2,456 research outputs found

    Byron Hawk, David M. Rieder, Ollie Oviedo (eds), Small Tech: The Culture of Digital Tools

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    Byron Hawk, David M. Rieder, Ollie Oviedo (eds), Small Tech: The Culture of Digital Tool

    Byron Hawk, David M. Rieder, Ollie Oviedo (eds), Small Tech: The Culture of Digital Tools

    Get PDF
    Byron Hawk, David M. Rieder, Ollie Oviedo (eds), Small Tech: The Culture of Digital Tool

    Microtubule disassembly delays the G2–M transition in vertebrates

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    AbstractWhen cell cultures in growth are treated with drugs that cause microtubules to disassemble, the mitotic index (MI) progressively increases as the cells accumulate in a C-mitosis. For many cell types, however, including rat kangaroo kidney PtK1 cells, the MI does not increase during the first several hours of treatment [1–3] (Figure 1). This ‘lag’ implies either that cells are entering mitosis but rapidly escaping the block, or that they are delayed from entering division. To differentiate between these possibilities, we fixed PtK1 cultures 0, 90 and 270 minutes after treatment with nocodazole, colcemid, lumi-colcemid, taxol or cytochalasin D. After 90 minutes, we found that the numbers of prophase cells in cultures treated with nocodazole or colcemid were reduced by ∼80% relative to cultures treated with lumi-colcemid, cytochalasin D or taxol. Thus, destroying microtubules delays late G2 cells from entering prophase and, as the MI does not increase during this time, existing prophase cells do not enter prometaphase. When mid-prophase cells were treated with nocodazole, the majority (70%) decondensed their chromosomes and returned to G2 before re-entering and completing prophase 3–10 hours later. Thus, a pathway exists in vertebrates that delays the G2–M transition when microtubules are disassembled during the terminal stages of G2. As this pathway induces mid-prophase cells to transiently decondense their chromosomes, it is likely that it downregulates the cyclin A–cyclin-dependent kinase 2 (CDK2) complex, which is required in vertebrates for the early stages of prophase [4]

    Highly sensitive micro coriolis mass flow sensor

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    We have realized a micromachined micro Coriolis mass flow sensor consisting of a silicon nitride resonant tube of 40 ?m diameter and 1.2 μm wall thickness. Actuation of the sensor in resonance mode is achieved by Lorentz forces. First measurements with both gas and liquid flow have demonstrated a resolution in the order of 10 milligram per hour. The sensor can simultaneously be used as a density sensor

    Gender-Specific Protection from Microvessel Rarefaction in Female Hypertensive Rats

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    Epidemiologic studies reveal that women have a significantly lower age-adjusted morbidity and mortality from cardiovascular disease than men, suggesting that gender is a cardiovascular disease risk factor. The mechanism of the “gender protection” is unknown. In this study, we investigated the microvascular remodeling in reduced renal mass plus a high salt (4.0% NaCl) diet model of hypertension (RRM + HS). We hypothesized that women would be protected from the increase in blood pressure and from the microvascular rarefaction associated with RRM + HS hypertension. Studies were designed to determine whether female rats were less susceptible to changes in microvessel density during RRM + HS. Microvessel density was measured in male and female low salt (0.4% LS) sham-operated controls (Sham + LS) and after 3 days or 4 weeks of RRM + HS hypertension. The microcirculation of hind limb (medial and lateral gastrocnemius, plantaris, soleus) muscles was visualized using rhodamine-labeled Griffonia simplicifolia I lectin. Tissue sections were examined by videomicroscopy and microvessel density was determined by quantitative stereology. As shown previously, mean arterial pressure increased to 160 ± 8 mm Hg and microvessel density decreased (\u3e30% decrease in all beds) in male RRM + HS. In contrast, mean arterial pressure of female RRM + HS rats was modestly increased from 101 ± 2 to 118 ± 4 mm Hg. Despite previous results showing a reduction in microvessel density of both normotensive and hypertensive male rats on a high salt diet, microvessel density of female RRM + HS rats was not reduced at either time. These results suggest that gender protection in the RRM rat extends beyond an attenuation of the increase in pressure to an immunity from microvascular rarefaction

    Science Fiction

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    Science fiction (SF) emerges as a distinct literary and cultural genre out of a familiar set of world-famous texts ranging from Mary Shelley’s Frankenstein (1818) to Gene Roddenberry’s Star Trek (1966–) to the Marvel Cinematic Universe (2008–) that have, in aggregate, generated a colossal, communal archive of alternate worlds and possible future histories. SF’s dialectical interplay between utopian optimism and apocalyptic pessimism can be felt across the genre’s now centuries-long history, only intensifying in the 20th century as the clash between humankind’s growing technological capabilities and its ability to use those powers safely or wisely has reached existential-threat propositions, not simply for human beings but for all life on the planet. In the early 21st century, as in earlier cultural moments, the writers and critics of SF use the genre’s articulation of different societies and different possible futures as the occasion to reflect on our own present, in ways that range from full-throated defense of the status quo to the ruthless denunciation of all institutions that currently exist in the name of some other, better world. SF’s global popularity has grown to the point where it now looms quite large over cultural production generally, becoming arguably the most popular narrative genre in existence, particularly in the sorts of SF action spectacles that have dominated the global box office of the first two decades of the 21st century. It has also become increasingly difficult to tell the difference between the things we used to think of as SF and the advanced communication, transportation, and entertainment technologies that have become so ubiquitous and familiar that we now take them for granted, as well as the growing prevalence of political, economic, and ecological crises now erupting out of the pages of our science fictions, like our very worst dreams come to life

    Micro Coriolis mass flow sensor for chemical micropropulsion systems

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    We have designed a micromachined micro Coriolis flow sensor for the measurement of hydrazine (N2H4, High Purity Grade) propellant flow in micro chemical propulsion systems [1]. The sensor measures mass flow up to 6 mg/s for a single thruster or up to 24 mg/s for four thrusters. The sensor will first be used for measurement and characterization of the micro thruster system in a simulated space vacuum environment. Integration of the sensor chip within the micro thruster flight hardware will be considered at a later stage. The new chip has an increased flow range because of an integrated on-chip bypass channel

    Spectroscopic Analysis and Xray Diffraction of Zinnwaldite

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    This paper describes an X-ray diffraction and spectroscopic study, including infrared, near-infrared and Raman spectroscopy of some selected zinnwaldites. In general, zinnwaldite forms a member of the trioctahedral true micas with characteristically Li in the octahedral positions and low iron contents. Although the infrared spectrum of zinnwaldite has been described before, near infrared and Raman spectroscopy have not been used so far to study this mineral. X-ray diffraction showed that all the samples reported in this study have the 1M structure. The Raman spectra are characterised by a strong band at 700-705 cm-1 plus a broad band associated with the SiO modes around 1100 cm-1. Less intense bands are observed around 560, 475, 403 and 305 cm-1. The corresponding IR spectra show strong overlapping SiO modes around 1020 cm-1 plus less intense bands around 790, 745, 530, 470-475 and 440 cm-1. Two overlapping OH-stretching modes can be observed around 3550-3650 cm-1, in agreement with a broad band in the IR around 3450 cm-1 and a complex band around 3630 cm-1. The near-IR spectra basically reflect combination and overtone bands associated with protons in the zinnwaldite structure. A very broad band observed around 5230 cm-1 is characteristic for adsorbed water while bands around 4530, 4435 and 4260 cm-1 can be ascribed to metal-hydroxyl groups
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