bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scales of Nucleophilicity and Electrophilicity: A System for Ordering Polar Organic and Organometallic Reactions
Authors: Mayr Herbert , Patz Matthias 
Published: December 2003

AbstractContrary to widely held opinion, for many reactions in organic and organometallic chemistry it is possible to define nucleophilicity and electrophilicity parameters that are independent of the reaction partners. This phenomenon, discovered by Ritchie during the early 1970s for reactions of highly stabilized carbenium and diazonium ions with n‐nucleophiles, also occurs with reactions of carbenium ions with aliphatic and aromatic π‐electron systems and in hydride transfer reactions. With the aid of the scales of nucleophilicity and electrophilicity set out here, which extend over eighteen orders of magnitude, forecasts can be made about the feasibility and rate of a given CC bond formation, ionic reduction, or diazo coupling. Linkage with the reactivity scales of Ritchie and Sweigart/Kane‐Maguire enables a unified treatment of a large number of polar reactions.
The Photochemical Synthesis of Fine Chemicals with Sunlight
Authors: Esser Peter , Pohlmann Bettina , Scharf Hans‐Dieter 
Published: December 2003

AbstractThe light of the sun can be used directly for changing chemical structures photochemically. Any industrial application must conform to the limitations imposed by the spectral distribution of the photons from the sun, the interruptions to the radiation due to the day/night rhythm, and the weather. In this review, we describe the photochemical potential of the sun, give a fundamental treatment of the concept of photoreactors driven by sunlight (abbreviated to solar photoreactors), and give an account of the realization of this concept in the first pilot plant on the “Plataforma Solar de Almeria” in southern Spain and in other activities in this field. Based on experimental data from photochemical investigations on the pilot plant scale, possibilities, limitations, and the potential growth of solar photochemistry are described. Solar photochemistry, in our opinion, is a technique which could make a contribution to the chemistry of the future because of its photochemical synthesis potential, the avoidance of waste products, and the direct utilization of the sun, not only as a primary energy source, but also as a reaction partner.
The Kinetics of Heterogeneous Electron Transfer Reaction in Polar Solvents
Authors: Fawcett William Ronald , Opallo Marcin 
Published: December 2003

AbstractData for heterogeneous electron transfer reactions obtained in the last ten years have been examined within the context of contemporary theory. Special attention is focused on systems for which rate constants and activation parameters are available as functions of solvents and of temperataure. The role of reactant structure in deteriming the kinetic parameters is also considered. Double layer effects both at unmodified and modified electrodes are discussed in detail. Experimental techniques, especially those suited to measuring fast reactions, are also outlined.
Technetium Radiopharmaceuticals—Fundamentals, Synthesis, Structure, and Development
Authors: Schwochau Klaus 
Published: December 2003

AbstractTechnetium‐99m radiopharmaceuticals are increasingly finding application in nuclear medicine for scintigraphic and emission tomographic imaging, morphologic description and functional testing of organs. Over 80% of the radiopharmaceuticals currently clinically used are labeled with the short‐lived, metastable nuclide 99mTc, whose nuclear properties are almost optimal with regard to a low radiation exposure of the patient and an effective detection of the emitted γ quanta. 99mTcO can be easily prepared without the use of accelerator systems through generator columns. Most of the 99mTc radiopharmaceuticals are complexes which are synthesized by reduction of 99mTcO in the presence of suitable ligands. To achieve a high organ specificity, some understanding of the relationship between the structure of the diagnostic agent and its organ distribution is necessary. Structure analyses can be carried out on analogous compounds of the long‐lived nuclide technetium‐99g; these compounds are obtainable in weighable quantities. The development of new 99mTc radiopharmaceuticals is a challenge to coordination chemists. The syntheses, molecular structures, and applications of the most important 99mTc radiopharmaceuticals will be described in this review, and current directions and tendencies of the development will be shown.
Regio‐ and Stereoselective Syntheses with Organocopper Reagents
Authors: Krause Norbert , Gerold Andreas 
Published: December 2003

AbstractOf all of the organometallic reagents currently used to form carbon–carbon bonds, organocopper reagents rank amongst the most important. Interest in these reagents centers not only on their regioselectivity, but also increasingly on their application in stereoselective transformations (principally Michael additions and SN2′ reactions); the use of suitable substrates or chirally modified cuprates can lead to highly diastereo‐ and enantioselective reactions. Simultaneously, extensions of methods for the preparation and application of these reagents (for example functionalized organocopper species and Lewis acid catalysis, respectively) have opened up new horizons for organocopper reagents. Mechanistically, the reactions are well‐documented and understood, but this aspect of the subject has not kept pace with the many rapid developments in preparative chemistry. Organocopper ragents have proved to be indispensable in the synthesis of complex natural products and pharmaceuticals, chiral auxiliaries, and molecules with interesting structural features. In this review we will discuss some of the more recent important developments in this area; the organization will follow the type of selectivity (regio‐, diastereo‐, and enantioselectivity).
Phanes with Three‐ and Four‐Membered Rings as Building Elements
Authors: Gleiter Rolf , Merger Martin 
Published: December 2003

AbstractThe systematic integration of the small 2π‐ and 4π‐electron systems cyclopropenylium ion, cyclopropenone, oxo‐cyclobutenylium ion, and cyclobutadiene into phane chemistry was initiated only a few years ago. [n2]Cyclopropenylophanes, [n2]cyclopropenonophanes, metal‐capped [n4]cyclobutadienosuperphanes, and other new families of double‐decker phane species became available from cycloalkydiynes through special methods of double [2+1]cycloaddition with carbenes and metal complex induced dimerization by double [2+2]cycloaddition. Phane‐specific structural features were elucidated by X‐ray structural analyses. Cyclic voltammetry and PE spectroscopy as well as MO calculations reealed considerable interactions between closely spaced π‐electron systems. Decapping cyclobutadienosuperphanes formally extended the synthetic principle to threefold [2+2]cycloadditions resulting in [n4]‐bridged tricyclo‐[4.2.0.03, 5]octa‐3,7‐dienes, which represent a new type of cage compounds. Moreover, completion to fourfold [2+2]addition was achieved with the photoinduced transformation of [34]bridged tricyclo[4.2.0.03, 5]octa‐3,7‐diene into propella[34]cubane.
Charge Transfer through the DNA Base Stack
Authors: Holmlin R. Erik , Dandliker Peter J. , Barton Jacqueline K. 
Published: December 2003

AbstractWhether the DNA base pair stack might serve as a medium for efficient, long‐range charge transfer has been debated almost since the first proposal of the double‐helical structure of DNA. The consequences of long‐range radical migration through DNA are important with respect to understanding carcinogenesis and mutagenesis. Double‐helical DNA has in its core a stacked array of aromatic heterocyclic base pairs, and this molecular π stack represents a unique system in which to explore the chemistry of electron transfer. We designed a family of metal complexes which bind to DNA by intercalative stacking within the helix; these metallointercalators may be usefully applied in probing DNA‐mediated electron transfer. Here we describe a range of electron transfer reactions we carried out which are mediated by the DNA base paired stack. In some cases, DNA serves as a bridge, and spectroscopic analyses permit us to probe how the π stack couples DNA‐bound donors and acceptors. These studies point to the sensitivity of coupling to DNA intercalation. However, if the DNA π stack effectively bridges donors and acceptors, the base‐pair stack itself might serve not only as a conduit for electron transfer in DNA, but also in reactions initiated from a remote position. We carried out a series of reactions involving oxidative damage to DNA arising from the remotely positioned oxidant on the helix. The implications of long‐range charge migration through DNA to effect damage are substantial. As in other DNA‐mediated charge transfers, these reactions are highly dependent on DNA intercalation and the integrity of the intervening base‐pair stack, but not on molecular distance. Furthermore, a physiologically important DNA lesion, the thymine dimers, can be reversed in a reaction initiated by electron transfer. This repair reaction can also be promoted from a distance as a result of long‐range charge migration through the DNA base pair stack.
Comparative psychology is still alive but may be losing relevance
Authors: Denenberg Victor H. 
Published: December 2003

AbstractGreenberg et al., in their perspective on the current state and fate of comparative psychology, present convincing data that the field is viable and that comparative psychologists are making important contributions to the research literature. The central feature of the field is its emphasis upon evolution. This is also its weakness since advances in genetic techniques permit researchers to create laboratory animals that have no counterpart in the natural world, and thus have no evolutionary history. These “unnatural” animals are widely used in behavioral, biological, and medical studies, but the findings cannot be interpreted within a comparative psychology framework. As the use of these preparations expand, the relevance of comparative psychology diminishes. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 44: 21–25, 2004.
Antioxidant effect of acetylsalicylic and salicylic acid in rat brain slices subjected to hypoxia
Authors: De La Cruz J.P. , Guerrero A. , González‐Correa J.A. , Arrebola M.M. , Sánchez de la Cuesta F. 
Published: December 2003

AbstractAcetylsalicylic acid (ASA) reduces the incidence of ischemic stroke mainly through its antithrombotic action; however, it also has a direct neuroprotective effect. The present study was designed to evaluate the effect of ASA on oxidative stress and the activity of nitric oxide synthase (NOS) in an in vitro model of hypoxia in rat brain slices. Rat brain slices were perfused with nitrogen (hypoxia) for a maximum of 120 min, after which we measured lipid peroxidation, glutathione levels, glutathione‐related enzyme activities, and constitutive nitric oxide synthase (cNOS) and inducible nitric oxide synthase (iNOS) activities. In brain tissue subjected to hypoxia, ASA reduced oxidative stress and iNOS activity (all increased by hypoxia), but only when used at higher concentrations. The effects of salicylic acid (SA) were similar but more intense than were those of ASA. After oral administration, the effect of SA was much greater than that of ASA, and the decrease in cell death with SA was seen much more clearly. In view of the greater effect of SA compared to ASA on changes in oxidative stress parameters in a model of hypoxia, and higher brain concentrations of SA when it is administered alone than when ASA is given (undetectable levels), we conclude that SA plays an important role in the cytoprotective effect in brain tissue after ASA administration. © 2003 Wiley‐Liss, Inc.
Axonal transport versus dendritic transport
Authors: Setou Mitsutoshi , Hayasaka Takahiro , Yao Ikuko 
Published: December 2003

AbstractNeurons have polarized processes for information output and input, axons, and dendrites. This polarized architecture is essential for the neuronal function. An increasing number of molecular components that mediate neuronal polarity establishment have been characterized over the past few years. The vast majority of these molecules include proteins that act in scaffolding protein complexes to sustain the polarized anchoring of molecules. In addition, more signaling and cytoskeleton‐associated proteins have been proposed for establishment of polarity. It has become evident that dendritic and axonal transport of molecules depends on scaffolding/adaptor proteins that are recognized by molecular motors. Current and future research in the neuronal cell polarity will be focused on how different cargo molecules transmit their signals to the cytoskeleton and change its dynamic properties to affect the rate and direction of vesicular movement. In this review, we discuss recent evidence that scaffolding proteins can regulate motor motility and guidance by a mechanism of substrate‐cytoskeletal coupling and amino acid modifications during polarized transport. © 2003 Wiley Periodicals, Inc. J Neurobiol 58: 201–206, 2004
Yield line mechanism analysis of steel members and connections
Authors: Zhao Xiao‐Ling 
Published: December 2003

AbstractYield line mechanism analysis has been widely used to study steel members and connections that involve local collapse mechanisms. In the application of the yield line method, a fundamental requirement is to determine the reduced plastic moment capacity of an inclined yield line under axial force. This paper reviews various theories dealing with inclined yield lines. Comparisons between these theories are presented. The paper also summarizes some basic or simple yield line mechanisms that may be adopted directly to solve more complicated problems. The application of yield line mechanism analysis is included, covering steel plates, open‐section members, closed‐section members, void‐filled members, welded connections and bolted connections. It is shown that this method can be used to study post‐collapse behaviour, load‐carrying capacity, ductility, rotation capacity and energy absorption.
Role of internship in higher education in environmental sciences
Authors: Scholz, Roland W. , Steiner Regula , Hansmann Ralf 
Published: December 2003

AbstractThe benefits of a compulsory internship in environmental science education were investigated with respect to the three institutional goals of university education: (a) training for research, (b) professional education, and (c) general natural science education. A survey examined which student qualifications are improved by an internship complementary to traditional university education. The survey assessed 14 qualifications of students participating in a compulsory 15‐week internship in the 5‐year diploma program at the Swiss Federal Institute of Technology (ETH Zürich). Pre‐ and postinternship questionnaires of 478 students and 293 supervisors are included. Results indicated that internships enhance general abilities and key qualifications, such as communication skills, report writing, organization of work, information acquisition, and the ability to operate independently. This suggests that internships are of high value to professional education. However, internships also seem to promote salient qualifications of complex environmental problem solving which are relevant for the development of research capabilities in environmental sciences. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 41: 24–46, 2004
Ethnic identity and self‐esteem: examining the role of social context
Authors: Umaña‐Taylor Adriana J. 
Published: December 2003

AbstractThis study explored ethnic identity and self‐esteem among 1062 Mexican‐origin adolescents who were attending one of three schools, which varied in their ethnic composition (i.e., predominately Latino, predominately non‐Latino, and balanced Latino/non‐Latino). Significant relationships emerged between ethnic identity and self‐esteem among adolescents in all school settings. Furthermore, controlling for generation and maternal education, adolescents attending the predominately non‐Latino school reported significantly higher levels of ethnic identity than adolescents in the other schools. Consistent with ecological theory, these findings challenge researchers to design future studies in ways such that multiple layers of context and their influence on development can be examined.
The Effects of the Plasminogen Pathway on Scar Tissue Formation
Authors: Samara Ghassan J. , Schaffner Adam D. , Eisenstat Jonathan , Nguyen Hoang‐Lan T. 
Published: December 2003

AbstractObjectives/Hypothesis The authors sought to determine the role of the plasminogen pathway in wound healing. They hypothesized that decreased fibrin degradation may lead to increased collagen deposition. Presuming that the degree of histopathological abnormality correlates with the aesthetic appearance of the scar, we conducted a study that attempted to determine the histopathological appearance of scar tissue in mice with and without impaired function of the plasminogen pathway.Study Design Mice with and without deficiencies in the plasminogen pathway underwent surgery. The role of the plasminogen pathway in wound healing was studied by analysis of scar tissue formation using the methods described.Methods A 2‐cm incision was made on the dorsum of mice with and without specified genetic deficiencies in the plasminogen pathway. After the animals were killed, the tissue was harvested, fixed, and prepared using hematoxylin and eosin as well as trichrome stains. Histopathological analysis and scoring were performed by two separate investigators in a blinded manner. Student's t test was used to determine statistical significance between groups.Results A statistically significant difference in collagen orientation was noted between mice with impaired plasminogen pathway function and the wild‐type (control) group (P = .0163). A statistical trend toward improved wound healing for plasminogen‐deficient mice was found for overall histomorphological score (P = .0706).Conclusion The role of the plasminogen pathway in wound healing is one that should be noted and may lead to the development of new therapies that reduce scar tissue formation. Hence, the role of other thrombolytic and anti‐thrombolytic agents in wound healing should be further investigated to precisely identify agents that play the most significant role in scar tissue formation.
Comparison of Free Radicals and Antioxidant Enzymes in Chronic Otitis Media With and Without Tympanosclerosis
Authors: Karldağ Turgut , İlhan Nevin , Kaygusuz İrfan , Keleş Erol , Yalçn Şinasi 
Published: December 2003

AbstractObjective/Hypothesis The pathogenesis of tympanosclerosis is unclear. The study was performed to investigate the role of nitric oxide, free oxygen radicals, and antioxidants in development of tympanosclerosis in patients with chronic otitis media.Study Design A prospective study in patients with nasal polyps.Methods Sixty‐five patients who underwent tympanoplasty or tympanoplasty together with mastoidectomy were included in the study. Preoperative venous blood samples were drawn, and serum sodium, potassium, calcium, alkaline phosphatase, inorganic phosphorus, parathormone, and calcitonin levels were measured. The patients who had tympanosclerotic plaques on tympanic membrane or middle ear mucosa or near the ossicular chain or mastoid bone were designated as group 1 (n = 34), and the remaining patients as group 2 (n = 31). Intraoperatively, specimens were obtained from the middle ear mucosa and tympanic membrane to measure nitric oxide and malondialdehyde levels. In addition, plasma malondialdehyde levels and erythrocyte superoxide dismutase and catalase activity were determined.Results All patients had similar demographic features and serum electrolyte and hormone levels. Nitric oxide and malondialdehyde levels of the specimens obtained from the middle ear mucosa (P = .001) and tympanic membrane (P = .01) and, in parallel to this, the plasma malondialdehyde activity level were higher in group 1 than in group 2. Moreover, group 2 had significantly lower erythrocyte catalase activity levels (P = .001) compared with group 1, whereas such a significant difference was not present for superoxide dismutase activity levels (P > .05).Conclusion The study results suggest that nitric oxide, free oxygen radicals, and catalase may have a role in the development of tympanosclerosis in patients with chronic otitis media.
Evaluation of the Inferior Turbinate in Patients With Deviated Nasal Septum by Using Computed Tomography
Authors: Egeli Erol , Demirci Levent , Yazýcý Burhan , Harputluoglu Ugur 
Published: December 2003

AbstractObjectives/Hypothesis The objective was to measure the dimensions, composition, and possible structural and radiological changes of the compensatory hypertrophic inferior turbinate in patients with deviated nasal septum.Study Design A prospective, nonrandomized clinical trial at a university medical center.Methods Twenty‐three patients with deviated nasal septum and compensatory hypertrophy of the inferior turbinate in the contralateral nasal cavity were examined by computed tomography.Results The dimensions of the compensatory hypertrophic inferior turbinate in patients with septal deviation were compared with normal control subjects. The difference in width of the medial and lateral mucosa and the conchal bone between the two groups was statistically significant (P < .05).Conclusion The present study uncovers the dimensions and composition of the inferior turbinate with compensatory hypertrophy in patients with nasal septum deviation. The findings support the decision to excise the inferior turbinate bone at the time of septoplasty, because of the significant bony and mucosal expansion.
Smoking in Chronic Rhinosinusitis: A Predictor of Poor Long‐Term Outcome After Endoscopic Sinus Surgery
Authors: Briggs Russell D. , Wright Steven T. , Cordes Stephanie , Calhoun Karen H. 
Published: December 2003

AbstractObjective This study was designed to determine whether smoking patients have poorer outcomes after endoscopic sinus surgery (ESS) based on a reliable validated rhinosinusitis‐specific quality‐of‐life outcomes test.Study Design Retrospective chart and computed tomography (CT) review with telephone and letter questionnaire.Methods Charts of 230 adult patients undergoing ESS for chronic rhinosinusitis between January 1995 and December 1998 were reviewed. Each participating patient completed a detailed questionnaire, including the Sino‐Nasal Outcome Test‐16 (SNOT‐16), at an average of 52 months after surgery. Preoperative CT scans were reviewed and the findings used to stage the patients' conditions. Multivariate analysis was used to assess these data.Results Eighty‐two patients completed the questionnaire, with 26 who smoked at the time of surgery and continued to smoke at the time of answering the questionnaire (Smokers). Average SNOT‐16 score in Smokers was 27.5, versus 18.2 in those who did not smoke at the time of surgery (Non‐Smokers). There was a statistically significant correlation between elevated SNOT‐16 scores and smoking (P < .001) and antibiotic use within the past year (P < .001). There was an association between high SNOT‐16 scores and both prior smoking and passive smoke exposure that did not reach statistical significance (P = .055 and P = .267, respectively). CT staging scores and prior ESS were not statistically correlated with SNOT‐16 scores.Conclusions Smoking is associated with statistically worse outcomes after ESS based on average SNOT‐16 scores. Although no investigator has proved that the effects of smoking on sinonasal health are reversible, we counsel smoking patients considering ESS about the desirability of smoking cessation (for this and many health reasons), and the possibility of a poorer postsurgery outcome should they continue smoking.