困难会激发我们的创造力——Flickr创始人之一卡泰丽娜·费克访谈

2002年夏天,卡泰丽娜·费克(Caterina Fake)、斯图尔特·巴特菲尔德(StewartButterfield)和杰森·克拉森(Jason Classon)创办了网络软件公司Ludicorp。Ludicorp公司的第一款产品是永不结束的游戏(Game Neverending),这是一种大型的多人在线角色扮演游戏。在2004年,他们为原来的游戏增加了一个新功能,就是即时交换照片功能的多人聊天室,正是这项新的功能,使得这款游戏迅速火爆起来,新加功能的受欢迎程度甚至超过了游戏本身。此时,整个开发团队意识到了其间的价值,于是他们决定抓住永不结束的游戏这个机会,在其基础上开发一款新的照片交换社区网站,网站的名字就叫做Flickr。果然,Flickr迅速崛起,成为最著名的Web2.0公司之一。尽管它在2005年3月被雅虎公司所收购,但卡泰丽娜·费克的创业激情永远不会停止。     

Evaluating stranger policies in P2P file-sharing systems with reciprocity mechanisms

How to deal with strangers efficiently is a big challenge for designing P2P systems, as ineffective stranger policies will cause the degradation of system performance and fairness. In this work, we focus on an open P2P file-sharing environment with reciprocity incentive mechanisms, and we evaluate the impact of different stranger policies to system performance and fairness using both numerical analyses and agent-based simulations. The results reveal that there exist tradeoffs between system performance and fairness; the optimal performance and fairness of the system cannot be reached simultaneously; free-riders will survive when system performance is optimal. The accuracy of this evaluation is verified through the analysis of stranger policies in BitTorrent and eMule/eDonkey. Therefore, this evaluation can effectively help P2P designers select appropriate stranger policies according to their individual design goals.     

Antiproliferative Effects of St. John’s Wort,Its Derivatives,and Other Hypericum Species in Hematologic Malignancies

Hypericum is a widely present plant, and extracts of its leaves, flowers, and aerial elements have been employed for many years as therapeutic cures for depression, skin wounds, and respiratory and inflammatory disorders. Hypericum also displays an ample variety of other biological actions, such as hypotensive, analgesic, anti-infective, anti-oxidant, and spasmolytic abilities. However, recent investigations highlighted that this species could be advantageous for the cure of other pathological situations, such as trigeminal neuralgia, as well as in the treatment of cancer. This review focuses on the in vitro and in vivo antitumor effects of St. John’s Wort (Hypericum perforatum), its derivatives, and other Hypericum species in hematologic malignancies. Hypericum induces apoptosis in both myeloid and lymphoid cells. Other Hypericum targets include matrix metalloproteinase-2, vascular endothelial growth factor, and matrix metalloproteinase-9, which are mediators of cell migration and angiogenesis. Hypericum also downregulates the expression of proteins that are involved in the resistance of leukemia cells to chemotherapeutic agents. Finally, Hypericum and its derivatives appear to have photodynamic effects and are candidates for applications in tumor photodynamic therapy. Although the in vitro studies appear promising, controlled in vivo studies are necessary before we can hypothesize the introduction of Hypericum and its derivatives into clinical practice for the treatment of hematologic malignancies.     

New MPLS network management techniques based on adaptive learning

The combined use of the differentiated services (DiffServ) and multiprotocol label switching (MPLS) technologies is envisioned to provide guaranteed quality of service (QoS) for multimedia traffic in IP networks, while effectively using network resources. These networks need to be managed adaptively to cope with the changing network conditions and provide satisfactory QoS. An efficient strategy is to map the traffic from different DiffServ classes of service on separate label switched paths (LSPs), which leads to distinct layers of MPLS networks corresponding to each DiffServ class. In this paper, three aspects of the management of such a layered MPLS network are discussed. In particular, an optimal technique for the setup of LSPs, capacity allocation of the LSPs and LSP routing are presented. The presented techniques are based on measurement of the network state to adapt the network configuration to changing traffic conditions.     

Seismic response of irregular multi-storey buildings with flexible inelastic diaphragms

The effectiveness of rigid floor modelling in the seismic design of multi-storey building structures as well as the influence of some structural parameters are deeply investigated through an extensive parametric study. The nonlinear behaviour of 216 structures has been simulated. The basic structural model consists of a symmetrical two-storey system which is supported by seven lateral load-resisting vertical elements with degrading stiffness properties. Different stiffness and strength distributions in the lateral load resisting system and in the floors are considered. The elastic design analysis is carried out by modelling floors as rigid diaphragms or, alternatively, as flexible beams, while the seismic inelastic analyses take into account the real in-plane stiffness and strength of floors. Diagrams show the behaviour of the most important structural element in detail, while statistical techniques are used to identify the most important structural parameters. The results of this study show that the rigid floor hypothesis generally leads to a conservative design for multi-storey buildings, thus confirming the findings of some previous studies on single-storey building structures. Moreover floors need to be adequately designed for strength when they have re-entrances and the stiffness distributions of the lateral-force resisting system is markedly non-uniform. © 1997 John Wiley & Sons, Ltd.     

Prony methods in NMR spectroscopy

The Prony method and a modified Prony method (MPM), developed to improve the performance of this technique at low signal-to-noise ratio, are described and applied to analysis of magnetic resonance spectroscopy (MRS) signals. Furthermore, the way in which results from MPM can be used as prior information in a Bayesian model is also described. First, analysis on simulated data is used to establish the methods' limits of reliability. Their performance with respect to peak identification and quantification of nuclear magnetic resonance parameters are then assayed on real data. Results of application of the methods to ¹H-MRS signals from cultured cells are discussed and compared with those deriving from application of fast Fourier transform. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 565–571, 1997     

Therapeutic Acellular Scaffolds for Limiting Left Ventricular Remodelling-Current Status and Future Directions

Myocardial infarction (MI) is one of the leading causes of heart-related deaths worldwide. Following MI, the hypoxic microenvironment triggers apoptosis, disrupts the extracellular matrix and forms a non-functional scar that leads towards adverse left ventricular (LV) remodelling. If left untreated this eventually leads to heart failure. Besides extensive advancement in medical therapy, complete functional recovery is never accomplished, as the heart possesses limited regenerative ability. In recent decades, the focus has shifted towards tissue engineering and regenerative strategies that provide an attractive option to improve cardiac regeneration, limit adverse LV remodelling and restore function in an infarcted heart. Acellular scaffolds possess attractive features that have made them a promising therapeutic candidate. Their application in infarcted areas has been shown to improve LV remodelling and enhance functional recovery in post-MI hearts. This review will summarise the updates on acellular scaffolds developed and tested in pre-clinical and clinical scenarios in the past five years with a focus on their ability to overcome damage caused by MI. It will also describe how acellular scaffolds alone or in combination with biomolecules have been employed for MI treatment. A better understanding of acellular scaffolds potentialities may guide the development of customised and optimised therapeutic strategies for MI treatment.     

Template polymerization of sodium vinyl sulphonate in the presence of poly(allylamine) hydrochloride

The radical polymerization in aqueous solution of sodium vinly sulphonate in the presence of poly(allylamine) hydrochloride as a template has been studied using dilatometry and the obtained polyelectrolyte complexes have been characterized by viscosimetric and thermal analysis. The time–conversion curves have shown an unusual trend characterized by a slowing down phase followed by an increase in the polymerization rate. The same trend has been observed at various reaction temperatures, and at different monomer concentrations. The results of the viscosimetric analysis have indicated that the molecular weight of the formed polymer increases by increasing the initial template concentration, the other operating conditions remaining unchanged. The mechanism of this template polymerization is discussed in this paper.     

Evaluation of real-time PCR assays for detection and quantification of fraudulent addition of bovine milk to caprine and ovine milk for cheese manufacture

Many typical Italian cheeses made from ovine milk are certified as Protected Designation of Origin (PDO). Because caprine and ovine milk production is limited, the fraudulent addition of cows' milk is widespread. In addition, some compounds in bovine milk have high allergenic potential; therefore, such fraud also has implications for consumer health. In this study, a real-time polymerase chain reaction (real-time PCR) test was developed to detect and quantify cow's milk in caprine and ovine cheeses, based on two target genes. The mitochondrial Cytochrome b gene (Cytb) of Bos taurus was used to detect and quantify bovine DNA. The nuclear gene myostatin (Myo), nuclear ribosomal gene 18S, or mitochondrial gene 16S were used alternatively as universal reference markers. Caprine (n = 30) and ovine (n = 51) cheese samples were purchased and analyzed and most were shown to be contaminated by bovine milk. Pairwise analysis of quantification data using a Spearmann Rank Correlation test demonstrated a highly significant correlation between data obtained with the different reference assays.     

Multiwalled carbon nanotubes functionalized with maleated poly(propylene) by a dry mechano-chemical process

Ball milling was used to graft maleated polypropylene (MAPP) on the surface of multiwalled carbon nanotubes (MWCNTs), with a view to preparing MWCNT/polypropylene composites with improved matrix/nanotube compatibility. The occurrence of the grafting reaction was evaluated by FTIR spectroscopy and the yield was quantified by thermogravimetric analysis, as a function of the milling time. Dispersion experiments confirmed the nanotube surface modification of the nanotubes since functionalized MWCNTs remained stably dispersed in an ethanol/xylene solution for more than 48 h after sonication. No evidences of significant structural damage after the mechano-chemical treatment were shown by Raman spectroscopy. Moreover, a layer attributable to the presence of grafted MAPP chains on MWCNT walls was clearly detected by transmission electron microscopy. The average thickness of this amorphous layer was evaluated and compared with quantitative TGA data.