What does it mean to be peasant in the Alexander Skutch Biological Corridor? "Struggles and hopes of the ASBC peasant communities"

One of the major challenges we face is how to reconcile economic growth under a neoliberal paradigm, with environmental conservation as proposed within a sustainable development paradigm. Peasants around the world are especially vulnerable to this contradiction. The peasants in the Alexander Skutch Biological Corridor in southern Costa Rica are no exception to this dilemma. Despite the fact that Costa Rica is well known for its commitment to environmental issues and for its history of having an effective social welfare state, its adoption of neoliberal policies is in contradiction with its commitment to sustainable development. This contradiction produces the social, economic, political and ideological context in which the peasants of the ASBC are embedded. In this context, this paper explores what it means to have a peasant identity, how they maintain their livelihoods as coffee growers, what level of environmental awareness they have, and how they navigate the complex current challenges of a neoliberal political economy

Design and test of a magnetic thrust bearing

A magnetic thrust bearing can be employed to take thrust loads in rotating machinery. The design and construction of a prototype magnetic thrust bearing for a high load per weight application is described. The theory for the bearing is developed. Fixtures were designed and the bearing was tested for load capacity using a universal testing machine. Various shims were employed to have known gap thicknesses. A comparison of the theory and measured results is presented

Advanced Active-Magnetic-Bearing Thrust-Measurement System

An advanced thrust-measurement system utilizes active magnetic bearings to both (1) levitate a floating frame in all six degrees of freedom and (2) measure the levitation forces between the floating frame and a grounded frame. This system was developed for original use in measuring the thrust exerted by a rocket engine mounted on the floating frame, but can just as well be used in other force-measurement applications. This system offers several advantages over prior thrust-measurement systems based on mechanical support by flexures and/or load cells: The system includes multiple active magnetic bearings for each degree of freedom, so that by selective use of one, some, or all of these bearings, it is possible to test a given article over a wide force range in the same fixture, eliminating the need to transfer the article to different test fixtures to obtain the benefit of full-scale accuracy of different force-measurement devices for different force ranges. Like other active magnetic bearings, the active magnetic bearings of this system include closed-loop control subsystems, through which the stiffness and damping characteristics of the magnetic bearings can be modified electronically. The design of the system minimizes or eliminates cross-axis force-measurement errors. The active magnetic bearings are configured to provide support against movement along all three orthogonal Cartesian axes, and such that the support along a given axis does not produce force along any other axis. Moreover, by eliminating the need for such mechanical connections as flexures used in prior thrust-measurement systems, magnetic levitation of the floating frame eliminates what would otherwise be major sources of cross-axis forces and the associated measurement errors. Overall, relative to prior mechanical-support thrust-measurement systems, this system offers greater versatility for adaptation to a variety of test conditions and requirements. The basic idea of most prior active-magnetic-bearing force-measurement systems is to calculate levitation forces on the basis of simple proportionalities between changes in those forces and changes in feedback-controlled currents applied to levitating electromagnetic coils. In the prior systems, the effects of gap lengths on fringing magnetic fields and the concomitant effects on magnetic forces were neglected. In the present system, the control subsystems of the active magnetic bearings are coupled with a computer-based automatic calibration system running special-purpose software wherein gap-length-dependent fringing factors are applied to current and magnetic-flux-based force equations and combined with a multipoint calibration method to obtain greater accuracy

Microstructures of cast silver-copper alloy archaeological artefacts

Cast silver-copper alloys objects form a significant part of the archaeological record from the first millenium BC onwards. Although age hardening of annealed and quenched material has been well studied there has been little study of cast microstructures. This work used a combination of scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and optical microscopy (OM) to explore the range of microstructures in archaeological cast silver and compare them with those in modern cast silver. Modern cast silver showed extensive fine scale precipitation of copper within the grains which was unconnected to the copper-rich phase of the primary eutectic. Ancient cast objects displayed a wide range of microstructures, some very similar to the modern cast silver but some quite different. EBSD allowed interpretation of the microstructure close to some grain boundaries whose detail was obscured by the cast structure in OM and SEM images. Orientation images showed fine-scale interpenetration of the adjoining grains suggesting cellular growth, suggesting that over archaeological time boundary modification may take place in cast as well as wrought and annealed structures

Glycine transport inhibitors for the treatment of pain.

Opioids, local anesthetics, anticonvulsant drugs, antidepressants, and non-steroidal anti-inflammatory drugs (NSAIDs) are used to provide pain relief but they do not provide adequate pain relief in a large proportion of chronic pain patients and are often associated with unacceptable side effects. Inhibitory glycinergic neurotransmission is impaired in chronic pain states, and this provides a novel target for drug development. Inhibitors of the glycine transporter 2 (GlyT2) enhance inhibitory neurotransmission and show particular promise for the treatment of neuropathic pain. N-arachidonyl-glycine (NAGly) is an endogenous lipid that inhibits glycine transport by GlyT2 and also shows potential as an analgesic, which may be further exploited in drug development. In this review we discuss the role of glycine neurotransmission in chronic pain and future prospects for the use of glycine transport inhibitors in the treatment of pain.NHMRC Grant: 104596

Underwater glider navigation error compensation using sea current data

Underwater glider is an emerging platform to explore the ocean with remarkably long operational endurance up to several months. Underwater glider navigation systems have significant limitations, on the other hand, in keeping the navigation error small. There is no reference coordinates information for position estimation and not enough immediate orientation reference for attitude estimation under the sea. Moreover, external disturbances including the sea currents make the navigation error increase further. In order to reduce the navigation error, we exploit a priori knowledge on the average current over the operation area. The performance and the robustness of the proposed algorithm are demonstrated using an experimental data obtained by Korea Institute of Ocean Science & Technology. The algorithm can be used to reduce the navigation error for one glider and also for multiple gliders by fusing the estimated errors. It can be also directly used to predict floating object path in order to use the prediction to design a collision avoidance path

A Role for BK Channels in Heart Rate Regulation in Rodents

The heart generates and propagates action potentials through synchronized activation of ion channels allowing inward Na+ and Ca2+ and outward K+ currents. There are a number of K+ channel types expressed in the heart that play key roles in regulating the cardiac cycle. Large conductance calcium-activated potassium (BK) ion channels are not thought to be directly involved in heart function. Here we present evidence that heart rate can be significantly reduced by inhibiting the activity of BK channels. Agents that specifically inhibit BK channel activity, including paxilline and lolitrem B, slowed heart rate in conscious wild-type mice by 30% and 42%, respectively. Heart rate of BK channel knock-out mice (Kcnma1−/−) was not affected by these BK channel inhibitors, suggesting that the changes to heart rate were specifically mediated through BK channels. The possibility that these effects were mediated through BK channels peripheral to the heart was ruled out with experiments using isolated, perfused rat hearts, which showed a significant reduction in heart rate when treated with the BK channel inhibitors paxilline (1 µM), lolitrem B (1 µM), and iberiotoxin (0.23 µM), of 34%, 60%, and 42%, respectively. Furthermore, paxilline was shown to decrease heart rate in a dose-dependent manner. These results implicate BK channels located in the heart to be directly involved in the regulation of heart rate

Glycine311, a determinant of paxilline block in BK channels: a novel bend in the BK S6 helix

The tremorogenic fungal metabolite, paxilline, is widely used as a potent and relatively specific blocker of Ca2+- and voltage-activated Slo1 (or BK) K+ channels. The pH-regulated Slo3 K+ channel, a Slo1 homologue, is resistant to blockade by paxilline. Taking advantage of the marked differences in paxilline sensitivity and the homology between subunits, we have examined the paxilline sensitivity of a set of chimeric Slo1/Slo3 subunits. Paxilline sensitivity is associated with elements of the S5–P loop–S6 module of the Slo1 channel. Replacement of the Slo1 S5 segment or the second half of the P loop results in modest changes in paxilline sensitivity. Replacing the Slo1 S6 segment with the Slo3 sequence abolishes paxilline sensitivity. An increase in paxilline affinity and changes in block kinetics also result from replacing the first part of the Slo1 P loop, the so-called turret, with Slo3 sequence. The Slo1 and Slo3 S6 segments differ at 10 residues. Slo1-G311S was found to markedly reduce paxilline block. In constructs with a Slo3 S6 segment, S300G restored paxilline block, but most effectively when paired with a Slo1 P loop. Other S6 residues differing between Slo1 and Slo3 had little influence on paxilline block. The involvement of Slo1 G311 in paxilline sensitivity suggests that paxilline may occupy a position within the central cavity or access its blocking position through the central cavity. To explain the differences in paxilline sensitivity between Slo1 and Slo3, we propose that the G311/S300 position in Slo1 and Slo3 underlies a structural difference between subunits in the bend of S6, which influences the occupancy by paxilline