552 research outputs found
The Apollonian decay of beer foam bubble size distribution and the lattices of young diagrams and their correlated mixing functions
We present different methods to characterise the
decay of beer foam by measuring the foam heights and recording
foam images as a function of time. It turns out that the foam
decay does not follow a simple exponential law but a higher-order
equation V(t)=aâbtâct2.5, which can be explained as a
superposition of two processes, that is, drainage and bubble
rearrangement. The reorganisation of bubbles leads to the
structure of an Apollonian gasket with a fractal
dimension of Dâ1.3058. Starting from foam images, we
study the temporal development of bubble size distributions and
give a model for the evolution towards the equilibrium state
based upon the idea of Ernst Ruch to describe irreversible
processes by lattices of Young diagrams. These lattices
generally involve a partial order, but one can force a total order
by mapping the diagrams onto the interval [0,1] using ordering functions such as the Shannon entropy. Several
entropy-like and nonentropy-like mixing
functions are discussed in comparison with the Young
order, each of them giving a special prejudice for understanding
the process of structure formation during beer foam decay
Graphentheoretische Uberlegungen zum Mechanismus der Solvolyse des Allylcarbinylamins
Es wird ein graphentheoretisches Modell zur Beschreibung der
Solvolysereaktion des Allylcarbinylamins unter bestimmten Grenzbedingungen
entwickelt, mit dem es gelingt, die Struktur des Molekillreaktionsraumes
zu erfassen. Es handelt sich hierbei um ein geschlossenes
graphentheoretisches Modell, dessen Aussagekraft auf
der Verwendung kombinatorischer Methoden beruht. Ausgeh_end von
der Struktur der Prodliktgraphen wird eine Formulierung fiir den
Chemismus der Reaktion vorgeschlagen, anhand derer denkbare
Reaktionsmechanismen dieser Solvolysereaktion iiberpriift werden
C4 olefin conversion on reduced nickel y faujasite. Evidence for C5 olefin formation via C4 olefin disproportionation
Sex-specific local life-history adaptation in surface- and cave-dwelling Atlantic mollies (Poecilia mexicana)
Cavefishes have long been used as model organisms showcasing adaptive diversification, but does adaptation to caves also facilitate the evolution of reproductive isolation from surface ancestors? We raised offspring of wild-caught surface- and cave-dwelling ecotypes of the neotropical fish Poecilia mexicana to sexual maturity in a 12-month common garden experiment. Fish were raised under one of two food regimes (high vs. low), and this was crossed with differences in lighting conditions (permanent darkness vs. 12:12âh light:dark cycle) in a 2âĂâ2 factorial design, allowing us to elucidate potential patterns of local adaptation in life histories. Our results reveal a pattern of sex-specific local life-history adaptation: Surface molly females had the highest fitness in the treatment best resembling their habitat of origin (high food and a light:dark cycle), and suffered from almost complete reproductive failure in darkness, while cave molly females were not similarly affected in any treatment. Males of both ecotypes, on the other hand, showed only weak evidence for local adaptation. Nonetheless, local life-history adaptation in females likely contributes to ecological diversification in this system and other cave animals, further supporting the role of local adaptation due to strong divergent selection as a major force in ecological speciation
Return-to-activity after anatomical reconstruction of acute high-grade acromioclavicular separation
Return-to-activity after anatomical reconstruction of acute high-grade acromioclavicular separation
BACKGROUND: To evaluate return-to-activity (RtA) after anatomical reconstruction of acute high-grade acromioclavicular joint (ACJ) separation. METHODS: A total of 42 patients with anatomical reconstruction of acute high-grade ACJ-separation (Rockwood Type V) were surveyed to determine RtA at a mean 31Â months follow-up (f-u). Sports disciplines, intensity, level of competition, participation in overhead and/or contact sports, as well as activity scales (DASH-Sport-Module, Tegner Activity Scale) were evaluated. Functional outcome evaluation included Constant score and QuickDASH. RESULTS: All patients (42/42) participated in sporting activities at f-u. Neither participation in overhead/contact sports, nor level of activity declined significantly (n.s.). 62Â % (nâ=â26) of patients reported subjective sports specific ACJ integrity to be at least the same as prior to the trauma. Sporting intensity (hours/week: 7.3Â h to 5.4Â h, pâ=â.004) and level of competition (pâ=â.02) were reduced. If activity changed, in 50Â % other reasons but clinical symptoms/impairment were named for modified behavior. QuickDASH (mean 6, range 0â54, SD 11) and DASH-Sport-Module (mean 6, range 0â56, SD 13) revealed only minor disabilities at f-u. Over time Constant score improved significant to an excellent score (mean 94, range 86â100, SD 4; pâ<â.001). Functional outcome was not correlated with RtA (n.s.). CONCLUSION: All patients participated in sporting activities after anatomical reconstruction of high-grade (Rockwood Type V) ACJ-separation. With a high functional outcome there was no significant change in activity level (Tegner) and participation in overhead and/or contact sports observed. There was no correlation between functional outcome and RtA. Limiting, there were alterations in time spent for sporting activities and level of competition observed. But in 50Â % those were not related to ACJ symptoms/impairment. Unrelated to successful re-established integrity and function of the ACJ it should be considered that patients decided not return-to-activity but are very content with the procedure
Identification and single-cell functional characterization of an endodermally biased pluripotent substate in human embryonic stem cells
Human embryonic stem cells (hESCs) display substantial heterogeneity in gene expression, implying the existence of discrete substates within the stem cell compartment. To determine whether these substates impact fate decisions of hESCs we used a GFP reporter line to investigate the properties of fractions of putative undifferentiated cells defined by their differential expression of the endoderm transcription factor, GATA6, together with the hESC surface marker, SSEA3. By single-cell cloning, we confirmed that substates characterized by expression of GATA6 and SSEA3 include pluripotent stem cells capable of long-term self-renewal. When clonal stem cell colonies were formed from GATA6-positive and GATA6-negative cells, more of those derived from GATA6-positive cells contained spontaneously differentiated endoderm cells than similar colonies derived from the GATA6-negative cells. We characterized these discrete cellular states using single-cell transcriptomic analysis, identifying a potential role for SOX17 in the establishment of the endoderm-biased stem cell state
Turbulence, instream wood and fish: ecohydraulic interactions under field conditions
This is the pre-peer reviewed version of the following article: Trinci, G, Harvey, GL, Henshaw, AJ, Bertoldi, W, Hölker, F. Turbulence, instream wood and fish: Ecohydraulic interactions under field conditions. Ecohydrology. 2020;e2211. https://doi.org/10.1002/eco.2211
, which has been published in final form at https://doi.org/10.1002/eco.2211. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions
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