High-temperature Increments Research Articles

Highly Efficient Photothermal Icephobic/de-Icing MOF-Based Micro and Nanostructured Surface.

Photothermal materials have gained considerable attention in the field of anti-/de-icing due to its environmental friendliness and energy saving. However, it is always significantly challenging to obtain solar thermal materials with hierarchical structure and simultaneously demonstrate both the ultra-long icing delay ability and the superior photothermal de-icing ability. Here, a photothermal icephobic MOF-based micro and nanostructure surface (MOF-MNS) is presented, which consists of micron groove structure and fluorinated MOF nanowhiskers. The optimal MOF-M250 NS can achieve solar absorption of over 98% and produce a high temperature increment of 65.5°C under 1-sun illumination. Such superior photothermal-conversion mechanism of MOF-M250 NS is elucidated in depth. In addition, the MOF-M250 NS generates an ultra-long icing delay time of ≈3960 s at -18°C without solar illumination, achieving the longest delay time, which isn't reported before. Due to its excellent solar-to-heat conversation ability, accumulated ice and frost on MOF-M250 NS can be rapidly melted within 720 s under 1-sun illumination and it also holds a high de-icing rate of 5.8kg m-2 h-1 . MOF-M250 NS possesses the versatility of mechanical robustness, chemical stability, and low temperature self-cleaning, which can synergistically reinforce the usage of icephobic surfaces in harsh conditions.

Effects of State-of-Charge and Penetration Location on Variations in Temperature and Terminal Voltage of a Lithium-Ion Battery Cell during Penetration Tests

The nail penetration test has been widely adopted as a battery safety test for reproducing internal short-circuits. In this paper, the effects of cell initial State-of-Charge (SOC) and penetration location on variations in cell temperature and terminal voltage during penetration tests are investigated. Three different initial SOCs (10%, 50%, and 90%) and three different penetration locations (one is at the center of the cell, the other two are close to the edge of the cell) are used in the tests. Once the steel cone starts to penetrate the cell, the cell terminal voltage starts to drop due to the internal short-circuit. The penetration tests with higher initial cell SOCs have larger cell surface temperature increases during the tests. Also, the penetration location always has the highest temperature increment during all penetration tests, which means the heat source is always at the penetration location. The absolute temperature increment at the penetration location is always higher when the penetration is close to the edge of the cell, compared to when the penetration is at the center of the cell. The heat generated at the edges of the cell is more difficult to dissipate. Additionally, a battery cell internal short-circuit model with different penetration locations is built in ANSYS Fluent, based on the specifications and experimental data of the tested battery cells. The model is validated with an acceptable discrepancy range by using the experimental data. Simulated data shows that the temperature gradually reduces from penetration locations to their surroundings. The gradients of the temperature distributions are much larger closer to the penetration locations. Overall, this paper provides detailed information on the temperature and terminal voltage variations of a lithium-ion polymer battery cell with large capacity and high power under penetration tests. The presented information can be used for assessing the safety of the onboard battery pack of electric vehicles.

Synthesis, characterization and photothermal conversion performance of three xanthene-functionalized dicopper complexes

For further elucidating the molecular absorption mechanisms in the photothermal conversion performance, three xanthene-functionalized dicopper coordination compounds have been isolated and structurally characterized by IR, Powder XRD, Solid-state UV, and TGA. They were prepared by solvothermal treatment the mixture of 9H-xanthene-9-carboxylic acid with Cu(CH3CN)4BF4 with/without the assistance of the auxiliary ligands {2,2′-bipyridine (bpy) or bis(diphenylphosphino)methane (dppm)}, namely, [Cu2(X9A)4(CH3CN)2] (1, X9A = xanthene-9-carboxylate), {[Cu2(X9A)(dppm)2(CH3CN)](BF4)∙(CH3CN)} (2), and {[Cu2(X9A)3(bpy)2](BF4)∙0.5(H2O)}2 (3). Single-crystal X-ray structural analysis and mass spectra revealed that the copper atoms in 2 were Cu(I), while in 1 and 3 were Cu(II) coordination compounds. The X9A ligands arranged in two types of coordination modes in 3: one in a bidentate bridging mode (μ2-η1, η1 mode) and two in an arrangement involving chelation and bridging mode (μ2-η1, η2 mode), while only simple bridging mode presented in 1 and 2. With the further stabilization of bpy ligands, compound 3 displayed excellent thermal stability, superior absorption ability as well as the best photothermal conversion performance (the highest temperature increment ~ 19 ℃ and equilibrium temperature ~ 32 ℃).

Synthesis, crystal structures and photo-thermal properties of five naphthyl-functionalized Copper(II) coordination compounds

For achieving solar absorber and conversion molecular materials with excellent photothermal conversion ability, five mononuclear Copper(II) coordination compounds have been designed and isolated. They are fully characterized by IR, Powder XRD, Solid-state UV, and TGA. Single-crystal X-ray structural analysis reveals that they are typical photothermal conversion molecules with double chromophores: one antenna chromophore (NT group here) and the second chromophores (Cu(dmap)42+, Cu(dmap)22+, Cu(bpy)22+ and Cu(phen)22+). Both chromophores have great influence on their solid-state optical absorption. Their photothermal conversion experiments show that compounds 3, 4 and 5 have the better results (the highest temperature increment 21.7 ℃ and equilibrium temperature ~ 60.7 ℃) than compounds 1 and 2. Those results give some clues for illustrating the molecular mechanisms of solar absorber and photothermal conversion molecular materials.

Target design and synthesis of three naphthyl-functionalized Copper(II) coordination compounds for their photothermal properties

In order to achieve a light-harvesting system with excellent photo-thermal conversion property, three naphthyl(NT)-functionalized Copper(II) coordination compounds have been designed and isolated. They are characterized by IR, Powder XRD, UV, and TGA. Single-crystal X-ray structural analysis reveals that {[Cu4(bpy)4(1-NTAA)5](BF4)3∙3(CH3OH)∙H2O}∞ (1) has 1D chain structure, {[Cu2(1-NTAA)4(CH3CN)2]∙2(CH3CN)} (2) and {[Cu2(2-NTA)4(CH3CN)2]∙2.5(CH3CN)} (3) have similar paddle-wheel structures. Utilizing the introduction of NT-groups into copper(II) centers, all three compounds exhibit good solid-state optical absorption in a nearly full solar spectral region. The coordination polymer 1 exhibits the quickest temperature rising (nearly 2 ℃/min from the very beginning), the highest temperature increment (12 ℃) and equilibrium temperature (40 ℃) over the other two compounds in the photothermal conversion experiments. Those results point out the direction of molecular design for enhancing photothermal conversion performance.

Numerical modeling of laser-induced heating effect in optical thermometry

The laser-induced heating effect leads to obvious inaccuracy in optical thermometry, since this heating effect adjusts the fluorescence intensity ratio from two adjacent thermally coupled energy levels, and is difficult to measure with some equipment. It is necessary to accurately evaluate this heating effect and understand its formation mechanism. To overcome this problem, a 3D heat transfer model was developed by using finite element methods. Three physical processes are considered in this work: energy absorption from CW or pulsed lasers, heat conduction inside the matrix materials and heat transfer to the ambient air. It was found that the heating effect induced by lasers is dependent on the pump power and the spot radii of the lasers. Higher laser power and a narrower laser spot led to greater heat energy, resulting in higher temperatures. A fairly high temperature increment of 25.60 K was observed when a CW laser was used as an excitation source. The excitation modes of the laser also affect the heating effect. The thermal effect was suppressed by using a pulsed laser due to its shorter interaction time; however, it still cannot be ignored in the application of optical temperature sensors.

Eclectic and economical synthesis, characterization of Li–Ba–Zn magnetic nanostructured mixed ferrites

Augmentation in magnetic and dielectric properties of Li0.25Ba0.5-XZnXFe2.25O4 (where X = 0–0.5) suggest the effectiveness of barium doped in lower concentrations in lithium–zinc nanoferrites synthesized by solution combustion route. Different instrumental techniques have been employed to characterize their phase, size, and structural properties. X-ray diffraction analysis indicated that lithium–barium–zinc nanoferrites crystallize in the cubic spinel single phase with lattice parameter ~8.60 A, while high-resolution transmission electron microscopic studies demonstrated the formation of cubic, uniformity, and crystalline nanoferrites. Mossbauer and magnetic parameters revealed the stability and magnetic character of doped ions with the phase transition from ferrimagnetism to superparamagnetism. Dielectric parameters as a function of frequency (100 Hz–5 MHz) and temperature (~500 °C) have also been studied which exhibited low dielectric losses as compared with other ferrite materials synthesized by conventional methods. This low loss values make these materials to be applicable in nanoelectronic devices and new generation wireless communication systems that can even work at high frequencies with derived high-temperature increments.

Quantifying long-term variability of precipitation and temperature over Zambia

A cursory or even detailed inspection of literature shows that while the annual cycle of precipitation and temperature in Zambia are well understood, there is a general lack of documentation on long term trends and periodicities over the country. In this study, we extensively examined the temporal and spatial changes in precipitation and temperature over Zambia for the period 1950–2016. We used the modified Mann–Kendall (m-MK) test with the aim of eliminating the effect of autocorrelation on precipitation and temperature trends based on Global Precipitation Climatology Centre (GPCC) and National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) products. Overall, significant decrease (increase) in precipitation (temperature) was evident. We further observed that, on average, precipitation has been decreasing by 1.1 mm yr−1. The highest drying rate was observed recently in the 2010s with a decrease of −24.4 mm/year. An abrupt change in the trend of precipitation was reported in 1980/1981 significant at 5% significance level. The highest amount in mean annual rainfall was 1093.5 mm reported in the 1960s while the lowest (966.4 mm) was reported in the 1990s. During the core of the rainy season, the western and southern provinces of the country are observed to generally experience negative rainfall anomalies implying more precipitation deficits in these areas. Temperature has been observed to be on the rise since the 1980s and no sudden changes have been observed in its trend over the country. Results further indicate that temperature has been increasing at a rate of 0.01 °C yr−1. The highest temperature increment (0.08 °C yr−1) was observed in the 2000s. Spatial analyses showed that temperature anomalies were positive across the whole country with higher anomalies being manifested in the 2000s and 2010s especially across North-eastern areas of the country. Findings embodied in this work provide a strong foundation for future climate monitoring and for studies that focus on examining extreme weather phenomena over Zambia.

Interaction mechanism between shock waves and supersonic film cooling with cracking reaction

In order to understand the interaction mechanism between shock waves and supersonic film cooling with cracking reaction, supersonic film cooling using gaseous hydrocarbon fuel as coolant in terms of cracking reaction of the coolant, with and without shock waves interaction, is investigated numerically. Theoretically, cracking reaction may be accelerated by the shock wave interaction, which may enhance the mixing of the coolant and absorb heat, which will lead to contradictory effects on supersonic film cooling. However, it turns out that, with shock waves interaction, cracking reaction only absorbs more heat but barely has any effect on the mixing either locally or further downstream due to the momentum change caused by the reaction is extremely small and the energy change plays the dominate role. It is worth mentioning that oblique shock wave causes energy accumulation in the shock wave interaction region, which deteriorates supersonic film cooling. However, with the cracking reaction considered, the negative effect brings by the oblique shock wave is weakened by the cracking reaction due to the increment of chemical heat absorption caused by the energy change. It is found that the absolute temperature in the shock wave interaction and the relative temperature increment caused by the shock wave interaction to be the decisive factors of the chemical heat absorption increment, especially for high absolute temperature or relative temperature increments, and the effect of the local reactant concentration plays the dominant role. Furthermore, the extent of weakened chemical reaction on the negative effect due to the oblique shock wave depends not only on the chemical heat absorption but also on the local absolute temperature.

A hyperelastic-thermoviscoplastic constitutive model for semi-crystalline polymers: Application to PEEK under dynamic loading conditions

In this work, a hyperelastic-thermoviscoplastic constitutive model including thermomechanical coupling is presented to predict the mechanical behavior of semi-crystalline polymers. The constitutive model is based on the original approach developed by Polanco-Loria and coauthors (2010) and it accounts for: material hardening due to strain rate sensitivity, temperature evolution during the deformation process due to heat generation induced by plastic dissipation, thermal softening and thermal expansion of the material. The parameters of the constitutive model have been identified for polyether-ether-ketone (PEEK) from experimental data published by Rae and coauthors (2007). In order to analyze the predictive capacity of the model under dynamic conditions, the constitutive model has been implemented in a FE code within a large deformation framework to study two different problems: low velocity impact test on PEEK thin plates and dynamic necking on PEEK slender bar. These problems involve large and irreversible deformations, high strain rates and temperature increment due to plastic dissipation. The analysis determines the interplay between strain rate and thermal effects in the material behavior. The constitutive model presented herein reproduces adequately the mechanical behavior of PEEK under different thermal and loading conditions, demonstrating the importance of considering the coupling between temperature and strain rate.

Numerical and Experimental Analyses on the Temperature Distribution in the Dental Implant Preparation Area when Using a Surgical Guide.

During dental implantation, if the temperature within the bone tissue exceeds a critical value, the thermal necrosis of bone cells may take place, inhibiting osseointegration. In contrast to conventional dental implant surgery, a surgery guided by a surgical template is a safer and more efficient technique; however, the temperature within the implant field is more difficult to control, because the surgical guide blocks irrigation water. The purpose of this study was to investigate the temperature distribution in the drilling site when preparing for dental implant placement with a surgical guide, and to derive suggestions for clinical operation. Initially, the sources of heat during drilling were investigated, and theoretical equations were listed. Subsequently, a measurement system using thermocouples was constructed, with which the temperature increments at specific points in the simulated bone samples were recorded during guided drilling with different cooling methods. Based on the equations and data assessed, a thermal simulation model with a finite element method (FEM) was created, and the temperature change of the whole surgical field was calculated on the basis of the numerical simulation results. Consequently, the point experiencing the highest temperature within the bone was determined. From the experimental measurements, the highest temperature increment was located at a depth of 6 mm without irrigation and at 8 mm with cooling, rather than at the deepest point of the prepared hole. Because the surgical guide blocks the cooling water from entering the drilling site, the biggest increment of temperature using conventional irrigation with the surgical guide was 1.95 times that recorded when using a surgical guide consisting of cooling channels, and 3.6 times that recorded using a drill with an internal cooling hole. And from numerical analysis, during drilling for implant placement site with conventional irrigation, the highest temperature (45.6°C) was close to the critical point at which bone necrosis occurs. Based on theoretical analysis, experimentation, and FEM simulation, the temperature distribution of the drilling area in the placement of dental implants under surgical guide was determined. For clinical operation, improved cooling methods, such as using a drill with an internal cooling channel, should be used, and the drill should be regularly withdrawn during drilling.

Damage evaluation regarding to contact zones of high-speed train wheel subjected to thermal fatigue

Repetitive high frictional forces, induced from braking, and running of a train during railway service, generate high frictional temperature increment at the contact surface, as a result, thermal fatigue damage occurs at the surface of the wheel. Microscopic deformation in the wheel surface due to repetitive fatigue damage causes an initiation and propagation of thermal crack. That is, if the microscopic deformation is accumulated beyond the tolerance of the material resistances including the hardening of material and residual stress, then the surface will be damaged and fractured. As a result, the derailment of railway vehicle may possibly happen.In the present paper, we study on the failure analyses at the tread of the thermally damaged wheel by doing the metallurgical transformation analysis, hardness analysis, and the residual stress analysis to understand the failure mechanism of thermal fatigue damaged wheel. For this purpose, the microstructure of tread surface was examined by applying non-destructive replication method, and the hardness along the tread surface was measured. Also, the change in residual stress in the tread surface of new and thermal-damaged wheels was investigated. Meanwhile, FE analyses were performed considering the heat treatment process of wheel manufacturing, and the braking process during railway service. From the analysis results, we understand that the degree of metallurgical transformation is not the same even in the same tread surface, and residual stress measured turns into tensile stress from the compressive stress in manufacturing in the magnitude of approximately 118MPa in the thermal damaged surface wheel. The finite element analysis (FEA) data of residual stress considering heat treatment process of wheel is in good agreement with the experimental results measured in the wheel tread.

A comparative experimental study of the thermal properties of cricket helmets

Extensive research into heat transfer properties of protective helmets using thermal manikin heads or other headforms has been conducted to date. However, most studies have focused on bicycle, motorcycle and industrial helmets, while literature on cricket helmets remains lacking. This study aimed to evaluate the thermal properties of selected, commercially available cricket helmets, which are widely used in recreational and international cricket games. Comprehensive experiments were conducted in controlled laboratory conditions. The effects of wind were not considered as the wind speed was maintained at <0.8 ± 0.1 ms−1. The average temperature at eight selected locations beneath the helmet shell and liner were continuously measured using k-type thermocouples. Five commercially available cricket helmets were used in this study. The research identified high temperature increments at the frontal and parietal regions of the tested helmets, which indicates that these regions have poor heat dissipation due to lack of ventilation outlets in existing designs. Two forms of heat transfer were investigated: convection and radiation. The total heat transfer from the headform to the surrounding environment decreased by 13–17% when wearing a cricket helmet. Based on the experimental results, several design strategies and features are recommended in order to improve the air ventilation in critical regions of the helmet. Relevance to industryProtective helmets currently used in cricket offer sufficient protection to players against impact. Thermal discomfort is one of the cricket players' main complaints when wearing protective helmets. This article identifies the main hot spots in cricket helmets and presents design strategies for improving heat dissipation and thermal comfort. Some design attributes of industrial helmets of relevance to thermal comfort are discussed in this context.

The thermodynamic functions of 4f metal trichlorides in the condensed state

The experimental low-temperature heat capacity values obtained for some solid 4f metal trichlorides were used to determine trends in the variable parameters of the equation that described the lattice heat capacity component in the quasi-harmonic approximation for the whole series of LnCl3 compounds (Ln = La,..., Lu). The results were used to describe the temperature dependences of the heat capacities over the temperature range from 0 K to melting point Tm. High-temperature enthalpy increment measurements for GdCl3 were used to determine the correction to quasi-harmonic description at T > ∼ 0.5Tm. Phase transition temperatures and enthalpies were selected. A procedure for estimating the heat capacities of liquid LnF3 and LnCl3 was described. The thermodynamic functions of LnCl3 in the condensed state were calculated over the temperature range 298.15–2000 K. The calculations were performed taking into account excited electronic states whose energies did not exceed 10 000 cm−1.

Internal dynamics of a paleoaccretionary wedge: insights from combined isotope tectonochronology and sandbox modelling of the South-Central Chilean forearc

Forearc accretionary wedges are cyclic systems in which material is frontally and/or basally accreted. Material cycling involves underthrusting, subduction, underplating, exhumation, erosion, transfer to the trench and underthrusting again. In this study we present a novel, tectonochronologic approach to constrain long-term exhumation rates of basally accreted wedge complexes, based on isotopic dating of structural features, on petrological data and sandbox analogue simulations. Congruence between the structural inventory in nature and structures generated in scaled sandbox experiments allows detailed insights into wedge dynamics. For the present-day surface material of the paleoaccretionary wedge of South-Central Chile (Valdivia area, 40°S), published U–Pb ages of detrital zircon place a maximum age of ∼278 Ma for subduction. Prograde metamorphism at transitional greenschist to blueschist facies conditions (420 °C, 8–9 kbar) was immediately followed by progressive penetrative deformation associated with basal accretion, dated at ∼250–245 Ma using Rb/Sr internal mineral isochrons. The accretion process involved duplex tectonics and antiformal stacking, with formation of near-horizontal mylonitic shear zones at around 241 Ma. Continuous basal accretion at depth gave rise to an extensional tectonic regime at higher structural levels. Both semi-ductile, small-scale extensional shear zones and post-kinematic vein mineralizations yield Rb/Sr ages of ∼235 Ma. Tension gashes, representing the latest isotopically dateable stage of structural evolution, were formed at ∼210 Ma, at conditions of ∼230 °C at 1.5–3 kbar, as constrained by fluid inclusion data. Zircon fission track data indicate final cooling to below ∼200 °C at 186±24 Ma. The results suggest continuous basal accretion for at least 50 Ma, with long-term average exhumation rates of 0.6±0.2 mm/a, most probably outbalanced by similar long-term average erosion rates. Changing plate boundary conditions at about 210–200 Ma terminated the accretion process, as evident from a dramatic decrease of exhumation rates at that time. Since then, the paleoaccretionary wedge remained stably in place despite its delicate geotectonic position within the Andean active margin. The tectonochronologic approach complements thermochronologic and geomorphologic methods of exhumation research as it provides direct constraints on mass flux rates even for high-temperature increments of P– T trajectories.

40Ar/39Ar age of the Manson impact structure, Iowa, and correlative impact ejecta in the Crow Creek Member of the Pierre Shale (Upper Cretaceous), South Dakota and Nebraska

A set of 34 laser total-fusion 40 Ar/ 39 Ar analyses of sanidine from a melt layer in crater-fill deposits of the Manson impact structure in Iowa has a weighted-mean age of 74.1 ± 0.1 Ma. This age is about 9.0 m.y. older than 40 Ar/ 39 Ar ages of shocked microcline from the Manson impact structure reported previously by others. The 74.1 Ma age of the sanidine, which is a melt product of Precambrian microcline clasts, indicates that the Manson impact structure played no part in the Cretaceous-Tertiary (K-T) mass extinction at 64.5 Ma. Moreover, incremental-heating 40 Ar/ 39 Ar ages of the sanidine show that it is essentially free of excess 40 Ar and has not been influenced by postcrystallization heating or alteration. An age spectrum of the matrix of the melt layer shows effects of 39 Ar recoil, including older ages in the low-temperature increments and younger ages in the high-temperature increments. At 17 places in eastern South Dakota and Nebraska, shocked quartz and feldspar grains are concentrated in the lower part of the Crow Creek Member of the Pierre Shale (Upper Cretaceous). The grains are largest (3.2 mm) in southeastern South Dakota and decrease in size (0.45 mm) to the northwest, consistent with the idea that the Manson impact structure was their source. The ubiquitous presence of shocked grains concentrated in a thin calcarenite at the base of the Crow Creek Member suggests it is an event bed recording an instant of geologic time. Ammonites below and above the Crow Creek Member limit its age to the zone of Didymoceras nebrascense of earliest late Campanian age. Plagioclase from a bentonite bed in this zone in Colorado has a 40 Ar/ 39 Ar age of 74.1 ± 0.1 Ma commensurate with our sanidine age of 74.1 Ma for the Manson impact structure. 40 Ar/ 39 Ar ages of bentonite beds below and above the Crow Creek are consistent with our 74.1 ± 0.1 Ma age for the Manson impact structure and limit its age to the interval ±74.5 0.1 to 73.8 ± 0.1 Ma. Recently, two origins for the Crow Creek have been proposed—eastward transgression of the Late Cretaceous sea and a Manson impact-triggered tsunami. We conclude that most data are in accord with an impact origin for the Crow Creek Member and are at odds with the marine transgression hypothesis.

Cadomian 40 Ar/ 39 Ar apparent age spectra of detrital muscovites from the Eastern Alps

Concentrates of detrital muscovite were prepared from the Bischofalm Quartzite (late Ordovician) exposed in the Southalpine Carnic Alps, Austria. Two size fractions (150–175 pm and 85-100 μm) from two samples display similarly discordant 40 Ar/ 39 Ar age spectra in which apparent ages systematically increase from c. 300 Ma to c. 600 Ma in low-temperature portions of each analysis. Intermediate- and high-temperature increments are characterized by apparent ages of c . 620–645 Ma. Characteristics of the age spectra suggest minor late Palaeozoic, Variscan or combined Variscan/Alpine rejuvenations of argon isotopic systems within detrital grains which originally crystallized within a late Precambrian source terrain. The detrital muscovite ages provide evidence for a Cadomian-age source region for some basement sequences within the Austroalpine/Southalpine sectors of the Eastern Alps. The occurrence of Cadomian-age detritus in the Eastern Alps suggests links with Armorica and other, similarly aged tectonic elements within Alpine chains initiating along northern margins of Gondwana.

The influence of surface roughness texture on the temperature and scuffing in sliding contact

The influence of the surface roughness value and surface roughness texture on temperature and scuffing was experimentally investigated using a machine in which a flat unmoving specimen interacted with a rotating roller. The frictional force and temperature under scuffing conditions were measured. To measure the temperature, a special system based on an IR technique was designed. The IR temperature measurements enabled an estimate of the temperature at micro-contacts between interacting asperities. Based on experimental data, the effect of surface roughness value and texture on scuffing load, surface temperature and power emitted in the contact was shown. Using an asperity deformation model, the forces in asperity contact were calculated. On the assumption that the heat source moves through the semi-infinite body, the temperature in micro-contact was also estimated. Two types of scuffing were observed: first, global scuffing which occurred mainly for transverse roughness; second, local scuffing which occurred mainly for longitudinal roughness. The global scuffing was an unstable process and was caused by exceeding the critical power emitted in the contact. The local scuffing was caused by high temperature increments which appeared between interacting asperities and which caused local melting of the steel surfaces. The IR measurements and the calculations of local temperatures in the micro-contacts between interacted asperities confirmed these hypotheses.

Foliage structure and shoot growth in heathlands in the mediterranean-type climate of southern Australia and South Africa

Three distinct strata (with occasional emergent plants) can be distinguished in heathlands in the mediterranean-type climate of southern Australia and South Africa. 1. The upper stratum is composed of deep-rooted nanophanerophytes (up to 2 m tall) with evergreen, broad sclerophyllous leaves and internodes 2-5 mm long, longer in emergent species. 2. The mid stratum is composed of relatively shallow-rooted nanophanerophytes (0.5-1.5 m tall) with evergreen, narrow semi-sclerophyllous leaves and internodes less than 1 mm long. 3 . The ground stratum contains a mixture of shallow-rooted chamaephytes, with densely -packed, small leaves, and evergreen, sclerophyllous “hemicryptophytes”, with varying numbers of culms/leaves in each clump (depending on the species). During calm, sunny days, the temperature of meristems on foliage shoots of dicotyledons increases above ambient air temperature, the increment being related to the density of packing of leaves on the foliage shoot. The temperature increment of meristems in rush-like, monocotyledonous clumps is related to the density of packing of the culms/leaves in the clump. Those plants with the highest temperature increment at foliage meristems grow during late winter to early spring ; plants with medium packing of foliage grow during spring ; while plants with sparse packing begin foliage growth in late spring through summer. The last group of plants must be deep-rooted to extract water from the deeper layers of the soil during the summer drought of the mediterranean-type climate.

K-Ar and 40Ar/39Ar whole-rock ages of slate/phyllite from allochthonous basement and cover in the tectonic windows of Finnmark, Norway: Evaluating the extent and timing of Caledonian tectonothermal activity

Slate/phyllite samples collected within allochthonous basement rocks (Raipas Super-group) exposed in the Komagfjord and Alfa-Kvaenangen tectonic windows in Finnmark, northern Norway, display variably discordant 40 Ar/ 39 Ar age spectra in which apparent ages systematically increase from ca. 400-425 Ma (recorded at low experimental temperatures) to dates as old as ca. 1750-1800 Ma (in some high-temperature increments). The apparent age variations are not matched by fluctuations in apparent K/Ca ratios and are therefore interpreted to reflect intracrystalline gradients in the concentration of 40 Ar within constituent fine-grained white mica. The gradients are suggested to have developed as a result of a variable Caledonian thermal rejuvenation of white-mica argon systems which had initially cooled through argon retention temperatures at ca. 1700-1800 Ma following the Sveco-karelian orogeny. The extent of whole-rock spectra discordancy is related to the proximity of the basal thrust of the structurally overlying Kalak Nappe Complex. Whole-rock sample suites were also collected structurally downward (0.6-20 m) from the Kalak Thrust within penetratively cleaved, allochthonous cover sequences (Lomvatn Formation) exposed along the northern edge of the Komagfjord window. These display discordant 40 Ar/ 39 Ar age spectra with most intermediate-temperature gas fractions recording mutually similar apparent 40 Ar/ 39 Ar ages of ∼410-430 m.y. Observed variations in K-Ar and 40 Ar/ 39 Ar ages suggest that a late Caledonian tectonothermal event (ca. 420-425 Ma) variably affected the allochthonous basement and cover units exposed in the two Finnmark windows. This thermal overprint is interpreted to have developed during emplacement of the structurally overlying Kalak Nappe Complex while it was maintained at post-Scandian metamorphic temperatures in excess of at least 350 °C. Although the effects of a Late Cambrian-Early Ordovician orogenic event have been described from portions of the Kalak Nappe Complex, no clear record of correlative tectonothermal activity has been documented within structurally underlying tectonic units. It is therefore likely that most of the Paleozoic metamorphism and deformation observed along the eastern margin of the Caledonide orogen in northern Scandinavia developed during eastward transport of previously assembled, composite Scandian nappes into their present structural position on the Baltoscandian platform between ca. 400 and 425 Ma.