Why softwoods develop compression wood and hardwoods develop tension wood is one of the unsolved mysteries of the plant world.
We’ll leave that unsolved mystery to Robert Stack.
Submitted by Marvin Shapiro of Teaneck, New Jersey. Thanks also to Herbert Kraut of Forest Hills, New York; and Gregory Laugle of Huber Heights, Ohio.
On nutrition labels, why does the total number of grams of fat often far exceed the sum of saturated and polyunsaturated fats?
Foraging through our kitchen cabinet, we lit upon a box of Nabisco Wheat Thins. A consultation with the nutritional panel-yielded the following information about the fat content of a half-ounce serving:
Fat:
3 grams
Polyunsaturated
*
Saturated
*
*contains less than one gram
And a look at the label on a Stouffer’s Lean Cuisine Oriental Beef with Vegetables and Rice Entree wasn’t much more enlightening:
Fat:
9 grams
Polyunsaturated
*
Saturated
2 grams
*contains less than one gram
We may not have been math whizzes, but even we know that two plus less than one does not equal nine.
What’s going on? Sally Jones, food technologist at the USDA’s food labeling division, told us that our arithmetic was impeccable but our nutritional IQ was in the dumper. We forgot that there is a third type of fat, monounsaturated, which can often, such as in the case of the Lean Cuisine entree, constitute more than half of a product’s fat.
Current labeling laws make it optional whether manufacturers list the grams of monounsaturated fat, often affectionately known as the “good fat.” The government doesn’t insist on listing monounsaturated levels, since there is some evidence that monos are actually good for us, fighting to raise our levels of HDLs, the “good cholesterol.”
When the giant upheaval of American food labels takes place, supposedly in 1993, but presumably later, food manufacturers will only be required to list their products’ percentage of saturated fat (i.e., the “bad fat”), the culprit that most consumers are trying to find out about when they consult the nutritional panel in the first place.
Submitted by Solomon Marmor of Portland, Oregon.
Why do ambulances have the emblem of a snake wrapped around a pole painted on them?
For as long as there have been ambulances, manufacturers have sought a symbol so that citizens could recognize the vehicle as an ambulance, even without the wail of the siren. As far back as the nineteenth century, the cross was the most frequently used symbol on ambulances around the world, but it never proved satisfactory, for two reasons. The cross was on the national flags of many countries, causing needless confusion, and the Red Cross Society screamed, pardon the pun, bloody murder whenever the cross was used on anything but military or Red Cross vehicles.
When the National Highway Traffic Safety Administration and the General Services Administration developed new federal specifications for ambulances in 1974, they decided that a new symbol specifically designating an ambulance was needed. The result: two new symbols were affixed to the exteriors of ambulances—a six-barred cross and the emblem in question, the “staff of Aesculapius.” Aesculapius was the son of Apollo and, in both Roman and Greek mythology, the god of medicine and healing; the snake was Aesculapius’s seal.
According to W. J. Buck Bension, national accounts manager for Southern Ambulance Builders, the staff of Aesculapius is a registered trademark of the NHTSA, designated for use only by and for ambulances and emergency medical personnel. But individual ambulance companies are free not to emblazon their vehicles with the staff of Aesculapius if they choose—if they want to risk incurring the wrath of the gods, that is.
Submitted by Gabe Miller of Ann Arbor, Michigan.
What’s the difference between “super” and ordinary glues?
The main difference between “super” glues and merely mortal ones is that Super and Krazy glues are fabricated from a manmade polymer called “cyanoacrylate,” while most other glues are a combination of natural resins in a solvent solution.
The different ingredients create a different bonding process, too, as Rich Palin, technical adviser to Loctite Corporation, reveals:
Most adhesives rely on mechanical fastening, meaning they penetrate into the tiny holes and irregularities of the substrate and harden there. Super Glue, on the other hand, creates a polar bond. The adhesive and substrate are attracted to one another like two magnets. Mechanical fastening also occurs with Super Glue, increasing the bond strength.
Borden Glue’s John Anderson adds that because super glues don’t rely solely on mechanical fastening, they are such better at bonding dissimilar surfaces than conventional glues. Thus, with super glues, the consumer is now able to accomplish many everyday tasks for which regular glue is frustratingly inadequate, such as applying glue to the top of a hardhat so that one can stick to steel girders without any other means of support.
Submitted by Tiffany Wilson (in Mary Helen Freeman’s Millbrook Elementary School class) of Aiken, South Carolina.
In what direction are our eyes facing when we are asleep?
Upward, usually. Our eye muscles relax when we are asleep, and the natural tendency, known as Bell’s Phenomenon, is for the eyes to roll back above their usual position. Of course, when we experience rapid eye movements during sleep, our eyes dart back and forth.
Submitted by Nadine Sheppard of Fairfield, California.
Why do weather thermometers use red chemical instead of the silver mercury found in medical thermometers?
The liquid found in weather thermometers is usually alcohol with red coloring. The main reason why alcohol is preferred over mercury for weather thermometers is that it is much, much cheaper. And alcohol is superior to water because alcohol is far hardier—it won’t freeze even at temperatures well below -40 degrees Fahrenheit.
Why the red additive in weather thermometers? So that you can read it more easily. If weather thermometers used a liquid the color of mercury, you’d have to take the thermometer off the wall to be able to read it.
Since the advantages of alcohol are so apparent, why don’t medical thermometers, notoriously difficult to read, contain red-colored alcohol instead of dingy mercury? Despite its greater cost, mercury is prized for its greater expansion coefficient—that is, it expands much more than alcohol or water when subjected to small increases in temperature. A weather thermometer might measure temperatures between -30 degrees and 120 degrees Fahrenheit, a span of 150 degrees, while a medical thermometer might cover only a ten- to twelve-degree range. A doctor might want to know your temperature to the nearest tenth of a degree; if a liquid with a small expansion coefficient were used, you would need a thermometer the length of a baseball bat to attain the proper degree of sensitivity. We don’t know about you, but we’ll stick with the stick thermometer.
Couldn’t the medical thermometer manufacturers color mercury, then? Actually, they could, but don’t, for reasons that Michael A. DiBiasi, of Becton Dickinson Consumer Products, explains:
When you produce medical instruments, the rule of the road states that the fewer additives that you incorporate into any device or component material, the better off you are in gaining approval to market the device, and in avoiding product recalls that may be tied in to those additives. So fever thermometers use mercury in its natural silver-white color, and the glass tube is usually silk-screened with a background color to make it easier to see the mercury level.
Submitted by Herbert Kraut of Forest Hills, New York.
How do they measure the vitamin content of foods?
Some vitamins are present in such small concentrations in food that there are only a few micrograms (millionths of a gram) of the vitamin per hundred grams of food, while other vitamins might constitute ten milligrams per hundred grams of food. The techniques that work to measure the
abundant vitamin often won’t work to evaluate the presence of the other.
Jacob Exler, nutritionist for the Nutrient Data Research Branch of the Human Nutrition Information Service, told Imponderables that there are two types of analytical procedures to measure the vitamin content of foods, chemical and microbiological:
The chemical procedures measure the actual amount of a vitamin or a derivative of the vitamin, and the microbiological procedures measure the biological activity of the vitamin on some selected organism.
Today, chemical procedures are in vogue. In the past, microbiological studies were more common, and researchers tested not only on bacteria but on live rats. In fact, as late as the 1970s, the FDA used approximately twenty thousand rats a year just to test foods for vitamin D content! Roger E. Coleman, of the National Food Processors Association, explains the theory behind microbiological studies:
An older, but still very acceptable method for vitamin assay is to measure the amount of microbiological growth a food supports. There are certain bacteria that require an outside source of one or more vitamins to grow. The growth of these bacteria is proportional to the amount of the required vitamin in the food.
But microbiological work is extremely sensitive. If conditions are not perfect, results can be skewed. As an example, an article in FDA Papers states that “the organism used for measuring vitamin B12 activity will show a measurable response when dosed with less than one ten-billionth of a gram of the vitamin.” Microbiological assays work more effectively than chemical methods for measuring B12 levels (and some other vitamins, such as biotin, B6) because chemical analysis isn’t sensitive enough to respond to the minute amounts of the vitamin contained in food.
In a chemical analysis, each vitamin in a given food must be measured separately. There are many chemical procedures to choose from, with catchy names like “gas-liquid chromatography” and “infra-red spectroscopy.” Coleman explains a few different types of chemical analysis that are a little more comprehensible:
Each measuring technique is based on a property of the vitamin. For example, riboflavin fluoresces [produces light when exposed to radiant energy] and is measured by a fluorometer or fluorescence detector. Vitamin C combines with a certain purple dye and makes it colorless. By measuring the amount of this dye that is changed from purple to colorless, we can calculate the amount of vitamin C present.
Despite the high-tech names, chemical analysis tends not to be as sensitive as old-fashioned microbiological methods, but it is cheaper and faster—and doesn’t necessitate twenty thousand rats a year sacrificing their life for vitamin D.
Submitted by Violet Wright of Hobbes, New Mexico. Thanks also to Todd Grooten of Kalamazoo, Michigan.
Why doesn’t the water in fire hydrants freeze during the winter?
It would…if the wrong type of fire hydrant were used. In areas that experience cold weather, fire departments use “dry barrel hydrants,” with operating valves located below the freezing level of the ground. The fire hydrant itself does not contain any water until the valve is opened.
In temperate climates, “wet barrel hydrants” are often utilized. These hydrants do contain water above ground level. What are the advantages of the wet barrel hydrant that help compensate for the risk of water in the hydrant freezing? We got the answer from the president of fire hydrant maker Hydra-Shield Manufacturing, Henry J. Stehling: “With wet barrel hydrants, each outlet has an operating valve. The wet barrel hydrant will have two or three outlets, each with its own operating valve, providing greater control.”
Submitted by Todd Sanders of Holmdel, New Jersey.
Why do baked goods straight from the oven often taste (sickeningly) richer than after they are cooled?
When you ponder this Imponderable for a while, you realize there are only two approaches to the answer: one, the baked item really is different straight from the oven than it is ten or twenty minutes later, or two, that for some reason, the taster perceives the same item differently depending upon when it is consumed. Turns out there are experts who subscribe to each explanation.
Bakery engineer Simon S. Jackel assures us that items really do change in structure after being cooled because of a process called “starch retrogradation.” In raw flour, starch exists in a coiled, closed structure. When flour is baked into bread or cakes, the starch uncoils and opens up when exposed to the water in the dough and the high temperature of the oven.
When the product comes out of the oven, it starts to cool down, and the starch begins to revert or “retrograde” to a partially coiled structure. Most importantly for our purposes, when the starch retrogrades, it absorbs some of the flavors and locks them up in the coiled starch so that the taste buds cannot process them. In other words, less flavor is available to the consumer as the product cools. Jackel states that retrogradation continues until the product is stale.
Two other baking experts lay the “blame” for the noxiousness of just-baked products on our noses. Joe Andrews, publicity coordinator for Pillsbury Brands, explains:
A great deal of taste perception is determined not only by the taste buds, but also by the olfactory senses…. When a food is hot, it releases many volatiles that the nose may perceive as sweet. Thus a cake may seem sweeter when it is warm than when it is cold.
The volatiles are perceived by the nose, both by sniffing through the nostrils and by the aromatics released in the mouth that make their way to the nose via a hole in the back of the mouth, the nasopharynx. We say we “taste” these, but in actuality we are smelling them.
Andrews believes that the “richness” our correspondent complains about may actually be sweetness.
Tom Lehmann, of the American Institute of Baking, also emphasizes the importance of volatiles in taste perception. Many aromatics, including spices, are simply too powerful when hot. Lehmann blames egg whites as particular culprits in making hot bakery items smell vile and taste noxious. Angel food cake, a dessert with a high concentration of egg whites, is particularly lousy hot, Lehmann says, because egg whites are volatiles that are released in heat and have to cool completely in order to avoid producing an unpleasant smell.
Of course, there is nothing mutually exclusive about the retrogradation and volatiles theories. Unlike arguments about genetic versus environmental factors in deviant behavior, or creationism versus evolution, the theories can coexist peacefully and respectfully. After all, bakers are engaged in an important and soul-lifting pursuit; it’s hard to get bitter and angry when your life revolves around a task as noble as trying to concoct the perfect doughnut.
Submitted by Connie Kuhn of Beaumont, Texas.
Why is gravel often placed on flat roofs?
We were taken aback when Scott Shuler, director of research at the Asphalt Institute, referred to this Imponderable as “oft-asked.” But he didn’t seem to be kidding, for he had a quick comeback: “Obviously, because it rolls off pitched roofs and there needs to be a place to put all that small gravel.”
Shuler put aside his burgeoning stand-up comedy routine long enough to inform us that flat roofs usually consist of aggregate (“there are generally two sources for this stuff: gravel from rivers and stone from quarries are both such materials”) embedded in the asphalt mopping. With this technology, often referred to as “built-up roofing,” alternating piles of roofing felt and asphalt are placed on the roof to provide a surface. According to Richard A. Boon, director of the Roofing Industry Educational Institute, the gravel is set in a “flood coat” of hot bitumen and is about the size of peas.
What function does the gravel serve?
1. According to William A. Good, executive vice-president of the National Roofing Contractors Association, the gravel helps to protect the roof membrane (“a combination of waterproofing and reinforcing materials” located just above the insulation and below the gravel) from puncture or tear by foot traffic from construction workers, dropped tools, hailstones, or stray meteorites.
2. Gravel provides a lighter, more
reflective, color than black asphalt, making the roof more energy-efficient. A side benefit: Gravel lessens the ultraviolet degradation of the roof membrane that would exist if the membrane were exposed directly to the sun.
3. The gravel acts as ballast. In windy conditions, the membrane, which is, in essence, tar paper, can actually lift up and even fly off if left exposed.
4. The gravel provides more secure, less sticky, footing for anyone walking on the roof, increasing the safety not only of maintenance workers but of civilians. (Remember, frisbees and baseballs have a much better chance of landing on a flat roof than a pitched roof.)
5. The gravel acts as a fire retardant.
But gravel’s status as the ballast of choice is in jeopardy, according to Boon:
Today, newer technology has allowed for single-layer roofing systems. Larger, ¾″-1½″-diameter stone is used…to hold the roofing system in place. The larger stones provide the same protection from sun, traffic, and fire, and the larger size reduces the potential for wind blow-off.
Are Lobsters Ambidextrous? Page 13