Banded and tapered estimates for autocovariance matrices and the linear process bootstrap

We address the problem of estimating the autocovariance matrix of a stationary process. Under short range dependence assumptions, convergence rates are established for a gradually tapered version of the sample autocovariance matrix and for its inverse. The proposed estimator is formed by leaving the main diagonals of the sample autocovariance matrix intact while gradually down‐weighting off‐diagonal entries towards zero. In addition, we show the same convergence rates hold for a positive definite version of the estimator, and we introduce a new approach for selecting the banding parameter. The new matrix estimator is shown to perform well theoretically and in simulation studies. As an application, we introduce a new resampling scheme for stationary processes termed the linear process bootstrap (LPB). The LPB is shown to be asymptotically valid for the sample mean and related statistics. The effectiveness of the proposed methods are demonstrated in a simulation study.     

Direct evidence of atmospheric secondary organic aerosol formation in forest atmosphere through heteromolecular nucleation

Atmospheric aerosols play a central role in climate and atmospheric chemistry. Organic matter frequently composes aerosol major fraction over continental areas. Reactions of natural volatile organic compounds, with atmospheric oxidants, are a key formation pathway of fine particles. The gas and particle atmospheric concentration of organic compounds directly emitted from conifer leaf epicuticular wax and of those formed through the photooxidation of alpha- and beta-pinene were simultaneously collected and measured in a conifer forest by using elaborated sampling and GC/ MS techniques. The saturation concentrations of acidic and carbonyl photooxidation products were estimated, by taking into consideration primary gas- and particle-phase organic species. Primary organic aerosol components represented an important fraction of the atmospheric gas-phase organic content Consequently, saturation concentrations of photooxidation products have been lowered facilitating new particle formation between molecules of photooxidation products and semi-volatile organic compounds. From the measured concentrations of the above-mentioned compounds, saturation concentrations (Csat,i) of alpha- and beta-pinene photooxidation products were calculated for nonideal conditions using a previously developed absorptive model. The results of these calculations indicated that primarily emitted organic species and ambient temperature play a crucial role in secondary organic aerosol formation.     

Physiological relevance of food grade microcapsules: Impact of milk protein based microcapsules on inflammation in mouse models for inflammatory bowel diseases

In order to increase beneficial effects of bioactive compounds in functional food and dietary supplements, enormous efforts are put in the technological development of microcapsules. Although these products are often tailor‐made for disease susceptible consumer, the physiological impact of microcapsule uptake on the respective target consumer has never been addressed. The present study aimed to assess the relevance of this aspect by analyzing the impact of milk protein based microcapsules on experimental inflammatory bowel disease. Long‐term feeding of sodium caseinate or rennet gel microcapsules resulted in significant alterations in the intestinal microbiota of healthy mice. In TNFΔARE/wt mice, a model for chronic ileal inflammation, rennet gel microcapsules resulted in further increased splenomegaly, whereas ileal inflammation was unchanged. In IL10^?/? mice, a model for chronic colitis, both types of microcapsules induced a local increase of the intestinal inflammation. The present study is the first to demonstrate that, independent of their cargo, microcapsules have the potential to affect the intestinal microbiota and to exert unprecedented detrimental effects on disease‐susceptible individuals. In conclusion, the impact of microcapsule uptake on the respective target consumer groups should be thoroughly investigated in advance to their commercial use in functional food or dietary supplements.     

A parametric investigation on seat/occupant contact forces and their relationship with initially perceived discomfort using a configurable seat

The present work investigates the contact forces between sitters and seat as well as their correlations with perceived discomfort. Twelve different economy class aeroplane seat configurations were simulated using a multi-adjustable experimental seat by varying seat pan and backrest angles, as well as seat pan compressed surface. Eighteen males and 18 females, selected by their body mass index and stature, tested these configurations for two sitting postures. Perceived discomfort was significantly affected by seat parameters and posture and correlated both with normal force distribution on the seat-pan surface and with normal forces at the lumbar and head supports. Lower discomfort ratings were obtained for more evenly distributed normal forces on the seat pan. Shear force at the seat pan surface was at its lowest when sitters were allowed to self-select their seat-pan angle, supporting that a shear force should be reduced but not zeroed to improve seating comfort.

Practitioner Summary: The effects of seat-pan and backrest angle, anthropometric dimensions and sitting posture on contact forces and perceived discomfort were investigated using a multi-adjustable experimental seat. In addition to preferred seat profile parameters, the present work provides quantitative guidelines on contact force requirement for improving seating comfort.     

Phase noise analysis in CMOS differential Armstrong oscillator topology

This paper reports a phase noise analysis in a differential Armstrong oscillator circuit topology in CMOS technology. The analytical expressions of phase noise due to flicker and thermal noise sources are derived and validated by the results obtained through SpectreRF simulations for oscillation frequencies of 1, 10, and 100 GHz. The analysis captures well the phase noise of the oscillator topology and shows the impact of flicker noise contribution as the major effect leading to phase noise degradation in nano‐scale CMOS LC oscillators. Copyright © 2016 John Wiley & Sons, Ltd.     

A GENERALIZED BLOCK BOOTSTRAP FOR SEASONAL TIME SERIES

When time‐series data contain a periodic/seasonal component, the usual block bootstrap procedures are not directly applicable. We propose a modification of the block bootstrap – the generalized seasonal block bootstrap (GSBB) – and show its asymptotic consistency without undue restrictions on the relative size of the period and block size. Notably, it is exactly such restrictions that limit the applicability of other proposals of block bootstrap methods for time series with periodicities. The finite‐sample performance of the GSBB is also illustrated by means of a small simulation experiment.     

Using symmetries in the eigenvalue method for polynomial systems

One way of solving polynomial systems of equations is by computing a Gröbner basis, setting up an eigenvalue problem and then computing the eigenvalues numerically. This so-called eigenvalue method is an excellent bridge between symbolic and numeric computation, enabling the solution of larger systems than with purely symbolic methods. We investigate the case that the system of polynomial equations has symmetries. For systems with symmetry, some matrices in the eigenvalue method turn out to have special structure. The exploitation of this special structure is the aim of this paper. For theoretical development we make use of SAGBI bases of invariant rings. Examples from applications illustrate our new approach.     

Effect on production traits of bovine somatotropin for up to three consecutive lactations.

Thirteen (control) cows were injected daily with saline and 22 with bST (12 at 10.3 mg/d and 10 at 20.6 mg/d) through wk 5 to 42 of lactation. Nine of the treated cows had received bST in the previous lactation, and 7 cows received bST in the previous two lactations. All control cows and 6 treated cows had not previously received bST. Treatment with bST caused substantial increases in milk production, feed intake, and efficiency of feed conversion in the current lactation, which is consistent with previous trials. Increases in feed intake were established fully within 9 wk of starting bST administration, somewhat earlier than usually reported. Treatment with bST in one or two previous lactations caused a statistically significant 14% reduction in production and 8% reduction in efficiency of feed conversion during the first 9 wk of bST treatment in the current lactation; reductions observed later in lactation were not statistically significant. Differences for other traits were not statistically significant. In combination with earlier trials, these results suggest that, although bST has beneficial effects on production and efficiency traits, these benefits may be considerably lower in the second and subsequent lactations of bST use. However, carry-over effects on cows not receiving bST in the current lactation were not explored in this trial.