一种用于说话人头部动画的Viseme语音识别系统

Viseme是在语音驱动说话人头部动画中一种常用的为口形建立的音频-视频模型。本文尝试建立viseme隐马尔可夫模型(HMM),用于驱动说话人头部的语音识别系统,称为前映射系统。为了得到更精确的模型以提高识别率,引入考虑发音口形上下文的Triseme模型。但是引入Triseme模型后,随着模型数量的急剧增加将导致训练数据的严重不足。本文使用决策树状态捆绑方法来缓解这一问题,同时引入了一种以口形相似度为基础的决策树视频问题设计方法。为了比较viseme系统的性能,本文也建立了一个以phoneme为基本HMM模型的语音识别系统。在评价准则上,使用了一种客观评价说话人头部动画的加权识别率。实验表明,以viseme为基本HMM模型的前映射系统可以为说话人头部提供更加合理的口形。     

Effect of de-methylesterification on network development and nature of Ca-pectin gels: Towards understanding structure-function relations of pectin

Pectins of varying degree and pattern of methylesterification were produced through controlled de-esterification of highly esterified citrus pectin, using carrot pectin methylesterase (PME) (P-pectins), Aspergillus aculeatus PME (F-pectins) or sodium hydroxide saponification (C-pectins). Estimation of the degree of methylesterification (DM) and quantification of the pattern of methylester distribution in terms of absolute degree of blockiness (DB_abs) enabled the characterisation of pectins. Characterised pectins were used for the preparation of Ca²⁺-pectin gels with varying calcium ion (Ca²⁺) concentration. The rheological characteristics of produced gels were evaluated by means of small-amplitude oscillatory tests. During gel formation, gel strength was monitored so as to allow assessment of network development. Based on the evaluation of mechanical spectra, the nature of the cured gels was established. Depending on Ca²⁺ concentration as well as DM and DB_abs, gels prepared from specific C-pectins (48 ≥ DM ≥ 26%; 9 ≤ DB_abs ≤ 37%) and F-pectins (64 ≥ DM ≥ 29%; 9 ≤ DB_abs ≤ 50%) showed a striking decrease of the gel strength with time, while gel networks produced from other pectins either displayed a continuous increase of the gel strength or verged towards pseudo-equilibrium within the observation time of 5 h. Furthermore, the DM, DB_abs and Ca²⁺ concentration influenced the evolution of Ca²⁺-pectin networks from “structured liquids” to “strong gels”. Based on the experimental results, specific mechanisms of Ca²⁺ interactions with pectins were (also) considered.     

Assessment of the N-nitrosopiperidine formation risk from piperine and piperidine contained in spices used as meat product additives

The N-nitrosopiperidine (NPIP) formation in blends of spices and nitrite curing salt was investigated in relation with the piperine and piperidine contents in spices. Firstly, two analytical methods were developed. Piperine was extracted with dichloromethane by means of accelerated solvent extraction (ASE) and determined by high-performance liquid chromatography (HPLC)–diode array detector (λ = 343 nm). A selective hydroextraction of piperidine using ASE and its quantification by HPLC–ELSD was applied. Both methods were sufficiently sensitive and accurate (limit of detection, limit of quantification, and recovery: 0.28, 0.84 μg, and 98.9 ± 2.6 % for piperine, and 5.76, 17.45 μg, and 95.9 ± 2.9 % for piperidine, respectively). Secondly, both compounds were quantified in commercial samples (black and white pepper, paprika, chili pepper, allspice, and nutmeg). The maximum amount of piperine (21.12 mg g^?1) was found in pepper, while the other spices contained only traces. Piperidine was detected mainly in the pepper samples, whereby the highest concentration was found in the white pepper extract (11.42 mg g^?1). Thirdly, during the storage of spices blended with nitrite curing salt, the NPIP content was determined, using a gas chromatograph coupled with a thermal energy analyzer. Against our expectations, no NPIP formation was observed in the curing mixture which contained white pepper extract. This result remains in contrast with the white pepper mixture, in which the NPIP content significantly increased from not detected to 9.80 ± 0.41 ng g^?1 after the 2 months storage period. In conclusion, high amounts of piperine or piperidine in spices do not systematically result in the formation of NPIP, when blended with nitrite curing salt .     

Effect of initial headspace oxygen level on growth and volatile metabolite production by the specific spoilage microorganisms of fresh-cut pineapple

The effect of initial headspace (IH) O₂ level on the shelf-life of fresh-cut pineapple was evaluated in this study. The results showed that although the IH O₂ level had a minor effect on the growth of Candida argentea, Candida sake and Meyerozyma caribbica on pineapple agar, the quantities of the volatile organic metabolites produced by these yeasts was generally smaller the lower the IH O₂ level. The only exception was the production of ethyl acetate by C. argentea, which was higher at low IH O₂ levels. In triangle tests performed with trained panellists, pineapple cubes packaged in an IH of 5% O₂ were determined to be significantly different (P < 0.05) to those packaged in 21% O₂ from day 5 of storage. Preference was shown for the pineapple cubes packaged in an IH of 5% O₂. The results imply that packaging in an IH O₂ level of 5% could be used to extend the shelf-life of fresh-cut pineapple.     

Dynamic simulation of human motion: numerically efficient inclusion of muscle physiology by convex optimization

Determining the muscle forces that underlie some experimentally observed human motion, is a challenging biomechanical problem, both from an experimental and a computational point of view. No non-invasive method is currently available for experimentally measuring muscle forces. The alternative of computing them from the observed motion is complicated by the inherent overactuation of the human body: it has many more muscles than strictly needed for driving all the degrees of freedom of the skeleton. As a result, the skeleton’s equations of motion do not suffice to determine the muscle forces unambiguously. Therefore, muscle force determination is often reformulated as a (large-scale) optimization problem. Generally, the optimization approaches are classified according to the formalism, inverse or forward, adopted for solving the skeleton’s equations of motion. Classical inverse approaches are fast but do not take into account the constraints imposed by muscle physiology. Classical forward approaches, on the other hand, do take the muscle physiology into account but are extremely costly from a computational point of view. The present paper makes a double contribution. First, it proposes a novel inverse approach that results from including muscle physiology (both activation and contraction dynamics) in the inverse dynamic formalism. Second, the efficiency with which the corresponding optimization problem is solved is increased by using convex optimization techniques. That is, an approximate convex program is formulated and solved in order to provide a hot-start for the exact nonconvex program. The key element in this approximation is a (global) linearization of muscle physiology based on techniques from experimental system identification. This approach is applied to the study of muscle forces during gait. Although the results for gait are promising, experimental study of faster motions is needed to demonstrate the full power and advantages of the proposed methodology, and therefore is the subject of subsequent research.     

Plant Parasites under Pressure: Effects of Abiotic Stress on the Interactions between Parasitic Plants and Their Hosts

Parasitic angiosperms, comprising a diverse group of flowering plants, are partially or fully dependent on their hosts to acquire water, mineral nutrients and organic compounds. Some have detrimental effects on agriculturally important crop plants. They are also intriguing model systems to study adaptive mechanisms required for the transition from an autotrophic to a heterotrophic metabolism. No less than any other plant, parasitic plants are affected by abiotic stress factors such as drought and changes in temperature, saline soils or contamination with metals or herbicides. These effects may be attributed to the direct influence of the stress, but also to diminished host availability and suitability. Although several studies on abiotic stress response of parasitic plants are available, still little is known about how abiotic factors affect host preferences, defense mechanisms of both hosts and parasites and the effects of combinations of abiotic and biotic stress experienced by the host plants. The latter effects are of specific interest as parasitic plants pose additional pressure on contemporary agriculture in times of climate change. This review summarizes the existing literature on abiotic stress response of parasitic plants, highlighting knowledge gaps and discussing perspectives for future research and potential agricultural applications.     

Terrace growth in partially melt-regrown EuBa2Cu3 δ high-T c superconductors

An SEM and STM study was made of terrace formation in partial melt-regrown EuBa₂Cu₃O_7?δ. Terraces form above 920°C, well below the bulk melting temperature (1075±10°C). The terrace formation is accompanied by significant grain growth, possibly triggered by a “surface-melting” transition. Melting occurs in a layer a few monolayers thick, and the highly mobile layers reconstruct into terraced form due to a faceting transition. The terrace growth can be reproduced by a theoretical faceting model. The STM also reveals a finer-scale sinusoidal modulation of the surface, of unknown origin.     

Previously uncultured β-Proteobacteria dominate in biologically active granular activated carbon (BAC) filters

Bacteria colonizing BAC filters used in drinking water purification from lake water were characterized by morphology, physiological tests, whole cell protein profiles and PLFA (phospholipid fatty acid) composition, and identified by partial 16S rRNA gene sequencing. Epifluorescence revealed prothecate bacteria to dominate in BAC. The majority of the isolates belonged to order Burkholderiales of β-Proteobacteria, a few to Comamonadaceae but the majority to an undescribed family and the related sequences belonged mainly to uncultured bacteria. Among the less common α-Proteobacteria the genus Sphingomonas and the genera Afipia, Bosea or Bradyrhizobium of the Bradyrhizobiaceae family were detected. The majority of cultured bacteria persisting in the BAC biofilter were Burkholderiales, which according to ecological information are efficient in the mineralisation of dissolved organic matter in BAC. The biotechnical potential of the previously uncultured dominant bacteria warrants to be further studied.     

Polyphasic taxonomy of acetic acid bacteria: an overview of the currently applied methodology

Acetic acid bacteria are Gram-negative, obligate aerobic bacteria that have the ability to incompletely oxidize alcohols or sugars to organic acids as end products. They are widespread in nature and most of them are capable to oxidize ethanol as substrate to acetic acid. This characteristic makes that acetic acid bacteria are often involved in foods and beverages, either in a beneficial, neutral or detrimental way, and therefore they have been studied extensively. The taxonomy of acetic acid bacteria has undergone many changes in the last 30 years. The early classification systems for these bacteria were based on morphological and biochemical characteristics. Today, the acetic acid bacteria are classified as the consensus result of a polyphasic analysis, combining phenotypic, chemotaxonomic and genotypic data. The present review aims at showing the various methods currently applied as well as their taxonomic resolution.