Underwater legged robotics: review and perspectives.

Nowadays, there is a growing awareness on the social and economic importance of the ocean. In this context, being able to carry out a diverse range of operations underwater is of paramount importance for many industrial sectors as well as for marine science and to enforce restoration and mitigation actions. Underwater robots allowed us to venture deeper and for longer time into the remote and hostile marine environment. However, traditional design concepts such as propeller driven remotely operated vehicles, autonomous underwater vehicles, or tracked benthic crawlers, present intrinsic limitations, especially when a close interaction with the environment is required. An increasing number of researchers are proposing legged robots as a bioinspired alternative to traditional designs, capable of yielding versatile multi-terrain locomotion, high stability, and low environmental disturbance. In this work, we aim at presenting the new field of underwater legged robotics in an organic way, discussing the prototypes in the state-of-the-art and highlighting technological and scientific challenges for the future. First, we will briefly recap the latest developments in traditional underwater robotics from which several technological solutions can be adapted, and on which the benchmarking of this new field should be set. Second, we will the retrace the evolution of terrestrial legged robotics, pinpointing the main achievements of the field. Third, we will report a complete state of the art on underwater legged robots focusing on the innovations with respect to the interaction with the environment, sensing and actuation, modelling and control, and autonomy and navigation. Finally, we will thoroughly discuss the reviewed literature by comparing traditional and legged underwater robots, highlighting interesting research opportunities, and presenting use case scenarios derived from marine science applications.

Learning to stop: a unifying principle for legged locomotion in varying environments.

Evolutionary studies have unequivocally proven the transition of living organisms from water to land. Consequently, it can be deduced that locomotion strategies must have evolved from one environment to the other. However, the mechanism by which this transition happened and its implications on bio-mechanical studies and robotics research have not been explored in detail. This paper presents a unifying control strategy for locomotion in varying environments based on the principle of 'learning to stop'. Using a common reinforcement learning framework, deep deterministic policy gradient, we show that our proposed learning strategy facilitates a fast and safe methodology for transferring learned controllers from the facile water environment to the harsh land environment. Our results not only propose a plausible mechanism for safe and quick transition of locomotion strategies from a water to land environment but also provide a novel alternative for safer and faster training of robots.

Bioinspired underwater legged robot for seabed exploration with low environmental disturbance.

Robots have the potential to assist and complement humans in the study and exploration of extreme and hostile environments. For example, valuable scientific data have been collected with the aid of propeller-driven autonomous and remotely operated vehicles in underwater operations. However, because of their nature as swimmers, such robots are limited when closer interaction with the environment is required. Here, we report a bioinspired underwater legged robot, called SILVER2, that implements locomotion modalities inspired by benthic animals (organisms that harness the interaction with the seabed to move; for example, octopi and crabs). Our robot can traverse irregular terrains, interact delicately with the environment, approach targets safely and precisely, and hold position passively and silently. The capabilities of our robot were validated through a series of field missions in real sea conditions in a depth range between 0.5 and 12 meters.

Fundamentals of soft robot locomotion.

Soft robotics and its related technologies enable robot abilities in several robotics domains including, but not exclusively related to, manipulation, manufacturing, human-robot interaction and locomotion. Although field applications have emerged for soft manipulation and human-robot interaction, mobile soft robots appear to remain in the research stage, involving the somehow conflictual goals of having a deformable body and exerting forces on the environment to achieve locomotion. This paper aims to provide a reference guide for researchers approaching mobile soft robotics, to describe the underlying principles of soft robot locomotion with its pros and cons, and to envisage applications and further developments for mobile soft robotics.

Retardation assisted enhanced Raman scattering from silicon nanostripes in the visible range.

Patterned silicon on insulator structures representing evenly spaced parallel 15 nm-thick nanostripes exhibit an enhanced Raman scattering response when excited in the visible range in an oblique incidence backscattering configuration. The enhancement phenomenon in two structures having different stripe widths, 200 and 50 nm, is investigated at various sample azimuthal orientations, excitation radiation polarizations as well as laser wavelengths and is shown to be of resonant nature. The enhanced Raman response of the patterned structures is attributed to the presence of Mie resonances, essentially resulting in the enhancement of the internal electric field within the nanostripes. It is quantitatively described in terms of the spheroid particle model extended beyond the electrostatic limit to include field retardation effects that are shown to be responsible for the resonant behaviour in the visible range.

The lakes of Titan.

The surface of Saturn's haze-shrouded moon Titan has long been proposed to have oceans or lakes, on the basis of the stability of liquid methane at the surface. Initial visible and radar imaging failed to find any evidence of an ocean, although abundant evidence was found that flowing liquids have existed on the surface. Here we provide definitive evidence for the presence of lakes on the surface of Titan, obtained during the Cassini Radar flyby of Titan on 22 July 2006 (T16). The radar imaging polewards of 70 degrees north shows more than 75 circular to irregular radar-dark patches, in a region where liquid methane and ethane are expected to be abundant and stable on the surface. The radar-dark patches are interpreted as lakes on the basis of their very low radar reflectivity and morphological similarities to lakes, including associated channels and location in topographic depressions. Some of the lakes do not completely fill the depressions in which they lie, and apparently dry depressions are present. We interpret this to indicate that lakes are present in a number of states, including partly dry and liquid-filled. These northern-hemisphere lakes constitute the strongest evidence yet that a condensable-liquid hydrological cycle is active in Titan's surface and atmosphere, in which the lakes are filled through rainfall and/or intersection with the subsurface 'liquid methane' table.

Titan Radar Mapper observations from Cassini's T3 fly-by.

Cassini's Titan Radar Mapper imaged the surface of Saturn's moon Titan on its February 2005 fly-by (denoted T3), collecting high-resolution synthetic-aperture radar and larger-scale radiometry and scatterometry data. These data provide the first definitive identification of impact craters on the surface of Titan, networks of fluvial channels and surficial dark streaks that may be longitudinal dunes. Here we describe this great diversity of landforms. We conclude that much of the surface thus far imaged by radar of the haze-shrouded Titan is very young, with persistent geologic activity.

The sand seas of Titan: Cassini RADAR observations of longitudinal dunes.

The most recent Cassini RADAR images of Titan show widespread regions (up to 1500 kilometers by 200 kilometers) of near-parallel radar-dark linear features that appear to be seas of longitudinal dunes similar to those seen in the Namib desert on Earth. The Ku-band (2.17-centimeter wavelength) images show approximately 100-meter ridges consistent with duneforms and reveal flow interactions with underlying hills. The distribution and orientation of the dunes support a model of fluctuating surface winds of approximately 0.5 meter per second resulting from the combination of an eastward flow with a variable tidal wind. The existence of dunes also requires geological processes that create sand-sized (100- to 300-micrometer) particulates and a lack of persistent equatorial surface liquids to act as sand traps.

Radar soundings of the ionosphere of Mars.

We report the first radar soundings of the ionosphere of Mars with the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument on board the orbiting Mars Express spacecraft. Several types of ionospheric echoes are observed, ranging from vertical echoes caused by specular reflection from the horizontally stratified ionosphere to a wide variety of oblique and diffuse echoes. The oblique echoes are believed to arise mainly from ionospheric structures associated with the complex crustal magnetic fields of Mars. Echoes at the electron plasma frequency and the cyclotron period also provide measurements of the local electron density and magnetic field strength.

Cassini radar views the surface of Titan.

The Cassini Titan Radar Mapper imaged about 1% of Titan's surface at a resolution of approximately 0.5 kilometer, and larger areas of the globe in lower resolution modes. The images reveal a complex surface, with areas of low relief and a variety of geologic features suggestive of dome-like volcanic constructs, flows, and sinuous channels. The surface appears to be young, with few impact craters. Scattering and dielectric properties are consistent with porous ice or organics. Dark patches in the radar images show high brightness temperatures and high emissivity and are consistent with frozen hydrocarbons.

Interferon-gamma inhibits expression of the long pentraxin PTX3 in human monocytes.

PTX3 is a prototypic long pentraxin expressed by various cell types, most prominently monocytes and endothelial cells, in response to interleukin-1 (IL-1), tumor necrosis factor (TNF) and bacterial products. In the present report, we show that interferon-gamma (IFN-gamma) inhibits the expression of the PTX3 gene induced by exposure to IL-1, TNF or lipopolysaccharide in human monocytes. This effect is dose dependent and observable when IFN-gamma is added from 24 h before up to 3 h after the addition of IL-1. While the time course of the IL-1-induced PTX3 mRNA expression is not affected, IFN-gamma reduces the stability of the PTX3 mRNA as well as its transcription. The inhibition of PTX3 expression is restricted to monocytes in that no inhibition occurs in cytokine-stimulated fibroblasts and endothelial cells. Under the same conditions, as expected, IFN-gamma augmented monocyte chemotactic protein-1 expression in the same cell preparations. PTX3 protein secretion by activated monocytes is also suppressed by exposure to IFN-gamma. Altogether, these data identify a negative pathway of regulation mediated by IFN-gamma, which may occur under inflammatory conditions.

Cloning of mouse ptx3, a new member of the pentraxin gene family expressed at extrahepatic sites.

Pentraxins, which include C reactive protein (CRP) and serum amyloid P component (SAP), are prototypic acute phase reactants that serve as indicators of inflammatory reactions. Here we report genomic and cDNA cloning of mouse ptx3 (mptx3), a member of the pentraxin gene family and characterize its extrahepatic expression in vitro and in vivo. mptx3 is organized into three exons on chromosome 3: the first (43 aa) and second exon (175 aa) code for the signal peptide and for a protein portion with no high similarity to known sequences the third (203 aa) for a domain related to classical pentraxins, which contains the "pentraxin family signature." Analysis of the N terminal portion predicts a predominantly alpha helical structure, while the pentraxin domain of ptx3 is accommodated comfortably in the tertiary structure fold of SAP. Normal and transformed fibroblasts, undifferentiated and differentiated myoblasts, normal endothelial cells, and mononuclear phagocytes express mptx3 mRNA and release the protein in vitro on exposure to interleukin-1beta (IL-1beta) and tumor necrosis factor (TNF)alpha. mptx3 was induced by bacterial lipopolysaccharide in vivo in a variety of organs and, most strongly, in the vascular endothelium of skeletal muscle and heart. Thus, mptx3 shows a distinct pattern of in vivo expression indicative of a significant role in cardiovascular and inflammatory pathology.

Possible role of the transcription factor interferon regulatory factor 1 (IRF-1) in the regulation of ornithine decarboxylase (ODC) gene expression during IFN gamma macrophage activation.

In this report we discuss the role of interferon regulatory factor 1 (IRF-1) in the regulation of ornithine decarboxylase (ODC) transcription during IFN gamma human macrophage activation. We show that a binding sequence for the transcription factor IRF-1 is contained in the first intron of the human ODC gene (from nt +2711 to nt +2722) and we demonstrate that the level of expression of IRF-1 increases in human macrophages and in the human promonocytic cell line, U937, previously differentiated in monocytes/macrophages by phorbol myristate acetate (PMA), after 2 h of IFN gamma stimulation. We also show that the hamster tk-ts13 cell line, stably transfected with the IRF-1 cDNA, over-expresses ODC. In addition, a specific complex was detected, by gel-shift assay after incubating a 20 bp double-stranded oligomer containing the binding sequence for IRF-1 with nuclear proteins extracted from human macrophages and from (PMA-differentiated) U937 cells stimulated with IFN gamma for 2 h.

[The reduction of beta-adrenoceptor density and the suppression of ectopic ventricular activity with low doses of amiodarone]. / Riduzione della densità beta-adrenocettoriale e soppressione dell'attività ectopica ventricolare con basse dosi di amiodarone.

In 5 patients with frequent premature ventricular ectopic beats, refractory to other antiarrhythmic treatments, amiodarone, given orally at the dose of 200 mg once a day for 4 weeks, reduced beta-adrenoceptor density from 202.9 +/- 62 to 101.1 +/- 33 fmol/mg protein (p < 0.01). Similarly, kd decreased from 21.0 +/- 6 to 3.9 +/- 1 (p < 0.05). Changes in beta-adrenoceptor population were accompanied by a marked reduction in mean premature ventricular complexes (PVC) frequency from the control value of 428.9 +/- 150.3 to 13.4 +/- 10.7 PVC/h (p < 0.05) and by a decrease in heart rate, from 83.8 +/- 4 to 73.9 +/- 4 b/min (p < 0.01). On the contrary, mean arterial pressure remained unchanged. Patients did not show side effects during treatment. Therefore, low dose oral amiodarone has important pharmacologic and therapeutic effects. It significantly reduces lymphocyte beta-adrenoceptor density and is effective in treatment of ventricular arrhythmias. Additional studies were performed in vitro exposing lymphocytes to increasing concentrations of amiodarone. The analysis of variance for repeated measures showed that amiodarone-induced reduction in lymphocyte beta-adrenoceptor density is a dose-depending phenomenon. Accordingly, treatment with doses of amiodarone higher than that used in the present study may induce a major reduction in lymphocyte beta-receptor density and exert a depressant cardiac effect.

Subclinical cardiotoxicity by doxorubicin: a pulsed Doppler echocardiographic study.

In order to detect subclinical levels of Doxorubicin (D) cardiotoxicity, 21 patients aged 42 +/- 8 years with malignancies and treated with D as a part of a multiple regimen, were evaluated. The mean cumulative dose of D was 242 +/- 112 mg.m-2 (150 to 520 mg.m-2). Patients with systemic hypertension, valvular diseases, suspected coronary artery disease, ejection fraction less than 55% as assessed by radionuclide angiography, and aged more than 50 years were excluded from the study. A Doppler echocardiographic examination was performed before and after the course of D therapy with a mean interval of 142 days. The following variables were assessed: fractional shortening (FS), ejection fraction (EF), stroke volume (SV), isovolumic relaxation time (IVRT), maximal early diastolic flow velocity (Emax), maximal late diastolic flow velocity (Amax), and mitral deceleration time (Mdt). Indices derived from 19 aged-matched normal subjects were compared to those of the patients before the course of therapy. Doppler echocardiographic measurements did not differ significantly between the control group and patients before the course of therapy. While there were no significant changes in FS, EF, and SV in the study group before and after therapy, indices of diastolic filling showed striking differences: IVRT changed from 72 +/- 11 to 87 +/- 19 ms (P less than 0.001), Emax from 81 +/- 12 to 65 +/- 17 cm.s-1 (P less than 0.001), Mdt from 174 +/- 25 to 183 +/- 34 ms (P less than 0.05), Amax from 44 +/- 17 to 52 +/- 16 cm.s-1 (P less than 0.01). These data demonstrate impaired diastolic filling after doxorubicin therapy at conventional dosages.

[A program of combined ECG and VCG automatic diagnosis. Note I. The atriogram]. / Su di un programma di diagnostica automatica combinata in ECG e VCG. Nota I. L'atriogramma

In this paper a new computer aided ECG and VCG data handling is analized. It is based on an optimum estimation of dipole moment, which is used as the main diagnosis parameter. Already known diagnostical methods (available in present literature) are compared with this new technique. The available diagnostical range has been increased widely. The sensitivity of such a program is being analyzed both for normal and abnormal cases.