Simultaneous electrokinetic flow and dielectrophoretic trapping using perpendicular static and dynamic electric fields

Microfluidics is a rapidly growing field that offers great potential for many biological and analytical applications. There are important advantages that miniaturization has to offer, such as portability, shorter response times, higher resolution and sensitivity. There is growing interest on the development of microscale techniques. Among these, electrokinetic phenomena have gained significant importance due to their flexibility for handling bioparticles. Dielectrophoresis (DEP), the manipulation of particles in non-uniform electric fields due to polarization effects, has become one of leading electrokinetic techniques. DEP has been successfully employed to manipulate proteins, DNA and a wide array of cells, form bacteria to cancer. Contactless DEP (cDEP) is a novel dielectrophoretic mode with attractive characteristics. In cDEP, non-uniform electric fields are created using insulating structures and external electrodes that are separated from the sample by a thin insulating barrier. This prevents bioparticle damage and makes cDEP a technique of choice for many biomedical applications. In this study, a combination of cDEP generated with AC potentials and electrokinetic liquid pumping generated with DC potentials is employed to achieve highly controlled particle trapping and manipulation. This allows for lower applied potentials than those used in traditional insulator-based DEP and requires a simpler sytem that does not employ an external pump. This is the first demonstration of electrokinetic (EK) pumping in which the driving electrodes are not in direct contact with the sample fluid. Multiphysics simulations were used to aid with the design of the system and predict the regions of particle trapping. Results show the advantages of combining AC-cDEP with DC EK liquid pumping for dynamic microparticle trapping, release and enrichment.     

Output tracking control of a parallel-flow heat exchange process

In this paper, we consider an output tracking problem of a parallel-flow heat exchange process with distributed and boundary inputs. As the distributed inputs to the system, the output feedback control is first applied. Under zero boundary inputs, it is shown that the C₀-semigroup describing the closed-loop system satisfies the spectrum determined growth condition. Next, we apply a backstepping method to the design of the boundary inputs for output tracking. Our main result shows that the output of the system reaches a reference signal in finite time under both the output feedback control and the boundary control law derived by the backstepping method.     

Triboelectric energy harvesting with surface-charge-fixed polymer based on ionic liquid

A novel triboelectric energy harvester has been developed using an ionic liquid polymer with cations fixed at the surface. In this report, the fabrication of the device and the characterization of its energy harvesting performance are detailed. An electrical double layer was induced in the ionic liquid polymer precursor to attract the cations to the surface where they are immobilized using a UV-based crosslinking reaction. The finalized polymer is capable of generating an electrical current when contacted by a metal electrode. Using this property, energy harvesting experiments were conducted by cyclically contacting a gold-surface electrode with the charge fixed surface of the polymer. Control experiments verified the effect of immobilizing the cations at the surface. By synthesizing a polymer with the optimal composition ratio of ionic liquid to macromonomer, an output of 77 nW/cm² was obtained with a load resistance of 1 MΩ at 1 Hz. This tuneable power supply with a μA level current output may contribute to Internet of Things networks requiring numerous sensor nodes at remote places in the environment.     

TNM classification: cancer of the stomach

The 5th edition of TNM Classification was published by the UICC (International Union Against Cancer) in 1997. In the classification of gastric cancer, anatomical subsites and N category were newly published. The new classification and role of the Japanese TNM Joint Committee were described in this paper. The Japanese committee had strongly advocated to continue "the anatomical N classification", because the hazard ratios were more significant for prognosis of patients with gastric cancer, and had many reasonable and scientific advantages. However, the UICC introduced "a new N classification by number of metastatic lymph nodes" because of the difficulty in studying nodes by anatomical classification. The new TNM can not be considered an improved classification, and so we are looking for a more scientific, practical, and internationally acceptable classification.     

Deoxidation equilibria of molten nickel by Mg-Al and Mn-Al

The deoxidation equilibria of aluminum-magnesium and aluminum-manganese in liquid nickel equilibrated with Al₂O₃-saturated MgAl₂O₄ and MnAl₂O₄, respectively, were investigated in the temperature range of 1773 to 1873 K. At 1773 K, the oxygen levels could be reduced to 5.8 to 6.6 ppm with 2.5 to 10 ppm magnesium and 0.05 to 0.9 mass pct aluminum in the Ni-Mg-Al-O system, and to less than 20 ppm with more than 1.5 mass pct manganese and 30 ppm aluminum in the Ni-Mn-Al-O system. With the experimental results mainly obtained in the present work, the interaction parameters, e _Mg ^Al , e _Mn ^Al , e _O ^Mg , e _O ^Mn , and e _O ^Al , and the equilibrium constants, log , log , log K _Mg(Ni), log K _Mn(Ni), and log K _Al(Ni), were estimated using a multiple regression analysis.     

Fabrication of micro-parts by high aspect ratio structuring and metal injection molding using the supercritical debinding method

 High aspect ratio micro-fabrication method using metal injection molding (MIM) is developed. In the MIM process, the powder is mixed with the binder and the mixture is injection molded. The binder is extracted from the molded parts using supercritical carbon dioxide, and the parts are sintered. Employing this process, micro-pattern which has aspect ratio more than 5 can be molded by stainless-steel powder. In this method, a micro-pattern made by laser ablation is used as a die. As compared with other micro-fabrication techniques, this method can utilize the molding die repeatedly. Consequently, the cost of production micro-parts can be decreased by this method in the actual production process.     

Growth rate dependence of enzyme synthesis in chemostat cultures: α-amylase, β-galactosidase,acid phosphatase and β-fructosidase

Specific rate of enzyme synthesis in microbial cells was correlated to specific growth rate in chemostat culture using three strains of microorganism. α-Amylase production by Bacillus subtilis was linearly associated with growth rate in a glucose-limited chemostat culture. β-Galactosidase production by Saccharomyces fragilis was rather invariable with growth rate in a galactose medium. β-Fructosidase production by Saccharomyces carlsbergensis in a phosphate-poor glucose medium was independent on growth rate, except at low dilution rates where it increased with growth rate. Production of acid phosphatase by the same microbe showed a maximum at a particular intermediate dilution rate. These relationships were summarised with an equation of induction—repression model. Comparison of the chemostat results with those of batch fermentation provided some enhancement factors of a continuous fermentation: 1.23–9.82 regarding enzyme productivity and 0.53–2.88 regarding enzyme concentration. The production of β-fructosidase was much improved among the enzymes tested when continuous culture methods were used.     

Mesoporous silicas containing carboxylic acid: Preparation,thermal degradation,and catalytic performance

The calcination and thermal degradation behaviors of surfactants in mesoporous silicas SBA-15 and MCM-41 were investigated by FT-IR, ¹³C CP/MAS NMR, TG/DTA, and GPC. It was found that carboxylic acid-containing products were generated as active components in the mesopores of SBA-15 and MCM-41 from the triblock copolymer (PEO)₂₀(PPO)₇₀(PEO)₂₀ and cetyltrimethylammonium bromide (CTAB), respectively; the latter materials were used as templates. The carboxylic acid-containing mesoporous silica obtained showed a catalytic activity for hydrolysis of sucrose. The acidity was evaluated by means of NaOH titration. The acidity sensitively depended on both the calcination temperature and the atmosphere; the maximum appeared at 150 °C in air for SBA-15 where the highest activity was observed. However, the product in MCM-41 showed a lower catalytic activity than that in SBA-15. The SBA-15 product was easily leached from the mesopores of SBA-15 into the solution, but the degree of leaching for MCM-41 was considerably smaller than that for SBA-15.     

Indenyl-silica xerogels: new materials for supporting metallocene catalysts

Inorganic–organic hybrid xerogels bearing indenyl groups on their surfaces have been synthesised by the sol–gel method. The hybrid xerogels were obtained by hydrolysis and polycondensation of bisindenyldiethoxysilane (Ind₂Si(OEt)₂) and tetraethoxysilane, TEOS (Si(OEt)₄) under two different conditions. Chemical structure was investigated by ultraviolet spectroscopy (UV–VIS), transmittance (FT-IR) and diffuse-reflectance (DRIFTS) infrared spectroscopy, magic angle spin nuclear magnetic resonance (MAS-NMR) and X-ray photoelectron spectroscopy (XPS). Xerogel texture and structure were analysed by nitrogen sorption based on the Brunauer–Emmett–Teller (BET) method, X-ray diffraction spectroscopy (XRD), and natural scanning electron microscopy (N-SEM). Under our experimental conditions, in alkaline milieu and 1:3 indenyl/TEOS ratio, a xerogel with higher indenyl content, but nonporous and showing agglomerate patterns was produced (xerogel I). Spherical particles of diameter about 6–8 μm where obtained in the absence of catalyst, using 1:5 indenyl/TEOS ratio, higher temperature and shorter reaction time (xerogel II). Xerogel II was used as support for heterogeneous metallocene catalyst synthesis. The resulting catalyst presented high Zr content (0.68 mmol Zr g_cat⁻¹) and high catalyst activity (40×10³ kg PE mol⁻¹ Zr h⁻¹) in ethylene polymerisation.     

A new triangle element for the axisymmetric UBET

UBET is a useful technique for the analysis of forging and other metal forming processes. However, geometrical shape of a element used in this technique is limited to a rectangle or a right angle triangle. To overcome this problem, an arbitrary shape triangle element which define a kinematically admissible velocity field using stream function is proposed and applied to the UBET. Although, this triangle element is a proper element to be used for the analysis of plane strain problem, it has several problems to be applied to axisymmetric problem. Therefore, a new arbitrary shape triangle element which has constant inlet flow at the side of the triangle is developed. On this element, a kinematically admissible velocity field is expressed easily using stream function and a second order isoparametric triangle element. The power consumption is calculated by the numerical integration. Also, a new conversion technique is introduced for the minimization of power consumption, and it makes possible to use many variables on UBET.