The proton electrochemical gradient induces a kinetic asymmetry in the symport cycle of LacY.

LacY catalyzes accumulation of galactosides against a concentration gradient by coupling galactoside and H+ transport (i.e., symport). While alternating access of sugar- and H+-binding sites to either side of the membrane is driven by binding and dissociation of sugar, the electrochemical H+ gradient ([Formula: see text]) functions kinetically by decreasing the Km for influx 50- to 100-fold with no change in Kd The affinity of protonated LacY for sugar has an apparent pK (pKapp) of ∼10.5, due specifically to the pKa of Glu325, a residue that plays an irreplaceable role in coupling. In this study, rates of lactose/H+ efflux were measured from pH 5.0 to 9.0 in the absence or presence of a membrane potential (ΔΨ, interior positive), and the effect of the imposed ΔΨ on the kinetics of efflux was also studied in right-side-out membrane vesicles. The findings reveal that [Formula: see text] induces an asymmetry in the transport cycle based on the following observations: 1) the efflux rate of WT LacY exhibits a pKapp of ∼7.2 that is unaffected by the imposed ΔΨ; 2) ΔΨ increases the rate of efflux at all tested pH values, but enhancement is almost 2 orders of magnitude less than observed for influx; 3) mutant Glu325 - Ala does little or no efflux in the absence or presence of ΔΨ, and ambient pH has no effect; and 4) the effect of ΔΨ (interior positive) on the Km for efflux is almost insignificant relative to the 50- to 100-fold decrease in the Km for influx driven by ΔΨ (interior negative)

Interference and Background Noise Effects in Wireless Networks with Poisson Fields of Transmitters

| openaire: EC/H2020/671639/EU//COHERENTIn this work, we analyze joint effects of background Gaussian noise and interference in wireless random networks where transmitting nodes form Poisson point processes (PPPs). We analyze different spatial models of interferers such as PPPs and Poisson cluster processes. In our analysis, Rayleigh fading and path-loss effects are taken into account.Peer reviewe

Statistics of ratios of random variables arising in analysis of wireless Poisson networks

In this study, the author analyses statistics of some typical ratios of random variables (RVs) occurring in analysis of large-scale wireless networks where node locations can be represented by Poisson point processes. In such networks, fading and path-loss effects are the most important factors affecting the signal strength. The author obtains formulas for the probability density, cumulative distribution and moment generating functions of ratios of RVs occurring under many typical scenarios in cellular-like, spectrum-sharing, and cooperative wireless networks. All obtained results are valid for arbitrary fading models of propagation paths.Peer reviewe

SIR Statistics and Average Rates in Cooperative Spectrum Sharing Networks

In this paper, we analyze cooperative wireless networks (primary networks) operating under randomly located interfering nodes (secondary networks). Applying Poisson point processes to modeling of network and interfering node locations, we derive statistics of signal-to-interference ratio (SIR) under different operational scenarios and show that the SIR statistical models can be viewed as special cases of the H-function distribution. On this basis, we obtain formulas for the average information rates. The presented results are general, and they are applicable to arbitrary fading conditions.Peer reviewe

A New Technique of Error Rate Evaluation in a Wireless Environment with Arbitrary Interference and AWGN

In this work, we present a new technique for the M-QAM symbol error rate evaluation in communication systems equipped with conventional detectors designed for additive white Gaussian noise (AWGN) model of interference but operating over a fading environment with arbitrary interference and AWGN. In contrast to many reported methods, the given technique is applicable to arbitrary interference and fading models, and it can efficiently be implemented numerically. These facts make the derived result especially convenient for practical purposes.Peer reviewe

Consensus-based Spectrum Sensing in Cognitive Radio Networks

In this work, we analyze a distributed cooperative spectrum sensing scheme where N secondary users (SUs) of a cognitive wireless net-work make a joint decision on the primary user (PU) presence based on an agreement reached through interchanging of SU’s individual decisions. The operational protocol assumes that each SU updates the personal de-cision by using the “K-out-of-N” rule, and the network detects the PU if the nodes reach the consensus. The problem of forming a joint opinion becomes challenging because a SU makes its personal decision based on local observations distorted by a wireless propagation medium. In this paper, we analyze statistics of factors affecting the algorithm efficiency and obtain sufficient conditions of reaching consensus. The presented analysis takes into account possible node disconnections caused by poor propagation conditions

Possibilities of Organizing Education for Preschool Children in the Forms of Children's Subculture

AbstractThe article describes the main theses of the concept of preschool children education organization in the forms of game by using fairy tales (in the forms of children's subculture), which is implemented in a number of preschool institutions in the city of Novosibirsk. It explains the role the fairy tale plays in child development and organization of preschool education according to the specifics of children's subculture. It submits the data of empirical research and formative experiment. The research of many years demonstrates that the preschool education organization under consideration actualizes a higher quality of intellectual, emotional and volitional, moral development, and the development of a child's individuality and subjectivity