US researchers believe they've figured out why some people are magnets for mosquito bites while others are ignored by the blood sucking insects.

Mosquitoes being more attracted to some people than others is an observed phenomenon but one that is poorly understood, the research to be published in the scientific journal Cell notes.

Researchers from The Rockefeller University, a New York-based postgraduate research institution, identified carboxylic acids on the skin as an attractant that could lure mosquitoes.

People with significantly higher levels of the acids were more attractive to mosquitoes.

Even mutant mosquitoes without the receptors to smell the acids were still more attracted to those with higher acid levels on their skin.

"This suggests that mosquitoes with significant olfactory deficits are still able to tell the difference between individual people," the research notes.

Attractiveness can vary wildly.

The researchers determined an "attraction score" based on how mosquitoes flocked to their subjects, finding the most attractive person for the mosquitoes scored four times higher than the second most.

Compared to the least attractive, their score was 100 times higher.

The researchers believe their findings provide more scientific reasoning for the phenomenon of mosquito attraction than existing theories based on blood type, or the consumption of B vitamins or garlic as a home repellent.

However, uncertainties remain.

The specific chemical mechanism that differentiates the attractiveness of people to mosquitoes is still unclear, the research notes, while the consistency of skin odour over time is also unknown, particularly "the markedly less intense skin odour that emanates from body sites commonly bitten by mosquitoes".

The research could inform the development of more effective insect repellents.

© AAP 2022

The trial for the man accused of raping Brittany Higgins is coming to an end with the defence set to complete its closing argument.

Former Liberal Party staffer Bruce Lehrmann has pleaded not guilty to sexual intercourse without consent.

He has undergone a nearly three week criminal trial in the ACT Supreme Court.

Closing arguments began on Tuesday after the prosecution completed its case with evidence from more than 20 witnesses.

Prosecutor Shane Drumgold urged the jury to disregard discussions of political movements and workplace cultures sparked by the case.

He said the case was not about the culture inside Parliament House or the Me Too movement, but about what happened on a couch inside a minister's office in the early hours of Saturday, March 23, 2019.

Mr Drumgold said Ms Higgins had been a credible and honest witness whose version of events that night had not wavered.

Meanwhile, the prosecutor said Lehrmann had given inconsistent accounts about his reasons for being at parliament on the night of the alleged assault to the security guards, to his boss and to the police.

He suggested Lehrmann's intent was to go to Parliament House so that he could be alone with the "drunk" and "vulnerable" Ms Higgins.

Mr Drumgold also said after the alleged rape Ms Higgins was caught in the middle of "strong political forces".

"We say she was right to be scared, she was right to be cautious and she was right to move slowly and carefully," he said.

But Lerhmann's defence lawyer Steven Whybrow attacked Ms Higgins' credibility, saying a closer look at her evidence made the prosecution's case against his client "totally untenable".

He suggested Ms Higgins had motive to make up the allegation because she feared she would lose her staffer job after being found asleep in a ministerial office in the middle of the night.

"Is there a reasonable possibility this complaint is being made because her 'dream job' is, from her perspective, in jeopardy?" Mr Whybrow said.

Mr Whybrow also suggested Ms Higgins fabricated doctor appointments at the time to "make it more believable" that she had been sexually assaulted.

He said there was no record of Ms Higgins attending these appointments and the reason she didn't go was because she didn't need to.

"She says things that superficially support her position and then they turn out to be not reliable," he said

Mr Whybrow is expected to continue with his closing argument on Wednesday.

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Brittany Higgins had 325,000 reasons to push ahead with her rape accusation against her former colleague, a jury has heard.

Bruce Lehrmann is facing a criminal trial in the ACT Supreme Court, charged with sexual intercourse without consent.

He has pleaded not guilty to the charge.

Closing arguments have concluded in the nearly three-week trial with Lehrmann's defence lawyer Steven Whybrow referencing a $325,000 book deal Ms Higgins was offered after giving two media interviews about her rape allegation in 2021.

Mr Whybrow said the $325,000 question in the case was whether the jury could accept beyond a reasonable doubt that Lehrmann sexually assaulted Ms Higgins in a ministerial office.

He told the jury there were very few statements Ms Higgins presented as facts that have not been demonstrated to be suspect in the trial.

He said there was no DNA evidence or medical complaints to support Ms Higgins' version of events, but instead "contemporaneous lies" about visiting a doctor.

Mr Whybrow said if Ms Higgins had convinced herself that she had been raped her emotional demeanour in the witness box may be genuine.

"She has reconstructed events to the point that she now genuinely believes they are true. That doesn't mean they are true," he said on Wednesday.

Mr Whybrow used an example of a photograph of a bruise Ms Higgins said she took after the alleged assault.

He said there was no evidence that bruise had anything to do with that night.

"She's been caught out. Other people have come along and checked ... and there's no evidence of this," he said.

Prosecutor Shane Drumgold on Tuesday said Ms Higgins had been a credible and honest witness whose version of events that night had not wavered.

Meanwhile, he said Lehrmann had given inconsistent accounts about his reasons for being at parliament on the night of the alleged assault to the security guards, to his boss and to the police.

He suggested Lehrmann's intent was to go to Parliament House so that he could be alone with the "drunk" and "vulnerable" Ms Higgins.

Mr Drumgold also said after the alleged rape Ms Higgins was caught in the middle of "strong political forces".

"We say she was right to be scared, she was right to be cautious and she was right to move slowly and carefully," he said.

But Mr Whybrow told the jury on Wednesday that, other than Ms Higgins, no other witnesses had given evidence about "political forces" at play.

Mr Whybrow finished his closing argument by reminding jurors Lehrmann was entitled to the presumption of innocence.

He said there was no evidence to reach the criminal standard of beyond a reasonable doubt.

Chief Justice Lucy McCallum is expected to give instructions to the jurors before they begin their deliberations.

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Ukraine says Russia has destroyed almost a third of its power stations over the past week as Moscow steps up a campaign to strike infrastructure, a move the West says is a calculated attempt to disrupt and demoralise.

Missiles struck power generating facilities in a clutch of Ukrainian cities home to millions of people and several people were killed.

Moscow acknowledged targeting energy plants, while Ukraine said water infrastructure had also been hit.

"The situation is critical now across the country ... the whole country needs to prepare for electricity, water and heating outages," Kyrylo Tymoshenko, deputy head of the Ukrainian president's office, told Ukrainian television.

At least one man died when a Russian missile reduced his apartment in the southern river port of Mykolaiv to rubble.

Another two people were reported killed in a strike on Kyiv.

Ukrainian President Volodymyr Zelenskiy said Russia was continuing to try to terrorise and kill civilians.

"Since October 10, 30 per cent of Ukraine's power stations have been destroyed, causing massive blackouts across the country," he wrote on Twitter.

Power cuts were reported in parts of Kyiv, many parts of the Zhytomyr region west of the capital and Dnipro, which, like Mykolaiv, is in the south but also far from the front line where Ukraine is pressing Russian forces occupying its southeast.

Zelenskiy reiterated his refusal to negotiate with Russian President Vladimir Putin whom he has accused of immorality.

"The terrorist state will not change anything for itself with such actions," he wrote on the Telegram messaging app. "It will only confirm its destructive and murderous essence, for which it will certainly be held to account."

Putin has dismissed Zelenskiy as a puppet of Washington, which has given Kyiv more than $US17.5 billion in security aid.

There was no immediate word on how many people had been killed in Tuesday's strikes overall, which came a day after Russia sent swarms of drones to attack infrastructure in Kyiv and other cities, killing at least five people.

The Russian defence ministry, whose troops have this month been forced to retreat on two separate fronts, reiterated that it was carrying out attacks on military targets and energy infrastructure across Ukraine with high-precision weapons.

Russia earlier this month named General Sergei Surovikin as overall commander of Moscow's forces in Ukraine. Surovikin served in Syria and Chechnya where Russian forces pounded cities to rubble in a brutal but effective scorched earth policy against its foes.

Nicknamed "General Armageddon" by the Russian media because of his alleged toughness, his appointment was followed by the biggest wave of missile strikes against Ukraine since Moscow invaded on February 24.

Putin cast those strikes as revenge for what he said was a Ukrainian attack on the bridge which links Russia to Crimea - the peninsula Russia annexed from Ukraine in 2014. At least three people were killed in the bombing for which Ukraine has not officially taken responsibility.

In Mykolaiv, a strategic port which Russia tried and failed to capture earlier in the war, a Reuters witness said they had heard three explosions in the early hours of Tuesday.

A missile had completely destroyed one wing of a building in the downtown area, leaving a massive crater, they said. A fire crew was seen pulling the dead body of a man from the rubble.

The governors of Russia's Kursk and Belgorod regions, which border Ukraine, on Tuesday reported cross-border shelling.

In Belgorod, a train station was shelled and train links suspended, and two villages were shelled in Kursk, leading to electricity outages, they said.

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