237 research outputs found
Universal Robotic Gripper based on the Jamming of Granular Material
Gripping and holding of objects are key tasks for robotic manipulators. The
development of universal grippers able to pick up unfamiliar objects of widely
varying shape and surface properties remains, however, challenging. Most
current designs are based on the multi-fingered hand, but this approach
introduces hardware and software complexities. These include large numbers of
controllable joints, the need for force sensing if objects are to be handled
securely without crushing them, and the computational overhead to decide how
much stress each finger should apply and where. Here we demonstrate a
completely different approach to a universal gripper. Individual fingers are
replaced by a single mass of granular material that, when pressed onto a target
object, flows around it and conforms to its shape. Upon application of a vacuum
the granular material contracts and hardens quickly to pinch and hold the
object without requiring sensory feedback. We find that volume changes of less
than 0.5% suffice to grip objects reliably and hold them with forces exceeding
many times their weight. We show that the operating principle is the ability of
granular materials to transition between an unjammed, deformable state and a
jammed state with solid-like rigidity. We delineate three separate mechanisms,
friction, suction and interlocking, that contribute to the gripping force.
Using a simple model we relate each of them to the mechanical strength of the
jammed state. This opens up new possibilities for the design of simple, yet
highly adaptive systems that excel at fast gripping of complex objects.Comment: 10 pages, 7 figure
Frequency Response Studies for a Wedge Probe in Viscoelastic Fluids
The response of a hot-film wedge probe in viscoelastic fluids has been investigated by imposing on the probe a sinusoidal vibration of known amplitude and frequency. Root-mean-square (rms) velocities calculated from the displacement of the probe were compared to rms velocities obtained with a constant temperature anemometer. The tests were performed under turbulent flow conditions and also at flow rates where viscoelastic effects (i.e., decrease of heat transfer rates from the probe to the fluid and drag reduction) were observed.
The frequency range covered was narrow ( \u3c 100 cps). This limitation was imposed by the decision to superimpose the sinusoidal vibrations on the turbulence signal, in order to have dynamic conditions similar to those encountered in actual turbulence measurements. Measurements were performed in mineral oil and four solutions of polyisobutylene (Vistanex L-200) In mineral oil.
The experimental technique was established by measuring the response of the probe in mineral oil. These are the first data available in which the frequency response of a hot-film probe in a purely viscous liquid has been observed to be correct in the range studied. The ratios of velocities calculated using the two different methods were approximately 1.0. The results for viscoelastic fluids are similar with ratios ranging from 0.90 to 1.10. These results establish the validity of intensity measurements in viscoelastic fluids performed with hot-film wedge probes. They indicate that objections raised in the literature concerning the use of film probes in this type of fluid are not correct or, at least, not applicable to wedge probes
Melanotransferrin gene expression in melanoma cells is correlated with high levels of Jun/Fos family transcripts and with the presence of a specific AP1-dependent ternary complex
Recommended from our members
The effect of maltreatment type on adolescent executive functioning and inner speech
There are indications that different types of maltreatment can lead to different cognitive and behavioural outcomes. This study investigated whether maltreatment type was related to executive functioning (EF) abilities and the use of inner speech. Forty maltreated adolescents and a comparison group of 40 non-maltreated typically developing (TD) adolescents completed a battery of tasks designed to assess both their EF abilities and their vulnerability to disruptions to inner speech. They also completed an IQ test. MANCOVA and ANCOVA analyses were carried out to examine potential effects of maltreatment type (abuse alone; neglect alone; abuse/neglect combined and no maltreatment) on EF and use of inner speech.
Maltreatment type was related to EF abilities. In particular, abuse only and abuse/neglect combined had a greater negative impact on EF than neglect only. However, the neglect alone group were more vulnerable to disruptions to inner speech than the other two maltreatment groups, suggesting that they may be more reliant on the use of inner speech. These findings provide new insights into the differential impact of maltreatment type on EF and the use of inner speech in adolescence, and could be used to improve the educational outcomes of these vulnerable young people
The BMP Antagonist Follistatin-Like 1 Is Required for Skeletal and Lung Organogenesis
Follistatin-like 1 (Fstl1) is a secreted protein of the BMP inhibitor class. During development, expression of Fstl1 is already found in cleavage stage embryos and becomes gradually restricted to mesenchymal elements of most organs during subsequent development. Knock down experiments in chicken and zebrafish demonstrated a role as a BMP antagonist in early development. To investigate the role of Fstl1 during mouse development, a conditional Fstl1 KO allele as well as a Fstl1-GFP reporter mouse were created. KO mice die at birth from respiratory distress and show multiple defects in lung development. Also, skeletal development is affected. Endochondral bone development, limb patterning as well as patterning of the axial skeleton are perturbed in the absence of Fstl1. Taken together, these observations show that Fstl1 is a crucial regulator in BMP signalling during mouse development
Differential transferrin expression in placentae from normal and abnormal pregnancies: a pilot study
Abstract Background The placenta is an important site for iron metabolism in humans. It transfers iron from the mother to the fetus. One of the major iron transport proteins is transferrin, which is a blood plasma protein crucial for iron uptake. Its localization and expression may be one of the markers to distinguish placental dysfunction. Methods In the experimental study we used antibody preparation, mass spectrometric analysis, biochemical and immunocytochemical methods for characterization of transferrin expression on the human choriocarcinoma cell line JAR (JAR cells), placental lysates, and cryostat sections. Newly designed monoclonal antibody TRO-tf-01 to human transferrin was applied on human placentae from normal (n = 3) and abnormal (n = 9) pregnancies. Results Variations of transferrin expression were detected in villous syncytiotrophoblast, which is in direct contact with maternal blood. In placentae from normal pregnancies, the expression of transferrin in the syncytium was significantly lower (p Conclusion These observations suggest that in the case of abnormal pregnancies, the fetus may require higher levels of transferrin in order to prevent iron depletion due to the stress from the placental dysfunction.</p
Intracellular iron uptake is favored in Hfe-KO mouse primary chondrocytes mimicking an osteoarthritis-related phenotype
HFE-hemochromatosis is a disease characterized by a systemic iron overload phenotype mainly associated with mutations in the HFE protein (HFE) gene. Osteoarthritis (OA) has been reported as one of the most prevalent complications in HFE-hemochromatosis patients, but the mechanisms associated with its onset and progression remain incompletely understood. In this study, we have characterized the response to high iron concentrations of a primary culture of articular chondrocytes isolated from newborn Hfe-KO mice and compared the results with that of a similar experiment developed in cells from C57BL/6 wild-type (wt) mice. Our data provide evidence that both wt- and Hfe-KO-derived chondrocytes, when exposed to 50 mu M iron, develop characteristics of an OA-related phenotype, such as an increased expression of metalloproteases, a decreased extracellular matrix production, and a lower expression level of aggrecan. In addition, Hfe-KO cells also showed an increased expression of iron metabolism markers and MMP3, indicating an increased susceptibility to intracellular iron accumulation and higher levels of chondrocyte catabolism. Accordingly, upon treatment with 50 mu M iron, these chondrocytes were found to preferentially differentiate toward hypertrophy with increased expression of collagen I and transferrin and downregulation of SRY (sex-determining region Y)-box containing gene 9 (Sox9). In conclusion, high iron exposure can compromise chondrocyte metabolism, which, when simultaneously affected by an Hfe loss of function, appears to be more susceptible to the establishment of an OA-related phenotype.European Regional Development FundEuropean Union (EU) [EMBRC.PT Alg-01-0145-FEDER-022121, Norte-01-0145-FEDER-000012]Fundacao para a Ciencia e a TecnologiaPortuguese Foundation for Science and Technology [SFRH/BD/77056/2011]Portuguese Foundation for Science and TechnologyPortuguese Foundation for Science and TechnologyPortuguese Science and Technology FoundationPortuguese Foundation for Science and Technologyinfo:eu-repo/semantics/publishedVersio
Physical attractiveness as a mediator of the impact of early pubertal changes for girls
The present study examined the effects of early pubertal development and physical attractiveness on the popularity, body image, and self-esteem of over 200 sixth-grade girls. Two rival hypotheses were explored. The first suggests that physically attractive girls, because of their more favorable social environment, will exhibit fewer psychosocial difficulties than unattractive girls during pubertal development. The second hypothesis argues that attractive girls will exhibit greater difficulty during pubertal transition because their self-image is more intimately connected with their physical appearance. Although there were no significant interactions between attractiveness and pubertal development for either popularity or body image, the second hypothesis was supported with respect to self-esteem. Specifically, developing attractive girls exhibited lower self-esteem than their unattractive counterparts. The results are discussed in terms of the relative vulnerability to bodily changes of girls differing in physical attractiveness.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45265/1/10964_2005_Article_BF02088640.pd
- …