Doublon-holon pairing mechanism via exchange interaction in two-dimensional cuprate Mott insulators

Coupling of charge and spin degrees of freedom is a critical feature of correlated electron oxides, as represented by the spin-related mechanism of a Cooper pair under high-T _c superconductivity. A doublon-holon pair generated on an antiferromagnetic spin background is also predicted to attract each other via the spin-spin interaction J, similar to a Cooper pair, while its evidence is difficult to obtain experimentally. Here, we investigate such an excitonic effect by electroreflectance spectroscopy using terahertz electric field pulses in undoped cuprates: Nd₂CuO₄, Sr₂CuO₂Cl₂, and La₂CuO₄. Analyses of the spectral changes of reflectivity under electric fields reveal that the splitting of odd-parity and even-parity excitons, a measure of doublon-holon binding energy, increases with J. This trend is reproduced by t-J-type model calculations, providing strong evidence of the spin-related doublon-holon pairing. Agreement with the calculations supports the s-wave symmetry of the doublon-holon pair in contrast to the d-wave Cooper pair in doped cuprates.

Plastid-to-Nucleus Retrograde Signalling during Chloroplast Biogenesis Does Not Require ABI4

Multiple abi4 alleles fail to show a deficiency in chloroplast-to-nucleus retrograde signalling indicating that, contrary to contemporary models, ABI4 is not a component of this signalling pathway

Smallest Optical Gap for Pt(II)-Pt(IV) Mixed-Valence Pt-Cl and Pt-Br Chain Complexes Achieved by Using a Multiple-Hydrogen-Bond Approach

A multiple-hydrogen-bond approach was applied to shorten Pt-X-Pt distances in Cl- and Br-bridged Pt chain complexes. [Pt(dabdOH)₂Cl]Cl₂ (5) and [Pt(dabdOH)₂Br]Br₂ (6) (dabdOH = (2 S,3 S)-2,3-diaminobutane-1,4-diol) contain hydroxy groups, which form additional hydrogen bonds with counteranions. 5 has the shortest Pt-Cl-Pt distance (5.0747(8) Å) of all Cl-bridged Pt chain complexes reported to date. Furthermore, the smallest optical gap (1.45 eV for 5 and 1.19 eV for 6) in any Cl- or Br-bridged Pt chain complex was achieved. 6 has the highest electrical conductivity (1.9 × 10^-5 S cm^-1 at room temperature) of all Br-bridged Pt chain complexes. This study shows that the introduction of additional hydrogen bonds between the ligands and halides is effective to enhance the electronic properties of halogen-bridged metal complexes.

Evidence for solitonic spin excitations from a charge-lattice-coupled ferroelectric order

Topological defects have been explored in different fields ranging from condensed matter physics and particle physics to cosmology. In condensed matter, strong coupling between charge, spin, and lattice degrees of freedom brings about emergent excitations with topological characteristics at low energies. One-dimensional (1D) systems with degenerate dimerization patterns are typical stages for the generation of topological defects, dubbed "solitons"; for instance, charged solitons are responsible for high electrical conductivity in doped trans-polyacetylene. Here, we provide evidence based on a nuclear magnetic resonance (NMR) study for mobile spin solitons deconfined from a strongly charge-lattice-coupled spin-singlet ferroelectric order in a quasi-1D organic charge-transfer complex. The NMR spectral shift and relaxation rate associated with static and dynamic spin susceptibilities indicate that the ferroelectric order is violated by dilute solitonic spin excitations, which were further demonstrated to move diffusively by the frequency dependence of the relaxation rate. The traveling solitons revealed here may promise the emergence of anomalous electrical and thermal transport.

Palisaded neutrophilic and granulomatous dermatitis associated with systemic lupus erythematosus: possible involvement of CD163+ M2 macrophages in two cases, and a review of published works

BACKGROUND

Palisaded neutrophilic and granulomatous dermatitis (PNGD) is a commonly occurring condition related to systemic autoimmune disease. It is characterized histopathologically by a distinct pattern of granulomatous inflammation in the presence or absence of leukocytoclastic vasculitis. The properties of granulomatous cells in PNGD are still uncertain.

OBJECTIVE

We sought further investigation on the phenotype of the infiltrated cells in PNGD from two patients with systemic lupus erythematosus (SLE) and reviewed the previous published reports in order to provide a comprehensive summary on the clinical features of PNGD in SLE.

METHODS

The immunohistochemical features of granulomatous cells in PNGD associated with SLE were analyzed. Immunohistochemical studies were performed on sections from our two cases using antibodies against CD68, CD163, CD15, Factor XIIIa, myeloperoxidase and neutrophil elastase. The clinical characteristics of the SLE patients who developed PNGD were also evaluated. We included all cases retrieved through a PubMed search with the key words PNGD and SLE.

RESULTS

Cutaneous lesions consisted of erythematous plaques distributed on the face and upper limbs in both cases. The infiltrated cells were mainly positive for CD68 and CD163, a phenotype suggestive of M2 macrophages. Some mature neutrophils and lymphocytes were also present. A review of the literature of PNGD associated with SLE revealed a predominance in females, high prevalence of lupus nephritis and a good response to systemic steroids, with frequent skin lesions relapses during tapering of the treatment.

LIMITATIONS

This study examined only two cases; the pathogenesis of the disease remains to be clarified.

CONCLUSION

PNGD lesions were abundantly infiltrated by M2 macrophages, suggesting that they may have a role in this condition. SLE accompanied by PNGD might be associated with lupus nephritis and frequent relapses of skin lesions.

Probing ultrafast spin-relaxation and precession dynamics in a cuprate Mott insulator with seven-femtosecond optical pulses

A charge excitation in a two-dimensional Mott insulator is strongly coupled with the surrounding spins, which is observed as magnetic-polaron formations of doped carriers and a magnon sideband in the Mott-gap transition spectrum. However, the dynamics related to the spin sector are difficult to measure. Here, we show that pump-probe reflection spectroscopy with seven-femtosecond laser pulses can detect the optically induced spin dynamics in Nd2CuO4, a typical cuprate Mott insulator. The bleaching signal at the Mott-gap transition is enhanced at ~18 fs. This time constant is attributable to the spin-relaxation time during magnetic-polaron formation, which is characterized by the exchange interaction. More importantly, ultrafast coherent oscillations appear in the time evolution of the reflectivity changes, and their frequencies (1400-2700 cm-1) are equal to the probe energy measured from the Mott-gap transition peak. These oscillations can be interpreted as the interference between charge excitations with two magnons originating from charge-spin coupling.

Vacuolar ATPase as a potential therapeutic target and mediator of treatment resistance in cancer

Vacuolar ATPase (V-ATPase) is an ATP-dependent H+ -transporter that pumps protons across intracellular and plasma membranes. It consists of a large multi-subunit protein complex and influences a wide range of cellular processes. This review focuses on emerging evidence for the roles for V-ATPase in cancer. This includes how V-ATPase dysregulation contributes to cancer growth, metastasis, invasion and proliferation, and the potential link between V-ATPase and the development of drug resistance.

Residual carcinoma cells after chemoradiotherapy for esophageal squamous cell carcinoma patients: striving toward appropriate judgment of biopsy

In esophageal squamous cell carcinoma (ESCC) patients who are treated with chemoradiotherapy (CRT), identification of the presence or absence of residual or recurrent carcinoma is usually pivotal in their clinical management. In addition, the extent of carcinoma invasion into the esophageal wall could determine the clinical outcome of these patients following CRT. Therefore, in this study, we evaluated the response to CRT both macroscopically and histologically in a consecutive series of 42 ESCC patients receiving neoadjuvant chemoradiotherapy following curative esophageal resection at Tohoku University Hospital between August 2011 and December 2012. The histological grading of tumor regression was as follows: grade 3, markedly effective (no viable residual tumor cells); grade 2, moderately effective (residual tumor cells in less than one-third of the tumor); grade 1, slightly effective (1b, residual tumor cells in one-third to two-thirds of the tumor; 1a, residual tumor cells in more than two-thirds of the tumor); and grade 0, ineffective. In this study, we selected grade 2 and 1b cases because they might show a complete response with definitive CRT. We evaluated the presence of any residual in situ lesions and tumor depth in detail. The grading of tumor regression in primary sites was as follows: grade 3 (7 cases), grade 2 (16 cases), grade 1b (13 cases), and grade 1a (6 cases). The concordance rate between macroscopic and histopathological evaluation on the depth of the tumor was 40% (17/42). Among 29 cases (grade 2 and grade 1b), intraepithelial lesions were not detected in 17 cases, and tumor nests were not detected in the lamina propria mucosae in 9 cases. The results of this study highlight the difficulties of detecting residual carcinoma cells using conventional endoscopic biopsy in patients who have received CRT. Therefore, when residual cancer is clinically suspected in patients who have received CRT, the biopsy specimen should be obtained from the deep layer of the esophagus whenever possible. Additionally, close follow-up is required using positron emission tomography/computed tomography, endoscopy, and other radiological evaluations.