High-fidelity phase and amplitude control of phase-only computer generated holograms using conjugate gradient minimisation.

We demonstrate simultaneous control of both the phase and amplitude of light using a conjugate gradient minimisation-based hologram calculation technique and a single phase-only spatial light modulator (SLM). A cost function, which incorporates the inner product of the light field with a chosen target field within a defined measure region, is efficiently minimised to create high fidelity patterns in the Fourier plane of the SLM. A fidelity of F = 0.999997 is achieved for a pattern resembling an LG10 mode with a calculated light-usage efficiency of 41.5%. Possible applications of our method in optical trapping and ultracold atoms are presented and we show uncorrected experimental realisation of our patterns with F = 0.97 and 7.8% light efficiency.

Identifying infertile homozygous Inverdale (FecXI) ewe lambs on the basis of genotype differences in reproductive hormone concentrations.

Introduction of the Inverdale prolificacy gene (FecXI) could markedly improve reproductive efficiency in commercial flocks, but as homozygous carrier Inverdale ewes are infertile, it is imperative that these animals are identified at an early age and excluded from breeding stock. As the ovaries of homozygous carrier ewes are nonfunctional, there are wide differences in reproductive hormone levels between these and other Inverdale genotypes. This study assesses the accuracy of using hormone concentrations alone, to identify infertile homozygous ewe lambs. Ewe lambs were blood sampled at 2, 5 and/or 8 months of age, and plasma analyzed for follicle-stimulating hormone (FSH), luteinizing hormone (LH) and inhibin content. These animals were either the offspring of both known carrier rams and known carrier ewes, and therefore would be either homozygous (II) or heterozygous (I+) for the Inverdale gene (group 1, N = 122), or had one parent that was a carrier and therefore would be either heterozygous or noncarriers (++) of the gene (group 2, N = 32). Animals were designated as either II or I+/++ on the basis of their plasma hormone concentrations. Inverdale genotype was also assigned from laparoscopic observation of the ovaries at each of these occasions. Definitive assignment of genotype was made at laparoscopy as adults during the breeding season. On the basis of laparoscopy as adults, 62 (51%) lambs in group 1 were identified as homozygous and 60 (49%) as heterozygous. At all three ages, both mean FSH and mean LH concentrations were significantly higher in II than in I+ lambs. Mean inhibin concentrations were significantly lower in II lambs at 8 months, but did not differ significantly between genotypes at 2 or 5 month of age. The use of discriminant analysis techniques to segregate individual animals in group 1 on the basis of their plasma FSH and LH concentrations, correctly identified Inverdale genotype in 50/52 (96%) lambs at 2 months, 75/79 (95%) at 5 months and 118/122 (97%) at 8 months of age. Discriminant analysis was equally effective for segregating II ewe lambs (group 1) from fertile ewe lambs of I+ and ++ genotype (group 2, 97% correct at 5 months and 98% at 8 months). At no stage did inclusion of inhibin concentrations into the discriminant function alter the number of homozygous ewes misclassified. This demonstrates that infertile homozygous ewe lambs can accurately be distinguished from their fertile flockmates by using plasma concentrations of gonadotrophins alone, and that this can be achieved from as early as 2 months of age.

Seasonal effects on gestation length and birth weight in alpacas.

Gestation lengths and birth weights were measured in 162 pregnancies in alpacas (Lama pacos) farmed in the high country of the South Island of New Zealand. A comparison of pregnancies from spring (mid-October to mid-December) and autumn (mid-February to late April) matings showed that gestation lengths were 12.5 days longer in spring (348.9 +/- 1.4 days vs. 336.4 +/- 1.2 days; P < 0.0001). For each day later in spring that a female was mated there was an increase in gestation length of 0.11 days (P < 0.05), whereas for each day later in autumn the gestation was reduced by 0.24 days. There were no significant effects of sex of cria or age of dam on gestation length. After adjustment for gestation length, crias born in autumn weighed 1.0 kg more than those born in spring (8.8 +/- 0.15 kg vs. 7.8 +/- 0.18 kg: P < 0.001). Female crias weighed 0.4 kg less than males at birth (P < 0.05). The results suggest that in this environment it will be difficult to maintain spring-mated females in a 12 month breeding cycle.