Different Levels Of Control Research Articles

Hydrogel scaffolds as in vitro models to study fibroblast activation in wound healing and disease.

Wound healing results from complex signaling between cells and their environment in response to injury. Fibroblasts residing within the extracellular matrix (ECM) of various connective tissues are critical for matrix synthesis and repair. Upon injury or chronic insult, these cells activate into wound-healing cells, called myofibroblasts, and repair the damaged tissue through enzyme and protein secretion. However, misregulation and persistence of myofibroblasts can lead to uncontrolled accumulation of matrix proteins, tissue stiffening, and ultimately disease. Extracellular cues are important regulators of fibroblast activation and have been implicated in their persistence. Hydrogel-based culture models have emerged as useful tools to examine fibroblast response to ECM cues presented during these complex processes. In this Mini-Review, we will provide an overview of these model systems, which are built upon naturally-derived or synthetic materials, and mimic relevant biophysical and biochemical properties of the native ECM with different levels of control. Additionally, we will discuss the application of these hydrogel-based systems for the examination of fibroblast function and fate, including adhesion, migration, and activation, as well as approaches for mimicking both static and temporal aspects of extracellular environments. Specifically, we will highlight hydrogels that have been used to investigate the effects of matrix rigidity, protein binding, and cytokine signaling on fibroblast activation. Last, we will describe future directions for the design of hydrogels to develop improved synthetic models that mimic the complex extracellular environment.

Evolutionary algorithm-based design of a fuzzy TBF predictive model and TSK fuzzy anti-sway crane control system

The efficiency of material handling system requires an automation on the different levels of control and supervision to keep availability of the material handling devices for fast, safety and precise transferring materials, as well as to reduce the maintenance cost, which is involved by enhancing the productivity of manufacturing process. In this paper, evolutionary-based algorithm for fuzzy logic-based data-driven predictive model of time between failures (TBF) and adaptive crane control system design is proposed. The heuristic searching strategy combining the arithmetical crossover, uniform and non-uniform mutation and deletion/insertion mutation is developed for optimizing the rules base (RB) and tuning the triangular-shaped membership functions to increase the efficiency and accuracy of a fuzzy rule-based system (FRBS). The evolutionary algorithm (EA) was employed to design a fuzzy predictive model based on the historical data of operational states monitored between the failures of the laboratory scaled overhead traveling crane electronic equipment. The fuzzy predictive model of TBF was implemented in the supervisory system created for supporting decision-making process through forecasting upcoming failure and delivering the user-defined maintenance strategies. The effectiveness of EA was also verified through designing a Takagi–Sugeno–Kang (TSK) fuzzy controller in the anti-sway crane control system.

The Returns to Education for Opportunity Entrepreneurs, Necessity Entrepreneurs and Paid Employees

We assess the relevance of formal education for the productivity of the self-employed and distinguish between opportunity entrepreneurs, who voluntarily pursue a business opportunity, and necessity entrepreneurs, who lack alternative employment options. We expect differences in the returns to education between these groups because of different levels of control. We use the German Socio-economic Panel and account for the endogeneity of education and non-random selection. The results indicate that the returns to a year of education for opportunity entrepreneurs are 3.5 percentage points higher than the paid employees’ rate of 8.1%, but 6.5 percentage points lower for necessity entrepreneurs.

The returns to education for opportunity entrepreneurs, necessity entrepreneurs, and paid employees

We assess the relevance of formal education on the productivity of the self-employed, distinguishing between opportunity entrepreneurs, who voluntarily pursue a business opportunity, and necessity entrepreneurs, who lack alternative employment options. We expect differences in the returns to education between these groups due to different levels of control over the use of their human capital. The analysis employs the German Socio-Economic Panel and accounts for the endogeneity of education and non-random selection. Results indicate that the returns to a year of education for opportunity entrepreneurs are similar to the paid employees’ rate of 8.8%, but 3 percentage points lower for necessity entrepreneurs. Pooling the two types of entrepreneurs tends to understate the value of education for opportunity entrepreneurs and may spark misguided hopes concerning necessity entrepreneurs. The results may also partly explain Europe/US differences in average entrepreneurial returns.

A prospective study of fusional convergence parameters in Chinese patients with intermittent exotropia

To evaluate the correlation between different fusional convergence parameters and the Newcastle Control Score (NCS) in children with intermittent exotropia. In this consecutive prospective observational series, 101 Chinese children with intermittent exotropia were examined by a single observer, who assessed the level of control using the revised NCS and measured the angle of deviation and fusional convergence. Levels of control were defined according to the NCS as good (0-3), moderate (4-6), or poor (7-9). The correlation between the different fusional convergence parameters and the NCS was evaluated. The total convergence amplitude was similar among the different control groups (P = 0.288 and P = 0.628 at near and at distance, respectively). The convergence reserve was higher in the good control group compared with the moderate and poor control groups, both at near (P = 0.001) and at distance (P = 0.001). Among all fusional convergence parameters, we determined that the fusional reserve ratio had strongest correlation with control (near ratio: r = -0.66, P = 0.001; distant ratio: r = -0.59, P = 0.001). Among patients with a fusional reserve ratio ≥ 2 at distance, 100% (5 of 5 patients) of these patients demonstrated good control (NCS ≤ 3). In children with intermittent exotropia, the total convergence amplitude was similar among different levels of control. The convergence reserve was lower in the poor control group. Fusional reserve ratio ≥ 2 was an indicator of good control in patients.

Alveolar nitric oxide and asthma control in mild untreated asthma

The role of the peripheral airways in asthma is increasingly being recognized as a potential target for the achievement of optimal control of the disease. We postulated that the inflammatory changes of the small airways are implicated in the lack of asthma control in mild asthma. To test this hypothesis, we measured the alveolar fraction of exhaled NO (CalvNO) in patients with mild asthma with different levels of control of symptoms. Seventy-eight patients with asthma (35 men, age, 37 ± 15 years; FEV1 percentage of predicted, 100% ± 9%) were studied. Asthma control was assessed by using the Asthma Control Test (ACT). Measurements of exhaled NO at multiple constant flows were performed. Bronchial NO concentrations were 27.1 ± 20 nL/min, [corrected] and CalvNO levels were 5.7 ± 3.4 ppb. The ACT score was 20 ± 4.2. The level of asthma control was not associated with bronchial NO concentrations (rs = 0.16, P = .15). However, a significant correlation was found between the ACT score and CalvNO (rs = 0.25, P = .03). Moreover, CalvNO was significantly higher in patients with uncontrolled asthma than in patients with controlled/partially controlled asthma (6.7 ± 2.6 ppb vs 4.9 ± 2.6 nL/min, [corrected] respectively, P = .02). In the subgroup of patients with asthma who underwent extrafine inhaled corticosteroid treatment, the magnitude of the inhaled corticosteroid-induced improvement in asthma control positively correlated with baseline CalvNO at 1 month (rs = 0.39, P = .003) and at 3 months (rs = 0.49, P < .0001). The alveolar component of exhaled NO is associated with the lack of asthma control in patients with mild, untreated asthma. This observation supports the notion that abnormalities of the peripheral airways are implicated in the mildest forms of asthma.

Voltage-Gated Synthetic Pores for Controlled Transport of Ions and Neutral Molecules

Synthetic nanopores similar to biological channels are designed to allow for controlled transport of ions and molecules. We have developed a synthetic mimic of a voltage-gated channel equipped with an electromechanical gate that restricts or permits the transport as a function of external voltage. The gate is built from single-stranded DNA molecules attached to the small opening of an asymmetric, conical shaped nanopore. Voltage-dependent conformations of the ssDNA lead to voltage-dependent opening of the pore. In addition, the DNA conformation was found to be dependent on the ionic strength of the electrolyte allowing one to achieve different levels of control as a function of KCl concentration. Since changes in the DNA conformation occur inside a very restricted volume of a nanopore, hysteresis effects were observed, which could become the basis for construction of an ionic memristor. The memory and hysteresis effects are most pronounced in pores with the effective diameter below 5 nm. Voltage-gated synthetic pores were also shown to exhibit an on/off transition as a function of pH and the sequence of DNA molecules attached to the pore walls. Voltage and pH dependent pore opening was confirmed by spectroscopic studies of neutral dyes through membranes containing 10⊥5 voltage-gated synthetic pores per cm⊥2. This voltage-controlled system could find application in building separation membranes which would permit transport of differently sized species as regulated by the controlled pore opening.

Parliamentary control of security information agency in terms of security culture: State and problems

Even though security services have the same function as before, today they have different tasks and significantly more work than before. Modern security problems of the late 20th and early 21st century require states to reorganize their security services, adapting them to the new changes. The reorganization involves, among other things, giving wider powers of the security services, in order to effectively counter the growing and sophisticated security threats, which may also lead to violations of human rights and freedoms. It is therefore necessary to define the right competence, organization, authority and control of these services. In democratic countries, there are several institutions with different levels of control of security services. Parliament is certainly one of the most important institutions in that control, both in the world and in our country. Powers, finance, the use of special measures and the nature and scope of work of the Security Information Agency are certainly object of the control of the National Assembly. What seems to be the problem is achieving a balance between the need for control of security services and security services to have effective methods for combating modern security problems. This paper presents the legal framework related to the National Assembly control of the Security Intelligence Agency, as well as the practical problems associated with this type of control. We analyzed the role of security culture as one of the factors of that control. In this regard, it provides guidance for the practical work of the members of parliament who control the Security Intelligence Agency, noting in particular the importance of and the need for continuous improvement of security culture representatives.

Power corrupts co-operation: cognitive and motivational effects in a double EEG paradigm

This study investigated the effect of interpersonal power on co-operative performance. We used a paired electro-encephalogram paradigm: pairs of participants performed an attention task, followed by feedback indicating monetary loss or gain on every trial. Participants were randomly allocated to the power-holder, subordinate or neutral group by creating different levels of control over how a joint monetary reward would be allocated. We found that power was associated with reduced behavioural accuracy. Event-related potential analysis showed that power-holders devoted less motivational resources to their targets than did subordinates or neutrals, but did not differ at the level of early conflict detection. Their feedback potential results showed a greater expectation of rewards but reduced subjective magnitude attributed to losses. Subordinates, on the other hand, were asymmetrically sensitive to power-holders' targets. They expected fewer rewards, but attributed greater significance to losses. Our study shows that power corrupts balanced co-operation with subordinates.

Bioinspiration and emerging actuator technologies

Biological systems in nature went through long evolution process that led to highly effective and efficient systems with excellent performance. Biomimetics is an interdisciplinary scientific research focuses on making nature as new sources of inspiration to study, analyze and design of creative and efficient engineering systems supported by innovative technologies. Smart materials are the foundation supporting the development of creative bioinspiration. Wide ranges of biologically inspired systems have been developed. However, engineering such as biomimetic intelligent creatures was hampered by physical and technological constraints, and it is still a challenge. Actuators are essential elements within mechatronical systems due to their important role in motion control systems and hence there is a need to develop new trend of actuators that can be inspired from biological actuation systems in nature associated with different levels of control. Making intelligent creatures that are actuated by biologically inspired modern actuators and artificial muscles would create new reality with great potentials. This paper provides the concept of biomimetic as an interdisciplinary field, discusses the enabling technologies, and presents the main development and bioinspired and emerging actuator technologies.

Chondrogenic Differentiation of Adult MSCs

Chondrogenesis is a vital part of adult life, as cartilage is important not only for articulation of joints but also maintenance functions of the body. Chondrogenesis is a five way process of intricate events controlled by specific genes and cell-cell interactions which has been documented over recent years. This review highlights the current literature regarding the process of endochondral ossification and covers the different level of control at agent level. Due to the proliferative nature of chondrogenesis and using chondrocytes for self renewal and repair, current research involves finding ways in which to improve and replicate expansion of chondrocytes. The review summarises ways in which ex vitro expansion can be manipulated using growth factors, external sources and scaffolds.

General self-efficacy influences affective task reactions during a work simulation: the temporal effects of changes in workload at different levels of control

This study investigated the effects of workload, control, and general self-efficacy on affective task reactions (i.e., demands-ability fit, active coping, and anxiety) during a work simulation. The main goals were (1) to determine the extent general self-efficacy moderates the effects of demand and control on affective task reactions and (2) to determine if this varies as a function of changes in workload. Participants (N=141) completed an inbox activity under conditions of low or high control and within low and high workload conditions. The order of trials varied so that workload increased or decreased. Results revealed individuals with high general self-efficacy reported better demands-abilities fit and active coping as well as less anxiety. Three interactive effects were found. First, it was found that high control increased demands-abilities fit from trial 1 to trial 2, but only when workload decreased. Second, it was found that low efficacious individuals active coping increased in trial 2, but only under high control. Third, it was found that high control helped high efficacious individuals manage anxiety when workload decreased. However, for individuals with low general self-efficacy, neither high nor low control alleviated anxiety (i.e., whether workload increased or decreased over time).

The Returns to Education for Opportunity Entrepreneurs, Necessity Entrepreneurs, and Paid Employees

We assess the relevance of formal education for the productivity of the self-employed and distinguish between opportunity entrepreneurs, who voluntarily pursue a business opportunity, and necessity entrepreneurs, who lack alternative employment options. We expect differences in the returns to education between these groups because of different levels of control. We use the German Socio-economic Panel and account for the endogeneity of education and non-random selection. The results indicate that the returns to a year of education for opportunity entrepreneurs are 3.5 percentage points higher than the paid employees' rate of 8.1%, but 6.5 percentage points lower for necessity entrepreneurs.

Scale, governance and the management of river basins: A case study from Central Iran

Aquatic socio-ecological systems show pervasive cross-scale interactions and problems of fit between ecosystems and institutions. Nested bio-hydrological processes within river basins are prone to third-party impacts, and equitable/sustainable management of water resources requires adequate governance patterns that both cover relevant scalar levels and handle cross-scale interactions. This paper provides the example of the Zayandeh Rud basin, in central Iran, and describes the historical evolution of water use at three different nested scales. It shows how the gradual overallocation of water resources (basin closure) and the manipulation of the hydrological cycle by the state and other actors have resulted in a constant spatial and social redistribution of water use and associated benefits and costs. State-centered modes of governance characterized by the priority to large-scale infrastructure, vested political and financial interests, lack of attention to local processes and hydrological interconnectedness, and the neglect of environmental degradation, must give way to forms of comanagement that better articulate the different levels of control and governance.

Monitoring Asthma Control in Children With Allergies by Soft Computing of Lung Function and Exhaled Nitric Oxide

Asthma control is emphasized by new guidelines but remains poor in many children. Evaluation of control relies on subjective patient recall and may be overestimated by health-care professionals. This study assessed the value of spirometry and fractional exhaled nitric oxide (FeNO) measurements, used alone or in combination, in models developed by a machine learning approach in the objective classification of asthma control according to Global Initiative for Asthma guidelines and tested the model in a second group of children with asthma. Fifty-three children with persistent atopic asthma underwent two to six evaluations of asthma control, including spirometry and FeNO. Soft computing evaluation was performed by means of artificial neural networks and principal component analysis. The model was then tested in a cross-sectional study in an additional 77 children with allergic asthma. The machine learning method was not able to distinguish different levels of control using either spirometry or FeNO values alone. However, their use in combination modeled by soft computing was able to discriminate levels of asthma control. In particular, the model is able to recognize all children with uncontrolled asthma and correctly identify 99.0% of children with totally controlled asthma. In the cross-sectional study, the model prospectively identified correctly all the uncontrolled children and 79.6% of the controlled children. Soft computing analysis of spirometry and FeNO allows objective categorization of asthma control status.

Frontiers in invertebrate physiology - grand challenge.

Another issue, which has been increasing enormously during the last years, is the inves-tigation of plasticity in the nervous control of physiological functions (Yamada et al., 2010). Adaptations to external and internal modifications in sensory and motor systems controlling different physiological functions become more and more evident. Detection of intra- and inter-specific stimuli is modi-fied by, e.g., experience and reproductive state (Iyengar et al., 2010). However, we are far from understanding the cellular mecha-nisms and signaling pathways involved in these forms of physiological plasticity. It will be important in the future to investigate the role of hormones, neuromodulators and their mechanisms of action ideally in parallel in different invertebrate species both during development and in adult organisms. New biochemical techniques allow us to detect and measure minute traces of neuropeptides in single cells, whose roles are still largely unknown ( Yew et al., 2009 ). Another impor -tant point is the rapidly developing field of research on post-transcriptional regulation mechanisms involving non-coding RNAs like microRNA (Vo et al., 2010). In addi-tion to plasticity of the individual, different levels of control of physiological plasticity should be taken into consideration at the populational level. Here genetic variation, epigenetic phenomena, and phenotypic plasticity might play together (Espinosa-Soto et al., 2011).Politically important issues such as envi-ronmental and climatic changes (global warming) have a severe impact on the physi-ology of invertebrate organisms. Classically insects, but also aquatic invertebrates have been, and are still, important indicators of pollution. The typically used models, such as the honeybee, allow to study the effects of, e.g., pesticides at multiple levels, from gene expression, over ion channel function to the physiology of the nervous system, behavior, and cognition. Thus ecophysiol-ogy is a growing field within invertebrate physiology and environmental effects on,

Symposium: Innovation, Skills and Training

The skills policies of the late 1980s and early 1990s that underlay the national training reform agenda and the unified national higher education system were predicated on the quest for a 'clever country', competing in global markets through high value added exports. In the past decade, the focus of government policy has shifted to the promotion of innovation, based on the creation of intangible intellectual capital in the quest for participation in a 'global know ledge economy'. Innovation is more than novelty or even invention: it involves change that results in improvement in products, processes, methods, systems and working relationships. The focus in this symposium is the role of workers in innovation. Dent, Fenwick and Newitt draw a distinction between the technological development that can be captured in intellectual property (patents, copyright, plant breeders' rights and so on) and the more nebulous, but equally important concept of 'know-how, based on complex, non-linear patterns of development and diffusion. The authors approach the question of how best to encourage worker innovation by drawing together scholarship from the fields of employment law, intellectual property law and equity. Arguing the incompleteness of existing approaches, which they classify as based either on economic or fairness perspectives, they advance a new framework, based on practices central to the relationship between employers and workers. Such practices include inventive activities, improvements to repetitive actions, creative insights, and attitudes or perceptions. Drawing on psychological contract theory to identify non-financial incentives, Dent, Fenwick and Newitt suggest that an important motivator of innovation is the allocation of control over its uses and outcomes. Drawing on his research on the contribution of worker skills to an industry's or a nation's potential for innovation, Fraser provides an empirically based re-examination of the deskilling thesis--a thesis which sees the underlying tendency of capitalist work organisation as a fragmentation of tasks in order to allow the pace of work to be intensified. Without rejecting this thesis as an underlying historical trend, Fraser investigates recent short-term shifts in the aggregate skill content of jobs in order to identify dynamic aspects of skill change. To the familiar skill criteria of job complexity and worker autonomy/ control, he adds a third dimension of change--skill-intensity. This is extent to which a job exercises, challenges and develops the skills of the person doing it. The analysis is applied across the spectrum of jobs at all qualification levels and organised to take account of different levels of control over the pace of work. Two sub-dimensions of skill-intensity--stretch and learning--provide insight into the psychology of workplace innovation. The distinction between radical and incremental innovation is highlighted in the article by Toner. Radical innovation is more focused on science and engineering, takes longer and requires further innovations in the process of take-up. It is likely eventually to generate Schumpeter's 'creative destruction' of existing techniques, skills, products and markets. By contrast, Toner emphasises the importance of investing in the cumulative productivity benefits of incremental innovation, based on small changes introduced by workers or required by consumers. He critiques the policy risks of placing too much emphasis on research, rather than development, in R&D, and emphasises the critical importance of diffusion in the development process. Stressing the importance of skilled production workers, particularly tradespersons and technicians, he argues that it has been a mistake not to include the Vocational Education and Training (VET) system in national innovation policy, programs and advisory structures. Contrasting the German and Anglophone models of skill development, Toner identifies ways in which Australia's recent under-resourcing of the VET system is likely to inhibit innovation. …

Evaluation of the COSHH Essentials Model with a Mixture of Organic Chemicals at a Medium-Sized Paint Producer

The Control of Substances Hazardous to Health (COSHH) Essentials model was evaluated using full-shift exposure measurements of five chemical components in a mixture [acetone, ethylbenzene, methyl ethyl ketone, toluene, and xylenes] at a medium-sized plant producing paint materials. Two tasks, batch-making and bucket-washing, were examined. Varying levels of control were already established in both tasks and the average exposures of individual chemicals were considerably lower than the regulatory and advisory 8-h standards. The average exposure fractions using the additive mixture formula were also less than unity (batch-making: 0.25, bucket-washing: 0.56) indicating the mixture of chemicals did not exceed the combined occupational exposure limit (OEL). The paper version of the COSHH Essentials model was used to calculate a predicted exposure range (PER) for each chemical according to different levels of control. The estimated PERs of the tested chemicals for both tasks did not show consistent agreement with exposure measurements when the comparison was made for each control method and this is believed to be because of the considerably different volatilities of the chemicals. Given the combination of health hazard and exposure potential components, the COSHH Essentials model recommended a control approach ‘special advice’ for both tasks, based on the potential reproductive hazard ascribed to toluene. This would not have been the same conclusion if some other chemical had been substituted (for example styrene, which has the same threshold limit value as toluene). Nevertheless, it was special advice, which had led to the combination of hygienic procedures in place at this plant. The probability of the combined exposure fractions exceeding unity was 0.0002 for the batch-making task indicating that the employees performing this task were most likely well protected below the OELs. Although the employees involved in the bucket-washing task had greater potential to exceed the threshold limit value of the mixture (P > 1 = 0.2375), the expected personal exposure after adjusting for the assigned protection factor for the respirators in use would be considerably lower (P > 1 = 0.0161). Thus, our findings suggested that the COSHH essentials model worked reasonably well for the volatile organic chemicals at the plant. However, it was difficult to override the reproductive hazard even though it was meant to be possible in principle. Further, it became apparent that an input of existing controls, which is not possible in the web-based model, may have allowed the model be more widely applicable. The experience of using the web-based COSHH Essentials model generated some suggestions to provide a more user-friendly tool to the model users who do not have expertise in occupational hygiene.

Phénotype des patients asthmatiques selon le score dérivé de l’Asthma Control Test ®

Today the control of asthma is a key element of national and international guidelines. The ER'Asthma survey, created in 2003, measured the control of asthma and its determinants in a primary care population. The aim of the current analysis of the ER'Asthma database was to characterize the phenotype of asthmatic patients according to three levels of control by using a score derived from the Asthma Control Test (ACT). An ancillary descriptive analysis of a cross-sectional epidemiological survey of 15,534 asthmatic patients. A score derived from the ACT was calculated for each patient by using an algorithm applied to five questions from the ER'Asthma questionnaire and similar to those of the ACT. The analysis looked for association between the patients' characteristics and the different levels of control. The uncontrolled patients were more likely to be obese, smokers, older, treated by a single drug, non-compliant and to have a poorer quality of life. The use of a validated three-level score has confirmed the phenotypes of poorly controlled patients. ACT not only evaluates asthma control but could also be the starting point of a discussion with the patients on the correction of modifiable risk-factors and the necessary compliance with treatment.

From monolithic to component-based performance evaluation of software architectures

Model-based performance evaluation methods for software architectures can help architects to assess design alternatives and save costs for late life-cycle performance fixes. A recent trend is component-based performance modelling, which aims at creating reusable performance models; a number of such methods have been proposed during the last decade. Their accuracy and the needed effort for modelling are heavily influenced by human factors, which are so far hardly understood empirically. Do component-based methods allow to make performance predictions with a comparable accuracy while saving effort in a reuse scenario? We examined three monolithic methods (SPE, umlPSI, Capacity Planning (CP)) and one component-based performance evaluation method (PCM) with regard to their accuracy and effort from the viewpoint of method users. We conducted a series of three experiments (with different levels of control) involving 47 computer science students. In the first experiment, we compared the applicability of the monolithic methods in order to choose one of them for comparison. In the second experiment, we compared the accuracy and effort of this monolithic and the component-based method for the model creation case. In the third, we studied the effort reduction from reusing component-based models. Data were collected based on the resulting artefacts, questionnaires and screen recording. They were analysed using hypothesis testing, linear models, and analysis of variance. For the monolithic methods, we found that using SPE and CP resulted in accurate predictions, while umlPSI produced over-estimates. Comparing the component-based method PCM with SPE, we found that creating reusable models using PCM takes more (but not drastically more) time than using SPE and that participants can create accurate models with both techniques. Finally, we found that reusing PCM models can save time, because effort to reuse can be explained by a model that is independent of the inner complexity of a component. The tasks performed in our experiments reflect only a subset of the actual activities when applying model-based performance evaluation methods in a software development process. Our results indicate that sufficient prediction accuracy can be achieved with both monolithic and component-based methods, and that the higher effort for component-based performance modelling will indeed pay off when the component models incorporate and hide a sufficient amount of complexity.