Inert Part Research Articles

Estimating the velocity of chemically-driven Janus colloids considering the anisotropic concentration field.

The application of the active colloids is strongly related to their self-propulsion velocity, which is controlled by the generated anisotropic concentration field. We investigated the effect of this anisotropy on velocity induced by numerical treatments and size of Janus colloids. The far-field approximation is effective in estimating the velocity, even though it neglects the shape effect on the anisotropy of the concentration field. If the surface mobility contrast between the active and the inert part is moderate, the spherical approximation is feasible for sphere-like Janus colloids. Legendre expansion of the concentration field causes artificial anisotropy. Raising the order of the expansion can suppress this effect, but also distorts the concentration field at the top of active part. Thus, the order of the expansion should be chosen carefully depending on the goal of the study. Based on the verified Legendre expansion method and ionic-diffusiophoresis model, we show that due to the size-effect on both the concentration field and the surface mobility, increasing size of colloids can lower the self-propulsion velocity. Our finding is consistent with previous experimental observations without fitting parameter, shedding new light on the self-propulsion mechanism of chemically-driven active colloids. We further show a velocity reversal at high overall ζ potential induced by increasing size, providing a new way for controlling the dynamics of acitve colloids.

Application of Anaerobic Digestion Model No. 1 for modeling anaerobic digestion of vegetable crop residues: Fractionation of crystalline cellulose

Abstract Crystalline cellulose is fully resistant during anaerobic digestion (AD), which brings uncertainty to the use of mathematical models to simulate the dynamic AD process of lignocellulosic waste. In present study, a modified mathematical model, with crystalline cellulose as the primary consideration, was established based on Anaerobic Digestion Model No.1 to simulate the anaerobic bioconversion of vegetable crop residues (VCR) under mesophilic condition. In this model, VCR was divided into inert fraction (contained lignin and crystalline cellulose), as well as biodegradation parts of slowly hydrolysis fraction (SHF, contained hemicellulose and amorphous cellulose), and readily hydrolysis fraction (RHF, contained other organic components in the VCR). Data from a series of batch experiments have been used for the calibration and verification of this model. As a result, the calibrated model was found to match reasonably well the methane production data of three different VCRs, which implies that it was feasible to fractioned VCR into three fractions (SHF, RHF and inert part), and the operation that classified crystalline cellulose into the inert part, while regarded amorphous cellulose as SHF was appropriate. In order to be suitable for simulating the AD process of more other types of lignocellulosic waste, the model needs further modification and inspection. • A novel feedstock characterization method was proposed to modify ADM1. • Methane production of three vegetable crop residues were simulated by ADM1. • The interaction of several sensitive parameters was evaluated.

Adsorption and recovery of phosphate from aqueous solution by the construction and demolition wastes sludge and its potential use as phosphate-based fertiliser

This study aimed to investigate phosphate removal from aqueous effluents by an inorganic sludge from the inert part of construction and demolition wastes (CSW) as adsorbent. It is also discussed the application of the loaded P adsorbent as potential fertiliser. The CSW was also thermally treated at 800 °C for 2 h (CSW-T), and its influence in the P removal was also investigated. The characterisation techniques highlighted low porosity on CSW and CSW-T adsorbents and that they are mainly formed by oxides which could enhance the P uptake and recovery. In pH experiments, P adsorption increased as initial pH increased, at pH higher than 7.8 the P removal sharply increased due to the formation of calcium phosphate precipitate. The mechanism of the P adsorption onto CSW indicated that the process was mainly controlled by chemical bonding or chemisorption. The results showed that CSW-T was more effective for P removal in comparison to CSW based on the Liu isotherm, the maximum sorption capacity attained was 24.04 (CSW) and 57.64 mg g−1 (CSW-T). Based on the Avrami’s kinetic models, the time for attaining 95% of saturation was 212.6 (CSW), and 136.6 min (CSW-T). CSW and CSW-T showed the highest phosphate-removal performance among many adsorbents found in the literature; therefore, this kind of waste can be used widely as an inexpensive phosphate-recovery adsorbent. Besides, the P loaded adsorbents could be used as potential fertilisers which could be an interesting and efficient way of reuse for this waste.

Pilot satellitome analysis of the model plant, Physcomitrellapatens, revealed a transcribed and high-copy IGS related tandem repeat.

Satellite DNA (satDNA) constitutes a substantial part of eukaryotic genomes. In the last decade, it has been shown that satDNA is not an inert part of the genome and its function extends beyond the nuclear membrane. However, the number of model plant species suitable for studying the novel horizons of satDNA functionality is low. Here, we explored the satellitome of the model “basal” plant, Physcomitrellapatens (Hedwig, 1801) Bruch & Schimper, 1849 (moss), which has a number of advantages for deep functional and evolutionary research. Using a newly developed pyTanFinder pipeline (https://github.com/Kirovez/pyTanFinder) coupled with fluorescence in situ hybridization (FISH), we identified five high copy number tandem repeats (TRs) occupying a long DNA array in the moss genome. The nuclear organization study revealed that two TRs had distinct locations in the moss genome, concentrating in the heterochromatin and knob-rDNA like chromatin bodies. Further genomic, epigenetic and transcriptomic analysis showed that one TR, named PpNATR76, was located in the intergenic spacer (IGS) region and transcribed into long non-coding RNAs (lncRNAs). Several specific features of PpNATR76 lncRNAs make them very similar with the recently discovered human lncRNAs, raising a number of questions for future studies. This work provides new resources for functional studies of satellitome in plants using the model organism P.patens, and describes a list of tandem repeats for further analysis.

Simulation of a thermoelectric gas sensor that determines hydrocarbon concentrations in exhausts and the light-off temperature of catalyst materials

Abstract. Catalyst materials can be characterized with a thermoelectric gas sensor. Screen-printed thermopiles measure the temperature difference between an inert part of the planar sensor and a part that is coated with the catalyst material to be analyzed. If the overall sensor temperature is modulated, the catalytic activity of the material can be varied. Exothermic reactions that occur at the catalyst layer cause a temperature increase that can then be measured as a sensor voltage due to the Seebeck coefficient of the thermopiles. This mechanism can also be employed at stationary conditions at constant sensor temperature to measure gas concentrations. Then, the sensor signal changes linearly with the analyte concentration. Many variables influence the sensing performance, for example, the offset voltage due to asymmetric inflow and the resulting inhomogeneous temperature distributions are an issue. For even better understanding of the whole sensing principle, it is simulated in this study by a 3-D finite element model. By coupling all influencing physical effects (fluid flow, gas diffusion, heat transfer, chemical reactions, and electrical properties) a model was set up that is able to mirror the sensor behavior precisely, as the comparison with experimental data shows. A challenging task was to mesh the geometry due to scaling problems regarding the resolution of the thin catalyst layer in the much larger gas tube. Therefore, a coupling of a 3-D and a 1-D geometry is shown. This enables to calculate the overall temperature distribution, fluid flow, and gas concentration distribution in the 3-D model, while a very accurate calculation of the chemical reactions is possible in a 1-D dimension. This work does not only give insight into the results at stationary conditions for varying feed gas concentrations and used substrate materials but shows also how various exhaust gas species behave under transient temperature modulation.

Experimental study of the injection conditions influence over n-dodecane and diesel sprays with two ECN single-hole nozzles. Part II: Reactive atmosphere

The second part of this experimental analysis, presented in this paper, seeks to go deep on the characterization of the Spray C and Spray D nozzles from the Engine Combustion Network, investigating the penetration of fuel spray at reacting conditions alongside characteristic parameters of combustion such as ignition delay and lift-off length. Both ECN mono-orifice injectors have similar nozzle flow capacity but different conicity degrees and corner sharpness, being Spray C more susceptible to cavitate. Schlieren imaging technique was employed to quantitatively measure reactive penetration and ignition delay, while lift-off length was identified through OH∗ chemiluminescence. As in the inert part of this research, n-dodecane and commercial diesel were selected for the tests, thereby the effect of the fuel properties in the measured parameters was analyzed. Also, once again the concept of R-parameter, defined as the penetration derivative respect to the square root of time was calculated to delve into the penetration behavior. The experiments were performed in a constant pressure-flow facility able to reproduce engine-like thermodynamic conditions. Results revealed that R-parameter evolution can be divided in four stages: an inert zone, a ‘bump’, a ‘valley’ part and a quasi-steady one that overlaps the previous inert part. Those stages are highly governed by ambient temperature and oxygen concentration. Nozzle geometry and fuel properties demonstrated to have a noteworthy influence on all measured parameters.

Kazakhstan black soil organic substance agrogenic transformation

Currently despite the extended study of the temporary dynamic of the cultivated soil organic substance on the global scale scientists pay much attention to the establishing the patterns of its quantitative transformation on the regional level depending on the systems of agricultural exploitation for the purpose of clarifying the worldwide estimate of humus reserve in relation to the issue of the greenhouse effect. In this regard we have examined the modern dynamic (19902015) of the regular and southern black soil organic substance in the conditions of long-term stationary field experiments in the primary grain-sowing region of the Northern Kazakhstan. Based on the data from alternative time periods on the proportion of Соргand N in the upper (mainly 025 cm) layer of virgin and agrogenic black soil of Akmolinsk and Kostanay regions of Kazakhstan we have discovered the distinctive characteristics of changes in the content of soil organic substance. It has been demonstrated that the content of humus in the regular black soil is significantly higher than that in the southern carbonated black soil. Evaluation of transforming and inert pool of organic carbon in virgin and agrogenic variants of southern black soil has been made. It has been established that currently in the result of influence from various methods of southern black soil treatment the rate of humus percentage decrease is slowing down in comparison with that of the previous period of its agricultural exploitation, however, in practice, those methods, including the subsurface tilling, do not halt the de-humusization process. Content of humus in soil of the variants with continuous spring wheat is approaching that with continuous complete fallow. There are sufficient grounds to suggest that the reason for de-humusization of the southern black soil could reside in biochemical (mineralization), as well as physical (deflation) loss of humus. Particular danger comes from the wind erosion resulting in percentage of humus dropping even below its minimal value, i.e. due to the decrease of nearly unrecoverable inert part. In agrogenic regular black soil, during the closing period of its agricultural exploitation, there has been no humus loss detected, which is most probably related to the existence of protective anti-erosion forest belts in the studied fields area.

A study on diesel spray tip penetration and radial expansion under reacting conditions

The shape of Diesel spray was investigated at real engine conditions in a constant pressure combustion chamber. Schlieren imaging technique was used to make quantitative measurements of spray tip penetration and radial width stressing the impact that the fuel combustion and heat release have on the spray shape. The heat-release region and the Lift-off length were identified measuring OH* chemiluminescence. The fuel (n-dodecane) as well as the operating conditions and the injector used (single axially-oriented hole, 89 μm-diameter) were chosen following the guidelines of the Engine Combustion Network. The effects of different operating parameters on the axial and radial expansion were also investigated. According to the results the reacting spray can be divided into three parts: an inert part, a transient one, and a quasi-steady one that lays between the two other regions. A new method for evaluating this radial expansion of reacting spray was developed, which was evaluated under the different operating conditions. Results show that the radial expansion increases with increasing injection pressure and decreasing ambient temperature and ambient density. The oxygen concentration has no obvious effect on the radial expansion.

Modeling of the methane production and pH value during the anaerobic co-digestion of dairy manure and spent mushroom substrate

A dynamic mathematical model, based on the IWA Anaerobic Digestion Model No. 1 (ADM1), was used to predict the methane production and pH value during anaerobic co-digestion of dairy manure (DM) and spent mushroom substrate (SMS) under different hydraulic retention times (HRT). In this model the degradation of DM was modeled according to classical ADM1, while SMS was divided into inert part as well as biodegradation parts of slowly hydrolysable fraction (SHF) and readily hydrolysable fraction (RHF). The data from lab-scale experiment was used to calibrate and validate this model. The results showed that the model was able to predict reasonably well the steady-state results of methane production and pH value at HRT of 12, 20 and 28 d. The results also indicated that the model suitability to assess the combined effects of HRT and substrate ratio on the methane production and pH value.

Liposome-encapsulated doxorubicin citrate (Myocet) for treatment of recurrent epithelial ovarian cancer

The aim of this study was to assess the clinical activity and toxicity of liposome-encapsulated doxorubicin citrate (Myocet) in a retrospective multicenter cohort of epithelial ovarian, primary peritoneal, and tubal cancer patients. Records of patients with recurrent epithelial ovarian, primary peritoneal, and tubal cancer treated with liposome-encapsulated doxorubicin citrate (60 mg/m on day 1 of a 21-day cycle) after failure of more than one previous regimen were reviewed. Fifty-three patients were evaluated for efficacy and toxicity. The median age of the patients was 59 (range 39-73). The median follow-up was 6 months (range 1-17). One patient (1.9%) showed a complete response and 13 patients (24.5%) showed a partial response, yielding an overall response rate of 26.4% (14/53 patients). Clinical benefit was achieved in 36 patients (67.9%). The median progression-free survival (PFS) for the entire study population was 4.0 months (range 1.0-14.8). The median PFS for platinum-sensitive and platinum-resistant patients was 4.0 months (ranges 1.0-14.8 and 1.0-9.4, respectively; P=0.652). The median overall survival from the start of liposome-encapsulated doxorubicin citrate was 10.0 months. Multivariate survival analysis showed no association between the liposome-encapsulated doxorubicin citrate line of treatment or platinum sensitivity to PFS in age and BRCA status-adjusted models. Only 11.3% of patients experienced grade 3-4 hematologic toxicities, 80% grade-2 alopecia, and 50% grade-1-2 fatigue. No other grade-4 toxicities, no significant cardiac events, or hand and foot syndromes were reported. Liposome-encapsulated doxorubicin citrate was well tolerated, with a good response and high clinical benefit rate. Further evaluation in a larger prospective cohort is warranted.

Dynamics of basaltic glass dissolution – Capturing microscopic effects in continuum scale models

The method of ‘multiple interacting continua’ (MINC) was applied to include microscopic rate-limiting processes in continuum scale reactive transport models of basaltic glass dissolution. The MINC method involves dividing the system up to ambient fluid and grains, using a specific surface area to describe the interface between the two. The various grains and regions within grains can then be described by dividing them into continua separated by dividing surfaces. Millions of grains can thus be considered within the method without the need to explicity discretizing them. Four continua were used for describing a dissolving basaltic glass grain; the first one describes the ambient fluid around the grain, while the second, third and fourth continuum refer to a diffusive leached layer, the dissolving part of the grain and the inert part of the grain, respectively.The model was validated using the TOUGHREACT simulator and data from column flow through experiments of basaltic glass dissolution at low, neutral and high pH values. Successful reactive transport simulations of the experiments and overall adequate agreement between measured and simulated values provides validation that the MINC approach can be applied for incorporating microscopic effects in continuum scale basaltic glass dissolution models. Equivalent models can be used when simulating dissolution and alteration of other minerals.The study provides an example of how numerical modeling and experimental work can be combined to enhance understanding of mechanisms associated with basaltic glass dissolution. Column outlet concentrations indicated basaltic glass to dissolve stoichiometrically at pH 3. Predictive simulations with the developed MINC model indicated significant precipitation of secondary minerals within the column at neutral and high pH, explaining observed non-stoichiometric outlet concentrations at these pH levels. Clay, zeolite and hydroxide precipitation was predicted to be most abundant within the column.

Algorithm for weight loss after gastric bypass surgery considering body mass index, gender, and age from the Bariatric Outcome Longitudinal Database (BOLD)

BackgroundInsight into the effects of gender and age on bariatric weight loss can be disturbed by the well-known influence of initial body mass index (BMI) on excess weight loss (%EWL). Alternative metrics can be found that eliminate this influence. Their formulas can be used to construct an algorithm in which mean weight loss becomes a constant value, describing the effectiveness of the operation independent of the initial BMI. The objective of this study was to create an algorithm describing weight loss after LRYGB in search for a better outcome metric to demonstrate unequivocally the influence of patient characteristics on bariatric results. MethodsNadir weight loss results of BOLD patients, grouped by gender and age (<40 yr and ≥40 yr), with ≥2 years follow-up after LRYGB and initial BMI ≥30 and<80 kg/m2, are expressed in 26 different metrics with formula: 100%×(initial BMI – nadir BMI)/(initial BMI – a) with “reference BMI” a = 0–25 kg/m2. For each subgroup, the “optimal reference BMI” (a) generating the smallest deviation and without significant difference in outcome between lighter and heavier patients is used to construct an algorithm (Mann-Whitney U test; P<.0002). Mean nadir relative weight loss results (b) are compared. ResultsA total of 8945 patients met inclusion criteria (mean initial BMI, 47.7 kg/m2; median age, 48 yr; 20.0% male). Both female subgroups had optimal reference BMI: a = 10 kg/m2; both male subgroups: a = 17 kg/m2. LRYGB effectiveness (b) was significantly higher for younger patients and for female patients. The %EWL metric rendered different significances. ConclusionsBoth genders have age-independent metrics for which nadir relative weight loss after LRYGB is not influenced by initial BMI. The resulting algorithm nadir BMI = a + (100%−b) × (initial BMI−a) consists of an inert part (a = 10–17 kg/m2) on which the bariatric effectiveness (b) does not act and an alterable part (initial BMI−a) on which it does. The proposed metric percentage alterable weight loss (%AWL) reduces results to constant values for bariatric effectiveness (b), facilitating research on the precise effect of patient characteristics and surgical variables on postoperative weight loss better than %EWL, a metric able to produce false conclusions. Women and younger patients had significantly more weight loss; initial BMI had no effect.

Dilution effects analysis of opposed-jet H2/CO syngas diffusion flames

This paper reported the analysis of dilution effects on the opposed-jet H2/CO syngas diffusion flames. A computational model, OPPDIF coupled with narrowband radiation calculation, was used to study one-dimensional counterflow syngas diffusion flames with fuel side dilution from CO2, H2O and N2. To distinguish the contributing effects from inert, thermal/diffusion, chemical, and radiation effects, five artificial and chemically inert species XH2, XCO, XCO2, XH2O and XN2 with the same physical properties as their counterparts were assumed. By comparing the realistic and hypothetical flames, the individual dilution effects on the syngas flames were revealed. Results show, for equal-molar syngas (H2/CO = 1) at strain rate of 10 s−1, the maximum flame temperature decreases the most by CO2 dilution, followed by H2O and N2. The inert effect, which reduces the chemical reaction rates by behaving as the inert part of mixtures, drops flame temperature the most. The thermal/diffusion effect of N2 and the chemical effect of H2O actually contribute the increase of flame temperature. However, the chemical effect of CO2 and the radiation effect always decreases flame temperature. For flame extinction by adding diluents, CO2 dilution favours flame extinction from all contributing effects, while thermal/diffusion effects of H2O and N2 extend the flammability. Therefore, extinction dilution percentage is the least for CO2. The dilution effects on chemical kinetics are also examined. Due to the inert effect, the reaction rate of R84 (OH+H2 = H+H2O) is decreasing greatly with increasing dilution percentage while R99 (CO+OH→CO2+H) is less affected. When the diluents participate chemically, reaction R99 is promoted and R84 is inhibited with H2O addition, but the trend reverses with CO2 dilution. Besides, the main chain-branching reaction of R38 (H+O2→O+OH) is enhanced by the chemical effect of H2O dilution, but suppressed by CO2 dilution. Relatively, the influences of thermal/diffusion and radiation effects on the reaction kinetics are then small.

Catalytic properties of Cu/SBA-3 in oxidative dehydrogenation of methanol—The effect of the support composition

Silicate, niobosilicate and aluminosilicate mesoporous sieves of SBA-3 type with hexagonal arrangement of pores were synthesised and modified by the wetness impregnation with copper (1 wt% loading). The physicochemical properties of the samples were investigated by XRD, N 2 adsorption–desorption, XRF, ICP, H 2-TPR, ESR, UV–vis, XPS techniques and in acid-basic test reactions—acetonyloacetone cyclisation, 2-propanol reaction as well as by pyridine adsorption combined with FTIR measurements. The oxidative/dehydrogenation catalytic activity of prepared catalysts was examined in the methanol oxidation reaction. Depending on the chemical composition of the SBA-3 support, various copper species were found to be formed and a range of catalytic activities could be achieved. On SBA-3, AlSBA-3 and NbSBA-3 the following copper species were found dominant: bulk CuO, oligonuclear [Cu δ+ ⋯O δ− ⋯Cu δ+ ] n clusters and isolated copper cationic species, respectively. Migration of niobium species from the inert part of walls onto the surface after copper loading was observed. The Si/Nb ratio in the support was established to determine the activity and selectivity of Cu modified samples. By the proper combination of the content of Nb and Cu on the surface of SBA-3 materials it can be possible to obtain the catalysts selective to the desired products in oxidation of methanol. The highest production of formaldehyde from methanol was obtained on Cu/NbSBA-3-64 (Si/Nb = 57 in bulk and 43 on the surface, Nb/Cu = 0.8 on the surface).

Plane isolation model for superconducting [formula omitted] prediction using an ‘parent-calibration’ obtained for Y Ba 2CuCu 2O y and applied to other model systems

An empirical bond order model indicates that a high degree of plane isolation increases both optimal T c and optimal hole concentrations. Within this plane isolation model Y Ba 2CuCu 2O y is analyzed with respect to structural literature data concerning distance to the apical O, d c . From d c the bond valences in the c -direction, s c , are calculated. They extrapolate to a finite intercept for the undoped parent, s c p . Subtracting s c p from s c , yields extra holes beyond the equilibrium distribution of the parent. This part is here identified to correspond to the inert part of the total holes, h c that extend into the c -direction. The remaining holes in the planes are effective in fixing the optimal T c . Accordingly a physically meaningful basis for the empirical rules is found and ‘all planar’ cuprates can be modeled purely on structure. As examples materials with high [Hg analogs] and low d c [Bi analogs] are successfully dealt with in this modified bond order model.

Total organic carbon and its composition in long-term field experiments in the Czech Republic

Total organic carbon content and its composition have been evaluated in the topsoil in the selected plots of 13 long-term field experiments conducted in different soil and climate conditions. The altitude of the sites ranged from 225 – 670 m above sea level. Four variants of the organic and mineral fertilization were selected in each experiment: Nil, which did not receive any organic or mineral fertilizers since the beginning of the experiment, mineral fertilized variant NPK, organic fertilized (manured) variant FYM and both organic and mineral fertilized variant FYM + NPK. Total organic carbon (C) content in the topsoil differed as a result of the soil and climate conditions (it ranged from 0.96 – 1.80% C in the Nil variants) and due to the organic and mineral fertilization. The inert and decomposable part of the soil organic C content was calculated and the hot water soluble carbon content was determined. Relationships between the individual SOM fractions have shown a highly significant correlation, except for the decomposable C calculated as a difference to Nil variant.

Non-equilibrium theories for macroscale heat transfer: ablative composite layer systems

An original model describing non-equilibrium heat transfer in ablative composite layers has been studied. The model is obtained as an extension of previous work involving the use of the volume averaging method to upscale the micro-scale equations. Using this methodology, it is shown that non-equilibrium models existing in the literature may lead to equilibrium conditions for typical aerospace applications. The new model presented in this paper takes into account two separate macro-scale “phases”, but, contrary to previous models, they are constituted of the inert part of the material, on one side, and the mixture of gas and pyrolysable part of the material on the other side. The theoretical development allows to estimate the transport properties in the macro-scale model from micro-scale unit cell characteristics. They are obtained for different types of unit cells: simple stratifed unit cells, and unit cells characteristic of woven composites. Quantitative indications are given for the estimates of the macro-scale thermal diffusivity tensors, and for the volume heat exchange coefficient.

Dynamics of Unsteady-State Catalytic Distillation in a Packed Column with a Varied Length of the Reaction Zone

Theoretical and experimental data are reported for steady- and unsteady-state distillation accompanied by a reversible catalytic reaction in the liquid phase, specifically, butyl acetate–ethanol transesterification in a packed column. It is demonstrated by a computational experiment that, at any initial composition of the reaction mixture in the reboiler, be it an equimolar mixture for the forward or back reaction or an equimolar four-component mixture, the system arrives at the same steady-state distribution of the component concentrations along the column height. The time it takes for the system to reach the steady state depends on the reaction zone length: it increases with decreasing ratio of the length of the catalytic part of the packed bed to the length of the inert part of the packed bed. The mathematical description of the process is in satisfactory agreement with experimental data.

Group functions, Löwdin partition, and hybrid QC/MM methods for large molecular systems

The problem of developing an exact form of the junction between the quantum and classical parts in a hybrid QC/MM approach is considered. We start from the full Hamiltonian for the whole system and assume a specific form of the electron wavefunction, which allows us to separate the electron variables relevant to the reactive (quantum) part of the system from those related to the inert (classical) part. Applying the Lowdin partition to the full Hamiltonian for the molecular system results in general formulae for the potential energy surfaces of a molecular system composed of different parts provided some of these parts are treated quantum mechanically whereas others are treated with use of molecular mechanics. These principles of separating electron variables have been applied to construct an efficient method for analysis of electronic structure and d-electron excitation spectra of transition metal complexes. This method has been also combined with the MM approximation in order to get a description for potential energy surfaces of the complexes and to develop a consistent approach to the known problem of extending molecular mechanics to transition metals.

Dynamics of internal diffusion during the hydrogenation of 1,5,9-cyclododecatriene on Pd/Al 2O 3

Dynamic and pseudo-steady state diffusion–reaction models were simulated for the three-phase consecutive hydrogenation of 1,5,9-cyclododecatriene on a shell Pd/Al 2O 3 catalyst in order to examine the time evolution of concentration profiles inside the catalyst pellet: a model accounting only for the dynamics of the active layer and a model taking also into account the inert part of the catalyst were compared. In the conditions of the semibatch experiments ( T=433 K, p H 2 =1.2 MPa), all the models lead to the same bulk concentration–time curves, but the hydrocarbon concentration profiles in the pores are dependent on the model. The influence of the diffusion in the inert part of the catalyst on the bulk concentrations becomes nonnegligible only when the external liquid volume (out of the catalyst) is reduced. The transient evolution of the concentration profiles in the pores show that hydrogen concentration reaches its steady state within a few seconds, while the evolution of the organic concentration profiles is slower. Furthermore, the reaction rate has been found to be only affected by the hydrogen diffusion. The diffusion of organics can control the reaction rate only for low values of organic concentration and higher pressure in hydrogen.