Photosynthesis

Although there has been considerable progress toward an understanding of the processes of photosyntehsis in recent years, the advances have been followed rather lcosely by symposia, monographs and reviews of the subject matter, particularly during the last three years. In view of the comprehensive coverage it would appear that the present review might very well be limited to a discussion of certain subjects of special interest to the authors and some with which they are especially familiar. These are (1) the extensive discussion by Warburg and his co-workers of their proposal for the existence of a light induced oxygen absorption (and corresponding carbon dioxide evolution) which can amount to three or four times the net oxygen evolution by the same light; and (2) the discovery of the early participation of 7 and 5 carbon sugars in carbon dioxide reduction in photosyntehsis together with some observations on the kinetics of the metabolic transformations. While it is true that a considerable number of significant publications have appears in other aspects of photosynthesis (the Hill reaction and its coupling with carbon dioxide reduction; photochemistry of chlorophyll and related synthetic materials as model reactions in relatively simple defined physical systems; transfer of light energy within the pigment systems) it is felt that they represent confirmation and extension of ideas which have already been discussed in a variety of earlier reviews and that a re-evaluation of them might very well be postponed until a later time

Ferromagnetic models for cooperative behavior: Revisiting Universality in complex phenomena

Ferromagnetic models are harmonic oscillators in statistical mechanics. Beyond their original scope in tackling phase transition and symmetry breaking in theoretical physics, they are nowadays experiencing a renewal applicative interest as they capture the main features of disparate complex phenomena, whose quantitative investigation in the past were forbidden due to data lacking. After a streamlined introduction to these models, suitably embedded on random graphs, aim of the present paper is to show their importance in a plethora of widespread research fields, so to highlight the unifying framework reached by using statistical mechanics as a tool for their investigation. Specifically we will deal with examples stemmed from sociology, chemistry, cybernetics (electronics) and biology (immunology).Comment: Contributing to the proceedings of the Conference "Mathematical models and methods for Planet Heart", INdAM, Rome 201

Angular size measurements of carbon Miras and S-type stars

In our continuing investigation of highly evolved stars, we report new interferometric angular diameter observations of 5 carbon and 4 S-type Mira variable stars, and 4 non-Mira S stars. From the data, effective temperatures and linear radii are calculated. We compare the values of these parameters obtained for stars discussed in this paper with the same parameters for oxygen-rich giants/supergiants, oxygen-rich Mira variables, and non-Mira carbon stars presented in Dyck et al. (1996a, AJ, 111, 1705), van Belle et al. (1996, AJ, 112, 2147), and Dyck et al. (1996b, AJ, 112, 294), respectively. There are two principal findings from a synthesis of these studies. First, the non-Mira variables of each chemical class are consistently hotter and smaller than their Mira-variable counterparts. Second, the S stars lie between the oxygen-rich and the carbon-rich stars in both effective temperature and linear radius, for both the Mira-type and non-Mira stars

Core Structure of Global Vortices in Brane World Models

We study analytically and numerically the core structure of global vortices forming on topologically deformed brane-worlds with a single toroidally compact extra dimension. It is shown that for an extra dimension size larger than the scale of symmetry breaking the magnitude of the complex scalar field at the vortex center can dynamically remain non-zero. Singlevaluedness and regularity are not violated. Instead, the winding escapes to the extra dimension at the vortex center. As the extra dimension size decreases the field magnitude at the core dynamically decreases also and in the limit of zero extra dimension size we reobtain the familiar global vortex solution. Extensions to other types of defects and gauged symmetries are also discussed.Comment: 6 two column pages, 3 figure

Shining a light on the evidence for hydroxychloroquine in SARS-CoV-2

Background The 2020 COVID-19 pandemic has stunned the world, financial markets, and healthcare systems. Researchers are rushing to identify effective treatments while maintaining rigorous adherence to the scientific method. Clinicians are doing their best to provide evidence-based care in a setting of very little good evidence. To date, no effective treatments exist for COVID-19 management. Unfortunately, traditional and social media coupled with world leader commentary have led some to believe hydroxychloroquine offers a bona fide cure and even prevention. The purpose of this commentary is to review the medical literature related to hydroxychloroquine building on knowledge over the past 17 years since the 2003 SARS-CoV epidemic

Duration and severity of Medieval drought in the Lake Tahoe Basin

This paper is not subject to U.S. copyright. The definitive version was published in Quaternary Science Reviews 30 (2011): 3269-3279, doi:10.1016/j.quascirev.2011.08.015.Droughts in the western U.S. in the past 200 years are small compared to several megadroughts that occurred during Medieval times. We reconstruct duration and magnitude of extreme droughts in the northern Sierra Nevada from hydroclimatic conditions in Fallen Leaf Lake, California. Stands of submerged trees rooted in situ below the lake surface were imaged with sidescan sonar and radiocarbon analysis yields an age estimate of ∼1250 AD. Tree-ring records and submerged paleoshoreline geomorphology suggest a Medieval low-stand of Fallen Leaf Lake lasted more than 220 years. Over eighty more trees were found lying on the lake floor at various elevations above the paleoshoreline. Water-balance calculations suggest annual precipitation was less than 60% normal from late 10th century to early 13th century AD. Hence, the lake’s shoreline dropped 40–60 m below its modern elevation. Stands of pre-Medieval trees in this lake and in Lake Tahoe suggest the region experienced severe drought at least every 650–1150 years during the mid- and late-Holocene. These observations quantify paleo-precipitation and recurrence of prolonged drought in the northern Sierra Nevada.Support for this work was provided by US Geological Survey/ Desert Research Institute under Project ID# 2003NV39B, a Geological Society of America graduate research grant and the IRIS undergraduate internship program. F. Biondiwas supported, in part by NSF Cooperative Agreement EPS-0814372 to the Nevada System of Higher Education. N. Driscoll was supported in part by a grant from CA DWR

BB flavour tagging using charm decays at the LHCb experiment

An algorithm is described for tagging the flavour content at production of neutral $B$ mesons in the LHCb experiment. The algorithm exploits the correlation of the flavour of a $B$ meson with the charge of a reconstructed secondary charm hadron from the decay of the other $b$ hadron produced in the proton-proton collision. Charm hadron candidates are identified in a number of fully or partially reconstructed Cabibbo-favoured decay modes. The algorithm is calibrated on the self-tagged decay modes $B^+ \to J/\psi \, K^+$ and $B^0 \to J/\psi \, K^{*0}$ using $3.0\mathrm{\,fb}^{-1}$ of data collected by the LHCb experiment at $pp$ centre-of-mass energies of $7\mathrm{\,TeV}$ and $8\mathrm{\,TeV}$. Its tagging power on these samples of $B \to J/\psi \, X$ decays is $(0.30 \pm 0.01 \pm 0.01) \%$.Comment: All figures and tables, along with any supplementary material and additional information, are available at http://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-027.htm

Measurements of long-range near-side angular correlations in sNN=5\sqrt{s_{\text{NN}}}=5TeV proton-lead collisions in the forward region

Two-particle angular correlations are studied in proton-lead collisions at a nucleon-nucleon centre-of-mass energy of $\sqrt{s_{\text{NN}}}=5$TeV, collected with the LHCb detector at the LHC. The analysis is based on data recorded in two beam configurations, in which either the direction of the proton or that of the lead ion is analysed. The correlations are measured in the laboratory system as a function of relative pseudorapidity, $\Delta\eta$, and relative azimuthal angle, $\Delta\phi$, for events in different classes of event activity and for different bins of particle transverse momentum. In high-activity events a long-range correlation on the near side, $\Delta\phi \approx 0$, is observed in the pseudorapidity range $2.0<\eta<4.9$. This measurement of long-range correlations on the near side in proton-lead collisions extends previous observations into the forward region up to $\eta=4.9$. The correlation increases with growing event activity and is found to be more pronounced in the direction of the lead beam. However, the correlation in the direction of the lead and proton beams are found to be compatible when comparing events with similar absolute activity in the direction analysed.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-040.htm