Hyperion's sponge-like appearance.

Hyperion is Saturn's largest known irregularly shaped satellite and the only moon observed to undergo chaotic rotation. Previous work has identified Hyperion's surface as distinct from other small icy objects but left the causes unsettled. Here we report high-resolution images that reveal a unique sponge-like appearance at scales of a few kilometres. Mapping shows a high surface density of relatively well-preserved craters two to ten kilometres across. We have also determined Hyperion's size and mass, and calculated the mean density as 544 +/- 50 kg m(-3), which indicates a porosity of >40 per cent. The high porosity may enhance preservation of craters by minimizing the amount of ejecta produced or retained, and accordingly may be the crucial factor in crafting this unusual surface.

Endoscopic laryngeal findings in patients undergoing thyroid and parathyroid surgery.

OBJECTIVES: This study aimed to report the pre- and post-operative laryngeal endoscopic findings in patients referred by non-otolaryngologists who are undergoing thyroid and/or parathyroid surgery, and to determine the number and nature of referrals before and after the release of the clinical practice guideline for improving voice outcomes after thyroid surgery. METHODS: This retrospective cohort study, conducted at a tertiary care academic hospital, comprised adult patients referred by the endocrine surgery service for laryngoscopy from 2007 to 2018 (n = 166). Data regarding patient demographics, reason for referral and endoscopic findings were recorded. RESULTS: The number of referrals increased significantly after the release of the practice guideline. The most common indication for referral pre- and post-operatively was voice change. The most common finding during laryngoscopy was normal examination findings (pre-operatively) and unilateral vocal fold immobility (post-operatively). CONCLUSION: Peri-operative thyroid and/or parathyroid patients have laryngoscopic findings other than vocal fold immobility. Laryngoscopy to detect structural and functional pathology is warranted.

Jupiter's Decametric Radio Emission and the Radiation Belts of Its Galilean Satellites.

Many of the observed properties of Jupiter's decametric radiation may be explained by postulation that the inner Galilean satellites of Jupiter have magnetic properties that strongly distort Jupiter's magnetic field in the region of each satellite. Charged particles from Jupiter's radiation belts are trapped by these distorted fields and emit synchrotron radiation.

Origin of Saturn's E Ring: Self-Sustained, Naturally.

Saturn's diffuse E ring spans the region between 3 and 8 saturnian radii (R(s)), has its peak brightness near the orbit of the satellite Enceladus (3.95 R(s)), and is thought to be composed primarily of icy particles 1.0 +/- 0.3 micrometers in radius. Such particles are shown to move periodically along highly elliptical paths that cross the orbits of several saturnian satellites; the resulting energetic collisions of E ring particles with embedded satellites are capable of sustaining the E ring at its current optical depth. With several reasonable assumptions, this model naturally selects Enceladus as the primary source of ring material and may also provide mechanisms that explain the generation of the unusual amount of submicrometer dust in the neighboring F and G rings, the excess of OH molecules observed within the E ring, and the orbital brightness variations of nearby satellites.

Galileo's First Images of Jupiter and the Galilean Satellites

The first images of Jupiter, Io, Europa, and Ganymede from the Galileo spacecraft reveal new information about Jupiter's Great Red Spot (GRS) and the surfaces of the Galilean satellites. Features similar to clusters of thunderstorms were found in the GRS. Nearby wave structures suggest that the GRS may be a shallow atmospheric feature. Changes in surface color and plume distribution indicate differences in resurfacing processes near hot spots on Io. Patchy emissions were seen while Io was in eclipse by Jupiter. The outer margins of prominent linear markings (triple bands) on Europa are diffuse, suggesting that material has been vented from fractures. Numerous small circular craters indicate localized areas of relatively old surface. Pervasive brittle deformation of an ice layer appears to have formed grooves on Ganymede. Dark terrain unexpectedly shows distinctive albedo variations to the limit of resolution.

Formation of Megachromosomes from Heterochromatic Blocks of NICOTIANA TOMENTOSIFORMIS.

A heterochromatic block (HB) from N. otophora occasionally undergoes great enlargement to form a "megachromosome" in hybrids and hybrid derivatives with N. tabacum. This paper shows that the two large HB's of closely related N. tomentosiformis, and perhaps a smaller one, also have the same capability. The evidence that both large HB's form megachromosomes is twofold. In a segregating backcross population from a parent possessing the two large HB's, all segregants with one block produced megachromosomes at metaphase or large heterochromatic clumps at interphase. Second, those segregants which possessed both heterochromatic blocks produced megachromosomes of two visibly different types. Proliferation to make megachromosomes thus may not be the property of merely one particular segment but a more common property of heterochromatin in a hybrid or otherwise disturbed background.

The molecular basis of dominance.

The best known genes of microbes, mice and men are those that specify enzymes. Wild type, mutant and heterozygote for variants of such genes differ in the catalytic activity at the step in the enzyme network specified by the gene in question. The effect on the respective phenotypes of such changes in catalytic activity, however, is not defined by the enzymes change as estimated by in vitro determination of the activities obtained from the extracts of the three groups. In vivo enzymes do not act in isolation, but are kinetically linked to other enzymes via their substrates and products. These interactions modify the effect of enzyme variation on the phenotype, depending on the nature and quantity of the other enzymes present. An output of such a system, say a flux, is therefore a systemic property, and its response to variation at one locus must be measured in the whole system. This response is best described by the sensitivity coefficient, Z, while is defined by the fractional change in flux over the fractional change in enzyme activity. (formula: see text). Its magnitude determines the extent to which a particular enzyme "controls" a particular flux or phenotype and, implicitly, determines the values that the three phenotypes will have. There are as many sensitivity coefficients for a given flux as there are enzymes in the system. It can be shown that the sum of all such coefficients equals unity. (formula: see text). Since n, the number of enzymes, is large, this summation property results in the individual coefficients being small. The effect of making a large change in enzyme activity therefore usually results in only a negligible change in flux. A reduction to 50% activity in the heterozygote, a common feature for many mutants, is therefore not expected to be detectable in the phenotype. The mutant would therefore be described as "recessive". The widespread occurrence of recessive mutants is thus seen to be the inevitable consequence of the kinetic structure of enzyme networks. The ad hoc hypothesis of "modifiers" selected to maximize the fitness of the heterozygote, as proposed by Fisher, is therefore unnecessary. It is based on the false general expectation of an intermediate phenotype in the heterozygote. Wright's analysis, substantially sound in its approach, proposed selection of a "safety factor" in enzyme activity. The derivation of the summation property explains why such safety factors are automatically present in almost all enzymes without selection.

Cytogenetics of flower modification of a cytoplasmic male-sterile tobacco.

Plants combining the cytoplasm of Nicotiana debneyi and the 48 chromosomes from N. tabacum are male sterile. Early backcross generations of the amphidiploid hybrid to male N. tabacum produced a great variety of plants from which a series of phenotypes with characteristic flower forms and transmission rates have been isolated. Type 1A possesses completely feminized stamens and deeply split corollas, breeds true when backcrossed to normal males and carries 48 N. tabacum chromosomes. Other phenotypes, 2C, 3E and 4H, range toward normal morphology of corollas and stamens. Like 1A, 2C forms no anther tissue and has 48 chromosomes. This type is transmitted to 36.3% of the backcross progeny, the remainder being of type 1A; presumably 2C carries a chromosome segment from N. debneyi that is responsible for the partial restoration of flower structure. In contrast, both 3E and 4H produce anthers and possess an extra chromosome. The extra chromosomes are transmitted to only 19.9% and 7.1% of the progeny, respectively. Significantly, the extra chromosomes found in the anther-forming types are nucleolus organizing and carry a satellite from N. debneyi. On the basis of these observations, we surmise that differentiation of anthers in plants with N. debneyi cytoplasm may depend on the presence of a nucleolus-organizing chromosome from that species. This chromosome is unstable; unaltered, it conditions a highly restored phenotype (4H), but when structurally modified, it may control different phenotypic expressions. Other examples of satellited restorer chromosomes had been reported for different cytoplasmically male-sterile combinations; therefore, the phenomenon may have more general significance.

Cytoplasmic male sterility in Nicotiana, restoration of fertility, and the nucleolus.

Plants with the cytoplasm of Nicotiana repanda and the chromosomes of N. tabacum produce nonfunctional and feminized anthers. Introduction of a satellited fragment chromosome, apparently derived from N. repanda, restores normal anthers and pollen fertility. The fragment is somatically stable and addition-homozygotes transmit it to the great majority of their offspring. Cells with the fragment exhibit amphiplasty, i.e. , in plants having one or two fragments, nucleolar organizers of N. tabacum are suppressed and the nucleoli are entirely or largely produced by the fragments. Formation of nucleoli by organizers from N. repanda in N. repanda cytoplasm may thus be a condition for male fertility. The manner in which nucleoli may influence the development of originally indeterminate sex primordia is discussed. Further cytological studies of cytoplasmically male-sterile plants and restorer chromosomes are needed to decide whether the observed relationship is of functional significance or merely accidental.

Cytoplasmic Male Sterility in Nicotiana, Restoration of Fertility, and the Nucleolus. II. N. DEBNEYI Cytoplasm.

Previously, it was shown that a fragment chromosome, apparently derived from the Nicotiana repanda chromosomal complement, restores to normal the morphology and fertility of the abortive and feminized anthers produced by plants that possess the N. tabacum genome in cytoplasm from N. repanda. Furthermore, that restorer chromosome organizes the nucleolus and inhibits the nucleolus-forming activity of the nucleolar organizers of N. tabacum chromosomes present in the same cells, particularly in pollen mother cells. To determine whether these relations are basic or only coincidental, restorer chromosomes for other cytoplasms are now being investigated. The present paper describes a study of a chromosome, presumably derived from N. debneyi, with partial restoring power. Acting in the cytoplasm of N. debneyi, it directs formation of morphologically normal anthers, without, however, restoring pollen fertility. We find that this chromosome also has a functioning nucleolar organizer, but only slightly inhibits the nucleolus-forming capacity of N. tabacum chromosomes. The suggestion of a relationship between the nucleolar apparatus and restoration of normal anthers is thus strengthened by the observation that restorers are found on nucleolus-forming chromosomes from two very distinct Nicotiana species, as well as in several comparable cases cited from the Triticinae. The manner in which the nucleolus, or its organizer, may direct defeminization and restoration of anther morphology is not known; suggestions were offered in the preceding paper in this series (Gerstel, Burns and Burk 1978).

A mild autosomal recessive form of osteopetrosis.

We report on four individuals in one kindred with relative or absolute short stature; increased upper/lower segment ratio with decreased arm span; mandibular prognathism and dental abnormalities; fractures following minimal trauma; mild to moderate anemia with extramedullary hematopoiesis; and radiographic changes of osteopetrosis, including sclerosis of the cranial base, generally increased bone density, sclerosis of the vertebral end plates, and transverse bands and poor diaphyseal modelling of the long bones. There is intrafamilial variability of clinical and radiographic findings in individuals with this mild, autosomal recessive form of osteopetrosis. We summarize ten families from the literature, which include 18 cases of mild recessive osteopetrosis. The manifestations of many are similar to those of the individuals reported here. Two other types of recessive osteopetrosis have been reported previously: osteopetrosis associated with renal tubular acidosis, and severe osteopetrosis with hepatosplenomegaly, pancytopenia, and early death. Autosomal dominant osteopetrosis is variable but usually mild. Pedigree analysis is currently the only reliable method of determining the pattern of inheritance in mild osteopetrosis.

Volume augmentation of the anophthalmic orbit with cross-linked collagen (Zyplast).

Injectable glutaraldehyde cross-linked collagen (Zyplast) has been used to augment the soft-tissue volume of the anophthalmic sockets of five patients. Follow-up of more than 1 year has demonstrated that this material can be used safely with long-lasting results. Enophthalmos and pseudoptosis were treated by injecting Zyplast transconjunctivally into the muscle cone. Superior sulcus deepening was treated by injecting Zyplast transcutaneously into the superior extraconal fat posterior to the orbital septum ("preaponeurotic fat pad"). In some cases the size of the ocular prosthesis required can be decreased. Surgical volume augmentation of the socket and superior sulcus was averted in all five patients.

Punctal-canalicular stenosis related to systemic fluorouracil therapy.

This is, to our knowledge, the first report in the ophthalmic literature of punctal-canalicular stenosis and concomitant epiphora associated with the prolonged administration of fluorouracil; to our knowledge, fluorouracil is the first systemically administered agent to cause obstruction in the lacrimal system. Each of three patients receiving this antimetabolite alone and one patient receiving it in combination with methotrexate and cyclophosphamide were studied for complaints of epiphora. All four patients exhibited stenosis or occlusion of one or more puncta, while three also had one or four of their canaliculi stenosed. Two patients exhibited recurrent epiphora, beginning one to two days after each administration of fluorouracil and resolving in two to three days. One patient experienced amelioration of her symptoms after Silastic tube intubation of her canalicular system.

Comparative in vitro sliding-wear study of conventional, microfilled, and light-cured composite restoratives.

The sliding-wear behavior of a number of commercially available microfilled and light-cured composite restoratives has been investigated and compared with the wear characteristics of conventional composites. The surface profiles of the composite restoratives, both pre- and post-test, have also been examined in order to study material attrition processes. The results indicate that: (1) microfilled composites are significantly more resistant to sliding wear than are restoratives containing conventionally-sized filler particles; (2) light-cured, microfilled composites exhibit a lower rate of sliding wear than do self-curing, microfilled restoratives; and (3) the wear process leads to an increase in surface roughness for all materials tested, but microfilled materials display lower surface roughness values, both before and after sliding-wear tests, than do restoratives containing conventional-sized filler particles.

Transnasal endoscopic repair of cranionasal fistulae: a refined technique with long-term follow-up.

Although the management of cranionasal fistulae has historically plagued otolaryngologists, recent reports of endoscopic techniques for repair of these lesions offer promising results. We present our series of 42 patients whose cranionasal fistulae were managed endoscopically between December 1989 and August 1995. Follow-up ranged from 5 to 68 months, thereby including long-term results from our previously reported series of 29 cases. Resolution of cerebrospinal fluid rhinorrhea was achieved in 35 (83.3%) of 42 patients with one endoscopic procedure, and 3 patients had successful closure at a second surgery. All five cephaloceles were successfully treated with one procedure. We have refined our technique to include specific indications for the use of free grafts depending on the location and size of the cranionasal fistula.

The zygomatic-sphenoid fracture line in malar reduction. A cadaver study.

OBJECTIVE: To demonstrate the persistent malar displacement and distraction of the zygomatic-sphenoid fracture line that is possible after alignment of the frontozygomatic and infraorbital rim fractures of a displaced malar fracture. DESIGN: Nonblinded cadaver study. SUBJECTS: Three fresh cadaver heads and 1 representative clinical example. INTERVENTION: The cadaver heads were subjected to blunt trauma to the malar eminence. Reduction of the malar unit was performed either with attention to the frontozygomatic and infraorbital rim fractures alone or with concomitant inspection of the zygomatic-sphenoid fracture line. The representative case was repaired with a trans-conjunctival approach for inspection of the zygomatic-sphenoid fracture line. RESULTS: Persistent malar asymmetry is possible after the reduction of displaced malar fractures when only the frontozygomatic and infraorbital rim buttresses are used for reference. In each case in our study, the zygomatic-sphenoid fracture line remained distracted. Alignment of the zygomatic-sphenoid fracture restored premorbid malar position. CONCLUSION: Inspection of the zygomatic-sphenoid fracture line can contribute significantly to the precise 3-dimensional reduction of displaced malar fractures.

Chromosome 11q13 amplification in head and neck squamous cell carcinoma. Association with poor prognosis.

OBJECTIVE: To determine the clinical and prognostic significance of chromosome 11q13 amplification in squamous cell carcinoma of the head and neck. DESIGN: Retrospective clinical analysis. SETTING: University and private cancer centers. PATIENTS: Fifty-six patients with pathologically confirmed head and neck squamous cell carcinoma whose tumors had been assayed for the presence or absence of chromosome 11q13 amplification. MEASUREMENTS: The degree of DNA amplification in each tumor was determined using chromosome 11q13 probes for the bcl-1 major translocation cluster, PRAD1/cyclin D1 (CCND1), the fibroblast growth factor gene HST1, EMS1, and glutathione-S-transferase-pi-1. The presence or absence of amplification in each patient was correlated with primary site, tumor stage, nodal status, presence or absence of distant metastasis, disease recurrence, time to recurrence, clinical outcome (disease status), and overall survival. RESULTS: Amplification of chromosome 11q13 was identified in 39% (22/56) of patients. Recurrent or persistent disease was identified in 82% (18/22) of cases with amplification and 50% (14/28) of nonamplified cases (P = .04). Mean time to recurrence was shorter in cases with amplification (6.2 months) than those without amplification (10.1 months) (P = .01). Eighteen patients (82%) with amplification and 10 patients (38%) without amplification died of disease or are alive with disease (P = .001). The mean follow-up period was 15.8 months for patients with amplification and 18.6 months for patients without amplification. Overall survival was significantly diminished in patients with amplification (P = .002). Amplification was not related to nodal status, distant metastases, or initial disease stage. CONCLUSIONS: Amplification of chromosome 11q13 loci may be an important biologic marker indicating poor prognosis, independent of clinical stage in head and neck squamous cell carcinoma, and it should be assessed in prospective trials to determine its utility for stratifying treatment and determining prognosis.

Demystifying ethical decision making.

Ethical dilemmas frequently occur in the practice of orthopaedic nursing. Nurses, however, are often unsure about how to resolve these dilemmas. The language of ethics remains elusive. Yet, because nurses have a central role in patient care, they need to become more comfortable making ethical decisions related to their practice. This article briefly describes the dialectical process of ethical decision making and demonstrates this process by using a case presentation. Readers are encouraged to put themselves into the role of the bedside nurse in the case, determine what they believe to be the right action, and provide a well-grounded rationale for that decision.