Influence of altitude and age in the accumulation of organochlorine compounds in fish from high mountain lakes

The analysis of hexachlorobenzene, hexachlorocyclohexanes, polychlorobiphenyls, and DDTs in muscle of fish from high mountain lakes shows that a proportion of their concentration variance depends on fish age and lake altitude. Interestingly, the magnitude of this share corresponds linearly with the log-transformed vapor pressure (Vp) of the organochlorine compounds (OC). Thus, the distributions of OC with Vp < 10(-2.5) Pa are mostly determined by these two variables. Altitude gradients mainly respond to temperature differences, involving concentration increases of 25-150 times between 8.7 and -2.3 degrees C. The age effect encompasses concentration increments of 2.4-7.8 for average lake differences between 2 and 13 yr. However, both effects are independent since no correlation between fish age and lake altitude is observed. Fish liver concentrations exhibit the same pattern, but the correlations are only significantfor age, suggesting thatthe temperature trend is more related to long-term accumulation than episodic intake. The temperature effect is independent from compound origin. In addition, the sites situated at highest altitude, those most distant from possible ground pollution sources, are the most polluted. The results can be explained by condensation effects such as those described for the latitudinal trends that support the global distillation theory. However, in the high altitude lakes a temperature-dependent amplification mechanism, probably related to low metabolism and respiration at lowtemperatures, enhances OC accumulation in fish beyond the increases predicted from theoretical condensation and solubilization enthalpies. The observed temperature dependence suggests that a general remobilization of OC accumulated in high mountain areas could take place as a consequence of the general warming of these areas anticipated in the climatic change studies.     

Novel ideas for fast muscle action potential simulations using the line source model

Using a signal processing approach, we analyze the line source model for muscle action potential (AP) modeling. We show that the original model presents a tradeoff between violating the Nyquist criterion on one hand and using a discretization frequency that is unnecessarily high with respect to the bandwidth of the generated AP on the other. Here, we present an improved line source model that, compared to the original, allows a lower discretization frequency while retaining the accuracy by simply introducing a continuous-time anti-aliasing filter. Moreover, a transfer function form of the transmembrane current is presented that promote the use of sophisticated signal processing methods on these type of signals. Both continuous-time and discrete-time models are presented. We also address and analyze the implications of the finite length of the muscle fibers. Including this in the model is straightforward, owing to the convolutional form of the line source model, and is manifested by a simple transformation of the associated weighting function. AP modeling is discussed for the three different electrode models: the concentric needle electrode, the single fiber electrode, and the macro electrode. The presented model is suitable for modeling large motor units, where both accuracy and computational efficiency are important factors. To simplify the selection of the discretization interval, we derive what we call the cumulative cutoff frequency that provides an estimate of the required Nyquist frequency.     

Are suicides by jumping off bridges preventable? An analysis of 50 cases from Sweden

This is a community-based sequential case series of 50 individuals who committed suicide by jumping from bridges in two regions of Sweden. Of the 50 subjects, 32 were men and 18 women, with a median age of 35 years. At least 40 had psychiatric problems. The frequency of suicide was highest during the summer months and during the weekends. A total of 27 bridges were used, with a total length of just under 9 km. Three bridges accounted for almost half of all suicides. Limiting the availability of one method of committing suicide is reported to reduce the overall suicide rate; why suicide and injury suicide preventive measures might be considered. Since this study demonstrates that few bridges attract suicide candidates, this injury mechanism needs to be acknowledged by the road system owners and included in the safety work.     

Revised Kubelka-Munk theory. II. Unified framework for homogeneous and inhomogeneous optical media

We extend the applicability of the recently revised Kubelka-Munk (K-M) theory to inhomogeneous optical media by treating inhomogeneous ink penetration of the substrate. We propose a method for describing light propagation in either homogeneous or inhomogeneous layers using series representations for the K-M scattering and absorption coefficients as well as for intensities of the upward and downward light streams. The conventional and matrix expressions for spectral reflectance and transmittance values of optically homogeneous media in the K-M theory are shown to be special cases of the present framework. Three types of ink distribution-homogeneous, linear, and exponential-have been studied. Simulations of spectral reflectance predict a depression of reflectance peaks and reduction of absorption bands characteristic of hue shifts and significant reduction of saturation and, in turn, color gamut.     

An application of a muscle model to study electromyographic signals

A simulation program for research and teaching electromyography (EMG) has been developed. It has a great number of parameters that may be optionally changed in simulations of normal and diseased muscle. The simulator is user-friendly and fast and can actually be run without much help from the manual. It is easy to introduce new motor units (MU), to change MU and individual muscle fibre parameters, to insert an EMG electrode and to change its position. The model allows simulation of the most common pathological situations. The resulting signals are displayed in a conventional form. The generated EMG signals obtained with the three electrodes that have been used so far are reasonably similar to the signals obtained in real recordings. A few shortcomings in simulating, e.g. end plate zone and abnormal volume conduction characteristics do not seem to influence the principal results. The simulator can, therefore, be used in teaching and even for research.     

Effect of induced fracturing based on a natural fracture system in a dimension stone quarry in the Offerdal Nappe, Sweden

The degree of induced fracturing related to bench blasting has been investigated in the Offerdal Nappe in the Landögssjö area, in the county of Jämtland, Sweden where the dimension stone "Flammet Quartzite" is quarried. Two fracture trace maps have been compiled; one from an area within the quarry, where natural and induced fracturing are analysed, and a second from an area where no quarrying has taken place, i.e. where only natural fractures appear. This means that it is possible to take into account differences between natural fractures and induced fractures. The fracture system has been described in the investigated areas according to fracture set orientation, size, frequency and occurrence. Two types of fracture occurrence related to blasting have been defined: (1) coalescing fractures with at least one end terminating in a drill hole (type A), and (2) coalescing fractures with one end terminating in a type A fracture (type B). Fractures of type A increase the fracture frequency by up to 23%. Considering fractures of type A and B together, an increase of up to 36% has been noted. In this investigation, approximately 17% of the rock volume shows increased fracturing from the blasting operation.     

Genotypes and enterotoxicity of Staphylococcus aureus isolated from the hands and nasal cavities of flight-catering employees

Hand and nasal samples of flight-catering staff were collected from 1995 to 1997 to find employees carrying Staphylococcus aureus. Altogether 153 hand samples and 136 nose samples were taken. Nasal sampling showed a higher prevalence of S. aureus among food handlers (29%) than hand sampling (9%). A high proportion of the strains (46%) were enterotoxigenic, and a considerable amount of food handlers carried enterotoxigenic S. aureus, 6% and 12% according to hand and nasal sampling, respectively. Pulsed-field gel electrophoresis macrorestriction profiles revealed a total of 32 different types associated with the 35 employees carrying S. aureus. In most cases, the same type colonized both the hand and nose of a person. Despite the wide variety of types found, one strain colonized five persons and the second most common strain was associated with four food handlers. The predominant toxin produced was B, which was produced by the most common strain. The results showed that nasal sampling is a good way to detect S. aureus carriers, whereas hand sampling may fail to reveal carriers. The high proportion of enterotoxigenic strains show that a food handler harboring S. aureus must be considered a potential source of enterotoxigenic strains for airline meals.     

Optical characterization of hybrid antireflective coatings using spectrophotometric and ellipsometric measurements

A hybrid antireflective coating combining homogeneous layers and linear gradient refractive index layers has been deposited using different techniques. The samples were analyzed optically based on spectrophotometric and spectroscopic ellipsometry measurements under different angles of incidence in order to precisely characterize the coatings. The Lorentz-Lorenz model has been used to calculate the refractive index of material mixtures in gradient and constant index layers of the coating. The obtained refractive index profiles have been compared with the targeted ones to detect errors in processes of deposition.     

Microvasculatory reaction of skeletal muscle to Ti–15Mo in comparison to well-established titanium alloys

Beta-titanium alloys such as Ti–15Mo are increasingly utilized for orthopaedic implant applications because of their excellent corrosion resistance and low elastic modulus. Particularly in osteosynthesis, where the biomaterial stands in direct contact to soft tissue, undesirable biologic reactions may have severe consequences especially in the vulnerable state of trauma and added iatrogenic damage to the microvascular system. In a comparative study we therefore assessed in vivo nutritive perfusion and leukocytic response of striated muscle to the biomaterials Ti–15Mo, Ti–6Al–4V and Ti–6Al–7Nb, thereby drawing conclusions on their short term inflammatory potential. Utilizing the well established skinfold chamber preparation in the hamster and intravital fluorescence microscopy, we could not demonstrate any significant discrepancies between the three alloys. All metals induced an initial moderate inflammatory response in skeletal muscle microcirculation. While recuperation of animals treated with Ti–15Mo and Ti–6Al–7Nb was prompt, we documented a slightly more sluggish recovery of Ti–6Al–4V treated animals. A gross toxicity was not observed for any of the alloys. Conclusively, Ti–15Mo, Ti–6Al–4V and Ti–6Al–7Nb induce an only transient inflammatory answer of the striated muscle microvascular system. Our results indicate that on the microvascular level the tested bulk Ti-alloys do not cause enduring biologic impairment in muscle. No benefit of any kind has or will be received either directly or indirectly by the authors.