Determination of zinc in fingernails by non-flame atomic absorption spectroscopy

The determination of Zn in fingernails directly using the graphite furnace presented certain difficulties due to the anomalous behavior of the analyte in the furnace. The appearance of two peaks which were due to Zn and not to any background interference was noted. The Zn value obtained by adding the area of these two peaks compared fairly well with Zn levels determined by wet ashing and subsequent determination either in the furnace or flame. Wet ashed samples gave only a single peak. It was possible to produce a model of the phenomenon with various Zn salts in a non aqueous matrix. Under these conditions ZnSO4 and ZnO gave a discretely different peak from ZnC12 or metallic Zn. Several tissues such as serum, whole blood, cuticle, and hair were examined for multiple peak formation. Direct determination of Zn in fingernails with the graphite furnace is possible for certain applications such as the determination of Zn levels of white spots in fingernails. For this purpose it is possible to use a sample size as small as 20 mug using the 2138 Zn line. This allows one to run several determinations on a single white spot. However, where sample size is not a limitation, wet ash digestion prior to determination in the furnace is probably the preferred procedure.     

Effect of stress on the superconducting transition temperature of SrTiO3

The superconducting transition temperatures of several specimens of reduced SrTiO₃ and of Nb-doped SrTiO₃ have been investigated as functions of hydrostatic and uniaxial compressive stresses up to 1.8 kbars. Decreases inT _c as large as 0.12 K have been observed in specimens under hydrostatic pressure. Because of the lowT _c and small compressibility of SrTiO₃, (lnT _c)/P and (lnT _c)/(lnV) are orders of magnitude greater than the corresponding effects in elemental superconductors. The effect of uniaxial stress onT _c varied with the direction of stress. Compression along a [111] direction caused large decreases inT _c, while both small increases and small decreases inT _c have been observed for [100] compression. It is believed that the present results reveal the presence of a sensitive volume dependence in one or more of the parameters important to superconductivity in SrTiO₃, and that no significant electron-transfer effects occurred in the range of stresses of this experiment.     

Growth hormone radiologand assay unresponsive to human prolactin

A specific and sensitive radioligand assay for growth hormone with female rat liver plasma membranes is presented. Growth hormones of different species are able to displace labelled human growth hormone from membrane binding sites with parallel standard curves. Human prolactin V-L-S is not equal to 1 and the international human prolactin standard MRC 71/222 do not affect the assay. Human prolactin preparations with different growth hormone content displace human growth hormone tracer only to the same extent as they contain growth hormone when measured by radioimmunoassay.     

The pigmentation of dark brown rigid PVC window frames in central Europe

Europe has experienced phenomenal growth in the market share of rigid vinyl windows. The American market has shown intensified interest in dark brown rigid vinyl windows. European experience with these pigmentation systems provides a useful data base for designing these dark brown shades suitable for use in North American climatic conditions. Criteria for pigment selection are discussed, including the suitability of both organic and inorganic pigments. Test data are provided for selected pigment systems to show their suitability with regard to several application parameters. The contribution of other additives to appearance retention of colored rigid PVC is discussed. Typical formulations are presented in detail.     

Die Wirkung mechanischer Einflußgrößen bei der Rißkorrosion von Kohlenstoff-Mangan-Stählen. Mechanical Factors Influencing Corrosion Cracking of Carbon-Manganese Steels

Knowledge about stress corrosion cracking and corrosion fatigue until 1970; specific aggressive media to cause stress corrosion cracking: alkali solution, nitrates, ammonia salts – meaning of the constant strain rate technique and stress corrosion cracking in bicarbonate solutions – dependence of tensile stress, strain and strain rate upon time; significance of strain rate – investigations in bicarbonate, carbonate and hydroxide solutions – critical potential ranges – relation between strain rate and low cycle fatigue – theoretical differences between stress corrosion cracking and corrosion fatigue in spite of gradual transient in physical appearances.     

Radiofrequency ablation of accessory pathways in pre-excitation syndrome

Various parameters relating to the radio-frequency ablation of accessory pathways were studied in 53 patients (27 males, 26 females: mean age 38.5 [14-64] years) with a history of paroxysmal tachycardia (over 1 month to 50 years), shown to be caused by an accessory pathway (Wolff-Parkinson-White syndrome). In all patients the following values were obtained: (1) number of procedures necessary to achieve permanent blockage of the accessory pathway (1-4); (2) duration of each procedure (45-420 min); (3) duration of fluoroscopy (5-102 min); (4) number of necessary radio-frequency applications (1-48); and (5) cumulative energy per procedure. To ablate left-lateral pathways (n = 10) required fewer procedures, shorter duration per procedure, shorter fluoroscopy time, fewer current applications and less total energy than coagulation of right-sided pathways (n = 10). Those various parameters were greatest for ablation of septal and para-septal pathways (n = 9). Pathways which conducted only retrogradely (n = 15) were more difficult to ablate than those with anterograde conduction (n = 38). There were two complications. In one case a tension pneumothorax occurred after faulty puncture of the subclavian vein; in the other, the left ventricle was perforated causing an acute tamponade which required pericardiocentesis with subsequent suture closure of the perforation. It is concluded that, in principle, all accessory pathways, regardless of their conduction potential and site, can be ablated by a radio-frequency current.