Thomas Sanford | University of Washington (original) (raw)

Papers by Thomas Sanford

Research paper thumbnail of A velocity profiler based on the principles of geomagnetic induction

Deep Sea Research, 1978

Abstraet--A technique to determine the variations of horizontal velocity between the sea surface ... more Abstraet--A technique to determine the variations of horizontal velocity between the sea surface and bottom, based on the measurement of electric currents generated by the motion of the seawater through the Earth's magnetic field, has been developed. A freely-falling Electro-Magnetic Velocity Profiler, EMVP, senses the currents as a function of depth. Velocity is inferred as the equivalent velocities required to generate the observed electric currents in the local geomagnetic field. The inferred velocity profile is relative to an unknown, but depth-independent, velocity contribution. Hence, the profiles are of the depth-variable velocity components. The device is released from the surface, falls to a preset depth or to the sea floor and returns to the surface. Both descent and ascent take about 90min in water 6000m deep. The r.m.s, velocity errors are about 1 to 2 cm s-~ at the vertical resolution of independent comparison methods, 50 m and larger. Simultaneous profiles by two identical EMVPs have r.m.s, velocity differences of less than 0.7cms -1 at a vertical resolution of 10m. A second electric measurement on the instrument yields a velocity profile within 0.3 cm s-1 r.m.s, of the first electric measurement every 10 m. A performance level of + I cm s-1 at a vertical resolution of 10 m is indicated. This level is expected in the absence of strong magnetoteiluric currents, which can produce errors as large as 10cm sduring infrequent (10 to 20 times per year) periods of strong temporal fluctuations of the geomagnetic field. Temperature, electrical conductivity, pressure, and other variables are recorded twice each second. The digitally recorded data are processed aboard ship to obtain velocity and density profiles.

Research paper thumbnail of Measurements of Gulf Stream Transport with a Towed Transport Meter (TTM2) on R/V Oceanus Cruise 216

Measurements of oceanic velocities were made with towed transport meter (TTM2) during R/V Oceanus... more Measurements of oceanic velocities were made with towed transport meter (TTM2) during R/V Oceanus cruise 216 from 30 November to 13 December 1989 to observe surface and subsurface flows under GEOSAT tracks between the continental United States and Bermuda. TTM2, a single-axis version of the TTM electromagnetic sensor package, determines the motionally induced electric field parallel to the ship's heading. The electric field is denoted as F(sub 2) nu - nu (-) where F(sub 2) is the vertical component of the earth's magnetic field, nu is the surface velocity component of the ocean normal to the ship's heading, and nu (-) is the conductivity-weighted, vertically averaged velocity component normal to the ship's heading. The electric field measurement is combined with vessel motion determined form LORAN-C to obtain nu (-). Corrections were made for electrical conductivity factors and vessel windage effects to yield continuous determination of the component nu (-) normal to...

Research paper thumbnail of The Momentum Balance at the Surface Reflection of an Internal Tide Beam

... nonacceleration theorems. Page 3. 3 1. Introduction While the deposition of internal-wave mom... more ... nonacceleration theorems. Page 3. 3 1. Introduction While the deposition of internal-wave momentum-flux is known to be important to the atmospheric mean winds (Eliassen and Palm 1960) for a number of processes including the quasi-biennial oscillation (Lindzen and ...

Research paper thumbnail of Associated multiplicities in proton-proton collisions with a charged hadron atX=0 at the CERN ISR

Research paper thumbnail of Spectral characteristics of velocity and vorticity fluxes in an unstratified turbulent boundary layer

Wavenumber spectral characteristics of the velocity and vorticity fluxes in an unstratified turbu... more Wavenumber spectral characteristics of the velocity and vorticity fluxes in an unstratified turbulent boundary layer are presented. The observed vertical and streamwise velocity spectra agree with empirical forms found in the atmospheric boundary layer. Spectral ratios of 4/3 between the vertical and streamwise velocity spectra and the agreement between the observed vorticity flux quad spectrum and that of isotropic turbulence suggest local isotropy at scales smaller than Z. The normalized cospectrum of the momentum flux agrees remarkably well with the empirical form found in the atmospheric boundary layer. In the inertial subrange the momentum flux cospectrum shows a clear spectral slope of -7/3. The observed composite vorticity flux cospectrum has most of its variance at the streamwise wavenumber k x =(1-10) Z −1 and has a spectral slope of -7/3 in the inertial subrange. The -7/3 spectral slope is consistent with a dimensional argument, assuming that the vorticity flux cospectrum is proportional to the gradient of the mean vorticity, and depends on the turbulence kinetic energy dissipation rate ε and the wavenumber. A model turbulent vorticity flux cospectrum is constructed based on the shape of observed spectra, a -7/3 spectral slope in the inertial subrange, and the similarity scaling of the vorticity flux in an unstratified turbulent boundary layer. The turbulence vorticity flux is directly related to the divergence of turbulence momentum flux, the force exerted by turbulence on the mean flow. Therefore our proposed empirical cospectral form of the vorticity fluxes might be useful for turbulence parameterization in numerical models.

Research paper thumbnail of Ocean mixing studied near Hawaiian Ridge

Eos, Transactions American Geophysical Union, 2000

Research paper thumbnail of Synoptic sections of the Denmark Strait Overflow

Geophysical Research Letters, 2001

We report on a rapid high-resolution survey of the Denmark Strait overflow (DSO) as it crosses th... more We report on a rapid high-resolution survey of the Denmark Strait overflow (DSO) as it crosses the sill, the first such program to incorporate full-water-column velocity profiles in addition to conventional hydrographic measurements. Seven transects with expendable profilers over the course of one week are used to estimate volume transport as a function of density. Our observations reveal the presence of a strongly barotropic flow associated with the nearly-vertical front dividing the Arctic and Atlantic waters. The sevensection mean transport of water denser than er0 = 27.8 is 2.7 + 0.6 Sv, while the mean transport of water colder than 2.0øC is 3.8 + 0.8 Sv. Although this is larger than the 2.9 Sv of 0 • 2øC water measured by a 1973 current meter array, we find that a sampling of our sections equivalent to the extent of that array also measures 2.9Sv of cold water. Both the structure and magnitude of the measured flow are reproduced well by a high-resolution numerical model of buoyancy-driven exchange with realistic topography.

Research paper thumbnail of From Tides to Mixing Along the

The cascade from tides to turbulence has been hypothesized to serve as a major energy pathway for... more The cascade from tides to turbulence has been hypothesized to serve as a major energy pathway for ocean mixing. We investigated this cascade along the Hawaiian Ridge using observations and numerical models. A divergence of internal tidal energy flux observed at the ridge agrees with the predictions of internal tide models. Large internal tidal waves with peak-to-peak amplitudes of up

Research paper thumbnail of Internal Tide Radiation from Mendocino Escarpment

Journal of Physical Oceanography, 2003

Strong semidiurnal internal tides are observed near Mendocino Escarpment in full-depth profile ti... more Strong semidiurnal internal tides are observed near Mendocino Escarpment in full-depth profile time series of velocity, temperature, and salinity. Velocity and density profiles are combined to estimate the internal tide energy flux. Divergence of this flux demonstrates that its source ...

Research paper thumbnail of Advanced Foam Target Component Fabrication as Applied the Sandia Z Pinch Experiments

The Sandia pulsed power machine, Z, has developed into a unique test bed with unique targets, man... more The Sandia pulsed power machine, Z, has developed into a unique test bed with unique targets, many of which incorporate foam components. These foam components must be very low density (5 - 14 mg/cm3), uniform and must meet tight dimensional tolerance. The experiments can also require an embedded diagnostic or capsule. To produce TPX (poly 4-methyl-1-pentene) foam of the required

Research paper thumbnail of Frameless Optical Computer-Aided Tracking of a Microscope for Otorhinology and Skull Base Surgery

To integrate a digitally controlled operating microscope without a laser autofocus system into a ... more To integrate a digitally controlled operating microscope without a laser autofocus system into a frameless optical computer-aided surgery system and to test the accuracy and usability of this system in otorhinological surgery. Experimental study and case series. Department of Oto-Rhino-Laryngology, Head and Neck Surgery, Inselspital, and the Maurice E. Müller Institute for Biomechanics, University of Bern, Bern, Switzerland. Eight computer-aided microscopic surgical procedures were performed between January and October 2000 on patients with various diseases of the anterior and lateral skull base. The practical accuracy of the navigated microscope on the lateral side of a cadaver skull was 2.27 +/- 0.25 mm and on the anterior side of the same skull was 2.07 +/- 0.35 mm. In all 8 cases of computer-aided microscopic surgery, no complications occurred. Clinical inaccuracy was 2 to 3 mm. Integration of a low-cost, non-laser autofocus microscope into our computer-aided surgery system was successfully performed and offers surgeons the ability to combine the precise optics of the operating microscope with the localization power of a computer-aided system.

Research paper thumbnail of Age Dependence of Cellular Properties of Human Septal Cartilage: Implications for Tissue Engineering

The persistent need for cartilage replacement material in head and neck surgery has led to novel ... more The persistent need for cartilage replacement material in head and neck surgery has led to novel cell culture methods developed to engineer cartilage. Currently, there is no consensus on an optimal source of cells for these endeavors. To evaluate human nasal cartilage as a potential source of chondrocytes and to determine the effect of donor age on cellular and proliferation characteristics. Nasal cartilage specimens were obtained after reconstructive surgery from 46 patients ranging in age from 15 to 60 years. Specimens were weighed and chondrocytes were isolated by digestion in 0.2% collagenase type II for 16 hours. Cells were maintained in primary cultures until confluency, then seeded onto polylactic acid-polyglycolic acid scaffolds. Seeding efficiency was determined by quantification of DNA content of seeded constructs by means of Hoechst dye 33258. Specimen weights, cell yields, cell content, and doubling time were also measured and correlated to donor age. Mean (+/-SD) cartilage mass obtained (648 +/- 229 mg) is higher than from typical biopsy specimens of auricular cartilage, and the cellular characteristics show a higher proliferation rate than auricular chondrocytes. Cell yield increased with age, while doubling time decreased with age in samples from patients ranging from 15 to 60 years old. The use of nasal septal cartilage as a source of cells for tissue engineering may be valid over a wide range of patient ages. The large tissue yield and consequent cell yield make this tissue a potential starting source of chondrocytes for large-volume tissue-engineered implants.

Research paper thumbnail of From Tides to Mixing Along the Hawaiian Ridge

Science, 2003

The following resources related to this article are available online at

Research paper thumbnail of Reduced mixing from the breaking of internal waves in equatorial waters

Nature, 2003

In the oceans, heat, salt and nutrients are redistributed much more easily within water masses of... more In the oceans, heat, salt and nutrients are redistributed much more easily within water masses of uniform density than across surfaces separating waters of different densities. But the magnitude and distribution of mixing across density surfaces are also important for the Earth's climate as well as the concentrations of organisms. Most of this mixing occurs where internal waves break, overturning the density stratification of the ocean and creating patches of turbulence. Predictions of the rate at which internal waves dissipate were confirmed earlier at mid-latitudes. Here we present observations of temperature and velocity fluctuations in the Pacific and Atlantic oceans between 42 degrees N and 2 degrees S to extend that result to equatorial regions. We find a strong latitude dependence of dissipation in accordance with the predictions. In our observations, dissipation rates and accompanying mixing across density surfaces near the Equator are less than 10% of those at mid-latitudes for a similar background of internal waves. Reduced mixing close to the Equator will have to be taken into account in numerical simulations of ocean dynamics--for example, in climate change experiments.

Research paper thumbnail of IMPACT OF ISCHEMIA AND TISSUE PROCUREMENT CONDITIONS ON GENE EXPRESSION IN RENAL CELL CARCINOMA

The Journal of Urology, 2009

Research paper thumbnail of An Estimate of Tidal Energy Lost to Turbulence at the Hawaiian Ridge

Journal of Physical Oceanography, 2006

An integrated analysis of turbulence observations from four unique instrument platforms obtained ... more An integrated analysis of turbulence observations from four unique instrument platforms obtained over the Hawaiian Ridge leads to an assessment of the vertical, cross-ridge, and along-ridge structure of turbulence dissipation rate and diffusivity. The diffusivity near the seafloor was, on average, 15 times that in the midwater column. At 1000-m depth, the diffusivity atop the ridge was 30 times that 10 km off the ridge, decreasing to background oceanic values by 60 km. A weak (factor of 2) spring-neap variation in dissipation was observed. The observations also suggest a kinematic relationship between the energy in the semidiurnal internal tide (E ) and the depth-integrated dissipation (D), such that D ϳ E 1Ϯ0.5 at sites along the ridge. This kinematic relationship is supported by combining a simple knife-edge model to estimate internal tide generation, with wave-wave interaction time scales to estimate dissipation. The along-ridge kinematic relationship and the observed vertical and cross-ridge structures are used to extrapolate the relatively sparse observations along the length of the ridge, giving an estimate of 3 Ϯ 1.5 GW of tidal energy lost to turbulence dissipation within 60 km of the ridge. This is roughly 15% of the energy estimated to be lost from the barotropic tide.

Research paper thumbnail of Descent and Modification of the Overflow Plume in the Denmark Strait*

Journal of Physical Oceanography, 2003

... J. Geophys. Res., 99, 12319–12341. Dickson, RR, J. Lazier, J. Meincke, P. Rhines, and J. Swif... more ... J. Geophys. Res., 99, 12319–12341. Dickson, RR, J. Lazier, J. Meincke, P. Rhines, and J. Swift, 1996: Long-term coordinated changes in the convective activity of the North Atlantic. Progress in Oceanography, Vol. 38, Pergamon, 241–295. ...

Research paper thumbnail of Internal Tides and Turbulence along the 3000-m Isobath of the Hawaiian Ridge

Journal of Physical Oceanography, 2006

Full-depth velocity and density profiles taken along the 3000-m isobath characterize the semidiur... more Full-depth velocity and density profiles taken along the 3000-m isobath characterize the semidiurnal internal tide and bottom-intensified turbulence along the Hawaiian Ridge. Observations reveal baroclinic energy fluxes of 21 Ϯ 5 kW m Ϫ1 radiating from French Frigate Shoals, 17 Ϯ 2.5 kW m Ϫ1 from Kauai Channel west of Oahu, and 13 Ϯ 3.5 kW m Ϫ1 from west of Nihoa Island. Weaker fluxes of 1-4 Ϯ 2 kW m Ϫ1 radiate from the region near Necker Island and east of Nihoa Island. Observed off-ridge energy fluxes generally agree to within a factor of 2 with those produced by a tidally forced numerical model. Average turbulent diapycnal diffusivity K is (0.5-1) ϫ 10 Ϫ4 m 2 s -1 above 2000 m, increasing exponentially to 20 ϫ 10 Ϫ4 m 2 s -1 near the bottom. Microstructure values agree well with those inferred from a finescale internal wave-based parameterization. A linear relationship between the vertically integrated energy flux and vertically integrated turbulent dissipation rate implies that dissipative length scales for the radiating internal tide exceed 1000 km.

Research paper thumbnail of Structure of the Baroclinic Tide Generated at Kaena Ridge, Hawaii

Journal of Physical Oceanography, 2006

Repeat transects of full-depth density and velocity are used to quantify generation and radiation... more Repeat transects of full-depth density and velocity are used to quantify generation and radiation of the semidiurnal internal tide from Kaena Ridge, Hawaii. A 20-km-long transect was sampled every 3 h using expendable current profilers and the absolute velocity profiler. Phase and amplitude of the baroclinic velocity, pressure, and vertical displacement were computed, as was the energy flux. Large barotropically induced isopycnal heaving and strong baroclinic energy-flux divergence are observed on the steep flanks of the ridge where upward and downward beams radiate off ridge. Directly above Kaena Ridge, strong kinetic energy density and weak net energy flux are argued to be a horizontally standing wave. The phasing of velocity and vertical displacements is consistent with this interpretation. Results compare favorably with the Merrifield and Holloway model.

Research paper thumbnail of The Depth Dependence of Shear Finestructure off Point Arena and near Pioneer Seamount

Journal of Physical Oceanography, 1992

ABSTRACT High-resolution velocity profiles to depths of 1600 m were collected off point Arena and... more ABSTRACT High-resolution velocity profiles to depths of 1600 m were collected off point Arena and near Pioneer Seamount, California. They reveal shear increasing with depth relative to the GM76 model spectrum. Using an empirical parameterization found to collapse microstructure data the "dissipation rate" and "eddy diffusivity" are estimated from these shears. Away from the seamount, dissipation rates are depth invariant at 3-6 (X 10(-10) W kg-1). As a result, the eddy diffusivity increases with depth, approaching 0.2-0.3(X 10(-4) m2 s-1) below 1200-m depth. This may be a result of the proximity of the continental rise and sloping topography, but there is evidence that it is a general result for the abyssal ocean. Immediately above the seamount, there is a 300-400-m thick layer of elevated shear, corresponding to an eddy diffusivity of approximately 10(-4) m2 s-1. If this localized enhancement is typical of seamounts, topographically induced mixing is insufficient to significantly modify global average mixing.

Research paper thumbnail of A velocity profiler based on the principles of geomagnetic induction

Deep Sea Research, 1978

Abstraet--A technique to determine the variations of horizontal velocity between the sea surface ... more Abstraet--A technique to determine the variations of horizontal velocity between the sea surface and bottom, based on the measurement of electric currents generated by the motion of the seawater through the Earth's magnetic field, has been developed. A freely-falling Electro-Magnetic Velocity Profiler, EMVP, senses the currents as a function of depth. Velocity is inferred as the equivalent velocities required to generate the observed electric currents in the local geomagnetic field. The inferred velocity profile is relative to an unknown, but depth-independent, velocity contribution. Hence, the profiles are of the depth-variable velocity components. The device is released from the surface, falls to a preset depth or to the sea floor and returns to the surface. Both descent and ascent take about 90min in water 6000m deep. The r.m.s, velocity errors are about 1 to 2 cm s-~ at the vertical resolution of independent comparison methods, 50 m and larger. Simultaneous profiles by two identical EMVPs have r.m.s, velocity differences of less than 0.7cms -1 at a vertical resolution of 10m. A second electric measurement on the instrument yields a velocity profile within 0.3 cm s-1 r.m.s, of the first electric measurement every 10 m. A performance level of + I cm s-1 at a vertical resolution of 10 m is indicated. This level is expected in the absence of strong magnetoteiluric currents, which can produce errors as large as 10cm sduring infrequent (10 to 20 times per year) periods of strong temporal fluctuations of the geomagnetic field. Temperature, electrical conductivity, pressure, and other variables are recorded twice each second. The digitally recorded data are processed aboard ship to obtain velocity and density profiles.

Research paper thumbnail of Measurements of Gulf Stream Transport with a Towed Transport Meter (TTM2) on R/V Oceanus Cruise 216

Measurements of oceanic velocities were made with towed transport meter (TTM2) during R/V Oceanus... more Measurements of oceanic velocities were made with towed transport meter (TTM2) during R/V Oceanus cruise 216 from 30 November to 13 December 1989 to observe surface and subsurface flows under GEOSAT tracks between the continental United States and Bermuda. TTM2, a single-axis version of the TTM electromagnetic sensor package, determines the motionally induced electric field parallel to the ship's heading. The electric field is denoted as F(sub 2) nu - nu (-) where F(sub 2) is the vertical component of the earth's magnetic field, nu is the surface velocity component of the ocean normal to the ship's heading, and nu (-) is the conductivity-weighted, vertically averaged velocity component normal to the ship's heading. The electric field measurement is combined with vessel motion determined form LORAN-C to obtain nu (-). Corrections were made for electrical conductivity factors and vessel windage effects to yield continuous determination of the component nu (-) normal to...

Research paper thumbnail of The Momentum Balance at the Surface Reflection of an Internal Tide Beam

... nonacceleration theorems. Page 3. 3 1. Introduction While the deposition of internal-wave mom... more ... nonacceleration theorems. Page 3. 3 1. Introduction While the deposition of internal-wave momentum-flux is known to be important to the atmospheric mean winds (Eliassen and Palm 1960) for a number of processes including the quasi-biennial oscillation (Lindzen and ...

Research paper thumbnail of Associated multiplicities in proton-proton collisions with a charged hadron atX=0 at the CERN ISR

Research paper thumbnail of Spectral characteristics of velocity and vorticity fluxes in an unstratified turbulent boundary layer

Wavenumber spectral characteristics of the velocity and vorticity fluxes in an unstratified turbu... more Wavenumber spectral characteristics of the velocity and vorticity fluxes in an unstratified turbulent boundary layer are presented. The observed vertical and streamwise velocity spectra agree with empirical forms found in the atmospheric boundary layer. Spectral ratios of 4/3 between the vertical and streamwise velocity spectra and the agreement between the observed vorticity flux quad spectrum and that of isotropic turbulence suggest local isotropy at scales smaller than Z. The normalized cospectrum of the momentum flux agrees remarkably well with the empirical form found in the atmospheric boundary layer. In the inertial subrange the momentum flux cospectrum shows a clear spectral slope of -7/3. The observed composite vorticity flux cospectrum has most of its variance at the streamwise wavenumber k x =(1-10) Z −1 and has a spectral slope of -7/3 in the inertial subrange. The -7/3 spectral slope is consistent with a dimensional argument, assuming that the vorticity flux cospectrum is proportional to the gradient of the mean vorticity, and depends on the turbulence kinetic energy dissipation rate ε and the wavenumber. A model turbulent vorticity flux cospectrum is constructed based on the shape of observed spectra, a -7/3 spectral slope in the inertial subrange, and the similarity scaling of the vorticity flux in an unstratified turbulent boundary layer. The turbulence vorticity flux is directly related to the divergence of turbulence momentum flux, the force exerted by turbulence on the mean flow. Therefore our proposed empirical cospectral form of the vorticity fluxes might be useful for turbulence parameterization in numerical models.

Research paper thumbnail of Ocean mixing studied near Hawaiian Ridge

Eos, Transactions American Geophysical Union, 2000

Research paper thumbnail of Synoptic sections of the Denmark Strait Overflow

Geophysical Research Letters, 2001

We report on a rapid high-resolution survey of the Denmark Strait overflow (DSO) as it crosses th... more We report on a rapid high-resolution survey of the Denmark Strait overflow (DSO) as it crosses the sill, the first such program to incorporate full-water-column velocity profiles in addition to conventional hydrographic measurements. Seven transects with expendable profilers over the course of one week are used to estimate volume transport as a function of density. Our observations reveal the presence of a strongly barotropic flow associated with the nearly-vertical front dividing the Arctic and Atlantic waters. The sevensection mean transport of water denser than er0 = 27.8 is 2.7 + 0.6 Sv, while the mean transport of water colder than 2.0øC is 3.8 + 0.8 Sv. Although this is larger than the 2.9 Sv of 0 • 2øC water measured by a 1973 current meter array, we find that a sampling of our sections equivalent to the extent of that array also measures 2.9Sv of cold water. Both the structure and magnitude of the measured flow are reproduced well by a high-resolution numerical model of buoyancy-driven exchange with realistic topography.

Research paper thumbnail of From Tides to Mixing Along the

The cascade from tides to turbulence has been hypothesized to serve as a major energy pathway for... more The cascade from tides to turbulence has been hypothesized to serve as a major energy pathway for ocean mixing. We investigated this cascade along the Hawaiian Ridge using observations and numerical models. A divergence of internal tidal energy flux observed at the ridge agrees with the predictions of internal tide models. Large internal tidal waves with peak-to-peak amplitudes of up

Research paper thumbnail of Internal Tide Radiation from Mendocino Escarpment

Journal of Physical Oceanography, 2003

Strong semidiurnal internal tides are observed near Mendocino Escarpment in full-depth profile ti... more Strong semidiurnal internal tides are observed near Mendocino Escarpment in full-depth profile time series of velocity, temperature, and salinity. Velocity and density profiles are combined to estimate the internal tide energy flux. Divergence of this flux demonstrates that its source ...

Research paper thumbnail of Advanced Foam Target Component Fabrication as Applied the Sandia Z Pinch Experiments

The Sandia pulsed power machine, Z, has developed into a unique test bed with unique targets, man... more The Sandia pulsed power machine, Z, has developed into a unique test bed with unique targets, many of which incorporate foam components. These foam components must be very low density (5 - 14 mg/cm3), uniform and must meet tight dimensional tolerance. The experiments can also require an embedded diagnostic or capsule. To produce TPX (poly 4-methyl-1-pentene) foam of the required

Research paper thumbnail of Frameless Optical Computer-Aided Tracking of a Microscope for Otorhinology and Skull Base Surgery

To integrate a digitally controlled operating microscope without a laser autofocus system into a ... more To integrate a digitally controlled operating microscope without a laser autofocus system into a frameless optical computer-aided surgery system and to test the accuracy and usability of this system in otorhinological surgery. Experimental study and case series. Department of Oto-Rhino-Laryngology, Head and Neck Surgery, Inselspital, and the Maurice E. Müller Institute for Biomechanics, University of Bern, Bern, Switzerland. Eight computer-aided microscopic surgical procedures were performed between January and October 2000 on patients with various diseases of the anterior and lateral skull base. The practical accuracy of the navigated microscope on the lateral side of a cadaver skull was 2.27 +/- 0.25 mm and on the anterior side of the same skull was 2.07 +/- 0.35 mm. In all 8 cases of computer-aided microscopic surgery, no complications occurred. Clinical inaccuracy was 2 to 3 mm. Integration of a low-cost, non-laser autofocus microscope into our computer-aided surgery system was successfully performed and offers surgeons the ability to combine the precise optics of the operating microscope with the localization power of a computer-aided system.

Research paper thumbnail of Age Dependence of Cellular Properties of Human Septal Cartilage: Implications for Tissue Engineering

The persistent need for cartilage replacement material in head and neck surgery has led to novel ... more The persistent need for cartilage replacement material in head and neck surgery has led to novel cell culture methods developed to engineer cartilage. Currently, there is no consensus on an optimal source of cells for these endeavors. To evaluate human nasal cartilage as a potential source of chondrocytes and to determine the effect of donor age on cellular and proliferation characteristics. Nasal cartilage specimens were obtained after reconstructive surgery from 46 patients ranging in age from 15 to 60 years. Specimens were weighed and chondrocytes were isolated by digestion in 0.2% collagenase type II for 16 hours. Cells were maintained in primary cultures until confluency, then seeded onto polylactic acid-polyglycolic acid scaffolds. Seeding efficiency was determined by quantification of DNA content of seeded constructs by means of Hoechst dye 33258. Specimen weights, cell yields, cell content, and doubling time were also measured and correlated to donor age. Mean (+/-SD) cartilage mass obtained (648 +/- 229 mg) is higher than from typical biopsy specimens of auricular cartilage, and the cellular characteristics show a higher proliferation rate than auricular chondrocytes. Cell yield increased with age, while doubling time decreased with age in samples from patients ranging from 15 to 60 years old. The use of nasal septal cartilage as a source of cells for tissue engineering may be valid over a wide range of patient ages. The large tissue yield and consequent cell yield make this tissue a potential starting source of chondrocytes for large-volume tissue-engineered implants.

Research paper thumbnail of From Tides to Mixing Along the Hawaiian Ridge

Science, 2003

The following resources related to this article are available online at

Research paper thumbnail of Reduced mixing from the breaking of internal waves in equatorial waters

Nature, 2003

In the oceans, heat, salt and nutrients are redistributed much more easily within water masses of... more In the oceans, heat, salt and nutrients are redistributed much more easily within water masses of uniform density than across surfaces separating waters of different densities. But the magnitude and distribution of mixing across density surfaces are also important for the Earth's climate as well as the concentrations of organisms. Most of this mixing occurs where internal waves break, overturning the density stratification of the ocean and creating patches of turbulence. Predictions of the rate at which internal waves dissipate were confirmed earlier at mid-latitudes. Here we present observations of temperature and velocity fluctuations in the Pacific and Atlantic oceans between 42 degrees N and 2 degrees S to extend that result to equatorial regions. We find a strong latitude dependence of dissipation in accordance with the predictions. In our observations, dissipation rates and accompanying mixing across density surfaces near the Equator are less than 10% of those at mid-latitudes for a similar background of internal waves. Reduced mixing close to the Equator will have to be taken into account in numerical simulations of ocean dynamics--for example, in climate change experiments.

Research paper thumbnail of IMPACT OF ISCHEMIA AND TISSUE PROCUREMENT CONDITIONS ON GENE EXPRESSION IN RENAL CELL CARCINOMA

The Journal of Urology, 2009

Research paper thumbnail of An Estimate of Tidal Energy Lost to Turbulence at the Hawaiian Ridge

Journal of Physical Oceanography, 2006

An integrated analysis of turbulence observations from four unique instrument platforms obtained ... more An integrated analysis of turbulence observations from four unique instrument platforms obtained over the Hawaiian Ridge leads to an assessment of the vertical, cross-ridge, and along-ridge structure of turbulence dissipation rate and diffusivity. The diffusivity near the seafloor was, on average, 15 times that in the midwater column. At 1000-m depth, the diffusivity atop the ridge was 30 times that 10 km off the ridge, decreasing to background oceanic values by 60 km. A weak (factor of 2) spring-neap variation in dissipation was observed. The observations also suggest a kinematic relationship between the energy in the semidiurnal internal tide (E ) and the depth-integrated dissipation (D), such that D ϳ E 1Ϯ0.5 at sites along the ridge. This kinematic relationship is supported by combining a simple knife-edge model to estimate internal tide generation, with wave-wave interaction time scales to estimate dissipation. The along-ridge kinematic relationship and the observed vertical and cross-ridge structures are used to extrapolate the relatively sparse observations along the length of the ridge, giving an estimate of 3 Ϯ 1.5 GW of tidal energy lost to turbulence dissipation within 60 km of the ridge. This is roughly 15% of the energy estimated to be lost from the barotropic tide.

Research paper thumbnail of Descent and Modification of the Overflow Plume in the Denmark Strait*

Journal of Physical Oceanography, 2003

... J. Geophys. Res., 99, 12319–12341. Dickson, RR, J. Lazier, J. Meincke, P. Rhines, and J. Swif... more ... J. Geophys. Res., 99, 12319–12341. Dickson, RR, J. Lazier, J. Meincke, P. Rhines, and J. Swift, 1996: Long-term coordinated changes in the convective activity of the North Atlantic. Progress in Oceanography, Vol. 38, Pergamon, 241–295. ...

Research paper thumbnail of Internal Tides and Turbulence along the 3000-m Isobath of the Hawaiian Ridge

Journal of Physical Oceanography, 2006

Full-depth velocity and density profiles taken along the 3000-m isobath characterize the semidiur... more Full-depth velocity and density profiles taken along the 3000-m isobath characterize the semidiurnal internal tide and bottom-intensified turbulence along the Hawaiian Ridge. Observations reveal baroclinic energy fluxes of 21 Ϯ 5 kW m Ϫ1 radiating from French Frigate Shoals, 17 Ϯ 2.5 kW m Ϫ1 from Kauai Channel west of Oahu, and 13 Ϯ 3.5 kW m Ϫ1 from west of Nihoa Island. Weaker fluxes of 1-4 Ϯ 2 kW m Ϫ1 radiate from the region near Necker Island and east of Nihoa Island. Observed off-ridge energy fluxes generally agree to within a factor of 2 with those produced by a tidally forced numerical model. Average turbulent diapycnal diffusivity K is (0.5-1) ϫ 10 Ϫ4 m 2 s -1 above 2000 m, increasing exponentially to 20 ϫ 10 Ϫ4 m 2 s -1 near the bottom. Microstructure values agree well with those inferred from a finescale internal wave-based parameterization. A linear relationship between the vertically integrated energy flux and vertically integrated turbulent dissipation rate implies that dissipative length scales for the radiating internal tide exceed 1000 km.

Research paper thumbnail of Structure of the Baroclinic Tide Generated at Kaena Ridge, Hawaii

Journal of Physical Oceanography, 2006

Repeat transects of full-depth density and velocity are used to quantify generation and radiation... more Repeat transects of full-depth density and velocity are used to quantify generation and radiation of the semidiurnal internal tide from Kaena Ridge, Hawaii. A 20-km-long transect was sampled every 3 h using expendable current profilers and the absolute velocity profiler. Phase and amplitude of the baroclinic velocity, pressure, and vertical displacement were computed, as was the energy flux. Large barotropically induced isopycnal heaving and strong baroclinic energy-flux divergence are observed on the steep flanks of the ridge where upward and downward beams radiate off ridge. Directly above Kaena Ridge, strong kinetic energy density and weak net energy flux are argued to be a horizontally standing wave. The phasing of velocity and vertical displacements is consistent with this interpretation. Results compare favorably with the Merrifield and Holloway model.

Research paper thumbnail of The Depth Dependence of Shear Finestructure off Point Arena and near Pioneer Seamount

Journal of Physical Oceanography, 1992

ABSTRACT High-resolution velocity profiles to depths of 1600 m were collected off point Arena and... more ABSTRACT High-resolution velocity profiles to depths of 1600 m were collected off point Arena and near Pioneer Seamount, California. They reveal shear increasing with depth relative to the GM76 model spectrum. Using an empirical parameterization found to collapse microstructure data the "dissipation rate" and "eddy diffusivity" are estimated from these shears. Away from the seamount, dissipation rates are depth invariant at 3-6 (X 10(-10) W kg-1). As a result, the eddy diffusivity increases with depth, approaching 0.2-0.3(X 10(-4) m2 s-1) below 1200-m depth. This may be a result of the proximity of the continental rise and sloping topography, but there is evidence that it is a general result for the abyssal ocean. Immediately above the seamount, there is a 300-400-m thick layer of elevated shear, corresponding to an eddy diffusivity of approximately 10(-4) m2 s-1. If this localized enhancement is typical of seamounts, topographically induced mixing is insufficient to significantly modify global average mixing.