Rate and timing of cortical responses driven by separate sensory channels

The sense of touch comprises multiple sensory channels that each conveys characteristic signals during interactions with objects. These neural signals must then be integrated in such a way that behaviorally relevant information about the objects is preserved. To understand the process of integration, we implement a simple computational model that describes how the responses of neurons in somatosensory cortex—recorded from awake, behaving monkeys—are shaped by the peripheral input, reconstructed using simulations of neuronal populations that reproduce natural spiking responses in the nerve with millisecond precision. First, we find that the strength of cortical responses is driven by one population of nerve fibers (rapidly adapting) whereas the timing of cortical responses is shaped by the other (Pacinian). Second, we show that input from these sensory channels is integrated in an optimal fashion that exploits the disparate response behaviors of different fiber types

General Scheme for Perfect Quantum Network Coding with Free Classical Communication

This paper considers the problem of efficiently transmitting quantum states through a network. It has been known for some time that without additional assumptions it is impossible to achieve this task perfectly in general -- indeed, it is impossible even for the simple butterfly network. As additional resource we allow free classical communication between any pair of network nodes. It is shown that perfect quantum network coding is achievable in this model whenever classical network coding is possible over the same network when replacing all quantum capacities by classical capacities. More precisely, it is proved that perfect quantum network coding using free classical communication is possible over a network with $k$ source-target pairs if there exists a classical linear (or even vector linear) coding scheme over a finite ring. Our proof is constructive in that we give explicit quantum coding operations for each network node. This paper also gives an upper bound on the number of classical communication required in terms of $k$, the maximal fan-in of any network node, and the size of the network.Comment: 12 pages, 2 figures, generalizes some of the results in arXiv:0902.1299 to the k-pair problem and codes over rings. Appeared in the Proceedings of the 36th International Colloquium on Automata, Languages and Programming (ICALP'09), LNCS 5555, pp. 622-633, 200

Leptogenesis, neutrino masses and gauge unification

Leptogenesis is considered in its natural context where Majorana neutrinos fit in a gauge unification scheme and therefore couple to some extra gauge bosons. The masses of some of these gauge bosons are expected to be similar to those of the heavy Majorana particles, and this can have important consequences for leptogenesis. In fact, the effect can go both ways. Stricter bounds are obtained on one hand due to the dilution of the CP-violating effect by new decay and scattering channels, while, in a re-heating scheme, the presence of gauge couplings facilitates the re-population of the Majorana states. The latter effect allows in particular for smaller Dirac couplings.Comment: 11pages, 7 figures. v2: definition of the lepton asymmetry corrected, small numerical changes for the baryon number, conclusion does not change; typos corrected and references adde

A Model for Neutrino Masses and Dark Matter

We propose a model for neutrino masses that simultaneously results in a new dark matter candidate, the right-handed neutrino. We derive the dark matter abundance in this model, show how the hierarchy of neutrino masses is obtained, and verify that the model is compatible with existing experimental results. The model provides an economical method of unifying two seemingly separate puzzles in contemporary particle physics and cosmology.Comment: 4 pages, submitted to PR

Zeros of the Partition Function and Pseudospinodals in Long-Range Ising Models

The relation between the zeros of the partition function and spinodal critical points in Ising models with long-range interactions is investigated. We find the spinodal is associated with the zeros of the partition function in four-dimensional complex temperature/magnetic field space. The zeros approach the real temperature/magnetic field plane as the range of interaction increases.Comment: 20 pages, 9 figures, accepted to PR

Challenging lanthanide relaxation theory: erbium and thulium complexes that show NMR relaxation rates faster than dysprosium and terbium analogues

Measurements of the proton NMR paramagnetic relaxation rates for several series of isostructural lanthanide(III) complexes have been performed in aqueous solution over the field range 1.0 to 16.5 Tesla. The field dependence has been modeled using Bloch–Redfield–Wangsness theory, allowing values for the electronic relaxation time, Tle and the magnetic susceptibility, μeff, to be estimated. Anomalous relaxation rate profiles were obtained, notably for erbium and thulium complexes of low symmetry 8-coordinate aza-phosphinate complexes. Such behaviour challenges accepted theory and can be interpreted in terms of changes in Tle values that are a function of the transient ligand field induced by solvent collision and vary considerably between Ln3+ ions, along with magnetic susceptibilities that deviate significantly from free-ion values

Modular Cosmology, Thermal Inflation, Baryogenesis and Predictions for Particle Accelerators

Modular cosmology is plagued by overproduction of unwanted relics, gravitinos and especially moduli, at relatively low energy scales. Thermal inflation provides a compelling solution to this moduli problem, but invalidates most baryogenesis scenarios. We propose a simple model in which the MSSM plus neutrino mass term $(LH_u)^2$ is supplemented by a minimal flaton sector to drive the thermal inflation, and make two crucial assumptions: the flaton vacuum expectation value generates the $\mu$-term of the MSSM and $m_L^2 + m_{H_u}^2 < 0$. The second assumption is particularly interesting in that it violates a well known constraint, implying that there exists a nearby deep non-MSSM vacuum, and provides a clear signature of our model which can be tested at future particle accelerators. We show that our model leads to thermal inflation followed by Affleck-Dine leptogenensis along the $LH_u$ flat direction. A key feature of our leptogenesis scenario is that the $H_uH_d$ flat direction is also induced to temporarily acquire a large value, playing a crucial role in the leptogenesis, as well as dynamically shielding the field configuration from the deep non-MSSM minimum, ensuring that the fields relax into our MSSM vacuum.Comment: v3; 19 pages, 3 figures; added a reference for section

Ammonia in a time of COVID-19. A submission of evidence to Defra/AQEG

A submission to the Air Quality Expert Group (AQEG), an expert committee of the Department for Environment, Food and Rural Affairs (Defra) • Ammonia gas (NH3) is a priority pollutant both as a precursor to particulate matter and for ecosystem impacts. • Three scenarios for UK emission reductions during COVID-19 in emission sectors, where activity is likely reduced ,have been assessed. • Total UK emissions of NH3 are likely to have decreased slightly (~2%), which is within the uncertainty and meteorological variability of the UK atmosphere. • Urban background and urban on road and roadside emissions of NH3 are likely to have decreased, by as much as 30% and 90% respectively compared with usual emissions before COVID-19. • Unratified data from three of the five UK automatic NH3 analysers (Auchencorth Moss, Chilbolton Observatory, and Manchester OSCA Observatory) show typical springtime NH3 concentrations across the UK. • Data from the non-automatic National Ammonia Monitoring Network will enable analysis at UK level in the months ahead. This includes roadside data from London Cromwell Rd. • Evidence gaps & future approaches are outlined. Future analysis of the Defra UKEAP rural networks proposed. • The key measurement gap is urban roadside NH3 (and PM ammonium) as there is only one long-term site in the UK measuring roadside NH3 concentrations. It is suggested that a roadside network of samplers and/or analysers are urgently put in place (perhaps aligned with the UK Urban NO2 Network; UUNN) to monitor NH3 at roadsides during and post COVID-19 lock down where possible

Soil-landscape and climatic relationships in the middle Miocene of the Madrid Basin

The Miocene alluvial-lacustrine sequences of the Madrid Basin, Spain, formed in highly varied landscapes. The presence of various types of palaeosols allows assessment of the effects of local and external factors onsedimentation, pedogenesis and geomorphological development. In the northern, more arid, tectonicallyactive arca, soils were weakly developed in aggrading alluvial fans, dominated by mass flows. reflecting high sedimentation rates. In more distal parts of the fans and in playa lakes calcretes and dolocretes developed: the former were associated with Mg-poor fan sediments whitc: the latter formed on Mg-rich lake clays exposed during minar lake lowstands. The nonh-east part of the basin had a less arid climate. Alluvial fans in this area were dominated by stream Aood deposits, sourced by carbonate terrains. Floodplain and freshwater lakc deposits formed in distal areas. The high local supply of calcium carbonate may have contributed to the preferential developmenl on calcretes on the fans. Both the fan and floodplain palaeosols exhibit pedofacies relationships and more mature soils developed in settings more distant from the sediment sources. Palaeosols also developed on pond and lake margin carbonates, and led to the formation of palustrine limestones. The spatial distributions and stratigraphies of palaeosols in the Madrid Basin alluvial fans suggest that soil formation was controlled by local factors. These palaeosols differ from those seen in Quatemary fans. Which are characterized by climatically induced periods of stability and instability

Primary decomposition and the fractal nature of knot concordance

For each sequence of polynomials, P=(p_1(t),p_2(t),...), we define a characteristic series of groups, called the derived series localized at P. Given a knot K in S^3, such a sequence of polynomials arises naturally as the orders of certain submodules of the sequence of higher-order Alexander modules of K. These group series yield new filtrations of the knot concordance group that refine the (n)-solvable filtration of Cochran-Orr-Teichner. We show that the quotients of successive terms of these refined filtrations have infinite rank. These results also suggest higher-order analogues of the p(t)-primary decomposition of the algebraic concordance group. We use these techniques to give evidence that the set of smooth concordance classes of knots is a fractal set. We also show that no Cochran-Orr-Teichner knot is concordant to any Cochran-Harvey-Leidy knot.Comment: 60 pages, added 4 pages to introduction, minor corrections otherwise; Math. Annalen 201