596 research outputs found
Critical Scale-invariance in Healthy Human Heart Rate
We demonstrate the robust scale-invariance in the probability density
function (PDF) of detrended healthy human heart rate increments, which is
preserved not only in a quiescent condition, but also in a dynamic state where
the mean level of heart rate is dramatically changing. This scale-independent
and fractal structure is markedly different from the scale-dependent PDF
evolution observed in a turbulent-like, cascade heart rate model. These results
strongly support the view that healthy human heart rate is controlled to
converge continually to a critical state.Comment: 9 pages, 3 figures. Phys. Rev. Lett., to appear (2004
Review of Engaging Education: Developing Emotional Literacy, Equity and Co-education. Brian Matthews. (Book Review)
The book is only about a fraction of its title Engaging Education. His section on ‘engaging the emotions’ sums this up: whereas the book is largely about engaging the emotions positively, the definition of ‘Engaging’ is more far reaching: “that pupils should be involved in their learning; be active and absorbed and not just passive recipients of a set curriculum. Additionally, they should feel engaged in the processes of education and have some input into creating their own agendas for learning” (p.2). Exploring the full impact of this statement across the curriculum really needs a different book
Ab Initio Study of Screw Dislocations in Mo and Ta: A new picture of plasticity in bcc transition metals
We report the first ab initio density-functional study of screw
dislocations cores in the bcc transition metals Mo and Ta. Our results suggest
a new picture of bcc plasticity with symmetric and compact dislocation cores,
contrary to the presently accepted picture based on continuum and interatomic
potentials. Core energy scales in this new picture are in much better agreement
with the Peierls energy barriers to dislocation motion suggested by
experiments.Comment: 3 figures, 3 table
Growing Environmental Activists: Developing Environmental Agency and Engagement Through Children’s Fiction.
We explore how story has the potential to encourage environmental engagement and a sense of agency provided that critical discussion takes place. We illuminate this with reference to the philosophies of John Macmurray on personal agency and social relations; of John Dewey on the primacy of experience for philosophy; and of Paul Ricoeur on hermeneutics, dialogue, dialectics and narrative. We view the use of fiction for environmental understanding as hermeneutic, a form of conceptualising place which interprets experience and perception. The four writers for young people discussed are Ernest Thompson Seton, Kenneth Grahame, Michelle Paver and Philip Pullman. We develop the concept of critical dialogue, and link this to Crick's demand for active democratic citizenship. We illustrate the educational potential for environmental discussions based on literature leading to deeper understanding of place and environment, encouraging the belief in young people that they can be and become agents for change. We develop from Zimbardo the key concept of heroic resister to encourage young people to overcome peer pressure. We conclude with a call to develop a greater awareness of the potential of fiction for learning, and for writers to produce more focused stories engaging with environmental responsibility and activism
Targeting the MAPK7/MMP9 axis for metastasis in primary bone cancer
Metastasis is the leading cause of cancer-related death. This multistage process involves contribution from both tumour cells and the tumour stroma to release metastatic cells into the circulation. Circulating tumour cells (CTCs) survive circulatory cytotoxicity, extravasate and colonise secondary sites effecting metastatic outcome. Reprogramming the transcriptomic landscape is a metastatic hallmark, but detecting underlying master regulators that drive pathological gene expression is a key challenge, especially in childhood cancer. Here we used whole tumour plus single-cell RNA-sequencing in primary bone cancer and CTCs to perform weighted gene co-expression network analysis to systematically detect coordinated changes in metastatic transcript expression. This approach with comparisons applied to data collected from cell line models, clinical samples and xenograft mouse models revealed mitogen-activated protein kinase 7/matrix metallopeptidase 9 (MAPK7/MMP9) signalling as a driver for primary bone cancer metastasis. RNA interference knockdown of MAPK7 reduces proliferation, colony formation, migration, tumour growth, macrophage residency/polarisation and lung metastasis. Parallel to these observations were reduction of activated interleukins IL1B, IL6, IL8 plus mesenchymal markers VIM and VEGF in response to MAPK7 loss. Our results implicate a newly discovered, multidimensional MAPK7/MMP9 signalling hub in primary bone cancer metastasis that is clinically actionable
Effects of antidepressant treatment on heart rate variability in major depression: A quantitative review
<p>Abstract</p> <p>Background</p> <p>The literature measuring effects of antidepressant and electroconvulsive therapy (ECT) for major depression on heart rate variability (HRV) in medically well individuals was reviewed.</p> <p>Methods</p> <p>Fourteen studies evaluating HRV were included. Twenty three pre-post or within group comparisons were available. Treatment impact on measures of HRV was pooled over studies. We examined different classes of antidepressants, and for short and long electrocardiogram (ECG) recordings separately.</p> <p>Results</p> <p>Tricyclic antidepressants (TCAs) were associated with declines in most measures of HRV and significant increase in heart rate (HR) in studies with short recording intervals. No significant changes were found for longer recording times.</p> <p>Treatment effects with selective serotonin reuptake inhibitors (SSRIs) were more variable. Short-recording studies revealed a significant decrease in HR and an increase in one HRV measure. In two 24-hour recording studies no significant changes were observed. No relationship between ECT and HRV has been established in the literature. The effects of other drugs are reported.</p> <p>Limitations</p> <p>Few studies measure the effects of treatment of depression on HRV. Existing studies have generally used very small samples, employing a variety of measurements and methodologies.</p> <p>Conclusion</p> <p>We confirm that TCAs are associated with a large decrease in HRV and increase HR. However, data for SSRIs is not clear. Although the effect of SSRIs on HRV is weaker than for TCAs, evidence shows that SSRIs are associated with a small decrease in HR, and an increase in one measure of HRV. The use of TCAs in depression leads to changes in HRV that are associated with increased risk of mortality.</p
A stochastic model for heart rate fluctuations
Normal human heart rate shows complex fluctuations in time, which is natural,
since heart rate is controlled by a large number of different feedback control
loops. These unpredictable fluctuations have been shown to display fractal
dynamics, long-term correlations, and 1/f noise. These characterizations are
statistical and they have been widely studied and used, but much less is known
about the detailed time evolution (dynamics) of the heart rate control
mechanism. Here we show that a simple one-dimensional Langevin-type stochastic
difference equation can accurately model the heart rate fluctuations in a time
scale from minutes to hours. The model consists of a deterministic nonlinear
part and a stochastic part typical to Gaussian noise, and both parts can be
directly determined from the measured heart rate data. Studies of 27 healthy
subjects reveal that in most cases the deterministic part has a form typically
seen in bistable systems: there are two stable fixed points and one unstable
one.Comment: 8 pages in PDF, Revtex style. Added more dat
Atomic structure of dislocation kinks in silicon
We investigate the physics of the core reconstruction and associated
structural excitations (reconstruction defects and kinks) of dislocations in
silicon, using a linear-scaling density-matrix technique. The two predominant
dislocations (the 90-degree and 30-degree partials) are examined, focusing for
the 90-degree case on the single-period core reconstruction. In both cases, we
observe strongly reconstructed bonds at the dislocation cores, as suggested in
previous studies. As a consequence, relatively low formation energies and high
migration barriers are generally associated with reconstructed
(dangling-bond-free) kinks. Complexes formed of a kink plus a reconstruction
defect are found to be strongly bound in the 30-degree partial, while the
opposite is true in the case of 90-degree partial, where such complexes are
found to be only marginally stable at zero temperature with very low
dissociation barriers. For the 30-degree partial, our calculated formation
energies and migration barriers of kinks are seen to compare favorably with
experiment. Our results for the kink energies on the 90-degree partial are
consistent with a recently proposed alternative double-period structure for the
core of this dislocation.Comment: 12 pages, two-column style with 8 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#rn_di
Paramagnetic structure for the soliton of the partial dislocation in silicon
Based on ab initio calculation, we propose a new structure for the
fundamental excitation of the reconstructed 30 partial dislocation in
silicon. This soliton has a rare structure involving a five-fold coordinated
atom near the dislocation core. The unique electronic structure of this defect
is consistent with the electron spin resonance signature of the hitherto
enigmatic thermally stable R center of plastically deformed silicon. This
identification suggests the possibility of an experimental determination of the
density of solitons, a key defect in understanding the plastic flow of the
material.Comment: 5 pages, 4 figure
Focal Distribution of Hepatitis C Virus RNA in Infected Livers
Background: Hepatitis C virus (HCV) is a plus-strand RNA virus that replicates by amplification of genomic RNA from minus strands leading to accumulation of almost one thousand copies per cell under in vitro cell culture conditions. In contrast, HCV RNA copy numbers in livers of infected patients appear to be much lower, estimated at a few copies per cell. Methodology/Principal Findings: To gain insights into mechanisms that control HCV replication in vivo, we analyzed HCV RNA levels as well as expression of interferon beta (IFNb) and several interferon stimulated genes (ISGs) from whole liver sections and micro-dissected subpopulations of hepatocytes in biopsy samples from 21 HCV-infected patients. The results showed that intrahepatic HCV RNA levels range form less than one copy per hepatocyte to a maximum of about eight. A correlation existed between viral RNA levels and IFNb expression, but not between viral RNA and ISG levels. Also, IFNb expression did not correlate with ISGs levels. Replication of HCV RNA occurred in focal areas in the liver in the presence of a general induction of ISGs. Conclusion/Significance: The low average levels of HCV RNA in biopsy samples can be explained by focal distribution of infected hepatocytes. HCV replication directly induces IFNb, which then activates ISGs. The apparent lack of a correlation between levels of IFNb and ISG expression indicates that control of the innate immune response during HCV infection
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