Environmental Effects on Gross Production and Respiration in a Facultative Oxidation Pond

Oxygen exchange by effluent samples taken at weekly intervals from a facultative oxidation pond was investigated over a 7 month period. Concentrations of ammonia, nitrate, nitrite, total and reactive phosphorus, alkalinity, total inorganic carbon, and free CO2 were measured over 12 months. Gross daily oxygen production within the community compensation depth ranged from 8 gO_2 m^-2 in winter to 43 gO_2 m^-2 in summer. The corresponding range for dark respiration was 5-17.5 gO_2 m^-2 d^-1. On average, light saturated rates of net oxygen production and total net production extended to the upper 2 and 15% of the 1.3 m mean depth profile respectively. Community respiration to gross production ratios ranged from 1.58-7.14. Light saturated rates of net oxygen production and dark rates of oxygen consumption increased with seasonal rise in pond temperature as did net production per unit detectable pigment. However, the most important factor affecting the rate of oxygen production was the concentration of detectable pigment. In laboratory studies, oxygen exchange rates were optimal at pH 5-8, but rates declined rapidly as the pH was increased from 8.0-8.5. Pond pH varied between 6.7 and 7.8 throughout the year. Net CO2 uptake under saturating irradiance (at pH 4.5) was maximal at 30 microM CO2 and compensation was reached at about 5 microM CO2. The minimum concentration of free CO2 observed in the pond was 190 microM

Assessment of flying-quality criteria for air-breathing aerospacecraft

A study of flying quality requirements for air breathing aerospacecraft gives special emphasis to the unusual operational requirements and characteristics of these aircraft, including operation at hypersonic speed. The report considers distinguishing characteristics of these vehicles, including dynamic deficiencies and their implications for control. Particular emphasis is given to the interaction of the airframe and propulsion system, and the requirements for dynamic systems integration. Past operational missions are reviewed to define tasks and maneuvers to be considered for this class of aircraft. Areas of special concern with respect to vehicle dynamics and control are identified. Experience with the space shuttle orbiter is reviewed with respect to flight control system mechanization and flight experience in approach and landing flying qualities for the National Aerospace Plane (NASP)

Aspects of Postharvest Quality Required by Papua New Guinea Sweet Potato Consumers in the Main Port Moresby Markets

Sweet potato (known locally as kaukau) is a major subsistence crop grown in the highlands of Papua New Guinea (PNG) and sold in local and coastal cities such as Lae and Port Moresby (POM). As farmers transition from subsistence to commercial farming, it is very important for them to know what quality the market (consumers) require. With this knowledge, farmers can prepare their produce for the appropriate market (local or coastal city). This paper reports on the sizes that POM consumers require of fresh sweet potato based on samples purchased from 3 to 5 open markets in POM on 3 sample dates. Within each market, we randomly selected sweet potato from 2, 5, and 10 kina (PNG currency) heaps that sellers had constructed, approximately 3–5 heaps per market. The sweet potatoes were bagged, labelled, and brought to the laboratory in POM for measurements of the minimum diameter, maximum diameter, length, counts of root number per heap, and weight of the heaps. Calculations were made of price per kg and mean root weight in each heap. Results showed the K5 and K10 heaps contained larger sweet potato (diameter, length, and weight) than the K2 heaps and suggests in POM, the fresh sweet potato market prefers a medium-sized sweet potato (165–187 mm, 282–464 g). The smaller roots were sold in the K2 heaps. Although all sizes of sweet potato are marketable, for highland farmers to make a sustainable business from sending sweet potato to POM, it is the medium-sized sweet potato they should be grading and packing on farm and shipping without delay

A Socio-Economic Analysis of the Factors Affecting Consumers’ Willingness to Pay for Good Quality Sweet Potato in Papua New Guinea

The increasing interest in health and nutrition has enhanced demand for quality of food products and subsequent desire by consumers to pay premiums for food quality. This study examines the influence of socio-economic and product quality attributes on consumers’ willingness to pay (WTP) for good quality sweet potato in Papua New Guinea. Information collected from 356 randomly selected consumers from the capital city of Port Moresby is used in this study. Using a structured pretested questionnaire, the survey was conducted in different pre-identified market locations based on the results of initial reconnaissance survey, market survey, and inputs from market experts. Using a two-step double hurdle model, we estimate the determinants of the discrete willingness-to-pay decision and the premiums consumers are willing to pay for good quality sweet potato. Of the total number of consumers, 80% were willing to pay a premium for good quality attributes in sweet potato. On average, consumers are willing to pay a premium of 2.22 kinas per kg with a minimum of 0.96 kinas per kg and a maximum of 3.47 kinas per kg. The premiums consumers were willing to pay are influenced by factors such as education, place of origin (highland regions), number of years the household has been living in Port Moresby, as well as other quality attributes such as the physical appearance of the roots (freshness, cleanliness, shape, and size), maturity of roots, and the sweet taste. Our results highlight two important implications: the importance of improving the quality of sweet potato by incorporating good quality attributes into research and development of new or improved varieties that meet consumer demand, and consideration of various factors in developing interventions in the sweet potato industry to enhance incomes of different stakeholders

Understanding Market Demand for Sweet Potato in Papua New Guinea

Sweet potato is the most important food crop in Papua New Guinea, grown by the majority of households throughout the country. In recent years, it has become an important source of income for smallholder farmers in a developing market economy at a time when demand is rising in urban centers, especially in coastal cities such as Lae and Port Moresby (POM). A transformation from subsistence to commercial farming requires new skills and a change of mindsets from production orientation to market orientation. A starting point is better understanding of what the market wants. The objective of the study was to understand the market requirements in POM of both consumers and institutional buyers through a consumer survey (350 households) and informant interviews (25 institutional buyers), respectively. The results show that while the demand for sweet potato is increasing in some segments of the POM market, rice poses a serious threat to the longer-term prospects of the sweet potato sector. Furthermore, the majority of consumers surveyed indicate a clear preference for some sweet potato varieties and associated product attributes, but lack of product information leads to confusion and high search costs. By contrast, institutional buyers demand good quality products and consistency in supply. The conclusion is that the sweet potato sector must improve its product quality and supply consistency, as well as reduce the marketing cost, in order to compete with rice and other food crops by changing their current postharvest and marketing practices

Integrated Experimental, Atomistic, and Microstructurally Based Finite Element Investigation of the Dynamic Compressive Behavior of 2139 Aluminum

The objective of this study was to identify the microstructural mechanisms related to the high strength and ductile behavior of 2139-Al, and how dynamic conditions would affect the overall behavior of this alloy. Three interrelated approaches, which span a spectrum of spatial and temporal scales, were used: (i) The mechanical response was obtained using the split Hopkinson pressure bar, for strain-rates ranging from 1.0×10^(−3) s to 1.0×10^4 s^(−1). (ii) First principles density functional theory calculations were undertaken to characterize the structure of the interface and to better understand the role played by Ag in promoting the formation of the Ω phase for several Ω-Al interface structures. (iii) A specialized microstructurally based finite element analysis and a dislocation-density based multiple-slip formulation that accounts for an explicit crystallographic and morphological representation of Ω and Θ' precipitates and their rational orientation relations were conducted. The predictions from the microstructural finite element model indicated that the precipitates continue to harden and also act as physical barriers that impede the matrix from forming large connected zones of intense plastic strain. As the microstructural FE predictions indicated, and consistent with the experimental observations, the combined effects of Θ' and Ω, acting on different crystallographic orientations, enhance the strength and ductility, and reduce the susceptibility of 2139-Al to shear strain localization due to dynamic compressive loads

High-flux hard X-ray microbeam using a single-bounce capillary with doubly focused undulator beam

A pre-focused X-ray beam has been used to illuminate a single-bounce capillary in order to generate a high-flux X-ray microbeam at the BioCAT undulator X-ray beamline at the Advanced Photon Source. The combined optical arrangement makes it suitable for many microprobe fluorescence applications and micro-XANES experiments for biological samples

Isotopic fractionation by shale micropore systems

Cover title.Bibliography: p. 28-32