48 research outputs found
Propriedades mesomórficas de tensioactivos cataniónicos
Dissertação apresentada à Universidade de Coimbra para cumprimento dos requisitos necessário à obtenção de grau de Mestre em QuÃmica, na especialidade de QuÃmica FÃsicaNeste trabalho foram preparados vários compostos de uma nova classe de moléculas
anfifÃlicas, os tensioactivos cataniónicos, resultantes da formação de um par tensioactivo
aniónico-catiónico com remoção dos respectivos contra-iões. Após a sÃntese dos compostos,
foi efectuado um estudo do seu comportamento de fase térmico (termotrópico) e em meio
aquoso (liotrópico).
Os tensioactivos preparados diferem quanto ao número total de caudas (2 ou 3
caudas), quanto ao número de carbonos nas caudas (de 8 até 18) e quanto à natureza quÃmica
das cabeças hidrofÃlicas (amónio, sulfato e carboxilato). Dada a diversidade dos compostos
preparados, pretendeu-se esclarecer a influência da geometria e natureza quÃmica dos
compostos no comportamento de fase desta classe de tensioactivos.
A caracterização da fase sólida e a análise dos comportamentos termotrópicos e
liotrópicos dos compostos foram realizadas com base nas técnicas de: microanálise elemental,
absorção atómica, condutividade, microscopia óptica com luz polarizada, análise térmica
diferencial (DTA), calorimetria diferencial de varrimento (DSC), difracção de raios-X de
pequeno ângulo (SAXS), penetração de fase com varrimento e microscopia de transmissão
electrónica com criogenia (Cryo-TEM).
Com base nos resultados experimentais pretende-se fazer um estudo de descrição e
racionalização das propriedades dos tensioactivos cataniónicos, nomeadamente o estudo do
efeito da assimetria estrutural das moléculas na natureza e sequência de mesofases formadas
Mayer and virial series at low temperature
We analyze the Mayer pressure-activity and virial pressure-density series for
a classical system of particles in continuous configuration space at low
temperature. Particles interact via a finite range potential with an attractive
tail. We propose physical interpretations of the Mayer and virial series'
radius of convergence, valid independently of the question of phase transition:
the Mayer radius corresponds to a fast increase from very small to finite
density, and the virial radius corresponds to a cross-over from monatomic to
polyatomic gas. Our results have consequences for the search of a low density,
low temperature solid-gas phase transition, consistent with the Lee-Yang
theorem for lattice gases and with the continuum Widom-Rowlinson model.Comment: 36 pages, 1 figur
Baxterization, dynamical systems, and the symmetries of integrability
We resolve the `baxterization' problem with the help of the automorphism
group of the Yang-Baxter (resp. star-triangle, tetrahedron, \dots) equations.
This infinite group of symmetries is realized as a non-linear (birational)
Coxeter group acting on matrices, and exists as such, {\em beyond the narrow
context of strict integrability}. It yields among other things an unexpected
elliptic parametrization of the non-integrable sixteen-vertex model. It
provides us with a class of discrete dynamical systems, and we address some
related problems, such as characterizing the complexity of iterations.Comment: 25 pages, Latex file (epsf style). WARNING: Postscript figures are
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Molecular systematics of the marine Dothideomycetes
Phylogenetic analyses of four nuclear genes, namely the large and small
subunits of the nuclear ribosomal RNA, transcription elongation factor 1-alpha
and the second largest RNA polymerase II subunit, established that the
ecological group of marine bitunicate ascomycetes has representatives in the
orders Capnodiales, Hysteriales, Jahnulales,
Mytilinidiales, Patellariales and Pleosporales.
Most of the fungi sequenced were intertidal mangrove taxa and belong to
members of 12 families in the Pleosporales: Aigialaceae,
Didymellaceae, Leptosphaeriaceae, Lenthitheciaceae,
Lophiostomataceae, Massarinaceae, Montagnulaceae,
Morosphaeriaceae, Phaeosphaeriaceae, Pleosporaceae,
Testudinaceae and Trematosphaeriaceae. Two new families are
described: Aigialaceae and Morosphaeriaceae, and three new
genera proposed: Halomassarina, Morosphaeria and
Rimora. Few marine species are reported from the
Dothideomycetidae (e.g. Mycosphaerellaceae,
Capnodiales), a group poorly studied at the molecular level. New
marine lineages include the Testudinaceae and Manglicola
guatemalensis in the Jahnulales. Significantly, most marine
Dothideomycetes are intertidal tropical species with only a few from
temperate regions on salt marsh plants (Spartina species and
Juncus roemerianus), and rarely totally submerged (e.g. Halotthia
posidoniae and Pontoporeia biturbinata on the seagrasses
Posidonia oceanica and Cymodocea nodosum). Specific
attention is given to the adaptation of the Dothideomycetes to the
marine milieu, new lineages of marine fungi and their host specificity
ELF5 suppresses estrogen sensitivity and underpins the acquisition of antiestrogen resistance in luminal breast cancer
We have previously shown that during pregnancy the E-twenty-six (ETS) transcription factor ELF5 directs the differentiation of mammary progenitor cells toward the estrogen receptor (ER)-negative and milk producing cell lineage, raising the possibility that ELF5 may suppress the estrogen sensitivity of breast cancers. To test this we constructed inducible models of ELF5 expression in ER positive luminal breast cancer cells and interrogated them using transcript profiling and chromatin immunoprecipitation of DNA followed by DNA sequencing (ChIP-Seq). ELF5 suppressed ER and FOXA1 expression and broadly suppressed ER-driven patterns of gene expression including sets of genes distinguishing the luminal molecular subtype. Direct transcriptional targets of ELF5, which included FOXA1, EGFR, and MYC, accurately classified a large cohort of breast cancers into their intrinsic molecular subtypes, predicted ER status with high precision, and defined groups with differential prognosis. Knockdown of ELF5 in basal breast cancer cell lines suppressed basal patterns of gene expression and produced a shift in molecular subtype toward the claudin-low and normal-like groups. Luminal breast cancer cells that acquired resistance to the antiestrogen Tamoxifen showed greatly elevated levels of ELF5 and its transcriptional signature, and became dependent on ELF5 for proliferation, compared to the parental cells. Thus ELF5 provides a key transcriptional determinant of breast cancer molecular subtype by suppression of estrogen sensitivity in luminal breast cancer cells and promotion of basal characteristics in basal breast cancer cells, an action that may be utilised to acquire antiestrogen resistance
Antibodies against endogenous retroviruses promote lung cancer immunotherapy
B cells are frequently found in the margins of solid tumours as organized follicles in ectopic lymphoid organs called tertiary lymphoid structures (TLS)1,2. Although TLS have been found to correlate with improved patient survival and response to immune checkpoint blockade (ICB), the underlying mechanisms of this association remain elusive1,2. Here we investigate lung-resident B cell responses in patients from the TRACERx 421 (Tracking Non-Small-Cell Lung Cancer Evolution Through Therapy) and other lung cancer cohorts, and in a recently established immunogenic mouse model for lung adenocarcinoma3. We find that both human and mouse lung adenocarcinomas elicit local germinal centre responses and tumour-binding antibodies, and further identify endogenous retrovirus (ERV) envelope glycoproteins as a dominant anti-tumour antibody target. ERV-targeting B cell responses are amplified by ICB in both humans and mice, and by targeted inhibition of KRAS(G12C) in the mouse model. ERV-reactive antibodies exert anti-tumour activity that extends survival in the mouse model, and ERV expression predicts the outcome of ICB in human lung adenocarcinoma. Finally, we find that effective immunotherapy in the mouse model requires CXCL13-dependent TLS formation. Conversely, therapeutic CXCL13 treatment potentiates anti-tumour immunity and synergizes with ICB. Our findings provide a possible mechanistic basis for the association of TLS with immunotherapy response
Detecting hierarchical organization in complex networks by nearest neighbor correlation
The hierarchical organization in complex networks is investigated from the point of view of nearest neighbor correlation. By plotting the mean total degree of the nearest neighbors versus degree of the given node, more than one linear branches will be observed for hierarchical network. An example of hierarchical network with 1-hub-4-peripheral is constructed for illustrative purpose and real data on the World Wide Web and AS Internet are analyzed for comparison. Two branches are clearly observed for the total degree of neighbors of the World Wide Web, indicative of the existence of hierarchical organization and the result is consistent with the analysis based on local clustering coefficient. Only one branch is observed for the AS Internet data set, but the result is not conclusive as the size of the data set is not sufficiently large. The total degree of nearest neighbor provides a good complementary test to the existing method based on the local clustering coefficients. © 2008 Springer-Verlag Berlin Heidelberg
Waarom een wetenschappelijk onderzoek in het kader van het Interuniversitair Centrum voor Huisartsenopleiding (ICHO)?
Objective: The purpose of this study was to examine the hypothesis that angiotensin II (Ang II) induced endothelial cyclooxygenase-2 (COX-2) expression, which in turn mediated the generation of proinflammatory cytokines. Methods and results: Western blot analysis on primary rat endothelial cells showed Ang II induced COX-2 expression, which was abolished by cotreatment of p38 mitogen-activated protein kinase (SB 202190) and extracellular signal-regulated kinase 1/2 (PD 98059) inhibitors. Protein kinase C{delta} (PKC{delta}) inhibitor (rottlerin) prevented extracellular signal-regulated kinase 1/2 phosphorylation and COX-2 expression. The pivotal role of PKC{delta} was further supported by a similar stimulatory effect of the PKC activator on COX-2 expression, signified by Ang II-stimulated translocation of PKC{delta} to the plasma membrane, and confirmed by PKC{delta} phosphorylation at Tyr311. Small interfering RNA targeting PKC{delta} diminished COX-2 expression, which was further abrogated by SB 202190. Human mesenteric arteries incubated with Ang II showed increased levels of endothelial COX-2 and monocyte chemoattractant protein-1; the former was inhibited by SB 202190 plus rottlerin, whereas the latter was prevented by COX-2 inhibitor. Conclusions: The present study pinpoints a novel role of PKC{delta} in Ang II-induced endothelial COX-2 upregulation and identifies a COX-2-dependent proatherosclerotic cytokine monocyte chemoattractant protein-1. The findings raise the possibility of curtailing endothelial COX-2 expression as a means of limiting or preventing vascular inflammation