Expanding the dairy herd in pasture-based systems: The role of sexed semen use in virgin heifers and lactating cows

A model was developed to examine the effects of sexed semen use in virgin heifers and lactating cows on replacement heifer numbers and rate of herd expansion in a seasonal dairy production system. Five separate herds were established according to the type of semen used: conventional frozen-thawed (Conv), sexed fresh semen used in lactating cows for the first 3 wk of the breeding season (SFre1), sexed frozen-thawed semen used in lactating cows for the first 3 wk of the breeding season (SFro1), sexed fresh semen used in lactating cows for the first 6 wk of the breeding season (SFre2), or sexed frozen-thawed semen used in lactating cows for the first 6 wk of the breeding season (SFro2). In the SFro1, SFre1, SFro2, and SFre2 herds, sexed semen was used for the first and second artificial insemination in virgin heifers. Pregnancy rates achieved with sexed fresh and sexed frozen-thawed semen were assumed to be 94 and 75% of those achieved with conventional frozen-thawed semen, respectively. Initial herd size was 100 cows, which was maintained for the first 2 yr of the 15-yr simulation, after which all available replacement heifers were retained to facilitate herd expansion. Two different scenarios of land availability were examined for each of the 5 herds: land available allowed expansion to a maximum herd size of 150 cows (S1), or land available allowed expansion to a maximum herd size of 300 cows (S2). Once maximum herd size was reached, sexed semen use was discontinued and all excess heifer calves were sold at 1 mo old. All capital expenditure associated with expansion was financed with a 15-yr loan. Each of the 10 different options was evaluated in terms of annual farm profit, annual cash flow, and total discounted net profit. The use of fresh sexed semen generated more replacement heifers, leading to faster herd expansion compared with frozen-thawed sexed semen and conventional frozen-thawed semen. Maximum herd size under S1 was reached in yr 5, 5, 4, 5, and 7 for the SFre1, SFro1, SFre2, SFro2, and Conv herds, respectively. Under S2, maximum herd size was reached in yr 8, 10, 7, 9, and 14 for the SFre1, SFro1, SFre2, SFro2, and Conv herds, respectively. Total discounted net profit under S1 for the SFre2 herd was €4,130, €38,869, €47,231, and €52,089 greater compared with the SFre1, SFro1, Conv, and SFro2 herds, respectively. Under S2, discounted net profit for the SFre2 herd was €44,204, €255,524, €280,373, and €325,815 greater compared with the SFre1, SFro1, SFro2, and Conv herds, respectively. The negative effects of the sexed frozen-thawed semen on herd fertility reduced farm profitability and will prevent its widespread use in lactating cows.     

Diagenesis of magnetic minerals in the intertidal sediments of the Yangtze Estuary, China, and its environmental significance

In this study, diagenesis of iron oxides in intertidal sediments of the Yangtze Estuary, China, has been investigated by combined environmental magnetic and geochemical methods. The results indicated that the magnetic properties of the sediments were dominated by ferrimagnetic magnetite. The content of Fe, DCB- and AOD-extractable iron oxides correlated positively with the concentration of fine grained magnetite near the superparamagnetic/stable single domain (SP/SSD, approximately 0.03 microm) boundary, and with anti-ferromagnetic minerals (hematite/goethite). The magnetic parameters for core SDK indicated a substantial decrease in magnetite concentration from a depth of approximately 20 cm toward the surface, together with a shift in the grain-size distribution of magnetic minerals toward the coarse end, suggesting selective dissolution of fine grained magnetite under reducing conditions. The reduction of iron oxides inferred from magnetic measurements was supported by the similar decrease in the concentration of Fe and Mn and a lower ratio of Mn/Fe. Magnetic measurements on another core from elsewhere also indicated substantial reductive dissolution of iron oxides. In conjunction with the results of heavy metal analysis, it was suggested that the dissolution of iron oxides had a direct effect on the cycling of heavy metals. Therefore, magnetic measurements may provide useful information as to early diagenesis within intertidal sediments, which greatly influences the behavior of heavy metals in coastal environments.     

Aminotetryls: Synthesis,spectral characterization,thermal decomposition and explosive properties

This paper describes the synthesis and spectral investigations of two amino derivatives of N-methyl-N-(2,4,6-trinitrophenyl)nitramine (tetryl). Also discussed are the results from thermal decomposition studies on the three explosives, viz. tetryl, 3-aminotetryl (3 AT) and 3,5-diaminotetryl (3,5 DAT) and preliminary work on the explosive properties of the last two compounds. The aminotetryls have been prepared by the amination of the corresponding chlorotetryls. The yield was 87% for 3 AT, but was only 33% for 3,5 DAT, probably due to steric crowding around the benzene nucleus. The mass spectra show interesting differences in the electron impact fragmentation patterns of the three tetryls with the M⁺ ion relative intensities following the order 3,5 DAT > 3 AT > tetryl, which could be due to (a) resonance stabilization and (b) hydrogen bonding effects. Evidence for the latter is also found in the infrared spectra of these compounds. Arrhenius kinetic parameters derived from thermal decomposition studies of the three compounds are presented and show that 3,5 DAT is thermally less stable than 3 AT. Explosive sensitiveness tests indicate that the diamino compound is the most sensitive, the trend being 3,5 DAT > 3 AT > tetryl. This is contrary to the generally found desensitizing influence of NH₂ groups on the thermal stability and explosive sensitiveness of trinitroaromatic energetic molecules. Mechanisms to account for the observed thermal decomposition behaviour and explosive sensitiveness patterns are discussed.     

Multiphoton Physics

Abstract

We discuss recent developments in the generation of ultra-intense laser pulses and show how these can be used to study matter in the presence of electric fields that compete with that due to the nucleus. This has led to a very rapid growth in a wide range of multiphoton studies, many of which are represented in this volume.     

The Development of a Spacer Layer Imaging Method (SLIM) for Mapping Elastohydrodynamic Contacts

Optical interferometry has proved to be a valuable experimental tool in the study of elastohydrodynamic lubrication (EHD). It is a technique that gives detailed information on the lubricant film distribution within the contact; however, the sensitivity is limited and it is only recently, with the development of the spacer layer optical technique, that the study of the thin film lubrication regime has been possible. The limitation of the spacer layer technique is that generally only one measurement is taken from the center of the contact. The next logical step in the development of this technique is, therefore, a system that combines the mapping capabilities of the original optical method with the thin film capabilities of the spacer layer approach.

This paper describes the development of a contact mapping technique that uses the spacer layer approach to visualize, and measure, thin lubricant films in concentrated contacts. The development of the technique is described and its application to both static and moving contacts reported. Thin EHD films (down to 10 nm) have been measured and mapped.     

Visual servo control. I. Basic approaches

This paper is the first of a two-part series on the topic of visual servo control using computer vision data in the servo loop to control the motion of a robot. In this paper, we describe the basic techniques that are by now well established in the field. We first give a general overview of the formulation of the visual servo control problem. We then describe the two archetypal visual servo control schemes: image-based and position-based visual servo control. Finally, we discuss performance and stability issues that pertain to these two schemes, motivating the second article in the series, in which we consider advanced techniques     

Graphing the death of Escherichia coli

The graphical presentation of measurements of the progress over time of bacterial death or inactivation is discussed. Specifically, the Weibull distribution may be a useful generalisation of the exponential distribution. Data from experiments on the non-thermal death of Escherichia coli reported by Shadbolt et al. [Int. J. Food Microbiol. 49 (1999) 129] are reexamined to support this claim.     

Enhancement of tumor killing using a combination of tumor immunization and HSV-tk suicide gene therapy

Tumor cells genetically modified with the herpes simplex virus thymidine kinase (HSV-tk) gene in combination with ganciclovir (GCV) demonstrate a "bystander effect". Previous attempts to enhance the bystander tumor killing by combining cytokine genes with HSV-tk/GCV have met with varying results. The present study was designed to determine the effects of tumor immunization in combination with HSV-tk gene-modified tumor cells and GCV on tumor killing and to determine if the bystander tumor killing could be enhanced. Tumor-bearing mice immunized with syngeneic tumor (KBALB) prior to treatment with an i.p. injection of xenogeneic HSV-tk gene-modified tumor cells (PA-1STK) had prolonged animal survival (group 4, 56.4 days). In contrast, unimmunized tumor-bearing mice (group 2) or tumor-bearing mice immunized to the xenogeneic PA-1STK tumor cells (group 5) showed a mean survival of about 27 days after receiving an i.p. injection of PA-1STK cells and GCV. Control groups, which were either not immunized and did not receive HSV-tk cells (group 1) or immunized but treated only with GCV (group 3) showed short survival (16-18 days). Analysis of tumors for cytokine mRNA expression revealed increased TNF-alpha and IL-1alpha mRNA expression in group 4 mice. Furthermore, IL-2 mRNA expression was detectable on days 2 and 4 only in group 4 mice. Immunophenotypic analysis for tumor-infiltrating lymphocytes demonstrated an increase in macrophage (4%, p = 0.0001) and T cells (1.8%, p < 0.001) in group 4 mice with an enhanced T-cell response as compared with mice from groups 1, 2 and 3. Our results demonstrate that tumor immunization combined with HSV-tk/GCV treatment results in increased animal survival with enhanced immune response. Furthermore, the cytokine milieu observed in the present study can modulate the tumor micro-environment in vivo from one that is immunosuppressive to one that is immune-stimulatory.     

Response of the hypothalamic neurons to stimulation of the vestibular nerve and lateral vestibular nucleus in rabbits

Effects of single, double, and rhythmic stimulation upon hypothalamic neurons responding to the 1st excitatory phase of lateral vestibular nucleus stimulation, were studied. The data obtained show that activation of some hypothalamic neurons following stimulation of the lateral vestibular nucleus has a monosynaptic character. The findings suggest that ascending afferents from the lateral vestibular nucleus to the hypothalamus pass via oligo- as well as polysynaptic pathways.     

Congenital abnormalities in Brazilian children associated with misoprostol misuse in first trimester of pregnancy

BACKGROUND: Misoprostol is commonly used to induce abortion in Brazil, and in other countries in South and Central America where abortions are illegal. However, misoprostol is not very effective in inducing abortions, and exposure to the drug in utero can cause abnormalities in the fetus. We aimed to define the common phenotypical effects of exposure to the drug. METHODS: We studied 42 infants from S?o Paulo, Brazil, who were exposed to misoprostol during the first 3 months of gestation, and then born with congenital abnormalities. We interviewed each of the infants' mothers to find out about misoprostol exposure and dosage. Each infant was physically examined by a geneticist or a neuropaediatrician. FINDINGS: 17 of the infants had equinovarus with cranial-nerve defects. Ten children had equinovarus as part of more extensive arthrogryposis. The most distinctive phenotypes were arthrogryposis confined to the legs (five cases) and terminal transverse-limb defects (nine cases) with or without Mobius sequence. The most common dose of misoprostol taken was 800 microg (range 200-16000 microg). INTERPRETATION: Deformities attributed to vascular disruption were found in these children. We suggest that the uterine contractions induced by misoprostol cause vascular disruption in the fetus, including brain-stem ischaemia. Information on the effects of taking misoprostol during pregnancy should be made more widely available, to dissuade women from misusing the drug.