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1.
The extracellular environment controls many cellular activities thereby linking external material cues to internal cell function. By better understanding these processes, synthetic extracellular material niches can be tailored to present cells with highly regulated physical and/or chemical cues that promote or suppress selected cell functions. Here, poly(ethylene glycol) (PEG) hydrogels were functionalized with fluvastatin-releasing grafts and growth factor binding heparin domains to enable the dynamic exchange of information between the material and cells from the outside-in and inside-out (i.e., bidirectional signaling). By incorporating a fluvastatin-releasing graft and carefully controlling the dose and temporal release, materials were designed to promote bone morphogenic protein (BMP2) and alkaline phosphatase (ALP) production by human mesenchymal stem cells (hMSCs). When the release of fluvastatin was controlled to occur over 2 weeks, BMP2 and ALP production was increased 2.2-fold and 1.7-fold, respectively, at day 28 compared to hMSCs cultured in the absence of fluvastatin. By introducing a heparin functionality into the gel to sequester and localize the hMSC-produced BMP2, the osteogenic differentiation of hMSCs was further augmented over fluvastatin delivery alone. Osteopontin and core binding factor α1 gene expression was 6-fold and 4-fold greater for hMSCs exposed to fluvastatin in the presence of the heparin functionalities, respectively. These results demonstrate how multifunctional gels that interact with cells in a bidirectional manner can efficiently promote selected cell functions, such as the osteogenic differentiation of hMSCs. 相似文献
2.
Construction of the La Grande Complex in Eastern Canada called for complete or partial diversion of six rivers, the mean annual discharge of which varied from 60 to 1600 m3 s?1, and the transfer of water from two adjoining watersheds (1586m3 s?1) into La Grande Rivière. Three of these rivers with reduced flow, Eastmain (from 700 to 95m3 s?1), Opinaca (from 260 to 35m3 s?1), and Caniapiscau (from 1708 to 960m3 s?1) and the waterways with increased flows, Boyd-Sakami (from 1 to 811m3 s?1) and La Grande Rivière (from 1760 to 3400m3 s?1) were intensively monitored from 1978 to 1988, while the others were surveyed sporadically. Very few modifications were observed, compared to previous conditions, in banks stability, water quality, and aquatic fauna of the affected rivers: those which appeared can be explained by the water level fluctuations, the water quality of the tributaries of the residual drainage basin, and/or by the direct influence of the reservoirs. In James Bay, the areal extent of the Eastmain River and La Grand Rivière plumes varied with discharge in an exponential relation, mostly under ice cover; resources from the coastal environment had not yet undergone any major changes. Because of the very small population dwelling in the area, less than 3000 inhabitants, modifications in the hydrological regime of these rivers did cause relatively few impacts, the main being greater banks instability in specific locations, reduction of the thickness and ice cover on La Grande Rivière, enhancement of navigation constraints on Eastmain River, and higher mercury levels in fish related to operation of the reservoirs. 相似文献
3.
Lung surfactant replacement has been tested clinically in recent years. In this study the outcome of 31 premature infants with moderate to severe neonatal respiratory distress syndrome (RDS) treated with surfactant was compared to that of 74 prematures with RDS treated conventionally by positive pressure ventilation and supportive care. The groups were well matched for gestational age, birthweight, sex, and Apgar scores at 1 and 5 min. Surfactant treatment resulted in a significant decrease in mortality--from 36.6% in the untreated group to 12.9% in the surfactant-treated group (P < 0.04). This improvement in survival was seen also in prematures with a birthweight < 1,000 g; in the untreated group mortality was 57.6% compared to 23.5% in the treated group (P < 0.05). The incidence of pneumothorax was lower in the treated group--42% vs. 13% (P < 0.01). Surfactant treatment resulted in a trend of more survivors without bronchopulmonary dysplasia or intraventricular hemorrhage, even though surfactant therapy did not change the incidence of either. 相似文献
4.
Bonenfant D Bourgeois FR Mimeault M Monette F Niquette P Hausler R 《Water science and technology》2011,63(12):2827-2832
Carboxymethylcellulose (CMC) and beta-cyclodextrin (beta-CD)-based polymers functionalized with two types of quaternary ammonium compounds (QACs), the alkaquat DMB-451 (N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride) (DMD-451) named polymer DMB-451, and FMB 1210-8 (a blend of 32 w% N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride and 48 w% of didecyldimethylammonium chloride) named polymer FMB 1210-8, were synthethized and characterized by Fourier transform infrared spectroscopy. The antimicrobial activities of these polymers against Eschericia coli were also evaluated at 25 degrees C in wastewater. The results have indicated that the polymer FMB 1210-8 possesses a high-affinity binding with bacterial cells that induces a rapid disinfection process. Moreover, in the same experimental conditions of disinfection (mixture of 1.0 g of polymer and 100 mL of wastewater), the polymer FMB 1210-8 has a higher antimicrobial efficiency (99.90%) than polymer DMB-451 (92.8%). This phenomenon might be associated to a stronger interaction with bacterial cells due to stronger binding affinity for E. coli cells and greater killing efficiency of the C10 alkyl chains QAC of polymer FMB 1210-8 to disrupt the bacterial cell membrane as compared to N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride. Together, these results suggest that the polymer FMB 1210-8 could constitute a good disinfectant against Escherichia coli, which could be advantageously used in wastewater treatments due to the low toxicity of beta-CD and CMC, and moderated toxicity of FMB 1210-8 to human and environment. 相似文献
5.
Critical thinking in E-learning environments 总被引:1,自引:0,他引:1
One of the primary aims of higher education in today’s information technology enabled classroom is to make students more active in the learning process. The intended outcome of this increased IT-facilitated student engagement is to foster important skills such as critical thinking used in both academia and workplace environments. Critical thinking (CT) skills entails the ability(ies) of mental processes of discernment, analysis and evaluation to achieve a logical understanding. Critical thinking in the classroom as well as in the workplace is a central theme; however, with the dramatic increase of IT usage the mechanisms by which critical thinking is fostered and used has changed. This article presents the work and results of critical thinking in a virtual learning environment. We therefore present a web-based course and we assess in which parts of the course, and to what extent, critical thinking was perceived to occur. The course contained two categories of learning modules namely resources and interactive components. Critical thinking was measured subjectively using the ART scale. Results indicate the significance of “interactivity” in what students perceived to be critical-thinking-oriented versus online material as a resource. Results and opportunities that virtual environments present to foster critical thinking are discussed. 相似文献
6.
Danielle M. Law Jennifer D. ShapkaShelley Hymel Brent F. OlsonTerry Waterhouse 《Computers in human behavior》2012,28(1):226-232
Electronic aggression, or cyberbullying, is a relatively new phenomenon. As such, consistency in how the construct is defined and operationalized has not yet been achieved, inhibiting a thorough understanding of the construct and how it relates to developmental outcomes. In a series of two studies, exploratory and confirmatory factor analyses (EFAs and CFAs respectively) were used to examine whether electronic aggression can be measured using items similar to that used for measuring traditional bullying, and whether adolescents respond to questions about electronic aggression in the same way they do for traditional bullying. For Study I (n = 17 551; 49% female), adolescents in grades 8-12 were asked to what extent they had experience with physical, verbal, social, and cyberbullying as a bully and victim. EFA and CFA results revealed that adolescents distinguished between the roles they play (bully, victim) in a bullying situation but not forms of bullying (physical, verbal, social, cyber). To examine this further, Study II (n = 733; 62% female), asked adolescents between the ages of 11 and 18 to respond to questions about their experience sending (bully), receiving (victim), and/or seeing (witness) specific online aggressive acts. EFA and CFA results revealed that adolescents did not differentiate between bullies, victims, and witnesses; rather, they made distinctions among the methods used for the aggressive act (i.e. sending mean messages or posting embarrassing pictures). In general, it appears that adolescents differentiated themselves as individuals who participated in specific mode of online aggression, rather than as individuals who played a particular role in online aggression. This distinction is discussed in terms of policy and educational implications. 相似文献
7.
This paper describes the results of a summative evaluation conducted to explore the usability and acceptability of an automated telephone-based technology, designed and developed as a screening tool for mental health disorders in the workplace. The system screens employees for symptoms and subsequently provides educational information and referrals to improve mental health and enhance productivity. The qualitative evaluation was a sub-study of a larger randomized controlled trial (RCT). We conducted in-depth interviews with 15 individuals who participated in the RCT and had used the system. A phenomenological theoretical framework was utilized to analyze the narrative data. Results indicated that participants had mostly positive experience with the system and perceived it as a confidential program that allowed them to reflect on their symptoms without inhibition, fear of judgment or embarrassment. We also learned that asking mere questions about mental health symptoms can be a positive, instructive and possibly a restorative experience. There is a likelihood that for many participants, exposure to questions about their emotional and mental distress validated their feelings about their symptoms and was sufficiently compelling to promote help-seeking behavior. This evaluation study demonstrates that computers can be utilized in the workplace as effective screening and educational tools to improve employees’ mental health. 相似文献
8.
Danielle M. Law Jennifer D. Shapka José F. Domene Monique H. Gagné 《Computers in human behavior》2012
Cyberbullying, or online aggression, is an issue of increasing concern, however little research has been conducted on the motivations underlying this form of aggression. Using a mixed-method approach, by means of survey and interview data, we explored whether online aggressive acts were motivated by proactive (intentionally aggressing to obtain a resource or a goal), and/or reactive (aggression that occurs in reaction to provocation) reasons. Participants for the survey portion of the study included 733 adolescents between the ages of 10 and 18, while a subset of 15 adolescents participated in semi-structured interviews. Factor analysis revealed that, in contrast to traditional forms of bullying, adolescents do not identify themselves according to the role they played in an internet aggressive situation (i.e. bully, victim, witness), but according to the method of aggression they used (i.e. sending mean messages, posting embarrassing photos, and developing hostile websites). More interestingly, regression analyses demonstrated that motivations for aggressing online also varied according to method of aggression rather than role. For example, adolescents who chose to aggress by posting mean messages or posting embarrassing photos were more likely to do so for reactive reasons, while adolescents who spent time creating hostile websites did so for proactive reasons. 相似文献
9.
This study extends the literature on eating disorder symptomatology by testing, based on extant literature on objectification theory (B. L. Fredrickson & T. Roberts, 1997) and the role of sociocultural standards of beauty (e.g., L. J. Heinberg, J. K. Thompson, & S. Stormer, 1995), a model that examines (a) links of reported sexual objectification experiences to eating disorder-related variables and (b) the mediating roles of body surveillance, body shame, and internalization of sociocultural standards of beauty. Consistent with hypotheses, with a sample of 221 young women, support was found for a model in which (a) internalization of sociocultural standards of beauty mediated the links of sexual objectification experiences to body surveillance, body shame, and eating disorder symptoms, (b) body surveillance was an additional mediator of the link of reported sexual objectification experiences to body shame, and (c) body shame mediated the links of internalization and body surveillance to disordered eating. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
Andronescu Mirela Dees Danielle Slaybaugh Laura Zhao Yinglei Condon Anne Cohen Barry Skiena Steven 《Natural computing》2003,2(4):391-415
We present an efficient algorithm for determining whether all moleculesin a combinatorial set of DNA or RNA strandsare structure free, and thus availablefor bonding to their Watson-Crick
complements.This work is motivated by the goalof testing whether strands used in DNAcomputations or as molecular bar-codesare
structure free, where the strands areconcatenations of short words. We alsopresent an algorithm for determining whetherall
words in S*, for some finite setS of equi-length words, are structure free.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献