The relationship between local scalp skin temperature and cutaneous perfusion during scalp cooling

Cooling the scalp during administration of chemotherapy can prevent hair loss. It reduces both skin blood flow and hair follicle temperature, thus affecting drug supply and drug effect in the hair follicle. The extent to which these mechanisms contribute to the hair preservative effect of scalp cooling remains unknown. The purpose of this study was to establish a relationship between local scalp skin temperature and cutaneous blood flow during scalp cooling. We measured skin temperature and cutaneous perfusion during a cooling and re-warming experiment. Experiments on a single subject showed that the measurements were reproducible and that the response was identical for the two positions that were measured. Inter-subject variability was investigated on nine subjects. We found that for the first 10 °C of cooling, perfusion of the scalp skin decreases to below 40%. Perfusion can be further reduced to below 30% by a few degrees more cooling, but a plateau is reached after that. We found that a generally accepted relation in thermal physiology between temperature and perfusion (i.e. Q10 relation) does not describe the data well, but we found an alternative relation that describes the average behavior significantly better

Final State Charge Exchange Interactions in the 12C(e,e′p)^{12}C(e,e'p) Reaction

The $^{12}C(e,e'p)$ reaction is analyzed in a model which explicitly includes final state interactions due to the coupling of the proton and neutron emission channels. We find that the effects of the final state interactions due to charge exchange reactions are important to get a good description of the symmetry properties of the recently measured Mainz spectral functions. We discuss the possible role the off-shell effects may play for the correct interpretation of spectral functions at large positive missing momenta.Comment: 9 pages Revtex, 4 figure

Sinuous breakdown in a flat plate boundary layer exposed to free-stream turbulence

In a flat plate boundary layer, perturbed with streaks, breakdown occurs due to a secondary instability acting on the streaks. An experimental study using a water channel with static turbulence grid, revealed the presence of a sinuous secondary instability mode in the bypass transition process. Five sinuous instabilities are investigated in detail in the horizontal plane. The streamwise length scale of the sinuous instability is around $40\delta^*_{300}$ and the spanwise scale equals around $\delta^*_{300}$. Four main features are found in the underlying streak configuration and developing streak-streak interactions. Firstly, all instabilities arise in a streak configuration where two low speed streaks are located at a small spanwise distance from each other. Patches of low speed fluid (forming a discontinuity in the streak pattern) are present in the high speed streaks surrounding the unstable low speed streak. As a consequence of the streak-streak interactions at the discontinuities vortices arise in a staggered configuration. Finally, the vortices develop into three-dimensional structures after which the flow falls apart into smaller three-dimensional flow regions

Estimation of instantaneous flow from the indicator-dilution curve after bolus injection of indicator

The indicator-dilution technique is commonly used to determine mean flow estimates. The estimation of instantaneous flow from the shape of an indicator-dilution curve is the objective of this study. Based on a mixing chamber approach to the flow system, a mathematical relationship is derived to reconstruct momentary flow from an indicator-dilution curve. This relationship is verified in a model setup both with only constant flow and with a sinusoidal flow variation superimposed. This method proved to give good flow estimates for limited values of flow parameters. Also, some preliminary experiments were performed in a pulsating flow system simulating heart action. The results were promising although the method proved to be very sensitive to baseline offset

PARTICULATE FOULING GROWTH RATE AS INFLUENCED BY THE CHANGE IN THE FOULING LAYER STRUCTURE

Particulate fouling in biomass gasifiers is a majorproblem, which may lead to inefficient operation. As the fouling layer grows, its thermal resistance increases resulting in an increase in the surface temperature of the fouling layer. The increase in the fouling layer surface temperature can lead to sintering of the layer, which changes the layer structure from a fragile powder to a robust coherent structure. The influence of the change in the fouling layer structure on the growth rate of particulate fouling is studied experimentally. Impaction experiments were carried out to determine the velocities at which an incident particle sticks, bounces off or removes particles outof the fouling layer as a function of fouling layer structure. The sticking velocity of a particle hitting a clean tube is determined theoretically. The sticking velocity of a bronze particle hitting a bronze plate is 0.006 m/s, for a powdery layer is 0.3 m/s and for a sintered layer is 0.04 m/s. The change in the heat exchanger surface from solid to powdery increases the sticking velocity, which consequently speeds up the fouling process. The further change in the heat exchanger surface from powdery to sintered decreases the sticking velocity, which reduces back the fouling process. The change in the fouling layer structures affects the sticking velocity as well as the removal velocity of incident particles, which consequently affect the fouling process

Removal of Particles from a Powdery Fouled Surface due to Impaction

Particulate fouling is defined as the unwanted deposition of particles on heat exchange surfaces. The fouling layer reduces the heat transfer rate and leads to inefficient operation. The net fouling rate is the result of the difference between the deposition rate and the removal rate of particles. One of the mechanisms that contribute to the removal of particles from powdery fouled surfaces is the collision of an incident particle with the fouled surface. In the present study, removal of particles from powdery fouled surfaces due to an incident particle impact is studied numerically and experimentally. A numerical model is developed to study the interaction of an incident particle with a bed of particles. The numerical model is based on the molecular dynamic theory of granular matter. The numerical model is tested for an incident copper particle hitting a bed of particles at different impact speeds. The numerical results are verified experimentally. An experimental setup has been built to study the removal of particles from powdery fouling layers due to an incident particle impact. It is shown that depending on the impact speed, zero, one, two or three particles are ejected from the powdery layer. By comparing the numerical results with the experimental measurements it is shown that the numerical results fit in the measured range of impact mentioned above. The numerical model will be used further to characterize the removal of particles from powdery fouling layers as function of particle size, material, incident particle impact speed and the bed of particles porosity

Restoration of Overlap Functions and Spectroscopic Factors in Nuclei

An asymptotic restoration procedure is applied for analyzing bound--state overlap functions, separation energies and single--nucleon spectroscopic factors by means of a model one--body density matrix emerging from the Jastrow correlation method in its lowest order approximation for $^{16}O$ and $^{40}Ca$ nuclei . Comparison is made with available experimental data and mean--field and natural orbital representation results.Comment: 5 pages, RevTeX style, to be published in Physical Review