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Previous small studies used individualized growth assessment (IGA) to characterize prenatal growth velocities of singletons and twins. We aimed to compare second-trimester growth velocities of individual anatomical parameters between monochorionic diamniotic (MCDA) twins, dichorionic diamniotic (DCDA) twins and singleton fetuses in a larger study.This was a study of a novel cohort of 222 MCDA twins and previously published cohorts of 40 DCDA twins and 118 singletons with serial ultrasound data. Fetal biometric measurements of biparietal diameter, head circumference, abdominal circumference and femur diaphysis length from prenatal ultrasound examinations were used to calculate second-trimester growth velocities using direct calculation or linear regression analysis. Linear fit was assessed based on the coefficient of determination (RThe majority of cases underwent three second-trimester ultrasound examinations with fetal biometry available. All fetuses had linear growth, with RExpanding on prior work using IGA, we found that second-trimester growth velocity of the four major anatomical parameters overall was similar between twins and singletons and between MCDA and DCDA twins, supporting the use of singleton-derived growth standards for IGA in twins. Twin growth potential appears to be similar to that of singletons in the second trimester, suggesting that subsequent growth divergence may be due to third-trimester physiological or pathological changes in twin pregnancies. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

In practical applications, robots are often required to handle payloads with unknown dynamics. This paper considers the path tracking control problem of a robot carrying an unknown payload. An adaptive control scheme is presented in which the uncertain dynamics of the payload is taken into account, and prior information about the payload's mass or inertia is not required. By introducing a generalized inner product, an alternative approach for stability analysis (rather than the more usual Lyapunov method) is established which proves the asymptotically stable control of the proposed strategy.

This paper proposes a practical robot control system based on off-the-shelf parts that will be used as a testbed for evaluating the performance of advanced, servo-level control algorithms. As designed the system is capable of implementing the distributed sampling control concept as applied to the model-based control of robots. Besides closed-loop position control, the proposed system also incorporates force/torque feedback. This is of particular interest in space-based robotics applications. Unimation's Puma 562 manipulator was chosen as the target plant for the control system called the Robotic Arm Control System (RACS). The control system replaces the existing low-level servo controllers in the associated VAL-II MkIII controller.

The coadsorption of water and preadsorbed oxygen on Ru{0001) was studied by synchrotron-based high-resolution x-ray photoelectron spectroscopy. A dramatic change was observed in the interaction of water with oxygen between low and high oxygen precoverages. Low oxygen coverages below 0.18 ML induce partial dissociation, which leads to an adsorbed layer of H2O and OH. Around half the oxygen atoms take part in this reaction. All OH recombines upon heating to 200 K and desorbs together with H2O. Oxygen coverages between 0.20 and 0.50 ML inhibit dissociation, instead a highly stable intact water species is observed, which desorbs at 220 K. This species is significantly more stable than intact water on the clean surface. The stabilization is most likely due to the formation of hydrogen bonds with neighboring oxygen atoms. For intermediate oxygen coverages around 0.18 ML, the dissociation behavior depends on the preparation conditions, which points toward possible mechanisms and pathways for partial dissociation of water on Ru{0001}.

In a previous report we constructed a synthetic DNA sequence that directed the deposition of histone octamers to a single site, and it was proposed that DNA distortion was involved in the positioning effect. In the present study we utilized the chemical probe potassium permanganate to identify sites of DNA distortion in the synthetic positioning sequence. A permanganate hypersite was identified 15 bp from the nucleosome pseudo-dyad at a site known to display DNA distortion in the mature nucleosome. The sequence of the site contained a TA step flanked by an oligo-pyrimidine tract. A series of substitutions were made in the region of the permanganate hypersite and the resulting constructs tested for affinity for histone octamers and translational positioning in in vitro studies. The results revealed that either a single base substitution at the TA step or in the adjacent homopolymeric tract dramatically affected affinity and positioning activity. The rotational orientation of the permanganate-sensitive sequence was shown to be important for functions, since altering the orientation of the site in a positioning fragment reduced positioning activity and octamer affinity, while altering the rotational orientation of the sequence in a non-positioning fragment had the opposite effects. A reconstituted 5 S rDNA positioning sequence from Lytechinus variegatus was also shown to display a permanganate hypersite 16 bp from its pseudo-dyad.

Intrinsic DNA curvature has previously been implicated in the condensation of satellite DNA in chromatin. In this article, electrophoretic methods and computer programs for predicting DNA structure from nucleotide sequence were used to determine if curvature is a conserved feature of satellite DNA. The results revealed that satellite sequences display wide variation in magnitude of intrinsic bending. Less than half of the satellites examined were strongly bent when compared with control DNA. However, a conserved pattern of bending was seen in all 57 satellite sequences that were studied. The pattern consisted of repeating units of two 50-60-base pair bending elements which were separated by a 20-30-base pair region of low curvature. This pattern resembles qualitatively the bending of DNA in the nucleosome where the helix is folded approximately two turns around the histone octomer with the turns interrupted by a less bent segment in the center of the particle. The distance between successive pairs of bending elements was also similar to the average spacing of nucleosomes in chromatin. Thus, the conserved structures could play some role in the positioning of nucleosomes along satellite chromatin. In order to strengthen the correlation between DNA structure and nucleosome positioning, sequences were examined which have been shown to position nucleosomes at single major sites. This analysis revealed a conserved pattern of DNA structure resembling the two peak units seen in satellites. In addition, the nucleotide sequence patterns responsible for the conserved patterns of bending were similar in both satellite and nucleosome positioning DNA. Likewise, nucleotide sequence patterns that are thought to direct the rotational orientation of DNA in the nucleosome were similar in both sequence sets. These results are considered in terms of a general model for the role of DNA bending and nucleotide sequence in the control of nucleosome positioning and chromatin condensation in eukaryotes.

A method for determining the distribution of olefinic bonds in elastomers has been developed using dual-detector gpc analysis of the polymer after derivatization with 2,4-dinitrobenzenesulfenyl chloride. The method is particularly useful for determining the distribution of olefinic bonds in hydrocarbon copolymers having small levels of unsaturation.

The study of molecular weight and functionality parameters of telechelic hydrocarbon-based prepolymers has received much attention in recent years owing to the influence that these parameters exert on the vulcanization and product properties. An excellent review of these systems has been presented by French. Previous work has been limited to the determination of the average functionality of the whole polymer or of fractions obtained by some appropriate fractionation procedure. Muenker and Law, for instance, used extensive column elution techniques for separating the various species and then determined the average functionality of the fractions. In the previous paper, we described a dual-detector gel permeation chromatography (GPC) method for simultaneously determining the molecular weight averages, molecular weight distribution, hydroxyl equivalent weight, functionality averages, and functionality distributions of hydroxyl-terminated polybutadienes. The method is based on the simultaneous use of a differential refractive index and ultraviolet GPC detectors to analyze the polymers before and after derivatization of the hydroxyl groups with phenyl isocyanate. In this paper, the method will be utilized to determine these parameters for several commercial hydroxyl-terminated polybutadiene prepolymers and to compare the data with existing literature values.

A method for simultaneously determining the molecular weight averages, molecular weight distribution, hydroxyl equivalent weight, functionality averages, and functionality distribution of hydroxyl-terminated polybutadienes using GPC has been developed. The method is based on the preparation of a UV absorbing derivative of the hydroxyl group and GPC analysis using dual differential refractive index and UV detectors. In order to determine the hydroxyl equivalent weight, quantitative derivatization of the hydroxyl group is required. If the equivalent weight can be determined by an independent method, the derivatization reaction can be less than quantitative if sufficient UV absorptivity can be obtained. The procedure used for calibrating the GPC columns and UV detector are presented. Equations for calculating number- and weight-average functionalities from GPC data were also developed. The number-average functionality is independent of the functionality distribution, but the weight-average functionality is dependent upon the distribution of functionality. The ratio of the weight-average to number-average functionality is indicative of how the functionality is skewed as a function of molecular weight.

In recent years, considerable attention has been focused on the structural characterization of functionally terminated hydrocarbon prepolymers used in propellant binders and other applications. The molecular weight averages and molecular weight distributions of hydroxyl-and carboxyl-terminated poly butadienes have been determined by gel permeation chromatography (GPC). The functionality distribution of these prepolymers has also been previously studied by column fractionation and a procedure combining GPC and column fractionation of the polymer by stepwise elution from silica gel. The carboxyl or hydroxyl equivalent weights of the fractions were determined by infrared or near-infrared spectroscopy. The fractionation procedure is quite laborious, and multiple peaks were observed in the elution profile, making it difficult to decide how the fractions were to be grouped for subsequent analysis. Previously, a technique for determining the distribution of unsaturation in copolymers containing a small number of double bonds as a function of GPC elution volume was developed. The technique utilized a GPC equipped with uv photometer and differential refractometer detectors to determine the ratio of the weight fraction of olefinic bonds to the weight fraction of polymer by GPC analysis of the polymer after derivatization of the double bonds with 2,4-dinitrobenzenesulfenyl chloride. It was suggested that the technique should be applicable for the determination of the distribution of other functional groups with the choice of suitable reagents for derivatization. The purpose of this investigation was to attempt to extend our previous study to simultaneously determine the molecular weight averages, molecular weight distribution, hydroxyl equivalent weight, functionality averages, and functionality distribution of hydroxyl-terminated polybutadienes by a GPC technique.

The strength of a brittle material depends upon the toughness of the material itself and the degree of perfection with which it can be placed. This study shows that both the compressive and tensile strength of calcium hydroxide lining materials is dependent on the fracture toughness at unstable crack propagation, KIC, and the size, number and distribution of pores (which are the defects that nucleate fracture). Of the products tested here, Dycal possesses the greatest actual strength due to a higher than average KIC value and relatively few isolated small pores. However, the greatest potential for strength exists in Reocap which has a KIC value a factor of 2.4 greater than its nearest rival (Dycal). Unfortunately its strength, as determinedhere, is less than Dycal due to the large number of pores in close proximity to each other.

The study of molecular weight and functionality parameters of telechelic hydrocarbon-based prepolymers has received much attention in recent years owing to the influence that these parameters exert on the vulcanization and product properties. An excellent review of these systems has been presented by French. Previous work has been limited to the determination of the average functionality of the whole polymer or of fractions obtained by some appropriate fractionation procedure. Muenker and Law, for instance, used extensive column elution techniques for separating the various species and then determined the average functionality of the fractions. In the previous paper, we described a dual-detector gel permeation chromatography (GPC) method for simultaneously determining the molecular weight averages, molecular weight distribution, hydroxyl equivalent weight, functionality averages, and functionality distributions of hydroxyl-terminated polybutadienes. The method is based on the simultaneous use of ...

In addition to the expected elimination of lithium hydride, metalation and addition reactions have been observed as competitive, thermolytic reactions of polybutadienyllithium. The importance of these reactions at temperatures frequently utilized for the polymerization of butadiene was illustrated and the effect of these reactions on the macrostructure of polybutadiene determined.

The Gordon—Taylor—Wood relationship between composition and glass temperature has been used as the basis of a DTA method for block styrene analysis in butadiene styrene copolymers having the same microstructure and a similar compositional distribution. The determined K value of the Gordon—Taylor—Wood equation for these polymers prepared with a butyllithium catalyst is in fair agreement with values previously determined for emulsion butadiene styrene copolymers. The total styrene content of the copolymer was determined using the refractive index method, and the composition of the “non-block” segment of the copolymer was obtained from DTA measurement using a Tg as a function of composition graph The amount of block styrene can then be obtained by difference. Evidence is presented supporting the validity of the method, and the results are compared with those obtained by a chemical method which involved polymer degradation by a hydroperoxide in the presence of osmium tetroxide. The thermal analysis requires approximately one-half hour. All measurements are made on the dry polymer eliminating the necessity of redissolving the polymer as required by most other methods of analysis.

The thermal stabilities of polybutadienyllithium, polyisoprenyllithium, and polystyryllithium solutions have been determined in hydrocarbon solvents. Kinetic analysis indicated that a complex mechanism was involved in the thermolysis of polybutadienyllithium. The thermal stability was observed to increase with increasing lithium concentration, suggesting the presence of competitive reactions in addition to the expected elimination of lithium hydride. The thermal stability of the three systems studied was consistent with their reported degrees of association: dimeric polystyryllithium was less stable than tetrameric polyisoprenyllithium or hexameric polybutadienyllithium.

Developments in reverberatory furnace practice at Noranda over the period 1928 to 1953 are described. Features of interest are increasing furnace tonnage from 700 to 2000 tons per furnace day, the use of the suspended basic roof, and improvements in furnace fuel ratio. Points of comparison and contrast between Canadian and American furnace practice are given.

Control techniques for one- and two-arm systems are presented. The first, reflex-action position (RAP) control, makes the single-arm manipulator dynamics, as seen by a position controller, independent of uncertain loading. With this form of load decoupling, the position controller can be designed for good performance while maintaining robustness. The second, load-sharing force (LSF) control, is for two manipulators grasping a rigid object, and is used in conjunction with RAP control. The LSF control addresses three problems: (1) load sharing, (2) control of interactive forces, and (3) accurate position control. A diagonal matrix determines how the load is apportioned to each manipulator. An external input specifies the desired compression, tension, or torsion to be applied to the object.

Antisera raised in mice to chromatins from different tissues of the chicken reacted preferentially with the chromatin type that was used for immunization. This tissue specificity was also evident in the spectrum of monoclonal antibodies generated when mice were immunized with erythrocyte chromatin. Three erythroid-specific antigens and one antigen that was present in a number of chicken tissues were characterized in further detail. These antigens, which comprised less than 0.1% of the erythrocyte chromatin proteins, were nuclear localized although three were also detected in the cytoplasm. Two of the erythroid-specific antigens existed as multiple polypeptides in isolated chromatin. The multiple chromatin forms of one antigen were derived from a precursor protein that was selectively cleaved within 1 min after erythrocyte lysis. Analysis of this antigen in extracts from erythrocytes and reticulocytes indicated that the cleavage of the precursor protein was developmentally regulated in vivo.

Estrogen activates transcription of the vitellogenin genes in livers of male Xenopus laevis. We have examined the conformation of the vitellogenin genes in chromatin and the methylation state of one vitellogenin gene during the process of estrogen stimulation and withdrawal. Sensitivity of the vitellogenin genes to DNase I digestion parallels transcription. The vitellogenin genes are insensitive to DNase I digestion in unstimulated liver cells, become more sensitive to DNase I digestion following estrogen activation of vitellogenin gene transcription, and are insensitive to DNase I digestion in liver cells withdrawn from estrogen. In contrast, the methylation state of nine potential methylation sites within the vitellogenin A1 gene is identical in red blood cells, unstimulated and withdrawn liver, estrogen-stimulated liver, and hepatocytes purified from estrogen-stimulated liver. Rapid transcription of the vitellogenin genes in estrogen-stimulated liver cells occurs with six of the nine methylation sites examined fully methylated.

A method for the dynamic simulation of two robots coupled via the object is described. The approach taken is to decouple the arms and model the effects of one arm on the other using an interaction force/moment vector which is treated as a part of the forces/moments exerted on the end effector. The result (limited to the case of a rigid-body object) is a closed form expression for the interaction force/moment vector which depends on the current values of the joint variable positions, velocities, and the input generalized forces. The integration of this result with well-known simulation methods is given.

The relationship between estrogen receptor(R) binding by uterine nuclei and uterotrophic responses was examined. Immature rats received a single injection of estradiol (E2) or estriol (E3) and the following parameters were measured: accumulation and retention of the estrogen receptor by the nuceus of uterine cells; incorporation of 14C-glucose into CO2 lipid, protein and RNA; RNA polymerase activity; water imbibition and increased dry weight. E2 and E3 were of equal potency with regard to the rapid accumulation of R by the nucleus but differed with respect to long term retention of R. The concentrations of nuclear RE2 and RE3 complexes were equivalent between 1 and 3 hr after estrogen injection; however, by 6 hr RE2 remained significantly elevated while RE3 levels had fallen to control values. E2 and E3 were also of equal potency with respect to the stimulation of enhanced glucose utilization, water imbibition, the incorporation of 14C-glucose into lipid, protein and RNA 3 hours following an injection of the hormone. Likewise the activity of RNA polymerase was equally stimulated by E2 and E3 3 hr after injection. Thus all early uterotropic responses (0-3 hrs) that were measured were equally stimulated by E2 and E3. However, E3 failed to stimulate true uterine growth (increase dry weight 24 hr after injection), whereas E2 produced a significant stimulation of true uterine growth. These data suggest that the RE complex is capable of stimulating early uterotrohic events regardless of which estrogen is present; however, in order to produce true uterine growth the RE complex must be retained in the nucleus for long periods of time. This proposal was tested by the administration of repetitive injections of E3. This treatment resulted in an increase in dry weight that was equivalent to the growth that was produced by repetitive injections of E2. These results demonstrate that E2 and E3 elicit early uterotrophic responses with equal facility following a single injection but that only E2 causes true uterine growth. The ability of E2 to stimulate true uterine growth appears to be related to the time of residence of the RE complex in the nucleus.

A method was developed which enables the characterization and fractionation of chromosomal proteins according to their chromatin binding properties. The method is based on the ability of hydroxyapatite to bind native chromatin in solutions which do not dissocciate chromosomal proteins from the DNA. The proteins are then selectively dissociated from the immobilized chromatin by treatment with NaCl, urea, or guanidine HCl. The hydroxyapatite dissociation method represents a rapid one-step fractionation procedure which results in the quantitative recovery of chromosomal proteins devoid of nucleic acids and is suitable for large preparations. The hydroxyapatite dissociation method provides a versatile procedure for the study and preparation of chromosomal proteins. The patterns of dissociation of both histones and nonhistone chromosomal proteins by NaCl and urea from chicken oviduct chromatin were characterized by this method. In addition, this technique enabled the purification of the major histone species in a single operation. Partial purification of specific nonhistone proteins, including the estrogen receptor, was also achieved. We suggest that this method will be a useful tool in elucidation of the chemical and biological properties of the proteins from chromatin.

A bronchopancreatic fistula developed in a 14-year-old boy two weeks following transabdominal splenectomy and repair of a ruptured diaphragm. This unusual entity should be suspected when a patient with pancreatitis or pancreatic trauma has pleural complications associated with profuse, frothy sputum. The diagnosis is established by the presence of high levels of amylase in the sputum or by the appearance in the sputum or the bronchi of dye or contrast material injected into the external fistula. The primary goal of treatment, in addition to the management of the thoracic complications, is subdiaphragmatic control of the pancreatic fistula. A brief summary of seven previously reported cases is presented.

Fibronectin is a high molecular weight adhesive glycoprotein present both on the cell surface (cellular fibronectin) and circulating free in the plasma (plasma fibronectin). To investigate the cellular origins of plasma fibronectin, monoclonal antibodies prepared against purified plasma fibronectin of the rat were used in both in vivo and in vitro pulse-chase experiments comparing livers of animals of different ages. For in vitro analyses, slices were pulsed with 3H-leucine and purified fractions of endoplasmic reticulum, Golgi apparatus and plasma membrane were prepared at various times post-chase and characterized morphologically. The total protein was solubilized with NP-40, and incorporation into fibronectin was determined from PAGE analysis of immunoprecipitates. Incorporation was greatest in 5-day-old animals, representing greater than 0.3% of the total radioactivity and was least in adults animals. Label appeared in fibronectin associated with the plasma membrane within 60 min. At earlier times, labeled fibronectin appeared first in the endoplasmic reticulum (30 min) and then in the Golgi apparatus (45 min). The findings demonstrate synthesis of fibronectin by rat liver and evidence for participation of liver endomembranes in its secretion.

Monoclonal antibodies were prepared against the high mobility group (HMG) proteins 1, 2a, and 2b from hen erythrocyte chromatin. One antibody that recognized multiple sites along HMG-1, -2a, and -2b reacted strongly with HMG proteins from all vertebrates tested. In contrast, five antibodies that detected unique epitopes on chicken HMG-1 and -2a recognized antigenic sites that exhibited restricted phylogenic distributions. The differential reactivity of these antibodies on vertebrate proteins was in agreement with traditional taxonomy in that the avian HMGs were most closely related to those from reptiles and less related to those from mammals, amphibians, bonyfish, and especially the jawless fish. Mononucleosomes generated by mild digestion of erythrocyte chromatin with micrococcal nuclease were highly enriched in HMG-2a. One antigenic determinant located within the N-terminal domain of HMG-2a was freely accessible to its antibody when the protein was bound to these mononucleosomes. In contrast, two antibodies that recognized determinants in the central region of HMG-2a exhibited little chromatin binding activity. The masking of the central domain by DNA binding was presumably not responsible for these results because all three determinants were available for antibody binding when HMG-2a was bound to DNA in vitro. Therefore, the central region of HMG-2a may be masked from antibody binding by protein-protein interactions in chromatin.

Monoclonal antibodies were prepared to nuclear nonhistone proteins from a 2-aminoacetyl fluorine-induced transplantable rat hepatocellular carcinoma. These antibodies recognized a total of six distinct antigens as revealed by molecular weight analysis. Studies of antigen specificity with respect to various tissues, tumors, cultured cells, and oncodevelopmental stages indicated that these nuclear species could be divided into two categories. Four antigens were classified as tumor related since they were significantly enriched in tumor tissue as compared to tissues of the normal adult rat. The remaining two antigens were detected only in tumors and transformed cells; one, only in certain hepatomas. Thus, these antigens were classified as tumor specific. As an initial step toward elucidating the function of these proteins, each antigen was isolated by immunoaffinity chromatography, radioiodinated in situ, and analyzed for the ability to bind DNA. Three antigens were positive for DNA binding, and one of these was selectively released from tumor nuclei with the transcriptionally active chromatin upon digestion with micrococcal nuclease. The implications of these results for the possible functional contribution of the six tumor antigens to transformation is discussed.

We have examined the effects of steroid hormones in the chromatin sensitivity of the ovalbumin gene to micrococcal nuclease and have attempted to define the importance of the nucleosome core, higher order chromatin folding, and transcription in the maintenance of the nuclease-sensitive conformation of the ovalbumin chromatin. Solution hybridization studies demonstrated that the sensitivity of the ovalbumin gene in oviduct nuclei to micrococcal nuclease paralleled the hormone-dependent transcription of the ovalbumin gene in the immature chick. Blot hybridization analysis also revealed a hormone-dependent change in this chromatin region since ovalbumin DNA fragments from nuclease-treated hen and estrogen-stimulated chick oviduct nuclei exhibited nucleosomal repeat patterns that were less discrete than those observed for the ovalbumin specific fragments from liver and hormone-withdrawn oviducts. This transcription-related conformation was not the result of enhanced sensitivity of the ovalbumin-containing nucleosomal cores since the bulk of the nucleosomes associated with the ovalbumin chromatin were not preferentially cleaved internally by micrococcal nuclease. Rather, an analysis of the fragmentation of the ovalbumin chromatin as a function of digestion extent suggested a mechanism in which the heightened sensitivity resulted from the collective expansion of the nuclease cutting sites in the linker regions of the ovalbumin chromatin because the gene was in an unfolded conformation. The transcription-specific conformation was not merely a consequence of RNA synthesis per se since the selective sensitivity of the gene was unaffected by treatment of oviduct nuclei with alpha-amanitin, actinomycin D, or RNase. In addition, the presence of the transcriptional complex on the ovalbumin chromatin was presumably not required for selective nuclease recognition since preferential cleavage was observed under conditions expected to deplete oviduct nuclei of template-bound RNA polymerase and nascent RNA chains. These results are consistent with a model in which the expressed ovalbumin gene is in an unfolded polynucleosomal structure whose formation is related to transcriptional activity but not dependent on the transcriptional process.