Minimum Divergence Research Articles

Genetic Characterization and Breeding Habitats of Black Fly (Diptera, Simuliidae) Vector Species in Laos

Genetic diversity and ecology are two important aspects of vector species crucial to a full understanding of disease epidemiology. In this study, we examined genetic diversity, genetic structure and the physiochemical parameters of the breeding habitats of the two significant black fly vector species, Simulium chumpornense Takaoka and Kuvangkadilok and S. nodosum Puri, from Laos. Genetic diversity of S. chumpornense in Laos was relatively high with maximum genetic divergence of 3.05% but no significant genetic differentiation between populations. Comparisons with conspecific populations from Thailand also found no genetic differentiation between the two countries. This possibly related to the recent history of this species, as a very recent (31,000 years ago) historical population expansion was detected. Physicochemical parameters of the breeding habitats suggest the ability to utilize diverse stream sizes from small flows (1 m wide) to huge rivers (290 m or more wide). Populations of S. nodosum from Laos had low genetic diversity with maximum genetic divergence of 2.56% and no genetic structuring among populations. Comparisons with those reported from other countries revealed five genetically divergent lineages (I–V) with minimum genetic divergence of 1.36%. The majority (42 of 52) of specimens from Laos belonged to lineage I and the remaining (10) comprised lineage II. Lineage I is the largest and representative of specimens from Thailand, Myanmar, Vietnam, Taiwan and Laos. Population history analysis revealed that lineage I had undergone recent demographic expansion dating back to 7000 years ago. This very recent population expansion resembles others reported from Thailand and possibly indicates a response to increasing human and domestic animals following the agricultural revolution. Breeding sites of S. nodosum are diverse in respect to elevation, velocity, water conductivity and streambed particle size. The ability to utilize a wide variety of breeding sites could promote the production of a large adult population, which can be a pest for humans and other animals.

Classification, identification, and DNA barcoding study for common cockroach species (Dictyoptera: Blattaria) from China

Cockroaches are well-known pests and quarantined organisms worldwide. Due to morphological diversity and a lack of molecular data, their classification and identification are facing challenges. This study performed classification, identification, and DNA barcoding for cockroaches collected from China. Seventy-six samples were morphologically identified as seven species of two superfamilies that included Blattella germanica, Eublaberus posticus and Blaptica dubia belonging to the superfamily Blaberoidea, and Periplaneta americana, Periplaneta lateralis, Periplaneta fuliginosa and Periplaneta australasiae belonging to the superfamily Blattoidea. Based on sequence alignments of nine ribosomal and mitochondrial genes across the order Blattaria retrieved from GenBank, rDNA ITS2-517 bp and mtDNA 16S-327 bp were screened as candidates for molecular identification. Universal primers were designed for PCR amplification, cloning, and sequencing of the 37 representative samples. Sequence alignments and phylogeny analysis showed that both ITS2 and 16S confirmed samples 1–9, 20–24, and 25–29 as B. germanica, P. americana, and P. lateralis, respectively; only 16S (not ITS2) confirmed samples 10–14, 15–19, 30–34, and 35–37 as E. posticus, Blap. dubia, P. fuliginosa, and P. australasiae, respectively, indicating that 16S was a better target than ITS2 for molecular identification of cockroaches. Conservative motif and divergence analysis further revealed that ITS2 sequences vary significantly among different taxa, whereas 16S sequences are relatively conserved. There is an obvious barcoding gap between maximum intraspecific divergence and minimum interspecific divergence (2.57 % vs. 5.62 %) for ITS2, but not for 16S (6.15 % vs. 2.63 %). Therefore, it was confirmed that ITS2 is an ideal DNA barcode for molecular identification of cockroaches at lower category.

Numerical solution of the boundary value problem for inertia-gravity internal waves

This paper presents a numerical calculation of the boundary value problem for the equation of free internal inertia-gravity waves in an unbounded basin of constant depth in the Boussinesq approximation and the presence of a two-dimensional vertically inhomogeneous flow. The boundary value problem for the vertical velocity amplitude has complex coefficients and is solved both numerically and by perturbation theory. Using the example of calculating the decrement of attenuation of internal waves and momentum wave flows, it is shown that the exact numerical calculation gives significantly better estimates in comparison with the perturbation method. In particular, at minimum divergence in the dispersion curves for both calculation methods, the imaginary part of the wave frequency, interpreted as the decrement of attenuation, can differ by two or three orders of magnitude. Vertical wave momentum fluxes are comparable to turbulent ones and may exceed them, with results obtained by the numerical method being almost an order of magnitude smaller than those calculated by the perturbation theory method.

Electrospray plume divergence: Background pressure influence

The influence of background pressure on electrospray plume evolution is observed by simulating the emission and propagation of an electrospray particle population into an electric field at a range of relevant background pressures. Differences in plume evolution from atmospheric pressure to one hundredth of atmospheric pressure are evident from plume characteristics such as (1) the overall domain of the resulting plumes and (2) the terminal angle at a downstream terminus of one standard deviation and three standard deviations of particle number density. Plume divergence and terminal angle are shown to correlate strongly with background pressure for pressures above which plume-background collision rates are significant, consistent with experimental observations of increased plume divergence with increased background pressure. The results suggest a simple expression for the pressure below which a system achieves minimum plume divergence: Pth=kT/7.7299σfld for a system of temperature T, background fluid molecules with cross-section σfl, and plume species of diameter d.

Identifying hemodynamic factors associated with the rupture of anterior communicating artery aneurysms based on global modeling of blood flow in the cerebral artery network

Anterior communicating artery (ACoA) aneurysms are more prone to rupture compared to aneurysms present in other cerebral arteries. We hypothesize that systemic blood flow in the cerebral artery network plays an important role in shaping intra-aneurysmal hemodynamic environment thereby affecting the rupture risk of ACoA aneurysms. The majority of existing numerical studies in this field employed local modeling methods where the physical boundaries of a model are confined to the aneurysm region, which, though having the benefit of reducing computational cost, may compromise the physiological fidelity of numerical results due to insufficient account of systemic cerebral arterial hemodynamics. In the present study, we firstly carried out numerical experiments to address the difference between the outcomes of local and global modeling methods, demonstrating that local modeling confined to the aneurysm region results in inaccurate predictions of hemodynamic parameters compared with global modeling of the ACoA aneurysm as part of the cerebral artery network. Motivated by this finding, we built global hemodynamic models for 40 ACoA aneurysms (including 20 ruptured and 20 unruptured ones) based on medical image data. Statistical analysis of the computed hemodynamic data revealed that maximum wall shear stress (WSS), minimum WSS divergence, and maximum WSS gradient differed significantly between the ruptured and unruptured ACoA aneurysms. Optimal threshold values of high/low WSS metrics were determined through a series of statistical tests. In the meantime, some morphological parameters of aneurysms, such as large nonsphericity index, aspect ratio, and bottleneck factor, were found to be associated closely with aneurysm rupture. Furthermore, multivariate logistic regression analyses were performed to derive models combining hemodynamic and morphological parameters for discriminating the rupture status of aneurysms. The capability of the models in rupture status discrimination was high, with the area under the receiver operating characteristic curve reaching up to 0.9. The findings of the study suggest that global modeling of the cerebral artery network is essential for reliable quantification of hemodynamics in ACoA aneurysms, disturbed WSS and irregular aneurysm morphology are associated closely with aneurysm rupture, and multivariate models integrating hemodynamic and morphological parameters have high potential for assessing the rupture risk of ACoA aneurysms.

Intersectional fair ranking via subgroup divergence

Societal biases encoded in real-world data can contaminate algorithmic decisions, perpetuating preexisting inequalities in domains such as employment and education. In the fair ranking literature, following the doctrine of affirmative action, fairness is enforced by means of a group-fairness constraint requiring “enough” individuals from protected groups in the top-k positions, for a ranking to be considered valid. However, which are the groups that need to be protected? And how much representation is “enough”? As the biases affecting the process may not always be directly observable nor measurable, these questions might be hard to answer in a principled way, especially when many different potentially discriminated subgroups exist. This paper addresses this issue by automatically identifying the disadvantaged groups in the data and mitigating their disparate representation in the final ranking. Our proposal leverages the notion of divergence to automatically identify which subgroups, defined as combination of sensitive attributes, show a statistically significant deviation, in terms of ranking utility, compared to the overall population. Subgroups with negative divergence experience a disadvantage. We formulate the problem of re-ranking instances to maximize the minimum subgroup divergence, while maintaining the new ranking as close as possible to the original one. We develop a method which is based on identifying the divergent subgroups and applying a re-ranking procedure which is monotonic w.r.t. the goal of maximizing the minimum divergence. Our experimental results show that our method effectively eliminates the existence of disadvantaged subgroups while producing rankings which are very close to the original ones.

Transcultural Adaptation of the Collaborative Model for Promoting Competence and Success for Students with Autism Spectrum Disorder (COMPASS)

ABSTRACT This study describes the transcultural adaptation of the Collaborative Model for Promoting Competence and Success for Students with Autism Spectrum Disorder (COMPASS) to Brazilian Portuguese (BP). A blind translation of the original version in English (OV) to the version in BP, blind back-translation of the BP version into English (BT), comparison of BT with OV to statistically verify the convergence (CO), minimum divergence (MD) and divergence of meaning (DM) between BT and OV, review of the BP version by a committee of experts, maintaining conceptual, idiomatic, semantic and cultural equivalence, and sending of the files to the author of the model, was carried out. 1372 items were translated from English to BP. After comparing BT/OV, 0.6% DM (9 items), 47.9% MD (657 items), and 51.5% CO (706 items) were found. 97 equivalences were made, 43 semantic and 54 conceptual. The author of the model received all files from steps 1 to 4. Having carried out this process, it is possible to state that COMPASS was transcultural adapted to BP. With the future availability of COMPASS in Brazil, we hope that it can contribute to the development of the quality of education for students with Autism Spectrum Disorder in the country.

Robust and efficient estimation in ordinal response models using the density power divergence

In real life, we frequently encounter ordinal variables depending upon independent covariates. The latent linear regression model is useful for modelling such data. One can find the model's parameters' maximum likelihood estimate (MLE). Though noted for its optimum properties, a small proportion of outliers may destabilize the MLE. This paper uses the minimum density power divergence estimate (MDPDE) as a robust alternative. The roles of different link functions are analysed in this context. We discuss their asymptotic properties in this setup. Unlike the MLE, the MDPDEs are robust for– lower values of the gross error sensitivity, and very high breakdown point. Also, the slope’s MDPDEs never implode. In simulation studies for pure data, MDPDEs perform almost as good as the MLE. However, the MDPDEs outperform the MLE in data contamination. Moreover, MDPDEs are very competitive with the other robust alternatives. Finally, this article is wrapped up with a real-data example.

Pembatasan Usia Minimal Perkawinan dalam Hukum Keluarga Islam Studi Komparasi Indonesia dan Yordania

The minimum age limit for marriage in Islamic Family Law is a provision that regulates the minimum age limit that must be met by individuals before legally entering into a marriage according to the principles of Islamic law. This is intended to protect the parties involved and ensure the physical, mental and emotional maturity of prospective partners before entering into marriage. This research uses a qualitative descriptive approach using literature study methods to investigate differences in minimum age restrictions for marriage between Islamic law and state policy. Data collection was carried out through direct surveys and literature searches from trusted sources, including international journals, books and e-books. The literature study method involves three essential steps: Literature Inventory, Literature Description, and Literature Comparison. The research focus is focused on analyzing laws regarding minimum age limits for marriage in various countries, with an emphasis on comparisons between Islamic legal views and implementation of state policies. The research findings produced several conclusions, including: 1) Differences in approach between Islamic law which does not set a minimum age limit and state policies such as Indonesia (19 years) and Jordan (18 years); 2) Limiting the age of marriage as an effort to protect and mature individuals in living a married life; 3) Rearranged minimum standardization divergence to prevent misuse; 4) Marriage as an institution with noble purposes, interpreted by Islamic law and adopted by the state taking into account local, social and cultural aspects.

Multilevel thresholding with divergence measure and improved particle swarm optimization algorithm for crack image segmentation

Crack formation is a common phenomenon in engineering structures, which can cause serious damage to the safety and health of these structures. An important method of ensuring the safety and health of engineered structures is the prompt detection of cracks. Image threshold segmentation based on machine vision is a crucial technology for crack detection. Threshold segmentation can separate the crack area from the background, providing convenience for more accurate measurement and evaluation of the crack condition and location. The segmentation of cracks in complex scenes is a challenging task, and this goal can be achieved by means of multilevel thresholding. The arithmetic-geometric divergence combines the advantages of the arithmetic mean and the geometric mean in probability measures, enabling a more precise capture of the local features of an image in image processing. In this paper, a multilevel thresholding method for crack image segmentation based on the minimum arithmetic-geometric divergence is proposed. To address the issue of time complexity in multilevel thresholding, an enhanced particle swarm optimization algorithm with local stochastic perturbation is proposed. In crack detection, the thresholding criterion function based on the minimum arithmetic-geometric divergence can adaptively determine the thresholds according to the distribution characteristics of pixel values in the image. The proposed enhanced particle swarm optimization algorithm can increase the diversity of candidate solutions and enhance the global convergence performance of the algorithm. The proposed method for crack image segmentation is compared with seven state-of-the-art multilevel thresholding methods based on several metrics, including RMSE, PSNR, SSIM, FSIM, and computation time. The experimental results show that the proposed method outperforms several competing methods in terms of these metrics.

Pembatasan Usia Minimal Perkawinan dalam Hukum Keluarga Islam Studi Komparasi Indonesia dan Yordania

The minimum age limit for marriage in Islamic Family Law is a provision that regulates the minimum age limit that must be met by individuals before legally entering into a marriage according to the principles of Islamic law. This is intended to protect the parties involved and ensure the physical, mental and emotional maturity of prospective partners before entering into marriage. This research uses a qualitative descriptive approach using literature study methods to investigate differences in minimum age restrictions for marriage between Islamic law and state policy. Data collection was carried out through direct surveys and literature searches from trusted sources, including international journals, books and e-books. The literature study method involves three essential steps: Literature Inventory, Literature Description, and Literature Comparison. The research focus is focused on analyzing laws regarding minimum age limits for marriage in various countries, with an emphasis on comparisons between Islamic legal views and implementation of state policies. The research findings produced several conclusions, including: 1) Differences in approach between Islamic law which does not set a minimum age limit and state policies such as Indonesia (19 years) and Jordan (18 years); 2) Limiting the age of marriage as an effort to protect and mature individuals in living a married life; 3) Rearranged minimum standardization divergence to prevent misuse; 4) Marriage as an institution with noble purposes, interpreted by Islamic law and adopted by the state taking into account local, social and cultural aspects.

Design of an ultra wideband THz reflectarray antenna based on orbital angular momentum

A Reflectarray antenna (RA) that can generate orbital angular momentum vortex waves in the THz band was proposed. First of all, a reflective phase-shifting element composed of a notched double-shaped ring and a single Matal structure was designed to form a radiation patch. The reflective phase-shifting element has the advantages of good linearity, high smoothness, and a large phase shift range, which is suitable for the subsequent production of reflective array antennas. Then, the phase distribution of the reflected wave of the OAM vortex wave carrying mode l=+1、+2、+3、+4 is given, and the size of each element is determined based on the reflected phase of each element. Using the proposed element, an OAM reflectarray antenna operating within the waveguide standard WR-5 (120GHz–220GHz) is designed. The optimal frequency band for antenna operation in mode l=+1 is 150GHz–190 GHz, and the maximum gain of the reflector array antenna is 19.4 dBi, and the minimum divergence angle of the antenna array is 5.2°, which has good directivity and beam radiation ability. The spiral structure of the OAM beam space generated by the RA in this paper is clearly visible, proving that the implementation of OAM vortex waves in the THz frequency band is feasible. This design also provides a new method for generating OAM vortex waves in wireless and microwave wireless communications. The proposed RA is suitable for 6G wireless communication systems.

Minimum density power divergence estimation for the generalized exponential distribution

Statistical modeling of rainfall data is an active research area in agro-meteorology. The most common models fitted to such datasets are exponential, gamma, log-normal, and Weibull distributions. As an alternative to some of these models, the generalized exponential (GE) distribution was proposed by Gupta and Kundu (2001a). Rainfall (specifically for short periods) datasets often include outliers, and thus, a proper robust parameter estimation procedure is necessary. Here, we use the popular minimum density power divergence estimation (MDPDE) procedure developed by Basu et al. (1998) for estimating the GE parameters. We derive the analytical expressions for the estimating equations and asymptotic distributions. We analytically compare MDPDE with maximum likelihood estimation in terms of robustness, through an influence function analysis. Besides, we study the asymptotic relative efficiency of MDPDE analytically for different parameter settings. We apply the proposed technique to some simulated datasets and two rainfall datasets from Texas, United States. The results indicate superior performance of MDPDE compared to the other existing estimation techniques in most of the scenarios.

Robust estimation of dependent competing risk model under interval monitoring and determining optimal inspection intervals

AbstractRecently, a growing interest is evident in modelling dependent competing risks in lifetime prognosis problems. In this work, we propose to model the dependent competing risks by Marshal‐Olkin bivariate exponential distribution. The observable data consists of a number of failures due to different causes across different time intervals. The failure count data is common in instances like one‐shot devices where the state of the subjects is inspected at different inspection times rather than the exact failure times. The point estimation of the lifetime distribution in the presence of competing risk has been studied through a divergence‐based robust estimation method called minimum density power divergence estimation (MDPDE) with and without constraint. The optimal value of the tuning parameter has been obtained. The testing of the hypothesis is performed based on a Wald‐type test statistic. The influence function is derived for the point estimator and the test statistic, reflecting the degree of robustness. Another key contribution of this work is determining the optimal inspection times based on predefined objectives. This article presents the determination of multi‐criteria‐based optimal design. Population‐based heuristic algorithm nondominated sorting‐based multiobjective Genetic algorithm is exploited to solve this optimization problem.

Assessment of genetic diversity of freshwater genus Labeo through DNA barcoding and phylogenetic analysis inhabited in the River Indus

ObjectivesGenus Labeo of family Cyprinidae comprising of important group of fish species are known for ornamental purpose, food, extracting oil, medicinal value and for potential viable aquaculture. The present study was conducted to assess the morphometric and molecular identification of freshwater fishes of genus Labeo including Catla catla, Labeo rohita, Labeo calbasu, Labeo gnius, Labeo bata from the three fish resources of River Indus, Punjab, Pakistan. MethodsOut of 75, thirty fish specimen were amplified and sequenced with 650 bp of mitochondrial COI gene for the evaluation of fish biodiversity, management and conservation by using different bioinformatics techniques. ResultsMaximum and minimum genetic divergence between fishes of C. catla, L. calbasu, L. boga, L. gonius and L. rohita, were 0.052 to 0.105, respectively. Highest divergence was found between Labeo bata and Labeo rohita. Interspecific mean distance was found higher than intraspecific distance. In nucleotide base composition, AT contents was higher than GC contents indicated the clear pattern of anti-G bias. Transition rate was k1 = 8.84 for purines and transversional rate was k2 = 15.47 for pyrimidines with transition/transversion bias R = 5.62. Tajima D test and nucleotide diversity was measured D = 1.382883 and π = 0.049981 respectively. Positive value of D indicated a strong selective pressure and lack of population expansion. Thirty species were identified with e-value 0.0 and similar identity 99.85 %–100 % with maximum 600 bp length. Phylogenetic tree revealed two major clades with 95 % high bootstrap values identity showed closet relationship among these species. ConclusionsCurrent study supported the efficacy of the COI gene for the species identification in River Indus and develop the concept for establishing Pakistani fish gene bank which is still needed.

Mathematical modeling of the ion extraction system of a radio-frequency ion source

In order to ensure space debris removal from the near-Earth space, the world scientific community is developing various technical means potentially capable of transporting the spent spacecraft to disposal orbits. The so-called Ion Beam Shepherd is among them. According to this method, in order to transfer momentum efficiently from an ion beam generated by a radio-frequency ion source mounted on board a service spacecraft, it is necessary to ensure the generation of an ion beam with the minimum divergence angle. In order to provide generation of a highly collimated ion beam for a system of contactless removal of technogenic space debris, an ion extraction system was modeled with the aim to study the influence of its geometric parameters on the angle of ion beam divergence at the ion source exit plane. Based on the preliminary study, a model of 28 full factorial experiment was developed for two types of electrodes in an ion extraction system. The regression coefficients have been defined that allow, without performing a large array of numerical studies, to assess the influence of various geometric parameters on the ion beam divergence angle.

Complete mitochondrial genome of golden variant of freshwater fish Labeo rajasthanicus (Cypriniformes: Cyprinidae): endemic to India

The complete mitochondrial genome of the freshwater fish species Labeo rajasthanicus was obtained, using Illumina NovaSeq 6000 with 2 × 150 bp paired-end sequencing. The mitogenome of L. rajasthanicus is 16,738 bp in length (GenBank accession no.: OQ834146), comprised of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and a control region, i.e. D-loop. The arrangement of genes was found to be identical to other Cypriniformes fish mitogenome, available in the NCBI database. The taxonomic status of L. rajasthanicus as a valid species was debated by some researchers and it was considered a synonym of L. boggut. However, phylogenetic analysis in the present study supports the species validity of L. rajasthanicus, as it showed a distinct node well separated from L. boggut and supported by a high bootstrap value. Furtherly, the pairwise genetic divergence among studied species showed the divergence between L. rajasthanicus and L. boggut as 1.6% whereas the minimum divergence was found to be 0.13% with L. dussumieri followed by L. fimbriatus (0.58%) and L. gonius (0.63%). The complete mitogenome of L. rajasthanicus will also be useful as a baseline reference genome for the reconstruction and annotation of the mitogenome of other Labeo species.

Species discrimination power of ITS DNA barcoding on Tristaniopsis species on Bangka Island, Indonesia

The rDNA ITS barcoding marker has been widely used for plant identification, along with other primers for the chloroplast sequence region. This study applied the ITS primer to discriminate Tristaniopsis spp. on Bangka Island. Twelve leaf samples were collected from five community forests in Bangka district. The pairwise distance between sequences calculated using Kimura’s two parameters in MEGA11 revealed that pelawan air is different from other pelawan specimens (1.58–2.1%), while pelawan orange and pelawan merah specimens showed low variation (0–0.78%). There is a barcoding gap in the application of the ITS markers (full-length ITS including 5.8s, ITS1, and ITS2) for Tristaniopsis, which is shown by the higher value of minimum interspecific divergence than the value of maximum interspecific divergence for all three regions. Phylogeny trees constructed from the nucleotide sequence of 12 pelawan and other related taxa clustered pelawan merah and pelawan orange together and separated them from pelawan air.

Robust small area estimation for unit level model with density power divergence.

Unit level model is one of the classical models in small area estimation, which plays an important role with unit information data. Empirical Bayesian(EB) estimation, as the optimal estimation under normal assumption, is the most commonly used parameter estimation method in unit level model. However, this kind of method is sensitive to outliers, and EB estimation will lead to considerable inflation of the mean square error(MSE) when there are outliers in the responses yij. In this study, we propose a robust estimation method for the unit-level model with outliers based on the minimum density power divergence. Firstly, by introducing the minimum density power divergence function, we give the estimation equation of the parameters of the unit level model, and obtain the asymptotic distribution of the robust parameters. Considering the existence of tuning parameters in the robust estimator, an optimal parameter selection algorithm is proposed. Secondly, empirical Bayesian predictors of unit and area mean in finite populations are given, and the MSE of the proposed robust estimators of small area means is given by bootstrap method. Finally, we verify the superior performance of our proposed method through simulation data and real data. Through comparison, our proposed method can can solve the outlier situation better.

Analysis of one-shot device testing data under logistic-exponential lifetime distribution with an application to SEER gallbladder cancer data

In the literature, the reliability analysis of one-shot devices is found under accelerated life testing in the presence of various stress factors. The application of one-shot devices can be extended to the bio-medical field, where we often evidence that inflicted with a certain disease, survival time would be under different stress factors like environmental stress, co-morbidity, the severity of disease etc. This work is concerned with a one-shot device data analysis and applies it to SEER gallbladder cancer data. The two-parameter logistic-exponential distribution is applied as a lifetime distribution. For robust parameter estimation, weighted minimum density power divergence estimators (WMDPDE) is obtained along with the conventional maximum likelihood estimators (MLE). The asymptotic behaviour of the WMDPDE and the robust test statistic based on the density power divergence measure are also studied. The performances of estimators are evaluated through extensive simulation experiments. Later those developments are applied to SEER gallbladder cancer data. Citing the importance of knowing exactly when to inspect the one-shot devices put to the test, a search for optimum inspection times is performed. This optimization is designed to minimize a defined cost function which strikes a trade-off between the precision of the estimation and experimental cost. The search is accomplished through the population-based heuristic optimization method genetic algorithm.