Perpendicular Force Research Articles

Study of Downhole Lateral Force Measurement Modelling and Devices in Petroleum Exploration

Measurement while drilling (MWD) technology is important for obtaining downhole parameters. As an essential parameter in drilling engineering, lateral force provides a powerful reference basis for judging the downhole drilling direction. Although stress measurement technology has matured, research on downhole lateral forces, especially near-bit lateral forces during the drilling process in petroleum exploration, is lacking. Based on the force analysis of a short measurement circuit, the lateral force measurement value of a drill bit and centralizer was converted to a drill string’s radial-bending-force measurement. Two perpendicular lateral force components were measured using strain gauge technology, a lateral force measurement theory model was established, and a set of MWD systems was designed according to the model. The systems’ function was verified through laboratory and field tests, and the field-test data were successfully obtained in the field application. The test results showed that the tested MWD system had acceptable accuracy, stability, and reliability and had the application potential to measure lateral force in the drilling industry. This article provides a new idea to study lateral force while drilling, which is of great significance to oil-drilling exploration and development.

Evaluation of Shear Bond Strength Between Denture Teeth and 3D-Printed Denture Base Resin.

The aim of this study was to evaluate the bond strength between two types of artificial teeth with a 3D-printed denture base resin using different bonding agents. Two types of artificial teeth were evaluated: 3D-printed (Cosmos TEMP) and prefabricated polymethylmethacrylate (Biotone) bonded to cylinders (2.5 mm in height and 5 mm in diameter) of 3D-printed denture bases (Cosmos Denture designing by Meshmixer and printed by Flashforge Hunter DLP Resin 3D Printer). Two combinations between denture base and artificial teeth were eveluated: Cosmos Denture - Biotone, n = 30, and Cosmos Denture - Cosmos TEMP, n = 30. For each combination, the specimens were randomly distributed according to the bonding agent: (1) autopolymerized acrylic resin-Duralay, n = 10; (2) 3D-printed resin Cosmos TEMP, n = 10; and (3) methylmethacrylate monomer (MMA) + 3D-printed resin Cosmos TEMP, n = 10, totaling 60 specimens. The application of MMA was done conditioning the tooth surface for 180 seconds; the other agents were applied on the same surface. The virtual design of the 3D-printed resin teeth was obtained by scanning the first maxillary molar of the prefabricated teeth as the same protocol of cylinders. The control group (n = 10) was a conventional heat-polymerized denture base resin (Lucitone 550) bonded to the prefabricated resin teeth (Biotone). The shear bond tests were performed by applying a perpendicular force to the artificial tooth - denture base resin, through a chisel at 1 mm/min until failure. Two-way ANOVA and Bonferroni post hoc tests (α = 0.05) were used for multiple comparisons. For the Biotone tooth, the bond strength was significantly higher using MMA + Cosmos TEMP (10.04 MPa), and similar to the control (11.84 MPa, p = 0.484). For the 3D-printed tooth (Cosmos TEMP), the bond strength using the agents Cosmos TEMP (9.57 MPa) and MMA + Cosmos TEMP (12.72 MPa) were similar to the control (11.84 MPa, p = 0.169 and p = 1, respectively), but different from each other (p = 0.016). From the results, it is recommended to use: MMA + Cosmos TEMP bonding agent for the Biotone tooth; and Cosmos TEMP or MMA + Cosmos TEMP bonding agents for the Cosmos TEMP tooth, both attached to the 3D-printed denture resin Cosmos Denture.

Multi-domain Vibrations Response of Externally Excited Fluid Conveyer Pipe in Industrial Steam Generator

Electric power is an indispensable consumer commodity for a little over a century now as all electric equipment in dwellings, commercial, and industry sectors are essentially dependent on electricity. Heat recovery steam generator, HRSG is an important system in combined cycle power plants. Indeed, excess vibrations induced on such devices may gradually lead to fatigue failure that affect the process of power output. This work investigates, models, and simulates the vibrations response of a fluid carrier pipe housed inside the cavity of the system while experiencing highly pressurized nearly perpendicular external force of extremely hot flue gas on the outside and pressurized water and water vapour from the inside. Transient and steady-state vibrations from initial conditions and the forcing function analysis are performed to account for the variation of damping, amplitude, and frequency responses of the system. Initial parameters used in the systems’ model are from industry subsequent to the OEM instructions. However, we introduce a new set of parameter values so as to observe the vibrational behaviour by varying these parameters. The purpose of performing a parameter-based vibration analysis is that parameter variation may point to different responses in the system. Indeed, this in turn indicates which set of parameters are suitable for rectifying the primary causes of undesired vibrations. To account for the consequence of mass flowrate, the model covers low pressure, intermediate pressure, and high-pressure constituents. The results obtained from the model are for the relationships of amplitude and phase angle as functions of frequency of the system. From these data, different interactions of quantities such as force, damping ratio, and number of dampers and vibration supports are observed. These results implores the implementation of new set of parameters to improve the agility of the system and minimize the impact of excess vibrations.

Gas pressure casting technique for manufacturing of W/OFHC-Cu monoblock

The important engineering part of the divertor vertical target is the quality of joint between armor materials and heat sink. To reduce the joint interface stresses, a pure copper (Cu) interlayer was provided between the tungsten(W) armor and the CuCrZr cooling tube. Gas pressure casting method was developed to reduce the porosity and improve the mechanical properties of the Cu interlayer of W/Cu monoblock. In the vacuum casting sample without pressure, porosities were found in Cu. These porosities become defects at the interface between W and Cu and decrease the mechanical properties of the Cu interlayer. In the cooling process of casting, argon gas was pressurized into a porous tube inserted in the Cu and tungsten monoblock applying perpendicular force on the joint surface. This method was effective to remove the porosity in Cu generated during the cooling process and to increase the bonding strength between Cu and tungsten. The quality of bonding interface, depth of the Cu diffusion, and hardness of Cu were compared by SEM, EDS, and Vickers hardness measurement. In the samples made by gas pressure casting method, the porosity was decreased in Cu, no defects on the interface between tungsten and Cu, Cu was diffused into tungsten with a depth of 2∼3 μm and the hardness of Cu was increased about 15%.Small mock-ups were manufactured by hot radial pressing (HRP) with gas pressure casted W/Cu monoblock and CuCrZr cooling tube and underwent high heat flux (HHF) of 10 MW/m2 up to 5,000 cycles. The ultrasonic test (UT) results before and after the HHF test showed no defects on interfaces and was confirmed by observation of SEM on the cutting surface of the monoblock mock-up after the HHF test.

Microtubule Dumbbells to Assess the Effect of Force Geometry on Single Kinesin Motors.

The cytoskeletal motors myosin, kinesin, and dynein and their corresponding tracks, actin and microtubules, are force generating ATPases responsible for motility and morphological changes at the intracellular, cellular, and tissue levels. The pioneering application of optical tweezers to measure the force-producing properties of cytoskeletal motors has provided an unparalleled understanding of their mechanochemistry. The mechanosensitivity of processive, microtubule-based motors has largely been studied in the optical trap using the "single-bead" assay, where a bead-attached motor is held adjacent to a cytoskeletal filament as it processively steps along it. However, because of the geometrical constraints in the conventional single-bead assay, the motor-filament bond is not only loaded parallel to the long axis of the filament, but also perpendicular to the long axis of the filament. This perpendicular force, which is inherent in the conventional single-bead assay, accelerates the motor-filament detachment and has not been carefully considered in prior experiments. An alternative approach is the "three-bead" assay, which was developed for the study of non-processive myosin motors. The vertical force component is minimized in this assay, and the total opposing force is mainly parallel to the microtubule. Experiments with kinesin show that microtubule attachment durations can be highly variable and last for up to tenfold longer times in the three-bead assay, compared to the single-bead assay. Thus, the ability of kinesin to bear mechanical load and remain attached to microtubules depends on the forces in more than one dimension. In this chapter, we provide detailed methods for preparing the proteins, buffers, flow chambers, and bead-filament assemblies for performing the three-bead assay with microtubules and their motors.

Cycloidal Magnetic Gear Combining Axial and Radial Topologies

Axial flux and radial flux cycloidal permanent magnetic gears are characterized by high gear ratios and high torque densities; however, their rotors experience large unbalanced forces, which stress the bearings used in the gear. This paper presents a new cycloidal magnetic gear topology that combines the radial and axial flux topologies. The paper analyzes the forces and torques contributed by the axial and radial magnets in this topology using 3D finite element analysis. It was found that the perpendicular force is necessary to transfer torque to the high-speed shaft and, thus, cannot be cancelled out, but the eccentric component of the magnetic forces can be largely cancelled out, potentially reducing bearing losses and increasing the lifespan of the bearings used in the gear. A proof-of-concept prototype was constructed. Experimental slip torque results matched 3D finite element analysis (FEA) simulations to within 15%, and testing showed that no-load losses were reduced and the slip torque was increased by combining both axial and radial topologies, compared to using an axial configuration alone.

Four Kinds of Potential Mass-Energy Space-Time Distribution Unified by a Dynamical Approach

The unification of gravity and electricity since the early 20th century and the unification of four fundamental forces since the 1970s have become a mainstream of physical study by using different theories and methods. This paper introduces a dynamical approach to respectively reveal the physical natures of gravity and electricity as well as strong and weak forces. The results showed that the nature of gravity is a dynamical product of mass-energy linear distributions between two adjacent objects and the nature of electricity is a dynamical product of mass-energy linear distributions between two adjacent unlike charges. Potential nuclear energies are mathematically shown by the products of mass-energy linear distributions between proton-neutron particles as well as hadron-lepton particles, which are also initially generated through external perpendicular forces with the maximum efficiency. Thus, four kinds of potential mass-energy space-time distribution rather than four long- and short-range forces showed a common mathematical expression or similarity among them by using this approach.

Study of Quantization of Space-Time Explains Matter and Its Aspects

By quantizing space-time in such a way that I can calculate all of the constants of physics and derive and explain every equation therein. The magnetic field appears when the electric field seems to travel faster than c. The same way an “anti-gravity” perpendicular field appears, totally depended on relative velocities, since the electric and gravitational forces are made of the micro field lines and are different aspects of the same force [1]. The “gravitational” perpendicular force can be repellant, when masses travel in the same direction, (massive distant galaxies repel enlarging the universe, new current mass just being released) and it can be attractive (opposite spiral arms moving in opposite directions, combined with a super-massive black hole). The recent detection of gravity waves, is clear evidence for all of this since these waves need a perpendicular field, like electro-magnetic waves. The magnetic style of the perpendicular field, at extremely high can cause matter and dark to interact

A novel hand exoskeleton to enhance fingers motion for tele-operation of a robot gripper with force feedback☆

This research describes a robotic system's design, optimization, and implementation processes for tele-operation with haptic feedback using the Hand Exoskeleton of New technologies research center (HEXON) as a novel haptic mechanism and the HEXON robotic gripper to work collaboratively with the exoskeleton. In particular, a force-sensitive robotic gripper is connected to a hand exoskeleton, mimics the user's hand movements, and transfers haptic feedback through the exoskeleton. The two-finger exoskeleton's design process consists of a multi-criteria optimization procedure to simultaneously maximize applied force to the finger and workspace of the attached exoskeleton, optimizing both the Perpendicular Impact Force (PIF) and the Global Isotropy Index (GII), considering worst-case collision avoidance. Due to the tele-operation application and using a robotic arm as a slave in the remote scenario, the gripper can be used as an end-effector for a palletizing 3-DOF robotic arm, and movement of the gripper can be achieved by using a visual sensor to pinpoint the user's hand location in 3D space. With the aim of the stress analysis software, the exoskeleton and gripper designs were analyzed to evaluate the system strength against applied forces. Finally, based on the achieved results, the gripper and two-fingered exoskeleton prototypes were fabricated. Simulations and experimental results are reported, showing the potential of the HEXON in haptics and tele-operation applications, and the exoskeleton is used to operate a robotic arm and gripper while the user can perceive the objects virtually.

A piecewise analytical model of bearingless switched reluctance motor for full rotor angular positions

PurposeThis paper aims to establish a piecewise Maxwell stress analytical model of bearingless switched reluctance motor (BSRM) for the full rotor angular positions. The proposed model varies from the existing models, which are only applicable to the partial-overlapping positions of stator and rotor poles. By extending the applicable rotor angular positions, this model provides a basic analytical model for the multi-phase excitation control of BSRM.Design/methodology/approachThe full rotor angular positions are classified into the partial-overlapping positions and the non-overlapping positions. At first, two different air gap subdividing methods are proposed, respectively, for the two-position ranges. Then, different integration paths are selected accordingly. Furthermore, two approximate methods are presented to calculate the average flux density of each air gap subdivision. Finally, considering the mutual coupling between the two perpendicular radial suspension forces, a piecewise Maxwell stress analytical model is derived for the full rotor angular positions of BSRM.FindingsA piecewise Maxwell stress analytical model of BSRM is built for the full rotor angular positions, and applicable to the multi-phase excitation mode of BSRM. For the partial-overlapping positions and the non-overlapping positions, two sets of air gap subdividing methods, integration paths and approximate calculation methods of air gap flux densities are proposed, respectively. The accuracy and reliability of the proposed model are verified by the finite element method.Originality/valueThe piecewise Maxwell stress analytical model of BSRM for the full rotor angular positions is proposed for the first time. The novel air gap subdividing methods, integration paths, approximate calculation methods of air gap flux densities and the coupling between the two radial suspension forces are adopted to improve the modeling accuracy. As the applicable range of rotor angular position is extended, this model overcomes the limitation of the existing models only for single-phase excitation mode and contributes to the accurate control of BSRM multi-phase excitation mode.

Dental undergraduate students' ability in the diagnosis of root fractures: Comparative analysis of different imaging methods

The aim of this study was to evaluate the diagnostic ability of dental undergraduate students to detect horizontal and oblique root fractures (ORFs) using different imaging techniques. Nine teeth were selected and randomly divided in three groups in order to create a fracture line without fragments separation: control (without fracture), horizontal root fracture (HRF), and ORF. The root fracture was created using perpendicular force and was confirmed by transillumination. A model with two adjacent teeth was created, and different imaging techniques were performed: conventional periapical radiograph; mesially and distally shifted periapical radiographs; cone-beam computer tomography (CBCT). Twenty students that had participation on dental trauma clinic at the year of 2019 were invited to identify root fractures by a five-point scale: (i) fracture definitely not present, (ii) fracture probably not present, (iii) uncertain whether fracture is present or not, (iv) fracture probably present, and (v) fracture definitely present. Data were analyzed by Kappa test for agreement evaluation. Comparing each student to the gold standard, there was a variation in reproducibility and performance from poor to substantial (0.042-0.667). Reproducibility values ranged from poor to good for all periapical radiographs both in the diagnosis of ORF (-0.33-0.667) and in HRF (0-1). In CBCT images, the students' ability was lower in HRF detection in comparison with the oblique ones. The students showed limited capacity to diagnose root fractures; however when CBCT was used, the performance was more satisfactory than when periapical radiographs were used.

189 Anterior Ankle Surface Pressures in Lower Extremity Splints: Minimizing Insult After Injury

Though ubiquitously utilized in lower extremity orthopaedic trauma, lower extremity splints are not without their associated iatrogenic risk of morbidity. In fact, improper splinting not only necessitates replacement, but splint- related soft tissue complications are the second most common iatrogenic cause for referral to plastic surgery. Pressure ulcers result from perpendicular forces that compress the soft tissues between body mass, bony prominences, and the support surfaces below. Within those soft tissues are vessels that run parallel to the surface of the site of skin collapse and may collapse easily from pressure loads. As such, prolonged pressure above the threshold for capillary tolerance results in occluded blood flow, interstitial fluid flow, ischemia, pain, necrosis, and sloughing of dead tissue. While clinicians commonly pad bony prominences to minimize the skin pressure, the effect of joint position on skin pressure and, more specifically, changing joint position, is real but has not been well studied or described. The purpose of this biomechanical study is to identify problems with anterior ankle skin pressure secondary to joint position change during splinting and ultimately to determine the optimal position of the ankle during application of the splint as well as the padding technique required over the anterior ankle to minimize iatrogenic skin pressure ulcers. Following ethics approval by our institutional review board, various constructs of lower extremity, short-leg splints were applied to two healthy subjects (two limbs total in this preliminary data set) with an underlying pressure transducer (Tekscan® I-Scan® system, (Tekscan Inc, South Boston, MA, USA) on the skin surface centered on the anterior ankle on the tibialis anterior tendon. All subjects underwent anterior ankle surface pressure assessment when padding was applied in maximum plantar flexion and neutral position for conventional short leg splints application. Percent change from initial contact pressure centered on the tibialis anterior with either Webril© (Covidien/Medtronic, Dublin, Ireland), or Specialist© Cotton Blend Cast Padding (BSN Medical, Charlotte, NC, USA) were calculated. Neutral position of the foot/ankle will be confirmed with a goniometer. There were two limbs total that were analyzed for presentation of pilot data for this study. The percent change in anterior ankle contact pressure when padding was applied in maximum plantar flexion (PF) and then placed in neutral was increased at least two-fold without the addition of plaster and subsequently with the addition of plaster in lower extremity short leg splints (Figure 1). In this pilot data, we report significant increases in anterior ankle contact pressures when splint padding is applied in plantar-flexion and re-positioned into neutral during splint application which may precipitate iatrogenic pressure ulcers. This data, though preliminary, underscores the importance of proper splinting techniques for all clinicians that manage lower extremity trauma (eg, orthopaedic surgery, emergency medicine, urgent care, etc).

Is a Parry Fracture—An Isolated Fracture of the Ulnar Shaft—Associated with the Probability of Abuse in Children between 2 and 16 Years Old?

A parry fracture is an isolated fracture of the ulnar shaft. It occurs when the ulna receives the full force of an impact when the forearm is raised to protect the face. The aim of this study is to assess a possible association between a parry fracture and the probability of abuse in children. In this retrospective, observational, multicenter study, we identified patients between 2 and 16 years old who had been treated for an isolated ulnar shaft fracture. Patient characteristics were registered, anonymized radiographs were rated, and charts were screened for referral to a child protective team. A total of 36 patients were analyzed. As no referrals were registered during follow-up, the primary outcome was changed to a perpendicular force as trauma mechanism. Univariable regression analysis and independent t-test both showed no significant association between patient factors or radiographic classification, and the reported trauma mechanism. We were unable to determine an association between a parry fracture and the probability of abuse. Since trauma mechanism does have a biomechanical effect on the fracture type, we would advise that a very clear reconstruction (and documentation) of the trauma mechanism should be established when a parry fracture is identified on radiographs.

On problem of determining the stress state of elasto-plastic compressible area weakened by ellipsoidal cavity

The work is one of the stages of solving the problem of determining the stress state for a compressible mass weakened by cavities. In the problem statement, there is no pressure inside the cavity, and mutually perpendicular forces are applied at infinity. The problem is solved by the small parameter method, in a spherical coordinate system, in dimensionless length units. The previously found values are taken as the known stress components in the zero approximation in the elastic area and as the perturbed stress components in the plastic area. Using the conjugation of stresses at the boundary of elasto-plastic zone, the stress components for the elastic area are determined in the first approximation. The obtained results can be used in the field of mining, construction mechanics and other related fields.

A New Frame-Based Calibration Method for Extended Octagonal Ring Transducers

HighlightsA simple frame was built to hold and apply uniaxial and biaxial loads to octagonal ring transducers for calibration.Similar results were obtained with the frame as with a universal tensile testing machine.The transducer outputs exhibited low cross-sensitivities and hysteresis (=0.4%), and R2 = 0.9998.The frame is portable and safe, and its concept can be adapted to take a wide range of non-gravitational loads.Abstract. An extended octagonal ring transducer (EORT) is a simple, single, and compact biaxial force measuring transducer, which is ideal for soil force measurement in tillage tool research. Calibration of EORTs is needed to ascertain their sensitivities and to determine an accurate calibration equation to convert voltage output to force measurement. Typically, calibration of EORTs involves the use of universal tensile testing machines, hydraulic systems and large gravitational loads (hanging weights) to apply loads. In this study, a simple calibration frame that enables application of non-gravitational loads was evaluated and used to hold and calibrate an EORT through both uniaxial and biaxial loading. The frame was suitable for both uniaxial and biaxial application of offset coincident force up to 3000 N and centered perpendicular force up to 1500 N. The EORT exhibited a strong linear relationship (R2 = 0.9998) between applied forces and voltage outputs, low hysteresis errors (=0.4%), and low cross-sensitivities (3.61% and 1.6% for coincident and perpendicular forces, respectively). Calibration equations developed from the primary bridge output data or from the biaxial loading data using the frame produced good force predictions, which also improved when taking into account the impacts of cross-sensitivity. The results confirmed that this calibration approach can integrate the interactions of output cross-sensitivity to deliver more accurate force prediction. Coefficients of determination of the relationships between applied and predicted forces were 0.9993 to 0.9996 and 0.9877 to 0.9984 for coincident and perpendicular forces, respectively. This calibration frame presents potential for safely applying large, non-gravitational loads in a contained and portable manner and its concept can easily be adapted to suit the scale of the transducer. Keywords: Biaxial loading, Cross-sensitivity, EORT calibration, Offset coincident force, Uniaxial loading.

Investigation of the effect of a 15-degree tilt-in-space on the fluctuation of shear forces exerted on the buttocks when the back support is reclined.

[Purpose] This study aimed to investigate the effect of the combination of 15° tilt-in-space and recline angles on the fluctuation of shear forces exerted on the buttocks. [Participants and Methods] The participants were 11 healthy adult males. The parameters of the shear forces were the parallel and perpendicular forces exerted on the buttocks as measured by a force plate. The two conditions tested were T0R100-130 and T15R100-130. The tilt-in-space angles were set to 0° and 15° in the T0R100-130 and T15R100-130 conditions, respectively. The reclining angles were determined to be 100° to 130° in both conditions. [Results] Upon comparing the two conditions, the parallel and the perpendicular forces exerted on the buttocks in the T15R100-130 condition were significantly lower than those in the T0R100-130 condition in all positions of back support. Upon comparing the fluctuation values of the parallel and perpendicular forces, those applied in the T15R100-130 condition were significantly higher than those in the T0R100-130 condition. [Conclusion] These results suggest that the fluctuation of shear forces exerted on the buttocks could be decreased by using a combination of 15° tilt-in-space and reclining functions.

Use of spherical particles to understand conidial attachment to surfaces using atomic force microscopy.

SummaryBinding of particles and spores to surfaces is a natural phenomenon which is a prerequisite for biofilm formation. Perpendicular force measurements were carried out using atomic force microscopy cantilevers modified with a polystyrene or glass sphere. The attachment of the spheres was tested against glass, PVAc, p(γ-MPSco-MMA), p(γ-MPS-co-LMA), PMMAsc, and silicon surfaces. The polystyrene spheres demonstrated less varied force and strength of attachment measurement to the surfaces than the glass spheres. The force of attachment of the polystyrene spheres was also influenced by mobility of the co-polymer surfaces. Surface wettability did not affect the force of polystyrene or glass sphere attachment. The force measurements of the non-biological spheres were similar to those seen in biological systems with fungal conidia, and this was due to their size, shape, and binding energies. The use of non-biological systems may present an insight into understanding the fundamentals of more complex biological processes.

Development of a Novel Heart Positioner for Minimally Invasive Coronary Surgery

We developed a heart positioner, the Tentacles NEO, specifically designed for minimally invasive coronary artery bypass grafting (MICS-CABG). The device has 3 flexible suction tubes, with a suction cup at the tip of each tube. The suction tubes can be detached from the device body, allowing them to be manipulated in any direction through a small incision around the small thoracotomy. When the device displaces the heart, the suction cup moves behind the chest wall and does not crowd the operative field. Although the sideways suction force of the new device was as strong as that of the original device, Tentacles, the longitudinal and perpendicular force exerted was approximately 80% of the original device. Nevertheless, the new device could safely and favorably displace the heart in a pig model and even during off-pump CABG via sternotomy. During MICS-CABG, the device was able to displace the heart without crowding the operative field. The new heart positioner, Tentacles NEO, is a useful and practical heart positioner suitable for MICS-CABG.

Collagen peptide simulated bending after applied axial deformation

Structural proteins in the extracellular matrix are subjected to a range of mechanical loading conditions, including varied directions of force application. Molecular modeling suggests that these mechanical forces directly affect collagen's conformation and the subsequent mechanical response at the molecular level is complex. For example, tensile forces in the axial direction result in collagen triple helix elongation and unwinding, while perpendicular forces can cause local triple helix disruption. However, the effects of more complicated mechanical loading, such as the effect of axial pretension on collagen bending and triple helix microunfolding are unknown. In this study we used steered molecular dynamics to first model a collagen peptide under axial tension and then apply a perpendicular bending force. Axial tension causes molecular elongation and increased the subsequent perpendicular bending stiffness, but surprisingly did not increase the predicted collagen triple helix microunfolding threshold. We believe these results elucidate a key potential mechanism by which microscale mechanical loads translate from cellular and micro scales down to the nano and atomistic. Further, these data predict that cryptic force-induced collagen triple helix unwinding is axial-deformation independent, supporting the possibility that cell traction forces could be a key molecular mechanism to alter the cellular matrix microenvironment to facilitate collagen enzymatic degradation and subsequent cellular migration, such as in tumor extravasation.

Anisotropic ultimate strength and microscopic fracture patterns during tensile testing in the dentin-enamel junction region.

The dentin-enamel junction (DEJ), which is the interface between the outer tooth enamel and the underlying dentin, has unique biomechanical properties that allow the two different materials to function together without fracture. The aim of this study was to investigate the anisotropic ultimate tensile strength of the DEJ. Twenty dumbbell-shaped samples were prepared from 10 extracted human molar teeth for tensile strength testing. The maximum tensile forces at fracture were measured in the direction parallel (10 samples) and perpendicular (10 samples) to the DEJ. The mean tensile strength of the samples was significantly higher under parallel forces (30.9±3.3 MPa) than under perpendicular forces (20.6±4.8 MPa; p<0.05). Our findings confirm the structural anisotropy of the DEJ.