ABSTRACT
We demonstrate the transfer of a cesium frequency standard steered to UTC(NIST) over 20 km of dark telecom optical fiber. Our dissemination scheme uses an active stabilization technique with a phase-locked voltage-controlled oscillator. Out-of-loop characterization of the optical fiber link performance is done with dual-fiber and single-fiber transfer schemes. We observe a fractional frequency instability of 1.5 × 10-12 and 2 × 10-15 at averaging intervals of 1 s and 105 s, respectively, for the link. Both schemes are sufficient to transfer the cesium clock reference without degrading the signal, with nearly an order of magnitude lower fractional frequency instability than the cesium clocks over all time scales. The simplicity of the two-fiber technique may be useful in future long-distance applications where higher stability requirements are not paramount, as it avoids technical complications involved with the single-fiber scheme.
ABSTRACT
According to Social Cognitive Theory (Bandura, 1997), nutritional risk would be predicted by perceptions of nutrition efficacy, which in turn would be predicted from four sources: modeling, verbal support, physiological conditions, and nutrition habits. In telephone interviews with 154 rural elderly adults (44 men, 110 women; mean age = 74.4 years), nutritional risk was measured with Nutritional Risk Index (NRI), Nutritional Screening Initiative (NSI), and seven-high-risk-nutrients consumed less than 50 percent of RDA (Diet Plus Analysis). Nutrition-efficacy was measured with a new twenty-five-item scale of Perceived Nutrition Barriers (PNB). Sources of nutrition-efficacy included: mealtime modeling--shared meals, household size; verbal support--people talk to each day, hours talked, number of confidants; physiological conditions that may affect nutrition--age, body mass, medications, disability, negative affect, and nutrition habits--daily food variety, use of meal services. Path analysis was performed with each measure of nutritional risk (NRI, NSI, 7-high-risk-nutrients) as a criterion variable, nutrition-efficacy (PNB) as a possible mediating variable, and sources of nutrition-efficacy as predictor variables. Social Cognitive variables accounted for 58 percent of variance in NRI, 49 percent of variance in NSI, and 29 percent of variance in seven-high-risk-nutrients. Nutritional risk was directly predicted by large households, few shared meals, few confidants, high body mass, many medications, and few daily foods; it was indirectly predicted (via PNB) by high levels of negative affect. Perceived Nutrition Barriers (PNB) most often mentioned were food cost, eating alone, food tastelessness, transportation to the store, and chewing difficulty.
