Adjustment Of Flow Rate Research Articles

Chip-Type Asymmetrical Flow Field-Flow Fractionation Channel Coupled with Mass Spectrometry for Top-Down Protein Identification

A chip-type design asymmetrical flow field-flow fractionation (AF4) channel has been developed for high-speed separation of proteins and top-down proteomic analysis using online coupled electrospray ionization mass spectrometry (ESI-MS). The new miniaturized AF4 channel was assembled by stacking multilayer thin stainless steel (SS, 1.5 mm each) plates embedded with an SS frit in such a way that the total thickness of the channel assembly was about 6 mm. The efficiency of the miniaturized AF4 channel at different channel lengths was examined with the separation of protein standards by adjusting flow rates in which an identical effective channel flow rate or an identical void time can be maintained at different channels. Detection limit, overloading effect, reproducibility, and influence of channel membrane materials on separation efficiency were investigated. Desalting and purification of proteins achieved during the AF4 operation by the action of an exiting crossflow and the use of aqueous mass-spectrometry-compatible (MS-compatible) buffer were advantageous for online coupling of the chip-type AF4 with ESI-MS. The direct coupling of AF4 and ESI-MS capabilities was demonstrated for the high-speed separation and identification of carbonic anhydrase (29 kDa) and transferrin (78 kDa) by full scan MS and for the first top-down identification of proteins with AF4-ESI-MS-MS using collision-induced fragmentation (CID). The presence of intact dimers (156 kDa) of transferrin was confirmed by AF4-ESI-MS via size separation of the dimers from monomers, followed by multiply charged ion spectral analysis of the dimers and molecular mass determinations. It was also found from these experiments that AF4-ESI-MS analysis of transferrin exhibited an increased signal-to-noise ratio compared to that of direct ESI-MS analysis due to online purification of the protein sample and size separation of dimers with AF4.

Low-Cost Venturi Meter: Understanding Bernoulli’s Equation Through A Demonstration

<p>This study intended to concretize Bernoulli’s principle through a low-cost Venturi meter designed and constructed by the researchers. Specifically, this paper aimed to improvise a device that can measure flow speeds of water both in the wide and narrow portions of a horizontal piping system for which the pressure difference is provided by a differential height revealed in the attached manometer. A mechanism which regulates volume flow rate of liquid was attached to Venturi meter to generate several trials required to establish accuracy of setup in demonstrating Bernoulli’s principle. This investigation about improvisation of apparatus required experimental development method especially in assembling various components which included PVC pipe, aluminum pipe, manometer, DC pump, variable flow controller, and a plastic container as water reservoir. The final model of the apparatus evolved from a series of functionality test sessions with experts and consultants. To determine the accuracy of the instrument, nine trials--that is three each for the three adjusted flow rates, were performed. Findings revealed that the improvised Venturi meter can concretize Bernoulli’s principle. Its accuracy in flow speed determination was high since average percentage of error for minor turbulent flow was 12.52 per cent while that for laminar was 3.86 per cent.</p>

Focus on vacuum and cryogenics

Focus on vacuum and cryogenics

Parallel flow of immiscible liquids in a microreactor: modeling and experimental study

Two-phase parallel flow can be utilized in microreactor engineering for performing reactions and extractions, and also for achieving efficient phase separation at the exit of the microreactor. Typical laminar flow at the microscale allows two phases to flow in parallel without mixing, allowing highly controlled conditions for a specific chemical process. Since the liquid with the higher viscosity has a tendency to occupy a larger fraction of the microchannel, the position of the interface can be controlled through the adjustment of flow rates. The prediction of the position of the interface is important for microreactor design and operation and requires the solution of the governing equations of fluid mechanics. In this work, the theoretical description for two-phase parallel flow, based on the Navier–Stokes equations in three dimensions was expressed with a mathematical model and validated with experimental observations. The movement of the interface was achieved through the adjustment of fluid properties according to the position of the central streamlines. The predicted position of the interface was in good agreement with experimental data. A correlation for the flow rate ratio required for positioning the interface in the middle of the channel for various viscosity ratios was proposed, as well as a correlation for the prediction of the parallel to slug transition for a water/n-hexane system.

Microbridge structures for uniform interval control of flowing droplets in microfluidic networks

Precise temporal control of microfluidic droplets such as synchronization and combinatorial pairing of droplets is required to achieve a variety range of chemical and biochemical reactions inside microfluidic networks. Here, we present a facile and robust microfluidic platform enabling uniform interval control of flowing droplets for the precise temporal synchronization and pairing of picoliter droplets with a reagent. By incorporating microbridge structures interconnecting the droplet-carrying channel and the flow control channel, a fluidic pressure drop was derived between the two fluidic channels via the microbridge structures, reordering flowing droplets with a defined uniform interval. Through the adjustment of the control oil flow rate, the droplet intervals were flexibly and precisely adjustable. With this mechanism of droplet spacing, the gelation of the alginate droplets as well as control of the droplet interval was simultaneously achieved by additional control oil flow including calcified oleic acid. In addition, by parallel linking identical microfluidic modules with distinct sample inlet, controlled synchronization and pairing of two distinct droplets were demonstrated. This method is applicable to facilitate and develop many droplet-based microfluidic applications, including biological assay, combinatorial synthesis, and high-throughput screening.

A micropump based on water potential difference in plants

In land plants, water vapor diffuses into the air through the stomata. The loss of water vapor creates a water potential difference between the leaf and the soil, which draws the water upward. Quantitatively, the water potential difference is 1–2 MPa which can support a water column of 100–200 m. Here we present the design and operation of a biomimetic micropump. The micropump is mainly composed of a 48-μm thick metal screen plate with a group of 102-μm diameter micropores and an agarose gel sheet with nanopores of 100 nm diameter. The micropores in the screen plate imitate the stomata to regulate the flow rate of the micropump. The agarose gel sheet is used to imitate the mesophyll cells around the stomata. The lost of water from the nanopores in the gel sheet can generate a water potential difference (more than 30 kPa) which can drive solution flow in a microfluidic chip. Results have shown that a precise flow rate of 4–8 nl/min can be obtained by using this micropump, and its ultra-high flow rate is 113–126 nl/min. The advantages of this biomimetic micropump include adjustable flow rate, simple structure and low fabrication cost. It can be used as a “plug and play” fluid-driven unit in microfluidic chips without any external power sources or equipments.

Factors influencing delay time and coronary arterial density during coronary angiography with DSCT

CT angiography (CTA) plays an important role in diagnosing coronary arterial disease. Delay time and density of the coronary arteries related with patient-specific factors are essential for getting an optimal CTA image. To investigate various factors influencing delay time and coronary arterial density during coronary CTA with dual source CT. One hundred and sixteen consecutive subjects who underwent cardiac DSCT with retrospective ECG-gating were included. Factors including gender, age, height, weight, transversal cardiac diameter (TCD), transversal thoracic diameter (TTD), heart rate (HR), body surface area (BSA = [weight × height/3600](1/2)) and cardiothoracic ratio (CTR = TCD/TTD) were recorded, measured and calculated before administration of contrast media during coronary CT angiography. Delay time was determined as duration from the beginning of the injection to the density in the descending aorta at the level of right main pulmonary artery reaching a threshold of 100 HU. Coronary arterial density was measured at the mid portion of the right coronary artery. Regression analysis and stepwise regression analysis were used to investigate the influence of these factors on delay time and coronary arterial density. Delay time decreased with an increasing HR and it was shorter in women than men. Delay time increased with an increasing TCD. Delay time could be predicted by the formula: DT = 16.651-0.110 × HR + 1.902 × gender + 0.394 × TCD (where DT is abbreviation for delay time, gender is 0 for women and 1 for men). Coronary arterial density decreased with an increasing HR and weight. Coronary arterial density could be predicted by the formula: CAD = 923.42-4.099 × HR-3.293 × weight (CAD = coronary arterial density). There was no relationship between the other factors mentioned above and delay time or coronary arterial density. Delay time is influenced by HR, gender and TCD. Coronary arterial density also changes with HR and weight. So HR, gender, TCD and weight can be used to adjust flow rate and dosage of contrast media before administration of contrast media during coronary CT angiography.

A bio-inspired micropump based on stomatal transpiration in plants

Stomatal transpiration, which is an efficient way to carry water from the roots up to the leaves, can be described by "diameter-law". According to the law, the flow rate induced by micropore transpiration far exceeded that induced by macroscale evaporation, and it can be controlled by opening (or closing) some micropores. In this research, a bio-inspired micropump based on stomatal transpiration is presented. The micropump is composed of three layers: the top layer is a 93 μm-thick PVC (polyvinylchloride) film with a group of slit-like micropores; the second layer is a PMMA sheet with adhesives to join the other two layers together; the third layer is a microporous membrane. Using this pump, controllable flow rates of 0.13-3.74 μl min(-1) can be obtained. This micropump features high and adjustable flow-rates, simple structure and low fabrication cost. It can be used as a "plug and play" fluid-driven unit without any external power sources and equipment.

The effect of amorphous carbon layer on the field emission characteristics of carbon nanotube film

Carbon nanotube (CNT) has excellent field emission characteristics and could play as a good cold cathode in the application of vacuum electronic devices. However, the practical application faces a big obstacle regarding current fluctuation and deterioration of the CNT cathode. In this research, the formation of amorphous carbon (ac) layer between the CNT film and the substrate, and the effect of the existence of this layer on field emission stability of the CNT film are studied. The formation of the ac layer could be controlled by adjustment of growth temperature and hydrocarbon flow rate. The field emission character and current stability of the CNT film without ac layer are better than those of the CNT film with ac layer. The results attribute to the ac layer a thermal disequilibrium state under high current level. Moreover, adhesion capacity of the CNT film without ac layer is also better than that with the ac layer. It is concluded that the ac layer between the CNT film and substrate is a key factor in the stability of field emission characteristics and should be eliminated before applications.

Water Allocation Network Design Concerning Process Disturbance

Water system integration can effectively reduce freshwater consumption and minimize wastewater discharge of a water-using system, but integration makes the resultant water network structurally more integrated among process units. Therefore, to design a flexible water allocation network that is easy to control becomes highly desirable. In this Article, a methodology is presented for water allocation network design with process disturbance taken into account. For a new design, the synthesized network structure can guarantee that the water system consumes minimum freshwater under both normal and disturbance conditions and with minimum number of control streams under disturbance. At the same time, the information needed to adjust flow rate under disturbance will be obtained. For an existing water system, an adjustment scheme under disturbance with minimum freshwater consumption for the existing structure will be obtained. The water network designed by the new methodology has the feature of minimum freshwater ...

Analytical Evaluation of an Integrated Ultrasonic Nebulizer-hydride Generator System for Simultaneous Determination of Hydride and Non-hydride Forming Elements by Microwave Induced Plasma Spectrometry

ABSTRACT The commercial ultrasonic nebulizer NOVA-DUO (ultrasonic nebulizer dual capillary system USN/DCS) has been evaluated for the simultaneous determination of classical hydride forming (As, Bi, Ge, Sb, Se, Sn) and conventional non-hydride forming (Ba, Ca, Fe, Li, Mg, Sr) elements by microwave induced plasma-optical emission spectrometry (MIP-OES). Simultaneous mixing and nebulization of the two solutions (acidified sample and reductant) on the piezoelectric transducer, with the possibility of flow rate adjustment, permits a wide variation of sensitivity. The hydrides and aerosols were rapidly transported via a stream of Ar carrier to a MIP for simultaneous multi-element determination by OES. A univariate approach and simplex optimization procedure was used to achieve optimized conditions and derive analytical figures of merit. Analytical performance of the ultrasonic nebulization system was characterized by determination of the limits of detection (LODs) and precision (RSDs) with the USN/DCS observed at 11 µL min−1 flow rate. The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times of standard deviation of the blank (LOD, 3σblank criterion, peak height) were 1.3, 5.9, 6.6, 1.8, 3.6, 2.6, 41, 8.1, 11, 7.5, 9.2, and 12 ng mL−1 for As, Bi, Ge, Sb, Se Sn, Ba, Ca, Fe, Li, Mg, and Sr, respectively. The method offers relatively good precision (RSD ranged from 9 to 13%) for liquid analysis and microsampling capability. Interference effects by transition metals have been shown to be corrected by the addition of thiourea, as a pre-reducing agent and masking agent. The accuracy of the method was verified by the use of certified reference materials (NRCC DOLT-2, NRC GBW 07302, NIST SRM 2710, NIST SRM 1643e) and by aqueous standard calibration technique. All results obtained for reference materials were in agreement with certified values at 95% confidence level by Student t-test.

Method Development for Simultaneous Determination of Transition (Au, Ag, Cd, Cu, Mn, Ni, Pb, Zn) and Noble (Pd, Pt, Rh) Metal Volatile Species by Microwave-Induced Plasma Spectrometry Using Ultrasonic Micronebulizer Dual Capillary Sample Introduction System

ABSTRACT The commercial ultrasonic nebulizer NOVA-DUO (Optolab, Warsaw, Poland) has been evaluated for the simultaneous determination of transition (Au, Ag, Cd, Cu, Mn, Ni, Pb, Zn) and noble (Pd, Pt, Rh) volatile metal species by microwave induced plasma–optical emission spectrometry (MIP-OES). Simultaneous mixing and nebulization of the two solutions (acidified sample and reductant) on the piezoelectric transducer, with the possibility of flow rate adjustment, permits a wide variation of sensitivity. The vapor-phase species were rapidly transported via a stream of Ar carrier to an MIP–OES for simultaneous multi-element determination. A univariate approach and simplex optimization procedure was used to achieve optimized conditions and derive analytical figures of merit. Analytical performance of the ultrasonic nebulization system was characterized by determination of the limits of detection (LODs) and precision (RSDs) with the ultrasonic nebulizer/dual capillary system (USN/DCS) observed at 15 µL min−1 flow rate. An improvement in detection limits was achieved compared with pneumatic nebulization. Detection limits are superior to conventional pneumatic nebulization of elements. The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times of standard deviation of the blank (LOD, 3σblank criterion, peak height), were 2.49, 1.75, 3.39, 2.13, 4.80, 6.21, 4.26, 2.01, 7.65, 3.92, and 4.65 ng mL−1 for Au, Ag, Cd, Cu, Mn, Ni, Pb, Pd, Pt, Rh, and Zn, respectively. The method offers relatively good precision (RSD ranged from 8 to 12%) for liquid analysis and microsampling capability. The accuracy of the method was verified by the use of digested certified reference materials (NRCC TORT-1, NIES CRM-13, NIST SRM 2710, INCT SBF-4) and by aqueous standard calibration technique. The measured elements content in reference materials was in satisfactory agreement with the certified values.

Experimental demonstration of rotating spiral microchannel distillation

A prototype device using a rotating spiral microchannel to produce multistage distillation has been designed and used to separate 2,2-dimethylbutane from an initial 50:50 mixture with 2-methyl-2-butene. Distillation or other phase-contacting processes in microchannels requires a strategy for handling surface forces so that the phases can interact in a controlled manner and efficient mass transfer can take place. The rotating spiral approach uses centrifugal force to maintain segregation of the phases into parallel-flowing liquid and vapour layers. When centrifugal force is opposed by pressure gradient along the channel, these layers can flow counter currently. Changing rotation rate and pressure allows adjustment of the phase flow rates and the contacting layer thicknesses. Thus, it is possible to control the phase contacting and take full advantage of the rapid mass transfer that is potentially available for small microchannel dimensions. This efficient contact can be maintained over long channel distances, allowing a large number of separation stages to be reached. A further advantage of the rotating spiral approach is that the mass transfer is augmented by secondary motions produced by Coriolis force. The paper describes the design of the prototype device, including flow and thermal aspects, and presents results for a simple binary distillation. The results obtained demonstrate the practical feasibility of rotating spiral contacting and provide initial quantitative data that are used to evaluate the performance achieved by the prototype device.

Compact semi-automatic incident sampler for personal monitoring of volatile organic compounds in occupational air

Suddenly occurring and time limited chemical exposures caused by unintended incidents might pose a threat to many workers at various work sites. Monitoring of exposure during such occasional incidents is challenging. In this study a compact, low-weight and personal semi-automatic pumped unit for sampling of organic vapor phase compounds from occupational air during sporadic and suddenly occurring incidents has been developed, providing simple activation by the worker potentially subjected to the sudden occurring exposures when a trained occupational hygienist is not available. The sampler encompasses a tube (glass or stainless steel) containing an adsorbent material in combination with a small membrane pump, where the adsorbent is capped at both ends by gas tight solenoid valves. The sampler is operated by a conventional 9 V battery which tolerates long storage time (at least one year), and is activated by pulling a pin followed by automatic operation and subsequent closing of valves, prior to shipping to a laboratory. The adjustable sampling air flow rate and the sampling time are pre-programmed with a standard setting of 200 mL min(-1) and 30 min, respectively. The average airflow in the time interval 25-30 min compared to average airflow in the interval 2-7 min was 92-95% (n = 6), while the flow rate between-assay precisions (RSD) for six different samplers on three days each were in the range 0.5-3.7%. Incident sampler recoveries of VOCs from a generated VOC atmosphere relative to a validated standard method were between 95 and 102% (+/-4-5%). The valves that seal the sampler adsorbent during storage have been shown to prevent an external VOC atmosphere (500 mg m(-3)) to enter the adsorbent tube, in addition to that the sampler adsorbent is storable for at least one month due to absence of ingress of contaminants from internal parts. The sampler was also suitable for trapping of semi-volatile organophosphates.

Characterization of an on-chip reconfigurable 3D optofluidic microlens by confocal laser scanning microscopy

This research describes the design, fabrication and performance of an optofluidic 3D microlens reconfigurable by hydrodynamic flow rate adjustments. The microflow device is realized by standard single-layer micromachining of the photoresist SU-8 on a silicon substrate. On-chip waveguides and microgrooves designed for the insertion of multimode glass fibers are integrated to serve as optical interconnection for incident light coupling and detection. The laminar flow regime in the structured microchannel and the use of two transparent fluids with different refractive indices enable smooth optical interfaces useful for the creation of optofluidic elements. The inertial microfluidic effects occurring in the channels allow the generation of a multiconvex 3D microlens. By altering the input flow rates the lens shape with different lens radii in the lateral and normal direction is adjusted. To confirm the fluid dynamic simulations and to three-dimensionally characterize the microflow system we conducted confocal laser scanning and fluorescent sample measurements. The unique features of this optical chip offer a novel 3D light focusing system attractive for enhanced low-cost cell parameter screening without the use of bulky/expensive single photon counting units.

Non-unique convection in a three-dimensional slot-vented cavity with opposed jets

This study aims to investigate multiple flow structures in a three-dimensional chamber with opposed jets. Numerical computations focus on the effect of inlet velocity on the air flow pattern, especially on multiple steady flow characteristics for Reynolds maintaining 10 5 . Three distinct branches of steady-state flows are found for this configuration. A complete study of stability of each branch is performed for varying velocity of the left inlet continuously between 0 and 3. The results are presented by stability diagrams showing the critical parameters corresponding to transition from one steady-state branch to the other state within multiple flow range. In parallel with numerical development, an experimental system was set up where adjustable flow rate was prescribed to produce variation of supplying jets. The corresponding vector flow fields, on a scale model, were measured by a laser-based particle image velocimetry (PIV) system. The multiple flow structures were validated both by numerical simulation and experimental investigation.

Change of energy consumption through the adjustment of feed flow rate in RO membrane process

The reverse osmosis (RO) process requires a large amount of energy for pressurizing feed flow, most of which is wasted through the brine stream. To recover the brine energy and deliver it to the feed, several methods using energy recovery devices (ERDs) have recently been used. However, the way to achieve efficient RO membrane process without ERD is also required in small RO desalination systems. In this work, the change of energy consumption upon the alteration of recovery ratio through the adjustment of feed flow rate was demonstrated. A variable frequency drive (VFD) was used to regulate feed flow rate. Permeate flux, recovery ratio, and salt rejection which are the key performance parameters of reverse osmosis were compared at the different feed flow rates, operating pressures, and feed temperatures. In addition, the power consumed in both high pressure (HP) pump and booster pump was measured and the specific energy consumption was compared. The control of feed flow rate reduced the specific energy consumption by 20%. Thus the adjustment of feed flow rate was effective to some extent in energy saving at a light cost of permeate volume and product water quality.

Simulating effects of gas flow on arc plasma to anode heat transfer during incinerator ash treatment

The conventional method for converting incineration ash to slag employs a plasma type furnace. An analysis of ash melting characteristics was undertaken by changing the inner shield N 2 gas flow rate, assuming a hollow cathode and the ash anode. Results show that heat input intensity characteristics on the ash depend strongly on the gas flow rate through the central hall of the tube cathode arc (TCA). The maximum temperature of the ash surface becomes about 3000–4000 K in a melting state. For a gas flow rate greater than 2 L/min, the shape of the heat input intensity on the ash is annular because of the gas flow. By adjustment of the inner shield gas flow rate, more practical melting of a wider area of the ash can be achieved with the intense annular heat input on the ash.

Design of a high-pressure circulating pump for viscous liquids

The design of a reciprocating dual action piston pump capable of circulating viscous fluids at pressures of up to 34 MPa (5000 psi) and temperatures up to 80 degrees C is described. The piston of this pump is driven by a pair of solenoids energized alternatively by a 12 V direct current power supply controlled by an electronic controller facilitating continuously adjustable flow rates. The body of this seal-less pump is constructed using off-the-shelf parts eliminating the need for custom made parts. Both the electronic controller and the pump can be assembled relatively easily. Pump performance has been evaluated at room temperature (22 degrees C) and atmospheric pressure using liquids with low and moderately high viscosities, such as ethanol and corn oil, respectively. At ambient conditions, the pump delivered continuous flow of ethanol and corn oil at a flow rate of up to 170 and 17 cm3/min, respectively. For pumping viscous fluids comparable to corn oil, an optimum reciprocation frequency was ascertained to maximize flow rate. For low viscosity liquids such as ethanol, a linear relationship between the flow rate and reciprocation frequency was determined up to the maximum reciprocation frequency of the pump. Since its fabrication, the pump has been used in our laboratory for circulating triglycerides in contact with supercritical carbon dioxide at pressures of up to 25 MPa (3600 psi) and temperatures up to 70 degrees C on a daily basis for a total of more than 1500 h of operation functioning trouble free.

Modelling and experimental studies on lipase-catalyzed isoamyl acetate synthesis in a microreactor

A lipase-catalyzed synthesis of isoamyl acetate was studied in a continuously operated pressure-driven microreactor. The esterification of isoamyl alcohol and acetic acid occurred at the interface between n-hexane and an aqueous phase with dissolved lipase B from Candida antarctica. By adjusting flow rates of both phases, a parallel laminar flow with liquid–liquid boundary in the middle of the microchannel could be reestablished and a separation of phases was achieved at the y-shaped exit of the microreactor. Since product remained in the organic phase, this also enabled its continuous separation from the aqueous phase with the enzyme. A three-dimensional mathematical model was developed, considering the velocity profile developed for steady-state conditions between two immiscible fluids. The model contained convection, diffusion, and enzyme reaction terms, where esterification rate was described with a Ping-Pong Bi-Bi mechanism and inhibition by both substrates. Experimental data, which were in good agreement with model simulations, have demonstrated 35% conversion at residence time 36.5 s at 45 °C and at 0.5 M acetic acid and isoamyl alcohol inlet concentrations, which is much faster as in any literature reported so far. According to model simulations, obtained by non-equidistant finite differences numerical solutions of complex non-linear equations system, further microreactor design and process optimization are feasible.