65 research outputs found
MetalâCation Recognition in Water by a TetrapyrazinoporphyrazineâBased Tweezer Receptor
A series of zinc azaphthalocyanines with two azacrowns in a rigid tweezer arrangement were prepared and the fluorescence sensing properties were investigated. The sizeâdriven recognition of alkali and alkaline earth metal cations was significantly enhanced by the close cooperation of the two azacrown units, in which both donor nitrogen atoms need to be involved in analyte binding to switch the sensor on. The monoâ or biphasic character of the binding isotherms, together with the binding stoichiometry and magnitude of association constants (KA), indicated specific complexation of particular analytes. Water solvation was shown to play an important role and resulted in a strong quenching of sensor fluorescence in the ON state. The lead compound was embedded into silica nanoparticles and advantageous sensing properties towards K+ were demonstrated in water (λF=671â
nm, apparent KA=82âmâ1, increase of 17Ă), even in the presence of (supra)physiological concentrations of Na+ and Ca2+.In a pinch: Close cooperation of azacrowns in fluorescence sensors derived from tetrapyrazinoporphyrazines is responsible for high sensitivity and selectivity towards particular cations. Water solvation, however, quenches the fluorescence strongly. Interestingly, embedding the sensor into silica nanoparticles overcomes this problem and result in an excellent redâemitting fluorescence sensor (see figure).Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137532/1/chem201504268.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137532/2/chem201504268-sup-0001-misc_information.pd
Cepstral and Perceptual Investigations in Female Teachers With Functionally Healthy Voice
Purpose. The present study aimed at measuring the smoothed and non-smoothed cepstral peak prominence (CPPS and CPP) in teachers who considered themselves to have normal voice but some of them had laryngeal pathology. The changes of CPP, CPPS, sound pressure level (SPL) and perceptual ratings with different voice tasks were investigated and the influence of vocal pathology on these measures was studied. Method. Eighty-four Finnish female primary school teachers volunteered as participants. Laryngoscopically, 52.4% of these had laryngeal changes (39.3% mild, 13.1% disordered). Sound recordings were made for phonations of comfortable sustained vowel, comfortable speech, and speech produced at increased loudness level as used during teaching. CPP, CPPS and SPL values were extracted using Praat software for all three voice samples. Sound samples were also perceptually evaluated by five voice experts for overall voice quality (10 point scale from poor to excellent) and vocal firmness (10 point scale from breathy to pressed, with normal in the middle). Results. The CPP, CPPS and SPL values were significantly higher for vowels than for comfortable speech and for loud speech compared to comfortable speech (P 0.05). Conclusion. Neither the acoustic measures (CPP, CPPS, and SPL) nor the perceptual evaluations could clearly distinguish teachers with laryngeal changes from laryngeally healthy teachers. Considering no vocal complaints of the subjects, the data could be considered representative of teachers with functionally healthy voice.Peer reviewe
Domestic cat larynges can produce purring frequencies without neural input
Most mammals produce vocal sounds according to the myoelastic-aerodynamic (MEAD) principle, through self-sustaining oscillation of laryngeal tissues.1,2 In contrast, cats have long been believed to produce their low-frequency purr vocalizations through a radically different mechanism involving active muscle contractions (AMC), where neurally driven electromyographic burst patterns (typically at 20â30 Hz) cause the intrinsic laryngeal muscles to actively modulate the respiratory airflow. Direct empirical evidence for this AMC mechanism is sparse.3 Here, the fundamental frequency (fo) ranges of eight domestic cats (Felis silvestris catus) were investigated in an excised larynx setup, to test the prediction of the AMC hypothesis that vibration should be impossible without neuromuscular activity, and thus unattainable in excised larynx setups, which are based on MEAD principles. Surprisingly, all eight excised larynges produced self-sustained oscillations at typical cat purring rates. Histological analysis of cat larynges revealed the presence of connective tissue masses, up to 4 mm in diameter, embedded in the vocal fold.4 This vocal fold specialization appears to allow the unusually low fo values observed in purring. While our data do not fully reject the AMC hypothesis for purring, they show that cat larynges can easily produce sounds in the purr regime with fundamental frequencies of 25 to 30 Hz without neural input or muscular contraction. This strongly suggests that the physical and physiological basis of cat purring involves the same MEAD-based mechanisms as other cat vocalizations (e.g., meows) and most other vertebrate vocalizations but is potentially augmented by AMC
Conceptual framework for programming skilss development based on microlearning and automated source code evaluation in virtual learning environment
Understanding how software works and writing a program are currently frequent requirements
when hiring employees. The complexity of learning programming often results in educational
failures, student frustration and lack of motivation, because different students prefer different learning
paths. Although e-learning courses have led to many improvements in the methodology and the
supporting technology for more effective programming learning, misunderstanding of programming
principles is one of the main reasons for students leaving school early. Universities face a challenging
task: how to harmonise studentsâ education, focusing on advanced knowledge in the development of
software applications, with studentsâ education in cases where writing code is a new skill. The article
proposes a conceptual framework focused on the comprehensive training of future programmers
using microlearning and automatic evaluation of source codes to achieve immediate feedback for
students. This framework is designed to involve students in the software development of virtual
learning environment software that will provide their education, thus ensuring the sustainability of
the environment in line with modern development trends. The paperâs final part is devoted to verifying
the contribution of the presented elements through quantitative research on the introductory
parts of the framework. It turned out that although the application of interactive features did not
lead to significant measurable progress during the first semester of study, it significantly improved
the results of students in subsequent courses focused on advanced programming
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