bluuebunny/crossref_metadata_2025 huggingface dataset:
Beschichtung von Kohlenstoff‐Fäden
Authors: Fitzer Erich , Kehr Dieter , Sahebkar Maschallah
Published: May 2005

Bei der Gasphasenbeschichtung von Kohlenstoff‐Fäden mit Siliciumcarbid und Pyrokohlenstoff aus CH3SiCl3 bei Temperaturen zwischen 1 100 und 1 400 °C und aus CH4 zwischen 1 200 und 1 700 °C konnten hochfeste Siliciumcarbid‐Monofile von 50 bis 60 μm Dicke, mit Festigkeiten von 1000 kp/mm2 und E‐Moduln von 55000 kp/mm2 erhalten werden. Dünne Schichten unter 1 μm Dmr. aus Siliciumcarbid und Pyrokohlenstoff sind auf Fäden, bestehend aus mehreren Tausend Monofilen, in einer kontinuierlich arbeitenden Laboratoriumsapparatur hergestellt worden. Die Abscheidungsbedingungen werden am Modell der Inporenabscheidung eingehend diskutiert. Sowohl die Siliciumcarbid‐Monofile als auch die beschichteten Fäden versprechen eine Verbesserung gegenüber unbeschichteten Kohlenstoff‐Fäden als Verstärkungskomponenten in Verbundwerkstoffen.
Spezifische Oberfläche und Sekundärporenstruktur von synthetischen Zeolithen mit und ohne Bindemittel
Authors: Eisenbach Dieter , Gallei Ewald
Published: May 2005

An den synthetischen Zeolithen der Typen 4A, 5A, 10X, 13X und 13Y wurde geprüft, inwieweit die aus Kohlendioxid‐Isothermen nach der BET‐2‐ und BET‐3‐ Parameter‐, der Langmuir‐, Punkt‐B‐ und Dubinin‐Kaganer‐Methode berechneten Oberflächen übereinstimmen. Weiterhin wurde der Eßnfluß des Bindemittels auf die spezifische Oberfläche und die Sekundärporenstruktur untersucht. Die BET‐2‐ Parameter‐Methode liefert bei den meisten Zeolithen um 10 bis 15% niedrigere Oberflächenwerte als die übrigen vier Verfahren. Ohne Bindemittel gepreßte synthetische Zeolithe besitzen niedrigere spezifische Oberflächen als die pulvrigen Proben. Durch Zusatz von Bindemittel erhält man noch niedrigere spezifische Oberflächen, und gleichzeitig werden die Porenweßten und das Porenvolumen der Sekundärporen vergrößert.
Konstruktive Probleme von Lufterhitzern und Rekuperatoren
Authors: Klapp E.
Published: May 2005

Rekuperatoren sind kontinuierlich betriebene Wärmeaustauscher, die der Abhitzegewinnung hinter Industrieöfen dienen und eine wirtschaftliche Vorwärmung der Verbrennungsluft bzw. des Brenngases ermöglichen. Beim Strahlungsrekuperator strömen die strahlenden Rauchgase durch einen Blechzylinder großen Durchmessers, während Luft durch einen konzentrisch um diesen angeordneten Ringspalt strömt. Beim Kanal‐ oder Röhren‐Rekuperator sind die luftdurchströmten Rohrbündel im Abgaskanal quer zum Rauchgasstrom untergebracht. Die wichtigsten Konstruktionsmerkmale für beide Bauarten werden erläutert. Hauptschadensursachen sind neben dem Korrosionsangriff in der wachsenden Einheitengröße, steigenden Temperaturen und daraus folgenden, früher häufig unbeachtet gebliebenen thermomechanischen Wechselwirkungen zu sehen. Einzelne Schadensphänomene werden geschildert und Wege zur Steigerung der Betriebsfestigkeit aufgezeigt. In Teilbereichen sind noch sorgfältige Untersuchungen notwendig, insbesondere zur Beherrschung des Thermobeulens.
Die Bedeutung der Chemischen Reaktionstechnik für die Industrie
Authors: Cappelli Antonio , Trambouze Pierre
Published: May 2005

Nach einem kurzen Überblick über die geschichtliche Entwicklung der chemischen Reaktionstechnik wird der derzeitige Stand der Kenntnisse bei den verschiedenen Reaktortypen behandelt. Dabei wird auch kritisch untersucht, inwieweit die theoretischen Vorstellungen Eingang in die Praxis bei der Auslegung von Reaktoren gefunden haben. Es schließt sich ein Kapitel über die Ermittlung kinetischer Daten und die Entwicklung mathematischer Modelle an. Generell läßt sich sagen, daß außerordentlich viele theoretische Arbeiten von häufig zweifelhaftem Wert für die industrielle Praxis durchgeführt werden. Demgegenüber besteht zumindest auf manchen Gebieten ein kaum zu übersehender Mangel an experimentellen Ergebnissen. Die Erkenntnisse der chemischen Reaktionstechnik werden zur Auslegung von industriellen Reaktoren nur sehr zögernd übernommen. Besonders vielversprechend ist eine intensive Zusammenarbeit von Hochschulforschern mit Ingenieuren und Chemikern aus der Industrie, um die theoretischen Konzepte in der Praxis zu überprüfen.
Stand der Arbeiten zur Wasserstoff‐Erzeugung mit nuklearer Prozeßwärme
Authors: Knoche Karl Friedrich
Published: May 2005

Die Nutzung der Kernenergie zur Erzeugung von gasförmigen Sekundärenergieträgern (Synthesegas, Methan und Wasserstoff) hat in den letzten Jahren zunehmend an Interesse gewonnen. Wasserstoff, der wegen seiner vielseitigen Einsatzmöglichkeiten und seiner hervorragenden und umweltfreundlichen Brenneigenschaften als ein besonders attraktiver Brennstoff anzusehen ist, sollte dabei langfristig ohne Verbrauch fossiler Rohstoffe ausschließlich aus Wasser hergestellt werden. Hochtemperaturreaktoren sollen die dazu erforderliche Energie liefern. Einige der aussichtsreichsten Prozesse hierzu werden beschrieben und auf den erreichbaren Wirkungsgrad analysiert.
Langsame Detonation, Dampfexplosion, Blasenresonanz‐explosion – Gemeinsamkeiten
Authors: Leiber Carl‐Otto
Published: May 2005

Es werden Explosionsphänomene in kondensierter, vorzugsweise flüssiger Phase beschrieben, bei welchen die Energie „chemisch”︁ oder „physikalisch”︁ eingebracht wird. Es wird gezeigt, daß zwischen der chemischen und physikalischen Explosion keine grundsätzlichen Unterschiede bestehen. Existenzbedingungen der Explosion werden angegeben, welche möglicherweise auch zu deren Unterdrückung herangezogen werden können. Da diese teils außerordentlich kritisch sind, wird diese Art der Explosion derzeitig technisch nicht ausgenutzt, ist aber von sicherheitstechnischem Interesse. Beispielhafte Unfälle werden beschrieben.
Die Anwendung der Risikoanalyse in der chemischen Industrie
Authors: Rose Livingstone Murray
Published: May 2005

Application of risk analysis to the chemical industry. It is surprising that such a well‐established method of investment analysis as risk analysis should find so little use in the chemical industry. A positive feature of risk analysis lies in its ability to influence decision‐making processes prior to their conclusion. Furthermore, it also directs attention to uncertainty factors of a project, which in turn can lead to the development of alternative proposals for risk reduction. The reason for the rather sparse use of this method in the chemical industry probably lies in the facts that former analyses were inadequately executed and that managerial staff regarded risk analysis as a method of locating uncertainties rather than a method for improving decision making. Provision of relevant aids for a comprehensive analytical method and a clear recognition of the inherent advantages should pave the way for wider acceptance of this procedure.
Absorption und Absorber
Authors: Mersmann Alfons , Hofer Helmut , Stichlmair Johann
Published: May 2005

Absorption and absorbers. In physical and chemical absorption, a gas is taken up in a liquid. Absorption methods are employed in particular in the production of synthesis gases and for the purification of gaseous effluents. The phase equilibrium is the essential deciding factor regarding the applicability of this method and its costing. A suitable absorber must be chosen, taking into account the properties of the gas and the liquid, and optimized for economic operation. Absorption processes and absorbers are briefly reviewed.
Untersuchungen zur Betriebscharakteristik pulsierter Füllkörperkolonnen für die Flüssig/Flüssig‐Extraktion
Authors: Bender Eberhard , Berger Rosemarie , Leuckel Wolfgang , Wolf Dieter
Published: May 2005

Studies on the operating characteristics of pulsed packed‐columns for liquid/liquid extraction. The dependence of capacity limit and extraction efficiency on the operating conditions, the properties, and the packing material is illustrated with the aid of experiments on two test mixtures in pilot plant columns. The direction of mass transfer has a large influence on the capacity limit and extraction efficiency. From the practical point of view, the operating characteristics of pulsed packed‐columns provide the chemical engineer with reference data for the estimation of column dimensions and rational planning of pilot plant experiments. Methods for the precalculation of capacity limits and extraction efficiencies of pulsed packed‐columns are reported in the literature. A comparison of the results obtained by these methods with the experimental data indicates the feasibilities and limits of such a calculation.
Naßabscheidung von Feinstäuben und Aerosolen
Authors: Holzer Klaus
Published: May 2005

Wet separation of fine dusts and aerosols. Wet scrubbers are frequently employed in the chemical industry for the separation of fine dusts and aerosols from gas streams. In order to choose the most suitable apparatus for a given purpose from the numerous scrubbers available, 35 wet scrubbers of differing construction were examined on full and pilot‐scale regarding separating efficiency and operating behaviour. According to their flow conception, the scrubbers can be divided into five fundamental types, providing an almost automatic classification according to separating efficiency. The experimentally determined degrees of fractionation used as apparatus‐specific parameters are discussed and a relation between separation efficiency and specific power consumption is presented. The particular requirements of such apparatus in the chemical industry are outlined with the aid of some operational examples.
Nachbehandlung von Halbzeugen und Apparaten aus austenitischen Stählen zur Vermeidung von Spannungsrißkorrosion
Authors: Risch Karl
Published: May 2005

After‐treatment of semifinished products and equipment made of austenitic steel to avoid stress corrosion. Among the factors initiating stress corrosion, the extent and distribution of internal tensile stress are the least tractable. Unknown internal stresses are always superposed on the estimable operational stresses. If they arise from distortions or welding, the former are distributed throughout the entire cross‐section. The action of tools, e.g. on turning or grinding, can also lead to high internal tensile stresses in a thin surface zone. Such stresses are of particular significance because stress corrosion is initiated on the surface. In this article, it is shown that it is usually sufficient to adequately reduce these surface‐proximate internal tensile stresses, e.g. by a pickling process removing a surface layer of material, in order to eliminate stress corrosion and thus to extend the scope of austenitic steels. Should the internal tensile stresses due to distortion and welding suffice to initiate stress corrosion under particularly aggressive conditions, one can attempt to reduce the stress by suitable heat treatment; however, no impermissable change in the microstructure of the steel may occur. Finally, it is also possible to produce compressive stress in a thin surface zone by shot peening so that no stress corrosion can take place. The advantages and disadvantages of the various possibilities are illustrated with the aid of examples.
Zum Stand des Schwingungsnachweises in Apparate‐ und Anlagenkomponenten
Authors: Klapp E.‐U. , Hartermann R.‐U.
Published: May 2005

Detection of vibrations in equipment and plant components. A survey of recent experimental investigations in the field of flow‐induced vibrations is based on selected examples of cylindrical structures in transverse and axial flow. During recent years, great efforts have been undertaken in order to comply with stringent safety standards required especially for nuclear power plant. With regard to plant design and construction of plant assemblies, however, there is a lack of experimental work in which the main parameters were varied systematically. It is consesquently very difficult to develop semi‐empirical models for the calculations in this field. Another problem is that the behaviour of the structure is often investigated in isolation, i. e. without consideration of the influence of the whole plant on the structure of interest.
Diversifikation von Separatoren mit Düsen‐, selbstreinigenden und Vollmantel‐Trommeln
Authors: Hemfort Heinz
Published: May 2005

Diversification of separators with nozzles, provision for selfcleaning, and solid bowls. The flow processes in most centrifuges, and thus also in disk separators, are still partly unknown. An empirical approach and experimentation are therefore of considerable importance for design and applications. Special designs are developed primarily for dealing with liquids having particular properties and the characteristics of various basic types are combined. Highly specialized machines usually result which are optimized for only very narrow fields of application. This development is illustrated for the combination of characteristics of separators having nozzles, provision for self‐cleaning, and solid bowls.
Kostenschätzungen mit Hilfe von Kostenstrukturanalysen
Authors: Burgert Werner
Published: May 2005

Cost estimation by cost structure analysis. During the various phases of a project, cost estimates for capital investments are necessary which satisfy the specific requirements at each stage, such as accuracy and degree of technical scope. A cost structure analysis enables satisfactory and accurate costing at an early stage with minimum cost. The evaluation of statistical data of numerous completed projects can provide an exact cost structure of different types of chemical plant. Examples of cost curves and their parameters for individual items of equipment are given and cost structures of various types of chemical plant are presented and discussed. Past experience in converting cost estimates based on German conditions into estimates that incorporate specific prevailing conditions at selected foreign sites is briefly mentioned.
Definition und Messung der Mischgüte in flüssigen Gemischen
Authors: Hiby Julius W.
Published: May 2005

Definition and measurement of quality of mixing in liquid mixtures.The relative deviation from homogeneity of a mixture can be defined in various ways. These expressions are adapted to the various methods of measuring the degree of mixing and the mixing time: probe methods; color change of chemical indicators; decoloration proportional to the conversion of a reaction; increase in temperature arising from heat of reaction. A comparative study of the various methods is presented (see also [1] in English language).
Fortschritte bei der Auslegung pneumatischer Förderanlagen
Authors: Bohnet Matthias
Published: May 2005

Advances in the design of pneumatic conveyors. Pneumatic conveyors can be constructed for a variety of flow conditions, such as, e. g. dilute phase conveying, strand conveying or plug‐flow conveying. The choice of the most favourable flow condition is naturally determined by the particular problem at hand, and, in particular by the physical data of the solid to be conveyed. In practice, when designing such conveyors, not only the processes taking place in the pipeline have to be taken into account but also those taking place during the feeding and separating of the solid, since these jointly influence the flow conditions of the whole system. The choice of fan is of considerable importance. The accuracy of the precalculation of pressure drops and the criteria for the choice of the most favourable gas velocity in the conveyor line are still unsatisfactory, in spite of the many previously confirmed findings. More recent investigations on the prediction of various flow conditions and on plug‐flow conveying enable a better choice of the most favourable method of conveying. Significant technical developments have been made, especially as regards calculated plug‐flow conveying.
Interkristalline Spannungsrißkorrosion an Hochtemperatur‐Winderhitzern. Werkstoffkundliche, fertigungs‐ und verfahrenstechnische Maßnahmen zur Minderung und Vermeidung der Schäden
Authors: Kalfa Horst , Bühler Hans‐Eugen
Published: May 2005

Intercrystalline stress corrosion cracking (SCC) in high temperature hot blast stoves. After a brief survey of known cases of stress corrosion cracking and today's protective or repair measures, the results of lab tests are presented which provide new knowledge about the course of nitrate stress corrosion cracking. The lab tests are dynamic stress corrosion cracking tests allowing direct simulation of SCC‐attack on structural steels under operational conditions. It thus becomes possible to specifically intervene in the mechanism of SCC. Modifying the factors material, tensile stress, and medium provides a basis for the construction of hot blast stoves not sensitive to SCC.
Computergestützte Auswertung von Informationssammlungen in der Verfahrenstechnik
Authors: Kwiatkowski Josef , Blaß Eckhart
Published: May 2005

Computer‐aided retrieval of data collections in chemical engineering. Data collections are an important tool for more efficient and economical engineering in the various fields of chemical process technology. The computer‐aided utilization of available data collections has major advantages compared with manual processing. Computer‐aided utilization can be based on the identification retrieval or rank retrieval method. The advantage of the rank retrieval method is that it provides a spectrum of solutions sorted by the degree of coincidence with the ideal solution. Rank retrieval can be integrated into larger program packages within an integrated computer system which supports the design of chemical plants.
Modelle und Berechnungsverfahren für die plötzliche Druckentlastung von Gas/Dampf‐Flüssigkeits‐Reaktionssystemen
Authors: Friedel Lutz , Purps Stefan
Published: May 2005

Models and computational methods for the sudden release of pressure in gas/vapour‐liquid reaction systems. Design of pressure‐release sections in safety installations such as safety discs or safety valves for gas/vapour‐liquid reaction systems is essentially determined by thermodynamic and fluid dynamic processes as well as by the occurrence of parallel chemical reactions in the reaction vessels and in closed blow‐off lines. However, because of the highly complex interrelations and, in part, insufficient detailed knowledge, an exact calculation frequently causes difficulties. In order to present and evaluate the current state of the art, the individual phases of pressure release and the most important influencing factors as well as their significance for the pressure distribution as a function of time are described first. There follows a comparison of several computational methods taken from the literature, but which because they treat of the processes involved in a simple way either only permit very imprecise design of pressure‐release sections or which because of their specific model assumptions only apply to particular chemical reaction systems with special boundary conditions. Finally, the problems associated with the development of a generally applicable, reliable computational method are briefly discussed.
Temperieren mit Kreisstromwasser in chemischen Verfahrensanlagen
Authors: Schupmehl Leo , Schäfer Eugen
Published: May 2005

Temperature control by recirculating water in chemical process plants. Temperature regulating systems that use water as circulating medium with direct feed of water vapour and cooling water are dynamically fast and favourable in price; therefore they are frequently installed. The designs produced show an according variety. First, the technical construction of such heating and cooling systems is described, concentrating on three different types – one circulation system for temperatures below 100 °C and two systems for higher temperatures with pressure regulation in circulating water by feed of additional water or by an appropriate steam bolster, respectively. Corresponding design factors such as heating and cooling capacity or pressure‐maintaining level and NPSH value are treated. It follows a description of the corresponding technical equipment for measurement and control. Depending on requirements, the different possibilities of instrumentation range from simple control to cascade control with limited regulation values and with P/PI‐structure changing during the start of process up to computer application. Even the selection of the regulation valves and the choice of valve characteristics are taken into consideration.
Auslegungskonzept für pulsierte Siebboden‐Extraktoren
Authors: Reissinger Karl‐Hermann , Marr Rolf
Published: May 2005

A concept for the design of pulsed sieve‐plate extractors. A concept is presented for the design of pulsed sieve‐plate extractors (PSE) according to which the column diameter is calculated via the flooding load and the column length by concentration profiles using the well known backmixing models. This concept requires some parameters to describe the hydrodynamic and mass transfer behaviour. The parameters depend on physical properties, operating conditions, and extractor geometry and subject to mutual influence. It is now possible to present correlations and models for prediction of these parameters. The mass transfer term can be determined by Sherwood correlations for single drops, using the Sauter mean drop diameter. The total mass transfer coefficient can be given as a function of column lenght. The calculated concentration profiles agree well with the measured profiles and thus the concept is confirmed.
Die Beschreibung der Partikelabscheidung durch Trägheitskräfte mit Hilfe einer dimensionsanalytisch abgeleiteten Kennzahl
Authors: Bürkholz Armin
Published: May 2005

Description of particle precipitation by inertial forces by means of a group derived by dimensional analysis. The fractional degree of precipitation depends upon many operating parameters: these can be attributed to three independent dimensionless groups: the Stokes, the Reynolds, and the Euler number. On the basis of extensive experimental material, dimensional analysis shows that, for sufficiently large Reynolds numbers and in a large range of the Euler number, the inertial precipitation depends upon a single dimensionless group, the precipitation parameter ΨA. It can be regarded as the ratio of two energies, viz. a characteristic precipitation energy, expressed as the product of the inertial energy of the particle and the pressure drop coefficient of the precipitators, and a frictional energy dissipated in the boundary surface of the impact body. Thus inertial precipitation is transformed from a complicated flow problem into an energetic problem in which pressure drop plays a major role. Simple approximation formulae can be given for the fractional degree of precipitation and the limiting droplet size for all types of separators.
Teilchengrößen‐Bestimmung mittels dynamischer Lichtstreuung
Authors: Wagner Joachim
Published: May 2005

Particle‐sizing by dynamic light scattering. The range of applications of colloidal systems is often defined merely by their particle‐size distribution. Dynamic light scattering has proven to be a fast and precise technique for sizing particles in the range of 3 nm to 3 μm. This paper describes the basis of measurement and the method of data analysis. Numerous applications of dynamic light scattering in the chemical industry are also given.
Aerosolbildung in Absorptionsprozessen – Ursachen und Lösungsansätze
Authors: Ulbrich Michael , Sachweh Bernd , Meckl Stefan , Schraut Armin , Hölemann Karl
Published: May 2005

Aerosol Formation During Absorption Processes ‐ Causes and Solution Strategies.

If a gas phase contains inerts or components with a wide range of volatility then supercooling may occur during an absorption or partial condensation process. The resulting supersaturation can lead to aerosol formation in the presence of condensation nuclei. During the production and processing of chemical products aerosol formation can lean, for instance, to corrosion, non‐fulfilment of specifications, or catalyst poisoning. Aerosol separators often represent a costly problem solution because they consume energy and require additional investment, whereas the avoidance of aerosol formation, if possible, represents a cost‐favourable alternative. In this article, the causes of aerosol formation are analysed and four strategies for solving the problem of aerosol formation are developed. Industrial aerosol problems are considered to illustrate how these strategies can be implemented in practice.
Praxisrelevante Simulationswerkzeuge für mehrstufige Batch‐Prozesse
Authors: Daun Gregor , Bartenbach Bernd , Battrum Mike
Published: May 2005

Practically Relevant Simulation Tools for Multistep Batch Processes During the development and improvement of multistep batch processes, the description and optimum design of the material and temporal link‐up of the various units for reaction, isolation, and solvent work‐up is becoming increasingly demanding and requires software support. Distinguishing criteria are first derived for the various simulation tools and these are then supplemented with specific industrial demands placed on simulation tools for overall processes. The authors then provide an overview of commercially available programs above all for simulation of overall processes and report on their own experience. The potential of tools for simulation of overall processes lies not in the reduction of the number of experiments but in better utilisation of plant capacity by improved batch planning, in centralised data storage, in a largely standardised, simplified and consistent documentation, and hence simplified communication.
Localization of glycine receptor alpha subunits on bipolar and amacrine cells in primate retina
Authors: Jusuf Patricia R. , Haverkamp Silke , Grünert Ulrike
Published: May 2005

The major inhibitory neurotransmitter glycine is used by about half of the amacrine cells in the retina. Amacrine cells provide synaptic output to bipolar, ganglion, and other amacrine cells. The present study investigated whether different bipolar and amacrine cell types in the primate retina differ with respect to the expression of glycine receptor (GlyR) subtypes. Antibodies specific for the α1, α2, and α3 subunits of the GlyR were combined with immunohistochemical markers for bipolar and amacrine cells and applied to vertical sections of macaque (Macaca fascicularis) and marmoset (Callithrix jacchus) retinae. For all subunits, punctate immunoreactivity was expressed in the inner plexiform layer. The GlyRα2 immunoreactive (IR) puncta occur at the highest density, followed by GlyRα3 and GlyRα1 IR puncta. Postembedding electron microscopy showed the postsynaptic location of all subunits. Double immunofluorescence demonstrated that the three α subunits are clustered at different postsynaptic sites. Two OFF cone bipolar cell types (flat midget and diffuse bipolar DB3), are predominantly associated with the α1 subunit. Two ON bipolar cell types, the DB6 and the rod bipolar cell, are predominantly associated with the α2 subunit. The glycinergic AII amacrine cell is presynaptic to the α1 subunit in the OFF‐sublamina, and postsynaptic to the α2 subunit in the ON‐sublamina. Another putative glycinergic cell, the vesicular glutamate transporter 3 cell, is predominantly presynaptic to the α2 subunit. The dopaminergic amacrine cell expresses the α3 subunit at a low density. J. Comp. Neurol. 488:113–128, 2005. © 2005 Wiley‐Liss, Inc.
Development of A9/A10 dopamine neurons during the second and third trimesters in the African green monkey
Authors: Morrow Bret A. , Redmond D. Eugene , Roth Robert H. , Elsworth John D.
Published: May 2005

Disruption in the development of dopamine‐containing neurons has been postulated to underlie several CNS disorders. However, there have been no quantitative studies on the normal development of primate dopamine neurons. Thus, the fetal maturation of primate midbrain dopamine neurons was examined to establish changes that occur in the A9/A10 groups during the second and third trimesters. Eleven fetal African green monkey midbrains were immunostained for tyrosine hydroxylase (TH‐ir) as a marker for dopamine neurons and quantified using stereological techniques (nucleator method). The number and size of defined dopamine neurons and the volume occupied by A9/A10 neurons increased in near linear fashion throughout the term. The estimated number of defined dopamine neurons in each hemisphere rose from ∼50,000 at embryonic day (E) 70 to 225,000 at birth (E165), similar to the adult population. The size and the area occupied by them at birth were, however, well below the estimated adult levels. Additionally, the younger fetal midbrains had far less diversity in dopamine cell volumes compared with older fetuses and adult brains. Until midway through gestation (E81), clusters of apparently immature midbrain TH‐ir cells were observed, but could not be counted. Even though the majority of cells destined to become dopamine neurons are generated in the first trimester, phenotypical maturation of A9 and A10 cell bodies continues steadily throughout gestation and extends well into the postnatal period. These data have relevance to transplantation studies that employ fetal dopaminergic grafts, and to disorders hypothesized to result from damage to developing midbrain dopamine neurons. J. Comp. Neurol. 488:215–223, 2005. © 2005 Wiley‐Liss, Inc.
Synaptic patterns in the visual cortex of the cat and monkey. Electron microscopy of Golgi Preparations
Authors: LeVay Simon
Published: May 2005

Primary visual cortex (area 17) from macaque monkeys, cats and kittens was stained by a rapid Golgi method modified to give optimal preservation of fine structure. Single impregnated neurons were identified in the light microscope, and then cut in serial thin sections for electron microscopy. As in conventional E.M. material, synapses in the Golgi preparations could be classified into types 1 and 2: type 1 synapses possessed round vesicles in the axon and a pronounced postsynaptic opacity; type 2 synapses had smaller, flattened vesicles in the axon and a slight postsynaptic opacity. Synapses onto impregnated cells were identified by the presynaptic opacities (dense projections), and classified as type 1 or 2 according to the shape and size of the vesicles.

Pyramidal cells and spiny stellate cells (found in layer 4) had a similar synaptic environment: type 1 synapses occurred only on the spines, while type 2 synapses were found on dendritic shafts, cell bodies, and axon initial segments. Spinefree stellate cells possessed both type 1 and type 2 synapses on the cell body and on the dendritic shafts, the type 2 synapses being most frequent near to, the type 1 synapses far from, the cell body.

Synapses formed by the axon terminals of nine cells were located, and were classified as type 1 or 2 on the basis of the thickness of the postsynaptic opacity. The axons of pyramidal and spiny stellate cells formed type 1 synapses; those of spinefree and sparsely spinous cells formed type 2 synapses. In the 12‐day old to 5‐week old kittens, cells corresponding to the spinefree cells of the adult cat did possess spines. These transient spines were commonest on and near the cell body, and were the sites of type 1 synapses.

On these and other grounds, the spiny stellate cells of layer 4 were concluded to be closely related to pyramidal cells, and quite distinct from the class of spinefree and sparsely spinous cells. The interpretation of conventional E.M. preparations of cerebral cortex is discussed.
Heart rate and blood pressure responses to electrical stimulation of the central nervous system in the pigeon (Columba livia)
Authors: MacDonald Robert L. , Cohen David H.
Published: May 2005

An extensive stereotaxic stimulation study of the pigeon brain was conducted with monitoring of heart rate, arterial blood pressure and respiration. Rostrally, short latency tachycardia, hypertension and hyperpnea were elicited from the archistriatum, occipitomesencephalic tract and hypothalamus. In addition, blood pressure decreases followed by long latency tachycardia were elicited from the septal complex, although occasionally slight bradycardia occurred.

Tachycardia, hypertension and hyperpnea were elicited from many midbrain sites including the lateral reticular formation, ventrolateral tegmentum, ventral area of Tsai, the midline region between nucleus interpeduncularis and the oculomotor complex, and nucleus mesencephalicus lateralis, pars dorsalis. In addition, moderate tachycardia and hypotension were elicited from the central gray and nucleus intercollicularis while tachycardia, hypertension and hyperpnea were elicited from the tegmental area in the region of the occipitomesencephalic tract.

At pontine levels, hypertension and cardioacceleration were elicited from a sparsely celled region lateral to the nucleus abducens and from a ventrolateral tegmental region. With respect to respiratory responses, hyperpnea was elicited from the ventrolateral brainstem at all pontine levels and from the dorsomedial region at rostral pontine levels. In caudal pons apnea was the consistent respiratory response to stimulation of the dorsomedial brainstem. In addition, cardio‐acceleration, hypertension and apnea were elicited from the region of the deep cerebellar nucleus cerebellus internus and from its major outflow, the uncinate fasciculus.

Finally, stimulation in the medulla elicited bradycardia and hypotension from the vagal rootlets, solitary complex, descending vestibular nucleus and lateral aspect of the dorsal motor nucleus just rostral to the obex. Tachycardia and hypertension were elicited from the medial aspect of the dorsal motor nucleus, medullary reticular formation ventral to the vagal rootlets and ventrolateral medulla.
Neural and vascular ultrastructure of the area postrema in the rat
Authors: Dempsey Edward W.
Published: May 2005

Electron microscopy of the area postrema reveals two types of small blood vessels, a large sinusoidal variety and one of smaller diameter. Both are surrounded by perivascular connective tissue sheaths bounded on both inner and outer aspects by well developed basal laminae. In experimental argyria, dense granules are massively deposited in the basal laminae of the large sinusoidal vessels, and more delicately in the laminae of smaller capillaries. By analogy with the similar massive deposits of silver in renal glomeruli, this suggests an extensive transport of fluid from the sinusoids into the perivascular spaces. Neurons, their processes and endings are present in the perivascular spaces, indicating an endocrine function to this neural structure. Scanning electron microscopy coupled with x‐ray analysis reveals the dense granules in argyric animals to contain both silver and sulfur, thus suggesting that much if not all of the stored silver is in the form of its sulfide.
Connections of the anterior commissure in the pigeon (Columba livia)
Authors: Zeier Hans J. , Karten Harvey J.
Published: May 2005

The projections of the anterior commissure of the pigeon (Columba livia) were studied experimentally using the Fink‐Heimer methods. The anterior commissure was sectioned immediately to one side of the midline, and animals sacrificed from 2 to 17 days post‐operatively.

The anterior commissure divides into two major fascicles on crossing the midline: a relatively diffuse anterior medial branch (or pars bulbaris), and a more compact laterally directed posterior branch (the pars temporalis).

The pars bulbaris passes rostrally medial to the lateral forebrain bundle (FPL), terminating, in course, in an area ventrolateral to the nucleus accumbens, the lobus parolfactorius, the dorsal portions of the olfactory tubercle, and in restricted regions on the medial edge of PA, neostriatum, and hyperstriatum ventrale. At the rostral end of the telencephalon the pars bulbaris converges with the pars temporalis in the region of the hyperstriatum intercalatus superior (HIS).

The pars temporalis of the anterior commissure terminates in the anterior one‐third of the contralateral archistriatum. Numerous fibers leave the archistriatum and follow two separate trajectories: a dorsolaterally projecting pathway terminating in the temporo‐parieto‐occipital corticoid area (TPO of Edinger 1903), which continues anterolaterally to HIS; a ventrolateral rostrally directed path which parallels the tractus fronto‐archistriaticus, terminating in the deep layers of the piriform cortex. At rostral levels this latter bundle turns dorsally to merge with the anteromedial and dorsolateral trajectories in the region of HIS.

The pattern of termination in the archistriatum indicates the presence of several discrete subnuclei within the anterior archistriatum. A tentative terminology is suggested for the major subdivisions of the anterior archistriatum.

There were no commissural projections to those specific sensory neuronal fields in direct receipt of thalamic efferents such as the ectostriatum, Field L or the visual wulst.
The structure of the dorsal lateral geniculate nucleus in the mouse. A golgi and electron microscopic study
Authors: Rafols Jose A. , Valverde F.
Published: May 2005

Two types of neurons have been distinguished in Golgi and electron microscopic preparations of the dorsal lateral geniculate nucleus of young mice. In addition to a thalamo‐striate relay cell (TSR neuron) with brush‐like dendritic arbors and a thick, unbranched axon, a small tomedium size cell (PA neuron) of oval or spindle shaped body and few, long and seldom branched dendrites is frequently identified in our Golgi preparations. This second type of cell may exhibit none, one or several sparsely branched axon‐like processes which terminate in the vicinity of the cell body. The dendrites of the PA neurons show characteristically large, spheroidal processes (p) 1–3 m̈ in diameter issuing forth singly, in clusters or as a “string of beads” from delicate, often long, pedicles attached to the dendritic shafts. Profiles comparable to these processes and in apparent continuity with PA dendrites have been identified with the electron microscope and show synaptic vesicles and a system of sacs of smooth E.R. The portions of the dendrites from which these vesicle‐containing processes issue also show clusters of vesicles, ribosomes and an orderly array of microtubules.

Golgi impregnated axons are followed from the optic tract and seen terminating as irregular enlargements (2–6 m̈) on proximal dendrites of relay cells and on distal dendrites of the PA neuron. The intimate contact of the terminal branches of an optic collateral with a distal PA dendrite is carefully illustrated. Small calibered axons are likewise traced from the internal medullary lamina and seen to end by means of end‐knobs on distal dendrites of both types of neurons.

Electron microscopic observations substantiate the Golgi images and reveal three different types (I, II, III) of endings in the geniculate neuropil. The large type I endings correspond to the retinal afferents which generally make asymmetric synapti contact with type II profiles and/or with clusters of microspines on the TSR dendrites. Type II, thought to be the spheroidal dendritic appendages of the PA neurons, form symmetrical synaptic contacts with profiles of its own kind or more commonly with dendrites of the TSR neuron. The type III ending, probably cortical in origin, establishes asymmetrical synaptic contacts with small dendritic profiles. Only profiles of types I and II endings, together with those of other dendritic profiles, form part of the nest‐like junctions known as the synaptic glomeruli. The significance of the unusual polarization of the geniculate interneurons is discussed.
Genesis of glioblasts in the human spinal cord as revealed by Feulgen cytophotometry
Authors: Fujita S.
Published: May 2005

To study gliogenesis in the spinal cord, Feulgen cytophotometry was carried out on cells in the cervical cord of human embryos ranging from 7–45 mm in crown‐rump length. Glioblasts synthesizing DNA are first detectable at eight‐week‐stage in the mantle and marginal zones in the basal plate and immediately thereafter in the alar plate. Coincidentally the matrix layer changes into a single‐layered ependymal lining. This pattern of the incipient stage of gliogenesis in the human spinal cord closely resembles that of the chick embryo.

Silver carbonate staining of the spinal cord at this stage showed diverse morphology of the glioblasts at their earliest stage of differentiation. The pattern of glioblast formation coincides with that of the genesis of the so‐called microglioblasts so far reported, not only in the space‐time relationships in embryogenesis but also in the morphology of the cells occurring at this stage. It is concluded that the so‐called genesis of the microglia in the spinal cord is nothing but the stage of glioblast formation from the matrix cells.
The central connections of the anterior lateral line nerve of Gnathonemus petersii
Authors: Maler L. , Karten H. J. , Bennett M. V. L.
Published: May 2005

The central connections of the lateral line nerve ganglia, the eithth nerve ganglia and the fused fifth‐seventh ganglion of Ganathonemus petersii have been studied with silver degeneration techniques. The anterior (NLLa) and posterior (NLLp) lateral line nerves have a topographically organised projection upon the posterior lateral line lobe. NLLa, representing the head region, distributes to the rostral half of the posterior lobe, while NLLp, representing the trunk, distributes to the caudal half of the posterior lobe. The lateral line nerves also end in the anterior nucleus of the anterior lobe. There is some overlap within the middle third of the anterior nucleus, although NLLp tends to have a more caudal distribution than NLLa. N VIII terminates within n. tangentialis and n. octavius; there appears to be little or no overlap between VIII and lateral line nerve territories.

The V–VIIth ganglion projects to entirely different parts of the brainstem. Terminal areas of V–VII are the sensory nucleus of the vagus, the nucleus of the descending trigeminus, and the funicular nuclei.
Time of neuron origin in the hippocampus and dentate gyrus of normal and reeler mutant mice: An autoradiographic analysis
Authors: Caviness V. S.
Published: May 2005

The hippocampus and dentate gyrus of reeler mutant mice contain the normal neuronal classes. The majority of cells are included in laminar aggregates reminiscent of normal structure though these are irregular in outline, interrupted at points, and less densely packed. Many hippocampal neurons and granule cells of the dentate gyrus are scattered in the external plexiform zone (strata radiatum and lacunosum‐moleculare) of the hippocampus rather than being included in the laminar aggregates.

Neurons in the reeler are generated at the same time as their normal homologs. However, the relationship of adult cell position to sequence of cell generation is abnormal in two general ways in the mutant. First, although in both the mutant and normal, cells in the external plexiform zone of the hippocampus are among the earliest formed, a relatively greater proportion of cells generated through a relatively longer embryonic time are destined to be scattered in this distal location in the mutant. Secondly, within the laminar aggregates of the hippocampus in reeler, the more superficial cells tend to be formed earlier, and the more deeply located ones are the latest formed. A reversed relationship exists in the normal in which the deepest cells are formed earliest, the more superficial ones last. The observations are consistent with the view that a mechanism which provides for orderly lamination of cells in the normal is defective in reeler.
Organization of pallidothalamic projections in the rhesus monkey
Authors: Kuo Jon‐Son , Carpenter Malcolm B.
Published: May 2005

Attempts were made to: (1) define the regions of origin of the ansa lenticularis (AL) and the lenticular fasciculus (LF), and (2) determine if particular regions of the medial pallidal segment (MPS) project in an organized fashion to thalamic nuclei. The MPS was divided into rostral and caudal (by a plane through the LF), dorsal and ventral (by an appropriate plane), and medial and lateral (by the accessory medullary lamina) parts. Attempts were made to categorize various lesions of the MPS and degeneration was studied in transverse, sagittal and horizontal sections stained by the Nauta and Wiitanen technics. Corresponding Nissl‐stained sections were used to delineate thalamic nuclei.

Localized lesions in portions of the MPS (11 rostral and 10 caudal) were worthy of anatomical analysis in 21 monkeys. Data support the thesis that fibers of the AL arise predominantly from the outer part of the MPS and pass ventrally and medially through portions of the inner part of the MPS to their site of emergence. Fibers of the LF appear to arise from the inner part of the MPS and project dorsomedially through the internal capsule.

Pallidothalamic projections to the rostral ventral tier thalamic nuclei [the ventral anterior (VApc) and the ventral lateral (VLo)] appear topographically organized in three cardinal dimensions. Rostral parts of the MPS project pre‐dominantly to parts of VApc, while caudal parts of the MPS project primarily to parts of VLo. There also is a dorsoventral and mediolateral correspondence in the pallidal projection to VApc and VLo which exhibits overlap. Pallidothalamic projections to the contromedian nucleus (CM) terminate preponderantly in rostral and medial regions of the nucleus, and there appears to be a definite correspondence between parts of the MPS and parts of CM, only in the dorsoventral dimension.
Brain mechanisms and feeding behavior in the pigeon (Columba livia) I. Quinto‐frontal structures
Authors: Zeigler H. Philip , Karten Harvey J.
Published: May 2005

Lesions were placed stereotaxically in the principal sensory trigeminal nucleus (PrV), the quinto‐frontal tract (QFT) and the nucleus basalis (NB) of the pigeon and their effects upon food and water intake were studied. Bilateral lesions of these three “quinto‐frontal” structures are followed by periods of aphagia and by a hypophagia whose persistence and severity are approximately proportional to the bilateral extent of the lesion. Such lesions also disrupt the neurosensory control of the consummatory response of feeding.

No effects upon food or water were seen following control lesions placed in a wide variety of regions at several levels of the brain, including the hypothalamus. Moreover, despite their marked effects upon feeding behavior, lesions of quinto‐frontal structures do not impair drinking.

The results have helped clarify previous studies of forebrain mechanisms in feeding behavior and they suggest that PrV, QFT and NB are afferent components of a network of structures controlling feeding behavior in the pigeon.
Degeneration and regeneration of severed crayfish sensory fibers: An ultrastructural study
Authors: Nordlander Ruth H. , Singer Marcus
Published: May 2005

In crayfish peripheral nerve, terminal processes of most sensory fobers degenerated within two to three weeks of nerve severance. First, large clear vesicles appeared in the axoplasm which subsequently lost its substructure, became more dense and compact, and was finally reduced to dense inclusions within glial cytoplasm. Considerable traumatic degeneration was also observed in proximal segments of severed axons. The rate of fiber degeneration was generally more rapid in the smallest fibers and slower in the larger intermediate axons. Large numbers of regenerating axons were first seen crossing the lesion site after four weeks. Growing fibers, found in bundles wrapped by glial processes, were at first small and tightly packed with no glial processes separating them. Later fibers enlarged and acquired wrapping patterns typical of normal sensory fibers. Growth cones were observed during early stages of regeneration. Some secondary degeneration may occur.