Sunday, March 15, 2009

What is Hair and Why is it So Different Among People?

Nora from Altoona, PA, wanted to know more about hair. She wrote in asking several questions about hair including: Is human hair different from animal hair? What is hair made of? Why is hair so different among the people she knows? These are all great questions about hair! So we will first learn some background about hair (e.g., structure, physical properties, and growth patterns), and then we’ll answer the questions.

We generally just think of humans having hair on the head and face but all land mammals have hairy skins. Humans are actually covered all over their bodies with hair except for the palms of the hands, soles of the feet and lips. Even though there is less visible hair on humans compared to other mammals (e.g., cats, dogs, chimpanzees), a square centimeter of human skin actually contains a greater number of follicles (or hair producing sites) than the same sized area of other mammals. The hair all over our bodies is less visible because we have lost the requirement for insulating our bodies, while mammals have not. Hair has more cosmetic value for humans but it also is for protection. For example, hair around the eyes, ears and in the nose prevent dust, insects and other debris from entering those organs where they could cause damage.

A hair is an outgrowth of the epidermis, or outermost part of the skin. Hair consists of the hair follicle and the hair shaft. The hair follicle is the point from which the hair grows, and it is a tiny cup-shaped pit buried deep in the fat of the scalp. The follicle is actually where the pigment, or color, of hair is produced. This pigment is called melanin and is carried upwards into the inner part of the hair as it grows. The hair shaft is the part of the hair that can be seen above the scalp. It consists mainly of dead cells that have turned into keratins (a special protein that is resistant to wear and tear, which is made up of very large molecules) and binding materials with small amounts of water. The center part of the hair shaft is called the cortex, while the outer layer is called the cuticle. If one thinks of the hair shaft like the trunk of a tree, then the cuticle would act as the bark protection the inner cortex where all its moisture lies. If the “bark” of the hair is well cared for, then the whole hair should remain in good condition. However, if the “bark” of the hair is damaged or stripped, then the exposed center of the hair may break.

Now that we know a little more about hair, we can answer Nora’s questions. We learned what hair is made of, but why is hair so different among the people she knows? In general, the type of hair you have is inherited from your parents. It’s actually possible that your hair type might be determined by the part of the world in which your ancestors came from. Nora also asked about animal and human hair differences. The coating of animal hair insulates just like human hair, but it also provides protection from rain. The growth pattern of hair for animals is more synchronized (or growing together), while human hairs tend to grow independently. Humans get their hair cut to their individual desires, while animal hair grows to a certain point and sheds (falls out) at certain times during the year (i.e., shedding often occurs when the coat is too heavy for the weather conditions related to the season) to be replaced by new hair when needed. Human hair is generally the same texture, but animals usually have two textures: there is a coarser top layer of hair and a finer layer (called under fur). These different textures help to insulate the animals. Another feature of hair on mammals is that sometimes their hair color blends with their surroundings, which provides protection against most predators.

Little Lion Experiment
As we have just learned, hair serves the purpose of body insulation and protection from other outside elements for both humans and mammals. This experiment will allow you to determine if the shade of human hair has an effect on its ability to insulate the human body.

You will need: access to dark colored hair and light colored hair (see if you can have the scraps of hair left behind at barber shops or hair salons), a scale (something that can measure in ounces), gloves, an apron or shirt that can get dirty, six paper lunch bags, two thermometers, a heat lamp or constant light source, ruler, stop watch and materials to record your results.

1) Collect the two different colors of hair from a barber shop (you will need approximately 6 ounces in weight of each color);
2) With gloves and apron on, put 1 ounce of each hair color into two different paper bags (remember to keep the hair colors separate);
3) Label the bags according to the type of hair inside and the weight;
4) Close the bags by folding the top down;
5) Repeat Steps 2-4 but put 2 ounces of each hair color into two more different paper bags;
6) Repeat Step 2-4 but put 3 ounces of each hair color into the last two paper bags;
7) Place the thermometers on a table about 15 inches apart from each other;
8) Put the 1 ounce bag of dark hair on one thermometer, and put the 1 ounce bag of light hair on the other thermometer;
9) Place the heat lamp approximately 10 inches in front of the bags and also try to center the lamp (center the lamp so that the light is evenly hitting both bags of hair);
10) Record the temperature changes every two minutes over a total of 10 minutes (do not leave the experiment while in progress);
11) Repeat Steps 8-10 for the other weights of samples;
12) You may want to repeat the experiment more than once for each weight of hair but that is up to you!

Look at your results. How do the temperatures recorded from under the dark hair samples compare to the temperatures under the light hair samples? Hopefully, your experiment was a success and you determined that the dark hair samples showed the greatest temperatures, whereas the bags containing the light hair showed the lowest temperatures. What does this mean exactly? Similar to light and dark colored clothing, dark hair absorbs heat better than light hair. So on sunny days, dark hair will prevent heat from passing through to your head while light hair will allow more heat to pass through.

Sunday, February 15, 2009

How Does Soundproofing Work?

Charles from Altoona, PA, has an older brother that plays the trumpet. His brother practices the trumpet in the bedroom next to his. He wrote in asking if it was possible to block out the sound so that he does hear the trumpet while he’s in his bedroom. Charles is essentially asking about soundproofing. While he probably won’t be able to block all the sound from his room, Charles can take steps to minimize the sound that he does hear.

Average volumes of people talking, television sounds, and music playing can often be heard through walls easily. This is due to the fact that sound is a series of vibrations that move surrounding particles. The series of vibrations, or sound waves, carries the noise from the noise source across the room to our ears. Since particles are required to carry the vibrations, sound cannot travel in a vacuum. The more densely packed those particles are, the better the sound moves through since the particles don’t have to move the surrounding particles much. When you’re in an open field, though, you would notice that sound will not carry as well since the particles are more spread out. The farther sound waves have to travel from one point to another, the fainter the sound will become. When sound waves collide with a solid surface (e.g., a bedroom wall), there are a few things that can happen. The surface will reflect some of those vibrations back toward the source, it will absorb some of the sound by converting the vibrations into heat energy or it will transmit the vibrations to the other side (i.e., into the bedroom).

There are two main things to consider when soundproofing: noise transmission and noise reception. The sound coming from the trumpet is a noise transmission issue, while the desire to block the sound out is a noise reception issue. Next the source of the noise should be considered: the indoor noise vibrations your body feels are structure-borne noise, while overhearing a conversation is airborne noise. Soundproofing can be achieved by considering space, mass, and dampening. Space increases the amount of air between your ears and the source, which diffuses the noise by taking away the vibration channels. Mass, like a bedroom wall, can act as a sound sponge that soaks in the sound waves. Dampening sound requires specific materials (like insulation) that will convert structure-borne sound waves to heat energy. Dampening can be expensive.

Without having to spend money, one step Charles can take while his brother is practicing the trumpet is to create more distance between himself and his brother. For example, Charles can plan to hang out in the basement or another room in the house that’s far away from his bedroom while his brother is practicing. Or Charles could ask his brother to practice in another room that’s far away from his bedroom.

Little Lion Experiment
You cannot see sound waves in the air, but you can see their effects. This experiment will help you see the effects of sound waves. You will need: 1 large cake or cookie tin, 1 sheet of plastic wrap, 1 long rubber band, 1 baking tray, 1 wooden spoon, and some fine sand.
Steps: 1) Make a drum by stretching a piece of plastic film over a large round tin; 2) Stretch the rubber band around the tin to hold the plastic taut; 3) Sprinkle a teaspoon of sand on to the top of the plastic drumskin; and 4) Hold a baking tray above your drum, and hit it sharply with a wooden spoon.

What did you observe? What do you think caused the sand to dance up and down on the drumskin? When you struck the baking tray, the metal continued to vibrate for a fraction of a second afterward. As it vibrated, the air around is also vibrated. These little vibrations in the air, the sound waves, quickly work their way out through the air in all directions. When the sound waves hit the drumskin, the drumskin is vibrated too, which causes the sand to dance up and down on the drumskin. The sound waves that reach your ear make you hear the bang.

Thursday, January 15, 2009

Heat Energy Movement and Heat Loss

Some of you from the Altoona area had recently read about why it feels colder on a windy day than on a day without wind. A few months ago, we had also discussed how it feels warmer on a cloudy day. So what is the science behind these questions, both of which seem to involve heat. It has a lot to do with the way heat moves from place to place, or as scientists call it – heat transfer. One of the basic facts in nature is that heat (which is a form of energy) always moves from a hotter object towards a colder object.

Heat can move in several ways from one place to another. Let us think about the different ways now. Do you know that when you touch a cold wall or a window, your warm hand is actually losing heat to the window glass? This form of heat movement is called conduction. This is the same manner heat moves from the stovetop to the kettle or to a soup pot. Conduction is heat movement by contact. Here the hot body has to touch the cold body for heat transfer by conduction.

But remember the cold wind story, there the heat is moved away from you by convection. Here there is usually a fluid medium, it can be air or water usually which carries the heat away from the hotter body. This is the same way how heat comes into your room through baseboard heaters when hot air is blown into the room. Convection involves another medium, usually air or water, transferring the heat. When cold air leaks into a house, it is convection which is to blame for our heat loss.

A third form of heat transfer, which does not require any medium or contact to occur, is radiation. Here the heat energy travels in the form of waves which can go through even vacuum. This is how the heat energy comes to earth from the sun, across millions of miles in the space. This is also how we lose heat from a closed car in winter, when it is left parked overnight. On a windy day, the wind can add to the loss of heat by taking heat away from the glass surface of windows and the body of the car. Radiation is also why we like to open our curtains on a sunny day in winter, to let warmth in through the glass windows.

One of the best examples of a man made object that tries to prevent heat loss is the thermos flask. If you ever get a chance to see one, you should examine it closely. One of the big benefits of a thermos flask is that it keeps colds things cold or hot things hot. You can read more about it at: . Also look up the words thermal insulation on the internet and find out what it means.

Little Lion Experiment
We will learn how different forms of heat transfer take place. Caution: We will NOT be using any kind of stove or electric heaters to do these experiments. We will be using hot water from the tap in the house to provide heat to some cold objects. But even with this you need to be extra careful not to spill any on yourself or get scalded. Be very careful and use only small amounts in small mugs. These experiments can all get pretty messy, so do NOT attempt them on carpeted floors at all. Also it is advised to not do it on a wooden floor either as any spill can be slippery and dangerous. Keep plenty of washcloths or paper towels around to take care of spills.

You will need:
1) Cold water
2) Hot water
3) A coffee mug or a cup to pour with
4) A small bucket or a quart saucepan
5) Aluminum foil
6) Plastic wrap
7) A newspaper
8) Two or three Hershey’s kisses kept in a cold place for an hour (yummy chocolate!)
9) A pencil and a small notepad to make notes.

Conduction Experiment Steps:
1) Keep a piece of aluminum foil (10 inch by 10 inch) larger than your hand over a cold glass window and keep your hand on the foil to feel the temperature.
2) Repeat the same step with a newspaper and also with your bare hand (only for a few seconds). Note the case when it felt coldest.

Radiation Experiment Steps:
1) Fill up hot water in a coffee mug almost till the top. Carefully cover the top with plastic wrap till it is snug and tight, tape the overhanging wrap around the cup if possible.
2) Keep the mug inside a bucket/saucepan.
3) Carefully place an unwrapped Hershey kiss on top of the plastic wrap.
4) After 5 minutes, check the condition of the chocolate, has it slightly melted?
5) Try the same experiment, but instead of the plastic wrap, cover the coffee mug with aluminum foil, making sure that the shinier side of the foil faces the hot water. And use a new chocolate.
6) Try the same experiment with newspaper taped to the top of the mug. Observe if any melting occurs.

Think about how the shiny side of the foil acts as a mirror to the radiation heat and prevents it from coming out of the mug. Final tip: you can probably eat the chocolate from the plastic wrap and the foil experiments, but the chocolate from the newspaper experiment may not be clean. Throw it away. Instead of chocolate you can also use small piece of candles/wax.

Monday, December 15, 2008

How Do Animals Survive the Winter?

With the winter months upon us, Julia from State College, PA, writes in to ask how animals survive during the colder months of winter. She asks does the cold weather affect them? She is also curious about the food they eat during the winter months.
Some animals hibernate all winter, which is actually just a very deep sleep. This allows the animal to avoid the cold weather without having to move to a warmer climate. Hibernation is a way to conserve energy by slowing down all of the body's processes. The animal's body produces less heat so its body temperature gets colder, and the animal also breathes much more slowly. These two bodily changes, along with the fact that the animal isn't moving, allow it to use up much less energy than it does when it is awake. These animals get ready for winter by eating extra food and storing it as body fat, which is used for energy while hibernating. Some also store food to eat later in the winter. Some animals that hibernate include bears, skunks and chipmunks. Cold-blooded animals like fish, turtles, frogs, and snakes, find shelter in holes or burrows. There they spend the winter inactive, or dormant, which is similar to hibernation.
Other animals stay pretty active during the winter, but they must adapt to the changing weather. Many make changes in their behavior or bodies. For example, animals may grow new, thicker fur in the fall to keep warm. Food is often hard to find in the winter, so the animals must adapt to this as well. Squirrels, mice and beavers, gather extra food in the fall and store it to eat later. Other animals like rabbits and deer, spend the winter months looking for moss, twigs, bark and leaves to eat. Some animals even eat different kinds of foods as the seasons change. For example, the red fox eats fruit and insects in the spring, summer and fall. However, in the winter, the red fox cannot find these foods so it eats small rodents instead. These active winter animals must also stay warm through the cold months. They sometimes find shelter in holes in trees or logs, under rocks or leaves, or even under the ground. Some mice and squirrels even huddle close together to stay warm.
Some birds migrate or travel to other places where the weather is warmer or they can find food. Many birds migrate in the fall. The trip can be dangerous, so the birds often travel in large flocks. Birds can fly very long distance but most birds will migrate shorter distances. Other animals migrate, too, including bats, caribou, elk, and whales.

Little Lion Experiment:
This experiment will allow you to determine how much energy animals are saving while hibernating! You will need ice cubes, a small pot and a thermometer that goes down to 40°F (5°C) or lower. If you don't have a thermometer like that, then put a cup of cold water in the fridge, which is almost exactly the same temperature (41°F) as a deep hibernating animal. Put a cup of warm water on the kitchen table. Let both cups sit for 20 minutes. You will need a pencil and some paper to record your observations.
Put an ice cube into the pot. Put the pot on the stove over low heat (get an adult to help you with this step). The ice cube will begin to melt into water. Keep checking the temperature of the water with your thermometer (or compare it to the refrigerated water) to see how long it takes for the water to reach 41°F. We'll call this the "deep hibernator time." Also note how much longer it takes to heat up to 60°F (the body temperature of an animal that is dormant). We'll call this the "dormant time." If you don't have a thermometer, then you can just wait until the water is almost as warm as the room temperature water. Also record how much more time it takes to warm up to 98.6°F, our body temperature (any household thermometer should be able to detect that temperature). We'll call this the "human time."
The amount of time it takes to reach a given temperature is directly related to the amount of energy (heat) that is needed to warm up the water to that temperature. So, the "deep hibernator time" shows how much energy is needed to go from freezing (which is about how cold it is when the animal is hibernating) to the animal's body temperature. Similarly, the "dormant time" shows how much energy is needed to go from freezing to that animal's body temperature. The "human time" shows how much energy is needed to go from freezing to our body temperature. The difference between the "human time" and one of the other times shows how much energy those animals are saving by only warming their bodies up to 41°F or 60°F instead of normal body temperature.

Saturday, November 15, 2008

Why Do Onions Make Us Cry?

Shanna from Altoona, PA, was helping her big sister prepare dinner one night, and she noticed that her eyes became really irritated when her big sister cut up an onion. She wrote in asking: why do onions make us cry? We will explore the answer to that question but we will also explore some methods that might minimize the eye irritation. Many people enjoy the taste of onions in their meals. In fact, the average American eats about 20 pounds of onions each year. Onions are healthy components of the human diet because they contain vitamins B and C, protein, calcium, and iron. They also contain quercetin (pronounced KWAIR-SUH-TEN), which is an antioxidant that works to neutralize harmful substances in our bodies that cause tissue damage and aging. In addition to being full of nutrients, onions are low in fat and sodium. However, if you have ever cut into an onion, it is likely that your eyes filled with tears because they became irritated just like Shanna described. But why does this happen? How can we enjoy the taste and benefits of onions without the tears? When you cut into an onion, an enzyme (a biomolecule that speeds up chemical reactions) is released into the air from the ruptured onion cells. This enzyme converts some of the proteins from the onion into sulfenic acids that then become a gas. These can then come in contact with your eyes. These acids contain sulfur compounds that are common eye irritants. The gas reaches your eyes and reacts with the water that keeps them moist. The eyes become irritated, and your brain reacts by telling your tear ducts to produce more water that helps keep the eyes protected. You may want to rub your eyes to help soothe the irritation, but this will only make the irritation worse since your hands may have onion juices all over them. Some people wear goggles to minimize any irritation produced when cutting onions, but some also try the different methods discussed in the Little Lion Experiment. Give each method a try to figure out which one works best for you so you can enjoy onions without any eye irritation!

Little Lion Experiment:

How can we enjoy the benefits and the great taste of onions without the tears? For this experiment, you will explore some methods that are thought to reduce the unpleasant eye irritation that occurs when cutting into an onion. You will need an adult present to help you with this, especially when cutting the onion. It is preferable to try these methods over 5 different days, but you can try each of these home remedies during the same time. Throughout each of these methods, keep track of whether your eyes were irritated when the onion was cut and try to determine which method works best for you.

Items Needed

  • 5 small onions with the outer layers peeled away
  • 1 lemon slice
  • Slice of bread
  • Sugar
  • Bowl of water
  • Access to a refrigerator
  • Knife


  1. Method 1: Put one onion into the refrigerator. After 30 minutes, take it out and cut the onion.
  2. Method 2: Put one onion into a bowl of water so that it is covered in water. Cut the onion while it is submerged in the water.
  3. Method 3: Put a lemon slice in your mouth. Then cut the onion (keeping your mouth open)
  4. Method 4: Put a bread slice in your mouth. Then cut the onion (keeping your mouth open).
  5. Method 5: Put some sugar in your mouth. Then cut the onion (keeping your mouth open with the sugar on your tongue)


Did any of these methods work to keep your eyes from being irritated? If so, which ones worked the best? Having the onion chilling in the refrigerator before cutting it, like in Method 1, is supposed to slow the release of the irritating gases. Keeping the onion under water while cutting it, like in Method 2, is supposed to keep the gases from even reaching your eyes. Keeping the sugar, bread, or lemon slice in your mouth while cutting the onion, like in Methods 3-5, is supposed to keep the gases from ever reaching your eyes since the food will absorb the gases. Try to remember these different methods each time you help out with the cooking at home. And remember to wash your hands after handling an onion since they will be coated in the onion's eye irritating compounds.

Wednesday, October 15, 2008

How Does Temperature Affect the Cleaning Ability of Soap?

James from Altoona, PA, was helping his older brother wash some dishes in their kitchen sink recently, and he noticed that the dish detergent seemed to rinse off the dishes better with cold water than with hot water. He also observed that the hot water helped make the dish detergent foam more (i.e., produce more soap suds). He wrote in asking: how does the temperature of water affect the cleaning ability of soap? The use of soaps and detergents is part of everyday life (at least it should be!) so let's first discuss what soap is and how it works. You have probably heard the terms soap and detergent used to describe the various products that are used to clean clothes, dishes, hands, cars, or pretty much anything that needs cleaning. While they are very similar, they are slightly different. A detergent is a substance that cleans dirty or soiled surfaces. It is usually made from synthetic ingredients, which means the ingredients are not naturally occurring and are maufactured from different chemicals. Soap is a type of detergent and is usually produced from natural ingredients. Just from looking around your home, you probably have noticed that soaps and detergents are produced in many different physical forms - for example, there are bars, flakes, pellets, liquids and even tablets! Detergents and soaps contain a basic cleaning agent called a surfactant, which stands for surface active agent. Surfactants consist of molecules that attach themselves to the dirt particles of the dirty material that is being cleaned. The dirt particles are pulled out of the dirty material and are then held in the wash water until they are rinsed away. Most detergents contain a synthetic surfactant in addition to other chemicals that are added to improve the detergent's cleaning ability. Other ingredients that are added to detergents include perfumes, coloring agents and germ-killing or antibacterial agents. When it comes to temperature, hot or cold water is acceptable when cleaning with soap. The most important part of cleaning is using the soap or detergent! You need something that will pull the dirt particles from the dirty areas. Water alone will work OK, but water with soap will work even better.

Little Lion Experiment:

Like James above, you may notice that more soap suds are produced when using hot water. The reasoning for this begins with the fact that warmer water evaporates faster than cold water (the warmer water changes from a liquid to a gas faster than cold water). Soap suds or bubbles are formed more easily when the warmer water is evaporating. Colder water evaporates slower so it is harder to make soap suds. With this information, do you think bubbles will last longer in hot or cold water? This experiment will help you determine the answer!

Items Needed

  • Two large bowls (or tubs)
  • Rubber gloves
  • Tablespoon measuring spoon
  • Access to cold and hot water (from your faucet is OK)
  • Stop watch
  • Some type of soap (you can use dish detergent, laundry detergent, hand soap, etc.)


  1. Fill one bowl with warm water and the other bowl with cold water.
  2. With the gloves on, add one tablespoon of your soap to each bowl.
  3. Use the tablespoon to mix the soap into each bowl for 30 seconds.
  4. After mixing, start the stop watch and observe how long the bubbles remain in each bowl. Did the bubbles last longer in the warmer water or the cold water? Why do you think this is so? With the faster evaporation of the warm water, the bubbles may form more quickly than the cold water but that also means that they will disappear sooner too. The slower evaporation of water means that the bubbles may take longer to form but they will also last longer once formed.

Monday, September 15, 2008

What is in the Air We Breathe?

Laura from Hollidaysburg, PA, was recently helping her parents clean her home, and she noticed how much dust there was on the tables, in the air, and coming from the couches! She wrote in asking: Where does dust come from and what happens to it when we breathe it in? About 21% of the air we breathe is actually oxygen, while the remaining air consists of other gases (e.g., nitrogen, argon, carbon dioxide). However, the air also consists of dust, tiny animals, and other stuff! Dust is defined as dry, solid particles that are less than 0.0625 millimeter in diameter, which is smaller than all grains of sand! Most dust is composed of mineral matter that originated from bare soil, plowed fields, river flood plains, and floors of desert basins. Dust also comes from ocean spray, smoke and ash produced by fires, decaying organic materials, and volcanic eruptions. The wind actually lifts up the dust particles and easily carries them long distances around the earth! The dust in your home can also be made up of dust, pollen, mold, sand, skin flakes, and pet dandruff. These air particles are actually the most common causes of allergies or asthma. Humans and animals can also act as carriers of dust and air particles because the air particles can cling to their skin or clothes. When you breathe in, you are also breathing in dust or air particles. Some of these air particles will get caught in your nose hairs, some will get caught in mucus in your airways, and some will make it into your lungs. However, don't worry too much about this, because most of what you breathe in will cling to the hairs on the inside of your nose. These hairs act as a filter, which works to trap the inhaled air particles inside your nose to keep them from traveling into your respiratory system. The hairs usually trap particles that are less than 5 nanometers in size (that is approximately 0.000005 mm!). Aside from the many nuisances of dust around your home, dust actually contributes to some beautiful sunsets and sunrises. That's right, dust is what makes sunsets and sunrises so pretty! The intense red and orange colors of the sky at sunset and sunrise are mainly caused by the scattering, or reflection, of sunlight off air and dust particles. So the next time you are cleaning your house or enjoying a beautiful sunset or sunrise, think of the dust that is contributing to these everyday events.

Little Lion Experiment:

This experiment will allow you to observe the types of air particles you breathe regularly.

Items Needed

  • 6 index cards
  • Scissors
  • A pen
  • 6 pieces of string
  • tape (scotch, masking, duct, or packing tape is good)
  • A magnifying glass
  • A ruler


  1. Cut squares into the center of each index card. Try to make all the squares the same size (e.g., about 2'' by 3'').
  2. Choose 6 locations within your home that you want to hang the air particle collectors. Some places to hang your air particle collector include: above your bed, on the inside or outside of a window, near a heating vent or air conditioner, above the cooking stove, on a wall near the floor or ceiling, on your main entry door, and under a tree.
  3. Write down the locations on the index cards so that each index card has a different location on it
  4. Write the starting date on each index card
  5. Cover the window on the index card with the tape so that the stick side up or out.
  6. Attach string to each index card, and then hang the cards at the appropriate locations.
  7. Wait a few days and then take the index cards down without touching the tape. Make sure to note the date. Which location had the most air particles collected? Were these locations inside or outside? Why do you think this is so? Think about where air is moving, and where the air particles could be coming from. Use your magnifying glass to examine the air particles up close. Can you recognize any common air particles?