Vibration Damping Characteristics of Typical Harpsichord Strings

Present-day builders of harpsichords disagree as to the use of iron or carbon-steel wire in their attempt to duplicate the tonal qualities of the early 16th century instruments. The variations in tone produced by vibrating iron and steel wires may be due, at least in part, to differences in their decay characteristics. A wire was set into vibration by placing a section in a magnetic field and passing a variable-frequency alternating current through it. A condition of resonance was established by appropriately selecting frequencies, lengths, and tensions that would simultaneously satisfy the relationship: fr = n/2L(T/p)1/2. Then measurements of decay time as a function of frequency were made for a variety of typical harpsichord strings: iron, steel, brass, bronze, etc. Samples varied in diameter from 170 mm to 600 mm and the resonant frequencies ranged from 20 Hz to 12,000 Hz. Changes in energy loss through the supports were measured by varying the size and mass of the supports and by modifying the method of attachment of the wire. Differences in loss of energy due to internal friction were noted in the comparison of decay times for different wire materials and diameters. The energy losses due to sound radiation and viscous damping were examined by placing the vibrating wire in a vacuum. Two significant conclusions, among others gathered from the data, indicate that: 1. For similar samples of iron and steel wire vibrating under like conditions, the steel wire will vibrate for a longer period of time than the iron wire. 2. Energy losses to sound radiation and viscous damping greatly exceed all other modes of energy loss from the wire. Suggestions for additional investigations based On the results of this paper are presented in the concluding pages

Geography of some important Illinois crops

Thesis (M.S.)--University of Illinois at Urbana-Champaign, 1936.Includes bibliographical references

Superspreading on hydrophobic substrates:effect of glycerol additive

The spreading of solutions of three trisiloxane surfactants on two hydrophobic substrates, polyethylene and polyvinylidenefluoride, was studied with the addition of 0–40 mass % of glycerol. It was found that all the surfactant solutions spread faster than silicone oil of the same viscosity, confirming the existence of a mechanism which accelerates the spreading of the surfactant solutions. For the non-superspreading surfactant, BT-233, addition of glycerol improved the spreading performance on polyvinylidenefluoride and resulted in a transition from partial to complete wetting on polyethylene. The fastest spreading was observed for BT-233 at a concentration of 2.5 g/L, independent of glycerol content. For the superspreading surfactants, BT-240 and BT-278, the concentration at which the fastest spreading occurs systematically increased with concentration of glycerol on both substrates from 1.25 g/L for solutions in water to 10 g/L for solutions in 40% glycerol/water mixture. Thus, the surfactant equilibration rate (and therefore formation of surface tension gradients) and Marangoni flow are important components of a superspreading mechanism. De-wetting of the solutions containing glycerol, once spread on the substrates, resulted in the formation of circular drop patterns. This is in contrast to the solely aqueous solutions where the spread film shrank due to evaporation, without any visible traces being left behind

Communicative Competence in Aphasia: Evidence from Compensatory Strategies

TB

Perceptions of Facial Expressions of Emotion in Autism Spectrum Disorders: Reading the “minds eye” Using Reverse Correlation

One of the “primary social deficits” of Autism Spectrum Disorders (ASDs) is understanding the emotions of others, yet current literature is inconclusive as to whether individuals with ASD perceive basic facial expressions of emotion differently from typically developed (TD) individuals [Simmons, et al. 2009, Vision Research, 49, 12705-2739] and, if so, which specific emotions are confused

Sperm storage by males causes changes in sperm phenotype and influences the reproductive fitness of males and their sons

Recent studies suggest that environmentally induced effects on sperm phenotype can influence offspring phenotype beyond the classic Mendelian inheritance mechanism. However, establishing whether such effects are conveyed purely through ejaculates, independently of maternal environmental effects, remains a significant challenge. Here, we assess whether environmentally induced effects on sperm phenotype affects male reproductive success and offspring fitness. We experimentally manipulated the duration of sperm storage by males, and thus sperm age, in the internally fertilizing fish Poecilia reticulata. We first confirm that sperm ageing influences sperm quality and consequently males reproductive success. Specifically, we show that aged sperm exhibit impaired velocity and are competitively inferior to fresh sperm when ejaculates compete to fertilize eggs. We then used homospermic (noncompetitive) artificial insemination to inseminate females with old or fresh sperm and found that male offspring arising from fertilizations by experimentally aged sperm suffered consistently impaired sperm quality when just sexually mature (four months old) and subsequently as adults (13 months old). Although we have yet to determine whether these effects have a genetic or epigenetic basis, our analyses provide evidence that environmentally induced variation in sperm phenotype constitutes an important source of variation in male reproductive fitness that has far reaching implications for offspring fitness

Addressing the Third Law of Gardening: Methodological Alternatives in Aphasiology

TB

Can video support improve attainment? Evaluating the impact of teaching videos on student performance

In 2017, the Faculty of Science and Engineering at Manchester Metropolitan University began an initiative that led to the creation of over 2000 videos and screencasts to support students across all their Departments. The videos cover solutions for tutorial problems, provide coursework briefing information, or support laboratory work and exam preparations. This paper reports the findings of the quantitative study to investigate the effectiveness of the initiative on unit performance. Whilst adjusting for key student characteristics, regression analysis was applied to measure the links between final unit marks of 1248 undergraduate students and their level of engagement with videos. A positive correlation was found, and a further qualitative study is now underway to elaborate on these results and to explain such impact