Single Stretch Research Articles

Rearrangement of Proline Complexes with Zn2+: An Infrared Multiple Photon Dissociation and Theoretical Investigation.

Complexes of proline (Pro) cationized with Zn2+ and Cd2+ were examined by infrared multiple photon dissociation (IRMPD) action spectroscopy using light generated from a free electron laser. Complexes of intact Pro with CdCl+, CdCl+(Pro), a complex of (Zn+Pro-H)+ where a proton has been lost, as well as Zn+(Pro-H)(Pro) were formed by electrospray ionization. In order to identify the structures formed experimentally, the IRMPD spectra were compared to those calculated from optimized structures at the B3LYP/6-311+G(d,p) level for zinc complexes and B3LYP/def2-TZVP level with an effective core potential on cadmium for the CdCl+(Pro) system. For the latter complex, the main binding motif observed has a zwitterionic proline ligand structure, [CO2-]cc, where the metal binds to the two carboxylate oxygens. In contrast, for Zn+(Pro-H)(Pro), both ligands interact with zinc via a [N,CO-][N,CO] binding motif, where binding is observed at the carbonyl oxygens and nitrogens for both ligands, consistent with previous work. In both cases, contributions from different puckers of the proline ring may contribute. For (Zn+Pro-H)+, we identify that the structure is actually ZnH+(Pro-2H), in which the proline has been dehydrogenated and one of the hydrogens has migrated to form a covalent bond with Zn, which verifies a previous report relying on a single OH stretch band.

Access to Diverse Glutamic Acid Dendrons and a Janus Peptide Dendrimer Using an Atypical Solid Phase Synthesis.

The negligible cytotoxicity of anion surface-linked dendrons makes glutamic acid-based dendrons a potential candidate for materials and biological applications. Despite the inherent drawbacks of the conventional solution phase synthesis of glutamic acid-based dendrons, there have been no advancements in these protocols. Herein, we demonstrate the first-ever convergent solid phase synthesis of dendrons, up to fourth generation, having glutamic acid branching points produced by preactivation of dicarboxylic acid groups with N-hydroxysuccinimide and simultaneous coupling with amine groups of two growing peptide chains, with excellent yields (30-70%). In addition to the general advantages, such as the easy workup, a final single purification step, and an overall short synthesis duration, the convergent solid phase synthesis allowed us to chemically synthesize glutamic acid branching-based dendrons that cannot be accessed by standard divergent solid phase synthesis. This method has also been validated for its application in synthesizing hard-to-achieve Janus peptide dendrimers in a single stretch on a solid support. Our work corroborates the efficacy of controlled -COOH activation to accomplish an atypical solid phase synthesis of diverse glutamic acid dendrons in a convergent fashion. This is the first example of a Janus peptide dendrimer being synthesized on a solid support, utilizing both convergent and divergent approaches simultaneously.

New two-parameter constitutive models for rubber-like materials: Revisiting the relationship between single chain stretch and continuum deformation

The connection between macroscopic deformation and microscopic chain stretch is a key element in constitutive models for rubber-like materials that are based on the statistical mechanics of polymer chains. A new micro-macro chain stretch relation is proposed, using the Irving–Kirkwood–Noll procedure to construct a Cauchy stress tensor from forces along polymer chains. This construction assumes that the deformed polymer network remains approximately isotropic for low to moderate macroscopic stretches, a starting point recently adopted in the literature to propose a non-affine micro-macro chain stretch relation (Amores et al., 2021). Requiring the constructed Cauchy stress to be consistent with the stress tensor derived from the strain energy density results in a new chain stretch relation involving the exponential function. A hybrid chain stretch relation combining the new chain stretch with the well-known affine relation is then proposed to account for the whole range of stretches in experimental datasets. Comparison of the model predictions to experimental data in the literature shows that the two new micro-macro chain stretch relations in this work result in two-parameter constitutive models that outperform those based on existing chain stretches with no increase in the number of fitting parameters used.

Deformation mechanism of conjugated polymer films during single and cyclic stretching

Reversibility and durability have become new bottlenecks for conjugated polymers to realize “stretchable” semiconducting devices. Therefore, the correlation between microstructure and mechanical properties requires explicit delineation. Herein, the deformation and fracture mechanisms of DPP-TVT (poly [2,5-bis(4-decyl tetradecyl) pyrrolo [3,4-c]pyrrole-1,4-(2H, 5H)-dione-(E)-1,2-di (2,2′-bithiophen-5-yl)ethene) films with various degree of lamellar order were investigated from microscopic view. In the medium ordered films, the lamellae and amorphous phase cooperate to form the fibrous network structure in respond to tensile deformation. When recovered, this fibrous network could deform and being compressed, providing an efficient stress transfer pathway to accommodate the residual strain. Therefore, the medium ordered films did not form cracks even under 100 cycles of 50 % strain. However, in near-amorphous films, the uniformly aligned chains in stretched films were difficult to reorient under compression, resulting in the formation of large wrinkles and poor fatigue resistance. And the highly ordered films generate cracks both under single and cyclic stretch due to lacking of stress dissipation pathways. This study lays the groundwork for enhancing the mechanical robustness of conjugated polymer films.

Piezo1 and Piezo2 channels in retinal ganglion cells and the impact of Piezo1 stimulation on light-dependent neural activity.

Activation of Piezo1 excites retinal ganglion cells, paralleling the early neurodegenerative progression in glaucoma mouse models and retinal degeneration.Piezo1 and Piezo2 were expressed in axons and soma of retinal ganglion cells in mice, rats, and human iPSC-RGCs.Functional assays confirmed Piezo1 in soma and neurites of neurons. Sustained elevation of Piezo1 and Piezo2 occurred after a single transient stretch may enhance damage from repeated traumatic nerve injury.

Hybrid Treatment and Natural Aging Behavior of Peak-Aged Eutectoid Steel Powder-Reinforced Al 7075 Matrix Composites

The current work focuses on the natural aging phenomenon of a eutectoid steel powder-(0.8 wt.%) reinforced Al-Zn-Mg (Al 7075) alloy, which was subjected to a hybrid heat treatment. The hybrid treatment comprises the aging treatment of a matrix and the conventional treatment of a steel reinforcement in a single stretch on the stir cast composite. This material finds uses in space and transportation applications. The hybrid treatment consists of a conventional heat treatment cycle to obtain pearlite, bainite, and martensite phases in steel powder, followed by an age-hardening treatment for the Al 7075 matrix. This hybrid heat treatment resulted in improvements in the hardness and strength over the conventional aging treatment. The peak-aged hybrid specimens were subjected to natural aging in an open atmosphere for a continuous duration of 25 weeks to study the stability of the properties after peak aging. Tests of the mechanical properties such as the hardness and tensile strength along with microstructure analysis were carried out. During natural aging, the hardness of composites decreases irrespective of the quantity of the reinforcement in the composites and the type of reinforcement phase alteration during hybrid heat treatment. Also, the composites subjected to hybrid heat treatment show better resistance to natural aging compared to the conventionally aged samples. Within the group, the hybrid-treated martensite formed into a composite with 6 wt.% reinforcement showed only a 4% reduction in hardness during natural aging, which is an indication of a decent level of resistance to natural aging.

Stretch-injury promotes microglia activation with enhanced phagocytic and synaptic stripping activities

Microglial cells, as the primary defense line in the central nervous system, play a crucial role in responding to various mechanical signals that can trigger their activation. Despite extensive research on the impact of chemical signaling on brain cells, the understanding of mechanical signaling in microglia remains limited. To bridge this gap, we subjected microglial cells to a singular mechanical stretch and compared their responses with those induced by lipopolysaccharide treatment, a well-established chemical activator. Here we show that stretching microglial cells leads to their activation, highlighting their significant mechanosensitivity. Stretched microglial cells exhibited distinct features, including elevated levels of Iba1 protein, a denser actin cytoskeleton, and increased persistence in migration. Unlike LPS-treated microglial cells, the secretory profile of chemokines and cytokines remained largely unchanged in response to stretching, except for TNF-α. Intriguingly, a single stretch injury resulted in more compacted chromatin and DNA damage, suggesting potential long-term genomic instabilities in stretched microglia. Using compartmentalized microfluidic chambers with neuronal networks, we observed that stretched microglial cells exhibited enhanced phagocytic and synaptic stripping activities. These findings collectively suggest that stretching events can unlock the immune potential of microglial cells, contributing to the maintenance of brain tissue homeostasis following mechanical injury.

Efficacy of Single Titanium Elastic Nail in the Treatment of Child Femur Fractures.

Femoral shaft fractures in childhood constitute an important part of emergency visits to orthopedic clinics. The aim of this study was to investigate the efficacy and reliability of a method in the treatment of simple fractures in the middle of the femoral diaphysis in patients with multiple injuries or in the treatment of cases with a medullary canal that is too narrow for two nails, with a single stretch nail thicker than half the diameter of the canal. Between July 2002 and November 2006, examinations were made of 11 femoral fractures in 11 patients who were admitted to the pediatric emergency department of Tepecik Training and Research Hospital with a diagnosis of femoral fracture and who were hospitalized and treated with a single flexible intramedullary titanium nail. In the follow-up, no problem was found in terms of union and length difference in any of the cases, except for a10º varus deformity present after surgery in one case. Elastic intramedullary nailing is an effective method in the treatment of simple femoral fractures in children. A single elastic nail provides adequate stability following open reduction with minimal incision in patients whose short operating time must be kept short such as those with head trauma, thoracic trauma, or intra-abdominal pathology, or patients with a narrow medullary canal where two flexible nails cannot pass. We think that it is a feasible method because it causes minimal soft tissue damage.

Single Stretch Wire and vibrating wire measurement system for characterization of multipole accelerator magnets

A stretch wire magnetometer is a versatile instrument and can be treated as the primary standard of magnetic qualification of accelerator magnets. Bhabha Atomic Research Centre has developed a Stretch wire magnetic measurement system to cater to the requirements of magnetic measurements on accelerator magnets. This bench also includes a vibrating wire system. The scheme used in this instrument for measurements of magnetic flux ensures drift compensations after each scan. This feature along with post-signal processing gives an accuracy of homogeneity measurements comparable to that of a rotating coil magnetometer. Unlike conventional stretch wire systems, wire moves in the r-z plane (along r-axis) at different azimuthal angles. This provides the opportunity for drift compensation at each scan. This has immensely enhanced the measurement accuracy of non-homogeneity of integral fields to less than 3 units. The same is cross-verified with a rotating coil system. The comparison between rotating coil and stretch wire is presented. The Paper gives the step-wise procedure for the measurement of key performance indicators of an accelerator magnet. This paper brings out salient features of the system along with design and calibration results.

The immediate effects of two pilates exercises with and without a foam roller on abdominal muscle activity

Pilates can be defined as exercises which are floor-based or use specialized equipment to provide resistance. The use of foam rollers (FR) have been purported to improve the recruitment of core muscles by creating an unstable surface, providing improvements to balance, posture and functional recovery in daily activities. However, there is a paucity of studies exploring the use of FR as an unstable surface. The aim of this study was to analyze the acute effects on the recruitment of core muscles during two Pilates exercises, a single leg stretch (SL) and single straight leg stretch (SS), on the ground and using a FR as an unstable surface. Thirty women aged between 25 and 35 years old who had not previously practiced Pilates participated in this study. Surface EMG signals were collected from rectus abdominis (RA) and external oblique (EO) muscles during an isometric contraction lasting 30 s during the exercises. Two-factor Repeated Measures ANOVA tests with post hoc pairwise comparisons were used to investigate the muscle activity between the two stretching exercises when performed on the ground and using the FR. No significant interaction effects were seen between the two exercises and positions, and no main effects were seen for either factor. These findings do not indicate the influence of the surface (ground versus FR) or exercise (SL versus SS) on the muscle activity of the rectus abdominis and external oblique muscles when considering the immediate effects. Future studies should consider the effects over a longer time period.

Achieving the high charge mobility of conjugated polymers under cyclic stretching by changing the interaction parameter between solvent and sidechain

Conjugated polymers have been well-known as a critical candidate for stretchable electronics applications. However, further research is still needed to fully understand what kind of film morphology is beneficial to keep the charge mobility under cycling deformation. Herein, we proposed that the co-deformation of crystalline domains and amorphous regions can effectively dissipate strain energy. To verify our idea, we developed three kinds of the morphology of a diketopyrrolopyrrole-based polymer (DPP-TVT) with different crystallinity by changing the interaction parameter between solvent and sidechain (Rasolvent-sidechain). The films cast from TCB with medium crystallinity exhibited 100% mobility retention (0.42 cm2V−1s−1) under 100% strain and after 100 stretch-release cycles at 50% strain. However, the mobility of CN films with high crystallinity decreased from 0.45 to 0.23 cm2V−1s−1 under a single stretch at 100% strain, while the performance of CF films with low crystallinity decreased from 0.34 to 0.052 cm2V−1s−1 after 100 stretch-release cycles at 50% strain. The optimized performance of TCB films stems from the fact that the dispersed crystallites embedded in the amorphous matrix provide an efficient and robust charge transport network under single and repeating deformation. This research would aid in manipulating the mechanical and electrical properties of conjugated polymers.

Architectural and Mechanical Changes after Five Weeks of Intermittent Static Stretch Training on the Medial Gastrocnemius Muscle of Active Adults

We investigated the effects of intermittent long-term stretch training (5 weeks) on the architectural and mechanical properties of the muscle-tendon unit (MTU) in healthy humans. MTU's viscoelastic and architectural properties in the human medial gastrocnemius (MG) muscle and the contribution of muscle and tendon structures to the MTU lengthening were analyzed. Ten healthy volunteers participated in the study (four females and six males). The passive stretch of the plantar flexor muscles was achieved from 0° (neutral ankle position) to 25° of dorsiflexion. Measurements were obtained during a single passive stretch before and after the completion of the stretching protocol. During the stretch, the architectural parameters of the MG muscle were measured via ultrasonography, and the passive torque was recorded by means of a strain-gauge transducer. Repeated-measure ANOVA was applied for all parameters. When expressed as a percentage for all dorsiflexion angles, the relative torque values decreased (p < 0.001). In the same way, architectural parameters (pennation angle and fascicle length) were compared for covariance and showed a significant difference between the slopes (ANCOVA p < 0.0001 and p < 0.001, respectively) suggesting a modification in the mechanical behavior after stretch training. Furthermore, the values for passive stiffness decreased (p < 0.05). The maximum ankle range of motion (ROM) (p < 0.01) and the maximum passive torque (p < 0.05) increased. Lastly, the contribution of the free tendon increased more than fascicle elongation to the total lengthening of the MTU (ANCOVA p < 0.001). Our results suggest that five weeks of intermittent static stretch training significantly change the behavior of the MTU. Specifically, it can increase flexibility and increase tendon contribution during MTU lengthening.

Driving Forces for Single DNA Stretching Assessed by In Situ TIRFM.

Herein, single DNA molecule stretching in a hydrodynamic flow was monitored by in situ total internal reflection fluorescence microscopy (TIRFM). Different driving forces for DNA stretching were assessed systematically. The binding force between the substrate and the DNA molecule significantly affected the dynamic stretching behavior of coiled DNA, where DNA stretched only on the substrate modified by -NH2 due to electrostatic adsorption. Proper flow force from the fluid was favorable for DNA stretching, which was in stark contrast to DNA stretching restricting at a lower flow rate or washing off DNA molecules at a higher flow rate of fluid. Moreover, DNA stretching was restricted in low pH solution but improved in high pH solution. This is due to the confrontation between contractive and repulsion forces in coiled DNA molecules in different pH, which is related to the Donnan equilibrium in a single condensed DNA molecule. Additionally, external Na+ would break this Donnan equilibrium, leading to a restriction for DNA stretching. This study will guide quantitative dynamics studies of DNA stretching in the future.

Effectiveness of the Natura 2000 network for freshwater fish conservation in a Mediterranean region

Protected areas (PAs) are the cornerstones of global biodiversity conservation efforts, but to fulfil this role they must be effective at conserving both habitat and species. Among protected taxa, freshwater fish are exposed to multiple disturbances and are considered one of the most endangered. The Natura 2000 reserves network was established with the aim of preserving biodiversity across Europe, but few assessments have been made on its effectiveness on the conservation of freshwater fish species. We tested the hypothesis that fish community is exposed to less anthropogenic pressures within the Natura 2000 sites than outside, hosting a higher number of native species and maintain lower number of non-native species. We tested these hypotheses considering 3,777 sampling sites, found across the entire Italian territory. Results showed that PAs did not guarantee less anthropogenic impacts and higher fish species richness than outside PAs, suggesting that PAs are not a panacea for anthropogenic pressures and safeguarding fish diversity. Nevertheless, more caution should be applied to the management measures and the design of new PAs due to the limitations of the protection of a single stretch within a whole river ecosystem. Moreover, the impossibility to operate any management of invasive fish species on the broad scale of a whole river basin is likely the most limiting factor to fish biodiversity conservation in Italy. Finally, it is also necessary to extend the analysis to other basins and Natura 2000 sites in Europe.

Structural Evolution of PGA Nascent Fiber during Single Low-Temperature and Segmented High-Temperature Hot Stretching

Structural Evolution of PGA Nascent Fiber during Single Low-Temperature and Segmented High-Temperature Hot Stretching

Patterned Colouring via Variable-Speed Single Stretching

We demonstrate a cost-effective, highly reliable/stable and environmentally friendly approach for the patterned colouring of a commercial transparent polyethylene terephthalate (PET). We show that different colour patterns (transparent, white/translucent, complete white/silver and different combinations of these three colours) can be realised in PET strips upon varying the speed during continuous stretching. The conditions for good quality colour patterns are investigated, and the length of transient region during speed change is investigated.

Repair of mismatched templates during Rad51-dependent Break-Induced Replication.

Using budding yeast, we have studied Rad51-dependent break-induced replication (BIR), where the invading 3' end of a site-specific double-strand break (DSB) and a donor template share 108 bp of homology that can be easily altered. BIR still occurs about 10% as often when every 6th base is mismatched as with a perfectly matched donor. Here we explore the tolerance of mismatches in more detail, by examining donor templates that each carry 10 mismatches, each with different spatial arrangements. Although 2 of the 6 arrangements we tested were nearly as efficient as the evenly-spaced reference, 4 were significantly less efficient. A donor with all 10 mismatches clustered at the 3' invading end of the DSB was not impaired compared to arrangements where mismatches were clustered at the 5' end. Our data suggest that the efficiency of strand invasion is principally dictated by thermodynamic considerations, i.e., by the total number of base pairs that can be formed; but mismatch position-specific effects are also important. We also addressed an apparent difference between in vitro and in vivo strand exchange assays, where in vitro studies had suggested that at a single contiguous stretch of 8 consecutive bases was needed to be paired for stable strand pairing, while in vivo assays using 108-bp substrates found significant recombination even when every 6th base was mismatched. Now, using substrates of either 90 or 108 nt-the latter being the size of the in vivo templates-we find that in vitro D-loop results are very similar to the in vivo results. However, there are still notable differences between in vivo and in vitro assays that are especially evident with unevenly-distributed mismatches. Mismatches in the donor template are incorporated into the BIR product in a strongly polar fashion up to ~40 nucleotides from the 3' end. Mismatch incorporation depends on the 3'→ 5' proofreading exonuclease activity of DNA polymerase δ, with little contribution from Msh2/Mlh1 mismatch repair proteins, or from Rad1-Rad10 flap nuclease or the Mph1 helicase. Surprisingly, the probability of a mismatch 27 nt from the 3' end being replaced by donor sequence was the same whether the preceding 26 nucleotides were mismatched every 6th base or fully homologous. These data suggest that DNA polymerase δ "chews back" the 3' end of the invading strand without any mismatch-dependent cues from the strand invasion structure. However, there appears to be an alternative way to incorporate a mismatch at the first base at the 3' end of the donor.

Characterization of coding areas of SPGA11B gene in Murrah bulls

The SPAG11 gene is one of pivotal molecules in reproduction as it takes part in spermatozoa maturation, acquiring motility, capacitation, and egg-sperm interaction as well. The current study was aimed to characterize SPAG11 gene in Indian Murrah bulls through direct DNA sequencing approach. Genomic DNA from Murrah animals were isolated from 130 Murrah bulls and amplified using three sets of forward and reverse primers which were based on reference sequence (Genbank accession no. AC_000164.1) of Bos taurus covering entire coding region of SPAG11B gene. The PCR products of 563, 340 and 373, bp covering exons 1 to 3 were subjected to sequencing and subsequently ClustalW analysis revealed the substitution at 34 positions and a single stretch of 22 bp deletion in comparison to the Bos taurus reference sequence. Total seven novel SNPs were observed as two in the coding region and five in 5ˈUTR. However, only one of SNPs resulted in amino acid substitution viz. p.1279 arginine to tryptophan in translated protein in Murrah buffaloes. Sequence alignment and homology across species for the targeted nucleotide sequence of SPAG11 gene in Murrah bulls was done by nucleotide BLAST (NCBI) that showed maximum identity of 97% with mRNA of Bos taurus and Capra hircus followed by 96% homology with Bos indicus and Bison bison and 95% homology with Ovis aries and Bos mutus.

Role of Skin Stretch on Local Vascular Permeability in Murine and Cell Culture Models.

Background:Excessive mechanical forces, particularly skin stretch, have been implicated in pathological cutaneous scarring. We hypothesize that this reflects, in part, stretch-induced vessel leakage that provokes prolonged wound/scar inflammation. However, this has never been observed directly. Here, a mouse model was used to examine the effect of skin flap stretching on vascular permeability. An in vitro model with pseudocapillaries grown in a stretchable chamber was also used to determine the effect of stretching on endothelial cell morphology and ion channel activity.Methods:Murine skin flaps were stretched with a biaxial stretching device, after which FITC-conjugated-dextran was injected and imaged with fluorescence stereomicroscopy. Endothelial cells were induced to form pseudocapillary networks in an elastic chamber. The chamber was stretched and differential interference contrast microscopy was used to assess cell morphology. In other experiments, markers for Ca2+ influx and K+ efflux were added before a single stretch was conducted. Histamine served as a positive-control in all experiments.Results:Cyclic stretching (20%) increased the vascular permeability of skin flaps almost as strongly as histamine. Both stimuli also partially disrupted the pseudocapillary networks, induced cell contraction, and created gaps between the cells. Both stimuli caused sustained K+ efflux; stretching had a milder effect on Ca2+ influx.Conclusions:Excessive cyclical stretching strongly increased the vascular permeability of skin vessels and in vitro pseudocapillaries. This effect associated with increased K+ efflux and some Ca2+ influx. Inhibiting such early stretch-induced signaling events may be an effective strategy for treating and preventing hypertrophic scars and keloids.

Effect of weight of reinforcement and coating thickness on the hardness of stir cast AL7075-nickel coated duralumin powder mmc

In the present work, it is experimented to reinforce duralumin powder (3 to 7 wt %.)into Al7075 matrix by stir casting technique. Since matrix and reinforcement both have almost similar melting temperatures,theleast expensive additive manufacturing metallurgical route seems to be the best fit. In this study, an effort was made to produce the Al7075 matrix composite reinforced with duralumin by a novel stir casting method by coating duralumin powders with nickel which has high temperature melting point compared to reinforcement material. Nickel has goodwettability and avoids undesirable chemical reactions between the reinforcement and matrix at higher temperatures, acting as a protector for both the duralumin and matrix. Since, aging kinetics of duralumin (Al2024) and Al7075 are different, both positively respond to heat treatment in a single stretch for propertyalteration. During stir casting, even though duralumin melts along with the matrix, it will be under the solid protection barrier (coat) of nickel, avoiding dissolution with the Al7075 matrix.To verify the presence of reinforcement duralumin in the matrix and to decide the soundness of the casting produced by stir casting, confirmation tests are made like microstructures with EDS and micro hardness distribution. The microstructure analysis of the compositeshowedan even distribution of nickel coated duralumin in the matrix when the coating thickness of a nickel is greater than 8 µm. The hardness test analysis has shown an improvement in the hardness with the increase in the weight % of the reinforcement. Improvement in the hardness of composites is due to an increase in dislocation number, which shows higher resistance to plastic deformation [2].Statistical analysis has shown that the coating of reinforcement does not have any significant effect on the mechanical properties. The regression equation is fit to determine the hardness of the composite involving the factors within the range of values considered for this study.