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ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAdditions and Corrections - Nuclear Magnetic Resonance Spectroscopy. The Configurational Stability of Primary Grignard Reagents. Structure and Medium Effects.George M. Whitesides and John D. RobertsCite this: J. Am. Chem. Soc. 1967, 89, 11, 2799Publication Date (Print):May 1, 1967Publication History Published online7 May 2004Published inissue 1 May 1967https://pubs.acs.org/doi/10.1021/ja00987a603https://doi.org/10.1021/ja00987a603research-articleACS PublicationsRequest reuse permissionsArticle Views38Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

The wavelike structure is observed on both sides of the deformed area but not at the base region. Moreover, the wave structures at opposite positions on the deformed surface appear to be identical in shape, except that they are mirror images. A cross section of the target system shows that the crest of the waves to the right of the bottom region are turned to the right, whereas those on the left of the bottom are turned to the left, as indicated in Fig. 5a. Figure 5b shows a close-up view of the wave form in the right weld region (see Fig. 2 for wave structure in the left weld region). This behavior of the crest indicates that the velocity of the base plate was somewhat higher than that of the second plate. It is not yet possible to provide an unequivocal solution to this problem nor to establish the value of the critcial contact angle, since the results of the flow are not well known. However, the results in the figures are in qualitative agreement with a plausible extension of the considerations of the references to the present case. Concluding Remarks Melting is the usual commercial method for bonding of metals. In this process, the surface films (principally oxides) dissolve in the melt and/or float to the liquid surface and ultimately are segregated in and removed with the slag. A mechanical method such as hot or cold rolling frequently is employed to disrupt these surface films in order to bring bare metal into contact and provide bonding. We believe this is the first evidence that multiplate metallic structures may be spot-welded as a result of hypervelocity particle impact. It is evident from this work that meteoroid impact may cause seizure between surfaces (e.g., bearing surfaces) that are intended to slide freely on each other, even without penetration to the bearing interface.

Fast‐flowing ice streams in West Antarctica are separated from the nearly stagnant ice in the adjacent ridge by zones of highly localized deformation known as shear margins. It is presently uncertain what mechanisms control the location of shear margins and possibly allow them to migrate. In this paper we show how subglacial hydrological processes can select the shear margin location, leading to a smooth transition from a slipping to a locked bed at the base of an ice stream. Our study uses a two‐dimensional thermomechanical model in a cross section perpendicular to the direction of flow. We confirm that the intense straining at the shear margins can generate large temperate regions within the deforming ice. Assuming that the melt generated in the temperate ice collects in a drainage channel at the base of the margin, we show that a channel locally decreases the pore pressure in the subglacial till. Therefore, the basal shear strength just outside the channel, assuming a Coulomb‐plastic rheology, can be substantially higher than that inferred under the majority of the stream. Results show that the additional basal resistance produced by the channel lowers the stress concentrated on the locked portion of the bed. Matching the model to surface velocity data, we find that shear margins are stable when the slipping‐to‐locked bed transition occurs less than 500 m away from a channel operating at an effective pressure of 200 kPa and for a hydraulic transmissivity equivalent to a basal water film of order 0.2 mm thickness.

Microcontact printing (CP) was used in conjunction with self-assembled monolayers (SAMs) of hexadecanethiolates to fabricate gold etch masks on GaAs and GaAs/AlGaAs quantum-well substrates; patterns in the mask were transferred into the semiconductor with an anisotropic dry chemical-etch process. The measured luminescence efficiency of the etched features in GaAs/AlGaAs was similar to that of samples patterned using conventional lithography; this observation indicates that no mechanical or chemical damage is incurred in the CP process.

A crack-like creep rupture cavity is considered to extend along the interface bet′een t′o grains by diffusive transport of material into the boundary ahead of its tip. The shape of the cavity surfaces is determined here on the assumptions that this is governed by surface diffusion, and that steady state conditions prevail, so that the cavity advances as a profile retaining a constant shape near its tip. A second order non-linear differential e′uation for the profile is derived and a simple approximate solution is given, ′hich is sho′n to be highly accurate by comparison to a numerical solution. This allo′s the crack velocity, the radius of curvature adjacent to the tip, and the rate of matter flux into the boundary ahead of the tip to be related to one another and to material constants. The information is useful as boundary conditions to a coupled analysis of diffusion and stress concentration ahead of the cavity, so as to determine the rate of cavity propagation in terms of applied stress.

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This paper addresses localization of the deformation due to buckling that occurs immediately following the onset of bifurcation in the axisymmetric buckling of a perfect spherical elastic shell subject to external pressure. The localization process is so abrupt that the buckling mode of the classical eigenvalue analysis, which undulates over the entire shell, becomes modified immediately after bifurcation transitioning to an isolated dimple surrounded by an unbuckled expanse of the shell. The paper begins by revisiting earlier attempts to analyze the initial post-buckling behavior of the spherical shell, illustrating their severely limited range of validity. The unsuccessful attempts are followed by an approximate Rayleigh-Ritz solution which captures the essence of the localization process. The approximate solution reveals the pathway that begins at bifurcation from the classical mode shape to the localized dimple buckle. The second part of the paper presents an exact asymptotic expansion of the initial post-buckling behavior which accounts for localization and which further exposes the analytic details of the abruptness of the transition.