Optical properties of porous GaAs Lockwood, D.J.; Schmuki, P.; Labbé, H.J. ...
Physica. E, Low-dimensional systems & nanostructures,
04/1999, Letnik:
4, Številka:
2
Journal Article
Recenzirano
The optical properties of porous GaAs formed electrochemically on n- and p-type GaAs in HCl electrolyte are reported. The porous structure comprises GaAs crystallites ranging in size from micrometers ...to nanometers and under certain chemical conditions other transparent crystallites of As
2
O
3
and Ga
2
O
3
form. Photoluminescence (PL) measurements at 295
K reveal an “infrared” PL at
∼840
nm and a “green” PL at
∼540
nm, which could easily be seen by the naked eye in some samples. The infrared and green PL peak wavelength and intensity varied from sample to sample consistent with an assignment to quantum confinement effects in GaAs micro- and nanocrystallites, respectively.
A 50 MHz ultrasound backscatter microscope has been built to measure the acoustic properties of vascular tissues and blood over the frequency range from 35-65 MHz. High resolution (45 microns) ...ultrasound backscatter microscope images of nine femoral and eight common carotid human artery samples were made and compared with corresponding histological sections. Individual tissue layers were selected using these images for quantitative measurement of the frequency dependent backscatter. Backscatter measurements were made in each layer of an artery at two different angles of incidence: along the axis of the artery (axial direction) and at 90 degrees to this measurement radially out from the center of the artery (radial direction). Scattering was found to be higher in elastic arteries (carotid) than in the muscular arteries (femoral). The largest difference was found in the media where the average scatter (measured in the radial direction at 50 MHz) increased from 0.002 sr-1 mm-1 in muscular arteries to 0.4 sr-1 mm-1 in elastic arteries. Large differences in scattering between measurements made in the axial and radial direction were also found. Again, the largest differences were found in the media where scattering (at 50 MHz) in carotid arteries increased from 0.003 sr-1 mm-1 measured in the axial direction to 0.4 sr-1 mm-1 measured in the radial direction. The speed of sound and attenuation in the artery wall of each sample were measured. Speed of sound measurements were found to range between 1579-1628 ms-1. The average attenuation in the artery wall increased from 4 dB mm-1 at 30 MHz to 10 dB mm-1 at 60 mHz. This is higher than the attenuation measured in blood which increased from 1.6 dB mm-1 to 5 dB mm-1 over the same frequency range. The backscatter coefficient for flowing blood was measured for flow velocities up to 36 cms-1. At flow velocities below 18 cms-1 a level of scattering of 0.0005 sr-1 mm-1 (at 50 MHz) was found. An increase in scattering of 1.6 times was measured when the flow velocity was increased to 36 cms-1. All measurements were made at 37 degrees C. The relevance of these results to clinical imaging and image interpretation is discussed.
The decahaem cytochrome MtrC from
Shewanella oneidensis
MR-1 was employed as a protein electron conduit between a porous indium tin oxide electrode and redox enzymes. Using a hydrogenase and a ...fumarate reductase, MtrC was shown as a suitable and efficient diode to shuttle electrons to and from the electrode with the MtrC redox activity regulating the direction of the enzymatic reactions.
The decahaem cytochrome MtrC from
Shewanella oneidensis
MR-1 was employed as a protein diode between an indium tin oxide electrode and fumarate reductase or hydrogenase.
This paper presents the dynamic hardware plugins (DHP) architecture for implementing multiple networking applications in hardware at programmable routers. By enabling multiple applications to be ...dynamically loaded into a single hardware device, the DHP architecture provides a scalable mechanism for implementing high-performance programmable routers. The DHP architecture is presented within the context of a programmable router architecture which processes flows in both software and hardware. Implementation options are described as well as the prototype testbed at Washington University in Saint Louis which utilizes the partial reconfiguration capability of modern field programmable gate arrays.
We propose that radiological features of breast tissue provide an index of cumulative exposure to the current and past hormonal and reproductive events that influence breast cancer incidence. The ...changes in breast tissue that occur with ageing, and changes in the associated radiological features of the breast, are similar to the concept of "breast tissue ageing" proposed by Pike, and may explain features of the age-specific incidence of breast cancer, both within the population and between populations. These radiological features can be observed and measured, can be related directly to risk of breast cancer, and are likely to be of value in research into the etiology of breast cancer. Identification of the sources of variation in this radiological characteristic of the breast is likely to lead to a better understanding of the factors that cause breast cancer and to new approaches to prevention of the disease.
Strength of Silicone Breast Implants Phillips, James W; de Camara, Donna L; Lockwood, Michelle D ...
Plastic and reconstructive surgery (1963)
97, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Rupture and leakage are recognized problems associated with silicone breast implants. Data are scarce about the durability of the silicone shell, and the life span of this device is unknown.The ...purpose of this study was to investigate the strength of silicone breast implants. Thirty implant shells were subjected to mechanical testing. Twenty-nine of the shells were tested after explantation, and one unused implant served as a control to validate the testing method. Implantation time varied from 4 months to 20 years, and all shells were tested, regardless of condition. Fourteen implant shells were intact, eight were leaking, and seven were ruptured. All ruptured implants had been in place for 10 years or longer.The breaking force of all excised shell specimens ranged from 2.6 to 22.4 N (0.6 to 5.0 lb). Specimens from the control “high performance” shell required 15.5 to 25.6 N (3.5 to 5.8 lb) of force to fail. The weakest group was from thin-shelled implants between 10 and 16 years of age. More than half these specimens failed with less than 1 lb of force. The average breaking force of ruptured shell material was less than that of intact shells.A comparison of strength data in this study with manufacturers’ data suggests that breaking force is dependent on implant type, shell thickness, and implantation time, (Plast. Reconstr. Surg. 971215, 1996.)
Variations between individuals in the radiographic appearance, or mammographic pattern, of the female breast arise because of differences in the relative amounts and X-ray attenuation characteristics ...of fat and connective and epithelial tissue. Studies using quantitative methods of assessment have consistently shown these variations to be strongly related to risk of breast cancer. Individuals with extensive areas of radiologically dense breast tissue on the mammogram have been found to have a risk of breast cancer that is four to six times higher than women with little or no density. In this paper, we propose a model for the relationship of mammographic densities to risk of breast cancer. We propose that the risk of breast cancer associated with mammographically dense breast tissue is due to the combined effects of two processes: cell proliferation (mitogenesis), induced by growth factors and sex hormones and influenced by reproductive risk factors for breast cancer; and damage to the DNA of dividing cells (mutagenesis) by mutagens generated by lipid peroxidation. We review the evidence that each of these processes is associated with mammographic densities and propose further work that we believe should be done to clarify these relationships.
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