William Harvey, an Aristotelian anatomist

William Harvey has long been celebrated as the founding father of physiology for refuting Galen and demonstrating that blood circulates round the body. Yet after his training at Padua, he became a committed Aristotelian: although strongly influencing the new observational sciences of the seventeenth century, Harvey himself looked back towards the classical past.     

Enantioselective assembly of multi-layer 3D chirality

The first enantioselective assembly of sandwich-shaped organo molecules has been achieved by conducting dual asymmetric Suzuki-Miyaura couplings and nine other reactions. This work also presents the first fully C-C anchored multi-layer 3D chirality with optically pure enantiomers. As confirmed by X-ray diffraction analysis that this chiral framework is featured by a unique C₂-symmetry in which a nearly parallel fashion consisting of three layers: top, middle and bottom aromatic rings. Unlike the documented planar or axial chirality, the present chirality shows its top and bottom layers restrict each other from free rotation, i.e., this multi-layer 3D chirality would not exist if either top or bottom layer is removed. Nearly all multi-layered compounds showed strong luminescence of different colors under UV irradiation, and several randomly selected samples displayed aggregation-induced emission (AIE) properties. This work is believed to have broad impacts on chemical, medicinal and material sciences including optoelectronic materials in future.     

Torbern Olof Bergman: from natural history to quantitative chemistry

This year marks the bicentenary of the death of the Swedish chemist Torbern Bergman. He took up chemical work comparatively late in life, but made important contributions to the classification and analysis of minerals and mineral waters. He is best known, however, for his work on chemical affinity, described in his Dissertation on Elective Attractions (1775). He corresponded with contemporary French chemists, including P. J. Macquer, the bicentenary of whose death also falls this year.     

The first 'molecular disease': a story of Linus Pauling, the intellectual patron

In November 1949, chemist Linus Pauling and three colleagues published an article on sickle-cell anemia, a study that opened up new and exciting possibilities for research into such 'molecular diseases'. Even before this celebrated publication appeared in Science, Pauling foresaw its potential benefits and announced it as a medical breakthrough: '... our structural chemistry and understanding of molecules is getting to the point where it should be of assistance in converting medicine into a real science' [Guiles, R. (1949) Discovery of blood disease called key to cancer research. The Detroit Times 13 Sep 1949, Newspaper Clippings 1949n.18, Pauling Papers.]. Their discovery--that this debilitating disorder was caused by an abnormal form of hemoglobin--was borne out of a rich mix of expertise, from Pauling's remarkable intuition to the careful experimental chemistry of his student Harvey A. Itano. It also relied upon technological innovation: a custom-made electrophoresis machine housed at the California Institute of Technology was the perfect tool to reveal fundamental chemical differences between normal and abnormal forms of hemoglobin. Not only did this work establish a new way of looking at inherited diseases, it also stimulated the mass production of the electrophoresis machine as an essential investigative and diagnostic tool. A close inspection of this case study illustrates just how Pauling ran his laboratory and helps to explain how one man could achieve so much over his lifetime.     

How to approximate users’ values while preserving privacy: experiences with using attitudes towards work tasks as proxies for personal value elicitation

Software users have different sets of personal values, such as benevolence, self-direction, and tradition. Among other factors, these personal values influence users’ emotions, preferences, motivations, and ways of performing tasks—and hence, information needs. Studies of user acceptance indicate that personal traits like values and related soft issues are important for the user’s approval of software. If a user’s dominant personal value were known, software could automatically show an interface variant which offers information and functionality that best matches his or her dominant value. A user’s dominant personal value is the one that most strongly influences his or her attitudes and behaviors. However, existing methods for measuring a user’s values are work intensive and/or interfere with the user’s privacy needs. If interface tailoring for very large groups of users is planned, value approximation has to be achieved on a large scale to assign individualized software to all users of the software. Our work focuses on approximating the dominant values of a user with less effort and less impact on privacy. Instead of probing for a user’s values directly, we explore the potential of approximating these values based on the user’s preferences for key tasks. Producing tailored versions of software is a separate topic not in the focus here. In this paper we rather describe a method to identify user values from task preferences and an empirical study of applying parts of this method. We are proposing the method in this paper for the first time except for a preliminary version orally presented at a workshop. The method consists of a research process and an application process. In the research process a researcher has to identify key tasks occurring in a context under investigation which have a relationship to personal values. These key tasks can be used in the application process to approximate the dominant values of new users in a similar context. In this empirical study we show that the research process of our method allows us to determine key tasks which approximate values in the shared context of nursing. The majority of the nurses were found to have one of the three following dominant values: benevolence, self-direction, or hedonism. Data confirmed common expectations: that nurses with the value of benevolence, when compared to all other nurses, had a higher preference for tasks which helped people immediately or improved their circumstances of the treatment. In relation to all other nurses, participants with self-direction disliked tasks which affected their personal freedom, and users with hedonism had a lower preference for tasks which involved physical work and preferred tasks which promised gratification. Our findings advance measurement of personal values in large user groups by asking questions with less privacy concern. However, the method requires substantial efforts during the initial research process to prepare such measurements. Future work includes replicating our method in other contexts and identifying value-dependent tasks for users with other values than the three values our empirical study mainly focused on.     

Extracting temporal and causal relations based on event networks

Event relations specify how different event flows expressed within the context of a textual passage relate to each other in terms of temporal and causal sequences. There have already been impactful work in the area of temporal and causal event relation extraction; however, the challenge with these approaches is that (1) they are mostly supervised methods and (2) they rely on syntactic and grammatical structure patterns at the sentence-level. In this paper, we address these challenges by proposing an unsupervised event network representation for temporal and causal relation extraction that operates at the document level. More specifically, we benefit from existing Open IE systems to generate a set of triple relations that are then used to build an event network. The event network is bootstrapped by labeling the temporal disposition of events that are directly linked to each other. We then systematically traverse the event network to identify the temporal and causal relations between indirectly connected events. We perform experiments based on the widely adopted TempEval-3 and Causal-TimeBank corpora and compare our work with several strong baselines. We show that our method improves performance compared to several strong methods.     

Output feedback stabilization for symmetric control systems

This work is devoted to the study of symmetric control systems. It establishes a relation between internal symmetry and external one for a linear invariant control system having n real simple poles. The symmetric stabilization problem is studied using a symmetric feedback gain such that the output control stabilizes the closed-loop system. A necessary and sufficient condition is given to solve this stabilization problem for a symmetric control system (A,B,C) and a generalized symmetric control system (E,A,B,C).     

一步之遥，八年光阴：丙肝病原体的发现到证明之路

2020年的诺贝尔生理学或医学奖授予了在发现丙肝病毒(HCV)方面作出突出贡献的哈维·阿尔特(Harvey J. Alter)、迈克尔·霍顿(Michael Houghton)和查尔斯·赖斯(Charles M. Rice)。然而,从1989年霍顿捕获HCV到1997年赖斯证明HCV能引发肝炎,间隔了8年时间。这看似一步之遥的距离何以耗时如此之久?文章通过回顾文献,对这一时期的研究脉络进行了梳理,明确了包括赖斯团队在内的不同研究者对于推进HCV相关认识所作的具体贡献。同时,针对研究过程中的两个关键节点——病毒RNA基因组3′末端的准确测序和感染性分子克隆的建立,文章从技术储备、路径依赖和目标定位的角度分析了赖斯团队为何能在科学研究竞争中拔得头筹。     

Toward incorporating a task-stage identification technique into the long-term document support process

Effective knowledge management in a knowledge-intensive environment can place heavy demands on the information filtering (IF) strategies used to model workers’ long-term task-needs. Because of the growing complexity of knowledge-intensive work tasks, a profiling technique is needed to deliver task-relevant documents to workers. In this study, we propose an IF technique with task-stage identification that provides effective codification-based support throughout the execution of a task. Task-needs pattern similarity analysis based on a correlation value is used to identify a worker’s task-stage (the pre-focus, focus formulation, or post-focus task-stage). The identified task-stage is then incorporated into a profile adaptation process to generate the worker’s current task profile. The results of a pilot study conducted in a research institute confirm that there is a low or negative correlation between search sessions and transactions in the pre-focus task-stage, whereas there is at least a moderate correlation between search sessions/transactions in the post-focus stage. Compared with the traditional IF technique, the proposed IF technique with task-stage identification achieves, on average, a 19.49% improvement in task-relevant document support. The results confirm the effectiveness of the proposed method for knowledge-intensive work tasks.     

Building user profiles based on sequences for content and collaborative filtering

Modeling user profiles is a necessary step for most information filtering systems – such as recommender systems – to provide personalized recommendations. However, most of them work with users or items as vectors, by applying different types of mathematical operations between them and neglecting sequential or content-based information. Hence, in this paper we study how to propose an adaptive mechanism to obtain user sequences using different sources of information, allowing the generation of hybrid recommendations as a seamless, transparent technique from the system viewpoint. As a proof of concept, we develop the Longest Common Subsequence (LCS) algorithm as a similarity metric to compare the user sequences, where, in the process of adapting this algorithm to recommendation, we include different parameters to control the efficiency by reducing the information used in the algorithm (preference filter), to decide when a neighbor is considered useful enough to be included in the process (confidence filter), to identify whether two interactions are equivalent (δ-matching threshold), and to normalize the length of the LCS in a bounded interval (normalization functions). These parameters can be extended to work with any type of sequential algorithm.We evaluate our approach with several state-of-the-art recommendation algorithms using different evaluation metrics measuring the accuracy, diversity, and novelty of the recommendations, and analyze the impact of the proposed parameters. We have found that our approach offers a competitive performance, outperforming content, collaborative, and hybrid baselines, and producing positive results when either content- or rating-based information is exploited.     

Effect of synthetic and natural media on lipid production from Fusarium oxysporum

BackgroundDependence on fossil resources, for the production of fuels and energy, has resulted in environmental and financial problems, which require our immediate action in order to reverse the situation. Use of renewable sources for the production of fuels and energy is an important alternative with biodiesel remains as one of the promising options. Aim of this work is to evaluate the fungus Fusarium oxysporum for its potentials to accumulate microbial lipids when grown on synthetic media and saccharified sweet sorghum stalks.ResultsThe effect of different carbon sources, nitrogen sources and C/N ratio on the lipid production was initially examined, which resulted in a lipid concentration of 4.4 g/L, with lipid content of 42.6% w/w. Sweet sorghum stalks were able to support growth and lipid production of the fungus, both as carbon source and as nitrogen source. It was also shown that saccharification of the dried stalks is an important step to increase lipid production. Removal of the remaining stalk solids enabled the lipid production during cultivation in increased initial solids of up to 16 w/w. This resulted in a lipid production of 3.81 g/L.ConclusionsIt was demonstrated that F. oxysporum can be used as an efficient oleaginous microorganism, with sweet sorghum serving as an excellent raw material for the cultivation of the fungus. The lipids obtained during this work were also found to have a fatty acid profile with good potentials to be used for biodiesel production.     

Stabilization of discrete-time stochastic systems via sliding mode technique

This paper considers the problem of sliding mode control for discrete-time stochastic systems with parameter uncertainties and state-dependent noise perturbation. An integral-like sliding surface is chosen and a discrete-time sliding mode controller is designed. The key feature in this work is that both the reachability of the quasi-sliding mode and the stability of system states are simultaneously analyzed, due to the existence of state-dependent noise perturbation. By utilizing an Lyapunov function involving system states and sliding mode variables, the sufficient condition for reachability is obtained. Finally, numerical simulation results are provided.     

New approach to the optimal control of delay systems via Chebyshev series

Based on the Chebyshev series, a directly computational formulation in matrix form is established for evaluating the optimal control and trajectory of time-delay systems. In a comparison with the previous work (3, Int. J. Control, Vol. 41, pp. 1221-1234, 1985), the formulation is shown to be more straightforward and convenient for digital computation. Thus the difficulty in obtaining a solution of the two-point boundary-value problem with both delayed and advanced arguments is circumvented. An example compares the actual solution with the one obtained using the technique of this paper.     

Optimum tearing in large scale systems and minimum feedback cutsets of a digraph

In this paper we consider the problem of finding a minimum number of nonzero elements of a given nxn matrix on removal of which the resulting matrix can be permuted to an nxn lower triangular matrix using summetric permutations on the rows and columns of the matrix. The problem is related to finding a minimum feedback cutset for the digraph of the matrix. A topological method for finding a minimum feedback cutset for a given digraph is presented. Possible extensions to our work are indicated.     

Modeling Arabic subjectivity and sentiment in lexical space

In spite of the vast amount of work on subjectivity and sentiment analysis (SSA), it is not yet particularly clear how lexical information can best be modeled in a morphologically-richness language. To bridge this gap, we report successful models targeting lexical input in Arabic, a language of very complex morphology. Namely, we measure the impact of both gold and automatic segmentation on the task and build effective models achieving significantly higher than our baselines. Our models exploiting predicted segments improve subjectivity classification by 6.02% F₁-measure and sentiment classification by 4.50% F₁-measure against the majority class baseline surface word forms. We also perform in-depth (error) analyses of the behavior of the models and provide detailed explanations of subjectivity and sentiment expression in Arabic against the morphological richness background in which the work is situated.     

Polytopic invariant and contractive sets for closed-loop discrete fuzzy systems

In this work a procedure for obtaining polytopic λ-contractive sets for Takagi–Sugeno fuzzy systems is presented, adapting well-known algorithms from literature on discrete-time linear difference inclusions (LDI) to multi-dimensional summations. As a complexity parameter increases, these sets tend to the maximal invariant set of the system when no information on the shape of the membership functions is available. λ-contractive sets are naturally associated to level sets of polyhedral Lyapunov functions proving a decay-rate of λ. The paper proves that the proposed algorithm obtains better results than a class of Lyapunov methods for the same complexity degree: if such a Lyapunov function exists, the proposed algorithm converges in a finite number of steps and proves a larger λ-contractive set.     

Circadian rhythms in Neurospora crassa on a polydimethylsiloxane microfluidic device for real-time gas perturbations

Racetubes, a conventional system employing hollow glass tubes, are typically used for monitoring circadian rhythms from the model filamentous fungus, Neurospora crassa. However, a major technical limitation in using a conventional system is that racetubes are not amenable for real-time gas perturbations. In this work, we demonstrate a simple microfluidic device combined with real-time gas perturbations for monitoring circadian rhythms in Neurospora crassa using bioluminescence assays. The developed platform is a useful toolbox for investigating molecular responses under various gas conditions for Neurospora and can also be applied to other microorganisms.     

Limit cycle analysis of nonlinear sampled-data systems by gain-phase margin approach

This work analyzes the limit cycle phenomena of nonlinear sampled-data systems by applying the methods of gain-phase margin testing, the M-locus and the parameter plane. First, a sampled-data control system with nonlinear elements is linearized by the classical method of describing functions. The stability of the equivalent linearized system is then analyzed using the stability equations and the parameter plane method, with adjustable parameters. After the gain-phase margin tester has been added to the forward open-loop system, exactly how the gain-phase margin and the characteristics of the limit cycle are related can be elicited by determining the intersections of the M-locus and the constant gain and phase boundaries. A concise method is presented to solve this problem. The minimum gain-phase margin of the nonlinear sampled-data system at which a limit cycle can occur is investigated. This work indicates that the procedure can be easily extended to analyze the limit cycles of a sampled-data system from a continuous-data system cases considered in the literature. Finally, a sampled-data system with multiple nonlinearities is illustrated to verify the validity of the procedure.     

Bidirectional delta files

A bidirectional delta file is a novel concept, introduced in this paper, for a two way delta file. Previous work focuses on single way differential compression called forwards and backwards delta files. Here we suggest to efficiently combine them into a single file so that the combined file is smaller than the combination of the two individual ones. Given the bidirectional delta file of two files S and T and the original file S, one can decode it in order to produce T. The same bidirectional delta file is used together with the file T in order to reconstruct S. This paper presents two main strategies for producing an efficient bidirectional delta file in terms of the memory storage it requires; a quadratic time, optimal, dynamic programming algorithm, and a linear time, greedy algorithm. Although the dynamic programming algorithm often produces better results than the greedy algorithm, it is impractical for large files, and it is only used for theoretical comparisons. Experiments between the implemented algorithms and the traditional way of using both forwards and backwards delta files are presented, comparing their processing time and their compression performance. These experiments show memory storage savings of about 25% using this bidirectional delta approach as compared to the compressed delta file constructed using the traditional way, while preserving approximately the same processing time for decoding.