Heterogeneity in susceptibility dictates the order of epidemiological models

The fundamental models of epidemiology describe the progression of an infectious disease through a population using compartmentalized differential equations, but do not incorporate population-level heterogeneity in infection susceptibility. We show that variation strongly influences the rate of infection, while the infection process simultaneously sculpts the susceptibility distribution. These joint dynamics influence the force of infection and are, in turn, influenced by the shape of the initial variability. Intriguingly, we find that certain susceptibility distributions (the exponential and the gamma) are unchanged through the course of the outbreak, and lead naturally to power-law behavior in the force of infection; other distributions often tend towards these "eigen-distributions" through the process of contagion. The power-law behavior fundamentally alters predictions of the long-term infection rate, and suggests that first-order epidemic models that are parameterized in the exponential-like phase may systematically and significantly over-estimate the final severity of the outbreak

Low-emissivity impact craters on Venus

An analysis of 144 impact craters on Venus has shown that 11 of these have floors with average emissivities lower than 0.8. The remaining craters have emissivities between 0.8 and 0.9, independent of the specific backscatter cross section of the crater floors. These 144 impact craters were chosen from a possible 164 craters with diameters greater than 30 km as identified by researchers for 89 percent of the surface of Venus. We have only looked at craters below 6053.5 km altitude because a mineralogical change causes high reflectivity/low emissivity above the altitude. We have also excluded all craters with diameters smaller than 30 km because the emissivity footprint at periapsis is 16 x 24 km and becomes larger at the poles

Influence of two different resection techniques (conventional liver resection versus anterior approach) of liver metastases from colorectal cancer on hematogenous tumor cell dissemination – prospective randomized multicenter trial

<p>Abstract</p> <p>Background</p> <p>Surgical hepatic resection remains the treatment of choice for patients with liver metastases from colorectal cancer despite the use of alternative therapeutic strategies. Although this procedure provides long-term survival in a significant number of patients, 50–75% of the patients develop intra- and/or extrahepatic recurrence. One possible reason for tumor recurrence may be intraoperative hematogenous tumor cell dissemination due to mechanical manipulation of the tumor during hepatic resection. Surgical technique may have an influence on hematogenous tumor cell spread. We hypothesize that hematogenous tumor cell dissemination may be reduced by using the anterior approach technique compared to conventional liver resection.</p> <p>Methods/Design</p> <p>This is a multi-centre prospective randomized controlled, superiority trial to compare two liver resection techniques of liver metastases from colorectal cancer. 150 patients will be included and randomized intraoperatively after surgical exploration just prior to resection. The primary objective is to compare the anterior approach with the conventional liver resection technique with regard to intraoperative haematogenous tumor cell dissemination. As secondary objectives we examine five year survival rates (OS and DFS), blood loss, duration of operation, requirement of blood transfusions, morbidity rate, prognostic relevance of tumor cell detection in blood and bone marrow and the comparison of tumor cell detection by different detection methods.</p> <p>Conclusion</p> <p>This trial will answer the question whether there is an advantage for the anterior approach technique compared to the conventional resection group with regard to tumor cell dissemination. It will also add further information about prognostic differences, safety, advantages and disadvantages of each technique.</p> <p>Trial registration</p> <p>Current controlled trials – <b>ISRCTN45066244</b></p

Microrheology probes length scale dependent rheology

We exploit the power of microrheology to measure the viscoelasticity of entangled F-actin solutions at different length scales from 1 to 100 mu m over a wide frequency range. We compare the behavior of single probe-particle motion to that of the correlated motion of two particles. By varying the average length of the filaments, we identify fluctuations that dissipate diffusively over the filament length. These provide an important relaxation mechanism of the elasticity between 0.1 and 30 rad/sec

X-ray dark-field tomography reveals tooth cracks

Abstract Cracked tooth syndrome (CTS) is a common clinical finding for teeth, it affects about 5% of all adults each year. The finding of CTS is favored by several risk factors such as restorations, bruxism, occlusion habits, and age. Treatment options range, depending on the severity, from no treatment at all to tooth extraction. Early diagnosis of CTS is crucial for optimal treatment and symptom reduction. There is no standard procedure for an evidence-based diagnosis up to date. The diagnosis is a challenge by the fact that the symptoms, including pain and sensitivity to temperature stimuli, cannot be clearly linked to the disease. Commonly used visual inspection does not provide in-depth information and is limited by the resolution of human eyes. This can be overcome by magnifying optics or contrast enhancers, but the diagnosis will still strongly rely on the practicians experience. Other methods are symptom reproduction with percussions, thermal pulp tests or bite tests. Dental X-ray radiography, as well as computed tomography, rarely detect cracks as they are limited in resolution. Here, we investigate X-ray dark-field tomography (XDT) for the detection of tooth microcracks. XDT simultaneously detects X-ray small-angle scattering (SAXS) in addition to the attenuation, whereas it is most sensitive to the micrometer regime. Since SAXS originates from gradients in electron density, the signal is sensitive to the sample morphology. Microcracks create manifold interfaces which lead to a strong signal. Therefore, it is possible to detect structural changes originating from subpixel-sized structures without directly resolving them. Together with complementary attenuation information, which visualizes comparatively large cracks, cracks are detected on all length-scales for a whole tooth in a non-destructive way. Hence, this proof-of principle study on three ex-vivo teeth shows the potential of X-ray scattering for evidence-based detection of cracked teeth

The Health Status of a Population estimated: The History of Health State Curves

Following the recent publication of our book on Exploring the Health State of a Population by Dynamic Modeling Methods in The Springer Series on Demographic Methods and Population Analysis (DOI 10.1007/978-3-319-65142-2) we provide this brief presentation of the main findings and improvements regarding the Health State of a Population. (See at: http://www.springer.com/gp/book/9783319651415). Here the brief history of the Health State or Health Status curves for individuals and populations is presented including the main references and important figures along with an illustrated Poster (see Figure 13 and http://www.smtda.net/demographics2018.html). Although the Survival Curve is known as long as the life tables have introduced, the Health State Curve was calculated after the introduction of the advanced stochastic theory of the first exit time. The health state curve is illustrated in several graphs either as a fit curve to data or produced after a large number of stochastic realizations. The Health State, the Life Expectancy and the age at mean zero health state are also estimated. Keywords: Health State and Survival Curves, Health status of a population, First exit time stochastic theory, stochastic simulations of health state, Age at Maximum Curvature, Healthy Life Expectancy and HALE, Standard Deviation, Health State Curves, Maximum human lifespan and other.Comment: 11 pages, 13 figure

Elastase-mediated fibrinogenolysis by chemoattractant-stimulated neutrophils occurs in the presence of physiologic concentrations of antiproteinases.

Plasma levels of the HNE-derived fibrinopeptide A alpha 1-21 reflect in vivo enzyme activity. To provide a possible explanation for the presence of circulating A alpha 1-21 in individuals with normal plasma antiproteinase concentrations we investigated whether PMN-associated HNE is more resistant to inhibition than the free enzyme. PMN were stimulated to migrate across 125I-fibrinogen-coated nitrocellulose filters in response to 10(-7) M FMLP, and the extent of fibrinogenolysis was determined by measuring release of A alpha 1-21 and 125I-labeled fibrinogen degradation products. The fibrinogenolytic activity of migrating PMN was then compared with that of free HNE present in PMN lysates or secreted by PMN stimulated with FMLP. Whereas the fibrinogenolytic activity of soluble HNE was completely inhibited by low concentrations (1%) of plasma or serum and macromolecular antiproteinase (alpha 1 proteinase-inhibitor and soybean trypsin-inhibitor), even in the presence of undiluted plasma or serum the activity of the migrating PMN was incompletely blocked (81-85%). Further, concentrations of alpha 1 proteinase-inhibitor and soybean trypsin-inhibitor that totally inhibited free HNE activity also incompletely blocked (88-89%) the fibrinogenolytic activity of migrating PMN, indicating that FMLP-stimulated PMN demonstrate significant fibrinogenolytic activity in the presence of antiproteinases as small as 20,000 mol wt. A specific low molecular weight HNE inhibitor (MeO-Suc-Ala2-Pro-ValCH2Cl), however, totally blocked PMN-mediated fibrinogenolysis without affecting intracellular HNE activity, HNE secretion from PMN, or PMN migration in response to FMLP. These findings support the hypothesis that PMN migrating on a fibrinogen-coated surface form zones of close contact with fibrinogen, thus preventing access of plasma antiproteinases to HNE released at the cell-substrate interface. The occurrence of this phenomenon in vivo would explain the presence of circulating A alpha 1-21 in individuals with normal antiproteinase concentrations

Drying of complex suspensions

We investigate the 3D structure and drying dynamics of complex mixtures of emulsion droplets and colloidal particles, using confocal microscopy. Air invades and rapidly collapses large emulsion droplets, forcing their contents into the surrounding porous particle pack at a rate proportional to the square of the droplet radius. By contrast, small droplets do not collapse, but remain intact and are merely deformed. A simple model coupling the Laplace pressure to Darcy's law correctly estimates both the threshold radius separating these two behaviors, and the rate of large-droplet evacuation. Finally, we use these systems to make novel hierarchical structures.Comment: 4 pages, 4 figure

Quantum gates with "hot" trapped ions

We propose a scheme to perform a fundamental two-qubit gate between two trapped ions using ideas from atom interferometry. As opposed to the scheme considered by J. I. Cirac and P. Zoller, Phys. Rev. Lett. 74, 4091 (1995), it does not require laser cooling to the motional ground state.Comment: 4 pages, 2 eps figure

Valley splitting of Si/SiGe heterostructures in tilted magnetic fields

We have investigated the valley splitting of two-dimensional electrons in high quality Si/Si$_{1-x}$Ge$_x$ heterostructures under tilted magnetic fields. For all the samples in our study, the valley splitting at filling factor $\nu=3$ ($\Delta_3$) is significantly different before and after the coincidence angle, at which energy levels cross at the Fermi level. On both sides of the coincidence, a linear density dependence of $\Delta_3$ on the electron density was observed, while the slope of these two configurations differs by more than a factor of two. We argue that screening of the Coulomb interaction from the low-lying filled levels, which also explains the observed spin-dependent resistivity, is responsible for the large difference of $\Delta_3$ before and after the coincidence.Comment: REVTEX 4 pages, 4 figure