Average ΔT Research Articles

Anisotropy patterns in the subducting lithosphere and in the mantle wedge: A case study—The southern Italy subduction system

[1] In this study we present a collection of high quality S wave splitting measurements in the southern Italy subduction system. We analyzed 76 deep earthquakes located within the descending slab using the method of Silver and Chan (1991) to determine the splitting parameters φ and δt. The local deep earthquakes allow us to analyze raypaths primarily sampling the slab and the wedge above it. Mainland Calabria is an outcropping forearc, enabling us to sample rays that propagate up the slab. S wave splitting parameters show a complex pattern of anisotropy with variable fast directions and with delay times ranging from 0.1 s to 2.2 s. We compared local S wave splitting data with SKS results at the same stations, and we found that the average δt is very different (1.8 s for SKS and 0.5 s for S). We found consistency between averaged S fast directions and the SKS splitting measurements, including a pattern of toroidal mantle flow at the SW edge of the slab. The S wave splitting parameters show frequency-dependent behavior that we attribute to the presence of small-scale anisotropic heterogeneities. Comparison of S splitting measurements to P wave velocity anomaly at 100–200 km depth shows that where the rays primarily sample the slab the delay times are small. In contrast, where S rays sample the mantle wedge, the delay times are quite high. This δt pattern depicts the slab as a weakly anisotropic region and suggests that the main source of anisotropy in the subduction zone is the surrounding asthenosphere.

High-affinity DNA targeting using readily accessible mimics of N2'-functionalized 2'-amino-α-L-LNA.

N2'-Pyrene-functionalized 2'-amino-α-L-LNAs (locked nucleic acids) display extraordinary affinity toward complementary DNA targets due to favorable preorganization of the pyrene moieties for hybridization-induced intercalation. Unfortunately, the synthesis of these monomers is challenging (~20 steps, <3% overall yield), which has precluded full characterization of DNA-targeting applications based on these materials. Access to more readily accessible functional mimics would be highly desirable. Here we describe short synthetic routes to a series of O2'-intercalator-functionalized uridine and N2'-intercalator-functionalized 2'-N-methyl-2'-aminouridine monomers and demonstrate, via thermal denaturation, UV-vis absorption and fluorescence spectroscopy experiments, that several of them mimic the DNA-hybridization properties of N2'-pyrene-functionalized 2'-amino-α-L-LNAs. For example, oligodeoxyribonucleotides (ONs) modified with 2'-O-(coronen-1-yl)methyluridine monomer Z, 2'-O-(pyren-1-yl)methyluridine monomer Y, or 2'-N-(pyren-1-ylmethyl)-2'-N-methylaminouridine monomer Q display prominent increases in thermal affinity toward complementary DNA relative to reference strands (average ΔT(m)/mod up to +12 °C), pronounced DNA-selectivity, and higher target specificity than 2'-amino-α-L-LNA benchmark probes. In contrast, ONs modified with 2'-O-(2-napthyl)uridine monomer W, 2'-O-(pyren-1-yl)uridine monomer X or 2'-N-(pyren-1-ylcarbonyl)-2'-N-methylaminouridine monomer S display very low affinity toward DNA targets. This demonstrates that even conservative alterations in linker chemistry, linker length, and surface area of the appended intercalators have marked impact on DNA-hybridization characteristics. Straightforward access to high-affinity building blocks such as Q, Y, and Z is likely to accelerate their use in DNA-targeting applications within nucleic acid based diagnostics, therapeutics, and material science.

Self-heating study of an AlGaN∕GaN-based heterostructure field-effect transistor using ultraviolet micro-Raman scattering

We report micro-Raman studies of self-heating in an AlGaN∕GaN heterostructure field-effect transistor using below (visible 488.0nm) and near (UV 363.8nm) GaN band-gap excitation. The shallow penetration depth of the UV light allows us to measure temperature rise (ΔT) in the two-dimensional electron gas (2DEG) region of the device between drain and source. Visible light gives the average ΔT in the GaN layer, and that of the SiC substrate, at the same lateral position. Combined, we depth profile the self-heating. Measured ΔT in the 2DEG is consistently over twice the average GaN-layer value. Electrical and thermal transport properties are simulated. We identify a hotspot, located at the gate edge in the 2DEG, as the prevailing factor in the self-heating.

Monitoring intraoperative effectiveness of caudal analgesia through skin temperature variation

A reliable noninvasive intraoperative marker of caudal analgesia effectiveness remains elusive. Caudal analgesia causes sympathetic inhibition resulting in vasodilatation, increased blood flow, and a resultant increase in temperature in the affected dermatomes. The authors hypothesize that this change in temperature between the affected and unaffected dermatomes is measurable and may represent a noninvasive method of monitoring effectiveness of caudal analgesia. Children undergoing lower abdominal surgery participated in the caudal or noncaudal (control) analgesia arm of the study. After induction of general anesthesia, 0.25% bupivicaine (1 mL/kg) was infiltrated for a field block in control patients or a caudal block in the experimental group. Temperature was measured at the C4 and L2 dermatomes starting after induction and 5 minutes before the caudal or field block and every 5 minutes after. T(o) is defined as the difference between the C4 and L2. Delta T (DeltaT) is the temperature variation between T(o). A change in the DeltaT is defined by an increase in the L2 temperature. Forty-six families enrolled (36 experimental, 10 control). The DeltaT for controls was 0.2+/-0.09 degrees C (SEM). Each child in the experimental group had 2 temperature measurements before the caudal with an average DeltaT of 0.3+/-0.07 degrees C (SEM), thus, were internal controls. A marked increase in DeltaT at 5 minutes 0.5+/-0.06 degrees C (SEM) and at 10 minutes 0.6+/-0.07 degrees C (SEM; P <.05) was noted in the experimental group. A significant transient change in temperature is observed after caudal analgesia and maybe a noninvasive marker of effectiveness. Further study may clarify its clinical utility.

Settling of small particles near vortices and in turbulence

The trajectories of small heavy particles in a gravitational field, having fall speed in still fluid V˜T and moving with velocity V˜ near fixed line vortices with radius R˜v and circulation Γ˜, are determined by a balance between the settling process and the centrifugal effects of the particles' inertia. We show that the main characteristics are determined by two parameters: the dimensionless ratio VT = V˜TR˜v/Γ˜ and a new parameter (Fp) given by the ratio between the relaxation time of the particle (t˜p) and the time (Γ˜/V˜2T) for the particle to move around a vortex when VT is of order unity or small.The average time ΔT˜ for particles to settle between two levels a distance Y˜0 above and below the vortex (where Y˜0 [Gt ] Γ˜/VT) and the average vertical velocity of particles 〈Vy〉L along their trajectories depends on the dimensionless parameters VT and Fp. The bulk settling velocity 〈Vy〉B = 2Y˜0/〈ΔT˜〉, where the average value of 〈ΔT˜〉 is taken over all initial particle positions of the upper level, is only equal to 〈V˜y〉L for small values of the effective volume fraction within which the trajectories of the particles are distorted, α = (Γ˜/V˜T)2/ Y˜20. It is shown here how 〈Vy〉B is related to Δ&amp;η;(X˜0), the difference between the vertical settling distances with and without the vortex for particles starting on (X˜0, Y˜0) and falling for a fixed period Δt˜T [Gt ] &amp;Γtilde;/V˜2T; 〈V˜y〉B = V˜T[1 − αD], where D = ∫∞−∞(Δ&amp;η;dX˜0/ (&amp;Γtilde;/V˜T)2) is the drift integral. The maximum value of 〈V˜〉B for any constant value of VT occurs when Fp = FpM ∼ 1 and the minimum when Fp = Fpm &gt; FpM, where typically 3 &lt; Fpm &lt; 5.Individual trajectories and the bulk quantities D and 〈Vy〉B have been calculated analytically in two limits, first Fp → 0, finite VT, and secondly VT [Gt ] 1. They have also been computed for the range 0 &lt; Fp &lt; 102, 0 &lt; VT &lt; 5 in the case of a Rankine vortex. The results of this study are consistent with experimental observations of the pattern of particle motion and on how the fall speed of inertial particles in turbulent flows (where the vorticity is concentrated in small regions) is typically up to 80% greater than in still fluid for inertial particles (Fp ∼ 1) whose terminal velocity is less than the root mean square of the fluid velocity, ũ′, and typically up to 20% less for particles with a terminal velocity larger than ũ′. If V˜T/ũ′ &gt; 4 the differences are negligible.

Modification of a Commercial Integrating Nephelometer for Outdoor Measurements

Abstract One of the major challenges in atmospheric aerosol research is the quantification of aerosol optical properties at ambient relative humidities (RHs) and their attribution to natural and anthropogenic aerosol sources. As an essential tool for this task, a commercial single wavelength integrating nephelometer built for dry indoor aerosol measurements was modified and complemented for outdoor operating conditions. The temperature difference ΔT between air inlet and outlet is the crucial parameter indicating the effect of the instrument on RH of the sampled aerosol. By removing all heat sources from the optics compartment and by doubling the length of the light pipe between lamp and sensing chamber, ΔT became smaller in the laboratory than the uncertainty of the temperature sensors. After mounting the instrument in a protective housing an average ΔT = 0.55°C (0.22°C standard deviation) was maintained under nonoptimized ventilation conditions for one week of unattended outdoor operation parallel with ...

Radial upper mantle attenuation structure of inactive back arc basins from differential shear wave measurements

We measure differential attenuation between sS‐S and sScS‐ScS phase pairs to characterize the variation of attenuation with depth in the upper mantle of five inactive back arc basins: the Kuril Basin, Sea of Japan, Banda Sea, the Celebes and Sulu Seas, and the Shikoku Basin. A spectral ratio technique is used to measure the differential attenuation operator of the transversely polarized waveforms over a frequency band of 10 to 83 mHz. Two algorithms are employed to compute the vertically averaged attenuation structure: a spectral stacking procedure and a least squares inversion. In the spectral stacking method, the individual spectra are corrected for the elastic structure at the sS or sScS bounce point, and the differential attenuation operator is computed by spectral division. The attenuation operators are then normalized and stacked by source depth to obtain more stable spectra, and an average δt* for sources within a restricted depth range is obtained from the slope of the log‐amplitude spectrum. A model for the depth dependent Q structure is then calculated from the δt* measurements assuming Q is frequency independent. Alternatively, δt* measurements for individual phase pairs are made using a similar technique and analyzed by ray tracing and a least squares inversion to obtain the Q−1 estimates. The Q results obtained from the stacking and inversion methods are generally in good agreement. The Q−1 structures for the various back arc regions are similar to each other within the uncertainties of the derived Q models. In addition to computing Q models for each individual region, we partitioned the data into three tectonic provinces based upon bounce point locations. The resulting average radial Qβ structure for an inactive basin shows a Q of 54 in the uppermost mantle, 115 at intermediate depths, and 173 in the transition zone; we also find a low Q zone of 36 beneath active island arcs. The Q values for inactive back arc basins are lower than the global averages derived from normal modes but are generally consistent with previous body and surface wave studies of other young oceanic regions. The most striking feature of this study is the observation of very strong attenuation concentrated at shallow depths (&lt;160 km) in the upper mantle beneath these basins.

Abnormal skin temperature and abnormal sympathetic vasomotor innervation in an experimental painful peripheral neuropathy

A chronic constriction injury to the sciatic nerve of the rat produces a neuropathic pain syndrome that has many of the symptoms that are seen in humans with painful peripheral neuropathy. In particular, both the clinical and experimental conditions are accompanied by an abnormality of cutaneous temperature regulation in the painful area. A time course study was made of this phenomenon in the experimental model. In normal rats, there is little or no difference between the temperature of the two hind paws (plantar skin). After nerve injury, however, approximately 75% of the rats (N = 30) had abnormally large (greater than +/- 0.9 degrees C) temperature differences (delta T) between the affected and sham-operated sides. The abnormal delta Ts could be either positive or negative, i.e., the affected side could be hotter or colder than normal. For individual cases, the temperature abnormality was highly variable over time periods of hours to days; abnormally hot skin could switch to being abnormally cold, and vice versa, and small delta Ts in the normal range could switch between abnormal extremes. Despite this individual variability, the average delta T of the group as a whole displayed a clear evolution over the course of the 30-day observation period: abnormally hot initially and progressing to abnormally cold. A parallel time course study was made of the status of the sympathetic vasoconstrictor innervation to the affected hind paw (plantar artery and vein). As demonstrated with a histofluorescence method that visualizes catecholamines, there was a gradual loss of norepinephrine (NE)-containing sympathetic efferents on the nerve-injured side. The decrease was first noted on postoperative day 5 (PO5), was very marked by PO10-PO14, and progressed to a complete or nearly complete loss by PO30. There was a concomitant decrease in staining for two other substances found in vasoconstrictor efferents, dopamine-beta-hydroxylase (DBH) and neuropeptide Y (NPY). The NE-containing innervation of the contralateral (sham-operated) plantar vessels appeared to be normal at all times. Lastly, in order to determine whether there was any relation between the temperature abnormality and the status of the sympathetic perivascular plexus, additional rats were sacrificed immediately after skin temperature measurement and the hind paw vessels were stained for NE. The vasculature of some abnormally cold paws had no detectable NE. Some rats that did not appear to have a temperature abnormality also had no detectable NE on the affected hind paw's vasculature. The vasculature of some abnormally hot paws had normal NE.(ABSTRACT TRUNCATED AT 400 WORDS)

Sensitivity of oxidant concentrations on changes in U.V. radiation and temperature

Depletion of the stratospheric ozone layer could result in increasing u.v. radiation at ground level. Increasing concentrations of greenhouse gases could result in increasing temperature. The response of boundary layer chemistry on increases in energy, in the form of increasing surface temperature or increasing u.v. radiation, will be an increased photochemical reactivity. In this paper we present the results of a model study on the sensitivity of episodic and long-term averaged ozone and oxidant (Ox, sum of O 3 and NO 2 ) concentrations on changes in temperature and u.v. radiation. Ground level ozone and oxidant concentrations are calculated for summer 1989 by means of a Lagrangian long-range transport model for a receptor point in the central part of The Netherlands. For a 10% decrease in ozone column density and a 10% increase in surface temperature (on average Δt = 1.6° C ) the increase in O 3 and Ox 98 percentile value is about 2.7%. The additional ozone production will increase the number of exceedences of threshold values; this may lead to greater human exposures during episodes. The calculations for the reference emission situation resulted for the period 1 May–1 October 1989 (total 3672 h) in 56 observations of 1-h averaged O 3 concentrations which exceed the level of 75 ppb; in one case the O 3 concentration exceeds 100 ppb. In the sensitivity calculations with increased temperature and reduced ozone column these numbers increase to 72 h (+29%) and 6 h (+600%), respectively. A possible increase in natural VOC emissions from forests due to a global warming may further enhance the number of exceedences.

Assessment of Thermal Discharges on Zooplankton in Conowingo Pond, Pennsylvania

Assessment of the impact of power station operation on zooplankton communities requires separation of natural variations from those due to the facility. Analysis of covariance (density of zooplankton at control station, ambient water temperature, and average daily river flow as covariates) proved powerful in separating the natural variations from those due to the operation of Peach Bottom Atomic Power Station (once-through cooling system) in Conowingo Pond, a 35.8-km2 impoundment on the lower Susquehanna River. The covariance technique overcame some of the problems associated with using ratio of density at control station to the density at an affected station to adjust for ambient variations. Significant differences in adjusted preoperational and postoperational means occurred but were not attributable to station operation. Multiple regression analysis indicated that an increase in zooplankton production, particularly in winter, would result with addition of heated water when river flows are &lt; 280 m3/s. The zooplankters were subjected to an average ΔT of 10.0 °C in winter and up to 8.0 °C in summer. Zooplankton population showed a great amount of resiliency in Conowingo Pond.Key words: zooplankton, heated effluents, statistical analysis, power plant impact

Technical and economic feasibility of Ocean Thermal Energy Conversion

Abstract Ocean Thermal Energy Conversion (OTEC) plants will employ the temperature difference ( ΔT ) between the solar-heated surface layer of a tropical ocean (24–29.5°C) and the water at 500–1200 m depth (7-3.5°C) as the source and sink for a Rankine cycle system to generate electric power. An annual average ΔT near 24°C is available to grazing tropical OTEC plants. The resource is tremendous in terms of suitable ocean siting areas and is available 24 hr per day. It could supply a significant fraction of the world's energy needs in the year 2000. The first commercial plants could be deployed in the mid 1980s, and we believe they will be competitive then with fossil fuel and nuclear energy sources for selected applications. Ammonia (for fertilizers) is a particularly attractive product, because 95 per cent of the ammonia produced in the U.S. is now made from natural gas, our scarcest resource. Direct delivery of electric power to shore may also be competitive for, e.g. the southeastern United States. In the late 1980s or early 1990s, ammonia produced by grazing tropical OTEC plants could also be used as a hydrogen carrier for production of electricity by fuel cells anywhere in the world, and production of other chemicals and metals (aluminum, magnesium) should become attractive. Various OTEC plant-ship concepts, their economics, onboard production plants and some of the environmental considerations are discussed.

Etude des modifications du m�tabolisme respiratoire de populations d'Acartia clausi (Crustacea: Copepoda) apr�s passage dans le circuit de refroidissement d'une centrale thermo-�lectrique

The respiratory metabolism of the copepod Acartia clausi, the most abundant species of zooplankton in the area investigated (Gulf of Fos, Mediterranean Sea, France) was studied at different temperatures during an annual cycle. Copepods were collected from three different stations: first the intake area, where sea water was pumped into the cooling circuit of a power plant; second, the outlet area of this circuit, where the heated effluents were discharged with an average Δt of 6°C; third, a small protected bay directly influenced by the flow of the heated waters. Seasonal variations in respiration intensity were observed, with a spring maximum. Specimens collected from the heated effluents exhibited comparatively reduced metabolism. Q10 varied with temperature and time of year, suggesting seasonal regulation of metabolism. Except in March, where metabolic curves differed markedly according to the origin of the sample (species from the heated effluents displaying a metabolic curve of the summer type), the principal difference in shape of the respiration-temperature curves appeared in the range of 10° to 14°C, where reduced respiration was observed in specimens from the heated effluents. When A. clausi from external areas were exposed to artificial thermal stress, they displayed a respiratory metabolism pattern similar to that of specimens sampled from the heated effluents. Experiments performed with warm-acclimated copepods revealed respiratory modifications similar to those observed in copepods from the heated effluent. These results are discussed in relation to the thermal conditions prevailing at the investigated site.

Effect of changing reagent energy on reaction probability and product energy-distribution

Experiment and theory have been used to ascertain the effect of various forms of reagent energy on the dynamics of three reactions; (a) F + HCl → HF + Cl, (b) F + D2→ DF + D and (c) H + Cl2→ HCl + Cl. The principal experimental technique was the arrested relaxation form of the infra-red chemiluminescence method, coupled with a quite wide variation in the temperature of the atomic or the molecular reagent. In addition, a novel approach was employed in which the “fluorescence depletion” of specified vibrational-rotational (v, J) states was measured, and hence the relative rate of reaction of these quantum states was obtained. The theoretical technique was the 3D classical trajectory method using LEPS (London, Eyring, Polanyi, Sato) potential-energy hypersurfaces. Some support was obtained from experiment and theory for the following generalisations. (1)ΔT and ΔV enhance the reaction rate-constant, but the former is more effective for these substantially-exothermic reactions. (ΔT and ΔV denote reagent translation and vibration enhancements, in excess of the activation-barrier). (2) On the average ΔT→ΔT′+ΔR′(the primed energies refer to reaction products; ΔR′ is enhancement in product rotational energy). (3) On the average ΔV→ΔV′. (1)–(3) are in accord with findings from earlier trajectory studies. The effect of substantial increase in collision-energy can be understood in terms of a contribution from “induced repulsive energy-release”, and that of increased reagent vibrational energy in terms of both induced repulsive energy-release and (more important)“induced attractive energy-release”. For the reaction F + HCl the increase in rate constant with reagent vibrational quantum number, k(v), was obtained for ν= 0–2, experimentally and theoretically. The fluorescence-depletion method was used for a preliminary measurement of the rotational dependence of reaction rate, k(J), in F + HCl(ν= 1). An estimate was obtained for the variation in threshold collision-energy, Ev′J′0, with the v′J′ state being formed in the reaction F + HCl(v= 0).