Unsolved problems in the lowermost mantle

Many characteristics of D '' layer may be attributed to the recently discovered MgSiO3 post-perovskite phase without chemical heterogeneities. They include a sharp discontinuity at the top of D '', regional variation in seismic anisotropy, and a steep Clapeyron slope. However, some features remain unexplained. The seismically inferred velocity jump is too large in comparison to first principles calculations, and the sharpness of the discontinuity may require a chemical boundary. Chemical heterogeneity may play an important role in addition to the phase transformation from perovskite to post-perovskite. Phase transformation and chemical heterogeneity and the attendant changes in physical properties, such as rheology and thermal conductivity, are likely to play competing roles in defining the dynamical stability of the D '' layer. Revealing the relative roles between phase transition and chemical anomalies is an outstanding challenge in the study of the role of D '' in thermal-chemical evolution of the Earth

Complete Riemannian manifold minimally immersed in a unit sphere Sn+p (1)

Let Mn be an n-dimensional Riemannian manicold which is minimally immersed in a unit sphere Sn+p(1) of dimension n+p. If Mn is compact, then many authors studied them and obtained many beautiful results (for examples [1], [3], [4], [5] and [6]). ..

Fluctuations of Quantum Radiation Pressure in Dissipative Fluid

Using the generalized Langevin equations involving the stress tensor approach, we study the dynamics of a perfectly reflecting mirror which is exposed to the electromagnetic radiation pressure by a laser beam in a fluid at finite temperature. Based on the fluctuation-dissipation theorem, the minimum uncertainty of the mirror's position measurement from both quantum and thermal noises effects including the photon counting error in the laser interferometer is obtained in the small time limit as compared with the "standard quantum limit". The result of the large time behavior of fluctuations of the mirror's velocity in a dissipative environment can be applied to the laser interferometer of the ground-based gravitational wave detector.Comment: 8 pages. Version published in Physics Letters

Review: Synthetic Jets and their Cooling Applications

O objetivo deste artigo é apresentar uma revisão do estado da arte da aplicação de jatos sintéticos para resfriamento. A aplicação de jatos sintéticos representa uma técnica alternativa aos sistemas de resfriamento líquido, que busca aumentar a troca térmica mantendo-se o ar como fluido de trabalho. Para isso, é necessário primeiro discursar sobre as variações de dispositivos de geração, as principais características fluidodinâmicas dos jatos sintéticos e seus parâmetros adimensionais de avaliação de desempenho. Jatos sintéticos são formados em dispositivos geradores a partir de uma cavidade equipada com um pequeno orifício. A oscilação de uma membrana ou parede da cavidade induz uma movimentação periódica de fluido e produz um jato sintético na região externa ao orifício de saída. O jato sintético possui características de velocidade média semelhantes a um jato contínuo, mas com um nível de turbulência maior devido a sua natureza oscilatória. O resfriamento pode ser realizado em configurações de jato de impactação ou tangencial. Independente da configuração, a interação da turbulência do jato com uma superfície resulta em um aumento da troca térmica tanto em relação à convecção natural como convecção forçada de escoamentos de regime permanente.Palavras-chave: jato sintético, resfriamento, convecção forçadaThe objective of this paper is to present a review of the state of the art in cooling applications of synthetic jets. Cooling by means of synthetic jets represent an alternative technique to liquid cooling, in which air is still the working fluid. To this end, it is necessary first to present the varying types of synthetic jet generators, the fluid dynamic characteristics and the dimensionless performance parameters of the jets themselves. Synthetic jets are produced in generators that consist of a sealed cavity containing a small orifice. A boundary oscillation induces fluid movement in and out of the cavity through the orifice that, in the region external to the orifice, develops into a synthetic jet. The synthetic jet has average velocity properties similar to a steady jet albeit with a higher level of turbulence due to its oscillatory nature. Cooling applications of synthetic jets can occur in an impacting or tangential configuration. Regardless of the configuration used, several experimental and numerical studies have demonstrated that there is a significant increase in heat transfer compared to natural convection and forced convection with steady state turbulent flows.Keywords: synthetic jets, cooling, forced convectio

The elastic constants of MgSiO3 perovskite at pressures and temperatures of the Earth's mantle

The temperature anomalies in the Earth's mantle associated with thermal convection1 can be inferred from seismic tomography, provided that the elastic properties of mantle minerals are known as a function of temperature at mantle pressures. At present, however, such information is difficult to obtain directly through laboratory experiments. We have therefore taken advantage of recent advances in computer technology, and have performed finite-temperature ab initio molecular dynamics simulations of the elastic properties of MgSiO3 perovskite, the major mineral of the lower mantle, at relevant thermodynamic conditions. When combined with the results from tomographic images of the mantle, our results indicate that the lower mantle is either significantly anelastic or compositionally heterogeneous on large scales. We found the temperature contrast between the coldest and hottest regions of the mantle, at a given depth, to be about 800K at 1000 km, 1500K at 2000 km, and possibly over 2000K at the core-mantle boundary.Comment: Published in: Nature 411, 934-937 (2001

A single residue substitution in the receptor-binding domain of H5N1 hemagglutinin is critical for packaging into pseudotyped lentiviral particles

© 2012 Tang et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Background: Serological studies for influenza infection and vaccine response often involve microneutralization and hemagglutination inhibition assays to evaluate neutralizing antibodies against human and avian influenza viruses, including H5N1. We have previously characterized lentiviral particles pseudotyped with H5-HA (H5pp) and validated an H5pp-based assay as a safe alternative for high-throughput serological studies in BSL-2 facilities. Here we show that H5-HAs from different clades do not always give rise to efficient production of H5pp and the underlying mechanisms are addressed. Methodology/Findings: We have carried out mutational analysis to delineate the molecular determinants responsible for efficient packaging of HA from A/Cambodia/40808/2005 (H5Cam) and A/Anhui/1/2005 (H5Anh) into H5pp. Our results demonstrate that a single A134V mutation in the 130-loop of the receptor binding domain is sufficient to render H5Anh the ability to generate H5Anh-pp efficiently, whereas the reverse V134A mutation greatly hampers production of H5Cam-pp. Although protein expression in total cell lysates is similar for H5Anh and H5Cam, cell surface expression of H5Cam is detected at a significantly higher level than that of H5Anh. We further demonstrate by several independent lines of evidence that the behaviour of H5Anh can be explained by a stronger binding to sialic acid receptors implicating residue 134. Conclusions: We have identified a single A134V mutation as the molecular determinant in H5-HA for efficient incorporation into H5pp envelope and delineated the underlying mechanism. The reduced binding to sialic acid receptors as a result of the A134V mutation not only exerts a critical influence in pseudotyping efficiency of H5-HA, but has also an impact at the whole virus level. Because A134V substitution has been reported as a naturally occurring mutation in human host, our results may have implications for the understanding of human host adaptation of avian influenza H5N1 virusesThis work was supported by grants from the Research Fund for the Control of Infectious Diseases of Hong Kong (RFCID#08070972), the Area of Excellence Scheme of the University Grants Committee (grant AoE/M-12/-06 of the Hong Kong Special Administrative Region, China), the French Ministry of Health, and the RESPARI project of the Institut Pasteur International Network

The use of augmented reality for solving arithmetic problems for preschool children

Preschool children are required to acquire problem-solving ability and related time and sequence concepts to solve mathematical story problems. The maturation and pervasion of disruptive technologies, such as augmented reality (AR), may help preschool children to better acquire this knowledge and skills. However, it is still unknown how preschoolers would make use of AR as a learning tool for tackling arithmetic story problems with the involvement of the concepts of time and sequence. Consequently, the present study attempted to employ direct observation and interview methods to compare and gain insights into young children’s learning behaviors under traditional 2D pictorial and AR contexts. In line with the early development trajectories of a normal child aged 4–6 years old, a series of planned arithmetic problems which primarily comprised seriation (e.g. first, second, third) and scheduling (e.g. arriving, leaving) concepts were structured in scenario-based stories and designed specifically for preschool children. The findings of the current study reveal that AR intervention may well develop the problem-solving and independent mathematical thinking ability for preschool children by encouraging them to consider all information involved in the story problems, rather than simply guessing the answer from a 2D pictorial mode. Finally, based on the fact that the majority of preschool children still rely on a concrete counting method, the recommendation is to integrate AR technology into the traditional pictorial scenarios for the purpose of supporting the development of children’s ability to solve arithmetic story problem

Protein profiling in hepatocellular carcinoma by label-free quantitative proteomics in two west african populations.

Background Hepatocellular Carcinoma is the third most common cause of cancer related death worldwide, often diagnosed by measuring serum AFP; a poor performance stand-alone biomarker. With the aim of improving on this, our study focuses on plasma proteins identified by Mass Spectrometry in order to investigate and validate differences seen in the respective proteomes of controls and subjects with LC and HCC. Methods Mass Spectrometry analysis using liquid chromatography electro spray ionization quadrupole time-of-flight was conducted on 339 subjects using a pooled expression profiling approach. ELISA assays were performed on four significantly differentially expressed proteins to validate their expression profiles in subjects from the Gambia and a pilot group from Nigeria. Results from this were collated for statistical multiplexing using logistic regression analysis. Results Twenty-six proteins were identified as differentially expressed between the three subject groups. Direct measurements of four; hemopexin, alpha-1-antitrypsin, apolipoprotein A1 and complement component 3 confirmed their change in abundance in LC and HCC versus control patients. These trends were independently replicated in the pilot validation subjects from Nigeria. The statistical multiplexing of these proteins demonstrated performance comparable to or greater than ALT in identifying liver cirrhosis or carcinogenesis. This exercise also proposed preliminary cut offs with achievable sensitivity, specificity and AUC statistics greater than reported AFP averages. Conclusions The validated changes of expression in these proteins have the potential for development into high-performance tests usable in the diagnosis and or monitoring of HCC and LC patients. The identification of sustained expression trends strengthens the suggestion of these four proteins as worthy candidates for further investigation in the context of liver disease. The statistical combinations also provide a novel inroad of analyses able to propose definitive cut-offs and combinations for evaluation of performance

Misremembering solitude : the role of personality and cultural self-concepts in shaping discrepancies between recalled and concurrent affect in solitude

Background Affect recall is key to psychological assessment and decision-making. However, self-concepts (self-beliefs) may bias retrospective affect reports such that they deviate from lived experiences. Does this experience-memory gap apply to solitude experiences? We hypothesized that individuals misremember how they feel overall and when in solitude, in line with self-concepts of introversion, self-determined/not-self-determined solitude motivations, and independent/interdependent self-construal. A pilot study comparing retrospective to daily affect reports captured over 2 weeks (N = 104 UK university students) provided preliminary evidence of introversion and not-self-determined solitude shaping affect recall. Methods In the main pre-registered study, participants aged 18–49 in the UK (N = 160) and Hong Kong (N = 159) reported their momentary affective states and social situations 5 times per day over 7 days, then recalled how they felt over the week. Results and Discussion Individuals higher in self-determined solitude were more prone to retrospectively overestimate their high- and low-arousal positive affect in solitude and showed less overestimation/more underestimation of negative affect in solitude. Higher not-self-determined solitude was associated with overestimating loneliness, and higher interdependent self-construal with overestimating loneliness and energy levels, in solitude. Comparisons based on residence/ethnicity suggest culture influences solitude-seeking and affective memory. Implications for well-being and affect measurement are discussed