Stretch State Research Articles

High-resolution spectroscopic study of asymmetric [formula omitted] stretch [formula omitted] Torsion [formula omitted] combination band and other higher-lying vibrational fundamental, overtone, combination, and hot bands of astrophysically significant methanol [formula omitted] molecule

In this paper, the spectrum of high energy vibrational bands has been recorded in the range 1900-6000cm-1with the highest possible resolution. New assignments have been obtained for a large number of transitions belonging to several fundamental and combination bands. Varios bands of importance in the range 1950 − 3420 cm-1 are shown in Fig. 1. Notable are those belonging to a new combination band comprising the asymmetric CH3- Stretch band and OH internal rotation (or torsion) band lying in a very crowded region of the three coupled fundamental CH3- stretching bands. A large number of ΔK=±1 transitions have been observed from the ground and the first excited torsional states of the ground vibrational state. In addition, new transitions have been obtained for the torsionally excited OH- stretch band. The majority of the transitions have been confirmed using closed combination loops. In addition, detailed assignment work has been performed with improved accuracy on the overtone CO stretch band 2ν8, CO- Stretch:CH3-rock (ν8+ν7) combination band, and the overtone asymmetric CH3-bending band 2ν4. Due to an accidental state mixing in the first excited torsional state of the ground vibrational state, many forbidden transitions have been detected in the torsional band of the OH–stretch state (ν1). Lastly, a new and elegant method has been employed to obtain the pure torsional energies of many vibrational states. The most exciting finding from these studies has been the inversion of A/E energy structure. Some explanations from the literature have been reviewed, and more work is needed to understand the coupling between torsion and vibration in methanol. The work should be helpful in the astronomical search for methanol in interstellar space.

Double-Modal Locomotion of a Hydrogel Ultra-Soft Magnetic Miniature Robot with Switchable Forms.

Flexible miniature robots are expected to enter difficult-to-reach areas invivo to carry out targeted operations, attracting widespread attention. However, it is challenging for the existing soft miniature robots to substantially alter their stable shape once the structure is designed. This limitation leads to a fixed motion mode, which subsequently restricts their operating environment. In this study, we designed a biocompatible flexible miniature robot with a variable stable form that is capable of adapting to complex terrain environments through multiple movement modes. Inspired by the reversible stretching reaction of alginate saline gel stimulated by changes in environmental ion concentration, we manufactured a morphologically changeable super-soft hydrogel miniature robot body. According to the stretch and contraction shapes of the flexible hydrogel miniature robot, we designed magnetic fields for swing and rolling motion modes to realize multi-shape movement. The experimental results demonstrate that the deflection angle of the designed flexible miniature robot is reversible and can reach a maximum of 180°. The flexible miniature robot can complete forward swinging in the bar stretch state and tumbling motion in the spherical state. We anticipate that flexible hydrogel miniature robots with multiple morphologies and multimodal motion have great potential for biomedical applications in complex, unstructured, and enclosed living environments.

A homogenized constrained mixture model of cardiac growth and remodeling: analyzing mechanobiological stability and reversal.

Cardiac growth and remodeling (G&R) patterns change ventricular size, shape, and function both globally and locally. Biomechanical, neurohormonal, and genetic stimuli drive these patterns through changes in myocyte dimension and fibrosis. We propose a novel microstructure-motivated model that predicts organ-scale G&R in the heart based on the homogenized constrained mixture theory. Previous models, based on the kinematic growth theory, reproduced consequences of G&R in bulk myocardial tissue by prescribing the direction and extent of growth but neglected underlying cellular mechanisms. In our model, the direction and extent of G&R emerge naturally from intra- and extracellular turnover processes in myocardial tissue constituents and their preferred homeostatic stretch state. We additionally propose a method to obtain a mechanobiologically equilibrated reference configuration. We test our model on an idealized 3D left ventricular geometry and demonstrate that our model aims to maintain tensional homeostasis in hypertension conditions. In a stability map, we identify regions of stable and unstable G&R from an identical parameter set with varying systolic pressures and growth factors. Furthermore, we show the extent of G&R reversal after returning the systolic pressure to baseline following stage 1 and 2 hypertension. A realistic model of organ-scale cardiac G&R has the potential to identify patients at risk of heart failure, enable personalized cardiac therapies, and facilitate the optimal design of medical devices.

Fluid–structure interaction and flow sensing of primary cilia in oscillating fluid flows

This study systematically investigates the interaction between an oscillating flow and primary cilia using numerical simulations. The primary cilia are modeled as elastic filaments with rotatable basal ends to mimic real ciliary deflections. How some governing parameters [i.e., the peak Reynolds number (Repeak), Womersley number (Wo), cilium length (L*), and streamwise spacing interval (Ld*)] regulate fluid–cilia interaction is explored. Our results indicate that within a certain range, both the span of deflection (SD) and the maximal curvature increase with the increase in Repeak, L*, and Ld*, while they decrease as the Wo increases. Compared with other parameters, Ld* affects ciliary deflection less significantly and its impact becomes nearly negligible when the cilia are separated over twice their length. Three typical stretch states are captured. For primary cilia with a short or medium length, an increase in the SD is accompanied by a greater propagation distance of the location of the maximal tensile stress (LMTS). However, this is not the case for long cilia that protrude into 1/3 of the lumen, as the arising third stretch state may greatly suppress the LMTS propagation. Our study further confirms the role of primary cilia in decreasing the wall shear stress (WSS) and altering its oscillating feature. The WSS decrease is more significant for cilia undergoing a larger SD and/or when Ld* is reduced. For a constant Ld*, a larger SD corresponds to a more uneven oscillatory shear index distribution, and the affected (i.e., less oscillatory) region appears to greatly depend on Ld*.

Anti‐Freezing Self‐Adhesive Self‐Healing Degradable Touch Panel with Ultra‐Stretchable Performance Based on Transparent Triboelectric Nanogenerators

AbstractThe development of next‐generation touch panels requires sensors that are highly sensitive, biocompatible, transparent, stretchable, self‐healing, and even anti‐freezing and self‐powered because the traditional touch panel based on stiff and brittle electrodes faces many challenges. Conductive hydrogels hold great promise as sensing materials for the new‐generation touch panel. However, most hydrogel‐based touch panels are developed based on single‐function gel materials with a lack of the anti‐freezing and self‐power capabilities. Herein, the authors demonstrate a multi‐functional surface‐capacitive touch panel based on a triboelectric nanogenerator with an instantaneous peak power density of 209 mW m−2 that uses zwitterionic network hydrogels as a highly transparent (98.1% transmittance), ultra‐stretchable (>11 500% strain), degradable, and flexible ionic conductor. The panel can be utilized as a human‐machine interactive interface with fast response, high resolution, low parasitic capacitance, functional recovery instantly upon damage, and without sacrificing its functionalities even in the high stretch state (1600% areal strain) and at the subzero environment (<−20 °C). Epidermal touch panels are operated on arbitrary and complex surfaces, with outstanding input property demonstrated by writing, and playing computer games. Simultaneously, the multifunctional touch panel is degradable in phosphate buffered saline solution, and no pollution is caused.

Time evolution of CO2 ro-vibrational excitation in a nanosecond discharge measured with laser absorption spectroscopy

CO2 dissociation stimulated by vibrational excitation in non-equilibrium discharges has drawn lots of attention. Nanosecond (ns) discharges are known for their highly non-equilibrium conditions. It is therefore of interest to investigate the CO2 excitation in such discharges. In this paper, we demonstrate the ability for monitoring the time evolution of CO2 ro-vibrational excitation with a well-selected wavelength window around 2289.0 cm−1 and a single continuous-wave quantum cascade laser with both high accuracy and temporal resolution. The rotational and vibrational temperatures for both the symmetric and the asymmetric modes of CO2 in the afterglow of CO2 + He ns-discharge were measured with a temporal resolution of 1.5 μs. The non-thermal feature and the preferential excitation of the asymmetric stretch mode of CO2 were experimentally observed, with a peak temperature of Tv 3, max = 966 ± 1.5 K, Tv 1,2, max = 438.4 ± 1.2 K and T rot = 334.6 ± 0.6 K reached at 3 μs after the nanosecond pulse. In the following relaxation process, an exponential decay with a time constant of 69 μs was observed for the asymmetric stretch (001) state, consistent with the dominant deexcitation mechanism due to VT transfer with He and deexcitation on the wall. Furthermore, a synchronous oscillation of the gas temperature and the total pressure was also observed and can be explained by a two-line thermometry and an adiabatic process. The period of the oscillation and its dependence on the gas components is consistent with a standing acoustic wave excited by the ns-discharge.

Design and kinematics analysis of coordinated variable wheel-track walking mechanism

Wheeled walking mechanism has the advantages of high mobility and low rolling resistance, but it is easy to sink and slip when working in soft and muddy terrain. Tracked walking mechanism has the advantages of high passability and stability, but it has the problems of difficult steering and slow walking speed. In order to make the walking mechanism possess a combination of passability, stability, and mobility, a coordinated variable wheel-track walking mechanism was designed. The coordinated variable triangle track can change the landing area through the deformation structure to improve the ability of the walking mechanism to adapt to different terrains. The kinematics equation of the wheel-track walking mechanism was established, and the front wheel steering angle equation during motion was derived. Based on RecurDyn software, the motion simulation of the walking mechanism was carried out under the conditions of straight walking and turning on the flat ground, climbing hillsides, and crossing ditches. The simulation results show that the coordinated variable wheel-track walking mechanism has the mobility of wheeled walking mechanism and the passability and stability of the tracked walking mechanism. The stability and climbing ability of the wheel-track walking mechanism was better when the coordinated variable triangle track in the stretch state, and the mobility and steering ability was better in the contraction state.

On the uniform stress/uniform stretch states of prestressed arteries

This work examines the mechanics of the circumferentially prestressed N-layer artery, subject to axial tethering force and the internal pressure of blood, focusing on the uniform stretch state, the uniform circumferential stress states and the transitional states between them. Under increasing pressure the ith layer is shown to experience five distinct stages, two of which are the uniform stretch state and the uniform circumferential stress state. For arbitrary strain energy density, simple analytical expressions are presented for the stress distributions and the internal pressure at these specialized states. For the 1-layer, uniform tubular model of an artery without axial tethering force, the results coincide with those of Destrade et al. (2012). For the 2-layer composite tube, which models the mechanically significant medial and adventitial layers of large elastic arteries, numerical solutions are obtained employing two microstructurally based constitutive models for medial and adventitial arterial tissues, respectively. These results indicate that the uniform stretch state, the uniform circumferential stress state of the medial layer, and the uniform circumferential stress state of the adventitial layer occur at the diastolic blood pressure, the mean blood pressure, and the systolic blood pressure, respectively.

Hooped Amino-Group Chains in Porous Organic Polymers for Enhancing Heavy Metal Ion Removal.

By adjusting the stretch state of a triethylenetetramine (TETA) chain in an amine-functionalized porous organic polymer (POP), two adsorbents were designed to study the rational microenvironment for heavy metal ion removal. The quantum calculation elucidated that the hooped amino chains in FC-POP-CH2TETA-H exhibited stronger interactions with Pb(II) than the extended one in FC-POP-CH2TETA-E, not only through metal-ligand chelation but also metal coordination. The high binding energy of -2624 kJ mol-1 as well as the constructed microenvironment by the hooped amino chains ensured an extremely high Pb(II) capacity of 1134 mg g-1 on FC-POP-CH2TETA-H. Meanwhile, no more than 5 min to approach adsorption equilibrium revealed its ultrafast adsorption rate. It also showed excellent broad removal capability for multiple metal ions and nonsensitivity to pH. Therefore, by controlling the microenvironmental structures with suitable porosity, functional group stretching states, and coordination modes, the removal efficiency of heavy metal ions would be significantly enhanced, which further provided a promising strategy for designing a rational microenvironment to improve the task-specific separation properties.

Mechanical stresses associated with flattening of human femoropopliteal artery specimens during planar biaxial testing and their effects on the calculated physiologic stress-stretch state.

Planar biaxial testing is commonly used to characterize the mechanical properties of arteries, but stresses associated with specimen flattening during this test are unknown. We quantified flattening effects in human femoropopliteal arteries (FPAs) of different ages and determined how they affect the calculated arterial physiologic stress-stretch state. Human FPAs from 472 tissue donors (age 12-82years, mean 53 ± 16years) were tested using planar biaxial extension, and morphometric and mechanical characteristics were used to assess the flattening effects. Constitutive parameters for the invariant-based model were adjusted to account for specimen flattening and used to calculate the physiologic stresses, stretches, axial force, circumferential stiffness, and stored energy for the FPAs in seven age groups. Flattened specimens were overall 12 ± 4% stiffer longitudinally and 19 ± 11% stiffer circumferentially when biaxially tested. Differences between the stress-stretch curves adjusted and non-adjusted for the effects of flattening were relatively constant across all age groups longitudinally, but increased with age circumferentially. In all age groups, these differences were smaller than the intersubject variability. Physiologic stresses, stretches, axial force, circumferential stiffness, and stored energy were all qualitatively and quantitatively similar when calculated with and without the flattening effects. Stresses, stretches, axial force, and stored energy reduced with age, but circumferential stiffness remained relatively constant between 25 and 65years of age suggesting a homeostatic target of 0.75 ± 0.02MPa. Flattening effects associated with planar biaxial testing are smaller than the intersubject variability and have little influence on the calculated physiologic stress-stretch state of human FPAs.

The origin of compression influences geometric instabilities in bilayers

Geometric instabilities in bilayered structures control the surface morphology in a wide range of biological and technical systems. Depending on the application, different mechanisms induce compressive stresses in the bilayer. However, the impact of the chosen origin of compression on the critical conditions, post-buckling evolution and higher-order pattern selection remains insufficiently understood. Here, we conduct a numerical study on a finite-element set-up and systematically vary well-known factors contributing to pattern selection under the four main origins of compression: film growth, substrate shrinkage and whole-domain compression with and without pre-stretch. We find that the origin of compression determines the substrate stretch state at the primary instability point and thus significantly affects the critical buckling conditions. Similarly, it leads to different post-buckling evolutions and secondary instability patterns when the load further increases. Our results emphasize that future phase diagrams of geometric instabilities should incorporate not only the film thickness but also the origin of compression. Thoroughly understanding the influence of the origin of compression on geometric instabilities is crucial to solving real-life problems such as the engineering of smart surfaces or the diagnosis of neuronal disorders, which typically involve temporally or spatially combined origins of compression.

Tactical Diversity in Militant Violence

AbstractMilitant groups, like all organizations, carefully consider the tactics and strategies that they employ. We assess why some militant organizations diversify into multiple tactics while others limit themselves to just one or a few. This is an important puzzle because militant organizations that employ multiple approaches to violence are more likely to stretch state defenses, achieve tactical success, and threaten state security. We theorize that militant organizations respond to external pressure by diversifying their tactics to ensure their survival and continued relevance, and that the primary sources of such pressure are government repression and interorganizational competition. We find consistent support for these propositions in tests of both the Global Terrorism Database (GTD) and Minorities at Risk Organizational Behavior (MAROB) data sets. We bolster these findings with an additional specification that employs ethnic fractionalization in the first stage of a multi-process recursive model. These findings are relevant not only for academic research but for policy as well. While it is difficult for countries to anticipate the character of future tactical choices, they may be able to anticipate which groups will most readily diversify and thereby complicate counterterrorism efforts.

Mechanical Properties of Steel Wire Rope Under Combination of Stretch and Bending State

This research through the tests of bending property of a certain steel wire rope in the conditions of no tension state and tension state, obtained a correlation between the bending performance and wire rope tension, defined a gain tension coefficient (k) to the bending stiffness of wire rope, then open a way to research steel wire rope, and developed steel wire rope tension measurement method by three points bending.

Acoustomechanical giant deformation of soft elastomers with interpenetrating networks

We demonstrate giant deformation caused by ultrasound waves in soft elastomers with interpenetrating networks and reveal the physical mechanisms underlying the snap-through instability and phase transition. The snap-through instability can be harnessed to generate large deformation when the elastomer is subjected to combined mechanical and acoustical loading. We further demonstrate that the preserved stresses can enhance not only the mechanical tangential stiffness but also the acoustical tangential stiffness of the elastomer. However, with fixed acoustical loads, the preserved stresses reduce the mechanical tangential stiffness because the dependence of acoustic radiation stress on the stretch state overturns the effect of the preserved stresses. Our findings enable new strategies of device designs based on acoustomechanical soft elastomers having interpenetrating networks.

High-resolution Fourier transform synchrotron spectroscopy of the C–S stretching band of methyl mercaptan, CH332SH

The C–S stretching fundamental band of 12CH332SH, the principal isotopologue of methyl mercaptan, has been investigated by Fourier transform infrared spectroscopy on the Far-Infrared beamline at the Canadian Light Source synchrotron. The band is centered around 710cm−1 and shows well-resolved a-type parallel structure. Most of the A and E spectral sub-bands have been assigned up to K=12 for the vt=0 torsional state and K=9 for the vt=1 state, along with a smaller variety of sub-bands for vt=2. C–S stretching energy term values have been determined employing known ground-state energies, and have been fitted to series expansions in powers of J(J+1) to determine the substate origins. The origins have in turn been fitted to a Fourier model to characterize the oscillatory torsional energy structure of the C–S stretching state. The amplitude of oscillation of the vt=0 torsional curves is significantly larger for the C–S stretch state compared to the ground state. A strategy devised to relate this amplitude to an effective torsional barrier height indicates a decrease of about 7% in the effective V3 for the C–S stretch. The vibrational frequency determined for the stretching fundamental from the Fourier fit is 710.3cm−1. The C–S stretching manifold is crossed by excited vt=4 torsional levels of the ground state, and strong torsion–vibrational resonant coupling is observed via perturbations in the spectrum together with forbidden sub-bands induced by mixing and intensity borrowing.

Online identification algorithms for integrated dielectric electroactive polymer sensors and self-sensing concepts

Transducers based on dielectric electroactive polymers (DEAP) use electrostatic pressure to convert electric energy into strain energy or vice versa. Besides this, they are also designed for sensor applications in monitoring the actual stretch state on the basis of the deformation dependent capacitive–resistive behavior of the DEAP. In order to enable an efficient and proper closed loop control operation of these transducers, e.g. in positioning or energy harvesting applications, on the one hand, sensors based on DEAP material can be integrated into the transducers and evaluated externally, and on the other hand, the transducer itself can be used as a sensor, also in terms of self-sensing. For this purpose the characteristic electrical behavior of the transducer has to be evaluated in order to determine the mechanical state. Also, adequate online identification algorithms with sufficient accuracy and dynamics are required, independent from the sensor concept utilized, in order to determine the electrical DEAP parameters in real time. Therefore, in this contribution, algorithms are developed in the frequency domain for identifications of the capacitance as well as the electrode and polymer resistance of a DEAP, which are validated by measurements. These algorithms are designed for self-sensing applications, especially if the power electronics utilized is operated at a constant switching frequency, and parasitic harmonic oscillations are induced besides the desired DC value. These oscillations can be used for the online identification, so an additional superimposed excitation is no longer necessary. For this purpose a dual active bridge (DAB) is introduced to drive the DEAP transducer. The capabilities of the real-time identification algorithm in combination with the DAB are presented in detail and discussed, finally.

Temperature-Responsive Chromatographic System Using N<i></i>-Isopropylacrylamide Polymer-Modified Columns

Temperature-responsive poly (N-isopropylacrylamide) (NIPAMn) was grafted onto porous silica (Sil-NIPAMn) to be used as stationary phase for normal-phase high performance liquid chromatography (NP-HPLC). Specific interaction ability and unique selectivity were detected between NIPAMn and polyaromatic hydrocarbons (PAHs) through monitoring the retention time with increasing the temperature in NP-HPLC process. The results showed that Sil-NIPAMn has better retention behaviors for structural isomers of PAHs when the temperature is above its lower critical solution temperature (LCST) in mixture of n-hexane/isopropanol. It indicates that NIPAMn grafted on the silica shows phase transition from random coil to stretch state to increase interaction between solutes and stationary phase when temperature is above its LCST.

Circulating serum levels of growth differentiation factor-15 and neuregulin-1 in patients with paroxysmal non-valvular atrial fibrillation

Growth differentiation factor-15 (GDF-15) is a stress-responsivememberofthetransforminggrowthfactor- βsuperfamilythatwasorig-inally cloned as a macrophage-inhibitory cytokine [1]. It rapidly in-creases following myocardial stretch, volume overload, oxidativestress and inflammatory state [2,3]. In recent years, it is emerging as anovel biomarker to predict mortality and adverse events in patientswith heart failure (HF) [4–7], acute coronary syndrome (ACS) [8–10]and acute pulmonary embolism [11]. Neuregulin-1 (NRG-1) is a mem-beroftheepidermalgrowthfactor(EGF)family[12]andplaysacriticalrole in cardiovascular development, cell survival, growth, and metabo-lism [13,14]. Recently, NRG-1 was shown to be a stress-related cardiacgrowth and angiogenic biomarker [15,16].Atrialfibrillation(AF)isthemostcommoncardiacarrhythmiaandisassociated with an increased risk of morbidity and mortality [17]. Therole of GDF-15 and NRG-1 in the setting of AF has not been studied.We soughttoinvestigate thepotentialrelationshipbetweencirculatingserum levels of GDF-15, NRG-1 and non-valvular AF.We enrolled 67 consecutive patients with paroxysmal AF and 67patientswithoutAFmatchedforsex,ageandatheroscleroticriskfactorspresenting to our institution between August 2012 and June 2013.Exclusioncriteriawerehistoryofmyocardialinfarction,ACS,congestiveHF, history of cardiac surgery, valvular heart disease, congenital heartdisease, cardiomyopathy, liver and kidney dysfunction, recent strokeor transient ischemic attack, inflammatory or neoplastic diseases, thy-roid disorder and anemia. The ethics committee of Second Hospital ofTianjin Medical University approved this study and written informedconsent was obtained from all patients enrolled.Baseline demographic and clinical characteristics were collected.Serumcreatinine(Cr),fastingblood-glucose(FBG),alanineaminotrans-ferase (ALT), and aspartate aminotransferase (AST) were measuredafter overnight fasting of 12 h with an automatic analyzer (TBA-120FR, Toshiba, Shenzhen, China). Blood samples were collected after supinerest for at least 10 min and overnight fasting of 12 h. The blood sampleswere then centrifuged for 15 min at 3500 r/min to obtain superna-tants which were stored at −80 °C until use. Serum levels of SOD andCAT were measured by colorimetry (Nanjing Jiancheng BioengineeringInstitute, China). Serum high-sensitivity C-reactive protein (hs-CRP)was measured using a high-sensitivity immmunonephelometric assay.Serum levels of NRG-1 and GDF-15 were assayed using commerciallyavailable ELISA kit (Cusabio Biotech Corporation, China). The kit has adetection range of 31.25 to 2000 pg/ml for GDF-15 with intra-assayand inter-assay variability of b8% and b10% respectively. The detectionrange for NRG-1 was 7.8 to 500 ng/ml with intra-assay and inter-assayvariability of b8% and b10% respectively. Transthoracic echocardio-graphicexaminationwasperformedusingtheVivid-7systemequippedwitha2.4 MHztransducer (GE Medical Systems, Milwaukee, WI,USA).Leftatrialdiameter(LAD), interventricularseptalwallthickness(IVST),left ventricular posterior wall thickness (LVPWT) and left ventricularend-diastolic diameter (LVEDD) were measured. Left ventricular ejec-tion fraction (LVEF) was determined from apical four-chamber andtwo-chamber views using Simpson's biplane formula.Categorical variables were reported as percentage and continuousvariables as means ± SD or median (interquartile range). Statisticalanalysis was performed using t-test or Kolmogorov–Smirnov test forcontinuousvariableswhiletheChisquaretestwasusedtocomparecat-egorical variables. Multivariable regressionanalyses were performed toinvestigate the relationship between GDF-15, NRG-1 and AF. A P valueof b0.05 was regarded as statistically significant. All tests were two-tailed and analyses were performed using SPSS 17.0 Statistical PackageProgram (SPSS Inc., Chicago, IL, USA).Clinical characteristics of study population are shown in Table 1.Patients with paroxysmal AF and controls had a similar distribution incardiovascular risk factors and medications. Baseline laboratory andechocardiographic characteristics of study population are shown inTable2.PatientswithAFhadhigherLAD, NRG-1andGDF-15comparedto non-AF patients. No significant difference in hs-CRP, SOD and CAT

Chapter Twelve - Mechanotransduction in C. elegans Morphogenesis and Tissue Function

Mechanobiology is an emerging field that investigates how living cells sense and respond to their physical surroundings. Recent interest in the field has been sparked by the finding that stem cells differentiate along different lineages based on the stiffness of the cell surroundings (Engler et al., 2006), and that metastatic behavior of cancer cells is strongly influenced by the mechanical properties of the surrounding tissue (Kumar and Weaver, 2009). Many questions remain about how cells convert mechanical information, such as viscosity, stiffness of the substrate, or stretch state of the cells, into the biochemical signals that control tissue function. Caenorhabditis elegans researchers are making significant contributions to the understanding of mechanotransduction in vivo. This review summarizes recent insights into the role of mechanical forces in morphogenesis and tissue function. Examples of mechanical regulation across length scales, from the single-celled zygote, to the intercellular coordination that enables cohesive tissue function, to the mechanical influences between tissues, are considered. The power of the C. elegans system as a gene discovery and in vivo quantitative bioimaging platform is enabling an important discoveries in this exciting field.

Optimization of the energy harvesting control for dielectric elastomer generators

Energy harvesting using dielectric elastomers is an upcoming possibility to convert ambient energy into electric energy. Published results for energy harvesting cycles deal with charging and discharging of the polymer during a constant stretch state. However, real applications feature a continuously changing stretch and thus the time frames of the charging- and discharging-intervals have a considerable influence on the amount of harvested energy. This paper presents the calculation of the optimal charging- and discharging-intervals to maximize the energy gain. For this purpose the authors investigate the physical model of a lossy generator to derive the converted energy as a function of the timing of the charging- and discharging-interval. The subsequent optimization results in an energy-optimal harvesting cycle that combines the fundamental harvesting cycles with constant electric field and constant charge. Finally, we present the achievable energy gain of this optimized harvesting cycle as well as control laws to realize the optimized harvesting cycle.