Approximating the Sachdev-Ye-Kitaev model with Majorana wires

The Sachdev-Ye-Kitaev (SYK) model describes a collection of randomly interacting Majorana fermions that exhibits profound connections to quantum chaos and black holes. We propose a solid-state implementation based on a quantum dot coupled to an array of topological superconducting wires hosting Majorana zero modes. Interactions and disorder intrinsic to the dot mediate the desired random Majorana couplings, while an approximate symmetry suppresses additional unwanted terms. We use random matrix theory and numerics to show that our setup emulates the SYK model (up to corrections that we quantify) and discuss experimental signatures.Comment: 7 pages, 2 figure

Attosecond Transient Absorption Spectroscopy in the Water Window

The push to study the atomic and molecular dynamics at ever smaller time scales has been the main driving force for developing laser systems with ever shorter pulse durations. Thus far, picosecond lasers and femtosecond lasers have been used with great success in femtochemistry to study molecular dynamics such as molecular rotation and vibration, which all occur in the tens to hundreds of femtosecond. To study electron dynamics however, which are on the order of attoseconds, one needs attosecond laser sources to be able to have the time resolution required to probe ultrafast electron dynamics such as AC Stark shifts, Rabi oscillations and other more complex dynamics such as charge migration. By using few-cycle Titanium:Sapphire femtosecond lasers focused tightly into a generating gas like argon and neon, extreme ultraviolet spectra could be produce through high harmonic generation (HHG). Initial attosecond light sources based on Titanium:Sapphire sources produced HHG spectra up to 150 eV. In order to be able to probe the inner valence shells of atoms and molecules, increasing the cutoff energy of the harmonic spectra becomes necessary. Since the harmonic cutoff energy scales with the square of λ2, longer wavelength driving lasers were developed to increase the harmonic cutoff energies. However, since the harmonic yield at constant laser intensity scales with ~λ-6, thus driving laser photon flux must also increase as the driving laser wavelength increases. It is for this reason that in our lab, a 3 mJ 1.7 µm optical parametric-chirp pulse amplification (OPCPA) laser system was developed and the spectra can reach as high as 450 eV using helium as the generating gas. A number of numerical simulations were done to make suggested improvements to the OPCPA and the DFG seed source. The Titanium:Sapphire amplifiers for the OPCPA were rebuilt from a three-stage system to a two-stage system while producing similar output pulse energies after compression. This laser system will thus be more stable and maintenance will be easier. In this work, an OPCPA system which delivers CEP stable 2 mJ 12-fs pulses centered at 1.7 µm was used to conduct experiments near the water window. This system was used to study below-threshold harmonics produced in Argon, to perform Attosecond Transient Absorption Spectroscopy (ATAS) of Argon at 249 eV and to develop the semi-infinite gas cell which is a high flux soft x-ray source

A rotating disc gauge for absolute total pressure measurement in a high vacuum.

SIGLEAvailable from British Library Document Supply Centre- DSC:DX174376 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Cost effectiveness of a general practice chronic disease management plan for coronary heart disease in Australia

Background. The cost effectiveness of a general practice-based program for managing coronary heart disease (CHD) patients in Australia remains uncertain. We have explored this through an economic model.Methods. A secondary prevention program based on initial clinical assessment and 3 monthly review, optimising of pharmacotherapies and lifestyle modification, supported by a disease registry and financial incentives for quality of care and outcomes achieved was assessed in terms of incremental cost effectiveness ratio (ICER), in Australian dollars per disability adjusted life year (DALY) prevented.Results. Based on 2006 estimates, 263 487 DALYs were attributable to CHD in Australia. The proposed program would add $115 650 000 to the annual national heath expenditure. Using an estimated 15$8081 per DALY prevented. With more conservative estimates of effectiveness and uptake, estimates of up to $38 316 per DALY are observed in sensitivity analysis.Conclusions. Although innovation in CHD management promises improved future patient outcomes, many therapies and strategies proven to reduce morbidity and mortality are available today. A general practice-based program for the optimal application of current therapies is likely to be cost-effective and provide substantial and sustainable benefits to the Australian community.What is known about this topic? Chronic disease management programs are known to provide gains with respect to reductions in death and disability among patients with coronary heart disease. The cost effectiveness of such programs in the Australian context is not known.What does this paper add? This paper suggests that implementing a coronary heart disease program in Australia is highly cost-effective across a broad range of assumptions of uptake and effectiveness.What are the implications for practitioners? These data provide the economic rationale for the implementation of a chronic disease management program with a disease registry and regular review in Australia

HOXA13 and HOXD13 expression during development of the syndactylous digits in the marsupial Macropus eugenii

<p>Abstract</p> <p>Background</p> <p>Kangaroos and wallabies have specialised limbs that allow for their hopping mode of locomotion. The hindlimbs differentiate much later in development but become much larger than the forelimbs. The hindlimb autopod has only four digits, the fourth of which is greatly elongated, while digits two and three are syndactylous. We investigated the expression of two genes, <it>HOXA13 and HOXD13</it>, that are crucial for digit patterning in mice during formation of the limbs of the tammar wallaby.</p> <p>Results</p> <p>We describe the development of the tammar limbs at key stages before birth. There was marked heterochrony and the hindlimb developed more slowly than the forelimb. Both tammar <it>HOXA13 </it>and <it>HOXD13 </it>have two exons as in humans, mice and chickens. <it>HOXA13 </it>had an early and distal mRNA distribution in the tammar limb bud as in the mouse, but forelimb expression preceded that in the hindlimb. <it>HOXD13 </it>mRNA was expressed earlier in the forelimb than the hindlimb and was predominantly detected in the interdigital tissues of the forelimb. In contrast, the hindlimb had a more restricted expression pattern that appeared to be expressed at discrete points at both posterior and anterior margins of the limb bud, and was unlike expression seen in the mouse and the chicken.</p> <p>Conclusions</p> <p>This is the first examination of <it>HOXA </it>and <it>HOXD </it>gene expression in a marsupial. The gene structure and predicted proteins were highly conserved with their eutherian orthologues. Interestingly, despite the morphological differences in hindlimb patterning, there were no modifications to the polyalanine tract of either <it>HOXA13 </it>or <it>HOXD13 </it>when compared to those of the mouse and bat but there was a marked difference between the tammar and the other mammals in the region of the first polyserine tract of <it>HOXD13</it>. There were also altered expression domains for both genes in the developing tammar limbs compared to the chicken and mouse. Together these findings suggest that the timing of <it>HOX </it>gene expression may contribute to the heterochrony of the forelimb and hindlimb and that alteration to <it>HOX </it>domains may influence phenotypic differences that lead to the development of marsupial syndactylous digits.</p

Potential lethal damage repair in glioblastoma cells irradiated with ion beams of various types and levels of linear energy transfer

Glioblastoma (GBM), a Grade IV brain tumour, is a well-known radioresistant cancer. To investigate one of the causes of radioresistance, we studied the capacity for potential lethal damage repair (PLDR) of three altered strains of GBM: T98G, U87 and LN18, irradiated with various ions and various levels of linear energy transfer (LET). The GBM cells were exposed to 12C and 28Si ion beams with LETs of 55, 100 and 200 keV/μm, and with X-ray beams of 1.7 keV/μm. Mono-energetic 12C ions and 28Si ions were generated by the Heavy Ion Medical Accelerator at the National Institute of Radiological Science, Chiba, Japan. Clonogenic assays were used to determine cell inactivation. The ability of the cells to repair potential lethal damage was demonstrated by allowing one identical set of irradiated cells to repair for 24 h before subplating. The results show there is definite PLDR with X-rays, some evidence of PLDR at 55 keV/μm, and minimal PLDR at 100 keV/μm. There is no observable PLDR at 200 keV/μm. This is the first study, to the authors’ knowledge, demonstrating the capability of GBM cells to repair potential lethal damage following charged ion irradiations. It is concluded that a GBM’s PLDR is dependent on LET, dose and GBM strain; and the more radioresistant the cell strain, the greater the PLDR

Mechanistic and genetic basis of single-strand templated repair at Cas12a-induced DNA breaks in Chlamydomonas reinhardtii

Single-stranded oligodeoxynucleotides (ssODNs) are widely used as DNA repair templates inCRISPR/Cas precision genome editing. However, the underlying mechanisms of single-strandtemplated DNA repair (SSTR) are inadequately understood, constraining rational improve-ments to precision editing. Here we study SSTR at CRISPR/Cas12a-induced DNA double-strand breaks (DSBs) in the eukaryotic model green microalgaChlamydomonas reinhardtii.Wedemonstrate that ssODNs physically incorporate into the genome during SSTR at Cas12a-induced DSBs. This process is genetically independent of the Rad51-dependent homologousrecombination and Fanconi anemia pathways, is strongly antagonized by non-homologousend-joining, and is mediated almost entirely by the alternative end-joining enzyme poly-meraseθ. Thesefindings suggest differences in SSTR betweenC. reinhardtiiand animals. Ourwork illustrates the promising potentially ofC. reinhardtiias a model organism for studyingnuclear DNA repair