Calculation of heterogeneous phase equilibria in oxide-nitride systems: I. The Quaternary System C  Si  N  O

A newly set up computer program based on the mathematical principles suggested by M. Hillert was used to calculate the phase equilibria in the system CSiN0. These calculations include phase equilibria with the vapour phase. Several isothermic and T-c-sections of the ternary boundary systems and of the quaternary system are given.     

Arbutin in marjoram and oregano

Arbutin is a hydroquinone derivative that has been found in species of several plant families. Within the genus Origanum the formation of arbutin is polymorphic, with arbutin present in considerable amounts (O. dubium 20.8 ± 15.3 mg/g; wild O. majorana 51.3 ± 15.4 mg/g, cultivated O. majorana 40.6 ± 11.2 mg/g), minor amounts (O. microphyllum 0.1 ± 0.1 mg/g, wild O. onites 0.3 ± 0.1 mg/g, cultivated O. onites 0.1 ± 0.1 mg/g, O. saccatum 0.1 ± 0.1 mg/g, O. solymicum 0.4 ± 1.0 mg/g) or completely absent (O. husnucan-baseri, O. syriacum, O. vulgare). Whereas the most important commercial oregano species (O. onites and O. vulgare) contain no or only minor amounts of arbutin, marjoram (O. majorana) has considerably high amounts. The high variability of arbutin in O. majorana would allow a selection into cultivars with high arbutin content and low arbutin varieties. In a segregating F₂-generation of a species crossing between O. majorana (high content of arbutin) and O. vulgare ssp. vulgare (free of arbutin), the presence of arbutin followed a Mendelian segregation of 3:1, indicating that only one gene is responsible for the polymorphism of arbutin in the genus Origanum. The absence of arbutin in O. vulgare ssp. vulgare or O. syriacum would even enable the breeding of marjoram with no arbutin at all.     

Predicting somatic cell count standard violations based on herd's bulk tank somatic cell count. Part II: Consistency index

The present study examines the capability of 1,501 herds in the Upper Midwest and the performance of statistical process control charts and indices as a way of monitoring and controlling milk quality on the farm. For 24 mo, daily or every other day bulk tank somatic cell count (SCC) data were collected. Consistency indices for 5 different SCC standards were developed. The indices calculate the maximum variation allowed to meet a desired SCC level at a given mean bulk tank SCC and were used to identify herds not capable of meeting a specific SCC standard. Consistency index method was compared with a test identifying future bulk tank SCC standard violators based on herds’ past violations. The performance of the consistency index test and the past violation method was evaluated by logistic regression. The comparison focused on detection probability and certainty associated with a result. For the 5 SCC levels, detection probability and certainty associated with a result ranged from 51 to 98%. Detection probability of all violators and certainty associated with a negative result was greater for the consistency index across all 5 SCC levels (by 0.7 to 7.4% and 2.1 to 5.1%, respectively). Control charts were plotted and monthly consistency indices calculated for individual farms. Charts in combination with the consistency indices would warn from 66 to 80% of the herds about an upcoming violation within 30 d before it occurred. They offer a proactive approach to maintaining consistently high milk quality. By assessing process capability and distinguishing between significant changes and random variation in bulk tank SCC, tools presented in this article encourage fact-based decisions in dairy farm milk quality management.     

Adding wind power to a wind-rich grid: Evaluating secondary suitability metrics

As the quantity of renewable electricity generation from wind farms increases in a region, the costs associated with integrating it into the broader electricity system also grow. This is primarily due to the need for dispatchable generators that vary power output to compensate for wind farm power variations. Such “balancing services” are an economic cost to the system that is typically not passed on to wind farms. We propose including the use of technical merits other than capacity factor and cost of energy for evaluating new wind farm sites and present a new graphical geospatial method, with the intention of identifying sites that minimize the need for additional electricity balancing service and transmission congestion. Specifically, locations with low correlation to existing wind farms, locations with high correlation to load, locations with high characteristic power time-shift from existing wind farms, and locations that relieve or do not negatively impact electricity transmission congestion are identified. A geospatial Venn diagram-based method of visualization is presented. These methods will equip regional planners with new tools to encourage wind farm development in areas that benefit the electricity grid beyond the lowest bid price.     

Measuring Local Crystallization Fouling in a Double-Pipe Heat Exchanger

Abstract

Although fouling is a problem varying in space and time, sizing and assessment of a process apparatus is almost always based on one single integral fouling resistance value. Furthermore, the integral fluid dynamic behavior, e.g. the development of time-dependent pressure drop in a heat exchanger, can be influenced by local constrictions. While it is generally possible to determine the time dependency of the integral fouling behavior, local differences are not taken into consideration at present. Therefore, this paper introduces a metrological, an incremental and a segmental approach to study the local development of crystallization fouling by calcium sulfate in a countercurrent double-pipe heat exchanger. The consecutive approaches allow for thermal, volumetric, gravimetric, and optical fouling investigations, aiming to examine the axial distribution of deposit as well as local differences in the deposit morphology. All methods provided congruent results and local fouling could be described properly. An almost clean surface at the colder end of the heat exchanger and an exponential increase of deposit thickness were observed towards the hot end. Hence, the section near to the hot water inlet turned out to be a key area with regards to increasing fouling mass and structural changes of the layer.     

Dissolved organic carbon enhances the mass transfer of hydrophobic organic compounds from nonaqueous phase liquids (NAPLs) into the aqueous phase

The hypothesis that dissolved organic carbon (DOC) enhances the mass transfer of hydrophobic organic compounds from nonaqueous phase liquids (NAPLs) into the aqueous phase above that attributable to dissolved molecular diffusion alone was tested. In controlled experiments, mass transfer rates of five NAPL-phase PAHs (log K(OW) 4.15-5.39) into the aqueous phase containing different concentrations of DOC were measured. Mass transfer rates were increased by up to a factor of 4 in the presence of DOC, with the greatest enhancement being observed for more hydrophobic compounds and highest DOC concentrations. These increases could not be explained by dissolved molecular diffusion alone, and point to a parallel DOC-mediated diffusive pathway. The nature of the DOC-mediated diffusion pathway as a function of the DOC concentration and PAH sorption behavior to the DOC was investigated using diffusion-based models. The DOC-enhanced mass transfer of NAPL-phase hydrophobic compounds into the aqueous phase has important implications for their bioremediation as well as bioconcentration and toxicity.     

Mycelia promote active transport and spatial dispersion of polycyclic aromatic hydrocarbons

To cope with heterogeneous subsurface environments mycelial microorganisms have developed a unique ramified growth form. By extending hyphae, they can obtain nutrients from remote places and transport them even through air gaps and in small pore spaces, repectively. To date, studies have been focusing on the role that networks play in the distribution of nutrients. Here, we investigated the role of mycelia for the translocation of nonessential substances, using polycyclic aromatic hydrocarbons (PAHs) as model compounds. We show that the hyphae of the mycelial soil oomycete Pythium ultimum function as active translocation vectors for a wide range of PAHs. Visualization by two-photon excitation microscopy (TPEM) demonstrated the uptake and accumulation of phenanthrene (PHE) in lipid vesicles and its active transport by cytoplasmic streaming of the hyphae ('hyphal pipelines'). In mycelial networks, contaminants were translocated over larger distances than by diffusion. Given their transport capacity and ubiquity, hyphae may substantially distribute remote hydrophobic contaminants in soil, thereby improving their bioavailability to bacterial degradation. Hyphal contaminant dispersal may provide an untapped potential for future bioremediation approaches.     

Temperature dependence and interferences of NO and N₂O microelectrodes used in wastewater treatment

Electrodes for nitric and nitrous oxide have been on the market for some time, but have not yet been tested for an application in wastewater treatment processes. Both sensors were therefore assessed with respect to their (non)linear response, temperature dependence and potential cross sensitivity to dissolved compounds, which are present and highly dynamic in nitrogen conversion processes (nitric oxide, nitrous oxide, nitrogen dioxide, ammonia, hydrazine, hydroxylamine, nitrous acid, oxygen, and carbon dioxide). Off-gas measurements were employed to differentiate between cross sensitivity to interfering components and chemical nitric oxide or nitrous oxide production. Significant cross sensitivities were detected for both sensors: by the nitrous oxide sensor to nitric oxide and by the nitric oxide sensor to ammonia, hydrazine, hydroxylamine and nitrous acid. These interferences could, however, be removed by correction functions. Temperature fluctuations in the range of ±1 °C lead to artifacts of ±3.5% for the nitric oxide and ±3.9% for the nitrous oxide sensor and can be corrected with exponential equations. The results from this study help to significantly shorten and optimize the determination of the correction functions and are therefore relevant for all users of nitric and nitrous oxide electrodes.     

An alternative method for calculation of semi-gray radiation heat transfer in solar central cavity receivers

This paper describes a general method to calculate the semi-gray radiation heat transfer that occurs within an enclosure comprised of diffuse surfaces. The method is implemented in an existing solar power tower cavity receiver model in the System Advisor Model (SAM, NREL, 2011). The semi-gray radiation model is used to find an optimal distribution of emissivities for the thermal- and solar radiation wavelength bands for surfaces that comprise the solar central cavity receiver. The optimal distribution of emissivities maximizes the overall thermal efficiency of a cavity receiver. The model shows an effective way to reduce heat loss from the cavity is to minimize the temperatures of the passive surfaces through manipulation of their radiative surface properties.For the cavity receiver design considered, an optimal emissivity distribution for the active absorber surfaces of the cavity is a selective surface with high absorptivity in the solar wavelength band and low emissivity in the thermal wavelength band. Passive surfaces within the cavity should be highly reflective for radiation over the full spectrum. For absorber surfaces with solar absorptivity of 0.95, thermal emissivity of 0.1 and reflective passive surfaces with emissivities of 0.1, for the full spectrum, the thermal efficiency of the receiver can be increased by about 0.7% in comparison to gray surfaces having an emissivity of 0.95 for all wavelengths.