Microporous polymer particles via phase inversion in microfluidics: impact of non-solvent quality

We investigate the impact of ternary phase behavior on the microstructure of porous polymer particles produced by solvent extraction of polymer solution droplets by a nonsolvent. Microfluidic devices fabricated by frontal photopolymerization are employed to produce monodisperse polymer (P)/solvent (S) droplets suspended in a carrier (C) phase before inducing solvent extraction by precipitation in a nonsolvent (NS) bath. Model systems of sodium poly(styrenesulfonate) (P), water (S), hexadecane (C), and either methyl ethyl ketone (MEK) or ethyl acetate (EA) as NS are selected. Extraction across the liquid–liquid interface results in a decrease in the droplet radius and also an ingress of nonsolvent, leading to droplet phase demixing and coarsening. As the concentration of the polymer-rich phase increases, droplet shrinkage and solvent exchange slow down and eventually cease, resulting in microporous polymer particles (of radius ≃50–200 μm) with a smooth surface. The internal structure of these capsules, with pore sizes of ≃1–100 μm, is found to be controlled by polymer solution thermodynamics and the extraction pathway. The ternary phase diagrams are measured by turbidimetry, and the kinetics of phase separation is estimated by stopped-flow small-angle neutron scattering. The higher solubility of water in MEK results in faster particle-formation kinetics than in EA. Surprisingly, however, the lower polymer miscibility with EA/water results in a deeper quench inside the phase boundary and small phase sizes, thus yielding particles with small pores (of narrow distribution). The effects of droplet size, polymer content, and nonsolvent quality provide comprehensive insight into porous particle and capsule formation by phase inversion, with a range of practical applications

Closed-Loop Control of Local Magnetic Actuation for Robotic Surgical Instruments

We propose local magnetic actuation (LMA) as an approach to robotic actuation for surgical instruments. An LMA actuation unit consists of a pair of diametrically magnetized single-dipole cylindrical magnets, working as magnetic gears across the abdominal wall. In this study, we developed a dynamic model for an LMA actuation unit by extending the theory proposed for coaxial magnetic gears. The dynamic model was used for closed-loop control, and two alternative strategies-using either the angular velocity at the motor or at the load as feedback parameter-were compared. The amount of mechanical power that can be transferred across the abdominal wall at different intermagnetic distances was also investigated. The proposed dynamic model presented a relative error below 7.5% in estimating the load torque from the system parameters. Both the strategies proposed for closed-loop control were effective in regulating the load speed with a relative error below 2% of the desired steady-state value. However, the load-side closed-loop control approach was more precise and allowed the system to transmit larger values of torque, showing, at the same time, less dependence from the angular velocity. In particular, an average value of 1.5 mN·m can be transferred at 7 cm, increasing up to 13.5 mN·m as the separation distance is reduced down to 2 cm. Given the constraints in diameter and volume for a surgical instrument, the proposed approach allows for transferring a larger amount of mechanical power than what would be possible to achieve by embedding commercial dc motors

Laparoscopic Camera Based on an Orthogonal Magnet Arrangement

In this letter, we present for the first time a magnetic anchoring-actuation link with an auto-flip feature. This orthogonal magnetic arrangement relies on the placement of two permanent magnets such that their magnetic moments are respectfully orthogonal. Though the arrangement may have many applications, in this study we integrate it in a small factor magnetic camera for minimally invasive procedures. Upon insertion through a trocar incision, the 5.5 mm diameter and 35 mm length magnetic camera is coupled with an external robotic controller and displaced from the port thus preventing clutter of the surgical workspace. The device allows for manual lateral translation as well as robotically controlled tilt and pan, resulting in four degrees of freedom. The auto-flip feature prevents the need for image adjustment in software as the camera tilts through its hemispherical workspace. A static model that relates an input external control tilt and output camera tilt has been developed and validated. Favorable results during bench and canine cadaver evaluation suggest promise for the proposed magnetic camera to improve the state of art in minimally invasive surgical procedures

Magnetic Surgical Instruments for Robotic Abdominal Surgery.

This review looks at the implementation of magnetic-based approaches in surgical instruments for abdominal surgeries. As abdominal surgical techniques advance toward minimizing surgical trauma, surgical instruments are enhanced to support such an objective through the exploration of magnetic-based systems. With this design approach, surgical devices are given the capabilities to be fully inserted intraabdominally to achieve access to all abdominal quadrants, without the conventional rigid link connection with the external unit. The variety of intraabdominal surgical devices are anchored, guided, and actuated by external units, with power and torque transmitted across the abdominal wall through magnetic linkage. This addresses many constraints encountered by conventional laparoscopic tools, such as loss of triangulation, fulcrum effect, and loss/lack of dexterity for surgical tasks. Design requirements of clinical considerations to aid the successful development of magnetic surgical instruments, are also discussed

Determinação da composição nutricional e sais minerais de frutos de juçara (Euterpe Edulis) coletados na região de Curitiba, PR.

bitstream/item/145214/1/CT-374-Cristiane-Helm.pd

O comportamento do aluno em um curso a distância dentro do ambiente Moodle: contrapontos entre a ótica inicial e seu uso atual.

O objetivo deste trabalho é analisar as dificuldades apresentadas pelos alunos de cursos em EaD. Para tanto, utilizou-se dados extraídos de um questionário de inscrição para um curso on-line, em que era solicitado aos alunos que listassem seus maiores problemas com os cursos que já haviam feito. Puderam ser identificadas seis categorias de problemas com: AVA, tutor, técnicos, de organização, de colaboração e de conteúdo

EZETIMIBE PROTECTS THP-1 CELLS FROM ISCHEMIA-REPERFUSION INJURY REDUCING OXIDATIVE STRESS AND UP-REGULATING NRF2/ ARE GENE EXPRESSION

Background and Aims: We demonstrated that physical training, characterized by repeated ischemia-reperfusion (I-R) episodes (ischemic conditioning, IC), protects circulating cells from peripheral artery disease (PAD) patients against ischemic harms by reducing oxidative stress (OS) and by up-regulating nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway expression. Ezetimibe (Eze) has been shown to alleviate OS enhancing Nrf2 nuclear translocation in an AMPK/p62-dependent manner. In a cellular I-R and IC model, we aimed to investigate: 1) the effect of Eze on OS and Nrf2/ARE gene expression 2) whether Eze could have a synergistic effect on IC. Methods: THP-1 cells were treated with or without Eze (50mM) overnight, then subjected to 1 or 6 repetitive I-R cycles using EVOS FL Auto Imaging System. Reactive oxygen species (ROS) formation was evaluated with DCF in cytofluorimetry. Nrf2/ARE and p62 gene expression were evaluated by RT-PCR and western blotting. Results: When THP-1 cells were exposed to 1 I-R cycle, the preincubation with Eze significantly reduced ROS formation (p<0.01) and up-regulated Nrf2/ARE pathway expression and p62 phosphorylation (p<0.001). Multiple I-R cycles, acting as IC, significantly reduced ROS formation and upregulated Nrf2/ARE gene expression (p<0.001); in these conditions, Eze preincubation was able not only to almost abolish ROS formation (p<0.01) but also further up-regulate Nrf2/ARE expression. Conclusions: In our I-R model, Eze not only restores I-R-induced oxidative damages through Nrf2/ARE signaling up-regulation but also has a synergistic effect on IC. This new \u201cpleiotropic\u201d effect, if confirmed in vivo, may strengthen the use of Eze in PAD patien