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P Spiller

Publications and source records attributed to P Spiller.

At least 19 recordsLinked to original sources
PubMed2005

Proposal for the study of thermophysical properties of high-energy-density matter using current and future heavy-ion accelerator facilities at GSI Darmstadt.

The subject of high-energy-density (HED) states in matter is of considerable importance to numerous branches of basic as well as applied physics. Intense heavy-ion beams are an excellent tool to create large samples of HED matter in the laboratory with fairly uniform physical conditions. Gesellschaft für Schwerionenforschung, Darmstadt, is a unique worldwide laboratory that has a heavy-ion synchrotron, SIS18, that delivers intense beams of energetic heavy ions. Construction of a much more powerful synchrotron, SIS100, at the future international facility for antiprotons and ion research (FAIR) at Darmstadt will lead to an increase in beam intensity by 3 orders of magnitude compared to what is currently available. The purpose of this Letter is to investigate with the help of two-dimensional numerical simulations, the potential of the FAIR to carry out research in the field of HED states in matter.

Journal Article↗
PubMed2002

[Candida albicans endocarditis with mycotic aneurysms of the lower leg arteries in a patient with mechanical heart valve prosthesis].

We report on a 53-year-old patient in whom the aortic and mitral valves had been replaced. This patient developed Candida albicans sepsis with mycotic aneurysms of the tibial arteries as well as cerebral emboli under immunosuppression. Dispensing with a valve replacement operation, a sustained freedom from recurrence (period of observation currently 24 months) could be attained with antimycotic therapy with amphotericin B and flucytosine i.v. and subsequent long-term therapy with fluconazole p.o. as well as surgical and interventional clearance of the mycotic aneurysms.

Adult↗
PubMed2001

Necessity of bunch compression for heavy-ion-induced hydrodynamics and studies of beam fragmentation in solid targets at a proposed synchrotron facility.

This paper presents two-dimensional numerical simulations of hydrodynamic response of a solid lead cylindrical target that is irradiated by an intense uranium beam having a particle energy of 1 GeV/u and that consists of 10(12) particles. Different time profiles have been considered for the beam power that include a case where the beam consists of five identical parabolic bunches with equal separation between neighboring bunches as well as a beam that consists of a single bunch. For the single bunch case we consider two different values for pulse length, namely, 1000 and 50 ns, respectively. Moreover we allow for two different values for the beam radius that is 0.5 and 1.0 mm, respectively. These calculations show that in order to achieve a high degree of beam-target coupling, it is absolutely essential to use a single bunched beam that has a reasonably short pulse length, which is 50 ns in this case. Such a large beam-target coupling efficiency is highly desirable for creating high-density strongly coupled plasmas as well as for studies that involve fragmentation of the projectile ions as the beam passes through solid matter. If the pulse length is assumed to be too long, substantial hydrodynamic expansion of the target material occurs during the early stages of irradiation that leads to significant reduction in the energy deposition by the ions that are delivered in the later part of the pulse. In case of the five-bunch configuration, heating caused by the first bunch is so strong that the target is completely distorted. As a result, the ions that are delivered in the later four bunches pass through the target without any interaction.

Journal Article↗
PubMed2000

Metallization of hydrogen using heavy-ion-beam implosion of multilayered cylindrical targets.

Employing a two-dimensional simulation model, this paper presents a suitable design for an experiment to study metallization of hydrogen in a heavy-ion beam imploded multilayered cylindrical target that contains a layer of frozen hydrogen. Such an experiment will be carried out at the upgraded heavy-ion synchrotron facility (SIS-18) at the Gesellschaft für Schwerionenforschung, Darmstadt by the end of the year 2001. In these calculations we consider a uranium beam that will be available at the upgraded SIS-18. Our calculations show that it may be possible to achieve theoretically predicted physical conditions necessary to create metallic hydrogen in such experiments. These include a density of about 1 g/cm(3), a pressure of 3-5 Mbar, and a temperature of a few 0.1 eV.

Journal Article↗
PubMed2000

Shaping of intense ion beams into hollow cylindrical form

A specifically tailored plasma lens could shape a high-energy, heavy-ion beam into the form of a hollow cylinder without loss of beam intensity. It has been experimentally confirmed that both a positive as well as a negative radial gradient of the current density in the active plasma lens can be the underlying principle. Calculations were performed that yield the ideal current density distribution for both cases. A numerical simulation of an experiment with an intense ion beam highlights that the shaping of the beam increases the achievable compression in a lead sample.

Journal Article↗
PubMed2000

X-ray densitometry for the measurement of regional myocardial perfusion.

The evaluation of regional myocardial blood flow (RMBF) during cardiac catheterization is of particular diagnostic interest. The purpose of this investigation was to validate x-ray densitometric parameters for the evaluation of RMBF. In five anesthetized dogs, arterial flow in the circumflex coronary artery was measured continuously with an electromagnetic flowmeter, and RMBF was determined by colored microspheres. Five different perfusion levels were created by mechanical obstruction of the coronary artery or by intravenous infusion of adenosine. At each steady-state perfusion level, digital subtraction coronary angiograms were obtained for densitometric analysis. Results documented a close correlation between the related time parameters 1/Mean Transit Time (1/MTT, r2 = 0.969), and 1/Rise Time (1/RT, r2 = 0.965) and RMBF over a wide range between 0.36 ml/(min x g) and 11.16 ml/(min x g). Maximum myocardial contrast density (Imax) also showed a good, but inverse correlation (r2 = 0.889) with RMBF and, therefore, did not reflect vascular volume. Contrast medium Appearance Time (AT) showed no correlation to RMBF (r2 = 0.017). Repeat densitometric measurements for different perfusion levels revealed a good reproducibility for MTT (accuracy: 0.001 s; precision: 0.447 s or 6.7 %) and RT (accuracy: 0.014 s; precision: 0.202 s or 10.4 %), while AT (accuracy: 0.072 s; precision: 0.420 s or 68.5%) and Imax (accuracy: 0.022 GL; precision: 1.197 GL or 44.5%) showed substantial variation. Myocardial perfusion reserve (MPR) calculated from RT (r2 = 0.90) or MTT (r2 = 0.94) showed better correlations to RMBF reserve than MPR calculated from AT (r2 = 0.04). In conclusion, only 1/MTT and 1/RT showed a good reproducibility and a close correlation to RMBF. Therefore, only these parameters can be recommended for calculations of RMBF and its reserve under clinical conditions.

Absorptiometry, Photon↗
PubMed2000

Shock compression of condensed matter using intense beams of energetic heavy ions

In this paper is presented, with the help of sophisticated two-dimensional hydrodynamic simulations, a suitable design with optimized parameters for a heavy-ion beam-matter interaction experiment that will be carried out at the Gesellschaft fur Schwerionenforschung (GSI) Darmstadt by the end of the year 2001 when the upgrade of the existing accelerator facility will be completed. Our simulations show that this upgraded heavy-ion beam is capable of generating strong shocks in solid targets that compress the target material to supersolid densities and generate multi-mbar pressures. This will open up, at the GSI, the possibility of investigation of the equation-of-state properties of matter under such extreme conditions. Numerical simulations can predict the experimental results with reasonable accuracy, which is helpful in designing the diagnostic tools for the experiment.

Journal Article↗
PubMed2000

Equation-of-state properties of high-energy-density matter using intense heavy ion beams with an annular focal spot

This paper presents two-dimensional numerical simulations of the hydrodynamic response of solid as well as hollow cylindrical targets made of lead that are irradiated by an intense beam of uranium ions which has an annular focal spot. Using a particle tracking computer code, it has been shown that a plasma lens can generate such a beam with parameters used in the calculations presented in this paper. The total number of particles in the beam is 2x10(11) and the particle energy is about 200 MeV/u that means a total energy of approximately 1.5 kJ. This energy is delivered in a pulse that is 50 ns long. These beam parameters lead to a specific energy deposition of 50-100 kJ/g and a specific power deposition of 1-2 TW/g in solid matter. These calculations show that in case of the solid lead cylinder, it may be possible to achieve more than 4 times solid lead density along the cylinder axis at the time of maximum compression. The pressure in the compressed region is about 20 Mbar and the temperature is a few eV. In the case of a hollow cylinder, one also achieves the same degree of compression but now the temperature in the compressed region is much higher (over 10 eV). Such samples of highly compressed matter can be used to study the equation-of-state properties of high-energy-density matter. It is expected that by the end of the year 2001, after completion of the upgrade of the existing facilities, the above beam parameters will be available at the Gesellschaft fur Schwerionenforschung (GSI), Darmstadt. This will open up the possibility to carry out very interesting experiments on a number of important problems including the investigation of the EOS of high-energy-density matter.

Journal Article↗
PubMed1999

Heavy-ion-beam-induced hydrodynamic effects in solid targets.

It is expected that after the completion of a new high current injector, the heavy-ion synchrotron (SIS) at the Gesellschaft für Schwerionforschung (GSI) Darmstadt will accelerate U(+28) ions to energies of the order of 200 MeV/u. The use of a powerful rf buncher will reduce the pulse length to about 50 ns, and employment of a multiturn injection scheme will provide 2 x 10(11) particles in the beam that correspond to a total energy of the order of 1 kJ. This upgrade of the SIS, hopefully, will be completed by the end of the year 2001. These beam parameters lead to a specific power deposition of the order of 1-2 TW/g in solid matter that will provide temperatures of about 10 eV. Such low specific power deposition will induce hydrodynamic effects in solid materials, and one may design appropriate beam-target interaction experiments that could be used to investigate the equation of state of matter under extreme conditions. The purpose of this paper is to propose suitable target designs with optimized parameters for the future GSI experiments with the help of one and two-dimensional hydrodynamic simulations. Cylindrical geometry is the natural geometry for highly focused ion beams, and therefore cylindrical targets are the most appropriate for this type of interaction experiments. The numerical simulations presented in this paper show that one can experimentally measure the characteristic sound speed in beam heated targets which is an important physical parameter. Moreover, one can study the propagation of ion-beam-induced shock waves in the solid materials. Different values for the specific power deposition, namely, 10, 25, 50, and 100 kJ/g, have been used. In some cases the pulse length is assumed to be 40 ns while in others it is considered to be 50 ns. Various materials including lead, aluminum, and solid neon have been used.

Journal Article↗
PubMed1997

[New developments in parameter-oriented roentgen densitometry perfusion analysis within the scope of heart catheter studies].

X-ray densitometric evaluation of digital subtraction coronary arteriograms allows a qualitative and quantitative detection of contrast medium propagation through the epicardial coronary arteries, the capillary system and the coronary venous system. So-called "time-density-curves" (TDCs) can be generated following Lambert-Beer's law similar to indicator dilution curves by using contrast medium as the indicator. Several time and density parameters can be derived from these TDCs, which are related to local myocardial perfusion. Different animal validation studies have shown the applicability of this concept for in-vivo evaluation of coronary blood flow and myocardial perfusion. Nevertheless, absolute measurement of volumetric coronary blood flow or myocardial perfusion failed. Therefore, relative changes in coronary blood flow or myocardial perfusion in response to pharmacologically induced maximum hyperemia were measured and coronary or myocardial perfusion reserve was calculated as the ratio of hyperemic flow or perfusion divided by baseline values. Despite theoretical attractions for an application during routine cardiac catheterization, this densitometric approach did not get a wide acceptance. Primary reason for this limited use in specialized centers was the time consuming process of densitometric evaluation of the subtraction coronary arteriograms, which require digital cine angiography and necessitates enormous computer hard ware. This main limitation has been overcome since more powerful computer hard ware (processor speed, hard disk space, digitization boards) has become rapidly available during the last years at more moderate pricing and digital techniques today are state of the art in cardiac catheterization laboratories. In addition, soft ware program packages allowed an automatization of the digitization and densitometric evaluation process. These programs include ECG triggered cine image digitization with improved temporal resolution, semiautomatic definition of regions-of-interest including definition of reference regions-of-interest for the detection of background density changes and quality-controlled densitometric parameter analysis. This progress made an application during routine cardiac catheterization feasible. In animal validation studies this improved X-ray densitometric approach for evaluation of local myocardial perfusion was validated versus colour-coded microsphere techniques. The time parameter "rise time", defined as the time from the start of local contrast medium induced density change to its maximum revealed a close correlation (r2 = 0.965) to the results of the microsphere technique over a wide range of perfusion. We have applied this technique before and after coronary interventions such as balloon angioplasty and stenting. Results documented an improvement of poststenotic myocardial perfusion reserve immediately after coronary balloon angioplasty and an additional improvement after adjunct coronary stenting. Only after stenting but usually not after coronary balloon angioplasty alone poststenotic myocardial perfusion reserve gained the intraindividual reference level, measured in a perfusion bed supplied by an epicardial coronary artery without stenoses. These results documented the functional benefit of coronary stenting on poststenotic myocardial perfusion in addition to the well known morphologic benefit with the creation of a larger and more circular conduit.

Absorptiometry, Photon↗
PubMed1990

[The determination of myocardial perfusion parameters from coronary angiograms by analysing the passage of contrast media through the myocardium].

Digital subtraction angiography allows to record the passage of contrast material through the myocardium as a time-intensity curve, the so-called densogram. Temporal changes of contrast material in a region of interest are described by a differential equation. The free parameters of this model equation are determined by a curve-fitting procedure. Four parameters of the model equation are expected to be connected with myocardial perfusion. We intended to verify this assumption by comparing changes in coronary blood flow (CBF) with changes of the different parameters. The angiograms of 9 patients without coronary artery disease were studied before and after intravenous application of dipyridamole. Changes in CBF were assessed by a videodensitometric method. Linear regressions between changes of CBF and the parameters of the differential equation show the following results: one parameter of the model equation--the ratio of regional blood flow and regional volume--remarkably underestimated CBF changes. This can be explained by an increase of regional blood volume after increased CBF due to dipyridamole. However, a close correlation was found between CBF changes and the remaining parameters. This study suggests that digital measurements from coronary angiograms using the presented model equation provide a means of assessing myocardial perfusion.

Adult↗
PubMed1989

[The reliability of angiographic volume determination of the left ventricle using digital image subtraction--significance in stress tests].

Using the technique of digital subtraction angiography (DSA), left ventricular volumes can be determined after intravenous injection of contrast medium at rest and during exercise. The significance of the well known errors of angiographic determination of left ventricular volumes was investigated in 22 patients before and during a bicycle exercise test. Before and after exercise 40 ml of contrast medium were injected (18 ml/s) intravenously to calculate left ventricular volumes. Enddiastolic and endsystolic contours of the left ventricle were traced by two investigators (A and B) on five different days. Using these contours, volumes were calculated by a computer system. The first calculation of both investigators (single measurement) and the mean value of all five calculations (repetitive measurements) were compared. In the same procedure left ventricular contours of six patients were calculated after conventional contrast ventriculography (40 ml of contrast medium). No systematic deviations were found in comparing the results of both investigators using the single or repetitive method by means of DSA: (VolB = 0.86 VolA + 12.2, r = 0.97 versus VolB = 0.96 VolA + 9.1, r = 0.99). Compared to single method the residuals (Syx) of the repetitive method were significantly smaller: Syx = +/- 16.3 ml vs +/- 8.9 ml (p less than 0.01). Similar results were found in conventional ventriculography: single method Syx = +/- 18.7 ml and repetitive method Syx = +/- 8.8 ml (p less than 0.01). Comparing the volumes determined by DSA and by conventional ventriculography, respectively, no significant differences were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1987

[Systolic and diastolic blood flow velocities in the left coronary artery before and following i.v. dipyridamole. Comparative measurements using a digital image processing in 2 unstenosed vessel branches].

The hemodynamic significance of coronary artery stenoses cannot be assessed by presently-used methods. Especially stenoses of small and moderate degree only reveal hemodynamic relevance during augmentation of coronary flow. It can be expected that the increase in flow is limited in a stenotic branch, compared with an unstenosed branch of the same vessel. The increase in coronary blood flow in two unstenosed branches of the same vessel, however, should be nearly identical. To prove this hypothesis, the relative increase in coronary flow was measured in two unstenosed branches of the left coronary artery by means of digital subtraction angiocardiography. Ten patients were examined before and after intravenous administration of 20 mg (on average 0.29 mg/kg body weight) dipyridamole. Dipyridamole resulted in an increase in the diameter of the left anterior descending branch (LAD) of 11% (p less than 0.005) and of the circumflex artery (RCx) of 13% (p less than 0.005). The increase in flow velocity during systole amounted to 49% in the LAD (p less than 0.001) and to 58% in the RCx (p less than 0.005); during diastole to 60% in the LAD (p less than 0.005) and 83% in the RCx (p less than 0.005). The increase in volume flow during systole amounted to 78% in the LAD (p less than 0.005) and to 89% in the RCx (p less than 0.005), during diastole to 84% in the LAD (p less than 0.005) and to 113% in the RCx (p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

[Percutaneous transluminal coronary angioplasty: determination of left ventricular function in physical stress using intravenous digital subtraction angiocardiography].

24 patients with coronary artery disease underwent intravenous digital subtraction angiocardiography at rest and during exercise before and after percutaneous transluminal coronary angioplasty (PTCA). Before PTCA mean pulmonary artery pressure increased pathologically in 20 patients (on average from 22 +/- 4 to 40 +/- 9 mm Hg, p less than 0.001). The increase in cardiac index from 4.2 +/- 1.3 to 6.2 +/- 2.01 I X min-1 X m-2 (p less than 0.01) was achieved by an increase in heart rate from 77 +/- 13 to 119 +/- 16 min-1 (p less than 0.001) as stroke volume remained unchanged during exercise (52 +/- 14 ml X m-2, resting value: 53 +/- 13 ml X m-2). Though end-systolic volume increased from 32 +/- 11 to 41 +/- 13 ml X m-2 (p less than 0.001) and ejection fraction fell from 63 +/- 8% to 56 +/- 10% (p less than 0.005), stroke volume remained unchanged due to an enhanced diastolic filling (EDVI: 86 +/- 19 ml X m-2 at rest, 92 +/- 18 ml X m-2 during exercise, p less than 0.001). After angiographically successful PTCA in 21 of 24 patients average mean pulmonary artery pressure during exercise remained pathologically elevated (36 +/- 9 mm Hg, no significant difference from value before PTCA). It normalized in only 6 of 17 patients. On the other hand there was a marked improvement of left ventricular systolic performance. Ejection fraction during exercise (65 +/- 11%) was higher than before PTCA (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

[Significance of lipids in the diagnosis of coronary heart disease in patient groups and individuals].

Several epidemiologic studies confirmed the significance of the risk ratio cholesterol/HDL-cholesterol in predicting coronary heart disease. Therefore we examined the lipid values of 364 men and 133 females who underwent coronary arteriography because of angina pectoris and/or pathological ECG changes at rest or during exercise stress testing. Although patients with coronary heart disease showed higher cholesterol (male 238 mg/dl vs. 210 mg/dl, female 251 mg/dl vs. 219 mg/dl, p less than 0.001), higher triglycerides (male 204 mg/dl vs. 162 mg/dl, female 179 mg/dl vs. 125 mg/dl, p less than 0.001) and significantly lower HDL-cholesterol levels (male 39.9 mg/dl vs. 44 mg/dl, female 45.9 mg/dl vs. 54.9 mg/dl, p less than 0.01) than the control group, lipid values did not lead to a good discrimination between patients with or without coronary heart disease. The patients' histories and ECGs showed a higher sensitivity (male 83%/male 85%) and specificity (male 81%/female 83%) than the lipids (sensitivity male 57%/female 67%, specificity male 55%/female 74%). We conclude from our results that blood lipids, the risk ratio cholesterol/HDL-cholesterol and other risk factors are diagnostic tools which have to be handled with caution when applied to the individual patient with suspected coronary heart disease.

Angina Pectoris↗