Adiabatic charge pumping in carbon nanotube quantum dots.

We investigate charge pumping in carbon nanotube quantum dots driven by the electric field of a surface acoustic wave. We find that, at small driving amplitudes, the pumped current reverses polarity as the conductance is tuned through a Coulomb blockade peak using a gate electrode. We study the behavior as a function of wave amplitude, frequency, and direction and develop a model in which our results can be understood as resulting from adiabatic charge redistribution between the leads and quantum dots on the nanotube.

Therapy conversion to insulin detemir among patients with type 2 diabetes treated with oral agents: a modeling study of cost-effectiveness in the United States.

The aim of this study was to gain a preliminary indication of the long-term clinical and economic implications of converting treatment for patients with type 2 diabetes to insulin detemir+/-oral hypoglycemic agents (OHAs) in a routine clinical practice setting in the United States. With the use of outcome data and patient characteristics reported from an ongoing prospective observational trial, a validated computer simulation model of diabetes was used to project the clinical and cost outcomes associated with therapy conversion to insulin detemir over a 35-y period from (1) OHA only, (2) neutral protamine Hagedorn insulin (NPH)+/-OHA, and (3) insulin glargine+/-OHA. Cost-effectiveness was assessed from a third-party healthcare payer perspective for the year 2005. Costs and clinical outcomes were discounted at a rate of 3%. Treatment with insulin detemir+/-OHA was associated with increases in quality-adjusted life expectancy of 0.309, 0.350, and 0.333 quality-adjusted life-years (QALYs) versus treatment with OHA alone, NPH+/-OHA, and insulin glargine+/-OHA, respectively. Increases in pharmacy costs were partially offset by reduced complications, rticularly renal complications and neuropathy. Projected incremental cost-effectiveness ratios were well within the range considered to represent good value in the United States, at $7412, $6269, and $3951 per QALY gained for treatment with Idet+/-OHA versus OHA alone, NPH+/-OHA, and Iglarg+/-OHA, respectively. On the basis of preliminary evidence of short-term improvements in glycemic control and reduced hypoglycemia, therapy conversion to insulin detemir+/-OHA from OHA alone, NPH+/-OHA, or insulin glargine+/-OHA was projected to increase quality-adjusted life expectancy and to represent a cost-effective treatment option in the United States.

Insulin therapy in type 2 diabetes patients failing oral agents: cost-effectiveness of biphasic insulin aspart 70/30 vs. insulin glargine in the US.

OBJECTIVES: To project the long-term clinical and economic outcomes of treatment with biphasic insulin aspart 30 (BIAsp 70/30, 30% soluble and 70% protaminated insulin aspart) vs. insulin glargine in insulin-naïve type 2 diabetes patients failing to achieve glycemic control with oral antidiabetic agents alone (OADs). METHODS: Baseline patient characteristics and treatment effect data from the recent 'INITIATE' clinical trial served as input to a peer-reviewed, validated Markov/Monte-Carlo simulation model. INITIATE demonstrated improvements in HbA1c favouring BIAsp 70/30 vs. glargine (-0.43%; p < 0.005) and greater efficacy in reaching glycaemic targets among patients poorly controlled on OAD therapy. Effects on life expectancy (LE), quality-adjusted life expectancy (QALE), cumulative incidence of diabetes-related complications and direct medical costs (2004 USD) were projected over 35 years. Clinical outcomes and costs were discounted at a rate of 3.0% per annum. Sensitivity analyses were performed. RESULTS: Improvements in glycaemic control were projected to lead to gains in LE (0.19 +/- 0.24 years) and QALE (0.19 +/- 0.17 years) favouring BIAsp 70/30 vs. glargine. Treatment with BIAsp 70/30 was also associated with reductions in the cumulative incidences of diabetes-related complications, notably in renal and retinal conditions. The incremental cost-effectiveness ratio was $46 533 per quality-adjusted life year gained with BIAsp 70/30 vs. glargine (for patients with baseline HbA1c >/= 8.5%, it was $34 916). Total lifetime costs were compared to efficacy rates in both arms as a ratio, which revealed that the lifetime cost per patient treated successfully to target HbA1c levels of <7.0% and

Improving life expectancy and decreasing the incidence of complications associated with type 2 diabetes: a modelling study of HbA1c targets.

To project the long-term clinical and cost outcomes that accompany predefined improvements in glycaemic control in patients with type 2 diabetes. A peer-reviewed, validated, non-product-specific Markov model of type 2 diabetes was used to project the long-term clinical and cost outcomes associated with three HbA1c reduction scenarios (vs. no reduction): (i) decreasing mean HbA1c from 9.5% to 8.0%; (ii) from 8.0% to 7.0%; and (iii) from 7.0% to 6.5%. A typical baseline US type 2 diabetes cohort derived from National Health and Nutrition Examination Survey data was simulated over a lifetime horizon (35 years). Incidence of diabetes-related complications and costs (2005 USD) were accounted based on published data. Discount rates (3% per annum) were applied to clinical benefits and costs. Sensitivity analyses were performed. Stepwise reductions in HbA1c as an independent variable correlated with delayed time to diabetes-related complications and a reduced cumulative incidence of complications, including cardiovascular, renal and neurologic comorbidities. Related costs also decreased. Reductions in both poorly- (9.5-8.0%) and better-controlled (7.0-6.5%) patients produced incremental gains in undiscounted life expectancy (LE) [1.06 (0.31) and 0.32 (0.34) years [mean (SD)], respectively]. Similar improvement patterns were observed in quality-adjusted life expectancy (QALE). Benefits from sequential reduction scenarios, when aggregated, exhibited the most dramatic effect. Improved glycaemic control was associated with reductions in complication rates and costs, as well as increased LE and QALE among type 2 patients. These data illustrate the long-term importance of reaching normoglycaemia and support intensified HbA1c control as a cornerstone of effective long-term type 2 diabetes management.

Mesoscopic oscillations of the conductance of disordered metallic samples as a function of temperature.

We show theoretically and experimentally that the conductance of small disordered samples exhibits random oscillations as a function of temperature. The amplitude of the oscillations decays as a power law of temperature, and their characteristic period is of the order of the temperature itself.

Charge pumping in carbon nanotubes.

We demonstrate charge pumping in semiconducting carbon nanotubes by a traveling potential wave. From the observation of pumping in the nanotube insulating state we deduce that transport occurs by packets of charge being carried along by the wave. By tuning the potential of a side gate, transport of either electron or hole packets can be realized. Prospects for the realization of nanotube based single-electron pumps are discussed.

Kondo physics in carbon nanotubes.

The connection of electrical leads to wire-like molecules is a logical step in the development of molecular electronics, but also allows studies of fundamental physics. For example, metallic carbon nanotubes are quantum wires that have been found to act as one-dimensional quantum dots, Luttinger liquids, proximity-induced superconductors and ballistic and diffusive one-dimensional metals. Here we report that electrically contacted single-walled carbon nanotubes can serve as powerful probes of Kondo physics, demonstrating the universality of the Kondo effect. Arising in the prototypical case from the interaction between a localized impurity magnetic moment and delocalized electrons in a metallic host, the Kondo effect has been used to explain enhanced low-temperature scattering from magnetic impurities in metals, and also occurs in transport through semiconductor quantum dots. The far greater tunability of dots (in our case, nanotubes) compared with atomic impurities renders new classes of Kondo-like effects accessible. Our nanotube devices differ from previous systems in which Kondo effects have been observed, in that they are one-dimensional quantum dots with three-dimensional metal (gold) reservoirs. This allows us to observe Kondo resonances for very large electron numbers (N) in the dot, and approaching the unitary limit (where the transmission reaches its maximum possible value). Moreover, we detect a previously unobserved Kondo effect, occurring for even values of N in a magnetic field.