Electronic Stopping of Slow Protons in Transition and Rare Earth Metals: Breakdown of the Free Electron Gas Concept.

The electronic stopping cross sections (SCS) of Ta and Gd for slow protons have been investigated experimentally. The data are compared to the results for Pt and Au to learn how electronic stopping in transition and rare earth metals correlates with features of the electronic band structures. The extraordinarily high SCS observed for protons in Ta and Gd cannot be understood in terms of a free electron gas model, but are related to the high densities of both occupied and unoccupied electronic states in these metals.

Extracellular DNA in single- and multiple-species unsaturated biofilms.

The extracellular polymeric substances (EPS) of bacterial biofilms form a hydrated barrier between cells and their external environment. Better characterization of EPS could be useful in understanding biofilm physiology. The EPS are chemically complex, changing with both bacterial strain and culture conditions. Previously, we reported that Pseudomonas aeruginosa unsaturated biofilm EPS contains large amounts of extracellular DNA (eDNA) (R. E. Steinberger, A. R. Allen, H. G. Hansma, and P. A. Holden, Microb. Ecol. 43:416-423, 2002). Here, we investigated the compositional similarity of eDNA to cellular DNA, the relative quantity of eDNA, and the terminal restriction fragment length polymorphism (TRFLP) community profile of eDNA in multiple-species biofilms. By randomly amplified polymorphic DNA analysis, cellular DNA and eDNA appear identical for P. aeruginosa biofilms. Significantly more eDNA was produced in P. aeruginosa and Pseudomonas putida biofilms than in Rhodococcus erythropolis or Variovorax paradoxus biofilms. While the amount of eDNA in dual-species biofilms was of the same order of magnitude as that of of single-species biofilms, the amounts were not predictable from single-strain measurements. By the Shannon diversity index and principle components analysis of TRFLP profiles generated from 16S rRNA genes, eDNA of four-species biofilms differed significantly from either cellular or total DNA of the same biofilm. However, total DNA- and cellular DNA-based TRFLP analyses of this biofilm community yielded identical results. We conclude that extracellular DNA production in unsaturated biofilms is species dependent and that the phylogenetic information contained in this DNA pool is quantifiable and distinct from either total or cellular DNA.

Elongation correlates with nutrient deprivation in Pseudomonas aeruginosa-unsaturates biofilms.

Bacteria in nature frequently grow as biofilms, yet little is known regarding how biofilm bacteria morphologically adapt to low nutrient availability, which is common in unsaturated environments such as the terrestrial subsurface or on plant leaves. For unsaturated biofilms, in which the substratum may provide all nutrients, what are the relationships between nutrition and cell size and shape-the simplest metrics of cellular morphology? To address this question, we cultured Pseudomonas aeruginosa, a ubiquitous gram-negative bacterium that is environmentally and medically important, on membranes overlaying solid media, and then measured cellular dimensions using atomic force microscopy (AFM). Nutrition was controlled chemically by media composition and physically by stacking membranes to increase the path length for nutrient diffusion. Under conditions of carbon-nitrogen imbalance, low carbon bioavailability, or increased nutrient diffusional path length, cells elongated while maintaining constant width. A mathematical relationship suggests that, by elongating, biofilm bacteria strategically enlarge their nutrient collection surface without substantially changing the ratio of surface area to volume (SA/V). We conclude that P. aeruginosa growing as unsaturated biofilm with a planar nutrient source morphologically adapt to starvation by elongating. This adaptation, if generalizable, differs from a better-understood starvation response (i.e., cell size decreases; thus SA/V in-creases) for planktonic bacteria in well-mixed environments.

Paleoproterozoic snowball earth: extreme climatic and geochemical global change and its biological consequences.

Geological, geophysical, and geochemical data support a theory that Earth experienced several intervals of intense, global glaciation ("snowball Earth" conditions) during Precambrian time. This snowball model predicts that postglacial, greenhouse-induced warming would lead to the deposition of banded iron formations and cap carbonates. Although global glaciation would have drastically curtailed biological productivity, melting of the oceanic ice would also have induced a cyanobacterial bloom, leading to an oxygen spike in the euphotic zone and to the oxidative precipitation of iron and manganese. A Paleoproterozoic snowball Earth at 2.4 Giga-annum before present (Ga) immediately precedes the Kalahari Manganese Field in southern Africa, suggesting that this rapid and massive change in global climate was responsible for its deposition. As large quantities of O(2) are needed to precipitate this Mn, photosystem II and oxygen radical protection mechanisms must have evolved before 2.4 Ga. This geochemical event may have triggered a compensatory evolutionary branching in the Fe/Mn superoxide dismutase enzyme, providing a Paleoproterozoic calibration point for studies of molecular evolution.

Nifedipine pretreatment for autonomic dysreflexia during electroejaculation.

Ten spinal-cord-injured males who exhibited autonomic dysreflexia during electroejaculation were given sublingual calcium channel blocker nifedipine pretreatment to prevent this complication. Nifedipine was successful in decreasing peak systolic, diastolic, and mean blood pressures during the procedure. The use of nifedipine resulted in fewer aborted trials and allowed higher energy delivery during the procedure.

[Influence of a highly purified D-thyroxine medication on thyroid iodine uptake and in vitro tests of thyroid function (author's transl)]. / Beeinflussung laborchemischer und nuklearmedizinischer Schilddrüsenparameter unter der Behandlung mit einem hochgereinigten D-Thyrosin-Präparat.

25 euthyroidal patients with elevated serum cholesterol levels were treated with 4 mg of D-thyroxine daily for 4 weeks; controls were made after this period and after a withdrawal period of another 4 weeks. At the end of the treatment period there was a significant decrease of the serum cholesterol level, of the basal and TRH-stimulated serum TSH and of the thyroidal radioiodine uptake. The radioimmunologically determined values of total T 3 and Free Thyroxine index and of the serum iodine level rose significantly without being accompanied by clinical hyperthyroid symptoms. These changes can be explained on one hand by the well known cholesterol lowering effect of D T-4 and by the inclusion of D-isomeres of thyroid hormones in the radioimmunoassay, and, on the other hand, by the fact that the above-mentioned medication causes an uptake of iodine, and, possibly, by a direct inhibitory effect of D T-4 on the pituitary gland.

Pulsed illumination, closed circuit television system for real-time viewing of unsteady (> 1 micros) events.

A pulsed illumination closed circuit television system is described whereby fast (times <<33 ms), unsteady events can be observed in real time. A low-power helium-neon laser beam is modulated to send a short duration light pulse through the unsteady test medium. The light is refracted according to the instantaneous optical properties of the medium. The refracted light travels to a solid state television camera, known as a charge injection device (CID), in which the sensor array is charged within microseconds. The scanning of the charged array then follows, requiring the standard 33 ms for information transfer to video tape and a TV monitor. The image is thus formed during the laser pulse duration (which presently is 10 to 100 micros, but shorter duration pulses are possible with more powerful lasers), but no more than one image every 33 ms can be observed and recorded. Thus this method is particularly suited for the investigation of high frequency periodic events in which one can observe both a single image, or an ensemble average of as many as 100 images, occurring at corresponding times in different cycles. The reported applications include the recording of steady and transient propane torch flames, of the transient fuel injection process in a motored internal combustion engine, and of the propagation of a flame under firing conditions in the engine. In the shadowgraph and Schlieren modes the method is particularly suited for application to periodic combustion events such as those occurring in internal combustion engines. The method then presents the following advantages over high-speed filming (> 3000 pictures/s); real-time observation and recording of chamber events at any crankangle; real-time observation and recording of the effects of changes in the engine variables (speed, load, spark timing, injection pressure and duration, chamber swirl, etc.) on the combustion events; real-time observation and recording of ensemble averages and cycle-to-cycle variations. The technique also eliminates the delays and unknowns of film processing. Finally, the cost of this system is similar to that of a high-speed camera.

Prevention of postoperative deep-vein thrombosis by low-dose heparin in urological surgery. A double-blind, randomised study.

The efficacy of low-dose heparin in preventing deep-vein thrombosis (D. V. T.) after urological surgery was investigated in a double-blind trial. Thromboses were detected by the 125I-labelled fibrinogen technique. The incidence of D. V. T. was 36% in the control group (25 patients) and 9% in the treated group (22 patients) (p less than 0.05). Contrary to the current opinion this form of prophylaxis was effective following open prostatectomy.

Infarction of testicle and Schistosoma mansoni.

The first case of clinical involvement and infarction of the testes caused the Schistosoma mansoni is reported. Although a rare rhenomenon, one must consider this in the differential diagnosis of testicular disease in patients who have resided in endemic areas of S. mansoni.