Spectroscopy of PAH species in the gas phase Robinson, Michael S.; Beegle, Luther W.; Wdowiak, Thomas J.
Planetary and space science,
10/1995, Volume:
43, Issue:
10
Journal Article
Peer reviewed
At elevated temperatures, the structured CH stretch absorption occurring at room temperature of polycyclic aromatic hydrocarbon (PAH) molecules encapsulated in KBr coalesces to a single peak whose ...wavelength is a very close match for that of the observed 3.3 μm unidentified infrared band (UIR) emission feature (Flickinger and Wdowiak.
Astrophys. J.
362, L71-L74. 1990). The temperature of approximately 800 K is significant because a PAH molecule in the interstellar radiation field, upon absorption of an ultraviolet photon, is expected to be excited to an energy equivalent to temperatures of this order (Sellgren,
Astrophys. J.
277, 623 1984). Our previous study of PAH molecules in the vapor phase at 600–800 K showed that the C-H stretch PAH feature near 3.3 μm is at a shorter wavelength than in the condensed state (Flickinger
et al.,
Astrophys. J.
380, L43-L46, 1991). Recent work by Joblin
et al. (
1st Symp. on the Infrared Cirrus and Diffuse Interstellar Clouds. 1994) in a short path length diamond cell indicates the gas phase wavelength of the 3.3 μm region C-H stretch feature of naphthalene is directly proportional to temperature over a large temperature range. Laser-excited IR fluorescence studies have also suggested that the wavelength is sensitive to laser photon energy in a direct relationship (Williams and Leone,
The Diffuse Interstellar Bands Conf., 1994). Comprehensive studies of PAHs thermally excited up to the decomposition temperature are therefore important to carry out. We have utilized a long-path-length optical heat pipe to confirm that the wavelength of the peak of the C-H stretch band of naphthalene vapor obeys a direct relationship with temperature as reported by Joblin, and to demonstrate that this feature undergoes a strengthening with respect to the longer wavelength band due to an out-of-plane deformation (782 cm
−1) as temperature increases. The shift from 3067.6 to 3063.7 cm
−1 over the temperature range of 316–996 K seems to be linear and follows the relationship 1/λ (cm
−1) = 3071.4–7.89 × 10
−3
T (K). From this relationship we calculated the temperatures equivalent to excitation energies in both Type 1 (3.289 μm and Type 11 (3.296 μm) UIR objects (Tokunaga
et al.,
Astrophys. J.
380, 452–460, 1991) to be 3925 and 4691 K. respectively. The ratio of the strength of the C-H stretch feature relative to the CH out-of-plane deformation feature is observed to increase from 0.33 at 316 K to 0.57 at 996 K.
DIBs in captivity (?) Wdowiak, Thomas J.; Beegle, Luther W.; Robinson, Michael S. ...
Planetary and space science,
10/1995, Volume:
43, Issue:
10
Journal Article
Peer reviewed
Experiments involving the electrical discharge of trace amounts (0.5%) of methane in argon gas followed by freezing out of products of the discharge in an argon matrix at 10 K have produced ...absorption bands of known interstellar molecular species, including CH, C
2 (anion form), C
3 and HCO (“a frozen interstellar cloud”). These experiments also repeatedly produce absorption bands that correlate in approximate wavelength with those of some of the stronger diffuse interstellar bands (DIBs). Among the interesting absorption bands produced in our experiments is a strong, broad band at 4500 Å. It is well known that because there is a difference between interaction of lower and higher energy states of a molecule or ion with the matrix, the absorption for a matrix-isolated species occurs at a different wavelength(s) than for the gas phase. Progressing from polar matrices to argon. and on to neon, the absorption wavelength converges toward what occurs in or is expected for the gas phase. Neon matrices affect an isolated species the least, with the result that wavelengths of absorptions are very close (∼ 0.1%) to that of the gas phase. The two 9700 Å region bands of the matrix-isolated C
60 cation shift blueward when isolated in neon, by 94 and 86 Å from what they are in argon (Gasyna. Z.
et al., J. phys. Chem.,
96, 1525–1527. 1992; Joblin. C. M., Ph.D. thesis, University of Paris. 1992). Isolated in neon, the pyrene cation exhibits an absorption at 4395 Å. which is blueward by 40 Å from the wavelength measured in argon (Salami, F. and Allamandola, L. J.,
Astrophys. J.,
395, 301–306, 1992;
Nature,
358, 42–43, 1992). These results strongly suggested that the 4500 Å band due to a reactive and as yet unidentified species isolated in argon in our experiments could shift blueward in the gas phase to coincide with the strong DIB at 4428 Å (Wdowiak. T. J.
et al., The Diffuse Interstellar Bands, 1994;
Molecules and Grains in Space, 1994). Recently, it has been demonstrated that the absorption seen in an argon matrix at 4500 Å for the photolysis product of methylpyrene shifts 60 Å to 4440 Å (Leger, A. and d'Hendecourt, L.,
The Diffuse Interstellar Bands, 1995) or 4442 Å (Salarna, F. and Allamandola, L. J.,
The Diffuse Interstellar Bands, 1995). All of this strongly argues for intensive investigation of the band found in our experiments at 4500 Å as a significant laboratory analog for the 4428 Å DIB. Efforts are in progress to better characterize the nature of the absorption, optimize its production in a more controlled manner and identify the ‘culprit’. This report discusses the relative strength of the 4500 Å band as compared with that of those bands due to identified species such as C
2 (anion) and C
3, and the results of laser-induced fluorescence experiments. Future experiments will include the more difficult neon matrix isolation technique and laser desorption mass spectroscopy.
Pluripotent stem cells are a promising source of endothelial cells (ECs) for the treatment of vascular diseases. We have developed a robust protocol to differentiate human induced pluripotent stem ...cells (hiPSCs) and embryonic stem cells (hESCs) into ECs with high purities (94%‐97% CD31+ and 78%‐83% VE‐cadherin+) in 8 days without cell sorting. Passaging of these cells yielded a nearly pure population of ECs (99% of CD31+ and 96.8% VE‐cadherin+). These ECs also expressed other endothelial markers vWF, Tie2, NOS3, and exhibited functions of ECs such as uptake of Dil‐acetylated low‐density lipoprotein and formation of tubes in vitro or vessels in vivo on matrigel. We found that FGF2, VEGF, and BMP4 synergistically induced early vascular progenitors (VPs) from hiPSC‐derived mesodermal cells. The MAPK and PI3K pathways are crucial not only for the initial commitment to vascular lineages but also for the differentiation of vascular progenitors to ECs, most likely through regulation of the ETS family transcription factors, ERG and FLI1. We revealed novel roles of the p38 and JNK MAPK pathways on EC differentiation. Furthermore, inhibition of the ERK pathway markedly promoted the differentiation of smooth muscle cells. Finally, we demonstrate that pluripotent stem cell‐derived ECs are capable of forming patent blood vessels that were connected to the host vasculature in the ischemic limbs of immune deficient mice. Thus, we demonstrate that ECs can be efficiently derived from hiPSCs and hESCs, and have great potential for vascular therapy as well as for mechanistic studies of EC differentiation. Stem Cells 2017;35:909–919
Following the 2010 Deepwater Horizon accident of a massive blow-out in the Gulf of Mexico, scientists from government, industry, and academia collaborated to advance oil spill modeling and share best ...practices in model algorithms, parameterizations, and application protocols. This synergy was greatly enhanced by research funded under the Gulf of Mexico Research Initiative (GoMRI), a 10-year enterprise that allowed unprecedented collection of observations and data products, novel experiments, and international collaborations that focused on the Gulf of Mexico, but resulted in the generation of scientific findings and tools of broader value. Operational oil spill modeling greatly benefited from research during the GoMRI decade. This paper provides a comprehensive synthesis of the related scientific advances, remaining challenges, and future outlook. Two main modeling components are discussed: Ocean circulation and oil spill models, to provide details on all attributes that contribute to the success and limitations of the integrated oil spill forecasts. These forecasts are discussed in tandem with uncertainty factors and methods to mitigate them. The paper focuses on operational aspects of oil spill modeling and forecasting, including examples of international operational center practices, observational needs, communication protocols, and promising new methodologies.
Background
Synaptic Ras GTPase activating protein 1 (SYNGAP1)‐related non‐specific intellectual disability is a neurodevelopmental disorder caused by an insufficient level of SynGAP1 resulting in a ...dysfunction of neuronal synapses and presenting with a wide array of clinical phenotypes. Hematopoietic stem cell gene therapy has the potential to deliver therapeutic levels of functional SynGAP1 to affected neurons upon transduction of hematopoietic stem and progenitor cells with a lentiviral vector.
Methods
As a novel approach toward the treatment of SYNGAP1, we have generated a lentiviral vector expressing a modified form of SynGAP1 for transduction of human CD34+ hematopoietic stem and progenitor cells. The gene‐modified cells were then transplanted into adult immunodeficient SYNGAP1+/− heterozygous mice and evaluated for improvement of SYNGAP1‐related clinical phenotypes. Expression of SynGAP1 was also evaluated in the brain tissue of transplanted mice.
Results
In our proof‐of‐concept study, we have demonstrated significant improvement of SYNGAP1‐related phenotypes including an improvement in motor abilities observed in mice transplanted with the vector transduced cells because they displayed decreased hyperactivity in an open field assay and an increased latency to fall in a rotarod assay. An increased level of SynGAP1 was also detected in the brains of these mice.
Conclusions
These early‐stage results highlight the potential of this stem cell gene therapy approach as a treatment strategy for SYNGAP1.
A lentiviral vector encoding a modified form of SYNGAP1 is transduced into hematopoietic stem and progenitor cells (HSPCs). These gene‐modified HSPC will differentiate into mature immune system cells. A portion of these cells will migrate to the brain where they will reside as microglia. The gene‐modified microglia will express and secrete functional SynGAP1 protein to the affected neurons.
Since the 2010 Deepwater Horizon (DWH) oil spill, the Gulf of Mexico Research Initiative (GOMRI) has studied the oil spill from the perspectives of ocean environment, ecosystems, socioeconomics and ...human health. As GOMRI sunsets in its tenth year after the DWH oil spill, synthesis efforts recently took place to assess the accomplishments of the program. In this paper, we report on DWH modeling as part of GOMRI's Synthesis and Legacy effort. We compile a list of 330 published applications by GOMRI, the Natural Resource Damage Assessment (NRDA), and others studying the DWH oil spill and look at a wide range of subjects, tools, achievements, and integration with field research. We offer highlights and synthesis based on discussions and public webinars held in 2019 and 2020. We synthesize the significant achievements and advancements that have been made in integrating the various disciplines and domains from a modeling perspective. There was a large diversity of tools used, including at least 74 unique modeling systems. Most studies employed circulation models. These hydrodynamic models were often coupled to wave, river, and atmosphere models, as well as representations of high pressure physics and oil chemistry. Several research groups used Lagrangian transport models and statistical inference to track subsurface oil. Some coupled biophysical models were also employed to study oil fate and weathering, larval transport, biological effects, and population dynamics. In a few cases, such biophysical models were linked to marine populations and to humans through socioeconomics effects and ecosystem services. We consider models made for response planning and remediation, damage assessment, and restoration planning. There are relatively few socioeconomic or human health models, although those few examples make good use of biophysical modeling products. Our conclusions offer some insights on how the development of new tools has better prepared us for studying environmental management challenges in the Gulf of Mexico.
Winter manure application elevates nutrient losses and impairment of water quality as compared to manure applications in other seasons. In conjunction with reviewing global distribution of animal ...densities, we reviewed worldwide mandatory regulations and voluntary guidelines on efforts to reduce off-site nutrient losses associated with winter manure applications. Most of the developed countries implement regulations or guidelines to restrict winter manure application, which range from a regulative ban to guidelines based upon weather and field management conditions. In contrast, developing countries lack such official directives, despite an increasing animal production industry and concern over water quality. An analysis of five case studies reveals that directives are derived from a common rationale to reduce off-site manure nutrient losses, but they are also affected by local socio-economic and biophysical considerations. Successful programs combine site-specific management strategies along with expansion of manure storage to offer farmers greater flexibility in winter manure management.
Timing of manure application to agricultural soils remains a contentious topic in nutrient management planning, particularly with regard to impacts on nutrient loss in runoff and downstream water ...quality. We evaluated the effects of seasonal manure application and associated manure storage capacity on phosphorus (P) losses at both field and watershed scales over an 11‐yr period, using long‐term observed data and an upgraded, variable‐source water quality model called Topo‐SWAT. At the field level, despite variation in location and crop management, manure applications throughout fall and winter increased annual total P losses by 12 to 16% and dissolved P by 19 to 40% as compared with spring. Among all field‐level scenarios, total P loss was substantially reduced through better site targeting (by 48–64%), improving winter soil cover (by 25–46%), and reducing manure application rates (by 1–23%). At the watershed level, a scenario simulating 12 mo of manure storage (all watershed manure applied in spring) reduced dissolved P loss by 5% and total P loss by 2% but resulted in greater P concentrations peaks compared with scenarios simulating 6 mo (fall‐spring application) or 3 mo storage (four‐season application). Watershed‐level impacts are complicated by aggregate effects, both spatial and temporal, of manure storage capacity on variables such as manure application rate and timing, and complexities of field and management. This comparison of the consequences of different manure storage capacities demonstrated a tradeoff between reducing annual P loss through a few high‐concentration runoff events and increasing the frequency of low peaks but also increasing the annual loss.
Core Ideas
Spring manure application had less field‐level P loss than fall or winter application.
The impact of application timing depended on precipitation and field characteristics.
Changes in manure storage capacity did not significantly affect annual watershed P loss.
Twelve‐month storage barely reduced P loads but created greater P concentration peaks.
Optimizing site targeting and soil cover is needed for all seasonal applications.
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