共查询到20条相似文献,搜索用时 15 毫秒
1.
Shuzhen Yang Rui Zhang Changchao Hu Jie Xie Jingquan Zhao 《Photosynthesis research》2009,99(2):99-106
Light state transition is a physiological function of oxygenic organisms to balance the excitation of photosystem II (PSII)
and photosystem I (PSI), hence a prerequisite of oxygen-evolving photosynthesis. For cyanobacteria, phycobilisome (PBS) movement
during light state transition has long been expected, but never observed. Here the dynamic behavior of PBS movement during
state transition in cyanobacterium Synechocystis PCC6803 is experimentally detected via time-dependent fluorescence fluctuation. Under continuous excitation of PBSs in the
intact cells, time-dependent fluorescence fluctuations resemble “damped oscillation” mode, which indicates dynamic searching
of a PBS in an “overcorrection” manner for the “balance” position where PSII and PSI are excited equally. Based on the parallel
model, it is suggested that the “damped oscillation” fluorescence fluctuation is originated from a collective movement of
all the PBSs to find the “balance” position. Based on the continuous fluorescence fluctuation during light state transition
and also variety of solar spectra, it may be deduced that light state transition of oxygen-evolution organisms is a natural
behavior that occurs daily rather than an artificial phenomenon at extreme light conditions in laboratory. 相似文献
2.
Dieter Korn 《Pal?ontologische Zeitschrift》2003,77(2):445-470
The anti-Darwinian “Typostrophe Theory” of O.H.Schindewolf can be put to the test by revisiting the ammonoid examples on which this macroevolutionary model was founded. It is shown
that none of the three theoretical elements saltationism, internalism, and cyclism can be supported by empirical data obtained
from ammonoid research. Putative saltations (“Typogenesis”) were feigned because of the lack of knowledge of intermediate
forms. Internalistic and orthogenetic development (“Typostasis”) can only be favoured by neglecting possible functions of
morphological characters. Preprogrammed extinction of “degenerated” clades (“Typolysis”) is unlikely when ruling out anthropocentric
views regarding ammonoid morphology. In terms of evolution of Palaeozoic ammonoids, there is no basis for the preference of
the “Typostrophe Theory” or some of its composing elements, including the “Type Concept” and “Proterogenesis”, over the Darwinian
evolutionary model and the Modern Synthesis.
相似文献
3.
Theodosios Pavlidis 《Bulletin of mathematical biology》1965,27(2):215-229
The results of a previous theoretical study of a class of systems are applied for the design of neural nets which try to simulate
biological behavior.
Besides the models for single aperiodic and periodic neurons, a “neural oscillator” is developed which consists of two cross-excited
neurons. Its response is similar to the firing pattern of certain biological neural oscillators, like the flying system of
the locust. Also, by proper change of its parameters, it can be made highly irregular, providing a deterministic model for
the spontaneous neural activity. 相似文献
4.
Yoshifumi Yamawaki 《Journal of Ethology》1998,16(1):23-27
Adult females of the praying mantisTenodera angustipennis were presented with computer-generated images, and the attractiveness of “non-locomotive” prey models was examined. Mantises
fixated and struck the “body and leg” model (consisting of an immobile black square on a white background with 2 black lines
oscillating randomly at its sides) more frequently than the “leg” model (only oscillating lines) or the “body” model (static
square only). This indicates that the model consisting of a static object and moving lines effectively elicits mantis strike
behavior, although it is “non-locomotive.” 相似文献
5.
The behavior of wild chimpanzees at Bossou, Guinea, was studied from November 1976 to May 1977 recognizing each chimpanzee
without artificial feeding. During the study period some tool-using and tool-making behavior was observed, as follows: (1)
Although water drinking using a “leaf-sponge” was not seen, that using a “leaf-spoon” was observed for taking water from the
hollow of a tree. (2) “Termite fishing” was not seen in this group although there were many termite hills in the moving range
of the chimpanzees. They dug termites from the hollow of a tree by pounding with a small stick. Similar use of a stick was
made for digging up the resin from a tree. (3) “Aimed throwing” was frequently observed in adult males for attacking an observer,
and in adolescents and juveniles as mischief against an observer or for their own play. (4) “Nut cracking” with a pair of
stones was seen for removing the ovule from palm-seeds. Particular stones were repeatedly used by many chimpanzees for a long
period. (5) “Branch hauling” represented difficult work. Patient and inventive manufacture of proper sticks was necessary
for capturing branches which they were unable to reach normally.
Local variations in the tool-using patterns and manufacturing ability of chimpanzees are discussed. 相似文献
6.
Masayoshi Maehata 《Ichthyological Research》2001,48(3):283-287
The mating behavior of the rock catfish Silurus lithophilus (Siluriformes: Siluridae), a species endemic to the Lake Biwa system, was observed from May to July in 1989–1994 along the
rocky shore of the lake's outlet, the Seta River. The mating behavior of S. lithophilus involved a certain behavioral sequence: “chasing,”“clinging,” and “enfolding” while “squeezing” by the male; and “circling”
by the spawned pair. The mating behavior of this species was basically similar to that of S. biwaensis, but greatly different from that of S. asotus, which spawns in running water (in ditches). The mating behavior of S. lithophilus (and S. biwaensis) might have developed as an adaptation to lentic environments such as the shores of the large river or the lake.
Received: October 25, 2000 / Revised: February 25, 2001 / Accepted: March 8, 2001 相似文献
7.
A mathematical model of HIV dynamics in the presence of a rescuing virus with replication deficiency
Recently, an enzyme (Cre recombinase) has been developed by directed evolution that successfully removes the HIV genome from
the nuclear DNA of infected cells. To explore this idea further, we hypothesized that a replication deficient virus (called
“police virus”), added externally, can deliver such a recombinase which excises the integrated HIV DNA from the genome of
infected cells. Such a “police virus” could attack and remove the integrated provirus which is not possible using contemporary
strategies. The hypothesis was tested by developing a mathematical model that describes the dynamics of virus-host cell interaction
and the consequences of introducing the “police virus”. The simulations show that such a therapeutic vector may eradicate
all HIV viruses from the system in the long term. All components of the HIV infection (free virus, latently, and actively
infected cells) can be cleared and the system ends up only with susceptible CD4+ cells. The proposed model may provide new
insights in the dynamical behavior and future alternative treatments of HIV. 相似文献
8.
Patrick J. Brennan 《Journal of biosciences》1984,6(5):685-689
There is now a considerable body of evidence to suggest that the phthiocerol-containing lipids, including the phenolic glycolipids,
comprise the so-called “peribacillary substance”, “spherical droplets”, “foamy structures” and “capsular materials” ofMycobacterium leprae. Thus, the phthiocerol-containing lipid capsule may be directly responsible for the intracellular survival ofMycobacterium leprae. 相似文献
9.
N. Rashevsky 《Bulletin of mathematical biology》1947,9(1):1-8
We may consider that most of the human behavior is a set of learned responses to certain patterns which recur frequently in
the course of human life. Some “abnormal” events or experiences may result in the learning of abnormal responses, and thus
in abnormal behavior. The “abnormal” responses may begin to be learned after some of the normal response patterns have been
fairly well established. The development of both normal and abnormal behavior may thus be represented by learning curves of
the type studied by H. D. Landahl. Applying some of the results of the theory of learning curves and considering that the
normal and abnormal reactions may reciprocally inhibit each other, a quantitative theory of some psychoses may be developed.
In particular, the effects of shock may be deduced from the assumption that they cause the more recently learned abnormal
reactions to be “unlearned” more readily, than the earlier learned “normal” reactions. The effectiveness of shock treatments
as a function of the duraction of psychosis is discussed from this point of view. 相似文献
10.
Source-sink landscape theory and its ecological significance 总被引:2,自引:0,他引:2
Exploring the relationships between landscape pattern and ecological processes is the key topic of landscape ecology, for
which, a large number of indices as well as landscape pattern analysis model were developed. However, one problem faced by
landscape ecologists is that it is hard to link the landscape indices with a specific ecological process. Linking landscape
pattern and ecological processes has become a challenge for landscape ecologists. “Source” and “sink” are common concepts
used in air pollution research, by which the movement direction and pattern of different pollutants in air can be clearly
identified. In fact, for any ecological process, the research can be considered as a balance between the source and the sink
in space. Thus, the concepts of “source” and “sink” could be implemented to the research of landscape pattern and ecological
processes. In this paper, a theory of sourcesink landscape was proposed, which include: (1) In the research of landscape pattern
and ecological process, all landscape types can be divided into two groups, “source” landscape and “sink” landscape. “Source”
landscape contributes positively to the ecological process, while “sink” landscape is unhelpful to the ecological process.
(2) Both landscapes are recognized with regard to the specific ecological process. “Source” landscape in a target ecological
process may change into a “sink” landscape as in another ecological process. Therefore, the ecological process should be determined
before “source” or “sink” landscape were defined. (3) The key point to distinguish “source” landscape from “sink” landscape
is to quantify the effect of landscape on ecological process. The positive effect is made by “source” landscape, and the negative
effect by “sink” landscape. (4) For the same ecological process, the contribution of “source” landscapes may vary, and it
is the same to the “sink” landscapes. It is required to determine the weight of each landscape type on ecological processes.
(5) The sourcesink principle can be applied to non-point source pollution control, biologic diversity protection, urban heat
island effect mitigation, etc. However, the landscape evaluation models need to be calibrated respectively, because different
ecological processes correspond with different source-sink landscapes and evaluation models for the different study areas.
This theory is helpful to further study landscape pattern and ecological process, and offers a basis for new landscape index
design.
__________
Translated from Acta Ecologica Sinica, 2006, 26(5): 1444–1449 [译自: 生态学报] 相似文献
11.
Regarding the arts as something peopledo — as behaviors, rather than the residue or artifacts of behavior — makes possible a theoretical grounding about their nature
and importance, an endeavor that current anthropology of art has largely abandoned. A reconsideration of the suspect and largely
discarded terms “functionalism” and “evolutionism” is presented in light of current evolutionary thinking. It is suggested
that a contemporary reformulation of these concepts, illustrated by the author's Darwinian or “adaptationist” perspective
on art, supports aims and claims of current anthropology of art, and contributes new focus and direction to its endeavors. 相似文献
12.
Microtubules (MT) are composed of 13 protofilaments, each of which is a series of two-state tubulin dimers. In the MT wall,
these dimers can be pictured as “lattice” sites similar to crystal lattices. Based on the pseudo-spin model, two different
location states of the mobile electron in each dimer are proposed. Accordingly, the MT wall is described as an anisotropic
two-dimensional (2D) pseudo-spin system considering a periodic triangular “lattice”. Because three different “spin-spin” interactions
in each cell exist periodically in the whole MT wall, the system may be shown to be an array of three types of two-pseudo-spin-state
dimers. For the above-mentioned condition, the processing of quantum information is presented by using the scheme developed
by Lloyd. 相似文献
13.
Protein–protein interactions (PPIs) play a central role in virtually all biological processes and have been the focus of intense
investigation from structural molecular biology to cell biology for the majority of the last two decades and, more recently,
are emerging as important targets for pharmaceutical intervention. A common motif found at the interface of PPIs is the α-helix,
suggesting that, in the same way as the “lock and key” model has evolved for competitive inhibition of enzymes, it should
be possible to elaborate “rule-based” approaches for inhibition of helix-mediated PPIs. This review will describe the biological
function and structural features of a series of representative helix-mediated PPIs and discuss approaches that are being developed
to target these interactions with small molecules that employ non-natural amino acids. 相似文献
14.
N. Rashevsky 《Bulletin of mathematical biology》1969,31(4):789-795
The author's theory of the adoption of certain types of behavior patterns (Rashevsky, N., 1957, “Contributions to the Theory
Initiative Behavior”.Bull. Maths. Biophysics,19, 91–119; 1968,Looking at History through Mathematics, Cambridge, Massachusetts: M.I.T. Press) consisting of elementary behaviors for each of which there is an opposite one and
the two are mutually exclusive, is applied to describe the changes in the general type of behavior of a society. The elementary
acts of which the whole problem consists may be either overt activities or beliefs or opinions. The general behavior patternsadopted by the society are considered as the “proper” or “just” ones. Any deviation from it in either one or more of the component
elementary behaviors is considered as “unjust” and is subject to some punitive action. The total number of possible mutually
exclusive behavior patterns is very large but finite. Within this very large range of possible patterns, we find that this
notion of justice is relative, because changes from any behavior pattern to any other may occur. It is further shown that
the amount of punishment for the deviation from the accepted pattern in order to be effective as well as efficient must be
applied in different ways to different individuals even for the same transgression. 相似文献
15.
This report describes a method by which the concepts of the lead vector and the lead field may be extended to include equivalent
cardiac singularities above the first order. The theoretical treatment results in generalization of the well-known lead vector
principle into a lead tensor apparatus. The specific electrocardiographic contribution of annth order multipole is found to be the product of annth rank contravariant (“heart”) tensor by a covariant (“lead”) tensor of the same rank, and with identical indices. Methods
are also described whereby lead tensor components may be cast into a form which relates them directly to the more usual, spherical
harmonic notation of multipolar current generators. Some attention is devoted to the possibility of applying lead tensors
to biomedical problems, particularly to the prospect of quantitatively evaluating the significant multipolar components of
the human heart. 相似文献
16.
V. N. Mikheev 《Journal of Ichthyology》2009,49(11):1032-1041
A review of experimental, field and theoretical papers on several topics related to the study of variability of fish shoaling
behavior caused by separate impacts of predators and parasites as well as by combined effects of these factors. First, antipredator
functions and changes in fish shoal parameters caused by predation risk are briefly discussed. Then, effects of parasites
that have the potential to act as a force that can select for either larger or smaller group size, or even for solitary behavior
are reviewed. Predation- and parasitism-induced variations in the shoal size and shape, distance between members of a shoal,
position of fish within a shoal, effects of habitat complexity, parasite-assortative shoaling are described. Finally, an interplay
between the parasitism and predation risks that could influence protective functions of fish shoaling is discussed. It is
emphasized that not only the binary “predator-prey” and “host-parasite” systems, but a three-component system “parasite.-host-predator”
which embrace both direct and indirect effects have to be studied. 相似文献
17.
Anatol Rapoport 《Bulletin of mathematical biology》1961,23(4):321-335
As a “base line” of memorization performance, the behavior of a “perfect learner” is considered. He is characterized by a
perfect memory and by the ability to choose the best search procedure in problems where the correct response from a given
repertoire is to be found to each of several stimuli under the condition of “right” and “wroing” promptings by the experimenter.
Expected learning curves are derived for the case of disjoint response repertoires associated with the stimuli under cyclic
and random presentation of the stimuli and for the case of a single response repertoire (a one-to-one matching problem) under
cyclic presentation. 相似文献
18.
R. Bernhard 《Bulletin of mathematical biology》1965,27(3):435-447
A correspondence is established between a tangible model of brain structure (and function) and a system of observer-observed
interactions. The observed quantities are “stimuli” in the form of signal amplitude distributions in a mass of neuron-like
units; the observer is a set of neurons (not circumscribed in a local region) in which a distributed parameter mirrors the
stimulus history of the set, i.e., represents a “memory”. Utilizing the theory of the Perceptron, a contemporary brain model,
it is demonstrated that large systems composed of many observer-observed interactions exhibit quantum mechanical behavior
on a “macroscopic” scale. This behavior entails wave-like phenomena and the need of applying the superposition mechanics to
system information content calculations. 相似文献
19.
Akio Mori 《Primates; journal of primatology》1995,36(1):11-26
The feeding process of Japanese monkeys on soy beans which were scattered over a sandy beach on Koshima islet was studied.
Younger monkeys were able to pick up more beans when 8 kg of beans were divided and given two times (“two times feeding”)
than when the whole amount (8 kg) of beans was given at one time (“one time feeding”). The effect of saturation of the food
intake capacity in younger monkeys at the first feeding in “two times feeding” did not appear at the second feeding one hour
later. The minutely intake of soy beans (feeding speed) for each age class was analyzed. The decline of feeding speed in adult
females after the peak in “one time feeding” was not related to the decline in density of beans on the ground, and this decline
was caused by saturation of their food intake capacity.
Adult females were divided into four classes according to their dominance rank order: high, lower-high, higher-low, and low
classes. The total amount of intake in “one time feeding” was far larger in the high class than in any of the other classes.
The total amount of feeding in the first feeding of “two times feeding” increased in accordance with rise in the dominance
rank class, and there was no relation to rank and total feeding amount in the second feeding of “two times feeding.” Differences
existed in the process of feeding between the rank classes. The feeding speed of the low class was as high as that of the
high class on the curve of minutely intake, while the low class stopped feeding much earlier than the high class. The lower-high
class displayed a low feeding speed, and stopped feeding the latest. The order of the duration to stay and to feed in the
feeding area was lower-high > high > higher-low > low, and this order did not change under the three different feeding conditions,
“one time feeding,” and the first and second feedings of “two times feeding.” Adolescent females tended to stay the longest
duration in the feeding area among all age classes. Both the lower-high class females and adolescent females had an unstable
social status in the Koshima group, and their social status affected their feeding behaviors. The feeding behaviors were similar
in attitude depending on social status, and are considered to be maintained for a fairly long time.
The feeding strategy of the lower-high class, in staying a longer duration in the artificial feeding area, and departing later,
may be effective under the artificial feeding conditions, but it may be a bad strategy in a natural habitat where the food
is not so clumped as in artificial feeding, and where choice of other food patches is possible. The above results agree well
with previous reports for the Koshima group, indicating that the rank of the lower-high class females was unstable (Mori et al., 1989), and that their reproductive success was low (Watanabe et al., 1992). 相似文献
20.
The inheritance of resistance to Plum pox virus (PPV) has been studied in 1,178 apricot hybrids. Seven hundred and eighteen F1 hybrids, obtained from controlled crosses
between the susceptible Greek cultivar “Bebecou” and the resistant PPV cultivars of American origin (“Stark Early Orange,”
‘NJA2,” ‘Veecot,” “Sunglo,” “Harlayne,” and “Orangered”) were evaluated for resistance to the PPV-M (Marcus) strain, 8 years
after artificial inoculation. The inheritance of resistance to PPV has been additionally studied for the first time in a BC1 population of 95 apricot hybrids for four vegetative periods. Reaction of each hybrid to PPV-M was scored through visual
symptoms, indexing onto GF-305 and double-antibody sandwich enzyme-linked immunosorbent assay tests. Segregation within the
hybrids, determined by Chi-squared analysis, fits a 1:1 ratio (P ≤ 0.05) of the resistant vs susceptible, indicating that resistance to PPV is controlled by a single dominant gene locus
and that the above six resistant cultivars are heterozygous for the trait. Plants carrying this gene may initially develop
disease symptoms on leaves but eventually recover and no virus can be detected in leaves. Susceptible plants show similar
symptoms initially but remain symptomatic. Inheritance of resistance to PPV also has been studied in 365 F1 hybrids by crossing
the resistant cultivar “Stella” with the susceptible “Bebecou” and the resistant cultivars “Sunglo” and “NJA2,” for 8 years
after inoculation. The segregation ratio was 1:0 (resistant/susceptible) suggesting that “Stella” is homozygous for the resistance
trait. The purpose of this work was the enhancement of the knowledge of inheritance of resistance to PPV for the selection
of new cultivars. 相似文献