Usability of the low frequency mode in southwest monsoon circulation for long range prediction of rainfall activity over central India

pro pagation have been ctudicd on the hasi, of upper air data of a few sta tions,The frequency of occurrence Ill' significant periodicity in th is mode i.. rchuively high for Visakhapatnam andMadras. 1 here appears a large inter-annual variability of the maximum amplitudes of rhe filtered series with nospecial preference to any latitudinal bell. Northward propagation of this mode also slums large inn.....-annunlvarisbility. In some ~ears the propaga tion " as totally absent. The phusc changes in the filtered ser ies o fVisakbapnma rn match ed with the cha nges in weekly ra infall activity over central India and thi.. may, pcrhups.be used to foreshadow the activ ity of the monsoon over central India ,

Diel oscillations in the feeding activity of heterotrophic and mixotrophic nanoplankton in the North Pacific Subtropical Gyre

Daily oscillations in photosynthetically active radiation strongly influence the timing of metabolic processes in picocyanobacteria, but it is less clear how the light-dark cycle affects the activities of their consumers. We investigated the relationship between marine picocyanobacteria and nanoplanktonic consumers throughout the diel cycle to determine whether heterotrophic and mixotrophic protists (algae with phagotrophic ability) display significant periodicity in grazing pressure. Carbon biomass of Prochlorococcus and Synechococcus was estimated continuously from abundances and cell size measurements made by flow cytometry. Picocyanobacterial dynamics were then compared to nanoplankton abundances and ingestion of fluorescently labeled bacteria measured every 4 h during a 4 d survey in the North Pacific Subtropical Gyre. Grazing of the labeled bacteria by heterotrophic nanoplankton was significantly greater at night than during the day. The grazing activity of mixotrophic nanoplankton showed no diel periodicity, suggesting that they may feed continuously, albeit at lower rates than heterotrophic nanoplankton, to alleviate nutrient limitation in this oligotrophic environment. Diel changes in Prochlorococcus biomass indicated that they could support substantial growth of nanoplankton if those grazers are the main source of picocyanobacterial mortality, and that grazers may contribute to temporally stable abundances of picocyanobacteria.

Confirmed short periodic variability of subparsec supermassive binary black hole candidate Mrk 231

ABSTRACT Here we confirm the short periodic variability of a subparsec supermassive binary black hole (SMBBH) candidate Mrk 231 in the extended optical photometric data set collected by the Catalina Real-Time Transient Survey (CRTS) and All-Sky Automated Survey for Supernovae (ASAS-SN). Using the Lomb–Scargle periodogram and 2DHybrid method, we detected the significant periodicity of ∼1.1 yr beyond a damped random walk model in the CRTS+ASAS-SN optical data set. Mrk 231 has been previously proposed as an SMBBH candidate with a highly unequal mass ratio (q ∼ 0.03), very tight mutual separation of ∼590 au, and an orbital period of ∼1.2 yr. Hence, our result further supports, even though not prove, the intriguing hypothesis that SMBBHs with low mass ratios may be more common than close-equal mass SMBBHs. This result, however, was obtained from the contribution of the CRTS data with limited sampling cadence and photometric accuracy, and further monitoring of Mrk 231 is crucial to confirm the periodicity.

Photometry and spectroscopy of massive stars observed during K2 Campaign 8

ABSTRACT We report in this paper spectroscopic and photometric analysis of eight massive stars observed during Campaign 8 of the Kepler/K2 mission from 2016 January to March. Spectroscopic data were obtained on these stars at OPD/LNA, Brazil, and their stellar parameters determined using sme. Periodic analyses of the light curves were performed through cleanest and period04 algorithms. Mass, luminosity, and radius of our stars were estimated employing cesam + posc grids. Three of our stars show significant periodicity. K2 ID 220679442 and K2 ID 220532854 have periods linked to the stellar rotation. K2 ID 220532854 has prominent silicon lines (Si ii 4128–4131 Å), a characteristic presented in the peculiar class of Ap magnetic main-sequence stars. However, in our spectral analysis, this object was found to be an evolved, luminous giant star. K2 ID 220466722 was revealed to be a δ Scuti variable, and 40 individual frequencies were determined for this star. No significant periodicity was found in the light curves for the remaining stars analysed in this work, besides the instrumental one.

Periodic optical variability of AGN

Here we present the evidence for periodicity of an optical emission detected in several AGN. Significant periodicity is found in light curves and radial velocity curves. We discuss possible mechanisms that could produce such periodic variability and their implications. The results are consistent with possible detection of the orbital motion in proximity of the AGN central supermassive black holes.

Isotopic and lithologic variations of one precisely-dated stalagmite across the Medieval/LIA period from Heilong Cave, central China

Lithologic and isotopic changes of one stalagmite (224 mm in length) from Heilong Cave, Central China, are investigated here in order to explore multiple proxies of monsoon climate. High uranium concentrations (6–10 ppm) ensure Th-230 dates precisely and resultant chronology ranges from ~790 to 1780 AD across the Medieval Warm Period (MWP) to Little Ice Age (LIA). Annually resolved oxygen and carbon isotopic data, gray level and elemental Sr are highly related to macroscopic lithologic changes. A lamination sequence is composed of alternations of white-porous and dark-compact calcite clearly discerned on the polished surface. The dark-compact laminae have low values of gray level, high Sr and δ13C values, indicating periods of low growth rate under dry climate conditions, and vice versa for the white-porous laminae. This suggests that changes in hydrology, matter input of drip water and crystallization process were controlled by cave environments and climates. The alternation of dry and wet periods with a significant periodicity of ~90 yr, as indicated by spectral analyses of the multiple proxies, is further supported by a reconstructed precipitation index from historical documents and instrumental data extending back to 1470 AD. A strong coherence between monsoon proxy of calcite δ18O and the other proxies was observed during the LIA but not during the MWP. This is likely due to changes in atmospheric circulation pattern at the boundary of MWP/LIA. When the Intertropical Convergence Zone shifted southward during the LIA, summer monsoon precipitation at the cave site was probably dominated by the Mei-Yu, resulting in water vapor mainly originated from adjacent oceanic sources.

Isotopic and lithologic variations of one precisely dated stalagmite across the Medieval/LIA period from Heilong Cave, Central China

Lithologic and isotopic changes of one stalagmite (224 mm in length) from Heilong Cave, Central China, are here investigated in order to explore multiple speleothem proxies of monsoon climate. High uranium concentrations (6–10 ppm) ensure Th-230 dates precisely and resultant chronology ranges from ~790 AD to 1780 across the Medieval Warm Period (MWP) to Little Ice Age (LIA). Annually resolved oxygen and carbon isotopic data, gray level and elemental Sr are highly related to macroscopic lithologic changes. A lamination sequence is composed of alternations of white-porous and dark-compact calcite clearly discerned on the polished surface. The dark-compact laminae have low values of gray level, high Sr and δ13C values, indicating periods of low growth rate under dry climate conditions, and vise versa for the white-porous laminae. This suggests that changes in hydrology, matter input of drip water and crystallization process were controlled by cave environments and climates. The alternation of dry and wet periods with a significant periodicity of ~90 yr, as indicated by spectral analysis of the multiple proxies, is further supported by a reconstructed precipitation index by historical documents and instrumental data extending back to 1470 AD. A strong coherence between monsoon proxy of calcite δ18O and the other proxies was observed during the LIA but not during the MWP. This is likely due to changes in atmospheric circulation pattern at the boundary of MWP/LIA. When the Intertropical Convergence Zone shifted southward during the LIA, summer monsoon precipitation at the cave site was probably dominated by the Mei-Yu, resulting in water vapor mainly originated from adjacent oceanic sources.

CORRELATION PROPERTIES OF PROTEIN SEQUENCES OF DIFFERENT STRUCTURAL CLASSES

We analyze the amino acid sequences of the proteins of different structural classes using the method of power spectrum density. It was found that the protein hydrophobicity sequences of different structural classes show different significant periodicity, which relates closely to the order of the α-helices and β-strands in their polypeptide chains.

In vivo pulsatility of pancreatic islet peptides

In vivo oscillations of pancreatic peptides are recognized in primates. To determine whether such oscillations also occur in other mammalian species and to examine their underlying mechanisms, portal vein levels of insulin, C-peptide, glucagon, somatostatin, pancreatic polypeptide (PP), and glucose were measured simultaneously at 1- or 2-min intervals in nine conscious dogs. For comparison with primates, additional experiments were conducted in baboons and humans. Computer-assisted pulse identification for both raw and smoothed data was performed and spectral estimations calculated after detrending. Concomitance and comovement between the fluctuations of the various peptides and glucose were tested. Prominent pulses at 10- to 14-min intervals were detected most regularly for insulin and glucagon and were frequently reflected in PP and somatostatin levels. Corresponding relative increments in plasma concentration averaged 54% for insulin, 16% for glucagon, 25% for PP, and 24% for somatostatin. Insulin pulses were concomitant with glucagon pulses in 80% of the cases. Pulses of PP were less frequent, although consistently associated with insulin pulses. Somatostatin pulses were less consistently associated with those of other peptides. Peptide oscillations were unrelated to glucose changes. Spectral analysis confirmed these results with peaks in the 10- to 14-min range for all peptides but no significant periodicity for glucose. No consistent delays or advances between the oscillations of the various peptides could be demonstrated. It is speculated that oscillatory behavior in the pancreas may be related to a central pacemaker mechanism, which involves insulin tightly coupled to glucagon, entraining the fluctuations of PP, and, inconsistently, of somatostatin.

Radiocarbon Variations in Consecutive Single Rings of A 4000-Year-Old Pine from the British Isles

At the Ninth International Radiocarbon Conference a paper was presented concerning possible short-term 14C variations in 4000-year-old red deer antlers (Cervus elaphus) found in Neolithic flint mines in Norfolk, England (Burleigh and Hewson, 1980). It was argued, on archaeologic grounds, that the true age of the samples varied by a few years at most. Their radiocarbon ages, however, varied by a considerably greater amount than could be explained by the errors in the measurements. Duplication of the measurements confirmed this unexpected variation.Farmer and Baxter (1972) claimed a significant correlation of atmospheric 14C levels in the northern hemisphere with sunspot number based on radiocarbon assay of single tree rings for the period 1829 to 1865. In contrast, Stuiver (1978) stated that a series of single-year Douglas Fir measurements did not show a statistically significant periodicity.This paper reports measurements made on a series of single-year dendrochronologic samples of approximately the same age as the red deer antlers, which have been carried out at the British Museum Research Laboratory. The results show that the variation in 14C between rings is not statistically significant; some other explanation must be sought for the anomalous antler measurements.