Flexible bifunctional monoethylphosphonate/carboxylates of Zn(ii) and Co(ii) reinforced with DABCO co-ligand: paradigmatic structural organization with pcu topology

The prototypal [M2(EtBCP)2(DABCO)0.5] MOFs, compliant with isoreticular expansion in two-dimensions, show flexibility manifested by a two-step CO2 adsorption isotherm, which might be associated to the “lever-action” of the metal-phosphonate moieties.

A lever action hypothesis for pendulous hummingbird flowers: experimental evidence from a columbine

Background and Aims Pendulous flowers (due to a flexible pedicel) are a common, convergent trait of hummingbird-pollinated flowers. However, the role of flexible pedicels remains uncertain despite several functional hypotheses. Here we present and test the ‘lever action hypothesis’: flexible pedicels allow pendulous flowers to move upwards from all sides, pushing the stigma and anthers against the underside of the feeding hummingbird regardless of which nectary is being visited. Methods To test whether this lever action increased pollination success, we wired emasculated flowers of serpentine columbine, Aquilegia eximia, to prevent levering and compared pollination success of immobilized flowers with emasculated unwired and wire controls. Key Results Seed set was significantly lower in wire-immobilized flowers than unwired control and wire control flowers. Video analysis of visits to wire-immobilized and unwired flowers demonstrated that birds contacted the stigmas and anthers of immobilized flowers less often than those of flowers with flexible pedicels. Conclusions We conclude that flexible pedicels permit the levering of reproductive structures onto a hovering bird. Hummingbirds, as uniquely large, hovering pollinators, differ from flies or bees which are too small to cause levering of flowers while hovering. Thus, flexible pedicels may be an adaptation to hummingbird pollination, in particular due to hummingbird size. We further speculate that this mechanism is effective only in radially symmetric flowers; in contrast, zygomorphic hummingbird-pollinated flowers are usually more or less horizontally oriented rather than having pendulous flowers and flexible pedicels.

Visualizing Winchester: a brand history through iconic Western images

Purpose This paper aims to present a visually documented brand history of Winchester Repeating Arms through a cultural analysis of iconic Western images featuring its lever action rifles. Design/methodology/approach The study applies visual culture perspectives and methods to the research and writing of brand history. Iconic Western images featuring Winchester rifles have been selected, examined, and used as points of departure for gathering and interpreting additional data about the brand. The primary sources consist chiefly of photographs from the nineteenth century and films and television shows from the twentieth century. Most visual source materials were obtained from the US Library of Congress, the Smithsonian Institution, the Buffalo Bill Center of the West and the Internet Movie Firearms Database. These have been augmented by written sources. Findings Within a few years of the launch of the Winchester brand in 1866, visual images outside company control associated its repeating rifles with the settlement of the American West and with the colorful people involved. Some of these images were reproduced in books and others sold to consumers in the form of cartes de visite, cabinet cards and stereographs made from albumen prints. Starting in the 1880s, the live Wild West shows of William F. Cody and his stars entertained audiences with a heroic narrative of the period that included numerous Winchesters. During the twentieth century and into the present, Winchesters have been featured in motion pictures and television series with Western themes. Research limitations/implications Historical research is an ongoing process. The discovery of new primary data, both written and visual, may lead to a revised interpretation of the selected images. Originality/value Based largely on images as primary data sources, this study approaches brand history from the perspective of visual culture theory and data. The research shows how brands acquire meaning not just from the companies that own them but also from consumers, the media and other producers of popular culture.

Experimental study of loosening behavior of plain shank bolted joint under dynamic loading

Purpose – Bolted joints are commonly used to connect structural members. These joints can be disassembled whenever required. Various types of washers are used between nut and the connected member to keep the joints tight. However, these joints often become loose over time under dynamic loading conditions. The purpose of this paper is to know the reasons of loosening of bolted joints and to identify the main parameters that contribute to the bolt loosening, and to verify them with previous work. Design/methodology/approach – This work studies loosening of bolted joint in a test rig under varying tightening torque as well as for various types of washers used as the number of load cycles increases. Four trial runs are taken for each case considered and the average results are found out to minimize possible sources of errors. For the purpose, a specifically made test rig is used which is capable of applying harmonic load on the bolted joint by the lever action. Findings – The study compares the loosening of bolted joint with and without washer, and also under different initial tightening conditions. This study has shown the suitability of the test rig, methodology and parameters for study of loosening in bolted joints. This study presents an indigenous test, capable of applying harmonic load on bolted joint. Originality/value – The results establish that the methodology and parameters selected were appropriate for the purpose of study of loosening of bolted joints. This study has provided a base line for further work to understand the loosening of bolted joints.

Study on Flow-Induced Vibration Characteristics of Hydraulic Hoist of Large-Span Upwelling Radial Steel Gate

In this paper we conduct study on flow-induced vibration of large-span upwelling radial steel Gate and its hydraulic hoist. Place an emphasis on vibration response characteristics under two working conditions of diversion and drainage, which proves the safety of hydraulic hoist gate vibration caused by gate vibration. Firstly, we study on dynamic characteristics of fluid-structure interaction of association system of gate and start and stop lever, reveals the discipline of the effect fluid having on structural dynamic characteristics. On this basis, flow-induced vibration characteristics under two conditions of with and without start and stop lever action considered. The results indicate that the gate vibration response with hydraulic hoist used decreases, which explains start and stop lever has certain effect of restraining vibration on gate vibration. In addition, under the working condition of drainage the vibration magnitude of start and stop lever is smaller than that of gate body, which explains there is damping action during transference of gate vibration through start and stop lever. The results find out that on the assumption of optimized gate structure and hydraulic arrangement, it is practicable, safe and reliable to adopt hydraulic hoist. The achievement has directive significance on similar projects construction in the future