, Martin; Endo, Akira; Mocek, Tomas

2018-02-01

In many fields of modern physics and industrial applications high-average power pulsed diode-pumped solid-state lasers are essential. Scaling of these lasers towards higher pulse energies is often limited by the onset of thermal effects which are determined by the average power. In this paper we would like to propose a way of increasing the pulse energies by operating the PERLA B laser system in 100 Hz burst mode with 1 ms burst duration and intra-burst repetition rate of 10 kHz. The CPA-based system incorporates fiber front-end, regenerative amplifier and the multipass amplifier followed by the booster amplifier and <2ps compressor.

Effects of LDEF flight exposure on selected polymer matrix resin composite materials

NASA Technical Reports Server (NTRS)

Slemp, Wayne S.; Young, Philip R.; Witte, William G., Jr.; Shen, James Y.

1992-01-01

The characterization of selected graphite fiber reinforced epoxy (934 and 5208) and polysulfone (P1700) matrix resin composites materials which received over five years and nine months of exposure to the low earth orbit (LEO) environment in experiment AO134 on the Long Duration Exposure Facility is reported. The changes in mechanical properties of ultimate tensile strength and tensile modulus for exposed flight specimens are compared to the three sets of control specimens. Marked changes in surface appearance are discussed, and resin loss is reported. The chemical characterization including infrared, thermal, and selected solution property measurements showed that the molecular structure of the polymetric matrix had not changed significantly in response to this exposure.

Evaluation of the analgesic properties of acepromazine maleate, oxymorphone, medetomidine and a combination of acepromazine-oxymorphone.

PubMed

Barnhart, Matthew D; Hubbell, John A E; Muir, William W

2000-07-01

To determine the presence and duration of analgesia after oxymorphone, acepromazine maleate, acepromazine-oxymorphone combination and medetomidine administration in dogs. Blinded, controlled study. Six adult beagle dogs. Each dog participated in five trials receiving acepromazine maleate (0.2 mg kg -1 IM), oxymorphone (0.2 mg kg -1 IM), acepromazine-oxymorphone drug combination (0.2 mg kg -1 each IM), medetomidine (20 μg kg -1 IM) and sterile saline (control). Two specially designed instruments were used for analgesia determination: a heat device (HD) utilized a linear ramped intensity incandescent bulb and a pressure device (PD) consisted of a pneumatic cylinder that protruded a 2.5-cm bolt. The minimum pressure and heat necessary to produce an avoidance response were determined. Analgesia testing was performed prior to and at 30-minute intervals for six hours after drug administration. Oxymorphone, acepromazine-oxymorphone and medetomidine significantly elevated both pressure and heat response thresholds compared to controls and acepromazine. Both medetomidine and acepromazine-oxymorphone provided a significantly longer duration of analgesia than oxymorphone. No adverse effects were observed at any of the thermal or pressure application sites. Oxymorphone, medetomidine and acepromazine-oxymorphone produced significant analgesia with medetomidine and acepromazine-oxymorphone providing the longest duration of analgesia. Copyright © 2000 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.

Mathematical estimation of melt depth in conduction mode of laser spot remelting process

NASA Astrophysics Data System (ADS)

Hadi, Iraj

2012-12-01

A one-dimensional mathematical model based on the front tracking method was developed to predict the melt depth as a function of internal and external parameters of laser spot remelting process in conduction mode. Power density, pulse duration, and thermophysical properties of material including thermal diffusivity, melting point, latent heat, and absorption coefficient have been taken into account in the model of this article. By comparing the theoretical results and experimental welding data of commercial pure nickel and titanium plates, the validity of the developed model was examined. Comparison shows a reasonably good agreement between the theory and experiment. For the sake of simplicity, a graphical technique was presented to obtain the melt depth of various materials at any arbitrary amount of power density and pulse duration. In the graphical technique, two dimensionless constants including the Stefan number (Ste) and an introduced constant named laser power factor (LPF) are used. Indeed, all of the internal and external parameters have been gathered in LPF. The effect of power density and pulse duration on the variation of melt depth for different materials such as aluminum, copper, and stainless steel were investigated. Additionally, appropriate expressions were extracted to describe the minimum power density and time to reach melting point in terms of process parameters. A simple expression is also extracted to estimate the thickness of mushy zone for alloys.

Thermomechanical effect of pulse-periodic laser radiation on cartilaginous and eye tissues

NASA Astrophysics Data System (ADS)

Baum, O. I.; Zheltov, G. I.; Omelchenko, A. I.; Romanov, G. S.; Romanov, O. G.; Sobol, E. N.

2013-08-01

This paper is devoted to theoretical and experimental studies into the thermomechanical action of laser radiation on biological tissues. The thermal stresses and strains developing in biological tissues under the effect of pulse-periodic laser radiation are theoretically modeled for a wide range of laser pulse durations. The models constructed allow one to calculate the magnitude of pressures developing in cartilaginous and eye tissues exposed to laser radiation and predict the evolution of cavitation phenomena occurring therein. The calculation results agree well with experimental data on the growth of pressure and deformations, as well as the dynamics of formation of gas bubbles, in the laser-affected tissues. Experiments on the effect of laser radiation on the trabecular region of the eye in minipigs demonstrated that there existed optimal laser irradiation regimens causing a substantial increase in the hydraulic permeability of the radiation-exposed tissue, which can be used to develop a novel glaucoma treatment method.

Development of thermal control methods for specialized components and scientific instruments at very low temperatures (follow-on)

NASA Technical Reports Server (NTRS)

Wright, J. P.; Wilson, D. E.

1976-01-01

Many payloads currently proposed to be flown by the space shuttle system require long-duration cooling in the 3 to 200 K temperature range. Common requirements also exist for certain DOD payloads. Parametric design and optimization studies are reported for multistage and diode heat pipe radiator systems designed to operate in this temperature range. Also optimized are ground test systems for two long-life passive thermal control concepts operating under specified space environmental conditions. The ground test systems evaluated are ultimately intended to evolve into flight test qualification prototypes for early shuttle flights.

Transverse Uniaxial Composite Thermal Properties Data Base of Thermally Conductive Graphite Fibers with and without Contiguous Grown Graphite Fins

DTIC Science & Technology

2013-07-01

Vacuum Heat Capacity: Test Method: Conventional MCDS Heating Rate 2 oC/min Temperature(oC): -75 -50 -25 0 25 50 75 100 Average (J/goC): 0.5555...PreConditioning Time-Duration: 24hrs at 125oC and -29inch Vacuum Heat Capacity: Test Method: Conventional MCDS Heating Rate 2 oC/min Temperature(oC...29inch Vacuum Heat Capacity: Test Method: Conventional MCDS Heating Rate 2 oC/min Temperature(oC): -75 -50 -25 0 - - - - Average (J/goC

Data bases for LDEF results

NASA Technical Reports Server (NTRS)

Bohnhoff-Hlavacek, Gail

1993-01-01

The Long Duration Exposure Facility (LDEF) carried 57 experiments and 10,000 specimens for some 200 LDEF experiment investigators. The external surface of LDEF had a large variety of materials exposed to the space environment which were tested preflight, during flight, and post flight. Thermal blankets, optical materials, thermal control paints, aluminum, and composites are among the materials flown. The investigations have produced an abundance of analysis results. One of the responsibilities of the Boeing Support Contract, Materials and Systems Special Investigation Group, is to collate and compile that information into an organized fashion. The databases developed at Boeing to accomplish this task is described.

Analysis of erythema after Er:YAG laser skin resurfacing.

PubMed

Ko, Na Young; Ahn, Hyo-Hyun; Kim, Soo-Nam; Kye, Young-Chul

2007-11-01

Postoperative erythema can be expected to occur in every patient after laser resurfacing, and pigmentary disturbances may be related to the intensity and the duration of erythema. This study was undertaken to assess the clinical features of erythema, the factors that influence its duration, and the relation between the duration of erythema and the incidence of hyperpigmentation and hypopigmentation in skin of Asian persons after Er:YAG laser resurfacing. A total of 218 patients (skin phototypes III to V) were recruited and treated with a short-pulsed Er:YAG laser, a variable-pulsed Er:YAG laser, or a dual-mode Er:YAG laser for skin resurfacing. Clinical assessments were performed retrospectively using medical charts and serial photographs. Postoperative erythema was observed in all patients after Er:YAG laser resurfacing with a mean duration of 4.72 months. In 98.2% of patients, erythema faded completely within 12 months. Postinflammatory hyperpigmentation was observed in 38.1% of patients after Er:YAG laser resurfacing. Skin phototype, level of ablation, and depth of thermal damage caused by a long-pulsed laser appear to be important factors that affect the duration of erythema. Moreover, prolonged erythema was related to the risk of postinflammatory hyperpigmentation.

Phaeodarian radiolarians as potential indicators of thermal maturation

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

Casey, R.E.

1986-04-01

Phaeodarian radiolarian skeletons contain large amounts of organic matter, and discolored phaeodarian skeletons are observed in the fossil record, which suggests that the skeletons may be useful as thermal maturation indicators. Such a maturation index would be useful in Monterey-type rocks that are difficult to interpret with conventional thermal maturation indexes. Phaeodarians extracted from plankton samples, Holocene Santa Barbara and Orca basin sediments, and Neogene Monterey rocks with siliceous facies were subjected to different temperatures of varying duration in pyrolysis experiments. To calibrate the observed phaeodarian color changes with a known standard, Holocene pine pollen were subjected to the samemore » treatment. These phaeodarian go through the same color change spectrum as do the pollen, but they appear to lag slightly behind the pollen color changes.« less

Thermal Analysis and Testing of Fastrac Gas Generator Design

NASA Technical Reports Server (NTRS)

Nguyen, H.

1998-01-01

The Fastrac Engine is being developed by the Marshall Space Flight Center (MSFC) to help meet the goal of substantially reducing the cost of access to space. This engine relies on a simple gas-generator cycle, which burns a small amount of RP-1 and oxygen to provide gas to drive the turbine and then exhausts the spent fuel. The Fastrac program envisions a combination of analysis, design and hot-fire evaluation testing. This paper provides the supporting thermal analysis of the gas generator design. In order to ensure that the design objectives were met, the evaluation tests have started on a component level and a total of 15 tests of different durations were completed to date at MSFC. The correlated thermal model results will also be compared against hot-fire thermocouple data gathered.

Discovery of a Powerful, Transient, Explosive Thermal Event at Marduk Fluctus, Io, in Galileo NIMS Data

NASA Astrophysics Data System (ADS)

Davies, A. G.; Davies, R. L.; Veeder, G. J.; de Kleer, K.; de Pater, I.; Matson, D. L.; Johnson, T. V.; Wilson, L.

2018-04-01

Analysis of Galileo Near-Infrared Mapping Spectrometer observations of Marduk Fluctus, a volcano on the Jovian moon Io, reveals a style of volcanic activity not previously seen there—a powerful thermal event lasting only a few minutes in 1996. The thermal emission rapidly fades, suggesting extremely rapid cooling of small clasts. The duration and evolution of the explosive eruption are akin to what might be expected from a strombolian or vulcanian explosion. The presence of such events provides an additional volcanic process that can be imaged by future missions with the intent of determining lava composition from eruption temperature, an important constraint on the internal composition of Io. These data promise to be of particular use in understanding the mechanics of explosive volcanic processes on Io.

Growth of WSi2 in phosphorous-implanted W/«Si» couples

NASA Astrophysics Data System (ADS)

Ma, E.; Lim, B. S.; Nicolet, M.-A.; Alvi, N. S.; Hamdi, A. H.

1988-05-01

The thermal reaction of rf-sputter-deposited tungsten films with a (100) silicon substrate is investigated by vacuum furnace annealing and rapid thermal annealing. An irradiation of the W/Si interface by a phosphorous ion beam at room temperature prior to annealing promotes a uniform interfacial growth of WSi2. The growth of WSi2 follows diffusion-controlled kinetics during both furnace annealing and rapid thermal processing. A growth law of x2 = kt is obtained for furnace annealing between 690 and 740° C, where x is the thickness of the compound, t is the annealing duration after an initial incubation period and k = 62 (cm2/s) exp (--3.0 eV/kT). The surface smoothness of the suicide films improves with increasing ion dose.