RESUMEN
Platinum(II) complexes bearing terpyridyl (tpy) and thiolate ligands were used to test the design of a "dual layer" self-sorting system in the presence of Cucurbit[8]uril (CB[8]). Pt(II) thiolates and CB[8] form 2:1 assemblies, with both metallic centers sitting on top of one another at one of the macrocycle portals. We showed that any pair of these CB[8]-secured Pt(II) complex dimers bearing different tpy "heads" and thiolate "tails" scrambles to afford up to 10 ternary assemblies via two processes: (1) supramolecular exchanges (i.e., the egression and ingression of Pt complexes from and into CB[8]) and (2) ligand exchanges between the Pt thiolates. The mixtures of 10 assemblies were fully characterized by nuclear magnetic resonance spectroscopy. While the thiolate tails do not significantly affect the rate of the supramolecular exchanges, they were found to control (1) the kinetics of ligand exchange, with bulkier thiolates causing dramatic rate retardations, as well as (2) the thermodynamics of the self-sorting process, i.e., the distribution of assemblies at equilibrium, via intra-CB[8] assembly interactions between pairs of thiolates. Ligand exchanges are consistently slower than supramolecular exchanges. An associative pathway that involves the formation of dimers of CB[8]-secured Pt dimers (a total of 4 Pt complexes) during the ligand exchange process was invoked to rationalize the observed kinetics.
RESUMEN
The trans- and cis conformations of 5,5'-substituted 2,2'-dithiophenes can be stabilized when those are secured with two Cucurbit[8]uril macrocycles (CB[8]) on top of rigid 2,6- and 2,7-substituted naphthalenes, which respectively mimic the trans and cis conformations of the dithiophene. The substituents are Pt(ii) terpyridyl groups bearing CB[8]-binding sites at their 4'-position, as those form dimers in the presence of the macrocycle through Pt-Pt and dispersive interactions between the terpyridyl ligands.
RESUMEN
A well-known stopping rule in adaptive mastery testing is to terminate the assessment once the examinee's ability confidence interval lies entirely above or below the cut-off score. This article proposes new procedures that seek to improve such a variable-length stopping rule by coupling it with curtailment and stochastic curtailment. Under the new procedures, test termination can occur earlier if the probability is high enough that the current classification decision remains the same should the test continue. Computation of this probability utilizes normality of an asymptotically equivalent version of the maximum likelihood ability estimate. In two simulation sets, the new procedures showed a substantial reduction in average test length while maintaining similar classification accuracy to the original method.
RESUMEN
PURPOSE: To compare ophthalmic practice productivity and performance attributes, as rated by employing ophthalmologists, of noncertified and three levels of certified ophthalmic medical personnel. METHODS: Three hundred eighty-five American and Canadian ophthalmologists in a clinic-based, stratified, random sample were surveyed regarding productivity performance and attributes of the ophthalmic medical personnel they employ. Instrument scales assessed 14 desirable professional attributes and 10 practice productivity measures. The attributes were credibility, reliability, competence, quality assurance, quality of patient care, knowledge base to make adjustments, increased skills (expertise), ability to work independently, broader knowledge base, ability to detect errors, ability to be trained to perform multiple roles in the practice, professional image, good judgment, and initiative and drive. The productivity measures were patient satisfaction, doctor productivity, trouble-shooting rapport, triage screening, effective patient flow, reduced patient complaints, increased referrals, number of patients per hour, revenue per patient, and patient follow-up. Participants indicated whether certified personnel more often showed these attributes and contributed to practice productivity measures as compared to noncertified personnel or whether there was no difference. Results were analyzed with a chi-square goodness-of-fit test. Survey reliability and validity were evaluated. RESULTS: Significantly more ophthalmologists responded that the three levels of certified personnel contributed more to 5 of the 10 practice productivity measures (i.e., doctor productivity, trouble-shooting rapport, triage screening, effective patient flow, and number of patients per hour). A statistically significant number of ophthalmologists also believed that certified personnel showed more of all 14 of the personal attributes considered desirable compared to noncertified ophthalmic medical personnel. CONCLUSIONS: Compared to noncertified personnel, the employment of certified ophthalmic personnel enhances the quality and productivity of an ophthalmic practice. Overall practice productivity is increased with certified ophthalmic medical personnel.
