bluuebunny/crossref_metadata_2025 huggingface dataset:
La conception des formes de carène sur les galères de la fin du XVIIe siècle
Authors: Daeffler Michel
Published: February 2011

Mediterranean shipbuilding is mostly known due to archaeological data a large part of which consist in wrecks of ancient sailing merchant ships. Galleys are practically never encontered in underwater excavations, which oblige us to utilise written records and iconographical data.

No plan of a 17th century galley has been discovered to this day because shipbuilding emerged from a non-graphic culture in which other existing methods enabled the form of the lower part of a hull to be designed. The first galley plans appeared in France around the 1730s on the impulse of shipbuilders such as Reynoir the younger. When the shipbuilder proceeded by trial and error it was on paper and not on the building site. Thanks to the graphic documents, the builder preserved and exploited the experience gained dunng his career and that ofhis predecessors.

The methods used in the 17th century by the galley builders, the direct heritage of the medieval period, were very different from those used in the 18th century. The carpenters used «technical formulas », obtained empirically, to define all the dimensions and draw theform ofthe lower part of the hulls.

The builders used moulas and rising squares, kinds of model for the frame, as well as ribbands. The latter are wooden rods fixed longitudinally onto the hull after the central ribs have been placed. They enable the builder to draw the frame of the ends by means of appropriate measurements. The ribs of the central part are drawn with the help of moulds and rising squares taken from the tracing ofthe midship frame. The evolution of the forms of the lower part of the hull is obtained by moving these moulds and rising squares around over each other. The ribs of the hull's aft extremity are made by associating the ribbands and moulds, moving them to give the shape of the frame. The form of the ribs ofthe hull's fore part is solely defìned by a network of ribbands.

Experience and good judgement play a determining role especially for the shaping of the fore and aft parts, the pronounced sharp bottom of the extremities is not conducive to the sole use of moulds.
Quelques remarques sur la construction française des chébecs entre la fin du XVIIIe et le début du XIXe siècle
Authors: Delhaye Marion
Published: February 2011

The object of thispaper is specially to insist on the architectural modification which can happened during the utilisation of the vessel. In fact, from a simple example such as the architectural analysis of a vessel like the xebec, we rapidly fìnd ourselves faced with the problem ofa generalised study ο f Mediterranean trade little vessels.
Structures and vessels for transport in early Swedish iron production.
Authors: Cederlund Carl Olof
Published: February 2011

Des bateaux à voile construits à clin, naviguant dans les eaux intérieures, ont servi longtemps en Suède au transport de marchandises souvent très lourdes: fer et minerai de fer, pour ne citer que les plus importantes. Ces navires peuvent être comparés et même reliés à certains bateaux à quille américains. Il semble qu'il ait existé un type de navire nordique/suédois et qu'il ait été transféré vers les états de la côte est de l'Amérique. Certaines sources démontrent, en outre, l'existence d'une continuité ethnique due à l'émigration suédoise, ainsi qu'une même utilisation de ce type de navire en Amérique du Nord et en Suède.

Cet article expose les résultats préliminaires et les informations dont nous disposons à ce sujet avec des représentations, notamment, de différents navires suédois présentant les caractéristiques citées précédemment afin qu'ils puissent être comparés avec les bateaux à quille américains.
History and design research on Eastern American mountain boats
Authors: Newell Mark M.
Published: February 2011

Cet article présente en détail un type précis d'embarcations utilisées pour le transport du coton et du tabac sur le cours supérieur de la rivière Savannah, qui marque la frontière entre la Géorgie et la Caroline du Sud. L'historique de l'utilisation de ces bateaux dans les régions montagneuses de la côte est accompagné de commentaires sur la conception supposée du modèle. Un compte rendu de reconstruction est proposé après étude d'un exemplaire local.

Les recherches qui portent en Caroline du Sud sur ce type de petites embarcations ont permis, depuis 1983, d'identifier ce bateau caractéristique de la zone montagneuse de la côte est, comme l'une des deux embarcations historiquement connues dans la région, et ce, en dépit de l'absence apparente de témoignage archéologique. Ce fait a conduit l'auteur à les choisir de préférence, pour un essai de reconstruction, grandeur nature.
A pre-history of the dry-dock
Authors: Barker Richard
Published: February 2011

Au sens moderne et large du terme, le «dry-dock», ou cale sèche, fait partie du processus d'exploitation des navires depuis environ cinq cents ans mais les origines du terme plus général « dock » se perdent dans la nuit des temps. Ce mot, cependant, a déjà une existence historique bien avant que l'on puisse savoir ce qu'il recouvre concrètement. Les premières indications concrètes notables dont nous disposons à ce sujet et qui concernent le « dock » de Portsmouth en 1495-97 ne permettent pas encore de reconstituer une description convaincante de sa forme; il s'agissait indubitablement d'un «dry-dock» mais nous ne pouvons même pas être certain qu'il s'agisse bien du premier qui ait existé, ni en quoi il se distinguait des structures antérieures. Il n'existe pas d'indices archéologiques, au sens restrictif du terme, à ce sujet, ni de données historiques pour cette époque reculée.

Le point crucial réside cependant, en un détail critique et curieusement peu compris que l'on remarque pour la première fois à Portsmouth: la forme de la porte. Des éléments plus récents seront utilisés pour démontrer que les descriptions de la porte de 1496 pouvaient concerner un système beaucoup plus sophistiqué que ne le suggère Oppenheim dans ses publications de 18961. Il est vrai également que, bien plus tard, les «dry-docks » réalisés principalement en bois pouvaient être des structures remarquablement simples pour des navires assez gros et, qu'à partir de ce modèle, on peut concevoir que certains «docks» médiévaux ont pu être structuralement assez élaborés sans trop s'éloigner de la description d'un «hedge».
Les tourbières irlandaises à l'ordre du jour : essai de mise au point
Authors: Reffay Annie
Published: February 2011

RÉSUMÉ

Beaucoup d'études récentes concernent les tourbières d'Irlande qu'une exploitation mécanisée menace de disparition. Elles en affinent la classification, en retirent de nouvelles données paléochronologiques fondées sur la téphrochronologie et l'archéologie et inclinent en faveur de l'origine naturelle de ces milieux humides. Elles tendent à considérer l'érosion des tourbières-couverture comme un processus naturel, mais n'écartent pas son accélération sous l'effet d'actions anthropiques. Elles envisagent les délicats problèmes, juridiques, financiers et techniques soulevés par leur conservation.
Gens de Basse Normandie, et si l'eau vous était comptée ?
Authors: Trzpit Jean-Paul
Published: February 2011

Par son climat réputé très humide, la Basse-Normandie fait couramment figure de région plantureuse où tout pousse à foison. Or cette image banale, maintes fois démentie par la chronique lors de ces dernières décennies, ne se vérifie pas vraiment. En témoignent les enseignements contraires tirés d'une analyse rigoureuse fondée sur l'exploitation de nombreux bilans hydriques, dûment quantifiés. Ainsi, en s' inscrivant en faux de l'imagerie traditionnelle, cette approche climatique, renouvelée dans sa méthode comme dans ses conclusions, inclinera peut-être vers une gestion toujours plus rationnelle et vers une utilisation plus parcimonieuse de l'eau. Car pour être renouvelable, cette ressource naturelle vitale n'en reste pas moins contingentée... et ce jusqu'en Basse-Normandie.
Des épisodes climatiques actuels. A propos des pluies exceptionnelles de janvier 1995 dans le Calvados
Authors: Cantat Olivier , Gires Jean-Olivier
Published: February 2011

Janvier 1995 restera marqué dans la mémoire de nombreux calvadosiens en raison de ces inondations catastrophiques. Seule la conjonction de plusieurs facteurs peut aboutir à des conséquences aussi désastreuses. Dans notre exemple, les causes sont principalement une pluviométrie d'une durée de retour centenaire, liée à une situation météorologique caractéristique des mois d'automne et qui a perduré en cette fin d'hiver, et la présence d'un sol déjà gorgé d'eau après les pluies abondantes des mois qui ont précédé.
La baie du Mont-Saint-Michel et ses bordures : vers une approche géosystémique
Authors: Gross Vincent
Published: February 2011

This article aims at presenting a research about the evolution of landscapes and societies around Mont-Saint-Michel bay, and at insisting in the interest of systemic analysis for the understanding of studied area. Some geosy stems are described. They indicate that Mont-Saint-Michel bay is an area where différents spatial systems skirt.
Un renouveau rural qui se fait attendre
Authors: Calmès Roger
Published: February 2011

C'est dans la phase de modernisation des structures économiques et de mobilités sociales que par contraste apparaissent les caractères régressifs de certains espaces ruraux. Analysés en Basse-Normandie, les résultats montrent clairement qu 'il y a accentuation de la devitalisation depuis quelques décennies et que le renouveau rural tant évoqué n 'est pas encore au rendez-vous.
La Basse-Normandie et les fonds structurels européens
Authors: Madeline Philippe
Published: February 2011

La nouvelle politique régionale européenne en faveur des régions les plus défavorisées de l'Union européenne s'inscrit dans la recherche d'un rééquilibrage spatial communautaire. Moins défavorisée que les espaces dits en retard de développement, la Basse-Normandie bénéficie toutefois d'aides communautaires qui renforcent les priorités régionales et départementales à la recherche de nouvelles voies de développement.
Le pont de Normandie
Authors: Chesnais Michel
Published: February 2011

Le franchissement de la Seine est un enjeu économique important. La récente construction du Pont de Normandie sur l'estuaire de la Seine a amélioré les relations régionales et a eu des implications locales inattendues.
La constuction de la grande agglomération caennaise : du plan d'urbanisme directeur de 1965 au schéma directeur révisé 1994
Authors: Rabec Alain
Published: February 2011

For thirty years, the town planning of the «agglomération caennaise» often changed and sustained somme difficulties with the different SDA U. However, now Caen is a well balanced, pleasant and modern agglomeration. The lessons of history are and will be advantageous.
Le Contrat de Plan 1994 - 1998
Authors: Garrec René
Published: February 2011

L'aménagement du territoire et le développement économique de la Basse- Normandie ne vont pas sans le soutien financier de l'Etat. Le Contrat de Plan permet de définir les objectifs communs de l'Etat et de la Région et de fixer les aides correspondantes. Le IIIe Contrat de Plan a été exceptionnel et mobilisateur.
La Maison de la Recherche en Sciences Humaines de Caen: des perspectives nouvelles pour les géographes
Authors: Herin Robert
Published: February 2011

The Maison de la Recherche en Sciences Humaines of Caen receive research groups of human, economic, social and juridical sciences from university of Caen and CNRS.

It is a research center with a high scientific level and opens new views for geographers and region of Low Normandy.
Virological Characterization of Patients Failing Darunavir/Ritonavir or Lopinavir/Ritonavir Treatment in the Artemis Study: 96-Week Analysis
Authors: Lathouwers Erkki , De Meyer Sandra , Dierynck Inge , Van de Casteele Tom , Lavreys Ludo , de Béthune Marie-Pierre , Picchio Gaston
Published: February 2011

Background

In the Phase III ARTEMIS Trial, treatment-naive patients received once-daily darunavir/ritonavir (DRV/r) 800/100 mg ( n=343) or lopinavir/ritonavir (LPV/r) 800/200 mg (total daily dose; n=346) plus fixed-dose tenofovir disoproxil fumarate/emtricitabine. The primary outcome measure was non-inferiority of DRV/r versus LPV/r (HIV type-1 [HIV-1] RNA<50 copies/ml). Here, a detailed 96-week resistance analysis is presented.

Methods

Virological failures (VFs) were defined as patients who had lost (rebounders) or who had never achieved (never suppressed) HIV-1 RNA<50 copies/ml after week 12. Genotypic and phenotypic determinations were performed on plasma samples with HIV-1 RNA≥50 copies/ml. The end point was defined as the last on-treatment visit with available genotype and/or phenotype.

Results

The VF rate was significantly lower in DRV/r (12%, n=40) versus LPV/r patients (17%, n=59; P=0.0437). Among DRV/r patients, 24 rebounded and 16 were never suppressed, whereas among LPV/r patients, 33 rebounded and 26 were never suppressed. Transient HIV-1 RNA increases (≥50 copies/ml) occurred in 50% ( n=12) DRV/r and 48% ( n=16) LPV/r rebounders; these viral levels returned to undetectable by end point without any changes to the study regimen. No major (primary) protease inhibitor (PI) resistance-associated mutations (RAMs) developed in VFs with an available genotype at baseline and end point, and almost all developing minor PI RAMs were polymorphic. At end point, all VFs with available phenotypes at baseline and end point remained susceptible to all PIs, including study PIs.

Conclusions

The VF rate was lower with DRV/r than LPV/r. The findings of this resistance analysis confirmed the lack of development of major PI RAMs and the preservation of phenotypic susceptibility to all PIs in patients with VF.
A UK-Wide Survey of Life-Threatening Thyroidectomy Complications
Authors: Hassan-Smith Z. K. , Gopinath P. , Mihaimeed F.
Published: February 2011

Background and Aims. Complications following thyroidectomy can prolong hospital stay and cause significant morbidity particularly for patients treated for benign thyroid conditions. Our aim was to administer a UK-wide survey of thyroid surgery units on frequency and timing of the onset of life-threatening airway complications & correlate to factors that might be associated with them.Methods. A questionnaire including the number of and timing of the onset of life-threatening airway complications, number of thyroidectomy procedures performed per year, surgeon years of experience, the use of difficult airway management protocol, post-operative patient destination, and patient deaths, was sent to 80 UK surgical units.Results. 23/41 hospitals responded reported no postthyroidectomy airway complications. Life-threatening airways complications all occurred within the first 12 hours postoperatively, with 9 cases occurring in the recovery room and in less than 2 hours, 3 cases occurring 2–6 hours, and 3 cases occurring 6 to 12 hours after surgery.Conclusion. The results may support recent publications that advocate thyroidectomy as a less-than-24-hour surgery procedure in selected patients. Further a larger study and standardised protocol are required to establish patients' selection criteria to determine who are likely to develop serious postoperative complication and may require HDU bed.
Maturation of neurotransmission in the developing rat cochlea: immunohistochemical evidence from differential expression of synaptophysin and synaptobrevin 2
Authors: He S. , Yang J.
Published: February 2011

Synaptophysin and synaptobrevin 2 associate closely with packaging and storage of synaptic vesicles and transmitter release, and both play important roles in the development of rat cochlea. We examined the differential expression of synaptophysin and synaptobrevin 2 in the developing Sprague-Dawley rat cochlea, and investigated the relationship between their expression and auditory development. The expression of synaptophysin and synaptobrevin 2 was not observed in Kolliker’s and Corti’s organ at postnatal 1 day (P1) and P5, and the top turn of the cochlea at P10. Expression was detected in the outer spiral bundle (OSB), the inner spiral bundle (ISB), and the medial wall of the Deiters’ cell of the cochlea at P14, and P28, and in the middle or the basal turn of Corti’s organ at P10. Synaptobrevin 2 was expressed in the top of the inner hair cells (IHCs) in Corti’s organ of both P14 and P28 rats. All spiral ganglion neurons (SGNs) were stained at all ages examined. The localization of synaptophysin and synaptobrevin 2 in the cochlea was closely associated with the distribution of nerve fibers and neural activity (the docking and release of synaptic vesicles). Synaptophysin and synaptobrevin 2 were expressed in a dynamic manner during the development of rat cochlea. Their expression differences during the development were in favor of the configuration course constructed between nerve endings and target cells. It also played a key role in the formation of the correct coding of auditory information during auditory system development.
Relating hygroscopicity and composition of organic aerosol particulate matter
Authors: Duplissy J. , DeCarlo P. F. , Dommen J. , Alfarra M. R. , Metzger A. , Barmpadimos I. , Prevot A. S. H. , Weingartner E. , Tritscher T. , Gysel M. , Aiken A. C. , Jimenez J. L. , Canagaratna M. R. , Worsnop D. R. , Collins D. R. , Tomlinson J. , Baltensperger U.
Published: February 2011

Abstract. A hygroscopicity tandem differential mobility analyzer (HTDMA) was used to measure the water uptake (hygroscopicity) of secondary organic aerosol (SOA) formed during the chemical and photochemical oxidation of several organic precursors in a smog chamber. Electron ionization mass spectra of the non-refractory submicron aerosol were simultaneously determined with an aerosol mass spectrometer (AMS), and correlations between the two different signals were investigated. SOA hygroscopicity was found to strongly correlate with the relative abundance of the ion signal m/z 44 expressed as a fraction of total organic signal (f44). m/z 44 is due mostly to the ion fragment CO2+ for all types of SOA systems studied, and has been previously shown to strongly correlate with organic O/C for ambient and chamber OA. The analysis was also performed on ambient OA from two field experiments at the remote site Jungfraujoch, and the megacity Mexico City, where similar results were found. A simple empirical linear relation between the hygroscopicity of OA at subsaturated RH, as given by the hygroscopic growth factor (GF) or "ϰorg" parameter, and f44 was determined and is given by ϰorg = 2.2 × f44 − 0.13. This approximation can be further verified and refined as the database for AMS and HTDMA measurements is constantly being expanded around the world. The use of this approximation could introduce an important simplification in the parameterization of hygroscopicity of OA in atmospheric models, since f44 is correlated with the photochemical age of an air mass.
Urban organic aerosols measured by single particle mass spectrometry in the megacity of London
Authors: Dall'Osto M. , Harrison R. M.
Published: February 2011

Abstract. During the month of October 2006, as part of the REPARTEE-I experiment (Regent's Park and Tower Environmental Experiment) an Aerosol Time-Of-Flight Mass Spectrometer (ATOFMS) was deployed at an urban background location in the city of London, UK. Fifteen particle types were classified, some of which were accompanied by Aerosol Mass Spectrometer (AMS) quantitative aerosol mass loading measurements (Dall'Osto et al., 2009a, b). In this manuscript the origins and properties of four particle types associated with locally generated aerosols, independent of the air mass type advected into London, are examined. One particle type, originating from lubricating oil (referred to as Ca-EC), was associated with morning rush hour traffic emissions. A second particle type, composed of both inorganic and organic species (called Na-EC-OC), was found enhanced in particle number concentration during evening time periods, and is likely to originate from a source operating at this time of day, or more probably from condensation of semi-volatile species, and contains both primary and secondary components. A third class, internally mixed with organic carbon and sulphate (called OC), was found to spike both in the morning and evenings. The fourth class (SOA-PAH) exhibited maximum frequency during the warmest part of the day, and a number of factors point towards secondary production from traffic-related volatile aromatic compounds. Single particle mass spectra of this particle type showed an oxidized polycyclic aromatic compound signature. Finally, a comparison of ATOFMS particle class data is made with factors obtained by Positive Matrix Factorization from AMS data.. Both the Ca-EC and OC particle types correlate with the AMS HOA primary organic fraction (R2 = 0.65 and 0.50 respectively), and Na-EC-OC, but not SOA-PAH, which correlates weakly with the AMS OOA secondary organic aerosol factor (R2 = 0.35). A detailed analysis was conducted to identify ATOFMS particle type(s) representative of the AMS COA cooking aerosol factor, but no convincing associations were found.
Can one detect small-scale turbulence from standard meteorological radiosondes?
Authors: Wilson R. , Dalaudier F. , Luce H.
Published: February 2011

Abstract. It has been recently proposed by Clayson and Kantha (2008) to evaluate the climatology of atmospheric turbulence in the free atmosphere by applying a Thorpe analysis on standard radiosoundings obtained with relatively low resolution (LR) in the vertical. Since then, several studies based on this idea have been published. However, the impact of instrumental noise on the detection of turbulent layers was completely ignored in these works. The present study aims to evaluate the feasibility of turbulence detection from radiosoundings. For this purpose, we analyzed data of two field campaigns during which high-resolution (HR) soundings (10–20 cm) were performed simultaneously with standard LR soundings. We here used the raw data of standard radiosondes, the vertical resolution ranging from 5 to 8 m. A Thorpe analysis was performed on both LR and HR potential temperature profiles. A denoising procedure was first applied in order to reduce the probability of occurrence of artificial inversions, i.e. inversions due to instrumental noise only. We then compare the empirical probability of the sizes of the selected overturns from LR and HR profiles. From HR profiles in the troposphere, the scales of the detected turbulent overturns range from 4 to ~1000 m. The shape of the distribution of the size of overturns is found to sharply decrease with increasing scales. From LR profiles, the smallest scale of detected overturns is ~32 m, a similar decrease in the shape of the size distribution being observed. These results suggest that turbulent events can indeed be detected from standard radiosondes measurements in the troposphere. However these events are rather rare as they belong to the tail of the size distribution of the turbulent overturns: they only represent the 7% largest events. Similar conclusions are obtained from radiosondes data collected in the lower stratosphere, but the fraction of the detectable events is even smaller than in the troposphere since they are the 4% largest events.
Spatio-temporal variations in soil hydrology of a typical semiarid sand-meadow-desert landscape
Authors: Duan L. , Liu T. , Wang X. , Wang G. , Ma L. , Luo Y.
Published: February 2011

Abstract. A good understanding of the interrelations between land cover alteration and changes in hydrologic conditions (e.g., soil moisture) as well as soil physicochemical properties (e.g., fine particles and nutrients) is crucial for maintaining the fragile hydrologic and environmental conditions of semiarid land, such as the Horqin Sandy Land in China, but is lacking in existing literature. The objectives of this study were to examine: (1) spatio-temporal variations of soil moisture and physicochemical properties in semiarid land; and (2) how those variations are influenced by land cover alteration. Using the data collected in a 9.71 km2 well-instrumented area of the Horqin Sandy Land, this study examined by visual examination and statistical analyses the spatio-temporal variations of soil moisture and physicochemical properties. The results indicated that for the study area, the soil moisture and physicochemical properties were dependent on local topography, soil texture, vegetation density, and human activity. Long-term reclamation for agriculture was found to reduce soil moisture by over 23% and significantly (p-value < 0.05) lower the contents of soil organic matter, fine particles, and nutrients.
North Atlantic 20th century multidecadal variability in coupled climate models: sea surface temperature and ocean overturning circulation
Authors: Medhaug I. , Furevik T.
Published: February 2011

Abstract. Output from a total of 24 state-of-the-art Atmosphere-Ocean General Circulation Models is analyzed. The models were integrated with observed forcing for the period 1850–2000 as part of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. All models show enhanced variability at multi-decadal time scales in the North Atlantic sector similar to the observations, but with a large intermodel spread in amplitudes and frequencies for both the Atlantic Multidecadal Oscillation (AMO) and the Atlantic Meridional Overturning Circulation (AMOC). The models, in general, are able to reproduce the observed geographical patterns of warm and cold episodes, but not the phasing such as the early warming (1930s–50s) and the following colder period (1960s–80s). This indicates that the observed 20th century extreme in temperatures are due to primarily a fortuitous phasing of intrinsic climate variability and not dominated by external forcing. Most models show a realistic structure in the overturning circulation, where more than half of the available models have a mean overturning transport within the observed estimated range of 13–24 Sverdrup. Associated with a stronger than normal AMOC, the surface temperature is increased and the sea ice extent slightly reduced in the North Atlantic. Individual models show potential for decadal prediction based on the relationship between the AMO and AMOC, but the models strongly disagree both in phasing and strength of the covariability. This makes it difficult to identify common mechanisms and to assess the applicability for predictions.
Low-Temperature Set as a Measure of State of Vulcanization
Authors: Fielding J. H.
Published: February 2011

In his various patents on vulcanization, Charles Goodyear made several references to the change produced in the low-temperature behavior of rubber. In his earliest patent he stated that vulcanized rubber would not be “injuriously affected by exposure to cold”. The reissues of this patent stated the problem more clearly. “The leading object of my exertions was to render india-rubber capable of resisting the action of heat and cold within the range of atmospheric temperatures…. When compounded with sulfur, by the application of a high degree of artificial heat, I obtained good results, and when compounded with sulfur and the carbonate of lead I obtained the best results.”…. The new product “is water-proof, permanently and highly elastic under all conditions of its use”. Whether Goodyear was referring to the freezing of rubber under tension or under no tension we do not know, but it is probable that he had experienced both effects without distinguishing between them. It is interesting to find now that, one hundred years later, rubber chemists are still looking at this change in low-temperature behavior which he recognized as an effect of vulcanization, and are using the effect as a measure of degree of vulcanization. In recent years the T-50 test has gained considerable popularity as a quantitative measure of the tendency of rubber to freeze under tension. Its popularity is justified, since it can be applied over a broad range of cure and since it measures very precisely a seemingly fundamental property of rubber. It is, however, not the only means of expressing this effect quantitatively. The purpose of the present paper is to demonstrate a simpler method which yields surprisingly precise results, in spite of the fact that none of the usual scientific equipment is used and no measurements other than length measurements are required. Although other papers have approached this subject, none has as yet offered a simple substitute for T-50.
Colloidal Structure of Rubber in Solution. Colloidal Aspects of Vulcanization
Authors: Gehman S. D. , Field J. E.
Published: February 2011

Colloidal changes in solutions of purified rubber due to a vulcanizing system consisting of piperidinium pentamethylenedithiocarbamate, sulfur, and zinc propionate have been followed by means of measurements of the depolarization and intensity of the transversely scattered light and by viscosity measurements. A study was made of the time required for vulcanization of benzene solutions of rubber with the above vulcanizing agents. The temperature coefficient of vulcanization was approximately the same as that for cures of solid stocks. The light scattering results are interpreted as showing that, upon the addition of the vulcanizing agents to the solutions, the colloidal units become larger. The decrease in viscosity is explained as being due to a diminished “interlocking” of the units. In the vulcanization of the solutions, an equilibrium of colloidal processes occurs which results in a constant viscosity for the larger part of the time required for vulcanization, although the light scattering measurements show a continuous change. The magnitude of the light scattering changes indicates that the molecular clusters in the gelled solution are probably not very different from those in the original solution. The viscosity measurements show that the forces between the clusters have been radically strengthened.
Macromolecular Compounds. CCXVI. Determination of the Lattice of Rubber
Authors: Sauter E.
Published: February 2011

In an earlier work a rotating crystal diagram, three different Schiebold-Sauter (rotating goniometer) equatorial diagrams and two different photomicrographs of the same sample of a single crystal were described and shown to be conclusive proof of the single-crystal texture of the sample under examination. If, in their work on the same subject, Meyer and Mark had likewise taken numerous photographs of different kinds, instead of a single photographic film, a comparison of the various photographs would speak for itself. In taking his rotating crystal goniometric photographs, the present author used uniformly thick, frozen small cubes of rubber, the intensities in the reflections of which were the same in all directions. On the contrary, in the photographs of Meyer and Mark, a stretched film of rubber, which reflected considerably less uniformly than did the samples used by the present author, was photographed at rest and therefore without being rotated. Although Meyer and Mark agree to the interference 300, they maintain that this does not explain in any way the appearance of reflection A2.
Application of the Interferometer to the Measurement of Dimensional Changes in Rubber
Authors: Wood Lawrence A. , Bekkedahl Norman , Peters Chauncey G.
Published: February 2011

The interferometer method for the measurement of small dimensional changes is adapted here to measurements on soft rubber. A detailed dsecription is given concerning the preparation of specimens, the apparatus, the procedure and the calculations necessary for the application of this method. Particular emphasis is placed on the measurement of thermal expansivity and the dimensional changes involved in transitions between the different forms of rubber. The lower limit of temperature is set only by the refrigerating liquid, temperatures as low as −185° C. being utilized. The upper limit of temperature is set only by the rubber itself. Results obtained in a study of the expansivity and transitions of “stark” (frozen) rubber are given as an illustration of the application of the method. Other possible applications are the measurement of the swelling of rubber by vapors and the determination of stress-strain relations under compressive loads. The chief limitation of the application of this method to rubber arises from the plastic flow of unvulcanized rubber at elevated temperatures. The method also possesses the inconvenience of requiring continuous observation. Compared with alternative methods of measuring small dimensional changes, the method possesses advantages arising from its high sensitivity, from the small size of the specimens required, from the ease of obtaining temperature equilibrium, from the absence of a confining liquid and from the simplicity of the calculations.
The Heat Conductivity of Rubber
Authors: Frumkin L. S. , Dubinker Yu B.
Published: February 2011

1. In rubber technology, the important factor is the heat conductivity of rubber mixtures, which is characterized by the rate of temperature change of the inner layers. 2. The method proposed makes it possible to compare the heat conductivities of rubber mixtures. 3. The heat conductivities of all types of rubber mixtures increase with increase in temperature. 4. Addition of zinc oxide in the usual proportions decreases the heat conductivity of mixtures containing no carbon black; in mixtures containing carbon blacks the addition of zinc oxide increases slightly their heat conductivty. It follows that the addition of zinc oxide for the acceleration of the vulcanization process has an insignificant influence on thermal conductivity. 5. With increasing additions of carbon black up to 25 per cent by weight of the rubber mixtures result the heat conductivity increases; but with further increases in the percentage of carbon blacks the heat conductivity decreases. 6. Rubber mixtures of the same composition but containing different kinds of carbon black show different heat conductivities. The lowest heat conductivity was found in rubber mixtures containing P-33 carbon black, followed in increasing order of heat conductivity by mixtures with Mai˘kop, Gastex, Thermax, Kudinov and Yaroslav carbon blacks. Thus lampblacks have a greater effect on the heat conductivity of rubber mixtures than do gas blacks.
The Creaming of Rubber Latex
Authors: Schweitzer Otto
Published: February 2011

Among methods of concentrating rubber latex, the creaming process has, quite independently of the evaporation and centrifuge processes, aroused increasing interest because of its special technical features. The tendency of the rubber particles in latex to cream as a result of the difference in specifie gravity of the rubber and serum is a phenomenon which has been known for a long time. Hancock himself observed that when latex is stored, displacements in the concentration take place and he proposed to utilize this phenomenon in the preparation of very pure rubber particularly free of colored impurities. In 1824 Hancock suggested that rubber latex be diluted with water to one-fourth its concentration and the serum removed after a short period of standing. By repeating this process several times, a particularly pure product was said to result. In 1826 Faraday too described the same process. However, the displacements in concentration which become evident in latices which have stood for a long time without the addition of any creaming agent do not lead to any clearly defined layers. The first important observation on the spontaneous separation of two phases in latex by the addition of definite substances was by Traube. Among the substances described by Traube were colloidal mucilages such as gum tragacanth, soluble extract of Irish moss, etc.
Hevea Latex of Large Particle Size
Authors: McGavack J.
Published: February 2011

The purpose of this paper is to report, primarily, the particle size distribution of modified Hevea latices. In addition, the purpose is to show that the amount of nitrogen absorbed by the rubber particles in a latex thoroughly washed by aqueous ammonia depends on the surface exposed. Until the careful and complete work of Lucas (Ind. Eng. Chem. 30, 146 (1938)), there were no reliable particle size distribution data on a normal latex by which the distribution curves of modified latices could be compared. Now, as a result of his excellent technique for measuring all of the particles, even the very small ones, we are able to discuss clearly surface and volume changes when these smaller sized particles are removed. This work was so conducted as to eliminate particle sizes which could not be photographed with microscopical equipment in visible light. It was eventually carried out in such a way as to remove all water-soluble materials not adsorbed on or dissolved in the latex particles which were to be subsequently analyzed for nitrogen.
Preliminary Studies of the Conductivity of Latex
Authors: van Gils G. E.
Published: February 2011

Most of the measurements were made with the philoscope, which is a new instrument made by Philips Gloeilampenfabriek. With this instrument the conductivity of latex can be measured easily and with sufficient accuracy. Obviously conductivity measurements are highly important for latex research. It is shown in Tables 1 and 2 that the conductivity of latex continually increases on standing. If enough ammonia has been added, this increase becomes smaller after two days ; if not, it continues unabated, and in time the latex coagulates. The dry rubber content has a great influence on conductivity, which may be explained by assuming that the serum is the only electrically conducting medium. However, the conductivity decrease is somewhat greater than can be explained on this assumption alone. Ammonia has a great influence on conductivity in dialyzed latex (Figure 4). But since the conductivity of ammoniated latex is less than the sum of the individual (latex and aqueous ammonia) conductivities, a great deal of ammonia must be adsorbed on the latex particles. When ammonia is added to fresh latex or to serum prepared by freezing latex, the conductivity curve shows a remarkable bend, caused by precipitation of magnesium ammonium phosphate (Curve III, Figure 3; Figure 4). Conductivity measurements in dialyzed latex after adding salts show that the salts are partially adsorbed by the rubber globules. Divalent calcium ion especially is strongly adsorbed. It was found that acid coagulation of latex yields rubber with a much lower ash content than when latex is coagulated without acid, as by heat or by alcohol. This may be explained by the fact that, in acid medium, the charge on the latex particles is small and, consequently, adsorption of electrolytes is also small.
The Use of Synthetic Rubber in the Automotive Industry from the Viewpoint of the Rubber Technologist
Authors: Street J. N. , Ebert H. L.
Published: February 2011

The primary interest of the automotive and of the rubber industry in so-called synthetic rubbers is to obtain products which will stand up under service conditions in which present rubber compounds either do not perform satisfactorily over their entire expected life, or are approaching their limit; or because of these factors, are limiting automotive engineering development. In addition, the last few months have seen a trend of thinking toward a nationalistic program of at least partial self-sufficiency, in case of emergency, or a possibility of the limitation of the poundages of crude rubber available to us at an economic price. The subject “The Use of Synthetic Rubber in the Automotive Industry” is consequently being considered in the light of both viewpoints. Activity in the field of synthetic rubbers as far as laboratories in this country are concerned has increased considerably over the last three years, and it is quite likely that the data and viewpoints herein presented on present polymers may very well be obsolete within a matter of months, and certainly within a year or two, with the appearance of new polymers and modifications of present ones. The object of this paper is consequently to summarize the present state of affairs regarding materials now available. The literature on synthetic rubbers is abundant as to the preparation of the various kinds and varieties, their compounding, and the characteristics of fabricated products. A very excellent and interesting summary is that by Wood. From a general viewpoint, the article entitled “Synthetic Rubber” in the August issue of Fortune is very much to the point. The characteristics of Neoprene are well known. Those of the butadiene types have been described in several articles by Stöcklin and by Koch. Similarly other products have been described. Anderson and Garner and Westhead have given some comparative data on Neoprene and Buna types. In view of these articles, the present paper appears superfluous. It has been pointed out by Wood, however, that it would be desirable to have additional confirming data on a comparable basis on the materials now available. It has been with the hope of supplying such data, at least in part, and particularly as applied to usage of synthetic rubbers in the automotive field, that the authors continued with the preparation of this paper.
Cotton Fibers. Constitution, Structure, and Mechanical Properties
Authors: Nickerson R. F.
Published: February 2011

The study by chemical methods of the constitution, derivatives, and properties of cellulose has yielded a voluminous literature and a wealth of useful information. Microscopic and x-ray investigations have produced much new and valuable knowledge of cellulose and its structure. But relatively little attention is given to the mechanical properties of cellulosic fibers, although such properties reflect fiber structure and frequently determine suitability to specific applications. An exhaustive review of the relevant literature on cotton has not been undertaken in this paper; rather, the object is to summarize the available data on constitution and properties and, wherever possible, to indicate their relations to the most probable fiber structure. In this way the material as a whole is integrated into a working concept of the cotton fiber.
Hysteresis in Crystallization of Stretched Vulcanized Rubber from X-Ray Data. Correlation with Stress-Strain Behavior and Resilience
Authors: Clark George L. , Kabler Marian , Blaker Ernest , Ball John M.
Published: February 2011

1. For sample H, with high modulus and high resilience, there is a greater crystallizing tendency above 350 per cent for the first cycle and above 400 per cent after previous flexing. 2. Both H and L have narrow loops, which indicate an approach to reversibility in the formation and deformation of crystalline regions above 400 per cent for the first and later cycles. 3. The crystallization of H is greatly enhanced above 400 per cent after the first cycle of stretching and retraction; L remains essentially unchanged by previous history over this range; this is analogous to the much greater change in the stress-strain loop from the first to third cycles for H, as compared with L. 4. At elongations below 400 per cent for the first cycle and 350 per cent for subsequent cycles, L has a far greater hysteresis or tendency to retain the crystalline arrangement, and this greatly increases after the first cycle, so that the fiber interferences persist on retraction to elongations 150 per cent below the elongation required for institution of organization on extension of the sample. Sample H is considerably more consistent in its behavior over the lower elongations, and between the first and later cycles. In other words, the tendency of H to return to the normal state on release of a deforming force is clearly evident, whereas L shows a marked tendency to retain a structure once set up. If resilience is the property of an elastic body related to the percentage of the potential energy introduced by applied stresses which is returned as work when the body returns to its original shape and size upon release of the stresses, then these x-ray data would seem to be consistent with the higher resilience of H; for ordinary measurements of resilience are evidently related to the lower ranges of deformation over which H returns to its normal state (disorder of macromolecules as in a liquid) so much more easily than L.
X-Ray Structure of Rubber-Carbon Black Mixtures
Authors: Gehman S. D. , Field J. E.
Published: February 2011

The position of carbon black as an indispensable compounding ingredient for present-day rubber technology has led to many experimental and theoretical inquiries regarding the manner in which it functions to improve the properties of rubber into which it is incorporated. The general term “reinforcement” is used to express improvements in physical properties brought about by the mixing of powders into rubber. Shepard, Street, and Park reviewed the concepts which have been employed in efforts to define reinforcement. Reinforcing effects are made evident in measurements of plasticity, viscosity of solutions, stress-strain relations, tear, and abrasion resistance. By all criteria which have been proposed, channel black heads the list of reinforcing powders, although there is some indication that even more pronounced reinforcing effects can be obtained with finer carbon blacks. Available explanations of reinforcement constitute an involved maze of contradictory evidence, speculations, and controversies in strong contrast to the practical importance of having a clear understanding of what occurs. The literature on the subject has been ably reviewed by Shepard, Street, and Park. Characteristics of a powder which have been held responsible for reinforcement are:
Analysis of Proteins Occurring in Hevea Latex. II. Properties and Identification of the Isolated Products
Authors: Altman R. F. A.
Published: February 2011

In a previous paper the separation and analysis of proteins remaining in rubber serum, after coagulating the rubber with formic acid, were described. The present paper is concerned with the properties and identification of the products thus isolated. As for nonamino acids, it may be recalled that these are composed mainly of the unsaponifiable thick brownish red oil A4. Of the other byproducts remaining to be identified, which were designated as BII, BIII, BV and BVI, only small amounts were obtained. Of the amino acids, alanine, arginine, asparagic acid, glutamic acid, histidine, leucine, ornithine, hydroxyproline, proline, tyrosine and valine were isolated in weighable amounts. In addition to these, it was possible to identify dihydroxyphenylalanine. In this connection the results obtained by Midgley, Henne and Renoll are of interest. These investigators found, as the principal components of proteins occurring in crepe rubber, the following amino acids: arginine, asparagic acid, glycine, histidine, leucine, lysine and proline. They considered it highly probable that alanine, phenylalanine, hydroxyproline and serine were also present in these proteins. On the other hand, it was definitely established that cystine, glutamic acid and tyrosine were not present. Table I summarizes the results of Midgley and his coworkers in comparison with ours. From this table it is evident that certain proteins, viz., those containing, among other compounds, tyrosine, glutamic acid and valine, do not coagulate with the rubber, but remain in the serum. The absence of sulfur-containing amino acids can probably be attributed to certain shortcomings in the analytical method. At any rate, the presence of sulfur in proteins precipitated from latex was established when the test was repeated.