Analogy Between Surface Shock Waves in a Liquid and Shocks in Compressible Gases: Experimental Study of Hydraulic-Jump Interactions

It has been known for some time that an analogy exists between the flow of a liquid with a free surface and the flow of a compressible gas. A less accurate analogy has been shown to obtain between hydraulic jumps and compression shocks. The interaction of shocks can occur in two forms; the regular or two-shock configuration and the Mach or three-shock configuration. The latter configuration is not yet completely understood, either in the case of hydraulic jumps in a free-surface liquid or in the case of shocks in a compressible gas. This experimental study was primarily concerned with the Mach interactions of hydraulic jumps. The conclusions of this study are: (a) there is a definite disagreement between experiment and existing theory; (b) a depth discontinuity, or wave, rather than a velocity discontinuity separates the region behind the Mach wave from the region behind the reflected wave; (c) there is evidence that, for interactions of weak hydraulic jumps, there is a deviation from constant depth between waves; (d) the Mach wave is convex for the interaction of the stronger hydraulic jumps, but is concave for the interaction of weak hydraulic jumps; (e) measurements should not be made so as to allow for curvature of the Mach without considering the curvature of the incident and reflected waves in the neighborhood of the triple point

Adjustable mount for electro-optic transducers in an evacuated cryogenic system

The invention is an adjustable mount for positioning an electro-optic transducer in an evacuated cryogenic environment. Electro-optic transducers are used in this manner as high sensitivity detectors of gas emission lines of spectroscopic analysis. The mount is made up of an adjusting mechanism and a transducer mount. The adjusting mechanism provided five degrees of freedom, linear adjustments and angular adjustments. The mount allows the use of an internal lens to focus energy on the transducer element thereby improving the efficiency of the detection device. Further, the transducer mount, although attached to the adjusting mechanism, is isolated thermally such that a cryogenic environment can be maintained at the transducer while the adjusting mechanism remains at room temperature. Radiation shields also are incorporated to further reduce heat flow to the transducer location

The analogy between surface waves in a liquid and shocks in compressible gases: experimental study of wave forms

The subject matter covered in this report concerns the characteristics of the surface waves produced in the ripple tank by the wave generators and the effect on the wave form of adding detergents to the working fluid. The results will be presented under the following headings: 1. Experimental procedure. 2. The wave generators. 3. Variables affecting wave strength. 4. Effect of adding detergents to working fluid. 5. Summary and conclusions

Scaling of axial muscle architecture in juvenile Alligator mississippiensis reveals an enhanced performance capacity of accessory breathing mechanisms

Quantitative functional anatomy of amniote thoracic and abdominal regions is cru-cial to understanding constraints on and adaptations for facilitating simultaneous breathing and locomotion. Crocodilians have diverse locomotor modes and variable breathing mechanics facilitated by basal and derived (accessory) muscles. However, the inherent flexibility of these systems is not well studied, and the functional spe-cialisation of the crocodilian trunk is yet to be investigated. Increases in body size and trunk stiffness would be expected to cause a disproportionate increase in mus-cle force demands and therefore constrain the basal costal aspiration mechanism, necessitating changes in respiratory mechanics. Here, we describe the anatomy of the trunk muscles, their properties that determine muscle performance (mass, length and physiological cross- sectional area [PCSA]) and investigate their scaling in juvenile Alligator mississippiensis spanning an order of magnitude in body mass (359 g– 5.5 kg). Comparatively, the expiratory muscles (transversus abdominis, rectus abdominis, ili-ocostalis), which compress the trunk, have greater relative PCSA being specialised for greater force- generating capacity, while the inspiratory muscles (diaphragmaticus, truncocaudalis ischiotruncus, ischiopubis), which create negative internal pressure, have greater relative fascicle lengths, being adapted for greater working range and contrac-tion velocity. Fascicle lengths of the accessory diaphragmaticus scaled with positive allometry in the alligators examined, enhancing contractile capacity, in line with this muscle's ability to modulate both tidal volume and breathing frequency in response to energetic demand during terrestrial locomotion. The iliocostalis, an accessory expira-tory muscle, also demonstrated positive allometry in fascicle lengths and mass. All accessory muscles of the infrapubic abdominal wall demonstrated positive allometry in PCSA, which would enhance their force- generating capacity. Conversely, the basal tetrapod expiratory pump (transversus abdominis) scaled isometrically, which may in-dicate a decreased reliance on this muscle with ontogeny. Collectively, these find-ings would support existing anecdotal evidence that crocodilians shift their breathing mechanics as they increase in size. Furthermore, the functional specialisation of the diaphragmaticus and compliance of the body wall in the lumbar region against which it works may contribute to low- cost breathing in crocodilian

A questionnaire to identify patellofemoral pain in the community: an exploration of measurement properties

Background Community-based studies of patellofemoral pain (PFP) need a questionnaire tool that discriminates between those with and those without the condition. To overcome these issues, we have designed a self-report questionnaire which aims to identify people with PFP in the community. Methods Study designs: comparative study and cross-sectional study. Study population: comparative study: PFP patients, soft-tissue injury patients and adults without knee problems. Cross-sectional study: adults attending a science festival. Intervention: comparative study participants completed the questionnaire at baseline and two weeks later. Cross-sectional study participants completed the questionnaire once. The optimal scoring system and threshold was explored using receiver operating characteristic curves, test-retest reliability using Cohen’s kappa and measurement error using Bland-Altman plots and standard error of measurement. Known-group validity was explored by comparing PFP prevalence between genders and age groups. Results Eighty-four participants were recruited to the comparative study. The receiver operating characteristic curves suggested limiting the questionnaire to the clinical features and knee pain map sections (AUC 0.97 95 % CI 0.94 to 1.00). This combination had high sensitivity and specificity (over 90 %). Measurement error was less than the mean difference between the groups. Test–retest reliability estimates suggest good agreement (N = 51, k = 0.74, 95 % CI 0.52–0.91). The cross-sectional study (N = 110) showed expected differences between genders and age groups but these were not statistically significant. Conclusion A shortened version of the questionnaire, based on clinical features and a knee pain map, has good measurement properties. Further work is needed to validate the questionnaire in community samples

Insect Species on Vegetation of the White Oak Lake Bed, Oak Ridge, Tennessee

White Oak Lake, Oak Ridge, Tennessee, received lowlevel radioactive wastes from Oak Ridge National Laboratory for 12 years prior to draining in 1955. Studies on the insects inhabiting the vegetation on White Oak Lake bed revealed 401 species present during 1956 and 1957. Most numerous were members of the insect Orders Hymenoptera, Diptera, and Coleoptera. In the summer of 1956, the first summer following draining of the lake, there were relatively fewer species of insects represented by large numbers of individuals. In 1957, there were relatively more species of insects but fewer individuals were present. By the end of the summer of 1957, only two years after the lake was drained, the vegetation supported a rich and varied insect fauna. (C.H.

Synthetically tuneable biomimetic artificial photosynthetic reaction centres that closely resemble the natural system in purple bacteria

© 2016 The Royal Society of Chemistry. Porphyrin-based photosynthetic reaction centre (PRC) mimics, ZnPQ-Q2HP-C60 and MP2Q-Q2HP-C60 (M = Zn or 2H), designed to have a similar special-pair electron donor and similar charge-separation distances, redox processes and photochemical reaction rates to those in the natural PRC from purple bacteria, have been synthesised and extensive photochemical studies performed. Mechanisms of electron-transfer reactions are fully investigated using femtosecond and nanosecond transient absorption spectroscopy. In benzonitrile, all models show picosecond-timescale charge-separations and the final singlet charge-separations with the microsecond-timescale. The established lifetimes are long compared to other processes in organic solar cells or other organic light harvesting systems. These rigid, synthetically flexible molecules provide the closest mimics to the natural PRC so far synthesised and present a future direction for the design of light harvesters with controllable absorption, redox, and kinetics properties

A new fundamental type of conformational isomerism

© 2018 The Author(s). Isomerism is a fundamental chemical concept, reflecting the fact that the arrangement of atoms in a molecular entity has a profound influence on its chemical and physical properties. Here we describe a previously unclassified fundamental form of conformational isomerism through four resolved stereoisomers of a transoid (BF)O(BF)-quinoxalinoporphyrin. These comprise two pairs of enantiomers that manifest structural relationships not describable within existing IUPAC nomenclature and terminology. They undergo thermal diastereomeric interconversion over a barrier of 104 ± 2 kJ mol-1, which we term 'akamptisomerization'. Feasible interconversion processes between conceivable synthesis products and reaction intermediates were mapped out by density functional theory calculations, identifying bond-angle inversion (BAI) at a singly bonded atom as the reaction mechanism. We also introduce the necessary BAI stereodescriptors parvo and amplo. Based on an extended polytope formalism of molecular structure and stereoisomerization, BAI-driven akamptisomerization is shown to be the final fundamental type of conformational isomerization