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Sodium smectite clays were enriched with ferric ions (Argel-Fe and Volclay-Fe) to convert the surface charge of the clays from negative to positive and to use the clays in the discolouration of a synthetic effluent composed of seven anionic dyes (mixed from tartrazine, Brilliant Blue FCF and amaranth). The iron content increased from 5.99% to 11.02% for Argel-Fe and from 5.39% to 10.54% for Volclay-Fe. The efficiency of the discolouration of the anion dye mixture was evaluated by measuring the absorbance of the mixture at 562 nm, where the band with the greatest intensity was found. The contact time required for the system to reach equilibrium was ~5 min for both adsorbents. The kinetic adsorption data supported a pseudo-second-order kinetic model. The experimental data support the dual-site Langmuir–Freundlich isotherm model. The maximum adsorption capacities were 88.68 mg g–1 for Argel-Fe and 392.21 mg g–1 for Volclay-Fe. The enrichment of clays with Fe(III) added functionality to the clays and generated adsorbents with rapid adsorption abilities and high discolouration capacities.
The indications for expanded endoscopic transnasal approaches continue to increase, with more complex skull base defects needing to be repaired. This study reviews the management of large anterior skull base defects with opening of the sellar diaphragm.
A prospective analysis of endonasal endoscopic surgery carried out at Son Espases University Hospital between January 2013 and December 2018 was performed. The analysis included only the cases with a significative intra-operative cerebrospinal fluid leak. In all cases, reconstruction was performed by combining the gasket seal technique with a pedicled mucosal endonasal flap.
Twenty-eight patients were included. The mucoperiosteal nasoseptal flap, the lateral wall flap and the middle turbinate flap were used in 13, 8 and 7 patients, respectively, combined with the gasket seal technique. One case of post-operative cerebrospinal fluid leak was observed (3.57 per cent).
The combination of a gasket seal with an endonasal mucosal flap is an excellent technique for repairing large anterior skull base defects.
Currently, the types and distribution of the lesions induced in the central nervous system (CNS) by Trypanosoma cruzi remain unclear as the available evidence is based on fragmented data. Therefore, we developed a systematic review to analyse the main characteristics of the CNS lesions in non-human hosts infected. From a structured search on the PubMed/Medline and Scopus platforms, 32 studies were retrieved, subjected to data extraction and methodological bias analysis. Our results show that the most frequent alterations in the CNS are the presence of different forms of T. cruzi and intense lymphocytes infiltrates. The encephalon is the main target of T. cruzi, and inflammatory changes in the CNS are more frequent and severe in the acute phase of infection. The parasite's genotype and phenotype are associated with the tropism and severity of the CNS lesions. The methodological limitations found in the studies were divergences in inoculation pathways, under-reporting of animal age and weight, sample calculation strategies and histopathological characterization. Since the changes were dependent on the pathogenicity and virulence of the T. cruzi strains, the genotype and phenotype characterization of the parasite are extremely relevant to predict changes in the CNS and the neurological manifestations associated with Chagas’ disease.
Circular data originates in a wide range of scientific fields and can be analyzed on the basis of directional statistics and special distributions wrapped around the circumference. However, both propensity to transform non-linear to linear data and complexity of directional statistics limited the generalization of the circular paradigm in the animal breeding framework, among others. Here, we generalized a circular mixed (CM) model within the context of Bayesian inference. Three different parametrizations with different hierarchical structures were developed on basis of the von Mises distribution; moreover, both goodness of fit and predictive ability from each parametrization were compared through the analyses of 110 116 lambing distribution records collected from Ripollesa sheep herds between 1976 and 2017. The naive circular (NC) model only accounted for population mean and homogeneous circular variance, and reached the lowest goodness-of-fit and predictive ability. The CM model assumed a hierarchical structure for the population mean by accounting for systematic (ewe age and lambing interval) and permanent environmental sources of variation (flock-year-season and ewe). This improved goodness of fit by reducing both the deviance information criterion (DIC; −2520 units) and the mean square error (MSE; −12.4%) between simulated and predicted lambing data when compared against the NC model. Finally, the last parametrization expanded CM model by also assuming a hierarchical structure with systematic and permanent environmental factors for the variance parameter of the von Mises distribution (i.e. circular canalization (CC) model). This last model reached the best goodness of fit to lambing distribution data with a DIC estimate 5425 units lower than the one for NC model (MSE reduced 13.2%). The same pattern revealed when models were compared in terms of predictive ability. The superiority revealed by CC model emphasized the relevance of heteroskedasticity for the analysis of lambing distribution in the Ripollesa breed, and suggested potential applications for the sheep industry, even genetic selection for canalization. The development of CM models on the basis of the von Mises distribution has allowed to integrate flexible hierarchical structures accounting for different sources of variation and affecting both mean and dispersion terms. This must be viewed as a useful statistical tool with multiple applications in a wide range of research fields, as well as the livestock industry. The next mandatory step should be the inclusion of genetic terms in the hierarchical structure of the models in order to evaluate their potential contribution to current selection programs.
Seasonal reproduction patterns are typically observed in small ruminants and are a major limitation for production efficiency in most meat- and dairy-type production systems. Indeed, selection for reduced seasonality could be an appealing strategy for the small ruminant industry worldwide, although its genetic background has been poorly analyzed. One of the main limitations relied on the availability of appropriate analytical tools to cope with the circular (i.e. year-round) pattern of lambing and kidding data. The recent development of a heteroskedastic circular mixed model provided the statistical tool to go deeply into the knowledge of seasonality in small ruminants. In this study, 26 005 lambing distribution records from 4764 Ripollesa ewes collected in 20 purebred flocks were analyzed. The model accounted for systematic (lambing interval and ewe age), permanent environmental (flock-year-season and ewe) and additive genetic sources of variation influencing both mean and dispersion pattern (i.e. heteroskedasticity). Systematic effects suggested that first-lambing ewes and short lambing intervals delayed lambing date (~30 days) and increased dispersion of the lambing period. Nevertheless, this was partially compensated by ewe age, given that youngest females tended to concentrate the lambing peak. Flock-year-season, permanent ewe and additive genetic sources of variation reached moderate variance components for direct (and residual) effects on lambing distribution, they being 0.119 (0.156), 0.092 (0.132) and 0.195 (0.170) radians2, respectively. Moreover, all 95% credibility intervals were placed far from the null estimate. Covariances between direct and residual effects where high and positive for additive genetic (posterior mean, 0.814) and permanent ewe effects (posterior mean, 0.917), whereas it was not relevant for flock-year-season. Selection for direct additive genetic effects should be able to advance or delay the lambing peak, whereas selection applied on residual additive genetic effects should increase or reduce seasonality (i.e. concentrate or flatten the lambing peak). Moreover, the positive and relevant genetic covariance between direct and residual effects also suggested correlated genetic responses. As example, genetic selection for earlier lambing peaks must also reduce seasonality, whereas selection for narrower lambing seasons may originate a delay in the lambing peak. These results must be viewed as the first attempt to analyze systematic, environmental and genetic sources of variation of lambing distribution within the circular paradigm, they providing a reliable characterization of these effects within the context of an heteroskedastic model.
Plant secondary metabolites (PSM) are one of the promising options to control gastrointestinal nematodes in sheep and goats. The objective of this study was to assess the abilities of sheep and goats to self-medicate with tannin-rich sainfoin (Onobrychis viciifolia) (SF) when infected with gastrointestinal nematodes, using a cafeteria and an operant conditioning trial. Hypotheses were that parasitized (P) lambs and goat kids would show greater intake and preference for SF than their non-parasitized (NP) counterparts, that kids would eat more SF than lambs (due to their lower resistance against parasites and their greater ability to consume PSM), and that SF intake would increase over time for P animals. We used 20 female kids and 20 ewe lambs aged 3 months. Half of the animals per species (n = 10) were experimentally infected with 170 L3 larvae of Haemonchus contortus/kg of BW (P). The other half were free from parasites throughout the study (NP). Five weeks after infection, animals were exposed to a 24-day cafeteria trial (three 8-day periods) offering a free choice between two legume pellets: SF (3.8% condensed tannins) and alfalfa (ALF, Medicago sativa; no tannin). Subsequently, animals were involved in an operant conditioning trial of two 4-day long sessions, to assess in short-term tests their motivation to walk for a SF reward when offered in choice with freely available ALF. In the cafeteria trial, SF preference was greater in kids than in lambs, particularly in the first two periods. We did not observe a greater preference for SF in P animals, which was even greater in NP animals for periods 1 and 2. Sainfoin intake increased through periods for P animals, which led to similar SF preferences for all groups during period 3. In the operant-conditioning trial, motivation to get the SF reward was similar between P and NP animals. These results support the hypotheses that goats are more willing to consume tanniferous feeds than sheep, and that P animals increased SF intake through time. However, the emergence of a curative self-medicative behaviour was not supported, as P individuals did not show greater SF intake, preference, nor a greater motivation to get SF than NP animals, regardless of animal species. These findings are discussed with previous results and some explanations are presented.
Detailed representation of ingesta inflow to and digesta outflow from the rumen is critical for improving the modelling of rumen function and herbage intake of grazing ruminants. The objective of the current work was to extend a mechanistic model of a grazing ruminant, MINDY, to simulate the dynamic links between ingestive and digestive processes as affected by forage and sward features (e.g. sward structure, herbage chemical composition) as well as the internal state of the animal. The work integrates existing aspects of forage ingestion, oral physiology and rumen digestion that influence ingesta characteristics and digesta outflows from the rumen, respectively. The paper describes the structure and function of the new development, assessing the new model in terms of dynamic changes of oral processing of ingesta and rumen dilution rate under different grazing contexts. MINDY reproduces characteristics of ingesta inflow to and digesta outflow from the rumen of grazing ruminants, achieving temporal patterns of occurrence within and between meals, similar to those for grazing animals reported in the literature. The model realistically simulates changes in particle size distribution of the ingestive bolus, bolus weight and rumen dilution rate in response to contrasting grazing management regimes. The new concepts encoded in MINDY capture the underlying biological mechanisms that drive the dynamic link between ingestion and digestion patterns. This development advances in the understanding and modelling of grazing and digestive behaviour patterns of free-ranging ruminants.
American trypanosomiasis is a neglected tropical disease whose spectrum has not been quite understood, including the impact of Trypanosoma cruzi infection on the haematological parameters of different vertebrate hosts. Thus, this study was designed to compare the pattern of haematological changes induced by T. cruzi infection in order to identify possible species-specific differences among taxons. We also aimed at evaluating the use of this parameter as a tool for diagnosis during the acute phase, when symptoms are usually masked. For this purpose, we performed a systematic search on PubMed and Scopus databases to retrieve original studies published until August 2016. Thirty-one studies were selected using Prisma strategy, which were then submitted to data extraction and methodological bias analysis. Half of the studies showed that the number of erythrogram decreased in infected animals, indicating anaemia. In 68.2% of the studies, the total amount of leukogram values increased, suggesting infection. The main methodological limitations were insufficient information for T. cruzi strains identification, inoculation routes and parasitological characterization. Most of the mammalian species analysed showed the same pattern of haematological changes following T. cruzi infection, indicating that haematological parameters might direct the diagnosis of Chagas disease in the initial phase.
Marteilia refringens causes marteiliosis in oysters, mussels and other bivalve molluscs. This parasite previously comprised two species, M. refringens and Marteilia maurini, which were synonymized in 2007 and subsequently referred to as M. refringens ‘O-type’ and ‘M-type’. O-type has caused mass mortalities of the flat oyster Ostrea edulis. We used high throughput sequencing and histology to intensively screen flat oysters and mussels (Mytilus edulis) from the UK, Sweden and Norway for infection by both types and to generate multi-gene datasets to clarify their genetic distinctiveness. Mussels from the UK, Norway and Sweden were more frequently polymerase chain reaction (PCR)-positive for M-type (75/849) than oysters (11/542). We did not detect O-type in any northern European samples, and no histology-confirmed Marteilia-infected oysters were found in the UK, Norway and Sweden, even where co-habiting mussels were infected by the M-type. The two genetic lineages within ‘M. refringens’ are robustly distinguishable at species level. We therefore formally define them as separate species: M. refringens (previously O-type) and Marteilia pararefringens sp. nov. (M-type). We designed and tested new Marteilia-specific PCR primers amplifying from the 3’ end of the 18S rRNA gene through to the 5.8S gene, which specifically amplified the target region from both tissue and environmental samples.
Sperm-mediated gene transfer (SMGT) is a simple, fast, and economical biotechnological tool for producing transgenic animals. However, transgene expression with this technique in bovine embryos is still inefficient due to low uptake and binding of exogenous DNA in spermatozoa. The present study evaluated the effects of sperm membrane destabilization on the binding capacity, location and quantity of bound exogenous DNA in cryopreserved bovine spermatozoa using Triton X-100 (TX-100), lysolecithin (LL) and sodium hydroxide (NaOH). Effects of these treatments were also evaluated by intracytoplasmic sperm injection (ICSI)-SMGT. Results showed that all treatments bound exogenous DNA to spermatozoa including the control. Spermatozoa treated with different membrane destabilizing agents bound the exogenous DNA throughout the head and tail of spermatozoa, compared with the control, in which binding occurred mainly in the post-acrosomal region and tail. The amount of exogenous DNA bound to spermatozoa was much higher for the different sperm treatments than the control (P < 0.05), most likely due to the damage induced by these treatments to the plasma and acrosomal membranes. Exogenous gene expression in embryos was also improved by these treatments. These results demonstrated that sperm membrane destabilization could be a novel strategy in bovine SMGT protocols for the generation of transgenic embryos by ICSI.
Measurement of water consumption and urinary nitrogen (UN) excretion of individual grazing ruminants is difficult, time-consuming and expensive. Therefore, prediction and modelling are critical for research to improve N and water use efficiency. The objective of the current work was to use a mechanistic model of a grazing ruminant, MINDY, to represent drinking and urination diurnal patterns, and the resulting pattern of UN excretion. This work is primarily an integration of existing knowledge of basic urination physiology and water dynamics in ruminants. MINDY reproduces observed patterns of urination achieving the correct temporal occurrence, relative volumes and nitrogen (N) concentration of individual urination events for a grazing dairy cow, comparable with those reported in the literature. The model simulates daily water imbibed and UN realistically, as well as ingestion rates for herbages with different protein content and contrasting grazing managements. Results of a cross-validation indicate that the root mean square prediction error and mean absolute error as % of the observed mean, respectively, were 26 and 23% for daily water imbibed, 26 and 27% for urination volume, and 25 and 19% for the frequency of urination. Although further parameterization and validation are needed, for a new development in an exploratory model like MINDY, these numbers are encouraging and reflect that the concepts encoded capture many of the underlying biological mechanisms that drive the diurnal pattern and daily UN excretion, as well as thirst, acceptable.
Direct numerical simulations of a temporally developing, low-speed, variable-density, turbulent, plane mixing layer are performed. The Navier–Stokes equations in the low-Mach-number approximation are solved using a novel algorithm based on an extended version of the velocity–vorticity formulation used by Kim et al. (J. Fluid Mech., vol 177, 1987, 133–166) for incompressible flows. Four cases with density ratios
and 8 are considered. The simulations are run with a Prandtl number of 0.7, and achieve a
up to 150 during the self-similar evolution of the mixing layer. It is found that the growth rate of the mixing layer decreases with increasing density ratio, in agreement with theoretical models of this phenomenon. Comparison with high-speed data shows that the reduction of the growth rates with increasing density ratio has a weak dependence with the Mach number. In addition, the shifting of the mixing layer to the low-density stream has been characterized by analysing one-point statistics within the self-similar interval. This shifting has been quantified, and related to the growth rate of the mixing layer under the assumption that the shape of the mean velocity and density profiles do not change with the density ratio. This leads to a predictive model for the reduction of the growth rate of the momentum thickness, which agrees reasonably well with the available data. Finally, the effect of the density ratio on the turbulent structure has been analysed using flow visualizations and spectra. It is found that with increasing density ratio the longest scales in the high-density side are gradually inhibited. A gradual reduction of the energy in small scales with increasing density ratio is also observed.
The influence that the kinematics of pitching and heaving 2D airfoils has on the aerodynamic forces is investigated using direct numerical simulations and a force decomposition algorithm. Large-amplitude motions are considered (of the order of one chord), with moderate Reynolds numbers and reduced frequencies of order
, varying the mean pitch angle and the phase shift between the pitching and heaving motions. Our results show that the surface vorticity contribution (viscous effect) to the aerodynamic force is negligible compared with the contributions from the body motion (fluid inertia) and the vorticity within the flow (circulation). For the range of parameters considered here, the latter tends to be instantaneously oriented in the direction normal to the chord of the airfoil. Based on the results discussed in this paper, a reduced-order model for the instantaneous aerodynamic force is proposed, taking advantage of the force decomposition and the chord-normal orientation of the contribution from vorticity within the flow to the total aerodynamic force. The predictions of the proposed model are compared with those of a similar model from the literature, showing a noticeable improvement in the prediction of the mean thrust, and a smaller improvement in the prediction of the mean lift and the instantaneous force coefficients.
The low intake of medusahead grass (Taeniatherum caput-medusae ssp. asperum) by sheep is attributed to the high silica content of the plant and its negative impact on digestibility, making this weed a successful competitor in grazed plant communities. The goals of this study were to determine the influence of (1) plant maturity stage (from late vegetative stage to beginning of senescence and thatch), (2) particle size (1, 5, 10 and 20 mm), and (3) high-quality feeds (alfalfa hay and a high-energy concentrate) on fermentation kinetics and apparent digestibility of medusahead relative to palatable feeds (alfalfa and tall fescue hays, and high-energy concentrates). In vitro gas production was estimated and apparent digestible organic matter (DOM) of the substrates was assessed after incubation. Medusahead from late vegetative to senescence stage had greater DOM (65% to 71%; P<0.05) than alfalfa hay (53%), similar to tall fescue hay (67%; P>0.05), and lower than the high-energy concentrates assayed (77% to 79%; P<0.05). Fermentation kinetics showed slow fermentation rates for medusahead relative to alfalfa (P<0.05), and a decline in fermentation rates with plant maturity (P<0.05). Fermentation rates of the substrates were reduced with particle sizes ⩾5 mm (P<0.05), and apparent DOM for medusahead declined as particle size increased, a relationship not found for alfalfa or tall fescue hays (P<0.05). No effects (P>0.05) on digestibility parameters were observed by the addition of high-quality feeds to medusahead. Slow fermentation kinetics and a significant inhibitory effect of particle size on apparent digestibility of organic matter contribute to explain the low use of medusahead by sheep. Such inhibitory effect may also underlie the lack of positive associative effects observed during the study.
Sperm-mediated gene transfer (SMGT) is based on the capacity of sperm to bind exogenous DNA and transfer it into the oocyte during fertilization. In bovines, the progress of this technology has been slow due to the poor reproducibility and efficiency of the production of transgenic embryos. The aim of the present study was to evaluate the effects of different sperm transfection systems on the quality and functional parameters of sperm. Additionally, the ability of sperm to bind and incorporate exogenous DNA was assessed. These analyses were carried out by flow cytometry and confocal fluorescence microscopy, and motility parameters were also evaluated by computer-assisted sperm analysis (CASA). Transfection was carried out using complexes of plasmid DNA with Lipofectamine, SuperFect and TurboFect for 0.5, 1, 2 or 4 h. The results showed that all of the transfection treatments promoted sperm binding and incorporation of exogenous DNA, similar to sperm incorporation of DNA alone, without affecting the viability. Nevertheless, the treatments and incubation times significantly affected the motility parameters, although no effect on the integrity of DNA or the levels of reactive oxygen species (ROS) was observed. Additionally, we observed that transfection using SuperFect and TurboFect negatively affected the acrosome integrity, and TurboFect affected the mitochondrial membrane potential of sperm. In conclusion, we demonstrated binding and incorporation of exogenous DNA by sperm after transfection and confirmed the capacity of sperm to spontaneously incorporate exogenous DNA. These findings will allow the establishment of the most appropriate method [intracytoplasmic sperm injection (ICSI) or in vitro fertilization (IVF)] of generating transgenic embryos via SMGT based on the fertilization capacity of transfected sperm.
The Paramyxida, closely related to haplosporidians, paradinids, and mikrocytids, is an obscure order of parasitic protists within the class Ascetosporea. All characterized ascetosporeans are parasites of invertebrate hosts, including molluscs, crustaceans and polychaetes. Representatives of the genus Marteilia are the best studied paramyxids, largely due to their impact on cultured oyster stocks, and their listing in international legislative frameworks. Although several examples of microsporidian hyperparasitism of paramyxids have been reported, phylogenetic data for these taxa are lacking. Recently, a microsporidian parasite was described infecting the paramyxid Marteilia cochillia, a serious pathogen of European cockles. In the current study, we investigated the phylogeny of the microsporidian hyperparasite infecting M. cochillia in cockles and, a further hyperparasite, Unikaryon legeri infecting the digenean Meiogymnophallus minutus, also in cockles. We show that rather than representing basally branching taxa in the increasingly replete Cryptomycota/Rozellomycota outgroup (containing taxa such as Mitosporidium and Paramicrosoridium), these hyperparasites instead group with other known microsporidian parasites infecting aquatic crustaceans. In doing so, we erect a new genus and species (Hyperspora aquatica n. gn., n.sp.) to contain the hyperparasite of M. cochillia and clarify the phylogenetic position of U. legeri. We propose that in both cases, hyperparasitism may provide a strategy for the vectoring of microsporidians between hosts of different trophic status (e.g. molluscs to crustaceans) within aquatic systems. In particular, we propose that the paramyxid hyperparasite H. aquatica may eventually be detected as a parasite of marine crustaceans. The potential route of transmission of the microsporidian between the paramyxid (in its host cockle) to crustaceans, and, the ‘hitch-hiking’ strategy employed by H. aquatica is discussed.
Many plant tissues contain plant secondary compounds (PSC), which have long been recognised as defensive chemicals that deter herbivory via their toxic effects. However, herbivores may also benefit from including PSC into their diets. Plant-derived phenolics, terpenes and alkaloids have antiparasitic properties and sesquiterpene lactones have antibacterial, antifungal and antiparasitic properties. These actions are in part a consequence of the negative actions that PSC exert across several trophic levels, including the bacteria, parasites and fungi that inhabit herbivores’ bodies. Given the dual action, toxin and medicine, it is possible to hypothesise that self-selection of PSC by herbivores should occur when the benefits outweigh the costs of PSC ingestion. Recent research suggests that sheep and goats self-medicate against parasitic infections. They increase preference for condensed tannin-containing foods when experiencing a parasitic burden. This behaviour improves health; it is triggered by parasitism and weakens when parasitism subsides. However, the causes underlying these responses are not straightforward when viewed under a unidimensional cost–benefit analysis. This is because the intensity of antinutritional/toxic and medicinal effects of PSC is not static or just dependent upon the isolated post-ingestive effects of single PSC. Nutrient–PSC and PSC–PSC interactions, social models, as well as feeding patterns, all influence the perceived net benefit of incorporating medicines into a diet. A better understanding of the net benefit of self-medication in complex feeding environments will allow for the development of innovative managing strategies aimed at providing the food alternatives and conditions for improving the nutrition, health and welfare of grazing animals.
The crop rotation is a practice to protect and improve the soil properties and an alternative to improve the quality of crop residues is the application of fertilizers at the planting of cover crops. Thus, we evaluated the effect of fertilization with nitrogen, phosphorus and potassium (NPK) on organic matter production and chemical composition of cover crops succeeding the corn crop. The treatments consisted of the cultivation of Avena sativa L., Lupinus albus L., Pennisetum glaucum L., Raphanus sativus L. and Sorghum bicolor L. with (200 kg ha−1 of NPK [08-28-16] applied by broadcast seeding) and without fertilization at planting. Organic matter production by all cover crops, as well as concentrations of neutral detergent fibre (NDF) in shoots and roots of A. sativa L. and R. sativus L. were higher when they were fertilized. L. albus L. showed higher NDF and acid detergent fibre (ADF) contents than the other cover crops, with and without fertilization. Nitrogen concentration increased, but the carbon/nitrogen ratio (C/N) in the shoots of L. albus L., R. sativus L. and S. bicolor L. decreased when fertilization was applied. The use of N by the A. sativa L. and P. glaucum L. and of P and K by S. bicolor L. was 16, 54, 82 and 20% more efficient, respectively, when fertilization was applied. The A. sativa L., P. glaucum L. and R. sativus L. showed higher NDF/N, ADF/N and hemicellulose/N ratios in the fertilized treatment. Although the results obtained in this study are highly satisfactory, more research should be conducted to evaluate the decomposition of crop residues from cover crops fertilized with NPK, and the effects of this strategy on corn crops in succession.
Four tree ring-index site chronologies, representing standardised annual growth rates for spruce trees growing at high altitude sites in Colorado, have been employed as proxy data in a regression model for the annual variation of solar radio flux at 2800 MHz (F10·7) and the Catania sunspot area (Ac). These dendrochronological time series all exhibit significant power spectrum peaks at about 11 years and separately correlate with the annual values of Rz, F10·7 and Ac, as solar activity indicators. The two models constructed give the cyclic variation of F10·7 and Ac back to AD1673.
Initially some simple analytical properties based on the annual Zürich relative sunspot number are established for the 22-year Hale solar magnetic cycle. Since about AD1850, successive maximum sunspot numbers in a Hale cycle are highly correlated. Also, a regression model for the reconstruction of the 22-year Hale cycle has been formulated from proxy tree-ring data, obtained from spruce trees growing at a high altitude site in White River National Forest in Colorado. Over a considerable fraction of the past 300 years to AD1986, the ring-index time series power spectrum exhibits a strong 22-year periodicity, and more recently a significant spectral peak (at the 95% confidence level) at approximately 11 years. The model shows that the greatest variation in ‘amplitude’ in the magnetic cycle occurs over the early decades of the eighteenth century, when the sample size is small. Thereafter, a nearly constant amplitude is maintained until about AD1880 when a break occurs in both phase correspondence and amplitude, extending over the next three cycles. From AD1950 the signal recovers phase with the solar cycle, with reduced but increasing amplitude.