Time evolution of decay of two identical quantum particles

An analytical solution for the time evolution of decay of two identical non interacting quantum particles seated initially within a potential of finite range is derived using the formalism of resonant states. It is shown that the wave function, and hence also the survival and nonescape probabilities, for factorized symmetric and entangled symmetric/antisymmetric initial states evolve in a distinctive form along the exponentially decaying and nonexponential regimes. Our findings show the influence of the Pauli exclusion principle on decay. We exemplify our results by solving exactly the s-wave delta shell potential model.Comment: 14 pages, 3 figures, added references and discussio

Guidelines Based on Need-Findings Study and Communication Types to Design Interactions for MOOCs

Experts affirm that interaction in learning settings represent a necessary process for knowledge acquisition and cognitive development. In this vein, is crucial to ensure effective interaction and communication through the user interface of MOOCs. This work proposes a set of design guidelines as starting point for developers to integrate a set of interactive elements into the MOOCs' user interface oriented to foster the four basic types for communication in distance education. The design guidelines were conformed through a need-findings process (observing people-interviewing), in which 35 participants provided their user experience perceptions after using MOOCs from edX; Coursera; and Udacity. Obtained results suggest a particular set of interactive communication elements that should be incorporated in every MOOC's user interface

Evaluation of the antimicrobial activity and cytotoxicity of different components of natural origin present in essential oils

Even though essential oils (EOs) have been used for therapeutic purposes, there is now a renewed interest in the antimicrobial properties of phytochemicals and EOs in particular. Their demonstrated low levels of induction of antimicrobial resistance make them interesting for bactericidal applications, though their complex composition makes it necessary to focus on the study of their main components to identify the most effective ones. Herein, the evaluation of the antimicrobial action of different molecules present in EOs against planktonic and biofilm-forming Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria was assessed. The bactericidal mechanisms of the different molecules, as well as their cytocompatibility, were also studied. Carvacrol, cinnamaldehyde, and thymol exhibit the highest in vitro antimicrobial activities against E. coli and S. aureus, with membrane disruption the bactericidal mechanism identified. The addition of those compounds (=0.5 mg/mL) hampers S. aureus biofilm formation and partially eliminates preformed biofilms. The subcytotoxic values of the tested EO molecules (0.015–0.090 mg/mL) are lower than the minimum inhibitory and bactericidal concentrations obtained for bacteria (0.2–0.5 mg/mL) but are higher than that obtained for chlorhexidine (0.004 mg/mL), indicating the reduced cytotoxicity of EOs. Therefore, carvacrol, cinnamaldehyde, and thymol are molecules contained in EOs that could be used against E. coli– and S. aureus–mediated infections without a potential induction of bactericidal resistance and with lower cell toxicity than the conventional widely used chlorhexidine

The chemical composition of the Orion star-forming region: II. Stars, gas, and dust: the abundance discrepancy conundrum

We re-examine the recombination/collisional emission line (RL/CEL) nebular abundance discrepancy problem in the light of recent high-quality abundance determinations in young stars in the Orion star-forming region. We re-evaluate the CEL and RL abundances of several elements in the Orion nebula and estimate the associated uncertainties, taking into account the uncertainties in the ionization correction factors for unseen ions. We estimate the amount of oxygen trapped in dust grains for several scenarios of dust formation. We compare the resulting gas+dust nebular abundances with the stellar abundances of a sample of 13 B-type stars from the Orion star-forming region (Ori\,OB1), analyzed in Papers I and III of this series. We find that the oxygen nebular abundance based on recombination lines agrees much better with the stellar abundances than the one derived from the collisionally excited lines. This result calls for further investigation. If the CEL/RL abundance discrepancy were caused by temperature fluctuations in the nebula, as argued by some authors, the same kind of discrepancy should be seen for the other elements, such as C, N and Ne, which is not what we find in the present study. Another problem is that with the RL abundances, the energy balance of the Orion nebula is not well understood. We make some suggestions concerning the next steps to undertake to solve this problem.Comment: 11 pages, 8 tables, 5 figures (To be published in A&A

Seed Size and Its Relationship with Crop Establishment, Productivity and Nutritive Value in Genotypes of Maize for Silage

For a high dry matter (DM) yield of forage maize an adequate population of plants is required, which is related to germination, vigour, and seed size (Ellis, 1992). The objective of the present study was to investigate seed size and its relationship to establishment, productive and nutritional potential of silage maize, which has not before been reported in the literature

Biodiversity of Bacteriocin-Producing Lactic Acid Bacteria from Mexican Regional Cheeses and their Contribution to Milk Fermentation

The aim of this work was to examine the biodiversity of bacteriocin-producing lactic acid bacteria from homemade cheeses produced in Veracruz (México) and assess their contribution as adjunct cultures in dairy products. Ninety-three presumptive bacteriocinogenic strains were detected by direct antagonism assays and 29 of them were active against Enterococcus faecalis NRRL-B537, Listeria innocua 062 AST, or Listeria monocytogenes ATCC19115 by the well diffusion test using cell-free supernatants, adjusted to pH 6.0 to exclude inhibition by organic acids. Positive isolates were identified by partial sequencing of the 16s rDNA as Pediococcus acidilactici (four isolates), Enterococcus faecium (17 isolates), Lactobacillus plantarum (six isolates) and Lactobacillus fermentum (two isolates). RAPD-PCR discriminated seven groups with a 50% similarity and revealed the presence of the same isolates. The coding genes for the synthesis of plantaricin EF, plantaricin JK, plantaricin N, plantaricin NC8 and the inducing peptide plantaricin A were detected by PCR in L. plantarum. Similarly, enterocin P and pediocin PA-1 genes were amplified from Enterococcus and Pediococcus genomic DNA, respectively. Overall, co-culturing of bacteriocin producing Lactobacillus and Pediococcus strains with the dairy starter Lactococcus lactis IPLA947 did not interfere with milk acidification. Lactose consumption, acidification rate and production of lactic acid were unchanged. Nonetheless, higher levels of acetic acid, ethanol and succinic acid were detected depending on the strain. Our results demonstrate the diversity of bacteriocinogenic species in homemade Mexican cheeses which may be used as adjunct cultures to enhancing safety of this well-appreciated cheese while providing a richer range of metabolites.This work was supported by Tecnológico Nacional de México (5486.14.15-P), the Mexican National Council for Science and Technology (Consejo Nacional de Ciencia y Tecnología -CONACYT) and partially by the Ministry of Economy and Competitiveness of Spain (MINECO) through grant BIO2013-46266-R. Funding by GRUPIN14-139 Plan de Ciencia, Tecnología e Innovación 2013-2017 (Principado de Asturias, Spain), supported by FEDER EU funds, is also acknowledged. S. Portilla-Vázquez held a CONACYT fellowship as well as an i-COOP mobility grant COOPA20015 funded by Consejo Superior de Investigaciones Científicas (CSIC), Spain.Peer reviewe

Análisis del potencial de innovación en apósitos para tratar heridas crónicas en la ciudad de Lima, Perú: Analysis of the potential of innovation in dressings to treat chronic wounds in the city of Lima, Peru.

Objective: To analyze the potential for innovation in dressings to treat chronic wounds in the City of Lima.  Methods: A qualitative study was carried out by means of interviews to medical experts and purchasing managers of medical supplies for the treatment of difficult-to-resolve wounds in 8 representative public health institutions with categories 1-4 within the only  54 of Lima, Peru - 2018. Results: It was determined that an average of 17 patients is treated in public health institutions on a monthly basis (60% from hospitalization and 40% from an outpatient office). It is equivalent to say that 11,016 patients present chronic wounds of difficult resolution each year, which will require specialized treatment and an average annual demand of 110,160 dressings in stock. The dressings with the highest demand correspond to the Hydrogels and Hydrocolloids, respectively; used because of the positive results they offer in wound healing, despite economic limitations. The market  price per unit ranges between 20 and 90 soles (S/.), representing an economic investment of 1500 soles on average per patient, in some cases causing complications or abandonment of treatment when resources are scarce. Conclusions: There is a high demand for patients with chronic wounds of difficult resolution in the public health institutions of Lima. It is important to promote and incentivize the investigation of new therapeutic alternatives and / or biomedical devices that favor its treatment.Objetivo: Analizar el potencial de innovación en apósitos para tratar heridas crónicas en la Ciudad de Lima. Métodos: Se realizó un estudio cualitativo mediante una encuesta y análisis de las entrevistas realizadas a expertos médicos y gestores de compras en insumos para el tratamiento de heridas de difícil resolución en 8 instituciones representativas de salud pública con categorías 1 – 4 dentro de las 54 existentes solo en Lima Metropolitana, Perú - 2018. Resultados: Se determinó que en las instituciones de salud pública son atendidos un promedio 17 pacientes mensualmente (60% provenientes de hospitalización y 40% de consultorio externo). Equivale decir que 11,016 pacientes presentan heridas crónicas de difícil resolución al año, los cuales requerirán de tratamiento especializado y una demanda anual promedio de 110,160 apósitos en stock. Los apósitos con mayor demanda corresponden a los Hidrogeles e Hidrocoloides, respectivamente que son utilizados por los resultados positivos que ofrecen en la curación de las heridas, aunque en ocasiones la limitante es el aspecto económico. En el mercado, el precio unitario oscila entre los 20 y 90 soles, esto representa una inversión económica de 1500 soles en promedio por paciente, produciendo en algunos casos complicaciones o abandono del tratamiento cuando los recursos son escasos. Conclusiones: La demanda de pacientes con heridas crónicas de difícil resolución en las instituciones de salud públicas de Lima metropolitana es alta. Es importante promover e incentivar la investigación de nuevas alternativas terapéuticas y/o dispositivos biomédicos que favorezcan su curación

The Iron abundance in Galactic Planetary Nebulae

We constrain the iron abundance in a sample of 33 low-ionization Galactic planetary nebulae (PNe) using [Fe III] lines and correcting for the contribution of higher ionization states with ionization correction factors (ICFs) that take into account uncertainties in the atomic data. We find very low iron abundances in all the objects, suggesting that more than 90% of their iron atoms are condensed onto dust grains. This number is based on the solar iron abundance and implies a lower limit on the dust-to-gas mass ratio, due solely to iron, of M_dust/M_gas>1.3x10^{-3} for our sample. The depletion factors of different PNe cover about two orders of magnitude, probably reflecting differences in the formation, growth, or destruction of their dust grains. However, we do not find any systematic difference between the gaseous iron abundances calculated for C-rich and O-rich PNe, suggesting similar iron depletion efficiencies in both environments. The iron abundances of our sample PNe are similar to those derived following the same procedure for a group of 10 Galactic H II regions. These high depletion factors argue for high depletion efficiencies of refractory elements onto dust grains both in molecular clouds and AGB stars, and low dust destruction efficiencies both in interstellar and circumstellar ionized gas.Comment: Accepted for publication in ApJ. 15 pages, 4 Postscript figures, corrected typos, Tables 2 and 3 correcte

Topology and excited state multiplicity as controlling factors in the carbazole-photosensitized CPD formation and repair

Photosensitized thyminethymine (ThyThy) formation and repair can be mediated by carbazole (Cbz). The former occurs from the Cbz triplet excited state via energy transfer, while the latter takes place from the singlet excited state via electron transfer. Here, fundamental insight is provided into the role of the topology and excited state multiplicity, as factors governing the balance between both processes. This has been achieved upon designing and synthesizing different isomers of trifunctional systems containing one Cbz and two Thy units covalently linked to the rigid skeleton of the natural deoxycholic acid. The results shown here prove that the Cbz photosensitized dimerization is not counterbalanced by repair when the latter, instead of operating through-space, has to proceed through-bond. © 2022 The Authors. Published by American Chemical Society