Search

In this paper, a model for intermediate band solar cells is built based on the generally understood physical concepts ruling semiconductor device operation, with special emphasis on the behavior at low temperature. The model is compared to JL-VOC measurements at concentrations up to about 1000 suns and at temperatures down to 20 K, as well as measurements of the radiative recombination obtained from electroluminescence. The agreement is reasonable. It is found that the main reason for the reduction of open circuit voltage is an operational reduction of the bandgap, but this effect disappears at high concentrations or at low temperatures. [ABSTRACT FROM AUTHOR]

Intermediate band solar cells (IBSCs) fabricated to date from In(Ga)As/GaAs quantum dot arrays (QD-IBSC) exhibit a quantum efficiency (QE) that extends to below bandgap energies. However, the production of sub-bandgap photocurrent relies often on the thermal and/or tunneling escape of carriers from the QDs, which is incompatible with preservation of the output voltage. In this work, we test the effectiveness of introducing a thick GaAs spacer in addition to an InAlGaAs strain relief layer (SRL) over the QDs to reduce carrier escape. From an analysis of the QE at different temperatures, it is concluded that escape via tunneling can be completely blocked under short-circuit conditions, and that carriers confined in QDs with an InAlGaAs SRL exhibit a thermal escape activation energy over 100 meV larger than in the case of InAs QDs capped only with GaAs. [ABSTRACT FROM AUTHOR]

A photovoltaic device based on an intermediate electronic band located within the otherwise conventional band gap of a semiconductor, the so-called intermediate band solar cell (IBSC), has been proposed for a better utilization of the solar spectrum. Experimental IBSC devices have been engineered using quantum dot technology, but their practical implementation results in a departure of key underpinning theoretical principles, assumed to describe the operation of the IBSC, away from the ideal. Two principles which are only partially fulfilled are that (i) the intermediate band should be half filled with electrons and (ii) the region containing the quantum dots should not be located fully within the junction depletion region. A model to describe the operation of the devices under these nonidealized conditions is presented and is used to interpret experimental results for IBSCs with ten layers of quantum dots. Values for the electron and hole lifetimes, associated with recombination from the conduction band to the intermediate band and from the intermediate band to the valence band (0.5 and 40 ps, respectively) are thus obtained. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to evaluate the impacts on forage use and beef cattle performance of incorporating divergent wheat milling byproducts in a 30% CP supplement. The by-products were wheat bran (high fiber) and second clears (high starch). The by-products were added as 1) 100% wheat bran; 2) 67% wheat bran, 33% second clears; or 3) 33% wheat bran, 67% second clears to constitute approximately 47 to 49% of the supplement. In Exp. 1, 90 Hereford x Angus cows (BW = 554 kg) grazing winter, tallgrass-prairie range were fed the supplement treatments (2.27 kg/cow daily) from early December 1997 until calving (average calving date = 3/11/98). Cumulative BW and condition changes from trial initiation through calving were not significantly different among treatments. Similarly, significant treatment effects on cow pregnancy rates as well as calf birth weights, ADG, and ending weights were not evident. In Exp. 2, 16 ruminally fistulated Hereford x Angus steers (BW = 484 kg) were blocked by weight and assigned to one of the same three supplement treatments or to a negative control (forage only). Steers had ad libitum access to tallgrass-prairie hay (76.4% NDF, 3.1% CP) and were fed supplement at the same rate (relative to BW) as the cows in Exp. 1. Forage OM, NDF, and digestible OM intakes were lower (P [is less than] 0.01) for the negative control than for supplemented steers but were not significantly different among the supplemented steers. Digestion of OM was lower (P = 0.03) for the negative control than for supplemented steers, although significant treatment differences were not evident among the supplemented groups. Digestion of NDF was not affected (P = 0.49) by treatment. Within the context of the amount of supplemental protein offered, changes in the combination of wheat milling by-products in the supplement did not affect cow performance or intake and digestion of low-quality forage. Key Words: Beef Cattle, Byproduct, Forage, Wheat

Two experiments were conducted to quantify the impact on forage use and performance of varying supplementation frequency of cattle consuming forage diets across a range of frequencies. In both experiments, a common supplement was used that contained a relatively high concentration of CP (43%) and was fed at the following frequencies: 1) 2 d/wk; 2) 3 d/wk; 3) 5 d/wk; and 4) 7 d/wk. In Exp. 1, 120 Hereford x Angus cows (BW = 537 kg) grazing winter tallgrass-prairie range were supplemented at the various frequencies from December 7 until calving (average calving date = 3/7/99). All treatments provided the same quantity of supplement on a weekly basis (12.74 kg, as-fed) but divided the amount delivered on a given day equally among the number of supplementation events for that treatment. Less BW was lost from December 7 through calving (linear effect, P = 0.02) as frequency of supplementation increased, but the magnitude of difference in weight change was relatively small. Body condition responded similarly through early February (linear effect, P = 0.02), although treatment effects were not as distinct at calving (cubic effect, P = 0.11). In Exp. 2, 16 ruminally fistulated Hereford x Angus steers (BW = 257 kg) were blocked by weight and assigned to one of the four frequencies of supplementation. Steers were offered tallgrass prairie hay (73.5% NDF, 4.8% CP) ad libitum and were supplemented at a rate (relative to BW) similar to that of the cows in Exp. 1. Increasing frequency of supplementation increased (linear effect, P [is less than or equal to] 0.02) forage OM intake, OM and NDF digestion, and digestible OM intake. However, the most prominent differences in forage OM intake tended (cubic effect, P = 0.07) to occur with the two extreme frequencies of supplementation. In conclusion, forage use was improved with an increased frequency of supplementation, but the impact on performance is not likely to be large unless extreme differences in frequency occur. Key Words: Feed Supplements, Feeding Frequency, Forage

An experiment was designed to determine the effects of ruminal and postruminal infusions of ruminally degradable protein (casein) on intake and digestion of low-quality hay by beef steers. Twelve ruminally fistulated Angus x Hereford steers (initial BW = 563 kg) were blocked by weight and assigned to one of three treatments: control (C; hay only) or hay plus ruminal (R) or postruminal (P) infusion of 400 g/d of sodium caseinate. The trial consisted of five periods: 1) 10-d adaptation to the hay diet; 2) 7-d measurement of hay intake (without infusions); 3) 10-d adaptation to protein infusion treatments (intake measurements continued); 4) 7-d measurement of hay intake and digestibility (infusions continued); and 5) 3-d ruminal sampling period (infusions continued). Steers were given ad libitum access to tallgrass-prairie hay (3.4% CP, 76.6% NDF) throughout the study. Casein was administered once daily before feeding, either directly into the rumen or via anchored infusion lines into the abomasum. Hay intake was increased by supplementation (P [is less than] 0.01). Ruminal infusion elicited a greater (P = 0.04) increase in hay intake than postrumina] infusion. Intake tended (P = 0.11) to be lower in period 4 than in period 2 for control steers but was greater in period 4 than in period 2 (P [is [is less than or equal to] 0.03) for both R and P steers. The increase in intake between periods 2 and 4 was greater for R than for P steers (P = 0.03). Supplementation improved diet OM digestion (P = 0.04) but not NDF digestion (P = 0.18); however, greater relative error for NDF digestion may have limited the ability to elucidate significant treatment effects. There were no differences in either OM digestion (P = 0.42) or NDF digestion (P = 0.35) between R and P steers. Plasma urea N at 0 and 3 h after feeding on the last day of the experiment was lower (P = 0.05) for C than for R and P steers, but no difference (P = 0.48) was evident between R and P steers. Ruminal ammonia N levels also were increased by supplementation (P [is less than] 0.01), with a much larger increase for R than for P steers (P [is less than] 0.01). Total VFA concentrations were not affected (P = 0.21) by treatment, but R steers exhibited lower proportions of acetate and higher proportions of isobutyrate, valerate, and isovalerate than P steers (P [is less than] 0.01). In conclusion, ruminal and postruminal infusion of a degradable protein source improved forage utilization, although the response in forage OM intake and total digestible OM intake was greater for ruminal infusion than for postruminal infusion. Key Words: Beef Cattle, Forage, Protein, Supplementary Feeding

Prolactin is required for mammary development in various species but its possible role for mammogenesis in pigs is not known. The goal of the present study was therefore to determine the effect of prolactin inhibition by bromocriptine during the last third of gestation on mammary gland development in gilts. Twenty-eight primigravid gilts were assigned as controls (n = 15) or received 10 mg of bromocriptine orally thrice daily (n = 13) from d 70 to 110 of gestation. Jugular blood samples were collected on d 70 of gestation and every 8 d thereafter and were assayed for prolactin, IGF-I, estradiol, and progesterone. Gilts were slaughtered on d 110 of gestation and fetuses were counted and weighed. One row of mammary glands was used for dissection of parenchymal and extraparenchymal tissues and for determination of DNA, RNA, dry matter, protein, and fat contents. Tissue from the other row was used for measures of prolactin receptor number and affinity. Concentrations of prolactin were drastically reduced throughout the bromocriptine treatment period (P [is less than] .001), whereas there was no overall treatment effect on progesterone and IGF-I levels (P [is greater than] .10). Total weight and extraparenchymal tissue weight of the mammary glands were unaffected by treatment (P [is greater than] .1), but weight of parenchymal tissue, total DNA, and total RNA decreased (P [is less than] .01) with bromocriptine treatment. Percentages of fat and dry matter in patenchymal tissue increased with bromocriptine treatment (P [is less than] .01) and the percentage of protein decreased (P [is less than] .01). Number of prolactin receptors in parenchymal tissue decreased with bromocriptine treatment (P [is less than] .001) and receptor affinity increased (P [is less than] .001). Average fetal weight was lower in gilts receiving bromocriptine than in control gilts (P = .05), but fetal number did not differ (P [is greater than] .1). These results clearly demonstrate that prolactin is essential for normal mammary gland development and can affect fetal growth during the last third of gestation in gilts. Key Words: Bromocriptine, Mammary Development, Mammary Glands, Pregnancy, Prolactin, Sows

Objective:To conduct a systematic literature review (SLR) and network meta-analysis (NMA) of real-world studies comparing major bleeding risk among patients with non-valvular atrial fibrillation (NVAF) on direct oral anticoagulants (DOACs) or warfarin. Methods:Systematic searches were conducted in MEDLINE and Embase for full-text articles published between January 1, 2003 and March 18, 2017. Eligible studies compared at least two of the following in a real-world setting: warfarin, apixaban, dabigatran, rivaroxaban, or edoxaban. A Bayesian NMA was conducted to estimate hazard ratios (HRs) for major bleeding using a random-effects model. Results:Eleven studies were included in the NMA. Nine studies included DOACs vs Warfarin comparisons, and four studies included DOACs vs DOACs comparisons (two studies included both comparisons). Median follow-up duration ranged from 2.6–31.2 months. No evidence was identified for edoxaban. Apixaban was associated with a significantly lower risk of major bleeding compared to other oral anticoagulants (warfarin HR = 0.58; 95% credible interval [CrI] = 0.48–0.69; dabigatran = 0.73; 0.61–0.87; rivaroxaban = 0.55; 0.46–0.66). Dabigatran was associated with a significantly lower risk than warfarin (0.79; 0.71–0.88) and rivaroxaban (0.76; 0.67–0.85), and rivaroxaban was not statistically different from warfarin (1.05; 0.91–1.19). Sensitivity analyses with standard dose and sponsorship showed consistent results. Conclusion:DOACs were associated with lower or similar risk of major bleeding compared with warfarin in NVAF patients. Apixaban was associated with a significantly lower risk of major bleeding than other DOACs. Dabigatran was associated with a significantly lower risk of major bleeding compared to rivaroxaban and warfarin. [ABSTRACT FROM PUBLISHER]