Liquid Water: A Single Approach to Its Two Continuous Phase Transitions.

In this paper, we show that both continuous phase transitions of liquid water, the liquid-gas and the liquid-liquid, can be articulated within a single thermodynamic analytical formalism. This result follows from a combination of the two-liquid model (TLM), recently confirmed for water, with the idea of a thermal-dependent excluded volume, ve, concept introduced by van der Waals, in his famous state equation. Starting from the fundamentals of thermodynamics, it will be shown that the TLM naturally leads to the idea of an extensive thermal-dependent ve that acts as a parameter of the sample thermodynamic potentials. This procedure effectively separates the thermodynamics of the system into two parts: the first concerns the clusters' thermodynamics, taken as wandering particles, and the second concerns the thermal behavior of its internal structure (geometry and number of particles). From this result, we demonstrate that the condition of mechanical instability leads to not one but two critical points, each happening in one of the above-described parts of the system.

Thermal diffusivity and the conformal transformation on nematic liquid crystals.

In this paper, we will study theoretically and experimentally the anisotropy of the thermal diffusivity in nematic liquid crystals. We will show that the Baalss-Hess conformal transformation [D. Baalss and S. Hess, Phys. Rev. Lett. 57, 86 (1986)], can be used to obtain a free of adjustable parameters equation that describes the anisotropy of the heat diffusion in these materials. The results of this theory will be compared with experimental data. This study will partially confirm the widely known experimental evidences that indicate that the thermal diffusivity is larger in the director direction than in the one perpendicular to it. For calamitic nematic phases this is true; for discotic nematic ones the reverse situation would be found; the diffusivity would become larger in the direction perpendicular to the director. We will also present experimental data supporting this theoretical prediction. The data comprehend the calamitic and discotic nematic lyotropic phases and a nematic thermotropic phase.

[In vivo measurement of tissue relaxation times using localized 31P and 1H MR spectroscopy]. / In-vivo-Messung von Geweberelaxationszeiten mit lokalisierter 31P- und 1H-MR-Spektroskopie.

Methods of in vivo determination of 31P longitudinal relaxation times within image-determined volume selected MRI spectroscopy have been investigated. T1 values for phosphor compounds in skeletal muscle and in brain have been measured. The 1H relaxation times of T1 and T2 of diffuse parenchymal liver disease, using inversion recovery and spin echo sequences were compared with quantitative MR tomography. Clinically, spectroscopic techniques are particularly useful where there is superimposition of water and lipid signals during MR imaging.

[Digital subtraction angiography of acquired arteriovenous fistulas of the extremities]. / Digitale Subtraktionsangiographie (DSA) bei erworbenen arteriovenösen Fisteln der Extremitäten.

The signs of arterio-venous fistulae in the extremities have been evaluated by DSA in 20 patients. Angiographic signs for the presence of A-V fistulae are the following findings: dilatation of the supplying artery, elongation of the supplying artery, solitary A-V aneurysm, angiomatous A-V aneurysm, reduced blood flow distal to the A-V fistula, early venous filling, development of a venous collateral circulation and demonstration of retrograde venous flow. Angiography remains the method of choice for demonstrating A-V fistulae.

[Non-selective digital subtraction angiography of aortocoronary bypasses]. / Nicht-selektive digitale Subtraktionsangiographie aortokoronarer Bypasses.

Intra-arterial DSA was performed on 225 patients with a total of 552 coronary bypasses (515 aorto-coronary venous bypasses and 37 internal mammary artery bypasses). Four hundred and ninety-five bypasses were examined in the four weeks following surgery; of these, 428 (85.9%) were patent. Demonstration of the distal anastomosis was obtained in 40.4% of bypasses of the right anterior interventricular artery and in 36.1% of the right coronary artery, at least in their proximal parts. Bypasses of smaller branches showed filling in 12.8 to 19.2%. Because of the unsatisfactory demonstration of distal vessels by non-selective intra-arterial DSA, this method is suitable only for showing the patency of a bypass in the postoperative phase, but should not be used for investigating cardiac signs and symptoms following a bypass examination.

[Optimization of examining sequences in MR tomography using isosignal displays]. / Optimierung von Untersuchungssequenzen in der MR-Tomographie mit Hilfe von Isosignaldarstellungen.

Contrast performance in MR tomography is influenced by the choice of technical parameters such as pulse repetition time (TR), echo time (TE) and inversion time (TI) in the same manner as by differences in the tissue parameters relaxation time and proton density. To optimise image contrast it is therefore suggested to preselect the imaging sequence. Such presselection is possible on the basis of isosignal visualisations S(T1, T2). In the inversion recovery sequence (IR) the isosignal images obtained with the parameters TE, TI, TR enable determination of relaxation time T1 by graphic representation, from the time of zero passage of the longitudinal tissue magnetisation.

[MR tomography, CT and angiography of vascular malformations of the central nervous system]. / MR-Tomographie, CT und Angiographie vaskulärer Malformationen des zentralen Nervensystems.

The findings on MR tomography in 31 vascular malformations of the central nervous system are described; 26 of these had angiography and 24 were examined by CT. There were 19 A-V angiomas, 7 cavernomas and 5 large aneurysms. MRT provided a correct diagnosis in 29 out of 31 cases, angiography succeeded in 19 out of 26 cases and CT in 20 of 24. MRT was superior to CT and angiography. Nevertheless, it cannot replace arteriography, since this is the only method for demonstrating the vascular supply of angiomas and small aneurysms can be demonstrated only by arteriography.

[CT portography in malignant space-occupying lesions of the liver]. / CT-Portographie bei malignen Raumforderungen der Leber.

CT portography was performed in 32 patients with liver tumours and in four patients with cirrhosis of the liver, but without evidence of tumour, after angiographic injection of contrast into the superior mesenteric or splenic arteries. Compared with CT using no contrast, or contrast by intravenous injection, CT portography has the following advantages: better tumour detection, better detection of tumour size, better demarcation and localisation of tumours, better demonstration of the portal system, more inhomogeneity of the parenchyma. Of 12 patients with a number of tumours shown on CT, CT portography demonstrated tumours in four cases, which could not be shown by any other imaging method. Problems concerning CT portography in patients with cirrhosis of the liver are discussed.

[Qualitative and quantitative NMR tomographic findings in focal nodular hyperplasia of the liver]. / Qualitative und quantitative kernspintomographische Befunde der fokal nodulären Hyperplasie der Leber.

The qualitative and quantitative MRI findings in 16 patients with focal nodular hyperplasia (FNH) of the liver are described; nine of these were confirmed histologically. A central scar is typical of FNH and provides a reliable diagnosis. This finding was seen in half the cases. If the scar is not demonstrable, the following features suggest the diagnosis: smooth margins, homogeneous signal distribution, increased signal intensity in T2-weighted spin-echo images and reduced signal intensity in inversion-recovery sequences. The T1 and T2 relaxation times in FNH are increased by about 30% compared with normal liver tissue.

[Qualitative control over quantitative MR tomography: in vitro and in vivo checks on relaxation time measurements]. / Qualitätskontrolle der quantitativen MR-Tomographie: In-vitro- und In-vivo-Uberprüfung von Relaxationszeitmessungen.

In-vivo and in-vitro checks on measurements of relaxation times in MRI have been carried out as part of quality control. For the in-vitro experiments we used 13 reagents consisting of varying concentrations of copper sulphate manganese sulphate, gadolinium solutions and various oils as well as water. For in-vivo measurements we used liver parenchyma and fat in three subjects. Eight different sequences were performed; intra- and interindividual variations and comparison of three similar MRI units showed average variations of 2-3% for T1 and 3-4% variations for T2 relaxation times. This margin of error makes quantitative MRI acceptable for clinical use.

[Computed tomography in orbital trauma]. / Zur Computertomographie beim Trauma der Orbita.

The results of CT in 104 patients with traumatic lesions of the orbits have been analysed retrospectively. Eighty-four fractures of the orbital skeleton were diagnosed in 58 patients; in 18 cases there was peri-orbital, retrobulbar or intrabulbar bleeding and two patients had a ruptured globe. A foreign body was demonstrated in 20 cases. Additional fractures of neighbouring paranasal sinuses were present in 22 cases. Mucosal swelling or bleeding in the sinus was found in 59 cases and orbital emphysema in 22 patients. The particular value of CT in the diagnosis of orbital trauma lies in the certainty with which bony injury of the orbit and peri-orbital structures can be demonstrated.

[Manganese-DPDP in the MR tomography of malignant liver tumors. The initial results with a new hepatobiliary contrast agent]. / Mangan-DPDP in der MR-Tomographie maligner Lebertumoren. Erste Ergebnisse mit einem neuen hepatobiliären Kontrastmittel.

The new hepatobiliary contrast agent Mangan-DPDP, unlike extracellular Gd-DTPA, leads to a constant increase in signal intensity of normal liver tissue in MR imaging of the liver which lasts at least for 30 minutes. In 19 patients with malignant liver tumors there was no difference in the contrast between tumor and liver when using a dose of 5 or 10 mumol/kg. Contrast enhanced T1-w SE- and T1-w GE sequences show a significant increase in tumor/liver contrast compared with T1-weighted unenhanced sequences. This increase was also significant when compared with T2-w SE sequences. In 16% additional focal lesions were detected on the enhanced scan.

[Multiple circular liver foci in latent porphyria cutanea tarda]. / Multiple Leberrundherde bei latenter Porphyria cutanea tarda.

A 41-year-old patient with latent porphyria cutanea tarda is described; 8 years after mastectomy for carcinoma, sonography and CT showed multiple hepatic foci, which were at first interpreted as liver metastases. A liver biopsy was carried out during laparoscopy and u/v fluorescence and subsequent laboratory tests confirmed the diagnosis of porphyria cutanea tarda. Treatment with resochin produced almost complete resolution of the liver abnormalities within 9 months. Magnetic resonance tomography using proton-weighted SE sequences showed a few foci of high signal intensity.

[MR tomography of hemophilic arthropathy of the knee joint]. / MR-Tomographie der hämophilen Arthropathie des Kniegelenks.

The value of MR tomography in the diagnosis and follow-up of haemophilic arthropathy of the knee was studied in 40 examinations, using special surface coils. Good spatial resolution and reconstruction in various planes provide an accurate demonstration of the lesion, particularly of the intra-articular structures. Abnormalities of the synovia and of hyaline cartilage can be demonstrated. MR tomography is an important imaging method which is superior to sonography or CT in demonstrating complications resulting from the bleeding, such as effusions and haemarthroses.

[Results of percutaneous transhepatic bile duct drainage]. / Ergebnisse der perkutanen transhepatischen Gallengangsdrainage.

Significant reduction in serum bilirubin levels was obtained in 90.7% of 75 patients on whom percutaneous transhepatic biliary drainage had been carried out, either immediately before operation or as a prolonged palliative procedure. The technical requirements, complications, mortality rate and length of stay in hospital are less than following palliative surgery.

[Diagnosis of muscle hematomas and pseudotumors in hemophilia]. / Diagnostik von Muskelhämatomen und Pseudotumoren bei Hämophilie.

Two hundred and twenty-six patients with haemophilia A and B were examined by CT. In 135 cases, some form of bleeding was demonstrated. CT permits exact anatomical localisation of the haematoma and its delineation from neighbouring structures. Measurements of the densities of the haematomas make it possible to determine their age from the change in absorption values. Computed tomography makes it easier for the clinician to choose between conservative or surgical treatment and to determine the duration of treatment during the regression of the haematoma.

[Digital subtraction angiography in traumatology]. / Digitale Subtraktionsangiographie in der Traumatologie.

The methods, indications and results of digital subtraction angiography in traumatology are presented, based on 56 examinations. The different use of intravenous or intraarterial DSA will be discussed with respect to expanding and localisation of traumatic vascular injury. DSA is recommended as the method of choice for follow-up after vascular reconstructive procedure.

[Relaxation time measurements in the differential magnetic resonance tomographic diagnosis of liver tumors]. / Relaxationszeitmessungen in der kernspintomographischen Differentialdiagnose von Lebertumoren.

T1-weighted IR sequences and T2-weighted SE sequences and combined SE/IR sequences were carried out in 62 patients with malignant and 50 patients with benign liver tumours and the T1 and T2 relaxation times were measured. IR sequences proved the most sensitive method for imaging focal liver lesions and providing good contrast between liver tissue and tumour. For lesions above 1.5 cm, quantitative MRI achieved an accuracy better than 95% in distinguishing between haemangiomas and malignant lesions. Routine quantitative measurements of relaxation times were sufficiently reproducible for clinical use.

[MR tomography of non-tumor diseases of the brain and cervical cord]. / MR-Tomographie nicht-tumoröser Erkrankungen des Gehirns und des Zervikalmarkes.

118 examinations were carried out for non-tumorous diseases of the brain and cervical cord. The sensitivity of MRT was analysed and compared with 77 cases where CT had been performed or with sonography in children. MRT showed an abnormality in 80%, whereas CT or sonography lead to a diagnosis in only 43%. Because of the significantly higher sensitivity of MRT, this should be the primary means of examination for this type of case.

[Artifact reduction via motion-compensating gradient shifting in MR tomography]. / Artefaktreduktion durch bewegungskompensierende Gradientenschaltung in der MR-Tomographie.

In 62 patients spinecho or gradientecho sequences compensated for motion were compared with corresponding non-compensated sequences. Compensation during MRT reduces those artifacts which are caused by regular motion. This is particularly effective during examination of the brain stem, spinal canal and the heart. The improved demonstration of the morphology of normal and diseases organs simplifies the analysis of the types of movement.