Analysis of natural frequencies of concert harp soundboard shapes

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaf 24).Two possible soundboard shapes for a concert harp were modeled and their lowest natural frequencies compared in order to evaluate the claim that a harp with a bulbous extension has richer sound in the lower notes than one with a simple trapezoidal shape. Two models for the soundboards were evaluated, the first using a stiff plate approximation and the second using a membrane approximation. The lowest modes and frequencies generated by the two models agreed fairly well, and the simpler membrane model was used for the remainder of the analysis. The natural frequencies of an actual harp were determined by impulse response and the frequency spectrum was compared with the modeled frequencies for soundboard and strings. It was determined that many of the important frequencies in the region under 250 Hz could be attributed to the strings. Powerful resonances and clusters coincided with features of the model, indicating that it contains useful qualitative information.by Katherine L. Rorschach.S.B

Research on the physics of solid materials Semiannual status report, 1 May - 31 Oct. 1967

Research projects on defect structure, mechanical behavior, electrical and optical properties, and thermodynamics of solid materials at universit

Research on the physics of solid materials Semiannual status report, 1 Jan. - 30 Jun. 1969

Research in solid state physics including mechanical properties, and optical propertie

Diffusion of Water in Biological Tissues

A method is presented for obtaining simple approximate solutions for the problem of self-diffusion in an ordered array of obstacles. Our results are compared with some previous exact and approximate solutions, and we find that our method agrees well with the exact results over a large range of the volume fraction of the obstructions. It is shown that there is an important distinction between measurements of the diffusion coefficient by the capillary flow method and the spin-echo method. The modifications for the spin-echo case are given and applied to recent measurements on the anisotropy of the self-diffusion of water in striated muscle and to measurements on cysts of the brine shrimp. The analysis shows that very large volume fractions of obstructive barriers are required in order to account for the reduction in the diffusion coefficient in biological systems. Thus this model analysis leads to the supposition that a substantial fraction (20- 40%) of the cell water is hydration water, or that the diffusion coefficient of the cytoplasmic water is reduced substantially from the free water value. In either case, the conclusion that a substantial fraction of cell water has diffusive properties that are altered by the macromolecules of the cytoplasm seems inescapable. In the case of NMR methodology, the measuring times are such that the values for diffusion are often influenced by the presence of macromolecular structures (obstructions) within the cells. This suggests that obstructions make a significant contribution to the value of the NMR diffusion coefficient and that NMR may have practical value for the evaluation of obstruction effects

Quasi-Elastic Scattering Studies of Water Diffusion

Quasi-elastic neutron scattering is a powerful method to study the dynamics of protons in biological systems. The technique has been used both for the study of water diffusion and protein motion. The neutron scattering measurements on water show that the translational and rotational diffusion coefficients in biological systems are reduced from bulk values. We review the measurements on water in frog muscle, cysts of artemia, and phycocyanin. Measurements on dry trypsin and trypsin-D2O solutions over the temperature range 75-300K show that there is proton motion at the one angstrom level even in the dry or frozen state

Low Temperature Physics

Contains reports on six research projects

覚せい剤を乱用した少女たちのロールシャッハテスト

覚せい剤を乱用した少女たちのうち、覚せい剤の薬害により、中程度以上の症状が発現した人には覚せい剤の使用を中断しでも猜疑的になったり被害感や関係念慮を持ちやすくなったりする人格上の変化を残すといわれる。そこで、覚せい剤を乱用し、猜疑的・被害的に物事を受け止める傾向が強く見られるようになり、さらに進んで幻覚や妄想などの精神症状を体験したことのある人たちと、覚せい斉由を乱用はしたが、使用時に一過的に初期的な症状があったのみで、覚せい剤を使用中も中断後も大きな異状を示さなかったものとを、断薬後おおむねl年を経過した時点でロールシャッハテストを実施し比較した。その結果、覚せい剤の乱用により、中程度以上の影響を受けた人は、情緒的に不安定になりやすく感情統制が不良であること、対人関係に敏感で傷つきやすく、周囲と円滑な関係を持ちにくい傾向が見られた

Low-Temperature Physics

Contains reports on eight research projects

Dynamic nuclear polarization and spin-diffusion in non-conducting solids

There has been much renewed interest in dynamic nuclear polarization (DNP), particularly in the context of solid state biomolecular NMR and more recently dissolution DNP techniques for liquids. This paper reviews the role of spin diffusion in polarizing nuclear spins and discusses the role of the spin diffusion barrier, before going on to discuss some recent results.Comment: submitted to Applied Magnetic Resonance. The article should appear in a special issue that is being published in connection with the DNP Symposium help in Nottingham in August 200