Computer-aided discovery of a metal-organic framework with superior oxygen uptake.

Current advances in materials science have resulted in the rapid emergence of thousands of functional adsorbent materials in recent years. This clearly creates multiple opportunities for their potential application, but it also creates the following challenge: how does one identify the most promising structures, among the thousands of possibilities, for a particular application? Here, we present a case of computer-aided material discovery, in which we complete the full cycle from computational screening of metal-organic framework materials for oxygen storage, to identification, synthesis and measurement of oxygen adsorption in the top-ranked structure. We introduce an interactive visualization concept to analyze over 1000 unique structure-property plots in five dimensions and delimit the relationships between structural properties and oxygen adsorption performance at different pressures for 2932 already-synthesized structures. We also report a world-record holding material for oxygen storage, UMCM-152, which delivers 22.5% more oxygen than the best known material to date, to the best of our knowledge

Observation of reduced thermal conductivity in a metal-organic framework due to the presence of adsorbates

Whether the presence of adsorbates increases or decreases thermal conductivity in metal-organic frameworks (MOFs) has been an open question. Here we report observations of thermal transport in the metal-organic framework HKUST-1 in the presence of various liquid adsorbates: water, methanol, and ethanol. Experimental thermoreflectance measurements were performed on single crystals and thin films, and theoretical predictions were made using molecular dynamics simulations. We find that the thermal conductivity of HKUST-1 decreases by 40 – 80% depending on the adsorbate, a result that cannot be explained by effective medium approximations. Our findings demonstrate that adsorbates introduce additional phonon scattering in HKUST-1, which particularly shortens the lifetimes of low-frequency phonon modes. As a result, the system thermal conductivity is lowered to a greater extent than the increase expected by the creation of additional heat transfer channels. Finally, we show that thermal diffusivity is even more greatly reduced than thermal conductivity by adsorption

Current trend in synthesis, Post-Synthetic modifications and biological applications of Nanometal-Organic frameworks (NMOFs)

Since the early reports of MOFs and their interesting properties, research involving these materials has grown wide in scope and applications. Various synthetic approaches have ensued in view of obtaining materials with optimised properties, the extensive scope of application spanning from energy, gas sorption, catalysis biological applications has meant exponentially evolved over the years. The far‐reaching synthetic and PSM approaches and porosity control possibilities have continued to serve as a motivation for research on these materials. With respect to the biological applications, MOFs have shown promise as good candidates in applications involving drug delivery, BioMOFs, sensing, imaging amongst others. Despite being a while away from successful entry into the market, observed results in sensing, drug delivery, and imaging put these materials on the spot light as candidates poised to usher in a revolution in biology. In this regard, this review article focuses current approaches in synthesis, post functionalization and biological applications of these materials with particular attention on drug delivery, imaging, sensing and BioMOFs

How reproducible are surface areas calculated from the BET equation?

Porosity and surface area analysis play a prominent role in modern materials science. At the heart of this sits the Brunauer-Emmett-Teller (BET) theory, which has been a remarkably successful contribution to the field of materials science. The BET method was developed in the 1930s for open surfaces but is now the most widely used metric for the estimation of surface areas of micro- and mesoporous materials. Despite its widespread use, the calculation of BET surface areas causes a spread in reported areas, resulting in reproducibility problems in both academia and industry. To prove this, for this analysis, 18 already-measured raw adsorption isotherms were provided to sixty-one labs, who were asked to calculate the corresponding BET areas. This round-robin exercise resulted in a wide range of values. Here, the reproducibility of BET area determination from identical isotherms is demonstrated to be a largely ignored issue, raising critical concerns over the reliability of reported BET areas. To solve this major issue, a new computational approach to accurately and systematically determine the BET area of nanoporous materials is developed. The software, called "BET surface identification" (BETSI), expands on the well-known Rouquerol criteria and makes an unambiguous BET area assignment possible

Rupture of a Nonaneurysmal Abdominal Aorta due to Spondylitis

Contiguous arterial infections are extremely rare, and their actual rate of occurrence is not known. These infections occur as a result of direct invasion of an artery from an adjacent septic focus. Reaching the diagnosis of infected aorta is very difficult when there are contiguous infections from spondylitis or psoas abscess, because the clinical features are nonspecific. Although computed tomography is the most useful diagnostic tool in the detection of aortic infections, the most frequent findings mimic those of other diseases, such as retroperitoneal fibrosis, lymphoma, and periaortic lymphadenopathy. Diagnosis becomes even more challenging when an infected aorta is of normal diameter

Composite Graft Endocarditis: Repair with a Mechanical Prosthesis

We report the case of a 64-year-old man who developed a mediastinal pseudoaneurysm due to severe endocarditis, 2 years after aortic root replacement with a prosthetic composite graft containing a mechanical valve. After a short period of stabilization and antibiotic therapy, the patient underwent surgery. The coronary buttons and the sewing ring of the composite graft were found to be detached from the graft and the annulus, respectively. Re-replacement with a prosthetic composite graft (Dacron graft with a mechanical valve) by the Cabrol procedure was performed. Although the homograft is considered by many surgeons to be the best graft for aortic root replacement, the synthetic composite graft can also be used to treat composite graft endocarditis successfully. The technical aspects of homograft versus synthetic aortic root replacement in patients with endocarditis are discussed briefly

Malperfusion Remains the Major Cause of Mortality in Proximal Aortic Operations

WOS: 000293244200014PubMed ID: 21507058Background: This study was undertaken to identify the incremental risk factors for early mortality in operations for proximal aortic pathologies. Methods: Between September 2000 and May 2010, 240 consecutive patients underwent replacement of various portions of the proximal aorta. Mean age was 56 +/- 13 years (range 18 to 84) and female/male ratio was 3/7. Operations were performed emergently in 97, urgently in 21, and electively in 122 patients. Thirty-four patients had previous cardiac or aortic operations. Etiology was acute dissection in 102, chronic dissection in 41, degenerative aneurysm in 61, and other factors (endocarditis, pseudoaneurysm, aortitis, etc.) in 36 patients. The ascending aorta was replaced in all patients. In addition, the aortic arch was replaced in 20 and the root was replaced in 106 patients. Results: The in-hospital mortality rate was 10.4% in the overall group (25/240), 21.6% in emergent cases (21/97), 9.5% in urgent cases (2/21), and 1.6% in elective cases (2/122). Morbidity rates were as follows: stroke 2.7%, temporary neurological dysfunction 13.3%, nonoliguric renal failure 3%, dialysis 5.4%, tracheostomy 3.3%, bleeding requiring revision 3.3%. In multivariate analysis, the presence of malperfusion in patients with acute aortic dissection emerged as the incremental risk factor for mortality (p < 0.0001, odds ratio = 10.37). There was no variable associated with stroke. Emergency/urgency of operation did not emerge as incremental risk factors for mortality. Conclusion: Immediate outcomes of elective aortic operations for proximal aortic pathologies are excellent. Complicated acute dissections with malperfusion remain the major cause of early mortality. doi: 10.1111/j.1540-8191.2011.01250.x (J Card Surg 2011; 26: 393-396

Immediate Clinical Outcome after Prolonged Periods of Brain Protection: Retrospective Comparison of Hypothermic Circulatory Arrest, Retrograde, and Antegrade Perfusion

WOS: 000269540900001PubMed ID: 19549051Background and Aim: We aimed to compare the immediate clinical outcome after different cerebral perfusion methods, and examine the factors affecting the mortality and neurological outcome. Methods: Between 1993 and 2006, 339 patients underwent proximal aortic operations using a period of cerebral protection. Among these, 161 patients (mean age of 55 +/- 12 years) who required cerebral protection longer than 25 minutes were included in the analysis. Ascending aorta with or without root was replaced in all patients. In addition, total arch replacement was performed in 36 patients. All patients were cooled to rectal temperature of 16 degrees C. Hypothermic circulatory arrest without adjunctive perfusion was used in 48 patients. Retrograde or antegrade cerebral perfusion was added in 94 and 19 patients, respectively. The mean duration of total cerebral protection was 42 +/- 17 minutes. Results: Overall mortality was 15.5% (25/161) and did not differ among the perfusion groups. There was no difference in the incidence of overall neurological events, temporary neurological dysfunction, or major stroke among the groups. Multivariate analysis revealed that transfusion of > 3 units of blood (p 3 units of blood (p < 0.04) were predictors of temporary neurological dysfunction. Conclusion: In proximal aortic operations requiring prolonged periods of cerebral protection, the mortality and neurological morbidity are not determined by the type of cerebral protection method only. Factors like hypertension and diabetes may play a role in the development of temporary neurological dysfunction. doi: 10.1111/j.1540-8191.2008.00772.x (J Card Surg 2009; 24: 486-489

Cerebral Perfusion through Separate Grafts for Repair of Acute Aortic Dissection with Torn Arch

We have modified the technique of cerebral perfusion through anastomosed grafts for repair of acute arch dissections that require total arch replacement. We have performed this operation on a 71-year-old man with an acute type-A dissection and an arch tear between the orifices of the brachiocephalic arteries. We used 2 separate grafts for the brachiocephalic arteries and minimized brain ischemia by initiating antegrade selective cerebral perfusion after the 1st anastomosis. The patient had an excellent outcome. This method is simple and provides effective protection. Cerebral ischemic time can be kept under 30 minutes without need of a sophisticated pump setup or a multibranched graft. This affords extra time in case the surgeon encounters an unexpected lesion in the arch. (Tex Heart Inst J 2001;28:288–91