Lifeboat Foundation: Safeguarding Humanity
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Blog – Page 2055

It has been known for more than century that increases in neural activity in the brain drive changes in local blood flow, known as neurovascular coupling. The colloquial explanation for these increases in blood flow (referred to as functional hyperemia) in the brain is that they serve to supply the needs of metabolically active neurons. However, there is an large body of evidence that is inconsistent with this idea. In most cases, baseline blood flow is adequate to supply even elevated neural activity. Neurovascular coupling is irregular, absent, or inverted in many brain regions, behavioral states, and conditions. Increases in respiration can generate increases in brain oxygenation independently of flow changes. Simulations have shown that areas with low blood flow are inescapable and cannot be removed by functional hyperemia given the architecture of the cerebral vasculature. What physiological purpose might neurovascular coupling serve? Here, we discuss potential alternative functions of neurovascular coupling. It may serve supply oxygen for neuromodulator synthesis, to regulate cerebral temperature, signal to neurons, stabilize and optimize the cerebral vascular structure, deal with the non-Newtonian nature of blood, or drive the production and circulation of cerebrospinal fluid around and through the brain via arterial dilations. Understanding the ‘why’ of neurovascular coupling is an important goal that give insight into the pathologies caused by cerebrovascular disfunction.

Like all energy demanding organs, the brain is highly vascularized. When presented with a sensory stimulus or cognitive task, increases in neural activity in many brain regions are accompanied by local dilation of arterioles and other microvessels, increasing local blood flow, volume and oxygenation. The increase in blood flow in response to increased neural activity (known as functional hyperemia) is controlled by a multitude of different signaling pathways via neurovascular coupling (reviewed in [1,2]). These vascular changes can be monitored non-invasively in humans and other species, with techniques (like BOLD fMRI) that are cornerstones in modern neuroscience [3,4]. Chronic disruptions of neurovascular coupling have adverse health effects on the brain. Stress affects neurovascular coupling [5,6], and many neurodegenerative diseases are marked by vascular dysfunction [7].

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Scientists hoped that capturing a time-lapse from Mars could reveal cloud or dust devil activity, leading to insights about the weather on the planet. The images were taken while the rover was parked on Nov. 8, 2023, just over 4,000 sols – Martian days – into the mission.

Though the images did not reveal any weather anomalies, scientists did get a detailed look at the planet’s surface.

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Radar altimeters are the sole indicators of altitude above a terrain. Spectrally adjacent 5G cellular bands pose significant risks of jamming altimeters and impacting flight landing and takeoff. As wireless technology expands in frequency coverage and utilizes spatial multiplexing, similar detrimental radio-frequency (RF) interference becomes a pressing issue.

To address this interference, RF front ends with exceptionally low latency are crucial for industries like transportation, health care, and the military, where the timeliness of transmitted messages is critical. Future generations of wireless technologies will impose even more stringent latency requirements on RF front-ends due to increased data rate, carrier frequency, and user count.

Additionally, challenges arise from the physical movement of transceivers, resulting in time-variant mixing ratios between interference and signal-of-interest (SOI). This necessitates real-time adaptability in mobile wireless receivers to handle fluctuating interference, particularly when it carries safety-to-life critical information for navigation and autonomous driving, such as aircraft and ground vehicles.

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Quantum engineering, a dynamic discipline bridging the fundamentals of quantum mechanics and established engineering fields has developed significantly in the past few decades. Two-level systems such as superconducting quantum bits are the building blocks of quantum circuits. Qubits of this type are currently the most researched and used in quantum computing applications1,2,3,4,5. The characteristics of the superconducting qubits such as eigen energies, non-linearity, coupling strengths etc. can be tailored easily by adjusting the design parameters6,7. Qubits have large non-linearity, which makes it possible to selectively address and control them1,3,7,8. This dynamic property makes superconducting qubits a strong candidate for plethora of applications. Other two-level microscopic quantum systems9,10,11,12,13,14 also have certain advantages and may be used in the future.

Quantum devices operate at low temperatures and require good isolation from external noises. Microwave devices, such as circulators and isolators, protect quantum circuits by unidirectionally routing the output signal, whilst simultaneously isolating noise from the output channel back to the quantum circuit. Their non-reciprocal character relies on the properties of ferrites15,16,17. Ferrite-based non-reciprocal devices are bulky15,16,17, and they cannot be positioned near the quantum circuit because they require strong magnetic fields. Although commercial ferrite based non-reciprocal devices harness high isolation and low insertion loss, their dependency on magnetic components limits the scalability of cryogenic quantum circuits15,16,18,19. Various ferrite-free approaches based on non-linear behavior of artificial atoms16, dc superconducting quantum interference devices (dc-SQUID)20,21, and arrays of Josephson junctions (JJ’s)19,22,23,24, have been experimentally demonstrated and implemented. Recently, a circuit based on semiconductor mixers has been used to realize a compact microwave isolator, which the authors claim could be extended to an on-chip device using Josephson mixers, although the “on-chip” demonstration is not yet reported25. Additionally, mesoscopic circulators exploiting the quantum Hall effect to break time-reversal symmetry of electrical transport in 2D systems are explored at a cost of larger magnetic fields deleterious to superconducting circuits18,26,27,28,29. More recently, a passive on-chip circulator based on three Josephson elements operating in charge-sensitive regime was demonstrated30. Such devices are frequently limited by their parameter regime, leaving them charge sensitive and therefore difficult to implement in a practical scenario. However, it is possible to mitigate the charge-sensitivity by carefully tuning the device parameters. Our device operates in a parameter regime that is not sensitive to charge fluctuations or charge parity switching, a fundamental requirement for any practical implementation, and requires small magnetic field. The reported device is a proof of concept (PoC), potentially useful in the applications relevant to microwave read-out components in the field of superconducting quantum circuits.

In this work, we present a robust and simple on-chip microwave diode demonstrating transmission rectification based on a superconducting flux qubit8. The concept of the device is shown in Fig. 1a. The flux qubit is inductively coupled to two superconducting resonators of different lengths with different coupling strengths. The design details are reported later in this section. Probing the qubit at the half-flux (degeneracy point) with one tone-spectroscopy, we observe identical patterns of transmission coefficient for signals propagating in the opposite directions, which are shifted by 5 dB in power. This shift indicates the non-reciprocal behaviour in our device, expressed in terms of transmission rectification ratio ® in this article. The origin of this effect is the non-linearity of the flux qubit, which controls the transmission coefficient of the whole structure.

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New findings from the James Webb Space Telescope reveal a surprising abundance of oxygen in the early Universe. Researchers discovered that oxygen levels in galaxies surged within 500–700 million years following the Universe’s birth, reaching levels comparable to those in contemporary galaxies. This suggests that the essential elements for life were present much earlier than previously believed.

In the early Universe, shortly after the Big Bang, only light elements such as hydrogen, helium, and lithium existed. Heavier elements like oxygen were subsequently formed through nuclear fusion reactions within stars and dispersed into galaxies, primarily through events like supernova explosions. This ongoing process of element synthesis, unfolding over the vast expanse of cosmic history, created the diverse elements that constitute the world and living organisms around us.

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Astronomers have proposed a new way to solve the so-called “Hubble tension,” but the approach ultimately raises more questions than it answers.

By way of background, cosmologists are in a bit of a crisis these days. One of the most important numbers they can measure is the so-called Hubble constant, the rate of expansion of the present-day universe. At their disposal cosmologists have two sets of tools to measure this number. On one side are tools that probe the relatively nearby universe, like measuring the brightnesses of a certain kind of exploding star known as Type 1a supernovae. These supernovae all erupt with the same absolute brightness, so by measuring their observed magnitudes, astronomers can calculate their distances, and then use that to estimate how quickly the universe is expanding.

The downside of this approach is that supernovae don’t always explode with exactly the same brightness, and for the kind of precision measurements astronomers are aiming for, they have to include assumptions and modeling of supernovae, which can potentially introduce inaccuracies.

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I’ve been diving into this cool concept called gravitational time dilation, and it’s like this mind-bending thing predicted by Albert Einstein in his theory of relativity. This concept highlights the actual difference in elapsed time between events observed by individuals situated at varying distances from a massive gravitational source.

If you’re hanging out close to a massive gravitational source, like a planet or star, time slows down for you. It’s like a cosmic slow-motion effect. But if you move away from it, time speeds up. This has been proven in experiments with atomic clocks placed at different heights — the closer to the Earth’s surface, the slower the clock ticks compared to those higher up.

Einstein first talked about this in 1907 when he was figuring out special relativity in speedy frames of reference. In general relativity, it’s like time is doing a dance based on where you are in space, as described by this thing called a metric tensor.

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