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J L Jacobsen

Publications and source records attributed to J L Jacobsen.

6 recordsLinked to original sources
PubMed2004

Traveling salesman problem, conformal invariance, and dense polymers.

We propose that the statistics of the optimal tour in the planar random Euclidean traveling salesman problem is conformally invariant on large scales. This is exhibited in the power-law behavior of the probabilities for the tour to zigzag repeatedly between two regions, and in subleading corrections to the length of the tour. The universality class should be the same as for dense polymers and minimal spanning trees. The conjectures for the length of the tour on a cylinder are tested numerically.

Journal Article↗
PubMed2003

Dense loops, supersymmetry, and Goldstone phases in two dimensions.

Loop models in two dimensions can be related to O(N) models. The low-temperature dense-loops phase of such a model, or of its reformulation using a supergroup as symmetry, can have a Goldstone broken-symmetry phase for N<2. We argue that this phase is generic for -2<N<2 when crossings of loops are allowed, and distinct from the model of noncrossing dense loops first studied by Nienhuis [Phys. Rev. Lett. 49, 1062 (1982)]]. Our arguments are supported by our numerical results, and by a lattice model solved exactly by Martins et al. [Phys. Rev. Lett. 81, 504 (1998)]].

Journal Article↗
PubMed2003

A randomized trial of insulin aspart with intensified basal NPH insulin supplementation in people with Type 1 diabetes.

AIMS: Insulin aspart has been shown to improve post-prandial and overall glycaemic control in people with Type 1 diabetes. We hypothesized that insulin aspart with intensified basal NPH insulin supplementation would result in better overall glycaemic control than human regular insulin with standard basal NPH insulin. METHODS: The trial was conducted in 43 centres in seven countries. People with Type 1 diabetes were randomized to mealtime insulin aspart with up to four daily NPH doses if meals were > 5 h apart and a 25% increase in bedtime NPH dose (n = 187), or to mealtime human unmodified insulin with once or twice daily basal NPH insulin (n = 181). Efficacy and safety were evaluated at 12 weeks (primary evaluation period) and 64 weeks. RESULTS: At 12 and 64 weeks there was no statistically significant difference in HbA1c between the insulin aspart and regular insulin groups: -0.09 (95% confidence interval (CI) -0.23, +0.05)% and -0.14 (-0.32, +0.04)%. Post-prandial glucose values were lower and the area under the 24-h self-monitored blood glucose curve above 7.0 mmol/l was 28% smaller with insulin aspart (35.2 +/- 3.2 vs. 48.9 +/- 3.1 mmol/l h, P = 0.0015). No significant differences were found in mild or severe hypoglycaemia, or adverse event rate. At 64 weeks treatment satisfaction was higher in the insulin aspart group (difference 1.57 (95% CI 0.49, 2.64) points, P = 0.004), while quality of life was not different. CONCLUSIONS: Improved post-prandial glycaemic control and treatment satisfaction with insulin aspart were confirmed. Intensifying basal insulin supplementation resulted in a similar HbA1c decrement as previously found with the use of insulin aspart and standard NPH insulin supplementation. This does not support routinely basal NPH insulin intensification when using rapid-acting insulin analogues in daily practice.

Adult↗
PubMed2000

Anopheles arabiensis and An. funestus are equally important vectors of malaria in Matola coastal suburb of Maputo, southern Mozambique.

Transmission characteristics of malaria were studied in Matola, a coastal suburb of Maputo, the capital City, in southern Mozambique, from November 1994 to April 1996. The local climate alternates between cool dry season (May-October) and hot rainy season (November-April) with mean annual rainfall 650-850 mm. Saltmarsh and freshwater pools provide mosquito breeding sites in Matola. Malaria prevalence reached approximately 60% among people living nearest to the main breeding sites of the vectors. Plasmodium falciparum caused 97% of malaria cases, others being P. malariae and P. ovale. Potential malaria vector mosquitoes (Diptera: Culicidae) collected at Matola during daytime indoor-resting (n = 1021) and on human bait at night (n = 5893) comprised 12% Anopheles coustani Laveran (93% biting outdoors), 46% An. funestus Giles (68% biting indoors) and 42% An. gambiae Giles sensu lato (60% biting outdoors). All 215 specimens of An. gambiae s.l. identified genetically were An. arabiensis Patton. Anopheles funestus populations remained stable throughout the year, whereas densities of the An. gambiae complex fluctuated considerably, with An. arabiensis peaking during the rainy season. No concomitant rise in malaria incidence was observed. Human landing indices of An. funestus and An. arabiensis averaged 1.8 and 3.8 per man-night, respectively. Overall Plasmodium sporozoite rates were 2.42+/-1.24% in 2181 An. funestus and 1.11+/-1.25% in 1689 An. arabiensis dissected and examined microscopically. Mean daily survival rates were 0.79 for both vector species. Estimated infective bites/person/year were 15 An. funestus and 12 An. arabiensis. Biting rates were greatest at 2100-24.00 hours for An. funestus (68% endophagic) and 21.00-03.00 hours for An. arabiensis (40% endophagic). The entomological inoculation rate (EIR) declined sharply over very short distances (50% per 90m) away from breeding-sites of the vectors. Consequently, P. falciparum prevalence among Matola residents was halved 350 m within the town. Implications for the protective effectiveness of a 'cordon sanitaire' by residual house-spraying and/or the use of insecticide-treated bednets are discussed.

Animals↗