EXPERIMENTS ON PHOTOSYNTHESIS

Test tube and funnel experiment

The test tube funnel experiment demonstrates that oxygen is evolved during photosynthesis. A few branches of Hydrilla are kept in a beaker containing pond water in which a small amount of sodium bicarbonate is dissolved. The branches are covered with a glass funnel and a test tube full of water is kept inverted over the stem of the funnel as shown in the figure. Now the apparatus is kept in sunlight for 4 to 6 hours. The gas bubbles may be observed from the ends of hydrilla branches kept within the glass funnel. These gas bubbles are collected in the test tube by the downward displacement of water. The gas is tested for oxygen. When a burnt splinter is taken near the mouth of the tube, it glows brightly and proves that the gas is oxygen.The test tube and funnel experiment demonstrates that oxygen evolves during photosynthesis.

You tube link : http://youtu.be/4oNeULIg_Yo

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What is Holme’s signal ?

          Containers which have a perforated bottom and a hole at the top are filled with calcium phosphide and calcium carbide. These are thrown into the sea. Water enters the container through the bottom and reacts with calcium carbide and calcium phosphide to give acetylene and phosphine. Phosphine gets ignited spontaneously as it comes in contact with air and also ignites acetylene. Thus a bright red flame is produced which is accompanied by huge smoke due to the burning of phosphine. This serves as a signal to the approaching ships.

Youtube link :   http://www.youtube.com/watch?v=wdMEF6MbJB4&feature=plcp


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Bittersweet result for dark chocolate

UK scientists have clinically proven that consuming polyphenol-rich dark chocolate has health benefits for overweight and obese females, whilst showing adverse effects for polyphenol-deficient chocolate.

Evidence already shows that polyphenol-rich dark chocolate can benefit blood pressure and glucose levels in healthy people, thanks to dark chocolate's antioxidant properties. Fewer studies have examined the involvement of the endocrine system – glands that secrete hormones – in mediating the cardiometabolic health-effects of polyphenols, until now.

Suzana Almoosawi from Medical Research Council Human Nutrition Research, in Cambridge, and her colleagues, applied these findings to a group of healthy women with a range of body mass indexes (BMIs). Obesity is often linked to numerous chronic diseases, such as hypertension and type 2 diabetes, so the team were keen to study the metabolic effects observed for different concentrations of polyphenols in dark chocolate, across a range of BMIs.

BMI is a number calculated using a person’s weight and height, which provides an indication of body fat. In this study, the group consisted of normal (19–25kg/m²), overweight (>25kg/m²) and obese (>30kg/m²) women. The single-blind, randomised study involved the consumption of polyphenol-rich dark chocolate (500mg of polyphenols), or a polyphenol-deficient dark chocolate placebo, over a four week period. ‘The placebo matched the polyphenol-rich dark chocolate for taste, texture, colour and macronutrient composition, but contained no polyphenols,’ explains Almoosawi.

On examining the metabolic effects on each female, the team found that the polyphenol-deficient placebo had an adverse effect on insulin sensitivity, antioxidant status, glucose levels and blood pressure. ‘Of note is that beneficial effects on metabolic endpoints were most readily observed in subjects with a BMI over 25,’ says Francisco Villarreal, an expert in cardiac mechanics from the University of California-San Diego, US. ‘This suggests that polyphenol-rich dark chocolate is helping to counter the effects of a high BMI, and in this manner potentially reducing cardiometabolic risks,’ he adds.

‘We hope that the findings from this research will encourage the industry to consider making polyphenol-rich chocolate available on the market,’ says Almoosawi. ‘However, we are still faced by many challenges. We still don’t know the implications of consuming large amounts of polyphenols and whether there could be adverse effects associated with long-term consumption.The health benefits of consuming polyphenol-rich dark chocolate should still be carefully balanced against any long-term adverse effects.’

Courtesy RSC Advancing the chemical sciences (Chemistry World)
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"A bacterium that did not live on arsenic"

Life as we know it does not include a bacterium that is able to live off arsenic, according to two papers published online by the journal Science.

In December 2010, a sensational discovery of a unique bacterium isolated from the toxic waters of Mono Lake in California was announced in the same journal. The bacterial strain, GFAJ-1, was substituting “arsenic for phosphorus to sustain its growth,” declared Felisa Wolfe-Simon, then at the NASA Astrobiology Institute in the U.S., and 11 other scientists in their paper.

Life forms on Earth rely on six elements to build their molecules — oxygen, carbon, hydrogen, nitrogen, sulphur and phosphorus. There was, it seemed, at least one organism capable of substituting arsenic, which is usually toxic, when phosphorus was not available. The GFAJ-1 bacterium was able to use arsenic in this manner in its DNA and proteins, according to Dr. Wolfe-Simon and her colleagues.

The implications were enormous. “The definition of life has just expanded,” remarked a senior official of the U.S. space agency, NASA, in a press release.

But many in the scientific community were unimpressed, arguing that extraordinary claims should be matched by similar levels of proof. The evidence that had been put forward for arsenic being incorporated into the bacterium’s DNA was seen as questionable. In May last year, Science published eight technical comments that raised several issues with the paper.

Now, two teams of scientists have independently studied the bacterium using much more stringent procedures and tests. One of them was led by Rosemary Redfield of the University of British Columbia in Canada, whose forthright critique of the original paper on her blog garnered a great deal of attention . The other was a group of Swiss scientists at ETH Zurich.

The GFAJ-1 bacterium “does not break the long-held rules of life, contrary to how Wolfe-Simon had interpreted her group’s data,” said Science in an editorial statement that accompanied the publication of the two papers.

The new research clearly showed that the bacterium could not substitute arsenic for phosphorus to survive. Instead, the two papers revealed that the medium used to growth the organism in the original experiments contained enough phosphate contamination to support its growth.

This bacterium was likely to be adept at scavenging phosphate under harsh conditions, which would help to explain why it could grow even when arsenic was present within the cells, statement noted.

But, as the journal also pointed out, the bacterium’s extraordinary resistance and its arsenic tolerance mechanisms would be of interest for further study.

Courtesy The Hindu
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Girls suffer from maths anxiety more than boys

LONDON: Girls often fail to do just as well at math as boys because of heightened fear and apprehension over number problems, a new study has claimed. The study, published in the journal Behavioral and Brain Functions, found that a number of school-age children suffer from mathematics anxiety, but girls' maths performance is more likely to suffer than boys as a result.

Mathematics anxiety is a state of discomfort associated with performing mathematics tasks and is thought to affect a notable proportion of both children and adults, having a negative impact on their mathematics performance.

In the study, researchers from Cambridge University in the UK investigated 433 secondary school children whether mathematics anxiety has any effect on mathematics performance on boys and girls. The researchers controlled for test anxiety, a related construct, but which isn't typically controlled for in mathematics anxiety studies.

They found children with higher mathematics anxiety have a lower mathematics performance, and girls showed higher levels of mathematics anxiety than boys.

http://timesofindia.indiatimes.com/home/science/Girls-suffer-from-maths-anxiety-more-than-boys/articleshow/14791441.cms

Courtesy The Times of India

What next after a Higgs boson-like particle?

The ATLAS (A Toroidal LHC Apparatus) collaboration at CERN has announced the sighting of a Higgs boson-like particle in the energy window of 125.3 ± 0.6 GeV. The observation has been made with a statistical significance of 5 sigma. This means the chances of error in their measurements are 1 in 3.5 million, sufficient to claim a discovery and publish papers detailing the efforts in the hunt.

Rolf-Dieter Heuer, Director General of CERN since 2009, said at the special conference called by CERN in Geneva, “It was a global effort, it is a global effort. It is a global success.” He expressed great optimism and concluded the conference saying this was “only the beginning.”

Another collaboration, called CMS (Compact Muon Solenoid), announced the mass of the Higgs-like particle with a 4.9 sigma result. While insufficient to claim a discovery, it does indicate only a one-in-two-million chance of error.

Joe Incandela, CMS spokesman, added, “We’re reaching into the fabric of the universe at a level we’ve never done before.”

The LHC will continue to run its experiments so that results revealed on Wednesday can be revalidated before it shuts down at the end of the year for maintenance. Even so, by 2013, scientists, such as Dr. Rahul Sinha, a participant of the Belle Collaboration in Japan, are confident that a conclusive result will be out.

“The LHC has the highest beam energy in the world now. The experiment was designed to yield quick results. With its high luminosity, it quickly narrowed down the energy-ranges. I’m sure that by the end of the year, we will have a definite word on the Higgs boson’s properties,” he said.

However, even though the Standard Model, the framework of all fundamental particles and the dominating explanatory model in physics today, predicted the particle’s existence, slight deviations have been observed in terms of the particle’s predicted mass. Even more: zeroing in on the mass of the Higgs-like particle doesn’t mean the model is complete. While an answer to the question of mass formation took 50 years to be reached, physicists are yet to understand many phenomena. For instance, why aren’t the four fundamental forces of nature equally strong?

The weak, nuclear, electromagnetic, and gravitational forces were born in the first few moments succeeding the Big Bang 13.75 billion years ago. Of these, the weak force is, for some reason, almost 1 billion, trillion, trillion times stronger than the gravitational force! Called the hierarchy problem, it evades a Standard Model explanation.

In response, many theories were proposed. One theory, called supersymmetry (SUSY), proposed that all fermions, which are particles with half-integer spin, were paired with a corresponding boson, or particles with integer spin. Particle spin is the term quantum mechanics attributes to the particle’s rotation around an axis.

Technicolor was the second framework. It rejects the Higgs mechanism, a process through which the Higgs boson couples stronger with some particles and weaker with others, making them heavier and lighter, respectively.

Instead, it proposes a new form of interaction with initially-massless fermions. The short-lived particles required to certify this framework are accessible at the LHC. Now, with a Higgs-like particle having been spotted with a significant confidence level, the future of Technicolor seems uncertain. However, “significant constraints” have been imposed on the validity of these and such theories, labelled New Physics, according to Prof. M.V.N. Murthy of the Institute of Mathematical Sciences (IMS), whose current research focuses on high-energy physics

Courtesy The Hindu

Satellite communication

Space technology has witnessed a phenomenal growth, since the launch of man-made satellite Sputnik in 1957. One of the most significant applications of space technology has been in the field of communications. The people over world watch international events like Olympic games via satellite. A number of countries are using satellites for military communications, which include services to ships, air crafts and land mobile terminals. Several direct TV broadcasting satellite systems are also being used.

Satellite communication is basically a microwave link repeater. A satellite receives energy from an earth station, amplifies it and returns it to each at a frequency about 2 GHz away from the uplink frequency (earth to satellite) . This prevents interference between the uplink and the downlink (satellite to earth). Satellite so used is a geostationary satellite which appears to be stationary at a given spot above the equator. Actually, it moves with the same angular velocity as the earth i.e. it completes one revolution per 24 hours and hence appears to be stationed over one spot on the globe. Satellite orbiting the earth will be geostationary when it is about 36,000 km away from the earth. A satellite in space links many earth stations. The user is connected to the earth station through terrestrial network. This network may assume various configurations including a telephone switch or a dedicated link to the earth station. Signal generated by the user is processed and transmitted from the earth station to the satellite. The satellite receives the modulated RF carrier at the pre-determined uplink frequencies from all the earth stations in the network, amplifies these frequencies and then re-transmits them back to earth at downlink frequencies. The downlink frequencies are kept different from the uplink frequencies in order to avoid interference. The modulated carrier received at receiving earth station is processed to get back the original baseband signal. This signal is then sent to the user through a terrestrial network. As per WARC (World Administrative Radio Conference) 1979 allocation, commercial communication satellites use 500 MHz bandwidth near 6 GHz for uplink transmission and use 500 MHz bandwidth near 4 GHz for downlink transmission. In actual practice, uplink of 5.725 -- 7.075 GHz is used while downlink of 3.4 -- 4.8 GHz is used.

REF : http://www.youtube.com/watch?v=t9nDMl9xNmg