Engineering Li/Na selectivity in 12-Crown-4-functionalized polymer membranes.

Lithium is widely used in contemporary energy applications, but its isolation from natural reserves is plagued by time-consuming and costly processes. While polymer membranes could, in principle, circumvent these challenges by efficiently extracting lithium from aqueous solutions, they usually exhibit poor ion-specific selectivity. Toward this end, we have incorporated host-guest interactions into a tunable polynorbornene network by copolymerizing 1) 12-crown-4 ligands to impart ion selectivity, 2) poly(ethylene oxide) side chains to control water content, and 3) a crosslinker to form robust solids at room temperature. Single salt transport measurements indicate these materials exhibit unprecedented reverse permeability selectivity (∼2.3) for LiCl over NaCl-the highest documented to date for a dense, water-swollen polymer. As demonstrated by molecular dynamics simulations, this behavior originates from the ability of 12-crown-4 to bind Na+ ions more strongly than Li+ in an aqueous environment, which reduces Na+ mobility (relative to Li+) and offsets the increase in Na+ solubility due to binding with crown ethers. Under mixed salt conditions, 12-crown-4 functionalized membranes showed identical solubility selectivity relative to single salt conditions; however, the permeability and diffusivity selectivity of LiCl over NaCl decreased, presumably due to flux coupling. These results reveal insights for designing advanced membranes with solute-specific selectivity by utilizing host-guest interactions.

Origins of Lithium/Sodium Reverse Permeability Selectivity in 12-Crown-4-Functionalized Polymer Membranes.

Direct lithium extraction via membrane separations has been fundamentally limited by lack of monovalent ion selectivity exhibited by conventional polymeric membranes, particularly between sodium and lithium ions. Recently, a 12-Crown-4-functionalized polynorbornene membrane was shown to have the largest lithium/sodium permeability selectivity observed in a fully aqueous system to date. Using atomistic molecular dynamics simulations, we reveal that this selectivity is due to strong interactions between sodium ions and 12-Crown-4 moieties, which reduce sodium ion diffusivity while leaving lithium ion mobility relatively unaffected. Moreover, the ion diffusivities in the membrane, when scaled by their respective solution diffusivities and free ion fractions, can be collapsed to an almost universal relationship depending on solvent volume fraction.

Comparison of colistin and colistin/sulbactam for the treatment of multidrug resistant Acinetobacter baumannii ventilator-associated pneumonia.

PURPOSE: To compare clinical and microbiological efficacy of colistin and colistin/sulbactam for the treatment of multidrug-resistant (MDR) Acinetobacter baumannii VAP in intensive care units (ICUs). PATIENTS AND METHODS: In this retrospective analysis, patients (>16 years-old) who received IV colistin or colistin/sulbactam for the treatment of MDR A. baumannii VAP were evaluated. The clinical and microbiological responses to therapies were assessed on the fifth day and at the end of the therapy. RESULTS: During the study period, 89 patients were enrolled into the study. Fifty-two (58.4 %) patients received colistin and 37 (41.6 %) patients received colistin/sulbactam therapy. The median APACHE II score was higher and diabetes mellitus was more common in the colistin/sulbactam group (p < 0.05). However, other demographic characteristics were not statistically significant between groups. On the fifth day of colistin and colistin/sulbactam therapies, clinical response rates were 40.4 and 43.2 %, respectively. At the end of the therapies, clinical response rates were 29.8 and 40 %, respectively. The bacteriological response rates were 72.3 and 85.7 % in colistin and colistin/sulbactam groups, respectively. There were no statistically significant differences in clinical cure rates or bacteriological clearance rates between the two groups. CONCLUSIONS: The colistin/sulbactam combination therapy is promising in severe MDR A. baumannii VAP. Although, the difference was not statistically significant, clinical cure rates or bacteriological clearance rates were better in the combination group than colistin monotherapy.

Economic burden of ventilator-associated pneumonia in a developing country.

Ventilator-associated pneumonia (VAP) developed in 96 (60%) of 159 patients with 37.2 cases per 1000 ventilation-days in a medical intensive care unit (MICU). Median time for VAP development was 5.5 days (range: 2-25). The most significant risk factors for VAP were stay in hospital before MICU and length of stay in MICU. The mean length of stay in MICU for VAP patients was 23.8 ± 19.8 days, which was four-fold higher than for non-VAP patients. The daily cost for VAP patients was half that for non-VAP patients. The total costs for VAP patients were about three-fold higher than for non-VAP patients.

[The incidence of some angiotensin-1 converting enzyme gene alleles in patients with coronary heart disease].

The results of several studies which have been published since 1992 evidence a significant correlation between DD genotype of angiotensin 1-converting enzyme (ACE) gene and development of coronary artery disease (CAD) in some populations. The authors of this article studied distribution of ACE gene I/D genotypes (II, ID, DD) in 102 patients with CAD and 50 controls without cardiovascular pathology or diabetes mellitus. The CAD diagnosis was confirmed by coronaroangiography. The study established a significant correlation between the presence of DD-ACE genotype and development of CAD. After exclusion of patients with classic risk factors (body mass index greater than 26 kg/m2; arterial hypertension; dislipidemia), this correlation remained. The results of the study demonstrate a significant positive correlation between the presence of DD genotype and high risk of CAD in this population, including people without such classic risk factors as obesity, arterial hypertension, or dislipidemia.

False-positive diagnosis in fine-needle aspiration of an atypical Warthin's tumor: histochemical differential stains for cytodiagnosis.

Cytologic smears of a Warthin's tumor (WT) typically consist of sheets of oncocytic (oxyphilic) cells and scattered lymphocytes. Reparative foci within this neoplasm can occur, which may give rise to exfoliated, malignant-appearing, squamous-like cells. A false-positive diagnosis of squamous carcinoma can occur when these atypical cells dominate the cytologic aspirate. Histochemical and immunoperoxidase stains may aid in diagnosing an atypical WT when the usual cytologic features are absent.

Tryptophan urinary bladder absorption and bladder cancer.

Local vesical absorption of organic compounds may play a role in the pathogenesis of bladder cancer. An associated increased absorption of tryptophan in patients with bladder cancer has been demonstrated.