A tight coupling between β\u3csub\u3e2\u3c/sub\u3eY97 and β\u3csub\u3e2\u3c/sub\u3eF200 of the GABA\u3csub\u3eA\u3c/sub\u3e receptor mediates GABA binding

The GABAA receptor is an oligopentameric chloride channel that is activated via conformation changes induced upon the binding of the endogenous ligand, GABA, to the extracellular inter-subunit interfaces. Although dozens of amino acid residues at the α/β interface have been implicated in ligand binding, the structural elements that mediate ligand binding and receptor activation are not yet fully described. In this study, double-mutant cycle analysis was employed to test for possible interactions between several arginines (α1R67, α1R120, α1R132, and β2R207) and two aromatic residues (β2Y97 and β2F200) that are present in the ligand-binding pocket and are known to influence GABA affinity. Our results show that neither α1R67 nor α1R120 is functionally coupled to either of the aromatics, whereas a moderate coupling exists between α1R132 and both aromatic residues. Significant functional coupling between β2R207 and both β2Y97 and β2F200 was found. Furthermore, we identified an even stronger coupling between the two aromatics, β2Y97 and β2F200, and for the first time provided direct evidence for the involvement of β2Y97 and β2F200 in GABA binding. As these residues are tightly linked, and mutation of either has similar, severe effects on GABA binding and receptor kinetics, we believe they form a single functional unit that may directly coordinate GABA

Promoting clean technologies: The energy market structure crucially matters

We develop a general equilibrium vintage capital model with embodied energy- saving technological progress and an explicit energy market to study the impact of investment subsidies on investment and output. Energy and capital are assumed to be complementary in the production process. New machines are less energy con- suming and scrapping is endogenous. It is shown that the impact of investment subsidies heavily depends on the structure of the energy market, the mechanism explaining this outcome relying on the tight relationship between the lifetime of capital goods and energy prices via the scrapping conditions inherent to vintage models. In particular, under a free entry structure for the energy sector, invest- ment subsidies boost investment, while the opposite result emerges under natural monopoly if increasing returns in the energy sector are not strong enough.Energy-saving technological progress; vintage capital; energy market; natural monopoly; investment subsidies

A Structural nonparametric reappraisal of the CO2 emissions-income relationships.

Relying on a structural nonparametric estimation, we show that CO2 emissions clearly increase with income at low income levels. For higher income levels, we observe a decreasing relationship, though not significant. We also find that CO2 emissions monotonically increases with energy use at a decreasing rate.Nonparametric triangular systems, EKC; Energy use; CO2 emissions.

Promoting clean technologies under imperfect competition

We develop a general equilibrium multi-sector vintage capital model with energy-saving technological progress and an explicit energy market to study the impact of investment subsidies on investment and output. Energy and capital are assumed to be complementary in the production process. New machines are less energy consuming and scrapping is endogenous. The intermediate inputs sector is modelled à la Dixit-Stiglitz (1977). Two polar market structures are considered for the energy market, free entry and natural monopoly. The impact of imperfect competition on the outcomes of the decentralized equilibria are deeply characterized. We identify an original paradox: adoption subsidies may induce a larger investment into cleaner technologies either under free entry or natural monopoly. However, larger diffusion rates do not necessarily mean lower energy consumption at equilibrium, which may explain certain empirical puzzles.Energy-saving technological progress; vintage capital; market imperfections; natural monopoly; investment subsidies

Promoting Clean Technologies: The Energy Market Structure Crucially Matters

We develop a general equilibrium vintage capital model with embodied energy- saving technological progress and an explicit energy market to study the impact of investment subsidies on investment and output. Energy and capital are assumed to be complementary in the production process. New machines are less energy consuming and scrapping is endogenous. It is shown that the impact of investment subsidies heavily depends on the structure of the energy market, the mechanism explaining this outcome relying on the tight relationship between the lifetime of capital goods and energy prices via the scrapping conditions inherent to vintage models. In particular, under a free entry structure for the energy sector, investment subsidies boost investment, while the opposite result emerges under natural monopoly if increasing returns in the energy sector are not strong enough.Energy-saving technological progress; vintage capital; energy market; natural monopoly; investment subsidies

Secrecy performance of TAS/SC-based multi-hop harvest-to-transmit cognitive WSNs under joint constraint of interference and hardware imperfection

In this paper, we evaluate the secrecy performance of multi-hop cognitive wireless sensor networks (WSNs). In the secondary network, a source transmits its data to a destination via the multi-hop relaying model using the transmit antenna selection (TAS)/selection combining (SC) technique at each hop, in the presence of an eavesdropper who wants to receive the data illegally. The secondary transmitters, including the source and intermediate relays, have to harvest energy from radio-frequency signals of a power beacon for transmitting the source data. Moreover, their transmit power must be adjusted to satisfy the quality of service (QoS) of the primary network. Under the joint impact of hardware imperfection and interference constraint, expressions for the transmit power for the secondary transmitters are derived. We also derive exact and asymptotic expressions of secrecy outage probability (SOP) and probability of non-zero secrecy capacity (PNSC) for the proposed protocol over Rayleigh fading channel. The derivations are then verified by Monte Carlo simulations.Web of Science195art. no. 116

Rateless codes-based secure communication employing transmit antenna selection and harvest-to-jam under joint effect of interference and hardware impairments

In this paper, we propose a rateless codes-based communication protocol to provide security for wireless systems. In the proposed protocol, a source uses the transmit antenna selection (TAS) technique to transmit Fountain-encoded packets to a destination in presence of an eavesdropper. Moreover, a cooperative jammer node harvests energy from radio frequency (RF) signals of the source and the interference sources to generate jamming noises on the eavesdropper. The data transmission terminates as soon as the destination can receive a sufficient number of the encoded packets for decoding the original data of the source. To obtain secure communication, the destination must receive sufficient encoded packets before the eavesdropper. The combination of the TAS and harvest-to-jam techniques obtains the security and efficient energy via reducing the number of the data transmission, increasing the quality of the data channel, decreasing the quality of the eavesdropping channel, and supporting the energy for the jammer. The main contribution of this paper is to derive exact closed-form expressions of outage probability (OP), probability of successful and secure communication (SS), intercept probability (IP) and average number of time slots used by the source over Rayleigh fading channel under the joint impact of co-channel interference and hardware impairments. Then, Monte Carlo simulations are presented to verify the theoretical results.Web of Science217art. no. 70

Critical behavior of magnetic thin films as a function of thickness

We study the critical behavior of magnetic thin films as a function of the film thickness. We use the ferromagnetic Ising model with the high-resolution multiple histogram Monte Carlo (MC) simulation. We show that though the 2D behavior remains dominant at small thicknesses, there is a systematic continuous deviation of the critical exponents from their 2D values. We observe that in the same range of varying thickness the deviation of the exponent $\nu$ is rather small, while exponent $\beta$ suffers a larger deviation. We explain these deviations using the concept of "effective" exponents suggested by Capehart and Fisher in a finite-size analysis. The shift of the critical temperature with the film thickness obtained here by MC simulation is in an excellent agreement with their prediction.Comment: 10 pages, 19 figure

Crossover from First to Second-Order Transition in Frustrated Ising Antiferromagnetic Films

In the bulk state, the Ising FCC antiferromagnet is fully frustrated and is known to have a very strong first-order transition. In this paper, we study the nature of this phase transition in the case of a thin film, as a function of the film thickness. Using Monte Carlo (MC) simulations, we show that the transition remains first order down to a thickness of four FCC cells. It becomes clearly second order at a thickness of two FCC cells, i.e. four atomic layers. It is also interesting to note that the presence of the surface reduces the ground state (GS) degeneracy found in the bulk. For the two-cell thickness, the surface magnetization is larger than the interior one. It undergoes a second-order phase transition at a temperature $T_C$ while interior spins become disordered at a lower temperature $T_D$. This loss of order is characterized by a peak of the interior spins susceptibility and a peak of the specific heat which do not depend on the lattice size suggesting that either it is not a real transition or it is a Kosterlitz-Thouless nature. The surface transition, on the other hand, is shown to be of second order with critical exponents deviated from those of pure 2D Ising universality class. We also show results obtained from the Green's function method. Discussion is given.Comment: 20 pages, 14 figure