Induction of Changes Over time in the Rat Proximal Femur Following Ovariectomy: A Model with Clinical Implications

The menopause-related expansion of the proximal femoral marrow cavity is thought to have implications  for the long-term cohesion of hip prostheses. This theory would be further strengthened if there was evidence  to show that the expansion of the proximal femur marrow cavity takes place after the occurrence of  a femoral neck fracture, which, it is often recommended, should be fixed with a hip prosthesis. But till now,  the temporal relationship between those two osteoporotic-related changes has not been checked carefully.  The objective of the current study was to examine the temporal relationship between the marrow cavity  expansion of the proximal femur and the biomechanical deterioration of the femoral neck in a rat model.  To do so, a cross-sectional study with multiple time points was carried out on 6-month old Sprague-Dawley  rats, which were ovariectomized or sham-operated (as controls). The biomechanical properties of the femur  neck and geometrical parameters of the femur shaft were evaluated at 0, 3, 6, 9, 12, 15, 18, and 21 weeks  postoperatively, with special reference to the timescale of the observed changes. We found that the maximum  load of the femoral neck in ovariectomized rats could bear decreased significantly compared, to that  of controls, at 9 weeks postoperatively (p=0.03), while the marrow cavity of the proximal femur in ovariectomized  rats turned out to be significantly enlarged at 15 weeks postoperatively (p=0.04). Conclusion: Our  result demonstrated that the osteoporosis-related marrow-enlarged posterior led to the collapse of femoral  neck strength. If the change in postmenopausal women is analogous to that in ovariectomized rats, the  menopause-related marrow cavity expansion would be a risk factor for the longevity of hip prostheses.

X-ray line spectrometry in experiments with the aluminium Z-pinch

X-ray line spectrometry with temporal resolution was developed for registration of [He]- and [H]-like aluminium ions spectrum. It was chosen a scheme with scintillator converting X-ray spectrum into the visible image, which was transferred through the flexible optical fiber to the entrance slit of the streak camera. In Z-pinch experiment on the high current S-300 generator the aluminium line spectrum was registered with nanosecond time resolution. The simultaneous appearance of [He]- and [H]-like aluminium ions radiation was observed, that is the evidence of high electron temperature existence in the plasma for a long time before the main part of the load mass comes to the axis. The noticeably changing of radiating plasma parameters was found after the computer treatment of line spectra: the electron concentration is varied in five times ((3…14)×10^19 cm^-3), electron temperature in three times (0.3…1 keV), ion temperature in five times (20…100 keV), – during 50 ns. The great difference between the electron and ion temperature holds during all radiation time and demonstrates the ineffective energy transfer from the kinetic energy of ions to electron.Разработана методика для регистрации с временным разрешением рентгеновских линий [He]- и [H]-подобных ионов алюминия. Рентгеновский спектр преобразовывался с помощью сцинтиллятора в видимое изображение, которое переносилось гибким световодом на входную щель электронно-оптического преобразователя. Регистрация спектра проводилась с наносекундным разрешением в экспериментах с Z-пинчем на сильноточном генераторе С-300. Наблюдалось одновременное появление линий [He]- и [H]-подобных ионов алюминия, что является свидетельством наличия высокой электронной температуры в плазме задолго до момента прихода к оси основной массы Z-пинча. Компьютерная обработка спектров выявила значительные изменения параметров плазмы в процессе сжатия: концентрации в пять раз ((3…14)×10^19 см^-3), электронной температуры в три (0.3…1 кэВ), ионной температуры в пять раз (20…100 кэВ) – за 50 нс. Большой разрыв между ионной и электронной температурами демонстрирует неэффективность передачи энергии от ионов к электронам.Розроблено методику для реєстрації з часовим дозволом рентгенівських ліній [He]- і [H]-подібних іонів алюмінію. Рентгенівський спектр перетворювався за допомогою сцинтиллятора у видиме зображення, що переносилося гнучким світловодом на вхідну щілину електронно-оптичного перетворювача. Реєстрація спектра проводилася з наносекундним дозволом в експериментах з Z-пінчем на потужнострумовому генераторі С-300. Спостерігалася одночасна поява ліній [He]- і [H]-подібних іонів алюмінію, що є свідченням наявності високої електронної температури в плазмі задовго до моменту приходу до осі основної маси Z-пінча. Комп'ютерна обробка спектрів виявила значні зміни параметрів плазми в процесі стиску: концентрації в п'ять разів ((3...14)×10^19см^-3), електронної температури в три (0.3...1кеВ), іонної температури в п'ять разів (20...100 кеВ) – за 50 нс. Великий розрив між іонною й електронною температурами демонструє неефективність передачі енергії від іонів до електронів

Using soft lithography to pattern highly oriented polyacetylene (HOPA) films via solventless polymerization

A new application of the combination of soft lithography and solventless polymerization is described (see Figure)-the patterning of ultra-hard microstructures in selected areas using highly oriented polyacetylene (HOPA) films as a precursor. It is expected that this simple, low-cost, and mild process will lead to the formation of highly oriented films of other materials, e.g., electro-optically active polymers

Comparison of Measurements with Finite-Element Analysis of Silicon-Diaphragm-Based Fiber-Optic Fabry–Perot Temperature Sensors

Silicon-diaphragm-based fiber-optic Fabry–Perot sensors with different intracavity pressures were fabricated by anodic bonding and microelectromechanical techniques. The thermal stress and thermal expansion of the Fabry–Perot (FP) sensor caused by high-temperature bonding and temperature change were simulated by finite-element analysis. The calculated thermal stress is largest in the center and edge regions of the resonance cavity, reaching from 2 to 6 MPa. The reflection spectra and temperature sensitivity of the sensors were simulated by using a two-dimensional wave-optic model in Comsol. Theoretical calculations were also made for the FP cavity without considering silicon-diaphragm deformation and thermal stress. Four sensors with intracavity pressures of 0.01, 0.03, 0.04, and 0.05 MPa were tested at low temperatures, showing a high degree of consistency with the simulation results rather than theoretical calculation, especially for high intracavity pressure. This method is expected to aid the analysis of thermal stress generated during the bonding process and to facilitate better design and control of the temperature sensitivity of the sensor

Nitrilotriacetic acid-modified magnetic nanoparticles as a general agent to bind histidine-tagged proteins

Using N_α,N_α-bis(carboxymethyl)lysine to react with FePt magnetic nanoparticles, we synthesized the FePt?NTA conjugate, which immobilizes Ni²⁺ ions and selectively binds to histidine-tagged proteins at concentration as low as 0.5 pM. This simple system serves as a useful alternative to existing protocols for protein separation and also acts as a versatile agent for transporting and anchoring proteins. Copyright © 2004 American Chemical Society

Dopamine as a robust anchor to immobilize functional molecules on the iron oxide shell of magnetic nanoparticles

We report on the use of dopamine (DA) as a robust molecular anchor to link functional molecules to the iron oxide shell of magnetic nanoparticles. Using nitrilotriacetic acid (NTA) as the functional molecule, we created a system with an M/Fe₂O₃-DA-NTA (M = Co or SmCo_5.2) nanostructure, which possesses high stability and specificity for separating histidine-tagged proteins. The well-established biocompatibility of iron oxide and the robust covalent bonds between DA and Fe₂O₃ render this strategy attractive for constructing biofunctional magnetic nanoparticles containing iron oxide. Copyright © 2004 American Chemical Society

Dynamic comparison between the cylindrical and quasi-spherical implosions based on thin-shell models

The quasi-spherical electromagnetic implosions are capable of generating hot dense plasmas more efficiently than the cylindrical ones. The dynamic properties of stagnated cylindrical and quasi-spherical shells are compared numerically based on the thin-shell models. The cylindrical implosions are simulated with the zero-dimensional thin-shell model, and the quasi-spherical implosions with the multi-element thin-shell model. The simulated velocity, areal mass density, and areal kinetic energy density of the stagnated quasi-spherical plasma shell increase with the latitude increasing, which is different from the cylindrical case. The kinetic energy densities are optimized for both of stagnated cylindrical and quasi-spherical shells in a quite large span of initial radii and load linear masses. The kinetic energy density in the spherical radiation converter can be over four times as large as that in the cylindrical radiation converter. The numerical results can help optimize quasi-spherical load parameters for Z-pinch driver with peak current of 1.5 MA and rising time of 80 ns, and the method described here is also feasible to optimize load parameters for various-scale Z-pinch drivers

Geometrical optimization of quasi-spherical wire-array implosion

A geometrical optimization method based on the multi-element model is developed for electromagnetic implosion of quasi-spherical wire-array loads. The shapes of the initial quasi-spherical wire arrays are described with the parabolic formation, and the shapes of the final plasma shells are estimated with the multipole expansion method. By scanning the aspect ratios of the initial loads, we can obtain the most nearly-spherical final plasma shell with certain mean radius, i.e. the shell has the smallest quadrupole and hexadecapole deformation. As a typical case, starting with the preshaped cylindrical load (with height of 15.4 mm and with diameter of 8 mm), the imploding plasma shell with mean radius of 1.5 mm is almost spherical when the initial aspect ratio takes the value of 1.089, and the results is consistent with the synchronization analysis. The optimization calculations for different current waveforms and different initial load masses indicate that the shape of the optimized plasma shell is not sensitive to the drive current and load mass. The geometrical optimization method here can be served as a primary designing tool for the quasi-spherical wire-array load