Comparative analysis: CapEx in diamond mining versus diamond growing, based on open data sources and experimental results.

The diamond industry has long been associated with environmental and social problems, ranging from mining practices to ethical concerns related to diamond sourcing. In recent years, there has been a growing interest in lab-grown diamonds as a sustainable alternative for diamond consumers. However, the production of lab-grown diamonds has own challenges. This article examines the capital expenditures per annualized carat of rough diamonds obtained through mining and two fabrication methods: high-pressure high-temperature (HPHT) and microwave plasma-assisted chemical vapour deposition (MP CVD). Lab-grown diamonds produced using HPHT and MP CVD methods require significantly higher capital expenditures per annualized carat compare to mined diamonds. HPHT diamonds require on-time CapEx of 500-833 US$ per carat annually, while MP CVD diamonds demand 549-1648 US$ per carat annually. Finding ways to reduce production cost and increase efficiency will be crucial in realizing the potential of lab-grown diamonds as a sustainable alternative to mined diamonds.

Comparative analysis of labor input required to produce one carat at different methods of synthesis and mining of diamonds.

Diamond is a form of carbon that has been attracting attention for hundreds of years, owing to its physical and chemical properties of hardness, thermal conductivity, chemical inertness, and transparency. Labor and the long-term impact of a diverse workforce, is one of the most important factors in diamond mining and production and must be considered when assessing economic benefits. In the present study, we examined the labor input required to obtain one carat of diamond, via three methods: open-cast mining, high-pressure high-temperature synthesis and 2.45-GHz microwave plasma chemical vapor deposition. We discovered that to produce a carat of (near-) colorless diamond, the labor inputs are approximately 1.83 h and 3.43 h of work using the HPHT and 2.45-GHz MP CVD methods, respectively. We noted a lower labor input of work per carat for the mining of diamonds of assorted sizes and colors from the two main DeBeers diamond fields in Botswana (Orapa and Jwaneng). This paper is based on our observations and public reports, and we think that our findings will be helpful in understanding the labor input per carat for the analyzed methods, understanding the main technological challenges facing the diamond industry that could potentially affect future labor productivity.

Mechanistic Insight into the Limiting Factors of Graphene-Based Environmental Sensors.

Graphene has demonstrated great promise for technological use, yet control over material growth and understanding of how material imperfections affect the performance of devices are challenges that hamper the development of applications. In this work, we reveal new insight into the connections between the performance of the graphene devices as environmental sensors and the microscopic details of the interactions at the sensing surface. We monitor changes in the resistance of the chemical-vapor deposition grown graphene devices as exposed to different concentrations of ethanol. We perform thermal surface treatments after the devices are fabricated, use scanning probe microscopy to visualize their effects down to nanometer scale and correlate them with the measured performance of the device as an ethanol sensor. Our observations are compared to theoretical calculations of charge transfers between molecules and the graphene surface. We find that, although often overlooked, the surface cleanliness after device fabrication is responsible for the device performance and reliability. These results further our understanding of the mechanisms of sensing in graphene-based environmental sensors and pave the way to optimizing such devices, especially for their miniaturization, as with decreasing size of the active zone the potential role of contaminants will rise.

Solid-state nanopore fabrication by automated controlled breakdown.

Solid-state nanopores are now well established as single-biomolecule sensors that hold great promise as sensing elements in diagnostic and sequencing applications. However, until recently this promise has been limited by the expensive, labor-intensive, and low-yield methods used to fabricate low-noise and precisely sized pores. To address this problem, we pioneered a low-cost and scalable solid-state nanopore fabrication method, termed controlled breakdown (CBD), which is rapidly becoming the method of choice for fabricating solid-state nanopores. Since its initial development, nanopore research groups around the world have applied and adapted the CBD method in a variety of ways, with varying levels of success. In this work, we present our accumulated knowledge of nanopore fabrication by CBD, including a detailed description of the instrumentation, software, and procedures required to reliably fabricate low-noise and precisely sized solid-state nanopores with a yield of >85% in less than 1 h. The assembly instructions for the various custom instruments can be found in the Supplementary Manual, and take approximately a day to complete, depending on the unit that the user is building and their level of skill with mechanical and electrical assembly. Unlike traditional beam-based nanopore fabrication technologies, the methods presented here are accessible to non-experts, lowering the cost of, and technical barriers to, fabricating nanoscale pores in thin solid-state membranes.

Ultra-high density optical data storage in common transparent plastics.

The ever-increasing demand for high data storage capacity has spurred research on development of innovative technologies and new storage materials. Conventional GByte optical discs (DVDs and Bluray) can be transformed into ultrahigh capacity storage media by encoding multi-level and multiplexed information within the three dimensional volume of a recording medium. However, in most cases the recording medium had to be photosensitive requiring doping with photochromic molecules or nanoparticles in a multilayer stack or in the bulk material. Here, we show high-density data storage in commonly available plastics without any special material preparation. A pulsed laser was used to record data in micron-sized modified regions. Upon excitation by the read laser, each modified region emits fluorescence whose intensity represents 32 grey levels corresponding to 5 bits. We demonstrate up to 20 layers of embedded data. Adjusting the read laser power and detector sensitivity storage capacities up to 0.2 TBytes can be achieved in a standard 120 mm disc.

A novel stretching platform for applications in cell and tissue mechanobiology.

Tools that allow the application of mechanical forces to cells and tissues or that can quantify the mechanical properties of biological tissues have contributed dramatically to the understanding of basic mechanobiology. These techniques have been extensively used to demonstrate how the onset and progression of various diseases are heavily influenced by mechanical cues. This article presents a multi-functional biaxial stretching (BAXS) platform that can either mechanically stimulate single cells or quantify the mechanical stiffness of tissues. The BAXS platform consists of four voice coil motors that can be controlled independently. Single cells can be cultured on a flexible substrate that can be attached to the motors allowing one to expose the cells to complex, dynamic, and spatially varying strain fields. Conversely, by incorporating a force load cell, one can also quantify the mechanical properties of primary tissues as they are exposed to deformation cycles. In both cases, a proper set of clamps must be designed and mounted to the BAXS platform motors in order to firmly hold the flexible substrate or the tissue of interest. The BAXS platform can be mounted on an inverted microscope to perform simultaneous transmitted light and/or fluorescence imaging to examine the structural or biochemical response of the sample during stretching experiments. This article provides experimental details of the design and usage of the BAXS platform and presents results for single cell and whole tissue studies. The BAXS platform was used to measure the deformation of nuclei in single mouse myoblast cells in response to substrate strain and to measure the stiffness of isolated mouse aortas. The BAXS platform is a versatile tool that can be combined with various optical microscopies in order to provide novel mechanobiological insights at the sub-cellular, cellular and whole tissue levels.

Echoes in x-ray speckles track nanometer-scale plastic events in colloidal gels under shear.

We report x-ray photon correlation spectroscopy experiments on a concentrated nanocolloidal gel subject to in situ oscillatory shear strain. The strain causes periodic echoes in the speckle pattern that lead to peaks in the intensity autocorrelation function. Above a threshold strain that is near the first yield point of the gel, the peak amplitude decays exponentially with the number of shear cycles, signaling irreversible particle rearrangements. The wave-vector dependence of the decay rate reveals a power-law distribution in the size of regions undergoing shear-induced rearrangement. The gel also displays strain softening well below the threshold, indicating a range of strains at which the rheology is nonlinear but the microscopic deformations are reversible.

Actin and microtubules play distinct roles in governing the anisotropic deformation of cell nuclei in response to substrate strain.

Physical forces arising in the cellular microenvironment have been hypothesized to play a major role in governing cell function. Moreover, it is thought that gene regulation may be sensitive to nuclear deformations taking place in response to extracellular forces over short and long timescales. Although nuclear responses to mechanical stimuli over long timescales are relatively well studied, the short-term responses are poorly understood. Therefore, to characterize the short-term instantaneous deformation of the nucleus in a mechanically dynamic environment, we exposed MDCK epithelial monolayers to varying mechanical strain fields. The results reveal that nuclei deform anisotropically in response to substrate strain, specifically, the minor nuclear axis is significantly more deformable than the major axis. We show that upon microtubule depolymerization, nuclear deformation anisotropy completely disappears. Moreover, the removal of actin causes a significant increase in nuclear deformation along the minor axis and a corresponding increase in mechanical anisotropy. The results demonstrate that the nucleus deforms in a manner that is very much dependent on the direction of strain and the characteristics of the strain field. Actin and microtubules also appear to play distinct roles in controlling the anisotropic deformation of the nucleus in response to mechanical forces that arise in the cellular microenvironment.

Msl2 is a novel component of the vertebrate DNA damage response.

hMSL2 (male-specific lethal 2, human) is a RING finger protein with ubiquitin ligase activity. Although it has been shown to target histone H2B at lysine 34 and p53 at lysine 351, suggesting roles in transcription regulation and apoptosis, its function in these and other processes remains poorly defined. To further characterize this protein, we have disrupted the Msl2 gene in chicken DT40 cells. Msl2(-/-) cells are viable, with minor growth defects. Biochemical analysis of the chromatin in these cells revealed aberrations in the levels of several histone modifications involved in DNA damage response pathways. DNA repair assays show that both Msl2(-/-) chicken cells and hMSL2-depleted human cells have defects in non-homologous end joining (NHEJ) repair. DNA damage assays also demonstrate that both Msl2 and hMSL2 proteins are modified and stabilized shortly after induction of DNA damage. Moreover, hMSL2 mediates modification, presumably ubiquitylation, of a key DNA repair mediator 53BP1 at lysine 1690. Similarly, hMSL1 and hMOF (males absent on the first) are modified in the presence of hMSL2 shortly after DNA damage. These data identify a novel role for Msl2/hMSL2 in the cellular response to DNA damage. The kinetics of its stabilization suggests a function early in the NHEJ repair pathway. Moreover, Msl2 plays a role in maintaining normal histone modification profiles, which may also contribute to the DNA damage response.

Field-flow fractionation and hydrodynamic chromatography on a microfluidic chip.

We present gravitational field-flow fractionation and hydrodynamic chromatography of colloids eluting through 18 µm microchannels. Using video microscopy and mesoscopic simulations, we investigate the average retention ratio of colloids with both a large specific weight and neutral buoyancy. We consider the entire range of colloid sizes, including particles that barely fit in the microchannel and nanoscopic particles. Ideal theory predicts four operational modes, from hydrodynamic chromatography to Faxén-mode field-flow fractionation. We experimentally demonstrate, for the first time, the existence of the Faxén-mode field-flow fractionation and the transition from hydrodynamic chromatography to normal-mode field-flow fractionation. Furthermore, video microscopy and simulations show that the retention ratios are largely reduced above the steric-inversion point, causing the variation of the retention ratio in the steric- and Faxén-mode regimes to be suppressed due to increased drag. We demonstrate that theory can accurately predict retention ratios if hydrodynamic interactions with the microchannel walls (wall drag) are added to the ideal theory. Rather than limiting the applicability, these effects allow the microfluidic channel size to be tuned to ensure high selectivity. Our findings indicate that particle velocimetry methods must account for the wall-induced lag when determining flow rates in highly confining systems.