547 Publications

Page 14 of 22

On the Performance of the Logistic-growth Population Projection

Author(s): GUASA O, OBAHIAGBON K. O., ODION A. E. (2013)
Published at :Mathematical theory of Modelling ISSN 2224-5804(paper) ISSN 2225-0522 (Onlien) Vol 3, No. 14, 2013.
In this paper, we proposed two mathematical models for population projection, the exponential growth and the Logistic Model. Thereafter, both models were transformed and since Logistic Model is not linear in its parameters hence a surgry was performed on the data values separated by a fixed time. This enables the logistic parameters to be sometimes estimated by Least-Square. It was shown that the estimates were quite close to the data set from the National Population Commission of Nigeria.
Download Full Abstract

Operations Technology and Management of Small and Medium-scale Enterprises in Nigeria

Author(s): INEGBENEBOR, A.U. (2006)
Published at :Nigerian Journal of Business Administration, 8(1&2), 46-57
The study was designed to evaluate the operations technology used in small and medium–scale enterprises in Nigeria using Inkson et al (1970) abbreviated scale. The pattern of choices made by the entrepreneur in terms of specialization, formalization and centralization as well as the impact of the choices on the effectiveness of the sample firms were also studied. The results indicated that the operations technology used in the sample firms was low and did not have any significant impact on the organizational structure of the firm. Neither did the entrepreneur’s response to variations in technology account for differences in enterprise performance. While the results of the study did not support treating technology as an imperative, the limited range of the technology available in the enterprises may not have provided the necessary scope to induce the expected response. To encourage entry into the high technology subsector, engineers, scientists and technologists should be exposed to Entrepreneurial Development Programmes (EDP), and industrial parks should be established around Research Institutes and Universities to encourage the commercialisation of the research results of these institutions.
Download Full Abstract

Optimal Ordering Policies for Inventory System with Fixed Lifetime” Australian Journal of Basic and Applied Sciences

This paper deals with the problem of computing optimal ordering policies for a single product with fixed lifetime of exactly m periods. We presents a proposed cost function for the inventory system with fixed lifetime. The necessary condition for a minimum was derived. Decisions regarding when to order or not is investigated under some conditions. Guidelines for managing a real fixed lifetime perishable inventory system are given.
Download Full Abstract

Optimum Downtilt Gain Correction and Performance Optimization of Wireless Communication Network in Built- Up Terrains.

Author(s): ISABONA J. AND OJUH O. D. (2013)
Published at : African Journal of Computing & ICT Vol 6. No. 3, Afr J Comp & ICT - ISSN 2006-1781 www.ajocict.net
ABSTRACT Utilizing the correct elevation angle on each cell in a cellular network is important to ensure that the signal level is maximized within the dominance area of a cell and minimized everywhere else. Consequently, by deploying the most appropriate tilt angle, the network service quality within the dominance area of a cell is maximized, leading to optimum system performance. In this paper, the coverage shaping and interference impacting capabilities of BS antenna tilt technique was explored to optimise the performance of networks. It was found based on empirical model predictions that at optimum downtilt angles which ranged from 50 to 70, the networks coverage, capacity and service quality can be improved by 10%, 15% and 20% respectively on the average using SNR, Service outage probability, and throughput as key performance indicators. The conclusion arising from the above approach is of special importance to engineers involved directly in cellular wireless network planning and optimisation. Keywords: Downtilt, Performance, Correction, Network, Communication & Terrain.
Download Full Abstract

Organizational Learning in Nigerian Institutions: Constraints and Challenges.

Author(s): OISAMOJE, M. D.. AND IDUBOR, E. E. (2013)
Published at :IOSR Journal of Business and Management, 11(1), (May-June, 2013), 54-61.
Organisations are recognised as legal and corporate entities. They have an image, and they can sue and be sued. To that extent therefore, this paper posits that organizations can also learn, and asserts that the absence or dearth of adequate organisational learning culture denies organizations the much needed competitive edge necessary to survive and remain viable in the contemporary and highly globalised world. The paper x-rays the technical and social perspectives of organisational learning and argues that the learning process is context and culture-driven. Conceding that effective organisational learning practice enhances performance, it highlights some hindrances to the learning process, suggests remedies and concludes with a case study of the organisational learning problems of a Nigerian public sector organization. Keywords: Corporate organisations, globalised world, learning culture, organizational learning
Download Full Abstract

Osaigbovo, J.a. & Egbulefu, C.c. (2013).global Ranking of Nigerian Universities: Challenges and Way Forward.

Author(s): OSAIGBOVO, J.A. & EGBULEFU, C.C. (2013)
Published at :Journal of Collaborative Research and Development (JRRD). Vol. 1, No.2, p.107 - 122.
The unofficial ranking of tertiary institutions which many Nigerian have often engaged in unconsciously is taken more seriously in other climes. The business of ranking tertiary institutions all over the world has been fuelled by various factors: students who are looking for a good institution to pursue their careers, academics, who are desirous of finding appropriate institutions also for career fulfillment, and even cooperate bodies looking for expertise and research results in various fields, in order to overtake their competitors and enhance their profits. In the recent ranking of Nigerian tertiary institutions, only eight federal universities, one private and one federal polytechnic, made the list of t he top 100 in Africa (Webometrics Ranking of the World Universities, 2012). But no Nigerian tertiary institution was featured among the world’s best 500 universities in the global ranking released recently by the global ranking agencies. Hence, this paper examined the global ranking of Nigerian universities, challenges and the way forward. It was concluded that the global ranking of universities is a desirable tool for assessment and motivation. The paper recommended that Nigerian universities should carry out quality teaching and research activities to elicit global ranking.
Download Full Abstract

Palm Oil Splitting Using a Sulphonic Acid Catalyst: a Preliminary Investigation.

Author(s): F.O.J. OBOH (2006)
Published at :Nigerian Journal of Applied Science
Abstract The analysis of a Nigerian crude palm oil revealed a low amount of peroxides and high levels of the pro-oxidants copper, iron, and free fatty acids (FFA). The oil was highly susceptible to oxidation under Schall oven conditions at 60±0.5oC: peroxide value rose to a maximum of 32.0 meq /kg in 13 days. The addition of BHT (0.02%) and citric acid (0.02%) to the oil inhibited the formation of peroxides. Keywords: Palm oil, oxidative stability, peroxides, BHT, citric acid.
Download Full Abstract

Patent Law Responsibilities for Access to Medicines in Developing Countries

Author(s): O. T. UMAHI & T. C. NWANO (2006)
This article advocates effective corporate social responsibility (CSR) for multinational pharmaceutical companies in research and development of drug needs of developing countries. It acknowledges access to medicines as a global problem created by patent law and equally as a fundamental right in the global public domain, which leaves problems associated with moral responsibility for multinational pharmaceutical companies. The article suggests that access to medicines will be enhanced if the pharmaceutical companies become responsible in their patents, pricing, testing, research and development, joint public private initiative and appropriate use of drugs.
Download Full Abstract

Patterns and Correlates of Decentralization in Private Nigerian Enterprises

Author(s): INEGBENEBOR, A.U. (1992)
Published at :Annals of the Social Science Council Nigeria, 4, 36-48
The ability of private Nigerian entrepreneurs to initiate and institutionalize effective organizational structures and processes needed to carry out complex industrial activities is crucial to the realization of the objective of rapid, self-reliant, industrial development of Nigeria. This study examined the patterns and correlates of a key structural variable in the organizational process – decentralization of decision-making authority. The study was based on a sample of forty-one manufacturing enterprises in the Midwestern Zone of Nigeria which were wholly owned by private Nigerian entrepreneurs. The results indicate that decentralization of decision making was generally limited. Participation of the Board of Directors was restricted. There was marked variation in decentralization in the functional areas with finance function as the least decentralized and production/operations function as the most decentralised. The response to the contingencies of size and technology was considered appropriate while the response to competition was contrary to expectation. Apart from this, the nature of decentralization in the enterprises was in the direction generally found in more advanced economics.
Download Full Abstract

Patterns of Conversion to Islam in Colonial Nigeria: a Critical Appraisal

The Article examines the various patterns of conversion to Islam in colonial Nigreia and finds that conversion was more through peaceful means than violent ones and recommends that, that should obtain in contemporary Nigeria bedeviled by forceful conversion. The paper also find that the period was also a period of decline for Islam due to the allure and attraction of Western education provided by Christian mission schools as some Muslims who went to Christian mission schools converted to Christianity.
Download Full Abstract

Patterns of Iconicity in the Benin City Palimpsest

Author(s): RICHARD A. MASAGBO (2006)
The combination overlaying of institutional, socio- culture and ante factual elements over the decades coupled with the current beautification and modernization of city has been aptly described as a palimpsest (Greek: Writing Upon Writing). This is reflected in the iconic patterns, overtly and covertly decipherable in the landscape in difference pattern of governance, cultural practices and landmark signs. The paper considers the triadic application of the term iconicity viz: image, metaphor and diagram to Benin city. Some of these have varying motivating factors- some deliberate, others accidental processes of history. From the visual perspective, there are architectural indices of royalty as well as dress indexicalities of the place, structure (diagrammatic) procedural pattern conventionally characteristic and metaphorically centre names and titular references all laced together in a semiosphere that is palimpsest
Download Full Abstract

Pcaob Inspection Reports: Quality Control and Firms’ Characteristics.

Author(s): OBASI, R. (2014)
Published at : International Journal of Accounting and Taxation vol. 2, no. 3, 1-10. Published by American Research Institute for Policy Development. DOI: 10.15640/ijat/
This study compared the weaknesses identified in the audit engagement performance and quality control (that have been made public by the PCAOB after a lack of progress report within 12 months by the firms) sections of the PCAOB’s published reports. It also, examined the relationship between firms’ characteristics (i.e. size of workforce, number of clients, number of audit offices, and number of audit engagement deficiencies) and PCAOB’s report, to achieve these, 108 PCAOB Inspection reports for inspected firms were analyzed. The reports were grouped into two panels (i.e. clean reports-panel A and unresolved reports-panel B); 52 and 56 firms’ reports respectively were analyzed for each group. The OLS regression results indicate that clean reports are positively and significantly associated with the size of work force, while, it is negatively associated with the number of clients, number of audit offices and number of audit engagement deficiencies. Unresolved reports increase as number of audit offices, and number of audit engagements increase, but it decreases as size of workforce and audit clients increase. We conclude that the number of audit clients is a key quality control determinant as well as the size of work force. We therefore recommend that the PCAOB should encourage firms to increase workforce because, the result of this study has shown that, the number of employees and partners impact greatly on the quality of report by audit firms.
Download Full Abstract

Perceived Application of Quality Assurance in the Management of Nigerian Tertiary Institutions

Published at :Journal of Educational Research and Development, 5(3) Dec. pp 1-5. A journal of the faculty of Education,Ahmadu Bello University Zaria.
Abstract: The study looks at the management of tertiary institutions in Nigeria and application of quality assurance following the general dissatisfaction among the academicians and administrators that quality assurance is not maximally applied. Tertiary institutions are supposed to put in their best to produce globally and nationally acceptable manpower. The population was made up of all the teaching and administrative staff of 291 tertiary institutions in the six geo-political zones of the federation of Nigeria. A samples size of 100 academic staff and 100 administrative staff were selected by stratified Radom sampling method from each geographical zone of the federation. A total sample`of 600 teaching staff (335 males and 265 females) and 600 administrative staff (302 males and 298 females) participated in the study. The data were collected using questionnaire which was augmented by oral interview. The major findings are that quality assurance is applied on the average. Also new and some old private tertiary institutions have low application of quality assurance due to inadequate funding which affected hiring of highly qualified personnel, provision of adequate facilities etc. Based on the above, it is recommended that no tertiary institution should take off without adequate facilities and qualified personnel.
Download Full Abstract

Perceived Factors Influencing Examination Misconducts: Implications for the Nigerian Educational System.

Author(s): HEPHZIBAH-AWULOR, B.N. (2014)
This study investigated the perceived factors influencing examination misconducts in Nigerian Secondary Schools: Implications to the Nigerian Educational system. In this study, four research questions and two hypotheses were formulated. The hypotheses were tested at alpha level of 0.05. a descriptive survey was adopted for the study. The sample for the study is made up of one hundred and fifty SS1 students drawn from three secondary schools in Oredo Local Government Area of Edo State. Both the schools and students were randomly selected. The instrument used for data collection was a questionnaire titled PFIEM. Data collected were analyzed using independent t-test and simple percentages. The findings of the study showed that parents, educational stakeholders, even students themselves are all constructors to examination misconducts in Oredo local Government Area of Edo State. The paper pin points the implication of examination misconducts on the Nigerian Educational system and also recommendations were made.
Download Full Abstract

Persistence of the Osu Caste System Among the Igbos of Nigeria; a Therapeutic Analysis

The author extrays the phenomenon of Osu Caste System among the Igbos and why it still persists despite the predominance of Christianity in Igboland. He makes suggestions on how to eradicate the cultural incubus which has left over two million Igbos stigmatized.
Download Full Abstract

Persistent Factors Influencing Examination Malpractices Among Secondary School Students in Edo State: a Case Study of Ikpoba-okha Local Government Area

Author(s): OMOREGIE, N. O. (2009)
This research identified persistent factors influencing examinations malpractices among secondary school students in Edo state using Ikpoba-Okha local government area as a case study. The factors indentified were also ranked I order of their influence. The research confirmed increase in examination malpractices in secondary school level. Out of the eighteen factors identified to persistently influenced examination malpractice, love of money by invigilators, ill preparation of students, inadequate school facilities, lack of science laboratories, lack of equipped libraries and insufficient teachings in this level of education ranked highest respectively. Recommendations to eradicate this evil in the nations’ educational system include implementation of examination malpractices Act 33 of 1999, urgent implementation of Teachers’ Salary Scale in all States of the Federation, the examination bodies to carry out appropriate supervision during their examination and moral and religious studies to be made compulsory subjects for primary and secondary schools.
Download Full Abstract

Persistent Gender Inequality in Nigerian Education.

The research reviewed persistent gender- inequality in Nigerian education at all levels, including the effect in turn-out of the Nigerian Youth Service Corps. The introduction of the free Universal Primary Education (UPE) in the Nation in 1976 and the current Universal Basic Education (UBE) since 2000 did not revert the situation. Statistics collected from various sources and analyzed ascertained the contention of the research. Reasons for this continuous gender inequality in Nigerian education were found to be traditional and cultural. The implication is revealed in poor national development is the contribution of the females is very significant. Recommendations include promulgation of the laws by the federal government to make parents release their girl- children for education and enforcing 50:50 quota system of admission in all levels of Nigerian educational system
Download Full Abstract

Pharmacists As Entrepreneurs or Employees: the Role of Locus of Control

Author(s): INEGBENEBOR, A.U. (2007)
Published at :Indian Journal of Pharmaceutical Education and Research, 41(3)
The enlarged version of Rotter’s I-E scale designed to measure an individual’s locus of control was used to survey a sample of pharmacists in two major cities in Southern Nigeria. the sample consisted of 34 pharmacists who were owners/proprietors of retail pharmacies and 35 pharmacists employed in retail pharmacies or hospitals. The difference between entrepreneur pharmacists and employee pharmacists in terms of locus of control was analysed using student’s t-test. The mean locus of control score for entrepreneur pharmacists was significantly different from that of employee pharmacists (P<0.1). Entrepreneur pharmacists had higher scores on the variable than employee pharmacists indicating greater locus of control internality. The study has drawn following conclusions, pharmacists characterized by locus of control internally are more likely to assume entrepreneurial rather than employee roles in pharmaceutical undertakings. Such pharmacists are more disposed to adopt innovative pharmaceutical care philosophy. Hence there is need to incorporate entrepreneurial education in the curriculum of pharmacy programmes to encourage positive attitude toward entrepreneurship.
Download Full Abstract

Physical, Chemical and Performance Evaluation of Different Commercial Brands of Layers, Broilers Starter and Finisher Feeds.

Published at :Albanian j. agric. sci.12 (2): 267-273
Abstract In completely randomized design that comprised two studies, physical, chemical and performance evaluations were conducted to determine the quality of commercial four layers feeds, three broiler starter and three broiler finisher feeds. In study 1, eighty 20-week in–lay black harco hens were used in four replicate groups to evaluate the effects of the selected layer feeds on their laying performance for twelve weeks. While in study 2, seventy two broiler chicks were used (0-8 weeks) in three replicate groups to evaluate the broiler feeds. All feeds were packaged in standard polyethylene woven bags with no presence of insects or mould. All feeds were in mash form except two layers feeds in crumbled form and one pelleted feed. There were also variations in crude protein, crude fat and crude fibre contents of the various feeds as analyzed. There were no significant differences in Hen Day Production and egg diameters(P>0.05). However, total number of eggs laid and egg weight were significantly reduced among hens on two treatments(P<0.05). The highest cost of producing a dozen eggs was recorded with the pelleted feed(P<0.05). There were significant differences in feed intake, weight gain and feed conversion ratio among broilers on the different treatments(p<0.05), with the poorest performance recorded among broilers fed starter and finisher feeds from same producer. Percentage mortality was however not significant (p>0.05). It was concluded that none of the feeds investigated met all the requirements of an ideal feed either for broilers or layers. Keywords: Harco hens, layers feed, hen day production, egg weight, broilers, weight gain
Download Full Abstract

Physico- Chemical Properties, Species Diversity and Abundance of the Fishes of Ibiekuma Stream, Ekpoma, Edo State, Nigeria. Nigerian Annals of Natural Sciences, Vol. 6 (2): 68-80

Author(s): OBASOHAN, E. E.; OBAMWONYI, C. AND ORONSAYE, J. A. O. (2006)
This study examined and monitored the diversity and abundance of the fishes of Ibiekuma Stream, Ekpoma, Edo State, Nigeria. 226 individual fishes classified into 9 families, 13 genera and 15 species were recorded. The Cichlidae family dominated the collection, while the dominant species were Tilapia zilli and Tilapia mariae. The results revealed that the overall abundance and diversity of the fishes in the stream were low. The species diversity and abundance varied at the study stations, but the variations were not significant. The variations in the physico-chemical properties of the water, monitored during the study were also not significant, except for DO and pH which values were also very low. The differences in fish diversity and abundance among the stations were attributed to the differential responses of the fishes to the different to the different DO and pH at the stations. The low DO and pH in the stream indicated organic pollution responsible for the comparatively low fish population in the stream
Download Full Abstract

Physico-chemical Evaluation of Bore-hole Water from Selected Fish Farms in Edo State, Nigeria. *international Journal of Biology and Chemical Sciences (ijbcs), Vol. 3 No. 3: 431- 440

Author(s): OBASOHAN, E. E. (2009)
This study investigated the physical and chemical properties of water from bore-holes in selected fish farms in the three districts of Edo State, Nigeria. Sample collection, treatment and determination of physical chemical properties were according to approved standards. The results showed that all the parameters analyzed were within the required standards for aquaculture and drinking purposes, except pH which was slightly acidic,, alkalinity in Edo South which was very low, and the metals Mn and Pb whose concentrations exceeded the standard limits for drinking water. Based on the acceptable levels of most of the parameters, it was concluded that the water of the study area was suitable for aquaculture, drinking and other domestic purposes. However, because of the pH and the heavy metals Mn and Pb, it was recommended that the water be treated with lime before use especially in aquaculture facilities in order to increase pH and possibly reduce metal concentrations to tolerable limits through precipitation and or adsorption, to sediment particles and thus lead to production of suitable fish for consumers.
Download Full Abstract

Physicochemical Quality of an Urban Municipal Wastewater Effluent and Its Impact on the Receiving Environment.

Published at :Environmental Monitoring and Assessment, Doi: 0.1007/s10661-009-1240-y. Available online at http://www.springerlink.com/content/bw8x83467383g556/.
The physicochemical qualities of the final effluents of an urban wastewater treatment plant in South Africa were assessed between August 2007 and July 2008 as well as their impact on the receiving watershed. The pH values across all sampling points ranged between 6.8 and 8.3, while the temperature varied from 18?C to 25?C. Electrical conductivity (EC) of the samples was in the range of 29–1,015 ?S/cm, and turbidity varied between 2.7 and 35 NTU. Salinity and total dissolved solids (TDS) varied from 0.36 to 35 psu and 16 to 470 mg/L, respectively. The concentrations of the other physicochemical parameters are as follows: chemical oxygen demand (COD, 48–1,180 mg/L); dissolved oxygen (DO, 3.9–6.6 mg/L); nitrate (0.32–6.5 mg NO? 3 as N/L); nitrite (0.06–2.4 mg NO?2 as N/L); and phosphate (0.29–0.54 mg PO3?4 as P/L). pH, temperature, EC, turbidity, TDS, DO, and nitrate varied significantly with season and sampling point (P < 0.05 and P < 0.01, respectively), while salinity varied significantly with sampling point (P < 0.01) and COD and nitrite varied significantly with season (P < 0.05). Although the treated effluent fell within the recommended water quality standard for pH temperature, TDS, nitrate and nitrite, it fell short of stipulated standards for other parameters. The result generally showed a negative impact of the discharged effluent on the receiving watershed and calls for a regular and consistent monitoring program by the relevant authorities to ensure best practices with regard to treatment and discharge of wastewater into the receiving aquatic milieu in South Africa. Keywords Physicochemical qualities . Wastewater effluent · Receiving watershed
Download Full Abstract

Phytochemical Analysis and Antibacterial Activity of Khaya Grandifoliola, Stem Bark

Published at :Journal of Biological Sciences. 9(1): 63-67
The powdered crude sample of Khaya grandifoliola was subjected to phytochemical analysis using standard experimental procedures. The phytochemical evaluation revealed the presence of alkaloids, tannins, saponins and flavonoids. The methanolic extract of Khaya grandifoliola stem bark was screened for antimicrobial activity against bacterial isolates MRSA, Bacillus subtilis, Klebsiella pneumonia and Proteus mirabilis at different concentrations. The isolates showed a minimum inhibitory concentrations (MIC) of 0.4 mg mL-1 except B. subtilis of 0.002 g mL-1.
Download Full Abstract

Phytochemical Analysis, Proximate and Mineral Composition and in Vitro Antioxidant Activities in Telfairia Occidentalis Aqueous Leaf Extract.

Author(s): USUNOBUN, U. AND EGHAREBVA, E. (2015)
Published at :Benson Idahosa University Journal of Science
The present study sought to undertake the phytochemical analysis (using standard methods of analysis), proximate and mineral composition as well as in vitro antioxidant properties (involving inhibition of DPPH and reducing power ability) of aqueous leaf extract of Telfairia occidentalis consumed in Ekpoma, Edo state, Nigeria. The preliminary phytochemical analysis showed that the leaf of T. occidentalis contains flavonoids, tannins, saponins, alkaloids and phenolics. Quantitative analysis showed that phenol, flavonoids, tannins, alkaloids and saponins in percentage were 0.19±0.12, 7.12±0.50, 0.12±0.08, 1.03±0.24 and 7.01±0.30 respectively. Result on proximate analysis showed 89.01% dry matter, 10.99% moisture content, 21.14% crude protein, 6.46% lipid, 11.56% crude fiber, 8.31% Ash content, and 53.10% carbohydrate. Result on Mineral composition in mg/100g dry matter showed Calcium (61.03±0.04), Sodium (51.49±1.32), Iron (25.75±1.65), Zinc (13.15±0.31), Potassium (801.21±0.45), Magnesium 85.11±1.22), Phosphorus (18.09±0.09), Manganese (21.27±0.32) and Copper (0.93±0.03). In vitro antioxidant scavenging activity using 2, 2-diphenyl 1-picrylhydrazyl (DPPH) and Ascorbic as standard and reducing power ability of the plant extract was found to be concentration dependent with maximum inhibition and reducing power ability at 0.4mg/ml which were 69% (lower than 89% for ascorbic acid) and 0.199 respectively. Our findings provide evidence that aqueous extract of Telfairia occidentalis is a potential source of natural antioxidants. The result of these findings also revealed that Telfairia occidentalis leaves are good source of carbohydrates and energy. The leaves are also a good source of minerals.
Download Full Abstract

Phytochemical Screening and Proximate Composition of Annon Muricata Leaves

Published at : European Journal of Botany, Plant Sciences and Phytology. 2(1):18-28
Proximate composition and phytochemical analyses were carried out on the leaves of Annona muricata using standard methods. The result of the proximate composition showed that the leaves contained 88.99% dry matter, 11.01% moisture, 25% crude protein, 14.96% ash, 22.20% crude fiber, 21.22 % fat and 16.62% carbohydrate contents. The phytochemicals detected in the ethanolic leaf extracts were flavonoids, alkaloids, cardiac glycoside, tannins, triterpenoid, saponin and reducing sugar. The findings indicate that Annona muricata leaves is a potential source of highly nutritious feed stuff and phytomedicine. They are of nutritional, clinical and veterinary relevance considering the diverse ethnopharmacological uses of the plant in different parts of the world.
Download Full Abstract