772 research outputs found
Decomposition of wheat and barley straw treated with urea-sulfuric acid
Wheat straw treated with 0.5 or 1.0 ml/g
urea-sulfuric acid (1 : 1 acid in water v/v) and incubated
in Protneuf or Woodburn silt loam soils in the
laboratory decomposed faster than nontreated straw
the first 4-6 weeks but at 12 weeks the nontreated
straw had decomposed 25% – 45% more. In a field experiment,
urea-sulfuric acid treated straw, removed at
40-day intervals over 160 days, decomposed faster
than nontreated straw. The differences were attributed
to salt buildup in the laboratory samples, where electrical
conductivities up to 17.6 dS/m were observed. In
the field, leaching removed the excess salts. Nitrification
produced up to 1875 mg NO3-N/kg Portneuf
silt loam soil in the laboratory, indicating that nitrifying
bacteria were not suppressed by the salt. Total
plate counts with no straw were 1.8 x 10^6 microorganisms/g
and with urea-sulfuric acid treated straw were
15.7 x 10^6/g soil after 14 days incubation. The respective
actinomycete counts were 0.3 x 10^6 and 6.7 x 10^6/g
for the no straw and straw-treated soils, respectively.
The urea-sulfuric acid treatments suppressed straw
decomposition in the laboratory and accelerated straw
decomposition in the field
Effect of Potassium Salts on Extractable Soil Manganese
Incubation experiments with an acid, poorly drained soil
(Typic Albaqualf) showed that the level of extractable Mn
was increased by salt treatments. The relative order of the
salt effect was KBr > KCl > KNO? > K?SO?. Soil pH changes
accounted for the majority of the KNO? and K?SO? treatment
effects, but the KCl and KBr effects could not be explained on
this basis. In addition, ionic strength considerations and differential
biological activities were not found to be factors influencing
the K salt effects in the soil system. A hypothesis is
presented to explain the KCl or KBr effect, in which the anion
would function in an oxidation-reduction reaction. This hypothesis
is supported by the fact that the soil treated with KBr
contained more extractable Mn than that treated with KCl, in
accordance with theory. Theoretical calculations also suggested
the possibility that both Cl- and Br- could reduce the lower
valency Mn oxides under the experimental soil conditions
Haptic User Interfaces for the Visually Impaired: Implications for Haptically Enhanced Science Learning Systems
The overall quality of haptic user interfaces designed to support visually impaired students\u27 science learning through sensorial feedback was systematically studied to investigate task performance and user behavior. Fourteen 6th- to 11th-grade students with visual impairments recruited from a state-funded blind school were asked to perform three main tasks (i.e., menu selection, structure exploration, and force recognition) using haptic user interfaces and a haptic device. This study used several dependent measures that are categorized into three types of variables: (a) task performance including success rate, workload, and task completion time; (b) user behavior defined as cursor movements proportionately represented from the user\u27s cursor positional data; and (c) user preference. Results showed that interface type has significant effects on task performance, user behavior, and user preference, with varying degree of impact to participants with severe visual impairments performing the tasks. The results of this study as well as a set of refined design guidelines and principles should provide insights to the future research of haptic user interfaces that can be used when developing haptically enhanced science learning systems for the visually impaired
CCL2 and CCR2 regulate pain-related behaviour and early gene expression in post-traumatic murine osteoarthritis but contribute little to chondropathy
SummaryObjectiveThe role of inflammation in structural and symptomatic osteoarthritis (OA) remains unclear. One key mediator of inflammation is the chemokine CCL2, primarily responsible for attracting monocytes to sites of injury. We investigated the role of CCL2 and its receptor CCR2 in experimental OA.DesignOA was induced in 10 weeks old male wild type (WT), Ccl2−/− and Ccr2−/− mice, by destabilisation of the medial meniscus (DMM). RNA was extracted from whole joints at 6 h and 7 days post-surgery and examined by reverse transcription polymerase chain reaction (RT-PCR). Gene expression changes between naïve and DMM-operated mice were compared. Chondropathy scores, from mice at 8, 12, 16 and 20 weeks post DMM were calculated using modified Osteoarthritis Research Society International (OARSI) grading systems. Changes in hind paw weight distribution, as a measure of pain, were assessed by Linton incapacitance.ResultsAbsence of CCL2 strongly suppressed (>90%) selective inflammatory response genes in the joint 6 h post DMM, including arginase 1, prostaglandin synthase 2, nitric oxide synthase 2 and inhibin A. IL6, MMP3 and tissue inhibitor of metalloproteinase 1 were also significantly suppressed. Similar trends were also observed in the absence of CCR2. A lower average chondropathy score was observed in both Ccl2−/− and Ccr2−/− mice at 12, 16 and 20 weeks post DMM compared with WT mice, but this was only statistically significant at 20 weeks in Ccr2−/− mice. Pain-related behaviour in Ccl2−/− and Ccr2−/− mice post DMM was delayed in onset.ConclusionThe CCL2/CCR2 axis plays an important role in the development of pain in murine OA, but contributes little to cartilage damage
SRAO CO Observation of 11 Supernova Remnants in l = 70 to 190 deg
We present the results of 12CO J = 1-0 line observations of eleven Galactic
supernova remnants (SNRs) obtained using the Seoul Radio Astronomy Observatory
(SRAO) 6-m radio telescope. The observation was made as a part of the SRAO CO
survey of SNRs between l = 70 and 190 deg, which is intended to identify SNRs
interacting with molecular clouds. The mapping areas for the individual SNRs
are determined to cover their full extent in the radio continuum. We used
halfbeam grid spacing (60") for 9 SNRs and full-beam grid spacing (120") for
the rest. We detected CO emission towards most of the remnants. In six SNRs,
molecular clouds showed a good spatial relation with their radio morphology,
although no direct evidence for the interaction was detected. Two SNRs are
particularly interesting: G85.4+0.7, where there is a filamentary molecular
cloud along the radio shell, and 3C434.1, where a large molecular cloud appears
to block the western half of the remnant. We briefly summarize the results
obtained for individual SNRs.Comment: Accepted for publication in Astrophysics & Space Science. 12 pages,
12 figures, and 3 table
Emergence of Anti-Cancer Drug Resistance: Exploring the Importance of the Microenvironmental Niche via a Spatial Model
Practically, all chemotherapeutic agents lead to drug resistance. Clinically,
it is a challenge to determine whether resistance arises prior to, or as a
result of, cancer therapy. Further, a number of different intracellular and
microenvironmental factors have been correlated with the emergence of drug
resistance. With the goal of better understanding drug resistance and its
connection with the tumor microenvironment, we have developed a hybrid
discrete-continuous mathematical model. In this model, cancer cells described
through a particle-spring approach respond to dynamically changing oxygen and
DNA damaging drug concentrations described through partial differential
equations. We thoroughly explored the behavior of our self-calibrated model
under the following common conditions: a fixed layout of the vasculature, an
identical initial configuration of cancer cells, the same mechanism of drug
action, and one mechanism of cellular response to the drug. We considered one
set of simulations in which drug resistance existed prior to the start of
treatment, and another set in which drug resistance is acquired in response to
treatment. This allows us to compare how both kinds of resistance influence the
spatial and temporal dynamics of the developing tumor, and its clonal
diversity. We show that both pre-existing and acquired resistance can give rise
to three biologically distinct parameter regimes: successful tumor eradication,
reduced effectiveness of drug during the course of treatment (resistance), and
complete treatment failure
Self-Consistent Quasi-Particle RPA for the Description of Superfluid Fermi Systems
Self-Consistent Quasi-Particle RPA (SCQRPA) is for the first time applied to
a more level pairing case. Various filling situations and values for the
coupling constant are considered. Very encouraging results in comparison with
the exact solution of the model are obtained. The nature of the low lying mode
in SCQRPA is identified. The strong reduction of the number fluctuation in
SCQRPA vs BCS is pointed out. The transition from superfluidity to the normal
fluid case is carefully investigated.Comment: 23 pages, 18 figures and 1 table, submitted to Phys. Rev.
A Mathematical Model of Liver Cell Aggregation In Vitro
The behavior of mammalian cells within three-dimensional structures is an area of intense biological research and underpins the efforts of tissue engineers to regenerate human tissues for clinical applications. In the particular case of hepatocytes (liver cells), the formation of spheroidal multicellular aggregates has been shown to improve cell viability and functionality compared to traditional monolayer culture techniques. We propose a simple mathematical model for the early stages of this aggregation process, when cell clusters form on the surface of the extracellular matrix (ECM) layer on which they are seeded. We focus on interactions between the cells and the viscoelastic ECM substrate. Governing equations for the cells, culture medium, and ECM are derived using the principles of mass and momentum balance. The model is then reduced to a system of four partial differential equations, which are investigated analytically and numerically. The model predicts that provided cells are seeded at a suitable density, aggregates with clearly defined boundaries and a spatially uniform cell density on the interior will form. While the mechanical properties of the ECM do not appear to have a significant effect, strong cell-ECM interactions can inhibit, or possibly prevent, the formation of aggregates. The paper concludes with a discussion of our key findings and suggestions for future work
Field Measurements of Terrestrial and Martian Dust Devils
Surface-based measurements of terrestrial and martian dust devils/convective vortices provided from mobile and stationary platforms are discussed. Imaging of terrestrial dust devils has quantified their rotational and vertical wind speeds, translation speeds, dimensions, dust load, and frequency of occurrence. Imaging of martian dust devils has provided translation speeds and constraints on dimensions, but only limited constraints on vertical motion within a vortex. The longer mission durations on Mars afforded by long operating robotic landers and rovers have provided statistical quantification of vortex occurrence (time-of-sol, and recently seasonal) that has until recently not been a primary outcome of more temporally limited terrestrial dust devil measurement campaigns. Terrestrial measurement campaigns have included a more extensive range of measured vortex parameters (pressure, wind, morphology, etc.) than have martian opportunities, with electric field and direct measure of dust abundance not yet obtained on Mars. No martian robotic mission has yet provided contemporaneous high frequency wind and pressure measurements. Comparison of measured terrestrial and martian dust devil characteristics suggests that martian dust devils are larger and possess faster maximum rotational wind speeds, that the absolute magnitude of the pressure deficit within a terrestrial dust devil is an order of magnitude greater than a martian dust devil, and that the time-of-day variation in vortex frequency is similar. Recent terrestrial investigations have demonstrated the presence of diagnostic dust devil signals within seismic and infrasound measurements; an upcoming Mars robotic mission will obtain similar measurement types
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