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At least 559 records · Page 31Linked to original sources
PubMed2002

Non-ablative laser treatment of facial rhytides: a comparison of 1450-nm diode laser treatment with dynamic cooling as opposed to treatment with dynamic cooling alone.

BACKGROUND AND OBJECTIVE: Non-ablative dermal remodeling has been shown to create new dermal collagen. This is thought to occur secondary to a laser-induced injury to the skin. Other mechanisms of injury may lead to similar results. The aim of this study was to evaluate the efficacy and complication rate of a 1450-nm diode laser and compare clinical effect when the laser is used in conjunction with cryogen cooling as compared to the use of cryogen cooling alone. STUDY DESIGN/MATERIALS AND METHODS: Twenty subjects, skin types I-IV, age range 42-70 years, with Class I and II rhytides were enrolled in the study. Subjects were treated with 2-4 laser treatments and cryogen cooling on one side of their face, while the contralateral side was treated with cryogen cooling alone. Subjects were evaluated six months after their final treatment. RESULTS: Thirteen subjects showed clinical improvement on the laser/cryogen treated side. No subjects were noted to have any improvement at the cryogen alone side. CONCLUSION: The 1450-nm diode laser can lead to non-ablative improvement of rhytides. This effect appears to be a direct laser induced effect.

Adult↗
PubMed2001

Essential dynamics of reversible peptide folding: memory-free conformational dynamics governed by internal hydrogen bonds.

A principal component analysis has been applied on equilibrium simulations of a beta-heptapeptide that shows reversible folding in a methanol solution. The analysis shows that the configurational space contains only three dense sub-states. These states of relatively low free energy correspond to the "native" left-handed helix, a partly helical intermediate, and a hairpin-like structure. The collection of unfolded conformations form a relatively diffuse cloud with little substructure. Internal hydrogen-bonding energies were found to correlate well with the degree of folding. The native helical structure folds from the N terminus; the transition from the major folding intermediate to the native helical structure involves the formation of the two most C-terminal backbone hydrogen bonds. A four-state Markov model was found to describe transition frequencies between the conformational states within error limits, indicating that memory-effects are negligible beyond the nanosecond time-scale. The dominant native state fluctuations were found to be very similar to unfolding motions, suggesting that unfolding pathways can be inferred from fluctuations in the native state. The low-dimensional essential subspace, describing 69% of the collective atomic fluctuations, was found to converge at time-scales of the order of one nanosecond at all temperatures investigated, whereas folding/unfolding takes place at significantly longer time-scales, even above the melting temperature.

Computer Simulation↗
PubMed1988

Effects of chamber shape and fiber orientation on relations between fiber dynamics and chamber dynamics.

The function of a chamber depends on its hydrodynamic properties: isometric pressures it can exert in the operating range of distensions, compliances in the operating range of distensions, and wall-displacement resistances in the operating range of distensions. Wall-displacement resistance is the departure of pressure from isometric pressure relative to rate of cavity-volume change. The dependence of pressure on average stress and wall/cavity volume ratio is indifferent to chamber shape, which suggests that the volume-based compliance-elastance and resistance-viscosity equations would be only moderately shape dependent. The present study shows that this supposition is correct. If the wall is thin, these relations are shape indifferent. At higher wall/cavity volume ratio, cylindricity increases slightly the P-V-curve slope relative to elastance and either increases slightly or does not affect resistance relative to viscosity. The compliance-elastance and resistance-viscosity relations also depend only slightly on fiber orientation. Therefore, with the sphere equations, one can account accurately for normal and abnormal function of a prolate spheroid in terms of volume dimensions of the wall and apparent average fiber properties.

Blood Vessels↗