Revealing soil microbial ecophysiological indicators in acidic environments laden with heavy metals via predictive modeling: Understanding the impacts of black diamond excavation

Appraising the activity of soil microbial community in relation to soil acidity and heavy metal (HM) content can help evaluate it's quality and health. Coal mining has been reported to mobilize locked HM in soil and induce acid mine drainage. In this study, agricultural soils around coal mining areas were studied and compared to baseline soils in order to comprehend the former's effect in downgrading soil quality. Acidity as well as HM fractions were significantly higher in the two contaminated zones as compared to baseline soils (p < 0.01). Moreover, self-organizing and geostatistical maps show a similar pattern of localization in metal availability and soil acidity thereby indicating a causal relationship. Sobol sensitivity, cluster, and principal component analyses were employed to enunciate the relationship between the various metal and acidity fractions with that of soil microbial properties. The results indicate a significant negative impact of metal bioavailability, and acidity on soil microbial activity. Lastly, Taylor diagrams were employed to predict soil microbial quality and health based on soil physicochemical inputs. The efficiency of several machine learning algorithms was tested to identify Random Forrest as the best model for prediction. Thus, the study imparts knowledge about soil pollution parameters, and acidity status thereby projecting soil quality which can be a pioneer in sustainable agricultural practices.

A high-resolution study of PM2.5 accumulation inside leaves in leaf stomata compared with non-stomatal areas using three-dimensional X-ray microscopy

Plant leaves retain atmospheric particulate matter (PM) on their surfaces, helping PM removal and risk reduction of respiratory tract infection. Several processes (deposition, resuspension, rainfall removal) can influence the PM accumulation on leaves and different leaf microstructures (e.g., trichomes, epicuticular waxes) can also be involved in retaining PM. However, the accumulation and distribution of PM on leaves, particularly at the stomata, are unclear, and the lack of characterization methods limits our understanding of this process. Thus, in this study, we aimed to explore the pathway through which PM_2.5 (aerodynamic diameter ≤ 2.5 μm) enters plant leaves, and the penetration depth of PM_2.5 along the entry route. Here, an indoor experiment using diamond powder as a tracer to simulate PM_2.5 deposition on leaves was carried out. Then, the treated and non-treated leaves were scanned by using three-dimensional (3D) X-ray microscopy. Next, the grayscale value of the scanned images was used to compare PM_2.5 accumulation in stomatal and non-stomatal areas of the treated and non-treated leaves, respectively. Finally, a total PM_2.5 volume from the abaxial epidermis was calculated. The results showed that, first, a large amount of PM_2.5 accumulates within leaf stomata, whereas PM_2.5 does not accumulate at non-stomatal areas. Then, the penetration depth of PM_2.5 in stomata of most tree species was 5-14 μm from the abaxial epidermis. For the first time, 3D X-ray microscope scanning was used to confirm that a pathway by which PM_2.5 enters the leaves is through the stomata, which is fundamental for further research on how PM_2.5 translocates and interacts with tissues and cells in leaves.

Electron tomography of prolamellar bodies and their transformation into grana thylakoids in cryofixed Arabidopsis cotyledons

The para-crystalline structures of prolamellar bodies (PLBs) and light-induced etioplast-to-chloroplast transformation have been investigated via electron microscopy. However, such studies suffer from chemical fixation artifacts and limited volumes of 3D reconstruction. Here, we examined Arabidopsis thaliana cotyledon cells by electron tomography (ET) to visualize etioplasts and their conversion into chloroplasts. We employed scanning transmission ET to image large volumes and high-pressure freezing to improve sample preservation. PLB tubules were arranged in a zinc blende-type lattice-like carbon atoms in diamonds. Within 2 h after illumination, the lattice collapsed from the PLB exterior and the disorganized tubules merged to form thylakoid sheets (pre-granal thylakoids), which folded and overlapped with each other to create grana stacks. Since the nascent pre-granal thylakoids contained curved membranes in their tips, we examined the expression and localization of CURT1 (CURVATURE THYLAKOID1) proteins. CURT1A transcripts were most abundant in de-etiolating cotyledon samples, and CURT1A was concentrated at the PLB periphery. In curt1a etioplasts, PLB-associated thylakoids were swollen and failed to form grana stacks. In contrast, PLBs had cracks in their lattices in curt1c etioplasts. Our data provide evidence that CURT1A is required for pre-granal thylakoid assembly from PLB tubules during de-etiolation, while CURT1C contributes to cubic crystal growth in the dark.

Diamondoid characterization in condensate by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry: The Junggar Basin of Northwest China

Diamondoids in crude oil are useful for assessing the maturity of oil in high maturation. However, they are very difficult to separate and accurately quantify by conventional geochemical methods due to their low abundance in oil. In this paper, we use comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS) to study the compounds in condensates from the Junggar Basin of northwest China and address their geological and geochemical applications. GC×GC-TOFMS improves the resolution and separation efficiency of the compounds. It not only separates the compounds that coelute in conventional GC-MS (e.g., 4, 8-dimethyl-diamantane and trimethyl-diamantane) but also allows the identification of compounds that were not previously detected (e.g., trimethyl-diamantane (15A)). A reversed-phase column system improves the separation capabilities over the normal phase column system. The diamondoid indexes indicate that a representative condensate from Well DX 10 is highly mature with equivalent Ro being approximately 1.5%.

Use of the Raman spectrometer in gemmological laboratories: review

The current paper gives an overview of the development of Raman spectrometry in gemmological laboratories. While before 1990s, no commercial gemmological laboratory possessed such an instrument, all larger international labs have acquired these instruments by now. The Raman spectrometer is routinely used for the detection of emerald fillers, HPHT treatment of diamonds, analysis of the nature of a gemstone, analysis of gemstone inclusions and treatments, and the characterisation of natural or colour enhanced pearls and corals. Future developments in gemstone research lie in the closer analysis of the features of Raman and PL spectra and in the combination of several instruments.

Spectroscopic research on ultrahigh pressure (UHP) macrodiamond at Copeton and Bingara NSW, Eastern Australia

Millions of macrodiamonds were mined from Cenozoic placers across Eastern Australia, 98% from within the Copeton and Bingara area (85 km across) in the Phanerozoic New England region of New South Wales (NSW). Raman spectroscopy of inclusions in uncut diamond, from the Copeton and Bingara parcels, identifies them as ultrahigh pressure (UHP) macrodiamond formed during termination of subduction by continental collision. Infrared spectral properties of the two parcels are critically similar in terms of nitrogen abundance (low in zoned diamond, high in unzoned diamond), requiring a pair of different growth mechanisms/protoliths. Within each parcel, the degrees of nitrogen aggregation are relatively strong and coherent, but they are so different from each other (moderate aggregation for Bingara, strong for Copeton) that the two parcels require separate primary and local sources. The local sources are post-tectonic alkali basaltic intrusions which captured UHP minerals (garnet, pyroxene, diamond) from eclogite-dominated UHP terranes (density stranded at depth-mantle, lower crust). X-ray diffraction studies on Copeton diamond indicate a normal density, despite previous reports of anomalously high density. For non-fluorescent diamond, a 2nd order Raman peak, which is prominent in theoretical perfect diamond and in African cratonic diamond, is suppressed in Copeton and Bingara UHP macrodiamond. Pervasive deformation during macrodiamond growth probably causes this suppression, the strong nitrogen aggregation, and the exceptional durability documented through industrial use.

Brown diamonds from an eclogite xenolith from Udachnaya kimberlite, Yakutia, Russia

We have performed petrographic and spectroscopic studies of brown diamonds from an eclogite xenolith from the Udachnaya pipe (Yakutia, Russia). Brown diamonds are randomly intermixed with colorless ones in the rock and often located at the grain boundaries of clinopyroxene and garnet. Brown diamonds can be characterized by a set of defects (H4, N2D and a line at 490.7 nm) which are absent in colorless diamonds. This set of defects is typical for plastically deformed diamonds and indicates that diamonds were likely annealed for a relatively short period after deformation had occurred. Excitation of brown colored zones with a 632.8 nm He-Ne laser produced the typical diamond band plus two additional bands at 1730 cm(-1) and 3350 cm(-1). These spectral features are not genuine Raman bands, and can be attributed to photoluminescence at ∼710 nm (1.75 eV) and ∼802 nm (1.54 eV). No Raman peak corresponding to graphite was observed in regions of brown coloration. Comparison with previous reports of brown diamonds from eclogites showed our eclogitic sample to have a typical structure without signs of apparent deformation. Two mechanisms with regard to diamond deformation are proposed: deformation of eclogite by external forces followed by subsequent recrystallization of silicates or, alternatively, deformation by local stress arising due to decompression and expansion of silicates during ascent of the xenolith to surface conditions.

Diamonds in the rough: identification of individual naphthenic acids in oil sands process water

Expansion of the oil sands industry of Canada has seen a concomitant increase in the amount of process water produced and stored in large lagoons known as tailings ponds. Concerns have been raised, particularly about the toxic complex mixtures of water-soluble naphthenic acids (NA) in the process water. To date, no individual NA have been identified, despite numerous attempts, and while the toxicity of broad classes of acids is of interest, toxicity is often structure-specific, so identification of individual acids may also be very important. Here we describe the chromatographic resolution and mass spectral identification of some individual NA from oil sands process water. We conclude that the presence of tricyclic diamondoid acids, never before even considered as NA, suggests an unprecedented degree of biodegradation of some of the oil in the oil sands. The identifications reported should now be followed by quantitative studies, and these used to direct toxicity assays of relevant NA and the method used to identify further NA to establish which, or whether all NA, are toxic. The two-dimensional comprehensive gas chromatography-mass spectrometry method described may also be important for helping to better focus reclamation/remediation strategies for NA as well as in facilitating the identification of the sources of NA in contaminated surface waters.

Two-photon fluorescence correlation spectroscopy of lipid-encapsulated fluorescent nanodiamonds in living cells

Dynamics of fluorescent diamond nanoparticles in HeLa cells has been studied with two-photon fluorescence correlation spectroscopy (FCS). Fluorescent nanodiamond (FND) is an excellent fluorescent probe for bioimaging application, but they are often trapped in endosomes after cellular uptake. The entrapment prohibits FCS from being performed in a time frame of 60 s. Herein, we show that the encapsulation of FNDs within a lipid layer enhances the diffusion of the particles in the cytoplasm by more than one order of magnitude, and particles as small as 40 nm can be probed individually with high image contrast by two-photon excited luminescence. The development of the technique together with single particle tracking through one-photon excitation allows probing of both short-term and long-term dynamics of single FNDs in living cells.

Selective targeting of green fluorescent nanodiamond conjugates to mitochondria in HeLa cells

Fluorescent cellular biomarkers play a prominent role in biosciences. Most of the available biomarkers have some drawbacks due to either physical and optical or cytotoxic properties. In view of this, we investigated the potential of green fluorescent nanodiamonds as biomarkers in living cells. Nanodiamonds were functionalized by attaching antibodies that target intracellular structures such as actin filaments and mitochondria. Then, the nanodiamond conjugates were transfected into HeLa cells. Transfections were mediated by 4(th)-generation dendrimers, cationic liposomes and protamine sulfate. Using fluorescence microscopy, we confirmed successful transfections of the nanodiamonds into HeLa cells. Nanodiamond fluorescence could be easily differentiated from cellular autofluorescence. Furthermore, nanodiamonds could be targeted selectively to intracellular structures. Therefore, nanodiamonds are a promising tool for intracellular assays.

UV and VIS Raman spectra of natural lonsdaleites: towards a recognised standard

A UV laser has now been used to measure the Raman spectrum of lonsdaleite. This mineral species is a little-known hexagonal form of carbon having no known P-T field of stability. Lonsdaleite is known to coexist with diamond and/or graphite in certain impact structures and meteorites. Its presence in microinclusions in some ultrahigh-pressure eclogites is under discussion as there is a considerable wavenumber overlap of the sp(3) Raman band of lonsdaleite in the 1200-1400 cm(-1) region with certain bands of haematite, graphite and diamond, and also with "disordered-diamond" having a downshifted wavenumber. Various incoherent previously published values of the Raman bands are briefly reviewed and an attempt is made to establish a reference spectrum. Four samples of lonsdaleite from the Zapadnaya and Popigai impact structures (Ukraine) were measured with three different laser sources (488, 514.5 and 325 nm) with two Raman spectrometers. UV-Raman was less fluorescent. All the new data were coherent in establishing an sp(3) band centred at 1324+/-4 cm(-1) with a FWHM about five times wider than that of diamond and an intensity about 500 times weaker. The presence of a second band giving a weak shoulder around 1225 cm(-1) is discussed with respect to the alternative of one continuous asymmetrical band.

Characterization and application of single fluorescent nanodiamonds as cellular biomarkers

Type Ib diamonds emit bright fluorescence at 550-800 nm from nitrogen-vacancy point defects, (N-V)(0) and (N-V)(-), produced by high-energy ion beam irradiation and subsequent thermal annealing. The emission, together with noncytotoxicity and easiness of surface functionalization, makes nano-sized diamonds a promising fluorescent probe for single-particle tracking in heterogeneous environments. We present the result of our characterization and application of single fluorescent nanodiamonds as cellular biomarkers. We found that, under the same excitation conditions, the fluorescence of a single 35-nm diamond is significantly brighter than that of a single dye molecule such as Alexa Fluor 546. The latter photobleached in the range of 10 s at a laser power density of 10(4) W/cm(2), whereas the nanodiamond particle showed no sign of photobleaching even after 5 min of continuous excitation. Furthermore, no fluorescence blinking was detected within a time resolution of 1 ms. The photophysical properties of the particles do not deteriorate even after surface functionalization with carboxyl groups, which form covalent bonding with polyL-lysines that interact with DNA molecules through electrostatic forces. The feasibility of using surface-functionalized fluorescent nanodiamonds as single-particle biomarkers is demonstrated with both fixed and live HeLa cells.

Thermal conductivity of diamond nanorods: Molecular simulation and scaling relations

Thermal conductivities of diamond nanorods are estimated from molecular simulations as a function of radius, length, and degree of surface functionalization. While thermal conductivity is predicted to be lower than carbon nanotubes, their thermal properties are less influenced by surface functionalization, making them prime candidates for thermal management where heat transfer is facilitated by cross-links. A scaling relation based on phonon surface scattering is developed that reproduces the simulation results and experimental measurements on silicon nanowires.

Imaging and sizing of diamond nanoparticles

Typical disturbances of biological environment such as background scatter and refractive index variations have little effect on the size-dependent scattering property of highly refractive nanocrystals, which are potentially attractive optical labels. We report on what is to our knowledge the first investigation of these scattering optical labels, and their sizing, in particular, by imaging at subvideo frame rates and analyzing samples of diamond nanocrystals deposited on a glass substrate in air and in a matrix of weakly scattering polymer. The brightness of a diffraction-limited spot appears to serve as a reliable measure of the particle size in the Rayleigh scattering limit.

Simulation and bonding of dopants in nanocrystalline diamond

The doping of the wide-band gap semiconductor diamond has led to the invention of many electronic and optoelectronic devices. Impurities can be introduced into diamond during chemical vapor deposition or high pressure-high temperature growth, resulting in materials with unusual physical and chemical properties. For electronic applications one of the main objectives in the doping of diamond is the production of p-type and n-type semiconductors materials; however, the study of dopants in diamond nanoparticles is considered important for use in nanodevices, or as qubits for quantum computing. Such devices require that bonding of dopants in nanodiamond must be positioned substitutionally at a lattice site, and must exhibit minimal or no possibility of diffusion to the nanocrystallite surface. In light of these requirements, a number of computational studies have been undertaken to examine the stability of various dopants in various forms of nanocrystalline diamond. Presented here is a review of some such studies, undertaken using quantum mechanical based simulation methods, to provide an overview of the crystal stability of doped nanodiamond for use in diamondoid nanodevices.

Gas chromatographic analysis of volatiles in fluid and gas inclusions

Most geological samples and some synthetic materials contain fluid inclusions. These inclusions preserve for us tiny samples of the liquid and/or the gas phase that was present during formation, although in some cases they may have undergone significant changes from the original material. Studies of the current composition of the inclusions provide data on both the original composition and the change since trapping. These conclusions are seldom larger than 1 millimeter in diameter. The composition varies from a single major compound (e.g., water) in a single phase to a very complex mixture in one or more phases. The concentration of some of the compounds present may be at trace levels. We present here some analyses of inclusion on a variety of geological samples, including diamonds. We used a sample crusher and a gas chromatography-mass spectrometry (GC-MS) system to analyze for organic and inorganic volatiles present as major to trace constituents in inclusions. The crusher is a hardened stainless-steel piston cylinder apparatus with tungsten carbide crushing surfaces, and is operated in a pure helium atmosphere at a controlled temperature. Samples ranging from 1 mg to 1 g were crushed and the released volatiles were analyzed using multi-chromatographic columns and detectors, including the sensitive helium ionization detector. Identification of the GC peaks was carried out by GC-MS. This combination of procedures has been shown to provide geochemically useful information on the processes involved in the history of the samples analyzed.

Aromatic hydrocarbons, diamonds, and fullerenes in interstellar space: puzzles to be solved by laboratory and theoretical astrochemistry

New research is presented, and previous research is reviewed, on the emission and absorption of interstellar aromatic hydrocarbons. Emission from aromatic hydrocarbons dominates the mid-infrared emission of many galaxies, including our own Milky Way galaxy. Only recently have aromatic hydrocarbons been observed in absorption in the interstellar medium, along lines of sight with high column densities of interstellar gas and dust. Much work on interstellar aromatics has been carried out, with astronomical observations and laboratory and theoretical astrochemistry. In many cases, the predictions of laboratory and theoretical work are confirmed by astronomical observations but, in other cases, clear discrepancies exist that provide problems to be solved by a combination of astronomical observations, laboratory studies, and theoretical studies. The emphasis of this paper will be on current outstanding puzzles concerning aromatic hydrocarbons that require further laboratory and theoretical astrochemistry to resolve. This paper will also touch on related topics where laboratory and theoretical astrochemistry studies are needed to explain astrophysical observations, such as a possible absorption feature due to interstellar 'diamonds' and the search for fullerenes in space.

Dental diamond burs made with a new technology

STATEMENT OF PROBLEM

Conventional diamond burs show several limitations such as the heterogeneity of grain shapes, the difficulty of automation during fabrication, the decrease of cutting effectiveness due to repeated sterilization, and short lifetime. An additional shortcoming may be represented by the potential release of Ni+2 ions from the metallic binder into the body fluids.

PURPOSE

This study investigated a new diamond rotative instrument made of a continuous diamond film obtained by chemical vapor deposition (CVD). This bur, characterized by a pure diamond cutting surface without metallic binder between crystals, was compared with a conventional diamond bur.

MATERIAL AND METHODS

Cutting tests were followed by SEM examination and electron microprobe analysis (EMA) to trace metallic residues both at the surface of the bur and the substrate.

RESULTS

EMA demonstrated that the metals Ni, Cr, Si, and Fe were present in the metallic binder matrix of the conventional bur and could be smeared on the surface of the substrate during cutting. SEM showed that significant loss of diamond particles occurred during cutting. On the other hand, no discrete particles sheared off the CVD bur. The smearing of the metallic binder cannot occur using the new bur.

CONCLUSION

The new CVD bur not only proves to be more efficient in its cutting ability and longevity, but also excludes the risk of metal contamination. This last aspect concerns both the pollution of the oral environment and the contamination of the ceramic during the laboratory manufacturing of dental restorations.

The origin of chondritic macromolecular organic matter: a carbon and nitrogen isotope study

The N and C abundances and isotopic compositions of acid-insoluble carbonaceous material in thirteen primitive chondrites (five unequilibrated ordinary chondrites, three CM chondrites, three enstatite chondrites, a CI chondrite and a CR chondrite) have been measured by stepped combustion. While the range of C isotopic compositions observed is only delta 13C = 30%, the N isotopes range from delta 15N approximately -40 to 260%. After correction for metamorphism, presolar nanodiamonds appear to have made up a fairly constant 3-4 wt% of the insoluble C in all the chondrites studied. The apparently similar initial presolar nanodiamond to organic C ratios, and the correlations of elemental and isotopic compositions with metamorphic indicators in the ordinary and enstatite chondrites, suggest that the chondrites all accreted similar organic material. This original material probably most closely resembles that now found in Renazzo and Semarkona. These two meteorites have almost M-shaped N isotope release profiles that can be explained most simply by the super-position of two components, one with a composition between delta 15N = -20 and -40% and a narrow combustion interval, the other having a broader release profile and a composition of delta 15N approximately 260%. Although isotopically more subdued, the CI and the three CM chondrites all appear to show vestiges of this M-shaped profile. How and where the components in the acid-insoluble organics formed remains poorly constrained. The small variation in nanodiamond to organic C ratio between the chondrite groups limits the local synthesis of organic matter in the various chondrite formation regions to at most 30%. The most 15N-rich material probably formed in the interstellar medium, and the fraction of organic N in Renazzo in this material ranges from 40 to 70%. The isotopically light component may have formed in the solar system, but the limited range in nanodiamond to total organic C ratios in the chondrite groups is consistent with most of the organic material being, presolar.

The nature and origin of interstellar diamond

Microscopic diamond was recently discovered in oxidized acid residues from several carbonaceous chondrite meteorites (for example, the C delta component of the Allende meteorite). Some of the reported properties of C delta seem in conflict with those expected of diamond. Here we present high spatial resolution analytical data which may help to explain such results. The C delta diamond is an extremely fine-grained (0.5-10 nm) single-phase material, but surface and interfacial carbon atoms, which may comprise as much as 25% of the total, impart an 'amorphous' character to some spectral data. These data support the proposed high-pressure conversion of amorphous carbon and graphite into diamonds due to grain-grain collisions in the interstellar medium although a low-pressure mechanism of formation cannot be ruled out.