Breaking Step Research Articles

Mechanism and control of strong rock pressure in the gully area under compound key strata

AbstractIn view of the problem strong rock pressure is easy to occur in coal seam mining in western gully terrain. Based on the coal seam mining conditions in the gully area under the compound key strata of Zhujiamao Coal Mine, the methods of similar simulation, theoretical calculation and analysis, numerical simulation and field measurement are adopted. The dynamic structure model of the key strata of the gully is constructed, and the mechanism and prevention and control measures of the strong rock pressure in the gully area of the working face under the compound key strata are analyzed. The research shows that the upper slope section of the gully area first undergoes rotary deformation, and then the chain structure formed by the broken block occurs sliding instability and impacts inferior key strata, resulting in strong rock pressure behavior in the working face. The calculation formula of the first breaking step distance of the main key strata rotation deformation and sliding instability during the movement of the overlying strata is derived. The calculation results show that the initial rotation deformation and sliding instability breaking step distances are 27 and 142 m, respectively, which are in good agreement with the support crushing at 145 m of the first gully. Using 3DEC numerical simulation, the stress of the second gully is reduced by 3.8 MPa after pressure relief, which verifies the position of strong rock pressure calculated by the formula and provides a theoretical basis for subsequent hydraulic fracturing. According to the mechanism, the comprehensive prevention and control measures of strong rock pressure in gully terrain are put forward. The support resistance of the working face is calculated to be 10,011 kN by the support resistance formula, and the ZY11000/14/34D hydraulic support is used. The working resistance of the calculated dangerous area after hydraulic fracturing is basically lower than 30 MPa, and the control effect is good. It has reference significance for coal seam mining through gully terrain.

Animating hydrogel knotbots with topology-invoked self-regulation

Steering soft robots in a self-regulated manner remains a grand challenge, which often requires continuous symmetry breaking and recovery steps for persistent motion. Although structural morphology is found significant for robotic functions, geometric topology has rarely been considered and appreciated. Here we demonstrate a series of knotbots, namely hydrogel-based robots with knotted structures, capable of autonomous rolling and spinning/rotating motions. With symmetry broken by external stimuli and restored by self-regulation, the coupling between self-constraint-induced prestress and photothermal strain animates the knotbots continuously. Experiments and simulations reveal that nonequilibrium processes are regulated dynamically and cooperatively by self-constraints, active deformations, and self-shadowing effect of the photo-responsive gel. The active motions enable the knotbots to execute tasks including gear rotation and rod climbing. This work paves the way to devise advanced soft robots with self-regulated sustainable motions by harnessing the topology.

Simulation Study and Engineering Application of Weakening Mine Pressure Behavior in Stope through Ground Fracturing Thick and Hard Rock Strata

Fracturing hard roofs by ground hydraulic action is an important control technology for the strong mine pressure in the stope. In this paper, a new simulation method, “separate + interface,” is proposed, and two physical simulation experiments are conducted; the phenomenon of increased goaf pressure and decreased front abutment pressure is discovered after fracturing in the key strata, and then the influence of different fractured crack shapes on the front abutment pressure and the goaf stress is revealed. The results are as follows: Firstly, the separation under the high-level hard strata blocks the transmission of overburden load to the goaf, leading to the high-stress concentration of the coal seam, which is the main reason for the large deformation of roadways and the breakage of a single hydraulic prop in the roadway. Secondly, the weakening effect of mine pressure differs when hard rock strata are fractured artificially with different types of cracks. The peak value of abutment pressure is reduced from 24.91 to 20.60 MPa, 17.80 MPa, and 16.13 MPa with the vertical crack spacing of 20 m, 15 m, and 10 m, respectively, and the related goaf pressure is increased from 2.61 to 3.54 MPa, 3.91 MPa, and 4.34 MPa, respectively. The peak value of abutment pressure decreased from 24.79 to 22.08 MPa, 19.88 MPa, and 17.73 MPa. The related goaf pressure increased from 2.61 to 3.39 MPa, 3.81 MPa, and 4.43 MPa, respectively, with the key strata also fractured into two horizontal layers, three horizontal layers, and four horizontal layers with horizontal fractures. Thirdly, after the hard roof is fractured above the No. 8202 working face, the first breaking step distance of the main roof decreased from 112.6 to 90.32 cm, while the first breaking step distances of KS2 and KS3 decreased from 106.3 and 135.8 cm to 93.5 cm and 104.8 cm, respectively, and the goaf pressure also increased. Compared to the adjacent unfractured No. 8203 working face, the mine pressure intensity of the No. 8202 working face is significantly reduced. The research results can provide useful guidance for the treatment of strong mine pressure.

Site-selective benzylic C-H hydroxylation in electron-deficient azaheterocycles.

Benzylic C-H bonds can be converted into numerous functional groups, often by mechanisms that involve hydrogen atom transfer as the key bond breaking step. The abstracting species is most often an electrophilic radical, which makes these reactions best suited to electron-rich C-H bonds to achieve appropriate polarity matching. Thus, electron deficient systems such as pyridine and pyrimidine are relatively unreactive, and therefore underrepresented in substrate scopes. In this report, we describe a new method for heterobenzylic hydroxylation-essentially an unknown reaction in the case of pyrimidines-that makes use of an iodine(III) reagent to afford very high selectivity towards electron-deficient azaheterocycles in substrates with more than one reactive position and prevents over-oxidation to carbonyl products. The identification of key reaction byproducts supports a mechanism that involves radical coupling in the bond forming step.

Optimized Electronic Modification of S-Doped CuO Induced by Oxidative Reconstruction for Coupling Glycerol Electrooxidation with Hydrogen Evolution

HighlightsS-doped CuO nanorod arrays (S-CuO/CF) constructed by sulfur leaching and oxidative remodeling strategy require only 1.23 and 1.33 V versus hydrogen evolution reaction (HER) to provide glycerol oxidation currents of 100 and 500 mA cm−2.S-CuO/CF shows satisfactory performance (at 100 mA cm−2, Vcell = 1.37 V) assembled as the anode in asymmetric coupled electrolytic cell of glycerol oxidation reaction and HER.The study identifies the key factors involved in the GOR reaction pathway, which include the C–C bond breaking and lattice oxygen deintercalation steps.

Insights into manganese(VII) enhanced oxidation of benzophenone-8 by ferrate(VI): Mechanism and transformation products

Benzophenones (BPs) are commonly used as UV filters in cosmetics and plastics products and are potentially toxic to the environment. This paper presents kinetics and products of BPs oxidation by ferrate(VI) (FeO42−, Fe(VI)) promoted by permanganate (Mn(VII)) . Degradation of 10.0 µM 2,2′-dihydroxy-4-methoxybenzophenone (BP-8)were determined under different experimental conditions ([Mn(VII)] = 0.5–1.5 µM, [Fe(VI)] = 50–150 µM, and pH = 7.0–10.0). The addition of Mn(VII) traces to Fe(VI)-BP-8 solution enhanced kinetics and efficiency of the removal. Similar enhanced removals were also seen for other BPs (BP-1, BP-3, and BP-4) under optimized conditions. The second-order rate constants (k, M−1s−1) of the degradation of BPs showed positive relationship with the energy of the highest occupied orbital (EHOMO). The possible interaction between Mn(VII) and BP-8 and the enhanced generation of Fe(V)/Fe(IV) and •OH was proposed to facilitate the oxidation of the target benzophenone, supported by in-situ electrochemical measurements, theoretical calculations and reactive species quenching experiments. Thirteen oxidation products of BP-8 suggested hydroxylation, bond breaking, polymerization and carboxylation steps in the oxidation. Toxicity assessments by ECOSAR program showed that the oxidized intermediate products posed a tapering ecological risk during the degradation process. Overall, the addition of Mn(VII) could improve the oxidation efficiency of Fe(VI).

Electroweak-flavour and quark-lepton unification: a family non-universal path

We present a family-non-universal extension of the Standard Model where the first two families feature both quark-lepton and electroweak-flavour unification, via the SU(4) Sp(4)L Sp(4)R gauge group, whereas quark-lepton unification for the third family is realised à la Pati-Salam. Via staggered symmetry breaking steps, this construction offers a natural explanation for the observed hierarchical pattern of fermion masses and mixings, while providing a natural suppression for flavour-changing processes involving the first two generations. The last-but-one step in the symmetry-breaking chain is a non-universal 4321 model, characterised by a vector leptoquark naturally coupled mainly to the third generation. The stability of the Higgs sector points to a 4321 → SM symmetry-breaking scale around the TeV, with interesting phenomenological consequences in B physics and collider processes that differ from those of other known 4321 completions.

Research on composite dynamic disaster prevention and control system of mine earthquake and shock in thick and hard rock mines

Abstract With the rapid entry into deep mining of coal mines in China, the impact composite dynamic disaster of thick and hard layer mines and mine earthquakes has increasingly become a major disaster that threatens the safe and efficient mining of deep coal. Studying its occurrence mechanism, disaster prevention and control system has become a new major scientific issue in the field of coal mine safety. This paper proposes a framework for a composite dynamic disaster prevention and control system framework for thick and hard rock mines. First, the gravity forms, extents and deformation characteristics of different rock layers of the structural model are analysed, and the expressions of concentrated force and periodic breaking step distance of rock beams in thick and hard rock layers at the fixed support end are deduced. Then, according to the cause of the shock composite dynamic disaster, finally, the specific testing and calculation methods of mine earthquakes in thick hard rock mines are designed. The regional and local measures to manage compound dynamic disasters are put forward. Experiments show that the system is successfully applied to the mining practice of working face, and the results of water conservancy and stress monitoring support the rationality of the system. And through the implementation of impact prevention and control measures, the safety and disaster prevention and control of the working face was finally realised.

Study on Initial Fracture Characteristics of the Main Roof in Fully Mechanized Caving Mining of Inclined Coalbed

In view of the occurrence conditions of inclined coalbed, the deformation and failure characteristics of the main roof will affect the safe production of the working face. Therefore, the study of the deformation and failure characteristics of the main roof in the inclined coalbed has guiding significance for the control of surrounding rock. This paper takes the II1042 working face of Taoyuan Coal Mine as the research background, adopts the methods of theoretical analysis, numerical calculation, and field practice to analyze the evolutionary characteristics of the initial failure of the main roof of the working face under the background of the inclined coalbed, and explores the mechanical behavior characteristics of the working face roof during the mining of inclined coalbed. Based on the elastic thin plate theory, a mechanical model of the overlying rock roof of a large-angle coal seam is established, and the mechanical characteristics of the surrounding rock under the initial failure of the main roof under the unbalanced load are studied. The stress distribution characteristics of the lower surface are summarized, and the evolution law of the initial fracture of the main roof is summarized. According to the actual geological conditions of the II1042 working face of Taoyuan Coal Mine, the failure characteristics of the main roof and the initial breaking step distance are obtained by analysis, and the analysis results are verified by monitoring the mine pressure of each part of the target working face on site. The research results show that: ① Under the unbalanced load of the inclined coalbed, the deflection surface of the main roof of the coal seam is asymmetrical with respect to the arrangement direction of the working face, and the maximum deflection point is located at the upper middle position of the working face, namely (a/2, 1.836 b/π), and the main roof of the working face breaks for the first time when it advances to 35 m. ② With the advancement of the working face, the two long sides of the roof break first. With the deflection and deformation of the roof, the tensile stress in the middle of the main roof reaches the tensile strength of the rock and breaks, and then the two short sides of the roof break under the action of the breaking and turning of the rock, and the upper short side will break before the lower one. ③ According to the monitoring and analysis of the rock pressure at each part of the working face, it is judged that the initial pressure step distance is between 28.2 m and 34.6 m, which is consistent with the theoretical analysis results.

Removal of large fibrotic bladder blood clots using prostatic tissue morcellator under real-time ultrasound guidance.

ObjectiveLarge fibrotic bladder blood clots are difficult to treat via conventional methods. Hence, we investigated the safety and reliability of real-time ultrasound guidance combined with prostate tissue morcellator in the removal of large fibrotic bladder blood clots in this study.MethodsWe chose 9 patients with large fibrotic bladder blood clots who were treated in our department from January 2019 to December 2020. Under the condition that conventional methods were ineffective in removing the bladder blood clot, real-time ultrasound guidance combined with a prostatic tissue morcellator was used to remove the large fibrotic bladder blood clot through the steps of positioning, breaking, adjusting repositioning and recrushing. After removal, the bipolar electrocautery was replaced to stop bleeding of the bladder mucosa.ResultsAll patients successfully underwent the operation. After the blood clot was removed, the bladder mucosa was examined. There was no damage to the bladder mucosa or muscle layer. The urine was clear at the end of the procedure with slow irrigation, and no bleeding was found again.ConclusionReal-time ultrasound guidance combined with a prostate tissue morcellator was a safe, effective and quick method for the removal of large fibrotic bladder blood clots.

Screening of transition metal doped two-dimensional C2N (TM-C2N) as high-performance catalyst for the non-oxidative propane dehydrogenation

Since last decade, single atom catalysts have massive development in the field of propane dehydrogenation (PDH). In this study, both the catalytic activity and reaction mechanism of 3d, 4d, and 5d transition metal atom anchored on C2N (TM-C2N) for non-oxidative PDH are studied in detail using the density functional theory methods. Firstly, six stable catalysts (Cr-, Mn-, Fe-, Co-, Cu-, and Ag-C2N) are screened out by calculating the difference between the formation energy of the single atom and the cohesive energy of the corresponding bulk metal. Combining the results of adsorption energy and density of states, it is demonstrated that propane and propylene can be stably adsorbed on all screened TM-C2N. The calculated activation barrier and reaction energy of elementary reactions involved in PDH indicate that the initial C−H bond breaking step is determined as the rate-determining step on almost all the screened TM-C2N catalysts. Among all studied TM-C2N, the Fe-C2N possesses excellent catalytic activity even better than other promising catalysts. In addition, the d-band center values of transition metal atoms in screened TM-C2N show a stronger liner relationship with the interaction energy, suggesting that the d-band center may be served as a priority descriptor for the interaction energy between reaction species and catalyst surface rather than for the adsorption energy of reaction species.

Hydrothermal single crystal growth and structural investigation of the stuffed tridymite family as NLO materials

The structures, crystal growth and preliminary NLO properties of a broad class of compounds known as the stuffed tridymites are investigated. The stuffed tridymites of the formula ABC O 4 , where A are the alkali metal ions and B and C are Group 13 and 14 metal ions, respectively, form an extensive series of structures, all of which are based on symmetry breaking of the parent tridymite (SiO 2 ) structure. In all cases the alkali ion resides in channels running parallel to the c- axis formed from six-membered rings of tetrahedra of the metal ions. A large array of structures can be formed though combinations of ordering of the B / C sites, staggered and eclipsed tetrahedra, up/down orientations of the tetrahedra relative to the c -axis, and distortions of the six-membered rings. These symmetry breaking steps can be mixed and matched to form many different structures, and nearly all are in polar acentric space groups. The primary cause of centrosymmetric crystal formation is disorder of the B / C sites. When the sites are well ordered most of the structures are acentric with polar axes. High quality single crystals of most products can be grown using a high pressure hydrothermal method. Preliminary NLO experiments indicate that the compounds are acentric, but have low NLO conversions, which is expected due to the low polarizability of the building blocks. The extremely high percentage of polar acentric structure types, and the ability to correlate the structures to systematic variations of the very large and flexible tridymite structural class, suggests that this can serve as a starting point for designing crystals with many other useful physical properties. • Stuffed tridymites of various compositions were synthesized hydrothermally. • Structural factors affecting symmetry reduction from parent tridymite were identified. • The family exhibits a high percentage of noncentrosymmetric structures. • Powder NLO data was measured on stuffed tridymites.

Homolytic X-H Bond Cleavage at a Gold(III) Hydroxide: Insights into One-Electron Events at Gold.

C(sp3)‐H and O−H bond breaking steps in the oxidation of 1,4‐cyclohexadiene and phenol by a Au(III)‐OH complex were studied computationally. The analysis reveals that for both types of bonds the initial X−H cleavage step proceeds via concerted proton coupled electron transfer (cPCET), reflecting electron transfer from the substrate directly to the Au(III) centre and proton transfer to the Au‐bound oxygen. This mechanistic picture is distinct from the analogous formal Cu(III)‐OH complexes studied by the Tolman group (J. Am. Chem. Soc. 2019, 141, 17236–17244), which proceed via hydrogen atom transfer (HAT) for C−H bonds and cPCET for O−H bonds. Hence, care should be taken when transferring concepts between Cu−OH and Au−OH species. Furthermore, the ability of Au−OH complexes to perform cPCET suggests further possibilities for one‐electron chemistry at the Au centre, for which only limited examples exist.

Molecular insights for uranium(VI) adsorption at nano-TiO2 surfaces and reduction by alcohols and biomass sugars

Titanium oxide (TiO2) plays a critical role for controlling uranium bioavailability, mobility and fate. Adsorption and reduction at nano-TiO2 surfaces represent two effective approaches for uranium remediation, while underlying mechanisms remain poorly understood. A comprehensive first-principles investigation is conducted for U(VI) adsorption and reduction by alcohols at surfaces of rutile and anatase, two major TiO2 polymorphs. Various bidentate/tridentate surface complexes are produced by U(VI) adsorption at rutile (110) and anatase (101) surfaces. Their structures generally resemble each other, while U(VI) adsorption energies differ significantly and reach -347.2 and -267.3 kJ/mol for the most preferred surface complexes, respectively. Hence, both nano-TiO2 polymorphs are effective adsorbents for U(VI), whereas rutile is apparently superior. U(VI) reduction is triggered preferentially by ethanol chemisorption at nano-TiO2 surfaces rather than non-covalent interaction with U(VI) species. Path 3 with hydroxyl‑H1 transfer prior to methylene-H2 transfer is kinetically preferred, and follows cooperative hydrogen/electron transfer mechanism, with U(VI) reduction to U(IV) finishing within one step. Rate-limiting C-H bond breaking steps have energy barriers of 135.5 kJ/mol for rutile and 88.4 kJ/mol for anatase, and U(IV) production occurs more favorably for anatase. U(VI) reduction at nano-TiO2 surfaces is further extended to biomass sugars, and mechanisms remain essentially unaltered. Compared to ethanol, adsorption and reactivity of glucose via secondary rather than primary alcohol sites are more enhanced and U(IV) produces favorably at ambient conditions. Results provide significant molecular insights for U(VI) adsorption and reduction at mineral surfaces that are pivotal to uranium management, and conduce to biomass utilization for environmental remediation.

Quantum Mechanical Methods for Thermal Hazard Risk Assessment in Early Phase Pharmaceutical Development

Quantum mechanical (QM) applications to predict heat of reaction (ΔHr) and thermal stability of strained aminocarbocylic salts, diazo compounds, and nitroalkanes for early phase thermal hazard risk assessment is presented. We provide examples on the use of explicit solvation to predict accurate ΔHr. Based on the QM calculations, the criticality class of a copper-catalyzed C–N coupling reaction is determined according to Stoessel’s reaction criticality class and the predictions are consistent with RC1 calorimetric experiment. We emphasize that to predict accurate ΔHr, it is important to consider the roles of reagents and solvents in QM calculations rather than simply considering the bond formation and bond breaking steps involved with reactants and products. Further, the use of predicted ΔHr for salt formation is applied to predict the thermal stability of bromoacetylene azetidine compounds to establish structure–stability relationship which would be useful to identify stable salt intermediates for safe reaction design. A strong correlation between ΔHr and the left limit of the DSC onset temperature (Tinit, °C) of the of exothermic peak is identified (Tinit = −2.85 ΔHr − 99.5). We propose that this model can be used as a prediction tool for novel azetidine salts to provide an estimate of thermal stability before synthesis. In this paper, for the first time we report molecular electrostatic potential (MESP) descriptor for the prediction of Tinit of diazo compounds. The deepest MESP minimum (Vmin) on the diazo group is considered as a probe to quantify the variation in structural effects. A strong correlation between Vmin and Tinit is found which would provide a new way of interpreting the thermal stability of novel diazo molecules just based on chemical structure. Further, the applicability of Vmin is verified on another set of compounds (nitroalkanes) and a good correlation is obtained. The structure–stability relationships that involves Vmin can be a useful QM descriptor for thermal stability prediction of a variety of molecules.

Remdesivir: Mechanism of Metabolic Conversion from Prodrug to Drug.

Remdesivir (GS-5734) has emerged as a promising drug during the challenging times of COVID-19 pandemic. Being a prodrug, it undergoes several metabolic reactions before converting to its active triphosphate metabolite. It is important to establish the atomic level details and explore the energy profile of the prodrug to drug conversion process. In this work, Density Functional Theory (DFT) calculations were performed to explore the entire metabolic path. Further, the potential energy surface (PES) diagram for the conversion of prodrug remdesivir to its active metabolite was established. The role of catalytic triad of Hint1 phosphoramidase enzyme in P-N bond hydrolysis was also studied on a model system using combined molecular docking and quantum mechanics approach. The overall energy of reaction is 11.47 kcal/mol exergonic and the reaction proceeds through many steps requiring high activation energies. In the absence of a catalyst, the P-N bond breaking step requires 41.78 kcal/mol, which is reduced to 14.26 kcal/mol in a catalytic environment. The metabolic pathways of model system of remdesivir (MSR) were explored completely and potential energy surface diagrams at two levels of theory, B3LYP/6-311++G(d, p) and B3LYP/6-31+G(d), were established and compared. The results highlight the importance of an additional water molecule in the metabolic reaction. The PN bond cleavage step of the metabolic process requires the presence of an enzymatic environment.

Implications of gravitational waves for supersymmetric grand unification

Supersymmetric grand unification based on $SO(10)$ is one of the most attractive paradigms in physics beyond the Standard Model. Inspired by the recent NANOGrav signal, we discuss the implications of detecting a stochastic gravitational wave background emitted by a network of cosmic strings for the $SO(10)$ grand unification. Starting from a minimal model with multiple steps of symmetry breaking, we show that it generally prefers a high intermediate scale above ${10}^{14}\text{ }\text{ }\mathrm{GeV}$ that is favored by observable primordial gravitational waves. The observed spectrum can potentially narrow the possible range of the cosmic string scale and restricts the unified couplings and the unification scale by requiring gauge coupling unification. As an indirect consequence of the high cosmic string scale, the monopole abundance places nontrivial constraints on the theory. These are complementary to the proton decay constraints and probe different facets of supersymmetric $SO(10)$ unification theories.

Pyrrole-Modified Porphyrins Containing Eight-Membered Heterocycles Using a Reversal of the "Breaking and Mending" Strategy.

The conversion of meso-aryl-porphyrins/chlorins to porphyrinoids containing nonpyrrolic heterocycles (so-called pyrrole-modified porphyrins, PMPs) along an approach we dubbed "the breaking and mending of porphyrins" is well known. However, examples are limited to the synthesis of PMPs containing up to six-membered heterocycles; the syntheses of larger rings failed. We report here hitherto unavailable eight-membered chlorin-type PMPs using an inverted "mending and breaking" approach. All examples are based on the addition of N,N'-dimethylurea derivatives to a meso-phenyl-β,β'-dioxoporphyrin, followed by oxidative cleavage of the intermediate diol adduct. We correlate the extremely nonplanar solid-state structures of three crystallographically characterized PMPs containing an eight-membered ring with their solution-state optical properties. The first examples of bis-modified, bacteriochlorin-type PMPs containing either two eight-membered rings or an eight-membered ring and an imidazolone ring are also detailed. Using other N,N'-nucleophiles failed to either generate chlorins containing a β,β'-dihydroxypyrroline, a prerequisite for the "breaking step," or the cleavage of those substrates that did generate a diol underwent subsequent reactions that thwarted the generation of the desired PMPs. This contribution adds novel PMPs containing eight-membered rings, highlights the effects these derivatizations have on the macrocycle conformation, and how that affects their optical properties.

Life cycle assessment of cleaning-in-place operations in egg yolk powder production

The manufacture of egg yolk powder by spray drying requires regular cleaning in order to remove fouling deposits and prevent microbiological growth on the pasteurisation heat exchanger and the spray dryer. A life cycle assessment (LCA) study on a typical powder manufacturing plant, using literature data, indicated that the egg breaking, storage and pasteurisation steps were the major contributors to the plant’s environmental impacts rather than the cleaning-in-place (CIP) operations owing to their high water and electricity consumption (for refrigerated storage). CIP impacts on thermal energy and wastewater emissions were nevertheless significant, and the benefits of using intermittent flows of aqueous NaOH solution in the dryer CIP stage, reported by Yang et al. (2019), were assessed. The latter gave a 21% improvement in terrestrial ecotoxicity impact. Optimising the NaOH/temperature conditions based on experimental data gave more efficient cleaning with lower water, chemicals and energy consumption. Over-cleaning had significant impacts on terrestrial and marine ecotoxicity as well as reducing productivity. Three changes in cleaning technology were considered briefly: electrical heating, solar heating and pumping, and membrane treatment of wastewater. These gave little overall global improvement, partly due to the polluting nature of the available electricity supply (coal-fired) and local benefits to the factory being offset by impacts associated with equipment manufacture.

Evaluation of Different Oocyst DNA Extraction Methods for Cryptosporidium spp. Research in Environmental Samples.

The major problem of the PCR method for the search of protozoan cysts/oocysts in environmental samples is the presence of inhibitors. DNA extraction methods capable of removing inhibitory substances of environmental origin and recovering the DNA are decisive for the efficiency of PCR. This study aimed to compare the efficiency of different DNA extraction methods for the search by Cryptosporidium oocysts in water samples by molecular methods. DNA extraction from water samples was performed using four different methods. Two methods use a chaotropic buffer to extract DNA and promote the selective binding of DNA to a silica membrane (GuSCN-silica and GFX Kit). The other method is based on the lysis and digestion of the samples in buffer and proteinase K, adsorption of impurities by an "InhibitEX" insertion matrix and purification of the DNA by a silica column (QIAamp Kit). The fourth method uses ionic and non-ionic detergents and proteinase K, to solubilize and separate the DNA from proteins, and a paramagnetic resin for DNA purification in the presence of high concentrations of guanidine ions (MAGNEX DNA Kit). Nested-PCR was performed, and the Cryptosporidium SSU rDNA gene amplified. The results demonstrated that MAGNEX and GFX commercial kits showed higher sensitivity, with detection of up to 100 oocysts/mL and 104 oocysts/mL respectively. In conclusion, this study confirmed that for low-DNA environmental samples, extraction methods should include an efficient oocyst wall breaking step, and showed that the best Cryptosporidium DNA extraction methods are those that use paramagnetic resins.