Temperature-dependent Processes Research Articles

Origin of annual laminations in tufa deposits, southwest Japan

Laminated tufas and a tufa-depositing stream in SW Japan (Shirokawa, Ehime Prefecture) were studied monthly over a 3-yr period. A series of samples from the tufa clearly reveals the pattern of annual laminations. The annual layering pattern was primarily controlled by changes in the rate of calcite precipitation, as calculated from water chemistry. The concentration of dissolved CaCO 3, which correlates with the precipitation rate, was high in summer–autumn and low in winter–spring, owing to changes in the partial pressure of CO 2 in underground air. Regular seasonal changes in underground PCO 2 probably resulted from two temperature-dependent processes, the diffusion of soil CO 2 and the ventilation of underground air. These changes, in addition to water temperature changes, altered the precipitation rate, which has a clear seasonal pattern, especially in the lower stream. The seasonal precipitation rate was high in summer–autumn and low in winter–spring, which is consistent with the seasonal lamination pattern seen in the tufas. The textures of collected samples show that the laminations consist of densely calcified summer–autumn (June–October) laminae and lightly calcified winter–spring (November–May) laminae. We infer that the increased precipitation rate stimulated thick calcite encrustation on cyanobacterial filaments to produce the dense textures. This interpretation is supported by the lowered organic/inorganic carbon-production ratio in summer–autumn. Seasonal variations in cyanobacterial assemblages are present, but do not reflect the seasonal lamination pattern. Because the relevant processes are temperature dependent, the seasonal lamination pattern at Shirokawa is thought to generally apply to other laminated tufas deposited in temperate climates. However, a reversed pattern can result from local and climatic circumstances. Dense laminae were deposited in winter near the source of the spring at Shirokawa, because calcite precipitation was high owing to low underground PCO 2 in winter. Reversed patterns reported from northwestern Europe were probably influenced by seasonal rainfall, which is reflected in hydrological conditions.

A Simple Statistical Mechanical Model of Water

We introduce a statistical mechanical model for the physical properties of water. Each water molecule is a two-dimensional disk with three radial hydrogen-bonding arms. Energetic interactions are based on water triplets, a central water molecule interacting with two neighbors via hydrogen bonds, van der Waals attractions, and steric repulsions. Interactions with more distant molecules are treated in a mean-field way. Each molecular triplet can be in one of three energy levels: cage-like hydrogen-bonded structures, denser nonbonded structures, and expanded structures with no near-neighbor interactions. The model predicts water's thermodynamic anomalies, including maxima in density, minima in isothermal compressibility and heat capacity, and expansion upon freezing at low pressure. It predicts the main features of water's phase diagram, including multiple crystalline phases and the proposed liquid−liquid transition in supercooled water. Also, it captures qualitatively the fragile-to-strong transition in the liquid's temperature-dependent relaxation processes. This model is intended to give simple insights into the microscopic origins of water's distinctive physical properties.

Effect of temperature on synaptic transmission between identified neurones of the mollusc Lymnaea stagnalis

The mollusc, Lymnaea stagnalis, has been used as a model to study the mechanisms of temperature-dependent processes in the central nervous system. Effects of temperature changes on transmission in monosynaptic connections, made by the FMRFamide-containing neurone VD4 and the giant dopaminergic neurone RPeD1 with follower neurones, were recorded with intracellular microelectrodes. In the temperature range of 4–6°C, inhibitory postsynaptic potentials (IPSP) in response to VD4 stimulation were not observed in postsynaptic cells while the IPSPs persisted in the RPeD1 followers. A temperature rise resulted in a sharp increase in the IPSP amplitude in followers of both VD4 and RPeD1. In isolated nervous systems taken from molluscs which have been kept at 4–6°C for 2 weeks and more, no coupling between VD4, RPeD1 and synaptically connected cells was seen in the full experimental temperature range. The synaptic coupling recovered only after maintaining the molluscs at a water temperature of 14–16°C for at least 2 days. The changes observed in synaptic responses to temperature alterations correspond to the behaviour of the molluscs.

On the capacity fading of LiCoO 2 intercalation electrodes: : the effect of cycling, storage, temperature, and surface film forming additives

The electrochemical behavior and surface chemistry of LiCoO 2 intercalation cathodes as a function of cycling and storage at 25, 45, and 60 °C was studied. The standard solutions for this work comprised ethylene carbonate (EC), ethyl-methyl carbonate (EMC), (1:2) and 1 M LiPF 6. The effect of two surface film-forming additives, vinylene carbonate (VC) and an organo-borate complex (denoted as Merck's AD25) in solutions was also explored. We analyzed temperature-dependent processes of surface film formation on the cathodes, which increase their impedance upon cycling and storage, thus making their electrochemical kinetics sluggish. We also analyzed cobalt dissolution from the cathodes at 25, 45 and 60 °C. The apparent capacity fading of the LiCoO 2 electrodes is attributed mostly to changes on their surface, rather than to bulk degradation. There are signs that the presence of HF in solutions may play a major negative role. Hence, as the electrode's surface/solution volume ratio is higher, the capacity fading of the LiCoO 2 electrodes should be lower. The main tools for this study were cyclic voltammetry, chronopotentiometry, impedance spectroscopy, electrochemical quartz crystal microbalance (EQCM), IR-spectroscopy, XRD, XPS, and SEM.

Temperature dependence of the optically induced production and annealing of silicon dangling bonds in hydrogenated amorphous silicon

In hydrogenated amorphous silicon the kinetics of the optically induced production and thermal annealing of silicon dangling bonds have been measured at temperatures between 25 and 480 K using electron spin resonance (ESR). Below about 150 K the measurement of optically induced silicon dangling bonds is masked by long-lived, band-tail carriers that accumulate with time t as ${t}^{1/3}.$ It is known that these long-lived carriers can be quenched by infrared light. However, optically, it is not possible to completely remove them. The production rate for optically induced silicon dangling bonds decreases with decreasing temperature. Below about 100 K degradation is at most half as efficient as at room temperature and is nearly temperature independent below approximately 100 K. Additionally, defects created by 10 h of irradiation below 100 K almost entirely anneal at $T\ensuremath{\cong}300\mathrm{K}.$ It is common procedure to anneal a-Si:H samples for 30 min at 175 \ifmmode^\circ\else\textdegree\fi{}C to restore the as-deposited defect density. However, by repeatedly performing degradation and annealing cycles we find that a small fraction of defects is not restored by annealing at 175 \ifmmode^\circ\else\textdegree\fi{}C and that these defects slowly accumulate with degradation. For defects created at all temperatures we find the same ESR fingerprint, indicating that only one dominant type of defect is created, presumably the silicon dangling bond, and we conclude that different, temperature-dependent stabilization processes must exist. These results lead to new constraints for models that attempt to explain the Staebler-Wronski effect.

Cirrus Cloud Ice Water Content Radar Algorithm Evaluation Using an Explicit Cloud Microphysical Model

Abstract A series of cirrus cloud simulations performed using a model with explicit cloud microphysics is applied to testing ice water content retrieval algorithms based on millimeter-wave radar reflectivity measurements. The simulated ice particle size spectra over a 12-h growth/dissipation life cycle are converted to equivalent radar reflectivity factors Ze and visible optical extinction coefficients σ, which are used as a test dataset to intercompare the results of various algorithms. This approach shows that radar Ze-only approaches suffer from significant problems related to basic temperature-dependent cirrus cloud processes, although most algorithms work well under limited conditions (presumably similar to those of the empirical datasets from which each was derived). However, when lidar or radiometric measurements of σ or cloud optical depth are used to constrain the radar data, excellent agreement with the modeled contents can be achieved under the conditions simulated. Implications for the satelli...

Release of snRNP and RNA from Transcription Sites in Adenovirus-Infected Cells

Small nuclear ribonucleoprotein (snRNP) splicing factors colocalize with nascent RNA in the nucleus of adenovirus-infected cells in a pattern that appears as a series of rings surrounding viral replication centers. We have studied the release of snRNP and RNA from transcription sites following transcription inhibition by actinomycin D. SnRNP, poly(A) RNA, and viral RNA were no longer detected in the ring pattern following transcription inhibition and were instead detected in nuclear clusters. Release of snRNP from transcription sites was blocked when transcription was inhibited at 4°C, suggesting that release requires temperature-dependent processes. Release of snRNP was also inhibited when transcription was blocked in the presence of 9-β-D-arabinofuranosyladenine, to inhibit 3′-end cleavage and polyadenylation, or staurosporine, to inhibit kinases. By contrast, release of snRNP was not inhibited when transcription was blocked in the presence of cordycepin, to inhibit RNA polyadenylation without affecting 3′-end cleavage, or okadaic acid, to inhibit phosphatase activity. Our results suggest that temperature-dependent processes involved in the release of splicing factors from transcription sites could include 3′-end cleavage of pre-mRNA and phosphorylation events inhibited by stauropsorine.

Infrared thermography in the quality assurance of manufacturing systems

The present work will focus its attention on the aid provided by infrared thermography (IR) in the evolution of manufacturing towards the achievement of highest quality at the lowest price; which is to say: improve manufacturing processes and avoid waste of time. IR can be fruitfully exploited to monitor temperature variations in-process in temperature-dependent manufacturing processes. It is possible to control efficiency of cooling systems in-processes involving material shaping like extrusion and injection moulding. It is also possible to control the temperature rises which can affect the integrity of components and life of tools in material removal processes involving cut, mill, drill. IR is also attractive for non-destructive inspection of end products to assure quality. Experimental tests are carried out to control temperature rises during mill finish, to visualize material inhomogeneities linked to extrusion or injection moulding processes, inclusions of spurious materials during welding or bonding processes and to determine variations of adhesive thickness in metallic joints and composites. Results, presented and discussed here, prove the possibility of using IR as a tool of quality assurance of manufacturing systems.

NITROGEN OXIDE TRACE GAS TRANSPORT AND TRANSFORMATION: II. MODEL SIMULATIONS COMPARED WITH DATA

The development of process-based models describing N oxide trace gas emissions from agricultural soils will assist in the assessment of pre- sent sources, prediction of future trends, and development of mitigation strategies. We compare the predictions of a transport and transformation model with data from intact soil core experiments and then use the model to evaluate the relative importance of individual processes after application of anhydrous ammonia to moderately acidic soil. Soil-gas concentrations of NO and N2O are adequately described using previously obtained kinetic expressions. Net NO surface fluxes are shown to be the result of high rates of subsurface gross NO production (>100 mg N m � 2 h � 1 ) balanced by gross consumption rates equivalent to 92-97% of gross production. The overall temperature dependency of NO emissions is de- scribed adequately as the net result of individual temperature-dependent processes. Denitrification was estimated to contribute only 8-14% of the total N2O source under primarily aerobic conditions, with the balance caused by abiotic nitrous acid decomposition. The bulk soil reactivity of NO2 was estimated to be at least 500 times greater than the reactivity of NO. The potential for nonbiological nitrate formation is examined, and the effectiveness of pH control and subsurface fertilizer injection for min- imizing gas losses are evaluated. (Soil Science 2002;167:49-61)

Field estimations of temperature-dependent processes: case growth of young burbot

In this study, the growth of young burbot (Lota lota) was temperature-dependent, but varied between age-groups. The growth of age-0 increased with temperatures 4–18 °C. Growth of age-groups 1 and 2 was not significantly related to surface water temperatures and varied between the 2 years studied. This study was a re-evaluation of burbot sampled between 1978 and 1980 by plankton net, beach seine, and electric fishing in Lake Kuohijarvi, the Finnish Lake District. In the re-evaluation, growth was studied both as mm day−1 and as absolute growth (mm), whereas the original study did not include absolute growth. Though the methods should be equivalent, they are not. In our example, time between measurements, temperature, and growth were negatively correlated. When analysing mm day−1 the estimate variability, therefore, increased with temperature, whereas the variability was homogenously spread on the two axes, growth and degree-day, when analysing absolute growth. Field rate analyses contain an error risk that should be recognised when assessing the temperature-dependency of any processes, e.g. growth or mortality.

Application of a novel resolution approach combining soft- and hard-modelling features to investigate temperature-dependent kinetic processes

A new resolution method based on the combination of hard- and soft-modelling is applied to the analytical study of spectrometrically monitored kinetic processes. This method results from the modification of the iterative soft-modelling multivariate curve resolution-alternating least-squares method (MCR-ALS) by the inclusion of a new hard constraint that forces some or all the concentration profiles to fulfil a kinetic model. In this way, strengths of both soft- and hard-modelling data analysis methods are combined and limitations linked to the application of only one of these pure approaches are overcome. The new method is applied to a real example of cyclometallation reaction. This is a challenging case where the extent of the process changes with temperature and the spectra of the different species formed do not differ extremely from each other. Besides, due to the lability of the initial reagent, the nature and the concentrations of all the reacting components present at the beginning of the process are not always known. The example presented is representative of many other complex kinetic problems, which could not be solved by the use of traditional methods based exclusively on the straightforward fitting of kinetic models.

The effect of temperature on the electron work function of adsorbed europium films on tungsten and silicon surfaces

The temperature dependence of the electron work function ϕ was studied for the clean surfaces of tungsten (textured ribbons with predominant (100) surface orientation) and silicon ((111)-oriented single crystals), as well as for the same substrates covered with adsorbed europium films. It was found that the ϕ value may exhibit significant reversible variations reflecting temperature-dependent atomic and electronic processes occurring on the substrate surface.

Temperature-induced decoupling of phycobilisomes from reaction centers

Temperature-induced decoupling of phycobilisomes (PBSs) from the reaction centers in the PBS-thylakoid membrane complexes was observed at 0°C. The fluorescence yields of photosystem (PS) I and PSII decreased and that of PBSs increased with selective excitation of PBSs at 0°C, while the yield of PBSs decreased and those of the two photosystems increased with selective excitation of chlorophyll a at room temperature (RT). It indicated that the decoupling of PBSs from the two photosystems led to changes of energy transfer efficiencies, which can be explained by partial detachment of PBSs from thylakoid membrane. The temperature-dependent processes were reversible, i.e. with temperature going up to RT, the complexes could restore to the functionally coupled state with a time constant about 30 s. Based on these results, it could be deduced that PBSs should be in parallel connection with the two photosystems.

Concurrent Multiscale Modeling of Embedded Nanomechanics

ABSTRACTWe discuss concurrent multiscale simulations of dynamic and temperature-dependent processes found in nanomechanical systems coupled to larger scale surroundings. We focus on the behavior of sub-micron Micro-Electro-Mechanical Systems (MEMS), especially micro-resonators. The coupling of length scales methodology we have developed for MEMS employs an atomistic description of small but key regions of the system, consisting of millions of atoms, coupled concurrently to a finite element model of the periphery. The result is a model that accurately describes the behavior of the mechanical components of MEMS down to the atomic scale. This paper reviews some of the general issues involved in concurrent multiscale simulation, extends the methodology to metallic systems and describes how it has been used to identify atomistic effects in sub-micron resonators.

Diapause in the gypsy moth: a model of inhibition and development

We present here the first recorded age-specific estimates of the developmental response to temperature in diapausing gypsy moth, Lymantria dispar (L.). The effect of temperature on diapause development in gypsy moth eggs was examined by exposing individual eggs to temperature regimes of 5°C interrupted by a single, brief exposure to an experimental temperature. Exposure to each of six experimental temperatures took place at six different times during diapause. The relative effect of the exposure on diapause development was estimated by comparing the duration of diapause in each of the treatments to the duration in a control treatment of constant 5°C. The effect of each temperature did not remain constant throughout the diapause phase and the pattern of change was not uniform among the experimental temperatures. We propose a model of diapause where the developmental phase is controlled by two simultaneous temperature-dependent processes: a typical developmental response to temperature that is inhibited by a temperature-activated biochemical agent, and the temperature-dependent removal of the inhibiting agent. This simple model of two simultaneous and temperature-dependent processes explains 92% of the variability in diapause duration observed in the experimental regimes.

Temperature-dependent carrier trapping processes in short period quantum wire superlattices grown by flow rate modulation epitaxy

We report the first systematic investigation of the temperature-dependent carrier transferring processes of very short period V-grooved GaAs/AlGaAs quantum wire superlattice structures grown by flow rate-modulated metal-organic vapor phase epitaxy. The one monolayer (1 ML) fluctuation causes carrier confinement in sidewall (111) facet superlattice structures, and is shown to play an important role in the carrier transferring process. At low temperatures, the carrier transfer is blocked by the barriers of 1 ML fluctuation, while at high temperatures the carrier transfer from (111) superlattice to the wire region is shown to be very efficient after thermally overcoming the barriers. The temperature-dependent decay times of the different parts give direct evidence of the carrier transferring process, which demonstrates that the carriers can trap into the wire region within 50 ps at temperatures higher than 100 K.

Mechanisms of Fatigue in Cemented Carbides at Elevated Temperatures

Cemented carbides are mainly used as cutting tools in various fields of application. In nearly all industrial uses they have to resist wear and concurrent complex thermomechanical loading, often including alternating mechanical loads at high temperatures. It has been shown that cemented carbides suffer lifetime-limiting fatigue under cyclic loads at 25 °C caused by subcritical crack growth. Present investigations show that strong, temperature-dependent fatigue effects occur in cemented carbides at elevated temperatures. TEM investigations revealed temperature-dependent processes that are responsible for the changes in the fatigue behavior: at low temperatures a phase transformation of the Co-binder phase and at higher temperatures oxidation in the cracks and brittle–ductile transitions of cubic carbides.

Mechanisms of Fatigue in Cemented Carbides at Elevated Temperatures

Cemented carbides are mainly used as cutting tools in various fields of application. In nearly all industrial uses they have to resist wear and concurrent complex thermomechanical loading, often including alternating mechanical loads at high temperatures. It has been shown that cemented carbides suffer lifetime-limiting fatigue under cyclic loads at 25 °C caused by subcritical crack growth. Present investigations show that strong, temperature-dependent fatigue effects occur in cemented carbides at elevated temperatures. TEM investigations revealed temperature-dependent processes that are responsible for the changes in the fatigue behavior: at low temperatures a phase transformation of the Co-binder phase and at higher temperatures oxidation in the cracks and brittle–ductile transitions of cubic carbides.

Thermotolerant fungi erroneously reported in applied research work as possessing thermophilic attributes

In applied research work dealing with heat-tolerant fungi, currently classified into two groups: namely thermotolerants and thermophiles, information on levels of thermotolerance is generally scant. Cited binomials are often referred to as representatives of thermophilic taxa. The present contribution attempts to specify proper heat-tolerance levels of species cited in biotechnological papers of academic and applied research types published in the last four decades. This assessment integrates relevant available information concerning well defined thermotolerant taxa. Distinction between both groups of heat-tolerant fungi is a mean to optimize investigations of temperature-dependent physiological processes. The nomenclatural status of the binomials retrieved was also re-appraised following the International Code of Botanical Nomenclature. Articles of the code govern the legal validity of fungal names. The goal is to deter `ghost names' that have no status of any kind. Their use in the literature is not only a source of confusion but also hinders the preparation of sound reviews and reference documents. The intention was also to detect names which do not fulfill all criteria for a valid legal publication. Their status could then be validated if the taxonomic position of the fungus justifies this procedure. The taxonomic status of these thermotolerants was also re-examined following present-day knowledge of their respective genera. Integration of warranted taxonomic decisions in the literature of applied research is crucial. These decisions consider the status of a fungus as a valid species (proposed synonymies) or the nature of its generic affinities (name change). Strict application of these decisions severly reduces levels of heterogeneity regarding names used for the same organism. It also clarifies its generic affinities with other thermotolerant fungi. The present note is not an exhaustive assessment on the nomenclatural and taxonomic positions of known thermotolerant fungi, an ecological group for which a global document remains to be produced. It only deals with those taxa most commonly cited in the literature examined. Over 130 fungi are here considered. The group manifests a diversity of taxonomic characters since it includes members of the following systematic groupings: Oomycetes, Zygomycetes, Ascomycetes, anamorphic fungi and Holobasidiomycetes. Few new taxonomic synonyms and invalid binomials are introduced in the present contribution. The former concern the following taxa: Gilmaniella thermophila, Mucor thermoaerospora, Sporotrichum lignicola and Zalerion thermophylii. Three binomials proved to have no taxonomic status of any sort: Acremonium cellulophilum, Nodulisporium microsporum and N. thermoroseum.

Occurrence of C 10–C 13 polychlorinated n-alkanes in the atmosphere of the United Kingdom

Short-chain (C 10–C 13) polychlorinated n-alkanes (PCAs) have been measured in the air in the United Kingdom at 2 week intervals over a period of 12 months. The mean concentration of PCAs over the sampling period was 320±320 pg m −3 (arithmetic mean±1 S.D.) with a geometric mean of 160 pg m −3. Hexa- and hepta-chlorinated dodecane congeners are the predominant PCA components in the UK atmosphere. Analyses of gas phase and particulate phase PCAs indicate that 95% of the PCA content of the atmosphere is in the gas phase. No seasonal trend or dependence on temperature was observed. The data can be divided into 2 significantly different ( P<0.01) populations: one group of incidences of lower concentrations of 150±110 pg m −3 and one of higher concentrations of 800±170 pg m −3. The incidences of elevated concentrations could not be related to increased air temperature or other meteorological factors on the time-scale employed and suggest that atmospheric PCA concentrations in the UK may be dominated by episodic incidences of advective transport of contaminated air masses and/or releases to the environment from regional primary point sources rather than by temperature-dependent transport processes. Levels of PCAs in the UK atmosphere are similar to values obtained at a semi-rural location in Canada and at least an order of magnitude higher than in the Canadian Arctic atmosphere. These data represent the first detailed study on the occurrence of PCAs in the atmosphere and show that PCAs can be a major component of the persistent organic pollutant burden of the atmosphere which has the potential of undergoing long-range atmospheric transport processes.