Short-term climate response to a freshwater pulse in the Southern Ocean

The short-term response of the climate system to a freshwater anomaly in the Southern Ocean is investigated using a coupled global climate model. As a result of the anomaly, ventilation of deep waters around Antarctica is inhibited, causing a warming of the deep ocean, and a cooling of the surface. The surface cooling causes Antarctic sea-ice to thicken and increase in extent, and this leads to a cooling of Southern Hemisphere surface air temperature. The surface cooling increases over the first 5 years, then remains constant over the next 5 years. There is a more rapid response in the Pacific Ocean, which transmits a signal to the Northern Hemisphere, ultimately causing a shift to the negative phase of the North Atlantic Oscillation in years 5–10

Factors affecting the performance of eddy current densification sensors

Hot Isostatic Pressing (HIP) is an increasingly important near net shape process for producing fully dense components from powders [1]. It involves filling a preshaped metal canister with alloy powder, followed by evacuation, and sealing. The can is then placed in a HIP (a furnace that can be pressurized to ~200MPa with an inert gas such as argon). The can is subjected to a heating/pressurization cycle that softens and compacts the powder particles to a fully dense mass and a shape determined by the can shape, the powders initial packing and the thermal-mechanical cycle imposed [2]. Today, many metals, alloys and intermetallics are processed this way (including nickel based superalloys, titanium alloys, NiA1, etc.) and it is increasingly used to produce metal matrix composites

Antiferromagnetic CuMnAs multi-level memory cell with microelectronic compatibility

Antiferromagnets offer a unique combination of properties including the radiation and magnetic field hardness, the absence of stray magnetic fields, and the spin-dynamics frequency scale in terahertz. Recent experiments have demonstrated that relativistic spin-orbit torques can provide the means for an efficient electric control of antiferromagnetic moments. Here we show that elementary-shape memory cells fabricated from a single-layer antiferromagnet CuMnAs deposited on a III–V or Si substrate have deterministic multi-level switching characteristics. They allow for counting and recording thousands of input pulses and responding to pulses of lengths downscaled to hundreds of picoseconds. To demonstrate the compatibility with common microelectronic circuitry, we implemented the antiferromagnetic bit cell in a standard printed circuit board managed and powered at ambient conditions by a computer via a USB interface. Our results open a path towards specialized embedded memory-logic applications and ultra-fast components based on antiferromagnets

Current polarity-dependent manipulation of antiferromagnetic domains

Antiferromagnets have several favourable properties as active elements in spintronic devices, including ultra-fast dynamics, zero stray fields and insensitivity to external magnetic fields. Tetragonal CuMnAs is a testbed system in which the antiferromagnetic order parameter can be switched reversibly at ambient conditions using electrical currents. In previous experiments, orthogonal in-plane current pulses were used to induce 90° rotations of antiferromagnetic domains and demonstrate the operation of all-electrical memory bits in a multi-terminal geometry. Here, we demonstrate that antiferromagnetic domain walls can be manipulated to realize stable and reproducible domain changes using only two electrical contacts. This is achieved by using the polarity of the current to switch the sign of the current-induced effective field acting on the antiferromagnetic sublattices. The resulting reversible domain and domain wall reconfigurations are imaged using X-ray magnetic linear dichroism microscopy, and can also be detected electrically. Switching by domain-wall motion can occur at much lower current densities than those needed for coherent domain switching

Pharmacological treatment of painful HIVassociated sensory neuropathy

Background. HIV-associated sensory neuropathy (HIV-SN) is a common and frequently painful  complication of HIV infection and its treatment. However, few data exist describing the frequency, type and dosage of pain medications patients are receiving in the clinic setting to manage the painful symptoms of HIV-SN.Objective. To report on analgesic prescription for painful HIV-SN and factors influencing that prescription in adults on combination antiretroviral therapy.Methods. Using validated case ascertainment criteria to identify patients with painful HIV-SN, we  recruited 130 HIV-positive patients with painful HIV-SN at Chris Hani Baragwanath Hospital,  Johannesburg, South Africa. Demographic and clinical data (including current analgesic use) were collected on direct questioning of the patients and review of the medical files.Results. We found significant associations, of moderate effect size, between higher pain intensity and lower CD4 T-cell counts with prescription of analgesic therapy. Factors previously identified as predicting analgesic treatment in HIV-positive individuals (age, gender, level of education) were not associated with analgesic use here. Consistent with national guidelines, amitriptyline was the most commonly used agent, either alone or in combination therapy. Importantly, we also found that despite the relatively high analgesic treatment rate in this setting, the majority of patients described their current level of HIV-SN pain as moderate or severe.Conclusion. Our findings highlight the urgent need for both better analgesic options for HIV-SN pain  treatment and ongoing training and support of clinicians managing this common and debilitating condition

Terahertz electrical writing speed in an antiferromagnetic memory

The speed of writing of state-of-the-art ferromagnetic memories is physically limited by an intrinsic gigahertz threshold. Recently, realization of memory devices based on antiferromagnets, in which spin directions periodically alternate from one atomic lattice site to the next has moved research in an alternative direction. We experimentally demonstrate at room temperature that the speed of reversible electrical writing in a memory device can be scaled up to terahertz using an antiferromagnet. A current-induced spin-torque mechanism is responsible for the switching in our memory devices throughout the 12-order-of-magnitude range of writing speeds from hertz to terahertz. Our work opens the path toward the development of memory-logic technology reaching the elusive terahertz band