Fundamentals of the direct measurement of sound intensity and practical applications

Sound intensity is a measure of the magnitude and direction of the flow of sound energy. Developments in sound intensity measurement capabilities in the last quarter century have occurred because of several reasons. The main ones include the derivation of the cross-spectral formulation for sound intensity and developments in digital signal processing. This paper begins with a brief historical introduction of sound intensity measurements. Then elementary theory for sound intensity is presented. A section on sound intensity measurements is then included. The next section of the paper discusses sources of measurement error; the major sources of error are described in some detail. The paper continues with a discussion of the main applications of sound intensity measurements: sound power determination, noise source identification, and transmission loss measurements. The paper concludes with a discussion of ISO and ANSI intensity related standards and relevant references.     

Multiparameter Polynomial Adaptive Stabilizers

In 1983 Morse proved, for unknown scalar one-dimensional linearsystems, the nonexistence of rational or polynomial universalstabilizers (UAS). In 1983, Nussbaum gave an example of an analyticUAS. In our paper, it is shown that there exist time-invariantpolynomial UAS's with multidimensional gain adaptation. Thedesign procedure is developed for linear, minimum-phase systemsof relative degree one. Convergence of the closed-loop systemis proved. Some numerical simulations are provided.     

A new ent-labdane eiterpenoid lactone from Andrographis paniculata

A new ent-labdane diterpenoid lactone with a new natural product was isolated from Andrographis paniculata. Their structures were elucidated on the basis of spectral evidences including 2D NMR.     

Colloidal interactions and self-assembly using DNA hybridization

The specific binding of complementary DNA strands has been suggested as an ideal method for directing the controlled self-assembly of microscopic objects. We report the first direct measurements of such DNA-induced interactions between colloidal microspheres, as well as the first colloidal crystals assembled using them. The interactions measured with our optical tweezer method can be modeled in detail by well-known statistical physics and chemistry, boding well for their application to directed self-assembly. The microspheres' binding dynamics, however, have a surprising power-law scaling that can significantly slow annealing and crystallization.     

Rheological microscopy: local mechanical properties from microrheology

We demonstrate how tracer microrheology methods can be extended to study submicron scale variations in the viscoelastic response of soft materials; in particular, a semidilute solution of lambda-DNA. The polymer concentration is depleted near the surfaces of the tracer particles, within a distance comparable to the polymer correlation length. The rheology of this microscopic layer alters the tracers' motion and can be precisely quantified using one- and two-point microrheology. Interestingly, we found this mechanically distinct layer to be twice as thick as the layer of depleted concentration, likely due to solvent drainage through the locally perturbed polymer structure.     

The effect of a low-frequency sound source (acoustic thermometry of the ocean climate) on the diving behavior of juvenile northern elephant seals,Mirounga angustirostris

Changes in the diving behavior of individual free-ranging juvenile northern elephant seals, Mirounga angustirostris, exposed to the acoustic thermometry of the ocean climate (ATOC) sound source were examined using data loggers. Data loggers were attached to the animals and measured swim speed, maximum depth of dive, dive duration, surface interval, descent and ascent rate, and descent and ascent angle along with sound pressure level (SPL). The ATOC sound source was at a depth of 939 m and transmitted at 195 dB re: 1 microPa at 1 m centered at 75 Hz with a 37.5-Hz bandwidth. Sound pressure levels (SPL) measured at the seal during transmissions averaged 128 dB and ranged from 118 to 137 dB re: 1 microPa for the 60-90 Hz band, in comparison to ambient levels of 87-107 dB within this band. In no case did an animal end its dive or show any other obvious change in behavior upon exposure to the ATOC sound. Subtle changes in diving behavior were detected, however. During exposure, deviations in descent rate were greater than 1 s.d. of the control mean in 9 of 14 seals. Dive depth increased and descent velocity increased in three animals, ascent velocity decreased in two animals, ascent rate increased in one animal and decreased in another, and dive duration decreased in only one animal. There was a highly significant positive correlation between SPL and descent rate. The biological significance of these subtle changes is likely to be minimal. This is the first study to quantify behavioral responses of an animal underwater with simultaneous measurements of SPL of anthropogenic sounds recorded at the animal.     

Asymmetric synthesis of pedamide using I_2-induced heterocyclization to construct the skeleton

An alternative approach to synthesize pedamide,a key building block of pederin was described.Iodine-induced asymmetric heterocyclization was used as the key step to construct the skeleton,a tetrahydropyran ring with three chiral centers.Brown's asymmetric allylation and Lewis acid-mediated allylation were investigated to introduce chains and chiral alcohols.Sharpless dihydroxylation decorated the side chain.And high optically pure target was obtained by removing the epimers formed in these reactions on c...     

Microwave-assisted one-pot synthesis of 3-substituted-3,4-dihydrocoumarins via tendem Konevenagel and Hantzsch reactions

A convenient route for the synthesis of 3,4-dihydrocoumarin derivates from salicylaldehyde derivates and 1,3-dicarbonyl compounds under solvent-free microwave irradiation conditions was described. In this way, a range of compounds was obtained in moderate to good yields in a short reaction time.