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Leukemia Limfoblastik Akut (LLA) adalah penyakit keganasan sel progenitor limfoid yang berasal dari sumsum tulang. Tanda khasdari diagnosis leukemia akut adalah sel blas. Pemeriksaan mikroskopis dilakukan untuk menentukan persentase sel blas pada diagnosisleukemia akut. Immunophenotyping merupakan metode diagnostik yang dapat membantu menegakkan diagnosis pada keganasanhematologi. CD34 merupakan antigen yang sering digunakan untuk identifikasi sel induk hemopoeisis atau blas. Penelitian ini bertujuanuntuk mengetahui kenasaban antara persentase blas dengan ekspresi CD34 di sumsum tulang di pasien leukemia limfoblastik akut anaksebelum dan sesudah pengobatan kemoterapi fase induksi.

The anaerobic fluidized-bed membrane bioreactor (AnFMBR) makes use of fluidized granular activated carbon (GAC) to mechanically scour the membrane to mitigate fouling. The question addressed in the current study is whether fluidizing bidisperse mixtures (i.e., particles of two different sizes) can improve the energy-efficiency in mitigating membrane fouling. The hydrodynamic parameters (including particle velocity, particle concentration, particle momentum and extent of segregation) of the fluidized media numerically obtained via a Two-Fluid Model (TFM) were correlated with the fouling rate experimentally obtained. Three bidisperse mixtures with the same mean particle diameter (namely, 1 mm) but different particle diameter ratios (namely, d p2 /d p1 = 1.22 – 1.86) were studied over a range of superficial liquid velocities. The key highlights are that (i) the fouling rate decreased (i.e., fouling mitigation was more effective) as the particle diameter ratio increased, which indicates the benefits of fluidizing multi-sized particle mixtures over monodisperse ones, (ii) the fouling rate (dTMP/d t ) was positively correlated to the mixing index ( M ), which implies that segregated systems were more effective at mitigating membrane fouling, and (iii) the effect of bidispersity was more significant at the lower power input, which suggests that the advantages of fluidizing such bidisperse mixtures should only be harnessed at moderate power but not higher ones.

The impacts of particle diameter ( d p ), particle density ( ρ p ) and particle sphericity ( φ ) on the minimum pickup velocity ( U pu ) of binary mixtures of Geldart group B particles were investigated. Three types of binary mixtures were tested, whereby the two constituents vary in (i) only d p (i.e., binary-size), (ii) only ρ p (i.e., binary-density), and (iii) both d p and ρ p (i.e., binary-size-density). Notably, there is a lack of data on the pickup characteristics of the latter two types of binary mixtures, although behavioral differences are acknowledged. The minimum pickup velocity, U pu , was experimentally determined by the weight loss method and also derived using a force balance model developed here. The key results were: (1) d p exerts a more dominant influence on U pu than ρ p ; (2) particle sphericity ( φ ) has a non-negligible impact on U pu ; and (3) a drag and frictional force balance analysis accounting for particle sphericity gives reasonable predictions of U pu , which in turn provides a mechanistic insight on U pu .

The mechanical scouring of membranes induced by fluidized particles is a promising method for mitigating membrane fouling. In order to further improve this technique in terms of scouring efficiency and energy requirement, the goal of the current study is to understand the hydrodynamics of the fluidized granular activated carbon (GAC) particles, and correspondingly the relationship between the particle behavioral characteristics and the extent of membrane-fouling mitigation. In this study, the impact of GAC particle diameter (dp), superficial liquid velocity (Ul) and axial position of the membrane (h/H) on particle behavior (namely, particle velocity, concentration and momentum) and membrane fouling was investigated. A high-speed video camera and the ImageJ software were used to characterize particle velocity and concentration, and membrane fouling was characterized by the rate of trans-membrane pressure (TMP) rise. Directly correlating particle behavior with membrane fouling trends shows that higher particle velocities, particle concentration and particle momentum generally all showed a negative correlation with dTMP/dt (i.e., improved fouling control). Of the three characteristics (namely, particle velocity, concentration and momentum), the negative correlation between dTMP/dt and particle momentum was the most pronounced, which suggests that momentum transfer between the GAC particles and the membrane represents a key mechanism effecting the scouring to diminish membrane fouling. Finally, the lack of a strong correlation between dTMP/dt and power input was observed, which indicates that a higher energy expenditure did not guarantee a more effective reduction in membrane fouling. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) EDB (Economic Devt. Board, S’pore)

The dispersion behavior of the solid phase in a three-dimensional spout-fluid bed was numerically investigated via the approach of coupled computational fluid dynamics and discrete element method (CFD–DEM), in which the fluid and solid phases were solved using the Eulerian and Lagrangian framework, respectively. Detailed trends of both the local and overall dispersion behaviors of the solid phase in the system were quantitatively studied, and the impact of various operating parameters (namely, spouting gas velocity (Usp), background velocity (Ubg), particle diameter (dp), the bed depth (L) and bed height) and flow regime on lateral and vertical solid dispersion was investigated. The results show that varying Usp, Ubg and dp affects the local solid dispersion in the spout and fountain regions more than the annulus. To enhance the overall solid dispersion, either Usp or Ubg or L can be increased, or dp and bed height can be decreased. Meanwhile, the total gas flow rate plays the dominated role for overall dispersion of solid phase. Finally, solid dispersion is the most effective in the Jet-in-fluidization regime, followed by the Spouting-with-aeration then the Intermediate/spout-fluidization regimes.

Particles suspended within feed flow or added into membrane-filtration systems may behave as foulant or fouling mitigation agent. The fine boundary between these two roles warrant attention to promote the beneficial role of particles and avoid their undermining impact. The particle back-transport phenomenon is first elucidated, then the four possible enhancing roles of particles in membrane-filtration systems are discussed, namely, mechanical scouring, as adsorbents of organic foulants, as coagulants to form porous flocs, and as dynamic membranes to protect the primary membrane matrix. Process variables governing such phenomena and possible adverse effects that need to be mitigated are also summarized. Finally, future research directions are recommended based on the understanding accumulated, namely, hybridization of the various beneficial roles, development of customized particles, and more understanding/optimization of the energy – fouling mitigation tradeoff. Economic Development Board (EDB) Ministry of Education (MOE) The authors gratefully acknowledge the financial support from the Singapore Ministry of Education Academic Research Funds Tier 2 (MOE2014-T2-2-074; ARC16/15) and Tier 1 (2015-T1-001-023; RG7/15), the GSK (GlaxoSmithKline) -EDB (Economic Development Board, Singapore) Trust Fund, the Joint Singapore-Germany Research Project Fund (SGP-PROG3-019). The Singapore Membrane Technology Center acknowledges funding support from the Singapore Economic Development Board.

Transport Disengaging Height (TDH), defined as the freeboard height whereby the entrainment rate does not change appreciably [1–6], is an important parameter in the design of gas–solid fluidized bed systems to minimize particle loss. Unfortunately, despite the initiation and subsequent development of TDH correlations since 1958 [4], poor agreement between predicted and experimental values persists [1] due to the reliance on empirical data-fitting in the absence of a fundamental understanding of the TDH phenomenon. Accordingly, this work aims to provide a comprehensive review of the available TDH correlations. TDH values predicted by 25 correlations were evaluated over a range of superficial gas velocities, particle sizes, particle size distributions, and column diameters. Four observations are worth highlighting: (i) Discrepancies of up to five orders of magnitude were found among TDH values predicted by the various correlations, (ii) Unphysical phenomena predicted include negative TDH values, (iii) Geldart Group B correlations perform better for Geldart Group B particles than Geldart Group A correlations for Geldart Group A particles, and (iv) Prediction often fails in the transition from the freely bubbling to the slugging regime. The ad hoc inclusion and/or exclusion of parameters, and the use of empirical constants to improve empirical data-fitting in the generation of empirical TDH correlations are not useful in either improving predictions of TDH values or advancing the understanding of the TDH phenomenon. Correlations empirically derived do not perform well beyond the narrow scope of experimental condition tested, while semi-empirical or theoretical models available fall short. The lack of predictive capability of the available TDH correlations appears to stem from a deficiency in an understanding of the impact of inter-particle (e.g., cohesion or clustering effects) and inter-species interactions (e.g., collisional momentum transfer effects).

Despite the abundance of entrainment correlations in gas–solid fluidization made available in the past few decades, the discrepancy between empirical prediction and experimental data has been noted to be up to a hundredfold in some cases. Hence, a comprehensive review of the available correlations is warranted, with the goal of extracting the underlying physics giving rise to the disparities, and thereby providing insights towards an enhanced understanding of entrainment. This review addresses a comprehensive spectrum of particle systems, ranging from monodisperse to binary to continuous particle size distribution (PSD) systems for the more predominant Geldart Groups A and B classifications. Three key observations are highlighted. First, comparisons of the predicted entrainment values among available correlations reveal discrepancies spanning several orders of magnitude, with the maximum being 20 orders of magnitude, evidencing that available empirical correlations do not extrapolate well beyond the scope of tested parameters. Second, unphysical phenomena predicted include qualitative discordance on the shapes of the elutriated PSDs, the most notable of which is the anomaly whereby larger particles are preferentially elutriated. Third, whether a particular correlation was developed for a specific Geldart Group or for monodisperse and/or polydisperse systems seems inconsequential to giving better predictions even when appropriately applied to the particular subset. These observations underscore the need for more physically-based models to enable a more accurate prediction of entrainment and elutriation phenomena.

The anaerobic fluidized bed membrane bioreactor (AnFMBR) utilizes the fluidization of granular activated carbon (GAC) particles as an unsteady-state shear means for mitigating membrane fouling. In this study, a two-fluid model (TFM) was validated against experimental results and used to obtain a comprehensive landscape of local water and particle velocities and concentrations throughout the reactor. The results provided interesting insights. Firstly, both water and particle velocities tended to be non-uniform vertically and laterally, which indicate that the extent of fouling across the membrane would be non-uniform. Secondly, to attain the same water shear stress or particle momentum values, the power required was greater for the larger particles, which indicate that smaller particles were more energy-efficient. Thirdly, at the same power input, the water shear stress or particle momentum values for the different particle diameters overlapped, which indicates that other parameters can be manipulated to improve performance even when particle diameter has been fixed. Fourthly, generally negative correlations existed between fouling rate and the hydrodynamics of both phases, but fouling rate and power input were poorly correlated, which suggests surprisingly that increasing power would not improve the fouling mitigation. MOE (Min. of Education, S’pore)