Constant Research Articles

Effect of Hexadiene and Vinyl Acetate Content on the EPDM and EVA Blends

Melt mixed blends of EPDM rubber and thermoplastic/elastomeric EVA copolymer in the presence of dicumyl peroxide have been studied over the entire composi tion range with special reference to the effect of hexadiene (HD) content of EPDM and vinyl acetate (VA) content of EVA copolymer. Viscosity of the blends decreases as the EPDM/EVA ratio decreases with more pronounced effect associated with VA content of EVA for high HD containing EPDM. For low HD content, VA has no effect up to 20% of EVA in the blend. Lower VA and higher HD are associated with lowering of scorch safety of the compound. For higher HD containing EPDM, state of cure drastically decreases as EVA percentage in the blend increases. With lower HD containing EPDM, there is an in flexion around 50:50 blend ratio irrespective of the VA content of EVA. Initially, rate con stant decreases rapidly for higher HD containing EPDM up to 55 % of EVA in the blend, whereas high VA containing EVA gives rise to flat minimum extending up to 55 % of EVA. A sharp increase in activation energy was observed beyond 60% of EVA especially for high VA containing EVA. Weight loss is more in the case of low HD containing EPDM and high VA containing EVA blends as observed from DTA/TGA study. Failure mode of the blend depends on the HD and VA content as observed from an SEM study, which once again depends on the crystallinity of the blends.

Permeability of Unidirectional Reinforcements for RTM

The permeability of an idealized unidirectional reinforcement consisting of regularly ordered, parallel fibres is derived starting from first principles (Navier-Stokes equations) both for flow along and for flow perpendicular to the fibres. First, an approx imate analytical solution for transverse flow is derived which differs from the Kozeny- Carman equation for the permeability of a porous medium [9] in that the transverse flow stops when the maximum fibre volume fraction is reached. The solution for flow along the fibres has the same form as the Kozeny-Carman equation. A comparison shows excellent agreement between a numerical solution of the full flow equations and the approximate one at medium to high fibre volume fractions ( V f > 0.35). The theoretical predictions of permeability were tested in a specially designed mould. The results from the experiments with an unsaturated polyester resin (Jotun PO-2454) and the unidirectional reinforcement did in all cases show excellent agreement with results predicted by Darcy's law (the square of the flow front position increases linearly with time if the injection pressure is kept con stant). The theoretical model could be fitted to the experimental data both for flow along the fibres and for cross flow based on data for flow along the fibres only. The fitting is ob tained by adjusting one parameter in the model, the effective fibre radius, to a value about four times larger than the real fibre radius (15 μm). Scanning electron microscopy shows that the fibres are arranged in bundles looking like cylinders with ellipsoidal cross section which may be the explanation for the effective fibre radius in the fitted model equation be ing larger than the real fibre radius.

A New Joint Proof of the Theorems of Picard and Montel

Bloch's principle says that in general those prope rties. which reduce a meromorphic funct ion in Q; to a consta nt , make families of meromorphic functions in a domain G normal, with a number of special exceptions (see (3]) . Zalcman asked the quest ion . whet her t here are joint proofs for bot h, th e normality criteria and t he t heorems of Picard type. T his pape r gives a simple proof in t he wellknown case that a function omits th ree values.

Specific Amplification of Rearranged Immunoglobulin Variable Region Genes from Mouse Hybridoma Cells

In this article we show how the polymerase chain reaction (PCR) and primers designed for conserved sequences of leader (L), framework one (FR1) and constant (CONST) regions of immunoglobulin light and heavy chain genes can be used for the cloning and sequencing of rearranged antibody variable regions from mouse hybridoma cells. RNA was extracted from the mouse hybridoma cells secreting MAbs: IOR-T3a (anti-CD3), C6 (anti-P1 of N. meningitidis B385), IOR-T1 (anti-CD6), CB-CEA.1 (anti-carcinoembryonic antigen), and CB-Fib.1 (anti-human fibrin). First strand cDNA was synthesized and amplified using PCR. The newly designed primers are superior to others reported recently in the literature. Isolated PCR DNA fragments of C6 and IOR-T3a were sequenced after asymmetric amplification, or M13 cloning. The FR1/CONST primer combinations selectively amplified mouse lights chain of groups kappa II, V, and VI, and heavy chains of groups IIa and IIc. The L/CONST primers for light chains amplified light chains from all four hybridomas. These methods greatly facilitate structural and functional studies of antibodies by reducing the efforts required to clone and sequence their variable regions.

Effect of day and night temperature alternations and of plant growth regulators on stem elongation and flowering of the long-day plant Campanula isophylla Moretti

Stem elongation in Campanula isophylla Moretti was influenced more by the difference (DIF) between day temperature (DT) and night temperature (NT) than by average daily temperature (ADT) or absolute DT and NT from 12 to 24°C. Plant height at anthesis increased 230% as DIF increased from −12 to +12°C. When DT and NT were constant (CT), plant height was reduced 24.9% as CT increased from 12 to 24°C. DIF only affected internode length as the number of leaves on the stem was not influenced by DIF. A daminozide spray reduced plant height by 51, 33 and 37% for 12, 0 and −12°C DIF treatments, respectively. Daminozide overcame positive DIF-induced stem elongation, while gibberellic acid (GA 3) could overcome inhibition of stem growth in negative DIF-grown plants. Morphogenetic responses of DIF were mimicked by GA 3 application. Mean relative growth rate (RGR) reached a maximum level at an ADT of ∼ 19–20°C. Although the final dry weight at marketing stage was highest at 12°C NT, as averaged over all DT, highest plant quality was found at an ADT of 18°C when the DT and NT were delivered as −3 to −6°C DIF. The number of days to marketing stage was reduced from 120 to 68 days for cultivar ‘Alba’ and from 110 to 63 days for cultivar ‘Blå’ when CT or ADT was increased from 12 to 24°C. Rate of flower initiation and flower development were mainly a function of ADT. However, under high natural irradiance in summer, negative DIF resulted in 5–9 days earlier flowering compared with a positive DIF. GA 3 application had a small influence on flowering. Daminozide spray (3.12 × 10 −2M) delayed visible bud from 0 to 4 days and anthesis from 9 to 16 days for various temperature treatments and cultivars. Plant morphogenesis seemed to be controlled in a different way to flower initiation and flower development in C. isophylla.

Spectral analysis of heart rate variability during constant and pseudorandom exercise.

The purpose of this study was to investigate the limitation for applying a linear model to the cardiorespiratory control system. Four subjects performed the two types of exercise bouts, constant (CONST) and pseudorandom (PRBS) exercise, on an electrically braked cycle ergometer at three different work rates. The target work rate of CONST were set to 80, 100, 120% of the individual anaerobic threshold (AT). In PRBS, the work rates were varied between +/- 10% of the individual AT around the respective target work rates of CONST. Although the spectral density of beat-to-beat heart rate fluctuations showed the conventional patterns for most cases, there was no obvious difference between CONST and PRBS. These results indicated that the variation of +/- 10% of AT did not affect the heart rate variation as the output response, suggesting a dilemma inevitable to apply a linear model based on the transfer function.

Three discrete Kirchhoff elements for shell analysis with large geometrical non‐linearities and bifurcations

The comparative efficiency of three flat triangular shell elements is being assessed for analysing non‐linear behaviour of general shell structures. The bending formulation of the three elements is based on a discrete Kirchhoff model (namely the well‐known 3‐node DKT element and a new 6‐node DKTP element). The in‐plane behaviour is defined by constant (CST), linear (LST)and quadratic (QST) strain approximations. The super‐position of bending and membrane elements leads to the 3‐node DCT element (DKT plus CST), the 3‐node DQT element (DKT plus QST) and the 6‐node DLT element (DKTP plus LST). The geometrically non‐linear formulation is based on an approximate updated Lagrangian formulation (AULF) and the solution is obtained by using the Newton‐Raphson method with an automatic arc‐length control method. Illustrative examples include pre‐ and post‐buckling of different shell structures showing, in particular, some bifurcation points, large rotations and displacements and very important membrane‐bending coupling.

グルタチオン（還元形）を用いるビニル重合

The polymerization of methyl methacrylate (MMA) or acrylamide using glutathione (reduced form. GSH) as an, initiator was carried out. It was found that GSH showed initiating activity of radical polymerization in the presence of formic acid. Detailed study for the polymerization of MMA gave the following results. The overall activation energy for the polymerization was estimated to be 54.8 kJ.mol-1. The rate of polymerization (Rp) was shown by the following equation.Rp = k [MMA]1.05 [GSH]0.53The chain-transfer consta nt to GSH was approximately evaluated as 3.0x10-2 at 60°C.

Polymerization of Methyl Methacrylate Using β-Picolinium p-Chlorophenacylide as Initiator

Abstract The β-picolinium p-chlorophenacylide-initiated radical polymerization of methyl methacrylate was carried out at 60, 65, and 70°C by employing the dilatometric technique in a nitrogen atmosphere. A master graph of volume contraction vs percentage conversion was used to calculate the rate of polymerization (Rp), which is a direct function of the initiator concentration. The value of the exponent is 1.10 ± 0.10. The molecular weight of the polymer also increases with an increase in ylide concentration. The overall activation energy is calculated as 7.02 kcal/mol. The reaction involves bimolecular termination. Hydroquinone retards the reaction. Polar solvents do not affect Rp whereas the nonpolar solvent CC14 favors Rp but decreases the molecular weight of the polymer due to a chain transfer reaction. The value of the chain transfer constant (CS) is 6.67 × 10−4

An Empirical Criterion for the Convergence of the Fast Decoupled Load Flow Method

This paper presents a study of the reliability and convergence characteristics of the rast Decoupled Load Flow (FDLF) method. The results presented in the paper clearly show that the reliability of the FDLF mcathod cannot be taken for granted for systems having lines of large R/X ratios and/or capacitive series branches. An empirical criterion for testing the reliability of the FDLF method for any given system is proposed. This involves the estimation of a scalar con stant from the given system parameters. It is shown that the magnitude of this constant is correlated to the rate of convergence of the FULF method and the convergence could be expected only when the constant is less than unity. Results oF studies on a large number of test cases are prpsented in order to validate the proposed critprion. In addition the results presented in the paper provide significant information on a number of aspects of the behaviour of the FDLF method.

Liquid phase epitaxial growth of Zn and S doped GaAs

Zn-doped liquid phase epitaxial GaAs layers, in which Zn is added in a Zn/Ga weight ratio varying from 1.1 X 10 -4 to 1 X 10 -2, are grown at temperatures of 700, 800 and 900°C. The effect of Zn evaporation from the melt before epitaxial growth was examined. It was found that the relation between the carrier density, p, in the Zn-doped GaAs layers and the heating time, t, of the melt prior to the growth is expressed by p = p o exp(- CP Zn t ), where P Zn is the vapor pressure of Zn and C is a cons tant. Sulfur doped GaAs layers are grown at 800°C from Ga solutions in a hydrogen gas flow containing H 2S in concentrations ranging from 0.09 to 1000 ppm. The results show that the carrier density in the S-doped layers varies between 1 X 10 16 and 3 X 10 18 cm -3 at room temperature and that broad bands in the photoluminescence spectrum appear at longer wavelengths together with near- band-gap emission for highly S-doped layers. It seems that the broad bands result from the formation of the deep levels caused by the incorporated S.

The Sisyphus Syndrome and Professor Cogent

TTE image of the benign, hard working purveyor of knowledge surrounded by mesmerized and ado ing students seems to have died with Mr. Chips and tele vision's Halls of Ivy. Today, Professor Cogent (his name is Legion) is afflicted with a destructive and debilitating syndrome. He feels he is rolling imponder ables up an academic hillside, and like Sisyphus of old is sure no one appreciates his efforts. Each semester brings nothing more than the chore of rolling the same boulders up the same slope again. There is ample evidence that he may be right. Stu dents Flunk the Faculty is the title of a chapter in a recent (1969) book College Scene, a collection of essays by students from coast to coast: The College Poll study on what students really want puts better teachers as the first area for improvement. (p. 78) Newspaper editorials excoriate professors for inciting students to riot by being too critical of American foreign and domestic policy. Student editorials in campus publi cations, on the other hand, lambast professors for being irrelevant, and not addressing themselves to critical issues of the day. Hate mail from parents and com munity leaders brings accusations of everything from obfuscation of issues to dangerous meddling, to outright subversion. State legislatures climax the assault by budgetary cuts. There is nothing new about town and gown conflict, but seldom has the teaching profession itself been so vilified as it is today in so many quarters of society. parameter of the problem is created by the pressures of that much overworked term, adminis trivia. In addition to his teaching load, the professor is expected to serve on committees. Such service in many instances seems to serve no purpose and to keep him from the research and writing which he must perform to justify his retention, promotion, and/or tenure. He then must create a variety of subterfuges and engage in what Hodgkinson calls, selective negligence (cf. Finding the Levers in Effective College Teaching, by William Morris, 1970). Still another problem for the professor is the con stant demand by students and fellow faculty to become in some cause. Professor Cogent wants to be liked, to be regarded as a man with a conscience. He is at the same time sensitive to the voice of caution (often arising as much from the administration as from his own psyche), which warns that getting involved may cost him the respect of his academic elders and con servative community members. He begins to rationalize that it is, after all, easier for protesting students to get into another college than for a faculty member to secure another position. Most syndromes have no specific cure. They are symptomatic of a complex of problems beyond immedi ate diagnosis. But while these deeper issues are being addressed, there is something every faculty member can do for himself each morning while driving into the college parking lot. Though it may seem only a hortatory exercise, he can say to himself: Another day; another chance to enrich a few more students' lives, and maybe even add an increment to the store of human knowledge. This will not motivate him to set the world on fire (a Quixotic ambition anyway), but will keep him at his task, and provide an antidote to that most corrosive of all emotions: self-pity.

Nonlinear in-plane bending of a plane stress-strain finite element model

Many classes of problems in structural geology can be idealized into two-dimensional mathematical models. Folding of multilayered sequences during tectonism is a key example of a type of structure that can be analyzed two dimensionally. Any finite element model that simulates this type of behavior must be organized around a basic element capable of bending in its own plane. To assure that the basic element assumptions will give correct answers, a validation procedure is outlined. It consists of subjecting mathematical assumptions governing element behavior to a displacement compatibility criterion to ascertain whether the element will perform satisfactorily. If the behavior is satisfactory, the element is coded and tested against exact analytical solutions. Once validation is completed, the finite element method can be used to obtain generalized solutions of geologic problems with a high degree of confidence. Two elements are contrasted by means of this procedure. Elastic displacements of long, slender structures are modeled by using a cantilever beam comprised of constant (CST) and linear (LST) strain triangles. The CST tends to diverge from analytical bending displacements as the structure becomes longer but may be satisfactory for short, square structures. The LST is found to give excellent bending displacements for all aspect ratios. The folding process, which might occur as an inelastic deformation, can be simulated with incremental finite element models. Although validations exist for many different types of elements in the engineering field, none exists for an in-plane bending element using plane stress-strain assumptions that might be required in geology. With a linear strain quadrilateral as the basic element (an element condensed from 4 LST's) an incremental nonlinear validation is presented for the bending of a plane stress-strain element. It is found to agree quite closely with numerical and exact analytical solutions.

Dimerisation of bilirubin diglucuronide and formation of a complex of bilirubin and the diglucuronide.

The reversible formation of a complex of bilirubin and bilirubin diglu curonide is demonstrated. The dissociation constant is 2 × 10−6M. Dimerisa tion of bilirubin diglucuronide has also been shown. The dissociation con stant for the dimer, 7 × 10−5M, is of the same order of magnitude as for dimer bilirubin and much higher than that of the above-mentioned complex. The complex is sufficiently stable to be present in blood plasma in vivo in certain types of icterus.

Fundamental research on a radial face seal : J. G. Pape, ASLE Trans., 11 (4) (1968) 302–309; 9 figs., 18 refs.

Radial face seals generally speak ing operate under full hydroflynmnic lub ricatinq conditions, 'JU t tk e m echa ni sm of lubrication i s not completely understood. I n a primarily ex peri mental i nres ti qation the auth or has attempted to establish a description of the basic lubricati nq m echanism. i n radial [nr« seals. Th e ex perime ntal ap para tus and mcusurinq techniques are IJriejl y described. . Th e ex perimental results dis play a high degree of reproducibili ty . D yn am ic measu rem ents oj fi lm thickness reveal fluct uations at twice shajt speed f requency that are concluded to be due to surf ace WIl1'i­ ness. Thi s conclus ion is corroborated by the topograph y of the scaling [aces. A t consta nt geom etry the friction coefficien t and film thick ness appear to depend on two dimensionless numbers incorporati nq: average fa ce pressure, seali n g pressur e, viscos'ity and speed. A sim plified theory that lakes i nto accoun t the macrorouqhness of the seali n g f aces shows close correlatio n wi th the ex perimental daia obtai ned. H avin g obtained a strong indica tio n that macrorouqhnees of the seali nq fa ces is the pri me fa ctor causing lu brica tio n, II f ew practical con .~ equences are di scussn] ,

A variant of the two-dimensional Riemann integral

For a va riant of the two-d imensional Ri e mann int egra l suggested by S. Marcus , it is shown that the only integrab le fun c tions which are continuous (o r merely continuou se parately in one of th e variables) are the cons ta nt fun ctions . The int egrab le di scontinuou functions a re proven to be cons ta nt except poss ib ly on a se t which is s ma ll in a sense made precise in the paper.

Kinetics and Catalysis of Urethane Foam Reactions

Since the rates of chemical reactions in volved in cellular urethane formation are decisive for product quality, model reactions were kinetically investigated and the mech anism of catalysis was studied. A simple rela tionship found between the specific rate con stant and the molar ratio of alcohol/catalyst for an alcohol/isocyanate reaction catalyzed by stannous octoate suggests the formation of an activated intermediate complex. The balance between the alcohol/isocyan ate and water/isocyanate reaction rates is important. Organotin compounds promote the former rate more than the latter whereas the reverse holds for amine catalysts. The rates of both reactions, catalyzed by amines with and without stannous octoate as co catal yst, demonstrate a synergistic effect ex plained by the extra stability imparted to the activated intermediate complex by attach ment of the amine.

A cardiac output computer for the rapid analysis of indicator dilution curves

The determination of cardiac output and central blood volume is of considerable importance, not only in cardiac research but i the diagnosis and treatment of heart disease. At present, the most clinically adaptable method of determining these parameters is the indicator-dilution technique. However, analysis of indicator-dilution curves is laborious, requiring 20–40 min. of a skilled operator's time. A simple instrument has been devised which permits the determination of cardiac output and central blood volume in less than one min. The computer described in this paper makes use of an electronically-generated curve which is displayed on a CRT and optically superimposed on the actual indicator-dilution curve. Three manual controls, used to match the curves, yield the desired parameters. The computer may be used to analyse curves within the following ranges: Curve amplitude (2A)—2.5–10 cm; Period (T)—2.5–10 sec; Time constant (CT)—(0.25–1)×T sec; Injection (I)—5–12.5 mgm; Calibration (M)—5–1.2 cm/mgm-liter; Cardiac output—0–48 liters/min Mean transit time—25 sec full scale.

Studies on the mechanism of salt and water secretion from the lacrimal gland.

By stimulating the lacrimal gland of rabbit with pilocarpine, the tears were collected through the fistula inserted into the nasolacrimal duct, and the ionic composition was analysed with special reference to the rate of lacrimal flow, and the ionic concentrations in serum. The secretion potential wasalso measured with reference to the secretion of ions in tears. Results obtained are as follows:1. The osmolarity of tears is mainly produced by salts which are mainly composed of Na+ and Cl-and partly of K+and HCO3-and is kept almost con stant at a slightly higher level than that of serum, irrespective of the rate of tear flow. The concentrations of Nat HCO3-and Cl- in tears are all kept constant, irrespective of the rate of tear flow, while the K+concentration changes parallel to changes of the rate of tear flow.2. The concentrations of Na+and HCO3- in tears are approximately the same as that of the respective ion in serum even when the concentration in serum is changed by salt infusion, while K+ and Cl- concentrations are always higher in tears than in serum. The Cl- concentration in tears bears a linear relation with that in serum of which the regression coefficient is 1 and the intercept constant is about 25mEq. The pH of tears is approximately the same as the serum pH and is determined by HCO3- concentration and CO2 partial pressure which equilibrate with those in serum.3. The potential being measured by external leading from the luminal side and the outside of the lacrimal gland, a resting potential of about 4-27mV was detected. The negative side of the potential is in the lumen of gland. The negativity of the potential in the luminal side increases as the rate of tear flow is increased by stimulation of lacrirnal gland, and thus the secretion potential of about 7-22mV appears. The secretion potential runs parallel to the time course of the rate of tear flow, though the peak of the former somewhat lags behind that of the latter.4. The increase of the resting potential as well as the secretion potential was provoked by raising the Cl concentration in serum by NaCl infusion. The changes of potential may be due to the acceleration of secretion. On the other hand, the potential was reduced after KCl infusion, probably owing to the promotion of K+ secretion by a rise of serum K+ concentration.5. From the above results and analysis of the interrelation between the rate of tear flow and the rate of ionic secretion as well as the secretion potential, it was deduced that the secretion potential as well as the water secretion (tear flow) of the lacrimal gland is associated with the active secretion of Cl- through the lacrimal gland cells, while Nat HCO3- are all transported passively in equilibration with those in serum. The K+ secretion is also an active process and affects the secretion potential to decrease.

Mortality Rates from Cancer and Tuberculosis

These findings have been used by Cherry, Cruick shank, and Paxon to support the suggestion that there is a causal relationship between cancer and tuberculosis. Campbell (1961a), however, has criticized this suggestion on the grounds that the relationships have been based upon crude and not age-standardized mortality rates, and he points out that if the age-structure of the population not changed, th joint tuberculosis and cancer mortality rate would not have remained constant. This c iticism, although valid, cannot be applied to the cohort analysis used by Cherry (1925), and the fact that the proportion of each cohort ultimately dying of either cancer or tuberculosis has remained re markably constant seems unlikely to be an artefact produced entirely by the interaction of the factors mentioned by Campbell, i.e. improving social con ditions, improving health services, and more urbanization, industrialization, and tobacco smoking. Although these factors might interact in such a way as to cause a decrease in the tuberculosis rate and an increase in the cancer rate to occur concurrently, the fact that the fall in the probability that an individual will ultimately die of tuberculosis may have been almost exactly compensated for by the increase in the probability that he will ultimately die of cancer is an unexpected finding. It would be of particular interest to extend Cherry's cohort analysis to later cohorts in whom more recent changes in cancer mortality such as the increase in deaths from lung cancer might be taking effect. Unfortunately the data required for this extension is not yet available, but use may be made of an alternative approach which has been described in a previous paper (Haybittle, 1962). The method is to study mortality trends in the birth-standardized populations of England and Wales, i.e. the popula tions that would have existed at any time if the number of live births per year had remained con stant. It has been shown (Haybittle, 1962) that the ratio, R', of deaths from cancer to deaths from all causes in the birth-standardized populations can be used to show trends in the probability, R, that an individual will ultimately die of cancer. Further more, trends in R may be observed by this means 23