A variational perturbation scheme for many-particle systems in the functional integral approach

A variational Perturbation theory based on the functional integral approach is formulated for many-particle systems. Using the variational action obtained through Jensen-Peierls' inequality, a perturbative expansion scheme for the thermodynamic potential is established. A modified Wick's theorem is obtained for the variational perturbation expansions. This theorem allows one to carry out systematic calculations of higher order terms without worrying about the double counting problem. A model numerical calculation was carried out on a nucleon gas system interacting through the Yukawa-type potential to test the efficiency of the present method.Comment: accepted for publication in Phys. Rev.

Superficial cervical plexus block for management of herpes zoster neuralgia in the C3 dermatome: a case report

INTRODUCTION: Herpes zoster is a well-known reactivating viral disease that gives rise to painful skin lesions. Although this vesicular rash heals up within a few weeks, pain sometimes continues, becoming postherpetic neuralgia. In the case of those at high risk of developing postherpetic neuralgia, early interventional pain management is generally recommended as a preventive measure. Pain specialists usually do not see patients face-to-face for chronic refractory pain until the stage of postherpetic neuralgia. However, active and aggressive management, including antiviral treatment, of herpetic neuralgia during the acute stage of herpes zoster promises better results. In this respect, superficial cervical plexus block can help patients, such as the case reported here, by relieving the pain of herpes zoster involving the C3 dermatome. CASE PRESENTATION: A 65-year-old Korean man with severe pain in his left C3 dermatome due to herpes zoster was admitted to our hospital. His pain was so refractory to medication that he consulted our pain clinic for pain control. Due to the medication limitations imposed by his underlying diseases (hepatitis B, liver cirrhosis, atrial fibrillation, and asthma), early interventional therapy including stellate ganglion block was planned. In addition, because his painful C3 dermatome overlapped significantly with the superficial cervical plexus dermatome, ultrasound-guided superficial cervical plexus block was utilized for pain control of the intractable herpes zoster neuritis in his C3 dermatome. The result with respect to his sporadic neuralgia was satisfactory. CONCLUSIONS: We found superficial cervical plexus block to be an effective interventional procedure for pain management of herpes zoster, particularly at the C3-dermatomal level

Epitaxially strained ultrathin LaNiO3_3/LaAlO3_3 and LaNiO3_3/SrTiO3_3 superlattices: a density functional theory + UU study

By employing first-principles electronic structure calculations we investigate nickelate superlattices [LaNiO$_3$]$_1$/[LaAlO$_3$]$_1$ and [LaNiO$_3$]$_1$/[SrTiO$_3$]$_1$ with (001) orientation under epitaxial tensile strain. Within density functional theory augmented by mean-field treatement of on-site electronic correlations, the ground states show remarkable dependence on the correlation strength and the strain. In the weakly and intermediately correlated regimes with small epitaxial strain, the charge-disproportionated insulating states with antiferromagneitc order is favored over the other orbital and spin ordered phases. On the other hand, in the strongly correlated regime or under the large tensile strain, ferromagnetic spin states with Jahn-Teller orbital order become most stable. The effect from polar interfaces in LaNiO$_3$]$_1$/[SrTiO$_3$]$_1$ is found to be noticeable in our single-layered geometry. Detailed discussion is presented in comparison with previous experimental and theoretical studies.Comment: 9 pages, 8 figure

Synthesis and Properties of Fluorinated Polyimides from Rigid and Twisted Bis(Trifluoromethyl)Benzidine for Flexible Electronics

Fluorinated polyimides were prepared from the twisted benzidine monomer containing two trifluoromethyl (CF3) groups on one aromatic ring. The diamine monomer having a rigid and nonplanar structure was polymerized with typical dianhydride monomers including BPDA, BTDA, ODPA, 6-FDA, and PMDA, to obtain the corresponding polyimides. Most polyimides are soluble in organic solvents due to their twisted chain structure and can be solution cast into flexible and tough films. These films have a UV-vis absorption cut-off wavelength at 354–398 nm and a light transparency of 34–90% at a wavelength of 550 nm. They also have tensile strengths of 92–145 MPa and coefficients of thermal expansion (CTE) of 6.8–63.1 ppm/°C. The polymers exhibited high thermal stability with 5% weight loss at temperatures ranging from 535 to 605°C in nitrogen and from 523 to 594°C in air, and high glass temperature (Tg) values in the range of 345–366°C. Interestingly, some of the soluble polyimides showed thermo-responsive behaviors in organic solvents presumably due to the multiple hydrogen bondings with unsymmetrically positioned two CF3 groups along the polymer chains