Sudden, unexpected death of infants and electromagnetic fields (author's transl)

The examination of 337 cases of Sudden Infant Death Syndorme (SIDS) ro Crib Deaths in Philadelphia, Penn., USA, and 294 cases in Hamburg, Federal Republic of Germany, shows regional concentrations which are close to uncommon magnetic fields or stray electric currents in the ground. The risk in the cellar and first floor of houses is higher than in the other floors. Therefore a possible causal relationship between electromagnetic fields and SIDS cases must be considered and checked by on-site measurements, animal experiments, and by more research on magnetic fields as stressor for infants.     

A prosthetic vas deferens

Six dogs were implanted with the synthetic vas deferens device as part of our continuing research into the development of a reversible occlusive device for implant in the transected vas deferens. The experimental objectives were to assess the effects of sperm path length and duration of aspermia on total sperm count and motility by implanting three different lengths of the device in animals with different degrees of aspermic duration induced by bilateral vasectomy. Device lengths varied from 1.55 cm to 4.3 cm including the pilot tubes. The prosthesis is fabricated entirely of silicone rubber with Dacron velour tissue ingrowth material bonded to the outside surface of the ring to which vas ends are sutured. The pilot tubes extend 4 mm beyond the suture rings and are 0.6 mm OD with a 0.3 mm ID that extends through the entire length of the device. The flexible pilot tubes are an important feature of this design and insert into the vas lumen ensuring alignment between the device and the vas deferens while maintaining the necessary resiliency to adapt to the inherent movements of the vas without perforation. All animals included in these experiments were carefully selected and conditioned before implant. The evaluation of performance was based on semen samples collected at one week intervals. Sperm subsequently appeared in the ejaculate of all 6 dogs, demonstrating that the restoration of sperm transport can be restored after bilateral vasectomy through the implantation of a prosthetic vas deferens. The potential application of this device to the human male for the restoration of fertility appears excellent.     

Ag surface diffusion and out-of-bulk segregation in CrN-Ag nano-composite coatings

CrN-Ag nanocomposite coatings are deposited on Si(100) wafers and 20MnCr5 steel disks in a mixed Ar+N2 atmosphere by reactive magnetron sputtering. Structure, composition and morphology were investigated by Scanning Electron Microscopy (SEM), Auger Electron Spectroscopy (AES), X-ray Photoemission Spectroscopy (XPS), X-ray Diffraction (XRD) and Focused Ion Beam (FIB) cross sectional analysis. The as deposited film matrix is mainly composed by CrN phase (78%), but a relevant part (28%) is composed by Cr2N. Ag agglomerates in the CrN matrix forming elongated grains 200-400 nm wide and 50-100 nm high, which extends on the top of CrN columns. At the surface Ag aggregates into two different structures: large tetrahedral crystalline clusters, with typical dimension ranging from 200 to 500 nm, and smaller Ag nanoparticles with diameter of 15-25 nm. The annealing in N2 atmosphere up to 500 degrees C does not affect size and distribution of the Ag grains in the sub-surface region, while it induces a size increase of the bigger Ag clusters on the surface, mainly related to Ag surface diffusion and clusters coalescence. Annealing at higher temperature leads to an evident Ag out-of-bulk segregation, generating Ag depleted voids in the near-surface region, and further increasing of the Ag clusters size at the surface. Tribological tests on as deposited CrN-Ag film reveal a coefficient of friction against a steel ball reduced with respect to CrN film, probably related to the presence of Ag which acts as solid lubricant, but the coating is removed after a very short sliding distance. The poor mechanical properties of the realized Ag-based coatings are confirmed by lower hardness and Young modulus values with respect to pure CrN.     

The adaptation-protective effect of corticosteroids on the rat gastric mucosa and its mechanism

The influence of stress-induced corticosteroid production on gastric ulceration, blood flow velocity in gastric microvessels and blood pressure was studied in rats. The role of plasma corticosteroids was investigated by means of blockade of the pituitary-adrenocortical system (PACS) and following corticosterone replacement therapy (400 mu/100 g b.w.). The blockade which was induced by Fi. hydrocortisone administration (7 days before stress, 30 mg/100 g b. w.) resulted in an insufficient corticosteroid production. To evaluate the influence of corticosteroids on blood flow velocity in gastric microvessels of muscular, submucosal and mucosal coats it was used intravital microfilming by means of a dark-field contact epiobjective. Stress (water immersion + restraint) induces an ulceration, a decrease in the systemic arterial blood pressure (3 h after stress onset) and a decrease in blood flow velocity in the gastric microvessels (3 h after stress onset). In rats with insufficient corticosteroid production stress-induced ulceration, a decrease in blood pressure and gastric blood velocity were more greater than in rats with intact PACS. Replacement corticosterone therapy corrected all parameters. The results revealed that antiulcerogenic effect of stress-induced glucocorticoid production is realised owing to normalisation of gastric blood supply which is provided by an increase in systemic blood pressure.     

Experiments on two-phase flow in hydraulic jump on pebbled rough bed: Part 2–Bubble clustering

A survey on bubble clustering in air–water flow processes may provide significant insights into turbulent two-phase flow. These processes have been studied in plunging jets, dropshafts, and hydraulic jumps on a smooth bed. As a first attempt, this study examined the bubble clustering process in hydraulic jumps on a pebbled rough bed using experimental data for 1.70 < Fr₁ < 2.84 (with Fr₁ denoting the inflow Froude number). The basic properties of particle grouping and clustering, including the number of clusters, the dimensionless number of clusters per second, the percentage of clustered bubbles, and the number of bubbles per cluster, were analyzed based on two criteria. For both criteria, the maximum cluster count rate was greater on the rough bed than on the smooth bed, suggesting greater interactions between turbulence and bubbly flow on the rough bed. The results were consistent with the longitudinal distribution of the interfacial velocity using one of the criteria. In addition, the clustering process was analyzed using a different approach: the interparticle arrival time of bubbles. The comparison showed that the bubbly flow structure had a greater density of bubbles per unit flux on the rough bed than on the smooth bed. Bed roughness was the dominant parameter close to the jump toe. Further downstream, Fr₁ predominated. Thus, the rate of bubble density decreased more rapidly for the hydraulic jump with the lowest Fr₁.