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PubMed2006

A method on calculating high-dimensional mutual information and its application to registration of multiple ultrasound images.

Using mutual information as a criterion for medical image registration, which requires no prior segmentation or preprocessing, has been both theoretically and practically proved to be an effective method in these years. However, this technique is confined in registering two images and hard to apply to multiple ones. The reason is that unlike mutual information between two variables, high-dimensional mutual information is ill defined. In textbooks and theoretical essays, three-dimensional mutual information is proposed based on Venn diagram. Unfortunately, mutual information defined in this way is not necessarily nonnegative. In order to overcome the problem, in this paper, we introduce the mutual information matrix. By calculating its eigenvalues, high-dimensional mutual information is defined. This definition is nonnegative, bounded, and could be extended to higher dimensions, thus enables us to register more than three images. In the end, this definition is tested and proved to be effective on registration of multiple US images through simulation.

Algorithms↗
PubMed2000

Image registration by maximization of combined mutual information and gradient information.

Mutual information has developed into an accurate measure for rigid and affine monomodality and multimodality image registration. The robustness of the measure is questionable, however. A possible reason for this is the absence of spatial information in the measure. The present paper proposes to include spatial information by combining mutual information with a term based on the image gradient of the images to be registered. The gradient term not only seeks to align locations of high gradient magnitude, but also aims for a similar orientation of the gradients at these locations. Results of combining both standard mutual information as well as a normalized measure are presented for rigid registration of three-dimensional clinical images [magnetic resonance (MR), computed tomography (CT), and positron emission tomography (PET)]. The results indicate that the combined measures yield a better registration function does mutual information or normalized mutual information per se. The registration functions are less sensitive to low sampling resolution, do not contain incorrect global maxima that are sometimes found in the mutual information function, and interpolation-induced local minima can be reduced. These characteristics yield the promise of more robust registration measures. The accuracy of the combined measures is similar to that of mutual information-based methods.

Entropy↗
PubMed2006

The evolution of plant-insect mutualisms.

Mutualisms (cooperative interactions between species) have had a central role in the generation and maintenance of life on earth. Insects and plants are involved in diverse forms of mutualism. Here we review evolutionary features of three prominent insect-plant mutualisms: pollination, protection and seed dispersal. We focus on addressing five central phenomena: evolutionary origins and maintenance of mutualism; the evolution of mutualistic traits; the evolution of specialization and generalization; coevolutionary processes; and the existence of cheating. Several features uniting very diverse insect-plant mutualisms are identified and their evolutionary implications are discussed: the involvement of one mobile and one sedentary partner; natural selection on plant rewards; the existence of a continuum from specialization to generalization; and the ubiquity of cheating, particularly on the part of insects. Plant-insect mutualisms have apparently both arisen and been lost repeatedly. Many adaptive hypotheses have been proposed to explain these transitions, and it is unlikely that any one of them dominates across interactions differing so widely in natural history. Evolutionary theory has a potentially important, but as yet largely unfilled, role to play in explaining the origins, maintenance, breakdown and evolution of insect-plant mutualisms.

Animals↗
PubMed2004

Patterns of mutual and nonmutual spouse abuse in the U.S. Army (1998-2002).

The pattern and severity of substantiated mutual and nonmutual spouse abuse between U.S. Army enlisted personnel and their spouses was determined for 1998 to 2002. The number of nonmutual and mutual abuse victims was equal in 1998, but by 2002 there were about twice as many non mutual as mutual victims. The rate per thousand of mutual abuse decreased by 58% while that of nonmutual abuse decreased by 13%. The rate per thousand of female victims was always greater than male victims for non-mutual abuse and the severity of abuse of female victims was always more severe than male victims. The active duty female had the highest risk of becoming a victim. These patterns of mutual and nonmutual domestic abuse in the U.S. Army suggest that prevention and educational approaches could be developed that would be useful to prevention specialists and to clinicians as the Army pursues avenues to reduce domestic violence.

Adult↗
PubMed2005

Antagonisms, mutualisms and commensalisms affect outbreak dynamics of the southern pine beetle.

Feedback from community interactions involving mutualisms are a rarely explored mechanism for generating complex population dynamics. We examined the effects of two linked mutualisms on the population dynamics of a beetle that exhibits outbreak dynamics. One mutualism involves an obligate association between the bark beetle, Dendroctonus frontalis and two mycangial fungi. The second mutualism involves Tarsonemus mites that are phoretic on D. frontalis ("commensal"), and a blue-staining fungus, Ophiostoma minus. The presence of O. minus reduces beetle larval survival ("antagonistic") by outcompeting beetle-mutualistic fungi within trees yet supports mite populations by acting as a nutritional mutualist. These linked interactions potentially create an interaction system with the form of an endogenous negative feedback loop. We address four hypotheses: (1) Direct negative feedback: Beetles directly increase the abundance of O. minus, which reduces per capita reproduction of beetles. (2) Indirect negative feedback: Beetles indirectly increase mite abundance, which increases O. minus, which decreases beetle reproduction. (3) The effect of O. minus on beetles depends on mites, but mite abundance is independent of beetle abundance. (4) The effect of O. minus on beetles is independent of beetle and mite abundance. High Tarsonemus and O. minus abundances were strongly correlated with the decline and eventual local extinction of beetle populations. Manipulation experiments revealed strong negative effects of O. minus on beetles, but falsified the hypothesis that horizontal transmission of O. minus generates negative feedback. Surveys of beetle populations revealed that reproductive rates of Tarsonemus, O. minus, and beetles covaried in a manner consistent with strong indirect interactions between organisms. Co-occurrence of mutualisms embedded within a community may have stabilizing effects if both mutualisms limit each other. However, delays and/or non-linearities in the interaction systems may result in large population fluctuations.

Animals↗
PubMed2004

Mother- and father-child mutuality in Anglo and Indian British families: a link with lower externalizing problems.

We observed mother- and father-child dyadic mutuality (responsiveness, interaction reciprocity, and cooperation), and its association with child behavior problems, in a socioeconomically and ethnically diverse sample of 125 male (51%) and female 7-to-9-year-old children. Dyadic mutuality and positivity were coded from in-home videotaped structured tasks, and parents completed ratings of child externalizing problems. Mothers showed more mutuality than fathers. The same child showed moderately similar mutuality with both of her or his parents (r = .47). Mutuality was higher among Anglo parents compared to Indian parents, an effect that was due in part to acculturation (i.e., years since immigration, native language use, traditional native culture attitudes). Greater mutuality, when coupled with dyadic positive affect, was associated with fewer externalizing problems (R2 = .24). This pattern held across gender, ethnic, and sociocconomic groups.

Acculturation↗
PubMed1975

Mutual assistance and support in retirement housing.

Among the advantages claimed for elderly residents of age-concentrated housing are the networks of mutual assistance among neighbors that may ensue. The extent to which these serve compensatory functions to replace mutual assistance with children has been a source of debate. The present paper compares networks of mutual assistance reported (in peronal interviews) by 600 residents of six facilities for the well-elderly with such assistance reported by matched controls living in dispersed housing. An earlier paper reported that site residents, relative to their controls, had less frequent contact with children but more frequent contact with neighbors. The present analysis shows, however, that there was little test-control difference in help received from children. More mutual assistance with neighbors, relative to controls, was found at two sites, less mutual assistance at two sites, and no difference at two. Finally, a cumulative rather than a compensatory effect was found between mutual assistance with children and with neighbors.

Aged↗
PubMed2006

As you reap, so shall you sow: coupling of harvesting and inoculating stabilizes the mutualism between termites and fungi.

At present there is no consensus theory explaining the evolutionary stability of mutualistic interactions. However, the question is whether there are general 'rules', or whether each particular mutualism needs a unique explanation. Here, I address the ultimate evolutionary stability of the 'agricultural' mutualism between fungus-growing termites and Termitomyces fungi, and provide a proximate mechanism for how stability is achieved. The key to the proposed mechanism is the within-nest propagation mode of fungal symbionts by termites. The termites suppress horizontal fungal transmission by consuming modified unripe mushrooms (nodules) for food. However, these nodules provide asexual gut-resistant spores that form the inoculum of new substrate. This within-nest propagation has two important consequences: (i) the mutualistic fungi undergo severe, recurrent bottlenecks, so that the fungus is likely to be in monoculture and (ii) the termites 'artificially' select for high nodule production, because their fungal food source also provides the inoculum for the next harvest. I also provide a brief comparison of the termite-fungus mutualism with the analogous agricultural mutualism between attine ants and fungi. This comparison shows that--although common factors for the ultimate evolutionary stability of mutualisms can be identified--the proximate mechanisms can be fundamentally different between different mutualisms.

Agaricales↗
PubMed2006

A novel obligate cultivation mutualism between damselfish and Polysiphonia algae.

In cultivation mutualisms, farming animals prepare fields for cultivars, enhance their growth and harvest them. For example, in terrestrial ecosystems, plant-herbivore cultivation mutualisms arose between humans and their crops only relatively recently. We discovered an obligate cultivation mutualism between a damselfish and an alga in a coral reef ecosystem. The damselfish, Stegastes nigricans, manages algal farms through territorial defence against the invading grazers and through weeding of unpalatable algae. As a result, the algal farms of S. nigricans are dominated by one species, Polysiphonia sp. We performed an exhaustive survey of algal assemblages inside and outside the territories of five damselfish species around the Ryukyu Islands, Japan, using molecular and morphological characteristics. Polysiphonia sp. 1 grew exclusively inside the farms of S. nigricans, and never elsewhere. Since only Polysiphonia sp. 1 is harvested and consumed by the damselfish as a staple food, this interdependent relationship is an obligate cultivation mutualism. This is the first record of an obligate plant-herbivore cultivation mutualism in a marine ecosystem. Our data also suggest that three other Polysiphonia species are facultatively mutual with, commensal with, or parasitic on other damselfish species.

Animals↗
PubMed2004

Evolutionary stability of mutualism: interspecific population regulation as an evolutionarily stable strategy.

Interspecific mutualisms are often vulnerable to instability because low benefit : cost ratios can rapidly lead to extinction or to the conversion of mutualism to parasite-host or predator-prey interactions. We hypothesize that the evolutionary stability of mutualism can depend on how benefits and costs to one mutualist vary with the population density of its partner, and that stability can be maintained if a mutualist can influence demographic rates and regulate the population density of its partner. We test this hypothesis in a model of mutualism with key features of senita cactus (Pachycereus schottii)-senita moth (Upiga virescens) interactions, in which benefits of pollination and costs of larval seed consumption to plant fitness depend on pollinator density. We show that plants can maximize their fitness by allocating resources to the production of excess flowers at the expense of fruit. Fruit abortion resulting from excess flower production reduces pre-adult survival of the pollinating seed-consumer, and maintains its density beneath a threshold that would destabilize the mutualism. Such a strategy of excess flower production and fruit abortion is convergent and evolutionarily stable against invasion by cheater plants that produce few flowers and abort few to no fruit. This novel mechanism of achieving evolutionarily stable mutualism, namely interspecific population regulation, is qualitatively different from other mechanisms invoking partner choice or selective rewards, and may be a general process that helps to preserve mutualistic interactions in nature.

Animals↗
PubMed2005

Statistical validation of mutual information calculations: comparison of alternative numerical algorithms.

Given two time series X and Y , their mutual information, I (X,Y) = I (Y,X) , is the average number of bits of X that can be predicted by measuring Y and vice versa. In the analysis of observational data, calculation of mutual information occurs in three contexts: identification of nonlinear correlation, determination of an optimal sampling interval, particularly when embedding data, and in the investigation of causal relationships with directed mutual information. In this contribution a minimum description length argument is used to determine the optimal number of elements to use when characterizing the distributions of X and Y . However, even when using partitions of the X and Y axis indicated by minimum description length, mutual information calculations performed with a uniform partition of the XY plane can give misleading results. This motivated the construction of an algorithm for calculating mutual information that uses an adaptive partition. This algorithm also incorporates an explicit test of the statistical independence of X and Y in a calculation that returns an assessment of the corresponding null hypothesis. The previously published Fraser-Swinney algorithm for calculating mutual information includes a sophisticated procedure for local adaptive control of the partitioning process. When the Fraser and Swinney algorithm and the algorithm constructed here are compared, they give very similar numerical results (less than 4% difference in a typical application). Detailed comparisons are possible when X and Y are correlated jointly Gaussian distributed because an analytic expression for I (X,Y) can be derived for that case. Based on these tests, three conclusions can be drawn. First, the algorithm constructed here has an advantage over the Fraser-Swinney algorithm in providing an explicit calculation of the probability of the null hypothesis that X and Y are independent. Second, the Fraser-Swinney algorithm is marginally the more accurate of the two algorithms when large data sets are used. With smaller data sets, however, the Fraser-Swinney algorithm reports structures that disappear when more data are available. Third, the algorithm constructed here requires about 0.5% of the computation time required by the Fraser-Swinney algorithm.

Journal Article↗
PubMedDate not supplied

Mother-child mutually responsive orientation and conscience development: from toddler to early school age.

We examined whether positive implications of mother-child mutually responsive orientation, demonstrated earlier at toddler and preschool age, extend longitudinally into early school age. The focus of the present study was on the long-term consequences of mutually responsive orientation for the development of conscience. Mutually responsive orientation encompassed shared cooperation and shared positive affect between mother and child. It was measured as a composite of those qualities observed in dyadic naturalistic interactions and reported by mothers, at toddler and preschool age. Children's conscience was assessed at early school age (N = 83) using multiple measures, including observations of moral behavior, alone and in the peer context, and moral cognition. Mother-child mutually responsive orientation at toddler and preschool ages predicted children's future conscience, even after controlling for the developmental continuity of conscience. Model-fitting analyses revealed that mutually responsive orientation at toddler age had a direct effect on future conscience, not mediated by such orientation at preschool age. The findings extend those of earlier work that revealed the importance of mother-child mutually responsive orientation for socialization, and they confirm the value of the relationship approach to social development, including long-term outcomes.

Age Factors↗
PubMed2004

Effects of mutual impedance on the radiation characteristics of transducer arrays.

The mutual resistance of transducer arrays is investigated in order to design arrays with improved performance for high intensity sounds at a given frequency. This work proposes the theory that the mutual resistance is related to the loading effects of pressure waves propagated from a piston driver on the surface of another driver. Using this interpretation, the important characteristics of the mutual resistance of two piston drivers are explained and the conditions for local maxima in the mutual resistance are easily determined. On the basis of analyses of the interactions between a driver and acoustic pressure waves, we propose a method to determine the driver radius and the distance between two drivers that give maximum mutual radiation resistance. To evaluate the proposed method, the total resistance of a transducer array is calculated using the formulas for mutual and self-resistance established by Pritchard. The results of the calculations of the total resistances of arrays with many drivers show that a transducer array with drivers arranged sparsely can achieve a larger value of the radiation power per unit area as well as better radiation efficiency than an array in which the drivers are in a closely packed arrangement at a given frequency.

Journal Article↗
PubMed2004

Minimax mutual information approach for independent component analysis.

Minimum output mutual information is regarded as a natural criterion for independent component analysis (ICA) and is used as the performance measure in many ICA algorithms. Two common approaches in information-theoretic ICA algorithms are minimum mutual information and maximum output entropy approaches. In the former approach, we substitute some form of probability density function (pdf) estimate into the mutual information expression, and in the latter we incorporate the source pdf assumption in the algorithm through the use of nonlinearities matched to the corresponding cumulative density functions (cdf). Alternative solutions to ICA use higher-order cumulant-based optimization criteria, which are related to either one of these approaches through truncated series approximations for densities. In this article, we propose a new ICA algorithm motivated by the maximum entropy principle (for estimating signal distributions). The optimality criterion is the minimum output mutual information, where the estimated pdfs are from the exponential family and are approximate solutions to a constrained entropy maximization problem. This approach yields an upper bound for the actual mutual information of the output signals - hence, the name minimax mutual information ICA algorithm. In addition, we demonstrate that for a specific selection of the constraint functions in the maximum entropy density estimation procedure, the algorithm relates strongly to ICA methods using higher-order cumulants.

Algorithms↗
PubMed1982

Validity of the Rorschach Mutuality of Autonomy Scale: a replication using excerpted responses.

This study examines the use of excerpted Rorschach responses for rating object relations. This assessment of object relations focuses on a dimension defined as Mutuality of Autonomy. A Rorschach Scale for Mutuality of autonomy is presented. Its application to excerpted Rorschach data is described. Raters did not apply the Mutuality of Autonomy Scale to the entire protocol as had been done previously (Urist, 1977). Instead, in an attempt to argue that Rorschach ratings in fact reflected Mutuality of Autonomy and not extraneous factors, ratings were based exclusively on excerpted responses. Reliability for the excerpting was at a high level of agreement, and the Rorschach Mutuality of Autonomy Scores based on these excerpts correlated significantly with independent clinical ratings of Mutuality of Autonomy.

Adolescent↗
PubMed1990

Mutual support groups to reduce alcohol consumption by pregnant women: marketing implications.

This paper reports on a study of social support and alcohol consumption of 153 women during pregnancy. The majority of women changed their alcohol intake patterns during pregnancy because of concern for the health of the fetus. Most women decreased the amount and frequency of drinking and changed their beverage of choice. Social support was found to be significantly related to reduction in alcohol use during pregnancy. Social support came from relationships with specific individuals and groups of individuals. Health care providers may be able to extend the range of their work by designing specific prevention strategies targeted toward the development and implementation of mutual support groups for pregnant women. The marketing discipline has identified certain characteristics of the mutual benefit association, an organization which exists exclusively for the benefit of its members. The authors propose that the mutual support group, often used to promote health-related behaviors, is a special case of the mutual benefit association; further, that appropriate application of established marketing principles and practices will be effective in promulgating the mutual support group. The authors offer a marketing strategy for the mutual support of pregnant women, a strategy which should be effective in further reducing the alcohol intake of pregnant women.

Alcohol Drinking↗
PubMed1994

The sickle cell mutual assistance movement.

The purpose of this paper is to describe the mutual help movement that is occurring in the sickle cell community. As sickle cell disease primarily affects African Americans in the United States, the research can show how mutual assistance groups are proliferating among this group of individuals. The study will provide the only qualitative analysis of mutual assistance groups known to exist that are primarily comprised of African Americans. In addition, demographic information on the leaders of these groups will be reported. This information can serve to educate individuals interested in forming mutual assistance groups for individuals affected by sickle cell disease. It is hoped that this information will broaden the perspective of mutual assistance groups and will illustrate that mutual assistance groups also serve diverse cultures in this country.

Black or African American↗
PubMed2004

Empirical study on mutual fund objective classification.

Mutual funds are usually classified on the basis of their objectives. If the activities of mutual funds are consistent with their stated objectives, investors may look at the latter as signals of their risks and incomes. This work analyzes mutual fund objective classification in China by statistical methods of distance analysis and discriminant analysis; and examines whether the stated investment objectives of mutual funds adequately represent their attributes to investors. That is, if mutual funds adhere to their stated objectives, attributes must be heterogeneous between investment objective groups and homogeneous within them. Our conclusion is to some degree, the group of optimized exponential funds is heterogeneous to other groups. As a whole, there exist no significant differences between different objective groups; and 50% of mutual funds are not consistent with their objective groups.

Journal Article↗