Network of earthquakes and recurrences therein

We quantify the correlation between earthquakes and use the same to distinguish between relevant causally connected earthquakes. Our correlation metric is a variation on the one introduced by Baiesi and Paczuski (Phys Rev E 69:066,106, 2004). A network of earthquakes is constructed, which is time-ordered and with links between the more correlated ones. Data pertaining to the California region has been used in the study. Recurrences to earthquakes are identified employing correlation thresholds to demarcate the most meaningful ones in each cluster. The distribution of recurrence lengths and recurrence times are analyzed subsequently to extract information about the complex dynamics. We find that the unimodal feature of recurrence lengths helps to associate typical rupture lengths with different magnitude earthquakes. The out-degree of the network shows a hub structure rooted on the large magnitude earthquakes. In-degree distribution is seen to be dependent on the density of events in the neighborhood. Power laws are also obtained with recurrence time distribution agreeing with the Omori law.     

Significance of biofilm proteins in modulating cyprid metamorphosis of Balanus amphitrite (Cirripedia: Thoracica)

The role of biofilm proteins in modulating cyprid metamorphosis is not well understood. In the present investigation this possibility was explored by disrupting biofilm proteins using commercially available protease. The influence of natural biofilm and artificial biofilms of Aeromonas salmonicida salmonicida and Bacillus brevis and their culture supernatants and exopolysaccharides obtained under different nutritional conditions was evaluated. Natural biofilm facilitated cyprid metamorphosis in Balanus amphitrite, whereas monospecies biofilms did not. The treatment of biofilms with protease resulted in a decline in metamorphosis, except in B. brevis, where although metamorphosis was negated initially, it increased with the protease concentration and observation days. As the response of cyprids to exopolysaccharides produced by A. salmonicida salmonicida was dependent on protein concentration, protease treatment resulted in a decrease in metamorphosis, whereas in case of B. brevis biofilms, protease hydrolysis products could be important in providing settlement cues. Thus, biofilm bacterial components play an important role in the cyprid metamorphosis of Balanus amphitrite.     

The steady‐state structure of the natural stratosphere and ozone distribution in a 2‐D model incorporating radiation and O‐H‐N photochemistry and the effects of stratospheric pollutants

A mean meridional circulation model of the stratosphere, incorporating radiative heating and photochemistry of the oxygen‐hydrogen‐nitrogen atmosphere, is used to simulate the meridional distributions of O₃, HO_X, N₂O,NO_X, temperature and the three components of mean motion for the summer and winter seasons under steady‐state conditions. The results are generally in good agreement with the available observations in the normal stratosphere. The model has been applied to assess the effects of water vapour and nitrogen oxide perturbations resulting from aircraft emissions in the stratosphere. It is found that a fleet of 500 Boeing‐type sst's, flying at 20 km and 45°N in the summer hemisphere and inserting NO_x at a rate of 1.8 megatons per year, has the effect of reducing the global total ozone by 14.7%. Similar calculations for 342 Concorde/TU‐114's, cruising at 17 km and injecting NO_x at a rate of 0.35 megatons per year, show a global‐average total‐ozone reduction of 1.85%. Although water vapour is considered important, because of its ability to convert NO₂ into HNO₃, the direct effect on global‐average total‐ozone reduction resulting from the 100% increase in the stratospheric water content is less than 1%. The changes in the chemical structure (HO^NO^), temperature, and mean motions associated with the ozone reduction are also investigated in the case of the 1.8‐megaton‐per‐year NO_X perturbation. It is shown that the reduced meridional temperature gradient in the middle and upper stratosphere resulting from the NO_x perturbation leads to the weakening of the tropical easterly jet in the summer hemisphere and mid‐latitude westerlies in the winter season.

The sensitivity of the model solutions to an alternate choice of input parameters (diffusion coefficients and solar photodissociation data) is tested and the main deficiency of the model is pointed out.     

Role of ocean–atmosphere interaction on northward propagation of Indian summer monsoon intra-seasonal oscillations (MISO)

Atmospheric dynamical mechanisms have been prevalently used to explain the characteristics of the summer monsoon intraseasonal oscillation (MISO), which dictates the wet and dry spells of the monsoon rainfall. Recent studies show that ocean–atmosphere coupling has a vital role in simulating the observed amplitude and relationship between precipitation and sea surface temperature (SST) at the intraseasonal scale. However it is not clear whether this role is simply ‘passive’ response to the atmospheric forcing alone, or ‘active’ in modulating the northward propagation of MISO, and also whether the extent to which it modulates is considerably noteworthy. Using coupled NCEP–Climate Forecast System (CFSv2) model and its atmospheric component the Global Forecast System (GFS), we investigate the relative role of the atmospheric dynamics and the ocean–atmosphere coupling in the initiation, maintenance, and northward propagation of MISO. Three numerical simulations are performed including (1) CFSv2 coupled with high frequency interactive SST, the GFS forced with both (2) observed monthly SST (interpolated to daily) and (3) daily SST obtained from the CFSv2 simulations. Both CFSv2 and GFS simulate MISO of slightly higher period (~60 days) than observations (~45 days) and have reasonable seasonal rainfall over India. While MISO simulated by CFSv2 has realistic northward propagation, both the GFS model experiments show standing mode of MISO over India with no northward propagation of convection from the equator. The improvement in northward propagation in CFSv2, therefore, may not be due to improvement of the model physics in the atmospheric component alone. Our analysis indicates that even with the presence of conducive vertical wind shear, the absence of meridional humidity gradient and moistening of the atmosphere column north of convection hinders the northward movement of convection in GFS. This moistening mechanism works only in the presence of an ‘active’ ocean. In CFSv2, the lead-lag relationship between the atmospheric fluxes, SST and convection are maintained, while such lead-lag is unrealistic in the uncoupled simulations. This leads to the conclusion that high frequent and interactive ocean–atmosphere coupling is a necessary and crucial condition for reproducing the realistic northward propagation of MISO in this particular model.     

Simultaneous infrared and H-alpha measurements of Be stars

The observed infrared excess in Be stars is usually interpreted as free-free and free-bound emission from a hot gas envelope around the Be star. This hot gas should also emit H-alpha line radiation. Earlier observations had suggested that the infrared excess and Hα radiation were not consistent with models in which they arise from the same ionized region; however the observations were made at different times. We have made simultaneous observation of infrared and H-alpha line radiation. Our observations imply that either both these radiations cannot arise from the same hot gas or additional processes have to be invoked to account for the observed excess infrared radiation.     

Effects of rotation and tidal distortions on the periods of adiabatic oscillations of composite models of stars

Mohan and Saxena's approach of using the averaging technique of Kippenhahn and Thomas in conjunction with Kopal's method of evaluating various parameters on the Roche equipotentials has been used to compute the effects of rotation and tidal distortions on the periods of small adiabatic radial and nonradial modes of oscillations of a series of composite models of stars. In these stars the density decreases slowly in the core from the centre to the interface and then falls of rapidly in the envelope from the interface to the outer surface.     

The occultation of MKE 31 by Neptune on September 12, 1983

The predicted occultation of the star No. 31 (Mink et al., 1981) by Neptune on September 12, 1983 was observed photoelectrically. Four secondary occultations were recorded before the immersion event.     

Radio and infrared flares in CYG X-3

The observed radio and infrared flares in Cyg X-3 are explained as due to interaction of X-rays and high-energy gamma-rays with clumps of matter in a cocoon around the object. The observed repetitive period of the radio flares is explained as the beat period between the 4.8 hr periodicity and the Keplerian period of matter in the cocoon.     

GSFC optical ozonesonde results during the Gap,France, intercomparisons,June 1981

A GSFC Super Loki optical ozonesonde instrument was flown as part of the ozone sensor intercomparison balloon campaign at Gap, France, in June 1981. A primary objective was to confirm biases between external absorption techniques, such as the GSFC sonde, and in situ techniques, which include ECC, Mast-Brewer, and DASIBI sondes. Ozone distributions were obtained with the GSFC sonde on three of the four ascent-descent legs of the first flight on 19 June. Ozone densities were measured redundantly over altitudes from 22 to 32 km using filters centered at 303 and 300 nm. The three profiles obtained by averaging the data from the two channels are in close agreement with an average S.E. of 1.4%. However, small but consistent differences were found between the ozone densities measured at the two wavelengths. The average difference is 5% using Vigroux cross sections and 4% using preliminary Bass cross sections. The integral ozone amount above the first ceiling altitude of 32.85 km was determined by the Langley plot method to be 45 D.U. The total ozone derived by integrating the optical ozonesonde and ECC profiles is within 2% of the Chiran Dobson Spectrophotometer observation based on a pre-campaign calibration but is 9% greater than the amount derived using a post-campaign calibration.