High Degree Of Stiffness Research Articles

Bio-inspired selective nodal decoupling for ultra-compliant interwoven lattices

Architected materials such as lattices are capable of demonstrating extraordinary mechanical performance. Lattices are often used for their stretch-dominated behavior, which gives them a high degree of stiffness at low-volume fractions. At the other end of the stiffness spectrum, bending-dominated lattices tend to be more compliant and are of interest for their energy absorption performance. Here, we report a class of ultra-compliant interwoven lattices that demonstrate up to an order of magnitude improvement in compliance over their traditional counterparts at similar volume fractions. This is achieved by selectively decoupling nodes and interweaving struts in bending-dominated lattices, inspired by observations of this structural principle in the lattice-like arrangement of the Venus flower basket sea sponge. By decoupling nodes in this manner, we demonstrate a simple and near-universal design strategy for modulating stiffness in lattice structures and achieve among the most compliant lattices reported in the literature.

Response comparison of PLC and SLC with magnetic resonance elastography after TACE

The aim of this study was to detect a response difference in primary (PLC) and secondary liver tumors (SLC) with magnetic resonance elastography (MRE) after TACE therapy. Thirty-one patients (25/31 male; mean age 69.6 years [range: 39–85 years]) with repeated TACE therapy of HCC were compared with twenty-seven patients (27/27 female; mean age 61.2 years [range 39–81 years]) with repeated TACE therapy of metastatic liver disease due to breast cancer. Both groups underwent either one (n = 31) or two (n = 27) repetitive magnetic resonance imaging (MRI) and MRE exams in 4- to 6-week intervals using a 1.5-T-scanner. MRE-based liver stiffness and size measurements were evaluated in tumorous lesions and in healthy liver lobe controls. PLC showed a significantly larger tumor size compared to SLC (26.4 cm2 vs. 11 cm2, p = 0.007) and a higher degree of stiffness (5.8 kPa vs. 5.1 kPa, p = 0.04). Both tumors decreased in size during the cycles (PLC: p = 0.8 and SLC: p < 0.0001) and lesions showed an increase in stiffness (PLC: p = 0.002 and SLC: p = 0.006). MRE demonstrates that PLC and SLC have similar responses to TACE therapy. PLC had a greater increase in stiffness and SLC got smaller. An increasing stiffness and decrease in size could show a good response.

Evaluation of MR elastography as a response parameter for transarterial chemoembolization of colorectal liver metastases

ObjectiveThe aim of this study was to evaluate magnetic resonance elastography (MRE) as a response parameter in patients who received transarterial chemoembolization (TACE) for the treatment of colorectal liver metastases.Materials and methodsForty-two patients (29 male patients; mean age, 61.5 years; range, 41–84 years) with repeated TACE therapy of colorectal liver metastases underwent on average 2 repetitive magnetic resonance imaging (MRI) and MRE exams in 4- to 6-week intervals using a 1.5-T scanner. MRE-based liver stiffness measurements were performed in normal liver parenchyma and in metastatic lesions. Moreover, the size of the liver metastases was assessed during treatment and compared with the results of the MRE analysis.ResultsLiver metastases showed a significantly higher degree of stiffness compared with the normal liver parenchyma (p < 0.001). However, only a weak correlation was found between the lesion size and stiffness (r = − 0.32, p = 0.1). MRE analysis revealed an increase in stiffness of the colorectal liver metastases from 4.4 to 7.1 kPa after three cycles of TACE (p < 0.001). Also, the mean size of the metastases decreased from 17.0 to 11.3 cm2 (p < 0.001). Finally, the entire liver stiffness increased from 2.9 to 3.1 kPa over the three cycles of TACE therapy.ConclusionIn conclusion, MRE showed a significant change in stiffness and size of liver metastases. Therefore, MRE may provide an added value for an evaluation of treatment response in patients with colorectal liver metastases undergoing TACE.Key Points• MRE showed an increase in stiffness of the colorectal liver metastases during TACE therapy.• Liver metastases showed a significantly higher degree of stiffness compared with the normal liver parenchyma.• However, only a weak correlation was found between the lesion size and stiffness.

Round-knit or flat-knit compression garments for maintenance therapy of lymphedema of the leg? - Review of the literature and technical data.

To date, there have been no studies comparing flat-knit and round-knit compression garments for maintenance therapy of lymphedema of the leg. According to expert opinion, flat-knit fabrics are generally recommended for this purpose. Given the differences in the clinical presentation of lymphedema in terms of disease stage and location as well as patient adherence, and, last but not least, for economic reasons, it seems questionable whether all patients with lymphedema of the leg actually do require flat-knit compression garments. Considering technical aspects, published data and our own clinical experience, it seems reasonable that the choice of compression stockings be based on clinical findings and not on the diagnosis. Typical indications for flat-knit garments include significant differences in leg circumference as well as deep skin folds and edema of the toes/forefoot. However, there are also patients with lymphedema who benefit from round-knit fabrics with a high degree of stiffness. In any case, prior to maintenance therapy, it is essential to adequately decongest the legs using compression bandages and/or adaptive compression systems.

An Overview of the Recent Progress in the Synthesis and Applications of Carbon Nanotubes

Carbon nanotubes (CNTs) are known as nano-architectured allotropes of carbon, having graphene sheets that are wrapped forming a cylindrical shape. Rolling of graphene sheets in different ways makes CNTs either metals or narrow-band semiconductors. Over the years, researchers have devoted much attention to understanding the intriguing properties CNTs. They exhibit some unusual properties like a high degree of stiffness, a large length-to-diameter ratio, and exceptional resilience, and for this reason, they are used in a variety of applications. These properties can be manipulated by controlling the diameter, chirality, wall nature, and length of CNTs which are in turn, synthesis procedure-dependent. In this review article, various synthesis methods for the production of CNTs are thoroughly elaborated. Several characterization methods are also described in the paper. The applications of CNTs in various technologically important fields are discussed in detail. Finally, future prospects of CNTs are outlined in view of their commercial applications.

Development of an end-effector device for loose body removal in hip arthroscopy.

This article describes a novel hand-operated end-effector device developed for loose body removal in hip arthroscopy. This sterilizable and reusable device incorporates a wire-ball joint mechanism that provides motion with 5 degrees of freedom. The design accounted for the following: (1) the diameter of the femoral head, (2) range of motion of the wrist joint of the operator, (3) ease of assembly of modular parts, and (4) material stiffness and durability. The developed device is composed of three parts: a pistol-shaped hand-held unit, forceps module, and end-effector module, all of which were constructed using polyamide-imide. Experiments were conducted to characterize the range of motion, pushing force, and lateral stiffness of the end-effector. Seven consulting surgeons evaluated the performance of the device in arthroscopic hip model and cadaveric studies in comparison with that of a conventional linear grasper. The experimental results show that the developed device can perform tasks that conventional linear graspers cannot. A specialized end-effector device was developed for hip arthroscopy where a high degree of stiffness is required. The end-effector module is interchangeable based on the required outer diameter, and it is also reusable after sterilization at high temperature.

Tailoring Polyelectrolyte Architecture To Promote Cell Growth and Inhibit Bacterial Adhesion.

An important challenge facing the application of implanted biomaterials for tissue engineering is the need to facilitate desirable tissue interactions with the implant while simultaneously inhibiting bacterial colonization, which can lead to implant-associated infection. In this study, we explore the relevance of the physical parameters of polyelectrolyte multilayers, such as surface charge, wettability, and stiffness, in tissue cell/surface and bacteria/surface interactions, and investigate the tuning of the multilayer architecture to differentially control such interactions. Polyions with different side-chain chemical structures were paired with polyethylenimine to assemble multilayers with parallel control over surface charge and wettability under controlled conditions. The multilayers can be successfully cross-linked to yield stiffer (the apparent Young's modulus was increased more than three times its original value) and more stable films while maintaining parallel control over surface charge and wettability. The initial adhesion and proliferation of 3T3 fibroblast cells were found to be strongly affected by surface charge and wettability on the non-cross-linked multilayers. On the other hand, these cells adhered and proliferated in a manner similar to those on the cross-linked multilayers (apparent Young's modulus ∼2 MPa), regardless of surface charge and wettability. In contrast, Staphylococcus aureus ( S. aureus) and Escherichia coli ( E. coli) adhesion was primarily controlled by surface charge and wettability on both cross-linked and non-cross-linked multilayers. In both cases, negative charge and hydrophilicity inhibited their adhesion. Thus, a surface coating with a relatively high degree of stiffness from covalent cross-linking coupled with negative surface charge and high wettability can serve as an efficient strategy to enhance host cell growth while resisting bacterial colonization.

Pain Syndrome, Markers of Bone Metabolism in Patients with Osteoarthritis, Approaches to Drug Therapy and the Impact of Obesity

The objective: to assess the nature of pain in patients with osteoarthritis, the impact of obesity on the clinical efficacy of treatment of osteoarthritis (OA) and dynamics of bone metabolism markers. Patients and methods. The research included 150 patients with OA, who were divided into two groups, according to the receiving therapy. Patients of the main group – received diacerein (drug «Flexirin» PC «Kyiv Vitamin Factory») and patients of control group – received only nonsteroidal anti-inflammatory drugs (NSAIDs). Results. The prevalence of neuropathic pain component in patients with OA was 64,7%, among which 80,7% use NSAIDs as an analgesic therapy. Obesity in patients with OA was associated with significantly higher levels of pain from the side of knee joints and higher degree of stiffness according to WOMAC index. The results of the study demonstrated a direct moderate correlation (R = 0,49; p = 0,04) between PICP level and the severity of pain at physical load from the side of hands and hip joints. The therapy by diacerein within 3 months resulted in a reliable decrease of pain syndrome intensity from the side of all articular zones, unlike to isolated NSAIDs use, where a reliable analgesic effect was demonstrated only from the side of knee joints. Obesity in patients with OA led to a significant decrease in clinical efficacy of therapy in point of functional status of the joints. Conclusions. Neuropathic pain is quite common among patients with OA, which at the same time is associated with the lack of patient’s awareness about possible risks during NSAID’s use. Medical treatment by diacerein (drug “Flexirin”) causes stability of osteocalcin level, in contrast to the isolated NSAIDs use, where priority changes have been demonstrated against osteocalcin level decrease. The use of diacerein also resulted to additional positive effects from the side of zonal prevalence of analgesic effect and improving of functional ability of joints. Obesity in patients with OA was associated with a reliable increase of pain level intensity from the side of knee joints and the higher degree of functional limitation, causing at the same time, reduction of clinical efficacy of therapy in point of achieving analgesic effect and improving functional ability of joints.

Alterations in Platelet Activity and Elastic Modulus of Healthy Subjects, Carriers of G20210A Polymorphism in the Prothrombin Gene

Summary Platelet activation is a complex process in which platelet reorganization takes place associated with changes in the cell shape, topology, membrane elasticity and microparticle production. The aim of this study was to investigate the changes/aberrations in the platelet activity, elasticity and morphology in healthy subjects, carriers of A allele of prothrombin G20210A polymorphism. Blood samples from 18 healthy subjects were used for platelet analysis by force-mode atomic force microscopy. Restriction analysis was used to investigate the carriage of G20210A polymorphism in the prothrombin gene. Flow- cytometry was applied to evaluate platelet activation. Young’s modulus of the plasma membranes of platelets derived from healthy subjects, carriers of variant A allele of prothrombin 20210G&gt;A polymorphism (407±69 kPa) is two times higher than the one determined for non­carriers (195.4±48.7 kPa; p&lt;0.05). The background activity of platelets measured as an interrelation of Cd41/Cd61 and CD62 by flow cytometry was also higher in carriers of variant A allele of prothrombin 20210G&gt;A polymorphism (5.0%) than in non-carriers (1.3%). Platelets isolated from healthy carriers of variant A allele of prothrombin 20210G&gt;A polymorphism exhibited a higher level of activity and a higher degree of stiffness at the stage of spreading as compared to platelets from non­carriers.

Explicit schemes for time propagating many-body wave functions

Accurate theoretical data on many time-dependent processes in atomic and molecular physics and in chemistry require the direct numerical ab initio solution of the time-dependent Schr\"odinger equation, thereby motivating the development of very efficient time propagators. These usually involve the solution of very large systems of first-order differential equations that are characterized by a high degree of stiffness. In this contribution, we analyze and compare the performance of the explicit one-step algorithms of Fatunla and Arnoldi. Both algorithms have exactly the same stability function, therefore sharing the same stability properties that turn out to be optimum. Their respective accuracy, however, differs significantly and depends on the physical situation involved. In order to test this accuracy, we use a predictor-corrector scheme in which the predictor is either Fatunla's or Arnoldi's algorithm and the corrector, a fully implicit four-stage Radau IIA method of order 7. In this contribution, we consider two physical processes. The first one is the ionization of an atomic system by a short and intense electromagnetic pulse; the atomic systems include a one-dimensional Gaussian model potential as well as atomic hydrogen and helium, both in full dimensionality. The second process is the decoherence of two-electron quantum states when a time-independent perturbation is applied to a planar two-electron quantum dot where both electrons are confined in an anharmonic potential. Even though the Hamiltonian of this system is time independent the corresponding differential equation shows a striking stiffness which makes the time integration extremely difficult. In the case of the one-dimensional Gaussian potential we discuss in detail the possibility of monitoring the time step for both explicit algorithms. In the other physical situations that are much more demanding in term of computations, we show that the accuracy of both algorithms depends strongly on the degree of stiffness of the problem.

B cell activation is regulated by the stiffness properties of the substrate presenting the antigens (P1152)

Abstract B lymphocytes are activated upon the sensing of antigens by BCRs. The substrate presenting the antigens can show different degree of stiffness. However it is not clear if B cells can respond to substrate stiffness changes. In this report, we use high resolution, high speed live cell imaging techniques to capture the early events in B cell activation shortly after the recognition of antigens tethered to polyacrylamide gel substrates with variable degrees of stiffness as quantified by Young’s modulus (2.6-22.1 kPa). We show that the initiation of B cell activation is extremely sensitive to substrate stiffness. B cells exhibit much stronger activation responses when encountering antigens tethered to substrates with a high degree of stiffness as measured by the accumulation of BCRs, pSyk and pTyr molecules into B cell immunological synapse. Moreover, BCR and pSyk microclusters induced by antigens on stiffer substrate are more prominent and show significantly enhanced colocalization compared to activation with antigens on softer substrate. As a result, the expression of the B cell activation marker CD69 is greatly enhanced in B cells encountering antigens on stiffer substrate. Using a series of cytoskeleton inhibitors, we determine that the mechanosensing capability of B cell is strictly dependent on microtubules, and only mildly linked to actin cytoskeleton. These results suggest the importance of mechanical properties mediated by substrate stiffness in B cell activation.

B Cell Activation Is Regulated by the Stiffness Properties of the Substrate Presenting the Antigens

B lymphocytes are activated upon Ag sensing by BCRs. The substrate presenting the Ag can show different degrees of stiffness. It is not clear whether B cells can respond to changes in substrate stiffness. In this study we use high-resolution, high-speed live cell imaging techniques to capture the molecular events in B cell activation after the recognition of Ags tethered to polyacrylamide gel substrates with variable degrees of stiffness as quantified by Young's modulus (2.6-22.1 kPa). We show that the initiation of B cell activation is extremely sensitive to substrate stiffness. B cells exhibit much stronger activation responses when encountering Ags tethered to substrates with a high degree of stiffness as measured by the accumulation of BCR, phospho-spleen tyrosine kinase, and phosphotyrosine molecules into the B cell immunological synapse. Ags tethered to stiff substrates induce the formation of more prominent BCR and phospho-spleen tyrosine kinase microclusters with significantly enhanced colocalization as compared with Ags tethered to soft substrates. Moreover, the expression of the B cell activation marker CD69 is enhanced in B cells encountering Ags on stiffer substrates. Through time-lapse live cell imaging, we find that the different responses of B cells to substrate stiffness are only demonstrated 5 min after BCR and Ag recognition. Using a series of cytoskeleton inhibitors, we determine that the mechanosensing ability of B cells is dependent on microtubules, and only mildly linked to the actin cytoskeleton. These results suggest the importance of the mechanical properties mediated by substrate stiffness in B cell activation.

A novel high speed/high precision ball screw

As a tried and tested technology, ball screw drive systems are still used in a majority of machine tools which can meet the demands of higher productivity and tight part tolerances due to their low cost and high degree of stiffness. High speed ball screw drive system generates more heat and it results in greater positioning error, adversely affecting the accuracy of high precision machined parts. In this paper, a novel/well designed high speed/high precision nut air cooling ball screw system was developed to avoid thermal errors which affect the positioning accuracy and the temperature rise of ball screw. In order to discuss the effectiveness of the developed high speed/high precision nut air cooling ball screw system, a series of tests was done. As the results, it shows that the positioning accuracy will significantly improve with the use of the nut air cooling ball screw drive system shown in this paper.

A study on improvement of ball screw system positioning error with liquid-cooling

The demand for higher productivity and tight part tolerances requires machine tools to have faster and more accurate feed drive systems. As tried and tested technology, ball screw drive systems are still used in a majority of machine tools due to their low cost and high degree of stiffness. A high-speed ball screw drive system generates more heat and results in greater positioning error, adversely affecting the accuracy of machined parts. In this paper, we discuss the placement of a liquid-cooling system using water, coolant oil, light oil and cutting oil as coolants in a ball screw shaft to avoid thermal errors and achieve temperature equilibrium faster. In order to estimate the positioning error and thermal distribution of the ball system and effectiveness of the liquid-cooling system, all possible heat gain-loss sources were analyzed and considered calculation factors. The following paper also presents degree of positioning error improvement when a circulation liquid-cooling system and forced liquid-cooling system were employed. When comparing the predictions and the experimental results, we can see very significant cooling performance and a high degree of consistency between prediction and reality.

Ultrasound Elastography Is Not Superior to Grayscale Ultrasound in Predicting Malignancy in Thyroid Nodules

Several studies have evaluated the ability of ultrasound elastography (USE) to diagnose malignant nodules. However, these studies had important limiting factors, selection bias and small sample size. The aims of the present study were to prospectively assess, in a large group of patients, the diagnostic power of USE for detecting malignancy in thyroid nodules, and to compare this technique with B-mode grayscale ultrasonography (BUS) and power Doppler ultrasonography (PD). There were 194 patients with 237 thyroid nodules who were examined using BUS, PD, and USE. USE scores were classified according to the elasticity: score 1 as high, score 2 as intermediate, and score 3 as low (i.e., a high degree of stiffness). Fine-needle aspiration cytology (FNAC) was performed in all nodules at least two different times. Nodules having two benign FNAC readings that did not change the diameter during a 6-month follow-up period were classified as benign. Patients having thyroid nodules with indeterminate, suspicious, or malignant cytology had total or hemithyroidectomy to remove the nodule and treat the malignancy. Fifty eight (25%) nodules in 45 (23%) patients were found to be malignant. USE had a limited sensitivity and a positive predictive value in detecting malignant thyroid nodules and was not superior to BUS. USE had almost the same specificity and a negative predictive value as BUS. A power Doppler type-3 pattern was not of sufficient sensitivity to detect malignancies in thyroid nodules. In contrast to earlier reports, this current study noted a lower sensitivity and specificity of USE for the diagnosis of malignancy in thyroid nodules than previously reported.

Stem biomechanics of the giant moss Dendroligotrichum dendroides s.l. and its significance for growth form diversity in mosses

The giant moss Dendroligotrichum dendroides s.l. grows as self-supporting plants up to 40 cm in height in forest habitats in Chile and New Zealand. This moss represents one of the tallest self-supporting bryophytes. Biomechanical tests indicate that the stems can develop a high degree of stiffness (Young’s modulus) via a dense hypodermal sterome that is comparable with that of woody stems of vascular plants. A comparison with mechanical properties of other terrestrial and aquatic mosses indicates that different moss growth and life forms can produce very different mechanical architectures. Values of stem stiffness can vary between different growth forms of mosses to a comparable extent to that observed among diverse growth forms of vascular plants. Plants varying profoundly in overall size, development, and phylogenetic position nevertheless appear to develop comparable mechanical adaptations and growth forms in response to certain environmental conditions.

Conductive Metal Nanowires Templated by the Nucleoprotein Filaments, Complex of DNA and RecA Protein

Development of preprogrammable conductive nanowires is a requisite for the future fabrication of nanoscale electronics based on molecular assembly. Here, we report the synthesis of conductive metal nanowires from nucleoprotein filaments, complexes of single- or double-stranded DNA and RecA protein. A genetically engineered RecA derivative possessing a reactive and surface accessible cysteine residue was reacted with functionalized gold particles, resulting in nucleoprotein filaments with gold particles attached. The template-based gold particles were enlarged by chemical deposition to form uniformly metallized nanowires. The programming information can be encoded in DNA sequences so that an intricate electrical circuit can be constructed through self-assembly of each component. As the RecA filament has higher degree of stiffness than double-stranded DNA, it provides a robust scaffold that allows us to fabricate more reliable and well-organized electrical circuitry at the nanoscale. Furthermore, the function of homologous pairing provides sequence-specific junction formation as well as sequence-specific patterning metallization.

Kinetics and thermal analysis of copolymerization ofm-isopropenyl-?,??-dimethylbenzyl isocyanate with styrene

The copolymerizations of m-isopropenyl-α,α'-dimethylbenzyl isocyanate (m-TMI) with styrene (STY) was investigated. The weight conversion of the copolymerization reaction increased as the duration of copolymerization increased. The reaction temperature was maintained between 60 and 75°C. Molecular weights of the copolymers decreased with increasing molar fraction of m-TMI in the feed. This study obtained reactivity ratios, Alfrey-Price parameters, Mark-Houwink constant, characteristic ratio, thermal degradation activation energy, difference of reactive propagation activation energy, and intrinsic viscosity for the copolymers. The copolymers were characterized by using elemental analysis (EA), gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry. The copolymer chains in solution were observed to have a high degree of stiffness and a lack of rotational freedom.

Molecular characterization of a copolymer of 2-allylphenoxyorganocyclotriphosphazene with styrene, methyl methacrylate and vinylbenzyl chloride

The monomer 2-allylphenoxyorganocyclotriphosphazene was synthesized by reacting hexachlorocyclotriphosphazene with 2-allylphenol, phenol and 2,2,2-trifluoroethanol by phase transfer catalysis in a dichloromethane/alkaline solution. The copolymerizations of 2-allylphenoxyorganocyclotriphosphazene with styrene, methyl methacrylate and vinylbenzyl chloride were investigated. Nine copolymers of 2-allylphenoxyorganocyclotriphosphazene were identified in the solution. These copolymers were characterized by using light scattering, viscometry and 31P n.m.r. spectroscopic techniques. The micelles were observed to hydrodynamically and thermodynamically behave as impermeable spheres. The structure of the micellar shell was determined. The translational diffusion coefficient, Mark-Houwink constants, hydrodynamic radius, micellar weight, aggregation number, characteristic ratio and intrinsic viscosity were obtained. The chains of copolymer were observed to have a high degree of stiffness and a lack of rotational freedom in solution.

Lyotropic Phases Formed by “Molecular Bottlebrushes”

Extremely stiff macromolecules in the form of “hairy rods” or more precisely “molecular bottlebrushes” (without a handle) are easily accessible by the polymerization of polymacromonomers. As anticipated from their high degree of stiffness, these molecules form lyotropic, liquid‐crystalline phases, although they consist of “commodity” monomers like styrene and methylacrylate.