MOLECULAR SWITCH BASED ON BITHIOPHENE-AZOBENZENE: HOW TO CONTROL CONDUCTANCE THROUGH THE MONOLAYER USING LIGHT

Молекулярные переключатели на основе азобензола (азо) являются светочувствительными молекулами, которые могут переключаться между двумя конфигурационными состояниями под действием света. Светочувствительные азо -монослои можно использовать для модуляции работы выхода, то есть они влияют на свойства электродов. В данной работе мы отвечаем на вопрос, что происходит со структурами, электронными свойствами и перераспределением заряда в монослоях азобитиофена (азо-бт) в зависимости от светового стимула, используя теорию функционала плотности. Моделируются два типа переключателей, различающихся расположением азо и бт от группы пришивки молекулы к поверхности: азо-бт и бт-азо . Один из них (бт-азо) описан в литературе, другой же является продуктом молекулярного дизайна. Мы описываем транс- и цис-изомеры для каждого переключателя, находящегося в контакте с кластером золота. Наше моделирование объясняет гигантское соотношение в проводимости ON/OFF-состояний при воздействии УФ-излучения на монослой улучшенной электронной связью между цис-изомерами (состояние ON) и кластером золота. Транс-изомеры же (OFF состояние) моделируемых переключателей играют роль изоляторов. Кроме того, мы показываем, какие именно свойства улучшаются после молекулярного дизайна. Данное исследование открывает новые возможности в разработке инновационных модификаций поверхности электродов. Molecular switches based on azobenzene (azo) are defined as light-responsive molecules which can change between two configurational states under light stimuli. Responsive azo monolayers can be used to modulate the work function, i.e. they tune the properties of the interfaces at the electrodes. In this work, we investigate what happens to the structures, electronic properties, and the charge redistribution within azo-bithiophene (azo-bt) monolayers depending on the light stimulus using density functional theory. Two types of switches differing in the order of azo and bt counting from the anchor group are modelled: azo-bt and bt-azo . One of them (bt-azo) is known from the literature, the remaining one is a product of rational design. We describe trans- and cis-isomers for each switch being in a contact with a gold cluster. Our simulations explain a giant ON/OFF conductance ratio upon UV light stimulus by improved electronic coupling between the cis-isomers (ON-state) and the gold cluster. The trans-isomers (OFF-state) of the simulated switches play the role of the insulators. Moreover, we show which molecular properties are enchanced by molecular design. This study opens up new avenues to the development of the innovative design of electrode surface modifications.

Double Row Absorbable Anchor Bridge Suture Versus Hollow Nails for Treating Acute Posterior Cruciate Ligament Avulsion Fracture

Objective To compare the outcomes of open reduction through double row absorbable anchor bridge suture with hollow nails for acute posterior cruciate ligament (PCL) avulsion fracture. Methods From May 2015 to May 2019, 35 patients with acute PCL avulsion fractures were treated by open reduction through double row absorbable anchor bridge suture or hollow nails. There were 15 cases in double row absorbable anchor group and 20 cases in hollow nails group. The operation time, incision length, postoperative ambulation time, hospitalization expenses, healing time of fracture and Lysholm score of patients at the last follow-up were compared between the two groups. Result All the patients in both group had operation perfromed smoothly without serious complication. The operation time in double row absorbable anchor group was (77.33±9.88) min which was longer compared to (59.75±7.86) min in the hollow nails group (p＜0.05). The hospitalization expenses indouble row absorbable anchor group was (28132±2096)yuan which was higher compared to (15904±1113) yuan in the hollow nails group (p＜0.05).The postoperative ambulation time in double row absorbable anchor group was (2.07±0.70) d which was shorter compared to (3.80±1.64) d in the hollow nails group (p＜0.05). There were no significant difference between the two groups in incision length, healing time of fracture and Lysholm score of patients at the last follow-up (p＞0.05). Conclusion Both open reduction through double row absorbable anchor bridge suture and hollow nails for acute PCL avulsion fracture have good clinical result. Double row absorbable anchor bridge suture had advantage of reliable fixation and shorter postoperative ambulation time incision length, however, hollow nails fixation had advantages of less operation time and lower hospitalization expenses.

Suture Anchor Versus Transosseous Tunnel Repair for Inferior Pole Patellar Fractures Treated With Partial Patellectomy and Tendon Advancement: A Biomechanical Study

Background: Comminuted inferior pole patellar fractures can be treated in numerous ways. To date, there have been no studies comparing the biomechanical properties of transosseous tunnels versus suture anchor fixation for partial patellectomy and tendon advancement of inferior pole patellar fractures. Hypothesis: Suture anchor repair will result in less gapping at the repair site. We also hypothesize no difference in load to failure between the groups. Study Design: Controlled laboratory study. Methods: Ten cadaveric knee extensor mechanisms (5 matched pairs; patella and patellar tendon) were used to simulate a fracture of the extra-articular distal pole of the patella. The distal simulated fracture fragment was excised, and the patellar tendon was advanced and repaired with either transosseous bone tunnels through the patella or 2 single-loaded suture anchors preloaded with 1 suture per anchor. Load to failure and elongation from cycles 1 to 250 between 20 and 100 N of force were measured, and modes of failure were recorded. Statistical analysis was performed using a paired 2-tailed Student t test. Results: The suture anchor group had less gapping during cyclic loading as compared with the transosseous tunnel group (mean ± SD, 6.83 ± 2.23 vs 13.30 ± 5.74 mm; P = .047). There was no statistical difference in the load to failure between the groups. The most common mode of failure was at the suture-anchor interface in the suture anchor group (4 of 5) and at the knot proximally on the patella in the transosseous tunnel group (4 of 5). Conclusion: Suture anchors yielded similar strength profiles and less tendon gapping with cyclic loading when compared with transosseous tunnels in the treatment of comminuted distal pole of the patellar fractures managed with partial patellectomy and patellar tendon advancement. Clinical Relevance: Suture anchors may offer robust repair and earlier range of motion in the treatment of fractures of the distal pole of the patella. Clinical randomized controlled trials would help clinicians better understand the difference in repair techniques and confirm the translational efficacy in clinical practice.

Comparison of Function- and Activity-Related Outcomes After Anterior Talofibular Ligament Repair With 1 Versus 2 Suture Anchors

Background: Few studies have compared the clinical outcomes of using 1 versus 2 suture anchors for anterior talofibular ligament (ATFL) repair. Purpose: To compare the function and activity-related outcomes of arthroscopic ATFL repair using 1 versus 2 suture anchors. Study Design: Cohort study; Level of evidence, 3. Methods: This retrospective study involved 46 patients (22 patients in the 1-anchor group, 24 patients in the 2-anchor group) who underwent ATFL repair between January 2015 and December 2017. American Orthopaedic Foot & Ankle Society score, Karlsson and Peterson score, and Tegner activity level were evaluated preoperatively and ≥2.5 years postoperatively. At follow-up, patients were also asked about time to return to sport as well as level and intensity of physical fitness. Satisfaction was evaluated with the Sefton grading system. Results: After ≥2.5 years of follow-up (30 months in the 1-anchor group, 33 months in the 2-anchor group), patients in the 2-anchor group had a higher Tegner activity level than those in the 1-anchor group (mean ± SD, 4.75 ± 1.07 vs 4.05 ± 1.17; P = .039). As compared with patients in the 2-anchor group, fewer patients in the 1-anchor group returned to their preoperative activity level (54.2% vs 22.9%; P = .029); the rate of activity at the same or higher intensity as preinjury was also lower in the 1-anchor group (50% vs 79.2%; P = .038). However, there were no differences between the groups in terms of American Orthopaedic Foot & Ankle Society and Karlsson and Peterson scores, time to return to work/sport, duration of activity participation, level of physical fitness, or satisfaction according to Sefton grading. Conclusion: Arthroscopic ATFL repair appears to be an effective treatment regardless of whether 1 or 2 suture anchors are used. The techniques had similar functional outcome scores, but 1-anchor repair produced inferior activity-related outcomes.

The Effect of Anchor Group on the Phonon Thermal Conductance of Single Molecule Junctions

There is a worldwide race to convert waste heat to useful energy using thermoelectric materials. Molecules are attractive candidates for thermoelectricity because they can be synthesised with the atomic precision, and intriguing properties due to quantum effects such as quantum interference can be induced at room temperature. Molecules are also expected to show a low thermal conductance that is needed to enhance the performance of thermoelectric materials. Recently, the technological challenge of measuring the thermal conductance of single molecules was overcome. Therefore, it is timely to develop strategies to reduce their thermal conductance for high performance thermoelectricity. In this paper and for the first time, we exploit systematically the effect of anchor groups on the phonon thermal conductance of oligo (phenylene ethynylene) (OPE3) molecules connected to gold electrodes via pyridyl, thiol, methyl sulphide and carbodithioate anchor groups. We show that thermal conductance is affected significantly by the choice of anchor group. The lowest and highest thermal conductances were obtained in the OPE3 with methyl sulphide and carbodithioate anchor groups, respectively. The thermal conductance of OPE3 with thiol anchor was higher than that with methyl sulphide but lower than the OPE3 with pyridyl anchor group.

Adjustable Cortical Fixation Device for Quadriceps Tendon Repair: A Cadaveric Biomechanical Study

Background: Adjustable cortical fixation devices have demonstrated utility in orthopaedic applications, such as ankle syndesmosis repair. Purpose: To assess the cyclic gap formation of a quadriceps tendon repair technique using an adjustable cortical fixation device compared with repair with knotless suture anchors and suture tape, a modification of conventional suture anchor repair. Study Design: Controlled laboratory study. Methods: Eight fresh-frozen matched pairs of cadaveric knees were used. Specimens in each pair were randomized to undergo either modified suture anchor repair (control) or adjustable cortical fixation repair. The control repair was performed as previously described. The experimental repair was performed using 2 No. 2 FiberWire sutures placed into the quadriceps tendon in a running locked Krackow configuration and 2 adjustable loop devices passed through transosseous tunnels. The lagging strands of the devices were tensioned to seat the cortical fixation buttons at the inferior patellar pole and then tied to the free Krackow strands at the superior pole to complete the repair. The mean plastic gap (permanent tendon displacement that did not recover with cyclic extension) and mean maximum gap (peak displacement that occurred with cyclic knee flexion and partially recovered with extension) were evaluated during cyclic loading for 500 cycles of full knee extension to 90° of flexion. Results: At all testing intervals, the mean plastic gap was significantly smaller for the cortical fixation group versus the suture anchor group ( P < .02). Similarly, the mean maximum gap was significantly smaller for the cortical fixation specimens at all testing intervals ( P < .01). After cyclic loading, the mean maximum gap was significantly smaller in the cortical fixation group (4.80 ± 1.56 mm) versus the suture anchor group (8.47 ± 1.47 mm; P = < .001). The mean plastic gap was also significantly smaller in the cortical fixation versus the suture anchor group (3.25 ± 1.10 mm vs 6.57 ± 1.62 mm, respectively; P = < .001). Conclusion: Quadriceps tendon repair using an adjustable cortical fixation device demonstrated superior biomechanical properties in cyclic displacement testing compared with repair using the suture anchor technique. Clinical Relevance: These results suggest that an adjustable cortical fixation device is a biomechanically viable alternative for quadriceps tendon repair.

pH control of conductance in a pyrazolyl Langmuir–Blodgett monolayer

In this contribution pyrazole is identified as an excellent anchor group that forms high quality films under pH controlled conditions, allowing the modulation of the electrical properties with a more efficient electronic coupling in basic conditions.

Experimental Exploration of Bearing Capacity of Clay with Multiple Inflatable Anchors

Inflatable anchors have been applied to reinforce foundations because soft soil deposits have a low bearing capacity. However, previous research on the mechanical behaviors of inflatable anchors has focused on a single anchor. Since anchors are always used in a group, the uplift behavior of multiple inflatable anchors in soft soil should be investigated. A series of pull-out tests were conducted in this framework by changing the number, spacing, and layout of inflatable anchors. Additionally, the effect coefficient (ECO) of multiple inflatable anchors is discussed. It is found that the failure behavior of multiple inflatable anchors exhibits a three-stage curve: an initial linear stage, followed by nonlinear, and steady-state stages. In addition, the ultimate bearing capacity of multiple inflatable anchors is maximized if the ratio of the spacing of inflatable anchors to the equivalent expanding section diameter of an inflatable anchor is 6.84. It is recognized that the ECO of this new multiple inflatable anchor group is sometimes greater than 1, unlike that of conventional anchors, which have ECOs of less than 1. In addition, the layout of multiple inflatable anchors in the shape of a cinquefoil is recommended due to its high ECO.

Analysis of the Rock Failure Cone Size Relative to the Group Effect from a Triangular Anchorage System

This study employs the numerical analysis and experimental testing to analyze the fracturing mechanics and the size of rock cones formed in the pull-out of a system of three undercut anchors. The research sets out to broaden the knowledge regarding: (a) the potential of the undercut anchor pull-out process in mining of the rock mass, and (b) estimating the load-carrying capacity of anchors embedded in the rock mass (which is distinctly different from the anchorage to concrete). Undercut anchors are most commonly applied as fasteners of steel components in concrete structures. The new application for undercut anchors postulated in this paper is their use in rock mining in exceptional conditions, such as during mining rescue operations, which for safety considerations may exclude mechanical mining techniques, mining machines, or explosives. The remaining solution is manual rock fracture, whose effectiveness is hard to assess. The key issue in the analyzed aspect is the rock fracture mechanics, which requires in-depth consideration that could provide the assistance in predicting the breakout prism dimensions and the load-displacement behavior of specific anchorage systems, embedment depth, and rock strength parameters. The volume of rock breakout prisms is an interesting factor to study as it is critical to energy consumption and, ultimately, the efficiency of the process. Our investigations are supported by the FEM (Finite Element Method) analysis, and the developed models have been validated by the results from experimental testing performed in a sandstone mine. The findings presented here illuminate the discrepancies between the current technology, test results, and standards that favor anchorage to concrete, particularly in the light of a distinct lack of scientific and industry documentation describing the anchorage systems’ interaction with rock materials, which exhibit high heterogeneity of the internal structure or bedding. The Concrete Capacity Design (CCD) method approximates that the maximum projected radius of the breakout cone on the free surface of concrete corresponds to the length of at the most three embedment depths (hef). In rock, the dimensions of the breakout prism are found to exceed the CCD recommendations by 20–33%. The numerical computations have demonstrated that, for the nominal breakout prism angle of approx. 35% (CCD), the critical spacing for which the anchor group effect occurs is ~4.5 (a cross-section through two anchor axes). On average, the observed spacing values were in the range of 3.6–4.0.