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The effect of breast cancer screening is declining

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The effect of breast cancer screening is declining

Screening for breast cancer has a cost. This is shown by a Danish/Norwegian study that analysed 10,580 breast cancer deaths among Norwegian women aged 50 to 75 years.

“The beneficial effect of screening is currently declining because the treatment of cancer is improving. Over the last 25 years, the mortality rate for breast cancer has been virtually halved,” says Henrik Støvring, who is behind the study.

According to the researcher, the problem is that screenings lead to both overdiagnosis and overtreatment, which has a cost both on a human level and in terms of the economy.

Overdiagnosis and overtreatment

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When the screening was introduced, the assessment was that around twenty per cent of the deaths from breast cancer among those screened could be averted. While this corresponded to approximately 220 deaths a year in Denmark 25 years ago, today the number has been halved.

The study shows that in 1996 it was necessary to invite 731 women to avoid a single breast cancer death in Norway, you would have to invite at least 1364 and probably closer to 3500 to achieve the same result in 2016.

On the other hand, the adverse effects of screening are unchanged.

“One in five women aged 50-70, who is told they have breast cancer, has received a ‘superfluous’ diagnosis because of screening — without screening, they would never have noticed or felt that they had breast cancer during their lifetime,” says the researcher.

One in five corresponds to 900 women annually in Denmark. In addition, every year more than 5000 women are told that the screening has given rise to suspicion of breast cancer — a suspicion that later turns out to be incorrect.

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Peaceful, small nodes — but in who?

Henrik Støvring notes that the result is not beneficial for the screening programmes. According to him, the Norwegian results can also be transferred to Denmark. Here, women between 50 and 69 are offered a mammogram screening every second year. This is an X-ray examination of the breast, which can show whether the woman has cellular changes that could be breast cancer.

The Danish screening programme became a national programme offered to all woman in the age group in 2007 — three years after the Norwegians. Approx. 300,000 Danish women are invited to screening for breast cancer every year.

According to the researcher, the challenge is that we are not currently able to tell the difference between the small cancer tumours that will kill you and those that will not. Some of these small nodes are so peaceful or slow-growing that the woman would die a natural death with undetected breast cancer, if she had not been screened. But once a cancer node has been discovered, it must of course be treated, even though this was not necessary for some of the women — we just do not know who.

“The women who are invited to screening live longer because all breast cancer patients live longer, and because we have got better drugs, more effective chemotherapy, and because we now have cancer care pathways, which mean the healthcare system reacts faster than it did a decade ago,” says Henrik Støvring.

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Materials provided by Aarhus University. Original written by Helle Horskjær Hansen. Note: Content may be edited for style and length.

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Thin-film photovoltaic technology combines efficiency and versatility

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Thin-film photovoltaic technology combines efficiency and versatility

Stacking solar cells increases their efficiency. Working with partners in the EU-funded PERCISTAND project, researchers at the Karlsruhe Institute of Technology (KIT) have produced perovskite/CIS tandem solar cells with an efficiency of nearly 25percent- the highest value achieved thus far with this technology. Moreover, this combination of materials is light and versatile, making it possible to envision the use of these tandem solar cells in vehicles, portable equipment, and devices that can be folded or rolled up. The researchers present their results in the journal ACS Energy Letters.

Perovskite solar cells have made astounding progress over the past decade. Their efficiency is now comparable to that of the long-established silicon solar cells. Perovskites are innovative materials with a special crystal structure. Researchers worldwide are working to get perovskite photovoltaic technology ready for practical applications. The more electricity they generate per unit of surface area, the more attractive solar cells are for consumers

The efficiency of solar cells can be increased by stacking two or more cells. If each of the stacked solar cells is especially efficient at absorbing light from a different part of the solar spectrum, inherent losses can be reduced and efficiency boosted. The efficiency is a measure of how much of the incident light is converted into electricity. Thanks to their versatility, perovskite solar cells make outstanding components for such tandems. Tandem solar cells using perovskites and silicon have reached a record efficiency level of over 29percent, considerably higher than that of individual cells made of perovskite (25.7percent) or silicon (26.7percent).

Combining Perovskites with CIS for Mobility and Flexibility

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Combining perovskites with other materials such as copper-indium-diselenide (CIS) or copper-indium-gallium-diselenide (CIGS) promises further benefits. Such combinations will make it possible to produce light and flexible tandem solar cells that can be installed not only on buildings but also on vehicles and portable equipment. Such solar cells could even be folded or rolled up for storage and extended when needed, for example on blinds or awnings to provide shade and generate electricity at the same time.

An international team of researchers headed by Dr. Marco A. Ruiz-Preciado and tenure-track professor Ulrich W. Paetzold from the Light Technology Institute (LTI) and the Institute of Microstructure Technology (IMT) at KIT has succeeded in producing perovskite/CIS tandem solar cells with a maximum efficiency of 24.9percent (23.5percent certified). “This is the highest reported efficiency for this technology and the first high efficiency level reached at all with a nearly gallium-free copper-indium diselenide solar cell in a tandem,” says Ruiz-Preciado. Reducing the amount of gallium results in a narrow band gap of approximately one electron volt (eV), which is very close to the ideal value of 0.96eV for the lower solar cell in a tandem.

CIS Solar Cells with Narrow Band Gap- Perovskite Solar Cells with Low Bromine Content

The band gap is a material characteristic that determines the part of the solar spectrum that a solar cell can absorb to generate electricity. In a monolithic tandem solar cell, the band gaps must be such that the two cells can produce similar currents to achieve maximum efficiency. If the lower cell’s band gap changes, the upper cell’s band gap has to be adjusted to the change, and vice versa.

To adjust the band gap for efficient tandem integration, perovskites with high bromine content are usually used. However, this often leads to voltage drops and phase instability. Since the KIT researchers and their partners use CIS solar cells with a narrow band gap at the base of their tandems, they can produce their upper cells using perovskites with low bromine content, which results in cells that are more stable and efficient.

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“Our study demonstrates the potential of perovskite/CIS tandem solar cells and establishes the foundation for future development to make further improvements in their efficiency,” says Paetzold. “We’ve reached this milestone thanks to the outstanding cooperation in the EU’s PERCISTAND project and, in particular, thanks to our close cooperation with the Netherlands Organisation for Applied Scientific Research.” Important groundwork was done in the CAPITANO project funded by Germany’s Federal Ministry for Economic Affairs and Climate Action (BMWK).

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Materials provided by Karlsruher Institut für Technologie (KIT). Note: Content may be edited for style and length.

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Ancient microbes may help us find extraterrestrial life forms

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Ancient microbes may help us find extraterrestrial life forms

Using light-capturing proteins in living microbes, scientists have reconstructed what life was like for some of Earth’s earliest organisms. These efforts could help us recognize signs of life on other planets, whose atmospheres may more closely resemble our pre-oxygen planet.

The earliest living things, including bacteria and single-celled organisms called archaea, inhabited a primarily oceanic planet without an ozone layer to protect them from the sun’s radiation. These microbes evolved rhodopsins — proteins with the ability to turn sunlight into energy, using them to power cellular processes.

“On early Earth, energy may have been very scarce. Bacteria and archaea figured out how to use the plentiful energy from the sun without the complex biomolecules required for photosynthesis,” said UC Riverside astrobiologist Edward Schwieterman, who is co-author of a study describing the research.

Rhodopsins are related to rods and cones in human eyes that enable us to distinguish between light and dark and see colors. They are also widely distributed among modern organisms and environments like saltern ponds, which present a rainbow of vibrant colors.

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Using machine learning, the research team analyzed rhodopsin protein sequences from all over the world and tracked how they evolved over time. Then, they created a type of family tree that allowed them to reconstruct rhodopsins from 2.5 to 4 billion years ago, and the conditions that they likely faced.

Their findings are detailed in a paper published in the journal Molecular Biology and Evolution.

“Life as we know it is as much an expression of the conditions on our planet as it is of life itself. We resurrected ancient DNA sequences of one molecule, and it allowed us to link to the biology and environment of the past,” said University of Wisconsin-Madison astrobiologist and study lead Betul Kacar.

“It’s like taking the DNA of many grandchildren to reproduce the DNA of their grandparents. Only, it’s not grandparents, but tiny things that lived billions of years ago, all over the world,” Schwieterman said.

Modern rhodopsins absorb blue, green, yellow and orange light, and can appear pink, purple or red by virtue of the light they are not absorbing or complementary pigments. However, according to the team’s reconstructions, ancient rhodopsins were tuned to absorb mainly blue and green light.

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Since ancient Earth did not yet have the benefit of an ozone layer, the research team theorizes that billions-of-years-old microbes lived many meters down in the water column to shield themselves from intense UVB radiation at the surface.

Blue and green light best penetrates water, so it is likely that the earliest rhodopsins primarily absorbed these colors. “This could be the best combination of being shielded and still being able to absorb light for energy,” Schwieterman said.

After the Great Oxidation Event, more than 2 billion years ago, Earth’s atmosphere began to experience a rise in the amount of oxygen. With additional oxygen and ozone in the atmosphere, rhodopsins evolved to absorb additional colors of light.

Rhodopsins today are able to absorb colors of light that chlorophyll pigments in plants cannot. Though they represent completely unrelated and independent light capture mechanisms, they absorb complementary areas of the spectrum.

“This suggests co-evolution, in that one group of organisms is exploiting light not absorbed by the other,” Schwieterman said. “This could have been because rhodopsins developed first and screened out the green light, so chlorophylls later developed to absorb the rest. Or it could have happened the other way around.”

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Moving forward, the team is hoping to resurrect model rhodopsins in a laboratory using synthetic biology techniques.

“We engineer the ancient DNA inside modern genomes and reprogram the bugs to behave how we believe they did millions of years ago. Rhodopsin is a great candidate for laboratory time-travel studies,” Kacar said.

Ultimately, the team is pleased about the possibilities for research opened up by techniques they used for this study. Since other signs of life from the deep geologic past need to be physically preserved and only some molecules are amenable to long-term preservation, there are many aspects of life’s history that have not been accessible to researchers until now.

“Our study demonstrates for the first time that the behavioral histories of enzymes are amenable to evolutionary reconstruction in ways that conventional molecular biosignatures are not,” Kacar said.

The team also hopes to take what they learned about the behavior of early Earth organisms and use it to search the skies for signs of life on other planets.

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“Early Earth is an alien environment compared to our world today. Understanding how organisms here have changed with time and in different environments is going to teach us crucial things about how to search for and recognize life elsewhere,” Schwieterman said.

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