Analysis and improvement of the vector quantization in SELP (Stochastically Excited Linear Prediction)

The Stochastically Excited Linear Prediction (SELP) algorithm is described as a speech coding method employing a two-stage vector quantization. The first stage uses an adaptive codebook which efficiently encodes the periodicity of voiced speech, and the second stage uses a stochastic codebook to encode the remainder of the excitation signal. The adaptive codebook performs well when the pitch period of the speech signal is larger than the frame size. An extension is introduced, which increases its performance for the case that the frame size is longer than the pitch period. The performance of the stochastic stage, which improves with frame length, is shown to be best in those sections of the speech signal where a high level of short-term correlations is present. It can be concluded that the SELP algorithm performs best during voiced speech where the pitch period is longer than the frame length

GpABC: a Julia package for approximate Bayesian computation with Gaussian process emulation

Motivation Approximate Bayesian computation (ABC) is an important framework within which to infer the structure and parameters of a systems biology model. It is especially suitable for biological systems with stochastic and nonlinear dynamics, for which the likelihood functions are intractable. However, the associated computational cost often limits ABC to models that are relatively quick to simulate in practice. Results We here present a Julia package, GpABC, that implements parameter inference and model selection for deterministic or stochastic models using i) standard rejection ABC or ABC-SMC, or ii) ABC with Gaussian process emulation. The latter significantly reduces the computational cost. Availability and Implementation https://github.com/tanhevg/GpABC.jl Supplementary information Supplementary data are available at Bioinformatics online

Ecologische kenmerken van weidevogeljongen en de invloed van beheer op overleving. Kennisoverzicht en effectiviteit van maatregelen

Rapport over de effectiviteit van beheersmaatregelen voor overleving van primaire weidevogelkuikens in graslanden, op basis van wetenschappelijke en niet-wetenschappelijke literatuur. Per sprake komen: Ecoprofielen weidevogeljongen van: Kievit (Vanellus vanellus); Grutto (Limosa limosa); Tureluur (Tringa totanus); Scholekster (Haematopus ostralegus); Watersnip (Gallinago gallinago); Kemphaan (Philomachus pugnax); Slobeend (Anas clypeata); Zomertaling (Anas querquedula); Kuifeend (Aythya fuligula); Veldleeuwerik (Alauda arvensis); Graspieper (Anthus pratensis); Gele kwikstaart (Motacilla flava

Factoren die de overleving van weidevogelkuikens beïnvloeden

Uit onderzoek naar de effectiviteit van het huidige weidevogelbeheer komt telkens naar voren dat er voor de ontwikkeling van een beter beheer op een aantal punten nog onvoldoende kennis aanwezig is over factoren die van belang zijn voor de overleving van weidevogelkuikens. Die ontbrekende kennis spitst zich toe op de invloed die weer, voedsel en beheer op de conditie en daarmee op de overleving van kuikens hebben. Een deel van de vragen kan alleen worden beantwoord door nieuw opgezet veldwerk, maar een deel kan wel beantwoord worden op grond van nieuwe analyses en bestaande datasets . De belangrijkste uitkomsten van die analyses worden hieronder beschreven

Enhanced stability of complex coacervate core micelles following different core-crosslinking strategies

Complex coacervate core micelles (C3Ms) are formed by mixing aqueous solutions of a charged (bio)macromolecule with an oppositely charged-neutral hydrophilic diblock copolymer. The stability of these structures is dependent on the ionic strength of the solution; above a critical ionic strength, the micelles will completely disintegrate. This instability at high ionic strengths is the main drawback for their application in, e.g., drug delivery systems or protein protection. In addition, the stability of C3Ms composed of weak polyelectrolytes is pH-dependent as well. The aim of this study is to assess the effectiveness of covalent crosslinking of the complex coacervate core to improve the stability of C3Ms. We studied the formation of C3Ms using a quaternized and amine-functionalized cationic-neutral diblock copolymer, poly(2-vinylpyridine)-block-poly(ethylene oxide) (QP2VP-b-PEO), and an anionic homopolymer, poly(acrylic acid) (PAA). Two different core-crosslinking strategies were employed that resulted in crosslinks between both types of polyelectrolyte chains in the core (i.e., between QP2VP and PAA) or in crosslinks between polyelectrolyte chains of the same type only (i.e., QP2VP). For these two strategies we used the crosslinkers 1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and dimethyl-3,3′-dithiopropionimidate dihydrochloride (DTBP), respectively. EDC provides permanent crosslinks, while DTBP crosslinks can be broken by a reducing agent. Dynamic light scattering showed that both approaches significantly improved the stability of C3Ms against salt and pH changes. Furthermore, reduction of the disulphide bridges in the DTBP core-crosslinked micelles largely restored the original salt-stability profile. Therefore, this feature provides an excellent starting point for the application of C3Ms in controlled release formulations

Charged Polypeptide Tail Boosts the Salt Resistance of Enzyme-Containing Complex Coacervate Micelles

[Image: see text] Encapsulation of proteins can have advantages for their protection, stability, and delivery purposes. One of the options to encapsulate proteins is to incorporate them in complex coacervate core micelles (C3Ms). This can easily be achieved by mixing aqueous solutions of the protein and an oppositely charged neutral-hydrophilic diblock copolymer. However, protein-containing C3Ms often suffer from salt-inducible disintegration due to the low charge density of proteins. The aim of this study is to improve the salt stability of protein-containing C3Ms by increasing the net charge of the protein by tagging it with a charged polypeptide. As a model protein, we used CotA laccase and generated variants with 10, 20, 30, and 40 glutamic acids attached at the C-terminus of CotA using genetic engineering. Micelles were obtained by mixing the five CotA variants with poly(N-methyl-2-vinyl-pyridinium)-block-poly(ethylene oxide) (PM2VP(128)-b-PEO(477)) at pH 10.8. Hydrodynamic radii of the micelles of approximately 31, 27, and 23 nm for native CotA, CotA-E20, and CotA-E40, respectively, were determined using dynamic light scattering (DLS) and fluorescence correlation spectroscopy (FCS). The encapsulation efficiency was not affected using enzymes with a polyglutamic acid tail but resulted in more micelles with a smaller number of enzyme molecules per micelle. Furthermore, it was shown that the addition of a polyglutamic acid tail to CotA indeed resulted in improved salt stability of enzyme-containing C3Ms. Interestingly, the polyglutamic acid CotA variants showed an enhanced enzyme activity. This study demonstrates that increasing the net charge of enzymes through genetic engineering is a promising strategy to improve the practical applicability of C3Ms as enzyme delivery systems