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Resumen Introduccion Evaluar el impacto de la fatiga por incorrecto descanso nocturno en la realizacion de una anastomosis manual laparoscopica. Metodos Se lleva a cabo un estudio prospectivo observacional evaluando la realizacion de una anastomosis manual enteroenteral en endotrainer por residentes. Se dividen en dos grupos; el grupo descanso incluye a residentes que han dormido en casa siete o mas horas vs. al grupo fatiga formado por residentes de guardia o que han dormido menos de siete horas. Se evalua el tiempo empleado, la longitud de la anastomosis, la correcta tension de la linea de sutura, la correcta aposicion de los bordes, la distancia entre puntos y la fuga de aire, en prueba neumatica de estanqueidad. Resultados Se evaluan 402 anastomosis, siendo 211 pertenecientes al grupo descanso y 191 al grupo fatiga. Se detecta fuga en el 33,5% de las anastomosis del grupo fatiga frente al 19,4% en el grupo descanso (p Discusion La fatiga aumenta el riesgo de fuga y el tiempo que se tarda en completar el ejercicio.

Resumen Introduccion El aprendizaje de las tecnicas quirurgicas es un proceso dinamico. David Kolb describio en los anos ochenta un modelo de aprendizaje que permite adaptar el tipo de ensenanza y mejorar los resultados de esta. El objetivo del estudio es identificar los estilos de aprendizaje segun Kolb de los participantes en un curso de habilidades tecnicas laparoscopicas y comprobar si existe relacion con el rendimiento final de la tarea realizada. Metodos Estudio observacional descriptivo que incluye 64 participantes que completaron un curso intensivo donde realizaron anastomosis intestinales manuales laparoscopicas. Todos ellos completaron el inventario de estilos de aprendizaje de Kolb. En cada anastomosis se recogio el tiempo de ejecucion y se valoro su calidad. Posteriormente, los datos fueron analizados estadisticamente. Resultados El estilo de aprendizaje mas frecuente fue el asimilador (39,1%). No se observan diferencias significativas entre los estilos y el sexo de los participantes, su categoria profesional, el tiempo en realizar la anastomosis o su calidad. Conclusiones El estilo de aprendizaje predominante es el asimilador, sin diferencias entre categorias, edad o sexo. No existe relacion entre el estilo de aprendizaje de los participantes y los resultados obtenidos en el curso.

Introduction Learning surgical techniques is a dynamic process. In the 1980s David Kolb described developed a learning model that enabled teaching styles to adapt for better learner outcomes. The aim of this study was to identify the Kolb learning styles of the participants in a laparoscopic technical skills course and to check see if there was any relationship with performance. Methods An observational descriptive study was conducted with 64 participants in an intensive course in which they performed laparoscopic manual intestinal anastomoses. All completed Kolb's inventory of learning styles. For each anastomosis, join quality was assessed and the performing time recorded. After that, they were analyzed through statistical studies. Results The most frequent learning style was assimilating type (39.1%). No significant differences were observed between different learning styles and gender, professional category, the time taken or the quality of the anastomoses. Conclusions Assimilating type was the most frequent Kolb learning style, with no differences observed between categories, age or gender. There is no relationship between the learning style of the participants and the results obtained in the course.

Resumen Introduccion El entrenamiento quirurgico basado en simulacion busca la adquisicion de habilidades en los participantes noveles y la capacitacion en los expertos. El objetivo de este estudio es valorar la evolucion de los alumnos en un curso intensivo de anastomosis laparoscopica y el analisis de sus resultados dependiendo de su nivel y experiencia previa. Metodos Se analizaron los alumnos de todos los cursos de anastomosis realizados durante 30 meses en el Hospital virtual Valdecilla (Santander). Se realizaron anastomosis intestinales latero-laterales manuales con visceras «ex vivo» porcinas en un endotrainer laparoscopico. Se analizaron las diferencias tecnicas y de calidad entre la primera y la ultima anastomosis y se comparo la progresion entre residentes y los facultativos especialistas. Resultados Se analizaron 45 participantes, 22 de ellos residentes y 23 especialistas. Se observo una mejoria estadisticamente significativa del 80,5% en todos los parametros procedimentales (94,8% residentes vs. 67,3% especialistas). El tiempo se redujo un 48,1% en los residentes y un 43,2% en los especialistas (p En cuanto a calidad, se obtuvieron mejorias significativas en el grupo de residentes: incremento del 90% de tension adecuada, reduccion del 75% de bordes evertidos y 60% de las fugas. Ademas, obtuvieron resultados comparables a los especialistas (27,3% fuga en ultima anastomosis vs. 34,8% especialistas, p = 0,59), los cuales presentaron mejoria sin significacion estadistica. Conclusiones El grupo de residentes presenta una mejora mayor y significativa en habilidades procedimentales y en calidad de la tecnica, alcanzando el nivel de los especialistas tras completar el curso.

Refraction between isotropic media is characterized by light bending towards the normal to the boundary when passing from a low- to a high-refractive-index medium. However, refraction between anisotropic media is a more exotic phenomenon which remains barely investigated, particularly at the nanoscale. Here, we visualize and comprehensively study the general case of refraction of electromagnetic waves between two strongly anisotropic (hyperbolic) media, and we do it with the use of nanoscale-confined polaritons in a natural medium: α-MoO3. The refracted polaritons exhibit non-intuitive directions of propagation as they traverse planar nanoprisms, enabling to unveil an exotic optical effect: bending-free refraction. Furthermore, we develop an in-plane refractive hyperlens, yielding foci as small as λp/6, being λp the polariton wavelength (λ0/50 compared to the wavelength of free-space light). Our results set the grounds for planar nano-optics in strongly anisotropic media, with potential for effective control of the flow of energy at the nanoscale., G.Á.-P. and J.T.-G. acknowledge support through the Severo Ochoa Program from the Government of the Principality of Asturias (nos. PA-20-PF-BP19-053 and PA-18-PF-BP17-126, respectively). S.X. acknowledges the support from Independent Research Fund Denmark (Project No. 9041-00333B). B.C. acknowledges the support from VILLUM FONDEN (No. 00027987). The Center for Nanostructured Graphene is sponsored by the Danish National Research Foundation (Project No. DNRF103.) K.V.V. and V.S.V. gratefully acknowledge the financial support from the Ministry of Science and Higher Education of the Russian Federation (Agreement No. 075-15-2021-606). J.M.-S. acknowledges financial support through the Ramón y Cajal Program from the Government of Spain (RYC2018-026196-I). A.Y.N. and J.I.M. acknowledge the Spanish Ministry of Science, Innovation and Universities (national projects MAT201788358-C3-3-R and PID2019-104604RB/AEI/10.13039/501100011033). R.H. acknowledges financial support from the Spanish Ministry of Science, Innovation and Universities (national project RTI2018-094830-B-100 and the project MDM-2016-0618 of the Marie de Maeztu Units of Excellence Program) and the Basque Government (grant No. IT1164-19). A.Y.N. also acknowledges the Basque Department of Education (grant no. PIBA-2020-1-0014). P.A.-G. acknowledges support from the European Research Council under starting grant no. 715496, 2DNANOPTICA and the Spanish Ministry of Science and Innovation (State Plan for Scientific and Technical Research and Innovation grant number PID2019-111156GB-I00).

Resumen La ensenanza de la cirugia se ha visto afectada por multiples factores a lo largo de estos ultimos anos, como son la reduccion de la jornada laboral, la optimizacion del uso del quirofano o la seguridad del paciente. La metodologia de ensenanza tradicional no logra minimizar el impacto de estos factores en la formacion de los cirujanos. La simulacion como modelo de ensenanza minimiza dicho impacto y es mas eficaz que los metodos docentes tradicionales para integrar los conocimientos y las habilidades clinico-quirurgicas complejas. La simulacion complementa la asistencia clinica al paciente con la formacion, creando un entorno de aprendizaje seguro en el que no se ve afectada la seguridad del paciente ni se generan conflictos eticos ni legales. Las metodologias de aprendizaje que utilizan la simulacion permiten individualizar la ensenanza adaptandola a las necesidades de aprendizaje de cada alumno. Ademas, permiten entrenar todo tipo de habilidades tecnicas, cognitivas o de comportamiento.

Teaching of surgery has been affected by many factors over the last years, such as the reduction of working hours, the optimization of the use of the operating room or patient safety. Traditional teaching methodology fails to reduce the impact of these factors on surgeońs training. Simulation as a teaching model minimizes such impact, and is more effective than traditional teaching methods for integrating knowledge and clinical-surgical skills. Simulation complements clinical assistance with training, creating a safe learning environment where patient safety is not affected, and ethical or legal conflicts are avoided. Simulation uses learning methodologies that allow teaching individualization, adapting it to the learning needs of each student. It also allows training of all kinds of technical, cognitive or behavioural skills.

Combination of a pulsed glow discharge (PGD) source with time-of-flight mass spectrometry (TOFMS) enables for fast multielemental transient signals detection of solid samples. Such instrument is ideal for depth profiling of layered materials with depth resolution down to the low nm range. In this work, depth profile capabilities of radiofrequency (rf) PGD-TOFMS system have been investigated when dealing with thin layers (GexNi100-x/Ni/NdyNi100-y with total thicknesses between 15 nm and 75 nm) deposited on two substrates with different electrical properties (non-conductive glasses and silicon wafers). Attention has been paid towards the selection of the different PGD operational parameters aiming at achieving best instrument performance for each substrate in terms of depth resolution of the thin coating layers. Particularly, the applied pulse width has proven to have a direct influence in the temporal regions (prepeak, plateau and afterglow) responsible of the analytical signals detected by TOFMS. Experimental results showed that shorter pulses (0.16 ms was finally selected) and periods (1.32 ms) allowed for better depth profile resolution of the layers deposited onto the glass substrate. However, such selection for the nonconductive substrate hindered obtaining analytical information from the prepeak and plateau regions. On the other hand, the effect of pulse width on depth resolution was not so critical when coatings were deposited onto the silicon wafer., Work supported by Spanish MINECO under grant FIS2016-76058 (AEI/FEDER, EU).

Introduction Surgical training based on simulation seeks the acquisition of skills in novice participants and ongoing skill development in experts. The aim of this study is to assess the evolution of students in an intensive laparoscopic anastomosis course and to analyze their results depending on their level and previous experience. Methods The students of all the anastomosis courses conducted during 30 months in the Valdecilla virtual hospital (Santander) were analyzed. Manual side-to-side intestinal anastomoses with porcine ‘ex vivo’ viscera were performed in a laparoscopic endotrainer. The technical and quality differences between the first and the last anastomoses were analyzed and the progression between residents and specialists was compared. Results We analyzed 45 participants, 22 of them residents and 23 specialists. A statistically significant improvement of 80.5% was observed in all procedural parameters (94.8% residents vs. 67.3% specialists). The time was reduced by 48.1% in the residents and 43.2% in the specialists ( P In terms of quality, significant improvements were obtained in the group of residents: an increase of 90% in adequate tension, and a reduction of 75% of everted edges and 60% of leaks. In addition, they obtained results comparable to the specialists (27.3% leak in the last anastomosis vs. 34.8% by the specialists, P =.59), which presented improvement without statistical significance. Conclusions The group of residents presented a major and significant improvement in procedural skills and in the quality of the technique, reaching the level of the specialists after completion of the course.

The development of magnetic nanostructures for applications in spintronics requires methods capable of visualizing their magnetization. Soft X-ray magnetic imaging combined with circular magnetic dichroism allows nanostructures up to 100–300 nm in thickness to be probed with resolutions of 20–40 nm. Here a new iterative tomographic reconstruction method to extract the three-dimensional magnetization configuration from tomographic projections is presented. The vector field is reconstructed by using a modified algebraic reconstruction approach based on solving a set of linear equations in an iterative manner. The application of this method is illustrated with two examples (magnetic nano-disc and micro-square heterostructure) along with comparison of error in reconstructions, and convergence of the algorithm., The following funding is acknowledged: Spanish MINECO (grant No. FIS2013-45469; grant No. FIS2016-76058 (AEI/FEDER, EU); contract No. FIS2016-76058 (AEI/FEDER, EU) to AHR); FICYT-Asturias (grant No. FC-GRUPIN14-040); US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory (contract No. DE-AC02-06CH11357 to DG); US Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division (contract to CP). AHR acknowledges support from European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Action (reference H2020-MSCA-IF-2016-746958).

Anterior resection with total mesorectal excision is the standard method of rectal cancer resection. However, this procedure remains technically difficult in mid and low rectal cancer. A robotic transanal proctectomy with total mesorectal excision and laparoscopic assistance is reported in a 57 year old male with BMI 32 kg/m 2 and rectal adenocarcinoma T2N1M0 at 5 cm from the dentate line. Operating time was 420 min. Postoperative hospital stay was 6 days and no complications were observed. Pathological report showed a 33 cm specimen with ypT2N0 adenocarcinoma at 2 cm from the distal margin, complete TME and non affected circumferential resection margin. Robotic technology might reduce some technical difficulties associated with TEM/TEO or SILS platforms in transanal total mesorectal excision. Further clinical trials will be necessary to assess this technique.

Resumen La reseccion anterior con escision total mesorrectal es el tratamiento estandar para el cancer de recto. Este tratamiento sigue siendo tecnicamente dificultoso en los tumores localizados en el recto medio e inferior. Presentamos un caso de escision total mesorrectal robotica transanal con asistencia robo tica en un varon de 57 anos e IMC 32 kg/m2 con un adenocarcinoma T2N1M0 a 5 cm de linea pectinea tras tratamiento neoadyuvante. El tiempo quirurgico fue de 420 min. La estancia postoperatoria fue de 6 dias, sin objetivarse complicaciones. El estudio anatomopatologico demostro una pieza de 33 cm, una tumoracion ypT2N0 con margen distal de 2 cm, margen circunferencial libre y buena calidad del mesorrecto. La tecnologia robotica puede disminuir la dificultad inherente a las plataformas TEO/TEM o SILS para la realizacion de este tipo de procedimientos. La realizacion de ensayos clinicos es necesaria para la completa evaluacion de esta tecnica.

Introduction Advanced laparoscopic surgery requires supplementary training outside the operating room. Clinical simulation with animal models or cadavers facilitates this learning. Objective We measured the impact on clinical practice of a laparoscopic colorectal resection training programme based on surgical simulation. Materials and methods Between March 2007 and March 2012, 163 surgeons participated in 30 courses that lasted 4 days, of 35 h (18 h in the operating room, 12 h in animal models, and 4 h in seminars). In May 2012, participants were asked via an on-line survey about the degree of implementation of the techniques in their day-to-day work. Results Seventy surgeons (47%) from 60 different hospitals answered the survey. Average time elapsed after the course was 11.5 months (2–60 months). A total of 75% initiated or increased the number of surgeries performed after the training. The increase in practice was >10 cases/month in 19%, and Conclusions Seventy-five percent of the surveyed surgeons increased the clinical implementation of a complicated surgical technique, such as laparoscopic colorectal surgery, after attending a training course based on clinical simulation.

Resumen La tularemia es una zoonosis infrecuente en Espana. En el brote iniciado en 2007, destaca la elevada incidencia de su forma orofaringea. Describimos nuestra experiencia en el tratamiento de 8 pacientes con adenopatias cervicales por tularemia orofaringea. El estudio se realizo en 5 varones y 3 mujeres, con una edad media de 45,3 (rango: 11-76) anos. En todos aparecieron dolor orofaringeo, fiebre y astenia. El tiempo desde el comienzo de los sintomas hasta la consulta a nuestro servicio oscilo entre 8 y 60 dias. La duracion media de los sintomas orofaringeos fue de 11,7 dias, y las adenopatias aparecieron en los primeros 3 dias. La resolucion de estas adenopatias ocurrio al cabo de 2-3,5 meses. Tres casos precisaron el drenaje quirurgico, y 2 fistulizaron de forma espontanea. Se trato a 7 pacientes con ciprofloxacino y a uno con eritromicina. Un correcto tratamiento antibiotico temprano, y en algunos casos el drenaje quirurgico, podrian acelerar la curacion.

Tularaemia is an uncommon zoonosis in our country. During the outbreak in 2007, there was a notably high incidence of the oropharyngeal form. We report our experience in 8 patients with oropharyngeal tularaemia with cervical adenopathies. The mean age was 45 years (11–76), with 5 males. All suffered oropharyngeal pain, fever, and asthenia. The time elapsed between the onset of symptoms and attending our clinic varied from 8 to 60 days. Mean duration of oropharyngeal symptoms was 11.7 days, and adenopathies appeared in the first 3 days. Resolution of adenopathies occurred at 2 to 3.5 months. Three cases needed surgical drainage and 2 fistulized spontaneously. Seven patients were treated with ciprofloxacin and 1 with erythromycin. A correct and precocious antibiotic therapy, and sometimes surgical drainage, could accelerate the healing process.

Background The identification of developmental curve patterns generated by a simulation-based educational method and the variables that can accelerate the learning process will result in cost-effective training. This study describes the learning curves of a simulation-based instructional design (ID) that uses ex vivo animal models to teach laparoscopic latero-lateral small bowel anastomosis. Methods Twenty general surgery residents were evaluated on their performance of laparoscopic latero-lateral jejuno-jejunal anastomoses (JJA) and gastro-jejunal anastomoses (GJA), using swine small bowel and stomach on an endotrainer. The ID included the following steps: (1) provision of references and videos demonstrating the surgical technique, (2) creation of an engaging context for learning, (3) critical review of the literature and video on the procedures, (4) demonstration of the critical steps, (5) hands-on practice, (6) in-action instructor’s feedback, (7) quality assessment, (8) debriefing at the end of the session, and (9) deliberate and repetitive practice. Time was recorded from the beginning to the completion of the procedure, along with the presence or absence of anastomotic leaks. Results The participants needed to perform 23.8 ± 6.96 GJA (12–35) and 24.2 ± 6.96 JJA (9–43) to attain proficiency. The starting point of the learning curve was higher for the GJA than for the JJA, although the slope and plateau were parallel. Further, four types of learning curves were identified: (1) exponential, (2) rapid, (3) slow, and (4) no tendency. The type of pattern could be predicted after procedure number 8. Conclusions These findings may help to identify the learning curve of a trainee early in the developmental process, estimate the number of sessions required to reach a performance goal, determine a trainee’s readiness to practice the procedure on patients, and identify the subjects who lack the innate technical abilities. It may help motivated individuals to become reflective and self-regulated learners. Moreover, the standardization of the ID may help to measure the effectiveness of learning strategies and make comparisons with other educational strategies.

We describe the cases of two men, one of whom was a non-alcoholic 50-year-old man who had been on hunger strike for 50 days and who was admitted to hospital with dysarthria, unstable gait, disorientation, ophthalmoplegia and ataxia. The suspected diagnosis was Wernicke's encephalopathy and treatment consisted of intramuscular thiamine shots followed by oral administration of the same drug, which produced rapid symptom resolution. In both patients, magnetic resonance imaging showed bilateral and symmetrical injuries around Silvio's aqueduct and in the periventricular region of both thalami.

PURPOSE: The aim of this study was to analyze the diagnostic accuracy of C-reactive protein and its possible advantage, if any, over leukocyte counts in acute appendicitis in children. METHODS: We performed a retrospective study of 124 children (72 males) with a mean age of 9.3 (range, 2–14) years operated on under a clinical diagnosis of acute appendicitis. The diagnosis of acute appendicitis, confirmed by pathologic examination of the removed appendix, was then correlated with C-reactive protein, leukocyte count, and a combination of both C-reactive protein and leukocyte count, with a logistic regression model. C-reactive protein serum measurements were performed by an immunoturbidimetric test. The patients were divided into two groups according to the pathologic features of the removed appendix: Group A (n=104), patients with acute appendicitis, and Group B (n=20), patients without acute appendicitis. To assess the accuracy of C-reactive protein, leukocyte counts, and a combination of both parameters, receiver operating characteristic curves were used. The areas under the curve were compared using the maximum likelihood estimation method. RESULTS: There were 95 cases (76.6 percent) of nonperforated appendicitis, 9 cases (7.3 percent) of perforated appendicitis and 20 cases (16.1 percent) of normal appendix. Mean C-reactive protein in Group A was 4.3 (standard deviation, 6.6) and in Group B was 1.2 (standard deviation, 1.7;P=0.03). The C-reactive protein and leukocyte count values were correlated with the pathologic diagnosis of acute appendicitis. Mean C-reactive protein values increase as the pathologic inflammation type progresses (P=0.007). The C-reactive protein receiver operating characteristic curve shows that the C-reactive protein value with highest accuracy was 1.7 mg/dl. The sensitivity, specificity, and accuracy rates calculated in the 1.7 cutoff were 58, 80, and 83.8 percent, respectively. A comparison of the respective receiver operating characteristic curves demonstrates that C-reactive protein, leukocyte count, and the combination of both tests all have a good diagnostic value but without any significant difference (P=0.2). CONCLUSIONS: In children, 1) serum C-reactive protein is increased in acute appendicitis; 2) such increase is related to the severity of the appendiceal inflammation; and 3) although serum C-reactive protein has an adequate diagnostic accuracy, neither individually nor in combination with the leukocyte count is it significantly better than the leukocyte count alone.

One-step fabrication on PMMA resist of relatively large area arrays of dots by electron beam lithography (EBL) is reported when using one of the most conventional systems from Raith(TM) company. Analyzing the effect of the microscope conditions on the homogeneity and shape of the dots, it has been found that aberrations problems that appear in the dots far off from the array centre at usual working distances can be solved by carefully adjusting the microscope at a much larger working distance (WD). In these conditions, good circular dots, with a diameter of about 300nm, can be obtained in one-step on every part of the array over [email protected]@mm areas in write fields of [email protected]@mm.

Resumen El mixoma es un tumor de partes blandas, de muy infrecuente presentacion; la localizacion en la musculatura de la pared abdominal es totalmente excepcional. Se presenta un caso en el que la probabilidad de que se trate de una recidiva de un mixoma extirpado anos antes es muy elevada, condicion muy rara en este tipo de tumores. Se detallan los aspectos histologicos, radiologicos y de diagnostico diferencial de este tumor, que optimamente tratado presenta un pronostico magnifico.

Magnetization reversal processes have been analyzed by Magnetic Force Microscopy in dense arrays of Co bars with well defined shape anisotropy and strong magnetostatic interactions. Two different geometries have been used: rectangular and rhombic so that the sign of dipolar interactions between adjacent chains of bars is changed from antiferromagnetic (rectangular array) to ferromagnetic (rhombic array), having a profound influence on the shape of a nucleus of inversion at the magnetization reversal., Spanis MICINN: FIS2008-06249, HP 2008-0032; Asturias FICYT: IB 08-106; CRUP of Portugal: E41/09 and FCT of Portugal: SFRH/BD/24012/2005.

The fabrication method of arrays of iron squares separated by submicrometric distances is presented. The magnetic elements are defined on a single crystal Fe(001) film by electron beam lithography followed by a ion beam etching process. The obtained Fe squares present smooth surfaces and homogeneous sizes over areas as large as 500 μm x 500 μm as analyzed by scanning electron and atomic force microscopies. The lateral size of the squares have been varied in the range 1–10 μm in order to analyze the size dependence. The magnetic properties of the single crystalline squares have been studied by magnetooptical Kerr effect. The results reveal an important change in the hysteresis loops as the square dimensions are reduced below a threshold of 3 μm.

Magneto-optic (MO) studies are performed on regular arrays of Fe(100) micrometric squares, where the elements are patterned with different sizes (2.5–10 μm) and separations (0.2–0.6 μm). When a laser beam is focused inside the patterned structure a Bragg diffraction pattern is produced allowing MO studies on both reflected and diffracted spots. The magnetic anisotropy has been analyzed by in-plane MO hysteresis loops finding that, for square sizes below 2.5 μm, it is not consistent with the Fe crystalline cubic anisotropy, presenting a uniaxial-like behavior. The magnitude of the corresponding anisotropy constants has been determined by analyzing the array response (on reflected and diffracted spots) to a rotational magnetic field in a magneto-optical torque setup. For square sizes of 10 μm the anisotropy induced by patterning is negligible whereas for the small squares (2.5 μm) the uniaxial magnetic constant has been found to be roughly 0.2 times the Fe cubic anisotropy constant., This work was supported by the Spanish CICYT under Contract Nos. MAT99-0724, MAT99-1063-C04-03, and MAT98-0974, and Comunidad de Madrid under Contract No. 07N/0056/1999.

Proceedings of the International Conference on Magnetism (ICM 2000), Arrays of single crystalline Fe (0 0 1) squares separated by submicrometric distances have been fabricated by electron beam lithography and ion beam etching to study the influence of size reduction on the magnetic anisotropy properties. This magnetic behaviour has been analysed by in-plane magneto-optical hysteresis loops. For large square sizes, the angular dependence of the remanence is consistent with the Fe cubic magnetic anisotropy. On the other hand, a dramatic change is found for square sizes smaller than 3 μm, where an uniaxial magnetic behaviour is observed., This work was supported by Spanish CICYT and Comunidad de Madrid under contracts MAT99-0724 and CAM-07N/0056/1999.

The biaxial van der Waals semiconductor α‐phase molybdenum trioxide (α‐MoO3) has recently received significant attention due to its ability to support highly anisotropic phonon polaritons (PhPs)—infrared (IR) light coupled to lattice vibrations—offering an unprecedented platform for controlling the flow of energy at the nanoscale. However, to fully exploit the extraordinary IR response of this material, an accurate dielectric function is required. Here, the accurate IR dielectric function of α‐MoO3 is reported by modeling far‐field polarized IR reflectance spectra acquired on a single thick flake of this material. Unique to this work, the far‐field model is refined by contrasting the experimental dispersion and damping of PhPs, revealed by polariton interferometry using scattering‐type scanning near‐field optical microscopy (s‐SNOM) on thin flakes of α‐MoO3, with analytical and transfer‐matrix calculations, as well as full‐wave simulations. Through these correlative efforts, exceptional quantitative agreement is attained to both far‐ and near‐field properties for multiple flakes, thus providing strong verification of the accuracy of this model, while offering a novel approach to extracting dielectric functions of nanomaterials. In addition, by employing density functional theory (DFT), insights into the various vibrational states dictating the dielectric function model and the intriguing optical properties of α‐MoO3 are provided., G.Á-P. and J.T.-G. acknowledge support through the Severo Ochoa Program from the I of the Principality of Asturias (grants No. PA-20-PF-BP19-053 and PA-18-PF-BP17-126, respectively). I.E. acknowledges support from the Spanish Ministry of Economy and Competitiveness (FIS2016-76617-P). J.M.-S. acknowledges support through a Clarín Marie Curie-COFUND grant from the Government of the Principality of Asturias and the EU (PA18-ACB17-29), and the Ramón y Cajal Program (RYC2018-026196-I) from the Government of Spain. Q. B. acknowledges support from Australian Research Council (ARC, FT150100450, IH150100006 and CE170100039). J.D.C. was supported by the National Science Foundation (U.S.A.) under grant number U0048926. A.Y.N. acknowledges the Spanish Ministry of Science, Innovation and Universities (national project MAT2017-88358-C3-3-R) and Basque Government (grant No. IT1164-19). P.A-G. acknowledges support from the European Research Council under Starting Grant 715496, 2DNANOPTICA.