71,825 research outputs found
Computed tomography measurement of the bone matrix of vertebral pedicle and its clinical significance
Background: To provide the anatomic basis for the clinical application of the transpedicular screw fixation.
Materials and methods: Thirty spine (C2–L5) specimens were used. The width of the pedicle cortex and width of the pedicle medullary cavity (WPC and WPMC), and the height of the pedicle cortex and height of the pedicle medullary cavity (HPC and HPMC) were measured at the isthmus of the pedicle using computed
tomography (CT) scanning.
Results: Width of the pedicle medullary cavity changed in a three-dovetailed-saddle shape with four peaks and three valleys, namely C2 (high), C4`5 (low), T2 (high), T4 (the lowest), T12 (high), L1 (low) and L5 (the highest). HPMC of the cervical pedicle changed in a saddle shape, gradually increasing from C5–L5. WPC, WPMC, HPC and HPMC showed a regular change, respectively. In each segment, the superior border of the pedicle cortex had a nearly consistent thickness to the interior border within an identical pedicle, while the pedicle cortex thickness radio of the medial and lateral border was nearly 3:1 among the cervical pedicles, 2:1 among thoracic pedicles, and 1:1 among lumbar pedicles.
Conclusions: Both HPMC and WPMC are the dominant factors for the choice of screw diameter, but HPMC should also be considered in C2–T1 pedicles, especially C6 and C7. Additionally, the screw for C3–6 or T4–6 pedicles should be about 3.0 mm in diameter
Coexistence of superconductivity and magnetism in K0.8Fe2Se1.4S0.4
High-quality single crystals of K0.8Fe2Se1.4S0.4 are successfully synthesized
by self-flux method with the superconducting transition temperatures Tconset =
32.8 K and Tczero = 31.2 K. In contrast to external pressure effect on
superconductivity, the substitution of S for Se does not suppress Tc, which
suggests that chemical doping may mainly modulate the anion height from
Fe-layer rather than compressing interlayer distance. The investigation of the
micromagnetism by electron spin resonance shows clear evidence for strong spin
fluctuation at temperatures above Tc. Accompanied by the superconducting
feature spectra, a novel resonance signal develops gradually upon cooling below
Tc, indicating the coexistence of superconductivity and magnetism in
K0.8Fe2Se1.4S0.4 crystal
Multiparty Quantum Secret Report
A multiparty quantum secret report scheme is proposed with quantum
encryption. The boss Alice and her agents first share a sequence of
(+1)-particle Greenberger--Horne--Zeilinger (GHZ) states that only Alice
knows which state each (+1)-particle quantum system is in. Each agent
exploits a controlled-not (CNot) gate to encrypt the travelling particle by
using the particle in the GHZ state as the control qubit. The boss Alice
decrypts the travelling particle with a CNot gate after performing a
operation on her particle in the GHZ state or not. After the GHZ states (the
quantum key) are used up, the parties check whether there is a vicious
eavesdropper, say Eve, monitoring the quantum line, by picking out some samples
from the GHZ states shared and measure them with two measuring bases. After
confirming the security of the quantum key, they use the GHZ states remained
repeatedly for next round of quantum communication. This scheme has the
advantage of high intrinsic efficiency for qubits and the total efficiency.Comment: 4 pages, no figure
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