The crystal structure of Haloferax volcanii proliferating cell nuclear antigen reveals unique surface charge characteristics due to halophilic adaptation

Background: The high intracellular salt concentration re quired to maintain a halophilic lifestyle poses challenges to haloarchaeal proteins that must stay soluble, stable and functional in this extreme environment. Proliferating cell nuclear antigen (PCNA) is a fundamental protein involved in maintaining genome integrity, with roles in both DNA replication and repair. To investigate the halophilic adaptation of such a key protein we have crystallised and solved the structure of Haloferax volcanii PCNA (HvPCNA) to a resolution of 2.0 Å. Results: The overall architecture of HvPCNA is very similar to other known PCNAs, which are highly structurally conserved. Three commonly observed adaptations in halophilic proteins are higher surface acidity, bound ions and increased numbers of intermolecular ion pairs (in oligomeric proteins). HvPCNA possesses the former two adaptations but not the latter, despite functioning as a homotrimer. Strikingly, the positive surface charge considered key to PCNA's role as a sliding clamp is dramatically reduced in the halophilic protein. Instead, bound cations within the solvation shell of HvPCNA may permit sliding along negatively charged DNA by reducing electrostatic repulsion effects. Conclusion: The extent to which individual proteins adapt to halophilic conditions varies, presumably due to their diverse characteristics and roles within the cell. The number of ion pairs observed in the HvPCNA monomer-monomer interface wasunexpectedly low. This may reflect the fact that the trimer is intrinsically stable over a wide range of salt concentrations and therefore additional modifications for trimer maintenance in high salt conditions are not required. Halophilic proteins frequently bind anions and cations and in HvPCNA cation binding may compensate for the remarkable reduction in positive charge in the pore region, to facilitate functional interactions with DNA. In this way, HvPCNA may harness its environment as opposed to simply surviving in extreme halophilic conditions

Critical Flavor Number in the Three Dimensional Thirring Model

We present results of a Monte Carlo simulation of the three dimensional Thirring model with the number of fermion flavors N_f varied between 2 and 18. By identifying the lattice coupling at which the chiral condensate peaks, simulations are be performed at couplings g^2(N_f) corresponding to the strong coupling limit of the continuum theory. The chiral symmetry restoring phase transition is studied as N_f is increased, and the critical number of flavors estimated as N_{fc}=6.6(1). The critical exponents measured at the transition do not agree with self-consistent solutions of the Schwinger-Dyson equations; in particular there is no evidence for the transition being of infinite order. Implications for the critical flavor number in QED_3 are briefly discussed.Comment: 4 pages, 5 figure

Data Envelopment Analysis as a Complement to Marginal Analysis

The consideration in the present study is mainly conceptual. The objective is to show how Data Envelopment Analysis (DEA) can be used to reveal the true input-output relations in an industry. In the estimation of a production function it is assumed that all firms use the existing technology efficiently. However, in the real world the observed firms produce homogeneous outputs with differences in factor intensities and in managerial capacity. Hence, inefficiencies are hidden in the estimated production functions. In order to overcome this drawback of the parametric approach and to reveal the true nature of the input-output relations in production, given the available technology, the DEA approach is applied. In this study DEA is applied in order to select the farms that utilize efficiently the existing technology, allowing the estimation of a production function that reveals the true input-output relations in sheep-goat farming, using farm accounting data from a sample of 108 sheep-goat farms.Research Methods/ Statistical Methods,

EXPRESSION DE LA CAUSE DANS DES PRODUCTIONS ECRITES ET ORALES EN FLE : APPRENANTS CHYPRIOTES HELLENOPHONES

International audienceThe aim of this contribution is to present a case study on the causal expression by Greek Cypriot learners of French as a foreign language. We have examined the writing and speaking performances of learners who already studied causal expression, in order to realize what grammatical and lexical items they use

The Cypriot Banking Sector During the Financial Crisis and Its Reforms: An Examination in Light of the Case of the UK

The article focuses on the role of banks in the financial crisis and compares the UK and Cyprus, since the banking sector of the latter was founded on the former’s model, because of its colonialism by the British Empire. However, Cyprus financial sector has been influenced by its accession to the EMU, while the UK remains outside Euro-zone. The article begins with the theoretical background; namely the ‘Too-Big-to-Fail’ theory, the deficient banking corporate governance and their ineffective supervision, and its reflection in the UK and Euro crisis. Afterwards, the measures imposed by the UK government to its banking sector and the corresponding EU financial measures are discussed. A brief evaluation of the causes of the crisis in Cyprus follows. The article concludes that Cyprus can follow the UK example and focus its efforts on the banks’ supervision, to improve its financial industry and avoid a future financial crisis

Identifying and improving deficient business processes to prepare SMEs for ERP implementation

The study reported in this paper aims to identify, explore and improve hitherto deficient business processes for SMEs in order to prepare them for ERP implementation projects. When business process improvement is traditionally perceived as a task that is particularly related to the ERP project phase, this paper argues that broad changes of business processes should actually be performed well before implementing the system. The research took a Cypriot SME as a case study, and adopted in-depth interview as the main method of data collection. The qualitative data collected was analysed by using an inductive thematic analysis approach. The findings identified that business deficiencies and problems, which can impact potential ERP adoption and usage in SMEs, can be localised across business processes, e.g. sales ordering and stock controlling processes. Disregarding these deficient business processes and business drawbacks in the ERP preparation stage will have implications not just for the subsequent ERP project, but also for the long-term ERP usage

Three dimensional four-fermion models - A Monte Carlo study

We present results from numerical simulations of three different 3d four-fermion models that exhibit Z_2, U(1), and SU(2) x SU(2) chiral symmetries, respectively. We performed the simulations by using the hybrid Monte Carlo algorithm. We employed finite size scaling methods on lattices ranging from 8^3 to 40^3 to study the properties of the second order chiral phase transition in each model. The corresponding critical coupling defines an ultraviolet fixed point of the renormalization group. In our high precision simulations, we detected next-to-leading order corrections for various critical exponents and we found them to be in good agreement with existing analytical large-N_f calculations.Comment: 15 pages, 7 figures, and 2 table

Towards a combined Rotational-Differential Cryptanalytic Framework

In this report, we suggest a new cryptanalytic framework of constructing distinguishers which can be eventually extended to full attacks in the related-key scenario. We name this new paradigm as ”Relational Cryptanalysis”. The main idea is to exhibit the non-randomness of a given encryption algorithm by observing the propagation of specific sets of plaintexts of the form (P,P′) such that these pairs satisfy some rotational and differential properties of the form R1(P) = P′ and P ⊕ P′ ∈ ∆P, for some rotational symmetry R1 and fixed set of differences ∆P . Except of rotational and differential properties, we can add any other relation which seems to hold for a reduced number of rounds of the cryptographic primitive we study. Intuitively, we expect that by adding more relations we increase the observed probability of the propagation and this result to stronger statistical distinguishers