Can we learn more from the data underlying the statistical α-β model with respect to the dynamical behavior of avalanches?

Hazard and risk assessment in avalanche-prone areas involves estimation of runout distances of potential avalanches. Methods for determination of the runout may be divided into two categories: 1) methods based on statistical approaches such as the well known α-β model or 2) methods based on numerical avalanche models such as the PCM-model or VS-type models (just to name the more traditional ones). Methods in the second group have the advantage that besides the runout distance, velocity and impact pressure distributions along the avalanche track can also be obtained, this being a requisite for meaningful risk assessments. However, the predictive power of dynamical models depends on the use of appropriate rheological models and their parameters.In the statistical α-β model, the maximum runout distance is solely a function of topography. The runout distance equations were found by regression analysis, correlating the longest registered runout distance of several hundred avalanche paths with a selection of topographic parameters.In this paper, we re-evaluate Norwegian and Austrian avalanche data, which served as basis for the α-β model in the respective countries, and additional avalanche data with respect to dynamical measures. As most of those avalanche data originate more or less from extreme events (i.e. avalanches with return periods of the order of 100 years), the dynamical measures may give hints about an appropriate rheology for dynamical models suitable for extreme avalanche events.The analysis raises reasonable doubt whether the classical ansatz for the retarding acceleration of snow avalanches with additive terms involving Coulomb-friction and a velocity-squared dependency, which is used in many avalanche models, is adequate for a physically-based model. Back-calculations of runout distances using a simple block model show a discrepancy between commonly proposed parameter values (and of the underlying rheological models) and the observations.     

On the Synergy Effect in MoO3–Fe2(MoO4)3 Catalysts for Methanol Oxidation to Formaldehyde

Methanol oxidation to formaldehyde was studied over a series of Fe–Mo–O catalysts with various Mo/Fe atomic ratio and the end compositions Fe₂O₃ and MoO₃. The activity data show that the specific activity passes through a maximum with increase of the Mo content and is the highest for Fe₂(MoO₄)₃. The selectivity to formaldehyde, on the other hand, increases with the Mo content in the catalyst. A synergy effect is observed in that a catalyst with the Mo/Fe ratio 2.2 is almost as active as Fe₂(MoO₄)₃ and as selective as MoO₃. Imaging of a MoO₃/Fe₂(MoO₄)₃ catalyst by SEM and TEM shows that the two phases form separate crystals, and HRTEM reveals the presence of an amorphous overlayer on the Fe₂(MoO₄)₃ crystals. EDS line-scan analysis in STEM mode demonstrates that the Mo/Fe ratio in the amorphous layer is ~2.1 in the fresh catalyst and ~1.7 in the aged catalyst. The enrichment of Mo at the catalyst surface is confirmed by XPS data. Raman spectra give evidence for the Mo in the amorphous material being in octahedral coordination, which is in contrast to the crystalline Fe₂(MoO₄)₃ bulk structure where Mo has tetrahedral coordination. X-ray diffraction (XRD) analysis gives no support for the formation of a defective molybdate bulk structure. The results presented give strong support for the Mo rich amorphous structure being observed on the Fe₂(MoO₄)₃ crystal surfaces being the active phase for methanol oxidation to formaldehyde.     

Simulation Model for the Model-Based Control of a Biofuel Dryer at an Industrial Combined Heat and Power Plant

The primary aim of this article is to present a simulation model for a bark dryer integrated into a combined heat and power plant. The same model can be used for the model-based control of the dryer. The secondary aim is to evaluate how useful the control is from an economic point of view. Results show that the final fuel moisture content can be stabilised by controlling the drying temperature(s). On the other hand, the deviation in final bark moisture decreases even when the dryer has no control at all. Net incomes resulting from drying increase in most cases compared to dryers without control. The need for control cannot be justified on economic grounds.     

Optimization and probabilistic calibration of avalanche block models

The Norwegian Geotechnical Institute (NGI) has been performing full-scale avalanche tests at Ryggfonn in western Norway for more than 30 years. During those years, measurements from about three dozen dry-snow avalanches have provided information on front velocities and runout distances.Some of those measurements were used to evaluate “optimal parameters” for a simple avalanche model and to calibrate the model, following a well-defined probabilistic method. Traditionally, parameters of those kinds of models were evaluated from runout analysis disregarding any dynamics. The set of roughly 20 observed avalanches from one single path including, estimations of the front velocities at three points in the lower third of the track provide a unique opportunity for introducing uncertainty quantification methods for evaluating the performance of similar kinds of mass block models.We present the optimization, the model calibration and results from the model performance testing.     

Enzymatic preparation of monoglycerides in microemulsion

Monoglycerides have been obtained in 80% yield by enzyme catalyzed hydrolysis of the corresponding triglyceride. The reaction was carried out in an oil-rich microemulsion (L 2 phase) formulated without cosurfactant. Best results were obtained with the anionic surfactant sodium bis(2-ethylhexyl)sulfosuccinate (AOT), isooctane as hydrocarbon component and a molar ratio of aqueous buffer of pH 7 to surfactant of 12. The enzyme used was a 1,3-specific lipase which leaves the 2- position intact. However, the 2-monoglyceride formed slowly undergoes acyl migration to 1-monoglyceride which subsequently is hydrolyzed to glycerol and fatty acid. Optimal reaction time at 35 C reaction temperature was found to be three hr.     

Coexistence of enkephalin- and tyrosine hydroxylase-like immunoreactivities in nerve fibers of the temporomandibular joint capsule of the guinea pig

This case report describes the intraoperative improvement of somatosensory evoked potentials (SEPs) during the removal of a broached pedicle screw that had been placed in an unmonitored procedure 1 month earlier. Postoperatively, there was improved neurologic function and reversal of the neurologic deficit that had been caused by the first procedure. To our knowledge, this is the first report of a correlation of intraoperative SEP improvement with improved postoperative neurologic function after neurologic deficit because of nerve irritation or compression from a pedicle screw. Nerve damage occurs in about 15% of patients who undergo instrumentation after lumbar fusion. The potential utility of neurophysiologic methods during initial screw placement is suggested and supported, as proper use of such intraoperative tools may have prevented the need for the second procedure.     

Multiple transrectal ultrasound-guided biopsies for the detection of prostate cancer and determination of tumor volume, grade, and seminal vesicle invasion

Of 60 cases of neurotoxicity related to occupational exposures of workers at plants producing acrylamide monomers, cases involving neurotoxicity related to jobs using polymers with acrylamide monomer contamination have not been widely reported. In 1992, two patients were referred to the Division of Occupational and Environmental Health, Department of Family and Community Health, Marshall University School of Medicine, in Huntington, West Virginia for evaluation. The patients had worked in different coal preparation plants in southern West Virginia for over 10 years and had exposure to an acrylamide polymer flocculent contaminated with acrylamide monomer. Both patients had no instruction on proper use of, or the dangers of, acrylamide and were not given adequate safety equipment. Patient A developed Parkinsonism and Patient B peripheral neuropathies with a neurogenic bladder. These two case reports highlight the need to reemphasize the basic tenets of occupational health and safety. Many chemicals are being introduced into mining operations and awareness of potential toxic exposures and new diseases not previously reported in the mining industry must become part of the surveillance system by mine management and labor safety committees. Further studies on the extent of acrylamide neurotoxicity in the mining industry is encouraged.     

Simulation Model for the Model-Based Control of a Biofuel Dryer at an Industrial Combined Heat and Power Plant

The primary aim of this article is to present a simulation model for a bark dryer integrated into a combined heat and power plant. The same model can be used for the model-based control of the dryer. The secondary aim is to evaluate how useful the control is from an economic point of view. Results show that the final fuel moisture content can be stabilised by controlling the drying temperature(s). On the other hand, the deviation in final bark moisture decreases even when the dryer has no control at all. Net incomes resulting from drying increase in most cases compared to dryers without control. The need for control cannot be justified on economic grounds.     

Marked point process framework for living probabilistic safety assessment and risk follow-up

We construct a model for living probabilistic safety assessment (PSA) by applying the general framework of marked point processes. The framework provides a theoretically rigorous approach for considering risk follow-up of posterior hazards. In risk follow-up, the hazard of core damage is evaluated synthetically at time points in the past, by using some observed events as logged history and combining it with re-evaluated potential hazards. There are several alternatives for doing this, of which we consider three here, calling them initiating event approach, hazard rate approach, and safety system approach. In addition, for a comparison, we consider a core damage hazard arising in risk monitoring. Each of these four definitions draws attention to a particular aspect in risk assessment, and this is reflected in the behaviour of the consequent risk importance measures. Several alternative measures are again considered. The concepts and definitions are illustrated by a numerical example.