Characteristics and alteration origins of matrix minerals in volcaniclastic kimberlite of the Muskox pipe (Nunavut, Canada)

The matrix of volcaniclastic kimberlite (VK) from the Muskox pipe (Northern Slave Province, Nunavut, Canada) is interpreted to represent an overprint of an original clastic matrix. Muskox VK is subdivided into three different matrix mineral assemblages that reflect differences in the proportions of original primary matrix constituents, temperature of formation and nature of the altering fluids. Using whole rock X-ray fluorescence (XRF), whole rock X-ray diffraction (XRD), microprobe analyses, back-scatter electron (BSE) imaging, petrography and core logging, we find that most matrix minerals (serpentine, phlogopite, chlorite, saponite, monticellite, Fe-Ti oxides and calcite) lack either primary igneous or primary clastic textures. The mineralogy and textures are most consistent with formation through alteration overprinting of an original clastic matrix that form by retrograde reactions as the deposit cools, or, in the case of calcite, by precipitation from Ca-bearing fluids into a secondary porosity. The first mineral assemblage consists largely of serpentine, phlogopite, calcite, Fe-Ti oxides and monticellite and occurs in VK with relatively fresh framework clasts. Alteration reactions, driven by deuteric fluids derived from the juvenile constituents, promote the crystallisation of minerals that indicate relatively high temperatures of formation (> 400 °C). Lower-temperature minerals are not present because permeability was occluded before the deposit cooled to low temperatures, thus shielding the facies from further interaction with fluids. The other two matrix mineral assemblages consist largely of serpentine, phlogopite, calcite, +/- diopside, and +/- chlorite. They form in VK that contains more country rock, which may have caused the deposit to be cooler upon emplacement. Most framework components are completely altered, suggesting that larger volumes of fluids drove the alteration reactions. These fluids were likely of meteoric provenance and became heated by the volcaniclastic debris when they percolated into the VK infill. Most alteration reactions ceased at temperatures > 200 °C, as indicated by the absence or paucity of lower-temperature phases in most samples, such as saponite. Recognition that Muskox VK contains an original clastic matrix is a necessary first step for evaluating the textural configuration, which is important for reconstructing the physical processes responsible for the formation of the deposit.

The association between ambient temperature and children's lung function in Baotou, China

The objective of this study is to examine the association between ambient temperature and children’s lung function in Baotou, China. We recruited 315 children (8–12 years) from Baotou, China in the spring of 2004, 2005, and 2006. They performed three successive forced expiratory measurements three times daily (morning, noon, and evening) for about 5 weeks. The highest peak expiratory flow (PEF) was recorded for each session. Daily data on ambient temperature, relative humidity, and air pollution were monitored during the same period. Mixed models with a distributed lag structure were used to examine the effects of temperature on lung function while adjusting for individual characteristics and environmental factors. Low temperatures were significantly associated with decreases in PEF. The effects lasted for lag 0–2 days. For all participants, the cumulative effect estimates (lag 0–2 days) were −1.44 (−1.93, −0.94) L/min, −1.39 (−1.92, −0.86) L/min, −1.40 (−1.97, −0.82) L/min, and −1.28 (−1.69, −0.88) L/min for morning, noon, evening, and daily mean PEF, respectively, associated with 1 °C decrease in daily mean temperature. Generally, the effects of temperature were slightly stronger in boys than in girls for noon, evening, and daily mean PEF, while the effects were stronger in girls for morning PEF. PM2.5 had joint effects with temperature on children’s PEF. Higher PM2.5 increased the impacts of low temperature. Low ambient temperatures are associated with lower lung function in children in Baotou, China. Preventive health policies will be required for protecting children from the cold weather.

High temperature deformation and densification in alumina-yttria composites

Pinning by second phase particles offers a potent means for limiting grain growth and enhancing superplasticity in alumina-based ceramics. In the present study, a colloidal technique was used to produce green bodies of alumina-yttria composites; at elevated temperatures, the yttria particles react with alumina to produce YAG particles. The densification and high temperature deformation characteristics of alumina-YAG composites were studied using conventional free sintering and sinter-forging, which involves the application of a compressive stress without any lateral constraints. It is shown that the YAG particles retard both densification and grain growth. The experiments indicate also that the presence of YAG particles does not significantly alter the stress exponent for creep deformation.

Excellent rectifying characteristics in Au/n-CdTe diodes upon exposure to rf nitrogen plasma

Nitrogen plasma exposure (NPE) effects on indium doped bulk n-CdTe are reported here. Excellent rectifying characteristics of Au/n-CdTe Schottky diodes, with an increase in the barrier height, and large reverse breakdown voltages are observed after the plasma exposure. Surface damage is found to be absent in the plasma exposed samples. The breakdown mechanism of the heavily doped Schottky diodes is found to shift from the Zener to avalanche after the nitrogen plasma exposure, pointing to a change in the doping close to the surface which was also verified by C-V measurements. The thermal stability of the plasma exposure process is seen up to a temperature of 350 degrees C, thereby enabling the high temperature processing of the samples for device fabrication. The characteristics of the NPE diodes are stable over a year implying excellent diode quality. A plausible model based on Fermi level pinning by acceptor-like states created by plasma exposure is proposed to explain the observations.

Time-temperature histories of spherical food products during bulk forced-air precooling

A general mathematical model for forced air precooling of spherical food products in bulk is developed. The food products are arranged inline to form a rectangular parallelepiped. Chilled air is blown along the height of the package. The governing equations for the transient two-dimensional conduction with internal heat generation in the product, simultaneous heat and mass transfer at the product-air interface and one-dimensional transient energy and species conservation equations for the moist air are solved numerically using finite difference methods. Results are presented in the form of time-temperature histories. Experiments are conducted with model foods in a laboratory scale air precooling tunnel. The agreement between the theoretical and experimental results is found to be good. In general, a single product analysis fails to predict the precooling characteristics of bulk loads of food products. In the range of values investigated, the respiration heat is found to have a negligible effect.

Effects of mass of charge on loop heat pipe operational characteristics

Experimental results on a loop heat pipe, using R134a as the working fluid, indicates that the liquid inventory in the compensation chamber can significantly influence the operating characteristics. The large liquid inventory in the compensation chamber, under terrestrial conditions, can result in loss of thermal coupling between the compensation chamber and the evaporator core. This causes the operating temperature to increase monotonically. This phenomenon, which has been experimentally observed, is reported in this paper. A theoretical model to predict the steady-state performance of a loop heat pipe with a weak thermal link between the compensation chamber and the core, as observed in the experiment, is also presented. The predicted and the experimentally determined temperatures correlate well.

Photosynthetic responses of seven tropical seagrasses to elevated seawater temperature

This study uses chlorophyll a fluorescence to examine the effect of environmentally relevant (1-4 h) exposures of thermal stress (35-45 [deg]C) on seagrass photosynthetic yield in seven tropical species of seagrasses. Acute response of each tropical seagrass species to thermal stress was characterised, and the capacity of each species to tolerate and recover from thermal stress was assessed. Two fundamental characteristics of heat stress were observed. The first effect was a decrease in photosynthetic yield (Fv / Fm) characterised by reductions in F and Fm'. The dramatic decline in Fv / Fm ratio, due to chronic inhibition of photosynthesis, indicates an intolerance of Halophila ovalis, Zostera capricorni and Syringodium isoetifolium to ecologically relevant exposures of thermal stress and structural alterations to the PhotoSystem II (PSII) reaction centres. The decline in Fm' represents heat-induced photoinhibition related to closure of PSII reaction centres and chloroplast dysfunction. The key finding was that Cymodocea rotundata, Cymodocea serrulata, Halodule uninervis and Thalassia hemprichii were more tolerant to thermal stress than H. ovalis, Z. capricorni and S. isoetifolium. After 3 days of 4 h temperature treatments ranging from 25 to 40 [deg]C, C. rotundata, C. serrulata and H. uninervis demonstrated a wide tolerance to temperature with no detrimental effect on Fv / Fm' qN or qP responses. These three species are restricted to subtropical and tropical waters and their tolerance to seawater temperatures up to 40 [deg]C is likely to be an adaptive response to high temperatures commonly occurring at low tides and peak solar irradiance. The results of temperature experiments suggest that the photosynthetic condition of all seagrass species tested are likely to suffer irreparable effects from short-term or episodic changes in seawater temperatures as high as 40-45 [deg]C. Acute stress responses of seagrasses to elevated seawater temperatures are consistent with observed reductions in above-ground biomass during a recent El Nino event.

The freezing characteristics of wheat at ear emergence

Wheat is occasionally exposed to freezing temperatures during ear emergence and can suffer severe frost damage. Few studies have attempted to understand the characteristics of freezing and frost damage to wheat during late development stages. It was clearly shown that wheat appears to have an inherent frost resistance to temperatures down to −5 °C but is extensively damaged below this temperature. Acclimation, whilst increasing the frost resistance of winter wheat in a vegetative state was incapable of increasing frost resistance of plants at ear emergence. It is proposed that the ability to upregulate frost resistance is lost once vernalisation requirement is fulfilled. Culms and ears of wheat were able to escape frost damage at temperatures below −5 °C by supercooling even to as low as −15 °C and evidence collected by infrared thermography suggested that individual culms on a plant froze as independent units during freezing with little or no cross ice-nucleation strategies to protect wheat from frost damage in the field appear to revolve around avoiding ice nucleation.

Growth and carcass characteristics of cast-for-age Merino ewes fed sorghum-based feedlot diets

Grain feeding low bodyweight, cast-for-age (CFA) sheep from pastoral areas of eastern Australia at the end of the growing season can enable critical carcass weight grades to be achieved and thus yield better economic returns. The aim of this work was to compare growth and carcass characteristics for CFA Merino ewes consuming either simple diets based on whole sorghum grain or commercial feed pellets. The experiment also compared various sources of additional nitrogen (N) for inclusion in sorghum diets and evaluated several introductory regimes. Seventeen ewes were killed initially to provide baseline carcass data and the remaining 301 ewes were gradually introduced to the concentrate diets over 14 days before being fed concentrates and wheaten hay ad libitum for 33 or 68 days. Concentrate treatments were: (i) commercial feed pellets, (ii) sorghum mix (SM; whole sorghum grain, limestone, salt and molasses) + urea and ammonium sulfate (SMU), (iii) SMU + whole cottonseed at 286 g/kg of concentrate dry matter (DM), (iv) SM + cottonseed meal at 139 g/kg of concentrate DM, (v) SMU + virginiamycin (20 mg/kg of concentrate) for the first 21 days of feeding, and (vi) whole cottonseed gradually replaced by SMU over the first 14 days of feeding. The target carcass weight of 18 kg was achieved after only 33 days on feed for the pellets and the SM + cottonseed meal diet. All other whole grain sorghum diets required between 33 and 68 days on feed to achieve the target carcass weight. Concentrates based on whole sorghum grain generally produced significantly (P < 0.05) lower carcass weight and fat score than pellets and this may have been linked to the significantly (P < 0.05) higher faecal starch concentrations for ewes consuming sorghum-based diets (270 v. 72 g/kg DM on day 51 of feeding for sorghum-based diets and pellets, respectively). Source of N in whole grain sorghum rations and special introductory regimes had no significant (P > 0.05) effects on carcass weight or fat score of ewes with the exception of carcass weight for SMU + whole cottonseed being significantly lower than SM + cottonseed meal at day 33. Ewes finished on all diets produced acceptable carcasses although muscle pH was high in all ewe carcasses (average 5.8 and 5.7 at 33 and 68 days, respectively). There were no significant (P > 0.05) differences between diets in concentrate DM intake, rumen fluid pH, meat colour score, fat colour score, eye muscle area, meat pH or meat temperature.

An apparatus for the study of switching characteristics in ferroelectrics

A circuit capable of producing bipolar square pulses of voltages up to +or-400 V, employing an integrated circuit timer and two mercury wetted relays is described. The frequency of the pulses can be varied from a cycle min-1 to 2 kHz. A variable temperature sample chamber and the temperature control and measurement circuits are also described. The performance of the circuit is evaluated using samples of TGS and NaNO2.

Estimation Of Properties Of Rare-Gas Solids From Compression Characteristics Of Closed-Shell Ions

We present a unified approach to repulsion in ionic and van der Waals solids based on a compressible-ion/atom model. Earlier studies have shown that repulsion in ionic crystals can be viewed as arising from the compression energy of ions, described by two parameters per ion. Here we obtain the compression parameters of the rare-gas atoms Ne. Ar. Kr and Xe by interpolation using the known parameters of related equi-electronic ions (e.g. Ar from S2-. Cl-, K- and Ca2-). These parameters fit the experimental zero-temperature interatomic distances and compressibilities of the rare-gas crystals satisfactorily. A hightemperature equation of state based on an Einstein model of thermal motions is used to calculate the thermal expansivities, compressibilities and their temperature derivatives for Ar. Kr and Xe. It is argued that an instability at higher temperatures represents the limit to which the solid can be superheated. beyond which sublimation must occur.

Wear characteristics and bearing performance of aluminium-mica particulate composite material

Some tribological properties of a mica-dispersed Al-4%Cu-1.5%Mg alloy cast by a conventional foundry technique are reported. The effect of mica dispersion on the wear rate and journal bearing performance of the matrix alloy was studied under different pressures and under different interface friction conditions. The dispersion of mica was found (a) to increase the wear rate of the base alloy, (b) to decrease the temperature rise during wear and (c) to improve the ability of the alloy to resist seizure.

Fuel conditions and fire behavior characteristics of managed Picea abies and Pinus sylvestris forests in Finland

The objectives of this study were to analyze the impact of structural stand characteristics on ignition potential, surface fuel moisture, and fire behavior in Pinus sylvestris L. and Picea abies (L.) Karst stands in Finland and to explain stand-specific fire danger using the Canadian Fire Weather Index System and the Finnish Fire Risk Index. Additionally, the study analyzes the relationship between observed fire activity and fire weather indices at different stages of growing season. Field experiments were carried out in Pinus sylvestris or Picea abies dominated stands during fire seasons 2001 and 2002. Observations on ignition potential, fuel moisture, and fire behavior were analyzed in relation to stand structure and the outputs of the Finnish and Canadian fire weather indices. Seasonal patterns of fire activity were examined based on national fire statistics 1996 2003, effective temperature sum, and the fire weather indices. Point fire ignition potential was highest in Pinus clear-cuts and lowest in closed Picea stands. Moss-dominated surface fuels were driest in clear-cut and sapling stage stands and presented the highest moisture content under closed Picea canopy. Pinus sylvestris stands carried fire under a wide range of fire weather conditions under which Picea abies stands failed to sustain fire. In the national fire records, the daily number of reported ignitions presented its highest value during late fire season whereas the daily area burned peaked most substantially during early season. The fire weather indices correlated significantly with ignition potential and fuel moisture but were unable to explain fire behavior in the experimental fires. During the initial and final stages of the growing season, fire activity was disconnected from weather-based fire danger ratings. Information on stand structure and season stage would benefit the assessment of fire danger in Finnish forest landscape for fire suppression and controlled burning purposes.

Maximum likelihood estimation of natural mortality and quantification of temperature effects on catchability of brown tiger prawn (Penaeus esculentus) in Moreton Bay (Australia) using logbook data

It is common to model the dynamics of fisheries using natural and fishing mortality rates estimated independently using two separate analyses. Fishing mortality is routinely estimated from widely available logbook data, whereas natural mortality estimations have often required more specific, less frequently available, data. However, in the case of the fishery for brown tiger prawn (Penaeus esculentus) in Moreton Bay, both fishing and natural mortality rates have been estimated from logbook data. The present work extended the fishing mortality model to incorporate an eco-physiological response of tiger prawn to temperature, and allowed recruitment timing to vary from year to year. These ecological characteristics of the dynamics of this fishery were ignored in the separate model that estimated natural mortality. Therefore, we propose to estimate both natural and fishing mortality rates within a single model using a consistent set of hypotheses. This approach was applied to Moreton Bay brown tiger prawn data collected between 1990 and 2010. Natural mortality was estimated by maximum likelihood to be equal to 0.032 ± 0.002 week−1, approximately 30% lower than the fixed value used in previous models of this fishery (0.045 week−1).

Negative differential resistance in GaN nanocrystals above room temperature

Negative differential resistance (NDR) has been observed for the first time above room temperature in gallium nitride nanocrystals synthesized by a simple chemical route. Current-voltage characteristics have been used to investigate this effect through a metal-semiconductor-metal (M-S-M) configuration on SiO2. The NDR effect is reversible and reproducible through many cycles. The threshold voltage is similar to 7 V above room temperature.