Computer simulation data on junction fluctuations in end-linked model networks are analyzed using the framework of the constraint junction model and the slip tube model for entangled networks. It is ...argued that cross-linking freezes in conformational fluctuations of chains and cross-links, which creates a small preload of entangled strands. This can be modeled using a “confinement degree of polymerization” N c(N) with a weak dependence on the degree of polymerization N. The confined motion of network junctions with f active connections to the network is well described by using the exact solution of the constrained junction model with a constraining term that is given by the superposition of f/2 entanglement tubes with confinement N c(N). It is shown that the modulus of end-linked model networks is the sum of a phantom and an entanglement contribution, whereby the entanglement contribution shows the same correction N c(N) as both the cross-link fluctuations and the time average bond orientations. The results for the cross-link fluctuations allow to compute instantaneous or time average segment orientations and, thus, are necessary to understand birefringence experiments or double quantum nuclear magnetic resonance data of entangled networks.
The gel point of end-linked model networks is determined from computer simulation data. It is shown that the difference between the true gel point conversion, p c, and the ideal mean field prediction ...for the gel point, p c,id, is a function of the average number of cross-links per pervaded volume of a network strand, P, and thus, exhibits an explicit dependence on junction functionality, f. In contrast, the amount of intramolecular reactions at the gel point is independent of f in a first approximation and exhibits a different power-law dependence on the overlap number of elastic strands as compared to the gel point delay, p c – p c,id. Therefore, p c – p c,id cannot be predicted from intramolecular reactions and vice versa in contrast to a long standing proposal in the literature. Instead, the main contribution to p c – p c,id for P > 1 arises from the extra bonds needed to bridge the gaps between giant molecules separated in space and scales roughly ∝ (P – 1)−1/2. Further corrections to scaling are due to nonideal reaction kinetics, composition fluctuations, and incompletely screened excluded volume, which are discussed briefly.
The size of rings (also called cyclic polymers) in bidisperse blends of chemically identical rings is analyzed by computer simulations. Data of entangled ring blends and blends of interpenetrating ...rings are compared, and it is shown that the compression of entangled rings can be explained by the changes in the penetrable fraction of the minimal surface bounded by the ring. Corrections for small rings can be approximated by a concatenation probability 1 – P OO that a ring entraps at least one other ring. Both results are in line with a previous work to explain the compression of entangled rings in monodisperse melts. Bond–bond correlations in melts of interpenetrating rings lead to similar corrections for ring sizes as reported previously for monodisperse linear melts. For entangled rings, bond–bond correlations show an anticorrelation peak at a curvilinear distance of about ten segments that coincides with a horizontal tangent in the normalized mean-square internal distances along the ring. Both observations become independent of melt molecular weight for sufficiently large degrees of polymerization, and such behavior is not found in samples with entanglements switched off. In consequence, the length scale of topological interactions (entanglement length) in a melt of entangled rings must be considered as constant in contrast to a recent proposal by Sakaue.
Abstract Objectives This study sought to observe the relationship between left atrial (LA) strain and left ventricular diastolic function and determine whether LA strain could be used to detect ...diastolic dysfunction (DD) and classify its degree when present. Background The assessment of diastolic function is complex and multiparametric because most conventional parameters do not follow the progression of DD. Strain imaging is an emerging index of LA function, with recent data demonstrating that LA strain is diminished in diastolic heart failure. However, LA strain is not part of the standard assessment of diastolic function. We hypothesized that LA strain decreases with worsening DD in a stepwise fashion and could thus be useful in evaluating DD. Methods We performed a retrospective derivation and validation cohort study to derive and test LA strain thresholds for DD grades (0 to 3) in patients with preserved left ventricular ejection fraction (N = 229). Two-dimensional speckle tracking was used to measure peak LA strain, which was applied as a single parameter to classify DD. American Society of Echocardiography guidelines were used as the reference standard. Results In the derivation cohort (n = 90), peak LA strain was significantly different between DD groups, with gradual decreases seen with worsening DD. Receiver-operating characteristic analysis resulted in 3 distinct LA strain thresholds for categorization of DD grades, with good to excellent diagnostic utility (area under the curve: 0.86 to 0.91). In an independent validation group (n = 139) with a spectrum of diastolic function, 11 patients (8%) had indeterminate DD grades using standard criteria, whereas LA strain was measured in all patients and its cutoffs resulted in diagnostic accuracy up to 95%. Conclusions LA strain measurements are feasible and allow accurate categorization of DD, because unlike the traditional parameters, it changes progressively with severity of DD. LA strain may become a useful tool for diastolic assessment in future clinical practice.
Patients with pulmonary hypertension due to left heart disease (PH-LHD) and a diastolic pulmonary vascular pressure gradient ≥ 7 mm Hg, representing PH out of proportion to pulmonary arterial wedge ...pressure, have pulmonary vascular disease and increased mortality. Little information exists on this condition, recently labeled as "combined pre- and post-capillary PH" (Cpc-PH).
To investigate epidemiology, risk factors, right ventricular function, and outcomes in patients with chronic heart failure and Cpc-PH.
The study population was identified from a retrospective chart review of a clinical database of 3,107 stable patients who underwent first diagnostic right heart catheterization and from a prospective cohort of 800 consecutive patients at a national university-affiliated tertiary center.
The retrospective cohort had 664 patients with systolic heart failure (SHF) and 399 patients with diastolic heart failure (DHF), 12% of whom were classified as Cpc-PH. The prospective cohort had 172 patients with SHF (14% Cpc-PH) and 219 patients with DHF (12% Cpc-PH). Chronic obstructive pulmonary disease (P = 0.034) and the tricuspid annular plane systolic excursion to systolic pulmonary artery pressure ratio (P = 0.015) predicted Cpc-PH in SHF. Younger age (P = 0.004), valvular heart disease (P = 0.046), and the tricuspid annular plane systolic excursion to systolic pulmonary artery pressure ratio predicted Cpc-PH in DHF (P = 0.016). Right ventricular-pulmonary vascular coupling was worse in Cpc-PH patients (end-systolic elastance to effective arterial elastance Ees/Ea: SHF: 1.05 ± 0.25; P = 0.002; DHF: 1.17 ± 0.27; P = 0.027) than in those with isolated post-capillary PH (Ees/Ea: SHF: 1.52 ± 0.51; DHF: 1.45 ± 0.29).
Cpc-PH is rare in chronic heart failure. Right ventricular-pulmonary vascular coupling is poor in Cpc-PH and could be one explanation for dismal outcomes.
Immune recovery was retrospectively analyzed in a cohort of 41 patients with acute leukemia, myelodysplastic syndrome and nonmalignant diseases, who received αβ T- and B-cell-depleted allografts from ...haploidentical family donors. Conditioning regimens consisted of fludarabine or clofarabine, thiotepa, melphalan and serotherapy with OKT3 or ATG-Fresenius. Graft manipulation was carried out with anti-TCRαβ and anti-CD19 Abs and immunomagnetic microbeads. The γδ T cells and natural killer cells remained in the grafts. Primary engraftment occurred in 88%, acute GvHD (aGvHD) grades II and III-IV occurred in 10% and 15%, respectively. Immune recovery data were available in 26 patients and comparable after OKT3 (n=7) or ATG-F (n=19). Median time to reach >100 CD3+ cells/μL, >200 CD19+ cells/μL and >200 CD56+ cells/μL for the whole group was 13, 127 and 12.5 days, respectively. Compared with a historical control group of patients with CD34+ selected grafts, significantly higher cell numbers were found for CD3+ at days +30 and +90 (267 vs 27 and 397 vs 163 cells/μL), for CD3+4+ at day +30 (58 vs 11 cells/μL) and for CD56+ at day +14 (622 vs 27 cells/μL). The clinical impact of this accelerated immune recovery will be evaluated in an ongoing prospective multicenter trial.
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