Rotational Freedom Research Articles

Dynamin-dependent vesicle twist at the final stage of clathrin-mediated endocytosis.

Dynamin plays an important role in clathrin-mediated endocytosis (CME) by cutting the neck of nascent vesicles from the cell membrane. Here through using gold nanorods as cargos to image dynamin action during live CME, we show that near the peak of dynamin accumulation, the cargo-containing vesicles always exhibit abrupt, right-handed rotations that finish in a short time (~0.28 s). The large and quick twist, herein named the super twist, is the result of the coordinated dynamin helix action upon GTP hydrolysis. After the super twist, the rotational freedom of the vesicle drastically increases, accompanied with simultaneous or delayed translational movement, indicating that it detaches from the cell membrane. These observations suggest that dynamin-mediated scission involves a large torque generated by coordinated actions of multiple dynamins in the helix, which is the main driving force for vesicle scission.

Temperature-Triggered Supramolecular Assembly of Organic Semiconductors.

Supramolecular assembly is a promising bottom-up approach for producing materials that behave as charge transporting components in electronic devices. Although extensive advances have been made during the past two decades, formidable challenges exist in controlling the local randomness present in supramolecular assemblies. Here, a temperature-triggered supramolecular assembly strategy using heat to heal defects and disorders is reported. The central concept of the molecular design-named the "Tetris strategy" in this research-is to: i) increase the rotational freedom of the molecules through thermal perturbation, ii) induce conformation-fitting of adjacent molecules through two different kinds of intermolecular [π···π] interactions, and finally iii) lock the nearby molecules in inactive co-conformations. Experimentally, upon heating to 57°C, amorphous solid-state films undergo spontaneous assembly, leading to the growth of uniform and highly ordered microwire arrays. Temperature-triggered supramolecular assembly provides an approach closer to the precision control of assembled structures and presents with a broad canvas to work on in approaching a new generation of supramolecular electronics. Tetris is a registered trademark of Tetris Holding, LLC, used with permission.

Abutment rotational freedom on five implant systems with different internal connections

Statement of problemInformation regarding the rotational freedom of internal connection implants is sparse. PurposeThe purpose of this in vitro study was to compare the rotational freedom of different internal conical and internal nonconical connections. Material and methodsThirty implants, 30 straight manufactured standard abutments, and 30 standard abutment screws were obtained for each of the 5 implant systems tested. Three implant systems had indexed internal conical connections with different antirotational geometries: hexagon (Naturall+), cam-groove (ID CAM M), and octagon (Bone Level). Two implant systems had internal nonconical connections with hexagonal antirotational geometry (Tapered Screw-Vent and Seven). The implants were mounted in a steel plate, and a metal reference arm was attached to the abutment. Before tightening the standard abutment screw, a modified torque wrench was used to rotate the abutment clockwise until reaching the clockwise rotational endpoint. This modified torque wrench was connected to the abutment's outer surface. It allowed free access to the standard abutment screw for a second torque wrench, specific to each implant system. The modified torque wrench applied a controlled torque of 5 Ncm, which held the abutment at the clockwise rotational endpoint. The standard abutment screw was then tightened to the manufacturer’s specified torque value with the second torque wrench. Angle value corresponding to the clockwise endpoint was measured microscopically between a fixed reference point on the steel plate and the reference arm. The abutment was then unscrewed and removed. The same procedure was carried out to rotate the abutment counterclockwise and measure the angle value corresponding to the counterclockwise rotational endpoint. The rotational freedom was finally determined from the differences in the angles between the clockwise and counterclockwise rotational endpoints. Rotational freedom angle values were summarized as descriptive statistics (means, standard deviations). The normality test (Kolmogorov-Smirnov) was applied, and the Kruskal-Wallis test was performed. The Wilcoxon signed-rank test was used to isolate the implant system differences from each other (α=.05). ResultsThe lowest mean rotational freedom angles were obtained for Bone Level (conical connection, 0.17 degrees) and Tapered Screw-Vent (nonconical connection, 0.05 degrees). These systems were followed in increasing order by ID CAM M (conical connection, 0.50 degrees), Seven (nonconical connection, 1.98 degrees), and Naturall+ (conical connection, 2.49 degrees). Compared with each other, all implant systems had significant statistical differences in rotational freedom angles (P<.05). ConclusionsSignificant differences were found among the 5 implant systems. The lowest mean rotational freedom angles were obtained both with a conical connection (Bone Level) and a nonconical connection (Tapered Screw-Vent).

Excimer Formation of Perylene Bisimide Dyes within Stacking-Restrained Folda-Dimers: Insight into Anomalous Temperature Responsive Dual Fluorescence

Excimer Formation of Perylene Bisimide Dyes within Stacking-Restrained Folda-Dimers: Insight into Anomalous Temperature Responsive Dual Fluorescence

Load bearing performance of mechanical joints inspired by elbow of quadrupedal mammals

One of the biggest issues of the mechanical cylindrical joints is related to premature wear appearing. Application of bioinspiration principles in an engineering context taking advantage of smart solutions offered by nature in terms of kinematic joints could be a way of solving those problems. This work is focussed on joints of one degrees of freedom in rotation (revolute or ginglymus joints in biological terms), as this is one of the most common type of mechanical joints. This type of joints can be found in the elbow of some quadrupedal mammals. The articular morphology of the elbow of these animals differs in the presence/absence of a trochlear sulcus. In this study, bio-inspired mechanical joints based on these morphologies (with/without trochlear sulcus) were designed and numerically tested. Their load bearing performance was numerically analysed. This was done through contact simulations using the finite element method under different external loading conditions (axial load, radial load and turnover moment). Results showed that the tested morphologies behave differently in transmission of external mechanical loads. It was found that bio-inspired joints without trochlea sulcus showed to be more specialized in the bearing of turnover moments. Bio-inspired joints with trochlea sulcus are more suitable for supporting combined loads (axial and radial load and turnover moments). Learning about the natural rules of mechanical design can provide new insights to improve the design of current mechanical joints.

Influence of Monomer Structures for Polymeric Multivalent Ligands: Consideration of the Molecular Mobility of Glycopolymers.

Molecular mobility is important for interactions of biofunctional polymers with target molecules. Monomer structures for synthetic biofunctional polymers are usually selected based on their compatibility with polymerization systems, whereas the influence of monomer structures on the interaction with target molecules is hardly considered. In this report, we evaluate the correlation between the monomer structures of glycopolymers and their interactions with concanavalin A (ConA) with respect to the molecular mobility. Two types of glycopolymers bearing mannose are synthesized with acrylamide or acrylate monomers. Despite the similar structures, except for amide or ester bonds in the side chains, the acrylate-type glycopolymers exhibit stronger interaction with ConA both in the isothermal titration calorimetry measurement and in a hemagglutination inhibition assay. Characterization of the acrylate-type glycopolymers suggests that the higher binding constant arises from the higher molecular mobility of mannose units, which results from the rotational freedom of ester bonds in their side chains.

Towards Reducing Risk of Injury in Nursing: Design and Analysis of a New Passive Exoskeleton for Torso Twist Assist

Nursing is among the most physically challenging occupations and involves intensive lifting activities often including twisting of torso while performing tasks such as patient handling. Frequent and repetitive twisting of the body is known to induce large demands on the musculature, which may lead to MSD with direct and indirect costs to the hospital governance. One solution proposed through this article includes an exoskeleton specifically designed to assist in twisting movements of the trunk. This involves a double-actuator fully passive system that assists in rotation of the torso with the help of mechanical springs and cable modules. Our study provides a conceptual design of the mechanism, and a preliminary analysis using the concepts of kinematics, dynamics, usability, wearability, and freedom of movement. Results show that the mechanism could offer freedom of rotation for the wearer’s torso up to 52, 25 and 22 degrees (with stationary hip joint) along the transverse, sagittal and coronal planes, respectively. Moreover, similar force generation (up to 80N) was obtained in both actuators for same rotation on transverse plane in both directions for a combination of spring stiffness (0.5 – 1 N/mm) and damping (0.1 - 0.5 N-sec/mm) parameters. Our proposed design could also be integrated to the current exoskeletons in the form of a module and could be beneficial in more general work settings.

The Click-On gamma probe, a second-generation tethered robotic gamma probe that improves dexterity and surgical decision-making

PurposeDecision-making and dexterity, features that become increasingly relevant in (robot-assisted) minimally invasive surgery, are considered key components in improving the surgical accuracy. Recently, DROP-IN gamma probes were introduced to facilitate radioguided robotic surgery. We now studied if robotic DROP-IN radioguidance can be further improved using tethered Click-On designs that integrate gamma detection onto the robotic instruments themselves.MethodsUsing computer-assisted drawing software, 3D printing and precision machining, we created a Click-On probe containing two press-fit connections and an additional grasping moiety for a ProGrasp instrument combined with fiducials that could be video tracked using the Firefly laparoscope. Using a dexterity phantom, the duration of the specific tasks and the path traveled could be compared between use of the Click-On or DROP-IN probe. To study the impact on surgical decision-making, we performed a blinded study, in porcine models, wherein surgeons had to identify a hidden 57Co-source using either palpation or Click-On radioguidance.ResultsWhen assembled onto a ProGrasp instrument, while preserving grasping function and rotational freedom, the fully functional prototype could be inserted through a 12-mm trocar. In dexterity assessments, the Click-On provided a 40% reduction in movements compared to the DROP-IN, which converted into a reduction in time, path length, and increase in straightness index. Radioguidance also improved decision-making; task-completion rate increased by 60%, procedural time was reduced, and movements became more focused.ConclusionThe Click-On gamma probe provides a step toward full integration of radioguidance in minimal invasive surgery. The value of this concept was underlined by its impact on surgical dexterity and decision-making.

Concussions in Boxers: Head Rotations and Neck Stiffness

Background: The human head-and-neck has three degrees of rotational freedom – pitch, roll, and yaw. While the evolution of the head-and-neck mobility may have increased the overall fitness of homo sapiens, our head-and-neck mobility may have also introduced some differential vulnerability to injuries in impact-induced head rotations about the pitch, roll, and yaw axes. Methods and Findings: We examined impact-induced head rotations in boxing matches by analyzing videos. Our objective was to seek a quantitative relationship between impact-induced head kinematics and the knockout outcome. For each of the three rotational degrees of freedom, head angular velocities of impact-induced head rotations were significantly higher in knockout hits than in control hits without a knockout (p &lt; 0.02). Knockout thresholds in pitch-roll-yaw measured as impact-induced head angular velocities were anisotropic with the lowest threshold in roll and became progressively higher in yaw and pitch, in that order. Regardless of the pitch-roll-yaw bearing, the velocities of the striking fists in knockout hits were not significantly higher than those in control hits. Conclusions: Accurate prediction of knockout via head kinematics was possible with pitch-roll-yaw information. Impact-induced head kinematics was strongly influenced by neck stiffness, making a case for the utility of reflexively increasing neck stiffness as an effective way to reduce impact-induced head rotations and concussion risk.

The Control of Intramolecular Through-Bond and Through-Space Coupling in Single-Molecule Junctions

The Control of Intramolecular Through-Bond and Through-Space Coupling in Single-Molecule Junctions

Exomorphism of jacobsite precipitates in bixbyite single crystals from the Thomas Range in Utah

Abstract Naturally occurring single crystals of bixbyite, (Fe,Mn)2O3, from the Thomas Mountain Range in Utah, U.S.A., were studied via (scanning) transmission electron microscopy (S)TEM. With up to 5 cm edge length, these mineral specimens are the largest bixbyite crystals found worldwide. Their hexahedral shapes are often modified by {211} facets at the corners and small {211} truncations along their cube edges. Characteristic lamellar defects, running parallel to the {100} planes, can be observed via TEM imaging. The defects are, according to EDS analyses, attributed to the tetragonal manganese silicate braunite, Mn7[SiO12]. In the present study, electron nano-diffraction and atomic resolution (S)TEM were employed to verify the presence of braunite lamellae and to investigate their orientation relationship with bixbyite. The analysis confirmed an epitaxial intergrowth of both phases, with their main-axes being parallel and the unique c-axis of braunite always aligned perpendicularly to the lamellar plane. Moreover, small rectangular-shaped precipitates, which had been, due to their almost identical chemical composition, previously interpreted as small bixbyite inclusions within the host crystal, were often observed in contact with the braunite lamellae. Electron nano-diffraction and atomic resolution (S)TEM imaging revealed these crystallites not to be bixbyite but jacobsite, a cubic iron-manganese spinel with the stoichiometric formula MnFe2O4, whose occurrence in this unique context had not been reported before. Moreover, due to the higher temperatures needed for spinel crystallization, the occurrence of jacobsite may serve as a geo-thermometer. (S)TEM in conjunction with automated crystal orientation mapping (ACOM)-TEM showed that no orientation relationship exists between the jacobsite inclusions and the bixbyite/braunite matrix. Nevertheless, their characteristic rectangular shape is typically aligned concordantly with the (001) plane of the braunite lamellae. The resulting crystal shape of jacobsite is determined by the presence of the braunite lamellae, while the respective crystallites maintain their freedom of rotation. To the authors’ knowledge, this is a novel observation of exomorphosis of jacobsite, i.e., the change in the habit of the spinel crystallites due to external conditions. Note that the term “exomorphosis” is used here in the mineralogical sense in contrast to the often-used petrological aspect. Based on the TEM results, the formation of the jacobsite precipitates is discussed and a growth model suggested.

HDAC7 Inhibition by Phenacetyl and Phenylbenzoyl Hydroxamates.

The zinc-containing histone deacetylase enzyme HDAC7 is emerging as an important regulator of immunometabolism and cancer. Here, we exploit a cavity in HDAC7, filled by Tyr303 in HDAC1, to derive new inhibitors. Phenacetyl hydroxamates and 2-phenylbenzoyl hydroxamates bind to Zn2+ and are 50-2700-fold more selective inhibitors of HDAC7 than HDAC1. Phenylbenzoyl hydroxamates are 30-70-fold more potent HDAC7 inhibitors than phenacetyl hydroxamates, which is attributed to the benzoyl aromatic group interacting with Phe679 and Phe738. Phthalimide capping groups, including a saccharin analogue, decrease rotational freedom and provide hydrogen bond acceptor carbonyl/sulfonamide oxygens that increase inhibitor potency, liver microsome stability, solubility, and cell activity. Despite being the most potent HDAC7 inhibitors to date, they are not selective among class IIa enzymes. These strategies may help to produce tools for interrogating HDAC7 biology related to its catalytic site.

Particle size segregation in two-dimensional circular granular aggregates.

Although many previous studies have focused on the Brazil nut effect, segregation in a self-gravitating circular aggregate remains relatively unexplored. In this paper, size segregation in a two-dimensional assembly of grains in a circular geometry is studied through discrete element method (DEM) numerical simulations. We show that radial segregation within an asteroid submitted to periodic perturbations is not limited to the surface but also occurs in its core. The characteristic time and the overall efficiency of the segregation mechanism are studied as the intensity of the perturbation, the frictional properties, and rotational freedom of individual grains are varied.

Redundancy-Free Models for Mathematical Descriptions of Three-Phase Catalytic Hydrogenation of Cinnamaldehyde

A new approach on how to formulate redundancy-free models for mathematical descriptions of three-phase catalytic hydrogenation of cinnamaldehyde is presented. An automatically created redundant (generalized) model is formulated according to the complete reaction network. Models based on formal kinetics and kinetics concerning the Langmuir-Hinshelwood theory for three-phase catalytic hydrogenation of cinnamaldehyde were investigated. Redundancy-free models were obtained as a result of a step-by-step elimination of model parameters using sensitivity and interval analysis. Starting with 24 parameters in the redundant model, the redundancy-free model based on the Langmuir-Hinshelwood mechanism contains 6 parameters, while the model based on formal kinetics includes only 4 parameters. Due to less degrees of freedom of molecular rotation in the adsorbed state, the probability of a direct conversion of cinnamaldehyde to 3-phenylpropanol according to the redundancy-free model based on Langmuir-Hinshelwood approach is practically negligible compared to the model based on formal kinetics.

Aβ Oligomers Dysregulate Calcium Homeostasis by Mechanosensitive Activation of AMPA and NMDA Receptors.

Alzheimer’s disease, which is the most common form of dementia, is characterized by the aggregation of the amyloid β peptide (Aβ) and by an impairment of calcium homeostasis caused by excessive activation of glutamatergic receptors (excitotoxicity). Here, we studied the effects on calcium homeostasis caused by the formation of Aβ oligomeric assemblies. We found that Aβ oligomers cause a rapid influx of calcium ions (Ca2+) across the cell membrane by rapidly activating extrasynaptic N-methyl-d-aspartate (NMDA) receptors and, to a lower extent, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. We also observed, however, that misfolded oligomers do not interact directly with these receptors. Further experiments with lysophosphatidylcholine and arachidonic acid, which cause membrane compression and stretch, respectively, indicated that these receptors are activated through a change in membrane tension induced by the oligomers and transmitted mechanically to the receptors via the lipid bilayer. Indeed, lysophosphatidylcholine is able to neutralize the oligomer-induced activation of the NMDA receptors, whereas arachidonic acid activates the receptors similarly to the oligomers with no additive effects. An increased rotational freedom observed for a fluorescent probe embedded within the membrane in the presence of the oligomers also indicates a membrane stretch. These results reveal a mechanism of toxicity of Aβ oligomers in Alzheimer’s disease through the perturbation of the mechanical properties of lipid membranes sensed by NMDA and AMPA receptors.

Installation of an aryl boronic acid function into the external section of N-aryl-oxazolidinones: Synthesis and antimicrobial evaluation.

N-aryl-oxazolidinones is a prominent family of antimicrobials used for treating infections caused by clinically prevalent Gram-positive bacteria. Recently, boron-containing compounds have displayed intriguing potential in the antibiotic discovery setting. Herein, we report the unprecedented introduction of a boron-containing moiety such as an aryl boronic acid in the external region of the oxazolidinone structure via a chemoselective acyl coupling reaction. As a result, we accessed a series of analogues with a distal aryl boronic pharmacophore on the oxazolidinone scaffold. We identified that a peripheric linear conformation coupled with freedom of rotation and no further substitution on the external aryl boronic ring, an amido linkage with hydrogen bonding character, in addition to a para-relative disposition between boronic group and linker, are the optimal combination of structural features in this series for antimicrobial activity. In comparison to linezolid, the analogue comprising all those features, compound 20b, displayed levels of antimicrobial activity augmented by an eight-fold to a thirty-two-fold against a panel of Gram-positive strains, and a near one hundred-fold against Escherichia coli JW5503, a Gram-negative mutant strain with a defective efflux capability.

Inverse Kinematics Data Adaptation to Non-Standard Modular Robotic Arm Consisting of Unique Rotational Modules

The paper describes the original robotic arm designed by our team kinematic design consisting of universal rotational modules (URM). The philosophy of modularity plays quite an important role when it comes to this mechanism since the individual modules will be the building blocks of the entire robotic arm. This is a serial kinematic chain with six degrees of freedom of unlimited rotation. It was modeled in three different environments to obtain the necessary visualizations, data, measurements, structural changes measurements and structural changes. In the environment of the CoppeliaSim Edu, it was constructed mainly to obtain the joints coordinates matching the description of a certain spatial trajectory with an option to test the software potential in future inverse task calculations. In Matlab, the model was constructed to check the mathematical equations in the area of kinematics, the model’s simulations of movements, and to test the numerical calculations of the inverse kinematics. Since the equipment at hand is subject to constant development, its model can also be found in SolidWorks. Thus, the model’s existence in those three environments has enabled us to compare the data and check the models’ structural designs. In Matlab and SolidWorks, we worked with the data imported on joints coordinates, necessitating overcoming certain problems related to calculations of the inverse kinematics. The objective was to compare the results, especially in terms of the position kinematics in Matlab and SolidWorks, provided the initial joint coordinate vector was the same.

Chemical Design and Physical Properties of Dynamic Molecular Assemblies

Abstract The thermally activated motional freedom of protons (H+), ions (M+), and molecules can be controlled using supramolecular approaches. In single crystals, motional freedom is enabled because of the small size of H+ and M+ (e.g., Li+ and Na+), and the thermally activated motion of small molecular units can yield molecular rotator structures in electrically conducting and magnetic crystals. The design of hydrogen-bonded networks and rotator–stator structures is a rational method to form functional dynamic molecular assemblies, and the thermally activated motional freedom of alkylamide (–CONHCnH2n+1) chains in discotic hexagonal columnar (Colh) and lamellar (La) liquid crystal phases enables the dipole inversion of polar N–H⋯O= hydrogen-bonded chains, enabling a ferroelectric response to an applied external electric field. The thermally activated rotational freedom of neutral radicals in plastic crystals results in multifunctional dielectric, magnetic, and optical properties at the order–disorder phase transition. In hydrogen-bonded host–guest molecular crystals, dynamic structural transformations are coupled with highly reversibly guest adsorption–desorption in the crystalline state. Further, changes in the fluorescence colour of excited-state intramolecular proton transfer (ESIPT) systems can be exploited for solid-state molecular sensing, in which both dynamic molecular rotation and conformational transformations drastically affect the fluorescent responses.

A Comparative Study of Cycloidal Reluctance Machine and Switched Reluctance Machine

A variable reluctance electric machine with a two-degree of freedom rotor motion characterized by rotation around the center of the rotor and orbiting around the center of the stator is studied. One motivation for adopting such rotor motion would be to allow torque generation through both the radial and tangential components of the electromagnetic forces created in the airgap, as opposed to common rotary machines in which torque is a byproduct of only the tangential component of the airgap electromagnetic forces. Furthermore, the rotor motion provides a built-in gearing action similar to that of a cycloidal drive, which allows natural torque multiplication and the tight integration of the electromagnetic and mechanical systems. The two-degree of freedom rotor motion also results in a counter-intuitive inertia characteristic of this machine concept which is elaborated in this paper for the first time. Due to the reluctance nature of the torque, and because of the distinctive rotor motion profile which resembles the motion of a cycloid, the studied machine is called a cycloidal reluctance (CR) electric machine (CRM). In this paper, the principle of operation of the CRM is explained, and its performance is compared to a counterpart switched reluctance machine (SRM). A prototype is built, and the theoretical torque calculations are validated by experimental measurements.

Effect of the Features of Mandibular Implant Overdenture Attachments on the Bending Strain Around Implants

To examine the effect of the attachment features (abutment height, retention, and freedom of rotation) of implant overdentures on the bending strain around implants under an overdenture. Mandibular and maxillary edentulous models were fabricated and covered with silicone rubber. Strain gauges were attached to the four sides of each implant. Two implants (tissue-level implant, 4.1-mm diameter, 10-mm length) were placed bilaterally in the area between the mandibular canines and lateral incisors. A maxillary conventional denture and a mandibular overdenture were made to fit the edentulous models. Three levels of peri-implant bone resorption were created sequentially: no bone resorption, 0.8 mm, and 1.5 mm. Three kinds of attachments (magnetic, stud, and ball attachments) were used. Bending strains generated from a 98-N occlusal load through the maxillary denture were measured using a sensor interface, and the data were analyzed using the Kruskal-Wallis and Bonferroni tests. Multiple regression analysis was used to find the relationship between independent variables (peri-implant bone resorption level, abutment height, retention, and freedom of rotation) and the dependent variable (bending strain). For all attachment types, the bending strains were smallest with no bone resorption and largest with 1.5-mm bone resorption (P < .05). Multiple regression analysis showed that abutment height had the greatest impact on the reduction of bending strain (beta = .413), followed by freedom of rotation (beta = -.349), and retention (beta = .107). Low abutment height, large freedom of rotation, and low retention can minimize bending strain around implants.