In the last 16 years, more than 200 research articles were published about research-paper recommender systems. We reviewed these articles and present some descriptive statistics in this paper, as well as a discussion about the major advancements and shortcomings and an overview of the most common recommendation concepts and approaches. We found that more than half of the recommendation approaches applied content-based filtering (55 %). Collaborative filtering was applied by only 18 % of the reviewed approaches, and graph-based recommendations by 16 %. Other recommendation concepts included stereotyping, item-centric recommendations, and hybrid recommendations. The content-based filtering approaches mainly utilized papers that the users had authored, tagged, browsed, or downloaded. TF-IDF was the most frequently applied weighting scheme. In addition to simple terms, n-grams, topics, and citations were utilized to model users' information needs. Our review revealed some shortcomings of the current research. First, it remains unclear which recommendation concepts and approaches are the most promising. For instance, researchers reported different results on the performance of contentbased and collaborative filtering. Sometimes content-based filtering performed better than collaborative filtering and Linnaeus University, Kalmar, Sweden sometimes it performed worse. We identified three potential reasons for the ambiguity of the results. (A) Several evaluations had limitations. They were based on strongly pruned datasets, few participants in user studies, or did not use appropriate baselines. (B) Some authors provided little information about their algorithms, which makes it difficult to re-implement the approaches. Consequently, researchers use different implementations of the same recommendations approaches, which might lead to variations in the results. (C) We speculated that minor variations in datasets, algorithms, or user populations inevitably lead to strong variations in the performance of the approaches. Hence, finding the most promising approaches is a challenge. As a second limitation, we noted that many authors neglected to take into account factors other than accuracy, for example overall user satisfaction. In addition, most approaches (81 %) neglected the user-modeling process and did not infer information automatically but let users provide keywords, text snippets, or a single paper as input. Information on runtime was provided for 10 % of the approaches. Finally, few research papers had an impact on research-paper recommender systems in practice. We also identified a lack of authority and long-term research interest in the field: 73 % of the authors published no more than one paper on research-paper recommender systems, and there was little cooperation among different co-author groups. We concluded that several actions could improve the research landscape: developing a common evaluation framework, agreement on the information to include in research papers, a stronger focus on non-accuracy aspect...

Poly(ether ester) block-copolymer scaffolds of different pore size were implanted into the dorsal skinfold chamber of balb/c mice. Using intravital fluorescent microscopy, the temporal course of neovascularization into these scaffolds was quantitatively analyzed. Three scaffold groups (diameter, 5 mm; 220 -260 thickness, m; n ϭ 30) were implanted. Different pore sizes were evaluated: small (20 -75 m), medium (75-212 m) and large pores (250 -300 m). Measurements were performed on days 8, 12, 16, and 20 in the surrounding normal tissue, in the border zone, and in the center of the scaffold. Standard microcirculatory parameters were assessed (plasma leakage, vessel diameter, red blood cell velocity, and functional vessel density). The largepored scaffolds showed significantly higher functional vessel density in the border zone and in the center (days 8 and 12) compared with the scaffold with the small and mediumsized pores. These data correlated with a larger vessel diameter and a higher red blood cell velocity in the largepored scaffold group. Interestingly, during the evaluation period the microcirculatory parameters on the edge of the scaffolds returned to values similar to those found in the surrounding tissue. In the center of the scaffold, however, neovascularization was still active 20 days after implantation. Plasma leakage and vessel diameter were higher in the center of the scaffold. Red blood cell velocity and functional vessel density were 50% lower than in the surrounding tissue. In conclusion, the dorsal skinfold chamber model in mice allows long-term study of blood vessel growth and remodeling in porous biomedical materials. The rate of vessel ingrowth into poly(ether ester) block-copolymer scaffolds is influenced by pore size and was highest in the scaffold with the largest pores. The data generated with this model contribute to knowledge about the development of functional vessels and tissue ingrowth into biomaterials.

Host defense peptides are effector molecules of the innate immune system. They show broad antimicrobial action against gram-positive and -negative bacteria, and they likely play a key role in activating and mediating the innate as well as adaptive immune response in infection and inflammation. These features make them of high interest for wound healing research. Nonhealing and infected wounds are a major problem in patient care and health care spending. Increasing infection rates, growing bacterial resistance to common antibiotics, and the lack of effective therapeutic options for the treatment of problematic wounds emphasize the need for new approaches in therapy and pathophysiologic understanding. This review focuses on the current knowledge of host defense peptides affecting wound healing and infection. We discuss the current data and highlight the potential future developments in this field of research.

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