Non-Invasive in Vivo Quantification of Directional Dependent Variation in Mechanical Properties for Human Skin

Skin is the body’s largest organ, and it shows non-linear and anisotropic behavior under the deformation. This behavior of the skin is due to the waviness and preferred orientation (in a particular direction) of collagen fibers. This preferred orientation of collagen fibers results in natural pre-tension and anisotropy of the skin. The knowledge of natural skin pre-tension and anisotropy is essential during incisions and surgery. The available suction-based devices quantify the anisotropy through the displacement field and cannot measure the stress-strain relation in particular directions. Therefore, in the current study, an in vivo full-field measurement suction apparatus was developed to measure the stress and strain of skin in all planar directions through a single experiment. First, this apparatus was tested on silicone substrates of known properties, and then it was used to test the skin of 12 human forearms. Further, to check the effect of hand stability on the measurements, the obtained results of the skin were compared with the results of a standard test performed in the same skin using a steady setup. The consistency between these two results confirms that the stability of the hand does not influence the measurements of skin properties. Furthermore, using the developed apparatus, the skin’s anisotropy and its relation with the Kraissl’s lines orientation was quantified by measuring the toe and linear moduli at an interval of one degree. The minimum and maximum values of the toe and linear moduli were 0.52 ± 0.09 and 0.59 ± 0.11 MPa, and 3.09 ± 0.47 and 5.52 ± 1.13 MPa, respectively. Also, the direction of maximum moduli was found almost similar to Kraissl’s lines’ orientation. These results confirm the contribution of skin pre-tension on the anisotropy of the skin. The present apparatus mimics the tissue expansion procedure, where observation of the test may be helpful in the selection of size and shape of the expander.

Analysis of the liquids composition by the sound produced by their heating

When a liquid is heated and the power of the heater is high enough (about 1MW/m2), bubbles are formed at the surface of the heater. Their expansion and collapse are the source of a specific sound, known to everybody who uses a kettle to prepare water for tea or coffee. The main goal of this study is to investigate whether it is possible to judge about the composition of the heated liquid by this sound. A specialized experimental set up is assembled and a systematic study of all known factors, influencing the sound is carried out. It is found out that the most crucial parts of the set up are the container for the liquids and the heater. They are discussed in detail and considerations for further improvements are given. It is demonstrated that with the present apparatus it is possible to detect changes in the sound spectrum when changing the composition of the liquid. For example, one can distinguish between pure water and water with less than 0.1% of ethanol. Along with admixtures of different alcohols, experiments with a soap solution in water and carbonated water are performed.

Pengukuran solubilitas n-amylalkohol dalam poly (n-butyl methacrylate) dan polyisobutylene menggunakan metode piezoelectric-quartz crystal microbalance sorption

The Piezoelectric Quartz Crystal Microbalance (QCM) method was used to measure the solubilities of n-amylalcohol in poly (n-butyl methac1ylate) and polyisobutylene at temperatures of 333.15 K, 353.15 K and 353.15 K. The crystals used were 5 MHz, AT-Cut, 5.5 mm in diameter and 0.3 mm in thick. Reliability of the measurements was comfirmed by comparing the present data with the literature data for the system of benzene-polyisobutylene at temperature 338.15K. The solubilities n-amyl alcohol in polyisobutylene were undectedable in the range of temperature experiments by the present apparatus because of the low solubility. For the solubilities of n-amyl alcohol in ploy (n-butyl methacryalate) the higher temperature, the lower solubility and the experimental data could be correlated by the UNIQUAC equation with average absolute deviation between experimental and calculated solvent activities of 3.8%. Keywords: Solubility, Quartz Crystal Microbalance, Solvent, Polymer AbstrakDalam penelitian ini, metode Piezoelectric Quartz Crystal Microbalance (QCM) digunakan untuk mengukur kelarutan pelarut n-amylalkohol dalam polimer poly (n-butyl methacrylate) dan polyisobutylene pada temperatur 333,15 K, 343,15 K dan 353,15 K. Kristal yang digunakan adalah jenis AT-Cut 5 MHz, diameter 5,5 mm dan ketebalan 0,3 mm. Reliabilitas dari pengukuran di tes dengan membandingkan hasil pengukuran dengan data literatur untuk sistem benzene­polyisobutylene pada temperatur 338, I 5K. Kelarutan n-amyl alkohol dalam polyisobutylene tidak dapat terdeteksi pada range temperatur eksperimen dengan peralatan yang ada karena kelarutannya rendah. Untuk kelarutan n-amylalkohol dalam poly(n-butyl methacrylate), semakin besar suhu, kelarutannya semakin rendah dan data eksperimen dapat dikorelasikan menggunakan persamaan UNIQUAC dengan rata-rata deviasi ahsolut sebesar 3,8%.Kata Kunci: Kelarutan, Quartz Crystal Microbalance, Pelarut, Polimer

Measurement of Wavelength-Dependent Complex Refractive Index of Transparent and Absorbing Liquids by a Multifunction Reflectometer

We have modified a recently developed reflectometer so that surface plasmon resonance (SPR) sensing is now possible. Thus, the complex refractive index of liquids can be obtained at a desired wavelength (the existing setup allows the use of the visible-NIR spectral range) using both the SPR and conventional measurement modes of the reflectometer. The multifunction operation of the present apparatus offers possibilities for off- and on-line industrial inspection of liquids.

Experimental Study of Quantum Structures in Solids

The object of the experiment is to measure electron binding energy spectra in solids at a series of selected bound electron momenta. The present apparatus is based on developments in atomic and molecular spectroscopy and uses a 10 keY electron beam incident on a thin (80 A) amorphous carbon film. The exit electrons in the (e,2e) reaction are studied in a symmetric coplanar geometry using hemispherical analysers and position-sensitive detectors. The resultant coincidence count rate is proportional to the probability of finding a target electron with a given binding energy and momentum. Data were obtained with binding energies from 0 to 40 eV with momentum as parameter. Contributions from the rr and u bands are clearly demonstrated. Future investigations in a new experimental system will be devoted to single crystals of metals, semiconductors and macro-molecules.

Induction Electrohydrodynamic Pump in a Vertical Configuration: Part 2—Experimental Study

An induction electrohydrodynamic (EHD) pump in axisymmetric, vertical configuration was designed and built. The flow rates were measured for various temperature profiles and several values of frequency, voltage, wavelength, and electric conductivity. The experimental data are generally in good agreement with the theoretical model presented in Part 1. With the present apparatus at relatively low voltages, velocities four times higher than natural circulation velocity are easily obtained. The external pressure load and entrance temperature profile play important roles on the operation of the pump and must be considered carefully in the design.

Automated temperature control system for vagal cooling

An automated cooling system for vagal cold blockade was developed. A simple electronic circuit is described that enabled regulation of the steady-state nerve or circulant temperature to within +/- 0.1 degree C by alternating the cold circulant between low and high flows (10 and 350 ml/min, respectively). The 90% rise time ranged from 15 to 40 s depending on the desired steady state and the surrounding temperatures. The present apparatus can be conveniently and safely used, especially for differential vagal cold blockade.

Quantitative studies on the polarization optical properties of living cells. I. Microphotometric birefringence detection system.

A method of polarization optical analysis is described in which phase retardation attributable to birefringence of a minute area in a microscopic object is determined. The optical system consists of a polarizing microscope with "rectified" strain-free lenses, a photoelectric detector to determine the intensity of the light passing through a minute window located at the image plane of the specimen, and a stage that moves the specimen at appropriate velocities for scanning. The error resulting from any flare of light emerging from outside of the area to be measured is minimized by limiting the illuminated area. The specimen can be observed during the measurement of light intensity by illuminating the whole microscope field at a wavelength different from that of the light used for the measurement. The retardation of the specimen is determined by comparing the specimen and background intensities as functions of the azimuth of a Brace-Köherl compensator. Alternatively, retardation is obtained directly from the light intensity at a fixed compensator angle, using the theory of polarization optics. The basal noise level for the present apparatus is approximately 0.03 nm when measuring birefringence of a 4-micron2 area in 0.1 s, using a X 40, NA 0.65 objective. The noise decreases in inverse proportion to the square root of the area times the duration of measurement.

Electrogoniometer for the Measurement of Human Elbow Joint Rotation

Since the electrogoniometric method has been justified for the measurement of lower extremity joint motion, a similar device is developed for the measurement of elbow joint and forearm rotations. In this design, the axis of forearm rotation coincides with the anatomical axis which eliminates the cross talk existing in the regular triaxial goniometer. Although the axis of abduction-adduction is still offset from the elbow joint, special linkage arrangement was used to obtain equivalent motion. Experimental method was used to validate the accuracy of the device and model simulation was performed to emphasize the importance of accurate placement of the instrument on test subjects. Application of the present apparatus to normal subjects was studied to illustrate the range of elbow motion required in performing normal activities of daily living. This device is currently used in the functional evaluation of patients with elbow and forearm problems.

Design and Construction of a Wind Tunnel for Mass Transfer Studies in Incompressible Boundary Layers

The apparatus of previous workers are described in order to evaluate the need for further studies of mass transfer into turbulent boundary layers. The apparatus built at the University of Waterloo is then described with particular reference to the areas where it is felt that significant improvement has been achieved over other apparatus. Some suction data obtained on the present apparatus is presented.