Background/Context Earlier research on various forms of distance learning concluded that these technologies do not differ significantly from regular classroom instruction in terms of learning outcomes. Now that web-based learning has emerged as a major trend in both K–12 and higher education, the relative efficacy of online and face-to-face instruction needs to be revisited. The increased capabilities of web-based applications and collaboration technologies and the rise of blended learning models combining web-based and face-to-face classroom instruction have raised expectations for the effectiveness of online learning. Purpose/Objective/Research Question/Focus of Study This meta-analysis was designed to produce a statistical synthesis of studies contrasting learning outcomes for either fully online or blended learning conditions with those of face-to-face classroom instruction. Population/Participants/Subjects The types of learners in the meta-analysis studies were about evenly split between students in college or earlier years of education and learners in graduate programs or professional training. The average learner age in a study ranged from 13 to 44. Intervention/Program/Practice The meta-analysis was conducted on 50 effects found in 45 studies contrasting a fully or partially online condition with a fully face-to-face instructional condition. Length of instruction varied across studies and exceeded one month in the majority of them. Research Design The meta-analysis corpus consisted of (1) experimental studies using random assignment and (2) quasi-experiments with statistical control for preexisting group differences. An effect size was calculated or estimated for each contrast, and average effect sizes were computed for fully online learning and for blended learning. A coding scheme was applied to classify each study in terms of a set of conditions, practices, and methodological variables. Findings/Results The meta-analysis found that, on average, students in online learning conditions performed modestly better than those receiving face-to-face instruction. The advantage over face-to-face classes was significant in those studies contrasting blended learning with traditional face-to-face instruction but not in those studies contrasting purely online with face-to-face conditions. Conclusions/Recommendations Studies using blended learning also tended to involve additional learning time, instructional resources, and course elements that encourage interactions among learners. This confounding leaves open the possibility that one or all of these other practice variables contributed to the particularly positive outcomes for blended learning. Further research and development on different blended learning models is warranted. Experimental research testing design principles for blending online and face-to-face instruction for different kinds of learners is needed.
Oligodeoxyribonucleotides complementary to the DNA of the wild type (wt) bacteriophage phi chi 174 have been synthesized by the phosphotriester method. The oligomers, 11, 14, and 17 bases long, are complementary to the region of the DNA which accounts for the am-3 point mutation. When hybridized to am-3 DNA, the oligonucleotides form duplexes with a single base pair mismatch. The thermal stability of the duplexes formed between wt and am-3 DNAs has been measured. The am-3 DNA:oligomer duplexes dissociate at a temperature about 10 degrees C lower than the corresponding wt DNA:oligomer duplexes. This dramatic decrease in thermal stability due to a single mismatch makes it possible to eliminate the formation of the mismatched duplexes by the appropriate choice of hybridization temperature. These results are discussed with respect to the use of oligonucleotides as probes for the isolation of specific cloned DNA sequences.
The usefulness and efficacy of cisplatin, a chemotherapeutic drug, are limited by its toxicity to normal tissues and organs, including the kidneys. The uptake of cisplatin in renal tubular cells is high, leading to cisplatin accumulation and tubular cell injury and death, culminating in acute renal failure. While extensive investigations have been focused on the signaling pathways of cisplatin nephrotoxicity, much less is known about the mechanism of cisplatin uptake by renal cells and tissues. In this regard, evidence has been shown for the involvement of organic cation transporters (OCT), specifically OCT2. The copper transporter Ctr1 is highly expressed in the renal tubular cells; however, its role in cisplatin nephrotoxicity is not known. In this study, we demonstrate that Ctr1 is mainly expressed in both proximal and distal tubular cells in mouse kidneys. We further show that Ctr1 is mainly localized on the basolateral side of these cells, a proposed site for cisplatin uptake. Importantly, downregulation of Ctr1 by small interfering RNA or copper pretreatment results in decreased cisplatin uptake. Consistently, downregulation of Ctr1 suppresses cisplatin toxicity, including cell death by both apoptosis and necrosis. Cimetidine, a pharmacological inhibitor of OCT2, can also partially attenuate cisplatin uptake. Notably, cimetidine can further reduce cisplatin uptake and cisplatin toxicity in Ctr1-downregulated cells. The results have demonstrated the first evidence for a role of Ctr1 in cisplatin uptake and nephrotoxicity.
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