Process intensification of synthesis of metal organic framework particles assisted by ultrasound irradiation.

This study synthesized UiO-66, a typical Zr-Metal Organic Framework (MOF), by using an ultrasound-assisted synthesis method to reduce the synthesis time. This method was short-time ultrasound irradiation at the initial stage of the reaction. As compared with average particle size of conventional solvothermal method (=192 nm), averaged particle size by the ultrasound-assisted synthesis method showed particle sizes that were smaller on average, ranging from 56 to 155 nm. In order to compare the relative reaction rates of the solvothermal method and the ultrasound-assisted synthesis method, the cloudiness of the reaction solution in the reactor was observed with a video camera, and the luminance was calculated from the images obtained by the video camera. It was found that the ultrasound-assisted synthesis method showed a faster increase in luminance and shorter induction time than the solvothermal method. The slope of the luminance increase during the transient period was also found to become increase with the addition of ultrasound, which also affects the growth of particles. Observation of the aliquoted reaction solution confirmed that particle growth was faster in the ultrasound-assisted synthesis method than in the solvothermal method. Numerical simulations were also performed using MATLAB ver. 5.5 to analyze the unique reaction field generated by ultrasound. Bubble radius and temperature inside a cavitation bubble was obtained using the Keller-Miksis equation, which reproduces the motion of a single bubble. The bubble radius expanded and contracted repeatedly according to the ultrasound sound pressure, and eventually collapsed. The temperature at the time of collapse was extremely high, exceeding 17,000 K. It was confirmed that the high-temperature reaction field generated by ultrasound irradiation promoted nucleation, leading to a reduction in particle size and induction time.

Thermo-fluid dynamics and synergistic enhancement of heat transfer by interaction between Taylor-Couette flow and heat convection.

This study experimentally and numerically investigated the thermo-fluid dynamics of Taylor-Couette flow with an axial temperature gradient from the chemical engineering perspective. A Taylor-Couette apparatus with a jacket vertically divided into two parts was used in the experiments. Based on the flow visualization and temperature measurement for glycerol aqueous solutions with various concentrations, the flow pattern was classified into six modes: heat convection dominant mode (Case I), heat convection-Taylor vortex flow alternate mode (Case II), Taylor vortex flow dominant mode (Case III), fluctuation maintaining Taylor cell structure mode (Case IV), segregation between Couette flow and Taylor vortex flow mode (Case V) and upward motion mode (Case VI). These flow modes weremapped in terms of the Reynolds and Grashof numbers. Cases II, IV, V and VI are regarded as transition flow patterns between Case I and Case III, depending on the concentration. In addition, numerical simulations showed that in Case II, heat transfer was enhanced when the Taylor-Couette flow was altered by heat convection. Moreover, the average Nusselt number with the alternate flow was higher than that with the stable Taylor vortex flow. Thus, the interaction between heat convection and Taylor-Couette flow is an effective tool to enhance heat transfer. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (Part 2)'.

Drying rate of latex coating affected by the deformability of resin particles in convection drying.

Latex paints are widely used, and many researchers pointed out that the film formation process depends on the deformability of dispersed polymer particles. However, the relationship between the film formation process and drying rate has not been totally understood due to the lack of accurate data on drying rate throughout the drying process. In the present study, we measured the drying rate of latex coating by the temperature change method proposed by Imakoma in convective drying. We revealed that the drying process significantly depends on particle deformability, especially in the former stage of the falling drying rate period. At a low drying temperature, the close-packed structure of polymer particles is formed throughout the film at the end of the constant drying rate period. On the other hand, partially deformed soft particles due to wet sintering inhibit the drying rate even under high moisture content at high drying temperatures. In either case, after forming the closest-packed structure, the shrinkage of the gap space between particles due to capillary deformation decreases the drying rate, proportional to the moisture content.

Effect of Baffle Clearance on Scale Deposition in an Agitated Vessel.

The material deposition in a mixing tank agitated by the MAXBLEND impeller in a turbulent state was quantified and compared between cases with and without baffle clearance. Magnesium hydroxide formed from the chemical reaction between calcium hydroxide and magnesium chloride was used as a model of scale formation. Flow velocity in the tank was investigated by employing computational fluid dynamics simulation and experimentally validated by an ultrasonic velocity profiler method. Results showed that the amount of scale decreased with the increase in the rotational speed of the impeller due to the erosion effect on the tank wall. In the case without baffle clearance, the smaller weight of the scale was deposited on the front of the baffle plate due to the flow impingement, which enhanced the removal of the scale deposition. However, the lower-velocity magnitude behind the baffles resulted in an enhancement in the formation of scale. Installation of baffle clearance caused a contraction flow in between the tank wall and baffles, and consequently, the higher flow velocity reduced the amount and thickness of the scale. Measurement of the torque showed that the baffle clearance did not affect the power consumption, so the installation of baffle clearance can be a promising approach to reduce scale deposition in terms of saving operational costs and increasing process efficiency and safety.

Advances in Biological Liquid Crystals.

Biological liquid crystals, a rich set of soft materials with rod-like structures widely existing in nature, possess typical lyotropic liquid crystalline phase properties both in vitro (e.g., cellulose, peptides, and protein assemblies) and in vivo (e.g., cellular lipid membrane, packed DNA in bacteria, and aligned fibroblasts). Given the ability to undergo phase transition in response to various stimuli, numerous practices are exercised to spatially arrange biological liquid crystals. Here, a fundamental understanding of interactions between rod-shaped biological building blocks and their orientational ordering across multiple length scales is addressed. Discussions are made with regard to the dependence of physical properties of nonmotile objects on the first-order phase transition and the coexistence of multi-phases in passive liquid crystalline systems. This work also focuses on how the applied physical stimuli drives the reorganization of constituent passive particles for a new steady-state alignment. A number of recent progresses in the dynamics behaviors of active liquid crystals are presented, and particular attention is given to those self-propelled animate elements, like the formation of motile topological defects, active turbulence, correlation of orientational ordering, and cellular functions. Finally, future implications and potential applications of the biological liquid crystalline materials are discussed.

Effect of geometrical configuration of reactor on a ZrP nano-dispersion process using ultrasonic irradiation.

This study investigated the position of ultrasonic irradiation source and reactor geometry on fragmentation rate of a layered compound, α-zirconium phosphate (α-ZrP). By numerically solving the acoustic pressure distribution using COMSOL Multiphysics®, it is clarified the mechanism whereby the operating factors influenced the α-ZrP dispersion to make a suggestion of guideline of the process design method. Two vessels made of glass with a flat-bottom and a spherical-bottom, respectively, were used. Although the flat-bottom vessel at lower horn position showed the best performance of fragmentation, the region of high acoustic pressure field in the flat bottom vessel sharply narrowed and the transmittance became prominently low. On the other hand, no significant difference of the transmittance value in the spherical bottom vessel between the cases of low and high horn positions could be observed and the spherical bottom vessel was robust for the horn position. These results suggest that not only the magnitude of acoustic pressure but also the size of high acoustic pressure region is also an important factor and a spherical bottom vessel is one of suitable shape which gives large size of high acoustic pressure region regardless of the horn position.

Process development of starch hydrolysis using mixing characteristics of Taylor vortices.

In food industries, enzymatic starch hydrolysis is an important process that consists of two steps: gelatinization and saccharification. One of the major difficulties in designing the starch hydrolysis process is the sharp change in its rheological properties. In this study, Taylor-Couette flow reactor was applied to continuous starch hydrolysis process. The concentration of reducing sugar produced via enzymatic hydrolysis was evaluated by varying operational variables: rotational speed of the inner cylinder, axial velocity (reaction time), amount of enzyme, and initial starch content in the slurry. When Taylor vortices were formed in the annular space, efficient hydrolysis occurred because Taylor vortices improved the mixing of gelatinized starch with enzyme. Furthermore, a modified inner cylinder was proposed, and its mixing performance was numerically investigated. The modified inner cylinder showed higher potential for enhanced mixing of gelatinized starch and the enzyme than the conventional cylinder.

Characterizations of the submerged fermentation of Aspergillus oryzae using a Fullzone impeller in a stirred tank bioreactor.

A Fullzone (FZ) impeller was used in the first study of the characteristics involved in the fermentation of Aspergillus oryzae. Both the experimental and simulation results of this study revealed novel findings into the positive relationship between the global-axial mixing patterns of a FZ impeller and fermentation efficiency. The mixing results when using the FZ impeller compared with a double Rushton turbine (DRT) impeller indicated that the culture mixed by the FZ resulted in a more homogeneous medium with higher values for oxygen mass transfer, cell growth rate, and alpha amylase activity. The simulation of fluid flow was done in a laminar regime using a two-fluid model. According to the simulation results, the maximum shear stress when using the DRT was higher than that with the FZ at the same power input (Pin). A high degree of local shear stress and the shear rate near the turbine blade of the DRT resulted in cell damage and a reduction in the enzyme activity, biomass, pellet diameter, and dissolved oxygen concentration. Calculations using the Brown equation showed that the maximum and average shear rates during mixing with the FZ impeller were lower than that when using the DRT. Therefore, the use of an FZ impeller, particularly at low Pin, enhanced the cultivation of A. oryzae.

Using a flexible shaft agitator to enhance the rheology of a complex fungal fermentation culture.

The rheology behavior of biological fluids particularly when the viscosity is high and rheology is complex, is an important issue to understand, particularly for studies in mass-transfer and for solving technical problems with mixing in stirred bioreactors. In this paper, the use of a Swingstir(®) impeller during the fermentation of Aspergillus oryzae resulted in decreases from the parameters of a power-law model, in viscosity and in the thixotropic behavior of a cultivation broth. The results showed that both the K L a and the alpha amylase activity were improved when using the Swingstir(®) in comparison with Fullzone(®) impeller (FZ) at the same level of energy consumption. Increasing the pellet porosity during mixing via the Swingstir(®) resulted in increases in oxygen mass transfer and the average shear stress.

Effect of ultrasonic pretreatment on emulsion polymerization of styrene.

This study investigated the effect of pretreatment of ultrasonic irradiation on emulsion polymerization of styrene to propose a process intensification method which gives high conversion, high reaction rate, and high energy efficiency. The solution containing styrene monomer was irradiated by a horn mounted on the ultrasonic transducer with the diameter of 5mm diameter and the frequency of 28 kHz before starting polymerization. The pretreatment of ultrasound irradiation as short as 1 min drastically improved monomer dispersion and increased reaction rate even under the agitation condition with low rotational speed of impeller. Furthermore, the ultrasonic pretreatment resulted in higher monomer concentration in polymer particles and produced larger polymer particles than conventional polymerization without ultrasonic pretreatment.

Diffusion-weighted echo-planar imaging of the head and neck using 3-T MRI: Investigation into the usefulness of liquid perfluorocarbon pads and choice of optimal fat suppression method.

PURPOSE: To investigate whether image quality can be improved using liquid perfluorocarbon pads (Sat Pad) and clarify the optimal fat-suppression method among chemical shift selective (CHESS), water excitation (WEX), and short TI inversion recovery (STIR) methods in diffusion-weighted imaging (DWI) of the head and neck using 3-T magnetic resonance imaging. Correlations between results of visual inspection and quantitative analysis were also examined. MATERIAL AND METHODS: This study was approved by our Institutional Review Board and informed consent was waived. DWI was performed on 25 subjects with/without Sat Pad and using three fat-suppression methods (6 patterns). Image quality was evaluated visually (4-point scales and lesion-depiction capability) and by quantitative analysis (signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR)). Two-way repeated-measures analysis of variance (ANOVA) was used to detect significant differences in scores of visual evaluation, SNR, and CNR. RESULTS: Mean visual evaluation scores were significantly higher with Sat Pad using STIR than without Sat Pad for all fat-suppression methods (P<0.05). DWI with Sat Pad using STIR tended to be useful for depicting lesions. DWI using STIR showed reduced W-SNR (W: whole area of depicted structure) and CNR (between semispinalis capitis muscle and subcutaneous fat) due to fewer artifacts and uniform fat suppression. CONCLUSION: Combining Sat Pad with STIR provides good image quality for visual inspections. When numerous artifacts are present and fat suppression is insufficient, higher SNR and CNR do not always provide good diagnostic image quality.

Sugar consumption and ethanol fermentation by transporter-overexpressed xylose-metabolizing Saccharomyces cerevisiae harboring a xyloseisomerase pathway.

Four kinds of transporters, HXT1 and HXY7 from Saccharomyces cerevisiae, and GXF1 and GXS1 from Candida intermedia, were overexpressed in xylose-metabolizing S. cerevisiae harboring a xyloseisomerase-based pathway. Overexpression of transporter enhanced sugar consumption and ethanol production, and GXF1 was efficient for ethanol fermentation from both glucose and xylose.

Construction of a xylose-metabolizing yeast by genome integration of xylose isomerase gene and investigation of the effect of xylitol on fermentation.

A yeast with the xylose isomerase (XI) pathway was constructed by the multicopy integration of XI overexpression cassettes into the genome of the Saccharomyces cerevisiae MT8-1 strain. The resulting yeast strain successfully produced ethanol from both xylose as the sole carbon source and a mixed sugar, consisting of xylose and glucose, without any adaptation procedure. Ethanol yields in the fermentation from xylose and mixed sugar were 61.9% and 62.2% of the theoretical carbon recovery, respectively. Knockout of GRE3, a gene encoding nonspecific aldose reductase, of the host yeast strain improved the fermentation profile. Not only specific ethanol production rates but also xylose consumption rates was improved more than twice that of xylose-metabolizing yeast with the XI pathway using GRE3 active yeast as the host strain. In addition, it was demonstrated that xylitol in the medium exhibits a concentration-dependent inhibition effect on the ethanol production from xylose with the yeast harboring the XI-based xylose metabolic pathway. From our findings, the combination of XI-pathway integration and GRE3 knockout could be result in a consolidated xylose assimilation pathway and increased ethanol productivity.

Hourglass-shaped sublingual dermoid cyst: MRI features.

Dermoid cysts located in the floor of the mouth are classified as submental or sublingual based on their location with respect to the mylohyoid muscle. The lesion was located in the midline, involved the genioglossus and geniohyoid muscles, and extended down to the area superior to the mylohyoid muscle. An hourglass-shaped cyst of the floor of mouth was seen. Such magnetic resonance imaging findings appear to be characteristic of an extended sublingual dermoid cyst.

Leiomyoma of the trachea: CT and MRI findings.

A 47-year-old woman with a tracheal leiomyoma is described. Leiomyoma is a rare benign tumor of the trachea. Only 43 cases have been reported in the English- and Japanese-language literature. To our knowledge, this is the second time magnetic resonance imaging (MRI) findings have been reported. MRI can help discriminate between masses with a stalk and masses with a broad base, which in turn can help determine whether surgical resection of the tracheal leiomyoma is appropriate.

Spontaneous rupture of a necrotic hepatic angiosarcoma: findings on dual-phase computed tomography and angiography.

We present dual-phase computed tomographic (CT) and angiographic findings of a ruptured hepatic angiosarcoma. These tumors can be divided into two types: those with and those without gross central necrosis with hemorrhage. In our case, the tumor had gross central necrosis, and CT and angiographic findings showed a small number of areas with a centripetal enhancement pattern and the rest of the tumor with avascular areas. We found that dual-phase CT and angiographic findings are able to distinguish angiosarcoma, which mimics a hemangioma, as these lesions show avascular areas that reflect a mass with gross central necrosis.

Non-necrotic invasive squamous cell carcinoma associated with an inverted papilloma: MRI features.

We present the MRI findings of a carcinoma associated with an inverted papilloma located in the nasal cavity. This tumor can be divided into 2 types, those with and those without gross central necrosis. In our case, the tumor did not have any gross central necrosis, and MRI showed convoluted cerebriform patterns. We found that MRI is unable to distinguish malignant and benign regions in a central mass with no gross necrosis, since this lesion does not alter the basic morphological pattern of inverted papilloma.

Cellular leiomyoma of the nasal cavity: findings of CT and MR imaging.

Nasal leiomyoma, a benign tumor composed of smooth muscle cells, is rare in the head and neck region. Cellular leiomyomas of the uterus exhibit high intensity on T2-weighted images. Here we present a case of nasal leiomyoma in which the pathologic findings are similar to those of cellular leiomyoma. The present case exhibited slightly elevated intensity on T2-weighted images and marked enhancement on postcontrast images. CT findings showed a soft tissue lesion without bone erosion. These findings appear to be characteristic of intranasal leiomyoma.

Multislice computed tomography of pneumoparotid: a case report.

Pneumoparotid is a rare cause of parotid gland swelling that is often misdiagnosed and therefore incorrectly treated. It is the result of an increase in intraoral pressure and the subsequent forced entry of air through Stensen's duct. We report a case of a 15-year-old boy with a history of recurrent swelling of both parotid glands. The final diagnosis of pneumoparotid was established by multislice computed tomography (CT). The clinical presentation, pathogenesis, and radiographic findings are discussed.

Peripheral vascular coil for peripheral MR angiography: phantom-based comparison with body coil by SNR, CNR, and visual evaluation.

AIM: To evaluate the image quality of MR angiography (MRA) with a peripheral vascular coil. MATERIALS AND METHODS: A peripheral vascular coil, a technical coil used in MRA of the pelvis and lower extremities, has 12 individual coil elements arranged in six pairs. We evaluated the performance of a peripheral vascular coil for image quality, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and visual evaluation by comparing it to a body coil using a phantom. RESULTS: SNR with the peripheral vascular coil was 1.5-2.2 times higher than that with the body coil in vertical distance, and 1.6-1.8 times higher in horizontal distance. CNR with the peripheral vascular coil was 2.1-3.8 times higher than that with the body coil. Visual evaluation with the peripheral vascular coil was 1.1-1.2 times higher than with the body coil in spin echo sequences, and 1.2-1.9 times higher in 3D fast spoiled GRASS (3D-FSPGR) sequences. CONCLUSION: The peripheral vascular coil for peripheral MRA is robust and accurate in evaluating peripheral vascular diseases.