HomeLatest ThreadsGreatest ThreadsForums & GroupsMy SubscriptionsMy Posts
DU Home » Latest Threads » NNadir » Journal
Page: « Prev 1 2 3 4 5 6 7 8 9 10 ... 67 Next »

NNadir

Profile Information

Gender: Male
Current location: New Jersey
Member since: 2002
Number of posts: 23,503

Journal Archives

In New Jersey, if you see this beautiful insect, you are advised to kill it.

It is killing our trees.



Remember those exotic-looking insects that some agriculture officials feared would hitch a ride on Christmas trees last winter and expand their turf? Turns out the Christmas tree threat never materialized, but during recent months spotted lanternflies have invaded a few more counties in New Jersey.



Spotted Lantern Fly found in 7 NJ counties.

This species is native to China, Vietnam and Bangladesh.

PA Dept of Agriculture: Spotted Lantern Fly



Properties of Alkali Metal Salts of the Radioactive Pertechnetate Ion.

The paper I will discuss in this brief post is this one: Chemical Trends in Solid Alkali Pertechnetates (McCloy et al, Inorg. Chem. 2017 56 5 2533-2544)

Happily the paper is open sourced under a Creative Commons license and anyone can read it in its entirety in itself.

From time to time, I like to read about the Hanford Reservation Waste tanks, which feature some extremely interesting radiochemistry, because of the complex nature of their contents, which have undergone a rather interesting series of chemical processes on an industrial scale.

Several of the tanks are famously leaking, exciting the bizarre selective attention of anti-nukes. With a few exceptions, anti-nukes are a spectacularly poorly educated set of people, whose poor educations and poor ethical and moral sense lead them to consider the events at the Hanford plant, which was essentially a nuclear weapons plant, as one of the most dire emergencies ever. Thus they love to proudly point out that billions of dollars are being spent to clean up Hanford, even though these billions of dollars will save far fewer lives than spending billions of dollars on improved sanitation for the billions of people who lack access to even primitive forms of it. The reason that cleaning up Hanford will not save very many lives is because very few lives are actually at risk.

It is true that left unattended, some radionuclides, dominated by technetium in the form of the pertechnate ion, will leak into the Columbia River, but at concentrations that are not likely to have profound health consequences. It is well known among medical types that people either eat or are injected with technetium - the 99m isomer which decays in vivo to exactly the same isotope as in the Hanford tanks, Tc-99 - for medical diagnostics and treatment.

To wit, from the introduction to the paper:

Technetium (Tc, element 43) was first isolated in 1937 by the Italian researchers Perrier and Segre from molybdenum foil that had been bombarded with deuterons. Since its discovery, it has been found to have uses in the medical industry (∼85% of all radionuclear scans in the U.S. utilize short-lived 99mTc1), in the steel industry as a corrosion inhibitor,(2) and as a low-temperature superconductor.(3) Additionally, identification of Tc in the spectrum of a variety of star types leads to new research in the solar production of heavy elements.(4, 5) From the standpoint of inorganic chemistry, the research completed on the element since the late 1930s has worked to fill in the gaps of understanding the periodic trends for transitions metals, particularly those related to the formation of chromium and rhenium oxyanions.(6)

Of its 21 isotopes (mass numbers 90–111), all of which are radioactive, 99Tc is the most common and abundant, and because of its high mobility under oxidizing conditions in the subsurface environment and long half-life (t1/2 = 2.11 × 105 years), 99Tc is considered to be a significant environmental hazard.(1, 2)99Tc is common on earth today because it is a byproduct of the fission of uranium and plutonium in nuclear reactors: 6.1% and 5.9% mass yields, respectively. It is the only long-lived Tc isotope produced on a gram scale by this pathway. It is also the daughter product in the decay of 99mTc. For long-term nuclear waste management, 99Tc is the dominant producer of radiation in the period from about 104–106 years, in becquerels (Bq) per mass of spent fuel. Because of its radiotoxicity (99Tc is a soft β emitter, 292 keV), high environmental mobility, and long half-life, its immobilization and safe long-term storage is a priority goal to countries that are in the process of disposing of nuclear waste. A current challenge to efficient immobilization of the radioisotope can be linked to a lack of understanding of the behavior of Tc during vitrification, the process of turning nuclear waste into glass, and it localized chemistry in waste glasses.


The bold is mine.

Most of the papers on the interesting chemistry of technetium focus on medical use, but the second most common class of papers focuses on immobilizing technetium in order to treat it as a waste product. I personally object to this second focus, since I regard technetium as an extremely valuable metal, owing to its close similarity, as a consequence of the lanthanide contraction, to its rare cogener rhenium, a valuable element utilized most importantly in the preparation of superalloys, showing high thermal and corrosion resistance.

The migration of radionuclides from the Hanford tanks is of interest to compare to geologically historical migrations of the natural nuclear reactors that operated about two billion years ago, most famously at Oklo in modern day Gabon, but in several other places as well. Analysis of these situations shows that these nuclides traveled hundreds of meters before decaying, although their stable decay products are notably depleted in ruthenium-99, the decay product of technetium-99.

From the leaking tanks at Hanford, a similar effect is being observed.

It is very likely that, as at Oklo, many of the shorter lived nuclides will decay before they travel the distance reach the Columbia River, although some will not. Consider the Cs-137 of a tank filled in the 1950's. About 77% of the cesium dumped into the tanks in 1955 have decayed to stable barium. Moreover, much of the radiocesium in some of the tanks has been removed for use as radiation sources, meaning that the concentration is low. After years and years of effective ion exchange in components of the soil, slowing the migration, invariably coupled with dilution, it is unlikely that concentrations of cesium comparable to the natural radioactivity associated with essential potassium will effectively harm anyone. If it did or does, the number of persons so injured will be dwarfed by the number of people who die today from air pollution, which will be about 19,000 people. They may ultimately harm someone, but compared to other risks experienced by humanity, notably climate change, these risks are exceedingly small.

This is why the people who love to complain about events are Hanford are so morally stupid. They think that their poor educations, and lack of even a shred of education about radiochemistry, implies that Hanford - a nuclear weapons plant largely unconnected with nuclear power - trumps concern about the 7 million people who will die this year who will die from air pollution. And "trumps" is the right word. Their selective attention is Trumpian in its stupidity.

Anyway, the paper is open sourced, and anyone can read it.

I was drawn to it because I was thinking about the technetium at Hanford - there are about 1200 kg of these valuable metal there, and I found myself wondering about the alkali metal salts of the pertechenetate ion.

The part that caught my eye was the experimental section, which I reproduce here:

Tc was obtained from the U.S. DOE Isotopes Program, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN. As received, Tc was in the form of solid NH4TcO4, black and badly decomposed from its own β radiation. The as-received material (approximately 10 g) was transferred to a 125 mL glass Erlenmeyer flask. All chemicals used in this work, except 99Tc, were analytical reagent grade. Water was taken from a Millipore deionizer, 18 MΩ cm or higher resistivity. Approximately 50 mL of concentrated NH4OH and several milliliters of 30% H2O2 were added. The mixture was stirred with a magnetic stir bar and gently warmed, with a small glass funnel serving as a spray trap on the top of the flask. NH4TcO4 dissolved in a few minutes to give a colorless solution of NH4TcO4. The solution was warmed at near boiling for 1 h to decompose H2O2, and then the spray trap was removed to allow the water and NH4OH to evaporate. After nearly all of the water had evaporated, fine crystalline NH4TcO4 was centrifuged out of the solution, washed with dry ethanol to remove water, and then dried to a constant weight at ∼90 °C.
Ammonium pertechnetate was converted into aqueous HTcO4 by cation exchange. Crystalline ammonium pertechnetate was dissolved in water and then passed through a column of hydrogen-form cation resin (Dowex 50W-X8, 50–100 mesh, 15 mL resin volume, in water). This volume of resin has a cation capacity of about 1.8 g of NH4TcO4, loaded to 50% of theoretical capacity. By loading to only 50% of the cation capacity of the resin, no cations break through the column to contaminate the pertechnic acid. The cation column effluent was periodically checked with pH strips to confirm that the effluent was always acidic. The column effluent was transferred to a 125 mL round-bottom flask. The solution was stirred and heated, while dry nitrogen gas was gently blown over the surface of the solution to evaporate the water. The nitrogen gas quickly evaporated the water and kept the temperature low enough to avoid bubbles breaking at the surface, even with the heat set high, so that no spray from bursting bubbles could carry Tc out of the flask. This apparatus permits dilute pertechnic acid to be safely evaporated and concentrated without causing airborne β contamination in the fume hood.

Sodium pertechnetate was prepared by neutralizing aqueous HTcO4 with aqueous NaOH to pH 7. The product NaTcO4 solution was then evaporated under flowing nitrogen in a 125 mL round-bottom flask, with heat and stirring, until only wet-crystalline NaTcO4 remained in the flask. The solid NaTcO4 was dried to a constant weight at 120 °C to make the anhydrous salt. Potassium pertechnetate was prepared in the same way, using KOH. Cesium and rubidium pertechnetates were prepared by combining stoichiometric amounts of Rb2CO3 and Cs2CO3, weighed as dry solids, with accurately weighed amounts of NH4TcO4 dissolved in water. The product solutions of RbTcO4 and CsTcO4 were evaporated to expel water and ammonium carbonate. When the volume was 2–3 mL, the crystalline products were centrifuged out of solution and then dried to a constant weight at 120 °C.


What I found interesting is the state of the ammonium pertechnate as received, which was black. This indicates radiochemical self reduction of the metal to TcO2, which is largely insoluble, suggesting that in high radiation fields, the migration is retarded by self-reduction and reoxidation.

Secondly I was intrigued by the description of the preparation of the cesium salt, which involved crystallization from water. While the solubility of cesium pertechnetate was not given, this means that the solubility is limited, an interesting fact of potential utility in considering the chemistry of used nuclear fuels.

I hope you're having a pleasant Saturday. I'm feeling a little under the weather myself, but reading this paper made me feel a little better.

Aluminum & Regions of the US Where the Climate Impact of Electric Cars Is Worse than Gasoline Cars.

The two papers I'll discuss in this post are these: Regional Heterogeneity in the Emissions Benefits of Electrified and Lightweighted Light-Duty Vehicles (Kirchain et al Environ. Sci. Technol. 2019 53 18 10560-10570) and Source Risks As Constraints to Future Metal Supply (Éléonore Lèbreet al Environ. Sci. Technol. 2019 53 18 10571-10579)

The first paper is open sourced, and the interested reader can read it in its entirety; I will nonetheless excerpt it and reproduce some graphics here with my commentary. The second paper is not open sourced, but I will excerpt it in any case.

Both papers discuss the well known metal aluminum. For example, the first paper, which is all about how "green" electric cars actually are - they are routinely assumed to be so in rote language, language that I regard as dangerous in the extreme, since the consequences of climate change are extreme - has this to say about aluminum:

Driven by economic pressures, market competition, and environmental regulations, auto manufacturers are actively pursuing technological solutions to reduce the greenhouse gas (GHG) emissions associated with personal transportation. Although much of the recent discussions of automotive technology change center around electrification of the drivetrain,(1−6) there are, in fact, other technology strategies that can reduce vehicle fuel consumption.(7−11) One important strategy is mass reduction, which the industry refers to as lightweighting.(9−11) By reducing the mass of the vehicle, the inertial forces and rolling resistances that the engine has to overcome are lowered, and the energy required to drive the vehicle is reduced. Assuming that vehicles stay about the same size, substantial mass reduction generally requires material substitution.(7−9)

There are two major factors that complicate the evaluation of alternative vehicle technologies. First, manufacturing processes for alternative technologies are often more carbon-intensive than those of conventional analogs. While mass reduction lowers energy requirements during vehicle use, alternative materials used to reduce vehicle mass tend to be more carbon-intensive to produce than the steels they would replace.(9,11,12) For example, an aluminum component with the same stiffness as its steel counterpart can require nearly three times more energy to produce.(13) (A notable exception to this trend is high strength steels with similar production burden as conventional steels.)(9,10,12) Similarly, functionally equivalent battery electric vehicles (BEVs) are generally more carbon-intensive to produce than conventional internal combustion engine vehicles (ICEVs).(14) As a consequence, any evaluation of alternative automotive technologies must consider impacts during both use and production to ensure an overall net improvement.


The bold is mine.

By the way, before going too far into this, should this post attract readership not familiar with my personal eccentricities, I personally believe that the concept of a "green car" - whether or electric or otherwise - is an oxymoron.

Sometimes the claim that a car can be "green" is based on lies told my the manufacturers, for example the Audi A3 TDI won the 2010 "Green Car of the Year Award" probably because the Volkswagen people installed software to minimize its pollution while being tested by regulatory authorities, even though while actually driving the car it was quite dirty. Several Volkswagen Executives are looking at jail time as a result; but haven't yet been convicted. Rich liars, as we know from US politics, take a long time to convict.

Other times the belief in "Green Cars" result from lies we tell ourselves. In the case of electric cars, the belief that they are "green," derives from the absurd and easily disproved fantasy that the electricity that comes out of our wall socket is green, that it is almost all produced from so called "renewable energy," that, despite the chanted belief system has not, is not, and will not do anything meaningful to address climate change. In reality the amount of dangerous fossil fuels utilized to produce electricity is, not falling, but is rising rapidly. The committed power plant construction is expected to result in an increase of approximately 3 degrees centigrade in this century.

My contention is that the car CULTure never was, is not now, and never will be sustainable and is therefore has not, is not and will not be green, no matter how much snake oil people like Elon Musk sell.

The authors in this paper extend their consideration of the value of battery electric cars (BEV), hybrid cars (HEV), plug in hybrids (PHEV), light weight internal combustion engine cars (ICEV), and light weight internal combustion engine cars (LW-ICEV). They consider the type of driving being done, depending on whether it takes place in a rural setting, where energy efficiency tens to be higher, and also the effect of temperature, since the use of a heater or an air conditioner will reduce the driving range of electrified cars.

They write:

There are two major factors that complicate the evaluation of alternative vehicle technologies. First, manufacturing processes for alternative technologies are often more carbon-intensive than those of conventional analogs. While mass reduction lowers energy requirements during vehicle use, alternative materials used to reduce vehicle mass tend to be more carbon-intensive to produce than the steels they would replace.(9,11,12) For example, an aluminum component with the same stiffness as its steel counterpart can require nearly three times more energy to produce.(13) (A notable exception to this trend is high strength steels with similar production burden as conventional steels.)(9,10,12) Similarly, functionally equivalent battery electric vehicles (BEVs) are generally more carbon-intensive to produce than conventional internal combustion engine vehicles (ICEVs).(14) As a consequence, any evaluation of alternative automotive technologies must consider impacts during both use and production to ensure an overall net improvement.

Second, although both mass reduction and electrification improve the rated fuel economy of the vehicle, actual in-use GHG emission rate is strongly influenced by the driving context,(6,15−22) including driving habits, climate, and the local electrical grid. Moreover, the influence of these contextual conditions is not the same for mass reduction and electrification

Considering both of these issues together, we see the need for not only a cradle-to-grave assessment,(1,2,9,23) but also an assessment that considers a range of driving contexts. Although in practice, both strategies may be applied together, this paper considers mass reduction and electrification separately to better understand how the two perform differently in different contexts...

To make this possible, we propose a novel model of climate impact on drivetrain performance calibrated against a vehicle performance data set comprising over 300 million miles of driving records from approximately 33 000 BEV and plug-in hybrid electric vehicle (PHEV) customers.(30,31) Overall, we consider the impact of regional differences in electric grid, driving patterns, and ambient temperature.

From that high-resolution modeling, our results suggest that an aluminum lightweight ICEV would have similar emissions to HEVs in about 25% of the counties in the US and emissions lower than BEVs in a little over 20% of counties. These results indicate that lightweight ICEVs can be more environmentally beneficial than electrified vehicles in more than 500 counties. Generally, these counties are characterized by rural driving (i.e., driving where vehicle fuel efficiency is better represented by a highway driving cycle) and carbon-intensive grids and are located in the Midwest and Midsouth.


Some graphics from the paper are useful:



The caption:

Figure 3. Life cycle GHG emissions per km for different powertrain types (ICEV, LW-ICEV HEV, PHEV, and BEV) in selected counties. LW-ICEV here is one mass reduced through the use of aluminum.


A second, a map, gives regions of the United States where the greenhouse gas emissions of electric cars are actually worse or than gasoline cars or essentially equivalent:



The caption:

Figure 4. Life cycle GHG emission benefits for electrification compared to the: (a) baseline, no-lightweighting ICEV scenario, (b) lightweighting with aluminum ICEV scenario. Darker blue areas show counties with greater emission savings from EVs. The values in the boxes are the percent of counties where HEVs/PHEVs/BEVs have less emissions (blue box), similar (±5%) emissions to ICEV comparator (white box), or more emissions than the ICEV comparator (light orange).

Underlying map images and geographic data Copyright Mapbox and Copyright OpenStreetMap contributors.


The carbon, nitrogen oxide, sulfur oxide, and methane intensity of subgrids (2016 data) can be found in the summary tables available here:

Emissions & Generation Resource Integrated Database (eGRID)

Regrettably it gives these values in pounds, and to convert the units to more useful SI units, one needs to use an Excel formula to clean it up.

From the first graphic produced above (figure 3 from the paper), it is clear that in the "best" case where an electric vehicle is superior to a gasoline car, Los Angeles, where one can spend hours a day sitting on the 405 freeway without moving 2 meters in ten minutes, that because an electric car doesn't need to idle, the greenhouse gas cost of the car is environmentally unacceptable: It's about 100 grams of CO2 per km, meaning that to drive to Walmart in LA to buy a Sierra Club calendar to show how "green" you are, in your swell Tesla electric car for millionaires and billionaires, one is likely to dump a kg of the dangerous fossil fuel waste carbon dioxide into the atmosphere where it will impact all future generations and all living things in a way that may prove irreversible.

It also matters in LA when you charge your piece of shit electric car. As I noted in a previous post, California is one of the few places on Earth where solar energy - which is not green, and not sustainable - represents a significant source of energy. However the peak amount of energy available from allegedly (but not practically) "green" solar energy does not coincide with the peak demand on the grid, which is roughly 6 pm.


Hours of the Top 50 CAISO Electricity Loads in California, July 2019.

During the peak hours of solar production, electricity prices can fall to negative pricing, which because the fixed costs of the necessary back up plants - the majority of which are dangerous fossil fuel plants in California do not vanish when they cannot sell their product, ends up raising the grid prices paid by all consumers, including poor people, not that we give a rat's ass about poor people anymore, even on the left, where we would all rather discuss our bourgeois electronic toys that did not, are not and will not save the world.

This is why Denmark and Germany have, respectively, the highest and second highest household electricity prices in the OECD.

Now let's turn to the second paper I mentioned above, the paper on metal supply.

I have written in this space about aluminum production several times and its energy costs. The most recent discussion was a highly esoteric discussion of the physics of bubbles as relevant to aluminum anodes in the commonly utilized Hall process for aluminum production. (These anodes are made from petroleum coke and are gasified in the process of producing aluminum, releasing carbon dioxide and a number of highly recalcitrant carbon fluorides.)

Here is a recent highly technical musing on the subject:

Contact Angles And Bubble Motions in the Aluminum Reduction Electrochemical Cell.

Because we hold all future generations in contempt, handing out interminable garbage about how "by 2050" or "by 2075" our children and grandchildren and great great grandchildren will live in an electric car/"renewable energy" nirvana, and can easily do that which have clearly demonstrated an ability to do ourselves, we are rapidly consuming all of the world's high quality ores. The lower quality ores - some of which may be our landfill - will be far more energy intensive to isolate, meaning that we have not only dumped our irresponsibility to embrace carbon free energy - only one example of this type of energy is sustainable, nuclear energy - but we will require them to use far more energy than we do.

This the paper having this graphic in the abstract which is open as opposed to the paper itself:



From the paper's introduction:

Human development, as an objective, involves enhancing people’s freedoms and opportunities, and improving their well-being. This objective relies on the viability of the education, health care, telecommunications, agriculture, transportation, construction, water, and energy sectors. Technology is a fundamental enabler across these sectors, and requires metals for manufacture or application. As technologies advance, the number of metals in use has increased to 60 out of 91 known metals.1 Future demand for the most widely used metalsiron, aluminum, manganese, copper, zinc, lead, and nickelis predicted to at least double, and possibly triple, by midcentury1,84 with a potential 8-fold increase in aluminum demand.2−4 A doubling or tripling of demand is likewise anticipated for specialty metals such as lithium, rhenium, and some rare earths.2 Two concurrent drivers for this demand include the continued increase in global population and human development measured in per-capita wealth.5,84 A third driver is the rise in metal demand to support the decarbonization of economies to mitigate climate change. Renewable energy generation, transmission, and storage systems have considerably higher metal requirements on a per kWh basis than their fossil fuels counterparts.6,7

Such radical increases in demand can only be satisfied if there is sufficient global supply of the appropriate metals. Presently, these metals are primarily sourced from mining, as recycling can only supply a fraction of the demand in the foreseeable future.8 Even for steel and aluminum, which have substantial recycling programs in place, predictive modeling indicates that the majority of these metals will be from primary sources for at least another 30 years.9,85

Several publications, including Vidal et al.,10 Kleijn et al.,11 Graedel et al.,12 Northey et al.,13 and the reports of the International Panel on Climate Change (IPCC),14 acknowledge potential material constraints in the global transition to renewable energy sources. Methodologies are emerging to assess the supply risk of metals across the value chain, according to reviews by Northey et al.,15 Achzet et al.,16 and Erdmann and Graedel.17 The methodology on metal “criticality” developed by Graedel et al.18 includes 16 macro-level indicators that aggregate either national or global supply chain data, and three types of users: global analysts, national governments, and corporations...


The authors will not discuss 57 of the 60 essential elements in the periodic table, and mention obliquely the metal intensity of so called "renewable energy" which relies on an unsustainable supply of some exotic metals, leaving open the question of whether the word "renewable" is entirely fallacious, as I claim it is.

Some people say, "no problem," which is easy for them to say since they'll be dead when any such "problem" arises, rather like the assholes who have bet the planetary atmosphere on wishful thinking about "renewable energy" with "by 2050" type rhetoric:

Concerns about availability are often inclusive of nongeological considerations around the issue of access. 13,25,30−32 Arndt et al.33 and Mudd and Jowitt34 argue that resource depletion is overstated because reporting codes represent conservative estimates of available resources. Such estimates are based on economic considerations and are bound to evolve as metal prices and available technologies influence which portion of the orebody is considered to be extractable at a profit. Declining ore grades raise technical and economic challenges that can be and have been addressed through technological innovation. Greater project footprint area, larger material movements, greater quantities of waste rock, and increased water and energy requirementsall consequences of lower gradescan partially be offset through enhanced selectivity, for example, underground block caving, ore sorting, or in situ leaching. ESG factors, however, are not easily overcome by technological innovation, can restrict access to the orebody, and affect the longer term feasibility of mineral extraction.15,19,25 ESG factors tend to accumulate, and are exacerbated by geological scarcity. Local ESG factors remain an unresolved gap for researchers conducting assessments on metal availability,15 as well for asset managers undertaking due diligence for the acquisition of mining properties.24


Anyway, some graphics from the paper:



F
igure 1. Methodological framework–spatial coincidence between the set of ESG risk categories and the orebodies sample.




Figure 2. Global distribution of iron ore, bauxite, and copper orebodies samples considered in the analysis (source: S&P database 2019).




Figure 3. Cumulative reserves and resources for iron ore, copper and bauxite, ordered by risk co-occurrence. Color shades correspond to the average grades of individual orebodies, expressed in percentages. Dashed lines highlight the portion of the sample that is located in high risk co-occurrence contexts (i.e., four or more concurrent ESG risks).




Figure 4. Distribution of tonnage and average grade by medium-to-high risk co-occurrence for iron ore (top), bauxite (center), and copper (bottom). Proportion of specific ESG risk categories represented by different pattern and shading scale. Numbers above bars correspond to the number of orebodies.


A lot of the stuff in the paper is stuff we couldn't care less about while we fall all over ourselves carrying on about Elon Musk, his cars for millionaires and billionaires, and his rockets with which utilizes as a marketing tool while he works to make precious orbital space unavailable for future generations.

An excerpt from the paper's conclusion:

Research on metal criticality has predominately assessed the supply risk for metals at a macro-scale. Our methodology expands current thinking about resource criticality by including source-based risks. Criticality studies focus on the likelihood of supply disruption and its consequences for importing nations. Scholars have called for a restructuring of global supply and demand networks, and propose strategies of supply diversification, subsidies for national production, and development of strategic stockpiles.

Our methodology assesses source risks for the supplying regions of the globe. Without this, understandings of metal criticality are incomplete. This research has major implications for the mining industry, investors, governments, and downstream users of metals. The results indicate the presence of multiple concurrent risks and raise concerns about the ability of the mining industry to meet demand, which has been projected to grow significantly for copper and iron1 as well as for aluminum.85 To address the complexity associated with these factors, major innovations are required in the design and development of resource projects. Innovations will not only need to “cut across” disciplines but also stakeholder groups to ensure that the responsibility for solutions extends beyond governments and individual companies. Our methodology identifies critical issues associated with the future supply of metals. This is best highlighted in the case of Water, which rated as medium to high risk for two-thirds of the undeveloped world copper orebodies. By building a global picture of the ESG risks surrounding current undeveloped orebodies, we draw attention to the feasibility and potential consequences of taking these projects forward into production.


The availability of water is a big one by the way. We have largely destroyed the world's riverine systems to make "green" energy and "green" agriculture but we're not quite finished yet.

If any of this post troubles you, don't worry, be happy. Head over to the E&E forum and learn all about how "green energy" and electric cars will save the day. They haven't, they aren't, and they won't, but in the joy associated with impeachment times it's best to focus only on happy thoughts.

Donald Trump will be a footnote to history "by 2050," but climate change won't. History will not forgive us, nor should it.

Enjoy the weekend.

Germany Is Succeeding Quite Well With Phasing Out Nuclear Energy With So Called "Renewable Energy."

The following graphic and table come from the 2019 International Energy Agency's Electricity Information Overview report.

2019 IEA Electricity Information Overview



Presumably people who hate the science of Fermi, Seaborg, Wigner et al, expressed as nuclear engineering are dancing on the graves of dead people, and let's be clear, dead people are very much involved.

Notice that the German so called "renewable energy" program has done essentially zero to address climate change.

We hit 415 ppm of CO2 in the atmosphere this May, and the rate of increases is now the highest ever recorded, about 2.3-2.4 ppm per year.

It is worthwhile to look at the table from the report describing exactly how this so called "renewable energy" breaks down:



It appears that 2/3 of the German so called "renewable energy" 30.3 MTOE (Million Tons Oil Equivalent) comes from the combustion of waste and biomass. This compares to about 14.33 MTOE from that magical wind and solar energy that was supposed to save the world, but didn't do so, isn't doing so and won't do so.

Gas has grown faster than wind and solar combined, somewhat at the expense of coal, but a gas plant puts out between 500-550 grams of carbon dioxide per kWh, a nuclear plant, 25 grams or less per kWh.

The Germans are spectacularly uninterested in practice in phasing out dangerous fossil fuels. Oh, I'm sure they carry on with "by 2050" or "by 2040" or "by 2075" bullshit by which they dump their irresponsibility on future generations by insisting that they will do what modern Germans have been incompetent to do, intellectually, morally or spiritually, phasing out dangerous fossil fuels now. The line for dangerous fossil fuel consumption is almost flat, a slight marginal decrease, although this doesn't reflect what Germany does when the wind isn't blowing and the sun isn't shining. Electricity in Poland is generated almost exclusively be coal.

Germany has the second highest electricity prices in the OECD, this being, ironically, a consequence of the fact that their peak electricity is in no way connected with demand, and they have to dump their electrical product at negative prices. It can be shown that negative pricing for random moments actually drives electricity prices up, because of the fixed costs of the required redundant dangerous fossil fuel facilities that power Germany when the sun isn't shining and the wind isn't blowing. (This fact may be seen in the "Electricity 'Imports'" row in the chart, where the "imports" are negative.

OECD electricity prices, with Germany coming in behind that offshore oil and gas drilling hellhole, Denmark:



I'm sure poor people in those countries really, really, really, really appreciate how "green" the bourgeoisie in Germany and Denmark are.

Slightly less than half of the 7 million deaths that occur each year from air pollution come from the combustion of biomass and waste, so yes, there are people, anti-nukes, quite literally dancing on graves, because despite all the fear, loathing and ignorance directed at nuclear energy in Germany, in it's 40 years of operations, very few, if any Germans died from exposure to radiation from nuclear power plants. It is the purview of anti-nukes to elevate their imaginations over reality.

I noticed that the 16 year old who lectured the UN today paraphrased something I've been saying here for some time: "History will not forgive us, nor should it."

I'm not sure she knows much about engineering or about what might might be practically done to address climate change were it not for fear and ignorance on the left and plain denial on the right - almost certainly she doesn't - but at least she is stating clearly that her generation will control how we are remembered.

It won't be pretty. History will record what we have done.

Have a nice day tomorrow.

I would like to thank my arms...

...for always being on my side, my legs for supporting me, and of course, my fingers for being the ones I could always count on.

Look here. I'm not a vegetarian because I love animals.

I'm a vegetarian because I hate plants.

That is all.

Contact Angles And Bubble Motions in the Aluminum Reduction Electrochemical Cell.

The paper I'll discuss in this post is this one: Effects of Contact Angle on Single and Multiscale Bubble Motions in the Aluminum Reduction Cell (Seyed Mohammad Taghavi et al Ind. Eng. Chem. Res. 2019, 58, 37, 17568-17582)

One of my peculiarities is to spend a lot of time thinking about anodes, since any serious effort to address climate change - no such serious efforts are underway - will be very much involved in electrochemistry, and to the extent that electrode chemistry involves cokes obtained from dangerous fossil fuels, which must be banned, it is supremely necessary that they be considered. (Another important reason to consider anodes is in the anodic dissolution of used nuclear fuels, which in my view, is the best of all potential processes for dissolving them.)

I have written about anodes in the electrochemical reduction aluminum elsewhere on this website: Can Biocoke Address the Anode CO2 Problem (Owing to Petroleum Coke) for Aluminum Production?

It turns out that a consideration in the behavior of anodes is the behavior of bubbles, the physics of which are rather complex. In addition, the physics of bubbles also play key roles in many other processes of extreme environmental importance, notably heat transfer, with particular respect to nucleate and film boiling. It turns out that the only viable path to removing the carbon dioxide we have dumped and continue to dump on future generations in our contempt for them while we all wait for the grand renewable energy nirvana that did not come, is not here, and will not come, will involve issues in heat transfer at extraordinarily high temperatures, and the physics of bubbles will be very much involved in the processes that our children, grandchildren and great grandchildren will need to clean up from the wild party of our sybaritic consumer excesses.

Thus this complex and rather long paper caught my eye in my general reading.

From the introduction:

Bubble nucleation, growth, coalescence, and detachment play important roles in many engineering applications such as the gas–liquid separation, chemical reaction, boiling, bubble column motion, and cavitations. Several researchers have studied bubble movements(1−5) on the upward-facing and vertical surfaces. However, in some applications, such as in the aluminum electrolysis process, bubble behaviors beneath downward-facing surfaces are not fully understood. In the aluminum electrolysis process, microdispersed bubbles are formed under the anode when the electrochemical reaction happens. Then, the bubbles move along the anode bottom as they grow, coalesce, and detach from the surface. Bubble motion is a part of the magneto-hydrodynamics in the cell and not only affects the electrical resistance but also changes the current efficiency. However, it is hard to measure the bubble motion directly under the harsh operating environment and high temperatures in the industrial aluminum reduction cell. In the previous studies, some researchers(6−17) have considered the bubble motion via experimental models. Many factors, such as the current densities,(6) the anode surface shapes,(7−9) the liquid properties,(10,11) the gas–liquid surface tensions,(12,13) the anode types(14,15) and the wettability,(16,17) have been explored to reveal the bubble dynamics beneath downward-facing surfaces.

To understand the bubble dynamics, the contact angle is an essential factor, which quantifies the wettability of the anode surface and affects the bubble motion. The contact angle is calculated with the Young–Dupre equation considering the function of the solid–gas, liquid–solid, and liquid–gas surface tensions(37,38) (as seen in Figure 1)



for which the parameters are presented in the caption of Figure 1...


Figure 1:



The caption:

Figure 1. Schematic diagram of a single bubble (black line) beneath the anode (orange block) in the liquid with the contact angle θw determined by the liquid–solid surface tension σLS, solid–gas surface tension σSG, and liquid–gas surface tension σLG. The green dash line represents the bubble length L, H is the bubble thickness, and the yellow point is the intersection point of gas–liquid–solid phases.


...Based on our brief review of the literature, it is clear that there is a lack of deep understating of the effects of the contact angle on the bubble dynamics in the aluminum reduction cells, which is the subject of our numerical study. The outline of the paper includes the followings: “Model Description,” “Numerical Details”, and “Results and Discussion”. In the Section 2, a three-dimensional (3D) transient mathematical model is employed to study the effect of the contact angle on the single bubble flow using the VOF method (Section 2.1). Then, a 3D transient model coupled with the discrete phase model (DPM)-VOF method is applied for predicting the multiscale bubble motion with various contact angles. A transition model from dispersed bubbles to continuous gas is used to bridge the conversion of bubbles in the Eulerian and Lagrangian frames (Section 2.2), which is achieved by a user-defined function (UDF) in the Fluent software. The Section 3 introduces the boundary conditions, flow regimes, and some material properties. The Section 4 presents the model validation and bubble behaviors with various contact angles. Finally, the Section 5 summarizes the main findings...


It follows from this portion of the introduction that this is a very long and elegant paper, and cannot be covered in too much depth in a brief blog post, and the post is merely a teaser for an interested party to look into the original.

Here though, is some flavor of the paper which, no, does not involve, um, Beto:

2.1.2. Collision and Coalescence Model

In the Fluent software, the collision and coalescence models are calculated by O’rourke’s algorithm,(30) which is a stochastic estimate of collisions and it also assumes that two bubbles collide in the same continuous-phase cell. The collisions among three or more bubbles are not explored within this method. If a smaller bubble moves in a flat circle around a larger bubble of the area πr1 + r2)2, a collision takes place. The collision volume Vcol for the 3D model can be written as the smaller bubble traveling distance in a given time step



where r1, r2, u⃗rel, and Δt are the small bubble radius, the large bubble radius, the relative velocity of the two bubbles, and the time step, respectively.

If the bubble has a uniform probability being anywhere in the cell, the probability of the two bubbles’ collision can be defined as the ratio of the collision volume and the cell volume Vcell(31)



The actual probability distribution of the number of collisions Nc based on the Poisson distribution is calculated by the expected collision number N̅



where N1 is the number of smaller bubbles.
To calculate the collision and the coalescence between the bubbles, O’rourke’s algorithm(30) selects two random numbers, x and y, in the range of [0, 1]. If x > P(0), the collision happens between the two bubbles. After the collision, the second random number y is adopted to determine if there a two-bubble coalescence or a grazing collision...


...and so on...

A few pictures from the paper:



The caption:

Figure 2. Schematic diagram of multiscale bubbles regarding the mesh at the anode bottom. (a) Macrobubble surface, (b) macro–microbubbles, and (c) microdispersed bubbles.





The caption:

Figure 4. Schematic our 3D model (symmetric with respect to x and y) for a single bubble motion. Gas is injected into the bath from the inlet surface (red surface) at the anode bottom and escapes from the outer surface.





The caption:

Figure 5. Force analysis of a single bubble (black line) beneath the anode (orange block) with static contact angles θw of (a) 0 < θw ≤ 90° and (b) 90° < θw ≤ 180°. The forces are the pressure gradient force F⃗p (red vectors), the surface tension force F⃗s (blue vectors), and the buoyancy force F⃗b (green vectors). F⃗sx and F⃗sy are the components of surface tension force along x and y directions, respectively. F⃗px and F⃗py are the components of pressure gradient force along x and y directions, respectively.





The caption:

Figure 8. Evolution of a single bubble shape in the plane of y = 0, with the contact angles of (a) 45°, (b) 60°, (c) 75°, (d) 90°, (e) 105°, and (f) 120° with the mass flow rate of 0.0000735 g·s–1 at (black short dash-dotted line) t = 1.0 s, (red dashed lines) t = 2.0 s, (blue dotted line) t = 3.0 s, (pink dash-dotted line) t = 4.0 s, (green dash-dotted-dotted line) t = 5.0 s, and (blue short dash line) t = 6.0 s. The operating parameters are listed in Table 2.




The caption:

Figure 9. Bubble shapes beneath the horizontal downward-facing surface in the plane of y = 0, with the contact angles of (black short dash-dotted line) 45°, (red dash line) 60°, (blue dotted line) 75°, (pink dash-dotted line) 90°, (green dash-dotted-dotted line) 105°, and (blue short dash line) 120° at 2.0 s with the mass flow rate of 0.0000735 g·s–1. The operating parameters are listed in Table 2.




The caption:

igure 10. Velocities at 6 s in the plane of y = 0, with the contact angles of (a) 45°, (b) 60°, (c) 75°, (d) 90°, (e) 105°, and (f) 120° with the mass flow rate of 0.0000735 g·s–1. The red line represents the bubble surface. The operating parameters are listed in Table 2.




The caption:

Figure 14. Evolution of the (a) gas coverage and (b) bubble thickness with a contact angle of 90° at a current density of 9000 A·m–2. The operating parameters are listed in Table 3.





The caption:

Figure 15. Minimum gas coverages (■ points 1–4) in the first cycle after bubble detaching from the anode bottom at a current density of 9000 A·m–2 with the contact angles of (red dashed line) 75°, (green dash-dotted line) 90°, (blue short dashed line) 105°, and (pink dash-dotted-dotted line) 120°. The operating parameters are listed in Table 3.




The caption:

Figure 16. Multiscale bubble distribution at 2 s with the contact angles of 75, 90, 105, and 120° (columns from top to bottom) in the current densities of 5000, 7000, and 9000 A·m–2 (rows from left to right). (a) θw = 75°, J = 5000 A · m–2, (b) θw = 90°, J = 5000 A · m–2, (c) θw = 150°, J = 5000 A · m–2, (d) θw = 120°, J = 5000 A · m–2, (e) θw = 75°, J = 7000 A · m–2, (f) θw = 90°, J = 7000 A · m–2, (g)θw = 105°, J = 7000 A · m–2, (h) θw = 120°, J = 7000 A · m–2, (i) θw = 75°, J = 9000 A · m–2, (j) θw = 90°, J = 9000 A · m–2, (k) θw = 105°, J = 9000 A · m–2, (l) θw = 120°, J = 9000 A · m–2. The operating parameters are listed in Table 3.


...and so on...

I do not know these authors nor am I familiar with their work, but it has to be a joyous exercise to contemplate these things, to think about them.

Hell, it would be a wonderful thing to just have the time to thoroughly read and understand the paper, because things like this, more than many things on which we spend our time are important to humanity and to the future, whether we recognize it as such or not.

Have a wonderful work week.




A Fabulous Lecture Was Just On CSPAN: Shakespeare in US Politics.

It contains all this wonderful witty allusions, using Shakespeare, to rip apart the Trump administration.

Shakespeare in US Politics

I recommend it highly.

We may have reached the annual minimum for CO2 concentrations in the atmosphere: 408.50 ppm.

Each year, the minimal value for carbon dioxide levels in the atmosphere for a particular year is observed in the Northern Hemisphere's early autumn, usually in September. The Mauna Loa Observatory reports weekly year to year increases for each week of the current year compared to the same week in the previous year.

This year, in 2019, as is pretty much the case for the entire 21st century, these minima are uniformly higher than the carbon dioxide minima going back to 1958, when the Mauna Loa carbon dioxide observatory first went into operation. Weekly data is available on line, however, only going back to the week of May 25, 1975, when the reading was 332.98 ppm.

For many years now, I have kept spreadsheets of the data for annual, monthly, and weekly Mauna Loa observatory data with which I can do calculations.

In the weekly case, the week ending May 12, 2019 set the all time record for such readings: 415.39 ppm.

These readings, as I often remark vary in a sinusoidal fashion, where the sine wave is imposed on a monotonically increasing more or less linear axis, not exactly linear in the sense that the slope of the line is actually rising slowly while we all wait with unwarranted patience for the bourgeois wind/solar/electric car nirvana that has not come, is not here and will not come.

This graphic from the Mauna Loa website shows this behavior:



Here is the data for the week beginning on September 15, 2019

Up-to-date weekly average CO2 at Mauna Loa

Week beginning on September 15, 2019: 408.50 ppm
Weekly value from 1 year ago: 405.67 ppm
Weekly value from 10 years ago: 384.59 ppm

As of this writing, there have been 2,277 such weekly readings recorded at Mauna Loa, going back to 1975. The increase over the same week of 2018, is "merely" 2.83 ppm, I say "merely," because the average for 2019 is 3.07 ppm over the previous year. This is only the second year in history in which this average has exceeded 3.00 ppm. The first was the El Nino year of 2016, when the average was 3.40 ppm.

The operative point is that this reading is only 0.09 ppm lower than last week's reading, which was, 408.59 ppm. This suggests, if one is experienced with working with such data, that this is most likely the annual September minimum reading. For the rest of this year, and through May of 2020 the readings will be rising. We will surely see next May readings around 418 ppm, if not higher.

Seven of the 50 highest year to year weekly comparison increases ever recorded have been in 2019. This includes the week beginning on April 28, 2019, when the increase measured 4.48 ppm, the eighth worst in recorded history. Six of the 10 worst readings have taken place in the last 5 years, all of them well over 4.00 ppm. Thirty-four of the top 50 such readings have taken place in the last 5 years; 38 in the top 50 recorded in last ten years, and 41 of the top 50 recorded in this century.

The average increases over the last 4 weeks when compared to the same week in 2018 has been 3.10 ppm.

In the 20th century these figures averaged 1.54 ppm; in the 21st, 2.15 ppm (and rising).

Early in this century, beginning with Germany, the world bought into the "renewable energy will save us" meme.

It hasn't. It isn't. It won't.

If the fact that this week's reading is 23.93 ppm higher than it was ten years ago bothers you, don't worry, be happy. You can read all about how wonderful things will be "by 2050" or "by 2100." Wind. Solar. Elon Musk. Tesla Car. And all that.

My impression that I've been hearing all about how rapidly bird and bat grinding wind turbines are being installed since I began writing here in 2002, when the reading on April 21, 2002 was 375.42 ppm.

This should not disturb you since it is better to think everything is fine rather than focus on reality and focusing on reality - particularly in Trumpian times - is as annoying here as elsewhere.

Don't worry. Be happy. Head over to the E&E forum, and read about "largest" solar facilities are being installed in place x or place y. Celebrate the victory.

All this jawboning about the wonderful growth of so called "renewable energy" has had no effect on climate change, is having no effect on climate change, and won't have any effect on climate change, but it's not climate change that counts: It's all that wonderful marketing showing pictures giant sleek wind turbines on steel posts that counts.

Don't be angry, be happy and nice. Say nice things. Be pleasant.

If the fact that steel is made by coking coal at high temperatures in coal fired furnaces enters your mind, I suggest you meditate and say, "OM...om...om...om..." until you're only left with happy thoughts.

At the risk of repetitively asserting that reality - as opposed to cheering for our own wishful thinking - matters, though let me say again and again and again and again:

In this century, world energy demand grew by 164.83 exajoules to 584.95 exajoules.

In this century, world gas demand grew by 43.38 exajoules to 130.08 exajoules.

In this century, the use of petroleum grew by 32.03 exajoules to 185.68 exajoules.

In this century, the use of coal grew by 60.25 exajoules to 157.01 exajoules.

In this century, the solar, wind, geothermal, and tidal energy on which people so cheerfully have bet the entire planetary atmosphere, stealing the future from all future generations, grew by 8.12 exajoules to 10.63 exajoules.

10.63 exajoules is under 2% of the world energy demand.

Nuclear energy, provided 28.81 exajoules, or 4.9% of world energy demand in 2017, this while under constant attack by people who think it is "too dangerous." In it's entire history, stretching over half a century nuclear has not killed as many people as will die today from air pollution, which is roughly 19,000 people; seven million people will die from air pollution this year.

2018 Edition of the World Energy Outlook Table 1.1 Page 38 (I have converted MTOE in the original table to the SI unit exajoules in this text.)

Nuclear energy was the last, best hope for humanity and, in fact, for the planet.

Fukushima.

Really? Really?

Facts matter and it is a fact that on the scale of disasters, Fukushima is demonstrably trivial. The average year to year weekly comparison increases since 2011, when Japan shut it's nuclear reactors to see if they were "safe" is 2.40 ppm.

According to the data published in Lancet in 2016 on causes of worldwide mortality, the number of people who died from air pollution since the Fukushima event can be roughly estimated at 60 million people. Sixty million people is roughly half the current population of Japan. How many people died from radiation from the Fukushima reactors again? If this is the focus of all your fears, Fukushima, let me know.

If you think that unlike you, I am worrying and not being happy, you can always chant stuff about how "by 2050" or "by 2075" or "by 2100" future generations will all live in a so called "renewable energy" nirvana powered by the sun and the wind and tooling around in Tesla electric cars.

I'll be dead "by 2050," as will most of the people doing such soothsaying about that magic year, but I'm sure that the future generation living through 2050 will all be cheering for our wonderful insight into the world in which they will be living.

Or maybe not. Maybe they won't forgive us for our wishful thinking by which we casually dumped responsibility on them to do what we were purely incompetent to do ourselves, this while we consumed every last drop of rare elements to live in our bourgeois moral hell.

We will not be forgiven, nor should we be.

I wish you a pleasant work week.

Palladium is a fission product.

The paper I will discuss in this very brief post is this one: Enhancement of Thermoelectric Properties in Pd–In Co-Doped SnTe and Its Phase Transition Behavior. (Wang et al ACS Appl. Mater. Interfaces 2019 11 37 33792-33802)

I don't have time this morning for much more than this.

Thermoelectric devices are well known and have been utilized, most famously in the space program, for the direct conversion of heat into electricity.

As an advocate of the last, best hope of saving the planet, nuclear energy, I follow the science around these devices rather closely.

The historical thermoelectric devices, including those that powered the Voyager spacecraft - with which we are still in contact after many decades - had low energy efficiency: Typically the heat energy converted to electrical energy was less than 10%. The efficiency of these devices is described in science and engineering by a parameter known as the Seeback coefficient, usually referred to by the somewhat confusing symbol "ZT" which is not an algebraic product.

I consider that all of the components of so called "nuclear waste" are valuable and need to be recovered, both as useful radioactive materials and as non-radioactive materials.

It is possible to isolate non-radioactive palladium from fission products in the case where fast separation of ruthenium is undertaken, since ruthenium-106 has a relatively short half-life, roughly a year. This is possible for fluid phased reactors of a type that has been popularly discussed among modern nuclear engineers. Ru-106 decays to stable palladium-106.

However the isolation of palladium from used nuclear fuel that has been foolishly allowed to accumulate without being put to use will contain a long lived radioactive isotope, Pd-107, which decays with a long half life to stable Ag-107. I believe that this palladium is also useful and that the risk associated with its radioactivity is vanishingly small if it is utilized in devices, which is why this paper caught my eye.

In the fast fission of plutonium - which in my view is the key to making nuclear fuel inexhaustible - about 6% of the fission products are palladium. (Natural palladium contains the 102 isotope which is observationally stable but probably radioactive with an a half-life so long as to be undetectable. Used nuclear fuel will contain this mass number in the form of stable ruthenium-102)

Here is figure 10 from the paper:



Here is the caption:

Figure 10. a) ZT values as a function temperature for Sn1.03–2xPdxInxTe; b) ZT contrast


From the conclusion of the paper:

In summary, we first confirmed that the existence of Pd can introduce the valence band convergence of SnTe, proven by first-principles calculation, and then carried out the experiment of doped Pd. In addition to valence band convergence and no deterioration of conductivity, chemical bond softening and grain refinement can also be introduced into SnTe doped with Pd. Moreover, the neutron and synchrotron powder diffraction experiments show that the significant change in the thermal conductivity of the codoped system is caused by local structural distortion. This persistent local structural distortion and the instability strongly affect the high temperature thermal conductivity, which affects overall thermoelectric performance. Therefore, we obtain a low thermal conductivity in this work. For instance, doped 2.5 mol % of In and Pd can reduce the thermal conductivity to 1.13 Wm–1K–1. The purpose of improving thermoelectric performance can be achieved by adjusting local structural distortion. Finally, due to the above synergistic effect, the ZT value of the Sn0.98Pd0.025In0.025Te sample reached 1.51 at 800 K.


This is a very high ZT value. To save the world from climate change, it is necessary to utilize high temperature nuclear reactors with high thermal efficiency in a combined cycle fashion, with some of the energy being utilized to make chemical fuels that can be obtained from hydrogen and carbon oxides, both CO and CO2. CO2 can also be reduced to carbon for use in materials, which is essentially combustion in reverse.

Temperatures of 800 K are readily accessible under these conditions, and may be utilized in the cooling phases necessary in the thermochemical conversion of carbon oxides to economically viable closed cycles approaches to carbon utilization.

It's cool I think.

None of this is likely to happen by the way, since fear and ignorance are obviously triumphant in modern times, but it is feasible that ignorance will fail, both on the right, where it is politically popular, and on the left, where anti-nuclear stupidity is popular.

I hope you will have a wonderful weekend.
Go to Page: « Prev 1 2 3 4 5 6 7 8 9 10 ... 67 Next »