266 research outputs found
Fluctuations in a superconducting quantum critical point of multi-band metals
In multi-band metals quasi-particles arising from different atomic orbitals
coexist at a common Fermi surface. Superconductivity in these materials may
appear due to interactions within a band (intra-band) or among the distinct
metallic bands (inter-band). Here we consider the suppression of
superconductivity in the intra-band case due to hybridization. The fluctuations
at the superconducting quantum critical point (SQCP) are obtained calculating
the response of the system to a fictitious space and time dependent field,
which couples to the superconducting order parameter. The appearance of
superconductivity is related to the divergence of a generalized susceptibility.
For a single band superconductor this coincides with the \textit{Thouless
criterion}. For fixed chemical potential and large hybridization, the
superconducting state has many features in common with breached pair
superconductivity with unpaired electrons at the Fermi surface. The T=0 phase
transition from the superconductor to the normal state is in the universality
class of the density-driven Bose-Einstein condensation. For fixed number of
particles and in the strong coupling limit, the system still has an instability
to the normal sate with increasing hybridization.Comment: 10 pages, 8 figure
Quantum criticality in inter-band superconductors
In fermionic systems with different types of quasi-particles, attractive
interactions can give rise to exotic superconducting states, as pair density
wave (PDW) superconductivity and breached pairing. In the last years the search
for these new types of ground states in cold atom and in metallic systems has
been intense. In the case of metals the different quasi-particles may be the up
and down spin bands in an external magnetic field or bands arising from
distinct atomic orbitals that coexist at a common Fermi surface. These systems
present a complex phase diagram as a function of the difference between the
Fermi wave-vectors of the different bands. This can be controlled by external
means, varying the density in the two-component cold atom system or, in a
metal, by applying an external magnetic field or pressure. Here we study the
zero temperature instability of the normal system as the Fermi wave-vectors
mismatch of the quasi-particles (bands) is reduced and find a second order
quantum phase transition to a PDW superconducting state. From the nature of the
quantum critical fluctuations close to the superconducting quantum critical
point (SQCP), we obtain its dynamic critical exponent. It turns out to be
and this allows to fully characterize the SQCP for dimensions .Comment: 5 pages, 1 figur
Association of single nucleotide polymorphisms in Pre-miR-27a, Pre-miR-196a2, Pre-miR-423, miR-608 and Pre-miR-618 with breast cancer susceptibility in a South American population
Indexación: Web of ScienceBackground
MicroRNAs (miRNAs) are a novel class of endogenous, non-coding, single-stranded RNAs capable of regulating gene expression by suppressing translation or degrading mRNAs. Single nucleotide polymorphisms (SNP) can alter miRNA expression, resulting in diverse functional consequences. Previous studies have examined the association of miRNA SNPs with breast cancer (BC) susceptibility. The contribution of miRNA gene variants to BC susceptibility in South American women had been unexplored. Our study evaluated the association of the SNPs rs895819 in pre-miR27a, rs11614913 in pre-miR-196a2, rs6505162 in pre-miR-423, rs4919510 in miR-608, and rs2682818 in pre-mir-618 with familial BC and early-onset non-familial BC in non-carriers of BRCA1/2 mutations from a South American population.
Results
We evaluated the association of five SNPs with BC risk in 440 cases and 807 controls. Our data do not support an association of rs11614913:C > T and rs4919510:C > G with BC risk. The rs6505162:C > A was significantly associated with increased risk of familial BC in persons with a strong family history of BC (OR = 1.7 [95 % CI 1.0–2.0] p = 0.05). The rs2682818:C > A genotype C/A is associated with an increased BC risk in non-familial early-onset BC. For the rs895819:A > G polymorphism, the genotype G/G is significantly associated with reduced BC risk in families with a moderate history of BC (OR = 0.3 [95 % CI 0.1–0.8] p = 0.01).
Conclusions
The contribution of variant miRNA genes to BC in South American women had been unexplored. Our findings support the following conclusions: a) rs6505162:C > A in pre-miR-423 increases risk of familial BC in families with a strong history of BC; b) the C/A genotype at rs2682818:C > A (pre-miR-618) increases BC risk in non-familial early-onset BC; and c) the G/G genotype at rs895819:A > G (miR-27a) reduces BC risk in families with a moderate history of BC.http://bmcgenet.biomedcentral.com/articles/10.1186/s12863-016-0415-
Contemporary characteristics and outcomes in chagasic heart failure compared with other nonischemic and ischemic cardiomyopathy
Background: Chagas’ disease is an important cause of cardiomyopathy in Latin America. We aimed to compare clinical characteristics and outcomes in patients with heart failure (HF) with reduced ejection fraction caused by Chagas’ disease, with other etiologies, in the era of modern HF therapies.
Methods and Results: This study included 2552 Latin American patients randomized in the PARADIGM-HF (Prospective Comparison of ARNI With ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure) and ATMOSPHERE (Aliskiren Trial to Minimize Outcomes in Patients With Heart Failure) trials. The investigator-reported etiology was categorized as Chagasic, other nonischemic, or ischemic cardiomyopathy. The outcomes of interest included the composite of cardiovascular death or HF hospitalization and its components and death from any cause. Unadjusted and adjusted Cox proportional hazards models were performed to compare outcomes by pathogenesis. There were 195 patients with Chagasic HF with reduced ejection fraction, 1300 with other nonischemic cardiomyopathy, and 1057 with ischemic cardiomyopathy. Compared with other etiologies, Chagasic patients were more often female, younger, and had lower prevalence of hypertension, diabetes mellitus, and renal impairment (but had higher prevalence of stroke and pacemaker implantation) and had worse health-related quality of life. The rates of the composite outcome were 17.2, 12.5, and 11.4 per 100 person-years for Chagasic, other nonischemic, and ischemic patients, respectively—adjusted hazard ratio for Chagasic versus other nonischemic: 1.49 (95% confidence interval, 1.15–1.94; P=0.003) and Chagasic versus ischemic: 1.55 (1.18–2.04; P=0.002). The rates of all-cause mortality were also higher.
Conclusions: Despite younger age, less comorbidity, and comprehensive use of conventional HF therapies, patients with Chagasic HF with reduced ejection fraction continue to have worse quality of life and higher hospitalization and mortality rates compared with other etiologies.
Clinical Trial Registration: PARADIGM-HF: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01035255; ATMOSPHERE: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00853658
Fishers and groupers (epinephelus marginatus and E. morio) in the coast of Brazil : integrating information for conservation
Groupers are a vulnerable but economically important group of fish, especially for small-scale fisheries. We investigated catches and local ecological knowledge (LEK) of diet, habitat, and past fishing experiences. Landings, prices, interviews, and restaurants demand for two species, Epinephelus marginatus (dusky grouper) and Epinephelus morio (red grouper), were registered. We visited 74 markets and 79 sites on the coast of Brazil in 2017–2018, and we interviewed 71 fishers: Bahia (NE), Rio de Janeiro and São Paulo (SE), and Santa Catarina (S). The landings sampled of dusky grouper (2016–2017) in Rio de Janeiro were: n = 222, size 38–109 cm, weight 1–24 kg, average 3.84 kg; in São Paulo, São Sebastião were: n = 47, size 39–106 cm, weight 2–8 kg, average of 2.77 kg; and at Santos: n = 80, 26–120 cm, weight 0.36–15 kg, average 2.72 kg. Red grouper was observed in markets in the northeastern Brazil. We did not observe Epinephelus marginatus from Bahia northward; a maximum size of 200 cm was reported south of the Bahia, besides Rio de Janeiro and São Paulo coasts, 20 years ago (or longer) by 12 fishers. Local knowledge of fishers was important for grouper data of habitat and diet; the reproduction period was identified by fishers as September to March. Groupers can be considered as a cultural and ecological keystone species. We suggest protective measures: 1) fishing zoning, 2) islands (MPAs) with the surveillance of fishers, 3) late Spring and early Summer as key periods for management (grouper reproduction), 4) studies on grouper larvae, 5) mapping of fishing spots, 6) studies on local knowledge. Collaboration with small-scale fishers and local knowledge could contribute to low-conflict management measures. In that regard, integrative models of management from Latin America, by using local knowledge and citizen science, could produce successful grouper management for Brazilian data-poor fisheries, a contrasting reality to the Mediterranean areas. Finally, the distribution of E. marginatus in Brazil leave us with questions: a) Have dusky groupers disappeared from Bahia because of a decline in the population? b) Was it uncommon in Northeast Brazil? c) Did changes in water temperatures forced a movement southward?151CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP307762/2013–0; 301592/2017–914/16939–7In addition to FAPESP and CNPq, we acknowledge Eduardo Camargo and
Marco Antonio A. G. Araújo for helping with fieldwork in NE Brazil and Mara
Magenta (UNISANTA) for helping us with infrastructure for fish larvae
observation in the laboratory. We are grateful to the fisher-buyers Antonio,
Elenilson and Valdecir. We are also very grateful to Rodrigo Caires, who supported us with taxonomic matter
Five-year follow-up of angiographic disease progression after medicine, angioplasty, or surgery
<p>Abstract</p> <p>Background</p> <p>Progression of atherosclerosis in coronary artery disease is observed through consecutive angiograms. Prognosis of this progression in patients randomized to different treatments has not been established. This study compared progression of coronary artery disease in native coronary arteries in patients undergoing surgery, angioplasty, or medical treatment.</p> <p>Methods</p> <p>Patients (611) with stable multivessel coronary artery disease and preserved ventricular function were randomly assigned to CABG, PCI, or medical treatment alone (MT). After 5-year follow-up, 392 patients (64%) underwent new angiography. Progression was considered a new stenosis of ≥ 50% in an arterial segment previously considered normal or an increased grade of previous stenosis > 20% in nontreated vessels.</p> <p>Results</p> <p>Of the 392 patients, 136 underwent CABG, 146 PCI, and 110 MT. Baseline characteristics were similar among treatment groups, except for more smokers and statin users in the MT group, more hypertensives and lower LDL-cholesterol levels in the CABG group, and more angina in the PCI group at study entry. Analysis showed greater progression in at least one native vessel in PCI patients (84%) compared with CABG (57%) and MT (74%) patients (p < 0.001). LAD coronary territory had higher progression compared with LCX and RCA (P < 0.001). PCI treatment, hypertension, male sex, and previous MI were independent risk factors for progression. No statistical difference existed between coronary events and the development of progression.</p> <p>Conclusion</p> <p>The angioplasty treatment conferred greater progression in native coronary arteries, especially in the left anterior descending territories and treated vessels. The progression was independently associated with hypertension, male sex, and previous myocardial infarction.</p
Formation of bone-like apatite layer on chitosan fiber mesh scaffolds by a biomimetic spraying process
Bone-like apatite coating of polymeric substrates
by means of biomimetic process is a possible
way to enhance the bone bonding ability of the
materials. The created apatite layer is believed to have
an ability to provide a favorable environment for
osteoblasts or osteoprogenitor cells. The purpose of
this study is to obtain bone-like apatite layer onto
chitosan fiber mesh tissue engineering scaffolds, by
means of using a simple biomimetic coating process
and to determine the influence of this coating on
osteoblastic cell responses. Chitosan fiber mesh scaffolds
produced by a previously described wet spinning
methodology were initially wet with a Bioglass"–water
suspension by means of a spraying methodology and
then immersed in a simulated body fluid (SBF)
mimicking physiological conditions for one week. The
formation of apatite layer was observed morphologically
by scanning electron microscopy (SEM). As a
result of the use of the novel spraying methodology, a
fine coating could also be observed penetrating into the
pores, that is clearly within the bulk of the scaffolds.
Fourier Transform Infrared spectroscopy (FTIRATR),
Electron Dispersive Spectroscopy (EDS) and
X-ray diffraction (XRD) analysis also confirmed the
presence of apatite-like layer. A human osteoblast-like
cell line (SaOs-2) was used for the direct cell contact assays. After 2 weeks of culture, samples were observed
under the SEM. When compared to the control
samples (unmodified chitosan fiber mesh scaffolds) the
cell population was found to be higher in the Ca–P
biomimetic coated scaffolds, which indicates that the
levels of cell proliferation on this kind of scaffolds
could be enhanced. Furthermore, it was also observed
that the cells seeded in the Ca–P coated scaffolds have
a more spread and flat morphology, which reveals an
improvement on the cell adhesion patterns, phenomena
that are always important in processes such as
osteoconduction
Biological response to pre-mineralized starch based scaffolds for bone tissue engineering
It is known that calcium-phosphate (Ca-P) coatings are able not only to improve the bone
bonding behaviour of polymeric materials, but at the same time play a positive role on
enhancing cell adhesion and inducing the differentiation of osteoprogenitor cells. Recently
an innovative biomimetic methodology, in which a sodium silicate gel was used as a
nucleative agent, was proposed as an alternative to the currently available biomimetic
coating methodologies. This methodology is especially adequate for coating biodegradable
porous scaffolds. In the present work we evaluated the influence of the referred to
treatment on the mechanical properties of 50/50 (wt%) blend of corn starch/ethylene-vinyl
alcohol (SEVA-C) based scaffolds. These Ca-P coated scaffolds presented a compressive
modulus of 224.6 ± 20.6 and a compressive strength of 24.2 ± 2.20. Cytotoxicity evaluation
was performed according ISO/EN 10993 part 5 guidelines and showed that the biomimetic
treatment did not have any deleterious effect on L929 cells and did not inhibit cell growth.
Direct contact assays were done by using a cell line of human osteoblast like cells (SaOS-2).
3 × 105 cells were seeded per scaffold and allowed to grow for two weeks at 37 ◦C in a
humidified atmosphere containing 5% CO2. Total protein quantification and scanning
electron microscopy (SEM) observation showed that cells were able to grow in the
pre-mineralized scaffolds. Furthermore cell viability assays (MTS test) also show that cells
remain viable after two weeks in culture. Finally, protein expression studies showed that
after two weeks osteopontin and collagen type I were being expressed by SaOS-2 cells
seeded on the pre-mineralized scaffolds. Moreover, alkaline phosphatase (ALP) activity was
higher in the supernatants collected from the pre-mineralized samples, when compared to
the control samples (non Ca-P coated). This may indicate that a faster mineralization of the
ECM produced on the pre-mineralized samples was occurring. Consequently, biomimetic
pre-mineralization of starch based scaffolds can be a useful route for applying these
materials on bone tissue engineering
Characterization of bone repair in rat femur after treatment with calcium phosphate cement and autogenous bone graft
<p>Abstract</p> <p>Background</p> <p>In this study, the biocompatibility, stability and osteotransductivity of a new cement based on alpha-tricalcium phosphate (alpha-TCP) were investigated in a bone repair model using a rat model.</p> <p>Methods</p> <p>The potential of alpha-TCP on bone repair was compared to autogenous bone grafting, and unfilled cavities were used as negative control. Surgical cavities were prepared and designated as test (T), implanted with alpha-TCP blocks; negative control (C - ), unfilled; and positive control (C + ), implanted with autogenous bone graft. Results were analyzed on postoperative days three, seven, 14, 21 and 60.</p> <p>Results</p> <p>The histological analyses showed the following results. Postoperative day three: presence of inflammatory infiltrate, erythrocytes and proliferating fibroblasts in T, C - and C + samples. Day seven: extensive bone neoformation in groups T and C + , and beginning of alpha-TCP resorption by phagocytic cells. Days 14 and 21: osteoblastic activity in the three types of cavities. Day 60: In all samples, neoformed bone similar to surrounding bone. Moderate interruption on the ostectomized cortical bone.</p> <p>Conclusions</p> <p>Bone neoformation is seen seven days after implantation of alpha-TCP and autogenous bone. Comparison of C - with T and C + samples showed that repair is faster in implanted cavities; on day 60, control groups presented almost complete bone repair. Alpha-TCP cement presents biocompatibility and osteotransductivity, besides stability, but 60 days after surgery the cavities were not closed.</p
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