Low-energy Sensitivity Research Articles

Exploring DNA Computers: Advances in Storage, Cryptography and Logic Circuits.

Over the last four decades, research on DNA as a functional material has primarily focused on its predictable conformation and programmable interaction. However, its low energy consumption, high responsiveness and sensitivity also make it ideal for designing specific signaling pathways, and enabling the development of molecular computers. This review mainly discusses recent advancements in the utilization of DNA nanotechnology for molecular computer, encompassing applications in storage, cryptography and logic circuits. It elucidates the challenges encountered in the application process and presents solutions exemplified by representative works. Lastly, it delineates the challenges and opportunities within this filed.

Blade Airfoil Optimization and Its Impact on Vertical Axis Wind Turbine Performance

Abstract Amidst the emergence of crises in petroleum prices and supply, the imperative for the development of clean energy has become increasingly apparent. Vertical axis wind turbines (VAWT), as a type of wind turbine, still grapple with challenges such as low wind energy utilization and sensitivity to dynamic wind speeds. This study focuses on optimizing the airfoil of a two-dimensional vertical axis wind turbine and analyzes the performance variations in a three-dimensional model. Following the optimization, the average power coefficients of the dual-blade two-dimensional VAWT increased by 7.9% and 4%, respectively, while those of the dual-blade three-dimensional model rose by 7.9% and 1.2%. However, the performance of the three-dimensional model was compromised due to the influence of tip vortices, resulting in inferior performance compared to the two-dimensional model. Both three-dimensional optimized blade designs exhibited a substantial reduction in the flow separation region downstream and improved pressure distribution fluctuations caused by the shedding of tip vortices, leading to decreased pressure differentials. Along the spanwise section, the power coefficient gradually decreased from the central segment to the tip segment. Notably, the power coefficient of the optimized blades at the tip segment increased significantly, accompanied by an augmented pressure differential between the upper and lower surfaces. This augmentation contributed to a significant enhancement in lift, thereby facilitating the rotation of the vertical axis wind turbine.

Design, construction, and operation of a 1-ton Water-based Liquid scintillator detector at Brookhaven National Laboratory

Water-based liquid scintillators (WbLS) are a new class of detector materials that provide efficient and tunable detection of both Cherenkov and scintillation light. A massive WbLS neutrino detector with suitable photosensor coverage for low intensity light detection could therefore reconstruct the momentum of an energetic charged particle and also have enhanced low-energy sensitivity. These materials are also better suited for metal doping broadening the potential scientific utility. We recently constructed and commissioned a 1-ton WbLS detector with good photosensor coverage and a capable data acquisition and calibration system. We intend to use this flexible detector system as a testbed for WbLS R&D. In this paper we give an overview of the 1-ton system and provide some early results.

Exploring curcumin interaction with PLGA nanoparticles via various functional groups: A dispersion-corrected density functional theory and molecular dynamics simulation approach

Density functional theory (DFT)-D3 dispersion corrections and molecular dynamic (MD) techniques were used to research how curcumin (CUR) and poly (lactic-co-glycolic acid) (PLGA) interact in the water phase. Relaxation based on machine learning (ML) algorithms was used to identify the state configuration that was the most stable. The electronic, optical, and infrared (IR) vibrational properties of the studied configurations were then computed. The findings show that since PLGA nanoparticle can transport CUR via chemical interactions, the binding energy of CUR through carbonyl group to PLGA is about −1.092 eV (complex A). The theoretical IR spectrum supports the observation that the functional groups of CUR interacting with PLGA undergo changes, which is consistent with the experimental data. Hence, the Bader charge analysis indicates a charge of about 0.14 (complex A) and 0.17 (complex B) |e| transferred from the PLGA to CUR. The charges in CUR exhibit strong charge transfer to the PLGA structure. The calculated results of the CUR-PLGA complex match the main peak in the 500–580 nm range observed in experiments, and the stable optimal optical absorption diagram aligns with the reported spectra. The total density of states (TDOS) of the studied configurations shows that CUR is having an impact on the HOMO and LUMO levels. The PLGA nanoparticle demonstrates a higher sensitivity (86%) towards the presence of CUR in complex D compared to complex B (67%), which can be attributed to the change in the energy gap. This low adsorption energy and high sensitivity suggest that the PLGA nanoparticle indicates its potential to serve as both a carrier and a sensor for detecting CUR in the water phase.

Research on Multilevel Filtering Algorithm Used for Denoising Strong and Weak Beams of Daytime Photon Cloud Data with High Background Noise

The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) is equipped with the Advanced Topographic Laser Altimeter System (ATLAS), which can achieve high-precision ground detection. However, due to its low pulse energy and high sensitivity, it is also affected by noise when obtaining data. Therefore, data denoising is critical to the subsequent processing and application. In this study, a multilevel filtering algorithm is proposed to denoise the daytime photon cloud data with high background noise. Firstly, the Random Sample Consensus (RANSAC) algorithm is used to roughly denoise the daytime photon cloud data with high background noise, and a signal point cloud buffer is established to remove most of the noise points. Subsequently, the horizontal continuity parameter is calculated based on the photon cloud data following the rough denoising process. Based on this parameter, the shape and size of the search domain of the results of the subsequent fine denoising algorithm are adaptively improved. Finally, three filtering directions (a horizontal direction, an intra-group unified direction, and an adaptive direction for each photon) are proposed, and a hybrid algorithm combining the Ordering Points to Identify the Clustering Structure (OPTICS) density clustering algorithm and the Relative Neighboring Relationship K-nearest neighbors-based noise removal (RNR−KNNB) algorithm is employed to accurately denoise the photon cloud data in the three filtering directions. Furthermore, the RANSAC algorithm based on a sliding overlap window is used to remove outliers for the weak beam fine denoising photon cloud data. The results indicate that, for the strong beams, the denoising accuracy of the multilevel filtering algorithm in the three filtering directions is comparable (Rs ≥ 0.96, F ≥ 0.67), and they are all better than that of the ATL08 algorithm (Rs/Rn/p/F = 0.85/0.67/0.52/0.65). For weak beams, the denoising accuracy of the multilevel filtering algorithm in the horizontal direction and the intra-group unified direction is similar (Rs = 0.92, F = 0.69), and it is superior to the denoising results in the adaptive direction of each photon and the ATL08 algorithm (Rs/Rn/p/F = 0.94/0.84/0.51/0.65, 0.88/0.87/0.55/0.67, respectively). For strong and weak beams, the p-value and F-value of the denoising results of multilevel filtering algorithms in three different filtering directions increase with the increase of SNR value. It is demonstrated that SNR is an important factor affecting the denoising results of algorithms. The multilevel filtering algorithm proposed in the study can effectively achieve precise denoising of daytime photon cloud data with high background noise, and the three different filtering directions have different effects on the denoising results of strong and weak beam photon cloud data. This can provide technical and methodological guidance for subsequent photon cloud data filtering processing.

Design analyst of low energy, high gm/Id, and high sensitivity comparator

This paper analyses three innovative designs of comparators and those structures have better performance than the traditional comparator. The dynamic floating inverter amplifier improves energy efficiency by preventing full discharging and charging. The Dynamic Bias Latch-Type Comparator used a double-tails latch to decrease energy consumption. The charge-injection compensations comparator has better sensitivity and less noise by utilizing the feedback loop. Those methods have greatly increased voltage gain, energy efficiency, and gm/Id

Time-dependent Numerical Model for Studying the Very-high-energy Emissions of Distant Gamma-Ray Burst GRB 201216C

Recently, the MAGIC Collaboration reported a ∼5σ statistical significance of the very-high-energy (VHE) emission from a distant gamma-ray burst (GRB), GRB 201216C. Such distant GRB may be effectively absorbed by the extragalactic background light (EBL). The origin of the VHE emission from such distant objects is still unknown. Here, we propose a numerical model for studying the afterglow emission of this distant GRB. The model solves the continuity equation governing the temporal evolution of electron distribution, and the broadband observed data can be explained by the synchrotron plus synchrotron self-Compton (SSC) radiation of the forward shock. The predicted observed 0.1 TeV flux can reach ∼10−9−10−10 erg cm−2 s−1 at t ∼ 103−104 s, even with strong EBL absorption, such strong sub-teraelectronvolt (sub-TeV) emissions still can be observed by the MAGIC telescope. Using this numerical model, the shock parameters in the modeling are similar to two other sub-TeV GRBs (i.e., GRB 190114C and GRB 180720B), implying that the sub-TeV GRBs have some commonalities: they have energetic burst energy, low circumburst medium density, and a low magnetic equipartition factor. We regard GRB 201216C as a typical GRB, and estimate the maximum redshift of GRB that can be detected by the MAGIC telescope, i.e., z ∼ 1.6. We also find that the VHE photon energy of such distant GRB can only reach ∼0.1 TeV. Improving the low energy sensitivity of the VHE telescope is very important to detect the sub-TeV emissions of these distant GRBs.

Constructing hotspots through star-shaped gold-copper alloy nanocrystals for laser initiation of explosives

Laser initiation technology is an effective way to detonate high energy materials safely and reliably, which has broad application prospect in military blasting. However, there are many obstacles in high-power laser propagating through optical fiber, which directly affect the initiation of high-energy explosives under low-power conditions. Photosensitizer is a necessary substance for initiating low energy and low sensitivity explosives. Herein we developed gold-copper alloys nanocrystals as free-standing laser energy converter material to reduce the laser initiation threshold and delay time. By controlling the nanocrystals morphology, more hotspots were created in the nanocrystals and the ultraviolet–visible-near infrared (UV–VIS-NIR) absorption peak of nanocrystals was regulated to around 808 nm. The laser irradiation result showed that the temperature of the gold-copper alloys nanocrystals was close to 280 ℃ within 10 s (808 nm, 1 W·cm−2). In the practical applications, the cyclotrimethy lenetrinitramine (RDX) initiation threshold can be reduced by 83.47% and B/KNO3 delay time by 43.95% by using gold-copper alloy nanocrystals as laser energy absorber. This result indicates that the gold-copper alloy as an independent laser absorbing material can effectively initiate low-sensitive explosives under low-power conditions.

Flexible Bielectrode‐Based Highly Sensitive Triboelectric Motion Sensor: A Sustainable and Smart Electronic Material

The self‐powered and autonomous sensors are incredibly important in advanced engineering, especially defence science. The increasing necessity of simple and smart electronics requires to be sustainably flexible, wearable, and waterproof. Triboelectricity has been a widely used mechanism for motion sensing nowadays. Almost all devices based on triboelectricity require contact between two surfaces. Herein, a touchless triboelectric motion sensor for human motion sensing and movement monitoring is developed. The device was primarily fabricated using simple latex (cis‐1,4‐polyisoprene) structures and copper (electrode materials), which make it a very cost‐effective device for sensory applications. The device is tested with specimens of different areas and heights in motion. The maximum output of the device is noted as 12 V at a specimen height of 5 cm. Further different types of human motions are applied in front of the device to ensure low energy sensitivity using triboelectric phenomena. The lightweight smart device precisely provides significant output signals for each movement of the human body which makes the device a prospective medium for motion sensing and movement monitoring which can be applied in the fields of security, energy, and medicine.

The ASTAROTH Project: enhanced low-energy sensitivity to Dark Matter annual modulation

ASTAROTH is a novel R&D project which aims at improving the physics reach of future direct dark matter detection experiments based on NaI(Tl) scintillating crystals. There is a strong need to test the long standing DAMA positive observation of an annual modulation that could be due to Dark Matter (DM), with the same target material and in a model independent way. ASTAROTH aim is the enhancement of the sensitivity to the annual modulation signal, compared with present technology, by lowering the detection energy threshold in order to observe sub-keV recoils for the first time. This can be achieved by reading the scintillation light from the NaI(Tl) crystals with arrays of Silicon PhotoMultipliers (SiPM), and placing the detectors in a cryogenic environment. SiPMs feature lower dark noise than Photomultiplier Tubes (PMTs) at T < 150 K and allow for higher light collection. The cooling medium is liquid Argon, as it is an excellent scintillator that can be instrumented to act as a veto against several backgrounds.Here we present the status of the ASTAROTH project, introducing the innovative design of the detector chamber that will be used for the demonstration of the technology. Then, we will show the preliminary results of our first ever measurements performed on a single NaI(Tl) crystal read out by one SiPM array in a cryogenic set-up cooled with liquid nitrogen.

Detection of Low-Energy X-rays Using YSO Scintillation Crystal Arrays for GRB Experiments

We developed an X-ray detector using 36 arrays, each consisting of a 64-pixellated yttrium oxyorthosilicate (YSO) scintillation crystal and a 64-channel multi-anode photomultiplier tube. The X-ray detector was designed to detect X-rays with energies lower than 10 keV, primarily with the aim of localizing gamma-ray bursts (GRBs). YSO crystals have no intrinsic background, which is advantageous for increasing low-energy sensitivity. The fabricated detector was integrated into UBAT, the payload of the Ultra-Fast Flash Observatory (UFFO)/Lomonosov for GRB observation. The UFFO was successfully operated in space in a low-Earth orbit. In this paper, we present the responses of the X-ray detector of the UBAT engineering model identical to the flight model, using 241Am and 55Fe radioactive sources and an Amptek X-ray tube. We found that the X-ray detector can measure energies lower than 5 keV. As such, we expect YSO crystals to be good candidates for the X-ray detector materials for future GRB missions.

Vibrationally Hot and Cold Triplets. Sensitizer-Dependent Dynamics and Localized Vibrational Promotion of a Di-π-methane Rearrangement.

Large intramolecular 13C kinetic isotope effects (KIEs) for the di-π-methane rearrangement of benzobarrelene fit with statistical expectations from heavy-atom tunneling when a low-energy sensitizer is employed, but much lower KIEs are observed with higher-energy sensitizers. These results in combination with trajectory studies suggest that the excess vibrational energy available from triplet energy transfer leads to hot and nonstatistical dynamics in the rearrangement.

A new measure of Italian hidden energy poverty

As highlighted by European policymakers and academic research, the global economic crisis of 2008 emphasized the energy poverty phenomenon. A number of households have had to considerably reduce their energy expenditure but the traditional criteria adopted to calculate energy poverty are not able to measure their number.Placed in this framework, the paper aims to define a new measure of hidden energy poverty suitable to identify which Italian households restrain their energy consumption due to their inability to afford energy services. A review of the available energy poverty metrics supports the definition of a new indicator that is able to include hidden energy-poor consumers considering some key peculiarities such as the poor energy efficiency of buildings, the poverty situation, low energy consumption and sensitivity to the climate. Using data from the Household Budget Survey provided by the Italian National Institute of Statistics in 2018, the newly identified indicator supports the assessment of the percentage of Italian households in hidden energy poverty and supplies useful insight to policymakers in their effort to support vulnerable consumers.

Utility of Squaraine Dyes for Dye-Sensitized Photocatalysis on Water or Carbon Dioxide Reduction.

Red light-sensitized squaraine (SQ) dyes were developed and incorporated into dye-sensitized catalysts (DSCs) with the formula of SQ/TiO2/Cat, and their efficacies were evaluated in terms of performance on either water or carbon dioxide reduction. Pt nanoparticles or fac-[Re(4,4′-bis-(diethoxyphosphorylmethyl)-2,2′-bipyridine)(CO)3Cl] were used as each catalytic center within the DSC frame of SQ/TiO2/Pt (Type I) or SQ/TiO2/Re(I) (Type II). In order to convey the potential utility of SQ in low energy sensitization, the following catalytic reductions were carried out under selective lower energy irradiation (>500 nm). Type I and II showed different catalytic performances, primarily due to the choice of solvent for each catalytic condition: hydrogenation was carried out in H2O, but CO2 reduction in dimethylformamide (DMF), and SQ was more stable in aqueous acid conditions for hydrogen generation than CO2 reduction in DMF. A suspension of Type I in 3 mL water containing 0.1 M ascorbic acid (pH = 2.66) resulted in efficient photocatalytic hydrogen evolution, producing 37 μmol of H2 for 4 h. However, in photocatalysis of Type II (SQ/TiO2/Re(I)) in 3 mL DMF containing 0.1 M 1,3-dimethyl-2-phenyl-1,3-dihydrobenzimidazole, the TiO2-bound SQ dyes were not capable of working as a low energy sensitizer because SQ was susceptible to dye decomposition in nucleophilic DMF conditions, resulting in DSC deactivation for the CO2 reduction. Even with the limitation of solvent, the DSC conditions for the utility of SQ have been established: the anchoring group effect of SQ with either phosphonic acid or carboxylic acid onto the TiO2 surface; energy alignment of SQ with the flat band potentials (Efb) of TiO2 semiconductors and the reduction power of electron donors; and the wavelength range of the light source used, particularly when >500 nm.

Particle transport within the pulsar wind nebula HESS J1825–137

Context. We present a detailed view of the pulsar wind nebula (PWN) HESS J1825–137. We aim to constrain the mechanisms dominating the particle transport within the nebula, accounting for its anomalously large size and spectral characteristics. Aims. The nebula was studied using a deep exposure from over 12 years of H.E.S.S. I operation, together with data from H.E.S.S. II that improve the low-energy sensitivity. Enhanced energy-dependent morphological and spatially resolved spectral analyses probe the very high energy (VHE, E &gt; 0.1 TeV) γ-ray properties of the nebula. Methods. The nebula emission is revealed to extend out to 1.5° from the pulsar, ~1.5 times farther than previously seen, making HESS J1825–137, with an intrinsic diameter of ~100 pc, potentially the largest γ-ray PWN currently known. Characterising the strongly energy-dependent morphology of the nebula enables us to constrain the particle transport mechanisms. A dependence of the nebula extent with energy of R ∝ Eα with α = −0.29 ± 0.04stat ± 0.05sys disfavours a pure diffusion scenario for particle transport within the nebula. The total γ-ray flux of the nebula above 1 TeV is found to be (1.12 ± 0.03stat ± 0.25sys) × 10−11 cm−2 s−1, corresponding to ~64% of the flux of the Crab nebula. Results. HESS J1825–137 is a PWN with clearly energy-dependent morphology at VHE γ-ray energies. This source is used as a laboratory to investigate particle transport within intermediate-age PWNe. Based on deep observations of this highly spatially extended PWN, we produce a spectral map of the region that provides insights into the spectral variation within the nebula.

Molecular engineering of boryl oxasmaragdyrins through peripheral modification: structure-efficiency relationship.

Expanded porphyrins with the absorption profile down to the infrared region through increased π-conjugation are suitable candidates for a low energy sensitizer. Oxasmaragdyrin boron complexes, a class of aromatic-core-modified expanded porphyrin with 22 π-electrons, have been recently utilized as an efficient low energy sensitizer in dye-sensitized solar cells. In this paper, we have prepared a series of eight novel boryl oxasmaragdyrins through molecular engineering on the periphery and their overall photovoltaic performances in dye-sensitized solar cells are evaluated. With the help of photophysical, electrochemical, and photovoltaic studies, it is revealed that molecular structure, especially the number and position of the donor-acceptor groups play a pivotal role in their photovoltaic performance. Presence of the two well-separated split Soret bands in the 400-500 nm region of UV/Vis spectrum ensures broader coverage of absorption wavelengths. Even though the two-anchoring-group dyes (SM5-SM8) bind strongly to TiO2 compared to one-anchoring-group dyes (SM1-SM4), the latter have superior photovoltaic performance than the former. Dye SM1, with two hexyloxyphenyl donors and one carboxylic acid anchor showed the best overall conversion efficiency of 4.36% (JSC = 10.91 mA cm(-2); VOC = 0.59 V; FF = 0.68). This effective modulation of photovoltaic performance through structural engineering of the dyes will serve as a guideline for the future design of efficient low energy light-harvesting sensitizers.

IACT observations of gamma-ray bursts: prospects for the Cherenkov Telescope Array

Gamma rays at rest frame energies as high as 90 GeV have been reported from gamma-ray bursts (GRBs) by the Fermi Large Area Telescope (LAT). There is considerable hope that a confirmed GRB detection will be possible with the upcoming Cherenkov Telescope Array (CTA), which will have a larger effective area and better low-energy sensitivity than current-generation imaging atmospheric Cherenkov telescopes (IACTs). To estimate the likelihood of such a detection, we have developed a phenomenological model for GRB emission between 1 GeV and 1 TeV that is motivated by the high-energy GRB detections of Fermi-LAT, and allows us to extrapolate the statistics of GRBs seen by lower energy instruments such as the Swift-BAT and BATSE on the Compton Gamma-ray Observatory. We show a number of statistics for detected GRBs, and describe how the detectability of GRBs with CTA could vary based on a number of parameters, such as the typical observation delay between the burst onset and the start of ground observations. We also consider the possibility of using GBM on Fermi as a finder of GRBs for rapid ground follow-up. While the uncertainty of GBM localization is problematic, the small field-of-view for IACTs can potentially be overcome by scanning over the GBM error region. Overall, our results indicate that CTA should be able to detect one GRB every 20 to 30 months with our baseline instrument model, assuming consistently rapid pursuit of GRB alerts, and provided that spectral breaks below 100 GeV are not a common feature of the bright GRB population. With a more optimistic instrument model, the detection rate can be as high as 1 to 2 GRBs per year.

Low energy polarization sensitivity of the Gas Pixel Detector

An X-ray photoelectric polarimeter based on the Gas Pixel Detector has been proposed to be included in many upcoming space missions to fill the gap of about 30 years from the first (and to date only) positive measurement of polarized X-ray emission from an astrophysical source. The estimated sensitivity of the current prototype peaks at an energy of about 3 keV, but the lack of readily available polarized sources in this energy range has prevented the measurement of detector polarimetric performances. In this paper we present the measurement of the Gas Pixel Detector polarimetric sensitivity at energies of a few keV and the new, light, compact and transportable polarized source that was devised and built to this aim. Polarized photons are produced, from unpolarized radiation generated with an X-ray tube, by means of Bragg diffraction at nearly 45 ∘ . The diffraction angle is constrained with two orthogonal capillary plates, which allow good collimation with limited size thanks to the 10 μ m diameter holes. Polarized photons at energy as low as a few keV can be produced with a proper choice of diffracting crystal, while the maximum energy is limited by the X-ray tube voltage, since all the orders defined by the crystal lattice spacing are diffracted. The best trade-off between reasonable fluxes and high degree of polarization can be achieved selecting the degree of collimation provided by capillary plates. The employment of mosaic graphite and flat aluminum crystals allow the production of nearly completely polarized photons at 2.6, 3.7, and 5.2 keV from the diffraction of unpolarized continuum or line emission. The measured modulation factor of the Gas Pixel Detector at these energies is in good agreement with the estimates derived from a Monte Carlo software, which was up to now employed for driving the development of the instrument and for estimating its low energy sensitivity. In this paper we present the excellent polarimetric performance of the Gas Pixel Detector at energies where the peak sensitivity is expected. These measurements not only support our previous claims of high sensitivity but confirm the feasibility of astrophysical X-ray photoelectric polarimetry.

Efficiency for close geometries and extended sources of a p-type germanium detector with low-energy sensitivity

Typically, germanium detectors designed to have good sensitivity to low-energy photons and good efficiency at high energies are constructed from n-type crystals with a boron-implanted outer contact. These detectors usually exhibit inferior resolution and peak shape compared to ones made from p-type crystals. To overcome the resolution and peak-shape deficiencies, a new method of construction of a germanium detector element was developed. This has resulted in a gamma-ray detector with high sensitivity to photon energies from 14 keV to 2 MeV, while maintaining good resolution and peak shape over this energy range. Efficiency measurements, done according to the draft IEEE 325-2004 standard, show efficiencies typical of a GMX or n-type detector at low energies. The detectors are of large diameter suitable for counting extended samples such as filter papers. The Gaussian peak shape and good resolution typical of a GEM or p-type are maintained for the high count rates and peak separation needed for activation analysis.

Time-resolved EPR investigation of charge recombination to a triplet state in a carotene-diporphyrin triad

Photoinduced charge separation and recombination were investigated in a triad consisting of a carotenoid (C), a tetraarylporphyrin (P) and a tris(heptafluoropropyl)porphyrin (PF), C–P–PF, by means of time-resolved electron paramagnetic resonance. The electron transfer process was studied in a glass of 2-methyltetrahydrofuran at 10 K, in the crystalline phase at 150 K and in the liquid nematic phase of the uniaxial LC E-7 at 295 K, and in the nematic phase of the LC ZLI-1167 at 300 K. In all the different media and in the different phases, the molecular triad undergoes two-step photoinduced electron transfer, with the generation of a long-lived charge-separated state (C•+–P–), and charge recombination to the triplet state, localized in the carotene moiety 3C–P–PF. Low-temperature charge separation and triplet recombination are common features of both fullerene-based and diporphyrin molecular triads, proving that the large delocalized π-electron system of the porphyrin electron acceptor leads to low total reorganization energy and low sensitivity to solvent stabilization of the radical ions in a similar way as for fullerene systems.