RESUMO
The problem of nonlocal interactions in density functional theory calculations has in part been mitigated by the introduction of range-corrected functional methods. While promising solutions, the continued evaluation of range corrections in the structural simulations of complex molecular crystals is required to judge their efficacy in challenging chemical environments. Here, three pyridinium-based crystals, exhibiting a wide range of intramolecular and intermolecular interactions, are used as benchmark systems for gauging the accuracy of several range-corrected density functional techniques. The computational results are compared to low-temperature experimental single-crystal X-ray diffraction and terahertz spectroscopic measurements, enabling the direct assessment of range correction in the accurate simulation of the potential energy surface minima and curvatures. Ultimately, the simultaneous treatment of both short- and long-range effects by the ωB97-X functional was found to be central to its rank as the top performer in reproducing the complex array of forces that occur in the studied pyridinium solids. These results demonstrate that while long-range corrections are the most commonly implemented range-dependent improvements to density functionals, short-range corrections are vital for the accurate reproduction of forces that rapidly diminish with distance, such as quadrupole-quadrupole interactions.
RESUMO
The electrostatic assembly between a series of differently charged Mo-132-type Keplerates present in the compounds (NH4)42[{(Mo(VI))Mo(VI)5O21(H2O)6}12 {Mo(V)2O4(CH3COO)}30].ca. {300 H2O+10 CH3COONH4} (Mo-132a), (NH4)72-n[{(H2O)81-n+(NH4)n} {(Mo(VI))Mo(VI)5O21(H2O)6}12 {Mo(V)2O4(SO4)}30].ca. 200 H2O (Mo-132b), and Na10(NH4)62[{(Mo(VI))Mo(VI)5O21(H2O)6}12 {Mo(V)2O4(HPO4)}30]. ca. {300H2O+2Na(+)+2NH4(+)+4H2PO4(-)} (Mo-132c) with cationic gold nanoparticles (AuNPs) was investigated for the first time. The rapid electrostatic assembly from nanoscopic entities to micron scale aggregates was observed upon precipitation, which closely matched the point of aggregate electroneutrality. Successful assembly was demonstrated using UV-vis, DLS, TEM, and zeta-potential analysis. Results indicate that the point at which precipitation occurs is related to charge balance or electroneutrality, and that counterions at both the Mo-132 and AuNP play a significant role in assembly.
RESUMO
BACKGROUND: Brain Trauma Foundation guidelines recommend seizure prophylaxis for preventing early posttraumatic seizure (PTS). Phenytoin (PHE) is commonly used. Despite a paucity of data in traumatic brain injury, levetiracetam (LEV) has been introduced as a potential replacement, which is more costly but does not require serum monitoring. The purpose of this study was to compare the efficacy of PHE with that of LEV for preventing early PTS. METHODS: Consecutive blunt traumatic brain injury patients undergoing seizure prophylaxis were prospectively enrolled at two Level 1 trauma centers during a 33-month period. Seizure prophylaxis was administered according to local protocol. Patients were monitored prospectively throughout their hospital stay for clinical evidence of seizure activity. PHE was compared with LEV with clinical early PTS as the primary outcome measure, defined as a seizure diagnosed clinically, occurring within 7 days of admission. RESULTS: A total of 1,191 patients were screened for enrollment, after excluding 378 (31.7%) who did not meet inclusion criteria; 813 (68.3%) were analyzed (406 LEV and 407 PHE). There were no significant differences between LEV and PHE in age (51.7 [21.3] vs. 53.6 [22.5], p = 0.205), male (73.9% vs. 68.8%, p = 0.108), Injury Severity Score (ISS) (20.0 [10.0] vs. 21.0 [10.6], p = 0.175), Marshall score of 3 or greater (18.5% vs. 14.7%, p = 0.153), or craniectomy (8.4% vs. 11.8%, p = 0.106). There was no difference in seizure rate (1.5% vs.1.5%, p = 0.997), adverse drug reactions (7.9% vs. 10.3%, p = 0.227), or mortality (5.4% vs. 3.7%, p = 0.236). CONCLUSION: In this prospective evaluation of early PTS prophylaxis, LEV did not outperform PHE. Cost and need for serum monitoring should be considered in guiding the choice of prophylactic agent. LEVEL OF EVIDENCE: Therapeutic study, level III.