The degree of an eight-dimensional real quadratic division algebra is 1, 3, or 5

A celebrated theorem of Hopf, Bott, Milnor, and Kervaire states that every finite-dimensional real division algebra has dimension 1, 2, 4, or 8. While the real division algebras of dimension 1 or 2 and the real quadratic division algebras of dimension 4 have been classified, the problem of classifying all 8-dimensional real quadratic division algebras is still open. We contribute to a solution of that problem by proving that every 8-dimensional real quadratic division algebra has degree 1, 3, or 5. This statement is sharp.Comment: 8 page

Angular momentum of a strongly focussed Gaussian beam

A circularly polarized rotationally symmetric paraxial laser beams carries hbar angular momentum per photon as spin. Focussing the beam with a rotationally symmetric lens cannot change this angular momentum flux, yet the focussed beam must have spin less than hbar per photon. The remainder of the original spin is converted to orbital angular momentum, manifesting itself as a longitudinal optical vortex at the focus. This demonstrates that optical orbital angular momentum can be generated by a rotationally symmetric optical system which preserves the total angular momentum of the beam.Comment: 4 pages, 3 figure

Latest Advances in Aging Research and Drug Discovery

An increasing aging population poses a significant challenge to societies worldwide. A better understanding of the molecular, cellular, organ, tissue, physiological, psychological, and even sociological changes that occur with aging is needed in order to treat age-associated diseases. The field of aging research is rapidly expanding with multiple advances transpiring in many previously disconnected areas. Several major pharmaceutical, biotechnology, and consumer companies made aging research a priority and are building internal expertise, integrating aging research into traditional business models and exploring new go-to-market strategies. Many of these efforts are spearheaded by the latest advances in artificial intelligence, namely deep learning, including generative and reinforcement learning. To facilitate these trends, the Center for Healthy Aging at the University of Copenhagen and Insilico Medicine are building a community of Key Opinion Leaders (KOLs) in these areas and launched the annual conference series titled “Aging Research and Drug Discovery (ARDD)” held in the capital of the pharmaceutical industry, Basel, Switzerland (www.agingpharma.org). This ARDD collection contains summaries from the 6th annual meeting that explored aging mechanisms and new interventions in age-associated diseases. The 7th annual ARDD exhibition will transpire 2nd-4th of September, 2020, in Basel.DB is supported by the German Research Foundation (Forschungsstipendium; BA 6276/1-1) and the Lundbeckfonden (#R303-2018-3159). DC is funded by the NIH (R01AG 063389, R01AG063404, R01DK117481, R01DK101885) and the NIFA. VNG is supported by NIH grants. AT is supported by the Russian Federation grant 14.W03.31.0012. TH is supported by the Deutsche Forschungsgemeinschaft (DFG) (CECAD) and the European Research Council (consolidator grant 616499). DCR is grateful for funding from the UK Dementia Research Institute (funded by the MRC, Alzheimer’s Research UK and the Alzheimer’s Society) (DCR), an anonymous donation to the Cambridge Centre for Parkinson-Plus, The Rosetrees Trust, The Tau Consortium and The Roger de Spoelberch Foundation (DCR). MSK is funded by the Nordea Foundation (#02-2017-1749), the Novo Nordisk Foundation (#NNF17OC0027812), the Danish Cancer Society (#R167-A11015_001), the Independent Research Fund Denmark (#7016-00230B), the Neye Foundation and Insilico Medicine

Orientation of biological cells using plane-polarized Gaussian beam optical tweezers

Optical tweezers are widely used for the manipulation of cells and their internal structures. However, the degree of manipulation possible is limited by poor control over the orientation of trapped cells. We show that it is possible to controllably align or rotate disc shaped cells - chloroplasts of Spinacia oleracea - in a plane polarised Gaussian beam trap, using optical torques resulting predominantly from circular polarisation induced in the transmitted beam by the non-spherical shape of the cells.Comment: 9 pages, 6 figure

Cell biology: Receptors for selective recycling.

This is the author accepted manuscript. The final version is available from Nature at http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14532.html

Nanotrapping and the thermodynamics of optical tweezers

Particles that can be trapped in optical tweezers range from tens of microns down to tens of nanometres in size. Interestingly, this size range includes large macromolecules. We show experimentally, in agreement with theoretical expectations, that optical tweezers can be used to manipulate single molecules of polyethylene oxide suspended in water. The trapped molecules accumulate without aggregating, so this provides optical control of the concentration of macromolecules in solution. Apart from possible applications such as the micromanipulation of nanoparticles, nanoassembly, microchemistry, and the study of biological macromolecules, our results also provide insight into the thermodynamics of optical tweezers.Comment: 5 pages, 3 figures, presented at 17th AIP Congress, Brisbane, 200

Autophagy Induction Rescues Toxicity Mediated by Proteasome Inhibition

The ubiquitin-proteasome and macroautophagy-lysosome pathways are major routes for intracytosolic protein degradation. In many systems, proteasome inhibition is toxic. A Nature article by Pandey et al. shows that this toxicity can be modulated by altering autophagic activity. Their tantalizing results suggest that overexpression of HDAC6 may increase flux through the autophagy pathway, thereby attenuating the toxicity resulting from proteasome inhibition