Determination of collector chemicals from flotation process waters using capillary electrophoresis

Vaahdotusprosessia käytetään yleisesti erottamaan arvokkaita mineraaleja malmeista. Toimiakseen tehokkaasti prosessi tarvitsee kokoojakemikaaleja, joiden tehtävänä on sitoa halutut mineraalit ilmakupliin. Jotta näiden kemikaalien käyttäytymistä prosessissa voitaisiin ymmärtää paremmin ja prosessin ohjausta tehostaa, pitää kokoojia pystyä analysoimaan prosessivesistä. Työn kirjallisuusosassa on koottu ja vertailtu erilaisia kirjallisuudesta löytyneitä analyysimenetelmiä kokoojakemikaaleille. Kokeellisessaosassa on kehitetty kaksi kapillaarielektroforeesimenetelmää näiden kemikaalien tutkimiseen. Menetelmien toteamisrajat tutkituille kemikaaleille olivat seuraavanlaiset: natrium diiosobutylditiofosfaattille (DTP) 2,7 mg/L puhtaassa vedessä ja 6,7 mg/L prosessivedessä; natrium diisobutyldithiofosfinaatille (DTPI) vastaavasti 4,5 mg/L ja 6,7 mg/L; etyyli ksantaatille 0,025 mg/L ja 0,16 mg/L; ja isobutyyli ksantaatille 0,41 mg/L ja 0,62 mg/L. Näitä menetelmiä voidaan tulevaisuudessa kehittää kokoojien hajoamistuotteiden analysointia varten sekä prosessien on-line mittauksiin.

Capillary electrophoresis for monitoring of carboxylic, phenolic and amino acids in bioprocesses

Bioprocess technology is a multidisciplinary industry that combines knowledge of biology and chemistry with process engineering. It is a growing industry because its applications have an important role in the food, pharmaceutical, diagnostics and chemical industries. In addition, the current pressure to decrease our dependence on fossil fuels motivates new, innovative research in the replacement of petrochemical products. Bioprocesses are processes that utilize cells and/or their components in the production of desired products. Bioprocesses are already used to produce fuels and chemicals, especially ethanol and building-block chemicals such as carboxylic acids. In order to enable more efficient, sustainable and economically feasible bioprocesses, the raw materials must be cheap and the bioprocesses must be operated at optimal conditions. It is essential to measure different parameters that provide information about the process conditions and the main critical process parameters including cell density, substrate concentrations and products. In addition to offline analysis methods, online monitoring tools are becoming increasingly important in the optimization of bioprocesses. Capillary electrophoresis (CE) is a versatile analysis technique with no limitations concerning polar solvents, analytes or samples. Its resolution and efficiency are high in optimized methods creating a great potential for rapid detection and quantification. This work demonstrates the potential and possibilities of CE as a versatile bioprocess monitoring tool. As a part of this study a commercial CE device was modified for use as an online analysis tool for automated monitoring. The work describes three offline CE analysis methods for the determination of carboxylic, phenolic and amino acids that are present in bioprocesses, and an online CE analysis method for the monitoring of carboxylic acid production during bioprocesses. The detection methods were indirect and direct UV, and laser-induced frescence. The results of this work can be used for the optimization of bioprocess conditions, for the development of more robust and tolerant microorganisms, and to study the dynamics of bioprocesses.

University Image vs. University Identity: Congruence between Expectations and Experience

The aim of this thesis was to examine congruencies between university identity and university images of prospective and current students. Therefore, factors essentially influencing on expected and experienced university images were identified. Providing an understanding on the differences in the formation of both concepts allowed the analysis of potential incongruities between a university’s identity and the perceptions its students hold. The study was conducted in July and August 2013 at Lappeenranta University of Technology by means of a web-based research survey. The sample consisted of 160 international Master’s degree students who were admitted in 2011, 2012 and 2013. Descriptive and multivariate statistical analysis methods were used to process the data. The results of the study indicated statistically significant incongruities between the case university’s identity and its students’ images. Further, the expected and experienced university images showed incongruities to each other. Deviations were additionally detected to be dependent on the students’ home regions. All in all, there is potential for an improvement of the students’ experiences resulting from a low perception of the student’s preparation for future job life.

Differentiation of Metabolically Distinct Areas within Head and Neck Region using Dynamic 18F-FDG Positron Emission Tomography Imaging

Positron Emission Tomography (PET) using ¹⁸F-FDG is playing a vital role in the diagnosis and treatment planning of cancer. However, the most widely used radiotracer, ¹⁸F-FDG, is not specific for tumours and can also accumulate in inflammatory lesions as well as normal physiologically active tissues making diagnosis and treatment planning complicated for the physicians. Malignant, inflammatory and normal tissues are known to have different pathways for glucose metabolism which could possibly be evident from different characteristics of the time activity curves from a dynamic PET acquisition protocol. Therefore, we aimed to develop new image analysis methods, for PET scans of the head and neck region, which could differentiate between inflammation, tumour and normal tissues using this functional information within these radiotracer uptake areas. We developed different dynamic features from the time activity curves of voxels in these areas and compared them with the widely used static parameter, SUV, using Gaussian Mixture Model algorithm as well as K-means algorithm in order to assess their effectiveness in discriminating metabolically different areas. Moreover, we also correlated dynamic features with other clinical metrics obtained independently of PET imaging. The results show that some of the developed features can prove to be useful in differentiating tumour tissues from inflammatory regions and some dynamic features also provide positive correlations with clinical metrics. If these proposed methods are further explored then they can prove to be useful in reducing false positive tumour detections and developing real world applications for tumour diagnosis and contouring.

Managing Customer Issues through a Support Channel Network

The importance of after-sales service or service in general can be seen and experienced by customers every day with industrial as well as other non-industrial services or products. This dissertation, drawing on theory and experience, focuses on practical engineering implications, specifically the management of customer issues in the after-sales phase in the mobile phone arena. The main objective of this doctoral dissertation is to investigate customer after-sales issue management, specifically regarding mobile phones. The case studies focus on issue resolution time and the issue of corrective actions. This dissertation consists of a main body and four peer-reviewed journal articles and one manuscript currently under review by a peer-reviewed journal. The main body of this dissertation examines the elements of customer satisfaction, loyalty, and retention with respect to corrective actions to address customer issues and issue resolution time through literature and empirical studies. The five independent works are case studies supporting the thesis research questions. This study examines four questions: 1) What are the factors affecting corrective actions for customers? 2) How can customer issue resolution time be controlled? 3) What are the factors affecting processes in the service chain? and 4) How can communication be measured in a service chain? In this work, both quantitative and qualitative analysis methods are used. The main body of the thesis reviews the literature regarding the elements that bridge the five case studies. The case studies of the articles and surveys lean more toward the methodology of critical positivism and then apply the interpretive approach in interpreting the results. The case study articles employ various statistical methods to analyze and to interpret the empirical and survey data. The statistical methods were used to create a model that is useful for significantly optimizing issue resolution time. Moreover, it was found that samples for verifying issues provided by the customer neither improve the perceived quality of corrective actions nor the perceived quality of issue resolution time. The term “service” in this work is limited to the technical services that are provided by product manufacturers and after-sales authorized service vendors. On the basis of this research work, it has been observed that corrective actions and issue resolution time are associated with customer satisfaction and hence, according to induction theory, to customer loyalty and retention. This thesis utilizes knowledge of marketing and customer relationships to contribute to the existing body of knowledge concerning information and communication technology for after-sales service recovery of mobile terminals. The established models in the thesis contribute to the existing knowledge of the after-sales process of dealing with customer issues in the field of mobile phones. The findings suggest that process managers could focus more on communication and training provided to the staff as new technology evolves rapidly. The study also suggest the managers formulate strategies for how customers can be kept informed on a regular basis of the status of issues that have been escalated for corrective action. The findings also lay the foundation for the comprehensive objective to control the entire product development process, starting with conceptualization. This implies that robust design should be applied to the new products so that problems affecting customer service quality are not repeated. The objective will be achieved when the entire service chain from product development to the final user can be modeled and this model can be used to support the organization at all levels.

Kestomagnetoidun roottorin mekaniikkasuunnittelu ja -analysointi

Työssä kehitettiin suurnopeuskäyttöön soveltuva kestomagnetoitu roottori olemassa olevan induktiokoneen staattorirunkoon. Kehitystyön tarkoituksena oli selvittää roottorin mekaaniset raja-arvot, kuten maksimi kehänopeus. Samalla otettiin kantaa myös tarvittaviin analysointi- ja mitoitusmenetelmiin. Maksimi kehänopeuden, laakeroinnin ja roottorin skaalattavuuden selvittäminen edellytti myös tarkkaa materiaaliselvitystä ja optimointia. Tästä syystä työn aikana tehtiin tiivistä yhteistyötä materiaalitoimittajien kanssa. Työn tuloksena syntyi uusi menetelmä toteuttaa radiaalisen magneettivuon luova kestomagneettiroottori 200 m/s kehänopeudelle. Suunniteltua roottoriratkaisua käytetään testausroottorina, jolla selvitetään valmistuksen, kokoonpanon ja sähkötehon rajoitteet käytännössä. Suunnittelutyö edellyttikin jatkuvaa iterointia sähkösuunnittelun ja roottorin osien valmistajien kanssa, jotta löydettiin paras kompromissiratkaisu roottorin prototyyppiin. Tämän seurauksena saatiin luotua varsin tarkat suunnittelu- ja analysointiraja-arvot kestomagneettiroottorin tuotteistettavia versioita varten.

Algorithmic Techniques in Gene Expression Processing. From Imputation to Visualization

The amount of biological data has grown exponentially in recent decades. Modern biotechnologies, such as microarrays and next-generation sequencing, are capable to produce massive amounts of biomedical data in a single experiment. As the amount of the data is rapidly growing there is an urgent need for reliable computational methods for analyzing and visualizing it. This thesis addresses this need by studying how to efficiently and reliably analyze and visualize high-dimensional data, especially that obtained from gene expression microarray experiments. First, we will study the ways to improve the quality of microarray data by replacing (imputing) the missing data entries with the estimated values for these entries. Missing value imputation is a method which is commonly used to make the original incomplete data complete, thus making it easier to be analyzed with statistical and computational methods. Our novel approach was to use curated external biological information as a guide for the missing value imputation. Secondly, we studied the effect of missing value imputation on the downstream data analysis methods like clustering. We compared multiple recent imputation algorithms against 8 publicly available microarray data sets. It was observed that the missing value imputation indeed is a rational way to improve the quality of biological data. The research revealed differences between the clustering results obtained with different imputation methods. On most data sets, the simple and fast k-NN imputation was good enough, but there were also needs for more advanced imputation methods, such as Bayesian Principal Component Algorithm (BPCA). Finally, we studied the visualization of biological network data. Biological interaction networks are examples of the outcome of multiple biological experiments such as using the gene microarray techniques. Such networks are typically very large and highly connected, thus there is a need for fast algorithms for producing visually pleasant layouts. A computationally efficient way to produce layouts of large biological interaction networks was developed. The algorithm uses multilevel optimization within the regular force directed graph layout algorithm.

Liquid cooling solutions for rotating permanent magnet synchronous machines

In the design of electrical machines, efficiency improvements have become very important. However, there are at least two significant cases in which the compactness of electrical machines is critical and the tolerance of extremely high losses is valued: vehicle traction, where very high torque density is desired at least temporarily; and direct-drive wind turbine generators, whose mass should be acceptably low. As ever higher torque density and ever more compact electrical machines are developed for these purposes, thermal issues, i.e. avoidance of over-temperatures and damage in conditions of high heat losses, are becoming of utmost importance. The excessive temperatures of critical machine components, such as insulation and permanent magnets, easily cause failures of the whole electrical equipment. In electrical machines with excitation systems based on permanent magnets, special attention must be paid to the rotor temperature because of the temperature-sensitive properties of permanent magnets. The allowable temperature of NdFeB magnets is usually significantly less than 150 ˚C. The practical problem is that the part of the machine where the permanent magnets are located should stay cooler than the copper windings, which can easily tolerate temperatures of 155 ˚C or 180 ˚C. Therefore, new cooling solutions should be developed in order to cool permanent magnet electrical machines with high torque density and because of it with high concentrated losses in stators. In this doctoral dissertation, direct and indirect liquid cooling techniques for permanent magnet synchronous electrical machines (PMSM) with high torque density are presented and discussed. The aim of this research is to analyse thermal behaviours of the machines using the most applicable and accurate thermal analysis methods and to propose new, practical machine designs based on these analyses. The Computational Fluid Dynamics (CFD) thermal simulations of the heat transfer inside the machines and lumped parameter thermal network (LPTN) simulations both presented herein are used for the analyses. Detailed descriptions of the simulated thermal models are also presented. Most of the theoretical considerations and simulations have been verified via experimental measurements on a copper tooth-coil (motorette) and on various prototypes of electrical machines. The indirect liquid cooling systems of a 100 kW axial flux (AF) PMSM and a 110 kW radial flux (RF) PMSM are analysed here by means of simplified 3D CFD conjugate thermal models of the parts of both machines. In terms of results, a significant temperature drop of 40 ̊C in the stator winding and 28 ̊C in the rotor of the AF PMSM was achieved with the addition of highly thermally conductive materials into the machine: copper bars inserted in the teeth, and potting material around the end windings. In the RF PMSM, the potting material resulted in a temperature decrease of 6 ̊C in the stator winding, and in a decrease of 10 ̊C in the rotor embedded-permanentmagnets. Two types of unique direct liquid cooling systems for low power machines are analysed herein to demonstrate the effectiveness of the cooling systems in conditions of highly concentrated heat losses. LPTN analysis and CFD thermal analysis (the latter being particularly useful for unique design) were applied to simulate the temperature distribution within the machine models. Oil-immersion cooling provided good cooling capability for a 26.6 kW PMSM of a hybrid vehicle. A direct liquid cooling system for the copper winding with inner stainless steel tubes was designed for an 8 MW directdrive PM synchronous generator. The design principles of this cooling solution are described in detail in this thesis. The thermal analyses demonstrate that the stator winding and the rotor magnet temperatures are kept significantly below their critical temperatures with demineralized water flow. A comparison study of the coolant agents indicates that propylene glycol is more effective than ethylene glycol in arctic conditions.

Lämpökynttilän palo-ominaisuuksiin vaikuttavien tekijöiden analytiikka: raaka-aineet, sydänlanka, rakenne ja olosuhteet

Työn tavoitteena oli tutkia lämpökynttilän palo-ominaisuuksiin vaikuttavia tekijöitä. Työn taustalla on yhteistyö suomalaisen kynttilävalmistajan kanssa. Kynttilävalmistajan lämpökynttilöissään käyttämän raaka-aineen hinnan noustessa, on valmistaja kiinnostunut käyttämään edullisempia raaka-aineita. Palamisen kriteerit saavuttavan kynttilän valmistaminen markkinoilla olevista uusista raaka-aineista on havaittu olevan haastavaa, ja vaatii edelleen kehitystyötä. Teoriaosassa käytiin läpi kynttilänvalmistusta yleisesti, RAL-laatustandardin asettamat kriteerit lämpökynttilälle, palamiseen vaikuttavia tekijöitä sekä työn kokeellisessa osassa käytettyjen analyysimenetelmien periaatteet. Työn kokeellisessa osassa tutkittiin erilaisten kynttiläraaka-aineiden koostumusta ja ominaisuuksia sekä sydänlankojen rakennetta. Lisäksi tutkittiin, miten sydänlangan sisältämien säikeiden määrä, eri raaka-aineiden seossuhteiden muutos sekä jäähdytyslämpötilan muutos vaikuttavat lämpökynttilän palo-ominaisuuksiin. Työssä myös selvitettiin muutaman markkinoilla olevan kynttilän raaka-ainekoostumus. Tutkimuksissa havaittiin, että vaadittavan liekin korkeuden saavuttamiseksi viskositeetti on yksi raaka-aineen tärkeimmistä ominaisuuksista. Raaka-aineen viskositeetin kasvaessa tarvitaan paksumpi sydänlanka. Raaka-aineen viskositeetin kasvaessa liekin korkeus ei aina pienene, koska liekin korkeuteen vaikuttaa myös langalle tehty kemiallinen käsittely. Mitä korkeampi kynttilän liekki on, sitä suurempi on raaka-aineen kulutus eli palovuo ja tällöin liekin korkeus vaikuttaa myös kynttilän paloaikaan. Kokeissa havaittiin, että liekin korkeuden ollessa vakio, palovuo oli korkein steariinilla. Steariinin jälkeen tulivat palmuvaha ja parafiini. Tällöin parafiinia tarvittiin vähemmän vastaavan paloajan saavuttamiseksi. Nopean jäähdytyksen havaittiin vaikuttavan palmuvahan palovuohon alentavasti, vaikka jäähdytystavalla ei ollut vaikutusta liekin korkeuteen.

Quantitative Magnetic Resonance Imaging of the Liver and Heart In Iron Overload

Systemic iron overload (IO) is considered a principal determinant in the clinical outcome of different forms of IO and in allogeneic hematopoietic stem cell transplantation (alloSCT). However, indirect markers for iron do not provide exact quantification of iron burden, and the evidence of iron-induced adverse effects in hematological diseases has not been established. Hepatic iron concentration (HIC) has been found to represent systemic IO, which can be quantified safely with magnetic resonance imaging (MRI), based on enhanced transverse relaxation. The iron measurement methods by MRI are evolving. The aims of this study were to implement and optimise the methodology of non-invasive iron measurement with MRI to assess the degree and the role of IO in the patients. An MRI-based HIC method (M-HIC) and a transverse relaxation rate (R2*) from M-HIC images were validated. Thereafter, a transverse relaxation rate (R2) from spin-echo imaging was calibrated for IO assessment. Two analysis methods, visual grading and rSI, for a rapid IO grading from in-phase and out-of-phase images were introduced. Additionally, clinical iron indicators were evaluated. The degree of hepatic and cardiac iron in our study patients and IO as a prognostic factor in patients undergoing alloSCT were explored. In vivo and in vitro validations indicated that M-HIC and R2* are both accurate in the quantification of liver iron. R2 was a reliable method for HIC quantification and covered a wider HIC range than M-HIC and R2*. The grading of IO was able to be performed rapidly with the visual grading and rSI methods. Transfusion load was more accurate than plasma ferritin in predicting transfusional IO. In patients with hematological disorders, the prevalence of hepatic IO was frequent, opposite to cardiac IO. Patients with myelodysplastic syndrome were found to be the most susceptible to IO. Pre-transplant IO predicted severe infections during the early post-transplant period, in contrast to the reduced risk of graft-versus-host disease. Iron-induced, poor transplantation results are most likely to be mediated by severe infections.

Working fluid selection and design of small-scale waste heat recovery systems based on organic Rankine cycles

Demand for the use of energy systems, entailing high efficiency as well as availability to harness renewable energy sources, is a key issue in order to tackling the threat of global warming and saving natural resources. Organic Rankine cycle (ORC) technology has been identified as one of the most promising technologies in recovering low-grade heat sources and in harnessing renewable energy sources that cannot be efficiently utilized by means of more conventional power systems. The ORC is based on the working principle of Rankine process, but an organic working fluid is adopted in the cycle instead of steam. This thesis presents numerical and experimental results of the study on the design of small-scale ORCs. Two main applications were selected for the thesis: waste heat re- covery from small-scale diesel engines concentrating on the utilization of the exhaust gas heat and waste heat recovery in large industrial-scale engine power plants considering the utilization of both the high and low temperature heat sources. The main objective of this work was to identify suitable working fluid candidates and to study the process and turbine design methods that can be applied when power plants based on the use of non-conventional working fluids are considered. The computational work included the use of thermodynamic analysis methods and turbine design methods that were based on the use of highly accurate fluid properties. In addition, the design and loss mechanisms in supersonic ORC turbines were studied by means of computational fluid dynamics. The results indicated that the design of ORC is highly influenced by the selection of the working fluid and cycle operational conditions. The results for the turbine designs in- dicated that the working fluid selection should not be based only on the thermodynamic analysis, but requires also considerations on the turbine design. The turbines tend to be fast rotating, entailing small blade heights at the turbine rotor inlet and highly supersonic flow in the turbine flow passages, especially when power systems with low power outputs are designed. The results indicated that the ORC is a potential solution in utilizing waste heat streams both at high and low temperatures and both in micro and larger scale appli- cations.

High frequencies of plexiform neurofibromas, mental retardation, learning difficulties, and scoliosis in Brazilian patients with neurofibromatosis type 1

A clinical study of Brazilian patients with neurofibromatosis type 1 (NF1) was performed in a multidisciplinary Neurofibromatosis Program called CEPAN (Center of Research and Service in Neurofibromatosis). Among 55 patients (60% females, 40% males) who met the NIH criteria for the diagnosis of NF1, 98% had more than six café-au-lait patches, 94.5% had axillary freckling, 45% had inguinal freckling, and 87.5% had Lisch nodules. Cutaneous neurofibromas were observed in 96%, and 40% presented plexiform neurofibromas. A positive family history of NF1 was found in 60%, and mental retardation occurred in 35%. Some degree of scoliosis was noted in 49%, 51% had macrocephaly, 40% had short stature, 76% had learning difficulties, and 2% had optic gliomas. Unexpectedly high frequencies of plexiform neurofibromas, mental retardation, learning difficulties, and scoliosis were observed, probably reflecting the detailed clinical analysis methods adopted by the Neurofibromatosis Program. These same patients were screened for mutations in the GAP-related domain/GRD (exons 20-27a) by single-strand conformation polymorphism. Four different mutations (Q1189X, 3525-3526delAA, E1356G, c.4111-1G>A) and four polymorphisms (c.3315-27G>A, V1146I, V1317A, c.4514+11C>G) were identified. These data were recently published.

A conceptual and practical overview of cDNA microarray technology: implications for basic and clinical sciences

cDNA microarray is an innovative technology that facilitates the analysis of the expression of thousands of genes simultaneously. The utilization of this methodology, which is rapidly evolving, requires a combination of expertise from the biological, mathematical and statistical sciences. In this review, we attempt to provide an overview of the principles of cDNA microarray technology, the practical concerns of the analytical processing of the data obtained, the correlation of this methodology with other data analysis methods such as immunohistochemistry in tissue microarrays, and the cDNA microarray application in distinct areas of the basic and clinical sciences.

Yrityksen vaihto-omaisuustavoitteet kunnossapidon näkökulmasta

Varaosavarastoihin kohdistuu entistä enemmän samoja vaihto-omaisuuden hallinnan vaatimuksia kuin raaka-aine ja lopputuotevarastoihin. Tämän tutkimuksen tavoitteena oli selvittää, miten kunnossapito-organisaatio voi vastata näihin tavoitteisiin heikentämättä koneiden ja laitteiden teknistä käytettävyyttä ja lisäämättä riskiä tuotannon menetyksille. Kirjallisuudessa on esitetty suuri joukko eri lähtökohdista kehitettyjä analysointimalleja ja varastonpitopolitiikoita. Niiden avulla varaosia voidaan jakaa eri luokkiin ja niiden muodostamaa kokonaisuutta hallita. Teoriaosiossa on suoritettu kirjallisuuskatsaus käytetyimpiin menetelmiin ja tapaustutkimuksiin. Empiiriaosiossa menetelmien soveltuvuutta tutkittiin käytännössä. Tiedonkeruussa käytettiin case-yrityksen dokumentteja ja tietojärjestelmistä saatavaa tietoa, sekä havainnointia ja avoimia haastatteluita. Tutkimuksen tuloksena havaittiin merkittävä kehityspotentiaali, jonka hyödyntämiseksi saatiin määriteltyä tarpeisiin ja tutkimuksen lähtökohtana olleeseen viitekehykseen sopivat analysointi- ja varastonhallintamenetelmät. Varastokokonaisuuden hallintapolitiikka ehdotettiin lisättäväksi osaksi laatujärjestelmää. Sen avulla menetelmien johdonmukainen noudattaminen ja ohjeiden ajan tasalla pitäminen toteutuvat myös käytännössä.

Adsorption of arsenic from ammonia containing waste water by ferrous hydroxide waste

Arsenic is a toxic substance. The amount of arsenic in waste water is a raising problem because of increasing mining industry. Arsenic is connected to cancers in areas where arsenic concentration in drinking water is higher than recommendations. The main object in this master’s thesis was to research how ferrous hydroxide waste material is adsorbed arsenic from ammonia containing waste water. In this master’s thesis there is two parts: theoretical and experimental part. In theoretical part harmful effects of arsenic, theory of adsorption, isotherms modeling of adsorption and analysis methods of arsenic are described. In experimental part adsorption capacity of ferrous hydroxide waste material and adsorption time with different concentrations of arsenic were studied. Waste material was modified with two modification methods. Based on experimental results the adsorption capacity of waste material was high. The problem with waste material was that at same time with arsenic adsorption sulfur was dissolving in solution. Waste material was purified from sulfur but purification methods were not efficient enough. Purification methods require more research.