Showing papers by "University of Maryland, Baltimore County published in 1983"
TL;DR: In this article, it is shown that if the Jacobian determinant of a map is greater than one and a ball is mapped into itself, then generically, the attractor will have positive two-dimensional measure.
448 citations
TL;DR: It is argued that the ability to abstract numerical invariance from small-set visual arrays and may be evidence for complex information processing during the first week of life.
Abstract: 40 healthy, normal newborn infants were evaluated with reference to their ability to discriminate among visual stimulus arrays consisting of 2 versus 3 or 4 versus 6 black dots. Infants made this discrimination within a habituation/dishabituation paradigm for the small number sets (2 to 3 and 3 to 2) but not for the larger sets (4 to 6 and 6 to 4). We argue that this suggests the ability to abstract numerical invariance from small-set visual arrays and may be evidence for complex information processing during the first week of life.
444 citations
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TL;DR: Structural and amino acid sequence comparisons suggest that this bihelical fold occurs in a number of proteins that regulate gene expression, and is an intrinsic part of the DNA-protein recognition event.
Abstract: The structures of three proteins that regulate gene expression have been determined recently and suggest how these proteins may bind to their specific recognition sites on the DNA. One protein (Cro) is a repressor of gene expression, the second (CAP) usually stimulates gene expression, and the third (lambda repressor) can act as either a repressor or an activator. The three proteins contain a substructure consisting of two consecutive alpha helices that is virtually identical in each case. Structural and amino acid sequence comparisons suggest that this bihelical fold occurs in a number of proteins that regulate gene expression, and is an intrinsic part of the DNA-protein recognition event. The modes of repression and activation by Cro and lambda repressor are understood reasonably well, but the mode of action of CAP is still unclear.
262 citations
TL;DR: In this article, the authors show that the notions of stability and the implicit normative criteria associated with the two theories are very close to being logically incompatible, which suggests that the social choice ideal of collective rationality may not be one that we should endorse.
Abstract: Pluralist political theory identifies certain patterns of political preferences as promoting the “stability” of democratic political systems and others as threatening to such stability. Social choice theory likewise identifies certain patterns of political preferences as leading to “stability” in social choice under majority rule and related collective decision rules, and other patterns as leading to “unstable” social choice. But the preference patterns identified by pluralist theory as promoting stability are essentially those identified by social choice theory as entailing instability. Thus the notions of stability and the implicit normative criteria associated with the two theories are very close to being logically incompatible. This incompatibility suggests that the social choice ideal of collective rationality may not be one that we should endorse. Indeed, the generic instability of the pluralist political process and its consequent collective irrationality may contribute to the stability of pluralist political systems.
164 citations
TL;DR: This article found that farmers "inherit" their occupation at a rate five times greater than the next highest category of occupational inheritors, and that sons of farmers tend to become farmers rather than rent or rent or work in the industry.
Abstract: It used to be common, if not expected, that a son would grow up and take over the family business or follow in his father's footsteps. Today we still observe varying degrees of occupational inheritance in business, politics, the arts, and other occupations. However, Blau and Duncan find that farmers "inherit" their occupation at a rate five times greater than the next-highest category of occupational inheritors. Despite a growing concern about the future of the family farm, there seem to be no successful attempts to explain why occupational mobility studies consistently find higher rates of intergenerational occupational mobility among farmers than among other groups. In this paper we attempt to explain the tendency of farmers to be sons of farmers. By itself, the preponderance of family farms is not particularly surprising. It is interesting that ownership of these farms tends to remain within families across generations. Moreover, sons of farmers tend to become farmers rather than rent or
114 citations
TL;DR: Chloramphenicol-mediated destabilization of the stem-loop is suggested as the basis for the chlorampshenicol inducibility phenotype.
94 citations
TL;DR: Restriction sites exist within the gene that should permit the product of inserted heterologous coding sequences to be synthesized in B. subtilis as fusion proteins.
91 citations
TL;DR: In this paper, 231 fourth-sixth grade children were asked to judge aggressive, assertive, and submissive solutions to interpersonal conflict situations along "evaluative" and "potency" dimensions, and assess the consequences of such behaviors for themselves and for others.
Abstract: In this study, 231 fourth‐sixth grade children were asked to judge aggressive, assertive, and submissive solutions to interpersonal conflict situations along “evaluative”; and “potency”; dimensions, and to assess the consequences of such behaviors for themselves and for others. Significant differences were obtained between boys and girls, and among children designated “highly aggressive,”; “highly assertive,”; and “highly submissive.”; In contrast to the great disparity between the judgments of aggressive and assertive children, assertive and submissive children differed significantly only in their ratings of assertive alternatives on particular “evaluative”; dimensions (i.e., “good‐bad,”; “wise‐foolish,”; “kind‐cruel"). Clinical implications of these findings are discussed.
83 citations
TL;DR: Observed field experiments in 1979 and 1980 provide indirect evidence of the importance of physical factors and possibly vegetation in the distribution and abundance of A. au- rantia and A. trifasciata.
Abstract: Nonexperimental studies by several investigators have provided indirect evidence of interspecific competition between Argiope aurantia and A. trifasciata, two syntopic orb-weaving spiders common in old fields. We performed replicated field experiments in 1979 and 1980 to test directly for both inter- or intraspecific competition among these spiders. Densities of one or both species were altered within open 12 x 12 m plots in an old field in Maryland, USA. Evidence for competition was based upon the effects of the density manipulations upon web location, prey capture, growth, and survival. The experiments yielded no evidence of interspecific competition between A. aurantia and A. trifasciata. The manipulations did provide statistically significant evidence of intraspecific competition during 1979. However, no treatment effects were evident in 1980, though densities of both species were higher that year and prey appeared to have been less available than in 1979. Increasing the density of conspecifics caused an increase in the mean web height of both species during the early census periods of 1979. The growth rate of A. aurantia was slightly less at the higher density in 1979, and survival (net effect of mortality, immi- gration, and emigration) of A. trifasciata was negatively density dependent that year. Responses to the density manipulations were variable between experimental plots and years. Some of the responses were correlated with seasonal changes in the weather and with variation in the composition and structure of the vegetation. Thus our observations provide indirect evidence of the importance of physical factors and possibly vegetation in the distribution and abundance of A. au- rantia and A. trifasciata. Interspecific competition appears to have no, or only minor, influence on resource utilization, growth, and survival of these species.
72 citations
TL;DR: The results permit a more detailed analysis of the omp regulon and they may shed light on one of the mechanisms by which local anaesthetics exert their effect.
60 citations
TL;DR: It is concluded that other factors better explain the absence of exploitative competition among most M. labyrinthea spiders, which appears to be a food-limited species in which exploitative Competition for food is weak or absent.
Abstract: Field experiments were conducted to clarify the relationship between the extent of food limitation and the amount and nature of intraspecific competition in an orb weaver, the labyrinth spider Metepeira labyrinthea. In one experiment agonistic encounters between marked adult females were induced at natural web sites. In other experiments populations were established by adding spiders to standardized, open experimental units in the spider's natural habitat. Replicate low and high density populations of marked adult females were established in one study. The other density manipulation was with immature spiders and incorporated a third treatment in which prey availability was increased over ambient levels. The larger female gained control of the web in 76% of the induced encounters. Resident status of the spider did not significantly influence the outcome of a contest. Apparently labyrinth spiders will spontaneously invade webs, since some females in the density-manipulation experiment appeared in recently occupied webs of other spiders. Despite this evidence of interference competition and indirect evidence that prey scarcity limited fecundity, neither survival nor egg production was lower at higher spider densities. The experiment with juvenile spiders provided direct experimental evidence that prey were scarce for M. labyrinthea. Spiders that received supplemental food were significantly larger at the end of the experiment than those that fed at natural prey levels only (24±3 mg versus 15±2 mg, respectively). However, density of immature spiders did not affect their growth or survival. The labyrinth spider appears to be a food-limited species in which exploitative competition for food is weak or absent. Most spiders never build webs close enough together to interfere indirectly with each other's prey capture. Occurrence of aggressive interactions between some females suggests that territorial behavior may lead to spacing patterns that eliminate exploitative competition. This hypothesis is evaluated and it is concluded that other factors better explain the absence of exploitative competition among most M. labyrinthea. Aggressive encounters occur between some labyrinth spiders and clearly constitute interference competition, but such interactions do not contribute significantly to density-dependent regulation of this population.
TL;DR: The time-dependent absorbance change that occurs when benzo[alpha]pyrene 7,8-diol-9,10-epoxide is added to solutions of calf thymus DNA has been shown, by an unequivocal chromatographic method, to correspond to DNA-catalyzed hydrolysis of the diol-EPoxide.
TL;DR: Results indicate that promoter fragments that allow phenotypic expression of the mouse DHFR gene contain two regulatory signals: one signal is essential to transcription of both DHFR and CAT and therefore functions as a promoter and the second signal may be necessary for translation of that portion of the mRNA specifying mouse DH FR.
TL;DR: The data suggest that antiemetics do not disrupt lithium chloride- induced taste aversions as previously reported, nor do they effect radiation-induced taste aversion learning.
Abstract: A series of experiments were run to evaluate the effect of antiemetics on the acquisition and recall of a conditioned taste aversion induced by exposure to ionizing radiation or by injection of lithium chloride. Groups of male rats were exposed to 100 rad gamma radiation or 3 mEq/kg lithium chloride following consumption of a 10% sucrose solution. They were then injected with saline or with one of three antiemetics (prochlorperazine, trimethobenzamide, or cyclizine) at dose levels that have been reported to be effective in attenuating a previously acquired lithium chloride-induced taste aversion. The pretreatments with antiemetics had no effect on the acquisition or recall of either the lithium chloride- or radiation-induced taste aversion. The data suggest that antiemetics do not disrupt lithium chloride-induced taste aversions as previously reported, nor do they effect radiation-induced taste aversion learning.
TL;DR: In this paper, the relative importance of major role losses experienced in widowhood and retirement, personal characteristics, and prior level of participation as predictors of formal and informal social participation in old age was examined.
Abstract: This article examines the relative importance of major role losses experienced in widowhood and retirement, personal characteristics, and prior level of participation as predictors of formal and informal social participation in old age. Data obtained from the Longitudinal Retirement History Survey (LRHS) of a panel (N = 6603) of males in their sixties are analyzed. Stepwise regression analysis reveals that prior level of participation and personal characteristics explain more variance in participation than major role losses considered alone or in conjunction with related deteriorative changes such as income loss. When the effects of these variables are simultaneously controlled, persons with major role losses have lower levels of participation in formal organizations and in selected areas of informal activity than those without comparable losses. Examination of the cumulative effects of experiencing both major role losses exacerbated these results. Policy implications for preretirement education and progr...
TL;DR: The results are interpreted as suggesting that pituitary/adrenal hormones do not mediate the acquisition of a conditioned taste aversion following injections of lithium chloride or following exposure to ionizing radiation in a two-bottle preference test, and consistent with other research suggesting that the involvement of pituitarians in taste aversion learning may be related to the conflict induced by using a one-Bottle test and not to the learning itself.
Abstract: The effects of hypophysectomy on the acquisition of conditioned taste aversions following injection of lithium chloride and following exposure to ionizing radiation were studied using a two-bottle preference test. Hypophysectomy did not disrupt the acquisition of a taste aversion following either treatment. The results are interpreted as: (a) suggesting that pituitary/adrenal hormones do not mediate the acquisition of a conditioned taste aversion following injections of lithium chloride or following exposure to ionizing radiation in a two-bottle preference test, and (b) consistent with other research suggesting that the involvement of pituitary/adrenal hormones in taste aversion learning may be related to the conflict induced by using a one-bottle test and not to the learning itself.
TL;DR: The authors explored why an effective speaker-training technique failed to generalize to listener skills by comparing the relative effectiveness of speaker and listener training and found that listening tasks utilize different skills than speaking tasks.
TL;DR: Results strongly suggest that a two-helical structural unit occurs in the DNA-binding region of many proteins that regulate gene expression, however, the results to date do not suggest that there is a simple one-to-one recognition code between amino acids and bases.
Abstract: Cro repressor is a small dimeric protein that binds to specific sites on the DNA of bacteriophage lambda. The structure of Cro has been determined and suggests that the protein binds to its sequence-specific sites with a pair of two-fold related alpha-helices of the protein located within successive major grooves of the DNA. From the known three-dimensional structure of the repressor, model building and energy refinement have been used to develop a detailed model for the presumed complex between Cro and DNA. Recognition of specific DNA binding sites appears to occur via multiple hydrogen bonds between amino acid side chains of the protein and base pair atoms exposed within the major groove of DNA. The Cro:DNA model is consistent with the calculated electrostatic potential energy surface of the protein. From a series of amino acid sequence and gene sequence comparisons, it appears that a number of other DNA-binding proteins have an alpha-helical DNA-binding region similar to that seen in Cro. The apparent sequence homology includes not only DNA-binding proteins from different bacteriophages, but also gene-regulatory proteins from bacteria and yeast. It has also been found that the conformations of part of the presumed DNA-binding regions of Cro repressor, lambda repressor and CAP gene activator proteins are strikingly similar. Taken together, these results strongly suggest that a two-helical structural unit occurs in the DNA-binding region of many proteins that regulate gene expression. However, the results to date do not suggest that there is a simple one-to-one recognition code between amino acids and bases. Crystals have been obtained of complexes of Cro with six-base-pair and nine-basepair DNA oligomers, and X-ray analysis of these co-crystals is in progress.
TL;DR: In this article, the authors employed the 4-31G basis set to evaluate the strain energies of gem-difluoro derivatives of cyclopropane and found that the increased strain energy of these molecules account for the relative ease of their thermal rearrangements.
TL;DR: It is concluded that foretarsal contact chemoreceptors employed during drumming are used for host verification in environmental conditions where olfaction is unreliable.
Abstract: The role of antennae and foretarsi in oviposition and host discrimination was investigated in Chlosyne lacinia Geyer (Nymphalidae, Lepidoptera) a cluster laying nymphalid butterfly which exhibits drumming and antennal dipping behavior prior to oviposition. Ablation of the entire antennae drastically reduced oviposition, while fractional antennectomy reduced it in proportion to the number of antennal receptors removed. Host/non-host ovipositional discrimination was not significantly affected by antennal ablations. Ablation of the foretarsi abolished discrimination in a controlled environment chamber, but did not affect it in outdoor cages or in a greenhouse. This difference was retrospectively associated with a diminished release of host volatiles due to cooler leaf surface temperatures in the environmental chamber or with continuous air turbulance caused by humidifier fans in the environmental chamber. Electrophysiological techniques were used to demonstrate chemosensory activity in setae located on the foretarsi. We conclude that foretarsal contact chemoreceptors employed during drumming are used for host verification in environmental conditions where olfaction is unreliable.
RESUME
Influence sur la ponte de Chlosyne lacinia Geyer (Lep. Nymphalidae) des structures sensorielles et du comportement precedant la ponte
Le role des antennes et des tarses anterieurs sur la ponte et la selection des hotes a ete etudie chez Chlosyne lacinia, papillon nymphalide aux pontes groupees, dont le comportement avant la ponte comporte un tambourinage et un picotage antennaire. L'ablation integrate des antennes reduit brutalement la ponte, une antennotectomie partielle la reduit proportionnellement au nombre de recepteurs antennaires elimines. Les ablations antennaires n'affectent pas significativement la discrimination entre plantes — hotes ou non. L'ablation des tarses anterieurs supprime la discrimination en piece climatisee, mais non en serre ou en cages a l'exterieur. Cette difference peut etre expliquee par une liberation reduite de substances volatiles dans les chambres climatisees avec des surfaces foliaires plus froides ou par la turbulence permanente de l'air qui y etait provoquee par les ventilateurs des humidificateurs. Des techniques electrophysiologiques ont ete utilisees pour deceler l'activite chimiosensorielle des setae des tarses anterieurs. Nous concluons que des recepteurs chimiques de contact des tarses anterieurs sont utilises pendant le tambourinage pour controler l'hote dans des conditions ecologiques ou l'olfaction est inutilisable.
TL;DR: In this paper, it was shown that for both discounted and long-term average cost criteria, the adaptive control law Cesaro-converges to the set of optimal control laws and that the actual cost incurred by the use of the adaptive controller is optimal and cannot be bettered.
Abstract: The problem considered is one of simultaneously identifying an unknown system while adequately controlling it. The system can be any fairly general discrete-time system and the cost criterion can be either of a discounted type or of a long-term average type, the chief restriction being that the unknown parameter lies in a finite parameter set. For a previously introduced scheme of identification and control based on "biased" maximum likelihood estimates, it is shown that 1) every Cesaro-limit point of the parameter estimates is "closed-loop equivalent" to the unknown parameter; 2) for both the discounted and long-term average cost criteria, the adaptive control law Cesaro-converges to the set of optimal control laws; and 3) in the case of the long-term average cost criterion, the actual cost incurred by the use of the adaptive controller is optimal and cannot be bettered even if one knew the value of the unknown parameter at the start.
01 Jan 1983
TL;DR: The interaction of fluorescent dyes with nucleic acids has evolved into one of the most active areas of research in biochemistry and biophysics with ramifications which extend far beyond the cytological applications and range from structural studies of nucleic acid to molecular genetics and the action of antibiotics.
Abstract: During the past 20 years, the interaction of fluorescent dyes with nucleic acids has evolved into one of the most active areas of research in biochemistry and biophysics with ramifications which touch on a wide variety of topics. These extend far beyond the cytological applications which originally drew the attention of biologists and range from structural studies of nucleic acids to molecular genetics and the action of antibiotics.
TL;DR: Analysis of dissolved crystals shows that they respectively contain approximately two hexamers per Cro dimer and one nonamer per dimer, which appear suitable for structural studies.
TL;DR: An in vitro method for culturing Limax maximus albumen glands was described in which the biosynthetic activity of the slug albumen gland was monitored by measuring the incorporation of [14C]glucose into galactogen, suggesting that it is probably a polypeptide.
TL;DR: Preliminary experiments suggest that these plasmids encode a polypeptide with Gam activity that corresponds to the 98-amino acid “shorter” open reading frame assigned to gam by Sanger et al.
TL;DR: The structure of the cro repressor from bacteriophage λ suggests that a pair of α-helices of this gene-regulatory protein bind to its sequence-specific sites on the DNA.
TL;DR: It appears that both the synthesis and the secretion of MFG are stimulated in slugs that are in their male developmental phase as a result of prior exposure to long-day photoperiods.
TL;DR: Results are consistent with, and suggest, that an increase in probe mobility accompanies an expansion of the calmodulin molecule under conditions of high electrostatic stress.
TL;DR: Intimate communications, on the part of both male and female speakers, were associated with a slow pacing of speech but not with a decrease in productivity level, independently of the seating arrangement.
Abstract: The mutual reduction of visual feedback, which in this study did not interfere with the synchronization of turns, reduced the productivity levels and increased the silent pauses of female speakers, even though it had no effect on their subjective discomfort, anxiety, and ease of communication self-ratings. The same reduction of visual feedback, which was achieved by seating the participants back-to-back rather than face-to-face, caused male speakers to feel anxious and uncomfortable and reduced the duration of their silent pauses, but only in samegender dyads. These findings are explained in terms of previously noted gender differences in the need for visual feedback and in the anxiety-arousing effects of back-to-back interactions. Intimate communications, on the part of both male and female speakers, were associated with a slow pacing of speech but not with a decrease in productivity level, independently of the seating arrangement. These findings are interpreted in terms of the self-monitoring and self-censoring that is usually associated with the communication of intimate messages.