Non-monotonic dependence of the rupture force in polymer chains on their lengths

We consider the rupture dynamics of a homopolymer chain pulled at one end at a constant loading rate. Our model of the breakable polymer is related to the Rouse chain, with the only difference that the interaction between the monomers is described by the Morse potential instead of the harmonic one, and thus allows for mechanical failure. We show that in the experimentally relevant domain of parameters the dependence of the most probable rupture force on the chain length may be non-monotonic, so that the medium-length chains break easier than the short and the long ones. The qualitative theory of the effect is presented

Magnification Bias Corrections to Galaxy-Lensing Cross-Correlations

Galaxy-galaxy or galaxy-quasar lensing can provide important information on the mass distribution in the Universe. It consists of correlating the lensing signal (either shear or magnification) of a background galaxy/quasar sample with the number density of a foreground galaxy sample. However, the foreground galaxy density is inevitably altered by the magnification bias due to the mass between the foreground and the observer, leading to a correction to the observed galaxy-lensing signal. The aim of this paper is to quantify this correction. The single most important determining factor is the foreground redshift z: the correction is small if the foreground galaxies are at low redshifts but can become non-negligible for sufficiently high redshifts. For instance, we find that for the multipole l=1000, the correction is above 1%*(5s-2)/b for z<0.37, and above 5%*(5s-2)/b for z<0.67, where s is the number count slope of the foreground sample, and b its galaxy bias. These considerations are particularly important for geometrical measures, such as the Jain and Taylor ratio or its generalization by Zhang et al. Assuming (5s-2)/b=1, we find that the foreground redshift should be limited to z<0.45 in order to avoid biasing the inferred dark energy equation of state w by more than 5%, and that even for a low foreground redshift (< 0.45), the background samples must be well separated from the foreground to avoid incurring a bias of similar magnitude. Lastly, we briefly comment on the possibility of obtaining these geometrical measures without using galaxy shapes, using instead magnification bias itself.Comment: 10 pages, 7 figures; v2: minor revisions, as accepted for publication in Physical Review

Investigation of Wire Structures for Heat Transfer Enhancement in Compact Heat Exchangers

Verbesserte Wärmeübertrageroberflächen ermöglichen energieeffizientere, kompaktere und leichtere Wärmeübertrager. Eine spezifische Oberfläche, die in allen drei Kriterien optimal ist, gibt es nicht. Mit der Existenz dieses Zielkonflikts wurden und werden eine Vielzahl unterschiedlicher verbesserter Oberflächendesigns entwickelt. Innerhalb dieser Arbeit werden Wärmeübertrageroberflächen auf Basis zylindrischer Drähte/Stiftrippen mit Drahtdurchmessern in der Größenordnung von 100 μm für Flachrohranwendungen untersucht. Sehr hohe konvektive Wärmeübergangskoeffizienten und deutliche Materialeinsparungen können erwartet werden. Das Ziel dieser Arbeit ist es, das Potenzial dieser Drahtstrukturen abzuschätzen. Vier Schritte werden für die Abschätzung durchgeführt. Zunächst wird eine Methode zur Bewertung unterschiedlicher Oberflächenentwicklungen ausgearbeitet. Die Zielgrößen der Methode sind definiert als eine energetische, eine volumenspezifische und eine massenspezifische Effizienz. Im zweiten Schritt wird eine numerische Simulation der Fluidströmung durch verschiedene Drahtstrukturgeometrien durchgeführt und es werden Korrelationen für Kennzahlen der Thermo- und Fluiddynamik entwickelt. Im dritten Schritt wird die Machbarkeit der Herstellung von Drahtstruktur-Wärmeübertragern untersucht und eine Reihe von Wärmeübertragerproben wird experimentell im Hinblick auf ihre thermische und hydraulische Leistung geprüft. Im letzten Schritt werden die neu entwickelten Korrelationen verwendet, um die energetische, volumenspezifische und massenspezifische Effizienz der Drahtstrukturen unter geometrischen und operativen Randbedingungen zu optimieren. Die Begutachtung zeigt Vorteile der Drahtstrukturen auf für Anwendungen, bei denen Volumen- und insbesondere Masseneffizienz eine wesentliche Rolle spielen. Wird eine Kombination aus energie- und volumenbezogener Bewertung durchgeführt, sind die Drahtstrukturen bei kleinen und mittleren Luftgeschwindigkeiten unterhalb etwa 2.5 m/s vorteilhaft. Für höhere Geschwindigkeiten sind die untersuchten Drahtstrukturen nicht vorteilhaft im Vergleich zu üblichen Lamellen

Are dietary factors and exercise levels related to fertility status?

BACKGROUND: Infertility is a major public health concern as it affects up to 25% of couples in Western Countries. While there is some evidence that diet and exercise may be linked to fertility, there is no official dietary or exercise guidance for couples when trying to conceive. Additional information regarding the relationship between diet, exercise, and fertility is needed to better inform the development of guidelines for couples trying to conceive. PURPOSE: To examine the relationships between diet, exercise, and fertility among women. METHODS: Participants were selected from on ongoing pregnancy study (N=33). All participants went on to have healthy pregnancies. Participants completed a survey regarding how long it took them to conceive, what methods they had to employ, if they ever had to seek treatment, and any other pertinent information regarding their fertility status prior to conception. In addition, they were asked detailed information regarding their dietary and exercise habits while trying to conceive. In addition, information on their significant other was collected. RESULTS: The amount of time it took to conceive (TTC) ranged from 1 month to 6 years. TTC and sedentary time were positively correlated (r=0.569, p=0.002), while light, moderate, and vigorous activities were not correlated to TTC. Regarding diet, TTC was positively correlated with total calories consumed (r=0.376, p=0.048) and total carbohydrates consumed (r=0.716, p\u3c0.001). CONCLUSION: Women hoping to conceive should consider decreasing time spent sedentary as well as their total caloric intake and total carbohydrate intake in order to conceive sooner. This study supports the idea that diet, activity level (or lack thereof), and fertility status may all be closely related. These topics should be carefully discussed with a health care provider when trying to conceive

An Automated Constellation Design & Mission Analysis Tool for Finding the Cheapest Mission Architecture

Identifying the optimal mission architecture for a space mission is critical for mission success, especially for large constellations. Here, optimizing the entire mission architecture for cost is necessary for the business case to work. This paper presents an automated system that combines constellation design and mission analysis functions in the context of a distributed engineering environment. It utilizes analytical methods, commercial simulation software and other specialized tools to identify multiple eligible constellations for the user-defined case, perform the associated mission analysis tasks, and provide input for additional tools like cost estimation software to eventually identify the optimal constellation. This allows assessing more options to fulfill the mission in less time, establishing the benefits of each constellation analyzed, and also allows non-expert users to quickly understand and evaluate consequences of design or requirement changes

Thermally activated breakdown in a simple polymer model

We consider the thermally activated fragmentation of a homopolymer chain. In our simple model the dynamics of the intact chain is a Rouse one until a bond breaks and bond breakdown is considered as a first passage problem over a barrier to an absorbing boundary. Using the framework of the Wilemski-Fixman approximation we calculate activation times of individual bonds for free and grafted chains. We show that these times crucially depend on the length of the chain and the location of the bond yielding a minimum at the free chain ends. Theoretical findings are qualitatively confirmed by Brownian dynamics simulations

Anisotropic Magnification Distortion of the 3D Galaxy Correlation: II. Fourier and Redshift Space

In paper I of this series we discuss how magnification bias distorts the 3D correlation function by enhancing the observed correlation in the line-of-sight (LOS) orientation, especially on large scales. This lensing anisotropy is distinctive, making it possible to separately measure the galaxy-galaxy, galaxy-magnification {\it and} magnification-magnification correlations. Here we extend the discussion to the power spectrum and also to redshift space. In real space, pairs oriented close to the LOS direction are not protected against nonlinearity even if the pair separation is large; this is because nonlinear fluctuations can enter through gravitational lensing at a small transverse separation (or i.e. impact parameter). The situation in Fourier space is different: by focusing on a small wavenumber $k$, as is usually done, linearity is guaranteed because both the LOS and transverse wavenumbers must be small. This is why magnification distortion of the galaxy correlation appears less severe in Fourier space. Nonetheless, the effect is non-negligible, especially for the transverse Fourier modes, and should be taken into account in interpreting precision measurements of the galaxy power spectrum, for instance those that focus on the baryon oscillations. The lensing induced anisotropy of the power spectrum has a shape that is distinct from the more well known redshift space anisotropies due to peculiar motions and the Alcock-Paczynski effect. The lensing anisotropy is highly localized in Fourier space while redshift space distortions are more spread out. This means that one could separate the magnification bias component in real observations, implying that potentially it is possible to perform a gravitational lensing measurement without measuring galaxy shapes.Comment: 14 pages, minor revisions, as accepted for publication in Physical Review

Transcription, Splicing, and Release: Are We There Yet?

A systematic analysis of LPS-induced gene expression in macrophages by Bhatt et al. demonstrates that inflammatory responses are governed primarily at the level of transcription initiation. Unexpectedly, full-length nascent RNAs that contain introns appear to accumulate on chromatin, presumably to complete processing, prior to release of functional mRNA for export to the cytoplasm

Bound and Radiation Fields in the Rindler Frame

The energy-momentum tensor of the Li\'enard-Wiechert field is split into bound and emitted parts in the Rindler frame, by generalizing the reasoning of Teitelboim applied in the inertial frame. Our analysis proceeds by invoking the concept of ``energy'' defined with respect to the Killing vector field attached to the frame. We obtain the radiation formula in the Rindler frame (the Rindler version of the Larmor formula), and it is found that the radiation power is proportional to the square of acceleration $\alpha^\mu$ of the charge relative to the Rindler frame. This result leads us to split the Li\'enard-Wiechert field into a part II', which is linear in $\alpha^\mu$, and a part I', which is independent of $\alpha^\mu$. By using these, we split the energy-momentum tensor into two parts. We find that these are properly interpreted as the emitted and bound parts of the tensor in the Rindler frame. In our identification of radiation, a charge radiates neither in the case that the charge is fixed in the Rindler frame, nor in the case that the charge satisfies the equation $\alpha^\mu=0$. We then investigate this equation. We consider four gedanken experiments related to the observer dependence of the concept of radiation.Comment: 30 pages 2 figure