Real-time imaging of tunable adenosine 5-triphosphate release from an MCM-41-type mesoporous silica nanosphere-based delivery system

We studied a mesoporous silica nanosphere (MSN) material with tunable release capability for drug delivery applications. We employed luciferase chemiluminescence imaging to investigate the kinetics and mechanism of the adenosine 5-triphosphate (ATP) release with various disulfide-reducing agents as uncapping triggers. ATP molecules were encapsulated within the MSNs by immersing dry nanospheres in aqueous solutions of ATP followed by capping of the mesopores with chemically removable caps, such as cadmium sulfide (CdS) nanoparticles and poly(amido amine) dendrimers (PAMAM), via a disulfide linkage. By varying the chemical nature of the 'cap' and 'trigger' molecules in our MSN system, we discovered that the release profiles could indeed be regulated in a controllable fashion.     

High-throughput single-cell fluorescence spectroscopy

A high-throughput method for measuring single-cell fluorescence spectra is presented. Upon excitation with a 488 nm argon-ion laser many bacterial cells were imaged by a 20x microscope objective while they moved through a capillary tube. Fluorescence was dispersed by a transmission diffraction grating, and an intensified charge-coupled device (ICCD) camera simultaneously recorded the zero and the first orders of the fluorescence from each cell. Single-cell fluorescence spectra were reconstructed from the distance between zero-order and first-order maxima as well as the length and the pixel intensity distribution of the first-order images. By using this approach, the emission spectrum of E. coli cells expressing green fluorescent protein (GFP) was reconstructed. Also, fluorescence spectra of E. coli cells expressing non-fluorescent apo-subunits of R-phycoerythrin (R-PE) were recorded after incubation of the cells with phycoerythrobilin (PEB) chromophore. The fluorescence spectra are in good agreement with results obtained on the same cells using a fluorescence spectrometer or a fluorescence microscope. When spectra are to be acquired, this approach has a higher throughput, better sensitivity, and better spectral resolution compared to flow cytometry.     

Direct observation of anomalous single-molecule enzyme kinetics

We report the direct measurement of the single-molecule enzymatic cleavage rates of ApaI-DNA complex in the presence of various concentrations of MgCl2 solution with total internal reflection fluorescence microscopy. We made use of the native adsorption properties of the two 12-base sticky ends of the DNA molecules to partially immobilize and stretch out the ApaI-DNA complex onto a glass surface. Synchronous initiation of reaction was achieved by the influx of Mg2+ solution. Once the DNA was cut, the two fragments (38 and 10 kb) would either collapse or further stretch out depending on the solution flow. The time required for cleaving each ApaI-lambda-DNA complex was recorded and analyzed. At low concentrations, the higher the concentration of Mg2+, the faster the DNA was cut. However, Mg2+ ion is no longer the limiting factor when its concentration is greater than 5 mM. A surprising result is that at all concentrations the decrease in intact DNA population as a function of time is linear rather than exponential. This suggests that there exists a distribution of ApaI conformations around the restriction site.     

Mining Customer Value: From Association Rules to Direct Marketing

Direct marketing is a modern business activity with an aim to maximize the profit generated from marketing to a selected group of customers. A key to direct marketing is to select a subset of customers so as to maximize the profit return while minimizing the cost. Achieving this goal is difficult due to the extremely imbalanced data and the inverse correlation between the probability that a customer responds and the dollar amount generated by a response. We present a solution to this problem based on a creative use of association rules. Association rule mining searches for all rules above an interestingness threshold, as opposed to some rules in a heuristic-based search. Promising association rules are then selected based on the observed value of the customers they summarize. Selected association rules are used to build a model for predicting the value of a future customer. On the challenging KDD-CUP-98 dataset, this approach generates 41% more profit than the KDD-CUP winner and 35% more profit than the best result published thereafter, with 57.7% recall on responders and 78.0% recall on non-responders. The average profit per mail is 3.3 times that of the KDD-CUP winner.     

Cyanogen bromide treatment of methionine-containing compounds

The preparation of a series of X-Met-Gly-OEt and X-Met-Phe-OMe and their treatment with CNBr in either 70% or 97-100% formic acid at 25 degrees C are described where X is methanesulfonyl (mesyl), p-nitrobenzyloxycarbonyl, phthaloyl, trifluoroacetyl, acetyl, formyl, or tert-butyloxycarbonyl. Total cleavage of the peptide esters was found with mesyl-, p-nitrobenzyloxycarbonyl-, phthaloyl-, and trifluoroacetylmethionyl derivatives which indicated the suitability of these derivatives as amino protecting groups in peptide synthesis. Treatment of the acetylmethionyl peptide esters with CNBr in 70 and 97-100% formic acid resulted in 92 and 98% cleavage, respectively. With formylmethionyl peptide esters, about 85-95% cleavage was estimated when either 70 or 97-100% formic acid was used as the solvent. With the tert-butyloxycarbonylmethionyl derivatives, CNBr treatment in 70% formic acid resulted in about 93% cleavage of peptides, while treatment in 97-100% formic acid led to only 30-33% release of C-terminal amino acid esters. Quantitative cleavage of the carbonylbis(methionyl peptide esters) was observed. The reaction of CNBr with N-terminal methionyl derivatives containing free alpha-amino groups revealed that free methionine was quantitatively converted to homoserine lactone, whereas methionine ethyl ester and methionyl peptides (Met-Gly and Met-Phe) disappeared from the reaction mixture in 70% formic acid with only partial splitting of the ester (16%) or peptide bond (45%).     

A possible alternative approach to the thermal insulation of pipelines

The concept of internally lining pipes to achieve the required degree of thermal insulation is examined with respect to minimising the rate of energy losses. Suggestions are made concerning the optimal dimensions for district-heating horizontal pipelines conveying hot water at 95°C. These design recommendations arise out of the presented analysis for minimising the total rate of financial expenditure upon energy for pumping and heating the water.     

Evaluation of conduction mixing lengths for subchannel analysis of finite LMFBR bundles

An analytical, two-dimensional, multi-region, multi-cell technique was developed for the thermal analysis of LMFBR rod bundles. Local temperature fields of various unit cells were obtained for seven- and nineteen-rod bundles of different geometries and power distributions. The validity of the technique was verified by its excellent agreement with the THTB calculational result. By comparing the calculated fully-developed circumferential cladding temperature distribution with those of the experimental measurements, an axial correction factor has been derived to account for the entrance effect under practical conditions.A scheme was also developed to couple the two-dimensional distributed analysis and lumped parameter calculation such that the entrance effect can be implanted into the distributed parameter analysis. The technique has demonstrated its applicability for a seven-rod bundle. The results of calculation were compared to those of three-dimensional analysis.     

Zeolites in Microsystems for Chemical Synthesis and Energy Generation

Zeolites were incorporated as membrane and catalyst in chemical microsystems for portable energy generation and fine chemical synthesis. Microfabricated HZSM-5 micromembrane was used as a proton-exchange membrane in a miniature direct methanol fuel cell (μ-DMFC). The good proton conductivity of HZSM-5 micromembrane was attributed to a Grotthus-like diffusion of protons along the water molecules bridging neighboring aluminum sites in the hydrated HZSM-5. The 6-μm thick HZSM-5 micromembrane exhibited comparable proton flux as Nafion^® 117 and delivered a P _max of 2.9 mW cm^?2 (E = 0.33 V) at room temperature. This is smaller compared to 16.5 mW cm^?2 (E = 0.23 V) for a Nafion^®-based μ-DMFC and was believed to be caused by adsorbed methanol molecules interrupting the proton transport along the water bridge. A Cs-exchanged NaX on NaA bilayer catalyst-membrane incorporated in microreactor channels was used for the Knoevenagel condensation reactions between benzaldehyde and (1) ethyl cyanoacetate, (2) ethyl acetoacetate (EAA) and (3) diethyl malonate. Microreactor and membrane microreactor gave higher conversion compared to fixed-bed and batch reactors, but the reaction of benzaldehyde and EAA in the microreactor had poorer selectivity due to the slow diffusion of the product molecules in the microchannel that allowed their further reactions to form undesired byproducts.     

The influence of heat treatment on the properties of shape memory fibers. II. Tensile properties,dimensional stability,recovery force relaxation,and thermomechanical cyclic properties

Shape memory fibers (SMFs) were prepared via a melt spinning process. The fibers were subject to different heat treatments to eliminate internal stress and structure deficiency caused during the melt spinning process. The influences of heat treatments on the SMF thermal properties, molecular orientation, tensile properties, dimensional stability, recovery force relaxation, and thermomechanical cyclic properties were studied. It was found that the heat treatments increased soft segment crystallinity and phase separation while decreased molecular orientation. The low‐temperature heat treatment increased the breaking elongation, shape fixity ratios, and decreased boiling water shrinkage while shape recovery ratios were decreased. High‐temperature treatment increased both the shape recovery ratios, fixity ratios, recovery stress stability and at the same time decreasing the fiber mechanical strength. The results from differential scanning calorimetry, molecular orientation apparatus, and cyclic tensile testing were used to illustrate the mechanism governing the mechanical properties and shape memory effect. To obtain comprehensive outstanding properties, the SMF is expected to be treated at a high temperature because of the hard segment high glass transition temperature. Unfortunately, the heat treatment could not be conducted at a too high temperature because the SMF became too tacky and soft due to the melting of the soft segment phase. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dynamic modelling of CO2 absorption for post combustion capture in coal-fired power plants

Power generation from fossil fuel-fired power plants is the largest single source of CO₂ emissions. Post combustion capture via chemical absorption is viewed as the most mature CO₂ capture technique. This paper presents a study of the post combustion CO₂ capture with monoethanolamine (MEA) based on dynamic modelling of the process. The aims of the project were to compare two different approaches (the equilibrium-based approach versus the rate-based approach) in modelling the absorber dynamically and to understand the dynamic behaviour of the absorber during part load operation and with disturbances from the stripper. A powerful modelling and simulation tool gPROMS was chosen to implement the proposed work. The study indicates that the rate-based model gives a better prediction of the chemical absorption process than the equilibrium-based model. The dynamic simulation of the absorber indicates normal absorber column operation could be maintained during part load operation by maintaining the ratio of the flow rates of the lean solvent and flue gas to the absorber. Disturbances in the CO₂ loading of the lean solvent to the absorber significantly affect absorber performance. Further work will extend the dynamic modelling to the stripper for whole plant analysis.