Journal articles on the topic 'Position-position auto-correlation function'

Abstract The spot auto-focusing (AF) method with a unique high-definition auto-correlation function (HD-ACF) proposed in the previous paper is improved and is now applicable to general specimens at a wide range of magnifications. According to the definition where the AF is defocused to obtain the highest resolution, the proposed method achieves the sharpest HD-ACF profile in the AF spot image. The relationship where the sharpest HD-ACF profile gives the highest resolution is theoretically explained, and practical AF examples for different specimens and magnifications are experimentally demonstrated. Specimens include a yeast cell thin section at 10-k magnification, a standard grating replica used as a ruler at 50-k, a crystal lattice of graphitized carbon at 400-k and a 60°-tilted thin section (yeast cell) at 10-k. Different procedures are prepared to actively identify the defocus position that gives the sharpest HD-ACF profile. Every AF result demonstrates the highest-resolution image.

This paper reviews the basis of the beamformer and polar correlation phased array methods and shows that these provide different information about axially distributed, non-compact noise sources, which nevertheless satisfy a simple integral relationship. The conventional beamformer method provides an image of the source power or auto spectral density, whereas the polar correlation method yields a ‘source strength’ which is an image of the axial wavenumber transform of the source cross-spectral density. However, the beamformer method can be generalised to provide an image of the source cross-spectral density. At first sight, the generalised beamformer method is therefore more useful for diagnostic purposes but the results presented here suggest that the combined effects of resolution and source convection place serious limitations on the source cross-spectral density image information. For the same reasons, although the source power or auto spectral density axial shape can be obtained with the conventional beamformer method, it cannot yield its absolute level for this type of source. The polar correlation method yields a source strength axial distribution at each ‘reference’ microphone, which when integrated over the source length, yields the far-field power or auto spectral density at that reference microphone. Therefore, the polar correlation source strength is arguably the more relevant quantity to measure when determining what proportion of the sound at a particular microphone position comes from each region of the jet axis, as a function of radiation angle.

We present a measurement of baryon acoustic oscillations (BAO) in the cross-correlation of quasars with the Lyα-forest flux transmission at a mean redshift of z = 2.40. The measurement uses the complete Sloan Digital Sky Survey (SDSS-III) data sample: 168 889 forests and 234 367 quasars from the SDSS data release DR12. In addition to the statistical improvement on our previous study using DR11, we have implemented numerous improvements at the analysis level enabling a more accurate measurement of this cross-correlation. We have also developed the first simulations of the cross-correlation that allow us to test different aspects of our data analysis and to search for potential systematic errors in the determination of the BAO peak position. We measure the two ratios DH(z = 2.40) /rd = 9.01 ± 0.36 and DM(z = 2.40) /rd = 35.7 ± 1.7, where the errors include marginalization over the non-linear velocity of quasars and the cross-correlation of metals and quasars, among other effects. These results are within 1.8σ of the prediction of the flat-ΛCDM model describing the observed cosmic microwave background anisotropies. We combine this study with the Lyα-forest auto-correlation function, yielding DH(z = 2.40) /rd = 8.94 ± 0.22 and DM(z = 2.40) /rd = 36.6 ± 1.2, within 2.3σ of the same flat-ΛCDM model.

In this paper, a novel computationally affordable method to generate long binary sequences featuring desired properties is presented, based on the use of a number of shorter non linear binary sub-sequences. The paper shows the relationship of the Auto- and Cross-Correlation (AC, CC) ofthe generated long binary sequences with the AC and CC ofconstituent sub-sequences. It is also shown that the starting bit position of sub-sequences has an important role on AC and CC of the generated sequences. To generate the optimal long binary sequence from correlation points of view, Particle Swarm Optimization (PSO) algorithm is employed. All the techniques stated in the literature to improve the PSO are implemented and it is clearly shown that the constriction factor and the variable population size turn out to have a great impact on minimizing the fitness function (RMS of AC) representing the target Correlationproperties expected for the resulting long sequence. Possible application scenarios for the long sequences generated by the proposed method are also discussed and evaluated.

The fractal and multifractal theory have provided new approaches for radar signal processing and target-detecting under the background of ocean. However, the related research mainly focuses on fractal dimension or multifractal spectrum (MFS) of sea clutter. In this paper, a new dynamic singularity analysis method of sea clutter using MFS distribution is developed, based on moving detrending analysis (DMA-MFSD). Theoretically, we introduce the time information by using cyclic auto-correlation of sea clutter. For transient correlation series, the instantaneous singularity spectrum based on multifractal detrending moving analysis (MF-DMA) algorithm is calculated, and the dynamic singularity spectrum distribution of sea clutter is acquired. In addition, we analyze the time-varying singularity exponent ranges and maximum position function in DMA-MFSD of sea clutter. For the real sea clutter data, we analyze the dynamic singularity spectrum distribution of real sea clutter in level III sea state, and conclude that the radar sea clutter has the non-stationary and time-varying scale characteristic and represents the time-varying singularity spectrum distribution based on the proposed DMA-MFSD method. The DMA-MFSD will also provide reference for nonlinear dynamics and multifractal signal processing.

ABSTRACT Several phenomena in astrophysics generate light curves with time delays. Among these are reverberation mapping and lensed quasars. In these systems, the measurement of the time delay is complicated by the fact that the delayed components are unresolved and that the light curves are generated from a stochastic process. We derive the likelihood function of the observations given a model of either a combination of time-delayed light curves or a single light curve. This likelihood function is different from the auto-correlation-function-based investigated by previous studies. We demonstrate that given a single-band light curve that is a linear combination of two (or more) time-shifted copies of an original light curve, generated from a probability distribution with some roughly known power spectrum, it is possible to test if the total-flux light curve is a composition of time-delayed copies or, alternatively, is consistent with being a single copy of the original light curve. Furthermore, it is possible to measure the time delays between these components even when the flux ratio is about 1/10. In the era of synoptic sky surveys, this method is useful for identifying lensed quasars and simultaneously measuring their time delays, and also for estimating the reverberation time scales of active galactic nuclei. In a companion paper, we derive another method that uses the centre-of-light astrometric position (e.g. of a lensed quasar) along with the combined flux. We also present the proper likelihood function for fitting a power-law model to a power spectrum. We test the new method on simulations and provide python and matlab implementations.

Abstract Motivation Mitochondria are an essential organelle in most eukaryotes. They not only play an important role in energy metabolism but also take part in many critical cytopathological processes. Abnormal mitochondria can trigger a series of human diseases, such as Parkinson's disease, multifactor disorder and Type-II diabetes. Protein submitochondrial localization enables the understanding of protein function in studying disease pathogenesis and drug design. Results We proposed a new method, SubMito-XGBoost, for protein submitochondrial localization prediction. Three steps are included: (i) the g-gap dipeptide composition (g-gap DC), pseudo-amino acid composition (PseAAC), auto-correlation function (ACF) and Bi-gram position-specific scoring matrix (Bi-gram PSSM) are employed to extract protein sequence features, (ii) Synthetic Minority Oversampling Technique (SMOTE) is used to balance samples, and the ReliefF algorithm is applied for feature selection and (iii) the obtained feature vectors are fed into XGBoost to predict protein submitochondrial locations. SubMito-XGBoost has obtained satisfactory prediction results by the leave-one-out-cross-validation (LOOCV) compared with existing methods. The prediction accuracies of the SubMito-XGBoost method on the two training datasets M317 and M983 were 97.7% and 98.9%, which are 2.8–12.5% and 3.8–9.9% higher than other methods, respectively. The prediction accuracy of the independent test set M495 was 94.8%, which is significantly better than the existing studies. The proposed method also achieves satisfactory predictive performance on plant and non-plant protein submitochondrial datasets. SubMito-XGBoost also plays an important role in new drug design for the treatment of related diseases. Availability and implementation The source codes and data are publicly available at https://github.com/QUST-AIBBDRC/SubMito-XGBoost/. Supplementary information Supplementary data are available at Bioinformatics online.

This paper presents the development of an active vibration control for vibration suppression of the horizontal flexible plate structure using proportional–integral–derivative controller tuned by a conventional method via Ziegler–Nichols and an intelligent method known as particle swarm optimization algorithm. Initially, the experimental rig was designed and fabricated with all edges clamped at the horizontal position of the flexible plate. Data acquisition and instrumentation systems were designed and integrated into the experimental rig to collect input–output vibration data of the flexible plate. The vibration data obtained through experimental study was used to model the system using system identification technique based on auto-regressive with exogenous input structure. The plate system was modeled using particle swarm optimization algorithm and validated using mean squared error, one-step ahead prediction, and correlation tests. The stability of the model was assessed using pole zero diagram stability. The fitness function of particle swarm optimization algorithm is defined as the mean squared error between the measured and estimated output of the horizontal flexible plate system. Next, the developed model was used in the development of an active vibration control for vibration suppression on the horizontal flexible plate system using a proportional–integral–derivative controller. The proportional–integral–derivative gains are optimally determined using two different ways, the conventional method tuned by Ziegler–Nichols tuning rules and the intelligent method tuned by particle swarm optimization algorithm. The performances of developed controllers were assessed and validated. Proportional–integral–derivative-particle swarm optimization controller achieved the highest attenuation value for first mode of vibration by achieving 47.28 dB attenuation as compared to proportional–integral–derivative-Ziegler–Nichols controller which only achieved 34.21 dB attenuation.

Abstract The dominant gain-of-function mutation in the tyrosine kinase JAK2 (1849 G to T) has been detected in over 80% PV patients and in approximately half of ET or PMF patients. The mutation results in a non-synonymous amino acid substitution at position 617 (valine to phenylalanine) in the JH2 pseudo-kinase auto-inhibitory domain. Current models predict that expression of mutant JAK2V617F in patient hematopoietic stem cells leads to activation of signaling pathways important for proliferation and survival. Furthermore, experimental evidence using murine models, in which JAK2V617F is retrovirally over-expressed, display a phenotype that closely resembles PV, including progression to myelofibrosis. Previous reports have indicated that “in vitro” expansion of PV progenitors favors erythroid precursors with decreased JAK2V617F mutational burden (Exp. Hematol. (2007) 35(4): 587–95). Investigators in these studies, however, did not report changes in JAK2V617F frequency in sorted live erythroid progenitors after “in vitro” expansion. Furthermore, CD34+cells from PV patients cultured in the presence of 20% serum indicated an inverse relationship between JAK2V617F frequency and Epo dose (Blood (2006) 108(9):3128–34). However, these reports failed to correlate Epo dose, and JAK2V617F frequency, with live “in vitro” expanded purified erythroid progenitor cells. Using our published procedure (Exp. Hematol. (2007) 35(4): 587–95), we expanded erythroid progenitors from healthy volunteers and JAK2V617F positive PV patients (mutational burden ranging from 20–90%) in serum-free media supplemented with SCF, Tpo, and Flt3L (100 ng/mL each - week 1) followed by SCF (50 ng/mL), IGF1 (50 ng/mL), and Epo (0, 0.003, 0.03, 0.3, and 3 Units/mL - week 2). Progression of progenitor expansion, erythroid lineage commitment, live/dead cells, and JAK2 mutation frequency was followed by flow cytometry and real-time PCR. At the end of week 2, cells were harvested, stained with anti-CD71 (transferrin receptor), anti-CD235A (glycophorin A), and the Aqua Live/Dead cell reagent. Stained cells were fixed in 2% paraformaldehyde, analyzed, and sorted on a FACSAria flow cytometer. Live, expanded progenitor cells were sorted into CD235A positive and negative populations, and subsequently used for estimation of JAK2 frequency by quantitative real-time PCR (Exp. Hematol. (2007) 35(1): 32–38). Our results indicate expansion and erythroid commitment of PV progenitor cells in the absence of Epo correlates with the patients’ intrinsic JAK2V617F burden. Furthermore, irrespective of JAK2V617F frequency in purified peripheral blood granulocytes, an inverse correlation between Epo dose and mutation frequency in “in vitro” expanded purified erythroid progenitors was not observed in all patients examined.

A method to refine organic crystal structures from powder diffraction data with incorrect lattice parameters has been developed. The method is based on the similarity measure developed by de Gelderet al.[J. Comput. Chem.(2001),22, 273–289], using the cross- and auto-correlation functions of a simulated and an experimental powder pattern. The lattice parameters, molecular position, molecular orientation and selected intramolecular degrees of freedom are optimized until the similarity measure reaches a maximum; subsequently, a Rietveld refinement is carried out. The programFIDEL(FIt with DEviating Lattice parameters) implements this method. The procedure is also suitable for unindexed powder data, powder diagrams of very low quality and powder diagrams of non-phase-pure samples. Various applications are shown, including structure determinations from powder data using crystal structure predictions by standard force-field methods. Other useful applications include the automatic structure determination from powder data starting from the crystal structures of isostructural compounds (e.g.a solvate, hydrate or chemical derivative), or from crystal data measured at a different temperature or pressure.

Wavelet neural networks (WNN) combine the functions of time–frequency localization from the wavelet transform and of self-studying from the neural network, which make them particularly suitable for the classification of complex patterns. Based on auto-regressive (AR) model and WNN, pattern recognition of prothesis movements was studied in this paper. Firstly, an AR model was used to analysis the surface myoelectric signals (SMES) which recorded on the ulnar flexor carpi and extensor carpi region of the right hand in resting position. Four types of prosthesis movements are recognized by extracting four-order AR coefficient and construct them as eigenvector into WNN, which was used to study the correlation between SMES and wristwork. This paper compares the classification accuracy of four movements such as hand open (HO), hand close (HC), forearm intorsion (FI) and forearm extorsion (FE).The experimental results show that the proposed method can classify correctly for at least 93.75% of the test data.

Trajectories of endosomes inside living eukaryotic cells are highly heterogeneous in space and time and diffuse anomalously due to a combination of viscoelasticity, caging, aggregation and active transport. Some of the trajectories display switching between persistent and anti-persistent motion, while others jiggle around in one position for the whole measurement time. By splitting the ensemble of endosome trajectories into slow moving subdiffusive and fast moving superdiffusive endosomes, we analyzed them separately. The mean squared displacements and velocity auto-correlation functions confirm the effectiveness of the splitting methods. Applying the local analysis, we show that both ensembles are characterized by a spectrum of local anomalous exponents and local generalized diffusion coefficients. Slow and fast endosomes have exponential distributions of local anomalous exponents and power law distributions of generalized diffusion coefficients. This suggests that heterogeneous fractional Brownian motion is an appropriate model for both fast and slow moving endosomes. This article is part of a Special Issue entitled: “Recent Advances In Single-Particle Tracking: Experiment and Analysis” edited by Janusz Szwabiński and Aleksander Weron.

We derive the non-adiabatic ring polymer molecular dynamics (RPMD) approach in the phase space of the SU(N) Lie Group. This method, which we refer to as the spin mapping non-adiabatic RPMD (SM-NRPMD), is based on the spin-mapping formalism for the electronic degrees of freedom (DOFs) and ring polymer path- integral description for the nuclear DOFs. Using the Stratonovich-Weyl transform for the electronic DOFs, and the Wigner transform for the nuclear DOFs, we derived an exact expression of the Kubo-transformed time-correlation function (TCF). We further derive the spin mapping non-adiabatic Matsubara dynamics using the Matsubara approximation that removes the high frequency nuclear normal modes in the TCF and derive the SM-NRPMD approach from the non-adiabatic Matsubara dynamics by discarding the imaginary part of the Liouvillian. The SM-NRPMD method has numerical advantages compared to the original NRPMD method based on the MMST mapping formalism, due to a more natural mapping using the SU(N) Lie Group that preserves the symmetry of the original system. We numerically compute the Kubo-transformed position auto-correlation function and electronic population correlation function for three-state model systems. The numerical results demonstrate the accuracy of the SM-NRPMD method, which outperforms the original MMST-based NRPMD. We envision that the SM-NRPMD method will be a powerful approach to simulate electronic non-adiabatic dynamics and nuclear quantum effects accurately.

Abstract Using synthetic Lyman-α forests from the Dark Energy Spectroscopic Instrument (DESI) survey, we present a study of the impact of errors in the estimation of quasar redshift on the Lyman-α correlation functions. Estimates of quasar redshift have large uncertainties of a few hundred km s−1 due to the broadness of the emission lines and the intrinsic shifts from other emission lines. We inject Gaussian random redshift errors into the mock quasar catalogues, and measure the auto-correlation and the Lyman-α-quasar cross-correlation functions. We find a smearing of the BAO feature in the radial direction, but changes in the peak position are negligible. However, we see a significant unphysical correlation for small separations transverse to the line of sight which increases with the amplitude of the redshift errors. We interpret this contamination as a result of the broadening of emission lines in the measured mean continuum, caused by quasar redshift errors, combined with the unrealistically strong clustering of the simulated quasars on small scales.

Introduction: Game Culture and GenderAs texts with the potential to help mediate specific forms of identity, video games are rich and complex sites for analysis. A tendency, however, still exists in scholarship to treat video games as just another kind of text, and work that explores the expression of masculine identity persists in drawing from cinematic analysis without proper consideration of game design and how these games are played (Triana). For example, insights from studies into horror cinema may illuminate the relationship between players and game systems in survival horror video games (Habel & Kooyman), but further study is needed to explore how people interact with the game.This article aims to build towards a scholarly definition of the term “Power Fantasy”, a concept that seems well established in wider discourse but is not yet well theorised in the scholarly literature. It does so through a case of the most recent reboot of Doom (2016), a game that in its original incarnation established an enduring tradition for high-action Power Fantasy. In the first-person shooter game Doom, the player fills the role of the “Doom Guy”, a faceless hero who shuttles between Earth and Hell with the sole aim of eviscerating demonic hordes as graphically as possible.How, then, do we begin to theorise the kind of automediation that an iconic game text like Doom facilitates? Substantial work has been done to explore player identification in online games (see Taylor; Yee). Shaw (“Rethinking”) suggests that single-player games are unexplored territory compared to the more social spaces of Massively Multiplayer Online games and other multiplayer experiences, but it is important to distinguish between direct identification with the avatar per se and the ways in which the game text mediates broader gender constructions.Abstract theorisation is not enough, though. To effectively understand this kind of automediation we also need a methodology to gain insights into its processes. The final part of this article, therefore, proposes the analysis of “Let’s Play” videos as a kind of gender identity performance which gives insight into the automediation of dominant masculine gender identities through Power Fantasy video games like Doom. This reflexive performance works to denaturalise gender construction rather than reinforce stable hegemonic identities.Power Fantasy and Gender IdentityPower Fantasy has become an established trope in online critiques and discussions of popular culture. It can be simply defined as “character imagines himself taking revenge on his bullies” (TVTropes). This trope takes on special resonance in video games, where the players themselves live out the violent revenge fantasy in the world of the game.The “power fantasy” of games implies escapism and meaninglessness, evoking outsize explosions and equally outsized displays of dominance. A “power gamer” is one who plays with a single-minded determination to win, at the expense of nuance, social relationships between players, or even their own pleasure in play. (Baker)Many examples apply this concept of Power Fantasy in video games: from God of War to Metroid: Prime and Grand Theft Auto, this prevalent trope of game design uses a kind of “agency mechanics” (Habel & Kooyman) to convince the player that they are becoming increasingly skilful in the game, when in reality the game is simply decreasing in difficulty (PBS Digital Studios). The operation of the Power Fantasy trope is also gendered; in a related trope known as “I Just Want To Be a Badass”, “males are somewhat more prone to harbour [the] wish” to feel powerful (TVTropes). More broadly, even though the game world is obviously not real, playing it requires “an investment in and commitment to a type of masculine performance that is based on the Real (particularly if one is interested in ‘winning’, pummelling your opponent, kicking ass, etc.)” (Burrill 2).Indeed, there is a perceived correlation (if not causation) between the widespread presence of Power Fantasy video games and how “game culture as it stands is shot through with sexism, racism, homophobia, and other biases” (Baker). Golding and van Deventer undertake an extended exploration of this disconcerting side of game culture, concluding that games have “become a venue for some of the more unsophisticated forms of patriarchy” (213) evidenced in the highly-publicised GamerGate movement. This saw an alignment between the label of “gamer” and extreme misogyny, abuse and harassment of women and other minorities in the industry.We have, then, a tentative connection between dominant gameplay forms based on high skill that may be loosely characterised as “Power Fantasy” and some of the most virulent toxic gender expressions seen in recent times. More research is needed to gain a clearer understanding of precisely what Power Fantasy is. Baker’s primary argument is that “power” in games can also be characterised as “power to” or “power with”, as well as the more traditional “power over”. Kurt Squire uses the phrase “Power Fantasy” as a castaway framing for a player who seeks an alternative reward to the usual game progression in Sid Meier’s Civilisation. More broadly, much scholarly work concerning gameplay design and gender identity has been focussed on the hot-button question of videogame violence and its connection to real-world violence, a question that this article avoids since it is well covered elsewhere. Here, a better understanding of the mediation of gender identity through Power Fantasy in Doom can help to illuminate how games function as automedia.Auto-Mediating Gender through Performance in Doom (2016) As a franchise, Doom commands near-incomparable respect as a seminal text of the first-person shooter genre. First released in 1993, it set the benchmark for 3D rendered graphics, energetic sound design, and high-paced action gameplay that was visceral and deeply immersive. It is impossible to mention more recent reboots without recourse to its first seminal instalment and related game texts: Kim Justice suggests a personal identification with it in a 29-minute video analysis entitled “A Personal History of Demon Slaughter”. Doom is a cherished game for many players, possibly because it evokes memories of “boyhood” gaming and all its attendant gender identity formation (Burrill).This identification also arises in livestreams and playthroughs of the game. YouTuber and game reviewer Markiplier describes nostalgically and at lengths his formative experiences playing it (and recounts a telling connection with his father who, he explains, introduced him to gaming), saying “Doom is very important to me […] this was the first game that I sat down and played over and over and over again.” In contrast, Wanderbots confesses that he has never really played Doom, but acknowledges its prominent position in the gaming community by designating himself outside the identifying category of “Doom fan”. He states that he has started playing due to “gushing” recommendations from other gamers. The nostalgic personal connection is important, even in absentia.For the most part, the critical and community response to the 2016 version of Doom was approving: Gilroy admits that it “hit all the right power chords”, raising the signature trope in reference to both gameplay and music (a power chord is a particular technique of playing heavy metal guitar often used in heavy metal music). Doom’s Metacritic score is currently a respectable 85, and, the reception is remarkably consistent between critics and players, especially for such a potentially divisive game (Metacritic). Commentators tend to cite its focus on its high action, mobility, immersion, sound design, and general faithfulness to the spirit of the original Doom as reasons for assessments such as “favourite game ever” (Habel). Game critic Yahtzee’s uncharacteristically approving video review in the iconic Zero Punctuation series is very telling in its assessment of the game’s light narrative framing:Doom seems to have a firm understanding of its audience because, while there is a plot going on, the player-character couldn’t give a half an ounce of deep fried shit; if you want to know the plot then pause the game and read all the fluff text in the character and location database, sipping daintily from your pink teacup full of pussy juice, while the game waits patiently for you to strap your bollocks back on and get back in the fray. (Yahtzee)This is a strident expression of the gendered expectations and response to Doom’s narratological refusal, which is here cast as approvingly masculine and opposed to a “feminine” desire for plot or narrative. It also feeds into a discourse which sees the game as one which demands skill, commitment, and an achievement orientation cast within an exclusivist ideology of “toxic meritocracy” (Paul).In addition to examining reception, approaches to understanding how Doom functions as a “Power Fantasy” or “badass” trope could take a variety of forms. It is tempting to undertake a detailed analysis of its design and gameplay, especially since these feed directly into considerations of player interaction. This could direct a critical focus towards gameplay design elements such as traversal and mobility, difficulty settings, “glory kills”, and cinematic techniques in the same vein as Habel and Kooyman’s analysis of survival horror video games in relation to horror cinema. However, Golding and van Deventer warn against a simplistic analysis of decontextualized gameplay (29-30), and there is a much more intriguing possibility hinted at by Harper’s notion of “Play Practice”.It is useful to analyse a theoretical engagement with a video game as a thought-experiment. But with the rise of gaming as spectacle, and particularly gaming as performance through “Let’s Play” livestreams (or video on demand) on platforms such as TwitchTV and YouTube, it becomes possible to analyse embodied performances of the gameplay of such video games. This kind of analysis allows the opportunity for a more nuanced understanding of how such games mediate gender identities. For Judith Butler, gender is not only performed, it is also performative:Because there is neither an “essence” that gender expresses or externalizes nor an objective ideal to which gender aspires, and because gender is not a fact, the various acts of gender create the idea of gender, and without those acts, there would be no gender at all. (214)Let’s Play videos—that show a player playing a game in real time with their commentary overlaying the on screen action—allow us to see the performative aspects of gameplay. Let’s Plays are a highly popular and developing form: they are not simple artefacts by any means, and can be understood as expressive works in their own right (Lee). They are complex and multifaceted, and while they do not necessarily provide direct insights into the player’s perception of their own identification, with sufficient analysis and unpacking they help us to explore both the construction and denaturalisation of gender identity. In this case, we follow Josef Nguyen’s analysis of Let’s Plays as essential for expression of player identity through performance, but instead focus on how some identity construction may narrow rather than expand the diversity range. T.L. Taylor also has a monograph forthcoming in 2018 titled Watch Me Play: Twitch and the Rise of Game Live Streaming, suggesting the time is ripe for such analysis.These performances are clear in ways we have already discussed: for example, both SplatterCat and Markiplier devote significant time to describing their formative experiences playing Doom as a background to their gameplay performance, while Wanderbots is more distanced. There is no doubt that these videos are popular: Markiplier, for example, has attracted nearly 5 million views of his Doom playthrough. If we see gameplay as automediation, though, these videos become useful artefacts for analysis of gendered performance through gameplay.When SplatterCat discovers the suit of armor for the game’s protagonist, Doom Guy, he half-jokingly remarks “let us be all of the Doom Guy that we can possibly be” (3:20). This is an aspirational mantra, a desire for enacting the game’s Power Fantasy. Markiplier speaks at length about his nostalgia for the game, specifically about how his father introduced him to Doom when he was a child, and he expresses hopes that he will again experience “Doom’s original super-fast pace and just pure unadulterated action; Doom Guy is a badass” (4:59). As the action picks up early into the game, Markiplier expresses the exhilaration and adrenaline that accompany performances of this fastpaced, highly mobile kind of gameplay, implying that he is becoming immersed in the character and, by performing Doom Guy, inhabiting the “badass” role and thus enacting a performance of Power Fantasy:Doom guy—and I hope I’m playing Doom guy himself—is just the embodiment of kickass. He destroys everything and he doesn’t give a fuck about what he breaks in the process. (8:45)This performance of gender through the skilled control of Doom Guy is, initially, unambiguously mediated as Power Fantasy: in control, highly skilled, suffused with Paul’s ‘toxic meritocracy. A similar sentiment is expressed in Wanderbots’ playthrough when the player-character dispenses with narrative/conversation by smashing a computer terminal: “Oh I like this guy already! Alright. Doom Guy does not give a shit. It’s like Wolf Blascowicz [sic], but like, plus plus” (Wanderbots). This is a reference to another iconic first-person shooter franchise, Wolfenstein, which also originated in the 1980s and has experienced a recent successful reboot, and which operates in a similar Power Fantasy mode. This close alignment between these two streamers’ performances suggests significant coherence in both genre and gameplay design and the ways in which players engage with the game as a gendered performative space.Nonetheless, there is no simple one-to-one relationship here—there is not enough evidence to argue that this kind of gameplay experience leads directly to the kind of untrammelled misogyny we see in game culture more broadly. While Gabbiadini et al. found evidence in an experimental study that a masculinist ideology combined with violent video game mechanics could lead to a lack of empathy for women and girls who are victims of violence, Ferguson and Donnellan dispute this finding based on poor methodology, arguing that there is no evidence for a causal relationship between gender, game type and lack of empathy for women and girls. This inconclusiveness in the research is mirrored by an ambiguity in the gendered performance of males playing through Doom, where the Power Fantasy is profoundly undercut in multiple ways.Wanderbots’ Doom playthrough is literally titled ‘I have no idea what I’m Dooming’ and he struggles with particular mechanics and relatively simple progression tools early in the game: this reads against masculinist stereotypes of superior and naturalised gameplay skill. Markiplier’s performance of the “badass” Doom Guy is undercut at various stages: in encountering the iconic challenge of the game, he mentions that “I am halfway decent… not that good at video games” (9:58), and on the verge of the protagonist’s death he admits “If I die this early into my first video I’m going to be very disappointed, so I’m going to have to kick it up a notch” (15:30). This suggests that rather than being an unproblematic and simple expression of male power in a fantasy video game world, the gameplay performances of Power Fantasy games are ambiguous and contested, and not always successfully performed via the avatar. They therefore demonstrate a “kind of gender performance [which] will enact and reveal the performativity of gender itself in a way that destabilizes the naturalized categories of identity and desire” (Butler 211). This cuts across the empowered performance of videogame mastery and physical dominance over the game world, and suggests that the automediation of gender identity through playing video games is a complex phenomenon urgently in need of further theorisation.ConclusionUltimately, this kind of analysis of the mediation of hegemonic gender identities is urgent for a cultural product as ubiquitous as video games. The hyper-empowered “badass” digital avatars of Power Fantasy video games can be expected to have some shaping effect on the identities of those who play them, evidenced by the gendered gameplay performance of Doom briefly explored here. This is by no means a simple or unproblematic process, though. Much further research is needed to test the methodological insights possible by using video performances of gameplay as explorations of the auto-mediation of gender identities through video games.ReferencesBaker, Meguey. “Problematizing Power Fantasy.” The Enemy 1.2 (2015). 18 Feb. 2018 <http://theenemyreader.org/problematizing-power-fantasy/>.Burrill, Derrick. Die Tryin’: Video Games, Masculinity, Culture. New York: Peter Lang, 2008.Butler, Judith. Gender Trouble. 10th ed. London: Routledge, 2002.Ferguson, Christopher, and Brent Donellan. “Are Associations between “Sexist” Video Games and Decreased Empathy toward Women Robust? A Reanalysis of Gabbiadini et al. 2016.” Journal of Youth and Adolescence 46.12 (2017): 2446–2459.Gabbiadini, Alessandro, Paolo Riva, Luca Andrighetto, Chiara Volpato, and Brad J. 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