The cationic polymerization of 3-chloro-2-methyl-1-propene

The polymerization of 3-chloro-2-methyl-1-propene was investigated at temperatures between 0 and ?80°C, using AlCl₃ and AlBr₃ as initiators. The molecular weights of the resulting oily products depend on the polymerization temperature and varied in the range of the number-average molecular weight M?_n = 400–620. The course of polymerization was studied and the characteristic groupings in the oligomeris were identified by means of ¹H NMR and ¹³C NMR spectroscopy. Based on the results the mechanism of partial reactions was discussed to explain the new type of propagation in the cationic polymerization.     

Adherence to osteoporosis guideline: survey among Czech general practitioners

Rationale and objectives

General practitioners (GPs) play an important role in management of patients at risk of osteoporosis (OP). The objectives were to assess (1) knowledge about OP and use of OP clinical guideline in comparison with other information sources and (2) association between the use of individual information sources and knowledge and self-reported quality of care among GPs.

Methods

Survey among random sample of Czech GPs was performed to find out their attitudes and role in OP management. The return rate of the postal questionnaire was 38% (525 respondents). Quality of care was assessed using three indicators: suspicion on OP, referral to the specialist and initial check-up.

Results

Respondents (median age 52 years, 59% women) had a very good knowledge of several risk factors, while others, namely low body mass index, history of hip fracture in mother and smoking were perceived as risk factors by only 40%, 45% and 55% of respondents, respectively. 10% of GPs stated the correct answer regarding daily calcium intake recommended for postmenopausal women. The OP guideline was considered accessible by 83% of respondents and used repeatedly by 54%. Use of the guideline correlated positively with knowledge score (P < 0.001), while use of each individual other source of information did not. Use of the guideline correlated with all three indicators of quality of care. Use of each other information source correlated only with a maximum of two indicators.

Conclusion

We identified areas of insufficient knowledge that should be targeted in educational activities for GPs. It is recommended to further motivate GPs to use their clinical guidelines regularly.     

Über die thermischen umwandlungen des chloroprens

The kinetics of the conversion of chloroprene into cyclic dimers and polychloroprene was investigated using gel-chromatography. The temperature dependences of velocity constants for the formation of individual dimers were determined within the range from 50 to 70°C. The order of dimerization equaled two at the beginning of the reaction and decreased during its course. The polymerization was inhibited by diphenylpicrylhydrazyl and accelerated by iodine. The rate of polymerization in the solutions of dimethyl sulphoxide and dimethyl sulphate was several times higher than that in pure chloroprene. The addition of 2.4-pentadione-bis-ethylene-rhodium accelerated the polymerization; however, it slowed down the formation of 1.2-dichloro-1.2-divinylcyclobutane. The equations for the formation of the last dimer and for the conversion of monomer were derived.     

150-Day Survival of a Calf with a Polymethylmethacrylate Total Artificial Heart: TNS-BRNO-II

A 150-day experiment in a calf with an implanted total artificial heart, TNS-BRNO-II, is described. The Czechoslovak TAH-BRNO-II device is a hybrid; the outer housing is made of polymethylmethacrylate, the moving parts of segmented polyurethane. The blood flow through the device after the surgery gradually increased from 7 L/min to 12 L/min by the end of the experiment. Atrial pressures were automatically maintained at the same level, about one kPa on both sides. The left systolic time was automatically derived from the pump emptying phase; the right systolic time was maintained between 40% and 50%. After the surgery, normal values of blood gases, stabilization of respiratory activity, and normalization of gastrointestinal functions were reached very soon. Anticoagulant therapy was performed during the whole experiment, with several periods of increased bleeding tendency. The clinical state of the calf was essentially physiological until the 94th day of the experiment, when acute bronchopneumonia, with a high fever, over 41°C, initiated a series of complications (pseudomembranous enterocolitis, followed by sepsis lenta). The fatal complication was sudden impairment of the coagulation mechanisms on the 149th to 150th day of the experiment. This was the basic reason for the subsequent death of the animal, caused by acute cerebral anemic anoxia, which could not be prevented by immediate therapeutic procedures. In spite of these complications, the clinical state of this calf was relatively good until the end of the experiment. Autopsy revealed minimal thromboembolization at the valves. The outer surface of the diaphragm was covered with pseudoneointimal deposits and the inlet orifices were free of pannus or other connective tissue crescents. Macroscopic signs of infection were not seen, but bacteriological cultivation from internal organs confirmed Klebsiella infection. The state of the device at the time of autopsy, with simultaneous undisturbed function of the control and driving unit, showed the possibility of still longer survival.     

The influence of orthognathic surgery on ventilation during sleep

Orthognathic surgery has varying effects on respiratory parameters. The authors undertook a prospective study of patients requiring mandibular advancement, mandibular setback and maxillary Le Fort I advancement, and surgically assisted rapid maxillary expansion (SARME). Breathing parameters were monitored in a sleep laboratory the night before the operation and in a mean of 9.5 months after the operation. In patients treated with mandibular advancement, the respiratory disturbance index (RDI), oxygen desaturation index (ODI), and number of obstructive apnoeas (OAs) improved significantly. In patients treated with mandibular setback and maxillary Le Fort I advancement, the RDI, ODI, index of flow limitations (IFL), number of obstructive hypopnoeas (OHs), OA, and oxygen saturation deteriorated. In contrast, patients treated with SARME improved only mildly. These results indicate that bimaxillary surgery for Class III malocclusion increased upper airway resistance, probably because of a more dorsal positioning of the base of the tongue, representing an iatrogenic obstructive sleep apnoea (OSA). A young person would probably be able to balance such a decline in respiratory function using different adaptative mechanisms. Mandibular advancement significantly improved respiratory parameters during sleep. The possible effect of orthognathic surgery on the upper airways should be incorporated into the treatment plan.     

Mechanical Thrombectomy for Acute Ischemic Stroke in Czech Republic: Technical Results from the Year 2016

CardioVascular and Interventional Radiology - Experienced multidisciplinary stroke team and well-organized hospital management are considered necessary to achieve good results after mechanical...     

Indication and radicality of surgical treatment in spinal myeloma

In our set of 19 operated patients with spinal myeloma it was in 17 patients (89%) the first manifestation of malignant haematological disease. Indication for admission for surgery were in 18 patients (92%) graphical signs of spinal compression of osteolytic affliction of the vertebra of unclear aetiology, which in 17 (63%) of patients were demonstrated by neurological deficit. On the basis of graphical examinations the most frequent suspicion was on metastatic affliction of the spine at unknown primary focus and the basic diagnosis was determined after the operation at most of cases. In decision about the choice of radicalness of surgery intervention important data about the type of tumour in the spine were usually missing and it especially did not make possible to estimate the life expectation of the patient. When deciding about the radicalness of the surgery, we started from the degree of spinal compression and surgical character of pathological process in the spine. The aim of the operation is to decompress the spinal cord in tumour and to stabilize the afflicted part of the spine. Radical extirpation of tumour followed with stabilization and spine reconstruction we decided to carry out in 7 patients, i.e. 37%, all of them clinically improved and from this group only 2 patients (29%) died till now. We carried out only palliative surgery on the spine in next 12 patients, i.e. in 63%, only 6 patients improved neurologically, i.e. 50% and 10 patients, i.e. 83% died till now.     

Metalloester, 10. Untersuchung des anfangsstadiums der anionischen polymerisation von methylmethacrylat. einfluß von reaktionsbedingungen auf die umsetzung von methyl-2-sodioisobutyrat mit methylmethacrylat

In continuation of a preceding study, the course of the reaction between methyl methacrylate (2) and methyl 2-sodioisobutyrate ( 1 ) was investigated, applying reaction times between 0,02 and 1,4 s, as a function of the following conditions: character of the solvent, effect of the addition of sodium tert-butoxide, mole ratio 2 / 1 , concentration of the reactants, and temperature. Under all conditions used, the reaction between 2 and 1 was very fast and gave rise, along with other compounds, to a mixture of oligomers of 2 with the average molecular weight obeying the ratio [ 2 ]:[ 1 ]_eff.. The balance of products showed that in some cases only a part of 1 has reacted with 2 , giving rise to the expected oligomers. The efficiency of 1 varied in the range from 24 to 100%, being mainly dependent on the character of the solvent (efficiency in THF > in toluene). Moreover, it was higher in the presence of sodium tert-butoxide and with a higher 2 / 1 mole ratio. In experiments with a low efficiency of 1 a certain part of it remained unreacted, in spite of the presence of 2 , for reasons not yet clear. The resulting oligomers undergo consecutive reactions. Starting with the trimer 3b , cyclizing selfcondensation was the most important of the consecutive reactions and could be easily investigated in the case of the trimer. The rate of this cyclization was much higher in THF than in other solvents used, and it was, therefore, difficult to obtain the linear trimer at room temperature. On the contrary, the addition of sodium tert-butoxide or lowering the temperature suppressed the cyclization, which was especially easy to perceive in THF. Using the experience described in the study, it is possible to choose such conditions of the reaction between 1 and 2 , under which the required oligomers are formed in good yield.