79 research outputs found
Coupling of nuclear wavepacket motion and charge separation in bacterial reaction centers
AbstractThe mechanism of the charge separation and stabilization of separated charges was studied using the femtosecond absorption spectroscopy. It was found that nuclear wavepacket motions on potential energy surface of the excited state of the primary electron donor P* leads to a coherent formation of the charge separated states P+BA−, P+HA− and P+HB− (where BA, HB and HA are the primary and secondary electron acceptors, respectively) in native, pheophytin-modified and mutant reaction centers (RCs) of Rhodobacter sphaeroides R-26 and in Chloroflexus aurantiacus RCs. The processes were studied by measurements of coherent oscillations in kinetics at 890 and 935 nm (the stimulated emission bands of P*), at 800 nm (the absorption band of BA) and at 1020 nm (the absorption band of BA−) as well as at 760 nm (the absorption band of HA) and at 750 nm (the absorption band of HB). It was found that wavepacket motion on the 130–150 cm−1 potential surface of P* is accompanied by approaches to the intercrossing region between P* and P+BA− surfaces at 120 and 380 fs delays emitting light at 935 nm (P*) and absorbing light at 1020 nm (P+BA−). In the presence of Tyr M210 (Rb. sphaeroides) or M195 (C. aurantiacus) the stabilization of P+BA− is observed within a few picosseconds in contrast to YM210W. At even earlier delay (∼40 fs) the emission at 895 nm and bleaching at 748 nm are observed in C. aurantiacus RCs showing the wavepacket approach to the intercrossing between the P* and P+HB− surfaces at that time. The 32 cm−1 rotation mode of HOH was found to modulate the electron transfer rate probably due to including of this molecule in polar chain connecting PB and BA and participating in the charge separation. The mechanism of the charge separation and stabilization of separated charges is discussed in terms of the role of nuclear motions, of polar groups connecting P and acceptors and of proton of OH group of TyrM210
СОВРЕМЕННЫЕ ТЕХНОЛОГИИ В ХИРУРГИЧЕСКОМ ЛЕЧЕНИИ ПОСЛЕДСТВИЙ ТРАВМЫ ЧЕРЕПА И ГОЛОВНОГО МОЗГА
The paper presents main types of surgically relevant posttraumatic lesions in 4136 patients with skull vault as well as skull base defects, craniofacial deformities, recurrent CSF leaks, arterio-venous fistulas, aneurysms and pseudoaneurysms etc. Classification of TBI sequelae and complications as well as its clinical course grading is presented. The use of modern neuroimaging techniques for studying pathophysiologic mechanisms and complications of TBI has been demonstrated. Special emphasis was given to minimally invasive and reconstructive surgery; computer modeling with subsequent full-copy stereolitographic laser implant setup was shown which is of great importance in cases of large and complex skull base and craniofacial deformities. Patient selection for transcranial and endonasal CSF leak closure techniques was justified. Treatment of post-traumatic vascular injuries using Serbinenko balloon-catheters as well as modern techniques such as stents, coils and embolization has been demonstrated. В сообщении (созданном по материалам доклада, представленного на Сессии общего собрания РАМН, Санкт-Петербург, 14−15 июня 2012 г.) представлены основные хирургически значимые формы посттравматической патологии у 4136 пациентов с дефектами и деформациями костей свода, основания черепа и лицевого скелета, рецидивирующей ликвореей, артериосинусными соустьями, истинными и ложными аневризмами и др. Разработана классификация последствий и осложнений черепно-мозговой травмы, а также периодизация ее клинического течения. Раскрыты возможности современных нейровизуализационных технологий распознавания и исследования патогенеза последствий и осложнений черепно-мозговой травмы. Особое внимание уделено реконструктивной и минимально инвазивной хирургии, детально описан метод компьютерного моделирования и последующего стереолитографического лазерного воспроизведения полномасштабных копий черепа, его дефектов и имплантатов, что особенно значимо при обширных и сложных краниобазальных и краниофациальных повреждениях. Обосновано дифференцированное применение интракраниальных и эндоназальных доступов для закрытия хронических ликворных фистул. Вместе с впервые созданной в НИИ нейрохирургии им. Н.Н. Бурденко методикой эндоваскулярной реконструкции магистральных сосудов с помощью баллонов-катетеров Ф.А. Сербиненко представлены новые подходы, опирающиеся на современные технологии с использованием стентов, микроспиралей и эмболизирующих композиций.
Two-loop Anomalous Dimensions of Heavy Baryon Currents in Heavy Quark Effective Theory
We present results on the two-loop anomalous dimensions of the heavy baryon
HQET currents with arbitrary Dirac matrices
and . From our general result we obtain the two-loop
anomalous dimensions for currents with quantum numbers of the ground state
heavy baryons , and . As a by-product of our
calculation and as an additional check we rederive the known two-loop anomalous
dimensions of mesonic scalar, pseudoscalar, vector, axial vector and tensor
currents in massless QCD as well as in HQET.Comment: 21 pages, LaTeX, 2 figures are included in PostScript forma
Calculations of binding energies and masses of heavy quarkonia using renormalon cancellation
We use various methods of Borel integration to calculate the binding ground
energies and masses of b-bbar and t-tbar quarkonia. The methods take into
account the leading infrared renormalon structure of the hard+soft part of the
binding energies E(s), and of the corresponding quark pole masses m_q, where
the contributions of these singularities in M(s) = 2 m_q + E(s) cancel.
Beforehand, we carry out the separation of the binding energy into its
hard+soft and ultrasoft parts. The resummation formalisms are applied to
expansions of m_q and E(s) in terms of quantities which do not involve
renormalon ambiguity, such as MSbar quark mass, and alpha_s. The
renormalization scales are different in calculations of m_q, E(s) and E(us).
The MSbar mass of b quark is extracted, and the binding energies of t-tbar and
the peak (resonance) energies for (t+tbar) production are obtained.Comment: 23 pages, 8 double figures, revtex4; the version to appear in
Phys.Rev.D; extended discussion between Eqs.(25) and (26); the paragraph
between Eqs.(32) and (33) is new and explains the numerical dependence of the
residue parameter on the factorization scale; several new references were
added; acknowledgments were modified; the numerical results are unchange
An Analysis of Diagonal and Non-diagonal QCD Sum Rules for Heavy Baryons at Next-to-Leading Order in \alpha_S
We consider diagonal and non-diagonal QCD sum rules for the ground state
heavy baryons to leading order in and at next-to-leading order in
. In the non-diagonal case we evaluate the eight different two-loop
diagrams which determine the perturbative -corrections to the Wilson
coefficient of the quark condensate in the Operator Product Expansion. The QCD
corrections to the non-diagonal sum rules are moderate compared to the QCD
corrections in the diagonal case. We also consider constituent type sum rules
using constituent type interpolating currents. The obtained results are in
reasonable agreement with the corresponding results obtained in the diagonal
case. As central values for the bound state energies we find and . The central values for the residues
are given by and .Comment: 17 pages, LaTeX, 8 figures are included in PostScript forma
Stellar structure and compact objects before 1940: Towards relativistic astrophysics
Since the mid-1920s, different strands of research used stars as "physics
laboratories" for investigating the nature of matter under extreme densities
and pressures, impossible to realize on Earth. To trace this process this paper
is following the evolution of the concept of a dense core in stars, which was
important both for an understanding of stellar evolution and as a testing
ground for the fast-evolving field of nuclear physics. In spite of the divide
between physicists and astrophysicists, some key actors working in the
cross-fertilized soil of overlapping but different scientific cultures
formulated models and tentative theories that gradually evolved into more
realistic and structured astrophysical objects. These investigations culminated
in the first contact with general relativity in 1939, when J. Robert
Oppenheimer and his students George Volkoff and Hartland Snyder systematically
applied the theory to the dense core of a collapsing neutron star. This
pioneering application of Einstein's theory to an astrophysical compact object
can be regarded as a milestone in the path eventually leading to the emergence
of relativistic astrophysics in the early 1960s.Comment: 83 pages, 4 figures, submitted to the European Physical Journal
Coherent nuclear and electronic dynamics in primary charge separation in photosynthetic reaction centers: A redfield theory approach
Primary charge separation dynamics is modeled in the pheophytin-modified Rhodobacter sphaeroides R-26 reaction center (RC). To explain the observed spectral evolution, it is assumed that the process is coupled to coherent nuclear motion. A density matrix equation with the Redfield relaxation superoperator is used for simulation of the electron-vibratibnal dynamics and its spectral signatures. The model includes two diabatic - states, i.e., an excited state P* of the primary donor (i.e., special pair, P), and a charge-transfer state (
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