Productivity Analysis and System Coherence

Productivity analyses have been undertaken by such a variety of specialists and in such differing contexts that few can cope with the broadly dispersed literature. It is not surprising, therefore, that the same problems are rediscovered time and again, that faulty concepts remain in use and that empirical findings are often misinterpreted. Such shortcomings will continue to hamper the development of this field until past advances are more effectively consolidated and the current frontiers more clearly delineated. In this paper, therefore, certain past findings will be used as points of departure for considering the problems and means of effecting further gains.One comprehensive exploration of productivity analysis suggested four general conclusions, along with their analytical foundations, which seem to have withstood subsequent consideration well enough to serve as bases for this undertaking:

1. 1)
   That productivity analysis serves a variety of purposes and hence requires a corresponding variety of appropriately designed measures:
    
2. 2)
   That the productivity of any activity system should refer not to any single input-output ratio, but to an integrated network of such measures;
    
3. 3)
   That the effects of productivity adjustments depend not only on their magnitudes, but also on the sources responsible for them, on the nature of the changes in input-output relationships involved, and on managerial choices among alternative means of harnessing their potential benefits;
    
4. 4)
   That evaluating such effects requires supplementing physical with cost measures and then with successively broader criteria until these come to reflect the guiding objectives of the system under study.
    

Such conclusions imply that productivity adjustments may assume many forms, that apparent increases in productivity levels need not always be beneficial, that the very same pattern of productivity changes may have quite different effects in dissimilar circumstances and, finally, that productivity increases are not ends in themselves but merely one means of promoting more fundamental ends. Further development may seek to extend the original analysis beyond standardized commodity production to other economic activities, beyond a plant or firm to larger aggregates, and beyond short periods. But such elaborations of this framework require the strengthening of its conceptual foundations. Hence, it is to these that primary attention will be given.     

Entropy of transfer of n-nitroalkanes from n-octane to water at 25°C

Entropy of transfer of nitromethane, nitroethane, 1-nitrobutane, 1-nitropentane, and 1-nitrohexane from n-octane to water at 25°C is calculated using an electrostatic model. The calculations indicate that the electrostatic transfer entropy depends primarily on the dipole moment and the size of the-C–NO₂ group, showing a trend which is similar to that previously found for the transfer free energy of the same process.     

On a Non-Periodic Modified Euler Equation: Well-Posedness and Quasi-Invariant Measures

Potential Analysis - We consider a modified Euler equation on $\mathbb {R}^{2}$ . We prove existence of weak global solutions for bounded (and fast decreasing at infinity) initial conditions and...     

Gas chromatography-mass spectrometry of the trimethylsilyl (oxime) ether/ester derivatives of cholic acids: their presence in the aquatic environment

This paper presents a derivatization, mass fragmentation study relating to the most common six cholic acids, such as cholic, lithocholic, chenodeoxycholic, ursodeoxycholic, 3-hydroxy,7-ketocholanic and dehydrocholic acids, identified and quantified as pollutants in the aquatic environment at the first time. Derivatizations have been performed with the two-step process (1: oximation, 2: silylation) varying the time and temperature of both reactions. Optimum responses have been obtained after 30 min oximation with hydroxylamine.HCl and 90 min silylation with hexamethyldisilazane and trifluoroacetic acid at 70 degrees C. Fragmentation patterns of the trimethylsilyl (oxime) ether/ester derivatives of all six cholic acids provided the theoretically expected, fully derivatized compounds. Reproducibility/linearity of derivatives calculated on the basis of the corresponding selective fragment ions, characterized by the relative standard deviation percentages of measurements, proved to be < or =4.9 (RSD%). The practical utility of the method was shown by the identification and quantification of cholic acids as pollutants in the aquatic environment. Subsequently to a solid phase extraction study varying the pH of extractions (pH 2, pH 4 and pH 7), applying the OASIS cartridges, it has been confirmed that the recoveries for all six cholic acids are acceptable, varying between 77% and 104%, and are independent on the pH. The total cholic acid content of a Hungarian wastewater plants' influent wastewater varied between 184 microg/L and 356 microg/L, while the Danube rivers' cholic acid content was 4.1 microg/L, only.     

PELDOR measurements on a nitroxide-labeled Cu(II) porphyrin: orientation selection, spin-density distribution, and conformational flexibility

Metal ions are functionally or structurally important centers in metalloproteins or RNAs, which makes them interesting targets for spectroscopic investigations. In combination with site-directed spin labeling, pulsed electron-electron double resonance (PELDOR or DEER) could be a well-suited method to characterize and localize them. Here, we report on the synthesis, full characterization, and PELDOR study of a copper(II) porphyrin/nitroxide model system. The X-band PELDOR time traces contain besides the distance information a convolution of orientational selectivity, conformational flexibility, exchange coupling, and spin density distribution, which can be deconvoluted by experiments with different frequency offsets and simulations. The simulations are based on the known experimental and spin Hamiltonian parameters and make use of a geometric model as employed for structurally similar bis-nitroxides and spin density parameters as obtained from density functional theory calculations. It is found that orientation selection with respect to dipolar angles is only weakly resolvable at X-band frequencies due to the large nitrogen hyperfine coupling of the copper porphyrin. On the other hand, the PELDOR time traces reveal a much faster oscillation damping than observed for structurally similar bis-nitroxides, which is mainly assigned to a small distribution in exchange couplings J. Taking the effects of orientation selectivity, distribution in J, and spin density distribution into account leads finally to a narrow distance distribution caused solely by the flexibility of the structure, which is in agreement with distributions from known bis-nitroxides of similar structure. Thus, X-band PELDOR measurements at different frequency offsets in combination with explicit time trace simulations allow for distinguishing between structural models and quantitative interpretation of copper-nitroxide PELDOR data gives access to localization of copper(II) ions.     

Zwitterionic Polymeric Sulfur Ylides with Minimal Charge Separation Open a New Generation of Antifouling and Bactericidal Materials**

Zwitterionic polymers are widely employed hydrophilic building blocks for antifouling coatings with numerous applications across a wide range of fields, including but not limited to biomedical science, drug delivery and nanotechnology. Zwitterionic polymers are considered as an attractive alternative to polyethylene glycol because of their biocompatibility and effectiveness to prevent formation of biofilms. To this end, zwitterionic polymers are classified in two categories, namely polybetaines and polyampholytes. Yet, despite a fundamental interest to drive the development of new antifouling materials, the chemical composition of zwitterionic polymer remains severely limited. Here, we show that poly(sulfur ylides) that belong to the largely overlooked class of poly(ylides), effectively prevent the formation of biofilms from pathogenic bacteria. While surface energy analysis reveals strong hydrogen-bond acceptor capabilities of poly(sulfur ylide), membrane damage of pathogenic bacteria induced by poly(sulfur ylides) indicates toxicity towards bacteria while not affecting eucaryotic cells. Such synergistic effect of poly(sulfur ylides) offers distinct advantages over polyethylene glycol when designing new antifouling materials. We expect that our findings will pave the way for the development of a range of ylide-based materials with antifouling properties that have yet to be explored, opening up new directions at the interface of chemistry, biology, and material science.     

Accurate Extraction of Nanometer Distances in Multimers by Pulse EPR

Pulse electron paramagnetic resonance (EPR) is gaining increasing importance in structural biology. The PELDOR (pulsed electron–electron double resonance) method allows extracting distance information on the nanometer scale. Here, we demonstrate the efficient extraction of distances from multimeric systems such as membrane‐embedded ion channels where data analysis is commonly hindered by multi‐spin effects.     

Quantifying the intrinsic effects of two point mutation models of proline-proline diamino acid diamide: a first-principle computational study

Two sites of a Pro-Pro diamide were subjected to individual Pro --> Thr point mutations. The parent diamide Pro-Pro as well as selected conformers of the Pro-Thr and Thr-Pro mutant models were subjected to molecular computations at the B3LYP/6-31G(d) level of theory. At the optimized geometries, thermodynamic functions (S, H, and G) were computed. In order to assess relative stabilities of the mutant models, isodesmic reactions were constructed to calculate DeltaS, DeltaH, and DeltaG, relative to the initial Pro-Pro state. The importance of intramolecular hydrogen bonds, involving the -OH group of the Thr side chain, which emerged after the point mutations were also examined. Our findings suggest a novel approach to analyzing the stability of point mutants in peptide models through the analysis of thermodynamic functions.     

Interpretation of synchrotron radiation circular dichroism spectra of anionic, cationic, and zwitterionic dialanine forms

Electronic absorption and synchrotron radiation circular dichroism (SRCD) spectra of the anionic, cationic, and zwitterionic forms of L-alanyl-L-alanine (AA) in aqueous solutions were measured and interpreted by molecular dynamics (MD) and ab initio computations. Time-dependent density functional theory (TD DFT) was applied to predict the electronic excited states. The modeling enabled the assessment of the role of molecular conformation, charge, and interaction with the polar environment in the formation of the spectral shapes. Particularly, inclusion of explicit solvent molecules in the computations appeared to be imperative because of the participation of water orbitals in the amide electronic structure. Implicit dielectric continuum solvent models gave inferior results for clusters, especially at low-energy transitions. Because of the dispersion of transition energies, tens of water/AA clusters had to be averaged in order to obtain reasonable spectral shapes with a more realistic inhomogeneous broadening. The modeling explained most of the observed differences, as the anionic and zwitterionic SRCD spectra were similar and significantly different from the cationic spectrum. The greatest deviation between the experimental and theoretical curves observed for the lowest-energy negative anion signal can be explained by the limited precision of the TD DFT method, but also by the complex dynamics of the amine group. The results also indicate that differences in the experimental spectral shapes do not directly correlate with the peptide main-chain conformation. Future peptide and protein conformational studies based on circular dichroic spectroscopy can be reliable only if such effects of molecular dynamics, solvent structure, and polar solvent-solute interactions are taken into account.