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For fabricating complex AISI304 parts with high performance by advanced powder/ metallurgy technologies, cold isostatic pressing (CIP) is introduced into selective laser sintering (SLS) combined with hot isostatic pressing (HIP), which is abbreviated to selective laser sintering/isostatic pressed (SLS/IP). The effect of processing parameters on the densification of Cu-AISI304 parts is analyzed and then the influence of Cu on their relative densities, metallurgical structures, and mechanical performances are investigated. The results show that relative densities of Cu-AISI304 parts fabricated by SLS/IP are mainly influenced by CIP pressure and sintering temperature, and it is interesting to find that the formula 1 - D = [(1 - [D.sub.0])e.sup.-KP] is testified by the CIP of SLS/IP. There is an antidensification phenomenon resulting from Cu and AISI304 in liquid sintering, but the relative densities of Cu-AISI304 parts can be gradually improved in HIP with Cu content increasing from 1 wt % to 3 wt %. After the above-mentioned Cu-AIS304 parts are finally hot isostatic pressed, their metallurgical structures consist of sosoloid (Cu,Ni) and (Fe, Ni) besides austenite (Fe, Cr, Ni, C), their best mechanical performances are close to those of solution treated compact AISI304 when Cu content is 3 wt %. [DOI: 10.1115/1.3168444] Keywords: selective laser sintering, isostatic pressing, relative density, metallurgical structure, mechanical performance

Voltage-dependent sodium ([Na.sup.+]) channels are heterogeneously distributed through the pacemaker of the heart, the sinoatrial node (SA node). The measured sodium channel current ([i.sub.Na]) density is higher in the periphery but low or zero in the center of the SA node. The functional roles of [i.sub.Na] in initiation and conduction of cardiac pacemaker activity remain uncertain. We evaluated the functional roles of [i.sub.Na] by computer modeling. A gradient model of the intact SA node and atrium of the rabbit heart was developed that incorporates both heterogeneities of the SA node electrophysiology and histological structure. Our computations show that a large [i.sub.Na] in the periphery helps the SA node to drive the atrial muscle. Removal [i.sub.Na] from the SA node slows down the pacemaking rate and increases the sinoatrial node-atrium conduction time. In some cases, reduction of the SA node [i.sub.Na] results in impairment of impulse initiation and conduction that leads to the SA node-atrium conduction exit block. Decrease in active SA node cell population has similar effects. Combined actions of reduced cell population and removal of [i.sub.Na] from the SA node have greater impacts on weakening the ability of the SA node to pace and drive the atrium. sodium current; sinoatrial node; aging; dysfunction; conduction block; computer simulation

A simple relationship is obtained between the external force F and the fracture toughness R for thin sheets in steady state elastoplastic combined tearing and peeling along self-similar paths. The relationship depends only on the material properties (E, [[sigma].sub.y], and [alpha] for an elastoplastic material with linear hardening) and strip cross section (B and H). An earlier analysis (which incorporates transient tearing and peeling) requires lengthy computations over the whole length of the strip. The present analysis avoids that complication. Experiments in steady-state agree with the theory. [DOI: 10.1115/1.1387020]

The controversy regarding the fate of the Chinese white dolphin (Sousa chinensis) was addressed. The habitat and future existence of the local Indo-Pacific humped-back dolphin in Hongkong is threatened by marine pollution, fishing, increasing shipping movements and major infrastructure projects. A dolphin sanctuary within a designated marine park area was proposed. Lack of an overall conservation strategy, shortcomings in the territory's environmental impact assessment system, and the limited local scientific knowledge concerning the dolphin population were cited as causes of the dolphin problem.