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Primiparous (n = 76) and multiparous (n = 328) lactating Angus cows were randomly assigned to receive either a 50 g or 100 g dose of GnRH at either the first or second GnRH injection of the CO-Synch estrus synchronization protocol to evaluate the efficacy of a reduced dosage in inducing a fertile ovulation. The result was four separate treatment groups: 50:50, 50:100, 100:50 and 100:100. The CO-Synch protocol traditionally consists of GnRH on d 0, followed by an injection of PGF2a on d 7. On d 9 cows were injected with another GnRH injection and mass inseminated. On d -10, and again on d 0, blood samples were obtained to examine progesterone levels and determine the proportion of anestrous cows. Calves were removed for a 48 h period on d 7 and were put back with the cows immediately after breeding. Clean-up bulls were turned in with the cows on 14 d following AI. Cows were pregnancy checked via transrectal ultrasonography 68 d after AI. Serum progesterone levels indicated that 34.9% of the cows were estrual at the start of breeding. All treatments were equally effective (P>0.05) in inducing anestrus cows to ovulate and become pregnant. There was no difference in pregnancy rates among the treatment groups (50:50=50.7%; 50:100=49.3%; 100:50=50.3%; and 100:100=44.6%, P>0.05), thus indicating that a reduced dosage of GnRH is effective in inducing fertile ovulation in the CO-Synch timed insemination protocol. We conclude that using a lower dose of GnRH is an effective method of reducing cost of synchronization with the CO-Synch protocol. Key Words: Estrous synchronization, Beef cows, Fixed-time AI

Objectives were to examine effects of exogenous bovine somatotropin (bST) on pregnancy rates in conjunction with two separate estrus synchronization protocols: CO-Synch and Select Synch. In the CO-Synch trial, lactating beef cows (n=690) from 3 locations were administered 100 g of GnRH, followed 7 d later by 25 mg of PGF2a and on d 9 another 100 g of GnRH and were also inseminated. Cows were assigned to the following treatments: 500 mg of bST administered at the first GnRH injection (Trt 1), bST with PGF2a (Trt 2), bST with the second GnRH injection (Trt 3) and no bST (Control). Cows were examined for pregnancy at approx. 60 d post-AI. Pregnancy rates for treatments 1, 2, 3 and Control were 30.0%, 26.9%, 33.1%, and 27.1%, respectively, and did not differ (P>0.05). Thus, bST had no effect on pregnancy results in the CO-Synch estrous synchronization protocol. In the second trial, lactating beef cows (n=581) were synchronized using the Select Synch protocol. On d 0, cows were administered 100 g of GnRH, followed 7 d later by 25 mg of PGF2a, combined with heat detection and AI on d 6-11. Cows were assigned to the following treatments: 500 mg of bST injected at the time of GnRH administration (Trt 1), bST with PGF2a (Trt 2) and no bST administration (Control). Estrus response rates were higher for Trt 1 (69.84 +/- 4.9; P0.05). Conception rates were higher for cows injected with bST at the time of the GnRH (64.1%) than for the animals administered bST in conjunction with PGF2a (35.5%), P0.05). Based on this trial, bST does not have a beneficial effect on conception rates, but does have a deleterious effect when administered at the time of PGF2a. Key Words: Estrus synchronization, Beef cows, Bovine somatotropin

A selected ion flow tube study of the reactions of a series of gas-phase atomic cations (S+, Xe+, O+, Kr+, N+, Ar+ and Ne+) and molecular ions (SFn+ (n = 1-5), CFn+ (n = 1-3), CF2Cl+, H3O+, NO+, N2O+, CO2+, CO+, and N2+) spanning a large range of recombination energies (6.3-21.6 eV), with acetone, 1,1,1-trifluoroacetone, and hexafluoroacetone has been undertaken with the objective of exploring the nature of the reaction ion chemistry as the methyl groups in acetone are substituted for CF3. The reaction rate coefficients and product ion branching ratios for all 66 reactions, measured at 298 K, are reported. The experimental reaction rate coefficients are compared to theoretically calculated collisional values. Several distinct reaction processes were observed among the large number of reactions studied, including charge transfer (non-dissociative and dissociative), abstraction, ion-molecule associations and, in the case of the reactions involving the reagent ion H3O+, proton transfer. [ABSTRACT FROM AUTHOR]

It is known that a random walk model yields the multiplicative representation of a coherent scattered amplitude in terms of a complex Ornstein-Uhlenbeck process modulated by the square root of the cross-section. A corresponding biased random walk enables the derivation of the dynamics of a weak coherent scattered amplitude as a stochastic process in the complex plane. Strong and weak scattering patterns differ regarding the correlation structure of their radial and angular fluctuations. Investigating these geometric characteristics yields two distinct procedures to infer the scattering cross-section from the phase and intensity fluctuations of the scattered amplitude. These inference techniques generalize an earlier result demonstrated in the strong scattering case. Their significance for experimental applications, where the cross-section enables tracking of anomalies, is discussed. [ABSTRACT FROM AUTHOR]

Dissociative electron attachment to the highly reactive difluoromethylene molecule, CF2, produced in a C3F6/He microwave plasma and stepwise via the fast atom reaction CF3I +H→CF3 + HI and CF3 +H→CF2 + HF, has been investigated. The upper limit for the cross section of formation of F- via dissociative electron attachment to CF2 is estimated to be 5×10-4 Å2. This value is four orders of magnitude smaller than the cross section previously predicted from scattering calculations. It is concluded that difluoromethylene plays a negligible role in negative ion formation in fluorocarbon plasmas. [ABSTRACT FROM AUTHOR]

In the context of a stochastic framework based on Jakeman's random walk model, Field and Tough demonstrated how the radar cross-section could be inferred from the intensity-weighted fluctuations of the phase (coherent data). With regard to the compound representation of the scattered amplitude, this property holds for an arbitrary texture. Extending previous work pertaining to the more specific K-distributed case (where the texture is Gamma distributed), the authors discuss the error arising during this inference process for a broader range of texture distributions. For three different texture models the authors then derive a condition, on the number of samples over which the phase fluctuations should be averaged, to optimise the extraction of the cross-section. Simulated data assert the viability of their findings. The practical implications of this technique for radar clutters are then discussed. [ABSTRACT FROM AUTHOR]