Structure Determination of Hydroxytrypargine: A New Tetrahydro‐β‐Carboline Toxin from the Venom of the Spider Parawixia bistriata

A new, highly active tetrahydro‐β‐carboline toxin from the spider Parawixia bistriata, the most‐common species of social spider occurring in Brazil, was isolated. The new toxin was identified as 1,2,3,4‐tetrahydro‐6‐hydroxy‐β‐carboline (=N‐[3‐(2,3,4,9‐tetrahydro‐6‐hydroxy‐1H‐pyrido[3,4‐b]indol‐1‐yl)propyl]guanidine; 3 ). This type of alkaloid, not common among spider toxins, was found to be the most‐potent constituent of the spider's chemical weaponry to kill prey. When P. bistriata catch arthropods in their web, they apparently attack their prey in groups of many individuals injecting their venoms. In vivo toxicity assays with 3 demonstrated a potent lethal effect to honeybees, giving rise to clear neurotoxic effects (paralysis) before death. The compound's toxicity (LD₅₀ value) was determined to be ca. 8 ng/g of honeybee. The investigation of the pharmacological properties and neurotoxic actions of 3 may be used in the future for the development of new drugs to be applied for pest control in agriculture.     

Bounded rational expectations and the stability of interest rate policy

The New Keynesian model has recently been subject to two serious criticisms: the model cannot produce plausible inflation and output dynamics following a monetary shock, and the stability of its dynamics suffers from indeterminacy. The procedures that have been proposed to eliminate these two shortcomings fall into two categories: the introduction of some sort of backward price indexation into the standard model and/or other forms of stickiness (like sticky information); and the adoption of some form of policy rule that completely offsets the effects of forward looking dynamics in the optimization process. In this paper we do not eradicate forward looking behavior from the dynamics of the New Keynesian model, neither do we impose some form of backward price indexation. We assume that private economic agents have forward looking behavior and that they do try to optimize with all available information; the only novelty is that they are allowed to make small mistakes near the rational expectations equilibrium, in a fully deterministic setup. These “near rational” or “bounded rational” expectations show that the dynamics of the model with active interest rate rules is much richer than the simple problem of local indeterminacy as is usually found in the literature.     

An inflationary bianchi V model with shear and rotation

A Bianchi V model, in the presence of a fluid with shear and rotation, is investigated. Asymptotic solutions are worked out, showing that shear and rotation may give rise to a conflict with present day observations, a problem that can be solved with the help of an inflationary solution.     

Stochastic processes and the non-perturbative structure of the QCD vacuum

Based on a local Gaussian evaluation of the functional integral representation, a method is developed to obtain ground state functionals. The method is applied to the gluon sector of QCD. For the leading term in the ground state functional, stochastic techniques are used to check consistency of the quantum theory, finiteness of the mass gap and the scaling relation in the continuum limit. The functional also implies strong chromomagnetic fluctuations which constrain the propagators in the fermion sector.     

Hydrogen and deuterium trapping at nitrogen in tantalum studied by PAC

PAC experiments using¹⁸¹Hf as probe atom were performed in Ta samples containing 1.1 at% of N and loaded with 0.2 at% of H or of 1.6 at% of D. At room temperature only the known frequency due to N is present. Below 100K or 140K, for H and D respectively, the amplitude of this interaction decreases and two new interaction frequencies characterized by V₀=240MHz, η=0.80 and V₀=250 MHz, η=0.40 appear. These frequencies are attributed to H(D) trapped by N in the vicinity of the probe atom¹⁸¹Hf. The disappearance of these interactions at 100K and 140K is interpreted as a release of H (D) from Hf but not from N. From the data the jump rates of H(D) around N in Ta are derived.     

Selective glycoprotein detection through covalent templating and allosteric click-imprinting

Many glycoproteins are intimately linked to the onset and progression of numerous heritable or acquired diseases of humans, including cancer. Indeed the recognition of specific glycoproteins remains a significant challenge in analytical method and diagnostic development. Herein, a hierarchical bottom-up route exploiting reversible covalent interactions with boronic acids and so-called click chemistry for the fabrication of glycoprotein selective surfaces that surmount current antibody constraints is described. The self-assembled and imprinted surfaces, containing specific glycoprotein molecular recognition nanocavities, confer high binding affinities, nanomolar sensitivity, exceptional glycoprotein specificity and selectivity with as high as 30 fold selectivity for prostate specific antigen (PSA) over other glycoproteins. This synthetic, robust and highly selective recognition platform can be used in complex biological media and be recycled multiple times with no performance decrement.     

Inelastic constitutive equations for complex flows

A new class of inelastic constitutive equations is presented and discussed. In addition to the rate-of-strain tensor, the stress is assumed to depend also on the relative-rate-of-rotation tensor, a frame-indifferent quantity that brings information about the nature of the flow. The material functions predicted by these constitutive equations are given for simple shear and uniaxial extension. A special case of these equations takes the Newtonian form, except that the viscosity is a function of the invariants of both kinematic tensors on which the stress depends. This simple constitutive equation has potential applications in liquid flow process simulations, since it combines simplicity with the capability of responding independently to shear and extension, as real liquids seem to do. Finally, possible forms for the new viscosity function are discussed.     

Temperature dependent Raman scattering study of l-ascorbic acid

Temperature dependent Raman study of l-ascorbic acid has been performed from 15 to 418 K. Changes in the wavenumber vs. temperature plots for some internal modes were interpreted as conformational molecular change and the discontinuity in the wavenumber vs. temperature plots along with the appearance of a new vibrational mode in the temperature range 200-270 K suggests that l-ascorbic acid undergoes a structural phase transition. For temperatures higher than 300 K, no relevant modification was observed on the Raman spectra thus indicating a stable structure at high temperatures. Additionally, a correlation between OH stretching wavenumber and the behavior of hydrogen bond is also made.