498 research outputs found
Domain-wall profile in the presence of anisotropic exchange interactions: Effective on-site anisotropy
Starting from a D-dimensional XXZ ferromagnetic Heisenberg model in an
hypercubic lattice, it is demonstrated that the anisotropy in the exchange
coupling constant leads to a D-dependent effective on-site anisotropy
interaction often ignored for D>1. As a result the effective width of the wall
depends on the dimensionality of the system. It is shown that the effective
one-dimensional Hamiltonian is not the one-dimensional XXZ version as assumed
in previous theoretical work. We derive a new expression for the wall profile
that generalizes the standard Landau-Lifshitz form. Our results are found to be
in very good agreement with earlier numerical work using the Monte Carlo
method. Preceding theories concerning the domain wall contribution to
magnetoresistance have considered the role of D only through the modification
of the density of states in the electronic band structure. This Brief Report
reveals that the wall profile itself contains an additional D dependence for
the case of anisotropic exchange interactions.Comment: 4 pages; new title and abstract; 1 figure comparing our results with
earlier numerical work; a more general model containing the usual on-site
anisotropy; new remarks and references on the following two topics: (a)
experimental evidence for the existence of spin exchange anisotropy, and (b)
preceding theories concerning the domain wall contribution to
magnetoresistance; to appear in Phys. Rev.
Bricolage as Survival, Growth and Transformation:the Role of Patchworking in the Social Agency of Migrant Entrepreneurs
This article examines the patch-working strategies of migrant entrepreneurs as a form of social agency. âPatch-workingâ â the reliance on supplementary forms of income to support business activity â is often seen as a means of cushioning the financial vulnerability of small firms. However, the mechanisms and forms that patch-working takes tend to be overlooked. Evidence from 42 West Midlandsâ firms shows that, despite the highly constrained operating environment, the exercise of social agency can help to cushion against disadvantage and to rework their current conditions through patch-working. This allows for business growth, and even transformational growth in some cases, rather than sheer survival. Even so, our findings show that the agency of migrant entrepreneurs brings about only minor improvements in revenue and is certainly not capable of fundamentally changing either the nature of the sector or the structure of the labour market in which they are embedded
Case report: A novel case of parental mosaicism in SMC1A gene causes inherited Cornelia de Lange syndrome
Ultimate advances in genetic technologies have permitted the detection of transmitted cases of congenital diseases due to parental gonadosomatic mosaicism. Regarding Cornelia de Lange syndrome (CdLS), up to date, only a few cases are known to follow this inheritance pattern. However, the high prevalence of somatic mosaicism recently reported in this syndrome (âŒ13%), together with the disparity observed in tissue distribution of the causal variant, suggests that its prevalence in this disorder could be underestimated. Here, we report a new case of parental gonadosomatic mosaicism in SMC1A gene that causes inherited CdLS, in which the mother of the patient carries the causative variant in very low allele frequencies in buccal swab and blood. While the affected child presents with typical CdLS phenotype, his mother does not show any clinical manifestations. As regards SMC1A, the difficulty of clinical identification of carrier females has been already recognized, as well as the gender differences observed in CdLS expressivity when the causal variant is found in this gene. Currently, the use of DNA deep-sequencing techniques is highly recommended when it comes to molecular diagnosis of patients, as well as in co-segregation studies. These enable us to uncover gonadosomatic mosaic events in asymptomatic or oligosymptomatic parents that had been overlooked so far, which might have great implications regarding genetic counseling for recurrence risk
A rain and scintillation Ka-band channel simulator
This paper describes the implementation of a
Ka-band satellite channel simulator with emphasis on the
synthesis of scintillation processes. The problem becomes
one of generating a given probability density function, the
Moulsley-Vilar distribution, with a specified power spectral
density using aWiener model based on orthogonal Hermite
polynomials for the nonlinearity. A numerical procedure is
devised to calculate the filter and non-linearity coefficients
of the Wiener model. The generation of rain processes
conforms to the Maseng-Bakken model.Postprint (published version
Hydroxybenzoic acid derivatives as dual-target ligands: mitochondriotropic antioxidants and cholinesterase inhibitors
Alzheimer's disease (AD) is a multifactorial age-related disease associated with oxidative stress (OS) and impaired cholinergic transmission. Accordingly, targeting mitochondrial OS and restoring cholinergic transmission can be an effective therapeutic strategy toward AD. Herein, we report for the first time dual-target hydroxybenzoic acid (HBAc) derivatives acting as mitochondriotropic antioxidants and cholinesterase (ChE) inhibitors. The studies were performed with two mitochondriotropic antioxidants AntiOxBEN1 (catechol derivative), and AntiOxBEN2 (pyrogallol derivative) and compounds 15â18, which have longer spacers. Compounds AntiOxBEN1 and 15, with a shorter carbon chain spacer (six- and eight-carbon) were shown to be potent antioxidants and BChE inhibitors (IC50 = 85 ± 5 and 106 ± 5 nM, respectively), while compounds 17 and 18 with a 10-carbon chain were more effective AChE inhibitors (IC50 = 7.7 ± 0.4 and 7.2 ± 0.5 ÎŒM, respectively). Interestingly, molecular modeling data pointed toward bifunctional ChEs inhibitors. The most promising ChE inhibitors acted by a non-competitive mechanism. In general, with exception of compounds 15 and 17, no cytotoxic effects were observed in differentiated human neuroblastoma (SH-SY5Y) and human hepatocarcinoma (HepG2) cells, while AÎČ-induced cytotoxicity was significantly prevented by the new dual-target HBAc derivatives. Overall, due to its BChE selectivity, favorable toxicological profile, neuroprotective activity and drug-like properties, which suggested blood-brain barrier (BBB) permeability, the mitochondriotropic antioxidant AntiOxBEN1 is considered a valid lead candidate for the development of dual acting drugs for AD and other mitochondrial OS-related diseases.This work was funded by FEDER funds through the Operational
Programme Competitiveness Factors-COMPETE and national funds by FCT â Foundation for Science and Technology under research grants (QUI/UI0081/2013, NORTE-01-0145-FEDER-000028 and PTDC/DTP-FTO/2433/2014, POCI-01-0145-FEDER-016659, POCI-01-0145-FEDER-007440. CO (SFRH/BD/88773/2012), FC (SFRH/BPD/74491/2010), JT (PTDC/DTP-FTO/2433/2014 and NORTE-01-0145-FEDER000028) RA (PTDC/DTP-FTO/2433/2014) grants are supported by FCT, POPH, and QREN. The authors also thank the COST action CA15135 for supportS
Biochemical parameters of silver catfish (Rhamdia quelen) after transport with eugenol or essential oil of Lippia alba added to the water
The transport of live fish is a routine practice in aquaculture and constitutes a considerable source of stress to the animals. The addition of anesthetic to the water used for fish transport can prevent or mitigate the deleterious effects of transport stress. This study investigated the effects of the addition of eugenol (EUG) (1.5 or 3.0 mu L L-1) and essential oil of Lippia alba (EOL) (10 or 20 mu L L-1) on metabolic parameters (glycogen, lactate and total protein levels) in liver and muscle, acetylcholinesterase activity (AChE) in muscle and brain, and the levels of protein carbonyl (PC), thiobarbituric acid reactive substances (TBARS) and nonprotein thiol groups (NPSH) and activity of glutathione-S-transferase in the liver of silver catfish (Rhamdia quelen; Quoy and Gaimard, 1824) transported for four hours in plastic bags (loading density of 169.2 g L-1). The addition of various concentrations of EUG (1.5 or 3.0 mu L L-1) and EOL (10 or 20 mu L L-1) to the transport water is advisable for the transportation of silver catfish, since both concentrations of these substances increased the levels of NPSH antioxidant and decreased the TBARS levels in the liver. In addition, the lower liver levels of glycogen and lactate in these groups and lower AChE activity in the brain (EOL 10 or 20 mu L L-1) compared to the control group indicate that the energetic metabolism and neurotransmission were lower after administration of anesthetics, contributing to the maintenance of homeostasis and sedation status.Fundacao de Amparo a Pesquisa do Estado do Rio Grande do Sul (FAPERGS/PRONEX) [10/0016-8]; Conselho Nacional de Pesquisa e Desenvolvimento Cientifico (CNPq) [470964/2009-0]; Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES); CNPqinfo:eu-repo/semantics/publishedVersio
Feasibility study for a spacecraft navigation system relying on pulsar timing information
Estudi de fiabilitat per un sistema de navegacio d'espai profund basat en referencies de radio-estrelles pulsants (pulsar).Preprin
Chemical and biological analysis of 4-acyloxy-3-nitrocoumarins as trypanocidal agents
Chagas disease is the most widespread contagious tropical disease in Latin America, being an important public health problem. Treatments against this disease are still very ineffective, presenting several side effects. Therefore, the search for alternative therapeutic solutions is urgent. In the present work, we evaluate the trypanocidal activity and the mechanism of action of a select series of synthetic 4-acyloxy-3-nitrocoumarins. All the coumarin derivatives showed moderate trypanocidal activity in trypomastigotes, along with low cytotoxicity. In addition, compound 1 decreased the number of infected Vero cells in an intracellular T. cruzi model. Electron spin resonance and electrochemical studies showed the formation of nitro radical anions. The Fukui index provided additional information to elucidate the proposed reduction mechanism. Furthermore, in vitro radical formation studies demonstrated the potential of these compounds to achieve higher concentrations of intracellular free radicals, proposing oxidative stress as a possible trypanocidal mechanism. Furthermore, no correlation was observed between the diffusion of these compounds, which shows that lipophilicity is not a predominant factor for activity. Elsevier Ltd. All rights reservedThis project was partially supported by the University of Porto and University of Santiago de Compostela. MJM would like to thank Xunta de Galicia (Galician Plan of Research, Innovation and Growth 2011â2015, Plan I2C, ED481B 2014/086â0 and ED481B 2018/007) and Fundação para a CiĂȘncia e Tecnologia (CEECIND/02423/2018 and UIDB/00081/2020). FS would like to thank FONDECYT 1190340 and REDES170126, COA would like to thank FONDECYT 1190340, JDM would like to thank FONDECYT 1170126 and ANID/PCI REDES 170126, and MMB would like to thank FONDECYT Postdoctoral 3190449S
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