Recoil Properties Research Articles

Viscoelastic modelling of impacted morsellised bone accurately describes unloading behaviour: An experimental study of stiffness moduli and recoil properties

Morsellised bone impaction grafting is commonly used for revision arthroplasty surgery. Several reports have described the mechanical behaviour of this bone material during impaction and loading. In this study we observed the unloading progress. The loose morsellised bone was modified by particle size, particle size distribution, water and fat content. Bone pellets were constructed using different impaction energies. After impaction, the pellets were loaded statically, after which their swelling was recorded at three unloading levels. We deduced two time-dependent recoil properties, the time resistant number (TRN) and the half total swelling time (HTST), and also one stiffness property, the unloading confined modulus of elasticity (UCME). In impacted morsellised bone, the progress of swelling is visco-elastic. Bone pellets with an even distribution of particle sizes have the most rapid recoil. Those with a high liquid content recoil more slowly, and to a significantly greater extent, than pellets with low liquid content. The recoil of pellets with low liquid content is instantaneous, i.e. unrecordable, and the displacement is significantly less than in other pellet samples.

Respiratory Mechanics in Children with Post-Viral Chronic Pulmonary Disease (PCPD)

Viral lower respiratory tract infections can cause severe lung injury resulting in a chronic condition known as PCPD. We have previously shown that patients with PCPD have a severe and fixed airway obstruction and changes in the elastic recoil properties of the lung [increased resistance (R) and decreased compliance (C)] during the first two years of life. The aim of the study was to evaluate the respiratory mechanics with the forced oscillation technique (FOT), in older children with PCPD. Methods. Respiratory mechanics of patients diagnosed with PCPD and followed at our hospital was prospectively evaluated (6 years after initial injury) during 2000/2001. Measurements were done using FOT (Vmax machine series 2, SensorMedics). Bronchodilator response (BDR) was evaluated 30 min after the inhalation of 200 mcg salbutamol. Inclusion critera were: diagnosis of PCPD, older than 4 yrs, capable of performing PFTs, and clinically stable. A control group of children older than 4 yrs with a normal spirometry was included for comparison. Study group (SG): 17 patients (12 male; mean age 7 yrs; age-range 4–14); Control group (CG): 17 children (5 male; mean age 7 yrs; range 4–15). Results were as follows (mean ± SD): R 4–16 (cmH2O/l/s) SG 8.5±3 & CG 4.9±1 (p<0.01); R 0 SG 10.1±4 & CG 5±1 (p<0.01); R Mn SG 7.5±2 & CG 4.9±1 (p<0.01); C (ml/cmH2O) SG 5.4±3 & CG 20.5±12 (p<0.01). Coefficients of variation were adequate (7.3, 8, 7.6, and 16 for R 4–16, R 0, R Mn and C, respectively). BDR (SG only) was: R 4–16: 16.5 %, R 0: 21 %, R Mn: 13.3%, C: 41.8%. Children with PCPD showed persistent changes in their respiratory mechanics 6 years after the initial insult. They showed an increase in resistance and a decrease in compliance compared to the control group.

Mechanical Forces Impeding Exocytotic Surfactant Release Revealed by Optical Tweezers

The release of surfactant from alveolar type II cells is essential to lower the surface tension in the lung and to facilitate inspiration. However, the factors controlling dispersal and diffusion of this hydrophobic material are still poorly understood. Here we report that release of surfactant from the fused vesicle, termed lamellar body (LB), resisted mechanical forces applied by optical tweezers: At constant trapping force, the probability to expand LB contents, i.e., to “pull” surfactant into the extracellular fluid, increased with time after LB fusion with the plasma membrane, consistent with slow fusion pore expansion in these cells. Elevations of the cytoplasmic Ca 2+ concentration ([Ca 2+] c) had a similar effect. Inasmuch as surfactant did not disintegrate in the extracellular space, this method permitted for the first time the determination of elastic and recoil properties of the macromolecular complex, yielding a spring constant of ∼12.5 pN/ μm. This is the first functional evidence that release of hydrophobic material is mechanically impeded and occurs in an “all-or-none” fashion. This mode of release is most probably the result of cohesive forces of surfactant, combined with adhesive forces and/or retaining forces exerted by a constrictive fusion pore acting as a regulated mechanical barrier, withstanding forces up to 160 pN. In independent experiments equiaxial strain was exerted on cells without optical tweezers. Strain facilitated surfactant release from preexisting fused vesicles, consistent with the view of mechanical impediments during the release process, which can be overcome by cell strain.

Photofission of 197Au and 209Bi at intermediate energies

Recoil properties and yields of radionuclides formed in the photofission of 197Au and 209Bi by bremsstrahlung of end-point energies (E 0) from 300 to 1100 MeV have been investigated using the thick-target thick-catcher method. The kinetic energies T of the residual nuclei were deduced based on the two-step vector model and discussed by comparing with the reported results on protoninduced reactions as well as those on photospallation. The charge distribution was reproduced by a Gaussian function with the most probable charge Zp expressed by a linera function of the product mass number A and with the A-independent width FWHM CD. Based on the charge distribution parameters, the symmetric mass yield distribution with the most probable mass A p of 92 m.u. and the width FWHM MD of 39 m.u. was obtained for 197Au at E 0≥600 MeV. The A p value for 209Bi was larger by 4 m.u. than that for 197Au and the FWHM MD was smaller by 6 m.u. A comparison with the calculations using the Photon-induced Intranuclear Cascade Analysis 3 code combined with the Generalized Evaporation Model code (PICA3/GEM) was also performed.

Exercise.

Exercise.

Elastic-Fiber Pathologies: Primary Defects in Assembly—and Secondary Disorders in Transport and Delivery

Accession numbers and the URL for data in this article are as follows:Online Mendelian Inheritance in Man (OMIM), www.ncbi.nlm.nih.gov/Omim (for congenital contractural arachnodactyly [MIM 121050], adCL [MIM 123700], MFS [MIM 154700]), SVAS [MIM 185500], Williams-Beuren syndrome [MIM 194050], Costello syndrome [MIM 218040], GM1-gangliosidosis [MIM 230500, MIM 230600, and MIM 230650], MPSI [MIM 252800], and MPS IVB [MIM 253010])

Recoil properties of radionuclides formed in photospallation reactions on complex nuclei at intermediate energies

The recoil properties of 14, 24, 26, 31, 21 and 20 radionuclides formed in photospallation reactions onnatV,natCu,93Nb,natAg,natTa, and197Au, respectively, induced by bremsstrahlung of end-point energies (E0) from 600 to 1100 MeV, have been investigated using the thick-target thick-catcher method based on the two-step vector model. The measured forward-to-backward ratios (F/B) were found to be independent of the mass difference (ΔA) between a product (Ap) and a target (At) and also of At. The recoil velocities ν from the first step and the mean kinetic energies T of the residual nuclei in the second step were deduced and discussed by comparing with the reported results on proton-induced reactions. A comparison with T values calculated by the PICA (Photon-Induced Intranuclear Cascade Analysis) code at E0= 400 MeV was also performed. It was found that although the code well reproduces the experimental results ofnatV andnatCu, the same calculation for heavier targets gives T values lower than the experimental results, indicating some nuclear-structure effect, such as a medium effect notably at At≥ 100. The parameter values of εs= T/(ΔA/At), the average kinetic energy of the emitted particles in a random-walk process of both the photon- and proton-reactions, were found to increase along with an increase of At, but change slopes to become constant above At= 100.

The structures of elastins and their function

Elastin structures and their significance towards elastic recoil properties have been reviewed. Starting from the initial hypothesis that elastin conformation is conditioned by that of its monomer, the structure of tropoelastin was first described using theoretical and experimental methods and a β class folding type was evidenced for the isolated unbound tropoelastin molecules. The structure of elastin in the solid state was consistent with that of its monomer and consequently, fibrous elastin appeared constituted of globular tropoelastin molecules. Finally, theoretical and experimental considerations have led us to the conclusion that the functional form of the elastomer, water swollen elastin, could be a triphasic system comprising the protein chains, hydration water and solvent water. Following this description, the dynamic structural equilibria occurring within elastin hydrophobic domains and the plastisizing effect of water could explain elastin elasticity, in keeping with a classical entropic mechanism.

Heavy residue production in the interaction of 29 MeV/nucleon208Pbwith197Au

The yields, recoil properties, and angular distributions of the fragments of the target nucleus were measured for the 29 MeV/nucleon ${}^{208}\mathrm{Pb}{+}^{197}\mathrm{Au}$ reaction using radiochemical techniques. The fragment isobaric yield distribution and mean energies were deduced from these data. The fission cross section is $2.2\ifmmode\pm\else\textpm\fi{}0.5 \mathrm{b}$ while the residue formation cross section is 3.9 b. Heavy residues form a part of a large central bump (usually associated with fission) in the fragment mass distribution. Comparing the data from this reaction to other reactions involving massive nuclei at projectile energies from 7 to 45 MeV/nucleon shows the locus of fragment yields $[\ensuremath{\sigma}(Z,A)]$ to be roughly independent of the reacting system or projectile energy. The fragment angular distributions evolve from sidewise peaked (for near target, quasielastic residues) to forward peaked as the mass number decreases. The isomer ratios for the residues indicate their formation from the lowest partial wave events while the fission fragments appear to originate in higher l events. Attempts to use the nucleon transport model (or some modification of it) to calculate the residue cross sections were only partially successful. It is suggested the the lack of dynamic multifragmentation mechanisms in these models is the cause of the shortcomings.

Recoil studies of photonuclear reactions on natCu, natAg, natTa, and 197Au at intermediate energies

The recoil properties of nuclides produced in the photonuclear reactions on natCu, natAg, natTa, and 197Au induced by bremsstrahlung of end-point energies (E o) of 250 to 1000 MeV have been investigated using the thick-target thick-catcher method. The obtained mean ranges of produced nuclides smoothly increase with an increase of the mass difference (ΔA) between products and target, and show E 0-independence at E 0≥600 MeV, reflecting the limiting behavior above (3, 3) resonance region. The mean kinetic energies, T, deduced from the mean ranges show the following two components; (1) (γ, xn) products by giant-resonance and/or quasi-deuteron resonance absorption, (2) (γ, xnyp) products by mainly (3, 3) resonance absorption. Slightly rapid increase of T was found around ΔA=15, 18, 24, and 25 for natCu, natAg, natTa and 197Au, respectively, reflecting a change in mechanism. Kinematic properties of the product nuclei were calculated by using the PICA (Photon-Induced Intranuclear Cascade Analysis) code. The T calculated by the PICA code at E 0=400 MeV well reproduced the experimental results of natCu, but the same calculation for natAg, natTa, and 197Au gave lower mean kinetic energies than the experimental results.

Recoil properties of radionuclides formed in the photonuclear reactions onnatCu at intermediate energies

The recoil properties of 26 radionuclides produced in the photonuclear reactions on Cu at bremsstrahlung end-point energies (E0) of 250 to 1000 MeV have been investigated using the thick-target thick-catcher method. Kinematic properties of the product nuclei were calculated by the two-step vector velocity model. The calculated mean kinetic energies,T, of product nuclei increase with increase of the mass difference between products and target, reflecting the resonance natures and absorption mechanisms. TheT atE0≥600 MeV were well reproduced by a calculation performed by PICA code byGabriel andAlsmiller atE0=400 MeV, except for (γ,xn) products by giant-resonance.

Detection of elastin in the human fetal membranes: Proposed molecular basis for elasticity

The human fetal membranes provide a sterile biomechanical container which adjust by growth to mid-pregnancy to the increase in fetal size, and by elasticity to the forceful movements of the fetus. The molecular basis for this elasticity is not known, yet reduced elasticity may lead to their premature rupture and preterm birth, a major problem in perinatal medicine. Classically, elastin confers the property of elastic recoil to elastic fibres which are assembled from a family of tropoelastin precursors. These are covalently cross-linked to form insoluble elastin by formation of desmosine and isodesmosine, catalysed by the enzyme lysyl oxidase. The amnion, chorion and decidua were shown by Northern analysis and RT-PCR to contain detectable levels of tropoelastin mRNA and the mRNA encoding lysyl oxidase. The proteins encoded by these mRNAs were also identified by Western blotting and immunolocalization. Further, insoluble elastin was extracted from the human fetal membranes and shown by comparison to elastin preparations from other elastic tissues to have a reasonable desmosine content. Finally, scanning electron microscopy confirmed the presence of multiple layers of an apparently very thin elastic system in this tissue. This biochemical and histopathologic study has demonstrated therefore that the human fetal membranes synthesize and deposit a novel elastic fibre. The presence of such an elastic system in these tissues provides, for the first time, a probable molecular basis for the elastic properties of this tissue.

Elastin in Lung Development

Elastin is a critical component of the lung interstitium, providing the property of recoil to the vascular, conducting airway, and terminal airspace compartments of the lung. Elastic fibers, consisting of soluble tropoelastin monomers cross-linked on a preexisting scaffold of microfibrils, are produced primarily during late fetal and neonatal stages of development. The factors and molecular mechanisms regulating the cell type-specific and tightly temporally regulated expression of tropoelastin are currently under investigation. The onset and inductive phase of tropoelastin expression are characterized by increased transcription of the tropoelastin gene. Glucocorticoids accelerate this induction in fetal rats during the canalicular stage of lung development. Many additional factors regulate tropoelastin expression in cultured lung fibroblasts and vascular smooth muscle cells, but the in vivo roles of such mediators are still under investigation. Cell-cell interactions may also promote elastogenesis during lung development, as localization of tropoelastin mRNA in pseudo-glandular and canalicular lungs demonstrates a close spatial relationship between epithelium and adjacent elastogenic mesenchyme. Elastin metabolism is altered in several experimental models of bronchopulmonary dysplasia, characterized by abnormal lung morphological development, suggesting that normal elastin production and deposition is necessary for proper development of alveoli. Studies employing reverse genetics may prove useful in further defining the role of elastin in lung development.

A Modification of Retrograde Wire-Guided, Fiberoptic-Assisted Endotracheal Intubation in a Patient with Ankylosing Spondylitis

A Modification of Retrograde Wire-Guided, Fiberoptic-Assisted Endotracheal Intubation in a Patient with Ankylosing Spondylitis

Heavy-residue production in Ar-Th collisions at 44, 77, and 95 MeV/nucleon.

The yields and recoil properties of the targetlike fragments produced in the interaction of 44, 77, and 95 MeV/nucleon Ar with $^{232}\mathrm{Th}$ have been measured. From these data, the fragment mass distributions, average energies, and the linear momentum transfer leading to their formation have been deduced. The residue yields are large at all energies [790 mb, 790 mb, and 710 mb (\ifmmode\pm\else\textpm\fi{}30%) at 44, 77, and 95 MeV/nucleon, respectively] while the average residue energies are low [mean fractional linear momentum transfer (FLMT) is 0.14, 0.12, and 0.13 for the 44, 77, and 95 MeV/nucleon experiments]. Because of the low mean FLMT values associated with the residues, we conclude that, on average, they do not result from fusion-like events. The residue energies and their dependence on fragment mass number agree with predictions of BUU calculations. The substantial survival of the residues of excited, fissionable nuclei is shown to be a result of retardation of fission decay and the broad primary fragment distributions. The intranuclear cascade model is shown to give an incorrect description of the primary fragment properties in these reactions.

Recoil studies of nuclei produced in photonuclear reactions

The recoil properties of the radioactive residual nuclei formed in the interaction of bremsstrahlung with maximum energy 4.0–4.5 GeV with targets Al, Cu, Ag, Ta has been measured by catch foils technique. The experimental data were analyzed by the two-step velocity model and compared with the results of proton- and ion-induced reactions. The recoil properties of the target residuals strongly depend on the product mass, but show only a weak dependence on the projectile type, which can be considered as an indication of the limiting fragmentation hypothesis. The value of the longitudinal velocity transferred to the nucleus in the primary interaction (v¦|) differs from that in the reactions initiated by different projectiles. The presented data indicate to a lower exciting level of the photonuclear reaction products.

Cross section and recoil properties of the products from the interaction of 240 MeV 12C ions with natAg

We have measured the formation cross sections and the recoil properties of the products from the interaction of 240 MeV 12C with natural Ag targets. From the data, we have constructed charge- and mass-distribution curves. With the measured recoil range and forward-to-backward ratios, we deduced the formation mechanisms, and found that the yields in the mass range between A = 40 and A = 70, with a total cross section of 6 ± 1 mb, were mainly formed by the fission process. The yields between A = 70 and A = 130, with a total cross section of 2300 ± 200 mb, were formed by direct reactions in which the target-like transfer reaction products contributed 1000 ± 100 mb and spallation reactions contributed 1306 ± 200 mb.

Recoil properties of 24Na and 28Mg produced in nucleus–nucleus collisions at 3.65 AGeV

Target recoil properties of intermediate 24Na and 28Ng fragments produced in the reactions induced by 3.65 AGeV 12C-ions and 3.65 AGeV protons on Mn, Co, Cu, Y, Nb, Ag, Tb, Ta, Au, Pb, Th and U targets are systemized within the framework of the two-step vector velocity model.

Yields and Recoil Properties of Products from the Interaction of Natural Copper with Intermediate-Energy 14N, 15N and 40Ar Ions

Yields and Recoil Properties of Products from the Interaction of Natural Copper with Intermediate-Energy ¹⁴N, ¹⁵N and ⁴⁰Ar Ions

Emission of light fragments in relativistic nucleus-nucleus collisions

Recoil properties of 24Na and 28Mg fragments emitted in the reactions of 2.35 A GeV and 3.65 A GeV 16O ions with Mn, Cu, Ag, Ta and Au target nuclei have been measured by the thick-target, thick-catcher technique and gamma-ray spectroscopy. The kinematic parameters were deduced from the data. The results are discussed in the framework of the two-step vector velocity model and compared to the systematics of the momentum distributions.