794 research outputs found
Information transfer in signaling pathways : a study using coupled simulated and experimental data
Background: The topology of signaling cascades has been studied in quite some detail. However, how information is processed exactly is still relatively unknown. Since quite diverse information has to be transported by one and the same signaling cascade (e.g. in case of different agonists), it is clear that the underlying mechanism is more complex than a simple binary switch which relies on the
mere presence or absence of a particular species. Therefore, finding means to analyze the information transferred will help in deciphering how information is processed exactly in the cell. Using the information-theoretic measure transfer entropy, we studied the properties of information transfer in an example case, namely calcium signaling under different cellular
conditions. Transfer entropy is an asymmetric and dynamic measure of the dependence of two (nonlinear) stochastic processes. We used calcium signaling since it is a well-studied example of complex cellular signaling. It has been suggested that specific information is encoded in the
amplitude, frequency and waveform of the oscillatory Ca2+-signal.
Results: We set up a computational framework to study information transfer, e.g. for calcium
signaling at different levels of activation and different particle numbers in the system. We stochastically coupled simulated and experimentally measured calcium signals to simulated target proteins and used kernel density methods to estimate the transfer entropy from these bivariate
time series. We found that, most of the time, the transfer entropy increases with increasing particle numbers. In systems with only few particles, faithful information transfer is hampered by random fluctuations. The transfer entropy also seems to be slightly correlated to the complexity (spiking, bursting or irregular oscillations) of the signal. Finally, we discuss a number of peculiarities of our approach in detail.
Conclusion: This study presents the first application of transfer entropy to biochemical signaling pathways. We could quantify the information transferred from simulated/experimentally measured calcium signals to a target enzyme under different cellular conditions. Our approach, comprising stochastic coupling and using the information-theoretic measure transfer entropy, could also be a valuable tool for the analysis of other signaling pathways
Information transfer in signaling pathways : a study using coupled simulated and experimental data
Background: The topology of signaling cascades has been studied in quite some detail. However, how information is processed exactly is still relatively unknown. Since quite diverse information has to be transported by one and the same signaling cascade (e.g. in case of different agonists), it is clear that the underlying mechanism is more complex than a simple binary switch which relies on the
mere presence or absence of a particular species. Therefore, finding means to analyze the information transferred will help in deciphering how information is processed exactly in the cell. Using the information-theoretic measure transfer entropy, we studied the properties of information transfer in an example case, namely calcium signaling under different cellular
conditions. Transfer entropy is an asymmetric and dynamic measure of the dependence of two (nonlinear) stochastic processes. We used calcium signaling since it is a well-studied example of complex cellular signaling. It has been suggested that specific information is encoded in the
amplitude, frequency and waveform of the oscillatory Ca2+-signal.
Results: We set up a computational framework to study information transfer, e.g. for calcium
signaling at different levels of activation and different particle numbers in the system. We stochastically coupled simulated and experimentally measured calcium signals to simulated target proteins and used kernel density methods to estimate the transfer entropy from these bivariate
time series. We found that, most of the time, the transfer entropy increases with increasing particle numbers. In systems with only few particles, faithful information transfer is hampered by random fluctuations. The transfer entropy also seems to be slightly correlated to the complexity (spiking, bursting or irregular oscillations) of the signal. Finally, we discuss a number of peculiarities of our approach in detail.
Conclusion: This study presents the first application of transfer entropy to biochemical signaling pathways. We could quantify the information transferred from simulated/experimentally measured calcium signals to a target enzyme under different cellular conditions. Our approach, comprising stochastic coupling and using the information-theoretic measure transfer entropy, could also be a valuable tool for the analysis of other signaling pathways
Transition from stochastic to deterministic behavior in calcium oscillations
Simulation and modeling is becoming more and more important when studying complex biochemical systems. Most often, ordinary differential equations are employed for this purpose. However, these are only applicable when the numbers of participating molecules in the biochemical systems are large enough to be treated as concentrations. For smaller systems, stochastic simulations on discrete particle basis are more accurate. Unfortunately, there are no general rules for determining which method should be employed for exactly which problem to get the most realistic result. Therefore, we study the transition from stochastic to deterministic behavior in a widely studied system, namely the signal transduction via calcium, especially calcium oscillations. We observe that the transition occurs within a range of particle numbers, which roughly corresponds to the number of receptors and channels in the cell, and depends heavily on the attractive properties of the phase space of the respective systems dynamics. We conclude that the attractive properties of a system, expressed, e.g., by the divergence of the system, are a good measure for determining which simulation algorithm is appropriate in terms of speed and realism
Australia's policy towards the aged: 1890-1972
Sections of the Australian aged community have
received cash allowances on a non-contributory and
selective basis since 1900. This makes Australia one
of the first countries to establish an age pension
scheme. It is also one of the very few that has not
followed the world trend by adopting some form of compulsory
social insurance.
This thesis has three aims. Firstly, to explain
why Australia decided to provide non-contributory and
selective cash age pensions around the turn of the
century. Secondly, to examine the various abortive
attempts that were subsequently made to establish a
comprehensive social insurance scheme. Thirdly, to
examine the various changes that were made to the
Australian age pension scheme between 1909 and 1972.
The study has been divided into four sections
Alyawarr children's variable present temporal reference expression in two, closely-related languages of Central Australia
In a small, remote central Australian community, young children
go about their daily lives mainly speaking Alyawarr English
(AlyE), a new Central Australian contact language. At school they
are acquiring Standard Australian English (SAE) as a second
language. Much of what they encounter in SAE will seem familiar
and much will be obviously different. In between, there will be
many subtle differences that are possibly harder to detect, parse
and maintain. This study investigates this remarkable bi-varietal
language use, considering whether separate ‘codes’ are indeed
evidenced, how they can be quantitatively modelled, and what they
tell us about the impact of formal similarity between languages
and emerging bilingualism.
The use in childhood of multiple closely-related languages is
somewhat of a final frontier for several strands of research:
child language development, second language acquisition, and
creole studies. However, the methodologies common in these fields
don’t easily import to the present scenario: for while the
assumption of existing, separate codes may be operationally
practical (even if theoretically contestable), the presence of
overlapping structures (i.e. morphemes that are used in both AlyE
and SAE) in the present data set makes code separation on
structural grounds problematic. The solution tested here takes a
corpus of 50+ hours of naturalistic video recordings of six focus
children, and first creates two maximally contrastive,
contextually defined data sets: HOME (home, Alyawarr
interlocutor) and SCHOOL (school, non-Alyawarr interlocutor).
Each data set is then analysed using the Comparative Variationist
method. Three variables of present temporal references clauses
were selected: aspect morphology with variants V (e.g.
‘look’), Ving (e.g. ‘looking’), and Vbat (e.g.
‘lookbat’), 1sg subject pronouns (‘I’ and ‘AM’) and
verb transitivity marking (-im and unmarked). In both HOME and
SCHOOL data, variants, their distributions, respective envelopes
of variation and variable grammar (modelled using logistic
multiple regression conducted in Goldvarb X) are examined.
The results show that code-separation is evidenced for all three
variables, but that the locus of change is not the same in each
case. For transitive marking and 1sg subject pronouns, the same
variable grammar is deployed in both HOME and SCHOOL data, while
non-SAE-like variants are increasingly avoided in the SCHOOL
(i.e. -im and ‘AM’) and
thus the envelope of variation for the SAE-compatible variant
(i.e. -Ø and ‘I’) expands its range of use on the way to
becoming the categorical variant in the children’s SAE. For
aspectual morphology, the locus of change is located within the
variable grammar where complex patterns of reorganisation are
evidenced (e.g. HOME V is strongly associated with ‘stative’
clauses; SCHOOL V with ‘stative’ and ‘habitual’).
Additionally, fundamental changes in the envelope of variation
(e.g. Ving is not used on transitive verbs in the HOME but is in
the SCHOOL) and the range of variants (e.g. Vbat is not used in
the SCHOOL) indicate that these remain central considerations in
the use of all three variables.
This study therefore breaks new ground in both methodological
terms, with the application of variationist modelling to child
bi-varietal language use, and in advancing our understanding of
the vectors of code-separation in the complex ecologies of the
region
Acculturation and wellness of native american adolescents in the United States of North America
Cultural conflicts and the process of acculturation contribute to feelings of boredom, anxiety, depression, isolation, stress, self-doubt, alienation, and rejection among Native American high school students. Further, acculturation may have a negative impact on the identity development and wellness of these students. The purpose of this pilot study was to: (a) assess and compare the levels of acculturation of Native American and non-Native American 9th, 10th, 11th, and 12th grade students; and (b) examine the relationship between level of acculturation and wellness for the Native American students. Results indicated significant differences between Native American and non-Native American students’ levels of acculturation; and significant differences between the Native students’ three levels of acculturation on some of the 17 scales of wellness.
Resumen: Conflictos culturales y el proceso de aculturación contribuyen a sentimientos de aburrimiento, ansiedad, depresión, aislamiento, presión, desconfianza, alienación, y del rechazo entre estudiantes de escuela superior que son indios americanos. Aún más, la aculturación puede tener un impacto negativo en el desarrollo de identidad y bienestar de estos estudiantes. El propósito de este estudio piloto fue: (a) evaluar y comparar los niveles de aculturación de estudiantes que eran indios americanos y no-indio americano en los grados académicos del noveno, décimo, décimo primero y de duodécimos; y (B) examinar la relación entre nivel de aculturación y bienestar de los estudiantes indio americanos. Los resultados indicaron diferencias significativas entre estudiantes indio americanos y estudiantes no-indio americano en los niveles de aculturación; y diferencias significativas entre los estudiantes indio americanos en tres niveles de aculturación en la parte de las 17 escalas del bienestar
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