Drosophila bloom helicase maintains genome integrity by inhibiting recombination between divergent DNA sequences

DNA double strand breaks (DSB) can be repaired either via a sequence independent joining of DNA ends or via homologous recombination. We established a detection system in D. melanogaster to investigate the impact of sequence constraints on the usage of the homology based DSB repair via single strand annealing (SSA), which leads to recombination between direct repeats with concomitant loss of one repeat copy. First of all, we find the SSA frequency to be inversely proportional to the spacer length between the repeats, for spacers up to 2.4 kb in length. We further show that SSA between divergent repeats (homeologous SSA) is suppressed in cell cultures and in vivo in a sensitive manner, recognizing sequence divergences smaller than 0.5%. Finally, we demonstrate that the suppression of homeologous SSA depends on the Bloom helicase (Blm), encoded by the Drosophila gene mus309. Suppression of homeologous recombination is a novel function of Blm in ensuring genomic integrity, not described to date in mammalian systems. Unexpectedly, distinct from its function in S. cerevisiae, the mismatch repair (MMR) factor Msh2 encoded by spel1 does not suppress homeologous SSA in Drosophil

Irrigation Efficiency and Uniformity, and Crop Water Use Efficiency

This Extension Circular describes various irrigation efficiency, crop water use efficiency, and irrigation uniformity evaluation terms that are relevant to irrigation systems and management practices currently used in Nebraska, in other states, and around the world. The definitions and equations described can be used by crop consultants, irrigation district personnel, and university, state, and federal agency personnel to evaluate how efficiently irrigation water is applied and/or used by the crop, and can help to promote better or improved use of water resources in agriculture. As available water resources become scarcer, more emphasis is given to efficient use of irrigation water for maximum economic return and water resources sustainability. This requires appropriate methods of measuring and evaluating how effectively water extracted from a water source is used to produce crop yield. Inadequate irrigation application results in crop water stress and yield reduction. Excess irrigation application can result in pollution of water sources due to the loss of plant nutrients through leaching, runoff, and soil erosion

Irrigation Efficiency and Uniformity, and Crop Water Use Efficiency

This Extension Circular describes various irrigation efficiency, crop water use efficiency, and irrigation uniformity evaluation terms that are relevant to irrigation systems and management practices currently used in Nebraska, in other states, and around the world. The definitions and equations described can be used by crop consultants, irrigation district personnel, and university, state, and federal agency personnel to evaluate how efficiently irrigation water is applied and/or used by the crop, and can help to promote better or improved use of water resources in agriculture. As available water resources become scarcer, more emphasis is given to efficient use of irrigation water for maximum economic return and water resources sustainability. This requires appropriate methods of measuring and evaluating how effectively water extracted from a water source is used to produce crop yield. Inadequate irrigation application results in crop water stress and yield reduction. Excess irrigation application can result in pollution of water sources due to the loss of plant nutrients through leaching, runoff, and soil erosion

Text Entry in Immersive Head-Mounted Display-Based Virtual Reality Using Standard Keyboards

We study the performance and user experience of two popular mainstream text entry devices, desktop keyboards and touchscreen keyboards, for use in Virtual Reality (VR) applications. We discuss the limitations arising from limited visual feedback, and examine the efficiency of different strategies of use. We analyze a total of 24 hours of typing data in VR from 24 participants and find that novice users are able to retain about 60% of their typing speed on a desktop keyboard and about 40-45\% of their typing speed on a touchscreen keyboard. We also find no significant learning effects, indicating that users can transfer their typing skills fast into VR. Besides investigating baseline performances, we study the position in which keyboards and hands are rendered in space. We find that this does not adversely affect performance for desktop keyboard typing and results in a performance trade-off for touchscreen keyboard typing

Dark matter within high surface brightness spiral galaxies

We present results from a detailed dynamical analysis of five high surface brightness, late type spirals, studied with the aim to quantify the luminous-to-dark matter ratio inside their optical radii. The galaxies' stellar light distribution and gas kinematics have been observed and compared to hydrodynamic gas simulations, which predict the 2D gas dynamics arising in response to empirical gravitational potentials, which are combinations of differing stellar disk and dark halo contributions. The gravitational potential of the stellar disk was derived from near-infrared photometry, color-corrected to constant (M/L); the dark halo was modelled by an isothermal sphere with a core. Hydrodynamic gas simulations were performed for each galaxy for a sequence of five different mass fractions of the stellar disk and for a wide range of spiral pattern speeds. These two parameters mainly determine the modelled gas distribution and kinematics. The agreement between the non-axisymmetric part of the simulated and observed gas kinematics permitted us to conclude that the galaxies with the highest rotation velocities tend to possess near-maximal stellar disks. In less massive galaxies, with v_max<200 km/s, the mass of the dark halo at least equals the stellar mass within 2-3 R_disk. The simulated gas morphology provides a powerful tool to determine the dominant spiral pattern speed. The corotation radius for all galaxies was found to be constant at R_corotation ~ 3 R_disk and encloses the strong part of the stellar spiral in all cases.Comment: 28 pages, 7 figures; to appear in the Astrophysical Journal, Vol. 586, March 200

FIB Based Micro Fabrication Technique for a Novel Type of Scanning Electrochemical Microscopy Probes

Scanning Electrochemical Microscopy is a powerful technique to obtain in situ information of a wide range of processes occurring at interfaces. However, one major drawback of this technique is the lack of high spatial resolution compared with AFM or STM, due to the interference of the currents originated by the topographical and the electrochemical effects, respectively. Hence, a simultaneous but independent sensing of both, the topographical and the electrochemical information with high spatial resolution is a major issue in the field of scanning electrochemical microscopy (SECM). In this paper, we present a Focused Ion Beam (FIB) based technology, which, for the first time, enables the realization of an independent, simultaneous sensing of both the topography and the electrochemically active interfac

8-(Naphthalen-1-yl)quinoline

In the title mol­ecule, C19H13N, the angle between the mean planes of the naphthalene and quinoline ring systems is 68.59 (2)°. The compound is of inter­est with respect to its potential for spontaneous resolution. In the crystal structure, the R and S isomers are arranged in alternating homochiral layers. The mol­ecules of a given layer are oriented with their major axes (i.e. the axis perpendicular to the interannular bond) in the same direction and their naphthalene and quinoline ring systems are arranged parallel. Like the configurations, this orientation alternates in adjacent layers

Inorganic carbon and pH dependency of Trichodesmium's photosynthetic rates.

We established the relationship between photosynthetic carbon fixation rates and pH, CO2 and HCO3- concentrations in the diazotroph Trichodesmium erythraeum IMS101. Inorganic 14C-assimilation was measured in TRIS-buffered ASW medium where the absolute and relative concentrations of CO2, pH and HCO3- were manipulated. First, we varied the total dissolved inorganic carbon concentration (TIC) (< 0 to ~ 5 mM) at constant pH, so ratios of CO2 and HCO3- remained relatively constant. Second, we varied pH (~ 8.54 to 7.52) at constant TIC, so CO2 increased whilst HCO3- declined. We found that 14C-assimilation could be described by the same function of CO2 for both approaches but showed different dependencies on HCO3- when pH was varied at constant TIC than when TIC was varied at constant pH. A numerical model of Trichodesmium's CCM showed carboxylation rates are modulated by HCO3- and pH. The decrease in Ci assimilation at low CO2, when TIC was varied, is due to HCO3- uptake limitation of the carboxylation rate. Conversely, when pH was varied, Ci assimilation declined due to a high-pH mediated increase in HCO3- and CO2 leakage rates, potentially coupled to other processes (uncharacterised within the CCM model) that restrict Ci assimilation rates under high-pH conditions

Bodies, technologies and action possibilities: when is an affordance?

Borrowed from ecological psychology, the concept of affordances is often said to offer the social study of technology a means of re-framing the question of what is, and what is not, ‘social’ about technological artefacts. The concept, many argue, enables us to chart a safe course between the perils of technological determinism and social constructivism. This article questions the sociological adequacy of the concept as conventionally deployed. Drawing on ethnographic work on the ways technological artefacts engage, and are engaged by, disabled bodies, we propose that the ‘affordances’ of technological objects are not reducible to their material constitution but are inextricably bound up with specific, historically situated modes of engagement and ways of life