The existence and stability of MNg42+(Sb2F11−1)2 (Ng=Ar,Ne,He,M=Au, Ag, Cu) salt compounds are theoretically investigated in this study. This undertaking is carried out to address the following challenges: (1) synthesizing a bulk salt compound containing a noble gas lighter than krypton and (2) synthesizing the congeners of AuXe42+(Sb2F11−1)2 containing noble gases other than Xe. The reliability of our calculations on the MNg42+(Sb2F11−1)2 (Ng=Ar,Ne,He,M=Au, Ag, Cu) systems is assessed by benchmark calculations of the well-known AuXe42+(Sb2F11−1)2 salt. In the benchmark calculations, a two-pronged evaluation strategy, including direct and indirect evaluation methods, is used to theoretically investigate the spectroscopic constants of AuXe42+and the existence and stability of the AuXe42+(Sb2F11−1)2 salt. The validity of the theoretical calculation methods in the benchmark calculations of AuXe42+(Sb2F11−1)2 allows us to adopt a similar methodology to effectively predict the existence and stability of MNg42+(Sb2F11−1)2 (Ng=Ar,Ne,He,M=Au, Ag, Cu) salt compounds. Calculations based on the Born–Haber cycle using estimated lattice energies and some necessary ancillary thermochemical data show that MAr42+(Sb2F11−1)2 (M=Au, Ag, Cu) salt compounds can be synthesized. The upper-limit stable temperatures are estimated to be −224.43, −146.21, and −80.39 °C. The CuAr42+(Sb2F11−1)2salt compound is a promising candidate. Our calculations also show that the MNg42+(Sb2F11−1)2 (Ng=Ne,He,M=Au, Ag, Cu) salt compounds cannot be stabilized.
Grassland ecosystems account for more than 10% of the global CH4 sink in soils. A 4-year field experiment found that addition of P alone did not affect CH4 uptake and experimental addition of N alone significantly suppressed CH4 uptake, while concurrent N and P additions suppressed CH4 uptake to a lesser degree. A meta-analysis including 382 data points in global grasslands corroborated these findings. Global extrapolation with an empirical modeling approach estimated that contemporary N addition suppresses CH4 sink in global grassland by 11% and concurrent N and P deposition alleviates this suppression by 6%. The P alleviation of N-suppressed CH4 sink is primarily attributed to substrate competition, defined as the competition between ammonium and CH4 for the methane monooxygenase enzyme. The N and P impacts on CH4 uptake indicate that projected increases in N and P depositions might substantially affect CH4 uptake and alter the global CH4 cycle.
Carbazole (Cz) dimers in various cofacial conformations, including staggered (Stg), anti, and syn, were explored by means of ab initio calculations at SOS-MP2, SOS-CIS(D0), and additional coupled cluster calculation levels. As in other π-conjugated molecules, strong Cz excimers form in the syn conformation in both the S1 and T1 states, leading to significantly reduced optical excitation energies, whereas the dimers in the Stg and anti conformations, upon excitation, remain as simple excited dimers, showing similar optical energy gaps to that of the monomer. Being far more stable in the ground state, however, the Stg dimer turned out to be nearly isoenergetic to the syn dimer in the S1 state, and even more stable in the T1 state. In addition, a considerable potential energy barrier between the syn and Stg dimers was found in the calculated S1-state potential energy surface. Given that the ground-state intermolecular interactions are expected to govern the dimer conformations of Cz-based materials in the solid-state films of organic electronics, these results strongly demonstrate that the electronic excitation of Cz dimers do not necessarily lead to the strong excimer formation, unless Cz molecules were forced to be arranged in the syn conformation.
In this study, data from MODIS land surface temperature product level 3 (MOD11A2) were used to investigate the spatiotemporal variation of Eurasian lakes water surface temperature (LWST) from 2001 to 2015, and to examine the most influencing factors of that variation. The temperature of most lakes in the dry climate zone and in the equatorial climatic zone varied from 17 to 31°C and from 23 to 27 °C, respectively. LWSTs in the warm temperate and cold climatic zones were in the range of 20 to 27 °C and -0.6 and 17 °C, respectively. The average daytime LWST in the polar climate zone was -0.71°C in the summer. Lakes in high latitude and in the Tibetan Plateau displayed low LWST, ranging from –11°C to 26°C during the nighttime. Large spatial variations of diurnal temperature difference (DTD) was observed in lakes across Eurasia. However, variations in DTDs were small in lakes located in high latitude and in tropical rainforest regions. The shallow lakes showed a rapid response of LWST to solar and atmospheric forcing, while in the large and deep lakes, that response was sluggish. Results of this study demonstrated the applicability of remote sensing and MODIS LST products to capture the spatial-temporal variability of LWST across continental scales, in particular for the vast wilderness areas and protected environment in high latitude regions of the world. The approach can be used in future studies examining processes and factors controlling large scale variability of LWST.
Mussel adhesive proteins (MAPs) have great potential as bioglues, in particular in wet conditions. Although in vivo residue-specific incorporation of 3,4-dihydroxyphenylalanine (Dopa) in tyrosine-auxotrophic Escherichia coli cells allows production of bioengineered MAPs (bMAPs), the low production yield hinders the practical application of bMAPs. Such low production yield of Dopa-incorporated bMAPs (Dopa-bMAPs) was known to be caused by low translational activity of a noncanonical amino acid, Dopa, in E. coli cells. Herein, in order to enhance the production yield of Dopa-bMAPs, we investigated the coexpression of Dopa-recognizing tyrosyl-tRNA synthetases (TyrRSs). In order to use the Dopa-specific Methanococcus jannascii TyrRS (MjTyrRS-Dopa), we altered the anti-codon of tyrosyl-tRNA amber suppressor into AUA (MjtRNATyrAUA) to recgonize a tyrosine codon (MjtRNATyrAUA). Co-overexpression of MjTyrRS-Dopa and MjtRNATyrAUA increased the production yield of Dopa-MAP by 57%. Similarly, overexpression of E. coli TyrRS (EcTyrRS) led to a 72% higher production yield of Dopa-incorporated bMAP. Even with coexpression of Dopa-recognizing TyrRSs, Dopa-bMAPs have a high Dopa incorporation yield (over 90%) compared to Dopa-bMAPs prepared without any coexpression of TyrRS.
Taking hydrophilic and water-repellent soils from the Guishui River Basin as the research object, one-dimensional infiltration experiments were conducted to study the effects of soil water repellency on cumulative infiltration (CI) and the infiltration rate (IR). The test results show that, for the hydrophilic soil (HS) sample, the CI increases monotonously with time and the IR decreases monotonously. For the water-repellent soil (W-RS), however, the following characteristics were observed: (1) There is an inflection point in the CI and a sudden increase in IR. Larger values of the initial soil water content produce an earlier and more significant inflection point in CI, and a larger peak value of IR. (2) The post-peak stable IR is greater than that the pre-peak value, ignoring the beginning of rapid infiltration, and the overall IR presents a single peak. The applicability of various water infiltration models was analyzed for the two soil types. Numerical analysis suggests the following conclusions: (1) For both HS and W-RS, the Kostiakov function, Gamma function, and Beta function (BF) models exhibit good applicability. (2) For W-RS, the Gauss function model not only reflects the monotonous decrease in IR, but also produces a steady IR in the initial stage, a gradual increase before the peak value, and a gradual decrease after the peak value. Similarly, the BF model reflects the monotonous decrease in IR. A piecewise BF can also reflect the U-shaped change in rapid infiltration before the inflection point, as well as the gradual increase and right-skewed distribution curve of W-RS infiltration before and after the inflection point. The BF model achieves the best simulation accuracy and has the widest applicability.
Rationale, aims and objectives. Applying traditional industrial Quality Improvement (QI) methodologies to primary care is often inappropriate because primary care is best thought of as a network of highly interconnected agents in a complex adaptive system (CAS) that is particularly responsive to bottom-up rather than top-down management approaches. We report on a demonstration case study of improvements made in the Family Health Center (FHC) of the JPS Health Network in a refugee patient population that illustrate features of QI in a CAS framework as opposed to a traditional QI approach. Methods. We report on changes in health system utilization by new refugee patients of the FHC from 2016-2017 and summarize relevant theoretical understandings of quality management in complex adaptive systems. Results. Applying CAS principles in the FHC, utilization of the Emergency Department and Urgent Care by newly arrived refugee patients before their first clinic visit was reduced by more than half (total visits decreased from 31% to 14% of the refugee patients). Our review of the literature demonstrates that traditional top-down QI processes are most often unsuccessful in improving even a few single-disease metrics, and increases clinician burnout and penalizes clinicians who care for vulnerable patients. Improvement in a CAS occurs when front-line clinicians identify care gaps and are given the flexibility to learn and self-organize to enable new care processes to emerge, which are created from bottom-up leadership that utilize existing interdependencies made more sustainable as front-line clinicians use sensemaking to improve care processes. Conclusions and future directions. Recent reforms announced in primary care in Scotland, a few examples in the medical literature, and statements from some healthcare system leaders are examples of early adapters who are applying the principles of CAS to their QI efforts. Such initiatives and our example provide models for others to follow.
Pyrazolidines are very important compounds that widely exist in many natural products. Herein, we have employed high-level DFT calculations to systematically investigate the underlying mechanism of Cu(OTf)2 catalyzed [3+2] cycloaddition reactions that synthesis CF3substituted pyrazolidines. About eight possible initial configurations of the [3+2] reaction is considered and all relevant reactants, transition states and products are optimized. Based on these structures, IRC paths and the wavefunction analysis, we concluded that the Cu(OTf)2 catalyzed [3+2] cycloaddition follow a concerted asynchronous mechanism. The CN bond forms immediately after the formation of the CC bond. Among all eight reaction paths, the energy barrier for the [3+2] reaction that lead to the CF3substituted synpyrazolidine is the lowest one, ca. 3.2 kcal/mol, which might result in the diastereoselectivity that observed in experiment. We have also investigated the reaction processes that without Cu(OTf)2 molecule. The computational results indicate that the energy barriers that form the diastereoisomers are much closer and also larger than the Cu(OTf)2 catalyzed one. Therefore, Cu(OTf)2 catalyst plays an important role for the diastereoselectivity of the [3+2] cycloaddition reaction. Our present work not only gives the detail mechanism of the Cu(OTf)2 catalyzed [3+2] cycloaddition, but can also be helpful for the future designation of Cu(OTf)2 based cycloaddition processes.
Pathogen persistence in host communities is influenced by a hierarchy of heterogeneities from individual host to landscape-level attributes, but isolating the relative contributions of these heterogeneities is challenging. We developed theory to partition the influence of host species, habitat patches, and landscape connectivity on pathogen persistence within host-pathogen metacommunities. We used the framework to quantify the contributions of host species composition and habitat patch identity on the persistence of an amphibian pathogen across the landscape. By sampling over 11,000 hosts of six amphibian species, we found that a single host species could maintain the pathogen in 91% of the metacommunities we observed. Moreover, this dominant maintenance species contributed, on average, twice as much to landscape-level pathogen persistence compared to the most influential source patch in a metacommunity. Our analysis demonstrates substantial inequality in how species and patches contribute to pathogen persistence, with important implications for targeted disease management.
Clinical use of pancreatic beta islets for regenerative medicine applications requires mass production of functional cells. Current technologies are insufficient for large-scale production in a cost-efficient manner. Here, we evaluate advantages of a porous cellulose scaffold and demonstrate scale-up to a wicking-matrix bioreactor as a platform for culture of human endocrine cells. Scaffold modifications were evaluated in a multi-well platform to find the optimum surface condition for pancreatic cell expansion followed by bioreactor culture to confirm suitability. Preceding scale-up, cell morphology, viability and proliferation of primary pancreatic cells were evaluated. Two optimal surface modifications were chosen and evaluated further for insulin secretion, cell morphology and viable cell density for human induced pluripotent stem cell-derived pancreatic cells at different stages of differentiation. Scale-up was accomplished with uncoated, amine-modified cellulose in a miniature bioreactor, and insulin secretion and cell metabolic profiles were determined for 13 days. We achieved 10-fold cell expansion in the bioreactor along with a significant increase in insulin secretion compared with cultures on tissue-culture plastic. Our findings define a new method for expansion of pancreatic cells on wicking-matrix cellulose platform to advance cell therapy biomanufacturing for diabetes.
Calcium carbonate (CaCO3) is an inorganic compound which is widely used in industry, chemistry, construction, ocean acidification and biomineralization due to its rich constituent on earth and excellent performance, in which calcium carbonate hydrates are important systems. In Z.Y. Zou et al’s work (Science, 2019, 363, 396–400), they found a novel calcium carbonate hemihydrate phase, but the structure stability, optical and mechanical properties has not been studied. In this work, the stability, electronic, optical, and mechanical properties of novel calcium carbonate hydrates were investigated by using the first-principles calculations within density functional theory (DFT). CaCO3·xH2O (x=1/2, 1 and 6) are determined dynamically stable phases by phonon spectrum, but the Gibbs energy of reaction of CaCO3·1/2H2O is higher than other calcium carbonate hydrates. That’s why the CaCO3·1/2H2O is hard to synthesize in the experiments. In addition, the optical and mechanical properties of CaCO3·xH2O (x=1/2, 1 and 6) are expounded in detail. It shows that the CaCO3·1/2H2O has the largest bulk modulus, shear modulus, Young’s modulus with the values 60.51, 36.56 and 91.28 GPa with respect to other two calcium carbonate hydrates investigated in this paper. This work will provide guidance for experiments and its applications, such as biomineralization, geology, and industrial processes.
On the example of forty ion pairs, the study demonstrates how the core-level binding energy values can be calculated and used to plot theoretical spectra at a low computational cost using density functional theory methods. Three approaches for obtaining the binding energy values are based on delta Kohn–Sham (ΔKS) calculations, 1s Kohn–Sham orbital energies, and atomic charges. The ΔKS results show a good agreement between the available experimental X-ray photoelectron data. 1s Kohn–Sham orbital energies and atomic charges also correlate with the ΔKS results.
The Irtysh River is the main water resource of eastern Kazakhstan and its upper basin is severely affected by spring floods each year, primarily as a result of snowmelt. Knowledge of the large scale processes that influence the timing of these snow-induced floods is currently lacking, but critical for the management of water resources in the area. In this study, we evaluated the variability in winter-spring snow cover in five major sub-basins of the Upper Irtysh basin between 2000 and 2017 as a possible explanatory factor of spring flood events, assessing the time of peak snow cover depletion rate and snow cover disappearance from the MODIS MOD10A2 dataset. We found that on average, peak snow cover retreat occurs between 22 March and 14 April depending on the basin, with large inter-annual variations but no clear trend over the observation period. In contrast, the annual peak snow cover depletion rate displays a weak increasing trend over the study period and exceeded 5900 km2 day-1 in 2017. The timing of snow disappearance in spring shows significant correlations of up to 0.82 for the largest basin with winter indices of the Arctic Oscillation over the region. The primary driver is the impact of the large scale pressure anomalies upon the mean spring (MAM) air temperatures and resultant timing of snow cover disappearance, particularly at elevations 500-2000 m above sea level. This suggests a lagged effect of this atmospheric circulation pattern in spring snow cover retreat. The winter Arctic Oscillation index could therefore be incorporated into long-term runoff forecasts for the Irtysh. Our approach is easily transferable to other similar catchments, and could support flood management strategies in Kazakhstan and other countries.
Manually collected snow data are often considered as ground truth for many applications such as climatological or hydrological studies. However, there are many sources of uncertainty that are not quantified in detail. For the determination of water equivalent of snow cover (SWE), different snow core samplers and scales are used, but they are all based on the same measurement principle. We conducted two field campaigns with 9 samplers commonly used in observational measurements and research in Europe and northern America to better quantify uncertainties when measuring depth, density and SWE with core samplers. During the first campaign, as a first approach to distinguish snow variability measured at the plot and at the point scale, repeated measurements were taken along two 20 m long snow pits. The results revealed a much higher variability of SWE at the plot scale (resulting from both natural variability and instrumental bias) compared to repeated measurements at the same spot (resulting mostly from error induced by observers or very small scale variability of snow depth). The exceptionally homogeneous snowpack found in the second campaign permitted to almost neglect the natural variability of the snowpack properties and focus on the separation between instrumental bias and error induced by observers. Under such measurement conditions, the uncertainty in bulk snow density estimation is about 5% for an individual instrument and is close to 10% among different instruments. Results confirmed that instrumental bias exceeded both the natural variability and the error induced by observers, even in the case when observers were not familiar with a given snow core sampler.
The onset of acute illness may be accompanied by a profound sense of disorientation for patients. Addressing this vulnerability is a key part of a physician’s purview, yet well-intended efforts to do so may be impeded by myriad competing tasks in clinical practice. Resolving this dilemma goes beyond appealing to altruism, as its limitless demands may lead to physician burnout, disillusionment, and a narrowed focus on the biomedical aspects of care in the interest of self-preservation. The authors propose an ethic of hospitality that may better guide physicians in attending to the comprehensive needs of patients that have entered “the kingdom of the sick”. Using philosophical methods, the authors explore what compels people to present to emergent medical attention and why altruism may not offer physicians a sustainable way to address the vulnerabilities that occur in such situations. They then present the concept of hospitality from a Derridean perspective and use it to interpret a narrative case of an on-call paediatrician caring for an infant with bronchiolitis to demonstrate how this approach may be practically implemented in the acute care hospital context. Hospitality allows physicians to acknowledge that clinical presentations that are routine in their world may be disorienting and frightening to patients experiencing them acutely. Further, it recognizes that the vulnerability that accompanies acute illness may be compounded by the unfamiliarity of the hospital environment in which patients have sought support. While it is unlikely that anything physicians do will make the hospital a place where patients and caregivers will desire to be, hospitality may focus their efforts upon making it less unwelcoming. Specifically, it offers an orientation that supports patients in navigating the disorienting and unfamiliar terrains of acute illness, the hospital setting in which help is sought, and engagement with the health care system writ large.
We investigate the ability of mechanical and electronic density functional theory (DFT)-based embedding approaches to describe the solvent effects on nuclear magnetic resonance (NMR) shielding constants of the ⁹⁵Mo nucleus in the molybdate ion in aqueous solution. From the description obtained from calculations with two- and four-component relativistic Hamiltonians, we find that for such systems spin-orbit coupling effects are clearly important for absolute shielding values, but for relative quantities a scalar relativistic treatment provides a sufficient estimation of the solvent effects. We find that the electronic contributions to the solvent effects are relatively modest yet decisive to provide a more accurate magnetic response of the system, when compared to reference supermolecular calculations. We analyze the errors in the embedding calculations by statistical methods as well as through a real-space representation of NMR shielding densities, which are shown to provide a clear picture of the physical processes at play.
Local correlation methods rely on the assumption that electronic correlation is nearsighted. In this work, we develop a method to alleviate this assumption. The first step is to approximately decompose the electron correlation to the nearsighted and farsighted components based on the wavelength decomposition of electron correlation by Langreth and Perdew. The nearsighted component is then calculated using the recently developed embedded cluster density approximation (ECDA) which is a local correlation method formulated in the context of density functional theory. The farsighted component is calculated based on the system’s Kohn-Sham orbitals. The accuracy of this new method depends on the quality of the decomposition. We examined the method’s accuracy by patching the random phase approximation (RPA) correlation energy in a H₂₄ chain in which the electron correlation is highly nonlocal. This new method predicts bond stretching energies, RPA correlation potential, and Kohn-Sham eigenvalues in good agreement with the benchmarks. Our results demonstrate the importance of including the farsighted part of electron correlation for studying systems having nonlocal correlations.
In this work, geometries, stabilities and electronic properties of carbon monoxide (CO) molecule as an adsorbent on simple carbon nanotube (CNT) and N, B, S-doped carbon nanotubes (NCNT, BCNT and SCNT) with parallel and perpendicular configurations are fully considered using ONIOM, natural bond orbital (NBO), and quantum theory of atom in molecule (QTAIM) calculations. The adsorption energies (Ead) demonstrate that CO molecule could be adsorbed on the surface of the simple carbon nanotube with parallel configuration (CNT-p) and N-doped carbon nanotube with perpendicular configuration (NCNT-d) in exothermic process. QTAIM calculations are showed the close-shell (non-covalent) interactions between CO molecule and CNT or N, B, S-doped CNTs. Also, the energy gap (Eg) values between the highest occupied molecular orbital and the lowest unoccupied molecular orbital are calculated. In accordance to the results of energy gap, simple and N-doped carbon nanotubes could be used as CO-sensors.