Naturally safe: Cellular noise for document security

Modern document protection relies on the simultaneous combination of many optical features with micron and submicron structures, whose complexity is the main obstacle for unauthorized copying. In that sense, documents are best protected by the diffractive optical elements generated lithographically and mass‐produced by embossing. The problem is that the resulting security elements are identical, facilitating mass‐production of both original and counterfeited documents. Here, we prove that each butterfly wing‐scale is structurally and optically unique and can be used as an inimitable optical memory tag and applied for document security. Wing‐scales, exhibiting angular variability of their color, were laser‐cut and bleached to imprint cryptographic information of an authorized issuer. The resulting optical memory tag is extremely durable, as verified by several century‐old insect specimens still retaining their coloration. The described technique is simple, amenable to mass‐production, low cost and easy to integrate within the existing security infrastructure.     

Rheological behavior of living cells is timescale-dependent

The dynamic mechanical behavior of living cells has been proposed to result from timescale-invariant processes governed by the soft glass rheology theory derived from soft matter physics. But this theory is based on experimental measurements over timescales that are shorter than those most relevant for cell growth and function. Here we report results measured over a wider range of timescales which demonstrate that rheological behaviors of living cells are not timescale-invariant. These findings demonstrate that although soft glass rheology appears to accurately predict certain cell mechanical behaviors, it is not a unified model of cell rheology under biologically relevant conditions and thus, alternative mechanisms need to be considered.     

Predispersal predation of an understory rainforest herb Aphelandra aurantiaca (Acanthaceae) in gaps and mature forest

The opening of a canopy gap at Los Tuxtlas rainforest has an impact on populations of the understory herb Aphelandra aurantiaca: the ratio of recruited seedlings per reproductive individual is 1:17 in mature forest vs. gaps. Predation occurring before seed dispersal seems a plausible explanation for this observed difference. In a field experiment, in which insecticide was applied to plants growing in gaps and mature forest, we evaluated the extent to which herbivore damage to flowers, fruits, and seeds reduces the number of seeds available for seedling establishment. Under natural conditions, ∼30% of the flowers and >70% of the capsules of A. aurantiaca showed herbivore damage, but its impact changed depending on the type of forest habitat. Flower and fruit herbivores caused more damage in closed forest than in gaps, and this difference was even bigger under the insecticide treatment. Insecticide effectiveness varied depending on the type of forest patch. The highest herbivore impact on seeds was found in the mature forest without insecticide treatment, where most seeds were destroyed. The percentages of seed damage reported here show that predispersal predation is limiting seedling recruitment, especially in mature forest. Other possible explanations might be differences in insect composition, densities, and behavior between gaps and mature forest.     

Effect of phenolic compounds on the germination of six weeds species

Low molecular weight phenolic compounds have been identified in fresh leaves and in soils in which leaves of five varieties of Capsicum annuum L. were decomposing. Six phenolic compounds were tested in laboratory bioassays for their allelopathic effects on germination and seedling growth of six weeds. Ferulic acid, gallic acid, p-coumaric acid, p-hydroxybenzoic acid, vanillic acid, and p-vanillin were bioassayed in concentrations of 10, 1, 0.1, and 0.01 mM. Equimolar mixtures containing all these phenolics were prepared at the final total concentration of 10, 1, 0.1, and 0.01 mM to test for possible interactive effects. Chenopodium album L., Plantago lanceolata L., Amaranthus retroflexus L., Solanum nigrum L., Cirsium sp. and Rumex crispus L. were the selected target weeds. The highest concentration of the compounds inhibited the germination of all these weeds, but lower concentrations had no effect or were stimulatory. However, effects varied with the weed species, the concentration of the compound tested and the compound itself. In assays with the mixture of phenolics we found evidence of some additive effects.     

Landscape,Climate and Hantavirus Cardiopulmonary Syndrome Outbreaks

We performed a literature review in order to improve our understanding of how landscape and climate drivers affect HCPS outbreaks. Anthropogenic landscape changes such as forest loss, fragmentation and agricultural land uses are related with a boost in hantavirus reservoir species abundance and hantavirus prevalence in tropical areas, increasing HCPS risk. Additionally, higher precipitation, especially in arid regions, favors an increase in vegetational biomass, which augments the resources for reservoir rodents, also increasing HCPS risk. Although these relationships were observed, few studies described it so far, and the ones that did it are concentrated in few places. To guide future research on this issue, we build a conceptual model relating landscape and climate variables with HCPS outbreaks and identified research opportunities. We point out the need for studies addressing the effects of landscape configuration, temperature and the interaction between climate and landscape variables. Critical landscape thresholds are also highly relevant, once HCPS risk transmission can increase rapidly above a certain degree of landscape degradation. These studies could be relevant to implement preventive measures, creating landscapes that can mitigate disease spread risk.     

C-prenylated flavonoids with potential cytotoxic activity against solid tumor cell lines

Phytochemistry Reviews - Natural products of plant origin or their semisynthetic derivatives acting as chemopreventive or chemotherapeutic agents for various types of cancer are under study as...     

A One-dimensional Finite Element Method for Simulation-based Medical Planning for Cardiovascular Disease

We have previously described a new approach to planning treatments for cardiovascular disease, Simulation-Based Medical Planning, whereby a physician utilizes computational tools to construct and evaluate a combined anatomic/physiologic model to predict the outcome of alternative treatment plans for an individual patient. Current systems for Simulation-Based Medical Planning utilize finite element methods to solve the time-dependent, three-dimensional equations governing blood flow and provide detailed data on blood flow distribution, pressure gradients and locations of flow recirculation, low wall shear stress and high particle residence. However, these methods are computationally expensive and often require hours of time on parallel computers. This level of computation is necessary for obtaining detailed information about blood flow, but likely is unnecessary for obtaining information about mean flow rates and pressure losses. We describe, herein, a space-time finite element method for solving the one-dimensional equations of blood flow. This method is applied to compute flow rate and pressure in a single segment model, a bifurcation, an idealized model of the abdominal aorta, in three alternate treatment plans for a case of aorto-iliac occlusive disease and in a vascular bypass graft. All of these solutions were obtained in less than 5 min of computation time on a personal computer.     

Viscoelastic and dynamic nonlinear properties of airway smooth muscle tissue: roles of mechanical force and the cytoskeleton

The viscoelastic and dynamic nonlinear properties of guinea pig tracheal smooth muscle tissues were investigated by measuring the storage (G') and loss (G") moduli using pseudorandom small-amplitude length oscillations between 0.12 and 3.5 Hz superimposed on static strains of either 10 or 20% of initial length. The G" and G' spectra were interpreted using a linear viscoelastic model incorporating damping (G) and stiffness (H), respectively. Both G and H were elevated following an increase in strain from 10 to 20%. There was no change in harmonic distortion (K(d)), an index of dynamic nonlinearity, between 10 and 20% strains. Application of methacholine at 10% strain significantly increased G and H while it decreased K(d). Cytochalasin D, isoproterenol, and HA-1077, a Rho-kinase inhibitor, significantly decreased both G and H but increased K(d). Following cytochalasin D, G, H, and K(d) were all elevated when mean strain increased from 10 to 20%. There were no changes in hysteresivity, G/H, under any condition. We conclude that not all aspects of the viscoelastic properties of tracheal smooth muscle strips are similar to those previously observed in cultured cells. We attribute these differences to the contribution of the extracellular matrix. Additionally, using a network model, we show that the dynamic nonlinear behavior, which has not been observed in cell culture, is associated with the state of the contractile stress and may derive from active polymerization within the cytoskeleton.