Neutron-proton analyzing power at 12 MeV and inconsistencies in parametrizations of nucleon-nucleon data

We present the most accurate and complete data set for the analyzing power Ay(theta) in neutron-proton scattering. The experimental data were corrected for the effects of multiple scattering, both in the center detector and in the neutron detectors. The final data at En = 12.0 MeV deviate considerably from the predictions of nucleon-nucleon phase-shift analyses and potential models. The impact of the new data on the value of the charged pion-nucleon coupling constant is discussed in a model study.Comment: Six pages, four figures, one table, to be published in Physics Letters

Polyacrylamide in Glycerol Solutions From an Atomistic Perspective of the Energetics, Structure, and Dynamics

All-atom molecular dynamics is used to investigate the structural, energetic, and dynamical properties of polyacrylamide (PAM) oligomers of different lengths solvated in pure glycerol, a 90:10 glycerol–water mixture, and pure water. We predict that the oligomers’ globular structure is obtained only when the modeling strategy considers the solvent as a continuous background. Meanwhile, for all-atom modeled solvents, the glycerol solutions display a strong tendency of trapping the oligomers in instantaneous elongated random coiled structures that remain locked-in over tens of nanoseconds. In pure water, the oligomers acquire considerably shorter random coiled structures of increased flexibility. The all-atom force field, generalized amber force field, is modified by including restrained electrostatic potential atomic charges for both glycerol and PAM. Three PAM oligomer lengths containing 10, 20, and 30 monomers are considered in detail by monitoring the radius of gyration, end-to-end distance, intra-potential energy, and solvent–oligomer interaction energies for decades of nanoseconds. The density and radial distribution function of glycerol solutions are calculated when modeled with the modified atomic charges, showing a very good agreement with the experimental results at temperatures around 300 K. Glycerol has multiple applications, including its use in gel formation for PAM gel electrophoresis. Our findings are relevant for the design of sensors based on microfluidics and tailored pharmaceutical buffer solutions

Standalone smartphone apps for mental health—a systematic review and meta-analysis

While smartphone usage is ubiquitous, and the app market for smartphone apps targeted at mental health is growing rapidly, the evidence of standalone apps for treating mental health symptoms is still unclear. This meta-analysis investigated the efficacy of standalone smartphone apps for mental health. A comprehensive literature search was conducted in February 2018 on randomized controlled trials investigating the effects of standalone apps for mental health in adults with heightened symptom severity, compared to a control group. A random-effects model was employed. When insufficient comparisons were available, data was presented in a narrative synthesis. Outcomes included assessments of mental health disorder symptom severity specifically targeted at by the app. In total, 5945 records were identified and 165 full-text articles were screened for inclusion by two independent researchers. Nineteen trials with 3681 participants were included in the analysis: depression (k = 6), anxiety (k = 4), substance use (k = 5), self-injurious thoughts and behaviors (k = 4), PTSD (k = 2), and sleep problems (k = 2). Effects on depression (Hedges’ g = 0.33, 95%CI 0.10–0.57, P = 0.005, NNT = 5.43, I2 = 59%) and on smoking behavior (g = 0.39, 95%CI 0.21–0.57, NNT = 4.59, P ≤ 0.001, I2 = 0%) were significant. No significant pooled effects were found for anxiety, suicidal ideation, self-injury, or alcohol use (g = −0.14 to 0.18). Effect sizes for single trials ranged from g = −0.05 to 0.14 for PTSD and g = 0.72 to 0.84 for insomnia. Although some trials showed potential of apps targeting mental health symptoms, using smartphone apps as standalone psychological interventions cannot be recommended based on the current level of evidence

Compression-induced structural and mechanical changes of fibrin-collagen composites

Fibrin and collagen as well as their combinations play an important biological role in tissue regeneration and are widely employed in surgery as fleeces or sealants and in bioengineering as tissue scaffolds. Earlier studies demonstrated that fibrin-collagen composite networks displayed improved tensile mechanical properties compared to the isolated protein matrices. Unlike previous studies, here unconfined compression was applied to a fibrin-collagen filamentous polymer composite matrix to study its structural and mechanical responses to compressive deformation. Combining collagen with fibrin resulted in formation of a composite hydrogel exhibiting synergistic mechanical properties compared to the isolated fibrin and collagen matrices. Specifically, the composite matrix revealed a one order of magnitude increase in the shear storage modulus at compressive strains>0.8 in response to compression compared to the mechanical features of individual components. These material enhancements were attributed to the observed structural alterations, such as network density changes, an increase in connectivity along with criss-crossing, and bundling of fibers. In addition, the compressed composite collagen/fibrin networks revealed a non-linear transformation of their viscoelastic properties with softening and stiffening regimes. These transitions were shown to depend on protein concentrations. Namely, a decrease in protein content drastically affected the mechanical response of the networks to compression by shifting the onset of stiffening to higher degrees of compression. Since both natural and artificially composed extracellular matrices experience compression in various (patho)physiological conditions, our results provide new insights into the structural biomechanics of the polymeric composite matrix that can help to create fibrin-collagen sealants, sponges, and tissue scaffolds with tunable and predictable mechanical properties

Vascular endothelial growth factor transgene expression in cell-transplanted hearts

AbstractObjectiveWe evaluated the effect of transplanted cell type, time, and region of the heart on transgene expression to determine the potential of combined gene and cell delivery for myocardial repair.MethodsLewis rats underwent myocardial cryoinjury 3 weeks before transplantation with heart cells (a mixed culture of cardiomyocytes, smooth muscle cells, endothelial cells and fibroblasts, n = 13), vascular endothelial growth factor–transfected heart cells (n = 13), skeletal myoblasts (n = 13), vascular endothelial growth factor–transfected skeletal myoblasts (n = 13), or medium (control, n = 12). Vascular endothelial growth factor expression in the scar, border zone, and normal myocardium was evaluated at 3 days and at 1, 2, and 4 weeks by means of quantitative polymerase chain reaction. Transplanted cells and vascular endothelial growth factor protein were identified immunohistologically on myocardial sections.ResultsVascular endothelial growth factor levels were very low in control scars but increased transiently after medium injection. Transplantation with heart cells and skeletal myoblasts significantly increased vascular endothelial growth factor expression in the scar and border zone. Transplantation of vascular endothelial growth factor–transfected heart cells and vascular endothelial growth factor–transfected skeletal myoblasts further augmented vascular endothelial growth factor expression, resulting in 4- to 5-fold greater expression of vascular endothelial growth factor in the scar at 1 week. Peak vascular endothelial growth factor expression was greater and earlier in vascular endothelial growth factor–transfected heart cells than in vascular endothelial growth factor–transfected skeletal myoblasts. Vascular endothelial growth factor was primarily expressed by the transplanted cells. Some of the transplanted heart cells and vascular endothelial growth factor–transfected heart cells were identified in the endothelial layer of blood vessels in the scar.ConclusionsTransplantation of heart cells and skeletal myoblasts induces vascular endothelial growth factor expression in myocardial scars and is greatly augmented by prior transfection with a vascular endothelial growth factor transgene. Vascular endothelial growth factor expression is limited to the scar and border zone for 4 weeks. Both heart cells and skeletal myoblasts may be excellent delivery vehicles for cell-based myocardial gene therapy