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It is demonstrated that scanning tunneling microscopy (STM) images often contain three‐dimensional ghost images of the tunneling tip. These ghost images directly reflect the shape of the tip, as is proven by comparing them with tip indentations made in Si. Tip images appear as a set of identical protrusions, and have been observed regularly on Si surfaces annealed at 1200 K in ultrahigh vacuum. Imaging of rough surfaces may be fully dominated by this effect which can lead to incorrect image interpretations in STM and AFM.

We have studied the morphology and distribution of atomic steps on Si(001) with scanning tunneling microscopy. We find that native oxide removal at temperatures up to 1350 K leads to step pinning and bunching. Cleaning at temperatures above 1450 K leads to regular step distributions which reflect the macroscopic misorientation of the sample. Steps running parallel to the 2×1 dimer rows on the upper terrace are straight, whereas steps perpendicular to these rows are ragged.

Initial stages of Si molecular beam epitaxy (MBE) on Si(001) substrates, misoriented 0.5° towards [110], were investigated using scanning tunneling microscopy (STM). Images from samples grown at 750 K and subsequently quenched to room temperature indicate that after deposition of more than about 0.5 monolayers both step flow and island growth occur. The islands have an anisotropic shape while in‐between islands antiphase boundaries can be seen.

Shallow indentations with diameters of 2–10 nm have been made directly in clean Si(110) and Si(001) surfaces using the W tip of a scanning tunneling microscope. The shape of the holes formed depends on the shape of the tip and is not influenced by the presence or absence of a tunneling current during the indentation process. The sharpness of the tip is not degraded by the intimate tip–sample contact. Arbitrary line and bit patterns can therefore be written and read repeatedly using the same tip.

The duration of the interoestrous interval and plasma concentrations of prolactin were determined in seven bitches treated with 0.1 mg metergoline kg-1 body mass orally, twice a day during anoestrus to determine whether shortening of the interoestrous interval in dogs is due to suppression of prolactin secretion. The results were compared with those of a previous experiment in which four bitches were treated with 20 micrograms bromocriptine kg-1 body mass orally during the luteal period and anoestrus. The interoestrous interval of the dogs treated with metergoline, 240 +/- 67 days, was similar to the interoestrous interval before treatment, 225 +/- 54 days. However in the dogs treated with bromocriptine, the interoestrous interval was shortened to 123 +/- 46 days. The average of the means of the plasma concentrations of prolactin during metergoline treatment, 1.5 +/- 0.5 micrograms l-1, was lower (P = 0.03) than the average of the means of the plasma concentrations of prolactin during the 2 weeks before treatment, 3.6 +/- 2.3 micrograms l-1, but did not differ from the average of the means of the plasma concentrations of prolactin, 2.1 +/- 0.5 micrograms l-1, of the dogs treated with bromocriptine during anoestrus. As the plasma concentrations of prolactin were similar during metergoline and bromocriptine treatment, and the anoestrous period was shortened during bromocriptine treatment, but not during metergoline treatment, these results suggest that the induction of oestrus by dopamine agonists is not initiated by suppression of prolactin secretion, but by other direct or indirect dopaminergic effects.

The effect of metergoline, a 5-hydroxytryptamine (serotonin) antagonist, on the plasma concentrations of prolactin in overtly pseudopregnant Afghan hounds and on the clinical symptoms of overt pseudopregnancy were studied. Plasma concentrations of prolactin and progesterone were determined in six Afghan hounds with signs of overt pseudopregnancy for 2-3 weeks and in three Afghan hounds that were not pseudopregnant at the time of blood sampling. In the overtly pseudopregnant bitches the plasma concentrations of prolactin before treatment (35.5 +/- 8.5 micrograms l-1) were significantly higher than the plasma concentrations of prolactin of the three bitches that were not pseudopregnant (6.3 +/- 0.5 micrograms l-1); the latter values were similar to those of non-pseudopregnant beagle bitches during the total luteal phase. The six pseudopregnant Afghan hounds were treated for 10 days with the antiserotoninergic drug metergoline. At 2 h after the onset of treatment with metergoline, the mean plasma concentration of prolactin had decreased to 10.8 +/- 2.9 micrograms l-1. The plasma concentrations of prolactin continued to decline to 5.4 +/- 1.0 micrograms l-1 at 4 h and to 1.0 +/- 0.1 microgram l-1 during treatment days 3-10. Signs of pseudopregnancy, such as swelling of the mammary glands and digging, decreased during the treatment period. The treatment was associated with mild behavioural side effects such as whimpering and aggressiveness. These side effects are probably not related to suppression of prolactin but are due to a direct effect on serotoninergic pathways in the brain. It is concluded that high plasma concentrations of prolactin are associated with the development and maintenance of pseudopregnancy. The serotonin antagonist metergoline strongly suppresses plasma concentrations of prolactin in pseudopregnant dogs and decreases the clinical signs of pseudopregnancy.

The excimer laser-assisted etching of Si and Cu in chlorine atmospheres is studied using angular-resolved time-of-flight measurements on the products desorbed combined with time-resolved surface reflectivity and pyrometry. Monte-Carlo simulations on the interaction of the desorbing molecules and a continuum hydrodynamical description are used to support the interpretation of the above measurements. It is proven that fast etching of Si only occurs at and above the melting point. Etching of Cu is accompanied by laser-stimulated diffusion of chlorine into the Cu.Consequences for practical applications are discussed.

Dose-response relationships between GnRH and LH, and between GnRH and testosterone, were investigated in six male dogs by intravenous administration of a GnRH analogue at different doses. Each dose of GnRH analogue induced an immediate rise in the plasma concentration of LH and then a rise in plasma testosterone concentration. Irrespective of the dose used, the rise in testosterone began 10 min after the GnRH injection. Administration of GnRH at doses of 0.01, 0.1, 1, 10 and 100 micrograms kg-1 resulted in maximum LH concentrations in plasma (mean +/- SEM; n = 6) of 22 +/- 7, 27 +/- 6, 40 +/- 7, 57 +/- 13 and 56 +/- 10 micrograms l-1, respectively. These doses induced maximum concentrations of testosterone in plasma (mean +/- SEM; n = 6) of 16 +/- 4, 20 +/- 4, 22 +/- 3, 22 +/- 4 and 24 +/- 7 nmol l-1, respectively. The lag time between peak concentrations of LH and testosterone varied from 35 to 55 min. The calculated maximum response of testosterone to LH, secreted by the anterior pituitary after GnRH injection, was 1.8 times higher than to GnRH. It was concluded that intravenous administration of GnRH induced marked and dose-dependent increases in plasma concentrations of LH and testosterone, and that there does not appear to be a direct effect of GnRH on Leydig cells in male dogs.

Molecular dynamics simulations are performed of Cu thin film growth on Cu (111). Ion-Assisted Deposition is simulated by bombarding the substrate with Cu+ ions with a kinetic energy of 80 eV, while 1 eV Cu atoms are used for the simulation of Laser Ablation Deposition. It appears that Ion-Assisted Deposition leads to sputtering, enhanced surface mobility, surface disorder, mixing and rather deep damage. This is discussed in some detail. Laser Ablation Deposition, using laser fluences just above the ablation threshold, does not lead to damage and mixing. Sharper interfaces and more perfect heterostructures and superlattices can be produced using Laser Ablation Deposition.

To investigate whether calving could be controlled by the withdrawal of progestogen implants from cows treated near term with prostaglandin three cows (group 1) received an intramuscular injection of 5 mg flumethasone on day 270 of pregnancy, and four cows (group 2) and three cows (group 3) received implants containing 3 mg norgestomet in both ears on day 262 of gestation and were treated with a prostaglandin F2 alpha analogue on day 264. On day 270 the implants were removed and at the same time the cows of group 3 were treated with 5 mg flumethasone. Jugular blood samples were taken daily to estimate progesterone concentrations in the plasma. Luteolysis was achieved by the injection of prostaglandin, as judged by the decrease in plasma progesterone concentration in the cows of groups 2 and 3 on day 264. Pregnancy was maintained in these cows until after the removal of the norgestomet implants. The interval from the removal of the implants and, or, the injection of flumethasone on day 270 until the onset of second stage labour ranged from 36 to 47 hours and the mean intervals for the three groups were not significantly different. In all the cows except one from group 3 the dilatation of the cervix and vagina and the softening of the pelvic ligaments appeared normal at calving. It is concluded that calving near term can be synchronised by a progestogen in the absence of a corpus luteum.

The role of prolactin and LH in the control of the function of the corpus luteum in the dog was studied. Experiments were performed to interfere with the secretion of a) prolactin by administering a dopamine agonist and b) LH by desensitisation with a long-acting LHRH and by stimulation. Treatments with prolactin-lowering dosages of bromocriptine, (20 micrograms/kg body weight twice a day, orally; n = 8) which started between day 1-5 (n = 4) and day 20-24 (n = 4) of the luteal period resulted in a similar pattern of progesterone, concentration in peripheral blood in both groups. The progesterone release in the second half of the luteal period (13.1 +/- 1.8% (sem) of the progesterone release of the total luteal period) was significantly lower than in control dogs (24.7 +/- 2.2%). Treatment at about day 30 of the luteal period with LHRH CR (1.34 mg, intramuscularly; n = 3), which significantly suppressed the LH level, did not reduce the progesterone release in the second half of the luteal period, 21.3 +/- 4.7% compared to 24.7 +/- 2.2% in the control dogs. The endogenous LH peak resulting from treatment with LHRH had no effect on the progesterone concentration in the blood. It is concluded that prolactin is the main luteotrophic factor in the cyclic dog during the second half of the luteal period.

The temporal relationship among changes of the concentrations of the 13,14-dihydro-15-keto metabolite of prostaglandin F2 alpha (PGFM), estrone (E1) and estrone sulphate (E1S) in maternal arterial plasma (MP) and amniotic fluid (AF), the prepartum progesterone (P4) decline in MP, and the evolution of uterine electromyographic (EMG) activity was investigated in 6 cows. Calving was induced by a single i.m. injection of 5 mg flumethason on Day 270 of gestation. The period under investigation was subdivided into four consecutive periods: Period 1 covered the last 2 days before flumethason treatment; Period 2 (mean +/- SEM duration: 16.1 +/- 2.5 h), Period 3 (8.8 +/- 1.1 h), and Period 4 (13.0 +/- 1.5 h) together included the interval between injection and the onset of the expulsive stage of induced parturition. Each was defined by its pattern of uterine EMG activity. During Periods 1 and 2, this activity occurred in long episodes (2-20 min; contractures) at a similar mean (+/- SEM) frequency (0.51 +/- 0.14/h and 0.42 +/- 0.07/h, respectively). No significant differences in hormonal concentrations in MP and AF between these two periods were detected. During Period 3, contractures nearly disappeared (freq: 0.09 +/- 0.05/h), and in MP mean P4 levels were significantly lower and PGFM levels were significantly higher than before. Mean PGFM concentrations in AF were not significantly changed during Period 3. Finally, during Period 4, EMG activity reappeared and a parturient EMG pattern gradually evolved in the presence of a further significant decline of P4 levels and significant increase of PGFM concentrations in MP.(ABSTRACT TRUNCATED AT 250 WORDS)

Thirty-three preovulatory bovine oocytes and their follicles were collected during the period of final maturation in normally cyclic cows. Cell density of the membrana granulosa, mitotic index of the membrana granulosa, and the occurrence of eosinophylic granulocytes around the basal membrane as well as the maturational stage of the oocyte were determined. Cell density decreased during the period of final maturation. Mitotic indices also decreased after an initial high level in the first hours of the final maturation. Eosinophylic granulocytes were only seen during the last hours of final maturation. The maturational stages of the oocytes were related to distinct maturational stages of the follicular wall as determined by morphological characteristics. We propose a scoring system for the maturity of the follicular wall based on cell density, presence of mitotic figures and the presence of eosinophylic granulocytes outside the vascular compartment.

The maturational stage of oocytes and their follicles was assessed at 24/26 h after the preovulatory luteinizing hormone (LH) peak by means of morphological criteria. Follicles were obtained from cows treated for superovulation (PMSG/PG) with additional anti-PMSG to neutralize the residual PMSG. Follicular fluid was also recovered and analyzed for progesterone and estradiol levels. Seventy-two percent of the oocytes were at the Metaphase II (M(II)) stage of meiosis, whereas only 28% of the follicular walls were at the proper maturational stage; assessed on morphological characteristics, 78% of the follicles were progesterone-dominated. Earlier maturational stages of oocytes and follicles were also present, including those that are restricted to periods shortly after the LH peak in the normally cyclic cow. It is concluded that upon treatment for superovulation not all oocytes and follicles mature synchronously, and that not all oocytes mature in harmony with their follicles.

Intradermal injection of 46 micrograms E coli endotoxin had no effect on the plasma cortisol and noradrenaline concentrations of four dairy cows. Mean values were similar to normal values reported in the literature. Intravenous injection of 75 micrograms of endotoxin on the following day caused a massive increase in plasma cortisol concentrations which lasted for seven hours. Plasma noradrenaline concentrations increased rapidly after the intravenous administration of endotoxin and remained high for at least one hour. A possible relationship between endotoxaemia and the pathogenesis of acute laminitis is discussed.

The use of lasers in etching and deposition processes has been studied extensively, especially during the last decade. Progress in the understanding of the mechanisms of pulsed laser-enhanced chemical etching is largely of recent data. An overview of the mechanisms of laser-enhanced etching is given and discussed. Experimental results of the excimer laser-enhanced chemical etching of copper and silicon in a low-pressure chlorine environment are emphasized. In particular the measured detection angle and time-of-flight distributions are discussed. Calculations of the effects of post-desorption collisions between the etch products on the measurement of the kinetic energy of the etch products are presented and used to explain the experimental results. It is shown that both the laser-driven diffusion of chlorine into copper and the dependence of etch behaviour on surface coverage are effects which have to be taken into account in the description of the etch mechanism.

Initial stages of Si Molecular Beam Epitaxy (MBE) on Si(001) surfaces have been studied using Scanning Tunneling Microscopy (STM) and Monte Carlo computer simulations.

The competence of oocytes to develop into healthy offspring is determined by many factors including oocyte quality, embryo culture conditions, and energy requirements. Although glucose metabolism has been studied extensively, little is known about lipid metabolism during oocyte maturation and in the blastocyst. In general, cells can obtain fatty acids (FA) by transport (1) from outside across the cell membrane or by synthesis (2) inside the cell, and loose FA by catabolic processes (3). Therefore, we analyzed mRNA abundance for (1) FA translocase (FAT/CD36) and FA transport protein (FATP1), (2) acetyl-CoA carboxylase (ACC) α and FA synthase (FAS), and (3) AMP-activated protein kinase gamma 1 (AMPK) and carnitine palmitoyltransferase I (CPT-I) in bovine oocytes during resumption of meiosis in vivo vs.in vivo blastocysts. Cyclic Holstein-Friesian cows (n = 16) were treated with oFSH and a controlled LH surge (Knijn et al. 2002 Reproduction 124, 365–375) to collect oocytes at onset of maturation, 2 h before LH, and after the start of germinal vesicle breakdown (6 h after LH). A second group of cows (n = 10) was treated with eCG/anti-eCG (Voset al. 1994 Theriogenology 41, 829–840) to flush blastocysts at Day 7 after ovulation. Following ovariectomy, oocytes from all follicles between 10 and 18 mm were denuded and stored separately at -80�C. Oocytes were selected on the basis of the relative steroid concentration in the follicular fluid, producing 3 replicate pools of 13 competent oocytes each, at both 2 h before and 6 h after LH. Four replicates of 5 expanded blastocysts grade 1 (IETS) each were stored at -80�C. Total RNA was isolated using a microspin column, and DNA was digested (Absolutely RNA Microprep Kit; Stratagene, San Diego, CA, USA) and reverse transcribed using the iScript cDNA Synthesis Kit (Bio-Rad Laboratories, Hercules, CA, USA). Amplification of cDNA was achieved by real-time PCR using specific primers and 2X iQ SYBR Green Supermix (Bio-Rad Laboratories) in duplicate. Relative levels of expression were analyzed using a modified delta-Ct method. Statistical analysis was done using ANOVA and the Tukey post-hoc test. Relative abundance of mRNA for FA transport and catabolism was >10 times higher during oocyte maturation than in blastocysts; CPT-I was not detected in blastocysts. In contrast, transcripts of FA synthesis were sharply increased (>5 times) during the blastocyst stage. Alterations in the expression of these mRNA indicate that they play a key role in mediating cell type-specific differences in energy requirement and that exogenous FA and FA catabolism could be a main source of energy during oocyte maturation. A high level of FA biosynthesis mRNA in blastocysts may reflect high demands of de novo long-chain FA synthesis and elongation that probably are essential for protection against stress.

The cumulus–oocyte complex (COC) from a preovulatory follicle is better equipped than a COC from a small healthy follicle to develop into a blastocyst. This might be due to the presence of mRNAs and proteins in the oocyte and/or cumulus cells from which the expression is increased or induced during the prematuration period. There are several reports that beginning atresia enhances in vitro oocyte competence and the processes of atresia show similarities with prematuration on an ultrastructural level. Therefore, we investigated the effect of in vivo prematuration and atresia on the protein synthesis in bovine oocytes collected from preovulatory and small follicles during the first period of IVM. To study the follicular population of an undisturbed cycle we synchronized 14 cows with a norgestomet ear implant. We performed progesterone and LH analysis (Hendriksen et al. 2003 Biol. Reprod. 69, 2036–2044) to determine the start of luteolysis and the LH surge. At 48–62 h after the start of luteolysis, 10 cows were ovariectomized (OVX) and were considered to be shortly before the LH surge. At 1.5–3 days after the LH surge, at the beginning of a new cycle, four cows were OVX. From the ovaries collected before the LH surge the preovulatory follicle (POF) and all follicles ≥3 mm were dissected. From the ovaries collected at the start of a new cycle all follicles ≥3 mm were dissected. All follicles were classified for degree of atresia as non-atretic (NA), light atretic (LA), and atretic (A) by the proportion of apoptotic granulosa cells and levels of estradiol and progesterone, and of small IGF-binding proteins (IGFBPs) in the follicular fluid (Hendriksen et al. 2003). The COCs were individually incubated for 4 h in maturation medium containing 35S-labeled methionine/cysteine (Amersham-Pharmacia, Sweden). After separation of oocyte and cumulus cells, the proteins produced in the oocyte were analyzed by 1-D electrophoresis (SDS-PAGE, ExcelGel-12.5%, Amersham-Pharmacia). Gels were dried and digitized images were obtained by use of a Phosphor Imaging System (Molecular Imager, Bio-Rad, Hercules, CA, USA). Twenty-eight different proteins were distinguished. To compare different oocytes, the 35S incorporation per protein band was calculated as proportion of the 35S incorporation of all bands of the oocyte. The total amount of newly synthetized proteins per oocyte was normalized to the oocyte on the gel with the highest incorporation of 35S. In all POF oocytes (n = 7), the total amount of newly synthetized protein was lower than that in the oocytes from the NA and LA follicles (Table 1). This suggests that already during in vivo prematuration new proteins were synthesized in POFs and therefore less protein synthesis occurs during maturation. We can speculate that oocytes from small follicles have to synthesize many proteins during the beginning of IVM to make up for what is normally produced during the prematuration period. In atretic oocytes fewer proteins were synthesized, which suggests that these oocytes have either undergone prematuration-like processes or are less viable. Nevertheless, some proteins remain to be synthesized in POFs, such as, for example, protein number ‘p 23’. Table 1. New proteins at the onset of IVM in oocytes from small follicles and POFs

Multiple preovulatory follicles developing upon superovulation (SO) are heterogeneous in quality, which may be the consequence of follicular development deviating from that in untreated cyclic cows. Therefore, we investigated follicle performance in terms of estradiol (E), progesterone (P), and testosterone (T) concentrations in the fluid of stimulated preovulatory follicles (FF), in particular at onset of final maturation as initiated by the LH surge. Pre-synchronized HF cows (n = 25) were treated with oFSH (Ovagen; ICP, Auckland, New Zealand) for SO, and FF were collected 2 h pre-LH surge (n = 9 cows), and 6 h (n = 8) and 22 h C(n = 8) post-LH. At Day 9 (estrus = Day 0), a norgestomet ear implant (Crestar; Intervet International BV, Boxmeer, The Netherlands) was inserted, and SO treatment was started at Day 10 using oFSH i.m. twice daily in decreasing doses during 4 days (total dose 17 mL). Prostaglandin (22.5 mg PG; Prosolvin, Intervet) was administered i.m. concomitant with the 5th dose of FSH. Ear implants were removed 50 h after PG and then GnRH (0.021 mg Receptal; Intervet) was administered i.m. inducing the LH surge 2 h later. Ovaries were collected by laparotomy at the time of GnRH, and 8 and 24 h later and all follicles sized >10 and 8 mm from 23 cows at 30 h after PG, that is, preceding the LH surge, following treatment with 3000 IU eCG i.m. (Folligon; Intervet) on Day 10 and 15 mg PG on Day 12; (2) 12 FF of the dominant follicle from 12 untreated cyclic cows after ovariectomy 48 to 62 h after onset of luteolysis, that is, shortly before the natural LH surge. The concentrations (ng/mL FF) of E, P, and T were estimated by our validated RIAs. Data (mean ± SEM) were analyzed by ANOVA. The levels of E, P and T of the oFSH group were pre-LH: 399 ± 35, 49 ± 6 and 13 ± 2; 6 h post-LH: 194 ± 11, 202 ± 12, and 14 ± 1; and 22 h post-LH: 35 ± 2, 200 ± 23, and 7 ± 1, respectively. Although the change in E and P levels between the different time points after LH is in agreement with that reported for untreated cyclic cows (Dieleman et al. 1983 J.Endocrinol. 97, 31–42), the concentrations were lower. However, the most striking finding was the significantly lower E in pre-LH FF after oFSH compared to that after eCG (1302 ± 82) or of cyclic cows (1942 ± 200). The P levels in FF of the respective pre-LH groups were not significantly different. The much lower E level after oFSH is possibly due to the low or even absent LH bioactivity for oFSH in comparison to eCG. It could also indicate a lower developmental potential of oocytes following oFSH. However, it is known that SO with oFSH results in regular yields of transferable embryos similar to that after eCG. In view of the high variability of the E level in FF, it is concluded that selection of follicles for high E levels is a prerequisite when investigating oocyte development and maturation.

Especially in the eighties and early nineties laser ablation has drawn increasing attention for application in thin film deposition (and etching). For a variety of inorganic materials, at the practically most interesting laser fluence values just above the ablation threshold, the pulsed ablation clouds arriving at the substrate consist mainly of ground state atoms (≥99%, E kin∼a few eV), Rydberg atoms (∼0.1 to 1%, E kin∼near 10 eV), positive ions (≤10-2%, E kin∼a few tens eV), electrons and “droplets”. The atoms are strongly peaked along the target surface normal, while the angular distribution of the ions is largely isotropic. A hydrodynamic model describes the ablation cloud quite well. As compared to other advanced thin film deposition techniques, laser ablation deposition produces high-quality, stoichiometric films of even very complex materials at lower substrate temperatures.

Chemical etching of Cu is studied using Cl2 and a ns pulsed UV laser at 308 nm. At Cl2 pressures in the range of 10−6–10−4mbar and a laser fluence up to 0.82 J/cm2 the velocity distributions of the ejected species are determined. CuCl and Cu3Cl3 are the main products. The time-of-flight spectra of these particles can be fitted with Maxwell-Boltzmann distributions at high temperatures viz. 1750

Interrelationships of circulating hormone levels and their implications for follicular development were studied throughout the oestrous cycle with emphasis on the perioestrous period in heifers and cows. The oestradiol level showed a major peak (45 pmol/1) before and coinciding with oestrus, and a second peak (27 pmol/1) around day 5–6 (day 0: day of first standing oestrus); it was low during the luteal phase of the cycle when progesterone was higher than 14 nmol/1 from day −12 to day −2. Large antral follicles, which had developed during the luteal phase, did not secrete significant amounts of oestradiol, degenerated after luteolysis, and were replaced by a newly developing follicle which became preovulatory. Parallel with this development the oestradiol level increased from the onset of luteolysis to reach a plateau about 26 h before the onset of oestrus. The interval between the onset of luteolysis and the onset of oestrus was 58 h; luteolysis proceeded at a slower rate in heifers than in cows. At 4.6 h after the onset of oestrus the maximum of the LH surge was recorded; the LH surge appeared to be postponed in the period October–December in comparison to the period August–September. The maximum of the LH surge was higher in heifers (45 μg/l) than in cows (30 μg/l), but its duration was similar (8.0 h). The oestradiol level decreased significantly from 6 h after the maximum of the LH surge, and standing oestrus (duration 18 h) was terminated almost at the same time as the return to basal values of oestradiol. Cortisol and prolactin levels did not show a peak during the peri-oestrus period. Cortisol fluctuated irrespective of the stage of the oestrus cycle and prolactin was significantly higher during the luteal phase. The results of this study indicate that development of the preovulatory follicle starts in the cow at the onset of luteolysis, about 2.5 days before the preovulatory LH surge, and that oestradiol secretion by this follicle is possibly inhibited by the LH surge.

Nine heifers received an intramuscular injection of 15 mg of bromocryptine twice daily from Day 1 (the day of first standing oestrus defined as Day 0) until 50 h after the onset of luteal regression. At this time the ovaries were collected and the number and quality of follicles > 2 mm were determined. Binding of 125 I-labelled hCG and 125 I-labelled ovine prolactin to follicles > 5 mm and concentrations of progesterone, oestradiol and androstenedione in the follicular fluid were estimated. Plasma concentrations of prolactin, LH and oestradiol were studied from the onset of luteal regression until ovariectomy. Seven heifers served as a control group. Prolactin was effectively suppressed during bromocryptine treatment (0.21 ± 0.01 μg / l , mean ± SEM; n = 9) as compared to control heifers (16.8 ± 3.6 μg / l ; n = 7). Concentrations of LH were not affected by the low level of prolactin (0.99 ± 0.08 μg / l vs . 0.95 ± 0.11 μg /1). Both groups showed a similar time-course of the oestradiol concentration in the peripheral blood during the 50-h period. No specific binding of prolactin to granulosa cells and thecal tissue of follicles > 5 mm could be demonstrated, regardless of their quality or diameter. Preovulatory follicles of bromocryptine-treated and control heifers did not differ with regard to the number of specific binding sites for hCG and the concentrations of oestradiol, progesterone and androstenedione in the follicular fluid. It is concluded that prolactin is not involved in the growth and development of antral follicles during the normal oestrous cycle of the cow.

A polycrystalline Cu target has been bombarded with 3 keV Ar ions. The time-of-flight distributions of the resputtered Ar atoms have been measured for several detection angles. The distribution show a fast and a slow (thermal) contribution. The fast contribution is ascribed to expansions of gas atoms from bubbles. A model is proposed in which the velocity distribution after the expansion is described as a Maxwell-Boltzmann distribution on a constant flow velocity, analogous to expansion from a nozzle. Both the intensity and the shape of the TOF distributions are well described by this two-parameter model.

Nonatretic bovine follicles were cultured on grids in a conventional static system, in roller tubes or in a continuous flux system. Culture medium from the static and roller tube system was replaced after 24 h of culture, while in the continuous flux system, only a small sample was taken aseptically at that time. Steroid concentrations in these samples were estimated by radioimmunoassay (RIA) and related to intrinsic factors like follicle size, day of cycle and micromorphological appearance at the end of culture and to extrinsic factors like the culture system, O 2 -concentration applied in the gasphase and time of culture. Bovine nonatretic follicles from 2 to 8 mm showed the same amount of estradiol-17β (E2) production as pmol mg protein −1 24 h. Follicles over 8 mm had a significantly higher E2 production. Follicles from the follicular phase of the cycle produced more E2 than follicles from the luteal phase, independent of follicular size and culture system. Degeneration of follicles during culture resulted, independent of the culture system, in a decline of E2-production, and in an increase of P4-production; whereas the T-production initially (primary atresia) rose but subsequently (secondary and tertiary atresia) declined. The difference between the culture systems were reflected by quantitative differences in the production of the steroids measured. The most striking difference between the continuous flux system on one hand and the static and rolling tube system on the other is the predominant E2 production in the former by every follicle. It is thought that this difference might be caused by a better 02 supply in the continuous flux system. This hypothesis is tested in the static culture system. The more 02 the more E2 production. The increase in culture time resulted in an increase of E2 and P4, whereas the testosterone production was not significantly decreased.

Recently energy spectra of reaction products emitted during Ar+ ion bombardment induced etching of Si by SF6 condensed on top of it have been reported [8]. The Si(SF6; Ar+) system differs from all others studied to date in that multilayer adsorption of reactive gas occurred during the experiments. This is shown here to induce an additional ejection mechanism. The matrix from which reaction products are finally emitted changes from a “SF6-mixed-into-Si” into a “Si-mixed-into-SF6” type and finally into pure SF6 when the SF6 flux is increased or the substrate temperature is lowered. The profound changes observed in the kinetic energy distributions of specific emitted products upon variation of experimental conditions are reinterpreted and attributed largely to an alteration of the thickness of the condensed SF6 “buffer” layer.

The use of lasers in etching and deposition processes has been studied extensively, especially during the last decade. Progress in the understanding of the mechanisms of pulsed laser-enhanced chemical etching is largely of recent data. An overview of the mechanisms of laser-enhanced etching is given and discussed. Experimental results of the excimer laser-enhanced chemical etching of copper and silicon in a low-pressure chlorine environment are emphasized. In particular the measured detection angle and time-of-flight distributions are discussed. Calculations of the effects of post-desorption collisions between the etch products on the measurement of the kinetic energy of the etch products are presented and used to explain the experimental results. It is shown that both the laser-driven diffusion of chlorine into copper and the dependence of etch behaviour on surface coverage are effects which have to be taken into account in the description of the etch mechanism.

A Si substrate is bombarded by 3-keV Ar/sup +/ ions. From time-of-flight spectra of resputtered Ar neutrals at various target temperatures, we conclude that Ar-bubble formation takes place in the amorphized-Si top layer. The bubbles form and open during etching. The average kinetic energy of the Ar atoms is in agreement with the calculated average potential energy of the Ar atoms inside the bubbles.

Using infrared absorption spectroscopy the kinetics of the initial oxidation of silicon by atomic and molecular oxygen is studied and the stoichiometry of the oxide formed is determined as a function of oxide layer thickness.

Uterine electromyography was performed by means of chronically implanted surface electrodes in 3 Pony mares during spontaneous oestrous cycles and following luteolysis induced by a prostaglandin analogue (fluprostenol). Three distinct patterns were recognized during the oestrous cycle. (1) During oestrus well defined phases of activity with closely grouped high-amplitude spikes were separated by long periods (10-45 min) of complete inactivity. (2) During dioestrus more diffuse phases of activity with low-amplitude spikes were separated by variable periods of relative inactivity. (3) During luteolysis, short and frequently occurring phases of activity were propagated between the two electrodes on one uterine horn; a similar pattern also occurred between 1 and 3 h after injection of fluprostenol. Peripheral plasma progesterone, but not total inconjugated oestrogen, concentrations were closely related to characteristics of the myographic activity during the cycle. Insemination during oestrus and injection of fluprostenol during dioestrus caused a marked and prolonged increase in myometrial electrical activity. Almost any non-specific environmental stimulus, including entry by palpation of the genital tract per rectum and vaginoscopic examination, but these were of brief duration and the normal resting pattern of activity was quickly re-established after completion of the manipulations.

Previous rates of expansion of irrigated areas are not being maintained except possibly in Africa. Reasons for this reduction in the rate of new irrigation development include greater availability of agricultural produce, static or even reduced prices, very high costs of development and maintenance plus severe financial constraints. Concurrently, an increasing number of countries are approaching full development of their surface water resources. This combination of factors dictates new management objectives including: improved system performance, reducing operating costs, increasing production through higher levels of inputs, more emphasis on research and training plus transfer of some operational responsibilities to farmers. Health aspects are likely to assume greater importance as are upstream considerations including watershed hydrology and protection. Key elements to irrigation in Africa have been well identified by the 1986 FAO Consultation on Irrigation in Africa in Lome.

Bovine antral follicles ranging between 2 and 20 mm in diameter were dissected free of stromal tissue and classified under a stereomicroscope using criteria similar to those of Moor et al. (1978). For light-microscopic evaluation of the macroscopic classification, 191 follicles were fixed in Bouin's fluid, embedded in paraffin, sectioned through the cumulus and oocyte and stained with haematoxylin-eosin. To study the relation between the macroscopically determined morphological characteristics and the oestradiol-17 beta (E2) level in the follicular fluid (FF), 39 follicles of one animal were selected. The E2 level, expressed as pmol/ml of FF, was estimated by RIA. The overall correlations between macroscopic classification and histological qualification of non-atretic and atretic follicles were 93.3 and 95.5 p. 100, respectively. Furthermore, the results indicated that the E2 level of small non-atretic follicles was lower than that of larger follicles and that the level in the FF decreased with increasing degeneration. It is concluded that macroscopic criteria offer a highly reliable means of identifying bovine follicles in terms of both micromorphology and functionality.