Curvature-induced stabilization and field-driven dynamics of magnetic hopfions in toroidal nanorings

Three dimensional magnetic textures are a cornerstone in magnetism research. In this work, we analyze the stabilization and dynamic response of a magnetic hopfion hosted in a toroidal nanoring with intrinsic Dzyaloshinskii-Moriya interaction simulating FeGe. Our results evidence that unlike their planar counterparts, where perpendicular magnetic anisotropies are necessary to stabilize hopfions, the shape anisotropy originated on the torus symmetry naturally yields the nucleation of these topological textures. We also analyze the magnetization dynamical response by applying a magnetic field pulse to differentiate among several magnetic patterns. Finally, to understand the nature of spin wave modes, we analyze the spatial distributions of the resonant mode amplitudes and phases and describe the differences among bulk and surface modes. Importantly, hopfions lying in toroidal nanorings present a non-circularly symmetric poloidal resonant mode, which is not observed in other systems hosting hopfions.

P–543 Inhibition of cell proliferation and extracellular matrix formation in human uterine leiomyomas by 5-aza–2’-deoxycitidine via Wnt/ β-catenin pathway

Study question

Is DNA methylation reversion through DNA methyltransferases (DNMT) inhibitors, such as 5-aza–2’-deoxycitidine, a potential therapeutic option for treatment of patients with uterine leiomyomas (UL)?

Summary answer

5-aza–2’-deoxycitidine reduces proliferation and extracellular matrix (ECM) formation by inhibition of Wnt/ β-catenin pathway on UL cells, suggesting DNMT inhibitors as an option to treat UL. What is known already: UL is a multifactorial disease with an unclear pathogenesis and inaccurate treatment. Aberrant DNA methylation have been found in UL compared to myometrium (MM) tissue, showing hypermethylation of tumor suppressor genes, which contributes to the development of this tumor. The use of DNMT inhibitors, such as 5-aza–2’-deoxycytidine (5-aza-CdR), has been suggested to treat tumors in which altered methylation pattern is related to tumor progression, as occurs in UL. Based on this, we aimed to evaluate whether DNA methylation reversion through 5-aza-CdR reduces cell proliferation and ECM formation in UL cells, being a potential option for UL medical treatment.

Study design, size, duration

Prospective study comparing UL versus MM tissue and human uterine leiomyoma primary (HULP) cells treated with/without 5-aza-CdR at 0 µM (control), 2 µM, 5 µM and 10 µM for 72 hours. UL and MM tissue were collected from women without any hormonal treatment for the last 3 months (n = 16) undergoing myomectomy or hysterectomy due to symptomatic leiomyoma pathology. Participants were recruited between January 2019 and February 2020 at Hospital Universitario y Politecnico La Fe (Spain).

Participants/materials, setting, methods

Samples were collected from Caucasian premenopausal women aged 31–48 years, with a body mass index of < 30 and without hormonal treatment. DNMT1 gene expression was analysed in UL vs MM tissue by qRT-PCR and activity of DNMT was measured in UL and MM tissue and cells by ELISA. 5-aza-CdR effect on proliferation was assessed by CellTiter test and Western blot (WB), apoptosis and ECM analyzed by WB and Wnt/ β-catenin pathway by qRT-PCR and WB. Main results and the role of chance: DNMT1 gene expression was increased in UL compared to MM tissue (fold change [FC]=2.49, p-value [p]=0.0295). Similarly, DNMT activity was increased in both UL compared to MM tissue and HULP cells versus MM cells (6.50 vs 3.76 OD/h/mg, p = 0.026; 211.30 vs 63.67 OD/h/mg, p = 0.284, respectively). After 5-aza-CdR treatment, cell viability of HULP cells was reduced in a dose dependent manner, being statistically significant at 10 µM (85.25%, p = 0.0001). Accordantly, PCNA protein expression was significantly decreased at 10 µM in HULP cells (FC = 0.695, p = 0.034), demonstrating cell proliferation inhibition. Additionally, 5-aza-CdR inhibited ECM protein expression in HULP cells in a dose-dependent manner being statistically significant at 10 µM for COLLAGEN I (FC = 0.654, p = 0.023) and PAI–1 (FC = 0.654, p = 0.023), and at 2 µM and 10 µM for FIBRONECTIN (FC = 0.812, p = 0.020; FC = 0.733, p = 0.035; respectively). Final targets of Wnt/ β-catenin pathway were decreased after 5-aza-CdR treatment, protein expression of WISP1 was significantly inhibited at 10 µM (FC = 0.699, p = 0.026), while expression levels of Wnt/ β-catenin target genes C-MYC (FC = 0.745, p = 0.028 at 2 µM; FC = 0.728, p = 0.019 at 10 µM) and MMP7 (FC = 0.520, p = 0.003 at 5 µM, FC = 0.577, p = 0.007 at 10 µM) were also significantly downregulated in HULP-treated cells vs untreated cells. Limitations, reasons for caution: This study has strict inclusion criteria to diminish epigenetic variability, thereby we should be cautious extrapolating our results to general population. Besides, this is a proof of concept with the inherent cell culture limitations. Further studies are necessary to determine 5-aza-CdR dose and adverse effects on UL in vivo.

Wider implications of the findings: 5-aza-CdR treatment reduces cell proliferation and ECM formation through Wnt/ β-catenin pathway inhibition, suggesting that inhibition of DNA methylation could be a promising new therapeutic approach to treat UL.

Trial registration number

Not applicable

Dynamic and static properties of stadium-shaped antidot arrays

In this work we performed a detailed numerical analysis on the static and dynamic properties of magnetic antidot arrays as a function of their geometry. In particular, we explored how by varying the shape of these antidot arrays from circular holes to stadium-shaped holes, we can effectively control the magnetic properties of the array. Using micromagnetic simulations we evidenced that coercivity is very sensitive to the shape of antidots, while the remanence is more robust to these changes. Furthermore, we studied the dynamic susceptibility of these systems, finding that it is possible to control both the position and the number of resonance peaks simply by changing the geometry of the holes. Thus, this work provides useful insights on the behavior of antidot arrays for different geometries, opening routes for the design and improvement of two-dimensional technologies.

Co/Ni multilayers ordered according to a periodic, Fibonnacci and Thue Morse sequence obtained by Atomic Layer Deposition

Co/Ni multilayers ordered according to a periodic, Fibonnacci and Thue Morse sequence have been obtained by Atomic Layer Deposition and a subsequent process of thermal reduction. The morphology of the multilayers was investigated by scanning electron microscopy, while longitudinal hysteresis curves were obtained by magneto-optical magnetometry of Kerr effect. The morphology of the films varies as a function of their sequence and thickness. Multilayers exhibit coercivities much higher than expected from samples synthesized with other methods. The control of the magnetic properties of multilayers, as a function of their sequence, may allow their use in spintronic devices.

Magnetic and electrical characterization of nickel-rich NiFe thin films synthesized by atomic layer deposition and subsequent thermal reduction

Nickel-rich NiFe thin films (Ni92Fe8, Ni89Fe11 and Ni83Fe17) were prepared by combining atomic layer deposition (ALD) with a subsequent thermal reduction process. In order to obtain Ni x Fe1-x O y films, one ALD supercycle was performed according to the following sequence: m NiCp2/O3, with m = 1, 2 or 3, followed by one FeCp2/O3 cycle. The supercycle was repeated n times. The thermal reduction process in hydrogen atmosphere was investigated by in situ x-ray diffraction studies as a function of temperature. The metallic nickel iron alloy thin films were investigated and characterized with respect to crystallinity, morphology, resistivity, and magnetism. As proof-of-concept magnetic properties of an array of Ni83Fe17, close to the perfect Permalloy stoichiometry, nanotubes and an isolated tube were investigated.

A soft/hard magnetic nanostructure based on multisegmented CoNi nanowires

In this paper we have introduced a new soft/hard nanostructure based on multisegmented CoNi nanowire arrays having diameters of around 110 nm and made of five segments with nominal compositions of Co, Co66Ni33, Co50Ni50, Co33Ni66 and Ni, each of which has a length of 800 nm, so that the total length of the multisegmented nanowire is 4 μm. These arrays have been synthesized by means of potentiostatic electrodeposition into the pores of hard-anodic alumina templates. The morphology, chemical composition and microstructure of the multisegmented CoNi nanowires were determined by high-resolution scanning electron microscopy, energy dispersive X-ray microanalysis, and powder X-ray diffraction method, respectively. The room temperature magnetic behavior of the multisegmented nanowire arrays is also studied and compared with CoNi nanowire arrays with homogeneous composition (non-segmented nanowires), synthesized in the same templates and having the same dimensions as the segmented ones. These nanostructures could be used to control the movement of magnetic domain walls. In this way, these nanostructures can be an alternative to store information or even perform logic functions.

Asymmetric hysteresis loop in magnetostatic-biased multilayer nanowires

The hysteresis of multilayer nanowires composed by a soft magnetic cylindrical wire, a non-magnetic spacer layer and an external hard magnetic shell is investigated. The external magnetic shell originates a non-homogeneous magnetic field on the inner wire, which is responsible for a displacement and a change of the width of the hysteresis curve of the wire. Moreover, different reversal modes occur at each branch of the hysteresis loop, which can be understood by analyzing the interaction magnetostatic field along the wire. Our results open the possibility of controlling two parameters of the hysteresis loop, the coercivity and the bias, providing an interesting system to be investigated.

Magnetic phase diagrams of barcode-type nanostructures

The magnetic configurations of barcode-type magnetic nanostructures consisting of alternate ferromagnetic and nonmagnetic layers arranged within a multilayer nanotube structure are investigated as a function of their geometry. Based on a continuum approach we have obtained analytical expressions for the energy which lead us to obtain phase diagrams giving the relative stability of characteristic internal magnetic configurations of the barcode-type nanostructures.

Geometry dependence of coercivity in Ni nanowire arrays

Magnetic properties of arrays of nanowires produced inside the pores of anodic alumina membranes have been studied by means of vibrating sample magnetometer techniques. In these systems the length of the wires strongly influences the coercivity of the array. A simple model for the coercivity as a function of the geometry is presented which exhibits good agreement with experimental results. Magnetostatic interactions between the wires are responsible for a decrease of the coercive field.

Trocar site hernia after laparoscopic ventral hernia repair

BACKGROUND

The incidence of trocar site hernia (TSH) after laparoscopic ventral hernia repair (LVHR) is reported to be low. The present study investigates the associated risk factors, with a view to preventing this complication.

METHODS

A retrospective study was made of the incidence of TSH in a personal series of LVHR, recording anthropometric and clinical data on the patients. Risk factors were assessed by bivariate and multivariate analyses. The patients were subjected to clinical and telephone follow-up.

RESULTS

In a series of 27 LVHR, the incidence of TSH was 22% (6 patients). The use of meshes larger than 10 x 15 cm for LVHR was the only TSH risk factor to reach statistical significance. Female gender and diabetes showed a higher incidence in the TSH group.

CONCLUSIONS

The use of large meshes may be a risk factor for TSH. We believe this to be due to dilatation of the trocar orifice during introduction of the mesh, and also to postoperative retraction of the mesh.

Video-laparoscopic staging of gastric cancer. A prospective multicenter comparison with noninvasive techniques

BACKGROUND

The high proportion of gastric carcinomas present in an unresectable stage, together with the emergence of multimodal treatments, increases the usefulness of objective staging methods that avoid unnecessary laparotomies.

METHODS

A prospective evaluation of the accuracy of laparoscopy in the staging of 71 patients with gastric adenocarcinoma is presented. Serosal infiltration, retroperitoneal fixation, metastasis to lymph nodes, peritoneal and liver metastasis, and ascites were determined in the staging workup. Sensitivity, specificity, and predictive values were calculated and compared with those obtained with ultrasonography (US) and computed tomography (CT).

RESULTS

The diagnostic accuracy of laparoscopy in the determination of resectability was 98.6%. Consequently, over 40% of patients were spared unnecessary laparotomies. Laparoscopy yielded diagnostic indices superior to US and CT for all the tumoral attributes studied. Our technique permits accurate assessment and pathologic verification of liver and the peritoneal and retroperitoneal extent of tumor invasion in the majority of patients.

CONCLUSIONS

Laparoscopy in gastric adenocarcinoma is a reliable technique that provides accurate assessment of resectability and stage, thus avoiding unnecessary laparotomies in patients in whom surgical palliation is not indicated. A stepwise diagnostic workup combining imaging and minimally invasive techniques is proposed.