Saturation of electrical resistivity

Resistivity saturation is observed in many metallic systems with a large resistivity, i.e., when the resistivity has reached a critical value, its further increase with temperature is substantially reduced. This typically happens when the apparent mean free path is comparable to the interatomic separations - the Ioffe-Regel condition. Recently, several exceptions to this rule have been found. Here, we review experimental results and early theories of resistivity saturation. We then describe more recent theoretical work, addressing cases both where the Ioffe-Regel condition is satisfied and where it is violated. In particular we show how the (semiclassical) Ioffe-Regel condition can be derived quantum-mechanically under certain assumptions about the system and why these assumptions are violated for high-Tc cuprates and alkali-doped fullerides.Comment: 16 pages, RevTeX, 15 eps figures, additional material available at http://www.mpi-stuttgart.mpg.de/andersen/saturation

Acute kidney injury in patients treated with immune checkpoint inhibitors

Background: Immune checkpoint inhibitor-associated acute kidney injury (ICPi-AKI) has emerged as an important toxicity among patients with cancer. Methods: We collected data on 429 patients with ICPi-AKI and 429 control patients who received ICPis contemporaneously but who did not develop ICPi-AKI from 30 sites in 10 countries. Multivariable logistic regression was used to identify predictors of ICPi-AKI and its recovery. A multivariable Cox model was used to estimate the effect of ICPi rechallenge versus no rechallenge on survival following ICPi-AKI. Results: ICPi-AKI occurred at a median of 16 weeks (IQR 8-32) following ICPi initiation. Lower baseline estimated glomerular filtration rate, proton pump inhibitor (PPI) use, and extrarenal immune-related adverse events (irAEs) were each associated with a higher risk of ICPi-AKI. Acute tubulointerstitial nephritis was the most common lesion on kidney biopsy (125/151 biopsied patients [82.7%]). Renal recovery occurred in 276 patients (64.3%) at a median of 7 weeks (IQR 3-10) following ICPi-AKI. Treatment with corticosteroids within 14 days following ICPi-AKI diagnosis was associated with higher odds of renal recovery (adjusted OR 2.64; 95% CI 1.58 to 4.41). Among patients treated with corticosteroids, early initiation of corticosteroids (within 3 days of ICPi-AKI) was associated with a higher odds of renal recovery compared with later initiation (more than 3 days following ICPi-AKI) (adjusted OR 2.09; 95% CI 1.16 to 3.79). Of 121 patients rechallenged, 20 (16.5%) developed recurrent ICPi-AKI. There was no difference in survival among patients rechallenged versus those not rechallenged following ICPi-AKI. Conclusions: Patients who developed ICPi-AKI were more likely to have impaired renal function at baseline, use a PPI, and have extrarenal irAEs. Two-thirds of patients had renal recovery following ICPi-AKI. Treatment with corticosteroids was associated with improved renal recovery

Contemporary issues in glass science

7-11Glasses-including non-oxide glasses-continue to be investigated for basic understanding and potential applications. The inter-related issues: glass formation as a self-organization process, glass transition, fast-ion relaxation in glasses, nanocrystallization and mixed alkali effect have been presented. Last two issues in the light of relevant experimental work including our own work on tellurite glasses have been focussed

ESR-A technique exclusive for understanding semiconductor processes

810-815ESR has recently emerged as an exclusive technique for the study of processes in semiconductor materials and devices. Four cases namely H in Si, O-related centers in porous Si, VLSI failure analysis and localized electrons and holes in a Si3N4 have been discussed, in an attempt to demonstrate the power of the technique. Some problems for the future are indicated

Sublattice magic?!-Phase transitions in superionics

296-304Mobile-ion sublattice formation and instability lead to interesting superionic phase transitions crucial to realization of Ag+ and Li+ superionic conductors. Superionicity is focused as ‘sublattice magic’ underscoring the mystery that is fundamentally interesting for further progress. AgCuSe, Ag3CuS2 and Li3DyBr6 are typical of an emerging breed of new superionics with as interesting physics as AgI and its ternaries. Mechanochemical reaction of Ag,Cu and I has given a facile new fabrication technology to investigate phase transitions by novel techniques such as EPR and electronic conductivity. HTXRD of AgI-CuI system has helped to investigate the phase diagram which has shown features including extended stability of γ-AgI and suppression of diffuse scattering in α-AgI. LiFePO4 made from a novel non-aqueous sol-gel technology is Fe3+ and enable para-antiferromagnetic phase transition to be investigated. Plasmon-exciton transition-a novel quasi-particle transition in iodized Ag thin films has promise for Surface Plasmon Resonance (SPR) sensing and iodine detection

Three strategies for fabrication of I-VII semiconductor nano(particles)structures

149-155Three methods of I-VII nanoparticle/nanostructure synthesis/fabrication as applied to AgI and AgI-CuI solid solutions (1) hot solution controlled precipitation, (2) mechanochemical reaction for metastable nanopowders such as γ-AgI and and (3) controlled iodization of Ag, Ag-Cu and Cu nanostructured thin films using a specially fabricated hourglass iodinator jig, are briefly outlined. They have applications in sensor and optoelectronic technologies. Focused though on I-VII semiconductors, they are equally applicable to chalcogenides and chalcohalides of transition and post-transition metals. These materials are used to investigate such exotic physics as stress-induced confinement of excitons in thin films and plasmon-exciton ‘transitions’. The efficacy of brief iodization for a modification of nanostructured Ag surfaces for photonic applications has recently been demonstrated. III-V and II-VI–type nanostructures could as well be fabricated and studied for I-VII semiconductors and their chalcogenide combinations I-VII-VI-an area that beckons the explorer and the exploiter

EPR probes ion dynamics of superionic conductors

637-643Superionic conductors possess large concentrations of monovalent mobile ions such as Ag+ in AgI and Li+ in LiClO4:PEG that travel through diffusion even larger number of defect sites leading to ionic conductivities of the order of 1S/cm around ambient temperature often through structural phase transitions. Any mobile ion complex that is part of a network or unit cell becoming paramagnetic through electron/hole capture, can serve as a probe for ion dynamics and phase transitions. This paper identifies the basic issues of superionic conductors from EPR standpoint and demonstrates through five case studies the power of the technique to investigate conduction mechanisms in terms of changes in structure and dynamics around the probe

Effect of Etching on the Optical, Morphological Properties of Ag Thin Films for SERS Active Substrates

Structural, optical, and morphological properties of Ag thin films before and after etching were investigated by using X-ray diffraction, UV-Vis spectrophotometer, and field emission scanning electron microscopy (FESEM). The HNO3 roughened Ag thin films exhibit excellent enhancement features and better stability than pure Ag thin films. Further, the Ag nanostructures are covered with Rhodamine 6G (Rh6G) and then tested with surface enhanced raman spectroscopy (SERS) for active substrates. Etched Ag films were found to exhibit a strong SERS effect and excellent thermal stability. Hence, the present method is found to be useful in the development of plasmon-based analytical devices, especially SERS-based biosensors