Discover the most talked about and latest scientific content & concepts.

Concept: Solid-state drive


The advent of devices based on single dopants, such as the single-atom transistor, the single-spin magnetometer and the single-atom memory, has motivated the quest for strategies that permit the control of matter with atomic precision. Manipulation of individual atoms by low-temperature scanning tunnelling microscopy provides ways to store data in atoms, encoded either into their charge state, magnetization state or lattice position. A clear challenge now is the controlled integration of these individual functional atoms into extended, scalable atomic circuits. Here, we present a robust digital atomic-scale memory of up to 1 kilobyte (8,000 bits) using an array of individual surface vacancies in a chlorine-terminated Cu(100) surface. The memory can be read and rewritten automatically by means of atomic-scale markers and offers an areal density of 502 terabits per square inch, outperforming state-of-the-art hard disk drives by three orders of magnitude. Furthermore, the chlorine vacancies are found to be stable at temperatures up to 77 K, offering the potential for expanding large-scale atomic assembly towards ambient conditions.

Concepts: Density, SI prefix, Magnetic field, Earth's magnetic field, Computer, Hard disk drive, Solid-state drive, Atom


Delivery of proteins to mucosal tissues of GI tract typically utilize formulations which protect against proteolysis and target the mucosal tissues. Using case studies from literature and the authors' own work, the in-process stability and solid state storage stability of biopharmaceuticals formulated in delivery systems designed for oral delivery to the GI tract will be reviewed. Among the range of delivery systems, biodegradable polymer systems for protection and controlled release of proteins have been the most studied; hence these systems will be covered in greater depth. These delivery systems include polymeric biodegradable microspheres or nanospheres that contain proteins or vaccines, which are designed to reduce the number of administrations/inoculations and the total protein dose required to achieve the desired biological effect. Specifically, this review will include a landscape survey of the systems that have been studied, the manufacturing processes involved, stability through the manufacturing process, key pharmaceutical formulation parameters that impact stability of the encased proteins, and storage stability of the encapsulated proteins in these delivery systems.

Concepts: Polysaccharide, DNA, Solid-state drive, Literature, Pharmaceutical formulation, Protein, Polymer, Pharmacology


Flash memory devices-that is, non-volatile computer storage media that can be electrically erased and reprogrammed-are vital for portable electronics, but the scaling down of metal-oxide-semiconductor (MOS) flash memory to sizes of below ten nanometres per data cell presents challenges. Molecules have been proposed to replace MOS flash memory, but they suffer from low electrical conductivity, high resistance, low device yield, and finite thermal stability, limiting their integration into current MOS technologies. Although great advances have been made in the pursuit of molecule-based flash memory, there are a number of significant barriers to the realization of devices using conventional MOS technologies. Here we show that core-shell polyoxometalate (POM) molecules can act as candidate storage nodes for MOS flash memory. Realistic, industry-standard device simulations validate our approach at the nanometre scale, where the device performance is determined mainly by the number of molecules in the storage media and not by their position. To exploit the nature of the core-shell POM clusters, we show, at both the molecular and device level, that embedding [(Se(iv)O3)2](4-) as an oxidizable dopant in the cluster core allows the oxidation of the molecule to a [Se(v)2O6](2-) moiety containing a {Se(v)-Se(v)} bond (where curly brackets indicate a moiety, not a molecule) and reveals a new 5+ oxidation state for selenium. This new oxidation state can be observed at the device level, resulting in a new type of memory, which we call ‘write-once-erase’. Taken together, these results show that POMs have the potential to be used as a realistic nanoscale flash memory. Also, the configuration of the doped POM core may lead to new types of electrical behaviour. This work suggests a route to the practical integration of configurable molecules in MOS technologies as the lithographic scales approach the molecular limit.

Concepts: Chemistry, Solid-state drive, Memory card, USB flash drive, Flash memory, Non-volatile memory, Computer data storage, Computer storage


Three-dimensional (3D) NAND flash memory devices having a poly-silicon channel with grain boundaries, the cylindrical macaroni channel being outside the inter-oxide filler layer and inside the tunneling oxide layer, were evaluated. The effects of the grain size, grain boundary trap density, and interface trap density at the interfaces between the channel and the oxide layers on the electrical characteristics of 3D NAND flash memory devices were investigated. The electron density of the channel was changed depending on the grain boundary trap density and the position of the grain boundary trap in the channel. The grain boundary traps increased the potential barrier and decreased the electron density of the channel. The threshold voltage increased with increasing grain boundary trap density and interface trap density.

Concepts: Solid-state drive, Memory card, USB flash drive, Non-volatile memory, Object-oriented programming, Electron, OSI model, Flash memory


Current perpendicular-to-plane (CPP) giant magnetoresistance (GMR) effects are of interest in a possible application of magnetic sensor elements, such as read-head of hard disk drives. To improve the junction performance, the interface tailoring effects were investigated for the Heulser alloy, Co₂Fe0.4Mn0.6Si (CFMS), based CPP-GMR junctions with an L 1 2 -Ag₃Mg ordered alloy spacer. Ultra-thin Fe or Mg inserts were utilized for the CFMS/Ag₃Mg interfaces, and CPP-GMR at low bias current density, J and the J dependence were evaluated for the junctions. Although, at low bias J, MR ratio decreased with increasing the inserts thickness, the device output at high bias J exhibited quite weak dependence on the insert thickness. The output voltages of the order of 4 mV were obtained for the junctions regardless of the insert at an optimal bias J for each. The critical current density J c was evaluated by the shape of MR curves depending on J. J c increased with the insert thicknesses up to 0.45 nm. The enhancement of J c suggests that spin-transfer-torque effect may reduce in the junctions with inserts, which enables a reduction of noise and can be an advantage for device applications.

Concepts: Solid-state drive, Electromagnetism, Magnetic field, User interface, Magnetoresistance, Spintronics, Giant magnetoresistance, Hard disk drive


The observation of a reversible chemical transformation corresponding to an external stimulus in the solid state is intriguing in the exploration of smart materials, which can potentially be applied in molecular machines, molecular switches, sensors, and data storage devices. The solid-state photodimerization reaction of 1,3-bis[2-(4-pyridyl)ethenyl]benzene (1,3-bpeb) in a one-dimensional coordination polymer {[Cd2(1,3-bpeb)2(4-FBA)4]·H2O}n (4-FBA = 4-fluorobenzoate) with 365 nm UV light afforded syn-tetrakis(4-pyridyl)-1,2,9,10-diethano[2.2]metacyclophane (syn-tpmcp) in quantitative yield via a single-crystal-to-single-crystal (SCSC) transformation. Upon irradiation with 254 nm UV light, an SCSC conversion from syn-tpmcp to 1,3-bpeb was also achieved in quantitative yield within the syn-tpmcp-supported coordination polymer {[Cd2(syn-tpmcp)(4-FBA)4]·H2O}n. In particular, accompanied by the reversible transformation between 1,3-bpeb and syn-tpmcp, the coordination chain exhibits photocontrollable fluorescence-switching behavior, which makes this intelligent material an appealing candidate for practical applications.

Concepts: Data storage device, Chemical substance, Fluorescence, Recording, Integrated circuit, Solid-state drive, Computer data storage, Electron


In the era of big data, there exists a growing gap between data generated and storage capacity using two-dimensional (2D) magnetic storage technologies (for example, hard disk drives), because they have reached their performance saturation. 3D volumetric all-optical magnetic holography is emerging rapidly as a promising road map to realizing high-density capacity for its fast magnetization control and subwavelength magnetization volume. However, most of the reported light-induced magnetization confronts the problems of impurely longitudinal magnetization, diffraction-limited spot, and uncontrollable magnetization reversal. To overcome these challenges, we propose a novel 3D light-induced magnetic holography based on the conceptual supercritical design with multibeam combination in the 4π microscopic system. We theoretically demonstrate a 3D deep super-resolved [Formula: see text] purely longitudinal magnetization spot by focusing six coherent circularly polarized beams with two opposing high numerical aperture objectives, which allows 3D magnetic holography with a volumetric storage density of up to 1872 terabit per cubic inches. The number and locations of the super-resolved magnetization spots are controllable, and thus, desired magnetization arrays in 3D volume can be produced with properly designed phase filters. Moreover, flexible magnetization reversals are also demonstrated in multifocal arrays by using different illuminations with opposite light helicity. In addition to data storage, this magnetic holography may find applications in information security, such as identity verification for a credit card with magnetic stripe.

Concepts: 2D computer graphics, Computer storage media, Hard disk drive, Storage media, Solid-state drive, Volume, Density, Computer data storage


The Chemical Aquatic Fate and Effects (CAFE) database is a tool that facilitates assessments of accidental chemical releases into aquatic environments. CAFE contains aquatic toxicity data used in the development of species sensitivity distributions (SSDs) and the estimation of hazard concentrations (HCs). For many chemicals, gaps in species diversity and toxicity data limit the development of SSDs, which may be filled with Interspecies Correlation Estimation (ICE) models. Optimization of ICE model selection and integration ICE-predicted values into CAFE required a multistep process that involved the use of different types of data to assess their influence on SSDs and HC estimates. Results from multiple analyses showed that SSDs supplemented with ICE-predicted values generally produced HC5 estimates that were within a 3-fold difference of estimates from measured SSDs (58%-82% of comparisons), but that were often more conservative (63%-76% of comparisons) and had lower uncertainty (90% of comparisons). ICE SSDs did not substantially underpredict toxicity (<10% of comparisons) when compared to estimates from measured SSD. The incorporation of ICE-predicted values into CAFE allowed the development of >800 new SSDs, increased diversity in SSDs by an average of 34 species, and augmented data for priority chemicals involved in accidental chemical releases.

Concepts: Chemical industry, Solid-state drive, Nature, Toxicity, Assessment, Chemical substance, Chemistry, Biodiversity


We report reproducible multibit transparent flash memory in which a single solution-derived Ta2O5 layer is used simultaneously as charge trapping and tunneling layer. This is different from conventional flash cells, where two different dielectric layers are typically used. Under optimized programming/erasing operations, the memory device shows excellent programmable memory characteristics with a maximum memory window of ~10 V. Moreover, the flash memory device shows a stable 2-bit memory performance, good reliability, including data retention for more than 10(4) sec and endurance performance for more than 100 cycles. The use of a common charge trapping and tunneling layer can simplify advanced flash memory fabrication.

Concepts: Solid-state drive, Memory card, USB flash drive, Capacitor, Data, Flash memory, Non-volatile memory, OSI model


The introduction of hierarchy and chirality into structure is of great interest, and can result in new optical and electronic properties due to the synergistic effect of helical and anisotropic structures. Herein, we demonstrate a simple and straightforward route toward the fabrication of hierarchical chiral materials based on the assembly of two-dimensional graphene oxide nanosheets (GO) and one-dimensional cellulose nanocrystals (CNCs). The unique layered structure of CNC/GO could be preserved in the solid state, allowing electrode active SnO2 to be loaded for potential applications in energy storage. The resultant SnO2/CNC/reduced GO (SnO2/CNC/rGO) composite could be processed into film, fiber, and textile with an extremely high tensile strength of 100 MPa. The free-standing SnO2/CNC/rGO electrodes exhibit highly improved energy storage performance, with a reversible capacity of ∼500 mA h g(-1) maintained for 1500 cycles in the film and ∼800 mA h g(-1) maintained for 150 cycles in the textile at a current density of 500 mA g(-1). This is attributed to the prepared hierarchical chiral structures. The presented technique provides an effective approach to producing hierarchical functional materials from nanoparticles as building blocks, which might open an avenue for the creation of new flexible energy storage devices.

Concepts: Nanomaterials, Solid-state drive, Chirality, Greek loanwords, Carbon nanotube, Hierarchy, Structure, Tensile strength