high-work-function contact. For the same reason, electrons are extracted from C60 at the CalMEH-PPV:C,, interface. The result, then, is that separated carriers are not "wasted": thev are automaticallv collected by the prope; electrode so that external work can be done.The substantial enhancement in n ' C achieved with the bicontinuous D-A network material results from the large increase in the interfacial area over that in a D-A bilayer and from the relatively short distance from any point in the polymer to a charge-separating interface. Moreover, the internal D-A junctions inhibit carrier recombination and thereby improve the lifetime of the photoinduced carriers (6), so that the separated charge carriers can be efficiently collected by the built-in field from the asymmetric electrodes. Similar effects have been observed in MEH-PPV:Cyano-PPV polymer blends (10 , 1 1).The device efficiencies are not yet optimized. Because only -60% of the incident power was absorbed at 430 nm in the thinfilm devices used for obtaining the data in u Fig. 3, the internal carrier collection efficiency and energy conversion efficiency are approximately 1.7 times larger; that is, qc.= 90% e/ph and qr;-5.5% at 10 p,W/cm2. Although nearly 100% absorption can be achieved"by using thicker films, qc is currently limited in thick-film devices by internal resistive losses. Further imorovements in device efficiencies are expected when the blend com~ositionand the network morphology are optimized. SCIENCE VOL. 270 15 DECEMBER 1995

Methanolysis of {t-Bu2In[μ-P(SiMe3)2]}2 (1) in aromatic solvents gives polycrystalline InP fibers (dimensions 10−100 nm × 50−1000 nm) at 111−203 °C. The chemical pathway consists of a molecular component, in which precursor substituents are eliminated, and a nonmolecular component, in which the InP crystal lattices are assembled. The two components working in concert comprise the solution−liquid−solid (SLS) mechanism. The molecular component proceeds through a sequence of isolated and fully characterized intermediates:  1 → [t-Bu2In(μ-OMe)]2 (2) → [t-Bu2In(μ-PHSiMe3)]2 (3) → 2 → [t-Bu2In(μ-PH2)]3 (4). Complex 4, which is alternatively prepared from t-Bu3In and PH3, undergoes alkane elimination, the last steps of which are catalyzed by the protic reagent MeOH, PhSH, Et2NH, or PhCO2H. In the subsequent nonmolecular component of the pathway, the resulting (InP) n fragments dissolve into a dispersion of molten In droplets, and recrystallize as the InP fibers. Important criteria are identified for crystal growth of covalent nonmolecular solids from (organic) solution. The outcomes of other solution-phase semiconductor syntheses are rationalized according to the functioning of molecular and nonmolecular pathway components of the kind identified here.

A new performance-based plastic design procedure for steel moment frames is presented in this paper. The role of plastic analysis in seismic design of structures is illustrated. The ultimate design base shear for plastic analysis is derived by using the input energy from the design pseudo-velocity spectrum, a pre-selected yield mechanism, and an ultimate target drift. The proposed design procedure eliminates the need for a drift check after the structure is designed for strength as is done in the current design practice. Also, there is no need for response modification factors since the load deformation characteristics of the structure, including ductility and post-yield behavior, are explicitly used in calculating the design forces. The results of nonlinear static and nonlinear dynamic analyses of an example steel moment frame designed by the proposed method are presented and discussed. The implications of the new design procedure for future generation of seismic design codes are also discussed.

This paper presents a brief overview of performance‐based plastic design method as applied to the seismic design of building structures. The method uses pre‐selected target drift and yield mechanisms as key performance criteria. The design base shear for a selected hazard level is calculated by equating the work needed to push the structure monotonically up to the target drift to that required by an equivalent single degree of freedom to achieve the same state. Plastic design is performed to detail the frame members and connections in order to achieve the targeted yield mechanism and behaviour. The method has been successfully applied to a variety of common steel framing systems and, more recently, to Reinforced Concrete (RC) moment frames. Results of extensive inelastic static and dynamic analyses showed that the frames developed desired strong column‐sway mechanisms, and the storey drifts and ductility demands were well within the target values, thus meeting the desired performance objectives. The examples of 20‐storey steel and RC moment frames, as presented in the paper, showed that the method is especially advantageous for tall frames, where cumbersome and lengthy iterative design work in current practice can be completely eliminated, while leading to excellent performance as targeted. The basic work‐energy equation can also be used for seismic evaluation of existing structures. The results, as presented in this paper, showed excellent agreement with those obtained from more elaborate inelastic time‐history analyses. Copyright © 2009 John Wiley & Sons, Ltd.

It is well recognized that structures designed by current codes undergo large inelastic deformations during major earthquakes. However, lateral force distributions given in the seismic design codes are typically based on results of elastic-response studies. In this paper, lateral force distributions used in the current seismic codes are reviewed and the results obtained from nonlinear dynamic analyses of a number of example structures are presented and discussed. It is concluded that code lateral force distributions do not represent the maximum force distributions that may be induced during nonlinear response, which may lead to inaccurate predictions of deformation and force demands, causing structures to behave in a rather unpredictable and undesirable manner. A new lateral force distribution based on study of inelastic behavior is developed by using relative distribution of maximum story shears of the example structures subjected to a wide variety of earthquake ground motions. The results show that the suggested lateral force distribution, especially for the types of framed structures investigated in this study, is more rational and gives a much better prediction of inelastic seismic demands at global as well as at element levels.