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1.
Michael Mesterton-Gibbons 《Journal of mathematical biology》1999,39(2):91-108
In principle there are two approaches to modelling a trade-off between the positive and negative outcomes of a behavior:
after suitably defining a value for the behavior in the absence of any trade-off, one can either multiply that value by an
appropriate discount or subtract an appropriate cost. In a prospective analysis of sperm competition, Parker (Proc. Roy. Soc.
Lond. B (1990) 242, 120–126) adopted the multiplicative approach to model the trade-off between the value of a mating and the cost of its acquisition.
He obtained two paradoxical results. First, if two males ‘know’ whether they are first or second to mate, but these roles
are assigned randomly, then sperm numbers should be the same for both males whether the ‘raffle’ for fertilization is fair
or unfair. Second, if mating order is constant, then a favored male should expend less on sperm. His results are puzzling
not only in terms of intuition about nature, but also in terms of his model’s consistency. In other words, they present both
an external and an internal paradox.
Parker assumed the fairness of the raffle to a disfavored male to be independent of how much sperm a favored male deposits.
This article both generalizes Parker’s analysis by allowing fairness to decrease with sperm expenditure by the favored male
and compares Parker’s results to those obtained by the additive approach. In many respects, results are similar. Nevertheless,
if the costs of mating are assumed to increase with sperm expenditure but not to depend on the role in which sperm is expended,
as Parker assumed, then the additive approach is more fundamentally correct. In particular, Parker’s constant-role paradox
is an artifact of his approach. His random-role paradox is internally rationalized in terms of standard microeconomic theory.
When fairness decreases, however slightly, with sperm expenditure by the favored male, both models demonstrate that the evolutionarily
stable strategy is for more sperm to be deposited during a favored mating than during a disfavored mating. The lower the costs,
the greater the divergence. Thus a possible resolution of the external paradox is that fairness is not constant in nature.
Received: 7 December 1998 相似文献
2.
Model averaging is gaining popularity among ecologists for making inference and predictions. Methods for combining models
include Bayesian model averaging (BMA) and Akaike’s Information Criterion (AIC) model averaging. BMA can be implemented with
different prior model weights, including the Kullback–Leibler prior associated with AIC model averaging, but it is unclear
how the prior model weight affects model results in a predictive context. Here, we implemented BMA using the Bayesian Information
Criterion (BIC) approximation to Bayes factors for building predictive models of bird abundance and occurrence in the Chihuahuan
Desert of New Mexico. We examined how model predictive ability differed across four prior model weights, and how averaged
coefficient estimates, standard errors and coefficients’ posterior probabilities varied for 16 bird species. We also compared
the predictive ability of BMA models to a best single-model approach. Overall, Occam’s prior of parsimony provided the best
predictive models. In general, the Kullback–Leibler prior, however, favored complex models of lower predictive ability. BMA
performed better than a best single-model approach independently of the prior model weight for 6 out of 16 species. For 6
other species, the choice of the prior model weight affected whether BMA was better than the best single-model approach. Our
results demonstrate that parsimonious priors may be favorable over priors that favor complexity for making predictions. The
approach we present has direct applications in ecology for better predicting patterns of species’ abundance and occurrence. 相似文献
3.
Three categories of wetland assessment methods have been recognized by the United States Environmental Protection Agency,
including Level 1—Landscape-scale Assessment; Level 2—Rapid Field Methods; and Level 3—Intensive Biological and Physico–Chemical
Measures. This study incorporates wetland assessment methods for each assessment level, including the Level 1 Landscape Development
Intensity (LDI) index, Level 2 Wetland Rapid Assessment Procedure (WRAP), and Level 3 Florida Wetland Condition Index (FWCI).
Using a neighborhood analysis in Geographic Information Systems (GIS), an LDI index map was created using 1995 land use, creating
a calculated LDI index value for each 30 m2 area in Florida. Level 1–3 assessment procedures were employed at 193 palustrine emergent (n = 75) and forested (n = 118) wetlands. Significant correlations were found among the multiple Level 1–3 assessment procedures using the nonparametric
Spearman’s correlation coefficient for pair-wise comparisons of LDI and WRAP, LDI and diatom FWCI, WRAP and diatom FWCI, LDI
and macrophyte FWCI, WRAP and macrophyte FWCI, LDI and macroinvertebrate FWCI, and WRAP and macroinvertebrate FWCI (|r| > 0.50, P < 0.01). Defining the relationship between Level 1–3 assessment methods may be used to estimate the more intensive and species
assemblage-specific Level 3 FWCI assessment scores for wetlands with Level 1 or Level 2 scores. Inferences can then be made
as to wetland condition based on established correlations with intensive assessment methods. 相似文献
4.
Spencer HG 《Genetica》2009,136(2):285-293
Standard Mendelian genetic processes incorporate several symmetries, one of which is that the level of expression of a gene
inherited from an organism’s mother is identical to the level should that gene have been inherited paternally. For a small
number of loci in a variety of taxa, this symmetry does not hold; such genes are said to be “genomically imprinted” (or simply
“imprinted”). The best known examples of imprinted loci come from mammals and angiosperms, although there are also cases from
several insects and some data suggesting that imprinting exists in zebra fish. Imprinting means that reciprocal heterozygotes
need not be, on average, phenotypically identical. When this difference is incorporated into the standard quantitative-genetic
model for two alleles at a single locus, a number of standard expressions are altered in fundamental ways. Most importantly,
in contrast to the case with euMendelian expression, the additive and dominance deviations are correlated. It would clearly
be of interest to be able to separate imprinting effects from maternal genetic effects, but when the latter are added to the
model, the well-known generalized least-squares approach to deriving breeding values cannot be applied. Distinguishing these
two types of parent-of-origin effects is not a simple problem and requires further research. 相似文献
5.
About 30% of the world’s soil carbon is stored in peat soils. Peat land’s functional principle of carbon storage greatly depends
on management strategies. Therefore, agricultural peat land use becomes a focal point of interest in the current debate on
climate protection. Agricultural management demands a drawdown of the water-level that causes degradation of the soils, as
well as trace-gas emissions which have a negative impact on greenhouse-gas balance. Climate-friendly peat land management
strategies, however, demand enhanced groundwater tables and decreased land-use intensity. Against this background, we analyse
ways of re-organising agricultural peat land use within a case study located in Germany, where intensive peat land use accounts
for 2.3–5.1% of the country’s overall greenhouse-gas emission. The study takes place in six regions which represent all possible
socio-economic and natural conditions with regard to the range of existing peat land types, range of management and cultivation
types, as well as the range of land-use intensity. To analyse potentials and effects of re-organising peat land use, stakeholder
workshops and extensive farm surveys were carried out. The results indicate that reservations exist as regards a re-organisation
of peat land management. Financial compensation for farmers appears necessary. The results also show that the potential of
rearrangement throughout the regions varies significantly, mainly according to the existing level of interconnection and cooperation
between local stakeholders, the technical feasibility of restoration and water logging and the level of agricultural profitability
of peat land cultivation with regard to income, capital commitment and the share of affected peat land area. 相似文献
6.
Ernesto Trucco 《Bulletin of mathematical biology》1963,25(4):343-366
This is the continuation of part I, which was published in the September, 1963, issue ofThe Bulletin. Section 5 treats the special case in which the left absorbing barrier recedes to −∞, leaving essentially only one barrier
at a finite distance Λ (>0) from the origin. The eigenfunctions are now parabolic cylinder functions. The limiting cases Λ→+∞
and Λ→0 are also considered. Though meaningless for practical applications to our problem, they are of interest, mathematically,
because the Green’s function for the solution of the Fokker-Planck equation assumes a particularly simple form. In section
6 we study, by means of an example, how the “force of mortality” may vary with time before attaining its final asymptotic
value. Section7, still dealing with only one absorbing barrier, shows that our results for “strong homeostasis” are identical with those
derived by Chandrasekhar for the escape of particles through a potential barrier in the limiting case of quasi-static flow.
Precise conditions are given for the validity of both the quasi-static and the Smoluchowski approximations to the Fokker-Planck
equation. Finally, in section 8, a brief mention is made of Gevrey’s method for the solution of parabolic partial differential
equations. 相似文献
7.
We consider the Stag Hunt in terms of Maynard Smith’s famous Haystack model. In the Stag Hunt, contrary to the Prisoner’s
Dilemma, there is a cooperative equilibrium besides the equilibrium where every player defects. This implies that in the Haystack
model, where a population is partitioned into groups, groups playing the cooperative equilibrium tend to grow faster than
those at the non-cooperative equilibrium. We determine under what conditions this leads to the takeover of the population
by cooperators. Moreover, we compare our results to the case of an unstructured population and to the case of the Prisoner’s
Dilemma. Finally, we point to some implications our findings have for three distinct ideas: Ken Binmore’s group selection
argument in favor of the evolution of efficient social contracts, Sewall Wright’s Shifting Balance theory, and the equilibrium
selection problem of game theory. 相似文献
8.
The levels of selection problem was central to Maynard Smith’s work throughout his career. This paper traces Maynard Smith’s
views on the levels of selection, from his objections to group selection in the 1960s to his concern with the major evolutionary
transitions in the 1990s. The relations between Maynard Smith’s position and those of Hamilton and G.C. Williams are explored,
as is Maynard Smith’s dislike of the Price equation approach to multi-level selection. Maynard Smith’s account of the ‘core
Darwinian principles’ is discussed, as is his debate with Sober and Wilson (1998) over the status of trait-group models, and
his attitude to the currently fashionable concept of pluralism about the levels of selection. 相似文献
9.
Jeanne Guillemin 《Human nature (Hawthorne, N.Y.)》1994,5(1):1-22
The diffusion of medical technology is largely determined by the marketplace demands supported by national and historical
contexts. Using the cases of cesarean delivery and newborn intensive care in the United States, this article presents the
argument that the interaction of four factors accounts for the rapid diffusion of untested technologies. These factors are
economic expansion in an unrestricted market, the vulnerability of the patient population, a social disposition towards emergency
medicine, and the vested interest of medical specialists.
Jeanne Guillemin is a professor of sociology at Boston College. She served on the National Institutes of Health Consensus
Task Force on Cesarean Birth and authored the section of the task force’s 1981 report on international data on cesarean rates.
She is also the coauthor, with Lynda Lytle Holmstrom, ofMixed Blessings: Intensive Care for Newborns, which analyzes the national and international development of this hospital service, as well as authoring numerous articles
on medical policy. 相似文献
10.
Malcolm Parker 《Journal of bioethical inquiry》2006,3(3):133-136
Stewart and DeMarco’s economic theory of patient decision-making applied to the case of diabetes is flawed by clinical inaccuracies and an unrealistic depiction of patients as rational traders. The theory incorrectly represents patients’ struggles to optimize their management as calculated trade-offs against the costs of care, and gives an unrealistic, inflexible account of such costs. It imputes to physicians the view that their patients’ lack of compliance is unreasonable, but physicians are accustomed to the variety of human factors which contribute to suboptimal compliance, and work with patients to minimize their influence. By depicting patients as rational traders rather than human beings with a range of motivations and burdens, the economic theory distorts the proper function of informed consent. 相似文献
11.
Shigeru Takasaki 《Journal of bioenergetics and biomembranes》2009,41(5):407-410
The relationships between Japanese Alzheimer’s disease (AD) patients and their mitochondrial single nucleotide polymorphism
(mtSNP) frequencies at individual mtDNA positions of the entire mitochondrial genome are described using the radial basis
function (RBF) network and the modified method. Japanese AD patients are associated with the haplogroups G2a, B4c1, and N9b1.
In addition, to compare mitochondrial haplogroups of the AD patients with those of other classes of Japanese people, the relationships
between four classes of Japanese people (i.e., Japanese centenarians, Parkinson’s disease (PD) patients, type 2 diabetic (T2D)
patients, and non-obese young males) and their mtSNPs are also described. The four classes of people are associated with following
haplogroups: Japanese centenarians—M7b2, D4b2a, and B5b; Japanese PD patients—M7b2, B4e, and B5b; Japanese T2D patients—B5b,
M8a1, G, D4, and F1; and Japanese healthy non-obese young males—D4g and D4b1b. The haplogroups of the AD patients are therefore
different from those of the other four classes of Japanese people. As the analysis method described in this article can predict
a person’s mtSNP constitution and the probabilities of becoming an AD patient, centenarian, PD patient, or T2D patient, it
may be useful in initial diagnosis of various diseases. 相似文献
12.
In the information processing procedure of stereo vision, the uniqueness constraint has been used as one of the constraints
to solve the “correspondence problem”. While the uniqueness constraint is valid in most cases, whether it is still valid in
some particular stimulus configuration (such as Panum’s limiting case) has been a problem of widespread debate for a long
time. To investigate the problem, we adopted the Panum’s limiting case as its basic stimulus configuration, and delved into
the phenomenon of binocular fusion from two distinct aspects: visual direction and orientation disparity. The results show
that in Panum’s limiting case binocular fusion does not comply with the rules governing regular binocular fusion as far as
visual direction and orientation disparity are concerned. This indicates that double fusion does not happen in Panum’s limiting
case and that the uniqueness constraint is still valid. 相似文献
13.
Culture is an essential variable of diagnosis and treatment. A cultural perspective draws attention to the social context
within which symptoms arise, are given meaning, and are managed. Ethno-cultural work on illness narratives suggests that most
people can provide culturally-based explanations for their symptoms. While these explanations are inconsistent with biomedical
theory, they relieve patient distress by allowing the patient to create meaning for symptoms. Exploring the characteristics,
context, and antecedents of the symptoms enables the patient to convey them to the clinician who may have a divergent explanation
of sickness. This case study uses the Outline for Cultural Formulation of the DSM-IV created for clinicians to elicit a narrative
account of the illness experience from the patient. Our study examines how the patient, a Laotian used social indignation
(“Kwam khem keuang”) as an explanatory model for his ailment. He was diagnosed with post-traumatic stress disorder after having undergone a
traumatic amputation. In the process of explaining his illness through a cultural idiom, the patient was able to reveal both
personal and collective meaning of repressed anger and frustration, expressing them in a context that was acceptable to him.
This cultural idiom allowed the patient to reflect upon the structure of the health care system and the specific context in
which symptoms and their possible origins are recounted and explored. It also clarified to the treating clinicians some categories
of experience and causal explanations that did not fit easily with western biomedical and psychiatric understanding. The case
study illustrates how a cultural approach to illness from the patient’s perspective offers a reflexive stance on the clinician–patient
interaction that allows for better patient care. 相似文献
14.
Stephen M. Ferkovich Herbert Oberlander Charles Dillard Eddie Leach 《In vitro cellular & developmental biology. Animal》1994,30(4):279-282
Summary Embryos of the parasitoidMicropolitis croceipes develop from pregerm band stage to first larval instar in cell culture medium conditioned by a cell line (IPLB-LdFB) derived
from fat body from an atypical hostLymantria dispar. However, the percentage of eggs that develop normally to the first larval instar stage is significantly less than for those
maintained in IPL-52B medium conditioned with host fat body tissue. Therefore, we examined the capacity of five insect cell
lines to promote growth and development of pregerm band eggs in five media, IPL-52B, TC-199, TC-100, Grace’s, and ExCell 400.
The developmental response ofM. croceipes was dependent both on the cell line and the cell culture medium used. TC-100, TC-199, and Grace’s media promoted development
to the germ band stage without the need for conditioning with host tissue. IPL-52B supported development to the germ hand
stage when a defined lipid concentrate was added. In IPL-52B medium, the IPLB-LdFB cell line promoted a significantly higher
number of eggs developing to germ band relative to the other cell lines; however, none of the cell line-conditioned IPL-52B
medium significantly stimulated egg hatch relative to the control medium. None of the cell line-conditioned Grace’s media
had a significant effect on eggs attaining germ band stage compared with the Grace’s control medium. However, Grace’s medium
conditioned with the IAL-TND1 and IPLB-LdFB cell lines promoted development beyond germ band, resulting in a significantly
higher percentage of hatching eggs than the Grace’s control medium. Although the BCIRL-HZ-AMI cell line, which is derived
from the parasitoid’s typical host, did not induce hatch in either IPL-52B medium or Grace’s medium, it promoted hatch in
TC-199 and Excell 400 media. Fat body taken from the same species that the cell lines were derived from was a better predictor
of a cell line’s embryotrophic activity in Grace’s medium rather than in IPL-52B medium. Thus, the composition of the medium
and the species and tissue type of the cell line source must be evaluated interactively to determine optimal conditions for
promoting development ofM. croceipes in vitro. 相似文献
15.
To clarify the modulation of dragon’s blood on the tetrodotoxin-resistant (TTX-R) sodium currents in dorsal root ganglion
(DRG) neurons and explore its corresponding material basis for the efficacy, using whole-cell patch clamp technique, the effects
of dragon’s blood and the combined effects of three components (cochinchinenin A, cochinchinenin B, and loureirin B) extracted
from dragon’s blood on the TTX-R sodium currents in acute-isolated DRG neurons of rats were observed. According to the operational
definition of material basis for the efficacy of TCM established, the material basis of the modulation on the TTX-R sodium
currents in DRG neurons of dragon’s blood was judged from the experimental results. The drug interaction equation of Greco
et al. was used to assess the interaction of the three components extracted from dragon’s blood. This investigation demonstrated
that dragon’s blood suppressed the peak TTX-R sodium currents in a dose-dependent way and affected the activations of TTX-R
sodium currents. The effects of the combination of cochinchinenin A, cochinchinenin B, and loureirin B were in good agreement
with those of dragon’s blood. Although the three components used alone could modulate TTX-R sodium currents, the concentrations
of the three components used alone were respectively higher than those used in combination when the inhibition rates on the
TTX-R sodium currents of them used alone and in combination were the same. The combined effects of the three components were
synergistic. These results suggested that the interference with pain messages caused by the modulation of dragon’s blood on
TTX-R sodium currents in DRG neurons may explain some of the analgesic effect of dragon’s blood and the corresponding material
basis for the efficacy is the combination of cochinchinenin A, cochinchinenin B, and loureirin B. 相似文献
16.
Richard Karban 《Plant Ecology》2007,191(2):295-303
Many examples of associational resistance have been reported, in which a plant’s neighbors reduce the rate of damage by herbivores
that it experiences. Despite 30 years of interest and hundreds of examples of associational resistance, we still know very
little about how plants avoid their herbivores. This lack of mechanistic understanding prevents us from predicting when or
where associational resistance will be important or might affect species’ distributions. I demonstrate here that the plant
neighborhoods that surrounded focal mule’s ears (Wyethia mollis) individuals affected the damage they received. In particular, distance between a focal mule’s ears individual and its nearest
sagebrush neighbor (Artemisia tridentata) was a good predictor of how much leaf area the mule’s ears would lose to herbivores over 2 years. Mule’s ears close to sagebrush
suffered less loss than those with more distant nearest sagebrush neighbors. Mule’s ears with near sagebrush neighbors suffered
half the leaf loss as mule’s ears with sagebrush experimentally removed. This associational resistance was probably not caused
by sagebrush attracting or increasing populations of predators of generalist herbivores. Sagebrush is known to emit chemicals
that are feeding deterrents to generalist grasshoppers and these deterrents were probably involved here. Volatile chemicals
emitted by damaged sagebrush have been found to induce resistance in neighboring plants of several species. However, I found
no evidence for such eavesdropping here as mule’s ears gained associational resistance from sagebrush neighbors whether or
not those sagebrush neighbors had been experimentally damaged. Understanding the mechanisms responsible for associational
resistance is critical to predicting where and when it will be important. 相似文献
17.
How do we quantify division of labor? We review several fields (sociology, landscape ecology, statistics, information theory,
and biogeography) that have been cognizant of these questions and been somewhat successful at answering them. We review fourteen
indices for quantifying division of labor, sensu lato, which can be categorized into four families: Shannon’s index/entropy, Simpson’s index, geometric mean, and standard/absolute
deviation (including coefficients of variation). We argue that those indices using matrix inputs will simultaneously quantify
the interplay between all individuals and all tasks and will thus best capture the essence of division of labor.
Received 29 March 2006; revised 16 November 2006; accepted 12 February 2007. 相似文献
18.
Alexandra Flávia Gazzoni Cecília Bittencourt Severo Marines Bizarro Barra Luiz Carlos Severo 《Mycopathologia》2009,167(4):197-202
Here we report an unusual case of disseminated cryptococcosis in a patient with AIDS. Although typical Cryptococcus neoformans micromorphology was observed in tongue biopsy, cervical lymph node examination revealed atypical histopathologic findings.
These included pseudohyphae, chains of budding yeasts and structures resembling germ tubes. Cryptococcus neoformans infection in supraclavicular lymph nodes was also confirmed by culture. The importance of using special histochemical techniques—Mayer’s
mucicarmine stain for mucicarminophilic capsule and Grocott’s silver stain—in the diagnosis of cryptococcosis is reinforced. 相似文献
19.
“Genomic medicine” refers to the diagnosis, optimized management, and treatment of disease—as well as screening, counseling,
and disease gene identification—in the context of information provided by an individual patient’s personal genome. Genomic
medicine, to some extent synonymous with “personalized medicine,” has been made possible by recent advances in genome technologies.
Genomic medicine represents a new approach to health care and disease management that attempts to optimize the care of a patient
based upon information gleaned from his or her personal genome sequence. In this review, we describe recent progress in genomic
medicine as it relates to neurological disease. Many neurological disorders either segregate as Mendelian phenotypes or occur
sporadically in association with a new mutation in a single gene. Heritability also contributes to other neurological conditions
that appear to exhibit more complex genetics. In addition to discussing current knowledge in this field, we offer suggestions
for maximizing the utility of genomic information in clinical practice as the field of genomic medicine unfolds. 相似文献
20.
Danwei as a cornerstone of Chinese urban society has received great research attention. The relationship between the Danwei and psychiatric patients, however, remains unclear. This article aims to shed light on the subject with an integrated micro–macro
approach. It introduces a historical understanding of mental health in urban China under the “economic state in transition”
framework. A detailed case study in clinical sociology is provided to reveal the many social factors affecting the experience
of a schizophrenic patient and his significant others. A changing role of the Danwei is hypothesized and validated with qualitative data. The Danwei was shown to have changed significantly before the mid-1990s, yet it still played a major role in urban workers’ lives, including
those of psychiatric patients, and even more so in people’s expectations. This lends support to the need for a more responsive
public policy to address various social issues brought about by economic reform, with the learning of worldwide experiences
including “community care,” “social support” and “social rehabilitation.” Implications for social research, policymaking and
professional practice are discussed.
相似文献
Robert SévignyEmail: |