Unpredictable Sequence Research Articles

Design And Analysis of Analog TRNG Using Sample and Hold Circuit

Implementation of analog True random number generators is inevitable in almost all the security applications and encryption protocols nowadays. Although many digital True Random Number Generators are available, we proposed a method of random number generation using analog module of mixed signals. In actual fact generation of True Random Numbers is by utilizing the sample and hold circuit which is controlled by another random clock source, and a post processing circuit for generation of unpredictable binary sequence of numbers. The primary input source is an analog signal, essentially highly random noise from the external environment. The high unpredictability, less resource and simple circuit design are some highlights of the proposed work. Finally, the randomness is evaluated using NIST test suites and results are plotted and analyzed.

Battle of the Mondrians: Investigating the Role of Unpredictability in Continuous Flash Suppression.

In continuous flash suppression (CFS), a dynamic sequence of Mondrian patterns presented to one eye suppresses a static target in the other eye for several seconds at a time. Its effectiveness has been linked to low-level properties such as spatial frequency and orientation, but the role of higher order influences remains unstudied. Here, using a tracking paradigm, we asked if the spatial and temporal predictability of the Mondrian sequence affects CFS dynamics. Predictable temporal sequences were regularly updated every 100 ms or modulated sinusoidally in pixel luminance at 2 Hz. Unpredictable temporal sequences were irregularly updated or had stochastic pixel luminance changes across time. To vary spatial predictability, sequences were either updated with different Mondrian patterns or had a fixed spatial pattern. We found a modest effect of spatial uncertainty when the target modulation was low (0.125 Hz) but not temporal uncertainty, which had no significant effects regardless of target modulation. Similar results were obtained when we pitted the standard Mondrian sequence against sequences with a fixed spatial pattern and temporally low-pass filtered sequences in a binocular rivalry paradigm. Thus, not only was the effect of information predictability was modest and spatial, but it was also dependent on the presence of higher temporal frequencies. Together, the results demonstrate the significance of low-level properties in affecting CFS dynamics and the possible involvement of pattern structure masking in CFS.

Three different motor task strategies to assess neuromuscular adjustments during fatiguing muscle contractions in young and older men.

Healthy aging is associated with a marked decline in motor performance. The functional consequences of applying varying novel or unexpected motor stimuli during intermittent isometric prolonged (fatiguing) motor tasks for lower limb neuromuscular fatigability and steadiness, perception of effort, and blood markers of stress in healthy aged men compared with young men have not been investigated. The participants in this study were 15 young men (aged 22 ± 4years) and 10 older men (aged 67 ± 6years). They performed 100 intermittent isometric knee extensions under three experimental conditions involving intermittent isometric contraction tasks according to constant, predictable, and unpredictable torque target sequences. The variability in maximal voluntary contraction averaged 50%, and was 25, 50, and 75% for the three strategies. All included a 5-s contraction and 20-s rest. The main variables were measured before exercise, after 100 repetitions, and 1h after exercise. In all experimental trials, the decreases in the maximal voluntary contraction and central activation ratio, and the increases in effort sensation and muscle temperature, were smaller in older men than in younger men. The coefficient of variation during the motor performance did not differ between age groups. However, in all three strategies, the dopamine concentration was significantly higher in older than in younger men. The prolactin concentration did not differ significantly between age groups or conditions, although its decrease during loading correlated negatively with the central activation ratio.

Non-autonomous equations with unpredictable solutions

To make research of chaos more amenable to investigating differential and discrete equations, we introduce the concepts of an unpredictable function and sequence. The topology of uniform convergence on compact sets is applied to define unpredictable functions [1,2]. The unpredictable sequence is defined as a specific unpredictable function on the set of integers. The definitions are convenient to be verified as solutions of differential and discrete equations. The topology is metrizable and easy for applications with integral operators. To demonstrate the effectiveness of the approach, the existence and uniqueness of the unpredictable solution for a delay differential equation are proved as well as for quasilinear discrete systems. As a corollary of the theorem, a similar assertion for a quasilinear ordinary differential equation is formulated. The results are demonstrated numerically, and an application to Hopfield neural networks is provided. In particular, Poincaré chaos near periodic orbits is observed. The completed research contributes to the theory of chaos as well as to the theory of differential and discrete equations, considering unpredictable solutions.

On the Nth linear complexity of automatic sequences

The Nth linear complexity of a sequence is a measure of predictability. Any unpredictable sequence must have large Nth linear complexity. However, in this paper we show that for q-automatic sequences over Fq the converse is not true.We prove that any (not ultimately periodic) q-automatic sequence over Fq has Nth linear complexity of order of magnitude N. For some famous sequences including the Thue–Morse and Rudin–Shapiro sequence we determine the exact values of their Nth linear complexities. These are non-trivial examples of predictable sequences with Nth linear complexity of largest possible order of magnitude.

Hyper-chaotic Feeded GA (HFGA): a reversible optimization technique for robust and sensitive image encryption

In recent years, due to their straightforward structure and efficiency, the chaos-based cryptographic algorithms have become a good candidate for image encryption. However, they still suffer from many weaknesses, such as insensitivity to the plain image, weak key streams, small key space, non-resistance to some attacks and failure to meet some security criteria. For this purpose in this paper, a novel hybrid image encryption algorithm named Hyper-chaotic Feeded GA (HFGA) is proposed to fill the gaps in two stages; initial encryption by using a hyper-chaotic system, and then outputs reinforcement by employing a customized Genetic Algorithm (GA). By applying an innovative technique, called gene-labelling, the proposed algorithm not only optimizes the preliminary encrypted images in terms of security criteria but also allows the legal receiver to easily and securely decrypt the optimized cipher image. In fact, in the first stage, besides unpredictable random sequences generated by a hyper-chaotic system, a new sensitive diffusion function is proposed which makes the algorithm resistant to differential attacks. In the second stage, the generated cipher images, which are labeled in a special way, will be used as the initial population of a GA which enhances randomness of the cipher images. The results of several experiments and statistical analysis show that the proposed image encryption scheme provides an efficient and secure way for fast image encrypting as well as providing robustness against some well-known statistical attacks.

Enzyme discovery beyond homology: a unique hydroxynitrile lyase in the Bet v1 superfamily

Homology and similarity based approaches are most widely used for the identification of new enzymes for biocatalysis. However, they are not suitable to find truly novel scaffolds with a desired function and this averts options and diversity. Hydroxynitrile lyases (HNLs) are an example of non-homologous isofunctional enzymes for the synthesis of chiral cyanohydrins. Due to their convergent evolution, finding new representatives is challenging. Here we show the discovery of unique HNL enzymes from the fern Davallia tyermannii by coalescence of transcriptomics, proteomics and enzymatic screening. It is the first protein with a Bet v1-like protein fold exhibiting HNL activity, and has a new catalytic center, as shown by protein crystallography. Biochemical properties of D. tyermannii HNLs open perspectives for the development of a complementary class of biocatalysts for the stereoselective synthesis of cyanohydrins. This work shows that systematic integration of -omics data facilitates discovery of enzymes with unpredictable sequences and helps to extend our knowledge about enzyme diversity.

Effects of temporal coherence and signal-frequency uncertainty for tone detection in a random-frequency multi-tonal masker

Detection thresholds tend to be lower when the spectral and/or temporal characteristics of the signal are predictable than unpredictable, particularly in an unpredictable masker. The present study evaluated the detrimental effect of frequency uncertainty and the beneficial effect of temporal coherence for a pure-tone signal presented in a multi-tonal masker with unpredictable frequency sequences. Stimuli were composed of 80-ms tone bursts. The signal was 1, 2, 4, or 8 sequential tone bursts, and burst frequency was either fixed across trials or randomly varied across trials but fixed across bursts. The masker was composed of four streams of tone bursts; the frequency of each burst was randomly drawn from a uniform distribution 250-4000 Hz, with the caveat that synchronous masker and signal bursts were separated by 1/5 oct or more. Signal and masker bursts were synchronously gated, and the masker played continuously throughout a threshold estimation track. Thresholds tended to improve with increasing numbers of signal bursts and worsen with increasing signal frequency uncertainty. These factors appeared to interact; signal frequency uncertainty was less detrimental when the signal was composed of larger numbers of bursts. Preliminary models of detection will be discussed.

Hybrid image crypto system for secure image communication– A VLSI approach

This work presents permutation and diffusion based hybrid image crypto system in transform domain using combined chaotic maps and Haar Integer Wavelet Transform (HIWT). HIWT is used to transform the plain image and four sub-bands of the image coefficients are encrypted by combined chaotic maps. The combination of two one-dimensional chaotic maps results in better chaotic behavior and generates unpredictable large random sequence that can be used for the encryption of the image. To manage the trade-offs between security, speed and power consumption, the proposed encryption algorithm is modeled in Cyclone II Field Programmable Gate Array (FPGA). The proposed design occupies only 4025 logical elements and takes 0.28ms for encrypting an image of size 256 × 256. Robustness of the algorithm is estimated using quality metrics including statistical and differential attack analysis. The proposed scheme is resistant to most of the known attacks and is more secure than other image encryption schemes.

The effect of task difficulty on motor performance and frontal-striatal connectivity in cocaine users

BackgroundThere is growing recognition that chronic cocaine users have alterations in sensorimotor control that are positively related to low frontal-striatal connectivity within the motor system. These frontal-striatal motor circuits however, are modulated by circuits governing attention, which are also disrupted in cocaine users. This study’s aim was to determine if sensorimotor control deficits are positively related to the difficulty of a motor task or exist independent of the increasing cognitive demand. MethodsFunctional MRI data was collected from 40 individuals (20 non-treatment seeking chronic cocaine users, 20 age and gender matched non-drug using controls) as they mimicked an unpredictable finger-tapping sequence at various speeds. Dependent measures included task accuracy, percent BOLD signal change in sensorimotor regions of interest (ROIs), and functional connectivity (temporal correlations) between ROIs. ResultsIn both groups, as speed increased, the BOLD signal change increased in the primary motor cortex, supplementary motor area (SMA), cerebellum, and anterior cingulate cortex. Compared to controls, cocaine user SMA-Caudate and ACC-Putamen connectivity was lower at all speeds in the contralateral hemisphere. Furthermore, as speed increased there was a decrease in connectivity between additional ROI pairs among users. ConclusionsThese data support previous observations of sensorimotor performance deficits and dorsal frontal-striatal connectivity impairments among cocaine users. While previous studies demonstrate these deficits when performing a finger-tapping task at a single speed, we show that these same impairments exist at multiple levels of task difficulty. These data suggest that previously observed frontal-striatal connectivity in cocaine users during sensorimotor task performance are stable and not directly related to cognitive demands of the task.

Intra and interspecific sequence variation in closely related species of Cereus (CACTACEAE)

In comparative phylogenetic and population genetic studies, one of the most crucial steps is to select appropriate DNA markers, a decision based primarily on the estimated variation in markers in cross-taxonomic surveys. To assess whether genetic variation at the intraspecific level in one species predicts the variation in another closely related species we used two congeneric species of Cereus (Cactaceae: Cereeae). We screened and characterized eight noncoding plastid regions (trnS-trnG, atpI-atpH, trnT-trnL, psbD-trnT, petL-psbE, 3'rps16-5'trnk, trnG intron, and trnL intron), and one nuclear gene (PhyC) in Cereus fernambucensis and C. hildmannianus. A total of 40 individuals from 15 populations were characterized according to nucleotide diversity, number of haplotypes, and number of potentially informative characters. The results revealed that nucleotide substitutions and indels are the main source of variation, with the largest divergence between species found in trnS-trnG. The trnL intron and petL-psbE showed intraspecific variability in both species. The psbD-trnT, atpI-atpH, trnS-trnG, and trnT-trnL, which are the most variable regions in one species, showed no variation in the other. Finally, the nuclear gene PhyC showed more resolution between Cereus species than within species. We thus found considerable heterogeneity among widely used plastid markers, even between closely related species, and suggest the use of PhyC as a marker for phylogenetic inference in these species. These results reinforce the need of screening as a preliminary step to conduct phylogeographic or phylogenetic studies in face of unpredictable sequence variation of molecular markers in plants.

Fundamentals of Randomization in Clinical Trial

The randomized control trial (RCTs) is widely accepted to be the best design for evaluating the efficacy of new therapies, and thus it is accepted as the gold standard to evaluate treatment effects. Random assignment of patients to the treatment ensures the internal validity of the comparison of new treatment with a control group. Unfortunately, the randomization process in most research studies is not implemented properly. The purpose of this review is to provide researchers and scholarly clinicians with a better understanding of different options to achieve proper randomization. The information presented in this article will also help to better design and interpret the results of clinical trials. Therefore, a brief definition of randomization plus its concise benefits in clinical trials, and the processes of an accurate randomization procedure, generation of unpredictable random allocation sequence and allocation concealment are considered. Recommendations are made to select the suitable techniques of generation of random allocation and allocation concealment. Finally, the authors describe how the appropriate implementation of these two procedures reduces the potential for biases throughout the study and improves the power of the study.

WeNA: Deterministic Run-time Task Mapping for Performance Improvement in Many-core Embedded Systems

Many-core embedded systems will feature an extremely dynamic workload distribution where massive applications arranged as an unpredictable sequence enter and leave the system at run-time. Efficient mapping strategy is required to allocate system resources to the incoming application. Noncontiguous mapping improves system throughput by utilizing disjoint nodes, however, the increasing communication distance and external congestion lead to high power consumption and network delay. This paper thus presents an enhanced noncontiguous dynamic mapping algorithm, aiming at decreasing interprocessor communication overhead and improving both network and application performance. Communication volumes are utilized to arrange the mapping order of tasks belong to the same application. Moreover, expanding parameter of each task is developed which directs the optimized mapping decision comparing to the current neighborhood and occupancy information. Experimental results show that our modified mapping algorithm Weighted-based Neighborhood Allocation (WeNA) makes considerable improvements on Average Weighted Manhattan Distance (8.06%) and network latency (9.8%) in comparison with the state-of-the-art algorithm.

The impact of an unpredictable context and intolerance of uncertainty on the electrocortical response to monetary gains and losses.

There is growing evidence that unpredictability and uncertainty can alter reward system functioning. The present study examined the impact of (1) a task-irrelevant unpredictable relative to predictable context and (2) individual differences in intolerance of uncertainty (IU) on the reward-related positivity (RewP), an event-related potential (ERP) response to monetary gains relative to losses. Specifically, 64 participants listened to predictable and unpredictable tone sequences while electroencephalography was recorded during a monetary gambling task. Participants also completed the Intolerance of Uncertainty Scale, which measures both cognitive distress (prospective IU) and behavioral inhibition (inhibitory IU) elicited by uncertainty, in addition to the Depression Anxiety Stress Scale-21 and Penn State Worry Questionnaire. Results indicated that the RewP was reduced during the unpredictable relative to the predictable context. Greater self-reported anxiety elicited by the unpredictable context was associated with a decreased RewP, and a decreased RewP was associated with poorer lose-shift behavioral adjustment. Furthermore, the RewP mediated the relationship between self-reported anxiety elicited by the unpredictable context and lose-shift behavioral adjustment. The IU subscales demonstrated the opposite relationship with the RewP across both contexts-inhibitory IU was associated with an attenuated RewP and prospective IU was associated with an enhanced RewP. In contrast, anxiety, depression, stress, and worry symptomatology were not associated with the RewP. This is the first study to demonstrate that an unpredictable context and individual differences in the degree to which people cannot tolerate uncertainty impact an ERP measure of reward system functioning.

Temporally Unpredictable Sounds Exert a Context-Dependent Influence on Evaluation of Unrelated Images.

Temporally unpredictable stimuli influence murine and human behaviour, as previously demonstrated for sequences of simple sounds with regular or irregular onset. It is unknown whether this influence is mediated by an evaluation of the unpredictable sound sequences themselves, or by an interaction with task context. Here, we find that humans evaluate unrelated neutral pictures as more negative when these are presented together with a temporally unpredictable sound sequence, compared to a predictable sequence. The same is observed for evaluation of neutral, angry and fearful face photographs. Control experiments suggest this effect is specific to interspersed presentation of negative and neutral visual stimuli. Unpredictable sounds presented on their own were evaluated as more activating, but not more aversive, and were preferred over predictable sounds. When presented alone, these sound sequences also did not elicit tonic autonomic arousal or negative mood change. We discuss how these findings might account for previous data on the effects of unpredictable sounds, in humans and rodents.

Stable odor recognition by a neuro-adaptive electronic nose.

Sensitivity, selectivity and stability are decisive properties of sensors. In chemical gas sensors odor recognition can be severely compromised by poor signal stability, particularly in real life applications where the sensors are exposed to unpredictable sequences of odors under changing external conditions. Although olfactory receptor neurons in the nose face similar stimulus sequences under likewise changing conditions, odor recognition is very stable and odorants can be reliably identified independently from past odor perception. We postulate that appropriate pre-processing of the output signals of chemical sensors substantially contributes to the stability of odor recognition, in spite of marked sensor instabilities. To investigate this hypothesis, we use an adaptive, unsupervised neural network inspired by the glomerular input circuitry of the olfactory bulb. Essentially the model reduces the effect of the sensors’ instabilities by utilizing them via an adaptive multicompartment feed-forward inhibition. We collected and analyzed responses of a 4 × 4 gas sensor array to a number of volatile compounds applied over a period of 18 months, whereby every sensor was sampled episodically. The network conferred excellent stability to the compounds’ identification and was clearly superior over standard classifiers, even when one of the sensors exhibited random fluctuations or stopped working at all.

In an uncertain world, errors are more aversive: evidence from the error-related negativity.

Unpredictability increases amygdala activity and vigilance toward threat. The error-related negativity (ERN) is an electrophysiological response to errors and is posited to reflect sensitivity to potential threat. The present study examined whether the ERN was modulated by predictable or unpredictable task-irrelevant auditory stimuli. Twenty-three participants completed a speeded response task designed to elicit the ERN, and were simultaneously exposed to predictable and unpredictable tone sequences. Participants retrospectively rated their anxiety to the predictable and unpredictable tone sequences and indicated which tone sequence they disliked the most. Unpredictable tones were rated as slightly more anxiety-provoking compared to predictable tones, but participants were evenly split regarding which sequence they disliked the most. Fewer errors were committed during unpredictable relative to predictable tones. Finally, the ERN--but not the correct response negativity (CRN)--was increased during unpredictable relative to predictable tones. The present study demonstrated that an unpredictable context can increase vigilance and potentiate neural processing of errors. These data suggest that an unpredictable environmental context may increase error value. Implications for understanding anxiety disorders are discussed.

Ad-hoc and context-dependent adjustments of selective attention in conflict control: An ERP study with visual probes

Cognitive conflict control in flanker tasks has often been described using the zoom-lens metaphor of selective attention. However, whether and how selective attention – in terms of suppression and enhancement – operates in this context has remained unclear. To examine the dynamic interplay of selective attention and cognitive control we used electrophysiological measures and presented task-irrelevant visual probe stimuli at foveal, parafoveal, and peripheral display positions. Target–flanker congruency varied either randomly from trial to trial (mixed-block) or block-wise (fixed-block) in order to induce reactive versus proactive control modes, respectively. Three EEG measures were used to capture ad-hoc adjustments within trials as well as effects of context-based predictions: the N1 component of the visual evoked potential (VEP) to probes, the VEP to targets, and the conflict-related midfrontal N2 component.Results from probe-VEPs indicate that enhanced processing of the foveal target rather than suppression of the peripheral flankers supports interference control. In incongruent mixed-block trials VEPs were larger to probes near the targets. In the fixed-blocks probe-VEPs were not modulated, but contrary to the mixed-block the preceding target-related VEP was affected by congruency. Results of the control-related N2 reveal largest amplitudes in the unpredictable context, which did not differentiate for stimulus and response incongruency. In contrast, in the predictable context, N2 amplitudes were reduced overall and differentiated between stimulus and response incongruency.Taken together these results imply that predictability alters interference control by a reconfiguration of stimulus processing. During unpredictable sequences participants adjust their attentional focus dynamically on a trial-by-trial basis as reflected in congruency-dependent probe-VEP-modulation. This reactive control mode also elicits larger N2 amplitudes. In contrast, when task demands are predictable, participants focus selective attention earlier as reflected in the target-related VEPs. This proactive control mode leads to smaller N2 amplitudes and absent probe effects.

Magnitude and mechanisms of persistent crop sequence effects on wheat

The impacts of broadleaf crop, pasture or fallow breaks within cereal-based cropping systems are widely acknowledged, but most studies have focussed on the first cereal crop after the break. We report a series of four field experiments in a semi-arid cropping zone of Southern Australia in which the impacts of a range of Year 1 sequence options (crops, pasture and fallow) on Year 3 and 4 wheat crops were investigated. In three of the experiments, two phases of the same experiment were commenced in successive years, providing seven sequence phases. In three of the seven phases (at three of the four sites), the Year 1 treatments influenced the yield of Year 3 or Year 4 wheat crops by 0.6, 0.9 and 0.9tha−1, although different responses between phases of the same experiments at two sites provided clear evidence of significant seasonal interactions. Interactions of Year 1 sequence treatments with tillage, crop species/varieties and/or added P-fertiliser treatments in intervening years also occurred at some sites. The largest persistent yield impacts related to the preservation of differences in residual nitrogen (N), and in some cases water following Year 1 crops through subsequent dry seasons, which were frequent in most experimental phases. Higher residual N levels after legumes and canola could persist for 2–3 years and induce yield penalties due to “haying-off” when Year 3 or 4 wheat crops experienced dry spring conditions. Such effects were offset following Year 1 fallow due to increased residual water at depth. Increases in the cereal root diseases take-all (Gaeumannomyces tritici) and rhizoctonia (Rhizoctonia solani AG8) due to Year 1 wheat also persisted through dry seasons and reduced Year 3 wheat yield in some experiments. We found no evidence for a significant role for arbuscular mycorrhizal fungi in yield of Year 3 and 4 wheat crops. We demonstrate that large and significant yield impacts (>0.5tha−1), both positive and negative, can persist for 3–4 years in semi-arid environments as a result of water, N and disease inoculum legacies of Year 1 crop sequence choices. Prolonged dry periods help to preserve these legacies, so that persistent and unpredictable crop sequence effects will be a feature of cropping systems in semi-arid areas with variable climates.

Factors affecting auditory streaming of random tone sequences

As the frequency separation of A and B tones in an ABAABA tone sequence increases the tones are heard to split into separate auditory streams (fission threshold). The phenomenon is identified with our ability to ‘hear out’ individual sound sources in natural, multisource acoustic environments. One important difference, however, between natural sounds and the tone sequences used in most streaming studies is that natural sounds often vary unpredictably from one moment to the next. In the present study, fission thresholds were measured for ABAABA tone sequences made more or less predictable by sampling the frequencies, levels or durations of the tones at random from normal distributions having different values of sigma (0–800 cents, 0–8 dB, and 0–40 ms, respectively, for frequency, level, and duration). Frequency variation on average had the greatest effect on threshold, but the function relating threshold to sigma was non-monotonic; first increasing then decreasing for the largest value of sigma. Differences in the sigmas for A and B tones tended to reduce thresholds, but covariance in the A and B tones had little effect. The results suggest that the principles of perceptual organization underlying streaming may differ for predictable and unpredictable tone sequences.