Development of a method for calculating high-dimension heat networks

A transition from the mass balance equations based on Kirchhoff’s first and second laws to modeling on the basis of a discretized continuity equation is made for describing a hydraulic network. A technique for calculating high-dimension hydraulic and heat networks based on the numerical finite-difference control volume method is developed. Unlike the existing approaches, the proposed technique does not involve the need to determine hydraulic loops and boils down to solving the problem of obtaining a unified field of pressures for the entire calculation region. This advantage of the proposed method opens the possibility of applying it for solving high-dimension problems containing more than a million of hydraulic links. The proposed numerical method features stable operation for hydraulic networks the neighboring links of which may have pressure drop coefficients differing from each other by more than 10 orders of magnitude. In contrast, the global gradient algorithm implemented in the standard software system EPANET is of little use for such applications. The convergence rate of the proposed technique is close to that of the Todini gradient algorithm and is almost independent of the problem dimension.     

Lifshitz topological impurity transitions in bismuth wires doped with acceptor and donor impurities

This paper reports the results of an experimental study of electronic topological transitions in bismuth glass-covered wires doped with acceptor (Sn) and donor (Te) impurities. The temperature dependences of the thermoelectric power and resistance are measured within the temperature range from 1.5 to 300 K and magnetic fields up to 14T. The position of the Fermi level ε_F and the concentration of charge carriers at doping are estimated from the Shubnikov de Haas (SdH) oscillations which are clearly visible from both L electrons and L and T holes in all crystallographic directions. We demonstrate anomalies in the temperature dependences of the thermopower in Bi wires doped with acceptor (Sn) and donor (Te) impurities in the form of a triple (doping by Sn) and double (doping by Te) change in the sign of the thermopower. The effect is interpreted with relation to the manifestation of impurity Lifshitz topological transitions. The SdH oscillation method was used to determine the energy position of the Σ band by doping Bi wires with the acceptor impurity Sn and the T band conduction by doping with Te. It is shown that the appearance of the Σ and T bands in Bi wires doped with the acceptor and donor impurities is responsible for the anomalies in the diffusive thermoelectric power, which gives a good conform with to the theoretical models and predictions.     

Urinary free cortisol excretion in chronic fatigue syndrome, major depression and in healthy volunteers

Urinary free cortisol excretion (UFC) was compared in 21 patients with chronic fatigue syndrome (CFS), in 10 melancholic depressives and in 15 healthy controls. Patients with depression had UFC values which were significantly higher than healthy comparison subjects, whereas UFC excretion of CFS patients was significantly lower than the comparison group. These findings are in keeping with currently held hypotheses of hyperactivity and hypoactivity of the hypothalamic-pituitary-adrenal (HPA) axis in depression and chronic fatigue syndrome respectively. Five of the 21 CFS patients had a co-morbid depressive illness. This sub-group retained the profile of UFC excretion of those with CFS alone, suggesting a different pathophysiological basis for depressive symptoms in CFS.     

Comparison of the pharmacological profile of S-nitrosothiols, nitric oxide and the nitrergic neurotransmitter in the canine ileocolonic junction

1. In organ bath experiments, hydroquinone (30-100 microM) and hydroxocobalamin (30-100 microM) concentration-dependently inhibited the relaxations induced by NO (0.3-30 microM) but not those by nitroglycerin (GTN, 1 microM) in the canine ileocolonic junction (ICJ). Hydroxocobalamin reduced the relaxation to low frequency (2 Hz) stimulation of the non-adrenergic, non-cholinergic (NANC) nerves, whereas hydroquinone only reduced the NANC nerve-mediated relaxations to electrical stimulation at 16 Hz, 0.5 ms. 2. Relaxations to S-nitroso-L-cysteine (CysNO, 1-30 microM), or S-nitroso-N-acetyl-D,L-penicillamine (SNAP, 1-30 microM) were not inhibited by hydroquinone (30-100 microM), hydroxocobalamin (30-100 microM), pyrogallol (30-100 microM) or L-cysteine (1-3 microM). Hydroquinone (100 microM) only reduced the relaxation to 10 microM CysNO. Hydroxocobalamin, but not hydroquinone, pyrogallol or L-cysteine, potentiated the relaxations to the lowest concentration (1 microM) of S-nitrosoglutathione (GSNO, 1-30 microM). 3. In the superfusion bioassay, hydroquinone (100 microM) and hydroxocobalamin (1 microM) concentration-dependently inhibited the biological activity of authentic NO (1-4 pmol) to the same extent as that of the transferable nitrergic factor, released from the canine ICJ in response to NANC nerve stimulation (8-16 Hz, 2 ms). Responses to GTN (10 pmol) or adenosine 5'-triphosphate (10 nmol) were not affected. 4. In conclusion, the nitrosothiols CysNO, SNAP and GSNO relax the canine ileocolonic junction, but these relaxations, pharmacologically, behave differently from the NANC nerve-mediated relaxations. From the bioassay experiments, we conclude that the nitrergic factor, released in response to NANCnerve stimulation of the canine ICJ, behaves pharmacologically like NO but not like a nitrosothiol.Therefore, we suggest NO, and not CysNO, SNAP or GSNO as the inhibitory NANC neurotransmitter in the canine ICJ.     

Efficacy of low-dose dopamine in preventing amphotericin B nephrotoxicity in bone marrow transplant patients and leukemia patients

This study evaluated the efficacy of low-dose dopamine for prevention of amphotericin B-induced nephrotoxicity in autologous bone marrow transplant and leukemia patients. Seventy-one patients undergoing cytoreductive therapy who required amphotericin B were randomly assigned in an unblinded fashion to a group receiving continuous-infusion low-dose dopamine (3 microgram/kg/min) or a group receiving no dopamine. Amphotericin B was dosed at 0.5 or 1.0 mg/kg/day based on computerized tomography scan results or presence of positive blood cultures. No patient received saline boluses. The rate of nephrotoxicity, severity as graded by Southwest Oncology Group toxicity criteria, and time to each grade of nephrotoxicity were compared between the two groups. Eighty percent of the no-dopamine group and 66.7% of the dopamine group developed nephrotoxicity, defined as a 1.5-fold or greater increase in baseline serum creatinine level (P = 0.20). No statistical difference was noted at any grade of nephrotoxicity between the two groups. Thirty-four percent of patients in the no-dopamine group versus 17.6% in the dopamine group had a 2.5-fold or greater increase in serum creatinine level, which was not statistically significant (P = 0.0888). Ten patients developed grade IV nephrotoxicity and were withdrawn from the study, 7 in the no-dopamine group and 3 in the dopamine group (P = 0.19). The time to each grade of nephrotoxicity was also not significantly different for the two groups. Eleven adverse drug reactions were reported in the dopamine group in comparison to one in the no-dopamine group. Thus, dopamine offers little in the way of prevention of nephrotoxicity associated with amphotericin B therapy. Although the significance of drug reactions in the dopamine group is not clearly established due to lack of cardiac monitoring in the no-dopamine group, dopamine therapy is not without complications.     

Genetic susceptibility testing: ethical and social quandaries

We have isolated a novel human C-C chemokine, MIP-1 delta from a human fetal spleen cDNA library. The human MIP-1 delta cDNA has an unusually long 400-bp 5-prime untranslated region and a predicted 113-amino acid protein of 10 kDa. The coding sequence contains a signal peptide of 21 amino acids, indicating that the mature protein has 92 amino acids (8 kDa). Recombinant human MIP-1 delta produced by transfected human embryonic kidney 293 cells produced an 8-kDa protein, which confirmed the presence of a signal peptide. Compared with other human C-C chemokines, human MIP-1 delta shows the highest homology with human HCC-1, CK beta-8, murine C10, and CCF18 (MIP-1 gamma). The human MIP-1 delta gene is localized on chromosome 17 where most of the C-C chemokine superfamily is located. Human MIP-1 delta is expressed in T and B lymphocytes, NK cells, monocytes, and monocyte-derived dendritic cells, but not in bone marrow-derived dendritic cells. Its expression can be induced by other proinflammatory cytokines in monocytes and dendritic cells. Human MIP-1 delta is chemotactic for T cells and monocytes, but not for neutrophils, eosinophils, or B cells. Human MIP-1 delta induced calcium flux in human CCR1-transfected cells.