Photon Acceleration in a Flying Focus.

A high-intensity laser pulse propagating through a medium triggers an ionization front that can accelerate and frequency upshift the photons of a second pulse. The maximum upshift is ultimately limited by the accelerated photons outpacing the ionization front or the ionizing pulse refracting from the plasma. Here, we apply the flying focus-a moving focal point resulting from a chirped laser pulse focused by a chromatic lens-to overcome these limitations. Theory and simulations demonstrate that the ionization front produced by a flying focus can frequency upshift an ultrashort optical pulse to the extreme ultraviolet over a centimeter of propagation. An analytic model of the upshift predicts that this scheme could be scaled to a novel tabletop source of spatially coherent x rays.

Picosecond Thermodynamics in Underdense Plasmas Measured with Thomson Scattering.

The rapid evolutions of the electron density and temperature in a laser-produced plasma were measured using collective Thomson scattering. Unprecedented picosecond time resolution, enabled by a pulse-front-tilt compensated spectrometer, revealed a transition in the plasma-wave dynamics from an initially cold, collisional state to a quasistationary, collisionless state. The Thomson-scattering spectra were compared with theoretical calculations of the fluctuation spectrum using either a conventional Bhatnagar-Gross-Krook (BGK) collision operator or the rigorous Landau collision terms: the BGK model overestimates the electron temperature by 50% in the most-collisional conditions.

Toward streaked collective Thomson scattering measurements on an extreme ultraviolet plasma light source.

We show through forward modeling calculations that streaked collective Thomson scattering measurements are feasible on laser-produced tin plasmas generated under conditions relevant for extreme ultraviolet lithography. Using a 532 nm probe laser beam, the feasibility of simultaneous measurements of electron plasma wave (EPW) and ion acoustic wave (IAW) spectra is investigated. Absolute photon counts for laser scattering off both waves are calculated. Probe laser electron heating and bremsstrahlung background radiation effects are accounted for. While a large spatiotemporal region can be successfully probed based on the IAW feature, only one measurement location can be accessed through the EPW as a result of the low signal to noise ratio. A portable/traveling tabletop system is proposed.

Single-shot frequency-resolved optical gating for retrieving the pulse shape of high energy picosecond pulses.

Accurate characterization of laser pulses used in experiments is a crucial step to the analysis of their results. In this paper, a novel single-shot frequency-resolved optical gating (FROG) device is described, one that incorporates a dispersive element which allows it to fully characterize pulses up to 25 ps in duration with a 65 fs per pixel temporal resolution. A newly developed phase retrieval routine based on memetic algorithms is implemented and shown to circumvent the stagnation problem that often occurs with traditional FROG analysis programs when they encounter a local minimum.

Induction of relative growth changes in the musculoskeletal system of the sheep by limb immobilisation.

The function of the limbs of the sheep was modified to study growth changes in the musculoskeletal system. Seven lambs treated with one hindlimb bound to the body, with the hip fully flexed and the stifle and hock fully extended, were reared from the day after birth to about three months old, together with two untreated controls. The effects of this functional alteration were measured by dissecting and weighing components of the whole carcase, by histometry and electron microscopy of the semitendinosus muscles, and by measurements and ashing of the femurs and tibias. With the particular exception of the hip bone and the muscles extending the hip on the bound side, muscles and bones tended to be heavier on the contralateral side in the hindlimb and on the ipsilateral side in the forelimb. The semitendinosus muscle of the bound limb weighed nearly twice as much as that of the controls. The increase in mass was due to a proportionate enlargement of all the muscle components studied. There was, however, a significant increase in the number of myosine adenosine triphosphatase low reacting fibres, as a percentage of the regional fibre population, in the deeper part of the muscle. It was concluded that the enlargement of the semitendinosus muscle was due to stretch and that the histochemical changes were due to chronic nervous stimulation.

Rostral displacement of the palatopharyngeal arch: a case report.

A horse with rostral displacement of the palatopharyngeal arch was found to have a bilaterally symmetrical deformity of the laryngeal area. Both left and right cricopharyngeal muscles were absent. The shape of the thyroid cartilage was grossly abnormal and vestiges of the cricothyroid muscles were attached only to the cricoid cartilage. It was suggested that such an anomaly could have resulted from aberrant development of the fourth branchial arch.

An objective measure of muscularity: Changes with animal growth and differences between Genetic lines of southdown sheep.

A measure of muscularity, based on objective measurements, and expressed in terms of muscle depth relative to skeletal dimensions, is proposed and investigated using a simulation model. Average muscle depth is assessed as the square root of the muscle weight per unit length of a bone adjacent to the muscle. Muscularity is then defined as average muscle depth divided by bone length. Evidence based on a theoretical model, results from the literature and data from backfat selection lines of Southdown sheep is used to illustrate how muscularity defined in this way changes with growth, and the extent to which it parallels changes in muscle to bone ratio. It is concluded that although these two characteristics often change together there are situations where differences in muscularity are not accompanied by differences in muscle to bone ratio and vice versa.

Meat quality and muscle fibre type characteristics of Southdown Rams from high and low backfat selection lines.

Characteristics of the meat of 15-18-month Southdown rams from lines selected for high or low backfat depths (assessed ultrasonically at position C over the last rib) were compared. Half of the carcasses were electrically stimulated (ES) and within each carcass post-mortem treatments chosen to produce effects on meat tenderness were ageing periods of 1 or 15 days (Semimembranosus), early or delayed chilling (Biceps femoris), and trimming of the s.c. fat cover (Longissimus dorsi). These treatments had the expected effects on shear values, but the sizes of the effects were little affected by selection line or ES treatment. Selection line did not have any direct effects on shear values, reflectance values at several wavelengths, waterholding capacity, cooking loss or sarcomere length. The Semitendinosus muscle had a higher proportion of predominantly oxidative fibres for the high-backfat line, based on succinic dehydrogenase activity (P < 0·05), but there was no line difference in alkaline-stable ATPase activity in the same muscle. Muscle fibre diameter was similar for the two lines.

The effect of different methods of electrical stunning of lambs on blood pressure and muscular activity.

The effect on blood pressure and muscular activity of a 'head-only' and a 'head-to-body' method of electrical stunning was measured in groups of lambs. A two- to three-fold increase in arterial pressure followed 'head-only' stunning, along with moderate increases in venous pressure. By contrast, after 'head-to-body' stunning, arterial pressure decreased, but venous pressure increased to above 50 mm Hg. Electromyographic recordings showed there was a greater increase in the intensity of muscular activity following 'head-to-body' stunning compared with 'head-only' stunning and there was a direct correlation between the degree of muscular activity and the increase in venous pressure. It is argued that the resultant pressure changes in the microcirculatory bed are likely to be associated with the occurrence of haemorrhagic defects following stunning by electrical methods.

Real-time ultrasonography for pregnancy diagnosis and estimation of fetal age in farmed red deer.

Twenty-nine farmed red deer hinds two years of age or older were observed during mating in April, and the dates of oestrus and, or, mating were recorded. From May 28 to August 13, at approximately weekly intervals, the deer's uteri and associated structures were examined by rectal ultrasound using a 5 MHz transducer while the deer were held standing in a restraining device. The uterine diameter, amniotic sac diameters, crown-rump length, head length, nose length, chest depth, chest width and placentome base-apex and width were measured for each scan. Quadratic regression equations were computed for each measurement with age, using data from hinds with known mating dates, and the chronological sequence of appearance of a range of uterine and fetal characteristics was recorded. There were significant quadratic regressions. (P less than 0.001) for each of the measurements. The accuracy of pregnancy detection to 117 days after conception was 99.3 per cent and to 132 days after conception 97.4 per cent. The confirmation of non-pregnancy was 96.5 per cent accurate. The regressions of each measurement by age should provide an accurate method for the estimation of fetal age in red deer.

A large dermoid cyst of the neck. Case report.

An elderly patient presented with a large asymptomatic submental swelling which had been present for about fifteen years. The clinical diagnosis was a dermoid cyst and the lesion was removed in toto. Histological examination confirmed the clinical diagnosis. Unless such lesions are very large and cause displacement of the tongue, there is usually no associated dyspnoea, dysphagia or dysphonia.

The perivascular spaces of ovine and canine brains.

Abstract The specialised histology and anatomy of the central nervous system (CNS) is reflected in its pathology. This is particularly so for the perivenular/periarterial spaces in which inflammatory cells accumulate in inflammation. These spaces, although structurally not lymphatics, act as lymphatics draining fluid from brain to subarachnoid space and to lymphatics draining to deep cervical lymph nodes. Inflammatory cells may enter or leave the CNS by this route. In immune-based inflammation, they are colonised by subsets of immune cells allowing the processing of antigen, synthesis of antibody and development of cell mediated immune reactions.

Acinic cell carcinoma--Plymouth's experience with postoperative radical radiotherapy.

Acinic cell carcinoma represents 2.5% of all parotid neoplasms. Experience in its management is limited and its initial clinical diagnosis may be incorrect. This paper examines six patients who received less than ideal primary surgical care. Duration of follow up ranges from 1.25 years to 10.5 years, mean 6.7 years. Prophylactic postoperative radiotherapy appears to be of marked benefit in preventing recurrence and cervical node metastases.

Postnatal development of the lower canine and cheek teeth of the pig.

Postnatal development of the teeth of German Landrace and Göttingen Miniature pigs was studied by measuring the areas of each tooth visible on lateral radiographs of the mandibles. It was concluded that the appearance of the teeth at each stage, and the relation of their growth to that of the rest of the masticatory apparatus, relates mainly to postnatal changes in the relative location of the jaw pivot.

The function of the equine carpal joint: a review.

The most consistent published ideas on the function of the carpal joint of the horse concern the elasticity of the joint, and its limits to extension. Most of these are not well substantiated experimentally. Compression stress appears to be absorbed by the intercarpal ligaments as the carpal bones are separated by a wedge action during loading. Overextension is prevented by occlusion of dorsally located stop facets on the rows of carpal bones, and by the support of a stay apparatus.

A preliminary study of hyperextension of the carpal joint in the racing Thoroughbred.

A photographic study of the angles of 71 carpal joints of horses at the end of a race has shown that overextension of the joint is normal at this stage. Further study is needed to determine the factors which may influence hyperextension, and whether they are relevant to carpal injury.

Antenatal anticipation of postnatal muscle function.

The semitendinosus muscle of the sheep was used as an experimental model to test antenatal anticipation of muscle postnatal function using the alkali-stabile myosin ATPase technique. Areas of variable fibre type population density were seen from 80 days of gestation. The highest population density of ATPase-low fibres was observed in the craniomedial aspect of the muscle (the ATPase-low dense area). The lowest ATPase-low fibre population density area (the ATPase-low sparse area) was seen in the caudolateral aspect of the muscle. Simultaneous electromyographic studies indicated that the ATPase-low dense area is preferentially used for posture and during quiet co-ordinated activity, while the ATPase-low sparse area is recruited only intermittently when the hip and stifle are less co-ordinated in movement. The ATPase-low fibre percentage within the ATPase-low dense area of the muscle increased from 10 to 30% from 80 days of gestation to adulthood. The part of this change occurring antenatally is expected to be the result of genetic anticipation.

The anatomy of the auricular conchae of cattle, sheep and deer.

The anatomy of the auricular conchae of ruminants has been studied by intravascular injection of radiopaque latex, by dissection and by histological sectioning. Drawings were made of the vascular network. The arrangement of nerves and blood vessels in association with the ridges on the rostral (concave) surface was observed. The spaces between the ridges are relatively free of larger blood vessels, nerves, hair and sebaceous glands. This distribution is discussed in relation to the insertion of ear tags.