no / Batch and semi-batch reactors are widely used for fine chemical productions. The target in the fine chemical industry is to produce a high quality product and operational optimization is the key-element to match it. This work investigates how batch and semi-batch reactors can be optimized in order to increase the yield of a desired product. Optimization problem is formulated and applied to calculate the optimal operating parameters such as the reactor temperature and the feed flow rate. Comparison and considerations on the two reactor configurations are given.

Yes / Waxy crude oils are pumped hot but upon power cut, pumping stops, the oil cools leading below the wax appearance temperature to precipitation of the wax and the formation of a gel throughout the pipe. In such a situation, what is the minimum pressure required to restart flow, not to merely deform the gel or break it? This paper provides a solution to this problem using microscopic observations under controlled cooling conditions and rheological data conducted in constant stress mode under controlled temperature and cooling conditions and restart experiments in laboratory pipelines replicating the rheometric conditions and deviations from them to inform large diameter operation in the field. Three important findings derive from the experimental data collected: (i) A fragmentation stress , rather than the static stress that precedes it, is found to be the more accurate predictor of flow re-start pressures; (ii) Waxy crude oils gels exhibit true yield stress and yielding process but also show flow on application of the slightest stress below yielding; (iii) This flow, in the elastic region, is jagged rather than continuous suggesting a consolidation process of the crystals and their agglomerates forming the gel. In the broader context of the existence of a yield stress, the data presented here show that there is such a thing as a yield stress and the concepts of a yield stress and that everything flows are not mutually exclusive.

no abstract provided by author / Master of Science

Cyclosporine (CsA), a fungal peptide with remarkable anti-lymphocytic properties, has been shown to be an effective immunosuppressive agent. In three separate experiments, mice receiving CsA at various doses (8 mg/kg/day in the first two experiments and 70-100 mg/kg/day in the third), were implanted with ovine mammary tissue expants at various sites (subcutaneous dorsum, ovarian fat-pad, and cleared mammary gland fat-pad). After different periods of time, (day 3, 7, 14, 21, and 35) implants were removed, fixed, stained, and embedded. Epithelial morphology of the implants was evaluated via a grading system that classified epithelium from 1 (poor) to 5 (excellent). Leukocyte type and number was determined in subepithelial stroma of implants in the third experiment. In the first two experiments, histological evaluation revealed that the transplanted tissue did not survive, regardless of site of implantation or developmental stage of donor tissue. In experiment three higher, dosages of CsA and different donor tissue were used, this resulted in significantly higher (P < .05) mean epithelial scores (indicative of healthier epithelium) for two CsA treated groups vs two control groups (3.75 and 2.33 vs 2.0 and 1.25, respectively). Within each treatment group (CsA and control), one group of mice received exogenous estrogen and progesterone (EjP) implants. CsA treated mice receiving E/P had significantly higher (P < .05) epithelial scores than those not receiving hormones (3.68 vs 2.83). The reverse was true for lymphocyte number (18.9 vs 40.5 cells per 117,600 um² of subepithelial stroma) which were significantly less in CsA + E/P treated mice. The overall correlation between lymphocyte number and epithelial score was -.55 (P < .0001). These results indicate that ovine mammary tissue xenografted into mice treated with high doses of CsA, are capable of surviving for extended periods of time (at least 35 days). / Master of Science

The ability of mammary tissue from mature Holstein bulls to respond to hormonal stimuli in organ culture to synthesize and secrete milk proteins was studied. Sixteen bulls from the genetic selection and control lines developed at Virginia Polyteclmic Institute were randomly assigned to either a non-treated or steroid pretreated group. The steroid pretreated group received estradiol 17-B and progesterone at 0.1 and 0.25 mg/kg/day, respectively, for 7 d starting 15 d before slaughter. Mammary tissue was explanted and cultured for up to 96 h in basal medium (B) which consisted of Media 199 supplemented with fetal calf serum and bovine insulin, or stimulatory medium (St), which was further supplemented with triiodothyronine, estradiol 17-B, hydrocortisone, and bovine prolactin (PRL). Explants in duplicate multi-well culture dishes were incubated in the presence of 3H-Iabeled amino acids or 3H-Iabeled thymidine. Measurements made included: casein in media and homogenized tissue, alpha-lactalbumin in homogenized tissue, tri-chloro-acetic acid precipitable 3H-protein in media and homogenized tissue, and DNA content of cultured tissue. A subset of cultured explants from each bull was fixed and embedded for histological evaluation and auto radiographic localization of incorporated 3H-labeled thymidine. Synthesis and secretion data, as well as growth responses of the epithelium were compared between selection and control bulls. / Master of Science

Increasing feeding costs has led many dairy farmers to use pasture for lactating cows to reduce their production cost. Little is known about the efficiency of nutrient utilization by lactating cows under grazing conditions. The objective of this study, therefore, was to investigate ruminal turnover, intake and site and extent of nutrient digestion in grazing lactating cows. Four dual cannulated (rumen and proximal duodenum) cows were randomly assigned to two groups to graze permanent pasture with no supplement or with 6.4 kg/d corn-mineral mix in a switchback design with three periods of two wk each. Solid and liquid markers (chromic oxide and CoEDTA), used to estimate duodenal flow, fecal output, and ruminal turnover, were administered through the rumen cannula twice daily at 1100 and 2300 h. The supplemented cows had greater milk production (23.7 kg/d) than those on pasture only (19.5 kg/d) with an increase of .66 kg of milk production per kg of concentrate. Corn, however, depressed milk fat percentage resulting in a similar milk fat yield between the two diets. Supplemental corn reduced rumen ammonia-N (22 vs 17 mg/dl) and increased N recovery at the duodenum (86 vs 75% of N intake). True Nitrogen digestibility averaged 72% and microbial N flowing to the duodenum was 67% of the total N flow. This results indicated that grazing cows may benefit from concentrates containing undegradable protein. Daily OM intake was not different, but when cows were fed the supplemented diet, pasture OM was lower than when fed pasture only. Organic matter, NDF and ADF digestibility in the rumen and whole digestive tract were greater when cows were fed. Cellulolytic activity may have been reduced by grain supplementation due to decreased ruminal pH (6.4 vs 6.2). The reduction in fiber digestibility may explain the decrease in forage intake when cows were fed supplemental grain. Ruminal rates of passage (kp) for solid (7.3 %/h) and liquid (18.2 %/h) markers were similar for both diets. The kp values observed for solid and liquid indicate that grazing cows may have a faster ruminal turnover than cows fed diets containing primarily hay or silage. / Master of Science

Millets are C4 annual grasses that are mainly used for food and feed. This thesis describes two studies that evaluated drought tolerance of pearl millet cultivars (Pennisetum glaucum [L.] R. Br) grown for grain. A third study is also included in the thesis that evaluated foxtail millet (Setaria italica [L] Beauv) and pearl millet grown as cover crops and forage during a pasture renovation. The main focus of the thesis involved evaluation of Senegalese pearl millet cultivars for drought tolerance. Drought is one of the most important threats to pearl millet production in Senegal as it limits yield in most parts of the country. Although water stress on pearl millet is common during the growing season, a little is known about how terminal drought affects yield in Senegalese pearl millet cultivars. To address this issue, two field experiments were conducted in 2014 and 2015. The first field study evaluated 20 pearl millet cultivars under water stress and categorized based on their yield response. Whereas the second year field trial used four cultivars from the first field trial in a more detailed study to give recommendations for farmers in Senegal. The experiments were complete randomized block designs. Pearl millet cultivars were grown under irrigation until flowering then the stress treatment was applied by stopping the irrigation in half of the plots. Eleven cultivars showed a statistical indifference to water stress and considered the most drought tolerant. Four cultivars were selected from the 11 for the second year experiment. Of these, cultivar 4 (ICMV IS 89305) and 10 (SOSAT c 88) exhibited higher tolerance to terminal water stress based on evaluation of yield components and drought stress indices. These cultivars could be a good target for further breeding and selection in Senegal. Although the cultivars were more drought tolerant, both had relatively low total biomass. When used in a larger scale, these cultivars could potentially benefit farmers in Senegal and enhance food security. The second part of this thesis addressed use of a forage type millets – specifically foxtail and pearl millet. In the US, these millets are primarily serve as a summer cover crops that can be used for forage. The objective of this experiment was to compare yield and forage quality of foxtail and pearl millet cover crops and their effect on subsequent pasture establishment. A field experiment was conducted in Virginia in 2014 to address this objective. Pearl millet and foxtail millet were randomly planted in 12 plots each and harvested in late summer. Plots were then converted to tall fescue (Schedonorus phoenix (Scop.) Holub) pasture. Foxtail millet had a significantly higher soil cover than pearl millet but the two species did not differ in terms of total biomass, forage quality, or their effect on tall fescue pasture establishment. / Master of Science

Matua prairie grass has a potential to extend the grazing season in Virginia due to its higher early spring and fall production. However, little is known about the compatibility of Matua prairie grass with legumes or the effects of legumes on the yield and quality of Matua prairie grass/legume mixtures. An experiment was conducted in 1998 and 1999 to investigate the botanical composition, yield, and chemical composition of Matua prairie grass grown with legumes. Legume treatments consisting of ladino clover (Trifolium repens), red clover (Trifolium pratense), alfalfa (Medicago sativa), and annual lespedeza (Lespedeza stipulacea) were drilled into a Matua prairie grass stand. Nitrogen was applied once each fall at two treatment levels of 0 or 84 kg/ha. The experiment was arranged in a randomized split block design with four replications. Legume treatments had no effect on percentage Matua prairie grass or total dry matter yield in 1998. However, in 1999 the ladino clover and red clover treatments increased (P<0.05) total dry matter yield, but also resulted in a substantial decrease (P<0.05) in percentage Matua prairie grass. Nitrogen application in the fall of 1998 had a residual effect (P<0.05) on the percentage Matua prairie grass and yield in 1999. The highest response to nitrogen fertilization occurred in the harvest immediately after fertilization, in October of 1999, which resulted in the largest increase (P<0.05) in percentage Matua prairie grass and yield, and the greatest decrease (P<0.05) in percentage legumes. The legume and nitrogen treatments similarly influenced the chemical composition of the Matua prairie grass/legume mixed forage. Ladino clover, red clover, and alfalfa treatments generally improved forage quality as indicated by a decrease (P<0.05) in NDF, ADF, hemicellulose, and cellulose, and an increase (P<0.05) in CP and IVDMD. Nitrogen fertilization did not influence the chemical composition of the forages to the same extent as the legume treatments, as a decrease in fiber components and an increase in CP and IVDMD were observed due to nitrogen. Overall, alfalfa appeared to be most compatible with Matua prairie grass, and the incorporation of alfalfa into a Matua prairie grass stand resulted in some improvements in total dry matter yield and nutritive value of the forage, without the detrimental suppression of Matua prairie grass. / Master of Science

Monthly milk production data collected by DHI supervisors in 28 Virginia dairy herds over a three year period were analyzed. Relationships between somatic cell count and milk production were determined. A curvilinear relationship between somatic cell count and daily milk yield was shown to exist. The relationship indicated daily milk yield declined more rapidly as somatic cell counts increased from 50 X 10³ through 300 X 10³ cells per ml compared to daily milk decline as somatic cell counts rose from 400 X 10³ through 1,200 X 10³ cells per ml. Daily milk yield declined at a slower rate at somatic cell levels above 400 X 10³ cells per ml. There was an apparent cumulative or continual relationship between somatic cell count and daily milk yield. Losses and declines in test day milk production were greater when cumulative somatic cell count was considered. Complete lactation records of 305-day, mature equivalent milk production were compared to weighted, lactational somatic cell counts. Lactational milk production losses were not as great as daily milk production losses, extended to full lactation, indicated. Design difficulties and inadequacies of models used in complete lactation evaluation may explain the discrepancies. A maximum somatic cell count of 150 X 10³ to 200 X 10³ cells per ml was indicated as an optimum level for somatic cell count. Above this level milk losses were excessive. / Master of Science

The Virginia-Carolina (VC) region including Virginia, North Carolina, and South Carolina, is the most important peanut production region for the large seeded, virginia-type peanut in the United States.  In recent years, an increased frequency of heat and drought episodes with significant effects on peanut yield was observed in the VC region.  Because limited information is available on the mechanisms virginia-type peanut develops in response to heat and water stress, the present study evaluated several physiological and metabolic characteristics and their relationship with yield for eight cultivars and breeding lines.  Experiments were conducted under rainfed and irrigated field trials in 2011 and 2012, and in a growth chamber under optimum (30/25 "C) and high temperature (40/35 "C) conditions.  The long term goal of this study is to help development of more tolerant peanut cultivars to heat and drought in the VC region. Visible symptoms of water-deficit stress were observed in peanut during the field experiments in both years.  Significant (p d 0.05) variations for yield, membrane injury, chlorophyll fluorescence (Fv/Fm ratio), specific leaf area, SPAD chlorophyll content, and relative levels of polar and non-polar metabolites were observed in response to water regime, growth stage, and genotype in both years during the field studies.  Similarly each year, the Fv/Fm ratio, organic acids, and saturated fatty acids decreased in rainfed vs. irrigated plants, while the sugar and sugar alcohol relative levels increased.  Regardless the water regime, lower levels of saturated fatty acids and sugars, and higher levels of unsaturated fatty acids and sugar alcohols were associated (p < 0.05) with higher pod yield in field conditions.  Genotypes Phillips, SPT06-07, and N05006 showed potential tolerance and N04074FCT, CHAMPS, and Bailey susceptibility to water deficit in field studies.  Significant physiological and metabolic changes were also observed in response to heat stress under controlled conditions in peanut seedlings.  A general decrease in organic acid and saturated fatty acid levels and an increase in membrane injury, sugar, and unsaturated fatty acid levels were observed under both water deficit and heat stress conditions.  Overall, results from both experiments were suggestive of natural stress responses rather than adaptive mechanisms to water deficit and heat stress of the virginia-type genotypes used in this study. Among all genotypes, SPT 06-07 showed improved tolerance to both stresses.  Our results suggest that monitoring chlorophyll fluorescence and changes in the levels of selected metabolites can be used to screen new peanut lines for drought and heat stress tolerance. / Master of Science in Life Sciences