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Atomically-Thin Carbon Generates its Own Magnetic Field – AZoQuantum

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A new study performed by an international research team under the guidance of the University of Göttingen determines the fact that atomically thin carbon produces its own magnetic field.

Scanning electron microscope image of a contacted, two-atom-thick, free-floating graphene flake with a free-floating metal bridge hovering above it. Image Credit: Fabian Geisenhof/Jakob Lenz.

Generally, the electrical resistance of a material relies greatly on its basic properties and physical dimensions. Yet, under special conditions, this resistance has the ability to adopt a determined value that is independent of the fundamental material properties and “quantized” (implying that it varies in discrete steps instead of changing constantly).

Mostly, this quantization of electrical resistance takes place within powerful magnetic fields and at very low temperatures when electrons tend to move in a two-dimensional fashion. Currently, a research group headed by the University of Göttingen has been successful in illustrating this effect at low temperatures in the total absence of a magnetic field in naturally occurring double-layer graphene, which is merely two atoms thick.

The findings of the study have been published in the journal Nature.

The research team from the University of Göttingen, Ludwig Maximilian University of Munich, and the University of Texas (Dallas) has utilized two-layer graphene in its natural form. The contact of fragile graphene flakes is done with the help of standard microfabrication methods, and the flake is placed so that it freely hangs, similar to a bridge, and connected at the edges with the help of two metal contacts.

A quantization of electrical resistance at low temperatures and nearly undetectable magnetic fields has been displayed by the highly clean double-layers of graphene. The electrical current also flows without losing energy.

The reason behind this mechanism is a form of magnetism that is not produced in the normal way as seen in traditional magnets (that is, by the arrangement of the intrinsic magnetic moments of electrons), but by the motion of the charged particles in the graphene double-layer itself.

In other words, the particles generate their own intrinsic magnetic field, which leads to the quantization of the electrical resistance.

Thomas Weitz, Professor, Institute of Physics, University of Göttingen

The reason why this effect is considered to be unique is not just that it only needs an electric field, but also that it takes place in eight various versions that could be regulated by applied electric and magnetic fields. This leads to a high degree of control since the effect can be enabled and disabled and the direction of movement of the charged particles can also be reversed.

This makes it a really interesting candidate for potential applications, for example, in the development of innovative computer components in the field of spintronics, which could have implications for data storage.

Thomas Weitz, Professor, Institute of Physics, University of Göttingen

Weitz added, “In addition, it is an advantage that we can show this effect in a system comprising a simple and naturally occurring material. This is in stark contrast to the recently popularizedheterostructures’, which require a complex and precise composition of different materials.”

Yet, the effect should first be further analyzed, and ways to stabilize it at higher temperatures need to be discovered. This has to be done as at present it can only occur at up to 5 degrees above absolute zero (the latter being 273 °C below 0 °C).”

Journal Reference:

Geisenhof, F. R., et al. (2021) Quantum anomalous Hall octet driven by orbital magnetism in bilayer graphene. Nature. doi.org/10.1038/s41586-021-03849-w.

Source: https://www.uni-goettingen.de/en/1.html

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The body of a Ugandan Olympic athlete who was set on fire by her partner is received by family

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NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.

Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.

She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.

Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.

“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.

It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.

Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.

Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.

Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.

“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.

He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.

Kenya’s high rates of violence against women have prompted marches by ordinary citizens in towns and cities this year.

Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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B.C. sets up a panel on bear deaths, will review conservation officer training

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VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.

Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”

Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.

“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.

B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.

Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.

Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.

Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.

“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”

Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”

“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.

Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.

“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.

This report by The Canadian Press was first published Sept. 9, 2024.

The Canadian Press. All rights reserved.

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