Treatment of Thoracolumbar Fractures Through Different Short Segment Pedicle Screw Fixation Techniques: A Finite Element Analysis.

OBJECTIVE: To compare the von Mises stresses of the pedicle screw system and the displacement of injured vertebrae using 3-D finite element analysis, and to evaluate the curative effect of the pedicle screw system. METHODS: Finite element methods were used for biomechanical comparison of four posterior short segment pedicle screw fixation techniques. The different pedicle screw models are traditional trajectory (TT), Universal Spine System (USS), cortical bone trajectory (CBT), and CBT at the cranial level and pedicle screw (PS) at the caudal level (UP-CBT). The stress distribution of the screws and connecting rods under different working conditions and the displacement of the injured vertebrae were compared and analyzed. RESULTS: After the pedicle screw system was fixed, the stress under vertical compression was mainly concentrated at the proximal end of the screw, while the stress was mainly concentrated on the connecting rod during flexion, extension, lateral flexion, and rotation. The TT group had the greatest stress during the flexion, extension, and left and right rotation. The UP-CBT group was most stressed when the left and right sides were flexed; the stress of the USS screw system was less than that of the other three models during flexion, lateral flexion, and rotation. The maximum von Mises stress values of pedicle screws in all exercise states were 556.2, 340.7, 458.1, and 533.4 MPa, respectively. In the USS group, the displacement of the injured vertebra was small in the flexion, and the left and right lateral flexion and the right rotation were higher than in the TT group and the CBT group. The maximum displacements of the injured vertebrae in all motion states were 1.679, 1.604, 1.752, and 1.777 mm, respectively. CONCLUSION: Universal Spine System pedicle screws are relatively less stressed under different working conditions, the risk of breakage is small, and the model is relatively stable; CBT screws do not exhibit better mechanical properties than conventional pedicle screws and USS pedicle screws.

Cs2 Bi2 O(Ge2 O7 ) (CBGO): A Larger SHG Effect Induced by Synergistic Polarizations of BiO5 Polyhedra and GeO4 Tetrahedra.

A cesium bismuth germanate, Cs2 Bi2 O(Ge2 O7 ) (CBGO), was synthesized by a traditional high-temperature solid-state reaction. Its structure features a 3D network composed of a 1D chains composed of Bi2 O8 dimers that are further bridged by Ge2 O7 dimers, forming tunnels of seven member rings (MRs) that are filled by the Cs+ cations. CBGO exhibits extraordinary larger second harmonic generation (SHG) response of about 13.7 times that of KDP (KH2 PO4 ) under 1064 nm laser radiation and 1.1 times that of KTP (KTiOPO4 ) under 2.05 µm laser radiation, which is the highest among all of the metal germanates reported so far. CBGO possesses a moderate birefringence (0.073 at 1064 nm) and is phase matchable. Furthermore, CBGO melts congruently and exhibits high thermal stability.

Highly Polarizable Hg2+ Induced a Strong Second Harmonic Generation Signal and Large Birefringence in LiHgPO4.

A new ultraviolet nonlinear optical material, namely LiHgPO4, was synthesized using the mild hydrothermal method. The structure of LiHgPO4 features novel double layers constructed by severely distorted HgO6 octahedra and PO4 tetrahedra, which are further interconnected by LiO4 tetrahedra to form a three-dimensional structure. LiHgPO4 exhibits a very strong second harmonic generation (SHG) response of 11.0 times that of KH2PO4 and a relatively large birefringence (0.068 at 1064 nm) among the reported SHG-active phosphates. Theoretical calculations revealed that the introduction of the Hg2+ in a highly distorted HgO6 octahedral geometry is crucial to produce the strong SHG response and large birefringence.

(H3O)HCs2Nb(IO3)9 and SrNbO(IO3)5: a facile synthetic method using hydrofluoric acid as a solubilizer.

By using hydrofluoric acid as a solubilizer, the first alkali-metal niobium iodate and an alkali-earth metal niobium iodate, i.e. (H3O)HCs2Nb(IO3)9 and SrNbO(IO3)5, have been obtained. An obvious cation-controlled polarity shift is observed in the Ae/A-Nb5+-IO3 system. (H3O)HCs2Nb(IO3)9 gives a strong second harmonic generation (SHG) signal about 6 times that of KH2PO4 (KDP), making it a promising nonlinear optical (NLO) material.

HBa2.5(IO3)6(I2O5) and HBa(IO3)(I4O11): Explorations of Second-Order Nonlinear Optical Materials in the Alkali-Earth Polyiodate System.

Two new barium polyiodate compounds in the alkali-earth system, namely, HBa2.5(IO3)6(I2O5) ( Fdd2) and HBa(IO3)(I4O11) ( P1̅) have been obtained through hydrothermal reaction. Interestingly, the structures of both compounds feature different polyiodate groups, i.e., I2O5 and I4O11 groups. HBa2.5(IO3)6(I2O5) can be depicted as an alternative stacking of two-dimensional (2D) [Ba4(IO3)8(I2O5)2] and [Ba(IO3)4(I2O5)2]2- layers with the I2O5 and IO3 group serving as linkers. HBa(IO3)(I4O11) can be depicted as a 3D network with 2D [Ba(I4O11)] layers being interconnected by IO3 groups. The 0D I4O11 polyiodate group can be seen also viewed as formed by an I3O8 group further corner-sharing with an IO3 group or an I2O5 group further corner-sharing with two IO3 groups. Powder second harmonic generation (SHG) measurements show that HBa2.5(IO3)6(I2O5) crystals display a moderate SHG efficiency of ∼1.6 times that of KH2PO4 (KDP) and are phase-matchable. Optical properties measurements, thermal analyses, and laser damage threshold (LDT) measurements have been performed. Results of theoretical calculation show that the formation of I4O112- is thermodynamically much easier than I3O8- and I2O5, because of the lower reaction energy. Our studies shed light on exploring alkali-earth polyiodates as potential NLO materials.

Near-infrared light-triggered theranostics for tumor-specific enhanced multimodal imaging and photothermal therapy.

The major challenge in current clinic contrast agents (CAs) and chemotherapy is the poor tumor selectivity and response. Based on the self-quench property of IR820 at high concentrations, and different contrast effect ability of Gd-DOTA between inner and outer of liposome, we developed "bomb-like" light-triggered CAs (LTCAs) for enhanced CT/MRI/FI multimodal imaging, which can improve the signal-to-noise ratio of tumor tissue specifically. IR820, Iohexol and Gd-chelates were firstly encapsulated into the thermal-sensitive nanocarrier with a high concentration. This will result in protection and fluorescence quenching. Then, the release of CAs was triggered by near-infrared (NIR) light laser irradiation, which will lead to fluorescence and MRI activation and enable imaging of inflammation. In vitro and in vivo experiments demonstrated that LTCAs with 808 nm laser irradiation have shorter T1 relaxation time in MRI and stronger intensity in FI compared to those without irradiation. Additionally, due to the high photothermal conversion efficiency of IR820, the injection of LTCAs was demonstrated to completely inhibit C6 tumor growth in nude mice up to 17 days after NIR laser irradiation. The results indicate that the LTCAs can serve as a promising platform for NIR-activated multimodal imaging and photothermal therapy.