A Brownian-pumping model for oceanic trace metal scavenging: Evidence from Th isotopes

Two observed characteristics of Th isotope and stable metal sorption in natural aquatic systems are seemingly at odds with physico-chemical adsorption theory: (1) characteristic sorption times of days to weeks and (2) Kds which are inversely related in magnitude to particle concentrations. In addition, sorption rate constants are positiveiy correlated with particle concentrations and Kd. This paper presents a conceptual and mathematical model with which it is proposed that these metal sorption characteristics have the same underlying physical process in common: the coagulation of colloidal (nonfilterable) particles onto larger (filterable) particles. “Brownian pumping” (the transfer of truly dissolved metal species to filterable particles through a colloidal intermediate) consists of two rate steps: (1) rapid formation of metal/colloid surface site complexes (adsorption) and (2) slow coagulation of colloids with filterable particles. The Brownian-pumping model is tested against field and laboratory data. The field data, obtained from the literature, covers different regions of the oceans: deep ocean environments, euphotic zone, coastal and estuarine systems. The laboratory data involved 228Th sorption in suspensions of goethite and polystyrene latexes. Although the model has general applicability, results and discussions herein emphasize thorium isotope behavior. The Brownian-pumping model suggests that Th or other strongly sorbing elements may be useful as in situ “coagulometers” either at relatively high (e.g., greater than 5–10 mg/l) particle concentrations or when the mass ratio of colloids (C*p) to filterable particles (Cp) is known. The model also indicates that the ratio of colloids to filterable particles in marine systems, may be, by a first approximation, described by the relationship log C*p = 0.7 log Cp – 2.6 (in units of kg/l)

Segregated Early Weaning (SEW) of Pasture-farrowed Pigs

Segregated early weaning (SEW) works well with pasture-farrowed pigs. The SEW pasture-farrowed pigs weighed about the same as conventionally weaned pigs at 9 weeks of age with lower death losses (about 2% less). For the period 5–9 weeks of age the SEW pigs gained more rapidly and were more efficient converting feed to live gain than pigs weaned at 5 weeks of age and moved to an open-front shelter. However, costs were presumably higher for the SEW pigs because of higher labor costs from multiple feedings per day, higher-priced pig feed for early weaned pigs, higher utility costs, and the added cost of a nursery unit. Based on the results of this trial, SEW is compatible with pasture farrowing. However, pasture farrowing may not be as compatible with the mechanics of SEW. For example, because pasture farrowing is seasonal, the SEW nursery may not be kept full at all times. This would reduce the throughput, the number of pigs through the unit, which would increase the fixed building costs per pig. A new approach of putting newly weaned 2-week-old, 10-lb pigs directly into a finishing unit would partially alleviate this situation or lower fixed cost SEW nurseries are needed that then could be used on a seasonal basis. On the other hand, the technique of early weaning pasture-farrowed pigs has the potential of extending the farrowing season while reducing piglet mortality and minimizing the negative effects of weather extremes. By its nature, a one-litter pasture-farrowing system may benefit less from SEW than other more intensive or continuous pig production systems. In a one-litter system considerable age segregation of pigs occurs on the farm at all times. The sows are sold after weaning. At most times throughout the year the pigs on the farm are the same age. If the herd already has a high health status, the advantages of SEW are much less. Therefore, SEW will work for pasture farrowed pigs but herd health status and overall SEW costs need to be carefully evaluated. A cost comparison of SEW for pasture-farrowed pigs is elsewhere in this report

A Robert Fulton Exhibit

An exhibit of monographs by or on Robert Fulton from the Library\u27s rare book collection and two torpedo drawings by Robert Fulton that were given to the library by Robert B. Honeyman, Lehigh Class of 1920, and Mrs. Honeyman

The Economics of Finishing Hogs in Hoop Structures and Confinement; Financial Comparison

From June 30, 1998 to Feb 21, 2001, a study to compare swine production facility types was conducted at the Iowa State University Rhodes Research and Demonstration. The two types of pork grow-finish production facilities compared in this study were hoop and total confinement. This report evaluates financial measurements from six groups of hogs; three groups fed in during the winter and three groups fed during the summer. This financial examination provides mixed results. The hoop facilities have superior return on investment, internal rate of return, modified internal rate of return, and a shorter pay back period. These advantages can be attributed largely to the hoops’ smaller initial investment. However, the confinement facility has the advantage of a longer service life as well as higher net profit per year per pig space. This gives the confinement system an advantage of a higher net present value. Hoop operations will need to invest in more pig spaces to generate the same net present value. The report goes on to examine the sensitivity of the financial measures to changes in input and output values such as carcass prices, ration cost, and cost of capital. The result is that due to its lower investment per pig space, shorter service life, and lower net profit per year the hoop facilities are more sensitive to changes in hog prices, ration costs, facility costs, and net profit per head. However, the confinement facility is more sensitive to changes in the cost of capital due to its longer service life and higher initial investment level. This makes the question of which system is a better financial investment dependent on several issues. The availability of initial capital, operating capital, land for manure application, labor available, and pig flow are all important in order to make a decision on which investment is best. Operators must also consider the cost of capital, value of alternative uses for the capital, market conditions, risk aversion level, as well as intrinsic values of the alternatives when deciding on which pig finishing option to select

An Economic Analysis of Pork Production in Hoop and Confinement Facilities: A Winter Comparison

The two types of pork grow-finish production facilities compared in this study are hoop and total confinement. Results of this study, which was conducted from September 27, 2000 until February 21, 2001 showed profit to be $9.26 per pig greater for the confinement-raised pigs. This study represents the seventh group of pigs finished at the pig research facilities at the Iowa State University Rhodes Research Farm. The profit difference experienced with this group was the largest experienced to date. An important issue with this group was that extreme weather conditions prevented marketing the pigs at optimal times. Neither system’s pigs could be sold at the proper time because of extreme cold and heavy snow. Moreover, the hoop pigs were placed on feed over a three week period but were all sold on the same day (Table 2) causing a wide range in market weight and a disparagement of premiums. Additionally, the weather was more severe during this trial than with any of the previous trials. The daily highs and lows during December 2000 averaged 15 and 12 degrees, respectively, below the 50-year averages for the area. The lower fixed cost advantage of the hoops was offset by the significantly higher variable input needs such as feed and bedding. Results of this group point out the importance of management and weather in determining the profit differences between the two systems. Average daily gain and feed efficiency has constantly been lower for the hoopraised pigs for the winter trials. However, the difference for this trial was much more dramatic. The extreme weather conditions were likely a major contributor. The hoop pigs expended far more energy in keeping warm. This points out the importance of weather in production systems which have limited control on air temperature and flow

An Analysis of the Cost of Producing Pork in Hoop Structures and Confinement during the Winter

This research is aimed at comparing two types of facilities for pork production--hoops and confinement systems. This report provides results from a group of pigs finished during the winter season. Hogs were on test from December to April. Results are evaluated by using the actual production efficiency values and the average or typical costs for feeder pigs, feed, etc., along with average market hog prices. This allows for comparison of expected costs and returns for normal input costs and hog price conditions