2,543 research outputs found
Fabrication and Actuation of Hierarchically-Patterned Polymer Substrates for Dynamic Surface and Optical Properties
Switchable optical materials, which possess reversible color and transparency change in response to external stimuli, are of wide interest for potential applications such as windows and skylights in architectural and vehicular settings or optical sensors for environmental monitoring. This thesis considers the tuning of optical properties by tailoring and actuating responsive materials. Specifically, we demonstrate the design and fabrication of tilted pillar arrays on wrinkled elastomeric polydimethylsiloxane (PDMS) as a reversibly switchable optical window. While the original PDMS film exhibits angle-dependent colorful reflection due to Bragg diffraction of light from the periodic pillar array, the tilted pillar film appears opaque due to random scattering. Upon re-stretching the film to the original pre-strain, the grating color is restored due to the straightened pillars and transmittance is recovered. Then, we develop a composite film, consisting of a thin layer of quasi-amorphous array of silica nanoparticles (NPs) embedded in bulk elastomeric PDMS, with initial high transparency and angle-independent coloring upon mechanical stretching. The color can be tuned by the silica NP size. The switch between transparency and colored states could be reversibly cycled at least 1000 times without losing the film’s structural and optical integrity.
We then consider the micropatterning of nematic liquid crystal elastomers (NLCEs) as micro-actuator materials. Planar surface anchoring of liquid crystal (LC) monomers is achieved with a poly(2-hydroxyethyl methacrylate)-coated PDMS mold, leading to monodomains of vertically aligned LC monomers within the mold. After cross-linking, the resulting NLCE micropillars show a relatively large radial strain when heated above nematic to isotropic transition temperature, which can be recovered upon cooling. Finally, the understanding of liquid crystal surface anchoring under confined boundary conditions is applied to the self-assembly of gold nanorods (AuNRs) driven by LC defect structures and to dynamically tune the surface plasmon resonance (SPR) properties. By exploiting the confinement of the smectic liquid crystal, 4-octyl-4’-cyanobiphenyl (8CB), to patterned pillars treated with homeotropic surface anchoring, topological defects are formed at precise locations around each pillar and can be tuned by varying the aspect ratio of the pillars and the temperature of the system. As a result, the AuNR assemblies and SPR properties can be altered reversibly by heating and cooling between smectic, nematic and isotropic phases
The trade union movement in Rhodesia, 1910-1924
A RJE article on the early Trade Union Movement in Rhodesia during the formative years 1910 to 1924.One of the effects of the first World War was that circumstances became more favourable to artisan organisation, particularly on the railways, where the only permanent trade union in Rhodesia was formed by white employees in 1916. This was by no means the first attempt to form a union, but earlier efforts in various industries had usually proved ineffective and ephemeral. It has been pointed out by Gray that on average, the white working class in Rhodesia was paid substantially more than its equivalent in South Africa or Britain. As Arrighi has indicated, white labour had to be attracted to Rhodesia, and unlike South Africa, the white working class was a consequence of capitalist development and did not precede it, which meant that this class tended to be in a good bargaining position.* This initially undermined the need for formal organisation, which was further discouraged by the small scale of industries in the country; the railways were the only large employers of white labour. The war altered this situation in two important respects, the increased cost of living and loss of manpower. Employers failed to respond favourably to early demands by white workers, and the trade union movement was the result
“Buy Now, Pay Later: No Fees. No Credit Check.”
Afterpay and Affirm, are financial technology (“fintech”) platforms that allow consumers to split their low-cost purchases into four installment payments–with seemingly no interest, fees, or hard credit inquiries. Similar to retailer fees on credit card transactions, these companies generate most of their profits as the intermediary between consumers and merchants. By flaunting celebrities like A$AP Rocky and Keke Palmer, the loan products are heavily advertised as the “cool” alternative to traditional credit cards and are particularly well-received among Millennials and Generation Z (“Gen Z”) consumers. Consequently, consumer advocates are duly concerned that lenders irresponsibly extend credit to a young generation, who remain particularly vulnerable to the “present bias,” which undervalues future losses and overvalues present satisfaction. Currently, U.S. regulators have not confined lenders to proper regulatory parameters and remain silent on the regulatory gaps caused by the third-party lenders’ intentional “skirt[ing] of the definition of a [covered] loan under some U.S. laws.
An analysis of the Rhodesian referendum, 1922
A journal article analyzing the Rhodesian referendum of 1922.The success of the Resposible Government Association in the referendum of October 1922, in which the electorate supported Responsible Government in preference to Union with South Africa, is clearly a significant turning- point in Southern Rhodesian history. There has been little analysis, however, of how and why this result came about,' and the vote for Responsible Government has simply been attributed to the natural outcome of ‘British instincts’ and Imperial sentiment. These factors undoubtedly contributed to some extent, but were not the prime causes underlying the settlers’ decision
Knowledge Of Blood Transfusion Among Nurses In Hospital Pulau Pinang: Nursing Responsibilities And Patient Management Related To Transfusion Reactions
Darah adalah produk yang berharga dan unik yang diperolehi daripada manusia. Darah amat penting untuk menyelamatkan nyawa dan memulihkan kesihatan manusia
Blood is precious and unique products, derived from human being. It is essential in saving lives and improve human healt
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