30 research outputs found
Understanding Ion Rejection Mechanism of Freeze Desalination by Molecular Dynamics Simulation
No full textThis study explores a method called freeze desalination, which uses the natural process of ice formation to remove salt from water at lower than freezing temperature of water, which is 235K (Freezing temperature of this water model is 249K), making it safe for potable water. Unlike traditional methods, freeze desalination can be more efficient and environmentally friendly, but how it rejects salt at the molecular level is not very clear to understand. Using molecular dynamics simulation, this research aims to uncover the details of this process. We focused on understanding how water molecules interact with salt ions during freezing. Our findings showed that over 90% of salt ions can be successfully removed from the water under optimal conditions, with certain temperatures and settings leading to the best results. Specifically, we found that sodium ions are removed more effectively than chloride ions. This difference is due to how sodium and chloride ions interact with the surrounding water molecules, which was measure by calculation of free energies. These insights are crucial for improving the technique and making it a viable option for purifying water in different settings. Overall, this work provides a clearer picture of how freeze desalination works at a microscopic level, offering guidance on how to optimize this process for better performance. This could have significant implications for water purification technology, potentially leading to more widespread use of freeze desalination in the future
COVID-19 Challenges to Human Resource Management and Its Future Directions – a study on Banking Industry of Bangladesh
No full textThe Covid-19 has disrupted the normalcy of almost all organizations in the world. As a result of COVID-19's profound impact on all organizations, HRM practitioners are faced with a complex and challenging environment in which to work. They must come up with innovative solutions to ensure the continuity of their companies and help their employees cope with this extraordinary crisis. In developing nation like Bangladesh while there is a developing middle economy, Covid-19 effect the management of Human Resource division intensely. It is rare to find studies that examine the impact of this crisis on HR management in Bangladesh. From this new pandemic, the study highlights the major challenges and possibilities of HRM in Bangladesh, and gives possible future organizational directions that may result from these threats and issues
DEVELOPMENT OF CONTINUOUS ENZYMATIC PROCESSES USING MILLIFLUIDIC DEVICES
No full textPh.DDOCTOR OF PHILOSOPHY (FOE
Influence of Stepwise Increased Organic Loading on Anaerobic Mono-digestion of Dead Fish in Sequencing Batch Reactor Process
No full text© 2022, The Author(s), under exclusive licence to Springer Nature B.V.Highly nutrient content dead fish (DF) waste can be considered a potentially valuable substrate for the anaerobic digestion (AD) to produce biogas. The effects of stepwise increased organic loading rate (OLR) on the process performance were investigated during mono-digestion of DF waste in anaerobic sequencing batch reactor mode. Two different sets of experiments have been conducted using whole dead fish (RDF) and boneless dead fish (RBDF) and OLR increased in five steps (1.95, 2.39, 2.73, 3.19, and 3.64 g VS/L/days) during the operational period. With the increasing of OLR, the biogas production rate increased by 79.07% and 58.20% at the end of the operation of RDF and RBDF, respectively. Higher alkalinity values throughout the experiment maintained stable pH values in between 7.87 to 8.01 for both RDF and RBDF. Total volatile fatty acids kept accumulating with the increasing OLR and the final concentrations were 7.69 ± 0.16 and 8.33 ± 0.19 g/L in RDF and RBDF, respectively. Overall, decreasing COD and VS removal efficiencies resulted in decreasing methane yields. The energy recovery rate was maintained at > 60% with the maximum OLR of 3.64 g VS/L/d of DF waste demonstrating its feasibility in the AD process as the only carbon source. Graphical Abstract: [Figure not available: see fulltext.].11Nsciescopu
Immobilization of Enzymes on Flexible Tubing Surfaces for Continuous Bioassays
No full textImmobilized
enzymes can be used to catalyze biochemical reactions
in a batch process, however, it is more difficult to use them in a
continuous process. Herein, we develop an enzyme immobilization technique
for flexible tubing surfaces, which can be used to catalyze biochemical
reactions in a continuous process. In this technique, the tubing is
first treated with (3-aminopropyl)triethoxysilane at 50 °C and
baked at 100 °C in vacuum to form a network of reactive amine
functional group on the inner tubing surface. Subsequently, dextran
polyaldehyde, a polymeric cross-linker, is used to immobilize crude
protease extract and catalase for hydrolyzing casein and degrading
H2O2, respectively, in a continuous process.
The immobilized proteases are highly stable even after a long-term
storage at 4 °C. After 12 weeks of storage, 90% of the original
protease activity can be preserved. Meanwhile, the immobilized catalase
is able to degrade 0.1% H2O2 solution flowing
at 5 μL/min. The immobilization technique is potentially useful
for bioassays and industrial wastewater treatments when continuous
processes are preferred
A Millifluidic Device with Embedded Cross-Linked Enzyme Aggregates for Degradation of H<sub>2</sub>O<sub>2</sub>
No full textMillifluidic devices decorated with
enzymes have been used for enzymatic reactions in continuous processes,
but low enzymatic activity and enzyme leaching remain as challenges.
Herein, we develop a strategy to embed cross-linked enzyme aggregates
(CLEAs) on the surfaces of millifluidic devices to achieve higher
enzymatic activity and better stability. Catalase was chosen as a
model enzyme to degrade H2O2 in wastewater samples.
First, CLEA of catalase (153 ± 10 nm) was formed by simultaneous
precipitation and cross-linking with 25.0 wt % acetonitrile containing
0.025 wt % glutaraldehyde in a millifluidic device. To immobilize
CLEA, we first swell a piece of plastic tubing by using 5.0 wt % acetonitrile
and then immerse it in an aqueous solution with 5.0 wt % (3-aminopropyl)triethoxysilane
(APTES) and 5.0 wt % dextran polyaldehyde (DPA) subsequently. After
CLEA is absorbed inside the expanded polymer network of the tubing,
the tubing is tightened by using a vacuum to secure the immobilized
CLEA. The millifluidic device decorated with CLEA of catalase has
total activity of 660 U for degradation of H2O2, and it shows good stability under a flow rate of 200 μL/min.
The tubing can be used to degrade 0.1 wt % H2O2 solution continuously for 3 h or remove 2 wt % residual H2O2 in wastewater for 2 h. The technique is general enough
and can be applied to other types of enzymes for continuous enzymatic
reactions
Stability Analysis of Biological Systems Under Threshold Conditions
No full textIn biological models exhibiting symmetric interactions within each compartmental group, threshold dynamics are typically governed by a key parameter known as the basic reproduction number R0. The stability of an equilibrium often hinges on whether R0 is greater than or less than one. However, general results for stability at the critical threshold—when R0 equals one—remain scarce. In this paper, we establish two theorems to analyze the stability of both trivial and boundary equilibria under this threshold condition. Our results provide explicit expressions for the threshold parameters in terms of partial derivatives of the nonlinear reaction function, making them readily applicable to a wide range of biological systems
