Electrical Properties and Defect Structure in The Sr-Fe-Co-O System

ABSTRACTThe ceramic Sr-Fe-Co-O has potential use as a membrane in gas separation. This material exhibits high conductivity of both electrons and oxygen ions. It allows oxygen to penetrate at high flux rates without other gas components. Electrical properties are essential to understanding the oxygen transport mechanism and defect structure of this material. By using a gas-tight electrochemical cell with flowing air as the reference environment, we were able to achieve an oxygen partial pressure (P02) as low as 10−16 atm. Total and ionic conductivities of Sr-Fe-Co-O have been studied as a function of P02 at elevated temperature. In air, both total and ionic conductivities increase with temperature, while the ionic transference number is almost independent of temperature, with a value of ≈0.4. Experimental results show that ionic conductivity decreases with decreasing P02 at high P02 (≥10−6 atm). This suggests that interstitial oxygen ions and electron holes are the dominant charge carriers. At 800°C in air, total conductivity and ionic conductivity are 17 and 7 S/cm, respectively. Defect dynamics in this system can be understood by means of the trivalence-to-divalence transition of Fe ions when P02 is reduced. By using the conductivity results, we estimated oxygen penneation through a ceramic membrane made of this material. The calculated oxygen permeability agrees with the experimental value obtained directly from an operating methane conversion reactor.</jats:p

Polarization angle accuracy for future CMB experiments. The COSMOCal project and its prototype in the 1mm band

The Cosmic Microwave Background (CMB) radiation offers a unique window into the early Universe, facilitating precise examinations of fundamental cosmological theories. However, the quest for detecting B-modes in the CMB, predicted by theoretical models of inflation, faces substantial challenges in terms of calibration and foreground modeling. The COSMOCal (COsmic Survey of Millimeter wavelengths Objects for CMB experiments Calibration) project aims at enhancing the accuracy of the absolute calibration of the polarization angle $\psi$ of current and future CMB experiments. The concept includes the build of a very well known artificial source emitting in the frequency range [20-350] GHz that would act as an absolute calibrator for several polarization facilities on Earth. A feasibility study to place the artificial source in geostationary orbit, in the far field for all the telescopes on Earth, is ongoing. In the meanwhile ongoing hardware work is dedicated to build a prototype to test the technology, the precision and the stability of the polarization recovering in the 1 mm band (220-300 GHz). High-resolution experiments as the NIKA2 camera at the IRAM 30m telescope will be deployed for such use. Once carefully calibrated ($\Delta\psi$ < 0.1 degrees) it will be used to observe astrophysical sources such as the Crab nebula, which is the best candidate in the sky for the absolute calibration of CMB experiments.Comment: to appear in Proc. of the mm Universe 2023 conference, Grenoble (France), June 2023, published by F. Mayet et al. (Eds), EPJ Web of conferences, EDP Science

Polarization angle accuracy for future CMB experiments

The Cosmic Microwave Background (CMB) radiation offers a unique window into the early Universe, facilitating precise examinations of fundamental cosmological theories. However, the quest for detecting B-modes in the CMB, predicted by theoretical models of inflation, faces substantial challenges in terms of calibration and foreground modeling. The COSMOCal (COsmic Survey of Millimeter wavelengths Objects for CMB experiments Calibration) project aims at enhancing the accuracy of the absolute calibration of the polarization angle ψ of current and future CMB experiments. The concept includes the build of a very well known artificial source emitting in the frequency range [20-350] GHz that would act as an absolute calibrator for several polarization facilities on Earth. A feasibility study to place the artificial source in geostationary orbit, in the far field for all the telescopes on Earth, is ongoing. In the meanwhile ongoing hardware work is dedicated to build a prototype to test the technology, the precision and the stability of the polarization recovering in the 1 mm band (220-300 GHz). High-resolution experiments as the NIKA2 camera at the IRAM 30m telescope will be deployed for such use. Once carefully calibrated (Δψ < 0.1◦) it will be used to observe astrophysical sources such as the Crab nebula, which is the best candidate in the sky for the absolute calibration of CMB experiments

Chronic scapholunate instability treated by scaphocapitate fusion: A midterm outcome perspective

SummaryIntroductionChronic scapholunate instability can lead to functional deficits and radiocarpal osteoarthritis. A number of procedures, namely scapho-trapezio-trapezoid (STT) fusion, scaphocapitate (SC) fusion or soft tissue reconstruction procedures, aim to improve function while protecting the wrist from osteoarthritis.HypothesisDefine the role of scaphocapitate fusion in comparison to STT fusion and capsulodesis and ligament reconstruction.Material and methodsA clinical, radiographic and functional evaluation was performed on 31 SC fusion cases with an average follow-up of 5years.ResultsRange of motion was 41° in flexion and 39° in extension. Radial-ulnar deviation was 43°. Strength was 32.5kgf (Jamar). The DASH was 27% and the PRWE was 25%. Fifty percent of the wrists were pain-free at rest. Ninety-four percent of patients were satisfied with the procedure. Seventy-eight percent of patients had returned to their occupation. Radiographic analysis revealed that consolidation was obtained at 10.1weeks. The postoperative radioscaphoid angle was 55° with good radioscaphoid congruence. There was no osteoarthritis in the radioscaphoid joint in 84% of the cases. The non-union rate was 13%.DiscussionThese data are similar to the few series that exist. STT fusion leads the same clinical results, but it is technically more difficult and has a higher rate of complications. Capsulodesis and ligament reconstruction provide the same functional results as SC fusion, but with slightly less stiffening. However, these techniques do not seem to protect the wrist from arthritic degeneration at longer follow-up. SC fusion is superior to STT fusion for the treatment of chronic scapholunate instability. This is a pain-relieving intervention with good clinical results and preservation of scaphoid stability. As a component of the surgeon's armamentarium, it can be held in the same regard as capsulodesis and ligament reconstruction for cases of chronic scapholunate instability with a non-reducible scaphoid, or after failure of a soft tissue reconstruction procedure.Level of evidenceLevel 4, retrospective study

Dorsal locking plates versus staples in four-corner fusion: A comparative clinical and radiological study

AbstractIntroductionFour-corner fusion was described in 1984 by HK Watson for the treatment of SLAC wrist. This intervention has undergone few changes since that description, but the debate on the fixation method is still not resolved.HypothesisDorsal locking plates provide better stability, short immobilization and a quicker return to daily activities than traditional fixation methods such as staples.Materials and methodsThirty-one fusions using the Medartis Aptus Four-Corner Fusion® plate at a mean 13.1months’ follow-up and 35 using staples at a mean 80.4months’ follow-up were reviewed in a clinical and radiographic retrospective comparative study.ResultsResults were comparable between the two groups in terms of range of motion (flexion-extension arc of 67.3° for plates and 60.6° for staples), force (29.6 and 28kg.F), pain and disability (PRWE 34.8/150 and 40.9; QuickDASH 19.83/100 and 30). Mean time off work was significantly shorter in the plate group (4.5 vs. 7.9months). There were no non-unions in the plate group, versus 2 in the staples group. Dorsal impingement implicating hardware was also less frequent in the plate group (2 vs. 11).DiscussionThe dorsal locking plate did not improve final results in four-corner fusion in terms of range of motion, force, pain or function compared to staples. However, it provided stable fixation, allowing a shorter immobilization and a quicker return to work. Although the initial cost is higher, it could allow significant savings on postoperative costs, shifting the technical debate into the field of public health.Level of evidenceLevel IV, retrospective study

The role of three-ligament tenodesis in the treatment of chronic scapholunate instability

Restoring ligamentous control in dissociative carpal instability is a major issue in protecting against osteoarthritis. We present clinical and radiological results for 20 patients who underwent flexor carpi radialis three-ligament tenodesis and were prospectively reviewed at a mean follow-up of 25.1 months. Three-ligament tenodesis significantly relieved pain and increased grip strength, wrist function at the expense of joint stiffness. This improvement was not seen in cases of dynamic instability. However, ligamentous loosening did result in rapid recurrence of radiological anomalies and frequent complications. This study challenges the long-term benefit of three-ligament tenodesis in both dynamic and static chronic scapholunate instability. </jats:p

Venus night side measurements of winds at 115 km altitude from NO bright patches tracking.

N and O atoms produced by photo-dissociation of CO2 and N2 on the day side of Venus are transported to the night side in the thermospheric circulation. When the air parcel is descending, the recombination N+O→ NO produces the famous γ and δ bands of NO emission. Pioneer Venus (1978) suggested that the statistical center of the emission is off from the anti-solar point, about one- two hours in Local time after midnight. This is confirmed from SPICAV/VEX results, and the explanation generally accepted is the influence of retrograde super rotation. However, the emission takes place at 115 km, while VIRTIS/VEX, with maps of O2 emission (peak altitude 95 km) in the night side of Venus (recombination of O+O coming from the day side), has shown that the maximum of emission is statistically centered on the antisolar point. Therefore, there is no influence of super-rotation at 95 km. One way to explain this paradox is that the cause of the super rotation is different at 115 km and in the lower atmosphere. Alternately, some gravity waves could propagate from below, crossing the altitude 95 km with minimal interaction, and breaking around 115, depositing their momentum. Another consideration is that the altitude of N2 photo-dissociation is higher in the thermosphere than CO2, therefore the thermospheric circulation pattern may be different for the transport of N atoms, and O atoms. We have started building maps of the NO emission by moving around the spacecraft along its orbit on the night side. The idea is that NO emission is concentrated generally in rather well defined patches of light. Therefore, by comparing maps taken at 1 hour or 24 hr interval, we can make a “bright patch tracking”, and derive directly the velocity of the moving air parcel containing N and O (we are aware that a part of the motion could be due to a phase shift of a gravity wave, if it has some influence on the NO emission). Preliminary results from this exercise with Venus Express will be presented and discussed