Biomedical subjects

A P Mayer

Publications and source records attributed to A P Mayer.

5 recordsLinked to original sources

PubMed2004

Solitary surface acoustic waves.

Solitary acoustic pulses can propagate along the surface of a coated homogeneous and inhomogeneous medium. It is shown how these nonlinear surface acoustic waves evolve out of initial pulselike conditions generated by pulsed laser excitation and how they can be monitored by optical detection. The solitary pulse shapes at the surface are computed on the basis of an evolution equation with nonlocal nonlinearity. They depend on the anisotropy of the substrate. Various approaches for the derivation of the evolution equation from nonlinear elasticity theory are critically compared. The behavior of the solitary pulses in collisions is investigated and is found to strongly depend on the linear dispersion law. The nontrivial depth dependence of these solitary pulses is also analyzed.

Journal Article↗

PubMed2002

Solitary Rayleigh waves in the presence of surface nonlinearities.

The propagation of Rayleigh waves is investigated in a solid substrate of linear material covered by a film consisting of a material with large nonlinear elastic moduli. For this system, a nonlinear evolution equation is derived that may be regarded as a special case in a wider class of evolution equations with a specific type of nonlocal nonlinearity. Periodic pulse train solutions are computed. For a certain member of the class of nonlinear evolution equations, several families of solitary wave solutions and their associated periodic stationary wave solutions are derived analytically.

Journal Article↗

PubMed2002

Observation of solitary elastic surface pulses.

The formation of solitary elastic surface pulses from laser-generated pulselike initial conditions is reported. The nonlinearity of the medium is compensated by both normal dispersion and anomalous dispersion, which were realized by coating isotropic fused silica by a metal and titanium nitride film, respectively. As an anisotropic material, silicon covered with an oxide layer was studied. The experimental results agree with numerical simulations carried out with a nonlocal evolution equation, which describes nonlinear propagation of surface acoustic waves in a dispersive medium.

Journal Article↗

PubMed1996

FNB diagnosis of breast carcinoma associated with HIV infection: a case report and review of HIV associated malignancy.

A 48 yr old HIV seropositive female presented with a right breast mass and bilateral axillary lymphadenopathy. Fine needle biopsy (FNB) revealed an adenocarcinoma with abundant mucin production and features suggestive of a cribriform and micropapillary ductal carcinoma in situ (DCIS). Histopathological examination of the tumor confirmed an invasive mixed colloid carcinoma with extensive DCIS. There have been 4 previous reports in the literature of breast carcinoma associated with HIV seropositivity. This case initially diagnosed by FNB is the first case reported in Australia. In spite of the somewhat more favourable histological type of breast carcinoma, this tumor shows numerous unfavourable prognostic factors and has had an aggressive clinical course with relapse of disease in the contralateral breast and distant metastases within 4 wks of surgery, probably related to the patient's immunodeficiency.

Adenocarcinoma↗

PubMed1991

Saltpeter ingestion.

A 37-year-old man presented to the emergency department after an attempt to self-treat his priapism with saltpeter (K+NO3). Initially he had a potassium of 7.6 with electrocardiographic changes and a markedly elevated CO2. The potassium and carbon dioxide normalized in less than 24 hours with standard treatment for hyperkalemia. Hyperkalemia is expected with large oral potassium ingestion; and the elevated CO2 was spurious, caused by the misreading of serum nitrates by the Ektachrom 700 system. Ingestion of K+NO3 should be added to the differential of hyperkalemia with a markedly elevated CO2.

Adult↗