Re: Carbon Scatter 2015.epub
Roan Distilo
We investigated the relationship between daily growth rates and diel variation of carbon (C) metabolism and C to nitrogen (N) ratio under P- and N-limitation in the green algae Chlorella autotrophica. To do this, continuous cultures of C. autotrophica were maintained in a cyclostat culture system under 14:10 light:dark cycle over a series of P- and N-limited growth rates. Cell abundance, together with cell size, as reflected by side scatter signal from flow cytometric analysis demonstrated a synchronized diel pattern with cell division occurring at night. Under either type of nutrient limitation, the cellular C:N ratio increased through the light period and decreased through the dark period over all growth rates, indicating a higher diel variation of C metabolism than that of N. Daily average cellular C:N ratios were higher at lower dilution rates under both types of nutrient limitation but cell enlargement was only observed at lower dilution rates under P-limitation. Carbon specific growth rates during the dark period positively correlated with cellular daily growth rates (dilution rates), with net loss of C during night at the lowest growth rates under N-limitation. Under P-limitation, dark C specific growth rates were close to zero at low dilution rates but also exhibited an increasing trend at high dilution rates. In general, diel variations of cellular C:N were low when dark C specific growth rates were high. This result indicated that the fast growing cells performed dark C assimilation at high rates, hence diminished the uncoupling of C and N metabolism at night.
Context. In the course of the Turn Off Primordial Stars (TOPoS) survey, aimed at discovering the lowest metallicity stars, we have found several carbon-enhanced metal-poor (CEMP) stars. These stars are very common among the stars of extremely low metallicity and provide important clues to the star formation processes. We here present our analysis of six CEMP stars.
Conclusions. Our measured carbon abundances confirm the bimodal distribution of carbon in CEMP stars, identifying a high-carbon band and a low-carbon band. We propose an interpretation of this bimodality according to which the stars on the high-carbon band are the result of mass transfer from an AGB companion, while the stars on the low-carbon band are genuine fossil records of a gas cloud that has also been enriched by a faint supernova (SN) providing carbon and the lighter elements. The abundance pattern of the UIP stars shows a large star-to-star scatter in the [X/Ca] ratios for all elements up to aluminium (up to 1 dex), but this scatter drops for heavier elements and is at most of the order of a factor of two. We propose that this can be explained if these stars are formed from gas that has been chemically enriched by several SNe, that produce the roughly constant [X/Ca] ratios for the heavier elements, and in some cases the gas has also been polluted by the ejecta of a faint SN that contributes the lighter elements in variable amounts. The absence of lithium in four of the five known unevolved UIP stars can be explained by a dominant role of fragmentation in the formation of these stars. This would result either in a destruction of lithium in the pre-main-sequence phase, through rotational mixing or to a lack of late accretion from a reservoir of fresh gas. The phenomenon should have varying degrees of efficiency.
Analysis of the Raman spectral parameters of the polychrome samples and comparison with those of carbon-based pigment references allowed the identification of wood charcoal, lampblack, bistre and a black earth pigment. Complementary analysis by infrared spectroscopy and elemental analysis supported the assignments.
In this study we have provided new evidence that Raman microscopy is a powerful technique for the discrimination of carbon-based pigments in works of art. This is the first time that bistre, lampblack and a black earth pigment are identified in colonial art. The chemical information obtained on the black pigments contributed to increase our knowledge on available resources and technology used in the manufacture of the polychrome sculptures at the Jesuit Mission. This information is relevant for our studies on Colonial art.
Black layers of samples SGM8, TRI8, SLP6 and SBN1 showed Raman spectra with D and G broad bands (Figure 5), characteristic of amorphous carbon. On the other hand, spectra from SGM8 sample also revealed the presence of iron-manganese oxide compounds.
In Figure 6, references and sculpture samples were arranged according to the increasing value of ID/IG ratio, suggesting different sources for the carbon-based pigments in samples SGM8, TRI8, SLP6, and SBN1 (0.67, 0.75, 0.95, and 0.82, respectively).
Multi-walled carbon nanotubes (MWCNTs) constitute one of the most promising types of nanomaterials in industry today. With their increasing use, the potential toxicity and carcinogenicity of MWCNT needs to be evaluated in bioassay studies using rodents. Since humans are mainly exposed to MWCNT by inhalation, we performed a 104-week carcinogenicity study using whole-body inhalation exposure chambers with a fibrous straight type of MWCNT at concentrations of 0, 0.02, 0.2, and 2 mg/m3 using male and female F344 rats.
One of the most important developments in industrial technology is nanotechnology. Various nanomaterials, especially carbon nanotubes (CNTs), have exceptional electrical, mechanical, and thermal properties, enabling the commercialization of various types of CNTs for use with numerous applications in industry, and in recent years the production of CNTs has significantly increased [1]. On the other hand, with the rapid growth of CNT use, serious concerns have been expressed about their adverse effects on the health of workers during CNT manufacturing and handling processes and on the health of consumers exposed to commercial end products containing CNTs. At present, however, neither epidemiological nor medical case studies have been reported on health consequences in CNT-exposed workers or consumers.
a MWNT-7 concentrations in the inhalation chambers during the 104-week experimental period. Concentrations of MWNT-7 particles in the inhalation chamber were monitored by the optical particle controller throughout each 6 h exposure period during the 104 weeks of the study. Mass concentrations (mg/m3) of MWNT-7 in the chambers was calibrated by multiplying the CPM by the mass per particle (see Methods for details). The target concentrations of MWNT-7 were 0.02, 0.2, and 2 mg/m3; panel A shows the measured concentrations of MWNT-7 aerosols in the chambers. b and c SEM images of MWNT-7 in the inhalation chamber. SEM images of MWNT-7 in the chamber are shown in panels b and c. The fibers shown in the figure were collected on a polycarbonate filter at 1-week and 102 weeks. The MWNT-7 aerosol was in the form of individual and fibers in all groups. Bar, 5 μm
Based on animal experimental studies, IARC [53] evaluated MWNT-7 as being a possible carcinogen to humans (Group 2B). NIOSH (2013) [54] proposed an 8-h time-weighted average concentration of 1 μg/m3 as the Recommended Exposure Limit (REL) for the respirable mass fraction of elemental carbon, single or multi-walled carbon nanotubes, and carbon nanofibers.
To observe MWNT-7 in the lung, lung tissues were digested according to the method of Kohyama et al. [61]. The lung tissues were left for 5 days in the digestion solution. The solution was then filtered and specimens collected on polycarbonate membrane filters (Isopore, Millipore, MA, USA) pre-coated with Pt for electron charge avoidance. The specimens were observed by SEM.
At terminal necropsy, the pleural cavity of ten animals was lavaged once with 8 ml MEM, and the abdominal cavity of ten other animals was lavaged once with 40 ml MEM. The washout was collected and centrifuged at 12,000 rpm (3000 g) at 15 C for 10 min. The supernatant was removed and the pellet was digested according to the method of Kohyama et al. [61]. A polycarbonate membrane filter (Isopore, Millipore, MA, USA) pre-coated with Pt for electron charge avoidance was positioned on a suction filtration apparatus, and MWNT-7 fibers were collected onto the filter. The morphology of the fibers was determined by SEM examination, and the number of MWNT-7 fibers was counted.
Abstract:Global carbon fluxes describe the carbon exchange between land and atmosphere. However, already available global carbon fluxes datasets have not been adjusted by the available site data and deep learning tools. In this work, a global carbon fluxes dataset (named as GCFD) of gross primary productivity (GPP), terrestrial ecosystem respiration (RECO), and net ecosystem exchange (NEE) has been developed via a deep learning based convolutional neural network (CNN) model. The dataset has a spatial resolution of 1 km at three time steps per month from January 1999 to June 2020. Flux measurements were used as a training target while remote sensing of vegetation conditions and meteorological data were used as predictors. The results showed that CNN could outperform other commonly used machine learning methods such as random forest (RF) and artificial neural network (ANN) by leading to satisfactory performance with R2 values of the validation stage as 0.82, 0.72 and 0.62 for GPP, RECO, and NEE modelling, respectively. Thus, CNN trained using reanalysis meteorological data and remote sensing data was chosen to produce the global dataset. GCFD showed higher accuracy and more spatial details than some other global carbon flux datasets with reasonable spatial pattern and temporal variation. GCFD is also in accordance with vegetation conditions detected by remote sensing. Owing to the obtained results, GCFD can be a useful reference for various meteorological and ecological analyses and modelling, especially when high resolution carbon flux maps are required.Keywords: carbon flux; machine learning; gross primary production; terrestrial ecosystem respiration; net ecosystem exchange
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