A discrete event simulation model in the case of managing a software project

The design and development of large-scale software projects is a complex endeavor, often facing problems like cost and schedule overruns as well as low quality. Over the last years the management of software development projects has been recognized as the cornerstone point of seeking improvement and solutions. Simulation modeling of the software project process is gaining interest among academics and practitioners, as a method to tackle the complex questions with which relevant enterprises are confronted. It offers support on several issues, such as defining software product development strategies, decision-making regarding process improvement and training, in a time span ranging from a short portion of the life cycle to long term product evolution, with organization-wide implications. The aim of this work is to implement a model simulating a core part of a software project process, enabling the estimation of several project development details such as delivery times and quality metrics. The purpose of the model is to assist project managers in control and monitoring, but also in identifying the best planning alternatives. The model scope covers a portion of the life cycle of an incremental software development venture.     

Regioselective ortho lithiation of 3-aryl and 3-styryl furans

[structure: see text]. An unusual regioselectivity pattern for the ortho lithiation of 3-aryl and 3-styryl furans has been uncovered wherein lithiation occurs preferentially at the sterically encumbered 2-position. The results are attributed, at least in part, to stabilization of the intermediate furyl anion by through-space donation of pi-electron density from the substituent appended at the 3-position to the lithium cation. This ortho lithiation reaction may be applied as a useful synthetic tool for accessing 2,3-disubstituted furans.     

Bacterial biosynthesis of cadmium sulfide nanocrystals

Semiconductor nanocrystals, which have unique optical and electronic properties, have potential for applications in the emerging field of nanoelectronics. To produce nanocrystals cheaply and efficiently, biological methods of synthesis are being explored. We found that E. coli, when incubated with cadmium chloride and sodium sulfide, have the capacity to synthesize intracellular cadmium sulfide (CdS) nanocrystals. The nanocrystals are composed of a wurtzite crystal phase with a size distribution of 2-5 nm. Nanocrystal biosynthesis increased about 20-fold in E. coli cells grown to stationary phase compared to late logarithmic phase. Our results highlight how different genetic and physiological parameters can enhance the formation of nanocrystals within bacterial cells.     

MEASUREMENT OF THE RATE OF UPTAKE AND SUBCELLULAR LOCALIZATION OF PORPHYRINS IN CELLS USING FLUORESCENCE DIGITAL IMAGING MICROSCOPY

Abstract A fluorescence imaging system incorporating a cooled slow-scan charge-coupled device camera was used to study the rate of uptake and subcellular localization of porphyrins in living cells. Measurements were carried out on human dermal fibroblasts (D532) using two different porphyrins meso -tetra(4- N -methylpyridyl)porphine (TMPP) and meso -tetra(4- N -hexylpyridyl)porphine (THPP). It was observed that TMPP was rapidly taken up by cells and principally located in the nucleus. The THPP, on the other hand, internalized more slowly and exhibited a particulate distribution in the cytoplasm.     

Classification of edible and lampante virgin olive oil based on synchronous fluorescence and total luminescence spectroscopy

Total luminescence and synchronous fluorescence spectroscopies were tested as regards their ability to differentiate edible from lampante virgin olive oils. Total luminescence spectra were recorded by measuring the emission spectra in the range 350-720 nm at excitation wavelengths from 320 to 535 nm. The synchronous fluorescence spectra of 41 edible and 32 lampante virgin olive oils were acquired by synchronous scanning the excitation and emission monochromator maintained at an offset value of 80 nm. Classification of virgin olive oils based on their synchronous fluorescence spectra was performed by hierarchical cluster analysis and principal component analysis using the spectral range of 429-545 nm. Principal component analysis provided better discrimination between the two classes, without any classification error, while hierarchical cluster analysis allowed 97.3% correct classification. These results indicate the capability of fluorescence techniques to differentiate virgin olive oils according to their quality.     

Isolation and X-ray crystal structure of tetrahydroisoquinoline alkaloids from Calycotome villosa Subsp. intermedias

Two tetrahydroisoquinoline alkaloids were extracted from the alkaloid fraction of a methanol extract of the seeds of Calycotome Villosa Subsp. intermedia. Their structures were established as (R)-1-hydroxymethyl-7-8-dimethoxy-1,2,3,4-tetrahydro- isoquinoline (1) and (S)-7-hydroxymethyl-2-3-dimethoxy-7,8,9,10-tetrahydroisoquinoline chloride (2) by spectroscopic techniques and X-ray diffraction analysis.     

Continuum limits for classical sequential growth models

A random graph order, also known as a transitive percolation process, is defined by taking a random graph on the vertex set {0,…,n ? 1} and putting i below j if there is a path i = i₁…i_k = j in the graph with i₁ < … < i_k. Rideout and Sorkin 14 provide computational evidence that suitably normalized sequences of random graph orders have a “continuum limit.” We confirm that this is the case and show that the continuum limit is always a semiorder. Transitive percolation processes are a special case of a more general class called classical sequential growth models. We give a number of results describing the large‐scale structure of a general classical sequential growth model. We show that for any sufficiently large n, and any classical sequential growth model, there is a semiorder S on {0,…,n ‐ 1} such that the random partial order on {0,…,n ‐ 1} generated according to the model differs from S on an arbitrarily small proportion of pairs. We also show that, if any sequence of classical sequential growth models has a continuum limit, then this limit is (essentially) a semiorder. We give some examples of continuum limits that can occur. Classical sequential growth models were introduced as the only models satisfying certain properties making them suitable as discrete models for spacetime. Our results indicate that this class of models does not contain any that are good approximations to Minkowski space in any dimension ≥ 2. © 2009 Wiley Periodicals, Inc. Random Struct. Alg., 2010     

The potential of UV femtosecond laser ablation for varnish removal in the restoration of painted works of art

Despite significant advances, laser ablation with nanosecond pulses presents limitations in dealing with the restoration of classes of painted works of art, such as paintings with a very thin layer of varnish. Femtosecond laser processing promises the means for overcoming such limitations. To this end, femtosecond ablation of two typical varnishes, dammar and mastic, is examined. For these varnishes, processing by Ti:Sapphire irradiation (800 nm) turns out to be ineffective. In contrast, irradiation with 248 nm ∼500 fs laser pulses results in a higher etching resolution (etching rates of ∼1 μm/pulse or less). For irradiation with few laser pulses at moderate laser fluences, etched morphology is far smoother than in the processing with nanosecond laser pulses. Furthermore, chemical modifications are considerably reduced (by nearly an order of magnitude), and exhibit a number of additional novel differences. Both etching rates and extent of chemical modifications are largely independent of varnish absorptivity. In all, femtosecond UV laser irradiation is indicated to hold a high potential, offering new perspectives for the restoration of painted works of art. Finally, a tentative model is advanced accounting in a consistent way for the observations.     

On a universal best choice algorithm for partially ordered sets

For the only known universal best choice algorithm for partially ordered sets with known cardinality and unknown order (proposed by J. Preater) we improve the estimation of the lower bound of its chance of success from the hitherto known constant 1/8 to 1/4. We also show that this result is the best possible for this algorithm, i.e., the 1/4 bound cannot be further improved. © 2007 Wiley Periodicals, Inc. Random Struct. Alg., 2008