Delta Ln Research Articles

Exercise intensity is associated with progression of coronary artery calcification in middle-aged and older athletes: findings from the MARC-2 study

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Dutch Heart Foundation Background Recent studies have reported increased coronary artery calcification (CAC) in middle-aged male athletes, which is related to the amount and intensity of lifelong exercise. However, previous studies are limited by their cross-sectional study design. Purpose We prospectively assessed progression of CAC and its association to exercise volume and intensity in middle-aged and older athletes. Methods 318 asymptomatic middle-aged and older men were recruited in the Measuring Athlete’s Risk of Cardiovascular events (MARC) study between 2012-2014 and invited for follow-up (MARC-2) between 2019-2020. During both study visits, computed tomography imaging was performed to assess CAC. Exercise characteristics during follow-up were used to calculate exercise volumes (Metabolic equivalent of task [MET]-hours/week), whereas intensities were classified as moderate (3-6 MET), vigorous (6-9 MET) and very vigorous (>9 MET). For linear regression analyses, CAC scores were transformed (Ln delta CAC score + 1) and analyses were adjusted for baseline confounders, CAC at baseline and time between CT scans. Exercise intensities were assessed as proportion of MET-hrs/week and separately included, while adjusting for exercise volume. Results We included 289 men (54.9 ± 6.4 years) for MARC-2, with a follow-up of 6.3 ± 0.5 years. Participants exercised for 41 [25-57] MET-hrs/week, of which the median percentage was 0% [interquartile range 0-19] at moderate, 44% [0-84] at vigorous and 34% [0-80] at very vigorous intensity. At baseline, CAC was present in 151 (52%) men, and increased to 205 (71%) men at follow-up. CAC scores increased from 1 [0-32] to 31 [0-132]. Delta CAC score (26 [0-104]) was not associated with overall exercise volume. However, delta CAC score was negatively associated with vigorous intensity exercise and positively associated with very vigorous intensity exercise (Table). Conclusion Progression of CAC was not associated with overall exercise volume during 6-year follow-up. However, the degree of vigorous intensity exercise was associated with attenuated CAC progression, whereas very vigorous intensity exercise was associated with accelerated CAC progression. Linear regression analyses Progression of CAC (Ln Delta CAC score +1) B (95% CI) P-Value Exercise volume (MET-hours/week) .001 (-.005 - .008) .70 Exercise Intensity Moderate intensity (%) -.002 (-.009 - .005) .65 Vigorous intensity (%) -.005 (-.009 - .000) .03 Very vigorous intensity (%) .005 (.001 - .009) .02

Sport specific incidence and progression of coronary artery calcification among amateur athletes: a follow-up of the Measuring Athletes Risk of Cardiovascular events (MARC) study

Abstract Background Emerging evidence indicates increased coronary atherosclerosis in amateur athletes. However, previous studies were limited by its cross-sectional design and limited sample size, preventing the exploration of sport specific associations with coronary atherosclerosis. Purpose We aimed to compare the incidence and progression of coronary artery calcification (CAC) between runners, cyclists and other types of athletes using a prospective cohort study with repetitive measurements. Methods Asymptomatic middle-aged men, who previously underwent a sports medical evaluation without abnormalities, were recruited in the Measuring Athlete's Risk of Cardiovascular events (MARC) study (n=318) and were asked to participate in this follow-up study. CT imaging was performed to assess CAC scores. Data was collected between 2012–2014 (i.e. baseline) and 2019–2020 (i.e. follow-up). We categorized participants as runners, cyclists or “other” sports (e.g. water polo, tennis, hockey, etc.) based on their dominant sport performance at baseline. Results We included 260 men in this interim analysis, with an average follow-up time of 6.3±0.5 years. Age (61.4±6.4 years), systolic blood pressure (143±20 mmHg), BMI (25.2±2.8 kg/m2), LDL-cholesterol (3.2±0.9 mmol/L), smoking (0.3 [0–8] pack years) and family history of coronary heart disease (28%) did not differ between runners (n=64), cyclists (n=75) and other athletes (n=121, all p>0.05). CAC was present in 137 (53%) men at baseline, which increased to 181 (70%) at follow-up. CAC scores increased from 1 [0–33] to 33 [0–129]. Cyclists had a lower CAC prevalence and CAC scores compared to individuals performing other sports at follow-up (Figure 1). Of those without CAC at baseline (n=123, 47%), cyclists less often developed CAC during follow-up compared with runners (adjusted OR=0.36 [0.17–0.79], p=0.01). In the entire cohort, CAC progression (ln delta CAC+1) was less prominent in cyclists than runners (adjusted B=−0.75 [−1.39 to −0.11], p=0.02), whereas progression of CAC in participants performing other sports did not differ from the runners. In participants with CAC at baseline, cyclists also had less CAC progression than runners (B=−0.49 [−0.95 to −0.02], p=0.04). Conclusion Cyclists have a lower incidence and less progression of CAC during 6 years of follow-up compared with runners and individuals performing other sports. Figure 1. Sport specific CAC prevalence and scores Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Hartstichting

Greed is Good for Deterministic Scale-Free Networks

Large real-world networks typically follow a power-law degree distribution. To study such networks, numerous random graph models have been proposed. However, real-world networks are not drawn at random. Therefore, Brach et al. (27th symposium on discrete algorithms (SODA), pp 1306–1325, 2016) introduced two natural deterministic conditions: (1) a power-law upper bound on the degree distribution (PLB-U) and (2) power-law neighborhoods, that is, the degree distribution of neighbors of each vertex is also upper bounded by a power law (PLB-N). They showed that many real-world networks satisfy both properties and exploit them to design faster algorithms for a number of classical graph problems. We complement their work by showing that some well-studied random graph models exhibit both of the mentioned PLB properties. PLB-U and PLB-N hold with high probability for Chung–Lu Random Graphs and Geometric Inhomogeneous Random Graphs and almost surely for Hyperbolic Random Graphs. As a consequence, all results of Brach et al. also hold with high probability or almost surely for those random graph classes. In the second part we study three classical textsf {NP}-hard optimization problems on PLB networks. It is known that on general graphs with maximum degree Delta, a greedy algorithm, which chooses nodes in the order of their degree, only achieves a Omega (ln Delta )-approximation for Minimum Vertex Cover and Minimum Dominating Set, and a Omega (Delta )-approximation for Maximum Independent Set. We prove that the PLB-U property with beta >2 suffices for the greedy approach to achieve a constant-factor approximation for all three problems. We also show that these problems are APX-hard even if PLB-U, PLB-N, and an additional power-law lower bound on the degree distribution hold. Hence, a PTAS cannot be expected unless P = NP. Furthermore, we prove that all three problems are in MAX SNP if the PLB-U property holds.

Upper bounds for adjacent vertex-distinguishing edge coloring

An adjacent vertex-distinguishing edge coloring of a graph is a proper edge coloring such that no pair of adjacent vertices meets the same set of colors. The adjacent vertex-distinguishing edge chromatic number is the minimum number of colors required for an adjacent vertex-distinguishing edge coloring, denoted as $$\chi '_{as}(G)$$ . In this paper, we prove that for a connected graph G with maximum degree $$\Delta \ge 3$$ , $$\chi '_{as}(G)\le 3\Delta -1$$ , which proves the previous upper bound. We also prove that for a graph G with maximum degree $$\Delta \ge 458$$ and minimum degree $$\delta \ge 8\sqrt{\Delta ln \Delta }$$ , $$\chi '_{as}(G)\le \Delta +1+5\sqrt{\Delta ln \Delta }$$ .

Spatial arrangement of collagen fibrils in normal and keratoconus human cornea studied by low‐frequency dielectric spectroscopy

AbstractPurpose Spatial structure of collagen lamellae of the human cornea is thought to be an important determinant of corneal rigidity. Analysis of the low‐frequency (1–107 Hz) dielectric spectra of the normal and keratoconus human cornea in the temperature range of 140‐300 K and for different hydration states were examined.Methods For the measurements, the 100 – 200 μm specimens containing the middle layers of corneal stroma were used. The 9 specimens of healthy, control corneas from Eye Bank were obtained with second microkeratom section during Ultra Thin‐DSAEK. The 12 specimens of keratoconus corneas were manually prepared from corneas removed during penetrating keratoplasty.Results Experimental results were interpreted in terms of ionic diffusion and space charge polarization according to the Sawada’s theory. The new presentation of the dielectric spectra, i.e.: (delta eps’/delta ln f)*f, was used. The presented method and the Sawada’s expression were applied to the analysis of the changes in spatial molecular structure of collagen fibril network in human cornea.Conclusion Fitting procedure of the theoretical function to the experimental data allowed us to determine two diffusive relaxation regions with two structural distance parameters ds, describing spatial arrangement of collagen fibrils in cornea.

A SENSITIVITY AND ARRAY-CONFIGURATION STUDY FOR MEASURING THE POWER SPECTRUM OF 21 cm EMISSION FROM REIONIZATION

Telescopes aiming to measure 21cm emission from the Epoch of Reionization must toe a careful line, balancing the need for raw sensitivity against the stringent calibration requirements for removing bright foregrounds. It is unclear what the optimal design is for achieving both of these goals. Via a pedagogical derivation of an interferometer's response to the power spectrum of 21cm reionization fluctuations, we show that even under optimistic scenarios, first-generation arrays will yield low-SNR detections, and that different compact array configurations can substantially alter sensitivity. We explore the sensitivity gains of array configurations that yield high redundancy in the uv-plane -- configurations that have been largely ignored since the advent of self-calibration for high-dynamic-range imaging. We first introduce a mathematical framework to generate optimal minimum-redundancy configurations for imaging. We contrast the sensitivity of such configurations with high-redundancy configurations, finding that high-redundancy configurations can improve power-spectrum sensitivity by more than an order of magnitude. We explore how high-redundancy array configurations can be tuned to various angular scales, enabling array sensitivity to be directed away from regions of the uv-plane (such as the origin) where foregrounds are brighter and where instrumental systematics are more problematic. We demonstrate that a 132-antenna deployment of the Precision Array for Probing the Epoch of Reionization (PAPER) observing for 120 days in a high-redundancy configuration will, under ideal conditions, have the requisite sensitivity to detect the power spectrum of the 21cm signal from reionization at a 3\sigma level at k<0.25h Mpc^{-1} in a bin of \Delta ln k=1. We discuss the tradeoffs of low- versus high-redundancy configurations.

Non-Gaussianity from step features in the inflationary potential

We provide analytic solutions for the power spectrum and bispectrum of curvature fluctuations produced by a step feature in the inflaton potential, valid in the limit that the step is short and sharp. In this limit, the bispectrum is strongly scale dependent and its effective non-linearity attains a large oscillatory amplitude. The perturbations to the curvature power spectrum, on the other hand, remain a small component on top of the usual spectrum of fluctuations generated by slow roll. We utilize our analytic solutions to assess the observability of the predicted non-Gaussian signatures and show that, if present, only very sharp steps on scales larger than ~ 2 Gpc are likely to be able to be detected by Planck. Such features are not only consistent with WMAP7 data, but can also improve its likelihood by 2 Delta ln L ~ 12 for two extra parameters, the step location and height. If this improvement were due to a slow roll violating step as considered here, a bispectrum or corresponding polarization power spectrum detection would provide definitive checks as to its primordial origin.

INCREASING EVIDENCE FOR HEMISPHERICAL POWER ASYMMETRY IN THE FIVE-YEARWMAPDATA

(Abridged)Motivated by the recent results of Hansen et al. (2008) concerning a noticeable hemispherical power asymmetry in the WMAP data on small angular scales, we revisit the dipole modulated signal model introduced by Gordon et al. (2005). This model assumes that the true CMB signal consists of a Gaussian isotropic random field modulated by a dipole, and is characterized by an overall modulation amplitude, A, and a preferred direction, p. Previous analyses of this model has been restricted to very low resolution due to computational cost. In this paper, we double the angular resolution, and compute the full corresponding posterior distribution for the 5-year WMAP data. The results from our analysis are the following: The best-fit modulation amplitude for l <= 64 and the ILC data with the WMAP KQ85 sky cut is A=0.072 +/- 0.022, non-zero at 3.3sigma, and the preferred direction points toward Galactic coordinates (l,b) = (224 degree, -22 degree) +/- 24 degree. The corresponding results for l <~ 40 from earlier analyses was A = 0.11 +/- 0.04 and (l,b) = (225 degree,-27 degree). The statistical significance of a non-zero amplitude thus increases from 2.8sigma to 3.3sigma when increasing l_max from 40 to 64, and all results are consistent to within 1sigma. Similarly, the Bayesian log-evidence difference with respect to the isotropic model increases from Delta ln E = 1.8 to Delta ln E = 2.6, ranking as "strong evidence" on the Jeffreys' scale. The raw best-fit log-likelihood difference increases from Delta ln L = 6.1 to Delta ln L = 7.3. Similar, and often slightly stronger, results are found for other data combinations. Thus, we find that the evidence for a dipole power distribution in the WMAP data increases with l in the 5-year WMAP data set, in agreement with the reports of Hansen et al. (2008).

Stacking clusters in the ROSAT All-Sky Survey

Ongoing and planned wide-area surveys at optical and infrared wavelengths should detect a few times 10^5 galaxy clusters, roughly 10% of which are expected to be at redshifts >~ 0.8. We investigate what can be learned about the X-ray emission of these clusters from the ROSAT All-Sky Survey. While individual clusters at redshifts >~ 0.5 contribute at most a few photons to the survey, a significant measurement of the mean flux of cluster subsamples can be obtained by stacking cluster fields. We show that the mean X-ray luminosity of clusters with mass M >~ 2 x 10^{14} M_sun/h selected from the Sloan Digital Sky Survey should be measurable out to redshift unity with signal-to-noise >~ 10, even if clusters are binned with Delta z=0.1 and Delta ln M ~ 0.3. For such bins, suitably chosen hardness ratio allows the mean temperature of clusters to be determined out to z ~ 0.7 with a relative accuracy of Delta T/T 10^{14} M_sun/h.

Extension of the pole decomposition for the multidimensional Burgers equation

It is shown that the generalizations to more than one space dimension of the pole decomposition for the Burgers equation with finite viscosity nu and no force are of the form u=-2nu inverted Delta ln P, where the P's are explicitly known algebraic (or trigonometric) polynomials in the space variables with polynomial (or exponential) dependence on time. Such solutions have pole singularities on the complex algebraic varieties.

Effects of high pressure on glucose transport in the human erythrocyte.

The effects of raised hydraulic pressure on D-glucose exit from human red cells at 25 degrees C were determined using light scattering measurements in a sealed pressurized spectrofluorimeter cuvette. The reduction in the rates of glucose exit with raised pressure provides an index of the activation volume, deltaV++ (delta ln k/deltaP)(T) = -deltaV++/RT. Raised pressure decreased the rate constant of glucose exit from 0.077 +/- 0.003 s(-1) to 0.050 +/- 0.002 s(-1) (n = 5, P < 0.003). The Ki for glucose binding to the external site was 2.7 +/- 0.4 mm (0.1 MPa) and was reduced to 1.45 +/- 0.15 mm (40 MPa), (P < 0.01, Student's t test). Maltose had a biphasic effect on deltaV++. At [maltose] <250 microM, deltaV++ of glucose exit increased above that with [maltose = 0 mM], at >1 mm maltose, deltaV++ was reduced below that with [maltose = 0 mM]. Pentobarbital (2 mM) decreased the deltaV++ of net glucose exit into glucose-free solution from 30 +/- 5 ml mol(-1) (control) to 2 +/- 0.5 ml mol(-1) (P < 0.01). Raised pressure had a negligible effect on L-sorbose exit. These findings suggest that stable hydrated and liganded forms of GLUT with lower affinity towards glucose permit higher glucose mobilities across the transporter and are modelled equally well with one-alternating or a two-fixed-site kinetic models.

The volume dependence of the magnetization and NMR of Fe4N and Mn4N

The forced volume magnetostriction and the NMR of ferromagnetic FeN and ferrimagnetic Mn4N have been measured in the ordered state. At 4.2 K the magnetization ( sigma ) per unit mass and the effective field (HI) at the nucleus of the Fe(I) site of Fe4N are found to change with pressure such that delta ln sigma / delta P approximately= delta ln mod HI mod / delta P<0, while for Mn4N delta ln sigma / delta P approximately=6 delta ln mod HI mod / delta P>0. The result for Mn4N is interpreted as showing that the magnitude of the small (negative) moment on the Mn(II) site decreases more rapidly under pressure than does the large Mn(I) moment. The value of delta ln mod HI mod / delta P for Mn4N was found to be a strong function of temperature such that delta lnTN/ delta P approximately=5.2 Mbar-1. An analysis of the Mn4N NMR data suggests that the discrepancy between the calculated (spin) and measured moment at the Mn(I) site may be due to a small orbital moment at that site.

Subepicardial fiber strain and stress as related to left ventricular pressure and volume.

In a mathematical model of the mechanics of the left ventricle (LV) by Arts et al. (1), assuming uniformity of fiber stress (sigma f) and fiber strain (delta epsilon f) in the wall during the ejection phase, fiber stress and fiber strain were related to LV cavity pressure (Plv), LV cavity volume (Vlv) and wall volume (Vw) by the following pair of equations: sigma f = Plv (1 + 3 Vlv/Vw) and delta epsilon f = 1/3 delta ln (1 + 3 Vlv/Vw). The ratio of Vlv to Vw appeared to be the most important geometric parameter, whereas the actual LV shape was of minor importance. The relationships on fiber strain and stress were evaluated experimentally in six anesthetized open-chest dogs during normal and elevated (volume loading) end-diastolic LV pressure. Subepicardial fiber strain was measured simultaneously in 16 adjacent regions of the LV anterior wall, using optical markers that were attached to the epicardial surface and recorded on video. Changes in Vlv were measured by use of four inductive coils sutured to the LV in a tetrahedric configuration. Vw was measured postmortem. During control as well as hypervolemia the following results were found. At the anterior free wall of the LV, the slope of the estimated linear relationship between measured and calculated fiber strain was 1.017 +/- 0.168 (means +/- SD), which is not significantly different from unity. Calculated fiber stress corresponded qualitatively and quantitatively with experimental results reported on isolated cardiac muscle. Calculated subepicardial contractile work per unit of tissue volume was not significantly different from global pump work as normalized to Vw. These findings support the assumption of homogeneity of muscle fiber strain and stress in the left ventricular wall during the ejection phase. Furthermore, average values of fiber stress and strain can be estimated on the basis of measured left ventricular pressure and volume.

Algorithms for Computing Operating Characteristic and Average Sample Number Functions for Sequential Sampling Plans Based on Binomial Count Models and Revised Plans for European Red Mite (Acari: Tetranychidae) on Apple

Algorithms and computer code (Fortran 77) were developed for computing operating characteristic (OC) and average sample number (ASN) functions for sequential classification sampling plans based on presence-absence counts. Two models that relate the proportion of sample units with more than T (tally threshold) organisms (p(T)) to mean density (m) were considered; an empirical model of the form ln(-ln(1-p(T))) = gamma + delta ln(m) where m is the mean density, and the negative binomial distribution (NBD). The algorithms compute OC and ASN for nominal model parameters and for model parameters used to characterize the effect of p(t) -- m model variability on the OC and ASN functions. Changes in the OC and ASN functions as a result of change in the p(T) -- m model are a measure of the robustness of the sampling procedure. Both p(T) -- m models provided good descriptions of counts of European red mite (Panonychus ulmi (Koch), on apple trees, Malus domestica (Borkh). The robustness of sampling plans that used T = 0 was poor. Expected OC and ASN functions for sampling plans based on the two p(T) -- m models were similar. Robustness of sampling plans based on NBD improved significantly with larger values of T. When sampling using thresholds of 2.5, 5.0, and 7.5 mites per leaf, recommended values of T are 4, 6, and 6, respectively

Thermal conductivity and heat capacity of amorphous SiO2: pressure and volume dependence

The thermal conductivity ( lambda ) and heat capacity per unit volume ( rho cp) of amorphous SiO2 have been measured under hydrostatic pressure up to 1 GPa at room temperature using a transient two-strip method. The thermal conductivity was found to decrease slightly with increasing pressure. For the volume dependence of lambda expressed by the Bridgman parameter, g=-( delta ln lambda / delta ln V)T, the authors obtained g=-1.5. The experimental value of g is discussed in conjunction with predicted g-values based on theoretical models of lambda (T). The specific heat capacity (cp) calculated from measured rho cp was found to be almost constant with increasing pressure.

Experimental study of an ion-temperature-gradient driven instability in a linear machine

An ion-temperature-gradient driven instability is investigated in the Columbia Linear Machine (CLM). A transit-time RF technique is used to heat the core of the plasma column. This produces the peaked ion temperature profile with the parameter eta i= delta ln Ti/ delta ln n exceeding the critical value ( approximately 1.4) required for onset of the instability. Along with the peaked temperature profile, a new feature in the density fluctuation spectrum is observed. This mode has an azimuthal mode number m=2 and propagates in the ion diamagnetic drift direction. It is identified as an eta i mode. The mode is similar to the one studied previously in the CLM using DC biased meshes for heating the ions.

Pressure dependence of the electric field gradient at the 63Cu nucleus of Cu2O and CuO; implications for the analysis of NQR measurements on high Tc superconductors

The electric field gradient (EFG) at the 63Cu nucleus of Cu2O and CuO has been measured as a function of pressure using the nuclear quadrupole resonance frequency (vQ). The value of ( delta ln vQ/ delta P)T was 1.40+or-0.02(1.33+or-0.05) Mbar-1 for Cu2O at 295 (77) K and 5.4+or-0.1 Mbar-1 for CuO at 295 K. The value of ( delta ln vQ/ delta ln V) for Cu2O is -1.5, showing that Cu2O is not a purely ionic compound, as is often assumed in the analysis of the EFG of high Tc superconductors. The magnitude of ( delta ln vQ/ delta P) tau for 63Cu in CuO suggests that meaningful measurements of the pressure dependence of vQ in the high Tc superconductors can be made at easily accessible pressures.

Comparison between conventional flux creep in constant magnetic field and the effect of creep on the shape of magnetic hysteresis loops in high-Tc superconductors

The effect of the magnetic induction sweep rate B= delta Bext/ delta t on the shape of magnetic hysteresis loops, in particular on the induced magnetic moment m ( implies/implied by critical current jc) was calculated directly from the basic mechanism of thermally activated flux creep introduced by Anderson taking jc constant through the sample. It was found (a) that m changes linearly with ln mod B mod , and (b) that delta m/ delta ln mod B mod is equal to - delta m/ delta ln t in conventional relaxation at Bext=constant. Similar results were obtained recently from a phenomenological model using differential susceptibility chi to characterize the effect of sweeping Bext.

Volume magnetostriction and pressure dependence of the Curie point and spontaneous magnetization of weakly ferromagnetic Y(Co1-xAlx)2

The pressure dependence of the Curie point of weakly ferromagnetic Y(Co1-xAlx)2 alloys for x approximately 0.15 has been measured at pressures up to 8 kbar. The pressure dependence of the spontaneous magnetization per unit mass at 0 K ( sigma 0) has been deduced for the same alloys from measurements of the forced volume magnetostriction in fields up to 12 T. It was found that ( delta ln Tc/ delta ln V)=( delta ln sigma 0/ delta P)=120+or-17, one of the largest values known for a ferromagnetic material. The critical pressure for the collapse of ferromagnetism is approximately 9+or-1 kbar for 0.14<x<0.18, while the chemical pressure exerted by the Al in Y(Co0.85Al0.15)2 is approximately -40 kbar, so weak ferromagnetism would not be possible in this Y-Co-Al system if the material was clamped to the volume of YCo2.

Thermal conductivity and heat capacity of single-crystal LiF and CaF2under hydrostatic pressure

The thermal conductivity, lambda , and heat capacity per unit volume, rho cp, have been measured under hydrostatic pressure up to 1 GPa at room temperature, using a dynamic two-strip method. The standard deviation of lambda and rho cp was always better than 0.2%. The volume dependence of lambda expressed in terms of the Bridgman parameter, -( delta ln lambda / delta ln V)T, was found to be 7.9 for LiF and 9.2 for CaF2. The specific heat capacity, cp, calculated from the measured rho cp, was found to decrease slightly with increasing pressure.