Optimization of magnetic actuation protocol to enhance mass transfer in solid/liquid microfluidic systems

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The dynamic properties of a 250 m magnetic microparticle in a time varying magnetic field have been studied in a PDMS microreactor with a diameter of 13 mm using a dual coupled quadrupolar arrangement of electromagnets. A sinusoidal applied magnetic field has dictated a circular motion of the particles in the microreactor in the frequency range below 0.6 Hz. Different circular motion modes have been observed at higher frequencies of the applied field. The particular symmetric arrangement of the magnets has allowed a non-steady-state motion with variation in velocity between magnetic poles. The motion of magnetic particle has been described in terms of average velocity and mean square deviation from average velocity. The effect of actuation protocol parameters (frequency, magnetic field strength and phase shift) on particle velocity and acceleration has been investigated. The maximum average velocity of 0.016 m/s has been observed under an optimized actuation protocol. The mass transfer rate towards the particle surface is mainly influenced by the average velocity while the effect of acceleration/deceleration of the particle has an order of magnitude less influence

Relationship of daily arterial blood pressure monitoring readings and arterial stiffness profile in male patients with chronic obstructive pulmonary disease combined with arterial hypertension

The aim of the study was to determine correlation between arterial blood pressure daily rhythm and daily profile of arterial stiffness in male patients with chronic obstructive pulmonary disease (COPD) and arterial hypertension. Materials et methods: Prospective investigation comprised 45 male patients with COPD and arterial hypertension. Individuals of 40 years younger and 80 years elder, patients with diabetes, stroke, angina pectoris, or heart infarction, vascular diseases, and exacerbation of chronic disease, bronchial and pulmonary diseases of other etiology were excluded from the analyses. Comparison group included 47 patients with essential arterial hypertension and without chronic respiratory diseases closely similar on general parameters with patients from main clinical series. Twenty-four-hour arterial blood pressure monitoring (ABPM) and daily arterial stiffness monitoring were performed using BPLab® MnSDP-2 apparatus (Petr Telegin, Russian Federation). Results: Patients with COPD combined with arterial hypertension with raised arterial stiffness measures prevail over individuals in essential hypertension group. There is pathological alteration of the ABPM circadian rhythm and raised «Pressure load» values in raised arterial stiffness group. Conclusion: We found ABPM raised parameters in patients with COPD and arterial hypertension. It confirms necessity of ABPM in daily arterial stiffness assessment in patients with COPD

Зондоформирующая система ядерного сканирующего микрозонда на базе интегрированных дублетов магнитных квадропольных линз

Современные достижения науки в области микроанализа и высокий уровень технологий в этой сфере деятельности, позволили человеку найти решение многих макрозадач при помощи изучения законов микромира. Именно структура и элементный состав вещества, а также расположение микроэлементов в нем в совокупности определяют его физико-химические свойства. В частности, в медицине при исследовании нейронов головного мозга методами микроанализа было установлено, что причиной таких болезней как Alzheimer и Parkinson является изменение структуры нейромеланина - связующего звена между мозгом и интеллектом . Изучение содержания и распределения в нейромеланине таких элементов как Fe, Ca, Cu, Ni, P, S подтверждает, что именно эти элементы определяют его свойства. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/1586

Зондоформуюча система ядерного скануючого мікрозонда на базі інтегрованих дублетів магнітних квадрупольних лінз

Локальність аналізу мікрозонда обумовлена роздільною здатністю системи і задається геометричними розмірами і величиною струму зонда, які визначили критерій і напрямок досліджень при оптимізації іонно-оптичних параметрів ЗФС мікрозонда. На основі чисельного моделювання нелінійних процесів фокусування заряджених частинок визначені фізичні й геометричні параметри оптимізованої ЗФС з урахуванням яскравості пучка і величини енергетичного розкиду іонів у пучку, який забезпечує електростатичний прискорювач. Розроблено прецизійний інтегрований дублет магнітних квадрупольних лінз нового типу. Ярмо і полюсні наконечники лінз дублета складають одне ціле, що дозволяє значно зменшити аберації, пов’язані з помилками юстування ЗФС у цілому. Проведені експериментальні дослідження структури магнітного поля лінз дублета, які показали необхідну співвісність лінз і те, що величина паразитних мультипольних компонент перебуває на допустимому рівні. Експериментальне дослідження процесу фокусування пучка грунтується на детектуванні вторинних електронів при скануванні мідних каліброваних сіток. Порівняльний аналіз проведено на зіставленні експериментальних інтегральних профілів інтенсивності виходу вторинних електронів і аналогічних розрахункових профілів, які визначалися з використанням теоретичних розподілів густини струму пучка на мішені з урахуванням отриманих оптимізованих параметрів базової ЗФС. У результаті порівняльного аналізу показана адекватність теоретичної моделі, прийнятої для розрахунків зондоформуючої системи з інтегрованими дублетами магнітних квадрупольних лінз. При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/24318Диссертация посвящена исследованию нелинейных процессов фокусировки пучка заряженных частиц в зондоформирующей системе ядерного сканирующего микрозонда с интегрированными дублетами магнитных квадрупольных линз. Метод исследования нелинейной динамики пучков заряженных частиц в магнитных квадрупольных линзах, позволяет представить ионно-оптические свойства ЗФС в виде параметрической зависимости. Задача оптимизации на множестве определенных параметров принадлежит к классу задач нелинейного программирования, в которой ионно-оптические свойства ЗФС входят в ограничивающие условия. В качестве целевой функции выбрана величина аксептанса системы при заданных размерах зонда. Оптимизация процесса фокусировки пучка в ЗФС на базе двух прецизионных интегрированных дублетов МКЛ нового типа позволяет определить физические и геометрические параметры системы с учетом яркости пучка и величины энергетического разброса ионов, который обеспечивает электростатический ускоритель. Интегрированный дублет магнитных квадрупольных линз новой конструкции позволяет уменьшить паразитные аберрации, связанные с ошибками юстирования ЗФС в целом. Проведенные экспериментальные исследования структуры магнитного поля линз дублета показали, что соосность линз находится в пределах величины 20 мкм, которая не приводит к ухудшению параметров зонда, а величина паразитных мультипольных компонент не превышает допустимых расчетных значений. Определение размеров зонда осуществлялось в результате детектирования эмиссии вторичных электронов в режиме сканирования калиброванной медной сетки. Сравнительный анализ проведен на основании сопоставления экспериментальных интегральных профилей интенсивности выхода вторичных электронов и аналогичных расчетных профилей, которые вычислялись с использованием теоретических распределений плотности тока пучка на мишени с учетом полученных оптимизированных параметров базовой зондоформирующей системы. В результате показана адекватность теоретической модели, принятой для расчетов зондоформирующей системы с интегрированными дублетами магнитных квадрупольных линз. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/24318A locality of microprobe analysis is directly related to the probe-forming system resolution and assigned by probe dimensions and its current which defined of merit function in the optimization task of ion-optical parameters of probe-forming system of nuclear microprobe and aims of investigation in this direction. The physical and geometrical parameters of optimized probe-forming system are obtained on the base of numerical simulation of nonlinear processes of charged particle beam focusing. The simulation is carried out taking into account of the beam brightness and the momentum spread which are provided for electrostatic accelerator “SOKOL”. The integrated doublet of magnetic quadrupole lenses of new design is developed. The yoke and poles of doublet lenses were manufactured from a single piece of soft iron by means of wire cutting of electro-discharged machining. This design permits parasitic aberration enormously to be decreased related to alignment errors of probe-forming system in general. In result of the performed experimental investigations of magnetic field structure of doublet lenses are shown that lenses have required coincidence of lens axes and parasitic multipole components have tolerance limits. The experimental investigations of beam focusing processes are based on the detecting of secondary electron emission under scanning of copper calibrated grids. Comparative analysis is carried out by means of comparing of experimental integral intensity profiles of secondary electron emission and analogous simulated profiles which are calculated with using theoretical beam current density distributions on the target with allowance for optimized parameters of base probe-forming system. In result of comparative analysis the adequacy of theoretical model taking in simulation of probe-forming system with integrated doublets of magnetic quadrupole lenses is shown. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2431

Magnetic actuation of microparticles for mass transfer enhancement

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The motion of magnetic microparticles (250μm diameter) in a circular microfluidic reactor with a diameter of 10 mm under time dependent magnetic field has been studied using CFD code COMSOL. The effect of actuation protocol on the local and average particle velocity has been investigated. The local Sh numbers were obtained as a function of angular particle position in the range of Re numbers between 0.05 and 10 while the particle velocity was changed over two orders of magnitude. Under time dependent magnetic field, the thickness of the boundary layer continuously changes which results in an increased mass transfer towards the particle surface under periodic particle velocity conditions as compared to steady state velocity conditions. A good agreement between numerical and experimental data has been observed

Direct amide synthesis over core-shell TiO2@NiFe2O4 catalysts in a continuous flow radio frequency-heated reactor

Core-shell composite magnetic catalysts TiO2@NiFe2O4 with a titania loading of 9–32 wt. % have been synthesised by sol-gel method for direct amide synthesis in a radiofrequency (RF)-heated continuous flow reactor. The catalyst calcination temperature was optimised in the range of 350-500 ºC and the highest activity was observed for the catalyst calcined at 500 ºC due to conversion of titania into catalytically active anatase phase. No reaction between the magnetic core and the titania shell was observed up to the calcination temperature of 1000 ºC and no sintering of titania shell was observed after calcination at 500 ºC. The comparison of direct amide synthesis in a continuous flow fixed bed reactor under conventional and RF heating demonstrated that the RF heating mode increased the apparent reaction rate by 60 % and decreased the deactivation rate due to a better temperature uniformity. The titania weight normalised reaction rate in the RF-heated reactor was constant for titania loadings above 17 wt. %, while it decreased by a factor of 3 at lower titania loadings because of interactions between the ferrite core on the thin layer of the catalyst. The catalyst deactivation study showed that the deactivation rate could be accurately described by a first order kinetics and that the main reason of deactivation was coking. The catalyst regeneration via calcination at 400 ºC resulted in the catalyst sintering, while a treatment with a hydrogen peroxide solution at 90 ºC fully recovered catalytic activity

Counting bubbles : precision process control of gas-liquid reactions in flow with an optical inline sensor

Quality by Design encouraged by the US Food and Drug Administration (FDA) in the continuous flow synthesis requires tight monitoring of all the reaction input and output parameters to improve reproducibility and eliminate the process rejects. The reaction monitoring, however, relies on costly (above 10,000$) process analytical technology (PAT) – one of the factors that prevents a wider utilisation of continuous processes. In the work, we show that gas-liquid reactions can be monitored using low-cost (10$) hardware – optical liquid inline sensors – that allows instantaneous analysis of gas fraction in the moving stream. We discuss the application of the sensor for various gas-liquid reactions. The gas-consuming reactions such as hydrogenation are the easiest to implement because the sensor without calibration provides accurate readings close to complete consumption of the gas. The gas-evolving reactions can be monitored but require sensor calibration to determine the gas fraction accurately. Operation of the sensor was demonstrated for various hydrogenation reactions self-optimised using a proportional-integral (PID) algorithm which adjusted the substrate concentration to provide high (but not full) pre-defined hydrogen consumption. The optimised hydrogen consumption agreed with the product analysis for a range of the substrates hydrogenated under various pressures and with different selectivities. The optical sensor was also proven to be an efficient tool in adapting the reaction condition to the catalyst deactivation in the reaction of 2-methyl-3-butyn-2-ol semi-hydrogenation – the autonomous reactor allowed reaching a turn-over number (TON) of 2.7·106 with the value of 1.5·107 expected till a twofold decrease in the catalyst activity. The TON values demonstrated are significantly higher than those observed in batch reactors (~103) even in case of catalyst re-use (105) demonstrating a substantial improvement of process sustainability operating with the process control

Modeling the flow of activated H 2

Algorithm of the direct simulation Monte Carlo method for the flow of hydrogen and methane mixture in a cylindrical channel is developed. Heterogeneous reactions on tungsten channel surfaces are included into the model. Their effects on flows are analyzed. A one-dimensional approach based on the solution of equilibrium chemical kinetics equations is used to analyze gas-phase methane decomposition. The obtained results may be useful for optimization of gas-dynamic sources of activated gas diamond synthesis

Controllable synthesis of one-dimensional isolated Ni 0.5 Zn 0.5 Fe 2 O 4 microtubes for application as catalyst support in RF heated reactors

One-dimensional isolated Ni0.5Zn0.5Fe2O4 microtubes have been prepared via a template assisted sol–gel method. Temperature dependence of the structural and magnetic properties was studied via XRD, N2 adsorption, SEM, TEM, and VSM. An increase in calcination temperature from 873 to 1273 K caused a decrease in the specific surface area from 80.7 to 17.0 m2/g due to an increase of the grain size from 25.3 to 112 nm. All samples demonstrated anomalous coercivity behavior due to mechanical stresses acting on their domain walls. The porous microtubes calcined at 1073 K have a mean external diameter of 3.7 μm with a length-to-diameter ratio exceeding 12. The microtubes calcined at 973 K have the highest coercivity of 88.1 Oe and demonstrated the largest specific heating rate of 4.36 W/g in a radiofrequency field at 295 kHz