Grasping and releasing agarose micro beads in water drops

The micromanipulation of micro objects is nowadays the focus of several investigations, specially in biomedical applications. Therefore, some manipulation tasks are required to be in aqueous environment and become more challenging because they depend upon observation and actuation methods that are compatible with MEMS Technology based micromanipulators. This paper describes how three grasping-releasing based tasks have been successfully applied to agarose micro beads whose average size is about 60 \u3bcm: (i) the extraction of a single micro bead from a water drop; (ii) the insertion of a single micro bead into the drop; (iii) the grasping of a single micro bead inside the drop. The success of the performed tasks rely on the use of a microgripper previously designed, fabricated, and tested

IGF-1 and IGF-Binding Proteins and Bone Mass, Geometry, and Strength: Relation to Metabolic Control in Adolescent Girls With Type 1 Diabetes

Children and adolescents with poorly controlled type 1 diabetes mellitus (T1DM) are at risk for decreased bone mass. Growth hormone (GH) and its mediator, IGF-1, promote skeletal growth. Recent observations have suggested that children and adolescents with T1DM are at risk for decreased bone mineral acquisition. We examined the relationships between metabolic control, IGF-1 and its binding proteins (IGFBP-1, -3, -5), and bone mass in T1DM in adolescent girls 12–15 yr of age with T1DM (n = 11) and matched controls (n = 10). Subjects were admitted overnight and given a standardized diet. Periodic blood samples were obtained, and bone measurements were performed. Serum GH, IGFBP-1 and -5, glycosylated hemoglobin (HbA1c), glucose, and urine magnesium levels were higher and IGF-1 values were lower in T1DM compared with controls (p < 0.05). Whole body BMC/bone area (BA), femoral neck areal BMD (aBMD) and bone mineral apparent density (BMAD), and tibia cortical BMC were lower in T1DM (p < 0.05). Poor diabetes control predicted lower IGF-1 (r2 = 0.21) and greater IGFBP-1 (r2 = 0.39), IGFBP-5 (r2 = 0.38), and bone-specific alkaline phosphatase (BALP; r2 = 0.41, p < 0.05). Higher urine magnesium excretion predicted an overall shorter, lighter skeleton, and lower tibia cortical bone size, mineral, and density (r2 = 0.44–0.75, p < 0.05). In the T1DM cohort, earlier age at diagnosis was predictive of lower IGF-1, higher urine magnesium excretion, and lighter, thinner cortical bone (r2 ≥ 0.45, p < 0.01). We conclude that poor metabolic control alters the GH/IGF-1 axis, whereas greater urine magnesium excretion may reflect subtle changes in renal function and/or glucosuria leading to altered bone size and density in adolescent girls with T1DM

Establishment and cryptic transmission of Zika virus in Brazil and the Americas

Transmission of Zika virus (ZIKV) in the Americas was first confirmed in May 2015 in northeast Brazil1. Brazil has had the highest number of reported ZIKV cases worldwide (more than 200,000 by 24 December 20162) and the most cases associated with microcephaly and other birth defects (2,366 confirmed by 31 December 20162). Since the initial detection of ZIKV in Brazil, more than 45 countries in the Americas have reported local ZIKV transmission, with 24 of these reporting severe ZIKV-associated disease3. However, the origin and epidemic history of ZIKV in Brazil and the Americas remain poorly understood, despite the value of this information for interpreting observed trends in reported microcephaly. Here we address this issue by generating 54 complete or partial ZIKV genomes, mostly from Brazil, and reporting data generated by a mobile genomics laboratory that travelled across northeast Brazil in 2016. One sequence represents the earliest confirmed ZIKV infection in Brazil. Analyses of viral genomes with ecological and epidemiological data yield an estimate that ZIKV was present in northeast Brazil by February 2014 and is likely to have disseminated from there, nationally and internationally, before the first detection of ZIKV in the Americas. Estimated dates for the international spread of ZIKV from Brazil indicate the duration of pre-detection cryptic transmission in recipient regions. The role of northeast Brazil in the establishment of ZIKV in the Americas is further supported by geographic analysis of ZIKV transmission potential and by estimates of the basic reproduction number of the virus

A pseudo-rigid body model based on finite displacements and strain energy

During the last decades, the modeling of flexures undergoing large deflections has been the subject of many investigations. Various rigid body models have been proposed in an effort to reproduce with high accuracy the path followed by the free-end section of the flexible element. Systems with multiple degrees of freedom have been also presented considering the possible occurrence of an inflection point. However, as the number of DoFs increases, optimization techniques must be implemented to define the characteristic parameters. In this investigation, a one-DoF rigid body model is developed focusing on the pole of the displacements associated to the poses of the free-end section. Two different cases are analyzed, depending on whether the pole is a proper point or an improper point. Strain energy is evaluated to calculate the stiffness coefficients of the rigid body model. Considering end moments and combined loads, two different formulations are elaborated to achieve analytical and numerical solutions, respectively. The proposed model is load dependent and provides an exact solution of the modeling problem, both in the case of rotation and in the case of translation of the free-end section. Occurrence of an inflection point is also considered and various examples are presented

Analysis of the center of rotation in primitive flexures: Uniform cantilever beams with constant curvature

Precision of rotation is a fundamental characteristic of primitive flexures, especially when compliant mechanisms are designed for micro-scale applications. In case of single leaf flexures, distributed compliance allows flexible beams to undergo large deflections. Nevertheless, the center of rotation changes its position during such deflections. In this paper, large deflection analysis is performed on cantilever beams with uniform cross section and constant curvature, subjected to end-moment loads. Analytical expressions to determine the position of the center of rotation of the flexure are derived. The center of rotation refers to the displacement of the free-end section of the beam, occurring when the flexure, due to the external load application, moves from its neutral configuration to the deformed one. Several examples are considered and the analytical solutions are compared to the results obtained by finite element analysis. A final example focuses on the determination of the pseudo-rigid body model

Effect of initial curvature in uniform flexures on position accuracy

Position accuracy is a prerequisite for compliant mechanisms, especially in micro-scale applications. Generally, this feature depends on the flexures ability to imitate the revolute joints of the pseudo-rigid body model. In case of flexible elements, the center of the relative rotation varies its position during the deflections, affecting the position accuracy. In this paper, the role played by the initial curvature is investigated, in case of uniform primitive flexures. Analytical expressions are derived to evaluate the shift of the rotation axis with respect to the flexure centroid. An example shows the performance of four flexures with different curvatures, evaluated by comparing the rotation axis shift and the position error

Comparative Analysis of Isotropy Indices in RR and RRP Arms

In this paper isotropy and manipulability in RR dyads and RRP arms are analyzed and the solutions are obtained in algebraic symbolic forms. Such analysis is performed by means of two different methods: the classical approach based on the condition number and the Lie product. Although both the methods are known since decades, an accurate comparison of the two approaches has never been presented in literature. In particular, the geometrical interpretation of the Lie Product allows to appreciate some interesting differences between the two methods