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Reactive Process (reactive + process)
Selected AbstractsInfluence of Transient Flow on Contaminant BiodegradationGROUND WATER, Issue 2 2001Mario Schirmer The rate of biodegradation in contaminated aquifers depends to a large extent on dispersive mixing processes that are now generally accepted to result from spatial variations in the velocity field. It has been shown, however, that transient flow fields can also contribute to dispersive mixing. The influence of transient flow on biodegrading contaminants is particularly important since it can enhance mixing with electron acceptors, further promoting the reactive process. Using numerical simulations, the effect of transient flow on the behavior of a biodegradable contaminant is evaluated here both with respect to the development of apparently large horizontal transverse dispersion and also with respect to enhanced mixing between the substrate (electron donor) and electron acceptor. The numerical model BIO3D, which solves for advective-dispersive transport coupled with Monod-type biodegradation of substrates in the presence of an electron acceptor, was used for the simulations. The model was applied in a two-dimensional plan view mode considering a single substrate. Transient flow fields were found to yield larger apparent transverse dispersion because the longitudinal dispersivity also acts transverse to the mean flow direction. In the reactive case, the transient flow field increases substrate-oxygen mixing, which in turn enhances the overall rate of biodegradation. The results suggest that in the case of moderate changes of flow directions, a steady-state flow field can be justified, thereby avoiding the higher computational costs of a fully transient simulation. The use of a higher transverse horizontal dispersivity in a steady flow field can, under these conditions, adequately forecast plume development. [source] Variational transition-state theory study of the atmospheric reaction OH + O3 , HO2 + O2INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2007Li-Ping Ju We report variational transition-state theory calculations for the OH + O3, HO2 + O2 reaction based on the recently reported double many-body expansion potential energy surface for ground-state HO4 [Chem Phys Lett 2000, 331, 474]. The barrier height of 1.884 kcal mol,1 is comparable to the value of 1.77,2.0 kcal mol,1 suggested by experimental measurements, both much smaller than the value of 2.16,5.11 kcal mol,1 predicted by previous ab initio calculations. The calculated rate constant shows good agreement with available experimental results and a previous theoretical dynamics prediction, thus implying that the previous ab initio calculations will significantly underestimate the rate constant. Variational and tunneling effects are found to be negligible over the temperature range 100,2000 K. The O1O2 bond is shown to be spectator like during the reactive process, which confirms a previous theoretical dynamics prediction. © 2007 Wiley Periodicals, Inc. 39: 148,153, 2007 [source] Adiabatic decoupling of the reaction coordinateINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 10 2008J. C. Lorquet Abstract When the dynamics is constrained by adiabatic invariance, a reactive process can be described as a one-dimensional motion along the reaction coordinate in an effective potential. This simplification is often valid for central potentials and for the curved harmonic valley studied in the reaction path Hamiltonian model. For an ion,molecule reaction, the action integral ,P,, = (1/2,),P,d, is an adiabatic invariant. The Poisson bracket of ,P,,2 with Hamiltonians corresponding to a great variety of long-range electrostatic interactions is found to decrease with the separation coordinate r, faster than the corresponding potential. This indicates that the validity of the adiabatic approximation is not directly related to the shape of the potential energy surface. The leading role played by the translational momentum is accounted for by Jacobi's form of the least action principle. However, although the identification of adiabatic regions by this procedure is limited to a specific range of coordinate configurations, equivalent constraints must persist all along the reaction coordinate and must operate during the entire reaction, as a result of entropy conservation. The study of the translational kinetic energy released on the fragments is particularly appropriate to detect restrictions on energy exchange between the reaction coordinate and the bath of internal degrees of freedom. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Cutaneous Rosai-Dorfman DiseaseJOURNAL OF CUTANEOUS PATHOLOGY, Issue 1 2005L. Lin Rosai-Dorfman disease, or sinus histiocytosis with massive lymphadenopathy (SHML), is a rare benign disease of unknown etiology that involves the cervical lymph nodes. Histologic findings include emperiopolesis of lymphocytes and S-100 protein positivity. Extranodal involvement occurs in 30,40% of cases, often involving skin. However, cutaneous Rosai-Dorfman disease without lymph node involvement is uncommon. We describe a case of cutaneous Rosai-Dorfman disease and discuss its clinical and histopathologic findings. A 69-year-old Caucasian male presented with a two-year history of a slowly enlarging violaceous mass on the mid-upper abdomen. He had a history of renal cell carcinoma two-year ago and was asymptomatic without any systemic symptoms. Physical examination revealed a large, violaceous mass of mid-upper abdomen with several violaceous nodules surrounding the periphery. There was no palpable lymphadenopathy. Punch biopsy showed diffuse dermal infiltrates composed of central xanthomatous cells surrounded by lymphoplasmacytic cells. Focal germinal center was noted. Immunostaining revealed strong S-100 and CD68 reactivity of central xanthomatous cells and kappa and lambda polyclonal lymphoplasmacytic cells. Special stains for infectious disorder were negative. Cutaneous Rosai-Dorfman disease is a benign reactive process, often under-recognized due to lack of systemic symptoms and lymphadenopathy. A high index of diagnostic awareness is required for its recognition. [source] Acral pseudolymphomatous angiokeratoma of children: immunohistochemical and clonal analyses of the infiltrating cellsJOURNAL OF CUTANEOUS PATHOLOGY, Issue 5 2002Yoshitaka Hagari Background:, Acral pseudolymphomatous angiokeratoma of children (APACHE) is a disorder characterized clinically by red nodules and histopathologically by a massive subepidermal lymphohistiocytic infiltrate. Although it was initially thought to be a vascular nevus, it has never been regarded as a pseudolymphoma. Case report: We report a 7-year-old-girl with small red nodules on the dorsum of the right foot and a 73-year-old man with asymptomatic brown-red nodules on the lower extremities. Results:, Histopathologic examination revealed a massive lymphohistiocytic infiltrate with plasma cells, some eosinophils, or a multinucleated giant cell immediately beneath the epidermis. Thick-walled vessels were observed in the infiltrate. These characteristics are identical to those of acral pseudolymphomatous angiokeratoma of children. The infiltrate was composed mainly of equal numbers of CD4+ or CD8+ T cells and equal numbers of B cells stained for , or , light chains. PCR amplification of rearranged immunoglobulin heavy chain genes or T-cell receptor , genes showed no evidence of clonality, suggesting that these infiltrates were polyclonal both for B and T cells. Conclusions:, Our data support the idea that this disorder represents a reactive process. The modified term ,papular angiolymphoid hyperplasia' would define this disorder more appropriately. [source] Pagetoid dyskeratosis of the prepuce.JOURNAL OF CUTANEOUS PATHOLOGY, Issue 8 2000An incidental histologic finding resembling extramammary Paget's disease Background: Pale cells resembling those of paget's disease have been seen as an incidental finding within the epidermis in a variety of benign papules most commonly located in intertriginous areas. This lesion, called pagetoid dyskeratosis, is considered a reactive process in which a small part of the normal population of keratinocytes is induced to proliferate. Among the inductors friction is suspected. As far as we know, these cells have not been reported in the penis. Methods: Here we describe the location of the lesion in the foreskin and the incidence of this lesion in a group of 281 unselected patiets surgically treated for phimosis. In selected cases histochemical staining and immunohistochemical studies were performed. Results: Pagetoid dyskeratosis was found in 105 cases (37.4%) but only in 5 cases (1.8%) the lesion was conspicuous. The cells of pagetoid dyskeratosis show an immunohistochemical profile different from the surrounding keratinocytes characterized by premature keratinization. Pagetoid dyskeratosis cells must be distinguished from the artefactual clear cells of the epidermis, from reactive melanocytes, and from pale-cell acanthosis. In cases in which pagetoid dyskeratosis shows a florid expression there is a hazard of overdiagnosis to the patient. The main differential diagnosis includes extramammary Paget's disease, pagetoid squamous cell carcinoma in situ, epidermotropic metastasis, superficial spreading malignant melanoma, clear cell papulosis, and penile koilocytoses. Conclusions: The pathologist should be familiar with the histologic features of pagetoid dyskeratosis in the foreskin in order to avoid misdiagnosis and unnecessary treatment. Routine histologic study is usually sufficient to identify the lesion. [source] Cutaneous plasmacytosis associated with lung and anal carcinomasJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 4 2006JM Martín Abstract Cutaneous plasmacytosis is a rare disorder characterized by a benign proliferation of mature plasma cells that appears as multiple dark-brown to purplish skin lesions, often associated with polyclonal hypergammaglobulinaemia. We present the case of a 55-year-old Caucasian man who suffered from a cutaneous plasmacytosis associated with two different carcinomas. Cutaneous plasmacytosis seems to be a reactive process because most cases reported are not associated with any apparent underlying disease. Nevertheless, because few reported cases were associated with malignancies, screening of additional neoplasms would be justified. [source] Transparent ohmic contacts to GaSb/In(Al)GaAsSb photovoltaic cellsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2007K. Golaszewska Abstract In this paper we present the results of study of thin oxide films: CdO, ZnO and RuSiO4 used as transparent ohmic contacts to GaSb/InGaAsSb/AlGaAsSb photodiodes. Thin oxide films with thickness of 50 nm were deposited by magnetron sputtering. CdO and RuSiO4 were formed in a reactive process in Ar,O2 atmosphere, from Cd and Ru1Si1 targets, respectively. ZnO films were deposited directly from ZnO target by rf sputtering. We have shown that application of CdO, ZnO and RuSiO4 transparent films instead of conventional metal-based contacts enables to improve of photodiode properties. As a result, GaSb/InGaAsSb/AlGaAsSb photodiodes with detectivity D * increased by factor of 2 and reduced by factor of 3 the series resistance were obtained. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Reactive doping of PAni,CSA and its use in microwave absorbing materialsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2009R. S. Biscaro Abstract Conductive coatings have been studied for static dissipation and as microwave absorbing materials. The doping process of polyaniline (PAni), which makes it conductive, is an important stage that determines the coating performance. For this purpose, polyaniline was doped by reactive processing in a torque rheometer using different molar ratios between PAni and acid (PAni:CSA) at three different temperatures (80, 90, and 100°C). Aqueous solution doping was also used in the ratio of 1:2 of PAni/CSA, with the aim to investigate the influence of different methods of PAni doping on its characteristics and, consequently, on the performance of coatings. Thermal analyses of the processed materials showed that PAni doped by both routes, reactive and solution processing, showed similar behaviors. X-ray diffraction analyses showed a semicrystalline structure for the PAni,CSA doped by reactive processing using high CSA concentrations and temperature. It was also observed that the doping process affects the dispersion of the components into the conductive coatings. Microwave absorption measurements (8,12,GHz) of PU-doped PAni blends showed the dependence of the doping type, the PAni,CSA concentration, and the mixing conditions of the components on the coating performance; it was found up to 99% of attenuation of the incident radiation for some composites in a narrow frequency range. The microwave absorption efficiency of the coating samples prepared by using the reactive doping process indicates the advantage of this methodology over solution doping. Moreover, the reactive process addresses the environmental requirements. Copyright © 2008 John Wiley & Sons, Ltd. [source] Evidence-based medicine: the time has come to set standards for staging,THE JOURNAL OF PATHOLOGY, Issue 4 2010Phil Quirke Abstract For international communication in cancer, staging systems such as TNM are essential; however, the principles and processes used to decide about changes in every new edition of TNM need to be subject to debate. Changes with major impact for patient treatment are introduced without evidence. We think that TNM should be a continual reactive process, rather than a proactive process. Changes should only occur after extensive discussion within the community, and before the introduction of any changes these should be tested for reproducibility and compared to the currently used gold standard. TNM should not be used to test hypotheses. It should introduce established facts that are beneficial to predicting patient prognosis. TNM should thus be restructured on a basis equivalent to evidence-based guidelines. The strength of the evidence should be explicitly stated and the evidence base given. It is time for the principles of staging to be widely debated and new principles and processes to be introduced to ensure that we are not in the same situation in the future. The disparity between therapeutic decision making and TNM staging is marked and we would appeal for the radical overhaul of TNM staging to make it fit for the twenty-first century. TNM is central to the management of cancer patients and we must protect and enhance its reputation. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [source] Meningothelial Hyperplasia: A Detailed Clinicopathologic, Immunohistochemical and Genetic Study of 11 CasesBRAIN PATHOLOGY, Issue 2 2005Arie Perry MD Meningothelial hyperplasia is a poorly characterized entity, often associated with advanced age, chronic renal failure, trauma, hemorrhage, and neoplasia. In order to elucidate the nature of this lesion, 11 cases defined by the presence of nests of 10 or more cell layers thick, were compared with normal arachnoidal cap cells and meningiomas. Immunohistochemistry and FISH were performed to determine NF2 (merlin), protein 4.1 B, EMA, progesterone receptor (PR), EGFR, survivin, VEGF, PDGF-BB, PDGFR,, E-cadherin, and cathepsin D status. All cases had at least one putative predisposing factor, including hemorrhage (7), chronic renal disease (5), old age (5), trauma (1), and an adjacent optic nerve pilocytic astrocytoma (1). There was typically a discontinuous growth pattern, with no invasion of surrounding normal tissue. No gene deletions were found, though scattered polyploid cells were seen in 2 cases. The immunoprofile was similar to normal cap cells with one exception; whereas normal cells were uniformly negative for PR, nuclear positivity was seen in 64% of hyperplasias, a frequency similar to that of benign meningiomas. Our data suggest that meningothelial hyperplasia is a reactive process that is usually distinguishable from meningioma based on clinicopathologic and genetic features. It may be preneoplastic in some, though further studies are needed to test this hypothesis. SUMMARY Based on our data and that of others, we conclude that meningothelial hyperplasia is a reactive process characterized by a proliferation of arachnoidal cap cells that is often non-invasive, multicentric, and at least focally reaches a thickness of 10 or more cell layers. Florid examples are often difficult to distinguish from meningioma. However, they are commonly associated with inciting factors, such as chronic renal disease, hemorrhage, trauma, intracranial hypotension, and neoplasia, particularly optic pathway gliomas. Although meningothelial hyperplasia shares many immunohistochemical and genetic features with normal cap cells, it differs in terms of its frequent PR immunoreactivity and occasional polyploid cells. In contrast to classic meningiomas, there is no evidence for either NF2 or 4.1 B gene deletions by FISH or merlin or protein 4.1 B losses of expression by immunohistochemistry. The data suggest that meningothelial hyperplasia may represent a preneoplastic lesion in some cases, although additional studies are needed to rigorously test this hypothesis. [source] Fine-needle aspiration diagnosis of Hodgkin lymphoma using current WHO classification,Re-evaluation of cases from 1999,2004 with new proposalsDIAGNOSTIC CYTOPATHOLOGY, Issue 6 2006Jue-Rong Zhang M.D., Ph.D. Abstract With the advent of modern therapy, the differences in prognoses and treatment regimens among different subtypes of Hodgkin lymphoma (HL) have largely vanished. Stage and the presence of systemic symptoms are much more important than histologic subtypes as predictive factors. The current (2001) WHO classification markedly de-emphasizes spatial relationships as critical to the diagnosis of lymphoma and emphasizes cell morphology, immunophenotype, genetic features, and clinical information to define the disease states. This classification, thus, greatly enhances the capability of fine-needle aspiration (FNA) to accurately diagnose HL. We searched all the FNA cases in our institute in years 1999 through 2004 and found 42 cases, for which 13 were primarily diagnosed (31.0%), 2 were recurrent (4.8%), 5 were highly suspicious (11.9%), and 22 were suspicious (52.3%) for HL. On follow-up tissue biopsy, all the primarily diagnosed, recurrent, and highly suspicious cases were confirmed to be HL (100% agreement). For the 22 suspicious cases, 13 were HL (59.1%), 5 were other lymphomas (22.8%), 1 was lymphoma unclassifiable (4.5%), and 3 were reactive processes (13.6%). The effect of immunostains on the diagnosis of HL was examined, and its importance was emphasized. Analysis of demographic data and the distribution of HL subtypes demonstrate that the study sample is representative of the general HL patient population. On the basis of these results, we propose: (1) If the FNA diagnosis of HL is confirmed both by morphology and immunostains, no further tissue confirmation, subclassification and grading is necessary, and appropriate treatment regimens should follow. (2) The nodular lymphocyte predominant HL and classical HL can be differentiated by adequate immunostaining. (3) If a definitive diagnosis cannot be achieved by FNA, a second FNA or a tissue biopsy should be recommended. Diagn. Cytopathol. 2006;34:397,402. © 2006 Wiley-Liss, Inc. [source] MODFLOW/MT3DMS-Based Reactive Multicomponent Transport ModelingGROUND WATER, Issue 2 2003H. Prommer This paper presents a three-dimensional, MODFLOW/MT3DMS-based reactive multicomponent transport model for saturated porous media. Based on a split-operator technique, the model, referred to as PHT3D, couples the transport simulator MT3DMS and the geochemical modeling code PHREEQC-2. Through the flexible, generic nature of PHREEQC-2, PHT3D can handle a broad range of equilibrium and kinetically controlled reactive processes, including aqueous complexation, mineral precipitation/dissolution, and ion exchange. The diversity of potential applications is demonstrated through simulation of five existing literature benchmarks and a new three-dimensional sample problem. The model might be applied to simulate the geochemical evolution of pristine and contaminated aquifers as well as their cleanup. The latter problem class includes the natural and enhanced attenuation/remediation schemes of a wide range of organic and inorganic contaminants. Processes/reactions not included in the standard PHREEQC-2 database but typical for this type of application (e.g., NAPL dissolution, microbial growth/decay) can be defined and included via the extensible PHREEQC-2 database file. [source] Kinetic study of the curing of mixtures of DGEBA and five-membered cyclic carbonates with lanthanum triflate as cationic initiatorJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007Roser Cervellera Abstract Mixtures of diglycidylether of bisphenol A (DGEBA) with 1,3-benzodioxolane-2-one (CC) or 4-phenoxymethyl-1,3-dioxolane-2-one (PGEC) were cured in the presence of lanthanum triflate. FTIR/ATR was used to study the evolution of carbonate and epoxide groups to follow the reactive processes that take place during curing. DSC was applied to study the thermal characteristics of the curing process and to determine the glass-transition temperatures of the cured materials. The kinetics of the curing was studied isothermally by means of FTIR and the kinetic model was selected through the isokinetic relationships. DSC experiments were used to study the kinetics in nonisothermal conditions by means of isoconversional procedures and the Coats,Redfern and Criado methodologies. By TMA we could monitor the evolution of the shrinkage during isothermal curing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2875,2884, 2007 [source] Membrane engineering for process intensification: a perspectiveJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2007Enrico Drioli Abstract Pushed by the increasing demand for materials, energy and products, chemical engineering today faces a crucial challenge: to support a sustainable industrial growth. One possible solution is process intensification (PI), the innovative design strategy aiming to improve manufacturing and processing by decreasing the equipment size/productivity ratio, energy consumption and waste production using innovative technical solutions. Membrane processes meet the requirements of PI because they have potential to replace conventional energy-intensive techniques, to accomplish the selective and efficient transport of specific components, and to improve the performance of reactive processes. Here, we identify the most interesting aspects of membrane engineering in some strategic industrial sectors. The opportunity to integrate conventional membrane units with innovative systems in order to exploit the potential advantages coming from their synergic applications is also emphasized. Copyright © 2007 Society of Chemical Industry [source] Experimental study of reactive chaotic flows in tubular reactorsAICHE JOURNAL, Issue 8 2005C. Boesinger For many reactive processes, fluid mixing has a significant effect on the rate of a chemical reaction and on the quality of the product. Mixing in a chaotic flow reactor is a promising phenomenon to control and optimize chemical processes. The effect of three-dimensional (3-D) chaotic flow advection on mixing efficiency and on chemical reaction advancement is examined. An experimental comparison is made, for low Reynolds number flows, between two tubular reactors made of successive bends, with the same number of bends (equal to 80) mounted in different configurations : a helical configuration (for regular flow) and a chaotic flow configuration with bends in perpendicular planes. We show that the mixing and the chemical reaction (for an instantaneous bimolecular chemical reaction) are more efficient in the chaotic flow reactor than in the helical reactor. The different effects of chaotic advection, molecular diffusion and reaction are discussed in view of laboratory findings. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source] New thermosets obtained by the cationic copolymerization of diglycidyl ether of bisphenol A with ,-caprolactone with an improvement in the shrinkage.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2007Abstract Diglycidyl ether of bisphenol A was cured with different proportions of ,-caprolactone with ytterbium triflate as an initiator. The curing was studied by means of differential scanning calorimetry and Fourier transform infrared in the attenuated total reflection mode. The latter was used to monitor the competitive reactive processes and to quantify the conversions of the epoxide, lactone, and intermediate spiroorthoester groups. A partial depolymerization process from the cured material to free ,-caprolactone was also identified. The formation of a stable carbocation and the coordinative capability of ytterbium triflate were the reasons for this unexpected process. The thermal and dynamic mechanical properties of the cured materials were determined with differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis. An increase in the proportion of ,-caprolactone resulted in an increased curing rate, a decrease in the shrinkage after gelation, and a significant decrease in the glass transition temperature. The introduction of ester linkages into the three-dimensional structure led to more thermally degradable thermosets. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1968,1979, 2007 [source] N,N -dimethylaminopyridine as initiator in the copolymerization of diglycidylether of bisphenol A with six-membered cyclic carbonatesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2006Roser Cervellera Abstract N,N -Dimethylaminopyridine (DMAP) was used as initiator to cure mixtures of diglycidylether of bisphenol A (DGEBA) and 1,3-dioxan-2-one (TMC) or 5,5-dimethyl-1,3-dioxan-2-one (DMTMC). The curing was studied by differential scanning calorimetry (DSC) and Fourier transform infrared in the attenuated-total-reflection mode (FTIR/ATR). FTIR/ATR was used to monitor the competitive reactive processes and to quantify the evolution of the groups involved in the curing. We observed the formation of five-membered cyclic carbonates and anionic carbonate groups that remain unreacted at the chain ends. The formation of these groups was explained by the attack of the anionic propagation species on the methylene carbon of the carbonate group, which leads to an alkyl-oxygen rupture. By performing the cure in the thermobalance we could evaluate the loss of CO2 produced in the samples containing carbonates. The kinetics were studied by DSC and analyzed with isoconversional procedures. The addition of carbonates slows down the curing rate. Thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) experiments were used to evaluate the properties of the materials obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2873,2882, 2006 [source] | ||||||||||||||||||||||||||||