The aim of this study was to develop a robust, quality controlled, and reproducible erythroid culture system to obtain high numbers of mature erythroblasts and red blood cells (RBCs). This was achieved using a fully controlled stirred‐tank bioreactor by the design of experiments (DOE) methods in the serum‐free medium by defining the appropriate culture parameters. Human cord blood CD34+ cells were first cultured in static flasks and then inoculated to stirred‐tank bioreactors. Cell diameter was gradually decreased and final RBC yields were significantly higher when cells were inoculated at sizes smaller than 12 μm. The larger immature cells in the basophilic stage did not survive, while smaller mature erythroid cells were successfully expanded at high agitation speeds, demonstrating that appropriate seeding timing is critical. A high inoculation cell density of 5 × 106 cells/ml was achieved reaching 1.5 × 107 cells/ml. By using DOE analysis fitted to precise stages of erythropoiesis, we were able to acquire the optimal culture parameters for pH (7.5), temperature (37°C), dissolved oxygen, agitation speed (500 rpm), inoculation timing (cell diameter 12–13 μm), media feeding regimen, and cell seeding density (5 × 106 cells/ml). The final pure RBCs showed appropriate functions compared with fresh donor RBCs, confirming that manufacturing mature RBCs with reproducibility is possible.

Presence is one of the goals of many virtual reality systems. Historically, in the context of virtual reality, the concept of presence has been associated much with spatial perception (bottom up process) as its informal definition of "feeling of being there" suggests. However, recent studies in presence have challenged this view and attempted to widen the concept to include psychological immersion, thus linking more high level elements (processed in a top down fashion) to presence such as story and plots, flow, attention and focus, identification with the characters, emotion, etc. In this paper, we experimentally studied the relationship between two content elements, each representing the two axis of the presence dichotomy, perceptual cues for spatial presence and sustained attention for (psychological) immersion. Our belief was that spatial perception or presence and a top down processed concept such as voluntary attention have only a very weak relationship, thus our experimental hypothesis was that sustained attention would positively affect spatial presence in a virtual environment with impoverished perceptual cues, hut have no effect in an environment rich in them. In order to confirm the existence of the sustained attention in the experiment, fMRI of the subjects were taken and analyzed as well.The experimental results showed that that attention had no effect on spatial presence, even in the environment with impoverished spatial cues.

Hudson Bay (HB), a large subarctic inland sea, is impacted by rapid climate change and anthropogenic disturbance. HB plays crucial roles in supporting resident and migratory species of birds and marine mammals, providing subsistence to coastal communities, and exporting nutrients into the western Labrador Sea. To better constrain the impact of river nutrients on the HB ecosystem and to obtain a contemporary reference point by which future change can be evaluated, we estimated fluxes of nitrate plus nitrite (N), phosphate (P), and silicate using contemporary and historical nutrient data in conjunction with discharge estimates produced by three global climate models. Concentrations and molar ratios of the different nutrients exhibited large contrasts between different sectors of HB, which is attributed to the diversity of geological settings across distinct watersheds. With respect to the needs of primary producers, river waters were characterized by a shortage of P during winter and spring (N:P molar ratios in dissolved nutrients >16), nearly balanced N:P ratios in summer, and a shortage of N during fall (N:P < 16). Southwestern rivers made the largest regional contribution to the total annual delivery of all nutrients, followed by modest contributions from southern and eastern rivers, and minor ones from northwestern rivers. While the regulation of river flow in the Nelson and La Grande rivers had no discernible impact on nutrient concentrations and ratios, it clearly shifted nutrient transports toward the winter when biological activity in the estuaries is reduced. Finally, the potential amount of new production supported by riverine N inputs was nearly two orders of magnitude (1.8 × 1011 g C yr−1) lower than the new production supported by marine nutrients (7.3 × 1012 g C yr−1). Although the potential contribution of river nutrients to new primary production is small (2.4%) at the bay-wide scale, it can be significant locally.

No abstract

Understanding of the primary production of phytoplankton in the Kara Sea (KS), the Laptev Sea (LS), and the East Siberian Sea (ESS) remains limited, despite the recognized importance of phytoplankton in the Arctic Ocean. To address this knowledge gap, we conducted three NABOS (Nansen and Amundsen Basins Observational System) expeditions in 2013, 2015, and 2018 to measure in situ primary production rates using a 13C-15N dual-tracer method and examine their major controlling factors. The main goals in this study were to investigate regional heterogeneity in primary production and derive its contemporary ranges in the KS, LS, and ESS. The daily primary production rates in this study (99 ± 62, 100 ± 77, and 56 ± 35 mg C m−2 d−1 in the KS, LS, and ESS, respectively) are rather different from the values previously reported in each sea mainly because of spatial and regional differences. Among the three seas, a significantly lower primary production rate was observed in the ESS in comparison to those in the KS and LS. This is likely mainly because of regional differences in freshwater content based on the noticeable relationship (Spearman, rs = −0.714, p < 0.05) between the freshwater content and the primary production rates observed in this study. The contemporary ranges of the annual primary production based on this and previous studies are 0.96–2.64, 0.72–50.52, and 1.68–16.68 g C m−2 in the KS, LS, and ESS, respectively. Further intensive field measurements are warranted to enhance our understanding of marine microorganisms and their community-level responses to the currently changing environmental conditions in these poorly studied regions of the Arctic Ocean.