Characterization of high molecular weight polyethylenes using high temperature asymmetrical flow field-flow fractionation with on-line infrared, light scattering, and viscometry detection.

High temperature asymmetrical flow field-flow fractionation (HTAF4) coupled to infrared (IR), multi-angle light scattering (MALS), and viscometry (Visc) detection is introduced as a tool for the characterization of high molecular weight polyethylenes. The high molecular weight fraction strongly affects the rheological behaviour and processability of polyethylene materials and can often not be accurately resolved by current technology such as high temperature size-exclusion chromatography (HTSEC). Molecular weight (M), radius of gyration (Rg), and intrinsic viscosity [eta] of linear high density polyethylene (HDPE) and branched low density polyethylene (LDPE) samples are studied in detail by HTAF4 and are compared to HTSEC. HTAF4 showed a better separation and mass recovery than HTSEC for very high molecular weight fractions in HDPE and LDPE samples. As no stationary phase is present in an HTAF4 channel, the technique does not show the typical drawbacks associated with HTSEC analysis of high molecular weight polyethylenes, such as, exclusion effects, shear degradation, and anomalous late elution of highly branched material. HTAF4 is applied to study the relation between the molecular weight and the zero shear viscosity eta0 for high molecular weight HDPE. It was found that the zero shear viscosity values predicted from HTAF4 results are in good qualitative agreement with measured values obtained from dynamic mechanical spectroscopy (DMS) experiments, whereas eta0 values predicted from HTSEC do not show a strong correlation. The low molecular weight cutoff of HTAF4 is approximately 5x10(4) as a result of relatively large pores in the HTAF4 channel membrane. HTAF4 is, therefore, currently not suited to analyze low molecular weight materials.

[RNA synthesis by T7 RNA polymerase supported primer extension]. / Sintez RNK posredstvom udlineniia praimera pri pomoshchi RNK-polimerazy faga T7.

Transcription of RNA molecules from synthetic DNA templates with T7 RNA polymerase is a common procedure for the preparation of long RNA molecules. However, enzymatic synthesis does not allow for site-specific incorporation of modified nucleotides. RNA synthesis by chemical methods on the other side can satisfy this purpose, but it is limited to RNA fragments of about 80 nucleotides at maximum. We aimed to combine both chemical and enzymatic procedures to synthesise RNA molecules by RNA primed transcription with T7 RNA polymerase. To this end we have chemically synthesised a fluorescein labelled RNA primer and studied elongation of this primer by T7 RNA polymerase on a single-stranded DNA template. We show that the enzyme is capable of extending the primer to the full-length product. The 34-mer RNA that has been synthesised by RNA primed transcription served as substrate for a twin ribozyme and was successfully cleaved in the expected manner.

Spermine supports catalysis of hairpin ribozyme variants to differing extents.

Because of the ability to cleave RNA substrates in trans, the hairpin ribozyme has great potential for therapeutic application. Activity of a three-stranded version of the minimal truncated form is enhanced by the presence of the polyamine spermine. Since spermine is the most abundant polyamine in eucariots, improved prospects for the hairpin ribozyme as therapeutic agent were predicted. We have found that not all hairpin ribozyme variants accept spermine equally well as counter-ion. Particularly the two-stranded versions commonly used for therapeutic studies show rather decreased activity when spermine is present. We have investigated a number of hairpin ribozyme derivatives regarding their ability to carry out spermine supported catalysis. Among the studied structures a two-stranded reverse-joined hairpin ribozyme displayed the highest cleavage rates in a synergistic mixture of magnesium ions and spermine. The specific features of this ribozyme along with its potential for in vivo application are discussed.

Development of an electronic radiologist's office in a private institute.

A computer system that improves the quality, user-friendliness, accessibility, and management of radiology data (images, reports, databases, knowledge) was implemented at a private institute. A picture archiving and communication system (PACS) was integrated with the radiology information system (RIS). Two servers and 12 personal computers form the integrated system. The first server is dedicated to management and archiving of Digital Imaging and Communications in Medicine (DICOM) images. The second server is dedicated to management of the RIS and archiving of patient data (Structured Query Language database), reports (hypertext markup language [HTML]), and images in the Joint Photographic Experts Group (JPEG) format (mini-PACS). There are three main client-server networks: a common network of imaging modalities (magnetic resonance imaging, computed tomography, ultrasonography, digital radiography) and two fast Ethernet networks (the PACS network and the RIS network). The RIS-PACS is linked remotely with other workstations and servers via Integrated Services Digital Network (ISDN). Images and reports can be distributed to referring physicians in the form of multimedia HTML and JPEG documents, which can also be used for quick and easy archiving, distribution, and reviewing within the institute. However, referring physicians have been reluctant to use electronic reports and images.

RNA double cleavage by a hairpin-derived twin ribozyme.

The hairpin ribozyme is a small catalytic RNA that catalyses reversible sequence-specific RNA hydrolysis in trans. It consists of two domains, which interact with each other by docking in an antiparallel fashion. There is a region between the two domains acting as a flexible hinge for interdomain interactions to occur. Hairpin ribozymes with reverse-joined domains have been constructed by dissecting the domains at the hinge and rejoining them in reverse order. We have used both the conventional and reverse-joined hairpin ribozymes for the design of a hairpin-derived twin ribozyme. We show that this twin ribozyme cleaves a suitable RNA substrate at two specific sites while maintaining the target specificity of the individual monoribozymes. For characterisation of the studied ribozymes we have evaluated a quantitative assay of sequence-specific ribozyme activity using fluorescently labelled RNA substrates in conjunction with an automated DNA sequencer. This assay was found to be applicable with hairpin and hairpin-derived ribozymes. The results demonstrate the potential of hairpin ribozymes for multi-target strategies of RNA cleavage and suggest the possibility for employing hairpin-derived twin ribozymes as powerful tools for RNA manipulation in vitro and in vivo.

Design of a cooperative teleradiology system.

The article describes a teleradiology system intended to provide a user-friendly environment for exchanging images and working cooperatively on them. With the development of a hospital-wide picture archiving and communication system (PACS), the University Hospital of Geneva and several other health institutions in the region became interested in teleradiology. Because of the heterogeneous needs of the potential participants, the following requirements were identified: (1) remote consultation and interpretation of images; and (2) cooperative interpretation of medical images, allowing real-time interaction between physicians. To satisfy these needs, a multipoint teleradiology system has been implemented that incorporates an innovative image display and manipulation software program known as OSIRIS, which supports the full spectrum of imaging modalities. Images and data are transmitted over the public telecommunications Integrated Services Digital Network (ISDN). To accommodate different computing environments at the various locations, platform-independent software has been designed that has the same "look and feel" for PC-Windows, Macintosh, and UNIX-X11 work-stations. The teleradiology system can be used in two modes: synchronous (cooperative) or asynchronous. Special efforts have been made in the development of the synchronous mode. Within the European Telemed Project, a specific protocol has been designed to allow cooperative work between remotely located workstations.

The social supports of suicide attempters: the different roles of family and friends.

The social support patterns of a sample of 101 suicide attempters were compared with the patterns of a control sample on the basis of structured interview data. Network characteristics and the extent of support in different functional categories were examined as to their absolute and relative power to discriminate between the suicide attempters and the controls. A clear separation of the functions of kin and of friends/acquaintances emerged. The crucial difference between the attempters and the controls lay in the number of friends with whom the subjects had agreeable everyday interactions and in the number of kin that provided crisis support, both psychological and instrumental. Other support differences between the two groups were of secondary importance. While there was no overall difference in the frequency of social interactions between the two groups, the size of the social network differed greatly. Consequences for the conceptualization and measurement of social support as well as for the prevention of suicidal behavior are discussed.

[Attempted suicide and depressive disorders]. / Selbstmordversuche und depressive Störungen.

211 persons consecutively seen for parasuicidal behavior by the various services of the CIMH (Central Institute of Mental Health) in Mannheim were investigated with regard to the seriousness of intention and the real risk to die. Seriousness and real risk to die were measured by a scale which was divided into two parts - the interviewer rating scale and the self-rating scale. The highest suicide risk was found in depressed patients. This group showed higher scores on the self- and interviewer rating scale than the non-depressed patients. It could be shown that the high risk of suicidal attempts of depressed patients cannot be explained by the older age of this group. However, it can be assumed that psychological factors, influencing the intention to die, are more important.

[Psychosocial care structures in urband and rural districts (author's transl)]. / Psychosoziale Versogrungsstrukturen städtischer und ländlicher Regionen.

The present study is based on a complete institutional and personal coverage of psychosocial care institutions in nine local regions within the Federal Republic of Germany. The study was carried out by means of a short structured questionnaire and was supported by local psychosocial working groups. The following questions were considered on the basis of a sociodemographic differentiation, in urband and rural districts: 1. To what extent do differences appear between urban and rural districts with regard to outpatient-, inpatient- and complementary treatment facilities? 2. To what extent do differences appear in regard to the quantity and quality of specialized professional personel operating there? 3. In what way, and to what extent, compensatory care mechanism do exist? The results show important and systematic differences with regard to the outpatient, inpatient and complementary treatment facilities. Rural districts are characterised by an emphasis on inpatient facilities, including homes, as well as by a marked lack of outpatient facilties, especially of a psychotherapeutic nature. Psychosocial professions with high qualifications, especially in psychotherapeutic respect, are mainly found in regions characterised as urban, while they are nearly completely absent in rural districts. In addition the results point at a underprivileged treatment structure of rural district. However there are indications of compensatory care mechanisms. This means that persons without any specialized training are often engaged in treatment jobs requiring specialisation. This applies in particular to the complementary field of patient care. The article discusses overlapping problems of proper geographic distribution of psychosocial treatment facilities in accordance with actual requirements. Furthermore political conclusions resulting from this aiming at improvementsof the care structure for mentally ill persons are discussed.