Unequivocal Identification of Spin-Triplet and Spin-Singlet Superconductors with Upper Critical Field and Flux Quantization.

Spin-triplet superconductors play central roles in Majorana physics and quantum computing but are difficult to identify. We show the methods of kink-point upper critical field and flux quantization in superconducting rings can unequivocally identify spin-singlet, spin-triplet in centrosymmetric superconductors, and singlet-triplet admixture in noncentrosymmetric superconductors, as realized in γ-BiPd, ß-Bi_{2}Pd, and α-BiPd, respectively. Our findings are essential for identifying triplet superconductors and exploring their quantum properties.

Observation of half-quantum flux in the unconventional superconductor ß-Bi2Pd.

Magnetic flux quantization is one of the defining properties of a superconductor. We report the observation of half-integer magnetic flux quantization in mesoscopic rings of superconducting ß-Bi2Pd thin films. The half-quantum fluxoid manifests itself as a π phase shift in the quantum oscillation of the superconducting critical temperature. This result verifies unconventional superconductivity of ß-Bi2Pd and is consistent with a spin-triplet pairing symmetry. Our findings may have implications for flux quantum bits in the context of quantum computing.

Hidden Antipolar Order Parameter and Entangled Néel-Type Charged Domain Walls in Hybrid Improper Ferroelectrics.

Hybrid improper ferroelectricity (HIF) denotes a new class of polar instability by the mixture of two octahedral-distortion modes and can feature the coexistence of abundant head-to-head and tail-to-tail polar domains, of which the domain walls tend to be charged due to the respective screening charges with an opposite sign. However, no such coexisting carriers are available in the materials. Using group-theoretical, microscopic, and spectroscopic analyses, we establish the existence of a hidden antipolar order parameter in model HIF (Ca,Sr)_{3}Ti_{2}O_{7} by the condensation of a weak, previously unnoticed antipolar lattice instability, turning the order-parameter spaces to be multicomponent with the distinct polar-antipolar intertwining and accompanied formation of Néel-type twinlike antipolar domain walls (few nanometers) between the head-to-head and tail-to-tail domains. The finite-width Néel walls and correlated domain topology inherently lift the polar divergences between the domains, casting an emergent exemplification of charged domain-wall screening by an antipolar ingredient.

Off-Stoichiometry Driven Carrier Density Variation at the Interface of LaAlO3/SrTiO3.

The interface between LaAlO3 (LAO) and SrTiO3 (STO) has attracted enormous interests due to its rich physical phenomena, such as metallic nature, magnetism and superconductivity. In this work, we report our experimental investigations on the influence of the LAO stoichiometry to the metallic interface. Taking advantage of the oxide molecular beam epitaxy (MBE) technique, a series of high quality LAO films with different nominal La/Al ratios and LAO thicknesses were grown on the TiO2-terminated STO substrates, where systematic variations of the LAO lattice constant and transport property were observed. In particular, the sheet density can be largely reduced by nearly an order of magnitude with merely about 20% increase in the nominal La/Al ratio. Our finding provides an effective method on tuning the electron density of the two-dimensional electron liquid (2DEL) at the LAO/STO interface.

Hidden lattice instabilities as origin of the conductive interface between insulating LaAlO3 and SrTiO3.

The metallic interface between insulating LaAlO3 and SrTiO3 opens up the field of oxide electronics. With more than a decade of researches on this heterostructure, the origin of the interfacial conductivity, however, remains unsettled. Here we resolve this long-standing puzzle by atomic-scale observation of electron-gas formation for screening hidden lattice instabilities, rejuvenated near the interface by epitaxial strain. Using atomic-resolution imaging and electron spectroscopy, the generally accepted notions of polar catastrophe and cation intermixing for the metallic interface are discounted. Instead, the conductivity onset at the critical thickness of 4-unit cell LaAlO3 on SrTiO3 substrate is accompanied with head-to-head ferroelectric-like polarizations across the interface due to strain-rejuvenated ferroelectric-like instabilities in the materials. The divergent depolarization fields of the head-to-head polarizations cast the interface into an electron reservoir, forming screening electron gas in SrTiO3 with LaAlO3 hosting complementary localized holes. The ferroelectric-like polarizations and electron-hole juxtaposition reveal the cooperative nature of metallic LaAlO3/SrTiO3.

Large single crystal growth, transport property, and spectroscopic characterizations of three-dimensional Dirac semimetal Cd3As2.

The three dimensional (3D) Dirac semimetal is a new quantum state of matter that has attracted much attention recently in physics and material science. Here, we report on the growth of large plate-like single crystals of Cd3As2 in two major orientations by a self-selecting vapor growth (SSVG) method, and the optimum growth conditions have been experimentally determined. The crystalline imperfections and electrical properties of the crystals were examined with transmission electron microscopy (TEM), scanning tunneling microscopy (STM), and transport property measurements. This SSVG method makes it possible to control the as-grown crystal compositions with excess Cd or As leading to mobilities near 5-10(5) cm(2)V(-1)s(-1). Zn-doping can effectively reduce the carrier density to reach the maximum residual resistivity ratio (RRRρ300K/ρ5K) of 7.6. A vacuum-cleaved single crystal has been investigated using angle-resolved photoemission spectroscopy (ARPES) to reveal a single Dirac cone near the center of the surface Brillouin zone with a binding energy of approximately 200 meV.

Development of our TAVI protocol for emergency initiation of cardiopulmonary bypass.

All transcatheter aortic valve implantation (TAVI) cases are done in our hybrid operating room with a multidisciplinary team and a primed cardiopulmonary bypass (CPB) circuit on pump stand-by. We decided that we would resuscitate all patients undergoing a TAVI procedure via a transfemoral, transapical or transaortic approach, if required. Perfusion plays an essential role in providing rescue CPB for patient salvage when catastrophic complications occur. To coordinate the multidisciplinary effort, we have developed a written safety checklist that assigns a pre-determined role for team members for the rapid sequence initiation of CPB. Although many TAVI patients are not candidates for conventional aortic valve replacements, we feel strongly that rescue CPB should be offered to all TAVI patients to allow the correction of potentially reversible complications. This protocol is included in every surgical "Time Out" involving a TAVI procedure (Figure 1). The protocol has led to rapid and safe CPB initiation in less than five minutes of cardiac arrest. It has also led to a coordinated and consistent team, with pre-specified roles and improved communication. We discuss a case series of four TAVI patients who required emergent use of CPB. The first few cases did not have a written protocol. The experience from these cases led to the development of our protocol. We identified a lack of coordination, wasted movements, unnecessary delayed resuscitation and overall chaos, each of which was targeted for correction with the protocol. We will discuss the merits of the protocol in two recent TAVI cases which required emergent CPB.

Condensation of two-dimensional oxide-interfacial charges into one-dimensional electron chains by the misfit-dislocation strain field.

The success of semiconductor technology is largely ascribed to controlled impacts of strains and defects on the two-dimensional interfacial charges. Interfacial charges also appear in oxide heterojunctions such as LaAlO3/SrTiO3 and (Nd0.35Sr0.65)MnO3/SrTiO3. How the localized strain field of one-dimensional misfit dislocations, defects resulting from the intrinsic misfit strains, would affect the extended oxide-interfacial charges is intriguing and remains unresolved. Here we show the atomic-scale observation of one-dimensional electron chains formed in (Nd0.35Sr0.65)MnO3/SrTiO3 by the condensation of characteristic two-dimensional interfacial charges into the strain field of periodically arrayed misfit dislocations, using chemical mapping and quantification by scanning transmission electron microscopy. The strain-relaxed inter-dislocation regions are readily charge depleted, otherwise decorated by the pristine charges, and the corresponding total-energy calculations unravel the undocumented charge-reservoir role played by the dislocation-strain field. This two-dimensional-to-one-dimensional electronic condensation represents a novel electronic-inhomogeneity mechanism at oxide interfaces and could stimulate further studies of one-dimensional electron density in oxide heterostructures.

Blood conservation strategies reduce the need for transfusions in ascending and aortic arch surgery.

INTRODUCTION: Ascending and aortic arch surgery is associated with higher levels of blood loss and subsequent need for allogeneic blood transfusions. We hypothesized that aggressive, comprehensive blood conservation strategies may limit the need for transfusions and, subsequently, improve postoperative outcomes. METHODS: Over a five-year period, 189 patients underwent proximal aortic surgery at our institution. Fifty-one patients underwent surgery using a comprehensive blood conservation strategy (BCS), including preoperative hemoglobin optimization, antifibrinolytic therapy, intraoperative acute normovolemic hemodilution, cell salvage and meticulous surgical technique. The remaining 138 patients underwent surgery using conventional techniques (CONV). RESULTS: Patients in the BCS group required fewer transfusions during their hospital stay compared to the conventional group (56.9% vs. 72.5%, p=0.041). When examining elective cases, this trend widens, with 40.0% of BCS patients requiring any transfusions compared to 72.9% patients in the conventional group (p=0.001). Red cell (47.1% vs. 62.3%, p=0.06), plasma (43.1% vs. 61.6%, p=0.02) and platelets (27.5% vs. 47.8%, p=0.01) were also less frequently required in the BCS group than the conventional group, respectively. When a transfusion was required, patients in the BCS group received significantly fewer units of red blood cells (2.8 ± 7.0 units) than the conventional group (5.81 ± 9.5 units; p=0.039). Mortality was similar in both groups (BCS 7.8%, conventional 10.9%, p=0.54); however, there was significantly less morbidity in the BCS group, using a composite of any of 10 major postoperative complications (23.5% vs. 39.1%; p=0.046). Median intensive care unit (ICU) and hospital lengths of stay were 2 and 7 days in the BCS group and 2 and 8 days in the CONV group (p=0.15), respectively. CONCLUSIONS: The aggressive use of a comprehensive blood conservation strategy in ascending and aortic arch surgery can significantly reduce the need for blood transfusions and is associated with less postoperative morbidity. Further evaluation with a randomized, controlled trial is warranted.

Site occupancy and magnetic properties of pyrochlore-structured AgOs2O6.

AgOs(2)O(6) prepared from ion-exchanged superconducting ß-pyrochlore KOs(2)O(6) has been shown to be non-superconducting. Synchrotron x-ray structure refinement suggests that AgOs(2)O(6) has the Ag ion mostly occupying the low-symmetry 32e site in the [Formula: see text] space group of proper occupancy, which is different from the original major occupancy at the high-symmetry 8b site for KOs(2)O(6), and similar to non-superconducting Na(1.4)Os(2)O(6)·H(2)O. Magnetic susceptibility measurements found no magnetic ordering down to ~1.7 K. The trace amount of isolated spins suggests that the Ag could be neutral and lead to a pure Os(6+) valence state of zero spin in the newly prepared AgOs(2)O(6).

Clinical and biochemical outcomes for additive mesenteric and lower body perfusion during hypothermic circulatory arrest for complex total aortic arch replacement surgery.

Surgical repair of transverse aortic arch aneurysms frequently employ hypothermia and antegrade cerebral perfusion as protective strategies during circulatory arrest. However, prolonged mesenteric and lower limb ischemia can lead to significant lactic acidosis and end organ dysfunction, which remains a significant cause of post-operative morbidity and mortality. We report our experience with additive warm mesenteric and lower body perfusion (1-3 L/min, 30°C) in addition to continuous cerebral and myocardial perfusion in 5 patients who underwent total aortic arch replacement with trifurcated head vessel re-implantation and distal elephant trunk reconstruction. Concomitant surgical procedures included re-operations (2), aortic root operations (2), coronary artery bypass (2) and descending thoracic aortic replacement (1). Serum lactate levels demonstrated a rapid decline from a peak 9.9 ± 2.6 post circulatory arrest to 3.4 ± 2.0 in the intensive care unit (ICU). The lowest serum bicarbonate levels were 19.3 ± 3.5 mmol/L, intra-operatively, which normalized to 28.4 ± 2.4 mmol/L on return to the ICU. The lowest pH levels were 7.25 ± 0.10, corrected to 7.43 ± 0.04 on return to the ICU. Mean cardiopulmonary bypass and aortic cross-clamp times were 361 ± 104 and 253 ± 85 minutes, respectively. Mean cerebral and lower body circulatory arrest times were 0 (0) and 50 ± 35 minutes, respectively. The mean time required for systemic rewarming was 95 ± 66 minutes. There were no in-hospital mortalities and no patient experienced any neurological, mesenteric, renal or lower limb ischemic complications. Two patients required mechanical ventilation >24 hours, and one patient returned for reoperation for bleeding. Median intensive care unit and total hospital lengths of stay were 5 and 16 days, respectively. Our results suggest early serum lactate clearance, normalization of acidosis, and metabolic recovery when utilizing a simultaneous cerebral perfusion and warm body protection strategy for complex aortic arch surgery. This additive perfusion strategy may attenuate visceral and lower body ischemia that normally develops during periods of deep hypothermic circulatory arrest.

Emergent chemical mapping at atomic-column resolution by energy-dispersive x-ray spectroscopy in an aberration-corrected electron microscope.

Chemical mapping at atomic-column resolution by energy-dispersive x-ray spectroscopy in a spherical aberration-corrected scanning transmission electron microscope (STEM) has been demonstrated for the 1.47-A dumbbell structure in InGaAs. The structural imaging and the chemical information in the two-dimensional map are directly correlated. Comparisons with the other existing mapping techniques of STEM in conjunction with electron energy-loss spectroscopy were discussed from aspects of ionization interactions.

Scanning transmission electron microscopy using selective high-order laue zones: three-dimensional atomic ordering in sodium cobaltate.

A new scanning transmission electron microscopy (STEM) imaging technique using high-order Laue zones (named HOLZ-STEM), a diffraction contrast which has been strenuously avoided or minimized in traditional STEM imaging, can be used to obtain the additional 1D periodic information along the electron propagation axis without sacrificing atomic resolution in the lateral (2D) dimension. HOLZ-STEM has been demonstrated to resolve the 3D long-range Na ordering of Na0.71CoO2. Direct evidence of spiral-like Na-trimer chains twisting along the c axis is unambiguously established in real space.

Sodium ion ordering and vacancy cluster formation in NaxCoO2 (x=0.71 and 0.84) single crystals by synchrotron X-Ray diffraction.

In the rich phase diagram of NaxCoO2, x=0.71 enjoys special stability and is called the Curie-Weiss metal due to its anomalous properties. Similarly, x=0.84 prepared from high temperature melt is a special end point beyond which the system phase separates. Using synchrotron x-ray diffraction on single crystals, we discovered sqrt[12]a and sqrt[13]a superlattice structures which we interpret as the ordering of Na (vacancy) clusters. These results lead to a picture of coexisting local moments and itinerant carriers and form the first step towards understanding the many anomalous properties of cobaltates.

Urgent heart surgery for an atrial mass: metastatic hepatocellular carcinoma.

Extension of metastatic hepatocellular carcinoma into the right atrium is exceedingly rare and has a very poor prognosis. We report a case of successful surgical excision of hepatic tumor extension into the right atrium that was causing hemodynamic compromise.

Empyema thoracis: lack of awareness results in a prolonged clinical course.

OBJECTIVE: To assess the hypothesis that empyema thoracis (ET) is a problem often not optimally treated. Long delays in diagnosis are common, long hospital stays are typical and recovery with surgery is relatively rapid. DESIGN: A chart review. SETTING: The Regina Health District associated hospitals, a tertiary referral centre. PATIENTS: The charts of 34 consecutive patients having primary respiratory tract disease and seen during the 6-year period Apr. 1, 1991, to Mar. 31, 1997, were identified. OUTCOME MEASURES: Patient presentation, time until diagnosis of ET, number of radiologic investigations, microbiologic features, treatment methods, postoperative course and mortality. RESULTS: The mean delay in diagnosis, defined as the time of admission to the time of correct diagnosis, was 44.2 days (range from 0 to 573 days) and the mean delay until thoracic surgery referral was 47.4 days (range from 0 to 578 days). On average each patient underwent CT 10.1 times, had 2.6 percutaneous drainage procedures and 2.0 chest tube insertions. The mean time from the first percutaneous chest drainage to the date of diagnosis was 29.8 days (range from 0 to 564 days). Of the 26 patients who underwent CT, the mean time from the first CT of the chest to the date of diagnosis was 9.5 days (range from 0 to 75 days). Cultures of pleural fluid grew no organisms in 17 patients; in the remaining 17 patients cultures grew 23 different microorganisms. Of 26 patients who were referred for surgical opinion, 18 underwent decortication; 8 were not considered to be surgical candidates. Pathological examination showed 17 cases of inflammatory empyema and 1 case of mesothelioma (unrecognized clinically). The mean length of hospital stay postoperatively was 15.2 days. CONCLUSIONS: Early suspicion of ET facilitates its treatment, resulting in fewer investigations and shorter hospital stays. When percutaneous drainage does not eliminate pleural effusions, empyema must be considered. Recovery from surgical decortication is rapid in comparison with the typical protracted preoperative hospital course.

Horizontal transposition of the vertical rectus muscles for cyclotropia.

PURPOSE: We studied the effect of horizontal transposition of the vertical rectus muscles on incyclotropia and excyclotropia in terms of the amount of correction obtained and the stability of the outcome. METHOD: Preoperative measurements for cyclotropia were compared in 11 patients with measurements during the immediate postoperative period and last follow-up. Excyclotropia was treated with nasal transposition of the inferior rectus muscle and incyclotropia with nasal transposition of the superior rectus muscle, to which we added temporal transposition to the inferior rectus muscle in one patient to enhance the effect. RESULTS: Fusion in all gaze positions was restored in six patients and functional improvement occurred in five. The average effect of horizontal transposition of one vertical rectus muscle for cyclotropia was a correction of 7 degrees in primary position and of 11 degrees in depression. This effect remained stable after a mean follow-up of 17 months, and additional improvement occurred in one patient. One patient developed a hypertropia, eliminated by an additional operation, in the treated eye. CONCLUSIONS: For excyclotropia, nasal transposition of the inferior rectus muscle is a viable alternative to lateral and anterior transposition of the anterior portion of the superior oblique tendon. It becomes the procedure of choice when surgery on the superior oblique tendon is precluded, either by the tendon's congenital absence or by previous surgery on the tendon. Nasal transposition of the superior rectus muscle or temporal transposition of the inferior rectus muscle is ideally suited for incyclotropia. No comparably effective operation exists.

Visual results and complications following posterior iris-fixated posterior chamber lenses at penetrating keratoplasty.

We retrospectively reviewed the records of 13 patients with pseudophakic bullous keratopathy who had undergone penetrating keratoplasty combined with suturing of a posterior chamber intraocular lens (PC-IOL) with angulated haptics to the posterior iris using the four optic positioning holes. Corneal endothelial decompensation was associated with anterior chamber IOLs in nine cases, with iris-fixated lenses in three cases, and a subluxated PC-IOL in one case. Visual acuity was 20/40 or better in 46%, 20/50 to 20/100 in 31%, and 20/200 or worse in 23%. These visual results are comparable with those reported for other similar surgical series. In four of seven eyes that had preoperative peripheral anterior synechiae (PAS), postoperative extension of at least 2 clock hours occurred; progressive angle-closure glaucoma developed in two of the four. In all four eyes, the extension occurred in the region directly overlying the lens haptics. The angulated haptics of iris-sutured PC-IOLs may predispose to extension of PAS and development of progressive angle-closure glaucoma.

Surgical treatment options in cyclotropia.

We report our experience with a procedure involving the transposition and realignment of the vertical recti muscles, in two cases. In the first case, 11 degrees of unilateral excyclotropia was corrected by a one muscle width nasal transposition of the ipsilateral inferior rectus muscle. In the second case, excyclotropia was created in both eyes by a one-half muscle width nasal transposition of both superior recti, and, in a second operation, reversed by a horizontal realignment of these muscles. We found this procedure to be useful in the treatment of both incyclo- and excyclotropia.