Degree Of Settling Research Articles

Suspension and Mixing Characterization of Intermittent Agitation Modes in DASGIP Bioreactors

AbstractIntermittent agitation strategies have been increasingly used for a range of process development applications, i.e., to modulate physical cues, to improve stem cell differentiation yields, and to control hydrodynamic shear stresses in microcarrier suspension; however, there is a distinct lack of characterization. Both continuous and intermittent agitation modes in relation to suspension and mixing dynamics within a DASGIP bioreactor were characterized. Suspension dynamics were found to be affected by microcarrier porosity and the degree of settling was found to be more pronounced at the top of the bioreactor. Mixing time characterization showed a marked improvement in mixing efficiency for intermittent agitation, with an overall dependence on the timing of tracer insertion.

ДОСЛІДЖЕННЯ ВІДМІННОСТЕЙ ОРИГІНАЛЬНОГО ТА ДЖЕНЕРИЧНИХ ПРЕПАРАТІВ, ЩО МІСТЯТЬ БЕТАМЕТАЗОНУ ДИПРОПІОНАТ І БЕТАМЕТАЗОНУ НАТРІЮ ФОСФАТ

Мета роботи. Проведення дослідження, що дасть змогу виявити різницю між оригінальним і дженеричними препаратами, лікарські форми яких мають двофазний вміст бетаметазону (бетаметазону натрію фосфат у складі водного розчину і бетаметазону дипропіонат у вигляді суспензії в цьому розчині).Матеріали і методи. Використано оригінальний препарат бетаметазону натрію фосфату та бетаметазону дипропіонату у вигляді суспензії та його дженеричні аналоги, доступні на ринку України. Для оцінки кількості суспензії БМДП препаратів А, В, С, що перейшла у розчин 15 % водного ізопропанолу, нами була розроблена методика з використанням приладу «Лічильник числа та розміру часток в рідких середовищах» APSS-2000.Результати й обговорення. Здійснено візуальне вивчення механічної стабільності суспензій у запаяних ампулах, що показало різну швидкість осідання суспендованих часток у досліджуваних препаратах. Вивчено можливий вплив розчинника (розчину лідокаїну) на швидкість та ступінь осідання часток. Виявлено, що дженеричні препарати В і С суттєво відрізняються від оригінального препарату А за розподілом маси суспензії бетаметазону дипропіонату за розмірами часток. В оригінального препарату А основну масу суспензії БМДП складають частинки меншого розміру, ніж у дженериків.Розроблено методику для визначення розчинності, за допомогою якої виявлено, що суспензія оригінального препарату А за 130 хв експозиції на орбітальному струшувачі розчиняється майже повністю (99 %), тоді як у дженериків В і С за цей час переходить (розчиняється) у водно-ізопропанольну фазу відповідно, лише 66 і 53 % кристалічної маси БМДП. Показано, що динаміка розчинення суспензії БМДП досліджуваних препаратів може бути відстежена з використанням приладу «Лічильник числа та розміру часток в рідких середовищах» APSS-2000.Висновки. Встановлено, що оригінальний препарат та його дженерики мають суттєві відмінності в розподілі за розмірами часток. Розроблено методику визначення розчинності оригінального препарату та дженериків. Вказана різниця стосується суспензії бетаметазону дипропіонату: дженерики відрізняються від оригінального препарату тим, що мають інший розподіл часток за розмірами, і, як наслідок, іншу поведінку в розроблених тестах на розчинність.

Magnetic fabrics in Quaternary sediments, Ursa Basin, northern Gulf of Mexico record transport processes, compaction and submarine slumping

The continental slope of the northern Gulf of Mexico seaward of the Mississippi Delta is characterized by very rapid Quaternary sedimentation. Thick sequences of underconsolidated muds and mudstones are present, which are severely overpressured. In the Ursa Basin, Site U1322 of the Integrated Ocean Drilling Program (IODP) provided an excellent coring record of interleaved fine-grained turbidites and hemipelagic sediments, in part severely affected by submarine slumping and sliding after deposition. Cores were continuously sampled and analyzed for anisotropy of magnetic susceptibility (AMS), to elucidate the effects of different transport mechanisms and degree of settling and consolidation on magnetic fabric properties. Generally AMS ellipticity increases with depth irrespective of transport mode, due to loss of porosity. Samples from slumped mass transport deposits (MTD), however, have higher AMS if compared to immediately overlying non-slumped material. MTD samples dominantly show triaxial magnetic fabrics whereas those found in non-slumped sediments are much more oblate. Long axes of the fabric ellipsoid reflect the direction of eastward to southward suspension transport in samples not overprinted by sliding or slumping. Short ellipsoid axes in non-slumped material are vertical, and thus parallel to the axis of maximum uniaxial shortening. In the MTD samples, many short ellipsoid axes are inclined, reflecting an overprint of the uniaxial shortening by bed-parallel shearing induced by the slumping. Shear and MTD transport direction deduced from the fabrics is top-to-SE, downslope along the morphological axis of Ursa Basin. Generally we show that magnetic fabrics of muds and mudstones are sensitive recorders of sedimentary and tectonic processes, and can be used to reconstruct essential parts of basin history.

THE EVOLUTIONARY STATE OF THE PRE-MAIN SEQUENCE POPULATION IN OPHIUCHUS: A LARGE INFRARED SPECTROGRAPH SURVEY

Variations in molecular cloud environments have the potential to affect the composition and structure of the circumstellar disks therein. To this end, comparative analyses of nearby star-forming regions are essential to informing theoretical work. In particular, the Ophiuchus molecular clouds are ideal for comparison as they are more compact with much higher extinction than Taurus, the low-mass exemplar, and experience a moderate amount of external radiation. We have carried out a study of a collection of 136 young stellar objects in the <1 Myr old Ophiuchus star-forming region, featuring Spitzer Infrared Spectrograph spectra from 5 to 36 μm, supplemented with photometry from 0.3 μm to 1.3 mm. By classifying these objects using the McClure new molecular cloud extinction law to establish an extinction-independent index, we arrive at a ~10% embedded objects fraction, producing an embedded lifetime of 0.2 Myr, similar to that in Taurus. We analyze the degree of dust sedimentation and dust grain processing in the disks, finding that the disks are highly settled with signs of significant dust processing even at ~0.3 Myr. Finally, we discuss the wealth of evidence for radial gap structures which could be evidence for disk-planet interactions and explore the effects of stellar multiplicity on the degree of settling and radial structure.

Magnetorheology of submicron diameter iron microwires dispersed in siliconeoil

We investigate the magnetorheological (MR) properties of suspensions containingiron microwires with 260 nm diameter and two distinct length distributions of5.4 ± 5.2 µm and 7.6 ± 5.1 µm suspended in silicone oil (0.45 Pa s). The rheological properties of these fluids were determinedusing a parallel plate rheometer equipped with a variable strength electromagnet. Theshear stress was measured as a function of shear rate for increasing applied magnetic fields.These results were modeled using the Bingham-plastic constitutive model to determine theapparent yield stress and viscosity as a function of increasing volume fraction and lengthof microwires. At a saturated magnetic flux density, the yield stress using the5.4 µm microwires was found to be 0.65, 2.23, and 4.76 kPa for the 2, 4, and 6 vol% suspensions, respectively. Forthe 7.6 µm wires, the yield stress increases to 8.2 kPa for the 6 vol% suspension. Compared withconventional MR fluids employing spherical particles, the degree of settling is markedlydecreased in the microwire-based fluids. At 6 vol%, conventional fluids display appreciablesettling whereas the microwire-based fluids display no discernable settling. Moreover, therod-shaped microwires are shown to increase the yield stress of the fluids and enhance theMR performance.

SpitzerObservations of the Orion OB1 Association: Disk Census in the Low‐Mass Stars

We present new Spitzer observations of two fields in the Orion OB1 association. We report IRAC/MIPS observations for 115 confirmed members and 41 photometric candidates of the ~10 Myr 25 Orionis aggregate in the OB1a subassociation, and 106 confirmed members and 65 photometric candidates of the 5 Myr region located in the OB1b subassociation. The 25 Orionis aggregate shows a disk frequency of 6%, while the field in the OB1b subassociation shows a disk frequency of 13%. Combining IRAC, MIPS, and 2MASS photometry, we place stars bearing disks in several classes: those with optically thick disks (class II systems), with an inner transitional disks (transitional disk candidates), and with evolved disks; the last exhibit smaller IRAC/MIPS excesses than class II systems. In all, we identify one transitional disk candidate in the 25 Orionis aggregate and three in the OB1b field; this represents ~10% of the disk-bearing stars, indicating that the transitional disk phase can be relatively fast. We find that the frequency of disks is a function of the stellar mass, suggesting a maximum around stars with spectral type M0. Comparing the infrared excess in the IRAC bands among several stellar groups, we find that inner disk emission decays with stellar age, showing a correlation with the respective disk frequencies. The disk emission at the IRAC and MIPS bands in several stellar groups indicates that disk dissipation takes place faster in the inner region of the disks. Comparison with models of irradiated accretion disks, computed with several degrees of settling, suggests that the decrease in the overall accretion rate observed in young stellar groups is not sufficient to explain the weak disk emission observed in the IRAC bands for disk-bearing stars with ages 5 Myr or older; larger degrees of dust settling are necessary to explain these objects.

Response of a Hard-to-PressVitis rotundifoliaCultivar and a Hard-to-ClarifyEuvitisHybrid to Commercial Enzyme Preparations

A hard-to-press white grape cultivar, Dixie (<i>Vitis rotundifolia</i>), and a hard-to-clarify white cultivar, Stover (<i>Euvitis</i> hybrid), were treated with three concentrations of a commercial pectinase preparation and a pectinase-cellulase-hemicellulase preparation in an effort to improve press yields and/or the degree of settling. Both the standard pectinase preparation and the pectinase-cellulase-hemicellulase preparation were effective in increasing total press yields and free-run juice from both cultivars. However, the pectinase-cellulase-hemicellulase mixture did not increase settleable solids or total suspended solids in the <i>Euvitis</i> hybrid to nearly the extent of the pectinase preparation. The pectinase-cellulase-hemicellulase preparation was slightly more effective in increasing free-run yields than was the standard pectinase preparation.