A note concerning primary source knowledge

We present the results of running 4 different papers through the automated filtering system used by the open access preprint server “arXiv” to classify papers and implement quality control barriers. The exercise was carried out in order to assess whether these highly sophisticated, state-of-the-art filters can distinguish between papers that are controversial or have gone past their “sell-by date,” and otherwise normal papers. We conclude that not even the arXiv filters, which are otherwise successful in filtering fringe-topic papers, can fully acquire “Domain-Specific Discrimination” and thus distinguish technical papers that are taken seriously by an expert community from those that are not. Finally, we discuss the implications this has for citizen and policy-maker engagement with the Primary Source Knowledge of a technical domain

Las plantas como evidencia legal. Desarrollo de la Botánica Forense en Colombia

La botánica aporta información de gran importancia en el ámbito forense para el estudio de la escena de los hechos en los procesos de investigación judicial. En Colombia, desde comienzos de siglo XX se vienen realizando solicitudes judiciales para determinar, la causa de muerte por ingestión de plantas tóxicas y más recientemente la identificación de elementos materia de prueba procedentes de los cultivos ilícitos. Acá se muestra el estado del tema en el país, con base en los registros oficiales del Instituto Nacional de Medicina Legal y Ciencias Forenses y del Instituto de Ciencias Naturales de la Universidad Nacional de Colombia, que reflejan un incremento de las solicitudes judiciales referentes a plantas de coca, amapola y marihuana. Se presentan algunos avances y perspectivas sobre el tema y se tratan las principales plantas de interés forense y algunos aspectos sobre protocolos de recolección, tratamiento e identificación de muestras.Peer reviewe

Synthesis of new fluorescent pyrylium dyes and study of their interaction with N-protected amino acids

Six new 6-styryl-2,4-diarylpyrylium salts have been synthesized and fully characterized by means of 1H/13C NMR, HRMS, UV-vis and Steady-State/Time-Resolved Fluorescence spectroscopies. This set of molecules is composed of a core pyrylium fluorophore, an amino acid (valine or phenylalanine), and an alkylic chain of variable length. The emissive properties (fluorescence quantum yields and lifetimes and radiative deactivation rate constants) in dichloromethane, acetonitrile and PBS have been recorded. The interaction of these pyrylium salts with aminoacids in their N-protected forms has been studied by means of fluorescence quenching, using the Stern–Volmer methodology. It has been found that dynamic (collisional) quenching is the most prevalent process for all the fluorescent molecules, irrespective of the amino acid building block or the length of the alkyl chain. The emission of the pyrylium molecules is strongly quenched by Z-Trp-OH and to a lesser extent by Z-Tyr-OH and Z-Met-OH and no quenching was measured with Z-Ala-OH, Z-Val-OH and Z-Phe-OH. A small degree of ground-state complexation was observed for receptor 8a and by Z-Trp-OH (upward curvature in the Stern–Volmer plot). Complementary 1H-NMR titrations demonstrated the existence of such a weak ground state complex

Sex differences in the inflammatory response of primary astrocytes to lipopolysaccharide

<p>Abstract</p> <p>Background</p> <p>Numerous neurological and psychiatric disorders show sex differences in incidence, age of onset, symptomatology or outcome. Astrocytes, one of the glial cell types of the brain, show sex differences in number, differentiation and function. Since astrocytes are involved in the response of neural tissue to injury and inflammation, these cells may participate in the generation of sex differences in the response of the brain to pathological insults. To explore this hypothesis, we have examined whether male and female astrocytes show a different response to an inflammatory challenge and whether perinatal testosterone influences this response.</p> <p>Methods</p> <p>Cortical astrocyte cultures were prepared from postnatal day 1 (one day after birth) male or female CD1 mice pups. In addition, cortical astrocyte cultures were also prepared from female pups that were injected at birth with 100 μg of testosterone propionate or vehicle. Cultures were treated for 5 hours with medium containing lipopolysaccharide (LPS) or with control medium. The mRNA levels of IL6, interferon-inducible protein 10 (IP10), TNFα, IL1β, Toll-like receptor 4 (TLR4), steroidogenic acute regulatory protein and translocator protein were assessed by quantitative real-time polymerase chain reaction. Statistical significance was assessed by unpaired <it>t</it>-test or by one-way analysis of variance followed by the Tukey <it>post hoc </it>test.</p> <p>Results</p> <p>The mRNA levels of IL6, TNFα and IL1β after LPS treatment were significantly higher in astrocytes derived from male or androgenized females compared to astrocytes derived from control or vehicle-injected females. In contrast, IP10 mRNA levels after LPS treatment were higher in astrocytes derived from control or vehicle-injected females than in those obtained from males or androgenized females. The different response of male and female astrocytes to LPS was due neither to differences in the basal expression of the inflammatory molecules nor to differences in the expression of the LPS receptor TLR4. In contrast, the different inflammatory response was associated with increased mRNA levels of translocator protein, a key steroidogenic regulator, in female astrocytes that were treated with LPS.</p> <p>Conclusions</p> <p>Male and female cortical astrocytes respond differentially to an inflammatory challenge and this may be predetermined by perinatal testosterone exposure.</p

Quantum phases of a qutrit

We consider various approaches to treat the phases of a qutrit. Although it is possible to represent qutrits in a convenient geometrical manner by resorting to a generalization of the Poincare sphere, we argue that the appropriate way of dealing with this problem is through phase operators associated with the algebra su(3). The rather unusual properties of these phases are caused by the small dimension of the system and are explored in detail. We also examine the positive operator-valued measures that can describe the qutrit phase properties.Comment: 6 page

The interaction of amino acids with macrocyclic pH probes of pseudopeptidic nature

The fluorescence quenching, by a series of amino acids, of pseudopeptidic compounds acting as probes for cellular acidity has been investigated. It has been found that amino acids containing electron-rich aromatic side chains like Trp or Tyr, as well as Met quench the emission of the probes mainly via a collisional mechanism, with Stern–Volmer constants in the 7–43 M−1 range, while other amino acids such as His, Val or Phe did not cause deactivation of the fluorescence. Only a minor contribution of a static quenching due to the formation of ground-state complexes has been found for Trp and Tyr, with association constants in the 9–24 M−1 range. For these ground-state complexes, a comparison between the macrocyclic probes and an open chain analogue reveals the existence of a moderate macrocyclic effect due to the preorganization of the probes in the more rigid structure

Resonances in the one-dimensional Dirac equation in the presence of a point interaction and a constant electric field

We show that the energy spectrum of the one-dimensional Dirac equation in the presence of a spatial confining point interaction exhibits a resonant behavior when one includes a weak electric field. After solving the Dirac equation in terms of parabolic cylinder functions and showing explicitly how the resonant behavior depends on the sign and strength of the electric field, we derive an approximate expression for the value of the resonance energy in terms of the electric field and delta interaction strength.Comment: 9 pages. To appear in Physics Letters

Turn-on fluorescent probes for nitric oxide sensing based on the the ortho-hydroxyamino structure showing no interference with dehydroascorbic acid

A new family of fluorescent synthetic molecular probes for nitric oxide sensing based on ortho-hydroxyamino-triarylpyrylium salts is presented

Resonant states in an attractive one dimensional cusp potential

We solve the two-component Dirac equation in the presence of a spatially one dimensional symmetric attractive cusp potential. The components of the spinor solution are expressed in terms of Whittaker functions. We compute the bound states solutions and show that, as the potential amplitude increases, the lowest energy state sinks into the Dirac sea becoming a resonance. We characterize and compute the lifetime of the resonant state with the help of the phase shift and the Breit-Wigner relation. We discuss the limit when the cusp potential reduces to a delta point interaction.Comment: 11 pages. To appear in Physica Script

Tunneling and transmission resonances of a Dirac particle by a double barrier

We calculate the tunneling process of a Dirac particle across two square barriers separated a distance $d$, as well as the scattering by a double cusp barrier where the centers of the cusps are separated a distance larger than their screening lengths. Using the scattering matrix formalism, we obtain the transmission and reflection amplitudes for the scattering processes of both configurations. We show that, the presence of transmission resonances modifies the Lorentizian shape of the energy resonances and induces the appearance of additional maxima in the transmission coefficient in the range of energies where transmission resonances occur. We calculate the Wigner time-delay and show how their maxima depend on the position of the transmission resonance.Comment: To appear in Physica Script