Assessing the Sampleability of Bennu's Surface for the OSIRIS-REx Asteroid Sample Return Mission.

NASA's first asteroid sample return mission, OSIRIS-REx, collected a sample from the surface of near-Earth asteroid Bennu in October 2020 and will deliver it to Earth in September 2023. Selecting a sample collection site on Bennu's surface was challenging due to the surprising lack of large ponded deposits of regolith particles exclusively fine enough ( ≤ 2 cm diameter) to be ingested by the spacecraft's Touch-and-Go Sample Acquisition Mechanism (TAGSAM). Here we describe the Sampleability Map of Bennu, which was constructed to aid in the selection of candidate sampling sites and to estimate the probability of collecting sufficient sample. "Sampleability" is a numeric score that expresses the compatibility of a given area's surface properties with the sampling mechanism. The algorithm that determines sampleability is a best fit functional form to an extensive suite of laboratory testing outcomes tracking the TAGSAM performance as a function of four observable properties of the target asteroid. The algorithm and testing were designed to measure and subsequently predict TAGSAM collection amounts as a function of the minimum particle size, maximum particle size, particle size frequency distribution, and the tilt of the TAGSAM head off the surface. The sampleability algorithm operated at two general scales, consistent with the resolution and coverage of data collected during the mission. The first scale was global and evaluated nearly the full surface. Due to Bennu's unexpected boulder coverage and lack of ponded regolith deposits, the global sampleability efforts relied heavily on additional strategies to find and characterize regions of interest based on quantifying and avoiding areas heavily covered by material too large to be collected. The second scale was site-specific and used higher-resolution data to predict collected mass at a given contact location. The rigorous sampleability assessments gave the mission confidence to select the best possible sample collection site and directly enabled successful collection of hundreds of grams of material.

A cardiologist's view of hypoglycemia.

Recent studies have failed to show an improvement in cardiovascular mortality with intensive glycemic control and aggressive glycated hemoglobin (A(1c)) targets less than 7.0%. Excessive hypoglycemic episodes with intensive glucose-lowering therapy are thought to be a major factor in the failure to show cardiovascular benefit in these trials. In this article, we review the physiology of glucose metabolism, the cardiovascular pathophysiology of hypoglycemia, and the trials with an intensive glucose-lowering strategy that have studied microvascular and macrovascular complications. We also review the current non-insulin drugs available for the treatment of diabetes and their potential hypoglycemic and cardiovascular impacts.

Cardiovascular comorbidities of type 2 diabetes mellitus: defining the potential of glucagonlike peptide-1-based therapies.

The global epidemic of diabetes mellitus (~95% type 2 diabetes) has been fueled by a parallel increase in obesity and overweight. Together, these metabolic disease epidemics have contributed to the increasing incidence and prevalence of cardiovascular disease. The accumulation of metabolic and cardiovascular risk factors in patients with type 2 diabetes--risk factors that may exacerbate one another--complicates treatment. Inadequate treatment, treatment that fails to achieve goals, increases the risk for cardiovascular morbidity and mortality. From a clinical perspective, type 2 diabetes is a cardiovascular disease, an observation that is supported by a range of epidemiologic, postmortem, and cardiovascular imaging studies. Vascular wall dysfunction, and particularly endothelial dysfunction, has been posited as a "common soil" linking dysglycemic and cardiovascular diseases. Vascular wall dysfunction promoted by environmental triggers (e.g., sedentary lifestyle) and metabolic triggers (chronic hyperglycemia, obesity) has been associated with the upregulation of reactive oxygen species and chronic inflammatory and hypercoagulable states, and as such with the pathogenesis of type 2 diabetes, atherosclerosis, and cardiovascular disease. Glucagon-like peptide-1 (GLP)-1, an incretin hormone, and synthetic GLP-1 receptor agonists represent promising new areas of research and therapeutics in the struggle not only against type 2 diabetes but also against the cardiovascular morbidity and mortality associated with type 2 diabetes. In a number of small trials in humans, as well as in preclinical and in vitro studies, both native GLP-1 and GLP-1 receptor agonists have demonstrated positive effects on a range of cardiovascular disease pathologies and clinical targets, including such markers of vascular inflammation as high-sensitivity C-reactive protein, plasminogen activator inhibitor-1, and brain natriuretic peptide. Reductions in markers of dyslipidemia such as elevated levels of triglycerides and free fatty acids have also been observed, as have cardioprotective functions. Larger trials of longer duration will be required to confirm preliminary findings. In large human trials, GLP-1 receptor agonists have been associated with significant reductions in both blood pressure and weight.

Effect of glitazones on the progression of coronary artery disease in type 2 diabetes patients.

The effect of thiazolidinediones (TZDs) on the progression of atherosclerosis in diabetes patients remains unclear. There has been heightened interest in recent years in this class of diabetes medications due to the non-glycemic lowering effects, such as altering lipids, inflammation and hematologic profiles. There have been several exciting studies over the past few years focused on the mechanism of action of the TZDs with respect to alteration in the cardio-metabolic profile in diabetes patients. New tools such as intravascular ultrasound have been used to follow plaques characteristics over time on a much more sensitive scale than has ever been possible in the past by coronary angiograms. These advances have enabled researchers to follow closely the macrovascular effects of different anti-atherosclerotic medications such as statins and TZDs. This article reviews the pathophysiology of atherosclerosis in diabetes, the role that TZDs play in this process and the imaging trials looking at the progression or regression of atherosclerosis in patients treated with TZDs.

Aortic stenosis catheterization revisited: a long sheath single-puncture technique.

OBJECTIVES: To evaluate the accuracy of a new long sheath single-puncture technique in obtaining accurate transvalvular gradients in aortic stenosis. BACKGROUND: Despite advances in echo Doppler, the evaluation of aortic stenosis continues to be a common procedure in the cardiac catheterization laboratory. Experts agree that simultaneous evaluation of the proximal aortic and left ventricular pressures yields the most accurate data; however, this is difficult to achieve unless two arterial punctures are performed. METHODS: We postulated that using a 4 Fr pigtail catheter inside a 55-cm long 6 Fr sheath would provide accurate simultaneous pressure data, yet avoid the complications of two arterial punctures. We performed this technique in 13 male patients, and placed a second arterial catheter in the aortic root as a control aortic pressure. We then performed this technique in 55 other male patients without placing an additional control arterial catheter. RESULTS: In the test population, correlation of aortic valve areas and transvalvular gradients was excellent. In the larger population, adequate hemodynamic data was obtained in 52 patients, with no difficulty engaging coronary arteries or grafts via the long sheath, and with an acceptable major complication rate of 1.5%. CONCLUSIONS: Using a 4 Fr pigtail catheter with a 55-cm long 6 Fr sheath is a safe, efficient way to obtain excellent hemodynamic data in an aortic stenosis catheterization procedure.