Neuronal Processing of Complex Mixtures Establishes a Unique Odor Representation in the Moth Antennal Lobe

Animals typically perceive natural odor cues in their olfactory environment as a complex mixture of chemically diverse components. In insects, the initial representation of an odor mixture occurs in the first olfactory center of the brain, the antennal lobe (AL). The contribution of single neurons to the processing of complex mixtures in insects, and in particular moths, is still largely unknown. Using a novel multicomponent stimulus system to equilibrate component and mixture concentrations according to vapor pressure, we performed intracellular recordings of projection and interneurons in an attempt to quantitatively characterize mixture representation and integration properties of single AL neurons in the moth. We found that the fine spatiotemporal representation of 2–7 component mixtures among single neurons in the AL revealed a highly combinatorial, non-linear process for coding host mixtures presumably shaped by the AL network: 82% of mixture responding projection neurons and local interneurons showed non-linear spike frequencies in response to a defined host odor mixture, exhibiting an array of interactions including suppression, hypoadditivity, and synergism. Our results indicate that odor mixtures are represented by each cell as a unique combinatorial representation, and there is no general rule by which the network computes the mixture in comparison to single components. On the single neuron level, we show that those differences manifest in a variety of parameters, including the spatial location, frequency, latency, and temporal pattern of the response kinetics

Mathematical Properties of a New Levin-Type Sequence Transformation Introduced by \v{C}\'{\i}\v{z}ek, Zamastil, and Sk\'{a}la. I. Algebraic Theory

\v{C}\'{\i}\v{z}ek, Zamastil, and Sk\'{a}la [J. Math. Phys. \textbf{44}, 962 - 968 (2003)] introduced in connection with the summation of the divergent perturbation expansion of the hydrogen atom in an external magnetic field a new sequence transformation which uses as input data not only the elements of a sequence $\{s_n \}_{n=0}^{\infty}$ of partial sums, but also explicit estimates $\{\omega_n \}_{n=0}^{\infty}$ for the truncation errors. The explicit incorporation of the information contained in the truncation error estimates makes this and related transformations potentially much more powerful than for instance Pad\'{e} approximants. Special cases of the new transformation are sequence transformations introduced by Levin [Int. J. Comput. Math. B \textbf{3}, 371 - 388 (1973)] and Weniger [Comput. Phys. Rep. \textbf{10}, 189 - 371 (1989), Sections 7 -9; Numer. Algor. \textbf{3}, 477 - 486 (1992)] and also a variant of Richardson extrapolation [Phil. Trans. Roy. Soc. London A \textbf{226}, 299 - 349 (1927)]. The algebraic theory of these transformations - explicit expressions, recurrence formulas, explicit expressions in the case of special remainder estimates, and asymptotic order estimates satisfied by rational approximants to power series - is formulated in terms of hitherto unknown mathematical properties of the new transformation introduced by \v{C}\'{\i}\v{z}ek, Zamastil, and Sk\'{a}la. This leads to a considerable formal simplification and unification.Comment: 41 + ii pages, LaTeX2e, 0 figures. Submitted to Journal of Mathematical Physic

Representation of a complex Green function on a real basis: I. General Theory

When the Hamiltonian of a system is represented by a finite matrix, constructed from a discrete basis, the matrix representation of the resolvent covers only one branch. We show how all branches can be specified by the phase of a complex unit of time. This permits the Hamiltonian matrix to be constructed on a real basis; the only duty of the basis is to span the dynamical region of space, without regard for the particular asymptotic boundary conditions that pertain to the problem of interest.Comment: about 40 pages with 5 eps-figure

In vitro assays for bioactivity-guided isolation of antisalmonella and antioxidant compounds in Thonningia sanguinea flowers

Bioguided fractionation of the aqueous extract of Thonningia sanguinea flowers, used traditionally in the treatment of microbial diseases, led to the isolation of two phenolic compounds. The structure of these compounds was elucidated by 1H, 13C 1D NMR and mass spectrometry experiments. The antibacterial activity against Salmonella strains and antioxidant activity of the crude extract, fractions and isolated compounds was evaluated using the DPPH method. The isolated compounds identified asbrevifolin carboxylic acid and gallic acid demonstrates moderate antibacterial activity against Salmonella enteritidis, Salmonella typhimurium, and Salmonella abony. The results indicated that thetwo isolated compounds, gallic acid (IC50 = 13.5 ìM) and brevifolin carboxylic acid (IC50 = 18.0 ìM) were mainly responsible for the good scavenging activity of the aqueous extract

ANTIPROTOZOAL ACTIVITIES OF COMPOUNDS ISOLATED FROM CROTON LOBATUS L

In a preliminary evaluation of ethnobotanically selected Beninese medicinal plants for their in vitro antiplasmodial activity, the methanolic extract of the aerial parts of C. lobatus was found to have significant activity against P. falciparum, antileishmainal and antiprotoazoal assays carried out on some of the isolated compounds. Phytochemical investigation of this extract resulted in the isolation of five compounds: tiliroside (kaempferol-3-O-β-D-(6-E-p-coumaroyl) glycopyranoside) (1), isovitexin (apigenin-6-C-β-D-glucopyranoside) (2), vitexin (apigenin-8-C- β-D-glucopyranoside) (3), chlorogenic acid (acid-5-O-cafféoylquinic) (4) and 4,5-O-dicaffeoylquinic acid (5). Vitexin and tiliroside showed the best in vitro antiplasmodial activity against P. falciparum, with IC50 values of 4.4 and 7.1 µM, respectively. Vitexin also exhibited strong in vitro leishmanicidal and antitrypanosomal activities against Leishmania donovani amastigotes and Trypanosoma brucei rhodensiense trypomastigotes, with IC50 values of 0.6 and 0.1 µM, respectively

Asymptotic Improvement of Resummation and Perturbative Predictions in Quantum Field Theory

The improvement of resummation algorithms for divergent perturbative expansions in quantum field theory by asymptotic information about perturbative coefficients is investigated. Various asymptotically optimized resummation prescriptions are considered. The improvement of perturbative predictions beyond the reexpansion of rational approximants is discussed.Comment: 21 pages, LaTeX, 3 tables; title shortened; typographical errors corrected; minor changes of style; 2 references adde

Quantified HI Morphology III: Merger Visibility Times from HI in Galaxy Simulations

Major mergers of disk galaxies are thought to be a substantial driver in galaxy evolution. To trace the fraction and the rate galaxies are in mergers over cosmic times, several observational techniques, including morphological selection criteria, have been developed over the last decade. We apply this morphological selection of mergers to 21 cm radio emission line (HI) column density images of spiral galaxies in nearby surveys. In this paper, we investigate how long a 1:1 merger is visible in HI from N-body simulations. We evaluate the merger visibility times for selection criteria based on four parameters: Concentration, Asymmetry, M20, and the Gini parameter of second order moment of the flux distribution (GM). Of three selection criteria used in the literature, one based on Concentration and M20 works well for the HI perspective with a merger time scale of 0.4 Gyr. Of the three selection criteria defined in our previous paper, the GM performs well and cleanly selects mergers for 0.69 Gyr. The other two criteria (A-M20 and C-M20), select isolated disks as well, but perform best for face-on, gas-rich disks (T(merger) ~ 1 Gyr). The different visibility scales can be combined with the selected fractions of galaxies in any large HI survey to obtain merger rates in the nearby Universe. All-sky surveys such as WALLABY with ASKAP and the Medium Deep Survey with the APETIF instrument on Westerbork are set to revolutionize our perspective on neutral hydrogen and will provide an accurate measure of the merger fraction and rate of the present epoch.Comment: 12 pages, 6 figures, 4 tables, accepted by MNRAS, appendix not include

Resummation of Nonalternating Divergent Perturbative Expansions

A method for the resummation of nonalternating divergent perturbation series is described. The procedure constitutes a generalization of the Borel-Pad\'{e} method. Of crucial importance is a special integration contour in the complex plane. Nonperturbative imaginary contributions can be inferred from the purely real perturbative coefficients. A connection is drawn from the quantum field theoretic problem of resummation to divergent perturbative expansions in other areas of physics.Comment: 5 pages, LaTeX, 2 tables, 1 figure; discussion of the Carleman criterion added; version to appear in Phys. Rev.