Rigid body trajectories in different 6D spaces

The objective of this paper is to show that the group SE(3) with an imposed Lie-Poisson structure can be used to determine the trajectory in a spatial frame of a rigid body in Euclidean space. Identical results for the trajectory are obtained in spherical and hyperbolic space by scaling the linear displacements appropriately, since the influence of the moments of inertia on the trajectories tend to zero as the scaling factor increases. The semi-direct product of the linear and rotational motions gives the trajectory from a body frame perspective. It is shown that this cannot be used to determine the trajectory in the spatial frame. The body frame trajectory is thus independent of the velocity coupling. In addition, it is shown that the analysis can be greatly simplified by aligning the axes of the spatial frame with the axis of symmetry which is unchanging for a natural system with no forces and rotation about an axis of symmetry

Closed form solution for p-curves in SO(4)

This paper describes the solution for p-curves in SO(4) and gives its closed form. The rotational symmetry was exploited in order to simplify the algebra. The relationship between the Casimir invariant functions and Lax operator is provided, along with its use as part of a Lax pair. The double cover by SU(2) SU(2) enables two simpler problems to be found and integrated using Philip Hall coordinates and the solutions are then projected onto SO (4). The methodology is generic and can be applied to other problems

An Investigation of the Molecular Genetics of Tetronasin Biosynthesis and Resistance in Streptomyces longisporoflavus

Streptomyces longisporoflavus makes tetronasin, a polyketide, polyether antibiotic. This thesis describes the isolation and preliminary characterisation of sequences from longisporoflavus which are probably involved in biosynthesis of, and/or resistance to tetronasin. A DNA library representative of the genome of a high-producing mutant, S. longisporoflavus strain 83E6, was constructed in the positive selection vector pIJ699 and contained in S. lividans TK64. The sensitivity of S. lividans to tetronasin was increased in the presence of 0.2M NaCl enabling tetronasin resistance determinants to be selected directly in the primary cloning recipient. Two non-identical recombinants (tetR1 and tetR5) containing 5.0 and 5.5kb of DNA respectively, were found to increase the tolerance of S. lividans to tetronasin. TetR5 also conferred resistance upon a tetronasin-super-sensitive strain of S. albus to a level comparable with that found in the wild-type S. longisporoflavus 4584. Although the functions of these sequences in the parental strain remain undetermined, they may by virtue of their activity in heterologous hosts, represent the first examples of the isolation of resistance determinants to an ionophore antibiotic. The 2.1kb actl fragment (Malpartida et al., 1987) which encodes components of the actinorhodin polyketide synthase, hybridized at low stringency to a 5kb BamHI fragment (AC36) from S. lonqisporoflavus. Paradoxically, a 4.3kb BamHI fragment from S. cinnamonensis (monl) with good sequence homology to actl (J. A. Robinson, pers. comm. ) failed to hybridize with the 5kb fragment in Southern analysis of total DNA. However monl did anneal to a 7kb BamHI fragment (MB74). Both fragments were isolated from partial libraries of S. longisporoflavus DNA constructed in pTZ18 R and contained in E. coli JM101. Cross hybridization of AC36 and MB74 with total DNA from several Streptomyces sp. which were known to produce polyketide antibiotics was investigated. At 65 C in 0.5xSSC both probes failed to hybridize with DNA fragments which correlated with restriction fragments known to be involved in polyketide biosynthesis. MB74 also had greater sequence homology with an 11kb BamHI fragment from S. cinnamonensis than the 4.3kb monl. Cross hybridization with isolated sequences involved in oxytetracycline (otcY). actinorhodin (actl) and putatively in monensin (monl) biosynthesis was tested. Not surprisingly, MB74 hybridized to a different restriction fragment from monl than actl and otcY. Interestingly, a fragment with a low level of homology to AC36 and otcY was discovered in MB74. It did not overlap with the sequences which hybridized to monl. A 2.8kb EcoRV/PvuII fragment from AC36 hybridized with actl and at 60 C, 2xSSC with monl. These data suggested that both AC36 and MB74 could be involved in polyketide biosynthesis but did not uniquely indicate sequences which might encode components of the tetronasin synthase. Recombinant bacteriophages which contained flanking DNA of each of the clones (AC36, MB74, tetR1 and tetR5) were identified by hybridization of radiolabelled probe to a representative library of S. longisporoflavus DNA contained in the lambda replacement vector EMBL3. Close linkage between any of the four clones was not established. However, sequences with homology to tetR1 were found, overlapping with, and in the DNA flanking, MB74. On its own MB74 was unable to confer resistance to tetronasin upon C. lividans or S. albus. Although S. longisporoflavus 4584 was shown to possess a photoreactivation system, conditions were defined for mutagenesis using short-wavelength UV light. Attempts to complement mutants which were deficient in the biosynthesis of tetronasin were inconclusive. Similarly, preliminary experiments designed to disrupt transcription of the endogenous copies of AC36 and MB74 in S. lonqisporoflavus 4584, require repitition. Therefore until otherwise established AC36, MB74 and sequences flanking the tetronasin resistance determinants must remain merely candidates for genes involved in tetronasin biosynthesis in longisporoflavus

Multi-fluid simulations of chromospheric magnetic reconnection in a weakly ionized reacting plasma

We present results from the first self-consistent multi-fluid simulations of chromospheric magnetic reconnection in a weakly ionized reacting plasma. We simulate two dimensional magnetic reconnection in a Harris current sheet with a numerical model which includes ion-neutral scattering collisions, ionization, recombination, optically thin radiative loss, collisional heating, and thermal conduction. In the resulting tearing mode reconnection the neutral and ion fluids become decoupled upstream from the reconnection site, creating an excess of ions in the reconnection region and therefore an ionization imbalance. Ion recombination in the reconnection region, combined with Alfv\'{e}nic outflows, quickly removes ions from the reconnection site, leading to a fast reconnection rate independent of Lundquist number. In addition to allowing fast reconnection, we find that these non-equilibria partial ionization effects lead to the onset of the nonlinear secondary tearing instability at lower values of the Lundquist number than has been found in fully ionized plasmas.These simulations provide evidence that magnetic reconnection in the chromosphere could be responsible for jet-like transient phenomena such as spicules and chromospheric jets.Comment: 8 Figures, 32 pages tota

Environmental and Infectious Causes of Malignancy

This chapter in Cancer Concepts: A Guidebook for the Non-Oncologist presents a summary of the most relevant causative agents of cancer. Exposure to many environmental agents is associated with an increased incidence of certain malignancies, although causation is usually difficult to prove. Certain chemicals, infections (parasitic, viral, and bacterial) and ionizing radiation are known carcinogens. Variable genetic susceptibility to carcinogenesis is apparent. Up to 2/3 of human cancers are believed to have an environmental component.https://escholarship.umassmed.edu/cancer_concepts/1007/thumbnail.jp

Staging of Cancer

The “stage” of a cancer is a short-hand way of describing the extent of cancer in a patient. Stage is based on macroscopic involvement of tissues by cancer. Staging of cancer occurs prior to the beginning of treatment, or at the first definitive surgery. Clinical staging, which includes radiography and exam findings, takes place initially. Pathologic staging, which is obtained from surgical specimens, can be acquired during the course of surgical treatment. Patients then carry either the clinical stage or the pathologic stage for the duration of their illness. This chapter in Cancer Concepts: A Guidebook for the Non-Oncologist will describe principles of cancer staging.https://escholarship.umassmed.edu/cancer_concepts/1003/thumbnail.jp

Distribution of Electric Currents in Solar Active Regions

There has been a long-lasting debate on the question of whether or not electric currents in solar active regions are neutralized. That is, whether or not the main (or direct) coronal currents connecting the active region polarities are surrounded by shielding (or return) currents of equal total value and opposite direction. Both theory and observations are not yet fully conclusive regarding this question, and numerical simulations have, surprisingly, barely been used to address it. Here we quantify the evolution of electric currents during the formation of a bipolar active region by considering a three-dimensional magnetohydrodynamic simulation of the emergence of a sub-photospheric, current-neutralized magnetic flux rope into the solar atmosphere. We find that a strong deviation from current neutralization develops simultaneously with the onset of significant flux emergence into the corona, accompanied by the development of substantial magnetic shear along the active region's polarity inversion line. After the region has formed and flux emergence has ceased, the strong magnetic fields in the region's center are connected solely by direct currents, and the total direct current is several times larger than the total return current. These results suggest that active regions, the main sources of coronal mass ejections and flares, are born with substantial net currents, in agreement with recent observations. Furthermore, they support eruption models that employ pre-eruption magnetic fields containing such currents.Comment: 6 pages, 5 figures, to appear in Astrophysical Journal Letter

Death by certainty: the Vinca dam and the withering of canal associations in the Têt basin of the Eastern French Pyrenees

Panel : "Water and social relations: Wittfogel's legacy and hydrosocial futures"International audienceThis paper considers the ongoing social effects of a large dam in the Eastern Pyrenees region of France. In 1976, the French state constructed a dam near the town of Vinça on the Têt River, altering the hydrological conditions that had co-produced a complex system of hydro-social relations evolved since the Middle Ages.Wittfogel's dialectical insights into the relations between the control of water and the control of people help explain the effects of the dam, which we argue was built partly as a means of gaining territorial presence in a region historically resistant to the control of the French state. However, a more complex set of dialectical relations is at play in this situation, requiring a subtler explanatory tool. We show that the dam has had the effect of transferring expertise and social power from local to central authority, but not in a direct way. Rather, the production of hydrological certainty in the form of assured and regular flows has weakened the local social structures and relations that had evolved to accommodate - and were sustained by - hydrological uncertainty and periodical scarcity. We employ the concept of the hydrosocial cycle - which borrows from Wittfogel's dialectic, but demands a more complex account of hydrosocial relations - to explain these developments.We conclude by hypothesizing some of the longer-term consequences of the dam in terms of its unintended impacts on the agricultural sector of the region and, ultimately, on the influence of the state