Amazon.com

About: Amazon.com is a company organization based out in Seattle, Washington, United States. It is known for research contribution in the topics: Computer science & Service (business). The organization has 13363 authors who have published 17317 publications receiving 266589 citations.

Effects of Water pH and Calcium Concentration on Ion Balance in Fish of the Rio Negro, Amazon

Abstract: We examined the effects of acute low-pH exposure on ion balance (Na+, Cl-, K+) in several species of fish captured from the Rio Negro, a dilute, acidic tributary of the Amazon. At pH 5.5 (untreated Rio Negro water), the four Rio Negro species tested (piranha preta, Serrasalmus rhombeus; piranha branca, Serrasalmus cf. holandi; aracu, Leporinus fasciatus; and pacu, Myleus sp.) were at or near ion balance; upon exposure to pH 3.5, while Na+ and Cl- loss rates became significant, they were relatively mild. In comparison, tambaqui (Colossoma macropomum), which were obtained from aquaculture and held and tested under the same conditions as the other fish, had loss rates seven times higher than all the Rio Negro species. At pH 3.0, rates of Na+ and Cl- loss for the Rio Negro fish increased three- to fivefold but were again much less than those observed in tambaqui. Raising water Ca2+ concentration from 10 micromol L-1 to 100 micromol L-1 during exposure to the same low pH's had no effect on rates of ion loss in the three species tested (piranha preta, piranha branca, aracu), which suggests that either they have such a high branchial affinity for Ca2+ that all sites are saturated at 10 micromol L-1 and additional Ca2+ had no effect, or that Ca2+ may not be involved in regulation of branchial ion permeability. For a final Rio Negro species, the cardinal tetra (Paracheirodon axelrodi), we monitored body Na+ concentration during 5 d of exposure to pH 6.0, 4.0, or 3.5. These pH's had no effect on body Na+ concentration. These data together suggest that exceptional acid tolerance is a general characteristic of fish that inhabit the dilute acidic Rio Negro and raise questions about the role of Ca2+ in regulation of branchial ion permeability in these fish.

Floristic variation across 600 km of inundation forests (Igapó) along the Negro River, Central Amazonia

Abstract: We inventoried 10 ha of late-successional and seasonally inundated black-water floodplain (igapo) forest along four river sections of the Negro River, Central Amazonia, Brazil The aim of the study was to test if tree species composition and diversity changes along the river course, and whether these changes reflect the different geological formations of the Negro River On a continental-wide scale, we assessed alpha-diversity patterns of black-water flooded forests across the Amazon and Orinoco basins Phytosociological analyses include family and species importance, species similarity, and Fisher’s alpha-diversity, as well as Detrended Correspondence Analysis A total of 6126 individuals were recorded, belonging to 243 tree species Only few tree species occurred in more than one river section, and floristic composition changed abruptly from one section to the other Tree species richness ranged from 57 to 79 species ha−1, and alpha-diversity was highest (2724) in the lower river section upon sediments of Pliocene–Pleistocene origin We found a gradual decrease in species diversity with increasing age of the geological formations The igapo forest is relatively species-poor, which we interpret to be the result of general low nutrient availability in alluvial substrates of the Negro River

The Rate and Extent of Deforestation in Brazilian Amazonia

Abstract: Examination of the often contradictory estimates of the rate and extent of deforestation in Brazilian Amazonia leads to a ‘best estimate’ of the cumulative area of forest cleared through 1988 as 345 × 103 km2 (including old clearings), or 8.2% of the 4 × 106 km2 forested portion of Brasil's 5 × 106 km2 ‘Legal Amazon’ region.

Audio ALBERT: A Lite BERT for Self-supervised Learning of Audio Representation

Abstract: For self-supervised speech processing, it is crucial to use pretrained models as speech representation extractors. In recent works, increasing the size of the model has been utilized in acoustic model training in order to achieve better performance. In this paper, we propose Audio ALBERT, a lite version of the self-supervised speech representation model. We use the representations with two downstream tasks, speaker identification, and phoneme classification. We show that Audio ALBERT is capable of achieving competitive performance with those huge models in the downstream tasks while utilizing 91\% fewer parameters. Moreover, we use some simple probing models to measure how much the information of the speaker and phoneme is encoded in latent representations. In probing experiments, we find that the latent representations encode richer information of both phoneme and speaker than that of the last layer.

Multiple touch sensing modes

Abstract: A touch controller of a computing device can adjust various modes of operation of a touch panel in order to conserve resources on the device. The touch controller can dynamically adjust a rate at which touch sensors are scanned, or can scan touch sensors for the display panel using a different mode than for a single input button or other such element. The touch controller can also operate in a low power mode while the device is in standby, and then activate a high power mode of operation upon detecting an input such as a double tap. The touch controller can also alternate between low and high power modes of operation based at least in part upon a current application executing on the device.