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1.
Foveal flicker sensitivity at 0.5-30 Hz was measured as a function of the spectral density of external, white, purely temporal noise for a sharp-edged 2.5 deg circular spot (mean luminance 3.4 log phot td). Sensitivity at any given temporal frequency was constant at low powers of external noise, but then decreased in inverse proportion to the square root of noise spectral density. Without external noise, sensitivity as function of temporal frequency had the well-known band-pass characteristics peaking at about 10 Hz, as previously documented in a large number of studies. In the presence of strong external noise, however, sensitivity was a monotonically decreasing function of temporal frequency. Our data are well described (goodness of fit 90%) by a model comprising (i) low-pass filtering by retinal cones, (ii) high-pass filtering in the subsequent neural pathways, (iii) adding of the temporal equivalent of internal white spatiotemporal noise, and (iv) detection by a temporal matched filter, the efficiency of which decreases approximately as the power -0.58 of temporal frequency. 相似文献
2.
The Rules of Beeping: Exchanging Messages Via Intentional "Missed Calls" on Mobile Phones 总被引:1,自引:0,他引:1
Jonathan Donner 《Journal of Computer-Mediated Communication》2007,13(1):1-22
This article explores the practice of "beeping" or "missed calling" between mobile phone users, or calling a number and hanging up before the mobile's owner can pick up the call. Most beeps are requests to call back immediately, but they can also send a pre-negotiated instrumental message such as "pick me up now" or a relational sign, such as "I'm thinking of you." The practice itself is old, with roots in landline behaviors, but it has grown tremendously, particularly in the developing world. Based on interviews with small business owners and university students in Rwanda, the article identifies three kinds of beeps (callback, pre-negotiated instrumental, and relational) and the norms governing their use. It then assesses the significance of the practice using adaptive structuration theory. In concluding, the article contrasts beeping with SMS/text messaging, discusses its implications for increasing access to telecommunications services, and suggests paths for future research. 相似文献
3.
In Deutschland geh?rt der Einsatz von NEDAP-Wahlcomputern in immer mehr Gemeinden zum Alltag. Durch Untersuchungen zur Sicherheit
und Manipulierbarkeit konnten Erkenntnisse gewonnen werden, mit welchen Methoden manipulierte Software in den Wahlcomputer
eingebracht und Hardwarekomponenten ausgetauscht werden k?nnen. Dadurch ist erstmals eine Beurteilung der Eignung der NEDAP-Wahlcomputer
hinsichtlich der Anforderungen an manipulationsfeste, nachvollziehbare und transparente Wahlen m?glich. 相似文献
4.
A. Goifman J. Gun V. Gitis A. Kamyshny Jr. O. Lev J. Donner H. Brnick E. Worch 《Applied catalysis. B, Environmental》2004,54(4):225-235
Pyrolysed carbon supported cobalt porphyrin, an electrocatalyst that is frequently used for oxygen reduction in fuel cells, is evaluated for catalytic oxidation of hydrogen sulfide by dissolved dioxygen. The catalyst performs best after heat treatment at 880 °C, at pH 8. Analysis of the reaction products reveals that sulfur is the dominant product throughout the investigated pH range 5–10. The catalyst performs much better than powdered activated carbon, granular activated carbon and different other forms of unmodified carbon catalysts. This is as far as we know the first time that heat treated cobalt porphyrins are evaluated for non-electrocatalytic applications. 相似文献
5.
6.
One of the special pleasures of the Harry Potter stories is their send-up of modern consumer culture--from Bertie Botts' Every Flavour Beans (and they do mean every flavor) to Chocolate Frogs, which come complete with a collectible card featuring a celebrity witch or wizard. Potter's creator, J.K. Rowling, pokes fun at contemporary marketing and advertising with tongue-in-cheek warmth that manages to make her simultaneously attractive to Madison Avenue and the rest of us--a remarkable achievement. Max Barry's Jennifer Government, the satirical successor to his well-received first novel Syrup, takes a different angle on the consumer-marketing-gone-mad theme. 相似文献
7.
Laura Chekli Sherub Phuntsho Maitreyee Roy Enzo Lombi Erica Donner Ho Kyong Shon 《Water research》2013,47(13):4585-4599
Iron nanoparticles are becoming increasingly popular for the treatment of contaminated soil and groundwater; however, their mobility and reactivity in subsurface environments are significantly affected by their tendency to aggregate. Assessing their stability under environmental conditions is crucial for determining their environmental fate. A multi-method approach (including different size-measurement techniques and the DLVO theory) was used to thoroughly characterise the behaviour of iron oxide nanoparticles (Fe2O3NPs) under environmentally relevant conditions. Although recent studies have demonstrated the importance of using a multi-method approach when characterising nanoparticles, the majority of current studies continue to use a single-method approach.Under some soil conditions (i.e. pH 7, 10 mM NaCl and 2 mM CaCl2) and increasing particle concentration, Fe2O3NPs underwent extensive aggregation to form large aggregates (>1 μm). Coating the nanoparticles with dissolved organic matter (DOM) was investigated as an alternative “green” solution to overcoming the aggregation issue instead of using the more commonly proposed polyelectrolytes. At high concentrations, DOM effectively covered the surface of the Fe2O3NPs, thereby conferring negative surface charge on the particles across a wide range of pH values. This provided electrostatic stabilisation and considerably reduced the particle aggregation effect. DOM-coated Fe2O3NPs also proved to be more stable under high ionic strength conditions. The presence of CaCl2, however, even at low concentrations, induced the aggregation of DOM-coated Fe2O3NPs, mainly via charge neutralisation and bridging. This has significant implications in regards to the reactivity and fate of these materials in the environment. 相似文献
8.
9.
Carolin J. Curtaz Leonie Reifschlger Linus Strhle Jonas Feldheim Julia J. Feldheim Constanze Schmitt Matthias Kiesel Saskia-Laureen Herbert Achim Wckel Patrick Meybohm Malgorzata Burek 《International journal of molecular sciences》2022,23(7)
Brain metastases are the most severe tumorous spread during breast cancer disease. They are associated with a limited quality of life and a very poor overall survival. A subtype of extracellular vesicles, exosomes, are sequestered by all kinds of cells, including tumor cells, and play a role in cell-cell communication. Exosomes contain, among others, microRNAs (miRs). Exosomes can be taken up by other cells in the body, and their active molecules can affect the cellular process in target cells. Tumor-secreted exosomes can affect the integrity of the blood-brain barrier (BBB) and have an impact on brain metastases forming. Serum samples from healthy donors, breast cancer patients with primary tumors, or with brain, bone, or visceral metastases were used to isolate exosomes and exosomal miRs. Exosomes expressed exosomal markers CD63 and CD9, and their amount did not vary significantly between groups, as shown by Western blot and ELISA. The selected 48 miRs were detected using real-time PCR. Area under the receiver-operating characteristic curve (AUC) was used to evaluate the diagnostic accuracy. We identified two miRs with the potential to serve as prognostic markers for brain metastases. Hsa-miR-576-3p was significantly upregulated, and hsa-miR-130a-3p was significantly downregulated in exosomes from breast cancer patients with cerebral metastases with AUC: 0.705 and 0.699, respectively. Furthermore, correlation of miR levels with tumor markers revealed that hsa-miR-340-5p levels were significantly correlated with the percentage of Ki67-positive tumor cells, while hsa-miR-342-3p levels were inversely correlated with tumor staging. Analysis of the expression levels of miRs in serum exosomes from breast cancer patients has the potential to identify new, non-invasive, blood-borne prognostic molecular markers to predict the potential for brain metastasis in breast cancer. Additional functional analyzes and careful validation of the identified markers are required before their potential future diagnostic use. 相似文献
10.
The physicochemical properties and in vitro digestibility of selected cereals,tubers and legumes grown in China 总被引:1,自引:0,他引:1
Digestibility, gelatinization, retrogradation and pasting properties of starch in various cereal, tuber and legume flours were determined. Rapidly and slowly digestible starch and resistant starch were present in 11 selected flours. In general, cereal starches were more digestible than legume starches and tuber starches contained a high amount of resistant starch. Thermal and rheological properties of flours were different depending on the crop source. 相似文献