Unoptimized Conditions Research Articles

Passively Q-switched Yb3+laser with Yb3+-doped CaF2crystal as saturable absorber

Passive Q-switching of a diode-pumped Yb:LYSO laser at 1060 nm with a Yb(3+) ions-doped CaF(2) crystal without the excited-state absorption (ESA) was demonstrated. An average output power of 174 mW with pulse duration of 5.6 mus and repetition rate of 27 kHz have been obtained under the unoptimized conditions. And the Q-switching conversion efficiency was as high as 51.7%.

NO Removal using Multipoint-to-plane DBD Ozone Injector

This paper describes an improvement of NO removal efficiency using dielectric barrier discharge (DBD) ozone injection system, with focusing comparison with a conventional plasma remediation system and effect of electrode configuration employed in the DBD reactor. Ozone was generated in the DBD reactor, and was fed to an oxidizing chamber to convert NO into NO2. The experiments were carried out with applying sinusoidal voltage of 10 kHz. Nitrogen, oxygen, and NO gas with concentration of several hundreds ppm was used as simulated gas of a diesel engine exhaust gas. For ozone injection system, we obtained the 18-g/kWh energy yield close to well-known 20 g/kWh. However, for the conventional plasma remediation system, we obtained the 10-g/kWh energy yield lower than well-optimized DBD reactor. Under well-optimized conditions, there was little difference in energy yield between the ozone injection system and the conventional plasma remediation system. On the other hand, the ozone injection system was also effective under unoptimized conditions. The electric fields of the needle-type electrodes were strongly distorted in spatial distribution, as a result, it caused the low-voltage operation and the dielectric loss compared with the plane electrode. The pyramid projection height was not dominant factor for the DBD reactor performance.

Optimization of polysaccharide and ergosterol production from Agaricus brasiliensis by fermentation process

Statistically based experimental designs were applied for the fermentation optimization of polysaccharide and ergosterol production from Agaricus brasiliensis in a stirred-fermenter. Culture temperature, agitation speed and initial pH were identified to have significant effects on polysaccharide and ergosterol production by a Plackett–Burman design. These three significant factors were subsequently optimized using steepest ascent method and Box–Behnken design. The validity of the optimum conditions was verified by separate experiments in which the polysaccharide and ergosterol yields were increased by 57% and 43%, respectively, as compared to those under unoptimized fermentation conditions.

Processing dependent behavior of soft imprint lithography on the 1-10-nm scale

This paper examines aspects of a soft nanoimprint lithography technique for operation at resolutions that approach the 1-nm regime. Systematic studies using polymer molds made with single walled carbon nanotubes (diameters between 0.5 and 5 nm) and high-resolution electron beam patterned layers of hydrogen silsesquioxane (line widths and heights /spl sim/10 and 20 nm, respectively) as templates reveal a dependence of the resolution limits on the polymer processing conditions. In particular, using a single choice of polymers for the molds and the molded materials, imprint results show that the conditions for spin casting and curing the polymers determine, to a large degree, the resolution and replication fidelity that can be achieved. Optimized procedures enable imprinted polymer surfaces that have a root mean squared surface roughness of /spl sim/0.26 nm or lower and a resolution as high as /spl sim/1 nm. These characteristics are significantly better than previous results obtained using these same polymers with unoptimized conditions. A diversity of molded polymers, including Bisphenol-F epoxy resin, polyacrylic acid, and polyurethane, show similar high-fidelity imprinting capabilities. Different procedures enable accurate relief replication for features with modest aspect ratios and dimensions of /spl sim/10 nm. The results indicate that choice of processing conditions is, in addition to materials selections, extremely important in achieving high-fidelity soft nanoimprint lithography in the 1-10-nm regime.

Enhanced production of extracellular ribonuclease from Aspergillus niger by optimization of culture conditions using response surface methodology

Response surface methodology were used to study the cumulative effect of the culture conditions and to enhance the production of extracellular ribonuclease in shake flask fermentation by Aspergillus niger. These conditions considered include initial pH, inoculum size, total carbon, ratio of glucose to corn powder, NH 4NO 3 and K 2SO 4. The relative importance of these conditions on ribonuclease production was investigated by using the Plackett–Burman experimental design. Initial pH, ratio of glucose to corn powder and NH 4NO 3 were found to significantly influence the ribonuclease production. For obtaining the mutual interaction between the variables and optimizing these variables, a 2 3 factorial central composite design using response surface methodology was employed. Initial pH has a significant positive effect on the ribonuclease production. NH 4NO 3 has a significant negative effect. The mutual interactions have no significant effect. The ribonuclease production was increased by 23.2% compared to that under unoptimized conditions. The fermentation time was also shortened after optimization.

Bioprocess development for the production of an antifungal molecule by Bacillus licheniformis BC98

The optimization of process parameters for the production of an antifungal molecule produced by Bacillus licheniformis BC98 was carried out using novel statistical tools. The parameters studied were pH, temperature and agitation rate. Fed batch cultivations were carried out since the maximum production of the molecule was observed in the late log phase. The statistical design used allows the evaluation of the effects of several different process variables in a single batch. Data from several batches indicated that while the effects of two of the variable factors, viz., temperature and agitation rate, were significant at 95% confidence intervals, the agitation rate was most critical for the production of the molecule, and pH had no significant effect. The cultivation of the bacterium under optimized conditions (fed batch, 150 rpm, 32°C, pH 5.8) resulted in a 30-fold increase compared with that under unoptimized conditions (shake flask, 100 rpm, 29°C, pH 5.8) in the production of the antifungal molecule.

Bioprocess Development for the Production of an Antifungal Molecule by Bacillus licheniformis BC98

The optimization of process parameters for the production of an antifungal molecule produced by Bacillus licheniformis BC98 was carried out using novel statistical tools. The parameters studied were pH, temperature and agitation rate. Fed batch cultivations were carried out since the maximum production of the molecule was observed in the late log phase. The statistical design used allows the evaluation of the effects of several different process variables in a single batch. Data from several batches indicated that while the effects of two of the variable factors, viz., temperature and agitation rate, were significant at 95% confidence intervals, the agitation rate was most critical for the production of the molecule, and pH had no significant effect. The cultivation of the bacterium under optimized conditions (fed batch, 150 rpm, 32°C, pH 5.8) resulted in a 30-fold increase compared with that under unoptimized conditions (shake flask, 100 rpm, 29°C, pH 5.8) in the production of the antifungal molecule.

Analysis of pharmaceutical tablets by laser ablation inductively coupled plasma atomic emission spectrometry and mass spectrometry (LA-ICP-AES and LA-ICP-MS)Electronic supplementary information (ESI) available: images of the ablation craters and trenches in the tablets. See http://www.rsc.org/suppdata/ja/b3/b314732k/

Laser ablation was studied with inductively coupled plasma atomic emission spectrometry (LA-ICP-AES) and with inductively coupled mass spectrometry (LA-ICP-MS) for the analysis of pharmaceutical tablets (10% and 20% Neusilin). For spot analysis with LA-ICP-AES, precision ranged from 12–31% relative standard deviation (RSD), but improved to 1–6% when ratios of signals were used. For continuous scanning, the precision ranged from 1–7% RSD. Weaker laser conditions required for ICP-MS gave precisions of 47–61% RSD (29% when signal ratios were used). Under unoptimized conditions, the detection limits for LA-ICP-AES of tablets were 70 µg g−1 for Al and 20 µg g−1 for Mg. The detection limits for LA-ICP-MS were 40 µg g−1 for Al and 6 µg g−1 for Mg. These results suggest that LA-ICP spectroscopy may find application in tablet analysis.

Biological, Pharmaceutical, and Analytical Considerations with Respect to the Transport Media Used in the Absorption Screening System, Caco-2

During the evaluation and selection of drug candidates, the Caco-2 cell culture system is commonly used for the determination of intestinal transport characteristics and to anticipate permeability limited drug absorption. Although classic HBSS-like buffered salt solutions are commonly used to perform Caco-2 transport experiments, different shortcomings (e.g., adsorption and low solubility) have been associated with the use of plain aqueous buffers. As transport experiments performed with unoptimized conditions may compromize the value of the Caco-2 model as a permeation screening tool, many efforts have been made to optimize the experimental conditions of Caco-2 transport assays. In this minireview, the hurdles associated with the use of saline aqueous buffers in Caco-2 transport experiments are summarized and the different options, which have been proposed to overcome these issues, are reviewed and discussed. Biologically, pharmaceutically, as well as analytically relevant media affecting the outcome of the transport experiments are described. Unfortunately, up to now, no systematic studies comparing the different experimental conditions have been performed, jeopardizing the possibility to define a (single) optimal solution to overcome the different issues associated with the use of saline aqueous buffers. Based on the reported options it can be proposed to use DMSO (<or=1%) in standard screening procedures for the ranking of compounds based on their apical to basolateral transport. If compounds are not soluble in DMSO 1%, dimethylacetamide (3%) or N-1-methyl-pyrrolidone (2.5%) are good alternatives. However, these options do not imitate the in vivo situation. If one wants to take into account the physiological relevance of the media, the use of a biologically relevant apical medium (e.g., FASSIF) in combination with an analytically friendly, sink condition creating basolateral solvent (e.g., containing a micelle forming agent) can be suggested.

A general approach for the use of oligonucleotide effectors to regulate the catalysis of RNA-cleaving ribozymes and DNAzymes.

A general approach is described for controlling the RNA-cleaving activity of nucleic acid enzymes (ribozymes and DNAzymes) via the use of oligonucleotide effectors (regulators). In contrast to the previously developed approaches of allosteric and facilitator-mediated regulation of such enzymes, this approach, called 'expansive' regulation, requires that the regulator bind simultaneously to both enzyme and substrate to form a branched three-way complex. Such three-way enzyme-substrate-regulator complexes are catalytically competent relative to the structurally unstable enzyme-substrate complexes. Using the 8-17 and bipartite DNAzymes and the hammerhead ribozyme as model systems, 20- to 30-fold rate enhancements were achieved in the presence of regulators of engineered variants of the above three enzymes, even under unoptimized conditions. Broadly, using this approach ribozyme and DNAzyme variants that are amenable to regulation by oligonucleotide effectors can be designed even in the absence of any knowledge of the folded structure of the relevant ribozyme or DNAzyme. Expansive regulation therefore represents a new and potentially useful technology for both the regulation of nucleic acid enzymes and the detection of specific RNA transcripts.

Optimization of microbiological parameters for enhanced griseofulvin production using response surface methodology

Central composite design was used to determine the optimal levels of microbiological parameters, viz., slant age, seed age and inoculum level, for enhanced griseofulvin production by Penicillium griseofulvum MTCC 1898 and Penicillium griseofulvum MTCC 2004 in shake flask fermentation. The optimal levels of slant age, seed age and inoculum level for Penicillium griseofulvum MTCC 1898 were found to be 8.8772 days, 4.2093 days, 12% (v/v) (≡17.56 kg dry cell mass/m3) and for Penicillium griseofulvum MTCC 2004, 8.221 days, 3.4875 days and 9% (v/v) (≡8.09 kg dry cell mass/m3) respectively. The yield of griseofulvin under optimal conditions was found to be 1.65 times for Penicillium griseofulvum MTCC 1898 and 1.07 times for Penicillium griseofulvum MTCC 2004 higher than that obtained using unoptimized conditions. The fermentation time for maximum production of griseofulvin by Penicillium griseofulvum MTCC 1898 and Penicillium griseofulvum MTCC 2004 decreased by 4 days and 2 days respectively.

Self-directing optimization of parameters for extracellular chitinase production by Trichoderma harzianum in batch mode

A novel optimization procedure has been developed to determine the best combination of variables in large scale fermentation systems. The self-directing optimization or the rotating simplex method of optimization was employed to determine the best suitable combination of parameters, pH (controlled), aeration rate and agitation rate for maximal production of chitinase by Trichoderma harzianum in batch culture. Extracellular enzyme activity increased from an initial value of 0.109 U under unoptimized conditions to a final value of 0.384 U after optimization. A controlled pH of 4.9, an aeration rate of 1.5 l l −1 per min, and an agitation rate of 224 rpm was found to be the best combination.

Performance of pectolytic enzymes during hydrolysis of pectic substances under assay conditions: a statistical approach

The reaction conditions were optimized for enzymatic hydrolysis of pectic substances using pectolytic enzymes produced by Aspergillus niger NCIM 548. Response surface methodology was used to optimize the reaction parameters and the central composite design was employed for this purpose. Pectin was used as the substrate for polymethylgalacturonase and pectinlyase, whereas polygalacturonic acid was the substrate for polygalacturonase. The volume ratio of reactants for maximum hydrolysis was determined under the assay conditions. The optimum amount of substrate and enzyme were found to be 0.2 cm 3 and 0.074 cm 3 for polymethylgalacturonase, 0.4 cm 3 and 0.086 cm 3 for polygalacturonase, and 0.63 cm 3 and 0.7 cm 3 for pectinlyase. The pH and temperature optima were found to be 5.3 and 30°C for polymethylgalacturonase, 6.6 and 26°C for polygalacturonase, and 4.8 and 35°C for pectinlyase. Under optimized conditions the enzyme activities were higher when compared to unoptimized conditions.

Effects of agitation and aeration on the production of extracellular glucose oxidase from a recombinant Saccharomycescerevisiae

A recombinant strain of Saccharomyces cerevisiae, GAL-GO2, was developed to facilitate the production of extracellular glucose oxidase (GOD). The recombinant strain secreted 85% (8.7 U/ml) of the total GOD (10.3 U/ml) produced in shake flask culture. For further enhancement of GOD production, optimization of the speed of agitation and the rate of aeration in a stirred tank fermentor was carried out. Response surface methodology with appropriate statistical experimental design was employed for this purpose. The maximal level of extracellular GOD was achieved when the speed of agitation and the rate of aeration were 420 rpm and 0.25 vvm, respectively. The enzyme production was increased by 74% compared to the level obtained under unoptimized conditions.

Scanning electron microscope studies of AlGaN films grown by organometallic vapor phase epitaxy

Microcathodoluminescence (MCL) and electron beam induced current (EBIC) studies were carried out on AlGaN films grown by organometallic vapor phase epitaxy (OMVPE) on sapphire and SiC. It is shown that both non-uniformities of distribution of deep recombination centers and of electron concentration can exist in AlGaN layers and in some cases these non-uniformities can be associated with the presence of certain types of defects. For example, regions adjacent to pores in AlGaN films are often depleted of deep centers one of which is the center responsible for yellow luminescence in AlGaN. Electron concentration is enhanced in hexagonal hillocks commonly observed for unoptimized growth conditions of AlGaN. There were also found non-uniformities in concentration of deep centers or in electron concentration that could not be related to particular morphological features or structural defects. Diffusion lengths measurements for various AlGaN films are also reported. The diffusion lengths are shown to be in the 0.3–0.5 μm range for most of the samples. In some of the studied AlGaN films it was found necessary to introduce two diffusion length values to describe the experimental EBIC distribution profiles. The longer diffusion length is found to increase in value for lower donor densities. Minority carriers lifetimes are found to be longer in AlGaN compared to GaN films.

The influence of sloped absorber sidewalls in deep x-ray lithography

An unfavourable transition region exists in deep x-ray lithography between the exposed and unexposed resist both when the absorbers on the mask are inclined as well as when the mask and substrate are tilted with respect to the x-ray beam. The slope of the resist walls is calculated according to an idealized assumption to exceed the slope of the absorber by a factor of more than 200. In experiments, however, a value of approximately 40 has been found. This lower value can be explained by the characteristics of the developer. For a very large transition region such as obtained by a tilt of some ten degrees, unoptimized development conditions lead to debris in deep and narrow trenches. When clean development occurs, the sidewall quality is the same as when there is a step increase in absorber height. Optically patterned resist templates may therefore be used for x-ray masks. In addition, tilting the mask and substrate offers a way to obtain three dimensional resist structures.

Novel decaffeination process using cyclodextrins

Various monomeric and polymerized cyclodextrins were investigated for their potential application in decaffeination. Treatment of aqueous caffeine solutions with monomeric gammacyclodextrin resulted in a significant reduction in the caffeine content of solutions over a wide range of caffeine concentration. Polymerized beta- and gamma-cyclodextrins were also demonstrated to be effective in removing caffeine by either a batch or column decaffeination process. Under the as-yet unoptimized process conditions, caffeine reduction of around 80% could readily be achieved. The process was applicable to caffeine-containing beverages (including coffee, tea, cocoa, and cola drinks) as well as theobromine-containing beverages (such as cocoa).