An SU(N) Mott insulator of an atomic Fermi gas realized by large-spin Pomeranchuk cooling

The Hubbard model, containing only the minimum ingredients of nearest neighbor hopping and on-site interaction for correlated electrons, has succeeded in accounting for diverse phenomena observed in solid-state materials. One of the interesting extensions is to enlarge its spin symmetry to SU(N>2), which is closely related to systems with orbital degeneracy. Here we report a successful formation of the SU(6) symmetric Mott insulator state with an atomic Fermi gas of ytterbium (173Yb) in a three-dimensional optical lattice. Besides the suppression of compressibility and the existence of charge excitation gap which characterize a Mott insulating phase, we reveal an important difference between the cases of SU(6) and SU(2) in the achievable temperature as the consequence of different entropy carried by an isolated spin. This is analogous to Pomeranchuk cooling in solid 3He and will be helpful for investigating exotic quantum phases of SU(N) Hubbard system at extremely low temperatures.Comment: 20 pages, 6 figures, to appear in Nature Physic

Correlating corneal arcus with atherosclerosis in familial hypercholesterolemia

Abstract Background A relationship between corneal arcus and atherosclerosis has long been suspected but is controversial. The homozygous familial hypercholesterolemia patients in this study present a unique opportunity to assess this issue. They have both advanced atherosclerosis and corneal arcus. Methods This is a cross-sectional study of 17 patients homozygous for familial hypercholesterolemia presenting to the Clinical Center of the National Institutes of Health. Plasma lipoproteins, circumferential extent of arcus, thoracic aorta and coronary calcific atherosclerosis score, and Achilles tendon width were measured at the National Institutes of Health. Results Patients with corneal arcus had higher scores for calcific atherosclerosis (mean 2865 compared to 412), cholesterol-year score (mean 11830 mg-yr/dl compared to 5707 mg-yr/dl), and Achilles tendon width (mean 2.54 cm compared to 1.41 cm) than those without. Corneal arcus and Achilles tendon width were strongly correlated and predictive of each other. Although corneal arcus was correlated with calcific atherosclerosis (r = 0.67; p = 0.004), it was not as highly correlated as was the Achilles tendon width (r = 0.855; p Conclusion Corneal arcus reflects widespread tissue lipid deposition and is correlated with both calcific atherosclerosis and xanthomatosis in these patients. Patients with more severe arcus tend to have more severe calcific atherosclerosis. Corneal arcus is not as good an indicator of calcific atherosclerosis as Achilles tendon thickness, but its presence suggests increased atherosclerosis in these hypercholesterolemic patients.</p

Achalasia in the elderly patient: a comparative study

CONTEXT: Achalasia is a primary esophageal motor disorder secondary to the degeneration of ganglion cells of the inhibitory intramural myenteric plexus. It affects both sexes similarly and has two peaks of incidence, one in the 3rd to 4th decades of life and the other after 60 years of age. The effect of age on esophageal motility of patients with achalasia is not well known. Studies have shown that healthy older people, when compared to the young, have: a) a lower number of ganglion cells in the intramural myenteric plexus; b) a reduced normal relaxation of the lower esophageal sphincter; and c) a reduced esophageal peristalsis. Thus, as both age and achalasia can produce comparable degenerative changes in the intramural myenteric plexus, it is possible that advanced age could be an important factor in enhancing the clinical and manometric abnormalities commonly found in patients with achalasia. OBJECTIVES: To compare the clinical, radiological and manometric findings in young as compared to elderly (>60 years old) achalasia patients. METHODS: A retrospective study of a group of patients with untreated achalasia separated into young and elderly patients. Demographic, clinical, serology for Chagas' disease, radiological and manometric data were compared between these groups. The level of significance was P<0.05. RESULTS: The study included 105 patients, 52 young (25 M/27 F, mean age 40 years old) and 53 elderly (21 M/32 F, mean age 70 years old). The elderly group had a higher prevalence of Chagas' disease (P = 0.004) and a lower pressure of the lower esophageal sphincter [26.4 mm Hg vs 31.9 mm Hg] P = 0.001, a difference that persisted when analyzed only elderly and young patients with idiopathic achalasia. Younger patients had a higher prevalence of heartburn (P = 0.001) and chest pain (P = 0.012) than the elderly. CONCLUSION: Elderly patients with achalasia had a lower esophageal sphincter pressure than the young, even when we excluded patients with Chagas' disease but, as a group, they were less symptomatic