Showing papers by "Dartmouth College published in 1981"
TL;DR: This article used meta-analytic methodology to synthesize research on the relationship between student ratings of instruction and student achievement and found that ratings of instructors were positively associated with student achievement, but not with specific rating dimensions such as skill and structure.
Abstract: The present study used meta-analytic methodology to synthesize research on the relationship between student ratings of instruction and student achievement. The data for the meta-analysis came from 41 independent validity studies reporting on 68 separate multisection courses relating student ratings to student achievement. The average correlation between an overall instructor rating and student achievement was .43; the average correlation between an overall course rating and student achievement was .47. While large effect sizes were also found for more specific rating dimensions such as Skill and Structure, other dimensions showed more modest relationships with student achievement. A hierarchical multiple regression analysis showed that rating/achievement correlations were larger for full-time faculty when students knew their final grades before rating instructors and when an external evaluator graded students’ achievement tests. The results of the meta-analysis provide strong support for the validity of s...
850 citations
TL;DR: In this article, 11 passes of the ISEE satellites through the frontside terrestrial magnetopause were identified, where the plasma velocity in the magnetic field and boundary layer was substantially larger than in the magnetosheath, with a view to determining whether the velocity enhancements can be explained by magnetic field reconnection.
Abstract: Eleven passes of the ISEE satellites through the frontside terrestrial magnetopause were identified, where the plasma velocity in the magnetopause and boundary layer was substantially larger than in the magnetosheath. The nature of the plasma flow, magnetic field, and energetic particle fluxes in these regions were examined, with a view to determining whether the velocity enhancements can be explained by magnetic field reconnection.
756 citations
TL;DR: The hypothesis that sentence production is organized into independent positional and functional stages is tested and it was found that sound misordering errors tend to create words and that word errors, such as substitutions and misorderings, tend to involve similar sounding words.
453 citations
01 Jan 1981
TL;DR: Application of the AVEC-DIC microscopy method to the reticulopodial network of Allogromia has shown that cytoplasmic organelles are translocated only in contact with single microtubules or bundles of micro Tubules, and that these organelle fail to move when separated from microtubule-related motility.
Abstract: A new method called Allen Video-enhanced Contrast, Differential Interference Contrast (AVEC-DIC) microscopy is shown to be sufficiently sensitive to detect several new features of microtubule-related motility in the reticulopodial network of the foraminifer, Allogromia. The method takes advantage of the variable gain and offset features of a binary video camera to operate the DIC microscope under conditions highly favorable for video imaging, but in which the optical image is virtually invisible to the eye yet retains its full information when viewed by a suitable video camera. The improvements are made possible by setting a de Senarmont compensator to lambda/9-lambda/4 at maximal working aperture of internally corrected planapochromatic objectives. Under these conditions, the offset feature of the video camera can reject so much stray light from the instrument and specimen that contrast compares favorably with that observed in high-extinction images, and polarizing rectifiers offer scarcely any advantage. Freed from the constraints of the light-limited conditions of DIC microscopy, video images can be recorded 60 times per second, or over 1,000 times the rate of photomicrographs at comparable magnifications under high-extinction conditions. Application of this method to the reticulopodial network of Allogromia has shown that cytoplasmic organelles are translocated only in contact with single microtubules or bundles of microtubules, and that these organelles fail to move when separated from microtubules. Microtubules themselves undergo both axial translatory ("sliding") and lateral "zipping and unzipping" movements that have been suggested to occur during mitosis and other biological processes.
415 citations
TL;DR: In the Hubhard Brook watershed, the water path length in the soil zone is the crucial factor in the state of acid rain neutralization, aluminum chemistry and chemical weathering as mentioned in this paper.
382 citations
TL;DR: In this article, high-resolution observations of the frontside magnetopause and boundary layer were made with the LASL/MPE fast plasma analyzer onboard the ISEE 1 and 2 spacecraft, revealing a complex quasiperiodic structure of some of the observed boundary layers.
Abstract: Observations at high temporal resolution of the frontside magnetopause and plasma boundary layer, made with the LASL/MPE fast plasma analyzer onboard the ISEE 1 and 2 spacecraft, revealed a complex quasiperiodic structure of some of the observed boundary layers. A cool tailward streaming boundary layer plasma was seen intermittently, with intervening periods of hot tenuous plasma which has properties similar to the magnetospheric population. While individual encounters with the boundary layer plasma last only a few minutes, the total observation time may extend over one hour or more.
372 citations
336 citations
TL;DR: A statutory definition of death is proposed based on the criterion of total and irreversible cessation of whole brain functions but allowing physicians to declare death according to their customary practices in most cases.
Abstract: The permanent cessation of functioning of the organism as a whole is the definition underlying the traditional understanding of death We suggest the total and irreversible loss of functioning of the whole brain as the sole criterion of death; this has always been an implicit criterion of death If artificial ventilation is present, only completely validated brain dysfunction tests should be used to show that this criterion of death is satisfied In most cases without artificial ventilation, permanent loss of cardiopulmonary function is sufficient We propose a statutory definition of death based on the criterion of total and irreversible cessation of whole brain functions but allowing physicians to declare death according to their customary practices in most cases
321 citations
TL;DR: It has been pointed out that some developmental defects involving the occipital bone and the caudal vertebral column, such as those which characterize ACM type II, may be more closely related than previously recognized.
321 citations
TL;DR: Birds searching for insects in the canopy of a northern hardwoods forest depart significantly from random in their use of tree species, even when these trees are generally similar in life form.
Abstract: Birds searching for insects in the canopy of a northern hardwoods forest depart significantly from random in their use of tree species, even when these trees are generally similar in life form. All 10 foliage-dwelling bird species in the Hubbard Brook forest showed preferences for Yellow Birch, most had an aversion to Beech and Sugar Maple, and a few had special preferences for conifers or White Ash. Birds that glean prey from leaves had stronger tree species preferences than those that often hover for their prey, and were more influenced by tree species differences in foliage structure. The less common bird species and those for which northern hardwoods are marginal habitat had the most pronounced tree-species preferences. Food densities which are higher on Yellow Birch and specific adaptations to foraging in trees with particular foliage structures are considered major factors responsible for the observed tree species preferences. The implications of these findings for bird community structure and for forest management practices are discussed.
268 citations
TL;DR: In this article, the authors examined the impact of convertible security calls on securityholder's wealth and found that on average common stock values fall by approximately two percent at the announcements of convertible debt calls, but common stockholders wealth is unaffected by convertible preferred stock calls.
TL;DR: The results suggest that warfarin may be useful in the treatment of SCCL and also support the hypothesis that the blood coagulation mechanism may be involved in the growth and spread of cancer in man.
Abstract: In a controlled, randomized study, survival of patients with small cell carcinoma of the lung (SCCL) was prolonged on addition of warfarin sodium to combination chemotherapy plus radiation therapy. Median survival for 25 control patients was 24 weeks and for 25 warfarin-treated patients was 50 weeks. This difference could not be accounted for by differences between groups in performance status, extent of disease, age, or sex. The survival advantage associated with warfarin administration was observed both for patients with extensive disease and for those who failed to achieve complete or partial remission. The warfarin-treated group also demonstrated a significantly increased time to first evidence of disease progression. These results suggest that warfarin may be useful in the treatment of SCCL and also support the hypothesis that the blood coagulation mechanism may be involved in the growth and spread of cancer in man. ( JAMA 1981;245:831-835)
Posted Content•
TL;DR: In this article, the authors examined the effect of institutional constraints in addition to mandatory retirement which limit the opportunity to retire partially in the main job, and found that the importance of partial retirement even for those who do not face mandatory retirement, are not covered by a pension and are healthy.
Abstract: This paper examines the phenomenon of partial retirement . Topics covered include: (1) the quantitative importance of partial retirement, (2) institutional constraints in addition to mandatory retirement which limit the opportunity to retire partially in the main job, (3) the effect of these constraints on the specification of the relevant structural equations in a life cycle retirement model, (4) the impact of standard explanatory variables on four outcomes -- complete retirement, partial retirement both in and outside the main job, and non-retirement, (5) the importance of partial retirement even for those who do not face mandatory retirement, are not covered by a pension and are healthy, (6) the sensitivity of results based on a dichotomous retirement variable to whether the partially retired are classified as retired or not retired. A number of studies have either treated partial retirement inappropriately or have adopted unrealistic assumptions about the opportunity set facing potential retirees. Our findings call their results into question.
TL;DR: The prostaglandin-E-mediated suppression of lectin-initiated T- cell proliferation could be traced to an inhibition of both the production and action of the T-cell-specific mitogen, TCGF.
TL;DR: This review discusses recent experimental evidence and new concepts relating to ubiquinone function in the mitochondrial respiratory chain, focusing on possible protonmotive mechanisms and properties of the ubiquin one molecule which may relate to its biological function.
Abstract: Ubiquinone participates in the oxidation-reduction reactions of the mitochondrial respiratory chain. In addition, this molecule possesses the necessary properties to function as a hydrogen carrier, thereby stoichiometrically coupling proton translocation to respiration by a direct chemiosmotic mechanism. This review discusses recent experimental evidence and new concepts relating to ubiquinone function in the mitochondrial respiratory chain. Emphasis is placed on possible protonmotive mechanisms of ubiquinone function, recent evidence implicating stable forms of ubisemiquinone in the respiratory chain, and properties of the ubiquinone molecule which may relate to its biological function.
TL;DR: This paper conducted interviews with chief executive and operating officers in 30 major U.S. corporations to identify a number of important issues for consideration by marketing managers and educators and found that education is one of the most important areas for consideration.
Abstract: Interviews conducted with chief executive and operating officers in 30 major U.S. corporations identify a number of important issues for consideration by marketing managers and educators.
TL;DR: Both sialylated and asialo-TCGF mediated continuous in vitro T-cell proliferation over successive passages, consistent with a variably glycosylated protein as the entity responsible for T- cell growth.
TL;DR: In this article, a three-valued propositional logic is presented, within which the three values are read as "true", "false" and "nonsense", and a threevalued extended functional calculus, unrestricted by the theory of types is developed.
Abstract: A three-valued propositional logic is presented, within which the three values are read as ‘true’, ‘false’ and ‘nonsense’. A three-valued extended functional calculus, unrestricted by the theory of types, is then developed. Within the latter system, Bochvar analyzes the Russell paradox and the Grelling-Weyl paradox, formally demonstrating the meaninglessness of both.
TL;DR: The acoustic properties of unstressed medial and, to a substantially lesser extent, of stressed medial, are found to be assimilated to the properties of their flanking vocalic contexts.
Abstract: A pair of experiments examines first the coarticulatory relations among certain stressed and unstressed vowels, and next the perception of coarticulated unstressed vowels. The first study finds the...
Posted Content•
TL;DR: There is a complex relationship between the type and degree of user involvement and other organizational and individual factors; this relationship affects both users satisfaction with and usage of the resulting systems.
Abstract: 'User involvement' in the development of informationsystems is often assumed to be key to successfulimplementation. However, few empirical studies have clearlydemonstrated a relationship between user involvement and twokey indicators of system success: system usage and userinformation satisfaction. The authors test the generalhypothesis that user involvement is a more complex conceptthan previous research would indicate; there are differenttypes of involvement and different stages in the systemdevelopment life cycle in which users may become involved.In a study of 83 users and 23 information systems managersin 23 companies, they found that only the activity of usersign-offs on project phases had a significant correlationwith both user information satisfaction and satisfaction with the information systems group. The authors concludethat there is a complex relationship between the type anddegree of user involvement and other organizational andindividual factors; this relationship affects both usersatisfaction with and usage of the resulting systems. Somesuggestions for further research taking this complexity intoaccount are given.
TL;DR: In this article, a new flooding correlation is presented which solves the obvious contradiction between the Wallis correlation and the study by Pushkina and Sorokin concerning the scaling question at zero penetration of liquid.
TL;DR: In this paper, a study of 83 users in 23 companies found that only the activity of user sign-offs on project phases had a significant correlation with both user information satisfaction and satisfaction with the information systems group.
TL;DR: Results indicate that the Mr 43,000 protein is located in the innervated membrane of Torpedo electrocytes and that an immunologically similar component is highly concentrated in the postsynaptic membrane of mammalian muscle.
Abstract: Highly purified cholinergic postsynaptic membranes from Torpedo electric tissue contain, in addition to the acetylcholine receptor (AcChoR), major proteins of Mr 43,000 and Mr approximately 90,000 and minor proteins that can be removed from the membranes by alkaline treatment. We have prepared an antiserum to these alkaline-extractable proteins that reacts with the Mr 43,000 protein but not with any of the other major membrane proteins, including the AcChoR subunits. Immunofluorescent staining of sections of Torpedo electric tissue shows that this antiserum binds to the innervated but not the uninnervated surface of the electrocytes. In rat diaphragm muscle, the antigens recognized by this antiserum are highly concentrated at the synapse. Synaptic staining of muscle is eliminated by prior incubation of the antiserum with the Mr 43,000 protein but not by incubation with affinity-purified AcChoR. This antiserum stains end plates of muscles denervated for 7 days. Antiserum to AcChoR binds to the subsynaptic membranes of electrocytes and muscle but does not react with the Mr 43,000 protein. Purified AcChoR blocks staining of synapses by anti-AcChoR but the Mr 43,000 protein does not. These results indicate that the Mr 43,000 protein is located in the innervated membrane of Torpedo electrocytes and that an immunologically similar component is highly concentrated in the postsynaptic membrane of mammalian muscle.
TL;DR: In this article, the Mancos Shale and its stratigraphic equivalents in the southern Rocky Mountain and Colorado Plateau have been analyzed by X-ray powder diffraction methods.
Abstract: Clay samples from shales and bentonites in the Mancos Shale (Cretaceous) and its stratigraphic equivalents in the southern Rocky Mountain and Colorado Plateau have been analyzed by X-ray powder diffraction methods. The major clay in the shales is mixed layered illite/smectite, with 20-60% illite layers. The regional distribution of ordered vs. random interstratification in the illite/smectite is consistent with the concept of burial metamorphism in which smectite intedayers are converted to illite, resulting finally in ordered interstratification. The interstratification data correlate with other geologic information, includ- ing rank of coal and Laramide tectonic activity. In addition, contact metamorphism of the shale by Tertiary igneous intrusions produced a similar clay suite. Chemical variation within these shales (particularly the presence or absence of carbonate) affected the clay conversion reactions in the interbedded bentonites and the shale itself during the early stages of transformation. In extreme cases, shales and bentonites from a single outcrop may contain clays that range from pure smectite (calcareous shales) to ordered illite/smectite containing/>50% illite layers (noncalcareous shales). The use of mixed-layered illite/smectite compositions to infer thermal regimes, therefore, may be misleading unless allowance is made for local chemical controls.
TL;DR: Insomniacs treated with the biofeedback that seemed appropriate for their specific deficiencies showed significant sleep improvements, while those who received inappropriate feedback did not.
Abstract: • After evaluating 165 insomniacs, 48 psychophysiologic insomniacs were randomly assigned to one of the following four groups: electromyographic (EMG) feedback, combined EMG and theta feedback, sensorimotor rhythm (SMR) feedback, and no treatment (control). Sleep evaluations by home logs and in the laboratory were done before and after biofeedback and nine months later. No feedback group showed improved sleep significantly more than did the controls. The amount of feedback learning correlated significantly with sleep improvement for the SMR group but not for the other groups. Initial tension of the insomniacs correlated positively with sleep improvement for the EMG group, but negatively with sleep improvement for the SMR group. Those treated with the biofeedback that seemed appropriate for their specific deficiencies showed significant sleep improvements, while those who received inappropriate feedback did not. Appropriate biofeedback methods may be effective for specific types of insomnia, but these procedures offer no panacea for all poor sleep.
TL;DR: Experimental results on the chondrostean sturgeon Acipenser are compared and contrasted with those on Salmo and Xenopus, showing in new elaborate detail how close the early development of AcIPenser is to that of modern amphibia, closer to Xenopus than to Rana , closer to anura than to urodeles.
Abstract: SYNOPSIS. Fate maps are totally lacking for hagfishes, rays, holocephals, dipnoi, holostei and mammals, and for all except two of the thirty or so orders of the huge teleost assemblage. Important errors have been found in earlier studies of the movements by closer control of marking techniques, but there are still major elements in the literature that remain unconfirmed. Recent studies on Salmo, Xenopus and chick suggest that a wider sampling of major vertebrate groups will uncover more unsuspected variations in this phase of embryology. Experimental results on the chondrostean sturgeon Acipenser are here compared and contrasted with those on Salmo and Xenopus . Though chondrostei and teleosts had a relatively recent common ancestry, the morphogenetic movements and fate map of Acipenser give no hint as to how the uniquely teleostean behavior could have arisen. Instead the experiments have shown in new elaborate detail how close the early development of Acipenser is to that of modern amphibia, closer to Xenopus than to Rana , closer to anura than to urodeles. The search for unity in the field of comparative morphogenetic movements is plagued by lack of breadth in the sample of vertebrates hitherto studied but also by a vocabulary too much loaded with ancient homological thinking. It is pointed out that when a group of movements, all called invagination—or all called epiboly, is studied closely it can be discovered that they may be doing quite different things, controlled by different environmental factors. General theory of this part of embryology requires the bringing together of the knowledge of cellular movements from in vitro and non-embryonic systems with the knowledge of the full variety of normal patterns of morphogenetic movements in the vertebrates. Before this can be accomplished, we will need a precise knowledge of what the cells are actually doing in all the sectors of these patterned movements, and in all the major patterns that the phylum has produced.
01 Jan 1981
TL;DR: The AVEC-POL method of polarization microscopy achieves significant improvements in resolution, contrast, and the visibility of fine detail by a combination of novel adjustments to a standard (unrectified) polarizing microscope and video camera.
Abstract: A new method is described for recording rapid processes of cell motility in polarized light. The Allen video-enhanced contrast (AVEC-POL) method of polarization microscopy achieves significant improvements in resolution, contrast, and the visibility of fine detail by a combination of novel adjustments to a standard (unrectified) polarizing microscope and video camera. Using the full working aperture of a high-power planapochromatic objective lens and compensator setting of lambda/9-lambda/4, visible images appear lacking in contrast. However, the same images viewed with an appropriate video camera equipped with an electronic offset adjustment can be made to appear with as much contrast as desired, revealing a significantly greater amount of fine detail in the image than can be seen by high extinction visual microscopy alone. At bias retardations between one-ninth and one-quarter wave, the diffraction anomaly observed near extinction disappears. Consequently, polarizing rectifiers are not required with the AVEC-POL method, and images previously requiring photographic exposures of around 20 seconds are sufficiently bright to be registered on the video monitor in 1/60 second. Using an intensity monitor, quantitative measurements of cellular birefringence can be retrieved from live or videotaped images displaying a linear relationship between contrast and phase retardation due to birefringence. The AVEC-POL method also renders accessible to polarized light analysis a number of objects that scatter or depolarize too much light to be studied by high extinction methods. The method is demonstrated on model objects and applied to the highly motile reticulopodial network of Allogromia laticollaris. Rapid motion in close association with microtubules can now be analyzed in greater detail at a significant reduction in the cost of recording.
Journal Article•
TL;DR: Diet high in unsaturated fat appear to promote pancreatic carcinogenesis in the azaserine-treated rat while a diet high in saturated fat failed to show a similar degree of enhancement of pancreatic cancerogenesis.
Abstract: Diet has been shown to modulate the incidence of a wide variety of chemically induced cancers in animals. Various diets fed either during the initiation stage or the postinitiation (promotion) stage of carcinogenesis were evaluated for their ability to modulate the incidence of pancreatic cancer. Male Wistar/Lewis rats were treated with multiple injections of the pancreatic carcinogen, azaserine, during a 6- to 7-week-long initiation phase and were autopsied after a postinitiation phase of 34 or 44 weeks. The following diets were evaluated for their effects on the incidence of pancreatic neoplasms during each stage of carcinogenesis: high saturated fat; two high unsaturated fats (corn oil and safflower oil); low protein; and caloric restricted. A purified control diet was fed during that stage when the test diets were not fed. The incidence of pancreatic adenomas and adenocarcinomas was evaluated by light microscopy. Feeding of the caloric-restricted diet during the initiation phase suppressed the pancreatic neoplasm incidence. None of the ther diets tested had an effect on the incidence of pancreatic cancer during the initiation phase. During the postinitiation phase, both high-unsaturated-fat diets but not the high-saturated-fat diet significantly elevated the pancreatic neoplasm incidence. The low-protein and caloric-restricted diets had no effect on the neoplasm incidence when fed during the postinitiation phase. Thus, diets high in unsaturated fat appear to promote pancreatic carcinogenesis in the azaserine-treated rat while a diet high in saturated fat failed to show a similar degree of enhancement of pancreatic carcinogenesis.