Apport du CT-3D dans le diagnostic et le traitement des fractures des plateaux tibiaux [Value of 3D CT in diagnosis and treatment of fractures of the tibial plateau]

A precise classification and an optimal understanding of tibial plateau fractures are the basis of a conservative treatment or adequate surgery. The aim of this prospective study is to determine the contribution of 3D CT to the classification of fractures (comparison with standard X-rays) and as an aid to the surgeon in preoperative planning and surgical reconstruction. Between November 1994 and July 1996, 20 patients presenting 22 tibial plateau fractures were considered in this study. They all underwent surgical treatment. The fractures were classified according to the Müller AO classification. They were all investigated by means of standard X-rays (AP, profile, oblique) and the 3D CT. Analysis of the results has shown the superiority of 3D CT in the planning (easier and more acute), in the classification (more precise), and in the exact assessment of the lesions (quantity of fragments); thereby proving to be of undeniable value of the surgeon.

Routine use of intravascular ultrasound for endovascular aneurysm repair: angiography is not necessary.

INTRODUCTION: to assess the outcome of endovascular aortic aneurysm repair (EVAR) using intravascular ultrasound (IVUS) without angiography. MATERIALS/METHODS: eighty consecutive patients (median age 69 years (range 25-90): male 72 (90%), female 8 (10%)) underwent endovascular aneurysm repair (AAA 68 (85%), TAA 12 (15%)) using either angiography in 31/80 patients (39%) or IVUS in 49/80 patients (61%) in accordance to the surgeons preference. RESULTS: hospital mortality was 2/80 (3%), 1/68 for AAA (2%), 1/12 for TAA (8%), 2/31 for angiography (7%), and 0/49 for IVUS (0.0%: NS). Median quantity of contrast medium was 190 ml (range: 20-350) for angiography versus 0 ml for IVUS (p<0.01). Median X-ray exposure time 24 min (range 9-65 min) versus 8 min (range 0-60 min) for IVUS (p<0.05). No coverage of renal or suprarenal artery orifices occurred in either group. Conversion to open surgery was necessary in 4/80 patients (5%), 1/31 for angiography (3%) and 3/49 patients for IVUS (6%: NS). Early endoleaks were observed in 13/80 patients (16%): 8/31 patients for angiography (26%) versus 5/49 for IVUS (10%: p<0.05): 5/13 endoleaks resolved spontaneously (39%) whereas 8/13 (61%) required additional procedures. CONCLUSIONS: IVUS is a reliable tool for EVAR. In most cases, perprocedural angiography is not necessary.

A framework for hybrid simulations of two-phase flow in porous media

Rough a global coarse problem. Although these techniques are usually employed for problems in which the fine-scale processes are described by Darcy's law, they can also be applied to pore-scale simulations and used as a mathematical framework for hybrid methods that couples a Darcy and pore scales. In this work, we consider a pore-scale description of fine-scale processes. The Navier-Stokes equations are numerically solved in the pore geometry to compute the velocity field and obtain generalized permeabilities. In the case of two-phase flow, the dynamics of the phase interface is described by the volume of fluid method with the continuum surface force model. The MsFV method is employed to construct an algorithm that couples a Darcy macro-scale description with a pore-scale description at the fine scale. The hybrid simulations results presented are in good agreement with the fine-scale reference solutions. As the reconstruction of the fine-scale details can be done adaptively, the presented method offers a flexible framework for hybrid modeling.

Generation and nonlinear evolution of shore-oblique/transverse sand bars

The coupling between topography, waves and currents in the surf zone may selforganize to produce the formation of shore-transverse or shore-oblique sand bars on an otherwise alongshore uniform beach. In the absence of shore-parallel bars, this has been shown by previous studies of linear stability analysis, but is now extended to the finite-amplitude regime. To this end, a nonlinear model coupling wave transformation and breaking, a shallow-water equations solver, sediment transport and bed updating is developed. The sediment flux consists of a stirring factor multiplied by the depthaveraged current plus a downslope correction. It is found that the cross-shore profile of the ratio of stirring factor to water depth together with the wave incidence angle primarily determine the shape and the type of bars, either transverse or oblique to the shore. In the latter case, they can open an acute angle against the current (upcurrent oriented) or with the current (down-current oriented). At the initial stages of development, both the intensity of the instability which is responsible for the formation of the bars and the damping due to downslope transport grow at a similar rate with bar amplitude, the former being somewhat stronger. As bars keep on growing, their finite-amplitude shape either enhances downslope transport or weakens the instability mechanism so that an equilibrium between both opposing tendencies occurs, leading to a final saturated amplitude. The overall shape of the saturated bars in plan view is similar to that of the small-amplitude ones. However, the final spacings may be up to a factor of 2 larger and final celerities can also be about a factor of 2 smaller or larger. In the case of alongshore migrating bars, the asymmetry of the longshore sections, the lee being steeper than the stoss, is well reproduced. Complex dynamics with merging and splitting of individual bars sometimes occur. Finally, in the case of shore-normal incidence the rip currents in the troughs between the bars are jet-like while the onshore return flow is wider and weaker as is observed in nature.

Optimization of Snow Drifting Mitigation and Control Methods for Iowa Conditions Part II, TR-626, 2015

Blowing and drifting of snow is a major concern for transportation efficiency and road safety in regions where their development is common. One common way to mitigate snow drift on roadways is to install plastic snow fences. Correct design of snow fences is critical for road safety and maintaining the roads open during winter in the US Midwest and other states affected by large snow events during the winter season and to maintain costs related to accumulation of snow on the roads and repair of roads to minimum levels. Of critical importance for road safety is the protection against snow drifting in regions with narrow rights of way, where standard fences cannot be deployed at the recommended distance from the road. Designing snow fences requires sound engineering judgment and a thorough evaluation of the potential for snow blowing and drifting at the construction site. The evaluation includes site-specific design parameters typically obtained with semi-empirical relations characterizing the local transport conditions. Among the critical parameters involved in fence design and assessment of their post-construction efficiency is the quantification of the snow accumulation at fence sites. The present study proposes a joint experimental and numerical approach to monitor snow deposits around snow fences, quantitatively estimate snow deposits in the field, asses the efficiency and improve the design of snow fences. Snow deposit profiles were mapped using GPS based real-time kinematic surveys (RTK) conducted at the monitored field site during and after snow storms. The monitored site allowed testing different snow fence designs under close to identical conditions over four winter seasons. The study also discusses the detailed monitoring system and analysis of weather forecast and meteorological conditions at the monitored sites. A main goal of the present study was to assess the performance of lightweight plastic snow fences with a lower porosity than the typical 50% porosity used in standard designs of such fences. The field data collected during the first winter was used to identify the best design for snow fences with a porosity of 50%. Flow fields obtained from numerical simulations showed that the fence design that worked the best during the first winter induced the formation of an elongated area of small velocity magnitude close to the ground. This information was used to identify other candidates for optimum design of fences with a lower porosity. Two of the designs with a fence porosity of 30% that were found to perform well based on results of numerical simulations were tested in the field during the second winter along with the best performing design for fences with a porosity of 50%. Field data showed that the length of the snow deposit away from the fence was reduced by about 30% for the two proposed lower-porosity (30%) fence designs compared to the best design identified for fences with a porosity of 50%. Moreover, one of the lower-porosity designs tested in the field showed no significant snow deposition within the bottom gap region beneath the fence. Thus, a major outcome of this study is to recommend using plastic snow fences with a porosity of 30%. It is expected that this lower-porosity design will continue to work well for even more severe snow events or for successive snow events occurring during the same winter. The approach advocated in the present study allowed making general recommendations for optimizing the design of lower-porosity plastic snow fences. This approach can be extended to improve the design of other types of snow fences. Some preliminary work for living snow fences is also discussed. Another major contribution of this study is to propose, develop protocols and test a novel technique based on close range photogrammetry (CRP) to quantify the snow deposits trapped snow fences. As image data can be acquired continuously, the time evolution of the volume of snow retained by a snow fence during a storm or during a whole winter season can, in principle, be obtained. Moreover, CRP is a non-intrusive method that eliminates the need to perform man-made measurements during the storms, which are difficult and sometimes dangerous to perform. Presently, there is lots of empiricism in the design of snow fences due to lack of data on fence storage capacity on how snow deposits change with the fence design and snow storm characteristics and in the estimation of the main parameters used by the state DOTs to design snow fences at a given site. The availability of such information from CRP measurements should provide critical data for the evaluation of the performance of a certain snow fence design that is tested by the IDOT. As part of the present study, the novel CRP method is tested at several sites. The present study also discusses some attempts and preliminary work to determine the snow relocation coefficient which is one of the main variables that has to be estimated by IDOT engineers when using the standard snow fence design software (Snow Drift Profiler, Tabler, 2006). Our analysis showed that standard empirical formulas did not produce reasonable values when applied at the Iowa test sites monitored as part of the present study and that simple methods to estimate this variable are not reliable. The present study makes recommendations for the development of a new methodology based on Large Scale Particle Image Velocimetry that can directly measure the snow drift fluxes and the amount of snow relocated by the fence.

Insight in the factors associated with the presence of protective antiviral T-cell response.

T cells play a primordial role in antiviral immunity. Virus-specific T-cell responses can be characterized by a number of independent variables. These include the magnitude of the response; the functional quality of the response, i.e. the types of cytokines secreted after stimulation and the proliferative or lytic potential; the tissue distribution of the T cells; the breadth of the response; and the avidity of the response. All of these together constitute the T-cell response to antigen (Ag) and comprise potential variables that may correlate with antiviral protective immunity. Substantial advances have recently been obtained in the characterization of virus-specific T-cell responses. These studies have shown that the quality (in term of functional profile) rather than the quantity of Ag-specific T cells was associated with protection. Recently, the term polyfunctional has been used to define T-cell responses that, in addition to typical effector functions such as secretion of IFN-g, TNF-a and MIP-1b and cytotoxic activity, comprise distinct T-cell populations, also able to secrete IL-2 and retaining Ag-specific proliferation capacity. The term \only effector" defines T-cell responses/ populations able to secrete cytokines such as IFN-g, TNF-a and MIP-1b and endowed with cytotoxic activity but lacking IL-2 and proliferation capacity. Several models of virus infections (HIV-1, cytomegalovirus [CMV], Epstein Barr virus [EBV], influenza [Flu] and Herpes Simplex virus) exclusively differentiated on the basis of Ag exposure and persistence, were investigated: 1) antigen clearance, 2) protracted Ag exposure and persistence and low Ag levels, 3) Ag persistence and high Ag levels, and 4) acute Ag exposure/re-exposure. These analyses have demonstrated that polyfunctional and not \only effector" T-cell responses were associated with protective antiviral immunity. However, the factors and mechanisms governing the generation of functionally distinct T-cell populations remain to be elucidated. Recently, several studies have shown a major influence of HLA genotype in the evolution of HIV and the progression of HIV-associated disease. In particular, certain HLA-B alleles were most closely associated with non-progressive disease and low viral load or disease and had a dominant involvement on the clinical course of HIV-associated diseases. In this study, we have investigated the relationship between HLA restriction and the functional profile of Tcell responses in order to determine whether HLA-B influenced the generation of polyfunctional CD8 T-cell responses. To be able to address this issue, we studied CD8 T-cell responses against HIV-1, CMV, EBV and Flu in 128 subjects. These analyses enabled us to demonstrate that HLA-Arestricted epitopes were mostly associated with \only effector" T-cell responses while, in contrast, polyfunctional CD8 T-cell responses were predominantly driven by virus epitopes restricted by HLA-B alleles. We then characterized eventual differences in the responsiveness of CD8 T-cell populations restricted by different HLA-A and HLA-B alleles. For this purpose, we investigated the T-cell receptor (TCR) avidity for the cognate epitope of polyfunctional and \only effector" CD8 T-cell populations. Our results indicated that overall virus-specific CD8 T-cell populations recognizing virus epitopes restricted by HLA-B alleles were equipped with lower avidity TCR for the cognate epitopes when compared to those recognizing epitopes restricted by HLA-A alleles. In conclusion, these results provide the rationale for the observed protective role of HLA-B genotypes in HIV-1- infection and new insights into the relationship between TCR avidity and functional profile of virus-specific CD8 Tcells.

Investigation of Plastic Pipes for Highway Applications, HR-373A, Phase II, 1997

It is generally accepted that high density polyethylene pipe (HDPE) performs well under live loads with shallow cover, provided the backfill is well compacted. Although industry standards require carefully compacted backfill, poor inspection and/or faulty construction may result in soils that provide inadequate restraint at the springlines of the pipes thereby causing failure. The objectives of this study were: 1) to experimentally define a lower limit of compaction under which the pipes perform satisfactorily, 2) to quantify the increase in soil support as compaction effort increases, 3) to evaluate pipe response for loads applied near the ends of the buried pipes, 4) to determine minimum depths of cover for a variety of pipes and soil conditions by analytically expanding the experimental results through the use of the finite element program CANDE. The test procedures used here are conservative especially for low-density fills loaded to high contact stresses. The failures observed in these tests were the combined effect of soil bearing capacity at the soil surface and localized wall bending of the pipes. Under a pavement system, the pipes' performance would be expected to be considerably better. With those caveats, the following conclusions are drawn from this study. Glacial till compacted to 50% and 80% provides insufficient support; pipe failureoccurs at surface contact stresses lower than those induced by highway trucks. On the other hand, sand backfill compacted to more than 110 pcf (17.3 kN/m3) is satisfactory. The failure mode for all pipes with all backfills is localized wall bending. At moderate tire pressures, i.e. contact stresses, deflections are reduced significantly when backfill density is increased from about 50 pcf (7.9 kN/m^3) to 90 pcf (14.1 kN/m^3). Above that unit weight, little improvement in the soil-pipe system is observed. Although pipe stiffness may vary as much as 16%, analyses show that backfill density is more important than pipe stiffness in controlling both deflections at low pipe stresses and at the ultimate capacity of the soil-pipe system. The rate of increase in ultimate strength of the system increases nearly linearly with increasing backfill density. When loads equivalent to moderate tire pressures are applied near the ends of the pipes, pipe deflections are slighly higher than when loaded at the center. Except for low density glacial till, the deflections near the ends are not excessive and the pipes perform satisfactorily. For contact stresses near the upper limit of truck tire pressures and when loaded near the end, pipes fail with localized wall bending. For flowable fill backfill, the ultimate capacity of the pipes is nearly doubled and at the upper limit of highway truck tire pressures, deflections are negligible. All pipe specimens tested at ambient laboratory room temperatures satisfied AASHTO minimum pipe stiffness requirements at 5% deflection. However, nearly all specimens tested at elevated pipe surface temperatures, approximately 122°F (50°C), failed to meet these requirements. Some HDPE pipe installations may not meet AASHTO minimum pipe stiffness requirements when installed in the summer months (i.e. if pipe surface temperatures are allowed to attain temperatures similar to those tested here). Heating of any portion of the pipe circumference reduced the load carrying capacity of specimens. The minimum soil cover depths, determined from the CANOE analysis, are controlled by the 5% deflection criterion. The minimum soil cover height is 12 in. (305 mm). Pipes with the poor silt and clay backfills with less than 85% compaction require a minimum soil cover height of 24 in. (610 mm). For the sand at 80% compaction, the A36 HDPE pipe with the lowest moment of inertia requires a minimum of 24 in. (610 mm) soil cover. The C48 HDPE pipe with the largest moment of inertia and all other pipes require a 12 in. (305 mm) minimum soil cover.

Study and modeling of the desintegration kinetics of coated paper

The disintegration of recovered paper is the first operation in the preparation of recycled pulp. It is known that the defibering process follows a first order kinetics from which it is possible to obtain the disintegration kinetic constant (KD) by means of different ways. The disintegration constant can be obtained from the Somerville index results (%lsv and from the dissipated energy per volume unit (Ss). The %slv is related to the quantity of non-defibrated paper, as a measure of the non-disintegrated fiber residual (percentage of flakes), which is expressed in disintegration time units. In this work, disintegration kinetics from recycled coated paper has been evaluated, working at 20 revise rotor speed and for different fiber consistency (6, 8, 10, 12 and 14%). The results showed that the values of experimental disintegration kinetic constant, Ko, through the analysis of Somerville index, as function of time. Increased, the disintegration time was drastically reduced. The calculation of the disintegration kinetic constant (modelled Ko), extracted from the Rayleigh’s dissipation function, showed a good correlation with the experimental values using the evolution of the Somerville index or with the dissipated energy

Quantification of thermotolerant campylobacter in Swiss water treatment plants, by real-time quantitative polymerase chain reaction

A total of 49 wastewater samples from 23 different wastewater treatment plants (WWTPs) were analyzed using real-time quantitative polymerase chain reaction for the presence and quantity of thermotolerant campylobacters. Thermotolerant campylobacters were detected in 87.5% (21/24) and 64% (16/25) of untreated and treated wastewater samples, respectively. Their concentration was sufficiently high to be quantified in 20.4% (10/49) of the samples. In these samples, the concentration ranged from 68 000 to 2292 000 cells/L in untreated wastewater and from 10 800 to 28 000 cells/L in treated water. We conclude that thermotolerant campylobacters present a health hazard for workers at WWTPs in Switzerland. [Authors]

Development of Concepts for Pavement Management, MLR-79-04, 1979

Sufficient evidence was not discovered in this brief search to alter the general opinion that the Serviceability (Present Serviceability Index-PSI) - Performance Concepts developed by the AASHO Road Test provides the optimum engineering basis for pavement management. Use of these concepts in Iowa has the additional advantage in that we have a reasonable quantity of historical data over a period of time on the change in pavement condition as measured by PSI's. Some additional benefits would be the ability to better assess our needs with respect to those being recommended to Congress by AASHTO Committees. These concepts have been the basis used for developing policies on dimensions and weight of vehicles and highway needs which the AASHTO Transport Committees have recommended to the United States House Committee on Ways and Means. The first recommendation based on these concepts was made in the mid 1960's. Iowa's participation in the evaluation for this recommendation was under the direction of our present Director of Transportation, Mr. Raymond Kassel. PSI Indexes had to be derived from subjective surface ratings at that time. The most recent recommendation to Congress was made in November of 1977. Based on the rationale expressed above, a pilot study of the major part of the rural interstate system was conducted. The Objective of the study was to measure pavement performance through the use of the Present Serviceability Index (PSI) - Pavement Performance concepts as developed by the AASHO Road Test and to explore the usefulness of this type of data as a pavement management tool. Projects in the vicinity of the major urban centers were not included in this study due to the extra time that would be required to isolate accurate traffic data in these areas. Projects consisting of asphalt surface courses on crushed stone base sections were not included.

Performance of Poly-Carb, Inc. Flexogrid Bridge Overlay System, MLR-86-04, 2001

Intrusion of deicing materials and surface water into concrete bridge decks is a main contributor in deck reinforcing steel corrosion and concrete delamination. Salt, spread on bridge decks to melt ice, dissolves in water and permeates voids in the concrete deck. When the chloride content of the concrete in contact with reinforcing steel reaches a high enough concentration, the steel oxidizes. In Iowa, the method used to reduce bridge deck chloride penetration is the application of a low slump dense concrete overlay after the completion of all Class A and Class B floor repairs. A possible alternative to the use of dense concrete overlays, developed by Poly-Carb, Inc., is the MARK-163 FLEXOGRID Overlay System. FLEXOGRID is a two component system of epoxy and urethane which is applied on a bridge deck to a minimum thickness of ¼ inch. An aggregate mixture of silica quartz and aluminum oxide is broadcast onto the epoxy at a prescribed rate to provide deck protection and superior friction properties. The material is mixed on site and applied to the deck in a series of lifts (usually two) until the desired overlay thickness has been attained.

Study and modeling of the desintegration kinetics of coated paper

The disintegration of recovered paper is the first operation in the preparation of recycled pulp. It is known that the defibering process follows a first order kinetics from which it is possible to obtain the disintegration kinetic constant (KD) by means of different ways. The disintegration constant can be obtained from the Somerville index results (%lsv and from the dissipated energy per volume unit (Ss). The %slv is related to the quantity of non-defibrated paper, as a measure of the non-disintegrated fiber residual (percentage of flakes), which is expressed in disintegration time units. In this work, disintegration kinetics from recycled coated paper has been evaluated, working at 20 revise rotor speed and for different fiber consistency (6, 8, 10, 12 and 14%). The results showed that the values of experimental disintegration kinetic constant, Ko, through the analysis of Somerville index, as function of time. Increased, the disintegration time was drastically reduced. The calculation of the disintegration kinetic constant (modelled Ko), extracted from the Rayleigh’s dissipation function, showed a good correlation with the experimental values using the evolution of the Somerville index or with the dissipated energy

Investigation of Electromagnetic Gauges for Determination of In-Place Density of HMA Pavements, TR-576, 2009

This study evaluated the use of electromagnetic gauges to determine the adjusted densities of HMA pavements. Field measurements were taken with two electromagnetic gauges, the Pavement Quality Indicator (PQI) 301 and the Pavetracker Plus 2701B. Seven projects were included in the study with 3 to 5 consecutive paving days. For each day/lot 20 randomly selected locations were tested along with seven core locations. The analysis of PaveTracker and PQI density consisted of determining which factors are statistically significant, and core density residuals and a regression analysis of core as a function of PaveTracker and PQI readings. The following key conclusions can be stated: 1. Core density, traffic and binder content were all found to be significant for both electromagnetic gauges studied, 2. Core density residuals are normally distributed and centered at zero for both electromagnetic gauges, 3. For PaveTracker readings, statistically one third of the lots do not have an intercept that is zero and two thirds of the lots do not rule out a scaler correction factor of zero, 4. For PQI readings, statistically the 95% confidence interval rules out the intercept being zero for all seven projects and six of the seven projects do not rule out the scaler correction factor being zero, 5. The PQI 301 gauge should not be used for quality control or quality assurance, and 6. The Pavetracker 2701B gauge can be used for quality control but not quality assurance. This study has found that with the limited sample size, the adjusted density equations for both electromagnetic gauges were determined to be inadequate. The PaveTracker Plus 2701B was determined to be better than the PQI 301. The PaveTracker 2701B could still be applicable for quality assurance if the number of core locations per day is reduced and supplemented with additional PaveTracker 2701B readings. Further research should be done to determine the minimum number of core locations to calibrate the gauges each day/lot and the number of additional PaveTracker 2701B readings required.

Economics of Using Calcium Chloride vs. Sodium Chloride for Deicing/Anti-Icing, TR-488, 2008

The use of chemicals is a critical part of a pro-active winter maintenance program. However, ensuring that the correct chemicals are used is a challenge. On the one hand, budgets are limited, and thus price of chemicals is a major concern. On the other, performance of chemicals, especially at lower pavement temperatures, is not always assured. Two chemicals that are used extensively by the Iowa Department of Transportation (Iowa DOT) are sodium chloride (or salt) and calcium chloride. While calcium chloride can be effective at much lower temperatures than salt, it is also considerably more expensive. Costs for a gallon of salt brine are typically in the range of $0.05 to $0.10, whereas calcium chloride brine may cost in the range of $1.00 or more per gallon. These costs are of course subject to market forces and will thus change from year to year. The idea of mixing different winter maintenance chemicals is by no means new, and in general discussions it appears that many winter maintenance personnel have from time to time mixed up a jar of chemicals and done some work around the yard to see whether or not their new mix “works.” There are many stories about the mixture turning to “mayonnaise” (or, more colorfully, to “snot”) suggesting that mixing chemicals may give rise to some problems most likely due to precipitation. Further, the question of what constitutes a mixture “working” in this context is a topic of considerable discussion. In this study, mixtures of salt brine and calcium chloride brine were examined to determine their ice melting capability and their freezing point. Using the results from these tests, a linear interpolation model of the ice melting capability of mixtures of the two brines has been developed. Using a criterion based upon the ability of the mixture to melt a certain thickness of ice or snow (expressed as a thickness of melt-water equivalent), the model was extended to develop a material cost per lane mile for the full range of possible mixtures as a function of temperature. This allowed for a comparison of the performance of the various mixtures. From the point of view of melting capacity, mixing calcium chloride brine with salt brine appears to be effective only at very low temperatures (around 0° F and below). However, the approach described herein only considers the material costs, and does not consider application costs or other aspects of the mixture performance than melting capacity. While a unit quantity of calcium chloride is considerably more expensive than a unit quantity of sodium chloride, it also melts considerably more ice. In other words, to achieve the same result, much less calcium chloride brine is required than sodium chloride brine. This is important in considering application costs, because it means that a single application vehicle (for example, a brine dispensing trailer towed behind a snowplow) can cover many more lane miles with calcium chloride brine than with salt brine before needing to refill. Calculating exactly how much could be saved in application costs requires an optimization of routes used in the application of liquids in anti-icing, which is beyond the scope of the current study. However, this may be an area that agencies wish to pursue for future investigation. In discussion with winter maintenance personnel who use mixtures of sodium chloride and calcium chloride, it is evident that one reason for this is because the mixture is much more persistent (i.e. it stays longer on the road surface) than straight salt brine. Operationally this persistence is very valuable, but at present there are not any established methods to measure the persistence of a chemical on a pavement. In conclusion, the study presents a method that allows an agency to determine the material costs of using various mixtures of salt brine and calcium chloride brine. The method is based upon the requirement of melting a certain quantity of snow or ice at the ice-pavement interface, and on how much of a chemical or of a mixture of chemicals is required to do that.

Magmatic fluids in the Breccia-hosted epithermal Au-Ag deposit of Rosia Montana, Romania

The breccia-hosted epithermal Au-Ag deposit of Rosia Montana is located 7 kin northeast of Abrud, in the northern part of the South Apuseni Mountains, Romania. Estimated total reserves of 214.91 million metric toils (Mt) of ore at 1.46 g/t An and 6.9 g/t Ag (10.1 Moz of An and 47.6 Moz of Ag) make Rosia Montana one of the largest gold deposits in Europe. At this location, Miocene calc-alkaline magmatic and hydrothermal activity was associated with local extensional tectonics within a strike-slip regime related to the indentation of the Adriatic microplate into the European plate during the Carpathian orogenesis. The host rocks of the magmatic complex consist of pre-Mesozoic metamorphosed continental crust covered by Cretaceous turbiditic sediment (flysch). Magmatic activity at Rosia Montana and its surroundings occurred in several pulses and lasted about 7 m.y, Rosia Montana is a breccia-hosted epithermal system related to strong phreatomagmatic activity due to the shallow emplacement of the Montana dacite. The Montana dacite intruded Miocene volcaniclastic material (volcaniclastic breccias) and crops out at Cetate and Carnic Hills. Current mining is focused primarily on the Cetate open pit, which was mapped in detail, leading to the recognition of three distinct breccia bodies: the dacite breccia with a dominantly hydrothermal matrix, the gray polymict breccia with a greater proportion of sand-sized matrix support, and the black polymict breccia, which reached to the surface, contains carbonized tree trunks and has a dominantly barren elastic matrix. The hydrothermal alteration is pervasive. Adularia alteration with a phyllic overprint is ubiquitous; silicification and argillic alteration occur locally. Mineralization consists of quartz, adularia, carbonates (commonly Mn-rich), pyrite, Fe-poor sphalerite, galena, chalcopyrite, tetrahedrite, and native gold and occurs as disseminations, as well as in veins and filling vugs within the Montana dacite and the different breccias. The age of mineralization (12.85 +/- 0.07 Ma) was determined by Ar-40- Ar-39 dating on hydrothermal adularia crystals from vugs in the dacite breccia in the Cetate open pit. Microthermometric measurements of fluid inclusions in quartz phenocrysts from the Montana dacite revealed two fluid types that are absent from the hydrothermal breccia and must have been trapped at depth prior to dacite dome emplacement: brine inclusions (32-55 -wt % NaCl equiv, homogenizing at T-h > 460 degrees C) and intermediate density fluids (4.9-15.6 wt % NaCl equiv, T, between 345 degrees-430 degrees C). Secondary aqueous fluid inclusion assemblages in the phenocrysts have salinities of 0.2 to 2.2 wt percent NaCl equiv and T-h of 200 degrees to 280 degrees C. Fluid inclusion assemblages in hydrothermal quartz from breccias and veins have salinities of 0.2 to 3.4 wt percent NaCl equiv and T-h, from 200 degrees to 270 degrees C. The oxygen isotope composition of several zones of an ore-related epithermal quartz crystal indicate a very constant delta O-18 of 4.5 to 5.0 per mil for the mineralizing fluid, despite significant salinity and temperature variation over time. Following microthermometry, selected fluid inclusion assemblages were analyzed by laser ablation-inductively coupled-plasma mass spectrometry (LA-ICMS). Despite systematic differences in salinity between phenocryst-hosted fluids trapped at depth and fluids from quartz in the epithermal breccias, all fluids have overlapping major and trace cation ratios, including identical Na/K/Rb/Sr/Cs/Ba. Consistent with the constant near-magmatic oxygen isotope composition of the hydrothermal fluids, these data strongly indicate a common magmatic component of these chemically conservative solutes in all fluids. Cu, Pb, Zn, and Mn show variations in concentration relative to the relatively non-reactive alkalis, reflecting the precipitation of sulfide minerals together with An in the epithermal breccia, and possibly of Cu in an inferred subjacent porphyry environment. The magmatic-hydrothermal processes responsible for epithermal Au-Ag mineralization at Rosia Montana are, however, not directly related to the formation of the spatially associated porphyry Cu-Au deposit of Rosia Poieni, which occurred lout 3 m.y. later.