Hitoshi Sasaki

A Multilegged Modular Robot That Meanders: Investigation of Turning Maneuvers Using Its Inherent Dynamic Characteristics

This paper deals with the motion of a multilegged modular robot. The robot consists of a set of homogenous modules, each of which has a body and two legs and is connected to the others through a three-degree-of-freedom rotary joint. The leg joints are manipulated to follow periodic desired trajectories, and the joints between the modules act like a passive spring with a damper. This robot has characteristic dynamic properties. Specifically, a straight walk naturally turns into a meandering walk by changing the compliance of the joints between the modules without incorporation of any oscillatory inputs. We first show that this transition is excited due to a Hopf bifurcation, based on a numerical simulation and Floquet analysis. Following that, we examine whether the maneuverability and agility of the robot increase by utilizing the dynamic characteristics inherent in the robot. In particular, we conduct an experiment in which the robot pursues a target moving across the floor. We propose a simple controlle...

Neuron attachment properties of carbon negative-ion implanted bioabsorbable polymer of poly-lactic acid

Abstract Modification of a bioabsorbable polymer of poly-lactic acid (PLA) by negative carbon ion implantation was investigated with resect to radiation effects on surface physical properties and nerve-cell attachment properties. Carbon negative ions were implanted to PLA at energy of 5–30 keV with a dose of 1014–1016 ions/cm2. Most C-implanted PLA samples showed contact angles near 80° and almost same as that of unimplanted PLA, although a few samples at 5 keV and less 3×1014 ions/cm2 had contact angles larger than 90°. The attachment properties of nerve cells of PC-12h (rat adrenal phechromocytoma) in vitro were studied. PC-12h cells attached on the unimplanted region in C-implanted PLA samples at 5 and 10 keV. On the contrary, the nerve cells attached on only implanted region for the C-implanted PLA sample at 30 keV and 1×1015 ions/cm2.

Negative-ion implanter for powders and its application to nanometer-sized metal particle formation in the surface of glass beads

We have developed a negative-ion implanter for uniform implantation into each powder surface without particle scattering. It consists of a plasma sputter-type negative-ion source, a mass separator, an acceleration tube, a lens, X–Y deflectors, a 90° deflector, and a Faraday cup with an agitator. The electrostatic 90° deflector bends a horizontal beam to a vertical direction and leads it into the Faraday cup. The agitator is an electromagnetic vibrator at a frequency of 120 Hz, which mixes particles for whole surface treatment and uniform implantation. In this implanter, we obtained no scattering implantation for spherical oxide beads with diameters ranging from 5 to 1000 μm in an agitated state, and also obtained a good uniformity of implanted atoms among beads. For an application of the negative ion implantation into powders, copper ions were implanted into soda-lime glass beads and plates at conditions of 50 and 30 keV, respectively, with 1×1017u200aions/cm2. In linear optical properties, both implanted sam...

Altered brain response to others׳ pain in major depressive disorder

BACKGROUNDnEmpathy has a central role in successful interpersonal engagement. Several studies have reported altered empathy in major depressive disorder (MDD), which could lead to interpersonal difficulties. However, the neural basis of altered empathy in the disorder is still largely unknown. To address this, we performed functional magnetic resonance imaging that tested empathy for others׳ pain in MDD patients.nnnMETHODSnEleven patients with MDD and 11 age-, gender-, handedness-, and education level-matched healthy control subjects were studied. We compared MDD patients and healthy controls for their regional hemodynamic responses to visual perception of videos showing human hands in painful situations. We also assessed subjective pain ratings of the videos in each group.nnnRESULTSnThe MDD patients showed lower pain ratings for the painful videos compared with the healthy controls. In addition, the MDD patients showed reduced cerebral activation in the left middle cingulate cortex, and the right somatosensory-related cortices, whereas they showed greater cerebral activation in the left inferior frontal gyrus.nnnLIMITATIONSnWe relied on a relatively small sample size and could not exclude effects of medications.nnnCONCLUSIONSnThese results suggest that in MDD patients the altered neural activations in these regions may be associated with a deficit in the identification of pain in others. This study adds to our understanding of the neural mechanism involved in empathy in MDD.

Anterior cingulate volume predicts response to cognitive behavioral therapy in major depressive disorder

BACKGROUNDnCognitive behavioral therapy (CBT) is widely used to treat major depressive disorder (MDD). Although improved response prediction could facilitate the development of individualized treatment plans, few studies have investigated whether underlying brain structure is related to CBT response in MDD.nnnMETHODSnTen MDD patients who received individual CBT were studied in this study. We investigated the relationship between the regional gray matter (GM) volume and subsequent responses to CBT using voxel-based morphometry.nnnRESULTSnThe degree of improvement in depressive symptoms was positively correlated with GM volume in the caudal portion of the anterior cingulate cortex.nnnLIMITATIONSnThe sample size was small, and the effects of medication on the results could not be excluded.nnnCONCLUSIONSnOur results, although preliminary, suggest that the anterior cingulate cortex is a key structure whose volume can be used to predict responses to CBT and is thus a potential prognostic marker in MDD.

Extracellular matrix absorption properties of negative ion-implanted polystyrene, polydimethylsiloxane and poly-lactic acid

Abstract Absorption properties of extracellular matrix (ECM) were investigated for carbon negative-ion-implanted polymers of polystyrene (PS), polydimethylsiloxane (PDMS) and poly-lactic acid (PLA) to estimate cell attachment properties of the modified surface without cell culture. Carbon negative ions were implanted to these polymers at 10 keV with a dose of 10 14 –10 16 ions/cm 2 . Implanted samples were dipped in a culture medium including serum for 2 h at 37 °C. After the samples were rinsed with phosphate-buffered saline (PBS) and with pure water and then dried, nitrogen atoms absorbed on the surface were investigated by XPS. The molecular structure of many kinds of extracellular matrix proteins contains nitrogen atoms; polymers of PS, PDMS and PLA do not include nitrogen. Therefore, we can evaluate the absorption properties of ECM by the nitrogen atoms absorbed on the surface. The nitrogen content increased after ion implantation for these polymers: from 5.5 to 8% for PS; from 1 to 5% for PDMS; and from 6 to 8.3% PLA. The contact angle for C-implanted PS and PDMS decreased with increasing ion dose, and corresponded well with the absorption properties of the extracellular matrix. However, the contact angle for PLA did not significantly change after ion implantation. Thus, the absorption properties of ECM represent another measure for the estimation of cell-attachment properties.

Turning Maneuvers of a Multi-legged Modular Robot Using Its Inherent Dynamic Characteristics

This paper deals with the motion of a multi-legged modular robot. The robot consists of six homogenous modules, each of which has a body and two legs and is connected to the others through a three-degree-of-freedom joint. The leg joints are manipulated to follow periodic desired trajectories, and the joints between the modules act like a passive spring with a damper. This robot has characteristic dynamic properties. Specifically, a straight walk naturally turns into a meandering walk by changing the compliance of the joints between the modules without incorporation of any oscillatory inputs. We first show that this transition is excited due to a Hopf bifurcation, based on a numerical simulation and Floquet analysis. Following that, we examine whether the maneuverability and agility increase by utilizing the dynamic characteristics inherent in the robot. In particular, we conduct an experiment in which the robot pursues a target moving across the floor. We propose a simple controller to accomplish the task and achieve high maneuverability and agility by making the most of the robots dynamic features

Additive Effect of Cigarette Smoking on Gray Matter Abnormalities in Schizophrenia

Abstract It is widely known that there is a high prevalence of cigarette smoking in schizophrenia. One of the explanations is the self-medication hypothesis. Based on this hypothesis, it has been suggested that nicotine has procognitive effect or even neuroprotective effect in schizophrenia. However, cigarettes contain numerous neurotoxic substances, making the net effect of cigarette smoking on brain function and structure complex. Indeed, recent studies have called into question the self-medication hypothesis. We aimed to test whether there is an interaction between diagnosis and smoking status in gray matter volume, ie, whether smoking has specific effects on gray matter or whether main effects of these 2 variables additively affect common brain regions. Magnetic resonance imaging (MRI) images were obtained from 4 groups: (1) normal controls with no smoking history, (2) normal controls currently smoking and/or with a past history of smoking, (3) schizophrenia patients with no smoking history, and (4) schizophrenia patients currently smoking and/or with a past history of smoking. We used voxel-based morphometry to compare gray matter volumes among the 4 groups. We did not find any interaction between diagnosis and smoking, but we did find negative additive effects of schizophrenia diagnosis and smoking status in the left prefrontal cortex. The decrease in left prefrontal volume was associated with greater numbers of cigarette pack years and severe positive and negative symptoms. The current findings do not support the neuroprotective effect of smoking on gross brain structure in schizophrenia, emphasizing the necessity of longitudinal studies to test causal relationships among these variables.

A negative ion beam application for improving biocompatibility of polystyrene surface

Improving biocompatibility of polystyrene surface by negative-ion implantation was investigated in respect to two kinds of cells: human umbilical vascular endothelial cells (HUVEC) and neurons (rat adrenal phechromocytoma: PC-12h). Negative ions of silver were implanted to non-treated polystyrene dishes (NTPS) at conditions of 20 keV and 3×1015ions/cm2 with or without a pattering mask with narrow slits array of 60 μm in width. Negative ions were used to avoid charge-up problem. The contact angle of pure water on ion-implanted NTPS surface was about 75°, which was lower than 86° for the original surface of NTPS. It was found from XPS surface analysis that this change to hydrophilic surface was caused by introduced functional groups of C-O, C=O, and O-C=O, during and after the ion implantation. After cell culture experiment, HUVEC cells attached only on the ion-implanted region of NTPS. On the ion-implanted narrow region with a width of 60 μm, attached HUVEC cells aligned with a longitudinal direction. As f...