A paraxial ray formalism is developed to study the evolution of an on axis intensity spike on a Gaussian laser beam in a plasma dominated by relativistic and ponderomotive non-linearities. Ion motion is taken to be frozen. A single beam width parameter characterizes the evolution of the spike. The spike introduces two competing influences: diffraction divergence and self-convergence. The former grows with the reduction in spot size of the spike, while the latter depends on the gradient in non-linear permittivity. Parameter δ = (ωpr00/c) a00/(3.5 r00/r01) characterizes the relative importance of the two, where r01 and r00 are the spike and main beam radii, ωp is the plasma frequency, and a00 is the normalized laser amplitude. For δ > 1, the intensity ripple causes faster self-focusing of the beam; higher the ripple amplitude stronger the focusing. In the opposite limit, diffraction divergence increases more rapidly, slowing down the self-focusing of the beam. As the beam intensity rises due to self-focusing, it causes stronger generation of the third harmonic.

Stimulated Brillouin backscattering of an intense hollow Gaussian laser beam (HGLB) from collisionless plasma has been investigated under relativistic–ponderomotive regime. The main feature of considered hollow Gaussian laser beam is having the same power at different beam orders with null intensity at the center. Backscattered radiation is generated due to nonlinear interaction between main beam (pump beam) with pre-excited ion acoustic wave (IAW). Modified coupled equations has been set up for the beam width parameters of the main beam, ion-acoustic wave, back-scattered wave, and back reflectivity of stimulated Brillouin scattering (SBS) with the help of the Wentzel–Kramers–Brillouin approximation, fluid equations and paraxial theory approach. These coupled equations are solved analytically and numerically to study the laser intensity in the plasma, the variation of amplitude of the excited IAW and back reflectivity of SBS. The back reflectivity of SBS is found to be highly sensitive to the order of the HGLB, intensity of main laser beam, and plasma density for typical laser and plasma parameters. The focusing of main laser beam (hollow Gaussian) and IAW significantly affected the back reflectivity of SBS. The results show that the self-focusing and back reflectivity is enhanced for higher order modes of HGLB.

This work presents an investigation of the self-focusing of a high-power laser beam having cosh Gaussian intensity profile in a collissionless plasma under weak relativistic-ponderomotove (RP) and only relativistic regimes and its effect on the excitation of electron plasma wave (EPW), and particle acceleration process. Nonlinear differential equations have been set up for the beam width and intensity of cosh Gaussian laser beam (CGLB) and EPW using the Wentzel-Kramers-Brillouin and paraxial-ray approximations as well as fluid equations. The numerical results are presented for different values of decentered parameter ‘b’ and intensity parameter ‘a’ of CGLB. Strong self-focusing is observed in RP regime as compared with only relativistic nonlinearity. Numerical analysis shows that these parameters play crucial role on the self-focusing of the CGLB and the excitation of EPW. It is also found that the intensity/amplitude of EPW increases with b and a. Further, nonlinear coupling between the CGLB and EPW leads to the acceleration of electrons. The intensity of EPW and energy gain by electrons is significantly affected by including the ponderomotive nonlinearity. The energy of the accelerated electrons is increased by increasing the value of ‘b’. The results are presented for typical laser and plasma parameters.

We describe a hybrid pixel array detector (electron microscope pixel array detector, or EMPAD) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128×128 pixel detector consists of a 500 µm thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit. The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity. A 1.1 kHz framing rate enables rapid data collection and minimizes sample drift distortions while scanning. By capturing the entire unsaturated diffraction pattern in scanning mode, one can simultaneously capture bright field, dark field, and phase contrast information, as well as being able to analyze the full scattering distribution, allowing true center of mass imaging. The scattering is recorded on an absolute scale, so that information such as local sample thickness can be directly determined. This paper describes the detector architecture, data acquisition system, and preliminary results from experiments with 80–200 keV electron beams.

The distribution of body water in the different body compartments of four highpotassium (HK) and four low-potassium (LK) type sheep of the Marwari breed of the Rajasthan desert was determined after imposing the following watering treatments, viz. watering ad lib., ¼, ½ and ¾ restrictions (each of five days ‘duration with a sevenday normal drinking regime between each treatment) and water deprivation (of three days’ duration). There was no difference in the voluntary water intake of the HK and LK animals. The HK animals normally have a higher blood and plasma volume status than the LK. In both types of animals, the total body water, total blood and plasma volumes and the extracellular, intracellular and interstitial fluid volumes started decreasing as water intake was reduced below 25% of the daily requirement. In both the phonotypes 75% reduction was similar in its effect to complete deprivation. The physiological status of the HK Marwari animals appears to be somewhat superior to that of the LK although both types seem to be equally adapted to the conditions of the habitat.

The role of straw yield and quality in farmers' decisions about the adoption of pearl millet cultivars in western Rajasthan was examined using farm household surveys. Information on the relative importance of grain versus straw yield, the perceived risks associated with the use of new cultivars under variable climatic conditions and perceptions of straw quality indicated that improved cultivars of pearl millet were not adopted primarily because of poor grain yield in years with low rainfall, though poor straw yield in such years was also important. These results are particularly pertinent in the light of farmers' perceptions of the likelihood of experiencing drought or low rainfall. If new cultivars of pearl millet are to replace the traditional ones, they must perform better under conditions of limited rainfall.

In the present investigation, the excitation of an upper hybrid wave (UHW) in a hot collisionless magneto-plasma by a relativistic laser beam propagating perpendicular to the static magnetic field and having its electric vector polarized along the direction of the static magnetic field (ordinary mode) is presented. Due to nonuniform intensity distribution of pump laser, the background electron concentration is modified. The amplitude of the UHW, which depends on the background electron concentration, is thus nonlinearly coupled with the laser beam. The effect of nonlinear coupling between the pump laser and UHW is studied. The effect of the relativistic electron mass nonlinearity and the relativistic self-focusing of the pump laser on the excitation of the UHW have been incorporated. The dynamics of the excitation of the UHW in different power domains of the laser beam is accordingly modified. It has been seen that the effect of changing the strength of the static magnetic field on the nonlinear coupling and the dynamics of the excitation of the UHW is significant. The focusing behavior of the UHW may find its relevance in the heating of plasmas near the upper hybrid resonance.

The efficiency of vaginal electrical resistance (VER) measurements for oestrous detection was determined in four experiments. The mean VER during oestrus, metoestrus, dioestrus, pro-oestrus and anoestrus was 32·68±0·46, 41·26±1·17, 50·23±0·55, 43·52±0·54 and 55·86±0·57 ohms, respectively. There were significant (P < 0·01) differences between VERs at the different oestrous cycle stages, except those during pro-oestrus and metoestrus which were similar. Twelve cows were induced in oestrus using prostaglandin (PG) administration to study the changes in VER during the peri-oestrus period. VER values changed both on a within-day (P < 0·05) and day-today (P < 0·001) basis following PG administration. Of the eight cows that responded, all were classified as in oestrus by VER in comparison to five detected in oestrus by a teaser bull. There was a significant association between VER and probability of conception (P < 0·01). Conception rates were 84, 61 and 20% when animals were inseminated at VER ranges of 26 to 30, 31 to 35 and 36 to 40 ohms, respectively. In the final experiment VER was recorded each day at the time of milking in 22 cyclic cows for 60 days. Animals were inseminated when the VER declined below 35 ohms. Of these 22 cows five cows showed overt signs of oestrus and 11/22 (50%) became pregnant. Twenty-one days post AI, five cows returned to oestrus, based on low VER, whereas 17 continued to show a high VER but eight of these (8/17) were subsequently classified as non-cyclic. It is concluded that VER can effectively be used for oestrus detection and identification of the optimum time for insemination but has limited value for pregnancy diagnosis. Cows should be inseminated when a VER reading of less than 36 ohms is recorded.

Uptake of oestrogens into breast tissue and their subsequent metabolism can be studied by infusing radio-labelled steroids into volunteer patients. Such studies show that oestradiol is preferentially accumulated in breast tumours, oestradiol concentrations exceeding those of oestrone. This contrasts with plasma, in which oestrone concentrations in postmenopausal women are greater than those of the oestradiol. This observation suggests that tissue factors can modulate local oestrogen metabolism, and thus local steroid concentrations.

We have studied the local production of oestrogens from androgen, and also the interconversion of the major oestrogens, oestrone and oestradiol. Using isotopic techniques, it is possible to calculate the proportion of endogenous oestrogen produced from androgen, as opposed to uptake from the circulation. These studies suggest that a very variable proportion of tissue oestrogen derives from endogenous synthesis. After administration of aromatase inhibitors, aromatase activity is substantially inhibited, both in vivo and in vitro.

Relative oestrogen concentrations are determined in part by the activity of oestradiol dehydrogenase. In breast tissue, dehydrogenase activity is present and this is modified by various factors, including androgens. In addition, we have demonstrated that normal, benign and malignant breast tissues produce factors which can modulate both growth and dehydrogenase activity of cancer cells in vitro.

We conclude that breast tissue is a site of synthesis of oestrogens, and that a number of factors can affect their local concentration. Tumour cells produce growth factors which can influence steroid metabolism, and may thus be able to enhance favourably their own endocrine environment.