1,284 research outputs found
The Polarization and the Recombination Mechanism
We use the recombination and the Thomas Precession Model to obtain a
prediction for the polarization in the
reaction. We study the effect of the recombination function on the
polarization.Comment: 4 pages, LaTex, 1 figures included, aipproc.sty included. Talk
presented at Simposio Latino Americano de Fisica de Altas Energias, Merida,
Mexico, November 199
Anticancer Activities of Meroterpenoids Isolated from the Brown Alga Cystoseira usneoides against the Human Colon Cancer Cells HT-29
Colorectal cancer (CRC) is one of the most common types of cancers and a leading cause of cancer death worldwide. The current treatment for CRC mainly involves surgery, radiotherapy, and chemotherapy. However, due to the side effects and the emergence of drug resistance, the search for new anticancer agents, pharmacologically safe and effective, is needed. In the present study, we have investigated the anticancer effects of eight algal meroterpenoids (AMTs, 1-8) isolated from the brown seaweed Cystoseira usneoides and their underlying mechanisms of action using HT-29, a highly metastatic human colon cancer cell line. All the tested meroterpenoids inhibited the growth of HT-29 malignant cells and were less toxic towards non-cancer colon cells, with the AMTs 1 and 5 exhibiting selectivity indexes of 5.26 and 5.23, respectively. Treatment of HT-29 cells with the AMTs 1, 2, 3, 4, 5, and 7 induced cell cycle arrest in G2/M phase and, in some instances, apoptosis (compounds 2, 3, and 5). Compounds 1-8 also exhibited significant inhibitory effects on the migration and/or invasion of colon cancer cells. Mechanistic analysis demonstrated that the AMTs 1, 2, 5, 6, 7, and 8 reduced phosphorylation levels of extracellular signal-regulated kinase (ERK) and the AMTs 2, 3, 4, 5, 7, and 8 decreased phosphorylation of c-JUN N-terminal kinase (JNK). Moreover, the AMTs 1, 2, 3, 4, 7, and 8 inhibited phosphorylation levels of protein kinase B (AKT) in colon carcinoma cells. These results provide new insights into the mechanisms and functions of the meroterpenoids of C. usneoides, which exhibit an anticancer effect on HT-29 colon cancer cells by inducing cell cycle arrest and apoptosis via the downregulation of ERK/JNK/AKT signaling pathways
Decays Z' -> \gamma\gamma\gamma{} and Z -> \gamma\gamma\gamma{} in the minimal 331 model
The possibility of a significant effect of exotic particles on the
Z'->\gamma\gamma\gamma{} and Z->\gamma\gamma\gamma{} decays is investigated in
the context of the minimal 331 model. This model, which is based in the
SU_C(3)xSU_L(3)xU_X(1) gauge group, predicts the existence of many exotic
charged particles that can significantly enhance the decay widths. It is found
that the standard model prediction for the Z->\gamma\gamma\gamma{} decay
remains essentially unchanged, as the new physics effects quickly decouples. On
the other hand, it is found that the contributions of the new exotic quarks and
gauge bosons predicted by this model lead to a branching fraction for the
Z'->\gamma\gamma\gamma{} decay of about 10^(-6), which is about three orders of
magnitude larger than that of the Z->\gamma\gamma\gamma{} decay.Comment: 20 pages and 20 figure
Deciphering the Symbiotic Significance of Quorum Sensing Systems of Sinorhizobium fredii HH103
Quorum sensing (QS) is a bacterial cell-to-cell signaling mechanism that collectively regulates and synchronizes behaviors by means of small diffusible chemical molecules. In rhizobia, QS systems usually relies on the synthesis and detection of N-acyl-homoserine lactones (AHLs). In the model bacterium Sinorhizobium meliloti functions regulated by the QS systems TraI-TraR and SinI-SinR(-ExpR) include plasmid transfer, production of surface polysaccharides, motility, growth rate and nodulation. These systems are also present in other bacteria of the Sinorhizobium genus, with variations at the species and strain level. In Sinorhizobium fredii NGR234 phenotypes regulated by QS are plasmid transfer, growth rate, sedimentation, motility, biofilm formation, EPS production and copy number of the symbiotic plasmid (pSym). The analysis of the S. fredii HH103 genomes reveal also the presence of both QS systems. In this manuscript we characterized the QS systems of S. fredii HH103, determining that both TraI and SinI AHL-synthases proteins are responsible of the production of short- and long-chain AHLs, respectively, at very low and not physiological concentrations. Interestingly, the main HH103 luxR-type genes, expR and traR, are split into two ORFs, suggesting that in S. fredii HH103 the corresponding carboxy-terminal proteins, which contain the DNA-binding motives, may control target genes in an AHL-independent manner. The presence of a split traR gene is common in other S. fredii strains.Spanish Ministerio de Economía y Competitividad (MINECO) BIO2016-78409-
Regional initiative for the evaluation of Queen Conch (Strombus gigas) exploitation under an historical perspective
Transforming the Field of Family Engagement: Co-designing Research Practices Measures for Ed Justice and Community Wellbeing
Our project — the Family Leadership Design Collaborative (FLDC) — is a national network of scholars, practitioners, and family and community leaders who work to center racial equity in family engagement. We do this by reimagining how families and communities can create more equitable schools and educational systems. We engage in research to develop "next" (beyond current "best")1 practices, measures, andtools to foster equitable toward community wellbeing and educational justice.The FLDC is a participatory design research project (PDR). PDR emerges from design- based research and is an iterative research process that attends to power, relationships, and histories of oppression/resilience through partnering with young people, families, and communities. PDR advances theories of human learning alongside new sets of relations, practices, and tools towardssocial justice and change-making.We do this through a practice of PDR called solidarity-driven co-design. Co- design is a process of partnering and decision- makingthat engages diverse peoples to collectively identify problems of practice and innovate solutions. raceCo- design has the potential to foster change- making that is responsive, adaptive, and equity- oriented.
Study of the lepton flavor-violating decay
The lepton flavor violating decay is studied in the
context of several extended models that predict the existence of the new gauge
boson named . A calculation of the strength of the lepton flavor
violating coupling is presented by using the most general
renormalizable Lagrangian that includes lepton flavor violation. We used the
experimental value of the muon magnetic dipole moment to bound this coupling,
from which the parameter
is constrained and it is found that
for a
boson mass of 2 TeV. Alongside, we employed the experimental
restrictions over the and processes
in the context of several models that predict the existence of the
gauge boson to bound the mentioned coupling. The most restrictive bounds come
from the calculation of the three-body decay. For this case, it was found that
the most restrictive result is provided by a vector-like coupling, denoted as
, for the case, finding around for a
boson mass of 2 TeV. We used this information to estimate the
branching ratio for the decay. According to the analyzed
models the least optimistic result is provided by the Sequential model,
which is of the order of for a boson mass around 2 TeV.Comment: Revised versio
STM-driven transition from rippled to buckled graphene in a spin-membrane model
We consider a simple spin-membrane model for rippling in graphene. The model exhibits transitions from a flat but rippled membrane to a buckled one. At high temperature the transition is second order, but it is first order at low temperature for appropriate strength of the spin-spin coupling. Driving the system across the first-order phase transition in nonequilibrium conditions that mimic interaction of the graphene membrane with a scanning tunneling microscopy (STM) tip explains recent experiments. In particular, we observe a reversible behavior for small values of the STM current and an irreversible transition from a flat rippled membrane to a rigid buckled membrane when the current surpasses a critical value. This work makes it possible to test the mechanical properties of graphene under different temperature and electrostatic conditions.Ministerio de Economía y Competitividad MTM2014-56948- C2-2-
Refractive Properties of Binary Mixtures Formed by an Isomer of Chlorobutane and Butyl Ethyl Ether
Refractive indices of the binary mixtures containing an isomer of chlorobutane (1-chlorobutane, 2-chlorobutane, 2-methyl-1-chloropropane, or 2-methyl-2-chloropropane) and butyl ethyl ether have been measured at seven temperatures from T = 283.15 to 313.15 K From these data refractive index deviations were calculated and correlated with a Redlich-Kister polynomial expansion. The refractive index deviations were found positive. Finally, from these refractive indices both densities and surface tensions of the studied systems were predicted and compared with previously reported values
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