17,211 research outputs found
A correlational study of areal surface texture parameters on some typical machined surfaces
A number of areal surface texture parameters have been adopted by standards bodies, namely ISO 25178-2, in which forty-one parameters within six groups are defined. The selection of the suitable areal parameters becomes an issue for a designer. The study of correlation among parameters is one of the ways to find the most suitable parameters for a specification. This paper presents a Spearman’s correlation study of areal surface texture parameters on some typical machined surfaces. Sixty surfaces, produced by nineteen machining methods, have been assessed by the use of an optical instrument; the operators adhered to ISO 25178-3; and parameters defined by ISO 25178-2. The correlation results are classified by using five correlation levels. It details the correlations between different groups of parameters, together with the correlation of parameters within the same group. The results are presented in Spearman’s rank correlation coefficient matrix and charts. A three-layer parameters tree is then proposed to help engineer in the selection of parameters
Exact Solution to the "Auxiliary Extra Dimension" Model of Massive Gravity
The "Auxiliary Extra Dimension" model was proposed in order to provide a
geometrical interpretation to modifications of general relativity, in
particular to non-linear massive gravity. In this context, the theory was shown
to be ghost free to third order in perturbations, in the decoupling limit. In
this work, we exactly solve the equation of motion in the extra dimension, to
obtain a purely 4-dimensional theory. Using this solution, it is shown that the
ghost appears at the fourth order and beyond. We explore potential
modifications to address the ghost issue and find that their consistent
implementation requires going beyond the present framework.Comment: v3:8 pages, LaTex, a comment and a reference added, version to appear
in PL
Flow injection determination of readily assimilable nitrogen compounds during vinification
A flow injection method for the determination of readily assimilable nitrogen (r.a.n.), i.e. ammonium and aminated nitrogen, is reported. The difference in pH of the sample in the presence and absence of formaldehyde, which blocks the amino function, provides the value of r.a.n. by monitoring the changes in absorbance of bromothymol blue at 616 nm. The detection and quantification limits are 10 and 11.6 mg l-1, respectively; the reproducibility and repeatability are 3.94 mg l-1 and 1.35 mg l-1, respectively; and the sample throughput is 20 samples h-1. The method has been applied to the analysis of 120 samples of must and wine subjected to biological aging. The proposed method also provides good correlation with the reference method used in routine analysis, and it is faster and gives sufficient precision for wineries requirements
Vorticity production through rotation, shear and baroclinicity
In the absence of rotation and shear, and under the assumption of constant
temperature or specific entropy, purely potential forcing by localized
expansion waves is known to produce irrotational flows that have no vorticity.
Here we study the production of vorticity under idealized conditions when there
is rotation, shear, or baroclinicity, to address the problem of vorticity
generation in the interstellar medium in a systematic fashion. We use
three-dimensional periodic box numerical simulations to investigate the various
effects in isolation. We find that for slow rotation, vorticity production in
an isothermal gas is small in the sense that the ratio of the root-mean-square
values of vorticity and velocity is small compared with the wavenumber of the
energy-carrying motions. For Coriolis numbers above a certain level, vorticity
production saturates at a value where the aforementioned ratio becomes
comparable with the wavenumber of the energy-carrying motions. Shear also
raises the vorticity production, but no saturation is found. When the
assumption of isothermality is dropped, there is significant vorticity
production by the baroclinic term once the turbulence becomes supersonic. In
galaxies, shear and rotation are estimated to be insufficient to produce
significant amounts of vorticity, leaving therefore only the baroclinic term as
the most favorable candidate. We also demonstrate vorticity production visually
as a result of colliding shock fronts.Comment: 9 pages, 10 figures, Accepted for publication in A&
Vortex ratchet reversal: The role of interstitial vortices
Triangular arrays of Ni nanotriangles embedded in superconducting Nb films
exhibit unexpected dynamical vortex effects. Collective pinning with a vortex
lattice configuration different from the expected fundamental triangular
"Abrikosov state" is found. The vortex motion which prevails against the
triangular periodic potential is produced by channelling effects between
triangles. Interstitial vortices coexisting with pinned vortices in this
asymmetric potential, lead to ratchet reversal, i.e. a DC output voltage which
changes sign with the amplitude of an applied alternating drive current. In
this landscape, ratchet reversal is always observed at all magnetic fields (all
numbers of vortices) and at different temperatures. The ratchet reversal is
unambiguously connected to the presence of two locations for the vortices:
interstitial and above the artificial pinning sites.Comment: 21 pages, 4 figures, 1 Tabl
Auditory Training Effects on the Listening Skills of Children With Auditory Processing Disorder
OBJECTIVES: Children with auditory processing disorder (APD) typically present with "listening difficulties,"' including problems understanding speech in noisy environments. The authors examined, in a group of such children, whether a 12-week computer-based auditory training program with speech material improved the perception of speech-in-noise test performance, and functional listening skills as assessed by parental and teacher listening and communication questionnaires. The authors hypothesized that after the intervention, (1) trained children would show greater improvements in speech-in-noise perception than untrained controls; (2) this improvement would correlate with improvements in observer-rated behaviors; and (3) the improvement would be maintained for at least 3 months after the end of training. DESIGN: This was a prospective randomized controlled trial of 39 children with normal nonverbal intelligence, ages 7 to 11 years, all diagnosed with APD. This diagnosis required a normal pure-tone audiogram and deficits in at least two clinical auditory processing tests. The APD children were randomly assigned to (1) a control group that received only the current standard treatment for children diagnosed with APD, employing various listening/educational strategies at school (N = 19); or (2) an intervention group that undertook a 3-month 5-day/week computer-based auditory training program at home, consisting of a wide variety of speech-based listening tasks with competing sounds, in addition to the current standard treatment. All 39 children were assessed for language and cognitive skills at baseline and on three outcome measures at baseline and immediate postintervention. Outcome measures were repeated 3 months postintervention in the intervention group only, to assess the sustainability of treatment effects. The outcome measures were (1) the mean speech reception threshold obtained from the four subtests of the listening in specialized noise test that assesses sentence perception in various configurations of masking speech, and in which the target speakers and test materials were unrelated to the training materials; (2) the Children's Auditory Performance Scale that assesses listening skills, completed by the children's teachers; and (3) the Clinical Evaluation of Language Fundamental-4 pragmatic profile that assesses pragmatic language use, completed by parents. RESULTS: All outcome measures significantly improved at immediate postintervention in the intervention group only, with effect sizes ranging from 0.76 to 1.7. Improvements in speech-in-noise performance correlated with improved scores in the Children's Auditory Performance Scale questionnaire in the trained group only. Baseline language and cognitive assessments did not predict better training outcome. Improvements in speech-in-noise performance were sustained 3 months postintervention. CONCLUSIONS: Broad speech-based auditory training led to improved auditory processing skills as reflected in speech-in-noise test performance and in better functional listening in real life. The observed correlation between improved functional listening with improved speech-in-noise perception in the trained group suggests that improved listening was a direct generalization of the auditory training
A New Comprehensive 2-D Model of the Point Spread Functions of the XMM-Newton EPIC Telescopes : Spurious Source Suppression and Improved Positional Accuracy
We describe here a new full 2-D parameterization of the PSFs of the three
XMM-Newton EPIC telescopes as a function of instrument, energy, off-axis angle
and azimuthal angle, covering the whole field-of-view of the three EPIC
detectors. It models the general PSF envelopes, the primary and secondary
spokes, their radial dependencies, and the large-scale azimuthal variations.
This PSF model has been constructed via the stacking and centering of a large
number of bright, but not significantly piled-up point sources from the full
field-of-view of each EPIC detector, and azimuthally filtering the resultant
PSF envelopes to form the spoke structures and the gross azimuthal shapes
observed. This PSF model is available for use within the XMM-Newton Science
Analysis System via the usage of Current Calibration Files XRTi_XPSF_0011.CCF
and later versions. Initial source-searching tests showed substantial
reductions in the numbers of spurious sources being detected in the wings of
bright point sources. Furthermore, we have uncovered a systematic error in the
previous PSF system, affecting the entire mission to date, whereby returned
source RA and Dec values are seen to vary sinusoidally about the true position
(amplitude ~0.8") with source azimuthal position. The new PSF system is now
available and is seen as a major improvement with regard to the detection of
spurious sources. The new PSF also largely removes the discovered astrometry
error and is seen to improve the positional accuracy of EPIC. The modular
nature of the PSF system allows for further refinements in the future.Comment: Accepted for publication in A&A. 15 pages, 13 figures (some of
reduced quality). A full-resolution version is available at
http://www.star.le.ac.uk/~amr30/amr_PSFpaper.pd
Macrophages promote the progression of premalignant mammary lesions to invasive cancer.
Breast cancer initiation, progression and metastasis rely on a complex interplay between tumor cells and their surrounding microenvironment. Infiltrating immune cells, including macrophages, promote mammary tumor progression and metastasis; however, less is known about the role of macrophages in early stage lesions. In this study, we utilized a transplantable p53-null model of early progression to characterize the immune cell components of early stage lesions. We show that macrophages are recruited to ductal hyperplasias with a high tumor-forming potential where they are differentiated and polarized toward a tumor-promoting phenotype. These macrophages are a unique subset of macrophages, characterized by pro-inflammatory, anti-inflammatory and immunosuppressive factors. Macrophage ablation studies showed that macrophages are required for both early stage progression and primary tumor formation. These studies suggest that therapeutic targeting of tumor-promoting macrophages may not only be an effective strategy to block tumor progression and metastasis, but may also have critical implications for breast cancer prevention
Clustering kinetics during natural ageing of Al-Cu based alloys with (Mg, Li) additions
Room temperature solute clustering in aluminium alloys, or natural ageing,
despite its industrial relevance, is still subject to debate, mostly due to its
experimentally challenging nature. To better understand the complex
multi-constituents' interactions at play, we have studied ternary and
quaternary subsystems based on the Al-Cu alloys, namely Al-Cu-Mg, Al-Cu-Li and
Al-Cu-Li-Mg. We used a recently introduced correlative technique using
small-angle neutrons and X-ray scattering (SANS and SAXS) to extract the
chemically resolved kinetics of room temperature clustering in these alloys,
which we completed with differential scanning calorimetry (DSC) and
micro-hardness measurements. The comparison of the clustering behaviours of
each subsystem allowed us to highlight the paramount role of Mg as a trigger
for diffusion and clustering. Indeed, while a strong natural ageing was
observed in the Al-Cu-Mg alloy, virtually none was shown for Al-Cu-Li. A very
slight addition of Mg (0.4%) to this system, however, drastically changed the
situation to a rapid formation of essentially Cu-rich hardening clusters, Mg
only joining them later in the reaction. This diffusion enabling effect of Mg
is discussed in terms of diffusion mechanism and complex interactions with the
quenched-in vacancies
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