Highly efficient optogenetic cell ablation in C. elegans using membrane-targeted miniSOG.

The genetically encoded photosensitizer miniSOG (mini Singlet Oxygen Generator) can be used to kill cells in C. elegans. miniSOG generates the reactive oxygen species (ROS) singlet oxygen after illumination with blue light. Illumination of neurons expressing miniSOG targeted to the outer mitochondrial membrane (mito-miniSOG) causes neuronal death. To enhance miniSOG's efficiency as an ablation tool in multiple cell types we tested alternative targeting signals. We find that membrane targeted miniSOG allows highly efficient cell killing. When combined with a point mutation that increases miniSOG's ROS generation, membrane targeted miniSOG can ablate neurons in less than one tenth the time of mito-miniSOG. We extend the miniSOG ablation technique to non-neuronal tissues, revealing an essential role for the epidermis in locomotion. These improvements expand the utility and throughput of optogenetic cell ablation in C. elegans

Study of controlled diffusion stator blading. 1. Aerodynamic and mechanical design report

Pratt & Whitney Aircraft is conducting a test program for NASA in order to demonstrate that a controlled-diffusion stator provides low losses at high loadings and Mach numbers. The technology has shown great promise in wind tunnel tests. Details of the design of the controlled diffusion stator vanes and the multiple-circular-arc rotor blades are presented. The stage, including stator and rotor, was designed to be suitable for the first-stage of an advanced multistage, high-pressure compressor

A geometric basis for the standard-model gauge group

A geometric approach to the standard model in terms of the Clifford algebra Cl_7 is advanced. A key feature of the model is its use of an algebraic spinor for one generation of leptons and quarks. Spinor transformations separate into left-sided ("exterior") and right-sided ("interior") types. By definition, Poincare transformations are exterior ones. We consider all rotations in the seven-dimensional space that (1) conserve the spacetime components of the particle and antiparticle currents and (2) do not couple the right-chiral neutrino. These rotations comprise additional exterior transformations that commute with the Poincare group and form the group SU(2)_L, interior ones that constitute SU(3)_C, and a unique group of coupled double-sided rotations with U(1)_Y symmetry. The spinor mediates a physical coupling of Poincare and isotopic symmetries within the restrictions of the Coleman--Mandula theorem. The four extra spacelike dimensions in the model form a basis for the Higgs isodoublet field, whose symmetry requires the chirality of SU(2). The charge assignments of both the fundamental fermions and the Higgs boson are produced exactly.Comment: 17 pages, LaTeX requires iopart. Accepted for publication in J. Phys. A: Math. Gen. 9 Mar 2001. Typos correcte

Genetic Suppression of Basement Membrane Defects in Caenorhabditis elegans by Gain of Function in Extracellular Matrix and Cell-Matrix Attachment Genes.

Basement membranes are extracellular matrices essential for embryonic development in animals. Peroxidasins are extracellular peroxidases implicated in the unique sulfilimine cross-links between type IV basement membrane collagens. Loss of function in the Caenorhabditis elegans peroxidasin PXN-2 results in fully penetrant embryonic or larval lethality. Using genetic suppressor screening, we find that the requirement for PXN-2 in development can be bypassed by gain of function in multiple genes encoding other basement membrane components, or proteins implicated in cell-matrix attachment. We identify multiple alleles of let-805, encoding the transmembrane protein myotactin, which suppress phenotypes of pxn-2 null mutants and of other basement membrane mutants such as F-spondin/spon-1 These let-805 suppressor alleles cause missense alterations in two pairs of FNIII repeats in the extracellular domain; they act dominantly and have no detectable phenotypes alone, suggesting they cause gain of function. We also identify suppressor missense mutations affecting basement membrane components type IV collagen (emb-9, let-2) and perlecan (unc-52), as well as a mutation affecting spectraplakin (vab-10), a component of the epidermal cytoskeleton. These suppressor alleles do not bypass the developmental requirement for core structural proteins of the basement membrane such as laminin or type IV collagen. In conclusion, putative gain-of-function alterations in matrix proteins or in cell-matrix receptors can overcome the requirement for certain basement membrane proteins in embryonic development, revealing previously unknown plasticity in the genetic requirements for the extracellular matrix

Do actions occur inside the body?

The paper offers a critical examination of Jennifer Hornsby's view that actions are internal to the body. It focuses on three of Hornsby's central claims: (P) many actions are bodily movements (in a special sense of the word “movement”) (Q) all actions are tryings; and (R) all actions occur inside the body. It is argued, contra Hornsby, that we may accept (P) and (Q) without accepting also the implausible (R). Two arguments are first offered in favour of the thesis (Contrary-R): that no actions occur inside the body. Three of Hornsby's arguments in favour of R are then examined. It is argued that we need to make a distinction between the causes and the causings of bodily movements (in the ordinary sense of the word “movement”) and that actions ought to be identified with the latter rather than the former. This distinction is then used to show how Hornsby's arguments for (R) may be resisted

Preliminary flight evaluation of an engine performance optimization algorithm

A performance seeking control (PSC) algorithm has undergone initial flight test evaluation in subsonic operation of a PW 1128 engined F-15. This algorithm is designed to optimize the quasi-steady performance of an engine for three primary modes: (1) minimum fuel consumption; (2) minimum fan turbine inlet temperature (FTIT); and (3) maximum thrust. The flight test results have verified a thrust specific fuel consumption reduction of 1 pct., up to 100 R decreases in FTIT, and increases of as much as 12 pct. in maximum thrust. PSC technology promises to be of value in next generation tactical and transport aircraft

Constraining the metallicities, ages, star formation histories, and ionizing continua of extragalactic massive star populations

We infer the properties of massive star populations using the far-ultraviolet stellar continua of 61 star-forming galaxies: 42 at low-z observed with HST and 19 at z~2 from the Megasaura sample. We fit each stellar continuum with a linear combination of up to 50 single age and single metallicity Starburst99 models. From these fits, we derive light-weighted ages and metallicities, which agree with stellar wind and photospheric spectral features, and infer the spectral shapes and strengths of the ionizing continua. Inferred light-weighted stellar metallicities span 0.05-1.5 Z$_\odot$ and are similar to the measured nebular metallicities. We quantify the ionizing continua using the ratio of the ionizing flux at 900\AA\ to the non-ionizing flux at 1500\AA\ and demonstrate the evolution of this ratio with stellar age and metallicity using theoretical single burst models. These single burst models only match the inferred ionizing continua of half of the sample, while the other half are described by a mixture of stellar ages. Mixed age populations produce stronger and harder ionizing spectra than continuous star formation histories, but, contrary to previous studies that assume constant star formation, have similar stellar and nebular metallicities. Stellar population age and metallicity affect the far-UV continua in different and distinguishable ways; assuming a constant star formation history diminishes the diagnostic power. Finally, we provide simple prescriptions to determine the ionizing photon production efficiency ($\xi_{ion}$) from the stellar population properties. $\xi_{ion}$ has a range of log($\xi_{ion})=24.4-25.7$ Hz erg$^{-1}$ that depends on stellar age, metallicity, star formation history, and contributions from binary star evolution. These stellar population properties must be observationally determined to determine the number of ionizing photons generated by massive stars.Comment: 31 pages, 23 figures, resubmitted to ApJ after incorporating the referee's comments. Comments encourage