RESUMEN
It has been shown that the relative stabilities of various superfluid states of ^{3}He can be influenced by anisotropy in a silica aerogel framework. We prepared a suite of aerogel samples compressed up to 30% for which we performed pulsed NMR on ^{3}He imbibed within the aerogel. We identified A and B phases and determined their magnetic field-temperature phase diagrams as a function of strain. From these results, we infer that the B phase is distorted by negative strain forming an anisotropic superfluid state more stable than the A phase.
RESUMEN
In recent work, it was shown that new anisotropic p-wave states of superfluid (3)He can be stabilized within high-porosity silica aerogel under uniform positive strain. In contrast, the equilibrium phase in an unstrained aerogel is the isotropic superfluid B phase. Here we report that this phase stability depends on the sign of the strain. For a negative strain of â¼ 20% achieved by compression, the B phase can be made more stable than the anisotropic A phase, resulting in a tricritical point for A, B, and normal phases with a critical field of â¼ 100 mT. From pulsed NMR measurements, we identify these phases and the orientation of the angular momentum.
RESUMEN
Superfluid ^{3}He confined to high porosity silica aerogel is the paradigm system for understanding impurity effects in unconventional superconductors. However, a crucial first step has been elusive: exact identification of the microscopic states of the superfluid in the presence of quenched disorder. Using a new class of highly uniform aerogel materials, we report pulsed nuclear magnetic resonance experiments that demonstrate definitively that the two observed superfluid states in aerogel are impure versions of the isotropic and axial p-wave states. The theoretically predicted destruction of long-range orbital order (Larkin-Imry-Ma effect) in the impure axial state is not observed.
RESUMEN
BACKGROUND: Widespread antibiotic use has fostered the emergence of antibiotic-resistant bacteria. Parental expectations have been cited as one reason for physicians to overprescribe antibiotics. The objective of this study was to determine parental knowledge about antibiotics and their use for common respiratory tract infections. METHODS: A survey was administered to 100 adults at a rural pediatric office. RESULTS: Many respondents had misconceptions about the etiology of common respiratory tract infections and the effects of antibiotic therapy. Only 54% knew that a virus is the usual cause of the common cold, and 33% thought that a virus causes strep throat. Almost half (46%) believed that antibiotics kill viruses, while 17% were not sure whether antibiotics kill viruses. Most respondents (60%) had never heard about antibiotic resistance. CONCLUSION: Parental knowledge about common respiratory tract infections and about antibiotic therapy is often lacking. Improved parent education may alter parents' expectations concerning antibiotic therapy for their ill children.
