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Minimum Length (minimum + length)
Selected AbstractsRandom controls on semi-rhythmic spacing of pools and riffles in constriction-dominated riversEARTH SURFACE PROCESSES AND LANDFORMS, Issue 11 2001Douglas M. Thompson Abstract Average pool spacing between five and seven bankfull widths has been documented in environments throughout the world, but has limited theoretical justification in coarse-bedded and bedrock environments. Pool formation in coarse-bedded and bedrock channels has been attributed to bedrock and boulder constrictions. Because the spacing of these constrictions may be irregular in nature, it is difficult to reconcile pool-formation processes with the supposedly rhythmic spacing of pools and riffles. To address these issues, a simulation model for pool and riffle formation is used to demonstrate that semi-rhythmic spacing of pools with an approximate spacing of five to seven bankfull widths can be recreated from a random distribution of obstructions and minimum pool- and riffle-length criteria. It is assumed that a pool,riffle couplet will achieve a minimum length based on dominant-discharge conditions. Values for the minimum-length assumption are based on field data collected in New England and California, while the theoretical basis relies on the demonstrated hydraulic response of individual pools to elongation. Results from the simulations show that the location of pools can be primarily random in character, but still assume an average spacing between four and eight bankfull widths for a variety of conditions. Field verification data generally support the model but highlight a highly skewed distribution of pool-forming elements and pool spacing. The relation between pool spacing and bankfull widths is attributed to the common geometric response of these features to dominant-discharge conditions. Copyright © 2001 John Wiley & Sons, Ltd. [source] Cyst-based toxicity tests XIII,Development of a short chronic sediment toxicity test with the ostracod crustacean Heterocypris incongruens: Methodology and precisionENVIRONMENTAL TOXICOLOGY, Issue 6 2002Belgis Chial Abstract Experiments were carried out with neonates of the freshwater ostracod Heterocypris incongruens to verify and complete previous choices of test parameters for a new culture/maintenance-free solid-phase microbiotest for freshwater sediments. From trials with increasing volumes of reference sediment, it was concluded that 300 ,L was the most appropriate amount of substrate to be put in 12-cup multiwell plates with 2 mL of standard freshwater. Tests in 3,9 replicates eventually showed that six parallels were needed to have good assay precision (repeatability). Application of the final test protocol to oil-contaminated sediments from the St. Lawrence River in Canada revealed that the 6-day chronic ostracod microbiotest had less variation in repeated tests than did the 10-day contact assay with Hyalella azteca and hence can be considered more precise. Based on the 95% confidence intervals for mortality and growth of the ostracods in the controls (reference sediment) of the 56 tests carried out for the Canadian project, a validity threshold of 20% for mortality was eventually selected, in analogy with the acceptability limits applied in many chronic bioassays. A minimum length of 600 ,m in the control sediment after 6 days' exposure was also taken as the threshold for good health of the test organisms and for reliable test conditions. The new microbiotest has been tailored in a handy and user-friendly new toxkit, the Ostracodtoxkit, which is particularly suited for cost-effective routine monitoring. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 528,532, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10086 [source] Increasing the vertical resolution of conventional sub-bottom profilers by parametric equalizationGEOPHYSICAL PROSPECTING, Issue 2 2002P. Cobo ABSTRACT Vertical resolution, i.e. the ability to resolve two close reflectors, is a crucial aspect of pulses used in geo-acoustic exploration of sea sub-bottoms. This paper deals with the problem of exploring the shallowest unconsolidated layers of the seafloor with conventional piezo-electric sonar pulses. Such transducers do not have a sufficiently broad transmission response to enable them to radiate short high-resolution pulses. Therefore, some kind of equalization process must be applied to broaden the transmission response. Here, inverse filtering is used to calculate the transducer driving waveform so that the subsequent acoustic pulse has a zero-phase cosine-magnitude nature. Within a specified bandwidth, this pulse has minimum length, i.e. maximum resolution. The method has been applied to compress the acoustic pulses radiated by two piezo-electric transducers. In conventional performance, these transducers radiate narrowband pulses which contain several cycles at the natural resonance frequency. Under equalized driving, both transducers emit broadband pulses, with resolving power greatly increased, at the cost of some amplitude loss. That is, the pulses radiated by both transducers have been shortened from 1 ms (low-frequency transducer) and 0.274 ms (high-frequency transducer) in conventional performance to 0.13 ms and 0.038 ms in equalized mode, with amplitude losses of 33% and 56%, respectively. The great improvement in the resolution of this technique is demonstrated by comparing the synthetic echograms that should be obtained when exploring a wedge model using zero-phase cosine-magnitude pulses with conventional ping pulses. [source] Investigation of penetratin peptides.JOURNAL OF PEPTIDE SCIENCE, Issue 12 2005Part 2. Abstract As endocytic uptake of the Antennapedia homeodomain-derived penetratin peptide (RQIKIWFQNRRMKWKK) is finally being revealed, some of the early views about penetratin need to be reconsidered. Endocytic uptake seems to contradict the indispensability of tryptophans and also the minimum length of 16 amino acid residues for efficient internalization. To revise the membrane translocation of penetratin, two penetratin analogs were designed and synthesized: a peptide in which tryptophans were replaced by phenylalanines (Phe6, 14 -penetratin, RQIKIFFQNRRMKFKK) and a shortened analog (dodeca-penetratin, RQIKIWF-R-KWKK) made up of only 12 residues. The peptides were fluorescently labeled and applied to live, unfixed cells from various lines. Cellular uptake was analysed by confocal microscopy and flow cytometry. Low temperature or ATP-depletion blocked the intracellular entry of all three penetratin peptides. A decrease in membrane fluidity or cholesterol depletion with methyl-,-cyclodextrin greatly inhibited peptide uptake, showing the involvement of cholesterol-rich lipid rafts in internalization. Exogenous heparan sulfate also diminished the internalization of penetratin and its derivatives, reflecting the paramount importance of electrostatic interactions with polyanionic cell-surface proteoglycans. The beneficial presence of tryptophans is supported by observations on the decreased cellular uptake of Phe6, 14 -penetratin. The maintained translocational efficiency of dodeca-penetratin demonstrates that a thorough understanding of penetratin internalization can yield new penetratin analogs with unaltered translocational abilities. This study provides evidence on the energy-dependent and lipid raft-mediated endocytic uptake of penetratin and highlights the necessity of revealing those pathways that cationic cell-penetrating peptides employ to enter live cells. Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd. [source] Diversity dual-band planar inverted-F antenna for WLAN operationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2003Kin-Lu Wong Abstract A printed diversity dual-band planar inverted-F antenna (PIFA) mounted vertically at the edge of a PCMCIA network card (such that the protruded portion of the network card from the housing of the laptop has a minimum length) for WLAN operation in the 2.4-GHz band (2400,2484 MHz) and 5.2-GHz band (5150,5350 MHz) is presented. The diversity antenna studied comprises two back-to-back stacked PIFAs and has a low profile of 10 mm to the network card. Across the two operating bands, the measured reflection coefficient S11 and isolation S21 are all less than ,14 dB (1.5:1 VSWR) and ,24 dB, respectively. In addition, the measured radiation patterns of the two stacked PIFAs in general cover complementary space regions, thereby making it possible for providing spatial diversity for WLAN operation. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 223,225, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11020 [source] Frequency Map Variations in Squirrel Monkey Primary Auditory Cortex,THE LARYNGOSCOPE, Issue 7 2005Steven W. Cheung MD Abstract Objective: The goal of this work is to understand the neural basis for cortical representation of hearing in highly vocal primates to gain insights into the substrates for communication. Variation patterns in frequency representation among animals are incorporated into an explanatory model to reconcile heterogeneous observations. Study Design: Prospective. Methods: Thirty-four squirrel monkeys underwent microelectrode mapping experiments in primary auditory cortex (AI) using tone pip stimuli. Characteristic frequency (CF) was extracted from the excitatory frequency receptive field. Frequency maps were reconstructed using Voronoi-Dirichlet tessellation. The spatial locations (rostral vs. caudal) of highest CF isofrequency contours (minimum length 1 mm) and highest CF neuronal clusters on the temporal gyral surface were analyzed. Results: Isofrequency contours at least 1 mm long with CFs greater than 2.9 kHz (75% cases) are accessible on the temporal gyrus. Variability of the highest CF isofrequency contours accessible on the temporal gyrus has an interquartile range from 2.9 to 5.1 (mean 4.3) kHz. The highest CF isofrequency contours are located mainly in rostral AI, whereas the highest CF neuronal clusters flanking fully expressed isofrequency contours are equally distributed in rostral and caudal locations. Conclusions: Squirrel monkey AI frequency map variations are sizeable across animals and small within single animals (interhemispheric comparison). AI frequency map variations, modeled as translations and rotations relative to the lateral sulcus, are independent transfers. Caution must be exercised when interpreting nominal frequency map changes that are attributed to hearing loss and auditory learning effects. [source] Characterization of New PPAR, Agonists: Analysis of Telmisartan's Structural ComponentsCHEMMEDCHEM, Issue 3 2009Matthias Goebel Abstract Telmisartan was originally designed as an AT1 antagonist but was later also characterized as a selective PPAR, modulator. This study focused on the identification of the essential structural motifs of telmisartan for PPAR, activation activity, elucidating the individual SAR of each different component (shown). In addition to a proven efficacy in lowering blood pressure, the AT1 receptor blocker telmisartan has recently been shown to exert pleiotropic effects as a partial agonist of the nuclear peroxisome proliferator-activated receptor gamma (PPAR,). Based on these findings and an excellent side-effect profile, telmisartan may serve as a lead structure for the development of new PPAR, ligands. Therefore, we analyzed the structural components of telmisartan to identify those necessary for PPAR, activation. Synthesized compounds were tested in a differentiation assay using 3T3-L1 preadipocytes and a luciferase assay with COS-7 cells transiently transfected with pGal4-hPPAR,DEF, pGal5-TK-pGL3 and pRL-CMV. The data obtained in this structure,activity relationship (SAR) study provide the basis for the development of new PPAR, ligands, which could lead to active compounds with a distinct, beneficial pharmacological profile compared with the existing full agonists. The basic 1-(biphenyl-4-ylmethyl)-1H -benzimidazole scaffold of telmisartan was identified as an essential moiety with either a carboxylic acid or tetrazole group at the C-2 position of the biphenyl. For maximum potency and activity, the alkyl chain in position 2 requires a minimum length of at least two C atoms (ethyl group), while the methyl group at position 4 of the benzimidazole core seems to contribute to partial activity. An additional benzimidazole at position 6 appears to be a further determinant of potency. Similar conclusions can be drawn for the methyl group in position 1. [source] Numerically stable algorithms for the computation of reduced unit cellsACTA CRYSTALLOGRAPHICA SECTION A, Issue 1 2004R. W. Grosse-Kunstleve The computation of reduced unit cells is an important building block for a number of crystallographic applications, but unfortunately it is very easy to demonstrate that the conventional implementation of cell reduction algorithms is not numerically stable. A numerically stable implementation of the Niggli-reduction algorithm of K,ivý & Gruber [Acta Cryst. (1976), A32, 297,298] is presented. The stability is achieved by consistently using a tolerance in all floating-point comparisons. The tolerance must be greater than the accumulated rounding errors. A second stable algorithm is also presented, the minimumreduction, that does not require using a tolerance. It produces a cell with minimum lengths and all angles acute or obtuse. The algorithm is a simplified and modified version of the Buerger-reduction algorithm of Gruber [Acta Cryst. (1973), A29, 433,440]. Both algorithms have been enhanced to generate a change-of-basis matrix along with the parameters of the reduced cell. [source] | |||||||||||||