2,189 research outputs found
Soft Interaction Between Dissolved Dendrimers: Theory and Experiment
Using small-angle neutron scattering and liquid integral equation theory, we
relate the structure factor of flexible dendrimers of 4th generation to their
average shape. The shape is measured as a radial density profile of monomers
belonging to a single dendrimer. From that, we derive an effective interaction
of Gaussian form between pairs of dendrimers and compute the structure factor
using the hypernetted chain approximation. Excellent agreement with the
corresponding experimental results is obtained, without the use of adjustable
parameters. The present analysis thus strongly supports the previous finding
that flexible dendrimers of low generation present fluctuating structures akin
to star polymers.Comment: 20 pages, 4 figures, submitted to Macromolecules on July 24, 200
Internal Friction of Amorphous Silicon in a Magnetic Field
The internal friction of e-beam amorphous silicon was measured in a magnetic
field between 0 and 6 T, from 1.5-20 K, and was found to be independent of the
field to better than 8%. It is concluded that the low energy excitations
observed in this experiment are predominantly atomic in nature.Comment: 4 pages, 4 figures, REVTe
Using legume-based mixtures to enhance the nitrogen use efficiency and economic viability of cropping systems - Final report (LK09106/HGCA3447)
As costs for mineral fertilisers rise, legume-based leys are recognised as a potential alternative nitrogen source for crops. Here we demonstrate that including species-rich legume-based leys in rotations helps to maximise synergies between agricultural productivity and other ecosystem services. By using functionally diverse plant species mixtures, these services can be optimised and fine-tuned to regional and farm-specific needs. Replicated field experiments were conducted over three years at multiple locations, testing the performance of 12 legume species and 4 grass species sown in monocultures, as well as in a mixture of 10 of the legumes and all 4 grasses (called the All Species Mix, ASM). In addition, we compared this complex mixture to farmer-chosen ley mixtures on 34 sites across the UK.
The trials showed that there is a large degree of functional complementarity among the legume species. No single species scored high on all evaluation criteria. In particular, the currently most frequently used species, white clover, is outscored by other legume species on a number of parameters such as early development and resistance to decomposition. Further complementarity emerged from the different responses of legume species to environmental variables, with soil pH and grazing or cutting regime being among the more important factors. For example, while large birdsfoot trefoil showed better performance on more acidic soils, the opposite was true for sainfoin, lucerne and black medic. In comparison with the monocultures, the ASM showed increased ground cover, increased above-ground biomass and reduced weed biomass. Benefits of mixing species with regard to productivity increased over time. In addition, the stability of biomass production across sites was greater in the ASM than in the legume monocultures. Within the on-farm trials, we further found that on soils low in organic matter the biomass advantage of the ASM over the Control ley was more marked than on the soils with higher organic matter content. Ecological modelling revealed that the three best multifunctional mixtures all contained black medic, lucerne and red clover.
Within the long term New Farming Systems (NFS) rotational study, the use of a clover bi-crop showed improvement to soil characteristics compared to current practice (e.g. bulk density and water infiltration rate). Improvements in wheat yield were also noted with respect to the inclusion of a clover bi-crop in 2010, but there was evidence of a decline in response as the N dose was increased. Cumulatively, over both the wheat crop and the spring oilseed rape crop, the clover bi-crop improved margin over N. The highest average yield response (~9%) was associated with the ASM legume species mix cover cropping approach
Acute Effects of Massage or Active Exercise in Relieving Muscle Soreness: Randomized Controlled Trial
Andersen, LL, Jay, K, Andersen, CH, Jakobsen, MD, Sundstrup, E, Topp, R, and Behm, DG. Acute effects of massage or active exercise in relieving muscle soreness: randomized controlled trial. J Strength Cond Res 27(12): 3352–3359, 2013—Massage is commonly believed to be the best modality for relieving muscle soreness. However, actively warming up the muscles with exercise may be an effective alternative. The purpose of this study was to compare the acute effect of massage with active exercise for relieving muscle soreness. Twenty healthy female volunteers (mean age 32 years) participated in this examiner-blind randomized controlled trial (ClinicalTrials.gov NCT01478451). The participants performed eccentric contractions for the upper trapezius muscle on a Biodex dynamometer. Delayed onset muscle soreness (DOMS) presented 48 hours later, at which the participants (a) received 10 minutes of massage of the trapezius muscle or (b) performed 10 minutes of active exercise (shoulder shrugs 10 × 10 reps) with increasing elastic resistance (Thera-Band). First, 1 treatment was randomly applied to 1 shoulder while the contralateral shoulder served as a passive control. Two hours later, the contralateral resting shoulder received the other treatment. The participants rated the intensity of soreness (scale 0–10), and a blinded examiner took measures of pressure pain threshold (PPT) of the upper trapezius immediately before treatment and 0, 10, 20, and 60 minutes after treatment 48 hours posteccentric exercise. Immediately before treatment, the intensity of soreness was 5.0 (SD 2.2) and PPT was 138 (SD 78) kPa. In response to treatment, a significant treatment by time interaction was found for the intensity of soreness (p \u3c 0.001) and PPT (p \u3c 0.05). Compared with control, both active exercise and massage significantly reduced the intensity of soreness and increased PPT (i.e., reduced pain sensitivity). For both types of treatment, the greatest effect on perceived soreness occurred immediately after treatment, whereas the effect on PPT peaked 20 minutes after treatment. In conclusion, active exercise using elastic resistance provides similar acute relief of muscle soreness as compared with that using massage. Coaches, therapists, and athletes can use either active warm-up or massage to reduce DOMS acutely, for example, to prepare for competition or strenuous work, but should be aware that the effect is temporary, that is, the greatest effects occurs during the first 20 minutes after treatment and diminishes within an hour
Multi-Scale Simulation Modeling for Prevention and Public Health Management of Diabetes in Pregnancy and Sequelae
Diabetes in pregnancy (DIP) is an increasing public health priority in the
Australian Capital Territory, particularly due to its impact on risk for
developing Type 2 diabetes. While earlier diagnostic screening results in
greater capacity for early detection and treatment, such benefits must be
balanced with the greater demands this imposes on public health services. To
address such planning challenges, a multi-scale hybrid simulation model of DIP
was built to explore the interaction of risk factors and capture the dynamics
underlying the development of DIP. The impact of interventions on health
outcomes at the physiological, health service and population level is measured.
Of particular central significance in the model is a compartmental model
representing the underlying physiological regulation of glycemic status based
on beta-cell dynamics and insulin resistance. The model also simulated the
dynamics of continuous BMI evolution, glycemic status change during pregnancy
and diabetes classification driven by the individual-level physiological model.
We further modeled public health service pathways providing diagnosis and care
for DIP to explore the optimization of resource use during service delivery.
The model was extensively calibrated against empirical data.Comment: 10 pages, SBP-BRiMS 201
Low temperature acoustic properties of amorphous silica and the Tunneling Model
Internal friction and speed of sound of a-SiO(2) was measured above 6 mK
using a torsional oscillator at 90 kHz, controlling for thermal decoupling,
non-linear effects, and clamping losses. Strain amplitudes e(A) = 10^{-8} mark
the transition between the linear and non-linear regime. In the linear regime,
excellent agreement with the Tunneling Model was observed for both the internal
friction and speed of sound, with a cut-off energy of E(min) = 6.6 mK. In the
non-linear regime, two different behaviors were observed. Above 10 mK the
behavior was typical for non-linear harmonic oscillators, while below 10 mK a
different behavior was found. Its origin is not understood.Comment: 1 tex file, 6 figure
Spectral Shape of Relaxations in Silica Glass
Precise low-frequency light scattering experiments on silica glass are
presented, covering a broad temperature and frequency range (9 GHz < \nu < 2
THz). For the first time the spectral shape of relaxations is observed over
more than one decade in frequency. The spectra show a power-law low-frequency
wing of the relaxational part of the spectrum with an exponent
proportional to temperature in the range 30 K < T < 200 K. A comparison of our
results with those from acoustic attenuation experiments performed at different
frequencies shows that this power-law behaviour rather well describes
relaxations in silica over 9 orders of magnitude in frequency. These findings
can be explained by a model of thermally activated transitions in double well
potentials.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Mechanical Relaxation in Glasses and at the Glass Transition
The Gilroy-Phillips model of relaxational jumps in asymmetric double-well
potentials, developed for the Arrhenius-type secondary relaxations of the glass
phase, is extended to a formal description of the breakdown of the shear
modulus at the glass transition, the flow process.Comment: 13 pages, 11 figures, 49 ref
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