Attack Frequencies Research Articles

Assessment of Attack Frequency in PFAPA Patients Based on Therapeutic Modalities.

This study aims to present the clinical characteristics of patients with PFAPA syndrome, and to compare the effects of corticosteroid usage, colchicine prophylaxis, and tonsillectomy on the frequency of attacks in patients with PFAPA syndrome. Patients aged between 6 months and 18 years presenting to our Paediatric Rheumatology clinic between 2017 and 2021 who were diagnosed with PFAPA syndrome and followed up for a minimum of 12 months were included in this study. The demographic and clinical characteristics of the patients, laboratory findings, attack durations, and treatments were recorded. Our study, comprised of 195 patients, included four groups: untreated (n = 58), corticosteroid (n = 43), colchicine (n = 62), and tonsillectomy (n = 32). There was no significant difference between the treatment groups in terms of attack frequencies before treatment initiation (p > 0.05). When attack frequencies before and after treatment initiation were observed, a decrease in attack frequency compared to the pre-treatment period was observed in the tonsillectomy group (from 12 to 3 attacks) (p < 0.001) and the colchicine group (from 12 attacks to 1 attack) (p < 0.001). It was noted that using steroids during three or more attacks increased attack frequency compared to the pre-treatment period (p < 0.0001). Tonsillectomy resulted in a more significant reduction in attack frequency compared to the colchicine group (p < 0.001). Using corticosteroids during an attack has been shown to effectively control attacks. However, the repeated use of corticosteroids increases the frequency of attacks. Colchicine prophylaxis leads to a reduction in attack frequency in the majority of cases. Tonsillectomy can successfully control the disease in most cases.

Characterization of plasma-derived small extracellular vesicle miRNA and protein cargo in hereditary angioedema

Hereditary angioedema (HAE) is an inherited disorder causing attacks of subcutaneous tissue or mucosa swelling. The disease burden and attack frequencies vary significantly among patients. This is the first pilot study investigating small extracellular vesicles (sEV) as potential disease modulators in HAE.Plasma-derived sEVs from HAE patients and healthy donors (HD) were thoroughly characterized by Western blot, transmission electron microscopy, nanoparticle tracking and bead-based flow cytometry. The miRNA content of sEVs was examined by nCounter technology and used to predict sEV-based pathomechanisms in silico. All sEV readouts were analyzed regarding HAE-related changes and associations with clinical parameters and attack frequency.Total sEV protein levels were elevated in HAE patients compared to HD. In HAE patients, lower levels of sEVs carrying CD8, CD209, CD81, CD24 and CD44 were measured. sEV miRNA profiling revealed 84 HAE-exclusive and 30 significantly HAE-upregulated candidates. Core hubs of their predicted interaction networks were AGO2, VEGF, RGS5, MTA1, IFG1 and BAX. A set of 12 and 36 sEV miRNAs were restricted to patients with absent attacks or patients with present attacks during prophylactic therapy, respectively.sEVs, especially sEV miRNAs, could contribute to disease pathogenesis and differential attack frequencies. They emerged as disease modulators in HAE and require further study to reveal underlying mechanisms.

The Superiority of Compressed Colchicine Tablets over Coated Colchicine Tablets for Familial Mediterranean Fever.

Background and Objectives: Familial Mediterranean fever (FMF) is an inherited autoinflammatory disease characterized by recurrent febrile attacks and serosal inflammation. The goals of FMF treatment are to prevent acute attacks and the development of amyloidosis. This study aimed to investigate the benefit of switching to compressed colchicine tablets in patients with FMF who are resistant or intolerant to the pharmaceutical preparation of coated colchicine tablets in terms of attack frequency and side effects. Materials and Methods: Patients who developed resistance and intolerance under coated colchicine tablet treatment and, therefore, switched to compressed colchicine tablets were identified. The attack frequencies and drug-related side effects in patients using the two different pharmaceutical colchicine preparations were compared. Results: The mean age of the 172 patients treated with compressed tablets alone following coated tablets was 36.3 ± 11.4 years, and 75 (43.6%) were male. The most common genetic mutation was detected as M694V in 111 (64.5%) patients, and 36 (20.9%) of them were homozygous. A decrease in the daily colchicine dose was found after switching to compressed colchicine tablets in patients followed for 7 years (2.1 ± 0.7 mg vs. 1.7 ± 0.5 mg; p < 0.001). Episodes lasted for one to three days and then resolved spontaneously. After treatment with the compressed tablet form of colchicine, 129 (75%), 33 (19%), and 10 (6%) patients had 0-3, 4-6, and more than 7 attacks, respectively (p < 0.001). Diarrhea and aminotransferase elevation, the most common side effects in patients using coated colchicine tablets, decreased after using compressed colchicine tablets (p < 0.001). Conclusions: Compressed colchicine tablets were shown to be effective in patients who did not respond to coated colchicine therapy and those with pre-treatment intolerance to biological agents.

Reproductive ecology and egg parasitism of the Samoan swallowtail butterfly

AbstractWe investigated the reproductive ecology and effects of egg parasitism on the Samoan swallowtail butterfly (Papilio godeffroyi), which survives only on Tutuila Island, American Samoa, after having disappeared from the much larger islands of Upolu and Savai‘i in independent Samoa. During monthly surveys of its only known host plant, Micromelum minutum, across eight sites in 2013 and 2014, we collected eggs, eggshells, larvae, pupae, and pupal exuviae. Live specimens were reared under laboratory conditions to determine reproductive outcomes, developmental rates, and sex ratios, as well as parasitoid attack frequencies, brood sizes, and sex ratios. Sixty‐six of 448 (14.7%) eggs produced larvae, 47 of which became adults. The sex ratio was approximately even overall and within each developmental stage. Eggs were slightly larger on individual host trees and in host tree stands that yielded more eggs per unit of foliage, indicating that ovipositing females responded to some features of host trees and stands. Eggs hatching female or male larvae were similar in size, and the sexes developed at similar rates. A newly described species of parasitoid wasp, Ooencyrtus pitosina (Encyrtidae), emerged from 73.6% of 382 butterfly eggs that failed to hatch in the laboratory (62.7% of 448 eggs overall). Forty‐one other eggs contained dead parasitoid larvae. An additional, unidentified Ooencyrtus wasp species emerged from a single P. godeffroyi egg. No parasitoids were reared from P. godeffroyi larvae or pupae. Of 656 P. godeffroyi eggshells collected in the field and examined in the laboratory, 62.2% showed signs of having been parasitized by O. pitosina. There was no evidence that parasitism rates were density‐dependent. O. pitosina brood sizes ranged from 1 to 5, with the sex ratio skewed toward females (2.40 F:1.00 M). Larger parasitoid broods were associated with slightly larger host eggs, indicating that female wasps may adjust brood size according to host egg size or that fewer wasp larvae are able to complete development in smaller eggs. Techniques used to rear both P. godeffroyi and O. pitosina in the laboratory could be applied to a captive‐rear, wild‐release program, which may facilitate reestablishment of the species in Samoa.

Analysis of disease burden in patients with hereditary angioedema from Japan by patient-reported outcomes.

Hereditary angioedema (HAE) symptoms can vary greatly. Disease burden evaluation is essential for providing adequate treatments for patients. Patient-reported outcome measures (PROMs), including the 12-Item Short Form Health Survey (SF-12), the Angioedema Quality of Life (AE-QoL), the Hospital Anxiety and Depression Scale (HADS), and the Work Productivity and Activity Impairment: Specific Health Problem (WPAI:SHP) questionnaires, were collected in 2021, before modern medications for long-term prophylaxis (LTP) of HAE were licensed in Japan. Patients also reported their HAE attack frequency as "annual" (several attacks annually), "monthly" (several attacks monthly) or "weekly" (several attacks weekly). Multiple linear regression analyses were conducted on the relationship between independent parameters (sex, age, attack frequency, HAE type, and HADS scores) and dependent parameters (AE-QoL and SF-12 scores). Fifty-four patients reported PROMs. All PROMs showed substantial health-related quality of life (HRQoL) impairment. Overall, the higher the attack frequencies, the greater the reported impairment in the PROMs tended to be. In multiple linear regression analyses, higher AE-QoL Fatigue/Mood and Fears/Shame domain scores (greater impairment) were associated with higher HADS anxiety subscale scores; higher AE-QoL total scores (greater HRQoL impairment) and lower SF-12 Physical and Mental Health Composite scores (greater general health impairment) were associated with higher HADS depression subscale scores. Patients with monthly or weekly HAE attacks reported numerically low absenteeism and numerically high presenteeism and work productivity loss as measured by the WPAI:SHP questionnaire. In this study, conducted before modern LTP options were available in Japan, patients with HAE reported notable impairment in HRQoL and work productivity. Weekly or monthly HAE attack frequencies were associated with a high disease burden. Furthermore, a substantial number of patients reported notable fatigue/mood impairment as measured by the AE-QoL and depression as measured by the HADS regardless of attack frequency. These results provide a basis for future studies evaluating the effect of LTP on the clinical manifestations and HRQoL in patients with HAE.

Comparison of two methods of greater occipital nerve block in patients with chronic migraine: ultrasound-guided and landmark-based techniques

BackgroundMigraine is a primary headache defined as moderate-to-severe pain lasting 4 to 72 h, ranking 2nd among the disabling conditions for both genders regardless of the age and the greater occipital nerve (GON) block has been reported as an efficient treatment method for migraine. The present study aims to evaluate and compare the efficiency of the two methods of GON block, i.e., the ultrasound (US)-guided technique and the landmark-based technique.MethodHaving a prospective and randomized design, the study assigned the patients with chronic migraine into two groups after which a neurologist performed landmark-based GON block in the first group while an algologist performed US-guided GON block in the second group. During the 3-month follow-up period, the number of days with pain, the duration of pain, the number of analgesic drugs taken in a month, and Visual Analogue Scale (VAS) scores were compared with the values ​​before treatment and at the 1st week, 1st month, and 3rd month after treatment.ResultsUS-guided GON block group included 34 patients while there were 32 patients in the landmark-based GON block group. US-guided GON block group showed significantly reduced VAS scores and frequency of attacks compared to the landmark-based GON block group at Month 1 after the procedure. After a 3-month follow-up period of the two groups, the frequency of attacks, analgesic intake and the duration of attacks were lower in both groups compared to the baseline. At 3-month follow-up, the mean of VAS scores decreased from 9,47 ± 2,69 to 4,67 ± 1,9 in US-guided GON block group and from 9,46 ± 0,98 to 7 ± 2,5 in the landmark-based GON block group.ConclusionIt was determined that both US-guided and landmark-based GON block were efficient techniques in patients with chronic migraine. US-guided GON block technique resulted in lower VAS scores, shorter durations of pain, lower frequencies of attack, and lower intake of analgesics compared to the landmark-based GON block technique.

Neurite Damage in Patients with Migraine.

We examined neurite orientation dispersion and density imaging in patients with migraine. We found that patients with medication overuse headache exhibited lower orientation dispersion than those without. Moreover, orientation dispersion in the body of the corpus callosum was statistically negatively correlated with migraine attack frequencies. These findings indicate that neurite dispersion is damaged in patients with chronic migraine. Our study results indicate the orientation preference of neurite damage in migraine.

Resilient control for networked control systems with dynamic quantization and DoS attacks

AbstractIn this article, the resilient control for networked control systems in the presence of denial‐of‐service (DoS) attacks is investigated in a sampled‐data and dynamic quantization scheme. A novel dynamic quantization strategy is designed for signal transmissions from encoding systems to decoding systems, in which the quantized states are transmitted through networks with a risk of DoS attacks. An estimator is introduced to the design of control laws. Some sufficient conditions in terms of quantization levels, DoS attack duration and frequencies are given for the asymptotic stability of networked control systems. Furthermore, an event‐triggered communication scheme is designed for signal transmissions in control channels to reduce network resource consumption. The Zeno behavior is excluded in the designed event‐triggered communication scheme. The quantization levels can be adaptively adjusted according to real‐time situations. Finally, the effectiveness of the proposed strategy is illustrated by simulations.

The relationship between the lunar cycle and epileptic attacks and their treatment

Objective: The purpose of the present study was to evaluate the potential association between the phases of the moon and seizure attacks and treatment in patients diagnosed with epilepsy at a pediatric neurology clinic. Materials and Methods: 199 patients presenting to the Balıkesir University Medical Faculty pediatric neurology clinic, Turkey, diagnosed with epilepsy based on ILAE criteria were included in the study. The patients’ demographic characteristics, medications used, and family histories, and the frequency and duration of attacks were investigated retrospectively. Results: The mean age of the patients enrolled in the study (N=199) was 10.07±4.90 years. The patients were most frequently in the 12-18 age range (N=83, 41.7%). The majority of patients were male (N=104, 52.3%). Analysis revealed that seizures were most frequent in the full moon (N=54, 27.1%), followed by the new moon (N=52, 26.1%) and first quarter (N=47, 23.6%), and were least common in the third quarter (N=46, 23.1%). No statistically significant variation was determined in terms of attack frequencies during the different lunar phases between patients receiving monotherapy and polytherapy (p=0.206). Conclusion: The results of the present study suggest that there is no relationship between the lunar cycle and the frequency

An Enhancement Method in Few-Shot Scenarios for Intrusion Detection in Smart Home Environments

Different devices in the smart home environment are subject to different levels of attack. Devices with lower attack frequencies confront difficulties in collecting attack data, which restricts the ability to train intrusion detection models. Therefore, this paper presents a novel method called EM-FEDE (enhancement method based on feature enhancement and data enhancement) to generate adequate training data for expanding few-shot datasets. Training intrusion detection models with an expanded dataset can enhance detection performance. Firstly, the EM-FEDE method adaptively extends the features by analyzing the historical intrusion detection records of smart homes, achieving format alignment of device data. Secondly, the EM-FEDE method performs data cleaning operations to reduce noise and redundancy and uses a random sampling mechanism to ensure the diversity of the few-shot data obtained by sampling. Finally, the processed sampling data is used as the input to the CWGAN, and the loss between the generated and real data is calculated using the Wasserstein distance. Based on this loss, the CWGAN is adjusted. Finally, the generator outputs effectively generated data. According to the experimental findings, the accuracy of J48, Random Forest, Bagging, PART, KStar, KNN, MLP, and CNN has been enhanced by 21.9%, 6.2%, 19.4%, 9.2%, 6.3%, 7%, 3.4%, and 5.9%, respectively, when compared to the original dataset, along with the optimal generation sample ratio of each algorithm. The experimental findings demonstrate the effectiveness of the EM-FEDE approach in completing sparse data.

How to Survive a (Juvenile) Piranha Attack: An Integrative Approach to Evaluating Predator Performance.

Cory cat panel figureDrawing of bite force measuring equipment and indentation rig Pygocentrus nattereri jaw muscle morphology and skull anatomyBox plot grid of number of Pygocentrus nattereri bites before puncture along different body regions of Corydoras trilineatus during feeding trials resultsDrawing of color-coded Corydoras trilineatus with attack frequencies and average bites until puncture by Pygocentrus nattereriBox plot of average voluntary juvenile Pygocentrus nattereri bite forces to standard lengthPanel of linear ordinary least-squares regressions of Pygocentrus nattereri bite force to adductor mandibulae mass, standard length, and body massOrdinary least-squares regressions of voluntary bites to restrained bites of Pygocentrus nattereriPanel of indentation tests for intact and removed Corydoras trilineatus scutesPanel of indentation tests for Corydoras trilineatus body region. There is an evolutionary arms race between predators and prey. In aquatic environments, predatory fishes often use sharp teeth, powerful bites, and/or streamlined bodies to help capture their prey quickly and efficiently. Conversely, prey are often equipped with antipredator adaptations including: scaly armor, sharp spines, and/or toxic secretions. This study focused on the predator-prey interactions between the armored threestripe cory catfish (Corydoras trilineatus) and juvenile red-bellied piranha (Pygocentrus nattereri). Specifically, we investigated how resistant cory catfish armor is to a range of natural and theoretical piranha bite forces and how often this protection translated to survival from predator attacks by Corydoras. We measured the bite force and jaw functional morphology of P. nattereri, the puncture resistance of defensive scutes in C. trilineatus, and the in situ predatory interactions between the two. The adductor mandibulae muscle in juvenile P. nattereri is robust and delivers an average bite force of 1.03 N and maximum bite force of 9.71 N, yet its prey, C. trilineatus, survived 37% of confirmed bites without any damage. The C. trilineatus armor withstood an average of nine bites before puncture by P. nattereri. Predation was successful only when piranhas bit unarmored areas of the body, at the opercular opening and at the caudal peduncle. This study used an integrative approach to understand the outcomes of predator-prey interactions by evaluating the link between morphology and feeding behavior. We found that juvenile P. nattereri rarely used a maximal bite force and displayed a net predation success rate on par with other adult vertebrates. Conversely, C. trilineatus successfully avoided predation by orienting predator attacks toward their resilient, axial armor and behavioral strategies that reduced the predator's ability to bite in less armored regions of the body.

The influence of anxiety and depression on headache in adolescent migraineurs: a case-control study

ABSTRACT Background Migraine is commonly linked to a range of psychiatric comorbidities, primarily anxiety and depression. The present study compared the frequency of anxiety and depression disorders in migraine and non-migraine adolescents and evaluated the relation of depression and anxiety to migraine characteristics. Methods In this case-control study, 234 adolescents (112 migraineurs and 122 non-migraine adolescents) aged 13–18 years were evaluated. A headache questionnaire as well as the Beck Anxiety Inventory and Children’s Depression Inventory were completed to investigate the prevalence of headache, anxiety, and depression. Results The average age of participants was 15.77±2 years in the case group and 15.39±1.79 years in the control group. We found significantly higher levels of mild, moderate, and severe anxiety (38.4%, 23.2%and 23.2% respectively) in the migraine group compared to the control group (24.2%, 5.8%and 10.0% respectively) (p<0.001). Significantly more children in the control group (29.6%) than in the case group (10.1%) had a non-depressive CDI score (p=0.005). There was a significant difference between patients with moderate and severe anxiety in terms of attack frequency and duration. Depressed migraineurs recorded higher attack severities and frequencies than migraineurs without depression. Conclusion Anxiety and depression are common in adolescents with migraine and can be associated with more burdensome attacks.

Brain volumetry by voxel-based-morphometry in migraineurs: comparison between groups and clinical correlations

Background&#x0D; Migraine was previously interpreted as “benign” disease since the major part of patients were asymptomatic between attacks and brain lesions are absent in primary headaches. Advances in structural neuroimaging have changed this point of view. Voxel-based-morphometry is an accurate technique to evaluate objectively structural brain damage. Our hypothesis was that some clinical features of migraine, as aura and attack frequencies, are more related to volumetric changes in migraineurs brains. &#x0D; &#x0D; Objectives&#x0D; To compare brain lobes volumetry between migraine patients (episodic migraine, with and without aura, chronic migraine) and healthy controls. To evaluate the correlations of brain volumetric variables with clinical variables.&#x0D; &#x0D; Methods&#x0D; This is a cross-sectional study performed with 60 female volunteers, aged between 18 and 55 years old, equally allocated into four groups: episodic migraine without aura, episodic migraine with aura, chronic migraine and controls. The sample was clinically characterized by the following variables: age, number of days with headache in the last month, number of days with aura in the last month, average pain intensity in the last month, disease duration calculated in number of years from the migraine diagnosis to the MRI performance, and the use of prophylactic drugs for migraine. Volunteers underwent brain MRI, and Free Surfer software was used to perform volumetric studies. Statistical analyses included Mann-Whitney test, Kruskal-Wallis test, Dunn test and Spearmann correlations.&#x0D; &#x0D; Results&#x0D; No statistically relevant differences were found in cerebral lobe volumes and supratentorial white matter in the comparison between groups. Regarding to clinical correlations, age influenced the brain lobes volumetric reduction, as expected, except for the parietal lobe, for which the correlation was not important. The disease duration was correlated with the reduction of the frontal (p&lt;0.001 / r=-0.531), temporal (p=0.003/r=-0.433), parietal (p=0.004/r=-0.431) lobes; when adjusted by age...&#x0D; &#x0D; (To see the complet abstract, please, check out the PDF.)

RADAMS: Resilient and adaptive alert and attention management strategy against Informational Denial-of-Service (IDoS) attacks

Attacks exploiting human attentional vulnerability have posed severe threats to cybersecurity. In this work, we identify and formally define a new type of proactive attentional attacks called Informational Denial-of-Service (IDoS) attacks that generate a large volume of feint attacks to overload human operators and hide real attacks among feints. We incorporate human factors (e.g., levels of expertise, stress, and efficiency) and empirical psychological results (e.g., the Yerkes-Dodson law and the sunk cost fallacy) to model the operators’ attention dynamics and their decision-making processes along with the real-time alert monitoring and inspection. To assist human operators in dismissing the feints and escalating the real attacks timely and accurately, we develop a Resilient and Adaptive Data-driven alert and Attention Management Strategy (RADAMS) that de-emphasizes alerts selectively based on the abstracted category labels of the alerts. RADAMS uses reinforcement learning to achieve a customized and transferable design for various human operators and evolving IDoS attacks. The integrated modeling and theoretical analysis lead to the Product Principle of Attention (PPoA), fundamental limits, and the tradeoff among crucial human and economic factors. Experimental results corroborate that the proposed strategy outperforms the default strategy and can reduce the IDoS risk by as much as 20%. Besides, the strategy is resilient to large variations of costs, attack frequencies, and human attention capacities. We have recognized interesting phenomena such as attentional risk equivalency, attacker’s dilemma, and the half-truth optimal attack strategy.

Forecasting network events to estimate attack risk: Integration of wavelet transform and vector auto regression with exogenous variables

Analyzing network traffic data to detect suspicious network activities (i.e., intrusions) requires tremendous effort due to the variability of the data and constant changes in network traffic patterns. This study introduces an approach to predict future network event (normal and attack) frequencies by generating forecast models and estimating their attack risks. Wavelet transform is used to extract features, and the multivariate time series method, Vector Auto Regression with eXogenous variables (VARX), is utilized to predict future network traffic events. Attack risks for network events are estimated with an adaptive threshold method and assessed by performing classification with two machine learning techniques. We also performed a comparative evaluation to examine the relationship among different time scales (one second, five seconds, and fifteen seconds) and three wavelets in determining attack risks. Our analysis results indicate that wavelet features with VARX show the capability to analyze multivariate network traffic time series data to forecast future network events and estimate their attack risks.

Task-switching abilities in episodic and chronic migraine.

Migraineurs show impaired cognitive functions interictally, mainly involving information processing speed, basic attention, and executive functions. We aimed to assess executive impairment in migraine patients with different attack frequencies through a task-switching protocol designed to assess different sub-processes of executive functioning. We enrolled 42 migraine patients and divided them into three groups based on the attack frequency: 13 subjects had episodic migraine with a low frequency (LFEM, 4-7 migraine days per month), 14 subjects had high-frequency episodic migraine (HFEM, 8-14days) and, finally, 15 subjects presented chronic migraine (≥ 15 headache days/month, CM); we compared them to 20 healthy control (HC), matched to both gender and education. Patients with high headache frequencies (CM and HFEM) showed worse performance than LFEM and HC controls, as indicated by poor accuracy, increased switch cost, and reaction times. Our study demonstrated a difference in task-switching abilities in patients with high frequency or chronic migraine compared with low-frequency episodic migraine and healthy controls. These difficulties in executive control processes could be related to altered functioning of the frontal cortex and its cortical and subcortical connections.

An assessment of the relation between vitamin D levels and electroencephalogram (EEG) changes in migraine patients.

The present study evaluated vitamin D therapy in migraine patients with vitamin D deficiency and EEG abnormality. 140 patients were divided into four groups: Group A; normal vitamin D and EEG, Group B; low vitamin D and normal EEG, Group C; normal vitamin D and pathological EEG, and Group D; low vitamin D and pathological EEG. Patients with low vitamin D received vitamin D therapy. Paediatric Migraine Disability Assessment Scale (PedMIDAS) scores and median attack frequencies time-dependent changes in the patients receiving vitamin D therapy in Group B were significant (p 0.05). Interictal EEG was pathological in 41 (29.3 %) patients. The main EEG findings were focal/hemispheric spike/sharp wave activity at 9.3 %, bilateral/generalized spike/sharp wave activity at 8.6 %, focal slowing at 5.8 %, and bilateral slow-wave activity/background rhythm irregularity at 3.6 %. Changes in EEG findings in between the groups C and D were not significant (p >0.05). There was no significant association between vitamin D levels 0.05). Vitamin D therapy positively affects attack frequency and PedMIDAS scores in migraine patients with vitamin D deficiency/insufficiency. No association was determined between EEG findings and vitamin D levels or therapy (Tab. 6, Ref. 35).

Geometric-control formulation and averaging analysis of the unsteady aerodynamics of a wing with oscillatory controls

Differential-geometric-control theory represents a mathematically elegant combination of differential geometry and control theory. Practically, it allows exploitation of nonlinear interactions between various inputs for the generation of forces in non-intuitive directions. Since its early developments in the 1970s, the geometric-control theory has not been duly exploited in the area of fluid mechanics. In this paper, we show the potential of geometric-control theory in the analysis of fluid flows, exemplifying it as a heuristic analysis tool for discovery of symmetry-breaking and unconventional force-generation mechanisms. In particular, we formulate the wing unsteady aerodynamics problem in a geometric-control framework. To achieve this goal, we develop a reduced-order model for the unsteady flow over a pitching–plunging wing that is (i) rich enough to capture the main physical aspects (e.g. nonlinearity of the flow dynamics at large angles of attack and high frequencies) and (ii) efficient and compact enough to be amenable to the analytic tools of geometric nonlinear control theory. We then combine tools from geometric-control theory and averaging to analyse the developed reduced-order dynamical model, which reveals regimes for lift and thrust enhancement mechanisms. The unsteady Reynolds-averaged Navier–Stokes equations are simulated to validate the theoretical findings and scrutinize the underlying physics behind these enhancement mechanisms.

Quantitative Analysis and Prediction of Global Terrorist Attacks Based on Machine Learning

Terrorist attacks pose a great threat to global security, and their analysis and prediction are imperative. Considering the high frequency of terrorist attacks and the inherent difficulty in finding related terrorist organizations, we propose a classification framework based on ensemble learning for classifying and predicting terrorist organizations. The framework includes data preprocessing, data splitting, five classifier prediction models, and model evaluation. Based on a quantitative statistical analysis of terrorist organization activities in GTD from 1970 to 2017 and feature selection using the SelectKBest method in scikit learn, we constructed five classification and prediction models of terrorist organizations, namely, decision tree, bagging, random forest, extra tree, and XGBoost, and utilized a 10-fold cross-validation method to verify the performance and stability of the proposed model. Experimental results showed that the five models achieved excellent performance. The XGBoost and random forest models achieved the best accuracies (97.16% and 96.82%, respectively) of predicting 32 terrorist organizations with the highest attack frequencies. The proposed classifier framework is useful for the accurate and efficient prediction of terrorist organizations responsible for attacks and can be extended to predict all terrorist organizations.

Collective Predator Perception Advertisement in Fish

The idea that prey might advertise their perception of predators to avoid attacks has received considerable attention in the literature. However, evidence for reduced attack frequencies or attack success in predators as a result of perception advertisement in prey is limited or indirect. Here we present a field study which investigated the benefits of waves produced by fish at the water surface when diving down collectively in response to attacks of avian predators. Instead of merely escaping, fish engaged in surface waves that were highly conspicuous, repetitive and rhythmic involving many thousands of individuals for up to 2 min. Experimentally-induced fish waves doubled the time birds waited until their next attack therefore substantially reducing attack frequency. In one avian predator, capture probability, too, decreased with wave number and birds switched perches in response to wave displays more often than in control treatments suggesting that they directed their attacks elsewhere. Taken together these results support fish waves’ function of perception advertisement. A predator confusion effect is also possible but so far is not known to be associated with waving behaviour especially given that rhythmic waving could make prey more predictable. Collectively produced perception advertisements raise some intriguing questions of how fish synchronise to produce such signals and which pathway has led to their evolution.