Biomedical subjects

J Michałowski

Publications and source records attributed to J Michałowski.

11 recordsLinked to original sources

PubMed2003

Significance of the fragmentation region in ultrarelativistic heavy-ion collisions.

We present measurements of the pseudorapidity distribution of primary charged particles produced in Au+Au collisions at three energies, sqrt[s(NN)]=19.6, 130, and 200 GeV, for a range of collision centrali-ties. The distribution narrows for more central collisions and excess particles are produced at high pseudorapidity in peripheral collisions. For a given centrality, however, the distributions are found to scale with energy according to the "limiting fragmentation" hypothesis. The universal fragmentation region described by this scaling grows in pseudorapidity with increasing collision energy, extending well away from the beam rapidity and covering more than half of the pseudorapidity range over which particles are produced. This approach to a universal limiting curve appears to be a dominant feature of the pseudorapidity distribution and therefore of the total particle production in these collisions.

Journal Article↗

PubMed2002

Pseudorapidity and centrality dependence of the collective flow of charged particles in Au+Au collisions at sqrt[s(NN)]=130 GeV.

This paper describes the measurement of collective flow for charged particles in Au+Au collisions at sqrt[s(NN)]=130 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider (RHIC). The measured azimuthal hit anisotropy is presented over a wide range of pseudorapidity (-5.0<eta<5.3) for the first time at this energy. The result, averaged over momenta and particle species, is observed to reach 7% for peripheral collisions at midrapidity, falling off with centrality and increasing |eta|. These results call into question the common assumption of longitudinal boost invariance over a large region of rapidity in RHIC collisions.

Journal Article↗

PubMed2001

Energy dependence of particle multiplicities in central Au+Au collisions.

We present the first measurement of the pseudorapidity density of primary charged particles in Au+Au collisions at root square[s(NN)] = 200 GeV. For the 6% most central collisions, we obtain dN(ch)/d(eta)/(/eta/<1) = 650+/-35(syst). Compared to collisions at root square[s(NN)] = 130 GeV, the highest energy studied previously, an increase by a factor of 1.14+/-0.05 at 90% confidence level, is found. The energy dependence of the pseudorapidity density is discussed in comparison with data from proton-induced collisions and theoretical predictions.

Journal Article↗

PubMed2001

Charged-particle pseudorapidity density distributions from Au+Au collisions at sqrt[s(NN)]=130 GeV.

The charged-particle pseudorapidity density dN(ch)/d eta has been measured for Au+Au collisions at sqrt[s(NN)] = 130 GeV at RHIC, using the PHOBOS apparatus. The total number of charged particles produced for the 3% most-central Au+Au collisions for /eta/<or=5.4 is found to be 4200+/-470. The evolution of dN(ch)/d eta with centrality is discussed, and compared to model calculations and to data from proton-induced collisions. The data show an enhancement in charged-particle production at midrapidity, while in the fragmentation regions, the results are consistent with expectations from pp and pA scattering.

Journal Article↗

PubMed2001

Ratios of charged antiparticles-to-particles near mid-rapidity in Au + Au collisions at sqrt[s(NN)]=130 GeV.

We have measured the ratios of antiparticles to particles for charged pions, kaons, and protons near mid-rapidity in central Au+Au collisions at sqrt[s(NN)] = 130 GeV. We observe / = 1.00+/-0.01(stat)+/-0.02(syst), / = 0.91+/-0.07(stat)+/-0.06(syst), and / = 0.60+/-0.04(stat)+/-0.06(syst). The / and / ratios give a consistent estimate of the baryo-chemical potential mu(B) of 45 MeV, a factor of 5-6 smaller than in central Pb+Pb collisions at sqrt[s(NN)] = 17.2 GeV.

Journal Article↗

PubMed2000

Charged-particle multiplicity near midrapidity in central Au+Au collisions at sqrt[SNN]=56 and 130 GeV.

We present the first measurement of pseudorapidity densities of primary charged particles near midrapidity in Au+Au collisions at sqrt[s(NN)] = 56 and 130 GeV. For the most central collisions, we find the charged-particle pseudorapidity density to be dN/deta|(|eta|<1) = 408+/-12(stat)+/-30(syst) at 56 GeV and 555+/-12(stat)+/-35(syst) at 130 GeV, values that are higher than any previously observed in nuclear collisions. Compared to proton-antiproton collisions, our data show an increase in the pseudorapidity density per participant by more than 40% at the higher energy.

Journal Article↗

PubMed2000

Chemiluminescence determination of thioridazine hydrochloride by flow-injection analysis.

Hydrogen peroxide, potassium permanganate, potassium dichromate, potassium hexacyanoferrate(III), cerium(IV) sulphate and sodium peroxidisulphate have been tested as potential reagents for chemiluminescence generation from the oxidation of phenothiazine derivatives. Only with potassium permanganate in acidic medium were satisfying results achieved. A total of 13 different phenothiazine derivatives produce luminescence of different intensities on oxidation. Thioridazine hydrochloride was chosen to develop a rapid and simple method for its determination in pharmaceutical formulations. The limit of detection is 1.2 x 10(-6) mol l(-1), and 110 samples per hour can be determined.

Antipsychotic Agents↗

PubMed1989

[Not Available].

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General Surgery↗

PubMed1980

Directly measured tension-time index as a correlate of myocardial oxygen consumption.

Left ventricular systolic pressure (LVSP) and stress in the outer layers of the left ventricular wall were directly recorded in 10 anaesthetised, open-chested dogs. Left ventricular oxygen consumption (VO2) was calculated from the difference in oxygen content in the arterial and in the coronary sinus blood and from the left ventricular coronary flow (LVCF). LVCF was measured in the shunt between the carotid artery and left coronary artery (2 experiments) or in the shunt between the coronary sinus and jugular vein. Tension-time index was calculated either as the product of the mean LVSP and time (TTI(P)), or as the product of mean systolic stress and time (TTI(sigma)). Both TTIs were changed within the broad range by means of exsanguination and blood infusion. Contractility was changed by means of Inderal or noradrenaline infusion. In all experimental conditions VO2/100 g/stroke correlated linearly (P less than 0.01) with TTI(sigma), with correlation coefficient r greater than 0.8. When TTI(P) was used, correlation coefficient r was less than 0.6 and no correlation was found in one series of experiments with noradrenaline infusion. It is concluded that TTI calculated from the directly measured wall stress is a very good correlate of the VO2, which is not the case when the 'classical' TTI is used.

Animals↗

PubMedDate not supplied

Evaluation of extravascular resistance in the unloaded fibrillating left ventricle of the dog.

In open-chest anaesthetized dogs the relative magnitude of extravascular resistance in the superficial and deep left ventricular myocardium was estimated from the flow through the isolated vascular segments inserted at different depths of the myocardium. It was confirmed that in the normally working heart extravascular resistance was significantly greater in the deep than in the superficial layer. In the unloaded fibrillating left ventricle no difference in extravascular resistance between these layers could be detected. Since it had been found previously that subendocardial preponderance of ischaemia persists in the unloaded fibrillating left ventricle (Sedek and Michałowski, submitted for publication), the present observation is a further challenge for the current view that the subendocardium is more vulnerable to ischaemia because extravascular resistance is greater in this layer.

Animals↗

PubMedDate not supplied

Influence of surgery and experimental myocardial infarction on blood levels of free fatty acids and triiodothyronine in dogs.

Preparatory operations (PO) including thoracotomy have been performed in 11 dogs. After 6 days in 6 dogs the left anterior descending coronary artery (LAD) was ligated leading to development of acute myocardial infarction (MI). Both after PO and during MI and increase in plasma free fatty acids (FFA) and a decrease in serum triiodothyronine (T3) was observed. There was a negative correlation between T3 and FFA 4--22 hours after PO and 9--22 hours after LAD ligation. In control dogs without LAD ligation a positive correlation between FFA and T3 levels was shown 8--18 days after PO during the period of wound healing. It seems that the combination of elevated FFA and depressed T3 reflects the metabolic disturbances which are more pronounced during MI than after surgical operation connected with thoracotomy.

Animals↗