The symbolic model for algebra : functions and mechanisms

The symbolic mode of reasoning in algebra, as it emerged during the sixteenth century, can be considered as a form of model-based reasoning. In this paper we will discuss the functions and mechanisms of this model and show how the model relates to its arithmetical basis. We will argue that the symbolic model was made possible by the epistemic justification of the basic operations of algebra as practiced within the abbaco tradition. We will also show that this form of model-based reasoning facilitated the expansion of the number concept from Renaissance interpretations of number to the full notion of algebraic numbers

Casein genetic variants in ovine Merino breed

The genetic polymorphism on Merina ewe milk was investigated, using polyacrylamide gel electrophoresis at pH 8.6 and ultra thin-layer isoelectric focusing techniques, according to Krause et al. (1988), and Chianese et al. (1992). The casein fractions identified were: - Seven as1-casein phenotypes: CC, BB, BC, AB, AC, BD and CD (Chianese et al.,1996). - Three as2-casein phenotypes, provisionally nominated F, S, and I. - Three b-casein phenotypes, also provisionally nominated K, L and M, because their genetic segregation is not well known yet. The phenotypical distribution of the observed casein fractions and their adjustment to a normal distribution is presented.El polimorfismo genético de la leche de oveja Merina fue investigado mediante electroforesis en gel de poliacrilamida a pH 8,6 (PAGE) e isoelectroenfoque en gel ultrafino (UTLIEF), siguiendo las técnicas descritas por Krause et al. (1988) y Chianese et al. (1992). Dentro de las fracciones caseínicas se identificaron siete fenotipos de as1-caseína (CC, BB, BC, AB, AC, BD y CD), según la nomenclatura establecida por Chianese et al. (1996). Mientras que, a nivel de as2- y b-caseína se han observado tres perfiles electroforéticos, denominados provisionalmente F, S e I; K, L y M respectivamente, ya que no se conoce su segregación genética. Se presenta la distribución fenotípica de las fracciones caseínicas estudiadas, así como su ajuste a la distribución normal

Rider energy expenditure during high intensity horse activity and the potential for health benefits

Obesity and disease associated with sedentary lifestyles have become major concerns in the United States. Exercise has been described as a crucial part of disease prevention and overall health, with activities such as biking or running cited as examples. Horseback riding is a popular activity; however, little information on the exercise value of horseback riding exists. The objective of this experiment was to define the energy expenditure of participants in several common riding events. All procedures were approved by the Texas A&M Institutional Review Board and Institutional Animal Care and Use Committee; subjects gave written consent prior to participation. Twenty subjects completed each of three riding tests: a 45min walk-trot-canter ride (WTC), a reining pattern, and a cutting pattern while wearing a telemetric gas analyzer. Anthropometric data were obtained for each subject through DEXA scans. Total energy expenditure (tEE), as well as mean and peak energy expenditure per minute (EE/min), metabolic equivalents of task (MET), heart rate (HR), respiratory frequency (RF), pulmonary ventilation (VE), oxygen consumption (VO2), relative oxygen consumption (relVO2) and carbon dioxide production (­VCO2)were measured. Mean energy expenditure per minute, and HR responses were greater (P \u3c 0.05) for reining (6.96±0.23Kcal/min, 163.28±4.2bpm) and cutting (4.98±0.23Kcal/min, 146.9±4.2bpm) than for WTC (4.27±0.23Kcal/min, 131.5±4.2bpm). When WTC test was evaluated by gait component, mean EE/min and MET increased as gait speed increased. Mean EE/min and MET were higher (P \u3c 0.05) for riders at long trot (6.9±0.21Kcal/min, 6.19±0.21MET) and canter (6.93±0.21Kcal/min, 5.95±0.21MET) gaits than during the walk (2.34±0.21Kcal.min, 2.01±0.21MET) or trot (3.5±0.21Kcal/min, 3.2±0.21MET) gaits. Similar patterns were observed for RF, VE, VO2, VCO2 and RelVO2 across disciplines and by gait component. The tEE (194.7±3.84kcal/min) and mean MET (4.27±0.23MET) observed during the 45-min WTC ride were within current national recommendations of intensity (3-6MET), time (\u3e30min) and calories burned (~1000Kcal/wk). The results of this study provide novel information about exercise intensity values for horseback activities and differences among riding disciplines measured in real time using a portable system. Riders engaged in cutting and reining experienced more intense exercise in short durations, while WTC provided a greater total energy expenditure. These data suggest that it is possible, if riding at the more intense gaits such as long trot and canter, for health benefits to be achieved through accumulated weekly horseback riding exercise

Pseudomorphic Growth of a Single Element Quasiperiodic Ultrathin Film on a Quasicrystal Substrate

An ultrathin film with a periodic interlayer spacing was grown by the deposition of Cu atoms on thefivefold surface of the icosahedral Al70 Pd21 Mn9 quasicrystal. For coverages from 5 to 25 monolayers, a distinctive quasiperiodic low-energy electron diffraction pattern is observed. Scanning tunneling microscopy images show that the in-plane structure comprises rows having separations of S = 4.5 �0.2 �A and L = 7.3 0.3 A, whose ratio equals � =1.618... within experimental error. The sequences of such row separations form segments of terms of the Fibonacci sequence, indicative of the formation of a pseudomorphic Cu film

Potential for modulation of the hydrophobic effect inside chaperonins

Despite the spontaneity of some in vitro protein folding reactions, native folding in vivo often requires the participation of barrel-shaped multimeric complexes known as chaperonins. Although it has long been known that chaperonin substrates fold upon sequestration inside the chaperonin barrel, the precise mechanism by which confinement within this space facilitates folding remains unknown. In this study, we examine the possibility that the chaperonin mediates a favorable reorganization of the solvent for the folding reaction. We begin by discussing the effect of electrostatic charge on solvent-mediated hydrophobic forces in an aqueous environment. Based on these initial physical arguments, we construct a simple, phenomenological theory for the thermodynamics of density and hydrogen bond order fluctuations in liquid water. Within the framework of this model, we investigate the effect of confinement within a chaperonin-like cavity on the configurational free energy of water by calculating solvent free energies for cavities corresponding to the different conformational states in the ATP- driven catalytic cycle of the prokaryotic chaperonin GroEL. Our findings suggest that one function of chaperonins may be to trap unfolded proteins and subsequently expose them to a micro-environment in which the hydrophobic effect, a crucial thermodynamic driving force for folding, is enhanced

Thermal/structural design and fabrication development of high power CCDTL and CCL structures

Thermal management, resonance control, and reliability requirements become predominant when designing ``conventional`` copper coupled- cavity linac (CCL) structures for very high duty factors and accelerating fields. Whereas the outer body of the coupled-cavity drift-tube linac (CCDTL) is in most ways comparable to the CCL, the cooling and support of the added drift tubes present totally new and interesting challenges. Making provisions to limit thermal distortion calls for many cooling passages, high quality materials, and new fabrication schemes and techniques. Thermal designs for a 700 MHz linac are presented, along with results of prototype tests and fabrication developments which offer solutions to all of these problems

Cross-continental emergence of Nannizziopsis barbatae disease may threaten wild Australian lizards

Members of the genus Nannizziopsis are emerging fungal pathogens of reptiles that have been documented as the cause of fatal mycoses in a wide range of reptiles in captivity. Cases of severe, proliferative dermatitis, debility and death have been detected in multiple free-living lizard species from locations across Australia, including a substantial outbreak among Eastern water dragons (Intellagama lesueurii) in Brisbane, Queensland. We investigated this disease in a subset of severely affected lizards and identified a clinically consistent syndrome characterized by hyperkeratosis, epidermal hyperplasia, dermal inflammation, necrosis, ulceration, and emaciation. Using a novel fungal isolation method, histopathology, and molecular techniques, we identified the etiologic agent as Nannizziopsis barbatae, a species reported only once previously from captive lizards in Australia. Here we report severe dermatomycosis caused by N. barbatae in five species of Australian lizard, representing the first cases of Nannizziopsis infection among free-living reptiles, globally. Further, we evaluate key pathogen and host characteristics that indicate N. barbatae-associated dermatomycosis may pose a concerning threat to Australian lizards