Induced tooth movement: standardization of terms to describe the effects of forces on the periodontal ligament: compression/Traction instead of Pressure/Tension

There is no reason for Dentistry to use different terms for phenomena defined in Physics, the specific field in which concepts associated with forces are established and adapted. In place of pressure/tension, the compression/traction pair should be used. This study defines each one of these terms and justifies their use. Our contemporary world demands standardized criteria, methods, measures, concepts and terms to ensure that study protocols, results and applications are used in the same way in any country or area of human action.

A semi-supervised classification technique based on interacting forces

Semi-supervised learning is a classification paradigm in which just a few labeled instances are available for the training process. To overcome this small amount of initial label information, the information provided by the unlabeled instances is also considered. In this paper, we propose a nature-inspired semi-supervised learning technique based on attraction forces. Instances are represented as points in a k-dimensional space, and the movement of data points is modeled as a dynamical system. As the system runs, data items with the same label cooperate with each other, and data items with different labels compete among them to attract unlabeled points by applying a specific force function. In this way, all unlabeled data items can be classified when the system reaches its stable state. Stability analysis for the proposed dynamical system is performed and some heuristics are proposed for parameter setting. Simulation results show that the proposed technique achieves good classification results on artificial data sets and is comparable to well-known semi-supervised techniques using benchmark data sets.

Evaluation of vertical forces in the pads of Pitbulls with cranial cruciate ligament rupture

Background: Cranial cruciate ligament rupture (CCLR) is one of the most important stifle injuries and a common cause of lameness in dogs. Our objective was to measure the vertical forces in the pads of Pitbulls with cranial cruciate ligament rupture (CCLR) using a pressure sensitive walkway. A pressure sensitive walkway was used to collect vertical force data from the pads of 10 Pitbulls affected with unilateral CCLR. Ten healthy Pitbulls were included in the study as controls. Velocity varied between 1.3 and 1.6 m/s and acceleration was kept below ± 0.1 m/s2. Differences between groups and between pads in the same limb within groups were investigated using ANOVA and the Tukey test. The paired Student t-test was employed to assess gait symmetry (p < 0.05). Results: Peak vertical forces (PVF) were lower in the affected limb, particularly in the metatarsal pad. Increased PVF values in the forelimb and the contralateral hind limb pads of affected dogs suggest a compensatory effect. Conclusions: A consistent pattern of vertical force distribution was observed in the pads of dogs with CCLR. These data are important for increased understanding of vertical force distribution in the limb of dogs with CCLR disease. Kinetic analysis using pressure sensitive walkways can be useful in follow-up assessment of surgically treated dogs regardless of the surgical technique employed.

Kinematic internal forces in deep foundations with inclined piles

[EN] This paper presents a parametric study that looks into the influence of pile rake angle on the kinematic internal forces of deep foundations with inclined piles. Envelopes of maximum kinematic bending moments, shear forces and axial loads are presented along single inclined piles and 2X2 symmetrial square pile groups with inclined elements subjected to an earthquake generated by vertically-incident shear waves.

The assessment of change in rural landscape and the analysis of the driving forces. Proposal of a spatial model for the rural built environment

The presented study carried out an analysis on rural landscape changes. In particular the study focuses on the understanding of driving forces acting on the rural built environment using a statistical spatial model implemented through GIS techniques. It is well known that the study of landscape changes is essential for a conscious decision making in land planning. From a bibliography review results a general lack of studies dealing with the modeling of rural built environment and hence a theoretical modelling approach for such purpose is needed. The advancement in technology and modernity in building construction and agriculture have gradually changed the rural built environment. In addition, the phenomenon of urbanization of a determined the construction of new volumes that occurred beside abandoned or derelict rural buildings. Consequently there are two types of transformation dynamics affecting mainly the rural built environment that can be observed: the conversion of rural buildings and the increasing of building numbers. It is the specific aim of the presented study to propose a methodology for the development of a spatial model that allows the identification of driving forces that acted on the behaviours of the building allocation. In fact one of the most concerning dynamic nowadays is related to an irrational expansion of buildings sprawl across landscape. The proposed methodology is composed by some conceptual steps that cover different aspects related to the development of a spatial model: the selection of a response variable that better describe the phenomenon under study, the identification of possible driving forces, the sampling methodology concerning the collection of data, the most suitable algorithm to be adopted in relation to statistical theory and method used, the calibration process and evaluation of the model. A different combination of factors in various parts of the territory generated favourable or less favourable conditions for the building allocation and the existence of buildings represents the evidence of such optimum. Conversely the absence of buildings expresses a combination of agents which is not suitable for building allocation. Presence or absence of buildings can be adopted as indicators of such driving conditions, since they represent the expression of the action of driving forces in the land suitability sorting process. The existence of correlation between site selection and hypothetical driving forces, evaluated by means of modeling techniques, provides an evidence of which driving forces are involved in the allocation dynamic and an insight on their level of influence into the process. GIS software by means of spatial analysis tools allows to associate the concept of presence and absence with point futures generating a point process. Presence or absence of buildings at some site locations represent the expression of these driving factors interaction. In case of presences, points represent locations of real existing buildings, conversely absences represent locations were buildings are not existent and so they are generated by a stochastic mechanism. Possible driving forces are selected and the existence of a causal relationship with building allocations is assessed through a spatial model. The adoption of empirical statistical models provides a mechanism for the explanatory variable analysis and for the identification of key driving variables behind the site selection process for new building allocation. The model developed by following the methodology is applied to a case study to test the validity of the methodology. In particular the study area for the testing of the methodology is represented by the New District of Imola characterized by a prevailing agricultural production vocation and were transformation dynamic intensively occurred. The development of the model involved the identification of predictive variables (related to geomorphologic, socio-economic, structural and infrastructural systems of landscape) capable of representing the driving forces responsible for landscape changes.. The calibration of the model is carried out referring to spatial data regarding the periurban and rural area of the study area within the 1975-2005 time period by means of Generalised linear model. The resulting output from the model fit is continuous grid surface where cells assume values ranged from 0 to 1 of probability of building occurrences along the rural and periurban area of the study area. Hence the response variable assesses the changes in the rural built environment occurred in such time interval and is correlated to the selected explanatory variables by means of a generalized linear model using logistic regression. Comparing the probability map obtained from the model to the actual rural building distribution in 2005, the interpretation capability of the model can be evaluated. The proposed model can be also applied to the interpretation of trends which occurred in other study areas, and also referring to different time intervals, depending on the availability of data. The use of suitable data in terms of time, information, and spatial resolution and the costs related to data acquisition, pre-processing, and survey are among the most critical aspects of model implementation. Future in-depth studies can focus on using the proposed model to predict short/medium-range future scenarios for the rural built environment distribution in the study area. In order to predict future scenarios it is necessary to assume that the driving forces do not change and that their levels of influence within the model are not far from those assessed for the time interval used for the calibration.

Thermal Casimir effect at fluid interfaces: Fluctuation-induced forces between anisotropic colloids

We study the effective interaction between two ellipsoidal particles at the interface of two fluid phases which are mediated by thermal fluctuations of the interface. Within a coarse-grained picture, the properties of fluid interfaces are very well described by an effective capillary wave Hamiltonian which governs both the equilibrium interface configuration and the thermal fluctuations (capillary waves) around this equilibrium (or mean-field) position. As postulated by the Goldstone theorem the capillary waves are long-range correlated. The interface breaks the continuous translational symmetry of the system, and in the limit of vanishing external fields - like gravity - it has to be accompanied by easily excitable long wavelength (Goldstone) modes – precisely the capillary waves. In this system the restriction of the long-ranged interface fluctuations by particles gives rise to fluctuation-induced forces which are equivalent to interactions of Casimir type and which are anisotropic in the interface plane. Since the position and the orientation of the colloids with respect to the interface normal may also fluctuate, this system is an example for the Casimir effect with fluctuating boundary conditions. In the approach taken here, the Casimir interaction is rewritten as the interaction between fluctuating multipole moments of an auxiliary charge density-like field defined on the area enclosed by the contact lines. These fluctuations are coupled to fluctuations of multipole moments of the contact line position (due to the possible position and orientational fluctuations of the colloids). We obtain explicit expressions for the behavior of the Casimir interaction at large distances for arbitrary ellipsoid aspect ratios. If colloid fluctuations are suppressed, the Casimir interaction at large distances is isotropic, attractive and long ranged (double-logarithmic in the distance). If, however, colloid fluctuations are included, the Casimir interaction at large distances changes to a power law in the inverse distance and becomes anisotropic. The leading power is 4 if only vertical fluctuations of the colloid center are allowed, and it becomes 8 if also orientational fluctuations are included.

Rupture forces of split aptamers

Rupture forces of ligand-receptor interactions, such as proteins-proteins, proteins-cells, and cells-tissues, have been successfully measured by atomic force spectroscopy (AFS). For these measurements, the ligands and receptors were chemically modified so that they can be immobilized on the tip and on a substrate, respectively. The ligand interact the receptor when the tip approaches the substrate. This interaction can be studied by measuring rupture force upon retraction. However, this technique is not feasible for measurements involving small molecules, since they form only few H-bonds with their corresponding receptors. Modifying small molecules for immobilization on surfaces may block or change binding sites. Thus, recorded rupture forces might not reflect the full scope of the involved small ligand-receptor interactions.rnIn my thesis, a novel concept that allows measuring the rupture force of small involved ligand-receptor interactions and does not require molecular modification for immobilization was introduced. The rupture force of small ligand-receptor interaction is not directly measured but it can be determined from measurements in the presence and in the absence of the ligand. As a model system, the adenosine mono phosphate (AMP) and the aptamer that binds AMP were selected. The aptamer (receptor) is a single stranded DNA that can partially self-hybridize and form binding pockets for AMP molecules (ligands). The bonds between AMP and aptamer are provided by several H-bonds and pair stacking.rnIn the novel concept, the aptamer was split into two parts (oligo a and oligo b). One part was immobilized on the tip and the other one on the substrate. Approaching the tip to the substrate, oligo a and oligo b partially hybridized and the binding pockets were formed. After adding AMP into the buffer solution, the AMP bound in the pockets and additional H-bonds were formed. Upon retraction of the tip, the rupture force of the AMP-split aptamer complex was measured. In the presence of excess AMP, the rupture force increased by about 10 pN. rnThe dissociation constant of the AMP-split aptamer complex was measured on a single molecular level (~ 4 µM) by varying the AMP concentrations and measuring the rupture force at each concentration. Furthermore, the rupture force was amplified when more pockets were added to the split aptamer. rnIn the absence of AMP, the thermal off-rate was slightly reduced compared to that in the presence of AMP, indicating that the AMP stabilized the aptamer. The rupture forces at different loading rates did not follow the logarithmic fit which was usually used to describe the dependence of rupture forces at different loading rates of oligonucleotides. Two distinguished regimes at low and high loading rates were obtained. The two regimes were explained by a model in which the oligos located at the pockets were stretched at high loading rates. rnThe contribution of a single H-bond formed between the AMP molecule and the split aptamer was measured by reducing the binding groups of the AMP. The rupture forces reduce corresponding to the reduction of the binding groups. The phosphate group played the most important role in the formation of H-bond network between the AMP molecule and the split aptamer. rn

The effect of elastic modulus and equilibrium vapor adsorption on capillary forces

Die Kapillarkraft entsteht durch die Bildung eines Meniskus zwischen zwei Festkörpen. In dieser Doktorarbeit wurden die Auswirkungen von elastischer Verformung und Flϋssigkeitadsorption auf die Kapillarkraft sowohl theoretisch als auch experimentell untersucht. Unter Verwendung eines Rasterkraftmikroskops wurde die Kapillarkraft zwischen eines Siliziumoxid Kolloids von 2 µm Radius und eine weiche Oberfläche wie n.a. Polydimethylsiloxan oder Polyisopren, unter normalen Umgebungsbedingungen sowie in variierende Ethanoldampfdrϋcken gemessen. Diese Ergebnisse wurden mit den Kapillarkräften verglichen, die auf einem harten Substrat (Silizium-Wafer) unter denselben Bedingungen gemessen wurden. Wir beobachteten eine monotone Abnahme der Kapillarkraft mit zunehmendem Ethanoldampfdruck (P) fϋr P/Psat > 0,2, wobei Psat der Sättigungsdampfdruck ist.rnUm die experimentellen Ergebnisse zu erklären, wurde ein zuvor entwickeltes analytisches Modell (Soft Matter 2010, 6, 3930) erweitert, um die Ethanoladsorption zu berϋcksichtigen. Dieses neue analytische Modell zeigte zwei verschiedene Abhängigkeiten der Kapillarkraft von P/Psat auf harten und weichen Oberflächen. Fϋr die harte Oberfläche des Siliziumwafers wird die Abhängigkeit der Kapillarkraft vom Dampfdruck vom Verhältnis der Dicke der adsorbierten Ethanolschicht zum Meniskusradius bestimmt. Auf weichen Polymeroberflächen hingegen hängt die Kapillarkraft von der Oberflächenverformung und des Laplace-Drucks innerhalb des Meniskus ab. Eine Abnahme der Kapillarkraft mit zunehmendem Ethanoldampfdruck hat demnach eine Abnahme des Laplace-Drucks mit zunehmendem Meniskusradius zur folge. rnDie analytischen Berechnungen, fϋr die eine Hertzsche Kontakt-deformation angenommen wurde, wurden mit Finit Element Methode Simulationen verglichen, welche die reale Deformation des elastischen Substrats in der Nähe des Meniskuses explizit berϋcksichtigen. Diese zusätzliche nach oben gerichtete oberflächenverformung im Bereich des Meniskus fϋhrt zu einer weiteren Erhöhung der Kapillarkraft, insbesondere fϋr weiche Oberflächen mit Elastizitätsmodulen < 100 MPa.rn

Development of a system measuring adhesion forces in powder collectives

Fine powders commonly have poor flowability and dispersibility due to interparticle adhesion that leads to formation of agglomerates. Knowing about adhesion in particle collectives is indispensable to gain a deeper fundamental understanding of particle behavior in powders. Especially in pharmaceutical industry a control of adhesion forces in powders is mandatory to improve the performance of inhalation products. Typically the size of inhalable particles is in the range of 1 - 5 µm. In this thesis, a new method was developed to measure adhesion forces of particles as an alternative to the established colloidal probe and centrifuge technique, which are both experimentally demanding, time consuming and of limited practical applicability. The new method is based on detachment of individual particles from a surface due to their inertia. The required acceleration in the order of 500 000 g is provided by a Hopkinson bar shock excitation system and measured via laser vibrometry. Particle detachment events are detected on-line by optical video microscopy. Subsequent automated data evaluation allows obtaining a statistical distribution of particle adhesion forces. To validate the new method, adhesion forces for ensembles of single polystyrene and silica microspheres on a polystyrene coated steel surface were measured under ambient conditions. It was possible to investigate more than 150 individual particles in one experiment and obtain adhesion values of particles in a diameter range of 3 - 13 µm. This enables a statistical evaluation while measuring effort and time are considerably lower compared to the established techniques. Measured adhesion forces of smaller particles agreed well with values from colloidal probe measurements and theoretical predictions. However, for the larger particles a stronger increase of adhesion with diameter was observed. This discrepancy might be induced by surface roughness and heterogeneity that influence small and large particles differently. By measuring adhesion forces of corrugated dextran particles with sizes down to 2 µm it was demonstrated that the Hopkinson bar method can be used to characterize more complex sample systems as well. Thus, the new device will be applicable to study a broad variety of different particle-surface combinations on a routine basis, including strongly cohesive powders like pharmaceutical drugs for inhalation.

Polizeigeschosse und ihre Deformation

In den Jahren 2001 bis 2007 ist bei den Polizeien der deutschen Bundesländer und bei den Polizeikorps der Schweiz die so genannte Polizeimunition eingeführt worden. Von dieser mit einem deformierenden Geschoss ausgerüsteten Munition verspricht man sich eine größere Wirksamkeit und wegen der begrenzten Durchschlagsleistung eine geringere Gefährdung unbeteiligter Personen. Bei geringerer Auftreffenergie deformiert sich jedoch das Geschoss weniger, die Wirksamkeit wird kleiner und die Eindringtiefe größer. In der hier vorgestellten Arbeit wurde die Abhängigkeit der Deformation und der Eindringtiefe in ballistische Seife von der Auftreffenergie für alle 4 gegenwärtig vorhandenen Polizeigeschosse untersucht. Bereits bei Schussdistanzen von 25–30 m ist mit einer verminderten Wirksamkeit zu rechnen. Bei einer viel gebrauchten Waffe kann zudem die Mündungsenergie so stark reduziert sein, dass sich bereits bei kurzen Schussdistanzen die Geschosse nicht mehr erwartungsgemäß deformieren.

In-vitro assessment of the forces generated by lingual fixed retainers

The aim of this article was to assess the effect of wire adaptation on the lingual surfaces of mandibular anterior teeth with 3 types of lingual retainers on the development of vertical and labiolingual forces.