Scenario-integrated on-line optimisation of batch reactors

A key problem area in recipe design for exothermic batch reactors is the possible occurrence of failure situations, in particular malfunctions of the cooling system. Scenario-integrated optimization has recently been developed in order to tackle these problems rigorously. This paper extends the ideas presented earlier to the on-line solution of scenario-integrated optimization problems. Due to high computational requirements, the problems are formulated only for special cases and on short time horizons. It is shown that the resulting MPC scheme can indeed optimize batch reactor recipes while simultaneously guaranteeing the enforcement of constraints, both for nominal operation as well as for failure situations. A literature example and an industrial polymerization reactor are treated to illustrate these properties.     

CADASIL: 2 case reports of hereditary multi-infarct dementia

OBJECTIVE: To further investigate the role that cytogenetic may play in the diagnosis and prognosis of leukemia, a study was conducted in 319 acute leukemias. METHODS: 100 patients with acute lymphoblastic leukemia (ALL) and 219 patients with acute non-lymphoblastic leukemia (ANLL) were from Rui Jin Hospital, Xin Hua Hospital, Ren Ji Hospital and Shanghai Children's Hospital. Their cytogenetic data were analyzed together with those of morphology, immunology and clinical prognosis. RESULTS: In ALL group, 48 cases were karyotypically normal whereas 52 cases revealed chromosomal changes, among which 32 had quantitative abnormalities and 20 had qualitative abnormalities. The translocation t(9; 22) was identified in 11 out of 20 cases of structural aberrations (55%). Specific structural aberrations t(9; 22) and t(8; 14) were detected to be related to B-lineage associated differentiation antigens and t(8; 14) also with ALL-L3 according to FAB classification. With regard to clinical prognosis, the survival rate of structural aberration subset decreased significantly compared with the normal karyotype subset (P < 0.05). However, no statistically significant difference was found between hyperdiploidy subset (not including near-triploidy) and normal karyotype subset (P > 0.75). In ANLL group, 80% of de novo patients and relapsed patients had chromosomal abnormalities. Importantly, structural aberrations accounted for 73% of these abnormalities and frequently corresponded to specific types of FAB classification. Relevant prognostic studies demonstrated that t(15; 17) subset had the best overall survival probability, followed by t(8; 21) and normal karyotype subset, while the numerical aberration subset showed a relatively poor prognosis. CONCLUSION: Our data confirmed that cytogenetic study is important for the molecular study of the leukemogenesis. On the other hand, it also provides an independent parameter for prognosis in acute leukemia.     

A 3D transient model of keyhole and melt pool dynamics in laser beam welding applied to the joining of zinc coated sheets

In order to get a deeper understanding of laser beam welding, a process model was developed at the Chair of Manufacturing Technology. It is based on the continuity equation, the equation of heat conduction and the Navier–Stokes equation. The model includes effects of Fresnel absorption, vapor pressure, surface tension, melting and evaporation enthalpy and energy loss due to evaporating material. This paper presents the results of a three-dimensional, transient finite volume simulation of a laser beam deep penetration welding process based on this model. The simulations show periodic keyhole oscillations and the complex fluid dynamics of the melt pool. A comparison of the evaporation rates calculated from the simulations and the experimentally observed process emissions shows good correlation. Furthermore, the simulations show pore formation at higher feed rates, the influence of a gap on the welding process and give an explanation for the welding behavior of zinc coated steel sheets.     

Inhibition of human hepatitis B virus replication by AT-61, a phenylpropenamide derivative, alone and in combination with (-)beta-L-2',3'-dideoxy-3'-thiacytidine

AT-61, a member of a novel class of phenylpropenamide derivatives, was found to be a highly selective and potent inhibitor of human hepatitis B virus (HBV) replication in four different human hepatoblastoma cell lines which support the replication of HBV (i.e., HepAD38, HepAD79, 2.2.15, and transiently transfected HepG2 cells). This compound was equally effective at inhibiting both the formation of intracellular immature core particles and the release of extracellular virions, with 50% effective concentrations ranging from 0.6 to 5.7 microM. AT-61 (27 microM) was able to reduce the amount of HBV covalently closed circular DNA found in the nuclei of HepAD38 cells by >99%. AT-61 at concentrations of >27 microM had little effect on the amount of viral RNA found within the cytoplasms of induced HepAD38 cells but reduced the number of immature virions which contained pregenomic RNA by >99%. The potency of AT-61 was not affected by one of the mutations responsible for (-)-beta-L-2', 3'-dideoxy-3' thiacytidine (3TC) resistance in HBV, and AT-61 acted synergistic with 3TC to inhibit HBV replication. AT-61 (81 microM) was not cytotoxic or antiproliferative to several cell lines and had no antiviral effect on woodchuck or duck HBV, human immunodeficiency virus type 1, herpes simplex virus type 1, vesicular stomatitis virus, or Newcastle disease virus. Therefore, we concluded that the antiviral activity of AT-61 is specific for HBV replication and most likely occurs at one of the steps between the synthesis of viral RNA and the packaging of pregenomic RNA into immature core particles.     

Dissolution of multicomponent microbubbles in the bloodstream: 2. Experiment

The effect of the nature of the filling gas on the persistence of microbubbles in the bloodstream was studied. All the microbubbles were covered with the same shells. Various perfluorocarbons and perfluoropolyethers alone and as mixtures with nitrogen were used as the filling gases. The persistence time of microbubbles in the bloodstream tau increased with the molecular weight of the filling gas, from approximately 2 min for perfluorethane, to > 40 min for perfluorodiglyme, C6F14O3, and then decreased again to 8 min for C6F14O5. An acceptable ultrasound scattering efficacy was exhibited by the filling gases with intermediate molecular weights that possessed both a high saturated vapor pressure and a comparatively low water solubility (Ostwald coefficient). On the basis of the experimental data, it is concluded that the microbubble persistence tau is controlled primarily by the dissolution of microbubbles and not by the removal of the microbubbles by the reticular endothelial system. Although the qualitative experimental trends are in good agreement with the theoretical model developed previously, there are some quantitative differences. Possible reasons for these differences are discussed.     

Synthesis of colloidal solutions with silicon nanocrystals from porous silicon

In this work, we have obtained colloidal solutions of Si nanocrystals (Si-ncs), starting from free-standing porous silicon (PSi) layers. PSi layers were synthesized using a two-electrode Teflon electrochemical cell; the etching solution contained hydrogen peroxide 30%, hydrofluoric acid 40% (HF), and methanol. The anodizing current density was varied to 250 mA cm^-2, 1 A cm^-2, and 1.2 A cm^-2. Thus obtained, PSi was mechanically pulverized in a mortar agate; then, the PSi powders were poured into different solutions to get the final Si-ncs colloidal solutions. The different optical, morphological, and structural characteristics of the colloidal solutions with Si-ncs were measured and studied. These Si-ncs colloidal solutions, measured by photoluminescence (PL), revealed efficient blue-green or violet emission intensities. The results of X-ray diffraction (XRD) indicate that the colloidal solutions are mainly composed of silicon nanocrystallites. The result of UV–vis transmittance indicates that the optical bandgap energies of the colloidal solutions varied from 2.3 to 3.5 eV for colloids prepared in methanol, ethanol, and acetone. The transmission electron microscopy (TEM) images showed the size of the nanocrystals in the colloidal solutions. Fourier transform infrared spectroscopy (FTIR) spectra showed different types of chemical bonds such as Si-O-Si, Si-CH₂, and SiH _x , as well as some kind of defects.

PACS

61.46Df.-a; 61.43.Gt; 61.05.cp; 78.55.-m; 81.15.Gh     

Interactions of Skin with Gold Nanoparticles of Different Surface Charge,Shape, and Functionality

The interactions between skin and colloidal gold nanoparticles of different physicochemical characteristics are investigated. By systematically varying the charge, shape, and functionality of gold nanoparticles, the nanoparticle penetration through the different skin layers is assessed. The penetration is evaluated both qualitatively and quantitatively using a variety of complementary techniques. Inductively coupled plasma optical emission spectrometry (ICP‐OES) is used to quantify the total number of particles which penetrate the skin structure. Transmission electron microscopy (TEM) and two photon photoluminescence microscopy (TPPL) on skin cross sections provide a direct visualization of nanoparticle migration within the different skin substructures. These studies reveal that gold nanoparticles functionalized with cell penetrating peptides (CPPs) TAT and R₇ are found in the skin in larger quantities than polyethylene glycol‐functionalized nanoparticles, and are able to enter deep into the skin structure. The systematic studies presented in this work may be of strong interest for developments in transdermal administration of drugs and therapy.     

Comparing intergranular corrosion in Al-Mg-Si-Cu alloys with and without α-Al(Fe,Mn,Cu)Si particles

In this study, a model alloy without Fe and Mn additions, is compared with a commercial AA6005 alloy to further understand how the α-Al(Fe,Mn,Cu)Si particles affect intergranular corrosion (IGC) behaviour. Both alloys were subjected to an accelerated IGC test for durations ranging from 1 to 120 h. Microstructures were studied using scanning and transmission electron microscopy, and electron backscatter diffraction. The presence of α-Al(Fe,Mn,Cu)Si particles yields significantly more uniform IGC attacks and higher corrosion rates. However, the maximum depth of IGC attacks reaches similar values after ~24 h of exposure. This is attributed to the formation of Cu-rich particles along the grain boundaries during the corrosion process, which further catalyses the cathodic reactions.     

Computational fluid dynamics analysis of greenhouse microclimates by heated underground tubes

One of the main problems of Mediterranean climates is the large diurnal amplitude of temperature, with too low temperature during winter nights and too high temperatures during summer days. This is particularly felt in the north of Portugal, where the low temperature during winter nights can be compensated by the introduction of a heat source. The objective of this is work is to simulate the effects in the temperature and velocity fields by the introduction of hot water tubes along a greenhouse in night conditions. Three different situations are simulated: natural convective heating (case A), artificial heating tubes (case B), artificial heating tubes, and natural ventilation (case C). The commercial CFD package ANSYS^® (FLOTRAN module) is used for this propose.The turbulence is modelled by the RNG turbulence model. The numerical results are compared with experimental values, the procedure for which is also presented.The average increase in air temperature for cases A, B and C was 2.2°C, 6.7°C and 3.5°C, respectively. Turbulence is lower in case A, increases slightly when the heating system is introduced (case B), and increases significantly in case C due to the effect of natural ventilation. A very good agreement between experimental and numerical temperature values was verified. This allows validating the RNG turbulence model as suitable to simulate arch-shaped greenhouse microclimates. Some improvements can be done to this work: introduction of night-time crop transpiration, 3D simulations, or optimizing the size of the element mesh in order to reduce the computation time.     

Response of soil phosphorus content,growth and yield of wheat to long-term phosphorus fertilization in a conventional cropping system

The effect of annual banding of superphosphate (0–45 kg P ha⁻¹) on soil phosphorus (P) content, growth, and yield of wheat was investigated from 1982 to 1998 in a major rainfed wheat production area of South Africa. Conventional tillage practices in a wheat monoculture cropping system were followed under summer rainfall conditions. The responses of wheat growth to fertilizer P application were evident during early and late tillering growth stages, with decreased responses towards maturity. Although average yields varied between cropping seasons (0.881 to 3.261 t ha⁻¹) due to climatic conditions, significant exponential response patterns between yield and fertilizer P applications existed. Optimum yields were achieved with P applications of 10 to 15 kg P ha⁻¹. The recovery of fertilizer P in the grain decreased with increasing P applications. Results of soil P analyses and calculated P balance indicated a more rapid increase in soil P content with application of fertilizer P at levels above 20 kg P ha⁻¹, with gradual increases occurring at lower levels. This revised version was published online in August 2006 with corrections to the Cover Date.