Role of van der Waals forces in the metal-insulator transition of transition metal oxides.

Transition metal oxides (TMOs) exhibit great potential in technological applications due to their ability to undergo a rapid metal-insulator transition (MIT). However, the phase stability of TMOs, which models the on/off voltages of electronic devices, remains controversial due to the incomplete knowledge of the determinants of its stability. Herein, we study the effect of van der Waals (vdW) interactions on the phase stability of TMOs by employing the pairwise and screened vdW methods. Our calculations manifest that the vdW interactions are crucial to the TMOs' phase stability and tend to stabilize the insulating phase. Furthermore, the long-range electrodynamic screening interactions correct the TMOs' phase stability by revising the vdW term.

Determinants of interchain coupling properties of Te atomic chains.

The coupling effect of one-dimensional (1D) materials is of great significance for the practical application of 1D materials in high-density memory devices and ultra-micro nanometer array lasers. However, the determinants of the coupling effect remain debated. Here, using first principles methods, we investigate the effects of chirality, size and stacking mode on the stability and electronic properties of few-chain Te nanowires. We find that the stacking mode and size play a dominant role in the stability of the nanowires, while the chirality and size have a key effect on the electronic structures. These phenomena are mainly due to the quantum size effect and the special helical structure of the Te chain. Our findings provide the means for adjusting the band gap and the candidates for constructing n-type spin devices, which serve as a basis for the research and manufacture of new nano electronic devices.

Similar Midterm Clinical Outcomes and Aortic Remodeling in Bifurcated and Straight Aortic Stent Grafts Used to Treat Isolated Abdominal Aortic Dissection.

PURPOSE: The optimal treatment for isolated abdominal aortic dissection (IAAD) is currently unknown. We compared the effects of straight and bifurcated aortic stent grafts on postoperative aortic remodeling in patients with IAAD. MATERIALS AND METHODS: From February 2012 to December 2019, 57 patients with IAAD were treated using endovascular methods, including either a bifurcated or a straight aortic stent graft. The clinical features, risk factors, computed tomography angiograms, midterm follow-up results, and aortic remodeling of these patients were reviewed and analyzed. RESULTS: In total, 44 (77%) patients were treated with a bifurcated graft and 13 (23%) patients were treated with a straight graft. Patients treated with straight grafts had fewer common iliac arteries involved (38% vs 73%, p=0.023), the dissection length was shorter (76.3 ± 40.0 vs 116.2 ± 56.7 mm, p=0.011), and the preoperative aortic diameter (26.0 ± 5.6 vs 35.2 ± 12.1 mm) and the false lumen diameter (13.1 ± 5.2 vs 21.2 ± 11.3 mm) were smaller. During the procedure, there were 3 (5.3%) type I endoleaks, 1 (1.8%) surgical conversion and 1 (1.8%) partial renal artery coverage without perioperative mortality. Patients with straight grafts had shorter operative time (96.5 ± 24.4 vs 144.2 ± 49.0 minutes, p<0.0001). The median follow-up duration was 37.6 ± 21.0 (range = 3-89) months with 1 (1.8%) aortic-related death. Type A aortic dissection occurred in 1 (1.8%) patient. New descending aortic dissection occurred in 3 (5.3%) patients, and 1 patient advanced to type A aortic dissection 3 months later. Two (3.5%) patients had limb occlusion. There was no significant difference in aortic remodeling, survival, and freedom from all adverse events between the 2 treatment strategies. CONCLUSIONS: Endovascular treatment provides a safe, minimally invasive treatment for IAAD in midterm follow-up. Compression of the true lumen at the aortic bifurcation is the main concern after treatment with a bifurcated graft. Straight grafts are an excellent alternative for some patients, with the benefit of reduced procedural time, effective aortic remodeling, and excellent clinical prognosis. More experience is needed to offer clear recommendations for making treatment decisions as well as determine long-term effectiveness and durability.

Understanding water slippage through carbon nanotubes.

It is a formidable challenge to understand water slippage through carbon nanotubes (CNTs), despite its great significance in fundamental research and technology. Herein, we propose an effective scheme to describe water slippage properties by extending two friction models - the phononic friction model and Einstein's diffusion model, both relying on the potential corrugation of water slippage. Our scheme effectively captures the tube-size effect on the viscosity and slippage of water molecules through CNTs. It also identifies the experimentally reported size-dependent transition from continuum to sub-continuum flow and further reveals that this transition is likely to be determined by the hydrogen bond instead of the structural transition or entropic change. Besides, the size-dependence of slip lengths is found to be controllable by temperature. Our methods are thus expected to be a useful basis for further studies on substance transport under confinement.

Innominate artery bifurcation pseudoaneurysm repair by "kissing stent-grafts technique": a case report.

BACKGROUND: We introduce the "kissing stent-grafts technique" for a patient who suffered from a pseudoaneurysm in bifurcation of innominate artery. This technique repaired an innominate artery bifurcation pseudoaneurysm; it successfully isolated the pseudoaneurysm and preserved both right subclavian and right common carotid artery. CASE PRESENTATION: A 60-year-old Asian (Chinese) woman complained of discovering a cervical pulsatile mass. A pseudoaneurysm at the location of innominate artery bifurcation is a rare and difficult situation that should be treated by vascular surgeons. To our knowledge, this is the first case to use the "kissing stent-grafts technique" in treating innominate bifurcation pseudoaneurysm. With this minimally invasive endovascular treatment, our patient avoided open surgery and recovered quickly. CONCLUSIONS: When treating vascular lesions with complicated anatomy, endovascular treatment always has the merit of being minimally invasive. "Kissing stent-grafts technique" can be useful in locations other than coronary and aortic bifurcation.

First experience with the double chimney technique in the treatment of aortic arch diseases.

OBJECTIVE: The objective of this study was to summarize our initial experience using the double chimney technique to treat aortic arch diseases. METHODS: From December 2009 to October 2016, 23 patients with aortic arch diseases, including 20 acute aortic dissections, 2 aortic arch aneurysms, and 1 type I endoleak after thoracic endovascular aortic repair (TEVAR), were treated using a double chimney technique. An emergent operation was performed in only one patient with an acute aortic dissection for severe left lower extremity ischemia. All patients were observed after TEVAR with computed tomography scans at 2 weeks, at 3 and 6 months, and annually thereafter. RESULTS: In all patients, aortic arch lesions were covered, and supra-aortic branches were patent without morbidity. In 22 patients, the innominate artery (IA) and left common carotid artery were reconstructed with the proximal landing zone in zone 0; in 1 patient, the left common carotid artery and left subclavian artery were reconstructed. During the procedure, there were three (13.0%) type I endoleaks. Chimney stent graft migration occurred in one (4.3%) patient perioperatively; compression of a chimney stent graft occurred in one (4.3%) patient 4 days after TEVAR. There were no type II endoleaks or perioperative mortality. Median follow-up was 28.0 ± 19.8 (range, 3-84) months, with no TEVAR-related deaths. Partial compression of the chimney stent graft in the IA occurred at 3 months after TEVAR in one (4.3%) patient; three patients had persistent but asymptomatic type I endoleaks. CONCLUSIONS: TEVAR using a double chimney technique to reconstruct the supra-aortic branches provides a safe and minimally invasive alternative procedure associated with low postoperative mortality. The main perioperative complications include type I endoleak and compression of the chimney stent grafts in the IA. More experience with long-term results is needed to evaluate the effectiveness and durability of this advanced endovascular procedure.

Thoracic Endovascular Aortic Repair With Single/Double Chimney Technique for Aortic Arch Pathologies.

PURPOSE: To summarize a single-center experience using the single/double chimney technique in association with thoracic endovascular aortic repairs (TEVAR) for aortic arch pathologies. METHODS: From November 2007 to March 2016, 122 patients (mean age 50.4±12.7 years, range 29-80; 92 men) with aortic arch pathologies underwent TEVAR combined with single (n=101) or double (n=21) chimney grafts to reconstruct the supra-aortic branches: 21 innominate arteries, 114 left common carotid arteries, and 8 left subclavian arteries (LSA). Pathologies included type B aortic dissection (n=47), aortic arch dissection (n=49), retrograde type A aortic dissection (n=8), thoracic aortic aneurysm (n=7), penetrating aortic arch ulcer (n=9), and post-TEVAR type I endoleak (n=2). Follow-up examinations included computed tomography at 0.5, 3, 6, and 12 months and yearly thereafter. RESULTS: The aortic stent-grafts were deployed in zone 0 (n=21), zone 1 (n=93), and zone 2 (n=8). One (0.8%) of the 122 patients died at 4 days due to a perforated peptic ulcer. Type Ia endoleaks were found intraoperatively in 13 (10.7%) patients, including 3 with the double chimney technique. Type II endoleaks occurred in 6 (4.9%) patients; 3 were treated with duct occluders in the LSA. Postoperative chimney graft migration occurred in 1 (0.8%) patient with double chimneys; additional stent-grafts were deployed in both chimneys. Median follow-up was 32.3 months, during which 1 (0.8%) patient died after a stroke at 3 months. Chimney stent-graft patency was observed in the remaining 120 patients. Two (1.7%) secondary TEVARs were performed for distal aortic dissection. Nine asymptomatic type Ia endoleaks and 1 type II endoleak persisted in follow-up; a type II endoleak in 1 patient with Marfan syndrome sealed in 52 months. CONCLUSION: TEVAR with the chimney technique provides a safe, minimally invasive alternative with good chimney graft patency and low postoperative mortality during midterm follow-up. The double chimney technique should be used judiciously owing to its potential complications.

Endovascular aortic repair combined with chimney technique in the treatment of stanford type B aortic dissection involving aortic arch.

BACKGROUND: In this study, we sought to explore the efficacy of endovascular aortic repair combined with the chimney technique in the treatment of Stanford type B aortic dissection involving the aortic arch. METHODS: Between June 2009 and June 2012, 41 consecutive patients were treated with chimney technique at our institute for aortic arch dissection with the primary entry tear adjacent to the orifices of the supra-aortic arteries. The chimney technique was used to reconstruct the left subclavian artery (n = 5) and the left common carotid artery (n = 34). Additionally, in 2 cases, the double chimney technique was used to simultaneously reconstruct the innominate artery and the left common carotid artery. RESULTS: Eight of the 41 patients had undergone emergent surgery. All the patients survived the surgery, and the mean follow-up period was 17.3 ± 6.1 months. None of the patients had type I endoleak. Four patients had type II endoleak, and 3 of them underwent implantation of the patent ductus arteriosus occluder in the left subclavian artery. Among these 3 patients, one patient who was pregnant with Marfan syndrome and pregnancy-induced hypertension required additional medication for recovery. None of the patients had any severe neurological complications, left ischemia of the subclavian artery, migration of the stent graft, or occlusion of the stent grafts. CONCLUSIONS: Thus, endovascular aortic repair combined with the chimney technique appears to be a feasible, safe, and effective treatment option for the management of Stanford type B aortic dissection involving the aortic arch.

Midterm results of intentional celiac artery coverage during TEVAR for type B aortic dissection.

PURPOSE: To report the outcome of intended celiac artery coverage during thoracic endovascular aortic repair (TEVAR) for type B aortic dissection with an intimal tear near the celiac artery (CA) orifice. METHODS: Between 2007 and 2011, 13 patients (10 men; mean age 61.3 years, range 46-70) with type B aortic dissection underwent primary (n=9) or secondary (n=4) TEVAR with intentional CA coverage. Preoperative imaging was performed to confirm the existence of collateral circulation between the celiac artery and superior mesenteric artery. A short stent-graft was then deployed to cover both the entry tear and the CA. Follow-up was at 2 weeks; 1, 3, and 6 months; and every year thereafter. Preoperative diameters of the true and false lumens at the CA level, 8 cm above the CA, and at the aortic bifurcation, along with the maximum aortic diameter in the dissected segment, were compared to similar measurements at 6 months. RESULTS: All stent-graft procedures were successful and without complication. No immediate or delayed endoleak was identified in 8 of 13 patients over a mean 25-month follow-up (range 3-38). The other 5 patients had type II endoleak on completion imaging; these all resolved within 3 months after operation. Postoperative blood liver function and amylase assays were normal in all patients. No abdominal symptoms or signs of spinal cord ischemia were discovered. Expansion of the true lumen after TEVAR was statistically significant vs. at baseline in both groups (primary p<0.001, secondary p=0.023). Both the false lumen and the entire aorta showed signs of shrinkage after TEVAR in the 2 groups as well, although only the secondary group showed significant change (p<0.005) vs. baseline. CONCLUSION: TEVAR with intentional CA coverage is effective in excluding an infradiaphragmatic entry tear near the CA level. The incidence of abdominal ischemia is low if collateral circulation has been confirmed preoperatively. Type II endoleak is a major complication, yet most cease under observation.

Thoracic endovascular aortic repair for retrograde type A aortic dissection with an entry tear in the descending aorta.

PURPOSE: To report the immediate and follow-up outcome of thoracic endovascular aortic repair (TEVAR) in highly selected patients with retrograde type A aortic dissection (RAAD) and an entry tear in the descending aorta. MATERIALS AND METHODS: TEVAR was performed in 17 patients with RAAD and an entry tear in the descending aorta. None of the patients had severe aortic regurgitation, cardiac tamponade, coronary artery involvement, or brain ischemia. The false lumen in the ascending aorta was patent in nine patients. Two patients had acute malperfusion of the branched artery. Computed tomography (CT) was performed 14 days, 3 months, and 6 months after the intervention and annually thereafter. RESULTS: All procedures were technically successful, with complete coverage of the entry tear and complete thrombosis of the false lumen in the ascending aorta. All patients survived through the follow-up period (25.7 months ± 17.2). TEVAR resulted in thrombosis of the false lumen, reabsorption of the false lumen thrombus, and enlargement of the true lumen. The mean maximal diameter of the ascending aorta and the false lumen in the ascending aorta significantly decreased after TEVAR. At the distal edge of the stent graft, the mean diameter of the descending aorta and the false lumen markedly decreased after TEVAR. Complete thrombosis of the false lumen was observed at the distal edge of the stent graft in 16 (94.1%) patients and at the diaphragmatic level in 9 (52.9%) patients. CONCLUSIONS: TEVAR for RAAD with an entry tear in the descending aorta is a safe and effective technique in highly selected patients.

[Endovascular aortic repair plus chimney technique in the treatment of Stanford type B aortic dissection involving aortic arch].

OBJECTIVE: To evaluate the efficacy of endovascular aortic repair plus chimney technique in the treatment of Stanford type B aortic dissection involving aortic arch. METHODS: From June 2009 to March 2012, 32 patients of aortic arch dissection with primary entry tear next to the orifices of supra-aortic arteries were treated with chimney technique. Chimney technique was used to reconstruct left subclavian artery (n = 2) and left common carotid artery (n = 28). Double chimney technique was use to reconstruct innominate artery and left common carotid artery simultaneously in 2 patients. RESULTS: Four patients received emergency operation. All patients survived and were followed up for 14.3 ± 7.4 months. No type I endoleak occurred. Among 4 patients with Type II endoleak, 3 received PDA occluding implantation in left subclavian artery and 1 patient in puerperium with Marfan syndrome and pregnancy-induced hypertension syndrome recovered by conservative treatment. No severe neurological complications and left subclavian artery ischemia occurred. The locations of aortic and chimney stent-grafts were stable without any migration. All stent-grafts remained patent. CONCLUSION: Endovascular aortic repair plus chimney technique is a safe and effective treatment for Stanford type B aortic dissection involving aortic arch.

Early results of left carotid chimney technique in endovascular repair of acute non-a-non-B aortic dissections.

PURPOSE: To report our early experience with endovascular repair of acute non-A-non-B aortic dissections using chimney grafts to preserve blood flow to a left common carotid artery (LCCA) located in the proximal landing zone. METHODS: From June 2009 to May 2010, 8 patients (7 men; mean age 49 years, range 29-75) with acute non-A-non-B aortic dissection and no adequate proximal sealing zones underwent thoracic endovascular aortic repair (TEVAR). Covered stents were placed parallel to the aortic stent-grafts to restore flow to the LCCAs while extending the proximal fixation zones; the left subclavian arteries were intentionally covered after carefully cerebrovascular assessment. Follow-up examinations included computed tomography (CT) at 2 weeks, 3 months, 6 months, 12 months, and yearly thereafter. RESULTS: All the procedures were completed successfully, with one main aortic stent-graft deployed and one chimney graft implanted in the LCCA. Two retrograde type II endoleaks identified intraoperatively were left untreated but followed closely using CT. There were no instances of puncture site complications, stroke, paralysis, or death during the hospital stay. The 30-day mortality was 0%. During the mean 11.4-month follow-up (range 6-15), there was no mortality, and duplex ultrasound and CT showed patency of all stent-grafts, enlargement of the true lumen, and compression of the false lumen. One type II endoleak disappeared in 2 weeks postoperatively, while the other gradually faded until it was nearly gone at 11 months postoperatively. During follow-up, no renal insufficiency, new late endoleaks, endograft migration, fracture, stent-graft related complications, or deaths were observed. CONCLUSION: In short-term follow-up, TEVAR combined with the chimney technique seems promising for aortic dissections that involve the aortic arch with inadequate proximal sealing zones. More cases and long-term results are needed to evaluate the safety and efficiency of this alternative endovascular technique.

[Endovascular repair of infrarenal abdominal aortic aneurysm with the complex aortic anatomy].

OBJECTIVE: To explore the safety and efficiency of endovascular repair (EVAR) of abdominal aortic aneurysms (AAAs) which have the complex aortic anatomy. METHODS: The clinical date of 48 AAA patients with complex aortic anatomy treated by EVAR from January 2003 to March 2011 was retrospectively analyzed. There were 37 male and 11 female patients, aged from 50 to 81 years with a mean of 71.4 years. Fourteen patients had short aortic neck (< 15 mm), 13 patients had severe infrarenal angulation (> 60°), 15 patients had severely tortuous iliac, 6 patients had small iliac (< 8 mm). The stent-grafts were deployed by both femoral arteries to treat the AAA. RESULT: The primary technical success rate was 100%. The perioperative survival rate was 100%. Intraoperative angiograms revealed two type I endoleaks, in which one disappeared in two weeks, another existed. Follow-up was available in 40 patients with a median of 63 months (4 to 122 months). During the follow-up period, 2 patients died with no relationship to the procedures. The rest patients survived well. The accumulative survival rate was 95.8%. There were no new endoleak, stent-graft migration, aneurysm expansion, or secondary intervention during the follow-up time. CONCLUSIONS: EVAR is safety and efficiency to treat the patient of infrarenal abdominal aortic aneurysm with the complex aortic anatomy. By the accumulation of experience, EVAR will play a more important role for these patients.