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Notes: A theoretical treatment is given for the formation of visible holes in an elastic solid. It differs from previous treatments of bubble formation in liquids by neglecting the problem of hole nucleation altogether. Instead, a small spherical hole is assumed to be present initially. The inflation of such a hole by a dissolved gas is then considered. A critical internal pressure is deduced, at which the hypothetical hole would become infinitely large. This pressure is given by 5G/2; where G is the shear modulus of the rubber. Some model experiments are described in which swollen rubber vulcanizates were rapidly heated to bring the dissolved liquid into a superheated conditions. The temperatures of rapid bubble formation were determined for a number of vulcanizates having different degrees of crosslinking and hence different values of shear modulus, and for different swelling liquids. The results are shown to be in reasonably good quantitative agreement with the theoretical predictions.

Notes: The structure of the polycarbonate chain has been analyzed from the point of view of the spatial configurations it may assume. The carbonate group is certainly planar, and the trans,trans configuration probably is strongly preferred. Rotations about the aryloxygen bonds are subject to symmetric, twofold potentials. It follows that the molecule can be treated as a freely rotating chain consisting of a succession of virtual bonds 7.0 Å in length, joined at angles of ca. 112°. Calculations carried out on this basis yield 〈r2〉0/M = 0.85 Å2/g-mole wt for the unperturbed random coil, in excellent agreement with the experimental results of Berry, Nomura, and Mayhan. The effect of occurrence of some of the carbonate groups in cis, trans configurations is investigated using more elaborate methods.

Notes: A brief description is given of a new parallel-plate rheogoniometer for normal stress measurements on polymer melts as functions of the rate of shear. A wire-resistance strain gauge is used as the pressure gauge. Measurements are reported on high-density polyethylene. It is found that the time-temperature superposition principle is applicable to the normal stress data as well as to shear stress in steady flow.

Notes: The surface of thin polyethylene films (ca. 1 mil) nucleated on high- and low-energy surfaces was studied. It was found that the degree of crystallinity in the surface region, as determined by transmission and reflection infrared spectroscopy, was dependent on the nature of the substrate. Relatively small and randomly oriented spherulites were observed in the surface region of thin polyethylene films nucleated on gold, a high-energy surface. The surface region of a thin polythylene film nucleated on polytetrafluoroethylene, a low-energy substrate, was observed to have considerably fewer spherulites, but much larger in size, with orientation restricted, in general, to the plane of the film. The relative intensity of the 720 cm-1 to the 730 cm-1 band in the reflectance spectra (ATR) indicates that the surface region of a polyethylene film nucleated on a high surface energy substrate is more crystalline than the surface region of a film nucleated on a low surface energy substrate.

Notes: The orientation of the crystallographic c axis (chain axis) was followed by x-ray diffraction during the crystallization of four samples of isotactic polystyrene differing in elongation ratio. The crystallite orientation can be expressed by 〈cos2 χc〉, where χc is the angle between the c axis and the stretching direction. The degrees of crystallinity w were estimated from the diffraction data by using density for calibration. It was found that 〈cos2 χc〉 decreases in a linear manner with crystallinity, the rate of decrease being very small when the elongation ratio α is 5, but becoming progressively larger as α is decreased toward unity. A qualitative measure suggests that amorphous orientation decreases during crystallization at a rate which is nearly independent of α. The variation of 〈cos2 χc〉 with w is therefore governed by the orientation of the statistical chain segments prior to crystallization. If the elongation ratio is small, the supply of well oriented statistical segments is limited, and 〈cos2 χc〉 will decrease at a rapid rate during crystallization. A treatment due to Krigbaum and Roe permits evaluation of the ratio, ν/N, where ν and N are the average numbers of statistical segments in the crystallization nucleus of critical size, and in a network chain, respectively. Our polystyrene samples were not crosslinked, so chain entanglements must serve as junction points. Values of ν could not be obtained, since N was unknown. However, the (ν/N) ratio for isotactic polystyrene decreases slowly with α, and the values agree reasonably well with those obtained in a previous study of oriented polychloroprene networks. After nearly complete crystallization (ω ca. 0.30), the long period spacing measured by low angle diffraction was approximately 135 Å, and varied only slightly with elongation ratio in the range α = 1 to 5. It therefore appears that chain folded lamellae are present in both drawn and undrawn samples of isotactic polystyrene.

Notes: The structure and cell types of the closely similar glands of Calamoichthys and Polypterus are described and a general comparison made with the teleost pituitary. The Polypterine gland shows some unsual features in the anatomical disposition of its parts and in the arrangement of its neurosecetory and vascular supply and an explanation of these differences is suggested, based on relative growth changes in later development, in order to include these glands in the evolutionary pattern of the actinopterygian pituitary.

Notes: About 10,000 sense organs are present on one antenna of a female mantis, Tenodera angustipennis, and nearly 40,000 on that of a male. These are of four kinds: (1) thick-walled pegs, (2) short thin-walled pegs, (3) medium length thin-walled pegs and (4) long thin-walled pegs. All have the structural characteristics of chemoreceptors. The dendrites of the sensory neurons of the thick-walled pegs are exposed to the air in an opening at its distal end and those of the thin-walled pegs terminate at many pores in the surface. The significance of the larger number of sense organs possessed by the male is discussed. No important differences were found between the antenna of Tenodera angustipennis and those of T. aridifolia and T. australasiae.

Notes: Light and electron microscopical studies allow a descriptive account to be given of the preadult development of the ovary of Drosophila melanogaster. The lineage of the cell groups which contribute to the tissues of the adult ovary has been determined. The earliest morphologically detectable event in the differeentiation of each ovariole is the formation during the larval period of its terminal filament. Oogonia play no role in the induction of terminal filaments. The developmental events which transform a spherical mass of ovarian cells into a collection of multicellular cylinders is described. The importance in morphogenesis of acellular membranes secreted at the interface separting cells of different prospective significances is stressed. Such membranes may serve to regulate the future migration of cell populations or as sites of attachment for monolayers of cells which later fuse to form multinucleated muscle sheaths. The transformation of oogonia to cystoblasts coincides with and presumably depends upon the same hormonal stimulus which causes metamorphosis. The first oocytes to undergo crossing over do so between 24 and 36 hours after puparium formation.

Notes: A morphological study of the presoma of adult Corynosoma hamanni (Linstow, 1892) was undertaken in an effort to clarify some problems encountered during analysis of a large collection of juveniles of this species assembled from fishes of McMurdo Sound. This study is based on approximately 600 adult specimens recovered from four Weddel seals, Leptonychotes weddelli, collected at McMurdo Sound.Morphologically the proboscis armature is more varied than previously reported and consists of 18 to 23 longitudinal rows each with 11 to 15 hooks of two distinct types. At the apex of the proboscis is an undivided, bi-nucleated apical organ unlike that described for species of Neoechinorhynchus. In the basal third of the proboscis is a thin-walled vesicle which extends into the anterior quarter of the proboscis receptacle. The more posterior of two external folds on the presoma is a cuticular invagination permitting recognition of the neck-trunk border of C. hamanni. Lemnisci originate between the two folds and extend into the trunk cavity between the body wall and extensive neck retractor muscles. Contrary to Linstow's original description, each lemniscus is a single structure.Several limitations in material prevent speculation at this time about the limits of intraspecific variation in C. hamanni.

Notes: The formation of cortical alveoli and yolk has been investigated in the pipe-fish, Syngnathus fuscus, and the killifish, Fundulus heteroclitus by techniques of light and electron microscopy. In addition to cortical alveoli and yolk components the ooplasm contains many mitochondria, numerous Golgi complexes, copious quantities of the endoplasmic reticulum of the rough variety, ribosomes and particulate glycogen. While the formation of cortical alveoli and yolk may proceed simultaneously, the cortical alveoli are the first to develop. Staining procedures indicate that cortical alveoli, like some of the yolk bodies contain a polysaccharide component and protein. It is suggested that the protein portion is made by the endoplasmic reticulum and is subsequently transferred to the Golgi complex via vesicles. Within the saccules of the Golgi complex the polysaccharide component is fabricated after which time the Golgi produce vesicles containing the products of either the cortical alveoli or yolk bodies.The precursors used in the production of the yolk are produced by the oocyte (endogenous) and by an organ other than the ovary (exogenous). The precursors made exogenously become associated with the morphologically and physiologically specialized oolemma and are subsequently internalized by the process of micropinocytosis.

Notes: In a variety of amphibians examined the stratum corneum was one cell in depth, although in Xenopus it was up to three cells deep. The flattened horny cells were closely fused together along their lateral membranes to form a continuous sheet. Disulphide bonds of keratin were most concentrated in the peripheral cytoplasm, but the interiors of the cornified cells were sufficiently well keratinized to prevent more than slight enzymatic cytolysis of the normal cell components. Characteristically large, weakly stainable, non-shrunken nuclear remnants were found in the salamander and frog horny layers, but the clawed toad had small pyknotic (parakeratotic) nuclei. The mature amphibian keratinocytes contained free fats, bound phospholipids, calcium and sulphydryl groups, together with acid phosphatase and non-specific esterase. Cornification appears to begin by a process of separate individual cell keratinization and lateral membranes of neighbouring cells only later become fused together. This differs from the process in higher vertebrates in which the cells undergoing keratinization form a uniform transitional layer in the epidermis. In the amphibian epidermis neighbouring cells occur in different stages of keratinization.

Notes: The oocyte-nurse cell complex of the polychaetous annelid, Diopatra cuprea, has been explored by various methods of light microscopy and by the technique of electron microscopy. Early in its development the complex appears as a string of cells floating within the coelomic cavity. As this string of cells develops, the volume of one cell (approximately the middle one) increases greatly; while that of the remaining cells, referred to as nurse cells, increase slightly. Due to this differential growth, the two opposing strands of nurse cells are displaced to one side of the oocyte.Nurse cells are joined to one another by cytoplasmic bridges. Cytoplasmic bridges also exist between the strands of nurse cells and the oocyte. The presence of numerous ribosomes within the bridges between the oocyte and nurse cells encourages us to suggest that this organelle may be transferred to the oocyte via this route. The transported ribosomes may be used by the maturing oocyte, or they may be stored by the egg to be utilized during embryogenesis. Moreover, we believe that the nurse cells are not involved in the production of the protein-carbohydrate yolk bodies for we think that these are elaborated by the endoplasmic reticulum in collaboration with certain Golgi complexes of the oocyte.

Notes: A series of nine features of the shoulder girdle, chosen as having functional significance in relation to the movements of the shoulder in arboreal locomotion, have been studied in 1188 specimens of 194 genera of mammals. The features were defined metrically and examined by means of a multivariate statistical technique: viz. canonical analysis. The study has shown that those mammals which are nonarboreal differ considerably among themselves and form the arboreal forms. But the myriad shapes of the shoulder girdle in a wide range of mammals (e.g. some marsupials, edentates, rodents, carnivores and primates) which climb or forage in trees, can be summarized mathematically by a very small number of similar canonical variates. This information correlates well with that of a previous series of studies carried out on the primates alone.The biological information that was postulated as being reflected by the individual canonical variates for the primates is also apparent for the arboreal mammals. The different variates separate the forms in ways which are consonant with what is known about the function of the shoulder in locomotion. Aspects of the shape of the shoulder defined by the analysis appear to be discernible from an examination of the contribution of the original variables to each individual canonical variate. This seems to confirm that the shape of the shoulder girdle within a very wide range of mammals is limited by a very small number of underlying factors of biological significance.One interpretation of the results suggests that the genetic model of the mammalian shoulder may have been sufficiently fixed at an early stage in the evolution of the class as to place considerable constraints upon the subsequent evolution of the shoulder in the different Orders.

Notes: Hypophysectomized adult newts exhibited 98% survival and limb regeneration at 23 days post-hypophysectomy when injected intraperitoneally every other day with prolactin (0.015 U/newt) and kept continuously in aquaria with 1 × 10-7 concentration of thyroxine. Thyroxine alone was no more effective than saline injections.Prolactin (1.2 U/newt every other day) alone increased survival and limb regeneration, but less effectively than did the prolactin-thyroxine combination.

Notes: Thin semi-serial ground sections of coronal dentin were examined radiographically. The bulk of the coronal dentin was characterized by the majority of the tubules having a distinct peritubular zone. With the exception of the tubules running from the tip of the cusp to the pulp cornu, the bulk of peritubular matrix forming the walls of the tubules was disposed eccentrically. The matrix was thicker on the cervical sides of the tubule than it was on the incisal sides. In a relatively narrow layer of the coronal dentin between the bulk of the dentin and the predentindentin border area the thickness of the peritubular matrix varied considerably. It was extremely narrow or absent in some tubules and reached its greatest thickness in others. The tubules in the predentin border area showed little or no evidence of peritubular matrix. The area of dentin beneath the central developmental groove differed somewhat from the bulk of the dentin. Many of the tubules at all levels of this area showed little radiographic evidence of peritubular matrix. Obliterated tubules were seen in some of the sections taken immediately above the predentin-dentin border area in the region of the pulp cornu and were always seen at the junction of the mantle dentin and the circumpulpal dentin beneath the central developmental groove.

Notes: Microscopic studies of human adrenal glands from 58 autopsy specimens, ranging in age from one month gestation to 69 years, revealed a pertinent developmental pattern in the establishment of definitive zonation. This pattern was established using the following criteria: (1) relationship of age to the developing zones; (2) times of formation of definitive zonation; and (3) the morphological determination of developmental patterns based on staining characteristics.Using these criteria, development was divided into five phases: (1) condensation of coelomic epithelium; (2) secondary proliferation of coelomic epithelium; (3) finding of PAS-positive material within the fetal cortex; (4) decline and disappearance of the fetal cortex; and (5) establishment and stabilization of the definitive zonular patterns.Significant features occurring in this development were: (1) the origin of both permanent and fetal cortex from proliferation of coelomic epithelium; (2) the appearance of PAS-positive granules surrounding a homogenous mass in the fetal cortex and the zona reticularis during maturation and organization; and (3) the gradual establishment of definitive zones by proliferation of the permanent cortex, maturation of the fetal cortex, and growth of the medulla; with the adult structure of the adrenal gland achieved by the eleventh to fifteenth year without any apparent major involution or hemorrhage.

Notes: The mesothoracic leg discs of the blowfly, Sarcophaga bullata (Parker) were studied by electron microscopy during the third larval instar. As the peripodial membrane and separation form, the cells of the disc become elongated and perpendicularly oriented toward the separation. The cellular organelles do not undergo significant changes until the late third instar. At this time, there is a significant increase in the amount of granular endoplasmic reticulum and in the number of inclusions, particularly in those cells located more deeply in the disc. Nucleolar enlargement and an increase in the number of mitochondria are also observed at this time.The cells at the border of the disc form a columnar epithelium whose surface develops microvilli-like projections. These projections. These projections reach their maximum development towards the end of third instar.It is suggested that some of the observed changes may represent a phenotypic expression of secretion of cuticular material.

Notes: Neurosecretory activity and fine structure of the supraesophageal and optic ganglia of Daphnia schødleri Sars were studied. The relative amount of paraldehyde fuchsin stainable material present was determined at “daylight” and at one and three hours following for animals maintained under photoperiods of 7.5, 10.5, 13.5, and 16.5 hours. More material was found after one hour in both ganglia and there was a tendency for more in the optic ganglion under 7.5- and 10.5-hour photoperiods.Sections made at two levels in the supraesophageal ganglion and one level in the optic ganglion were examined with an electron microscope. Posterior and anterior parts of the supraesophageal ganglion contain apparent nerve processes at the edge of the ganglion, parallel to the anterior-posterior axis; these have large granules. Neurons in both areas contain patches of presumed polysaccharide granules. In the posterior region are a dorsolateral and a ventrolateral glandular cell, presumably these occur on both sides of the brain. They have very well-developed endoplasmic reticulum and some large granules. The dorsal cell is usually at the tip of a glial attenuation.Concentric lamellar systems are located in dilated nerve processes of the first optic ganglion neuropile. Large whorls (about 3.5 μ) are composed of concentric lamellae. When lamellae do not form complete rings, they end in loops or in dilated tubules that are sometimes constricted as vesicles. Small whorls (1.5 μ) typically have lamellae joined into two or three thick layers. Mitochondria are frequently associated with the whorls. It is proposed that the whorls are active in synthesis, possibly neurohumor production.

Notes: In the spiroboloid millipeds the male gonopods develop from rudiments of both pairs of legs of the seventh body segment. They are first evident as “lumps” on the sternum of the seventh segment following the molt to instar 5; they replace the functional walking legs of the seventh segment of earlier instars. These “lumps” go through progressive morphological changes in each instar until they attain the adult form. It is evident that in the spirobolid millipeds the gonopods do not develop as a gradual modification of functional walking legs; rather they pass through a progressive growth and differentiation of their own.

Notes: A total of 1125 normal chick embryos, representing 25 each of the 45 stages of Hamburger and Hamilton, were removed, fixed in Bouin's solution, stored in 70% ethanol and weighed with a semi-micro analytical balance. Entire blastoderms of stages 1-8 were weighed, whereas only embryos-proper were weighed in stages 9-45. As a consequence, results constituted two groups, each of which showed a geometric rate of growth marked only by minor deviations which were related to specific events of normal growth and development.

Notes: Estimates of the number of ganglionic neurons of superior cervical sympathetic ganglia and the number of preganglionic axons in the trunks just caudal to these ganglia were obtained from a sample of primates that included: man, chimpanzee, baboon, stump-tailed macaque, rhesus monkey, and squirrel monkey. The number of ganglionic neurons ranged from 63,625 in a squirrel monkey ganglion to 1,041,652 neurons in a human ganglion. Estimates of the number of preganglionic fibers varied between 2,285 in a cervical sympathetic trunk of a squirrel monkey and 12,008 in a human specimen. The resulting ratios of preganglionic fibers to ganglionic neurons ranged from 1:28 in a squirrel monkey ganglion to 1:196 in a human ganglion.The data reported in this study reveal considerable variation in the ratio of pre- to post-ganglionic neurons, and as was noted in regard to the number of cells in the ganglion, the ratios of ganglionic to preganglionic neurons appear to increase as a function of body size. In contrast, the number of preganglionic fibers does not increase as strikingly with body size, but varies greatly in the same species. The resulting ratio between the two orders of neurons is, therefore, less predictable than the number of ganglionic neurons in any given ganglion.

Notes: The volumes of a sample of primate superior cervical sympathetic ganglia were measured and related to body weight and to the number of ganglionic neurons. Estimates of volumes of the ganglia varied between 1.956 mm3 in squirrel monkey and 173.530 mm3 in a human specimen. Average cell densities for the ganglia ranged from 4,455 cells/mm3 in a human ganglion to 32,528 cells/mm3 in a squirrel monkey ganglion. Mean cell territories varied from 0.0000307 mm3 in a squirrel monkey ganglion to 0.0002245 mm3 in a human ganglion.Analysis of the data reveals striking trends of correlation between body size, volume of ganglia, and average cell territories. Since similar correlations have been described for other types of neuronal cell aggregates, it is suggested that for any given nucleus, ganglion or cortical area, the neuronal packing density varies as a function of body size.

Notes: Electron microscope observations on the differentiating Drosophila eye show an extensive proliferation of parallel arrays of microtubules at periods preceding, or coinciding with, alterations in cellular morphology. In the retinular cells they are aligned in the direction of elongation and close to the developing rhabdomeres, forming a cylinder around the central ommatidial axis. At a later stage, in the cone cells, they are aligned in the direction of cellular contraction. Thus as in other developing systems microtubules appear to be directly involved in the morphogenesis of the Drosophila eye. In the retinular cells they gradually disappear during elongation, whereas they persist in the cone cells. The pigment cells contain few of these structures. The distribution of two types of specialised cell attachments, adhering zones and septate desmosomes is discussed in relation to intercellular morphogenesis and communication. The rhabdomeres originate from infoldings of the plasma membrane which later grow out into typical microvilli. Unusul cytoplasmic granules are described in the pigment cells of early pupae.

Notes: The structure of the cellular cyst which encapsulates the parasitic copepod, Scolecodes huntsmani, in the subendostylar blood vessel of the ascidian, Styela gibbsii, is described from light and electron microscopic studies.The cells comprising the cyst are contributed by the ascidian. The cells are columnar, contain large central reservoirs of glycogen and lipid, and have a conspicuous Golgi apparatus, many small cisternae of smooth endoplasmic reticulum and peripheral mitochondria. The cells are held together by complex basal interdigitations and a short apical zonula occludens. Long cilia emerge in circular clusters from the cell apices and beat in the lumen of the cyst. As atypical of a columnar epithelial layer, the nuclei are staggered in position in the cells and there is no basal lamina. One end of the cyst is blind, but the other end, which may be either anterior or posterior with respect to the longitudinal axis of the host, narrows to a profusely ciliated duct which opens through the wall of the blood vessel to the atrium of the ascidian by a ciliated funnel. The effective beat of the cilia of the duct and the funnel is outward toward the atrium.The first nauplii of the copepod emerge from the incubatory pouch of the adult and pass to the exterior sea water through the cyst funnel and the atrium and atrial siphon of the ascidian. As in other notodelphyid copepods, the life cycle of this incarcerated form also involves free-living naupliar stages followed by two free-living copepodid stages. The provision of an egress for the first nauplii is, therefore, important to the survival of the species.The adult females of Scolecodes, which range in length from 2 to 14.6 mm, are sluggish when removed from the cyst and fail to survive in sea water for more than 24 hours. The males, which have only been obtained when parasitic fifth copepodids molt in culture, are much smaller, averaging 0.8 mm, and are very active. Since one dead male has been found inside the cyst of an adult female and females are often found with attached spermatophores, it is suggested that the funnel of the cyst may also serve as an entrance for the males.Evidence is presented for the formation of the cyst as an accumulation of totipotent lymphocytes around the copepod. Cysts of parasitic developmental stages (third through fifth copepodids) are also described. All of these cysts and those of immature adult females lack funnels to the atrium. The funnel of the cyst of mature females is formed, in part, by modified cells of the wall of the blood vessel, but is induced after the major portion of the cellular cyst has been formed.Cells in the general circulation of the ascidian and those inside the lumen of the cyst are compared. The cells in the lumen of the mature cyst do not arise by diapedesis of blood cells from the subendostylar blood vessel, but by conversion and migration of cells composing the cyst proper. These cells have been found in the guts of the copepods and they may serve as a nutritive source.The ascidian appears not to be harmed by the association, but the copepod gains in many ways.

Notes: Autoradiographic studies combined with digestion tests of incorporated 3H-uridine showed that the peripheral nerve of Triturus contains ribonucleic acid. Localization studies revealed the presence of RNA in the axon, in the myelin and Schwann sheath, and in the Schwann cell body. Similar experiments on nerve separated by transection from its neuronal cell bodies yielded the same results. They showed that RNA of the nerve can be synthesized without the intervention of the neuronal cell body. The results strongly suggest that the radioactive substance, precursor or RNA, is transported inward from the Schwann cell to be deposited in the myelin sheath and axon. The route of passage and the possible sites of origin of the RNA in the nerve are discussed. A significant role is suggested for the Schmidt-Lantermann cleft because of its relations with the adaxonal layer of Schwann cytoplasm and with the myelin leaflets.

Notes: The respiratory organs of Amphipnous cuchia comprise a pair of aicsacs, vestigial gill filaments borne on second gill arch and vascular folds of the third gill arch. The volume of each air-sac, its surface area and its reltionship with the body weight of the fish have been determined. The air-sac is lined by a respiratory mucosa which is composed of vascular and non-vascular areas. Each vascular area, called here the ‘respiratory islet,’ studded with hundreds of vascular rosettes, which are formed of collagenous material and supported by endothelial cells. Pilaster cells are absent. The ‘islets’ are covered over by a single layer of squamous type of epithelial cells.The non-vascular areas (lanes') are the stratified part of the respiratory epithelium and contain a large number of mucous glands which secrete mainly acid mucopolysaccharides.The vascularisation of the gills have been studied by India ink injection methods. The secondary gill lamellae are absent, their place being taken up by coiled vascular loops.A quantitative estimation of haemoglobin in blood of ‘cuchia’ and other air- and water-breathing fishes have been made by colorimetric method and the results have been discussed in relation to their habit and habitats. The cranial muscles which are involved in respiration of ‘cuchia’ and the mechanics of muscle action in breathing have been described.

Notes: The sequence of events in posterior regeneration of the polychaete, Nephtys, has been examined in histological preparations from the fifth day to the end of the third week after amputation, that is from the time when wound healing is complete until several new segments are differentiated. The pygidium forms and begins to differentiate prior to segmentation. The first indication of each new segment is the appearance of a large pair of segmental blood vessels which arise from the vascular complex in the gut wall. Associated with these are fibroblasts, the anlagen of the new septum. Epidermal derivatives develop subsequently, appearing first ventrolaterally, close to the regenerating nerve cord. The mitotic rate appears to be highest prior to the period of maximum segment formation. Visible cell differentation follows, and subsequent growth of segments is primarily by cell enlargement. It appears likely that the blood-vascular system associated with the gut and the regenerating nerve cord, both of which are disproportionately large in the regenerate, are important for the initiation of new segments.

Notes: Adaptive explanations for the temporal fenestration in reptiles are briefly reviewed. With few possible exceptions, fenestrate appeared first in the reptiles, and have seemingly evolved independently in several different phyletic lines.The several explanations for fenestration offered by previous authors include speculations that open spaces in the skull permitted bulging of the jaw-closing muscles, and that fenestrae formed in areas of reduced stress where the presence of bone would be functionally useless. The first of these does not readily apply to initial evolutionary stages; the second is more satisfactory.Certain features of muscular attachments to bones are dealt with, and their implications applied to the fenestration problem to add another possible explanation (which need not contradict previously published suggestions).Considerations of cranial strength in tetrapod skulls led to speculations on the lack of fenestration in temnospondyls, anthracosaurs, microsaurs and cotylosaurs.Emargination of the skull roof in turtles is also discussed.

Notes: The down feather of the chick embryo has been examined by electron microscopy during three distinct stages of its early development; the presumptive stage, represented by dorsal skin of an area from which the feather organ will arise; the thickening stage, during which areas of the basal epidermis form spurs projecting into the mesenchyme, and the latter condenses under a thickened area of the epidermis; the elevation stage, at which time the basal epidermis flattens, the entire epidermis increases in thickness, and the underlying mesenchyme becomes more compact.As development proceeds the rough endoplasmic reticulum of the epidermal cells dilates, but during the elevation stage begins to flatten, and Golgi is observed with increasing frequency. The mitochondria do not appear to differ except for those in the periderm during the presumptive stage, in which case they reveal a vacant matrix and irregular cristae.Evidence is presented for actual contact between basal epidermal spurs and filopodia of cells within the mesenchyme, some of which contain numerous vesicles. The basal epidermal spurs are also seen in intimate association with collagen and anchor filaments and a network of reticulin.Evidence is also presented for the presence of neuronal elements within the mesenchyme during the thickening stage. Cross sections of cell processes within the condensations of the mesenchyme resemble unmyelinated nerve fibers, and cross sections of filopodia similar to arborizing axons abound at and within the basal lamina of both the thickening and elevation stages. Further support for the presence of nerve fibers within the mesenchyme comes from positive staining results with Bodian's and Ungewitter's methods.This comparative study of three stages of early development of the feather organ serves as a basis for more detailed investigations of each stage.

Notes: A fluorocarbon copolymer of chlorotrifluoroethylene (96%) and vinylidene fluoride has been isothermally crystallized and the quenched films analyzed by the light microscope, photographic light-scattering, and density measurements. Above a supercooling of 79°C., homogeneous nucleation dominates, giving a morphology that appears to be that of a twisted ribbon. At supercoolings below 79°C., heterogeneous nucleation dominates and leads to spherulitic morphology. Sheaf or rodlike morphology occurs at very low supercoolings. Crystallization rates determined from density measurements at room temperature indicate maximum rate due to heterogeneous nucleation occurring at a supercooling greater than 79°C., but the temperature for maximum rate cannot be identified because of the transition to homogeneous nucleation which causes a discontinuity in the rate versus temperature curve. Superposability of crystallization isotherms constructed from density values are inconsistent with the large melting point lowering from that of polychlorotrifluoroethylene for this copolymer. However, this may be explained by the presence of a different crystal system for each monomer in the copolymer.

Notes: The spherulitic growth data that exist in the literature for a wide diversity of polymers have been analyzed according to various possible nucleation mechanisms. It is demonstrated that, if allowed a reasonable choice for the equilibrium melting temperature, no unbiased selection of a unique nucleation process can be made. Moreover, a set of universal parameters exists for each of the allowable nucleation processes which enables the data to be represented by a single straight line which encompasses all the polymers. The only quantities specific to a given polymer are the equilibrium melting temperature and the activation energy for transport. The magnitude of the latter quantity is shown to be dependent on the glass temperature of the polymer.

Notes: Polyoctadecene-1, as isolated from a Ziegler-type polymerization, was examined by density and refractive index measurements and by differential thermal analysis. Two main transitions were observed, their sharpness suggesting that they are both first-order. Extraction with n-hexane at 25°C. separated the polymer into two almost equal fractions, each showing essentially one of these transitions. Transition temperatures were compared with those of certain other polymers having long n-alkyl side chains. From this comparison, and from the findings of other workers, it was concluded that the polymer of lower transition temperature is atactic polyoctadecene, in which the side chains only participate in crystallization, whereas the polymer of higher transition temperature is tactic polyoctadecene, in which crystallization involves both the main chain and side chains.

Notes: On the basis of an isoviscosity criterion for the glass transition (ηg ⋍ 1013 poise) in liquids of low molecular weight, theoretical Tg values were calculated for the n-alkane series by the equation log η = log A + B/(T - T0), with the use of values reported by Lewis for the parameters. The Tg/T0 ratio reaches a limiting value of 1.25 and φg = (Tg - T0)/2.3B = 0.027, a constant. Extrapolation to (CH2)∞ gives Tg = 200°K., T0 = 160°K., and B = 640°K. This Tg is consistent with other estimates for poly-ethylene, and T0 coincides with the temperature at which the “excess” liquid entropy for (CH2)∞ becomes zero from thermodynamic data. For polymer liquids it is proposed that E0 = 2.3RB is determined by the internal barriers to rotation for the “isolated” polymer chains. Thus, E0 = 2.9 kcal./mole for polyethylene, 3.0 kcal./mole for polystyrene, 5.7 kcal./mole for polyisobutylene, and 1.9 kcal./mole for polydimethylsiloxane.

Notes: The ESR spectra of peroxy radicals in irradiated powders and oriented samples of polytetrafluoroethylene (PTEE) have been measured with a K-band spectrometer, and the principal values and directions of the g tensor were determined both at room temperature and at 77°K. In contrast to the spectra of the usual peroxy radicals, those trapped in γ-irradiated PTFE exhibited an ESR spectrum apparently having a larger principal value for g⊥ than for g∥ when measured at room temperature, although the normal principal values were observed at 77°K. As for the directions of the principal axes, g∥ was directed along the chain axis at room temperature and was perpendicular to the chain axis at 77°K. From the temperature change of the g tensor and the line shapes in the oriented samples, it is shown that the observed temperature change of the spectra is due to rapid rotation at room temperature around the chain axis rather than around the C—O bond axis. Assuming this, the apparent principal values of the g tensor at room temperature were calculated from the g tensor obtained at 77°K. for the rigid state, and the results are in good agreement with observations at room temperature. A structure for the peroxy radicals is also proposed. In addition, the spectral line shape function for the uniaxially oriented samples has been derived.

Notes: Theoretical and experimental evidence is put forward to prove that the determination of the phase-volume ratio as a function of temperature and concentration is a sensitive and simple means of determining the liquid-liquid critical state. Knowledge of the critical conditions permits very accurate calculations of the interaction parameter g in the free-energy function. In experiments with polystyrene-cyclohexane, g was found to depend on the concentration. The value of g and its concentration dependence agree very well with the results of osmotic measurements by Rehage and Palmen. In experiments with polyethylene-diphenyl ether, g proved to be independent of concentration in the range of measurement. The temperature function was found to be: g = -0.6086 + 482.2/T (at 137-148°C.). Gibbs' expressions for the critical conditions were worked out for a free-energy relation in the form of an extended Flory-Huggins function.

Notes: Cloud-point curves (CPC) were calculated on the basis of the Flory-Huggins free-energy relation for various hypothetical polymer samples dissolved in a single solvent. Molecular weight distributions varying widely in shape and width were examined. The shape of the CPC reflects details of the molecular weight distribution. This appears from the location of the critical point on the right-hand branch of the CPC. The latter often shows a depression, which becomes more distinct as the Mz/Mw value increases. These theoretical results were confirmed experimentally with the system polyethylene-diphenyl ether. With the aid of the theoretical data collected it was possible to explain the remarkable agreement between the θ temperatures determined by light-scattering and by the Shultz-Flory method. The latter method is basically incorrect, since it identifies the polymer solution with a binary mixture. An explanation could also be given for the empirical relation which McIntyre et al. recently found between the shape of the top of the CPC and the width of the molecular weight distribution.

Notes: The electric birefringence of sodium polyethylenesulfonate in water has been studied. For a low molecular weight fraction, the electric field dependence followed the Kerr law quite closely. For a higher molecular weight fraction, the specific Kerr constant was much larger, and pronounced saturation of the electric birefringence was observed in fields of 15 kv./cm. The specific Kerr constant increased with decreasing polyelectrolyte concentration in pure water. On the other hand, it decreased on isoionic dilution. The saturation effect was the more marked, the lower the polyelectrolyte concentration. The saturation behavior resembled that of permanent dipole orientation, but this mechanism was not supported by the build-up of the birefringence. The magnitudes of specific Kerr constants of various types of macromolecules in solution are tabulated and discussed.

Notes: The results of measurement of the shear and tensile creep compliance of poly(methyl methacrylate) between -150 and 75°C. are presented. The master curves show the creep behavior from essentially elastic response to the onset of the α-process. The logarithmic retardation spectra and shear loss compliance reveal two molecular processes, one process being partially obscured by the α-process and therefore not as well defined as the other. These processes manifest themselves as breaks in an Arrhenius plot of the shift factors at about -35 and +25°C. The activation energies in the -35 to 25°C. and 25 to 80°C. ranges are 17.8 kcal./mole and 42.2 kcal./mole, respectively. The former temperature range and activation energy corresponds to the well-known ß-process in poly(methyl methacrylate), the latter to a process which is apparently detectable using various long-time experimental techniques but whose molecular interpretation is at present obscure. The activation energy in the -150 to -35°C. range is about 8.7 kcal./mole.

Notes: Nuclear magnetic resonance of poly-β-alanine samples differing in solubility in water was studied over a wide temperature range as part of an investigation of their physical properties. Water-soluble poly-β-alanine has more branches and a lower degree of crystallinity than water-insoluble poly-β-alanine. NMR spectra of poly-β-alanine show one component at 77°K. which splits into two components, broad and narrow, at room temperature. Two transition regions were observed in curves for line width and second moment versus temperature. The higher transition temperature, corresponding to the glass transition of the polymer, appears to decrease with increasing water content. The second moment for the water-soluble polymer differs from that of the water-insoluble polymer at 77°K. This is interpreted in terms of the difference in the degree of crystallinity of the polymers.

Notes: Viscoelastic properties of four linear and three very lightly crosslinked polybutadienes (microstructure about 50% trans) were studied. Of the latter, two had not reached the gel point, and their molecular weight distributions were determined by sedimentation velocity analysis; the third was crosslinked just past the gel point, with only 32% gel fraction present. The crosslinking agent was sulfur. Complex shear compliances were measured over a frequency range from 0.1 to 1000 cps at temperatures from -70 to 30°C. with a Fitzgerald transducer and a Plazek torsion pendulum; and torsional creep measurements were made over time periods up to about three days. The creep data were converted to the corresponding dynamic viscoelastic functions at very low frequencies by conventional approximation methods. All data were reduced to 25°C. by shift factors calculated from a previously adopted equation of the WLF form. In the transition zone, the viscoelastic properties of linear samples were almost independent of molecular weight. The entanglement spacing, derived from the minimum in the loss tangent and the inflection in the storage compliance, was 130 to 160 chain atoms. The maximum in the retardation spectrum attributable to motions of individual network strands was closely similar to the corresponding maxima for more highly crosslinked vulcanizates previously studied, showing that even in the latter it is associated with entanglement network strands rather than strands between chemical crosslinks. For a linear sample with molecular weight 180,000, the retardation processes disappear at times beyond about 10 sec. at 25°C. With crosslinking short of the gel point (i.e., branching) the slow retardation processes are enormously increased and prolonged to longer times. With further crosslinking through the gel point and beyond, the slow retardation processes decrease progressively in magnitude. Qualitatively, this behavior resembles the sharp maximum in content of highly branched and aggregated molecular species which is predicted at the gel point by crosslinking statistics; but the slow processes (or low-frequency losses) persist farther past the gel point than would be expected on this basis. The steady-state compliances of the linear samples were smaller, but for a sample crosslinked short of the gel point were much larger, than the prediction of the Rouse theory modified for molecular weight distribution.

Notes: The temperature dependence of the intrinsic viscosity [η] for the system polystyrene-cyclohexane in the interval -20 〈 (T - ψ) ≤ 0 near the ideal temperature ψ has been investigated. The observed diminution in size of the molecular coil with decreasing temperature is attributable to attractive net polymer-solvent interactions, denoted by negative values for the excluded volume parameter z. The data thus comprise an interesting selection for comparison with the predictions of various excluded volume theories. Among the approximate, closed-form expressions the functional relationship of Flory (x5 - α3 ∼ z) appears to describe best the variation of [η] with temperature in the region examined. The behavior of the Huggins constant k′ derived from the intrinsic viscosity plots is also examined, in accordance with the Peterson-Fixman model, suitably extended to the temperature region below ψ.

Notes: The product of the thermal polymerization of ß-carboxymethyl caprolactam has been identified as a poly[(2,6-dioxo-1,4-piperidinediyl)trimethylene]. An indication of various chain conformations has been explained by the possible existence of two different conformations of the dioxopiperidine moiety. One conformation pertains to an equatorial position of the trimethylene moiety with respect to the plane of the imide group. The other is derived from a structural unit in which the trimethylene group is positioned axially to the plane of the ring. While the former conformation has been ascribed to the crystalline modification the latter appears to be the predominant structure of the polymer in formic acid solution as indicated by NMR analysis. In the glassy state the macromolecule is assumed to be composed of segments of either conformation. The unoriented linear polymer crystallizes upon annealing in positively birefringent spherulites. A triclinic unit cell with the following parameters: a = 9.64 A., b = 11.32 A., c = 15.80 A., α = 98°, β = 96°, γ = 114° has been found to contain eight structural units. The calculated density, 1.30 g./cm.3, agrees with experimental data. A crystal structure is proposed on the basis of the x-ray data.

Notes: 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.

Notes: The results of an investigation of the viscoelastic and thermal properties of the gelatin-glycerol system are presented in the form of a complete temperature-composition diagram. This diagram shows the isochronal (10-sec.) mechanical behavior of the system along lines of constant modulus and thereby affords a convenient assessment of variation in viscoelastic behavior along any isotherm or isopleth of interest. Comparison of the results with previously obtained limited sets of data on a number of other polymer-dilent systems indicates the applicability and utility of such a presentation.

Notes: It is reported that mats formed by the sedimentation of single crystals of methyl- and ethyl-branched polyethylene exhibit strength and ductility comparable with that of melt-crystallized films. In fact, in the case of methyl-branched polymers, extensions of up to 50× were obtained on cold drawing. Observations on separate crystals suggest that this extension is due to the pulling out of individual lamellae. In view of the magnitude of the extension, this implies unfolding of the molecules. That considerable coherence can be obtained without original molecular ties between crystals is of significance as regards the molecular interpretation of the strength and ductility of crystalline polymers.

Notes: The unperturbed mean-square end-to-end distance 〈R02〉 and its temperature variation d In 〈R02〉/dT for isotactic polypropylene have been estimated from intrinsic viscosity data in three theta solvents, i.e., diphenyl, diphenyl ether, and dibenzyl ether, measured at their θ temperatures as determined by precipitation temperature measurements. The characteristic ratios, 〈R02〉/nl2, where n is the number of bonds of length l in the main chain, evaluated by assuming Φ = 2.87 × 1021, are 5.80 in diphenyl (at θ = 125.1°C.), 5.41 in diphenyl ether (at θ = 142.8°C.), and 4.56 in dibenzyl ether (at θ = 183.2°C.). These values lead to the temperature coefficient d In 〈R02〉/dT = -4.09 × 10-3 deg.-1 Results are compared with the data previously reported on polyethylene.

Notes: When cellulose triacetates and some hydrolyzed acetates are boiled in 2.5N hydrochloric acid there is no residue. Under the same conditions cellulose is hydrolyzed, and a residue is obtained with a limiting viscosity that is related to the average length of the cellulose crystallites. These findings are combined to develop a method for studying the progress of acetylation through the amorphous portion of cellulose and into the crystallites, and to investigate the relative reactivities of cellulose I and cellulose II. Acetates were made from cotton and wood cellulose by a “fibrous” (heterogeneous) esterification involving sulfoacetic acid or perchloric acid catalyst in acetic acid-acetic anhydride; the final acetyl contents (10-41%) were attained by stopping the reaction at various points short of the triester (rather than by hydrolyzing a triester). When these acetates were boiled in 2.5N HCI they did not disappear completely, and the residues were cellulose I, indicating that cellulose acetate had been removed. With increasing acetyl the yield of residue decreased, and beyond about 33% acetyl the viscosity and x-ray measurements showed that the length and width of the crystallites decreased. However, when a nonsolvent such as toluene was added to the acetylation medium, the limiting viscosity did not change over the same acetyl range (up to 40%). Samples of varying acetyl values were taken during a regular acetylation of cotton linters in a mixer with sulfuric acid catalyst. X-ray studies of the residues obtained by boiling the acetates in 2.5N HCI revealed the presence of unreacted cellulose I even after 40% acetyl had been reached. This explains why the manufacture of cellulose esters from cellulose I requires complete esterification before they are hydrolyzed to the desired acetyl level. It was shown that there is a distinct difference between the acetylation reactivity of cellulose I and cellulose II. This indicates the importance of avoiding cellulose II formation during the refinement of cellulose for the manufacture of cellulose acetate in a process involving activation with acetic acid.

Notes: The phase equilibria in polymer-liquid 1-liquid 2 ternary systems have been calculated on the basis of the Flory-Huggins theory of polymer solutions. A new approximation method based on the “cluster” concept has been introduced for mixed solvents comprising a solvent and a nonsolvent. This concept has been verified with polystyrene-solvent-methanol systems.

Notes: Highly crystalline polycaprolactam was prepared by zone polymerization of ε-caprolactam. Folded-chain crystallized and annealed, melt-crystallized, and solution-crystallized polycaprolactam was produced from commercial polycaprolactam. All samples were characterized by x-ray diffraction, electron microscopy, density measurement, and heat of fusion measurement. The determination of the time-dependent melting by DTA and scanning calorimetry revealed that all the different morphologies show different melting behavior. Zone-polymerized polycaprolactam superheats, and the other morphologies reorganize on heating to different degrees. Densities and heat of fusion vary in the same manner - from highest to lowest - in the order: zone-polymerized, solution-crystallized, annealed, and melt-crystallized. An estimate of heat of fusion, equilibrium melting point, and surface free energy was obtained from the melting points.

Notes: Precise heat capacity values are reported over the temperature range from 10 to 360°K. for a sample of atactic polystyrene having a narrow molecular weight distribution. This sample was taken from the stock from which National Bureau of Standards Standard Sample 705, Narrow Molecular Weight Distribution Polystyrene, was established. Data are reported for the sample as received, and after an annealing procedure. At temperatures below about 60°K. a systematic difference comparable with the limits of experimental precision appears between the values obtained for the present sample as received and after the annealing, although at higher temperatures the values for the two conditions showed no systematic difference beyond the limits of precision of the measurements. At temperatures above 100°K., previously published values for atactic polystyrene samples of various molecular weight distributions and for isotactic polystyrene agree within about 0.5% of the values from this investigation. At temperatures below 100°K. significant heat capacity differences appear, especially between values for the atactic and the isotactic isomers, and even between atactic samples of different molecular weight distribution.

Notes: The mechanical effects of association between pendant ionic groups are investigated in series of butadiene-lithium methacrylate copolymers, butadiene-methyl (2-methyl-5-vinyl)-pyridinium iodide copolymers, and mixtures of these polyelectrolytes. Thermal and mechanical tests reveal a new transition above Tg in the pyridinium copolymers, designated Tt*. Below this temperature the materials behave like covalently crosslinked elastomers. The complex between the metal carboxylates appears thermally dissociable at all temperatures. The mixing of the oppositely charged polyelectrolytes leads to the formation of more stable intermolecular pyridinium carboxylate links.

Notes: The vibration frequencies of a polyethylene crystal lattice have been computed for various structures in which a fully deuterated chain is mixed with a normal chain. Intermolecular potential functions previously developed by the authors were used in the calculation. It is shown that such structures make it possible to distinguish experimentally between chain folding in the (110) plane and folding parallel to the (100) plane. Calculations have also been done for a regular polymer of (CH2CD2). Such a structure would permit the determination of the parity of the number of methylene groups in the fold.

Notes: With an increasing gradient, the intrinsic viscosity of a high molecular weight polyisobutylene (M̄n = 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.

Notes: Depolymerization of amorphous polyacetaldehyde has been studied by measurements of weight loss versus time for thin films of the polymer in vacuum. Temperatures ranged from 40 to 80°C. The samples were prepared by freezing or melting the monomer in contact with treated glass surfaces. Light scattering, osmometry, and intrinsic viscosity measurements were used to characterize the polymers. Depolymerization rates were between second and third order with respect to the unvolatilized fraction, and the activation energy was 26.3 kcal. Much of the evidence points toward a slow unzipping reaction at the chain ends, but the analysis seems to be complicated by structural variations among the samples.

Notes: Phase relationships of isotactic polypropylene in various organic diluents were investigated. The diluents used were aliphatic alcohols, alkyl phenols, aryl phenols, diphenyl derivatives, alkyl aryl ethers, esters, and others. Among the diluents examined, n-butyl alcohol, p-tert-butyl phenol, p-tert-amyl phenol, diphenyl, diphenyl ether, benzyl phenyl ether, dibenzyl ether, and benzyl propionate were found to be theta solvents for isotactic polypropylene at temperatures in the range 120-190°C. For these theta solvents, the thermodynamic interaction parameters were determined. The results are discussed in relation to the type of diluent.

Notes: Droplet experiments have been performed on polybutene-1. It was found that this polymer can be cooled to room temperature without homogeneous nucleation of crystallization. It was also found that when the polymer was heterogeneously nucleated, form I (as well as form II) could be crystallized directly from the melt. The melting point of droplets crystallized in form I near room temperature decreased with increasing crystallization temperature, while the melting point of the droplets crystallized in form I at the highest temperatures increased with increasing crystallization temperature. There was a broad minimum at about 60°C. in the melting point versus crystallization temperature curve.

Notes: Time-temperature superposition can be successfully applied to both the stress relaxation and dynamic mechanical properties of oriented PET fibers. Two curves result; one is the time dependence of the modulus at constant temperature, while the other is the shift, log aT, of this curve along the time scale as a function of temperature. This temperature dependence is less than that for both unoriented PET and typical amorphous polymers above Tg. It is about the same as that for oriented nylon 66 and unoriented glassy poly(methyl methacrylate). The isothermal modulus has the same time dependence as that of the unoriented PET; however, it is a factor of 3.3 larger. The modulus curve is almost identical in both shape and magnitude with that of oriented nylon 66. However, a temperature of 82°C. is required to place the viscoelastic dispersion region of PET at the same time scale as nylon 66 at 25°C. This temperature increase is the major difference in viscoelasticity between these two oriented polymers.

Notes: Crosslinked samples of polyethylene were prepared by electron irradiation of both high- and low-density polymers in the crystalline state. A further crosslinked sample was obtained by curing a high-density polyethylene by reaction with dicumyl peroxide at 180°C. The stress-strain-birefringenece relations were obtained on specimens cut from these samples at temperatures between 130 and 250°C. All samples showed a substantial decrease in stress-optical coefficient with increasing degree of crosslinking and with increasing temperature. The stress-optical properties at each temperature were extrapolated to zero degree of crosslinking to give quantities characteristic of the Gaussian network. Comparison of these properties with the theory of networks of rotational isomeric chains with both independent and interdependent rotation allows estimates to be obtained for (1) the trans-gauche energy differences in rotation around skeletal bonds and (2) the difference in principal optical polarizabilities for the CH2 group in the elastomeric state. This latter quantity is shown to be more nearly given by Denbigh's than by Bunn and Daubeny's bond polarizability values.

Notes: A theory is developed that describes the diffusion of solute into the gel particles during a gel permeation chromatographic experiment. The particles are treated as homogeneous spheres of radius a, into which diffusion takes place with diffusion coefficient Ds. The concentration in the mobile phase at any level at any time is supposed to be uniform throughout the cross-section of the column. It is shown that in the usual columns the effect of diffusion in the mobile phase is unimportant. A determinative quantity in the process is the parameter a2/Dst, where t is the time. For large values of a2/Dst an explicit expression for concentration versus time in the mobile phase at the end of the column is derived [eq. (26) and Fig. 1]. It shows a relatively long tail at large efflux volumes V, where the concentration varies at V-3/2. For arbitrary values of a2/Dst the first three moments of the concentration versus time curve are calculated [eqs. (33)-(37)]. Pronounced skewness of the curve is found unless a2/Dst is small.

Notes: 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.

Notes: A comparison is made between measurements on polystyrene solutions and the relaxation characteristics and intrinsic birefringence and viscosity given by the theory for the flexible Gaussian chain of variable number of segments and with internal viscosity and internal hydrodynamic interaction. This is done in order to determine the applicability of the theory to polymers over a wide range of molecular weights, including the low molecular weight range in which there may be conflict with the theoretical assumption of chains having a large number of segments. The longest, terminal relaxation time and the number of chain segments are determined from measurements of the frequency dependence of oscillatory flow birefringence while the intrinsic birefringence and viscosity are determined from steady flow measurements. The range of molecular weights studied is from approximately 900 at 106. It is found that the segment weight is approximately 1000 and the number of segments is in direct proportion to the molecular weight for the range from 1 to 1000 segments. The terminal relaxation time has a molecular weight dependence of the type given by the theory but with better agreement for higher molecular weights. While the measured dependences of the intrinsic viscosity and birefringence are in agreement with theory for molecular weights greater than 5 × 104, they deviate significantly for molecular weights below 1 × 104. The ratio of the intrinsic birefringence to intrinsic viscosity, which in theory is a constant independent of molecular weight, is found to change at the lower molecular weights.

Notes: Dielectric properties of four methacrylate polymers (methyl, ethyl, n-butyl and n-octyl) were studied in the frequency range 0.0001 cps-300 kcps at temperatures above and below the glass transition temperature and at various pressures up to 2500 atm. At temperatures well above Tg a single relaxation peak (α′ peak) was observed in the case of the higher n-alkyl methacrylates. However, this peak was split into two peaks, α and β, with decrease in temperature or increase in pressure. The molecular motions corresponding to the α and the β relaxation processes are the micro-Brownian motions of amorphous main chains and of flexible side chains, respectively. From the temperature and the pressure dependence of the average dielectric relaxation time of these polymers the single relaxation process (the α′ process) was attributed to the micro-Brownian motion of the main chain coupled with that of the side chain. The effects of temperature and pressure on the d.c. conductivity of these polymers were also studied.

Notes: The sedimentation of the system polystyrene-cyclohexane at the Flory temperature has been studied with emphasis on the effects of pressure as well as concentration. The relation between the molecular weight M and the limiting sedimentation coefficient s00, is found to be s00 = 1.50 × 10-15 M1/2 (sec.) The concentration dependence parameter ks has the form, ks = k′M1/2 = k″s00 with k′ = 4.5-5.5 × 10-4. However, a rather unexpected dependence of ks on the rotor speed is also found. A procedure is proposed for deducing solute molecular weight distributions from boundary spreading data in sedimentation transport experiments, a so-called “single concentration” method, requiring only one sedimentation run. Application to several polystyrenes (in cyclohexane at 35°C) with narrow, broad, and very broad distributions demonstrates the feasibility of the procedure. Comparisons are made with data from elution chromatography and gel permeation chromatography. The GPC method predicts somewhat broader distributions than those obtained by the other two methods.

Notes: The infrared spectra of isotactic polystyrene, polypropylene, and poly-p-chlorostyrene were measured in dilute solutions or gels at various temperatures ranging from room temperature to -100°C. For isotactic polystyrene and polypropylene, all the absorption bands characteristic of the helical conformation of the molecules increase in intensity with decreasing temperature, and show intensities at low temperature as strong as in the highly crystallized samples. This suggests that the molecules can assume very regular conformations even in solution. Similar temperature dependence of the spectra was observed for a homogeneous gel of isotactic poly-p-chlorostyrene, which is believed to be noncrystalline. These experimental facts lead to the conclusion that the stability of the TG type helical conformation of these isotactic polymers may be ascribed to the intramolecular forces within a molecule. The fact that these spectral changes are reversible has permitted a thermodynamic treatment of the conformational regularity in solution on the basis of the infrared data. The temperature dependence of the absorption intensities has been interpreted quantitatively by a simple statistical mechanical model, and the enthaply and the entropy differences between the helical and the random states of the monomeric residue in the molecular chain have been estimated.

Notes: The Huggins constant k′ in the expression for the viscosity of dilute nonelectrolytic polymer solutions, η = η(1 + [η] c + k′[η]2c2 + …), is calculated. For polymers in the theta condition, k′ is estimated to be 0.5 〈 kθ′ ≤ 0.7. For good solvent systems, the Peterson-Fixman theory of k′ has been modified; the equilibrium radial distribution function in the original theory is replaced with a parametric distribution for interpenetrating macromolecules in the shear force field. Comparison of the modified theory with experimental k′ for polystyrenes and poly(methyl methacrylates) of different molecular weights in various solvents shows good agreement. An empirical equation which correlates the Huggins constant k′ and the viscosity expansion factor αη for polymers has been found to coincide well with the modified theory.

Notes: An approximate closed expression for the excluded volume effect of linear polymer molecules is developed with the aid of a uniform expansion model of perturbed chains. The linear expansion factor α for the end-to-end distance is given by (α3 - 1) + (3/8) (α5 - α3) = (5/2)z where z is the excluded volume parameter. This equation is numerically close to the Ptitsyn equation in the ordinary range of α; i.e., for 1 ≤ α ≤ 2.

Notes: The effects of temperature and water on the crystal transition of nylon 6 from the γ phase to the α phase, which is caused by stretching along the chain direction, were investigated. The γ-phase fibers with high crystallite orientation were stretched at constant load under various conditions. An inversion of the effect of water on the transition occurs at about -60°C. Stretching in the wet state is more effective for the transition at higher temperature. In contrast, at low temperatures water in the crystalline regions actsasa cohesive agent for the chains and increases the activation energy for the transition. Thus, dry stretching is more effective than wet stretching at very low temperature. The fraction of transformed α-phase crystallites increases abruptly over a narrow range of stress. Thus the critical stress can be determined for the transition. The critical stress changes appreciably with temperature; the higher the temperature, the lower the critical stress. The relation between stretching temperature and critical stress was analyzed by Flory's equation for the shift of transition temperature by stress. About 220°C. was estimated as the zero-stress transition temperature. The heat content of the γ-phase crystal was estimated to be smaller by 500 cal./mole than that of the α-phase crystal. This result suggests that the free energy of the γ-phase crystal is lower than that of the α-phase crystal at temperatures lower than the transition point. The irreversible strain of a sample in which the crystal transition has taken place is very small at low temperature. This small extension of the sample is evidence that the γ → α transition produced by stretching along the chain axis is a crystal-crystal transition.

Notes: Measurements of the complex shear compliance have been made from 0.1 to 7 cycles/sec. and from -5° to 45°C. on several samples of natural rubber cross-linked by dicumyl peroxide in the presence of a diluent oil (volume fraction of rubber, v2, = 0.63 and 0.76) which was subsequently extracted. The properties of the extracted vulcanizates were compared with those having the oil still present and with those of conventional undiluted vulcanizates. Measurements of the diffusion coefficient of radioactively tagged n-hexadecane in trace amounts through the polymer structure were also made both before and after extraction of the oil. The diffusion coefficient was higher in the presence of the oil by an amount consistent with the Fujita theory for concentration dependence of diffusion rate based on free volume considerations. The low-frequency mechanical losses (reduced to 25°C. by the method of reduced variables), as measured by the loss tangent, were shifted to higher frequencies by the presence of oil to a much larger degree than would be expected from the difference in local mobility gauged by the diffusion coefficient. The equilibrium modulus, derived by extrapolation to zero frequency, was diminished by the presence of oil to a greater extent than the factor of v2⅓ expected from the simple theory of rubberlike elasticity. The low-frequency losses in the extracted vulcanizates were smaller than those in conventional vulcanizates with comparable degrees of cross-linking; the differences are attributed to differences in network topology.

Notes: Decay reactions of the free radicals produced in irradiated polyethylene (high-density and low-density materials) were examined in connection with the molecular motion of the matrix polymer. Three temperature regions, in which the free radicals decay very rapidly, at around 120, 200, and 250°K, were designated TA, TL, and TB, respectively. The decay of the free radicals at these temperatures had activation energies in high-density polyethylene of 0.4 kcal/mole for TA, 9.4 kcal/mole for TL, and 18.4 kcal/mole for TB. In low-density polyethylene these quantities were 0.7 kcal/mole for TA, 23.1 kcal/mole for TL, and 24.8 kcal/mole for TB. Comparison of time constants for the decay reactions and for molecular motion of the matrix polymer indicate that the decay in TA and TB is closely related to molecular motion in the amorphous regions of the polymer. The decay of the free radicals at TL in high-density polyethylene is due to molecular motion associated with local mode relaxation at lamellar surfaces, while that of low-density polyethylene is due to local mode relaxation in the completely amorphous region. Steric configurations of the free radicals which decay in the respective temperature regions were also investigated.

Notes: Drawn, nylon 66 yarns have been annealed in oil under relaxed conditions. Shrinkage and tensile modulus were measured and the yarns were examined by wide- and small- angle x-ray diffraction. The results are similar to those obtained by Dismore and Statton, but there are significant differences. The data indicate a model for a drawn nylon 66 fiber in which substantial amounts of folds remain.

Notes: The structure of the crystalline complex of poly(ethylene oxide) with mercuric chloride, whose composition is (CH2CH2O)4 · HgCl2, has been determined by x-ray diffraction. The unit cell is orthorhombic with the dimensions of a = 13.55 Å, b = 8.58 Å, and c (fiber axis) = 11.75 Å, and the unit cell contains 4 HgCl2 molecules and 16 CH2CH2O units. Four chains pass through the lattice and four monomeric units are contained in the fiber identity period. The space group is Ccmm-D2h17, Ccm21-C2v12, Cc2m-C2v16 or C2221-D25. The positions of Hg and Cl atoms have been determined by the Patterson function synthesized by the use of intensity data of the fiber sample, and the molecular conformation of poly(ethylene oxide) has been determined by examining the space not occupied by mercuric chloride molecules in the crystal lattice. The conformation of polyethylene oxide in the complex has been found to be the form of T5GT5G; that is, where G and G mean the right- and left-handed gauche forms, respectively. This molecular structure has been confirmed further by the results of the Fourier syntheses by using the more accurate data refined by the intensity measurements with a diffractometer on the powder sample. The bond length between Hg and Cl in the complex (2.30 Å) is a little longer than that of HgCl2 in the crystal (2.25 Å). This is consistent with the fact that the infrared absorption band associated with the antisymmetric stretching vibration of HgCl2 shifts to 353 cm-1 in the complex from 367 cm-1 in the crystal. It was also found that another type of complex, giving a different infrared spectrum and x-ray diffraction pattern, was obtained when the original complex was soaked much longer in a saturated ether solution of HgCl2.

Notes: GPC appearance volumes have been determined for a series of linear polyethylene, polystyrene, and polybutadiene fractions (Mw/Mn 〈 1.1) in trichlorobenzene at 130°C. and for the latter two series in tetrahydrofuran at 23°C. A polymer-type independent relationship between appearance volumes and the equivalent hydrodynamic radii of the polymer molecules has been demonstrated. The equivalent hydrodynamic radius is calculated from intrinsic viscosity data. It is proposed that this relationship can be used to construct a universal GPC calibration curve for polymers that assume a spherical conformation in solution. Methods for applying the universal curve to the determination of molecular weight averages and molecular weight distribution are described. In addition, a method is outlined by which the universal calibration curve can be empolyed for determining number-average Mark-Houwink constants from polydisperse samples.

Notes: Dilute solution viscosity and osmotic pressure measurements were performed on polystyrene (PS), polybutadiene (PB), polystyrene-polybutadiene (SB) diblock and polystyrene-polybutadiene (SBS) triblock copolymers. Anionic polymerization was used in such a way that the molecular weight of the PS block was kept constant (ca. 10 000), while the molecular weight of the PB block varied from 18000 to 450000. The measurements were carried out at a fixed temperature of 34.20°C in three solvents, namely toluene, a good solvent for PS as well as for PB, dioxane, which is a good solvent for PS and almost a theta solvent for PB, and cyclohexane, which is nearly a theta solvent for PS and a good solvent for PB. The compositions of SB and SBS, as derived from kinetic data agree with ultraviolet measurements in CHCl3 solutions. The viscosity and osmotic pressure results indicate that the properties of SB and SBS are similar. Their intrinsic viscosities and second virial coefficients can be calculated from their chemical compositions, molecular weight, properties of parent polymers, and values of the interaction parameter \documentclass{article}\pagestyle{empty}\begin{document}$\bar \beta _{{\rm SB}}$\end{document} between styrene and butadiene units, for molecular weights not exceeding approximately 105. The magnitude of \documentclass{article}\pagestyle{empty}\begin{document}$\bar \beta _{{\rm SB}} $\end{document} varies with the solvent. The results suggest that the domains of the PS and PB blocks overlap to a great extent.

Notes: Measurements of conductivity, permittivity, and dissipation factor on polystyrene, low-density polyethylene, poly(ethylene terephthalate), and polytetrafluoroethylene under irradiation with x-rays at exposure rates from 0.004 to 400 r/sec. are presented. The radiation-induced anomalous conductivity as well as the induced dielectric loss are interpreted by Maxwell-Wagner polarization due to radiation imbalance in surface layers of the specimen. The nature of radiation-induced steady-state conductivity is also discussed.

Notes: The Rayleigh-Gans theory of light scattering by a homogeneous cylinder has been applied to the case of scattering by a pad of fibers immersed in a liquid. The theory enables one to locate precisely the matching wavelength at which the mean refractive index of a sample of optically heterogeneous fibers coincides with that of an immersion medium. Thereby it offers a method of determining the mean refractive index. Besides, it facilitates a quantitative estimation of the variability of refractive index. The new technique has been used to study the birefringence of untreated cotton and ramie. The results are presented and discussed.

Notes: Using the criterion that a coupling entanglement in a polymer network is trapped if all four strands radiating from it terminate in chemical cross-links (an approximation to a more rigorous treatment of Langley), an equation is derived relating the equilibrium modulus to the magnitude of the compliance in the frequency region where all coupling entanglements, whether trapped or not, contribute to the elasticity. The latter value is estimated from the storage compliance at the frequency where the storage compliance of the uncross-linked polymer corresponds to the entanglement compliance derived from integration over the loss compliance. The theory agrees rather well with data on vulcanizates of natural rubber. For 1,4-polybutadiene and styrene-butadiene rubbers, the agreement is somewhat less satisfactory, but the results support the hypothesis that the low-frequency losses observed in lightly cross-linked rubbers are due to relaxation of untrapped entanglements.

Notes: Measurements have been made of the anisotropy of viscoelastic behavior in specially oriented sheets of low-density polyethylene. The results for the cold-drawn sheets show a β relaxation process of very characteristic anisotropy. The annealed sheets show two relaxations in this region of temperature. The lower relaxation (about -10°C) is identified as an interlamellar shear process. The higher relaxation (about 70°C) has a very similar anisotropy to the β relaxation in cold-drawn samples. Isotropic sheets of low-density polyethylene have been also investigated. Two β relaxations are found in these materials.

Notes: The steady-flow behavior of five samples of branched poly(vinyl acetate) has been studied with the Weissenberg rheogoniometer. The branching densities and molecular weight distributions were known from an analysis of the polymerization kinetics. Measurements were made on concentrated diethyl phthalate solutions (0.170 and 0.225 g/ml) at temperatures of 30 and 70°C. The viscosities of all solutions at zero shear rate were less than of solutions of linear poly(vinyl acetate) with the same weight-average molecular weight. The amount of decrease was in excellent agreement with Bueche's theory of melt viscosity in branched systems. The viscosity versus shear rate curves were surprisingly independent of molecular weight distribution, the data from all samples being superimposable on the same master curve. Relaxation times derived independently from the viscosity behavior and the normal stress data were of similar magnitude and always close to the Rouse relaxation time of each solution.

Notes: A modus operandi is developed for characterizing, in quantitative morphological terms, the structural changes occurring during the preparation (spinning, drawing, and heat setting) and testing (tensile modulus) of isotactic polypropylene fiber. This involves the application of the following eight different physical techniques: wide-angle x-ray diffraction, birefringence, density, sonic modulus, small-angle x-ray diffraction, dark-field microscopy, small-angle light scattering, and tensile modulus. Structural changes on several organizational levels, the spherulitic, the interlamellar, and the molecular, are determined in this manner and related to the processes involved.

Notes: The rapid cracking of lightly stressed rubbery block polymers of styrene and isoprene in certain liquids and vapors has been examined experimentally, by using model test pieces containing a single crack. Solvents which preferentially dissolve the rigid molecular end blocks rather than the rubbery center blocks are efficient cracking agents. The stress required for crack growth to occur is shown to be in accord with a simple energy criterion: the stored elastic energy must be sufficient to provide a characteristic energy for the newly formed surface. This characteristic energy ranges from values close to the surface energy of simple liquids up to about 100 times this value for thicker test pieces or slowly diffusing vapors, when some tearing of an incompletely swollen core is inferred. “Induction times,” before the initial crack starts to grow, are shown to be due to a progressive increase in stored energy under a constant stress as the material absorbs solvent and softens until the critical energy criterion is met. Thus, a timedependent fracture process is shown to be in accord with a constant energy criterion. Above the critical condition the rate of crack growth depends strongly upon stress, like tearing of amorphous elastomers, and the crack then accelerates rapidly.

Notes: The testes, seminal vesicles and coagulating glands of hamsters subjected to bilateral optic enucleation (blinding) involuted within 6-8 weeks. During the first several weeks after blinding there was relatively little change in the weights of the reproductive organs, however, between 4-6 weeks the weights of these organs declined precipitously. Finally, the testes and accessory sex organs of 8-week blinded hamsters were about one-tenth and one-third their normal size, respectively. The atrophic testes exhibited a complete loss of spermatogensis and an apparent diminished secretion of androgens since the seminal vesicles and coagulating glands also regressed significantly. Despite the involution, the testes showed a high degree of deoxyribonucleic acid synthesis as evidenced by the large number of spermatogenic cells which took up tritiated thymidine. These findings indicate that the testes retained a certain level of regenerative capacity even in the presence of advanced tubular damage.If hamsters blinded for 9 weeks, had either their pineal gland or superior cervical ganglia removed, the involuted testes and accessory organs regenerated and returned to the normal size, and presumed function, within approximately 8 weeks. Regenerated testes were histologically indistinguishable from those of normal animals. Eyeless hamsters killed after 17 weeks still possessed involuted reproductive organs.

Notes: Organ and tissue phagocytosis of intravenously injected cobaltic oxide was studied quantitatively over a wide range of dose levels by means of radioassay of Co260O3 in rats.There is a single linear relationship between the amount of particulate administered and the amount recovered from liver, spleen, and lung combined. The same is true for the uptake by the liver alone. However, the spleen and lung each has two linear relationships. For the spleen the two different linear trends are related to the dose administered, while for the lung the determining parameter is the weight and (or) age of the animal. Notwithstanding these different linear trends, the uptake by spleen and lung is interdependent.Although the liver is the main phagocytic organ, per unit weight the phagocytic uptake of the spleen exceeds that of the liver at amounts of cobaltic oxide larger than 40 mg. The reverse is true for amounts less than or equal to 40 mg. The phagocytic uptake by other components of the RES was not sufficient for reliable quantitative estimation.

Notes: The possibility that the incidence of polyovular follicles and multinucleate ova may depend upon hormonal balance, in the hamster, has been investigated with respect to circulating estrogens. Samples were drawn at weekly intervals from the third through the seventh week of age. An inverse correlation was found to exist. Total blood estrogen decreased from day 21 to day 35, then increased through day 49. Polyovular follicles are most numerous at day 35 while multinucleate ova are most numerous on day 42. Non-polar estrogen decreased from day 21, achieving a low 28 day level which was maintained throughout the study period. More polar estrogens dropped to the thirty-fifth day and rose by the forty-ninth day. The limiting factor in the decrease of more active polar estrogens may be lack of conversion of non-polar to polar estrogens or a tendency toward rapid degradation and loss of polar estrogens. The role of the fluctuating estrogen titres in the development of ovarian abnormalities is discussed.

Notes: Electron micrographs of vagus and sciatic nerve fibers of different size from adult male mice were examined by planimetry to determine the distribution of axoplasm, Schwann cell cytoplasm and mitochondrial density. The findings revealed that the ratio of axoplasm to Schwann cell cytoplasm in normal mature fibers increased with fiber size. The increase appeared curvilinear from 61% axoplasm in nonmyelinated fibers to 90% in the thickest myelinated fibers. Schwann cell cytoplasm extended along the sheaths in longitudinal and interconnected strands. The number of strands varied between 2 and 5, depending on fiber size. An analysis of mitochondrial density in axoplasm and Schwann cell cytoplasm of nonmyelinated and myelinated fibers revealed a greater concentration of mitochondria in the Schwann cells with increasing fiber size. The mean ratio of mitochondrial density between axoplasm and Schwann cell cytoplasm was 1:0.24 for nonmyelinated fibers, 1:2.54 for fibers with less than 30 lamellae and 1:5.21 for fibers with 30 or more lamellae. The distribution of mitochondria observed in electron micrographs was confirmed histochemically by localization of NAD-diaphorase activity.

Notes: Fetal membranes grafted to the omentum in mice do not degenerate at a time corresponding to the normal termination of the donor pregnancy, as would be expected if a “biological clock” were matching their lifespan with that of the embryo and placenta. Neither, in our experience, did such grafted membranes form a variety of highly differentiated secondary tissues, as some authors have suggested. Rather, the fate of the various components of the membrane seemed different for each cell type. In allogeneic hosts a brisk cellular reaction occurred and the membranes were destroyed. In isogeneic hosts, the grafts was vascularized and healthy membrane-derived structures were still present after 33 days of grafting (48 days conceptual age). Mesothelial cells remained applied to well-preserved basement membrane, whereas visceral endoderm cells appeared to degenerate or else detach themselves and become free rounded cells with foamy cytoplasm, sometimes multinucleated. Mesodermal cells accompanying the blood vessels of the membrane probably accounted for the connective tissue stroma seen in these grafts. The normal failure of the fetal membranes to persist in situ after the termination of pregnancy may result from the resistance of the uterine lumen to grafts not having highly invasive properties, together with the general sloughing of the uterine lining which takes place after delivery.