2,866 research outputs found
Condensin and cohesin display different arm conformations with characteristic hinge angles
Structural maintenance of chromosomes (SMC) proteins play central roles in higher-order chromosome dynamics from bacteria to humans. In eukaryotes, two different SMC protein complexes, condensin and cohesin, regulate chromosome condensation and sister chromatid cohesion, respectively. Each of the complexes consists of a heterodimeric pair of SMC subunits and two or three non-SMC subunits. Previous studies have shown that a bacterial SMC homodimer has a symmetrical structure in which two long coiled-coil arms are connected by a flexible hinge. A catalytic domain with DNA- and ATP-binding activities is located at the distal end of each arm. We report here the visualization of vertebrate condensin and cohesin by electron microscopy. Both complexes display the two-armed structure characteristic of SMC proteins, but their conformations are remarkably different. The hinge of condensin is closed and the coiled-coil arms are placed close together. In contrast, the hinge of cohesin is wide open and the coiled-coils are spread apart from each other. The non-SMC subunits of both condensin and cohesin form a globular complex bound to the catalytic domains of the SMC heterodimers. We propose that the âclosedâ conformation of condensin and the âopenâ conformation of cohesin are important structural properties that contribute to their specialized biochemical and physiological functions
Flavour Issues in Leptogenesis
We study the impact of flavour in thermal leptogenesis, including the quantum
oscillations of the asymmetries in lepton flavour space. In the Boltzmann
equations we find different numerical factors and additional terms which can
affect the results significantly. The upper bound on the CP asymmetry in a
specific flavour is weaker than the bound on the sum. This suggests that --
when flavour dynamics is included -- there is no model-independent limit on the
light neutrino mass scale,and that the lower bound on the reheat temperature is
relaxed by a factor ~ (3 - 10).Comment: 19 pages, corrected equations for flavour oscillation
Leptogenesis beyond the limit of hierarchical heavy neutrino masses
We calculate the baryon asymmetry of the Universe in thermal leptogenesis
beyond the usual lightest right-handed (RH) neutrino dominated scenario (N_1DS)
and in particular beyond the hierarchical limit (HL), M_1 << M_2 << M_3, for
the RH neutrino mass spectrum. After providing some orientation among the large
variety of models, we first revisit the central role of the N_1DS, with new
insights on the dynamics of the asymmetry generation and then discuss the main
routes departing from it, focusing on models beyond the HL. We study in detail
two examples of `strong-strong' wash-out scenarios: one with `maximal phase'
and the limit of very large M_3, studying the effects arising when
delta_2=(M_2-M_1)/M_1 is small. We extend analytical methods already applied to
the N_1DS showing, for example, that, in the degenerate limit (DL), the
efficiency factors of the RH neutrinos become equal with the single decay
parameter replaced by the sum. Both cases disprove the misconception that close
RH neutrino masses necessarily lead to a final asymmetry enhancement and to a
relaxation of the lower bounds on M_1 and on the initial temperature of the
radiation-dominated expansion. We also explain why leptogenesis tends to favor
normal hierarchy compared to inverted hierarchy for the left-handed neutrino
masses.Comment: 30 pages, 8 figures; corrected typo in Eq. (67); shortened
Introduction, Section 3 and Conclusions; one figure removed; added 2
references; to appear in JCA
Using Machine Learning Techniques to Predict Adolescentsâ Involvement in Family Conflict
[Abstract] Many cases of violence against children occur in homes and other close environments. Machine leaning is a novel approach that addresses important gaps in ways of examining this socially significant issue, illustrating innovative and emerging approaches for the use of computers from a psychological perspective. In this paper, we aim to use machine learning techniques to predict adolescentsâ involvement in family conflict in a sample of adolescents living with their families(community adolescents) and adolescents living in residential care centers, who are temporarilyseparated from their families because of adverse family conditions. Participants were 251 Spanish adolescents (Mage= 15.59), of whom 167 lived in residential care and 84 lived with their families.We measured perceived interparental and family conflict, adolescentsâemotional security,emotional, cognitive, and behavioral immediate responses to analog interparental conflict (IPC),and adolescentsâ sociodemographic variables (i.e., age, gender). With a prediction accuracy of 65%, our results show that adolescents in residential care are not at greater risk for involvement in family conflict compared to adolescents living with their families. Age and gender are not salient predictive variables. We could identify that responses to analog IPC, adolescentsâemotiona lsecurity, triangulation in IPC, and the presence of insults or blame during family disputes predict adolescentsâ involvement in family conflict. These results point to variables with a potential predictive capacity, which is relevant for research and intervention.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was partially supported by projects PLEC2021-007,662 (MCIN/AEI/10.13,039/501100011033, Ministerio de Ciencia e InnovaciĂłn, Agencia Estatal de InvestigaciĂłn, Plan de RecuperaciĂłn, TransformaciĂłn y Resiliencia, UniĂłn Europea-Next GenerationEU), RTI2018-093,336-B-C21 & RTI2018-093,336-B-C22 (Ministerio de Ciencia e InnovaciĂłn, Agencia Estatal de InvestigaciĂłn & ERDF). The fourth and fifth authors also thank the financial support supplied by the ConsellerĂa de EducaciĂłn, Universidade e FormaciĂłn Profesional (accreditation 2019â2022 ED431G-2019/01 and GPC ED431 B 2019/03) and the European Regional Development Fund, which acknowledges the CITIC Research Center in ICT of the University of A Coruña as a Research Center of the Galician University System. The third author also thanks the financial support supplied by the ConsellerĂa de EducaciĂłn, Universidade e FormaciĂłn Profesional (accreditation 2019â2022 ED431G-2019/04, ED431 C 2018/29) and the European Regional Development Fund, which acknowledges the CiTIUS-Research Center in Intelligent Technologies of the University of Santiago de Compostela as a Research Center of the Galician University SystemXunta de Galicia; ED431G-2019/01Xunta de Galicia; ED431 B 2019/03Xunta de Galicia; ED431G-2019/04Xunta de Galicia; ED431 C 2018/2
Functional approach to the fermionic Casimir effect
We use a functional approach to calculate the Casimir energy due to Dirac
fields in interaction with thin, flat, parallel walls, which implement
imperfect bag-like boundary conditions. These are simulated by the introduction
of delta-like interactions with the walls. We show that, with a proper choice
for the corresponding coupling constants, bag-model boundary condition are
properly implemented. We obtain explicit expressions for the energies in 1+1
and 3+1 dimensions, for massless and massive fields.Comment: 15 pages, 4 figure
An approach to assess flooding and erosion risk for open beaches in a changing climate
This paper examines the vulnerability to flooding and erosion of four open beach study sites in Europe. A framework for the quantitative estimation of present and future coastal flood and erosion risks is established using methods, data and tools from across a range of disciplines, including topographic and bathymetric data, climate data from observation, hindcast and model projections, statistical modelling of current and future climates and integrated risk analysis tools. Uncertainties in the estimation of future coastal system dynamics are considered, as are the consequences for the inland systems. Different implementations of the framework are applied to the study sites which have different wave, tidal and surge climate conditions. These sites are: Santander, Spainâthe Atlantic Ocean; Bellocchio, Italyâthe Adriatic Sea; Varna, Bulgariaâthe Black Sea; and the Teign Estuary, UKâthe northern Atlantic Ocean. The complexity of each system is first simplified by sub-division into coastal "impact units" defined by homogeneity in the local key forcing parameters: wave, wind, tide, river discharge, run-off, etc. This reduces the simulation to that of a number of simpler linear problems which are treated by applying the first two components of the SourceâPathwayâReceptorâConsequence (SâPâRâC) approach. The case studies reveal the flexibility of this approach, which is found useful for the rapid assessment of the risks of flooding and erosion for a range of scenarios and the likely effectiveness of flood defences
Light Stop Decay in the MSSM with Minimal Flavour Violation
In supersymmetric scenarios with a light stop particle and a
small mass difference to the lightest supersymmetric particle (LSP) assumed to
be the lightest neutralino, the flavour changing neutral current decay
can be the dominant decay channel and can
exceed the four-body stop decay for certain parameter values. In the framework
of Minimal Flavour Violation (MFV) this decay is CKM-suppressed, thus inducing
long stop lifetimes. Stop decay length measurements at the LHC can then be
exploited to test models with minimal flavour breaking through Standard Model
Yukawa couplings. The decay width has been given some time ago by an
approximate formula, which takes into account the leading logarithms of the MFV
scale. In this paper we calculate the exact one-loop decay width in the
framework of MFV. The comparison with the approximate result exhibits
deviations of the order of 10% for large MFV scales due to the neglected
non-logarithmic terms in the approximate decay formula. The difference in the
branching ratios is negligible. The large logarithms have to be resummed. The
resummation is performed by the solution of the renormalization group
equations. The comparison of the exact one-loop result and the tree level
flavour changing neutral current decay, which incorporates the resummed
logarithms, demonstrates that the resummation effects are important and should
be taken into account.Comment: 29 page
Flavour physics constraints in the BMSSM
We study the implications of the presence of the two leading-order,
non-renormalizable operators in the Higgs sector of the MSSM to flavour physics
observables. We identify the constraints of flavour physics on the parameters
of the BMSSM when we: a) focus on a region of parameters for which electroweak
baryogenesis is feasible, b) use a CMSSM-like parametrization, and c) consider
the case of a generic NUHM-type model. We find significant differences as
compared to the standard MSSM case.Comment: 22 pages, 7 figure
- âŠ