2,941 research outputs found
Scorpion Biodiversity and Interslope Divergence at âEvolution Canyonâ, Lower Nahal Oren Microsite, Mt. Carmel, Israel
BACKGROUND: Local natural laboratories, designated by us as the "Evolution Canyon" model, are excellent tools to study regional and global ecological dynamics across life. They present abiotic and biotic contrasts locally, permitting the pursuit of observations and experiments across diverse taxa sharing sharp microecological subdivisions. Higher solar radiation received by the "African savannah-like" south-facing slopes (AS) in canyons north of the equator than by the opposite "European maquis-like" north-facing slopes (ES) is associated with higher abiotic stress. Scorpions are a suitable taxon to study interslope biodiversity differences, associated with the differences in abiotic factors (climate, drought), due to their ability to adapt to dry environments. METHODOLOGY/PRINCIPAL FINDINGS: Scorpions were studied by the turning stone method and by UV light methods. The pattern observed in scorpions was contrasted with similar patterns in several other taxa at the same place. As expected, the AS proved to be significantly more speciose regarding scorpions, paralleling the interslope patterns in taxa such as lizards and snakes, butterflies (Rhopalocera), beetles (families Tenebrionidae, Dermestidae, Chrysomelidae), and grasshoppers (Orthoptera). CONCLUSIONS/SIGNIFICANCE: Our results support an earlier conclusion stating that the homogenizing effects of migration and stochasticity are not able to eliminate the interslope intra- and interspecific differences in biodiversity despite an interslope distance of only 100 m at the "EC" valley bottom. In our opinion, the interslope microclimate selection, driven mainly by differences in insolance, could be the primary factor responsible for the observed interslope pattern
Sub-Sets of Cancer Stem Cells Differ Intrinsically in Their Patterns of Oxygen Metabolism
PMCID: PMC3640080This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Thermodynamic Properties of the One-Dimensional Extended Quantum Compass Model in the Presence of a Transverse Field
The presence of a quantum critical point can significantly affect the
thermodynamic properties of a material at finite temperatures. This is
reflected, e.g., in the entropy landscape S(T; c) in the vicinity of a quantum
critical point, yielding particularly strong variations for varying the tuning
parameter c such as magnetic field. In this work we have studied the
thermodynamic properties of the quantum compass model in the presence of a
transverse field. The specific heat, entropy and cooling rate under an
adiabatic demagnetization process have been calculated. During an adiabatic
(de)magnetization process temperature drops in the vicinity of a field-induced
zero-temperature quantum phase transitions. However close to field-induced
quantum phase transitions we observe a large magnetocaloric effect
Precursors of Cytochrome Oxidase in Cytochrome-Oxidase-Deficient Cells of Neurospora crassa
Three different cell types of Neurospora crassa deficient in cytochrome oxidase were studied: the nuclear mutant cni-1, the cytoplasmic mutant mi-1 and copper-depleted wild-type cells.
* 1.
The enzyme-deficient cells have retained a functioning mitochondrial protein synthesis. It accounted for 12â16% of the total protein synthesis of the cell. However, the analysis of mitochondrial translation products by gel electrophoresis revealed that different amounts of individual membrane proteins were synthesized. Especially mutant cni-1 produced large amounts of a small molecular weight translation product, which is barely detectable in wild-type.
* 2.
Mitochondrial preparations of cytochrome-oxidase-deficient cells were examined for precursors of cytochrome oxidase. The presence of polypeptide components of cytochrome oxidase in the mitochondria was established with specific antibodies. On the other hand, no significant amounts of heme a could be extracted.
* 3.
Radioactively labelled components of cytochrome oxidase were isolated by immunoprecipitation and analysed by gel electrophoresis. All three cell types contained the enzyme components 4â7, which are translated on cytoplasmic ribosomes. The mitochondrially synthesized components 1â3 were present in mi-1 mutant and in copper-depleted wild-type cells. In contrast, components 2 and 3 were not detectable in the nuclear mutant cni-1. Both relative and absolute amounts of these polypeptides in the enzyme-deficient cells were quite different from those in wild-type cells.
* 4.
The components of cytochrome oxidase found in the enzyme-deficient cells were tightly associated with the mitochondrial membranes.
* 5.
Processes, which affect and may control the production of enzyme precursors or their assembly to a functional cytochrome oxidase are discussed
Random walk with barriers: Diffusion restricted by permeable membranes
Restrictions to molecular motion by barriers (membranes) are ubiquitous in
biological tissues, porous media and composite materials. A major challenge is
to characterize the microstructure of a material or an organism
nondestructively using a bulk transport measurement. Here we demonstrate how
the long-range structural correlations introduced by permeable membranes give
rise to distinct features of transport. We consider Brownian motion restricted
by randomly placed and oriented permeable membranes and focus on the
disorder-averaged diffusion propagator using a scattering approach. The
renormalization group solution reveals a scaling behavior of the diffusion
coefficient for large times, with a characteristically slow inverse square root
time dependence. The predicted time dependence of the diffusion coefficient
agrees well with Monte Carlo simulations in two dimensions. Our results can be
used to identify permeable membranes as restrictions to transport in disordered
materials and in biological tissues, and to quantify their permeability and
surface area.Comment: 8 pages, 3 figures; origin of dispersion clarified, refs adde
Predicting the safety and efficacy of butter therapy to raise tumour pHe: an integrative modelling study
Background: Clinical positron emission tomography imaging has demonstrated the vast majority of human cancers exhibit significantly increased glucose metabolism when compared with adjacent normal tissue, resulting in an acidic tumour microenvironment. Recent studies demonstrated reducing this acidity through systemic buffers significantly inhibits development and growth of metastases in mouse xenografts.\ud
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Methods: We apply and extend a previously developed mathematical model of blood and tumour buffering to examine the impact of oral administration of bicarbonate buffer in mice, and the potential impact in humans. We recapitulate the experimentally observed tumour pHe effect of buffer therapy, testing a model prediction in vivo in mice. We parameterise the model to humans to determine the translational safety and efficacy, and predict patient subgroups who could have enhanced treatment response, and the most promising combination or alternative buffer therapies.\ud
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Results: The model predicts a previously unseen potentially dangerous elevation in blood pHe resulting from bicarbonate therapy in mice, which is confirmed by our in vivo experiments. Simulations predict limited efficacy of bicarbonate, especially in humans with more aggressive cancers. We predict buffer therapy would be most effectual: in elderly patients or individuals with renal impairments; in combination with proton production inhibitors (such as dichloroacetate), renal glomular filtration rate inhibitors (such as non-steroidal anti-inflammatory drugs and angiotensin-converting enzyme inhibitors), or with an alternative buffer reagent possessing an optimal pK of 7.1â7.2.\ud
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Conclusion: Our mathematical model confirms bicarbonate acts as an effective agent to raise tumour pHe, but potentially induces metabolic alkalosis at the high doses necessary for tumour pHe normalisation. We predict use in elderly patients or in combination with proton production inhibitors or buffers with a pK of 7.1â7.2 is most promising
Diffuse-Charge Dynamics in Electrochemical Systems
The response of a model micro-electrochemical system to a time-dependent
applied voltage is analyzed. The article begins with a fresh historical review
including electrochemistry, colloidal science, and microfluidics. The model
problem consists of a symmetric binary electrolyte between parallel-plate,
blocking electrodes which suddenly apply a voltage. Compact Stern layers on the
electrodes are also taken into account. The Nernst-Planck-Poisson equations are
first linearized and solved by Laplace transforms for small voltages, and
numerical solutions are obtained for large voltages. The ``weakly nonlinear''
limit of thin double layers is then analyzed by matched asymptotic expansions
in the small parameter , where is the
screening length and the electrode separation. At leading order, the system
initially behaves like an RC circuit with a response time of
(not ), where is the ionic diffusivity, but nonlinearity
violates this common picture and introduce multiple time scales. The charging
process slows down, and neutral-salt adsorption by the diffuse part of the
double layer couples to bulk diffusion at the time scale, . In the
``strongly nonlinear'' regime (controlled by a dimensionless parameter
resembling the Dukhin number), this effect produces bulk concentration
gradients, and, at very large voltages, transient space charge. The article
concludes with an overview of more general situations involving surface
conduction, multi-component electrolytes, and Faradaic processes.Comment: 10 figs, 26 pages (double-column), 141 reference
The relative influence of intellectual disabilities and autism on sensory impairments and physical disability:A wholeâcountry cohort of 5.3 million children and adults
Background:
Intellectual disabilities and autism are lifelong and often coâoccur. Little is known on their extent of independent association with sensory impairments and physical disability.
Methods:
For Scotland's population, logistic regressions investigated ageâgenderâadjusted odds ratios (OR) of associations, independently, of intellectual disabilities and autism with sensory impairments and physical disability.
Results:
1,548,819 children/youth, and 3,746,584 adults. In children/youth, the effect size of intellectual disabilities and autism, respectively, was as follows: blindness (OR = 30.12; OR = 2.63), deafness (OR = 13.98; OR = 2.31), and physical disability (OR = 43.72; OR = 5.62). For adults, the effect size of intellectual disabilities and autism, respectively, was as follows: blindness (OR = 16.89; OR = 3.29), deafness (OR = 7.47; OR = 2.36), and physical disability (OR = 6.04; OR = 3.16).
Conclusions:
Intellectual disabilities have greater association with the population burden of sensory impairments/physical disability, but autism is also associated regardless of overlap with intellectual disabilities. These may impact further on communication limitations due to autism and intellectual disabilities, increasing complexity of assessments/management of other health conditions. Clinicians need to be aware of these important issues
Dynamic Phase Transition in a Time-Dependent Ginzburg-Landau Model in an Oscillating Field
The Ginzburg-Landau model below its critical temperature in a temporally
oscillating external field is studied both theoretically and numerically. As
the frequency or the amplitude of the external force is changed, a
nonequilibrium phase transition is observed. This transition separates
spatially uniform, symmetry-restoring oscillations from symmetry-breaking
oscillations. Near the transition a perturbation theory is developed, and a
switching phenomenon is found in the symmetry-broken phase. Our results confirm
the equivalence of the present transition to that found in Monte Carlo
simulations of kinetic Ising systems in oscillating fields, demonstrating that
the nonequilibrium phase transition in both cases belongs to the universality
class of the equilibrium Ising model in zero field. This conclusion is in
agreement with symmetry arguments [G. Grinstein, C. Jayaprakash, and Y. He,
Phys. Rev. Lett. 55, 2527 (1985)] and recent numerical results [G. Korniss,
C.J. White, P. A. Rikvold, and M. A. Novotny, Phys. Rev. E (submitted)].
Furthermore, a theoretical result for the structure function of the local
magnetization with thermal noise, based on the Ornstein-Zernike approximation,
agrees well with numerical results in one dimension.Comment: 16 pp. RevTex, 9 embedded ps figure
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