Two-photon optics of Bessel-Gaussian modes

In this paper we consider geometrical two-photon optics of Bessel-Gaussian modes generated in spontaneous parametric down-conversion of a Gaussian pump beam. We provide a general theoretical expression for the orbital angular momentum (OAM) spectrum and Schmidt number in this basis and show how this may be varied by control over the radial degree of freedom, a continuous parameter in Bessel-Gaussian modes. As a test we first implement a back-projection technique to classically predict, by experiment, the quantum correlations for Bessel-Gaussian modes produced by three holographic masks, a blazed axicon, binary axicon and a binary Bessel function. We then proceed to test the theory on the down-converted photons using the binary Bessel mask. We experimentally quantify the number of usable OAM modes and confirm the theoretical prediction of a flattening in the OAM spectrum and a concomitant increase in the OAM bandwidth. The results have implications for the control of dimensionality in quantum states.Comment: 8 pages, 10 figure

Marital status and suicidal ideation among Australian older adults: the mediating role of sense of belonging

See also Corrigendum: Suzanne McLaren, Rapson Gomez, Peter Gill and Jessica Chesler (2015). Marital status and suicidal ideation among Australian older adults: the mediating role of sense of belonging – CORRIGENDUM. International Psychogeriatrics, 27, pp 155-155. doi:10.1017/S1041610214002166

The South Australian Heat Flow Anomaly in east Antarctica: hot rocks in a cool place.

第3回極域科学シンポジウム/第32回極域地学シンポジウム 11月30日（金） 統計数理研究所 ３階セミナー

Uncharted waters: the unintended impacts of residual chlorine on water quality and biofilms

Disinfection residuals in drinking water protect water quality and public heath by limiting planktonic microbial regrowth during distribution. However, we do not consider the consequences and selective pressures of such residuals on the ubiquitous biofilms that persist on the vast internal surface area of drinking water distribution systems. Using a full scale experimental facility, integrated analyses were applied to determine the physical, chemical and biological impacts of different free chlorine regimes on biofilm characteristics (composition, structure and microbiome) and water quality. Unexpectedly, higher free chlorine concentrations resulted in greater water quality degredation, observable as elevated inorganic loading and greater discolouration (a major cause of water quality complaints and a mask for other failures). High-chlorine concentrations also reduced biofilm cell concentrations but selected for a distinct biofilm bacterial community and inorganic composition, presenting unique risks. The results challenge the assumption that a measurable free chlorine residual necessarily assures drinking water safety

An investigation of the effects of stage of ensilage on Nassella neesiana seeds, for reducing seed viability and injury to livestock

The noxious weed Nassella neesiana is established on a wide range of productive land throughout southeastern Australia. N. neesiana seeds, when mature, are sharp, causing injury to livestock, thus posing a problem in fodder bales. To reduce infestations of agricultural weeds in situ, production of silage from weed-infested pastures is practised as part of integrated weed management (IWM). However, there is little data to demonstrate whether this process is useful to reduce infestations or the harmful properties of N. neesiana. Therefore, the minimum duration of ensilage required to reduce the viability of N. neesiana seeds was investigated, both with and without addition of ensilage inoculants in this process. Also, the decreasing propensity of the seeds to injure livestock, after various times and conditions of ensilage, was assessed. Ensilage inoculant reduced seed germination probability to zero after 35 days. When no inoculant was added, zero viability was achieved after 42 days. A qualitative assessment of the hardness of ensilaged seeds found seed husks were softer (and therefore safer) after 42 days, whether inoculant was used or not. Therefore, we suggest that both the viability of N. neesiana seeds and hardness of seed casings are significantly reduced after 42 days, thereby reducing the risks of seed dispersal and injury to livestock

Revised stratigraphy of the Blanchetown Clay, Murray Basin: age constraints on the evolution of paleo Lake Bungunnia

Paleo Lake Bungunnia covered more than 40 000 km2 of southern Australia during the Plio-Pleistocene, although the age and origin of the lake remain controversial. The Blanchetown Clay is the main depositional unit and outcrop at Nampoo Station in far-western New South Wales provides the most continuous lacustrine section preserved in the basin. Here the Blanchetown Clay represents the maximum lake fill and comprises: (i) a basal well-sorted sand with interbedded clay (Chowilla Sand), representing initial flooding at the time of lake formation; (ii) a thick sequence of green-grey clay comprised dominantly of kaolinite and illite, with the apparently cyclic occurrence of illite interpreted to represent cool and dry glacial climatic intervals; and (iii) a 2.6 m-thick sequence of finely laminated silt and silty clay, here defined as the Nampoo Member of the Blanchetown Clay. New magnetostratigraphic data constrain the age of the oldest lake sediments to be younger than 2.581 Ma (Matuyama-Gauss boundary) and probably as young as 2.4 Ma. This age is significantly younger than the age of 3.2 Ma previously suggested for lake formation. The youngest Blanchetown Clay is older than 0.781 Ma (Brunhes-Matuyama boundary) and probably as old as 1.2 Ma. The Nampoo Station section provides a framework for the construction of a regional Plio-Pleistocene stratigraphy in the Murray Basin.<br /

Defect Sizing Using Distance-Gain-Size Diagrams for Flat-Bottomed Holes in a Solid: Theoretical Analysis and Experimental Verification

Although there are a number of potential pitfalls, the classical method of relating defect area to echo amplitude is still the most widely used method to size defects using ultrasonic pulse-echo techniques. In 1959 Krautkramer [1] was the first to introduce a set of curves (DGS diagrams) showing the variation of echo amplitude with range and target size. As Krautkramer made clear, such curves are dependent on transducer pulse shape. For the very far field he gave theoretical results assuming a fluid-like medium of propagation, but he had to resort to a large number of experimental measurements to construct the near field portion of the curves. Well known problems in using DGS diagrams include the sensitivity of echo amplitudes to target angular and lateral alignment and the need to construct a new set of curves for each transducer pulse shape. Furthermore, when sizing targets in solids there are likely to be errors if curves constructed assuming a fluid medium are used. In 1987, McLaren and Weight [2] gave an impulse-response method to predict echo amplitudes for arbitrary target position in the field and for any transducer pulse shape. Normally-aligned, flat-ended cylindrical targets and a fluid medium were assumed. More recently, Schmerr and Sedov [3,4] have calculated single frequency DGS diagrams for flat-bottomed holes (FBH’s), for both direct and water coupling, but the holes are assumed to be in a fluid-like material. Their method takes account of diffraction and refraction effects but not mode conversion. A more exact treatment of the effect of a solid medium of propagation on DGS diagrams has been given by Sumbatyan and Buyove [5] who developed DGS diagrams for disc-like targets using a boundary element method to solve the elastodynamic equations, but again, only for the case of continuous sinusoidal waves. One disadvantage of such an approach is that the calculations can be rather time consuming

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