Terahertz generation in mid-infrared quantum cascade lasers with a dual-upper-state active region

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

Fujita, Kazuue, E-mail: kfujita@crl.hpk.co.jp; Hitaka, Masahiro; Ito, Akio

2015-06-22

We report the performance of room temperature terahertz sources based on intracavity difference-frequency generation in mid-infrared quantum cascade lasers with a dual-upper-state (DAU) active region. DAU active region design is theoretically expected to produce larger optical nonlinearity for terahertz difference-frequency generation, compared to the active region designs of the bound-to-continuum type used previously. Fabricated buried heterostructure devices with a two-section buried distributed feedback grating and the waveguide designed for Cherenkov difference-frequency phase-matching scheme operate in two single-mode mid-infrared wavelengths at 10.7 μm and 9.7 μm and produce terahertz output at 2.9 THz with mid-infrared to terahertz conversion efficiency of 0.8 mW/W{sup 2}more » at room temperature.« less

The coronal structure of active regions

NASA Technical Reports Server (NTRS)

Landini, M.; Monsignori Fossi, B. C.; Krieger, A.; Vaiana, G. S.

1975-01-01

A four-parameter model, which assumes a Gaussian dependence of both temperature and pressure on distance from center, is used to fit the compact part of coronal active regions as observed in X-ray photographs from a rocket experiment. The four parameters are the maximum temperature, the maximum pressure, the width of the pressure distribution, and the width of the temperature distribution. The maximum temperature ranges from 2.2 to 2.8 million K, and the maximum density from 2 to 9 by 10 to the 9th power per cu cm. The range of the pressure-distribution width is from 2 to 4 by 10 to the 9th power cm and that of the temperature-distribution width from 2 to 7.

>100% output differential efficiency 1.55-μm VCSELs using submonolayer superlattices digital-alloy multiple-active-regions grown by MBE on InP

NASA Astrophysics Data System (ADS)

Wang, C. S.; Koda, R.; Huntington, A. S.; Gossard, A. C.; Coldren, L. A.

2005-04-01

High-quality InAlGaAs digital-alloy active regions using submonolayer superlattices were developed and employed in a 3-stage bipolar cascade multiple-active-region vertical cavity surface emitting laser (VCSEL) design. The photoluminescence intensity and linewidth of these active regions were optimized by varying the substrate temperature and digitization period. These active regions exhibit considerable improvement over previously developed digital-alloy active regions and are comparable to analog-alloy active regions. Multiple-active-region VCSELs, grown all-epitaxially by MBE on InP, demonstrate greater than 100% output differential efficiency at 1.55-μm emission. A record high 104% output differential efficiency was achieved for a 3-stage long-wavelength VCSEL.

From blood oxygenation level dependent (BOLD) signals to brain temperature maps.

PubMed

Sotero, Roberto C; Iturria-Medina, Yasser

2011-11-01

A theoretical framework is presented for converting Blood Oxygenation Level Dependent (BOLD) images to brain temperature maps, based on the idea that disproportional local changes in cerebral blood flow (CBF) as compared with cerebral metabolic rate of oxygen consumption (CMRO₂) during functional brain activity, lead to both brain temperature changes and the BOLD effect. Using an oxygen limitation model and a BOLD signal model, we obtain a transcendental equation relating CBF and CMRO₂ changes with the corresponding BOLD signal, which is solved in terms of the Lambert W function. Inserting this result in the dynamic bioheat equation describing the rate of temperature changes in the brain, we obtain a nonautonomous ordinary differential equation that depends on the BOLD response, which is solved numerically for each brain voxel. Temperature maps obtained from a real BOLD dataset registered in an attention to visual motion experiment were calculated, obtaining temperature variations in the range: (-0.15, 0.1) which is consistent with experimental results. The statistical analysis revealed that significant temperature activations have a similar distribution pattern than BOLD activations. An interesting difference was the activation of the precuneus in temperature maps, a region involved in visuospatial processing, an effect that was not observed on BOLD maps. Furthermore, temperature maps were more localized to gray matter regions than the original BOLD maps, showing less activated voxels in white matter and cerebrospinal fluid.

[Biological soil crust nitrogenase activity and its responses to hydro-thermic factors in different erosion regions on the Loess Plateau, China].

PubMed

Ming, Jiao; Zhao, Yun-Ge; Xu, Ming-Xiang; Yang, Li-Na; Wang, Ai-Guo

2013-07-01

Based on field survey, the biological soil crusts at their stable development stage were collected from the water erosion region, water-wind erosion region, and wind erosion region on the Loess Plateau, aimed to study the effects of the variations of moisture and temperature on the crusts nitrogenase activity (NA). The NA of the crusts in the erosion regions decreased in the order of water erosion region (127.7 micromol x m(-2) x h(-1)) > water-wind erosion region (34.6 micromol x m(-2) x h(-1)) > wind erosion region (6.0 micromol x m(-2) x h(-1)), and the optimal temperature for the crust nitrogen fixation was 35 degrees C, 25 degrees C, and 15 degrees C, respectively. At the optimal temperature and 100% -40% field water-holding capacity, the NA of the crusts from the water erosion and water-wind erosion regions had no significant difference. The NA of the crusts from the wind erosion region was more sensitive to the variation of moisture, showing a dramatic decline when the moisture decreased to 80% field water-holding capacity, and totally lost when the moisture decreased to 20% field water-holding capacity. The differences in the NA of the crusts from the three erosion regions and the responses of the NA to the variations of moisture and temperature were likely associated with the climate, environment, and the crust species composition.

Evidence for Widespread Cooling in an Active Region Observed with the SDO Atmospheric Imaging Assembly

NASA Technical Reports Server (NTRS)

Viall, Nicholeen M.; Klimchuk, James A.

2012-01-01

A well known behavior of EUV light curves of discrete coronal loops is that the peak intensities of cooler channels or spectral lines are reached at progressively later times. This time lag is understood to be the result of hot coronal loop plasma cooling through these lower respective temperatures. However, loops typically comprise only a minority of the total emission in active regions. Is this cooling pattern a common property of active region coronal plasma, or does it only occur in unique circumstances, locations, and times? The new SDO/AIA data provide a wonderful opportunity to answer this question systematically for an entire active region. We measure the time lag between pairs of SDO/AIA EUV channels using 24 hours of images of AR 11082 observed on 19 June 2010. We find that there is a time-lag signal consistent with cooling plasma, just as is usually found for loops, throughout the active region including the diffuse emission between loops for the entire 24 hour duration. The pattern persists consistently for all channel pairs and choice of window length within the 24 hour time period, giving us confidence that the plasma is cooling from temperatures of greater than 3 MK, and sometimes exceeding 7 MK, down to temperatures lower than approx. 0.8 MK. This suggests that the bulk of the emitting coronal plasma in this active region is not steady; rather, it is dynamic and constantly evolving. These measurements provide crucial constraints on any model which seeks to describe coronal heating.

Constraining hot plasma in a non-flaring solar active region with FOXSI hard X-ray observations

NASA Astrophysics Data System (ADS)

Ishikawa, Shin-nosuke; Glesener, Lindsay; Christe, Steven; Ishibashi, Kazunori; Brooks, David H.; Williams, David R.; Shimojo, Masumi; Sako, Nobuharu; Krucker, Säm

2014-12-01

We present new constraints on the high-temperature emission measure of a non-flaring solar active region using observations from the recently flown Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket payload. FOXSI has performed the first focused hard X-ray (HXR) observation of the Sun in its first successful flight on 2012 November 2. Focusing optics, combined with small strip detectors, enable high-sensitivity observations with respect to previous indirect imagers. This capability, along with the sensitivity of the HXR regime to high-temperature emission, offers the potential to better characterize high-temperature plasma in the corona as predicted by nanoflare heating models. We present a joint analysis of the differential emission measure (DEM) of active region 11602 using coordinated observations by FOXSI, Hinode/XRT, and Hinode/EIS. The Hinode-derived DEM predicts significant emission measure between 1 MK and 3 MK, with a peak in the DEM predicted at 2.0-2.5 MK. The combined XRT and EIS DEM also shows emission from a smaller population of plasma above 8 MK. This is contradicted by FOXSI observations that significantly constrain emission above 8 MK. This suggests that the Hinode DEM analysis has larger uncertainties at higher temperatures and that > 8 MK plasma above an emission measure of 3 × 1044 cm-3 is excluded in this active region.

Observations and temperatures of Io's Pele Patera from Cassini and Galileo spacecraft images

USGS Publications Warehouse

Radebaugh, J.; McEwen, A.S.; Milazzo, M.P.; Keszthelyi, L.P.; Davies, A.G.; Turtle, E.P.; Dawson, D.D.

2004-01-01

Pele has been the most intense high-temperature hotspot on Io to be continuously active during the Galileo monitoring from 1996-2001. A suite of characteristics suggests that Pele is an active lava lake inside a volcanic depression. In 2000-2001, Pele was observed by two spacecraft, Cassini and Galileo. The Cassini observations revealed that Pele is variable in activity over timescales of minutes, typical of active lava lakes in Hawaii and Ethiopia. These observations also revealed that the short-wavelength thermal emission from Pele decreases with rotation of Io by a factor significantly greater than the cosine of the emission angle, and that the color temperature becomes more variable and hotter at high emission angles. This behavior suggests that a significant portion of the visible thermal emission from Pele comes from lava fountains within a topographically confined lava body. High spatial resolution, nightside images from a Galileo flyby in October 2001 revealed a large, relatively cool (< 800 K) region, ringed by bright hotspots, and a central region of high thermal emission, which is hypothesized to be due to fountaining and convection in the lava lake. Images taken through different filters revealed color temperatures of 1500 ?? 80 K from Cassini ISS data and 1605 ?? 220 and 1420 ?? 100 K from small portions of Galileo SSI data. Such temperatures are near the upper limit for basaltic compositions. Given the limitations of deriving lava eruption temperature in the absence of in situ measurement, it is possible that Pele has lavas with ultramafic compositions. The long-lived, vigorous activity of what is most likely an actively overturning lava lake in Pele Patera indicates that there is a strong connection to a large, stable magma source region. ?? 2003 Elsevier Inc. All rights reserved.

Dielectric relaxation and conduction mechanism studies of BNT-BT-BKT ceramics

NASA Astrophysics Data System (ADS)

Chandrasekhar, M.; Khatua, Dipak Kumar; Pattanayak, Ranjit; Kumar, P.

2017-12-01

Electrical properties of 0.884Bi0.5Na0.5TiO3-0.036BaTiO3-0.08Bi0.5K0.5TiO3 ceramic samples were investigated in 100Hz to 1 MHz frequency range and in 200-450 °C temperature range using impedance spectroscopy technique. Real part of impedance versus frequency plots in lower frequency region revealed its PTCR behavior and NTCR behaviors in higher frequency region. Impedance study also suggested the presence of non-Debye type relaxation mechanism. Cole-Cole plots suggested two relaxation regions, in which grain and grain, grain boundary effects were prominent in lower and high temperature regions, respectively. DC conductivity followed Arrhenius law with an activation energy of ∼0.79 and 1.2 eV, which suggested that the charge carrier were cation vacancies in lower temperature region whereas cation vacancies and oxygen vacancies in higher temperature region.

Modelling in situ enzyme potential of soils: a tool to predict soil respiration from agricultural fields

NASA Astrophysics Data System (ADS)

Shahbaz Ali, Rana; Poll, Christian; Demyan, Scott; Nkwain Funkuin, Yvonne; Ingwersen, Joachim; Wizemann, Hans-Dieter; Kandeler, Ellen

2014-05-01

The fate of soil organic carbon (SOC) is one of the largest uncertainties in predicting future climate and terrestrial ecosystem functions. Extra-cellular enzymes, produced by microorganisms, perform the very first step in SOC degradation and serve as key components in global carbon cycling. Very little information is available about the seasonal variation in the temperature sensitivity of soil enzymes. Here we aim to model in situ enzyme potentials involved in the degradation of either labile or recalcitrant organic compounds to understand the temporal variability of degradation processes. To identify the similarities in seasonal patterns of soil respiration and in situ enzyme potentials, we compared the modelled in situ enzyme activities with weekly measured soil CO2 emissions. Arable soil samples from two different treatments (4 years fallow and currently vegetated plots; treatments represent range of carbon input into soil) were collected every month from April, 2012 to April, 2013, from two different study regions (Kraichgau and Swabian Alb) in Southwest Germany. The vegetation plots were under crop rotation in both study areas. We measured activities of three enzymes including β-glucosidase, xylanase and phenoloxidase at five different temperatures. We also measured soil microbial biomass in form of microbial carbon (Cmic). Land-use and area had significant effects (P < 0.001) on the microbial biomass; fallow plots having less Cmic than vegetation plots. Potential activities of β-glucosidase (P < 0.001) and xylanase (P < 0.01) were significantly higher in the vegetation plots of the Swabian Alb region than in the Kraichgau region. In both study areas, enzyme activities were higher during vegetation period and lower during winter which points to the importance of carbon input and/or temperature and soil moisture. We calculated the temperature sensitivity (Q10) of enzyme activities based on laboratory measurements of enzyme activities at a range of incubation temperatures. Q10 of β-glucosidase activity changed significantly across the year (Q10 values ranges from 1.5 to 2.0 in Kraichgau and 1.6 to 2.1 in Swabian Alb), while for xylanase activity, no significant effects were found (Q10 values ranges from 1.2 to 3.0 in Kraichgau and 1.3 to 3.3 in Swabian Alb) in both study regions. By using laboratory based enzyme activities, calculated Q10 values, and daily soil temperature data, we modelled in situ enzyme potentials in soils for labile and recalcitrant carbon pools for both study regions. We observed an increase in modelled in situ enzyme activities during the summer period and a substantial decrease during winter indicating temperature as a strong controlling factor. A significant higher positive correlation of soil surface CO2 flux with modelled in situ β-glucosidase activity was found in both study regions compared to modelled in situ xylanase activity. These results demonstrate that (1) Q10 values are site and season specific and should be added into carbon models and (2) the indication of the relevance of greater contribution of labile carbon pool to soil CO2 emissions.

Rapid Temperature Changes and the Early Activity on Comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Alí-Lagoa, V.; Delbo', M.; Libourel, G.

2015-09-01

The so-called “early activity” of comet 67P/Churyumov-Gerasimenko has been observed to originate mostly in parts of the concave region or “neck” between its two lobes. Since activity is driven by the sublimation of volatiles, this is a puzzling result because this area is less exposed to the Sun and is therefore expected to be cooler on average. We used a thermophysical model that takes into account thermal inertia, global self-heating, and shadowing, to compute surface temperatures of the comet. We found that, for every rotation in the 2014 August-December period, some parts of the neck region undergo the fastest temperature variations of the comet’s surface precisely because they are shadowed by their surrounding terrains. Our work suggests that these fast temperature changes are correlated to the early activity of the comet, and we put forward the hypothesis that erosion related to thermal cracking is operating at a high rate on the neck region due to these rapid temperature variations. This may explain why the neck contains some ice—as opposed to most other parts of the surface—and why it is the main source of the comet’s early activity. In a broader context, these results indicate that thermal cracking can operate faster on atmosphereless bodies with significant concavities than implied by currently available estimates.

Simultaneous in vivo recording of local brain temperature and electrophysiological signals with a novel neural probe

NASA Astrophysics Data System (ADS)

Fekete, Z.; Csernai, M.; Kocsis, K.; Horváth, Á. C.; Pongrácz, A.; Barthó, P.

2017-06-01

Objective. Temperature is an important factor for neural function both in normal and pathological states, nevertheless, simultaneous monitoring of local brain temperature and neuronal activity has not yet been undertaken. Approach. In our work, we propose an implantable, calibrated multimodal biosensor that facilitates the complex investigation of thermal changes in both cortical and deep brain regions, which records multiunit activity of neuronal populations in mice. The fabricated neural probe contains four electrical recording sites and a platinum temperature sensor filament integrated on the same probe shaft within a distance of 30 µm from the closest recording site. The feasibility of the simultaneous functionality is presented in in vivo studies. The probe was tested in the thalamus of anesthetized mice while manipulating the core temperature of the animals. Main results. We obtained multiunit and local field recordings along with measurement of local brain temperature with accuracy of 0.14 °C. Brain temperature generally followed core body temperature, but also showed superimposed fluctuations corresponding to epochs of increased local neural activity. With the application of higher currents, we increased the local temperature by several degrees without observable tissue damage between 34-39 °C. Significance. The proposed multifunctional tool is envisioned to broaden our knowledge on the role of the thermal modulation of neuronal activity in both cortical and deeper brain regions.

Distribution of temperature changes and neurovascular coupling in rat brain following 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") exposure.

PubMed

Coman, Daniel; Sanganahalli, Basavaraju G; Jiang, Lihong; Hyder, Fahmeed; Behar, Kevin L

2015-10-01

(+/-)3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") is an abused psychostimulant that produces strong monoaminergic stimulation and whole-body hyperthermia. MDMA-induced thermogenesis involves activation of uncoupling proteins (UCPs), primarily a type specific to skeletal muscle (UCP-3) and absent from the brain, although other UCP types are expressed in the brain (e.g. thalamus) and might contribute to thermogenesis. Since neuroimaging of brain temperature could provide insights into MDMA action, we measured spatial distributions of systemically administered MDMA-induced temperature changes and dynamics in rat cortex and subcortex using a novel magnetic resonance method, Biosensor Imaging of Redundant Deviation in Shifts (BIRDS), with an exogenous temperature-sensitive probe (thulium ion and macrocyclic chelate 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethyl-1,4,7,10-tetraacetate (DOTMA(4-))). The MDMA-induced temperature rise was greater in the cortex than in the subcortex (1.6 ± 0.4 °C versus 1.3 ± 0.4 °C) and occurred more rapidly (2.0 ± 0.2 °C/h versus 1.5 ± 0.2 °C/h). MDMA-induced temperature changes and dynamics in the cortex and body were correlated, although the body temperature exceeded the cortex temperature before and after MDMA. Temperature, neuronal activity, and blood flow (CBF) were measured simultaneously in the cortex and subcortex (i.e. thalamus) to investigate possible differences of MDMA-induced warming across brain regions. MDMA-induced warming correlated with increases in neuronal activity and blood flow in the cortex, suggesting that the normal neurovascular response to increased neural activity was maintained. In contrast to the cortex, a biphasic relationship was seen in the subcortex (i.e. thalamus), with a decline in CBF as temperature and neural activity rose, transitioning to a rise in CBF for temperature above 37 °C, suggesting that MDMA affected CBF and neurovascular coupling differently in subcortical regions. Considering that MDMA effects on CBF and heat dissipation (as well as potential heat generation) may vary regionally, neuroprotection may require different cooling strategies. Copyright © 2015 John Wiley & Sons, Ltd.

ACTIVE REGION MOSS: DOPPLER SHIFTS FROM HINODE/EXTREME-ULTRAVIOLET IMAGING SPECTROMETER OBSERVATIONS

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

Tripathi, Durgesh; Mason, Helen E.; Klimchuk, James A.

2012-07-01

Studying the Doppler shifts and the temperature dependence of Doppler shifts in moss regions can help us understand the heating processes in the core of the active regions. In this paper, we have used an active region observation recorded by the Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode on 2007 December 12 to measure the Doppler shifts in the moss regions. We have distinguished the moss regions from the rest of the active region by defining a low-density cutoff as derived by Tripathi et al. in 2010. We have carried out a very careful analysis of the EIS wavelength calibrationmore » based on the method described by Young et al. in 2012. For spectral lines having maximum sensitivity between log T = 5.85 and log T = 6.25 K, we find that the velocity distribution peaks at around 0 km s{sup -1} with an estimated error of 4-5 km s{sup -1}. The width of the distribution decreases with temperature. The mean of the distribution shows a blueshift which increases with increasing temperature and the distribution also shows asymmetries toward blueshift. Comparing these results with observables predicted from different coronal heating models, we find that these results are consistent with both steady and impulsive heating scenarios. However, the fact that there are a significant number of pixels showing velocity amplitudes that exceed the uncertainty of 5 km s{sup -1} is suggestive of impulsive heating. Clearly, further observational constraints are needed to distinguish between these two heating scenarios.« less

Effect of Impedance Relaxation in Conductance Mechanisms in TiO2/ITO/ZnO:Al/p-Si Heterostructure

NASA Astrophysics Data System (ADS)

Nouiri, M.; El Mir, L.

2018-03-01

The electrical conduction of a TiO2/ITO/ZnO:Al/p-Si structure under alternating-current excitation was investigated in the temperature range of 80 K to 300 K. The frequency dependence of the capacitance and conductance revealed the response of a thermally activated trap characterized by activation energy of about 140 meV. The frequency dependence of the conductance obeyed the universal dynamic response according to the common relation G = Aωs . The temperature dependence of the frequency exponent s illustrates that, in the low frequency range, conduction is governed by the correlated barrier hopping (CBH) mechanism involving two distinct energy levels for all investigated temperatures. For the high frequency region, conduction takes place according to the overlapping large-polaron tunneling mechanism at low temperatures but the CBH mechanism becomes dominant in the high temperature region. This difference in electrical behavior between low and high temperatures can be attributed to the dominance of dielectric relaxation at low compared with high temperatures.

MAVEN observations of electron temperatures in the dayside ionosphere at Mars

NASA Astrophysics Data System (ADS)

Sakai, S.; Cravens, T.; Andersson, L.; Fowler, C. M.; Thiemann, E.; Eparvier, F. G.; Bougher, S. W.; Rahmati, A.; Reedy, N. L.; Mitchell, D. L.; Mazelle, C. X.; Mahaffy, P. R.; Jakosky, B. M.

2016-12-01

The Mars Atmosphere and Volatile EvolutioN (MAVEN) have observed the ionospheric electron temperature at Mars since November 2014. The only in-situ measurements of plasma temperatures were provided by the two Viking landers in 1976 before the MAVEN mission. The ionospheric electron temperatures are particularly important for determining the neutral escape rate from the atmosphere of Mars. We have investigated the electron temperatures on the dayside ionosphere using the Langmuir Probe and Waves instrument onboard MAVEN. The temperatures are studied in two regions of (1) the crustal magnetic field and (2) the solar wind/induced (or draped) magnetic field. We also focused on how temperatures vary with solar zenith angle (SZA) and the solar extreme ultraviolet (EUV) irradiances. The electron temperatures did not vary much due to the SZA variation, but increased when the solar EUV irradiances are high. This means the ionospheric temperatures are sensitive to the solar activity. Furthermore, we investigated the correlation of electron temperatures against magnetic field configurations under the same EUV irradiances. The electron temperatures in the crustal region were lower than those in the draped region. One possible explanation is that the energy input from high altitude, which is related to the tail and solar wind electrons, might control the temperatures in the draped region. Vertical heat conductance in the draped region could also affect the electron temperatures (with a greater effect in the draped region), so that electrons cooled at low altitude tend to transport to high altitude. However, the electron heating is more local in the draped region, and the electrons would be heated efficiently. Therefore, the electron temperatures in the draped region were higher than those in the crustal region. It is implied that the rate of atmospheric escape, which is attributed to photochemical escape, depends on the topology of the magnetic fields.

Mars Atmospheric Temperature and Dust Storm Tracking

NASA Image and Video Library

2016-06-09

This graphic overlays Martian atmospheric temperature data as curtains over an image of Mars taken during a regional dust storm. The temperature profiles extend from the surface to about 50 miles (80 kilometers) up. Temperatures are color coded, ranging from minus 243 degrees Fahrenheit (minus 153 degrees Celsius) where coded purple to minus 9 F (minus 23 C) where coded red. The temperature data and global image were both recorded on Oct. 18, 2014, by instruments on NASA's Mars Reconnaissance Orbiter: Mars Climate Sounder and Mars Color Imager. On that day a regional dust storm was active in the Acidalia Planitia region of northern Mars, at the upper center of this image. A storm from this area in typically travels south and grows into a large regional storm in the southern hemisphere during southern spring. That type of southern-spring storm and two other large regional dust storms repeat as a three-storm series most Martian years. The pattern has been identified from their effects on atmospheric temperature in a layer about 16 miles (25 kilometers) above the surface. http://photojournal.jpl.nasa.gov/catalog/PIA20747

Long-term variations and trends in the polar E-region

NASA Astrophysics Data System (ADS)

Bjoland, L. M.; Ogawa, Y.; Hall, C.; Rietveld, M.; Løvhaug, U. P.; La Hoz, C.; Miyaoka, H.

2017-10-01

As the EISCAT UHF radar system in Northern Scandinavia started its operations in the early 1980s, the collected data cover about three solar cycles. These long time-series provide us the opportunity to study long-term variations and trends of ionospheric parameters in the high latitude region. In the present study we have used the EISCAT Tromsø UHF data to investigate variations of the Hall conductivity and ion temperatures in the E-region around noon. Both the ion temperature and the peak altitude of the Hall conductivity are confirmed to depend strongly on solar zenith angle. However, the dependence on solar activity seems to be weak. In order to search for trends in these parameters, the ion temperature and peak altitude of the Hall conductivity data were adjusted for their seasonal and solar cycle dependence. A very weak descent (∼0.2 km/ decade) was seen in the peak altitude of the Hall conductivity. The ion temperature at 110 km shows a cooling trend (∼10 K/ decade). However, other parameters than solar zenith angle and solar activity seem to affect the ion temperature at this altitude, and a better understanding of these parameters is necessary to derive a conclusive trend. In this paper, we discuss what may cause the characteristics of the variations in the electric conductivities and ion temperatures in the high latitude region.

Distribution of temperature changes and neurovascular coupling in rat brain following 3,4-methylenedioxymethamphetamine (MDMA,‘ecstasy’) exposure

PubMed Central

Coman, Daniel; Sanganahalli, Basavaraju G.; Jiang, Lihong; Hyder, Fahmeed; Behar, Kevin L.

2015-01-01

(+/−)3,4-methylenedioxymethamphetamine (MDMA, ‘ecstasy’) is an abused psychostimulant producing strong monoaminergic stimulation and whole-body hyperthermia. MDMA-induced thermogenesis involves activation of uncoupling proteins (UCP), primarily a type specific to skeletal muscle (UCP-3) and which is absent in brain, although other UCP types are expressed in brain (e.g., thalamus) and might contribute to thermogenesis. Since neuroimaging of brain temperature could provide insights of MDMA action, we measured spatial distributions of systemically-administered MDMA-induced temperature changes and dynamics in rat cortex and subcortex using a novel magnetic resonance method, Biosensor Imaging of Redundant Deviation of Shifts (BIRDS), with an exogenous temperature-sensitive probe (thulium ion and macrocyclic chelate 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethyl-1,4,7,10-tetraacetate (DOTMA4−)). The MDMA-induced temperature rise in cortex was greater than in subcortex (1.6±0.4°C vs. 1.3±0.4°C) and occurred more rapidly (2.0±0.2°C/h vs. 1.5±0.2°C/h). MDMA-induced temperature changes and dynamics in cortex and body were correlated, although body temperature exceeded cortex before and after MDMA. Temperature, neuronal activity, and blood flow (CBF) were measured simultaneously in cortex and subcortex (i.e., thalamus) to investigate possible differences of MDMA-induced warming across brain regions. MDMA-induced warming correlated with increases in neuronal activity and blood flow in cortex, suggesting that the normal neurovascular response to increased neural activity was maintained. In contrast to cortex, a biphasic relationship was seen in subcortex (i.e., thalamus), with a decline in CBF as temperature and neural activity rose, transitioning to a rise in CBF for temperature >37°C, suggesting that MDMA affected CBF and neurovascular coupling differently in subcortical regions. Considering that MDMA effects on CBF and heat dissipation (as well as potential heat generation) may vary regionally, neuroprotection may require different cooling strategies. PMID:26286889

Modelling of active layer thickness evolution on James Ross Island in 2006-2015

NASA Astrophysics Data System (ADS)

Hrbáček, Filip; Uxa, Tomáš

2017-04-01

Antarctic Peninsula region has been considered as one of the most rapidly warming areas on the Earth. However, the recent studies (Turner et al., 2016; Oliva et al., 2017) showed that significant air temperature cooling began around 2000 and has continued until present days. The climate cooling led to reduction of active layer thickness in several parts of Antarctic Peninsula region during decade 2006-2015, but the information about spatiotemporal variability of active layer thickness across the region remains largely incoherent due to lack of active layer temperature data from deeper profiles. Valuable insights into active layer thickness evolution in Antarctic Peninsula region can be, however, provided by thermal modelling techniques. These have been widely used to study the active layer dynamics in different regions of Arctic since 1990s. By contrast, they have been employed much less in Antarctica. In this study, we present our first results from two equilibrium models, the Stefan and Kudryavtsev equations, that were applied to calculate the annual active layer thickness based on ground temperature data from depth of 5 cm on one site on James Ross Island, Eastern Antarctic Peninsula, in period 2006/07 to 2014/15. Study site (Abernethy Flats) is located in the central part of the major ice-free area of James Ross Island called Ulu Peninsula. Monitoring of air temperature 2 m above ground surface and ground temperature in 50 cm profile began on January 2006. The profile was extended under the permafrost table down to 75 cm in February 2012, which allowed precise determination of active layer thickness, defined as a depth of 0°C isotherm, in period 2012 to 2015. The active layer thickness in the entire observation period was reconstructed using the Stefan and Kudryavtsev models, which were driven by ground temperature data from depth of 5 cm and physical parameters of the ground obtained by laboratory analyses (moisture content and bulk density) and calculations from ground heat flux measurement (thermal conductivity and thermal capacity). Model results were validated using the reference active layer thicknesses from the summer seasons of 2012/13 to 2014/15 with very good accuracy of 0 to 4 cm and -4 to 1 cm for the Stefan and the Kudryavtsev models, respectively. Average active layer thickness on Abernethy Flats varied between 62 cm (Stefan model) and 60 cm (Kudryavtsev model) in period 2006/07-2014/15. Both models showed average active layer thinning of -1.3 cm.year-1 (Stefan model) and -2.3 cm.year-1 (Kudryavtsev model). Maximum active layer thickness was predicted in summer season 2008/09, reaching 75 cm (Stefan model) and 83 cm (Kudryavtsev model), while the minimum active layer thickness was observed in summer season 2009/10 when both models predicted 36 cm. Our results show that both models are well suited for conditions of Antarctica because their accuracy is in the order of the first centimetres. The nine-year series confirmed thinning of active layer in this part of Antarctic Peninsula region, which was mainly related to variability of summer air temperature. References: Turner, J., Lu, H., White, I., King, J. C., Phillips, T., Scott Hosking, J. Bracegirdle, T. J.,Marshall, G. J., Mulvaney, R., Deb, P., 2016. Absence of 21st century warming on Antarctic Peninsula consistent with natural variability. Nature 535, doi: 10.1038/nature18645 Oliva, M., Navarro, F., Hrbáček, F., Hernandéz, A., Nývlt, D., Perreira, P., Ruiz-Fernandéz, J., Trigo, R., in press. Recent regional climate cooling on the Antarctic Peninsula and associated impacts on the cryosphere. Science of Total Environment. dx.doi.org/10.1016/j.scitotenv.2016.12.030

Open magnetic fields in active regions

NASA Technical Reports Server (NTRS)

Svestka, Z.; Solodyna, C. V.; Howard, R.; Levine, R. H.

1977-01-01

Soft X-ray images and magnetograms of several active regions and coronal holes are examined which support the interpretation that some of the dark X-ray gaps seen between interconnecting loops and inner cores of active regions are foot points of open field lines inside the active regions. Characteristics of the investigated dark gaps are summarized. All the active regions with dark X-ray gaps at the proper place and with the correct polarity predicted by global potential extrapolation of photospheric magnetic fields are shown to be old active regions, indicating that field opening is accomplished only in a late phase of active-region development. It is noted that some of the observed dark gaps probably have nothing in common with open fields, but are either due to the decreased temperature in low-lying portions of interconnecting loops or are the roots of higher and less dense or cooler loops.

Effect of the glass transition temperature on alpha-amylase activity in a starch matrix.

PubMed

Chaudhary, Vinita; Panyoyai, Naksit; Small, Darryl M; Shanks, Robert A; Kasapis, Stefan

2017-02-10

This study optimises a protocol for the estimation of α-amylase activity in a condensed starch matrix in the vicinity of the glass transition region. Enzymatic activity on the vitrified starch system was compared with that of a reference substrate, maltodextrin. The activity was assayed as the rate of release of reducing sugar using a dinitrosalicylic acid procedure. The condensed carbohydrate matrices served the dual purpose of acting as a substrate as well as producing a pronounced effect on the ability to enzymatic hydrolysis. Activation energies were estimated throughout the glass transition region of condensed carbohydrate preparations based on the concept of the spectroscopic shift factor. Results were used to demonstrate a considerable moderation by the mechanical glass transition temperature, beyond the expected linear effect of the temperature dependence, on the reaction rate of starch hydrolysis by α-amylase in comparison with the low-molecular weight chain of maltodextrin. Copyright © 2016. Published by Elsevier Ltd.

[Preliminary observation on survival and reproduction of imported Oncomelania snails in water network regions: a simulated experiment].

PubMed

Tian, Jian-Guo; Zhong, Wen-Jiang; Li, Gui-Fu; Peng, Li-Xia; Xiang, Xiao-Ping

2011-04-01

To observe the survival and reproduction of exotic imported Oncomelania snails in water network regions. During a period between May 22, 2008 and August 7, 2009, a study pilot was established in a historical snail habitat in Qingpu District of Shanghai City. A total of 12 soil samples were collected from Qingpu, Jinshan and Songjiang districts and placed in the study area. Active marked adults snails without infections (with a female/male ratio of 1) were placed on soil surface, and the activity, survival and reproduction of snails on soil surface were observed. The temperature during the period of the study was recorded. During the experiment period, the highest temperature was 39 degrees C, the lowest was -3 degrees C, and the average was 20 degrees C. The activity of snails reduced significantly on the soil surface at high temperature in summer and low temperature in winter. There were 91 old snails (5.2%) that moved on soil surface in March and 73 (12.2% ) in June, 2009. A total of 26 and 59 offspring snails were found respectively in April and June, 2009, with average density of 2.17 snails/m2 (26/12) and 4.92 snails/m2 (59/12) respectively. The exotic imported snails can survive and reproduce in water network regions. Further monitoring should be strengthened on the imported snails in these regions.

Evidence for magnetic energy storage in coronal active regions

NASA Technical Reports Server (NTRS)

Krieger, A. S.; De Feiter, L. D.; Vaiana, G. S.

1976-01-01

Examination of X-ray images obtained by the S-054 X-ray spectrographic telescope on Skylab shows the presence of some atypical X-ray-emitting coronal structures in active regions which are not consistent with potential extrapolations of photospheric magnetic fields. Analysis of the observed temporal changes in the X-ray-emitting active-region structures demonstrates that the majority of these consist of brightness changes representing temperature (and perhaps density) variations of the material in the loops.

Analytic Expressions for the Inner-rim Structure of Passively Heated Protoplanetary Disks

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

Ueda, Takahiro; Okuzumi, Satoshi; Flock, Mario, E-mail: t_ueda@geo.titech.ac.jp

We analytically derive the expressions for the structure of the inner region of protoplanetary disks based on the results from the recent hydrodynamical simulations. The inner part of a disk can be divided into four regions: a dust-free region with a gas temperature in the optically thin limit, an optically thin dust halo, an optically thick condensation front, and the classical, optically thick region, in order from the innermost to the outermost. We derive the dust-to-gas mass ratio profile in the dust halo using the fact that partial dust condensation regulates the temperature relative to the dust evaporation temperature. Beyondmore » the dust halo, there is an optically thick condensation front where all the available silicate gas condenses out. The curvature of the condensation surface is determined by the condition that the surface temperature must be nearly equal to the characteristic temperature ∼1200 K. We derive the midplane temperature in the outer two regions using the two-layer approximation, with the additional heating by the condensation front for the outermost region. As a result, the overall temperature profile is step-like, with steep gradients at the borders between the outer three regions. The borders might act as planet traps where the inward migration of planets due to gravitational interaction with the gas disk stops. The temperature at the border between the two outermost regions coincides with the temperature needed to activate magnetorotational instability, suggesting that the inner edge of the dead zone must lie at this border. The radius of the dead zone inner edge predicted from our solution is ∼2–3 times larger than that expected from the classical optically thick temperature.« less

Analytic Expressions for the Inner-rim Structure of Passively Heated Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Ueda, Takahiro; Okuzumi, Satoshi; Flock, Mario

2017-07-01

We analytically derive the expressions for the structure of the inner region of protoplanetary disks based on the results from the recent hydrodynamical simulations. The inner part of a disk can be divided into four regions: a dust-free region with a gas temperature in the optically thin limit, an optically thin dust halo, an optically thick condensation front, and the classical, optically thick region, in order from the innermost to the outermost. We derive the dust-to-gas mass ratio profile in the dust halo using the fact that partial dust condensation regulates the temperature relative to the dust evaporation temperature. Beyond the dust halo, there is an optically thick condensation front where all the available silicate gas condenses out. The curvature of the condensation surface is determined by the condition that the surface temperature must be nearly equal to the characteristic temperature ˜1200 K. We derive the midplane temperature in the outer two regions using the two-layer approximation, with the additional heating by the condensation front for the outermost region. As a result, the overall temperature profile is step-like, with steep gradients at the borders between the outer three regions. The borders might act as planet traps where the inward migration of planets due to gravitational interaction with the gas disk stops. The temperature at the border between the two outermost regions coincides with the temperature needed to activate magnetorotational instability, suggesting that the inner edge of the dead zone must lie at this border. The radius of the dead zone inner edge predicted from our solution is ˜2-3 times larger than that expected from the classical optically thick temperature.

THE TEMPERATURE OF HOT GAS IN GALAXIES AND CLUSTERS: BARYONS DANCING TO THE TUNE OF DARK MATTER

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

Hansen, Steen H.; Maccio, Andrea V.; Romano-Diaz, Emilio

2011-06-10

The temperature profile of hot gas in galaxies and galaxy clusters is largely determined by the depth of the total gravitational potential and thereby by the dark matter (DM) distribution. We use high-resolution hydrodynamical simulations of galaxy formation to derive a surprisingly simple relation between the gas temperature and DM properties. We show that this relation holds not just for galaxy clusters but also for equilibrated and relaxed galaxies at radii beyond the central stellar-dominated region of typically a few kpc. It is then clarified how a measurement of the temperature and density of the hot gas component can leadmore » to an indirect measurement of the DM velocity anisotropy in galaxies. We also study the temperature relation for galaxy clusters in the presence of self-regulated, recurrent active galactic nuclei (AGNs), and demonstrate that this temperature relation even holds outside the inner region of {approx}30 kpc in clusters with an active AGN.« less

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

Tan, Jianguang; Piao, Shilong; Chen, Anping

Over the last century the Northern Hemisphere has experienced rapid climate warming, but this warming has not been evenly distributed seasonally, as well as diurnally. The implications of such seasonal and diurnal heterogeneous warming on regional and global vegetation photosynthetic activity, however, are still poorly understood. Here, we investigated for different seasons how photosynthetic activity of vegetation correlates with changes in seasonal daytime and night-time temperature across the Northern Hemisphere (>30°N), using Normalized Difference Vegetation Index (NDVI) data from 1982 to 2011 obtained from the Advanced Very High Resolution Radiometer (AVHRR). Our analysis revealed some striking seasonal differences in themore » response of NDVI to changes in day- versus night-time temperatures. For instance, while higher daytime temperature (T max) is generally associated with higher NDVI values across the boreal zone, the area exhibiting a statistically significant positive correlation between T max and NDVI is much larger in spring (41% of area in boreal zone – total area 12.6 × 10 6 km 2) than in summer and autumn (14% and 9%, respectively). In contrast to the predominantly positive response of boreal ecosystems to changes in T max, increases in T max tended to negatively influence vegetation growth in temperate dry regions, particularly during summer. Changes in night-time temperature (T min) correlated negatively with autumnal NDVI in most of the Northern Hemisphere, but had a positive effect on spring and summer NDVI in most temperate regions (e.g., Central North America and Central Asia). Such divergent covariance between the photosynthetic activity of Northern Hemispheric vegetation and day- and night-time temperature changes among different seasons and climate zones suggests a changing dominance of ecophysiological processes across time and space. Lastly, understanding the seasonally different responses of vegetation photosynthetic activity to diurnal temperature changes, which have not been captured by current land surface models, is important for improving the performance of next generation regional and global coupled vegetation-climate models« less

Free Magnetic Energy and Coronal Heating

NASA Technical Reports Server (NTRS)

Winebarger, Amy; Moore, Ron; Falconer, David

2012-01-01

Previous work has shown that the coronal X-ray luminosity of an active region increases roughly in direct proportion to the total photospheric flux of the active region's magnetic field (Fisher et al. 1998). It is also observed, however, that the coronal luminosity of active regions of nearly the same flux content can differ by an order of magnitude. In this presentation, we analyze 10 active regions with roughly the same total magnetic flux. We first determine several coronal properties, such as X-ray luminosity (calculated using Hinode XRT), peak temperature (calculated using Hinode EIS), and total Fe XVIII emission (calculated using SDO AIA). We present the dependence of these properties on a proxy of the free magnetic energy of the active region

Characterisation of regional skin temperatures in recreational surfers wearing a 2-mm wetsuit.

PubMed

Corona, Luis J; Simmons, Grant H; Nessler, Jeff A; Newcomer, Sean C

2018-05-01

The purpose of this study was to investigate skin temperatures across surfers' bodies while wearing a wetsuit during recreational surfing. Forty-six male recreational surfers participated in this study. Participants were instrumented with eight wireless iButton thermal sensors for the measurement of skin temperature, a Polar RCX5 heart rate monitor and a 2-mm full wetsuit. Following instrumentation, participants were instructed to engage in recreational surfing activities as normal. Significant differences (p < 0.001) in skin temperature (T sk ) were found across the body while wearing a wetsuit during recreational surfing. In addition, regional skin temperature changed across the session for several regions of the body (p < 0.001), and the magnitude of these changes varied significantly between regions. We show for the first time that significant differences exist in skin temperature across the body while wearing a wetsuit during a typical recreational surfing session. These findings may have implications for future wetsuit design. Practitioner Summary: This study investigated the impact of wearing a wetsuit during recreational surfing on regional skin temperatures. Results from this study suggest that skin temperatures differ significantly across the body while wearing a 2-mm wetsuit during recreational surfing. These findings may have implications for future wetsuit design.

Broadly continuously tunable slot waveguide quantum cascade lasers based on a continuum-to-continuum active region design

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

Meng, Bo; Zeng, Yong Quan; Liang, Guozhen

2015-09-14

We report our progress in the development of broadly tunable single-mode slot waveguide quantum cascade lasers based on a continuum-to-continuum active region design. The electroluminescence spectrum of the continuum-to-continuum active region design has a full width at half maximum of 440 cm{sup −1} at center wavelength ∼10 μm at room temperature (300 K). Devices using the optimized slot waveguide structure and the continuum-to-continuum design can be tuned continuously with a lasing emission over 42 cm{sup −1}, from 9.74 to 10.16 μm, at room temperature by using only current tuning scheme, together with a side mode suppression ratio of above 15 dB within the whole tuning range.

Data-driven modeling of surface temperature anomaly and solar activity trends

USGS Publications Warehouse

Friedel, Michael J.

2012-01-01

A novel two-step modeling scheme is used to reconstruct and analyze surface temperature and solar activity data at global, hemispheric, and regional scales. First, the self-organizing map (SOM) technique is used to extend annual modern climate data from the century to millennial scale. The SOM component planes are used to identify and quantify strength of nonlinear relations among modern surface temperature anomalies (<150 years), tropical and extratropical teleconnections, and Palmer Drought Severity Indices (0–2000 years). Cross-validation of global sea and land surface temperature anomalies verifies that the SOM is an unbiased estimator with less uncertainty than the magnitude of anomalies. Second, the quantile modeling of SOM reconstructions reveal trends and periods in surface temperature anomaly and solar activity whose timing agrees with published studies. Temporal features in surface temperature anomalies, such as the Medieval Warm Period, Little Ice Age, and Modern Warming Period, appear at all spatial scales but whose magnitudes increase when moving from ocean to land, from global to regional scales, and from southern to northern regions. Some caveats that apply when interpreting these data are the high-frequency filtering of climate signals based on quantile model selection and increased uncertainty when paleoclimatic data are limited. Even so, all models find the rate and magnitude of Modern Warming Period anomalies to be greater than those during the Medieval Warm Period. Lastly, quantile trends among reconstructed equatorial Pacific temperature profiles support the recent assertion of two primary El Niño Southern Oscillation types. These results demonstrate the efficacy of this alternative modeling approach for reconstructing and interpreting scale-dependent climate variables.

An inter-decadal increase in summer sea level pressure over the Mongolian region around the early 1990s

NASA Astrophysics Data System (ADS)

Zhang, Haiyan; Wen, Zhiping; Wu, Renguang; Li, Xiuzhen; Chen, Ruidan

2018-05-01

The East Asian summer monsoon is affected by processes in the mid-high latitudes in addition to various tropical and subtropical systems. The present study investigates the summer sea level pressure (SLP) variability over northern East Asia (NEA) and emphasizes the closed active center over the Mongolian region. It is found that the seasonal mean Mongolian SLP (MSLP) anomaly is closely connected with the variability of summertime regional synoptic extra-tropical cyclones on longer time scales. A significant inter-decadal increase in the MSLP around the early 1990s has been detected, which is accompanied by a weakening in the activity of regional extra-tropical cyclones. Recent warming over NEA may have a contribution to the inter-decadal change, which features evidently meridional inhomogeneity around 45°N. The inhomogeneous air temperature anomaly distribution results in decreased vertical wind shear, reduced atmospheric baroclinicity over the Mongolian region, and thus inactive regional cyclones and increased MSLP in the latter decade. The associated temperature anomaly distribution may be partly attributed to regional inhomogeneity in cloud and radiation anomalies, and it is further maintained by two positive feedback mechanisms associated with atmospheric internal processes: one via adiabatic heating and the other via horizontal temperature advection.

Low temperature resistivity studies of SmB6: Observation of two-dimensional variable-range hopping conductivity

NASA Astrophysics Data System (ADS)

Batkova, Marianna; Batko, Ivan; Gabáni, Slavomír; Gažo, Emil; Konovalova, Elena; Filippov, Vladimir

2018-05-01

We studied electrical resistance of a single-crystalline SmB6 sample with a focus on the region of the "low-temperature resistivity plateau". Our observations did not show any true saturation of the electrical resistance at temperatures below 3 K down to 70 mK. According to our findings, temperature dependence of the electrical conduction in a certain temperature interval above 70 mK can be decomposed into a temperature-independent term and a temperature-activated term that can be described by variable-range hopping formula for two-dimensional systems, exp [ -(T0 / T) 1 / 3 ]. Thus, our results indicate importance of hopping type of electrical transport in the near-surface region of SmB6.

Temperature variability inferred from tree-ring records in Weichang region, China, and its teleconnection with large-scale climate forcing

NASA Astrophysics Data System (ADS)

Wang, Yanchao; Liu, Yu; Zhang, Huifang; Wang, Hui; Guo, Jingli; Zhang, Erliang; Wang, Jun; Li, Xiao

2018-04-01

Based on the combination of two dendrochronologies, the annual mean temperature from May to June for the last 160 years was reconstructed in Weichang region, China, with the predictor variables accounting 43.3% of the variance during the calibration period of 1956-2012. Warm periods with temperature levels great than the mean (17.66 °C) occurred in 1853-1881, 1886-1891, 1904-1909, 1923-1930, 1964-1970, 1980-1988, 1998-2002 and 2007-2011; and cold periods with temperature levels less than the mean occurred in 1882-1885, 1892-1898, 1901-1903, 1910-1922, 1931-1963, 1971-1979, 1989-1997 and 2003-2006. The reconstruction showed that droughts usually occurred in the warm years. And the reconstructed temperature series showed an almost reverse trend to the total precipitation of previous August to present July from Chifeng-Weichang on inter-decadal scale, which indicate the basic feature of climate was warm-dry and cold-wet in Weichang region. The reconstructed temperature series showed a linear increasing trend with a rise 0.11 °C from 1880 to 2012. Comparisons with other temperature series revealed a consistently warming trend after the mid-1950s and confirmed a good repeatability and high reliability in our reconstruction. Spatial correlation implied the reconstruction could represent a regional temperature signal in the large parts of northern China and Central-Eastern Mongolia. The multi-taper method reveals several significant periodicities in our reconstruction over the past 160 years, suggesting possible linkages with the El Niño-Southern Oscillation, lunar gravity, Pacific Decadal Oscillation (PDO) and solar activity. Correlation analysis between the reconstruction and Southern Oscillation Index (SOI), lunar geocentric declination, PDO and sunspot number further demonstrates that the temperature variations in Weichang region are negatively correlated with SOI and positively correlated with lunar gravity, PDO and solar activity in the long term.

Digestive enzyme activities are higher in the shortfin mako shark, Isurus oxyrinchus, than in ectothermic sharks as a result of visceral endothermy.

PubMed

Newton, Kyle C; Wraith, James; Dickson, Kathryn A

2015-08-01

Lamnid sharks are regionally endothermic fishes that maintain visceral temperatures elevated above the ambient water temperature. Visceral endothermy is thought to increase rates of digestion and food processing and allow thermal niche expansion. We tested the hypothesis that, at in vivo temperatures, the endothermic shortfin mako shark, Isurus oxyrinchus, has higher specific activities of three digestive enzymes-gastric pepsin and pancreatic trypsin and lipase-than the thresher shark, Alopias vulpinus, and the blue shark, Prionace glauca, neither of which can maintain elevated visceral temperatures. Homogenized stomach or pancreas tissue obtained from sharks collected by pelagic longline was incubated at both 15 and 25 °C, at saturating substrate concentrations, to quantify tissue enzymatic activity. The mako had significantly higher enzyme activities at 25 °C than did the thresher and blue sharks at 15 °C. This difference was not a simple temperature effect, because at 25 °C the mako had higher trypsin activity than the blue shark and higher activities for all enzymes than the thresher shark. We also hypothesized that the thermal coefficient, or Q 10 value, would be higher for the mako shark than for the thresher and blue sharks because of its more stable visceral temperature. However, the mako and thresher sharks had similar Q 10 values for all enzymes, perhaps because of their closer phylogenetic relationship. The higher in vivo digestive enzyme activities in the mako shark should result in higher rates of food processing and may represent a selective advantage of regional visceral endothermy.

Synchronous fire activity in the tropical high Andes: an indication of regional climate forcing.

PubMed

Román-Cuesta, R M; Carmona-Moreno, C; Lizcano, G; New, M; Silman, M; Knoke, T; Malhi, Y; Oliveras, I; Asbjornsen, H; Vuille, M

2014-06-01

Global climate models suggest enhanced warming of the tropical mid and upper troposphere, with larger temperature rise rates at higher elevations. Changes in fire activity are amongst the most significant ecological consequences of rising temperatures and changing hydrological properties in mountainous ecosystems, and there is a global evidence of increased fire activity with elevation. Whilst fire research has become popular in the tropical lowlands, much less is known of the tropical high Andean region (>2000 masl, from Colombia to Bolivia). This study examines fire trends in the high Andes for three ecosystems, the Puna, the Paramo and the Yungas, for the period 1982-2006. We pose three questions: (i) is there an increased fire response with elevation? (ii) does the El Niño- Southern Oscillation control fire activity in this region? (iii) are the observed fire trends human driven (e.g., human practices and their effects on fuel build-up) or climate driven? We did not find evidence of increased fire activity with elevation but, instead, a quasicyclic and synchronous fire response in Ecuador, Peru and Bolivia, suggesting the influence of high-frequency climate forcing on fire responses on a subcontinental scale, in the high Andes. ENSO variability did not show a significant relation to fire activity for these three countries, partly because ENSO variability did not significantly relate to precipitation extremes, although it strongly did to temperature extremes. Whilst ENSO did not individually lead the observed regional fire trends, our results suggest a climate influence on fire activity, mainly through a sawtooth pattern of precipitation (increased rainfall before fire-peak seasons (t-1) followed by drought spells and unusual low temperatures (t0), which is particularly common where fire is carried by low fuel loads (e.g., grasslands and fine fuel). This climatic sawtooth appeared as the main driver of fire trends, above local human influences and fuel build-up cyclicity. © 2014 John Wiley & Sons Ltd.

Evaporative cooling over the Tibetan Plateau induced by vegetation growth.

PubMed

Shen, Miaogen; Piao, Shilong; Jeong, Su-Jong; Zhou, Liming; Zeng, Zhenzhong; Ciais, Philippe; Chen, Deliang; Huang, Mengtian; Jin, Chun-Sil; Li, Laurent Z X; Li, Yue; Myneni, Ranga B; Yang, Kun; Zhang, Gengxin; Zhang, Yangjian; Yao, Tandong

2015-07-28

In the Arctic, climate warming enhances vegetation activity by extending the length of the growing season and intensifying maximum rates of productivity. In turn, increased vegetation productivity reduces albedo, which causes a positive feedback on temperature. Over the Tibetan Plateau (TP), regional vegetation greening has also been observed in response to recent warming. Here, we show that in contrast to arctic regions, increased growing season vegetation activity over the TP may have attenuated surface warming. This negative feedback on growing season vegetation temperature is attributed to enhanced evapotranspiration (ET). The extra energy available at the surface, which results from lower albedo, is efficiently dissipated by evaporative cooling. The net effect is a decrease in daily maximum temperature and the diurnal temperature range, which is supported by statistical analyses of in situ observations and by decomposition of the surface energy budget. A daytime cooling effect from increased vegetation activity is also modeled from a set of regional weather research and forecasting (WRF) mesoscale model simulations, but with a magnitude smaller than observed, likely because the WRF model simulates a weaker ET enhancement. Our results suggest that actions to restore native grasslands in degraded areas, roughly one-third of the plateau, will both facilitate a sustainable ecological development in this region and have local climate cobenefits. More accurate simulations of the biophysical coupling between the land surface and the atmosphere are needed to help understand regional climate change over the TP, and possible larger scale feedbacks between climate in the TP and the Asian monsoon system.

Evaporative cooling over the Tibetan Plateau induced by vegetation growth

PubMed Central

Shen, Miaogen; Piao, Shilong; Jeong, Su-Jong; Zhou, Liming; Zeng, Zhenzhong; Ciais, Philippe; Chen, Deliang; Huang, Mengtian; Jin, Chun-Sil; Li, Laurent Z. X.; Li, Yue; Myneni, Ranga B.; Yang, Kun; Zhang, Gengxin; Zhang, Yangjian; Yao, Tandong

2015-01-01

In the Arctic, climate warming enhances vegetation activity by extending the length of the growing season and intensifying maximum rates of productivity. In turn, increased vegetation productivity reduces albedo, which causes a positive feedback on temperature. Over the Tibetan Plateau (TP), regional vegetation greening has also been observed in response to recent warming. Here, we show that in contrast to arctic regions, increased growing season vegetation activity over the TP may have attenuated surface warming. This negative feedback on growing season vegetation temperature is attributed to enhanced evapotranspiration (ET). The extra energy available at the surface, which results from lower albedo, is efficiently dissipated by evaporative cooling. The net effect is a decrease in daily maximum temperature and the diurnal temperature range, which is supported by statistical analyses of in situ observations and by decomposition of the surface energy budget. A daytime cooling effect from increased vegetation activity is also modeled from a set of regional weather research and forecasting (WRF) mesoscale model simulations, but with a magnitude smaller than observed, likely because the WRF model simulates a weaker ET enhancement. Our results suggest that actions to restore native grasslands in degraded areas, roughly one-third of the plateau, will both facilitate a sustainable ecological development in this region and have local climate cobenefits. More accurate simulations of the biophysical coupling between the land surface and the atmosphere are needed to help understand regional climate change over the TP, and possible larger scale feedbacks between climate in the TP and the Asian monsoon system. PMID:26170316

Seasonally different response of photosynthetic activity to daytime and night-time warming in the Northern Hemisphere

DOE PAGES

Tan, Jianguang; Piao, Shilong; Chen, Anping; ...

2014-08-27

Over the last century the Northern Hemisphere has experienced rapid climate warming, but this warming has not been evenly distributed seasonally, as well as diurnally. The implications of such seasonal and diurnal heterogeneous warming on regional and global vegetation photosynthetic activity, however, are still poorly understood. Here, we investigated for different seasons how photosynthetic activity of vegetation correlates with changes in seasonal daytime and night-time temperature across the Northern Hemisphere (>30°N), using Normalized Difference Vegetation Index (NDVI) data from 1982 to 2011 obtained from the Advanced Very High Resolution Radiometer (AVHRR). Our analysis revealed some striking seasonal differences in themore » response of NDVI to changes in day- versus night-time temperatures. For instance, while higher daytime temperature (T max) is generally associated with higher NDVI values across the boreal zone, the area exhibiting a statistically significant positive correlation between T max and NDVI is much larger in spring (41% of area in boreal zone – total area 12.6 × 10 6 km 2) than in summer and autumn (14% and 9%, respectively). In contrast to the predominantly positive response of boreal ecosystems to changes in T max, increases in T max tended to negatively influence vegetation growth in temperate dry regions, particularly during summer. Changes in night-time temperature (T min) correlated negatively with autumnal NDVI in most of the Northern Hemisphere, but had a positive effect on spring and summer NDVI in most temperate regions (e.g., Central North America and Central Asia). Such divergent covariance between the photosynthetic activity of Northern Hemispheric vegetation and day- and night-time temperature changes among different seasons and climate zones suggests a changing dominance of ecophysiological processes across time and space. Lastly, understanding the seasonally different responses of vegetation photosynthetic activity to diurnal temperature changes, which have not been captured by current land surface models, is important for improving the performance of next generation regional and global coupled vegetation-climate models« less

Localized superconductivity in the quantum-critical region of the disorder-driven superconductor-insulator transition in TiN thin films.

PubMed

Baturina, T I; Mironov, A Yu; Vinokur, V M; Baklanov, M R; Strunk, C

2007-12-21

We investigate low-temperature transport properties of thin TiN superconducting films in the vicinity of the disorder-driven superconductor-insulator transition. In a zero magnetic field, we find an extremely sharp separation between superconducting and insulating phases, evidencing a direct superconductor-insulator transition without an intermediate metallic phase. At moderate temperatures, in the insulating films we reveal thermally activated conductivity with the magnetic field-dependent activation energy. At very low temperatures, we observe a zero-conductivity state, which is destroyed at some depinning threshold voltage V{T}. These findings indicate the formation of a distinct collective state of the localized Cooper pairs in the critical region at both sides of the transition.

Thermally robust semiconductor optical amplifiers and laser diodes

DOEpatents

Dijaili, Sol P.; Patterson, Frank G.; Walker, Jeffrey D.; Deri, Robert J.; Petersen, Holly; Goward, William

2002-01-01

A highly heat conductive layer is combined with or placed in the vicinity of the optical waveguide region of active semiconductor components. The thermally conductive layer enhances the conduction of heat away from the active region, which is where the heat is generated in active semiconductor components. This layer is placed so close to the optical region that it must also function as a waveguide and causes the active region to be nearly the same temperature as the ambient or heat sink. However, the semiconductor material itself should be as temperature insensitive as possible and therefore the invention combines a highly thermally conductive dielectric layer with improved semiconductor materials to achieve an overall package that offers improved thermal performance. The highly thermally conductive layer serves two basic functions. First, it provides a lower index material than the semiconductor device so that certain kinds of optical waveguides may be formed, e.g., a ridge waveguide. The second and most important function, as it relates to this invention, is that it provides a significantly higher thermal conductivity than the semiconductor material, which is the principal material in the fabrication of various optoelectronic devices.

Simulation of C. elegans thermotactic behavior in a linear thermal gradient using a simple phenomenological motility model.

PubMed

Matsuoka, Tomohiro; Gomi, Sohei; Shingai, Ryuzo

2008-01-21

The nematode Caenorhabditis elegans has been reported to exhibit thermotaxis, a sophisticated behavioral response to temperature. However, there appears to be some inconsistency among previous reports. The results of population-level thermotaxis investigations suggest that C. elegans can navigate to the region of its cultivation temperature from nearby regions of higher or lower temperature. However, individual C. elegans nematodes appear to show only cryophilic tendencies above their cultivation temperature. A Monte-Carlo style simulation using a simple individual model of C. elegans provides insight into clarifying apparent inconsistencies among previous findings. The simulation using the thermotaxis model that includes the cryophilic tendencies, isothermal tracking and thermal adaptation was conducted. As a result of the random walk property of locomotion of C. elegans, only cryophilic tendencies above the cultivation temperature result in population-level thermophilic tendencies. Isothermal tracking, a period of active pursuit of an isotherm around regions of temperature near prior cultivation temperature, can strengthen the tendencies of these worms to gather around near-cultivation-temperature regions. A statistical index, the thermotaxis (TTX) L-skewness, was introduced and was useful in analyzing the population-level thermotaxis of model worms.

Simultaneous SMM flat crystal spectrometer and Very Large Array observations of solar active regions

NASA Technical Reports Server (NTRS)

Lang, Kenneth R.; Willson, Robert F.; Smith, Kermit L.; Strong, Keith T.

1987-01-01

High-resolution images of the quiescent emission from two solar active regions at 20 cm (VLA) and soft X-ray (SMM FCS) wavelengths are compared. There are regions where the X-ray coronal loops have been completely imaged at 20 cm wavelength. In other regions, the X-ray radiation was detected without detectable 20 cm radiation, and vice versa. The X-ray data were used to infer average electron temperatures of about 3-million K and average electron densities of about 2.5 x 10 to the 9th/cu cm for the X-ray emitting plasma in the two active regions. The thermal bremsstrahlung of the X-ray emitting plasma is optically thin at 20 cm wavelength. The 20 cm brightness temperatures were always less than T(e), which is consistent with optically thin bremsstrahlung. The low T(B) can be explained if a higher, cooler plasma covers the hotter X-ray emitting plasma. Thermal gyroresonance radiation must account for the intense 20 cm radiation near and above sunspots where no X-ray radiation is detected.

Colour change on different body regions provides thermal and signalling advantages in bearded dragon lizards

PubMed Central

Cadena, Viviana; Porter, Warren P.; Kearney, Michael R.

2016-01-01

Many terrestrial ectotherms are capable of rapid colour change, yet it is unclear how these animals accommodate the multiple functions of colour, particularly camouflage, communication and thermoregulation, especially when functions require very different colours. Thermal benefits of colour change depend on an animal's absorptance of solar energy in both UV–visible (300–700 nm) and near-infrared (NIR; 700–2600 nm) wavelengths, yet colour research has focused almost exclusively on the former. Here, we show that wild-caught bearded dragon lizards (Pogona vitticeps) exhibit substantial UV–visible and NIR skin reflectance change in response to temperature for dorsal but not ventral (throat and upper chest) body regions. By contrast, lizards showed the greatest temperature-independent colour change on the beard and upper chest during social interactions and as a result of circadian colour change. Biophysical simulations of heat transfer predicted that the maximum temperature-dependent change in dorsal reflectivity could reduce the time taken to reach active body temperature by an average of 22 min per active day, saving 85 h of basking time throughout the activity season. Our results confirm that colour change may serve a thermoregulatory function, and competing thermoregulation and signalling requirements may be met by partitioning colour change to different body regions in different circumstances.

Increased expression of fructan 1-exohydrolase in rhizophores of Vernonia herbacea during sprouting and exposure to low temperature.

PubMed

Asega, Amanda Francine; do Nascimento, João Roberto O; Carvalho, Maria Angela M

2011-04-15

Rhizophores of Vernonia herbacea, an Asteraceae found in the Brazilian Cerrado, store high amounts of fructans that vary in composition over the phenological cycle. Fructan 1-exohydrolase (1-FEH) activity is detectable during the sprouting phase, mainly in the proximal regions of rhizophores, of plants induced to sprout by defoliation and/or cold storage. We found an increase in 1-FEH gene expression during natural and induced sprouting and further enhancement through low-temperature treatment. Furthermore, a comparative analysis of 1-FEH gene expression in different regions of the rhizophores during the transition from dormancy to sprouting is presented. Transcripts were detected mainly in the proximal region, coinciding with high 1-FEH activity and a high concentration of free fructose. Low temperature promoted the accumulation of fructans of a low degree of polymerization (DP) and enhanced 1-FEH activity and gene expression. It is hypothesized that a set of 1-FEH proteins acts in two different ways during fructan mobilization: (1) by hydrolyzing fructo-oligosaccharides and -polysaccharides in sprouting plants (naturally or induced) for carbon supply and (2) by hydrolyzing preferably fructo-polysaccharides under low temperature to maintain the oligosaccharide pool for plant cold acclimation. Copyright © 2010 Elsevier GmbH. All rights reserved.

3D MHD Models of Active Region Loops

NASA Technical Reports Server (NTRS)

Ofman, Leon

2004-01-01

Present imaging and spectroscopic observations of active region loops allow to determine many physical parameters of the coronal loops, such as the density, temperature, velocity of flows in loops, and the magnetic field. However, due to projection effects many of these parameters remain ambiguous. Three dimensional imaging in EUV by the STEREO spacecraft will help to resolve the projection ambiguities, and the observations could be used to setup 3D MHD models of active region loops to study the dynamics and stability of active regions. Here the results of 3D MHD models of active region loops are presented, and the progress towards more realistic 3D MHD models of active regions. In particular the effects of impulsive events on the excitation of active region loop oscillations, and the generation, propagations and reflection of EIT waves are shown. It is shown how 3D MHD models together with 3D EUV observations can be used as a diagnostic tool for active region loop physical parameters, and to advance the science of the sources of solar coronal activity.

Human influence on sub-regional surface air temperature change over India.

PubMed

Dileepkumar, R; AchutaRao, Krishna; Arulalan, T

2018-06-12

Human activities have been implicated in the observed increase in Global Mean Surface Temperature. Over regional scales where climatic changes determine societal impacts and drive adaptation related decisions, detection and attribution (D&A) of climate change can be challenging due to the greater contribution of internal variability, greater uncertainty in regionally important forcings, greater errors in climate models, and larger observational uncertainty in many regions of the world. We examine the causes of annual and seasonal surface air temperature (TAS) changes over sub-regions (based on a demarcation of homogeneous temperature zones) of India using two observational datasets together with results from a multimodel archive of forced and unforced simulations. Our D&A analysis examines sensitivity of the results to a variety of optimal fingerprint methods and temporal-averaging choices. We can robustly attribute TAS changes over India between 1956-2005 to anthropogenic forcing mostly by greenhouse gases and partially offset by other anthropogenic forcings including aerosols and land use land cover change.

Coronal temperatures of selected active cool stars as derived from low resolution Einstein observations

NASA Technical Reports Server (NTRS)

Vilhu, Osmi; Linsky, Jeffrey L.

1990-01-01

Mean coronal temperatures of some active G-K stars were derived from Rev1-processed Einstein-observatory's IPC-spectra. The combined X-ray and transition region emission line data are in rough agreement with static coronal loop models. Although the sample is too small to derive any statistically significant conclusions, it suggests that the mean coronal temperature depends linearly on the inverse Rossby-number, with saturation at short rotation periods.

Seasonal variations of the atmospheric temperature response in mesosphere and lower thermosphere on solar activity

NASA Astrophysics Data System (ADS)

Semenov, A. I.; Shefov, N. N.

2003-04-01

On the basis of the measurement data of temperature by rocket and ground-based spectrophotometric (nightglow emissions of hydroxyl,sodium and atomic oxygen of 557.7 nm) methods obtained during 21 and 22 cycles of solar activity, the distributions with height of mean monthly temperature of an atmosphere for region of altitudes Z from 60 to 100 km have been constructed. The periods of maxima and minima of solar activity (1980 and 1991, F10.7=198 and 208; 1976 and 1986, F10.7=73 and 75) were considered. On the basis of these distributions with height of the seasonal variations of dependence of temperature from solar activity S = deltaT(Z)/deltaF, K/100 sfu have been analyzed. It was revealed, that character of seasonal variations essentially changes with growth of height. Mean annual solar response S at heights lower than 70 km is negative, and at higher heights is positive. This solar response S in mesopause region reaches 3 (sigma=1). Such character of influence of solar activity on temperature of the upper atmosphere is caused by features of mean annual and seasonal variations of its distributions with height. The distributions with height of amplitudes and phases of three harmonics of seasonal variations S are presented. This work was supported by the Grant N 2274 of ISTC.

Relationship between the Heat Tolerance of Photosynthesis and the Thermal Stability of Rubisco Activase in Plants from Contrasting Thermal Environments1

PubMed Central

Salvucci, Michael E.; Crafts-Brandner, Steven J.

2004-01-01

Inhibition of net photosynthesis (Pn) by moderate heat stress has been attributed to an inability of Rubisco activase to maintain Rubisco in an active form. To examine this proposal, the temperature response of Pn, Rubisco activation, chlorophyll fluorescence, and the activities of Rubisco and Rubisco activase were examined in species from contrasting environments. The temperature optimum of Rubisco activation was 10°C higher in the creosote bush (Larrea tridentata) compared with the Antarctic hairgrass (Deschampsia antarctica), resembling the temperature response of Pn. Pn increased markedly with increasing internal CO2 concentration in Antarctic hairgrass and creosote bush plants subjected to moderate heat stress even under nonphotorespiratory conditions. Nonphotochemical quenching of chlorophyll fluorescence, the effective quantum yield of photochemical energy conversion (ΔF/Fm′) and the maximum yield of PSII (Fv/Fm) were more sensitive to temperature in Antarctic hairgrass and two other species endemic to cold regions (i.e. Lysipomia pumila and spinach [Spinacea oleracea]) compared with creosote bush and three species (i.e. jojoba [Simmondsia chinensis], tobacco [Nicotiana tabacum], and cotton [Gossypium hirsutum]) from warm regions. The temperature response of activity and the rate of catalytic inactivation of Rubisco from creosote bush and Antarctic hairgrass were similar, whereas the optimum for ATP hydrolysis and Rubisco activation by recombinant creosote bush, cotton, and tobacco activase was 8°C to 10°C higher than for Antarctic hairgrass and spinach activase. These results support a role for activase in limiting photosynthesis at high temperature. PMID:15084731

InAs based terahertz quantum cascade lasers

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

Brandstetter, Martin, E-mail: martin.brandstetter@tuwien.ac.at; Kainz, Martin A.; Krall, Michael

2016-01-04

We demonstrate terahertz lasing emission from a quantum cascade structure, realized with InAs/AlAs{sub 0.16}Sb{sub 0.84} heterostructures. Due to the lower effective electron mass, InAs based active regions are expected to provide a higher optical gain compared to structures consisting of GaAs or InGaAs. The growth by molecular beam epitaxy enabled the fabrication of monolayer-thick barriers, required for the active region, which is based on a 3-well resonant phonon depletion design. Devices were processed in a double-metal waveguide geometry to ensure high mode confinement and low optical losses. Lasing emission at 3.8 THz was observed at liquid helium temperatures by applyingmore » a magnetic field perpendicular to the layered structure in order to suppress parasitic scattering channels. These results demonstrate the feasibility of InAs based active regions for terahertz quantum cascade lasers, potentially enabling higher operating temperatures.« less

Efficiency of True-Green Light Emitting Diodes: Non-Uniformity and Temperature Effects

PubMed Central

Titkov, Ilya E.; Karpov, Sergey Yu.; Yadav, Amit; Mamedov, Denis; Zerova, Vera L.

2017-01-01

External quantum efficiency of industrial-grade green InGaN light-emitting diodes (LEDs) has been measured in a wide range of operating currents at various temperatures from 13 K to 300 K. Unlike blue LEDs, the efficiency as a function of current is found to have a multi-peak character, which could not be fitted by a simple ABC-model. This observation correlated with splitting of LED emission spectra into two peaks at certain currents. The characterization data are interpreted in terms of non-uniformity of the LED active region, which is tentatively attributed to extended defects like V-pits. We suggest a new approach to evaluation of temperature-dependent light extraction and internal quantum efficiencies taking into account the active region non-uniformity. As a result, the temperature dependence of light extraction and internal quantum efficiencies have been evaluated in the temperature range mentioned above and compared with those of blue LEDs. PMID:29156543

Role of antimony in the charge transport mechanisms for La0.67Ca0.33Mn1-xSbxO3 manganites

NASA Astrophysics Data System (ADS)

Kataria, B. R.; Solanki, Pankaj; Pandya, D. D.; Solanki, P. S.; Shah, N. A.

2018-07-01

Single phasic La0.67Ca0.33Mn1-xSbxO3 (LCMSO; x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.10) samples were characterized by performing temperature and magnetic field dependent resistance measurements. Present study, mainly, aims for the better understanding of possible charge conduction mechanisms responsible for the low temperature resistivity and high temperature [well above metal to insulator transition temperature (TP)] semiconducting regions. Variation in resistivity and TP with Sb5+ content (x) and applied magnetic field has been discussed in the light of the modifications in structural and magnetic lattices of smaller diamagnetic Sb5+ doped LCMSO system. Various models and mechanisms have been theoretical employed to fit obtained experimental resistivity data for the low temperature resistivity and semiconducting regions of all LCMSO manganites. It is found that low temperature resistivity minima follows the coulomb blockade model while charge conduction in the semiconducting region obeys the variable range hopping (VRH) mechanism. Variation in low temperature blocking energy, activation energy in semiconducting region and magnetoresistance (MR) with Sb5+ content (x) and applied magnetic field has been discussed in detail.

Sub-seasonal temperature variability in the tropical upper troposphere and lower stratosphere observed with GPS radio occultation

NASA Astrophysics Data System (ADS)

Scherllin-Pirscher, Barbara; Randel, William J.; Kim, Joowan

2017-04-01

We investigate sub-seasonal temperature variability in the tropical upper troposphere and lower stratosphere (UTLS) region using daily gridded fields of GPS radio occultation measurements. The unprecedented vertical resolution (from about 100 m in the troposphere to about 1.5 km in the stratosphere) and high accuracy and precision (0.7 K to 1 K between 8 km and 25 km) make these data ideal for characterizing temperature oscillations with short vertical wavelengths. Long-term behavior of sub-seasonal temperature variability is investigated using the entire RO record from January 2002 to December 2014 (13 years of data). Transient sub-seasonal waves including eastward-propagating Kelvin waves (isolated with space-time spectral analysis) dominate large-scale zonal temperature variability in the tropical tropopause region and in the lower stratosphere. Above 20 km, Kelvin waves are strongly modulated by the quasi-biennial oscillation (QBO). Enhanced wave activity can be found during the westerly shear phase of the QBO. In the tropical tropopause region, however, sub-seasonal waves are highly transient in time. Several peaks of Kelvin-wave activity coincide with short-term fluctuations in tropospheric deep convection, but other episodes are not evidently related. Also, there are no obvious relationships with zonal winds or stability fields near the tropical tropopause. Further investigations of convective forcing and atmospheric background conditions along the waves' trajectories are needed to better understand sub-seasonal temperature variability near the tropopause. For more details, see Scherllin-Pirscher, B., Randel, W. J., and Kim, J.: Tropical temperature variability and Kelvin-wave activity in the UTLS from GPS RO measurements, Atmos. Chem. Phys., 17, 793-806, doi:10.5194/acp-17-793-2017, 2017. http://www.atmos-chem-phys.net/17/793/2017/acp-17-793-2017.html

The influence of convective blueshift on radial velocities of F, G, and K stars

NASA Astrophysics Data System (ADS)

Bauer, F. F.; Reiners, A.; Beeck, B.; Jeffers, S. V.

2018-02-01

Context. Apparent radial velocity (RV) signals induced by stellar surface features such as spots and plages can result in a false planet detection or hide the presence of an orbiting planet. Our ability to detect rocky exoplanets is currently limited by our understanding of such stellar signals. Aims: We model RV variations caused by active regions on the stellar surface of typical exoplanet-hosting stars of spectral type F, G, and K. We aim to understand how the stellar magnetic field strength, convective blueshift, and spot temperatures can influence RV signals caused by active regions. Methods: We use magneto-hydrodynamic (MHD) simulations for stars with spectral types F3V, a G2V, and a K5V. We quantify the impact of the magnetic field strength inside active regions on the RV measurement using the magnetic and non-magnetic FeI lines at 6165 Å and 6173 Å. We also quantify the impact of spot temperature and convective blueshift on the measured RV values. Results: Increasing the magnetic field strength increases the efficiency to suppress convection in active regions which results in an asymmetry between red- and blueshifted parts of the RV curves. A stronger suppression of convection also leads to an observed increase in RV amplitude for stronger magnetic fields. The MHD simulations predict convective motions to be faster in hotter stars. The suppression of faster convection leads to a stronger RV amplitude increase in hotter stars when the magnetic field is increased. While suppression of convection increases the asymmetry in RV curves,c a decreasing spot temperature counteracts this effect. When using observed temperatures for dark spots in our simulations we find that convective blueshift effects are negligible.

Multi-scale statistical analysis of coronal solar activity

DOE PAGES

Gamborino, Diana; del-Castillo-Negrete, Diego; Martinell, Julio J.

2016-07-08

Multi-filter images from the solar corona are used to obtain temperature maps that are analyzed using techniques based on proper orthogonal decomposition (POD) in order to extract dynamical and structural information at various scales. Exploring active regions before and after a solar flare and comparing them with quiet regions, we show that the multi-scale behavior presents distinct statistical properties for each case that can be used to characterize the level of activity in a region. Information about the nature of heat transport is also to be extracted from the analysis.

THz quantum cascade lasers with wafer bonded active regions.

PubMed

Brandstetter, M; Deutsch, C; Benz, A; Cole, G D; Detz, H; Andrews, A M; Schrenk, W; Strasser, G; Unterrainer, K

2012-10-08

We demonstrate terahertz quantum-cascade lasers with a 30 μm thick double-metal waveguide, which are fabricated by stacking two 15 μm thick active regions using a wafer bonding process. By increasing the active region thickness more optical power is generated inside the cavity, the waveguide losses are decreased and the far-field is improved due to a larger facet aperture. In this way the output power is increased by significantly more than a factor of 2 without reducing the maximum operating temperature and without increasing the threshold current.

Influence of geomagnetic activity on mesopause temperature over Yakutia

NASA Astrophysics Data System (ADS)

Gavrilyeva, Galina; Ammosov, Petr

2018-03-01

The long-term temperature changes of the mesopause region at the hydroxyl molecule OH (6-2) nighttime height and its connection with the geomagnetic activity during the 23rd and beginning of the 24th solar cycles are presented. Measurements were conducted with an infrared digital spectrograph at the Maimaga station (63° N, 129.5° E). The hydroxyl rotational temperature (TOH) is assumed to be equal to the neutral atmosphere temperature at the altitude of ˜ 87 km. The average temperatures obtained for the period 1999 to 2015 are considered. The season of observations starts at the beginning of August and lasts until the middle of May. The maximum of the seasonally averaged temperatures is delayed by 2 years relative to the maximum of the solar radio emission flux (wavelength of 10.7 cm), and correlates with a change in geomagnetic activity (Ap index). Temperature grouping in accordance with the geomagnetic activity level showed that in years with high activity (Ap > 8), the mesopause temperature from October to February is about 10 K higher than in years with low activity (Ap < = 8). Cross-correlation analysis showed no temporal shift between geomagnetic activity and temperature. The correlation coefficient is equal to 0.51 at the 95 % level.

Total lactate dehydrogenase activity of tail muscle is not cold-adapted in nocturnal lizards from cool-temperate habitats.

PubMed

Hare, K M; Miller, J H; Clark, A G; Daugherty, C H

2005-12-01

The dependence of metabolic processes on temperature constrains the behavior, physiology and ecology of many ectothermic animals. The evolution of nocturnality in lizards, especially in temperate regions, requires adaptations for activity at low temperatures when optimal body temperatures are unlikely to be obtained. We examined whether nocturnal lizards have cold-adapted lactate dehydrogenase (LDH). LDH was chosen as a representative metabolic enzyme. We measured LDH activity of tail muscle in six lizard species (n=123: three nocturnal, two diurnal and one crepuscular) between 5 and 35 degrees C and found no differences in LDH-specific activity or thermal sensitivity among the species. Similarly, the specific activity and thermal sensitivity of LDH were similar between skinks and geckos. Similar enzyme activities among nocturnal and diurnal lizards indicate that there is no selection of temperature specific LDH enzyme activity at any temperature. As many nocturnal lizards actively thermoregulate during the day, LDH may be adapted for a broad range of temperatures rather than adapted specifically for the low temperatures encountered when the animals are active. The total activity of LDH in tropical and temperate lizards is not cold-adapted. More data are required on biochemical adaptations and whole animal thermal preferences before trends can be established.

Solar Rotation Stereoscopy in Microwaves

NASA Astrophysics Data System (ADS)

Aschwanden, Markus J.; Lim, Jeremy; Gary, Dale E.; Klimchuk, James A.

1995-11-01

We present here the first stereoscopic altitude measurements of active region sources observed at microwave frequencies (10-14 GHz The active region NOAA 7128 was observed with the Owens Valley Radio Observatory (OVRO) on 1992 April 13, 14, 15, and 16 as it passed through the central meridian. From white-light data of the underlying sunspot we determined the rotation rate of the active region, which was found to have a relative motion of dL/dt = +0°.240 day-1 with respect to the standard photospheric differential rotation rate. Based on this rotation rate we determine for the microwave sources stereoscopic altitudes of 3.3-11.0 Mm above the photosphere. The altitude spectrum h(v) of the right circular polarization (RCP) main source shows a discontinuity at 12 GHz and can be satisfactorily fitted with a dipole model with a transition from the second to the third harmonic level at 12 GHz. The dominance of the third harmonic for frequencies above 12 GHz occurs because the second harmonic level drops below the transition region, at a height of 2.6±0.6 Mm according to the microwave data. The altitude spectrum h(v) serves also to invert the temperature profile T(h) from the optically thick parts of the radio brightness temperature spectrum TB(ν[h]). The microwave emission in both circular polarizations can be modeled with gyroresonance emission, with x-mode for RCP and o-mode in LCP, with the same harmonics at each frequency, but different emission angles in both modes. The contributions from free-free emission are negligible in both polarizations, based on the peak emission measure of EM ≍ 6 × 1028 cm-5 observed in soft X-rays by Yohkoh/SXT. This study demonstrates that the height dependence of the coronal magnetic field B(h) and the plasma temperature T(h) in an active region can be inverted from the stereoscopic altitude spectra h(v) and the observed brightness temperature spectra TB(ν).

Effect of solar activity on the repetitiveness of some meteorological phenomena

NASA Astrophysics Data System (ADS)

Todorović, Nedeljko; Vujović, Dragana

2014-12-01

In this paper we research the relationship between solar activity and the weather on Earth. This research is based on the assumption that every ejection of magnetic field energy and particles from the Sun (also known as Solar wind) has direct effects on the Earth's weather. The impact of coronal holes and active regions on cold air advection (cold fronts, precipitation, and temperature decrease on the surface and higher layers) in the Belgrade region (Serbia) was analyzed. Some active regions and coronal holes appear to be in a geo-effective position nearly every 27 days, which is the duration of a solar rotation. A similar period of repetitiveness (27-29 days) of the passage of the cold front, and maximum and minimum temperatures measured at surface and at levels of 850 and 500 hPa were detected. We found that 10-12 days after Solar wind velocity starts significantly increasing, we could expect the passage of a cold front. After eight days, the maximum temperatures in the Belgrade region are measured, and it was found that their minimum values appear after 12-16 days. The maximum amount of precipitation occurs 14 days after Solar wind is observed. A recurring period of nearly 27 days of different phases of development for hurricanes Katrina, Rita and Wilma was found. This analysis confirmed that the intervals of time between two occurrences of some particular meteorological parameter correlate well with Solar wind and A index.

Middle Atmosphere Program. Handbook for MAP. Volume 13: Ground-based Techniques

NASA Technical Reports Server (NTRS)

Vincent, R. A. (Editor)

1984-01-01

Topics of activities in the middle Atmosphere program covered include: lidar systems of aerosol studies; mesosphere temperature; upper atmosphere temperatures and winds; D region electron densities; nitrogen oxides; atmospheric composition and structure; and optical sounding of ozone.

Recurring slope lineae in equatorial regions of Mars

USGS Publications Warehouse

McEwen, Alfred S.; Dundas, Colin M.; Mattson, Sarah S.; Toigo, Anthony D.; Ojha, Lujendra; Wray, James J.; Chojnacki, Matthew; Byrne, Shane; Murchie, Scott L.; Thomas, Nicolas

2014-01-01

The presence of liquid water is a requirement of habitability on a planet. Possible indicators of liquid surface water on Mars include intermittent flow-like features observed on sloping terrains. These recurring slope lineae are narrow, dark markings on steep slopes that appear and incrementally lengthen during warm seasons on low-albedo surfaces. The lineae fade in cooler seasons and recur over multiple Mars years. Recurring slope lineae were initially reported to appear and lengthen at mid-latitudes in the late southern spring and summer and are more common on equator-facing slopes where and when the peak surface temperatures are higher. Here we report extensive activity of recurring slope lineae in equatorial regions of Mars, particularly in the deep canyons of Valles Marineris, from analysis of data acquired by the Mars Reconnaissance Orbiter. We observe the lineae to be most active in seasons when the slopes often face the sun. Expected peak temperatures suggest that activity may not depend solely on temperature. Although the origin of the recurring slope lineae remains an open question, our observations are consistent with intermittent flow of briny water. Such an origin suggests surprisingly abundant liquid water in some near-surface equatorial regions of Mars.

Analysis of X-ray observations of the 15 June 1973 flare in active region NOAA 131

NASA Technical Reports Server (NTRS)

Krall, K. R.; Reichmann, E. J.; Wilson, R. M.; Henze, W., Jr.; Smith, J. B., Jr.

1978-01-01

Observations and analyses of the 1B/M3 flare of 15 June, 1973 in active region NOAA 131 (McMath 12379) are presented. The X-ray observations, consisting of broadband photographs and proportional counter data from the Skylab/ATM NASA-MSFC/Aerospace S-056 experiment, are used to infer temperatures, emission measures, and densities for the flaring plasma. The peak temperature from the spatially resolved photographs is 25,000,000 K, while the temperature from the full-disk proportional counter data is approximately 15,000,000 K. The density is 3 times 10 to the 10th/cu cm. The X-ray flare emission appears to come primarily from two low-lying curvilinear features lying perpendicular to and centered on the line where the photospheric longitudinal magnetic field is zero. Similarities in the preflare and postflare X-ray emission patterns indicate that no large-scale relaxation of the coronal magnetic configuration was observed. Also discussed are H-alpha and magnetic field observations of the flare and the active region. Finally, results of numerical calculations, including thermal conduction, radiative loss, and chromospheric evaporation, are in qualitative agreement with the decay phase observations.

Single-residue molecular switch for high-temperature dependence of vanilloid receptor TRPV3

PubMed Central

Liu, Beiying; Qin, Feng

2017-01-01

Thermal transient receptor potential (TRP) channels, a group of ion channels from the transient receptor potential family, play important functions in pain and thermal sensation. These channels are directly activated by temperature and possess strong temperature dependence. Furthermore, their temperature sensitivity can be highly dynamic and use-dependent. For example, the vanilloid receptor transient receptor potential 3 (TRPV3), which has been implicated as a warmth detector, becomes responsive to warm temperatures only after intensive stimulation. Upon initial activation, the channel exhibits a high-temperature threshold in the noxious temperature range above 50 °C. This use dependence of heat sensitivity thus provides a mechanism for sensitization of thermal channels. However, how the channels acquire the use dependence remains unknown. Here, by comparative studies of chimeric channels between use-dependent and use-independent homologs, we have determined the molecular basis that underlies the use dependence of temperature sensitivity of TRPV3. Remarkably, the restoration of a single residue that is apparently missing in the use-dependent homologs could largely eliminate the use dependence of heat sensitivity of TRPV3. The location of the region suggests a mechanism of temperature-dependent gating of thermal TRP channels involving an intracellular region assembled around the TRP domain. PMID:28154143

Structure and physics of solar faculae. II - The non-thermal velocity field above faculae

NASA Astrophysics Data System (ADS)

Mouradian, Z.; Dumont, S.; Pecker, J.-C.; Chipman, E.; Artzner, G. E.; Vial, J. C.

1982-05-01

The OSO-8 satellite enabled the study of various characteristics of the profiles of Si II, Si IV, C IV, and O VI lines above active areas of the sun, as well as above quiet areas, and the derivation of some physical properties of the transition region between chromosphere and corona (CCT). The study of the lines shows a general tendency for the microvelocity fields on the average to be nearly constant for the heights corresponding to a temperature greater than 100,000 K; however they seem to slightly increase with height in quiet areas, and decrease in active areas. A multicomponent model of the CCT is necessary, and its geometry is far from being a set of plane-parallel columns. It is similar to an association of moving knots within the nonmoving principal component of the matter. The proportion of mass, in the knots relative to that in the nonmoving component, is several times larger in active regions than in quiet regions. In the knots, the nonthermal microvelocity fields are smaller in active regions and seem to decrease for temperature increasing above 100,000 K, contrary to what happens in the steady principal component.

Structure and physics of solar faculae. II - The non-thermal velocity field above faculae

NASA Technical Reports Server (NTRS)

Mouradian, Z.; Dumont, S.; Pecker, J.-C.; Chipman, E.; Artzner, G. E.; Vial, J. C.

1982-01-01

The OSO-8 satellite enabled the study of various characteristics of the profiles of Si II, Si IV, C IV, and O VI lines above active areas of the sun, as well as above quiet areas, and the derivation of some physical properties of the transition region between chromosphere and corona (CCT). The study of the lines shows a general tendency for the microvelocity fields on the average to be nearly constant for the heights corresponding to a temperature greater than 100,000 K; however they seem to slightly increase with height in quiet areas, and decrease in active areas. A multicomponent model of the CCT is necessary, and its geometry is far from being a set of plane-parallel columns. It is similar to an association of moving knots within the nonmoving principal component of the matter. The proportion of mass, in the knots relative to that in the nonmoving component, is several times larger in active regions than in quiet regions. In the knots, the nonthermal microvelocity fields are smaller in active regions and seem to decrease for temperature increasing above 100,000 K, contrary to what happens in the steady principal component.

Temperature dependence of emission measure in solar X-ray plasmas. 1: Non-flaring active regions

NASA Technical Reports Server (NTRS)

Phillips, K. J. H.

1974-01-01

X-ray and ultraviolet line emission from hot, optically thin material forming coronal active regions on the sun may be described in terms of an emission measure distribution function, Phi (T). A relationship is developed between line flux and Phi (T), a theory which assumes that the electron density is a single-valued function of temperature. The sources of error involved in deriving Phi (T) from a set of line fluxes are examined in some detail. These include errors in atomic data (collisional excitation rates, assessment of other mechanisms for populating excited states of transitions, element abundances, ion concentrations, oscillator strengths) and errors in observed line fluxes arising from poorly - known instrumental responses. Two previous analyses are discussed in which Phi (T) for a non-flaring active region is derived. A least squares method of Batstone uses X-ray data of low statistical significance, a fact which appears to influence the results considerably. Two methods for finding Phi (T) ab initio are developed. The coefficients are evaluated by least squares. These two methods should have application not only to active-region plasmas, but also to hot, flare-produced plasmas.

Three-dimensional and thermal surface imaging produces reliable measures of joint shape and temperature: a potential tool for quantifying arthritis

PubMed Central

Spalding, Steven J; Kwoh, C Kent; Boudreau, Robert; Enama, Joseph; Lunich, Julie; Huber, Daniel; Denes, Louis; Hirsch, Raphael

2008-01-01

Introduction The assessment of joints with active arthritis is a core component of widely used outcome measures. However, substantial variability exists within and across examiners in assessment of these active joint counts. Swelling and temperature changes, two qualities estimated during active joint counts, are amenable to quantification using noncontact digital imaging technologies. We sought to explore the ability of three dimensional (3D) and thermal imaging to reliably measure joint shape and temperature. Methods A Minolta 910 Vivid non-contact 3D laser scanner and a Meditherm med2000 Pro Infrared camera were used to create digital representations of wrist and metacarpalphalangeal (MCP) joints. Specialized software generated 3 quantitative measures for each joint region: 1) Volume; 2) Surface Distribution Index (SDI), a marker of joint shape representing the standard deviation of vertical distances from points on the skin surface to a fixed reference plane; 3) Heat Distribution Index (HDI), representing the standard error of temperatures. Seven wrists and 6 MCP regions from 5 subjects with arthritis were used to develop and validate 3D image acquisition and processing techniques. HDI values from 18 wrist and 9 MCP regions were obtained from 17 patients with active arthritis and compared to data from 10 wrist and MCP regions from 5 controls. Standard deviation (SD), coefficient of variation (CV), and intraclass correlation coefficients (ICC) were calculated for each quantitative measure to establish their reliability. CVs for volume and SDI were <1.3% and ICCs were greater than 0.99. Results Thermal measures were less reliable than 3D measures. However, significant differences were observed between control and arthritis HDI values. Two case studies of arthritic joints demonstrated quantifiable changes in swelling and temperature corresponding with changes in symptoms and physical exam findings. Conclusion 3D and thermal imaging provide reliable measures of joint volume, shape, and thermal patterns. Further refinement may lead to the use of these technologies to improve the assessment of disease activity in arthritis. PMID:18215307

Wellbore and groundwater temperature distribution eastern Snake River Plain, Idaho: Implications for groundwater flow and geothermal potential

DOE PAGES

McLing, Travis L.; Smith, Richard P.; Smith, Robert W.; ...

2016-04-10

A map of groundwater temperatures from the Eastern Snake River Plain (ESRP) regional aquifer can be used to identify and interpret important features of the aquifer, including aquifer flow direction, aquifer thickness, and potential geothermal anomalies. The ESRP is an area of high heat flow, yet most of this thermal energy fails to reach the surface, due to the heat being swept downgradient by the aquifer to the major spring complexes near Thousand Springs, ID, a distance of 300 km. Nine deep boreholes that fully penetrate the regional aquifer display three common features: (1) high thermal gradients beneath the aquifer,more » corresponding to high conductive heat flow in low-permeability hydrothermally-altered rocks; (2) isothermal temperature profiles within the aquifer, characteristic of an actively flowing groundwater; and (3) moderate thermal gradients in the vadose zone with values that indicate that over half of the geothermal heat flow is removed by advective transport in the regional aquifer system. This study utilized temperature data from 250 ESRP aquifer wells to evaluate regional aquifer flow direction, aquifer thickness, and potential geothermal anomalies. Because the thermal gradients are typically low in the aquifer, any measurement of groundwater temperature is a reasonable estimate of temperature throughout the aquifer thickness, allowing the construction of a regional aquifer temperature map for the ESRP. Mapped temperatures are used to identify cold thermal plumes associated with recharge from tributary valleys and adjacent uplands, and warm zones associated with geothermal input to the aquifer. Warm zones in the aquifer can have various causes, including local circulation of groundwater through the deep conductively dominated region, slow groundwater movement in low-permeability regions, or localized heat flow from deeper thermal features.« less

Mechanical relaxations of a Cu60Zr40 metallic glass studied by using a dynamic mechanical analysis

NASA Astrophysics Data System (ADS)

Jeong, H. T.; Park, C. O.

2013-03-01

The mechanical relaxation behaviors of a Cu60Zr40 metallic glass were investigated by using isothermal multi-frequency dynamic mechanical measurements. From the spectra of the elastic moduli, master curves were constructed using the time-temperature superposition principle. The temperature dependence of the shift factor was found to follow the Arrhenius relationship in two temperature regions, one below and the other above the glass transition temperature ( T g ), and the activation energies for low-temperature relaxation and viscous flow were 32.7 kJ/mol and 307.1 kJ/mol, respectively. The decoupling of these two relaxations, shown in the temperature dependent plot of the shift factor, manifests the dynamic glass transition temperature region of the Cu60Zr40 metallic glass. From the temperature dependence of the shift factor, the fragility index of this alloy was also estimated.

Temperature dependence of the electrode kinetics of oxygen reduction at the platinum/Nafion interface - A microelectrode investigation

NASA Technical Reports Server (NTRS)

Parthasarathy, Arvind; Srinivasan, Supramanian; Appleby, A. J.; Martin, Charles R.

1992-01-01

Results of a study of the temperature dependence of the oxygen reduction kinetics at the Pt/Nafion interface are presented. This study was carried out in the temperature range of 30-80 C and at 5 atm of oxygen pressure. The results showed a linear increase of the Tafel slope with temperature in the low current density region, but the Tafel slope was found to be independent of temperature in the high current density region. The values of the activation energy for oxygen reduction at the platinum/Nafion interface are nearly the same as those obtained at the platinum/trifluoromethane sulfonic acid interface but less than values obtained at the Pt/H3PO4 and Pt/HClO4 interfaces. The diffusion coefficient of oxygen in Nafion increases with temperature while its solubility decreases with temperature. These temperatures also depend on the water content of the membrane.

Electrical and Dielectric Properties of a n-Si Schottky Barrier Diode with Bismuth Titanate Interlayer: Effect of Temperature

NASA Astrophysics Data System (ADS)

Yıldırım, M.; Şahin, C.; Altındal, Ş.; Durmuş, P.

2017-03-01

An Au/Bi4Ti3O12/ n-Si Schottky barrier diode (SBD) was fabricated with a 51 nm Bi4Ti3O12 interfacial layer. Admittance measurements of the fabricated SBD were carried out in the bias voltage ( V) range of -4 V and 6 V. Capacitance ( C) and conductance ( G/ω) measurements were carried out in a wide temperature range of 120-380 K so that temperature effects on electrical and dielectric properties of the SBD were investigated. Main electrical parameters were extracted from reverse bias C -2- V plots. It was found that variance of electrical and dielectric parameters of the SBD with temperature is basically different for low and high temperature regions. A fair number (˜1012 eV-1 cm-2) was obtained for surface states ( N ss); however, N ss first decreased then increased with temperature. This result was associated with increased defects with temperature and higher activation energy in the high temperature region. Dielectric parameters of the SBD were also extracted and the dielectric constant of SBD was found as ˜10 at room temperature. Application of modulus formalism to the admittance data revealed temperature-activated dielectric relaxation at 340 K. Results showed that the temperature has considerable effects on electrical and dielectric properties of Au/Bi4Ti3O12/ n-Si SBD.

Determination of production regions for pollution-free Chinese medicinal materials by geographic information system: Achyranthes bidentata (Niu Qi) in Tianjin as an example

PubMed Central

2014-01-01

Background The land and ecology suitability for producing pollution-free Chinese medicinal materials should be evaluated based on Geographic Information System (GIS). This study aims to determine production regions for pollution-free Achyranthes bidentata in Tianjin as a case to illustrate the workflow based on GIS. Methods The slopes, land usage, residential areas and roads were selected to evaluate the land suitability, to avoid the potential pollution sources. The ecology suitability evaluation was performed based on the soil type and nine climate factors, such as active accumulated temperature, mean January temperature, mean July temperature, the lowest temperature in January, the highest temperature in July, mean annual temperature, sunshine duration, relative humidity, annual precipitation, affecting the natural growth of A. bidentata. Results The best production regions for pollution-free A. bidentata in Tianjin, with a total area of approximately 575 km2, were found in Jinghai County, Ninghe County, Wuqing District, and Dagang District. Conclusion This study illustrated a workflow based on GIS for determining the production regions in Tianjin for pollution-free A. bidentata. PMID:25342961

NHEXAS PHASE I REGION 5 STUDY--STANDARD OPERATING PROCEDURE--REFRIGERATORS AND FREEZERS (NHX/SOP-163-001)

EPA Science Inventory

This procedure describes the calibration and maintenance activities of a refrigerator custodian in ensuring that refrigerators and freezers are functioning within acceptable temperature ranges. Refrigerators and freezers were used as temperature-controlled repositories for reagen...

Temperature and Precipitation trends in Kashmir valley, North Western Himalayas

NASA Astrophysics Data System (ADS)

Shafiq, Mifta Ul; Rasool, Rehana; Ahmed, Pervez; Dimri, A. P.

2018-01-01

Climate change has emerged as an important issue ever to confront mankind. This concern emerges from the fact that our day-to-day activities are leading to impacts on the Earth's atmosphere that has the potential to significantly alter the planet's shield and radiation balance. Developing countries particularly whose income is particularly derived from agricultural activities are at the forefront of bearing repercussions due to changing climate. The present study is an effort to analyze the changing trends of precipitation and temperature variables in Kashmir valley along different elevation zones in the north western part of India. As the Kashmir valley has a rich repository of glaciers with its annual share of precipitation, slight change in the temperature and precipitation regime has far reaching environmental and economic consequences. The results from Indian Meteorological Department (IMD) data of the period 1980-2014 reveals that the annual mean temperature of Kashmir valley has increased significantly. Accelerated warming has been observed during 1980-2014, with intense warming in the recent years (2001-2014). During the period 1980-2014, steeper increase, in annual mean maximum temperature than annual mean minimum temperature, has been observed. In addition, mean maximum temperature in plain regions has shown higher rate of increase when compared with mountainous areas. In case of mean minimum temperature, mountainous regions have shown higher rate of increase. Analysis of precipitation data for the same period shows a decreasing trend with mountainous regions having the highest rate of decrease which can be quite hazardous for the fragile mountain environment of the Kashmir valley housing a large number of glaciers.

Long-term trend in ground-based air temperature and its responses to atmospheric circulation and anthropogenic activity in the Yangtze River Delta, China

NASA Astrophysics Data System (ADS)

Peng, Xia; She, Qiannan; Long, Lingbo; Liu, Min; Xu, Qian; Zhang, Jiaxin; Xiang, Weining

2017-10-01

The Yangtze River Delta (YRD), including Shanghai City, Jiangsu and Zhejiang Provinces, is the largest metropolitan region in China. In the past decades, the region has experienced massive urbanization and detrimentally affected the environment in the region. Identifying the spatio-temporal variations of climate change and its influencing mechanism in the YRD is an important task for assessing their impacts on the local society and ecosystem. Based on long-term (1958-2014) observation data of meteorological stations, three temperature indices, i.e. extreme maximum temperature (TXx), extreme minimum temperature (TNn), and mean temperature (TMm), were selected and spatialized with climatological calculations and spatial techniques. Evolution and spatial heterogeneity of three temperature indices over YRD as well as their links to atmospheric circulation and anthropogenic activity were investigated. In the whole YRD, a statistically significant overall uptrend could be detected in three temperature indices with the Mann-Kendall (M-K) trend test method. The linear increasing trend for TMm was 0.31 °C/10 a, which was higher than the global average (0.12 °C/10 a during 1951-2012). For TXx and TNn, the increasing rates were 0.41 °C/10 a and 0.52 °C/10 a. Partial correlation analysis indicated that TMm was more related with TXx (rp = 0.68, p < 0.001) than TNn (rp = 0.48, p < 0.001). Furthermore, it was detected with M-K analysis at pixel scale that 62.17%, 96.75% and 97.05% of the areas in the YRD showed significant increasing trends for TXx, TNn and TMm, respectively. The increasing trend was more obvious in the southern mountainous areas than the northern plains areas. Further analysis indicated that the variation of TXx over YRD was mainly influenced by anthropogenic activities (e.g. economic development), while TNn was more affected by atmospheric circulations (e.g., the Eurasian zonal circulation index (EAZ) and the cold air activity index (CA)). For TMm, it was a result of comprehensive effects of both atmospheric circulations and anthropogenic activities. On the whole, the northern plain areas was mainly dominated by atmospheric circulations, while the southern mountain areas of YRD was more affected by anthropogenic activities. The findings of this study might help to build a better understanding of the mechanics of temperature variations, and assess the potentially influencing factors on temperature changes.

A Blind Hydrothermal System in an Ocean Island Environment: Humu'ula Saddle, Hawaii Island

NASA Astrophysics Data System (ADS)

Thomas, D. M.; Wallin, E.; Lautze, N. C.; Lienert, B. R.; Pierce, H. A.

2014-12-01

A recently drilled groundwater investigation borehole, drilled to a depth of 1760 m in the Humu'ula Saddle of Hawaii Island, encountered an unexpectedly high temperature gradient of more than 160 ̊C/km. Although prior MT surveys across the region identified conductive formations of modest extent in the region, there were few surface manifestations of geologic structures likely to host a geothermal system and no evidence of an active, extensive hydrothermal system. Cores recovered from the borehole showed the presence of intrusive formations and moderate hydrothermal alteration at depth with progressive infilling of fractures and vesicles with depth and temperature. Independent modeling of gravity data (Flinders et al., 2013) suggests the presence of a broad intrusive complex within the region that is consistent with the borehole's confirmation of a high-elevation (~1400 m amsl) regional water table. A subsequent MT survey covering much of the western Saddle region has confirmed the presence of highly conductive conditions, consistent with thermal activity, to depths of 4 km and greater. Light stable isotope data for the borehole fluids indicate that the regional water table is derived from recharge from the upper elevations of Mauna Kea; major element chemistry indicates that formation temperatures exceed 200 ̊C. A conceptual model of the hydrothermal system, along with isotopic and fluid chemistry of the thermal fluids will be presented.

Synthesis and Electrical Resistivity of Nickel Polymethacrylate

NASA Astrophysics Data System (ADS)

Chohan, M. H.; Khalid, A. H.; Zulfiqar, M.; Butt, P. K.; Khan, Farah; Hussain, Rizwan

Synthesis of nickel polymethacrylate was carried out using methanolic solutions of sodium hydroxide and polymethacrylic acid. The electrical resistivity of the pellets made from Ni-polymethacrylate was measured at different voltages and temperatures. Results showed that the electrical resistivity of Ni-polymethacrylate decreases significantly with voltage in high temperature regions but the decrease is insignificant at temperatures nearing room temperature. The activation energy at low temperatures is approximately 0.8 eV whereas at high temperature it is in the range 0.21-0.27 eV.

Thermal biology in two syntopic lizards, Phymaturus extrilidus and Liolaemus parvus, in the Puna region of Argentina.

PubMed

Gómez Alés, Rodrigo; Acosta, Juan Carlos; Laspiur, Alejandro

2017-08-01

Body temperature is the most important ecophysiological variable affecting reptiles' life history. Moreover, thermoregulation in ectotherms implies a struggle to reach preferred temperatures in natural conditions due to the influence of biotic and abiotic factors. Our objective was to evaluate and compare the thermal biology of two syntopic species, Phymaturus extrilidus and Liolaemus parvus, in the Puna region of San Juan, Argentina. We determined body temperature (T b ), micro-environmental temperatures (T a and T s ) and operative temperatures (T e ) in the field. In the laboratory, we measured preferred temperatures (T pref ) and calculated the index of thermoregulatory efficiency (E). Neither body temperatures in the field nor preferred temperatures varied between seasons and sexes. Body temperatures were lower than preferred temperatures for both species. Nevertheless, regardless of the low thermal offer available in habitat, both species did achieve body temperatures higher than operative temperatures during activity. Thermoregulatory effectiveness was moderate in P. extrilidus (E=0.65), while L. parvus presented greater thermoregulatory efficiency (E=0.78). We conclude that under the rigorous climate conditions of the Puna, Phymaturus extrilidus and Liolaemus parvus are able to actively and efficiently thermoregulate, maintaining body temperatures close to the preferred and higher than those of its habitat. Differences in thermal characteristics between Phymaturus extrilidus and Liolaemus parvus are a consequence of differential limitations imposed on each species by the environment and of forces inherent to their life histories. Copyright © 2017 Elsevier Ltd. All rights reserved.

Solar coronal temperature diagnostics using emission line from multiple stages of ionization of iron

NASA Technical Reports Server (NTRS)

Brosius, Jeffrey W.; Davila, Joseph M.; Thomas, Roger J.; Thompson, William T.

1994-01-01

We obtained spatially resolved extreme-ultraviolet (EUV) spectra of AR 6615 on 1991 May 7 with NASA/ Goddard Space Flight Center's Solar EUV Rocket Telescope and Spectrograph (SERTS). Included are emission lines from four different stages of ionization of iron: Fe(+15) lambda 335 A, Fe(+14) lambda 327 A, Fe(+13) lambda 334 A, and Fe(+12) lambda 348 A. Using intensity ratios from among these lines, we have calculated the active region coronal temperature along the Solar Extreme Ultraviolet Telescope and Spectrograph (SERTS) slit. Temperatures derived from line ratios which incorporate adjacent stages of ionization are most sensitive to measurement uncertainties and yield the largest scatter. Temperatures derived from line ratios which incorporate nonadjacent stages of ionization are less sensitive to measurement uncertainties and yield little scatter. The active region temperature derived from these latter ratios has an average value of 2.54 x 10(exp 6) K, with a standard deviation approximately 0.12 x 10(exp 6) K, and shows no significant variation with position along the slit.

Raman Investigation of Temperature Profiles of Phospholipid Dispersions in the Biochemistry Laboratory

NASA Astrophysics Data System (ADS)

Craig, Norman C.

2015-06-01

The temperature dependence of self-assembled, cell-like dispersions of phospholipids is investigated with Raman spectroscopy in the biochemistry laboratory. Vibrational modes in the hydrocarbon interiors of phospholipid bilayers are strongly Raman active, whereas the vibrations of the polar head groups and the water matrix have little Raman activity. From Raman spectra increases in fluidity of the hydrocarbon chains can be monitored with intensity changes as a function of temperature in the CH-stretching region. The experiment uses detection of scattered 1064-nm laser light (Nicolet NXR module) by a Fourier transform infrared spectrometer (Nicolet 6700). A thermoelectric heater-cooler device (Melcor) gives convenient temperature control from 5 to 95°C for samples in melting point capillaries. Use of deuterium oxide instead of water as the matrix avoids some absorption of the exciting laser light and interference with intensity observations in the CH-stretching region. Phospholipids studied range from dimyristoylphosphotidyl choline (C14, transition T = 24°C) to dibehenoylphosphotidyl choline (C22, transition T = 74°C).

Spot temperatures and area coverages on active dwarf stars

NASA Technical Reports Server (NTRS)

Sarr, Steven H.; Neff, James E.

1990-01-01

Two active K dwarfs are examined to determine the temperatures of the stars and to estimate the locations and sizes of cool spots on the stellar surfaces. Two wavelength regions with TiO absorption bands at different temperature sensitivities are modeled simultaneously using the method developed by Huenemoerder and Ramsey (1987). The spectrum of BD +26deg730 shows excess absorption in the TiO band, and the absence of the 8860 A band in HD 82558 indicates that its spots are warmer than those of BD +26deg730.

High-frequency dielectric study of proustite crystals Ag3AsS3

NASA Astrophysics Data System (ADS)

Bordovsky, V. A.; Gunia, N. Yu; Castro, R. A.

2014-12-01

The dielectric properties of the crystals proustite in the frequency of 106-109 Hz and a temperature range of 173 to 473 K were studied. The dispersion of the dielectric parameters indicates the existence of non-Debye relaxation mechanism correlates with structural changes in the phase transition region. The charge transfer is temperature activated with an activation energy of 2.40 ± 0.01 eV.

High temperature structure in cool binary stars

NASA Technical Reports Server (NTRS)

Dupree, A. K.; Brickhouse, Nancy S.; Hanson, G. J.

1995-01-01

Strong high temperature emission lines in the EUVE spectra of binary stars containing cool components (Alpha Aur (Capella), 44 iota Boo, Lambda And, and VY Ari) provide the basis to define reliably the differential emission measure of hot plasma. The emission measure distributions for the short-period (P less than or equal to 13 d) binary systems show a high temperature enhancement over a relatively narrow temperature region similar to that originally found in Capella (Dupree et al. 1993). The emission measure distributions of rapidly rotating single stars 31 Com and AB Dor also contain a local enhancement of the emission measure although at different temperatures and width from Capella, suggesting that the enhancement in these objects may be characteristic of rapid rotation of a stellar corona. This feature might be identified with a (polar) active region, although its density and absolute size are unknown; in the binaries Capella and VY Ari, the feature is narrow and it may arise from an interaction region between the components.

The O2 reduction at the IFC modified O2 fuel cell electrode

NASA Technical Reports Server (NTRS)

Fielder, William L.; Singer, Joseph; Baldwin, Richard S.; Johnson, Richard E.

1992-01-01

The International Fuel Corporation (IFC) state of the art (SOA) O2 electrode (Au-10 percent Pt electrocatalyst by weight) is currently being used in the alkaline H2-O2 fuel cell in the NASA Space Shuttle. Recently, IFC modified O2 electrode, as a possible replacement for the SOA electrode. In the present study, O2 reduction data were obtained for the modified electrode at temperatures between 23.3 and 91.7 C. BET measurements gave an electrode BET surface area of about 2070 sq. cm/sq. cm of geometric surface area. The Tafel data could be fitted to two straight line regions. The slope for the lower region, designated as the 0.04 V/decade region, was temperature dependent, and the transfer coefficient was about 1.5. The 'apparent' energy of activation for this region was about 19 kcal/mol. An O2 reduction mechanism for this 0.04 region is presented. In the upper region, designated as the 0.08 V/decade region, diffusion may be the controlling process. Tafel data are presented to illustrate the increase in performance with increasing temperature.

Effects of solar activity and galactic cosmic ray cycles on the modulation of the annual average temperature at two sites in southern Brazil

NASA Astrophysics Data System (ADS)

Frigo, Everton; Antonelli, Francesco; da Silva, Djeniffer S. S.; Lima, Pedro C. M.; Pacca, Igor I. G.; Bageston, José V.

2018-04-01

Quasi-periodic variations in solar activity and galactic cosmic rays (GCRs) on decadal and bidecadal timescales have been suggested as a climate forcing mechanism for many regions on Earth. One of these regions is southern Brazil, where the lowest values during the last century were observed for the total geomagnetic field intensity at the Earth's surface. These low values are due to the passage of the center of the South Atlantic Magnetic Anomaly (SAMA), which crosses the Brazilian territory from east to west following a latitude of ˜ 26°. In areas with low geomagnetic intensity, such as the SAMA, the incidence of GCRs is increased. Consequently, possible climatic effects related to the GCRs tend to be maximized in this region. In this work, we investigate the relationship between the ˜ 11-year and ˜ 22-year cycles that are related to solar activity and GCRs and the annual average temperature recorded between 1936 and 2014 at two weather stations, both located near a latitude of 26° S but at different longitudes. The first of these stations (Torres - TOR) is located in the coastal region, and the other (Iraí - IRA) is located in the interior, around 450 km from the Atlantic Ocean. Sunspot data and the solar modulation potential for cosmic rays were used as proxies for the solar activity and the GCRs, respectively. Our investigation of the influence of decadal and bidecadal cycles in temperature data was carried out using the wavelet transform coherence (WTC) spectrum. The results indicate that periodicities of 11 years may have continuously modulated the climate at TOR via a nonlinear mechanism, while at IRA, the effects of this 11-year modulation period were intermittent. Four temperature maxima, separated by around 20 years, were detected in the same years at both weather stations. These temperature maxima are almost coincident with the maxima of the odd solar cycles. Furthermore, these maxima occur after transitions from even to odd solar cycles, that is, after some years of intense GCR flux. The obtained results offer indirect mathematical evidence that solar activity and GCR variations contributed to climatic changes in southern Brazil during the last century. A comparison of the results obtained for the two weather stations indicates that the SAMA also contributes indirectly to these temperature variations. The contribution of other mechanisms also related to solar activity cannot be excluded.

Relationship between skin temperature and muscle activation during incremental cycle exercise.

PubMed

Priego Quesada, Jose I; Carpes, Felipe P; Bini, Rodrigo R; Salvador Palmer, Rosario; Pérez-Soriano, Pedro; Cibrián Ortiz de Anda, Rosa M

2015-02-01

While different studies showed that better fitness level adds to the efficiency of the thermoregulatory system, the relationship between muscular effort and skin temperature is still unknown. Therefore, the present study assessed the relationship between neuromuscular activation and skin temperature during cycle exercise. Ten physically active participants performed an incremental workload cycling test to exhaustion while neuromuscular activations were recorded (via surface electromyography - EMG) from rectus femoris, vastus lateralis, biceps femoris and gastrocnemius medialis. Thermographic images were recorded before, immediately after and 10 min after finishing the cycling test, at four body regions of interest corresponding to the muscles where neuromuscular activations were monitored. Frequency band analysis was conducted to assess spectral properties of EMG signals in order to infer on priority in recruitment of motor units. Significant inverse relationship between changes in skin temperature and changes in overall neuromuscular activation for vastus lateralis was observed (r<-0.5 and p<0.04). Significant positive relationship was observed between skin temperature and low frequency components of neuromuscular activation from vastus lateralis (r>0.7 and p<0.01). Participants with larger overall activation and reduced low frequency component for vastus lateralis activation presented a better adaptive response of their thermoregulatory system by showing fewer changes in skin temperature after incremental cycling test. Copyright © 2014 Elsevier Ltd. All rights reserved.

EFFECT OF CORONAL TEMPERATURE ON THE SCALE OF SOLAR CHROMOSPHERIC JETS

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

Iijima; Yokoyama, T.H., E-mail: h.iijima@eps.s.u-tokyo.ac.jp

2015-10-20

We investigate the effect of coronal temperature on the formation process of solar chromospheric jets using two-dimensional magnetohydrodynamic simulations of the region from the upper convection zone to the lower corona. We develop a new radiative magnetohydrodynamic code for the dynamic modeling of the solar atmosphere, employing an LTE equation of state, optically thick radiative loss in the photosphere, optically thin radiative loss in the chromosphere and the corona, and thermal conduction along the magnetic field lines. Many chromospheric jets are produced in the simulations by shock waves passing through the transition region. We find that these jets are projectedmore » farther outward when the coronal temperature is lower (similar to that in coronal holes) and shorter when the coronal temperature is higher (similar to that in active regions). When the coronal temperature is high, the deceleration of the chromospheric jets is consistent with the model in which deceleration is determined by the periodic chromospheric shock waves. However, when the coronal temperature is low, the gravitational deceleration becomes more important and the chromospheric jets approach ballistic motion.« less

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Thermally induced stresses in stripe GaAs/GaAlAs laser diodes

NASA Astrophysics Data System (ADS)

Rimpler, R.; Both, W.

1988-11-01

Heating of the active region of stripe GaAlAs/GaAs double-heterostructure laser diodes by an injection current has a strong influence on the stresses in this region. An increase in the temperature of the region by 10 K can alter a shear stress by 5-10 MPa. In the case of lasers with a large thermal resistance the strong heating of the active region can induce mechanical stresses exceeding technological stresses (10 MPa) or even critical shear stresses for dislocation motion (20 MPa).

Magnetic Measurements in Hot Planetary Environments

NASA Astrophysics Data System (ADS)

Russell, Christopher T.; Leneman, David; Weygand, James M.; Parish, Helen F.

2017-04-01

While space exploration generally involves measurements where the temperature is low and can be restored to a normal operating range by heating the sensor, there are regions of space in which the environment is hotter than the laboratory, and it would be desirable but not easy to cool the sensor. Unexplored hot regions include the surface of Mercury, except very near the poles, the surface and atmosphere of Venus even at the poles, and planetary probes into the deep atmosphere of Jupiter. Magnetic measurements are highly desirable in all these regions, but the sensor has to be outside the spacecraft or lander where active cooling is impractical, and passive cooling impossible. Thus the sensors have to be designed to withstand the heat of the environment in which they must operate. The UCLA fluxgate magnetometer has no active parts in the sensor so that it is a candidate for operating at high temperatures. We have examined the materials available for replacing the present wiring and sensor structure that supports the windings and find that there are distinct temperatures at which the mechanical design needs to be altered with increasing cost and difficulty of machining, but that there are no limitations until the temperatures that affect the magnetic properties of the core material. In this paper we review what needs to be done to build a 'high' temperature fluxgate sensor, as well as what can be accomplished with the resulting design.

Switching phenomenon in a Se{70}Te{30-x}Cd{x} films

NASA Astrophysics Data System (ADS)

Afifi, M. A.; Bekheet, A. E.; Hegab, N. A.; Wahab, L. A.; Shehata, H. A.

2007-11-01

Amorphous Se{70}Te{30-x}Cd{x} (x = 0, 10) are obtained by thermal evaporation under vacuum of bulk materials on pyrographite and glass substrates. The I-V characteristic curves for the two film compositions are typical for a memory switch. They exhibited a transition from an ohmic region in the lower field followed by non-ohmic region in the high field region in the preswitching region, which has been explained by the Poole-Frenkel effect. The temperature dependence of current in the ohmic region is found to be of thermally activated process. The mean value of the threshold voltage bar{V}th increases linearly with increasing film thickness in the thickness range (100 491 nm), while it decreases exponentially with increasing temperature in the temperature range (293 343 K) for both compositions. The results are explained in accordance with the electrothermal model for the switching process. The effect of Cd on these parameters is also investigated.

Influence of climatic conditions on the distribution, abundance and activity of Agriotes lineatus L. adults in sex pheromone traps in Croatia

NASA Astrophysics Data System (ADS)

Kozina, Antonela; Čačija, Maja; Igrc Barčić, Jasminka; Bažok, Renata

2013-07-01

The aims of this work were: (i) to determine the distribution and abundance of Agriotes lineatus, (ii) correlate the abundance with the prevailing climatic conditions to establish how temperature and rainfall are influencing the dominance, and (iii) to determine the activity characteristics of the adults. Investigations were conducted in 17 fields grouped in four regions characterized by different climatic conditions. Using sex pheromone traps the most important Agriotes species ( A. lineatus L., A. sputator L., A. obscurus L., A. brevis Cand. and A. ustulatus Schall.) were collected. The monitoring period for A. brevis, A. sputator, A. lineatus and A. obscurus was from the 18th to the 32nd, and for A. ustulatus from the 23rd to the 32nd week of the year. A total of 61,247 individuals Agriotes were captured, of which 24,916 individuals were A. lineatus. Abundance and dominance of A. lineatus were significantly higher in the region of Zagreb compared to other regions. Moving east, rainfall decreased and temperatures increased and associated with that the abundance and dominance indices were lower. It was determined that the abundance of A. lineatus was negatively correlated with average air temperature ( r = -0.5201; p < 0.0001). Compared to earlier data from the region of Zagreb the dominance index decreased. This might be a result of climate change as established average yearly temperature in these regions increased for 1.04 °C compared to the average data for the period 1961-1990. Other potentially damaging Agriotes species ( A. brevis and A. ustulatus) were also present in high abundances in some micro-regions.

Volcanic activity at Tvashtar Catena, Io

USGS Publications Warehouse

Milazzo, M.P.; Keszthelyi, L.P.; Radebaugh, J.; Davies, A.G.; Turtle, E.P.; Geissler, P.; Klaasen, K.P.; Rathbun, J.A.; McEwen, A.S.

2005-01-01

Galileo's Solid State Imager (SSI) observed Tvashtar Catena four times between November 1999 and October 2001, providing a unique look at a distinctive high latitude volcanic complex on Io. The first observation (orbit I25, November 1999) resolved, for the first time, an active extraterrestrial fissure eruption; the brightness temperature was at least 1300 K. The second observation (orbit I27, February 2000) showed a large (??? 500 km 2) region with many, small, hot, regions of active lava. The third observation was taken in conjunction with Cassini imaging in December 2000 and showed a Pele-like, annular plume deposit. The Cassini images revealed an ???400 km high Pele-type plume above Tvashtar Catena. The final Galileo SSI observation of Tvashtar (orbit I32, October 2001), revealed that obvious (to SSI) activity had ceased, although data from Galileo's Near Infrared Mapping Spectrometer (NIMS) indicated that there was still significant thermal emission from the Tvashtar region. In this paper, we primarily analyze the style of eruption during orbit I27 (February 2000). Comparison with a lava flow cooling model indicates that the behavior of the Tvashtar eruption during I27 does not match that of simple advancing lava flows. Instead, it may be an active lava lake or a complex set of lava flows with episodic, overlapping eruptions. The highest reliable color temperature is ???1300 K. Although higher temperatures cannot be ruled out, they do not need to be invoked to fit the observed data. The total power output from the active lavas in February 2000 was at least 1011 W. ?? 2005 Elsevier Inc. All rights reserved.

Low temperature magneto-dielectric measurements on BiFeO{sub 3} lightly substituted by cobalt

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

Ray, J.; Biswal, A. K.; Vishwakarma, P. N., E-mail: prakashn@nitrkl.ac.in, E-mail: pnviisc@gmail.com

2015-04-07

Dielectric and magnetodielectric measurements are done on BiFe{sub 1−x}Co{sub x}O{sub 3}: x = 0, 0.01, and 0.02 in the temperature range 70–300 K and up to magnetic field 1.3 T. The dielectric data are well described by Haverliak–Negami expression plus an additional term for the Maxwell Wagner (MW) type relaxations, whose contribution is dominant near room temperature. The parameters obtained from the fitting of data using the above mentioned expression, suggest slowing down of relaxation and approach towards ideal Debye type relaxations, as the temperature is lowered. The dielectric relaxations obey polaronic variable range hopping model with distinct activation energies (E{sub a}) in themore » extrinsic (6.67T{sup 3/4 }meV) and intrinsic (2.88T{sup 3/4 }meV) regions for the parent sample (x = 0), and thus a distinct transition from extrinsic to intrinsic behavior is seen at 215 K while lowering the temperature. This distinct transition is missing for Co substituted samples probably due to the extrinsic region values of E{sub a} (3.42T{sup 3/4 }meV and 2.42T{sup 3/4 }meV for x = 0.01 and 0.02, respectively) comparable to that of the intrinsic region (see x = 0). The magnetodielectric measurement shows positive magnetodielectricity (MD) in the intrinsic region (T < 215 K for x = 0) and negative MD in the extrinsic region (T > 215 K for x = 0). The extrinsic region is found to be dominated by MW and magnetoresistance effects, whereas MD in intrinsic regions is due to the spin reorientation transitions. The Co substitution is found to increase the extrinsic and non-Debye contributions to dielectricity, which becomes so large that no spin reorientation transitions are seen in x = 0.02 sample. The pyroelectric active region in x = 0 is found to be dominated by the diffusive behavior having contribution of the form ω{sup −0.5}.« less

Yeasts from sub-Antarctic region: biodiversity, enzymatic activities and their potential as oleaginous microorganisms.

PubMed

Martinez, A; Cavello, I; Garmendia, G; Rufo, C; Cavalitto, S; Vero, S

2016-09-01

Various microbial groups are well known to produce a range of extracellular enzymes and other secondary metabolites. However, the occurrence and importance of investment in such activities have received relatively limited attention in studies of Antarctic soil microbiota. Sixty-one yeasts strains were isolated from King George Island, Antarctica which were characterized physiologically and identified at the molecular level using the D1/D2 region of rDNA. Fifty-eight yeasts (belonging to the genera Cryptococcus, Leucosporidiella, Rhodotorula, Guehomyces, Candida, Metschnikowia and Debaryomyces) were screened for extracellular amylolytic, proteolytic, esterasic, pectinolytic, inulolytic xylanolytic and cellulolytic activities at low and moderate temperatures. Esterase activity was the most common enzymatic activity expressed by the yeast isolates regardless the assay temperature and inulinase was the second most common enzymatic activity. No cellulolytic activity was detected. One yeast identified as Guehomyces pullulans (8E) showed significant activity across six of seven enzymes types tested. Twenty-eight yeast isolates were classified as oleaginous, being the isolate 8E the strain that accumulated the highest levels of saponifiable lipids (42 %).

Human presence diminishes the importance of climate in driving fire activity across the United States

USGS Publications Warehouse

Syphard, Alexandra D.; Keeley, Jon E.; Pfaff, Anne Hopkins; Ferschweiler, Ken

2017-01-01

Growing human and ecological costs due to increasing wildfire are an urgent concern in policy and management, particularly given projections of worsening fire conditions under climate change. Thus, understanding the relationship between climatic variation and fire activity is a critically important scientific question. Different factors limit fire behavior in different places and times, but most fire-climate analyses are conducted across broad spatial extents that mask geographical variation. This could result in overly broad or inappropriate management and policy decisions that neglect to account for regionally specific or other important factors driving fire activity. We developed statistical models relating seasonal temperature and precipitation variables to historical annual fire activity for 37 different regions across the continental United States and asked whether and how fire-climate relationships vary geographically, and why climate is more important in some regions than in others. Climatic variation played a significant role in explaining annual fire activity in some regions, but the relative importance of seasonal temperature or precipitation, in addition to the overall importance of climate, varied substantially depending on geographical context. Human presence was the primary reason that climate explained less fire activity in some regions than in others. That is, where human presence was more prominent, climate was less important. This means that humans may not only influence fire regimes but their presence can actually override, or swamp out, the effect of climate. Thus, geographical context as well as human influence should be considered alongside climate in national wildfire policy and management.

Plasma Properties and Magnetic Field Structure of the Solar Corona, Based on Coordinated Max '91 Observations from SERTS, the VLA, and Magnetographs

NASA Technical Reports Server (NTRS)

Brosius, Jeffrey W. (Principal Investigator)

1996-01-01

The plasma properties and magnetic field structure of the solar corona were determined using coordinated observations obtained with NASA/GSFC's Solar EUV Rocket Telescope and Spectrograph (SERTS), the Very Large Array (VLA), and Kitt Peak photospheric longitudinal magnetograms. A problem was identified with the SERTS calibration as determined from laboratory measurements. A revised calibration curve was derived by requiring that the numerous available measured line intensity ratios agreed with their respective theoretical values. Densities were derived from line intensity ratios, and active region densities were found to typically exceed quiet Sun densities by factors of only about 2. The active region density was found to remain constant across the SERTS slit, despite the fact that the emission line intensities vary significantly. This indicates that the product of the path length and the volume filling factor must vary significantly from the active region outskirts to the central core. Filling factors were derived and found to range from much less than one to nearly unity. Wavelength shifts were examined along the SERTS slit in the spatially resolved spectra, but no evidence was found for significant Doppler shifts in active region 7563 or in the quiet Sun. The numerical procedure developed by Monsignori-Fossi and Landini was used to derive the active region and quiet sun differential emission measure (DEM) from the spatially averaged spectra. A DEM was estimated for each spatial pixel in the two dimensional active region images by scaling the averaged active region DEM based upon corresponding pixel intensities of SERTS Mg IX, Fe XV, and Fe XVI images. These results, along with density measurements, were used in an IDL computer code which calculated the temperature dependence of the coronal magnetic field in each spatial pixel by minimizing the difference between the observed and calculated 20 and 6 cm microwave brightness temperatures.

Height Dependence of Plasma Properties of a Dark Lane and a Cool Loop in a Solar Limb Active Region Observed by Hinode/EIS

NASA Astrophysics Data System (ADS)

Lee, K.; Imada, S.; Moon, Y.; Lee, J.

2013-12-01

We investigate spectral properties of a cool loop and a dark lane over a limb active region on 2007 March 14 by the Hinode/EUV Imaging Spectrometer. The cool loop is clearly seen in the spectral lines formed at the transition region temperature. The dark lane is characterized by an elongated faint structure in coronal spectral lines and rooted on a bright point. We determine their electron densities, Doppler velocities, and non-thermal velocities with height over the limb. We derived electron densities using the density sensitive line pairs of Mg VII, Si X, Fe XII, Fe XIII and Fe XIV spectra. Under the hydrostatic equilibrium and isothermal assumption, we determine their temperatures from the density scale height. Comparing the scale height temperatures to the peak formation temperatures of the spectral lines, we note that the scale height temperature of the cool loop is consistent with a peak formation temperature of the Fe XII and the scale height temperatures of the dark lane from each spectral lines are much lower than their peak formation temperatures. The non-thermal velocity in the cool loop slightly decreases along the loop while that in the dark lane sharply falls off with height. The variation of non-thermal velocity with height in the cool loop and the dark lane is contrast to that in off-limb polar coronal holes which are considered as source of the solar wind. Such a decrease in the non-thermal velocity may be explained by wave damping near the solar surface or turbulence due to magnetic reconnection near the bright point.

Active Oxidation of a UHTC-Based CMC

NASA Technical Reports Server (NTRS)

Glass, David E.; Splinter, Scott C.

2012-01-01

The active oxidation of ceramic matrix composites (CMC) is a severe problem that must be avoided for multi-use hypersonic vehicles. Much work has been performed studying the active oxidation of silicon-based CMCs such as C/SiC and SiC-coated carbon/carbon (C/C). Ultra high temperature ceramics (UTHC) have been proposed as a possible material solution for high-temperature applications on hypersonic vehicles. However, little work has been performed studying the active oxidation of UHTCs. The intent of this paper is to present test data indicating an active oxidation process for a UHTC-based CMC similar to the active oxidation observed with Si-based CMCs. A UHTC-based CMC was tested in the HyMETS arc-jet facility (or plasma wind tunnel, PWT) at NASA Langley Research Center, Hampton, VA. The coupon was tested at a nominal surface temperature of 3000 F (1650 C), with a stagnation pressure of 0.026 atm. A sudden and large increase in surface temperature was noticed with negligible increase in the heat flux, indicative of the onset of active oxidation. It is shown that the surface conditions, both temperature and pressure, fall within the region for a passive to active transition (PAT) of the oxidation.

Relationships among seismic velocity, metamorphism, and seismic and aseismic fault slip in the Salton Sea Geothermal Field region

USGS Publications Warehouse

McGuire, Jeffrey J.; Lohman, Rowena B.; Catchings, Rufus D.; Rymer, Michael J.; Goldman, Mark R.

2015-01-01

The Salton Sea Geothermal Field is one of the most geothermally and seismically active areas in California and presents an opportunity to study the effect of high-temperature metamorphism on the properties of seismogenic faults. The area includes numerous active tectonic faults that have recently been imaged with active source seismic reflection and refraction. We utilize the active source surveys, along with the abundant microseismicity data from a dense borehole seismic network, to image the 3-D variations in seismic velocity in the upper 5 km of the crust. There are strong velocity variations, up to ~30%, that correlate spatially with the distribution of shallow heat flow patterns. The combination of hydrothermal circulation and high-temperature contact metamorphism has significantly altered the shallow sandstone sedimentary layers within the geothermal field to denser, more feldspathic, rock with higher P wave velocity, as is seen in the numerous exploration wells within the field. This alteration appears to have a first-order effect on the frictional stability of shallow faults. In 2005, a large earthquake swarm and deformation event occurred. Analysis of interferometric synthetic aperture radar data and earthquake relocations indicates that the shallow aseismic fault creep that occurred in 2005 was localized on the Kalin fault system that lies just outside the region of high-temperature metamorphism. In contrast, the earthquake swarm, which includes all of the M > 4 earthquakes to have occurred within the Salton Sea Geothermal Field in the last 15 years, ruptured the Main Central Fault (MCF) system that is localized in the heart of the geothermal anomaly. The background microseismicity induced by the geothermal operations is also concentrated in the high-temperature regions in the vicinity of operational wells. However, while this microseismicity occurs over a few kilometer scale region, much of it is clustered in earthquake swarms that last from hours to a few days and are localized near the MCF system.

On the effect of ballistic overflow on the temperature dependence of the quantum efficiency of InGaN/GaN multiple quantum well light-emitting diodes

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

Prudaev, I. A., E-mail: funcelab@gmail.com; Kopyev, V. V.; Romanov, I. S.

The dependences of the quantum efficiency of InGaN/GaN multiple quantum well light-emitting diodes on the temperature and excitation level are studied. The experiment is performed for two luminescence excitation modes. A comparison of the results obtained during photo- and electroluminescence shows an additional (to the loss associated with Auger recombination) low-temperature loss in the high-density current region. This causes inversion of the temperature dependence of the quantum efficiency at temperatures lower than 220–300 K. Analysis shows that the loss is associated with electron leakage from the light-emitting-diode active region. The experimental data are explained using the ballistic-overflow model. The simulationmore » results are in qualitative agreement with the experimental dependences of the quantum efficiency on temperature and current density.« less

Visual encoding and fixation target selection in free viewing: presaccadic brain potentials

PubMed Central

Nikolaev, Andrey R.; Jurica, Peter; Nakatani, Chie; Plomp, Gijs; van Leeuwen, Cees

2013-01-01

In scrutinizing a scene, the eyes alternate between fixations and saccades. During a fixation, two component processes can be distinguished: visual encoding and selection of the next fixation target. We aimed to distinguish the neural correlates of these processes in the electrical brain activity prior to a saccade onset. Participants viewed color photographs of natural scenes, in preparation for a change detection task. Then, for each participant and each scene we computed an image heat map, with temperature representing the duration and density of fixations. The temperature difference between the start and end points of saccades was taken as a measure of the expected task-relevance of the information concentrated in specific regions of a scene. Visual encoding was evaluated according to whether subsequent change was correctly detected. Saccades with larger temperature difference were more likely to be followed by correct detection than ones with smaller temperature differences. The amplitude of presaccadic activity over anterior brain areas was larger for correct detection than for detection failure. This difference was observed for short “scrutinizing” but not for long “explorative” saccades, suggesting that presaccadic activity reflects top-down saccade guidance. Thus, successful encoding requires local scanning of scene regions which are expected to be task-relevant. Next, we evaluated fixation target selection. Saccades “moving up” in temperature were preceded by presaccadic activity of higher amplitude than those “moving down”. This finding suggests that presaccadic activity reflects attention deployed to the following fixation location. Our findings illustrate how presaccadic activity can elucidate concurrent brain processes related to the immediate goal of planning the next saccade and the larger-scale goal of constructing a robust representation of the visual scene. PMID:23818877

Potential Impacts of Climate Change in the Great Lakes Region

NASA Astrophysics Data System (ADS)

Winkler, J. A.

2011-12-01

Climate change is projected to have substantial impacts in the Great Lakes region of the United States. One intent of this presentation is to introduce the Great Lakes Integrated Sciences and Assessments Center (GLISA), a recently-funded NOAA RISA center. The goals and unique organizational structure of GLISA will be described along with core activities that support impact and assessment studies in the region. Additionally, observed trends in temperature, precipitation including lake effect snowfall, and lake temperatures and ice cover will be summarized for the Great Lakes region, and vulnerabilities to, and potential impacts of, climate change will be surveyed for critical natural and human systems. These include forest ecosystems, water resources, traditional and specialized agriculture, and tourism/recreation. Impacts and vulnerabilities unique to the Great Lakes region are emphasized.

Waiting for chikungunya fever in Argentina: spatio-temporal risk maps

PubMed Central

Carbajo, Aníbal E; Vezzani, Darío

2015-01-01

Chikungunya virus (CHIKV) transmission has been detected in America in 2013 and recently reached south up to Bolivia, Brazil and Paraguay, bordering countries of Argentina. The presence of the mosquito Aedes aegypti in half of the country together with the regional context drove us to make a rapid assessment of transmission risk. Temperature thresholds for vector breeding and for virus transmission, together with adult activity from the literature, were mapped on a monthly basis to estimate risk. Transmission of chikungunya by Ae. aegypti in the world was seen at monthly mean temperatures from 21-34ºC, with the majority occurring between 26-28ºC. In Argentina temperatures above 21ºC are observed since September in the northeast, expanding south until January and retreating back to the northeast in April. The maximum area under risk encompasses more than half the country and around 32 million inhabitants. Vector adult activity was registered where monthly means temperatures exceeded 13ºC, in the northeast all over the year and in the northern half from September-May. The models herein proposed show that conditions for transmission are already present. Considering the regional context and the historic inability to control dengue in the region, chikungunya fever illness seems unavoidable. PMID:25946252

The energy input mechanism into the lower transition regions between stellar chromospheres and coronae

NASA Technical Reports Server (NTRS)

Boehm-Vitense, Erika

1988-01-01

The ratio of the emission line fluxes for the C II and C IV lines in the lower transition regions (T = 30,000 to 100,000 K) between stellar chromospheres and transition layers is shown to depend mainly on the temperature gradient in the line emitting regions which can therefore be determined from this line ratio. From the observed constant (within the limits of observational error) ratio of the emission line fluxes of the C II (1335 A) and C IV (1550 A) lines it is concluded that the temperature gradients in the lower transition layers are similar for the large majority of stars independently of T sub eff, L, and degree of activity. This means that the temperature dependence of the damping length for the mechanical flux must be the same for all these stars. Since for different kinds of mechanical fluxes the dependence of the damping length on gas pressure and temperature is quite different, it is concluded that the same heating mechanism must be responsible for the heating of all the lower transition layers of these stars, regardless of their chromospheric activity. Only the amount of mechanical flux changes. The T Tauri stars are exceptions: their emission lines are probably mainly due to circumstellar material.

Thermal signature analysis of human face during jogging activity using infrared thermography technique

NASA Astrophysics Data System (ADS)

Budiarti, Putria W.; Kusumawardhani, Apriani; Setijono, Heru

2016-11-01

Thermal imaging has been widely used for many applications. Thermal camera is used to measure object's temperature above absolute temperature of 0 Kelvin using infrared radiation emitted by the object. Thermal imaging is color mapping taken using false color that represents temperature. Human body is one of the objects that emits infrared radiation. Human infrared radiations vary according to the activity that is being done. Physical activities such as jogging is among ones that is commonly done. Therefore this experiment will investigate the thermal signature profile of jogging activity in human body, especially in the face parts. The results show that the significant increase is found in periorbital area that is near eyes and forehand by the number of 7.5%. Graphical temperature distributions show that all region, eyes, nose, cheeks, and chin at the temperature of 28.5 - 30.2°C the pixel area tends to be constant since it is the surrounding temperature. At the temperature of 30.2 - 34.7°C the pixel area tends to increase, while at the temperature of 34.7 - 37.1°C the pixel area tends to decrease because pixels at temperature of 34.7 - 37.1°C after jogging activity change into temperature of 30.2 - 34.7°C so that the pixel area increases. The trendline of jogging activity during 10 minutes period also shows the increasing of temperature. The results of each person also show variations due to physiological nature of each person, such as sweat production during physical activities.

Regional climate impacts of a possible future grand solar minimum.

PubMed

Ineson, Sarah; Maycock, Amanda C; Gray, Lesley J; Scaife, Adam A; Dunstone, Nick J; Harder, Jerald W; Knight, Jeff R; Lockwood, Mike; Manners, James C; Wood, Richard A

2015-06-23

Any reduction in global mean near-surface temperature due to a future decline in solar activity is likely to be a small fraction of projected anthropogenic warming. However, variability in ultraviolet solar irradiance is linked to modulation of the Arctic and North Atlantic Oscillations, suggesting the potential for larger regional surface climate effects. Here, we explore possible impacts through two experiments designed to bracket uncertainty in ultraviolet irradiance in a scenario in which future solar activity decreases to Maunder Minimum-like conditions by 2050. Both experiments show regional structure in the wintertime response, resembling the North Atlantic Oscillation, with enhanced relative cooling over northern Eurasia and the eastern United States. For a high-end decline in solar ultraviolet irradiance, the impact on winter northern European surface temperatures over the late twenty-first century could be a significant fraction of the difference in climate change between plausible AR5 scenarios of greenhouse gas concentrations.

Transition from direct to inverted charge transport Marcus regions in molecular junctions via molecular orbital gating

NASA Astrophysics Data System (ADS)

Yuan, Li; Wang, Lejia; Garrigues, Alvar R.; Jiang, Li; Annadata, Harshini Venkata; Anguera Antonana, Marta; Barco, Enrique; Nijhuis, Christian A.

2018-04-01

Solid-state molecular tunnel junctions are often assumed to operate in the Landauer regime, which describes essentially activationless coherent tunnelling processes. In solution, on the other hand, charge transfer is described by Marcus theory, which accounts for thermally activated processes. In practice, however, thermally activated transport phenomena are frequently observed also in solid-state molecular junctions but remain poorly understood. Here, we show experimentally the transition from the Marcus to the inverted Marcus region in a solid-state molecular tunnel junction by means of intra-molecular orbital gating that can be tuned via the chemical structure of the molecule and applied bias. In the inverted Marcus region, charge transport is incoherent, yet virtually independent of temperature. Our experimental results fit well to a theoretical model that combines Landauer and Marcus theories and may have implications for the interpretation of temperature-dependent charge transport measurements in molecular junctions.

Novel quantum well gallium arsenide-based lasers for all transmission windows in optical communication

NASA Astrophysics Data System (ADS)

Tansu, Nelson

The thesis covers the development of novel active regions for high-performance edge-emitting lasers (EEL) and vertical cavity surface-emitting lasers (VCSELs) in optical communication. Three main themes of the thesis cover the design, fabrication, and physics of the novel and alternative active regions for GaAs-based VCSELs for the three optical communications windows at wavelength regimes of 850-nm, 1300-nm, and 1500-nm, with the emphases on the 1300-nm InGaAsN QW GaAs-based active regions and on the novel design of 1500-nm GaAs-based active regions. The studies include the utilization of compressively-strained InGaAsP quantum well (QW) active regions for the 850-nm VCSELs. The research on the long-wavelength lasers covers the design, growth, temperature analysis, carrier transport, and gain analysis of the InGaAsN (lambda = 1.3 mum) quantum well lasers. The novel and original design of the GaAsSb-(In)GaAsN type-II QWs to achieve 1500--3000 nm GaAs-based active regions is discussed in detail.

Long-term Variations of The Solar Activity -- Lower Atmosphere Relationship

NASA Astrophysics Data System (ADS)

Zaitseva, S.; Akhremtchik, S.; Pudovkin, M.; Besser, B.; Rijnbeek, R.

Long-term variations of the air temperature in St.Petersburg, Stockholm, Salzburg and English Midlands are considered. There is shown that in the regions under consider- ation the air temperature distinctly depends on the intensity of the lower atmospheric zonal circulation (Blinova index and North Atlantic Oscillation index (NAO)). In turn, the NAO-index is shown to depend on the solar activity. However, this dependence is rather complicated and exhibits long-period variations associated with secular varia- tions of the solar activity. A possible mechanism of this phenomena is discussed.

Neural network analysis of Charpy transition temperature of irradiated low-activation martensitic steels

NASA Astrophysics Data System (ADS)

Cottrell, G. A.; Kemp, R.; Bhadeshia, H. K. D. H.; Odette, G. R.; Yamamoto, T.

2007-08-01

We have constructed a Bayesian neural network model that predicts the change, due to neutron irradiation, of the Charpy ductile-brittle transition temperature (ΔDBTT) of low-activation martensitic steels given a set of multi-dimensional published data with doses <100 displacements per atom (dpa). Results show the high significance of irradiation temperature and (dpa) 1/2 in determining ΔDBTT. Sparse data regions were identified by the size of the modelling uncertainties, indicating areas where further experimental data are needed. The method has promise for selecting and ranking experiments on future irradiation materials test facilities.

Temperature fluctuations inside savanna termite mounds: Do size and plant shade matter?

PubMed

Ndlovu, M; Pérez-Rodríguez, A

2018-05-01

Mound building termites are key ecosystem engineers of subtropical savanna regions. Mounds allow termites to maintain suitable conditions for termite reproduction and food cultivation ('fungus gardens'). We studied how the internal mound temperature of Macrotermes natalensis, a dominant mound-building termite of the subtropical savanna of southern Africa, responds to a number of environmental variables. We used general additive mixed models (GAMM) to determine how external temperature, mound size (volume) and the amount of vegetation shade affects mound internal temperature over a 24-h period. Internal mound temperature varied daily following changes of the external temperature, although the range of variation was much smaller. Active termite mounds maintained a higher internal temperature than inactive ones, and mound activity reinforced the positive effect of mound size and moderated the negative effect of vegetation shade on internal temperatures. In turn, external temperature fluctuations equally affected active and inactive mounds. Large mounds maintained near optimal internal temperatures compared to smaller sized mounds. We therefore conclude that termite mound size is a stronger determinant of internal mound temperature stability compared to plant shade cover. Copyright © 2018 Elsevier Ltd. All rights reserved.

Introduction to an Updated Analysis of Planetary Protection: "Special Regions" on Mars

NASA Astrophysics Data System (ADS)

Beaty, D. W.; Rummel, J. D.; Viola, D.

2014-03-01

Since the beginning of human activity in space science and exploration, there has been an appreciation of the negative consequences of transferring life from one planet to another. Given the unknown consequences of contact between two life forms and the fundamental value of studying a new form life, thoughtfulness and caution are warranted. The "special regions" concept is a component of the International Council for Science's Committee on Space Research (COSPAR) Planetary Protection Policy, as it applies to Mars. These are regions "within which terrestrial organisms are likely to replicate" as well as "any region which is interpreted to have a high potential for the existence of extant martian life." Robotic missions planning to have direct contact with such special regions are given planetary protection categorization (IVc), with stringent cleanliness constraints on the portions of the mission contacting such regions. The current, quantitative definition of "special regions based on temperature and water activity limits was adopted by COSPAR in 2008 after a two-year process that included meetings of the Mars Exploration Planning and Analysis Group's (MEPAG) Special Regions Science Analysis Group (SR-SAG) and COSPAR's Panel on Planetary Protection. In this study, the MEPAG SR-SAG2 will review and update the technical information that underlie NASA's and COSPAR's definition of special regions on Mars, enabling interpretations of when and where they could occur in light of new discoveries since 2007. This will include updates of current understanding in (1) the known physical limits to life on Earth, including low temperature and low water activity, the biological capture/use of vapor-phase water, and survival over long time scales with short periods of growth; (2) observational data sets and new models from Mars that could be relevant to our understanding of the natural variations on Mars of water activity and temperature, including recurring slope lineae (RSL), gullies, the distribution of surface and subsurface ice, brine stability, and atmosphere-regolith interactions; and (3) mineral and amorphous material water content and its potential biological availability, including mineral deliquescence. This information will be used to reconsider the parameters used to define the term "special region," including the temperature and water activity thresholds, timescales for the existence of a special region (episodic or continuous), and the spatial scale used to apply "special" or "non-special" designations. Additionally, both text and map forms will be prepared, describing Mars environments that are judged to be "special" or for which there is a significant (but still unknown) probability that the threshold conditions for a special region would be exceeded within the assumed 500-year limit. A preliminary analysis of the kinds and amounts of water-related resources on Mars of potential interest to the eventual human exploration of Mars will also be performed, and the planetary protection implications of attempting to access/exploit them will be evaluated. Members of the community who have information on any of these topics are encouraged to contact one of the authors of this abstract.

Extremophilic fungi in arctic ice: a relationship between adaptation to low temperature and water activity

NASA Astrophysics Data System (ADS)

Gunde-Cimerman, N.; Sonjak, S.; Zalar, P.; Frisvad, J. C.; Diderichsen, B.; Plemenitaš, A.

Little is known about fungal diversity in extremely cold regions. Low temperatures induce the formation of ice crystals and therefore also the creation of low water activity ( aw). These are the dominant factors in external chemistry that influence microbial biota in cold regions. Therefore, we have used selective low water activity media plus low incubation temperatures for the isolation of fungi from an Arctic environment. In comparison with the highest values of colony forming units (CFU) obtained on mesophilic media, considerably higher fungal CFU per litre of water were detected on low aw media, ranging from 1000 to 3000 l -1 in seawater, 6000 to 7000 l -1 in melted sea ice and up to 13,000 l -1 in melted glacier ice. The dominant taxa were ascomycetous and basidiomycetous yeasts, melanized fungi, mainly represented by the genera Cladosporium and Aureobasidium plus different species of the genus Penicillium. Preliminary taxonomic analyses revealed several new species and varieties. Further characterisations are needed to determine whether this diversity is due to geographic isolation, ecological conditions or independent evolutionary origin.

The differential response of photosynthesis to high temperature for a boreal and temperate Populus species relates to differences in Rubisco activation and Rubisco activase properties.

PubMed

Hozain, Moh'd I; Salvucci, Michael E; Fokar, Mohamed; Holaday, A Scott

2010-01-01

Significant inhibition of photosynthesis occurs at temperatures only a few degrees (

Spectroscopic study of transparency current in mid-infrared quantum cascade lasers.

PubMed

Revin, Dmitry G; Hassan, Randa S; Krysa, Andrey B; Wang, Yongrui; Belyanin, Alexey; Kennedy, Kenneth; Atkins, Chris N; Cockburn, John W

2012-08-13

We report measurements which give direct insight into the origins of the transparency current for λ ~5 µm In0.6Ga0.4As/In0.42Al0.58As quantum cascade lasers in the temperature range of 80-280 K. The transparency current values have been found from broadband transmission measurements through the laser waveguides under sub-threshold operating conditions. Two active region designs were compared. The active region of the first laser is based on double-LO-phonon relaxation approach, while the second device has only one lower level, without specially designed resonant LO-phonon assisted depopulation. It is shown that transparency current contributes more than 70% to the magnitude of threshold current at high temperatures for both designs.

Dynamics of the Exchange of Carbon Dioxide in Arctic and Subarctic Regions,

DTIC Science & Technology

1973-01-01

snow, at temperatures too low for significant biological activity. The phenomena of gas evasion under conditions of 3 freezing soil solution , confirmed...1972) have observed a de- pression rather than an acceleration in soil respiration, as the soil solution undergoes a phase change near 0C. On the other...temperatures are too low for significant biological activity. CO2 from biological sources expressed by freezing the soil solution , evidently leaks to the

High-temperature deformation processing of Ti-24Al-20Nb

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

Sagar, P.K.; Banerjee, D.; Muraleedharan, K.

1996-09-01

Power dissipation maps have been generated in the temperature range of 900 C to 1,150 C and strain rate range of 10{sup {minus}3} to 10 s{sup {minus}1} for a cast aluminide alloy Ti-24Al-20Nb using dynamic material model. The results define two distinct regimes of temperature and strain rate in which efficiency of power dissipation is maximum. The first region, centered around 975 C/0.1 s{sup {minus}1}, is shown to correspond to dynamic recrystallization of the {alpha}{sub 2} phase and the second, centered around 1,150 C/0.001 s{sup {minus}1}, corresponds to dynamic recovery and superplastic deformation of the {beta} phase. Thermal activation analysismore » using the power law creep equation yielded apparent activation energies of 854 and 627 kJ/mol for the first and second regimes, respectively. Reanalyzing the data by alternate methods yielded activation energies in the range of 170 to 220 kJ/mol and 220 to 270 kJ/mol for the first and second regimes, respectively. Cross slip was shown to constitute the activation barrier in both cases. Two distinct regimes of processing instability--one at high strain rates and the other at the low strain rates in the lower temperature regions--have been identified, within which shear bands are formed.« less

Insights into the dominant factors of porous gold for CO oxidation

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

Kameoka, Satoshi, E-mail: kameoka@tagen.tohoku.ac.jp; Miyamoto, Kanji; Tanabe, Toyokazu

2016-01-21

Three different porous Au catalysts that exhibit high catalytic activity for CO oxidation were prepared by the leaching of Al from an intermetallic compound, Al{sub 2}Au, with 10 wt. %-NaOH, HNO{sub 3}, or HCl aqueous solutions. The catalysts were investigated using Brunauer-Emmett-Teller measurements, synchrotron X-ray powder diffraction, hard X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy (TEM). Broad diffraction peaks generated during the leaching process correlated with high activity for all the porous Au catalysts. CO oxidation catalyzed by porous Au leached with NaOH and HNO{sub 3} is considered to be dominated by different mechanisms atmore » low (< 320 K) and high (> 370 K) temperatures. Activity in the low-temperature region is mainly attributed to the perimeter interface between residual Al species (AlO{sub x}) and porous Au, whereas activity in the high-temperature region results from a high density of lattice defects such as twins and dislocations, which were evident from diffraction peak broadening and were observed with high-resolution TEM in the porous Au leached with NaOH. It is proposed that atoms located at lattice defects on the surfaces of porous Au are the active sites for catalytic reactions.« less

FOXSI-2 Observations and Coronal Heating

NASA Astrophysics Data System (ADS)

Christe, S.; Glesener, L.; Krucker, S.; Ramsey, B.; Ishikawa, S. N.; Buitrago Casas, J. C.; Takahashi, T.; Foster, N.

2015-12-01

Energy release and particle acceleration on the Sun is a frequent occurrence associated with a number of different solar phenomenon including but not limited to solar flares, coronal mass ejections and nanoflares. The exact mechanism through which particles are accelerated and energy is released is still not well understood. This issue is related to the unsolved coronal heating problem, the mystery of the heating mechanism for the million degree solar corona. One prevalent theory posits the existence of a multitude of small flares, dubbed nanoflares. Recent observations of active region AR11890 by IRIS (Testa et al. 2014) are consistent with numerical simulations of heating by impulsive beams of nonthermal electrons, suggesting that nanoflares may be similar to large flares in that they accelerate particles. Furthermore, observations by the EUNIS sounding rocket (Brosius et al. 2014) of faint Fe XIX (592.2 Angstrom) emission in an active region is indicative of plasma at temperatures of at least 8.9 MK providing further evidence of nanoflare heating. One of the best ways to gain insight into accelerated particles on the Sun and the presence of hot plasma is by observing the Sun in hard X-rays (HXR). We present on observations taken during the second successful flight of the Focusing Optics X-ray Solar Imager (FOXSI-2). FOXSI flew on December 11, 2014 with upgraded optics as well as new CdTe strip detectors. FOXSI-2 observed thermal emission (4-15 keV) from at least three active regions (AR#12234, AR#12233, AR#12235) and observed regions of the Sun without active regions. We present on using FOXSI observations to test the presence of hot temperatures in and outside of active regions.

Effect of mild-temperature H2O2 oxidation on solubilization and anaerobic digestion of waste activated sludge.

PubMed

Junga, Heejung; Kim, Jaai; Lee, Seungyong; Lee, Changsoo

2014-08-01

Efficient sludge management is among the most challenging issues in wastewater treatment today, and anaerobic digestion is regarded as a viable solution. Mild-temperature H202 oxidation was examined for enhanced solubilization and biogas production of waste activated sludge (WAS). The effects of pretreatment factors (i.e. temperature and H202 concentration) on the degree of WAS disintegration (DD) and biogas yield (BY) were assessed by response surface analysis within the design space of 60-90 degrees C and 0-200mM H202. Significant sludge disintegration (up to 23.0% DD) and visibly enhanced BY (up to 26.9%) were shown in the pretreatment trials. Two response surface models to describe how DD and BY respond to changes in the pretreatment conditions were successfully constructed (R2 > 0.95, p < 0.05). The models showed totally different response surface shapes, indicating the DD and BY were influenced by pretreatment conditions in very different ways. DD was dominantly affected by temperature and showed higher model responses at the high-temperature region, while the BY response peaked in the low-temperature and mid-level H2O2 region. This observation implies that the enhanced solubilization of WAS was not directly translated into an increase in biogas production. Our results showed that WAS can be efficiently disintegrated by H202 oxidation under mild-temperature conditions for enhanced anaerobic digestibility. Within the explored region of pretreatment conditions, the maximum BY was estimated to be 82.1 mL/gCODadded (32.8% greater than the untreated control) at (60.0 degrees C, 74.2 mM H2O2).

Laser-diagnostic mapping of temperature and soot statistics in a 2-m diameter turbulent pool fire

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

Kearney, Sean P.; Grasser, Thomas W.

We present spatial profiles of temperature and soot-volume-fraction statistics from a sooting 2-m base diameter turbulent pool fire, burning a 10%-toluene / 90%-methanol fuel mixture. Dual-pump coherent anti-Stokes Raman scattering and laser-induced incandescence are utilized to obtain radial profiles of temperature and soot probability density functions (pdf) as well as estimates of temperature/soot joint statistics at three vertical heights above the surface of the methanol/toluene fuel pool. Results are presented both in the fuel vapor-dome region at ¼ base diameter and in the actively burning region at ½ and ¾ diameters above the fuel surface. The spatial evolution of themore » soot and temperature pdfs is discussed and profiles of the temperature and soot mean and rms statistics are provided. Joint temperature/soot statistics are presented as spatially resolved conditional averages across the fire plume, and in terms of a joint pdf obtained by including measurements from multiple spatial locations.« less

Laser-diagnostic mapping of temperature and soot statistics in a 2-m diameter turbulent pool fire

DOE PAGES

Kearney, Sean P.; Grasser, Thomas W.

2017-08-10

We present spatial profiles of temperature and soot-volume-fraction statistics from a sooting 2-m base diameter turbulent pool fire, burning a 10%-toluene / 90%-methanol fuel mixture. Dual-pump coherent anti-Stokes Raman scattering and laser-induced incandescence are utilized to obtain radial profiles of temperature and soot probability density functions (pdf) as well as estimates of temperature/soot joint statistics at three vertical heights above the surface of the methanol/toluene fuel pool. Results are presented both in the fuel vapor-dome region at ¼ base diameter and in the actively burning region at ½ and ¾ diameters above the fuel surface. The spatial evolution of themore » soot and temperature pdfs is discussed and profiles of the temperature and soot mean and rms statistics are provided. Joint temperature/soot statistics are presented as spatially resolved conditional averages across the fire plume, and in terms of a joint pdf obtained by including measurements from multiple spatial locations.« less

Regulation of body temperature in the blue-tongued lizard.

PubMed

Hammel, H T; Caldwell, F T; Abrams, R M

1967-06-02

Lizards (Tiliqua scincoides) regulated their internal body temperature by moving back and forth between 15 degrees and 45 degrees C environments to maintain colonic and brain temperatures between 30 degrees and 37 degrees C. A pair of thermodes were implanted across the preoptic region of the brain stem, and a reentrant tube for a thermocouple was implanted in the brain stem. Heating the brain stem to 41 degrees C activated the exit response from the hot environment at a colonic temperature 1 degrees to 2 degrees C lower than normal, whereas cooling the brain stem to 25 degrees C delayed the exit from the hot environment until the colonic temperature was 1 degrees to 2 degrees C higher than normal. The behavioral thermoregulatory responses of this ectotherm appear to be activated by a combination of hypothalamic and other body temperatures.

Sodium deficiency effect on the transport properties of La0.8Na0.2-x□xMnO3 manganites

NASA Astrophysics Data System (ADS)

Elghoul, N.; Wali, M.; Kraiem, S.; Rahmouni, H.; Dhahri, E.; Khirouni, K.

2015-12-01

Effect of sodium deficiency on the transport properties of La0.8Na0.2-x□xMnO3 manganites is investigated using impedance spectroscopy technique. In the whole explored temperature range (77-700 K), conductivity measurements show the appearance of a metal-semiconductor transition for all investigated samples. Also, a saturation region is observed in σ (T) curves. It is found that conduction mechanism is governed by hopping process. The conductivity of the material decreases with increasing sodium deficiency. The transition temperature and the activation energy values inferred from grain boundary resistance and conductivity analysis are closed to each other. Such result confirms the contribution of grain boundary on the electrical conductivity. The variation of the Average Normalized Change (ANC) and its derivative with temperature gives important information about the available density of trapped charge states. The obtained results explain the observed saturation region in conductivity at high temperature region.

Effects of short-term variability of meteorological variables on soil temperature in permafrost regions

NASA Astrophysics Data System (ADS)

Beer, Christian; Porada, Philipp; Ekici, Altug; Brakebusch, Matthias

2018-03-01

Effects of the short-term temporal variability of meteorological variables on soil temperature in northern high-latitude regions have been investigated. For this, a process-oriented land surface model has been driven using an artificially manipulated climate dataset. Short-term climate variability mainly impacts snow depth, and the thermal diffusivity of lichens and bryophytes. These impacts of climate variability on insulating surface layers together substantially alter the heat exchange between atmosphere and soil. As a result, soil temperature is 0.1 to 0.8 °C higher when climate variability is reduced. Earth system models project warming of the Arctic region but also increasing variability of meteorological variables and more often extreme meteorological events. Therefore, our results show that projected future increases in permafrost temperature and active-layer thickness in response to climate change will be lower (i) when taking into account future changes in short-term variability of meteorological variables and (ii) when representing dynamic snow and lichen and bryophyte functions in land surface models.

Kinetics of methane hydrate decomposition studied via in situ low temperature X-ray powder diffraction.

PubMed

Everett, S Michelle; Rawn, Claudia J; Keffer, David J; Mull, Derek L; Payzant, E Andrew; Phelps, Tommy J

2013-05-02

Gas hydrate is known to have a slowed decomposition rate at ambient pressure and temperatures below the melting point of ice. As hydrate exothermically decomposes, gas is released and water of the clathrate cages transforms into ice. Based on results from the decomposition of three nominally similar methane hydrate samples, the kinetics of two regions, 180-200 and 230-260 K, within the overall decomposition range 140-260 K, were studied by in situ low temperature X-ray powder diffraction. The kinetic rate constants, k(a), and the reaction mechanisms, n, for ice formation from methane hydrate were determined by the Avrami model within each region, and activation energies, E(a), were determined by the Arrhenius plot. E(a) determined from the data for 180-200 K was 42 kJ/mol and for 230-260 K was 22 kJ/mol. The higher E(a) in the colder temperature range was attributed to a difference in the microstructure of ice between the two regions.

Kinetics of Methane Hydrate Decomposition Studied via in Situ Low Temperature X-ray Powder Diffraction

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

Everett, Susan M; Rawn, Claudia J; Keffer, David J.

Gas hydrates are known to have a slowed decomposition rate at ambient pressure and temperatures below the melting point of ice termed self-preservation or anomalous preservation. As hydrate exothermically decomposes, gas is released and water of the clathrate cages transforms into ice. Two regions of slowed decomposition for methane hydrate, 180 200 K and 230 260 K, were observed, and the kinetics were studied by in situ low temperature x-ray powder diffraction. The kinetic constants for ice formation from methane hydrate were determined by the Avrami model within each region and activation energies, Ea, were determined by the Arrhenius plot.more » Ea determined from the data for 180 200 K was 42 kJ/mol and for 230 260 K was 22 kJ/mol. The higher Ea in the colder temperature range was attributed to a difference in the microstructure of ice between the two regions.« less

Characteristics of OMVPE grown GaAsBi QW lasers and impact of post-growth thermal annealing

NASA Astrophysics Data System (ADS)

Kim, Honghyuk; Guan, Yingxin; Babcock, Susan E.; Kuech, Thomas F.; Mawst, Luke J.

2018-03-01

Laser diodes employing a strain-compensated GaAs1-xBix/GaAs1-yPy single quantum well (SQW) active region were grown by organometallic vapor phase epitaxy (OMVPE). High resolution x-ray diffraction, room temperature photoluminescence, and real-time optical reflectance measurements during the OMVPE growth were used to find the optimum process window for the growth of the active region material. Systematic post-growth in situ thermal anneals of various lengths were carried out in order to investigate the impacts of thermal annealing on the laser device performance characteristics. While the lowest threshold current density was achieved after the thermal annealing for 30 min at 630 °C, a gradual decrease in the external differential quantum efficiency was observed as the annealing time increases. It was observed that the temperature sensitivities of the threshold current density increase while those of lasing wavelength and slope efficiency remain nearly constant with increasing annealing time. Z-contrast scanning transmission electron microscopic) analysis revealed inhomogeneous Bi distribution within the QW active region.

The response of the temperature of cold-point mesopause to solar activity based on SABER data set

NASA Astrophysics Data System (ADS)

Tang, Chaoli; Liu, Dong; Wei, Heli; Wang, Yingjian; Dai, Congming; Wu, Pengfei; Zhu, Wenyue; Rao, Ruizhong

2016-07-01

The thermal structure and energy balance of upper atmosphere are dominated by solar activity. The response of cold-point mesopause (CPM) to solar activity is an important form. This article presents the response of the temperature of CPM (T-CPM) to solar activity using 14 year Sounding of the Atmosphere using Broadband Emission Radiometry data series over 80°S-80°N regions. These regions are divided into 16 latitude zones with 10° interval, and the spatial areas of 80°S-80°N, 180°W-180°E are divided into 96 lattices with 10°(latitude) × 60°(longitude) grid. The annual-mean values of T-CPM and F10.7 are calculated. The least squares regression method and correlation analysis are applied to these annual-mean series. First, the results show that the global T-CPM is significantly correlated to solar activity at the 0.05 level of significance with correlation coefficient of 0.90. The global solar response of T-CPM is 4.89 ± 0.67 K/100 solar flux unit. Then, for each latitude zone, the solar response of T-CPM and its fluctuation are obtained. The solar response of T-CPM becomes stronger with increasing latitude. The fluctuation ranges of solar response at middle-latitude regions are smaller than those of the equator and high-latitude regions, and the global distribution takes on W shape. The corelationship analysis shows that the T-CPM is significantly correlated to solar activity at the 0.05 level of significance for each latitude zone. The correlation coefficients at middle-latitude regions are higher than those of the equator and high-latitude regions, and the global distribution takes on M shape. At last, for each grid cell, the response of T-CPM to solar activity and their correlation coefficient are presented.

Low temperature and defoliation affect fructan-metabolizing enzymes in different regions of the rhizophores of Vernonia herbacea.

PubMed

Portes, Maria Teresa; Figueiredo-Ribeiro, Rita de Cássia L; de Carvalho, Maria Angela M

2008-10-09

In addition to the storage function, fructans in Asteraceae from floras with seasonal growth have been associated with drought and freezing tolerance. Vernonia herbacea, native of the Brazilian Cerrado, bears underground reserve organs, rhizophores, accumulating inulin-type fructans. The rhizophore is a cauline branched system with positive geotropic growth, with the apex (distal region) presenting younger tissues; sprouting of new shoots occurs by development of buds located on the opposite end (proximal region). Plants induced to sprouting by excision of the aerial organs present increased 1-fructan exohydrolase (1-FEH) activity in the proximal region, while plants at the vegetative stage present high 1-sucrose:sucrose fructosyltransferase (1-SST) in the distal region. The aim of the present study was to analyze how low temperature (5 degrees C) could affect fructan-metabolizing enzymes and fructan composition in the different regions of the rhizophores of intact and excised plants. 1-SST and 1-fructan:fructan fructosyltransferase (1-FFT) were higher in the distal region decreasing towards the proximal region in intact plants at the vegetative phase, and were drastically diminished when cold and/or excision were imposed. In contrast, 1-FEH increased in the proximal region of treated plants, mainly in excised plants subjected to cold. The ratio fructo-oligo to fructo-polysaccharides was significantly higher in plants exposed to low temperature (1.17 in intact plants and 1.64 in excised plants) than in plants exposed to natural temperature conditions (0.84 in intact vegetative plants and 0.58 in excised plants), suggesting that oligosaccharides are involved in the tolerance of plants to low temperature via 1-FEH, in addition to 1-FFT. Principal component analysis indicated different response mechanisms in fructan metabolism under defoliation and low temperature, which could be interpreted as part of the strategies to undergo unfavorable environmental conditions prevailing in the Cerrado during winter.

Seasonal and Regional Differences in Gene Expression in the Brain of a Hibernating Mammal

PubMed Central

Schwartz, Christine; Hampton, Marshall; Andrews, Matthew T.

2013-01-01

Mammalian hibernation presents a unique opportunity to study naturally occurring neuroprotection. Hibernating ground squirrels undergo rapid and extreme physiological changes in body temperature, oxygen consumption, and heart rate without suffering neurological damage from ischemia and reperfusion injury. Different brain regions show markedly different activity during the torpor/arousal cycle: the cerebral cortex shows activity only during the periodic returns to normothermia, while the hypothalamus is active over the entire temperature range. Therefore, region-specific neuroprotective strategies must exist to permit this compartmentalized spectrum of activity. In this study, we use the Illumina HiSeq platform to compare the transcriptomes of these two brain regions at four collection points across the hibernation season: April Active, October Active, Torpor, and IBA. In the cerebral cortex, 1,085 genes were found to be differentially expressed across collection points, while 1,063 genes were differentially expressed in the hypothalamus. Comparison of these transcripts indicates that the cerebral cortex and hypothalamus implement very different strategies during hibernation, showing less than 20% of these differentially expressed genes in common. The cerebral cortex transcriptome shows evidence of remodeling and plasticity during hibernation, including transcripts for the presynaptic cytomatrix proteins bassoon and piccolo, and extracellular matrix components, including laminins and collagens. Conversely, the hypothalamic transcriptome displays upregulation of transcripts involved in damage response signaling and protein turnover during hibernation, including the DNA damage repair gene RAD50 and ubiquitin E3 ligases UBR1 and UBR5. Additionally, the hypothalamus transcriptome also provides evidence of potential mechanisms underlying the hibernation phenotype, including feeding and satiety signaling, seasonal timing mechanisms, and fuel utilization. This study provides insight into potential neuroprotective strategies and hibernation control mechanisms, and also specifically shows that the hibernator brain exhibits both seasonal and regional differences in mRNA expression. PMID:23526982

Determination of electrical properties of degraded mixed ionic conductors: Impedance studies with applied dc voltage

NASA Astrophysics Data System (ADS)

Bayer, T. J. M.; Carter, J. J.; Wang, Jian-Jun; Klein, Andreas; Chen, Long-Qing; Randall, C. A.

2017-12-01

Under electrical bias, mixed ionic conductors such as SrTiO3 are characterized by oxygen vacancy migration which leads to resistance degradation. The defect chemistry to describe the relationship between conductivity and oxygen vacancies is usually obtained by high temperature conductivity data or quenching experiments. These techniques can investigate the equilibrated state only. Here, we introduce a new approach using in-situ impedance studies with applied dc voltage to analyze the temperature dependent electrical properties of degraded SrTiO3 single crystals. This procedure is most beneficial since it includes electric field driven effects. The benefits of the approach are highlighted by comparing acceptor doped and undoped SrTiO3. This approach allows the determination of the temperature activation of both anodic and cathodic conductivity of Fe-doped SrTiO3 in the degraded state. The anodic activation energy matches well with the published results, while the activation energy of the degraded cathode region reported here is not in agreement with earlier assumptions. The specific discrepancies of the experimental data and the published defect chemistry are discussed, and a defect chemistry model that includes the strong temperature dependence of the electron conductivity in the cathode region is proposed.

Thermal regime of active layer at two lithologically contrasting sites on James Ross Island, Antarctic Peninsula.

NASA Astrophysics Data System (ADS)

Hrbáček, Filip; Nývlt, Daniel; Láska, Kamil

2016-04-01

Antarctic Peninsula region (AP) represents one of the most rapidly warming parts of our planet in the last 50 years. Despite increasing research activities along both western and eastern sides of AP in last decades, there is still a lot of gaps in our knowledge relating to permafrost, active layer and its thermal and physical properties. This study brings new results of active layer monitoring on James Ross Island, which is the largest island in northern AP. Its northern part, Ulu Peninsula, is the largest ice-free area (more than 200 km2) in the region. Due its large area, we focused this study on sites located in different lithologies, which would affect local thermal regime of active layer. Study site (1) at Abernethy Flats area (41 m a.s.l.) lies ~7 km from northern coast. Lithologically is formed by disintegrated Cretaceous calcareous sandstones and siltstones of the Santa Marta Formation. Study site (2) is located at the northern slopes of Berry Hill (56 m a.s.l.), about 0.4 km from northern coastline. Lithology is composed of muddy to intermediate diamictites, tuffaceous siltstones to fine grained sandstones of the Mendel Formation. Data of air temperature at 2 meters above ground and the active layer temperatures at 75 cm deep profiles were obtained from both sites in period 1 January 2012 to 31 December 2014. Small differences were found when comparing mean air temperatures and active temperatures at 5 and 75 cm depth in the period 2012-2014. While the mean air temperatures varied between -7.7 °C and -7.0 °C, the mean ground temperatures fluctuated between -6.6 °C and -6.1 °C at 5 cm and -6.9 °C and -6.0 °C at 75 cm at Abernethy Flats and Berry Hill slopes respectively. Even though ground temperature differences along the profiles weren't pronounced during thawing seasons, the maximum active layer thickness was significantly larger at Berry Hill slopes (80 to 82 cm) than at Abernethy Flats (52 to 64 cm). We assume this differences are affected by local lithology, especially by the higher proportion of fine particles and more thermally conductive minerals, together with higher water saturation are fundamental for higher maximum active layer thickness found at Berry Hill slopes.

Engineering activity and stability of Thermotoga maritima glutamate dehydrogenase. I. Introduction of a six-residue ion-pair network in the hinge region.

PubMed

Lebbink, J H; Knapp, S; van der Oost, J; Rice, D; Ladenstein, R; de Vos, W M

1998-07-10

Comparison of the recently determined three-dimensional structures of several glutamate dehydrogenases allowed for the identification of a five-residue ion-pair network in the hinge region of Pyrococcus furiosus glutamate dehydrogenase (melting temperature 113 degrees C), that is not present in the homologous glutamate dehydrogenase from Thermotoga maritima (melting temperature 93 degrees C). In order to study the role of this ion-pair network, we introduced it into the T. maritima enzyme using a site-directed mutagenesis approach. The resulting T. maritima glutamate dehydrogenases N97D, G376 K and N97D/G376 K as well as the wild-type enzyme were overproduced in Escherichia coli and subsequently purified. Elucidation of the three-dimensional structure of the double mutant N97D/G376 K at 3.0 A, showed that the designed ion-pair interactions were indeed formed. Moreover, because of interactions with an additional charged residue, a six-residue network is present in this double mutant. Melting temperatures of the mutant enzymes N97D, G376 K and N97D/G376 K, as determined by differential scanning calorimetry, did not differ significantly from that of the wild-type enzyme. Identical transition midpoints in guanidinium chloride-induced denaturation experiments were found for the wild-type and all mutant enzymes. Thermal inactivation at 85 degrees C occured more than twofold faster for all mutant enzymes than for the wild-type glutamate dehydrogenase. At temperatures of 65 degrees C and higher, the wild-type and the three mutant enzymes showed identical specific activities. However, at 58 degrees C the specific activity of N97D/G376 K and G376 K was found to be significantly higher than that of the wild-type and N97D enzymes. These results suggest that the engineered ion-pair interactions in the hinge region do not affect the stability towards temperature or guanidinium chloride-induced denaturation but rather affect the specific activity of the enzyme and the temperature at which it functions optimally. Copyright 1998 Academic Press

Outer atmospheres of cool stars. XII - A survey of IUE ultraviolet emission line spectra of cool dwarf stars

NASA Technical Reports Server (NTRS)

Linsky, J. L.; Bornmann, P. L.; Carpenter, K. G.; Hege, E. K.; Wing, R. F.; Giampapa, M. S.; Worden, S. P.

1982-01-01

Quantitative information is obtained on the chromospheres and transition regions of M dwarf stars, in order to determine how the outer atmospheres of dMe stars differ from dM stars and how they compare with the outer atmospheres of quiet and active G and K type dwarfs. IUE spectra of six dMe and four dM stars, together with ground-based photometry and spectroscopy of the Balmer and Ca II H and K lines, show no evidence of flares. It is concluded, regarding the quiescent behavior of these stars, that emission-line spectra resemble that of the sun and contain emission lines formed in regions with 4000-20,000 K temperatures that are presumably analogous to the solar chromosphere, as well as regions with temperatures of 20,000-200,000 K that are presumably analogous to the solar transition region. Emission-line surface fluxes are proportional to the emission measure over the range of temperatures at which the lines are formed.

Long-term active-layer dynamics: results of 22 years of field observations in Northern Hemisphere permafrost regions.

NASA Astrophysics Data System (ADS)

Shiklomanov, N. I.; Nelson, F. E.; Streletskiy, D. A.; Klene, A. E.; Biskaborn, B. K.

2016-12-01

The uppermost layer of seasonal thawing above permafrost (the active layer) is an important regulator of energy and mass fluxes between the surface and the atmosphere in the polar regions. Active layer monitoring is an important component of efforts to assess the effects of global change in permafrost environments. The Circumpolar Active Layer Monitoring (CALM) program, established in the early 1990s, is designed to observe temporal and spatial variability of the active layer and its response to changes and variations in climatic conditions. The CALM network is an integral part of the Global Terrestrial Network for Permafrost (GTN-P), operating under the auspices of the Global Terrestrial Observing System (GTOS) /Global Climate Observing System (GCOS). Standardized thaw depth observations in the Northern Hemisphere are available for more than 200 GTN-P/CALM sites in the Northern Hemisphere. At each of the sites spatially distributed ALT measurements have been conducted annually by mechanical probing. The locations of sites represent generalized surface and subsurface conditions characteristic of broader regions. The data are assimilated and distributed though the CALM (www.gwu.edu/ calm) and GTN-P (gtnpdatabase.org) online databases. In this presentation we use data from approximately 20 years of continuous observations to examine temporal trends in active-layer thickness for several representative Arctic regions. Results indicate substantial interannual fluctuations in active-layer thickness, primarily in response to variations in air temperature. Decadal trends in ALT vary by region. A progressive increase in ALT has been observed in the Nordic countries, the Russian European North, West Siberia, East Siberia, the Russian Far East, and the Interior of Alaska. North American Arctic sites show no apparent thaw depth trend over 22-years of record. However, combined active layer, ground temperature and heave/subsidence observations conducted in northern Alaska demonstrate a complex, non-linear response of the active-layer/upper permafrost system to changes in climatic conditions.

Pressure and Temperature Effects on the Activity and Structure of the Catalytic Domain of Human MT1-MMP

PubMed Central

Decaneto, Elena; Suladze, Saba; Rosin, Christopher; Havenith, Martina; Lubitz, Wolfgang; Winter, Roland

2015-01-01

Membrane type 1-matrix metalloproteinase (MT1-MMP or MMP-14) is a zinc-transmembrane metalloprotease involved in the degradation of extracellular matrix and tumor invasion. While changes in solvation of MT1-MMP have been recently studied, little is known about the structural and energetic changes associated with MT1-MMP while interacting with substrates. Steady-state kinetic and thermodynamic data (including activation energies and activation volumes) were measured over a wide range of temperatures and pressures by means of a stopped-flow fluorescence technique. Complementary temperature- and pressure-dependent Fourier-transform infrared measurements provided corresponding structural information of the protein. MT1-MMP is stable and active over a wide range of temperatures (10–55°C). A small conformational change was detected at 37°C, which is responsible for the change in activity observed at the same temperature. Pressure decreases the enzymatic activity until complete inactivation occurs at 2 kbar. The inactivation is associated with changes in the rate-limiting step of the reaction caused by additional hydration of the active site upon compression and/or minor conformational changes in the active site region. Based on these data, an energy and volume diagram could be established for the various steps of the enzymatic reaction. PMID:26636948

Bacterial and Archaeal Communities Variability Associated with Upwelling and Anthropogenic Pressures in the Protection Area of Arraial do Cabo (Cabo Frio region - RJ).

PubMed

Coelho-Souza, Sergio A; Araújo, Fábio V; Cury, Juliano C; Jesus, Hugo E; Pereira, Gilberto C; Guimarães, Jean R D; Peixoto, Raquel S; Dávila, Alberto M R; Rosado, Alexandre S

2015-09-01

Upwelling systems contain a high diversity of pelagic microorganisms and their composition and activity are defined by factors like temperature and nutrient concentration. Denaturing gradient gel electrophoresis (DGGE) technique was used to verify the spatial and temporal genetic variability of Bacteria and Archaea in two stations of the Arraial do Cabo coastal region, one under upwelling pressure and another under anthropogenic pressure. In addition, biotic and abiotic variables were measured in surface and deep waters from three other stations between these stations. Six samplings were done during a year and adequately represented the degrees of upwelling and anthropogenic pressures to the system. Principal Component Analysis (PCA) showed negative correlations between the concentrations of ammonia and phosphorous with prokaryotic secondary production and the total heterotrophic bacteria. PCA also showed negative correlation between temperature and the abundance of prokaryotic cells. Bacterial and archaeal compositions were changeable as were the oceanographic conditions, and upwelling had a regional pressure while anthropogenic pressure was punctual. We suggest that the measurement of prokaryotic secondary production was associated with both Bacteria and Archaea activities, and that substrate availability and temperature determine nutrients cycling.

Active Heat Injection to Investigate Seepage Conditions Along the Interface Between a Concrete Diversion Sluiceway and Earthen Embankment Dam

NASA Astrophysics Data System (ADS)

Ringeri, A.; Butler, K. E.; MacQuarrie, K. T. B.

2016-12-01

The interface between embankment dams and adjoining hydraulic structures are regions which can give rise to seepage defects. A field experiment was conducted at the Mactaquac Generating Station in New Brunswick, Canada using active thermometry to investigate seepage conditions along the interface of a diversion sluiceway and earth embankment. The method involved monitoring the time evolution of temperature following the injection of a controlled heat pulse from a subsurface heat cable acting as a line source. Transient anomalies in the induced temperature field can result from the aberration of thermal properties and flow conditions which accompany defects. An industrial heat trace cable and distributed temperature sensing (DTS) fibre optic cable were installed in two parallel, 42 m deep, sub-vertical boreholes separated by 3 m and offset 0.5 m from the core-concrete interface. The heat and DTS cables were installed in the upstream and downstream boreholes respectively. Heat was injected as a box car function at a constant rate of 78.72 W/m for 51 d while the DTS cable, with a 20 cm sampling resolution, was averaged over 10 min at 30 min intervals for 300 d. The DTS cable successfully detected temperature changes induced by the upstream heat pulse. A coherent temperature response occurred along a 13 m section of deep fibre, where mean peak temperatures rose 1.59 ± 0.03 °C above ambient temperatures with an average time lag of 8.2 d following the end of the heating cycle. Two temperature anomalies above this region coincided with the position of the water table and the location of a previously detected fibre break. The method appears to be particularly useful in seepage surveillance of the deeper regions of the interface. Further analysis is required to remove the influence of seasonal temperatures on the heat pulse response at shallow depths.

The Influence of Cold Temperature on Cellular Excitability of Hippocampal Networks

PubMed Central

Vara, Hugo; Caires, Rebeca; Ballesta, Juan J.; Belmonte, Carlos; Viana, Felix

2012-01-01

The hippocampus plays an important role in short term memory, learning and spatial navigation. A characteristic feature of the hippocampal region is its expression of different electrical population rhythms and activities during different brain states. Physiological fluctuations in brain temperature affect the activity patterns in hippocampus, but the underlying cellular mechanisms are poorly understood. In this work, we investigated the thermal modulation of hippocampal activity at the cellular network level. Primary cell cultures of mouse E17 hippocampus displayed robust network activation upon light cooling of the extracellular solution from baseline physiological temperatures. The activity generated was dependent on action potential firing and excitatory glutamatergic synaptic transmission. Involvement of thermosensitive channels from the transient receptor potential (TRP) family in network activation by temperature changes was ruled out, whereas pharmacological and immunochemical experiments strongly pointed towards the involvement of temperature-sensitive two-pore-domain potassium channels (K2P), TREK/TRAAK family. In hippocampal slices we could show an increase in evoked and spontaneous synaptic activity produced by mild cooling in the physiological range that was prevented by chloroform, a K2P channel opener. We propose that cold-induced closure of background TREK/TRAAK family channels increases the excitability of some hippocampal neurons, acting as a temperature-sensitive gate of network activation. Our findings in the hippocampus open the possibility that small temperature variations in the brain in vivo, associated with metabolism or blood flow oscillations, act as a switch mechanism of neuronal activity and determination of firing patterns through regulation of thermosensitive background potassium channel activity. PMID:23300680

Oviposition activity of Drosophila suzukii as mediated by ambient and fruit temperature

PubMed Central

2017-01-01

The invasive pest Drosophila suzukii was introduced to southern Europe in 2008 and spread throughout Central Europe in the following years. Precise reliable data on the temperature-dependent behavior of D. suzukii are scarce but will help forecasting and cultivation techniques. Depending on physico-chemical properties, surface temperature of objects may differ from ambient temperatures, determining physical activity, and affect oviposition on or into substrate, determining preimaginal development later. Therefore, the preferred ambient temperatures of D. suzukii and fruit temperature for oviposition were examined on a linear temperature gradient device. Thirty adults (15 ♀; 15 ♂) were adapted to different temperatures (10, 20, 30°C) for six days and then exposed to different temperature gradients (10–25, 20–35, 25–40°C). D. suzukii adapted to 10°C remained in cooler regions and suffered from a significantly higher mortality at the 25–40°C gradient. Animals adapted to warmer temperatures had a wider temperature preference on the gradient device. Acclimation to lower temperatures and the resulting lower temperature preferences may allow the flies to disperse better in spring to search for oviposition sites. The oviposition activity decreased continuously at a fruit temperature above 28°C and below 15°C, with highest oviposition activity in fruits with temperatures between 19.7°C and 24.8°C. The preferred fruit temperature is in accordance with the temperature optimum of reproduction biology and preimaginal development of D. suzukii reported in the literature. PMID:29121635

High ambient temperature increases 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy")-induced Fos expression in a region-specific manner.

PubMed

Hargreaves, G A; Hunt, G E; Cornish, J L; McGregor, I S

2007-03-16

3,4-Methylenedioxymethamphetamine (MDMA, "Ecstasy") is a popular drug that is often taken under hot conditions at dance clubs. High ambient temperature increases MDMA-induced hyperthermia and recent studies suggest that high temperatures may also enhance the rewarding and prosocial effects of MDMA in rats. The present study investigated whether ambient temperature influences MDMA-induced expression of Fos, a marker of neural activation. Male Wistar rats received either MDMA (10 mg/kg i.p.) or saline, and were placed in test chambers for 2 h at either 19 or 30 degrees C. MDMA caused significant hyperthermia at 30 degrees C and a modest hypothermia at 19 degrees C. The 30 degrees C ambient temperature had little effect on Fos expression in vehicle-treated rats. However MDMA-induced Fos expression was augmented in 15 of 30 brain regions at the high temperature. These regions included (1) sites associated with thermoregulation such as the median preoptic nucleus, dorsomedial hypothalamus and raphe pallidus, (2) the supraoptic nucleus, a region important for osmoregulation and a key mediator of oxytocin and vasopressin release, (3) the medial and central nuclei of the amygdala, important in the regulation of social and emotional behaviors, and (4) the shell of the nucleus accumbens and (anterior) ventral tegmental area, regions associated with the reinforcing effects of MDMA. MDMA-induced Fos expression was unaffected by ambient temperature at many other sites, and was diminished at high temperature at one site (the islands of Calleja), suggesting that the effect of temperature on MDMA-induced Fos expression was not a general pharmacokinetic effect. Overall, these results indicate that high temperatures accentuate key neural effects of MDMA and this may help explain the widespread use of the drug under hot conditions at dance parties as well as the more hazardous nature of MDMA taken under such conditions.

Temperature dependence of internal friction in enzyme reactions.

PubMed

Rauscher, Anna Á; Simon, Zoltán; Szöllosi, Gergely J; Gráf, László; Derényi, Imre; Malnasi-Csizmadia, Andras

2011-08-01

Our aim was to elucidate the physical background of internal friction of enzyme reactions by investigating the temperature dependence of internal viscosity. By rapid transient kinetic methods, we directly measured the rate constant of trypsin 4 activation, which is an interdomain conformational rearrangement, as a function of temperature and solvent viscosity. We found that the apparent internal viscosity shows an Arrhenius-like temperature dependence, which can be characterized by the activation energy of internal friction. Glycine and alanine mutations were introduced at a single position of the hinge of the interdomain region to evaluate how the flexibility of the hinge affects internal friction. We found that the apparent activation energies of the conformational change and the internal friction are interconvertible parameters depending on the protein flexibility. The more flexible a protein was, the greater proportion of the total activation energy of the reaction was observed as the apparent activation energy of internal friction. Based on the coupling of the internal and external movements of the protein during its conformational change, we constructed a model that quantitatively relates activation energy, internal friction, and protein flexibility.

Observed Local Impacts of Global Irrigation on Surface Temperature

NASA Astrophysics Data System (ADS)

Chen, L.; Dirmeyer, P.

2017-12-01

Agricultural irrigation has significant potential for altering local climate through reducing soil albedo, increasing evapotranspiration, and enabling greater leaf area. Numerous studies using regional or global climate models have demonstrated the cooling effects of irrigation on mean and extreme temperature, especially over regions where irrigation is extensive. However, these model-based results have not been validated due to the limitations of observational datasets. In this study, multiple satellite-based products, including the Moderate Resolution Imaging Spectroradiometer (MODIS) and Soil Moisture Active Passive (SMAP) data sets, are used to isolate and quantify the local impacts of irrigation on surface climate over the irrigated regions, which are derived from the Global Map of Irrigation Areas (GMIA). The relationships among soil moisture, albedo, evapotranspiration, and surface temperature are explored. Strong evaporative cooling of irrigation on daytime surface temperature is found over the arid and semi-arid regions, such as California's Central Valley, the Great Plains, and central Asia. However, the cooling effects are less evident in most areas of eastern China, India, and the Lower Mississippi River Basin in spite of extensive irrigation over these regions. Results are also compared with irrigation experiments using the Community Earth System Model (CESM) to assess the model's ability to represent land-atmosphere interactions in regards to irrigation.

Equivalent circuit-level model of quantum cascade lasers with integrated hot-electron and hot-phonon effects

NASA Astrophysics Data System (ADS)

Yousefvand, H. R.

2017-12-01

We report a study of the effects of hot-electron and hot-phonon dynamics on the output characteristics of quantum cascade lasers (QCLs) using an equivalent circuit-level model. The model is developed from the energy balance equation to adopt the electron temperature in the active region levels, the heat transfer equation to include the lattice temperature, the nonequilibrium phonon rate to account for the hot phonon dynamics and simplified two-level rate equations to incorporate the carrier and photon dynamics in the active region. This technique simplifies the description of the electron-phonon interaction in QCLs far from the equilibrium condition. Using the presented model, the steady and transient responses of the QCLs for a wide range of sink temperatures (80 to 320 K) are investigated and analysed. The model enables us to explain the operating characteristics found in QCLs. This predictive model is expected to be applicable to all QCL material systems operating in pulsed and cw regimes.

Staged storage and magma convection at Ambrym volcano, Vanuatu

NASA Astrophysics Data System (ADS)

Sheehan, Fionnuala; Barclay, Jenni

2016-08-01

New mineral-melt thermobarometry and mineral chemistry data are presented for basaltic scoriae erupted from the Mbwelesu crater of Ambrym volcano, Vanuatu, during persistent lava lake activity in 2005 and 2007. These data reveal crystallisation conditions and enable the first detailed attempt at reconstruction of the central magma plumbing system of Ambrym volcano. Pressures and temperatures of magma crystallisation at Ambrym are poorly constrained. This study focuses on characterising the magma conditions underlying the quasi-permanent lava lakes at the basaltic central vents, and examines petrological evidence for magma circulation. Mineral-melt equilibria for clinopyroxene, olivine and plagioclase allow estimation of pressures and temperatures of crystallisation, and reveal two major regions of crystallisation, at 24-29 km and 11-18 km depth, in agreement with indications from earthquake data of crustal storage levels at c. 25-29 km and 12-21 km depth. Temperature estimates are 1150-1170 °C for the deeper region, and 1110-1140 °C in the mid-crustal region, with lower temperatures of 1090-1100 °C for late-stage crystallisation. More primitive plagioclase antecrysts are thought to sample a slightly more mafic melt at sub-Moho depths. Resorption textures combined with effectively constant mafic mineral compositions suggest phenocryst convection in a storage region of consistent magma composition. In addition, basalt erupted at Ambrym has predominantly maintained a constant composition throughout the volcanic succession. This, coupled with recurrent periods of elevated central vent activity on the scale of months, suggest frequent magmatic recharge via steady-state melt generation at Ambrym.

Temperatures and Composition in the Saturn System from Cassini CIRS

NASA Technical Reports Server (NTRS)

Flasar, F. Michael

2008-01-01

We summarize recent observations by the Composite Infrared Spectrometer of Saturn, its rings, Titan, and the icy satellites. Limb observations of Saturn show vertical oscillations of temperatures and zonal-wind shears in the equatorial region that may be related to a temporal oscillation similar to the terrestrial QBO and Jupiter's QQO. There is also evidence of subsidence at mid-northern latitudes driven by the equatorial activity. Nadir-viewing observations show compact warm spots in the troposphere and stratosphere at both (summer and winter) poles, likely associated with subsidence. Observations of Titan have defined better the characteristics of the northern winter polar vortex, with 190 m/s winds surrounding a cold atmosphere at 1 microbar. The very warm polar stratopause at 10 microbar and the enhanced abundances of organic compounds suggest subsidence within the vortex. Analysis of the zonal structure in temperature indicates that the stratospheric zonal winds rotate about an axis that is displaced approximately 4.1 deg from the IAU pole. Additional flybys, including a close one in March 2008, continue to characterize the endogenic activity in Enceladus s south polar region. Temperature maps of bright and dark terrains on Iapetus indicate that its ice is approximately stable to sublimation in the bright regions and highly unstable in the dark regions. Thermal mapping of Saturn s rings continues to constrain their composition, and observations at different solar phase angles, spacecraft elevations, solar elevations, and local hour angles have elucidated the effects of ring-particle shadowing and vertical motions on the thermal structure, and revealed the presence of small-scale structure associated with self-gravity wakes.

Radio-derived three-dimensional structure of a solar active region

NASA Astrophysics Data System (ADS)

Tun, Samuel D.

Solar active regions are the source of the most violent events observed on the Sun, some of which have a direct impact to modern civilization. Efforts to understand and predict such events require determination of the three-dimensional distributions of density, temperature, and magnetic fields above such active regions. This thesis presents the structure of the solar atmosphere above active region AR 10923, observed on 2006 Nov 10, as deduced from multi-wavelength studies including combined microwave observations from the Very Large Array (VLA) and the Owens Valley Solar Array (OVSA). The VLA observations provide excellent image quality at a few widely spaced frequencies while the OVSA data provide information at many intermediate frequencies to fill in the spectral coverage. In order to optimize the OVSA data for spectroscopic studies, the L1 method of self-calibration was implemented at this observatory, producing the best single frequency maps produced to date. Images at the 25 distinct, available frequencies are used to provide spatially resolved spectra along many lines of sight in the active region, from which microwave spectral diagnostics are obtained for deducing two-dimensional maps of temperature, magnetic field strength, and column density. The derived quantities are compared with multi-wavelength observations from SoHO and Hinode spacecraft, and with a standard potential magnetic field extrapolation. It is found that a two component temperature model is required to fit the data, in which a hot (> 2 MK) lower corona above the strong-field plage and sunspot regions (emitting via the gyroresonance process) is overlaid with somewhat cooler (˜ 1 MK) coronal loops that partially absorb the gyroresonance emission through the free-free (Bremsstrahlung) process. It is also found that the potential magnetic field extrapolation model can quantitatively account for the observed gyroresonance emission over most of the active region, but in a few areas a higher field strength is required. These areas of discrepancy are found to coincide with the foot points of hot X-ray loops over the sunspot's penumbra. The results and the extrapolation are used to explore the coronal configuration needed to explain the observations, from which it is found that the bulk of radio and X-ray free-free emission emanates from two loop systems, distinguished by the location of their loop foot points. The proposed stratification may explain the observed distribution of column emission measure and the differences in this quantity as obtained from X-rays or radio emission.

Analysis of monthly, winter, and annual temperatures in Zagreb, Croatia, from 1864 to 2010: the 7.7-year cycle and the North Atlantic Oscillation

NASA Astrophysics Data System (ADS)

Sen, Asok K.; Ogrin, Darko

2016-02-01

Long instrumental records of meteorological variables such as temperature and precipitation are very useful for studying regional climate in the past, present, and future. They can also be useful for understanding the influence of large-scale atmospheric circulation processes on the regional climate. This paper investigates the monthly, winter, and annual temperature time series obtained from the instrumental records in Zagreb, Croatia, for the period 1864-2010. Using wavelet analysis, the dominant modes of variability in these temperature series are identified, and the time intervals over which these modes may persist are delineated. The results reveal that all three temperature records exhibit low-frequency variability with a dominant periodicity at around 7.7 years. The 7.7-year cycle has also been observed in the temperature data recorded at several other stations in Europe, especially in Northern and Western Europe, and may be linked to the North Atlantic Oscillation (NAO) and/or solar/geomagnetic activity.

The perils of climate change: In utero exposure to temperature variability and birth outcomes in the Andean region.

PubMed

Molina, Oswaldo; Saldarriaga, Victor

2017-02-01

The discussion on the effects of climate change on human activity has primarily focused on how increasing temperature levels can impair human health. However, less attention has been paid to the effect of increased climate variability on health. We investigate how in utero exposure to temperature variability, measured as the fluctuations relative to the historical local temperature mean, affects birth outcomes in the Andean region. Our results suggest that exposure to a temperate one standard deviation relative to the municipality's long-term temperature mean during pregnancy reduces birth weight by 20g. and increases the probability a child is born with low birth weight by a 0.7 percentage point. We also explore potential channels driving our results and find some evidence that increased temperature variability can lead to a decrease in health care and increased food insecurity during pregnancy. Copyright © 2016 Elsevier B.V. All rights reserved.

Shifts of Start and End of Season in Response to Air Temperature Variation Based on Gimms Dataset in Hyrcanian Forests

NASA Astrophysics Data System (ADS)

Kiapasha, K. H.; Darvishsefat, A. A.; Zargham, N.; Julien, Y.; Sobrino, J. A.; Nadi, M.

2017-09-01

Climate change is one of the most important environmental challenges in the world and forest as a dynamic phenomenon is influenced by environmental changes. The Hyrcanian forests is a unique natural heritage of global importance and we need monitoring this region. The objective of this study was to detect start and end of season trends in Hyrcanian forests of Iran based on biweekly GIMMS (Global Inventory Modeling and Mapping Studies) NDVI3g in the period 1981-2012. In order to find response of vegetation activity to local temperature variations, we used air temperature provided from I.R. Iran Meteorological Organization (IRIMO). At the first step in order to remove the existing gap from the original time series, the iterative Interpolation for Data Reconstruction (IDR) model was applied to GIMMS and temperature dataset. Then we applied significant Mann Kendall test to determine significant trend for each pixel of GIMMS and temperature datasets over the Hyrcanian forests. The results demonstrated that start and end of season (SOS & EOS respectively) derived from GIMMS3g NDVI time series increased by -0.16 and +0.41 days per year respectively. The trends derived from temperature time series indicated increasing trend in the whole of this region. Results of this study showed that global warming and its effect on growth and photosynthetic activity can increased the vegetation activity in our study area. Otherwise extension of the growing season, including an earlier start of the growing season, later autumn and higher rate of production increased NDVI value during the study period.

Diode Lasers and Light Emitting Diodes Operating at Room Temperature with Wavelengths Above 3 Micrometers

DTIC Science & Technology

2011-11-29

as an active region of mid - infrared LEDs. It should be noted that active region based on interband transition is equally useful for both laser and...IR LED technology for infrared scene projectors”, Dr. E. Golden, Air Force Research Laboratory, Eglin Air Force Base .  “A stable mid -IR, GaSb...multimode lasers. Single spatial mode 3-3.2 J.lm diode lasers were developed. LEDs operate at wavelength above 4 J.lm at RT. Dual color mid - infrared

Observed changes in the characteristics of Active and Break Spells in the Indian Summer Monsoon

NASA Astrophysics Data System (ADS)

Singh, D.; Tsiang, M.; Rajaratnam, B.; Diffenbaugh, N. S.

2013-12-01

South Asia is home to about 24% of the world's population and is one of the world's most disaster prone regions. The majority of the people in this region depend on agriculture for their livelihood. Substantial variability in the South Asian Summer Monsoon occurs on an intraseasonal timescale (30-60 day) during which it fluctuates between spells of heavy (active spells) and low rainfall (breaks or weak spells). Considering the potentially severe implications of such rainfall variations, we quantify historical changes in the active and break spell characteristics in an effort to understand how these events are likely to respond to future anthropogenic forcings using the 1degx1deg gridded rainfall dataset. We find a decreasing trend in peak season rainfall since 1951 and a statistically significant shift in the rainfall distribution, suggesting greater extremes. Consequently, our results suggest an intensification of the active spells and more frequent occurrence of break spells at the 95% significance level. To understand the cause of these changes, we explore the environmental parameters in the North Indian Ocean and the Western Pacific that influence the occurrence of such events over the core monsoon region. We use the NCEP/NCAR Reanalysis 1 (1948-present) to do a composite analysis for two periods - 1951-1980 and 1981-2011. First, we examine the energetics of the baroclinic instabilities that initiate cyclonic depressions in the northern Bay of Bengal and the net moisture flux into the region. Further, sea surface temperatures are known to influence the characteristics of active and break spells. Therefore, next, we study sea surface temperature patterns in the Bay of Bengal and the equatorial western Pacific preceding breaks. We also examine the persistence of breaks through the diabatic heating anomalies over this region.

The Abundance of Helium in the Source Plasma of Solar Energetic Particles

NASA Astrophysics Data System (ADS)

Reames, Donald V.

2017-11-01

Studies of patterns of abundance enhancements of elements, relative to solar coronal abundances, in large solar energetic-particle (SEP) events, and of their power-law dependence on the mass-to-charge ratio, A/Q, of the ions, have been used to determine the effective source-plasma temperature, T, that defines the Q-values of the ions. We find that a single assumed value for the coronal reference He/O ratio in all SEP events is often inconsistent with the transport-induced power-law trend of the other elements. In fact, the coronal He/O varies rather widely from one SEP event to another. In the large Fe-rich SEP events with T ≈ 3 MK, where shock waves, driven out by coronal mass ejections (CMEs), have reaccelerated residual ions from impulsive suprathermal events that occur earlier in solar active regions, He/O ≈ 90, a ratio similar to that in the slow solar wind, which may also originate from active regions. Ions in the large SEP events with T < 2 MK may be accelerated outside active regions, and have values of 40 ≤ He/O ≤ 60. Mechanisms that determine coronal abundances, including variations of He/O, are likely to occur near the base of the corona (at ≈ 1.1 RS) and thus to affect both SEPs (at 2 - 3 RS) and the solar wind. Other than He, reference coronal abundances for heavier elements show little temperature dependence or systematic difference between SEP events; He, the element with the highest first-ionization potential, is unique. The CME-driven shock waves probe the same regions of space, at ≈ 2 RS near active regions, which are also likely sources of the slow solar wind, providing complementary information on conditions in those regions.

Potential nitrogen fixation activity of different aged biological soil crusts from rehabilitated grasslands of the hilly Loess Plateau, China

USGS Publications Warehouse

Zhao, Y.; Xu, M.; Belnap, J.

2010-01-01

Biological soil crusts (biocrusts) cover up to 60–70% of the soil surface in grasslands rehabilitated during the "Grain for Green" project implemented in the hilly Loess Plateau region in 1999. As biocrusts fix nitrogen (N), they are an important part of restoring soil fertility. We measured nitrogenase activity (NA) in biocrusts from sites rehabilitated at six different time periods to estimate 1) the effects of moisture content and temperature on NA in biocrusts of different ages and 2) the potential N contribution from biocrusts to soils and plants in this region. Results show that NA in the biocrusts was mostly controlled by the species composition, as the activity of biocrusts dominated by free-living soil cyanobacteria was significantly higher than that of moss-dominated biocrusts. Nitrogenase activity was also influenced by soil moisture content and ambient temperature, with a significant decline in activity when moisture levels were decreased to 20% field water-holding capacity. The optimal temperature for NA was 35–40 °C and 30–40 °C for cyanobacteria- and moss-dominated biocrusts, respectively. Biocrust fixed N is likely an important source of N in this ecosystem, as we estimated annual potential N inputs per hectare in these grasslands to be up to 13 kg N ha-1 and 4 kg N ha-1 for cyanobacteria- and moss-dominated biocrusts, respectively.

Improving Representations of Near-Surface Permafrost and Soil Temperature Profiles in the Regional Arctic System Model (RASM)

NASA Astrophysics Data System (ADS)

Gergel, D. R.; Hamman, J.; Nijssen, B.

2017-12-01

Permafrost and seasonally frozen soils are a key characteristic of the terrestrial Arctic, and the fate of near-surface permafrost as a result of climate change is projected to have strong impacts on terrestrial biogeochemistry. The active layer thickness (ALT) is the layer of soil that freezes and thaws annually, and shifts in the depth of the ALT are projected to occur over large areas of the Arctic that are characterized by discontinuous permafrost. Faithful representation of permafrost in land models in climate models is a product of both soil dynamics and the coupling of air and soil temperatures. A common problem is a large bias in simulated ALT due to a model depth that is too shallow. Similarly, soil temperatures often show systematic biases, which lead to biases in air temperature due to poorly modeled air-soil temperature feedbacks in a coupled environment. In this study, we use the Regional Arctic System Model (RASM), a fully-coupled regional earth system model that is run at a 50-km land/atmosphere resolution over a pan-Arctic domain and uses the Variable Infiltration Capacity (VIC) model as its land model. To understand what modeling decisions are necessary to accurately represent near-surface permafrost and soil temperature profiles, we perform a large number of RASM simulations with prescribed atmospheric forcings (e.g. VIC in standalone mode in RASM) while varying the model soil depth, thickness of soil moisture layers, number of soil layers and the distribution of soil nodes. We compare modeled soil temperatures and ALT to observations from the Circumpolar Active Layer Monitoring (CALM) network. CALM observations include annual ALT observations as well as daily soil temperature measurements at three soil depths for three sites in Alaska. In the future, we will use our results to inform our modeling of permafrost dynamics in fully-coupled RASM simulations.

Response of eddy activities to localized diabatic heating in Held-Suarez simulations

NASA Astrophysics Data System (ADS)

Lin, Yanluan; Zhang, Jishi; Li, Xingrui; Deng, Yi

2018-01-01

Widespread air pollutions, such as black carbon over East Asia in recent years, could induce a localized diabatic heating, and thus lead to localized static stability and meridional temperature gradient (MTG) changes. Although effect of static stability and MTG on eddies has been addressed by the linear baroclinic instability theory, impacts of a localized heating on mid-latitude eddy activities have not been well explored and quantified. Via a series of idealized global Held-Suarez simulations with different magnitudes of localized heating at different altitudes and latitudes, responses of mid-latitude eddy activity and circulation to these temperature perturbations are systematically investigated. Climatologically, the localized heating in the lower atmosphere induces a wave-like response of eddy activity near the mid-latitude jet stream. Over the heating region, eddy activity tends to be weakening due to the increased static stability. However, there are cyclonic anomalies over the upstream and downstream of the heating region. The zonal mean eddy activity weakens along the baroclinic zone due to reduced MTG and increased static stability. Furthermore, the response of eddy activity increased as the heating magnitude is increased and moved to higher altitudes. The influence of the heating decreases as the heating is prescribed further away from the climatological mid-latitude jet. This implies that the localized heating is most effective over the region with the maximum baroclinicity. Besides, enhanced storm track downstream of the localized heating area found here suggests that increased aerosols over East Asia might strengthen the North Pacific storm track.

Latitudinal variability of large-scale coronal temperature and its association with the density and the global magnetic field

NASA Technical Reports Server (NTRS)

Guhathakurta, M.; Fisher, R. R.

1994-01-01

In this paper we utilize the latitiude distribution of the coronal temperature during the period 1984-1992 that was derived in a paper by Guhathakurta et al, 1993, utilizing ground-based intensity observations of the green (5303 A Fe XIV) and red (6374 A Fe X) coronal forbidden lines from the National Solar Observatory at Sacramento Peak, and establish it association with the global magnetic field and the density distributions in the corona. A determination of plasma temperature, T, was estimated from the intensity ratio Fe X/Fe XIV (where T is inversely proportional to the ratio), since both emission lines come from ionized states of Fe, and the ratio is only weakly dependent on density. We observe that there is a large-scale organization of the inferred coronal temperature distribution that is associated with the large-scale, weak magnetic field structures and bright coronal features; this organization tends to persist through most of the magnetic activity cycle. These high-temperature structures exhibit time-space characteristics which are similar to those of the polar crown filaments. This distribution differs in spatial and temporal characterization from the traditional picture of sunspot and active region evolution over the range of the sunspot cycle, which are manifestations of the small-scale, strong magnetic field regions.

Mid-latitude empirical model of the height distribution of atomic oxygen in the MLT region for different solar and geophysical conditions

NASA Astrophysics Data System (ADS)

Semenov, A.; Shefov, N.; Fadel, Kh.

The model of altitude distributions of atomic oxygen in the region of the mesopause and lower thermosphere (MLT) is constructed on the basis of empirical models of variations of the intensities, temperatures and altitudes of maximum of the layers of the emissions of atomic oxygen at 557.7 nm, hydroxyl and Atmospheric system of molecular oxygen. An altitude concentration distribution of neutral components is determined on the basis of systematization of the long-term data of temperature of the middle atmosphere from rocket, nightglow and ionospheric measurements at heights of 30-110 km in middle latitudes. They include dependence on a season, solar activity and a long-term trend. Examples of results of calculation for different months of year for conditions of the lower and higher solar activity are presented. With increasing of solar activity, the height of a layer of a maximum of atomic oxygen becomes lower, and the thickness of the layer increases. There is a high correlation between characteristics of a layer of atomic oxygen and a maximum of temperature at heights of the mesopause and lower thermosphere. This work is supported by grant of ISTC No. 2274.

Climatic change by cloudiness linked to the spatial variability of sea surface temperatures

NASA Technical Reports Server (NTRS)

Otterman, J.

1975-01-01

An active role in modifying the earth's climate is suggested for low cloudiness over the circumarctic oceans. Such cloudiness, linked to the spatial differences in ocean surface temperatures, was studied. The temporal variations from year to year of ocean temperature patterns can be pronounced and therefore, the low cloudiness over this region should also show strong temporal variations, affecting the albedo of the earth and therefore the climate. Photographs are included.

Interactive effects of water temperature and salinity on growth and mortality of eastern oysters, Crassostrea virginica: A meta-analysis using 40 years of monitoring data

USGS Publications Warehouse

Lowe, Michael R.; Sehlinger, Troy; Soniat, Thomas M.; LaPeyre, Megan K.

2017-01-01

Despite nearly a century of exploitation and scientific study, predicting growth and mortality rates of the eastern oyster (Crassostrea virginica) as a means to inform local harvest and management activities remains difficult. Ensuring that models reflect local population responses to varying salinity and temperature combinations requires locally appropriate models. Using long-term (1988 to 2015) monitoring data from Louisiana's public oyster reefs, we develop regionally specific models of temperature- and salinity-driven mortality (sack oysters only) and growth for spat (<25 mm), seed (25–75 mm), and sack (>75 mm) oyster size classes. The results demonstrate that the optimal combination of temperature and salinity where Louisiana oysters experience reduced mortality and fast growth rates is skewed toward lower salinities and higher water temperatures than previous models have suggested. Outside of that optimal range, oysters are commonly exposed to combinations of temperature and salinity that are correlated with high mortality and reduced growth. How these combinations affect growth, and to a lesser degree mortality, appears to be size class dependent. Given current climate predictions for the region and ongoing large-scale restoration activities in coastal Louisiana, the growth and mortality models are a critical step toward ensuring sustainable oyster reefs for long-term harvest and continued delivery of the ecological services in a changing environment.

A comparison of photospheric electric current and ultraviolet and X-ray emission in a solar active region

NASA Astrophysics Data System (ADS)

Haisch, B. M.; Bruner, M. E.; Hagyard, M. J.; Bonnet, R. M.

1986-01-01

This paper presents an extensive set of coordinated observations of a solar active region, taking into account spectroheliograms obtained with the aid of the Solar Maximum Mission (SMM) Ultraviolet Spectrometer Polarimeter (UVSP) instrument, SMM soft X-ray polychromator (XRP) raster maps, and high spatial resolution ultraviolet images of the sun in Lyman-alpha and in the 1600 A continuum. These data span together the upper solar atmosphere from the temperature minimum to the corona. The data are compared to maps of the inferred photospheric electric current derived from the Marshall Space Flight Center (MSFC) vector magnetograph observations. Some empirical correlation is found between regions of inferred electric current density and the brightest features in the ultraviolet continuum and to a lesser extent those seen in Lyman-alpha within an active region.

Electric Field-aided Selective Activation for Indium-Gallium-Zinc-Oxide Thin Film Transistors.

PubMed

Lee, Heesoo; Chang, Ki Soo; Tak, Young Jun; Jung, Tae Soo; Park, Jeong Woo; Kim, Won-Gi; Chung, Jusung; Jeong, Chan Bae; Kim, Hyun Jae

2016-10-11

A new technique is proposed for the activation of low temperature amorphous InGaZnO thin film transistor (a-IGZO TFT) backplanes through application of a bias voltage and annealing at 130 °C simultaneously. In this 'electrical activation', the effects of annealing under bias are selectively focused in the channel region. Therefore, electrical activation can be an effective method for lower backplane processing temperatures from 280 °C to 130 °C. Devices fabricated with this method exhibit equivalent electrical properties to those of conventionally-fabricated samples. These results are analyzed electrically and thermodynamically using infrared microthermography. Various bias voltages are applied to the gate, source, and drain electrodes while samples are annealed at 130 °C for 1 hour. Without conventional high temperature annealing or electrical activation, current-voltage curves do not show transfer characteristics. However, electrically activated a-IGZO TFTs show superior electrical characteristics, comparable to the reference TFTs annealed at 280 °C for 1 hour. This effect is a result of the lower activation energy, and efficient transfer of electrical and thermal energy to a-IGZO TFTs. With this approach, superior low-temperature a-IGZO TFTs are fabricated successfully.

Seasonal Temperature Pattern Indicating Martian Dust Storms

NASA Image and Video Library

2016-06-09

This graphic shows Martian atmospheric temperature data related to seasonal patterns in occurrence of large regional dust storms. The data shown here were collected by the Mars Climate Sounder instrument on NASA's Mars Reconnaissance Orbiter over the course of one-half of a Martian year, during 2012 and 2013. The color coding indicates daytime temperatures of a layer of the atmosphere centered about 16 miles (25 kilometers) above ground level, corresponding to the color-key bar at the bottom of the graphic. Three regional dust storms indicated by increased temperatures are labeled A, B and C. A similar sequence of three large regional dust storms has been seen in atmosphere-temperature data from five other Martian years. The vertical axis is latitude on Mars, from the north pole at the top to south pole at the bottom. Each graphed data point is an average for all Martian longitudes around the planet. The horizontal axis is the time of year, spanning from the beginning of Mars' southern-hemisphere spring (on the left) to the end of southern-hemisphere summer. This is the half of the year when large Martian dust storms are most active. http://photojournal.jpl.nasa.gov/catalog/PIA20746

Electron temperature maps of the low solar corona: ISCORE results from the total solar eclipse of 1 August 2008 in China

NASA Astrophysics Data System (ADS)

Reginald, Nelson L.; Davila, Joseph M.; St. Cyr, Orville C.; Rabin, Douglas M.

2017-06-01

We conducted an experiment in conjunction with the total solar eclipse of 1 August 2008 in China to determine the thermal electron temperature in the low solar corona close to the solar limb. The instrument, Imaging Spectrograph of Coronal Electrons (ISCORE), consisted of an 8 inch f/10 Schmidt Cassegrain telescope with a thermoelectrically cooled CCD camera at the focal plane. Results are electron temperatures of 1 MK at 1.08 R⊙ and 1.13 R⊙ from the Sun center in the polar and equatorial regions, respectively. This experiment confirms the results of an earlier experiment conducted in conjunction with the total eclipse of 29 March 2006 in Libya, and results are that at a given coronal height the electron temperature in the polar region is larger than at the equatorial region. In this paper we show the importance of using the correct photospheric spectrum pertinent to the solar activity phase at the time of the experiment, which is a required parameter for modeling the underlying theoretical concept for temperature interpretation of the measured intensity ratios using color filters.

A review of limits on microbial activity in the cryosphere: temperature and water availability

NASA Astrophysics Data System (ADS)

Bakermans, C.

2017-12-01

The extent of microbial activity in the cryosphere likely depends on many things: the presence of liquid water, an adequate energy and nutrient supply (amount and flux), the absence of damaging conditions, exposure to low temperatures, and the time to evolve adaptations to low temperature conditions. Determining the extent of microbial activity in the cryosphere is a challenge complicated by the reduced availability of liquid water as water freezes and the low rates of diffusion and reaction brought on by low temperatures. Despite these limitations, many studies have demonstrated that reproduction by microorganisms is possible at temperatures of -10 to -20°C and that metabolism continues to even lower temperatures of about -30°C. In addition, microcosm studies in frozen soils and permafrost have demonstrated respiration down to temperatures of -18°C and DNA synthesis at temperatures from 0 to -20°C. In the environment, low temperature conditions (and lack of liquid water) appear to limit microbial activity in a few places like Don Juan Pond and University Valley in Antarctica. Microorganisms may be metabolically active in Arctic permafrost, but metabolism may be so exceptionally slow as to escape detection. Given the slow metabolism expected and the short geological age of permafrost (3 million years at the longest), there is probably insufficient time for microorganisms to evolve to become better adapted to live at subfreezing temperatures. Indeed, terrestrial life may never have the chance to evolve to exploit the low temperature capabilities of its biomolecules in view of the limited times at which cold environments persist on Earth. These observational studies of microorganisms in low temperature environments of the Polar regions expose how the extent of microbial activity at low temperature is entangled with other factors (perhaps inextricably); how the lack of liquid water at low temperatures appears to be the true limit on activity at low temperatures, and not low temperature per se; and that time at low temperatures may limit cold adaptation of microorganisms.

Spectroscopy of Single Free Standing Quantum Wells

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

Williams, M D; Hollars, C W; Huser, T

2006-03-14

We investigated the interaction of quantum confined exciton states GaAs quantum wells with native surface states. Single molecule photoluminescence (PL) spectroscopy, developed by T. Huser at LLNL was used to probe the unique bare quantum wells in the free standing quantum well structure. The latter was developed by the M. D. Williams at Clark Atlanta University. The goals of the project during this budget cycle were to procure samples containing GaAs free standing QWs, identify suitable regions for PL analysis at Lawrence Livermore, analyze the structures at room temperature and at liquid nitrogen temperatures. The specific regions of interest onmore » the sample structures were identified by scanning electron microscopy at Clark Atlanta prior to transport to LLNL. Previous attempts at other facilities using NSOM, cathodoluminescence, and conventional PL showed little luminescence activity at room temperature from the 200 {angstrom} thick wells. This suggested either excess recombination due to surface states in the quantum well region or insufficient absorption length for photoluminescence. The literature suggested that the effect of the defects could be eliminated by reducing the sample temperature below their associated activation energies. In our previous subcontract work with LLNL, a significant amount of effort was expended to modify the apparatus to allow low temperature measurements. The modifications were not successful and we concluded that in order to do the measurements at low temperature we would need to purchase a commercial optical cryostat to get reliable results. Ms. Rochelle Bryant worked during the summer as an intern at LLNL on the project under the supervision of C. Hollars and in collaboration with T. Huser and found that PL emission could be obtained at room temperature. This was a surprising result as the literature and our experience shows that there is no PL emission from GaAs at room temperature. We speculate that this is due to the small interaction region excited by the laser source. We proceeded with the project using this new found room temperature capability and have analyzed the effect of various chemical species on the PL emission from the GaAs QWs. We were able to observe some significant intensity modifications of the PL spectra with chemical adsorbants. This progress holds promise for the development of this structure as a chemical or biological sensor.« less

Thermal regime of warm-dry permafrost in relation to ground surface temperature in the Source Areas of the Yangtze and Yellow rivers on the Qinghai-Tibet Plateau, SW China.

PubMed

Luo, Dongliang; Jin, Huijun; Wu, Qingbai; Bense, Victor F; He, Ruixia; Ma, Qiang; Gao, Shuhui; Jin, Xiaoying; Lü, Lanzhi

2018-03-15

Ecology, hydrology, and natural resources in the source areas of the Yangtze and Yellow rivers (SAYYR) are closely linked to interactions between climate and permafrost. However, a comprehensive study of the interactions is currently hampered by sparsely- and unevenly-distributed monitoring sites and limited field investigations. In this study, the thermal regime of warm-dry permafrost in the SAYYR was systematically analyzed based on extensive data collected during 2010-2016 of air temperature (T a ), ground surface temperature (GST) and ground temperature across a range of areas with contrasting land-surface characteristics. Mean annual T a (MAAT) and mean annual GST (MAGST) were regionally averaged at -3.19±0.71°C and -0.40±1.26°C. There is a close relationship between GST and T a (R 2 =0.8477) as obtained by a linear regression analysis with all available daily averages. The mean annual temperature at the bottom of the active layer (T TOP ) was regionally averaged at -0.72±1.01°C and mostly in the range of -1.0°C and 0°C except at Chalaping (~-2.0°C). Surface offset (MAGST-MAAT) was regionally averaged at 2.54±0.71°C. Thermal offset (T TOP -MAGST) was regionally averaged at -0.17±0.84°C, which was generally within -0.5°C and 0.5°C. Relatively consistent thermal conductivity between the thawed and frozen states of the soils may be responsible for the small thermal offset. Active layer thickness was generally smaller at Chalaping than that on other parts of the QTP, presumably due to smaller climatic continentality index and the thermal dampening of surface temperature variability under the presence of dense vegetation and thick peaty substrates. We conclude that the accurate mapping of permafrost on the rugged elevational QTP could be potentially obtained by correlating the parameters of GST, thermal offset, and temperature gradient in the shallow permafrost. Copyright © 2017 Elsevier B.V. All rights reserved.

Results from OSO-IV - The long term behavior of X-ray emitting regions.

NASA Technical Reports Server (NTRS)

Krieger, A.; Paolini, F.; Vaiana, G. S.; Webb, D.

1972-01-01

Analysis of images of the sun obtained with the aid of a grazing incidence X-ray telescope on board the OSO IV spacecraft in the 2.5 to 12-A waveband nearly continuously from Oct. 27, 1967, to May 12, 1968. The instrument had sufficient spatial resolution (one and four arc minutes) and temporal resolution (5 to 20 min) to estimate the spatial characteristics of X-ray emitting regions and to monitor the temporal behavior of individual active regions. Variations in the absence of flares of as much as a factor of 10 in the X-ray output of individual regions were observed, with typical durations ranging from several hours to several days. The X-ray time variations are related to observations at optical and radio wavelengths. The results are interpreted under the assumption that the X-ray time variations are caused by temperature changes in the coronal portions of active regions. The contribution of radiative losses to the energy budget of the coronal active region is estimated.

Thunderstorms observed by radio astronomy Explorer 1 over regions of low man made noise

NASA Technical Reports Server (NTRS)

Caruso, J. A.; Herman, J. R.

1974-01-01

Radio Astronomy Explorer (RAE) I observations of thunderstorms over regions of low man-made noise levels are analyzed to assess the satellite's capability for noise source differentiation. The investigation of storms over Australia indicates that RAE can resolve noise generation due to thunderstorms from the general noise background over areas of low man-made noise activity. Noise temperatures observed by RAE over stormy regions are on the average 10DB higher than noise temperatures over the same regions in the absence of thunderstorms. In order to determine the extent of noise contamination due to distant transmitters comprehensive three dimensional computer ray tracings were generated. The results indicate that generally, distant transmitters contribute negligibly to the total noise power, being 30DB or more below contributions arriving from an area immediately below the satellite.

Elevated-Confined Phase-Change Random Access Memory Cells

NASA Astrophysics Data System (ADS)

Lee; Koon, Hock; Shi; Luping; Zhao; Rong; Yang; Hongxin; Lim; Guan, Kian; Li; Jianming; Chong; Chong, Tow

2010-04-01

A new elevated-confined phase-change random access memory (PCRAM) cell structure to reduce power consumption was proposed. In this proposed structure, the confined phase-change region is sitting on top of a small metal column enclosed by a dielectric at the sides. Hence, more heat can be effectively sustained underneath the phase-change region. As for the conventional structure, the confined phase-change region is sitting directly above a large planar bottom metal electrode, which can easily conduct most of the induced heat away. From simulations, a more uniform temperature profile around the active region and a higher peak temperature at the phase-change layer (PCL) in an elevated-confined structure were observed. Experimental results showed that the elevated-confined PCRAM cell requires a lower programming power and has a better scalability than a conventional confined PCRAM cell.

Reconstructing fire history in central Mongolia from tree-rings

Treesearch

Amy E. Hessl; Uyanga Ariya; Peter Brown; Oyunsannaa Byambasuren; Tim Green; Gordon Jacoby; Elaine Kennedy Sutherland; Baatarbileg Nachin; R. Stockton Maxwell; Neil Pederson; Louis De Grandpre; Thomas Saladyga; Jacques C. Tardif

2012-01-01

Rising temperatures are expected to increase wildfire activity in many regions of the world. Over the last 60 years in Mongolia, mean annual temperatures have increased ~2°C and the recorded frequency and spatial extent of forest and steppe fires have increased. Few long records of fire history exist to place these recent changes in a historical perspective. The...

A study on the high temperature-dependence of the electrical properties in a solution-deposited zinc-tin-oxide thin-film transistor operated in the saturation region

NASA Astrophysics Data System (ADS)

Yu, Kyeong Min; Bae, Byung Seong; Jung, Myunghee; Yun, Eui-Jung

2016-06-01

We investigate the effects of high temperatures in the range of 292 - 393 K on the electrical properties of solution-processed amorphous zinc-tin-oxide (a-ZTO) thin-film transistors (TFTs) operated in the saturation region. The fabricated a-ZTO TFTs have a non-patterned bottom gate and top contact structure, and they use a heavily-doped Si wafer and SiO2 as a gate electrode and a gate insulator layer, respectively. In a-ZTO TFTs, the trap release energy ( E TR ) was deduced by using Maxwell-Boltzmann statistics. The decreasing E TR toward zero with increasing gate voltage (the density of trap states ( n s )) in the a-ZTO active layer can be attributed to a shift of the Fermi level toward the mobility edge with increasing gate voltage. The TFTs with low gate voltage (low n s ) exhibit multiple trap and release characteristics and show thermally-activated behavior. In TFTs with a high gate voltage (high n s ), however, we observe decreasing mobility and conductivity with increasing temperature at temperatures ranging from 303 to 363 K. This confirms that the E TR can drop to zero, indicating a shift of the Fermi level beyond the mobility edge. Hence, the mobility edge is detected at the cusp between thermally-activated transport and band transport.

1.55 um aluminum gallium indium arsenide strained MQW laser diodes

NASA Astrophysics Data System (ADS)

Yang, Chi

At the 1.55 mum eye-safe, telecommunications operating wavelength, semiconductor diode lasers must have low threshold currents and operate at high temperatures without thermoelectric coolers. Existing diode lasers in this wavelength range based on the GaInAsP/InP materials system are very sensitive to operating temperature. To obtain high temperature, high power 1.55 mum semiconductor diode lasers, the AlGaInAs/InP materials system with strained quantum well (QW) active regions was investigated with the goal of improving temperature performance. A set of lasers with active regions consisting of different numbers of QWs (2 to 4) and different QW strains (1.2% and 1.6%) were designed taking into account the quaternary alloy bandgap of AlGaInAs, the effect of strain on the bandgap, and the quantum size effects within the QW. The active region growth temperature was optimized using photoluminescence intensity. The wafers were first processed into broad-area lasers and measured under pulsed injection. The characteristic threshold current temperature, T0, for all AlGaInAs lasers was higher (60-70 K) than for GaInAsP lasers. No strong dependence of temperature parameters on strain was observed, while properties varied significantly with the number of QWs. With more QWs, both internal efficiency and T0 increases, but internal loss increases, reducing the characteristic temperature of the differential efficiency T1. The results show that uncooled laser operation at 1.55 mum is very promising with strained AlGaInAs QWs. Ridge waveguide devices demonstrated low threshold and high output power as well as good temperature performance under continuous wave operation. Devices with different ridge heights were fabricated from one wafer and their performance was compared. It was found that current spreading was significant in these devices and a simple current density-versus-applied voltage analysis was developed to determine the spreading factor. The analysis shows that the current spreading was not effectively limited until etching went below the doped cladding layer. A recombination coefficient analysis was performed to investigate the effect of strain on Auger recombination predicted by theory. An indirect method to infer both the nonradiative recombination coefficient and the Auger recombination coefficient was initially used. The measured values of the recombination coefficients were consistent with theoretical predictions and measurements based on other material systems. The Auger recombination was lower than expected, indicating that Auger recombination is reduced in these strained QWs. To understand the carrier dynamics, impedance measurements were carried out for the first time in AlGaInAs strained QW lasers. A small-signal, sub-threshold equivalent circuit model was derived from the laser rate equations to model the measured laser impedance. Several characteristic carrier lifetimes were obtained directly from these electrical impedance measurements. From the temperature dependence of the QW escape time, it was found that hole rather than electron leakage is dominant in the AlGaInAs system due to the relatively low valence band offset. This may explain why the improvement of T0 in AlGaInAs QW 1.55 mum active regions is limited.

Interdecadal modulation of the Atlantic Multi-decadal Oscillation (AMO) on southwest China's temperature over the past 250 years

NASA Astrophysics Data System (ADS)

Fang, Keyan; Guo, Zhengtang; Chen, Deliang; Wang, Lei; Dong, Zhipeng; Zhou, Feifei; Zhao, Yan; Li, Jinbao; Li, Yingjun; Cao, Xinguang

2018-05-01

The temperature gradient between southwestern China and Indian Ocean is one key driver of the Indian Summer Monsoon, suggesting the necessity to understand temperature variability in southwestern China. Contrary to the general warming experienced in most of China, a few regions in southwestern China have undergone a cooling trend since the 1950s. To place this cooling trend in a historical context, this study develops an Abies fabri tree-ring width chronology in the Sichuan Basin, the most populated region in southwest China. The chronology spans from 1590 to 2012, with its reliable portion from 1758 to 2012, by far the longest in the Sichuan Basin. To better extract regional climate signals encoded in tree rings with strong local disturbances, we incorporate climate signals of nearby tree-ring chronologies to generate a large-scale tree-ring chronology (LSC). The LSC shows higher correlations with temperature near the sampling site on Mount Emei and sea surface temperatures of the northern Atlantic Ocean than chronologies developed using traditional methods. The highest correlations between the LSC and temperature are found from current February to July in the Sichuan Basin for the period 1901-1950 (r = 0.70), with a sharp decrease afterwards. Interdecadal variations of the LSC match well with Atlantic Multi-decadal Oscillation reconstructions, except for the late nineteenth century and after 1980s. This study provides evidence that southwest China is a transitional region both affected by the interdecadal temperature variations of the northern Atlantic and Asian areas, although their influences weakened in recent possible due to enhanced human activities.

Joint NuSTAR and IRIS observation of a microflaring active region

NASA Astrophysics Data System (ADS)

Hannah, I. G.; Kleint, L.; Krucker, S.; Glesener, L.; Grefenstette, B.

2017-12-01

We present observations of a weakly microflaring active region observed in X-rays with NuSTAR, UV with IRIS and EUV with SDO/AIA. NuSTAR was pointed at this unnamed active region near the East limb between 23:27UT and 23:37UT 26-July-2016, finding mostly quiescent emission except for a small microflare about 23:35UT. The NuSTAR spectrum for the pre-microflare time (23:27UT to 23:34UT) is well fitted by a single thermal component of about 3MK and combined with SDO/AIA we can determine the differential emission measure (DEM), finding it, as expected, drops very sharply to higher temperatures. During the subsequent microflare, the increase in NuSTAR counts matches a little brightening loop observed with IRIS SJI 1400Å and SDO/AIA. Fortuitously the IRIS slit crosses this microflaring loop and we find an increased emission in Si IV 1394Å, Si IV 1403Å and O IV 1402Å but only average line widths and velocities. The NuSTAR microflare spectrum shows heating to higher temperatures and also allows us to investigate the energetics of this event.

The effect of urban heat island on Izmir's city ecosystem and climate.

PubMed

Corumluoglu, Ozsen; Asri, Ibrahim

2015-03-01

Depending on the researches done on urban landscapes, it is found that the heat island intensity caused by the activities in any city has some impact on the ecosystem of the region and on the regional climate. Urban areas located in arid and semiarid lands somehow represent heat increase when it is compared with the heat in the surrounding rural areas. Thus, cities located amid forested and temperate climate regions show moderate temperatures. The impervious surfaces let the rainfall leave the city lands faster than undeveloped areas. This effect reduces water's cooling effects on these lands. More significantly, if trees and other vegetations are rare in any region, it means less evapotranspiration-the process by which trees "exhale" water. Trees also contribute to the cooling of urban lands by their shade. Land cover and land use maps can easily be produced by processing of remote sensing satellites' images, like processing of Landsat's images. As a result of this process, urban regions can be distinguished from vegetation. Analyzed GIS data produced and supported by these images can be utilized to determine the impact of urban land on energy, water, and carbon balances at the Earth's surface. Here in this study, it is found that remote sensing technique with thermal images is a liable technique to asses where urban heat islands and hot spots are located in cities. As an application area, in Izmir, it was found that the whole city was in high level of surface temperature as it was over 28 °C during the summer times. Beside this, the highest temperature values which go up to 47 °C are obtained at industrial regions especially where the iron-steel factories and the related industrial activities are.

Spectroscopic Study of a Dark Lane and a Cool Loop in a Solar Limb Active Region by Hinode/EIS

NASA Astrophysics Data System (ADS)

Lee, K.; Imada, S.; Moon, Y.; Lee, J.

2012-12-01

We investigate a cool loop and a dark lane over a limb active region on 2007 March 14 by the Hinode/EUV Imaging Spectrometer (EIS). The cool loop is clearly seen in the EIS spectral lines formed at the transition region temperature (log T = 5.8). The dark lane is characterized by an elongated faint structure in coronal spectral lines (log T = 5.8 - 6.1) and rooted on a bright point. We examine their electron densities, Doppler velocities, and non-thermal velocities as a function of distance from the limb using the spectral lines formed at different temperatures (log T = 5.4 - 6.4). The electron densities of the cool loop and the dark lane are derived from the density sensitive line pairs of Mg VII, Fe XII, and Fe XIV spectra. Under the hydrostatic equilibrium and isothermal assumption, we determine their temperatures from the density scale height. Comparing the scale height temperatures to the peak formation temperatures of the spectral lines, we note that the scale height temperature of the cool loop is consistent with a peak formation temperature of the Mg VII (log T = 5.8) and the scale height temperature of the dark lane is close to a peak formation temperature of the Fe XII and Fe XIII (log T = 6.1 - 6.2). It is interesting to note that the structures of the cool loop and the dark lane are most visible in these temperature lines. While the non-thermal velocity in the cool loop slightly decreases (less than 7 km {s-1}) along the loop, that in the dark lane sharply falls off with height. The variation of non-thermal velocity with height in the cool loop and the dark lane is contrast to that in off-limb polar coronal holes which are considered as source of the fast solar wind. Such a decrease in the non-thermal velocity may be explained by wave damping near the solar surface or turbulence due to magnetic reconnection near the bright point.

Continental-Scale Temperature Reconstructions from the PAGES 2k Network

NASA Astrophysics Data System (ADS)

Kaufman, D. S.

2012-12-01

We present a major new synthesis of seven regional temperature reconstructions to elucidate the global pattern of variations and their association with climate-forcing mechanisms over the past two millennia. To coordinate the integration of new and existing data of all proxy types, the Past Global Changes (PAGES) project developed the 2k Network. It comprises nine working groups representing eight continental-scale regions and the oceans. The PAGES 2k Consortium, authoring this paper, presently includes 79 representatives from 25 countries. For this synthesis, each of the PAGES 2k working groups identified the proxy climate records for reconstructing past temperature and associated uncertainty using the data and methodologies that they deemed most appropriate for their region. The datasets are from 973 sites where tree rings, pollen, corals, lake and marine sediment, glacier ice, speleothems, and historical documents record changes in biologically and physically mediated processes that are sensitive to temperature change, among other climatic factors. The proxy records used for this synthesis are available through the NOAA World Data Center for Paleoclimatology. On long time scales, the temperature reconstructions display similarities among regions, and a large part of this common behavior can be explained by known climate forcings. Reconstructed temperatures in all regions show an overall long-term cooling trend until around 1900 C.E., followed by strong warming during the 20th century. On the multi-decadal time scale, we assessed the variability among the temperature reconstructions using principal component (PC) analysis of the standardized decadal mean temperatures over the period of overlap among the reconstructions (1200 to 1980 C.E.). PC1 explains 35% of the total variability and is strongly correlated with temperature reconstructions from the four Northern Hemisphere regions, and with the sum of external forcings including solar, volcanic, and greenhouse gases. PC2 captures 18% of the variability and is correlated most strongly with the Southern Hemisphere regions of Australasia and South America. PC3 captures 15% of the variability in the temperature reconstructions with a predominant loading from Antarctica. The timing of extremely warm and cold decades (10th percentiles) in each region were analyzed and compared with climate forcings. Only 22% of the regionally coldest decades can be ascribed to extreme minima in solar forcing, and 17% to volcanic forcing. The association between extremely warm regional temperatures and solar maxima is weaker than for cold temperatures and their corresponding solar minima. Spatially, volcanic forcing moderately increased the frequency of extremely cold decades in the Northern Hemisphere reconstructions, but had no significant effect in the Southern Hemisphere. Solar and volcanic impacts do not induce globally consistent decadal temperature shifts, but they increase the probability of cooling or warming at the continental scale. The majority of cold and warm decades identified here cannot be explained by changes in the records of volcanic activity or solar forcing. This indicates that at this timescale, prior to the anthropogenic buildup of greenhouse gases, unforced internal variability in the coupled ocean/atmosphere system was the dominant control on temperature variation.

Thermal shielding of an emerging active region

NASA Astrophysics Data System (ADS)

Régnier, S.

2012-08-01

Context. The interaction between emerging active regions and the pre-existing coronal magnetic field is important for better understanding the mechanisms of storage and release of magnetic energy from the convection zone to the high corona. Aims: We describe the first steps of an emerging active region within a pre-existing quiet-Sun corona in terms of the thermal and magnetic structure. Methods: We used unprecedented spatial, temporal and spectral coverage from the Atmospheric Imager Assembly (AIA) and from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). Results: Starting on 30 May 2010 at 17:00 UT, we followed the emerging active region AR11076 within a quiet-Sun region for 8 h. Using several SDO/AIA filters that cover temperatures from 50 000 K to 10 MK, we show that the emerging process is characterised by a thermal shield at the interface between the emerging flux and pre-existing quiet-Sun corona. Conclusions: The active region 11076 is a peculiar example of an emerging active region because (i) the polarities emerge in a photospheric quiet-Sun region near a supergranular-like distribution, and (ii) the polarities that form the bipolar emerging structure do not rotate with respect to each other, which indicates a slight twist in the emerging flux bundle. There is a thermal shield at the interface between the emerging active region and the pre-existing quiet-Sun region. The thermal shielding structure deduced from all SDO/AIA channels is strongly asymmetric between the two polarities of the active region, suggesting that the heating mechanism for one polarity is probably magnetic reconnection, whilst it is caused by increasing magnetic pressure for the opposite polarity. Appendix A and two movies are available in electronic form at http://www.aanda.org

The Heating of Solar Coronal Loops by Alfvén Wave Turbulence

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

Van Ballegooijen, A. A.; Asgari-Targhi, M.; Voss, A.

2017-11-01

In this paper we further develop a model for the heating of coronal loops by Alfvén wave turbulence (AWT). The Alfvén waves are assumed to be launched from a collection of kilogauss flux tubes in the photosphere at the two ends of the loop. Using a three-dimensional magnetohydrodynamic model for an active-region loop, we investigate how the waves from neighboring flux tubes interact in the chromosphere and corona. For a particular combination of model parameters we find that AWT can produce enough heat to maintain a peak temperature of about 2.5 MK, somewhat lower than the temperatures of 3–4 MKmore » observed in the cores of active regions. The heating rates vary strongly in space and time, but the simulated heating events have durations less than 1 minute and are unlikely to reproduce the observed broad differential emission measure distributions of active regions. The simulated spectral line nonthermal widths are predicted to be about 27 km s{sup −1}, which is high compared to the observed values. Therefore, the present AWT model does not satisfy the observational constraints. An alternative “magnetic braiding” model is considered in which the coronal field lines are subject to slow random footpoint motions, but we find that such long-period motions produce much less heating than the shorter-period waves launched within the flux tubes. We discuss several possibilities for resolving the problem of producing sufficiently hot loops in active regions.« less

Temperature independent infrared responsivity of a quantum dot quantum cascade photodetector

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

Wang, Feng-Jiao; Zhuo, Ning; Liu, Shu-Man, E-mail: liusm@semi.ac.cn

2016-06-20

We demonstrate a quantum dot quantum cascade photodetector with a hybrid active region of InAs quantum dots and an InGaAs quantum well, which exhibited a temperature independent response at 4.5 μm. The normal incident responsivity reached 10.3 mA/W at 120 K and maintained a value of 9 mA/W up to 260 K. It exhibited a specific detectivity above 10{sup 11} cm Hz{sup 1/2} W{sup −1} at 77 K, which remained at 10{sup 8} cm Hz{sup 1/2} W{sup −1} at 260 K. We ascribe the device's good thermal stability of infrared response to the three-dimensional quantum confinement of the InAs quantum dots incorporated in the active region.

THE HCN/HNC ABUNDANCE RATIO TOWARD DIFFERENT EVOLUTIONARY PHASES OF MASSIVE STAR FORMATION

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

Jin, Mihwa; Lee, Jeong-Eun; Kim, Kee-Tae, E-mail: mihwajin.sf@gmail.com, E-mail: jeongeun.lee@khu.ac.kr, E-mail: ktkim@kasi.re.kr

2015-07-20

Using the H{sup 13}CN and HN{sup 13}C J = 1–0 line observations, the abundance ratio of HCN/HNC has been estimated for different evolutionary stages of massive star formation: infrared dark clouds (IRDCs), high-mass protostellar objects (HMPOs), and ultracompact H ii regions (UCH iis). IRDCs were divided into “quiescent IRDC cores (qIRDCc)” and “active IRDC cores (aIRDCc),” depending on star formation activity. The HCN/HNC ratio is known to be higher at active and high temperature regions related to ongoing star formation, compared to cold and quiescent regions. Our observations toward 8 qIRDCc, 16 aIRDCc, 23 HMPOs, and 31 UCH iis showmore » consistent results; the ratio is 0.97 (±0.10), 2.65 (±0.88), 4.17 (±1.03), and 8.96 (±3.32) in these respective evolutionary stages, increasing from qIRDCc to UCH iis. The change of the HCN/HNC abundance ratio, therefore, seems directly associated with the evolutionary stages of star formation, which have different temperatures. One suggested explanation for this trend is the conversion of HNC to HCN, which occurs effectively at higher temperatures. To test the explanation, we performed a simple chemical model calculation. In order to fit the observed results, the energy barrier of the conversion must be much lower than the value provided by theoretical calculations.« less

Hydro-thermal processes and thermal offsets of peat soils in the active layer in an alpine permafrost region, NE Qinghai-Tibet plateau

NASA Astrophysics Data System (ADS)

Wang, Qingfeng; Jin, Huijun; Zhang, Tingjun; Cao, Bin; Peng, Xiaoqing; Wang, Kang; Xiao, Xiongxin; Guo, Hong; Mu, Cuicui; Li, Lili

2017-09-01

Observation data of the hydrothermal processes in the active layer are vital for the verification of permafrost formation and evolution, eco-hydrology, ground-atmosphere interactions, and climate models at various time and spatial scales. Based on measurements of ground temperatures in boreholes, of temperatures and moisture contents of soils in the active layer, and of the mean annual air temperatures at the Qilian, Yeniugou and Tuole meteorological stations in the upper Heihe River Basin (UHRB) and the adjacent areas, a series of observations were made concerning changes in the lower limit of permafrost (LLP) and the related hydrothermal dynamics of soils in the active layer. Because of the thermal diode effect of peat soils, the LLP (at 3600 m) was lower on the northern slope of the Eboling Mountains at the eastern branch of the UHRB than that (at 3650-3700 m) on the alluvial plain at the western branch of the UHRB. The mean temperature of soils at depths of 5 to 77 cm in the active layer on peatlands was higher during periods with subzero temperatures and lower during periods with above-zero temperatures in the vicinity of the LLP on the northern slope of the Eboling Mountains than those at the LLP at the western branch of the UHRB. The thawing and downward freezing rates of soils in the active layer near the LLP on the northern slope of the Eboling Mountains were 0.2 and 1.6 times those found at the LLP at the western branch of the UHRB. From early May to late August, the soil water contents at the depths of 20 to 60 cm in the active layer near the LLP on the northern slope of the Eboling Mountains were significantly lower than those found at the LLP at the western branch of the UHRB. The annual ranges of soil temperatures (ARSTs), mean annual soil temperatures (MASTs) in the active layer on peatlands, and the mean annual ground temperature (MAGT) at a depth of 14 m of the underlying permafrost were all significantly lower near the LLP on the northern slope of the Eboling Mountains. Moreover, the thermophysical properties of peat soils and high moisture contents in the active layer on peatlands resulted in the lower soil temperatures in the active layer close to the LLP on the northern slope of the Eboling Mountains than those found at the LLP at the western branch of the UHRB in the warm season, especially at the deeper depths (20-77 cm). They also resulted in the smaller freezing index (FI) and thawing index (TI) and larger FI/TI ratios of soils at the depths of 5 to 77 cm in the active layer near the LLP on the northern slope of the Eboling Mountains. In short, peatlands have unique thermophysical properties for reducing heat absorption in the warm season and for limiting heat release in the cold season as well. However, the permafrost zone has shrunk by 10-20 km along the major highways at the western branch of the UHRB since 1985, and a medium-scale retrogressive slump has occurred on the peatlands on the northern slope of the Eboling Mountains in recent decades. The results can provide basic data for further studies of the hydrological functions of different landscapes in alpine permafrost regions. Such studies can also enable evaluations and forecasts the hydrological impacts of changing frozen ground in the UHRB and of other alpine mountain regions in West China.

Satellite based assessment of recent permafrost extent and active layer trends over Alaska and Northwest Canada

NASA Astrophysics Data System (ADS)

Kim, Y.; Kimball, J. S.; PARK, H.; Yi, Y.

2017-12-01

Climate change in the Boreal-Arctic region has experienced greater surface air temperature (SAT) warming than the global average in recent decades, which is promoting permafrost thawing and active layer deepening. Permafrost extent (PE) and active layer thickness (ALT) are key environmental indicators of recent climate change, and strongly impact other eco-hydrological processes including land-atmosphere carbon exchange. We developed a new approach for regional estimation and monitoring of PE using daily landscape freeze-thaw (FT) records derived from satellite microwave (37 GHz) brightness temperature (Tb) observations. ALT was estimated within the PE domain using empirical modeling of land cover dependent edaphic factors and an annual thawing index derived from MODIS land surface temperature (LST) observations and reanalysis based surface air temperatures (SAT). The PE and ALT estimates were derived over the 1980-2016 satellite record and NASA ABoVE (Arctic Boreal Vulnerability Experiment) domain encompassing Alaska and Northwest Canada. The baseline model estimates were derived at 25-km resolution consistent with the satellite FT global record. Our results show recent widespread PE decline and deepening ALT trends, with larger spatial variability and model uncertainty along the southern PE boundary. Larger PE and ALT variability occurs over heterogeneous permafrost subzones characterized by dense vegetation, and variable snow cover and organic layer conditions. We also tested alternative PE and ALT estimates derived using finer (6-km) scale satellite Tb (36.5 GHz) and FT retrievals from a calibrated AMSR-E and AMSR2 sensor record. The PE and ALT results were compared against other independent observations, including process model simulations, in situ measurements, and permafrost inventory records. A model sensitivity analysis was conducted to evaluate snow cover, soil organic layer, and vegetation composition impacts to ALT. The finer delineation of permafrost and active layer conditions provides enhanced regional monitoring of PE and ALT changes over the ABoVE domain, including heterogeneous permafrost subzones.

Mass and energy flow in prominences

NASA Technical Reports Server (NTRS)

Poland, Arthur I.

1990-01-01

Mass and energy flow in quiescent prominences is considered based on the hypothesis that active region prominences have a different structure and thus different mass and energy flow characteristics. Several important physical parameters have been plotted using the computational model, representing the evolutionary process after the prominence formation. The temperature, velocity, conductive flux, and enthalpy flux are plotted against distance from the highest point in the loop to the coolest part of the prominence. It is shown that the maximum velocity is only about 5 km/s. The model calculations indicate that the transition region of prominences is dominated by complex processes. It is necessary to take into account mass flow at temperatures below 200,000 K, and both mass flow and optical depth effects in hydrogen at temperatures below 30,000 K. Both of these effects lead to a less steep temperature gradient through the prominence corona interface than can be obtained from the conduction alone.

Regionalization of surface lipids in insects

PubMed Central

Wang, Yiwen; Yu, Zhitao; Zhang, Jianzhen; Moussian, Bernard

2016-01-01

Cuticular hydrocarbons (CHCs) play a critical role in the establishment of the waterproof barrier that prevents dehydration and wetting in insects. While rich data are available on CHC composition in different species, we know little about their distribution and organization. Here, we report on our studies of the surface barrier of the fruit fly Drosophila melanogaster applying a newly developed Eosin Y staining method. The inert Eosin Y penetrates different regions of the adult body at distinct temperatures. By contrast, the larval body takes up the dye rather uniformly and gradually with increasing temperature. Cooling down specimens to 25°C after incubation at higher temperatures restores impermeability. Eosin Y penetration is also sensitive to lipid solvents such as chloroform indicating that permeability depends on CHCs. As in D. melanogaster adult flies, Eosin Y penetration is regionalized in Tenebrio molitor larvae, whereas it is not in Locusta migratoria nymphs. Regionalization of the fly surface implies tissue-specific variation of the genetic or biochemical programmes of CHC production and deposition. The Eosin Y-based map of CHC distribution may serve to identify the respective factors that are activated to accommodate ecological needs. PMID:27170708

Mutational analysis of Escherichia coli heat shock transcription factor sigma 32 reveals similarities with sigma 70 in recognition of the -35 promoter element and differences in promoter DNA melting and -10 recognition.

PubMed

Kourennaia, Olga V; Tsujikawa, Laura; Dehaseth, Pieter L

2005-10-01

Upon the exposure of Escherichia coli to high temperature (heat shock), cellular levels of the transcription factor sigma32 rise greatly, resulting in the increased formation of the sigma32 holoenzyme, which is capable of transcription initiation at heat shock promoters. Higher levels of heat shock proteins render the cell better able to cope with the effects of higher temperatures. To conduct structure-function studies on sigma32 in vivo, we have carried out site-directed mutagenesis and employed a previously developed system involving sigma32 expression from one plasmid and a beta-galactosidase reporter gene driven by the sigma32-dependent groE promoter on another in order to monitor the effects of single amino acid substitutions on sigma32 activity. It was found that the recognition of the -35 region involves similar amino acid residues in regions 4.2 of E. coli sigma32 and sigma70. Three conserved amino acids in region 2.3 of sigma32 were found to be only marginally important in determining activity in vivo. Differences between sigma32 and sigma70 in the effects of mutation in region 2.4 on the activities of the two sigma factors are consistent with the pronounced differences between both the amino acid sequences in this region and the recognized promoter DNA sequences.

Integration of Photothermal Effect and Heat Insulation to Efficiently Reduce Reaction Temperature of CO2 Hydrogenation.

PubMed

Zhang, Wenbo; Wang, Liangbing; Wang, Kaiwen; Khan, Munir Ullah; Wang, Menglin; Li, Hongliang; Zeng, Jie

2017-02-01

The photothermal effect is applied in CO 2 hydrogenation to reduce the reaction temperature under illumination by encapsulating Pt nanocubes and Au nanocages into a zeolitic imidazolate framework (ZIF-8). Under illumination, the heat generated by the photothermal effect of Au nanocages is mainly insulated in the ZIF-8 to form a localized high-temperature region, thereby improving the catalytic activity of Pt nanocubes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transequatorial loops interconnecting McMath regions 12472 and 12474

NASA Technical Reports Server (NTRS)

Svestka, Z.; Krieger, A. S.; Chase, R. C.; Howard, R.

1977-01-01

The paper reviews the life history of one transequatorial loop in a system observed in soft X-rays for at least 1.5 days and which interconnected a newly born active region with an old region. The birth of the selected loop is discussed along with properties of the interconnected active regions, sharpening and brightening of the loop, decay of the loop system, and physical relations between the interconnected regions. It is concluded that: (1) the loop was most probably born via reconnection of magnetic-field lines extending from the two active regions toward the equator, which occurred later than 33 hr after the younger region was born; (2) the fully developed interconnection was composed of several loops, all of which appeared to be rooted in a spotless magnetic hill of preceding northern polarity but were spread over two separate spotty regions of southern polarity in the magnetically complex new region; (3) the loop electron temperature increased from 2.1 million to 3.1 million K in one to three hours when the loop system brightened; and (4) the loops became twisted during the brightening, possibly due to their rise in the corona while remaining rooted in moving magnetic features in the younger region.

An observationally-driven kinetic approach to coronal heating

NASA Astrophysics Data System (ADS)

Moraitis, K.; Toutountzi, A.; Isliker, H.; Georgoulis, M.; Vlahos, L.; Chintzoglou, G.

2016-11-01

Aims: Coronal heating through the explosive release of magnetic energy remains an open problem in solar physics. Recent hydrodynamical models attempt an investigation by placing swarms of "nanoflares" at random sites and times in modeled one-dimensional coronal loops. We investigate the problem in three dimensions, using extrapolated coronal magnetic fields of observed solar active regions. Methods: We applied a nonlinear force-free field extrapolation above an observed photospheric magnetogram of NOAA active region (AR) 11 158. We then determined the locations, energy contents, and volumes of "unstable" areas, namely areas prone to releasing magnetic energy due to locally accumulated electric current density. Statistical distributions of these volumes and their fractal dimension are inferred, investigating also their dependence on spatial resolution. Further adopting a simple resistivity model, we inferred the properties of the fractally distributed electric fields in these volumes. Next, we monitored the evolution of 105 particles (electrons and ions) obeying an initial Maxwellian distribution with a temperature of 10 eV, by following their trajectories and energization when subjected to the resulting electric fields. For computational convenience, the length element of the magnetic-field extrapolation is 1 arcsec, or 725 km, much coarser than the particles' collisional mean free path in the low corona (0.1-1 km). Results: The presence of collisions traps the bulk of the plasma around the unstable volumes, or current sheets (UCS), with only a tail of the distribution gaining substantial energy. Assuming that the distance between UCS is similar to the collisional mean free path we find that the low active-region corona is heated to 100-200 eV, corresponding to temperatures exceeding 2 MK, within tens of seconds for electrons and thousands of seconds for ions. Conclusions: Fractally distributed, nanoflare-triggening fragmented UCS in the active-region corona can heat electrons and ions with minor enhancements of the local resistivity. This statistical result is independent from the nature of the extrapolation and the spatial resolution of the modeled active-region corona. This finding should be coupled with a complete plasma treatment to determine whether a quasi-steady temperature similar to that of the ambient corona can be maintained, either via a kinetic or via a hybrid, kinetic and fluid, plasma treatment. The finding can also be extended to the quiet solar corona, provided that the currently undetected nanoflares are frequent enough to account for the lower (compared to active regions) energy losses in this case.

Monitoring changes in body surface temperature associated with treadmill exercise in dogs by use of infrared methodology.

PubMed

Rizzo, Maria; Arfuso, Francesca; Alberghina, Daniela; Giudice, Elisabetta; Gianesella, Matteo; Piccione, Giuseppe

2017-10-01

The aim of this study was to evaluate the influence of moderate treadmill exercise session on body surface and core temperature in dog measured by means of two infrared instruments. Ten Jack Russell Terrier/Miniature Pinscher mixed-breed dogs were subjected to 15min of walking, 10min of trotting and 10min of gallop. At every step, body surface temperature (T surface ) was measured on seven regions (neck, shoulder, ribs, flank, back, internal thigh and eye) using two different methods, a digital infrared camera (ThermaCam P25) and a non-contact infrared thermometer (Infrared Thermometer THM010-VT001). Rectal temperature (T rectal ) and blood samples were collected before (T0) and after exercise (T3). Blood samples were tested for red blood cell (RBC), hemoglobin concentration (Hb) and hematocrit (Hct). A significant effect of exercise in all body surface regions was found, as measured by both infrared methods. The temperature obtained in the eye and the thigh area were higher with respect to the other studied regions throughout the experimental period (P<0.0001). RBC, Hb, Hct and T rectal values were higher at T3 (P<0.05). Statistically significant higher temperature values measured by infrared thermometer was found in neck, shoulder, ribs, flank, back regions respect to the values obtained by digital infrared camera (P<0.0001). The results obtained in this study showed that both internal and surface temperatures are influenced by physical exercise probably due to muscle activity and changes in blood flow in dogs. Both infrared instruments used in this study have proven to be useful in detecting surface temperature variations of specific body regions, however factors including type and color of animal hair coat must be taken into account in the interpretation of data obtained by thermography methodology. Copyright © 2017 Elsevier Ltd. All rights reserved.

Behavioral responses of Atlantic cod to sea temperature changes.

PubMed

Freitas, Carla; Olsen, Esben Moland; Moland, Even; Ciannelli, Lorenzo; Knutsen, Halvor

2015-05-01

Understanding responses of marine species to temperature variability is essential to predict impacts of future climate change in the oceans. Most ectotherms are expected to adjust their behavior to avoid extreme temperatures and minimize acute changes in body temperature. However, measuring such behavioral plasticity in the wild is challenging. Combining 4 years of telemetry-derived behavioral data on juvenile and adult (30-80 cm) Atlantic cod (Gadus morhua), and in situ ocean temperature measurements, we found a significant effect of sea temperature on cod depth use and activity level in coastal Skagerrak. During summer, cod were found in deeper waters when sea surface temperature increased. Further, this effect of temperature was stronger on larger cod. Diel vertical migration, which consists in a nighttime rise to shallow feeding habitats, was stronger among smaller cod. As surface temperature increased beyond ∼15°C, their vertical migration was limited to deeper waters. In addition to larger diel vertical migrations, smaller cod were more active and travelled larger distances compared to larger specimens. Cold temperatures during winter tended, however, to reduce the magnitude of diel vertical migrations, as well as the activity level and distance moved by those smaller individuals. Our findings suggest that future and ongoing rises in sea surface temperature may increasingly deprive cod in this region from shallow feeding areas during summer, which may be detrimental for local populations of the species.

Behavioral responses of Atlantic cod to sea temperature changes

PubMed Central

Freitas, Carla; Olsen, Esben Moland; Moland, Even; Ciannelli, Lorenzo; Knutsen, Halvor

2015-01-01

Understanding responses of marine species to temperature variability is essential to predict impacts of future climate change in the oceans. Most ectotherms are expected to adjust their behavior to avoid extreme temperatures and minimize acute changes in body temperature. However, measuring such behavioral plasticity in the wild is challenging. Combining 4 years of telemetry-derived behavioral data on juvenile and adult (30–80 cm) Atlantic cod (Gadus morhua), and in situ ocean temperature measurements, we found a significant effect of sea temperature on cod depth use and activity level in coastal Skagerrak. During summer, cod were found in deeper waters when sea surface temperature increased. Further, this effect of temperature was stronger on larger cod. Diel vertical migration, which consists in a nighttime rise to shallow feeding habitats, was stronger among smaller cod. As surface temperature increased beyond ∼15°C, their vertical migration was limited to deeper waters. In addition to larger diel vertical migrations, smaller cod were more active and travelled larger distances compared to larger specimens. Cold temperatures during winter tended, however, to reduce the magnitude of diel vertical migrations, as well as the activity level and distance moved by those smaller individuals. Our findings suggest that future and ongoing rises in sea surface temperature may increasingly deprive cod in this region from shallow feeding areas during summer, which may be detrimental for local populations of the species. PMID:26045957

A role for the thermal environment in defining co-stimulation requirements for CD4+ T cell activation

PubMed Central

Zynda, Evan R; Grimm, Melissa J; Yuan, Min; Zhong, Lingwen; Mace, Thomas A; Capitano, Maegan; Ostberg, Julie R; Lee, Kelvin P; Pralle, Arnd; Repasky, Elizabeth A

2015-01-01

Maintenance of normal core body temperature is vigorously defended by long conserved, neurovascular homeostatic mechanisms that assist in heat dissipation during prolonged, heat generating exercise or exposure to warm environments. Moreover, during febrile episodes, body temperature can be significantly elevated for at least several hours at a time. Thus, as blood cells circulate throughout the body, physiologically relevant variations in surrounding tissue temperature can occur; moreover, shifts in core temperature occur during daily circadian cycles. This study has addressed the fundamental question of whether the threshold of stimulation needed to activate lymphocytes is influenced by temperature increases associated with physiologically relevant increases in temperature. We report that the need for co-stimulation of CD4+ T cells via CD28 ligation for the production of IL-2 is significantly reduced when cells are exposed to fever-range temperature. Moreover, even in the presence of sufficient CD28 ligation, provision of extra heat further increases IL-2 production. Additional in vivo and in vitro data (using both thermal and chemical modulation of membrane fluidity) support the hypothesis that the mechanism by which temperature modulates co-stimulation is linked to increases in membrane fluidity and membrane macromolecular clustering in the plasma membrane. Thermally-regulated changes in plasma membrane organization in response to physiological increases in temperature may assist in the geographical control of lymphocyte activation, i.e., stimulating activation in lymph nodes rather than in cooler surface regions, and further, may temporarily and reversibly enable CD4+ T cells to become more quickly and easily activated during times of infection during fever. PMID:26131730

Hygroscopic salts and the potential for life on Mars.

PubMed

Davila, Alfonso F; Duport, Luis Gago; Melchiorri, Riccardo; Jänchen, Jochen; Valea, Sergio; de Los Rios, Asunción; Fairén, Alberto G; Möhlmann, Diedrich; McKay, Christopher P; Ascaso, Carmen; Wierzchos, Jacek

2010-01-01

Hygroscopic salts have been detected in soils in the northern latitudes of Mars, and widespread chloride-bearing evaporitic deposits have been detected in the southern highlands. The deliquescence of hygroscopic minerals such as chloride salts could provide a local and transient source of liquid water that would be available for microorganisms on the surface. This is known to occur in the Atacama Desert, where massive halite evaporites have become a habitat for photosynthetic and heterotrophic microorganisms that take advantage of the deliquescence of the salt at certain relative humidity (RH) levels. We modeled the climate conditions (RH and temperature) in a region on Mars with chloride-bearing evaporites, and modeled the evolution of the water activity (a(w)) of the deliquescence solutions of three possible chloride salts (sodium chloride, calcium chloride, and magnesium chloride) as a function of temperature. We also studied the water absorption properties of the same salts as a function of RH. Our climate model results show that the RH in the region with chloride-bearing deposits on Mars often reaches the deliquescence points of all three salts, and the temperature reaches levels above their eutectic points seasonally, in the course of a martian year. The a(w) of the deliquescence solutions increases with decreasing temperature due mainly to the precipitation of unstable phases, which removes ions from the solution. The deliquescence of sodium chloride results in transient solutions with a(w) compatible with growth of terrestrial microorganisms down to 252 K, whereas for calcium chloride and magnesium chloride it results in solutions with a(w) below the known limits for growth at all temperatures. However, taking the limits of a(w) used to define special regions on Mars, the deliquescence of calcium chloride deposits would allow for the propagation of terrestrial microorganisms at temperatures between 265 and 253 K, and for metabolic activity (no growth) at temperatures between 253 and 233 K.

Early evolution of an X-ray emitting solar active region

NASA Technical Reports Server (NTRS)

Wolfson, C. J.; Acton, L. W.; Leibacher, J. W.; Roethig, D. T.

1977-01-01

The birth and early evolution of a solar active region has been investigated using X-ray observations from the mapping X-ray heliometer on board the OSO-8 spacecraft. X-ray emission is observed within three hours of the first detection of H-alpha plage. At that time, a plasma temperature of four million K in a region having a density on the order of 10 to the 10th power per cu cm is inferred. During the fifty hours following birth almost continuous flares or flare-like X-ray bursts are superimposed on a monotonically increasing base level of X-ray emission produced by the plasma. If the X-rays are assumed to result from heating due to dissipation of current systems or magnetic field reconnection, it may be concluded that flare-like X-ray emission soon after active region birth implies that the magnetic field probably emerges in a stressed or complex configuration.

Identification and analysis of structures in the corona from X-ray photography

NASA Technical Reports Server (NTRS)

Vaiana, G. S.; Krieger, A. S.; Timothy, A. F.

1973-01-01

This paper summarizes the results of a program of rocket observations of the solar corona with grazing incidence X-ray telescopes. A series of five flights of a Kanigen-surfaced telescope with a few arc seconds resolution, together with the first flight of a newer telescope have resulted in the identification of six classes of coronal structures observable in the X-ray photographs. These are: active regions, active region interconnections, large loop structures associated with unipolar magnetic regions, coronal holes, coronal bright points, and the structures surrounding filament cavities. Two solar flares have been observed. The methods involved in deriving coronal temperature and density information from X-ray photographs are described and the analysis of a bright active region (McMath plage 11035) observed at the west limb on November 24, 1970 is presented as an example of these techniques.

Simultaneous Solar Maximum Mission and Very Large Array (VLA) observations of solar active regions

NASA Technical Reports Server (NTRS)

Lang, K. R.

1985-01-01

Simultaneous observations of solar active regions with the Solar Maximum Mission (SMM) Satellite and the Very Large Array (VLA) have been obtained and analyzed. Combined results enhance the scientific return for beyond that expeted from using either SMM or VLA alone. A total of two weeks of simultaneous SMM/VLA data were obtained. The multiple wavelength VLA observations were used to determine the temperature and magnetic structure at different heights within coronal loops. These data are compared with simultaneous SMM observations. Several papers on the subject are in progress. They include VLA observations of compact, transient sources in the transition region; simultaneous SMM/VLA observations of the coronal loops in one active region and the evolution of another one; and sampling of the coronal plasma using thermal cyclotron lines (magnetic field - VLA) and soft X ray spectral lines (electron density and electron temperaure-SMM).

Comparison of photospheric electric current and ultraviolet and x-ray emission in a solar active region

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

Haisch, B.M.; Bruner, M.E.; Hagyard, M.J.

This paper presents an extensive set of coordinated observations of a solar active region, taking into account spectroheliograms obtained with the aid of the Solar Maximum Mission (SMM) Ultraviolet Spectrometer Polarimeter (UVSP) instrument, SMM soft x-ray polychromator (XRP) raster maps, and high spatial resolution ultraviolet images of the sun in Lyman-alpha and in the 1600 A continuum. These data span together the upper solar atmosphere from the temperature minimum to the corona. The data are compared to maps of the inferred photospheric electric current derived from the Marshall Space Flight Center (MSFC) vector magnetograph observations. Some empirical correlation is foundmore » between regions of inferred electric current density and the brightest features in the ultraviolet continuum and to a lesser extent those seen in Lyman-alpha within an active region. 29 references.« less

Ground-based Observations for the Upper Atmosphere at King Sejong Station, Antarctica

NASA Astrophysics Data System (ADS)

Jee, Geonhwa; Kim, Jeong-Han; Lee, Changsup; Kim, Yong Ha

2014-06-01

Since the operation of the King Sejong Station (KSS) started in Antarctic Peninsula in 1989, there have been continuous efforts to perform the observation for the upper atmosphere. The observations during the initial period of the station include Fabry-Perot Interferometer (FPI) and Michelson Interferometer for the mesosphere and thermosphere, which are no longer in operation. In 2002, in collaboration with York University, Canada, the Spectral Airglow Temperature Imager (SATI) was installed to observe the temperature in the mesosphere and lower thermosphere (MLT) region and it has still been producing the mesopause temperature data until present. The observation was extended by installing the meteor radar in 2007 to observe the neutral winds and temperature in the MLT region during the day and night in collaboration with Chungnam National University. We also installed the all sky camera in 2008 to observe the wave structures in the MLT region. All these observations are utilized to study on the physical characteristics of the MLT region and also on the wave phenomena such as the tide and gravity wave in the upper atmosphere over KSS that is well known for the strong gravity wave activity. In this article, brief introductions for the currently operating instruments at KSS will be presented with their applications for the study of the upper atmosphere

Does temperature nudging overwhelm aerosol radiative effects in regional integrated climate models?

NASA Astrophysics Data System (ADS)

He, Jian; Glotfelty, Timothy; Yahya, Khairunnisa; Alapaty, Kiran; Yu, Shaocai

2017-04-01

Nudging (data assimilation) is used in many regional integrated meteorology-air quality models to reduce biases in simulated climatology. However, in such modeling systems, temperature changes due to nudging could compete with temperature changes induced by radiatively active and hygroscopic short-lived tracers leading to two interesting dilemmas: when nudging is continuously applied, what are the relative sizes of these two radiative forces at regional and local scales? How do these two forces present in the free atmosphere differ from those present at the surface? This work studies these two issues by converting temperature changes due to nudging into pseudo radiative effects (PRE) at the surface (PRE_sfc), in troposphere (PRE_atm), and at the top of atmosphere (PRE_toa), and comparing PRE with the reported aerosol radiative effects (ARE). Results show that the domain-averaged PRE_sfc is smaller than ARE_sfc estimated in previous studies and this work, but could be significantly larger than ARE_sfc at local scales. PRE_atm is also much smaller than ARE_atm. These results indicate that appropriate nudging methodology could be applied to the integrated models to study aerosol radiative effects at continental/regional scales, but it should be treated with caution for local scale applications.

Does temperature nudging overwhelm aerosol radiative ...

EPA Pesticide Factsheets

For over two decades, data assimilation (popularly known as nudging) methods have been used for improving regional weather and climate simulations by reducing model biases in meteorological parameters and processes. Similar practice is also popular in many regional integrated meteorology-air quality models that include aerosol direct and indirect effects. However in such multi-modeling systems, temperature changes due to nudging can compete with temperature changes induced by radiatively active & hygroscopic short-lived tracers leading to interesting dilemmas: From weather and climate prediction’s (retrospective or future) point of view when nudging is continuously applied, is there any real added benefit of using such complex and computationally expensive regional integrated modeling systems? What are the relative sizes of these two competing forces? To address these intriguing questions, we convert temperature changes due to nudging into radiative fluxes (referred to as the pseudo radiative forcing, PRF) at the surface and troposphere, and compare the net PRF with the reported aerosol radiative forcing. Results indicate that the PRF at surface dominates PRF at top of the atmosphere (i.e., the net). Also, the net PRF is about 2-4 times larger than estimated aerosol radiative forcing at regional scales while it is significantly larger at local scales. These results also show large surface forcing errors at many polluted urban sites. Thus, operational c

The great 2006 heat wave over California and Nevada: Signal of an increasing trend

USGS Publications Warehouse

Gershunov, A.; Cayan, D.R.; Iacobellis, S.F.

2009-01-01

Most of the great California-Nevada heat waves can be classified into primarily daytime or nighttime events depending on whether atmospheric conditions are dry or humid. A rash of nighttime-accentuated events in the last decade was punctuated by an unusually intense case in July 2006, which was the largest heat wave on record (1948-2006). Generally, there is a positive trend in heat wave activity over the entire region that is expressed most strongly and clearly in nighttime rather than daytime temperature extremes. This trend in nighttime heat wave activity has intensified markedly since the 1980s and especially since 2000. The two most recent nighttime heat waves were also strongly expressed in extreme daytime temperatures. Circulations associated with great regional heat waves advect hot air into the region. This air can be dry or moist, depending on whether a moisture source is available, causing heat waves to be expressed preferentially during day or night. A remote moisture source centered within a marine region west of Baja California has been increasing in prominence because of gradual sea surface warming and a related increase in atmospheric humidity. Adding to the very strong synoptic dynamics during the 2006 heat wave were a prolonged stream of moisture from this southwestern source and, despite the heightened humidity, an environment in which afternoon convection was suppressed, keeping cloudiness low and daytime temperatures high. The relative contributions of these factors and possible relations to global warming are discussed. ?? 2009 American Meteorological Society.

Permafrost and active layer monitoring in the maritime Antarctic: Preliminary results from CALM sites on Livingston and Deception Islands

USGS Publications Warehouse

Ramos, M.; Vieira, G.; Blanco, J.J.; Hauck, C.; Hidalgo, M.A.; Tome, D.; Nevers, M.; Trindade, A.

2007-01-01

This paper describes results obtained from scientific work and experiments performed on Livingston and Deception Islands. Located in the South Shetland Archipelago, these islands have been some of the most sensitive regions over the last 50 years with respect to climate change with a Mean Annual Air Temperature (MAAT) close to -2 ºC. Three Circumpolar Active Layer Monitoring (CALM) sites were installed to record the thermal regime and the behaviour of the active layer in different places with similar climate, but with different soil composition, porosity, and water content. The study’s ultimate aim is to document the influence of climate change on permafrost degradation. Preliminary results, obtained in 2006, on maximum active-layer thickness (around 40 cm in the CALM of Deception Island), active layer temperature evolution, snow thickness, and air temperatures permit early characterization of energy exchange mechanisms between the ground and the atmosphere in the CALM-S sites.

A simplified model for glass formation

NASA Technical Reports Server (NTRS)

Uhlmann, D. R.; Onorato, P. I. K.; Scherer, G. W.

1979-01-01

A simplified model of glass formation based on the formal theory of transformation kinetics is presented, which describes the critical cooling rates implied by the occurrence of glassy or partly crystalline bodies. In addition, an approach based on the nose of the time-temperature-transformation (TTT) curve as an extremum in temperature and time has provided a relatively simple relation between the activation energy for viscous flow in the undercooled region and the temperature of the nose of the TTT curve. Using this relation together with the simplified model, it now seems possible to predict cooling rates using only the liquidus temperature, glass transition temperature, and heat of fusion.

Landscape and hydrologic changes in the permafrost regions of the Western Canadian Arctic

NASA Astrophysics Data System (ADS)

Marsh, P.

2012-12-01

The Western Canadian Arctic, in the vicinity of the Mackenzie River Delta, is characterized by long cold winters, short summers, low precipitation, thin organic soils, and ice-rich continuous permafrost. Over the last few decades, this region has undergone dramatic changes in climate, with warming air temperature and decreasing winter and summer precipitation. This has resulted in various landscape changes, including the warming of the upper layers of the permafrost, deepening of the active layer, drainage of permafrost affected lakes, an ongoing change from tundra to shrub tundra, and earlier spring breakup of streams, rivers and lakes. However, interactions between climate, hydrology, snow, and vegetation greatly affect both the spatial and temporal changes to the permafrost and hydrology of this region. Knowledge of these changes is important to the understanding of methane dynamics in this permafrost landscape, and for predicting future changes. Two examples of observed landscape change will be discussed. First, ground based observations and analysis of air photo images has demonstrated that shrub expansion is not uniform across the landscape, but instead is characterized by shrub patches of varying size. This patchiness is likely related to existing variations in soil temperature and moisture, active layer depth, snowcover, and tundra fires. As shrub patches further develop, they impact soil temperature and active layer depth. For example, small patches of shrubs typically have snow depths that are deeper than surrounding tundra areas due to the accumulation of blowing snow, and as a result have much warmer soil temperatures and deeper active layers. In contrast to these small shrub patches, large shrub patches have snow depths only slightly larger than found in the surrounding tundra and therefore only slightly warmer winter soil temperatures. However, shading of the surface during the summer may result in cooler summer soil temperatures. The overall effect of large shrub patches may be either deeper or shallower active layer depths than the surrounding tundra areas, depending on the leaf area index, the degree of shrub bending during the winter, and snow accumulation. Second, in contrast to many areas in Alaska and Siberia where increased rates of lake drainage have been reported, the rate of lake drainage in the Western Canadian Arctic has been decreasing over the past 50 years. The primary factors causing lake drainage in this region are high lake levels and winter cracking of ice wedges in the area immediately around the lake. Hydrologic modelling has suggested that summer lake levels have not changed significantly over the last 50 years, and therefore are not responsible for the decrease in drainage. However, the role of factors such as snow dams at lake outlets that result in high spring water levels, or the offsetting factors of warmer, but less snowy winters on ice wedge cracking are not well understood. As a result, further research is required to better understand how these lakes will respond to future changes in climate. Given the potential changes to methane dynamics in areas of changing permafrost, there is an urgent need to better understand ongoing, and future, changes in the landscape of these permafrost regions.

Conformal thermal therapy using planar ultrasound transducers and adaptive closed-loop MR temperature control: demonstration in gel phantoms and ex vivo tissues

NASA Astrophysics Data System (ADS)

Tang, K.; Choy, V.; Chopra, R.; Bronskill, M. J.

2007-05-01

MRI-guided transurethral ultrasound therapy offers a minimally invasive approach for the treatment of localized prostate cancer. Integrating a multi-element planar transducer with active MR temperature feedback can enable three-dimensional conformal thermal therapy of a target region within the prostate gland while sparing surrounding normal tissues. Continuous measurement of the temperature distribution in tissue enables dynamic compensation for unknown changes in blood flow and tissue properties during treatment. The main goal of this study was to evaluate the feasibility of using active temperature feedback on a clinical 1.5 T MR imager for conformal thermal therapy. MR thermometry was performed during heating in both gel phantoms and excised tissue with a transurethral heating applicator, and the rotation rate and power were varied based on the thermal measurements. The capability to produce a region of thermal damage that matched a target boundary was evaluated. The influence of a cooling gradient (to simulate cooling of the rectum or urethra) on the desired pattern of thermal damage was also investigated in gel phantoms. Results showed high correlation between the desired target boundary and the 55 °C isotherm generated during heating with an average distance error of 0.9 mm ± 0.4 mm (n = 6) in turkey breasts, 1.4 mm ± 0.6 mm (n = 4) in gel phantoms without rectal cooling and 1.4 mm ± 0.6 mm (n = 3) in gel phantoms with rectal cooling. The results were obtained using a temporal update rate of 5 s, a spatial resolution of 3 × 3 × 10 mm for the control point, and a temperature uncertainty of approximately 1 °C. The performance of the control algorithm under these conditions was comparable to that of simulations conducted previously by our group. Overall, the feasibility of generating targeted regions of thermal damage with a transurethral heating applicator and active MR temperature feedback has been demonstrated experimentally. This method of treatment appears capable of accounting for unpredictable and varying tissue properties during the treatment.

Organic geochemical investigations of the Dali Lake sediments in northern China: Implications for environment and climate changes of the last deglaciation in the East Asian summer monsoon margin

NASA Astrophysics Data System (ADS)

Fan, Jiawei; Xiao, Jule; Wen, Ruilin; Zhang, Shengrui; Wang, Xu; Cui, Linlin; Yamagata, Hideki

2017-06-01

Millennial-scale environment and climate changes in the East Asian summer monsoon margin during the last deglaciation are reconstructed by systematic studies on the characteristic of sedimentary organic matter from Dali Lake in northern China. Concurrent increases in the TOC and TN concentrations indicate increases in terrestrial organic matter and nutrient inputs to the lake and a development of terrestrial vegetation and phytoplankton productivity related to increases in regional temperature and precipitation. C/N ratios reflect changes in the proportions of terrestrial and aquatic organic matter. Decreases in both δ13Corg and δ15N values indicate increases in the isotopically lighter, terrestrial carbon and nitrogen inputs to the lake, due to increases in surface runoffs; while a sharp decrease in the δ15N value implies a significant weakening in the biological activities of nitrifying and amonifying bacteria, due to abrupt decrease in the water temperature. The geochemical data indicate that regional temperature and precipitation exhibited increasing trends from 15,000 to 12,350 cal yr BP; temperature decreased abruptly at 12,350 cal yr BP and then maintained a low level from 12,350 to 11,400 cal yr BP, precipitation decreased to a relatively low level from 12,350 to 11,400 cal yr BP; and both temperature and precipitation returned to increase after 11,400 cal yr BP. The climate change in the Dali Lake region during the last deglaciation corresponds, within age uncertainties, to the Bølling-Allerød (BA) warm phase and Younger Dryas (YD) cold reversal occurring over northern high latitudes. However, the gradual and mild increasing trends of regional temperature and precipitation during the BA warm period contrasts with the general cooling trend in northern high latitude temperature, implying a dominant influence from increases in the Northern Hemisphere summer insolation; while the slight decreases in regional precipitation relative to the rapid and significant decreases in northern high latitude temperature during the YD cold period may have resulted from local moisture recycling or from an insensitive response of hydrology and ecology to the regional precipitation change.

Modeling large-scale human alteration of land surface hydrology and climate

NASA Astrophysics Data System (ADS)

Pokhrel, Yadu N.; Felfelani, Farshid; Shin, Sanghoon; Yamada, Tomohito J.; Satoh, Yusuke

2017-12-01

Rapidly expanding human activities have profoundly affected various biophysical and biogeochemical processes of the Earth system over a broad range of scales, and freshwater systems are now amongst the most extensively altered ecosystems. In this study, we examine the human-induced changes in land surface water and energy balances and the associated climate impacts using a coupled hydrological-climate model framework which also simulates the impacts of human activities on the water cycle. We present three sets of analyses using the results from two model versions—one with and the other without considering human activities; both versions are run in offline and coupled mode resulting in a series of four experiments in total. First, we examine climate and human-induced changes in regional water balance focusing on the widely debated issue of the desiccation of the Aral Sea in central Asia. Then, we discuss the changes in surface temperature as a result of changes in land surface energy balance due to irrigation over global and regional scales. Finally, we examine the global and regional climate impacts of increased atmospheric water vapor content due to irrigation. Results indicate that the direct anthropogenic alteration of river flow in the Aral Sea basin resulted in the loss of 510 km3 of water during the latter half of the twentieth century which explains about half of the total loss of water from the sea. Results of irrigation-induced changes in surface energy balance suggest a significant surface cooling of up to 3.3 K over 1° grids in highly irrigated areas but a negligible change in land surface temperature when averaged over sufficiently large global regions. Results from the coupled model indicate a substantial change in 2 m air temperature and outgoing longwave radiation due to irrigation, highlighting the non-local (regional and global) implications of irrigation. These results provide important insights on the direct human alteration of land surface water and energy balances, highlighting the need to incorporate human activities such as irrigation into the framework of global climate models and Earth system models for better prediction of future changes under increasing human influence and continuing global climate change.

Long wavelength vertical cavity surface emitting laser

DOEpatents

Choquette, Kent D.; Klem, John F.

2005-08-16

Selectively oxidized vertical cavity lasers emitting near 1300 nm using InGaAsN quantum wells are reported for the first time which operate continuous wave below, at and above room temperature. The lasers employ two n-type Al.sub.0.94 Ga.sub.0.06 As/GaAs distributed Bragg reflectors each with a selectively oxidized current aperture adjacent to the active region, and the top output mirror contains a tunnel junction to inject holes into the active region. Continuous wave single mode lasing is observed up to 55.degree. C.

High-resolution Mapping of Permafrost and Soil Freeze/thaw Dynamics in the Tibetan Plateau Based on Multi-sensor Satellite Observations

NASA Astrophysics Data System (ADS)

Zhang, W.; Yi, Y.; Yang, K.; Kimball, J. S.

2016-12-01

The Tibetan Plateau (TP) is underlain by the world's largest extent of alpine permafrost ( 2.5×106 km2), dominated by sporadic and discontinuous permafrost with strong sensitivity to climate warming. Detailed permafrost distributions and patterns in most of the TP region are still unknown due to extremely sparse in-situ observations in this region characterized by heterogeneous land cover and large temporal dynamics in surface soil moisture conditions. Therefore, satellite-based temperature and moisture observations are essential for high-resolution mapping of permafrost distribution and soil active layer changes in the TP region. In this study, we quantify the TP regional permafrost distribution at 1-km resolution using a detailed satellite data-driven soil thermal process model (GIPL2). The soil thermal model is calibrated and validated using in-situ soil temperature/moisture observations from the CAMP/Tibet field campaign (9 sites: 0-300 cm soil depth sampling from 1997-2007), a multi-scale soil moisture and temperature monitoring network in the central TP (CTP-SMTMN, 57 sites: 5-40 cm, 2010-2014) and across the whole plateau (China Meteorology Administration, 98 sites: 0-320 cm, 2000-2015). Our preliminary results using the CAMP/Tibet and CTP-SMTMN network observations indicate strong controls of surface thermal and soil moisture conditions on soil freeze/thaw dynamics, which vary greatly with underlying topography, soil texture and vegetation cover. For regional mapping of soil freeze/thaw and permafrost dynamics, we use the most recent soil moisture retrievals from the NASA SMAP (Soil Moisture Active Passive) sensor to account for the effects of temporal soil moisture dynamics on soil thermal heat transfer, with surface thermal conditions defined by MODIS (Moderate Resolution Imaging Spectroradiometer) land surface temperature records. Our study provides the first 1-km map of spatial patterns and recent changes of permafrost conditions in the TP.

Temperature effects on cathodoluminescence of enstatite

NASA Astrophysics Data System (ADS)

Ohgo, S.; Nishido, H.

2017-12-01

Cathodoluminescence (CL) of enstatite has been extensively investigated for planetary science applications. The CL features are affected by many factors of impurities such as transition metal elements, structural defects and sample temperature. However, the temperature effects on enstatite CL have not been clarified so far. In this study, we have quantitatively evaluated temperature effects on enstatite CL. Three samples of luminescent enstatite were employed for CL spectral measurements. Color CL imaging was carried out using a cold-cathode type Luminoscope with a cooled-CCD camera. CL spectroscopy was made by a SEM-CL system, which is comprised of SEM (JEOL: JSM-5410LV) combined with a grating monochromator (OXFORD: Mono CL2). The CL emitted from the sample was collected in the range of 300-800 nm with a photomultiplier tube by a photon counting method at various temperatures from -193-50 degree C. All CL spectra were corrected for total instrumental response. Color CL imaging reveals various CL emissions with red, reddish-purple and bluish-purple in the terrestrial and extraterrestrial enstatite. All of them have two broad emission bands at around 400 nm in a blue region and at around 670 nm in a red region at room and liquid nitrogen temperatures. The spectral peak in a red region is sharpened and enhanced at lower temperature due to reduction of thermal lattice vibration and an increase in luminescent efficiency. CL intensity at around 670 nm of enstatite decreases with an increase in sample temperature up to -110 degree C from -193 degree C, and increases with an increase in sample temperature between -110 and 50 degree C. This behavior is not able to be explained by a temperature quenching theory based on an increase in the probability of non-radiative transition with the rise of temperature. A least-square fitting of the Arrhenius plot by assuming a Mott-Seitz model provides an activation energy of less than 0.01 eV in temperature quenching process from -193 to -110 degree C. According to an analytical method proposed by Barnett and Bailiff (1996), an activation energy of 0.03-0.16 eV can be estimated as a sensitizing effect on the CL from -110 up to 50 degree C. The unusual sensitizing effect has not been reported so far in the pyroxene minerals.

The Role of Temperature and Humidity on Seasonal Influenza in Tropical Areas: Guatemala, El Salvador and Panama, 2008-2013

NASA Technical Reports Server (NTRS)

Soebiyanto, Radina P.; Clara, Wilfrido; Jara, Jorge; Castillo, Leticia; Sorto, Oscar Rene; Marinero, Sidia; Antinori, Maria E. Barnett de; McCracken, John P.; Widdowson, Marc-Alain; Azziz-Baumgartner, Eduardo;

The role of temperature and humidity on seasonal influenza in tropical areas: Guatemala, El Salvador and Panama, 2008-2013.

PubMed

Soebiyanto, Radina P; Clara, Wilfrido; Jara, Jorge; Castillo, Leticia; Sorto, Oscar Rene; Marinero, Sidia; de Antinori, María E Barnett; McCracken, John P; Widdowson, Marc-Alain; Azziz-Baumgartner, Eduardo; Kiang, Richard K

2014-01-01

The role of meteorological factors on influenza transmission in the tropics is less defined than in the temperate regions. We assessed the association between influenza activity and temperature, specific humidity and rainfall in 6 study areas that included 11 departments or provinces within 3 tropical Central American countries: Guatemala, El Salvador and Panama. Logistic regression was used to model the weekly proportion of laboratory-confirmed influenza positive samples during 2008 to 2013 (excluding pandemic year 2009). Meteorological data was obtained from the Tropical Rainfall Measuring Mission satellite and the Global Land Data Assimilation System. We found that specific humidity was positively associated with influenza activity in El Salvador (Odds Ratio (OR) and 95% Confidence Interval of 1.18 (1.07-1.31) and 1.32 (1.08-1.63)) and Panama (OR = 1.44 (1.08-1.93) and 1.97 (1.34-2.93)), but negatively associated with influenza activity in Guatemala (OR = 0.72 (0.6-0.86) and 0.79 (0.69-0.91)). Temperature was negatively associated with influenza in El Salvador's west-central departments (OR = 0.80 (0.7-0.91)) whilst rainfall was positively associated with influenza in Guatemala's central departments (OR = 1.05 (1.01-1.09)) and Panama province (OR = 1.10 (1.05-1.14)). In 4 out of the 6 locations, specific humidity had the highest contribution to the model as compared to temperature and rainfall. The model performed best in estimating 2013 influenza activity in Panama and west-central El Salvador departments (correlation coefficients: 0.5-0.9). The findings highlighted the association between influenza activity and specific humidity in these 3 tropical countries. Positive association with humidity was found in El Salvador and Panama. Negative association was found in the more subtropical Guatemala, similar to temperate regions. Of all the study locations, Guatemala had annual mean temperature and specific humidity that were lower than the others.

Sol-gel synthesis and densification of aluminoborosilicate powders. Part 2: Densification

NASA Technical Reports Server (NTRS)

Bull, Jeffrey; Selvaduray, Guna; Leiser, Daniel

1992-01-01

Aluminoborosilicate (ABS) powders, high in alumina content, were synthesized by the sol-gel process utilizing four different methods of synthesis. The effect of these methods on the densification behavior of ABS powder compacts was studied. Five regions of shrinkage in the temperature range 25-1184 C were identified. In these regions, the greatest shrinkage occurred between the gel-to-glass transition temperature (T sub g approximately equal to 835 C) and the crystallization transformation temperature (T sub t approximately equal 900 C). The dominant mechanism of densification in this range was found to be viscous sintering. ABS powders were amorphous to x-rays up to T sub t at which a multiphasic structure crystallized. No 2Al2O3.B2O3 was found in these powders as predicted in the phase diagram. Above T sub t, densification was the result of competing mechanisms including grain growth and boria fluxed viscous sintering. Apparent activation energies for densification in each region varied according to the method of synthesis.

Geothermic analysis of high temperature hydrothermal activities area in Western plateau of Sichuan province, China

NASA Astrophysics Data System (ADS)

Zhang, J.

2016-12-01

There is a high temperature hydrothermal activity area in the western plateau of Sichuan. More than 200 hot springs points have been found in the region, including 11 hot spring water temperature above local boiling point. Most of these distribute along Jinshajjiang fracture, Dege-Xiangcheng fracture, Ganzi-Litang fracture as well as Xianshuihe fracture, and form three high-temperature hydrothermal activity strips in the NW-SE direction. Using gravity, magnetic, seismic and helium isotope data, this paper analyzed the crust-mantle heat flow structure, crustal heat source distribution and water heating system. The results show that the geothermal activity mainly controlled by the "hot" crust. The ratio of crustal heat flow and surface heat flow is higher than 60%. In the high temperature hydrothermal activities area, there is lower S wave velocity zone with Vs<3.2 km/s in 15 30 km depth in middle and lower crust. Basing on the S wave velocity inversion temperature of crust-mantle, it has been found that there is a high temperature layer with 850 1000 ° in 20 40 km depth. It is the main heat source of high temperature hydrothermal activity area of western Sichuan. Our argument is that atmospheric precipitation, surface water infiltrated along the fault fracture into the crustal deep, heating by crustal hot source, and circulation to surface become high temperature hot water. Geothermal water mainly reserve in the Triassic strata of the containing water good carbonate rocks, and in the intrusive granite which is along the fault zone. The thermal energy of Surface heat thermal activities mainly comes from the high-temperature hot source which is located in the middle and lower crust. Being in the deep crustal fracture, the groundwater infiltrated to the deep crust and absorbed heat, then, quickly got back to the surface and formed high hot springs.

The effects of prostaglandin E2 on the firing rate activity of thermosensitive and temperature insensitive neurons in the ventromedial preoptic area of the rat hypothalamus.

PubMed

Ranels, Heather J; Griffin, John D

2003-02-21

In response to an immune system challenge with lipopolysaccharide (LPS), recent work has shown that Fos immunoreactivity is displayed by neurons in the ventromedial preoptic area of the hypothalamus (VMPO). In addition, neurons in this region show distinct axonal projections to the anterior perifornical area (APFx) and the paraventricular nucleus (PVN). It has been hypothesized that neurons within the VMPO integrate their local responses to temperature with changes in firing activity that result from LPS induced production of prostaglandin E(2) (PGE(2)). This may be an important mechanism by which the set-point regulation of thermoeffector neurons in the APFx and PVN is altered, resulting in hyperthermia. To characterize the firing rate activity of VMPO neurons, single-unit recordings were made of neuronal extracellular activity in rat hypothalamic tissue slices. Based on the slope of firing rate as a function of tissue temperature, neurons were classified as either warm sensitive or temperature insensitive. Neurons were then treated with PGE(2) (200 nM) while tissue temperature was held at a constant level ( approximately 36 degrees C). The majority of temperature insensitive neurons responded to PGE(2) with an increase in firing rate activity, while warm sensitive neurons showed a reduction in firing rate. This suggests that both warm sensitive and temperature insensitive neurons in the VMPO may play critical and contrasting roles in the production of a fever during an acute phase response to infection.

Auroral origin of medium scale gravity waves in neutral composition and temperature

NASA Technical Reports Server (NTRS)

Chandra, S.; Spencer, N. W.; Krankowsky, D.; Laemmerzahl, P.

1979-01-01

The kinetic temperature and neutral composition data obtained from the Aeros B neutral atmosphere temperature experiment and the neutral and ion mass spectrometer show spatial structures characteristic of medium scale gravity waves with a wavelength in the range of several hundred kilometers. These waves are associated with auroral activity, and their spatial structure reflects the time history of the auroral electrojet. The medium scale gravity waves tend to propagate to mid-latitudes on the nightside. On the dayside their range is limited to high latitudes. Gravity waves are carriers of auroral energy to middle and low latitudes where they may cause irreversible changes in temperature via viscous dissipation. Since auroral activity occurs frequently, it is suggested that this energy reaches the mid-latitude region of the thermosphere much more frequently than is indicated by planetary magnetic indices.

Thermal signatures of voluntary deception in ecological conditions

PubMed Central

Panasiti, Maria Serena; Cardone, Daniela; Pavone, Enea F.; Mancini, Alessandra; Merla, Arcangelo; Aglioti, Salvatore M.

2016-01-01

Deception is a pervasive phenomenon that greatly influences dyadic, groupal and societal interactions. Behavioural, physiological and neural signatures of this phenomenon have imporant implications for theoretical and applied research, but, because it is difficult for a laboratory to replicate the natural context in which deception occurs, contemporary research is still struggling to find such signatures. In this study, we tracked the facial temperature of participants who decided whether or not to deceive another person, in situations where their reputation was at risk or not. We used a high-sensitivity infrared device to track temperature changes to check for unique patterns of autonomic reactivity. Using a region-of-interest based approach we found that prior to any response there was a minimal increase in periorbital temperature (which indexes sympathetic activation, together with reduced cheek temperature) for the self-gain lies in the reputation-risk condition. Crucially, we found a rise in nose temperature (which indexes parasympathetic activation) for self-gain lies in the reputation-risk condition, not only during response preparation but also after the choice was made. This finding suggests that the entire deception process may be tracked by the nose region. Furthermore, this nasal temperature modulation was negatively correlated with machiavellian traits, indicating that sympathetic/parasympathetic regulation is less important for manipulative individuals who may care less about the consequences of lie-related moral violations. Our results highlight a unique pattern of autonomic reactivity for spontaneous deception in ecological contexts. PMID:27734927

Structural flexibility and protein adaptation to temperature: Molecular dynamics analysis of malate dehydrogenases of marine molluscs.

PubMed

Dong, Yun-Wei; Liao, Ming-Ling; Meng, Xian-Liang; Somero, George N

2018-02-06

Orthologous proteins of species adapted to different temperatures exhibit differences in stability and function that are interpreted to reflect adaptive variation in structural "flexibility." However, quantifying flexibility and comparing flexibility across proteins has remained a challenge. To address this issue, we examined temperature effects on cytosolic malate dehydrogenase (cMDH) orthologs from differently thermally adapted congeners of five genera of marine molluscs whose field body temperatures span a range of ∼60 °C. We describe consistent patterns of convergent evolution in adaptation of function [temperature effects on K M of cofactor (NADH)] and structural stability (rate of heat denaturation of activity). To determine how these differences depend on flexibilities of overall structure and of regions known to be important in binding and catalysis, we performed molecular dynamics simulation (MDS) analyses. MDS analyses revealed a significant negative correlation between adaptation temperature and heat-induced increase of backbone atom movements [root mean square deviation (rmsd) of main-chain atoms]. Root mean square fluctuations (RMSFs) of movement by individual amino acid residues varied across the sequence in a qualitatively similar pattern among orthologs. Regions of sequence involved in ligand binding and catalysis-termed mobile regions 1 and 2 (MR1 and MR2), respectively-showed the largest values for RMSF. Heat-induced changes in RMSF values across the sequence and, importantly, in MR1 and MR2 were greatest in cold-adapted species. MDS methods are shown to provide powerful tools for examining adaptation of enzymes by providing a quantitative index of protein flexibility and identifying sequence regions where adaptive change in flexibility occurs.

Thermal imaging of high power diode lasers subject to back-irradiance

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

Li, C.; Pipe, K. P.; Cao, C.

In this study, CCD-based thermoreflectance imaging and finite element modeling are used to study the two-dimensional (2D) temperature profile of a junction-down broad-area diode laser facet subject to back-irradiance. By determining the temperature rise in the active region (ΔΤAR) at different diode laser optical powers, back-irradiance reflectance levels, and back-irradiance spot locations, we find that ΔΤAR increases by nearly a factor of three when the back-irradiance spot is centered in the absorbing substrate approximately 5 μm away from the active region, a distance roughly equal to half of the back-irradiance spot FWHM (9 μm). This corroborates prior work studying themore » relationship between the back-irradiance spot location and catastrophic optical damage, suggesting a strong thermal basis for reduced laser lifetime in the presence of back-irradiance for diode lasers fabricated on absorbing substrates.« less

Comparative study on stained InGaAs quantum wells for high-speed optical-interconnect VCSELs

NASA Astrophysics Data System (ADS)

Li, Hui; Jia, Xiaowei

2018-05-01

The gain-carrier characteristics of InGaAs quantum well for 980 nm high-speed, energy-efficient vertical-cavity surface-emitting lasers are investigated. We specially studied the potentially InGaAs quantum well designs can be used for the active region of energy-efficient, temperature-stable 980-nm VCSEL, which introduced a quantum well gain peak wavelength-to-cavity resonance wavelength offset to improve the dynamic performance at high operation temperature. Several candidate quantum wells are being compared in theory and measurement. We found that ∼5 nm InGaAs QW with ∼6 nm barrier thickness is suitable for the active region of high-speed optical interconnect 980 nm VCSELs, and no significant improvement in the 20% range of In content of InGaAs QWs. The results are useful for next generation green photonic device design.

Experimental investigation of terahertz quantum cascade laser with variable barrier heights

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

Jiang, Aiting; Vijayraghavan, Karun; Belkin, Mikhail A., E-mail: mbelkin@ece.utexas.edu

2014-04-28

We report an experimental study of terahertz quantum cascade lasers with variable barrier heights based on the Al{sub x}Ga{sub 1–x}As/GaAs material system. Two new designs are developed based on semiclassical ensemble Monte Carlo simulations using state-of-the-art Al{sub 0.15}Ga{sub 0.85}As/GaAs three-quantum-well resonant phonon depopulation active region design as a reference. The new designs achieved maximum lasing temperatures of 188 K and 172 K, as compared to the maximum lasing temperature of 191 K for the reference structure. These results demonstrate that terahertz quantum cascade laser designs with variable barrier heights provide a viable alternative to the traditional active region designs with fixed barrier composition.more » Additional design space offered by using variable barriers may lead to future improvements in the terahertz quantum cascade laser performance.« less

Thermal imaging of high power diode lasers subject to back-irradiance

DOE PAGES

Li, C.; Pipe, K. P.; Cao, C.; ...

2018-03-07

In this study, CCD-based thermoreflectance imaging and finite element modeling are used to study the two-dimensional (2D) temperature profile of a junction-down broad-area diode laser facet subject to back-irradiance. By determining the temperature rise in the active region (ΔΤAR) at different diode laser optical powers, back-irradiance reflectance levels, and back-irradiance spot locations, we find that ΔΤAR increases by nearly a factor of three when the back-irradiance spot is centered in the absorbing substrate approximately 5 μm away from the active region, a distance roughly equal to half of the back-irradiance spot FWHM (9 μm). This corroborates prior work studying themore » relationship between the back-irradiance spot location and catastrophic optical damage, suggesting a strong thermal basis for reduced laser lifetime in the presence of back-irradiance for diode lasers fabricated on absorbing substrates.« less

Spectral gain profile of a multi-stack terahertz quantum cascade laser

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

Bachmann, D., E-mail: dominic.bachmann@tuwien.ac.at; Deutsch, C.; Krall, M.

2014-11-03

The spectral gain of a multi-stack terahertz quantum cascade laser, composed of three active regions with emission frequencies centered at 2.3, 2.7, and 3.0 THz, is studied as a function of driving current and temperature using terahertz time-domain spectroscopy. The optical gain associated with the particular quantum cascade stacks clamps at different driving currents and saturates to different values. We attribute these observations to varying pumping efficiencies of the respective upper laser states and to frequency dependent optical losses. The multi-stack active region exhibits a spectral gain full width at half-maximum of 1.1 THz. Bandwidth and spectral position of themore » measured gain match with the broadband laser emission. As the laser action ceases with increasing operating temperature, the gain at the dominant lasing frequency of 2.65 THz degrades sharply.« less

Thermal imaging of high power diode lasers subject to back-irradiance

NASA Astrophysics Data System (ADS)

Li, C.; Pipe, K. P.; Cao, C.; Thiagarajan, P.; Deri, R. J.; Leisher, P. O.

2018-03-01

CCD-based thermoreflectance imaging and finite element modeling are used to study the two-dimensional (2D) temperature profile of a junction-down broad-area diode laser facet subject to back-irradiance. By determining the temperature rise in the active region (ΔΤAR) at different diode laser optical powers, back-irradiance reflectance levels, and back-irradiance spot locations, we find that ΔΤAR increases by nearly a factor of three when the back-irradiance spot is centered in the absorbing substrate approximately 5 μm away from the active region, a distance roughly equal to half of the back-irradiance spot FWHM (9 μm). This corroborates prior work studying the relationship between the back-irradiance spot location and catastrophic optical damage, suggesting a strong thermal basis for reduced laser lifetime in the presence of back-irradiance for diode lasers fabricated on absorbing substrates.

Regional rat brain noradrenaline turnover in response to restraint stress.

PubMed

Glavin, G B; Tanaka, M; Tsuda, A; Kohno, Y; Hoaki, Y; Nagasaki, N

1983-08-01

Male Wistar rats were starved for 12 hr and then subjected to either 2 hr of wire mesh "envelope" restraint at room temperature; 2 hr of supine restraint in a specially constructed harness at room temperature or were not restrained. Eight brain regions were examined for NA level and the level of its major metabolite, MHPG-SO4. Plasma corticosterone and gastric ulcer incidence were also measured. All restrained rats displayed marked elevations in MHPG-SO4 levels in most brain regions. In addition, several brain regions in restrained animals showed a reduction in NA level. All restrained rats showed elevated plasma corticosterone levels and evidence of gastric lesions. In general, supine restraint produced greater alterations in regional brain NA turnover, greater evidence of ulcer disease, and higher plasma corticosterone levels than did wire mesh restraint. These data suggest that acute but intense stress in the form of restraint causes markedly altered brain NA activity--a possible neurochemical mechanism underlying the phenomenon of stress-induced disease.

Excited state intramolecular charge transfer reaction in nonaqueous electrolyte solutions: Temperature dependence

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

Pradhan, Tuhin; Gazi, Harun Al Rasid; Biswas, Ranjit

2009-08-07

Temperature dependence of the excited state intramolecular charge transfer reaction of 4-(1-azetidinyl)benzonitrile (P4C) in ethyl acetate (EA), acetonitrile (ACN), and ethanol at several concentrations of lithium perchlorate (LiClO{sub 4}) has been investigated by using the steady state and time resolved fluorescence spectroscopic techniques. The temperature range considered is 267-343 K. The temperature dependent spectral peak shifts and reaction driving force (-{Delta}G{sub r}) in electrolyte solutions of these solvents can be explained qualitatively in terms of interaction between the reactant molecule and ion-atmosphere. Time resolved studies indicate that the decay kinetics of P4C is biexponential, regardless of solvents, LiClO{sub 4} concentrations,more » and temperatures considered. Except at higher electrolyte concentrations in EA, reaction rates in solutions follow the Arrhenius-type temperature dependence where the estimated activation energy exhibits substantial electrolyte concentration dependence. The average of the experimentally measured activation energies in these three neat solvents is found to be in very good agreement with the predicted value based on data in room temperature solvents. While the rate constant in EA shows a electrolyte concentration induced parabolic dependence on reaction driving force (-{Delta}G{sub r}), the former in ethanol and ACN increases only linearly with the increase in driving force (-{Delta}G{sub r}). The data presented here also indicate that the step-wise increase in solvent reorganization energy via sequential addition of electrolyte induces the ICT reaction in weakly polar solvents to crossover from the Marcus inverted region to the normal region.« less

Cloning, expression and characterization of a metagenome derived thermoactive/thermostable pectinase.

PubMed

Singh, Rajvinder; Dhawan, Samriti; Singh, Kashmir; Kaur, Jagdeep

2012-08-01

The gene encoding a thermostable pectinase was isolated from a soil metagenome sample. The gene sequence corresponded to an open reading frame of 1,311 bp encoding a translation product of 47.9 kDa. It showed maximum (93 %) identity to a Bacillus licheniformis glycoside hydrolase. Deduced amino acid analysis showed an absence of highly conserved cysteine residues in the N-terminal region at positions 24 and 42, and in the C-terminal region at positions 389, 394, 413 and 424. pQpecJKR01 (pQE30 expression vector containing the pectinase gene) was expressed in Escherichia coli strain M15 as a recombinant fusion protein containing an N-terminal 6× His tag. Biochemical properties of this pectinase were novel. The enzyme had temperature and pH optima of 70 °C and 7.0, respectively, but was active over a broad temperature and pH range. The enzyme was stable at 60 °C with a half-life of 5 h and the enzyme activity was inhibited by 0.1 % diethyl pyrocarbonate and 5 mM dicyclohexyl carbodiimide. The enzyme could be of great use in industrial processes due to its activity over a broad pH range and at high temperature.

Use of a Blended Satellite and In situ Sea Surface Temperature Climate Data Record for Evaluating Long-term Impacts on Coral and Marine Mammal Communities

NASA Astrophysics Data System (ADS)

Banzon, P. V. F.; Liu, G.; Forney, K.; Becker, E.; Arzayus, K. M.; Sun, L.

2016-02-01

The NOAA ¼° daily Optimum Interpolation (OI) Sea Surface temperature (SST), an in situ and satellite-based climate data record of SST available from 1981, was used to examine potential impacts of long-term temperature change on marine ecosystems. As a benthic example, historical heat stress in key tropical coral reef regions was calculated from the daily temperature data, using the NOAA Coral Reef Watch methodology. The regions with long-term ocean warming trend and experiencing more frequent thermal stress are identified as the regions with high vulnerability. While corals may be able to adapt to slow changes, no systematic adaptation has been reported with temperature increase over the past few decades. In contrast to the attached corals, marine mammals respond to changes in their environment by changing their distributions, often over large geographic areas. Habitat-based species distribution models can be developed to predict changes in the spatial distribution and abundance of marine mammals. OISST is a good predictor of the distribution of some marine mammal species, including Bryde's whales, false killer whales, and striped dolphins, and SST-based distribution models provide a foundation for projecting potential impacts of future temperature changes on marine mammals. Preliminary results from some of our research activities will be presented.

B2 Grain Growth Behavior of a Ti-22Al-25Nb Alloy Fabricated by Hot Pressing Sintering

NASA Astrophysics Data System (ADS)

Jia, Jianbo; Liu, Wenchao; Xu, Yan; Chen, Chen; Yang, Yue; Luo, Junting; Zhang, Kaifeng

2018-05-01

Grain growth behavior of a powder metallurgy (P/M) Ti-22Al-25Nb alloy was investigated by applying a series of isothermal treatment tests over a wide range of temperatures and holding times. An isothermal treatment scheme was conducted in the B2 phase region (1070-1110 °C) and α 2 + B2 phase region (1010-1050 °C) at holding times of 10, 30 min, 1, 2, and 3 h, respectively. The effects of temperature and holding time on the microstructure evolution and microhardness of the P/M Ti-22Al-25Nb alloy at elevated temperatures were evaluated using optical microscope, scanning electron microscope, x-ray diffraction, and Vickers hardness test techniques. The results revealed that the alloy's treated microstructure was closely linked to temperature and holding time, respectively. The change law of B2 grain growth with holding time and temperature can be well interpreted by the Beck equation and Hillert equation, respectively. The B2 grain growth exponent n and activation energy Q were acquired based on experimental data in the α 2 + B2 and B2 phase regions. In addition, the grain growth contour map for the P/M Ti-22Al-25Nb alloy was constructed to depict variations in B2 grain size based on holding time and temperature.

Effect of chemical composition on the electrical conductivity of gneiss at high temperatures and pressures

NASA Astrophysics Data System (ADS)

Dai, Lidong; Sun, Wenqing; Li, Heping; Hu, Haiying; Wu, Lei; Jiang, Jianjun

2018-03-01

The electrical conductivity of gneiss samples with different chemical compositions (WA = Na2O + K2O + CaO = 7.12, 7.27 and 7.64 % weight percent) was measured using a complex impedance spectroscopic technique at 623-1073 K and 1.5 GPa and a frequency range of 10-1 to 106 Hz. Simultaneously, a pressure effect on the electrical conductivity was also determined for the WA = 7.12 % gneiss. The results indicated that the gneiss conductivities markedly increase with total alkali and calcium ion content. The sample conductivity and temperature conform to an Arrhenius relationship within a certain temperature range. The influence of pressure on gneiss conductivity is weaker than temperature, although conductivity still increases with pressure. According to various ranges of activation enthalpy (0.35-0.52 and 0.76-0.87 eV) at 1.5 GPa, two main conduction mechanisms are suggested that dominate the electrical conductivity of gneiss: impurity conduction in the lower-temperature region and ionic conduction (charge carriers are K+, Na+ and Ca2+) in the higher-temperature region. The electrical conductivity of gneiss with various chemical compositions cannot be used to interpret the high conductivity anomalies in the Dabie-Sulu ultrahigh-pressure metamorphic belt. However, the conductivity-depth profiles for gneiss may provide an important constraint on the interpretation of field magnetotelluric conductivity results in the regional metamorphic belt.

Global metabolic impacts of recent climate warming.

PubMed

Dillon, Michael E; Wang, George; Huey, Raymond B

2010-10-07

Documented shifts in geographical ranges, seasonal phenology, community interactions, genetics and extinctions have been attributed to recent global warming. Many such biotic shifts have been detected at mid- to high latitudes in the Northern Hemisphere-a latitudinal pattern that is expected because warming is fastest in these regions. In contrast, shifts in tropical regions are expected to be less marked because warming is less pronounced there. However, biotic impacts of warming are mediated through physiology, and metabolic rate, which is a fundamental measure of physiological activity and ecological impact, increases exponentially rather than linearly with temperature in ectotherms. Therefore, tropical ectotherms (with warm baseline temperatures) should experience larger absolute shifts in metabolic rate than the magnitude of tropical temperature change itself would suggest, but the impact of climate warming on metabolic rate has never been quantified on a global scale. Here we show that estimated changes in terrestrial metabolic rates in the tropics are large, are equivalent in magnitude to those in the north temperate-zone regions, and are in fact far greater than those in the Arctic, even though tropical temperature change has been relatively small. Because of temperature's nonlinear effects on metabolism, tropical organisms, which constitute much of Earth's biodiversity, should be profoundly affected by recent and projected climate warming.

Cool and hot emission in a recurring active region jet

NASA Astrophysics Data System (ADS)

Mulay, Sargam M.; Zanna, Giulio Del; Mason, Helen

2017-09-01

Aims: We present a thorough investigation of the cool and hot temperature components in four recurring active region jets observed on July 10, 2015 using the Atmospheric Imaging Assembly (AIA), X-ray Telescope (XRT), and Interface Region Imaging Spectrograph (IRIS) instruments. Methods: A differential emission measure (DEM) analysis was performed on areas in the jet spire and footpoint regions by combining the IRIS spectra and the AIA observations. This procedure better constrains the low temperature DEM values by adding IRIS spectral lines. Plasma parameters, such as Doppler velocities, electron densities, nonthermal velocities and a filling factor were also derived from the IRIS spectra. Results: In the DEM analysis, significant cool emission was found in the spire and the footpoint regions. The hot emission was peaked at log T [K] = 5.6-5.9 and 6.5 respectively. The DEM curves show the presence of hot plasma (T = 3 MK) in the footpoint region. We confirmed this result by estimating the Fe XVIII emission from the AIA 94 Å channel which was formed at an effective temperature of log T [K] = 6.5. The average XRT temperatures were also found to be in agreement with log T [K] = 6.5. The emission measure (EM) was found to be three orders of magnitude higher in the AIA-IRIS DEM compared with that obtained using only AIA. The O IV (1399/1401 Å) electron densities were found to be 2.0×1010 cm-3 in the spire and 7.6 × 1010 cm-3 in the footpoint. Different threads along the spire show different plane-of-sky velocities both in the lower corona and transition region. Doppler velocities of 32 km s-1 (blueshifted) and 13 km s-1 (redshifted) were obtained in the spire and footpoint, respectively from the Si IV 1402.77 Å spectral line. Nonthermal velocities of 69 and 53 km s-1 were recorded in the spire and footpoint region, respectively. We obtained a filling factor of 0.1 in the spire at log T [K] = 5. Conclusions: The recurrent jet observations confirmed the presence of significant cool emission co-spatial with the coronal emission. The movie attached to Fig. 3 is available at http://www.aanda.org

Ion Implantation in III-V Compound Semiconductors

DTIC Science & Technology

1984-09-01

activation D rO 1’j’ -- 147 z nob Or I Nov li is / " .".’*SDO ,jJ 1473 ,,K,•’,oIYo,,,ov4,SO-IO.-g,’€ Unclassified SECURIlY CLASSIFICATION OF ITHI PAGi (W...efficiency also increases rapidly with annealing temperature up to 24% at 10000C. The mobility of n-type samples remains low at annealing temperatures...they decrease rapidly as the depth increases. For a dose of 4 X 10M2 , the depth of an electrically active region is deeper than those for lower doses

Line formation in the solar chromosphere. II - An optically thick region of the chromosphere-corona transition region observed with OSO 8

NASA Technical Reports Server (NTRS)

Lites, B. W.; Hansen, E. R.; Shine, R. A.

1980-01-01

The University of Colorado ultraviolet spectrometer aboard the Orbiting Solar Observatory 8(OSO 8) has measured self-reversed profiles of the resonance line of C IV lamda 1548.2 at the limb passage of an active region. The degree of the self-reversal together with the absolute intensity of the line profile determine the electron density in the active region at 10 to the 10th/cu cm at temperatures where the C IV line is formed. The nonthermal component of the broadening velocity is no more than 14km/s, and the physical thickness of an equivalent plane-parallel slab in hydrostatic equilibrium that would give rise to the observed line profiles is about 430 km.

The solar atmosphere and the structure of active regions

NASA Technical Reports Server (NTRS)

Sturrock, P. A.

1974-01-01

The existence of 'holes' in the corona is reported characterized by abnormally low densities and temperatures. It was found that such coronal holes appear to be the source of high-velocity, enhanced-density streams in the solar wind as observed at the earth's orbit. It was further noted that coronal holes appear to be associated with regions of diverging magnetic fields in the corona. Models were developed to accomplish the objective for the principal energy flows in the transition region and corona.

Temperature Modulation of Electric Fields in Biological Matter

PubMed Central

Daniels, Charlotte S.; Rubinsky, Boris

2011-01-01

Pulsed electric fields (PEF) have become an important minimally invasive surgical technology for various applications including genetic engineering, electrochemotherapy and tissue ablation. This study explores the hypothesis that temperature dependent electrical parameters of tissue can be used to modulate the outcome of PEF protocols, providing a new means for controlling and optimizing this minimally invasive surgical procedure. This study investigates two different applications of cooling temperatures applied during PEF. The first case utilizes an electrode which simultaneously delivers pulsed electric fields and cooling temperatures. The subsequent results demonstrate that changes in electrical properties due to temperature produced by this configuration can substantially magnify and confine the electric fields in the cooled regions while almost eliminating electric fields in surrounding regions. This method can be used to increase precision in the PEF procedure, and eliminate muscle contractions and damage to adjacent tissues. The second configuration considered introduces a third probe that is not electrically active and only applies cooling boundary conditions. This second study demonstrates that in this probe configuration the temperature induced changes in electrical properties of tissue substantially reduce the electric fields in the cooled regions. This novel treatment can potentially be used to protect sensitive tissues from the effect of the PEF. Perhaps the most important conclusion of this investigation is that temperature is a powerful and accessible mechanism to modulate and control electric fields in biological tissues and can therefore be used to optimize and control PEF treatments. PMID:21695144

Martian Electron Temperatures in the Sub Solar Region.

NASA Astrophysics Data System (ADS)

Fowler, C. M.; Peterson, W. K.; Andersson, L.; Thiemann, E.; Mayyasi, M.; Yelle, R. V.; Benna, M.; Espley, J. R.

2017-12-01

Observations from Viking, and MAVEN have shown that the observed ionospheric electron temperatures are systematically higher than those predicted by many models. Because electron temperature is a balance between heating, cooling, and heat transport, we systematically compare the magnitude of electron heating from photoelectrons, electron cooling and heat transport, as a function of altitude within 30 degrees of the sub solar point. MAVEN observations of electron temperature and density, EUV irradiance, neutral and ion composition are used to evaluate terms in the heat equation following the framework of Matta et al. (Icarus, 2014, doi:10.1016/j.icarus.2013.09.006). Our analysis is restricted to inbound orbits where the magnetic field is within 30 degrees of horizontal. MAVEN sampled the sub solar region in May 2015 and again in May 2017, in near northern spring equinoctial conditions. Solar activity was higher and the spacecraft sampled altitudes down to 120 km in 2015, compared to 160 km in 2017. We find that between 160 and 200 km the Maven electron temperatures are in thermal equilibrium, in the sub solar region, on field lines inclined less than 30 degrees to the horizontal. Above 200km the data suggest that heating from other sources, such as wave heating are significant. Below 160 km some of the discrepancy comes from measurement limitations. This is because the MAVEN instrument cannot resolve the lowest electron temperatures, and because some cooling rates scale as the difference between the electron and neutral temperatures.

Active superconducting devices formed of thin films

DOEpatents

Martens, Jon S.; Beyer, James B.; Nordman, James E.; Hohenwarter, Gert K. G.

1991-05-28

Active superconducting devices are formed of thin films of superconductor which include a main conduction channel which has an active weak link region. The weak link region is composed of an array of links of thin film superconductor spaced from one another by voids and selected in size and thickness such that magnetic flux can propagate across the weak link region when it is superconducting. Magnetic flux applied to the weak link region will propagate across the array of links causing localized loss of superconductivity in the links and changing the effective resistance across the links. The magnetic flux can be applied from a control line formed of a superconducting film deposited coplanar with the main conduction channel and weak link region on a substrate. The devices can be formed of any type to superconductor but are particularly well suited to the high temperature superconductors since the devices can be entirely formed from coplanar films with no overlying regions. The devices can be utilized for a variety of electrical components, including switching circuits, amplifiers, oscillators and modulators, and are well suited to microwave frequency applications.

Effects of acute microinjections of the thyroid hormone derivative 3-iodothyronamine to the preoptic region of adult male rats on sleep, thermoregulation and motor activity

PubMed Central

James, Thomas D.; Moffett, Steven X.; Scanlan, Thomas S.; Martin, Joseph V.

2014-01-01

The decarboxylated thyroid hormone derivative 3-iodothyronamine (T1AM) has been reported as having behavioral and physiological consequences distinct from those of thyroid hormones. Here, we investigate the effects of T1AM on EEG-defined sleep after acute administration to the preoptic region of adult male rats. Our laboratory recently demonstrated a decrease in EEG-defined sleep after administration of 3,3′,5-triiodo-L-thyronine (T3) to the same brain region. After injection of T1AM or vehicle solution, EEG, EMG, activity, and core body temperature were recorded for 24 h. Sleep parameters were determined from EEG and EMG data. Earlier investigations found contrasting systemic effects of T3 and T1AM, such as decreased heart rate and body temperature after intraperitoneal T1AM injection. However, nREM sleep was decreased in the present study after injections of 1 or 3 μg T1AM, but not after 0.3 or 10 μg, closely mimicking the previously reported effects of T3 administration to the preoptic region. The biphasic dose–response observed after either T1AM or T3 administration seems to indicate shared mechanisms and/or functions of sleep regulation in the preoptic region. Consistent with systemic administration of T1AM, however, microinjection of T1AM decreased body temperature. The current study is the first to show modulation of sleep by T1AM, and suggests that T1AM and T3 have both shared and independent effects in the adult mammalian brain. PMID:23702093

Behavior of Solar Cycles 23 and 24 Revealed by Microwave Observations

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Yashiro, S.; Maekelae, P.; Michalek, G.; Shibasaki, K.; Hathaway, D. H.

2012-01-01

Using magnetic and microwave butterfly diagrams, we compare the behavior of solar polar regions to show that (1) the polar magnetic field and the microwave brightness temperature during solar minimum substantially diminished during the cycle 23/24 minimum compared to the 22/23 minimum. (2) The polar microwave brightness temperature (Tb) seems to be a good proxy for the underlying magnetic field strength (B). The analysis indicates a relationship, B = 0.0067Tb - 70, where B is in G and Tb in K. (3) Both the brightness temperature and the magnetic field strength show north-south asymmetry most of the time except for a short period during the maximum phase. (4) The rush-to-the-pole phenomenon observed in the prominence eruption (PE) activity seems to be complete in the northern hemisphere as of 2012 March. (5) The decline of the microwave brightness temperature in the north polar region to the quiet-Sun levels and the sustained PE activity poleward of 60degN suggest that solar maximum conditions have arrived at the northern hemisphere. The southern hemisphere continues to exhibit conditions corresponding to the rise phase of solar cycle 24. Key words: Sun: chromosphere Sun: coronal mass ejections (CMEs) Sun: filaments, prominences Sun: photosphere Sun: radio radiation Sun: surface magnetism

Regional Skin Temperature Response to Moderate Aerobic Exercise Measured by Infrared Thermography

PubMed Central

Fernandes, Alex de Andrade; Amorim, Paulo Roberto dos Santos; Brito, Ciro José; Sillero-Quintana, Manuel; Bouzas Marins, João Carlos

2016-01-01

Background: Infrared thermography (IRT) does not require contact with the skin, and it is a convenient, reliable and non-invasive technique that can be used for monitoring the skin temperature (TSK). Objectives: The aim of this study was to monitor the variations in the regional TSK during exercise on 28 regions of interest (ROIs) (forehead, face, chest, abdomen, back, lumbar, anterior and posterior neck, and posterior and anterior views of the right and left hands, forearms, upper arms, thighs, and legs) with IRT. Patients and Methods: 12 physically active young males were monitored with IRT during the following three phases: a) 30 minutes before exercise b) while performing one hour of moderate intensity exercise on a treadmill at 60% of the VO2max, and c) 60 minutes after exercise. Results: During pre-exercise, all TSK reached a steady-state (P ≤ 0.05), which ensured adequate thermal stabilisation. At the beginning of exercise, there was a significant reduction in the TSK in most ROIs after 10 minutes of activity, except for the lower limbs (legs and thighs). After one hour of recovery, in the anterior view of the hands and thighs and in the posterior view of the legs, there were significant increases in the TSK compared to pre-exercise. Conclusions: There were significant distinctions in the skin temperature distribution during exercise according to the activity of the area under consideration during exercise, which may be important in the development of physiological models and heat flux analyses for different purposes. PMID:27217931

THE AKARI 2.5-5.0 μm SPECTRAL ATLAS OF TYPE-1 ACTIVE GALACTIC NUCLEI: BLACK HOLE MASS ESTIMATOR, LINE RATIO, AND HOT DUST TEMPERATURE

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

Kim, Dohyeong; Im, Myungshin; Kim, Ji Hoon

2015-01-01

We present 2.5-5.0 μm spectra of 83 nearby (0.002 < z < 0.48) and bright (K < 14 mag) type-1 active galactic nuclei (AGNs) taken with the Infrared Camera on board AKARI. The 2.5-5.0 μm spectral region contains emission lines such as Brβ (2.63 μm), Brα (4.05 μm), and polycyclic aromatic hydrocarbons (3.3 μm), which can be used for studying the black hole (BH) masses and star formation activity in the host galaxies of AGNs. The spectral region also suffers less dust extinction than in the ultra violet (UV) or optical wavelengths, which may provide an unobscured view of dusty AGNs. Our sample is selectedmore » from bright quasar surveys of Palomar-Green and SNUQSO, and AGNs with reverberation-mapped BH masses from Peterson et al. Using 11 AGNs with reliable detection of Brackett lines, we derive the Brackett-line-based BH mass estimators. We also find that the observed Brackett line ratios can be explained with the commonly adopted physical conditions of the broad line region. Moreover, we fit the hot and warm dust components of the dust torus by adding photometric data of SDSS, 2MASS, WISE, and ISO to the AKARI spectra, finding hot and warm dust temperatures of ∼1100 K and ∼220 K, respectively, rather than the commonly cited hot dust temperature of 1500 K.« less

Seasonal dynamics of VLF signals amplitude Novosibirsk radio station and mesopause region temperature in 2009-2015

NASA Astrophysics Data System (ADS)

Kozlov, V. I.; Korsakov, A. A.; Ammosov, P. P.; Ammosova, A. M.; Gavrilyeva, G. A.; Koltovskoi, I. I.

2017-11-01

Dynamics of seasonal variations in the amplitude of the VLF radio signal received in Yakutsk from the navigation station near Novosibirsk and the radiation intensity in the wavelength range from 835 to 853 nm, where the P-branches of the OH band (6-2) are located, is present. The radiation variations give information about mesopause region measured at the Maimaga station (130 km from Yakutsk). Observation period from 2009 to 2015 covers period with minimum and maximum solar activity (solar flux F10.7). In the seasonal dynamics of the VLF amplitude signals and the mesopause temperature are observed annual, semiannual and third-annual variations, increasing during nighttime for VLF signals. The mesopause temperature and the VLF signal increase with increasing solar flux F10.7 in winter.

Semirational Directed Evolution of Loop Regions in Aspergillus japonicus β-Fructofuranosidase for Improved Fructooligosaccharide Production

PubMed Central

Trollope, K. M.; Görgens, J. F.

2015-01-01

The Aspergillus japonicus β-fructofuranosidase catalyzes the industrially important biotransformation of sucrose to fructooligosaccharides. Operating at high substrate loading and temperatures between 50 and 60°C, the enzyme activity is negatively influenced by glucose product inhibition and thermal instability. To address these limitations, the solvent-exposed loop regions of the β-fructofuranosidase were engineered using a combined crystal structure- and evolutionary-guided approach. This semirational approach yielded a functionally enriched first-round library of 36 single-amino-acid-substitution variants with 58% retaining activity, and of these, 71% displayed improved activities compared to the parent. The substitutions yielding the five most improved variants subsequently were exhaustively combined and evaluated. A four-substitution combination variant was identified as the most improved and reduced the time to completion of an efficient industrial-like reaction by 22%. Characterization of the top five combination variants by isothermal denaturation assays indicated that these variants displayed improved thermostability, with the most thermostable variant displaying a 5.7°C increased melting temperature. The variants displayed uniquely altered, concentration-dependent substrate and product binding as determined by differential scanning fluorimetry. The altered catalytic activity was evidenced by increased specific activities of all five variants, with the most improved variant doubling that of the parent. Variant homology modeling and computational analyses were used to rationalize the effects of amino acid changes lacking direct interaction with substrates. Data indicated that targeting substitutions to loop regions resulted in improved enzyme thermostability, specific activity, and relief from product inhibition. PMID:26253664

Highly temperature insensitive, low threshold-current density (λ = 8.7–8.8 μm) quantum cascade lasers

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

Kirch, J. D.; Chang, C.-C.; Boyle, C.

2015-04-13

By stepwise tapering, both the barrier heights and quantum-well depths in the active regions of 8.7–8.8 μm-emitting quantum-cascade-laser (QCL) structures, virtually complete carrier-leakage suppression is achieved. Such step-taper active-region-type QCLs possess, for 3 mm-long devices with high-reflectivity-coated back facets, threshold-current characteristic temperature coefficients, T{sub 0}, as high as 283 K and slope-efficiency characteristic temperature coefficients, T{sub 1}, as high as 561 K, over the 20–60 °C heatsink-temperature range. These high T{sub 0} and T{sub 1} values reflect at least a factor of four reduction in carrier-leakage current compared to conventional 8–9 μm-emitting QCLs. Room temperature, pulsed, threshold-current densities are 1.58 kA/cm{sup 2}; values comparable to those formore » 35-period conventional QCLs of similar injector-region doping level. Superlinear behavior of the light-current curves is shown to be the result of the onset of resonant extraction from the lower laser level at a drive level of ∼1.3× threshold. Maximum room-temperature slope efficiencies are 1.23 W/A; that is, slope efficiency per period values of 35 mW/A, which are 37%–40% higher than for same-geometry conventional 8–9 μm-emitting QCLs. Since the waveguide-loss coefficients are very similar, we estimate that the internal differential efficiency is at least 30% higher than in conventional QCLs. Such high internal differential efficiency values reflect the combined effect of nearly complete carrier-leakage suppression and high differential efficiency of the laser transition (∼90%), due to resonant extraction from the lower laser level.« less

Temperature and current coefficients of lasing wavelength in tunable diode laser spectroscopy.

PubMed

Fukuda, M; Mishima, T; Nakayama, N; Masuda, T

2010-08-01

The factors determining temperature and current coefficients of lasing wavelength are investigated and discussed under monitoring CO(2)-gas absorption spectra. The diffusion rate of Joule heating at the active layer to the surrounding region is observed by monitoring the change in the junction voltage, which is a function of temperature and the wavelength (frequency) deviation under sinusoidal current modulation. Based on the experimental results, the time interval of monitoring the wavelength after changing the ambient temperature or injected current (scanning rate) has to be constant at least to eliminate the monitoring error induced by the deviation of lasing wavelength, though the temperature and current coefficients of lasing wavelength differ with the rate.

Spectroscopic Study of a Dark Lane and a Cool Loop in a Solar Limb Active Region by Hinode/EIS

NASA Astrophysics Data System (ADS)

Lee, Kyoung-Sun; Imada, S.; Moon, Y.-J.; Lee, Jin-Yi

2014-01-01

We investigated a cool loop and a dark lane over a limb active region on 2007 March 14 using the Hinode/EUV Imaging Spectrometer. The cool loop is clearly seen in the spectral lines formed at the transition region temperature. The dark lane is characterized by an elongated faint structure in the coronal spectral lines and is rooted on a bright point. We examined their electron densities, Doppler velocities, and nonthermal velocities as a function of distance from the limb. We derived electron densities using the density sensitive line pairs of Mg VII, Si X, Fe XII, Fe XIII, and Fe XIV spectra. We also compared the observed density scale heights with the calculated scale heights from each peak formation temperatures of the spectral lines under the hydrostatic equilibrium. We noted that the observed density scale heights of the cool loop are consistent with the calculated heights, with the exception of one observed cooler temperature; we also found that the observed scale heights of the dark lane are much lower than their calculated scale heights. The nonthermal velocity in the cool loop slightly decreases along the loop, while nonthermal velocity in the dark lane sharply falls off with height. Such a decrease in the nonthermal velocity may be explained by wave damping near the solar surface or by turbulence due to magnetic reconnection near the bright point.

Electric Field-aided Selective Activation for Indium-Gallium-Zinc-Oxide Thin Film Transistors

NASA Astrophysics Data System (ADS)

Lee, Heesoo; Chang, Ki Soo; Tak, Young Jun; Jung, Tae Soo; Park, Jeong Woo; Kim, Won-Gi; Chung, Jusung; Jeong, Chan Bae; Kim, Hyun Jae

2016-10-01

A new technique is proposed for the activation of low temperature amorphous InGaZnO thin film transistor (a-IGZO TFT) backplanes through application of a bias voltage and annealing at 130 °C simultaneously. In this ‘electrical activation’, the effects of annealing under bias are selectively focused in the channel region. Therefore, electrical activation can be an effective method for lower backplane processing temperatures from 280 °C to 130 °C. Devices fabricated with this method exhibit equivalent electrical properties to those of conventionally-fabricated samples. These results are analyzed electrically and thermodynamically using infrared microthermography. Various bias voltages are applied to the gate, source, and drain electrodes while samples are annealed at 130 °C for 1 hour. Without conventional high temperature annealing or electrical activation, current-voltage curves do not show transfer characteristics. However, electrically activated a-IGZO TFTs show superior electrical characteristics, comparable to the reference TFTs annealed at 280 °C for 1 hour. This effect is a result of the lower activation energy, and efficient transfer of electrical and thermal energy to a-IGZO TFTs. With this approach, superior low-temperature a-IGZO TFTs are fabricated successfully.

Electric Field-aided Selective Activation for Indium-Gallium-Zinc-Oxide Thin Film Transistors

PubMed Central

Lee, Heesoo; Chang, Ki Soo; Tak, Young Jun; Jung, Tae Soo; Park, Jeong Woo; Kim, Won-Gi; Chung, Jusung; Jeong, Chan Bae; Kim, Hyun Jae

2016-01-01

A new technique is proposed for the activation of low temperature amorphous InGaZnO thin film transistor (a-IGZO TFT) backplanes through application of a bias voltage and annealing at 130 °C simultaneously. In this ‘electrical activation’, the effects of annealing under bias are selectively focused in the channel region. Therefore, electrical activation can be an effective method for lower backplane processing temperatures from 280 °C to 130 °C. Devices fabricated with this method exhibit equivalent electrical properties to those of conventionally-fabricated samples. These results are analyzed electrically and thermodynamically using infrared microthermography. Various bias voltages are applied to the gate, source, and drain electrodes while samples are annealed at 130 °C for 1 hour. Without conventional high temperature annealing or electrical activation, current-voltage curves do not show transfer characteristics. However, electrically activated a-IGZO TFTs show superior electrical characteristics, comparable to the reference TFTs annealed at 280 °C for 1 hour. This effect is a result of the lower activation energy, and efficient transfer of electrical and thermal energy to a-IGZO TFTs. With this approach, superior low-temperature a-IGZO TFTs are fabricated successfully. PMID:27725695

Internal quantum efficiency and carrier dynamics in semipolar (2021) InGaN/GaN light-emitting diodes

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

Okur, Serdal; Nami, Mohsen; Rishinaramangalam, Ashwin K.

Here, the internal quantum efficiencies (IQE) and carrier lifetimes of semipolar (more » $$20\\bar{2}$$$\\bar{1}$$) InGaN/GaN LEDs with different active regions are measured using temperature-dependent, carrier-density-dependent, and time-resolved photoluminescence. Three active regions are investigated: one 12-nm-thick single quantum well (SQW), two 6-nm-thick QWs, and three 4-nm-thick QWs. The IQE is highest for the 12-nm-thick SQW and decreases as the well width decreases. The radiative lifetimes are similar for all structures, while the nonradiative lifetimes decrease as the well width decreases. The superior IQE and longer nonradiative lifetime of the SQW structure suggests using thick SQW active regions for high brightness semipolar ($$20\\bar{2}$$$\\bar{1}$$) LEDs.« less

Internal quantum efficiency and carrier dynamics in semipolar (2021) InGaN/GaN light-emitting diodes

DOE PAGES

Okur, Serdal; Nami, Mohsen; Rishinaramangalam, Ashwin K.; ...

2017-01-26

Here, the internal quantum efficiencies (IQE) and carrier lifetimes of semipolar (more » $$20\\bar{2}$$$\\bar{1}$$) InGaN/GaN LEDs with different active regions are measured using temperature-dependent, carrier-density-dependent, and time-resolved photoluminescence. Three active regions are investigated: one 12-nm-thick single quantum well (SQW), two 6-nm-thick QWs, and three 4-nm-thick QWs. The IQE is highest for the 12-nm-thick SQW and decreases as the well width decreases. The radiative lifetimes are similar for all structures, while the nonradiative lifetimes decrease as the well width decreases. The superior IQE and longer nonradiative lifetime of the SQW structure suggests using thick SQW active regions for high brightness semipolar ($$20\\bar{2}$$$\\bar{1}$$) LEDs.« less

An Active Fire Temperature Retrieval Model Using Hyperspectral Remote Sensing

NASA Astrophysics Data System (ADS)

Quigley, K. W.; Roberts, D. A.; Miller, D.

2017-12-01

Wildfire is both an important ecological process and a dangerous natural threat that humans face. In situ measurements of wildfire temperature are notoriously difficult to collect due to dangerous conditions. Imaging spectrometry data has the potential to provide some of the most accurate and highest temporally-resolved active fire temperature retrieval information for monitoring and modeling. Recent studies on fire temperature retrieval have used have used Multiple Endmember Spectral Mixture Analysis applied to Airborne Visible applied to Airborne Visible / Infrared Imaging Spectrometer (AVIRIS) bands to model fire temperatures within the regions marked to contain fire, but these methods are less effective at coarser spatial resolutions, as linear mixing methods are degraded by saturation within the pixel. The assumption of a distribution of temperatures within pixels allows us to model pixels with an effective maximum and likely minimum temperature. This assumption allows a more robust approach to modeling temperature at different spatial scales. In this study, instrument-corrected radiance is forward-modeled for different ranges of temperatures, with weighted temperatures from an effective maximum temperature to a likely minimum temperature contributing to the total radiance of the modeled pixel. Effective maximum fire temperature is estimated by minimizing the Root Mean Square Error (RMSE) between modeled and measured fires. The model was tested using AVIRIS collected over the 2016 Sherpa Fire in Santa Barbara County, California,. While only in situ experimentation would be able to confirm active fire temperatures, the fit of the data to modeled radiance can be assessed, as well as the similarity in temperature distributions seen on different spatial resolution scales. Results show that this model improves upon current modeling methods in producing similar effective temperatures on multiple spatial scales as well as a similar modeled area distribution of those temperatures.

Regionalization of surface lipids in insects.

PubMed

Wang, Yiwen; Yu, Zhitao; Zhang, Jianzhen; Moussian, Bernard

2016-05-11

Cuticular hydrocarbons (CHCs) play a critical role in the establishment of the waterproof barrier that prevents dehydration and wetting in insects. While rich data are available on CHC composition in different species, we know little about their distribution and organization. Here, we report on our studies of the surface barrier of the fruit fly Drosophila melanogaster applying a newly developed Eosin Y staining method. The inert Eosin Y penetrates different regions of the adult body at distinct temperatures. By contrast, the larval body takes up the dye rather uniformly and gradually with increasing temperature. Cooling down specimens to 25°C after incubation at higher temperatures restores impermeability. Eosin Y penetration is also sensitive to lipid solvents such as chloroform indicating that permeability depends on CHCs. As in D. melanogaster adult flies, Eosin Y penetration is regionalized in Tenebrio molitor larvae, whereas it is not in Locusta migratoria nymphs. Regionalization of the fly surface implies tissue-specific variation of the genetic or biochemical programmes of CHC production and deposition. The Eosin Y-based map of CHC distribution may serve to identify the respective factors that are activated to accommodate ecological needs. © 2016 The Author(s).

Potential for thermal tolerance to mediate climate change effects on three members of a cool temperate lizard genus, Niveoscincus.

PubMed

Caldwell, Amanda J; While, Geoffrey M; Beeton, Nicholas J; Wapstra, Erik

2015-08-01

Climatic changes are predicted to be greater in higher latitude and mountainous regions but species specific impacts are difficult to predict. This is partly due to inter-specific variance in the physiological traits which mediate environmental temperature effects at the organismal level. We examined variation in the critical thermal minimum (CTmin), critical thermal maximum (CTmax) and evaporative water loss rates (EWL) of a widespread lowland (Niveoscincus ocellatus) and two range restricted highland (N. microlepidotus and N. greeni) members of a cool temperate Tasmanian lizard genus. The widespread lowland species had significantly higher CTmin and CTmax and significantly lower EWL than both highland species. Implications of inter-specific variation in thermal tolerance for activity were examined under contemporary and future climate change scenarios. Instances of air temperatures below CTmin were predicted to decline in frequency for the widespread lowland and both highland species. Air temperatures of high altitude sites were not predicted to exceed the CTmax of either highland species throughout the 21st century. In contrast, the widespread lowland species is predicted to experience air temperatures in excess of CTmax on 1 or 2 days by three of six global circulation models from 2068-2096. To estimate climate change effects on activity we reran the thermal tolerance models using minimum and maximum temperatures selected for activity. A net gain in available activity time was predicted under climate change for all three species; while air temperatures were predicted to exceed maximum temperatures selected for activity with increasing frequency, the change was not as great as the predicted decline in air temperatures below minimum temperatures selected for activity. We hypothesise that the major effect of rising air temperatures under climate change is an increase in available activity period for both the widespread lowland and highland species. The consequences of a greater available activity period will depend on the extent to which changes in climate alters other related factors, such as the nature and level of competition between the respective species. Copyright © 2015 Elsevier Ltd. All rights reserved.

Transition from compact to porous films in deposition with temperature-activated diffusion.

PubMed

di Caprio, Dung; Aarão Reis, F D A

2015-07-01

We study a thin-film growth model with temperature activated diffusion of adsorbed particles, allowing for the formation of overhangs and pores, but without detachment of adatoms or clusters from the deposit. Simulations in one-dimensional substrates are performed for several values of the diffusion-to-deposition ratio R of adatoms with a single bond and of the detachment probability ε per additional nearest neighbor, respectively, with activation energies are E(s) and E(b). If R and ε independently vary, regimes of low and high porosity are separated at 0.075≤ε(c)≤0.09, with vanishingly small porosity below that point and finite porosity for larger ε. Alternatively, for fixed values of E(s) and E(b) and varying temperature, the porosity has a minimum at T(c), and a nontrivial regime in which it increases with temperature is observed above that point. This is related to the large mobility of adatoms, resembling features of equilibrium surface roughening. In this high-temperature region, the deposit has the structure of a critical percolation cluster due to the nondesorption. The pores are regions enclosed by blobs of the corresponding percolating backbone, thus the distribution of pore size s is expected to scale as s(-τ̃) with τ̃≈1.45, in reasonable agreement with numerical estimates. Roughening of the outer interface of the deposits suggests Villain-Lai-Das Sarma scaling below the transition. Above the transition, the roughness exponent α≈0.35 is consistent with the percolation backbone structure via the relation α=2-d(B), where d(B) is the backbone fractal dimension.

Effect of temperature on crack growth rates of stress corrosion cracks in metal alloys exposed to water

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

Vogt, H.; Speidel, M.O.

1996-12-01

The effect of temperature on stress corrosion crack growth rates was studied using four commercial alloys: an Al-Mg-Zn alloy (7000-Series), an Al-Cu alloy (2000-Series), a Mg-rare earth alloy and a Zr 2.5% Nb alloy. Stress Corrosion crack growth rate data were obtained using fracture mechanic specimens which were tested in high purity water in the temperature range of {minus}10 C to 320 C, depending on the alloy. Attention was directed towards region 2 behavior, where the crack propagation rate is independent of stress intensity but sensitive to test temperature. The experimental activation energies of the different alloys were compared withmore » literature on rate-controlling steps in order to identify the possible stress corrosion cracking mechanisms. The results were also compared with the activation energies obtained from general corrosion and hydrogen diffusion experiments.« less

Toward the Active Control of Heat Transfer in the Hot Gas Path of Gas Turbines

NASA Technical Reports Server (NTRS)

Oertling, Jeremiah E.

2003-01-01

The work at NASA this summer has focused on assisting the Professor's project, namely "Toward the Active Control of Heat Transfer in the Hot Gas Path of Gas Turbines." The mode of controlling the Heat Transfer that the project focuses on is film cooling. Film cooling is used in high temperature regions of a gas turbine and extends the life of the components exposed to these extreme temperatures. A "cool" jet of air is injected along the surface of the blade and this layer of cool air shields the blade from the high temperatures. Cool is a relative term. The hot gas path temperatures reach on the order of 1500 to 2000 K. The "coo" air is on the order of 700 to 1000 K. This cooler air is bled off of an appropriate compressor stage. The next parameter of interest is the jet s position and orientation in the flow-field.

Using a Temperature Model and GIS Analysis of Landscape Features to Assess Headwater Resilience to Climate Change in the Driftless Area of Wisconsin

NASA Astrophysics Data System (ADS)

Schuster, Z.; Potter, K. W.

2015-12-01

Cold groundwater discharges in the headwaters of streams in the Driftless Area of Wisconsin help support cold-water fisheries that are valued by anglers throughout the Midwestern U.S. With climate change expected to increase temperatures and threaten the cold-water habitat of species such as brook and brown trout, the Wisconsin Department of Natural Resources is focusing resources on restoration as means of adapting to climate change. One of the challenges they face is a lack of site-specific temperature data in the headwaters streams that they are targeting for restoration activities. Previous work has shown that there is a strong relationship between air and stream temperature. In this study, we calculated weekly mean air-stream temperature relationships for Driftless region headwaters streams and used air temperature projections from a set of statistically-downscaled GCM models to model thermal metrics relevant to fish species suitability described by Lyons et al. (2009) for historical (1961-2000) and future (2046-2065) conditions. We then combined the stream temperature projections with a GIS analysis of physiographic and geologic features to attempt to develop a way of predicting ungaged headwaters streams in the region that are likely to be resilient to temperature increases due to climate change.

The role of the winter residual circulation in the summer mesopause regions in WACCM

NASA Astrophysics Data System (ADS)

Sanne Kuilman, Maartje; Karlsson, Bodil

2018-03-01

High winter planetary wave activity warms the summer polar mesopause via a link between the two hemispheres. Complex wave-mean-flow interactions take place on a global scale, involving sharpening and weakening of the summer zonal flow. Changes in the wind shear occasionally generate flow instabilities. Additionally, an altering zonal wind modifies the breaking of vertically propagating gravity waves. A crucial component for changes in the summer zonal flow is the equatorial temperature, as it modifies latitudinal gradients. Since several mechanisms drive variability in the summer zonal flow, it can be hard to distinguish which one is dominant. In the mechanism coined interhemispheric coupling, the mesospheric zonal flow is suggested to be a key player for how the summer polar mesosphere responds to planetary wave activity in the winter hemisphere. We here use the Whole Atmosphere Community Climate Model (WACCM) to investigate the role of the summer stratosphere in shaping the conditions of the summer polar mesosphere. Using composite analyses, we show that in the absence of an anomalous summer mesospheric temperature gradient between the equator and the polar region, weak planetary wave forcing in the winter would lead to a warming of the summer mesosphere region instead of a cooling, and vice versa. This is opposing the temperature signal of the interhemispheric coupling that takes place in the mesosphere, in which a cold and calm winter stratosphere goes together with a cold summer mesopause. We hereby strengthen the evidence that the variability in the summer mesopause region is mainly driven by changes in the summer mesosphere rather than in the summer stratosphere.

EUV observations of the active sun from the Harvard experiment on ATM. [Apollo Telescope Mount

NASA Technical Reports Server (NTRS)

Noyes, R. W.; Foukal, P. V.; Reeves, E. M.; Schmahl, E. J.; Timothy, J. G.; Vernazza, J. E.; Withbroe, G. L.; Huber, M. C. E.

1975-01-01

Some extreme UV observations of solar active regions made with a scanning spectroheliometer are described. Spectroheliograms constructed from digital data using a computer-driven cathode-ray tube display show clearly how the appearance of an active region changes as a function of temperature. Flare studies indicate that the impulsive rise in EUV emission occurs essentially simultaneously at all levels from the transition zone to the corona. Observations of sunspots reveal a very intense emission in transition zone lines. A matrix of Mg x rasters covering the entire sun reveals several hundred bright points having dimensions of 30 arc seconds or less. Other observations include coronal holes and prominences.

Regional Climate Change Hotspots over Africa

NASA Astrophysics Data System (ADS)

Anber, U.

2009-04-01

Regional Climate Change Index (RCCI), is developed based on regional mean precipitation change, mean surface air temperature change, and change in precipitation and temperature interannual variability. The RCCI is a comparative index designed to identify the most responsive regions to climate change, or Hot- Spots. The RCCI is calculated for Seven land regions over North Africa and Arabian region from the latest set of climate change projections by 14 global climates for the A1B, A2 and B1 IPCC emission scenarios. The concept of climate change can be approaches from the viewpoint of vulnerability or from that of climate response. In the former case a Hot-Spot can be defined as a region for which potential climate change impacts on the environment or different activity sectors can be particularly pronounced. In the other case, a Hot-Spot can be defined as a region whose climate is especially responsive to global change. In particular, the characterization of climate change response-based Hot-Spot can provide key information to identify and investigate climate change Hot-Spots based on results from multi-model ensemble of climate change simulations performed by modeling groups from around the world as contributions to the Assessment Report of Intergovernmental Panel on Climate Change (IPCC). A Regional Climate Change Index (RCCI) is defined based on four variables: change in regional mean surface air temperature relative to the global average temperature change ( or Regional Warming Amplification Factor, RWAF ), change in mean regional precipitation ( , of present day value ), change in regional surface air temperature interannual variability ( ,of present day value), change in regional precipitation interannual variability ( , of present day value ). In the definition of the RCCI it is important to include quantities other than mean change because often mean changes are not the only important factors for specific impacts. We thus also include inter annual variability, which is critical for many activity sectors, such as agriculture and water management. The RCCI is calculated for the above mentioned set of global climate change simulations and is inter compared across regions to identify climate change, Hot- Spots, that is regions with the largest values of RCCI. It is important to stress that, as will be seen, the RCCI is a comparative index, that is a small RCCI value does not imply a small absolute change, but only a small climate response compared to other regions. The models used are: CCMA-3-T47 CNRM-CM3 CSIRO-MK3 GFDL-CM2-0 GISS-ER INMCM3 IPSL-CM4 MIROC3-2M MIUB-ECHO-G MPI-ECHAM5 MRI-CGCM2 NCAR-CCSM3 NCAR-PCM1 UKMO-HADCM3 Note that the 3 IPCC emission scenarios, A1B, B1 and A2 almost encompass the entire IPCC scenario range, the A2 being close to the high end of the range, the B1 close to the low end and the A1B lying toward the middle of the range. The model data are obtained from the IPCC site and are interpolated onto a common 1 degree grid to facilitate intercomparison. The RCCI is here defined as in Giorgi (2006), except that the entire yea is devided into two six months periods, D J F M A M and J J A S O N. RCCI=[n(∆P)＋n(∆σP)+n(RWAF)+n(∆σT)]D...M + [n(∆P)＋n(∆σP)+n(RWAF)+n(∆σT)]J…N (1)

Ground temperature enhancements in seismic regions

NASA Astrophysics Data System (ADS)

Parrot, M.; Pokhotelov, O.; Surkov, V.; Hayakawa, M.

In the past decade, numerous observations of surface and near surface temperature anomalies before earthquakes have been published. Monitoring of the seismo -active regions from space have been made in visible and infrared ranges by various satellites: NOOA satellites, UARS, TERRA and etc. This paper presents some examples of these observations. A review of different mechanisms to explain the phenomenon is given and a more detailed explanation of the mechanism proposed by the authors is presented. It is shown that long term temperature anomalies can arise due to the rock warming resulting from the underground water upward filtrating. However, the short term temperature anomalies observed several days before an earthquake, are due to the change in the specific heat capacity and in the heat conductivity of the soil induced by the variations of the moisture. This research is partially supported by the Commission of the EU (Grant No. INTAS-2001-0456), by ISTC through Research Grant No. 1121 and by Russian Fund for Basic Research through Grant No. 02-05-64612.

Parametric Investigation of the Kinetics of Growth of Carbon-Nanotube Arrays on Iron Nanoparticles in the Process of Chemical Vapor Deposition of Hydrocarbons

NASA Astrophysics Data System (ADS)

Futko, S. I.; Shulitski, B. G.; Labunov, V. A.; Ermolaevaa, E. M.

2015-03-01

On the basis of the kinetic model of synthesis of carbon nanotubes on iron nanoparticles in the process of chemical vapor deposition of hydrocarbons, the parametric dependences of characteristics of arrays of vertically oriented nanotubes on the temperature of their synthesis, the concentration of acetylene in a reactor, and the diameter of the catalyst nanoparticles were investigated. It is shown that the maximum on the temperature dependence of the rate of growth of carbon nanotubes, detected in experiments at a temperature of ~700oC is due to the competing processes of increasing the catalytic activity of iron nanoparticles and decreasing the acetylene concentration because of the signifi cant gas-phase decomposition of acetylene in the reactor before it enters the substrate with the catalyst. Our calculations have shown that the indicated maximum arises near the transition point separating the low-temperature region where multiwall nanotubes are predominantly synthesized from the higher-temperature region of generation of single-wall nanotubes in the process of chemical vapor deposition of hydrocarbons.

Filling the Eastern European gap in millennium-long temperature reconstructions

PubMed Central

Büntgen, Ulf; Kyncl, Tomáš; Ginzler, Christian; Jacks, David S.; Esper, Jan; Tegel, Willy; Heussner, Karl-Uwe; Kyncl, Josef

2013-01-01

Tree ring–based temperature reconstructions form the scientific backbone of the current global change debate. Although some European records extend into medieval times, high-resolution, long-term, regional-scale paleoclimatic evidence is missing for the eastern part of the continent. Here we compile 545 samples of living trees and historical timbers from the greater Tatra region to reconstruct interannual to centennial-long variations in Eastern European May–June temperature back to 1040 AD. Recent anthropogenic warming exceeds the range of past natural climate variability. Increased plague outbreaks and political conflicts, as well as decreased settlement activities, coincided with temperature depressions. The Black Death in the mid-14th century, the Thirty Years War in the early 17th century, and the French Invasion of Russia in the early 19th century all occurred during the coldest episodes of the last millennium. A comparison with summer temperature reconstructions from Scandinavia, the Alps, and the Pyrenees emphasizes the seasonal and spatial specificity of our results, questioning those large-scale reconstructions that simply average individual sites. PMID:23319641

Analysis of breast thermograms for ROI extraction and description using mathematical morphology

NASA Astrophysics Data System (ADS)

Zermeño-Loreto, O. A.; Toxqui-Quitl, C.; Orozco Guillén, E. E.; Padilla-Vivanco, A.

2017-09-01

The detection of a temperature increase or hot spots in breast thermograms can be related with high metabolic activity of disease cells. Image processing algorithms to seek mainly temperature increases above 3°C which have a high probability of being a malignancy are proposed. Also a derivative operator is used to highlights breast regions of interest (ROI). In order to determinate a medical alert, a feature descriptor of the ROI is constructed using its maximum temperature, maximum increase of temperature, sector/quadrant position in the breast, and area. The proposed algorithms are tested in a home database and a public database for mastology research.

Temperature dependent charge transport in poly(3-hexylthiophene) diodes

NASA Astrophysics Data System (ADS)

Rahaman, Abdulla Bin; Sarkar, Atri; Banerjee, Debamalya

2018-04-01

In this work, we present charge transport properties of poly(3-hexylthiophene) (P3HT) diodes under dark conditions. Temperature dependent current-voltage (J-V) characteristics shows that charge transport represents a transition from ohomic to trap limited current. The forward current density obeys a power law J˜Vm, m>2 represents the space charge limited current region in presence of traps within the band gap. Frequency dependent conductivity has been studied in a temperature range 150K-473K. The dc conductivity values show Arrhenius like behavior and it gives conductivity activation energy 223 meV. Temperature dependent conductivity indicates a thermodynamic transition of our system.

Selective area growth and characterization of InGaN nanocolumns for phosphor-free white light emission

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

Albert, S.; Bengoechea-Encabo, A.; Sanchez-Garcia, M. A.

This work reports on the morphology and light emission characteristics of ordered InGaN nanocolumns grown by plasma-assisted molecular beam epitaxy. Within the growth temperature range of 750 to 650 Degree-Sign C, the In incorporation can be modified either by the growth temperature, the In/Ga ratio, or the III/V ratio, following different mechanisms. Control of these factors allows the optimization of the InGaN nanocolumns light emission wavelength and line-shape. Furthermore, yellow-white emission is obtained at room temperature from nanostructures with a composition-graded active InGaN region obtained by temperature gradients during growth.

Simultaneous Observation of High Temperature Plasma of Solar Corona By TESIS CORONAS-PHOTON and XRT Hinode.

NASA Astrophysics Data System (ADS)

Reva, A.; Kuzin, S.; Bogachev, S.; Shestov, S.

2012-05-01

The Mg XII spectroheliograph is a part of instrumentation complex TESIS (satellite CORONAS-PHOTON). This instrument builds monochromatic images of hot plasma of the solar corona (λ = 8.42 Å, T>5 MK). The Mg XII spectroheliograph observed hot plasma in the non-flaring active-region NOAA 11019 during nine days. We reconstructed DEM of this active region with the help of genetic algorithm (we used data of the Mg XII spectroheliograph, XRT and EIT). Emission measure of the hot component amounts 1 % of the emission measure of the cool component.

The Rice R2R3-MYB Transcription Factor OsMYB55 Is Involved in the Tolerance to High Temperature and Modulates Amino Acid Metabolism

PubMed Central

El-kereamy, Ashraf; Bi, Yong-Mei; Ranathunge, Kosala; Beatty, Perrin H.; Good, Allen G.; Rothstein, Steven J.

2012-01-01

Temperatures higher than the optimum negatively affects plant growth and development. Tolerance to high temperature is a complex process that involves several pathways. Understanding this process, especially in crops such as rice, is essential to prepare for predicted climate changes due to global warming. Here, we show that OsMYB55 is induced by high temperature and overexpression of OsMYB55 resulted in improved plant growth under high temperature and decreased the negative effect of high temperature on grain yield. Transcriptome analysis revealed an increase in expression of several genes involved in amino acids metabolism. We demonstrate that OsMYB55 binds to the promoter regions of target genes and directly activates expression of some of those genes including glutamine synthetase (OsGS1;2) glutamine amidotransferase (GAT1) and glutamate decarboxylase 3 (GAD3). OsMYB55 overexpression resulted in an increase in total amino acid content and of the individual amino acids produced by the activation of the above mentioned genes and known for their roles in stress tolerance, namely L-glutamic acid, GABA and arginine especially under high temperature condition. In conclusion, overexpression of OsMYB55 improves rice plant tolerance to high temperature, and this high tolerance is associated with enhanced amino acid metabolism through transcription activation. PMID:23251677

Heating the sun's lower transition region with fine-scale electric currents

NASA Technical Reports Server (NTRS)

Rabin, D.; Moore, R.

1984-01-01

Analytical and observational data are presented to show that the lower transition zone, a 100 km thick region at 10,000-200,000 K between the solar chromosphere and corona, is heated by local electric currents. The study was spurred by correlations between the enhanced atmospheric heating and magnetospheric flux in the chromospheric network and active regions. Field aligned current heated flux loops are asserted to mainly reside in and make up most of the transition region. It is shown that thermal conduction from the sides of hot gas columns generated by the current dissipation is the source of the observed temperature distribution in the transition regions.

The influence of mid-latitude storm tracks on hot, cold, dry and wet extremes

PubMed Central

Lehmann, Jascha; Coumou, Dim

2015-01-01

Changes in mid-latitude circulation can strongly affect the number and intensity of extreme weather events. In particular, high-amplitude quasi-stationary planetary waves have been linked to prolonged weather extremes at the surface. In contrast, analyses of fast-traveling synoptic-scale waves and their direct influence on heat and cold extremes are scarce though changes in such waves have been detected and are projected for the 21st century. Here we apply regression analyses of synoptic activity with surface temperature and precipitation in monthly gridded observational data. We show that over large parts of mid-latitude continental regions, summer heat extremes are associated with low storm track activity. In winter, the occurrence of cold spells is related to low storm track activity over parts of eastern North America, Europe, and central- to eastern Asia. Storm tracks thus have a moderating effect on continental temperatures. Pronounced storm track activity favors monthly rainfall extremes throughout the year, whereas dry spells are associated with a lack thereof. Trend analyses reveal significant regional changes in recent decades favoring the occurrence of cold spells in the eastern US, droughts in California and heat extremes over Eurasia. PMID:26657163

Reduced African Easterly Wave Activity with Quadrupled CO 2 in the Superparameterized CESM

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

Hannah, Walter M.; Aiyyer, Anantha

African easterly wave (AEW) activity is examined in quadrupled CO 2 experiments with the superparameterized CESM (SP-CESM). The variance of 2–10-day filtered precipitation increases with warming over the West African monsoon region, suggesting increased AEW activity. The perturbation enstrophy budget is used to investigate the dynamic signature of AEW activity. The northern wave track becomes more active associated with enhanced baroclinicity, consistent with previous studies. The southern track exhibits a surprising reduction of wave activity associated with less frequent occurrence of weak waves and a slight increase in the occurrence of strong waves. These changes are connected to changes inmore » the profile of vortex stretching and tilting that can be understood as interconnected consequences of increased static stability from the lapse rate response, weak temperature gradient balance, and the fixed anvil temperature hypothesis.« less

Reduced African Easterly Wave Activity with Quadrupled CO 2 in the Superparameterized CESM

DOE PAGES

Hannah, Walter M.; Aiyyer, Anantha

2017-10-01

African easterly wave (AEW) activity is examined in quadrupled CO 2 experiments with the superparameterized CESM (SP-CESM). The variance of 2–10-day filtered precipitation increases with warming over the West African monsoon region, suggesting increased AEW activity. The perturbation enstrophy budget is used to investigate the dynamic signature of AEW activity. The northern wave track becomes more active associated with enhanced baroclinicity, consistent with previous studies. The southern track exhibits a surprising reduction of wave activity associated with less frequent occurrence of weak waves and a slight increase in the occurrence of strong waves. These changes are connected to changes inmore » the profile of vortex stretching and tilting that can be understood as interconnected consequences of increased static stability from the lapse rate response, weak temperature gradient balance, and the fixed anvil temperature hypothesis.« less

Femtosecond Raman-Induced Kerr Effect Study of Temperature-Dependent Intermolecular Dynamics in Imidazolium-Based Ionic Liquids: Effects of Anion Species and Cation Alkyl Groups.

PubMed

Kakinuma, Shohei; Ishida, Tateki; Shirota, Hideaki

2017-01-12

The temperature dependence of the intermolecular vibrational dynamics in imidazolium-based ionic liquids (ILs) with 10 different anions was studied by femtosecond Raman-induced Kerr effect spectroscopy. For all ILs investigated in this study, the intensity in the low-frequency region below 50 cm -1 increases, and the spectral density in the high-frequency region above 80 cm -1 decreases (and shows a redshift) with increasing temperature. The first phenomenon would be attributed to the activation of the translational vibrational motions, whereas the second one is ascribed to the slowing librational motion of the imidazolium ring with increasing temperature. Calculated spectra of the density of states for the intermolecular vibrations of 1-butyl-3-methylimidazolium hexafluorophosphate, which is one of the experiment samples studied here, obtained by molecular dynamics simulation agreed well with the experimental results and confirmed the spectral assignments. When we compared the difference spectra between spectra measured at various temperatures and the spectrum measured at 293 K, a clear difference was found in the ∼50 cm -1 region of the Kerr spectra of 1-butyl-3-methylimidazolium thiocyanate and 1-butyl-3-methylimidazolium dicyanamide from those of the other ILs. The difference might have originated from the librational motions of the corresponding anions. We also compared the temperature-dependent Kerr spectra of hexafluorophosphate salts of 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, and 1-heptyl-3-methylimidazolium cations. These ILs showed a similar temperature dependence, which was not affected by the alkyl group length. The temperature-dependent viscosities and glass transition temperatures of the ILs were also estimated to determine their fragilities.

Geothermal Energy

DTIC Science & Technology

1975-11-15

temperature conditions, etc. It is also engaged on physiological studies, on studies of nutrition for increasing plants and studies on the agricultural...activity, especially in the Acapulco region. The zones known as Sierra Madre del Sur, Sierra de Chiapas, the Gulf coastal plain and the Yucatan

Hybrid activated sludge/biofilm process for the treatment of municipal wastewater in a cold climate region: a case study.

PubMed

Di Trapani, Daniele; Christensso, Magnus; Odegaard, Hallvard

2011-01-01

A hybrid activated sludge/biofilm process was investigated for wastewater treatment in a cold climate region. This process, which contains both suspended biomass and biofilm, usually referred as IFAS process, is created by introducing plastic elements as biofilm carrier media into a conventional activated sludge reactor. In the present study, a hybrid process, composed of an activated sludge and a moving bed biofilm reactor was used. The aim of this paper has been to investigate the performances of a hybrid process, and in particular to gain insight the nitrification process, when operated at relatively low MLSS SRT and low temperatures. The results of a pilot-scale study carried out at the Department of Hydraulic and Environmental Engineering at the Norwegian University of Science and Technology in Trondheim are presented. The experimental campaign was divided into two periods. The pilot plant was first operated with a constant HRT of 4.5 hours, while in the second period the influent flow was increased so that HRT was 3.5 hours. The average temperature was near 11.5°C in the overall experimental campaign. The average mixed liquor SRT was 5.7 days. Batch tests on both carriers and suspended biomass were performed in order to evaluate the nitrification rate of the two different biomasses. The results demonstrated that this kind of reactor can efficiently be used for the upgrading of conventional activated sludge plant for achieving year-round nitrification, also in presence of low temperatures, and without the need of additional volumes.

Unfolding and inactivation during thermal denaturation of an enzyme that exhibits phytase and acid phosphatase activities.

PubMed

Wang, Xiao-Yun; Meng, Fan-Guo; Zhou, Hai-Meng

2004-03-01

The thermostability of an enzyme that exhibits phytase and acid phosphatase activities was studied. Kinetics of inactivation and unfolding during thermal denaturation of the enzyme were compared. The loss of phytase activity on thermal denaturation is most suggestive of a reversible process. As for acid phosphatase activities, an interesting phenomenon was observed; there are two phases in thermal inactivation: when the temperature was between 45 and 50 degrees C, the thermal inactivation could be characterized as an irreversible inactivation which had some residual activity and when the temperature was above 55 degrees C, the thermal inactivation could be characterized as an irreversible process which had no residual activity. The microscopic rate constants for the free enzyme and substrate-enzyme complex were determined by Tsou's method [Adv. Enzymol. Relat. Areas Mol. Biol. 61 (1988) 381]. Fluorescence analyses indicate that when the enzyme was treated at temperatures below 60 degrees C for 60 min, the conformation of the enzyme had no detectable change; when the temperatures were above 60 degrees C, some fluorescence red-shift could be observed with a decrease in emission intensity. The inactivation rates (k(+0)) of free enzymes were faster than those of conformational changes during thermal denaturation at the same temperature. The rapid inactivation and slow conformational changes of phytase during thermal denaturation suggest that inactivation occurs before significant conformational changes of the enzyme, and the active site of this enzyme is situated in a relatively fragile region which makes the active site more flexible than the molecule as a whole.

Potential hydrothermal resource temperatures in the Eastern Snake River Plain, Idaho

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

Ghanashayam Neupane; Earl D. Mattson; Cody J. Cannon

The Eastern Snake River Plain (ESRP) in southern Idaho is a region of high heat flow. Sustained volcanic activities in the wake of the passage of the Yellowstone Hotspot have turned this region into an area with great potential for geothermal resources as evidenced by numerous hot springs scattered along the margins of the plain and several hot-water producing wells and hot springs within the plain. Despite these thermal expressions, it is hypothesized that the pervasive presence of an overlying groundwater aquifer in the region effectively masks thermal signatures of deep-seated geothermal resources. The dilution of deeper thermal water andmore » re-equilibration at lower temperature are significant challenges for the evaluation of potential resource areas in the ESRP. Over the past several years, we collected approximately 100 water samples from springs/wells for chemical analysis as well as assembled existing water chemistry data from literature. We applied several geothermometric and geochemical modeling tools to these chemical compositions of ESRP water samples. Geothermometric calculations based on principles of multicomponent equilibrium geothermometry with inverse geochemical modeling capability (e.g., Reservoir Temperature Estimator, RTEst) have been useful for the evaluation of reservoir temperatures. RTEst geothermometric calculations of ESRP thermal water samples indicated numerous potential geothermal areas with elevated reservoir temperatures. Specifically, areas around southern/southwestern side of the Bennett Hills and within the Camas Prairies in the western-northwestern regions of the ESRP and its margins suggest temperatures in the range of 140-200°C. In the northeastern portions of the ESRP, Lidy Hot Springs, Ashton, Newdale, and areas east of Idaho Falls have expected reservoir temperature =140 °C. In the southern ERSP, areas near Buhl and Twin Falls are found to have elevated temperatures as high as 160 °C. These areas are likely to host potentially economic geothermal resources; however, further detailed study is warranted to each site to evaluate hydrothermal suitability for economic use.« less

FTIR Study of Comustion Species in Several Regions of a Candle Flame

NASA Astrophysics Data System (ADS)

White, Allen R.

2013-06-01

The complex chemical structure of the fuel in a candle flame, parafin, is broken down into smaller hydrocarbons in the dark region just above the candle wick during combustion. This creates fuel-rich, fuel-lean, hydrocarbon reaction, and combustion product regions in the flame during combustion that are spectroscopically rich, particularly in the infrared. IR emissions were measured for each reaction region via collection optics focused into an FTIR and used to identify IR active species present in that region and, when possible, temperature of the sampling region. The results of the measurements are useful for combustion reaction modeling as well as for future validation of mass spectroscopy sampling systems.

Impact of different temperatures on survival and energy metabolism in the Asian citrus psyllid, Diaphorina citri Kuwayama.

PubMed

El-Shesheny, Ibrahim; Hijaz, Faraj; El-Hawary, Ibrahim; Mesbah, Ibrahim; Killiny, Nabil

2016-02-01

Temperature influences the life history and metabolic parameters of insects. Asian citrus psyllid (ACP), Diaphorina citri is a tropical and subtropical pest. ACP invaded new regions around the world and threatened the citrus industry as a vector for Huanglongbing (HLB) disease. ACP is widely distributed and can survive high (up to 45 °C) and low temperatures (as low as -6 °C). The precise mechanism of temperature tolerance in ACP is poorly understood. We investigated adult survival, cellular energy balance, gene expression, and nucleotide and sugar-nucleotide changes under the effect of different temperature regimes (0 °C to 45 °C with 5 °C intervals). The optimum temperatures for survival were 20 and 25 °C. Low temperatures of 0 °C and 5 °C caused 50% mortality after 2 and 4 days respectively, while one day at high temperature (40 °C and 45 °C) caused more than 95% mortality. The lowest quantity of ATP (3.69 ± 1.6 ng/insect) and the maximum ATPase enzyme activities (57.43 ± 7.6 μU/insect) were observed at 25 °C. Correlation between ATP quantities and ATPase activity was negative. Gene expression of hsp 70, V-type proton ATPase catalytic subunit A and ATP synthase α subunit matched these results. Twenty-four nucleotides and sugar-nucleotides were quantified using HPLC in ACP adults maintained at low, high, and optimum temperatures. The nucleotide profiles were different among treatments. The ratios between AMP:ATP and ADP:ATP were significantly decreased and positively correlated to adults survival, whereas the adenylate energy charge was increased in response to low and high temperatures. Exploring energy metabolic regulation in relation with adult survival might help in understanding the physiological basis of how ACP tolerates newly invaded regions. Copyright © 2015 Elsevier Inc. All rights reserved.

The cryptoendolithic microbial environment in the Ross Desert of Antarctica: satellite-transmitted continuous nanoclimate data, 1984 to 1986.

PubMed

Friedmann, E I; McKay, C P; Nienow, J A

1987-01-01

A satellite mediated station for monitoring nanoclimate (climate in the millimeter range) data, suitable for use in polar regions is described. The station, located in the Ross desert of Antarctica, has been in operation for more than 3 years, measuring rock temperatures, air temperature, light, snow, wind, and moisture. The data indicate that biological activity in the cryptoendolithic microbial ecosystem is limited to the period from mid November to mid February. The total number of hours of biological activity, based on assumptions of the minimum light, temperature and moisture requirements of the community, is less than 1000 h/year. The time above 0 degrees C, representing more nearly optimal conditions, is between 50 and 550 h/year, depending on the orientation of the surface.

The cryptoendolithic microbial environment in the Ross Desert of Antarctica: satellite-transmitted continuous nanoclimate data, 1984 to 1986

NASA Technical Reports Server (NTRS)

Friedmann, E. I.; McKay, C. P.; Nienow, J. A.

1987-01-01

A satellite mediated station for monitoring nanoclimate (climate in the millimeter range) data, suitable for use in polar regions is described. The station, located in the Ross desert of Antarctica, has been in operation for more than 3 years, measuring rock temperatures, air temperature, light, snow, wind, and moisture. The data indicate that biological activity in the cryptoendolithic microbial ecosystem is limited to the period from mid November to mid February. The total number of hours of biological activity, based on assumptions of the minimum light, temperature and moisture requirements of the community, is less than 1000 h/year. The time above 0 degrees C, representing more nearly optimal conditions, is between 50 and 550 h/year, depending on the orientation of the surface.

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

Hochstein, M.P.; Sudarman, Sayogi

There are at least 30 high temperatures systems (with inferred reservoir temperatures > 200 C) along the active Sumatra Arc that transfer heat from crustal intrusions to the surface. These systems, together with eleven active volcanoes, five degassing volcanoes and one caldera volcano (Lake Toba), are controlled by the Sumatra Fault Zone, an active mega shear zone that follows the median axis of the arc. At least half of the active and degassing volcanoes are associated with volcanic geothermal reservoirs containing magmatic gases and acid fluids. Large, low temperature resources exist in the Tertiary sedimentary basins of east Sumatra (back-arcmore » region), where anomalously higher thermal gradients (up to 8 C/100 m) have been measured. Volcanic activity was not continuous during the Cenozoic; subduction and arc volcanism probably decreased after the Eocene as a result of a clockwise rotation of Sumatra. In the Late Miocene, subduction started again, and andesitic volcanism reached a new peak of intensity in the Pliocene and has been continuous ever since. Rhyolitic volcanism, which has produced voluminous ignimbrite flows, began later (Pliocene/Pleistocene). All known rhyolitic centers associated with ignimbrite flows appear to lie along the Sumatra Fault Zone.« less

Remote enzyme activation using gold coated magnetite as antennae for radio frequency fields

NASA Astrophysics Data System (ADS)

Collins, Christian B.; Ackerson, Christopher J.

2018-02-01

The emerging field of remote enzyme activation, or the ability to remotely turn thermophilic increase enzyme activity, could be a valuable tool for understanding cellular processes. Through exploitation of the temperature dependence of enzymatic processes and high thermal stability of thermophilic enzymes these experiments utilize nanoparticles as `antennae' that convert radiofrequency (RF) radiation into local heat, increasing activity of the enzymes without increasing the temperature of the surrounding bulk solution. To investigate this possible tool, thermolysin, a metalloprotease was covalently conjugated to 4nm gold coated magnetite particles via peptide bond formation with the protecting ligand shell. RF stimulated protease activity at 17.76 MHz in a solenoid shaped antenna, utilizing both electric and magnetic field interactions was investigated. On average 40 percent higher protease activity was observed in the radio frequency fields then when bulk heating the sample to the same temperature. This is attributed to electrophoretic motion of the nanoparticle enzyme conjugates and local regions of heat generated by the relaxation of the magnetite cores with the oscillating field. Radio frequency local heating of nanoparticles conjugated to enzymes as demonstrated could be useful in the activation of specific enzymes in complex cellular environments.

Evaluating impacts of climate change on future water scarcity in an intensively managed semi-arid region using a coupled model of biophysical processes and water rights

NASA Astrophysics Data System (ADS)

Han, B.; Flores, A. N.; Benner, S. G.

2017-12-01

In semiarid and arid regions where water supply is intensively managed, future water scarcity is a product of complex interactions between climate change and human activities. Evaluating future water scarcity under alternative scenarios of climate change, therefore, necessitates modeling approaches that explicitly represent the coupled biophysical and social processes responsible for the redistribution of water in these regions. At regional scales a particular challenge lies in adequately capturing not only the central tendencies of change in projections of climate change, but also the associated plausible range of variability in those projections. This study develops a framework that combines a stochastic weather generator, historical climate observations, and statistically downscaled General Circulation Model (GCM) projections. The method generates a large ensemble of daily climate realizations, avoiding deficiencies of using a few or mean values of individual GCM realizations. Three climate change scenario groups reflecting the historical, RCP4.5, and RCP8.5 future projections are developed. Importantly, the model explicitly captures the spatiotemporally varying irrigation activities as constrained by local water rights in a rapidly growing, semi-arid human-environment system in southwest Idaho. We use this modeling framework to project water use and scarcity patterns under the three future climate change scenarios. The model is built using the Envision alternative futures modeling framework. Climate projections for the region show future increases in both precipitation and temperature, especially under the RCP8.5 scenario. The increase of temperature has a direct influence on the increase of the irrigation water use and water scarcity, while the influence of increased precipitation on water use is less clear. The predicted changes are potentially useful in identifying areas in the watershed particularly sensitive to water scarcity, the relative importance of changes in precipitation versus temperature as a driver of scarcity, and potential shortcomings of the current water management framework in the region.

The determinants of thermal comfort in cool water.

PubMed

Guéritée, J; House, J R; Redortier, B; Tipton, M J

2015-10-01

Water-based activities may result in the loss of thermal comfort (TC). We hypothesized that in cooling water, the hands and feet would be responsible. Supine immersions were conducted in up to five clothing conditions (exposing various regions), as well as investigations to determine if a "reference" skin temperature (Tsk) distribution in thermoneutral air would help interpret our findings. After 10 min in 34.5 °C water, the temperature was decreased to 19.5 °C over 20 min; eight resting or exercising volunteers reported when they no longer felt comfortable and which region was responsible. TC, rectal temperature, and Tsk were measured. Rather than the extremities, the lower back and chest caused the loss of overall TC. At this point, mean (SD) chest Tsk was 3.3 (1.7) °C lower than the reference temperature (P = 0.005), and 3.8 (1.5) °C lower for the back (P = 0.002). Finger Tsk was 3.1 (2.7) °C higher than the reference temperature (P = 0.037). In cool and cooling water, hands and feet, already adapted to colder air temperatures, will not cause discomfort. Contrarily, more discomfort may arise from the chest and lower back, as these regions cool by more than normal. Thus, Tsk distribution in thermoneutral air may help understand variations in TC responses across the body. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

EUV SPECTRAL LINE FORMATION AND THE TEMPERATURE STRUCTURE OF ACTIVE REGION FAN LOOPS: OBSERVATIONS WITH HINODE/EIS AND SDO/AIA

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

Brooks, David H.; Young, Peter R.; Warren, Harry P., E-mail: dhbrooks@ssd5.nrl.navy.mil

2011-04-01

With the aim of studying active region fan loops using observations from the Hinode EUV Imaging Spectrometer (EIS) and Solar Dynamics Observatory Atmospheric Imaging Assembly (AIA), we investigate a number of inconsistencies in modeling the absolute intensities of Fe VIII and Si VII lines, and address why spectroheliograms formed from these lines look very similar despite the fact that ionization equilibrium calculations suggest that they have significantly different formation temperatures: log(T{sub e} /K) = 5.6 and 5.8, respectively. It is important to resolve these issues because confidence has been undermined in their use for differential emission measure (DEM) analysis, andmore » Fe VIII is the main contributor to the AIA 131 A channel at low temperatures. Furthermore, the strong Fe VIII 185.213 A and Si VII 275.368 A lines are the best EIS lines to use for velocity studies in the transition region, and for assigning the correct temperature to velocity measurements in the fans. We find that the Fe VIII 185.213 A line is particularly sensitive to the slope of the DEM, leading to disproportionate changes in its effective formation temperature. If the DEM has a steep gradient in the log(T{sub e} /K) = 5.6-5.8 temperature range, or is strongly peaked, Fe VIII 185.213 A and Si VII 275.368 A will be formed at the same temperature. We show that this effect explains the similarity of these images in the fans. Furthermore, we show that the most recent ionization balance compilations resolve the discrepancies in absolute intensities. With these difficulties overcome, we combine EIS and AIA data to determine the temperature structure of a number of fan loops and find that they have peak temperatures of 0.8-1.2 MK. The EIS data indicate that the temperature distribution has a finite (but narrow) width < log ({sigma}{sub Te}/K) = 5.5 which, in one detailed case, is found to broaden substantially toward the loop base. AIA and EIS yield similar results on the temperature, emission measure magnitude, and thermal distribution in the fans, though sometimes the AIA data suggest a relatively larger thermal width. The result is that both the Fe VIII 185.213 A and Si VII 275.368 A lines are formed at log(T{sub e} /K){approx} 5.9 in the fans, and the AIA 131 A response also shifts to this temperature.« less

Impact of anthropogenic climate change and human activities on environment and ecosystem services in arid regions.

PubMed

Mahmoud, Shereif H; Gan, Thian Y

2018-08-15

The implications of anthropogenic climate change, human activities and land use change (LUC) on the environment and ecosystem services in the coastal regions of Saudi Arabia were analyzed. Earth observations data was used to drive land use categories between 1970 and 2014. Next, a Markov-CA model was developed to characterize the dynamic of LUC between 2014 and 2100 and their impacts on regions' climate and environment. Non-parametric change point and trend detection algorithms were applied to temperature, precipitation and greenhouse gases data to investigate the presence of anthropogenic climate change. Lastly, climate models were used to project future climate change between 2014 and 2100. The analysis of LUC revealed that between 1970 and 2014, built up areas experienced the greatest growth during the study period, leading to a significant monotonic trend. Urban areas increased by 2349.61km 2 between 1970 and 2014, an average increase of >53.4km 2 /yr. The projected LUC between 2014 and 2100 indicate a continued increase in urban areas and irrigated cropland. Human alteration of land use from natural vegetation and forests to other uses after 1970, resulted in a loss, degradation, and fragmentation, all of which usually have devastating effects on the biodiversity of the region. Resulting in a statistically significant change point in temperature anomaly after 1968 with a warming trend of 0.24°C/decade and a downward trend in precipitation anomaly of 12.2mm/decade. Total greenhouse gas emissions including all anthropogenic sources showed a statistically significant positive trend of 78,090Kt/decade after 1991. This is reflected in the future projection of temperature anomaly between 1900 and 2100 with a future warming trend of 0.19°C/decade. In conclusion, human activities, industrial revelation, deforestation, land use transformation and increase in greenhouse gases had significant implications on the environment and ecosystem services of the study area. Copyright © 2018 Elsevier B.V. All rights reserved.

Absolute determination of the cross sections of ozone in the wavelength region 339-355 nm at temperatures 220-293 K

NASA Astrophysics Data System (ADS)

Cacciani, Marco; di Sarra, Alcide; Fiocco, Giorgio; Amoruso, Antonella

1989-06-01

Absolute measurements of the ozone absorption coefficient in the Huggins bands at different temperatures have been carried out. Ozone is produced by an electrical discharge and stored cryogenically; differential absorption measurements are subsequently obtained in a slowly evolving mixture of ozone and molecular oxygen. High resolution (to 0.012 nm) measurements cover a spectral range (339-355 nm) where the ozone absorption shows a strong dependence on temperature. Results at 293 and 220 K are reported; they are particularly interesting in view of the utilization of this spectral region as a low-absorption reference channel for the observation of atmospheric ozone profiles by active probing techniques. Coherent radiation at two wavelengths, around 355 and 353 nm, respectively, can be obtained as third harmonic of the fundamental output of an Nd:YAG laser and by H2 Raman shifting of an XeCl excimer laser output.

Global Ultraviolet Imager (GUVI) investigation

NASA Technical Reports Server (NTRS)

Christensen, Andrew B.

1995-01-01

This report covers the activities performed under NAS5-32572. The results of those activities are included in this Final Report. TIMED Science Objectives: (1) To determine the temperature, density, and wind structure of the MLTI (mixed layer thermal inertia), including the seasonal and latitudinal variations; and (2) To determine the relative importance of the various radiative, chemical, electrodynamical, and dynamical sources and sinks of energy for the thermal structure of the MLTI. GUVI Science Goals: (1) Determine the spatial and temporal variations of temperature and constituent densities in the lower thermosphere; and (2) Determine the importance of auroral energy sources and solar EUV (extreme ultraviolet) to the energy balance of the region.

Forging property, processing map, and mesoscale microstructural evolution modeling of a Ti-17 alloy with a lamellar (α+β) starting microstructure

NASA Astrophysics Data System (ADS)

Matsumoto, Hiroaki; Naito, Daiki; Miyoshi, Kento; Yamanaka, Kenta; Chiba, Akihiko; Yamabe-Mitarai, Yoko

2017-12-01

This work identifies microstructural conversion mechanisms during hot deformation (at temperatures ranging from 750 °C to 1050 °C and strain rates ranging from 10-3 s-1 to 1 s-1) of a Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti-17) alloy with a lamellar starting microstructure and establishes constitutive formulae for predicting the microstructural evolution using finite-element analysis. In the α phase, lamellae kinking is the dominant mode in the higher strain rate region and dynamic globularization frequently occurs at higher temperatures. In the β phase, continuous dynamic recrystallization is the dominant mode below the transition temperature, Tβ (880 890 °C). Dynamic recovery tends to be more active at conditions of lower strain rates and higher temperatures. At temperatures above Tβ, continuous dynamic recrystallization of the β phase frequently occurs, especially in the lower strain rate region. A set of constitutive equations modeling the microstructural evolution and processing map characteristic are established by optimizing the experimental data and were later implemented in the DEFORM-3D software package. There is a satisfactory agreement between the experimental and simulated results, indicating that the established series of constitutive models can be used to reliably predict the properties of a Ti-17 alloy after forging in the (α+β) region.

Forging property, processing map, and mesoscale microstructural evolution modeling of a Ti-17 alloy with a lamellar (α+β) starting microstructure

PubMed Central

Matsumoto, Hiroaki; Naito, Daiki; Miyoshi, Kento; Yamanaka, Kenta; Chiba, Akihiko; Yamabe-Mitarai, Yoko

2017-01-01

Abstract This work identifies microstructural conversion mechanisms during hot deformation (at temperatures ranging from 750 °C to 1050 °C and strain rates ranging from 10−3 s−1 to 1 s−1) of a Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti-17) alloy with a lamellar starting microstructure and establishes constitutive formulae for predicting the microstructural evolution using finite-element analysis. In the α phase, lamellae kinking is the dominant mode in the higher strain rate region and dynamic globularization frequently occurs at higher temperatures. In the β phase, continuous dynamic recrystallization is the dominant mode below the transition temperature, T β (880~890 °C). Dynamic recovery tends to be more active at conditions of lower strain rates and higher temperatures. At temperatures above T β, continuous dynamic recrystallization of the β phase frequently occurs, especially in the lower strain rate region. A set of constitutive equations modeling the microstructural evolution and processing map characteristic are established by optimizing the experimental data and were later implemented in the DEFORM-3D software package. There is a satisfactory agreement between the experimental and simulated results, indicating that the established series of constitutive models can be used to reliably predict the properties of a Ti-17 alloy after forging in the (α+β) region. PMID:29152021

Forging property, processing map, and mesoscale microstructural evolution modeling of a Ti-17 alloy with a lamellar (α+β) starting microstructure.

PubMed

Matsumoto, Hiroaki; Naito, Daiki; Miyoshi, Kento; Yamanaka, Kenta; Chiba, Akihiko; Yamabe-Mitarai, Yoko

2017-01-01

This work identifies microstructural conversion mechanisms during hot deformation (at temperatures ranging from 750 °C to 1050 °C and strain rates ranging from 10 -3  s -1 to 1 s -1 ) of a Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti-17) alloy with a lamellar starting microstructure and establishes constitutive formulae for predicting the microstructural evolution using finite-element analysis. In the α phase, lamellae kinking is the dominant mode in the higher strain rate region and dynamic globularization frequently occurs at higher temperatures. In the β phase, continuous dynamic recrystallization is the dominant mode below the transition temperature, T β (880~890 °C). Dynamic recovery tends to be more active at conditions of lower strain rates and higher temperatures. At temperatures above T β , continuous dynamic recrystallization of the β phase frequently occurs, especially in the lower strain rate region. A set of constitutive equations modeling the microstructural evolution and processing map characteristic are established by optimizing the experimental data and were later implemented in the DEFORM-3D software package. There is a satisfactory agreement between the experimental and simulated results, indicating that the established series of constitutive models can be used to reliably predict the properties of a Ti-17 alloy after forging in the (α+ β ) region.

Use of MAGSAT anomaly data for crustal structure and mineral resources in the US midcontinent

NASA Technical Reports Server (NTRS)

Carmichael, R. S. (Principal Investigator); Black, R.

1982-01-01

Activities concerning the interpretation of processed MAGSAT data and maps are briefly reported. Work involving the identification of long wavelength 'regional' effects that might be associated with varying crustal thickness or Curie temperature depths is processing.

Energy balance in solar and stellar chromospheres

NASA Technical Reports Server (NTRS)

Avrett, E. H.

1981-01-01

Net radiative cooling rates for quiet and active regions of the solar chromosphere and for two stellar chromospheres are calculated from corresponding atmospheric models. Models of chromospheric temperature and microvelocity distributions are derived from observed spectra of a dark point within a cell, the average sun and a very bright network element on the quiet sun, a solar plage and flare, and the stars Alpha Boo and Lambda And. Net radiative cooling rates due to the transitions of various atoms and ions are then calculated from the models as a function of depth. Large values of the net radiative cooling rate are found at the base of the chromosphere-corona transition region which are due primarily to Lyman alpha emission, and a temperature plateau is obtained in the transition region itself. In the chromospheric regions, the calculated cooling rate is equal to the mechanical energy input as a function of height and thus provides a direct constraint on theories of chromospheric heating.

Global pattern of trends in streamflow and water availability in a changing climate

USGS Publications Warehouse

Milly, P.C.D.; Dunne, K.A.; Vecchia, A.V.

2005-01-01

Water availability on the continents is important for human health, economic activity, ecosystem function and geophysical processes. Because the saturation vapour pressure of water in air is highly sensitive to temperature, perturbations in the global water cycle are expected to accompany climate warming. Regional patterns of warming-induced changes in surface hydroclimate are complex and less certain than those in temperature, however, with both regional increases and decreases expected in precipitation and runoff. Here we show that an ensemble of 12 climate models exhibits qualitative and statistically significant skill in simulating observed regional patterns of twentieth-century multidecadal changes in streamflow. These models project 10–40% increases in runoff in eastern equatorial Africa, the La Plata basin and high-latitude North America and Eurasia, and 10–30% decreases in runoff in southern Africa, southern Europe, the Middle East and mid-latitude western North America by the year 2050. Such changes in sustainable water availability would have considerable regional-scale consequences for economies as well as ecosystems.

Global pattern of trends in streamflow and water availability in a changing climate.

PubMed

Milly, P C D; Dunne, K A; Vecchia, A V

2005-11-17

Water availability on the continents is important for human health, economic activity, ecosystem function and geophysical processes. Because the saturation vapour pressure of water in air is highly sensitive to temperature, perturbations in the global water cycle are expected to accompany climate warming. Regional patterns of warming-induced changes in surface hydroclimate are complex and less certain than those in temperature, however, with both regional increases and decreases expected in precipitation and runoff. Here we show that an ensemble of 12 climate models exhibits qualitative and statistically significant skill in simulating observed regional patterns of twentieth-century multidecadal changes in streamflow. These models project 10-40% increases in runoff in eastern equatorial Africa, the La Plata basin and high-latitude North America and Eurasia, and 10-30% decreases in runoff in southern Africa, southern Europe, the Middle East and mid-latitude western North America by the year 2050. Such changes in sustainable water availability would have considerable regional-scale consequences for economies as well as ecosystems.

Improving Accuracy in Arrhenius Models of Cell Death: Adding a Temperature-Dependent Time Delay.

PubMed

Pearce, John A

2015-12-01

The Arrhenius formulation for single-step irreversible unimolecular reactions has been used for many decades to describe the thermal damage and cell death processes. Arrhenius predictions are acceptably accurate for structural proteins, for some cell death assays, and for cell death at higher temperatures in most cell lines, above about 55 °C. However, in many cases--and particularly at hyperthermic temperatures, between about 43 and 55 °C--the particular intrinsic cell death or damage process under study exhibits a significant "shoulder" region that constant-rate Arrhenius models are unable to represent with acceptable accuracy. The primary limitation is that Arrhenius calculations always overestimate the cell death fraction, which leads to severely overoptimistic predictions of heating effectiveness in tumor treatment. Several more sophisticated mathematical model approaches have been suggested and show much-improved performance. But simpler models that have adequate accuracy would provide useful and practical alternatives to intricate biochemical analyses. Typical transient intrinsic cell death processes at hyperthermic temperatures consist of a slowly developing shoulder region followed by an essentially constant-rate region. The shoulder regions have been demonstrated to arise chiefly from complex functional protein signaling cascades that generate delays in the onset of the constant-rate region, but may involve heat shock protein activity as well. This paper shows that acceptably accurate and much-improved predictions in the simpler Arrhenius models can be obtained by adding a temperature-dependent time delay. Kinetic coefficients and the appropriate time delay are obtained from the constant-rate regions of the measured survival curves. The resulting predictions are seen to provide acceptably accurate results while not overestimating cell death. The method can be relatively easily incorporated into numerical models. Additionally, evidence is presented to support the application of compensation law behavior to the cell death processes--that is, the strong correlation between the kinetic coefficients, ln{A} and E(a), is confirmed.

Assessing operative natural and anthropogenic forcing factors from long-term climate time series of Uttarakhand (India) in the backdrop of recurring extreme rainfall events over northwest Himalaya

NASA Astrophysics Data System (ADS)

Agnihotri, Rajesh; Dimri, A. P.; Joshi, H. M.; Verma, N. K.; Sharma, C.; Singh, J.; Sundriyal, Y. P.

2017-05-01

The entire Indo-Himalayan region from northwest (Kashmir) to northeast (Assam) is facing prevalence of floods and landslides in recent years causing massive loss of property, human and animal lives, infrastructure, and eventually threatening tourist activities substantially. Extremely intense rainfall event of 2013 C.E. (between 15 and 17 June) kicked off mammoth flash floods in the Kedarnath area of Uttarakhand state, resulting in huge socioeconomic losses to the state and country. Uttarakhand is an important hilly region attracting thousands of tourists every year owing to numerous shrines and forested mountainous tourist spots. Though recent studies indicate a plausible weakening of Indian summer monsoon rainfall overall, recurrent anomalous high rainfall events over northwest Himalaya (e.g. -2010, 2013, and 2016) point out the need for a thorough reassessment of long-term time series data of regional rainfall and ambient temperatures in order to trace signatures of a shifting pattern in regional meteorology, if any. Accordingly, here we investigate 100-year-long monthly rainfall and air temperature time series data for a selected grid (28.5°N, 31.25°N; 78.75°E, 81.25°E) covering most parts of Uttarakhand state. We also examined temporal variance in interrelationships among regional meteorological data (temperature and precipitation) and key global climate variability indices using advance statistical methods. Major findings are (i) significant increase in pre-monsoon air temperature over Uttarakhand after 1997, (ii) increasing upward trend in June-July rainfall and its relationship with regional May temperatures (iii) monsoonal rainfall (June, July, August, and September; JJAS) showing covariance with interannual variability in Eurasian snow cover (ESC) extent during the month of March, and (iv) enhancing tendency of anomalous high rainfall events during negative phases of Arctic Oscillation. Obtained results indicate that under warming scenario, JJ rainfall (over AS) may further increase with occasional extreme rainfall spells when AO index (March) is negative.

Improved thermal stability of methylsilicone resins by compositing with N-doped graphene oxide/Co3O4 nanoparticles

NASA Astrophysics Data System (ADS)

Jiang, Bo; Zhao, Liwei; Guo, Jiang; Yan, Xingru; Ding, Daowei; Zhu, Changcheng; Huang, Yudong; Guo, Zhanhu

2016-06-01

Nanoparticles play important roles in enhancing the thermal-resistance of hosting polymer resins. Despite tremendous efforts, developing thermally stable methylsilicone resin at high temperatures is still a challenge. Herein, we report a strategy to increase the activation energy to slow down the decomposition/degradation of methylsilicone resin using synergistic effects between the Co3O4 nanoparticles and the nitrogen doped graphene oxide. The N-doped graphene oxides composited with Co3O4 nanoparticles were prepared by hydrolysis of cobalt nitrate hexahydrate in the presence of graphene oxide and were incorporated into the methylsilicone resin. Two-stage decompositions were observed, i.e., 200-300 and 400-500 °C. The activation energy for the low temperature region was enhanced by 47.117 kJ/mol (vs. 57.76 kJ/mol for pure resin). The enhanced thermal stability was due to the fact that the nanofillers prevented the silicone hydroxyl chain ends ``biting'' to delay the degradation. The activation energy for high-temperature region was enhanced by 11.585 kJ/mol (vs. 171.95 kJ/mol for pure resin). The nanofillers formed a protective layer to isolate oxygen from the hosting resin. The mechanism for the enhanced thermal stability through prohibited degradation with synergism of these nitrogen-doped graphene oxide nanocomposites was proposed as well.

Uncovering the role of the flexible C-terminal tail: A model study with Strep-tagged GFP.

PubMed

Lassalle, Michael W; Kondou, Shinobu

2016-06-01

Recently, it has been recognized that, much like an electric current in an electric circuit, dynamic disruptions from flexible, unstructured regions distal to the active region are transferred through the contact network to the active site and influence protein stability and/or function. As transmembrane proteins frequently possess the β-barrel structure, studies of proteins with this topology are required. The unstructured lid segments of the β-barrel GFP protein are conserved and could play a role in the backbone stabilization required for chromophore function. A study of the disordered C-terminus and the function within the lid is necessary. In this study, we entirely truncated the flexible C-terminal tail and investigated the N-terminal Strep-tagged GFP by fluorescence spectroscopy, and the temperature- and GdnHCl-induced unfolding by circular dichroism. The introduction of the unstructured Strep-tag itself changed the unfolding pathway. Truncating the entire flexible tail did not decrease the fluorescence intensity to a large extent; however, the protein stability changed dramatically. The temperature for half-denaturation T 1/2 changed significantly from 79 °C for the wild-type to 72.8 °C for the mutant. Unfolding kinetics at different temperatures have been induced by 4 M GdnHCl, and the apparent Arrhenius activation energy decreased by 40% as compared to the wild-type.

Accelerated life testing effects on CMOS microcircuit characteristics

NASA Technical Reports Server (NTRS)

1980-01-01

This report covers the time period from May 1976 to December 1979 and encompasses the three phases of accelerated testing: Phase 1, the 250 C testing; Phase 2, the 200 C testing; and Phase 3, the 125 C testing. The duration of the test in Phase 1 and Phase 2 was sufficient to take the devices into the wear out region. The wear out distributions were used to estimate the activation energy between the 250 C and the 200 C test temperatures. The duration of the 125 C test, 20,000 hours, was not sufficient to bring the test devices into the wear out region; consequently the third data point at 125 C for determining the consistency of activation energy could not be obtained. It was estimated that, for the most complex of the three device types, the activation energy between 200 C and 125 C should be at least as high as that between 250 C and 200 C. The practicality of the use of high temperature for the accelerated life tests from the point of view of durability of equipment was assessed. Guidelines for the development of accelerated life test conditions were proposed. The use of the silicon nitride overcoat to improve the high temperature accelerated life test characteristics of CMOS microcircuits was explored in Phase 4 of this study and is attached as an appendix to this report.

Impacts of large scale afforestation on regional climate: a case study in the Kubuqi Desert, Inner Mongolia based on WRF model

NASA Astrophysics Data System (ADS)

Wang, L.; Lin, G.; Feng, D.; Chen, S.; Schultz, N. M.; Fu, C.; Wei, Z.; Yin, C.; Wang, W.; Lee, X.

2017-12-01

To better design climate mitigation strategies, it is important to understand the response of regional climatic indicators and related biophysical forcings to large scale afforestation projects. The response of surface temperature (Ts) caused by afforestation activities in the Kubuqi Desert, Inner Mongolia, China is simulated by the weather research and forecasting (WRF) model and the temperature changes (ΔTs) are decomposed into contributions from changes in surface albedo, surface roughness, Bowen ratio and ground heat flux using the intrinsic biophysical mechanism (IBPM). The 30-m resolution land cover maps of the Kubuqi Desert corresponding to 2000 and 2010 conditions are analyzed and the major land use changes are found to be an increase in the area of grassland (6%) and shrubland (15%), but a decrease in the area of bare land (21%) owed to the aerial seeding afforestation activities organized by Elion Resources Group, Co. and local government agencies. Our WRF simulations show that during winter, the increased cover of vegetation mainly has a warming effect (0.38 K) in the daytime due to the changes in albedo (0.24 K) and Bowen ratio (0.15 K). In the nighttime, the vegetation has a slight warming effect (0.2 K) mainly caused by energy redistribution associated with roughness change (0.2 K) as a result of vegetation turbulence, which brought heat from aloft to the surface. Although both roughness change (-0.35 K) and Bowen ratio change (-0.35 K) have cooling effects during summer days, the warming effect caused by radiative forcing (0.93 K) dominates the ΔTs. During summer nights, the change in surface temperature is not significant. Our findings demonstrate that the large-scale afforestation project in the Kubuqi Desert during a decade alters the regional surface temperature and the analysis of biophysical forcings changes using WRF simulation provides useful information for developing climate change mitigation strategies in semi-arid and arid regions.

The Vegetation Trends and Drivers in Beijing-Tianjing Region from 1982 TO 2013 Based on Time Series Gimms NDVI3g

NASA Astrophysics Data System (ADS)

Liu, S.; Tian, H.; Wang, X.; Li, H.; He, Y.

2018-04-01

Vegetation plays a leading role in ecosystems. Plant communities are the main components of ecosystems. Green plants in ecosystems are the primary producers, and they provide the living organic matter for the survival of other organisms. The dynamics of most landscapes are driven by both natural processes and human activities. In this study, the growing season GIMMS NDVI3g and climatic data were used to analyse the vegetation trends and drivers in Beijing-Tianjin-Hebei region from 1982 to 2013. Result shows that, the vegetation in Beijing-Tianjin-Hebei region shows overall restoration and partial degradation trend. The significant restoration region accounts for 61.5 % of Beijing-Tianjin-Hebei region, while the significant degradation region accounts for 2.1 %. The dominant climatic factor for time series NDVI were analyzed using the multi-linear regression model. Vegetation growth in 17.9 % of Beijing-Tianjin-Hebei region is dominated by temperature, 35.5 % is dominated by precipitation, and 11.68 % is dominated by solar radiance. Human activities play important role for vegetation restoration in Beijing-Tianjin-Hebei Region, where the large scale forest restoration programs are the main human activities, such as the three-north shelterbelt construction project, Beijing-Tianjin-Hebei sandstorm source control project and grain for green projects.

Coronal Heating and the Magnetic Flux Content of the Network

NASA Technical Reports Server (NTRS)

Falconer, D. A.; Moore, R. L.; Porter, J. G.; Hathaway, D. H.; Rose, M. Franklin (Technical Monitor)

2001-01-01

Previously, from analysis of SOHO coronal images in combination with Kitt Peak magnetograms, we found that the quiet corona is the sum of two components: the large-scale corona and the coronal network. The large-scale corona consists of all coronal-temperature (T approximately 10(exp 6) K) structures larger than supergranules (greater than approximately 30,000 kilometers). The coronal network (1) consists of all coronal-temperature structures smaller than supergranules, (2) is rooted in and loosely traces the photospheric magnetic network, (3) has its brightest features seated on polarity dividing lines (neutral lines) in the network magnetic flux, and (4) produces only about 5% of the total coronal emission in quiet regions. The heating of the coronal network is apparently magnetic in origin. Here, from analysis of EIT coronal images of quiet regions in combination with magnetograms of the same quiet regions from SOHO/MDI and from Kitt Peak, we examine the other 95% of the quiet corona and its relation to the underlying magnetic network. We find: (1) Dividing the large-scale corona into its bright and dim halves divides the area into bright "continents" and dark "oceans" having spans of 2-4 supergranules. (2) These patterns are also present in the photospheric magnetograms: the network is stronger under the bright half and weaker under the dim half. (3) The radiation from the large-scale corona increases roughly as the cube root of the magnetic flux content of the underlying magnetic network. In contrast, the coronal radiation from an active region increases roughly linearly with the magnetic flux content of the active region. We assume, as is widely held, that nearly all of the large-scale corona is magnetically rooted in the network. Our results suggest that either the coronal heating in quiet regions has a large non-magnetic component, or, if the heating is predominantly produced via the magnetic field, the mechanism is significantly different than in active regions.

Satellite-based detection of global urban heat-island temperature influence

USGS Publications Warehouse

Gallo, K.P.; Adegoke, Jimmy O.; Owen, T.W.; Elvidge, C.D.

2002-01-01

This study utilizes a satellite-based methodology to assess the urban heat-island influence during warm season months for over 4400 stations included in the Global Historical Climatology Network of climate stations. The methodology includes local and regional satellite retrievals of an indicator of the presence green photosynthetically active vegetation at and around the stations. The difference in local and regional samples of the normalized difference vegetation index (NDVI) is used to estimate differences in mean air temperature. Stations classified as urban averaged 0.90??C (N. Hemisphere) and 0.92??C (S. Hemisphere) warmer than the surrounding environment on the basis of the NDVI-derived temperature estimates. Additionally, stations classified as rural averaged 0.19??C (N. Hemisphere) and 0.16??C (S. Hemisphere) warmer than the surrounding environment. The NDVI-derived temperature estimates were found to be in reasonable agreement with temperature differences observed between climate stations. The results suggest that satellite-derived data sets can be used to estimate the urban heat-island temperature influence on a global basis and that a more detailed analysis of rural stations and their surrounding environment may be necessary to assure that temperature trends derived from assumed rural environments are not influenced by changes in land use/land cover. Copyright 2002 by the American Geophysical Union.

Spatial variations in biomarkers of Mytilus edulis mussels at four polluted regions spanning the Northern Hemisphere

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

Gagne, F.; Burgeot, T.; Hellou, J.

2008-06-15

Economic and social developments have taken place at the expense of the health of the environment, both locally and on a global scale. In an attempt to better understand the large-scale effects of pollution and other stressors like climate change on the health status of Mytilus edulis, mussels were collected during the first two weeks of June 2005 at three sites (one pristine and two affected by pollution) located in each of the regions of the Canadian West Coast, the St. Lawrence estuary, the Atlantic East Coast and the northwestern coast of France, covering a total distance of some 11more » 000 km. The mussels were analyzed for morphologic integrity (condition factor), gametogenic activity (gonado-somatic and gonad maturation index, vitellogenin(Vtg)-like proteins), energy status (temperature-dependent mitochondrial electron transport activity and gonad lipid stores), defense mechanisms (glutathione S-transferase, metallothioneins, cytochrome P4503A activity and xanthine oxidoreductase-XOR), and tissue damage (lipid peroxidation-LPO and DNA strand breaks). The results showed that data from the reference sites in each region were usually not normally distributed, with discriminant factors reaching the number of regions (i.e. four), except for the biomarkers gonadal lipids, XOR and LPO in digestive gland. The integrated responses of the biomarkers revealed that biomarkers of stress were significantly more pronounced in mussels from the Seine estuary, suggesting that the impacts of pollution are more generalized in this area. Mussels from the Seine estuary and the Atlantic East Coast (Halifax Harbor) responded more strongly for Vtg-like proteins, but was not related to gonad maturation and gonado-somatic indexes, suggesting the presence of environmental estrogens. Moreover, these mussels displayed reduced DNA repair activity and increased LPO. Factorial analyses revealed that energy status, cytochrome P4503A activity and Vtg-like proteins were the most important biomarkers. Adaptation to warmer temperatures was reflected at the energy status levels, mussels from both the polluted and warmer sites displaying increased ratios of mitochondrial activity to lipid stores. Regional observations of biomarkers of energy status, gametogenesis and pollutant-related effects were influenced by nutrition, oxygen availability (eutrophication), and thermal history.« less

Temperature characteristics of epitaxially grown InAs quantum dot micro-disk lasers on silicon for on-chip light sources

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

Wan, Yating; Li, Qiang; Lau, Kei May, E-mail: eekmlau@ust.hk

2016-07-04

Temperature characteristics of optically pumped micro-disk lasers (MDLs) incorporating InAs quantum dot active regions are investigated for on-chip light sources. The InAs quantum dot MDLs were grown on V-groove patterned (001) silicon, fully compatible with the prevailing complementary metal oxide-semiconductor technology. By combining the high-quality whispering gallery modes and 3D confinement of injected carriers in quantum dot micro-disk structures, we achieved lasing operation from 10 K up to room temperature under continuous optical pumping. Temperature dependences of the threshold, lasing wavelength, slope efficiency, and mode linewidth are examined. An excellent characteristic temperature T{sub o} of 105 K has been extracted.

Determination of physical parameters of magnetic active regions in stars with different evolutionary stages

NASA Astrophysics Data System (ADS)

Biazzo, K.

2006-11-01

Understanding stellar magnetic activity phenomena is of paramount importance for stellar evolution and for planetary systems formation and their atmosphere and climate. The dynamo process that generates magnetic fields in stars is well understood and there is still no comprehensive model of solar and stellar magnetic activity. Stellar activity is characterized by tracers such as spots, plages, flares and winds. These features are the fingerprints of magnetic field lines and their detailed analysis provides constraints for theoretical models. Our knowledge can only advance if the active stars besides the Sun are included in our study. Therefore, it is essential to accomplish comprehensive studies of active stars with a wide range of stellar parameters and a variety of activity phenomena. In this thesis, I concentrate on emergence of active regions at photospheric and chromospheric levels, namely spots and plages, in stars with different evolutionary stages. Spots are cool areas on the surface of the stars and are supposed to be the result of the blocking effect on convection caused by magnetic flux-tube emersion. Plages are bright areas linked to emersion of magnetic flux tubes from the sub-photospheric convective level. Starspot temperature represents an important parameter for the investigation of stellar magnetic activity, but its precise determination, relying only on light curve inversion techniques, is strongly hampered by the lack of solution uniqueness. Therefore, a method based on line-depth ratios as temperature discriminant has been developed. This technique is capable of resolving temperature differences less than 10 K. Moreover, combining temperature and light curve solutions, I am able to determine in a univocal way starspot temperature and area. Using the net Halpha emission as indicator of plage presence, I have also studied the spot and plage association. As a matter of fact, the residual Halpha profiles, obtained as the difference between the observed spectra and non-active templates, allows to study the chromospheric structures simultaneously to the photospheric ones. In addition, I have also detected the intensity of the HeI-D3 line to analyse the presence of surface features in the high chromosphere. The observations of both standard and target stars have been performed with different instruments. In particular, the spectra have been acquired at Catania Astrophysical Observatory (Italy), Observatoire de Haute-Provence (France) and Nordic Optical Observatory (Canarian Islands). The photometric observations have been obtained at Catania Astrophysical Observatory, Fairnborn Observatory (USA) and Ege University Observatory (Turkey). Finally, starspot and plage physical parameters have been obtained for sixteen stars of different effective temperature and gravity and different evolutionary stages. The main results can be summarized as follows: - starspot temperatures are more similar to solar penumbrae; - dwarf stars tend to have smaller spots compared to giant stars; - stars with higher gravity seem to have cooler (relative to their photosphere) spots compared to stars with lower gravity; - spatial association exists between surface inhomogeneities at different atmospheric levels.

940nm QCW diode laser bars with 70% efficiency at 1 kW output power at 203K: analysis of remaining limits and path to higher efficiency and power at 200K and 300K

NASA Astrophysics Data System (ADS)

Frevert, C.; Bugge, F.; Knigge, S.; Ginolas, A.; Erbert, G.; Crump, P.

2016-03-01

Both high-energy-class laser facilities and commercial high-energy pulsed laser sources require reliable optical pumps with the highest pulse power and electro-optical efficiency. Although commercial quasi-continuous wave (QCW) diode laser bars reach output powers of 300…500 W further improvements are urgently sought to lower the cost per Watt, improve system performance and reduce overall system complexity. Diode laser bars operating at temperatures of around 200 K show significant advances in performance, and are particularly attractive in systems that use cryogenically cooled solid state lasers. We present the latest results on 940 nm, passively cooled, 4 mm long QCW diode bars which operate under pulse conditions of 1.2 ms, 10 Hz at an output power of 1 kW with efficiency of 70% at 203 K: a two-fold increase in power compared to 300 K, without compromising efficiency. We discuss how custom low-temperature design of the vertical layers can mitigate the limiting factors such as series resistance while sustaining high power levels. We then focus on the remaining obstacles to higher efficiency and power, and use a detailed study of multiple vertical structures to demonstrate that the properties of the active region are a major performance limit. Specifically, one key limit to series resistance is transport in the layers around the active region and the differential internal efficiency is closely correlated to the threshold current. Tailoring the barriers around the active region and reducing transparency current density thus promise bars with increased performance at temperatures of 200 K as well as 300 K.

Correlation of BAT activity with thyroid metabolic activity in patients with fibromyalgia

NASA Astrophysics Data System (ADS)

Costa, A. P. C.; Maia, J. M.; Brioschi, M. L.; Machado, J. E. M. M.

2017-03-01

The objective of this research is to correlate the brown fat activity (BAT) with the metabolic activity of thyroid in patients with fibromyalgia syndrome (FS). For the development of the research, it was select a database containing 132 patients of a thermography clinic, male and female, with age over 18 years old; where the images selected were anteroposterior orthostasis top and anteroposterior in cervical extension. In the program Flir Report, it was possible to demarcate the region of the left and right interscapular and thyroid of each patient by getting the respective temperatures, in addition to view the hyper-radiation ("signal of mantle") in the interscapular. Temperature was organized in table format, and statistical analysis was performed in the program Microcal Origin 6.0. As conclusion, it was found that the greater the metabolic activity of thyroid in patients with fibromyalgia, the greater will be the metabolic rate of brown fat (BAT).

Human and climate impacts on Holocene fire activity recorded in polar and mountain ice cores

NASA Astrophysics Data System (ADS)

Kehrwald, Natalie; Zennaro, Piero; Kirchgeorg, Torben; Li, Quanlian; Wang, Ninglian; Power, Mitchell; Zangrando, Roberta; Gabrielli, Paolo; Thompson, Lonnie; Gambaro, Andrea; Barbante, Carlo

2014-05-01

Fire is one of the major influences of biogeochemical change on local to hemispheric scales through emitting greenhouse gases, altering atmospheric chemistry, and changing primary productivity. Levoglucosan (1,6-anhydro-β-D-glucopyranose) is a specific molecular that can only be produced by cellulose burning at temperatures > 300°C, comprises a major component of smoke plumes, and can be transported across > 1000 km distances. Levoglucosan is deposited on and archived in glaciers over glacial interglacial cycles resulting in pyrochemical evidence for exploring interactions between fire, climate and human activity. Ice core records provide records of past biomass burning from regions of the world with limited paleofire data including polar and low-latitude, high-altitude regions. Here, we present Holocene fire activity records from the NEEM, Greenland (77° 27'N; 51° 3'W; 2454 masl), EPICA Dome C, Antarctica (75° 06'S; 123° 21'E; 3233 masl), Kilimanjaro, Tanzania (3° 05'S, 21.2° E, 5893 masl) and the Muztagh, China (87.17° E; 36.35° N; 5780 masl ice cores. The NEEM ice core reflects boreal fire activity from both North American and Eurasian sources. Temperature is the dominant control of NEEM levoglucosan flux over decadal to millennial time scales, while droughts influence fire activity over sub-decadal timescales. Our results demonstrate the prominence of Siberian fire sources during intense multiannual droughts. Unlike the NEEM core, which incorporates the largest land masses in the world as potential fire sources, EPICA Dome C is located far from any possible fire source. However, EPICA Dome C levoglucosan concentrations are consistently above detection limits and demonstrate a substantial 1000-fold increase in fire activity beginning approximately 800 years ago. This significant and sustained increase coincides with Maori arrival and dispersal in New Zealand augmented by later European arrival in Australia. The EPICA Dome C levoglucosan profile is similar to regional charcoal compilations from New Zealand and southeastern Australia. Evidence from Kilimanjaro demonstrates a major increase in fire activity centered around 800-1000 years ago, corresponding to both increased temperatures and aridity as recorded in regional lake cores. This peak in fire activity is an order of magnitude higher than at any other time in the record including the most recent period. Environmental and anthropological studies suggest that upslope human migrations have occurred in response to the warmer, drier conditions. Kilimanjaro is surrounded by flammable savanna vegetation, yet the Muztagh core is located in an especially arid section of the Tibetan Plateau and consistently contains levoglucosan concentrations that are 100 to 1000 times greater than the mean Kilimanjaro flux. These high concentrations and the lack of available fuel suggest that regional rather than local biomass burning may be the source of the fire products. Biomass burning aerosols are a major component of the South Asian Brown Cloud and may influence the composition and concentration of pyrogenic aerosols across the Tibetan Plateau. The relative impact of human activity versus climate change on Holocene biomass burning varies regionally. Combining ice and sediment core data with model output can help place these regional differences into a global context with implications for a warming climate.

Amplification and dampening of soil respiration by changes in temperature variability

USGS Publications Warehouse

Sierra, C.A.; Harmon, M.E.; Thomann, E.; Perakis, S.S.; Loescher, H.W.

2011-01-01

Accelerated release of carbon from soils is one of the most important feed backs related to anthropogenically induced climate change. Studies addressing the mechanisms for soil carbon release through organic matter decomposition have focused on the effect of changes in the average temperature, with little attention to changes in temperature vari-ability. Anthropogenic activities are likely to modify both the average state and the variability of the climatic system; therefore, the effects of future warming on decomposition should not only focus on trends in the average temperature, but also variability expressed as a change of the probability distribution of temperature.Using analytical and numerical analyses we tested common relationships between temperature and respiration and found that the variability of temperature plays an important role determining respiration rates of soil organic matter. Changes in temperature variability, without changes in the average temperature, can affect the amount of carbon released through respiration over the long term. Furthermore, simultaneous changes in the average and variance of temperature can either amplify or dampen there release of carbon through soil respiration as climate regimes change. The effects depend on the degree of convexity of the relationship between temperature and respiration and the magnitude of the change in temperature variance. A potential consequence of this effect of variability would be higher respiration in regions where both the mean and variance of temperature are expected to increase, such as in some low latitude regions; and lower amounts of respiration where the average temperature is expected to increase and the variance to decrease, such as in northern high latitudes.

Forward modeling transient brightenings and microflares around an active region observed with Hi-C

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

Kobelski, Adam R.; McKenzie, David E., E-mail: kobelski@solar.physics.montana.edu

Small-scale flare-like brightenings around active regions are among the smallest and most fundamental of energetic transient events in the corona, providing a testbed for models of heating and active region dynamics. In a previous study, we modeled a large collection of these microflares observed with Hinode/X-Ray Telescope (XRT) using EBTEL and found that they required multiple heating events, but could not distinguish between multiple heating events on a single strand, or multiple strands each experiencing a single heating event. We present here a similar study, but with extreme-ultraviolet data of Active Region 11520 from the High Resolution Coronal Imager (Hi-C)more » sounding rocket. Hi-C provides an order of magnitude improvement to the spatial resolution of XRT, and a cooler temperature sensitivity, which combine to provide significant improvements to our ability to detect and model microflare activity around active regions. We have found that at the spatial resolution of Hi-C (≈0.''3), the events occur much more frequently than expected (57 events detected, only 1 or 2 expected), and are most likely made from strands of the order of 100 km wide, each of which is impulsively heated with multiple heating events. These findings tend to support bursty reconnection as the cause of the energy release responsible for the brightenings.« less

Multi-Decadal Oscillations of the Ocean Active Upper-Layer Heat Content

NASA Astrophysics Data System (ADS)

Byshev, Vladimir I.; Neiman, Victor G.; Anisimov, Mikhail V.; Gusev, Anatoly V.; Serykh, Ilya V.; Sidorova, Alexandra N.; Figurkin, Alexander L.; Anisimov, Ivan M.

2017-07-01

Spatial patterns in multi-decadal variability in upper ocean heat content for the last 60 years are examined using a numerical model developed at the Institute of Numerical Mathematics of Russia (INM Model) and sea water temperature-salinity data from the World Ocean Database (in: Levitus, NOAA Atlas NESDIS 66, U.S. Wash.: Gov. Printing Office, 2009). Both the model and the observational data show that the heat content of the Active Upper Layer (AUL) in particular regions of the Atlantic, Pacific and Southern oceans have experienced prominent simultaneous variations on multi-decadal (25-35 years) time scales. These variations are compared earlier revealed climatic alternations in the Northern Atlantic region during the last century (Byshev et al. in Doklady Earth Sci 438(2):887-892, 2011). We found that from the middle of 1970s to the end of 1990s the AUL heat content decreased in several oceanic regions, while the mean surface temperature increased on Northern Hemisphere continents according to IPCC (in: Stocker et al. Contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change, Cambridge University Press, Cambridge, 2013). This means that the climate-forcing effect of the ocean-atmosphere interaction in certain energy-active areas determines not only local climatic processes, but also have an influence on global-scale climate phenomena. Here we show that specific regional features of the AUL thermal structure are in a good agreement with climatic conditions on the adjacent continents. Further, the ocean AUL in the five distinctive regions identified in our study have resumed warming in the first decade of this century. By analogy inference from previous climate scenarios, this may signal the onset of more continental climate over mainlands.

Perioperative warming with a thermal gown prevents maternal temperature loss during elective cesarean section. A randomized clinical trial.

PubMed

de Bernardis, Ricardo Caio Gracco; Siaulys, Monica Maria; Vieira, Joaquim Edson; Mathias, Lígia Andrade Silva Telles

2016-01-01

Decrease in body temperature is common during general and regional anesthesia. Forced-air warming intraoperative during cesarean section under spinal anesthesia seems not able to prevent it. The hypothesis considers that active warming before the intraoperative period avoids temperature loss during cesarean. Forty healthy pregnant patients undergoing elective cesarean section with spinal anesthesia received active warming from a thermal gown in the preoperative care unit 30min before spinal anesthesia and during surgery (Go, n=20), or no active warming at any time (Ct, n=20). After induction of spinal anesthesia, the thermal gown was replaced over the chest and upper limbs and maintained throughout study. Room temperature, hemoglobin saturation, heart rate, arterial pressure, and tympanic body temperature were registered 30min before (baseline) spinal anesthesia, right after it (time zero) and every 15min thereafter. There was no difference for temperature at baseline, but they were significant throughout the study (p<0.0001; repeated measure ANCOVA). Tympanic temperature baseline was 36.6±0.3°C, measured 36.5±0.3°C at time zero and reached 36.1±0.2°C for gown group, while control group had baseline temperature of 36.4±0.4°C, measured 36.3±0.3°C at time zero and reached 35.4±0.4°C (F=32.53; 95% CI 0.45-0.86; p<0.001). Hemodynamics did not differ throughout the study for both groups of patients. Active warming 30min before spinal anesthesia and during surgery prevented a fall in body temperature in full-term pregnant women during elective cesarean delivery. Copyright © 2015 Sociedade Brasileira de Anestesiologia. Published by Elsevier Editora Ltda. All rights reserved.

[Perioperative warming with a thermal gown prevents maternal temperature loss during elective cesarean section. A randomized clinical trial].

PubMed

Bernardis, Ricardo Caio Gracco de; Siaulys, Monica Maria; Vieira, Joaquim Edson; Mathias, Lígia Andrade Silva Telles

2016-01-01

Decrease in body temperature is common during general and regional anesthesia. Forced-air warming intraoperative during cesarean section under spinal anesthesia seems not able to prevent it. The hypothesis considers that active warming before the intraoperative period avoids temperature loss during cesarean. Forty healthy pregnant patients undergoing elective cesarean section with spinal anesthesia received active warming from a thermal gown in the preoperative care unit 30min before spinal anesthesia and during surgery (Go, n=20), or no active warming at any time (Ct, n=20). After induction of spinal anesthesia, the thermal gown was replaced over the chest and upper limbs and maintained throughout study. Room temperature, hemoglobin saturation, heart rate, arterial pressure, and tympanic body temperature were registered 30min before (baseline) spinal anesthesia, right after it (time zero) and every 15min thereafter. There was no difference for temperature at baseline, but they were significant throughout the study (p<0.0001; repeated measure ANCOVA). Tympanic temperature baseline was 36.6±0.3°C, measured 36.5±0.3°C at time zero and reached 36.1±0.2°C for gown group, while control group had baseline temperature of 36.4±0.4°C, measured 36.3±0.3°C at time zero and reached 35.4±0.4°C (F=32.53; 95% CI 0.45-0.86; p<0.001). Hemodynamics did not differ throughout the study for both groups of patients. Active warming 30min before spinal anesthesia and during surgery prevented a fall in body temperature in full-term pregnant women during elective cesarean delivery. Copyright © 2015 Sociedade Brasileira de Anestesiologia. Publicado por Elsevier Editora Ltda. All rights reserved.

Physiologic Responses Produced by Active and Passive Personal Cooling Vests

NASA Technical Reports Server (NTRS)

Ku, Yu-Tsuan E.; Lee, Hank C.; Montgomery, Leslie D.; Luna, Bernadette

2000-01-01

Personal thermoregulatory systems which provide chest cooling are used in the industrial and aerospace environments to alleviate thermal stress. However, little information is available regarding the physiologic and circulatory changes produced by routine operation of these systems. The objectives of this study were to document and compare the subjects' response to three cooling vests in their recommended configurations. The Life Enhancement Tech (LET) lightweight active cooling vest with cap, the MicroClimate Systems Change of Phase garment (MCS), and the Steele Vest were each used to cool the chest regions of 12 male and 8 female Healthy subjects (21 to 69 yr.) in this study. The subjects, seated in an upright position at normal room temperature (approx. 22 C), were tested for 60 min. with one of the cooling garments. The LET active garment had an initial coolant fluid inlet temperature of 60 F, and was ramped down to 50 F. Oral, right and left ear canal temperatures were logged manually every 5 min. Arm, leg, chest and rectal temperatures; heart rate; and respiration were recorded continuously on a U.F.I., Inc. Biolog ambulatory monitor. For men, all three vests had similar, significant cooling effects. Decreases in the average rectal temperature, oral temperature, and ear canal temperatures were approximately 0.2 C, 0.2 C and 0.1 C, respectively. In contrast to the men, the female subjects wearing the MCS and Steel vests had similar cooling responses in which the core temperature remained elevated and oral and ear canal temperatures did not drop. The LET active garment cooled most of the female subjects in this study; rectal, oral and ear temperature decreased about 0.2 C, 0.3 C and 0.3 C, respectively. These results show that the garment configurations tested do not elicit a similar thermal response in all subjects. A gender difference is evident. The LET active garment configuration was most effective in decreasing temperatures of the female subjects; the MCS vest was least effective. For male subjects, the three vests appear to be more nearly equivalent. The active garment system under study included a cooling cap, which may account for some of the difference in response.

The influence of p-doping on two-state lasing in InAs/InGaAs quantum dot lasers

NASA Astrophysics Data System (ADS)

Maximov, M. V.; Shernyakov, Yu M.; Zubov, F. I.; Zhukov, A. E.; Gordeev, N. Yu; Korenev, V. V.; Savelyev, A. V.; Livshits, D. A.

2013-10-01

Two-state lasing in devices based on undoped and p-type modulation-doped InAs/InGaAs quantum dots is studied for various cavity lengths and temperatures. Modulation doping of the active region strongly enhances the threshold current of two-state lasing, preserves ground-state lasing up to higher temperatures and increases ground-state output power. The impact of modulation doping is especially strong in short cavities.

Amber light-emitting diode comprising a group III-nitride nanowire active region

DOEpatents

Wang, George T.; Li, Qiming; Wierer, Jr., Jonathan J.; Koleske, Daniel

2014-07-22

A temperature stable (color and efficiency) III-nitride based amber (585 nm) light-emitting diode is based on a novel hybrid nanowire-planar structure. The arrays of GaN nanowires enable radial InGaN/GaN quantum well LED structures with high indium content and high material quality. The high efficiency and temperature stable direct yellow and red phosphor-free emitters enable high efficiency white LEDs based on the RGYB color-mixing approach.

Severe storms observing satellite (STORMSAT)

NASA Technical Reports Server (NTRS)

1976-01-01

The primary payload for this satellite is the Advanced Atmospheric Sounding and Imaging Radiometer which will perform precise infrared temperature sounding and visible/infrared imaging from geostationary orbit. A secondary payload instrument which may be utilized on STORMSAT is the Microwave Atmospheric Sounding Radiometer which provides an independent set of temperature and humidity sounding in cloudy, meteorologically active regions. The study provides satellite designs and identifies mission-unique subsystems using the Multimission Modular Spacecraft using a Shuttle/Interim Upper Stage launch vehicle.

Fire-climate interactions in the American West since 1400 CE

NASA Astrophysics Data System (ADS)

Trouet, Valerie; Taylor, Alan H.; Wahl, Eugene R.; Skinner, Carl N.; Stephens, Scott L.

2010-02-01

Despite a strong anthropogenic fingerprint on 20th Century wildland fire activity in the American West, climate remains a main driver. A better understanding of the spatio-temporal variability in fire-climate interactions is therefore crucial for fire management. Here, we present annually resolved, tree-ring based fire records for four regions in the American West that extend back to 1400 CE. In all regions, years with high fire activity were characterized by widespread yet regionally distinct summer droughts. Overall fire activity was high in late Medieval times, when much of the American West was affected by mega-droughts. A distinct decline in fire activity in the late 16th Century corresponds with anomalously low temperatures during the Little Ice Age and a decline in Native American fire use. The high spatiotemporal resolution of our fire record discloses a time-frequency dependent climatic influence on wildfire regimes in the American West that needs to be accounted for in fire models.

Deterministic Role of Collision Cascade Density in Radiation Defect Dynamics in Si

NASA Astrophysics Data System (ADS)

Wallace, J. B.; Aji, L. B. Bayu; Shao, L.; Kucheyev, S. O.

2018-05-01

The formation of stable radiation damage in solids often proceeds via complex dynamic annealing (DA) processes, involving point defect migration and interaction. The dependence of DA on irradiation conditions remains poorly understood even for Si. Here, we use a pulsed ion beam method to study defect interaction dynamics in Si bombarded in the temperature range from ˜-30 ° C to 210 °C with ions in a wide range of masses, from Ne to Xe, creating collision cascades with different densities. We demonstrate that the complexity of the influence of irradiation conditions on defect dynamics can be reduced to a deterministic effect of a single parameter, the average cascade density, calculated by taking into account the fractal nature of collision cascades. For each ion species, the DA rate exhibits two well-defined Arrhenius regions where different DA mechanisms dominate. These two regions intersect at a critical temperature, which depends linearly on the cascade density. The low-temperature DA regime is characterized by an activation energy of ˜0.1 eV , independent of the cascade density. The high-temperature regime, however, exhibits a change in the dominant DA process for cascade densities above ˜0.04 at.%, evidenced by an increase in the activation energy. These results clearly demonstrate a crucial role of the collision cascade density and can be used to predict radiation defect dynamics in Si.

Deterministic Role of Collision Cascade Density in Radiation Defect Dynamics in Si.

PubMed

Wallace, J B; Aji, L B Bayu; Shao, L; Kucheyev, S O

2018-05-25

The formation of stable radiation damage in solids often proceeds via complex dynamic annealing (DA) processes, involving point defect migration and interaction. The dependence of DA on irradiation conditions remains poorly understood even for Si. Here, we use a pulsed ion beam method to study defect interaction dynamics in Si bombarded in the temperature range from ∼-30 °C to 210 °C with ions in a wide range of masses, from Ne to Xe, creating collision cascades with different densities. We demonstrate that the complexity of the influence of irradiation conditions on defect dynamics can be reduced to a deterministic effect of a single parameter, the average cascade density, calculated by taking into account the fractal nature of collision cascades. For each ion species, the DA rate exhibits two well-defined Arrhenius regions where different DA mechanisms dominate. These two regions intersect at a critical temperature, which depends linearly on the cascade density. The low-temperature DA regime is characterized by an activation energy of ∼0.1  eV, independent of the cascade density. The high-temperature regime, however, exhibits a change in the dominant DA process for cascade densities above ∼0.04 at.%, evidenced by an increase in the activation energy. These results clearly demonstrate a crucial role of the collision cascade density and can be used to predict radiation defect dynamics in Si.

Generation of Plasma Density Irregularities in the Midlatitude/Subauroral F Region

NASA Astrophysics Data System (ADS)

Mishin, E. V.

2017-12-01

A concise review is given of the current state of the theoretical understanding of the creation of small- and meso-scale plasma density irregularities in the midlatitude/subauroral F region during quiet and disturbed periods. The former are discussed in terms of the temperature gradient instability (TGI) in the vicinity of the ionospheric projection of the plasmapause and the Perkins instability. During active conditions some part of the midlatitude ionosphere becomes the subauroral region dominated by enhanced westward flows (SAPS and SAID) driven by poleward electric fields. Their irregular, often nonlinear wave structure leads to the formation of plasma density irregularities in the plasmasphere and conjugate ionosphere. Here, meso-scale irregularities are due to the positive feedback magnetosphere-ionosphere coupling instability, while small scales resulted from the gradient drift instability (GDI), temperature GDI, and the ion frictional heating instability. The theoretical predictions are compared with satellite observations in the perturbed subauroral geospace.

Pollinator communities in strawberry crops - variation at multiple spatial scales.

PubMed

Ahrenfeldt, E J; Klatt, B K; Arildsen, J; Trandem, N; Andersson, G K S; Tscharntke, T; Smith, H G; Sigsgaard, L

2015-08-01

Predicting potential pollination services of wild bees in crops requires knowledge of their spatial distribution within fields. Field margins can serve as nesting and foraging habitats for wild bees and can be a source of pollinators. Regional differences in pollinator community composition may affect this spill-over of bees. We studied how regional and local differences affect the spatial distribution of wild bee species richness, activity-density and body size in crop fields. We sampled bees both from the field centre and at two different types of semi-natural field margins, grass strips and hedges, in 12 strawberry fields. The fields were distributed over four regions in Northern Europe, representing an almost 1100 km long north-south gradient. Even over this gradient, daytime temperatures during sampling did not differ significantly between regions and did therefore probably not impact bee activity. Bee species richness was higher in field margins compared with field centres independent of field size. However, there was no difference between centre and margin in body-size or activity-density. In contrast, bee activity-density increased towards the southern regions, whereas the mean body size increased towards the north. In conclusion, our study revealed a general pattern across European regions of bee diversity, but not activity-density, declining towards the field interior which suggests that the benefits of functional diversity of pollinators may be difficult to achieve through spill-over effects from margins to crop. We also identified dissimilar regional patterns in bee diversity and activity-density, which should be taken into account in conservation management.

Using the Landsat Thematic Mapper to detect and monitor active volcanoes - An example from Lascar volcano, northern Chile

NASA Technical Reports Server (NTRS)

Francis, P. W.; Rothery, D. A.

1987-01-01

The Landsat Thematic Mapper (TM) offers a means of detecting and monitoring thermal features of active volcanoes. Using the TM, a prominent thermal anomaly has been discovered on Lascar volcano, northern Chile. Data from two short-wavelength infrared channels of the TM show that material within a 300-m-diameter pit crater was at a temperature of at least 380 C on two dates in 1985. The thermal anomaly closely resembles in size and radiant temperature the anomaly over the active lava lake at Erta'ale in Ethiopia. An eruption took place at Lascar on Sept. 16, 1986. TM data acquired on Oct. 27, 1986, revealed significant changes within the crater area. Lascar is in a much more active state than any other volcano in the central Andes, and for this reason it merits further careful monitoring. Studies show that the TM is capable of confidently identifying thermal anomalies less than 100 m in size, at temperatures of above 150 C, and thus it offers a valuable means of monitoring the conditions of active or potentially active volcanoes, particularly those in remote regions.

Regional potential evapotranspiration in arid climates based on temperature, topography and calculated solar radiation

NASA Astrophysics Data System (ADS)

Shevenell, Lisa

1999-03-01

Values of evapotranspiration are required for a variety of water planning activities in arid and semi-arid climates, yet data requirements are often large, and it is costly to obtain this information. This work presents a method where a few, readily available data (temperature, elevation) are required to estimate potential evapotranspiration (PET). A method using measured temperature and the calculated ratio of total to vertical radiation (after the work of Behnke and Maxey, 1969) to estimate monthly PET was applied for the months of April-October and compared with pan evaporation measurements. The test area used in this work was in Nevada, which has 124 weather stations that record sufficient amounts of temperature data. The calculated PET values were found to be well correlated (R2=0·940-0·983, slopes near 1·0) with mean monthly pan evaporation measurements at eight weather stations.In order to extrapolate these calculated PET values to areas without temperature measurements and to sites at differing elevations, the state was divided into five regions based on latitude, and linear regressions of PET versus elevation were calculated for each of these regions. These extrapolated PET values generally compare well with the pan evaporation measurements (R2=0·926-0·988, slopes near 1·0). The estimated values are generally somewhat lower than the pan measurements, in part because the effects of wind are not explicitly considered in the calculations, and near-freezing temperatures result in a calculated PET of zero at higher elevations in the spring months. The calculated PET values for April-October are 84-100% of the measured pan evaporation values. Using digital elevation models in a geographical information system, calculated values were adjusted for slope and aspect, and the data were used to construct a series of maps of monthly PET. The resultant maps show a realistic distribution of regional variations in PET throughout Nevada which inversely mimics topography. The general methods described here could be used to estimate regional PET in other arid western states (e.g. New Mexico, Arizona, Utah) and arid regions world-wide (e.g. parts of Africa).

Thermodynamic Conditions Favorable to Superlative Thunderstorm Updraft, Mixed Phase Microphysics and Lightning Flash Rate. Revised

NASA Technical Reports Server (NTRS)

Williams, E.; Mushtak, V.; Rosenfeld, D.; Goodman, S.; Boccippio, D.

2004-01-01

Satellite observations of lightning flash rate have been merged with proximal surface station thermodynamic observations toward improving the understanding of the response of the updraft and lightning activity in the tropical atmosphere to temperature. The tropical results have led in turn to an examination of thermodynamic climatology over the continental United States in summertime and its comparison with exceptional electrical conditions documented in earlier studies. The tropical and mid-latitude results taken together support an important role for cloud base height in regulating the transfer of Convective Available Potential Energy (CAPE) to updraft kinetic energy in thunderstorms. In the tropics, cloud base height is dominated by the dry bulb temperature over the wet bulb temperature as the lightning-regulating temperature in regions characterized by moist convection. In the extratropics, an elevated cloud base height may enable larger cloud water concentrations in the mixed phase region, a favorable condition for the positive charging of large ice particles that may result in thunderclouds with a reversed polarity of the main cloud dipole. The combined requirements of instability and cloud base height serve to confine the region of superlative electrification to the vicinity of the ridge in moist entropy in the western Great Plains.

Subfreezing activity of microorganisms and the potential habitability of Mars' polar regions.

PubMed

Jakosky, Bruce M; Nealson, Kenneth H; Bakermans, Corien; Ley, Ruth E; Mellon, Michael T

2003-01-01

The availability of water-ice at the surface in the Mars polar cap and within the top meter of the high-latitude regolith raises the question of whether liquid water can exist there under some circumstances and possibly support the existence of biota. We examine the minimum temperatures at which liquid water can exist at ice grain-dust grain and ice grain-ice grain contacts, the minimum subfreezing temperatures at which terrestrial organisms can grow or multiply, and the maximum temperatures that can occur in martian high-latitude and polar regions, to see if there is overlap. Liquid water can exist at grain contacts above about -20 degrees C. Measurements of growth in organisms isolated from Siberian permafrost indicate growth at -10 degrees C and metabolism at -20 degrees C. Mars polar and high-latitude temperatures rise above -20 degrees C at obliquities greater than ~40 degrees, and under some conditions rise above 0 degrees C. Thus, the environment in the Mars polar regions has overlapped habitable conditions within relatively recent epochs, and Mars appears to be on the edge of being habitable at present. The easy accessibility of the polar surface layer relative to the deep subsurface make these viable locations to search for evidence of life.

Deep Geothermal Reservoir Temperatures in the Eastern Snake River Plain, Idaho using Multicomponent Geothermometry

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

Ghanashyam Neupane; Earl D. Mattson; Travis L. McLing

2014-02-01

The U.S. Geological survey has estimated that there are up to 4,900 MWe of undiscovered geothermal resources and 92,000 MWe of enhanced geothermal potential within the state of Idaho. Of particular interest are the resources of the Eastern Snake River Plain (ESRP) which was formed by volcanic activity associated with the relative movement of the Yellowstone Hot Spot across the state of Idaho. This region is characterized by a high geothermal gradient and thermal springs occurring along the margins of the ESRP. Masking much of the deep thermal potential of the ESRP is a regionally extensive and productive cold-water aquifer.more » We have undertaken a study to infer the temperature of the geothermal system hidden beneath the cold-water aquifer of the ESRP. Our approach is to estimate reservoir temperatures from measured water compositions using an inverse modeling technique (RTEst) that calculates the temperature at which multiple minerals are simultaneously at equilibrium while explicitly accounting for the possible loss of volatile constituents (e.g., CO2), boiling and/or water mixing. In the initial stages of this study, we apply the RTEst model to water compositions measured from a limited number of wells and thermal springs to estimate the regionally extensive geothermal system in the ESRP.« less

One-dimensional particle-in-cell simulation on the influence of electron and ion temperature on the sheath expansion process in the post-arc stage of vacuum circuit breaker

NASA Astrophysics Data System (ADS)

Mo, Yongpeng; Shi, Zongqian; Jia, Shenli; Wang, Lijun

2015-02-01

The inter-contact region of vacuum circuit breakers is filled with residual plasma at the moment when the current is zero after the burning of metal vapor arc. The residual plasma forms an ion sheath in front of the post-arc cathode. The sheath then expands towards the post-arc anode under the influence of a transient recovery voltage. In this study, a one-dimensional particle-in-cell model is developed to investigate the post-arc sheath expansion. The influence of ion and electron temperatures on the decrease in local plasma density at the post-arc cathode side and post-arc anode side is discussed. When the decay in the local plasma density develops from the cathode and anode sides into the high-density region and merges, the overall plasma density in the inter-contact region begins to decrease. Meanwhile, the ion sheath begins to expand faster. Furthermore, the theory of ion rarefaction wave only explains quantitatively the decrease in the overall plasma density at relatively low ion temperatures. With the increase of ion temperature to certain extent, another possible reason for the decrease in the overall plasma density is proposed and results from the more active thermal diffusion of plasma.

Simulation of regional temperature change effect of land cover change in agroforestry ecotone of Nenjiang River Basin in China

NASA Astrophysics Data System (ADS)

Liu, Tingxiang; Zhang, Shuwen; Yu, Lingxue; Bu, Kun; Yang, Jiuchun; Chang, Liping

2017-05-01

The Northeast China is one of typical regions experiencing intensive human activities within short time worldwide. Particularly, as the significant changes of agriculture land and forest, typical characteristics of pattern and process of agroforestry ecotone change formed in recent decades. The intensive land use change of agroforestry ecotone has made significant change for regional land cover, which had significant impact on the regional climate system elements and the interactions among them. This paper took agroforestry ecotone of Nenjiang River Basin in China as study region and simulated temperature change based on land cover change from 1950s to 1978 and from 1978 to 2010. The analysis of temperature difference sensitivity to land cover change based on Weather Research and Forecasting (WRF) model showed that the land cover change from 1950s to 1978 induced warming effect over all the study area, including the change of grassland to agriculture land, grassland to deciduous broad-leaved forest, and deciduous broad-leaved forest to shrub land. The land cover change from 1978 to 2010 induced cooling effect over all the study area, including the change of deciduous broad-leaved forest to agriculture land, grassland to agriculture land, shrub land to agriculture land, and deciduous broad-leaved forest to grassland. In addition, the warming and cooling effect of land cover change was more significant in the region scale than specific land cover change area.

The Miniature X-ray Solar Spectrometer (MinXSS) CubeSats: New soft X-ray spectrometer to investigate properties of hot plasma in the quiet Sun, active regions, and flares.

NASA Astrophysics Data System (ADS)

Moore, C. S.; Dennis, B. R.; Woods, T. N.

2017-12-01

Detection of soft X-rays from the Sun provides direct information on coronal plasma at temperatures in excess of 1 MK. The Miniature X-ray Solar Spectrometer (MinXSS) CubeSats provides new spectrally resolved measurements from 0.8 -12 keV. The MinXSS spectral resolving power (R 40 at 5.9 keV) allows plasma abundances to be determined for Fe, Mg, Ni, Ca, Si, S, and Ar. Long-term temporal variations during quiet-Sun times allow active region contributions to be extracted from the full solar flux. The MinXSS 10 second time cadence allows short-term variations of the soft X-ray flux, temperature, and abundances to be determined during flares. The MinXSS spectroscopic observations, combined with the imaging spectroscopy from the Hinode X-ray Telescope (XRT) and the Reuven Ramaty Solar Spectroscopic Imager (RHESSI), hold great potential for advancing our understanding of solar dynamics.

The International Reference Ionosphere - Status 2013

NASA Astrophysics Data System (ADS)

Bilitza, Dieter

2015-04-01

This paper describes the latest version of the International Reference Ionosphere (IRI) model. IRI-2012 includes new models for the electron density and ion densities in the region below the F-peak, a storm-time model for the auroral E-region, an improved electron temperature model that includes variations with solar activity, and for the first time a description of auroral boundaries. In addition, the thermosphere model required for baseline neutral densities and temperatures was upgraded from MSIS-86 to the newer NRLMSIS-00 model and Corrected Geomagnetic coordinates (CGM) were included in IRI as an additional coordinate system for a better representation of auroral and polar latitudes. Ongoing IRI activities towards the inclusion of an improved model for the F2 peak height hmF2 are discussed as are efforts to develop a "Real-Time IRI". The paper is based on an IRI status report presented at the 2013 IRI Workshop in Olsztyn, Poland. The IRI homepage is at

Non-Implanted Gallium-Arsenide and its Subsequent Annealing Effects.

NASA Astrophysics Data System (ADS)

Liou, Lih-Yeh

Infrared spectroscopy is used to study ion-implanted GaAs and its subsequent annealing effects. The damage in the implantation region causes a change in dielectric constant resulting in an infrared reflection spectrum which shows the interference pattern of a multilayer structure. Reflection data are fitted by values calculated from a physically realistic model by using computer codes. The first part in this work studies the solid state regrowth of amorphous GaAs made by Be implantation at -100(DEGREES)C. The regrowth temperature is around 200(DEGREES)C. The regrowth starts with a narrowing of the transition region and the transformation of the implanted layer from as-implanted amorphous (a-l) state to thermally-stablized amorphous (a-ll) state. The non-epitaxial recrystallization from both the surface and the interfacial region follows. The final regrown layer has a slightly higher refractive index than the crystalline value, indicating a high residual defect concentration. The temperature dependent regrowth velocity and the activation energy for this process are determined. The second part studies the free carrier activation in Be-implanted GaAs. Free holes are activated with prolonged annealing at 400(DEGREES)C ((TURN)50 hours) or a shorter time at higher temperature. The carrier contribution to the dielectric constant is calculated from the classical model and best fit to the reflection results show that the carrier profile can be approximated by a two half-Gaussians joined smoothly at their peaks. The peak position for the profile occurs deeper than that for the Be impurity profile measured by SIMS. The carrier distribution is speculated to be the result of the Be impurity, Ga vacancy and possible compensating defect distributions. The final part studies the free carrier removal by proton implantation in heavily doped, high carrier density, n-type GaAs. The as-implantation region is highly compensated until annealed at 550(DEGREES)C. After annealing between 300 and 400(DEGREES)C, the infrared results show a partially compensated region diffused deeply into substrate from the as-implanted region. The SIMS measurements show a well correlated hydrogen diffusion layer which suggests that the compensation defect is hydrogen related. After 500(DEGREES)C, the hydrogen diffusion layer is still observed, but the compensation layer has disappeared. The diffusion coefficient of the compensating defect and the activation energy for this process are determined. Carbon -implanted GaAs having a high carrier density substrate is also measured and compared with the H-implanted cases. (Copies available exclusively from Micrographics Department, Doheny Library, USC, Los Angeles, CA 90089 -0182.).

Characterization of dust activity from Martian Year (MY) 27 to MY 32 observed by the Planetary Fourier Spectrometer aboard the Mars Express spacecraft

NASA Astrophysics Data System (ADS)

Wolkenberg, Paulina; Giuranna, Marco; Aoki, Shohei; Scaccabarozzi, Diego; Saggin, Bortolino; Formisano, Vittorio

2016-04-01

More than 2,500,000 spectra have been collected by the Planetary Fourier Spectrometer aboard Mars Express spacecraft after 12 years of activity. The data span more than six Martian years, from MY26, Ls = 331°, to MY 33, Ls = 78°. This huge dataset has been used to build a new database of atmospheric parameters, including atmospheric and surface temperatures, and dust and water ice opacity. Dust aerosols suspended in the atmosphere affect its thermal structure and are a major driver of the circulation. They are always present in the Martian atmosphere, but the amount varies greatly depending on location and season. We analyze dust opacities at 1075 cm-1 retrieved from the PFS long-wavelength channel spectra to characterize the dust activity on Mars for the relevant period. The dust storm season (Ls= 185° - 310°) is monitored for each Martian year. All dust observations show a seasonal pattern, which is ruled by the occurrence of regional and/or global dust storms. Regional dust storms are observed every year, while a planet encircling dust storm occurred in MY 28, when the highest values of dust opacity are also observed (~ 2.45). We characterize the spatial and temporal evolution of these regional and global dust events and investigate the effect of dust on surface and atmospheric temperatures.

Starspots and active regions on IN Com: UBVRI photometry and linear polarization

NASA Astrophysics Data System (ADS)

Alekseev, I. Yu.; Kozlova, O. V.

2014-06-01

The activity of the variable star IN Com is considered using the latest multicolor UBVRI photometry and linear polarimetric observations carried out during a decade. The photometric variability of the star is fully described using the zonal spottedness model developed at the Crimean Astrophysical Observatory (CrAO). Spotted regions cover up to 22% of the total stellar surface, with the difference in temperatures between the quiet photosphere and the spot umbra being 600 K. The spots are located at middle and low latitudes (40°-55°). The intrinsic broad-band linear polarization of IN Com and its rotational modulation in the U band due to local magnetic fields at the most spotted (active) stellar longitudes were detected for the first time.

Microinjection of muscimol into caudal periaqueductal gray lowers body temperature and attenuates increases in temperature and activity evoked from the dorsomedial hypothalamus.

PubMed

de Menezes, Rodrigo C A; Zaretsky, Dmitry V; Fontes, Marco A P; DiMicco, Joseph A

2006-05-30

Microinjection of the neuronal inhibitor muscimol into the midbrain lateral/dorsolateral periaqueductal gray (l/dlPAG) suppresses increases in heart rate (HR) and mean arterial pressure (MAP) evoked by microinjection of the GABA(A) receptor antagonist bicuculline methiodide (BMI) into the dorsomedial hypothalamus (DMH) in rats. Injection of BMI into the DMH also increases body temperature (Tco) and motor activity. Here, our goal was to extend previous findings by examining the effect of microinjection of muscimol into the PAG on these thermogenic and behavioral responses in conscious freely moving rats. Microinjection of muscimol (300 pmol and 1 nmol) alone into the l/dlPAG reduced baseline Tco without affecting activity, HR, or MAP. Similar injection of a dose that failed to alter baseline Tco (100 pmol) suppressed the increases in Tco evoked from the DMH and significantly attenuated DMH-induced increases in locomotor activity. Whereas microinjection of 1 nmol muscimol into the ldlPAG abolished the increases in Tco evoked from the DMH and in fact lowered body temperature to a degree similar to that seen after this dose of muscimol alone, 1 nmol muscimol at adjacent sites outside the targeted region of the PAG had no significant effect on DMH-induced increases in Tco or any other parameter. These results indicate a role for neuronal activity in the l/dlPAG in (1) the temperature and behavioral responses to disinhibition of neurons in the DMH, and (2) the maintenance of basal body temperature in conscious freely moving rats.

Environmental Predictors of Seasonal Influenza Epidemics across Temperate and Tropical Climates

PubMed Central

Tamerius, James D.; Shaman, Jeffrey; Alonso, Wladmir J.; Bloom-Feshbach, Kimberly; Uejio, Christopher K.; Comrie, Andrew; Viboud, Cécile

2013-01-01

Human influenza infections exhibit a strong seasonal cycle in temperate regions. Recent laboratory and epidemiological evidence suggests that low specific humidity conditions facilitate the airborne survival and transmission of the influenza virus in temperate regions, resulting in annual winter epidemics. However, this relationship is unlikely to account for the epidemiology of influenza in tropical and subtropical regions where epidemics often occur during the rainy season or transmit year-round without a well-defined season. We assessed the role of specific humidity and other local climatic variables on influenza virus seasonality by modeling epidemiological and climatic information from 78 study sites sampled globally. We substantiated that there are two types of environmental conditions associated with seasonal influenza epidemics: “cold-dry” and “humid-rainy”. For sites where monthly average specific humidity or temperature decreases below thresholds of approximately 11–12 g/kg and 18–21°C during the year, influenza activity peaks during the cold-dry season (i.e., winter) when specific humidity and temperature are at minimal levels. For sites where specific humidity and temperature do not decrease below these thresholds, seasonal influenza activity is more likely to peak in months when average precipitation totals are maximal and greater than 150 mm per month. These findings provide a simple climate-based model rooted in empirical data that accounts for the diversity of seasonal influenza patterns observed across temperate, subtropical and tropical climates. PMID:23505366

Spectroscopic study of a dark lane and a cool loop in a solar limb active region by Hinode/EIS

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

Lee, Kyoung-Sun; Imada, S.; Moon, Y.-J.

2014-01-10

We investigated a cool loop and a dark lane over a limb active region on 2007 March 14 using the Hinode/EUV Imaging Spectrometer. The cool loop is clearly seen in the spectral lines formed at the transition region temperature. The dark lane is characterized by an elongated faint structure in the coronal spectral lines and is rooted on a bright point. We examined their electron densities, Doppler velocities, and nonthermal velocities as a function of distance from the limb. We derived electron densities using the density sensitive line pairs of Mg VII, Si X, Fe XII, Fe XIII, and Femore » XIV spectra. We also compared the observed density scale heights with the calculated scale heights from each peak formation temperatures of the spectral lines under the hydrostatic equilibrium. We noted that the observed density scale heights of the cool loop are consistent with the calculated heights, with the exception of one observed cooler temperature; we also found that the observed scale heights of the dark lane are much lower than their calculated scale heights. The nonthermal velocity in the cool loop slightly decreases along the loop, while nonthermal velocity in the dark lane sharply falls off with height. Such a decrease in the nonthermal velocity may be explained by wave damping near the solar surface or by turbulence due to magnetic reconnection near the bright point.« less

Active pain coping is associated with the response in real-time fMRI neurofeedback during pain.

PubMed

Emmert, Kirsten; Breimhorst, Markus; Bauermann, Thomas; Birklein, Frank; Rebhorn, Cora; Van De Ville, Dimitri; Haller, Sven

2017-06-01

Real-time functional magnetic resonance imaging (rt-fMRI) neurofeedback is used as a tool to gain voluntary control of activity in various brain regions. Little emphasis has been put on the influence of cognitive and personality traits on neurofeedback efficacy and baseline activity. Here, we assessed the effect of individual pain coping on rt-fMRI neurofeedback during heat-induced pain. Twenty-eight healthy subjects completed the Coping Strategies Questionnaire (CSQ) prior to scanning. The first part of the fMRI experiment identified target regions using painful heat stimulation. Then, subjects were asked to down-regulate the pain target brain region during four neurofeedback runs with painful heat stimulation. Functional MRI analysis included correlation analysis between fMRI activation and pain ratings as well as CSQ ratings. At the behavioral level, the active pain coping (first principal component of CSQ) was correlated with pain ratings during neurofeedback. Concerning neuroimaging, pain sensitive regions were negatively correlated with pain coping. During neurofeedback, the pain coping was positively correlated with activation in the anterior cingulate cortex, prefrontal cortex, hippocampus and visual cortex. Thermode temperature was negatively correlated with anterior insula and dorsolateral prefrontal cortex activation. In conclusion, self-reported pain coping mechanisms and pain sensitivity are a source of variance during rt-fMRI neurofeedback possibly explaining variations in regulation success. In particular, active coping seems to be associated with successful pain regulation.

Relationship between morphological change and crystalline phase transitions of polyethylene-poly(ethylene oxide) diblock copolymers, revealed by the temperature-dependent synchrotron WAXD/SAXS and infrared/Raman spectral measurements.

PubMed

Weiyu, Cao; Tashiro, Kohji; Hanesaka, Makoto; Takeda, Shinichi; Masunaga, Hiroyasu; Sasaki, Sono; Takata, Masaki

2009-02-26

The phase transition behaviors of low-molecular-weight polyethylene-poly(ethylene oxide) (PE-b-PEO) diblock copolymers with the monomeric units of PE/PEO = 17/40 and 39/86 have been successfully investigated through the temperature-dependent measurements of wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), infrared and Raman spectra, as well as thermal analysis. These diblock copolymers had been believed to show only order-to-disorder transition of lamellar morphology in a wide temperature region, but it has been found here for the first time that this copolymer clearly exhibits the three stages of transitions among lamella, gyroid, cylinder, and spherical phases in the heating and cooling processes. The WAXD and IR/Raman spectral measurements allowed us to relate these morphological changes to the microscopic changes in the aggregation states of PEO and PE segments. In the low-temperature region the PEO segments form the monoclinic crystal of (7/2) helical chain conformation and the PE segments of planar-zigzag form take the orthorhombic crystalline phase. These crystalline lamellae of PEO and PE segments are alternately stacked with the long period of 165 Angstroms. In a higher temperature region, where the PEO crystalline parts are on the way of melting but the PE parts are still in the orthorhombic phase, the gyroid morphology is detected in the SAXS data. By heating further, the gyroid morphology changes to the hexagonally packed cylindrical morphology, where the orthorhombic phase of PE segments is gradually disordered because of thermally activated molecular motion and finally transforms to the pseudohexagonal or rotator phase. Once the PE segments are perfectly melted, the higher-order structure changes from the cylinder to the spherical morphology. These morphological transitions might relate to the thermally activated motions of two short chain segments of the diblock copolymer, although the details of the transition mechanism are unclear at the present stage.

Velocity Measurements for a Solar Active Region Fan Loop from Hinode/EIS Observations

NASA Astrophysics Data System (ADS)

Young, P. R.; O'Dwyer, B.; Mason, H. E.

2012-01-01

The velocity pattern of a fan loop structure within a solar active region over the temperature range 0.15-1.5 MK is derived using data from the EUV Imaging Spectrometer (EIS) on board the Hinode satellite. The loop is aligned toward the observer's line of sight and shows downflows (redshifts) of around 15 km s-1 up to a temperature of 0.8 MK, but for temperatures of 1.0 MK and above the measured velocity shifts are consistent with no net flow. This velocity result applies over a projected spatial distance of 9 Mm and demonstrates that the cooler, redshifted plasma is physically disconnected from the hotter, stationary plasma. A scenario in which the fan loops consist of at least two groups of "strands"—one cooler and downflowing, the other hotter and stationary—is suggested. The cooler strands may represent a later evolutionary stage of the hotter strands. A density diagnostic of Mg VII was used to show that the electron density at around 0.8 MK falls from 3.2 × 109 cm-3 at the loop base, to 5.0 × 108 cm-3 at a projected height of 15 Mm. A filling factor of 0.2 is found at temperatures close to the formation temperature of Mg VII (0.8 MK), confirming that the cooler, downflowing plasma occupies only a fraction of the apparent loop volume. The fan loop is rooted within a so-called outflow region that displays low intensity and blueshifts of up to 25 km s-1 in Fe XII λ195.12 (formed at 1.5 MK), in contrast to the loop's redshifts of 15 km s-1 at 0.8 MK. A new technique for obtaining an absolute wavelength calibration for the EIS instrument is presented and an instrumental effect, possibly related to a distorted point-spread function, that affects velocity measurements is identified.

VELOCITY MEASUREMENTS FOR A SOLAR ACTIVE REGION FAN LOOP FROM HINODE/EIS OBSERVATIONS

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

Young, P. R.; O'Dwyer, B.; Mason, H. E.

2012-01-01

The velocity pattern of a fan loop structure within a solar active region over the temperature range 0.15-1.5 MK is derived using data from the EUV Imaging Spectrometer (EIS) on board the Hinode satellite. The loop is aligned toward the observer's line of sight and shows downflows (redshifts) of around 15 km s{sup -1} up to a temperature of 0.8 MK, but for temperatures of 1.0 MK and above the measured velocity shifts are consistent with no net flow. This velocity result applies over a projected spatial distance of 9 Mm and demonstrates that the cooler, redshifted plasma is physicallymore » disconnected from the hotter, stationary plasma. A scenario in which the fan loops consist of at least two groups of 'strands'-one cooler and downflowing, the other hotter and stationary-is suggested. The cooler strands may represent a later evolutionary stage of the hotter strands. A density diagnostic of Mg VII was used to show that the electron density at around 0.8 MK falls from 3.2 Multiplication-Sign 10{sup 9} cm{sup -3} at the loop base, to 5.0 Multiplication-Sign 10{sup 8} cm{sup -3} at a projected height of 15 Mm. A filling factor of 0.2 is found at temperatures close to the formation temperature of Mg VII (0.8 MK), confirming that the cooler, downflowing plasma occupies only a fraction of the apparent loop volume. The fan loop is rooted within a so-called outflow region that displays low intensity and blueshifts of up to 25 km s{sup -1} in Fe XII {lambda}195.12 (formed at 1.5 MK), in contrast to the loop's redshifts of 15 km s{sup -1} at 0.8 MK. A new technique for obtaining an absolute wavelength calibration for the EIS instrument is presented and an instrumental effect, possibly related to a distorted point-spread function, that affects velocity measurements is identified.« less

A ˜50 ka record of monsoonal variability in the Darjeeling foothill region, eastern Himalayas

NASA Astrophysics Data System (ADS)

Ghosh, Ruby; Bera, Subir; Sarkar, Anindya; Paruya, Dipak Kumar; Yao, Yi-Feng; Li, Cheng-Sen

2015-04-01

Pollen, phytoliths and δ 13C signatures of soil organic matter from two fluvial sedimentary sequences of the Darjeeling foothill region, eastern Himalayas are used to portray palaeoclimatic oscillations and their impact on regional plant communities over the last ˜50 ka. Quantitative palaeoclimate estimation using coexistence approach on pollen data and other proxies indicate significant oscillations in precipitation during the late part of MIS 3 (46.4-25.9 ka), early and middle part of MIS 2 (25.9-15.6 ka), and 5.4 to 3.5 ka. Middle to late MIS 3 (ca 46.4-31 ka.) was characterized by a comparatively low monsoonal activity and slightly higher temperature than that during ca 31 ka onwards. Simultaneous expansion of deciduous trees and chloridoid grasses also imply a drier and warmer phase. Between 31 and 22.3 ka (late MIS 3 to mid-MIS 2), higher precipitation and a slightly cooler temperature led to an increase in evergreen elements over deciduous taxa and wet-loving panicoid grasses over dry-loving chloridoid grasses than earlier. After ca 22.3 ka, shrinking of forest cover, expansion of C4 chloridoid grasses, Asteraceae and Cheno-ams in the vegetation with lowering of temperature and precipitation characterized the onset of the LGM which continued till 18.3 ka. End of the LGM is manifested by a restoration in the forest cover and in the temperature and precipitation regime. Later, during 5.4 to 4.3 ka, a strong monsoonal activity supported a dense moist evergreen forest cover that subsequently declined during 4.3 to 3.5 ka. A further increase in deciduous elements and non-arboreals might be a consequence of reduced precipitation and higher temperature during this phase. A comparison between monsoonal rainfall, MAT and palaeoatmospheric CO2 with floral dynamics since last ˜50 ka indicates that these fluctuations in plant succession were mainly driven by monsoonal variations.

Charge injection and transport properties of an organic light-emitting diode

PubMed Central

Juhasz, Peter; Nevrela, Juraj; Micjan, Michal; Novota, Miroslav; Uhrik, Jan; Stuchlikova, Lubica; Jakabovic, Jan; Harmatha, Ladislav

2016-01-01

Summary The charge behavior of organic light emitting diode (OLED) is investigated by steady-state current–voltage technique and impedance spectroscopy at various temperatures to obtain activation energies of charge injection and transport processes. Good agreement of activation energies obtained by steady-state and frequency-domain was used to analyze their contributions to the charge injection and transport. We concluded that charge is injected into the OLED device mostly through the interfacial states at low voltage region, whereas the thermionic injection dominates in the high voltage region. This comparison of experimental techniques demonstrates their capabilities of identification of major bottleneck of charge injection and transport. PMID:26925351

The evolution of active region loop plasma

NASA Technical Reports Server (NTRS)

Krall, K. R.; Antiochos, S. K.

1980-01-01

The adjustment of coronal active-region loops to changes in their heating rate is investigated numerically. The one-dimensional hydrodynamic equations are solved subject to boundary conditions in which heat flux-induced mass exchange between coronal and chromospheric components is allowed. The calculated evolution of physical parameters suggests that (1) mass supplied during chromospheric evaporation is much more effective in moderating coronal temperature excursions than when downward heat flux is dissipated by a static chromosphere, and (2) the method by which the chromosphere responds to changing coronal conditions can significantly influence coronal readjustment time scales. Observations are cited which illustrate the range of possible fluctuations in the heating rates.

Temperature and electrolyte optimization of the α-hemolysin latch sensing zone for detection of base modification in double-stranded DNA.

PubMed

Johnson, Robert P; Fleming, Aaron M; Jin, Qian; Burrows, Cynthia J; White, Henry S

2014-08-19

The latch region of the wild-type protein pore α-hemolysin (α-HL) constitutes a sensing zone for individual abasic sites (and furan analogs) in double-stranded DNA (dsDNA). The presence of an abasic site or furan within a DNA duplex, electrophoretically captured in the α-HL vestibule and positioned at the latch region, can be detected based on the current blockage prior to duplex unzipping. We investigated variations in blockage current as a function of temperature (12-35°C) and KCl concentration (0.15-1.0 M) to understand the origin of the current signature and to optimize conditions for identifying the base modification. In 1 M KCl solution, substitution of a furan for a cytosine base in the latch region results in an ∼ 8 kJ mol(-1) decrease in the activation energy for ion transport through the protein pore. This corresponds to a readily measured ∼ 2 pA increase in current at room temperature. Optimal resolution for detecting the presence of a furan in the latch region is achieved at lower KCl concentrations, where the noise in the measured blockage current is significantly lower. The noise associated with the blockage current also depends on the stability of the duplex (as measured from the melting temperature), where a greater noise in the measured blockage current is observed for less stable duplexes. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

CLASP/SJ Observations of Rapid Time Variations in the Ly α Emission in a Solar Active Region

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

Ishikawa, Shin-nosuke; Kubo, Masahito; Katsukawa, Yukio

The Chromospheric Ly α SpectroPolarimeter (CLASP) is a sounding rocket experiment launched on 2015 September 3 to investigate the solar chromosphere and transition region. The slit-jaw (SJ) optical system captured Ly α images with a high time cadence of 0.6 s. From the CLASP/SJ observations, many variations in the solar chromosphere and transition region emission with a timescale of <1 minute were discovered. In this paper, we focus on the active region within the SJ field of view and investigate the relationship between short (<30 s) temporal variations in the Ly α emission and the coronal structures observed by Solarmore » Dynamics Observatory/Atmospheric Imaging Assembly (AIA). We compare the Ly α temporal variations at the coronal loop footpoints observed in the AIA 211 Å (≈2 MK) and AIA 171 Å (≈0.6 MK) channels with those in the regions with bright Ly α features without a clear association with the coronal loop footpoints. We find more short (<30 s) temporal variations in the Ly α intensity in the footpoint regions. Those variations did not depend on the temperature of the coronal loops. Therefore, the temporal variations in the Ly α intensity at this timescale range could be related to the heating of the coronal structures up to temperatures around the sensitivity peak of 171 Å. No signature was found to support the scenario that these Ly α intensity variations were related to the nanoflares. Waves or jets from the lower layers (lower chromosphere or photosphere) are possible causes for this phenomenon.« less

Land radiative management as contributor to regional-scale climate adaptation and mitigation

NASA Astrophysics Data System (ADS)

Seneviratne, Sonia I.; Phipps, Steven J.; Pitman, Andrew J.; Hirsch, Annette L.; Davin, Edouard L.; Donat, Markus G.; Hirschi, Martin; Lenton, Andrew; Wilhelm, Micah; Kravitz, Ben

2018-02-01

Greenhouse gas emissions urgently need to be reduced. Even with a step up in mitigation, the goal of limiting global temperature rise to well below 2 °C remains challenging. Consequences of missing these goals are substantial, especially on regional scales. Because progress in the reduction of carbon dioxide emissions has been slow, climate engineering schemes are increasingly being discussed. But global schemes remain controversial and have important shortcomings. A reduction of global mean temperature through global-scale management of solar radiation could lead to strong regional disparities and affect rainfall patterns. On the other hand, active management of land radiative effects on a regional scale represents an alternative option of climate engineering that has been little discussed. Regional land radiative management could help to counteract warming, in particular hot extremes in densely populated and important agricultural regions. Regional land radiative management also raises some ethical issues, and its efficacy would be limited in time and space, depending on crop growing periods and constraints on agricultural management. But through its more regional focus and reliance on tested techniques, regional land radiative management avoids some of the main shortcomings associated with global radiation management. We argue that albedo-related climate benefits of land management should be considered more prominently when assessing regional-scale climate adaptation and mitigation as well as ecosystem services.

Turtle embryos move to optimal thermal environments within the egg.

PubMed

Zhao, Bo; Li, Teng; Shine, Richard; Du, Wei-Guo

2013-08-23

A recent study demonstrated that the embryos of soft-shelled turtles can reposition themselves within their eggs to exploit locally warm conditions. In this paper, we ask whether turtle embryos actively seek out optimal thermal environments for their development, as do post-hatching individuals. Specifically, (i) do reptile embryos move away from dangerously high temperatures as well as towards warm temperatures? and (ii) is such embryonic movement due to active thermoregulation, or (more simply) to passive embryonic repositioning caused by local heat-induced changes in viscosity of fluids within the egg? Our experiments with an emydid turtle (Chinemys reevesii) show that embryos avoid dangerously high temperatures by moving to cooler regions of the egg. The repositioning of embryos is an active rather than passive process: live embryos move towards a heat source, whereas dead ones do not. Overall, our results suggest that behavioural thermoregulation by turtle embryos is genuinely analogous to the thermoregulatory behaviour exhibited by post-hatching ectotherms.

Turtle embryos move to optimal thermal environments within the egg

PubMed Central

Zhao, Bo; Li, Teng; Shine, Richard; Du, Wei-Guo

2013-01-01

A recent study demonstrated that the embryos of soft-shelled turtles can reposition themselves within their eggs to exploit locally warm conditions. In this paper, we ask whether turtle embryos actively seek out optimal thermal environments for their development, as do post-hatching individuals. Specifically, (i) do reptile embryos move away from dangerously high temperatures as well as towards warm temperatures? and (ii) is such embryonic movement due to active thermoregulation, or (more simply) to passive embryonic repositioning caused by local heat-induced changes in viscosity of fluids within the egg? Our experiments with an emydid turtle (Chinemys reevesii) show that embryos avoid dangerously high temperatures by moving to cooler regions of the egg. The repositioning of embryos is an active rather than passive process: live embryos move towards a heat source, whereas dead ones do not. Overall, our results suggest that behavioural thermoregulation by turtle embryos is genuinely analogous to the thermoregulatory behaviour exhibited by post-hatching ectotherms. PMID:23760168

Eurasian Winter Storm Activity at the End of the Century: A CMIP5 Multi-model Ensemble Projection

NASA Astrophysics Data System (ADS)

Basu, Soumik; Zhang, Xiangdong; Wang, Zhaomin

2018-01-01

Extratropical cyclone activity over Eurasia has exhibited a weakening trend in the recent decade. Extratropical cyclones bring precipitation and hence supply fresh water for winter crops in the mid- and high-latitude regions of Eurasia. Any changes in extratropical cyclone activity over Eurasia in the future may have a critical impact on winter agriculture and the economies of affected communities. However, potential future changes in regional storm activity over Eurasia have not been studied in detail. Therefore, in this study, we investigate anticipated changes in extratropical storm activity by the end of the century through a detailed examination of the historical and future emission scenarios from six different models from CMIP5. A statistical analysis of different parameters of storm activity using a storm identification and tracking algorithm reveals a decrease in the number of storms over mid-latitude regions. However, intense storms with longer duration are projected over high latitude Eurasia. A further examination of the physical mechanism for these changes reveals that a decrease in the meridional temperature gradient and a weakening of the vertical wind shear over the mid-latitudes are responsible for these changes in storm activity.

Changes in gene expression and catalase activity in Oryza sativa L. under abiotic stress.

PubMed

Vighi, I L; Benitez, L C; do Amaral, M N; Auler, P A; Moraes, G P; Rodrigues, G S; da Maia, L C; Pinto, L S; Braga, E J B

2016-11-03

Different rice (Oryza sativa L.) genotypes were subjected to high salinity and low temperature (150 mM NaCl and 13°C, respectively) for 0, 6, 24, 48, or 72 h. We evaluated the simultaneous expression of the genes OsCATA, OsCATB, and OsCATC, correlated gene expression with enzyme activity, and verified the regulation of these genes through identification of cis-elements in the promoter region. The hydrogen peroxide content increased in a tolerant genotype and decreased in a sensitive genotype under both stress conditions. Lipid peroxidation increased in the tolerant genotype when exposed to cold, and in the sensitive genotype when exposed to high salinity. Catalase activity significantly increased in both genotypes when subjected to 13°C. In the tolerant genotype, OsCATA and OsCATB were the most responsive to high salinity and cold, while in the sensitive genotype, OsCATA and OsCATC responded positively to saline stress, as did OsCATA and OsCATB to low temperature. Cis-element analysis identified different regulatory sequences in the catalase promoter region of each genotype. The sensitive genotype maintained a better balance between hydrogen oxyacid levels, catalase activity, and lipid peroxidation under low temperature than the resistant genotype. OsCATA and OsCATB were the most responsive in the salt-tolerant genotype to cold, OsCATA and OsCATC were the most responsive to saline stress, and OsCATA and OsCATB were the most responsive to chilling stress in the sensitive genotype. There were positive correlations between catalase activity and OsCATB expression in the tolerant genotype under saline stress and in the sensitive genotype under cold stress.

Have human activities changed the frequencies of absolute extreme temperatures in eastern China?

NASA Astrophysics Data System (ADS)

Wang, Jun; Tett, Simon F. B.; Yan, Zhongwei; Feng, Jinming

2018-01-01

Extreme temperatures affect populous regions, like eastern China, causing substantial socio-economic losses. It is beneficial to explore whether the frequencies of absolute or threshold-based extreme temperatures have been changed by human activities, such as anthropogenic emissions of greenhouse gases (GHGs). In this study, we compared observed and multi-model-simulated changes in the frequencies of summer days, tropical nights, icy days and frosty nights in eastern China for the years 1960-2012 by using an optimal fingerprinting method. The observed long-term trends in the regional mean frequencies of these four indices were +2.36, +1.62, -0.94, -3.02 days decade-1. The models performed better in simulating the observed frequency change in daytime extreme temperatures than nighttime ones. Anthropogenic influences are detectable in the observed frequency changes of these four temperature extreme indices. The influence of natural forcings could not be detected robustly in any indices. Further analysis found that the effects of GHGs changed the frequencies of summer days (tropical nights, icy days, frosty nights) by +3.48 ± 1.45 (+2.99 ± 1.35, -2.52 ± 1.28, -4.11 ± 1.48) days decade-1. Other anthropogenic forcing agents (dominated by anthropogenic aerosols) offset the GHG effect and changed the frequencies of these four indices by -1.53 ± 0.78, -1.49 ± 0.94, +1.84 ± 1.07, +1.45 ± 1.26 days decade-1, respectively. Little influence of natural forcings was found in the observed frequency changes of these four temperature extreme indices.

Yeast activities involved in carbon and nitrogen cycles in Antarctica

USDA-ARS?s Scientific Manuscript database

Antarctica and sub Antarctic regions are characterized by extreme conditions for life such as low temperatures and nutrient availability, high solar radiation and dryness, however, microorganisms from the three domains of life have been found as common inhabitants of soils and waters from those zone...

Such Low Temperatures in the Arctic Region: How Can the Polar Bears Call It Home?

ERIC Educational Resources Information Center

Pringle, Rose M.

2002-01-01

Presents an activity on polar bears that integrates language arts and science. Teaches the characteristics of organisms and how distinct environments support distinct organisms. Uses both mathematics and science skills and targets students at the K-4 grade level. (YDS)

Effect of SiC Nanoparticles on Hot Deformation Behavior and Processing Maps of Magnesium Alloy AZ91

PubMed Central

Nie, Kaibo; Kang, Xinkai; Deng, Kunkun; Wang, Ting; Guo, Yachao; Wang, Hongxia

2018-01-01

The hot deformation behavior and processing characteristics of AZ91 alloy and nano-SiCp/AZ91 composite were compared at temperature ranges of 523 K–673 K and strain rates of 0.001–1 s−1. Positive impact of SiC nanoparticles on pinning grain boundaries and inhibiting grain growth was not obvious when deformation temperature was below 623 K, but was remarkable when the temperature was above 623 K. By comparing compressive stress-strain curves of AZ91 alloy and nano-SiCp/AZ91 composites, the addition of nanoparticles could improve the deformation ability of a matrix alloy under high-temperature conditions. There was no essential difference of deformation mechanism between AZ91 alloy and the composite, but hot deformation activation energy of the composite was significantly lower than that of the AZ91 alloy. The AZ91 alloy and the composite had the same workability region of 600 K–673 K and 0.001–1 s−1, while instability region for the composite was reduced compared with that of AZ91 alloy at high temperature. PMID:29389888

The influence of local sea surface temperatures on Australian east coast cyclones

NASA Astrophysics Data System (ADS)

Pepler, Acacia S.; Alexander, Lisa V.; Evans, Jason P.; Sherwood, Steven C.

2016-11-01

Cyclones are a major cause of rainfall and extreme weather in the midlatitudes and have a preference for genesis and explosive development in areas where a warm western boundary current borders a continental landmass. While there is a growing body of work on how extratropical cyclones are influenced by the Gulf Stream and Kuroshio Current in the Northern Hemisphere, there is little understanding of similar regions in the Southern Hemisphere including the Australian east coast, where cyclones that develop close to the coast are the main cause of severe weather and coastal flooding. This paper quantifies the impact of east Australian sea surface temperatures (SSTs) on local cyclone activity and behavior, using three different sets of sea surface temperature boundary conditions during the period 2007-2008 in an ensemble of Weather Research and Forecasting Model physics parameterizations. Coastal sea surface temperatures are demonstrated to have a significant impact on the overall frequency of cyclones in this region, with warmer SSTs acting as a trigger for the intensification of weak or moderate cyclones, particularly those of a subtropical nature. However, sea surface temperatures play only a minor role in the most intense cyclones, which are dominated by atmospheric conditions.

Significance of hair-dye base-induced sensory irritation.

PubMed

Fujita, F; Azuma, T; Tajiri, M; Okamoto, H; Sano, M; Tominaga, M

2010-06-01

Oxidation hair-dyes, which are the principal hair-dyes, sometimes induce painful sensory irritation of the scalp caused by the combination of highly reactive substances, such as hydrogen peroxide and alkali agents. Although many cases of severe facial and scalp dermatitis have been reported following the use of hair-dyes, sensory irritation caused by contact of the hair-dye with the skin has not been reported clearly. In this study, we used a self-assessment questionnaire to measure the sensory irritation in various regions of the body caused by two model hair-dye bases that contained different amounts of alkali agents without dyes. Moreover, the occipital region was found as an alternative region of the scalp to test for sensory irritation of the hair-dye bases. We used this region to evaluate the relationship of sensitivity with skin properties, such as trans-epidermal water loss (TEWL), stratum corneum water content, sebum amount, surface temperature, current perception threshold (CPT), catalase activities in tape-stripped skin and sensory irritation score with the model hair-dye bases. The hair-dye sensitive group showed higher TEWL, a lower sebum amount, a lower surface temperature and higher catalase activity than the insensitive group, and was similar to that of damaged skin. These results suggest that sensory irritation caused by hair-dye could occur easily on the damaged dry scalp, as that caused by skin cosmetics reported previously.

Room-temperature lasing operation of a quantum-dot vertical-cavity surface-emitting laser

NASA Astrophysics Data System (ADS)

Saito, Hideaki; Nishi, Kenichi; Ogura, Ichiro; Sugou, Shigeo; Sugimoto, Yoshimasa

1996-11-01

Self-assembled growth of quantum dots by molecular-beam epitaxy is used to form the active region of a vertical-cavity surface-emitting laser (VCSEL). Ten layers of InGaAs quantum dots are stacked in order to increase the gain. This quantum-dot VCSEL has a continuous-wave operating current of 32 mA at room temperature. Emission spectra at various current injections demonstrate that the lasing action is associated with a higher-order transition in the quantum dots.

Gas pressure and electron density at the level of the active zone of hollow cathode arc discharges

NASA Technical Reports Server (NTRS)

Minoo, M. H.

1984-01-01

A model for the longitudinal variations of the partial pressures of electrons, ions, and neutral particles is proposed as a result of an experimental study of pressure variations at the level of the active zone as a function of the various discharge parameters of a hollow cathode arc. The cathode region where the temperature passes through its maximum is called active zone. The proposed model embodies the very important variations which the partial electron and neutral particles pressures undergo at the level of the active zone.

Climate change projections over three metropolitan regions in Southeast Brazil using the non-hydrostatic Eta regional climate model at 5-km resolution

NASA Astrophysics Data System (ADS)

Lyra, Andre; Tavares, Priscila; Chou, Sin Chan; Sueiro, Gustavo; Dereczynski, Claudine; Sondermann, Marcely; Silva, Adan; Marengo, José; Giarolla, Angélica

2018-04-01

The objective of this work is to assess changes in three metropolitan regions of Southeast Brazil (Rio de Janeiro, São Paulo, and Santos) based on the projections produced by the Eta Regional Climate Model (RCM) at very high spatial resolution, 5 km. The region, which is densely populated and extremely active economically, is frequently affected by intense rainfall events that trigger floods and landslides during the austral summer. The analyses are carried out for the period between 1961 and 2100. The 5-km simulations are results from a second downscaling nesting in the HadGEM2-ES RCP4.5 and RCP8.5 simulations. Prior to the assessment of the projections, the higher resolution simulations were evaluated for the historical period (1961-1990). The comparison between the 5-km and the coarser driver model simulations shows that the spatial patterns of precipitation and temperature of the 5-km Eta simulations are in good agreement with the observations. The simulated frequency distribution of the precipitation and temperature extremes from the 5-km Eta RCM is consistent with the observed structure and extreme values. Projections of future climate change using the 5-km Eta runs show stronger warming in the region, primarily during the summer season, while precipitation is strongly reduced. Projected temperature extremes show widespread heating with maximum temperatures increasing by approximately 9 °C in the three metropolitan regions by the end of the century in the RCP8.5 scenario. A trend of drier climate is also projected using indices based on daily precipitation, which reaches annual rainfall reductions of more than 50 % in the state of Rio de Janeiro and between 40 and 45 % in São Paulo and Santos. The magnitude of these changes has negative implications to the population health conditions, energy security, and economy.

Antioxidant responses and photosynthetic behaviors of Kappaphycus alvarezii and Kappaphycus striatum (Rhodophyta, Solieriaceae) during low temperature stress.

PubMed

Li, Hu; Liu, Jianguo; Zhang, Litao; Pang, Tong

2016-12-01

Kappaphycus are farmed in tropical countries as raw material for carrageenan, which is widely used in food industry. The sea area available for farming is one limiting factor in the production of seaweeds. Though cultivation is spreading into subtropical regions, the lower seawater temperature is an important problem encountered in subtropical regions for the farming of Kappaphycus. This research of physiological response to low temperature stress will be helpful for screening Kappaphycus strains for growth in a lower temperature environment. Responses of antioxidant systems and photosystem II (PSII) behaviors in Kappaphycus alvarezii and Kappaphycus striatum were evaluated during low temperature treatments (23, 20, 17 °C). Compared with the controls at 26 °C, the H 2 O 2 concentrations increased in both species when the thalli were exposed to low temperatures (23, 20, 17 °C), but these increases were much greater in K. striatum than in K. alvarezii thalli, suggesting that K. striatum suffered more oxidative stress. The activities of some important antioxidant enzymes (e.g. superoxide dismutase and ascorbate peroxidase) and the hydroxyl free radical scavenging capacity were substantially higher at 23, 20 and 17 °C than at the control 26 °C in K. alvarezii, indicating that the antioxidant system of K. alvarezii enhanced its resistance to low temperature. However, no significant increases of antioxidant enzymes activities were observed at 20 and 17 °C in K. striatum. In addition, both the maximal efficiency of PSII photochemistry (F V /F m ) and the performance index (PI ABS ) decreased significantly in K. striatum at 23 °C, indicating that the photosynthetic apparatus was damaged at 23 °C. In contrast, no significant decreases of either F V /F m or PI ABS were observed in K. alvarezii at 23 °C. It is concluded that K. alvarezii has greater tolerance to low temperature than K. striatum.

Boreal temperature variability inferred from maximum latewood density and tree-ring width data, Wrangell Mountain region, Alaska

NASA Astrophysics Data System (ADS)

Davi, Nicole K.; Jacoby, Gordon C.; Wiles, Gregory C.

2003-11-01

Variations in both width and density of annual rings from a network of tree chronologies were used to develop high-resolution proxies to extend the climate record in the Wrangell Mountain region of Alaska. We developed a warm-season (July-September) temperature reconstruction that spans A.D. 1593-1992 based on the first eigenvector from principal component analysis of six maximum latewood density (MXD) chronologies. The climate/tree-growth model accounts for 51% of the temperature variance from 1958 to 1992 and shows cold in the late 1600s-early 1700s followed by a warmer period, cooling in the late 1700s-early 1800s, and warming in the 20th century. The 20th century is the warmest of the past four centuries. Several severely cold warm-seasons coincide with major volcanic eruptions. The first eigenvector from a ring-width (RW) network, based on nine chronologies from the Wrangell Mountain region (A.D. 1550-1970), is correlated positively with both reconstructed and recorded Northern Hemisphere temperatures. RW shows a temporal history similar to that of MXD by increased growth (warmer) and decreased growth (cooler) intervals and trends. After around 1970 the RW series show a decrease in growth, while station data show continued warming, which may be related to increasing moisture stress or other factors. Both the temperature history based on MXD and the growth trends from the RW series are consistent with well-dated glacier fluctuations in the Wrangell Mountains and some of the temperature variations also correspond to variations in solar activity.

Vegetation Response to Changing Climate - A Case Study from Gandaki River Basin in Nepal Himalaya

NASA Astrophysics Data System (ADS)

Panthi, J., Sr.; Kirat, N. H.; Dahal, P.

2015-12-01

The climate of the Himalayan region is changing rapidly - temperature is increasingly high and rainfall has become unpredictable. IPCC predicts that average annual mean temperature over the Asian land mass, including the Himalayas, will increase by about 3°C by the 2050s and about 5°C by the 2080s and the average annual precipitation in this region will increase by 10-30% by 2080s. Climate and the human activities can influence the land cover status and the eco-environmental quality. There are enough evidences that there is strong interaction between climate variability and ecosystems. A project was carried out in Gandaki river basin in central Nepal to analyze the relationship of NDVI vegetation index with the temperature, rainfall and snowcover information. The relationships were analyzed for different landuses classes-grassland, forest and agriculture. Results show that the snowcover area is decreasing at the rate of 0.15% per year in the basin. The NDVI shows seasonal fluctuations and lightly correlated with the rainfall and temperature.

3D-Stereoscopic Analysis of Solar Active Region Loops: I: SoHo/EIT Observations at Temperatures of 1.0-1.5 MK

NASA Technical Reports Server (NTRS)

Aschwanden, Markus J.; Newmark, Jeff; Delaboudiniere, Jean-Pierre; Neupert, Werner M.; Portier-Fozzani, Fabrice; Gary, G. Allen; Zucker, Arik

1998-01-01

The three-dimensional (3D) structure of solar active region NOAA 7986 observed on 1996 August 30 with the Extrem-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SoHO) is analyzed. We develop a new method of Dynamic Stereoscopy to reconstruct the 3D geometry of dynamically changing loops, which allows us to determine the orientation of the loop plane with respect to the line-of-sight, a prerequisite to correct properly for projection effects in 3D loop models. With this method and the filter-ratio technique applied to EIT 171 A and 195 A images we determine the 3D coordinates (x(s), y(s), z(s)), the loop width) w(s), the electron density n(sub e)(s), and the electron temperature T(sub e)(s) as function of the loop length s for 30 loop segments. Fitting the loop densities with an exponential density model n(sub e)(h) we find that the so inferred scale height temperatures, T(sub e)(sup lambda) = 1.22 +/- 0.23 MK, match closely the EIT filter-ratio temperatures, T(sub e)(sup FIT) = 1.21 +/- 0.06 MK. We conclude that these rather large-scale loops (with heights of h approx. equals 50 - 200 Mm) that dominate EIT 171 A images are close to thermal equilibrium. Most of the loops show no significant thickness variation w(s), but many exhibit a trend of increasing temperature (dT/ds greater than 0) above the footpoint.

Response to Extreme Temperatures of Mesoporous Silica MCM-41: Porous Structure Transformation Simulation and Modification of Gas Adsorption Properties.

PubMed

Zhang, Shenli; Perez-Page, Maria; Guan, Kelly; Yu, Erick; Tringe, Joseph; Castro, Ricardo H R; Faller, Roland; Stroeve, Pieter

2016-11-08

Molecular dynamics (MD) and Monte Carlo (MC) simulations were applied together for the first time to reveal the porous structure transformation mechanisms of mesoporous silica MCM-41 subjected to temperatures up to 2885 K. Silica was experimentally characterized to inform the models and enable prediction of changes in gas adsorption/separation properties. MD simulations suggest that the pore closure process is activated by a collective diffusion of matrix atoms into the porous region, accompanied by bond reformation at the surface. Degradation is kinetically limited, such that complete pore closure is postponed at high heating rates. We experimentally observe decreased gas adsorption with increasing temperature in mesoporous silica heated at fixed rates, due to pore closure and structural degradation consistent with simulation predictions. Applying the Kissinger equation, we find a strong correlation between the simulated pore collapse temperatures and the experimental values which implies an activation energy of 416 ± 17 kJ/mol for pore closure. MC simulations give the adsorption and selectivity for thermally treated MCM-41, for N 2 , Ar, Kr, and Xe at room temperature within the 1-10 000 kPa pressure range. Relative to pristine MCM-41, we observe that increased surface roughness due to decreasing pore size amplifies the difference of the absolute adsorption amount differently for different adsorbate molecules. In particular, we find that adsorption of strongly interacting molecules can be enhanced in the low-pressure region while adsorption of weakly interacting molecules is inhibited. This then results in higher selectivity in binary mixture adsorption in mesoporous silica.

Correlation of Coronal Plasma Properties and Solar Magnetic Field in a Decaying Active Region

NASA Technical Reports Server (NTRS)

Ko, Yuan-Kuen; Young, Peter R.; Muglach, Karin; Warren, Harry P.; Ugarte-Urra, Ignacio

2016-01-01

We present the analysis of a decaying active region observed by the EUV Imaging Spectrometer on Hinode during 2009 December 7-11. We investigated the temporal evolution of its structure exhibited by plasma at temperatures from 300,000 to 2.8 million degrees, and derived the electron density, differential emission measure, effective electron temperature, and elemental abundance ratios of Si/S and Fe/S (as a measure of the First Ionization Potential (FIP) Effect). We compared these coronal properties to the temporal evolution of the photospheric magnetic field strength obtained from the Solar and Heliospheric Observatory Michelson Doppler Imager magnetograms. We find that, while these coronal properties all decreased with time during this decay phase, the largest change was at plasma above 1.5 million degrees. The photospheric magnetic field strength also decreased with time but mainly for field strengths lower than about 70 Gauss. The effective electron temperature and the FIP bias seem to reach a basal state (at 1.5 x 10(exp 6) K and 1.5, respectively) into the quiet Sun when the mean photospheric magnetic field (excluding all areas <10 G) weakened to below 35 G, while the electron density continued to decrease with the weakening field. These physical properties are all positively correlated with each other and the correlation is the strongest in the high-temperature plasma. Such correlation properties should be considered in the quest for our understanding of how the corona is heated. The variations in the elemental abundance should especially be considered together with the electron temperature and density.

Effect of summer outdoor temperatures on work-related injuries in Quebec (Canada).

PubMed

Adam-Poupart, Ariane; Smargiassi, Audrey; Busque, Marc-Antoine; Duguay, Patrice; Fournier, Michel; Zayed, Joseph; Labrèche, France

2015-05-01

To quantify the associations between occupational injury compensations and exposure to summer outdoor temperatures in Quebec (Canada). The relationship between 374,078 injuries compensated by the Workers' Compensation Board (WCB) (between May and September, 2003-2010) and maximum daily outdoor temperatures was modelled using generalised linear models with negative binomial distributions. Pooled effect sizes for all 16 health regions of Quebec were estimated with random-effect models for meta-analyses for all compensations and by sex, age group, mechanism of injury, industrial sector and occupations (manual vs other) within each sector. Time lags and cumulative effect of temperatures were also explored. The relationship between daily counts of compensations and maximum daily temperatures reached statistical significance for three health regions. The incidence rate ratio (IRR) of daily compensations per 1°C increase was 1.002 (95% CI 1.002 to 1.003) for all health regions combined. Statistically significant positive associations were observed for men, workers aged less than 45 years, various industrial sectors with both indoor and outdoor activities, and for slips/trips/falls, contact with object/equipment and exposure to harmful substances/environment. Manual occupations were not systematically at higher risk than non-manual and mixed ones. This study is the first to quantify the association between work-related injury compensations and exposure to summer temperatures according to physical demands of the occupation and this warrants further investigations. In the context of global warming, results can be used to estimate future impacts of summer outdoor temperatures on workers, as well as to plan preventive interventions. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Comparison of thermal modeling, microstructural analysis, and Ti-in-quartz thermobarometry to constrain the thermal history of a cooling pluton during deformation in the Mount Abbot Quadrangle, CA

NASA Astrophysics Data System (ADS)

Nevitt, Johanna M.; Warren, Jessica M.; Kidder, Steven; Pollard, David D.

2017-03-01

Granitic plutons commonly preserve evidence for jointing, faulting, and ductile fabric development during cooling. Constraining the spatial variation and temporal evolution of temperature during this deformation could facilitate an integrated analysis of heterogeneous deformation over multiple length-scales through time. Here, we constrain the evolving temperature of the Lake Edison granodiorite within the Mount Abbot Quadrangle (central Sierra Nevada, CA) during late Cretaceous deformation by combining microstructural analysis, titanium-in-quartz thermobarometry (TitaniQ), and thermal modeling. Microstructural and TitaniQ analyses were applied to 12 samples collected throughout the pluton, representative of either the penetrative "regional" fabric or the locally strong "fault-related" fabric. Overprinting textures and mineral assemblages indicate the temperature decreased from 400-500°C to <350°C during faulting. TitaniQ reveals consistently lower Ti concentrations for partially reset fault-related fabrics (average: 12 ± 4 ppm) than for regional fabrics (average: 31 ± 12 ppm), suggesting fault-related fabrics developed later, following a period of pluton cooling. Uncertainties, particularly in TiO2 activity, significantly limit further quantitative thermal estimates using TitaniQ. In addition, we present a 1-D heat conduction model that suggests average pluton temperature decreased from 585°C at 85 Ma to 332°C at 79 Ma, consistent with radiometric age data for the field. Integrated with the model results, microstructural temperature constraints suggest faulting initiated by ˜83 Ma, when the temperature was nearly uniform across the pluton. Thus, spatially heterogeneous deformation cannot be attributed to a persistent temperature gradient, but may be related to regional structures that develop in cooling plutons.

Positive Selection at the Polyhomeotic Locus Led to Decreased Thermosensitivity of Gene Expression in Temperate Drosophila melanogaster

PubMed Central

Voigt, Susanne; Laurent, Stefan; Litovchenko, Maria; Stephan, Wolfgang

2015-01-01

Drosophila melanogaster as a cosmopolitan species has successfully adapted to a wide range of different environments. Variation in temperature is one important environmental factor that influences the distribution of species in nature. In particular for insects, which are mostly ectotherms, ambient temperature plays a major role in their ability to colonize new habitats. Chromatin-based gene regulation is known to be sensitive to temperature. Ambient temperature leads to changes in the activation of genes regulated in this manner. One such regulatory system is the Polycomb group (PcG) whose target genes are more expressed at lower temperatures than at higher ones. Therefore, a greater range in ambient temperature in temperate environments may lead to greater variability (plasticity) in the expression of these genes. This might have detrimental effects, such that positive selection acts to lower the degree of the expression plasticity. We provide evidence for this process in a genomic region that harbors two PcG-regulated genes, polyhomeotic proximal (ph-p) and CG3835. We found a signature of positive selection in this gene region in European populations of D. melanogaster and investigated the region by means of reporter gene assays. The target of selection is located in the intergenic fragment between the two genes. It overlaps with the promoters of both genes and an experimentally validated Polycomb response element (PRE). This fragment harbors five sequence variants that are highly differentiated between European and African populations. The African alleles confer a temperature-induced plasticity in gene expression, which is typical for PcG-mediated gene regulation, whereas thermosensitivity is reduced for the European alleles. PMID:25855066

Exploring the Effects of Subfreezing Temperature and Salt Concentration on Ice Growth Inhibition of Antarctic Gram-Negative Bacterium Marinomonas Primoryensis Using Coarse-Grained Simulation.

PubMed

Nguyen, Hung; Dac Van, Thanh; Tran, Nhut; Le, Ly

2016-04-01

The aim of this work is to study the freezing process of water molecules surrounding Antarctic Gram-negative bacterium Marinomonas primoryensis antifreeze protein (MpAFP) and the MpAFP interactions to the surface of ice crystals under various marine environments (at different NaCl concentrations of 0.3, 0.6, and 0.8 mol/l). Our result indicates that activating temperature region of MpAFPs reduced as NaCl concentration increased. Specifically, MpAFP was activated and functioned at 0.6 mol/l with temperatures equal or larger 278 K, and at 0.8 mol/l with temperatures equal or larger 270 K. Additionally, MpAFP was inhibited by ice crystal network from 268 to 274 K and solid-liquid hybrid from 276 to 282 K at 0.3 mol/l concentration. Our results shed lights on structural dynamics of MpAFP among different marine environments.

Effects of a temperature-dependent rheology on large scale continental extension

NASA Technical Reports Server (NTRS)

Sonder, Leslie J.; England, Philip C.

1988-01-01

The effects of a temperature-dependent rheology on large-scale continental extension are investigated using a thin viscous sheet model. A vertically-averaged rheology is used that is consistent with laboratory experiments on power-law creep of olivine and that depends exponentially on temperature. Results of the calculations depend principally on two parameters: the Peclet number, which describes the relative rates of advection and diffusion of heat, and a dimensionless activation energy, which controls the temperature dependence of the rheology. At short times following the beginning of extension, deformation occurs with negligible change in temperature, so that only small changes in lithospheric strength occur due to attenuation of the lithosphere. However, after a certain critical time interval, thermal diffusion lowers temperatures in the lithosphere, strongly increasing lithospheric strength and slowing the rate of extension. This critical time depends principally on the Peclet number and is short compared with the thermal time constant of the lithosphere. The strength changes cause the locus of high extensional strain rates to shift with time from regions of high strain to regions of low strain. Results of the calculations are compared with observations from the Aegean, where maximum extensional strains are found in the south, near Crete, but maximum present-day strain rates are largest about 300 km further north.

Bandlike Transport in Ferroelectric-Based Organic Field-Effect Transistors

NASA Astrophysics Data System (ADS)

Laudari, A.; Guha, S.

2016-10-01

The dielectric constant of polymer-ferroelectric dielectrics may be tuned by changing the temperature, offering a platform for monitoring changes in interfacial transport with the polarization strength in organic field-effect transistors (FETs). Temperature-dependent transport studies of FETs are carried out from a solution-processed organic semiconductor, 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), using both ferroelectric- and nonferroelectric-gate insulators. Nonferroelectric dielectric-based TIPS-pentacene FETs show a clear activated transport, in contrast to the ferroelectric dielectric polymer, poly(vinylidene fluoride-trifluoroethylene), where a negative temperature coefficient of the mobility is observed in the ferroelectric temperature range. The current-voltage (I -V ) characteristics from TIPS-pentacene diodes signal a space-charge-limited conduction (SCLC) for a discrete set of trap levels, suggesting that charge injection and transport occurs through regions of ordering in the semiconductor. The carrier mobility extracted from temperature-dependent I -V characteristics from the trap-free SCLC region shows a negative coefficient beyond 200 K, similar to the trend observed in FETs with the ferroelectric dielectric. At moderate temperatures, the polarization-fluctuation-dominant transport inherent in a ferroelectric dielectric, in conjunction with the nature of traps, results in an effective detrapping of the shallow-trap states into more mobile states in TIPS-pentacene.

Temperature performance of portable radiation survey instruments used for environmental monitoring and clean-up activities in Fukushima

NASA Astrophysics Data System (ADS)

Saegusa, Jun; Yanagisawa, Kayo; Hasumi, Atsushi; Shimizu, Takenori; Uchita, Yoshiaki

2017-08-01

Following the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011, extensive radiation monitoring and environmental clean-up activities have been conducted throughout the Fukushima region. Outside air temperatures there reach 40 °C in summer and -20 °C in winter, which are beyond the quoted operational range of many radiation survey instruments. Herein, temperature performance of four types of portable Japanese radiation survey instruments widely used in Fukushima was experimentally investigated using a temperature-controlled chamber. They included two ionization chamber type instruments, Fuji NHA1 and Aloka ICS-323C, and two NaI(Tl) scintillation type ones, Fuji NHC7 and Aloka TCS-172B. Experimental results showed significantly diverse characteristics on the temperature dependences from one type of instrument to another. For example, NHA1 overestimated the ambient dose-equivalent rate by as much as 17% at -30 °C and 10% at 40 °C, whereas the TCS-172B readings underestimated the rate by 30% at -30 °C and 7% at 40 °C.

The influence of climatic conditions on the transmission dynamics of the 2009 A/H1N1 influenza pandemic in Chile

PubMed Central

2012-01-01

Background The role of demographic factors, climatic conditions, school cycles, and connectivity patterns in shaping the spatio-temporal dynamics of pandemic influenza is not clearly understood. Here we analyzed the spatial, age and temporal evolution of the 2009 A/H1N1 influenza pandemic in Chile, a southern hemisphere country covering a long and narrow strip comprising latitudes 17°S to 56°S. Methods We analyzed the dissemination patterns of the 2009 A/H1N1 pandemic across 15 regions of Chile based on daily hospitalizations for severe acute respiratory disease and laboratory confirmed A/H1N1 influenza infection from 01-May to 31-December, 2009. We explored the association between timing of pandemic onset and peak pandemic activity and several geographical and demographic indicators, school vacations, climatic factors, and international passengers. We also estimated the reproduction number (R) based on the growth rate of the exponential pandemic phase by date of symptoms onset, estimated using maximum likelihood methods. Results While earlier pandemic onset was associated with larger population size, there was no association with connectivity, demographic, school or climatic factors. In contrast, there was a latitudinal gradient in peak pandemic timing, representing a 16-39-day lag in disease activity from the southern regions relative to the northernmost region (P < 0.001). Geographical differences in latitude of Chilean regions, maximum temperature and specific humidity explained 68.5% of the variability in peak timing (P = 0.01). In addition, there was a decreasing gradient in reproduction number from south to north Chile (P < 0.0001). The regional mean R estimates were 1.6-2.0, 1.3-1.5, and 1.2-1.3 for southern, central and northern regions, respectively, which were not affected by the winter vacation period. Conclusions There was a lag in the period of most intense 2009 pandemic influenza activity following a South to North traveling pattern across regions of Chile, significantly associated with geographical differences in minimum temperature and specific humidity. The latitudinal gradient in timing of pandemic activity was accompanied by a gradient in reproduction number (P < 0.0001). Intensified surveillance strategies in colder and drier southern regions could lead to earlier detection of pandemic influenza viruses and improved control outcomes. PMID:23148597

The Role of the Snow Covers in the Permafrost Temperature Dynamics at the Northern Yakutia over the last 30 Years

NASA Astrophysics Data System (ADS)

Kholodov, A. L.

2011-12-01

This report concerns the changes of the dynamics of snow warming influence on the permafrost temperature at the northern Yakutia. Snow is a key factor determines the thermal state of permafrost here. Despite of the absence of air temperature latitudinal zonality mean annual ground temperature decreases northward approximately 1 centigrade per latitude degree due to changes of the snow warming impact. At the north-western part with a relatively maritime climate warming influence of the snow is 0.5 to 1.5°C, while in the southern and eastern part with more continental climate it is 3.5 to 4.5°C. Snow redistribution within the some types of landscape at the beginning of the winter season can lead to the extremely fast freezing of the active layer and cooling of the permafrost within such types of landscapes. The main goal of the current research was to estimate snow warming impact dynamics over the last 30 years in the northern Yakutia. We took in consideration changes of the three main parameters, are determining snow cover thermal state: - snow thickness; - amplitude of air temperature seasonal oscillation; - temperature during the winter period during. Following conclusion can be done based on the data analysis: Interannual changes of snow warming influence are tenth to first centigrades, what is comparable with air temperature fluctuations. During the 1980-90s snow impact on the permafrost stood stable in the south-eastern part of the region or had a slightly negative trend in the western part. It could be explained by the changes of snow thickness, reduced thermal resistivity of snow due to winter warming and decreasing of the amplitude of seasonal temperature oscillation in the western part of the region. Since the end of 90s general increasing of the snow cover warming influence was noticed for the entire investigated territory. These results correspond with data of modern permafrost temperature observations have been done in the region during the last decades. Most of monitoring sites did not show sustainable changes of the permafrost temperature until the end of 90s years of the XX century, but recent measurements record increasing of the mean annual ground temperature at the most of monitoring sites in the region.

How Hot Are They? Neural Correlates of Genital Arousal: An Infrared Thermographic and Functional Magnetic Resonance Imaging Study of Sexual Arousal in Men and Women.

PubMed

Parada, Mayte; Gérard, Marina; Larcher, Kevin; Dagher, Alain; Binik, Yitzchak M

2018-02-01

The few studies that have examined the neural correlates of genital arousal have focused on men and are methodologically hard to compare. To investigate the neural correlates of peripheral physiologic sexual arousal using identical methodology for men and women. 2 groups (20 men, 20 women) viewed movie clips (erotic, humor) while genital temperature was continuously measured using infrared thermal imaging. Participants also continuously evaluated changes in their subjective arousal and answered discrete questions about liking the movies and wanting sexual stimulation. Brain activity, indicated by blood oxygen level-dependent (BOLD) response, was measured using functional magnetic resonance imaging. BOLD responses, genital temperature, and subjective sexual arousal. BOLD activity in a number of brain regions was correlated with changes in genital temperature in men and women; however, activation in women appeared to be more extensive than in men, including the anterior and posterior cingulate cortex, right cerebellum, insula, frontal operculum, and paracingulate gyrus. Examination of the strength of the correlation between BOLD response and genital temperature showed that women had a stronger brain-genital relation compared with men in a number of regions. There were no brain regions in men with stronger brain-genital correlations than in women. Our findings shed light on the neurophysiologic processes involved in genital arousal for men and women. Further research examining the specific brain regions that mediate our findings is necessary to pave the way for clinical application. A strength of the study is the use of thermography, which allows for a direct comparison of the neural correlates of genital arousal in men and women. This study has the common limitations of most laboratory-based sexual arousal research, including sampling bias, lack of ecologic validity, and equipment limitations, and those common to neuroimaging research, including BOLD signal interpretation and neuroimaging analysis issues. Our findings provide direct sex comparisons of the neural correlates of genital arousal in men and women and suggest that brain-genital correlations could be stronger in women. Parada M, Gérard M, Larcher K, et al. How Hot Are They? Neural Correlates of Genital Arousal: An Infrared Thermographic and Functional Magnetic Resonance Imaging Study of Sexual Arousal in Men and Women. J Sex Med 2018;15:217-229. Copyright © 2017 International Society for Sexual Medicine. Published by Elsevier Inc. All rights reserved.

Spatiotemporal investigation of long-term seasonal temperature variability in Libya

NASA Astrophysics Data System (ADS)

Elsharkawy, S. G.; Elmallah, E. S.

2016-09-01

Throughout this work, spatial and temporal variations of seasonal surface air temperature have been investigated. Moreover, the effects of relative internal (teleconnection) and external (solar) forcing on surface air temperature variability have been examined. Seasonal temperature time series covering 30 different meteorological locations and lasting over the last century are considered. These locations are classified into two groups based on their spatial distribution. One represents Coast Libya Surface Air Temperature (CLSAT), contains 19 locations, and the other represents Desert Libya Surface Air Temperature (DLSAT), contains 11 locations. Average temperature departure test is applied to investigate the nature of temperature variations. Temperature trends are analyzed using the nonparametric Mann-Kendall test and their coefficients are calculated using Sen's slope estimate. Cross-correlation and spectral analysis techniques are also applied. Our results showed temperature deviation from average within a band of ± 2°C at coast region, while ± 4°C at desert region. Extreme behavior intensions between summer and winter temperatures at coast region are noticed. Segmentation process declared reversal cooling/warming behavior within temperature records for all seasons. Desert region shows warming trend for all seasons with higher coefficients than obtained at coast region. Results obtained for spectral analysis show different short and medium signals and concluded that not only the spectral properties are different for different geographical regions but also different for different climatic seasons on regional scale as well. Cross-correlation results showed that highest influence for Rz upon coastal temperature is always in conjunction with highest influence of NAO upon coastal temperature during the period 1981-2010. Desert region does not obey this phenomenon, where highest temperature-NAO correlations at desert during autumn and winter seasons are not accompanied with highest correlations for temperature-Rz.

Seasonal, daily activity, and habitat use by three sympatric pit vipers (Serpentes, Viperidae) from southern Brazil.

PubMed

Rocha, Marcelo C; Hartmann, Paulo A; Winck, Gisele R; Cechin, Sonia Z

2014-04-25

Viperid snakes are widely distributed in the South America and the greater distribution range of the family is found at the Crotalinae subfamily. Despite the abundance of this snakes along their geographic distribution, some ecological aspects remain unknown, principally at subtropical areas. In the present study, we evaluated the activity (daily and seasonal) and the use of the habitat by Bothrops diporus, B. jararaca and B. jararacussu, in an Atlantic Forest area at southern Brazil. We observed higher incidence of viperid snakes during the months with higher temperatures, while no snakes were found during the months with lower temperatures. The data suggest the minimum temperature as environmental variable with the greatest influence on the seasonal activity of this species. Considering the daily activity, we observed a tendency of snakes to avoid the warmest hours. Bothrops jararacussu tend to avoid open areas, being registered only inside and at the edges of the forest. We compared our results with previous studies realized at tropical areas and we suggest the observed seasonal activity as an evolutive response, despite the influence of the different environmental variables, according to the occurence region.

Post-Activation Brain Warming: A 1-H MRS Thermometry Study

PubMed Central

Rango, Mario; Bonifati, Cristiana; Bresolin, Nereo

2015-01-01

Purpose Temperature plays a fundamental role for the proper functioning of the brain. However, there are only fragmentary data on brain temperature (Tbr) and its regulation under different physiological conditions. Methods We studied Tbr in the visual cortex of 20 normal subjects serially with a wide temporal window under different states including rest, activation and recovery by a visual stimulation-Magnetic Resonance Spectroscopy Thermometry combined approach. We also studied Tbr in a control region, the centrum semiovale, under the same conditions. Results Visual cortex mean baseline Tbr was higher than mean body temperature (37.38 vs 36.60, P<0.001). During activation Tbr remained unchanged at first and then showed a small decrease (-0.20 C°) around the baseline value. After the end of activation Tbr increased consistently (+0.60 C°) and then returned to baseline values after some minutes. Centrum semiovale Tbr remained unchanged through rest, visual stimulation and recovery. Conclusion These findings have several implications, among them that neuronal firing itself is not a major source of heat release in the brain and that there is an aftermath of brain activation that lasts minutes before returning to baseline conditions. PMID:26011731

The onset of chromospheric activity among the A- and F- type stars

NASA Technical Reports Server (NTRS)

Simon, Theodore; Landsman, Wayne

1987-01-01

IUE observations of C II lambda1335 and C IV lambda1549 and ground-based observations of He I lambda5876 have previously discovered intense levels of chromospheric activity among early F type stars. Virtually all F dwarfs show stronger chromospheric and transition region emission than do the cooler and more deeply convective dwarf stars like the Sun. The IUE spectra and those of He lambda5876 place the onset of stellar activity along the main sequence near a color B - V = 0.28, which corresponds approximately to spectral type FO and an effective temperature of 7300 K. However, existing X-ray observations of A and F stars suggest that coronal activity may reach a peak blueward of this high temperature boundary at B - V = 0.28 before vanishing among the early and mid A-type stars. Discussed are preliminary results of a new effort to refine the location of the high temperature boundary to chromospheric activity among A- and F- type stars, making use of low dispersion short-wavelength spectra from the IUE archives from which the strengths of C IV, C II, and Lyman alpha emission have been measured.

Conformational Changes in a Hyperthermostable Glycoside Hydrolase: Enzymatic Activity Is a Consequence of the Loop Dynamics and Protonation Balance

PubMed Central

de Oliveira, Leandro C.; da Silva, Viviam M.; Colussi, Francieli; Cabral, Aline D.; de Oliveira Neto, Mario; Squina, Fabio M.; Garcia, Wanius

2015-01-01

Endo-β-1, 4-mannanase from Thermotoga petrophila (TpMan) is a modular hyperthermostable enzyme involved in the degradation of mannan-containing polysaccharides. The degradation of these polysaccharides represents a key step for several industrial applications. Here, as part of a continuing investigation of TpMan, the region corresponding to the GH5 domain (TpManGH5) was characterized as a function of pH and temperature. The results indicated that the enzymatic activity of the TpManGH5 is pH-dependent, with its optimum activity occurring at pH 6. At pH 8, the studies demonstrated that TpManGH5 is a molecule with a nearly spherical tightly packed core displaying negligible flexibility in solution, and with size and shape very similar to crystal structure. However, TpManGH5 experiences an increase in radius of gyration in acidic conditions suggesting expansion of the molecule. Furthermore, at acidic pH values, TpManGH5 showed a less globular shape, probably due to a loop region slightly more expanded and flexible in solution (residues Y88 to A105). In addition, molecular dynamics simulations indicated that conformational changes caused by pH variation did not change the core of the TpManGH5, which means that only the above mentioned loop region presents high degree of fluctuations. The results also suggested that conformational changes of the loop region may facilitate polysaccharide and enzyme interaction. Finally, at pH 6 the results indicated that TpManGH5 is slightly more flexible at 65°C when compared to the same enzyme at 20°C. The biophysical characterization presented here is well correlated with the enzymatic activity and provide new insight into the structural basis for the temperature and pH-dependent activity of the TpManGH5. Also, the data suggest a loop region that provides a starting point for a rational design of biotechnological desired features. PMID:25723179

The paradox of characteristics of silicon detectors operated at temperature close to liquid helium

NASA Astrophysics Data System (ADS)

Eremin, V.; Shepelev, A.; Verbitskaya, E.; Zamantzas, C.; Galkin, A.

2018-05-01

The aim of this study is to give characterization of silicon p+/n/n+ detectors for the monitoring systems of the Large Hadron Collider machine at CERN with the focus on justifying the choice of silicon resistivity for the detector operation at the temperature of 1.9-10 K. The detectors from n-type silicon with the resistivity of 10, 4.5, and 0.5 kΩ cm were investigated at the temperature from 293 up to 7 K by the Transient Current Technique with a 660 nm pulse laser and alpha-particles. The shapes of the detector current pulse response allowed revealing a paradox in the properties of shallow donors of phosphorus, i.e., native dopants in the n-type Si. There was no carrier freeze-out on the phosphorus energy levels in the space charge region (SCR), and they remained positively charged irrespective of temperature, thus limiting the depleted region depth. As for the base region of a partially depleted detector, the levels became neutral at T < 28 K, which transformed silicon to an insulator. The reduction of the activation energy for carrier emission in the detector SCR estimated in the scope of the Poole-Frenkel effect failed to account for the impact of the electric field on the properties of phosphorus levels. The absence of carrier freeze-out in the SCR justifies the choice of high resistivity silicon as the only proper material for detector operation in a fully depleted mode at extremely low temperature.

Micromechanical properties of single crystals and polycrystals of pure α-titanium: anisotropy of microhardness, size effect, effect of the temperature (77-300 K)

NASA Astrophysics Data System (ADS)

Lubenets, S. V.; Rusakova, A. V.; Fomenko, L. S.; Moskalenko, V. A.

2018-01-01

The anisotropy of microhardness of pure α-Ti single crystals, indentation size effect in single-crystal, course grained (CG) pure and nanocrystalline (NC) VT1-0 titanium, as well as the temperature dependences of the microhardness of single-crystal and CG Ti in the temperature range 77-300 K were studied. The minimum value of hardness was obtained when indenting into the basal plane (0001). The indentation size effect (ISE) was clearly observed in the indentation of soft high-purity single-crystal iodide titanium while it was the least pronounced in a sample of nanocrystalline VT1-0 titanium. It has been demonstrated that the ISE can be described within the model of geometrically necessary dislocations (GND), which follows from the theory of strain gradient plasticity. The true hardness and others parameters of the GND model were determined for all materials. The temperature dependence of the microhardness is in agreement with the idea of the governing role of Peierls relief in the dislocation thermally-activated plastic deformation of pure titanium as has been earlier established and justified in macroscopic tensile investigations at low temperatures. The activation energy and activation volume of dislocation motion in the strained region under the indenter were estimated.

Engineering Rubisco activase from thermophilic cyanobacteria into high-temperature sensitive plants.

PubMed

Ogbaga, Chukwuma C; Stepien, Piotr; Athar, Habib-Ur-Rehman; Ashraf, Muhammad

2018-06-01

In the past decade, various strategies to improve photosynthesis and crop yield, such as leaf morphology, light interception and use efficiency, biochemistry of light reactions, stomatal conductance, carboxylation efficiency, and source to sink regulation, have been discussed at length. Leaf morphology and physiology are tightly coupled to light capturing efficiency, gas exchange capacity, and temperature regulation. However, apart from the photoprotective mechanism of photosystem-II (PSII), i.e. non-photochemical quenching, very low genetic variation in the components of light reactions has been observed in plants. In the last decade, biochemistry-based enhancement of carboxylation efficiency that improves photosynthesis in plants was one of the potential strategies for improving plant biomass production. Enhancement of activation of the ubiquitous enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) by Rubisco activase may be another potential strategy for improving a photosynthesis-driven increase in crop yield. Rubisco activase modifies the conformation of the active center in Rubisco by removing tightly bound inhibitors, thereby contributing to enzyme activation and rapid carboxylation. Thermophilic cyanobacteria are oxygenic photosynthetic bacteria that thrive in high-temperature environments. This critical review discusses the prospects for and the potential of engineering Rubisco activase from thermophilic cyanobacteria into temperature-sensitive plants, to increase the threshold temperature and survival of these plants in arid regions.

Frequency dependent electrical characteristics of ferroelectric Pb{4.0}K{1.0}Li{1.0}Nb{10}O{30} ceramics

NASA Astrophysics Data System (ADS)

Rao, K. S.; Krishna, P. M.; Prasad, D. M.; Latha, T. S.; Hussain, M.

2007-09-01

Dielectric, impedance, modulus and conductivity studies were performed over temperature 35 °C 600 °C and frequency 45 Hz 5 MHz range on the Lead Potassium Lithium Niobate (Pb{4.0}K{1.0}Li{1.0}Nb{10}O{30}, PKLN) ceramics. These studies established the conduction ion motion and polarization mechanism in the material. The dispersive dielectric loss at high temperature reveals the ionic conductivity. From frequency variation of \\varepsilonl response the pre-factor A(T) and critical exponent n(T) are evaluated, and are used in Jonscher's dielectric dispersion relation for \\varepsilon ' to fit with the experimental data. Complex impedance plots showed a non Debye type relaxation, are used to evaluate the grain and grain boundary conduction and relaxation activation energies. DC and ac conduction activation energies are estimated from Arrhenius plots. Occupancy of Li+ for C-sites gave a completely filled structure and enhanced the phase transition temperature to 520 °C compared to PKN. This is supported by the conduction activation energy in ferro region is more than the para region. Also, the dc conductivity characterized from bulk resistance and M^ll peak frequency. Polaron hoping mechanism at room temperature has been confirmed via the linear variation of the plot log (σ ac-σ dc) as a function of log ω 2. Stretched exponential parameter, β (0 < β ≤slant 1) has been evaluated from impedance plots, interpreted as a result of correlated motions between the Li+ ions and distribution of dielectric relaxation. Compared the results from different techniques, and discussed the conduction mechanism in the material.

Spatial and temporal distributions of Martian north polar cold spots before, during, and after the global dust storm of 2001

USGS Publications Warehouse

Cornwall, C.; Titus, T.N.

2009-01-01

In the 1970s, Mariner and Viking observed features in the Mars northern polar region that were a few hundred kilometers in diameter with 20 fj,m brightness temperatures as low as 130 K (considerably below C02 ice sublimation temperatures). Over the past decade, studies have shown that these areas (commonly called "cold spots") are usually due to emissivity effects of frost deposits and occasionally to active C02 snowstorms. Three Mars years of Mars Global Surveyor Thermal Emission Spectrometer data were used to observe autumn and wintertime cold spot activity within the polar regions. Many cold spots formed on or near scarps of the perennial cap, probably induced by adiabatic cooling due to orographic lifting. These topographically associated cold spots were often smaller than those that were not associated with topography. We determined that initial grain sizes within the cold spots were on the order of a few millimeters, assuming the snow was uncontaminated by dust or water ice. On average, the half-life of the cold spots was 5 Julian days. The Mars global dust storm in 2001 significantly affected cold spot activity in the north polar region. Though overall perennial cap cold spot activity seemed unaffected, the distribution of cold spots did change by a decrease in the number of topographically associated cold spots and an increase in those not associated with topography. We propose that the global dust storm affected the processes that form cold spots and discuss how the global dust storm may have affected these processes. ?? 2009 by the American Geophysical Union.

Interaction of Molecular Oxygen with a Hexagonally Reconstructed Au(001) Surface

DOE PAGES

Loheac, Andrew; Barbour, Andi; Komanicky, Vladimir; ...

2016-09-19

Kinetics of molecular oxygen/Au(001) surface interaction has been studied at high temperature and near atmospheric pressures of O 2 gas with in situ X-ray scattering measurements. In this study, we find that the hexagonal reconstruction (hex) of Au(001) surface lifts to (1 × 1) in the presence of O 2 gas, indicating that the (1 × 1) is more favored when some oxygen atoms present on the surface. The measured lifting rate constant vs temperature is found to be highest at intermediate temperature exhibiting a “volcano”-type behavior. At low temperature, the hex-to-(1 × 1) activation barrier (E act = 1.3(3)more » eV) limits the lifting. At high temperature, oxygen adsorption energy (E ads = 1.6(2) eV) limits the lifting. The (1 × 1)-to-hex activation barrier (E hex = 0.41(14) eV) is also obtained from hex recovery kinetics. The pressure–temperature (PT) surface phase diagram obtained in this study shows three regions: hex at low P and T, (1 × 1) at high P and T, and coexistence of the hex and (1 × 1) at the intermediate P and T.« less

Alfvén Wave Heating Model of an Active Region and Comparisons with the EIS Observations

NASA Astrophysics Data System (ADS)

Lawless, A. P.; Asgari-Targhi, M.

2013-12-01

We study the generation and dissipation of Alfvén waves in open and closed field lines using the images from the Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA) (van Ballegouijen et al. 2011; Asgari-Targhi & van Ballegouijen 2012; Asgari et al. 2013). The goal is to search for observational evidence of Alfvén waves in the solar corona and to understand their role in coronal heating. We focus on one particular active region on the 10th of December 2007. Using the MDI magnetogram and the potential field modeling of this region, we create three-dimensional MHD models for several open and closed field lines in different locations in the active region. For each model, we compute the temperature, pressure, magnetic field strength, average heating rate, and other parameters along the loop. We then compare these results with the EIS observations. This research is supported by the NSF grant for the Solar physics REU Program at the Smithsonian Astrophysical Observatory (AGS-1263241) and contract SP02H1701R from Lockheed-Martin to SAO.

Variability of a Stellar Corona on a Time Scale of Days: Evidence for Abundance Fractionation in an Emerging Coronal Active Region

NASA Technical Reports Server (NTRS)

Nordon, R.; Behar, E.; Drake, S. A.

2013-01-01

Elemental abundance effects in active coronae have eluded our understanding for almost three decades, since the discovery of the first ionization potential (FIP) effect on the sun. The goal of this paper is to monitor the same coronal structures over a time interval of six days and resolve active regions on a stellar corona through rotational modulation. We report on four iso-phase X-ray spectroscopic observations of the RS CVn binary EI Eri with XMM-Newton, carried out approximately every two days, to match the rotation period of EI Eri. We present an analysis of the thermal and chemical structure of the EI Eri corona as it evolves over the six days. Although the corona is rather steady in its temperature distribution, the emission measure and FIP bias both vary and seem to be correlated. An active region, predating the beginning of the campaign, repeatedly enters into our view at the same phase as it rotates from beyond the stellar limb. As a result, the abundances tend slightly, but consistently, to increase for high FIP elements (an inverse FIP effect) with phase. We estimate the abundance increase of high FIP elements in the active region to be of about 75% over the coronal mean. This observed fractionation of elements in an active region on time scales of days provides circumstantial clues regarding the element enrichment mechanism of non-flaring stellar coronae.

Dynamic Perturbation of the Active Site Determines Reversible Thermal Inactivation in Glycoside Hydrolase Family 12.

PubMed

Jiang, Xukai; Li, Wen; Chen, Guanjun; Wang, Lushan

2017-02-27

The temperature dependence of enzyme catalysis is highly debated. Specifically, how high temperatures induce enzyme inactivation has broad implications for both fundamental and applied science. Here, we explored the mechanism of the reversible thermal inactivation in glycoside hydrolase family 12 (GH12) using comparative molecular dynamics simulations. First, we investigated the distribution of structural flexibility over the enzyme and found that the active site was the general thermal-sensitive region in GH12 cellulases. The dynamic perturbation of the active site before enzyme denaturation was explored through principal-component analysis, which indicated that variations in the collective motion and conformational ensemble of the active site may precisely correspond to enzyme transition from its active form to the inactive form. Furthermore, the degree of dynamic perturbation of the active site was found to be negatively correlated with the melting temperatures of GH12 enzymes, further proving the importance of the dynamic stability of the active site. Additionally, analysis of the residue-interaction network revealed that the active site in thermophilic enzyme was capable of forming additional contacts with other amino acids than those observed in the mesophilic enzyme. These interactions are likely the key mechanisms underlying the differences in rigidity of the active site. These findings provide further biophysical insights into the reversible thermal inactivation of enzymes and potential applications in future protein engineering.

Shear wave velocity, seismic attenuation, and thermal structure of the continental upper mantle

USGS Publications Warehouse

Artemieva, I.M.; Billien, M.; Leveque, J.-J.; Mooney, W.D.

2004-01-01

Seismic velocity and attenuation anomalies in the mantle are commonly interpreted in terms of temperature variations on the basis of laboratory studies of elastic and anelastic properties of rocks. In order to evaluate the relative contributions of thermal and non-thermal effects on anomalies of attenuation of seismic shear waves, QS-1, and seismic velocity, VS, we compare global maps of the thermal structure of the continental upper mantle with global QS-1 and Vs maps as determined from Rayleigh waves at periods between 40 and 150 S. We limit the comparison to three continental mantle depths (50, 100 and 150 km), where model resolution is relatively high. The available data set does not indicate that, at a global scale, seismic anomalies in the upper mantle are controlled solely by temperature variations. Continental maps have correlation coefficients of <0.56 between VS and T and of <0.47 between QS and T at any depth. Such low correlation coefficients can partially be attributed to modelling arrefacts; however, they also suggest that not all of the VS and QS anomalies in the continental upper mantle can be explained by T variations. Global maps show that, by the sign of the anomaly, VS and QS usually inversely correlate with lithospheric temperatures: most cratonic regions show high VS and QS and low T, while most active regions have seismic and thermal anomalies of the opposite sign. The strongest inverse correlation is found at a depth of 100 km, where the attenuation model is best resolved. Significantly, at this depth, the contours of near-zero QS anomalies approximately correspond to the 1000 ??C isotherm, in agreement with laboratory measurements that show a pronounced increase in seismic attenuation in upper mantle rocks at 1000-1100 ??C. East-west profiles of VS, QS and T where continental data coverage is best (50??N latitude for North America and 60??N latitude for Eurasia) further demonstrate that temperature plays a dominant, but non-unique, role in determining the value of lithospheric VS and QS. At 100 km depth, where the resolution of seismic models is the highest, we compare observed seismic VS and QS with theoretical VST and QST values, respectively, that are calculated solely from temperature anomalies and constrained by experimental data on temperature dependencies of velocity and attenuation. This comparison shows that temperature variations alone are sufficient to explain seismic VS and QS in ca 50 per cent of continental regions. We hypothesize that compositional anomalies resulting from Fe depletion can explain the misfit between seismic and theoretical VS in cratonic lithosphere. In regions of active tectonics, temperature effects alone cannot explain seismic VS and QS in the lithosphere. It is likely that partial melts and/or fluids may affect seismic parameters in these regions. This study demonstrates that lithospheric temperature plays the dominant role in controlling VS and QS anomalies, but other physical parameters, such as compositional variations, fluids, partial melting and scattering, may also play a significant role in determining VS and QS variations in the continental mantle. ?? 2004 RAS.

Analysis of magnesium XI line profiles from solar active regions

NASA Technical Reports Server (NTRS)

Blake, R. L.; Cowan, R. D.; Felthauser, H.; Fenimore, E. E.; Hockaday, M. P.; Bely-Dubau, F.; Faucher, P.; Steenman-Clark, L.

1984-01-01

High-resolution solar spectra of the Mg XI 1s2 1S0-1s2p 1P1 resonance line at 9.169 A and the associated nearby satellite lines obtained from two rocket-borne crystal spectrometer measurements are presented. Comparisons with two independent sets of theoretical calculations for the 1s2nl-1s2pnl dielectronic satellite lines with n = 3-7 indicate electron temperatures of 4-4.5 million K. Measured line widths indicate either that the ion temperature exceeds the electron temperature by about a million K or that about 28 km/s of turbulence is present.

Monolithic integrated high-T.sub.c superconductor-semiconductor structure

NASA Technical Reports Server (NTRS)

Barfknecht, Andrew T. (Inventor); Garcia, Graham A. (Inventor); Russell, Stephen D. (Inventor); Burns, Michael J. (Inventor); de la Houssaye, Paul R. (Inventor); Clayton, Stanley R. (Inventor)

2000-01-01

A method for the fabrication of active semiconductor and high-temperature superconducting device of the same substrate to form a monolithically integrated semiconductor-superconductor (MISS) structure is disclosed. A common insulating substrate, preferably sapphire or yttria-stabilized zirconia, is used for deposition of semiconductor and high-temperature superconductor substructures. Both substructures are capable of operation at a common temperature of at least 77 K. The separate semiconductor and superconductive regions may be electrically interconnected by normal metals, refractory metal silicides, or superconductors. Circuits and devices formed in the resulting MISS structures display operating characteristics which are equivalent to those of circuits and devices prepared on separate substrates.

A modified integrated NDVI for improving estimates of terrestrial net primary production

NASA Technical Reports Server (NTRS)

Running, Steven W.

1990-01-01

Logic is presented for a time-integrated NDVI that is modified by an AVHRR derived surface evaporation resistance factor sigma, and truncated by temperatures that cause plant dormancy, to improve environmental sensitivity. With this approach, NDVI observed during subfreezing temperatures is not integrated. Water stress-related impairment in plant activity is incorporated by reducing the effective NDVI at each integration with sigma, which is derived from the slope of the surface temperature to NDVI ratio for climatically similar zones of the scene. A comparison of surface resistance before and after an extended drought period for a 1200 sq km region of coniferous forest in Montana is presented.

HOT PLASMA FROM SOLAR ACTIVE REGION CORES: A TEST OF AC AND DC CORONAL HEATING MODELS?

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

Schmelz, J. T.; Christian, G. M.; Dhaliwal, R. S.

2015-06-20

Direct current (DC) models of solar coronal heating invoke magnetic reconnection to convert magnetic free energy into heat, whereas alternating current (AC) models invoke wave dissipation. In both cases the energy is supplied by photospheric footpoint motions. For a given footpoint velocity amplitude, DC models predict lower average heating rates but greater temperature variability when compared to AC models. Therefore, evidence of hot plasma (T > 5 MK) in the cores of active regions could be one of the ways for current observations to distinguish between AC and DC models. We have analyzed data from the X-Ray Telescope (XRT) andmore » the Atmospheric Imaging Assembly for 12 quiescent active region cores, all of which were observed in the XRT Be-thick channel. We did Differential Emission Measure (DEM) analysis and achieved good fits for each data set. We then artificially truncated the hot plasma of the DEM model at 5 MK and examined the resulting fits to the data. For some regions in our sample, the XRT intensities continued to be well-matched by the DEM predictions, even without the hot plasma. This truncation, however, resulted in unacceptable fits for the other regions. This result indicates that the hot plasma is present in these regions, even if the precise DEM distribution cannot be determined with the data available. We conclude that reconnection may be heating the hot plasma component of these active regions.« less

Low temperature p-type doping of (Al)GaN layers using ammonia molecular beam epitaxy for InGaN laser diodes

NASA Astrophysics Data System (ADS)

Malinverni, M.; Lamy, J.-M.; Martin, D.; Feltin, E.; Dorsaz, J.; Castiglia, A.; Rossetti, M.; Duelk, M.; Vélez, C.; Grandjean, N.

2014-12-01

We demonstrate state-of-the-art p-type (Al)GaN layers deposited at low temperature (740 °C) by ammonia molecular beam epitaxy (NH3-MBE) to be used as top cladding of laser diodes (LDs) with the aim of further reducing the thermal budget on the InGaN quantum well active region. Typical p-type GaN resistivities and contact resistances are 0.4 Ω cm and 5 × 10-4 Ω cm2, respectively. As a test bed, we fabricated a hybrid laser structure emitting at 400 nm combining n-type AlGaN cladding and InGaN active region grown by metal-organic vapor phase epitaxy, with the p-doped waveguide and cladding layers grown by NH3-MBE. Single-mode ridge-waveguide LD exhibits a threshold voltage as low as 4.3 V for an 800 × 2 μm2 ridge dimension and a threshold current density of ˜5 kA cm-2 in continuous wave operation. The series resistance of the device is 6 Ω and the resistivity is 1.5 Ω cm, confirming thereby the excellent electrical properties of p-type Al0.06Ga0.94N:Mg despite the low growth temperature.

Vertical structure of atmospheric boundary layer over Ranchi during the summer monsoon season

NASA Astrophysics Data System (ADS)

Chandra, Sagarika; Srivastava, Nishi; Kumar, Manoj

2018-04-01

Thermodynamic structure and variability in the atmospheric boundary layer have been investigated with the help of balloon-borne GPS radiosonde over a monsoon trough station Ranchi (Lat. 23°45'N, Long. 85°43'E, India) during the summer monsoon season (June-September) for a period of 2011-2013. Virtual potential temperature gradient method is used for the determination of mixed layer height (MLH). The MLH has been found to vary in the range of 1000-1300 m during the onset, 600-900 m during the active and 1400-1750 m during the break phase of monsoon over this region. Inter-annual variations noticed in MLH could be associated with inter-annual variability in convection and rainfall prevailing over the region. Along with the MLH, the cloud layer heights are also derived from the thermodynamic profiles for the onset, active and break phases of monsoon. Cloud layer height varied a lot during different phases of the monsoon. For the determination of boundary-layer convection, thermodynamic parameter difference (δθ = θ es- θ e) between saturated equivalent potential temperature (θ es ) and equivalent potential temperature (θ e) is used. It is a good indicator of convection and indicates the intense and suppressed convection during different phases of monsoon.

Hyperechogenicity during high intensity focused ultrasound (HIFU)

NASA Astrophysics Data System (ADS)

Crum, Lawrence; Bailey, Michael; Rabkin, Brian; Khokhlova, Vera; Vaezy, Shahram

2005-09-01

Ultrasound guidance of HIFU therapy is attractive because of its portability, low cost, real-time image processing, simple integration with HIFU instruments, and the extensive availability of diagnostic ultrasound; however, the use of ultrasound visualization for the guidance and monitoring of HIFU therapy often relies on the appearance of a hyperechoic region in the ultrasound image. It is often assumed that the formation of a hyperechoic region at the HIFU treatment site results from bubble activity generated during HIFU exposure. However, it has been determined that this region can be generated with relatively short bursts of HIFU (on the order of 30 ms), bursts so short that negligible temperature elevations are expected to occur. In examining the histology associated with these hyperechoes, there is little evidence of traditional cavitation damage; rather, it appears as if there are many bubbles generated within the individuals cells, suggesting a thermal mechanism. Thermocouple measurements of the temperature elevation were inaccurate due to the short insonation period, but showed only a few-degree temperature rise. These anomalous results will be presented, along with additional data on HIFU hyperechogenicity, and a hypothesis given for the phenomenological origins of this effect. [Work supported in part by the NSBRI, U.S. Army, and the NIH.

24/7 Solar Minimum Polar Cap and Auroral Ion Temperature Observations

NASA Technical Reports Server (NTRS)

Sojka, Jan J.; Nicolls, Michael; van Eyken, Anthony; Heinselman, Craig; Bilitza, Dieter

2011-01-01

During the International Polar Year (IPY) two Incoherent Scatter Radars (ISRs) achieved close to 24/7 continuous observations. This presentation describes their data sets and specifically how they can provide the International Reference Ionosphere (IRI) a fiduciary E- and F-region ionosphere description for solar minimum conditions in both the auroral and polar cap regions. The ionospheric description being electron density, ion temperature and electron temperature profiles from as low as 90 km extending to several scale heights above the F-layer peak. The auroral location is Poker Flat in Alaska at 65.1 N latitude, 212.5 E longitude where the NSF s new Poker Flat Incoherent Scatter Radar (PFISR) is located. This location during solar minimum conditions is in the auroral region for most of the day but is at midlatitudes, equator ward of the cusp, for about 4-8 h per day dependent upon geomagnetic activity. In contrast the polar location is Svalbard, at 78.2 N latitude, 16.0 E longitude where the EISCAT Svalbard Radar (ESR) is located. For most of the day the ESR is in the Northern Polar Cap with a noon sector passage often through the dayside cusp. Of unique relevance to IRI is that these extended observations have enabled the ionospheric morphology to be distinguished between quiet and disturbed geomagnetic conditions. During the IPY year, 1 March 2007 - 29 February 2008, about 50 solar wind Corotating Interaction Regions (CIRs) impacted geospace. Each CIR has a two to five day geomagnetic disturbance that is observed in the ESR and PFISR observations. Hence, this data set also enables the quiet-background ionospheric climatology to be established as a function of season and local time. These two separate climatologies for the ion temperature at an altitude of 300 km are presented and compared with IRI ion temperatures. The IRI ion temperatures are about 200-300 K hotter than the observed values. However, the MSIS neutral temperature at 300 km compares favorably with the quiet-background in temperature, both in magnitude and climatology.

May–June Maximum Temperature Reconstruction from Mean Earlywood Density in North Central China and Its Linkages to the Summer Monsoon Activities

PubMed Central

Chen, Feng; Yuan, Yujiang

2014-01-01

Cores of Pinus tabulaformis from Tianshui were subjected to densitometric analysis to obtain mean earlywood density data. Climate response analysis indicates that May–June maximum temperature is the main factor limiting the mean earlywood density (EWD) of Chinese pine trees in the Shimen Mountains. Based on the EWD chronology, we have reconstructed May–June maximum temperature 1666 to 2008 for Tianshui, north central China. The reconstruction explains 40.1% of the actual temperature variance during the common period 1953–2008. The temperature reconstruction is representative of temperature conditions over a large area to the southeast and northwest of the sampling site. Preliminary analysis of links between large-scale climatic variation and the temperature reconstruction shows that there is a relationship between extremes in spring temperature and anomalous atmospheric circulation in the region. It is thus revealed that the mean earlywood density chronology of Pinus tabulaformis has enough potential to reconstruct the temperature variability further into the past. PMID:25207554

Chemical states of surface oxygen during CO oxidation on Pt(1 1 0) surface revealed by ambient pressure XPS

DOE PAGES

Yu, Youngseok; Koh, Yoobin Esther; Lim, Hojoon; ...

2017-10-20

Here, the study of CO oxidation on Pt(110) surface is revisited using ambient pressure x-ray photoemission spectroscopy. When the surface temperature reaches the activation temperature for CO oxidation under elevated pressure conditions, both the α-phase of PtO 2 oxide and chemisorbed oxygen are formed simultaneously on the surface. Due to the exothermic nature of CO oxidation, the temperature of the Pt surface increases as CO oxidation takes place. As the CO/O 2 ratio increases, the production of CO 2 increases continuously and the surface temperature also increases. Interestingly, within the diffusion limited regions, the amount of surface oxide changes littlemore » while the chemisorbed oxygen is reduced.« less

Chemical states of surface oxygen during CO oxidation on Pt(1 1 0) surface revealed by ambient pressure XPS

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

Yu, Youngseok; Koh, Yoobin Esther; Lim, Hojoon

Here, the study of CO oxidation on Pt(110) surface is revisited using ambient pressure x-ray photoemission spectroscopy. When the surface temperature reaches the activation temperature for CO oxidation under elevated pressure conditions, both the α-phase of PtO 2 oxide and chemisorbed oxygen are formed simultaneously on the surface. Due to the exothermic nature of CO oxidation, the temperature of the Pt surface increases as CO oxidation takes place. As the CO/O 2 ratio increases, the production of CO 2 increases continuously and the surface temperature also increases. Interestingly, within the diffusion limited regions, the amount of surface oxide changes littlemore » while the chemisorbed oxygen is reduced.« less

Supraclavicular skin temperature as a measure of 18F-FDG uptake by BAT in human subjects.

PubMed

Boon, Mariëtte R; Bakker, Leontine E H; van der Linden, Rianne A D; Pereira Arias-Bouda, Lenka; Smit, Frits; Verberne, Hein J; van Marken Lichtenbelt, Wouter D; Jazet, Ingrid M; Rensen, Patrick C N

2014-01-01

Brown adipose tissue (BAT) has emerged as a novel player in energy homeostasis in humans and is considered a potential new target for combating obesity and related diseases. The current 'gold standard' for quantification of BAT volume and activity is cold-induced 18F-FDG uptake in BAT. However, use of this technique is limited by cost and radiation exposure. Given the fact that BAT is a thermogenic tissue, mainly located in the supraclavicular region, the aim of the current study was to investigate whether cold-induced supraclavicular skin temperature and core body temperature may be alternative markers of BAT activation in humans. BAT volume and activity were measured in 24 healthy lean adolescent males (mean age 24.1±0.8 years), using cold-induced 18F-FDG uptake with PET-CT. Core body temperature was measured continuously in the small intestine with use of an ingestible telemetric capsule and skin temperature was measured by eighteen wireless iButtons attached to the skin following ISO-defined locations. Proximal and distal (hand/feet) skin temperatures markedly decreased upon cold exposure, while supraclavicular skin temperature significantly increased (35.2±0.1 vs. 35.5±0.1°C, p = 0.001). Furthermore, cold-induced supraclavicular skin temperature positively correlated with both total (R2 = 0.28, P = 0.010) and clavicular BAT volume (R2 = 0.20, P = 0.030) and clavicular SUVmax (R2 = 0.27, P = 0.010), while core body temperature did not. Supraclavicular skin temperature as measured by iButtons may have predictive value for BAT detection in adult humans. This is highly desirable considering the increasing interest in pharmacological interventions to stimulate BAT in human subjects. NTR 2473.

Thermal adaptation and diversity in tropical ecosystems: evidence from cicadas (Hemiptera, Cicadidae).

PubMed

Sanborn, Allen F; Heath, James E; Phillips, Polly K; Heath, Maxine S; Noriega, Fernando G

2011-01-01

The latitudinal gradient in species diversity is a central problem in ecology. Expeditions covering approximately 16°54' of longitude and 21°4' of latitude and eight Argentine phytogeographic regions provided thermal adaptation data for 64 species of cicadas. We test whether species diversity relates to the diversity of thermal environments within a habitat. There are general patterns of the thermal response values decreasing in cooler floristic provinces and decreasing maximum potential temperature within a habitat except in tropical forest ecosystems. Vertical stratification of the plant communities leads to stratification in species using specific layers of the habitat. There is a decrease in thermal tolerances in species from the understory communities in comparison to middle level or canopy fauna. The understory Herrera umbraphila Sanborn & Heath is the first diurnally active cicada identified as a thermoconforming species. The body temperature for activity in H. umbraphila is less than and significantly different from active body temperatures of all other studied species regardless of habitat affiliation. These data suggest that variability in thermal niches within the heterogeneous plant community of the tropical forest environments permits species diversification as species adapt their physiology to function more efficiently at temperatures different from their potential competitors.

[Characterization of structural change of ascorbate peroxidase from Chinese kale during denaturation by circular dichroism].

PubMed

Xi, Jia-Fu; Tang, Lei; Zhang, Jian-Hua; Zhang, Hong-Jian; Chen, Xu-Sheng; Mao, Zhong-Gui

2014-11-01

Circular dichroism (CD) is a special absorption spectrum. The secondary structure of protein such as α-helix, β-sheet and β-turn in the far ultraviolet region (190-250 nm) has a characteristic CD spectrum. In order to understand the activity and structural changes of ascorbate peroxidase from Chinese kale (BaAPX) during denaturation, specific activity and percentage of secondary structure of BaAPX under different time, temperature and concentration were analyzed by CD dynamically. In addition, the percentage of four secondary structures in BaAPX was calculated by CD analysis software Dichroweb. The results show that BaAPX is a full α-type enzyme whose specific activity is positively related to the percentage of α-helix. During denaturation of BaAPX, three kinds of structural changes were proposed: the one-step structural change from initial state (N state) to minimum state of α-helix (R state) under low concentration and low temperature; the one-step structural change from N state to equilibrium state (T state) under high concentration and low temperature; the two-step structural changes from N state through R state to final T state under heat treatment and low temperature renaturation.

Characterization of polyphenol oxidase from the Manzanilla cultivar (Olea europaea pomiformis) and prevention of browning reactions in bruised olive fruits.

PubMed

Segovia-Bravo, Kharla A; Jarén-Galan, Manuel; García-García, Pedro; Garrido-Fernandez, Antonio

2007-08-08

The crude extract of the polyphenol oxidase (PPO) enzyme from the Manzanilla cultivar (Olea europaea pomiformis) was obtained, and its properties were characterized. The browning reaction followed a zero-order kinetic model. Its maximum activity was at pH 6.0. This activity was completely inhibited at a pH below 3.0 regardless of temperature; however, in alkaline conditions, pH inhibition depended on temperature and was observed at values above 9.0 and 11.0 at 8 and 25 degrees C, respectively. The thermodynamic parameters of substrate oxidation depended on pH within the range in which activity was observed. The reaction occurred according to an isokinetic system because pH affected the enzymatic reaction rate but not the energy required to carry out the reaction. In the alkaline pH region, browning was due to a combination of enzymatic and nonenzymatic reactions that occurred in parallel. These results correlated well with the browning behavior observed in intentionally bruised fruits at different temperatures and in different storage solutions. The use of a low temperature ( approximately 8 degrees C) was very effective for preventing browning regardless of the cover solution used.

Accelerated life testing effects on CMOS microcircuit characteristics

NASA Technical Reports Server (NTRS)

1980-01-01

The 250 C, 200C and 125C accelerated tests are described. The wear-out distributions from the 250 and 200 C tests were used to estimate the activation energy between the two test temperatures. The duration of the 125 C test was not sufficient to bring the test devices into the wear-out region. It was estimated that, for the most complex of the three devices types, the activation energy between 200 C and 125 C should be at least as high as that between 250 C and 200 C. The practicality of the use of high temperature for the accelerated life tests from the point of view of durability of equipment is assessed. Guidlines for the development of accelerated life-test conditions are proposed. The use of the silicon nitride overcoat to improve the high temperature accelerated life-test characteristics of CMOS microcircuits is described.

Regional thermal comfort zone in males and females.

PubMed

Ciuha, Ursa; Mekjavic, Igor B

2016-07-01

Skin regions differ in their sensitivity to temperature stimuli. The present study examined whether such regional differences were also evident in the perception of thermal comfort. Regional thermal comfort was assessed in males (N=8) and females (N=8), by having them regulate the temperature of the water delivered to a water-perfused suit (WPS), within a temperature range considered thermally comfortable. In separate trials, subjects regulated the temperature of the WPS, or specific regions of the suit covering different skin areas (arms, legs, front torso and back torso). In the absence of subjective temperature regulation (TR), the temperature changed in a sinusoidal manner from 10°C to 50°C; by depressing a switch and reversing the direction of the temperature at the limits of the thermal comfort zone (TCZ), each subject defined TCZ for each body region investigated. The range of regulated temperatures did not differ between genders and skin regions. Local Tsk at the lower and upper limits of the TCZ was similar for both genders. Higher (p<0.05) local Tsk was preferred for the arms (35.4±2.1°C), compared to other regions (legs: 34.4±5.4°C, front torso: 34.6±2.8°C, 34.3±6.6°C), irrespective of gender. In thermally comfortable conditions, the well-established regional differences in thermosensitivity are not reflected in the TCZ, with similar temperature preferences by both genders. Thermal comfort of different skin regions and overall body is not achieved at a single skin temperature, but at range of temperatures, defined as the TCZ. Copyright © 2016 Elsevier Inc. All rights reserved.

Characterization of individual ice residual particles by the single droplet freezing method: a case study in the Asian dust outflow region

NASA Astrophysics Data System (ADS)

Iwata, Ayumi; Matsuki, Atsushi

2018-02-01

In order to better characterize ice nucleating (IN) aerosol particles in the atmosphere, we investigated the chemical composition, mixing state, and morphology of atmospheric aerosols that nucleate ice under conditions relevant for mixed-phase clouds. Five standard mineral dust samples (quartz, K-feldspar, Na-feldspar, Arizona test dust, and Asian dust source particles) were compared with actual aerosol particles collected from the west coast of Japan (the city of Kanazawa) during Asian dust events in February and April 2016. Following droplet activation by particles deposited on a hydrophobic Si (silicon) wafer substrate under supersaturated air, individual IN particles were located using an optical microscope by gradually cooling the temperature to -30 °C. For the aerosol samples, both the IN active particles and non-active particles were analyzed individually by atomic force microscopy (AFM), micro-Raman spectroscopy, and scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). Heterogeneous ice nucleation in all standard mineral dust samples tested in this study was observed at consistently higher temperatures (e.g., -22.2 to -24.2 °C with K-feldspar) than the homogeneous freezing temperature (-36.5 °C). Meanwhile, most of the IN active atmospheric particles formed ice below -28 °C, i.e., at lower temperatures than the standard mineral dust samples of pure components. The most abundant IN active particles above -30 °C were predominantly irregular solid particles that showed clay mineral characteristics (or mixtures of several mineral components). Other than clay, Ca-rich particles internally mixed with other components, such as sulfate, were also regarded as IN active particle types. Moreover, sea salt particles were predominantly found in the non-active fraction, and internal mixing with sea salt clearly acted as a significant inhibiting agent for the ice nucleation activity of mineral dust particles. Also, relatively pure or fresh calcite, Ca(NO3)2, and (NH4)2SO4 particles were more often found in the non-active fraction. In this study, we demonstrated the capability of the combined single droplet freezing method and thorough individual particle analysis to characterize the ice nucleation activity of atmospheric aerosols. We also found that dramatic changes in the particle mixing states during long-range transport had a complex effect on the ice nucleation activity of the host aerosol particles. A case study in the Asian dust outflow region highlighted the need to consider particle mixing states, which can dramatically influence ice nucleation activity.

Spatial differences of aeolian desertification responses to climate in arid Asia

NASA Astrophysics Data System (ADS)

Wang, Xunming; Hua, Ting; Lang, Lili; Ma, Wenyong

2017-01-01

Most areas of arid Asia are covered by aeolian dunes, sand sheets, gravels, and desert steppes, and may jeopardize nearly 350 million people if climate change increases aeolian desertification. Although the aeolian desertification is mainly triggered by climate changes are extensively acknowledged, the responses of aeolian desertification to various climate scenarios are poorly understood. Based on the tight combinations of dune activity index (DAI) trends and of aeolian desertification, here the spatial differences of aeolian desertification responses on various climate scenarios were reported. The analyzed results show that the variations in temperature, precipitation and wind regime have no significant contributions on aeolian desertification in the extremely arid Asia. From the early to blooming periods of vegetation growth, although temperature rise may benefit vegetation growths in some high latitudes and altitudes, the temperature rise may increase aeolian desertification in most arid Asia regions such as Mongolia, West and Central Asia. In arid Asia, although precipitation increases may benefit the rehabilitation, decreases in precipitation is not the key role on aeolian desertification occurrences in extremely arid regions. From the early to blooming periods of vegetation growths, spatial trends of the sensitivity of aeolian desertification to wind regime varied. Generally, at the regional scales there are relative high sensitivities for aeolian desertification to climate changes in the eastern and western regions of arid Asia, and the climate changes may not play important roles on aeolian desertification occurrence in the central regions. The spatial differences of aeolian desertification responses to climate changes indicate various strategies for aeolian desertification combating are needed in different regions of arid Asia.

Ultrasonic Imaging System

NASA Technical Reports Server (NTRS)

Youngquist, Robert C. (Inventor); Moerk, Steven (Inventor)

1999-01-01

An imaging system is described which can be used to either passively search for sources of ultrasonics or as an active phase imaging system. which can image fires. gas leaks, or air temperature gradients. This system uses an array of ultrasonic receivers coupled to an ultrasound collector or lens to provide an electronic image of the ultrasound intensity in a selected angular region of space. A system is described which includes a video camera to provide a visual reference to a region being examined for ultrasonic signals.

Photoluminescence nonuniformity from self-seeding nuclei in CVD-grown monolayer MoSe2.

PubMed

Tian, Xiangling; Wei, Rongfei; Liu, Shanshan; Zhang, Yeming; Qiu, Jianrong

2018-01-03

We present optical spectroscopy (photoluminescence and Raman spectrum) studies of monolayer transition metal dichalcogenide MoSe 2 , with spatial location, temperature and excitation power dependence. The investigated spectra show location-dependent behavior with an increase in photoluminescence and Raman intensity and a blue-shift in photoluminescence peak position in the inner region. The observed behaviors of a large shift in the photoluminescence peak position at the edge and biexciton emissions in the inner region confirm that the monolayer MoSe 2 crystals grow from nucleation centers during the CVD process. Temperature activated energy and dependence of the peak position are attributed to residual oxygen during the growth. Investigating this information provides a basis for precisely controlling the synthesis of TMDCs and their application in advanced optoelectronics.

How will the future warming climate impact the river discharge in the alpine mountain region of upper Heihe River Basin?

NASA Astrophysics Data System (ADS)

Wang, Y.; Yang, H.; Yang, D.; Gao, B.; Qin, Y.

2017-12-01

The Tibetan Plateau is more sensitive to the global climate change than other areas due to its special geography. Previous studies have shown that, besides the changes of temperature and precipitation, the changes in the cryosphere such as glacier and frozen ground also have important and far-reaching effects on the ecological and hydrological processes in the basin. In order to reliably predict the future runoff changing trend in the future, it's important to estimate the responses of cryosphere to the future climate change, as well as its impacts on the hydrological processes. Based on typical future climate scenarios (under emission scenario RCP4.5) from five general circulation models (GCMs) and one regional climate model (RCM), as well as a distributed eco-hydrological model (GBEHM), this study analyzes the possible future climate change (from 2011 to 2060) and its impacts on cryospheric and hydrological processes in upper Heihe River Basin, a typical cold mountain region located in the Northeast Tibetan Plateau. The results suggest that air temperature is expected to rise in the future by approximately 0.32 °C/10a, and precipitation is expected to rise slightly by about 3 mm/10a. Under the rising air temperature, the maximum frozen depth of seasonally frozen ground will decrease by about 4.1 cm/10a and the active layer depth of the frozen ground will increase by about 6.2 cm/10a. The runoff is expected to reduce by approximately 6 mm/10a and the evapotranspiration is expected to increase by approximately 9 mm/10a. These changes in hydrological processes are mainly caused by the air temperature rise. The impacts of air temperature change on the hydrological processes are mainly due to the changes of frozen ground. The thickening of active layer of the frozen ground increases the soil storage capacity, leading to the decrease of runoff and increase of evapotranspiration. Results show that, when the active layer depth increase by 1 cm, the runoff will decrease by about 1 2 mm and the evapotranspiration will increase by about 0.7 2 mm. Additionally, the changes from permafrost to seasonal frozen ground increase the groundwater infiltration, which also leads to the decrease of surface runoff.

Non-Ideal Properties of Gallium Nitride Based Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Shan, Qifeng

The spectacular development of gallium nitride (GaN) based light-emitting diodes (LEDs) in recent years foreshadows a new era for lighting. There are still several non-ideal properties of GaN based LEDs that hinder their widespread applications. This dissertation studies these non-ideal properties including the large reverse leakage current, large subthreshold forward leakage current, an undesired parasitic cyan luminescence and high-concentration deep levels in GaInN blue LEDs. This dissertation also studies the thermal properties of GaInN LEDs. Chapter 1 gives a brief introduction of non-ideal properties of GaN based LEDs. The leakage current of GaN based LEDs, defects in epitaxially grown GaN devices, and doping problems of p-type GaN materials are discussed. The transient junction temperature measurement technique for GaN based LEDs is introduced. The leakage current of an LED includes the subthreshold forward leakage current and the reverse leakage current. The leakage current of GaN based LEDs affects the reliability, electrostatic discharge resilience, and sub-threshold power consumption. In Chapter 2, the reverse leakage current of a GaInN LED is analyzed by temperaturedependent current-voltage measurements. At low temperature, the reverse leakage current is attributed to the variable-range-hopping conduction. At high temperature, the reverse leakage current is attributed to a thermally-assisted multi-step tunneling. The thermal activation energies (95 meV ~ 162 meV), extracted from the Arrhenius plot for the reverse current in the high-temperature range, indicate a thermally activated tunneling process. Additional room-temperature capacitance-voltage (C-V) measurements are performed to obtain information on the depletion width and doping concentration of the LED. The average internal electric field is estimated by the C-V measurements. The strong internal electric field enhances the thermal emission of electrons in the thermally-assisted multi-step tunneling process. Another problem of GaInN blue LEDs is the undesired parasitic cyan emission band. The undesired parasitic emission band strongly influence the electrical and optical properties of GaInN blue LEDs including the subthreshold forward leakage current and the color purity of the emission. In Chapter 3 , GaInN blue LEDs emitting at 445 nm with a parasitic cyan (blue-green) emission band (480 nm), which dominates the emission spectrum at low injection current, are analyzed. Photoluminescence using resonant optical excitation shows that the cyan emission originates from the active region of the LED. The current- and excitation-density-dependent blue-to-cyan intensity ratio reveals that the cyan emission is due to a transition from the conduction band to a Mg acceptor having diffused into the last-grown quantum well of the active region. The Mg in the active region provides an additional carrier-transport path, and therefore can explain the high subthreshold forward leakage current that is measured in these LEDs. Deep levels in GaN-based materials strongly affect the electrical and optical properties of GaN-based LEDs. Chapter 4 describes the basic principle and the setup of a deep-level transient spectroscopy (DLTS) measurement system. This DLTS system is used to determine the concentration and thermal activation energy of deep levels in the depletion region of the GaInN LED. Two types of hole traps in the n-type side of the depletion region are observed in the DLTS measurement. The thermal activation energies of these two types of hole traps are compared with the results reported in literature. The hole trap associated with the major DLTS peak with a thermal activation energy of 0.80 eV is presumably related to the “yellow luminescence band”. Self-heating of LEDs is an important issue that affects the efficiency and reliability. In Chapter 5, the thermal properties, including thermal time constants, of GaN LEDs are analyzed. The transient-junction-temperature behavior of unpackaged LED chips is described by a single time constant, which is the product of a thermal resistance Rth and a thermal capacitance Cth. Furthermore, a multistage RthCth thermal model for packaged LEDs is developed. The transient response of the junction temperature of LEDs after the power is switched on or switched off can be described by a multi-exponential function. Each time constant of this function is approximately the product of a thermal resistance, Rth, and a thermal capacitance, Cth. The transient junction temperature after the power is switched off is measured for a high-power flip-chip LED by the forward-voltage method. A two-stage RthCth model is used to analyze the thermal properties of the packaged LED. Two time constants, 2.72 ms and 18.7 ms are extracted from the junction temperature decay measurement and attributed to the thermal time constant of the LED GaN / sapphire chip and LED Si submount, respectively.

Resolving uncertainties in the urban air quality, climate, and vegetation nexus through citizen science, satellite imagery, and atmospheric modeling

NASA Astrophysics Data System (ADS)

Jenerette, D.; Wang, J.; Chandler, M.; Ripplinger, J.; Koutzoukis, S.; Ge, C.; Castro Garcia, L.; Kucera, D.; Liu, X.

2017-12-01

Large uncertainties remain in identifying the distribution of urban air quality and temperature risks across neighborhood to regional scales. Nevertheless, many cities are actively expanding vegetation with an expectation to moderate both climate and air quality risks. We address these uncertainties through an integrated analysis of satellite data, atmospheric modeling, and in-situ environmental sensor networks maintained by citizen scientists. During the summer of 2017 we deployed neighborhood-scale networks of air temperature and ozone sensors through three campaigns across urbanized southern California. During each five-week campaign we deployed six sensor nodes that included an EPA federal equivalent method ozone sensor and a suite of meteorological sensors. Each node was further embedded in a network of 100 air temperature sensors that combined a randomized design developed by the research team and a design co-created by citizen scientists. Between 20 and 60 citizen scientists were recruited for each campaign, with local partners supporting outreach and training to ensure consistent deployment and data gathering. We observed substantial variation in both temperature and ozone concentrations at scales less than 4km, whole city, and the broader southern California region. At the whole city scale the average spatial variation with our ozone sensor network just for city of Long Beach was 26% of the mean, while corresponding variation in air temperature was only 7% of the mean. These findings contrast with atmospheric model estimates of variation at the regional scale of 11% and 1%. Our results show the magnitude of fine-scale variation underestimated by current models and may also suggest scaling functions that can connect neighborhood and regional variation in both ozone and temperature risks in southern California. By engaging citizen science with high quality sensors, satellite data, and real-time forecasting, our results help identify magnitudes of climate and air quality risk variation across scales and can guide individual decisions and urban policies surrounding vegetation to moderate these risks.

Influences of summer water temperatures on the movement, distribution, and resources use of fluvial Westslope Cutthroat Trout in the South Fork Clearwater River basin

USGS Publications Warehouse

Dobos, Marika E.; Corsi, Matthew P.; Schill, Daniel J.; DuPont, Joseph M.; Quist, Michael C.

2016-01-01

Although many Westslope Cutthroat Trout Oncorhynchus clarkii lewisi populations in Idaho are robust and stable, population densities in some systems remain below management objectives. In many of those systems, such as in the South Fork Clearwater River (SFCR) system, environmental conditions (e.g., summer temperatures) are hypothesized to limit populations of Westslope Cutthroat Trout. Radiotelemetry and snorkeling methods were used to describe seasonal movement patterns, distribution, and habitat use of Westslope Cutthroat Trout in the SFCR during the summers of 2013 and 2014. Sixty-six radio transmitters were surgically implanted into Westslope Cutthroat Trout (170–405 mm TL) from May 30–June 25, 2013, and June 20–July 6, 2014. Sedentary and mobile summer movement patterns by Westslope Cutthroat Trout were observed in the SFCR. Westslope Cutthroat Trout were generally absent from the lower SFCR. In the upper region of the SFCR, fish generally moved from the main-stem SFCR into tributaries as water temperatures increased during the summer. Fish remained in the middle region of the SFCR where water temperatures were cooler than in the upper or lower regions of the SFCR. A spatially explicit water temperature model indicated that the upper and lower regions of the SFCR exceeded thermal tolerance levels of Westslope Cutthroat Trout throughout the summer. During snorkeling, 23 Westslope Cutthroat Trout were observed in 13 sites along the SFCR and at low density (mean ± SD, 0.0003 ± 0.0001 fish/m2). The distribution of fish observed during snorkeling was consistent with the distribution of radio-tagged fish in the SFCR during the summer. Anthropogenic activities (i.e., grazing, mining, road construction, and timber harvest) in the SFCR basin likely altered the natural flow dynamics and temperature regime and thereby limited stream habitat in the SFCR system for Westslope Cutthroat Trout.

Reconstructing last 2000 years of temperature variation from Pyrenean caves (N Spain)

NASA Astrophysics Data System (ADS)

Moreno, Ana; Bartolomé, Miguel; Pérez, Carlos; Sancho, Carlos; Cacho, Isabel; Stoll, Heather; Delgado-Huertas, Antonio; Edwards, R. Lawrence; Cheng, Hai

2016-04-01

The Central Pyrenees, and particularly the protected area known as Ordesa and Monte Perdido National Park, is a high-altitude karstic region rich in cavities with active drips and present precipitation of carbonates. Although not generally very abundant, there are speleothems growths in several of those cavities. We present here (1) a three-year seasonal monitoring survey to isolate the environmental parameters influencing isotopic composition of farmed carbonate and (2) the last 2000 years isotopic record resulting from compiling seven stalagmites from three different caves. In temperate regions such as the NE Iberian Peninsula is difficult to discern the influences on δ18O variation in speleothems since temperature, amount of precipitation or even source effect are usually acting simultaneously. Main results after three years monitoring period indicate a strong dependence on air temperature through its influence on rainfall δ18O, although a small amount effect is not discarded. The good overlapping during the observational period of δ18O from actively growing modern stalagmites and air temperature in the area supports this dependence and provides a reliable proxy for the temperature evolution along last millennia. The stalagmites belong to three different caves (Seso, Gloces and B-1 caves) but still present a very coherent isotopic signal allowing us to discard local effects (diagenetic imprint, non-equilibrium fractionation) and to produce a stacked record with decadal resolution. Interpreting this signal as regional temperature variation divides the temporal sequence in five main periods, in consonance with historical stages. Thus, a continuous decrease in temperature characterized the end of the Roman period (0-500 AD). Lower temperatures are dominant during "Dark Ages" (500-1000 AD) that increase during the Medieval Climate Anomaly (MCA, 1000-1400 AD). Following this warm period, the cold signal during the Little Ice Age is very well replicated in several speleothems, even for short events lasting less than a decade. The warming that identifies the Industrial Era (from 1850 AD to present day) is also well document. This reconstruction is in striking similarity with other high-resolution records in Europe and, particularly, with global temperature reconstructions for last 2000 years. In addition, the fact that the δ18O signal presented here is so well replicated in speleothems from different caves gives strong support to our interpretation and opens the door to further research on Pyrenean speleothems as exceptional archives of thermal oscillations.

Hot spots of wheat yield decline with rising temperatures.

PubMed

Asseng, Senthold; Cammarano, Davide; Basso, Bruno; Chung, Uran; Alderman, Phillip D; Sonder, Kai; Reynolds, Matthew; Lobell, David B

2017-06-01

Many of the irrigated spring wheat regions in the world are also regions with high poverty. The impacts of temperature increase on wheat yield in regions of high poverty are uncertain. A grain yield-temperature response function combined with a quantification of model uncertainty was constructed using a multimodel ensemble from two key irrigated spring wheat areas (India and Sudan) and applied to all irrigated spring wheat regions in the world. Southern Indian and southern Pakistani wheat-growing regions with large yield reductions from increasing temperatures coincided with high poverty headcounts, indicating these areas as future food security 'hot spots'. The multimodel simulations produced a linear absolute decline of yields with increasing temperature, with uncertainty varying with reference temperature at a location. As a consequence of the linear absolute yield decline, the relative yield reductions are larger in low-yielding environments (e.g., high reference temperature areas in southern India, southern Pakistan and all Sudan wheat-growing regions) and farmers in these regions will be hit hardest by increasing temperatures. However, as absolute yield declines are about the same in low- and high-yielding regions, the contributed deficit to national production caused by increasing temperatures is higher in high-yielding environments (e.g., northern India) because these environments contribute more to national wheat production. Although Sudan could potentially grow more wheat if irrigation is available, grain yields would be low due to high reference temperatures, with future increases in temperature further limiting production. © 2016 John Wiley & Sons Ltd.

Ecophysiological function of leaf 'windows' in Lithops species - 'Living Stones' that grow underground.

PubMed

Martin, C E; Brandmeyer, E A; Ross, R D

2013-01-01

Leaf temperatures were lower when light entry at the leaf tip window was prevented through covering the window with reflective tape, relative to leaf temperatures of plants with leaf tip windows covered with transparent tape. This was true when leaf temperatures were measured with an infrared thermometer, but not with a fine-wire thermocouple. Leaf tip windows of Lithops growing in high-rainfall regions of southern Africa were larger than the windows of plants (numerous individuals of 17 species) growing in areas with less rainfall and, thus, more annual insolation. The results of this study indicate that leaf tip windows of desert plants with an underground growth habit can allow entry of supra-optimal levels of radiant energy, thus most likely inhibiting photosynthetic activity. Consequently, the size of the leaf tip windows correlates inversely with habitat solar irradiance, minimising the probability of photoinhibition, while maximising the absorption of irradiance in cloudy, high-rainfall regions. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

Spatialization of Brazilian pig production: relationship between productive, physical, environmental, and socio-economic variables.

PubMed

da Silva, Isabel C M; Bremm, Bárbara; Teixeira, Jennifer L; Costa, Nathalia S; Barcellos, Júlio O J; Braccini, José; Cesconeto, Robson J; McManus, Concepta

2017-06-01

Brazilian pig production spans over a large territory encompassing regions of different climatic and socio-economic realities. Production, physical, socio-economic, and environmental data were used to characterize pig production in the country. Multivariate analysis evaluated indices including number productivity, production levels, and income from pigs, together with the average area of pig farm and socio-economic variables such as municipal human development index, technical guidance received from agricultural cooperatives and industrial companies, number of family farms, and offtake; and finally, environmental variables: latitude, longitude, annual temperature range, solar radiation index, as well as temperature and humidity index. The Southern region has the largest herd, number of pigs sold/sow, and offtake rate (p < 0.05), followed by the Midwest and Southeast. No significant correlations were seen between production rates and productivity with the socio-economic and environmental variables in the regions of Brazil. Production indexes, productivity, and offtake rate discriminated Northeast and Midwest and Northeast and Southeast regions. The Northern region, with a large area, has few and far-between farms that rear pigs for subsistence. The Northeast region has large herds, but low productivity. Number of slaughtered pigs has been variable over the past three decades, with few states responsible for maintaining high production in Brazil. However, the activity can be effective in any region of the country with technology and technical assistance adapted to regional characteristics.

TopA, the Sulfolobus solfataricus topoisomerase III, is a decatenase

PubMed Central

Yang, Xi; Débat, Hélène; Fogg, Jonathan M; Zechiedrich, Lynn; Strick, Terence R; Garnier, Florence

2018-01-01

Abstract DNA topoisomerases are essential enzymes involved in all the DNA processes and among them, type IA topoisomerases emerged as a key actor in the maintenance of genome stability. The hyperthermophilic archaeon, Sulfolobus solfataricus, contains three topoisomerases IA including one classical named TopA. SsoTopA is very efficient at unlinking DNA catenanes, grouping SsoTopA into the topoisomerase III family. SsoTopA is active over a wide range of temperatures and at temperatures of up to 85°C it produces highly unwound DNA. At higher temperatures, SsoTopA unlinks the two DNA strands. Thus depending on the temperature, SsoTopA is able to either prevent or favor DNA melting. While canonical topoisomerases III require a single-stranded DNA region or a nick in one of the circles to decatenate them, we show for the first time that a type I topoisomerase, SsoTopA, is able to efficiently unlink covalently closed catenanes, with no additional partners. By using single molecule experiments we demonstrate that SsoTopA requires the presence of a short single-stranded DNA region to be efficient. The unexpected decatenation property of SsoTopA probably comes from its high ability to capture this unwound region. This points out a possible role of TopA in S. solfataricus as a decatenase in Sulfolobus. PMID:29253195

One-dimensional particle-in-cell simulation on the influence of electron and ion temperature on the sheath expansion process in the post-arc stage of vacuum circuit breaker

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

Mo, Yongpeng; Shi, Zongqian; Jia, Shenli

2015-02-15

The inter-contact region of vacuum circuit breakers is filled with residual plasma at the moment when the current is zero after the burning of metal vapor arc. The residual plasma forms an ion sheath in front of the post-arc cathode. The sheath then expands towards the post-arc anode under the influence of a transient recovery voltage. In this study, a one-dimensional particle-in-cell model is developed to investigate the post-arc sheath expansion. The influence of ion and electron temperatures on the decrease in local plasma density at the post-arc cathode side and post-arc anode side is discussed. When the decay inmore » the local plasma density develops from the cathode and anode sides into the high-density region and merges, the overall plasma density in the inter-contact region begins to decrease. Meanwhile, the ion sheath begins to expand faster. Furthermore, the theory of ion rarefaction wave only explains quantitatively the decrease in the overall plasma density at relatively low ion temperatures. With the increase of ion temperature to certain extent, another possible reason for the decrease in the overall plasma density is proposed and results from the more active thermal diffusion of plasma.« less

Temperature monitoring and Forest Fires in Góis Council, Portugal

NASA Astrophysics Data System (ADS)

Rodrigues, M. A. S.; Costa, M. E. G.

2012-04-01

In our school the activities linked with sciences are developed in a partnership with other school subjects. Interdisciplinary projects are always valued from beginning to end of a project. It is common for teachers of different areas to work together in a Science project. Research of English written articles is very important not only for the development of our students' scientific literacy but also as a way of widening knowledge and a view on different perspectives of life instead of being limited to research of any articles in Portuguese language. As in this area there is a strong occurrence of forest fires, we are going to study the influence of temperature and its occurrence. For this study we have selected six meteorological stations, distributed through the region and placed in different altitudes. Through the analysis of the temperatures we have verified the lack of data from some stations, so we have proceeded to the homogenisation of the series, using the correlation coefficient of a reference series. In a second stage we will analyse forest fires episodes in the region, with data collected from the Civil Protection and the Meteorological Institute from 1980 to 2010 and correlate this with the series of temperatures for the different areas selected for this study. This research allows an evaluation of the forest fire propagation in the region and recognise the most affected areas.

[Effects of climate warming and drying on millet yield in Gansu Province and related countermeasures].

PubMed

Cao, Ling; Wang, Qiang; Deng, Zhen-yong; Guo, Xiao-qin; Ma, Xing-xiang; Ning, Hui-fang

2010-11-01

Based on the data of air temperature, precipitation, and millet yield from Ganzhou, Anding, and Xifeng, the representative stations in Hexi moderate arid oasis irrigation area, moderate sub-arid dry area in middle Gansu, and moderate sub-humid dry area in eastern Gansu, respectively, this paper calculated the regional active accumulated temperature of > or = 0 degrees C, > or =5 degrees C, > or =10 degrees C, > or =15 degrees C, and > or =20 degrees C in millet growth period, and the average temperature and precipitation in millet key growth stages. The millet climatic yield was isolated by orthogonal polynomial, and the change characteristics of climate and millet climatic yield as well as the effects of climate change on millet yield were analyzed by statistical methods of linear tendency, cumulative anomaly, and Mann-Kendall. The results showed that warming and drying were the main regional features in the modern climatic change of Gansu. The regional temperature had a significant upward trend since the early 1990s, while the precipitation was significantly reduced from the late 1980s. There were significant correlations between millet yield and climatic factors. The millet yield in dry areas increased with the increasing temperature and precipitation in millet key growth stages, and that in Hexi Corridor area increased with increasing temperature. Warming and drying affected millet yield prominently. The weather fluctuation index of regional millet yield in Xifeng, Anding, and Ganzhou accounted for 73%, 72%, and 54% of real output coefficient variation, respectively, and the percentages increased significantly after warming. Warming was conducive to the increase of millet production, and the annual increment of millet climatic yield in Xifeng, Anding, and Ganzhou after warming was 30.6, 43.1, and 121.1 kg x hm(-2), respectively. Aiming at the warming and drying trend in Gansu Province in the future, the millet planting area in the Province should be further expanded, and the millet planting structure should be adjusted. At the same time, according to the different regional and yearly climatic types, different varieties should be selected, and various planting measures should be taken.

Temperature Inversions and Nighttime Convection in the Martian Tropics

NASA Astrophysics Data System (ADS)

Hinson, D. P.; Spiga, A.; Lewis, S.; Tellmann, S.; Paetzold, M.; Asmar, S. W.; Häusler, B.

2013-12-01

We are using radio occultation measurements from Mars Express, Mars Reconnaissance Orbiter, and Mars Global Surveyor to characterize the diurnal cycle in the lowest scale height above the surface. We focus on northern spring and summer, using observations from 4 Martian years at local times of 4-5 and 15-17 h. We supplement the observations with results obtained from large-eddy simulations and through data assimilation by the UK spectral version of the LMD Mars Global Circulation Model. We previously investigated the depth of the daytime convective boundary layer (CBL) and its variations with surface elevation and surface properties. We are now examining unusual aspects of the temperature structure observed at night. Most important, predawn profiles in the Tharsis region contain an unexpected layer of neutral static stability at pressures of 200-300 Pa with a depth of 4-5 km. The mixed layer is bounded above by a midlevel temperature inversion and below by another strong inversion adjacent to the surface. The sharp temperature minimum at the base of the midlevel inversion suggests the presence of a thin water ice cloud layer, with the further implication that radiative cooling at cloud level can induce convective activity at lower altitudes. Conversely, nighttime profiles in Amazonis show no sign of a midlevel inversion or a detached mixed layer. These regional variations in the nighttime temperature structure appear to arise in part from large-scale variations in topography, which have several notable effects. First, the CBL is much deeper in the Tharsis region than in Amazonis, owing to a roughly 6-km difference in surface elevation. Second, large-eddy simulations show that daytime convection is not only deeper above Tharsis but also considerably more intense than it is in Amazonis. Finally, the daytime surface temperatures are comparable in the two regions, so that Tharsis acts as an elevated heat source throughout the CBL. These topographic effects are expected to enhance the vertical mixing of water vapor above elevated terrain, which might lead to the formation and regional confinement of nighttime clouds.

N2O and NO emissions during autotrophic nitrogen removal in a granular sludge reactor--a simulation study.

PubMed

Van Hulle, S W H; Callens, J; Mampaey, K E; van Loosdrecht, M C M; Volcke, E I P

2012-01-01

This contribution deals with NO and N2O emissions during autotrophic nitrogen removal in a granular sludge reactor. Two possible model scenarios describing this emission by ammonium- oxidizing biomass have been compared in a simulation study of a granular sludge reactor for one-stage partial nitritation--Anammox. No significant difference between these two scenarios was noticed. The influence of the bulk oxygen concentration, granule size, reactor temperature and ammonium load on the NO and N2O emissions has been assessed. The simulation results indicate that emission maxima of NO and N2O coincide with the region for optimal Anammox conversion. Also, most of the NO and N2O are present in the off-gas, owing to the limited solubility of both gases. The size of granules needs to be large enough not to limit optimal Anammox activity, but not too large as this implies an elevated production of N2O. Temperature has a significant influence on N2O emission, as a higher temperature results in a better N-removal efficiency and a lowered N2O production. Statistical analysis of the results showed that there is a strong correlation between nitrite accumulation and N2O production. Further, three regions of operation can be distinguished: a region with high N2O, NO and nitrite concentration; a region with high N2 concentrations and, as such, high removal percentages; and a region with high oxygen and nitrate concentrations. There is some overlap between the first two regions, which is in line with the fact that maximum emission of NO and N2O coincides with the region for optimal Anammox conversion.

Results of the IRIS UV Burst Survey, Part I: Active Regions Tracked Limb to Limb

NASA Astrophysics Data System (ADS)

Madsen, C. A.; DeLuca, E.

2017-12-01

We present results from the first phase of an effort to thoroughly characterize UV bursts within the Interface Region Imaging Spectrograph (IRIS) data catalogue. The observational signatures of these phenomena include dramatically intensified and broadened NUV/FUV emission line profiles with absorption features from cool metallic ions. These properties suggest that UV bursts originate from plasma at transition region temperatures (≥ 80,000 K) which is deeply embedded in the cool lower chromosphere ( 5,000 K). Rigorously characterizing the energetic and dynamical properties of UV bursts is crucial since they have considerable potential to heat active region chromospheres and could provide critical constraints for models of magnetic reconnection in these regions. The survey first focuses on IRIS observations of active regions tracked from limb to limb. All observations consist of large field-of-view raster scans of 320 or 400 steps each, which allow for widespread detection of many burst profiles at the expense of having limited short-term time evolution information. We detect bursts efficiently by applying a semi-automated single-Gaussian fitting technique to Si IV 1393.8 Å emission profiles that isolates the distinct burst population in a 4-D parameter space. The robust sample of NUV/FUV burst spectra allows for precise constraints of properties critical for modeling reconnection in the chromosphere, including outflow kinetic energy, density estimates from intensity ratios of Si IV 1402.8 Å and O IV 1401.2 Å emission lines, and coincident measures of emission in other wavelengths. We also track burst properties throughout the lifetimes of their host active regions, noting changes in detection rate and preferential location as the active regions evolve. Finally, the tracked active region observations provide a unique opportunity to investigate line-of-sight effects on observed UV burst spectral properties, particularly the strength of Ni II 1393.3 Å absorption, a feature that may be important in identifying the upward conduction of burst thermal energy through the chromosphere.

Stress studies in EFG

NASA Technical Reports Server (NTRS)

1984-01-01

Electrical characterization of defects induced in FZ and CZ silicon stress in four-point bending above 1200 C was started. Techniques to study electrical activity that will permit correlation of defect activity with diffusion length and with room and low temperature EBIC are being developed. Preliminary characterization of defects in ribbon grown at very low speeds of less than 1 cm/min shows that the dislocation density is very low over significant regions of cross section, while regions of high dislocation density (approx. 5 x 10(6)/cm(2)) occur in bands in a number of places. Addition measurements of stress distributions in EFG material were obtained at the University of Illinois using shadow-Moire interferometry.

Novel T-shaped GaSb/InAsN quantum wire for mid-infrared laser applications

NASA Astrophysics Data System (ADS)

Ridene, Said

2017-10-01

In this work, we investigate GaSb /InAs1-xNx T-shaped quantum wire active region in mid-infrared laser. Multi-band k.p model and variational formalism are applied to find the confinement energies, the band structures, and optical gain. We then present a method of numerical calculation that is suited to any T-shaped quantum wire. By tuning the quantum wire thickness, the TE- and TM-polarized optical gain up to 21 ×103 cm-1 can be obtained for λ = 3.11 μm at room temperature (RT), which is very promising to serve as an alternative active region for high-efficiency mid-infrared laser applications.

Docking, thermodynamics and molecular dynamics (MD) studies of a non-canonical protease inhibitor, MP-4, from Mucuna pruriens.

PubMed

Kumar, Ashish; Kaur, Harmeet; Jain, Abha; Nair, Deepak T; Salunke, Dinakar M

2018-01-12

Sequence and structural homology suggests that MP-4 protein from Mucuna pruriens belongs to Kunitz-type protease inhibitor family. However, biochemical assays showed that this protein is a poor inhibitor of trypsin. To understand the basis of observed poor inhibition, thermodynamics and molecular dynamics (MD) simulation studies on binding of MP-4 to trypsin were carried out. Molecular dynamics simulations revealed that temperature influences the spectrum of conformations adopted by the loop regions in the MP-4 structure. At an optimal temperature, MP-4 achieves maximal binding while above and below the optimum temperature, its functional activity is hampered due to unfavourable flexibility and relative rigidity, respectively. The low activity at normal temperature is due to the widening of the conformational spectrum of the Reactive Site Loop (RSL) that reduces the probability of formation of stabilizing contacts with trypsin. The unique sequence of the RSL enhances flexibility at ambient temperature and thus reduces its ability to inhibit trypsin. This study shows that temperature influences the function of a protein through modulation in the structure of functional domain of the protein. Modulation of function through appearance of new sequences that are more sensitive to temperature may be a general strategy for evolution of new proteins.

Physiological acclimation to elevated temperature in a reef-building coral from an upwelling environment

NASA Astrophysics Data System (ADS)

Mayfield, A. B.; Fan, T.-Y.; Chen, C.-S.

2013-12-01

Recent work has found that pocilloporid corals from regions characterized by unstable temperatures, such as those exposed to periodic upwelling, display a remarkable degree of phenotypic plasticity. In order to understand whether important reef builders from these upwelling reefs remain physiologically uncompromised at temperatures they will experience in the coming decades as a result of global climate change, a long-term elevated temperature experiment was conducted with Pocillopora damicornis specimens collected from Houbihu, a small embayment within Nanwan Bay, southern Taiwan that is characterized by 8-9 °C temperature changes during upwelling events. Upon nine months of exposure to nearly 30 °C, all colony (mortality and surface area), polyp ( Symbiodinium density and chlorophyll a content), tissue (total thickness), and molecular (gene expression and molecular composition)-level parameters were documented at similar levels between experimental corals and controls incubated at 26.5 °C, suggesting that this species can readily acclimate to elevated temperatures that cause significant degrees of stress, or even bleaching and mortality, in conspecifics of other regions of the Indo-Pacific. However, the gastrodermal tissue layer was relatively thicker in corals of the high temperature treatment sampled after nine months, possibly as an adaptive response to shade Symbiodinium from the higher photosynthetically active radiation levels that they were experiencing at that sampling time. Such shading may have prevented high light and high temperature-induced photoinhibition, and consequent bleaching, in these samples.

Rational design of thermostability in bacterial 1,3-1,4-β-glucanases through spatial compartmentalization of mutational hotspots.

PubMed

Niu, Chengtuo; Zhu, Linjiang; Xu, Xin; Li, Qi

2017-02-01

Higher thermostability is required for 1,3-1,4-β-glucanase to maintain high activity under harsh conditions in the brewing and animal feed industries. In this study, a comprehensive and comparative analysis of thermostability in bacterial β-glucanases was conducted through a method named spatial compartmentalization of mutational hotspots (SCMH), which combined alignment of homologous protein sequences, spatial compartmentalization, and molecular dynamic (MD) simulation. The overall/local flexibility of six homologous β-glucanases was calculated by MD simulation and linearly fitted with enzyme optimal enzymatic temperatures. The calcium region was predicted to be the crucial region for thermostability of bacterial 1,3-1,4-β-glucanases, and optimization of four residue sites in this region by iterative saturation mutagenesis greatly increased the thermostability of a mesophilic β-glucanase (BglT) from Bacillus terquilensis. The E46P/S43E/H205P/S40E mutant showed a 20 °C increase in optimal enzymatic temperature and a 13.8 °C rise in protein melting temperature (T m ) compared to wild-type BglT. Its half-life values at 60 and 70 °C were 3.86-fold and 7.13-fold higher than those of wild-type BglT. The specific activity of E46P/S43E/H205P/S40E mutant was increased by 64.4 %, while its stability under acidic environment was improved. The rational design strategy used in this study might be applied to improve the thermostability of other industrial enzymes.

What Fraction of Global Fire Activity Can Be Forecast Using Sea Surface Temperatures?

NASA Astrophysics Data System (ADS)

Chen, Y.; Randerson, J. T.; Morton, D. C.; Andela, N.; Giglio, L.

2015-12-01

Variations in sea surface temperatures (SSTs) can influence climate dynamics in local and remote land areas, and thus influence fire-climate interactions that govern burned area. SST information has been recently used in statistical models to create seasonal outlooks of fire season severity in South America and as the initial condition for dynamical model predictions of fire activity in Indonesia. However, the degree to which large-scale ocean-atmosphere interactions can influence burned area in other continental regions has not been systematically explored. Here we quantified the amount of global burned area that can be predicted using SSTs in 14 different oceans regions as statistical predictors. We first examined lagged correlations between GFED4s burned area and the 14 ocean climate indices (OCIs) individually. The maximum correlations from different OCIs were used to construct a global map of fire predictability. About half of the global burned area can be forecast by this approach 3 months before the peak burning month (with a Pearson's r of 0.5 or higher), with the highest levels of predictability in Central America and Equatorial Asia. Several hotspots of predictability were identified using k-means cluster analysis. Within these regions, we tested the improvements of the forecast by using two OCIs from different oceans. Our forecast models were based on near-real-time SST data and may therefore support the development of new seasonal outlooks for fire activity that can aid the sustainable management of these fire-prone ecosystems.

Temperature-sensitive junction transformations for mid-wavelength HgCdTe photovoltaic infrared detector arrays by laser beam induced current microscope

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

Qiu, Weicheng; National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083; Hu, Weida, E-mail: wdhu@mail.sitp.ac.cn

2014-11-10

In this paper, we report on the disappearance of the photosensitive area extension effect and the unusual temperature dependence of junction transformation for mid-wavelength, n-on-p HgCdTe photovoltaic infrared detector arrays. The n-type region is formed by B{sup +} ion implantation on Hg-vacancy-doped p-type HgCdTe. Junction transformations under different temperatures are visually captured by a laser beam induced current microscope. A physical model of temperature dependence on junction transformation is proposed and demonstrated by using numerical simulations. It is shown that Hg-interstitial diffusion and temperature activated defects jointly lead to the p-n junction transformation dependence on temperature, and the weaker mixedmore » conduction compared with long-wavelength HgCdTe photodiode contributes to the disappearance of the photosensitive area extension effect in mid-wavelength HgCdTe infrared detector arrays.« less

Temperature dependence of direct current conductivity in Ag-ED20 nanocomposite films

NASA Astrophysics Data System (ADS)

Novikov, G. F.; Rabenok, E. V.; Bogdanova, L. M.; Irzhak, V. I.

2017-10-01

The effect of silver nanoparticles (NPs) in the concentration range of ≤0.8 wt % have on direct current conductivity σdc of Ag-ED20 nanocomposite is studied by method of broadband dielectric spectroscopy (10-2-105 Hz) method of broadband dielectric spectroscopy. It is found that temperature dependence σdc consists of two sections: above the glass transition temperature ( T g), the dependence corresponds to the empirical Vogel-Fulcher-Tammann law (Vogel temperature T 0 does not depend on the NP concentration); below T g, the dependence is Arrhenius with activation energy E a ≈ 1.2 eV. In the region where T > T g, the σdc value grows along with NP concentration. It is concluded that the observed broken form of the temperature dependence is apparently due to a change in the conduction mechanism after the freezing of ion mobility at temperatures below T g.

Understanding CMEs using plasma diagnostics of the related dimmings

NASA Astrophysics Data System (ADS)

Vanninathan, Kamalam; Veronig, Astrid; Gomory, Peter; Dissauer, Karin; Temmer, Manuela; Hannah, Iain; Kontar, Eduard

2017-04-01

Coronal Mass Ejections (CMEs) are often associated with dimmings that are well observed in Extreme Ultra-violet (EUV) wavelengths. Such dimmings are suggested to represent the evacuation of mass that is carried out by CMEs and are a unique and indirect means to study CME properties. While Earth-directed CMEs (on-disk CMEs) are difficult to observe due to the bright background solar disk and projection effects, their corresponding dimmings are clearly discernible and ideally suited for analysis. Using data from the 6 EUV channels of Solar Dynamics Observatory/Atmospheric Imaging Assembly for Differential Emission Measure (DEM) diagnostics, we determine the plasma characteristics of the dimming region. These data are well suited for this kind of study due to the good temperature ranges covered by the multiple passbands of the instrument. We analyse 7 on-disk and 5 off-limb events and derive the weighted density and temperature as a function of time, from the DEMs. From such an analysis we differentiate 2 types of dimming regions: core and secondary dimmings. Core dimmings often occur in pairs lying on either sides of the active region and in opposite polarity regions while the secondary dimming is more extended. In both the regions the derived plasma parameters reach a minimum within 30-60 min after the flare. For each event the core dimming region shows a higher decrease in density and temperature than the corresponding secondary dimming regions. The values of these parameters remains low within the core dimming region for the entire duration of this study ( 10 hrs after the flare) while the secondary dimming region starts to show a gradual increase after 1-2 hrs. We also use spectroscopic data from Hinode/Extreme-Ultraviolet Imaging Spectrometer to differentiate core and secondary dimming regions. We find that the Fe XIII 202 Å line shows double component profiles within the core dimming region with strong blueshifts of 100 km/s while the secondary dimming region has weak upflows of 10 km/s. We conclude that the core dimming region corresponds to footpoints of the erupting flux rope from where there is continuous strong upflowing plasma for at least 10 hrs after the flare, while the secondary dimming region begins to refill within 1-2 hrs. These measurements can be used to deduce information about the mass of on-disk CMEs where white light measurements can fail. We also confirm that the dimmings are mainly caused by density decrease and not temperature changes. DEM analysis is a strong tool to decipher CME properties from dimming regions.

Type-I interband cascade lasers near 3.2 μm

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

Jiang, Yuchao; Li, Lu; Yang, Rui Q., E-mail: Rui.Q.Yang@ou.edu

2015-01-26

Interband cascade (IC) lasers have been demonstrated based on type-I InGaAsSb/AlAsSb quantum well (QW) active regions. These type-I IC lasers are composed of 6-cascade stages and InAs/AlSb superlattice cladding layers. In contrast to the use of quinary AlGaInAsSb barriers for active region in previous type-I QW lasers, the type-I QW active region in each stage is sandwiched by digitally graded multiple InAs/AlSb QW electron injector and GaSb/AlSb QW hole injector. The fabricated type-I IC lasers were able to operate in continuous wave and pulsed modes at temperatures up to 306 and 365 K, respectively. The threshold current densities of broad-area lasersmore » were around 300 A/cm{sup 2} at 300 K with a lasing wavelength near 3.2 μm. The implications and prospects of these initial results are discussed.« less

Responses of Biogeochemical Characteristics and Enzyme Activities in Sediment to Climate Warming under a Simulation Experiment in Geographically Isolated Wetlands of the Hulunbuir Grassland, China.

PubMed

Han, Liliang; Su, Derong; Lv, Shihai; Luo, Yan; Li, Xingfu; Jiao, Jian; Diao, Zhaoyan; Bu, He

2017-08-27

Climate warming generates a tremendous threat to the stability of geographically-isolated wetland (GIW) ecosystems and changes the type of evaporation and atmospheric precipitation in a region. The intrinsic balance of biogeochemical processes and enzyme activity in GIWs may be altered as well. In this paper, we sampled three types of GIWs exhibiting different kinds of flooding periods. With the participation of real-time temperature regulation measures, we assembled a computer-mediated wetland warming micro-system in June 2016 to simulate climate situation of ambient temperature (control group) and two experimental temperature differences (+2.5 °C and +5.0 °C) following a scientific climate change circumstance based on daily and monthly temperature monitoring at a two-minutes scale. Our results demonstrate that the contents of the total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) in the warmed showed, roughly, a balance or a slight decrease than the control treatment. Warming obstructed the natural subsidence of sediment, but reinforced the character of the ecological source, and reduced the activity of urease (URE), but promoted the activity of alkaline phosphatase (AKP) and sucrase (SUC). Redundancy analysis showed that sucrase, urease, available phosphorus (AP), and pH were the major correlating factors under warming conditions in our research scope. Total organic carbon, total nitrogen, sucrase, catalase (CAT), and alkaline phosphatase were the principal reference factors to reflect the ambient temperature variations. Nutrient compositions and enzyme activities in GIW ecosystems could be reconstructed under the warming influence.

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.

Satellite view of seasonal greenness trends and controls in South Asia

NASA Astrophysics Data System (ADS)

Sarmah, Sangeeta; Jia, Gensuo; Zhang, Anzhi

2018-03-01

South Asia (SA) has been considered one of the most remarkable regions for changing vegetation greenness, accompanying its major expansion of agricultural activities, especially irrigated farming. The influence of the monsoon climate on the seasonal trends and anomalies of vegetation greenness is poorly understood in this area. Herein, we used the satellite-based Normalized Difference Vegetation Index (NDVI) to investigate various spatiotemporal patterns in vegetation activity during summer and winter monsoon (SM and WM) seasons and among irrigated croplands (IC), rainfed croplands (RC), and natural vegetation (NV) areas during 1982–2013. Seasonal NDVI variations with climatic factors (precipitation and temperature) and land use and cover changes (LUCC) have also been investigated. This study demonstrates that the seasonal dynamics of vegetation could improve the detailed understanding of vegetation productivity over the region. We found distinct greenness trends between two monsoon seasons and among the major land use/cover classes. Winter monsoons contributed greater variability to the overall vegetation dynamics of SA. Major greening occurred due to the increased productivity over irrigated croplands during the winter monsoon season; meanwhile, browning trends were prominent over NV areas during the same season. Maximum temperatures had been increasing tremendously during the WM season; however, the precipitation trend was not significant over SA. Both the climate variability and LUCC revealed coupled effects on the long term NDVI trends in NV areas, especially in the hilly regions, whereas anthropogenic activities (agricultural advancements) played a pivotal role in the rest of the area. Until now, advanced cultivation techniques have proven to be beneficial for the region in terms of the productivity of croplands. However, the crop productivity is at risk under climate change.

Regional aerosol emissions and temperature response: Local and remote climate impacts of regional aerosol forcing

NASA Astrophysics Data System (ADS)

Lewinschal, Anna; Ekman, Annica; Hansson, Hans-Christen

2017-04-01

Emissions of anthropogenic aerosols vary substantially over the globe and the short atmospheric residence time of aerosols leads to a highly uneven radiative forcing distribution, both spatially and temporally. Regional aerosol radiative forcing can, nevertheless, exert a large influence on the temperature field away from the forcing region through changes in heat transport or the atmospheric or ocean circulation. Moreover, the global temperature response distribution to aerosol forcing may vary depending on the geographical location of the forcing. In other words, the climate sensitivity in one region can vary depending on the location of the forcing. The surface temperature distribution response to changes in sulphate aerosol forcing caused by sulphur dioxide (SO2) emission perturbations in four different regions is investigated using the Norwegian Earth System Model (NorESM). The four regions, Europe, North America, East and South Asia, are all regions with historically high aerosol emissions and are relevant from both an air-quality and climate policy perspective. All emission perturbations are defined relative to the year 2000 emissions provided for the Coupled Model Intercomparison Project phase 5. The global mean temperature change per unit SO2 emission change is similar for all four regions for similar magnitudes of emissions changes. However, the global temperature change per unit SO2 emission in simulations where regional SO2 emission were removed is substantially higher than that obtained in simulations where regional SO2 emissions were increased. Thus, the climate sensitivity to regional SO2 emissions perturbations depends on the magnitude of the emission perturbation in NorESM. On regional scale, on the other hand, the emission perturbations in different geographical locations lead to different regional temperature responses, both locally and in remote regions. The results from the model simulations are used to construct regional temperature potential (RTP) coefficients, which directly link regional aerosol or aerosol precursor emissions to the temperature response in different regions. These RTP coefficients can provide a simplified way to perform an initial evaluation of climate impacts of e.g. different emission policy pathways and pollution abatement strategies.

Quantifying the contribution of land use change to surface temperature in the lower reaches of the Yangtze River

NASA Astrophysics Data System (ADS)

Wang, Xueqian; Guo, Weidong; Qiu, Bo; Liu, Ye; Sun, Jianning; Ding, Aijun

2017-04-01

Anthropogenic land use has a significant impact on climate change. Located in the typical East Asian monsoon region, the land-atmosphere interaction in the lower reaches of the Yangtze River is even more complicated due to intensive human activities and different types of land use in this region. To better understand these effects on microclimate change, we compare differences in land surface temperature (Ts) for three land types around Nanjing from March to August, 2013, and then quantify the contribution of land surface factors to these differences (ΔTs) by considering the effects of surface albedo, roughness length, and evaporation. The atmospheric background contribution to ΔTs is also considered based on differences in air temperature (ΔTa). It is found that the cropland cooling effect decreases Ts by 1.76° and the urban heat island effect increases Ts by 1.25°. They have opposite impacts but are both significant in this region. Various changes in surface factors affect radiation and energy distribution and eventually modify Ts. It is the evaporative cooling effect that plays the most important role in this region and accounts for 1.40° of the crop cooling and 2.29° of the urban warming. Moreover, the background atmospheric circulation is also an indispensable part in land-atmosphere feedback induced by land use change and reinforces both these effects.

Dehydration and Lagrangian Cold Point in the extratropical Tropopause region

NASA Astrophysics Data System (ADS)

Hoor, P.; Wernli, H.

2012-04-01

The tropopause region of the tropics and extratropics is sensitive to modifications of the radiation budget through changes of radiatively active substances like ozone and water vapour. Both may also modify the temperature structure and the strengths of the tropopause inversion layer (TIL). Stratospheric water vapour is mainly controlled by dehydration in the tropics. Ascending air masses encounter their minimum temperature in the TTL region (tropical tropopause layer) which determines the water vapour fraction which enters the stratosphere. In the lowermost stratosphere of the extratropics however, the tropical signal might be lost due to mixing with airmasses which crossed the tropopause (TST: troposphere to stratosphere) at higher temperatures, therefore carrying more water vapour to the extratropical stratosphere. We investigate statistical 90 day backward trajectories to investigate the role of dehydration at the extratropical tropopause for the water vapour budget at the tropopause at mid and high latitudes. We use a set of 800000 trajectories for summer and winter, respectively, on the basis of ECMWF-T799L91 operational data (kinematic wind fields). We analyze the trajectories for the time and locations of their cold point and TST. Our results indicate that : 1) TST and dehydration occur at different locations 2) Dehydration occurs in general before trajectories enter the stratosphere 3) Dehydration of TST trajectories can occur in northern winter after TST in the region of high tropopauses over Siberia

Differences in ice nucleation behavior of arable and desert soil dust in deposition nucleation regime

NASA Astrophysics Data System (ADS)

Ullrich, Romy; Vogel, Franziska; Möhler, Ottmar; Höhler, Kristina; Schiebel, Thea

2017-04-01

Soil dust from arid and semi-arid regions is one of the most abundant aerosol types in the atmosphere with emission rates of about 1600 Tg per year (Andreae et al. (2009)). Therewith, soil dust plays an important role for the atmospheric radiative transfer and also for the formation of clouds. Soil dust refers to dust sampled from agricultural used areas, to dust from bare soil as well as to dust from desert regions. By mass-spectrometric measurements of the chemical composition of ice residuals, mineral dust as component of soil dust was found to be the major heterogeneous ice nucleating particle (INP) type (e.g. Cziczo et al. (2013)), in particular in the upper troposphere. Also in laboratory studies the ice nucleation efficiency of the different soil dusts was investigated. It was shown that desert dusts (Ullrich et al. (2017)) as well as soil dusts from arable regions (O'Sullivan et al. (2014), Tobo et al. (2014)) are efficient INP. However, there is still a lack of data for ice nucleation on soil dusts for temperatures below about 220 K. With the AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber, we are able to characterize the ice nucleation efficiency for different aerosol types to temperatures down to 180 K and high ice supersaturations. In order to extend the already existing AIDA data base for deposition nucleation on desert dusts and agricultural soil dusts, new experiments were done in the upper tropospheric temperature regime. This contribution will show the results of the new experiments with desert dust in comparison to existing data for higher temperatures. The first data analysis confirms the temperature dependent trend of the ice nucleation activity as discussed and parameterized in a recent paper by Ullrich et al. (2017). Furthermore, the update and extension of the recently published parameterization of deposition nucleation for desert dust to lower temperatures will be discussed. The experiments with agricultural soil dust will be compared to existing AIDA experiments at higher temperatures published by Steinke et al. (2016). Finally, the ice nucleation activity of both desert dust and agricultural soil dust will be compared for the upper tropospheric temperature regime. Andreae et al. (2009), Sources and Nature of Atmospheric Aerosols, in Aerosol Pollution Impact on Precipitation - A Scientific Review, Ch.3, Springer Netherlands, 45-89 Cziczo et al. (2013), Clarifying the Dominant Sources and Mechanisms of Cirrus Cloud Formation, Science, 340, 1320-1324 O'Sullivan et al. (2014), Ice nucleation by fertile soil dusts: relative importance of mineral and biogenic components, Atmos. Chem. Phys., 14, 1853-1867 Steinke et al. (2016), Ice nucleation activity of agricultural soil dust aerosols from Mongolia, Argentina and Germany, J. Geophys. Res., 121 Tobo et al. (2014), Organic matter matters for ice nuclei of agricultural soil origin, Atmos. Chem. Phys., 14, 8521-8531 Ullrich et al. (2017), A new ice nucleation active site parametrization for desert dust and soot, J. Atmos. Sci., in press

Origins of the Solar Wind

NASA Technical Reports Server (NTRS)

Warren, Harry; Gurman, Joseph (Technical Monitor)

2002-01-01

This paper presented the differential emission measure analysis of SUMER observations of a coroner streamer. We found that: The coroner streamer is isothermal at all heights. This suggests that the loops comprising the streamer must have very flat temperature profiles. The coroner streamer is "overdense" relative to the predictions of hydrostatic equilibrium at most heights. At the lowest heights the streamer is actually "underdense". The SUMER temperature measurements are not consistent with those derived from simultaneous SXT observations. SXT indicates systematically higher temperatures as well as a strong temperature gradient. These SUMER measurements yield somewhat lower temperatures and no gradient in the temperature with height. Previous work has suggested that there may be a hot component to the streamer that is preferentially observed with SXT. Our analysis shows that high temperature emission lines would be observed with SUMER if this were true and thus discounts this possibility. We suggested that scattered light in SXT might produce spurious temperature measurements. The temperature and density structure of this coroner streamer are very similar to "TRACE" active region loops (flat temperature profiles, overdense relative to uniform heating, and relatively cool temperatures).

Definition of the thermographic regions of interest in cycling by using a factor analysis

NASA Astrophysics Data System (ADS)

Priego Quesada, Jose Ignacio; Lucas-Cuevas, Angel Gabriel; Salvador Palmer, Rosario; Pérez-Soriano, Pedro; Cibrián Ortiz de Anda, Rosa M.^a.

2016-03-01

Research in exercise physiology using infrared thermography has increased in the last years. However, the definition of the Regions of Interest (ROIs) varies strongly between studies. Therefore, the aim of this study was to use a factor analysis approach to define highly correlated groups of thermographic ROIs during a cycling test. Factor analyses were performed based on the moment of measurement and on the variation of skin temperatures as a result of the cycling exercise. 19 male participants cycled during 45 min at 50% of their individual peak power output with a cadence of 90 rpm. Infrared thermography was used to measure skin temperatures in sixteen ROIs of the trunk and lower limbs at three moments: before, immediately after and 10 min after the cycling test. Factor analyses were used to identify groups of ROIs based on the skin absolute temperatures at each moment of measurement as well as on skin temperature variations between moments. All the factor analyses performed for each moment and skin temperature variation explained more than the 80% of the variance. Different groups of ROIs were obtained when the analysis was based on the moment of measurement or on the effect of exercise on the skin temperature. Furthermore, some ROIs were grouped in the same way in both analyses (e.g. the ROIs of the trunk), whereas other regions (legs and their joints) were grouped differently in each analysis. Differences between groups of ROIs are related to their tissue composition, muscular activity and capacity of sweating. In conclusion, the resultant groups of ROIs were coherent and could help researchers to define the ROIs in future thermal studies.

Overview of STEREO/EUVI and SOHO/EIT Data during the WHI Campaign

NASA Technical Reports Server (NTRS)

Kucera, Therese A.; Landi, E.

2008-01-01

The poster will present an overview of the data from the March-April,2008 Whole Heliospheric Interval Campaign. These instruments will show the targets during the campaign from three points of view at a range of temperatures. Targets are expected to include coronal cavities, coronal holes, active regions and prominences.

Relating Alfvén Wave Heating Model to Observations of a Solar Active Region

NASA Astrophysics Data System (ADS)

Yoritomo, J. Y.; Van Ballegooijen, A. A.

2012-12-01

We compared images from the Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA) with simulations of propagating and dissipating Alfvén waves from a three-dimensional magnetohydrodynamic (MHD) model (van Ballegooijen et. al 2011; Asgari-Targhi & van Ballegooijen 2012). The goal was to search for observational evidence of Alfvén waves in the solar corona and understand their role in coronal heating. We looked at one particular active region on the 5th of May 2012. Certain distinct loops in the SDO/AIA observations were selected and expanded. Movies were created from these selections in an attempt to discover transverse motions that may be Alfvén waves. Using a magnetogram of that day and the corresponding synoptic map, a potential field model was created for the active region. Three-dimensional MHD models for several loops in different locations in the active region were created. Each model specifies the temperature, pressure, magnetic field strength, average heating rate, and other parameters along the loop. We find that the heating is intermittent in the loops and reflection occurs at the transition region. For loops at larger and larger height, a point is reached where thermal non-equilibrium occurs. In the center this critical height is much higher than in the periphery of the active region. Lastly, we find that the average heating rate and coronal pressure decrease with increasing height in the corona. This research was supported by an NSF grant for the Smithsonian Astrophysical Observatory (SAO) Solar REU program and a SDO/AIA grant for the Smithsonian Astrophysical Observatory.

Reviews and perspectives of high impact atmospheric processes in the Mediterranean

NASA Astrophysics Data System (ADS)

Michaelides, Silas; Karacostas, Theodore; Sánchez, Jose Luis; Retalis, Adrianos; Pytharoulis, Ioannis; Homar, Víctor; Romero, Romualdo; Zanis, Prodromos; Giannakopoulos, Christos; Bühl, Johannes; Ansmann, Albert; Merino, Andrés; Melcón, Pablo; Lagouvardos, Konstantinos; Kotroni, Vassiliki; Bruggeman, Adriana; López-Moreno, Juan Ignacio; Berthet, Claude; Katragkou, Eleni; Tymvios, Filippos; Hadjimitsis, Diofantos G.; Mamouri, Rodanthi-Elisavet; Nisantzi, Argyro

2018-08-01

The Mediterranean region is a unique area characterized by a large spectrum of atmospheric phenomena, some of which have a high impact on many aspects of human activities, safety and wellbeing. The area is long considered as a hot spot of such atmospheric phenomena deserving multidisciplinary scientific attention. The scientific research that has been carried out on these high impact atmospheric processes that occur in the Mediterranean area is indeed widespread and the available international literature is very extensive. The paper touches initially the temperature and precipitation regimes, followed by a discussion of floods and droughts. The exciting cyclogenetic patterns of explosive cyclones and medicanes are presented in separate sections. The lightning activity and the presence of dust and other pollutants are also presented herein. The atmospheric chemistry of the region which is increasingly becoming of utmost importance for the area under study is distinctly discussed. Attempts to modify the weather (the precipitation, in particular) are outlined too. The effects of climatic change on various atmospheric processes are considered throughout this paper, in addition to a dedicated section on temperature and precipitation.

A study of El Niño-Southern oscillation impacts to the South China Sea region using ground-based GPS receiver

NASA Astrophysics Data System (ADS)

Suparta, Wayan; Iskandar, Ahmad; Singh Jit Singh, Mandeep; Alauddin Mohd Ali, Mohd; Yatim, Baharudin; Tangang, Fredolin

2013-04-01

We observe an ENSO activity by using ground-based GPS receiver as an effort to study the effects of global warming and climate change in the tropical region. The precipitable water vapor (PWV) derived from Global Positioning System (GPS) meteorology in line with the sea surface temperature anomaly (SSTa) is used to indicate their response on ENSO activities. The PWV data used in this study was taken from the station at Universiti Malaysia Sabah, Kota Kinabalu (UMSK) over 2011, together with NTUS station (in the Singapore), PIMO (in Philippines) and BAKO (in Indonesia) are also compared. The relationship between PWV and SSTa at all stations on weekly basis exhibited modest with correlation coefficients between -0.30 and -0.78 significantly at the 99% confidence level. The negative correlation indicates that during a La Niña phase, the PWV is increased when the sea surface temperatures getting cold causes warm air mass in the central Pacific moved to west Pacific. The increased of PWV causes the GPS signals will be getting slower.

IRTM brightness temperature maps of the Martian south polar region during the polar night: The cold spots don't move

NASA Technical Reports Server (NTRS)

Paige, D. A.; Crisp, D.; Santee, M. L.; Richardson, M. I.

1993-01-01

A series of infrared thermal mapper (IRTM) south polar brightness temperature maps obtained by Viking Orbiter 2 during a 35-day period during the southern fall season in 1978 was examined. The maps show a number of phenomena that have been identified in previous studies, including day to day brightness temperature variations in individual low temperature regions and the tendency for IRTM 11-micron channel brightness temperatures to also decrease in regions where low 20-micron channel brightness temperatures are observed. The maps also show new phenomena, the most striking of which is a clear tendency for the low brightness temperature regions to occur at fixed geographic regions. During this season, the coldest low brightness temperatures appear to be concentrated in distinct regions, with spatial scales ranging from 50 to 300 km. There are approximately a dozen of these concentrations, with the largest centered near the location of the south residual polar cap. Other concentrations are located at Cavi Angusti and close to the craters Main, South, Lau, and Dana. Broader, less intense regions appear to be well correlated with the boundaries of the south polar layered deposits and the Mountains of Mitchell. No evidence for horizontal motion of any of these regions has been detected.

Interaction of temperature, humidity, driver preferences, and refrigerant type on air conditioning compressor usage.

PubMed

Levine, C; Younglove, T; Barth, M

2000-10-01

Recent studies have shown large increases in vehicle emissions when the air conditioner (AC) compressor is engaged. Factors that affect the compressor-on percentage can have a significant impact on vehicle emissions and can also lead to prediction errors in current emissions models if not accounted for properly. During 1996 and 1997, the University of California, Riverside, College of Engineering-Center for Environmental Research and Technology (CE-CERT) conducted a vehicle activity study for the California Air Resources Board (CARB) in the Sacramento, CA, region. The vehicles were randomly selected from all registered vehicles in the region. As part of this study, ten vehicles were instrumented to collect AC compressor on/off data on a second-by-second basis in the summer of 1997. Temperature and humidity data were obtained and averaged on an hourly basis. The ten drivers were asked to complete a short survey about AC operational preferences. This paper examines the effects of temperature, humidity, refrigerant type, and driver preferences on air conditioning compressor activity. Overall, AC was in use in 69.1% of the trips monitored. The compressor was on an average of 64% of the time during the trips. The personal preference settings had a significant effect on the AC compressor-on percentage but did not interact with temperature. The refrigerant types, however, exhibited a differential response across temperature, which may necessitate separate modeling of the R12 refrigerant-equipped vehicles from the R134A-equipped vehicles. It should be noted that some older vehicles do get retrofitted with new compressors that use R134A; however, none of the vehicles in this study had been retrofitted.

Utilizing the social media data to validate 'climate change' indices

NASA Astrophysics Data System (ADS)

Molodtsova, T.; Kirilenko, A.; Stepchenkova, S.

2013-12-01

Reporting the observed and modeled changes in climate to public requires the measures understandable by the general audience. E.g., the NASA GISS Common Sense Climate Index (Hansen et al., 1998) reports the change in climate based on six practically observable parameters such as the air temperature exceeding the norm by one standard deviation. The utility of the constructed indices for reporting climate change depends, however, on an assumption that the selected parameters are felt and connected with the changing climate by a non-expert, which needs to be validated. Dynamic discussion of climate change issues in social media may provide data for this validation. We connected the intensity of public discussion of climate change in social networks with regional weather variations for the territory of the USA. We collected the entire 2012 population of Twitter microblogging activity on climate change topic, accumulating over 1.8 million separate records (tweets) globally. We identified the geographic location of the tweets and associated the daily and weekly intensity of twitting with the following parameters of weather for these locations: temperature anomalies, 'hot' temperature anomalies, 'cold' temperature anomalies, heavy rain/snow events. To account for non-weather related events we included the articles on climate change from the 'prestige press', a collection of major newspapers. We found that the regional changes in parameters of weather significantly affect the number of tweets published on climate change. This effect, however, is short-lived and varies throughout the country. We found that in different locations different weather parameters had the most significant effect on climate change microblogging activity. Overall 'hot' temperature anomalies had significant influence on climate change twitting intensity.

Modelling borehole temperatures in Southern Norway - insights into permafrost dynamics during the 20th and 21st century

NASA Astrophysics Data System (ADS)

Hipp, T.; Etzelmüller, B.; Farbrot, H.; Schuler, T. V.; Westermann, S.

2012-01-01

A transient heat flow model was used to simulate both past and future ground temperatures of mountain permafrost and associated active layer thickness in Southern Norway. The model was forced by reconstructed air temperature starting from 1860, approximately coinciding with the Little Ice Age in the region. The impact of climate warming on mountain permafrost until 2100 is assessed by using downscaled air temperatures from a multi-model ensemble for the A1B scenario. For 13 borehole locations, records over three consecutive years of ground temperatures, air temperatures and snow cover data are available for model calibration and validation. The boreholes are located at different elevations and in substrates with different thermal properties. With an increase of air temperature of ~+1.5 °C over 1860-2010 and an additional warming of +2.8 °C until 2100, we simulate the evolution of ground temperatures for the borehole locations. According to model results, the active-layer thickness has increased since 1860 by 0.5-5 m and >10 m for the sites Juvvasshøe and Tron, respectively. The simulations also suggest that at an elevation of about 1900 m a.s.l. permafrost will degrade until the end of this century with a probability of 55-75% given the chosen A1B scenario.

Energy saving incineration of waste

NASA Astrophysics Data System (ADS)

Meierzukoecker, H.; Voegtli, R.

1982-11-01

The machanism and the dimension of the preoxidation of the pollutants in the heat exchanger were investigated. A temperature control system was developed and tested. It is found that the preoxidation in the heat exchanger depends on the peculiarity of the pollutants and is inhibited by inactive walls with increasing of the specific surface. Active materials like copper only promote the oxidation of all pollutants in the low temperature region. Savings of supplemental energy about 25% are possible using process controlled auxiliary firing and combustion enthalpy of pollutants as a substitute for the supplemental energy.

Suppressing Nonradiative Recombination in Crown-Shaped Quantum Wells

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

Park, Kwangwook; Ju, Gunwu; Na, Byung Hoon

We examined the structural and optical properties of a crown-shaped quantum well (CSQW) to suppress nonradiative recombination. To reduce carrier loss in defect traps at the well/barrier interface, the CSQW was designed to concentrate carriers in the central region by tailoring the bandgap energy. Temperature-dependent photoluminescence measurements showed that the CSQW had a high activation energy and low potential fluctuation. In addition, the long carrier lifetime of the CSQW at high temperatures can be interpreted as indicating a decrease in carrier loss at defect traps.

Burst temperature from conditional analysis in Texas Helimak and TCABR tokamak

NASA Astrophysics Data System (ADS)

Pereira, F. A. C.; Hernandez, W. A.; Toufen, D. L.; Guimarães-Filho, Z. O.; Caldas, I. L.; Gentle, K. W.

2018-04-01

The procedure to estimate the average local temperature, density, and plasma potential by conditionally selecting points of the Langmuir probe characteristic curve is revised and applied to the study of intermittent bursts in the Texas Helimak and TCABR tokamak. The improvements made allow us to distinguish the burst temperature from the turbulent background and to study burst propagation. Thus, in Texas Helimak, we identify important differences with respect to the burst temperature measured in the top and the bottom regions of the machine. While in the bottom region the burst temperatures are almost equal to the background, the bursts in the top region are hotter than the background with the temperature peak clearly shifted with respect to the density one. On the other hand, in the TCABR tokamak, we found that there is a temperature peak simultaneously with the density one. Moreover, the radial profile of bursts in the top region of Helimak and in the edge and scrape-off layer regions of TCABR shows that in both machines, there are spatial regions where the relative difference between the burst and the background temperatures is significant: up to 25% in Texas Helimak and around 50% in TCABR. However, in Texas Helimak, there are also regions where these temperatures are almost the same.

Tropical Ocean Global Atmosphere (TOGA) Meteorological and Oceanographic Data Sets for 1985 and 1986

NASA Technical Reports Server (NTRS)

Halpern, D.; Ashby, H.; Finch, C.; Smith, E.; Robles, J.

1990-01-01

The Tropical Ocean Global Atmosphere (TOGA) Program is a component of the World Meteorological Organization (WMO)/International Council of Scientific Unions (ICSU) World Climate Research Program (WCRP). One of the objectives of TOGA, which began in 1985, is to determine the limits of predictability of monthly mean sea surface temperature variations in tropical regions. The TOGA program created a raison d'etre for an explosive growth of the tropical ocean observing system and a substantial improvement in numerical simulations from atmospheric and oceanic general circulation models. Institutions located throughout the world are involved in the TOGA-distributed active data archive system. The diverse TOGA data sets for 1985 and 1986, including results from general circulation models, are included on a CD-ROM. Variables on the CD-ROM are barometric pressure, surface air temperature, dewpoint temperature Cartesian components of surface wind, surface sensible and latent heat fluxes,Cartesian components of surface wind stress and of an index of surface wind stress, sea level, sea surface temperature, and depth profiles of temperature and current in the upper ocean. Some data sets are global in extent, some are regional and cover portions of an ocean basin. Data on the CD-ROM can be extracted with an Apple Macintosh or an IBM PC.

Future Changes to ENSO Temperature and Precipitation Teleconnections Under Warming

NASA Astrophysics Data System (ADS)

Perry, S.; McGregor, S.; Sen Gupta, A.; England, M. H.

2016-12-01

As the dominant mode of interannual climate variability, the El Niño-Southern Oscillation (ENSO) modulates temperature and rainfall globally, additionally contributing to weather extremes. Anthropogenic climate change has the potential to alter the strength and frequency of ENSO and may also alter ENSO-driven atmospheric teleconnections, affecting ecosystems and human activity in regions far removed from the tropical Pacific. State-of-art climate models exhibit considerable disagreement in projections of future changes in ENSO sea surface temperature variability. Despite this uncertainty, recent model studies suggest that the precipitation response to ENSO will be enhanced in the tropical Pacific under future warming, and as such the societal impacts of ENSO will increase. Here we use temperature and precipitation data from an ensemble of 41 CMIP5 models to show where ENSO teleconnections are being enhanced and dampened in a high-emission future scenario (RCP8.5) focusing on the changes that are occurring over land areas globally. Although there is some spread between the model projections, robust changes with strong ensemble agreement are found in certain locations, including amplification of teleconnections in southeast Australia, South America and the Maritime Continent. Our results suggest that in these regions future ENSO events will lead to more extreme temperature and rainfall responses.

Unexpected East-West effect in mesopause region SABER temperatures over El Leoncito

NASA Astrophysics Data System (ADS)

Reisin, Esteban R.; Scheer, Jürgen

2017-05-01

We find that mesopause region temperatures determined by the SABER instrument on the TIMED satellite during nocturnal overpasses at El Leoncito (31.8°S, 69.3°W) are several kelvins higher when SABER observes from the East than when it observes from the West. We distinguish between altitudes corresponding to the nominal emission heights of the OH and O2 airglow layers. The East-West temperature differences of 4.5 K obtained for OH-equivalent height, and of 3.5 K for O2-equivalent height are surprising, because an effect of the South Atlantic Anomaly on SABER temperature is unexpected. However, the ground-based data obtained with our airglow spectrometer at El Leoncito show that such a SABER artifact can be ruled out. Rather, the phenomenon is explained as a consequence of the temporal sampling of the nocturnal variation, which is mostly due to the semidiurnal tide. The monthly mean tide is strongest from April to September with a mean amplitude of 6.9 K for OH, and of 10.5 K for O2 rotational temperature, but the contribution to the East-West effect varies strongly from month to month because of differences in the temporal sampling. This mechanism should be active at other sites, as well.

Computation of heats of transport in crystalline solids: II

NASA Astrophysics Data System (ADS)

Grout, P. J.; Lidiard, A. B.

2008-10-01

This paper explores the application of classical molecular dynamics to the computation of the heat of transport of Au atoms in a model of solid gold at several elevated temperatures above the Debye temperature. It is assumed that the solid shows vacancy disorder. The work shows that to obtain consistent and reliable results it is necessary (a) to use very small time steps (≈1 fs) in the molecular dynamics integration routine and (b) to take averages over a very large number of vacancy displacements—a number which varies with temperature but which is of the order of 105. The results for the reduced heat of transport for the Au atoms show that: (1) it is positive in sign, i.e. that the diffusion of Au atoms in a temperature gradient is biassed towards the cold region or equivalently that the vacancies tend to migrate towards the hotter region; (2) it is predicted to fall as the average temperature increases and that the variation is closely linear in (1/T); (3) its value at high T relative to the energy of activation for vacancy movement is close to the corresponding ratio of experimental quantities. Analysis of these results indicates that the method and model may allow reliable predictions for other metals having the face centred cubic structure.

Direct and indirect ENSO modulation of winter temperature over the Asian–Pacific–American region

PubMed Central

Leung, Marco Y. T.; Zhou, Wen

2016-01-01

In this study, the direct and indirect atmospheric responses over the Asian–Pacific–American region to the El Niño–Southern Oscillation (ENSO) are documented. Since ENSO is likely to induce the northward displacement of the East Asian trough (NDEAT), some of the influence of ENSO on the Asian–Pacific–American region is possibly indirect and acts by inducing NDEAT. To separate corresponding influences of ENSO and NDEAT, partial regression is utilized. It is noted that temperature variations in the East Asian–Western Pacific region are controlled mainly by NDEAT. In contrast, ENSO demonstrates a weak direct relation to the temperature variation over the East Asian–Western Pacific region. This suggests that the influence of ENSO on this region is indirect, through modulation of NDEAT. On the other hand, temperature variation over the tropical eastern Pacific is dominated by ENSO forcing. Finally, temperature variation over the eastern North American–Western Pacific region is controlled by both ENSO and NDEAT. Nevertheless, their influences on temperature and circulation over this region tend to offset each other. This implies that temperature variation is controlled by their relative strengths. PMID:27821838

Method of forming thermally stable high-resistivity regions in n-type indium phosphide by oxygen implantation

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

Thompson, P.E.; Dietrich, H.B.

1985-12-12

Objects of this invention are: to form high-temperature stable isolation regions in InP; to provide InP wafers that allow greater flexibility in the design and fabrication of discrete devices; to provide new and improved InP semiconductor devices in n-type InP; to provide high-resisitivity isolation regions in InP; to extend the usefulness of damage-induced isolation in n-type InP by making possible processes in which the isolation implantation precedes the alloying of ohmic contacts; and to provide n-type InP substrates without unwanted conductive layers. The above and other object are realized by an InP wafer comprising a S.I. InP substrate; a n-typemore » InP active layer disposed on the substrate; and oxygen ion implanted isolation regions disposed in the active layer. The S.I. InP dopant may comprise either Fe or Cr.« less

Clasp/SJ Observation of Time Variations of Lyman-Alpha Emissions in a Solar Active Region

NASA Technical Reports Server (NTRS)

Ishikawa, S.; Kubo, M.; Katsukawa, Y.; Kano, R.; Narukage, N.; Ishikawa, R.; Bando, T.; Winebarger, A.; Kobayashi, K.; Trujillo Bueno, J.;

Comparison of surface temperature in 13-lined ground squirrel (Spermophilus tridecimlineatus) and yellow-bellied marmot (Marmota flaviventris) during arousal from hibernation.

PubMed

Phillips, P K; Heath, J E

2004-08-01

Surface temperatures (Ts) of eight 13-lined ground squirrels and seven yellow-bellied marmots were measured during arousal from hibernation using infrared thermography (IRT) and recorded on videotape. Animals aroused normally in 5 degrees C cold rooms. Body temperatures were recorded during arousal using both cheek pouch and interscapular temperature probes. Warming rate in arousal was exponential. Mean mass specific warming rates show the squirrels warm faster (69.76 degrees C/h/kg) than the marmots (4.49 degrees C/h/kg). Surface temperatures (Ts) for 11 regions were measured every few minutes during arousal. The smaller ground squirrel shows the ability to perfuse distal regions without compromising rise in deep body temperature (Tb). All squirrel Ts's remained low as Tb rose to 18 degrees C, at which point, eyes opened, squirrels became more active and all Ts's rose parallel to Tb. Marmot Ts remained low as Tb rose initially. Each marmot showed a plateau phase where Tb remained constant (mean Tb 20.3+/-1.0 degrees C, duration 9.4+/-4.1 min) during which time all Ts's rose, and then remained relatively constant as Tb again began to rise. An anterior to posterior Ts gradient was evident in the ground squirrel, both body and feet. This gradient was only evident in the feet of the marmots.

How the Emitted Size Distribution and Mixing State of Feldspar Affect Ice Nucleating Particles in a Global Model

NASA Technical Reports Server (NTRS)

Perlwitz, Jan P.; Fridlind, Ann M.; Knopf, Daniel A.; Miller, Ron L.; García-Pando, Carlos Perez

2017-01-01

The effect of aerosol particles on ice nucleation and, in turn, the formation of ice and mixed phase clouds is recognized as one of the largest sources of uncertainty in climate prediction. We apply an improved dust mineral specific aerosol module in the NASA GISS Earth System ModelE, which takes into account soil aggregates and their fragmentation at emission as well as the emission of large particles. We calculate ice nucleating particle concentrations from K-feldspar abundance for an active site parameterization for a range of activation temperatures and external and internal mixing assumption. We find that the globally averaged INP concentration is reduced by a factor of two to three, compared to a simple assumption on the size distribution of emitted dust minerals. The decrease can amount to a factor of five in some geographical regions. The results vary little between external and internal mixing and different activation temperatures, except for the coldest temperatures. In the sectional size distribution, the size range 24 micrometer contributes the largest INP number.

How the Emitted Size Distribution and Mixing State of Feldspar Affect Ice Nucleating Particles in a Global Model

NASA Astrophysics Data System (ADS)

Perlwitz, J. P.; Fridlind, A. M.; Knopf, D. A.; Miller, R. L.; Pérez García-Pando, C.

2017-12-01

The effect of aerosol particles on ice nucleation and, in turn, the formation of ice and mixed phase clouds is recognized as one of the largest sources of uncertainty in climate prediction. We apply an improved dust mineral specific aerosol module in the NASA GISS Earth System ModelE, which takes into account soil aggregates and their fragmentation at emission as well as the emission of large particles. We calculate ice nucleating particle concentrations from K-feldspar abundance for an active site parameterization for a range of activation temperatures and external and internal mixing assumption. We find that the globally averaged INP concentration is reduced by a factor of two to three, compared to a simple assumption on the size distribution of emitted dust minerals. The decrease can amount to a factor of five in some geographical regions. The results vary little between external and internal mixing and different activation temperatures, except for the coldest temperatures. In the sectional size distribution, the size range 2-4 μm contributes the largest INP number.

Cryotherapy-Induced Persistent Vasoconstriction After Cutaneous Cooling: Hysteresis Between Skin Temperature and Blood Perfusion.

PubMed

Khoshnevis, Sepideh; Craik, Natalie K; Matthew Brothers, R; Diller, Kenneth R

2016-03-01

The goal of this study was to investigate the persistence of cold-induced vasoconstriction following cessation of active skin-surface cooling. This study demonstrates a hysteresis effect that develops between skin temperature and blood perfusion during the cooling and subsequent rewarming period. An Arctic Ice cryotherapy unit (CTU) was applied to the knee region of six healthy subjects for 60 min of active cooling followed by 120 min of passive rewarming. Multiple laser Doppler flowmetry perfusion probes were used to measure skin blood flow (expressed as cutaneous vascular conductance (CVC)). Skin surface cooling produced a significant reduction in CVC (P < 0.001) that persisted throughout the duration of the rewarming period. In addition, there was a hysteresis effect between CVC and skin temperature during the cooling and subsequent rewarming cycle (P < 0.01). Mixed model regression (MMR) showed a significant difference in the slopes of the CVC-skin temperature curves during cooling and rewarming (P < 0.001). Piecewise regression was used to investigate the temperature thresholds for acceleration of CVC during the cooling and rewarming periods. The two thresholds were shown to be significantly different (P = 0.003). The results show that localized cooling causes significant vasoconstriction that continues beyond the active cooling period despite skin temperatures returning toward baseline values. The significant and persistent reduction in skin perfusion may contribute to nonfreezing cold injury (NFCI) associated with cryotherapy.

Cryotherapy-Induced Persistent Vasoconstriction After Cutaneous Cooling: Hysteresis Between Skin Temperature and Blood Perfusion

PubMed Central

Khoshnevis, Sepideh; Craik, Natalie K.; Matthew Brothers, R.; Diller, Kenneth R.

2016-01-01

The goal of this study was to investigate the persistence of cold-induced vasoconstriction following cessation of active skin-surface cooling. This study demonstrates a hysteresis effect that develops between skin temperature and blood perfusion during the cooling and subsequent rewarming period. An Arctic Ice cryotherapy unit (CTU) was applied to the knee region of six healthy subjects for 60 min of active cooling followed by 120 min of passive rewarming. Multiple laser Doppler flowmetry perfusion probes were used to measure skin blood flow (expressed as cutaneous vascular conductance (CVC)). Skin surface cooling produced a significant reduction in CVC (P < 0.001) that persisted throughout the duration of the rewarming period. In addition, there was a hysteresis effect between CVC and skin temperature during the cooling and subsequent rewarming cycle (P < 0.01). Mixed model regression (MMR) showed a significant difference in the slopes of the CVC–skin temperature curves during cooling and rewarming (P < 0.001). Piecewise regression was used to investigate the temperature thresholds for acceleration of CVC during the cooling and rewarming periods. The two thresholds were shown to be significantly different (P = 0.003). The results show that localized cooling causes significant vasoconstriction that continues beyond the active cooling period despite skin temperatures returning toward baseline values. The significant and persistent reduction in skin perfusion may contribute to nonfreezing cold injury (NFCI) associated with cryotherapy. PMID:26632263

Mountain building, strike-slip faulting, and landscape evolution in the Marlborough Fault System, NZ: Insights from new low-temperature thermochronology and modeling

NASA Astrophysics Data System (ADS)

Duvall, A. R.; Collett, C.; Flowers, R. M.; Tucker, G. E.; Upton, P.

2016-12-01

The 150 km wide Marlborough Fault System (MFS) and adjacent dextral-reverse Alpine Fault accommodate oblique convergence of the Australian and Pacific plates in a broad transform boundary that extends for much of the South Island New Zealand. Understanding the deformation history of the Marlborough region offers the opportunity to study topographic evolution in a strike-slip setting and a fuller picture of the evolving New Zealand plate boundary as the MFS lies at the transition from oceanic Pacific plate subduction to oblique continental collision. Here we present low-temperature thermochronology from the MFS to place new limits on the timing and style of mountain building. We sampled a range of elevations spanning 2 km within and adjacent to the Kaikoura Mountains, which stand high as topographic anomalies above active strike-slip faults. Young apatite (U-Th)/He ages ( 2-5 Ma) on both sides of range-bounding faults are consistent with regional distributed deformation since the Pliocene initiation of strike-slip faulting. However, large differences in both zircon helium and apatite fission track ages, from Paleogene/Neogene ages within hanging walls to unreset >100 Ma ages in footwalls, indicate an early phase of fault-related vertical exhumation. Thermal modeling using the QTQt program reveals two phases of exhumation within the Kaikoura Ranges: rapid cooling at 15-12 Ma localized to hanging wall rocks and regional rapid cooling reflected in all samples starting at 4-5 Ma. These results and landscape evolution models suggest that, despite the presence of active mountain front faults, much of the topographic relief in this region may predate the onset of strike-slip faulting and that portions of the Marlborough Faults are re-activated thrusts that coincide with the early development of the transpressive plate boundary. Regional exhumation after 5 Ma likely reflects increased proximity to the migrating Pacific plate subduction zone and the buoyant Chatham Rise.