1,163 research outputs found
Describing the ground state of quantum systems through statistical mechanics
We present a statistical mechanics description to study the ground state of
quantum systems. In this approach, averages for the complete system are
calculated over the non-interacting energy levels. Taking different interaction
parameter, the particles of the system fall into non-interacting microstates,
corresponding to different occupation probabilities for these energy levels.
Using this novel thermodynamic interpretation we study the Hubbard model for
the case of two electrons in two sites and for the half-filled band on a
one-dimensional lattice. We show that the form of the entropy depends on the
specific system considered.Comment: 8 page
Quantitative assessment of the effects of space allowance, group size and floor characteristics on the lying behaviour of growing-finishing pigs
To obtain quantitative information that can be later used in animal welfare modelling, the relationship between the lying behaviour of growing-finishing pigs (initial body weight (BW) between 19 and 87 kg) and different factors related to the housing conditions, with a potential negative effect on their welfare, was studied by means of a meta-analytical approach. Data from 22 experiments reported in 21 scientific publications were collected. The space allowance, expressed on an allometric basis by means of a k-value (m2/BW0.667), the group size (n) and the floor characteristics (fully and partly slatted v. non-slatted floor), as well as their significant two-way interactions were used as fixed effects, and the experiment was used as a random factor to take into account the interexperiment effect. Further regression analyses were performed on the predicted values of observations in order to improve the adjustment of data. A significant quadratic relationship was established between space allowance (k-value, P <0.05; squared k-value, P <0.01) and the percentage of time spent lying. A significant interaction between the k-value and the floor type was also found (P <0.05), showing that the relationship between space allowance and lying behaviour is affected by the presence or absence of slats. Threshold k-values were obtained using broken-line analyses, being about 0.039 for slatted floors and almost double for non-slatted floors. Compared to other studies, these values suggest that the ability to rest as space availability decreases may be compromised before a reduced performance becomes apparent. Group size did not show a significant effect. Additional information should be added to the model, as further data become available, to adjust the proposed parameters as well as to try to include the effect of other important aspects such as that of ambient temperature
In vitro growth characteristics of Fusarium langsethiae isolates recovered from oats and wheat grain in the UK
Fusarium langsethiae is a fungus that has recently been implicated in the contamination of small-grain cereal crops such as oats, wheat and barley with high levels of HT-2 and T-2 toxins in many European countries. The epidemiology of this fungus is not well known and may therefore be a bigger problem than currently thought to be. A study was carried out investigating the in vitro growth characteristics of F. langsethiae isolates from contaminated oats and wheat at various temperatures; 15, 20, 25 and 30 °C. Results indicated similar growth trends of oats and wheat isolates of F. langsethiae. Wheat isolates grew significantly (p<0.001) faster than oat isolates although this difference may have been confounded by the age of cultures, with oat isolates collected one year earlier. The estimated optimum growth temperature for all isolates was 24 °C. Isolates were macro-morphologically categorized as having lobed or entire colony margins, and either possessing one of the following colony colours: white, orange or purple. Since the estimated optimum growth temperature of F. langsethiae is typical in temperate summers when small-grain cereals are flowering, it is possible that this species can infect, colonise and possibly contaminate the developing grains with HT-2 and T-2 toxins which are of food safety concern
‘What’s it like to have ME?’ The discursive construction of ME in computer-mediated communication and face-to-face interaction
ME/CFS (chronic fatigue syndrome) is a debilitating illness for which no cause or medical tests have been identified. Debates over its nature have generated interest from qualitative researchers. However, participants are difficult to recruit because of the nature of their condition. Therefore, this study explores the utility of the internet as a means of eliciting accounts. We analyse data from focus groups and the internet in order to ascertain the extent to which previous research findings apply to the internet domain. Interviews were conducted among 49 members of internet (38 chatline, 11 personal) and 7 members of two face-to-face support groups. Discourse analysis of descriptions and accounts of ME/CFS revealed similar devices and interactional concerns in both internet and face-to-face communication. Participants constructed their condition as serious, enigmatic and not psychological. These functioned to deflect problematic assumptions about ME/CFS and to manage their accountability for the illness and its effects
Finite-volume meson propagators in quenched chiral perturbation theory
We compute meson propagators in finite-volume quenched chiral perturbation
theory.Comment: 3 pages, Lattice2001(chiral fermions
The Swinburne Intermediate Latitude Pulsar Survey
We have conducted a survey of intermediate Galactic latitudes using the
13-beam 21-cm multibeam receiver of the Parkes 64-m radio telescope. The survey
covered the region enclosed by 5 deg < |b| < 15 deg and -100 deg < l < 50 deg
with 4,702 processed pointings of 265 s each, for a total of 14.5 days of
integration time. Thirteen
2x96-channel filterbanks provided 288 MHz of bandwidth at a centre frequency
of 1374 MHz, one-bit sampled every 125 microsec and incurring ~DM/13.4 cm^-3 pc
samples of dispersion smearing. The system was sensitive to slow and most
millisecond pulsars in the region with flux densities greater than
approximately
0.3--1.1 mJy. Offline analysis on the 64-node Swinburne workstation cluster
resulted in the detection of 170 pulsars of which 69 were new discoveries.
Eight of the new pulsars, by virtue of their small spin periods and period
derivatives, may be recycled and have been reported elsewhere. The slow pulsars
discovered are typical of those already known in the volume searched, being of
intermediate to old age. Several pulsars experience pulse nulling and two
display very regular drifting sub-pulses. We discuss the new discoveries and
provide timing parameters for the 48 slow pulsars for which we have a
phase-connnected solution.Comment: 19 pages, 11 figures, accepted to MNRA
Square Patterns and Quasi-patterns in Weakly Damped Faraday Waves
Pattern formation in parametric surface waves is studied in the limit of weak
viscous dissipation. A set of quasi-potential equations (QPEs) is introduced
that admits a closed representation in terms of surface variables alone. A
multiscale expansion of the QPEs reveals the importance of triad resonant
interactions, and the saturating effect of the driving force leading to a
gradient amplitude equation. Minimization of the associated Lyapunov function
yields standing wave patterns of square symmetry for capillary waves, and
hexagonal patterns and a sequence of quasi-patterns for mixed capillary-gravity
waves. Numerical integration of the QPEs reveals a quasi-pattern of eight-fold
symmetry in the range of parameters predicted by the multiscale expansion.Comment: RevTeX, 11 pages, 8 figure
Studies on the Interactions Between Fungicides, Alternaria tenuissima, Cladosporium herbarum and Microdochium spp., on Fusarium Head Blight (FHB) Development and Deoxynivalenol (DON) Concentration in Grain Caused by Fusarium culmorum
Saprophytic microflora and non-toxin producing Microdochium spp. capable of causing Fusarium head blight (FHB) have been suggested to affect the development of FHB caused by Fusarium spp., the occurrence of mycotoxins and the efficacy of fungicides for the control of the disease. The effects of metconazole and azoxystrobin on the interactions between Fusarium culmorum and Microdochium spp., Alternaria tenuissima or Cladosporium herbarum on FHB symptom development, Tri5 DNA concentration and deoxynivalenol (DON) production were studied under glasshouse conditions. Results indicated that the sequence of infection of wheat heads and the relative timing of fungicide application can significantly affect FHB severity and the resulting mycotoxin contamination of harvested grain. Introduction of A. tenuissima, C. herbarum or Microdochium spp. to wheat heads at GS 57 before inoculation with F. culmorum at GS 65 generally resulted in increased FHB severity, Tri5 DNA and DON concentration in harvested grain. The greatest increases of FHB severity (266%), Tri5 DNA (79%) and DON (152%) were observed when Microdochium spp. were introduced first at GS 57 and F. culmorum inoculation followed at GS 65. Metconazole generally reduced FHB severity, Tri5 DNA and DON concentration in grain but azoxystrobin was most efficient at reducing DNA of Microdochium spp. in grain
Shared characteristics underpinning C 4 leaf maturation derived from analysis of multiple C 3 and C 4 species of Flaveria
Most terrestrial plants use C3 photosynthesis to fix carbon. In multiple plant lineages a modified system known as C4 photosynthesis has evolved. To better understand the molecular patterns associated with induction of C4 photosynthesis, the genus Flaveria that contains C3 and C4 species was used. A base to tip maturation gradient of leaf anatomy was defined, and RNA sequencing was undertaken along this gradient for two C3 and two C4Flaveria species. Key C4 traits including vein density, mesophyll and bundle sheath cross-sectional area, chloroplast ultrastructure, and abundance of transcripts encoding proteins of C4 photosynthesis were quantified. Candidate genes underlying each of these C4 characteristics were identified. Principal components analysis indicated that leaf maturation and the photosynthetic pathway were responsible for the greatest amount of variation in transcript abundance. Photosynthesis genes were over-represented for a prolonged period in the C4 species. Through comparison with publicly available data sets, we identify a small number of transcriptional regulators that have been up-regulated in diverse C4 species. The analysis identifies similar patterns of expression in independent C4 lineages and so indicates that the complex C4 pathway is associated with parallel as well as convergent evolution
Cluster Spin Glass Distribution Functions in LaSrCuO
Signatures of the cluster spin glass have been found in a variety of
experiments, with an effective onset temperature that is frequency
dependent. We reanalyze the experimental results and find that they are
characterized by a distribution of activation energies, with a nonzero glass
transition temperature . While the distribution of activation
energies is the same, the distribution of weights depends on the process.
Remarkably, the weights are essentially doping independent.Comment: 5 pages, 5 ps figure
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