Ultra-trace Cu isotope ratio measurements via multi-collector ICP-mass spectrometry using Ga as internal standard : an approach applicable to micro-samples

The capabilities of Cu isotope ratio measurements are often restricted by the small volumes of sample available and/or their low Cu concentration. In this work, an analytical approach was developed for performing Cu isotopic analysis via multi-collector ICP-mass spectrometry (MC-ICP-MS) at ultra-trace level using Ga as an internal standard for mass bias correction. The minimum concentration of Cu required for accurate and precise isotope ratio measurements was established to be 20 mu g L-1 with wet plasma conditions and 5 mu g L-1 with dry plasma conditions. The use of Ga as an internal standard for mass bias correction provided several advantages compared to Ni, i.e. improved internal precision on delta Cu-65 values and lower blank levels. Ga can also be used at a 4- fold lower concentration level than Ni. However, in wet plasma conditions, the signals of (ArO2H+)-Ar-36-O-16-H-1 and (ArNO+)-Ar-40-N-15-O-16 interfered with the signals of Ga-69(+) and Ga-71(+), respectively, while in dry plasma conditions, realized by the use of a desolvation unit, Ga-69(+) suffered from spectral interference from (ArN2H+)-Ar-40-N-14-H-1. These interferences were resolved by using medium mass resolution. For validation purposes, the approach was applied to commercially available blood and serum samples. The delta Cu-65 values for the samples measured at a concentration level of 5 mu g L-1 Cu and 5 mu g L-1 Ga using dry plasma conditions were in good agreement with those obtained for isotope ratio measurements at the "standard" concentration level of 200 mu g L-1 Cu and 200 mu g L-1 Ni using wet plasma conditions. In addition, the delta Cu-65 values obtained for micro-samples of serum/blood (volume of 100 mu L) were in good agreement with the corresponding ones obtained using the "standard" volume for isotopic analysis (500 mu L)

Black-hole binaries: life begins at 40 keV

In the study of black-hole transients, an important problem that still needs to be answered is how the high-energy part of the spectrum evolves from the low-hard to the high-soft state, given that they have very different properties. Recent results obtained with RXTE and INTEGRAL have given inconsistent results. With RXTE, we have found that the high-energy cutoff in GX 339-4 during the transition first decreases (during the low-hard state), then increases again across the Hard-Intermediate state, to become unmeasurable in the soft states (possibly because of statistical limitations). We show Simbol-X will be able to determine the spectral shape with superb accuracy. As the high-energy part of the spectrum is relatively less known than the one below 20 keV, Simbol-X will provide important results that will help out understanding of the extreme physical conditions in the vicinity of a stellar-mass black hole.Comment: Proc. "Simbol-X: Focusing on the Hard X-Ray Universe", Paris, 2-5 Dec. 2008, ed. J. Rodriguez and P. Ferrando; 4 pages, 3 figure

Interaction of particles with a cavitation bubble near a solid wall

Hard particle erosion and cavitation damage are two main wear problems that can affect the internal components of hydraulic machinery such as hydraulic turbines or pumps. If both problems synergistically act together, the damage can be more severe and result in high maintenance costs. In this work, a study of the interaction of hard particles and cavitation bubbles is developed to understand their interactive behavior. Experimental tests and numerical simulations using computational fluid dynamics (CFD) were performed. Experimentally, a cavitation bubble was generated with an electric spark near a solid surface, and its interaction with hard particles of different sizes and materials was observed using a high-speed camera. A simplified analytical approach was developed to model the behavior of the particles near the bubble interface during its collapse. Computationally, we simulated an air bubble that grew and collapsed near a solid wall while interacting with one particle near the bubble interface. Several simulations with different conditions were made and validated with the experimental data. The experimental data obtained from particles above the bubble were consistent with the numerical results and analytical study. The particle size, density and position of the particle with respect to the bubble interface strongly affected the maximum velocity of the particles

Numerical study of electrostatically-defined quantum dots in bilayer graphene

Màster Oficial de Ciència i Tecnologia Quàntiques / Quantum Science and Technology, Facultat de Física, Universitat de Barcelona. Curs: 2022-2023. Tutor: Iacopo TorreInteracting quantum many-body systems are so challenging to study that even simplified models, such as the Hubbard model, cannot be solved exactly. For this reason, it is interesting to engineer controllable quantum systems, called quantum simulators, that can emulate the behavior of these models. This makes quantum simulators a promising platform for studying the Hubbard model. These can be implemented, for example, using interacting arrays of quantum dots realized in semiconducting materials. The capability to tune the bands in bilayer graphene with patterned gate electrodes provides an innovative platform to study such a model, as it is the first time to explore the Hubbard model with quantum dots in a twodimensional material. Moreover, this platform opens a wide range of possibilities to study the different parameters of the model. In this work, we study theoretically and numerically realistic models of electrostatically defined quantum dots in bilayer graphene. We can calculate the proposed device’s potential and band-gap landscape induced in bilayer graphene by solving the Poisson equation. The result is then fed to a lowenergy model to calculate the bound states of the quantum dots. This allows calculating the parameters of the corresponding Hubbard model, including tunneling amplitudes and on-site interactions. Our results can be directly used to design quantum-simulation devices based on quantum dots that are realized electrostatically in bilayer graphene

‘Maybe we can turn the tide’ : an explanatory mixed-methods study to understand how knowledge brokers mobilise health evidence in low- and middle-income countries

Background: Little is known about how knowledge brokers (KBs) operate in low- and middle-income countries (LMICs) to translate evidence for health policy and practice. These intermediaries facilitate relationships between evidence producers and users to address public health issues. Aims and objectives: To increase understanding, a mixed-methods study collected data from KBs who had acted on evidence from the 2015 Global Maternal Newborn Health Conference in Mexico. Methods: Of the 1000 in-person participants, 252 plus 72 online participants (n=324) from 56 countries completed an online survey, and 20 participants from 15 countries were interviewed. Thematic analysis and application of knowledge translation (KT) theory explored factors influencing KB actions leading to evidence uptake. Descriptive statistics of respondent characteristics were used for cross-case comparison. Findings: Results suggest factors supporting the KB role in evidence uptake, which include active relationships with evidence users through embedded KB roles, targeted and tailored evidence communication to fit the context, user receptiveness to evidence from a similar country setting, adaptability in the KB role, and action orientation of KBs. Discussion and conclusions: Initiatives to increase evidence uptake in LMICs should work to establish supportive structures for embedded KT, identify processes for ongoing cross-country learning, and strengthen KBs already showing effectiveness in their roles

Planning for Pedestrians and Bicyclists in North Carolina.

Over the past decade, as obesity has continued to rise among both youth and adults, interest has grown in developing policies to promote community environments that support healthy lifestyles.1 A broad range of local, regional, state, and federal policies under the rubrics of active living, smart growth, and sustainable development share the underlying assumption that they can help people make healthier choices. From a transportation planning perspective, the benefits of pedestrian and bicycle plans resulting from the building of infrastructure to support pedestrian and bicycle travel include improved health (for example, through increased levels of physical activity and reduced obesity), a better environment (for example, through lower carbon emissions), and a stronger economy (for example, through lower fuel bills). However, until more recently, the health benefits have not been specifically explored

Processing advantage for emotional words in bilingual speakers

Effects of emotion on word processing are well established in monolingual speakers. However, studies that have assessed whether affective features of words undergo the same processing in a native and non-native language have provided mixed results: studies that have found differences between L1 and L2 processing, attributed it to the fact that a second language (L2) learned late in life would not be processed affectively, because affective associations are established during childhood. Other studies suggest that adult learners show similar effects of emotional features in L1 and L2. Differences in affective processing of L2 words can be linked to age and context of learning, proficiency, language dominance, and degree of similarity between the L2 and the L1. Here, in a lexical decision task on tightly matched negative, positive and neutral words, highly proficient English speakers from typologically different L1 showed the same facilitation in processing emotionally valenced words as native English speakers, regardless of their L1, the age of English acquisition or the frequency and context of English use

The Malawian co-operative movement: insights for resilience

Heavy government interference, lack or leadership and low levels of skills are some the factors that have for decades weakened and in some cases caused the failure of co-operatives in Africa. However, in the recent past, African co-operatives have experienced a remarkable renaissance. We examine whether these co-operatives are resilient forms of organisation, and if so, what are the key factors that are conducive to resilience. We examine the Malawian co-operative movement from which very little is known. We explore four of the biggest co-operative Unions in the country. Our analysis is guided by a framework compounded by five key factors conducive to co-operative resilience. Our results suggest that women’s inclusion, business income diversification, collective skills, and strategic partnerships with external agents are factors conducive to resilience. We also conclude that these factors need to be grounded on reflexive behaviour amongst leaders and cooperative members