Archive for the ‘Now I Know’ tag
No, really, from a post I wrote:
Make Your Own Bedbug Detector
To make the detector, turn the dog bowl upside down to create a moat and a dome. Next, mix water, sugar, and yeast in the coffee cup, and rest the cup on the upturned bowl’s dome. The researchers covered the outside of their bowl in cloth tape painted black; bedbugs are attracted to the color. The cloth tape made it easier for the bedbugs to climb the sloping wall before falling into the well. To trap the bedbugs inside, the researchers coated the well with sticky resin. For DIYers, a sprinkling of talcum powder will make the walls of the moat too slippery to climb back out. In fact, talc is what’s used in the ClimbUp Interceptor, the most popular commercial bedbug trap on the market.
The Science Behind It
The researchers experimented with a variety of chemical bedbug attractants, but none were more effective than the simple DIY mixture. Bedbugs are drawn to the CO2 a sleeper exhales, and the combination of sugar, water, and yeast produces prodigious amounts of it — that’s how beer gets its fizz and bread gets its rise. Hungry bedbugs on the prowl for CO2 and human blood crawl up the sides of the bowl and fall down into the well, never to escape. The scientists used large quantities of sugar, water, and yeast to generate the CO2 in their experiments. Smaller amounts — such as those one might mix in a paper coffee cup — are safer, although may not be as effective.
My explanation of Southern California’s June Gloom didn’t shed much sunlight on why it has become the June-July-August Gloom. Last week the National Weather Service released a brief statement explaining why: cooler than usual waters in the Pacific Ocean and a persistent “upper level trough” in the atmosphere above the coastline. That upper level trough — or low pressure system — has helped keep the air cool. Together, our cooler water and cooler air have prompted the formation of the clouds and fog that creep inland overnight. This combo has also kept monsoonal moisture at bay. So while the American Southwest is enjoying afternoon thunderstorms, Southern California’s mountains and deserts have not.
All that was supposed to have changed this weekend. Temps were up inland and slightly higher here at the beach. And this morning’s bright sunrise, among a handful of fogless dawns this summer, promised a scorcher. But by noon today dense fog had tumbled in from the harbor. If you listen, you can hear the ships’ fog horns booming in the distance, heralding the end of the heatwave that wasn’t.
June Gloom is the phrase many Southern Californians use to describe the generally overcast skies that hang over the region in late spring and early summer. The gloom is deepest just after dawn and heaviest near the beaches. But by midday — earlier over points inland — the clouds burn off and the basin’s familiar over-saturated sunlight washes over all. Well, the sunlight washes over all except those of us who live within a mile of the shoreline, where the overcast may linger deep into the afternoon.
The gloom and overcast are a result of the marine layer, which is a kind of temperature inversion layer. Normally, higher air temperatures are found near the ground and cooler temperatures are found aloft. An inversion layer sees this relationship turned upside down: cooler temperatures are found near the surface and warmer temperatures lie above. One effect of an inversion layer is a “capping” of normal convection currents — the rising and falling of air due to thermals — which traps dust and other particles under the inversion layer. LA’s famously bad air quality is partly a result of this meteorological quirk.
Our local inversion layer is generated by the especially chilly waters of the Pacific Ocean. The California Current carries frigid sea water south from the Gulf of Alaska to the tip of Baja. The sea water cools the air above, creating a temperature inversion. If there is enough moisture in the air, and the cooling effect is strong enough, then clouds and fog are generated within the marine layer. Depth of the marine layer is affected by the movement of much larger weather systems in the atmosphere above. High pressure systems squish the marine layer so that only coastal areas lie under the gloom. Low pressure systems allow the marine layer to expand upward and outward; fog along the shore rises and pushes inland.
It’s just after 2:00 pm PDT here in Long Beach, CA, and the sun is just beginning to burn through the clouds above. June Gloom has stretched all the way through July. But when the alternative is thunderstorms and sweltering heat, I don’t think many of the locals mind.
Breakfast most days is half-a-cup of nonfat plain yogurt mixed with a quarter-cup of granola chased with half-a-pot of coffee.
I buy Trader Joe’s French Village Nonfat Yogurt in the 32 ounce tub* (good enough for fourth place!). About a day after opening a fresh tub, a thin milky liquid rises to the top. It’s yellowish and unappetizing. Every morning I pour it down the drain before scooping out breakfast.
Not anymore. That stuff is whey.
Whey is a dairy byproduct usually associated with the making of cheese or butter. Old time cheese makers added rennet, a soup of enzymes found in mammalian stomachs that aids in milk digestion, or an edible acid such as lemon juice or vinegar to milk to begin the process. The additives cause the milk to curdle, or separate into solids (“curds”) and liquid (“whey”). Today cheese makers use a genetically engineered rennet substitute to induce curdling.
Whey is filled with protein and amino acids. It is used to fortify all sorts of food products, from Oreo Cookies to KFC’s coleslaw. It is fed to farm animals. It is powdered and poured into bulging plastic bottles with label designs that promise potency, power and vitality. Whey protein is popular with bodybuilders.
Yogurt is produced by introducing bacteria to heated milk. As the bacteria consume sugar (lactose), they release lactic acid, which causes the curds and whey to separate. When the right pH level and consistency are reached, the product is cooled quickly to stop fermentation. The whey is “immobilized” within the curd globules before it has a chance to get away. These globules of curd are not robust. Temperature changes weaken the bonds and allow trapped whey to escape curd’s milky grasp. Gravity, too, can overwhelm the curds’ ability to hang onto the whey. Such mechanical curdling is called syneresis.
Because most consumers don’t like the appearance of whey in their yogurt, producers add a variety of thickening agents — fruit pectin, various starches — to toughen up the curd. But now that I know whey is okay, I don’t think I mind.
*The tubs, after a turn through the dishwasher, make great paint or varnish pans. Or you can use them in the pantry to store granola.
Now that I know what causes thunderstorms here in Southern California (monsoon moisture + heat + topography), and despite this weekend’s return of the marine layer and the subsequent end of the thunderstorm cycle, I wondered: what causes lightning?
Updrafts and downdrafts in the thundercloud cause water and ice particles to collide and take on positive or negative electrical charges, much like a balloon will take on a negative electrical charge when rubbed with a woolen sock. For reasons not well understood, lighter, positively charged ice droplets migrate toward the top of the cloud formation and heavier, negatively charged ice droplets and rain settle toward the bottom of the formation. Eventually this separation creates electrical potential between the negatively charged part of the cloud and the positively charged part of the cloud. Lightning occurs when the electrical charge on both sides overcomes the resistance of the air between them. These “intra-cloud” strikes are the most common type of lightning. “Inter-cloud” strikes, or strikes between clouds, have similar causes. Cloud to ground strikes work somewhat differently.
As the negatively charged part of the cloud moves over the earth, the ground below becomes positively charged by induction. You have seen induction if you have played with magnets and noticed how one side of a magnet attracts its opposite and repels its like, or if you have replaced the batteries in your Wii controllers and noticed the “+” and “-” symbols telling you how to arrange everything. Under the storm cloud, positively charged ions in the earth are attracted to the negative ions accumulating above and negatively charged ions in the ground are pushed away. As with intra-cloud strikes, when the charge on either side becomes strong enough, resistance is overcome, electricity flows and shazzam! lighting strikes.
As for thunder, that’s easy. A bolt of lightning is fantastically energetic and it generates terrific heat, singeing the surrounding air to 30,000 to 50,000 degrees Farenheit. The Crack! you hear is the sound of the explosion made as super-heated lightning strike air expands, rapidly, into the cooler air around it.
Southern California’s monsoon and thunderstorm season got underway last Monday, and if you were paying attention, you felt it. At dawn the sky above was dull and gray — the so-called June Gloom — but by 10:00 am the marine layer had been beaten back out to sea. High altitude high pressure air had slipped in from the deserts to the east, sending the cooling gloom away. Temperatures have risen steadily since and everyday thunderstorms form over the mountains that ring the Los Angeles basin (such as seen from the beach, here).
Thunderstorms require three things to form: moisture, air instability, and a lifting force.
Moisture can come from oceans or from remnants of hurricanes or other storms.
Air instability occurs when a cool dry pocket of air rests over a warmer, wetter pocket of air; given a sufficient nudge, the warm, moist air will rise.
Lifting force usually comes from heat, whether by temperature differential (uneven heating of the ground, which creates thermals) or by boundaries between pockets of air (warmer air will rise over cooler; the heat differential between drier and wetter air will force the wetter air up; and the outflow boundary, on the edge of a thunderstorm, is cooler than the surrounding air, creating more thunderstorms). Lifting force can also come from topography — wind moving up mountain slopes and through canyons will provide the push the moist air needs to get aloft.
Once aloft, the air rises and cools, condensing its moisture into water droplets, which form clouds. More rising air pushes some droplets still higher, where they continue to cool and grow. Some fall as rain. Some freeze and fall and melt back into rain. Some freeze and fall and stay frozen and fall to the ground as hail.
The high pressure that arrived on Monday gave the thunderstorms two of the three necessary ingredients: air instability and lifting force. Without the marine layer to keep us cool, temperatures began to rise (in Downtown LA it was 75 on Monday, 86 on Tuesday, then 94, then 92, and 93 today). While heat differentials promote thundercloud formation, our topography probably plays a larger role. The Los Angeles basin is ringed with mountains — the San Gabriels to the north, the San Bernardinos to the northeast, the Santa Anas to the southeast. Air moving onshore from the ocean rises up the slopes and through the canyons, pushing warmer, moister air up. Upslope thunderstorms are common in the Rocky Mountains and the Sierra Nevadas and they occur here, too. We also have several convergence zones — regions where breezes, after having diverged around mountains and through canyons, collide and force air upward. One such convergence zone is near Lake Elsinore (the Lake Elsinore Convergence Zone), on the eastern side of the Santa Ana Mountains, where this supercell thunderstorm and funnel cloud was videotaped.
For the third element — moisture — we return to the opening line of this post and that word “monsoon”, which seems out of place when discussing Southern California. The North American, or Arizona, or Southwest monsoon occurs when high pressure moves over the southwest from the south and intense summertime heating of the desert creates rising air and low pressure. The monsoon takes place between June and mid-September. The result is a change in direction of prevailing, low level air flow that brings moisture up from the Gulf of California and the Western Gulf of Mexico. This moisture is then forced up by heat differentials and upslope winds to form into water droplets and clouds and eventually thunderstorms.
Other than that, all I know about our monsoon and thunderstorms is that mid-September is a long way off.
Household bleach is a 3-6% solution of the chemical sodium hypochlorite. The municipal water system chlorinates city water with a 15% solution of sodium hypochlorite and the city parks department chlorinates the public pools with a 30% solution of sodium hypochlorite. The chemical was discovered by a French chemist in 1787. Another French scientist, Louis Pasteur, discovered its disinfectant properties about a hundred years later.
Sodium hypochlorite is an oxidizer, which is a chemical, usually containing oxygen, that readily shares oxygen with another compound. Once on the loose in the wash, sodium hypochlorite attacks the stain in two ways. First, it combines with pieces of the stain and breaks it down into smaller, water soluble bits, much like standard laundry detergents do. But sodium hypochlorite gets its shine as a stain fighter from its second line of attack. Molecules get their color from chromophores — which are arrangements of atoms that absorb most colors of light and reflect back the color we see. Bleach messes with the structure of chromophores and reduces their ability to reflect light. Whatever bits of the stain that remain after the first attack lose their ability to reflect visible light. After a good bleaching a stain is not necessarily gone; it’s invisible.
Unfortunately, sodium hypochlorite does not distinguish between stains and fabric dyes. Colorsafe bleaches, on the other hand, contain much weaker oxidizers (hydrogen peroxide or sodium percarbonate) which, given enough time, are strong enough to tackle common stains but are over matched by durable industrial dyes.
Pasteur figured out how to use sodium hypochlorite as a disinfectant more than hundred years ago, but why it is so effective at germ killing is only now coming to light. Recent research has shown that sodium hypochlorite causes proteins that bacterial cells require for growth to lose their shape and clump into large, insoluble aggregates. The cell cannot make use of the larger, flatter proteins, causing the cell to die. Human immune systems, it turns out, produce hypochlorite when battling bacteria infections. As with shirt stains, hypochlorite attacks healthy cells along with bacterial cells, leading to tissue damage in areas of inflammation. Maybe our immune systems can be encouraged to switch to cell-safe bleach?
When I updated my eyeglass prescription recently, I decided to outfit my frames with photochromic lenses. What are photochromic lenses? They are lenses that change from transparent to dark as they and their wearer move from indoors to outdoors. We usually call them transitions lenses or just Transitions for the same reason we call synthetic floor coverings Linoleum and soda pop Coke; the people who make them know how to market their product. Unlike Linoleum and Coke, the brand name Transitions tells us something meaningful about the product, too.
But how do they do it?
At first I imagined millions of tiny shutters embedded in the lenses, opening and closing with the light. And, it turns out, that’s not far off. Instead of little Levolors, however, the outer layer of my plastic eyeglass lenses is embedded, to the depth of just 150 microns*, with millions of molecules of a light sensitive organic compound known as an oxazine. Organic compounds are those that include at least one carbon and an oxazine is an organic compound with one oxygen and one nitrogen arranged in a ring. When indoors or otherwise shielded from ultraviolet light, the molecules do not absorb visible light, and the lenses remain transparent. But when exposed to ultraviolet light, such as that from the sun, the molecules change shape, which causes them to absorb visible light, and the lenses gradually darken. The reverse happens when ultraviolet light is removed; the molecules return to their original shape and the lenses gradually become transparent again.
Had my eyeglasses been made of glass instead of plastic, they would have been embedded with the inorganic compound silver chloride, which has the same photochromic properties. Whatever the material, if eyes are windows to the soul, then photochromic lenses are blinds on those windows to the soul.
*How deep is that? A micron (or micrometre) is one one-millionth of a meter. A human hair is about 100 microns in diameter. So the oxazines in my glasses go down about a hair and a half.