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Periodicity in nematode egg excretion may be of evolutionary origin as it can favour dispersal of the eggs in the environment. We investigated whether egg excretion by Heterakis gallinarum shows a repeatable pattern of periodicity. The faecal egg concentration and total number of eggs excreted within 4-h intervals were significantly affected by the sampling time within 1 day, but remained unaffected by the sampling day or interaction effects. By contrast, the total number of eggs excreted within 24 h did not differ among the 4 days of the study, collectively indicating repeatable egg excretion patterns. Both host feces and parasite egg excretion increased from night to late afternoon, followed by a decrease in the evening, resulting in higher egg excretion during daytime than the dark period. Feces excretion and worm fecundity showed overlapping diurnal rhythms with similarly timed phases, suggesting the existence of synchronicity between the host feces and nematode egg excretion patterns. We conclude that egg excretion by H. gallinarum is synchronized with host feces excretion and is higher during the daytime than during the dark period. This overlaps with the maximum activity of the day-active host and allows a maximal dispersal of the eggs in the environment.
Active sun is characterized by compelling short-lived flash of solar eruption like solar flare, coronal mass ejections (CMEs), high-speed solar winds and solar energetic particles along with colossal release of energy and mass. This paper proposes a new method to evaluate solar wind parameters and geomagnetic indices based on wavelet analysis during the solar flares. The crucial role of IMF-Bz (interplanetary magnetic field) is examined for the two solar flares events. The key result obtained from our study is substantial dependence of solar flare intensity on IMF-Bz together with solar wind velocity. We also observed the duration of solar flares and their effect on ionospheric and ground based parameters.
Understanding how seasonal patterns change from year to year is important for the management of infectious disease epidemics. Here, we present a mathematical formalization of the application of complex demodulation, which has previously only been applied in an exploratory manner in the context of infectious diseases. This method extracts the changing amplitude and phase from seasonal data, allowing comparisons between the size and timing of yearly epidemics. We first validate the method using synthetic data that displays the key features of epidemic data. In particular, we analyse both annual and biennial synthetic data, and explore the effect of delayed epidemics on the extracted amplitude and phase. We then demonstrate the usefulness of complex demodulation using national notification data for influenza in Australia. This method clearly highlights the higher number of notifications and the early peak of the influenza pandemic in 2009. We also identify that epidemics that peaked later than usual generally followed larger epidemics and involved fewer overall notifications. Our analysis establishes a role for complex demodulation in the study of seasonal epidemiological events.
Insufficient weed control is a major constraint to adoption of reduced-tillage practices for organic grain production. Tillage, cover crop management, and crop planting date are factors that influence emergence periodicity and growth potential of important weed species in these systems. We assessed two hairy vetch cover crop management practices, disk-kill and roll-kill, across a range of corn planting dates from early May to late June in three experiments in Beltsville, MD. Patterns of seed dormancy, emergence, and early weed growth were determined for overseeded populations of common ragweed, giant foxtail, and smooth pigweed, three important species in the Mid-Atlantic states that represent early to late emergence. Common ragweed emergence was lowest and dormancy was highest of the three species across all planting dates. Giant foxtail emergence was higher than the other species in roll-killed hairy vetch and included a significant number of seeds that germinated before rolling operations in late June. Smooth pigweed had the highest emergence and lowest dormancy in disk-killed hairy vetch in June. Individual giant foxtail plant weight was higher in roll-killed than disk-killed hairy vetch in 2 of 3 yr, whereas that of smooth pigweed plants was higher in disk-killed than roll-killed vetch in 2 of 3 yr. Giant foxtail was the dominant species in roll-killed hairy vetch (averaged 79% of total weed biomass at corn silking), probably because of early germination and establishment before rolling operations. Smooth pigweed was the dominant species in disk-killed hairy vetch at June planting dates (averaged 77% of total weed biomass), probably because of high growth rates under warm conditions in tilled soil. This research demonstrated that cover crop management practices and the timing of planting operations can shift the dominant species of weed communities in organic farming systems and must be considered in long-term weed management planning.
be a finitely generated cancellative abelian monoid. A
is a natural generalization of a
-graph. A pullback of
is constructed by pulling it back over a given monoid morphism to
, while a pushout of
is obtained by modding out its periodicity, which is deduced from a natural equivalence relation on
. One of our main results in this paper shows that, for some
is isomorphic to the pullback of its pushout via a natural quotient map, and that its graph
-algebra can be embedded into the tensor product of the graph
-algebra of its pushout and
. As a consequence, in this case, the cycline algebra generated by the standard generators corresponding to equivalent pairs is a maximal abelian subalgebra, and there is a faithful conditional expectation from the graph
-algebra onto it.
As an application of our papers in hermitian K-theory, in favourable cases we prove the periodicity of hermitian K-groups with a shorter period than previously obtained. We also compute the homology and cohomology with field coeffcients of infinite orthogonal and symplectic groups of specific rings of integers in a number field.
Data from multiple ice and sediment cores in the North Atlantic show that Marine Oxygen Isotope Stage 3 (MIS 3) was characterized by recurring millennial-scale variations in climate, but the periodic behavior of the well-known millennial-scale variations, Heinrich events and Dansgaard–Oeschger events, is uncertain. We use oxygen isotope values from the Greenland Ice Sheet Project 2 (GISP2) and North Greenland Ice Core Project (NGRIP) ice cores and estimated sea-surface temperature derived from a Bermuda Rise marine sediment core as climate proxies to assess the periodic behavior of Heinrich events and Dansgaard–Oeschger events using Lomb–Scargle spectral decomposition and continuous time autoregressive models. We find that continuous time autoregressive models produce less variable estimates of periodicity for Heinrich events than Lomb–Scargle methods. Heinrich events during MIS 3 are periodic with an estimated periodicity of 6.29–6.49 ka in the GISP 2 ice core, 6.71–6.76 ka in the marine sediment core, and 7.89–8.23 ka in the NGRIP core. There is insufficient evidence from these data to conclude that Dansgaard–Oeschger events exhibit a single periodicity during MIS 3. We also find that the periodic behavior of millennial-scale variations depends on the observational time frame.
An algorithm is corrected here that was presented as Theorem 2 in [Š. Holub, RAIRO-Theor. Inf. Appl. 40 (2006) 583–591]. It is designed to calculate the maximum length of a nontrivial word with a given set of periods.
In the paper we study abelian versions of the critical factorization theorem. We investigate both similarities and differences between the abelian powers and the usual powers. The results we obtained show that the constraints for abelian powers implying periodicity should be quite strong, but still natural analogies exist.
We show that any positive integer is the least period of a factor of the Thue-Morse word.
We also characterize the set of least periods of factors of a Sturmian word. In particular,
the corresponding set for the Fibonacci word is the set of Fibonacci numbers.
As a by-product of our results, we give several new proofs and tightenings
of well-known properties of Sturmian words.
Suppose ƒ : X* → X* is a morphism and u,v ∈ X*. For every nonnegative integer n, let zn be the longest common
prefix of ƒn(u) and ƒn(v), and let un,vn ∈ X* be words such
that ƒn(u) = znun and ƒn(v) = znvn. We prove that there is a positive
integer q such that for any positive integer p, the prefixes of un
(resp. vn) of length p form an ultimately periodic sequence having period
q. Further, there is a value of q which works for all words u,v ∈ X*.
In this note we consider the longest word, which has periods p1,...,pn, and does not have the period gcd(p1,...,pn).
The length of such a word can be established by a simple algorithm. We give a short and natural way to prove that the algorithm is correct. We also give a new proof that the maximal word is a palindrome.
Knowing when weed species are likely to emerge can aid in developing effective integrated weed management programs. When using nonresidual herbicides such as glyphosate for weed control, treatment timing is critical. This study characterized the emergence patterns of common lambsquarters, common sunflower, common waterhemp, eastern black nightshade, ivyleaf morningglory, shattercane, and woolly cupgrass in soybean, in relation to common glyphosate application timings. Approximately 90% or more of common lambsquarters, common sunflower, and common waterhemp seedlings emerged before the end of May, both in 2000 and 2001. Both ivyleaf morningglory and shattercane emerged from late April to mid-August, allowing these species to avoid glyphosate applications timed to prevent early-season weed competition. Avoidance through periodicity in emergence underscores the importance of integrating multiple tactics to ensure that difficult to manage weeds are not selected for in this management system.
Many protein sequences present non trivial periodicities, such as
cysteine signatures and leucine heptads. These known periodicities
probably represent a small percentage of the total number of sequences
periodic structures, and it is useful to have general tools to
detect such sequences and their period in large databases of
sequences. We compare three statistics adapted from those used in time
series analysis: a generalisation of the simple autocovariance based
on a similarity score and two statistics intending to increase the
power of the method. Theoretical behaviour of these statistics are
derived, and the corresponding tests are then described. In this paper
we also present an application of these tests to a protein known to
have sequence periodicity.
A retrospective analysis was performed of parasite count data recorded from the first 7 days of blood or mosquito transmitted Plasmodium falciparum infections given for the treatment of neurosyphilis in the USA before 1963. The objective of this study was to characterize initial growth dynamics before host defences have significant effects on the infecting parasite population. Of the 328 patients' data available for analysis, 83 were excluded because they had received anti-malarial treatment during the first 7 days of the patent infection. Nonlinear mixed effects modelling was performed to estimate the parameters of interest; ‘parasite multiplication rate per 48 h’ (PMR), and length of the parasite life-cycle (periodicity). The parasitaemia versus time profiles showed great variability between patients. The mean population estimate of ‘PMR’ was approximately 8, and was highly dependent on the P. falciparum ‘strain’. PMR also varied significantly between patients with a 90% prediction interval varying from 5·5 to 12·3-fold. Both intrinsic parasite multiplication rate (an intrinsic virulence determinant), and host susceptibility and defence contribute to expansion of the parasite biomass and thus disease severity in falciparum malaria.
Objectives: Rapid cycling mood disorder is an important clinical phenomenon. The concept of rapid cycling has evolved since it was first described in 1974. The purpose of this review is to summarise current diagnostic criteria, postulated risk factors and suggested management strategies.
Method: A Medline and Psych-Lit computerised literature search was supplemented by tracing back through the references from existing review work.
Results: Over 80 papers were identified which discussed diagnosis and management of rapid cycling.
Conclusions: DSM-IV provides a useful but narrow definition of rapid cycling. Standard treatment of affective disorder may exacerbate rapid cycling. If a rapid cycling course develops, discontinuation of antidepressants and use of mood stabilisers is recommended.
The hypothesis of seasonality of twin births was investigated in two important maternity hospitals in the State of Sāo Paulo, Brazil. The study included 1,386 twin births that occurred among 154,699 deliveries from 1984 to 1993. No evidence of seasonality has been detected either for the twin birth rate considered as a whole or for dizygotic twinning rate. The distributions of these rates fitted well sinusoidal regression curves but the cyclic trend did not correspond to any specific season.
The phytoplankton periodicity of a tropical upland reservoir in Nigeria (Liberty Dam, Jos Plateau) and a temperate-type lake (L. Naranbagh) from the Kashmir Himalaya were compared. Variations in the phytoplankton communities in the water-bodies were both quantitative and qualitative. Liberty Dam conformed to the oligotrophic-desmid plankton type whilst in L.Naranbagh, phytoplankton resembled the eutrophic chlorococcales-diatom plankton type. Contrary to the general belief of muted (or lack of) seasonal changes in tropical regions, phytoplankton succession in the Jos reservoir was pronounced with dense persistence of some species for relatively short periods. The most striking fluctuations, typical of many temperate waters, were characteristic of L. Naranbagh with a build-up of plankton during summer and autumn. Variability in photosynthetic productivity was related to shifts in the climate-dependent population densities. The seasonal growth of the Jos phytoplankton reflected the alteration from the dry ‘Harmattan’ (December–February) to wetter (May–September) periods. These are analogous to the winter (December–February) and summer (June–August) seasons of the Kashmir Himalayan Valley. Phytoplankton associations and periodicities in each of the two warm-belt lakes were strongly driven by their respective local environments, including especially the marked seasonality of the climatic variables (rain, wind and solar radiation). Detailed comparisons of adequate long-term data from tropical and temperate waters are still required.
The cercariae of Schistosoma margrebowiei showed two peaks of emergence from Bulinus natalensis in a 12 h light/dark cycle. Peak emission occurred at 0700 h (one hour after the onset of light) and at 1900 h (one hour after the onset of darkness). Both peaks were of equal magnitude and were maintained during constant illumination indicating that the rhythm is innate. Delaying or advancing the timing of the dark period did not affect the timing of these two peaks. Following a five minute dark treatment elevation in cercarial output resulted irrespective of when the treatment was applied. Subjecting snails to various intensities of light only resulted in an elevation in output when a sudden change in intensity from 0 to 360 Lux or the reverse was applied. No response was seen to a gradual change in light intensity although the parasite could detect a change in light from 1 to 0 Lux. These responses appear to optimize the chances of host parasite contact.