Takens-Bogdanov bifurcation of travelling wave solutions in pipe flow

The appearance of travelling-wave-type solutions in pipe Poiseuille flow that are disconnected from the basic parabolic profile is numerically studied in detail. We focus on solutions in the 2-fold azimuthally-periodic subspace because of their special stability properties, but relate our findings to other solutions as well. Using time-stepping, an adapted Krylov-Newton method and Arnoldi iteration for the computation and stability analysis of relative equilibria, and a robust pseudo-arclength continuation scheme we unfold a double-zero (Takens-Bogdanov) bifurcating scenario as a function of Reynolds number (Re) and wavenumber (k). This scenario is extended, by the inclusion of higher order terms in the normal form, to account for the appearance of supercritical modulated waves emanating from the upper branch of solutions at a degenerate Hopf bifurcation. These waves are expected to disappear in saddle-loop bifurcations upon collision with lower-branch solutions, thereby leaving stable upper-branch solutions whose subsequent secondary bifurcations could contribute to the formation of the phase space structures that are required for turbulent dynamics at higher Re.Comment: 26 pages, 15 figures (pdf and png). Submitted to J. Fluid Mec

From travelling waves to mild chaos: a supercritical bifurcation cascade in pipe flow

We study numerically a succession of transitions in pipe Poiseuille flow that leads from simple travelling waves to waves with chaotic time-dependence. The waves at the origin of the bifurcation cascade possess a shift-reflect symmetry and are both axially and azimuthally periodic with wave numbers {\kappa} = 1.63 and n = 2, respectively. As the Reynolds number is increased, successive transitions result in a wide range of time dependent solutions that includes spiralling, modulated-travelling, modulated-spiralling, doubly-modulated-spiralling and mildly chaotic waves. We show that the latter spring from heteroclinic tangles of the stable and unstable invariant manifolds of two shift-reflect-symmetric modulated-travelling waves. The chaotic set thus produced is confined to a limited range of Reynolds numbers, bounded by the occurrence of manifold tangencies. The states studied here belong to a subspace of discrete symmetry which makes many of the bifurcation and path-following investigations presented technically feasible. However, we expect that most of the phenomenology carries over to the full state-space, thus suggesting a mechanism for the formation and break-up of invariant states that can sustain turbulent dynamics.Comment: 38 pages, 35 figures, 1 tabl

Synergy of Two Assembly Languages in DNA Nanostructures: Self-Assembly of Sequence-Defined Polymers on DNA Cages

DNA base-pairing is the central interaction in DNA assembly. However, this simple four-letter (A–T and G–C) language makes it difficult to create complex structures without using a large number of DNA strands of different sequences. Inspired by protein folding, we introduce hydrophobic interactions to expand the assembly language of DNA nanotechnology. To achieve this, DNA cages of different geometries are combined with sequence-defined polymers containing long alkyl and oligoethylene glycol repeat units. Anisotropic decoration of hydrophobic polymers on one face of the cage leads to hydrophobically driven formation of quantized aggregates of DNA cages, where polymer length determines the cage aggregation number. Hydrophobic chains decorated on both faces of the cage can undergo an intrascaffold “handshake” to generate DNA-micelle cages, which have increased structural stability and assembly cooperativity, and can encapsulate small molecules. The polymer sequence order can control the interaction between hydrophobic blocks, leading to unprecedented “doughnut-shaped” DNA cage-ring structures. We thus demonstrate that new structural and functional modes in DNA nanostructures can emerge from the synergy of two interactions, providing an attractive approach to develop protein-inspired assembly modules in DNA nanotechnology

Helping everyone do better: a call for validation studies of routinely recorded health data.

There has been a surge of availability and use for research of routinely collected electronic health data, such as electronic health records, health administrative data, and disease registries. Symptomatic of this surge, in 2012, Pharmacoepidemiology and Drug Safety (PDS) published a supplemental issue containing several reviews of validated methods for identifying health outcomes using routine health data,1 focusing on databases feeding the US Mini-Sentinel Program

Statistical analysis of coherent structures in transitional pipe flow

Numerical and experimental studies of transitional pipe flow have shown the prevalence of coherent flow structures that are dominated by downstream vortices. They attract special attention because they contribute predominantly to the increase of the Reynolds stresses in turbulent flow. In the present study we introduce a convenient detector for these coherent states, calculate the fraction of time the structures appear in the flow, and present a Markov model for the transition between the structures. The fraction of states that show vortical structures exceeds 24% for a Reynolds number of about Re=2200, and it decreases to about 20% for Re=2500. The Markov model for the transition between these states is in good agreement with the observed fraction of states, and in reasonable agreement with the prediction for their persistence. It provides insight into dominant qualitative changes of the flow when increasing the Reynolds number.Comment: 11 pages, 26 (sub)figure

Establishing General Working Population Norms for the Cognitive Symptom Checklist-Work

PURPOSE: The Cognitive Symptom Checklist-Work (CSC-W) is a self-report measure to assess cognitive symptoms (i.e., memory and executive function) in working adults with cancer. To date, general working population norm data are lacking worldwide. We established CSC-W norm values in the general working population, and assessed associations of CSC-W scores with work and health-related factors.METHODS: This cross-sectional study consisted of 1,000 Dutch working adults, of whom data was collected through an online respondent panel. The sample was stratified for sex and age, and data were weighted. Summary scores of the CSC-W total scale, and memory and executive function symptoms subscales, were determined (e.g., means, percentiles). Z- and T-scores were calculated, and analysis of (co)variance has been applied.RESULTS: Cognitive symptom scores were relatively stable across age groups, but 18-39-year-old respondents reported lower memory and executive function than respondents in other age groups. Symptom scores of memory function (mean 29.1; SD = 16.7) were higher for all age groups and in both sexes compared to executive function (mean 22.1; SD = 16.8). No sex differences in memory and executive function were observed. Higher symptom scores were associated with performing non-manual work only, manual work only, self-reported long-term illness, and higher levels of depressive symptoms and fatigue.CONCLUSION: The CSC-W norms may enhance the interpretation and facilitate the analysis of self-reported cognitive symptoms in patients with cancer at work. Our findings may support health care professionals in identifying working adults with cancer with cognitive symptoms and in developing personalized treatment.</p

Establishing General Working Population Norms for the Cognitive Symptom Checklist-Work

PURPOSE: The Cognitive Symptom Checklist-Work (CSC-W) is a self-report measure to assess cognitive symptoms (i.e., memory and executive function) in working adults with cancer. To date, general working population norm data are lacking worldwide. We established CSC-W norm values in the general working population, and assessed associations of CSC-W scores with work and health-related factors.METHODS: This cross-sectional study consisted of 1,000 Dutch working adults, of whom data was collected through an online respondent panel. The sample was stratified for sex and age, and data were weighted. Summary scores of the CSC-W total scale, and memory and executive function symptoms subscales, were determined (e.g., means, percentiles). Z- and T-scores were calculated, and analysis of (co)variance has been applied.RESULTS: Cognitive symptom scores were relatively stable across age groups, but 18-39-year-old respondents reported lower memory and executive function than respondents in other age groups. Symptom scores of memory function (mean 29.1; SD = 16.7) were higher for all age groups and in both sexes compared to executive function (mean 22.1; SD = 16.8). No sex differences in memory and executive function were observed. Higher symptom scores were associated with performing non-manual work only, manual work only, self-reported long-term illness, and higher levels of depressive symptoms and fatigue.CONCLUSION: The CSC-W norms may enhance the interpretation and facilitate the analysis of self-reported cognitive symptoms in patients with cancer at work. Our findings may support health care professionals in identifying working adults with cancer with cognitive symptoms and in developing personalized treatment.</p

Type of cancer treatment and cognitive symptoms in working cancer survivors:an 18-month follow-up study

Purpose: Cognitive symptoms are reported to affect cancer survivors’ functioning at work. However, little is known about the type of cancer treatment and cognitive symptoms in working cancer survivors. We examined the longitudinal association between type of cancer treatment and cognitive symptoms in cancer survivors post return to work, and whether the course of cognitive symptoms over 18 months differed per type of cancer treatment. Methods: Data from the Dutch longitudinal “Work-Life after Cancer” study were used. The study population consisted of 330 working cancer survivors who completed questionnaires at baseline, and 6, 12, and 18 months follow-up. Cognitive symptoms were assessed with the cognitive symptom checklist-work and linked with cancer treatment data from the Netherlands Cancer Registry. Data were analyzed using generalized estimating equations. Results: Cancer survivors who received chemotherapy reported comparable memory symptom levels (b: − 2.3; 95% CI = − 7.1, 2.5) to those receiving locoregional treatment. Executive function symptom levels (b: − 4.1; 95% CI = − 7.8, − 0.4) were significantly lower for cancer survivors who received chemotherapy, compared with those receiving locoregional treatment. In cancer survivors who received other systemic therapy, memory (b: 0.4; 95% CI = 0.1, 0.7) and executive function symptom levels (b: 0.4; 95% CI = 0.0, 0.7) increased over time. In cancer survivors who received chemotherapy and locoregional treatment, memory and executive function symptom scores were persistent during the first 18 months after return to work. Conclusions: The contradictory finding that cancer patients receiving chemotherapy report fewer cognitive symptoms warrants further research. Implications for Cancer Survivors: Working cancer survivors may have cognitive symptom management needs irrespective of the type of cancer treatment they received

Remodeling of central metabolism in invasive breast cancer compared to normal breast tissue - a GC-TOFMS based metabolomics study

BACKGROUND: Changes in energy metabolism of the cells are common to many kinds of tumors and are considered a hallmark of cancer. Gas chromatography followed by time-of-flight mass spectrometry (GC-TOFMS) is a well-suited technique to investigate the small molecules in the central metabolic pathways. However, the metabolic changes between invasive carcinoma and normal breast tissues were not investigated in a large cohort of breast cancer samples so far. RESULTS: A cohort of 271 breast cancer and 98 normal tissue samples was investigated using GC-TOFMS-based metabolomics. A total number of 468 metabolite peaks could be detected; out of these 368 (79%) were significantly changed between cancer and normal tissues (p80%. Two-metabolite classifiers, constructed as ratios of the tumor and normal tissues markers, separated cancer from normal tissues with high sensitivity and specificity. Specifically, the cytidine-5-monophosphate / pentadecanoic acid metabolic ratio was the most significant discriminator between cancer and normal tissues and allowed detection of cancer with a sensitivity of 94.8% and a specificity of 93.9%. CONCLUSIONS: For the first time, a comprehensive metabolic map of breast cancer was constructed by GC-TOF analysis of a large cohort of breast cancer and normal tissues. Furthermore, our results demonstrate that spectrometry-based approaches have the potential to contribute to the analysis of biopsies or clinical tissue samples complementary to histopathology

Tunability of solitary wave properties in one dimensional strongly nonlinear phononic crystals

One dimentional strongly nonlinear phononic crystals were assembled from chains of PTFE (polytetrafluoroethylene) and stainless steel spheres with gauges installed inside the beads. Trains of strongly nonlinear solitary waves were excited by an impact. A significant modification of the signal shape and an increase of solitary wave speed up to two times (at the same amplitude of dynamic contact force)were achieved through a noncontact magnetically induced precompression of the chains. Data for PTFE based chains are presented for the first time and data for stainless steel based chains were extended into a smaller range of amplitudes by more than one order of magnitude than previously reported. Experimental results were found to be in reasonable agreement with the long wave approximation and with numerical calculations based on Hertz interaction law for discrete chains.Comment: 36 pages, 7 figure