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1.
Didier G. Arqués Jean-Paul Fallot Christian J. Michel 《Bulletin of mathematical biology》1998,60(1):163-194
The self-complementary subset
∪{AAA,TTT} with
= {AAC, AAT, ACC, ATC, ATT, CAG, CTC, CTG, GAA, GAC, GAG, GAT, GCC, GGC, GGT, GTA, GTC, GTT, TAC, TTC} of 22 trinucleotides
has a preferential occurrence in the frame 0 (reading frame established by the ATG start trinucleotide) of protein (coding)
genes of both prokaryotes and eukaryotes. The subsets
∪{CCC} and
∪{GGG} of 21 trinucleotides have a preferential occurrence in the shifted frames 1 and 2 respectively (frame 0 shifted by
one and two nucleotides respectively in the 5′-3′ direction).
and
are complementary to each other. The subset
contains the subset
which has the rarity property (6 × 10−8) to be a complementary maximal circular code with two permutated maximal circular codes
and
in the frames 1 and 2 respectively.
is called a C3 code.
A quantitative study of these three subsets
in the three frames 0, 1, 2 of protein genes, and the 5′ and 3′ regions of eukaryotes, shows that their occurrence frequencies
are constant functions of the trinucleotide positions in the sequences. The frequencies of
in the frame 0 of protein genes are 49, 28.5 and 22.5% respectively. In contrast, the frequencies of
in the 5′ and 3′ regions of eukaryotes, are independent of the frame. Indeed, the frequency of
in the three frames of 5′ (respectively 3′) regions is equal to 35.5% (respectively 38%) and is greater than the frequencies
and
, both equal to 32.25% (respectively 31%) in the three frames.
Several frequency asymmetries unexpectedly observed (e.g. the frequency difference between
and
in the frame 0), are related to a new property of the subset
involving substitutions. An evolutionary analytical model at three parameters (p, q, t) based on an independent mixing of the 22 codons (trinucleotides in frame 0) of
with equiprobability (1/22) followed by t ≈ 4 substitutions per codon according to the proportions p ≈ 0.1; q ≈ 0.1 and r = 1 − p − q ≈ 0.8 in the three codon sites respectively, retrieves the frequencies of
observed in the three frames of protein genes and explains these asymmetries. Furthermore, the same model (0.1, 0.1, t) after t ≈ 22 substitutions per codon, retrieves the statistical properties observed in the three frames of the 5′ and 3′ regions.
The complex behaviour of these analytical curves is totally unexpected and a priori difficult to imagine. 相似文献
2.
M. -T. Linossier D. Dormois R. Fouquet A. Geyssant C. Denis 《European journal of applied physiology and occupational physiology》1996,74(5):420-427
A group of 15 untrained male subjects pedalled on a friction-loaded cycle ergometer as fast as possible for 5–7 s to reach
the maximal velocity (V{immax}) against different braking forces (F
B). Power was averaged during a complete crank rotation by adding the power dissipated againstF
B to the power necessary to accelerate the flywheel. For each sprint, determinations were made of peak power output (
) power output attained atV
max (
) calculated as the product ofV
max andF
B and the work performed to reachV
max expressed in mean power output (
). The relationships between these parameters andF
B were examined. A biopsy taken from the vastus lateralis muscle and tomodensitometric radiographs of both thighs were taken
at rest to identify muscle metabolic and morphometric properties. The
value was similar for allF
B. Therefore, the average of values was defined as corrected maximal power (
). This value was 11 higher than the maximal power output uncorrected for the acceleration. Whereas the
determination did not require high loads, the highest
value (
) was produced when loading was heavy, as evidenced by the
-F
B parabolic relationship. For each subject, the braking force (
) giving
was defined as optimal. The
, equal to 0.844 (SD 0.108) N · kg−1 bodymass, was related to thigh muscle area (r = 0.78,P < 0.05). The maximal velocity (
) reached against this force seemed to be related more to intrinsic fibre properties (% fast twitch b fibre area and adenylate
kinase activity). Thus, from the
determination, it is suggested that it should be possible to predict the conditions for optimal exercise on a cycle ergometer. 相似文献
3.
Robert Rosen 《Bulletin of mathematical biology》1963,25(2):231-241
It has been shown in earlier work that one approach to what Rashevsky has called “abstract biology” is through the study of
the class of (
)-systems that can be formed in an arbitrary subcategory of the category of sets. The concept of the (
)-system, however, depends on the availability of mappings that contain other mappings in their range. It is shown that, by
introducing an appropriate measure for this property, the problem of characterizing those categories suitable for a rich theory
of (
)-systems reduces to a problem familiar from the general theory of graphs. Some new results in these directions are obtained,
and it is then shown that any category with mappings that possess properties we might expect to hold in the physical world
will also admit a rich theory of (
)-systems. In particular, it is shown that a sufficiently large family of mappings drawn at random from such a category will
with overwhelming probability contain an (
)-system.
This research was supported by the United States Air Force through the Air Force Office of Scientific Research of the Air
Research and Development Command, under Grant No. AF-AFOSR-9-63. 相似文献
4.
Viktor Reinhardt 《Primates; journal of primatology》1987,28(1):123-125
The justification for the “generalization that primate males are more aggressive than females” (Fedigan & Baxter, 1984) was tested in a troop of 24 captive rhesus monkeys. Males (N=9) were more dominant than females (N=15), i.e., they had more subordinate partners (
m=17.0 vs.
f=6.6;p<0.01); hence, their aggression rate was higher (
m=77.6 vs.
m=38.1;p<0.05). However, adjusting the rate of aggression according to the number of subordinate targets revealed no gender difference
and males directed numbers of aggressive acts against individual subordinate partners that were not higher than those of females
(
m=4.4 vs.
f=5.4;p>0.1). It was concluded that aggressiveness is an individual attribute that is (1) independent of dominance status, and (2)
independent of sex. 相似文献
5.
Modelling the dynamics of West Nile Virus 总被引:1,自引:0,他引:1
Cruz-Pacheco G Esteva L Montaño-Hirose JA Vargas C 《Bulletin of mathematical biology》2005,67(6):1157-1172
In this work we formulate and analyze a mathematical model for the transmission of West Nile Virus (WNV) infection between
vector (mosquito) and avian population. We find the Basic Reproductive Number
in terms of measurable epidemiological and demographic parameters.
is the threshold condition that determines the dynamics of WNV infection: if
the disease fades out, and for
the disease remains endemic. Using experimental and field data we estimate
for several species of birds. Numerical simulations of the temporal course of the infected bird proportion show damped oscillations
approaching the endemic value. 相似文献
6.
The non-uniqueness of
distributions satisfying inert gas retention data without error is studied. The ability of such data to resolve blood flows
at particular
values is discussed through the application of linear programming and Backus-Gilbert theory. It is shown that the resolution
deteriorates away from the extremes of low and high
. 相似文献
7.
The thermodynamics of irreversible processes is derived from the principles of dynamical field theory independently of all
elements of thermostatics, in particular the assumption of local equilibrium. Field thermodynamics proceeds from the premise
that all driving forces experienced by the molecules in a continuum are conservative and arise from scalar potential functions.
Dynamically the temperature potentialT is no different from the pressure potentialp. A field is converted to a force upon multiplication by a scale factor. A potential is converted to potential energy by the
same scale factor. To scale the field −∇p to the force per mole of molecular speciesk, the partial molar, volume
is the scale factor. Similarly the partial molar entropy,
, scales the temperature field. The transition from the scale factors (which are physical parameters) to the systemic variables,
for example
, is not trivial. From the dynamics and the structure of the derived potential energy function are inducted the conjugate
variables such as (p, V
I) and (T, s). The meta-mechanical properties of the thermal variables (T, s) are discovered via the local First Law of Thermodynamics, which relates internal energy, thermal flux, and work, and from
the local Second Law, which prescribes, the possible partitions of internal energy between kinetic, potential, and thermal
energies. From the form of the potential energy come Maxwell's relationships. From the energy partition comes the equation
of continuity for entropy, with its important source term. In contrast to earlier theories of irreversible thermodynamics,
the dissipation function does not include the stress tensor, a constitutive parameter. 相似文献
8.
Hugo M. Martinez 《Bulletin of mathematical biology》1966,28(3):411-416
IfN(t) is the expected number of cells in a culture at timet,
the corresponding time derivative, andf(t−τ)dt the probability that a cell of aget−τ at timet will divide in the succeeding time intervaldt, then according to Hirsch and Engelberg (this issue) there obtains the integral equation
for describing the dynamics of the cell population. It is the purpose of this note to give two alternative derivations of
this equation, one based on the age density equation of Von Foerster, and the other based on a generalized form of the Harris-Bellman
equation describing the first moment of an age dependent, branching process. In addition, a probability model is posed from
which the Von Foerster equation and, hence, the Hirsch-Engelberg equation readily follows. 相似文献
9.
Summary The complete sequence of the 5S rRNA from the bioluminescent bacterium,Beneckea harveyi has been determined to be p U G C U U G G C G
C C A U A G C G A
U U-G G A C C C A
C U G A (U) C U U C
A U U C C-G A A C
C A G A A G U G A
A C G A A U U A-G
G C C G A U G G U
G U G U G G G G C
U-C C C C A U G U
A G A G U A G G A
A U C G-C C A G G
U (U)OH.Two sites of sensitivity to ribonuclease T2 cleavage were identified; at A41 and either A54 or A55. Comparison with existing sequence information fromEscherichia coli andPhotobacterium phosphoreum clarifies the amount of diversity among the bioluminescent bacteria and provides further insight into their phylogenetic position. Sequence heterogeneities were encountered and the importance of these in interpreting 5S rRNA data is discussed. 相似文献
10.
Fumio Yamazaki Nobuharu Fujii Ryoko Sone Haruo Ikegami 《European journal of applied physiology and occupational physiology》1994,69(3):228-232
To evaluate the mechanism of potentiation of sweating after long-term physical training, we compared sweating function in trained and untrained subjects using the frequency of sweat expulsion (f
sw) as an indicator of central sudomotor activity. Nine trained male subjects (trained group) and eight untrained male subjects (untrained group) performed 30-min cycle exercise at 35% maximal oxygen uptake at 25°C ambient temperature and 35% relative humidity. Oesophageal temperature (T
oes), mean body temperature
b, chest sweating rate (
sw,chest), forearm sweating rate (
forearm), andf
sw were measured. The slopes of the
sw,chest versus body temperature (T
oes and
b) and versusf
sw relationships in the trained group were significantly greater than those in the untrained group (both,P < 0.05), while there was no difference between the groups in the slopes of the
sw,chest versus body temperature or versusf
sw relationships. Neither the body temperature threshold for initiation of chest or forearm sweating nor the slope of thef
sw-
b relationship differed between groups. We concluded that, during light exercise at moderate ambient temperature, the
sw,chest in the subjects who had undergone long-term physical training was greater than that in the untrained subjects while the
sw,forearm was not changed. The greater
sw,chest in the trained subjects was concluded to be due to an increase of sensitivity of peripheral mechanisms. 相似文献
11.
We present a new model of the underlying dynamics of the oxygen uptake
kinetics for various exercise intensities. This model is in the form of a set of nonlinear coupled vector fields for the
and
, the derivative of the exercise intensity with respect to time. We also present a new and novel means for calculating the
oxygen demand, D(v, t), and hence also the oxygen deficit and debt, given the time series of the
. This enables us to give better predictions for these values especially for when exercising at or close to maximal exercise
intensities. Our model also allows us to predict the oxygen uptake time series given the time series for the exercise intensity
as well as to investigate the oxygen uptake response to nonlinear exercise intensities. Neither of these features is possible
using the currently used three-phase model. We also present a review of both the underlying physiology and the three-phase
model. This includes for the first time a complete set of the analytical solutions of the three-phase model for the oxygen
deficit and debt. 相似文献
12.
Undifferentiated Friend erythroleukemic cells (FL cells) acquire membrane microviscosity (
), in accord with the culture cell density. At low cell density
poise, whereas at confluency it increases to
poise. Concomitantly, the total number of available transferrin receptors per cell decreases by about 80% upon increase in
cell density. Modulation of membrane microviscosity, by artificial alteration of the membrane cholesterol level, mediates
similar modulations of the availability of the transferrin receptors. The correlation between the availability of the transferrin
receptors and the membrane lipid fluidity may take part in the overt decrease in iron uptake by erythroid cells along the
erythropoiesis pathway. 相似文献
13.
Gregory K. Snyder Wesley W. Weathers 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1977,117(3):291-301
Summary Resting rates of O2 consumption
against
, exercise endurance times and
during recovery from vigorous exercise were measured inSceloporus occidentalis captured near sea level and inS. graciosus captured above 2850 m. Oxygen consumption against
was also measured inS. occidentalis captured above 2850 m. When
was recorded continuously, as ambient
was slowly reduced from 155 Torr, it became directly dependent upon ambient
between 110 and 120 Torr. The critical
for the high altitude lizards was lower than that for the lowland lizards, which enabled the former to maintain relatively higher
's when ambient
was reduced below 120 Torr. The high altitude lizards also had significantly greater endurance when stimulated to exercise at 1600 m (
130 Torr). Both the higher
under hypoxia and the greater endurance roughly parallel a significantly greater maximum
in the high altitude lizards. At a simulated altitude of 3600 m (
100 Torr), maximum
and rate of recovery of the O2 debt calculated from post active
were significantly reduced in the lowland but not the high altitude lizards. The effects of simulated altitude conditions on the lowland but not the mountaine animals indicate adaptations to altitude in these sceloporine lizards. We did not find any consistent relationship between organ/body weight ratios or hematocrit and our measures of
endurance or the altitude at which the lizards were captured. 相似文献
14.
Shih-fang Fan M. M. Dewey B. Gaylinn B. Chu 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(6):508-512
Summary In dynamic light scattering, measurements of the intensity-intensity time correlation function from a suspension of rod-like particles of length L could reveal dynamical information related to translational and internal motions of those particles. For a suspension of thick filaments isolated from the myosin-regulated, striated muscles of Limulus at KL>1 (where K is the scattering vector), the average characteristic linewidth (
) increased with the addition of Ca2+ or with the depletion of ATP. The increase in the
with the addition of Ca2+ could be due to the presence of energy-requiring, high-frequency motions of the crossbridges activated by Ca2+. The increase in
which occurred with the depletion of ATP was assumed to be mainly due to the thermal motions of the crossbridges after they had moved radially away from the filament backbone. The percentage increase in
following the addition of Ca2+ was found to be seasonal, i.e., values of
obtained from thick filaments isolated between the middle of June and the middle of September were smaller than those obtained during the rest of the year. The effect of temperature on the percentage increase in
was also different. The increase showed a maximum at about 35°C during the summer and at about 25°C at other times. However, the percentage increase in
developed under ATP-depleted conditions showed no temperature-related maximum. The number of bound Ca2+ per myosin molecule was 1 during the summer and 2 at other times.Abbreviations DLS
dynamic light scattering
- L
length
- K
scattering vector
- SDS-PAGE
sodium dodecyl sulfate polyacrylamide gel electrophoresis
-
average characteristic line width
Deceased 相似文献
15.
Summary Barley plants (Hordeum vulgare L.) grown from seed for 28 days in flowing solution culture were subjected to different root temperatures (3, 5, 7, 9, 11, 13, 17, 25°C) for 14 days with a common air temperature of 25/15°C (day/night). Uptake of NH4 and NO3 ions was monitored separately and continuously from solutions maintained at 10 M NH4NO3 and pH 6.0. Effects of root temperature on unit absorption rate
, flux
and inflow
were compared. After 5 days
,
and
increased with temperature over the range 3–11°C for NH4 ions and over the range 3–13°C for NO3 ions, with little change for either ion above these temperatures. Q10 temperature coefficients for NH4 ions (3–13°C) were 1.9, 1.7 and 1.6 for
,
and
respectively, the corresponding values for NO3 ions being 5.0, 4.5 and 4.6. For both ions,
,
and
changed with time as did their temperature dependence over the range 3–25°C, suggesting that rates of ontogenetic development and the extent of adaptation to temperature may have varied among treatments. 相似文献
16.
Water uptake by barley roots as affected by the osmotic and matric potential in the rhizosphere 总被引:2,自引:0,他引:2
U. Schleiff 《Plant and Soil》1986,94(1):143-146
Summary The water uptake rates of roots in saline soils are depressed by the simultaneously decreasing matric
and osmotic
water potentials in the soil surrounding the roots (rhizospheric soil). Unfortunately there are no reliable tools available
for direct measurements of the effect of decreasing water potentials in the rhizospheric soil on the uptake rate of soil water
by roots. This paper presents some results of a vegetation technique for studying the effect of different combinations of
osmotic and matric water potentials in the rhizospheric soil on the water uptake rates of barley roots.
Water uptake rates were reduced to a greater extent by decreasing soil matric water potentials than by decreasing soil osmotic
water potentials. According to the results of this experiment, there was no relationship between the total soil water potential
of a sandy soil and the water uptake rates when the roots were exposed to different combinations of
and
. 相似文献
17.
Fumio Yamazaki Ryoko Sone Nobuharu Fujii Haruo Ikegami 《International journal of biometeorology》1993,37(4):212-217
Based on the hypothesis that the relation between sweating rate and body temperature should be different during exercise and rest after exercise, we compared the sweating response during exercise and recovery at a similar body temperature. Healthy male subjects performed submaximal exercise (Experiment 1) and maximal exercise (Experiment 2) in a room at 27° C and 35% relative humidity. During exercise and recovery of 20 min after exercise, esophageal temperature (Tes), mean skin temperature, mean body temperature (
), chest sweating rate (
), and the frequency of sweat expulsion (F
SW) were measured. In both experiments,
andF
SW were clearly higher during exercise than recovery at a similar body temperature (Tes,
).
was similar during exercise and recovery, or a little less during the former, at a similarF
SW. It is concluded that the sweating rate during exercise is greater than that during recovery at the same body temperature, due to greater central sudomotor activity during exercise. The difference between the two values is thought to be related to non-thermal factors and the rate of change in mean skin temperature. 相似文献
18.
Anthony F. Bartholomay 《Bulletin of mathematical biology》1958,20(3):175-190
A stochastic model for the basic unimolecular chemical reaction
is derived. This model provides a mathematical basis, altogether missing in the current kinetic theory, for the analysis
of inherent random fluctuations about the strict concentration-time course prescribed by the existing deterministic theory.
Limits on the extent of the predicted inherent variability are obtained and compared with those usually expected purely on
the basis of random experimental errors of extraneous origin (not associated with the mechanism of reaction). The results
support the extrapolation to chemical systems of a principle of statistical inaccuracy for physical systems which has been
called by E. Schroedinger “the
Law of Physics.” 相似文献
19.
Bowman C Gumel AB van den Driessche P Wu J Zhu H 《Bulletin of mathematical biology》2005,67(5):1107-1133
Since its incursion into North America in 1999, West Nile virus (WNV) has spread rapidly across the continent resulting in
numerous human infections and deaths. Owing to the absence of an effective diagnostic test and therapeutic treatment against
WNV, public health officials have focussed on the use of preventive measures in an attempt to halt the spread of WNV in humans.
The aim of this paper is to use mathematical modelling and analysis to assess two main anti-WNV preventive strategies, namely:
mosquito reduction strategies and personal protection. We propose a single-season ordinary differential equation model for
the transmission dynamics of WNV in a mosquito-bird-human community, with birds as reservoir hosts and culicine mosquitoes
as vectors. The model exhibits two equilibria; namely the disease-free equilibrium and a unique endemic equilibrium. Stability
analysis of the model shows that the disease-free equilibrium is globally asymptotically stable if a certain threshold quantity
, which depends solely on parameters associated with the mosquito-bird cycle, is less than unity. The public health implication
of this is that WNV can be eradicated from the mosquito-bird cycle (and, consequently, from the human population) if the adopted
mosquito reduction strategy (or strategies) can make
. On the other hand, it is shown, using a novel and robust technique that is based on the theory of monotone dynamical systems
coupled with a regular perturbation argument and a Liapunov function, that if
, then the unique endemic equilibrium is globally stable for small WNV-induced avian mortality. Thus, in this case, WNV persists
in the mosquito-bird population. 相似文献
20.
D. B. Sattelle K. H. Langley A. L. Obaid B. M. Salzberg 《European biophysics journal : EBJ》1987,15(2):71-76
Quasi-elastic laser light scattering has been used to investigate the size and dispersity of synaptosomes and synaptic vesicles isolated from optic lobes of the squid Loligo pealei. Synaptosomal fractions were highly polydisperse (
) and the mean diameter (
) ranged from 0.5–2.0 m. Size distribution histograms yielded two major components — smaller particles (
) and a larger group of particles (
). The heterogeneity of the synaptosomal particles detected in solution is in agreement with published data obtained using electron microscopy. Purified synaptic vesicle fractions also yielded complex particle size distribution data. A component with a mean diameter in the range 150–250 nm was detected, though a smaller particle (
) dominated the scattering signal. This smaller particle closely resembles in size the electron lucent vesicles seen in the majority of squid optic lobe nerve terminals when examined by electron microscopy. Osmotically-induced shirnkage and swelling of the synptosomes was detected. Depolarization by veratridine (1.0×10–4
M) did not result in a detectable change in the size of synaptosomal particles. 相似文献