A 2D ferroelectric vortex pattern in twisted BaTiO3 freestanding layers.

The wealth of complex polar topologies1-10 recently found in nanoscale ferroelectrics results from a delicate balance between the intrinsic tendency of the materials to develop a homogeneous polarization and the electric and mechanical boundary conditions imposed on them. Ferroelectric-dielectric interfaces are model systems in which polarization curling originates from open circuit-like electric boundary conditions, to avoid the build-up of polarization charges through the formation of flux-closure11-14 domains that evolve into vortex-like structures at the nanoscale15-17 level. Although ferroelectricity is known to couple strongly with strain (both homogeneous18 and inhomogeneous19,20), the effect of mechanical constraints21 on thin-film nanoscale ferroelectrics has been comparatively less explored because of the relative paucity of strain patterns that can be implemented experimentally. Here we show that the stacking of freestanding ferroelectric perovskite layers with controlled twist angles provides an opportunity to tailor these topological nanostructures in a way determined by the lateral strain modulation associated with the twisting. Furthermore, we find that a peculiar pattern of polarization vortices and antivortices emerges from the flexoelectric coupling of polarization to strain gradients. This finding provides opportunities to create two-dimensional high-density vortex crystals that would enable us to explore previously unknown physical effects and functionalities.

Severe rectus diastasis with midline hernia associated in males: high recurrence in mid-term follow-up of minimally invasive surgical technique.

PROPOSE: The present study aimed to assess clinical results, in terms of postoperative pain, functional recovery and recurrence rates of FESSA (Full Endoscopic Suprapubic Subcutaneous Access) technique compared to endoscopic anterior rectus sheaths plication and mesh, in male patients with midline ventral or incisional hernias and severe rectus diastasis (SRD) associated. Secondary aims were to identify intra- and postoperative complications associated with each technique. METHODS: Male patients with midline ventral or incisional hernia and severe rectus diastasis were included in a prospectively maintained databased and retrospectively analyzed from January 2017 to December 2020. From January 2017 to January 2019, male patients underwent to anterior rectus sheaths plication (ARSP) (Control group). From January 2019 to December 2020, male patients underwent to FESSA technique (FT) (Case group). RESULTS: 53 patients were finally included. 28 patients (52%) underwent to FT and 25 patients (48%) to ARSP. Regarding intraoperative complications, no significant differences were identified between the groups. Hospital stay was significantly improved in FT group when compared to ARSP group. No significant differences in terms of postoperative seroma or hematomas, were shown. FT group showed significantly less pain on 1st, 7th and 30th postoperative days than ARSP group. Functional recovery was significantly improved in FT group compared to ARSP group on the 30th day and no differences were observed on the 180th day after surgery. The mean follow-up was 17.3 ± 2.6 months in FT group and 24 ± 3 months in ARSP group. During the follow-up, 1(3%) and 9 (36%) diastasis recurrences were identified respectively, with significant differences in favor of FT group. CONCLUSION: In males with SRD and symptomatic midlines hernias, ARSP with onlay mesh placement shows high diastasis recurrence rate in mid-term follow-up. We propose FESSA technique in those patients, which decreases the excessive midline tension, improving the postoperative pain, functional recovery and recurrence rate, without increasing postoperative complications.

Initial experience with intraoperative testing and repair of colorectal anastomosis using a TAMIS approach after a positive leak test.

Anastomotic leak is one of the most feared complications of colorectal anastomosis. Different techniques have been described for intraoperative testing of anastomotic integrity. These include air insufflation, methylene blue and endoscopic visualisation. If an anastomotic leak is identified intraoperatively, there are various management options. Redo anastomosis is a possibility, but may be difficult in some cases. Defunctioning is another option, but there is an associated morbidity and signficant detrimental effect on quality of life. Direct transanal repair is only possible when a low anastomosis has been performed. When the anastomotic leak occurs high in the rectum or a partial mesorectal excision is performed a transanal approach is technically very challenging. We present our experience with transanal minimally invasive surgery (TAMIS) approach for anastomotic assessment and repair in four patients. In all cases, a colorectal anastomosis was performed and the air insufflation test was positive. We assessed the anastomosis with TAMIS. In three cases, a defect was found and subsequently sutured. In one case, a scar in the rectal mucosa was found and reinforced with a suture. A protective ileostomy was performed in two cases, while in the other two cases, no stoma was added. All four patients were discharged with no further complications. Both protective ileostomies were taken down after radiological and endoscopic confirmation of anastomotic integrity and all 4 anastomoses remain intact after follow-up. TAMIS intraoperative assessment and repair of anastomotic leak is a safe and feasible technique whcih may avoid the need for a defunctioning stoma.

Extremely long-range, high-temperature Josephson coupling across a half-metallic ferromagnet.

The Josephson effect results from the coupling of two superconductors across a spacer such as an insulator, a normal metal or a ferromagnet to yield a phase coherent quantum state. However, in junctions with ferromagnetic spacers, very long-range Josephson effects have remained elusive. Here we demonstrate extremely long-range (micrometric) high-temperature (tens of kelvins) Josephson coupling across the half-metallic manganite La0.7Sr0.3MnO3 combined with the superconducting cuprate YBa2Cu3O7. These planar junctions, in addition to large critical currents, display the hallmarks of Josephson physics, such as critical current oscillations driven by magnetic flux quantization and quantum phase locking effects under microwave excitation (Shapiro steps). The latter display an anomalous doubling of the Josephson frequency predicted by several theories. In addition to its fundamental interest, the marriage between high-temperature, dissipationless quantum coherent transport and full spin polarization brings opportunities for the practical realization of superconducting spintronics, and opens new perspectives for quantum computing.

Endoscopic retromuscular technique (eTEP) vs conventional laparoscopic ventral or incisional hernia repair with defect closure (IPOM +) for midline hernias. A case-control study.

PURPOSE: This study aimed at clinical results in terms of postoperative pain and functional recovery of new technique (eTEP) compared to IPOM + for ventral/incisional midline hernias. Recurrence rate, intra/postoperative complications and aesthetic results are secondary aims. METHODS: Data from consecutive patients requiring minimally invasive hernia repair were collected. From January 2015 to September 2018, patients with midline ventral/incisional hernias underwent IPOM + were compared to patients underwent eTEP procedure from October 2018 to December 2019 in a case/control study. RESULTS: Thirty-nine patients in IPOM + group and 40 in eTEP group were included. No significant differences were identified when hernias types, mean defect area, mean mesh area and intraoperative/postoperative complications (except seroma rate in favor of eTEP group) were compared. Operative time and hospital stay were significantly higher in eTEP group and IPOM + group, respectively. eTEP group showed significantly less pain on 1st, 7th and 30th postoperative days than IPOM + group. Restriction of activities was significantly decreased in eTEP group on the 30th and 180th day after surgery. Significant differences were observed in terms of cosmetic results 30th and 180th days after surgery in favor of eTEP group. Average follow-up was 15 months in eTEP group and 28 months in IPOM + group. No recurrences were identified in eTEP group and one recurrence in IPOM + group with no significant differences. CONCLUSION: Endoscopic retromuscular technique shows significant lower postoperative pain, better functional recovery and cosmesis than IPOM + without differences in intra/postoperative complications (except seroma rate) or recurrences during the follow-up. eTEP requires longer operative time.

Oxygen intercalation in PVD graphene grown on copper substrates: A decoupling approach.

We investigate the intercalation process of oxygen in-between a PVD-grown graphene layer and different copper substrates as a methodology for reducing the substrate-layer interaction. This growth method leads to an extended defect-free graphene layer that strongly couples with the substrate. We have found, by means of X-ray photoelectron spectroscopy, that after oxygen exposure at different temperatures, ranging from 280 °C to 550 °C, oxygen intercalates at the interface of graphene grown on Cu foil at an optimal temperature of 500 °C. The low energy electron diffraction technique confirms the adsorption of an atomic oxygen adlayer on top of the Cu surface and below graphene after oxygen exposure at elevated temperature, but no oxidation of the substrate is induced. The emergence of the 2D Raman peak, quenched by the large interaction with the substrate, reveals that the intercalation process induces a structural undoing. As suggested by atomic force microscopy, the oxygen intercalation does not change significantly the surface morphology. Moreover, theoretical simulations provide further insights into the electronic and structural undoing process. This protocol opens the door to an efficient methodology to weaken the graphene-substrate interaction for a more efficient transfer to arbitrary surfaces.

Controlled Sign Reversal of Electroresistance in Oxide Tunnel Junctions by Electrochemical-Ferroelectric Coupling.

The persistence of ferroelectricity in ultrathin layers relies critically on screening or compensation of polarization charges which otherwise destabilize the ferroelectric state. At surfaces, charged defects play a crucial role in the screening mechanism triggering novel mixed electrochemical-ferroelectric states. At interfaces, however, the coupling between ferroelectric and electrochemical states has remained unexplored. Here, we make use of the dynamic formation of the oxygen vacancy profile in the nanometer-thick barrier of a ferroelectric tunnel junction to demonstrate the interplay between electrochemical and ferroelectric degrees of freedom at an oxide interface. We fabricate ferroelectric tunnel junctions with a La_{0.7}Sr_{0.3}MnO_{3} bottom electrode and BaTiO_{3} ferroelectric barrier. We use poling strategies to promote the generation and transport of oxygen vacancies at the metallic top electrode. Generated oxygen vacancies control the stability of the ferroelectric polarization and modify its coercive fields. The ferroelectric polarization, in turn, controls the ionization of oxygen vacancies well above the limits of thermodynamic equilibrium, triggering the build up of a Schottky barrier at the interface which can be turned on and off with ferroelectric switching. This interplay between electronic and electrochemical degrees of freedom yields very large values of the electroresistance (more than 10^{6}% at low temperatures) and enables a controlled switching between clockwise and counterclockwise switching modes in the same junction (and consequently, a change of the sign of the electroresistance). The strong coupling found between electrochemical and electronic degrees of freedom sheds light on the growing debate between resistive and ferroelectric switching in ferroelectric tunnel junctions, and moreover, can be the source of novel concepts in memory devices and neuromorphic computing.

Ferroelectric Control of Interface Spin Filtering in Multiferroic Tunnel Junctions.

The electronic reconstruction occurring at oxide interfaces may be the source of interesting device concepts for future oxide electronics. Among oxide devices, multiferroic tunnel junctions are being actively investigated as they offer the possibility to modulate the junction current by independently controlling the switching of the magnetization of the electrodes and of the ferroelectric polarization of the barrier. In this Letter, we show that the spin reconstruction at the interfaces of a La_{0.7}Sr_{0.3}MnO_{3}/BaTiO_{3}/La_{0.7}Sr_{0.3}MnO_{3} multiferroic tunnel junction is the origin of a spin filtering functionality that can be turned on and off by reversing the ferroelectric polarization. The ferroelectrically controlled interface spin filter enables a giant electrical modulation of the tunneling magnetoresistance between values of 10% and 1000%, which could inspire device concepts in oxides-based low dissipation spintronics.

Morphological stabilization and KPZ scaling by electrochemically induced co-deposition of nanostructured NiW alloy films.

We have assessed the stabilizing role that induced co-deposition has in the growth of nanostructured NiW alloy films by electrodeposition on polished steel substrates, under pulsed galvanostatic conditions. We have compared the kinetic roughening properties of NiW films with those of Ni films deposited under the same conditions, as assessed by Atomic Force Microscopy. The surface morphologies of both systems are super-rough at short times, but differ at long times: while a cauliflower-like structure dominates for Ni, the surfaces of NiW films display a nodular morphology consistent with more stable, conformal growth, whose height fluctuations are in the Kardar-Parisi-Zhang universality class of rough two-dimensional interfaces. These differences are explained by the mechanisms controlling surface growth in each case: mass transport through the electrolyte (Ni) and attachment of the incoming species to the growing interface (NiW). Thus, the long-time conformal growth regime is characteristic of electrochemical induced co-deposition under current conditions in which surface kinetics is hindered due to a complex reaction mechanism. These results agree with a theoretical model of surface growth in diffusion-limited systems, in which the key parameter is the relative importance of mass transport with respect to the kinetics of the attachment reaction.

High-quality PVD graphene growth by fullerene decomposition on Cu foils.

We present a new protocol to grow large-area, high-quality single-layer graphene on Cu foils at relatively low temperatures. We use C60 molecules evaporated in ultra high vacuum conditions as carbon source. This clean environment results in a strong reduction of oxygen-containing groups as depicted by X-ray photoelectron spectroscopy (XPS). Unzipping of C60 is thermally promoted by annealing the substrate at 800ºC during evaporation. The graphene layer extends over areas larger than the Cu crystallite size, although it is changing its orientation with respect to the surface in the wrinkles and grain boundaries, producing a modulated ring in the low energy electron diffraction (LEED) pattern. This protocol is a self-limiting process leading exclusively to one single graphene layer. Raman spectroscopy confirms the high quality of the grown graphene. This layer exhibits an unperturbed Dirac-cone with a clear n-doping of 0.77 eV, which is caused by the interaction between graphene and substrate. Density functional theory (DFT) calculations show that this interaction can be induced by a coupling between graphene and substrate at specific points of the structure leading to a local sp3 configuration, which also contribute to the D-band in the Raman spectra.

Giant Seebeck effect in Ge-doped SnSe.

Thermoelectric materials may contribute in the near future as new alternative sources of sustainable energy. Unprecedented thermoelectric properties in p-type SnSe single crystals have been recently reported, accompanied by extremely low thermal conductivity in polycrystalline samples. In order to enhance thermoelectric efficiency through proper tuning of this material we report a full structural characterization and evaluation of the thermoelectric properties of novel Ge-doped SnSe prepared by a straightforward arc-melting method, which yields nanostructured polycrystalline samples. Ge does not dope the system in the sense of donating carriers, yet the electrical properties show a semiconductor behavior with resistivity values higher than that of the parent compound, as a consequence of nanostructuration, whereas the Seebeck coefficient is higher and thermal conductivity lower, favorable to a better ZT figure of merit.

Phase separation enhanced magneto-electric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films.

We study the origin of the magnetoelectric coupling in manganite films on ferroelectric substrates. We find large magnetoelectric coupling in La0.7Ca0.3MnO3/BaTiO3 ultra-thin films in experiments based on the converse magnetoelectric effect. The magnetization changes by around 30-40% upon applying electric fields on the order of 1 kV/cm to the BaTiO3 substrate, corresponding to magnetoelectric coupling constants on the order of α = (2-5) · 10(-7) s/m. Magnetic anisotropy is also affected by the electric field induced strain, resulting in a considerable reduction of coercive fields. We compare the magnetoelectric effect in pre-poled and unpoled BaTiO3 substrates. Polarized neutron reflectometry reveals a two-layer behavior with a depressed magnetic layer of around 30 Å at the interface. Magnetic force microscopy (MFM) shows a granular magnetic structure of the La0.7Ca0.3MnO3. The magnetic granularity of the La0.7Ca0.3MnO3 film and the robust magnetoelastic coupling at the La0.7Ca0.3MnO3/BaTiO3 interface are at the origin of the large magnetoelectric coupling, which is enhanced by phase separation in the manganite.

Proximity Driven Commensurate Pinning in YBa2Cu3O7 through All-Oxide Magnetic Nanostructures.

The design of artificial vortex pinning landscapes is a major goal toward large scale applications of cuprate superconductors. Although disordered nanometric inclusions have shown to modify their vortex phase diagram and to produce enhancements of the critical current ( MacManus-Driscoll , J. L. ; Foltyn , S. R. ; Jia , Q. X. ; Wang , H. ; Serquis , A. ; Civale , L. ; Maiorov , B. ; Hawley , M. E. ; Maley , M. P. ; Peterson , D. E. Nat. Mater. 2004 , 3 , 439 - 443 and Yamada , Y. ; Takahashi , K. ; Kobayashi , H. ; Konishi , M. ; Watanabe , T. ; Ibi , A. ; Muroga , T. ; Miyata , S. ; Kato , T. ; Hirayama , T. ; Shiohara , Y. Appl. Phys. Lett. 2005 , 87 , 1 - 3 ), the effect of ordered oxide nanostructures remains essentially unexplored. This is due to the very small nanostructure size imposed by the short coherence length, and to the technological difficulties in the nanofabrication process. Yet, the novel phenomena occurring at oxide interfaces open a wide spectrum of technological opportunities to interplay with the superconductivity in cuprates. Here, we show that the unusual long-range suppression of the superconductivity occurring at the interface between manganites and cuprates affects vortex nucleation and provides a novel vortex pinning mechanism. In particular, we show evidence of commensurate pinning in YBCO films with ordered arrays of LCMO ferromagnetic nanodots. Vortex pinning results from the proximity induced reduction of the condensation energy at the vicinity of the magnetic nanodots, and yields an enhanced friction between the nanodot array and the moving vortex lattice in the liquid phase. This result shows that all-oxide ordered nanostructures constitute a powerful, new route for the artificial manipulation of vortex matter in cuprates.

Interface and temperature dependent magnetic properties in permalloy thin films and tunnel junction structures.

Magnetization dynamics and field dependent magnetization of different devices based on 25-30 nm thick Permalloy (Py) films: such as single Py layers (Py/MgO; Py/CoFeB/Al2O3) and Py inserted as a magnetic layer in magnetic tunnel junctions (Py/CoFe/Al2O3/CoFe; Py/CoFeB/Al2O3/CoFe; Py/MgO/Fe) have been extensively studied within a temperature range between 300 K down to 5 K. The dynamic response was investigated in the linear regime measuring the ferromagnetic resonance response of the Py layers using broadband vector network analyzer technique. Both the static and the dynamic properties suggest the possible presence of a thermally induced spin reorientation transition in the Py interface at temperatures around 60 K in all the samples investigated. It seems, however, that the details of the interface between Py and the hardening ferromagnet/insulator structure, the atomic structure of Py layers (amorphous vs. textured) as well as the presence of dipolar coupling through the insulating barrier in the magnetic tunnel junction structures could strongly influence this low temperature reorientation transition. Our conclusions are indirectly supported by structural characterization of the samples by means of X-Ray diffraction and high resolution transmission electron microscopy techniques. Micromagnetic simulations indicate the possibility of strongly enhanced surface anisotropy in thin Py films over CoFe or CoFeB underlayers. Comparison of the simulations with experimental results also shows that the thermally-induced spin reorientation transition could be influenced by the presence of strong disorder at the surface.

[Bladder metastasis of signet-ring cell adenocarcinoma from the stomach]. / Metástasis vesical de adenocarcinoma de células en anillo de sello de origen gástrico.

OBJECTIVE: To describe an additional case of metastatic bladder tumor from gastric signet-ring cell adenocarcinoma. METHODS/RESULTS: Local recurrence was demonstrated by gastrointestinal endoscopy and biopsy in a 52-year-old female who underwent total gastrectomy for signet-ring cell gastric adenocarcinoma two years earlier. A CT scan showed bilateral hydronephrosis and diffuse thickening of the bladder wall. Bladder biopsy demonstrated signet-ring cell adenocarcinoma. Palliative treatment with ureteral catheterization was instituted. CONCLUSIONS: Signet-ring cell adenocarcinoma of the bladder is usually a primary tumor. Metastatic signet-ring cell adenocarcinoma to the urinary bladder is uncommon.