An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The plasmonic fields of silver and gold nanocubes are known to be among the strongest of any plasmonic metallic nanoparticles. Aggregation dominates their use in imaging and sensing applications due to the resulting enhancement of the plasmonic field in between the nanoparticles (hot spots). The first step in the aggregation process is dimerization. In the present work, we used the discrete dipole approximation (DDA) to calculate the interdimer separation dependence of the absorption and scattering components of the localized surface plasmon resonance (LSPR) extinction of homo and heterodimers of Ag and Au nanocubes when excited parallel to their interparticle axis. We also examined the changes in the nanocube surface plasmonic field distributions as the dimer separation was varied. The results from the homodimers were as expected: as the cubes were brought together, there was a red shift in the primary plasmon band in accordance with the universal scaling law. Additionally, as the particles moved together, scattering contributed more to the overall extinction. By examining the E-field distributions, we found that the hot spot geometry changes abruptly at small separations. At very short distances, the hot spot is located between the adjacent faces and away from the corners of these faces. At larger separations it moves toward the adjacent corners. We observed apparently anomalous behavior for the heterodimer. First, the E-field resulting from excitation of the Ag dominated plasmon resonance was significantly weaker than expected. Second, the red shift of the gold dominated plasmon resonance did not follow the universal scaling law. The most likely explanation for these observations is that the silver plasmon mixes strongly with the energetically resonant, but nonplasmonic, gold interband transition to form a hybrid resonance that produces weaker overall field intensity on the two nanocubes at short separation.
Rationale: Empirical antimicrobial therapy (EAT) for Acinetobacter infections may not be appropriate as it tends to be multidrug-resistant. This study evaluated the relationship between appropriate EAT and the outcomes of Intensive Care Unit (ICU) patients with Acinetobacter bacteremia. Methods: This is a retrospective study of patients admitted to a medical-surgical ICU (2005-2010) and developed Acinetobacter bacteremia during the stay. Patients were categorized according to EAT appropriateness, defined as administration of at least one antimicrobial agent to which the Acinetobacter was susceptible before susceptibility results were known. The relation between EAT appropriateness and outcomes was evaluated. Results: Sixty patients developed Acinetobacter bacteremia in the 6-year period (age = 50 ± 19 years; 62% males; Acute Physiology and Chronic Health Evaluation II score = 28 ± 9; 98.3% with central lines; 67% in shock and 59% mechanically ventilated) on average on day 23 of ICU and day 38 of hospital stay. All isolates were resistant to at least three of the tested antimicrobials. Appropriate EAT was administered to 60% of patients, mostly as intravenous colistin. Appropriate EAT was associated with lower ICU mortality risk (odds ratio: 0.15; 95% confidence interval: 0.03-0.96) on multivariate analysis. Conclusions: In this 6-year cohort, Acinetobacter bacteremia was related to multidrug-resistant strains. Appropriate EAT was associated with decreased ICU mortality risk.
