Method of drilling process control and experimental studies of resistance forces during bits drilling with PDC cutters

A rational, theoretically proved and empirically verified control system is a condition for optimal management of the drilling process in compliance with the criteria for minimizing the cost of time and material resources. A new generation of rock-cutting tools using PDC cutters (polycrystalline diamante cutters), which are extremely effective when drilling wells for various purposes in medium-hard rocks, dictates the need to develop methods and criteria for optimal control of the drilling process using this tool. The paper presents an analysis of the force interaction between rock-cutting elements, face rock, and drilling mud saturated with slam, highlights the influencing factors and provides dependencies for determining the parameters of rock failure. Empirical verification of the theoretical propositions was carried out based on the data analysis from experimental bit drilling of marble with PDC cutters with a diameter of 76.2 mm, processed using the method of full factor experiment to obtain mathematical models of factors and their graphical interpretation. The method of controlling the drilling process based on the optimal ratio of the tool rotation frequency, axial weight and deepening per one turnover is considered, which allows determining the rock failure mode at the well bottom by indirect signs and choose the optimal values of the drilling mode parameters that correspond to the most optimal conditions in terms of achieving the maximum mechanical drilling speed in conjunction with the rational mode of rock-cutting tool operation. A scheme is presented that contains possible variants of the bit run mode and ways to recognize them by the ratio of the deepening per turnover and the rotation frequency of the rock-cutting tool

Conservation Laws in Higher-Order Nonlinear Optical Effects

Conservation laws of the nonlinear Schr\"{o}dinger equation are studied in the presence of higher-order nonlinear optical effects including the third-order dispersion and the self-steepening. In a context of group theory, we derive a general expression for infinitely many conserved currents and charges of the coupled higher-order nonlinear Schr\"{o}dinger equation. The first few currents and charges are also presented explicitly. Due to the higher-order effects, conservation laws of the nonlinear Schr\"{o}dinger equation are violated in general. The differences between the types of the conserved currents for the Hirota and the Sasa-Satsuma equations imply that the higher-order terms determine the inherent types of conserved quantities for each integrable cases of the higher-order nonlinear Schr\"{o}dinger equation

Proizvodnja limunske kiseline pomoću kvasaca uzgojenih na podlogama s glicerolom, dobivenim pri proizvodnji biodizela

The possibility of using glycerol and glycerol-containing waste from biodiesel manufacture as a carbon and energy source for microbiological production of citric acid has been studied. Acid formation on the selective media had previously been tested in 66 yeast strains of different genera (Candida, Pichia, Saccharomyces, Torulopsis and Yarrowia). Under growth limitation by nitrogen, 41 strains (belonging mainly to species Yarrowia lipolytica) produced acids; unlike 25 strains of the genera Debaryomyces, Candida, Pichia, Saccharomyces and Torulopsis. Among the 41 acid-producing strains, mutant strain Yarrowia lipolytica N15 was selected since it was able to produce citric acid presumably in high amounts. The citric acid production by the selected strain was studied in dependence on the medium pH, aeration and concentration of glycerol. Under optimal conditions, the mutant Y. lipolytica N15 produced up to 98 g/L of citric acid when grown in a fermentor with the medium containing pure glycerol, and 71 g/L of citric acid when grown on glycerol-containing waste. The effect of growth phases on physiological peculiarities of the citric acid producer was discussed.Ispitana je mogućnost uporabe glicerola i otpada bogatoga glicerolom, dobivenih pri proizvodnji biodizela, kao izvora ugljika i energije za mikrobnu proizvodnju limunske kiseline. Prethodno je ispitana proizvodnja limunske kiseline na selektivnim podlogama pomoću 66 sojeva kvasaca različitih vrsta (Candida, Pichia, Saccharomyces, Torulopsis i Yarrowia). Pri smanjenim koncentracijama dušika 41 soj (uglavnom vrste Yarrowia lipolytica) mogao je proizvesti limunsku kiselinu, dok 25 sojeva vrsta Debaryomyces, Candida, Pichiа, Saccharomyces i Torulopsis to nije moglo. Od 41 soja odabran je mutant Yarrowia lipolytica N15, jer je mogao proizvesti veliku količinu limunske kiseline. Ispitan je utjecaj pH-vrijednosti podloge, prozračivanja tijekom reakcije i koncentracije glicerola u podlozi na proizvodnju limunske kiseline pomoću toga soja. U optimalnim uvjetima u fermentoru mutant Yarrowia lipolytica N15 proizveo je do 98 g/L limunske kiseline na podlozi sa čistim glicerolom, a do 71 g/L limunske kiseline na podlozi s otpadom bogatim glicerolom. U radu se raspravlja i o utjecaju faze rasta na fiziološke značajke kvasaca pri proizvodnji limunske kiseline

Shape Transition in the Epitaxial Growth of Gold Silicide in Au Thin Films on Si(111)

Growth of epitaxial gold silicide islands on bromine-passivated Si(111) substrates has been studied by optical and electron microscopy, electron probe micro analysis and helium ion backscattering. The islands grow in the shape of equilateral triangles up to a critical size beyond which the symmetry of the structure is broken, resulting in a shape transition from triangle to trapezoid. The island edges are aligned along $Si[110]$ directions. We have observed elongated islands with aspect ratios as large as 8:1. These islands, instead of growing along three equivalent [110] directions on the Si(111) substrate, grow only along one preferential direction. This has been attributed to the vicinality of the substrate surface.Comment: revtex version 3.0, 11 pages 4 figures available on request from [email protected] - IP/BBSR/93-6

Near Resonant Spatial Images of Confined Bose-Einstein Condensates in the '4D' Magnetic Bottle

We present quantitative measurements of the spatial density profile of Bose-Einstein condensates of sodium atoms confined in a new '4D' magnetic bottle. The condensates are imaged in transmission with near resonant laser light. We demonstrate that the Thomas-Fermi surface of a condensate can be determined to better than 1%. More generally, we obtain excellent agreement with mean-field theory. We conclude that precision measurements of atomic scattering lengths and interactions between phase separated cold atoms in a harmonic trap can be measured with high precision using this method.Comment: 15 pages, 3 figures. Submitted 10/30/97, accepted for publication in Phys. Rev. A Rapid Com

Surface reconstruction induced geometries of Si clusters

We discuss a generalization of the surface reconstruction arguments for the structure of intermediate size Si clusters, which leads to model geometries for the sizes 33, 39 (two isomers), 45 (two isomers), 49 (two isomers), 57 and 61 (two isomers). The common feature in all these models is a structure that closely resembles the most stable reconstruction of Si surfaces, surrounding a core of bulk-like tetrahedrally bonded atoms. We investigate the energetics and the electronic structure of these models through first-principles density functional theory calculations. These models may be useful in understanding experimental results on the reactivity of Si clusters and their shape as inferred from mobility measurements.Comment: 9 figures (available from the author upon request) Submitted to Phys. Rev.

Resonant versus nonresonant nuclear excitation of 115 In by positron annihilation

We have measured the resonant cross section σn for nuclear excitation of 115In via the radiationless annihilation of a positron with a K-shell electron using a monoenergetic positron beam and a thin In target. We find an upper limit on the resonant cross section σn<4.3×10−26cm2 at a 99% confidence level, compared to the cross section σβ=1.7×10−25cm2 determined by two previous measurements of nuclear excitation of 115In using the broad spectrum of positrons from the beta decay of 64Cu. Together these results imply the existence of a hitherto unidentified nonresonant channel for nuclear excitation via energetic positrons.Physic

The Potential and Challenges of Nanopore Sequencing

A nanopore-based device provides single-molecule detection and analytical capabilities that are achieved by electrophoretically driving molecules in solution through a nano-scale pore. The nanopore provides a highly confined space within which single nucleic acid polymers can be analyzed at high throughput by one of a variety of means, and the perfect processivity that can be enforced in a narrow pore ensures that the native order of the nucleobases in a polynucleotide is reflected in the sequence of signals that is detected. Kilobase length polymers (single-stranded genomic DNA or RNA) or small molecules (e.g., nucleosides) can be identified and characterized without amplification or labeling, a unique analytical capability that makes inexpensive, rapid DNA sequencing a possibility. Further research and development to overcome current challenges to nanopore identification of each successive nucleotide in a DNA strand offers the prospect of ‘third generation’ instruments that will sequence a diploid mammalian genome for ~$1,000 in ~24 h.Molecular and Cellular BiologyPhysic

Effect of SGLT2 inhibitors on stroke and atrial fibrillation in diabetic kidney disease: Results from the CREDENCE trial and meta-analysis

BACKGROUND AND PURPOSE: Chronic kidney disease with reduced estimated glomerular filtration rate or elevated albuminuria increases risk for ischemic and hemorrhagic stroke. This study assessed the effects of sodium glucose cotransporter 2 inhibitors (SGLT2i) on stroke and atrial fibrillation/flutter (AF/AFL) from CREDENCE (Canagliflozin and Renal Events in Diabetes With Established Nephropathy Clinical Evaluation) and a meta-Analysis of large cardiovascular outcome trials (CVOTs) of SGLT2i in type 2 diabetes mellitus. METHODS: CREDENCE randomized 4401 participants with type 2 diabetes mellitus and chronic kidney disease to canagliflozin or placebo. Post hoc, we estimated effects on fatal or nonfatal stroke, stroke subtypes, and intermediate markers of stroke risk including AF/AFL. Stroke and AF/AFL data from 3 other completed large CVOTs and CREDENCE were pooled using random-effects meta-Analysis. RESULTS: In CREDENCE, 142 participants experienced a stroke during follow-up (10.9/1000 patient-years with canagliflozin, 14.2/1000 patient-years with placebo; hazard ratio [HR], 0.77 [95% CI, 0.55-1.08]). Effects by stroke subtypes were: ischemic (HR, 0.88 [95% CI, 0.61-1.28]; n=111), hemorrhagic (HR, 0.50 [95% CI, 0.19-1.32]; n=18), and undetermined (HR, 0.54 [95% CI, 0.20-1.46]; n=17). There was no clear effect on AF/AFL (HR, 0.76 [95% CI, 0.53-1.10]; n=115). The overall effects in the 4 CVOTs combined were: Total stroke (HRpooled, 0.96 [95% CI, 0.82-1.12]), ischemic stroke (HRpooled, 1.01 [95% CI, 0.89-1.14]), hemorrhagic stroke (HRpooled, 0.50 [95% CI, 0.30-0.83]), undetermined stroke (HRpooled, 0.86 [95% CI, 0.49-1.51]), and AF/AFL (HRpooled, 0.81 [95% CI, 0.71-0.93]). There was evidence that SGLT2i effects on total stroke varied by baseline estimated glomerular filtration rate (P=0.01), with protection in the lowest estimated glomerular filtration rate (45 mL/min/1.73 m2]) subgroup (HRpooled, 0.50 [95% CI, 0.31-0.79]). CONCLUSIONS: Although we found no clear effect of SGLT2i on total stroke in CREDENCE or across trials combined, there was some evidence of benefit in preventing hemorrhagic stroke and AF/AFL, as well as total stroke for those with lowest estimated glomerular filtration rate. Future research should focus on confirming these data and exploring potential mechanisms