Computing the variance of the forecast error for the holt-winters seasonal models

This paper presents expressions for the variance of the forecast error for arbitrary lead times for both the additive and multiplicative Holt-Winters seasonal forecasting models. It is shown that even when the smoothing constants are chosen to have values between zero and one, when the period is greater than four, the variance may not be finite for some values of the smoothing constants. In addition, the regions where the variance becomes infinite are almost the same for both models. These results are of importance for practitioners, who may choose values for the smoothing constants arbitrarily, or by searching on the unit cube for values which minimize the sum of the squared errors when fitting the model to a data set. It is also shown that the variance of the forecast error for the multiplicative model is nonstationary and periodic.     

A procedure for the rapid freezing of whole embryos

Summary A procedure for the rapid freezing of whole chick embryos for histochemical treatment is described. The problems of deformation during preparation for quenching and orientation for sectioning have been largely overcome by placing embryos inside lengths of chicken trachea. The subsequenct disorientation of tissues that follows cracking and shattering due to the rapid freezing of whole embryos is avoided. The method permitted a more precise identification of the position and time of appearance of formaldehyde-induced fluorescence and myosin antibody immunofluorescence in serially sectioned embryos.We gratefully thank Dr Ute Gröschel-Stewart for preparing sections for immunofluorescence.     

Regression tree model for prediction of demand with heterogeneity and censorship

In this research we analyze a new approach for prediction of demand. In the studied market of performing arts the observed demand is limited by capacity of the house. Then one needs to account for demand censorship to obtain unbiased estimates of demand function parameters. The presence of consumer segments with different purposes of going to the theater and willingness-to-pay for performance and ticket characteristics causes a heterogeneity in theater demand. We propose an estimator for prediction of demand that accounts for both demand censorship and preferences heterogeneity. The estimator is based on the idea of classification and regression trees and bagging prediction aggregation extended for prediction of censored data. Our algorithm predicts and combines predictions for both discrete and continuous parts of censored data. We show that our estimator performs better in terms of prediction accuracy compared with estimators which account either for censorship or heterogeneity only. The proposed approach is helpful for finding product segments and optimal price setting.     

混凝土减水剂的发展与绿色化

混凝土实现绿色化生产,对节约资源、能源和保护环境具有特别重大的意义。为适应绿色高性能混凝土发展的需要,混凝土外加剂的绿色化也成为必然。本文概述了促进我国绿色高性能混凝土发展的绿色减水剂的发展与最新研究成果,并讨论了应进一步研究的问题。分析认为,沿用多年的萘系高效减水剂并不符合减水剂绿色化的要求,寻求其替代品是当今减水剂工作者的重要任务。从资源、环境和安全等绿色化发展的角度,改性木素磺酸盐高效减水剂最具生命力;然而,消除改性木素磺酸盐过度缓凝性使之适应于高强混凝土、以木素替代全部或部分苯酚生产氨基磺酸系减水剂、控制脂肪族高效减水剂中残余甲醛及其回收利用、利用工业副产品替代昂贵的石油基原料对现有的聚羧酸系高效减水剂的改性或开发新型高性能减水剂是实施高效减水剂绿色化所面临的长期而艰巨的挑战。     

Commercially available equipment suitable for post-implantation embryo culture

Summary There is a need for commercially manufactured equipment for use in post-implantation embryo culture techniques. A simple, inexpensive modification to an existing device is described that enables such an apparatus to be used for the roller-tube technique.Acknowledgments. I would like to thank Drs R.D. Barnes and F.E. Hytten for much encouragement and provision of facilities. Also, the Obstetric Research Fund, University College Hospital Medical School for financial support.     

Amino acid absorption in jejunum and ileum in vivo — a kinetic comparison of function on surface area and regional bases

Summary Maximum absorptive capacities (V_max) for the jejunum and ileum corrected for the presence of an unstirred layer of water have been calculated for glycine, valine and methioninein vivo in fowls per unit surface area and per region. V_max per cm² showed that ileal enterocytes had a greater absorbing capacity than jejunal for glycine and valine but not for methionine. V_max for glycine and valine, calculated for the whole jejunum and ileum, however, were not different but for methionine the jejunal value was 1.9 times greater than the ileal.MAM is supported by an A.R.C. research grant (No. A50/37).     

Forecasting euro area variables with German pre‐EMU data

It is investigated whether euro area variables can be forecast better based on synthetic time series for the pre‐euro period or by using just data from Germany for the pre‐euro period. Our forecast comparison is based on quarterly data for the period 1970Q1–2003Q4 for 10 macroeconomic variables. The years 2000–2003 are used as forecasting period. A range of different univariate forecasting methods is applied. Some of them are based on linear autoregressive models and we also use some nonlinear or time‐varying coefficient models. It turns out that most variables which have a similar level for Germany and the euro area such as prices can be better predicted based on German data, while aggregated European data are preferable for forecasting variables which need considerable adjustments in their levels when joining German and European Monetary Union (EMU) data. These results suggest that for variables which have a similar level for Germany and the euro area it may be reasonable to consider the German pre‐EMU data for studying economic problems in the euro area. Copyright © 2008 John Wiley & Sons, Ltd.     

区域水库群大坝安全评价体系的构建

结合江西省水库群大坝安全评价工作，介绍了区域水库群大坝安全评价体系的构建过程，包括大坝安全评价技术标准的制定、单座水库大坝工程险度评价和风险评估、区域性水库群除险加固全面规划、水库群大坝安全风险排序、大坝病险原因分析及对策研究、除险加固方案的实施效果评价及区域性水库群除险加固动态管理信息系统的建立等内容。该体系在江西省水库群大坝安全评价中的应用效果良好，可为决策者提供科学依据。     

Trace metals especially Fe+++ as dietary factors for leafhoppers

Summary Some trace metals are required for development and reproduction, and therefore for continuous rearing of the aster leafhopper,Macrosteles fascifrons, on a holidic diet. Requirement for Fe⁺⁺⁺ becomes apparent immediately in the 1st generation; for Cu⁺⁺ and Zn⁺⁺, in the 3rd. The leafhopper has grown normally and continuously for 3 generations in the absence of manganese.We acknowledge the Minnesota Agricultural Experiment Station and the National Institute of Allergy and Infectious Diseases, USA, for financial supports.     

Forecasts for leverage heterogeneous autoregressive models with jumps and other covariates

For leverage heterogeneous autoregressive (LHAR) models with jumps and other covariates, called LHARX models, multistep forecasts are derived. Some optimal properties of forecasts in terms of conditional volatilities are discussed, which tells us to model conditional volatility for return but not for the LHARX regression error and other covariates. Forecast standard errors are constructed for which we need to model conditional volatilities both for return and for LHAR regression error and other blue covariates. The proposed methods are well illustrated by forecast analysis for the realized volatilities of the US stock price indexes: the S&P 500, the NASDAQ, the DJIA, and the RUSSELL indexes.     

A method for chromosome preparations from large fish specimens using in vitro short-term treatment with colchicine

This paper describes a new technique for preparing mitotic fish chromosomes using short-term in vitro treatment with colchicine. The results show that a large number of good quality metaphases (many suitable for chromosome banding) can be obtained by this technique, which requires an average of 1 h and 30 min for all steps. The procedure considerably reduces the time normally required for chromosome preparations in fish.This work was supported by grants FUNCUNESP, FAPESP and CNPq.The authors are grateful to Mr Renato Devidé for technical assistance.     

Chemical studies on the silver staining of nucleoli

Summary The uptake of Ag-ions by isolated nucleoli of rat liver cells was studied. Nucleolar proteins separated by electrophoresis were examined for selective silver-staining. A mechanism for a preferential Ag-staining of the nucleoli is discussed.We thank Mrs L. Schwinn for her valuable technical assistance, and Mrs K. Jain for presenting us DNA. We would like to thank the Department of Biology V for making possible the measurements with the atomic absorption spectrophotometer. This work was supported by the Deutsche Forschungsgemeinschaft.     

Preferential hydrophobic interactions are responsible for a preference of D-amino acids in the aminoacylation of 5'-AMP with hydrophobic amino acids.

We have studied the chemistry of aminoacyl AMP to model reactions at the 3' terminus of aminoacyl tRNA for the purpose of understanding the origin of protein synthesis. The present studies relate to the D, L preference in the esterification of 5'-AMP. All N-acetyl amino acids we studied showed faster reaction of the D-isomer, with a generally decreasing preference for D-isomer as the hydrophobicity of the amino acid decreased. The beta-branched amino acids, Ile and Val, showed an extreme preference for D-isomer. Ac-Leu, the gamma-branched amino acid, showed a slightly low D/L ratio relative to its hydrophobicity. The molecular basis for these preferences for D-isomer is understandable in the light of our previous studies and seems to be due to preferential hydrophobic interaction of the D-isomer with adenine. The preference for hydrophobic D-amino acids can be decreased by addition of an organic solvent to the reaction medium. Conversely, peptidylation with Ac-PhePhe shows a preference for the LL isomer over the DD isomer.     

Antifertility activity of trimethylphosphate in male rats

Summary The toxic effect of trimethylphosphate on rat testes was investigated after oral dosing with 250 mg/kg for either 5 days/week for 30 days or 6 days/week for 60 days. After these prolonged treatments azoospermia resulted.Acknowledgments. The authors wish to thank Ms M. Michelles, Ms A. Murray and Ms R. Peake for their technical support.     

Effect of nerve stimulation on rat skeletal muscle. A study of plasma membrane

Summary The gastrocnemius muscle of the rat showed no morphological, histometric or plasma membrane changes, after sciatic nerve stimulation with a 5 mA current for 30 to 60 min, 10 mA for 30 min and 15 mA for 5 min. However, 10 mA for 60 and 200 min gave rise to mitochondrial and plasma membrane abnormalities. These changes were absent after a rest period. The results indicated the sciatic nerve stimulation at 10 mA for 60 and 200 min caused reversible changes in the rat skeletal muscle mitochondria and plasma membrane.     

Parthenogenetic reptiles: New subjects for laboratory research

Summary Problems preventing establishment of laboratory colonies of parthenogenetic lizards have been solved. Now, productive colonies of these lizards, which have remarkably little genetic variation, can be readily established and used not only for research on parthenogenesis but also for many kinds of experiments for which reptile systems are desirable. Research colonies can provide valuable specimens while reducing the exploitation of natural populations.We thank José P. O. Rosado and George W. Foley for technical assistance and Richard G. Zweifel for specimens, ideas and support.     

Holding plastic-embedded specimens for sectioning in a rotary microtome.

Three methods are evaluated for holding capsules of plastic-embedded tissue for rotary microtomy. Use of a V-block is rapid but deforms the capsule. Gluing the capsule to a supporting block is useful for reorientation of the capsule but otherwise time consuming. adapter is easy to use, does not deform the tissue, and is the preferred method for routine microtomy.     

MC环境下产品族加工时间确定方法研究

为更好地支持面向大规模定制的企业工时定额的制定，以产品族加工时间的快速确定为研究目标，提出了一套全新的面向产品族的加工时间确定方法。在产品族结构分析的基础上，把产品族的共享结构和变型结构分别作为静态工时模块和动态工时模块的构造基础。研究了柔性参数水平对产品族加工时间的影响机理，构建了产品族各工时模块加工时间模型，以柔性参数水平的匹配搜索算法实现定制产品加工时间的估算。通过实例验证了方法的有效性。     

Intravenous injections of cholecystokinin and caerulein suppress food intake in domestic fowls

Summary As with various mammals, cholecystokinin (CCK) and caerulein have short-term, dose-related, inhibitory effects on feeding when injected i.v. in domestic fowls. It is estimated that in meals lasting more than about 6 min there could be time for ingested food to reach the duodenum and for the release of CCK to act as a satiety signal.Acknowledgments. We thank I. Paul, D. Shaw and M. Thomson for technical assistance, C. McCorquodale and R. Morley Jones for designing the experiments and doing the statistical analyses, and S.J. Lucania of the Squibb Institute for Medical Research for kindly providing the synthetic CCK.     

A comparison of pyridoxal 5'-phosphate dependent decarboxylase and transaminase enzymes at a molecular level.

Pyridoxal 5'-phosphate is a coenzyme for a number of enzymes which catalyse reactions at C alpha of amino acid substrates including transaminases, decarboxylases and serine hydroxymethyltransferase. Using the X-ray coordinates for a transaminase, aspartate aminotransferase, and the results of stereochemical and mechanistic studies for decarboxylases and serine hydroxymethyltransferase, an active-site structure for the decarboxylase group is constructed. The structure of the active-site is further refined through active-site pyridoxyllysine peptide sequence comparison and a 3-D catalytic mechanism for the L-alpha-amino acid decarboxylases is proposed. The chemistry of serine hydroxymethyltransferase is re-examined in the light of the proposed decarboxylase mechanism.