24. Hector Bellerin (right back) 11 19. Santi Cazorla (central midfield) 20. Mathieu Flamini (central midfield) 6. Laurent Koscielny (centre back) 11 11 11 33. Petr Cech (goalkeeper) Arsenal face a do or die encounter tonight as they look to revive their Champions League hopes for the rest of the season.With just three points from their opening four games, the Gunners are in a precarious position as they welcome Dinamo Zagreb to the Emirates.Only one team in the last decade in Europe’s primary competition has progressed with the same number of points at the same stage – Stuttgart in 2009 – although Manchester City survived with just two from their first four games last season.So how will Arsene Wenger, faced with a mounting injury crisis that has seen Francis Coquelin become the latest first-team regular to be sidelined, approach the crucial game?talkSPORT takes a look… 11 12. Olivier Giroud (striker) 16. Aaron Ramsey (right midfield) 11 18. Nacho Monreal (left back) 17. Alexis Sanchez (left midfield) 11 11. Mesut Özil (midfield) 11 4. Per Mertesacker (centre back) – see the full line up, in squad number order, by clicking the arrow above 11 11 11
Mars has no liquid water today, but water must have covered much of the planet in the past. How? Nobody knows.Look at the diagram of Mars the way some secular planetary scientists believe it looked in ancient times (Phys.org). It’s almost covered with water. How could that be? There’s no liquid water there today, and Mars lacks the atmosphere that could keep it liquid. It’s also too cold for liquid water most of the time, although some may be locked up as ice in the polar caps.Scientists infer its presence by its effects. The surface of Mars today is covered with what look like drainage channels. A leading hypothesis is that liquid water carved them at some time in the unobservable past, perhaps about 3 billion years ago.A new study led by Northern Illinois University geography professor Wei Luo calculates the amount of water needed to carve the ancient network of valleys on Mars and concludes the Red Planet’s surface was once much more watery than previously thought.Dr. Luo and his two colleagues re-estimated the amount of water needed. The new estimate is an order of magnitude higher than previous estimates, and 4,000 times the volume of all the valley cavities. He envisions an earth-like Mars with a water cycle, rainfall, rivers, streams, and a large ocean covering over half the planet.Our most conservative estimates of the global volume of the Martian valley networks and the cumulative amount of water needed to carve those valleys are at least 10 times greater than most previous estimates.There are some problems, though. Nobody knows how the water got there, or how it could last if it did.But a large piece of the puzzle is missing, he added, because climate models have not been able to reproduce an early Mars climate sufficiently warm enough to promote an active hydrologic cycle.“Mars is much farther way from the sun than Earth, and when the sun was younger, it was not as bright as it is today,” Luo said. “So there’s still a lot to work out in trying to reconcile the evidence for more water.“Dr Luo needs a large ocean in his model to account for a water cycle that could drive rainfall and erosion to create the valley networks (VNs). Undoubtedly an ocean on a planet with 38% earth’s gravity would not just sit still like a placid sea. Even without a large moon, diurnal rotation and atmospheric winds would likely set up tides and currents. Some of the geological features are considered to be tsunami deposits. Could a sufficiently large impact or volcano move water over continents?Mars elevation map, 2002 MOLAThe paper in Nature Communications sets out some of the possibilities for a Martian ocean in motion: fluctuating shorelines, tsunami deposits, sedimentary layers and deltas. Luo does not speak of any floods. It’s amusing, however, to see planetary scientists routinely refer to a “Noachian epoch” on Mars.How solid is the evidence for a large ocean on Mars? “There is no ground truth to assess the real accuracy of our estimation,” he says. In planetary science, that’s OK these days. If your model requires it, that’s enough reason to believe in it, even if you can’t imagine how water could exist on Mars at all. Someone’s rule of speculating is that if you’re going to tell a whopper, you might as well tell a really big one:Our result is consistent with a warm and wet early Mars climate and the existence of an ancient northern ocean. If erosion of the VNs required significant chemical or physical weathering to produce transportable sediment, fluvial abrasion of channel beds or transport of appreciable quantities of gravel, the required volume of water may have been many times our conservative estimate.Luo justifies his whopper on the basis that something had to carve these channels. If not a wet, warm, oceanic Mars, what did?But on Earth, where the surface is 70% covered by water, could there have been a global flood? Oh, come now; that’s just a religious myth.We’re not disparaging scientific models. Creation geologists use models to try to retrofit observations to Noah’s flood. Dr Walt Brown, for instance, traced ancient shorelines north and west of Grand Canyon to model a large inland lake that could have carved the canyon by a dam breach. Models are useful tools, but they are only simulations of reality. The test of a model is how well it conforms to observable reality. If your assumptions do not hang together well (for instance, a faint young sun with a warm, wet Mars), you had better remain humble about your assumptions, and be open to alternatives. And if you are going to go out on a limb like Dr Luo does, don’t disparage the work of those whose models have much better correspondence with observable reality. Creation geologists can count ten or more clear evidences from the Grand Canyon alone that not only support a global flood, but rule out any other explanation. That’s ground truth. And when you have an eyewitness account from the One who brought it about, that’s truth.Recommended Resource: Want to see evidence for the Flood yourself at the Grand Canyon? Logos Research Associates has a trip planned for June 30 to July 2: 3 days, 2 nights for only $285. Click the link for full information. Highly recommended! (Visited 745 times, 1 visits today)FacebookTwitterPinterestSave分享0
Share Facebook Twitter Google + LinkedIn Pinterest By Mark Sulc and Rory Lewandowski, CCA, Ohio State University ExtensionThe best time to take a last harvest of forages is this week and next in Ohio, for the least risk to the long-term health of the stand. This is especially true for alfalfa and other legumes that need the fall period to replenish carbohydrate and protein reserves in the taproots that are used for winter survival and regrowth next spring. This fall rest period is particularly important this year, because our surviving stands have suffered a great deal of wet soil stress this year. Adding the stress of fall cutting will be like adding insult to injury, in our opinion carrying a higher degree of risk this year than normal.Unfortunately, many fields this year may not be at a reasonable harvest stage during the next two weeks, because the rainy weather early this season blew apart our normal harvest schedules. Many producers are faced with the choice between harvesting lower yields at a less mature stage now or waiting to harvest when yields will be higher. Like most farming decisions, there are trade-offs and risk factors to consider when making a fall legume harvest. This article reviews best management practices under the conditions we face this year.The decision of when to take the last harvest of alfalfa to ensure good winter survival and yield potential for the following year can be boiled down to two choices: 1) cut early enough in the fall (generally early September) to permit alfalfa to regrow and replenish carbohydrate root reserves, or 2) cut late enough so that alfalfa does not regrow and use up root reserves for that limited regrowth prior to winter dormancy. Cutting in between those times means more risk to the stand; however, there are factors such as previous cutting management, age of stand, soil fertility, variety, and soil moisture that affect the level of that risk.For those who are risk adverse, following the last cutting date recommendations offers the highest probability of promoting stand winter survival and vigorous green up and growth the following spring. The recommendation in the 15th edition of the Ohio Agronomy Guide is to complete the last regular harvest of alfalfa by September 7 in northern Ohio, September 12 in central Ohio and by September 15 in southern Ohio. The corollary is to delay final harvest until a killing frost (25F for several hours) has occurred.Another approach to fall harvest management uses growing degree-days (GDD) rather than calendar dates. Work done by Belanger et al. and published in 1998 in the Canadian Journal of Plant Science, indicates that alfalfa needs 500 GDD (based on degrees Celsius and base 5 C for alfalfa growth) between a late season cut and a killing frost to generate sufficient regrowth to provide good winter survival and yield potential for the following year. With regard to taking a late fall harvest, Dan Undersander, University of Wisconsin Extension retired forage specialist, wrote in a 2012 article “…we do not need to wait for a killing frost to take the last cutting. We must only wait until it is so cool that little or no regrowth will occur. Thus, harvesting in late fall, when less than 200 GDD will accumulate, minimizes winter injury…” The period between an accumulation of more than 200 GDD and less than 500 GDD is a no-cut period (GDD calculated from degrees Celsius scale with base 5C). This GDD approach provides flexibility in date of last harvest, but it involves more risk because the grower must predict or consider probability of either accumulating enough GDD or GDD not accumulating. Historic weather data, like that available from the OARDC weather stations (http://www.oardc.ohio-state.edu/weather1/), is useful to calculate those probabilities.Based on this GDD approach, we studied 5 years (2013-2017) of weather data at Wooster, OH. The date of a killing frost (25 F for several hours) ranged from November 3 to 22. The no cut zone of 500 to 200 GDD prior to the killing frost was September 17 to October 13 for three of the five years, but was September 4 to 30 in 2014 and September 10 to October 4 in 2013. So, the period of most risk for cutting alfalfa based on this GDD criterion agrees well with past recommendations to not cut alfalfa from early September to mid-October. Therefore, cutting in late October prior to a true killing frost of forage legumes, is likely to not result in little to no regrowth and no significant depletion of root reserves. However, there is still the risk of frost heaving with the late removal of forage cover (discussed more below).Previous harvest management should be a part of the risk equation and assessment of the probability of a fall harvest affecting stand survival and health. The cutting frequency during the growing season affects the energy status of the plant going into the fall. Frequent cutting (30-day intervals or less) results in the plant never reaching full energy reserve status during the growing season. A short regrowth period just prior to the fall harvest can be especially risky if that fall harvest occurs between mid-September and early October, because the regrowth uses root reserves and there won’t be enough growing weather remaining for the plants to accumulate a high level of root reserves before cold weather shuts down the plants. This lower root reserve status may limit winter survival and spring regrowth, depending on the winter and early spring growing conditions.Variety selection may also affect the risk assessment of fall cutting. Today’s top varieties have genetics selected to better withstand intensive cutting schedules. Alfalfa varieties with high disease resistance and good levels of winter hardiness will be more tolerant of a fall cutting. Adequate fertility, especially soil potassium levels, and a soil pH near 6.8 will improve plant health and increase tolerance to fall cutting. Stands under 3 years of age are generally more tolerant of fall cuttings than older stands where root and crown diseases are setting in. However, you have more productive stand life to lose if younger stands are harmed by fall cutting.Consider soil drainage and soil moisture. High soil moisture content slows down the cold hardening/fall dormancy process, increasing the risk of winter injury. Alfalfa stands on well-drained soils tolerate later fall cuttings better than alfalfa on moderately or poorly drained soils. But a word of CAUTION – Removing the top growth of alfalfa plants going into the winter on heavy soils and poorly drained soils increases the risk of damage from spring frost heaving, which is a significant risk on many Ohio soils with higher clay content. This would be a concern when cutting very late after the 200 GDD threshold date.Finally, consider the economics of a fall harvest. Often the height of the alfalfa is deceptive as an indicator of tonnage. The resulting windrow after cutting is often small or sparse. Thus, the cost of mechanically harvesting is high on a per ton basis.Fall cutting risk can be reduced but not eliminated. Nature bats last as we saw this spring and alfalfa stand health and survival will suffer when early freezes, open and very cold winters, early springs with ice, and/or extreme rainfall and temperature variations occur. Unfortunately, forage supplies are short this year, and some producers may be forced into taking more risk than they would like to take with fall cutting. But if at all possible, we urge producers to observe the fall rest period for forage legumes this year.