रविवार, 17 दिसंबर 2017

ये जमानती माँ बेटे देश में उथल पुथल करवा सकते हैं

ये जमानती माँ बेटे देश में उथल पुथल करवा सकते हैं। आग लगवा सकते हैं। जो कुछ भी व्यक्ति के दिल में होता है वह बहरूपिया जुबां पे आ जाता है। 

राहुल ने अपने इरादे साफ़ कर दिए हैं ये कहकर के बीजेपी देश में जगह जगह आग लगवा रही है। अम्मा तो इनकी इतनी घबराई हुईं हैं सांप्रदायिक शब्द तीन बार हिज्जै करने के बाद भी पढ़ बोल न सकीं। कहीं ऐसा नहीं लगा ये उत्सव में आईं हैं मातमी आवाज़ और मातमी कम्पन उनके पूरे हावभाव देह मुद्रा में  दिखा। 

जिस भवन की नींव हिली हुई होती है उसमें भूकंप आते हैं। कांग्रेस संगठन के पेड कार्य -करता देश में जगह जगह आग लगवा सकते हैं और बाद में राहुल ये कह सकते हैं मैंने तो पहले ही आगाह कर दिया था -भारत धर्मी समाज को के सरकार के इरादे नेक नहीं हैं वह सांप्रदायिक विष बो रही है। 

वर्तमान बीजेपी प्रबंध अपनी सुरक्षा व्यवस्था चाक चौबंद कर ले -आने वाले दिनों में कुछ भी हो सकता है।ये ज़मानती लोग हार को अभी तक भी पचा नहीं पाए हैं ,'नेशनल हेराल्ड' इन्हें घूर रहा है। कल क्या हो इसका कोई निश्चय नहीं।  

कल के चुनावों का नतीजा जो हो लोकतंत्र में वही सर्वोपरि होता है जो जनता का फैसला होता है -

फ़िल वक्त देश में जन- मन की आवाज़ बनी सरकार है जो बहुमत से आई है। भारत धर्मी  समाज की धड़कन बनी हुई है वर्तमान केंद्र सरकार और उसके कारिंदे। 

सन्दर्भ -सामिग्री :

(१ )https://www.youtube.com/watch?v=TFVRv4oGgRw

(२ )

Rahul Gandhi Takes Over As Congress President


(३ )

शनिवार, 16 दिसंबर 2017

कलि -संतरणोपनिषद -कृष्ण द्वैपायन व्यास (मंत्र संख्या तीन ,TEXT 3 )

कलि -संतरणोपनिषद -कृष्ण द्वैपायन व्यास (मंत्र संख्या तीन ,TEXT 3 )

भगवत आदि पुरुषस्य नारायणस्य नामोच्चारण ,

मात्रेण निर्धूत कलिर्भवति। 

केवल नारायण के नाम का स्मरण करने भर से जो सभी पापों का नाशक देवता है सर्वपापहर्ता है कलियुग के प्राणी के सारे पापों का नाश हो जाता है। वह निष्पाप ,अनघ, हो जाता है। भगवान् का नाम स्मरण ही कलियुग के मल (कलिमल )को धौ डालने वाला साबुन है।

भगवान् और उसके नाम में कोई फर्क नहीं है। यह उसकी अहेतुकी कृपा ही है के हमारे सारे पाप धुल जाते हैं। उसकी किरत करने से उसका नाम स्मरण करने से। उसके नाम में इतना पावित्र्य है जो हमारे जन्मजन्मान्तरों के पापकर्मों का नाश कर देता है। हमारी आत्मा पे जमा युग-युगान्तरों के पापकर्मों का बोझ हट जाता है।

कलियुग में नाम स्मरण ही उपाय है और कोई अन्य उपाय नहीं है पाप मुक्ति का। (इस उपनिषद में महामन्त्र की महिमा का ही बखान किया गया है जिसकी विस्तार से चर्चा आगे इसी उपनिषद में होगी ). 

इस कलियुग में ऐसे भ्रष्ट गुरु भी कम नहीं है जिनके अंदर ही  कलियुग रहता है जो महा -मंत्रोचार के अलग ही तरीके बतलाते हैं। इन चाण्डालों के हृदयरूपी घर में  ही कलियुग रहता है। इनसे बचना है। रौरव नर्क में ले जाएगा इनका संग  साथ। 

हमारा अति तुच्छ लघुतर वज़ूद पूर्व जन्मों के लोभ ,मोह ,अहंकार ,काम ,से आवृत है ,अज्ञान में लिपटा हुआ है नारायण की महिमा अपार है। इस कलिकाल में ही चांडाल रूप स्वयं भू ,अपने  को ही नारायण बतलाकर भोली भाली जनता को पाप मार्ग पे प्रवृत्त कर देते हैं । 

हम श्री कृष्ण(नारायण ) की दिव्यऊर्जा(Divine Energy ) के अंश जीव -आत्मा हैं।उसी की मटेरियल एनर्जी के मायाजाल (माया )से हम ताउम्र छले जाते हैं। वह विभु है हम अनु है। वह अनंतदिव्य गुणों वाला है ,सर्वज्ञाता है हम अल्पज्ञान ,अल्प  बुद्धि हैं। सिर्फ गुणात्मक रूप में ही हम उसकी दिव्यऊर्जा के अंश हैं मात्रात्मक रूप में नहीं। हम बूँद वह सागर है ,हम स्वर्ण के एक कण मात्र हैं वह स्वर्ण ही स्वर्ण  है। और हमारा यह तुच्छ लघु अस्तित्व भी  माया से लिपटा हुआ है। महामंत्र हमें हमारे निज स्वरूप का बोध करवाता है।हमारा उससे ऐक्य भी है हम उससे अलहदा भी हैं।  

भगवान् चैतन्य  महाप्रभु (जो स्वयं कृष्ण का ही भक्त रूप अवतार है )का अचिन्त्य भेदाभेद तत्व सार यही है। 






7:04

शुक्रवार, 15 दिसंबर 2017

Baby survives after being born with heart outside her body

A baby born with her heart outside her body has survived surgery to insert it back into her chest.

Vanellope Hope Wilkins, now three weeks old, was delivered by a team of 50 medical professionals at Glenfield Hospital in Leicester, UK, on November 22.
Born with ectopia cordis, a rare congenital condition causing her heart to grow outside her body, the baby girl underwent three intensive surgeries to put her heart inside her chest. She is now on the road to recovery.
"I had prepared myself for the worst; that was my way of dealing with it. I had brought an outfit to hospital that she could wear if she died," said Naomi Findlay, Vanellope's mother, in a statement on Tuesday. "I genuinely didn't think my baby would survive, but the staff at Glenfield have been amazing."
    "I deal with babies with heart problems all the time, some of them very complicated," said Dr. Frances Bu'Lock, consultant in pediatric cardiology at Glenfield Hospital.
    "This is only the second case in 30 years that I've seen this particular condition, it's extremely rare," she said. "Vanellope is the first baby to survive this operation in the UK."
    Odds stacked against them
    An initial ultrasound scan at nine weeks had alerted Vanellope's parents, Naomi Findlay and Dean Wilkins, that their baby's heart and part of her stomach had begun to grow outside of her body.
    Bu'Lock did Naomi's ultrasound at 16 weeks, and found that while Vanellope's bowel had moved back to the correct position, her heart was still out of place.

    Three-week-old Vanellope Hope Wilkins, with her parents Naomi Findlay and Dean Wilkins, at Glenfield Hospital in Leicester.
    A blood test confirmed that the risk of other chromosomal abnormalities was low, at which point Naomi and Dean chose to fight for their daughter's life.
    Bu'Lock did not expect the baby to survive, she said. "There were so many difficulties -- she might have other body organ problems. The chances against her surviving at that stage was huge."
    In most cases, the malformation is detected in the womb and the pregnancy is terminated or results in a stillbirth. A successful delivery also brings a very high risk of infection or associated defects, according to the hospital.
    Naomi and Dean received counseling throughout the process.


    Surgeons deliver miracle

    Four teams of doctors at Glenfield -- which is part of the UK's National Health Service (NHS) -- were scheduled to deliver the baby on November 22 by caesarean section to reduce the risk of infection as well as the risk of injuring the infant heart.
    After birth, Vanellope was placed in a sterile plastic bag to reduce infection risk to her heart and keep exposed tissues moist.
    "Vanellope was born in good condition. She cried at birth and coped well with the early stabilization and her heart continued to beat effectively," said Glenfield Consultant Neonatologist Jonathan Cusack.
    ""At around 50 minutes of age, it was felt that Vanellope was stable enough to be transferred back to the main theater where she had been born to the waiting anesthetists, congenital heart disease and pediatric surgical teams who began the task of putting her entire heart back inside her chest," he said.
    While the defect in Vanellope's chest was small, the surgeons were concerned about repositioning the heart correctly to ensure it was properly attached to the veins and arteries.
    "Now she's out, she's had three surgeries and her heart is covered -- I think her chances are a lot better," said Bu'Lock, who called the surgery "challenging (rather) than complicated."
    "Cases of ectopia cordis are extremely rare but Vanellope's situation is even more unusual," said Dr. Martin Ward-Platt of the Royal College of Paediatrics and Child Health, who was not involved in the procedure. "Usually babies like Vanellope are born with a number of other complications of the heart or other organs, but from the media reports it seems this could be the only abnormality -- which makes it even more rare."

    Heart out of place

    Ectopia cordis, literally translating to "out-of-place heart," is a heart abnormality that develops during the early stages of development in the womb.
    The condition causes the heart to form either partially or wholly outside the chest cavity, generally on the neck, chest, abdomen or cervix.
    It is generally accompanied by congenital heart disease and other associated defects, leaving those affected by it with a very low chance of survival.
    The condition is estimated to affect just under eight babies per million live births, according to the hospital, with less than a 10% chance of survival.
    "To put this in context, we wouldn't expect a case like this to happen in the UK more often than once every five to 10 years," said Ward-Platt.
    New father Dean Wilkins said in a statement: "The moment she was born I realized that we had made the right decision. People always knock the NHS, but all we have seen from the team at Glenfield is kindness and a desire to keep Naomi and Vanellope safe and I can't begin to thank them for what they have done for my girls."
    Reference:http://www.cnn.com/2017/12/13/health/baby-heart-chest-surgery-intl/index.html

    Ten Health Questions That Had You Googling This Year


    What is lupus? How long does the flu last? What causes hiccups?

    Those are just some of the health-related questions that Internet surfers in the United States asked Dr. Google in 2017, according to a list provided by Google spokeswoman Evan Barbour Grippi.

    The data were collected from January to mid-December.

    A separate CNN analysis of health-related "what" and "why" questions searched worldwide on Google in 2017 included queries about the keto diet and opioids, according to Google Trends.
    What did people search for last year? Zikatraumatic brain injuries and cupping were among the most popular health-related searches in 2016.
    Here are some of the most popular health-related questions searched for this year and the answers, as provided in CNN's coverage of each.
    What are opioids? And '13 Reasons Why'?
    Around the world, "What is keto diet?" "What are opioids?" "Why is addiction a disease?" and "13 Reasons Why" were among the most popular health-related queries on Google this year, according to Google Trends.
    The keto, or ketogenic, diet quadrupled in Google searches in the past year. It involves eating more healthy fats and less carbohydrates in order to force the body to burn fat.
    Though it has seen a recent rise in popularity, the diet actually dates to the early 1920s. It was developed for people with epilepsy, as it was observed that fasting had anti-seizure properties, according to a 2008 paper in the journal Current Treatment Options in Neurology.
    This year, many people also were curious about opioids and addiction in their Google searches. Around the same time, America's opioid crisis made headlines.
    President Donald Trump declared the opioid epidemic a national public health emergency in October, as more than 2 million Americans have become dependent on or abused prescription pain pills and street drugs.
    The opioid epidemic in the United States didn't just begin. In the past seven years, opioid addiction rates nationwide climbed nearly 500%, according to an analysis from Blue Cross Blue Shield published in June.
    Many experts describe opioid addiction -- and addiction in general -- as a disease.
    "Addiction is defined as a chronic, relapsing brain disease that is characterized by compulsive drug seeking and use, despite harmful consequences. It is considered a brain disease because drugs change the brain; they change its structure and how it works," according to the National Institute on Drug Abuse.
    Also this year, adults and children alike were searching for more about the Netflix series "13 Reasons Why," based on bestselling author Jay Asher's 2007 young adult novel.
    The series, which premiered in March, tells the fictional story of a teenage girl named Hannah Baker who leaves behind 13 audio recordings after ending her own life. She addresses each mysterious recording to a person who she says played a role in her decision to kill herself. Actress and pop star Selena Gomez is an executive producer of the show.
    Even before the show debuted, some mental health experts noted that the show could pose health risks for certain young people who already have suicidal thoughts.
    Just months later, researchers found that the controversial show's premiere correlated with Google searches tied to suicide awareness, prevention and ideation.
    The search phrase "how to commit suicide" rose 26% above what would normally have been expected for that time; "suicide prevention" went up 23%; and "suicide hotline number" climbed 21%, according to a research paper published in JAMA Internal Medicine in October.
    Other experts suggested that the show could provide an opportunity to discuss suicide risk with young people, including teaching them how to identify warning signs of depression or suicidal thoughts among their peers.
    The show has been renewed for a second season.

    What causes hiccups? What is lupus?

    Another popular health question this year was "What causes hiccups?" which topped the list of trending health-related questions in the US, according to Grippi.
    Hiccups are involuntary contractions of the diaphragm muscle that separates your chest from your abdomen, and those contractions may result from a large meal, alcoholic or carbonated drinks, or sudden excitement, according to Mayo Clinic.
    The list of trending health-related questions ends with "What is lupus?" at No. 10.
    Lupus, also known as systemic lupus erythematosus or SLE, is an autoimmune disease in which the body's immune system attacks its own healthy cells and tissues instead of viruses and bacteria.
    The condition garnered attention when Selena Gomez revealed in September that she received a kidney transplant from her friend and fellow actress Francia Raisa.
    "I needed to get a kidney transplant due to my lupus," Gomez wrote in an Instagram post that showed her and Raisa in hospital beds.
    Other celebrities who have been diagnosed with lupus include television personality Nick Cannon, Grammy-winning singer Toni Braxton, actress Kristen Johnston, retired US soccer team player Shannon Boxx and singer-songwriter Seal, who wears scars of the disease on his face.
    The name "lupus," which means "wolf" in Latin, has been attributed to 13th-century physician Rogerius Frugardi, as he probably thought that scars from the disease resembled those from a wolf's bite, according to a paper published in the Journal of Cutaneous and Aesthetic Surgery in 2012.
    It is estimated that up to 322,000 people in the US have definite or probable lupus, according to the Centers for Disease Control and Prevention.

    The questions you wanted Google to answer

    What other questions were trending across the US this year? The full list of 10 also included questions about snoring and kidney stones:
    1. What causes hiccups?
    2. How to stop snoring?
    3. What causes kidney stones?
    4. Why am I so tired?
    5. How long does the flu last?
    6. What is normal blood pressure?
    7. How to lower cholesterol?
    8. What causes high blood pressure?
    9. What is ADHD?
    10. What is lupus?
    According to Google Trends, among the most popular health-related "Why is" questions worldwide were:
    1. 13 reasons why
    2. Why is addiction a disease?
    3. Why is the roof of my mouth sore?
    4. Why is apple cider vinegar good for yo
    5. u?
    6. Why is my period blood dark?

    Reference:http://www.cnn.com/2017/12/15/health/health-trends-2017-google-explainer/index.html

    A record-tying eighth planet has been found in a faraway solar system, matching our own in number.(HINDI )

    हमारे सौर परिवार में आठ ग्रह  हैं पृथ्वी समेत ,प्लूटो से ग्रह होने का दर्ज़ा कुछ बरस पहले २००६ में अंतर -राष्ट्रीय खगोल संघ ने वापस ले लिया गया था क्योंकि वह आकार में हमारे चंद्र से भी छोटा रहा है। हालांकि कुछ खगोलविद ऐसा मानते हैं के एक नौंवा ग्रह भी मौजूद है जो अभी  हमारी पकड़ में नहीं आया है। यह विशालकाय है और सौरमंडल के सबसे बाहर के ग्रह नेप्चून से भी और बाहर है। इसे फिलवक्त प्लेनेट -X कहा जा रहा है। 

    अब पहली मर्तबा हमारे सौर मंडल के बाहर एक ऐसे सितारे के भी आठवें ग्रह  का पता चला है जिस सितारे का नाम केप्लर  -९०है। इसके नौवें ग्रह  को केप्लर -९० आई (Kepler 90 i )नाम दिया गया है।  

    यह भी अपने सौर -पिता से पृथ्वी की ही तरह तीसरे स्थान पर से उसकी परिक्रमा कर रहा है.लेकिन इसकी यह परिक्रमा मात्र १४ दिनी है। इसकी सतह का तापमान झुलसाने योग्य ४२७ सेल्सियस (८०० फ़ारेनहाइट )आंका गया है। लेकिन इस सौर मंडल जिसकी गणना हमारे सौरमंडल के बाहर मौजूद तारा -परिवारों में की जाती है के सबके सब आठ ग्रह एक तंग जगह में रहते हुए ही इसकी परिक्रमा करते हैं। इनकी दूरियां अपने पितृ - सितारे से उस दूरी से भी कमतर है जो हमारी पृथ्वी सूर्य से औसतन बनाये रहती है और जिसे एक एस्ट्रोनॉमिकल यूनिट कहा जाता है। 

    अनुमान है के चर्चित तारा -तंत्र(सौरमंडल ) प्लेनेट -९० का भी अपना एक और नौंवा ग्रह हो सकता है।यह अनुपम सौरमंडल हमसे २५४५ प्रकाश बरस दूर है जबकि एक प्रकाश वर्ष का मतलब है  ५. ८ ट्रिलियन माइल्स। 

    हमारे अपने सौर मंडल के बाहर जितने भी ग्रह आदिनांक मिले हैं उन्हें एक्सोप्लेनेट्स कहा जाता है। इनके अन्वेषण में अंतरिक्ष में घूमती दूरबीन केपलर स्पेस टेलिस्कोप का बड़ा हाथ रहा है। इस दूरबीन से प्राप्त आंकड़ों से कम्प्यूटर के लिए एक एक्सोप्लेनेट टोही सॉफ्टवेयर तैयार किया जाता है। 

    यह बहुचर्चित आठवां एक्सोप्लेनेट केप्लेर -९० आई ,इसी प्रोग्रेम की सौगात है। यानी इसकी खोज मशीन ने की है किसी मनुष्य ने नहीं। अलबत्ता मशीन करती वही है जो उसे करने को कहा  जाता है। 

    हमारे सौरमंडल के बाहर अब तक कुल ३५६० एक्सोप्लेनेट्स का पता चला है इनमें से दो तिहाई  की टोह लेने में २००९ से कक्षा में तैरते केप्लर टेलिस्कोप की महती भूमिका रही आई है। समझा जाता है ऐसे ही ४५०० एक्सोपलेंट्स अभी पक्की शिनाख्त होने का इंतज़ार कर रहे हैं। 

    आलेख की मूल प्रति अंग्रेजी में भी दी जा रही है : 

     A record-tying eighth planet has been found in a faraway solar system, matching our own in number.

    Even more amazing, machines and not humans made the discovery. NASA joined with Google on Thursday to announce the finding.
    This eighth planet orbits the star known as Kepler-90. Like Earth, this new planet, Kepler-90i, is the third rock from its sun. But it's much closer to its sun — orbiting in just 14 days — and therefore a scorching 800 degrees Fahrenheit (427 Celsius) at the surface. In fact, all eight planets are scrunched up around this star, orbiting closer than Earth does to our sun.
    This is the only eight-planet solar system found like ours — so far — tying for the most planets observed around a single star.
    Our solar system had nine planets until Pluto was demoted to a dwarf planet in 2006 by the International Astronomical Union, a decision that still stands. Some astronomers, however, suspect there could be a large ninth planet out there: an elusive Planet X the size of Neptune but much farther out.
    The Kepler-90 system also could have a ninth planet or more, according to the researchers. It is 2,545 light-years away; a light-year is 5.8 trillion miles.
    Google used data collected by NASA's keen planet hunter, the Kepler Space Telescope, to develop the machine-learning computer program. It focuses on weak planetary signals — so feeble and numerous it would take humans ages to examine.
    While machine learning has been used before in the search for exoplanets — planets beyond our solar system — it's believed to be the first time an artificial neural network like this has been used to find a new world.
    "This is a really exciting discovery, and we consider it to be a successful proof of concept to be using neural networks to identify planets, even in challenging situations where the signals are very weak," said Christopher Shallue, a senior software engineer at Google in Mountain View, California.
    NASA astrophysicist Jessie Dotson, the Kepler project scientist, is "so excited to see where this goes next."
    "Who knows what potential insights might be gained," she said.
    Shallue teamed up with astronomer Andrew Vanderburg of the University of Texas at Austin to develop the program. They essentially trained a computer to identify exoplanets based on Kepler's observations in changing stellar brightness — the subtle, fleeting dip in a star's brightness when a planet passes in front of it.
    The two used a technique similar to what had been previously used by others to enable machines to distinguish between pictures of cats and dogs.
    Besides identifying Kepler-90i, the machine-learning program also confirmed an exoplanet missed by astronomers in yet another solar system: Kepler-80g, the sixth planet in that particular solar system.
    Shallue and Vanderburg plan to keep up the hunt, using the program to scour the 150,000-plus stars observed by Kepler.
    In all, more than 3,560 exoplanets have been confirmed to date — two-thirds of them spotted by the 2009-launched Kepler — with another approximately 4,500 candidates awaiting verification.
    It will be up to more advanced telescopes, like the James Webb Space Telescope targeted for launch in 2019, to study the atmospheres of these distant worlds and sniff out any traces of possible life, Vanderburg noted.
    Shallue said Google plans to release all the code needed for someone to join the exoplanet search, using a basic home computer and the publicly available Kepler data. No specialized hardware should be needed, he said.
    Neither NASA nor Google expect to put astronomers out of business.
    Shallue sees this as a tool to help astronomers have more impact and increase their productivity.
    "It certainly will not replace them at all," he assured reporters.
    The Associated Press
    This illustration made available by NASA shows a comparison of the planets in the solar system and those orbiting the star Kepler-90. An eighth planet, Kepler-90i, has been found in the faraway solar system, matching our own in numbers. This is the only eight-planet solar system found like ours _ so far. (Wendy Stenzel/NASA, Ames Research Center via AP) The Associated Press

    Referenece:Online:
    NASA: https://exoplanets.nasa.gov/

    The very real health dangers of virtual reality

    Is the magical world of virtual reality arriving in your home this holiday season?
    You're not alone. Statistics show that more than a million VR headsets were shipped during the third quarter of 2017. That number is expected to rise rapidly in 2018 as more manufacturers enter the market.
    But before you or your children try out your shiny new VR gadgets, be sure you're fully aware of the potential health risks of this technology.

      Clear the playing field

      A quick glance at the safety warnings for the major manufacturers in this space makes it clear: Playing VR without supervision and in a crowded space is risky business.
      "While wearing the product's headset you are blind to the world around you," says the safety information page for HTC's Vive. "Do not rely on the product's chaperone system for protection."
      "I see more falling than anything else," said Marientina Gotsis, an associate professor of research at the Interactive Media and Games Division of the University of Southern California. "You can trip and hit your head or break a limb and get seriously hurt, so someone needs to watch over you when you are using VR. That's mandatory."
      That includes keeping pets, small children and other obstacles -- like ceiling fans -- out of the area. Facebook's Oculus Rift includes an infographic with the product and has an online safety center with video explanations to illustrate the safety issues.

      Keep an eye on it

      One of the major health concerns about virtual reality involves the eye.
      "There are a variety of potential issues," said University of California, Berkeley optometry Professor Martin Banks, who studies visual perception in virtual environments. "One is how we affect the growth of the eye, which can lead to myopia or nearsightedness."
      Myopia is a growing problem around the world. In the United States, studies show, nearsightedness rose from only 25% of the population in the 1970s to over 40% by 2000. About10 million American adults are considered "severely nearsighted."
      "Looking at tablets, phones and the like, there's pretty good evidence that doing near work can cause lengthening of the eye and increase risk for myopia," Banks said. "We're all worried that virtual reality might make things worse."

      Add 'motion sickness'

      A good many people who use virtual reality complain of eye strain, headaches and, in some cases, nausea. Experts say that's due to the way VR affects the eye-brain connection.
      In real life, our eyes naturally converge and focus on a point in space, and our brain is so used to this that it's coupled the two responses together. Virtual reality separates those, confusing the brain.
      Virtual reality can confuse the eye-brain connection.
      "In a virtual environment, the way we look and interact is changed because we may be projecting onto the eyes something that looks far away, but in reality, it's only a few centimeters from the eye," said Walter Greenleaf, a behavioral neuroscientist who has studied VR in medical settings for over 30 years.
      Science calls that the "vergence-accommodation conflict" and isn't quite sure how serious it might be. "We're tricking the brain," said Greenleaf, who works with Stanford University's Virtual Human Interaction Lab, "and we don't know the long-term effect of this."
      Most of us look at cell phones and tablets for a short time before looking up, which minimizes their negative effect on the eye. But with VR, it's all too easy to become immersed in that out-of-body experience.
      How long is too long to use virtual reality in one sitting? Manufacturers like Oculus suggest a "10 to 15 minute break every 30 minutes, even if you don't think you need it." But Gotsis says that's not based on much science.
      Little research has been done on the effects of VR on children.
      "Most of what is on the market right now has little research behind it," she says. "Cumulative exposure without us really knowing what is going on is an issue."
      Gotsis says the quality of the virtual reality game also plays a role in how we react.
      "A lot of content is not well-made, with a lot of flickering things and objects that come at you too fast or too close, and that can produce eye strain," she said She insists that any eyestrain be considered a signal to cease playing.
      "Damage from eye strain can sometimes be very sudden, so if something is uncomfortable, just stop, take it off and stop looking at it," Gotsis warned. "Don't feel trapped and mesmerized in the content. Just stop."

      Pre-existing conditions

      It's not just the eyes that might be harmed. "Listening to sound at high volumes can cause irreparable damage to your hearing," states Oculus Rift.
      "Over time, increasingly loud audio may start to sound normal but can actually be damaging your hearing," Sony's PlayStation adds, suggesting that a user lower the volume if they can't hear people speaking around them while they're playing.
      Most devices also include a warning to see a doctor before use if you are "pregnant, elderly, or have pre-existing conditions that may affect your virtual reality experience such as vision abnormalities, psychiatric disorders, heart conditions, or other serious medical conditions."
      That warning includes implanted medical devices, such as cardiac pacemakers, hearing aids and defibrillators, as well as anyone with epilepsy or a history of seizures and blackouts. But manufacturers say some people can seize even without a history of blackouts, especially those younger than 20, so manufacturers suggest keeping an eye out for involuntary muscle twitches and loss of balance as a signal of a potential problem.
      Daydream also suggests avoiding play entirely if you're "intoxicated, overly tired, or are suffering from a cold, headache, upset stomach, or other sickness" because the experience of virtual reality might make you feel worse.
      And if that's not enough, Daydream View warns that sharing the device could spread contagious diseases and infections and even cause skin irritation.

      Children at most risk

      Gotsis believes that families with younger children should be especially cautious with virtual reality, even if they purchased the game for teens or young adults.
      "It's almost impossible to hold up something shiny in front of a young child and then say 'no, you can't have this,' " she said. "So parents have to tell the older child that part of your responsibility is to take care of their younger siblings, to help them understand they shouldn't use it."
      If they do try it, Gotsis adds, the younger the child, the shorter the exposure should be.
      "Children may not know how to communicate discomfort of any sort, such as visual discomfort or motion sickness, so you don't want prolonged exposure on screen," she said.
      Jeremy Bailenson, director of Stanford's Virtual Human Interaction Lab, uses VR himself and on subjects in his lab daily. Yet he has let his 6-year-old daughter use it only four times in her life, each time for a duration of only five minutes.
      "We read a lot of new studies in our work," he said, "but what we are seeing is a ton of studies on medical applications and not many with young kids, and not really any with really young kids."
      Berkeley's Banks agrees. "The research has been done primarily in young adults ... so we don't really know what is going to happen to a young child."
      Most major manufacturers have set a cutoff age: no use of the device for children under the age of 13. Playstation VR set the age limit at 12; HTC's Vivedoesn't mention an age, only that it is not "designed to be used by children."
      Google Cardboard has no age restriction but says it should not be used without adult supervision.
      Stanford's Greenleaf believes that until research catches up, parents, "and in fact everyone, should be very judicious" about use.
      "I would be concerned for everyone who uses this," he said. "You don't have to have a young brain to have an impact."

      Content is key

      Virtual reality content can also affect your perception of reality.
      "VR can be stored in the brain's memory center in ways that are strikingly similar to real-world physical experiences," said Stanford's Bailenson, author of the forthcoming book "Experience on Demand," about his two decades of research on the psychological effects of virtual reality. "When VR is done well, the brain believes it is real."
      That's great if the content is fun, educational or inspirational. For example, research shows that adults can be taught to recycle, increase their physical activity or become more empathetic to those of different races if they see themselves doing so virtually.
      What happens if the VR content is scary or violent?
      But what if the content is scary or combative? Some of today's popular VR games allow you to fight off bloody zombies, get a "virtual tour of hell," battle "endless waves of combatants" and kill as many as you can in "survival horror." In one game, you can even shoot yourself in the head.
      The health and safety page for Google's Daydream View says it straight out:
      "If the content is frightening, violent, or anxiety provoking, it can cause your body to react physically, including increasing your heart rate and blood pressure. It can also, in some individuals, cause psychological reactions, including anxiety, fear, or even Post Traumatic Stress Disorder."
      Studies show that adolescents can react badly to being socially excluded in virtual environments.
      "If you were to do this in the real world, how would it affect you? That's the way to think about virtual reality," Bailenson said, adding that research shows becoming someone else in VR produces greater changes in real-life attitudes and behavior than watching video or doing role playing.
      "So don't think of VR as a 'media experience,' because the brain sees it as similar to an actual experience," he said. "If it's an activity that you're ethically not comfortable with in real life, don't do it. If you think of it that way, the guidelines on what you want to do in VR become very clear."

      Content and kids

      It should come as no surprise that studies show children may be even more susceptible to confusing virtual reality with the real thing, with the youngest at most risk. In a 2009 study, young elementary children watched their virtual doppelgänger swimming with orcas. When these kids were questioned a week later, they said they believed their virtual experience to be real.
      In a recent study by Jakki Bailey of the University of Texas, funded by the nonprofit Sesame Workshop, 55 children between the ages of 4 and 6 played the game Simon Says with the furry blue monster Grover, a popular character. Half of the children played in virtual reality; the other half played with Grover's character on a TV. The games lasted five minutes.
      The good news, says Bailenson, is that none of the children in the VR experience became dizzy or had unpleasant physical reactions to their short exposure.
      "But the children who saw Grover in VR saw him as more real," he said. "Grover was more influential in immersive VR than on TV, and it was harder for the children to inhibit their actions and not do what Grover did."
      It's not just little ones that might internalize a VR scenario. Older adolescents were also found to be painfully sensitive to being socially excluded in a virtual environment.
      This means parents need to be careful about the type of VR content they allow their children to view, experts say.
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      "A spider can be a fun spider or a scary spider. I don't know what it's like until I actually try it," Gotsis said. "So I find that nothing will replace the parent doing the experience themselves and saying 'OK, this is fine for my child.' And then do it with them. Walk them through it. There's a huge difference between experiencing something alone or with others."
      And as long as parents do their job, Bailenson believes, future research will show that virtual reality can be enjoyed by children without harm.
      "I'm not worried about kids using VR. I'm worried about kids using any media uncontrolled," he said. "Parents need to be careful, active and participating, because the VR medium is more powerful than traditional media. But with proper adult supervision, using it infrequently, I think it's going to turn out to be just fine."

      Reference:http://www.cnn.com/2017/12/13/health/virtual-reality-vr-dangers-safety/index.html