Inhibition of urease-mediated ammonia production by 2-octynohydroxamic acid in hepatic encephalopathy.

Hepatic encephalopathy is a neuropsychiatric complication of liver disease which is partly associated with elevated ammonemia. Urea hydrolysis by urease-producing bacteria in the colon is often mentioned as one of the main routes of ammonia production in the body, yet research on treatments targeting bacterial ureases in hepatic encephalopathy is limited. Herein we report a hydroxamate-based urease inhibitor, 2-octynohydroxamic acid, exhibiting improved in vitro potency compared to hydroxamic acids that were previously investigated for hepatic encephalopathy. 2-octynohydroxamic acid shows low cytotoxic and mutagenic potential within a micromolar concentration range as well as reduces ammonemia in rodent models of liver disease. Furthermore, 2-octynohydroxamic acid treatment decreases cerebellar glutamine, a product of ammonia metabolism, in male bile duct ligated rats. A prototype colonic formulation enables reduced systemic exposure to 2-octynohydroxamic acid in male dogs. Overall, this work suggests that urease inhibitors delivered to the colon by means of colonic formulations represent a prospective approach for the treatment of hepatic encephalopathy.

Multigait soft robot.

This manuscript describes a unique class of locomotive robot: A soft robot, composed exclusively of soft materials (elastomeric polymers), which is inspired by animals (e.g., squid, starfish, worms) that do not have hard internal skeletons. Soft lithography was used to fabricate a pneumatically actuated robot capable of sophisticated locomotion (e.g., fluid movement of limbs and multiple gaits). This robot is quadrupedal; it uses no sensors, only five actuators, and a simple pneumatic valving system that operates at low pressures (< 10 psi). A combination of crawling and undulation gaits allowed this robot to navigate a difficult obstacle. This demonstration illustrates an advantage of soft robotics: They are systems in which simple types of actuation produce complex motion.

Self-assembly of magnetically interacting cubes by a turbulent fluid flow.

Previous work has demonstrated that combining mechanical vibration with magnetic interactions can result in the self-assembly of complex structures, albeit at low yield. Here we introduce a system where the yield of self-assembled structures is quantitatively predicted by a theoretical analysis. Millimeter-sized magnetic blocks, designed to form chains as their minimal energy state, are placed in a turbulent fluid flow. The distribution of chain lengths that form is quantitatively consistent with predictions, showing that the chain length distribution coincides with that of monomers or polymers in a thermal bath, with the turbulence strength parametrizing the effective temperature.

Integrated fabrication and magnetic positioning of metallic and polymeric nanowires embedded in thin epoxy slabs.

This paper describes a process for the fabrication and positioning of nanowires (of Au, Pd, and conjugated polymers) embedded in thin epoxy slabs. The procedure has four steps: (i) coembedding a thin film of metal or conducting polymer with a thin film of nickel metal (Ni) in epoxy; (ii) sectioning the embedded structures into nanowires with an ultramicrotome ("nanoskiving"); (iii) floating the epoxy sections on a pool of water; and (iv) positioning the sections with an external magnet to a desired location ("magnetic mooring"). As the water evaporates, capillary interactions cause the sections to adhere to the substrate. Both the Ni and epoxy can be etched to generate free-standing metallic nanowires. The average translational deviation in the positioning of two nanowires with respect to each other is 16 +/- 13 mum, and the average angular deviation is 3 +/- 2 degrees . Successive depositions of nanowires yield the following structures of interest for electronic and photonic applications: electrically continuous junctions of two Au nanowires, two Au nanowires spanned by a poly(3-hexylthiophene) (P3HT) nanowire; single-crystalline Au nanowires that cross; crossbar arrays of Au nanowires; crossbar arrays of Au and Pd nanowires; and a 50 x 50 array of poly(benzimidazobenzophenanthroline ladder) (BBL) nanowires. Single-crystalline Au nanowires can be placed on glass wool fibers or on microfabricated polymeric waveguides, with which the nanowire can be addressed optically.