Strong Gamma Research Articles

Preparation and properties of strong gamma ray shielding and irradiation resistant glass

CeO2 doped lead silicate glasses samples were prepared by high temperature melting method. The structural, thermal and optical properties of the glasses were characterized by density, expansion coefficient, XPS and ultraviolet-visible spectroscopy. Additionally, the related theoretical work was carried out for verification. The changes in structure and optical properties of the glass before and after irradiation were investigated. The influence mechanism of different content of CeO2 (PbO) on the structure and properties of shielding glass was discussed. By comparing the three transmittance conversion formulas, it is found that the characteristic coefficient can be further calculated if the transmissivity with varied thicknesses is known. This coefficient method allows for accurate calculation of transmittance for glasses with arbitrary thicknesses while demonstrating experimental validation. The accuracy improves as more measured values of transmittance for glasses with different thicknesses are obtained and as more iterations of characteristic coefficients are performed. This method is suitable for both scientific research and production practice. The test results show that the transmittance of the glass with 45 wt% PbO and 2 wt% CeO2 content is above 60 % in the wavelength range of 400–800 nm before irradiation and decreased less than 10 % after irradiation. The measured shielding rate of 60Co gamma rays can reach more than 51 %. The calculated transmittance of 300 mm thickness glass is greater than 50 %. The superior gamma ray shielding capability along with its radiation resistance make this glass provide key support for window materials used in various fields such as nuclear industry, aerospace, military and medicine.

Gamma Responses to Colored Natural Stimuli Can Be Predicted from Local Low-Level Stimulus Features.

The role of gamma rhythm (30-80 Hz) in visual processing is debated; stimuli like gratings and hue patches generate strong gamma, but many natural images do not. Could image gamma responses be predicted by approximating images as gratings or hue patches? Surprisingly, this question remains unanswered, since the joint dependence of gamma on multiple features is poorly understood. We recorded local field potentials and electrocorticogram from two female monkeys while presenting natural images and parametric stimuli varying along several feature dimensions. Gamma responses to different grating/hue features were separable, allowing for a multiplicative model based on individual features. By fitting a hue patch to the image around the receptive field, this simple model could predict gamma responses to chromatic images across scales with reasonably high accuracy. Our results provide a simple "baseline" model to predict gamma from local image properties, against which more complex models of natural vision can be tested.

Scheme of construction of nonlinear polycryptosystem cryptographic protocols

The paper highlights the ways of constructing nonlinear encryption systems and proposes a scheme for constructing a nonlinear polycryptosystem cryptographic protocol that performs encryption of data blocks by various cryptographic systems in a pseudo-random sequence. Using the proposed scheme allows you to build a cryptographic protocol using ready-made and proven encryption systems, without making any changes to their design. The pseudo-random alternation of cryptosystems in the encryption process is based on a cryptographically strong gamma expansion algorithm, which increases the nonlinearity of encryption and improves the general cryptographically strong of systems. The article considered the structure of cryptosystems based on nonlinear cryptographic primitives, developed a model of the deployment process of modifiers of nonlinear cryptographic systems, and formed a general scheme of the structure of nonlinear cryptographic protocols using one or more different cryptosystems, provided they meet the specified requirements. The advantages of the proposed scheme are great flexibility, scalability, and the possibility of applying the highlighted concept both at the level of cryptographic algorithms or their fragments and at the level of cryptosystems and cryptographic protocols. The proposed solutions allow simple and effective improvement of existing cryptographic systems or their separate algorithms and are promising for further research.

Natural non-Hermitian interaction alignment with photon-phonon quantization in Eu3+: NaYF4

We investigated the photon and phonon alignment for two dressing interaction profile in Eu+3: NaYF4. The evolution from strong to weak interaction alignment can be controlled by time gate width and time gate position, which shows that time gate position seems more sensitive than time gate width, while changing both can make interaction alignment oscillation due to two phonon and one photon quantization. Fluorescence FL signal switch from dip to peak interaction profile due to strong gamma, while the Super-Fluorescence SFWM signal switch from peak to dip interaction profile due to strong Rabi frequency (G). Comparing single laser spectral alignment to two-laser interaction alignment, the FL and SFWM shows dressing peak dip switch (spectral to interaction profile). In contrast, there is no switch in AT (spectral to interaction profile) because, the phase difference of the second laser balances the destructive and constructive dressing quantization’s. Such results can have potential applications in fine and hyper structure interaction alignment in non-polar ion.

Do Miniature Eye Movements Affect Neurofeedback Training Performance? A Combined EEG-Eye Tracking Study

EEG-based neurofeedback is a prominent method to modulate one’s own brain activity in a desired direction. However, the EEG signal can be disturbed by artifacts, e.g., eye movements, which can consequently confound the neurofeedback performance. Involuntary miniature eye movements can be hardly detected by conventional EEG correction methods such as recording the electro-oculogram (EOG) and subtracting EOG activity from the EEG signal. However, such miniature eye movements can influence EEG activity, especially in the Gamma frequency range, enormously. In the present study, we investigated whether power in different EEG frequencies can be effectively modulated by self-control of brain signals during neurofeedback training and/or whether changes in EEG power are provoked by miniature eye movements during the training. To this end, 24 participants performed one session of SMR and one session of Gamma neurofeedback training. Additionally, in each training session sham feedback was performed. An eye tracker was used to detect miniature eye movements (< 1°) during neurofeedback training. About two thirds of the participants were able to increase their SMR power over the course of NF training, while one third was able to increase Gamma power. Generally, miniature eye movements induced a strong Gamma power increase. The number of eye movements also increased numerically over the course of the NF training. However, we did not find a significant relationship with the NF training performance. This is a first indication that miniature saccades do not affect NF training performance, but should not be neglected during NF training. Our results have to be confirmed in future studies.

Expanding microscopic black holes

Two interesting hypotheses about black holes have been proposed. The older one states that microscopic black holes can be accountable for the observed dark matter density. The newer one states that black holes are coupled to the expansion of the universe. Here, we combine those ideas and investigate the behavior of expanding microscopic black holes. We observe two temperatures at which the radiation balances the expansion. While one of the balance points might be important in the analysis of primordial scenarios, the other would lead to a strong diffuse gamma radiation background, which is contradicted by the lack of observations. This establishes another indirect evidence disfavoring the hypothesis of cosmological coupling of black holes.

First GMVA observations with the upgraded NOEMA facility: VLBI imaging of BL Lacertae in a flaring state

We analyze a single-epoch Global mm-VLBI Array (GMVA) observation of the blazar BL\,Lacertae (BL\,Lac) at 86\,GHz from April 2021. The participation of the upgraded, phased Northern Extended Millimetre Array (NOEMA) adds additional sensitivity to the GMVA, which has facilitated the imaging of BL\,Lac during an unprecedentedly strong gamma -ray flare. We aim to explore the nature of the inner subparsec jet of BL\,Lac and the impact of the NOEMA participation in the observation. For the data reduction, we employed two advanced automatic pipelines: rPICARD for the flux density calibration as well as the model-agnostic signal stabilization and GPCAL for the antenna leakage calibration. The conventional hybrid imaging (CLEAN\,$+$\,amplitude and phase self-calibration) was applied to the calibrated visibilities to generate final VLBI images. We performed a ridge-line analysis and Gaussian model-fits on the final jet image to derive the jet parameters. In our data, the presence of NOEMA improves the image sensitivity by a factor of 2.5. The jet shows a clear wiggling structure within 0.4\,mas from the core. Our ridge-line analysis suggests the presence of a helical jet structure (i.e., a sinusoidal pattern). Six circular Gaussian components were fitted to the inner jet region. We estimated an apparent brightness temperature of sim 3\,times \,1012\,K in the two innermost components. They are likely to be highly boosted by relativistic beaming effect. We find four significant polarized knots in the jet. Interestingly, two of them are located in the core region. Finally, we suggest a number of physical scenarios to interpret our results.

Bit error rate performance of underwater optical wireless communication with hybrid modulation

AbstractTurbulence effects can cause performance degradation for underwater optical wireless communication (UOWC) system. In this paper, a hybrid modulation (modulation–modulation, M–M) is presented to resist turbulence‐induced fading and improve the transmission performance of UOWC systems. The proposed differential phase shift keying‐multiple pulse position modulation (DPSK‐mPPM) is adopted as hybrid modulation to improve the bit error rate (BER) performance over UOWC turbulence channel of Gamma–Gamma distribution. Subsequently, the closed‐form average BER expressions of mPPM and hybrid DPSK‐mPPM modulation are derived and investigated, which are related to the oceanic turbulence parameters. The influence of the variation of anisotropy factor of ocean turbulence is analysed for the UOWC system over strong Gamma–Gamma turbulent channels. Finally, the numerical simulation results demonstrate the effectiveness of proposed DPSK‐mPPM to improve the BER performance compared to the traditional single modulation over UOWC channel under the same conditions. Furthermore, the work of this paper improves the practicality of the proposed DPSK‐mPPM scheme for underwater communication in complex oceanic environments.

Modelling atomic relaxation and bremsstrahlung in the deterministic code STREAM

STREAM, developed by the Computational Reactor Physics and Experiment laboratory (CORE) of the Ulsan National Institute of Science and Technology (UNIST), is a deterministic neutron- and photon-transport code primarily designed for light water reactor (LWR) analysis. Initially, the photon module in STREAM did not account for fluorescence and bremsstrahlung photons. This article presents recent developments regarding the integration of atomic relaxation and bremsstrahlung models into the existing photon module, thus allowing for the transport of secondary photons. The photon flux and photon heating computed with the newly incorporated models is compared to results obtained with the Monte Carlo code MCS. The incorporation of secondary photons has substantially improved the accuracy of photon flux calculations, particularly in scenarios involving strong gamma emitters. However, it is essential to note that despite the consideration of secondary photon sources, there is no noticeable improvement in the photon heating for LWR problems when compared to the photon heating obtained with the previous version of STREAM.

238Pu production: a State-of-the-Art review of NpO2 target fabrication technologies and processing of irradiated targets

Abstract Space mission beyond the solar system cannot rely on photovoltaic (PV) cells as primary power source, and combinations of PV cells and batteries. For such purpose, Radioisotope Power Systems powered with 238Pu have served well for all flagship space exploration missions since the early Apollo missions until today’s Mars Exploration Program and continue to be the preferred primary energy source for future missions. 238Pu production proceeds via neutron irradiation of 237Np, which is created as a by-product in nuclear fission reactors. Neutron irradiation of 237Np to produce 238Pu is conceptually very simple, but the production of sizeable quantities of 238Pu with acceptable isotopic purity, and the further separation and processing stages pose formidable technological challenges. 238Pu is a highly radiotoxic alpha emitter with an elevated specific activity and high decay energy with high risk for the workers, and its precursor, 237Np, is a radiotoxic alpha emitter whose daughter 233Pa decays to 233U with a strong gamma emission. Furthermore, the very rich and weakly explored chemistry of Np is also a challenge. The historical 238Pu inventory of US-DOE has been highly consumed and supplies of available 238Pu to support new missions have diminished. NASA and US-DOE have started an extensive project to re-establish 238Pu production for US space missions. In Europe, ESA has also shown some interest in an European production of 238Pu for the European space missions. In the present review, the manufacture of Np targets for 238Pu production by irradiation, and the target processing are discussed and assessed from an European production perspective by comparing mainly US state-of-the-art with the European know-how and the current facilities. Two principal options for target fabrication stand out: aluminium-clad NpO2–Al CERMET and zircaloy-clad full-ceramic NpO2 targets. The principal advantages of the well documented CERMET route can be found in the irradiation stage. These targets allow a high flexibility in heavy metal loading fraction and have high thermal performance. But, they have significant drawbacks in terms of the amount and type of nuclear waste that is generated at the back-end. Instead, the full-ceramic targets are conceptually very similar to conventional nuclear fuels, and would be preferred from back-end perspective, although a demonstration of large scale production remains yet to be done. Presently, there are no operational large scale Np target production, irradiation, processing or 238Pu handling facilities in Europe, but the nuclear infrastructure exists and is operational to study each of the steps at least at small scale and all steps have similarities with well-established industrial capabilities in Europe.

Development of a multi-channel gamma-blind fast neutron detector based on wavelength shifting fibers embedded in a ZnS:Ag epoxy mixture

This paper presents a fast neutron detector based on elastic scattering with hydrogen, a silver-activated zinc sulfide scintillator to convert the recoil proton energy to light, and wavelength-shifting fibers (WLSFs) to collect the scintillation light. The detector uses silicon photomultipliers (SiPMs) to recognize individual scintillation photons and a digital filter algorithm based on single photon counting to find clusters of photons belonging to neutron events. The detector presented in this paper features four detection channels, arranged in a 2 × 2 square. The sensitive volume of each detection channel covers a ∼5mm by ∼5mm area from the frontal direction, is 3 cm long, and contains 49 WLSFs. The detector is versatile and performs well under different conditions. Its performance can be tuned to match different applications by simply changing some parameters of the digital filter algorithm. This is illustrated in this paper by extensive measurements in different environments. Using one set of parameters, the detector achieved a gamma-blindness of 10−8 with an intrinsic neutron detection efficiency of ∼1%. With another set of parameters and with lower requirements for gamma blindness, the intrinsic neutron detection efficiency was increased to ∼11%. Yet another set of parameters allows the detector to time incoming fast neutrons with an accuracy of ∼60ns. Additionally, the decay time of the scintillation light created by neutron events was measured, falling to 10% of its peak value in ∼10 μs. Finally, the detector was exposed to strong gamma radiation for a prolonged time to test its radiation resistance. The detection efficiency dropped about linearly with the accumulated gamma fluence, reaching a drop of 40% compared to the initial efficiency at a total gamma fluence of ∼2⋅1013 cm−2.

Non-destructive analysis of spent fuel samples using a gamma-blind fast neutron detector

This paper presents the capabilities of a measurement setup built to measure the axial distribution of neutron emitters in spent fuel pins from nuclear power plants. The measurement system uses a custom gamma-blind detector based on a novel combination of silver-activated zinc sulfide scintillators and wavelength-shifting fibers for direct fast neutron detection while having a low sensitivity for gamma rays even in the strong gamma fields present during the inspection of spent fuel. A collimator with an opening of 2 cm is used to create axial resolved information. The system has been tested using UOX and MOX spent fuel samples with burn-ups between 40 and 90 GWd/t and with long cooling times (20–25 y). Measurements of the total neutron emission of the samples relative to each other achieved a 1σ uncertainty of 2%. Absolute values were measured by comparison with a calibrated 252Cf source, achieving a 1σ uncertainty of 5%. The neutron emission of the samples was previously measured using a thermal neutron detector. The results from that previous measurement agree within 2.5σ with the new results. The reconstruction of the axial neutron emission profile was performed for one of the samples. Based on the edges of the sample, the resolution of the reconstruction was estimated to be 2.5 cm. These promising results are the basis for future development of the measurement setup which should not only improve the accuracy of the results but also enable the measurement of spent fuel with much shorter cooling times of ∼1 y.

Technical basis for extended dry storage of aluminum-clad spent nuclear fuel

This paper presents the technical basis for extended dry storage of aluminum-clad spent nuclear fuel (ASNF). This basis addresses and closes five knowledge gaps defined by the U.S. Department of Energy (DOE) Spent Nuclear Fuel Working Group (SNFWG) in DOE-ID/RPT-1575 “Aluminum-clad Spent Nuclear Fuel: Technical Considerations and Challenges for Extended (>50 Years) Dry Storage.” The SNFWG's primary concern pertaining to dry storage of ASNF is rooted in the presence of (oxy)hydroxide layers adherent to the aluminum cladding of the spent fuel that formed in service, indicating a risk of radiolytic molecular hydrogen (H2) generation in a strong gamma radiation field—a process that can be associated with disintegration of (oxy)hydroxide and the molecular decomposition of chemisorbed and physisorbed water bonded to it. Potential consequences are overpressurization of sealed ASNF dry storage canisters and creation of a flammable atmosphere in sealed and vented canisters. Further, there is the concern that the generation of other chemical species due to chemical reactions, such as nitric acid (HNO3), could lead to canister component corrosion. To address these issues, experimental work was conducted, including investigations of the performance of surrogate aluminum specimens and actual ASNF material featuring adherent (oxy)hydroxide layers during wet or dry storage. Further, a comprehensive characterization of the sample material was completed. Drying experiments were executed, providing better estimations of the amount of residual, chemisorbed, and physisorbed water after ASNF dry storage canister conditioning. These empirical activities allowed for the development of predictive numerical models to simulate the chemical species yield within sealed and vented dry storage canisters for 50 years. The findings of these activities lead to the main conclusion that extending current ASNF dry storage durations by 50 years is both safe and viable.

Non-destructive evaluation of magnetic anisotropy associated with crystallographic texture of interstitial free steels

Interstitial free (IF) steels, as third generation of deep drawing steel, are used in the automotive industry for applications requiring good formability, strength and a superior surface quality. The formability is achieved by having a strong gamma fibre (γ-fibre) crystallographic texture and is quantified by measuring the r-value from tensile tests. Whereas the crystallographic texture is typically measured using EBSD or XRD on samples after careful surface preparation, it is desirable to be able to evaluate it non-destructively on production material. To do this aim, a magnetic anisotropy measurement is an attractive approach as the magnetic behaviour of steel is known to be affected by its crystallographic texture. A set of interstitial free steel samples, at different stages of recrystallisation process (i.e., commercially cold rolled and annealed to achieve fully and partially recrystallised microstructures) and consequently different texture components have been employed to study the measurement and possibility of model-wise predicting magnetic anisotropy in IF steels. In order to compare the predicted magnetic anisotropy to the measured values, a finite element (FE) microstructure model that takes into account crystallographic texture was applied.The findings indicate that the non-destructive technique deployed in this study - a U-shaped electromagnetic (EM) sensor that can be placed onto a sheet specimen - is promising for a rapid assessment of the magnetic anisotropy in IF steels.

Neutron and beta imaging with Micromegas detectors with optical readout

Recent developments have shown that coupling a Micromegas gaseous detector on a glass substrate with a transparent anode and a CMOS camera enables the optical readout of Micromegas detectors with a good spatial resolution, demonstrating that the glass Micromegas detector is well-suited for imaging. This feasibility test has been effectuated with low-energy X-ray photons also permitting energy resolved imaging. This test opens the way to different applications. Here we will focus on two applications. Namely, neutron imaging for non-destructive examination of highly gamma-ray emitting objects, such as irradiated nuclear fuel or radioactive waste. And secondly, we are developing a beta imager for the cell tagging in the field of anticancerous drug studies.Both applications require to design the detectors in view of the specific constraints of reactor dismantling and medical applications: spatial resolution and strong gamma suppression for neutron imaging and precise rate and energy spectrum measurements for the beta.A dedicated system consisting of a glass Micromegas detector and an ultrasensitive camera has been designed and assembled. Here we present the first results from the characterization of the detectors, as well as the first acquired images.

The solution to the ‘1/2 vs 3/2’ puzzle

Using an almost complete relativistic method based on the Bethe–Salpeter equation, we study the mixing angle theta , the mass splitting bigtriangleup M, the strong decay widths Gamma (D^{({prime })}_1) and the weak production rates Br(Brightarrow D^{({prime })}_1ell nu _{ell }) of the D_1(2420) and D_1^{prime }(2430). We find there is the strong cancellation between the ^1P_1 and ^3P_1 partial waves in D_1^{prime }(2430) with theta sim -,35.3^{circ }, which leads to the ‘1/2 vs 3/2’ puzzle. The puzzle can not be overcome by adding only relativistic corrections since in a large parameter range where bigtriangleup M is linear varying and not small, the theta , Gamma (D^{({prime })}_1) and Br(Brightarrow D^{({prime })}_1ell nu _{ell }) remain almost unchanged but conflict with data. While in a special range around the mass inverse point where bigtriangleup M=0 and theta =pm , 90^{circ }, they change rapidly but we find the windows where bigtriangleup M, Gamma (D^{({prime })}_1) and Br(Brightarrow D^{({prime })}_1ell nu _{ell }) are all consistent with data. The small bigtriangleup M confirmed by experiment, is crucial to solve the ‘1/2 vs 3/2’ puzzle.

Effects of Ionizing Radiation on Biopolymers for Applications as Biomaterials

Biopolymers, including extracellular matrix proteins and polysaccharides, are used as substrates for cell culture and scaffolds in tissue engineering. Ionizing radiation, for example with gamma rays or electron beams, is used to sterilize materials and to modify the physical and chemical properties of materials. The principles of the effect of ionizing radiation on biopolymers are discussed in this review article. Among the types of ionizing radiation, gamma rays and electron beams are widely used to sterilize biomaterials and construct medical devices. Water molecules are split by irradiation with ionizing radiation to give hydrated electrons, proton radicals and hydroxyl radicals. These reactive molecular species react with polymer chains to provoke scission or crosslinking reactions. Both the scission and crosslinking of the polymer chains can occur, depending on the types of polymer and irradiation conditions. Sterilization of materials is necessary if they are used in medical devices and implants. The advantages and disadvantages of ionizing radiation in comparison with other methods of sterilization are also discussed. Irradiations with strong gamma rays on the three types of biopolymers—Type I collagen, wool keratin and alginate—are described as examples of biopolymers. Ionizing radiation is a very useful tool for sterilizing materials and constructing medical devices, but it is important that we know its merits and demerits, as well as the limitations, safety and risks, of its applications.

Optimal flickering light stimulation for entraining gamma rhythms in older adults

With aging, optimal parameters of flickering light stimulation (FLS) for gamma entrainment may change in the eyes and brain. We investigated the optimal FLS parameters for gamma entrainment in 35 cognitively normal old adults by comparing event-related synchronization (ERS) and spectral Granger causality (sGC) of entrained gamma rhythms between different luminance intensities, colors, and flickering frequencies of FLSs. ERS entrained by 700 cd/m2 FLS and 32 Hz or 34 Hz FLSs was stronger than that entrained by 400 cd/m2 at Pz (p < 0.01) and 38 Hz or 40 Hz FLSs, respectively, at both Pz (p < 0.05) and Fz (p < 0.01). Parieto-occipital-to-frontotemporal connectivities of gamma rhythm entrained by 700 cd/m2 FLS and 32 Hz or 34 Hz FLSs were also stronger than those entrained by 400 cd/m2 at Pz (p < 0.01) and 38 Hz or 40 Hz FLSs, respectively (p < 0.001). ERS and parieto-occipital-to-frontotemporal connectivities of entrained gamma rhythms did not show significant difference between white and red lights. Adverse effects were comparable between different parameters. In older adults, 700 cd/m2 FLS at 32 Hz or 34 Hz can entrain a strong gamma rhythm in the whole brain with tolerable adverse effects.

Effect of Gamma Irradiation on the Structural, Optical, Electrical, and Ferroelectric Characterizations of Bismuth-Modified Barium Titanate Ceramics.

Materials with ferroelectric properties, low bandgap energies, high polarization, low loss, and thermal stability are essential for future solar-cell applications. Researchers have attempted to obtain such materials by using several approaches. In this vein, a novel approach is reported in this work using gamma ray irradiation. The effect of gamma radiation on the structural, optical, and ferroelectric characterizations of bismuth (Bi)-doped barium titanate (BaTiO3 (BT)), namely Ba0.95Bi0.05TiO3 ceramics (abbreviated as (Bi:BT)), was investigated. X-ray diffraction, structure refinement, and Raman study revealed the presence of a perovskite structure with a tetragonal phase in all investigated samples. Morphological study revealed a nonuniform grain size and some porosity. Gamma irradiation-induced combined effects were proved by a detailed analysis of bond lengths, bond angles, octahedral distortions, oxygen vacancies, and charge compensations. Electron paramagnetic resonance (EPR) study gave direct evidence of oxygen vacancies in the irradiated samples. After gamma irradiation, UV–vis study indicated a decrease in the bandgap from 3.14 to 2.80 eV and a significant increase in visible light absorption. Cole–Cole plots confirm as an increase in gamma-ray dose results in higher levels of electron hopping. Study of the P–E hysteresis loop demonstrated that ferroelectric properties could be maintained after gamma irradiation, with a slight decrease in remnant polarization. The behaviour of the P–E was correlated with increasing gamma dose in the investigated ceramics, demonstrating a strong gamma dependence in the loops’ profile. We guess that the present approach may be a promising technique for enhancing the multifunctionality of electronic devices.

Gamma oscillations in primate primary visual cortex are severely attenuated by small stimulus discontinuities.

Gamma oscillations (30 to 80 Hz) have been hypothesized to play an important role in feature binding, based on the observation that continuous long bars induce stronger gamma in the visual cortex than bars with a small gap. Recently, many studies have shown that natural images, which have discontinuities in several low-level features, do not induce strong gamma oscillations, questioning their role in feature binding. However, the effect of different discontinuities on gamma has not been well studied. To address this, we recorded spikes and local field potential from 2 monkeys while they were shown gratings with discontinuities in 4 attributes: space, orientation, phase, or contrast. We found that while these discontinuities only had a modest effect on spiking activity, gamma power drastically reduced in all cases, suggesting that gamma could be a resonant phenomenon. An excitatory-inhibitory population model with stimulus-tuned recurrent inputs showed such resonant properties. Therefore, gamma could be a signature of excitation-inhibition balance, which gets disrupted due to discontinuities.