Prenatal diagnosis of micrognathia: a systematic review

PurposeThis systematic review aimed to analyze the characteristics of different diagnostic techniques for micrognathia, summarize the consistent diagnostic criteria of each technique, and provide a simple and convenient prenatal diagnosis strategy for micrognathia.MethodsIn accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, the search was undertaken in three international databases (PubMed, Scopus, and Web of Science). The three reviewers assessed all papers and extracted the following variables: author's name and year of publication, country, study design, number of participants, gestational age, equipment for prenatal examination, biometric parameters related to micrognathia, main results.ResultsA total of 25 articles included in the analysis. Nineteen articles described cross-sectional studies (76 percent), 4 (16 percent) were case-control studies, and 2 (8 percent) were cohort studies. Fifteen studies (60 percent) had a prospective design, 9 (36 percent) had a retrospective design, and one (4 percent) had both prospective and retrospective design. Thirty-two percent of the studies (n = 8) were performed in USA, and the remaining studies were performed in China (n = 4), Israel (n = 3), Netherlands (n = 3), UK (n = 1), France (n = 1), Italy (n = 1), Belgium(n = 1), Germany (n = 1), Spain (n = 1), and Austria (n = 1). The prenatal diagnosis of micrognathia can be performed as early as possible in the first trimester, while the second and third trimester of pregnancy were the main prenatal diagnosis period. The articles that were included in the qualitative synthesis describe 30 biometric parameters related to the mandible.ConclusionOf the 30 biometric parameters related to the mandible, 15 can obtain the simple and convenient diagnostic criteria or warning value for micrognathia. Based on these diagnostic criteria or warning value, clinicians can quickly make a preliminary judgment on facial deformities, to carry out cytologic examination to further clarify the diagnosis of micrognathia

Modeling and control of active end effector for the AFM based nano robotic manipulators

Nanomanipulation using Atomic Force Microscope (AFM) has been extensively investigated for many years. However, control of tip position during nanomanipulation is still a major issue because of the deformation of the cantilever caused by manipulation force. The softness of the conventional cantilevers also cause the failure of the manipulation of relatively large and sticky nano-object because the tip can easily slip over the nano-object. In this paper, an active atomic force microscopy probe is used to solve these problems by changing the cantilever's flexibility or rigidity through different control strategies in imaging and manipulation modes respectively. During imaging mode, the active probe is controlled to bend up with respect to the interaction force between the tip and samples, thus making the tip response faster and increase the imaging speed. During manipulation mode, the active probe is controlled to bend down with respect to the interaction force between tip and the samples; thus increasing its nominal rigidity to avoid tip slipping over object. A detailed model of the active probe is presented in this paper and the controller designed based on the proposed active probe model is also implemented on the augmented reality system, which is an AFM based nanomanipulation system with both real-time visual and haptic feedback. The simulation results for the control strategies and the preliminary experimental results for the AFM based nanmomanipulation verified the validity of the model and effectiveness of the controller. © 2005 IEEE.Link_to_subscribed_fulltex

Energy efficient control of variable speed pumps in complex building central air-conditioning systems

This paper presents the optimal control strategies for variable speed pumps with different configurations in complex building air-conditioning systems to enhance their energy efficiencies. Through a detailed analysis of the system characteristics, the pressure drop models for different water networks in complex air-conditioning systems are developed and then used to formulate an optimal pump sequence control strategy. This sequence control strategy determines the optimal number of pumps in operation taking into account their power consumptions and maintenance costs. The variable speed pumps in complex air-conditioning systems can be classified into two groups: the pumps distributing water to terminal units and pumps distributing water to heat exchanges. The speeds of pumps distributing water to terminal units are controlled by resetting the pressure differential set-point using the online opening signals of water control valves. The speeds of pumps distributing water to heat exchanges are controlled using a water flow controller. The performances of these strategies are tested and evaluated in a simulated virtual environment representing the complex air-conditioning system in a super high-rise building by comparing with that of other reference strategies. The results showed that about 12–32% of pump energy could be saved by using these optimal control strategies

Optimal periodic-output-feedback control of active AFM probe for nanomanipulation

© 2007 EUCA. AFM based nanomanipulation has been widely studied during recent years. But the efficiency and accuracy are still hot issues. The main problems include nonlinearities and uncertainties such as drift, creep, hysteresis, the deformation of the cantilever caused by manipulation force, etc. These cause difficulties in precisely controlling the tip position, which will cause the tip to miss the object. In this paper an active AFM probe is used to eliminate the uncertainties caused by the deformation of cantilever. The active probe is modeled based on the Euler-Bernoulli theory. An active probe controller of optimal periodic-output-feedback control has been implemented to decrease the position error caused by deformation of cantilever. With the active probe controller the cantilever maintains a straight shape during manipulation by adjusting its flexibility or rigidity. The simulation and nanomanipulation experiments verified the system model and the controller demonstrated that the AFM tip can be controlled precisely.Link_to_subscribed_fulltex

Optimal control of flexible end effector in AFM based nanomanipulation

Atomic Force Microscope (AFM) based nanomanipulation has been extensively investigated for many years. However, the efficiency and accuracy of the AFM based nanomanipulation is still a major issue due to the nonlinearities and uncertainties in nanomanipulation operations. The deformation of the cantilever caused by manipulation force, in our experience, is one of the most major nonlinearities and uncertainties. It causes difficulties in precisely controlling the tip position, which will cause the tip to miss the position of the object. In order to solve this problem, the traditional approach is to use a rigid cantilever. However, this will significantly reduce the sensitivity of the force feeling during the manipulation, which is essential for achieving an efficient and reliable nanomanipulation. An active AFM probe is used to solve this problem by directly controlling the cantilever's flexibility or rigidity during manipulation. An infinite dimensional model of the active probe is developed. Control of the active probe employing an optimal LQR control law is also implemented. The experimental results have verified the theoretical model and demonstrated that the precise position control and high sensitive interaction force measurement can be achieved simultaneously. © 2005 IEEE.Link_to_subscribed_fulltex

Sensing in the nano-environment based on high order harmonic modes of flexible arm

An Atomic Force Microscope (AFM) explores the topography of a sample surface using a micro-sized flexible cantilever, which works as a flexible robot arm. The flexible cantilever is controlled to keep vibrating when an AFM works in the tapping mode. The cantilever is modeled as a flexible beam instead of a point mass system in this paper. The nonlinear interaction force between the tip and sample surface is also modeled. A simulation environment is developed to simulate the dynamics of cantilevers using the flexible beam model. Simulation results confirm that the flexible beam model can represent the system more accurately than the point-mass model. It has been shown that lower modes are more sensitive to changes of surface topography or surface materials when the cantilever is driven to vibrate at a higher harmonic mode. At the same time, this simulation environment also provides a more accurate way to validate the design of a new AFM probe and AFM controller than simulation packages which use the point-mass model.Link_to_subscribed_fulltex