W=0 Pairing in (N,N)(N,N) Carbon Nanotubes away from Half Filling

We use the Hubbard Hamiltonian $H$ on the honeycomb lattice to represent the valence bands of carbon single-wall $(N,N)$ nanotubes. A detailed symmetry analysis shows that the model allows W=0 pairs which we define as two-body singlet eigenstates of $H$ with vanishing on-site repulsion. By means of a non-perturbative canonical transformation we calculate the effective interaction between the electrons of a W=0 pair added to the interacting ground state. We show that the dressed W=0 pair is a bound state for resonable parameter values away from half filling. Exact diagonalization results for the (1,1) nanotube confirm the expectations. For $(N,N)$ nanotubes of length $l$, the binding energy of the pair depends strongly on the filling and decreases towards a small but nonzero value as $l \to \infty$. We observe the existence of an optimal doping when the number of electrons per C atom is in the range 1.2$\div$1.3, and the binding energy is of the order of 0.1 $\div$ 1 meV.Comment: 16 pages, 6 figure

Westeinde sciatica trial: randomized controlled study of bed rest and physiotherapy for acute sciatica.

OBJECT: The authors conducted a study to compare the efficacies of three nonsurgical treatment strategies in patients with sciatica. Their hypothesis was that bed rest, physiotherapy, and continuation of activities of daily living (ADLs) (control treatment) are each of equivalent efficacy. METHODS: This randomized controlled trial was designed for comparison of bed rest, physiotherapy, and continuation of ADLs. The setting was an outpatient clinic. General practitioners were asked to refer patients for treatment as soon as possible. The authors enrolled 250 patients (< 60 years of age) with sciatica of less than 1-month's duration and who had not yet been treated with bed rest or physiotherapy. Primary outcome measures were radicular pain (based on a visual analog pain scale [VAPS]) and hampered ADLs (Quebec Disability Scale [QDS]). Secondary outcome measures were the rates of treatment-related failure and surgical treatment. Measures were assessed at baseline and during follow up at 1, 2, and 6 months. Mean differences in VAPS and QDS scores between bed rest and control treatment were 2.5 (95% confidence interval [CI] -6.4 to 11.4) and -4.8 (95% CI -10.6 to 0.9) at 1 month and 0.9 (95% CI -8.7 to 10.4) and -2.7 (95% CI -9.9 to 4.4) at 2 months, respectively. The respective differences between physiotherapy and control treatment were 0.8 (95% CI -8.2 to 9.8) and -0.5 (95% CI -6.3 to 5.3) at 1 month and -0.3 (95% CI -9.4 to 10) and 0.0 (95% CI -7.2 to 7.3) at 2 months. The respective odds ratios for treatment failure and surgical treatment of bed rest compared with control treatment were 1.6 (95% CI 0.8-3.5) and 1.5 (95% CI 0.7-3.6) at 6 months. When physiotherapy was compared with control treatment, these ratios were 1.5 (95% CI 0.7-3.2) and 1.2 (95% CI 0.5-2.9) at 6 months, respectively. CONCLUSIONS: Bed rest and physiotherapy are not more effective in acute sciatica than continuation of ADLs

The Orbiting Carbon Observatory (OCO) mission

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Prolonged conservative care versus early surgery in patients with sciatica caused by lumbar disc herniation: two year results of a randomised controlled trial

Objectives To evaluate the effects of early lumbar disc surgery compared with prolonged conservative care for patients with sciatica over two years of follow-up