Science is perception: what can our sense of smell tell us about ourselves and the world around us?

Human sensory processes are well understood: hearing, seeing, perhaps even tasting and touch—but we do not understand smell—the elusive sense. That is, for the others we know what stimuli causes what response, and why and how. These fundamental questions are not answered within the sphere of smell science; we do not know what it is about a molecule that … smells. I report, here, the status quo theories for olfaction, highlighting what we do not know, and explaining why dismissing the perception of the input as ‘too subjective’ acts as a roadblock not conducive to scientific inquiry. I outline the current and new theory that conjectures a mechanism for signal transduction based on quantum mechanical phenomena, dubbed the ‘swipe card’, which is perhaps controversial but feasible. I show that such lines of thinking may answer some questions, or at least pose the right questions. Most importantly, I draw links and comparisons as to how better understanding of how small (10’s of atoms) molecules can interact so specially with large (10 000’s of atoms) proteins in a way that is so integral to healthy living. Repercussions of this work are not just important in understanding a basic scientific tool used by us all, but often taken for granted, it is also a step closer to understanding generic mechanisms between drug and receptor, for example

Clarification of the relationship between bound and scattering states in quantum mechanics: Application to 12C + alpha

Using phase-equivalent supersymmetric partner potentials, a general result from the inverse problem in quantum scattering theory is illustrated, i.e., that bound-state properties cannot be extracted from the phase shifts of a single partial wave, as a matter of principle. In particular, recent R-matrix analyses of the 12C + alpha system, extracting the asymptotic normalization constant of the 2+ subthreshold state, C12, from the l=2 elastic-scattering phase shifts and bound-state energy, are shown to be unreliable. In contrast, this important constant in nuclear astrophysics can be deduced from the simultaneous analysis of the l=0, 2, 4, 6 partial waves in a simplified potential model. A new supersymmetric inversion potential and existing models give C12=144500+-8500 fm-1/2.Comment: Expanded version (50% larger); three errors corrected (conversion of published reduced widths to ANCs); nine references added, one remove

Characterization of Knots and Links Arising From Site-specific Recombination on Twist Knots

We develop a model characterizing all possible knots and links arising from recombination starting with a twist knot substrate, extending previous work of Buck and Flapan. We show that all knot or link products fall into three well-understood families of knots and links, and prove that given a positive integer $n$, the number of product knots and links with minimal crossing number equal to $n$ grows proportionally to $n^5$. In the (common) case of twist knot substrates whose products have minimal crossing number one more than the substrate, we prove that the types of products are tightly prescribed. Finally, we give two simple examples to illustrate how this model can help determine previously uncharacterized experimental data.Comment: 32 pages, 7 tables, 27 figures, revised: figures re-arranged, and minor corrections. To appear in Journal of Physics

Possible production of exotic baryonia in relativistic heavy-ion collisions

Properties of a hypothetical baryonium with the quark content (uds\ov{u}\ov{d}\ov{s}) are discussed. The MIT bag model predicts its mass to be unexpectedly low, approximately 1210 MeV. Possible hadronic decay modes of this state are analyzed. Ultrarelativistic heavy-ion collisions provide favorable conditions for the formation of such particles from the baryon-free quark-gluon plasma. We estimate multiplicities of such exotic baryonia on the basis of a simple thermal model.Comment: 8 pages, 1 figur

The S0_0(0) structure in highly compressed hydrogen and the orientational transition

A calculation of the rotational S$_0$(0) frequencies in high pressure solid para-hydrogen is performed. Convergence of the perturbative series at high density is demonstrated by the calculation of second and third order terms. The results of the theory are compared with the available experimental data to derive the density behaviour of structural parameters. In particular, a strong increase of the value of the lattice constant ratio $c/a$ and of the internuclear distance is determined. Also a decrease of the anisotropic intermolecular potential is observed which is attributed to charge transfer effects. The structural parameters determined at the phase transition may be used to calculate quantum properties of the rotationally ordered phase.Comment: accepted Europhysics Letter

Isomorphic classical molecular dynamics model for an excess electron in a supercritical fluid

Ring polymer molecular dynamics (RPMD) is used to directly simulate the dynamics of an excess electron in a supercritical fluid over a broad range of densities. The accuracy of the RPMD model is tested against numerically exact path integral statistics through the use of analytical continuation techniques. At low fluid densities, the RPMD model substantially underestimates the contribution of delocalized states to the dynamics of the excess electron. However, with increasing solvent density, the RPMD model improves, nearly satisfying analytical continuation constraints at densities approaching those of typical liquids. In the high density regime, quantum dispersion substantially decreases the self-diffusion of the solvated electron. In this regime where the dynamics of the electron is strongly coupled to the dynamics of the atoms in the fluid, trajectories that can reveal diffusive motion of the electron are long in comparison to $\beta\hbar$.Comment: 24 pages, 4 figure

Gene Expression and the Diversity of Identified Neurons

Nervous systems consist of diverse populations of neurons that are anatomically and functionally distinct. The diversity of neurons and the precision with which they are interconnected suggest that specific genes or sets of genes are activated in some neurons but not expressed in others. Experimentally, this problem may be considered at two levels. First, what is the total number of genes expressed in the brain, and how are they distributed among the different populations of neurons? Second, can we identify specific genes expressed in individual neurons and relate the expression of these genes to the unique functional properties of these neurons

alpha-nucleus potentials for the neutron-deficient p nuclei

alpha-nucleus potentials are one important ingredient for the understanding of the nucleosynthesis of heavy neutron-deficient p nuclei in the astrophysical gamma-process where these p nuclei are produced by a series of (gamma,n), (gamma,p), and (gamma,alpha) reactions. I present an improved alpha-nucleus potential at the astrophysically relevant sub-Coulomb energies which is derived from the analysis of alpha decay data and from a previously established systematic behavior of double-folding potentials.Comment: 6 pages, 3 figures, accepted for publication in Phys. Rev.

Revisiting the validity of measures of social cognitive bias in schizophrenia : Additional results from the Social Cognition Psychometric Evaluation (SCOPE) study

Objective The ongoing Social Cognition Psychometric Evaluation (SCOPE) study is in the process of forming a gold-standard battery of social cognition tests for use in clinical trials. Previous SCOPE phases have not acknowledged key differences between social cognition skills and biases, and psychometric validity analyses might provide important information if tailored to bias-related outcomes. This study aims to validate these measures with such bias-related outcomes. Methods Two measures of social cognitive bias – the Ambiguous Intention Hostility Questionnaire (AIHQ; hostile attribution bias) and Trustworthiness Task (distrust bias) – were reviewed according to their relationships to (1) current and prospective symptom levels, (2) questionnaires of trait paranoia and hostility and informant-rated hostility, (3) interpersonal conflict, as well as (4) relationships to measures of trait paranoia, hostility, and interpersonal conflict above and beyond the influence of clinically rated symptoms. Results Results supported hypotheses that social cognitive bias provides information about cognition, symptoms, and functioning related to interpersonal conflict. Each bias demonstrated relationships to trait paranoia questionnaires, hostility, or interpersonal conflict outcomes, and these persisted above and beyond the influence of clinically rated symptoms. Hostile attribution bias also predicted change in symptom levels over a brief interval. Conclusions Overall, the current bias-specific psychometric analysis provides support for continued study of social cognitive biases. Practitioner points • Hostile attribution bias may play a role in important outcome variables given relationships to emotional discomfort and suspiciousness symptoms, trait paranoia and hostility, interpersonal conflict, as well as prospective hostility symptoms. • Distrust bias may also impact real-world functioning, as it is related to hostility, suspiciousness, and positive symptoms, trait paranoia, and hostility. • Relationships of social cognitive biases to interpersonal conflict outcomes exist independently of interview-rated symptoms and persist above and beyond the influence of social cognitive skills, which appear to demonstrate weaker relationships to these outcomes. • Understanding and assessing the individual's biases towards distrust or blame might help practioners predict interpersonal conflict and future increases in symptoms