Quantum thermodynamics at critical points during melting and solidification processes

We systematically explore and show the existence of finite-temperature continuous quantum phase transition (CTQPT) at a critical point, namely, during solidification or melting such that the first-order thermal phase transition is a special case within CTQPT. Infact, CTQPT is related to chemical reaction where quantum fluctuation (due to wavefunction transformation) is caused by thermal energy and it can occur maximally for temperatures much higher than zero Kelvin. To extract the quantity related to CTQPT, we use the ionization energy theory and the energy-level spacing renormalization group method to derive the energy-level spacing entropy, renormalized Bose-Einstein distribution and the time-dependent specific heat capacity. This work unambiguously shows that the quantum phase transition applies for any finite temperatures.Comment: To be published in Indian Journal of Physics (Kolkata

Temporal changes in tau phosphorylation and related kinase and phosphatases following two models of traumatic brain injury

Published: November 09, 2018A history of traumatic brain injury (TBI) is linked to later neurodegeneration, with a key feature accumulation of hyperphosphorylated tau. Tau is a microtubule stability protein that undergoes frequent cycles of phosphorylation and dephosphorylation due to kinases and phosphatase activity. Hyperphosphorylation of tau destabilizes microtubules interrupting axonal transport, as well as promotes aggregation disturbing synaptic dysfunction. Aberrant phosphorylation of tau post-injury is thought to be a key player in later neurodegeneration. However, it is not known whether type of TBI- a single severe injury compared to repeated mild injuries- affects the time course of tau accumulation or the pattern of changes in kinases and phosphatases that facilitate this phosphorylation. To investigate, male Sprague Dawley rats were subjected to either a single moderate/severe or 3 mild TBIs spaced 5 days apart (rmTBI) utlising the Marmarou impact-acceleration model. Levels of cortical ptau (AT180, pSer422, oligomeric tau), pGSK3β, pCDK5, pERK1/2, pAkt and PP2Ac were evaluated at 24h, 7 days, 1 month and 3 months post-injury, with changes in tau phosphorylation confirmed via immunohistochemistry. A similar time course of AT180 tau phosphorylation was seen irrespective of the nature of the initiating insult, with a spike at 24h post-injury return to baseline and then increasing chronically at 3 months post-injury. In line with this, levels of PP2Ac were decreased at 24h and 3 months post-injury, indicating a potential loss of phosphatase activity. Interestingly, minimal changes were seen in the kinases examined, with a spike in phosphorylation of GSK3β, at the inhibitory Ser site, at 24h and 3 months following rmTBI, but not single moderate severe TBI, suggesting a possible protective effect only post-rmTBI. This study highlights that changes in levels of phosphorylated tau are similar, regardless of the initiating injury, and highlights the need to further understand the driving mechanisms behind this phenomenon.Lyndsey Collins-Praino, Daniel Gutschmidt, Jessica Sharkey, Alina Arulsamy, and Frances Corriga

Understanding the Role of Hyponitrite in Nitric Oxide Reduction

Herein, we review the preparation and coordination chemistry of cis and trans isomers of hyponitrite, [N2O2](2-). Hyponitrite is known to bind to metals via a variety of bonding modes. In fact, at least eight different bonding modes have been observed, which is remarkable for such a simple ligand. More importantly, it is apparent that the cis isomer of hyponitrite is more reactive than the trans isomer because the barrier of N2O elimination from cis-hyponitrite is lower than that of trans-hyponitrite. This observation may have important mechanistic implications for both heterogeneous NOx reduction catalysts and NO reductase. However, our understanding of the hyponitrite ligand has been limited by the lack of a general route to this fragment, and most instances of its formation have been serendipitous