Self-contained Kondo effect in single molecules

Kondo coupling of f and conduction electrons is a common feature of f-electron intermetallics. Similar effects should occur in carbon ring systems(metallocenes). Evidence for Kondo coupling in Ce(C8H8)2 (cerocene) and the ytterbocene Cp*2Yb(bipy) is reported from magnetic susceptibility and L_III-edge x-ray absorption spectroscopy. These well-defined systems provide a new way to study the Kondo effect on the nanoscale, should generate insight into the Anderson Lattice problem, and indicate the importance of this often-ignored contribution to bonding in organometallics.Comment: 4 pages, 5 figures (eps

Thermodynamic evolution of a sigmoidal active region with associated flares

Active regions often show S-shaped structures in the corona called sigmoids. These are highly sheared and twisted loops formed along the polarity inversion line. They are considered to be one of the best pre-eruption signatures for CMEs. Here, we investigate the thermodynamic evolution of an on-disk sigmoid observed during December 24-28, 2015. For this purpose, we have employed Emission Measure (EM) and filter-ratio techniques on the observations recorded by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) and X-ray Telescope (XRT) onboard Hinode. The EM analysis showed multi-thermal plasma along the sigmoid and provided a peak temperature of 10-12.5 MK for all observed flares. The sigmoidal structure showed emission from Fe XVIII (93.93 {\AA}) and Fe XXI 128.75 {\AA}) lines in the AIA 94 and 131 {\AA} channels, respectively. Our results show that the hot plasma is often confined to very hot strands. The temperature obtained from the EM analysis was found to be in good agreement with that obtained using the XRT, AIA, and GOES filter-ratio methods. These results provide important constraints for the thermodynamic modeling of sigmoidal structures in the core of active regions. Moreover, this study also benchmarks different techniques available for temperature estimation in solar coronal structures.Comment: 19 pages, 13 figures, Accepted for publication in Monthly Notices of the Royal Astronomical Societ

Study of arthroscopic anterior cruciate ligament reconstruction using single bundle hamstring auto-graft by trans-portal technique

Background: Anterior cruciate ligament (ACL) tear is a serious injury that results in immediate knee instability, lengthy rehabilitation and increased risk of early onset knee osteoarthritis. The goal of anatomic reconstruction is to place the ACL graft at a more anatomic location on both tibia and femur. The purposes of the study were to evaluate the outcome of trans-portal arthroscopic ACL reconstruction clinically and radiologically and to compare the results with reported studies.Methods: 52 patients with complete tear of the ACL were treated with arthroscopic ACL reconstruction. The patients were regularly followed up at 4, 8, 12 and 24 weeks whereby laxity, pain and range of motion were assessed.Results: There were 43 male and 9 females with the mean age being 30.38 years. Left sided injury was more common seen in 31 patients (59.62%) where domestic twist injury caused most of the ACL tears. Only 4 cases (7.69%) had isolated ACL tears and lateral meniscus was the most common associated injury found in 25 patients (48.07%) Average operative time was 113 minutes. Pain was the most common post-op complication seen in 16 patients (30.76%) while laxity was noted in 4 patients. Average flexion of 111.44 degrees was reached at 6 months. 37 cases (71.15%) had excellent post-op outcome at 6 months as per the modified cincinnati rating system.Conclusions: ACL reconstruction using the arthroscopic trans-portal technique provides good post-op knee stability and satisfactory range of motion

Behaviour of molecular hydrogen emission in three solar flares

We have systematically investigated ultraviolet (UV) emission from molecular hydrogen (H$_{2}$) using the Interface Region Imaging Spectrometer (IRIS), during three X-ray flares of C5.1, C9.7 and X1.0 classes on Oct. 25, 2014. Significant emission from five H$_{2}$ spectral lines appeared in the flare ribbons, interpreted as photo-excitation (fluorescence) due to the absorption of UV radiation from two Si IV spectral lines. The H$_{2}$ profiles were broad and consisted of two non-stationary components in red and in the blue wings of the line in addition to the stationary component. The red (blue) wing components showed small redshifts (blue shifts) of ~5-15 km s$^{-1}$ (~5-10 km s$^{-1}$). The nonthermal velocities were found to be ~5-15 km s$^{-1}$. The interrelation between intensities of H$_{2}$ lines and their branching ratios confirmed that H$_{2}$ emission formed under optically thin plasma conditions. There is a strong spatial and temporal correlation between Si IV and H$_{2}$ emission, but the H$_{2}$ emission is more extended and diffuse, further suggesting H$_{2}$ fluorescence, and - by analogy with flare ''back-warming'' providing a means to estimate the depth from which the H$_{2}$ emission originates. We find that this is 1871$\pm$157 km and 1207$\pm$112 km below the source of the Si IV emission, in two different ribbon locations.Comment: 14 pages, 12 figures, accepted for publication in MNRA

Type 2 Endoleak With or Without Intervention and Survival After Endovascular Aneurysm Repair

Objective: The aims of the present study were to examine the impact of type 2 endoleaks (T2EL) on overall survival and to determine the need for secondary intervention after endovascular aneurysm repair (EVAR). Methods: A multicentre retrospective cohort study in the Netherlands was conducted among patients with an infrarenal abdominal aortic aneurysm (AAA) who underwent EVAR between 2007 and 2012. The primary endpoint was overall survival for patients with (T2EL+) or without (T2EL-) a T2EL. Secondary endpoints were sac growth, AAA rupture, and secondary intervention. Kaplan–Meier survival and multivariable Cox regression analysis were used. Results: A total of 2 018 patients were included. The median follow up was 62.1 (range 0.1 – 146.2) months. No difference in overall survival was found between T2EL+ (n = 388) and T2EL- patients (n = 1630) (p =.54). The overall survival estimates at five and 10 years were 73.3%/69.4% and 45.9%/44.1% for T2EL+/T2EL- patients, respectively. Eighty-five of 388 (21.9%) T2EL+ patients underwent a secondary intervention. There was no difference in overall survival between T2EL+ patients who underwent a secondary intervention and those who were treated conservatively (p =.081). Sac growth was observed in 89 T2EL+ patients and 44/89 patients (49.4%) underwent a secondary intervention. In 41/44 cases (93.1%), sac growth was still observed after the intervention, but was left untreated. Aneurysm rupture occurred in 4/388 T2EL patients. In Cox regression analysis, higher age, ASA classification, and maximum iliac diameter were significantly associated with worse overall survival. Conclusion: No difference in overall survival was found between T2EL+ and T2EL- patients. Also, patients who underwent a secondary intervention did not have better survival compared with those who did not undergo a secondary intervention. This study reinforces the need for conservative treatment of an isolated T2EL and the importance of a prospective study to determine possible advantages of the intervention

Evidence of chromospheric molecular hydrogen emission in a solar flare observed by the IRIS satellite

We have carried out the first comprehensive investigation of enhanced line emission from molecular hydrogen, H2 at 1333.79 Å, observed at flare ribbons in SOL2014-04-18T13:03. The cool H2 emission is known to be fluorescently excited by Si IV 1402.77 Å UV radiation and provides a unique view of the temperature minimum region (TMR). Strong H2 emission was observed when the Si IV 1402.77 Å emission was bright during the flare impulsive phase and gradual decay phase, but it dimmed during the GOES peak. H2 line broadening showed non-thermal speeds in the range 7-18 km s−1, possibly corresponding to turbulent plasma flows. Small red (blue) shifts, up to 1.8 (4.9) km s−1 were measured. The intensity ratio of Si IV 1393.76 Å and Si IV 1402.77 Å confirmed that plasma was optically thin to Si IV (where the ratio = 2) during the impulsive phase of the flare in locations where strong H2 emission was observed. In contrast, the ratio differs from optically thin value of 2 in parts of ribbons, indicating a role for opacity effects. A strong spatial and temporal correlation between H2 and Si IV emission was evident supporting the notion that fluorescent excitation is responsible

Analysis of Outcomes After Endovascular Abdominal Aortic Aneurysm Repair in Patients With Abnormal Findings on the First Postoperative Computed Tomography Angiography

PURPOSE: Lifelong follow-up after endovascular abdominal aortic aneurysm repair (EVAR) is recommended due to a continued risk of complications, especially if the first postoperative imaging shows abnormal findings. We studied the long-term outcomes in patients with abnormalities on the first postoperative computed tomography angiography (CTA) following EVAR. MATERIALS AND METHODS: This is a retrospective study of all consecutive patients who underwent elective EVAR for nonruptured abdominal aortic aneurysm (AAA) between January 2007 and January 2012 in 16 Dutch hospitals with follow-up until December 2018. Patients were included if the first postoperative CTA showed one of the following abnormal findings: endoleak type I–IV, endograft kinking, infection, or limb occlusion. AAA diameter, complications, and secondary interventions during follow-up were registered. Primary endpoint was overall survival, and other endpoints were secondary interventions and intervention-free survival. Kaplan-Meier analyses were used to estimate overall and intervention-free survival. Cox regression analyses were used to identify the association of independent determinants with survival and secondary interventions. RESULTS: A total of 502 patients had abnormal findings on the first postoperative CTA after EVAR and had a median follow-up (interquartile range IQR) of 83.0 months (59.0). The estimated overall survival rate at 1, 5, and 10 years was 84.7%, 51.0%, and 30.8%, respectively. Age [hazard ratio (HR) 1.06, 95% confidence interval (CI) 1.05 to 1.10] and American Society of Anesthesiologists (ASA) classification (ASA IV HR 3.20, 95% CI 1.99 to 5.15) were significantly associated with all-cause mortality. Overall, 167 of the 502 patients (33.3%) underwent 238 secondary interventions in total. Fifty-eight patients (12%) underwent an intervention based on a finding on the first postoperative CTA. Overall survival was 38.4% for patients with secondary interventions and 44.5% for patients without (log rank; p=0.166). The intervention-free survival rate at 1, 5, and 10 years was 82.9%, 61.3%, and 45.6%, respectively. CONCLUSIONS: Patients with abnormalities on the first postoperative CTA after elective EVAR for infrarenal AAA cannot be discharged from regular imaging follow-up due to a high risk of secondary interventions. Patients who had a secondary intervention had similar overall survival as those without secondary interventions