6,322 research outputs found
Sucrose- and H+-dependent charge movements associated with the gating of sucrose transporter ZmSUT1
No full textBackground: In contrast to man the majority of higher plants use sucrose as mobile carbohydrate. Accordingly proton-driven sucrose transporters are crucial for cell-to-cell and long-distance distribution within the plant body. Generally very negative plant membrane potentials and the ability to accumulate sucrose quantities of more than 1 M document that plants must have evolved transporters with unique structural and functional features.
Methodology/Principal Findings: To unravel the functional properties of one specific high capacity plasma membrane sucrose transporter in detail, we expressed the sucrose/H+ co-transporter from maize ZmSUT1 in Xenopus oocytes. Application of sucrose in an acidic pH environment elicited inward proton currents. Interestingly the sucrose-dependent H+ transport was associated with a decrease in membrane capacitance (Cm). In addition to sucrose Cm was modulated by the membrane potential and external protons. In order to explore the molecular mechanism underlying these Cm changes, presteady-state currents (Ipre) of ZmSUT1 transport were analyzed. Decay of Ipre could be best fitted by double exponentials. When plotted against the voltage the charge Q, associated to Ipre, was dependent on sucrose and protons. The mathematical derivative of the charge Q versus voltage was well in line with the observed Cm changes. Based on these parameters a turnover rate of 500 molecules sucrose/s was calculated. In contrast to gating currents of voltage dependent-potassium channels the analysis of ZmSUT1-derived presteady-state currents in the absence of sucrose (I = Q/τ) was sufficient to predict ZmSUT1 transport-associated currents.
Conclusions: Taken together our results indicate that in the absence of sucrose, ‘trapped’ protons move back and forth between an outer and an inner site within the transmembrane domains of ZmSUT1. This movement of protons in the electric field of the membrane gives rise to the presteady-state currents and in turn to Cm changes. Upon application of external sucrose, protons can pass the membrane turning presteady-state into transport currents
Healthcare Activism, Marketization, and the Collective Good
No full textThis chapter engages with three key dynamics of contemporary healthcare - digitalization, marketization and individualization. It draws on several theoretical frameworks to conceptualize the notion of collective good and to consider how healthcare activism may play into defining and defending the collective good when faced with the outlined societal, economic, and scientific dynamics. Presenting contemporary examples from the Covid-19 pandemic, the chapter argues that the way activists define and defend the collective good can only fully be understood by grasping how this good is shaped by other, often more dominant, stakeholders in healthcare: governmental institutions, professional experts, scientists, and private industry – the latter being a focal point of concern for this current volume.European Commission Horizon 2020Check for published version during checkdate report - AC2021-04-28 JG: PDF replaced at author's request2021-06-04 JG: embargo removed following documentation from author/publishe
Geiger H. Kent — The family in Soviet Russia
No full textB H. Geiger H. Kent — The family in Soviet Russia. In: Population, 24ᵉ année, n°4, 1969. p. 809
John H. Geiger statement to the 1972 Republican Platform Committee
No full textStatement by John H. Geiger, National Commander of the American Legion, to the Platform Committee at 1972 Republican National Convention
Sinezona hawaiiensis Geiger & Mclean, 2010, n. sp.
No full textSinezona hawaiiensis n. sp. Figure 4 Type material. Holotype (LACM 2466), leg. Twila Bratcher. Type locality. 30 m, off Waikiki, Oahu, HI, USA, 21.270 ˚N, 157.840 ˚W. Etymology. Named after its provenance from Hawaii, USA. Description. Shell small (0.5 mm), trochiform, globular. Protoconch of 1 whorl, with fine axial cords, no apertural varix. apertural margin prosocline. TI of 1.25 whorls. Shoulder with broad indistinct axial cords, approximately 30 on first whorl, without discernible spiral sculpture. Base with axials becoming more distinct towards umbilicus, approximately 13 low spiral cords between periphery and umbilicus, barely noticeable at periphery, becoming as strong as axials towards umbilicus. TII of 0.125 whorls, same sculpture as on TI. Umbilicus very narrow, bordered by strong cord, walls with distinct growth marks, no funiculus. Selenizone absent, foramen oval, keels low, strong. Aperture rounded, roof overhanging. Animal unknown. Differential diagnosis. Sinezona haliotimorpha (Bandel, 1998) from the Oligocene of France has a protoconch with fewer and stronger axials, and a teleococh with stronger axials and consistently finer spiral threads on the base, as well as a foramen with more elevated keels. Sinezona brevis Hedley, 1904 [= Ariella campbelli Bandel, 1998] from New Zealand has a protoconch like S. haliotimorpha, has a greater expansion rate of the shell giving it a more oval appearance, and when fully grown has a short selenizone. Distribution. Known only from type locality. Remarks. The absence of a selenizone has been taken as genus-level character by Bandel (1998) to establish Ariella Bandel, 1998. Marshall (2002), however, pointed out that there is significant intraspecific variability in the length of selenizone, with some species [e.g., Sinezona brevis (Hedley, 1904)] showing a distinct to no selenizone at all. Accordingly, the absence of a selenizone is not considered significant for generic classification. Equally, the presence and absence of a protoconch varix and details of teleoconch ornamentation vary extensively between species in the same genus and is also insignificant for beta taxonomy (Geiger 2003). The shell appears mature due to the descending apertural margin on the last portion of the whorl. The species is known from a single, but well-preserved specimen. The difference in protoconch sculpture, and the absence of any sign of a selenizone despite the sloping aperture indicating maturity, refutes the possibility of a mislocalized specimen from New Zealand.Published as part of Geiger, Daniel L. & Mclean, James H., 2010, New species and records of Scissurellidae and Anatomidae from the Americas (Mollusca: Gastropoda: Vetigastropoda), pp. 1-35 in Zootaxa 2356 on page 8, DOI: 10.5281/zenodo.27564
Complexity limitations of optical networks from out-of-band dispersion of grating filters
No full textAccumulated dispersion can limit the number of grating filters in a network. We derive a simple analytical equation for the out-of-band dispersion of any filter, and conclude on the resulting node-limitation of an optical network
Low-cost high-resolution time-domain reflectometry for monitoring the range of reflective points
No full textA new OTDR technique to interrogate the range of reflective markers in an optical fiber (or an electrical cable) is presented. The technique has been developed to monitor strain in sections of a fiber over gauge lengths of several meters. Signal-to-noise analysis shows that current OTDR systems do not fully exploit the spatial resolution theoretically available. The available resolution is explored with a new OTDR technique
Thieleella bathypacifica Geiger & Mclean, 2010, n. sp.
No full text<i>Thieleella bathypacifica</i> n. sp. <p>Figures 23–24</p> <p> <b>Type material.</b> Holotype (FMNH 307884), shell, operculum and radula mounted on SEM stubs. <i>RV Atlantis</i>, submersible grab, leg. J. Voight.</p> <p> <b>Type locality.</b> 2572 m, ALVIN Dive 3938, Genesis, East Pacific Rise, 12.811˚N, 103.940˚W [approximately midway between Acapulco, Mexico, and Clipperton Island]. Sample with anemone and serpulid rocks.</p> <p> <b>Etymology.</b> Bathy- referring to the deep-sea (bathyal) habitat of the species; -pacifica referring the Pacific Ocean; adjective.</p> <p> <b>Description.</b> Shell trochiform globular to 1.85 mm. Protoconch of 0.75 whorls, reticulate sculpture, no apertural varix, apertural margin straight. TI of 0.875 whorls, 15 indistinct axial cords, prominent spiral cord forming ridge in position of selenizone, at intersection forming thickenings. TII of at least 1.5 whorls. Shoulder convex, 26 distinct raised axial cords, first spiral line after 0.33 TII whorls, 7 spiral lines after 1.5 whorls on outer two thirds of shoulder, spiral lines running over axial cords. Base convex, barely constricted below selenizone, evenly curving into umbilicus, same density of axial cords as on shoulder, crossed by spiral lines, 23 after 1.25 TII whorls, spiral lines running over axial cords. Selenizone at periphery, keels of moderate strength, high (higher than width of selenizone), regular growth lunules; slit open, with parallel margins.</p> <p>Operculum round, thin, multispiral, central nucleus, covering aperture.</p> <p>Radula (Fig. 20). Rachidian trapezoid, central denticle often largest, approximately five denticles on each side (Fig. 20 A–C: R). Lateral teeth 1–3 similar, 6,4,4 cusps respectively (Fig. 20 B–C: L1–3). Lateral tooth 4 reduced, hook-shaped, apical denticle largest, two small denticles on inner cutting edge (Fig. 20 C: L4).</p> <p>Lateral tooth 5 enlarged by broadening, inner edge with 4–5 denticles, outer edge with three denticles (Fig. 20 B–C: L5). Inner marginal teeth triangular with approximately 3–4 denticles on each side (Fig. 20 D–E); with posterior projection on upper shaft (except marginal tooth 1: Fig. 20 C: M1); outer marginal teeth spoon or paddle shaped with many fine denticles along apical edge (Fig. 20 E–F).</p> <p> <b>Differential diagnosis.</b> <i>Thieleella baxteri</i> from the northeastern Pacific has elevated lamellar axial sculpture. <i>Anatoma janetae</i> Geiger, 2006, from deep water of the eastern Pacific has a protoconch with flocculent sculpture in spiral orientation, the spiral cord on TI does not form a marked angulation, and shows a marked change of sculpture from predominant axial elements to exclusively spiral elements after 1.25 TII whorls.</p> <p> <i>Thieleella peruviana</i> from deep water off Peru, on TI has only a week spiral cord not forming an angulation on the shell’s profile, and has more (42 vs. 15) and weaker axial cords on TI.</p> <p> <b>Remarks.</b> The only specimen at hand is most likely not fully mature, because the final quarter whorl does not markedly descend along the coiling axis. The specimen is sufficiently distinct to warrant description as new, and material from that depth is unlikely to be collected in the foreseeable future. The specimen was preserved with the body in the shell, hence, was collected live in its natural deep-sea habitat.</p> <p> The radula of the species shows a thus far unknown detail, namely the posterior projection on the apical portion of the shaft of the marginal teeth from marginal tooth 2 onwards. It is comparable to the food groove known from <i>Tegula funebralis</i> (A. Adams, 1855) and Liotiidae (see Morris & Hickman 1981, Hickman & McLean 1990). The occurrence of such a food groove in thus far a single species of Anatomidae demonstrates further the by now fairly well-documented variability of the radula within Anatomidae (Geiger 2006a, Geiger & Sasaki 2008, Sasaki <i>et al</i>. in press).</p>Published as part of <i>Geiger, Daniel L. & Mclean, James H., 2010, New species and records of Scissurellidae and Anatomidae from the Americas (Mollusca: Gastropoda: Vetigastropoda), pp. 1-35 in Zootaxa 2356</i> on pages 31-33, DOI: <a href="http://zenodo.org/record/275645">10.5281/zenodo.275645</a>
Dr. H. V. Neher checking a Geiger-Muller counter
No full textPhotograph shows Dr. H. V. Neher, one of a group of scientists from California Institute of Technology, checks a Geiger-Muller counter. The group is sending counters attached to balloons in a 50 mile radius of San Antonio to check cosmic rays
Anatoma plicatazona Geiger & Mclean, 2010, n. sp.
No full text<i>Anatoma plicatazona</i> n. sp. <p>Figure 15</p> <p> <i>Anatoma</i> <b>n. sp.</b>: Geiger, 2008: fig. 1.</p> <p> <b>Type material</b>. Holotype (SBMNH 83518, ex. CRC 12843). Paratype (BMSM 17981, ex CRC 12842) from type locality.</p> <p> <b>Type localit</b> y. 7 m, Sandy Cay, Abaco, Bahamas, 26.399˚N, 76.988˚W. August 13, 2005, leg. Colin Redfern.</p> <p> <b>Etymology.</b> Plicata, Latin for folded, -zona referring to the selenizone. Describing the diagnosing feature of the strongly upward folded selenizone.</p> <p> <b>Description.</b> Shell to 1.5 mm, trochiform, turreted. Protoconch 0.75 whorls, flocculent sculpture, no apertural varix, apertural margin straight. TI of 0.25–0.33 whorls, 11–12 axial cords, no spiral sculpture, interstices with irregularities. TII> 2 whorls. Shoulder convex, approximately 50 distinct axial cords on first whorl, becoming gradually less distinct to diffuse towards apertural margin; first spiral after 0.125–0.25 TII whorls, half to third strength of axials, increasing to 5–7 after 1 TII whorl, of equal strength as axials, forming raised points at intersection with axials; raised points best developed after 1.25 TII whorls; sculpture becoming less distinct with growth, forming subdued cancellate pattern. Suture little impressed, position descending with growth from 1.5 width of selenizone below selenizone, to mid base (~3 selenizone widths below selenizone). Base convex, evenly curving into umbilicus, barely constricted below selenizone; sculpture becoming weaker with growth and from selenizone towards base; reticulate sculpture with raised points at intersection below selenizone, subsequently approximately 13 low spiral steps. Aperture rounded, adumbilical portion of peristome flared. Selenizone slightly above periphery; keels of moderate strength, broken in early portion of whorl, appearing to have horizontal orientation, on last 0.5–0.66 whorls orientation of keels parallel to coiling axis; slit open, margins parallel. Animal unknown.</p> <p> <b>Differential diagnosis</b>. <i>Anatoma aedonia</i> Watson, 1886, from the Caribbean has a similar overall shape and similar protoconch. However, TI is of 1 whorl and has a distinct spiral cord in the position of the selenizone, the sculpture on TII remains the same throughout growth, with distinct axial cords, and very fine spiral lines, and the axial sculpture on the base extends to the umbilicus. Differential diagnosis based on examination of types in BMNH and NMW by SEM.</p> <p> <b>Distribution.</b> Known only from type locality.</p>Published as part of <i>Geiger, Daniel L. & Mclean, James H., 2010, New species and records of Scissurellidae and Anatomidae from the Americas (Mollusca: Gastropoda: Vetigastropoda), pp. 1-35 in Zootaxa 2356</i> on pages 20-22, DOI: <a href="http://zenodo.org/record/275645">10.5281/zenodo.275645</a>
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