Enhancement of Fe absorption by Mn in rice roots (Oryza sativa L.)

Summary The rates of absorption of Fe by excized rice roots were measured in the absence and presence of different concentrations of MnSO₄. Fe absorption from 0.1 and 5 mM FeSO₄ was enhanced by MnSO₄ at concentrations above 0.1 and 5 mM, respectively.     

Growth-controlling factors produced during the logarithmic and stationary phases ofTetrahymena pyriformis

Summary Tetrahymena pyriformis grown to logarithmic phase and then inoculated into either fresh or conditioned medium exhibited a shorter lag phase than ciliates taken from stationary phase cultures. The growth inhibiting substance(s), which is probably produced by the growing ciliates, is thermostable and can be adsorbed to activated charcoal.     

Variation in regulation of aflatoxin biosynthesis among isolates of Aspergillus flavus.

Two new phenotypes of Aspergillus flavus which exhibit novel patterns of aflatoxin production have been identified and characterized. In one of the new variants of A. flavus, aflatoxin is made in the absence of carbohydrate and concomitantly with growth, without a lag period. A second variant did not produce aflatoxin in the presence or absence of carbohydrate. Chemical mutagenesis of this nonaflatoxigenic strain resulted in mutant strains which produced aflatoxin on carbohydrate-containing media. The aflatoxin production pattern observed in these mutants resembled the typical production scheme, with a lag period through log phase growth.     

Variation in regulation of aflatoxin biosynthesis among isolates ofAspergillus flavus

Two new phenotypes ofAspergillus flavus which exhibit novel patterns of aflatoxin production have been identified and characterized. In one of the new variants ofA. flavus, aflatoxin is made in the absence of carbohydrate and concomitantly with growth, without a lag period. A second variant did not produce aflatoxin in the presence or absence of carbohydrate. Chemical mutagenesis of this nonaflatoxigenic strain resulted in mutant strains which produced aflatoxin on carbohydrate-containing media. The aflatoxin production pattern observed in these mutants resembled the typical production scheme, with a lag period through log phase growth.     

Back propagation in time-series forecasting

One of the major constraints on the use of back propagation neural networks as a practical forecasting tool is the number of training patterns needed. We propose a methodology that reduces the data requirements. The general idea is to use the Box-Jenkins model in an exploratory phase to identify the 'lag components' of the series, to determine a compact network structure with one input unit for each lag, and then apply the validation procedure. This process minimizes the size of the network and consequently the data required to train the network. The results obtained in eight studies show the potential of the new methodology as an alternative to the traditional time-series models.     

Kinetics of insulin secretion in response to glucose by isolated islands of Langerhans from the fetal rat]

Isolated islets of Langerhans from 21.5 day-old foetal Rats were studied in a perifusion system in vitro. The overall dynamics of insulin release by the foetal islets in response to glucose 13.9 mM is biphasic and qualitatively similar to that obtained with islets of adult Rats. The magnitude of the initial phase of insulin secretion is similar for the foetal and adult islets. The second phase is fourfold higher in the adult than in the foetus. The response of foetal islets occurs, 45 to 60 sec. after the increase of glucose concentration in the medium and a maximum insulin release for the first phase is obtained with a lag period of 2 min. The difference between foetal and adult islets is essentially quantitative.     

Chronobiology of sleep in humans

Periodic circadian (24-h) cycles play an important role in daily hormonal and behavioural rhythms. Usually our sleep/wake cycle, temperature and melatonin rhythms are internally synchronized with a stable phase relationship. When there is a desynchrony between the sleep/wake cycle and circadian rhythm, sleep disorders such as advanced and delayed sleep phase syndrome can arise as well as transient chronobiologic disturbances, for example from jet lag and shift work. Appropriately timed bright light is effective in re-timing the circadian rhythm and sleep pattern to a more desired time, ameliorating these disturbances. Other less potent retiming effects may also be obtained from the judicious use of melatonin and exercise.     

Inhibition sélective de quelques enzymes respiratoires chezEscherichia coli

Summary It is possible to dissociate the activity of different enzymatic systems of the bacteriumEscherichia coli by the action of high hydrostatic pressures. This activity is studied in the microbes after having been subjected to high hydrostatic pressure. Each enzymatic system is inhibited at different pressures. The enzymes of the bacteria submitted to pressures lower than the inhibiting limit show a residual enzymatic activity; sometimes this activity appears after a phase of lag.     

Forecasting Inflation Rates Using Daily Data: A Nonparametric MIDAS Approach

In this paper a nonparametric approach for estimating mixed‐frequency forecast equations is proposed. In contrast to the popular MIDAS approach that employs an (exponential) Almon or Beta lag distribution, we adopt a penalized least‐squares estimator that imposes some degree of smoothness to the lag distribution. This estimator is related to nonparametric estimation procedures based on cubic splines and resembles the popular Hodrick–Prescott filtering technique for estimating a smooth trend function. Monte Carlo experiments suggest that the nonparametric estimator may provide more reliable and flexible approximations to the actual lag distribution than the conventional parametric MIDAS approach based on exponential lag polynomials. Parametric and nonparametric methods are applied to assess the predictive power of various daily indicators for forecasting monthly inflation rates. It turns out that the commodity price index is a useful predictor for inflations rates 20–30 days ahead with a hump‐shaped lag distribution. Copyright © 2015 John Wiley & Sons, Ltd.     

Bootstrap prediction intervals for autoregressive models of unknown or infinite lag order

Recent studies on bootstrap prediction intervals for autoregressive (AR) model provide simulation findings when the lag order is known. In practical applications, however, the AR lag order is unknown or can even be infinite. This paper is concerned with prediction intervals for AR models of unknown or infinite lag order. Akaike's information criterion is used to estimate (approximate) the unknown (infinite) AR lag order. Small‐sample properties of bootstrap and asymptotic prediction intervals are compared under both normal and non‐normal innovations. Bootstrap prediction intervals are constructed based on the percentile and percentile‐t methods, using the standard bootstrap as well as the bootstrap‐after‐bootstrap. It is found that bootstrap‐after‐bootstrap prediction intervals show small‐sample properties substantially better than other alternatives, especially when the sample size is small and the model has a unit root or near‐unit root. Copyright © 2002 John Wiley & Sons, Ltd.     

Improvement of the Liu‐type Shiller estimator for distributed lag models

The problem of multicollinearity produces undesirable effects on ordinary least squares (OLS), Almon and Shiller estimators for distributed lag models. Therefore, we introduce a Liu‐type Shiller estimator to deal with multicollinearity for distributed lag models. Moreover, we theoretically compare the predictive performance of the Liu‐type Shiller estimator with OLS and the Shiller estimators by the prediction mean square error criterion under the target function. Furthermore, an extensive Monte Carlo simulation study is carried out to evaluate the predictive performance of the Liu‐type Shiller estimator.     

Modeling Realized Volatility Dynamics with a Genetic Algorithm

The heterogeneous autoregressive model of realized volatility (HAR‐RV) is inspired by the heterogeneous market hypothesis and characterizes realized volatility dynamics through a linear function of lagged daily, weekly and monthly realized volatilities with a (1, 5, 22) lag structure. Considering that different markets can have different heterogeneous structures and a market's heterogeneous structure can vary over time, we build an adaptive heterogeneous autoregressive model of realized volatility (AHAR‐RV), whose lag structure is optimized with a genetic algorithm. Using nine common loss functions and the superior predictive ability test, we find that our AHAR‐RV model and its extensions provide significantly better out‐of‐sample volatility forecasts for the CSI 300 index than the corresponding HAR models. Furthermore, the AHAR‐RV model significantly outperforms all the other models under most loss functions. Besides, we confirm that Chinese stock markets' heterogeneous structure varies over time and the (1, 5, 22) lag structure is not the optimal choice. Copyright © 2016 John Wiley & Sons, Ltd.     

Shell microlaminations of the freshwater bivalveHyridella depressa as an archival monitor of manganese water concentration: Experimental investigation by depth profiling using secondary ion mass spectrometry (SIMS)

Specimens of the freshwater unionid bivalveHyridella depressa were experimentally exposed to a synthetic river water containing an elevated Mn water concentration (20 mg l^–1) for 2 or 6 days. SIMS depth profiles through the incremental nacre microlaminations or tablets (0.6 m breadth) of the shells of these bivalves showed increases in the signal intensity of Ca-normalised Mn that corresponded to the period of exposure. These results support the proposition that bivalve shells can be used as retrospective monitors of water chemistry. They also indicate that 1) there is a lag phase between exposure to the elevated Mn water concentration and its expression in the shell, and 2) the period for Mn in the shell to reach equilibrium with the aquatic medium is greater that 2 to 6 days.     

The relationship of the vertical distribution of Japanese conifers to the maltol contents in their leaves

Summary Of 35 species of coniferous trees in Japan, only 4 species, found at subalpine zone, contain maltol in their leaves. Their leaves are also characteristic for their high content of sugar which protects the plants against freezing. It is interesting from the viewpoint of plant ecology that only the above 4 species contain high amounts of sugars and maltol in their leaves because maltol is biosynthesized from sugars.     

Impulse response analysis in vector autoregressions with unknown lag order

We show that the effects of overfitting and underfitting a vector autoregressive (VAR) model are strongly asymmetric for VAR summary statistics involving higher‐order dynamics (such as impulse response functions, variance decompositions, or long‐run forecasts) . Underfit models often underestimate the true dynamics of the population process and may result in spuriously tight confidence intervals. These insights are important for applied work, regardless of how the lag order is determined. In addition, they provide a new perspective on the trade‐offs between alternative lag order selection criteria. We provide evidence that, contrary to conventional wisdom, for many statistics of interest to VAR users the point and interval estimates based on the AIC compare favourably to those based on the more parsimonious Schwarz Information Criterion and Hannan – Quinn Criterion. Copyright © 2001 John Wiley & Sons, Ltd.     

Dynamic relationship analysis of us gasoline and crude oil prices

This paper studies the dynamic relationships between US gasoline prices, crude oil prices, and the stock of gasoline. Using monthly data between January 1973 and December 1987, we find that the US gasoline price is mainly influenced by the price of crude oil. The stock of gasoline has little or no influence on the price of gasoline during the period before the second energy crisis, and seems to have some influence during the period after. We also find that the dynamic relationship between the prices of gasoline and crude oil changes over time, shifting from a longer lag response to a shorter lag response. Box-Jenkins ARIMA and transfer function models are employed in this study. These models are estimated using estimation procedure with and without outlier adjustment. For model estimation with outlier adjustment, an iterative procedure for the joint estimation of model parameters and outlier effects is employed. The forecasting performance of these models is carefully examined. For the purpose of illustration, we also analyze these time series using classical white-noise regression models. The results show the importance of using appropriate time-series methods in modeling and forecasting when the data are serially correlated. This paper also demonstrates the problems of time-series modeling when outliers are present.     

Zur Kenntnis der Blattlipide vonAcer platanoides L. während der herbstlichen Vergilbung

Summary The lipids of green and yellow leaves ofAcer platanoides L. have been investigated. Yellow leaves were found to contain phytyl linolenate, a further example of the formation of esters containing terpenoid alcohols and unsaturated fatty acids in yellow autumn leaves. The determination af squalene in leaves of the same tree showed an increase of squalene content during the whole season and the autumn colouration. Regarding the leaf lipids we conclude autumn colouration to be characterized by 3 facts: (1) Lipid degradation, (2) formation of esters and (3) accumulation of lipid intermediates.     

Relationship between light diffraction intensity and tension development in frog skeletal muscle

Summary Laser diffraction intensity decrease in active muscles precedes tension development at sarcomere lenghts below 2.76 m, but not at greater lenghts. This suggests that the time lag is caused by random sarcomere shortenings inside each myofibril.     

Carcinogenicity examination of betel nuts and piper betel leaves.

A dry powder of betel nuts, piper betel leaves and lime was administered to rats. Epidermal thickening was frequently observed in the upper digestive tracts of rats in groups fed the betel nut diet mixed with lime and the betel leaves diet, and a forestomach papilloma was seen in 1 rat given betel leaves diet. These epidermal changes were scarcely seen in rats given either betel nut or normal diet alone.