Diffusive benefits of cylinders in front of a Schroeder diffuser

A numerical investigation is performed into the diffusive effects of cylinders positioned in front of a Schroeder diffuser. A regular line of cylinders is shown to offer notable improvements to diffusion from a periodic Schroeder device, provided lateral cylinder spacing is incommensurable with the Schroeder period width. Further investigation considers angular dependence and low frequency results in greater detail, as well as the effects on narrowband and modulated Schroeder devices. An optimization procedure is subsequently performed to investigate the effects of an irregular cylinder arrangement, which provides further diffusive benefits. (C) 2010 Acoustical Society of America

Volumetric diffusers : pseudorandom cylinder arrays on a periodic lattice

Most conventional diffusers take the form of a surface based treatment, and as a result can only operate in hemispherical space. Placing a diffuser in the volume of a room might provide greater efficiency by allowing scattering into the whole space. A periodic cylinder array (or sonic crystal) produces periodicity lobes and uneven scattering. Introducing defects into an array, by removing or varying the size of some of the cylinders, can enhance their diffusing abilities. This paper applies number theoretic concepts to create cylinder arrays that have more even scattering. Predictions using a Boundary Element Method are compared to measurements to verify the model, and suitable metrics are adopted to evaluate performance. Arrangements with good aperiodic autocorrelation properties tend to produce the best results. At low frequency power is controlled by object size and at high frequency diffusion is dominated by lattice spacing and structural similarity. Consequently the operational bandwidth is rather small. By using sparse arrays and varying cylinder sizes, a wider bandwidth can be achieved

Noncoding RNA Mediated Traffic of Foreign mRNA into Chloroplasts Reveals a Novel Signaling Mechanism in Plants

Communication between chloroplasts and the nucleus is one of the milestones of the evolution of plants on earth. Proteins encoded by ancestral chloroplast-endogenous genes were transferred to the nucleus during the endosymbiotic evolution and originated this communication, which is mainly dependent on specific transit-peptides. However, the identification of nuclear-encoded proteins targeted to the chloroplast lacking these canonical signals suggests the existence of an alternative cellular pathway tuning this metabolic crosstalk. Non-coding RNAS (NcRNAs) are increasingly recognized as regulators of gene expression as they play roles previously believed to correspond to proteins. Avsunviroidae family viroids are the only noncoding functional RNAs that have been reported to traffic inside the chloroplasts. Elucidating mechanisms used by these pathogens to enter this organelle will unearth novel transport pathways in plant cells. Here we show that a viroid-derived NcRNA acting as a 5′UTR-end mediates the functional import of Green Fluorescent Protein (GFP) mRNA into chloroplast. This claim is supported by the observation at confocal microscopy of a selective accumulation of GFP in the chloroplast of the leaves expressing the chimeric vd-5′UTR/GFP and by the detection of the GFP mRNA in chloroplasts isolated from cells expressing this construct. These results support the existence of an alternative signaling mechanism in plants between the host cell and chloroplasts, where an ncRNA functions as a key regulatory molecule to control the accumulation of nuclear-encoded proteins in this organelle. In addition, our findings provide a conceptual framework to develop new biotechnological tools in systems using plant chloroplast as bioreactors. Finally, viroids of the family Avsunviroidae have probably evolved to subvert this signaling mechanism to regulate their differential traffic into the chloroplast of infected cells

Vertical Distribution of Epibenthic Freshwater Cyanobacterial Synechococcus spp. Strains Depends on Their Ability for Photoprotection

Epibenthic cyanobacteria often grow in environments where the fluctuation of light intensity and quality is extreme and frequent. Different strategies have been developed to cope with this problem depending on the distribution of cyanobacteria in the water column. and either constant or enhanced levels of carotenoids were assayed in phycocyanin-rich strains collected from 1.0 and 0.5 m water depths. Protein analysis revealed that while the amount of biliproteins remained constant in all strains during light stress and recovery, the amount of D1 protein from photosystem II reaction centre was strongly reduced under light stress conditions in strains from 7.0 m and 1.0 m water depth, but not in strains collected from 0.5 m depth. spp. strains, depending on their genetically fixed mechanisms for photoprotection

Frequently asked questions about chlorophyll fluorescence, the sequel

[EN] Using chlorophyll (Chl) a fluorescence many aspects of the photosynthetic apparatus can be studied, both in vitro and, noninvasively, in vivo. Complementary techniques can help to interpret changes in the Chl a fluorescence kinetics. Kalaji et al. (Photosynth Res 122: 121-158, 2014a) addressed several questions about instruments, methods and applications based on Chl a fluorescence. Here, additionalChl a fluorescence-related topics are discussed again in a question and answer format. Examples are the effect of connectivity on photochemical quenching, the correction of F-V/F-M values for PSI fluorescence, the energy partitioning concept, the interpretation of the complementary area, probing the donor side of PSII, the assignment of bands of 77 K fluorescence emission spectra to fluorescence emitters, the relationship between prompt and delayed fluorescence, potential problems when sampling tree canopies, the use of fluorescence parameters in QTL studies, the use of Chl a fluorescence in biosensor applications and the application of neural network approaches for the analysis of fluorescence measurements. The answers draw on knowledge fromdifferent Chl a fluorescence analysis domains, yielding in several cases new insights.Kalaji, H.; Schansker, G.; Brestic, M.; Bussotti, F.; Calatayud, A.; Ferroni, L.; Goltsev, V.... (2017). Frequently asked questions about chlorophyll fluorescence, the sequel. 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Antiinflammatory Therapy with Canakinumab for Atherosclerotic Disease

Background: Experimental and clinical data suggest that reducing inflammation without affecting lipid levels may reduce the risk of cardiovascular disease. Yet, the inflammatory hypothesis of atherothrombosis has remained unproved. Methods: We conducted a randomized, double-blind trial of canakinumab, a therapeutic monoclonal antibody targeting interleukin-1β, involving 10,061 patients with previous myocardial infarction and a high-sensitivity C-reactive protein level of 2 mg or more per liter. The trial compared three doses of canakinumab (50 mg, 150 mg, and 300 mg, administered subcutaneously every 3 months) with placebo. The primary efficacy end point was nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death. RESULTS: At 48 months, the median reduction from baseline in the high-sensitivity C-reactive protein level was 26 percentage points greater in the group that received the 50-mg dose of canakinumab, 37 percentage points greater in the 150-mg group, and 41 percentage points greater in the 300-mg group than in the placebo group. Canakinumab did not reduce lipid levels from baseline. At a median follow-up of 3.7 years, the incidence rate for the primary end point was 4.50 events per 100 person-years in the placebo group, 4.11 events per 100 person-years in the 50-mg group, 3.86 events per 100 person-years in the 150-mg group, and 3.90 events per 100 person-years in the 300-mg group. The hazard ratios as compared with placebo were as follows: in the 50-mg group, 0.93 (95% confidence interval [CI], 0.80 to 1.07; P = 0.30); in the 150-mg group, 0.85 (95% CI, 0.74 to 0.98; P = 0.021); and in the 300-mg group, 0.86 (95% CI, 0.75 to 0.99; P = 0.031). The 150-mg dose, but not the other doses, met the prespecified multiplicity-adjusted threshold for statistical significance for the primary end point and the secondary end point that additionally included hospitalization for unstable angina that led to urgent revascularization (hazard ratio vs. placebo, 0.83; 95% CI, 0.73 to 0.95; P = 0.005). Canakinumab was associated with a higher incidence of fatal infection than was placebo. There was no significant difference in all-cause mortality (hazard ratio for all canakinumab doses vs. placebo, 0.94; 95% CI, 0.83 to 1.06; P = 0.31). Conclusions: Antiinflammatory therapy targeting the interleukin-1β innate immunity pathway with canakinumab at a dose of 150 mg every 3 months led to a significantly lower rate of recurrent cardiovascular events than placebo, independent of lipid-level lowering. (Funded by Novartis; CANTOS ClinicalTrials.gov number, NCT01327846.

Histone acetylation, vernalization insensitive 3, flowering locus C, and the vernalization response

The quantitative induction of VIN3 by low temperatures is required for PRC2 repression of FLC and promotion of flowering (vernalization) in Arabidopsis. Histone acetylation, a chromatin modification commonly associated with gene transcription, increased on VIN3 chromatin in two spatially and temporally distinct phases in response to low temperatures. During short-term cold exposure, histone H3 acetylation at the transcription start site rapidly increased, implying that it is required for VIN3 induction. Subsequent changes in histone H3 and H4 acetylation occurred following continued VIN3 transcription during prolonged cold exposure. Members of the SAGA-like transcriptional adaptor complex, including the histone acetyltransferase GCN5, which induces expression of the cold acclimation pathway genes, do not regulate VIN3 induction during cold exposure, indicating that the cold acclimation pathway and the cold-induction of VIN3 are regulated by different transcriptional mechanisms. Mutations in the other 11 histone acetyltransferase genes did not affect VIN3 induction. However, nicotinamide, a histone deacetylase inhibitor, induced VIN3 and altered histone acetylation at the VIN3 locus. VIN3 induction was proportional to the length of nicotinamide treatment, which was associated with an early-flowering phenotype and repression of FLC. However, unlike vernalization, the repression of FLC was independent of VIN3 activity. Nicotinamide treatment did not cause a change in the expression of any genes in the autonomous pathway or members of the PRC2 complex, the well characterized repressors of FLC. Our data suggest that FLC is repressed via a novel pathway involving the SIR2 class of histone deacetylases

Vernalization insensitive 3 (VIN3) is required for the response of Arabidopsis thaliana seedlings exposed to low oxygen conditions

VERNALIZATION INSENSITIVE 3 (VIN3), which is required for the vernalization-mediated epigenetic repression of FLOWERING LOCUS C (FLC) in Arabidopsis thaliana, is quantitatively induced in response to low temperatures. We found that hypoxic conditions also induce VIN3 in a quantitative manner but high salt, high temperatures and osmotic stress do not. Inhibition of mitochondrial respiration did not induce VIN3 expression, consistent with the lack of VIN3 induction in response to other stresses that affect the rate of mitochondrial respiration. De novo protein synthesis is required for VIN3 induction during hypoxic conditions; this situation is not the case for VIN3 induction by low temperatures, indicating that different mechanisms act to induce VIN3 expression in response to cold and hypoxic conditions. Without VIN3 activity, fewer seedlings survived following a 72-h period of hypoxic treatment, indicating that VIN3 is required for the survival of Arabidopsis thaliana in response to hypoxic stress. Complementation of the vin3 mutant with a VIN3 transgene restored the wild-type response to low oxygen and confirmed the role of VIN3 in protecting both shoots and roots during low oxygen conditions. Loss of VIN3 protein did not affect the transcriptional regulation of genes known to be important in the response to low oxygen stress, which suggests that there is a novel mechanism to combat hypoxia that involves VIN3. This mechanism is likely to involve chromatin remodelling and may be similar to the role of VIN3 in the epigenetic repression of FLC during the vernalization response. © 2009 Blackwell Publishing Ltd

Multiple scattering between cylinders and a schroeder diffuser

A multiple scattering method is developed to model an array of N cylinders positioned in front of a Schroeder diffuser. Results are compared against the more computationally intensive boundary element method, as well as existing multiple scattering methods for cylinders alone. An investigation of scattering performance from a cylinder arrangement in front of a Schroeder diffuser is also performed. The addition of cylinders is shown to offer potential benefits such as reducing the effects of periodicity in the Schroeder diffuser