3,419 research outputs found
Exploring How Eruption Source Parameters Affect Volcanic Radiative Forcing Using Statistical Emulation
The radiative forcing caused by a volcanic eruption is dependent on several eruption source parameters such as the mass of sulfur dioxide (SO2) emitted, the eruption column height, and the eruption latitude. General circulation models with prognostic aerosol and chemistry schemes can be used to investigate how each parameter influences the volcanic forcing. However, the range of multidimensional parameter space that can be explored is restricted because such simulations are computationally expensive. Here we use statistical emulation to explore the radiative impact of eruptions over a wide covarying range of SO2 emission magnitudes, injection heights, and eruption latitudes based on only 30 simulations. We use the emulators to build response surfaces to visualize and predict the sulfate aerosol e-folding decay time, the stratospheric aerosol optical depth, and net radiative forcing of thousands of different eruptions. We find that the volcanic stratospheric aerosol optical depth and net radiative forcing are primarily determined by the mass of SO2 emitted, but eruption latitude is the most important parameter in determining the sulfate aerosol e-folding decay time. The response surfaces reveal joint effects of the eruption source parameters in influencing the net radiative forcing, such as a stronger influence of injection height for tropical eruptions than high-latitude eruptions. We also demonstrate how the emulated response surfaces can be used to find all combinations of eruption source parameters that produce a particular volcanic response, often revealing multiple solutions
On the stability of high-speed milling with spindle speed variation
Spindle speed variation is a well-known technique to suppress regenerative machine tool vibrations, but it is usually considered to be effective only for low spindle speeds. In this paper, the effect of spindle speed variation is analyzed in the high-speed domain for spindle speeds corresponding to the first flip (period doubling) and to the first Hopf lobes. The optimal amplitudes and frequencies of the speed modulations are computed using the semidiscre- tization method. It is shown that period doubling chatter can effectively be suppressed by spindle speed variation, although, the technique is not effective for the quasiperiodic chatter above the Hopf lobe. The results are verified by cutting tests. Some special cases are also discussed where the practical behavior of the system differs from the predicted one in some ways. For these cases, it is pointed out that the concept of stability is understood on the scale of the principal period of the system—that is, the speed modulation period for variable spindle speed machining and the tooth passing period for constant spindle speed machining
Blocking T-cell egress with FTY720 extends DNA vaccine expression but reduces immunogenicity
Optimal immunogenicity from nucleic acid vaccines requires a balance of antigen expression that effectively engages the host immune system without generating a cellular response that rapidly destroys cells producing the antigen and thereby limiting vaccine antigen expression. We investigated the role of the cellular response on the expression and antigenicity of DNA vaccines using a plasmid DNA construct expressing luciferase. Repeated intramuscular administration led to diminished luciferase expression, suggesting a role for immune-mediated clearance of expression. To investigate the role of cell trafficking, we used the sphingosine 1-phosphate receptor (S1PR) modulator, FTY720 (Fingolimod), which traps lymphocytes within the lymphoid tissues. When lymphocyte trafficking was blocked with FTY720, DNA transgene expression was maintained at a constant level for a significantly extended time period. Both continuous and staggered administration of FTY720 prolonged transgene expression. However, blocking lymphocyte egress during primary transgene administration did not result in an increase of transgene expression during secondary administration. Interestingly, there was a disconnect between transgene expression and immunogenicity, as increasing expression by this approach did not enhance the overall immune response. Furthermore, when FTY720 was administered alongside a DNA vaccine expressing the HIV gp140 envelope antigen, there was a significant reduction in both antigen-specific antibody and T-cell responses. This indicates that the developing antigen-specific cellular response clears DNA vaccine expression but requires access to the site of expression in order to develop an effective immune response
Interstellar Dust Close to the Sun
The low density interstellar medium (ISM) close to the Sun and inside of the
heliosphere provides a unique laboratory for studying interstellar dust grains.
Grain characteristics in the nearby ISM are obtained from observations of
interstellar gas and dust inside of the heliosphere and the interstellar gas
towards nearby stars. Comparison between the gas composition and solar
abundances suggests that grains are dominated by olivines and possibly some
form of iron oxide. Measurements of the interstellar Ne/O ratio by the
Interstellar Boundary Explorer spacecraft indicate that a high fraction of
interstellar oxygen in the ISM must be depleted onto dust grains. Local
interstellar abundances are consistent with grain destruction in ~150 km/s
interstellar shocks, provided that the carbonaceous component is hydrogenated
amorphous carbon and carbon abundances are correct. Variations in relative
abundances of refractories in gas suggest variations in the history of grain
destruction in nearby ISM. The large observed grains, > 1 micron, may indicate
a nearby reservoir of denser ISM. Theoretical three-dimensional models of the
interaction between interstellar dust grains and the solar wind predict that
plumes of about 0.18 micron dust grains form around the heliosphere.Comment: 2011 AGOS Taiwan meeting; accepted for publication in Earth, Planets
and Spac
Why Are Male Social Relationships Complex in the Doubtful Sound Bottlenose Dolphin Population?
Copyright 2008 Elsevier B.V., All rights reserved.Peer reviewedPublisher PD
Development and Validation of the Behavioral Tendencies Questionnaire
At a fundamental level, taxonomy of behavior and behavioral tendencies can be described
in terms of approach, avoid, or equivocate (i.e., neither approach nor avoid). While there are
numerous theories of personality, temperament, and character, few seem to take advantage
of parsimonious taxonomy. The present study sought to implement this taxonomy by
creating a questionnaire based on a categorization of behavioral temperaments/tendencies
first identified in Buddhist accounts over fifteen hundred years ago. Items were developed
using historical and contemporary texts of the behavioral temperaments, described as
“Greedy/Faithful”, “Aversive/Discerning”, and “Deluded/Speculative”. To both maintain
this categorical typology and benefit from the advantageous properties of forced-choice
response format (e.g., reduction of response biases), binary pairwise preferences for items
were modeled using Latent Class Analysis (LCA). One sample (n1 = 394) was used to estimate
the item parameters, and the second sample (n2 = 504) was used to classify the participants
using the established parameters and cross-validate the classification against
multiple other measures. The cross-validated measure exhibited good nomothetic span
(construct-consistent relationships with related measures) that seemed to corroborate the
ideas present in the original Buddhist source documents. The final 13-block questionnaire
created from the best performing items (the Behavioral Tendencies Questionnaire or BTQ)
is a psychometrically valid questionnaire that is historically consistent, based in behavioral
tendencies, and promises practical and clinical utility particularly in settings that teach and
study meditation practices such as Mindfulness Based Stress Reduction (MBSR)
Electrically Tunable Excitonic Light Emitting Diodes based on Monolayer WSe2 p-n Junctions
Light-emitting diodes are of importance for lighting, displays, optical
interconnects, logic and sensors. Hence the development of new systems that
allow improvements in their efficiency, spectral properties, compactness and
integrability could have significant ramifications. Monolayer transition metal
dichalcogenides have recently emerged as interesting candidates for
optoelectronic applications due to their unique optical properties.
Electroluminescence has already been observed from monolayer MoS2 devices.
However, the electroluminescence efficiency was low and the linewidth broad due
both to the poor optical quality of MoS2 and to ineffective contacts. Here, we
report electroluminescence from lateral p-n junctions in monolayer WSe2 induced
electrostatically using a thin boron nitride support as a dielectric layer with
multiple metal gates beneath. This structure allows effective injection of
electrons and holes, and combined with the high optical quality of WSe2 it
yields bright electroluminescence with 1000 times smaller injection current and
10 times smaller linewidth than in MoS2. Furthermore, by increasing the
injection bias we can tune the electroluminescence between regimes of
impurity-bound, charged, and neutral excitons. This system has the required
ingredients for new kinds of optoelectronic devices such as spin- and
valley-polarized light-emitting diodes, on-chip lasers, and two-dimensional
electro-optic modulators.Comment: 13 pages main text with 4 figures + 4 pages upplemental material
Duality Invariant Actions and Generalised Geometry
We construct the non-linear realisation of the semi-direct product of E(11)
and its first fundamental representation at lowest order and appropriate to
spacetime dimensions four to seven. This leads to a non-linear realisation of
the duality groups and introduces fields that depend on a generalised space
which possess a generalised vielbein. We focus on the part of the generalised
space on which the duality groups alone act and construct an invariant action.Comment: 59 pages (typos fixed and added comments
Clinical practice guidelines for the foot and ankle in rheumatoid arthritis: a critical appraisal
Background: Clinical practice guidelines are recommendations systematically developed to assist clinical decision-making and inform healthcare. In current rheumatoid arthritis (RA) guidelines, management of the foot and ankle is under-represented and the quality of recommendation is uncertain. This study aimed to identify and critically appraise clinical practice guidelines for foot and ankle management in RA. Methods: Guidelines were identified electronically and through hand searching. Search terms 'rheumatoid arthritis', 'clinical practice guidelines' and related synonyms were used. Critical appraisal and quality rating were conducted using the Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument. Results: Twenty-four guidelines were included. Five guidelines were high quality and recommended for use. Five high quality and seven low quality guidelines were recommended for use with modifications. Seven guidelines were low quality and not recommended for use. Five early and twelve established RA guidelines were recommended for use. Only two guidelines were foot and ankle specific. Five recommendation domains were identified in both early and established RA guidelines. These were multidisciplinary team care, foot healthcare access, foot health assessment/review, orthoses/insoles/splints, and therapeutic footwear. Established RA guidelines also had an 'other foot care treatments' domain. Conclusions: Foot and ankle management for RA features in many clinical practice guidelines recommended for use. Unfortunately, supporting evidence in the guidelines is low quality. Agreement levels are predominantly 'expert opinion' or 'good clinical practice'. More research investigating foot and ankle management for RA is needed prior to inclusion in clinical practice guidelines
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