Peak Suppression Research Articles

Anisotropic Kondo screening induced by spin-orbit coupling in quantum wires

Using the numerical renormalization group (NRG) method we study a magnetic impurity coupled to a quantum wire with Rashba and Dresselhaus spin-orbit coupling (SOC) in an external magnetic field. We consider the low-filling regime with the Fermi energy close to the bottom of the band and report the results for local static and dynamic properties in the Kondo regime. In the absence of the field, local impurity properties remain isotropic in spin space despite the SOC-induced magnetic anisotropy of the conduction band. In the presence of the field, clear fingerprints of anisotropy are revealed through the strong field-direction dependence of the impurity spin polarization and spectra, in particular of the Kondo peak height. The detailed behavior depends on the relative magnitudes of the impurity and band $g$-factors. For the case of impurity $g$-factor somewhat lower than the band $g$-factor, the maximal Kondo peak suppression is found for field oriented along the effective SOC field axis, while for a field perpendicular to this direction we observe a compensation effect (``revival of the Kondo peak''): the SOC counteracts the Kondo peak splitting effects of the local Zeeman field. We demonstrate that the SOC-induced anisotropy, measurable by tunneling spectroscopy techniques, can help to determine the ratio of Rashba and Dresselhaus SOC strengths in the wire.

Salicylate Method for Ammonia Quantification in Nitrogen Electroreduction Experiments: The Correction of Iron III Interference

The salicylate method is one of the ammonia quantification methods that has been extensively used in literature for quantifying ammonia in the emerging field of nitrogen (electro)fixation. The presence of iron in the sample causes a strong negative interference on the salicylate method. Today, the recommended method to deal with such interferences is the experimental correction method: the iron concentration in the sample is measured using an iron quantification method, and then the corresponding amount of iron is added to the calibration samples. The limitation of this method is that when a batch of samples presents a great iron concentration variability, a different calibration curve has to be obtained for each sample. In this work, the interference of iron III on the salicylate method was experimentally quantified, and a model was proposed to capture the effect of iron III interference on the ammonia quantification result. This model can be used to correct the iron III interferences on ammonia quantification. The great advantage of this correction method is that it only requires three experimental curves in order to correct the iron III interference in any sample provided the iron III concentration is below the total peak suppression concentration.

Effect of hydrogen embrittlement towards thermal and mechanical behavior of NiTi shape memory alloy

NiTi arch wires are susceptible to hydrogen embrittlement upon contact with dental brackets in oral cavity during orthodontic treatment. This study investigated the effect of hydrogen absorption and diffusion over time towards the thermal and mechanical properties of NiTi shape memory wire. The hydrogen absorption process was carried out via electrolytic charging at constant current density for 16 hours in 1.0 weight percent (wt.%) sodium sulphate solution. The hydrogen charged wires were aged at room temperature in air for different durations to allow further inward diffusion of the hydrogen into the specimens. The results show that after hydrogen charging, the latent heat of forward and reverse martensitic phase transformation of the NiTi wire changed from 19.96 to 11.98 J/g, and 19.21 to 13.42 J/g, respectively. Further suppression and disappearance of thermal transformation peaks were observed as the charged specimen aged for 7 days. The transformation stress level on tensile deformation increased by almost 90 MPa after hydrogen charging, and exhibited non-flat stress plateau after further aging.

Synthesis and characterization of Ag@ETS-10 core-shell heterostructured photocatalyst for visible light photocatalysis

Abstract Surface modification of Engelhard titanosilicate (ETS-10) with silver (Ag) was carried out in efforts to promote the photocatalytic activity of ETS-10 towards the degradation of methylene blue (MB) under visible light irradiation. The core-shell heterostructure encapsulates the Ag nanoparticles, which would otherwise dislodge from the surface of ETS-10. The Ag@ETS-10 core-shell heterostructured photocatalyst was prepared by the photodeposition of Ag nanoparticles onto ETS-10 crystals to form the Ag-ETS-10 core, followed by secondary growth of ETS-10 shell using the Ag-ETS-10 as seeds. Ag@ETS-10 showed absorption in the visible light region, as well as a red shift in the UV region, compared to the unmodified ETS-10. The extent of shell growth depended on the seeding level. Increasing the seeding level from 1 wt.% to 50 wt.% resulted in a decreased mode of the particle size distribution of the products, and thus a decreased shell thickness. The Ag@ETS-10 photocatalyst grown using 50 wt.% seeding level (i.e., ∼0.1 μm shell) showed higher photocatalytic activity in the photodegradation of MB under visible light irradiation (k = 0.0159 min-1) than the unmodified ETS-10 sample (k = 0.007 min-1). However, the Ag@ETS-10 photocatalyst grown using 1 wt. % seeding levels (i.e., ∼ 0.8 μm shell) showed lower photocatalytic activity compared to the Ag@ETS-10 photocatalyst grown using 50 wt.% seeding level (i.e., ∼ 0.1 μm shell). This was attributed to the suppression of the plasmon resonance peak when a thicker ETS-10 shell was grown around the Ag-ETS-10 core.

Crosstalk Noise Suppression Between Single and Differential Transmission Lines Using Spoof Surface Plasmon Polaritons

Crosstalk noise suppression is a crux in the high-speed integrated circuit design, which requires weak-coupling between transmission lines (TLs) over a wide band. To overcome the difficulty, this article presents a novel method to suppress the broadband crosstalk noise between a single TL and the differential pair based on spoof surface plasmon polaritons (SPPs). Due to the subwavelength feature of spoof SPP TLs, a natural mode mismatching between the spoof SPP TL and conventional microstrip (MS) brings a broadband suppression of near-field coupling. In order to verify the crosstalk suppression effect, four different kinds of prototypes are discussed and compared. The simulated and measured results in the frequency domain and time domain demonstrate that the proposed scheme achieves more than 83% far-end noise peak suppression than the traditional MS technology by replacing the single MS TL to the spoof SPP TL. Accordingly, the time-domain crosstalk noise is significantly suppressed without any extra costs, demonstrating its potential applications in ultracompact high-speed integrated circuits.

Suppression of individual peaks in two-colour high harmonic generation

This work investigates the suppression of individual harmonics, simultaneously affecting specific even and odd orders in the high-harmonic spectra generated by strongly tailored, two-colour, multi-cycle laser pulses in neon. The resulting spectra are systematically studied as a function of the electric-field shape in a symmetry-broken (ω–2ω) and symmetry-preserved (ω–3ω) configuration. The peak suppression is reproduced by macroscopic strong-field approximation calculations and is found to be unique to symmetry-broken fields (ω–2ω). Additionally, semi-classical calculations further corroborate the observation and reveal their underlying mechanism, where a nontrivial spectral interference between subsequent asymmetric half-cycles is found to be responsible for the suppression.

Temperature dependent fluorescence properties and mid-infrared random lasing emission in Ho3+ and Tm3+ co-doped lead lanthanum zirconate titanate ceramics

In this study, obvious up-conversion emission peaks centred at 553 nm and 696 nm were investigated in transparent Ho3+ and Tm3+ co-doped lead lanthanum zirconate titanate (PLZT) ceramics. Temperature dependent visible up-conversion emission and mid-infrared photoluminescence at approximately 2.0 μm were studied, and obvious luminous color modulation from yellow-green to red was observed. Energy transfer between Ho3+ and Tm3+ ions was studied by analyzing the suppression and enhancement of the emission peaks. Moreover, random lasing emission peaks at 1.95 μm were achieved with a full width at half maximum of 5 nm, which was desirable for developing mid-infrared lasers in ceramics materials.

A laser-ARPES study of LaNiO3 thin films grown by sputter deposition

Thin films of the correlated transition-metal oxide LaNiO3 undergo a metal–insulator transition when their thickness is reduced to a few unit cells. Here, we use angle-resolved photoemission spectroscopy to study the evolution of the electronic structure across this transition in a series of epitaxial LaNiO3 films of thicknesses ranging from 19 u.c. to 2 u.c. grown in situ by RF magnetron sputtering. Our data show a strong reduction in the electronic mean free path as the thickness is reduced below 5 u.c. This prevents the system from becoming electronically two-dimensional, as confirmed by the largely unchanged Fermi surface seen in our experiments. In the insulating state, we observe a strong suppression of the coherent quasiparticle peak, but no clear gap. These features resemble previous observations of the insulating state of NdNiO3.

In Silico, Ex Vivo and In Vivo Studies of Roflumilast as a Potential Antidiarrheal and Antispasmodic agent: Inhibition of the PDE-4 Enzyme and Voltage-gated Ca++ ion Channels.

The aim of the present study was to evaluate the possible gut inhibitory role of the phosphodiesterase (PDE) inhibitor roflumilast. Increasing doses of roflumilast were tested against castor oil-induced diarrhea in mice, whereas the pharmacodynamics of the same effect was determined in isolated rabbit jejunum tissues. For in silico analysis, the identified PDE protein was docked with roflumilast and papaverine using the Autodock vina program from the PyRx virtual screening tool. Roflumilast protected against diarrhea significantly at 0.5 and 1.5 mg/kg doses, with 40% and 80% protection. Ex vivo findings from jejunum tissues show that roflumilast possesses an antispasmodic effect by inhibiting spontaneous contractions in a concentration-dependent manner. Roflumilast reversed carbachol (CCh, 1 µM)-mediated and potassium (K+, 80 mM)-mediated contractile responses with comparable efficacies but different potencies. The observed potency against K+ was significantly higher in comparison to CCh, similar to verapamil. Experiments were extended to further confirm the inhibitory effect on Ca++ channels. Interestingly, roflumilast deflected Ca++ concentration–response curves (CRCs) to the right with suppression of the maximum peak at both tested doses (0.001-0.003 mg/mL), similar to verapamil. The PDE-inhibitory effect was authenticated when pre-incubation of jejunum tissues with roflumilast (0.03-0.1 mg/mL) produced a leftward deflection of isoprenaline-mediated inhibitory CRCs and increased the tissue level of cAMP, similar to papaverine. This idea was further strengthened by molecular docking studies, where roflumilast exhibited a better binding affinity (-9.4 kcal/mol) with the PDE protein than the standard papaverine (-8.3 kcal/mol). In conclusion, inhibition of Ca++ channels and the PDE-4 enzyme explains the pharmacodynamics of the gut inhibitory effect of roflumilast.

Identification of two novel trace impurities in mobile phases prepared with commercial formic acid.

We observed a notable increase in the size of several impurity peaks in a reversed-phase gradient method upon switching suppliers of formic acid. We used LC/HRMS to separate and fragment these impurity compounds and assign probable formulae. The mass spectra were compared with those of compounds found in the literature with the same formulae, and the observed peaks were matched to two amine compounds not previously reported as impurities in LC/MS systems: trihexylamine and N-methyldihexylamine. The identities were confirmed by high-resolution accurate mass and retention time matching against commercially available standards of these compounds. To the best of our knowledge, this is the first time that trihexylamine and N-methyldihexylamine have been reported in such systems. We hypothesize that these are derived from the formic acid manufacturing process and recommend that users monitor purchased formic acid for the presence of impurities.

Matrix-assisted laser desorption/ionization behavior of neat linear and cyclic poly(L-lactide)s and their blends.

RationaleNumerous new tin catalysts that enable the synthesis of cyclic polylactides with broad variation in their molecular mass were recently developed. The abundance of cyclics in matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra is, however, frequently reported to greatly exceed that of linears. Thus, the MALDI ionization behavior of various end‐capped linear poly(L‐lactide)s and one cyclic poly(L‐lactide) was investigated and compared.MethodsNeat compounds and various blends of cyclic and linear species were prepared and studied under identical conditions with regard to sample preparation and instrumental condition, except for the laser power. For this purpose, two different MALDI‐TOF mass spectrometers were applied.ResultsOur results reveal that cyclics indeed show a slightly better ionization in MALDI, although their ionization as a neat compound seems to be less effective than that of linear polylactides. The ionization of most linear polylactides investigated does not depend on the end group structure. However, linear polylactides containing 12‐bromododecyl end groups reveal an unexpected saturation effect that is not caused by fragmentation of the polymer or the end group, or by electronic saturation of the detector digitizer. Furthermore, polylactides with a 2‐bromoethyl end group did not show such a saturation effect.ConclusionsAn overestimation of cyclic species in MALDI‐TOF mass spectra of poly(L‐lactide)s must be considered, but the commonly assumed peak suppression of linear polymers in mixtures of both structures can be excluded.

SCSA based MATLAB pre-processing toolbox for 1H MR spectroscopic water suppression and denoising

Abstract In vivo 1H Magnetic Resonance Spectroscopy (MRS) is a useful tool in assessing neurological and metabolic disease, and to improve tumor treatment. Different pre-processing pipelines have been developed to obtain optimal results from the acquired data with sophisticated data fitting, peak suppression, and denoising protocols. We introduce a Semi-Classical Signal Analysis (SCSA) based Spectroscopy pre-processing toolbox for water suppression and data denoising, which allows researchers to perform water suppression using SCSA with phase correction and apodization filters and denoising of MRS data, and data fitting has been included as an additional feature, but it is not the main aim of the work. The fitting module can be passed on to other software. The toolbox is easy to install and to use: 1) import water unsuppressed MRS data acquired in Siemens, Philips and .mat file format and allow visualization of spectroscopy data, 2) allow pre-processing of single voxel and multi-voxel spectra, 3) perform water suppression and denoising using SCSA, 4) incorporate iterative nonlinear least squares fitting as an extra feature. This article provides information about how the above features have been included, along with details of the graphical user interface using these features in MATLAB. The code can be downloaded from https://github.com/EMANG-KAUST/GUI_spectroscopy .

Study of a Combined Surge Protective Device for a Relay Protection Circuit in a UHV Converter Station

This article focuses on the problem that the voltage recovery time of relay protection circuits in converter stations is too long under lightning surges. A surge protective device (SPD) in a relay protection circuit in an ultrahigh-voltage (UHV) converter station is investigated. Based on the action characteristics of a gas discharge tube (GDT) and metal oxide varistor (MOV) under a 1.2/50 μs lightning surge, the equivalent circuit model of a series-combined SPD is established. In the equivalent circuit model, this study considers the breakdown voltage, nonlinear impedance, parasitic capacitance, stray inductance and other parameters of GDTs and MOVs. Simulation analysis shows that a series-combined SPD can significantly increase the residual voltage and shorten the voltage recovery time of the protected system. To verify the simulation results, a test platform based on a low-voltage DC voltage divider was built for the lightning surge test. The test results are consistent with the simulation results, verifying that a series-combined SPD can meet the dual surge protection requirements of peak suppression and fast voltage recovery.

A generalized approach for modeling and analysis of fiber Bragg grating based cavity structures

Z domain model of a single cavity structure as well as double cavity structure composed of fiber Bragg gratings (FBG) is developed and their performance analysis is presented in this article. A generalized approach for determination of transmittance in Z domain of FBG based cavities is introduced. Spectral characteristics in terms of peak transmittance, side lobes formation and bandwidth are determined for a single cavity structure of length 4.5 mm. The results are compared with previously published measured data of the same configuration and are found to be in very close agreement. An ultrashort single cavity structure is proposed and its transmission response is carried out in the article. The spectral characteristics of both symmetrical and asymmetrical double cavity structure of same length as that of single cavity FBG are determined. Performance parameters like FWHM, suppression of peaks, wavelength spacing are analyzed for the different configurations in Z domain.

Dynamics of the one-dimensional isotropic Heisenberg model with Dzyaloshinskii–Moryia interaction in a random transverse field

The dynamics of the one-dimensional spin-1∕2 isotropic Heisenberg model with Dzyaloshinskii–Moriya (DM) interaction in the presence of a random magnetic field perpendicular to the DM axis (a transverse field) is investigated by using the method of recurrence relations. A bimodal probability distribution function for this transverse field is considered. The first four recurrants, which are used to obtain the short-time expansion for the time-dependent correlation functions, are exactly obtained as function of the probabilities and of the transverse field. A recent proposed extrapolation procedure for the higher-order recurrants is used in order to extend the results to longer times. In the limit of infinite temperature the relaxation and the spectral density functions are computed for several values of the external field and different probability distributions. Depending on the probabilities and on the external fields one has stronger and faster oscillations in the relaxation functions, and a suppression of the central peak in the spectral density.

Pozelimab, a Human Antibody Against Complement Factor C5, Demonstrates Robust Inhibition of Alternative Complement Activity Both in Normal Human Serum and in Phase I Normal Healthy Volunteers

INTRODUCTION: Blockade of complement factor C5 has demonstrated benefit in paroxysmal nocturnal hemoglobinuria, atypical hemolytic uremic syndrome, generalized myasthenia gravis and neuromyelitis optica. We have completed a Phase I study of pozelimab, a fully human anti-C5 IgG4, in healthy volunteers. Pozelimab was well tolerated and resulted in dose-dependent inhibition of hemolytic activity through the classical complement pathway in normal healthy volunteers. Complete inhibition of hemolytic activity was maintained over a 4-week dosing period by a weekly subcutaneous (SC) regimen following an intravenous (IV) loading dose (ASH2018 abstract). OBJECTIVE: To further characterize the impact of pozelimab on the alternative complement pathway activity, we investigated the effect of pozelimab on alternative pathway-mediated hemolysis using an AH50 assay in the completed first-in-human (FIH) study. In addition, we compared the effect of pozelimab in both alternative and classical pathway hemolysis assays with those of in-house eculizumab and in-house ravulizumab in pooled normal human serum (NHS) samples, ex vivo. METHODS: In total, 56 subjects were randomized to 4 sequential ascending IV single dose cohorts plus 2 sequential ascending SC single dose cohorts followed by 1 multiple dose cohort (consisting of an IV loading dose and weekly SC doses). Each cohort consisted of 8 subjects randomized to receive pozelimab or placebo (6 active: 2 placebo). Serum collected at multiple time-points was utilized to assess the effect of pozelimab on alternative pathway activity. For ex vivo spike experiments, pooled NHS was used to compare the hemolytic function of pozelimab, in-house produced eculizumab and in-house produced ravulizumab. Comparator antibodies were synthesized from published sequence. The alternative pathway (AP) and classical pathway (CP) hemolysis assays were performed based on lysis of rabbit red blood cells (RBCs) and sensitized sheep RBCs, respectively. Both assays measure the amount of hemoglobin released from red blood cells at 412 nm. RESULTS: In the FIH study, baseline AH50 was comparable across treatment groups with a mean of 110 U/mL (standard deviation = 19, n = 56). Pozelimab exposure led to dose-dependent inhibition of AH50. In all 4 IV dosing cohorts, peak suppression of hemolysis was observed at end of infusion (EOI). Maximal suppression of hemolysis was approximately −85% change from baseline. This was achieved with the 30 mg/kg IV group and the repeat dose 15 mg/kg IV + 400 mg SC QW group. In the 2 SC cohorts, peak suppression of hemolysis was observed 3-7 days post dosing, which was consistent with observed peak concentrations of pozelimab in serum. In an ex vivo spike study, pozelimab, in-house eculizumab and in-house ravulizumab were spiked into 10, 25 or 48% pooled NHS for AP, and 5, 10 or 25% for CP. The results from AP hemolysis assays showed that, for a given concentration of spiked antibody, the maximal suppression of hemolysis for all the antibodies decreased with increased percentage of serum (Figure). The maximal suppression of hemolysis was consistently higher (32-169%) for pozelimab compared with in-house eculizumab, and lower for in-house ravulizumab compared with pozelimab and in-house eculizumab at all serum percentages tested. The results from CP hemolysis assays showed that, although the maximal suppression of hemolysis was similar for all antibodies tested, in-house ravulizumab was required to be at least a log higher in concentration to achieve a similar effect as the other two anti-C5 antibodies. CONCLUSIONS: Ex vivo studies with pooled NHS demonstrate that pozelimab robustly blocks both CP and AP hemolysis. In-house ravulizumab appeared to be less potent compared with in-house eculizumab in both CP and AP hemolysis assays. The Phase I healthy volunteer study of pozelimab demonstrated dose-dependent and significant inhibition of alternative pathway hemolysis, with the maximal suppression of hemolysis approximately −85% change from baseline. Figure Disclosures Devalaraja-Narashimha: Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Ni:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Huang:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Wang:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Chaudhari:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Prasad:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Harari:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Rankin:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Morton:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Weyne:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. OffLabel Disclosure: The drug is pozelimab and it is a fully human anti-C5 IgG4 being tested a Phase 1 study in healthy volunteers.

Evidence for dielectric suppression in non-magnetic modified multiferroic bismuth ferrite

Structural, magnetic, and electrical properties of polycrystalline Y-Sc codoped BiFeO3 (BFO) ceramics are investigated. Rietveld refinement and Raman spectroscopy analysis provide strong evidence of structural distortion without changing the structure of parent compound (rhombohedral: R3c) after codoping. Distortion due to nonmagnetic codoping marks an abrupt change in magnetic and electrical properties of BiFeO3. Ferromagnetic property is enhanced with a maximum remanent magnetization of 0.0045 emu/g at higher Sc-concentrations. Codoping improves the ferroelectric properties [Pr=13μC/cm2 at (Y,Sc)=(0.03,0.05)] due to the suppression of oxygen vacancies. The frequency-dependent dielectric properties at various temperatures are investigated. The relaxation peak shifts toward room temperature for Bi1−xYxFe1−yScyO3 ceramics, which eventually appeared above 100°C for parent BFO. The suppression of relaxation peak indicates the change in conduction mechanism for codoped ceramics. The conduction process and the relaxation mechanism in parent and Y-Sc codoped BiFeO3 are investigated with electrical modulus and impedance spectroscopy. Frequency-dependent ac conductivity at various temperatures indicates that the conduction mechanism follows the correlated barrier hopping model and is thermally activated. Temperature dependent conductivity studies at different frequencies reveal that the relaxation process in codoped ceramics is due to the long-range oxygen vacancy movement and the low loss values.

Effects of baryons on weak lensing peak statistics

Upcoming weak-lensing surveys have the potential to become leading cosmological probes provided all systematic effects are under control. Recently, the ejection of gas due to feedback energy from active galactic nuclei (AGN) has been identified as major source of uncertainty, challenging the success of future weak-lensing probes in terms of cosmology. In this paper we investigate the effects of baryons on the number of weak-lensing peaks in the convergence field. Our analysis is based on full-sky convergence maps constructed via light-cones from N-body simulations, and we rely on the baryonic correction model of [1] to model the baryonic effects on the density field. As a result we find that the baryonic effects strongly depend on the Gaussian smoothing applied to the convergence map. For a DES-like survey setup, a smoothing of θk≳8 arcmin is sufficient to keep the baryon signal below the expected statistical error. Smaller smoothing scales lead to a significant suppression of high peaks with \U0001d4ae/\U0001d4a9> 2, while lower peaks are not affected. The situation is more severe for a Euclid-like setup, where a smoothing of θk≳16 arcmin is required to keep the baryonic suppression signal below the statistical error. Smaller smoothing scales require a full modelling of baryonic effects since both low and high peaks are strongly affected by baryonic feedback.

Structural, optical and electronic properties of low energy N ion implanted InGaN/GaN heterostructures

The structural, optical, morphological and electrical properties of the low energy N ion implanted InGaN/GaN heterostructures have been investigated. These heterostructures were grown by metal-organic chemical vapor deposition. The compositional fluctuations and crystalline quality of pristine and implanted samples are measured by the high-resolution x-ray diffraction. The tricking asymmetric (1 0 −1 5) GaN and InGaN peaks of ω − 2θ and omega diffraction patterns are then resolved using reciprocal space mapping. The morphology of N ion implanted InGaN sample shows a decrease in density of the V-pits and hillocks with increasing N ion fluences. The atomic percentage of In, Ga and N are estimated using x-ray photoelectron spectroscopy. The Raman studies showed the E2 high and A1 (LO) modes of GaN and InGaN for pristine and implanted samples which also confirm that the linear dependence of In composition with the N ion implantation fluences. The photoluminence results confirm the suppression of yellow luminescence peak after implantation. The Hall measurements confirm the enhancement in electron mobility after implantation which inevitably suppressed the carrier concentration with decreased nitrogen vacancies. The low energy N ion implantation increases In composition and reduction of In clusters in the InGaN layer which have a technological significance in InGaN based optoelectronic applications.

Optical properties of zig-zag and armchair ZnO colloidal nanoribbons

Using the empirical pseudopotential method, the electronic and optical properties of zigzag and armchair colloidal ZnO nanoribbons have been studied focusing on their thickness and width dependence. Our results indicate that contrary to what has been theoretically predicted for epitaxially grown nanoribbons, both colloidal types exhibit semiconducting behavior. Furthermore the absorption spectra for both nanoribbons are mainly dominated by y-polarized transitions while for the case of zigzag nanoribbons there is a higher energy x-polarized peak. The increase of confinement along the y-direction in zigzag nanoribbons leads to a suppression of the y-polarized peak, leaving back a purely x-polarized optical gap.