Water vapour and gas induced phase transformations in an 8-fold interpenetrated diamondoid metal-organic framework.

In this work, we report the synthesis, structural characterisation and sorption properties of an 8-fold interpenetrated diamondoid (dia) metal-organic framework (MOF) that is sustained by a new extended linker ligand, [Cd(Imibz)2], X-dia-2-Cd, HImibz or 2 = 4-((4-(1H-imidazol-1-yl)phenylimino)methyl)benzoic acid. X-dia-2-Cd was found to exhibit reversible single-crystal-to-single-crystal (SC-SC) transformations between four distinct phases: an as-synthesised (from N,N-dimethylformamide) wide-pore phase, X-dia-2-Cd-α; a narrow-pore phase, X-dia-2-Cd-ß, formed upon exposure to water; a narrow-pore phase obtained by activation, X-dia-2-Cd-γ; a medium-pore CO2-loaded phase X-dia-2-Cd-δ. While the space group remained constant in the four phases, the cell volumes and calculated void space ranged from 4988.7 Å3 and 47% (X-dia-2-Cd-α), respectively, to 3200.8 Å3 and 9.1% (X-dia-2-Cd-γ), respectively. X-dia-2-Cd-γ also exhibited a water vapour-induced structural transformation to the water-loaded X-dia-2-Cd-ß phase, resulting in an S-shaped sorption isotherm. The inflection point occurred at 18% RH with negligible hysteresis on the desorption profile. Water vapour temperature-humidity swing cycling (60% RH, 300 K to 0% RH, 333 K) indicated hydrolytic stability of X-dia-2-Cd and working capacity was retained after 128 cycles of sorbent regeneration. CO2 (at 195 K) was also observed to induce a structural transformation in X-dia-2-Cd-γ and in situ PXRD studies at 1 bar of CO2, 195 K revealed the formation of X-dia-2-Cd-δ, which exhibited 31% larger unit cell volume than X-dia-2-Cd-γ.

Pillar Modularity in fsc Topology Hybrid Ultramicroporous Materials Based upon Tetra(4-pyridyl)benzene.

Hybrid ultramicroporous materials (HUMs) are porous coordination networks composed of combinations of organic and inorganic linker ligands with a pore diameter of <7 Å. Despite their benchmark gas sorption selectivity for several industrially relevant gas separations and their inherent modularity, the structural and compositional diversity of HUMs remains underexplored. In this contribution, we report a family of six HUMs (SIFSIX-22-Zn, TIFSIX-6-Zn, SNFSIX-2-Zn, GEFSIX-4-Zn, ZRFSIX-3-Zn, and TAFSEVEN-1-Zn) based on Zn metal centers and the tetratopic N-donor organic ligand tetra(4-pyridyl)benzene (tepb). The incorporation of fluorinated inorganic pillars (SiF6 2-, TiF6 2-, SnF6 2-, GeF6 2-, ZrF6 2-, and TaF7 2-, respectively) resulted in (4,6)-connected fsc topology as verified using single-crystal X-ray diffraction. Pure-component gas sorption studies with N2, CO2, C2H2, C2H4, and C2H6 revealed that the large voids and narrow pore windows common to all six HUMs can be leveraged to afford high C2H2 uptakes while retaining high ideal adsorbed solution theory (IAST) selectivities for industrially relevant gas mixtures: >10 for 1:99 C2H2/C2H4 and >5 for 1:1 C2H2/CO2. The approach taken, systematic variation of pillars with retention of structure, enables differences in selectivity to be attributed directly to the choice of the inorganic pillar. This study introduces fsc topology HUMs as a modular platform that is amenable to fine-tuning of structure and properties.

Flexible Coordination Network Exhibiting Water Vapor-Induced Reversible Switching between Closed and Open Phases.

That physisorbents can reduce the energy footprint of water vapor capture and release has attracted interest because of potential applications such as moisture harvesting, dehumidification, and heat pumps. In this context, sorbents exhibiting an S-shaped single-step water sorption isotherm are desirable, most of which are structurally rigid sorbents that undergo pore-filling at low relative humidity (RH), ideally below 30% RH. Here, we report that a new flexible one-dimensional (1D) coordination network, [Cu(HQS)(TMBP)] (H2HQS = 8-hydroxyquinoline-5-sulfonic acid and TMBP = 4,4'-trimethylenedipyridine), exhibits at least five phases: two as-synthesized open phases, α ⊃ H2O and ß âŠƒ MeOH; an activated closed phase (γ); CO2 (δ ⊃ CO2) and C2H2 (ϵ ⊃ C2H2) loaded phases. The γ phase underwent a reversible structural transformation to α ⊃ H2O with a stepped sorption profile (Type F-IV) when exposed to water vapor at <30% RH at 300 K. The hydrolytic stability of [Cu(HQS)(TMBP)] was confirmed by powder X-ray diffraction (PXRD) after immersion in boiling water for 6 months. Temperature-humidity swing cycling measurements demonstrated that working capacity is retained for >100 cycles and only mild heating (<323 K) is required for regeneration. Unexpectedly, the kinetics of loading and unloading of [Cu(HQS)(TMBP)] compares favorably with well-studied rigid water sorbents such as Al-fumarate, MOF-303, and CAU-10-H. Furthermore, a polymer composite of [Cu(HQS)(TMBP)] was prepared and its water sorption retained its stepped profile and uptake capacity over multiple cycles.

Associations of sleep duration and sleep-wake rhythm with lung parenchymal abnormalities on computed tomography: The MESA study.

Impairment of the circadian rhythm promotes lung inflammation and fibrosis in pre-clinical models. We aimed to examine whether short and/or long sleep duration and other markers of sleep-wake patterns are associated with a greater burden of lung parenchymal abnormalities on computed tomography among adults. We cross-sectionally examined associations of sleep duration captured by actigraphy with interstitial lung abnormalities (n = 1111) and high attenuation areas (n = 1416) on computed tomography scan in the Multi-Ethnic Study of Atherosclerosis at Exam 5 (2010-2013). We adjusted for potential confounders in logistic and linear regression models for interstitial lung abnormalities and high attenuation area, respectively. High attenuation area models were also adjusted for study site, lung volume imaged, radiation dose and stratified by body mass index. Secondary exposures were self-reported sleep duration, sleep fragmentation index, sleep midpoint and chronotype. The mean age of those with longer sleep duration (≥ 8 hr) was 70 years and the prevalence of interstitial lung abnormalities was 14%. Increasing actigraphy-based sleep duration among participants with ≥ 8 hr of sleep was associated with a higher adjusted odds of interstitial lung abnormalities (odds ratio of 2.66 per 1-hr increment, 95% confidence interval 1.42-4.99). Longer sleep duration and higher sleep fragmentation index were associated with greater high attenuation area on computed tomography among participants with a body mass index < 25 kg m-2 (p-value for interaction < 0.02). Self-reported sleep duration, later sleep midpoint and evening chronotype were not associated with outcomes. Actigraphy-based longer sleep duration and sleep fragmentation were associated with a greater burden of lung abnormalities on computed tomography scan.

The First Sulfate-Pillared Hybrid Ultramicroporous Material, SOFOUR-1-Zn, and Its Acetylene Capture Properties.

Hybrid ultramicroporous materials, HUMs, are comprised of metal cations linked by combinations of inorganic and organic ligands. Their modular nature makes them amenable to crystal engineering studies, which have thus far afforded four HUM platforms (as classified by the inorganic linkers). HUMs are of practical interest because of their benchmark gas separation performance for several industrial gas mixtures. We report herein design and gram-scale synthesis of the prototypal sulfate-linked HUM, the fsc topology coordination network ([Zn(tepb)(SO4 )]n ), SOFOUR-1-Zn, tepb=(tetra(4-pyridyl)benzene). Alignment of the sulfate anions enables strong binding to C2 H2 via O⋅⋅⋅HC interactions but weak CO2 binding, affording a new benchmark for the difference between C2 H2 and CO2 heats of sorption at low loading (ΔQst =24 kJ mol-1 ). Dynamic column breakthrough studies afforded fuel-grade C2 H2 from trace (1 : 99) or 1 : 1 C2 H2 /CO2 mixtures, outperforming its SiF6 2- analogue, SIFSIX-22-Zn.

The "Chemistree" of Porous Coordination Networks: Taxonomic Classification of Porous Solids to Guide Crystal Engineering Studies.

New approaches to gas/vapor storage and purification are urgently needed to address the large energy footprint, cost, and/or risk associated with existing technologies. In this context, new classes of porous physisorbents, exemplified by porous coordination networks (PCNs), have emerged. There are now >100 000 entries in the Cambridge Structural Database (CSD) metal-organic framework (MOF) subset and the rate of publication, >5000 per year, grows unabatedly. The number of PCNs makes it infeasible to test all of them for sorption performance and it is therefore timely to introduce a classification approach based upon taxonomy to supplement topological classification of PCNs. This taxonomic approach complements existing databases such as the CSD and enable the design (crystal engineering) of new families of PCNs. It also categorizes existing PCNs in a manner useful to crystal engineers. The internal consistency of the taxonomic approach is verified by case studies of several well-known PCNs whereas its utility is demonstrated upon understudied topologies and hard-to-rationalize infinite rod building blocks. Overall, taxonomic classification enables a traffic light system to direct crystal engineers towards finding a "needle in haystack," that is, a family (platform) of PCNs that is amenable to crystal engineering and systematic structure/property studies.

Agreement of sleep specialists with registered nurses' sleep study orders in supervised clinical practice.

STUDY OBJECTIVES: Incorporating registered nurses (RN-level) into obstructive sleep apnea (OSA) management decisions has the potential to augment the workforce and improve patient access, but the appropriateness of such task-shifting in typical practice is unclear. METHODS: Our medical center piloted a nurse triage program for sleep medicine referrals. Using a sleep specialist-designed decision-making tool, nurses triaged patients referred for initial sleep studies to either home sleep apnea test (HSAT) or in-laboratory polysomnography (PSG). During the first 5 months of the program, specialists reviewed all nurse triages. We compared agreement between specialists and nurses. RESULTS: Of 280 consultations triaged by nurses, nurses deferred management decisions to sleep specialists in 6.1% (n = 17) of cases. Of the remaining 263 cases, there was 88% agreement between nurses and specialists (kappa 0.80, 95% confidence interval 0.74-0.87). In the 8.8% (n = 23) of cases where supervising specialists changed sleep study type, specialists changed from HSAT to PSG in 16 cases and from PSG to HSAT in 7. The most common indication for change in sleep study type was disagreement regarding OSA pretest probability (n = 14 of 23). Specialists changed test instructions in 3.0% (n = 8) of cases, with changes either related to the use of transcutaneous carbon dioxide monitoring (n = 4) or adaptive servo-ventilation (n = 4). CONCLUSIONS: More than 80% of sleep study triages by registered nurses in a supervised setting required no sleep specialist intervention. Future research should focus on how to integrate nurses into the sleep medicine workforce in a manner that maximizes efficiency while preserving or improving patient outcomes.

[Cu(4-phenylpyridine)4(trifluoromethanesulfonate)2], a Werner complex that exhibits high selectivity for o-xylene.

[Cu(4-phenylpyridine)4(trifluoromethanesulfonate)2] is a new Werner complex that exhibits switching behaviour between non-porous (apohost) and porous (guest-loaded) phases upon exposure to o-xylene but not when exposed to other C8 isomers. High o-xylene selectivity (>6) vs. the other C8 isomers was observed from binary mixtures, only the third occurrence across all sorbent types.

Risk of Cardiovascular Disease Related to Smoking Is Greater Among Women With Sleep-Disordered Breathing.

STUDY OBJECTIVES: Although both sleep-disordered breathing (SDB) and smoking are associated with cardiovascular disease (CVD), the potential for an interactive effect on CVD risk has not been explored. Our objective was to determine if smoking-related risk for CVD rises with greater SDB severity. METHODS: Polysomnography and smoking history were obtained in 3,852 men and women in the Sleep Heart Health Study without baseline CVD. Fine-Gray proportional hazard models accounting for competing risk were used to calculate risk of incident CVD associated with SDB severity (defined by clinical cutoffs of the apnea-hypopnea index), smoking status (never, former, and current) and their interaction adjusting for potential confounders. RESULTS: Over a mean (standard deviation) follow-up period of 10.3 (3.4) years, there were 694 incident CVD events. We found a significant three-way interaction of sex, current smoking, and moderate to severe SDB (P = .039) in the adjusted proportional hazards model. In adjusted analyses, women who were current smokers with moderate to severe SDB had a hazard ratio for incident CVD of 3.5 (95% confidence interval 1.6-8.0) relative to women who were nonsmokers without SDB. No such difference in CVD risk was observed in men or women of other strata of smoking and SDB. CONCLUSIONS: In women, smoking-related risk for CVD is significantly higher among individuals with moderate to severe SDB.

Resistant hypertension and obstructive sleep apnea.

Hypertension (HTN) is a modifiable, highly prevalent risk factor for cardiovascular morbidity and renal dysfunction worldwide. In the United States, HTN affects one in three adults, contributes to one out of every seven deaths and to nearly half of all cardiovascular disease-related deaths. HTN is considered resistant when the blood pressure remains above goal despite lifestyle modification and administration of three antihypertensive agents of different classes including a diuretic. Large population-based studies have suggested that obstructive sleep apnea (OSA) is a risk factor for resistant HTN. The mechanism proposed is a pattern of intermittent hypoxia associated with hyperaldosteronism, increased sympathetic tone, endothelial dysfunction, and inflammation. In this review we discuss the association between OSA and resistant HTN, the physiologic mechanisms linking OSA with resistant HTN, and the effect of continuous positive airway pressure therapy (CPAP) on blood pressure in patients with resistant HTN. While the reduction in blood pressure with CPAP is usually modest in patients with OSA, a decrease of only a few mmHg in blood pressure can significantly reduce cardiovascular risk. Patients presenting to a center specializing in management of hypertension should be screened and treated for OSA as a potentially modifiable risk factor.

Lower extremity edema and pulmonary hypertension in morbidly obese patients with obstructive sleep apnea.

INTRODUCTION: In 70 consecutive male patients with obstructive sleep apnea (OSA) diagnosed at the Northport VA Medical Center Sleep Disorders Center, we have characterized the association between obesity, OSA, and pulmonary hypertension (PH). MATERIALS AND METHODS: By including anthropometric, pulmonary function, and sleep study parameters in a multivariate logistic regression model, we found that a BMI of >40 kg/m(2) and the minimum oxygen saturation in non-rapid eye movement (NREM) sleep predicted the presence of pretibial edema in this sleep apnea population. We then characterized the hemodynamics of those OSA patients that had lower extremity edema. Twenty-nine of the 70 consecutive patients with sleep apnea (41%) had pretibial edema, and right heart catheterization data was obtained for 28 (97%) of these patients. RESULTS AND DISCUSSION: Ninety-three percent (26/28) of the patients had right heart failure (mean RAP > 5 mm Hg; RAP range = 0-32 mmHg) and PH (PA mean >or= 20 mm Hg) was present in 86% (24/28.) The OSA patients with lower extremity edema had an increased cardiac output (7.0 + 1.4 l/min) with a normal cardiac index (2.9 + 0.5 l/min/m(2)) in the setting of an elevated pulmonary capillary wedge pressure (PCWP 17 +/- 7 mmHg) and a normal pulmonary vascular resistance (122 + 70 dynes s cm(-5)). While PCWP, FEV(1)% predicted, and the minimum oxygen saturation in NREM sleep all independently predicted PH, PCWP was the most important predictor of PH. CONCLUSION: We conclude that pulmonary hypertension is commonly seen in patients with OSA with pretibial edema and that pretibial edema is a highly specific sign of PH in OSA patients. Pulmonary hypertension appears to result from an elevated back pressure and diastolic dysfunction with contributions from lung function and nocturnal oxygen saturation.

Exhaled nasal nitric oxide output is reduced in humans at night during the sleep period.

The physiologic function of nasal nitric oxide (NO) release is unknown. In prior experiments, topical NG-nitro-L-arginine methyl ester (L-NAME) on nasal mucosa reduced exhaled nasal NO output and caused daytime sleepiness. We hypothesized that nasal NO output is reduced at night during the sleep period. We measured exhaled nasal NO concentration and minute ventilation and calculated nasal NO output in humans over 24 h. Daytime awake NO output was greater than NO output at night during sleep or transient wakefulness. Exhaled NO concentration decreased during sleep along with minute ventilation. A daytime voluntary reduction in minute ventilation also decreased nasal NO output but exhaled NO concentration increased. Nasal NO output was not changed by body position. We conclude that exhaled nasal NO output is decreased at night due to decreased mass flow of NO into nasal air in addition to decreased minute ventilation. Our findings suggest a role of nasal NO in sleep or in the physiologic processes accompanying sleep.

Upper airway response to electrical stimulation of the genioglossus in obstructive sleep apnea.

Contraction of the genioglossus (GG) has been shown to improve upper airway patency. In the present study, we evaluated responses in upper airway pressure-flow relationships during sleep to electrical stimulation (ES) of the GG in patients with obstructive sleep apnea. Five patients with chronically implanted hypoglossal nerve (HG) electrodes and nine patients with fine-wire electrodes inserted into the GG were studied. Airflow was measured at multiple levels of nasal pressure, and upper airway collapsibility was defined by the nasal pressure below which airflow ceased ["critical" pressure (Pcrit)]. ES shifted the pressure-flow relationships toward higher flow levels in all patients over the entire range of nasal pressure applied. Pcrit decreased similarly during both HG-ES and GG-ES (deltaPcrit was 3.98 +/- 2.31 and 3.18 +/- 1.70 cmH2O, respectively) without a significant change in upstream resistance. The site of collapse (velo- vs. oropharynx) did not influence the response to GG-ES. Moreover, ES-induced reductions in the apnea-hypopnea index of the HG-ES patients were associated with substantial decreases in Pcrit. Our findings imply that responses in apnea severity to HG-ES can be predicted by characterizing the patient's baseline pressure-flow relationships and response to GG-ES.