Superlocalization of Excitons in Carbon Nanotubes at Cryogenic Temperature

At cryogenic temperature and at the single emitter level, the optical properties of single-wall carbon nanotubes depart drastically from that of a one-dimensional (1D) object. In fact, the (usually unintentional) localization of excitons in local potential wells leads to nearly 0D behaviors such as photon antibunching, spectral diffusion, inhomogeneous broadening, etc. Here, we present a hyperspectral imaging of this spontaneous exciton localization effect at the single nanotube level using a super-resolved optical microscopy approach. We report on the statistical distribution of the trap localization, depth, and width. We use a quasi-resonant photoluminescence excitation approach to probe the confined quantum states. Numerical simulations of the quantum states and exciton diffusion show that the excitonic states are deeply modified by the interface disorder inducing a remarkable discretization of the excitonic absorption spectrum and a quenching of the free 1D exciton absorption.

[Effect of optimized integrated management on long-term effectiveness of cardiologic rehabilitation]

BACKGROUND AND OBJECTIVE

Long-term risk factor (RF) modification after cardiac rehabilitation (CR) is less than satisfactory. Problems of communication between the CR centre and the practising physician (GP) are one potential source of sub-optimal management. The goal of the PROTECT-study was to evaluate the influence of improved communication between rehabilitation centres and the GP on the quality of RF-modification.

PATIENTS AND METHODS

In 50 specialized CR centres 882 patients in the group with intensified communication were compared to 160 patients in the usual care group. All patients underwent a course of residential CR. Intensified communication was attempted by a total of four phone calls to the GP, a RF booklet in which the RF profile, the individual RF treatment goals and the current RF status were delineated. Main treatment goals with respect to RF-modification after 6 months were: Blood pressure < 140/90 mmHg, LDL-Cholesterol < 100 mg/dl or at least 115 mg/dl and a body mass index of < 25 or at least < 30.

RESULTS

The percentage of of patients with adequate blood pressure control (< 140/90 mmHg) was 85.1% vs. 85%, with LDL-cholesterol < 100 mg/dl 27.2% vs. 23.9%, with good body-mass index (< 25) 32.4% vs. 28.2% (intensified communication vs. control group; p = ns). The treatment initiated by the CR centres was continued in about 90% of patients.

CONCLUSION

The study has shown that improved communication between the CR centres and the GP's after CR had only a marginal effect on the quality of RF-management. One key element of secondary prevention could be to get the patient more strongly involved in reaching the targets of therapy.

Imaging the activity of nitrate reductase by means of a scanning electrochemical microscope

Scanning electrochemical microscopy (SECM) was used to characterize immobilized nitrate reductase (NaR) from Pseudonomonas stutzeri (E.C. 1.7.99.4). Nitrate reductase with membrane fragment was embedded in a polyurethane hydrogel in a capillary and solubilized NaR without membrane fragment was covalently coupled to a diaminoethyl-cellulose-carbamitate film on glass. After systematic studies of possible mediators, SECM feedback imaging of both forms of immobilized NaR was accomplished with methylviologen as redox mediator.

[Comparison of the pharmacokinetic behavior of Turivital, Acesal and Micristin]

The 3 acetylsalicylic acid preparations showed at normal patients at the same elimination phase no significant differences concerning the bioavailability (comparison of the area under the concentration-time-curve). The absorption kinetics of the preparations were different: the time up to the maximum serum concentration was at Turivital with 1,3 +/- 0,7 h and Micristin (2,1 +/- 0,8 h) the shortest, because the resorption delay was at Turivital the smallest. Absorption constant, fictive initial concentration and maximum concentration in serum are nearly the same in all 3 preparations.

[Stimulation of the renal excretion of p-aminohippuric acid by probenecid homologues (author's transl)]

Probenecid and five of its homologues showed increased lipophilicity with increasing chain length of the substituents. Parallel to this, the toxicity increased about 30 times. All the probenecide homologues under study stimulated the excretion of p-aminohippuric acid (PAH) when applied repeatedly. If a threshold dose is exceeded, an increase of the pretreatment dose will not result in a further increase in PAH excretion. As compared to non-pretreated control animals, the highest possible increase in PAH excretion lies between 40 and 80% independently of the structure of the respective probenecide homologue. Due to their more favourable therapeutic range (LD50 divided by D40-50), the probenecide homologues with shorter chains are better suited to stimulate the excretion of PAH, though the extent of stimulation is the same with all the probenicide homologues under study.

Influence of drugs on bile acid excretion

The hydroxylation of bile acids in rat liver microsomes in cyt P-450 dependent (Björkhem et al., 1975). To find out possible interactions between drugs and bile acid hydroxylation and/or active transport mechanisms we investigated the influence of the microsomal inhibitor metyrapon, the microsomal inducer phenobarbital and the intrahepatic cholestasis producing agents chlorpromazine, phenylbutazone and progesteron on bile flow and bile acid excretion. The excretion in monohydroxy (MBA), dihydroxy (DBA) and trihydroxy (TBA) bile acids were estimated in bile-fistula rats in three one hour periods. MBA, DBA and TBA were separated with thinlayer-chromatography and estimated fluorimetrically. Bile flow, bile acid excretion and relation TBA/DBA were influenced by acute and subchronic administration of the above mentioned drugs in different ways.

[Pharmacokinetics of indomethacin and indomethacin metabolites administered continuously to patients with healthy or damaged kidneys]

After oral administration of 75 mg Indomethacin dlimination half-life of the unchanged drug is not altered in patients with severely impaired renal function. In patients with renal insufficiency half-life of Indomethacin plus metabolites is twice that of the normal value. Repeated daily administration of 75 mg for 8 days does not influence Indomethacin kinetics. In the control group and in patients with moderate by impaired renal function Indomethacin half-life does not change during chronic administration.

[Age dependent differences in the pharmacokinetics of furosemide in rats]

After i.p. administration of 0,60 mg/100 g of furosemide, adult rats excreted 50 to 70% of this diuretic drug unchanged and 10% as desfurylmethylfurosemide. The renal excretion of furosemide is slower in 5- and 15-day-old rats. Age differences in absorption from the abdominal cavity or in the reabsorption rate in the kidney tubules can be excluded. The excretion of furosemide by the kidney is competitively inhibited by p-aminohippuric acid (PAH). The relative small inhibitory effect of PAH in young rats is caused by a smaller participation of tubular secretion in the renal excretion of furosemide in this age group. The half life time of furosemide is 83 min in 5-day-old rats and 47 min in 55-day-old rats. The distribution volume is 146% of body weight in both age groups. The concentration of furosemide in the kidney homogenate is higher in young rats than in adults. The slow renal excretion of furosemide in young rats is in accordance with the prolonged efficacy. The greater efficacy of furosemide in 5- and 15-day-old rats than in adults is caused particularly by differences in the conditions for diuretic effectiveness, especially by the retention of water and electrolytes in young rats.

[Age related effects of furosemide in the rat]

Furosemide (6 mg/kg i.p.) increases the renal excretion of water, osmotic active substances, sodium and chloride in 5 to 33 day old rats more than in adults. The dose-response-relations are the same in rats of all age groups: 6 mg/kg of furosemide i.p. are very effective, an increase in dose to 30-60 mg/kg i.p. is not followed by a significantly higher efficacy. The increase in the renal excretion of potassium, hydrogen ions, ammonium and hydrogen carbonate by furosemide is also small in young rats.