Do we know how much force we apply with latex intermaxillary elastics?

Objectives: The aim of our study was to evaluate the variation of the forces provided by different branded elastics and to compare the force diminution that occurs after 24-h of use in wet environment. Materials and Methods: Elastics from four different manufacturer (American Orthodontics [AO], USA; Dentaurum [DENT], Germany; Ormco, USA; RMO, USA) with 3/16-inch (4.8 mm) lumen diameter, and two different force degrees (medium/heavy) were included in the study with a total of eight groups of elastics. First force measurements were performed with 50 elastics of each group at various stretching distances; lumen diameter ×2 (9.52 mm), ×3 (14.28 mm), the average canine-first molar length (22.3 mm), and the canine-second molar length (38.7 mm) under room temperature and dry air conditions. In addition, ten the elastics from each group were stretched at 22.3 mm distance in a custom-made plate and kept in 37°C distilled water. Twenty-four hours later, the force measurements were repeated. Results: Regardless of the brand and type (medium-heavy), all the tested elastics showed variations in matter of generated forces at different stretching distances. The variation amount increased as the length of elongation increased. The lowest standard deviation values were observed for both medium and heavy DENT elastic groups. When stretched to 3 times of their lumen size, the medium and heavy elastics both produced either lower or higher forces compared to the levels of force indicated by the manufacturers. The closest mean force to the force level stated by the manufacturer was provided with medium AO (3.6 g difference) elastics and heavy RMO counterparts (7.9 g difference). A significant 20–23% reduction of force was observed in all brands, both in medium and heavy elastics after passing 24-h in aqueous environment. No significant difference was observed in matter of force degradation between groups for both medium and heavy elastics (P < 0.05). Conclusion: The forces exerted by intermaxillary elastics were not found to be standard and the force stated on the package is not always provided precisely. A significant force loss around 20% was observed with all the elastics after 24-h of use in wet environment at 37°C.

Effects of Different Hard Finishing Processes on Gear Excitation

Gearboxes are essential in mechanical drive trains for power transmission. A low noise emission and thus an optimized excitation behavior is a substantial design objective for many applications in terms of comfort and operational safety. There exist numerous processes for manufacturing gears, which all show different properties in relation to the process variables and, therefore, differences in the resulting accuracy and quality of the gear flank. In this paper, the influence of three different manufacturing processes for hard finishing—continuous generating grinding, polish grinding and gear skiving—on the surface structure of gear flanks and the excitation behavior is investigated experimentally and analyzed by the application force level. A tactile scanning of the gear flanks determines the flank surface structure and the deviations from the desired geometry. A torsional acceleration measurement during speed ramp-ups at different load levels is used to analyze the excitation of the gears. The results show only a minor influence of the surface structure on the application force level. The excitation behavior is dominated by the influence of the flank modification and its deviation from the design values.

Growth modulation of angular deformities with a novel constant force implant concept-preclinical results

Purpose Varus-valgus deformities in children and adolescents are often corrected by temporary hemi-epiphysiodesis, in which the physis is bridged by an implant to inhibit growth. With standard implant solutions, the acting forces cannot be regulated, rendering the correction difficult to control. Furthermore, the implant load steadily increases with ongoing growth potentially leading to implant-related failures. A novel implant concept was developed applying a controlled constant force to the physis, which carries the potential to avoid these complications. The study aim was to proof the concept in vivo by analyzing the effect of three distinct force levels on the creation of varus deformities. Methods The proposed implant is made of a conventional cerclage wire and features a twisted coil that unwinds with growth resulting in an implant-specific constant force level. The proximal medial tibial physes of 18 lambs were treated with the implant and assigned to three groups distinct by the force level of the implant (200 N, 120 N, 60 N). Results The treatment appeared safe without implant-related failures. Deformity creation was statistically different between the groups and yielded on average 10.6° (200 N), 4.8° (120 N) and 0.4° (60 N) over the treatment period. Modulation rates were 0.51°/mm (200 N), 0.23°/mm (120 N) and 0.05°/mm (60 N) and were constant throughout the treatment. Conclusion By means of the constant force concept, controlled growth modulation appeared feasible in this preclinical experiment. However, clinical trials are necessary to confirm whether the results are translatable to the human pathological situation.

Effect of bilateral contraction on the ability and accuracy of rapid force production at submaximal force level

The present study aims to clarify the effects of bilateral contraction on the ability and accuracy of rapid force production at the submaximal force level. Eleven right-handed participants performed rapid gripping as fast and precisely as they could in unilateral (UL) and bilateral (BL) contractions in a standing position. Participants were required to impinge a grip force of 30% and 50% of their maximal voluntary contraction (MVC). Ability and accuracy of rapid force production were evaluated using the rate of force development (RFD) and force error, respectively. The data analysis did not observe a significant difference in the RFD between UL and BL contractions in both 30% (420±86 vs. 413±106%MVC/s, p = 0.34) and 50% of MVC (622±84 vs. 619±103%MVC/s, p = 0.77). Although the RFD to peak force ratio (RFD/PF) in BL contraction was lower than in UL in 30% of MVC (12.8±2.8 vs. 13.4±2.7, p = 0.003), it indicated a small effect size (d = 0.22) of the difference between UL and BL in RFD/PF. The absolute force error of BL contraction was higher than of UL contraction in 30% (4.67±2.64 vs. 3.64±1.13%MVC, p = 0.005) and 50% of MVC (5.53±2.94 vs. 3.53±0.71%MVC, p = 0.009). In addition, medium and large effect sizes were observed in absolute force error from 30% (d = 0.51) and 50% of MVC (d = 0.94), respectively. In conclusion, results indicated that the bilateral contraction reduced in the ability and accuracy of rapid force production at the submaximal force level. Nevertheless, the present results suggest that the noticeable effect of bilateral contraction is more prominent on the accuracy than in the ability of rapid force production at the submaximal force level.

The C. elegans Notch proteins LIN-12 and GLP-1 are tuned to lower force thresholds for activation than Drosophila Notch

The conserved transmembrane receptor Notch mediates cell fate decisions in all animals. In the absence of ligand, a Negative Regulatory Region (NRR) in the Notch ectodomain adopts an autoinhibited confirmation, masking an ADAM protease cleavage site [1, 2]; ligand binding makes the cleavage site accessible, leading to shedding of the Notch ectodomain as the first step of signal transduction [3, 4]. In Drosophila and vertebrates, the ligands are all single-pass transmembrane Delta/Serrate/LAG-2 (DSL) proteins; the endocytic adaptor Epsin binds to the ubiquitinated intracellular domain, and the resulting Clathrin-mediated endocytosis exerts a “pulling force” that exposes the cleavage site in the NRR [4–6]. However, in C. elegans, the presence of natural secreted DSL proteins [7] and other observations suggested that Epsin-mediated endocytosis may not be required to activate the Notch proteins LIN-12 and GLP-1. Here, we confirm that neither Epsin nor the cytosolic domains of DSL proteins are required for Notch signaling in C. elegans. Furthermore, we provide evidence that the NRRs of LIN-12 and GLP-1 are tuned to a lower force level than the NRR of Drosophila Notch. Finally, we show that adding a Leucine “plug” that occludes the cleavage site in vertebrate and Drosophila Notch proteins but is absent in the C. elegans Notch proteins [1, 2] renders the LIN-12 and GLP-1 NRRs dependent on Epsin-mediated ligand endocytosis, indicating that greater force is now required to expose the cleavage site. Thus, the NRRs of LIN-12 and GLP-1 appear to be tuned to a lower force threshold, accounting for the different requirements for signaling in C. elegans.

Final inches: Tsar Nicholas II and Cannonry (battery) for Dreadnoughts

В канун Первой мировой войны линейные корабли представляли собой самое тяжелое и технически сложное оружие. Создание его требовало полного напряжения научных и промышленных ресурсов и было по силам лишь немногим странам. В целом успехи в вооружении флота дают своего рода мерило для объективной сравнительной оценки уровня культурного и экономического развития России, ее противников и союзников. В начале ХХ в. делались попытки установить производство морских дальнобойных орудий главного калибра — 14, 16 дюймов — на Обуховском заводе в Петербурге, Пермском (Мотовилихинском) на Урале и на новом Царицынском заводе на Волге. Источники показывают, что, вопреки существующим в литературе представлениям, ни один из этих заводов до конца войны не приспособился к выпуску орудий калибром более 12 дюймов. При этом 12-дюймовые пушки Обуховского завода с их малопрочным металлом не допускали использования новейших наиболее мощных снарядов. Причиной отставания являлась архаическая постановка сталелитейного дела, незнание тонкостей его технологии и слабость оборудования. Не научившись изготовлять подходящие болванки, нельзя было практически испытать также и степень пригодности станков и механизмов, предназначенных для дальнейших операций. Бодрые отчеты ведомств об успешном налаживании нового производства порождают противоречия в историческом освещении проблемы; планы и программы не всегда удается отделить от фактических реалий. On the eve of the First World War the battleship was the most powerful type of warship. During the late 19th and early 20th centuries, battleships were a symbol of naval dominance and national might. Construction of a battleship required top scientific and industry resources. Thus the navy-force level assessment is a perfect objective criterion for comparative evaluation of cultural and economic development of Russia, its allies and enemies. In the beginning of the XX c. attempts were made to install production of long range naval guns — 12-inch, 14-inch and 16-inch — in the Motovilikhinskiye Zavod,based in the city of Perm (Ural), the Obukhov State Plant in St. Petersburg and the Tsarytsin plant on the Volga river. According to the sources (which show information contrary to past beliefs), up to the end of the WWI noneof the plants mentioned above could produce arms larger then 12-inch caliber. Thus,the 12-inch navel guns produced by Obukhov State Plant had weak tubing results in a firearm, and the arms couldn’t use the newest war heads. The reasons for the backlog were the archaic staging of the steelwork, ignorance of the intricacies of technology, and weakness of equipment. Without knowing how to make suitable bars, it was also impossible to experience the degree of suitability of machines and mechanisms designed for further operations. Exiting reports from administration about successful tuning of the production process, lead to contradictions in the historical overview of the problem; it is sometimes difficult to separate the factual reality from plans and programs made.

Trends of Battle Line Formation

This article presents basic concepts regarding the establishment of the battle lines depending on the level of the warfare. Thus, at the operative level within the operations of the task force level division (brigades) will be used principles that determine the choice of the formation, organization and judicious use of the battle lines yet at the tactical level other principles will be used. At the same time, the article points out that the battle line of troops is an important element of the defensive or offensive structure in the course of the military actions, which exerts an influence on the other elements, due to which there is the possibility of gaining victory.