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Severe congenital aortic valve pathology in the growing patient remains a challenging clinical scenario. Bicuspidization of the diseased aortic valve has proven to be a promising repair technique with acceptable durability. However, most understanding of the procedure is empirical and retrospective. This work seeks to design the optimal gross morphology associated with surgical bicuspidization with simulations based on the hypothesis that modifications to the free edge length cause or relieve stenosis. Model bicuspid valves were constructed with varying free edge lengths and gross morphology. Fluid-structure interaction simulations were conducted in a single patient-specific model geometry. The models were evaluated for primary targets of stenosis and regurgitation. Secondary targets were assessed and included qualitative hemodynamics, geometric height, effective height, orifice area, and billow. Stenosis decreased with increasing free edge length and was pronounced with free edge length less than or equal to 1.3 times the annular diameter d. With free edge length 1.5 d or greater, no stenosis occurred. All models were free of regurgitation. Substantial billow occurred with free edge length 1.7 d or greater. Free edge length 1.5 d or greater was required to avoid aortic stenosis in simulations. Cases with free edge length 1.7 d or greater showed excessive billow and other changes in gross morphology. Cases with free edge length 1.5 d to 1.6 d have a total free edge length approximately equal to the annular circumference and appeared optimal. These effects should be studied in vitro and in animal studies. [Display omitted] [ABSTRACT FROM AUTHOR]

Aortic incompetence (AI) is observed to be accelerated in the continuous-flow left ventricular assist device (LVAD) population and is related to increased mortality. Using computational fluid dynamics (CFD), we investigated the hemodynamic conditions related to the orientation of the LVAD outflow in these patients. We identified 10 patients with new aortic regurgitation, and 20 who did not, after LVAD implantation between 2009 and 2018. Three-dimensional models of patients' aortas were created from their computed tomography scans. The geometry of the LVAD outflow graft in relation to the aorta was quantified using azimuth angles (AA), polar angles (PAs), and distance from aortic root. The models were used to run CFD simulations, which calculated the pressures and wall shear stress (rWSS) exerted on the aortic root. The AA and PA were found to be similar. However, for combinations of high values of AA and low values of PA, there were no patients with AI. The distance from aortic root to the outflow graft was also smaller in patients who developed AI (3.39 ± 0.7 vs 4.07 ± 0.77 cm, P =.04). There was no significant difference in aortic root pressures in the 2 groups. The rWSS was greater in AI patients (4.60 ± 5.70 vs 2.37 ± 1.20 dyne/cm2, P <.001). Qualitatively, we observed a trend of greater perturbations, regions of high rWSS, and flow eddies in the AI group. Using CFD simulations, we demonstrated that patients who developed de novo AI have greater rWSS at the aortic root, and their outflow grafts were placed closer to the aortic roots than those patients without de novo AI. Computed tomography images were used to created 3D models for computation fluid dynamics simulations in 30 patients who underwent LVAD placement. Certain geometric positions of the LVAD outflow grafts predict the risk of development of AI in LVAD patients. AI , Aortic incompetence. [Display omitted] [ABSTRACT FROM AUTHOR]

Hydrogen storage by physisorption in carbon based materials is hindered by low adsorption energies. In the last decade doping of carbon materials with alkali, earth alkali or other metal atoms was proposed as a means to enhance adsorption energies, and some experiments have shown promising results. We investigate the upper bounds of hydrogen storage capacities of C 60 Cs clusters grown in ultracold helium nanodroplets by analyzing anomalies in the ion abundance that indicate shell closure of hydrogen adsorption shells. On bare C 60 + , a commensurate phase with 32H 2 molecules was identified in previous experiments. Doping C 60 with a single cesium atom leads to an increase in relative ion abundance for the first 10H 2 molecules, and the closure of the commensurate phase is shifted from 32 to 42H 2 molecules. Density functional theory calculations indicate that thirteen energetically enhanced adsorption sites exist, where six of them fill the groove between Cs and C 60 and 7 are located at the cesium atom. We emphasize the large effect of the quantum nature of the hydrogen molecule on the adsorption energies, i.e. the adsorption energies are decreased by around 50% for (H 2 )C 60 Cs and up to 80% for (H 2 )C 60 by harmonic zero-point corrections, which represent an upper bound to corrections for dissociation energies (D e to D 0 ) by the vibrational ground states. Five normal modes of libration and vibration of H 2 physisorbed on the substrate contribute primarily to this large decrease in adsorption energies. A similar effect can be found for H 2 physisorbed on benzene and is expected to be found for any other weakly H 2 -binding substrate. [ABSTRACT FROM AUTHOR]

Abstract: In spite of extensive investigations of ethylene adsorbed on graphite, bundles of nanotubes, and crystals of fullerenes, little is known about the existence of commensurate phases; they have escaped detection in almost all previous work. Here we present a combined experimental and theoretical study of ethylene adsorbed on free C60 and its aggregates. The ion yield of measured by mass spectrometry reveals a propensity to form a structurally ordered phase on monomers, dimers and trimers of C60 in which all sterically accessible hollow sites over carbon rings are occupied. Presumably the enhancement of the corrugation by the curvature of the fullerene surface favors this phase which is akin to a hypothetical 1×1 phase on graphite. Experimental data also reveal the number of molecules in groove sites of the C60 dimer through tetramer. The identity of the sites, adsorption energies and orientations of the adsorbed molecules are determined by molecular dynamics calculations based on quantum chemical potentials, as well as density functional theory. The decrease in orientational order with increasing temperature is also explored in the simulations whereas in the experiment it is impossible to vary the temperature. [Copyright &y& Elsevier]

Abstract: Understanding the mechanisms of gas exchange regulation in insects currently is a hot topic of insect physiology. Endogenous variation of metabolism during pupal development offers a great opportunity to study the regulation of respiratory patterns in insects. Here we show that metabolic rates during pupal development of the tenebrionid beetle Zophobas rugipes reveal a typical U-shaped curve and that, with the exception of 9-day-old pupae, the time between two bursts of CO2 (interburst phase) was the only parameter of cyclic CO2 gas exchange patterns that was adjusted to changing metabolic rates. The volume of CO2 released in a burst was kept constant, suggesting a regulation for accumulation and release of a fixed amount of CO2 throughout pupal development. We detected a variety of discontinuous and cyclic gas exchange patterns, which were not correlated with any periods of pupal development, suggesting a high among individual variability. An occasional occurrence of continuous CO2 release patterns at low metabolic rates was very likely caused by single defective non-occluding spiracles. [Copyright &y& Elsevier]

Abstract: In Drosophila melanogaster and other insects, increases in atmospheric oxygen partial pressure (aPO2) tend to increase adult body size and decrease tracheal diameters and tracheolar proliferation. If changes in tracheal morphology allow for functional compensation for aPO2, we would predict that higher aPO2 would be associated with higher critical PO2 values (CritPO2) and lower maximal tracheal conductances (G max). We measured CritPO2 and G max for adult and larval vinegar flies reared for 7–9 generations in 10, 21 or 40kPa O2. The CritPO2, CO2 emission rates and G max values were generally independent of the rearing PO2 these flies had experienced, suggesting that minimal functional changes in tracheal capacities occurred in response to rearing PO2. Larvae were able to continue activity during 20min of anoxia. The lack of multigenerational rearing PO2 effects on tracheal function suggests that the functional compensation at the whole-body level due to tracheal morphological changes in response to aPO2 may be minimal; alternatively the benefits of such compensation may occur in specific tissues or during processes not assessed by these methods. In larvae, the CritPO2 and the capacity for movement in anoxia suggest adaptations for life in hypoxic organic matter. [Copyright &y& Elsevier]

Abstract: Flightless, diurnal tenebrionid beetles are commonly found in deserts. They possess a curious morphological adaptation, the subelytral cavity (an air space beneath the fused elytra) the function of which is not completely understood. In the tenebrionid beetle Eleodes obscura, we measured abdominal movements within the subelytral cavity, and the activity of the pygidial cleft (which seals or unseals the subelytral cavity), simultaneously with total CO2 release rate and water loss rate. First, we found that E. obscura has the lowest cuticular permeability measured in flow-through respirometry in an insect (0.90μg H2Ocm−2 Torr−1 h−1). Second, it does not exhibit a discontinuous gas exchange cycle. Third, we describe the temporal coupling between gas exchange, water loss, subelytral space volume, and the capacity of the subelytral space to exchange gases with its surroundings as indicated by pygidial cleft state. Fourth, we suggest possible mechanisms that may reduce respiratory water loss rates in E. obscura. Finally, we suggest that E. obscura cannot exchange respiratory gases discontinuously because of a morphological constraint (small tracheal or spiracular conductance). This “conductance constraint hypothesis” may help to explain the otherwise puzzling phylogenetic patterns of continuous vs. discontinuous gas exchange observed in tracheate arthropods. [Copyright &y& Elsevier]

Abstract: The clinical usefulness of aminoglycoside antibiotics is limited by their ototoxicity. In rodents, damage to the inner ear is often associated with rotational behavior and locomotor hyperactivity reminiscent of such behaviors resulting from an imbalance of forebrain dopamine systems. Based on previous observations in the circling (ci2/ci2) Lewis (LEW) rat mutant, a spontaneous mutation leading to hair cell loss, deafness, impairment of vestibular functions, lateralized circling, hyperactivity and alterations in the nigrostriatal dopamine system, we have recently hypothesized that vestibular defects during postnatal development, independent of whether induced or inherited, lead to secondary changes in the dopaminergic system within the basal ganglia, which would be a likely explanation for the typical behavioral phenotype seen in such models. In the present study, we directly compared the phenotype induced by streptomycin in LEW rats with that of the ci2 LEW rat mutant. For this purpose, we treated neonatal LEW rats over 3 weeks by streptomycin, which induced bilateral degeneration of cochlear and vestibular hair cells. Following this treatment period, the behavioral syndrome of the streptomycin-treated animals, including the lateralized rotational behavior, was almost indistinguishable from that of ci2 mutant rats. However, in contrast to the ci2 mutant rat, all alterations, except the hearing loss, were only transient, disappearing between 7 and 24 weeks following treatment. In conclusion, in line with our hypothesis, vestibular defects induced in normal LEW rats led to the same phenotypic behavior as the inherited vestibular defect of ci2 mutant rats. However, with increasing time for recovery, adaptation to the vestibular impairment developed in streptomycin-treated rats, while all deficits persisted in the mutant animals. At least in part, the transient nature of the abnormal behaviors resulting from treatment with streptomycin could be explained by adaptation to the vestibular impairment by the use of visual cues, which is not possible in ci2 rats because of progressive retinal degeneration in these mutants. Although further experiments are needed to prove this hypothesis, the present study shows that direct comparisons between these two models serve to understand the mechanisms underlying the complex behavioral phenotype in rodents with vestibular defects and how these defects are compensated. [Copyright &y& Elsevier]

Abstract: The sensitivity of behavioral and physiological parameters to even mildly stressful experiences such as drug injections creates a need for alternative methods. We have established a method of stress-free administration of drugs via drinking water that allows multiple, individually specific and exact dosages, even for socially-housed animals. The drug solution is supplied by a dispenser with automated volume control. Animals are PIT microchip-tagged with RFID transponders and identified in realtime at the water port. Computer control permits preprogramming of individual reward quantities so that drug administration is terminated after an individual has collected its daily dose. For our experiments, the substance 5-bromo-2′-deoxyuridine (BrdU) was given as a marker of proliferating cells that we quantified in the hippocampus of adult mice. Experimental groups received BrdU either via intraperitoneal injections or orally via the water dispensers. Immunohistochemical staining of BrdU-positive cells was of the same quality after oral administration as after injection. BrdU-positive cells did not differ statistically in cell numbers. Thus, water dispensers under transponder control allow the individual and stress-free application of drugs even to group-living animals without disturbing their behavior. This is useful where a complex temporal protocol of application is required, and for phenotyping experiments combining behavioral tests with neural, cellular or molecular analyses. [Copyright &y& Elsevier]

We are developing a transmission electron microscope that operates at extremely low electron energies, 0–40 eV. We call this technique eV-TEM. Its feasibility is based on the fact that at very low electron energies the number of energy loss pathways decreases. Hence, the electron inelastic mean free path increases dramatically. eV-TEM will enable us to study elastic and inelastic interactions of electrons with thin samples. With the recent development of aberration correction in cathode lens instruments, a spatial resolution of a few nm appears within range, even for these very low electron energies. Such resolution will be highly relevant to study biological samples such as proteins and cell membranes. The low electron energies minimize adverse effects due to radiation damage. [ABSTRACT FROM AUTHOR]