Moderate Temperature Regime Research Articles

Two-dimensional spin-imbalanced Fermi gases at nonzero temperature: Phase separation of a noncondensate

We study a trapped two-dimensional spin-imbalanced Fermi gas over a range of temperatures. In the moderate temperature regime, associated with current experiments, we find reasonable semi-quantitative agreement with the measured density profiles as functions of varying spin imbalance and interaction strength. Our calculations show that, in contrast to the three-dimensional case, the phase separation which appears as a spin balanced core, can be associated with non-condensed fermion pairs. We present predictions at lower temperatures where a quasi-condensate will first appear, based on the pair momentum distribution and following the protocols of Jochim and collaborators. While these profiles also indicate phase separation, they exhibit distinctive features which may aid in identifying the condensation regime.

Origin matters! Difference in drought tolerance and productivity of coastal Douglas-fir (Pseudotsuga menziesii (Mirb.)) provenances

Forests of the future should be resistant to exacerbating climatic conditions, especially to increasing drought, but at the same time provide a sufficient amount and quality of timber. In this context coastal Douglas-fir (Pseudotsuga menziesii (Mirb.)) is a promising species since it remains productive even under chronic drought. By choosing suitable provenances within the range of Douglas-fir (P. menziesii (Mirb.)) for a given site we can further optimise tree fitness under dry conditions or even increase timber yield.Eighteen coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) var. menziesii) provenances were tested for seedling survival, yield, wood quality, and drought tolerance by taking advantage of a Dutch provenance trial, established in 1971 within the framework of the 1966/1967 IUFRO seed collection program. The site of the Dutch trial is representative for many sites in Central Europe and is characterised by a moderate precipitation and temperature regime. Measurements on height and diameter growth were combined with a dendrochronological study on growth response to drought years.We found a clear latitudinal trend indicating that Douglas-fir provenances from the northern part of the species-distribution range are generally more productive than provenances from the south. In contrast, drought tolerance increased towards the south. This suggests that it is impossible to identify provenances combining maximum productivity with lowest susceptibility towards drought. However, based on the results from the trial we can give recommendations on suitable provenances that are expected to perform best under future conditions in Central Europe. On sites where severe drought events are unlikely to occur in future, fast growing provenances from the north, like Nimkish, should be planted. These provenances respond plastically to drought years, but the strong reduction of tree growth in the drought year itself indicates that these provenances will be harmed by an increasing frequency of drought events. However, on sites where water availability is likely to decrease, provenances from the Olympic Peninsula like Forks and Matlock are very promising since they showed still relatively high yield in combination with a high potential to cope with drought.If summer drought increases in frequency and severity as expected, the latewood/earlywood ratio will be drastically reduced with negative consequences for wood quality and cavitation resistance. However, some provenances, like Marblemount or Matlock, might compensate for the negative effect of summer drought on latewood/earlywood ratio by the contribution of photosynthesis in winter to whole-year carbon stock.

Surface Doping and Band Gap Tunability in Hydrogenated Graphene

We report the first observation of the n-type nature of hydrogenated graphene on SiO(2) and demonstrate the conversion of the majority carrier type from electrons to holes using surface doping. Density functional calculations indicate that the carrier type reversal is directly related to the magnitude of the hydrogenated graphene's work function relative to the substrate, which decreases when adsorbates such as water are present. Additionally, we show by temperature-dependent electronic transport measurements that hydrogenating graphene induces a band gap and that in the moderate temperature regime [220-375 K], the band gap has a maximum value at the charge neutrality point, is tunable with an electric field effect, and is higher for higher hydrogen coverage. The ability to control the majority charge carrier in hydrogenated graphene, in addition to opening a band gap, suggests potential for chemically modified graphene p-n junctions.

Regime dependent changes in global precipitation

Assessment of changes in precipitation (P) as a function of percentiles of surface temperature (T) and 500 hPa vertical velocity (ω) are presented, considering present-day simulations and observational estimates from the Global Precipitation Climatology Project (GPCP) combined with the European Centre for Medium-range Weather Forecasts Interim reanalysis (ERA Interim). There is a tendency for models to overestimate P in the warm, subsiding regimes compared to GPCP, in some cases by more than 100%, while many models underestimate P in the moderate temperature regimes. Considering climate change projections between 1980–1999 and 2080–2099, responses in P are characterised by dP/dT ≥ 4%/K over the coldest 10–20% of land points and over warm, ascending ocean points while P declines over the warmest, descending regimes (dP/dT ∼ − 4%/K for model ensemble means). The reduced Walker circulation limits this contrasting dP/dT response in the tropical wet and dry regimes only marginally. Around 70% of the global surface area exhibits a consistent sign for dP/dT in at least 6 out of a 7-member model ensemble when considering P composites in terms of dynamic regime.

Survival rates of immature Ixodes pacificus (Acari: Ixodidae) ticks estimated using field-placed enclosures

Survival rates of immature Ixodes pacificus (Acari: Ixodidae) ticks estimated using field-placed enclosures

Macroscopic Constitutive Law for Mastic Asphalt Mixtures from Multiscale Modeling

A well established framework of an uncoupled hierarchical modeling approach is adopted here for the prediction of macroscopic material parameters of the Generalized Leonov (GL) constitutive model intended for the analysis of flexible pavements at both moderate and elevated temperature regimes. To that end, a recently introduced concept of a statistically equivalent periodic unit cell (SEPUC) is addressed to reflect a real microstructure of Mastic Asphalt mixtures (MAm). While mastic properties are derived from an extensive experimental program, the macroscopic properties of MAm are fitted to virtual numerical experiments performed on the basis of first order homogenization scheme. To enhance feasibility of the solution of the underlying nonlinear problem a two-step homogenization procedure is proposed. Here, the effective material properties are first found for a mortar phase, a composite consisting of a mastic matrix and a fraction of small aggregates. These properties are then introduced in place of the matrix in actual unit cells to give estimates of the model parameters on macroscale. Comparison with the Mori-Tanaka predictions is also provided suggesting limitations of classical micromechanical models.

Electron-spin relaxation in bulk III-V semiconductors from a fully microscopic kinetic spin Bloch equation approach

Electron spin relaxation in bulk III-V semiconductors is investigated from a fully microscopic kinetic spin Bloch equation approach where all relevant scatterings, such as, the electron--nonmagnetic-impurity, electron-phonon, electron-electron, electron-hole, and electron-hole exchange (the Bir-Aronov-Pikus mechanism) scatterings are explicitly included. The Elliott-Yafet mechanism is also fully incorporated. This approach offers a way toward thorough understanding of electron spin relaxation both near and far away from the equilibrium in the metallic regime. The dependences of the spin relaxation time on electron density, temperature, initial spin polarization, photo-excitation density, and hole density are studied thoroughly with the underlying physics analyzed. We find that these dependences are usually qualitatively different in the nondegenerate and degenerate regimes. In contrast to the previous investigations in the literature, we find that: (i) In $n$-type materials, the Elliott-Yafet mechanism is less important than the D'yakonov-Perel' mechanism, even for the narrow band-gap semiconductors such as InSb and InAs. (ii) The density dependence of the spin relaxation time is nonmonotonic and we predict a peak in the metallic regime in both $n$-type and intrinsic materials. (iii) In intrinsic materials, the Bir-Aronov-Pikus mechanism is found to be negligible compared with the D'yakonov-Perel' mechanism. We also predict a peak in the temperature dependence of spin relaxation time which is due to the nonmonotonic temperature dependence of the electron-electron Coulomb scattering in intrinsic materials with small initial spin polarization. (iv) In $p$-type III-V semiconductors, the Bir-Aronov-Pikus mechanism dominates spin relaxation in the low-temperature regime only when the photoexcitation density is low. When the photoexcitation density is high, the Bir-Aronov-Pikus mechanism can be comparable with the D'yakonov-Perel' mechanism only in the moderate temperature regime roughly around the Fermi temperature of electrons, whereas for higher or lower temperature it is unimportant. The relative importance of the Bir-Aronov-Pikus mechanism decreases with the photoexcitation density and eventually becomes negligible at sufficiently high photoexcitation density. The effect of electric field on spin relaxation in $n$-type III-V semiconductors is also studied with behaviors very different from those in the two-dimensional case reported. Finally, we find good agreement of our calculation with the experimental results.

Glyphosate-induced anther indehiscence in cotton is partially temperature dependent and involves cytoskeleton and secondary wall modifications and auxin accumulation.

Yield reduction caused by late application of glyphosate to glyphosate-resistant cotton (Gossypium hirsutum; GRC) expressing CP4 5-enol-pyruvylshikmate-3-P synthase under the cauliflower mosaic virus-35S promoter has been attributed to male sterility. This study was aimed to elucidate the factors and mechanisms involved in this phenomenon. Western and tissue-print blots demonstrated a reduced expression of the transgene in anthers of GRC compared to ovules of the same plants. Glyphosate application to GRC grown at a high temperature regime after the initiation of flower buds caused a complete loss of pollen viability and inhibition of anther dehiscence, while at a moderate temperature regime only 50% of the pollen grains were disrupted and anther dehiscence was normal. Glyphosate-damaged anthers exhibited a change in the deposition of the secondary cell wall thickenings (SWT) in the endothecium cells, from the normal longitudinal orientation to a transverse orientation, and hindered septum disintegration. These changes occurred only at the high temperature regime. The reorientation of SWT in GRC was accompanied by a similar change in microtubule orientation. A similar reorientation of microtubules was also observed in Arabidopsis (Arabidopsis thaliana) seedlings expressing green fluorescent protein tubulin (tubulin alpha 6) following glyphosate treatment. Glyphosate treatment induced the accumulation of high levels of indole-3-acetic acid in GRC anthers. Cotton plants treated with 2,4-dichlorophenoxyacetic acid had male sterile flowers, with SWT abnormalities in the endothecium layer similar to those observed in glyphosate-treated plants. Our data demonstrate that glyphosate inhibits anther dehiscence by inducing changes in the microtubule and cell wall organization in the endothecium cells, which are mediated by auxin.

Pollen and spores in marine Cretaceous/Tertiary boundary sediments at mid‐Waipara River, North Canterbury, New Zealand

Terrestrial pollen and spores in late Maastrichtian to early Paleocene marine strata at mid‐Waipara, New Zealand, permit reconstruction of contemporary vegetation and paleoclimates. During the latest Cretaceous, spore‐pollen assemblages reflect a temperate rainforest with a prominent podocarp and tree ferns component, angiosperm pollen being mainly represented by Nothofagus and Proteaceae. Disruption of the vegetation at the Cretaceous/Tertiary (K/T) boundary is recorded by an increase in fern spores, reduction in gymnosperm pollen, and temporary loss of angiosperm pollen both in mid Waipara and in the terrestrial sections of Moody Creek Mine and Compressor Creek. Following an interval of fern dominance, gymnosperms and later angiosperms return to the palynological record. The floral turnover at the K/T boundary is comparable to palynological records from North America and Japan, indicating that disruption of vegetation was global. Fern dominance is estimated to have lasted several thousands of years, based on foraminiferal biostratigraphy of immediate post‐K/T boundary strata. This is orders of magnitude greater than seen in normal seral successions following deforestation. We suggest that the observed vegetation succession is due to a prolonged period of low ambient light levels, sufficient for photosynthesis but favouring plants already adapted to these levels (such as forest ground stratum), accompanied by a moderate temperature and moisture regime.

EFFECT OF TEMPERATURE ON INFLORESCENCE QUALITY AND SHELF LIFE OF LACHENALIA CV. RONINA

Three temperature regimes, representing a cool, moderate and warm winter climate, were chosen to grow bulbs during the bulb preparation phase (year 1) and afterwards to determine the morphology and shelf life of these bulbs’ inflorescences during the pot plant phase (year 2). The best temperature regimes for the bulb preparation phase were the low and moderate temperature regimes, which represent the cool and moderate winter climate in South Africa. The moderate and low temperature regime treated bulbs produced more inflorescences than those of the high temperature regime. The lower the temperature regime treatment during the bulb preparation phase the higher were the peduncle length, rachis length, floret number as well as the peduncle cross section of the primary, secondary and tertiary inflorescences during the pot plant phase. The pot plant shelf life from bulbs of all three temperature treatments averaged 24 days, however, the low temperature regime treated bulbs beared inflorescences with the longest keeping ability.

Growth of Tb(0 0 0 1) on Nb and Mo(1 1 0) surfaces

We study the growth of Tb(0 0 0 1) on Nb(1 1 0) and Mo(1 1 0) under UHV conditions by laser ablation. For this purpose we perform first chemical and structural characterisation of the annealed and as-grown Mo and Nb buffer layers prepared on sapphire (1 1 −2 0). In a second step we investigate the growth modes of Tb(0 0 0 1) at coverages ranging from 0.5 to 4 monolayers on these surfaces in the moderate and high temperature regime (200–700 °C). The methods employed are in situ scanning tunneling microscopy, Auger spectroscopy and reflection high-energy electron diffraction and ex situ X-ray diffraction. We discuss the results taking into account the structure of the buffer layers.

Effects of growth and storage temperature on Lachenalia cv. Ronina bulb morphology

Temperature plays an important role in the production of high quality Lachenalia bulbs, which is required for successful international bulb trade. The effects of three growth temperature regimes (high, moderate and low) on the development of bulbs prior to harvest and during the storage period were studied. Bulbs planted on 1 March were harvested at 15 November and subsequently stored at 25 °C until 15 December. From mid-September until 15 December, 10 plants were sampled randomly from each treatment at 2-week intervals and morphological studies were conducted on these bulbs by means of serial hand sections. The high temperature regime treated bulbs developed more modules, but inflorescence abortion occurred. Bulbs subjected to a low temperature regime treatment developed slightly slower than those of the moderate and high temperature regime treatments. In all the treatments, daughter bulbs were observed in the axils of both swollen leaf bases from mid-November. In spite of the slower development of bulbs subjected to the lower temperature regime, the overall quality was better than bulbs grown in the moderate and high temperature regimes.

Self-organized pattern formation in the oxidation of supported iron thin films. I. An experimental study

The evolution of patterned morphology during thermal oxidation of a supported metal thin film is examined as a case of strained reaction-diffusion system; the strain originates from the large density difference between the oxide and the metal. In the moderate temperature regime, where bulk diffusion is weak, the pattern reflects the length scale of the original metal film grain structure, with local features characteristic of self-organized chemical microreactors, as well as large scale polygonal surface undulations presumably caused by stress accommodation. At higher temperature, where bulk diffusion is brisk, the process of Ostwald ripening strongly reforms the morphology formed at lower temperature, and leads to distributed spiral-type configurations. These observations and analysis are supported by a simulation study reported in the accompanying paper II by Abhijit S. Ogale [Phys. Rev. B 64, 035409 (2001)]

Effect of temperature on the growth of Lachenalia cv. Ronina during the bulb preparation phase

Lachenalia cultivars have excellent characteristics as flowering pot plants. The effect of three temperature regimes on the growth of small bulbs of Lachenalia cv. Ronina to flowering size (± 7 g) was studied. Potted bulbs were grown in three temperature controlled cabinets with temperature regimes chosen to represent a cold, a moderate and a warm winter. Plants were destructively harvested to investigate environmental effects on plant morphology and additionally flowering, anthesis and flower senescence were monitored. Under all three temperature regimes bulb growth followed a typical sigmoidal curve. Root growth does not support optimal bulb size under the different temperature regimes. Leaf growth in plants under the moderate temperature regime was more vigorous and foliage had a healthier appearance than in the low and high temperature regime treatments. Inflorescence emergence was earlier under the low and moderate temperature regime. At the end of the growing season, bulbs grown in the high temperature treatment formed secondary inflorescences. The best temperature regimes for Lachenalia bulb production were the low and moderate temperature regime which represented the cool and moderate winter climate in South Africa.

Namaqualand, South Africa – an overview of a unique winter-rainfall desert ecosystem

Namaqualand is a winter-rainfall desert of some 50 000 km2, located in north-western South Africa. For a desert ecosystem, the region is characterized by a unique selective regime, namely highly predictable annual rainfall and a moderate temperature regime throughout the year. This selective regime is responsible for the unique plant ecological features of Namaqualand. These include: the dominance of communities by dwarf to low, shallow-rooted, short-lived and drought-sensitive leaf succulent shrubs; high abundance and diversity of geophytes; winter growth phenology; regular and spectacular spring flowering displays; rapid population turnover of perennials; weak competitive interactions; and high local and regional plant diversity. This paper provides a physiographical, biogeographical and ecological overview as background to this special issue. First, we outline the physiography and climate of Namaqualand, emphasizing unique components of its selective regime. Next we discuss the region's phytogeographical and floristic characteristics. Then we summarize what is known about plant form and function, focusing on growth form mix, phenology, carbon gain, water relations, and reproduction in vegetation dominated by leaf-succulent shrubs. Finally, we interpret Namaqualand's uniquely rich and dynamic plant communities in terms of plant functional processes. These plant ecological patterns and processes are discussed in terms of the predictions of a simple conceptual model for succulent-rich communities.

AN ANALYTICAL APPROACH TO THE FREDRICKSON–ANDERSEN MODEL WITH VACANCIES

The dynamics of the n-spin facilitated kinetic Ising model (Fredrickson–Andersen model) with mobile vacancies as a model for the glassy materials are studied analytically by means of the Fock-space representation of the master equation. The system is mapped onto a three state model characterizing mobile, immobile and vacant cells. The characteristic cooperativity for glass forming systems are introduced by restrictions influencing the local dynamics and subsequently the local mobility of different lattice cells. In a moderate temperature regime the relaxation time versus the inverse temperature T-1 reveals two processes. Whereas the slow process can be identified with the conventional α-process of the supercooled liquid, the fast one originated by the additional empty sites is suggested to be the β JG -process due to Johari–Goldstein. The results are accordant with numerical simulations and suggest that the modified n-spin facilitated kinetic Ising model is able to describe qualitatively the behaviour of a supercooled liquid near the glass transition temperature T g .

Influence of Temperature on Germination of Japanese Brome Seed

Japanese brome (Bromus japonicus Thunb.), an introduced annual grass, is now common in some northern mixed-prairie communities. This species has the potential to alter both the seasonality of standing crop and forage quality. We sought to gain a greater understanding of Japanese brome seed germination by subjecting seed to a series of 55 constant or alternating temperature regimes following 3 to 9 months of dry laboratory storage. Cold and moderate temperature regimes provided optimum germination conditions (defined as not lower than the maximum observed minus one-half its confidence interval at the 0.05 level of probability). Extremely cold or warm temperatures suppressed germination. Germination of afterripened seed over a wide range of temperature combinations, many of which occur during fall in the Northern Great Plains, should enhance establishment and perpetuation of Japanese brome on rangelands.

The thermal reaction of HNCO at moderate temperatures

AbstractThe thermal reaction of HNCO has been studied in a static cell at temperatures between 873 and 1220 K and a constant pressure of 800 torr under highly diluted conditions. The reaction was measurable above 1000 K by FTIR spectrometry. The products detected include CO, CO2, HCN, NH3, and the unreacted HNCO. In this moderate temperature regime, the rates of product formation and HNCO decay cannot be accounted for by a previously established high‐temperature mechanism, assuming HNCO → NH + CO (1) as the initiation process. Instead, a new bimolecular reaction, 2HNCO → CO2 + HNCNH (2), has been invoked to interpret the disappearance of HNCO as well as the formation of various products, most importantly CO2.The concentration profiles of all measured species can be quantitatively modeled, throughout the temperature range analyzed, by varying k2 using a modified mechanism. The kinetically modeled values of k2 can be effectively represented by This result agrees closely with that computed with the conventional transition‐state theory using the TST parameters predicted by the BAC‐MP4 method: The bimolecular reaction takes place via a stable 4‐membered ring intermediate which is isoelectronic with diketene; viz. magnified image

SEQUENTIAL PHOTOPERIODIC REQUIREMENT FOR FLOWER INITIATION AND DEVELOPMENT OF LEUCOSPERMUM PATERSONII (PROTEACEAE)

ABSTRACT Leucospermum patersonii was found to be an obligatory long-short day plant under a moderate temperature regime (22/17°C, day/night). The short-day (SD) requirement could be compensated by a low temperature (17/12°C) regime under long-day (LD) conditions. Long days had an inductive effect, whereas floral differentiation occurred under short days or a low temperature regime. The LD effect resembles that of the release from apical dominance following the production of a terminal bud. The morphological differentiation of the inflorescence was inhibited under LD and promoted under SD conditions. The effect of the low temperature regime or of short days on the initial stages of floral differentiation was similar; however, further inflorescence differentiation and development were faster under SD conditions and a moderate temperature regime. The correlative inhibition caused by the primary inflorescence under SD conditions could be overcome by treatment with cytokinin (benzyl adenine). All the infloresc...

Tensile instability in creep damaging solids

Tensile instability in creep damaging bars subject to geometrical and/or material non-uniformities is investigated for the constant load and constant stress tests provided the longwavelength approximation is maintained. The constitutive model employed in the study is valid for the moderate stress-elevated temperature regime which is dominated by completely creep constrained cavity growth. Two definitions of instability are used to study initial rates of imperfection growth and imperfection growth through failure. The first is concerned with the immediate response to a disturbance (stability in the small) while the second is related to a loss of correspondence between increments of perturbed and unperturbed field variables. A linearized stability analysis based on the first definition reveals that, like the pure viscous creep case, the deformation is unstable however, in contrast to viscous creep, the characteristic time for neck growth is much shorter. A nonlinear analysis based on the second definition associates the onset of instability with fracture occurring at a finite area but infinite local section strain. Histories of strain and area differences reveal the tendency for a highly localized neck to form, however this is countered by stability loss (fracture) at a finite area.