Quantum Monte Carlo (QMC) techniques are widely used in a variety ofscientific problems and much work has been dedicated to developing optimizedalgorithms that can accelerate QMC on standard processors (CPU). With theadvent of various special purpose devices and domain specific hardware, it hasbecome increasingly important to establish clear benchmarks of whatimprovements these technologies offer compared to existing technologies. Inthis paper, we demonstrate 2 to 3 orders of magnitude acceleration of astandard QMC algorithm using a specially designed digital processor, and afurther 2 to 3 orders of magnitude by mapping it to a clockless analogprocessor. Our demonstration provides a roadmap for 5 to 6 orders of magnitudeacceleration for a transverse field Ising model (TFIM) and could possibly beextended to other QMC models as well. The clockless analog hardware can beviewed as the classical counterpart of the quantum annealer and providesperformance within a factor of $<10$ of the latter. The convergence time forthe clockless analog hardware scales with the number of qubits as $\sim N$,improving the $\sim N^2$ scaling for CPU implementations, but appears worsethan that reported for quantum annealers by D-Wave.
Stimuli-responsive materials with reversible supramolecular networks controlled by a change in temperature are of interest in medicine, biomedicine and analytical chemistry. For these materials to become more impactful, the development of greener synthetic practices with more sustainable solvents, lower energy consumption and a reduction in metallic catalysts is needed. In this work, we investigate the polymerisation of N -acryloyl glycinamide monomer by single-electron transfer reversible-deactivation radical polymerisation and its effect on the cloud point of the resulting PNAGA polymers. We accomplished 80% conversion within 5 min in water media using a copper wire catalyst. The material exhibited a sharp upper critical solution temperature (UCST) phase transition (10-80% transition within 6 K). These results indicate that UCST-exhibiting PNAGA can be synthesized at ambient temperatures and under non-inert conditions, eliminating the cost- and energy-consuming deoxygenation step. The choice of copper wire as the catalyst allows the possibility of catalyst recycling. Furthermore, we show that the reaction is feasible in a simple vial which would facilitate upscaling.
Common fragile sites (CFS) are specific genomic regions prone to chromosomal instability under conditions of DNA replication stress. CFSs manifest as breaks, gaps, and constrictions on metaphase chromosomes under mild replication stress. These replication-sensitive CFS regions are preferentially unstable during cancer development, as reflected by their association with copy number variants (CNVs) frequently arise in most tumor types. Over the years, it became clear that a combination of different characteristics underlies the enhanced sensitivity of CFSs to replication stress. As of today, there is a strong evidence that the core fragility regions along CFSs overlap with actively transcribed large genes with delayed replication timing upon replication stress. Recently, the mechanistic basis for CFS instability was further extended to regions which span topologically associated domain (TAD) boundaries, generating a fragility signature composed of replication, transcription and genome organization. The presence of difficult-to-replicate AT-rich repeats was one of the early features suggested to characterize a subgroup of CFSs. These long stretches of AT-dinucleotide have the potential to fold into stable secondary structures which may impede replication fork progression, leaving the region under-replicated. Here, we focus on the molecular mechanisms underlying repeat instability at CFSs and on the proteins involved in the resolution of secondary structure impediments arising along repetitive sequence elements which are essential for the maintenance of genome stability.
We propose a new type of magnetoelectric memory device that stores magneticeasy-axis information or pseudo-magnetization, rather than a definitemagnetization direction, in piezoelectric/ferromagnetic (PE/FM)heterostructures. Theoretically, we show how a PE/FM combination can lead tonon-volatility in pseudo-magnetization exhibiting ferroelectric-like behavior.The pseudo-magnetization can be manipulated by extremely low voltagesespecially when the FM is a low-barrier nanomagnet. Using a circuit modelbenchmarked against experiments, we determine the switching energy, delay,switching probability and retention time of the envisioned 1T/1C memory devicein terms of magnetic and circuit parameters and discuss its thermal stabilityin terms of a key parameter called back-voltage vm which is an electricalmeasure of the strain-induced magnetic field. Taking advantage of ferromagneticresonance (FMR) measurements, we experimentally extract values for vm in CoFeBfilms and circular nano-magnets deposited on Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT)which agree well with the theoretical values. Our experimental findings indeedindicate the feasibility of the proposed novel device and confirm the assumedparameters in our modeling effort.