Flask Wall Research Articles

Electron Scattering in Conventional Cell Flask Experiments and Dose Distribution Dependency

Electron beam therapy (EBT) is commonly used for treating superficial and subdermal tumors. Previous cellular radiosensitivity research using EBT may be underestimating the contribution from flask wall scattering and the corresponding dose distribution. Single cell suspensions of Chinese hamster ovary (CHO) cells were plated on flasks and irradiated with 3, 4, 7, 9, and 18 MeV energy electron beams from two different institutions, and the spatial locations of surviving colonies were recorded. Gafchromic film dosimetry and Monte Carlo simulations were carried out to determine the spatial electron scattering contribution from the flask walls. Low electron irradiation resulted in an uneven surviving colony distribution concentrated near the periphery of the flasks, while spatial colony formation was statistically uniform at energies above 7 MeV. Our data demonstrates that without proper dosimetric corrections, studies using low energy electrons can lead to misinterpretations of energy dependent cellular radiosensitivity in culture vessels, and radiotherapeutic applications.

Liquid films on shake flask walls explain increasing maximum oxygen transfer capacities with elevating viscosity

In biotechnological screening and production, oxygen supply is a crucial parameter. Even though oxygen transfer is well documented for viscous cultivations in stirred tanks, little is known about the gas/liquid oxygen transfer in shake flask cultures that become increasingly viscous during cultivation. Especially the oxygen transfer into the liquid film, adhering on the shake flask wall, has not yet been described for such cultivations. In this study, the oxygen transfer of chemical and microbial model experiments was measured and the suitability of the widely applied film theory of Higbie was studied. With numerical simulations of Fick's law of diffusion, it was demonstrated that Higbie's film theory does not apply for cultivations which occur at viscosities up to 10 mPa s. For the first time, it was experimentally shown that the maximum oxygen transfer capacity OTRmax increases in shake flasks when viscosity is increased from 1 to 10 mPa s, leading to an improved oxygen supply for microorganisms. Additionally, the OTRmax does not significantly undermatch the OTRmax at waterlike viscosities, even at elevated viscosities of up to 80 mPa s. In this range, a shake flask is a somehow self-regulating system with respect to oxygen supply. This is in contrary to stirred tanks, where the oxygen supply is steadily reduced to only 5% at 80 mPa s. Since, the liquid film formation at shake flask walls inherently promotes the oxygen supply at moderate and at elevated viscosities, these results have significant implications for scale-up.

Calculating liquid distribution in shake flasks on rotary shakers at waterlike viscosities

Screening projects in biotechnological industry performed in shake flasks risk unwanted development if not failure, when operating conditions are not suitable. Limited knowledge, however, is available for the mechanistical design of operating conditions in this type of bioreactor. The fundamental engineering variables are influenced by the geometry of the rotating bulk liquid: for momentum transfer, the contact area between the liquid and the flask inner wall is the friction area, and for mass transfer, the wetted wall exposed to the surrounding air is the mass exchange area. To assess the geometry of the rotating bulk liquid moving inside a shaken Erlenmeyer flask, with respect to the mentioned important engineering variables mentioned, a mechanistical model for the liquid distribution in shake flasks is described in this work. The model is based on a superposition of two individual movements: a circular translatoric movement and a rotation of the flask counteracting the first motion to keep the shake flasks’ spatial orientation. If the effect of viscosity is neglected, the liquid distribution results in an exactly symmetrical paraboloid. A comparison of the calculated liquid distribution with photographs shows very good qualitative agreement of the real liquid distributions by the model equations. Quantitative agreement has been demonstrated by comparison of the liquid height. Furthermore, model equations are presented for the calculation of the contact area between the liquid and the flask wall. This may eventually lead to a prediction of the volumetric power consumption. Similarly, the calculation of the mass transfer area (i.e. liquid surface area and wetted flask wall) is presented.

Active and Passive Mechanisms Drive Secretory Granule Biogenesis during Differentiation of the Intestinal Parasite Giardia lamblia

The parasitic protozoan Giardia lamblia undergoes important changes to survive outside the intestine of its host by differentiating into infective cysts. During encystation, three cyst wall proteins (CWPs) are specifically expressed and concentrated within encystation-specific secretory vesicles (ESVs). ESVs are electron-dense secretory granules that transport CWPs before exocytosis and extracellular polymerization into a rigid cyst wall. Because secretory granules form at the trans-Golgi in higher eukaryotes and because Giardia lacks an identifiable Golgi apparatus, the aim of this work was to investigate the molecular basis of secretory granule formation in Giardia by examining the role of CWPs in this process. Although CWP1, CWP2, and CWP3 are structurally similar in their 26-kDa leucine-rich overlapping region, CWP2 is distinguished by the presence of a 13-kDa C-terminal basic extension. In non-encysting trophozoites, expression of different CWP chimeras showed that the CWP2 basic extension is necessary for biogenesis of ESVs, which occurs in a compartment derived from the endoplasmic reticulum. Nevertheless, the CWP2 basic extension per se is insufficient to trigger ESV formation, indicating that other domains in CWPs are also required. We found that CWP2 is a key regulator of ESV formation by acting as an aggregation factor for CWP1 and CWP3 through interactions mediated by its conserved region. CWP2 also acts as a ligand for sorting via its C-terminal basic extension. These findings show that granule biogenesis requires complex interactions among granule components and membrane receptors.

Regular and chaotic dynamics of a spherical bubble

The problem of the translational motion and oscillations of the radius of a spherical gas bubble in a spherical flask filled with a weakly compressible liquid is considered when there is forced radial perturbation of the flask wall. The translational motion is that of the bubble under the action of an acoustic field when there is viscous drag and the effect of added mass. A system of differential equations is proposed which describes the combined oscillations of the radius and the translational motion of the bubble. This system includes an ordinary differential equation of the Herring-Flinn-Gilmore type which describes the evolution of the radius of the bubble. Bifurcation diagrams are constructed for the radius of the bubble, which reveal a repeating structure of the bifurcation set within the limits of the harmonic resonances of the system. The dynamic characteristics of the bubble for different equilibrium radii are investigated numerically in connection with the analysis of the stability of its position in space.

Advances in understanding and modeling the gas–liquid mass transfer in shake flasks

The gas–liquid mass transfer in 250 ml shake flasks has previously been sucessfully modelled on basis of Higbie’s penetration theory. The current contribution presents advances in understanding and modelling the gas–liquid mass transfer in shake flasks at waterlike liquid viscosity in flask sizes between 50 and 1000 ml. An experimental investigation of the maximum gas–liquid mass transfer capacity OTR max using the sodium sulphite system was extended to relative filling volumes of 4–16%, shaking diameters of 1.25, 2.5, 5, 7, 10 cm and shaking frequencies of 50–500 rpm for the above flask sizes. Simultaneously, the previous model of the gas–liquid mass transfer was extended to a “two sub-reactor model” to account for different mechanisms of mass transfer in the liquid film on the flask wall and the bulk of the liquid rotating within the flask. The shake flask is for the first time considered to be a two-reactor system consisting of a stirred tank reactor (bulk liquid) and a film reactor (film on flask wall and base). The mass transfer into the film on the flask wall and base at “in-phase” operating conditions is described by Higbie’s penetration theory. Two different mass transfer theories were applied to successfully describe the mass transfer into the bulk liquid: a model by Kawase and Moo-Young and a model by Gnielinski. The agreement between the new modelling approach, which requires absolutely no fitting parameters and the experimental is within ±30%. The applicability of the models to a biological system was shown using a Pichia pastoris culture. This is particularly notable since geometrically non-similar liquid distributions in very different sizes of shaking flasks are covered. A comparable description of the gas–liquid mass transfer in bubble aerated reactors like stirred tanks is absolutely out of reach. A spatially- and time-resolved consideration of the mass transfer in the liquid film on the flask wall and base has shown that the validity of Higbie’s theory sensitively depends on the film thickness and contact time.

Characterisation of the gas–liquid mass transfer in shaking bioreactors

The maximum gas–liquid mass transfer capacity of 250 ml shaking flasks on orbital shaking machines has been experimentally investigated using the sulphite oxidation method under variation of the shaking frequency, shaking diameter, filling volume and viscosity of the medium. The distribution of the liquid within the flask has been modelled by the intersection between the rotational hyperboloid of the liquid and the inner wall of the shaking flask. This model allows for the calculation of the specific exchange area ( a), the mass transfer coefficient ( k L) and the maximum oxygen transfer capacity (OTR max) for given operating conditions and requires no fitting parameters. The model agrees well with the experimental results. It was furthermore shown that the liquid film on the flask wall contributes significantly to the specific mass transfer area ( a) and to the oxygen transfer rate (OTR).

On the forced oscillations of a small gas bubble in a spherical liquid-filled flask

A spherically-symmetric problem is considered in which a small gas bubble at the centre of a spherical flask filled with a compressible liquid is excited by small radial displacements of the flask wall. The bubble may be compressed, expanded and made to undergo periodic radial oscillations. Two asymptotic solutions have been found for the low-Mach-number stage. The first one is an asymptotic solution for the field far from the bubble, and it corresponds to the linear wave equation. The second one is an asymptotic solution for the field near the bubble, which corresponds to the Rayleigh–Plesset equation for an incompressible fluid. For the analytical solution of the low-Mach-number regime, matching of these asymptotic solutions is done, yielding a generalization of the Rayleigh–Plesset equation. This generalization takes into account liquid compressibility and includes ordinary differential equations (one of which is similar to the well-known Herring equation) and a difference equation with both lagging and leading time. These asymptotic solutions are used as boundary conditions for bubble implosion using numerical codes which are based on partial differential conservation equations. Both inverse and direct problems are considered in this study. The inverse problem is when the bubble radial motion is given and the evolution of the flask wall pressure and velocity is to be calculated. The inverse solution is important if one is to achieve superhigh gas temperatures using non-periodic forcing (Nigmatulin et al. 1996). In contrast, the direct problem is when the evolution of the flask wall pressure or velocity is given, and one wants to calculate the evolution of the bubble radius. Linear and nonlinear periodic bubble oscillations are analysed analytically. Nonlinear resonant and near-resonant periodic solutions for the bubble non-harmonic oscillations, which are excited by harmonic pressure oscillations on the flask wall, are obtained. The applicability of this approach bubble oscillations in experiments on single-bubble sonoluminescence is discussed.

Forced oscillations of a gas bubble in a spherical volume of a compressible liquid

A spherically symmetric problem of oscillations of a single gas bubble at the center of a spherical flask filled with a compressible liquid under the action of pressure oscillations on the flask wall is considered. A system of differential-difference equations is obtained that extends the Rayleigh-Plesset equation to the case of a compressible liquid and takes into account the pressure-wave reflection from the bubble and the flask wall. A linear analysis of solutions of this system of equations is performed for the case of harmonic oscillations of the bubble. Nonlinear resonance oscillations and nearly resonance nonharmonic oscillations of the bubble caused by harmonic pressure oscillations on the flask wall are analyzed.

On the theory of supercompression of a gas bubble in a liquid-filled flask

The spherically symmetric problem of the oscillations of a gas bubble in the center of a spherical flask filled with a compressible liquid that is excited by pressure oscillations on the flask wall is considered. A generalization of the Rayleigh–Plesset equation for a compressible liquid is given in the form of two ordinary difference-differential equations that take into account the pressure waves that are reflected from the bubble and those that are incident on the bubble from the flask wall. The initial value problem for the initiation of bubble oscillations due to flask wall excitation and for the evolution of these oscillations is considered. Linear and nonlinear periodic bubble oscillations are analyzed analytically. Nonlinear resonant and near-resonant solutions for the bubble nonharmonic oscillations, which are excited by harmonic pressure oscillations on the flask wall, are obtained. The influence of heat transfer phenomena on the bubble oscillations is analyzed.

THE RESONANT SUPERCOMPRESSION AND SONOLUMINESCENCE OF A GAS BUBBLE IN A LIQUID-FILLED FLASK

The spherically-symmetric problem of the oscillations of a small gas bubble in the center of a spherical flask filled with a compressible liquid that is excited by small radial displacement of the flask's wall is considered. Two asymptotic solutions have been found for the low Mach number stage. The first one is an asymptotic solution for the field far from the bubble, and it corresponds to linear wave theory. The second one is an asymptotic solution for the boundary layer near the bubble and it corresponds to an incompressible fluid. In the analytical solution of the low Mach number step matching of these asymptotic solutions is done. A generalization of the Rayleigh = Plesset equation for a compressible liquid is given in the form of two ordinary difference-differential equations that take into account the pressure waves which are reflecting from the bubble and those that are incident on the bubble from the flask wall. The initial value problem for the initiation of the bubble oscillations due to flask wall excitation and for the evolution of these oscillations was considered. Linear and non-linear periodic bubble oscillations were analyzed analytically, and resonant frequencies were identified. Non-linear resonant and near-resonant solutions for the bubble's non-harmonic oscillations, which are excited by harmonic pressure or velocity oscillations on the flask wall, are obtained.

Weak oscillations of a gas bubble in a spherical volume of compressible liquid

The following spherically symmetric problem is considered: a single gas bubble at the centre of a spherical flask filled with a compressible liquid is oscillating in response to forced radial excitation of the flask walls. In the long-wave approximation at low Mach numbers, one obtains a system of differential-difference equations generalizing the Rayleigh-Lamb-Plesseth equation. This system takes into account the compressibility of the liquid and is suitable for describing both free and forced oscillations of the bubble. It includes an ordinary differential equation analogous to the Herring-Flinn-Gilmore equation describing the evolution of the bubble radius, and a delay equation relating the pressure at the flask walls to the variation of the bubble radius. The solutions of this system of differential-difference equations are analysed in the linear approximation and numerical analysis is used to study various modes of weak but non-linear oscillations of the bubble, for different laws governing the variation of the pressure or velocity of the liquid at the flask wall. These solutions are compared with numerical solutions of the complete system of partial differential equations for the radial motion of the compressible liquid around the bubble.

ESTABLISHMENT OF HUMAN BLADDER-CANCER CELL-LINE (HAMT-1) AND LONG-TERM SUBCULTURE IN NUDE-MICE

Human bladder cancer cell line (HAMT-1) was established from a transitional cell carcinoma of the bladder (T4N3M0, grade 3) of a 61-year-old male by using a serum-free medium. HAMT-1 cells in serum-free medium were non-adhesive to the flask wall or to other cells. The cells grew in attached form by the addition of fetal calf serum. Heterotransplantation of HAMT-1 cells into nude mice and the long-term subculture were successful. Tumor bearing nude mice showed an elevated serum tissue polypeptide antigen as in the patient.

飽和食塩水浮遊法の改良による室内塵中のダニ検出について

An improved floatation method with saturated sodium chloride solution for isolation of house dust mites was described. Dust samples were collected from the houses of asthma patients by a vaccuum cleaner. A portion of the fine dust that passed through a 36-mesh sieve and retained on a 200-mesh sieve was suspended in saturated sodium chloride solution in a 100-ml flask (0.1g fine dust/flask) for 30min. Although mites have been isolated only from the upper fraction of the floatation solution in the conventional method, the recovery rates were low (31.7% in average) and varied by samples. Hence, in our method the mites were isolated from the whole floatation solution, except the residue fraction, as well as washed from the flask wall (whole isolation method). The recovery rates rose to 92.3% in average. Isolating mites from the residue fraction was not practical as it is a time-consuming procedure. The isolation efficiency of the method was compared with that of floatation and centrifugation methods by using two mite-culture media prepared in the laboratory. One medium was a mixture of powdered rat food pellets and yeast extract (1 : 1,Medium A); the other, a mixture of Medium A and fine dust (1 : 10,Medium B). D. farinae had been reared on these media for 2 months. The recovery rate from Medium A was 89.4% in average by the whole isolation method. The rate did not increase by soaking the medium in 80% ethanol solution for 4hr. The accumulative recovery rates of 3-time centrifugations were almost same as those of the whole isolation method. The whole isolation method was considered to be more efficient, simpler and cheeper than any other method so far described for isolation of house dust mites.

Modelling Simplifications in Flask Shielding

AbstractFlask shielding calculations are required to predict the dose rates external to the flask package. The flask package must ensure that the radiation levels are within the regulatory limits specified for the transportation of radioactive material. Modelling the geometrical heterogeneities in the flask design, such as neutron moderators embedded in the flask wall are often simplified for rapid solution/sensitivity studies for flask shielding problems. Examples of modelling simplifications used in flask shielding studies are described. The results presented show that the simplified approach may, in certain cases, under-predict the external dose rates compared with explicit modelling.

Measurement of the overall volumetric coefficient of heat transfer of a shaking flask

The overall volumetric coefficient of heat transfer ( Ua) of a shaking flask was measured under various shaking conditions using three types of flask. Ua was significantly affected by flask weight ( W F), which could be attributed to the thickness of the flask wall, the rotational speed of the shaker ( N), wind velocity ( V W), and the liquid volume in the flask ( V L). The limiting step of heat transfer seemed to be the heat radiation process from the surface of the flask to the surroundings. To predict the value of Ua, the following empirical equations were obtained for each type of flask by the least squares method: 1. (1) for deformed creased flask (M-type flask), Ua=17.4 W F −0.43 V L −0.61 N 0.12 V W 0.36 2. (2) for creased flask (N-type flask), Ua=9.2 W F −0.36 V L −0.57 N 0.17 V W 0.27 3. (3) for smooth flask (S-type flask), Ua=5.3 W F −0.26 V L −0.62 N 0.19 V W 0.25.

Platelet Adhesiveness to Glass

Summary1. When anticoagulated blood is placed in a rotating glass flask, the blood/air interface initiates platelet aggregation, and the aggregates are trapped on the flask wall, without adhering to it, by the thin film of blood which forms during rotation. The interface; allows CO2 loss so that the pH of the rotating blood rises markedly and this rise is associated with the release of 3H-5HT from platelet. When CO2 diffusion and consequent pH rise is prevented, platelet loss and 3H-HT release are significantly reduced.2. A simple method for assessing the adhesiveness of single platelets to glass using a Neubauer haemocytometer chamber has been developed. The results obtained are independent of platelet number which allows the test to be used in conditions in which abnormal platelet behaviour is associated with a low platelet-count.3. Adhesiveness was negligible in heparinised PRP, and was greater in EDTA PRP than in citrated PRP. Heparin abolished the increased adhesiveness observed with the other anticoagulants and adhesiveness did not seem to be directly related to residual plasma calcium concentrations. Platelets adhered more readily to siliconised glass surfaces than to untreated glass, and adhesion was markedly temperature-dependent, being maximal at 4°C in heparinised PRP, and at 20° C in EDTA PRP.4. Adhesiveness was enhanced by aggregating agents, this enhancement being prevented by inhibitors of aggregation such as the dipyridamole analogue VK 774. Adhesiveness was unaffected by acetyl-salicylic acid.5. Adhesiveness increased markedly after surgical operations and myocardial infarction. Within-person variation was considerable, and the test is of no value in individual patients.

Measurement of the frequency drift of a hydrogen standard owing to atomic impacts on the flask wall

Measurement of the frequency drift of a hydrogen standard owing to atomic impacts on the flask wall

Flat Panel Vacuum Thermal Insulation

Evacuated mats of glass fiber made up of fibers of proper size and orientation are capable of supporting a compressive mechanical loading of at least one atmosphere and yet maintain a thermal conductivity of less than 10 microcalories/cm°C sec. The use of such a glass fiber mat as a filler makes possible an evacuated flat-panel thermal insulation which is comparable to a Dewar flask in insulation efficiency. The rate of heat transfer through a Dewar flask wall was reduced several-fold at liquid nitrogen temperatures and below by adding a 2-cm-thick layer of orientated and evacuated glass fiber mat to the outer surface. This investigation showed that in evacuated glass fiber mats, supporting external atmospheric loading, the fiber to fiber contact area is less than 10−4 the mat area, making the contact pressure about 15 000 kg/cm2. The effective length of the thermal conduction paths along the fibers is about four times the mat thickness. The mean pore size for gas molecule motion in the mat was found to be about 54×10−4 cm and 2×10−4 cm for mean fiber sizes of 14×10−4 cm and 0.2×10−4 cm, respectively. The radiation mean free paths for the same fiber sizes were found to be 150×10−4 cm and 52×10−4 cm, respectively. The thermal diffusivity is about 10−4 cm2/sec, which is much smaller than any other insulating material.

The attainment of high potentials by the use of radium

The original aim of the work described in this note was to measure the energy and numerical importance of each of the many distinct kinds of β -particles emitted by a single radioactive substance. Calculation of the energy of a β -particle from observation of its deflection in a magnetic field involves assumptions which are as yet insufficiently supported by experiment. Theoretically both the energies and distribution of the particles could be directly measured by giving a gradually increasing positive charge to the source of radiation; for, when the potential of the source is +V, electrons possessing energy less than e V will be drawn back to the source of radiation. Unfortunately, more than a million volts would be necessary to stop the fastest β -particles, and no method is at present known of maintaining such a high potential in vacuo . It was thought that this difficulty might possibly be overcome by using the active material itself in order to produce the high potential according to the principle employed in Strutt's radium clock. If the source of radiation were perfectly insulated its potential would rise until the swiftest β -particles could no longer escape. The present note deals with experiments made to test whether this method were practicable. It was found that high potentials were readily obtained, but the attempt to attain to a million volts tailed through the difficulties of insulation encountered. But few experiments were completed, and many failed as the result of accident. This shows that, even if perseverance had been rewarded by greater success, technical difficulties, accentuated by every effort to improve the insulation, would probably have prevented the practical application of the method. It seemed, therefore, useless to pursue the matter further, until more is known of the reasons why the insulation of a vacuum breaks down. In these experiments the source of β -radiation was 20 millicuries or more of purified radium emanation contained in a thin bulb—marked B in fig. 1—of about 1 cm. diameter. The bulb, which was just thick enough to stop all α -radiation, was supported by a fine silica rod R inside an exhausted glass flask F of 1 litre capacity. The rod, of diameter about 0⋅8 mm., was freshly drawn from transparent fused silica. The surface of the bulb and the flask was coated with silver, which was found to retain a trace of conductivity when subsequently heated to 400° C., though it then became almost transparent. The potential gained by the bulb was measured by a simple form of attracted disc electrometer, a circular aluminium disc being hung from the arm of a horizontal silica spring, the other end of which was soldered with aluminium to a projection from one of the glass walls of the flask. By observing with a microscope the. displacement of the disc, the force of attraction exerted on it by the bulb was measured, and from this it was easy to calculate the charge and the potential acquired by the bulb. The force of a dyne displaced the spring by about 0⋅1 mm. The disc was hung just at the entrance to the mouth of the flask, so that the remainder of the flask wall served the purpose of a guard-ring.