345 research outputs found
Aging dynamics in interacting many-body systems
Low-dimensional, complex systems are often characterized by logarithmically
slow dynamics. We study the generic motion of a labeled particle in an ensemble
of identical diffusing particles with hardcore interactions in a strongly
disordered, one-dimensional environment. Each particle in this single file is
trapped for a random waiting time with power law distribution
, such that the values are
independent, local quantities for all particles. From scaling arguments and
simulations, we find that for the scale-free waiting time case ,
the tracer particle dynamics is ultra-slow with a logarithmic mean square
displacement (MSD) . This extreme
slowing down compared to regular single file motion is due to the high likelihood that the labeled
particle keeps encountering strongly immobilized neighbors. For the case
we observe the MSD scaling , where we recover Harris law
.Comment: 5 pages, 4 figure
project: III. Gas mass fraction shape in high redshift clusters
We study the gas mass fraction, behavior in
project. The typical shape of high redshift galaxy
clusters follows the global shape inferred at low redshift quite well. This
result is consistent with the gravitational instability picture leading to self
similar structures for both the dark and baryonic matter. However, the mean
XMM$ clusters, the apparent gas
fraction at the virial radius is consistent with a non-evolving universal value
in a high matter density model and not with a concordance.Comment: Accepted, A&A, in pres
The entropy and energy of intergalactic gas in galaxy clusters
Studies of the X-ray surface brightness profiles of clusters, coupled with
theoretical considerations, suggest that the breaking of self-similarity in the
hot gas results from an `entropy floor', established by some heating process,
which affects the structure of the intracluster gas strongly in lower mass
systems. Fitting analytical models for the radial variation in gas density and
temperature to X-ray spectral images from the ROSAT PSPC and ASCA GIS, we
derive gas entropy profiles for 20 galaxy clusters and groups. Scaling these
profiles to coincide in the self-similar case, the lowest mass systems are
found to have higher scaled entropy profiles than more massive systems. This
appears to be due to a baseline entropy of 70-140 h50^-1/3 keV cm^2, depending
on the extent to which shocks have been suppressed in low mass systems. The
extra entropy may be present in all systems, but is detectable only in poor
clusters, compared to the entropy generated by gravitational collapse. This
excess entropy appears to be distributed uniformly with radius outside the
central cooling regions. We determine the energy associated with this entropy
floor, by studying the net reduction in binding energy of the gas in low mass
systems, and find that it corresponds to a preheating temperature of ~0.3 keV.
Since the relationship between entropy and energy injection depends upon gas
density, we can combine the excesses of 70-140 keV cm^2 and 0.3 keV to derive
the typical electron density of the gas into which the energy was injected. The
resulting value of 1-3x10^-4 h50^1/2 cm-3, implies that the heating must have
happened prior to cluster collapse but after a redshift z~7-10. The energy
requirement is well matched to the energy from supernova explosions responsible
for the metals which now pollute the intracluster gas.Comment: 15 pages, 10 figures, accepted for publication in MNRA
Evidence and Ideology in Macroeconomics: The Case of Investment Cycles
The paper reports the principal findings of a long term research project on the description and explanation of business cycles. The research strongly confirmed the older view that business cycles have large systematic components that take the form of investment cycles. These quasi-periodic movements can be represented as low order, stochastic, dynamic processes with complex eigenvalues. Specifically, there is a fixed investment cycle of about 8 years and an inventory cycle of about 4 years. Maximum entropy spectral analysis was employed for the description of the cycles and continuous time econometrics for the explanatory models. The central explanatory mechanism is the second order accelerator, which incorporates adjustment costs both in relation to the capital stock and the rate of investment. By means of parametric resonance it was possible to show, both theoretically and empirically how cycles aggregate from the micro to the macro level. The same mathematical tool was also used to explain the international convergence of cycles. I argue that the theory of investment cycles was abandoned for ideological, not for evidential reasons. Methodological issues are also discussed
Mitochondrial Physiology and Gene Expression Analyses Reveal Metabolic and Translational Dysregulation in Oocyte-Induced Somatic Nuclear Reprogramming
While reprogramming a foreign nucleus after somatic cell nuclear transfer (SCNT), the enucleated oocyte (ooplasm) must signal that biomass and cellular requirements changed compared to the nucleus donor cell. Using cells expressing nuclear-encoded but mitochondria-targeted EGFP, a strategy was developed to directly distinguish maternal and embryonic products, testing ooplasm demands on transcriptional and post-transcriptional activity during reprogramming. Specifically, we compared transcript and protein levels for EGFP and other products in pre-implantation SCNT embryos, side-by-side to fertilized controls (embryos produced from the same oocyte pool, by intracytoplasmic injection of sperm containing the EGFP transgene). We observed that while EGFP transcript abundance is not different, protein levels are significantly lower in SCNT compared to fertilized blastocysts. This was not observed for Gapdh and Actb, whose protein reflected mRNA. This transcript-protein relationship indicates that the somatic nucleus can keep up with ooplasm transcript demands, whilst transcription and translation mismatch occurs after SCNT for certain mRNAs. We further detected metabolic disturbances after SCNT, suggesting a place among forces regulating post-transcriptional changes during reprogramming. Our observations ascribe oocyte-induced reprogramming with previously unsuspected regulatory dimensions, in that presence of functional proteins may no longer be inferred from mRNA, but rather depend on post-transcriptional regulation possibly modulated through metabolism
High school drinking mediates the relationship between parental monitoring and college drinking: A longitudinal analysis
<p>Abstract</p> <p>Background</p> <p>College drinking is a significant public health problem. Although parental monitoring and supervision reduces the risk for alcohol consumption among younger adolescents, few studies have investigated the impact of earlier parental monitoring on later college drinking. This study examined whether parental monitoring indirectly exerts a protective effect on college drinking by reducing high school alcohol consumption.</p> <p>Methods</p> <p>A longitudinal cohort of 1,253 male and female students, ages 17 to 19, attending a large, public, mid-Atlantic university was studied at two time points. First, data on high school parental monitoring and alcohol consumption were gathered via questionnaire during the summer prior to college entry. Second, during the first year of college, past-year alcohol consumption was measured via a personal interview. Multiple regression models tested the relationship between parental monitoring and past year alcohol use (i.e., number of drinks per drinking day).</p> <p>Results</p> <p>Holding constant demographics, SAT score, and religiosity, parental monitoring had a significant protective effect on both high school and college drinking level. However, the association between parental monitoring and college drinking level became non-significant once high school drinking level was held constant.</p> <p>Conclusion</p> <p>While parental monitoring did not directly influence college alcohol consumption, evidence for mediation was observed, whereby parental monitoring had an indirect influence on college drinking through reductions in high school drinking. Initiatives that promote effective parenting might be an important strategy to curb high-risk drinking among older adolescents. More research is needed to understand the nature and degree of parent-child communication that is necessary to extend the protective influence of parents into the college years.</p
Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018.
Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field
Development and validation of HERWIG 7 tunes from CMS underlying-event measurements
This paper presents new sets of parameters (âtunesâ) for the underlying-event model of the HERWIG7 event generator. These parameters control the description of multiple-parton interactions (MPI) and colour reconnection in HERWIG7, and are obtained from a fit to minimum-bias data collected by the CMS experiment at s=0.9, 7, and 13Te. The tunes are based on the NNPDF 3.1 next-to-next-to-leading-order parton distribution function (PDF) set for the parton shower, and either a leading-order or next-to-next-to-leading-order PDF set for the simulation of MPI and the beam remnants. Predictions utilizing the tunes are produced for event shape observables in electron-positron collisions, and for minimum-bias, inclusive jet, top quark pair, and Z and W boson events in proton-proton collisions, and are compared with data. Each of the new tunes describes the data at a reasonable level, and the tunes using a leading-order PDF for the simulation of MPI provide the best description of the dat
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