Fire-Shaped Nozzles to Produce a Stress Peak for Deformability Studies.

Fire-shaped nozzles can be used to study the deformability of microcapsules, particles, or cells traveling in a flow. Though their geometry depends on the dimensions of the original glass capillary and the heating conditions, they all produce a strain rate peak approximately at the section where the diameter is 1.5 times the minimum. The intensity of this peak and the time from its position to the neck can be easily estimated from the flow rate and three geometrical parameters, without the need for any simulation. In the convergent region of these nozzles, it is possible to observe the evolution of the deformation. It is necessary to use a sufficiently long nozzle to produce the maximum deformation before the neck.

Blood Particulate Analogue Fluids: A Review.

Microfluidics has proven to be an extraordinary working platform to mimic and study blood flow phenomena and the dynamics of components of the human microcirculatory system. However, the use of real blood increases the complexity to perform these kinds of in vitro blood experiments due to diverse problems such as coagulation, sample storage, and handling problems. For this reason, interest in the development of fluids with rheological properties similar to those of real blood has grown over the last years. The inclusion of microparticles in blood analogue fluids is essential to reproduce multiphase effects taking place in a microcirculatory system, such as the cell-free layer (CFL) and Fähraeus-Lindqvist effect. In this review, we summarize the progress made in the last twenty years. Size, shape, mechanical properties, and even biological functionalities of microparticles produced/used to mimic red blood cells (RBCs) are critically exposed and analyzed. The methods developed to fabricate these RBC templates are also shown. The dynamic flow/rheology of blood particulate analogue fluids proposed in the literature (with different particle concentrations, in most of the cases, relatively low) is shown and discussed in-depth. Although there have been many advances, the development of a reliable blood particulate analogue fluid, with around 45% by volume of microparticles, continues to be a big challenge.

Electrical Conductivity of a Stretching Viscoelastic Filament.

Long polymeric chains highly stretched and aligned with the flow confer a strong mechanical anisotropy on a viscoelastic solution. The electrically-driven transport of free ions under such conditions is far from being understood. In this paper, we determine experimentally whether the above-mentioned deviation from isotropy affects the electric charge transport across the liquid. To this end, we measure the electrical conductivity in the flow (stretching) direction of the cylindrical liquid filament formed in the elasto-capillary thinning that arises during the breakup of a viscoelastic liquid bridge. First, we examine the behavior of monodisperse solutions of polyethylene oxide (PEO) in a mixture of glycerine and water. For all the concentrations and molecular weights considered, the filament conductivity remains practically the same as the isotropic conductivity measured under hydrostatic conditions. However, we observe a decrease in the electric current at the end of elasto-capillary regime which may partially be attributed to the reduction of the liquid conductivity. Then, we measure the conductivity of bidisperse solutions of PEO with very different molecular weights. In this case, a significant decrease in conductivity is observed as the filament radius decreases. This constitutes the first experimental evidence of ion mobility reduction in stretching viscoelastic filaments, a relevant effect in applications such as electrospinning.

Factores predictores de mortalidad hospitalaria en pacientes con infarto agudo del miocardio / Predictor factors of hospital mortality in patients with acute myocardial infarction / Fatores preditivos de mortalidade hospitalar em pacientes com infarto agudo do miocárdio

RESUMEN Introducción: Las enfermedades cardiovasculares representan la principal causa de muerte de la población mundial. Objetivo: Identificar los factores predictores de mortalidad hospitalaria en pacientes con infarto agudo del miocardio en el Hospital General Docente "Dr. Agostinho Neto", durante el año 2017. Método: Se realizó un estudio retrospectivo analítico de tipo caso y control, en una población conformada por 90 pacientes con infarto. En el grupo caso se encontraron todos los pacientes fallecidos durante el ingreso (n=30) que cumplieron los criterios de inclusión y exclusión, mientras que el grupo control estuvo constituido por 60 pacientes que egresaron vivos, seleccionados al azar mediante un muestreo aleatorio simple. Resultados: La media de la edad fue mayor en el grupo de los casos 74,06 respecto a los controles, (p=0,021). El 86,6 % de los casos no recibió trombolisis y el 6,6 % tuvo algún criterio de reperfusión pos-estreptoquinasa (p=0,00). El 36,6 % de los casos presentó choque cardiogénico (p=0,003), ruptura cardíaca (30 %) (p=0,03), y taponamiento (23,3 %) (p=0,01). Conclusiones: Los factores predictores de mortalidad hospitalaria en pacientes con infarto agudo del miocardio son: la edad avanzada, el tiempo prolongado entre el inicio de los síntomas y la asistencia médica, la existencia de las complicaciones, tales como el choque cardiogénico, el taponamiento cardíaco y la ruptura cardíaca, así como la no administración de tratamiento trombolítico y la ausencia de reperfusión.

ABSTRACT Introduction: Cardiovascular disease is the main cause of death worldwide. Objective: To identify the predictor factors of hospital mortality in patients with acute myocardial infarction at the Hospital General Docente "Dr. Agostinho Neto" in 2017. Method: A retrospective analytical case-control study was performed in a population of 90 patients with myocardial infarction. The case-cohort study included all patients who died during admission (n=30) and met the inclusion and exclusion criteria, while the case-control study included 60 patients who were discharged alive, randomly selected by simple random sampling. Results: The mean age was higher in the case-cohort studied (74.06 years) than the case-control (p=0.021). The 86,6% of cases did not receive thrombolysis and 6.6% had some reperfusion criteria after the streptokinase (p=0.00). Cardiogenic shock (p=0.003), cardiac rupture (30%) (p=0.03), and cardiac tamponade (23.3%) (p=0.01) were present in 36.6% of cases. Conclusions: The predictor factors of hospital mortality in patients with acute myocardial infarction are as follows: age, the prolonged time between the onset of symptoms and medical attention, presence of complications such as cardiogenic shock, cardiac tamponade and cardiac rupture, as well as the non-administration of thrombolytic treatment and the absence of reperfusion.

RESUMO Introdução: As doenças cardiovasculares representam a principal causa de morte da população mundial. Objetivo: Identificar os fatores preditivos de mortalidade hospitalar em pacientes com infarto agudo do miocárdio no Hospital Geral Universitário "Dr. Agostinho Neto", durante 2017. Método: Foi realizado um estudo retrospectivo analítico caso-controle em uma população de 90 pacientes com infarto. No grupo caso, foram encontrados todos os pacientes que morreram na admissão (n=30) que atenderam aos critérios de inclusão e exclusão, enquanto o grupo controle foi composto por 60 pacientes que receberam alta com vida, selecionados aleatoriamente por amostragem aleatória simples. Resultados: A média de idade foi maior no grupo de casos 74,06 em relação aos controles (p=0,021). 86,6% dos casos não receberam trombólise e 6,6% tinham algum critério para reperfusão pós-estreptoquinase (p=0,00). 36,6% dos casos apresentaram choque cardiogênico (p=0,003), ruptura cardíaca (30%) (p=0,03) e tamponamento (23,3%) (p=0,01). Conclusões: Os fatores preditivos de mortalidade hospitalar em pacientes com infarto agudo do miocárdio são: idade avançada, longo tempo entre o início dos sintomas e o atendimento médico, a existência de complicações, como choque cardiogênico, tamponamento cardíaco e ruptura cardíaca, bem como a não administração de tratamento trombolítico e a ausência de reperfusão.

Radiation dose reduction, improved isocenter accuracy and CT scan time savings with automatic patient positioning by a 3D camera.

PURPOSE: To compare CT isocenter accuracy, patient dose, and scan time in adults imaged with and without use of a 3D camera. METHOD: 571 CT examinations utilizing a 3D camera for initial patient positioning (optional radiographer isocenter adjustment) and 504 examinations scanned without the camera between 10/1/2018 and 3/19/2019 were retrospectively identified. All exams were chest or abdominopelvic CTs. The isocenters of these exams were compared with the true isocenters defined as the manually delineated centroid of the body in the CT volume. The size specific dose estimate (SSDE) (mGy) of radiation dose obtained from departmental software for the 4 most common protocols on one CT scanner was compared before and after implementation of the 3D camera. The times required for the entire scan and just the topogram "scout" were compared with and without the 3D camera for noncontrast chest and abdominopelvic CT enterography protocols. 2-tailed t-tests and Mann-Whitney U tests were used (P < 0.05 indicated statistical significance). RESULTS: The deviation from true isocenter was 6.8 ±â€¯6.1 mm (P = 0.043) and 16.3 ±â€¯14.0 mm (P < 0.01) with and without the 3D camera, respectively (P < 0.01). CT radiographers accepted isocenter location without alteration in 93 % of examinations. Average SSDE savings with the 3D camera ranged 1.0-2.4 mGy (21-31 %) for the 4 most commonly performed protocols (p < 0.01). Median scout time savings was 32 s (Camera vs. No-Camera cohorts) (P < 0.01). Average noncontrast chest CT and CT enterography scan time savings were 19 s and 17 s with the 3D camera, respectively (P < 0.01). CONCLUSIONS: The 3D camera improved accuracy of patient positioning while reducing radiation dose and examination time. Implementation of a 3D camera helps standardize workflow in a busy clinical practice.

Breakup of an electrified viscoelastic liquid bridge.

We study both numerically and experimentally the breakup of a viscoelastic liquid bridge formed between two parallel electrodes. The polymer solutions and applied voltages are those commonly used in electrospinning and near-field electrospinning. We solve the leaky-dielectric finitely extensible nonlinear elastic-Peterlin (FENE-P) model to describe the dynamical response of the liquid bridge under isothermal conditions. The results show that the surface charge screens the inner electric field perpendicular to the free surface over the entire dynamical process. The liquid bridge deformation produces a normal electric field on the outer side of the free surface that is commensurate with the axial one. The surface conduction does not significantly affect the current intensity in the time interval analyzed in the experiments. The force due to the shear electric stress becomes comparable to both the viscoelastic and surface tension forces in the last stage of the filament. However, it does not alter the elastocapillary balance in the filament. As a consequence, the extensional relaxation times measured from the filament exponential thinning approximately coincides with the stress relaxation time prescribed in the FENE-P model. The above results allow us to interpret correctly the experiments. In the experiments, we measure the filament electrical conductivity and extensional relaxation time for polyethylene oxide (PEO) dissolved in deionized water and in a mixture of water and glycerine. We compare the filament electrical conductivity with the value measured in hydrostatic conditions for the same estimated temperature. Good agreement was found for PEO dissolved in water + glycerine, which indicates that the change in the filament microscopic structure due to the presence of stretched polymeric chains does not significantly alter the ion mobility in the stretching direction. Significant deviations are found for PEO dissolved in deionized water. These deviations may be attributed to the heat transferred to the ambient, which is neglected in the calculation of the filament temperature. We measure the extensional relaxation time from the images acquired during the filament thinning. The relaxation times obtained in the first stage of the exponential thinning hardly depend on the applied voltage. Little but measurable influence of the applied voltage is found in the last phase of the filament thinning.

Experimental Analysis of the Extensional Flow of Very Weakly Viscoelastic Polymer Solutions.

We study with ultra-high-speed imaging the thinning of the filament formed during the breakup of a pendant droplet of very weakly viscoelastic polymer solutions of polyvinylpyrrolidone (PVP) and polyethylene oxide (PEO). In the latter case, we consider two molecular weights: 10 5 g/mol (PEO100K) and 2 × 10 6 g/mol (PEO2M). The results allow us to measure with high reproducibility extensional relaxation times of the order of 10 µ s. Despite the noticeable differences between PVP and PEO100K, very similar values are obtained for the range of concentrations where the linear elasto-capillary is established. For PEO2M, the extensional relaxation time depends on the concentration even for values significantly smaller than the overlap one. The prediction c low for the concentration below which the linear elasto-capillary regime cannot be reached qualitatively agrees with the results for PVP and PEO2M, while it underestimates the critical concentration for PEO100K. The results for PEO2M are consistent with those reported in the literature for higher concentrations.

Measurement of relaxation times in extensional flow of weakly viscoelastic polymer solutions.

The characterization of the extensional rheology of polymeric solutions is important in several applications and industrial processes. Filament stretching and capillary breakup rheometers have been developed to characterize the extensional properties of polymeric solutions, mostly for high-viscosity fluids. However, for low concentration polymer solutions, the measurements are difficult using available devices, in terms of the minimum viscosity and relaxation times that can be measured accurately. In addition, when the slow retraction method is used, solvent evaporation can affect the measurements for volatile solvents. In this work, a new setup was tested for filament breakup experiments using the slow retraction method, high-speed imaging techniques, and an immiscible oil bath to reduce solvent evaporation and facilitate particle tracking in the thinning filament. Extensional relaxation times above around 100 µs were measured with the device for dilute and semi-dilute polymer solutions. Particle tracking velocimetry was also used to measure the velocity in the filament and the corresponding elongation rate, and to compare with the values obtained from the measured exponential decay of the filament diameter.

Algorithm Variability in the Estimation of Lung Nodule Volume From Phantom CT Scans: Results of the QIBA 3A Public Challenge.

RATIONALE AND OBJECTIVES: Quantifying changes in lung tumor volume is important for diagnosis, therapy planning, and evaluation of response to therapy. The aim of this study was to assess the performance of multiple algorithms on a reference data set. The study was organized by the Quantitative Imaging Biomarker Alliance (QIBA). MATERIALS AND METHODS: The study was organized as a public challenge. Computed tomography scans of synthetic lung tumors in an anthropomorphic phantom were acquired by the Food and Drug Administration. Tumors varied in size, shape, and radiodensity. Participants applied their own semi-automated volume estimation algorithms that either did not allow or allowed post-segmentation correction (type 1 or 2, respectively). Statistical analysis of accuracy (percent bias) and precision (repeatability and reproducibility) was conducted across algorithms, as well as across nodule characteristics, slice thickness, and algorithm type. RESULTS: Eighty-four percent of volume measurements of QIBA-compliant tumors were within 15% of the true volume, ranging from 66% to 93% across algorithms, compared to 61% of volume measurements for all tumors (ranging from 37% to 84%). Algorithm type did not affect bias substantially; however, it was an important factor in measurement precision. Algorithm precision was notably better as tumor size increased, worse for irregularly shaped tumors, and on the average better for type 1 algorithms. Over all nodules meeting the QIBA Profile, precision, as measured by the repeatability coefficient, was 9.0% compared to 18.4% overall. CONCLUSION: The results achieved in this study, using a heterogeneous set of measurement algorithms, support QIBA quantitative performance claims in terms of volume measurement repeatability for nodules meeting the QIBA Profile criteria.

Continuous Versus Sequential Acquisition Head Computed Tomography: A Phantom and Clinical Image Quality Comparative Study.

OBJECTIVE: Sequential computed tomography (CT) technique remains the most common protocol for CT evaluation of the head despite nearly universal adoption of continuous technique for all other body parts. This may be attributable to the belief by radiologists that this technique is superior to helical scanning uniquely for this indication. This study attempts to clarify the issue. METHODS: A phantom evaluation and a prospective randomized clinical image quality trial were performed comparing sequential and helical technique using the most current generation 128-row detector CT scanner. RESULTS: Phantom evaluation demonstrated equivalence between the 2 techniques for low-contrast resolution and line pair spatial discrimination. Continuous scanning provided the highest contrast-to-noise ratio. There was no significant difference between the 2 techniques regarding image quality except for cortical visualization at the cerebral hemispheres, which was subtly but significantly superior for sequential technique. CONCLUSIONS: Head CT image quality for sequential and continuous techniques are virtually equivalent.

Combination of increased flip angle, radial k-space trajectory, and free breathing acquisition for improved detection of a biliary variant at living donor liver transplant evaluation using gadoxetic acid-enhanced MRCP.

Gadoxetic acid-enhanced magnetic resonance cholangiopancreatography (MRCP) was performed for evaluation of living donor liver transplantation. T2-weighted MRCP and hepatobiliary-phase postcontrast MRCP showed an aberrant right posterior bile duct, although the precise variant was uncertain. Optimized hepatobiliary-phase MRCP was obtained using 3 sequence modifications: increased flip angle to improve contrast between the biliary tree and surrounding tissues; radial k-space sampling to minimize motion artifact; and free-breathing acquisition to improve signal-to-noise ratio and, in turn, spatial resolution (resolution of 1.28 × 1.28 × 1.5 mm). The optimized sequence demonstrated that the right posterior bile duct drained into the cystic duct, consistent with type 3C biliary variant, thus modifying surgical planning.

Phase II study of everolimus in children and adults with neurofibromatosis type 2 and progressive vestibular schwannomas.

BACKGROUND: Activation of the mammalian target of rapamycin (mTOR) signaling pathway is thought to be a key driver of tumor growth in Merlin (NF2)-deficient tumors. Everolimus is an oral inhibitor of mTOR complex 1 (mTORC1) with antitumor activity in a variety of cancers. METHODS: We conducted a single-institution, prospective, 2-stage, open-label phase II study to estimate the response rate to everolimus in neurofibromatosis type 2 (NF2) patients with progressive vestibular schwannoma (VS). Ten eligible patients were enrolled, including 2 pediatric patients. Everolimus was administered at a daily dose of 10 mg (adults) or 5 mg/m(2)/day (children <18 y) orally in continuous 28-day courses, for up to 12 courses. Response was assessed every 3 months with MRI, using 3-dimensional volumetric tumor analysis, and audiograms. Nine patients were evaluable for the primary response, defined as ≥15% decrease in VS volume. Hearing response was evaluable as a secondary endpoint in 8 patients. RESULTS: None of the 9 patients with evaluable disease experienced a clinical or MRI response. No objective imaging or hearing responses were observed in stage 1 of the trial, and the study was closed according to predefined stopping rules. CONCLUSION: Everolimus is ineffective for the treatment of progressive VS in NF2 patients. We are currently conducting a pharmacokinetic/pharmacodynamic ("phase 0") study of everolimus in presurgical VS patients to elucidate the biological basis for apparent treatment resistance to mTORC1 inhibition in these tumors.