Shaking Frequencies Research Articles

MoS2@Hydrochar nanocomposites with cost-effective fluid turbulent eddies induced piezoelectric catalytic peroxymonosulfate utilization efficiency for water polluted dye degradation

Piezoelectric materials can induce strain due to the fluid turbulent force produced during fluid shaking, which may be used to activate peroxymonosulfate (PMS). In this study, the effective interfacial interaction of few-odd-numbered layered MoS2 nanosheets and hydrochar (HC) nanocomposites as the piezoelectric material was used in a hydrodynamics energy-driven piezoelectric catalytic PMS activation process (piezo-PMS activation process) for Eriochrome Black T dye degradation. The results showed that Black T dye was efficiently degraded with an efficiency of 99.23 % within 15 min and a pseudo-first-order rate constant of 3.10 min−1 in the MoS2@HC-(6.5:3.5)/PMS/Shaking system. To clearly see the influence of hydraulic gradient (G) value, the hydrodynamics energy-driven piezo-PMS activation process for Black T dye degradation was performed at different shaking frequencies. The results indicated an optimal G value of (14.106 s−1) for Black T dye degradation. Notably, the MoS2@HC-(6.5:3.5)/ PMS/Shaking system produced the lowest EE/O value (34.05 kWhm−3 order−1), resulting in energy savings over 127 times of HC and 9 times of MoS2. Furthermore, piezoelectrochemical measurements of MoS2@HC-(6.5:3.5) indicated that these superior performances primarily resulted from the synergistic effects of MoS2 and HC. This led to a stronger piezoelectric response with effective piezo-generated charge separation, which in turn improved the efficiency of producing reactive species. Combining the scavenger test, FT-IR, and zeta potential analysis, we determined that •OH and SO4•− played a major role, while O2•− and 1O2 played a secondary role in Black T dye degradation. The steady-state concentrations of [•OH]ss, and [SO4•−]ss were 14.52 × 10−14 M and 20.00 × 10−14 M, respectively in the fluid turbulent force driven piezo-PMS activation process. Furthermore, a plausible degradation pathway of Black T dye was proposed based on the assessment of carbon number reduction, the mean oxidation number of organic carbon (MOC) and the predicted TOC/color index.

Understanding the flow behavior around marine biofilms

In vitro platforms capable of mimicking the hydrodynamic conditions prevailing in natural aquatic environments have been previously validated and used to predict the fouling behavior on different surfaces. Computational Fluid Dynamics (CFD) has been used to predict the shear forces occurring in these platforms. In general, these predictions are made for the initial stages of biofilm formation, where the amount of biofilm does not affect the flow behavior, enabling the estimation of the shear forces that initial adhering organisms have to withstand. In this work, we go a step further in understanding the flow behavior when a mature biofilm is present in such platforms to better understand the shear rate distribution affecting marine biofilms. Using 3D images obtained by Optical Coherence Tomography, a mesh was produced and used in CFD simulations. Biofilms of two different marine cyanobacteria were developed in agitated microtiter plates incubated at two different shaking frequencies for 7 weeks. The biofilm-flow interactions were characterized in terms of the velocity field and shear rate distribution. Results show that global hydrodynamics imposed by the different shaking frequencies affect biofilm architecture and also that this architecture affects local hydrodynamics, causing a large heterogeneity in the shear rate field. Biofilm cells located in the streamers of the biofilm are subjected to much higher shear values than those located on the bottom of the streamers and this dispersion in shear rate values increases at lower bulk fluid velocities. This heterogeneity in the shear force field may be a contributing factor for the heterogeneous behavior in metabolic activity, growth status, gene expression pattern, and antibiotic resistance often associated with nutrient availability within the biofilm.

Glass beads increase the formation kinetics of beta-lactoglobulin amyloid fibrils

In this study beta-lactoglobulin solutions were processed with glass beads in an orbital shaker at high temperatures and low pH value to identify the effect of mechanical stressing and surfaces on amyloid aggregation kinetics. The information will provide a better understanding on how specific mechanical factors provide a nucleation supporting effect on the assembling of building blocks for a more efficient production of functional amyloid aggregates. Because aggregate morphologies vary at pH 2 (semiflexible) or pH 3.5 (worm-like), examination at both pH values gives information about their specific formation and stability characteristics. Different diameters of glass beads (20–1000 μm), and different shaking frequencies (0 - 280 min−1) were used to vary mechanical stress energy, which was quantified by CFD-DEM simulations. To investigate surface effects, the hydrophobicity and surface roughness of glass beads was altered by modification with stearic acid. Amyloid aggregates and bead surfaces were analysed by ThT-assay, AFM and ATR-FTIR.Hydrophobic beads with high surface roughness affected the aggregation negatively. The use of non-hydrophobic beads increased the formation kinetics of fibrils but not of worm-like aggregates, although, both morphologies had a reduced mean length.

Investigation of the end bearing load in pile group model in dry soil under horizontal excitation

A series of 94 laboratory tests were conducted to measure the response of pile foundation when subjected to dynamic loads. Eight tests were conducted on single pile in dry soil at relative density 30 % (loose) and 50 % (medium); 66 tests on group of piles with different spacings and patterns. All tests were carried out under operating frequencies 0.5, 1 and 2 Hz under horizontal shaking. All tests were achieved with one embedment ratio (L/d = 30). These tests were grouped in three different numbers of piles; 2 piles in row and line patterns, 3 piles and 4 piles; and three pile spacing ratios (s/d = 3, 4 and 5). The results of dry soil indicating the mechanism of dynamic response of piles and soil subjected to dynamic horizontal shaking include the variation and distribution of acceleration with time in different states of soil in addition to the vertical and horizontal displacements, end-bearing load, peak acceleration and the peak velocity of foundation. It was concluded that for a dry soil bed, the acceleration amplitudes increase with frequency for both soil relative densities (loose and medium) and different pile patterns (number; single or group and different spacing ratios s/d). The maximum acceleration in the foundation is lower than in the soil bed for all operating shaking frequencies, pile spacing ratios and soil states. The decreasing of the maximum acceleration recorded in the foundation as compared to that in the soil bed is between 10-100 % for loose and medium state of soil, and the decrease in loose state is more than in medium state. This means that there is damping effect or attenuation of vibration waves. The amplitudes of recorded acceleration in the pile cap are much higher than in the soil bed for single pile and pile group with different pile spacing ratios, also these amplitudes are increasing with increase of shaking frequency and relative density of the soil.

In-situ identification of shaking frequency for adaptive vibratory fruit harvesting

The improvement of the fruit removal efficiency is important in vibratory fruit harvesting. Most relevant research has focused on the detection of dynamic parameters of the tree system by conducting experiments or simulations. The present study proposes a method of identifying multiple natural frequencies of a fruit tree in-situ during vibratory harvesting. An intelligent shaker system consisting of an eccentric shaker with adjustable speed and an acceleration signal acquisition analyzer is developed. A frequency sweeping experiment using the intelligent shaker system is carried out to measure natural frequencies by searching for extreme values of the acceleration signals. Additionally, a testing experiment for measuring acceleration responses at different shaking frequencies is performed to obtain the optimal shaking frequencies. The experiments show that the natural frequencies could be obtained effectively by the frequency sweeping experiment in-situ, and the identified natural frequencies of different branches are found to be different. All results indicate that the identified natural frequencies using the proposed method can be regarded as the optimal shaking frequencies for adaptive vibratory fruit harvesting, and that it is necessary to detect the natural frequency of each large branch of a tree during vibratory fruit harvesting.

A neutron tomography study: probing the spontaneous crystallization of randomly packed granular assemblies

We study the spontaneous crystallization of an assembly of highly monodisperse steel spheres under shaking, as it evolves from localized icosahedral ordering towards a packing reaching crystalline ordering. Towards this end, real space neutron tomography measurements on the granular assembly are carried out, as it is systematically subjected to a variation of frequency and amplitude. As expected, we see a presence of localized icosahedral ordering in the disordered initial state (packing fraction ≈ 0.62). As the frequency is increased for both the shaking amplitudes (0.2 and 0.6 mm) studied here, there is a rise in packing fraction, accompanied by an evolution to crystallinity. The extent of crystallinity is found to depend on both the amplitude and frequency of shaking. We find that the icosahedral ordering remains localized and its extent does not grow significantly, while the crystalline ordering grows rapidly as an ordering transition point is approached. In the ordered state, crystalline clusters of both face centered cubic (FCC) and hexagonal close packed (HCP) types are identified, the latter of which grows from stacking faults. Our study shows that an earlier domination of FCC gives way to HCP ordering at higher shaking frequencies, suggesting that despite their coexistence, there is a subtle dynamical competition at play. This competition depends on both shaking amplitude and frequency, as our results as well as those of earlier theoretical simulations demonstrate. It is likely that this involves the very small free energy difference between the two structures.

Evaluation of alternatives to cautery disbudding of dairy goat kids using behavioural measures of post-treatment pain

Alternatives to cautery disbudding (caustic paste and cryosurgical disbudding, and clove oil injection) were evaluated using behavioural measures of post-treatment pain in dairy goat kids. Fifty Saanen doe kids were randomly assigned to one of five treatments (n = 10/treatment): (i) cautery (CAUT), (ii) caustic paste (CASP), (iii) cryosurgical (liquid nitrogen; CRYO), (iv) clove oil (CLOV) or (v) sham disbudding (SHAM). Head and body shaking, head scratching, self-grooming and feeding were video-recorded for 24 h pre- and post-treatment. Frequencies of each behaviour were measured over 1 h pre- and post-treatment, as were the durations of head scratching, self-grooming and feeding. Accelerometers measured lying bouts and lying time for 24 h pre- and post-treatment. CASP kids displayed more head shakes (73.7 vs. 38.5 ± 11.06 No./h) and head scratches (35.1 vs. 13.1 ± 6.62 No./h) but less self-grooming (1.3 vs. 10.8 ± 2.00 No./h) and body shakes (1.6 vs. 4.3 ± 0.88 No./h), and shorter feeding durations (1.0 vs. 2.4 ± 0.61 min/h), than CAUT kids (P ≤ 0.05). CRYO kids performed more head scratches (28.8 vs. 13.1 ± 6.62 No./h) but less body shakes (2.1 vs. 4.3 ± 0.88 No./h), and spent less time lying (15.8 vs. 17.0 ± 0.32 h/24 h) but with more bouts (32.8 vs. 26.3 ± 2.25 No./24 h) than CAUT kids (P ≤ 0.05). Head shaking, scratching and self-grooming frequencies in CLOV kids (34.0 ± 11.06, 16.7 ± 6.62 and 12.6 ± 2.00 No./h, respectively) were no different to those for CAUT kids (P > 0.10). CLOV kids spent less time lying (16.1 vs. 17.0 ± 0.32 h/24 h) (but with more bouts [33.4 vs. 26.3 ± 2.25 No./24 h]) than CAUT kids (P ≤ 0.05), which suggests less pain, as SHAM kids spent less time lying than CAUT kids (16.2 vs. 17.0 ± 0.32 h/24 h; P ≤ 0.05). Our results suggest that caustic paste and cryosurgical disbudding were more painful than cautery disbudding and may not be suitable alternatives for goat kids. During the first hour after treatment, clove oil injection appeared to cause less pain than caustic paste or cryosurgical disbudding, but a similar behavioural response as cautery disbudding. Clove oil injection may show promise as an alternative to cautery disbudding. However, future research should first evaluate the efficacy clove oil in preventing horn growth; if effective, further research on the long-term effects of clove oil on goat welfare should be conducted.

Effect of isoflurane alone or in combination with meloxicam on the behavior and physiology of goat kids following cautery disbudding

Cautery disbudding of goat kids is painful, but may be alleviated with pain mitigation. We therefore evaluated the effect of administering general anesthesia (isoflurane) or a nonsteroidal anti-inflammatory drug (meloxicam) on goat kid behavior and physiology following cautery disbudding. Trial 1 (n = 12/treatment) evaluated behavioral responses in 72 female Saanen dairy goat kids (mean ± standard error of the mean; 3.9 ± 0.15 d old) and trial 2 (n = 10/treatment) evaluated physiological responses in 60 female Saanen dairy goat kids (4.3 ± 0.14 d old). Goat kids were randomly assigned to 1 of 6 treatment groups that were either (1) sham-handled only (simulated disbudding; SHAM) or disbudded with (2) no pain relief (CAUT), (3) isoflurane gas (ISO), (4) isoflurane and s.c. meloxicam combined (ISO+MEL), (5) meloxicam s.c. (0.5 mg/kg of body weight; I-MEL), or (6) oral meloxicam (0.2 mg/kg of body weight; O-MEL). Head shaking, head scratching, self-grooming, feeding, and body shaking were continuously video recorded for 24 h pre- and post-treatment. Lying behavior was recorded continuously for 24 h pre- and post-treatment using accelerometers. Plasma cortisol, glucose, and lactate concentrations were measured from blood samples collected immediately before treatment (baseline) and at 15, 60, and 120 min post-treatment. Body temperature was measured immediately after blood sampling at all blood sampling time points. Head shaking and body shaking frequencies were 50% higher in CAUT than SHAM kids 5 min post-treatment; ISO+MEL and ISO kids performed 25% less body shakes than CAUT kids. Head scratching durations 1 h post-treatment were higher in CAUT than SHAM kids, whereas O-MEL were similar to SHAM kids from 2 h post-treatment. Self-grooming, feeding, and lying did not differ between groups. Cortisol concentrations were higher in CAUT than SHAM kids (156.4 ± 26.41 and 104.1 ± 26.41 nmol/L, respectively), whereas ISO+MEL and ISO kids (88.3 ± 26.41 and 113.2 ± 26.41 nmol/L, respectively) had lower cortisol concentrations than CAUT kids over the 2-h sampling period. Moreover, O-MEL and I-MEL kids (163.0 ± 26.41 and 130.9 ± 26.41 nmol/L, respectively) had similar cortisol concentrations to CAUT kids. We found no evidence that plasma glucose and lactate concentrations or body temperature were affected by treatment. The administration of isoflurane, with or without meloxicam, appeared to reduce pain associated with cautery disbudding.

CFD studies on hydrodynamic characteristics of shaking bioreactors with wide conical bottom

AbstractBACKGROUNDDisposable bioreactors based on orbital shaking technology have been employed extensively for mammalian cell culture, which proved to be less expensive and more flexible compared with mechanical stirred‐tank bioreactors. However, it is difficult to evaluate flow parameters quantitatively since the flow field in bioreactors is complicated.RESULTSThe flow characteristics of shaking bioreactors with a wide conical bottom under different shaking frequencies and filling volumes were simulated by CFD method. The validity of the simulation model was investigated by comparing simulated free‐surface shapes and liquid levels with experimental results, and the CFD simulation results were shown to be in good agreement with experiment data.CONCLUSIONThe results show that: turbulence parameters (k and ϵ) increase with shaking frequency, while they decrease with filling volume proportionally; shaking frequency has no significant effect on specific gas–liquid interface area (a) but a positive effect on mass transfer coefficient (kL); the volumetric mass transfer coefficient (kLa) decreases with filling volume because of the combined effect of a and kL; the average shear strain rate (SSR) increases significantly with frequency, while it decreases with filling volume. Results also show that the SSR of shaking bioreactors is mainly distributed in low range which is acceptable for cell cultivation. © 2017 Society of Chemical Industry

Shaking table test on dynamic behaviours of tropical residual soils in Malaysia

Studies on dynamic behaviours of tropical residual soils are still very limited in the current available literature. This paper mainly aims to investigate the dynamic properties (shear modulus and damping ratio) of two selected tropical residual soils (sandy silt and silty sand) in Malaysia under different overburden pressures. A series of shaking table tests were performed by applying 13 combinations of input shaking frequencies and lateral displacements. The measured acceleration data were subjected to baseline corrections and filtering processes. The results showed that the shaking table setup was capable of facilitating a considerably large strain level of deformation. The shear modulus increases proportionally with the confining pressure. Under the same confining pressure, shear modulus attenuates with the increase of strain amplitude. The shear modulus of sandy silt was consistently larger than that of silty sand. The damping ratios of the tested soils approximately range between 1% and 12%.

Stability of a Bose-Einstein condensate in a driven optical lattice: Crossover between weak and tight transverse confinement

We explore the effect of transverse confinement on the stability of a Bose-Einstein condensate (BEC) loaded in a shaken one-dimensional or two-dimensional square lattice. We calculate the decay rate from two-particle collisions. We predict that if the transverse confinement exceeds a critical value, then, for appropriate shaking frequencies, the condensate is stable against scattering into transverse directions.

Shaken flasks by resonant acoustic mixing versus orbital mixing: Mass transfer coefficient kLa characterization and Escherichia coli cultures comparison

Shaken flasks are widely applied in bioprocesses due to their flexibility and ease of operation. Resonant acoustic mixing (RAM) enables non-contact mixing by the application of low frequency acoustic energy, and is proposed as an alternative to solve oxygen limitations in orbital mixing (OM). The aim of this study is to experimentally determine empirical kLa correlations for RAM and compare it with OM by its measurement at different shaking frequencies, nominal flask volumes, and filling volumes. The maximum kLa here obtained were 131.3±5.1h−1 for OM and 435.4±11.7h−1 for RAM. Empirical correlations were validated for kLa as a function of shaking frequency and superficial area/filling volume ratio and rendered adequate values for the adjusted R2 with an accuracy of ±30%. Further, we compared the Escherichia coli kinetics of growth, glucose uptake, dissolved oxygen tension (DOT), and organic acids production in RAM and OM at two equivalent initial kLa. Similar E. coli kinetics were observed at an initial kLa of 46h−1, but not at 92h−1 where differences in DOT and culture parameters were found, mainly in growth rate and biomass yield on glucose, which is the result of different oxygen transfer rates due to the increased gas pressures in RAM.

The Shaking Frequency Effect in the Dynamics of a Model Sandy Layer

Experimental results showing the frequency-dependent behavior of both dry and saturated sandy layers subjected to a horizontal excitation on a shaking table are presented. The largest settlements of a dry layer correspond to two specific frequencies. In the case of a saturated layer, there is a single peak frequency corresponding to the largest depth of sinking of a measuring plate in liquefied subsoil. The first peak of settlements coincides with the single peak of sinking in liquefied soil. The eigenfrequencies of the layer were estimated. A modification of the compaction law was proposed for low shaking frequencies.

The Millikan shaking experiments and high-frequency seismic wave propagation in Southern California

In order to study high-frequency seismic wave propagation, seismic wavefields generated by resonant-shaking experiments of the Millikan Library, on the campus of California Institute Technology (Pasadena, California, USA), were analysed. Because the resonant shaking frequencies are 1.12 Hz (the east–west direction) and 1.64 Hz (the north–south direction), this active-source experiment can provide opportunities for studying high-frequency seismic wave propagation in Southern California. Because they are very narrow frequency band data, the analyses must be quite different from ordinary time-domain analyses. We show, theoretically, that the signals must be dominated by surface waves. Adopting this surface wave assumption, we proceed to make two separate analyses, one on spectral amplitude and the other on phase. We present a new method to derive group velocity from phase based on the cross correlations between the station in the Millikan Library (MIK) and stations in the regional network. Our results support that an active-source experiment by resonant shaking of a building is a feasible approach for high-frequency seismic wave studies.

96-well microtiter plates for biofouling simulation in biomedical settings

Microtiter plates with 96 wells are routinely used in biofilm research mainly because they enable high-throughput assays. These platforms are used in a variety of conditions ranging from static to dynamic operation using different shaking frequencies and orbital diameters. The main goals of this work were to assess the influence of nutrient concentration and flow conditions on biofilm formation by Escherichia coli in microtiter plates and to define the operational conditions to be used in order to simulate relevant biomedical scenarios. Assays were performed in static mode and in incubators with distinct orbital diameters using different concentrations of glucose, peptone and yeast extract. Computational fluid dynamics (CFD) was used to simulate the flow inside the wells for shaking frequencies ranging from 50 to 200 rpm and orbital diameters from 25 to 100 mm. Higher glucose concentrations enhanced adhesion of E. coli in the first 24 h, but variation in peptone and yeast extract concentration had no significant impact on biofilm formation. Numerical simulations indicate that 96-well microtiter plates can be used to simulate a variety of biomedical scenarios if the operating conditions are carefully set.

In Vitro Study of Cerebrospinal Fluid Dynamics in a Shaken Basal Cistern after Experimental Subarachnoid Hemorrhage

BackgroundCerebral arterial vasospasm leads to delayed cerebral ischemia and constitutes the major delayed complication following aneurysmal subarachnoid hemorrhage. Cerebral vasospasm can be reduced by increased blood clearance from the subarachnoid space. Clinical pilot studies allow the hypothesis that the clearance of subarachnoid blood is facilitated by means of head shaking. A major obstacle for meaningful clinical studies is the lack of data on appropriate parameters of head shaking. Our in vitro study aims to provide these essential parameters.Methodology/Principal FindingsA model of the basal cerebral cistern was derived from human magnetic resonance imaging data. Subarachnoid hemorrhage was simulated by addition of dyed experimental blood to transparent experimental cerebrospinal fluid (CSF) filling the model of the basal cerebral cistern. Effects of various head positions and head motion settings (shaking angle amplitudes and shaking frequencies) on blood clearance were investigated using the quantitative dye washout method. Blood washout can be divided into two phases: Blood/CSF mixing and clearance. The major effect of shaking consists in better mixing of blood and CSF thereby increasing clearance rate. Without shaking, blood/CSF mixing and blood clearance in the basal cerebral cistern are hampered by differences in density and viscosity of blood and CSF. Blood clearance increases with decreased shaking frequency and with increased shaking angle amplitude. Head shaking facilitates clearance by varying the direction of gravitational force.Conclusions/SignificanceFrom this in vitro study can be inferred that patient or head shaking with large shaking angles at low frequency is a promising therapeutic strategy to increase blood clearance from the subarachnoid space.

Development of a four electrode sensor array for impedance spectroscopy in high content screenings of fermentation processes

There is an increasing demand of efficient screening techniques with high information output in biotechnological research and pharmaceutical industry. One effective method of monitoring biological cultures is the electrical impedance spectroscopy. In this work an integrated sensor array consisting of a four electrode sensor design on polyimide flextape in 96 well microtiter plates (MTPs) is characterised. FEM-simulations and measurements of different electrode designs are compared and show good agreement. Circular shaped electrodes are identified as optimal designs with stable signals even at high shaking frequencies. These high frequencies of at least 1000 rpm are necessary to provide high oxygen transfer in microbial cultivations. Fermentations in the MTPs were carried out with Hansenula polymorpha and Escherichia coli in filling volumes of 100–200 μL. The measured data of conductance and capacitance are shown and discussed in comparison to a reference signal obtained by a BioLector measurement system (m2p-labs GmbH, Germany). Biological phenomena, e.g. the change of carbon source of E. coli from glycerol to proteins can clearly be identified by analysing the measured capacitance and conductance during the fermentation.

Mechanical Cleaning of Oil Spills in Seawater Using Circular Conduits

Treatment of the crude oil pollution in seawater has attracted global attention during the last two decades. This study was undertaken using circular conduits as a mechanical means to clean oil spills in seawater under different conditions of temperature, oil gravity, shaking frequency, conduit diameter, and initial thickness of oil layer. An experimental model was designed and built to achieve the study. It consists of shaking water bath (to represent sea waves) fitted with temperature controller and glass tubes of different inside diameters of 0.3 cm, 0.5 cm, and 0.7 cm. Three crude oils of different oil gravity of 35°API, 38°API, and 47°API were investigated under different shaking frequencies of 20, 40, and 60 stroke/minute with different tube diameters. The results proved that application of mechanical cleaning of oil spills using circular conduits is a practical technique. The cleaning of black oil spills is more efficient than one of volatile oil. Furthermore, the results indicated that the increase of shaking frequency and/or water temperature provide(s) faster cleaning of oil spills while temperature increase recovers the maximum oil.

Oxygen transfer phenomena in 48‐well microtiter plates: Determination by optical monitoring of sulfite oxidation and verification by real‐time measurement during microbial growth

Oxygen limitation is one of the most frequent problems associated with the application of shaking bioreactors. The gas-liquid oxygen transfer properties of shaken 48-well microtiter plates (MTPs) were analyzed at different filling volumes, shaking diameters, and shaking frequencies. On the one hand, an optical method based on sulfite oxidation was used as a chemical model system to determine the maximum oxygen transfer capacity (OTR(max)). On the other hand, the Respiration Activity Monitoring System (RAMOS) was applied for online measurement of the oxygen transfer rate (OTR) during growth of the methylotropic yeast Hansenula polymorpha. A proportionality constant between the OTR(max) of the biological system and the OTR(max) of the chemical system were indicated from these data, offering the possibility to transform the whole set of chemical data to biologically relevant conditions. The results exposed "out of phase" shaking conditions at a shaking diameter of 1 mm, which were confirmed by theoretical consideration with the phase number (Ph). At larger shaking diameters (2-50 mm) the oxygen transfer rate in MTPs shaken at high frequencies reached values of up to 0.28 mol/L/h, corresponding to a volumetric mass transfer coefficient (k(L)a) of 1,600 1/h. The specific mass transfer area (a) increases exponentially with the shaking frequency up to values of 2,400 1/m. On the contrary, the mass transfer coefficient (k(L)) is constant at a level of about 0.15 m/h over a wide range of shaking frequencies and shaking diameters. However, at high shaking frequencies, when the complete liquid volume forms a thin film on the cylindric wall of the well, the mass transfer coefficient (k(L)) increases linearly to values of up to 0.76 m/h. Essentially, the present investigation demonstrates that the 48-well plate outperforms the 96-well MTP and shake flasks at widely used operating conditions with respect to oxygen supply. The 48-well plates emerge, therefore, as an excellent alternative for microbial cultivation and expression studies combining the advantages of both the high-throughput 96-well MTP and the classical shaken Erlenmeyer flask.

Vibration of an adhered microbeam under a periodically shaking electrical force

The vibration analysis of an adhered S-shaped microbeam under alternating sinusoidal voltage is presented. The shaking force is the electrical force due to the sinusoidal voltage. During vibration, both the microbeam deflection and the adhesion length keep changing. The microbeam deflection and adhesion length are numerically determined by the iteration method. As the adhesion length keeps changing, the domain of the equation of motion for the microbeam (unadhered part) changes correspondingly, which results in changes of the structure natural frequencies. For this reason, the system can never reach a steady state. The transient behaviors of the microbeam under different shaking frequencies are compared. We deliberately choose the initial conditions to compare our dynamic results with the existing static theory. The paper also analyzes the changing behavior of adhesion length during vibration and an asymmetric pattern of adhesion length change is revealed, which may be used to guide the dynamic de-adhering process. The abnormal behavior of the adhered microbeam vibrating at almost the same frequency under two quite different shaking frequencies is also shown. The Galerkin method is used to discretize the equation of motion and its convergence study is also presented. The model is only applicable in the case that the peel number is equal to 1. Some other model limitations are also discussed.