830 research outputs found
An Adaptive, Kink-Based Approach to Path Integral Calculations
A kink-based expression for the canonical partition function is developed
using Feynman's path integral formulation of quantum mechanics and a discrete
basis set. The approach is exact for a complete set of states. The method is
tested on the 3x3 Hubbard model and overcomes the sign problem seen in
traditional path integral studies of fermion systems. Kinks correspond to
transitions between different N-electron states, much in the same manner as
occurs in configuration interaction calculations in standard ab initio methods.
The different N-electron states are updated, based on which states occur
frequently during a Monte Carlo simulation, giving better estimates of the true
eigenstates of the Hamiltonian.Comment: 24 pages, to be published in J. Chem. Phy
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In vivo tau PET imaging in dementia: Pathophysiology, radiotracer quantification, and a systematic review of clinical findings.
In addition to the deposition of β-amyloid plaques, neurofibrillary tangles composed of aggregated hyperphosphorylated tau are one of the pathological hallmarks of Alzheimer's disease and other neurodegenerative disorders. Until now, our understanding about the natural history and topography of tau deposition has only been based on post-mortem and cerebrospinal fluid studies, and evidence continues to implicate tau as a central driver of downstream neurodegenerative processes and cognitive decline. Recently, it has become possible to assess the regional distribution and severity of tau burden in vivo with the development of novel radiotracers for positron emission tomography (PET) imaging. In this article, we provide a comprehensive discussion of tau pathophysiology, its quantification with novel PET radiotracers, as well as a systematic review of tau PET imaging in normal aging and various dementia conditions: mild cognitive impairment, Alzheimer's disease, frontotemporal dementia, progressive supranuclear palsy, and Lewy body dementia. We discuss the main findings in relation to group differences, clinical-cognitive correlations of tau PET, and multi-modal relationships among tau PET and other pathological markers. Collectively, the small but growing literature of tau PET has yielded consistent anatomical patterns of tau accumulation that recapitulate post-mortem distribution of neurofibrillary tangles which correlate with cognitive functions and other markers of pathology. In general, AD is characterised by increased tracer retention in the inferior temporal lobe, extending into the frontal and parietal regions in more severe cases. It is also noted that the spatial topography of tau accumulation is markedly distinct to that of amyloid burden in aging and AD. Tau PET imaging has also revealed characteristic spatial patterns among various non-AD tauopathies, supporting its potential role for differential diagnosis. Finally, we propose novel directions for future tau research, including (a) longitudinal imaging in preclinical dementia, (b) multi-modal mapping of tau pathology onto other pathological processes such as neuroinflammation, and (c) the need for more validation studies against post-mortem samples of the same subjects.The study is supported by the UK National Institute of Health Research Cambridge Biomedical Research Centre and Biomedical Research Unit in Dementia. JBR is supported by the Wellcome Trust (103838). EM is in receipt of a Gates Cambridge scholarship and an Alzheimer’s Research UK Research Grant
Innovation, financial development and economic growth in Eurozone countries
Using a panel vector auto-regressive model, we study interactions between innovation,
financial development and economic growth in 18 Eurozone countries between 1961
and 2013. We focus on whether causality runs between these variables both ways, one
way, the other way or not at all. Our empirical results show that development of the
financial sector and enhanced innovative capacity in the Eurozone contribute to longterm
economic growth in the countries in the region.http://www.tandfonline.com/loi/rael202018-05-31hb2016Financial Managemen
Causal nexus between economic growth, banking sector development, stock market development, and other macroeconomic variables : the case of ASEAN countries
This paper examines the relationship between banking sector development, stock market development, economic
growth, and four other macroeconomic variables in ASEAN countries for the period 1961–2012. Using principal
component analysis for the construction of the development indices and a panel vector auto-regressive model
for testing the Granger causalities, this study finds the presence of both unidirectional and bidirectional causality
links between these variables. The study contributes to understanding the importance of the interrelationship
between the variables and combines the different strands of the literature. It also contributes to the literature by
focusing on a group of countries that have not been studied before. One particular policy recommendation is to
make the banking sector more accessible for those country's inhabitants that do not have bank accounts.
Another policy recommendation is to nurture stock market development, which will facilitate the increased raising
of capital for investment purposes to enhance economic growth.http:// www.elsevier.com/locate/rfehb2016Financial Managemen
Modeling and design of T-probe-fed patch antennas using the finite difference time domain method
The dynamics of banking sector and stock market maturity and the performance of Asian economies : time series evidence
PURPOSE – The purpose of this paper is to examine the nature of causal relations between
banking sector maturity, stock market maturity, and four aspects of performance and operation
of the economy: economic growth, inflation, openness in trade, and the degree of government
involvement in the economy.
DESIGN/METHODOLOGY/APPROACH – The authors look for possible links between the variables by
conducting panel cointegration and causality tests, using a large sample of Asian countries over the
period 1960-2011. Novel panel data estimation methods allow for robust estimates, using both
variation between countries and variation over time.
FINDINGS – The study identifies interesting causal links among the variables deriving uniquely from
our innovations. In particular, The paper finds that for all regions considered, banking sector maturity
and stock market maturity are causally linked, sometimes in both directions. Furthermore, stock
market maturity may lead to economic growth, both directly and indirectly through indicators such as
inflation and trade openness. The findings also support the notion that economic growth affects the
maturity of the stock market in most regions.
PRACTICAL IMPLICATIONS – The results lend support to the notion that a mature financial sector is a
key contributor to generating economic growth. Furthermore, economic growth itself has the potential
to bring about maturity in the financial sector.
ORIGINALITY/VALUE – The paper uses sophisticated principal-component analysis, panel cointegration,
and Granger causality tests, methods not used in this literature before. The method was applied to
recent data pertaining to 35 Asian countries – a group of countries that has previously not been
adopted in this literature.http://www.emeraldinsight.com/1026-4116.htmhttp://www.emeraldinsight.com/loi/jeashj201
Dynamic Nuclear Polarization of Deuterated Proteins
For D's a jolly good fellow: Deuteration of proteins significantly increases the signal enhancements observed in dynamic nuclear polarization (DNP) magic-angle spinning (MAS) NMR experiments. In 13C CP-MAS spectra an enhancement of 120 is observed for perdeuterated SH3 with an exchangeable proton ratio of 50 %, whereas the enhancement is only 31 for the fully protonated SH3. The direct 13C excitation of the perdeuterated sample increases the enhancement to 148
The information revolution, innovation diffusion and economic growth : an examination of causal links in European countries
Over the last 5 decades, the economic landscape in Europe has been transformed rapidly due to innovation, digitisation of the economy, and emergence of new sources of growth. However, the complex dynamics among diffusion of innovation, penetration of information and communication technology (ICT), and economic growth have not been adequately studied. This paper investigates the relationships among these three variables for European countries over 1961–2016. The goal is to determine whether the direction of causality among the variables runs both ways, one way, or not at all. Using a vector error-correction model, we find that in the long run, both innovation diffusion and ICT penetration stimulate economic growth. In the short run, however, the causal links are not always uniform and depend on proxies that are used for innovation diffusion and ICT penetration. The results provide valuable insights on the types of policies and strategies that would sustain economic growth in European economies.http://link.springer.com/journal/11135hj2020Financial Managemen
Finance and growth : evidence from the ARF countries
This paper examines the relationships between economic growth and four different types of financial
development in ASEAN Regional Forum (ARF) countries over the period 1991–2011. Using principal component
analysis (PCA) to construct development indices, and a panel vector auto-regressive model to test
for Granger causalities, the study demonstrates unidirectional and bidirectional causality between the
variables. The study enhances understanding of the interrelationship between the variables, combining
different strands of the literature, and investigating countries previously neglected in this context. The
paper recommends making banking more accessible to residents without bank accounts in ARF countries
and promoting stock market development to facilitate access to investment capital in order to enhance
economic growth.http:// www.elsevier.com/locate/qref2018-11-01hb2017Financial Managemen
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