320 research outputs found
Human Arm simulation for interactive constrained environment design
During the conceptual and prototype design stage of an industrial product, it
is crucial to take assembly/disassembly and maintenance operations in advance.
A well-designed system should enable relatively easy access of operating
manipulators in the constrained environment and reduce musculoskeletal disorder
risks for those manual handling operations. Trajectory planning comes up as an
important issue for those assembly and maintenance operations under a
constrained environment, since it determines the accessibility and the other
ergonomics issues, such as muscle effort and its related fatigue. In this
paper, a customer-oriented interactive approach is proposed to partially solve
ergonomic related issues encountered during the design stage under a
constrained system for the operator's convenience. Based on a single objective
optimization method, trajectory planning for different operators could be
generated automatically. Meanwhile, a motion capture based method assists the
operator to guide the trajectory planning interactively when either a local
minimum is encountered within the single objective optimization or the operator
prefers guiding the virtual human manually. Besides that, a physical engine is
integrated into this approach to provide physically realistic simulation in
real time manner, so that collision free path and related dynamic information
could be computed to determine further muscle fatigue and accessibility of a
product designComment: International Journal on Interactive Design and Manufacturing
(IJIDeM) (2012) 1-12. arXiv admin note: substantial text overlap with
arXiv:1012.432
Barium & related stars and their white-dwarf companions II. Main-sequence and subgiant stars
Barium (Ba) dwarfs and CH subgiants are the less-evolved analogues of Ba and
CH giants. They are F- to G-type main-sequence stars polluted with heavy
elements by a binary companion when the latter was on the Asymptotic Giant
Branch (AGB). This companion is now a white dwarf that in most cases cannot be
directly detected. We present a large systematic study of 60 objects classified
as Ba dwarfs or CH subgiants. Combining radial-velocity measurements from
HERMES and SALT high-resolution spectra with radial-velocity data from CORAVEL
and CORALIE, we determine the orbital parameters of 27 systems. We also derive
their masses by comparing their location in the Hertzsprung-Russell diagram
with evolutionary models. We confirm that Ba dwarfs and CH subgiants are not at
different evolutionary stages and have similar metallicities, despite their
different names. Additionally, Ba giants appear significantly more massive than
their main-sequence analogues. This is likely due to observational biases
against the detection of hotter main-sequence post-mass-transfer objects.
Combining our spectroscopic orbits with the Hipparcos astrometric data, we
derive the orbital inclinations and the mass of the WD companion for four
systems. Since this cannot be done for all systems in our sample yet (but
should be with upcoming Gaia data releases), we also analyse the mass-function
distribution of our binaries. We can model this distribution with very narrow
mass distributions for the two components and random orbital orientation on the
sky. Finally, based on BINSTAR evolutionary models, we suggest that the orbital
evolution of low-mass Ba systems can be affected by a second phase of
interaction along the Red Giant Branch of the Ba star, impacting on the
eccentricities and periods of the giants.Comment: Accepted for publication in A&A on the 5th of April, 201
Effect of Fasciola gigantica excretory secretory antigen on rat hematological indices
The present study was undertaken to investigate the effect of Fasciola gigantica excretory secretory antigen (Fg-ESA) on rat hematological indices. Fg-ESA was prepared by keeping thoroughly washed 40 F. gigantica flukes in 100 ml phosphate buffer saline (PBS) for 2 h at 37℃, and centrifuging the supernatant at 12,000 g at 4℃ for 30 min. The protein content of Fg-ESA was adjusted to 1.8 mg/ml. The rats were randomly divided into two groups of six rats each. Rats in group A received 0.5 ml of Fg-ESA intraperitoneally (i.p.) for 7 days, whereas control rats in group B received 0.5 ml of PBS i.p. for 7 days. Hemograms of both groups were studied initially and on days 0, 2, 4, 14 and 21 after the final injection of Fg-ESA or PBS. Progressive and significant (p < 0.01) declines in the values of hemoglobin, hematocrit, and total erythrocyte count were observed without significant (p > 0.05) changes in the values of mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, or mean corpuscular volume in group A. Thus, we conclude that Fg-ESA induces normocytic normochromic anemia in rats
Binary-object spectral-synthesis in 3D (BOSS-3D) -- Modelling H-alpha emission in the enigmatic multiple system LB-1
Context: To quantitatively decode the information stored within an observed
spectrum, detailed modelling of the physical state and accurate radiative
transfer solution schemes are required. In the analysis of stellar spectra, the
numerical model often needs to account for binary companions and 3D structures
in the stellar envelopes. The enigmatic binary (or multiple) system LB-1
constitutes a perfect example of such a complex multi-D problem. Aims: To
improve our understanding of the LB-1 system, we directly modelled the
phase-dependent H-alpha line profiles of this system. To this end, we developed
a multi-purpose binary-object spectral-synthesis code in 3D (BOSS-3D). Methods:
BOSS-3D calculates synthetic line profiles for a given state of the
circumstellar material. The standard pz-geometry commonly used for single stars
is extended by defining individual coordinate systems for each involved object
and by accounting for the appropriate coordinate transformations. The code is
then applied to the LB-1 system, considering two main hypotheses, a binary
containing a stripped star and Be star, or a B star and a black hole with a
disc. Results: Comparing these two scenarios, neither model can reproduce the
detailed phase-dependent shape of the H-alpha line profiles. A satisfactory
match with the observations, however, is obtained by invoking a disc around the
primary object in addition to the Be-star disc or the black-hole accretion
disc. Conclusions: The developed code can be used to model synthetic line
profiles for a wide variety of binary systems, ranging from transit spectra of
planetary atmospheres, to post-asymptotic giant branch binaries including
circumstellar and circumbinary discs and massive-star binaries with stellar
winds and disc systems. For the LB-1 system, our modelling provides strong
evidence that each object in the system contains a disc-like structure
Empirical mass-loss rates and clumping properties of Galactic early-type O supergiants
International audienceAims. We investigate the impact of optically thick clumping on spectroscopic stellar wind diagnostics in O supergiants and constrain wind parameters associated with porosity in velocity space. This is the first time the effects of optically thick clumping have been investigated for a sample of massive hot stars, using models which include a full optically thick clumping description. Methods. We re-analyse existing spectroscopic observations of a sample of eight O supergiants previously analysed with the non-local-thermodynamic-equilibrium (NLTE) atmosphere code CMFGEN. Using a genetic algorithm wrapper around the NLTE atmosphere code FASTWIND we obtain simultaneous fits to optical and ultraviolet spectra and determine photospheric properties, chemical surface abundances and wind properties. Results. We provide empirical constraints on a number of wind parameters including the clumping factors, mass-loss rates and terminal wind velocities. Additionally, we establish the first systematic empirical constraints on velocity filling factors and interclump densities. These are parameters that describe clump distribution in velocity-space and density of the interclump medium in physical-space, respectively. We observe a mass-loss rate reduction of a factor of 3.6 compared to theoretical predictions from Vink et al. (2000), and mass-loss rates within a factor 1.4 of theoretical predictions from Björklund et al. (2021). Conclusions. We confirm that including optically thick clumping allows simultaneous fitting of optical recombination lines and ultraviolet resonance lines, including the unsaturated ultraviolet phosphorus lines (P v λλ1118-1128), without reducing the phosphorus abundance. We find that, on average, half of the wind velocity field is covered by dense clumps. We also find that these clumps are 25 times denser than the average wind, and that the interclump medium is 3-10 times less dense than the mean wind. The former result agrees well with theoretical predictions, the latter suggests that lateral filling-in of radially compressed gas might be critical for setting the scale of the rarefied interclump matter
Is HR 6819 a triple system containing a black hole? -- An alternative explanation
HR 6819 was recently proposed to be a triple system consisting of an inner
B-type giant + black hole binary with an orbital period of 40d and an outer Be
tertiary. This interpretation is mainly based on two inferences: that the
emission attributed to the outer Be star is stationary, and that the inner
star, which is used as mass calibrator for the black hole, is a B-type giant.
We re-investigate the properties of HR 6819 by spectral disentangling and an
atmosphere analysis of the disentangled spectra to search for a possibly
simpler alternative explanation for HR 6819. Disentangling implies that the Be
component is not a static tertiary, but rather a component of the binary in the
40-d orbit. The inferred radial velocity amplitudes imply an extreme mass ratio
of M_2/M_1 = 15 +/- 3. We infer spectroscopic masses of 0.4
Msun and 6 Msun for the primary and secondary, which agree well
with the dynamical masses for an inclination of i = 32 deg. This indicates that
the primary might be a stripped star rather than a B-type giant. Evolutionary
modelling suggests that a possible progenitor system would be a tight (P_i ~
2d) B+B binary system that experienced conservative mass transfer. While the
observed nitrogen enrichment of the primary conforms with the predictions of
the evolutionary models, we find no indications for the predicted He
enrichment. We suggest that HR 6819 is a binary system consisting of a stripped
B-type primary and a rapidly-rotating Be star that formed from a previous
mass-transfer event. In the framework of this interpretation, HR 6819 does not
contain a black hole. Interferometry can distinguish between these two
scenarios by providing an independent measurement of the separation between the
visible components.Comment: Submitted to A&A, 13 pages (16 figures and 2 tables); 4 pages
supplementary material (4 figures and 4 tables). Comments are welcom
HPV infection and immunochemical detection of cell-cycle markers in verrucous carcinoma of the penis
Penile verrucous carcinoma is a rare disease and little is known of its aetiology or pathogenesis. In this study we examined cell-cycle proteins expression and correlation with human papillomavirus infection in a series of 15 pure penile verrucous carcinomas from a single centre. Of 148 penile tumours, 15 (10%) were diagnosed as pure verrucous carcinomas. The expression of the cell-cycle-associated proteins p53, p21, RB, p16INK4A and Ki67 were examined by immunohistochemistry. Human papillomavirus infection was determined by polymerase chain reaction to identify a wide range of virus types. The expression of p16INK4A and Ki67 was significantly lower in verrucous carcinoma than in usual type squamous cell carcinoma, whereas the expression of p53, p21 and RB was not significantly different. p53 showed basal expression in contrast to usual type squamous cell carcinoma. Human papillomavirus infection was present in only 3 out of 13 verrucous carcinomas. Unique low-risk, high-risk and mixed viral infections were observed in each of the three cases. In conclusion, lower levels of p16INK4A and Ki67 expressions differentiate penile verrucous carcinoma from usual type squamous cell carcinoma. The low Ki67 index reflects the slow-growing nature of verrucous tumours. The low level of p16INK4A expression and human papillomavirus detection suggests that penile verrucous carcinoma pathogenesis is unrelated to human papillomavirus infection and the oncogenes and tumour suppressor genes classically altered by virus infection.Peer reviewedFinal Accepted Versio
The Tarantula massive binary monitoring: III. Atmosphere analysis of double-lined spectroscopic systems
Context. Accurate stellar parameters of individual objects in binary systems are essential to constrain the effects of binarity on stellar evolution. These parameters serve as a prerequisite to probing existing and future theoretical evolutionary models.
Aims. We aim to derive the atmospheric parameters of the 31 double-lined spectroscopic binaries in the Tarantula Massive Binary Monitoring sample. This sample, composed of detached, semi-detached and contact systems with at least one of the components classified as an O-type star, is an excellent test-bed to study how binarity can impact our knowledge of the evolution of massive stars.
Methods. In the present paper, 32 epochs of FLAMES/GIRAFFE spectra are analysed by using spectral disentangling to construct the individual spectra of 62 components. We then apply the CMFGEN atmosphere code to determine their stellar parameters and their helium, carbon, and nitrogen surface abundances.
Results. Among the 31 systems that we study in the present paper, we identify between 48 and 77% of them as detached, likely pre-interacting systems, 16% as semi-detached systems, and between 5 and 35% as systems in or close to contact phase. Based on the properties of their components, we show that the effects of tides on chemical mixing are limited. Components on longer-period orbits show higher nitrogen enrichment at their surface than those on shorter-period orbits, in contrast to expectations of rotational or tidal mixing, implying that other mechanisms play a role in this process. For semi-detached systems, components that fill their Roche lobe are mass donors. They exhibit higher nitrogen content at their surface and rotate more slowly than their companions. By accreting new material, their companions spin faster and are likely rejuvenated. Their locations in the N − v sin i diagram tend to show that binary products are good candidates to populate the two groups of stars (slowly rotating, nitrogen-enriched objects and rapidly rotating non-enriched objects) that cannot be reproduced through single-star population synthesis. Finally, we find no peculiar surface abundances for the components in (over-)contact systems, as has been suggested by evolutionary models for tidal mixing.
Conclusions. This sample, consisting of 31 massive binary systems, is the largest sample of binaries composed of at least one O-type star to be studied in such a homogeneous way by applying spectral disentangling and atmosphere modelling. The study of these objects gives us strong observational constraints to test theoretical binary evolutionary tracks
- …