Chest pain: First aid

 

By Mayo Clinic Staff Causes of chest pain can vary from minor problems, such as indigestion or stress, to serious medical emergencies, such as a heart attack or pulmonary embolism. The specific cause of chest pain can be difficult to interpret. Finding the cause of your chest pain can be challenging, especially if you've never had prior symptoms. Even doctors may have a difficult time deciding if chest pain is a sign of a heart attack or something less serious, such as indigestion. If you have unexplained chest pain lasting more than a few minutes, it is better to seek emergency medical assistance than to try and diagnose the cause yourself. As with other sudden, unexplained pains, chest pain may be a signal for you to get medical help. Use the following information to help determine whether your chest pain is a medical emergency. Heart attack A heart attack occurs when an artery that supplies oxygen to your heart muscle becomes blocked. A heart attack may cause chest pain that lasts 15 minutes or longer, or it can also be silent and produce no signs or symptoms. Many people who experience a heart attack have warning signs hours, days or weeks in advance. The earliest warning sign of an attack may be ongoing episodes of chest pain that start when you're physically active and are relieved by rest. Someone having a heart attack may experience none, any or all of the following: Uncomfortable pressure, fullness or squeezing pain in the center of the chest lasting more than a few minutes Pain spreading to the shoulders, neck, jaw or arms Lightheadedness, fainting, sweating, nausea or shortness of breath If you or someone else may be having a heart attack: Call 911 or emergency medical assistance. Don't tough out the symptoms of a heart attack for more than five minutes. If you don't have access to emergency medical services, have a neighbor or friend drive you to the nearest hospital. Drive yourself only as a last resort, and realize that driving yourself puts you and others at risk if your condition suddenly worsens. Chew a regular-strength aspirin. Aspirin reduces blood clotting, which can help blood flow through a narrowed artery that's caused a heart attack. However, don't take aspirin if you are allergic to aspirin, have bleeding problems or take another blood-thinning medication, or if your doctor previously told you not to do so. Take nitroglycerin, if prescribed. If you think you're having a heart attack and your doctor has previously prescribed nitroglycerin for you, take it as directed. Don't take anyone else's nitroglycerin. Begin CPR on the person having a heart attack, if directed. If the person suspected of having a heart attack is unconscious, a 911 dispatcher or another emergency medical specialist may advise you to begin cardiopulmonary resuscitation (CPR). If you haven't received CPR training, doctors recommend skipping mouth-to-mouth rescue breathing and performing only chest compressions (about 100 a minute). The dispatcher can instruct you in the proper procedures until help arrives. If an automated external defibrillator (AED) is available and the person's unconscious, begin CPR while the device is retrieved and set up. Attach the device and follow instructions that will be provided by the AED after it has evaluated the person's condition. Angina Angina is chest pain or discomfort caused by reduced blood flow to your heart muscle. Typically the term "angina" is used when you've already been given the diagnosis of heart disease related to atherosclerosis. Angina may be stable or unstable: Stable angina — persistent, recurring chest pain that usually occurs with exertion and is relatively predictable Unstable angina — sudden, new chest pain, or a change in the pattern of previously stable angina, that may signal an impending heart attack Angina is relatively common, but can be hard to distinguish from other types of chest pain, such as the pain or discomfort of indigestion. If you are having angina with any of the following signs and symptoms, it may indicate a more serious condition, such as a heart attack: Pain in your arms, neck, jaw, shoulder or back accompanying chest pain Nausea Fatigue Shortness of breath Anxiety Sweating Dizziness The severity, duration and type of angina can vary. If you have new or changing chest pain, these new or different symptoms may signal a more dangerous form of angina (unstable angina) or a heart attack. If your angina gets worse or changes, seek medical attention immediately. Pulmonary embolism Pulmonary embolism occurs when a clot — usually from the veins of your leg or pelvis — lodges in a pulmonary artery of your lung. The lung tissue served by the artery doesn't get enough blood flow, causing tissue death. This makes it more difficult for your lungs to provide oxygen to the rest of your body. Signs and symptoms of pulmonary embolism may include: Sudden, sharp chest pain often accompanied by shortness of breath Sudden, unexplained shortness of breath, even without pain Cough that may produce blood-streaked sputum Rapid heartbeat associated with shortness of breath Fainting Severe anxiety Unexplained sweating Pulmonary embolism can be life-threatening. As with a suspected heart attack, call 911 or emergency medical assistance immediately. Aortic dissection An aortic dissection is a serious condition in which a tear develops in the inner layer of the aorta, the large blood vessel branching off the heart. Blood surges through this tear into the middle layer of the aorta, causing the inner and middle layers to separate (dissect). If the blood-filled channel ruptures through the outside aortic wall, aortic dissection is usually fatal. Typical signs and symptoms include: Sudden severe chest or upper back pain, often described as a tearing, ripping or shearing sensation, that radiates to the neck or down the back Loss of consciousness (fainting) Shortness of breath Sudden difficulty speaking, loss of vision, weakness, or paralysis of one side of your body, such as having a stroke Sweating Weak pulse in one arm compared with the other If you are experiencing any of these signs or symptoms, they could be caused by an aortic dissection or some other serious condition. Seek emergency medical assistance immediately. Pneumonia with pleurisy Frequent signs and symptoms of pneumonia are chest pain accompanied by chills, fever and a cough that may produce bloody or foul-smelling sputum. When pneumonia occurs with an inflammation of the membranes that surround the lung (pleura), you may have considerable chest discomfort when taking a breath or coughing. This condition is called pleurisy. One sign of pleurisy is that the pain is usually relieved temporarily by holding your breath or putting pressure on the painful area of your chest. This isn't usually true of a heart attack. If you've recently been diagnosed with pneumonia and then start having symptoms of pleurisy, contact your doctor or seek immediate medical attention to determine the cause of your chest pain. Pleurisy alone isn't a medical emergency, but you shouldn't try to make the diagnosis yourself. Chest wall pain One of the most common varieties of harmless chest pain is chest wall pain. One kind of chest wall pain is costochondritis. It causes pain and tenderness in and around the cartilage that connects your ribs to your breastbone (sternum). In costochondritis, pressing on a few points along the edge of your sternum often results in considerable tenderness in those small areas. If the pressure of a finger causes similar chest pain, it's unlikely that a serious condition, such as a heart attack, is the cause of your chest pain. Other causes of chest pain include: Strained chest muscles from overuse or excessive coughing Chest muscle bruising from minor injury Short-term, sudden anxiety with rapid breathing Peptic ulcer disease Pain from the digestive tract, such as esophageal reflux, peptic ulcer pain or gallbladder pain that may feel similar to heart attack symptoms Pericarditis Jan. 27, 2015 References

Celiac disease diet: How do I get enough grains?

 

I have celiac disease, and I find it difficult to get enough grains in my diet. Do you have any suggestions? Answers from Michael F. Picco, M.D. Because people with celiac disease must avoid gluten — a protein found in foods containing wheat, barley and rye — it can be a challenge to get enough grains. Grains are an important part of a healthy diet. They are a good source of healthy carbohydrates, various vitamins and minerals, and fiber, and they are naturally low in fat. When possible, choose foods made with enriched flours for added vitamins and minerals. Whole grains are even better for you. These include brown or wild rice, quinoa, amaranth, pure buckwheat, flax, whole corn, millet, gluten-free oats, sorghum and teff. Many large grocery stores and specialty food stores carry ready-to-eat gluten-free grain products. The labels on such products will state that the product is "gluten-free." Consider the suggestions in the chart below for adding gluten-free grains to your diet. Gluten-free grains and grain products* Serving size Breads Breads, English muffins and bagels ready-made from rice, potato, bean, soy, corn, sorghum, teff or other flours Frozen, gluten-free waffles Gluten-free pizza crust made from a mix or frozen ready-made Homemade breads, biscuits, pancakes, waffles, muffins or quick breads made from gluten-free flours Corn tortillas 1 slice or piece Cereals Cooked cereal made from corn (hominy, grits), rice, pure buckwheat, amaranth or quinoa Gluten-free puffed rice Gluten-free cornflakes, rice flakes, amaranth flakes or other dry cereals 1/2 to 1 cup Snacks Crackers or crispbreads made from rice or corn Popcorn Rice cakes Pretzels made from gluten-free flours Corn chips 1 oz. (check label) Other Brown, wild or white rice Pasta made from rice, corn, amaranth, quinoa or pure buckwheat Kasha made with pure buckwheat Quinoa Millet 1/2 to 1 cup *Products vary by manufacturer, so be sure that the brand you purchase is gluten-free. Shopping guides that list gluten-free products are available. Check with a registered dietitian or celiac disease support group. Oats may not be harmful for most people with celiac disease. However, oat products are frequently contaminated with wheat, so it's best to avoid oats. If your doctor or dietitian suggests trying oats, be sure to look for oats from a reputable gluten-free supplier. Most gluten-free grain products aren't supplemented with vitamins, so it's a good idea to take a vitamin supplement. Grain products that are not gluten-free include any type of wheat (including farina, graham flour, semolina and durum), barley, rye, bulgur, Kamut, kasha, matzo meal, spelt, triticale, couscous, emmer and einkorn.   Celiac disease: Can gluten be absorbed through the skin? References See more Expert Answers source : mayoclinic.org

Nanoparticles can clean up the environment

 

Wed, 07/22/2015 - 7:56am Jonathan Mingle, MIT News correspondent Nanoparticles that lose their stability upon irradiation with light have been designed to extract endocrine disruptors, pesticides, and other contaminants from water and soils. The system exploits the large surface-to-volume ratio of nanoparticles, while the photoinduced precipitation ensures nanomaterials are not released in the environment. Image: Nicolas BertrandMany human-made pollutants in the environment resist degradation through natural processes, and disrupt hormonal and other systems in mammals and other animals. Removing these toxic materials—which include pesticides and endocrine disruptors such as bisphenol A (BPA)—with existing methods is often expensive and time-consuming. In a new paper published in Nature Communications, researchers from Massachusetts Institute of Technology (MIT) and the Federal University of Goiás in Brazil demonstrate a novel method for using nanoparticles and ultraviolet (UV) light to quickly isolate and extract a variety of contaminants from soil and water. Ferdinand Brandl and Nicolas Bertrand, the two lead authors, are former postdocs in the laboratory of Robert Langer, the David H. Koch Institute Professor at MIT’s Koch Institute for Integrative Cancer Research. (Eliana Martins Lima, of the Federal University of Goiás, is the other co-author.) Both Brandl and Bertrand are trained as pharmacists, and describe their discovery as a happy accident: They initially sought to develop nanoparticles that could be used to deliver drugs to cancer cells. Brandl had previously synthesized polymers that could be cleaved apart by exposure to UV light. But he and Bertrand came to question their suitability for drug delivery, since UV light can be damaging to tissue and cells, and doesn’t penetrate through the skin. When they learned that UV light was used to disinfect water in certain treatment plants, they began to ask a different question. “We thought if they are already using UV light, maybe they could use our particles as well,” Brandl says. “Then we came up with the idea to use our particles to remove toxic chemicals, pollutants, or hormones from water, because we saw that the particles aggregate once you irradiate them with UV light.” A trap for “water-fearing” pollution The researchers synthesized polymers from polyethylene glycol, a widely used compound found in laxatives, toothpaste, and eye drops and approved by the Food and Drug Administration as a food additive, and polylactic acid, a biodegradable plastic used in compostable cups and glassware. Nanoparticles made from these polymers have a hydrophobic core and a hydrophilic shell. Due to molecular-scale forces, in a solution hydrophobic pollutant molecules move toward the hydrophobic nanoparticles, and adsorb onto their surface, where they effectively become “trapped.” This same phenomenon is at work when spaghetti sauce stains the surface of plastic containers, turning them red: In that case, both the plastic and the oil-based sauce are hydrophobic and interact together. If left alone, these nanomaterials would remain suspended and dispersed evenly in water. But when exposed to UV light, the stabilizing outer shell of the particles is shed, and—now “enriched” by the pollutants—they form larger aggregates that can then be removed through filtration, sedimentation or other methods. The researchers used the method to extract phthalates, hormone-disrupting chemicals used to soften plastics, from wastewater; BPA, another endocrine-disrupting synthetic compound widely used in plastic bottles and other resinous consumer goods, from thermal printing paper samples; and polycyclic aromatic hydrocarbons, carcinogenic compounds formed from incomplete combustion of fuels, from contaminated soil. The process is irreversible and the polymers are biodegradable, minimizing the risks of leaving toxic secondary products to persist in, say, a body of water. “Once they switch to this macro situation where they’re big clumps,” Bertrand says, “you won’t be able to bring them back to the nano state again.” The fundamental breakthrough, according to the researchers, was confirming that small molecules do indeed adsorb passively onto the surface of nanoparticles. “To the best of our knowledge, it is the first time that the interactions of small molecules with pre-formed nanoparticles can be directly measured,” they write in Nature Communications. Nano cleansing Even more exciting, they say, is the wide range of potential uses, from environmental remediation to medical analysis. The polymers are synthesized at room temperature, and don’t need to be specially prepared to target specific compounds; they are broadly applicable to all kinds of hydrophobic chemicals and molecules. “The interactions we exploit to remove the pollutants are non-specific,” Brandl says. “We can remove hormones, BPA, and pesticides that are all present in the same sample, and we can do this in one step.” And the nanoparticles’ high surface-area-to-volume ratio means that only a small amount is needed to remove a relatively large quantity of pollutants. The technique could thus offer potential for the cost-effective cleanup of contaminated water and soil on a wider scale. “From the applied perspective, we showed in a system that the adsorption of small molecules on the surface of the nanoparticles can be used for extraction of any kind,” Bertrand says. “It opens the door for many other applications down the line.” This approach could possibly be further developed, he speculates, to replace the widespread use of organic solvents for everything from decaffeinating coffee to making paint thinners. Bertrand cites DDT, banned for use as a pesticide in the U.S. since 1972 but still widely used in other parts of the world, as another example of a persistent pollutant that could potentially be remediated using these nanomaterials. “And for analytical applications where you don’t need as much volume to purify or concentrate, this might be interesting,” Bertrand says, offering the example of a cheap testing kit for urine analysis of medical patients. The study also suggests the broader potential for adapting nanoscale drug-delivery techniques developed for use in environmental remediation. Source: Massachusetts Institute of Technology

Protect Your Baby from Group B Strep!

 

Protect your baby from group B strep. If you're 35-37 weeks pregnant, talk with your doctor or midwife about getting a group B strep test. If you are pregnant, talk with your doctor or midwife about getting a group B strep (GBS) test when you are 35–37 weeks pregnant. The test will let you know if you are carrying group B streptococcal bacteria, which you can pass to your baby during childbirth. If you have GBS, your baby can get very sick and even die if you are not tested and treated. Preventing Group B Strep Each time you are pregnant, you need to be tested for GBS. It doesn't matter if you did or did not have this type of bacteria before; each pregnancy is different. The test is an easy swab of the vagina and rectum that should not hurt. There are no risks to being tested for GBS. If the test shows that you are carrying the bacteria, you will be given medicine during labor to stop GBS from spreading to your baby. The antibiotic (usually penicillin) is given to you through an IV (in the vein) during childbirth. If you are allergic to penicillin, there are other antibiotics to help treat you during labor. If you think you might have a C-section or go into labor early (prematurely), talk with your doctor or midwife about making a personal GBS plan. Taking antibiotics before you go into labor will not protect your baby against GBS. The bacteria can grow back so fast that taking the medicine before you begin labor does not prevent the bacteria from spreading to your baby during childbirth. What You Can Do Before Labor Talk with your doctor or midwife about getting a GBS test when you are 35–37 weeks pregnant. If you test negative for GBS, you do not need to do anything more. If you test positive for GBS, talk with your doctor or midwife about a plan for labor. You will get IV antibiotics (medicine through the vein) during labor. If you are allergic to penicillin or other antibiotics, make sure to tell your doctor or midwife about any reactions you have had. Continue your regular check-ups, and always call your doctor or midwife if you have any problems. When Your Water Breaks or When You Go into Labor If you have not had the GBS test when labor starts, remind the staff that you do not know your GBS status. If you tested positive for GBS: Go to the hospital and expect to get IV antibiotics (medicine through the vein) during labor. The antibiotics work best if you get them for at least 4 hours before you deliver. Tell the labor and delivery staff at the hospital that you tested positive for GBS. Tell the labor and delivery staff if you are allergic to penicillin. Talk with your doctor about a GBS test when you are 35-37 weeks pregnant.  What is GBS? It is a common type of bacteria. GBS bacteria are often found in the vagina and rectum of healthy women of all races and ethnicities. In fact, about 1 out of 4 women in the United States carry this type of bacteria. These bacteria can come and go naturally in the body. What Does It Mean to "Test Positive" for GBS? If you test positive, that does not mean you have an infection. It only means you have these bacteria in your body. You would not feel sick or have any symptoms. GBS are usually not harmful to you, but can be to your newborn because these bacteria can be passed on to babies during childbirth. Other people in the house, including other children, are not at risk of getting sick from GBS. Testing positive for GBS does not mean that you are not clean. It also does not mean that you have a sexually transmitted disease. The bacteria are not spread from food, sex, water, or anything that you might have come into contact with. source : http://www.cdc.gov/features/groupbstrep/index.html

Mighty Mussel Glue for Surgery

 

Thu, 07/23/2015 - 4:30pm Greg Watry, Digital Reporter Image: MarumInspired by biological functions seen in mussels and insects, Korean scientists have manufactured a nontoxic surgical glue, which seals surgical openings within one minute, and may become a viable replacement for sutures and staples. Mussels, according to Live Science, use silky fibers known as byssus threads to attach themselves to underwater surfaces. Researchers later determined a part of the “mussel ‘glue’ molecule, called catechol, pushes water molecules out of the way to bind directly to (a) wide variety of surfaces,” according to the American Chemical Society. The researchers said the discovery could lead to developing adhesives that work underwater and in the body. Pohang Univ. of Science and Technology Prof. Hyung Joon Cha and his student Eun Young Jeon report their light-activated, mussel-based bioadhesive, called LAMBA, is compatible with the human body and strong in wet conditions. “LAMBA opens numerous doors for medical practices, ranging from blocking air leaks and suture-less wound closures of delicate organs (to) tissues beyond surgeons’ reach,” Cha said. The scientists’ findings were reported in Biomaterials. Unlike previous attempts utilizing mussel adhesive proteins (MAP), Cha and Jeon’s method, through a photochemical reaction, uses blue visible light to activate the adhesive. The idea came from dityrosine crosslinks found in dragonfly wings and insect cuticles. An illustration from the university shows MAP strands dotted with tyrosine. When blue visible light is applied, neighboring tyrosine are coupled into the aforementioned dityrosine crosslinks. According to the university, “the invasive nature of traditional methods,” such as sutures and staples, is a drawback due to severe tissue damage, complicated post-treatment management and scars. According to the university, biologically derived adhesives, such as LAMPA, have an advantage over chemically derived adhesives, such as cyanoacrylates. According to Medscape.org, cyanoacrylates are only used externally, as they cause an “intense inflammatory response” when in contact with surfaces other than skin.   The paper is based on tests performed on animals. source: http://www.rdmag.com

Donec eris felix…

 

 

Eu achei esta expressão, este olhar de Emma Watson muito especial, mas muito mesmo. Agora, você deve estar me perguntando : Mas porque as outras imagens? Bem, só sua imagem ficaria um tanto quanto solitária, a não ser que o tamanho fosse bem maior. E eu acho que esta foto é uma das melhores dessa doçura. Dá vontade de ficar namorando….  Mas existe uma razão para essa expressão, esse olhar tão especial….Consegue adivinhar?   Emma devia ter uns 20 anos nessa foto. Hoje continua bem jovem ainda, claro, mas já dá para notar algumas diferenças.  A coisa é assim, gente : O tempo passa, MESMO.

 

Playful Vibrant Rope Installation

Posted: 21 Jul 2015 10:00 AM PDT

L’architecte Inés Esnal a créé une installation ludique et originale. Baptisée Prism, elle est installée dans un complexe résidentiel de Brooklyn. Installée dans le hall de l’immeuble, l’oeuvre est constituée de cordes élastiques colorées, offrant un contraste avec les murs bétonnés et froids. Les formes géométriques de la sculpture évoluent selon le point de vue, donnant du relief au lieu.

 

Light Calligraphy Around the World

 

Posted: 23 Jul 2015 11:00 AM PDT

L’artiste français Julien Breton (aka Kaalam) utilise la technique du light painting pour créer des oeuvres de Light Calligraphy un peu partout dans le Monde : en Inde, en France, au Maroc ou encore à New York. Ses créations dont les messages sont parfois écrits en Arabe, en Français ou dans une calligraphie abstraite, rendent hommage à la liberté, la fraternité, la beauté, la spiritualité.

Review: Hitting the streets with the Dyson Hard Tail electric bike

 

Taking to the streets with the Dyson Hard Tail electric bike (Credit: Loz Blain/Gizmag.com) I'd always been hesitant to make the switch to an electric bike. Would that little nudge along eat away at my poor but hard-earned fitness base accumulated through cycling with nothing other than leg power? Would I be able to return to those grueling two-block city ascents without the luxury of an electric motor? Putting these concerns to one side for a couple of weeks, I climbed aboard the electrified Hard Tail, the flagship model from Australian company Dyson Bikes. And though it wasn't a dramatic enough leap to make a return to a conventional two-wheeler entirely unpalatable, the well-polished bike perfectly demonstrated the benefits of a little electrical assistance while whizzing around city streets. For the most part, electric bikes conjure up images of freaky frames with bulky batteries conspicuously latched on, resembling more a quirky DIY project than your regular pushbike. Dyson was very conscious of this in building its top-of-the-line model, aiming to offer commuters an easier transition to powered cycling. "Looking at the Hard Tail it seems just like a normal bike," Dyson Bikes co-owner David Metzke tells Gizmag. "It's a minimal design, so it doesn't look like you are riding a science experiment." It is kind of hard to disagree on this point. Aside from the sizeable girth of the downtube aside (this is where Metzke and his team have placed the removable Sony 36 V 11.6 Ah battery), the Hard Tail looks and rides much like a normal mountain bike. Its aluminum alloy frame is painted black with a satin clear coat finish and rolls on 26-inch alloy rims with Kenda tires. There's also Suntour NEX front fork suspension for when the streets get a little rugged, and a Shimano Alivio 9-speed gear set. These are parts not normally associated with high-performance bicycles and as such, we wouldn't recommend gearing up for serious off-road endurance racing, but they performed just fine in moving around the city. The law in Australia means that the legal maximum power output for an electric bike is 250 W, as it is in much of the world. Some countries and states in the US allow for electric bikes of up to 1,000 W, but these would be considered motorbikes Down Under, bringing on a whole other set of regulations. Motor assistance on the Hard Tail therefore cuts out at 25 km/h (15 mph). The pedal assist engages pretty much instantly and intuitively, giving the bike great acceleration off the mark. In two full weeks of riding it in place of my regular bike, and commuting around 10 km (6 mil) up and down hills everyday, I never once had to really exert myself physically. And in a pleasant departure from my typical arrival at the office in the mornings, I entered entirely free of sweat, something that didn't go unnoticed by my colleagues. The battery life came in just shy of the claimed 60 km (37 mi) range, though taking into account the hills and frequency of traffic stops this wasn't all that surprising. The battery can be monitored via a large backlit LCD display mounted on the handlebars, which also displays speed, power output, power consumption and allows you to flick between the six levels of motor assistance. On the negative side, 25 km/h just ain't that fast. The easy acceleration of the Hard Tail will bring you to this speed very quickly, possibly after just a few pedals depending on which gear you're in. I quickly came to realize how regularly I travel faster than this – pretty much any time I am going downhill or on uninterrupted stretches of road with time to build up momentum. So although the Hard Tail required much less energy to get me to my destination, it also actually took a little more time. And while you are free to keep pedaling beyond this point, it becomes progressively difficult after the motor cuts out, where the direct drive creates a small but still noticeable drag. This is of course completely out of Dyson's hands, as the company is simply adhering to the laws surrounding street legal electric vehicles. But for those that like to ride in the fast lane, something lighter might be more to their liking. Electric bikes come a lot heavier than the Hard Tail, which tips the scales at 23.2 kg (51.14 lb), but lighter options can be sniffed out. The US-based ProdecoTech offers 31.8-lb (14.4-kg) titanium-framed options, while English e-bike builder Cytronex offers modified Cannondales weighing as little as 28 lb (12.7 kg). Made from more expensive materials, these will come with a higher price tag (or more bizarre shapes) than the Hard Tail, but this is where Metzke believes he has found a sweet spot. Priced at AUD$2,000 (US$1,455), this e-bike is certainly on the cheaper side, and is not a world away from what could easily be spent on a high quality road bike or commuter. So for people who aren't in a rush and looking for a gentle, super-comfortable way to catch some fresh air on their way to work, we reckon the Hard Tail from Dyson Bikes might fit the bill just nicely. Product page: Dyson Bikes

Underwater Photography of Children Playing Sports

 

Posted: 22 Jul 2015 12:03 PM PDT

La photographe Alix Martinez a créé une série de magnifiques photographies sous-marines originales. Elle met en scène des enfants pratiquant leur sport individuel ou collectif, sous l’eau d’une piscine. La technique de l’artiste donne un aspect irréel et imaginaire à ses clichés .

Improving strength and modulus in carbon fibers

 

Thu, 07/23/2015 - 10:45am Rick Robinson, Georgia Institute of Technology Prof. Satish Kumar research engineer M.G. Kamath examine the precursor and carbon fibers processed at Georgia Tech. Photo: Gary MeekCarbon fibers are stronger and lighter than steel, and composite materials based on carbon-fiber-reinforced polymers are being used in an expanding range of aerospace, automotive and other applications—including major sections of the Boeing 787 aircraft. It’s widely believed, moreover, that carbon-fiber technology has the potential to produce composites at least 10 times stronger than those in use today. A research team at the Georgia Institute of Technology has developed a novel technique that sets a new milestone for the strength and modulus of carbon fibers. This alternative approach is based on an innovative technique for spinning polyacrylonitrile (PAN), an organic polymer resin used to make carbon fibers. The work is part of a four-year, $9.8 million project sponsored by the Defense Advanced Research Projects Agency (DARPA) to improve the strength of carbon-fiber materials. The research was reported recently in Carbon. "By using a gel-spinning technique to process polyacrylonitrile copolymer into carbon fibers, we have developed next-generation carbon fibers that exhibit a combination of strength and modulus not seen previously with the conventional solution-spun method," said Satish Kumar, a professor in the Georgia Tech School of Materials Science and Engineering who leads the project. “In addition, our work shows that the gel-spinning approach provides a pathway for even greater improvements.” Kumar explained that tensile modulus—a measure of stiffness—refers to the force needed to stretch a material by a given amount. Tensile strength expresses how much force is required to actually break the material. In gel spinning, the solution is first converted to a gel; this technique binds polymer chains together and produces robust inter-chain forces that increase tensile strength. Gel spinning also increases directional orientation of fibers, which also augments strength. By contrast, in conventional solution spinning, a process developed more than 60 years ago, PAN co-polymer solution is directly converted to a solid fiber without the intermediate gel state and produces less-robust material. The gel-spun carbon fiber produced by Kumar’s team was tested at 5.5 to 5.8 Gpa—a measure of ultimate tensile strength—and had a tensile modulus in the 354 to 375 GPa range. The material was produced on a continuous carbonization line at Georgia Tech that was constructed for this DARPA project. “This is the highest combination of strength and modulus for any continuous fiber reported to-date,” Kumar said. “And at short gauge length, fiber tensile strength was measured as high as 12.1 GPa, which is the highest tensile-strength value ever reported for a PAN-based carbon fiber.” Moreover, Kumar noted, the internal structure of these gel-spun carbon fibers measured at the nanoscale showed fewer imperfections than state-of-the-art commercial carbon fibers, such as IM7. Specifically, the gel-spun fibers display a lower degree of polymer-chain entanglements than those produced by solution spinning. This smaller number of entanglements results from the fact that gel spinning uses lower concentrations of polymer than solution-spinning methods. Kumar and his team convert the gel-spun polymer mix into carbon fibers via a selective treatment process called pyrolysis, in which the spun polymer is gradually subjected to both heat and stretching. This technique eliminates large quantities of hydrogen, oxygen, and nitrogen from the polymer, leaving mostly strength-increasing carbon. “It’s important to remember that the current performance of solution-spun PAN-based carbon fibers has been achieved after many years of material and process optimization—yet very limited material and process optimization studies have been carried out to date on the gel-spun PAN fiber,” Kumar said. “In the future, we believe that materials and process optimization, enhanced fiber circularity, and increased solution homogeneity will further increase the strength and modulus of the gel-spinning method.” Source: Georgia Institute of Technology