Results 51 to 60 of about 72,568 (270)

Can the Arrow of Time be understood from Quantum Cosmology?

, 2009
I address the question whether the origin of the observed arrow of time can be derived from quantum cosmology. After a general discussion of entropy in cosmology and some numerical estimates, I give a brief introduction into quantum geometrodynamics and ...
A. Simone, A.A. Starobinsky, B.S. DeWitt, C. Kiefer, C. Kiefer, C. Kiefer, C. Kiefer, C.A. Egan, G. Hinshaw, G.W. Gibbons, H.D. Zeh, J.J. Halliwell, M. Albers, M. Novello, R. Holman, R. Penrose   +15 more
core   +1 more source

Time arrow without past hypothesis: a toy model explanation

New Journal of Physics
The laws of Physics are time-reversible, making no qualitative distinction between the past and the future—yet we can only go towards the future. This apparent contradiction is known as the ‘arrow of time problem’.
Pablo Arrighi, Gilles Dowek, Amélia Durbec   +2 more
doaj   +1 more source

Thermodynamics of the $$R_{\mathrm{h}}=ct$$ R h = c t Universe: a simplification of cosmic entropy

European Physical Journal C: Particles and Fields, 2021
In the standard model of cosmology, the Universe began its expansion with an anomalously low entropy, which then grew dramatically to much larger values consistent with the physical conditions at decoupling, roughly 380,000 years after the Big Bang ...
Fulvio Melia
doaj   +1 more source

Revealing the structure of land plant photosystem II: the journey from negative‐stain EM to cryo‐EM

FEBS Letters, EarlyView.
Advances in cryo‐EM have revealed the detailed structure of Photosystem II, a key protein complex driving photosynthesis. This review traces the journey from early low‐resolution images to high‐resolution models, highlighting how these discoveries deepen our understanding of light harvesting and energy conversion in plants.
Roman Kouřil
wiley   +1 more source

A quantum solution to the arrow-of-time dilemma [PDF]

, 2008
The arrow of time dilemma: the laws of physics are invariant for time inversion, whereas the familiar phenomena we see everyday are not (i.e. entropy increases).
A. Peres, D. Z. Albert, D. Z. Albert, E. Borel, E. P. Gyftopoulos, F. Reif, H. Price, H. D. Zeh, J. Loschmidt, L. Szilard, L. S. Schulman, Lorenzo Maccone, P. C. W. Davies, R. Landauer, R. Penrose, T. Gold, W. H. Zurek   +16 more
core   +2 more sources

Mapping the evolution of mitochondrial complex I through structural variation

FEBS Letters, EarlyView.
Respiratory complex I (CI) is crucial for bioenergetic metabolism in many prokaryotes and eukaryotes. It is composed of a conserved set of core subunits and additional accessory subunits that vary depending on the organism. Here, we categorize CI subunits from available structures to map the evolution of CI across eukaryotes. Respiratory complex I (CI)
Dong‐Woo Shin, Tingting Chen, James A. Letts   +2 more
wiley   +1 more source

Arrow of time: Metaphorical construals of entropy and the second law of thermodynamics

Science Education, 2012
AbstractVarious features of scientific discourse have been characterized in the science education literature, and challenges students face in appropriating these features have been explored. Using the framework of conceptual metaphor, this paper sought to identify explicit and implicit metaphors in pedagogical texts dealing with the concept of entropy ...
Amin, Tamer, Jeppsson, Fredrik, Haglund, Jesper, Strömdahl, Helge   +3 more
openaire   +3 more sources

Structural instability impairs function of the UDP‐xylose synthase 1 Ile181Asn variant associated with short‐stature genetic syndrome in humans

FEBS Letters, EarlyView.
The Ile181Asn variant of human UDP‐xylose synthase (hUXS1), associated with a short‐stature genetic syndrome, has previously been reported as inactive. Our findings demonstrate that Ile181Asn‐hUXS1 retains catalytic activity similar to the wild‐type but exhibits reduced stability, a looser oligomeric state, and an increased tendency to precipitate ...
Tuo Li, Pedro A. Sánchez‐Murcia, Bernd Nidetzky   +2 more
wiley   +1 more source

Quantum Theory of Irreversibility

, 2005
A generalization of the Gibbs-von Neumann relative entropy is proposed based on the quantum BBGKY [Bogolyubov-Born-Green-Kirkwood-Yvon] hierarchy as the nonequilibrium entropy for an N-body system.
A. Pérez-Madrid, Bedeaux, Boercker, Bogoliubov, de Groot, Dorfman, Pérez-Madrid, Reguera, Rondoni, Schlöglm, van Kampen, Vollmer, von Neumann, Wehrl, Zwanzig   +14 more
core   +2 more sources

Does time exist in quantum gravity?

Zagadnienia Filozoficzne w Nauce, 2015
Time is absolute in standard quantum theory and dynamical in general relativity. The combination of both theories into a theory of quantum gravity leads therefore to a “problem of time”.
Claus Kiefer
doaj