15,922 research outputs found
Recycling and the Environment: a Comparative Review Between Mineral-based Plastics and Bioplastics
Since their conception in the 1950s, mineral-based plastics have completely revolutionised our society with production reaching record highs year upon year. This cheap, and durable material has seen usage across a plethora of diverse industries and products, replacing traditional materials such as metals and wood. However, our reliance on mineral-based plastics has led to their improper disposal across the global, affecting our environments and ecosystems. As a response, different methods have been developed to help dispose of the large amounts of plastic waste produced, such as incineration or dumping in landfill sites, but these methods are not without their drawbacks including release of toxic substances into the air and leachate into the soil and waters respectively. Consequently, much interest is generated and channelled in recent years to the introduction of several types of biopolymers. These include plastics based on cellulosic esters, starch derivatives, polyhydroxybutyrate and polylactic acid. These biopolymers have been viewed as a suitable replacement for mineral-based plastics, and their production a good strategy towards sustainable development as they are mainly composed of biocompounds such as starch, cellulose and sugars. This short review article provides an overview as to whether biopolymers can rival mineral-based plastics considering properties such as mechanical strength, Young’s modulus and crystallinity and could they be regarded as a suitable material to reduce our reliance on mineral-based plastics, whilst simultaneously reducing non-renewable energy consumption and carbon dioxide emissions
Heisenberg limited Sagnac interferometry
We show how the entangled photons produced in parametric down conversion can
be used to improve the sensitivity of a Sagnac interferometer. Two-photon and
four-photon coincidences increases the sensitivity by a factor of two and four
respectively. Our results apply to sources with arbitrary pumping and squeezing
parameters.Comment: 11 pages, 5 figure
Quantum interferometry using coherent beam stimulated parametric down-conversion
We show how stimulated parametric processes can be employed in experiments on
beyond the diffraction limit to overcome the problem of low visibility obtained
by using spontaneous down conversion operating in the high gain regime. We
further show enhancement of the count rate by several orders when stimulated
parametric processes are used. Both the two photon counts and the visibility
can be controlled by the phase of the stimulating coherent beam.Comment: 7 pages, 4 figure
Multi-reference approach to the calculation of photoelectron spectra including spin-orbit coupling
X-ray photoelectron spectra provide a wealth of information on the electronic
structure. The extraction of molecular details requires adequate theoretical
methods, which in case of transition metal complexes has to account for effects
due to the multi-configurational and spin-mixed nature of the many-electron
wave function. Here, the Restricted Active Space Self-Consistent Field method
including spin-orbit coupling is used to cope with this challenge and to
calculate valence and core photoelectron spectra. The intensities are estimated
within the frameworks of the Dyson orbital formalism and the sudden
approximation. Thereby, we utilize an efficient computational algorithm that is
based on a biorthonormal basis transformation. The approach is applied to the
valence photoionization of the gas phase water molecule and to the core
ionization spectrum of the complex.
The results show good agreement with the experimental data obtained in this
work, whereas the sudden approximation demonstrates distinct deviations from
experiments
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