Change point testing for the drift parameters of a periodic mean reversion process

In this paper we investigate the problem of detecting a change in the drift parameters of a generalized Ornstein–Uhlenbeck process which is defined as the solution of $$\begin{aligned} dX_t=(L(t)-\alpha X_t) dt + \sigma dB_t \end{aligned}$$ and which is observed in continuous time. We derive an explicit representation of the generalized likelihood ratio test statistic assuming that the mean reversion function $L(t)$ is a finite linear combination of known basis functions. In the case of a periodic mean reversion function, we determine the asymptotic distribution of the test statistic under the null hypothesis.     

Towards the Development of a Selective Ruthenium‐Catalyzed Hydroformylation of Olefins

The ruthenium‐catalyzed hydroformylation of 1‐ and 2‐octene to give preferentially the corresponding linear aldehyde is reported. The catalyst system comprising of Ru₃(CO)₁₂ and an imidazole‐substituted monophosphine ligand allows for high chemo‐ and regioselectivity. The hydroformylation proceeds with unprecedented rates for a ruthenium‐based catalyst.     

ASSIMILATION,DISTRIBUTION, AND METABOLISM OF (75Se)-SELENITE,SELENATE, AND SELENOAMINO ACIDS BY ESCHERICHIA COLI

Abstract

Assimilation of selenium (Se) by Escherichia coli as (⁷⁵Se)-selenite, selenate, selenomethionine, selenocystine and Se?CH₃-selenocystine revealed that (a) selenoamino acids from a culture media are more completely assimilated than selenite or selenate and (b) that the amount of selenite is assimilated three to four times selenate. Most (>95%) of the Se assimilated by E. coli could not be solubilized by sonication and ethanol extraction but much (28% to 70%) of the Se, except Se from selenomethionine, was removed by alkaline dialysis. Se from selenocystine and from Se?CH₃-selenocystine dialyzed from intact cells, whereas Se from selenite and selenate did not. Dialyzable Se is that Se probably present in selenotrisulfide (R?S?Se?S?R) bonds or bound nonspecifically. Analysis of the soluble Se metabolites from selenite, selenate, selenomethionine and selenocystine showed that E. coli produces at least one major metabolic product common to all substrates which upon chromatography appeared to be selenocysteic acid. In monogastric animals selenite and selenate Se does not enter the primary protein structure as amino acids yet metabolites of selenite, selenate and selenocystine produced by E. coli could enter the primary protein structure of animals in minute amounts.     

NSAIDs interactions with membranes: a biophysical approach

This work focuses on the interaction of four representative NSAIDs (nimesulide, indomethacin, meloxicam, and piroxicam) with different membrane models (liposomes, monolayers, and supported lipid bilayers), at different pH values, that mimic the pH conditions of normal (pH 7.4) and inflamed cells (pH 5.0). All models are composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) which is a representative phospholipid of most cellular membranes. Several biophysical techniques were employed: Fluorescence steady-state anisotropy to study the effects of NSAIDs in membrane microviscosity and thus to assess the main phase transition of DPPC, surface pressure-area isotherms to evaluate the adsorption and penetration of NSAIDs into the membrane, IRRAS to acquire structural information of DPPC monolayers upon interaction with the drugs, and AFM to study the changes in surface topography of the lipid bilayers caused by the interaction with NSAIDs. The NSAIDs show pronounced interactions with the lipid membranes at both physiological and inflammatory conditions. Liposomes, monolayers, and supported lipid bilayers experiments allow the conclusion that the pH of the medium is an essential parameter when evaluating drug-membrane interactions, because it conditions the structure of the membrane and the ionization state of NSAIDs, thereby influencing the interactions between these drugs and the lipid membranes. The applied models and techniques provided detailed information about different aspects of the drug-membrane interaction offering valuable information to understand the effect of these drugs on their target membrane-associated enzymes and their side effects at the gastrointestinal level.     

A reagent-free method based on a photo-induced fluorimetry in a sequential injection system

According to the current demands of environmentally friendly analytical chemistry and with a view to achieving lower reagent consumption with improved analytical performance, an automatic methodology composed of a photoreactor and fluorimetric detection (λ_exc = 287 nm, λ_em = 378 nm) was developed. To this end, a sequential injection analysis (SIA) system was developed for indomethacin determination using ultra-violet (UV) light which promotes an increase in the fluorescence of indomethacin. This increase in sensitivity makes it possible to apply this methodology to a dissolution test and to determine indomethacin in pharmaceutical formulations.The calibration graph for indomethacin was linear between 4.10 × 10⁻⁶ and 9.00 × 10⁻⁵ mol L⁻¹and the detection limit was 1.23 × 10⁻⁶ mol L⁻¹. The method was proven to be reproducible with a R.S.D. < 5% and sampling rate of approximately 20 per hour. The potential effect of several compounds commonly used as excipients on analytical signals was studied and no interfering effect was observed. Statistical evaluation at the 95% confidence level showed good agreement between the results obtained for the pharmaceutical samples with both the SIA system and comparison batch procedures.     

<Emphasis Type="Italic">Trans</Emphasis> to <Emphasis Type="Italic">cis</Emphasis> isomerization of an azobenzene derivative on a Cu(100) surface

We biosynthesized iron oxide nanoparticles with four different pH in the solution to see its influence in the oxides obtained. This method allowed for generating aggregates of 1–10 nm, and under optimal conditions (pH=10) we could control the size in the range of 1–4 nm. With the purpose to analyze the biosynthesized iron oxide clusters we employed electron transmission microscopy techniques. Because the biosynthetic method with alfalfa has been used, the presence of the biomass, which is dense and within which are contained the nanoparticles, makes their observation difficult. Using the HAADF (Z contrast) technique it is possible to locate the nanoparticles, which are then characterized using EDS and HRTEM. PACS 61.46.-w; 68.37.Lp; 81.07.-b; 81.16.Be     

Recovery of signal loss due to an in-plane susceptibility gradient in the gradient echo EPI through acquisition of extended phase-encoding lines

In gradient echo imaging the in-plane susceptibility gradient causes an echo shift which results in signal loss. The loss of signal becomes more severe in gradient echo EPI, due to the low amplitude of the gradient which is applied in the phase-encoding direction during a long echo train. As the readout gradient amplitude is set to be very high in gradient echo EPI, the echo shift in the readout direction is negligible compared to that in the phase-encoding direction. Traditionally, a z-shimming technique has been applied to the phase-encoding direction of gradient echo EPI to restore the lost signal. This technique, however, requires a significant increase of scan time, as is also the case with the through-plane z-shimming technique. A new approach that allows one to restore the lost signal is to acquire additional phase-encoding lines beyond the regular phase-encoding range. The extension of the phase-encoding lines prior to the regular phase-encoding range exploits the delay time for optimum echo time of the BOLD sensitivity. Therefore, scan time is increased only for the extended phase-encoding lines posterior to the regular phase-encoding range. This technique has been confirmed experimentally by imaging human subject's heads at 3T.     

Light Front Hamiltonian Approach

The semiphenomenological way to describe nonperturbative quantum chromodynamics using light front gluon zero mode is proposed and applied to quark-antiquark bound state.     

Controlling the Assembly of Cellulose-Based Oligosaccharides through Sequence Modifications

Peptides and nucleic acids with programmable sequences are widely explored for the production of tunable, self-assembling functional materials. Herein we demonstrate that the primary sequence of oligosaccharides can be designed to access materials with tunable shapes and properties. Synthetic cellulose-based oligomers were assembled into 2D or 3D rod-like crystallites. Sequence modifications within the oligosaccharide core influenced the molecular packing and led to the formation of square-like assemblies based on the rare cellulose IV_II allomorph. In contrast, modifications at the termini generated elongated aggregates with tunable surfaces, resulting in self-healing supramolecular hydrogels.     

Further Improvements in High Gain Observer Design for Systems with Structured Nonlinearities

Due to their simple implementation based on a constant gain matrix, high gain observers are very common in practical applications. We consider systems whose dynamics can be decomposed into a linear and a nonlinear part, where the nonlinear part meets some Lipschitz condition. In many cases there exists a finite bound on the maximum feasible Lipschitz constant for which the error dynamics can be stabilized. Necessary and in some sense sufficient conditions for this maximum Lipschitz constant are given in [1]. These results has been improved in [2,3] by taking the structure of the linear part into account. Having a system with one single nonlinearity, the results given in [2,3] are strict. If multiple nonlinearities occur, even this approach tends to be to conservative. In this case, one could additionally take the internal structure of the nonlinearities into account which leads to a larger set of systems for which convergence of the observer error can be guaranteed. Our new approach is based on an approximation of the structured singular value [4] which yields existence conditions in terms of linear matrix inequalities (LMIs). These LMIs may as well be used for the numerical computation of the observer gain. We demonstrate the advantage of our method on an example. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)