Complications and pitfalls of lumbar interlaminar and transforaminal epidural injections

Lumbar interlaminar and transforaminal epidural injections are used in the treatment of lumbar radicular pain and other lumbar spinal pain syndromes. Complications from these procedures arise from needle placement and the administration of medication. Potential risks include infection, hematoma, intravascular injection of medication, direct nerve trauma, subdural injection of medication, air embolism, disc entry, urinary retention, radiation exposure, and hypersensitivity reactions. The objective of this article is to review the complications of lumbar interlaminar and transforaminal epidural injections and discuss the potential pitfalls related to these procedures. We performed a comprehensive literature review through a Medline search for relevant case reports, clinical trials, and review articles. Complications from lumbar epidural injections are extremely rare. Most if not all complications can be avoided by careful technique with accurate needle placement, sterile precautions, and a thorough understanding of the relevant anatomy and contrast patterns on fluoroscopic imaging

Nonlinear optical properties of C-60 with explicit time-dependent electron dynamics

An explicit electron dynamics approach has been used to calculate the nonlinear optical properties of C-60 and its radical anion. An external perturbation, in the form of an oscillating electric field, induces the time-evolution of the molecular wavefunction. The time-averaged instantaneous dipole moment of the systems gives the molecular response to perturbations of varying field intensities and frequency of oscillation. The polarizabilities and the second-order hyperpolarizabilties have been calculated and are in good qualitative agreement with experimentally available data. In line with previous theoretical and experimental studies, the nonlinear effect is enhanced for the radical species

Optical limiting applications

Most promising applications of C60 fullerene are in the field of optoelectronics and nonlinear optics (NLO). Photovoltaic cells and infrared detectors are among actively pursued optoelectronic applications while, in the field of NLO, after some initial emphasis on third-order responses, such as intensity dependent refractive index, the focus is now mainly on optical limiting based on the mechanisms of reverse saturable absorption (RSA) and possibly other multiphoton processes. In the first section we define the ideal behavior of an optical limiter and summarize the physical mechanisms that may lead a real material to approach such an ideal behavior. The reverse saturable absorption (RSA) mechanism is emphasized and the nonlinear optical techniques for determining optical limiting properties are described. In section 3 the linear and nonlinear optical properties of fullerenes are illustrated. The third order NLO responses indicate that fullerene is a good optical material, while photophysical properties and absorption spectra of the ground the and excited states suggest the presence of a strong RSA in a large visible range. The experimental OL properties of fullerenes are described in section 4. The OL behavior of C60 in solution has been measured in a large wavelength range and compared with the calculated data, based on the RSA model. The presence of a prevailing RSA contribution is demonstrated but nonlinear scattering and nonlinear refractive changes are shown to contribute. In section 5 the optical properties of fullerene derivatives in solution are characterized, and compared with those of C60 and of a benchmark OL material like Sn-phthalocyanine. The issues related with preparing a solid OL material by inclusion of fullerene derivatives in a host matrix are discussed in section 6 and it is shown that with the use of suitably designed hybrid sol-gel glasses the OL performances of solution samples can be preserved. In section 7 it is shown that fullerenes, thanks to their electro-active properties, offer opportunities to implement different mechanisms of OL with the aim of extending the wavelength range of operation. Finally, section 8 addresses some current issues pertaining to the design and manufacture of practical OL devices and section 9 concludes this chapter with a summary and a few final remarks