Effects of lycopene from guava (Psidium guajava L.) derived products on breast cancer cells.

Polyphenols, condensed tannins, total flavonoids, total carotenoids, lycopene and ascorbic acid were determined besides verifying antioxidant capacity of peel, pulp and desserts (with and without sugar) of red guava (Psidium guajava L.) as well as the effects of lycopene on cytotoxicity, cell cycle and apoptosis on breast cancer cell line MCF-7. Guava peel contains 90% of the total ascorbic acid and heat treatment does not modify bioactive compounds content and antioxidant capacity. Sugar addition decreased guava pulp functional capacity. After heat treatment, lycopene content was stable, but sugar addition reduced its concentration by 57%. Lycopene (10 µM) extracted from guava and standard presented the same cytotoxic effect on MCF-7 cells. Lycopene influenced over G2-M transition check-point of the cell cycle and increased apoptotic cells percentages compared to untreated cells. The consumption of in natura guava, especially with peel can be considered an important source of bioactive compounds.

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.

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.

Factors associated with uninvestigated dyspepsia in students at 4 Latin American schools of medicine: A multicenter study. / Factores asociados a dispepsia no investigada en estudiantes de 4 facultades de medicina de Latinoamérica: estudio multicéntrico.

INTRODUCTION AND AIMS: Dyspepsia is a multifactorial disease that can involve alcohol, tobacco, or nonsteroidal anti-inflammatory drug use, as well as lifestyle, diet, socioeconomic elements, or psychologic factors. The aim of the present article was to establish the frequency of uninvestigated dyspepsia and determine its associated factors in students at 4 Latin American schools of medicine. MATERIALS AND METHODS: A cross-sectional, analytic study was conducted, in which a survey made up of closed-ended questions was applied at just one point in time. The association between the variables was then analyzed. A new questionnaire for the diagnosis of dyspepsia was one of the tests utilized to diagnose uninvestigated dyspepsia. Generalized linear models were used for the bivariate and multivariate analyses, employing the Poisson model with the log link function, obtaining crude prevalence ratios, adjusted prevalence ratios, and their 95% confidence intervals. RESULTS: Of the 1,241 individuals surveyed, 54% (841) were females and the median age was 21 years (range: 19-23 years). Prevalence of uninvestigated dyspepsia was 46%. The factors that had a direct association with dyspepsia were: depression, difficulty sleeping, and coffee consumption. On the contrary, eating regularly in a boarding house and the male sex had an inverse association. CONCLUSIONS: Uninvestigated dyspepsia frequency was high in students at 4 Latin American schools. Depression, difficulty sleeping, and steady coffee drinking were factors directly associated with dyspepsia, whereas male sex and eating out at regular hours were factors with a reverse association. Therefore, we recommend that universities implement early detection programs for this highly preventable pathology.

The impact of cardiovascular co-morbidities and duration of diabetes on the association between microvascular function and glycaemic control.

BACKGROUND: Good glycaemic control in type 2 diabetes (T2DM) protects the microcirculation. Current guidelines suggest glycaemic targets be relaxed in advanced diabetes. We explored whether disease duration or pre-existing macrovascular complications attenuated the association between hyperglycaemia and microvascular function. METHODS: 743 participants with T2DM (n = 222), cardiovascular disease (CVD = 183), both (n = 177) or neither (controls = 161) from two centres in the UK, underwent standard clinical measures and endothelial dependent (ACh) and independent (SNP) microvascular function assessment using laser Doppler imaging. RESULTS: People with T2DM and CVD had attenuated ACh and SNP responses compared to controls. This was additive in those with both (ANOVA p < 0.001). In regression models, cardiovascular risk factors accounted for attenuated ACh and SNP responses in CVD, whereas HbA1c accounted for the effects of T2DM. HbA1c was associated with ACh and SNP response after adjustment for cardiovascular risk factors (adjusted standardised beta (ß) -0.096, p = <0.008 and -0.135, p < 0.001, respectively). Pre-existing CVD did not modify this association (ß -0.099; p = 0.006 and -0.138; p < 0.001, respectively). Duration of diabetes accounted for the association between HbA1c and ACh (ß -0.043; p = 0.3), but not between HbA1c and SNP (ß -0.105; p = 0.02). CONCLUSIONS: In those with T2DM and CVD, good glycaemic control is still associated with better microvascular function, whereas in those with prolonged disease this association is lost. This suggests duration of diabetes may be a better surrogate for "advanced disease" than concomitant CVD, although this requires prospective validation.

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.

Measures of atherosclerotic burden are associated with clinically manifest cardiovascular disease in type 2 diabetes: a European cross-sectional study.

BACKGROUND: There is a need to develop and validate surrogate markers of cardiovascular disease (CVD) in subjects with diabetes. The macrovascular changes associated with diabetes include aggravated atherosclerosis, increased arterial stiffness and endothelial dysfunction. The aim of this study was to determine which of these factors is most strongly associated with clinically manifest cardiovascular events. METHODS: Vascular changes were measured in a cohort of 458 subjects with type 2 diabetes (T2D) and CVD (myocardial infarction, stroke or lower extremity arterial disease), 527 subjects with T2D but without clinically manifest CVD and 515 subjects without T2D and with or without CVD. RESULTS: Carotid intima-media thickness (IMT) and ankle-brachial pressure index were independently associated with the presence of CVD in subjects with T2D, whereas pulse wave velocity and endothelial function provided limited independent additive information. Measurement of IMT in the carotid bulb provided better discrimination of the presence of CVD in subjects with T2D than measurement of IMT in the common carotid artery. The factors most significantly associated with increased carotid IMT in T2D were age, disease duration, systolic blood pressure, impaired renal function and increased arterial stiffness, whereas there were no or weak independent associations with metabolic factors and endothelial dysfunction. CONCLUSIONS: Measures of atherosclerotic burden are associated with clinically manifest CVD in subjects with T2D. In addition, vascular changes that are not directly related to known metabolic risk factors are important in the development of both atherosclerosis and CVD in T2D. A better understanding of the mechanisms involved is crucial for enabling better identification of CVD risk in T2D.

Embedded purification for electron beam induced Pt deposition using MeCpPtMe3.

Two different room-temperature processes for the electron beam induced deposition of high purity platinum (Pt), using the standard MeCpPtMe3 precursor and oxygen for purification, have been investigated. The first process is a sequential method, which uses two independent gas injector systems (GIS) in order to perform a standard Pt deposition, followed by an e-beam post-irradiation under oxygen flux. The second process is a parallel, single-step process that includes a simultaneous flow of both precursor and oxygen, using an add-on device that can be mounted on the standard GIS needle. Both processes are effective in producing high purity Pt depositions close to 100 at%. The first method requires a high current and irradiation dose in the clean-up phase, and provides Pt structures with small voids, a maximum thickness of around 100 nm and resistivity of 88 ± 10 µΩ cm. The second method requires a high oxygen/precursor flux ratio and produces void-free structures with resistivity of 60 ± 5 µΩ cm, only six times the bulk value for Pt. The second method is easier to use and produces a void-free deposition of high purity Pt.

On-line monitoring of chemical reactions by using bench-top nuclear magnetic resonance spectroscopy.

Real-time nuclear magnetic resonance (NMR) spectroscopy measurements carried out with a bench-top system installed next to the reactor inside the fume hood of the chemistry laboratory are presented. To test the system for on-line monitoring, a transfer hydrogenation reaction was studied by continuously pumping the reaction mixture from the reactor to the magnet and back in a closed loop. In addition to improving the time resolution provided by standard sampling methods, the use of such a flow setup eliminates the need for sample preparation. Owing to the progress in terms of field homogeneity and sensitivity now available with compact NMR spectrometers, small molecules dissolved at concentrations on the order of 1 mmol L(-1) can be characterized in single-scan measurements with 1 Hz resolution. Owing to the reduced field strength of compact low-field systems compared to that of conventional high-field magnets, the overlap in the spectrum of different NMR signals is a typical situation. The data processing required to obtain concentrations in the presence of signal overlap are discussed in detail, methods such as plain integration and line-fitting approaches are compared, and the accuracy of each method is determined. The kinetic rates measured for different catalytic concentrations show good agreement with those obtained with gas chromatography as a reference analytical method. Finally, as the measurements are performed under continuous flow conditions, the experimental setup and the flow parameters are optimized to maximize time resolution and signal-to-noise ratio.

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.

Highly stable and finely tuned magnetic fields generated by permanent magnet assemblies.

Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Such stand-alone magnets are very attractive for many scientific and engineering areas, but they suffer from poor temporal field stability, which arises from the strong sensitivity of the magnetic materials and mechanical support to temperature variation. In this work, we describe a highly efficient method useful to cancel the temperature coefficient of permanent magnet assemblies in a passive and accurate way. It is based on the combination of at least two units made of magnetic materials with different temperature coefficients arranged in such a way that the ratio of the fields generated by each unit matches the ratio of their effective temperature coefficients defined by both the magnetic and mechanical contributions. Although typically available magnetic materials have negative temperature coefficients, the cancellation is achieved by aligning the fields generated by each unit in the opposite direction. We demonstrate the performance of this approach by stabilizing the field generated by a dipolar Halbach magnet, recently proposed to achieve high field homogeneity. Both the field drift and the homogeneity are monitored via nuclear magnetic resonance spectroscopy experiments. The results demonstrate the compatibility of the thermal compensation approach with existing strategies useful to fine-tune the spatial dependence of the field generated by permanent magnet arrays.

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.