Greater Contact Area Research Articles

Mechanics of dynamic compression plate application in fracture fixation

BackgroundDynamic compression plating is a fundamental type of bone fracture fixation used to generate interfragmentary compression. The goal of this study was to investigate the mechanics of the surgical application of these plates, specifically how plate prebend, screw location, fracture gap, and applied torque influence the resulting compressive pressures. MethodsSynthetic bones with transverse fractures were fixed with locking compression plates. One side of the fracture was fixed with locking screws. On the other side of the fracture, a nonlocking screw was inserted eccentrically to induce interfragmentary compression. A pressure mapping sensor within the fracture gap was used to record the resulting pressure distribution. Plate prebends of 0 mm, 1.5 mm, and 3 mm were tested. Three locations of the eccentric screw, four levels of screw torque, and two initial fracture gap conditions also were tested. FindingsWith increasing plate prebend, fracture compression pressures shifted significantly toward the far cortex; however, compression force decreased (P < 0.05). The 1.5 mm prebend plate resulted in the greatest contact area. Increasing screw torque generally resulted in greater fracture compression force. The introduction of a 1 mm fracture gap at the far cortex prior to dynamic compression resulted in little or no fracture compression. InterpretationThe model showed that increasing plate prebend results in an increasing shift of fracture compression pressures toward the far cortex; however, this is accompanied by decreases in compressive force. Initial fracture gaps at the far cortex can result in little or no compression.

3D modeling of bolus for producing by prototyping and use in radiation therapy

Due to its vast number of occurrences, cancer has caused an economic impact on the public and supplementary health care sectors. It is estimated that more than 50% of patients diagnosed with malignant neoplasms need radiotherapy at some stage of their treatment, most of them treated with photon and/or electron beams. Due to the build-up effect (increase in dose in the matter from deposition on the surface to a point of maximum dose) caused by the interaction of photon beams with the irradiated tissue, bolus is often used in routine radiotherapy sectors to superficialize the point of maximum dose in the treatment region. The human body has complex surfaces that are often treatment regions in radiotherapy, but commercial bolus with a standard shape and length do not adapt perfectly to these surfaces. When this happens, air gaps may appear in the region, causing differences between the dose defined in radiotherapy planning and the dose delivered during treatment. In order to eliminate these air gaps and possible dose distribution errors, two methodologies for individualized bolus construction were proposed. In both cases, computed tomography images of the Alderson Rando male anthropomorphic phantom were used as a reference of the anatomy of a human body. From these images, one bolus model was constructed in the 3D modeling software 3ds Max by creating a polygonal mesh, while the other bolus model was constructed in the image computing software 3D Slicer, using segmentation tools. The software Creality Slicer 1.2.3. prepared the files for 3D printing. The prints of the files were made on polylactic acid filament on the Tevo Tarantula Pro printer. The bolus construction methodology using the software 3ds Max showed better results, as a greater contact area between the bolus and the phantom was observed when testing the fit of the printed bolus to the physical phantom. The 3D files of the virtual bolus will be available for future computer simulations. The printed bolus could be used in dosimetry with linear accelerators.

Influence of school backpack load on plantar foot pressure during walking in 9-11 years old girls.

This study aimed to assess the relative load of the midfoot and the metatarsals of both feet when schoolchildren walked with backpacks of different loads. A group of 12 healthy girls (9.9 ± 0.8 years; 33.8 ± 6.7 kg, 1.40 ± 0.10 m) walked barefoot to assess plantar pressures during gait without load (L0%) and with a loaded backpack equal to 10% (L10%) and 20% (L20%) of their body weight. A Footscan® system (RSscan International, Belgium) was used to determine the contact area and relative pressure impulse in the midfoot and metatarsals on the dominant (DL) and non-dominant legs (NL). The effect of load was significant for the contact area of the midfoot for both NL (p = 0.013) and DL (p = 0.001). In the metatarsals, there was significantly greater relative impulse during L10% compared to L0% in the first (p = 0.041) and second (p = 0.050) metatarsals of the DL. Comparing the NL and DL showed significantly greater relative impulse on the DL in the fourth metatarsal during L10% (p = 0.023), greater contact area in the fifth metatarsal during L0% (p = 0.050), and greater impulse in the midfoot during L20% (p = 0.028) on the NL. The school backpack load influences relative plantar pressure distribution, especially in the midfoot. Further, our findings suggest greater propulsion of the DL and supporting function of the NL.

Impact of tamponade agent on retinal displacement following pars plana vitrectomy for rhegmatogenous retinal detachment repair: a computer simulation model.

AbstractPurposeRhegmatogenous retinal detachment (RRD) repair with silicone oil (SO) tamponade has been observed to cause less retinal displacement than gas tamponade. Here, we assessed the mechanism and theoretical extent of retinal displacement in SO versus air tamponade in pars plana vitrectomy (PPV).DesignComputer simulation model.MethodsTamponade scale and subretinal scale simulation models previously developed were used to assess the physical forces, fluid dynamics and retinal deformations in SO versus air PPV.ResultsWhen comparing a SO tamponade and an air tamponade occupying 93% of the ocular cavity, the SO tamponade has a Bond number that is an order of magnitude smaller and has a much lower contact angle (99° versus 125°) and contact pressure (0.0230 versus 1.44 mmHg). With a greater contact area and contact pressure, an air tamponade squeezes subretinal fluid away from contact points, displacing the retina by a maximum length of approximately 700 μm in our model. In contrast, for a SO tamponade, the contact pressure is much lower with a very small magnitude of retinal displacement (~ 50 μm).ConclusionsWe showed that SO tamponade leads to significantly less retinal displacement than air tamponades. Although we do not recommend the routine use of primary SO because of its several disadvantages compared with gas, our findings can be further utilized to develop novel tamponade agents that minimize the risk of retinal displacement following RRD repair.

Resident Commentary: Is There a Significant Difference in Relapse and Complication Rate of Surgically Assisted Rapid Palatal Expansion Using Tooth-Borne, Bone-Borne, and Orthodontic Mini-Implant-Borne Appliances (Ploder et al, 2020)?

Resident Commentary: Is There a Significant Difference in Relapse and Complication Rate of Surgically Assisted Rapid Palatal Expansion Using Tooth-Borne, Bone-Borne, and Orthodontic Mini-Implant-Borne Appliances (Ploder et al, 2020)?

Different conformations of the German shepherd dog breed affect its posture and movement

The conformation of the German shepherd dog (GSD) varies considerably within the breed. These differences may result in large variation in the movement and limb loading and undesirable consequences to their musculoskeletal health. This study aimed to investigate the relationship between conformation and biomechanical measures in 60 GSDs. Full body kinematic and kinetic measures were computed from 3D motion capture and pressure data. The dogs were divided into groups based on their back slope and curvature. Correlation analysis and statistical differences between groups showed that GSDs with a greater back slope have a greater contact area in their forelimbs and place them closer together when standing (n = 60). During trot, the dogs with sloped back showed a greater vertical force in the forelimbs and a greater mid-thoracic flexion (n = 60). Unilateral differences were found in the stifle flexion, hock flexion and hock adduction, suggesting greater movement asymmetry with an increase in the back slope (n = 30). In conclusion, several biomechanical parameters are affected by the GSD’s slope of the back and not by its curvature. Further studies are required to determine whether the variation in movement, posture and conformation within the breed relates to an increased susceptibility to musculoskeletal disorders.

A New Design Solution for Aircraft Wheels that Reduces Overpressure in the Tire while Retaining its Absorption Power and its Dimensions

It is well-known that high working overpressure in a tire adversely affects its service life, while a lower overpressure requires larger tire dimensions and weight. The goal of this research is to find the way to decrease the overpressure in a standard tire in order to increase its durability, while preserving or increasing its load-capacity and retaining the same geometric characteristics. This paper presents a new construction solution that consists of a standard (outer) tire and a smaller (inner) tire inserted in the standard one. This set of tires creates a unique kinetic energy absorption system that occurs when the aircraft lands in direct contact with the runway. During the aircraft hard landing, a large deformation of the tire occurs, i.e., the tire surface is drawn inward both in the cross-section and in the longitudinal section. In this case, the whole weight of the airplane is directed on the tire-shoulder, meaning that the actual contact surface is small. In the new solution, the inner tire prevents the standard tire from drawing inward and keeps it in contact with the runway during tire deflection. A comparative analysis of the change in deflection, track width, and stress distribution of a standard tire and a set of tires in the new solution is performed. It was shown that the new construction solution increases the tire track width by about 8 % and, therefore, the greater contact area between the tires and the runway. In addition, tire stress is decreased by about 40 %; therefore, it has higher tire durability, as well as the ability to absorb more kinetic energy by 56 % compared to a standard tire.

In vivo reverse total shoulder arthroplasty contact mechanics

Several invitro studies have investigated the biomechanics of reverse total shoulder arthroplasty (RTSA); however, few invivo studies exist. The purpose of this study was to examine invivo RTSA contact mechanics in clinically relevant arm positions. Our hypothesis was that contact would preferentially occur in the inferior region of the polyethylene liner. Forty patients receiving a primary RTSA were recruited for a prospective cohort study. All patients received the same implant design with a nonretentive liner. Stereo radiographs were taken at maximal active range of motion. Model-based radiostereometric analysis was used to identify implant position. Contact area between the polyethylene and glenosphere was measured as the geometric intersection of the 2 components and compared with respect to polyethylene liner size, arm position, and relative position within the liner. There were no differences in the proportion of contact area in any arm position between polyethylene liner sizes, ranging from 30% ± 17% to 38% ± 23% for 36-mm linersand 32% ± 21% to 41% ± 25% for 42-mm liners. Contact was equally distributed between the superior and inferior halves of the liner at each arm position (P = .06-.79); however, greater contact area was observed in the outer radius of the liner when the arm was flexed (P = .002). This study highlights that contact mechanics are similar between 36- and 42-mm liners. Contact area is generally equally distributed throughout the liner across the range of motionand not preferentially in the inferior region as hypothesized.

Relationship between seat surface shape and pressure distribution in school seat models.

Students remain in a sedentary position inside classrooms for 60% to 80% of their school day. As such, research has associated students' prolonged seated posture on school furniture with their discomfort and musculoskeletal pain. The correlation between the shape of the seat surface and the zones of the body making contact with these surfaces constitutes an essential factor in determining comfort-enhancing seat design. This study's primary aim lies in contrasting the standard, current school chair against two seat prototypes, both designed and built from digital models, comparing seat-user pressure distribution and contact area during students' performance of different school tasks. Participants (n = 13), ages 7 to 19, performed school tasks sitting on three different chairs' seat surfaces during the test: the current seat used in schools and two seat prototypes, each designed based on body anatomy. The seats were evaluated through a force-sensing array pressure-mapping system. The measurements from designed seat prototypes provide a better distribution of pressures and greater contact area with the students' anatomical areas (buttocks and thighs) than the seat currently used in the specified schools. The improvement in pressure values and contact area as seen in the second designed seat prototype is due to its inclination angle and contact with students' sacral zone. This research work found that a seat's shape based on human anatomical features (buttocks and thighs), compared to a completely flat seat, creates a higher reduction of body pressures and an increase in the body contact area, with the intent to increase comfort and reduce musculoskeletal pain.

Anchor placement to glenoid rim during Bankart repair recreates contact area of anterior capsulolabral complex on glenoid better than onto articular surface.

This study aimed to compare the contact areas of Bankart repair with suture anchors placed on the articular surface of the glenoid versus at the rim of the glenoid because it is unclear which technique most effectively restores the footprint after Bankart repair. Ten fresh frozen cadaveric shoulders (mean age 70.7years) were dissected. The attachment site of the capsulolabral complex from the 1 o' clock position to the 6 o'clock position was marked with ink, and the contact area of the anterior-inferior capsulolabral complex on the glenoid neck was measured using imageJ. Bankart lesions were created, and two types of Bankart repair were performed on each specimen. The suture anchors were inserted at the glenoid rim (Rim group) and onto the glenoid articular surface 2mm from the rim (Surface group). Using pressure-sensitive films, we examined the interface contact area. The Rim group recreated 64.9% of the native surface area, while the Surface group recreated 47.3% of the area. The Rim group recreated significantly greater contact area compared to the Surface group (P = 0.0008). The anchor placement to the glenoid rim recreates the footprint of the capsulolabral complex on the anterior inferior glenoid better than the anchor placement onto the articular surface.

A Novel Ultrastable and High‐Performance Electrode Material for Asymmetric Supercapacitors Based on ZIF‐9@Polyaniline

AbstractNanoflower‐like composites have greater contact area and more redox reactive centers, which have great potential in the application of electrode materials for supercapacitors. A nonconductive polymer binder is usually used in preparation of electrodes, which causes an increase in interface resistance and a decrease in material active sites. Here, polyaniline (PANI) and ZIF‐9 are directly grown on the Ni foam (ZIF‐9@PANI/NF) by a simple solvothermal method without a nonconductive polymer binder. A nanoflower array is grown on the NF, which can be directly used as electrode material of supercapacitor. The attachment of PANI facilitates electron transfer and increases the conductivity of the material. At a current density of 1 A g−1, the specific capacitance is up to 7 times that of the ZIF‐9. The assembled asymmetric supercapacitor has a high energy density of 52 Wh kg−1 at a power density of 800 W kg−1, remaining 90.1% after 50 000 cycles. These great electrochemical properties show the material has good market development prospects for energy storage device.

Sandwich-type electrochemical immunosensor constructed using three-dimensional lamellar stacked CoS2@C hollow nanotubes prepared by template-free method to detect carcinoembryonic antigen

Effective treatment of cancer depends on early detection of tumor markers. In this paper, an effective template-free method was used to prepare CoS2@C three-dimensional hollow sheet nanotubes as the matrix of the immunosensor. The unique three-dimensional hybrid hollow tubular nanostructure provides greater contact area and enhanced detection limit. The CoS2@C–NH2-HRP nanomaterial was synthesized as a marker and had a high specific surface area, which can effectively improve the electrocatalytic ability of hydrogen peroxide (H2O2) reduction while increasing the amount of capture-fixed carcinoembryonic antigen antibody (anti-CEA). In addition, the co-bonded horseradish peroxidase (HRP) can further promote the redox of H2O2 and amplify the electrical signal. Carcinoembryonic antigen (CEA) was quantified by immediate current response (i-t), and the prepared immunosensor had good analytical performance under optimized conditions. The current signal and the concentration of CEA were linear in the range of 0.001–80 ng/mL, and the detection limit was 0.33 pg/mL (S/N = 3). The designed immunosensor has good selectivity, repeatability and stability, and the detection of human serum samples shows good performance. Furthermore, electrochemical immunosensor has broad application prospects in the clinical diagnosis of CEA.

Review on Thermal Conductivity of the Graphene Reinforced Resin Matrix Composites

Graphene is a two-dimensional nanostructure filler with high thermal conductivity (5000 W/mK) and excellent mechanical properties, which has a very wide application prospect. Graphene is with super high specific surface area, which provides a greater contact area with polymer matrix. Then it is more easy to form the thermal conductive heat channels, which could improve the thermal conductivity of composite materials. The concentration, the ratio of geometrical diameters, the dispersion in the matrix and the interfacial bonding between graphene and the matrix materials will greatly affect the thermal conductivity of graphene reinforced composites. However, the graphene nanosheets can be easy to stack together and difficult to be dispersed into the solvent and polymer matrix. In order to improve the interfacial combination between graphene nanosheets and the matrix so as to reduce the interfacial thermal resistance of the composites, it is usually to modify the surface of graphene nanosheets, which mainly includes non-covalent modification and covalent modification. In this paper, researches on the thermal conductivity of graphene were reviewed, and the existing problems and the future research focus were also discussed.

Thermodynamics of Adsorption on Graphenic Surfaces from Aqueous Solution.

Adsorption of organic molecules from aqueous solution to the surface of carbon nanotubes or graphene is an important process in many applications of these materials. Here we use molecular dynamics simulation, supplemented by analytical chemistry, to explore in detail the adsorption thermodynamics of a diverse set of aromatic compounds on graphenic materials, elucidating the effects of the solvent, surface coverage, surface curvature, defects, and functionalization by hydroxy groups. We decompose the adsorption free energies into entropic and enthalpic components and find that different classes of compounds-such as phenols, benzoates, and alkylbenzenes-can easily be distinguished by the relative contributions of entropy and enthalpy to their adsorption free energies. Overall, entropy dominates for the more hydrophobic compounds, while enthalpy plays the greatest role for more hydrophilic compounds. Experiments and independent simulations using two different force field frameworks (CHARMM and Amber) support the robustness of these conclusions. We determine that concave curvature is generally associated with greater adsorption affinity, more favorable enthalpy, and greater contact area, while convex curvature reduces both adsorption enthalpy and contact area. Defects on the graphene surfaces can create concave curvature, resulting in localized binding sites. As the graphene surface becomes covered with aromatic solutes, the affinity for adsorbing an additional solute increases until a complete monolayer is formed, driven by more favorable enthalpy and partially canceled by less favorable entropy. Similarly, hydroxylation of the surface leads to preferential adsorption of the aromatic solutes to remaining regions of bare graphene, resulting in less favorable adsorption entropy, but compensated by an increase in favorable enthalpic interactions.

Fabrication of heterogeneous photocatalysts for insight role of carbon nanofibre in hierarchical WO3/ MoSe2 composite for enhanced photocatalytic hydrogen generation

Mimicking the natural photosynthesis system, artificial photocatalysis facilitates effective utilization of solar energy for environmental sustainability and hydrogen energy production. In this work, the robust and efficient carbon fiber has been successfully incorporated into the interface between WO3 nanodots and MoSe2 needles using the facile hydrothermal and solvothermal method. The suitable interfacial contact of heterogeneous photocatalysts plays a significant role in the separation/transfer of interfacial photogenerated electron-hole pairs and hetero-junction. It seems an efficient approach for enhanced photocatalytic performance since the greater area of contact could improve the interfacial rate of charge transfer. The phase structure of prepared WO3 nanodots changed from the monoclinic to hexagonal phase by the addition of co-catalyst. The experimental results exhibited that carbon fiber played a tri-functional role to boost up the photocatalytic activity over MoSe2 nanostructures. It's not only act as operative co-catalyst but could also serve as the conductive electron bridges, rather than general cocatalyst, to accumulate electrons and encourage the hydrogen generation kinetics over the WO3 photocatalysts. More interestingly, the WO3−1% MoSe2−1.5% carbon fiber and WO3−1%MoSe2 nanocomposites demonstrated the excellent rates of hydrogen evolution 438.7 and 356.2 mmol/g.h, which were 7.6 and 6.17 times higher when compared to that of pure MoSe2, respectively. Under the visible light excitation, the atomically junction encourages fast electron transfer from nanofibers to MoSe2 to suppress the rapid recombination kinetics within WO3 nanodots and extend the lifetime of WO3 charge carrier's, thereby releasing more photogenerated electrons with higher reducing power for hydrogen evolution. The current work can contribute with new perspectives and mechanistic insight for the design and development of heterogeneous photocatalysts WO3 based nanostructures using the combination of MoSe2 and trifunctional carbon nanofibers for environment and energy harvesting applications.

Moisture transport during contact sorption drying of coal fines

ABSTRACTStudies have shown that contact sorption drying is a feasible technique to dewater fine (+0.15mm–0.5mm) and ultra-fine (−0.15 mm) coal. The aim of this article is to further investigate the drying mechanism involved. It could be shown that moisture transfer occurred primarily in the liquid phase, requiring direct contact between the coal and sorbent particles to facilitate the movement of the water. Moisture transfer was enhanced by operating with a higher sorbent to coal mass ratio. When drying smaller coal particle size ranges, the resistance to liquid transport decreased, leading to better desorption results. These improvements were mainly as a result of a greater contact area between the sorbent and coal particles.

Ultrathin 2D/2D WO3/g-C3N4 step-scheme H2-production photocatalyst

The appropriate interfacial contact of heterojunction photocatalysts plays a critical role in transfer/separation of interfacial charge carriers. Design of two-dimensional (2D)/2D surface-to-surface heterojunction is an effective method for improving photocatalytic activity since greater contact area can enhance interfacial charge transfer rate. Herein, ultrathin 2D/2D WO3/g-C3N4 step-like composite heterojunction photocatalysts were fabricated by electrostatic self-assembly of ultrathin tungsten trioxide (WO3) and graphitic carbon nitride (g-C3N4) nanosheets. The ultrathin WO3 and g-C3N4 nanosheets were obtained by electrostatic-assisted ultrasonic exfoliation of bulk WO3 and a two-step thermal-etching of bulk g-C3N4, respectively. The thickness of ultrathin WO3 and g-C3N4 nanosheets are 2.5–3.5 nm, which is equivalent to 5–8 atomic or molecular layer thickness. This ultrathin layered heterojunction structure can enhance surface photocatalytic rate because photogenerated electrons and holes at heterogeneous interface more easily transfer to surface of photocatalysts. Therefore, the obtained ultrathin 2D/2D WO3/g-C3N4 step-scheme (S-scheme) heterojunction photocatalysts exhibited better H2-production activity than pure g-C3N4 and WO3 with the same loading amount of Pt as cocatalyst. The mechanism and driving force of charge transfer and separation in S-scheme heterojunction photocatalysts are investigated and discussed. This investigation will provide new insight about designing and constructing novel S-scheme heterojunction photocatalysts.

Melamine cyanurate tailored by base and its multi effects on flame retardancy of polyamide 6

In this paper, nitrogenous bases adenine (A), guanine (G), cytosine (C), and uracil (U), were used to tailor the hydrogen-bonded network of melamine cyanurate (MCA) and were noted as A-MCA, G-MCA, C-MCA, U-MCA, respectively. The results showed that the size, morphology and thermal behavior of MCA are regulated by base due to the formation of hydrogen bonds between them. These modified MCAs were used to improve the flame retardancy of polyamide 6 (PA6) which was evaluated by using the limiting oxygen index (LOI) and the vertical burning (UL-94) test, etc. The results showed that the PA6 sample containing 9 wt% C-MCA achieves the UL-94 V-0 rating and has a LOI value of 30.7%, while the other samples with equal amounts of MCA only pass the UL-94 V-2 rating. The flame retardant mechanism was studied, and the results reveal that C-MCA with smaller size has greater contact area with PA6 which helps to catalyze the decomposition of PA6; Thus the PA6/C-MCA releases more NH3, CO2 etc., and produces more droplets than others, which dilutes combustible gas and takes away heat to make the samples extinguish.

Myotendinous junction plasticity in aged ovariectomized rats submitted to aquatic training.

The study aims to describe the tissue plasticity of MTJ through the morphological analysis of MTJ soleus in ovariectomized aged female Wistar rats submitted to aquatic training. Forty aged Wistar rats, 1 year and 2 months of age, were divided into four groups: sedentary (S), trained (T), ovariectomized (O), and trained/ovariectomized (OT). Employing the transmission electron microscopy, the ultrastructural and morphometric elements were revealed. In the S group, changes in morphological characteristics as a consequence of the aging process were seen, demonstrated by the conical shape of the muscle cell extremity, a large area with collagen deposit, and misalignment of sarcomeres in series. The T group presented ample adjustments when revealed the organization of MTJ, through the increase of the contact area and greater lengths of sarcoplasmatic invaginations and evaginations. The O group revealed extensive tissue disorganization with muscle atrophy, reduction of MTJ contact area, and consequently, changes in sarcoplasmatic invaginations and evaginations. The OT group demonstrated extensive remodeling with restructuring MTJ through the increase of tissue contact area, extensive organization, parallel arrangement, and increased length of sarcoplasmatic invaginations and evaginations. The distal sarcomeres presented higher lengths compared to the proximal sarcomeres in both the groups. We conclude that aquatic training was effective in the organization and structural remodeling of the myotendinous interface of ovariectomized aged rats. There was a greater area of contact, and consequently, greater resistance in the myotendinous interface promoting a lower predisposition to injuries.

DEVELOPMENT OF BALLOON-BASED ORGAN RETRACTOR FOR LAPAROSCOPIC SURGERY

Effective organ retraction is essential to ensure safe and efficient surgery, in the case of laparoscopic surgery, organ retraction is particularly difficult to achieve. Currently such as cherry dissectors are used for retraction, however the small size results in excessive stress on the organ being retracted. Therefore, we are developing a balloon-based retractor that provides similar functionality as the cherry dissector, particularly being able to pass through a small port, yet being expandable to provide a much greater contact area as well as improved traction, thus providing increased operating efficiency and improved safety in organ retraction. In this paper, the relative merits and demerits of a number of currently available retractors are compared. Parameters under consideration include shape, size, effective traction (coefficient of friction), type of actuation and ease of use. While parameters such as pressure distribution and effective traction have been objectively measured, other attributes unique to the individual mechanisms are discussed, and finally feedback is provided from surgeons regarding the respective retractor’s ease of use and perceived efficacy.