Linear Increase In Volume Research Articles

Hydrogel Tissue Expanders for Stomatology. Part II. Poly(styrene-maleic anhydride) Hydrogels.

Self-inflating soft tissue expanders represent a valuable modality in reconstructive surgery. For this purpose, particularly synthetic hydrogels that increase their volume by swelling in aqueous environment are used. The current challenge in the field is to deliver a material with a suitable protracted swelling response, ideally with an induction period (for sutured wound healing) followed by a linear increase in volume lasting several days for required tissue reconstruction. Here, we report on synthesis, swelling, thermal, mechanical and biological properties of novel hydrogel tissue expanders based on poly(styrene-alt-maleic anhydride) copolymers covalently crosslinked with p-divinylbenzene. The hydrogels exerted hydrolysis-driven swelling response with induction period over the first two days with minimal volume change and gradual volume growth within 30 days in buffered saline solution. Their final swollen volume reached more than 14 times the dry volume with little dependence on the crosslinker content. The mechanical coherence of samples during swelling and in their fully swollen state was excellent, the compression modulus of elasticity being between 750 and 850 kPa. In vitro cell culture experiments and in vivo evaluation in mice models showed excellent biocompatibility and suitable swelling responses meeting thus the application requirements as soft tissue expanders.

Development of the synganglion and morphology of the adult nervous system in the mite Archegozetes longisetosus Aoki (Chelicerata, Actinotrichida, Oribatida).

Small arthropods show a highly condensed central nervous system, which is accompanied by the loss of the ancestral metameric organization. This results in the formation of one solid mass, a synganglion. Although numerous studies investigated the morphology of Archegozetes longisetosus, the organization of the nervous system is to date unknown. Using synchrotron X-ray microtomography, we investigated the organization of the nervous system in the adult stage and the development of the synganglion over all five free-living life stages (larva, proto-, deuto-, tritonymph and adult). The general morphology of the synganglion resembles that of other studied mites (in the classic sense) and ticks, being subdivided into a sub- and supraesophageal region, and consisting of cortex and neuropil. All nerves entering the walking legs except the first consist of two rami. This split is not based on a functional division into a motor and a sensory ramus, but both rami contain motor and sensory neurites. Within the synganglion, we found structures that resemble the ancestral metameric organization of the nervous system of arthropods. The development of the synganglion of A. longisetosus shows a more or less linear increase in volume, but cortex and neuropil grow at different rates over the five life stages. Between the second and third nymphal stage, the volume of the neuropil increases at a faster rate than the cortex.

Volume Expansion during Lithiation of Amorphous Silicon Thin Film Electrodes Studied by In-Operando Neutron Reflectometry

Amorphous silicon is a promising high-capacity anode material for the next generation of lithium-ion batteries. However, the enormous volume expansion of the active material during lithiation up to 400% (V/V0) is held responsible for capacity fading during cycling. In this study we measured continuously the volume modifications taking place during galvanostatic lithiation of amorphous silicon thin film electrodes by in-operando neutron reflectometry experiments. The results indicate (after initial effects) a linear increase in volume as a function of lithiation time and lithium content independent of current density and initial film thickness. The experimental results are in agreement with recent atomistic calculations.

Continuous growth facilitates feeding and reproduction: impact of size on energy allocation patterns for organisms with indeterminate growth

Body size has great influence on feeding, reproduction, and ecological importance. This study measures growth, reproduction, and feeding for several northeastern Pacific intertidal invertebrates that have indeterminate growth. In all species studied, linear size (length, diameter) showed asymptotic growth fit by the von Bertalanffy growth function, supporting the notion that less energy is allocated to growth with age because of increased reproduction. However, these same species displayed a continuous, roughly linear increase in volume with age. Both reproductive output and food intake were shown to scale proportionally with volume. This indicates that some species with indeterminate growth do not reduce energy allocation to growth with age but instead display continuous volumetric growth that facilitates increases in feeding rate and reproductive output with age and size. A simple allometric model is proposed to describe constant volumetric growth rates and linear increases in reproduction with age.

Repeated Sprint Training Improves Intermittent Peak Running Speed in Team-Sport Athletes

The aim of this study was to compare the effect of 2 repeated sprint training interventions on an intermittent peak running speed (IPRS) test designed for Australian Rules football. The test required participants to perform 10 × 10-m maximal efforts on an 80-m course every 25 seconds, for each of which the mean peak speed (kilometers per hour) was recorded to determine IPRS. The training interventions were performed twice weekly for 4 weeks immediately before regular football training. In the constant volume intervention (CVol), sprint repetition number remained at 10 (n = 9), and in the linear increase in volume (LIVol) intervention, repetition number increased linearly each week by 2 repetitions (n = 12). Intermittent peak running speed, 300-m shuttle test performance, and peak running speed were assessed before and upon completion of training. All measures were compared to a control group (CON; n = 8) in which players completed regular football training exclusively. Intermittent peak running speed performance in CVol and LIVol improved significantly (p < 0.01) by 5.2 and 3.8%, respectively, with no change in IPRS for CON. There were no differences in IPRS changes between CVol and LIVol. Additionally, peak running speed improved significantly (p < 0.01) by 5.1% for CVol, whereas 300-m shuttle performance improved significantly (p < 0.01) by 2.6% for LIVol only. Intermittent peak running speed, 300-m shuttle performance and peak running speed were improved after 4 weeks of training; however, progressively increasing sprint repetition number had no greater advantage on IPRS adaptation. Additionally, exclusive regular football training over a 4-week period is unlikely to improve IPRS, peak running speed, or 300-m shuttle performance.

Carbon Dioxide Diffusion and Plasticization in Fluorinated Polyimides

Extensive molecular dynamics (MD) simulations of 6FDA−6FpDA, 6FDA−6FmDA, and 6FDA−DAM polyimides with CO2 weight percentages up to ∼30%, were carried out to characterize the atomic level features associated with CO2 diffusivity in these glassy matrices. The fluorinated polyimide models were first loaded with CO2 in increments of 2% in order to mimic the experimental procedure of progressive loading and to avoid the necessity of artificially preswelling the simulation boxes. The sorption phase was then followed by a progressive desorption phase in decrements of 2%. This work covered nominal CO2 concentrations up to ∼200 cm3(STP) cm−3 and amounted to a total of more than 80 simulations of 5000 ps each at 308 K, as well as an additional 20 simulations at higher temperatures. In all cases, CO2 trajectories display the basic hopping-type mechanism, i.e. a combination of oscillations within available free volumes in the polymer matrix associated with occasional jumps from one site to another. There are no long-lived interactions with either the polymer or with the other penetrants, and thus, CO2 is a very mobile penetrant free to access any part of the matrix free-volume. Diffusion coefficients, DCO2, at 308 K were estimated from a novel trajectory-extending kinetic Monte Carlo (TEKMC) method, which, based on the actual CO2 trajectories during the MD production runs, allowed us to extend them by more than 3 orders of magnitude. These estimates of DCO2 compare very well with those obtained by a high-temperature Arrhenius extrapolation approach and with experimental evidence. Activation energies for diffusion are also validated by experimental data. All three polyimide models are able to reproduce both experimental penetrant-induced plasticization and sorption−desorption hysteresis during the few nanoseconds time scale available to MD simulations. The DCO2 are found to be very closely linked to the volume swelling−contraction behavior. They tend to remain low up to the start of plasticization and to be directly correlated to the gradual transition to an almost linear increase in volume at higher concentrations. The sorption−desorption hysteresis can be related to a fairly limited increase in polymer local mobility upon volume dilation, which means that the system is not able to come back to its initial structure upon desorption.

The effects of regional factors on the growth rate and the differentiation of mouse teratocarcinoma.

Murine embryonal carcinoma cells, the pluripotent stem cells of teratocarcinoma were injected simultaneously into caudal and cranial sites on the back of syngeneic recipients in order to determine whether regional anatomical differences affect their take and growth rate and differentiation. The overall tumour take rate was higher in caudal than cranial sites, but the initial weight of tumours was higher in the cranial than caudal sites. Tumours developing in the two anatomical sites grew at the same rate with a linear increase in volume. At the end of the 4-week experimental period the differences in the size of anterior and posterior tumours were negligible and no histological differences were noted between the two groups. Our data indicate that regional factors significantly affect the take rate and the initial growth of this murine teratocarcinoma, i.e. the establishment of solid tumours from injected stem cells. The growth rate of established tumours was not affected by regional factors.

The ‘kettle‐wax’ phase in soap systems: Dilatometric study of the systems sodium laurate‐water and sodium laurate‐sodium chloride‐water

AbstractBy a dilatometric method, curves depicting volume change with temperature were obtained for a number of sodium laurate—water systems containing from 50% to 75% by weight of soap. In these curves, the appearance of the ‘neat’ and middle soap phase is marked by a discontinuity. These phases exhibit a rather small but linear increase in volume with temperature. The transition temperatures as obtained from the dilatometric method were found to agree to within a few degrees with those predicted from the phase diagram of this system.These studies were extended to the ternary system sodium laurate—salt—water. For some of these ternary systems, the volume—temperature curves exhibited discontinuities at 80–90°, which were attributed to the appearance of a homogeneous phase termed ‘kettle‐wax’. The boundary of this kettle‐wax phase, which is capable of existing above 80–90° was delimited by means of these studies. The importance of this phase in determining various equilibria in soap boiling is discussed.