5,219 research outputs found

    The Balloon-Borne Large Aperture Submillimeter Telescope (BLAST) 2005: A 10 deg^2 Survey of Star Formation in Cygnus X

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    We present Cygnus X in a new multi-wavelength perspective based on an unbiased BLAST survey at 250, 350, and 500 μm, combined with rich data sets for this well-studied region. Our primary goal is to investigate the early stages of high-mass star formation. We have detected 184 compact sources in various stages of evolution across all three BLAST bands. From their well-constrained spectral energy distributions, we obtain the physical properties mass, surface density, bolometric luminosity, and dust temperature. Some of the bright sources reaching 40 K contain well-known compact H_(II) regions. We relate these to other sources at earlier stages of evolution via the energetics as deduced from their position in the luminosity-mass (L-M) diagram. The BLAST spectral coverage, near the peak of the spectral energy distribution of the dust, reveals fainter sources too cool (~10 K) to be seen by earlier shorter-wavelength surveys like IRAS. We detect thermal emission from infrared dark clouds and investigate the phenomenon of cold "starless cores" more generally. Spitzer images of these cold sources often show stellar nurseries, but these potential sites for massive star formation are "starless" in the sense that to date there is no massive protostar in a vigorous accretion phase. We discuss evolution in the context of the L-M diagram. Theory raises some interesting possibilities: some cold massive compact sources might never form a cluster containing massive stars, and clusters with massive stars might not have an identifiable compact cold massive precursor

    Synthesis of Combretastatin A-4 and 3 0 -Aminocombretastatin A-4 derivatives with Aminoacid Containing Pendants and Study of their Interaction with Tubulin and as Downregulators of the VEGF, hTERT and c-Myc Gene Expression

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    Natural product combretastatin A-4 (CA-4) and its nitrogenated analogue 3 0 -aminocombretastatin A-4 (AmCA-4) have shown promising antitumor activities. In this study, a range of CA-4 and AmCA-4 derivatives containing amino acid pendants have been synthesized in order to compare their biological actions with those of their parent compounds. Thus, inhibition of cell proliferation on tumor cell lines HT-29, MCF-7 and A-549, as well as on the nontumor cell line HEK-273; in vitro tubulin polymerization; mitotic cell arrest; action on the microtubule cell network and inhibition of VEGF, hTERT, and c-Myc genes have been evaluated. Some AmCA-4 derivatives bearing L-amino acids exhibited inhibition of cell proliferation at low nanomolar levels exceeding the values shown by AmCA-4. Furthermore, while CA-4 and AmCA-4 derivatives do not show significant effects on the in vitro tubulin polymerization and cell cycle arrest, some selected CA-4 and AmCA-4 derivatives are able to cause total depolymerization of the microtubule network on A-549 cells. The best results were obtained in the inhibition of gene expression, particularly on the VEGF gene, in which some AmCA-4 derivatives greatly exceeded the inhibition values achieved by the parent compound

    Fractional vs. ordinary control systems: What does the fractional derivative provide?

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    [EN] The concept of a fractional derivative is not at all intuitive, starting with not having a clear geometrical interpretation. Many different definitions have appeared, to the point that the need for order has arisen in the field. The diversity of potential applications is even more overwhelming. When modeling a problem, one must think carefully about what the introduction of fractional derivatives in the model can provide that was not already adequately covered by classical models with integer derivatives. In this work, we present some examples from control theory where we insist on the importance of the non-local character of fractional operators and their suitability for modeling non-local phenomena either in space (action at a distance) or time (memory effects). In contrast, when we encounter completely different nonlinear phenomena, the introduction of fractional derivatives does not provide better results or further insight. Of course, both phenomena can coexist and interact, as in the case of hysteresis, and then we would be dealing with fractional nonlinear models.Conejero, JA.; Franceschi, J.; Picó-Marco, E. (2022). Fractional vs. ordinary control systems: What does the fractional derivative provide?. Mathematics. 10(15):1-18. https://doi.org/10.3390/math10152719118101

    Efecto del sorgo de Alepo sobre la producción de soja, de maíz y de las malezas presentes en estos cultivos

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    p.123-129En dos lotes con diferentes historias agrícolas sembrados uno con maíz y otro con soja, se tomaron muestras de biomasa aérea cuando finalizó el ciclo de los cultivos. Se estudiaron las relaciones entre la biomasa aérea cosechada del sorgo de Alepo con la de las especies cultivadas y la de las otras especies de malezas presentes en las parcelas' muéstrales. Para ello se ajustaron los datos a modelos de regresión lineales y exponenciales. Sólo en uno de los lotes sembrados con maíz, cuya historia agrícola fue una larga monocultura de esa especie, el aumento de la biomasa de sorgo de Alepo se relacionó con disminuciones marcadas en la cantidad de materia seca del maíz y de las otras especies de maleza. La partición de la materia seca del cultivo entre el grano y la parte vegetativa se modificó en relación con la biomasa de sorgo de Alepo. En el lote sembrado con soja se observó una disminución de la materia seca de esta especie en relación con el aumento de la biomasa aérea del sorgo de Alepo, en cambio, la biomasa aérea de las otras malezas se mostró indiferente. Los modelos dé regresión exponenciales negativos fueron los más adecuados para describir las relaciones analizadas

    Detection of "bath salts" and other novel psychoactive substances in hair samples of ecstasy/MDMA/"Molly" users

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    BACKGROUND: Ecstasy (MDMA) in the US is commonly adulterated with other drugs, but research has not focused on purity of ecstasy since the phenomenon of “Molly” (ecstasy marketed as pure MDMA) arose in the US. METHODS: We piloted a rapid electronic survey in 2015 to assess use of novel psychoactive substances (NPS) and other drugs among 679 nightclub/festival-attending young adults (age 18–25) in New York City. A quarter (26.1%) of the sample provided a hair sample to be analyzed for the presence of select synthetic cathinones (“bath salts”) and some other NPS. Samples were analyzed using fully validated UHPLC-MS/MS methods. To examine consistency of self-report, analyses focused on the 48 participants with an analyzable hair sample who reported lifetime ecstasy/MDMA/Molly use. RESULTS: Half (50.0%) of the hair samples contained MDMA, 47.9% contained butylone, and 10.4% contained methylone. Of those who reported no lifetime use of “bath salts”, stimulant NPS, or unknown pills or powders, about four out of ten (41.2%) tested positive for butylone, methylone, alpha-PVP, 5/6-APB, or 4-FA. Racial minorities were more likely to test positive for butylone or test positive for NPS after reporting no lifetime use. Frequent nightclub/festival attendance was the strongest predictor of testing positive for MDMA, butylone, or methylone. DISCUSSION: Results suggest that many ecstasy-using nightclub/festival attendees may be unintentionally using “bath salts” or other NPS. Prevention and harm reduction education is needed for this population and “drug checking” (e.g., pill testing) may be beneficial for those rejecting abstinence

    Synthesis and evaluation of biphenyl derivatives as potential downregulators of VEGF protein secretion and telomerase-related gene expressions

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    A group of 47 biphenyl functionalized compounds, prepared by means of Suzuki couplings, has been investigated for their cytotoxicity on two tumoral cell lines (HT-29 and MCF-7) and one non tumoral cell line (HEK-293). 29 selected compounds have been investigated for their ability to inhibit the production of the vascular endothelial growth factor (VEGF). Subsequently, the capacity of the compounds to downregulate the expression of the VEGF, h-TERT and c-Myc genes, the two latter involved in the control of the activation of telomerase, has also been determined.Financial support has been granted to M.C. by the Ministerio de Economía y Competitividad of Spain (project CTQ2014- 52949-P), by the Consellería d´Empresa, Universitat i Ciencia de la Generalitat Valenciana (projects PROMETEO/2013/027 and ACOMP/2014/ 274) and by the University Jaume I (project PI- 1B2011-37). M. S.-P. thanks the University Jaume I for a predoctoral fellowship

    Aldol Reactions between L-Erythrulose Derivatives and Chiral α-Amino and α -Fluoro Aldehydes: Competition between Felkin–Anh and Cornforth Transition States

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    Both matched and mismatched diastereoselection have been observed in aldol reactions of a boron enolate of a protected l-erythrulose derivative with several chiral α-fluoro and α-Amino aldehydes. Strict adherence to the Felkin–Anh model for the respective transition structures does not account satisfactorily for all the observed results, as previously observed in the case of α-oxygenatedaldehydes. In some cases, only the Cornforth model provides a good explanation. The factors that influence this dichotomy are discussed and a general mechanistic model is proposed for aldol reactions with a-heteroatom-substituted aldehydes. Additional support for the model was obtained from density functional calculation

    Inhibitory effect of cytotoxic stilbenes related to resveratrol on the expression of the VEGF, hTERT and c-Myc genes

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    A group of thirty-nine stilbene derivatives, prepared by means of Heck coupling reactions, has been investigated for their cytotoxicity, as well as for their ability to inhibit the production of the vascular endothelial growth factor (VEGF) and the activation of telomerase. The ability of these compounds to inhibit proliferation of two tumoral cell lines (HT-29 and MCF-7) and one non tumoral cell line (HEK-293) was first determined. Subsequently, we determined the capacity of the compounds to inhibit the secretion of VEGF in the aforementioned cell lines and to downregulate the expression of the VEGF, hTERT and c-Myc genes, the two latter involved in the control of the activation of telomerase. One of the synthetic stilbenes, (E)-4-(4-methoxystyryl)aniline, showed strong cytotoxicity and proved able to cause a marked decrease both in the secretion of VEGF and in the expression of the hTERT and c-Myc genes, in all cases at concentrations in the low nanomolar range

    Convergent, stereoselective syntheses of the glycosidase inhibitors broussonetines D and M

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    The first syntheses of the polyhydroxylated alkaloids (iminosugars) broussonetines D and M glycosidase inhibitors of the pyrrolidine class, have been performed in a convergent, stereocontrolled way from D-serine as the chiral starting material. A cross metathesis step was one key feature of the synthesis. The versatility of the synthetic concept chosen permits the access to many members of this compound family, both natural ones and analogues thereo
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