Reversal of gulf stream circulation in a vertically vibrated triangular fluidized bed

Vibrated fluidized beds are a process intensification technique consisting in introducing vibratory kinetic energy in a fluidized bed (1). In this work we assess experimentally the effect of vibration on the gulf-stream circulation pattern of particles in a fluidized bed that is of triangular shape. The bed has 0.206 m span and 0.01 m thickness. The base of the bed is composed of two inclined walls, each one forming an angle of 45º with the horizontal. Air was injected through the inclined bed walls to fluidize the bed (see Figure 1a). This gas injection, together with vibration, can make the dynamics of this bed different to that found in a spouted fluidized bed (2). The bed is filled with ballotini particles with a mean diameter of 1.15 mm up to the top of the inclined walls. The bed vessel is made of antistatic PMMA to allow optical access with a high-speed camera. The bed was mounted on an electrodynamic shaker which produces the vibration. A high speed camera is used to record the motion of particles. The particle velocity was obtained via Particle Image Velocimetry (PIV). As a function of vibration amplitude and frequency, we observe several circulation patterns when the fluidization velocity is just below and above the minimum fluidization velocity. Noticeably, for zero gas velocity, particles ascend close to the side walls descend in the center of the bed. By injecting fluidization gas, the circulation pattern of the bed could be reversed (i.e. particles descending near the side walls ascend in the center of the bed) for certain conditions. For example, reversal of the gulf stream circulation of particles appeared in the triangular bed for gas superficial velocities higher than the minimum fluidization velocity and sufficiently high values of the vibration strength. This phenomenon is illustrated in Figure 1b in which, for the same vibrating conditions, the injection of gas superficial velocity through the walls reverses the gulf stream motion of particles in the bed. REFERENCES R. Gupta, A.S. Mujumdar, Hydrodynamic of vibrated fluidized bed, Can. J. Chem. Eng., 58:332-338, 1980. Vinayak S. Sutkar, Niels G. Deen, J.A.M. Kuipers, Spout fluidized beds: Recent advances in experimental and numerical studies, Chem. Eng. Sci., 86:124:136, 2013. Please click Additional Files below to see the full abstract

Segregation of equal-sized particles of different densities in a vertically vibrated fluidized bed

Many operations in the chemical and energy-conversion industries rely on the fluidization of heterogeneous materials. During fluidization, particles of different densities can segregate, even if they are of the same size. Segregation is typically an undesired phenomenon, especially in fluidized bed reactors (1). Thus, an understanding of segregation on a fundamental level is paramount to identify effective measures to control it. One approach to control segregation could be the vibration of the bed vessel. However, there is very little literature available concerning the effect of vibration on density-induced segregation dynamics (2). Thus, this work studies the influence of vibration on density-induced segregation dynamics in a gas fluidized bed. Experiments were carried out in a pseudo-2D bed of 0.2 m width, 0.5 m height and 0.01 m thickness. The bed was filled with black, ballotini spheres (density 2500 kg/m3) mixed with heavier, white, ceramic particles (density 4100 kg/m3 and 6000 kg/m3). All particles have an average diameter of 1.1 mm. The bed was fluidized by air and vibrated by an electrodynamic shaker. High-speed images were recorded through the transparent front wall of the bed. Digital Image Analysis (DIA) was used to characterize the rate and extent of particle mixing with time (see Figure 1). At the start of the experiments the particles were mixed. The results obtained indicate that both the vibration strength and the gas velocity have an important effect on both the rate and the maximum degree of segregation of particles. We observed that particles become segregated for fluidization velocities greater than the minimum fluidization velocity of the denser particles. Adding vertical vibration to this system tended to enhance density-induced segregation. Interestingly, we found that, for sufficiently high vibration strengths, the degree of segregation decreased with vibration. These results indicate that by a judicious choice of the vibration strength and the fluidization velocity density-induced segregation can be controlled. REFERENCES W-C. Yang, Handbook of fluidization and fluid-particle systems, CRC Press, 2003. L. Sun, F. Zhao, Q. Zhang, D. Li, H. Lu, Numerical simulation of particle segregation in vibration fluidized bed, Chem. Eng. Technol., 37(12):2109-2115, 2014. Please click Additional Files below to see the full abstract

The Involvement of Peripheral and Brain Insulin Resistance in Late Onset Alzheimer's Dementia

Nowadays, Alzheimer's disease (AD) is a severe sociological and clinical problem. Since it was first described, there has been a constant increase in its incidence and, for now, there are no effective treatments since current approved medications have only shown short-term symptomatic benefits. Therefore, it is imperative to increase efforts in the search for molecules and non-pharmacological strategies that are capable of slowing or stopping the progress of the disease and, ideally, to reverse it. The amyloid cascade hypothesis based on the fundamental role of amyloid has been the central hypothesis in the last 30 years. However, since amyloid-directed treatments have shown no relevant beneficial results other theories have been postulated to explain the origin of the pathology. The brain is a highly metabolically active energy-consuming tissue in the human body. It has an almost complete dependence on the metabolism of glucose and uses most of its energy for synaptic transmission. Thus, alterations on the utilization or availability of glucose may be cause for the appearance of neurodegenerative pathologies like AD. In this review article, the hypothesis known as Type 3 Diabetes (T3D) will be evaluated by summarizing some of the data that has been reported in recent years. According to published research, the adherence over time to low saturated fatty acids diets in the context of the Mediterranean diet would reduce the inflammatory levels in brain, with a decrease in the pro-inflammatory glial activation and mitochondrial oxidative stress. In this situation, the insulin receptor pathway would be able to fine tune the mitochondrial biogenesis in neuronal cells, regulation the adenosine triphosphate/adenosine diphosphate intracellular balance, and becoming a key factor involved in the preservation of the synaptic connexions and neuronal plasticity. In addition, new targets and strategies for the treatment of AD will be considered in this review for their potential as new pharmacological or non-pharmacological approaches

A novel rhein-huprine hybrid ameliorates disease-modifying properties in preclinical mice model of Alzheimer's disease exacerbated with high fat diet

Background: Alzheimer's disease (AD) is characterized by a polyetiological origin. Despite the global burden of AD and the advances made in AD drug research and development, the cure of the disease remains elusive, since any developed drug has demonstrated effectiveness to cure AD. Strikingly, an increasing number of studies indicate a linkage between AD and type 2 diabetes mellitus (T2DM), as both diseases share some common pathophysiological features. In fact, β-secretase (BACE1) and acetylcholinesterase (AChE), two enzymes involved in both conditions, have been considered promising targets for both pathologies. In this regard, due to the multifactorial origin of these diseases, current research efforts are focusing on the development of multi-target drugs as a very promising option to derive effective treatments for both conditions. In the present study, we evaluated the effect of rhein-huprine hybrid (RHE-HUP), a synthesized BACE1 and AChE inhibitor, both considered key factors not only in AD but also in metabolic pathologies. Thus, the aim of this study is to evaluate the effects of this compound in APP/PS1 female mice, a well-established familial AD mouse model, challenged by high-fat diet (HFD) consumption to concomitantly simulate a T2DM-like condition. Results: Intraperitoneal treatment with RHE-HUP in APP/PS1 mice for 4 weeks reduced the main hallmarks of AD, including Tau hyperphosphorylation, Aβ42 peptide levels and plaque formation. Moreover, we found a decreased inflammatory response together with an increase in different synaptic proteins, such as drebrin 1 (DBN1) or synaptophysin, and in neurotrophic factors, especially in BDNF levels, correlated with a recovery in the number of dendritic spines, which resulted in memory improvement. Notably, the improvement observed in this model can be attributed directly to a protein regulation at central level, since no peripheral modification of those alterations induced by HFD consumption was observed. Conclusions: Our results suggest that RHE-HUP could be a new candidate for the treatment of AD, even for individuals with high risk due to peripheral metabolic disturbances, given its multi-target profile which allows for the improvement of some of the most important hallmarks of the disease