Faraday polarization fluctuations and their dependence on post sunset secondary maximum and amplitude scintillations at Delhi

International audienceVHF Faraday rotation (FR) and amplitude scintillation data recorded simultaneously during May 1978?December 1980 at Delhi (28.63° N, 77.22° E; Dip 42.44° N) is analyzed in order to study the Faraday polarization fluctuations (FPFs) and their dependence on the occurrence of post sunset secondary maximum (PSSM) and amplitude scintillations. It is noted that FPFs are observed only when both PSSM and scintillations also occur simultaneously. FPFs are observed only during winter and the equinoctial months of high sunspot years. FPFs events are associated with intense scintillation activity, which is characterized by sudden onsets and abrupt endings, and are observed one to three hours after the local sunset. When FPFs and scintillation data from Delhi is compared with the corresponding data from a still lower latitude station, Hyderabad (17.35° N, 78.45° E), it is found that the occurrence of FPFs and scintillations at Delhi is conditional to their prior occurrence at Hyderabad, which indicates their production by a plasma bubble and the as-sociated irregularities generated initially over the magnetic equator. In addition, FPFs and scintillation data for October 1979, when their occurrence was maximum, is also examined in relation to daytime (11:00 LT) electrojet strength (EEj) values and evening hour h'F from an equatorial location, Kodaikanal (10.3° N, 77.5° E). It is interesting to note that FPFs and scintillations are most likely observed when the EEj was 100 nT or more and h'F reaches around 500 km. These results show that EEj and evening hours h'F values over the magnetic equator are important parameters for predicting FPFs and scintillation activity at locations such as Delhi, where scintillation activity is much more intense as compared to the equatorial region due to the enhanced back-ground ionization due to the occurrence of PSSM

Predicting the solar maximum with the rising rate

The growth rate of solar activity in the early phase of a solar cycle has been known to be well correlated with the subsequent amplitude (solar maximum). It provides very useful information for a new solar cycle as its variation reflects the temporal evolution of the dynamic process of solar magnetic activities from the initial phase to the peak phase of the cycle. The correlation coefficient between the solar maximum (Rmax) and the rising rate ({\beta}a) at {\Delta}m months after the solar minimum (Rmin) is studied and shown to increase as the cycle progresses with an inflection point (r = 0.83) at about {\Delta}m = 20 months. The prediction error of Rmax based on {\beta}a is found within estimation at the 90% level of confidence and the relative prediction error will be less than 20% when {\Delta}m \geq 20. From the above relationship, the current cycle (24) is preliminarily predicted to peak around October 2013 with a size of Rmax =84 \pm 33 at the 90% level of confidence.Comment: 7 pages, 3 figures, accepted for publication in SCIENCE CHINA Physics,Mechanics & Astronom

Assessment of the physical and mechanical properties of plaster of Paris bandage cast used as a splinting and casting materials

Abstract Aim: To assess the physical and mechanical properties of plaster of Paris (POP) bandage cast used as a splinting and casting materials. Materials and Methods: POP casts were divided into three Groups A, B and C with 2, 3 and 8 layer for POP bandage, respectively (n=6 in each group). Handling characters, technical easiness or difficulties, setting time, weight, diameter and thickness of the casts were recorded for different groups. The casts were mounted on universal testing machine and axial load was applied @ 10 mm/min until failure. The load deflection graphs were plotted. The maximum force at which failure of the casts occurred was recorded. Stress, strain, modulus of elasticity (MOE) and stiffness of casts were calculated. Result: Construction of POP bandage cast was messy and required 45-60 min for hardening. 8 layer POP cast was comparatively heavier in weight and thicker in cross section than 3 layer cast followed by 2 layer cast. Under axial compression, the load bearing capacity of 8 layer POP casts was more than 2 and 3 layer cast. Conclusion: The values of load bearing capacity, stress, stiffness and MOE of cast were the highest for 8 layer POP cast followed by 2 and 3 layer cast. Use if splints with POP cast is recommended due to its poor mechanical properties

The Solar Cycle: A new prediction technique based on logarithmic values

A new prediction technique based on logarithmic values is proposed to predict the maximum amplitude (Rm) of a solar cycle from the preceding minimum aa geomagnetic index (aamin). The correlation between lnRm and lnaamin (r = 0.92) is slightly stronger than that between Rm and aamin (r = 0.90). From this method, cycle 24 is predicted to have a peak size of Rm (24) = 81.7(1\pm13.2%). If the suggested error in aa (3 nT) before 1957 is corrected, the correlation coefficient between Rm and aamin (r = 0.94) will be slightly higher, and the peak of cycle 24 is predicted much lower, Rm(24) = 52.5\pm13.1. Therefore, the prediction of Rm based on the relationship between Rm and aamin depends greatly on the accurate measurement of aa.Comment: 6 pages, 3 figures, Accepted for publication in Astrophysics & Space Scienc

The Protein Kinase Tor1 Regulates Adhesin Gene Expression in Candida albicans

Eukaryotic cell growth is coordinated in response to nutrient availability, growth factors, and environmental stimuli, enabling cell–cell interactions that promote survival. The rapamycin-sensitive Tor1 protein kinase, which is conserved from yeasts to humans, participates in a signaling pathway central to cellular nutrient responses. To gain insight into Tor-mediated processes in human fungal pathogens, we have characterized Tor signaling in Candida albicans. Global transcriptional profiling revealed evolutionarily conserved roles for Tor1 in regulating the expression of genes involved in nitrogen starvation responses and ribosome biogenesis. Interestingly, we found that in C. albicans Tor1 plays a novel role in regulating the expression of several cell wall and hyphal specific genes, including adhesins and their transcriptional repressors Nrg1 and Tup1. In accord with this transcriptional profile, rapamycin induced extensive cellular aggregation in an adhesin-dependent fashion. Moreover, adhesin gene induction and cellular aggregation of rapamycin-treated cells were strongly dependent on the transactivators Bcr1 and Efg1. These findings support models in which Tor1 negatively controls cellular adhesion by governing the activities of Bcr1 and Efg1. Taken together, these results provide evidence that Tor1-mediated cellular adhesion might be broadly conserved among eukaryotic organisms

Review of nanomaterials in dentistry: interactions with the oral microenvironment, clinical applications, hazards, and benefits.

Interest in the use of engineered nanomaterials (ENMs) as either nanomedicines or dental materials/devices in clinical dentistry is growing. This review aims to detail the ultrafine structure, chemical composition, and reactivity of dental tissues in the context of interactions with ENMs, including the saliva, pellicle layer, and oral biofilm; then describes the applications of ENMs in dentistry in context with beneficial clinical outcomes versus potential risks. The flow rate and quality of saliva are likely to influence the behavior of ENMs in the oral cavity, but how the protein corona formed on the ENMs will alter bioavailability, or interact with the structure and proteins of the pellicle layer, as well as microbes in the biofilm, remains unclear. The tooth enamel is a dense crystalline structure that is likely to act as a barrier to ENM penetration, but underlying dentinal tubules are not. Consequently, ENMs may be used to strengthen dentine or regenerate pulp tissue. ENMs have dental applications as antibacterials for infection control, as nanofillers to improve the mechanical and bioactive properties of restoration materials, and as novel coatings on dental implants. Dentifrices and some related personal care products are already available for oral health applications. Overall, the clinical benefits generally outweigh the hazards of using ENMs in the oral cavity, and the latter should not prevent the responsible innovation of nanotechnology in dentistry. However, the clinical safety regulations for dental materials have not been specifically updated for ENMs, and some guidance on occupational health for practitioners is also needed. Knowledge gaps for future research include the formation of protein corona in the oral cavity, ENM diffusion through clinically relevant biofilms, and mechanistic investigations on how ENMs strengthen the tooth structure

La campaña experimental BLLAST 2011: Boundary Layer Late Afternoon and Sunset Turbulence

Presentación realizada para las XXXII Jornadas Científicas de la Asociación Meteorológica Española y 13º Encuentro Hispano-Luso de Meteorología celebrados en Alcobendas (Madrid), del 28 al 30 de mayo de 2012

Characterization of an Nmr Homolog That Modulates GATA Factor-Mediated Nitrogen Metabolite Repression in Cryptococcus neoformans

Nitrogen source utilization plays a critical role in fungal development, secondary metabolite production and pathogenesis. In both the Ascomycota and Basidiomycota, GATA transcription factors globally activate the expression of catabolic enzyme-encoding genes required to degrade complex nitrogenous compounds. However, in the presence of preferred nitrogen sources such as ammonium, GATA factor activity is inhibited in some species through interaction with co-repressor Nmr proteins. This regulatory phenomenon, nitrogen metabolite repression, enables preferential utilization of readily assimilated nitrogen sources. In the basidiomycete pathogen Cryptococcus neoformans, the GATA factor Gat1/Are1 has been co-opted into regulating multiple key virulence traits in addition to nitrogen catabolism. Here, we further characterize Gat1/Are1 function and investigate the regulatory role of the predicted Nmr homolog Tar1. While GAT1/ARE1 expression is induced during nitrogen limitation, TAR1 transcription is unaffected by nitrogen availability. Deletion of TAR1 leads to inappropriate derepression of non-preferred nitrogen catabolic pathways in the simultaneous presence of favoured sources. In addition to exhibiting its evolutionary conserved role of inhibiting GATA factor activity under repressing conditions, Tar1 also positively regulates GAT1/ARE1 transcription under non-repressing conditions. The molecular mechanism by which Tar1 modulates nitrogen metabolite repression, however, remains open to speculation. Interaction between Tar1 and Gat1/Are1 was undetectable in a yeast two-hybrid assay, consistent with Tar1 and Gat1/Are1 each lacking the conserved C-terminus regions present in ascomycete Nmr proteins and GATA factors that are known to interact with each other. Importantly, both Tar1 and Gat1/Are1 are suppressors of C. neoformans virulence, reiterating and highlighting the paradigm of nitrogen regulation of pathogenesis