Magnetic properties of Co-doped TiO(2) anatase nanopowders

This letter reports on the magnetic properties of Ti(1-x)Co(x)O(2) anatase phase nanopowders with different Co contents. It is shown that oxygen vacancies play an important role in promoting long-range ferromagnetic order in the material studied in addition to the transition-metal doping. Furthermore, the results allow ruling out the premise of a strict connection between Co clustering and the ferromagnetism observed in the Co:TiO(2) anatase system.

Electrical transport properties of CuS single crystals

Electrical resistivity, transverse magnetoresistance and thermoelectric power measurements were performed on CuS high quality single crystals in the range 1.2-300 K and under fields of up to 16 T. The zero field resistivity data are well described below 55 K by a quasi-2D model, consistent with a carrier confinement at lower temperatures, before the transition to the superconducting state. The transverse magnetoresistance develops mainly below 30 K and attains values as large as 470% for a 16 T field at 5 K, this behaviour being ascribed to a band effect mechanism, with a possible magnetic field induced DOS change at the Fermi level. The transverse magnetoresistance shows no signs of saturation, following a power law with field Delta rho/rho(0) proportional to H(1.4), suggesting the existence of open orbits for carriers at the Fermi surface. The thermoelectric power shows an unusual temperature dependence, probably as a result of the complex band structure of CuS.

Magnetic Field and Temperature Effects on Strangelets

The main properties of magnetized strangelets, namely, their energy per baryon, radius and electric charge, are studied in the unpaired strange quark matter phase. Temperature effects are taken into account in order to study their stability compared to the (56)Fe isotope and non-magnetized strangelets within the framework of the MIT bag model. It is concluded that the presence of a magnetic field tends to stabilize more the strangelets, even when temperature is considered. We find that the electric charge is modified in the presence of the magnetic field, leading to higher charge values for magnetized strangelets, when compared to the non-magnetized case.

Claustrophobia and adherence in magnetic resonance imaging procedure

Claustrophobia causes a huge discomfort to those who need to perform Magnetic Resonance examinations mainly due to the physical design of most equipment. This study aimed to maximize the success rate of Magnetic Resonance Imaging (MRI) clinical studies in claustrophobic patients by the identification of facilitative strategies.

Simulation of the Magnetic Induction Vector of a Magnetic Core to be Used in FFC NMR Relaxometry

This paper is a contribution for the assessment and comparison of magnet properties based on magnetic field characteristics particularly concerning the magnetic induction uniformity in the air gaps. For this aim, a solver was developed and implemented to determine the magnetic field of a magnetic core to be used in Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometry. The electromagnetic field computation is based on a 2D finite-element method (FEM) using both the scalar and the vector potential formulation. Results for the magnetic field lines and the magnetic induction vector in the air gap are presented. The target magnetic induction is 0.2 T, which is a typical requirement of the FFC NMR technique, which can be achieved with a magnetic core based on permanent magnets or coils. In addition, this application requires high magnetic induction uniformity. To achieve this goal, a solution including superconducting pieces is analyzed. Results are compared with a different FEM program.

Nonmonotonic Magnetic Susceptibility of Dipolar Hard-Spheres at Low Temperature and Density

We investigate, via numerical simulations, mean field, and density functional theories, the magnetic response of a dipolar hard sphere fluid at low temperatures and densities, in the region of strong association. The proposed parameter-free theory is able to capture both the density and temperature dependence of the ring-chain equilibrium and the contribution to the susceptibility of a chain of generic length. The theory predicts a nonmonotonic temperature dependence of the initial (zero field) magnetic susceptibility, arising from the competition between magnetically inert particle rings and magnetically active chains. Monte Carlo simulation results closely agree with the theoretical findings. DOI: 10.1103/PhysRevLett.110.148306

Structural, electrical and magnetic studies of Co:SnO2 and (Co,Mo):SnO2 films prepared by pulsed laser deposition

Here we report on the structural, optical, electrical and magnetic properties of Co-doped and (Co,Mo)-codoped SnO2 thin films deposited on r-cut sapphire substrates by pulsed laser deposition. Substrate temperature during deposition was kept at 500 degrees C. X-ray diffraction analysis showed that the undoped and doped films are crystalline with predominant orientation along the [1 0 1] direction regardless of the doping concentration and doping element. Optical studies revealed that the presence of Mo reverts the blue shift trend observed for the Co-doped films. For the Co and Mo doping concentrations studied, the incorporation of Mo did not contribute to increase the conductivity of the films or to enhance the ferromagnetic order of the Co-doped films. (C) 2012 Elsevier B.V. All rights reserved.

O casamento real de William e Kate : a cobertura jornal��stica nos jornais The Daily Mail, The Guardian e The Sun

Disserta����o apresentada �� Escola Superior de Comunica����o Social como parte dos requisitos para obten����o de grau de mestre em Jornalismo.

Maryam Mirzakhani : a primeira mulher vencedora da Medalha Fields

Este artigo apresenta uma breve biografia de Maryam Mirzakhani, a primeira mulher vencedora da Medalha Fields, pr��mio institu��do desde 1936 e que �� concedido de quatro em quatro anos a matem��ticos com menos de 40 anos.

A Medalha Fields

A Medalha Fields �� um pr��mio desconhecido (ou quase) para a maioria das pessoas. Algumas ter��o ouvido dizer que �� semelhante ao Pr��mio Nobel da Matem��tica. Outras dir��o que �� um pr��mio de excel��ncia s�� para os matem��ticos. A Medalha Fields, oficialmente conhecida como Medalha Internacional de Descobrimentos Proeminentes em Matem��tica, �� um conceituado pr��mio concedido a dois, tr��s ou quatro matem��ticos com menos de 40 anos e entregue durante o Congresso Internacional de Matem��tica que se realiza de quatro em quatro anos. �� equiparada, em termos de prest��gio, ao Pr��mio Nobel.

Magnetic and plagioclase linear fabric discrepancy in dykes: a new way to define the flow vector using magnetic foliation

In basaltic dykes the magnetic lineation K1 (maximum magnetic susceptibility axis) is generally taken to indicate the flow direction during solidification of the magma. This assumption was tested in Tertiary basaltic dykes from Greenland displaying independent evidence of subhorizontal flow. The digital processing of microphotographs from thin sections cut in (K1, K2) planes yields the preferred linear orientation of plagioclase, which apparently marks the magma flow lineation. In up to 60% of cases, the angular separation between K1 and the assumed flow direction is greater than 45degrees. This suggests that the uncorroborated use of magnetic lineations in dykes is risky. A simple geometrical method is proposed to infer the flow vector from AMS in dykes based solely on magnetic foliations.

STIR, SPIR and SPAIR techniques in magnetic resonance of the breast: a comparative study

The amount of fat is a component that complicates the clinical evaluation and the differential diagnostic between benign and malign lesions in the breast MRI examinations. To overcome this problem, an effective erasing of the fat signal over the images acquisition process, is essentials. This study aims to compare three fat suppression techniques (STIR, SPIR, SPAIR) in the MR images of the breast and to evaluate the best image quality regarding its clinical usefulness. To mimic breast women, a breast phantom was constructed. First the exterior contour and, in second time, its content which was selected based on 7 samples with different components. Finally it was undergone to a MRI breast protocol with the three different fat saturation techniques. The examinations were performed on a 1.5 T MRI system (Philips��). A group of 5 experts evaluated 9 sequences, 3 of each with fat suppression techniques, in which the frequency offset and TI (Inversion Time) were the variables changed. This qualitative image analysis was performed according 4 parameters (saturation uniformity, saturation efficacy, detail of the anatomical structures and differentiation between the fibroglandular and adipose tissue), using a five-point Likert scale. The statistics analysis showed that anyone of the fat suppression techniques demonstrated significant differences compared to the others with (p > 0.05) and regarding each parameter independently. By Fleiss��� kappa coefficient there was a good agreement among observers P(e) = 0.68. When comparing STIR, SPIR and SPAIR techniques it was confirmed that all of them have advantages in the study of the breast MRI. For the studied parameters, the results through the Friedman Test showed that there are similar advantages applying anyone of these techniques.

The influence of the blood pressure on the venous cerebral flow measured by magnetic susceptibility (SWI) technique

Susceptibility Weighted Image (SWI) is a Magnetic Resonance Imaging (MRI) technique that combines high spatial resolution and sensitivity to provide magnetic susceptibility differences between tissues. It is extremely sensitive to venous blood due to its iron content of deoxyhemoglobin. The aim of this study was to evaluate, through the SWI technique, the differences in cerebral venous vasculature according to the variation of blood pressure values. 20 subjects divided in two groups (10 hypertensive and 10 normotensive patients) underwent a MRI system with a Siemens�� scanner model Avanto of 1.5T using a synergy head coil (4 channels). The obtained sequences were T1w, T2w-FLAIR, T2* and SWI. The value of Contrast-to-Noise Ratio (CNR) was assessed in MinIP (Minimum Intensity Projection) and Magnitude images, through drawing free hand ROIs in venous structures: Superior Sagittal Sinus (SSS) Internal Cerebral Vein (ICV) and Sinus Confluence (SC). The obtained values were presented in descriptive statistics-quartiles and extremes diagrams. The results were compared between groups. CNR shown higher values for normotensive group in MinIP (108.89 �� 6.907) to ICV; (238.73 �� 18.556) to SC and (239.384 �� 52.303) to SSS. These values are bigger than images from Hypertensive group about 46 a.u. in average. Comparing the results of Magnitude and MinIP images, there were obtained lower CNR values for the hypertensive group. There were differences in the CNR values between both groups, being these values more expressive in the large vessels-SSS and SC. The SWI is a potential technique to evaluate and characterize the blood pressure variation in the studied vessels adding a physiological perspective to MRI and giving a new approach to the radiological vascular studies.

Modelling and segmentation of the vocal tract during speech production by using deformable models in magnetic resonance images

The first and second authors would like to thank the support of the PhD grants with references SFRH/BD/28817/2006 and SFRH/PROTEC/49517/2009, respectively, from Funda����o para a Ci��ncia e Tecnol ogia (FCT). This work was partially done in the scope of the project ���Methodologies to Analyze Organs from Complex Medical Images ��� Applications to Fema le Pelvic Cavity���, wi th reference PTDC/EEA- CRO/103320/2008, financially supported by FCT.

Seguran��a em resson��ncia magn��tica: exposi����o ocupacional a campos electromagn��ticos

Pretendeu-se contribuir para um melhor entendimento sobre a discuss��o patente ao redor da Diretiva EMF 2004/40/CE que limita a exposi����o dos profissionais aos campos eletromagn��ticos (CEM) utilizados em Resson��ncia Magn��tica (RM). A aplicabilidade da RM ser�� posta em causa se forem impostos, na pr��tica cl��nica, os limites expressos na diretiva. Foi explorada a evid��ncia cient��fica, sobre a controv��rsia gerada em torno do tema. Analisaram-se guidelines, leis e documentos oficiais e foi aplicado um inqu��rito a 11 grupos profissionais envolvidos na problem��tica, distribu��dos por v��rios pa��ses. Foi constru��do o diagrama do campo de for��as utilizando a aplica����o Policymaker K4 health�� afim de se especular sobre influ��ncias, for��as, poder e estrat��gias desenvolvidas que possam restringir ou facilitar a aplica����o da Diretiva. Verificou-se que 62% dos inquiridos desconhece a Diretiva e o seu conte��do bem como a posi����o da Sociedade Europeia de Radiologia (ESR) e 69% dos inquiridos n��o tem acompanhado os desenvolvimentos do tema. Referem n��o ter conhecimento da ocorr��ncia de incidentes, para al��m do efeito m��ssil e do aquecimento devido a Radiofrequ��ncia ��� Specific Absortion Ratio (SAR). Consideram que o impacto pol��tico da Diretiva ser�� neutro, mas o impacto cl��nico e econ��mico ser��o negativos. Existe uma subestima����o geral desta controv��rsia e um n��o reconhecimento das consequ��ncias que a aplica����o da Diretiva poder�� ter na pr��tica cl��nica. Admite-se o desenvolvimento de estrat��gias de press��o e influ��ncia para com o poder legislativo da Comiss��o Europeia e do Conselho, quanto a esta mat��ria.