Real-space observation of ultraconfined in-plane anisotropic acoustic terahertz plasmon polaritons.

Thin layers of in-plane anisotropic materials can support ultraconfined polaritons, whose wavelengths depend on the propagation direction. Such polaritons hold potential for the exploration of fundamental material properties and the development of novel nanophotonic devices. However, the real-space observation of ultraconfined in-plane anisotropic plasmon polaritons (PPs)-which exist in much broader spectral ranges than phonon polaritons-has been elusive. Here we apply terahertz nanoscopy to image in-plane anisotropic low-energy PPs in monoclinic Ag2Te platelets. The hybridization of the PPs with their mirror image-by placing the platelets above a Au layer-increases the direction-dependent relative polariton propagation length and the directional polariton confinement. This allows for verifying a linear dispersion and elliptical isofrequency contour in momentum space, revealing in-plane anisotropic acoustic terahertz PPs. Our work shows high-symmetry (elliptical) polaritons on low-symmetry (monoclinic) crystals and demonstrates the use of terahertz PPs for local measurements of anisotropic charge carrier masses and damping.

Hyperspectral Nanoimaging of van der Waals Polaritonic Crystals.

Phonon polaritons (PhPs) in van der Waals (vdW) crystal slabs enable nanoscale infrared light manipulation. Specifically, periodically structured vdW slabs behave as polaritonic crystals (vdW-PCs), where the polaritons form Bloch modes. Because the polariton wavelengths are smaller than that of light, conventional far-field spectroscopy does not allow for a complete characterization of vdW-PCs or for revealing their band structure. Here, we perform hyperspectral infrared nanoimaging and analysis of PhPs in a vdW-PC slab made of h-BN. We demonstrate that infrared spectra recorded at individual spatial positions within the unit cell of the vdW-PC can be associated with its band structure and local density of photonic states (LDOS). We thus introduce hyperspectral infrared nanoimaging as a tool for the comprehensive analysis of polaritonic crystals, which could find applications in the reconstruction of complex polaritonic dispersion surfaces in momentum-frequency space or for exploring exotic electromagnetic modes in topological photonic structures.

Defining hidradenitis suppurativa phenotypes based on the elementary lesion pattern: results of a prospective study.

BACKGROUND: It has been proposed that two main phenotypes of hidradenitis suppurativa (HS) exist. This proposal is based upon different elementary structures detected in the skin, namely follicular subtypes and inflammatory subtypes. Having an accurate definition of these two variants could help us to better identify patients who may require an early intervention with currently approved targeted immunomodulatory therapies. OBJECTIVE: To define and distinguish between the epidemiological, clinical and analytic characteristics of these two HS phenotypes. METHODS: An observational, descriptive, non-randomized and prospective study was conducted. Patients diagnosed with HS between May 2012 and April 2017 by a specialized unit were included. Ultrasound evaluation was performed in all cases. RESULTS: About 197 patients were included, 100 women and 97 men, aged between 25 and 47 years. The mean age of onset was significantly different between phenotypes, ranging between 26.69 ± 9.05 in the inflammatory subtype and 17.62 ± 6.42 in the follicular subtype. Follicular subtype patients exhibited a significantly higher number of nodules combined with the presence of multiple commedons (5.65 ± 3.38 versus 0.89 ± 2.72). This contrasted with the higher count of abscesses and fistulas detected in the inflammatory subtype (respectively, 4 ± 2.74 and 3.11 ± 2.56 versus 0.56 ± 1.02 and 0.26 ± 0.56). IgA levels were significantly higher in the inflammatory subtype (497.71 ± 262.26 versus 232.38 ± 84.06). Mean IHS4 score evaluation was higher in the inflammatory subtype (21.04 ± 11.9) compared with the follicular phenotype (7.54 ± 4.66). The inflammatory subtype was found to be an independent risk factor for disease aggressiveness in the multivariate analysis (OR 0.034 [95% CI 0.015-0.072]). LIMITATIONS: Small sample size. CONCLUSION: Preliminary data suggest the existence of an inflammatory HS phenotype that is associated with higher aggressiveness and major risk of progression during natural history of the disease.

Launching of hyperbolic phonon-polaritons in h-BN slabs by resonant metal plasmonic antennas.

Launching and manipulation of polaritons in van der Waals materials offers novel opportunities for field-enhanced molecular spectroscopy and photodetection, among other applications. Particularly, the highly confined hyperbolic phonon polaritons (HPhPs) in h-BN slabs attract growing interest for their capability of guiding light at the nanoscale. An efficient coupling between free space photons and HPhPs is, however, hampered by their large momentum mismatch. Here, we show -by far-field infrared spectroscopy, infrared nanoimaging and numerical simulations- that resonant metallic antennas can efficiently launch HPhPs in thin h-BN slabs. Despite the strong hybridization of HPhPs in the h-BN slab and Fabry-Pérot plasmonic resonances in the metal antenna, the efficiency of launching propagating HPhPs in h-BN by resonant antennas exceeds significantly that of the non-resonant ones. Our results provide fundamental insights into the launching of HPhPs in thin polar slabs by resonant plasmonic antennas, which will be crucial for phonon-polariton based nanophotonic devices.

Tuning the charge flow between Marcus regimes in an organic thin-film device.

Marcus's theory of electron transfer, initially formulated six decades ago for redox reactions in solution, is now of great importance for very diverse scientific communities. The molecular scale tunability of electronic properties renders organic semiconductor materials in principle an ideal platform to test this theory. However, the demonstration of charge transfer in different Marcus regions requires a precise control over the driving force acting on the charge carriers. Here, we make use of a three-terminal hot-electron molecular transistor, which lets us access unconventional transport regimes. Thanks to the control of the injection energy of hot carriers in the molecular thin film we induce an effective negative differential resistance state that is a direct consequence of the Marcus Inverted Region.

Deeply subwavelength phonon-polaritonic crystal made of a van der Waals material.

Photonic crystals (PCs) are periodically patterned dielectrics providing opportunities to shape and slow down the light for processing of optical signals, lasing and spontaneous emission control. Unit cells of conventional PCs are comparable to the wavelength of light and are not suitable for subwavelength scale applications. We engineer a nanoscale hole array in a van der Waals material (h-BN) supporting ultra-confined phonon polaritons (PhPs)-atomic lattice vibrations coupled to electromagnetic fields. Such a hole array represents a polaritonic crystal for mid-infrared frequencies having a unit cell volume of [Formula: see text] (with λ0 being the free-space wavelength), where PhPs form ultra-confined Bloch modes with a remarkably flat dispersion band. The latter leads to both angle- and polarization-independent sharp Bragg resonances, as verified by far-field spectroscopy and near-field optical microscopy. Our findings could lead to novel miniaturized angle- and polarization-independent infrared narrow-band couplers, absorbers and thermal emitters based on van der Waals materials and other thin polar materials.

Mohs micrographic surgery in the elderly: comparison of tumours, surgery and first-year follow-up in patients younger and older than 80 years old in REGESMOHS.

BACKGROUND: The elderly population is increasing and more patients in this group undergo Mohs micrographic surgery (MMS). The few publications investigating MMS in elderly people conclude that it is a safe procedure; however, these are single-centre studies without a comparison group. OBJECTIVE: To compare the characteristics of patients, tumours, MMS and 1-year follow-up in patients younger than 80 years, with patients older than 80 years at the time of surgery. METHODS: Data was analysed from REGESMOHS, a prospective cohort study of patients treated with MMS. The participating centres were 19 Spanish hospitals where at least one MMS is performed per week. Data on characteristics of the patient, tumour and surgery were recorded. Follow-up data were collected from two visits; the first within 1 month postsurgery and the second within the first year. RESULTS: From July 2013 to October 2016, 2575 patients that underwent MMS were included in the registry. Of them, 1942 (75.4%) were aged <80 years and 633 (24.6%) were ≥80 years old. In the elderly, the tumour size was significantly higher with a higher proportion of squamous cell carcinoma. Regarding surgery, elderly more commonly had tumours with deeper invasion and required a higher number of Mohs surgery stages, leaving larger defects and requiring more time in the operating room. Despite this, the incidence of postoperative complications was the same in both groups (7%) and there were no significant differences in proportion of relapses in the first-year follow-up. CONCLUSION: The risk of short-term complications and relapses were similar in elderly and younger groups. MMS is a safe procedure in the elderly.

Nanoimaging of resonating hyperbolic polaritons in linear boron nitride antennas.

Polaritons in layered materials-including van der Waals materials-exhibit hyperbolic dispersion and strong field confinement, which makes them highly attractive for applications including optical nanofocusing, sensing and control of spontaneous emission. Here we report a near-field study of polaritonic Fabry-Perot resonances in linear antennas made of a hyperbolic material. Specifically, we study hyperbolic phonon-polaritons in rectangular waveguide antennas made of hexagonal boron nitride (h-BN, a prototypical van der Waals crystal). Infrared nanospectroscopy and nanoimaging experiments reveal sharp resonances with large quality factors around 100, exhibiting atypical modal near-field patterns that have no analogue in conventional linear antennas. By performing a detailed mode analysis, we can assign the antenna resonances to a single waveguide mode originating from the hybridization of hyperbolic surface phonon-polaritons (Dyakonov polaritons) that propagate along the edges of the h-BN waveguide. Our work establishes the basis for the understanding and design of linear waveguides, resonators, sensors and metasurface elements based on hyperbolic materials and metamaterials.

Optical Nanoimaging of Hyperbolic Surface Polaritons at the Edges of van der Waals Materials.

Hyperbolic polaritons in van der Waals (vdW) materials recently attract a lot of attention, owing to their strong electromagnetic field confinement, ultraslow group velocities, and long lifetimes. Typically, volume-confined hyperbolic polaritons (HPs) are studied. Here we show the first near-field optical images of hyperbolic surface polaritons (HSPs), which are confined and guided at the edges of thin flakes of a vdW material. To that end, we applied scattering-type scanning near-field optical microscopy (s-SNOM) for launching and real-space nanoimaging of hyperbolic surface phonon polariton modes on a hexagonal boron nitride (h-BN) flake. Our imaging data reveal that the fundamental HSP mode exhibits a stronger field confinement (shorter wavelength), smaller group velocities, and nearly identical lifetimes, as compared to the fundamental HP mode of the same h-BN flake. Our experimental data, corroborated by theory, establish a solid basis for future studies and applications of HPs and HSPs in vdW materials.

Spin doping using transition metal phthalocyanine molecules.

Molecular spins have become key enablers for exploring magnetic interactions, quantum information processes and many-body effects in metals. Metal-organic molecules, in particular, let the spin state of the core metal ion to be modified according to its organic environment, allowing localized magnetic moments to emerge as functional entities with radically different properties from its simple atomic counterparts. Here, using and preserving the integrity of transition metal phthalocyanine high-spin complexes, we demonstrate the magnetic doping of gold thin films, effectively creating a new ground state. We demonstrate it by electrical transport measurements that are sensitive to the scattering of itinerant electrons with magnetic impurities, such as Kondo effect and weak antilocalization. Our work expands in a simple and powerful way the classes of materials that can be used as magnetic dopants, opening a new channel to couple the wide range of molecular properties with spin phenomena at a functional scale.

Determination of energy level alignment at metal/molecule interfaces by in-device electrical spectroscopy.

The energetics of metal/molecular semiconductor interfaces plays a fundamental role in organic electronics, determining the performance of very diverse devices. So far, information about the energy level alignment has been most commonly gained by spectroscopy techniques that typically require experimental conditions far from the real device operation. Here we demonstrate that a simple three-terminal device allows the acquisition of spectroscopic information about the metal/molecule energy alignment in real operative condition. As a proof of principle, we employ the proposed device to measure the energy barrier height between different clean metals and C60 molecules and we recover typical results from photoemission spectroscopy. The device is designed to inject a hot electron current directly into the molecular level devoted to charge transport, disentangling the contributions of both the interface and the bulk to the device total resistance, with important implications for spintronics and low-temperature physics.

Controlling graphene plasmons with resonant metal antennas and spatial conductivity patterns.

Graphene plasmons promise unique possibilities for controlling light in nanoscale devices and for merging optics with electronics. We developed a versatile platform technology based on resonant optical antennas and conductivity patterns for launching and control of propagating graphene plasmons, an essential step for the development of graphene plasmonic circuits. We launched and focused infrared graphene plasmons with geometrically tailored antennas and observed how they refracted when passing through a two-dimensional conductivity pattern, here a prism-shaped bilayer. To that end, we directly mapped the graphene plasmon wavefronts by means of an imaging method that will be useful in testing future design concepts for nanoscale graphene plasmonic circuits and devices.

Giant and reversible extrinsic magnetocaloric effects in La0.7Ca0.3MnO3 films due to strain.

Large thermal changes driven by a magnetic field have been proposed for environmentally friendly energy-efficient refrigeration, but only a few materials that suffer hysteresis show these giant magnetocaloric effects. Here we create giant and reversible extrinsic magnetocaloric effects in epitaxial films of the ferromagnetic manganite La(0.7)Ca(0.3)MnO(3) using strain-mediated feedback from BaTiO(3) substrates near a first-order structural phase transition. Our findings should inspire the discovery of giant magnetocaloric effects in a wide range of magnetic materials, and the parallel development of nanostructured bulk samples for practical applications.

Experimental verification of the spectral shift between near- and far-field peak intensities of plasmonic infrared nanoantennas.

Theory predicts a distinct spectral shift between the near- and far-field optical response of plasmonic antennas. Here we combine near-field optical microscopy and far-field spectroscopy of individual infrared-resonant nanoantennas to verify experimentally this spectral shift. Numerical calculations corroborate our experimental results. We furthermore discuss the implications of this effect in surface-enhanced infrared spectroscopy.

Resolving the electromagnetic mechanism of surface-enhanced light scattering at single hot spots.

Light scattering at nanoparticles and molecules can be dramatically enhanced in the 'hot spots' of optical antennas, where the incident light is highly concentrated. Although this effect is widely applied in surface-enhanced optical sensing, spectroscopy and microscopy, the underlying electromagnetic mechanism of the signal enhancement is challenging to trace experimentally. Here we study elastically scattered light from an individual object located in the well-defined hot spot of single antennas, as a new approach to resolve the role of the antenna in the scattering process. We provide experimental evidence that the intensity elastically scattered off the object scales with the fourth power of the local field enhancement provided by the antenna, and that the underlying electromagnetic mechanism is identical to the one commonly accepted in surface-enhanced Raman scattering. We also measure the phase shift of the scattered light, which provides a novel and unambiguous fingerprint of surface-enhanced light scattering.

A randomized comparative study of tolerance and satisfaction in the treatment of actinic keratosis of the face and scalp between 5% imiquimod cream and photodynamic therapy with methyl aminolaevulinate.

BACKGROUND: Photodynamic therapy (PDT) and imiquimod are two excellent treatments for actinic keratosis but are often not well tolerated by patients. OBJECTIVES: To ascertain which treatment is better tolerated and which produces greater patient satisfaction. A secondary objective was to determine the factors related to the patient's tolerance to each treatment. METHODS: Patients with at least five actinic keratosis lesions on the face and scalp were selected. The patients were randomized to receive treatment with PDT with methyl aminolaevulinate or treatment with imiquimod. Tolerance, satisfaction and predisposition to repeat the treatment were evaluated. RESULTS: Most patients exhibited good or acceptable tolerance to both PDT and imiquimod treatment. There was a higher percentage of patients treated with PDT (93%) who were very satisfied compared with imiquimod (62%) (P=0·004). Most patients treated with either one of the two options would repeat the same treatment. No significant relationship was found between age, sex, working time exposed to the sun, phototype and hair colour and the tolerance to both treatments. CONCLUSIONS: Both PDT and imiquimod are treatments that are generally well tolerated. While both treatments provide a high level of satisfaction, PDT appears to be slightly superior in this regard.

Liquen plano anular y atrófico / Annular atrophic lichen planus

El liquen plano anular y atrófico es una rara variante de liquen plano de la que solamente hay descritos 6 casos. Clínicamente se caracteriza porplacas pruriginosas de morfología anular con el centro atrófico. Histológicamente muestra imágenes típicas de liquen plano en la perifería de lalesión y una epidermis adelgazada en el centro de la lesión. Las fibras elásticas de la dermis papilar de ambas localizaciones están destruidas. Describimosun nuevo caso de liquen plano anular y atrófico en el que las lesiones se distribuian de forma lineal (AU)

Annular lichen planus is a rare variant of lichen planus that is clinically characterized by itching plaques of annular morphology with central atrophy. Histopathologic findings showed features of lichen planus in the active border whereas the centre showed epidermal atrophy. The elasticfibers had been destroyed in the papillary dermis. Six cases of this entity have been previously reported. We describe a new case of annularatrophic lichen planus (AU)

Smoking, sun exposure, number of nevi and previous neoplasias are risk factors for melanoma in older patients (60 years and over).

BACKGROUND: Malignant melanoma risk factors have been studied in different geographical area populations. However, no study has focused on risk factors which are more frequently associated to the over 60's age group. METHODS: A case-control study was performed that included 160 patients age > or = 60 years diagnosed of cutaneous melanoma and 318 controls matched for age and sex. Both groups were assessed, by personal interview and physical examination, for different phenotype characteristics (hair and eye color, phototype), the presence of other cutaneous lesions (solar lentigines, actinic keratoses and nevi), degree and type of solar exposure and personal and family past history of cutaneous or non-cutaneous cancer. Differences were evaluated by contingency tables and univariate and multivariate logistic regression. RESULTS: Of 17 factors, those risk factors with a strong effect on the development of melanoma in the elderly were: fair eyes, severe sunburns, years of occupational sun exposure, smoking, > 50 melanocytic nevi and personal history of NMSC and other non-cutaneous neoplasias. CONCLUSIONS: Tobacco smoking is an independent risk factor for cutaneous melanoma in the elderly. Intense (both acute and chronic) sun exposure and constitutional features, such as tumor susceptibility (NMSC, non-cutaneous neoplasias, and multiple nevi) are also associated with melanoma risk. All these factors should help to better design educational campaigns in older people.

Comparative study between cold air analgesia and supraorbital and supratrochlear nerve block for the management of pain during photodynamic therapy for actinic keratoses of the frontotemporal zone.

BACKGROUND: Photodynamic therapy (PDT) is an effective treatment for actinic keratoses, Bowen's disease and basal cell carcinoma. The main drawback of PDT is pain during application. OBJECTIVES: To compare the efficacy of supratrochlear and supraorbital nerve block with cold air analgesia to control the pain experienced during PDT. METHODS: A controlled open clinical trial was conducted in 34 patients having multiple actinic keratoses in the frontal region treated with PDT. On one side of the frontal region the supratrochlear and supraorbital nerves were blocked, while on the other side cold air was used as the method of analgesia. Pain was recorded on a visual analogue scale after treatment. RESULTS: Thirty-one of 34 patients reported less pain in the zone treated with nerve block. This difference was statistically significant. CONCLUSIONS: Nerve block is superior to cold air and is an easy, safe, effective means of controlling the pain associated with PDT.

[Clinical and epidemiologic profile of melanoma patients according to sun exposure of the tumor site]. / Perfil clínico y epidemiológico de los pacientes con melanoma cutáneo según el grado de exposición solar de la localización del melanoma.

INTRODUCTION: Melanomas arising in areas with comparable levels of sun exposure have been shown to have similar genetic profiles. The aim of this study was to characterize the clinical features of melanoma patients according to the pattern of sun exposure: chronic, intermittent, or none. MATERIAL AND METHODS: From our melanoma database, we selected 789 consecutive patients with melanoma diagnosed in our center since January 2000. Epidemiologic data, phenotype, and personal and family history of cancer were retrieved. The observed frequency of each variable was compared. RESULTS: Most melanoma patients presented tumors on areas exposed intermittently to sunlight. In addition, these patients presented higher numbers of common and atypical melanocytic nevi and the melanoma very frequently arose in a pre-existing nevus. The second largest group was formed by patients with tumors on areas chronically exposed to sun and that had all the clinical lesions (solar lentigines and actinic keratoses) and epidemiological characteristics typical of these areas. Finally, patients with melanomas on areas not exposed to sun were older, as occurred in the group with chronic exposure, and the diagnosis was made at more advanced stages of the disease. CONCLUSIONS: There are many patients who did not fit these patterns of melanoma development. Clinical and biological characterization is therefore necessary to determine alternative pathways of development in order to establish specific preventive measures.