Showing papers by "Research Triangle Park published in 1968"

Permeability of Solutes through Hydrated Polymer Membranes Part I. Diffusion of Sodium Chloride

Abstract: Based on an analysis by the free volume theory of diffusion, a study of the diffusion coefficients, D2, the distribution coefficients, κ2, and the permeability coefficients, P, of NaCl in various hydrophilic polymers was made with the assumptions that the free volume of a polymer/diluent system is linearly proportional to the volume fraction of diluent (H), and that NaCl permeates only through polymer/diluent systems in which the diluent of polymers is also a good solvent of the solute (NaCl). The values of D2 (over five orders of magnitude) were found to vary exponentially with changes in 1/H, as expected from the free volume theory of diffusion, in a wide range of H-values and converge to the value of the diffusion constant of NaCl in pure water. The values of κ2 defined by g NaCl per cm3 polymer/g NaCl per cm3 solution were found to be more characteristic to the type of polymers particularly at a lower range of H-values. At higher ranges of H-values, k2 is nearly equal to H, however, at lower H, k2 values deviate significantly from the value of H and its extent was found to be greatly dependent on the chemical nature of polymers, whereas the diffusion coefficient follows the normal pattern predicted by the free volume theory. The values of P which are given by the product of D2 and k2 also were found to vary exponentially with changes in 1/H at higher range of H, however, at lower range of H it deviates from the relationship due to the varying dependence of factor k2 on 1/H.

Terminal analog synthesis of continuous speech using the diphone method of segment assembly

Abstract: Diphone segmentation consists of the stylization and simulation of the perceptually meaningful dynamic portions of the acoustic continuum of speech. A primary requirement of the stylization is that any segment must be usable in a variety of morphemic environments. Diphone segment assembly is a technique for synthesizing a potentially unlimited variety of continuous utterances under computer control. A major requirement of this method of segment assembly is that there be no perceptually distracting discontinuities between contiguous segments. The presentation consists of two parts. The first is a brief description of the terminal analog synthesizer and the system for generating, storing, and assembling the control signals for diphone segments. The second part is a discussion, by example, of the analysis, synthesis, and assembly rationale for simulating continuous utterance. Parameters used for the simulation of prosodic features are discussed, and the evaluation methods are described.

Small‐angle x‐ray diffraction studies of plastically deformed polyethylene. II. Influence of draw temperature, draw ratio, annealing temperature, and time

Abstract: The angular dependence of scattering intensity of drawn polyethylene (PE) was investigated with a small-angle Kratky camera. At constant drawing temperature the intensity drops drastically with increasing draw ratio; however, the position and the half-width of the first maximum remain nearly unchanged. The drop in intensity can be explained only by a reduction of effective electron density difference between amorphous and crystalline components. The latter contains more vacancies, and the former contains more and better packed tie molecules. This increases the average density of the amorphous layer and decreases that of the crystalline component. As the temperature of the drawing increases, the draw ratio attainable at the applied draw rate drops and the intensity of scattering and the long period rapidly increase. In addition, a second-order maximum appears, indicating a better order of lamellar stacking, in good agreement with electron microscopy. The first annealing effect is an extremely rapid increase in scattering intensity and long period. The subsequent increase is rather slow and proportional to the logarithm of annealing time. The long period in such an experiment is independent of the draw ratio; however, the scattering intensity depends on it quite strongly even after prolonged annealing.

Automatic conditioning of speech signals

Abstract: As a part of the larger problem of providing speech input to a computer in a communications system, before either digital buffering, vocoding, or programmed recognition of the speech signals is performed, automatic conditioning of the input signal can significantly improve system performance. The signal conditioning sub-system described in this paper is intended to provide a constant-amplitude signal of the best quality possible from an uncontrolled speech source such as a telephone line, and to indicate the beginning and continued presence of a speech utterance. A fast-acting wide-range automatic level control is used both to compensate for the average strength of the received signal and to remove the word and phrase amplitude dynamics so that the amplitude-controlled signal is contained in a minimum dynamic range. The presence of an utterance is detected by comparison of the logarithm of signal amplitude to an automatic variable threshold set by the logarithm of the input noise as measured during the absence of signal, thus achieving a constant SNR threshold. The functions described for conditioning can be implemented with analog circuits without the aid of signal delay.

Fuming nitric acid treatment of polyethylene. IV. Morphology of drawn polyethylene

Abstract: Drawn PE of different draw ratios (ranging from 1 to 25) and thermal treatment (annealing temperature 80, 100, 110, 120, 127°C.) was treated with fuming nitric acid at 80°C. Weight loss, molecular weight, elastic modulus, and thermograms were measured for annealed and unannealed samples as a function of the treatment time and draw ratio. As a consequence of the preferential oxidation of the noncrystalline portions, there occurs initially a high rate of weight loss and a steep drop in molecular weight, followed by a lower rate of weight loss at nearly constant molecular weight. The elastic modulus stays practically constant up to the moment where the brittleness of the sample prevents further measurement. During the later period the thermograms exhibit one melting peak during the first melting. The remelt of the same sample, however, has two melting peaks with a relative intensity independent of the treatment time. That the two melting peaks are caused by two components of different molecular weights present in the sample is substantiated by fractionation. At very high annealing temperature (127°C.), two peaks appear, not only in the first melting curve of the etched sample, but also in the melting curve of the unetched material. Such an effect is the consequence of partial melting during annealing followed by new crystallization during cooling the sample to room temperature. The findings are related to the morphology of the drawn material under the assumption of preferential scission of chain loops in the amorphous-crystalline sandwich layer model.

Suppressing Microorganisms and Maintaining Turgidity in Coniferous Foliage Used to Rear Insects in the Laboratory

Abstract: An aseptic technique is described that retards the growth of micro flora attacking excised conifer stems kept in water, thus facilitating the rearing of foliage-feeding and tip-infesting insects. Treated foliage remained fresh for an average of 5 weeks or until the foliage was consumed, whereas untreated foliage averaged only 10 days. The technique is most useful when time or insufficient host material creates a difficult, expensive rearing situation.

Radiation grafting of vinyl monomers to wool. III. Location of the grafted polymer

Abstract: Studies of properties such as water sorption of grafted wool have shown the importance of the location of the polymer in the fiber. Electron microscopy and low-angle x-ray diffraction studies have been used to determine the location of grafted polystyrene in wool. Samples grafted from 15 to 800% (dry weight increase) all exhibit a large increase in contrast in the cell membranes (IR) and nuclear-remnant regions (NR) in the electron micrographs. This is considered to be due in part to an unevenness in mechanical response to sectioning and in part to the deposition of ungrafted homopolymer in IR and NR, particularly at grafts of greater than about 100%. Analysis of the change in the 83 A. equatorial x-ray reflection suggests that most of the grafted polymer resides in the keratinous matrix regions between the microfibrils within the cortical cells. At larger grafts the wool still retains its basic histological character, but the increase in this spacing is no longer proportional to the amount of graft, and the desposition of polymer becomes very inhomogeneous.

Intrinsic viscosity of polymers of low molecular weight

Abstract: Experimental evidence concerning the dependence of the intrinsic viscosity [η] on molecular weight M in the low molecular weight range (from oligomers to M = 5 × 104) has been collected in a variety of solvents for about ten polymers, i.e., polyethylene, poly(ethylene oxide), poly(propylene oxide), polydimethylsiloxane, polyisobutylene, poly(vinylacetate), poly(methyl methacrylate), polystyrene, poly-α-methylstyrene, and some cellulose derivatives. In theta solvents, the constancy of the ratio [η]Θ/M0.5 extends down to values of M much lower than those predicted by current hydrodynamic theories. In good solvents, and on decreasing M, the polymers examined, with the exception of polyethylene and some cellulose derivatives, show a decrease in the exponent a of the Mark-Houwink equation [η] = KMa. This upward curvature gives rise to the existence of a more or less extended linear region where the equation [η] = K0M0.5 is obeyed. Below the linear range, i.e., for even shorter chains, the exponent a can increase, i.e., polydimethylsiloxane, or decrease below 0.5, i.e., poly(ethylene oxide), depending on the particular chain properties. These different dependences have been discussed in terms of: (a) variations of thermodynamic interactions with molecular weight; (b) variations of conformational characteristics (as for instance the ratio) 〈r02/nl2〉, where 〈r02〉 is the unperturbed mean square end-to-end distance and n is the number of bonds each of length l; (c) hydrodynamic properties of short chains.

Phase changes in polyethylene single crystals. The effects of thermal stress and electron irradiation

Abstract: Single crystals of polyethylene have been reported to undergo a crystallographic phase change from an orthorhombic unit cell to monoclinic when heated to temperatures near their original crystallization temperatures. This change is shown to be due purely to thermal stresses set up between the crystals and substrate on which they lie, arising from a difference in expansion coefficients of crystals and substrate. The orientation of the monoclinic lattice with respect to the orthorhombic lattice is consistent with an effective deformation parallel to the orthorhombic b-axis. At temperatures above 110°C the monoclinic phase relaxes almost completely back to orthorhombic primarily through the greatly increased mobility of the chains in their folded portions. The effects of an electron beam on the polyethylene crystal lattice have been studied by electron diffraction during irradiation at temperatures from −161 to + 110°C. The changes in dimensions of the unit (sub)-cell were determined as functions of the time of irradiation. Above about 30°C a stable hexagonal phase is formed before the crystalline diffraction pattern degrades to a diffuse halo. This change is ascribed to (i) a depression of a transition temperature (due to defects) analogous to that found in n-paraffins when the orthorhombic unit cell becomes hexagonal, and (ii) elastic distortions around the lattice defects. It is also noted that the transformation proceeds readily at 110°C in the absence of radiation if a small dose is given initially: the number of defects under these conditions are few and consequently on cooling to room temperature the hexagonal and orthorhombic phase co-exist. Although no definitive conclusions as to the nature of the reaction can be determined, the evidence is that the defects are primarily scissions and cross-links in the crystal lattice. Es ist bekannt, das Polyathyleneinkristalle beim Erwarmen auf Temperaturen, die in der Nahe ihrer ursprunglichen Kristallisationstemperatur liegen, einer kristallographischen Phasenanderung von der orthorhombischen Einheitszelle zur monoklinen unterliegen. Es wird gezeigt, das diese Umwandlung nur auf die thermische Spannung zuruckzufuhren ist, die zwischen Kristallen und dem Substrat, auf des sie aufliegen, entsteht, und die von der Verschiedenheit der Ausdehnungskoeffizienten der Kristalle und des Substrats herruhrt. Die Orientierung des monoklinen Gitters in bezug auf das orthorhombische Gitter entspricht einer effektiven Deformation parallel zu der orthorhombischen b-Achse. Bei Temperaturen oberhalb 110°C wandelt sich die monokline Phase nahezu vollstandig wieder in die orthorhombische um, in erster Linie wegen der stark gesteigerten Beweglichkeit der Ketten in den Faltungsbogen. Die Wirkungen eines Elektronenstrahls auf das Polyathylenkristallgitter wurden durch Elektronenbeugung wahrend der Bestrahlung bei Temperaturen zwischen −160 und +ll0°C untersucht. Die Anderungen in den Dimensionen der Einheitszelle wurden als Funktion der Bestrahlungszeit bestimmt. Oberhalb etwa 30°C bildet sich eine stabile hexagonale Phase, bevor das kristalline Beugungsdiagramm in einen diffusen Halo ubergeht. Dieser Wechsel wird 1. der Erniedrigung einer Umwandlungstemperatur, die Gitterfehlern zuzuordnen ist, zugeschrieben, die derjenigen entspricht, die man bei n-Paraffien bei der Umwandlung der orthorhombischen in die hexagonale Einheitszelle findet, und 2. elastischen Verformungen in der Umgebung der Gitterfehlstellen. Ferner wurde festgestellt, das die Umwandlung schon bei 110°C in Abwesenheit von Bestrahlung fortschreitet, wenn man am Anfang eine kleine Dosis einwirken last : Unter diesen Bedingungen ist die Anzahl der Fehlstellen gering; infolgedessen finden sich nach dem Abkuhlen auf Raumtemperatur die hexagonale und die orthorhombische Phase nebeneinander. Obgleich es nicht moglich ist, endgultige Aussagen uber die Natur der Reaktion zu machen, so ist es doch offensichtlich, das die Fehlstellen in erster Linie in Kettenbruchen und Vernetzungen im Kristallgitter bestehen.

High-yield pre-irradiation grafting to wool leading to highly elastic fibers.

Abstract: Comparative studies of mutual and pre-irradiation grafting of vinyl monomers to wool [1] have shown that the yields per unit dose are generally lower when the pre-irradiation technique is employed. This is especially true when a common solvent for the swelling agent and monomer is included in the grafting medium. Such pre-irradiation grafting curves generally show a steady decrease in the grafting rate with time until the plateau level of grafting is reached. Considerable detail of this contrast in grafting behavior has been given in recent papers [2, 3, 4] and shows that the maximum level of pre-irradiation grafting is usually well below 100%. However, it has now been found that under special conditions substantially higher grafting yields can be obtained using a pre-irradiation technique of grafting. In fact, grafts of several hundred percent are easily obtained in the case of certain acrylic acid derivatives. A typical grafting-time curve for wool fibers and fabrics using ethyl acrylate is shown in Figure 1. It is apparent that the grafting-time curves are considerably different from those normally encountered in pre-irradiation grafting [1]. Instead of grafting yields leveling off to a plateau value, the yields continue to increase within the time scale of the experiment, reaching eventually levels beyond 5000%. In .this case, the monomer had been dispersed in the swelling agent (water) by using a non-ionic surfactant. Similar grafting behavior was also exhibited in the absence of an emulsifier. ’

Response of Pine Seedlings to Mechanical Stimulation

Abstract: When needles of pine seedlings are deflected downwards there is an electrical response which can be measured.

A storage-hierarchy system for batch processing

Abstract: Operating System/360 was designed to meet a severe core-memory constraint: a 14K-bytes resident supervisor plus a repertoire of compilers, utility programs, sort programs, and application packages fitting into 18K bytes (approximately 4500 data words and executable instructions). Many supervisory functions included in the nucleus of pre-360 systems were repackaged into 1000-byte overlays for OS/360 (e.g. logic to OPEN and CLOSE files---hereafter called data sets, following OS/360 nomenclature). Specification of device type, buffering technique, and data set identification---which was assembled, compiled, or link-edited into many pre-360 application programs --- is deferrable in OS/360 until the data set is actually opened for processing, essentially "latest-possible binding of data-set attributes and processing mode" (cf. Part 3 of Reference 5 for a complete discussion).

Kinetic studies in ethylene polymerization with ziegler type catalysts. VI. Characterization of catalyst sites by polymerization experiments in the presence of deuterium

Abstract: Ethylene polymerization in the presence of deuterium was investigated with the four catalyst systems resulting from Et3Al and Et2AlCl in combination with either TiCl4 or TiCl3. From the effect of catalyst ratio on the kind and the amount of deuterated products formed the existence of three kinds of titanium sites could be inferred. An H, D-exchange reaction involving the β-hydrogen of the growing chain was found to be characteristic for chain growth on Ti(IV) sites. The inactivity of BuLi or Et2Zn systems in such exchange reactions implied the existence of bimetallic complexes in alkylaluminum systems. The exclusive formation of CH2D groups in the polymer by a transfer reaction was found to be characteristic for chain growth on Ti(III) sites. The occurrence of an H,D-exchange reaction involving the monomer and the formaiton of deuterated ethanes was assigned to the presence of polymerization-inactive titanium hydride sites, formed at high catalyst ratios. Es wurde die Polymerisation von Athylen in Gegenwart von Deuterium untersucht unter Verwendung der vier durch Kombination von Et3Al und Et2AlCl mit TiCl4 und TiCl3 sich ergebenden Katalysatorsysteme. Aus dem Einflus der Katalysatorverhaltnisse auf Art und Menge der gebildeten Deuterierungsprodukte konnte auf die Bildung dreier verschiedener Titanzentren geschlossen werden. Eine H,D-Austauschreaktion am β-Wasserstoff der wachsenden Ketten erwies sich als charakteristisch fur das Kettenwachstum an Ti(IV)-Zentren. Die Abwesenheit einer solchen Austauschreaktion in BuLi- und Et2Zn Systemen legte die Annahme bimetallischer Komplexe in Alkylaluminiumsystemen nahe. Die ausschliesliche Bildung von CH2D-Gruppen im Polymeren durch Kettenubertragung kann als charakteristisch fur das Wachstum. an Ti(III)-Zentren angeschen werden. Das Auftreten einer H,D-Austauschreaktion mit dem Monomeren und die Bildung deuterierter Ahane wurde dem Vorhandensein polymerisationsinaktiver Titanhydride zugeordnet, die sich bei hohen Katalysatorverhaltnissen bilden.

Upturn effect in the Non‐Newtonian intrinsic viscosity of polymer solutions. II. Polyisobutylene in polybutene oil

Abstract: With an increasing gradient, the intrinsic viscosity of a high molecular weight polyisobutylene (Mn = 7 × 106) in polybutene oil L.100 (ηs = 5 poise) first drops to a minimum and then rises again. The minimum occurs at β = M[η]0ηsG/NkT = 240, which is about ten times the value predicted by the dumbbell model. Such a shift to larger gradient is in good agreement with the more realistic necklace model of macromolecules in a good solvent. The increase of intrinsic viscosity after the minimum is nearly linear with the gradient and continues beyond the value at zero gradient. Experiments with capillaries of different length-to-diameter ratios yield identical flow curves so that one may exclude the possibility that the observed upturn is an artifact caused by end effects or time dependence of viscosity.

The mean activity coefficient of polystyrenesulphonic acid

Abstract: The electromotive force of the concentration cell (Pt) H2/polystyrenesulphonic acid polystyrenesulphonic acid/H2 (Pt) with liquid-liquid junction was measured in the concentration range of the polystyrenesulphonic acid from 0.1 to 0.001 monomolal. The values of the mean activity coefficient, derived from these measurements, were compared with those calculated on the basis of the rodlike model. A very good agreement between theory and Zxperiment has been found. Die elektromotorische Kraft von Konzentrationsketten des Typs (Pt) H2/Polystyrolalfonsaure Polystyrolsulfonsaure/H2 (Pt) mit Flussigkeitsverbindung wurde im Molalitatsbereich von 0,1 bis 0,001 (bezogen auf Monomereinheiten) gemessen. Die aus diesen Messungen folgenden Werte fur den mittleren Aktivitatskoeffizienten wurden mit den auf Basis eines Stabehenmodells errechneten verglichen. Dabei ergab sich eine sehr gute Ubereinstimmung zwischen Theorie und Experiment.

Reactions of living polystyrene with difunctional nitriles to produce specifically placed grafting sites

Abstract: Graft polymers have been synthesized with two equal length branches and one or two branches of a different length or composition. The first step was a coupling reaction of living polystyrene with a difunctional nitrile. The product was hydrolyzed to form a ketone-containing backbone. Subsequently another sample of living polystyrene or of poly-2-vinylpyridine was added to the backbone to form the graft. Anionic polymerization was used for the synthesis of backbone and side chains, so all of the products are well defined. The products and reaction sequences also serve as models for a general synthesis of well-defined comb-shaped polymers, in which the length of the backbone, and the number, length, and spacing of the side chains may be controlled.

Murine Toxicity of Agrobacterium tumefaciens

Abstract: Eleven strains of the crown gall organism, Agrobacterium tumefaciens, tested by intraperitoneal injection into mice, were lethal within 48 hr. Five other species had some lethal strains. The lethal effect of A. tumefaciens appeared to be the result of a toxic rather than an infectious process, since histopathological anomalies were not found in mice injected with live cultures and since heat-killed cultures were lethal. The murine toxin disappeared when A. tumefaciens was grown at 36 C and reappeared when the organism was subsequently incubated below 30 C. The murine toxin itself was not inactivated by exposure to 100 C for 30 min. The toxin was associated with the cells and was not excreted into the medium. Centrifugal fractionation revealed that the toxin was associated with the smaller cells in 3-day stationary-phase cultures. These data suggested a possible relationship between toxin production and the production of the agents responsible for the initiation of plant tumors.

Murine Toxicity of Cochliobolus carbonum.

Abstract: Seventeen wild-type strains of the phytopathogenic fungus Cochliobolus carbonum, tested by intraperitoneal injection into mice, were lethal within 48 hr The lethal effect appeared to be a toxic rather than an infectious process, because death occurred within 3 hr after injection of two of the isolates and heat-killed cultures were lethal Assays of ascospore progeny from two crosses involving three isolates indicated that the toxic metabolites were under genetic control and quantitative regulation Studies of the toxicological, cultural, and chemical characteristics of these three strains indicated that more than one murine toxin was present

Effect of Fiber and Dyebath Variables on the Rate of Acid Dyeing of Nylon 6, 6:

Abstract: The results of an experimental study of the effects of several variables on the acid dyeing of nylon are presented. The dyeing rate was directly proportional to the number of amino-end groups (dye ...