Evaluating cost impacts on reverse logistics using an Economic Order Quantity (EOQ) model with environmental and social considerations

Central European Journal of Operations Research - Societal awareness and legislation changes concerning sustainability have affected how organizations generate value for stakeholders, as well as...     

Cycloparaphenylene (CPP) series are molecular models for graphene armchair edges: trends in their aromaticity and cyclic conjugation are evaluated

Cycloparaphenylene ([r]CPP) and cyclacene ([r]CA) series are models for short carbon nanotubes. It is shown that armchair edges in model cycloparaphenylenes possess greater aromaticity and cyclic conjugation than do zigzag edges in model cyclacenes. According to Aihara’s bond resonance energy (BRE) and Bosanac and Gutman energy effect (ef) measurements, cycloparaphenylenes are twice as aromatic as cyclacenes. The general solution of all eigenvalues of all members of the cycloparaphenylene series is given. The origin of the recurrence of some eigenvalues are determined.     

Amplitude des oscillations d'ondes solitaires généralisées

Various physical systems of dispersive waves admit solutions in the form of generalized solitary waves. Such waves result from the resonance between a long localized wave and short periodic oscillations. Many estimates (rigorous and numerical) have been given for the amplitude of the ripples in the tail of the generalized solitary wave when its central part has a sech² shape. This Note provides estimates (not yet rigorous) for the ripple amplitude when the central part is flat and wide. To cite this article: C. Fochesato, F. Dias, C. R. Acad. Sci. Paris, Ser. I 337 (2003).     

Linear theory of wave generation by a moving bottom

The computation of long wave propagation through the ocean obviously depends on the initial condition. When the waves are generated by a moving bottom, a traditional approach consists in translating the ‘frozen’ sea bed deformation to the free surface and propagating it. The present study shows the differences between the classical approach (passive generation) and the active generation where the bottom motion is included. The analytical solutions presented here exhibit some of the drawbacks of passive generation. The linearized solutions seem to be sufficient to consider the generation of water waves by a moving bottom. To cite this article: D. Dutykh et al., C. R. Acad. Sci. Paris, Ser. I 343 (2006).     

Endogenous phosphorus excretion by sheep fed hydrolyzed sugarcane bagasse, lucerne hay and citrus pulp

Summary The objective of this study was to determine endogenous phosphorus excretion in sheep fed with different diets. Sixteen male growing sheep, received a basic diet with: 42% hydrolyzed sugarcane bagasse (HSB), 45% lucerne hay (LH) plus 14% hydrolyzed sugarcane bagasse, and 30% citrus pulp (CTP) plus 40% hydrolyzed sugarcane bagasse. A dose of 7.7 MBq ³²P was injected into the left jugular vein of each animal. The P endogenous fecal losses were: 1.69, 2.50, 2.33 and 1.45 g/animal for treatments HSB, LH, and CTP respectively (P>0.05). The type of diet influenced slight endogenous P excretion but altered excretion of P in urine. Endogenous P excreted in feces (P_F) comes mainly from saliva and represents an important loss of P. The estimation of net requirements of phosphorus (P) for ruminants includes endogenous losses, which is also essential for calculating true absorption of this mineral. Physical structure of the feed may influence endogenous losses, altering the metabolism of P and also the demand of this mineral, therefore being important to know how different feeds affect endogenous P losses.     

Flow systems exploiting in-line prior assays

An expert sequential injection system involving a prior assay is proposed for spectrophotometric determination of phosphate and eventually zinc in soil extracts. The result of phosphate determination is the basis for a concentration-oriented decision regarding to the need or not for zinc determination. Zinc was only determined if a threshold value (peak height corresponding to 5.0 mg l⁻¹ P) was surpassed. The methods involved formation of molybdenum blue and the Rhodamine 6G/ammonium thiocyanate/Zn²⁺ ternary complex. Variations in the threshold value were < 2% during 4 h operating periods, false responses were not verified, and the analytical time was reduced in about 30%. Precise results (R.S.D. <3% P and < 1% Zn) in agreement with spectrophotometry and flame atomic absorption spectrometry were obtained. The innovation permits faster information processing, as well as a reduction in the number of measurements, number of analytical steps, laboratorial time, and consumption of sample and reagents, thus waste generation.     

Enzymatic kinetic of cellulose hydrolysis

The ethanol effect on the Trichoderma reesei cellulases was studied to quantify and clarify this inhibition type. To determine inhibition parameters of crude cellulase and purified exoglucanase Cel7A, integrated Michaelis-Menten equations were used assuming the presence of two inhibitors: cellobiose as the reaction product and ethanol as a possible bioproduct of cellulose fermentation. It was found that hydrolysis of cellulose by crude enzyme follows a model that considers noncompetitive inhibition by ethanol, whereas Cel7A is very slightly competitively inhibited. Crude cellulase is much more inhibited (K _iul=K _icl=151.9 mM) than exoglucanase Cel7A (K _icl=1.6 × 10¹⁵ mM). Also, calculated inhibition constants showed that cellobiose inhibition is more potent than ethanol inhibition both for the crude enzyme as well as exoglucanase Cel7A.