Finite sample properties of ARMA order selection

The cost of order selection is defined as the loss in model quality due to selection. It is the difference between the quality of the best of all available candidate models that have been estimated from a finite sample of N observations and the quality of the model that is actually selected. The order selection criterion itself has an influence on the cost because of the penalty factor for each additionally selected parameter. Also, the number of competitive candidate models for the selection is important. The number of candidates is, of itself, small for the nested and hierarchical autoregressive/moving average (ARMA) models. However, intentionally reducing the number of selection candidates can be beneficial in combined ARMA(p,q) models, where two separate model orders are involved: the AR order p and the MA order q. The selection cost can be diminished by creating a nested sequence of ARMA(r,r-1) models. Moreover, not evaluating every combination (p,q) of the orders considerably reduces the required computation time. The disadvantage may be that the true ARMA(p,q) model is no longer among the nested candidate models. However, in finite samples, this disadvantage is largely compensated for by the reduction in the cost of order selection by considering fewer candidates. Thus, the quality of the selected model remains acceptable with only hierarchically nested ARMA(r,r-1) models as candidates.     

Immunoelectron localization of mitochondrial F1 factor in cryosections of heart muscle cells

Immunocytochemistry was used to investigate the localization of F1 ATPase in mitochondria of cryosections of adult mouse heart muscle cells. The initial aldehyde fixation was the only denaturation step for antigens. The fine structure was preserved with contrast enhancement as the sections were maintained hydrated, with the advantage that the entire procedure is completed in one working day. The reaction was highly specific, and entire mitochondria were labeled with the Protein A-gold complex. A new analytical technique, electron spectroscopic imaging (ESI), contributed to a better visualization of the localization of the F1 factor.     

It takes two to mimic: Behavioral consequences of self-construals.

The present studies demonstrated the moderation of self-construal orientation on mimicry. Recent research has indicated that an interdependent self-construal is associated with assimilation of the other to the self whereas an independent self-construal is associated with minimizing the influence of others on the self (H. R. Markus & S. Kitayama, 1991; D. Stapel & W. Koomen, 2001). Therefore, the authors hypothesized that an interdependent self-construal would be associated with more mimicry than an independent self-construal. When self-construal orientations were experimentally primed. as in Studies 1 and 2, independent self-construals produced less nonconscious mimicry than interdependent self-construals. When self-construals were examined as cultural differences with either a chronically dominant independent (Americans) or interdependent (Japanese) construal of the self, these results were replicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Critical Shear Stress of Bimodal Sediment in Sand-Gravel Rivers

A new model for the critical shear stress and the transport of graded sediment is presented. The model is based on the size distribution of the bed surface and can be used to compute sediment transport rates in numerical simulations with an active layer model. This model makes a distinction between unimodal and bimodal sediments. It is assumed that all size fractions of unimodal sediments have the same critical shear stress while there is selective transport for the gravel fractions of bimodal sediments. A recently published laboratory transport data set is used to calibrate our model.     

Theory of Seepage into an Auger Hole in a Confined Aquifer Overlying a Gravel Substratum

An analytical solution is presented to the problem of steady groundwater flow seeping into a pumped cylindrical hole partially penetrating a homogeneous and anisotropic confined aquifer overlying a gravel substratum. Solutions are obtained for two general cases of the problem: (1) when the level of the pumped hole is below the confining layer; (2) when it is above it. The validity of the proposed theory is tested by comparing analytical predictions obtained for a few flow situations with corresponding results obtained by numerical means. The theory presented here can be utilized to convert the rate of rise of water in a pumped auger hole into directional conductivities of soil, in areas where water is found to be in a confined state overlying a gravel substratum. The study shows that the conductivity values calculated by neglecting the confining pressure of an artesian aquifer with a gravel base [i.e., by applying the existing (Boast and Kirkham in 1971), auger hole seepage theory for a phreatic aquifer with a gravel base to confined situations] may result in serious error; hence, the artesian head of an aquifer must be accounted for while computing the conductivity values. Further, it is observed that the area contributing flow to a pumped auger hole/well with a gravel base is mostly restricted to a short radial distance from the center of the hole, particularly for situations where the gravel substratum is located close to the bottom of the hole. This is in contrast to auger hole flow situations overlying an impervious substratum, where the domain contributing flow is mostly spread out to a considerable distance from the center of the hole.     

Development of New Sulphonyl Resin from Modification of Commercial Resin

Summary This article deals with the handy synthesis of sulfonyl resins, which were produced by the treatment of a commercial sulfonic resin (Lewatit VPOC1812^® based at divinylbenzene (DVB) and styrene (STY). The preliminary chemical modification was based on the reaction of the Lewatit VPOC1812^® with thionyl chloride aiming to produce the sulfonyl chloride groups. The best conditions to obtain the sulfonyl chloride groups were: SOCl₂/SO₃H (molar ratio) =13 at 79 °C during 72 h. The resin chlorinated was afterward treated with urea, thiourea or guanidine. The functionalized resins with urea, thiourea or guanidine were produced with 56, 68 and 93% yield, respectively. The commercial and modified resins were characterized by apparent density, swelling degree, elemental analysis (CHNS), FTIR, optical microscopy (OM) and scanning electron microscopy (SEM).     

Missed opportunities for immunisation at hospitals in the western Cape--a reappraisal

Immunisation practices were examined at 6 hospitals in the western Cape during the latter half of 1992 to determine whether these practices had improved subsequent to the February 1991 resolution of the Health Matters Committee (HMC) on immunisation in hospitals, and since a similar study was undertaken in 1990. Exit interviews were conducted with the escorts of all children aged 3-59 months who attended the study hospitals on the days designated for the study. In the second study, 88 of the 311 children studied (28.3%) were in need of immunisation on arrival, but only 12 of the 88 (13.6%) were immunised during the hospital visit. There was no evidence of an increase in requests to see children's Road-to-Health cards (37.1% compared with 35.2% previously). The incidence of missed opportunities for measles immunisation in children aged 6-59 months remained unacceptably high (51.4% compared with 63.7% previously, when a strict definition was used; and 15.7% compared with 18.1% previously, when a lenient definition was used). Health authorities at all levels need to take urgent action to address the problem of missed opportunities for immunisation at hospitals.