Typical Growth Rates Research Articles

Investigating the effect of acid stress on selected mesophilic micro-organisms implicated in bioleaching

During start-up of heap bioleaching, low grade ores may be treated with acid for agglomeration and to combat the acid neutralising capacity of the gangue minerals. This may stress the bioleaching inocula, particularly upon inoculation during ore agglomeration. Acid addition for agglomeration varies across operations, ore types and their neutralising capacity, with limited information published on recommended concentrations. The initial pH in the agglomeration mix is typically below pH 1.0 and may be as low as pH 0.5.This paper investigates the effect of acid stress in terms of initial acid concentration and duration of exposure in submerged culture on mesophilic micro-organisms typically implicated in mineral sulphide bioleaching and critical for heap colonisation at start-up. Following acid stress, cultures were returned to standard operating conditions in batch stirred slurry reactors and their performance assessed in terms of mineral leach rates, ferrous oxidation and the rate of microbial growth. Increasing acid stress resulted in an increase in the lag period before onset of microbial growth and iron oxidation due to decreased viable cell numbers, specific metabolic activity or both. Following adaptation, typical growth and ferrous iron oxidation rates were observed under low stress conditions while reduction in the rate and extent of microbial growth and ferrous iron oxidation persisted at extreme conditions. A reduction in yield (microbial cells produced per kg iron oxidised) was observed with increased acid concentration over comparative times. Microbial speciation analysis indicated a substantial decrease in the diversity of the microbial species surviving.

Modelling the effect of fluctuating herbicide concentrations on algae growth

Herbicide concentrations fluctuate widely in watercourses after crop applications and rain events. The level of concentrations in pulses can exceed the water chronic quality criteria. In the present study, we proposed modelling the effects of successive pulse exposure on algae. The deterministic model proposed is based on two parameters: (i) the typical growth rate of the algae, obtained by monitoring growth rates of several successive batch cultures in growth media, characterizing both the growth of the control and during the recovery periods; (ii) the growth rate of the algae exposed to pulses, determined from a dose–response curve obtained with a standard toxicity test. We focused on the herbicide isoproturon and on the freshwater alga Scenedesmus vacuolatus, and we validated the model prediction based on effect measured during five sequential pulse exposures in laboratory. The comparison between the laboratory and the modelled effects illustrated that the results yielded were consistent, making the model suitable for effect prediction of the herbicide photosystem II inhibitor isoproturon on the alga S. vacuolatus. More generally, modelling showed that both pulse duration and level of concentration play a crucial role. The application of the model to a real case demonstrated that both the highest peaks and the low peaks with a long duration affect principally the cell density inhibition of the alga S. vacuolatus. It is therefore essential to detect these characteristic pulses when monitoring of herbicide concentrations are conducted in rivers.

Influence of the V/III ratio in the gas phase on thin epitaxial AlN layers grown on (0001) sapphire by high temperature hydride vapor phase epitaxy

Thin (0001) epitaxial aluminum nitride (AlN) layers were grown on c-plane sapphire using high temperature hydride vapor phase epitaxy. The experimental set-up consists of a vertical cold-wall quartz reactor working at low pressure in which the reactions take place on a susceptor heated by induction. The reactants used are ammonia and aluminum chlorides in situ formed via hydrogen chloride reaction with high purity aluminum pellets. As-grown AlN layers have been characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, transmission electron microscopy, photoluminescence and Raman spectroscopies. The influence of the V/III ratio in the gas phase, from 1.5 to 15, on growth rate, surface morphology, roughness and crystalline quality is investigated in order to increase the quality of thin epitaxial AlN layers grown at high temperature. Typical growth rates of around 0.45μm/h were obtained for such thin epitaxial AlN layers. The growth rate was unaffected by the V/III ratio. An optimum for roughness, crystalline quality and optical properties seems to exist at V/III=7.5. As a matter of fact, for a V/III ratio of 7.5, best root mean square roughness and crystalline quality — measured on 0002 symmetric reflection — as low as 6.9nm and 898arcsec were obtained, respectively.

Kinetic theory of the electron bounce instability in two dimensional current sheets—Full electromagnetic treatment

In the general context of understanding the possible destabilization of a current sheet with applications to magnetospheric substorms or solar flares, a kinetic model is proposed for studying the resonant interaction between electromagnetic fluctuations and trapped bouncing electrons in a 2D current sheet. Tur et al. [A. Tur et al., Phys. Plasmas 17, 102905 (2010)] and Fruit et al. [G. Fruit et al., Phys. Plasmas 20, 022113 (2013)] already used this model to investigate the possibilities of electrostatic instabilities. Here, the model is completed for full electromagnetic perturbations. Starting with a modified Harris sheet as equilibrium state, the linearized gyrokinetic Vlasov equation is solved for electromagnetic fluctuations with period of the order of the electron bounce period. The particle motion is restricted to its first Fourier component along the magnetic field and this allows the complete time integration of the non local perturbed distribution functions. The dispersion relation for electromagnetic modes is finally obtained through the quasineutrality condition and the Ampere's law for the current density. It is found that for mildly strechted current, undamped modes oscillate at typical electron bounce frequency with wavelength of the order of the plasma sheet half thickness. As the stretching of the plasma sheet becomes more intense, the frequency of these normal modes decreases and beyond a certain threshold in ε = Bz/Blobes, the mode becomes explosive with typical growth rate of a few tens of seconds. The free energy contained in the bouncing motion of the electrons may trigger an electromagnetic instability able to disrupt the cross-tail current in a few seconds. This new instability–electromagnetic electron-bounce instability–may explain fast and global scale destabilization of current sheets as required to describe substorm phenomena.

Aerosols and nucleation in eastern China: first insights from the new SORPES-NJU station

Abstract. Aerosols and new particle formation were studied in the western part of the Yangtze River Delta (YRD) at the Station for Observing Regional Processes of the Earth System, Nanjing University (SORPES-NJU). Air ions in the diameter range 0.8–42 nm were measured using an air ion spectrometer, and a differential mobility particle sizer (DMPS) provided particle number size distributions between 6 and 800 nm. Additionally, meteorological data, trace gas concentrations, and PM2.5 values were recorded. During the measurement period from 18 November 2011 to 31 March 2012, the mean total particle concentration was found to be 23 000 cm−3 and the mean PM2.5 value was 90 μg m−3, well above national limits. We observed 26 new particle formation events occurred during the measurement period, producing 6 nm particles at a rate of about 1 cm−3 s−1. Typical particle growth rates were between 6 and 7 nm h−1. On average, new particle formation and growth were estimated to enhance cloud condensation nuclei concentration by about a factor of two during these event days. Ion measurements showed the typical cluster band below 2 nm, with total ion concentrations between about 600 and 1000 cm−3. A peculiar feature of the ion measurements were heightened ion cluster concentrations during the nights before the event days. At 2 nm, the formation rate of charged particles was only about 0.2% of the total rate, pointing towards an only marginal role of ion-induced nucleation. Based on observations, a simple empirical criterion was deducted to estimate particle formation probability. Dominated by radiation and relative humidity, the criterion can predict the occurrence of particle formation with a 90% accuracy. In a similar fashion, a reasonably accurate estimate of particle formation rates was derived. Combined, these parameters allow for a description of particle formation based on a few basic measured variables.

Adaptive responses of energy storage and fish life histories to climatic gradients

Energy storage is a common adaptation of fish living in seasonal environments. For some species, the energy accumulated during the growing season, and stored primarily as lipids, is crucial to preventing starvation mortality over winter. Thus, in order to understand the adaptive responses of fish life history to climate, it is important to determine how energy should be allocated to storage and how it trades off with the other body components that contribute to fitness. In this paper, we extend previous life history theory to include an explicit representation of how the seasonal allocation of energy to storage acts as a constraint on fish growth. We show that a strategy that privileges allocation to structural mass in the first part of the growing season and switches to storage allocation later on, as observed empirically in several fish species, is the strategy that maximizes growth efficiency and hence is expected to be favored by natural selection. Stochastic simulations within this theoretical framework demonstrate that the relative performance of this switching strategy is robust to a wide range of fluctuations in growing season length, and to moderate short-term (i.e., daily) fluctuations in energy intake and/or expenditure within the growing season. We then integrate this switching strategy with a biphasic growth modeling framework to predict typical growth rates of walleye Sander vitreus, a cool water species, and lake trout Salvelinus namaycush, a cold water specialist, across a climatic gradient in North America. As predicted, growth rates increased linearly with the duration of the growing season. Regression line intercepts were negative, indicating that growth can only occur when growing season length exceeds a threshold necessary to produce storage for winter survival. The model also reveals important differences between species, showing that observed growth rates of lake trout are systematically higher than those of walleye in relatively colder lakes. This systematic difference is consistent with both (i) the expected superior capacity of lake trout to withstand harsh winter conditions, and (ii) some degree of counter gradient adaptation of lake trout growth capacity to the climatic gradient covered by our data.

Modern Tasman Sea surface reservoir ages from deep-sea black corals

Marine reservoir ages are a key element in calculating and constraining uncertainty in radiocarbon age estimates and are also essential to better understand regional ocean circulation. In this study, we present a new method to reconstruct long-term, high-resolution sea surface reservoir ages based on analysis of the organic skeleton of deep-sea (560m) black coral (Anthozoa, Antipatharia). Our results confirm that antipatharians are extremely slow growing (typical radial growth rate for a South Pacific specimen around 0.03mm/yr). Coupled uranium series and radiocarbon measurements were made on black coral collected live from the Norfolk Ridge (north Tasman Sea) to provide the first modern reservoir ages for this region. At the Norfolk Ridge, the average reservoir age between 1790 AD and 1900AD was ∼330 years. This was followed by a steep decrease over time of about 70 years to 1950 AD (our most modern value). This indicates an increase in surface ocean ventilation of water masses in this region. These results are consistent with observational studies for the early twentieth century, which suggest significant changes in regional circulation of the southwest pacific.

Counting $$\beta $$ -expansions and the absolute continuity of Bernoulli convolutions

We study the typical growth rate of the number of words of length \(n\) which can be extended to \(\beta \)-expansions of \(x\). In the general case we give a lower bound for the growth rate, while in the case that the Bernoulli convolution associated to parameter \(\beta \) is absolutely continuous we are able to give the growth rate precisely. This gives new necessary and sufficient conditions for the absolute continuity of Bernoulli convolutions.

Deposition and characterization of diamond-like nanocomposite coatings grown by plasma enhanced chemical vapour deposition over different substrate materials

Diamond-like nanocomposite (DLN) coatings have been deposited over different substrates used for biomedical applications by plasma-enhanced chemical vapour deposition (PECVD). DLN has an interconnecting network of amorphous hydrogenated carbon and quartz-like oxygenated silicon. Raman spectroscopy, Fourier transform–infra red (FT–IR) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) have been used for structural characterization. Typical DLN growth rate is about 1 \({\upmu} \)m/h, measured by stylus profilometer. Due to the presence of quartz-like Si:O in the structure, it is found to have very good adhesive property with all the substrates. The adhesion strength found to be as high as 0·6 N on SS 316 L steel substrates by scratch testing method. The Young’s modulus and hardness have found to be 132 GPa and 14· 4 GPa, respectively. DLN coatings have wear factor in the order of 1 × 10 − 7 mm3/N-m. This coating has found to be compatible with all important biomedical substrate materials and has successfully been deposited over Co–Cr alloy based knee implant of complex shape.

Transport, Magnetic, and Thermal Properties of La0.7Ca0.24Sr0.06MnO3Single Crystal

We report the transport, magnetic, and thermal properties of La0.7Ca0.24Sr0.06MnO3single crystal. It was prepared using floating zone technique used under oxygen pressure of 1 bar with a typical growth rate of 1 mm/hr. The resistivity data shows the metal to insulator transition (M-I) occuring atTMI=290 K along thec-axis and atTMI=280 K along theab-plane. It is observed that theTMIis higher along thec-axis as compared to that in theab-plane, thus indicating that more favorable hoping of electrons is along thec-axis. From bolometric application point of view, the temperature coefficient of resistance (TCR) is found to be ~28% K−1. Theac-susceptibility measurement shows that this material exhibits ferromagnetic to paramagnetic transition temperature (TC) 277 K. Sharp peak around this temperature in heat capacity data indicates the onset of long-range ordering. The entropy change associated with this transition is found to be 2.3 J/mol K.

Chemical Vapor Deposition of12C Isotopically Enriched Polycrystalline Diamond

12C isotopically enriched polycrystalline diamond free-standing plates were synthesized by microwave plasma-assisted chemical vapor deposition. Diamond plates 30 mm in diameter and 100–600 µm in thickness were successfully obtained at a typical growth rate of 3–5 µm/h. The 12C isotopic enrichment was 99.997%, whereas the nitrogen content was as low as 4 ppb. The preferential orientation of the crystallographic direction normal to the substrate plane was proved using the X-ray diffraction pattern. The sharp Raman peak with a low background and a clear free-exciton recombination emission in a cathodoluminescence measurement at room temperature indicate that the polycrystalline diamond has a substantially high crystalline quality.

Chemical Vapor Deposition of 12C Isotopically Enriched Polycrystalline Diamond

12C isotopically enriched polycrystalline diamond free-standing plates were synthesized by microwave plasma-assisted chemical vapor deposition. Diamond plates 30 mm in diameter and 100–600 µm in thickness were successfully obtained at a typical growth rate of 3–5 µm/h. The 12C isotopic enrichment was 99.997%, whereas the nitrogen content was as low as 4 ppb. The preferential orientation of the <110 > crystallographic direction normal to the substrate plane was proved using the X-ray diffraction pattern. The sharp Raman peak with a low background and a clear free-exciton recombination emission in a cathodoluminescence measurement at room temperature indicate that the polycrystalline diamond has a substantially high crystalline quality.

Surface chemistry at the nanometer scale influences insulin aggregation

We synthesized surfaces with different hydrophobicities and roughness by forming self-assembled monolayers (SAMs) of mixed amine and octyl silanes. Insulin aggregation kinetics in the presence of the above surfaces is characterized by a typical lag phase and growth rate. We show that the lag time but not the growth rate varies as a function of the amine fraction on the surface. The amount of adsorbed protein and the adsorption rate during the aggregation process also vary with the amine fraction on the surface and are maximal for equal parts of amine and octyl groups. For all surfaces, the growth phase starts for identical amounts of adsorbed insulin. The initial surface roughness determines the rate at which protein adsorption occurs and hence the time to accumulate enough protein to form aggregation nuclei. In addition, the surface chemistry and topography influence the morphology of aggregates adsorbed on the material surface and the secondary structures of final aggregates released in solution.

A phase II study of the histone deacetylase inhibitor panobinostat (LBH589) in low-grade neuroendocrine tumors.

e14554 Background: Neuroendocrine tumors (NETs) are a diverse and rare group of neoplasms arising from the neuroendocrine system. The most common subtypes are pancreatic islet cell tumors and carcinoid tumors. Although they represent only 2% of all gastrointestinal malignancies, given their overall favorable prognosis, the prevalence is much higher. Histone deacetylase (HDAC) inhibitors have already been shown to suppress tumor growth and induce apoptosis in a variety of solid tumors in preclinical data. We have previously shown that in NET cells, HDAC inhibitors have resulted in increased Notch1 expression and subsequent inhibition of growth. Methods: A single arm phase II study was performed. Adult patients with histologically confirmed, metastatic, low-grade NETs and an ECOG performance status of ≤ 2 were treated with the oral HDAC inhibitor panobinostat 20 mg once daily three times per week. Treatment was continued until patients experienced unacceptable toxicities or disease progression. Results: 15 patients were accrued and 13 were evaluable for response (66.7% male, age range 40-80 years old (mean 59.4 years old), 66.7% carcinoid, 33.3% pancreatic NET). The median number of prior therapies was 1 (range 0-2) and no patient had previously received everolimus. The response rate was 0%. The stable disease rate was 92.3% as defined by stability seen on the first CT scan. Median progression-free survival was 11.8 months. The 1 year PFS was 42%. Thrombocytopenia and fatigue were the most common treatment-related grade 3 toxicities. There was one grade 4 toxicity of thrombocytopenia. The study was stopped early at the planned interim analysis based on lack of meaningful clinical efficacy outlined in the Simon two-stage design. Conclusions: The HDAC inhibitor panobinostat had infrequent grade 3 and 4 events in this patient population and resulted in a large percentage of subjects with disease control. The disease control rate, however, needs to be considered in the context of the typical slow growth rate of NETs. These data alone do not support continued evaluation of HDAC inhibitors in low-grade NETs. This study was supported by Novartis.

Phenology and duration of remigial moult in Surf Scoters (Melanitta perspicillata) and White-winged Scoters (Melanitta fusca) on the Pacific coast of North America

By quantifying phenology and duration of remigial moult in Surf Scoters ( Melanitta perspicillata (L., 1758)) and White-winged Scoters ( Melanitta fusca (L., 1758)), we tested whether timing of moult is dictated by temporal optima or constraints. Scoters (n = 3481) were captured during moult in Alaska, British Columbia, and Washington, and remigial emergence dates were determined. We provide evidence for a pre-emergence interval of 7.3 days that occurs after old primaries are shed and before new ones become visible. All age and sex classes of both scoter species exhibited a wide range of emergence dates (Surf Scoters: 26 June to 22 September; White-winged Scoters: 6 July to 21 September) suggestive of a lack of strong temporal optima for remigial moult. For both species, timing of moult was influenced by site, year, age, and sex. Relative to other waterfowl species, scoters have typical remigial growth rates (Surf Scoters: 3.9 mm·day–1; White-winged Scoters: 4.3 mm·day–1) but a long flightless period (34–49 days), in part because their relatively high wing-loading requires a greater proportion of feather regrowth to regain flight. Our data suggest that moulting scoters are not under strong selective pressure to complete moult quickly.

Structural and optical studies of thick freestanding GaN films deposited by Hydride vapor phase epitaxy

Thick freestanding films or bulk GaN substrates with very low background impurity levels (≤1×1015/cm3) and high crystalline quality are required for a number of electronic device applications. Low pressure chemical vapor and molecular beam epitaxy techniques can systematically deposit films with low residual impurity concentrations. However, their typical slow growth rate prevents their utilization for substrate growth. The hydride vapor phase epitaxy deposition technique can achieve hundreds of microns per hour growth rate, but these films have typically high free carrier concentration (≥3×1017/cm3). It is crucial to verify if this method can reproducibly deliver thick freestanding GaN films of high crystalline quality with exceptionally low free carrier concentration. Low temperature photoluminescence and room temperature Raman scattering experiments carried out on a number of samples indicate that they have high crystalline quality and uncommonly low donor background levels. Reduced concentration of uncompensated shallow donors verified by low temperature electron paramagnetic resonance was confirmed by detailed high sensitive SIMS analyses. In addition, it was verified by X-ray diffraction analysis that relatively low dislocation densities can be achieved.

Investment in Fine Roots and Arbuscular Mycorrhizal Fungi Decrease During Succession in Three Brazilian Ecosystems

The functional groups of plants that characterize different phases of succession are expected to show differences in root distribution, fine-root traits and degrees of association with arbuscular mycorrhizal (AM) fungi. The relationship involving fine-root traits and AM fungi that regulate the nutrient acquisition potential among different plant functional groups are still not well understood. We assessed fine-root morphology, AM fungal variables and soil fertility in grassland, secondary forest and mature forest in Atlantic, Araucaria and Pantanal ecosystems in Brazil. Soil cores were collected at 0–10 and 10–20 cm depths. Fine roots were extracted from soil by sieving and root morphological traits and AM colonization were determined. The AM spores were extracted from soil and counted. In all ecosystems, soil fertility, fine-root mass and root diameter increased with the succession, while root length, specific root length, root-hair length, root-hair incidence, AM colonization and AM spore density decreased. These results suggest that plant species from early stages of tropical succession with inherent rapid growth invest in fine roots and maintain a high degree of AM colonization in order to increase the capacity for nutrient acquisition. Conversely, fine root morphological characteristics and low degree of AM colonization exhibited by plants of the later stages of succession lead toward a low nutrient uptake capacity that combine with their typical low growth rates. Abstract in Portuguese is available at http://www.blackwell-synergy.com/loi/btp.

Epitaxial growth and characterization of cubic GaN on BP/Si(100) substrates

ABSTRACTWe have focused to grow cubic GaN (c-GaN) on Si(100) substrates using boronmonophosphide (BP) buffer crystals. The growth of GaN was carried out by MOVPE on BP/Si(100) substrate of 2 inches in diameter. By the several evaluations, it was recognized that when the growth temperature is around 750˚C, c-GaN was dominant. The typical growth rate was about 0.5μm/h. We obtained c-GaN layer over 2.5μm thick without cracking.

Thermal Cycling Induced Crack Nucleation and Propagation in Thermal Barrier Coating System

Failure of thermal barrier coating (TBC) system is associated with the morphological imperfection of thermally grown oxide (TGO) layer. The objective of this work is to numerically investigate the crack nucleation and propagation in TBC system upon thermal cycling based on a cohesive zone model, in which TGO thickness imperfection effect is incorporated. The results show that TGO/BC (bond coat) interface is subjected to high tensile stress in the vicinity of TGO thickness imperfection during thermal cycling, thereby inducing crack nucleation. Owing to the plastic deformation of BC, fracture behavior of TGO/BC interface is related to BC yield strength for a typical thermal growth rate of TGO. Furthermore, the embedded oxide in BC could be also ruptured as a result of the increasing transverse stress, which will lead to the coalescence of adjacent cracks.

High-Speed Growth of High-Quality 4H-SiC Bulk by Solution Growth Using Si-Cr Based Melt

High-speed solution growth using Si-Cr based melt has been performed on on-axis 4H-SiC(0001) at a high temperature of about 2000°C. The maximum growth rate for one-hour growth reaches to 1120 m/h, while the typical growth rate of growth for 2h is about 500 m/h. A large crystal that is about 25 mm in diameter and 1650 m in thickness can be obtained by growth for 5h. The crystal quality is confirmed to be homogeneous by X-ray diffraction and X-ray topography, because FWHM is less than 30 arcsec. Etch pit density of the threading dislocations in the grown crystal is 103-104 cm-2, and that of basal plane dislocation is 2×102-3×103 cm-2. Resistivity of the crystals grown by the solution growth is comparable to those of crystals grown by physical vapor transport technique.