钢琴技术问题——“折指”的解决方案

在上期文章中，我专门就手型的问题做了较全面的分析。这里，我对钢琴学习中手指关节立住的问题设计一个解决方案：

Laterally Electrostatically Driven Poly 3C-SiC Folded-Beam Resonant Microstructures

Micromachined comb-drive electrostatic resonators with folded-cantilever beams were designed and fabricated. A combination of Rayleigh＇s method and finite-element analysis was used to calculate the resonant frequency drift as we adjusted the device geometry and material parameters. Three micromachined lateral resonant resonators with different beam widths were fabricated. Their resonant frequencies were experimentally measured to be 64.5,147.2, and 255.5kHz, respectively, which are in good agreement with the simulated resonant frequency. It is shown that an improved frequency performance could be obtained on the poly 3C-SiC based device structural material systems with high Young＇s modulus.

How to realize a negative refractive index material at the atomic level in an optical frequency range?

The theoretical mechanism for realizing a negative refractive index material in an optical frequency range with an atomic gas system of electromagnetically induced transparency (EIT) is studied. It is shown that under certain conditions such a dense gas can exhibit simultaneously negative permittivity and negative permeability, and negligibly small loss.

Optical Absorption and Refractive Index Study of Ti： Al2O3 Single Crystal

The optical absorption of Ti：Al2O3 single crystal has been measured at room temperature, in the wavelength region between 200 nm and 800 nm. The main absorption peaks at 491 nm and 562 nm, the weak infrared absorption band with a peak at 650 nm and the strong UV absorption band below 300 nm were observed. The refractive index is discussed by using Fresnel＇s equation. In particular, the Sellmeier equation was determined in the visible region by means on non-conventional method based on the measurement of refraction by using UV-visible spectroscopy. The refractive indices decreased from 3.71 to 1.28 with wavelength in the range 400-800 nm.

Rare double fracture-dislocation of the thumb： a case report and review of the literature

Simultaneous fracture/dislocation of the thumb carpometacarpal （CMC）joint and dislocation of the metacarpophalangeal （MCP） joint is considered as a rare injury pattern. We report an unusual case of dorsal disloca- tion of MCP joint of the thumb associated with extraarticular fracture of the base of the first metacarpal in a 28-year-old man. The dislocation of MCP joint had been missed during initial presentation at a peripheral centre. The patient made an uneventful recovery following open reduction and fixa- tion with 1.25 mm Kirschner wire of the MCP joint along with repair of the ulnar collateral ligament. This injury pat- tern has not been previously reported to the best of our knowledge in the English-language based medical literature.

Inadvertent advancement of guide wire across the knee caused by incarcerated bone fragment at the nail tip during femoral nailing

Fracture of femoral shaft in adults is common and mostly managed with intramedullary interlocking nails. Complications during closed intramedullary femoral nailing are uncommon, and mostly of them are caused by technical reasons. We describe a case of closed nailing for a femoral shaft fracture in which a jammed intramedullary guide wire, due to an incarcerated bone fragment at the nail tip, was inadvertently advanced across the knee. Forceful attempt of nail insertion caused this complication, which was probably attributed to nail design.

Fracture of the radial sesamoid bone of the thumb： an unusual fracture

The hand consists of five sesamoids. Two of them are present at the metacarpophalangeal （MCP）joint of the thumb. Fracture of the sesamoid bones of the thumb is a rare injury and the literature on the radial side is seldom reported. We reported a case of a patient with a fracture of the radial sesamoid at the MCP joint of the thumb in order to increase attention regarding this type of injuries. A 44-year-old male, high level gymnastic trainer, was helping one of his athletes during an exercise while he reported a hyperextension trauma to the MCP joint of the right thumb.One week after trauma, he presented to the hand surgeon complaining of a painful thumb at the MCP joint level on its palmar aspect. Standard A-P and lateral X-rays revealed a fracture of the radial sesamoid and the fracture was treated with a splint for 3 weeks. He was able to resumed his entire work 6 weeks after the injury. The sesamoid fractures is an indicator of the magnitude of the hyperextension injury and sometimes associated with tears of the volar plate ligament of the MCP joint. And a failure to recognize the ligament injury may lead to a long-term hyperextension instability on pinching.

On the reconstruction of media inhomogeneity by inverse wave scattering model

Consider the reconstruction of the complex refraction index of an object, which is immersed in a known homogeneous background, from the knowledge of scattered waves of the point sources outside of the object. We firstly establish the uniqueness for this inverse problem, which provides the theoretical basis for the reconstruction scheme. Then based on the contrast source inversion(CSI) method, we propose an algorithm determining the refraction index and the artificial wave sources alternately by a dynamic iterative scheme. The algorithm defines the iterates by solving a series of minimization problems with uniformly convex penalty terms, which are allowed to be non-smooth to include L1 and total variation like functionals, ensuring the reconstruction quality when the unknown refraction index has the special features such as sparsity and discontinuity. By choosing the regularizing parameter automatically, the algorithm is terminated in terms of discrepancy principle. The convergence property of the iterative sequence is rigorously proven. Numerical implementations demonstrate the validity of the proposed algorithm.

Predictors of early outcome in unstable pelvic fractures

Objective： To define the preoperative and intraoperative variables which may affect the immediate postoperative outcome in surgically managed patients with unstable pelvic fractures. Methods： This study was performed prospectively from January 2009 to June 2011 on 36 consecutive patients admitted to the trauma ward of Postgraduate Institute of Medical Education and Research, Chandigarh, with unstable pelvic injuries. Results： In the present study of 36 patients, 29 were managed surgically. Surgical duration was 2 hours in pa- tients operated on within 1 week and 3.4 hours in those operated on after 1 week. The blood loss was 550 ml when surgery was done after a week, but when done within a week it was 350 ml. The average blood loss through Pfanenstial approach was 360 ml, through posterior approach was 408 ml and through combined approach was 660 ml which was significantly high. Conclusion： Anterior approach to the pelvis would cause significantly more amount of blood loss than poste- rior approach and extemal fixation. Surgical approaches do not have any influence on the surgical duration or the infec- tion rate. The blood loss significantly increases when the surgical time is more than 1 h. The infection rate is not influ- enced by the duration of surgery. Presence or absence of associated injuries to the head, chest or abdomen is the main determinants of patient＇s survival and it greatly influ- ences the duration of hospital stay.

Combined index finger pollicization with an anterolateral thiqh flap for thumb reconstruction

A severe crush injury to the hand is devastating to patients. Under conditions in which the crush force is too great, the digits are not viable candidates for replantation. We present two cases in which the patients suffered from loss of the thumb ray at the first carpometacarpal joint and skin defect at the radial side. The tendons, radial nerve and metacarpal bone of the index finger were injured, and the second metacarpal head was retained. There was a comminuted fracture of the trapezium in both patients. The treatment protocols consisted of the index finger pollicization and the free anterolateral thigh flap transfer. The procedure was performed in a single operation. The new thumb is able to provide a stable post for pinch and grip after six months follow-up. Both patients were satisfied with the function and appearance of the reconstructed thumb.