Study of Stick-slip torsional vibration in Drilling Operation

The purpose of this work is to analyze drill string torsional vibrations modes, and to advise on whether it is best to minimize, if not entirely eliminate these vibration or if they can be utilize to the benefit of the drilling performances. The work consists of two generic parts. One addressing resonance vibrations when employing roller cone bits, the other dealing with torsional vibrations when drilling using PDC bits. Furthermore , to equip the engineer with the knowledge to visualize and understand the shocks suffered by downhole tools, their distinction and causes to allows them to CORRECTLY interpret the shock data in Real Time, and subsequently take intelligent decisions to mitigate those vibrations and shocks. The methodology implemented in this project involved Simulating Drillstring and find out natural frequency behavior of vibration and the friction force side effect. The results would be interpreted in term of external force frequency and the force frequency of the system which resulted always into resonance, this resonance affect the drillstring by either „Twist off, or Washout‟ Phenomena. Simulating would entirely be conducted in Matlab software, Drillstring Dynamic Calculator would have been far better to run the simulation. Amodel describing the torsional behaviour of generic oil drillstring has been presented. This model is acombination of some previous model proposed in the literature. The problem of modeling is divided into two different problems, first, the problem of modeling of torsional behaviours of the drillstring. Second, the problem of modeling the rock bit interaction originating stick –slip self excited oscillations. This behavior are describes by the drilling parameters behaviour in the simulation. The result obtained shows that the most important of this modelingis to show that inserting RPM of more than 45m/h would endanger the drilling operation special when it hard formation as showing the drillstring disturbances

Validation of the Subtle and Blatant Racism Scale for Asian American College Students (SABR-A 2 )

This investigation describes the validation of a measure of perceived racism developed to assess racial experiences of Asian American college students. In three studies across two different regions of the United States, there was strong evidence for the validation of the 8-item Subtle and Blatant Racism Scale for Asian American College Students (SABR-A 2 ). The subtle racism subscale refers to instances of discrimination attributable implicitly to racial bias or stereotype, whereas the blatant racism subscale refers to instances of discrimination attributable explicitly to racial bias or stereotype. The two-subscale structure of the SABR-A 2 was supported by exploratory and confirmatory factor analyses and demonstrated discriminant, convergent, and incremental validity, as well as internal reliability and stability over 2 weeks

Leidenfrost behavior in drop-wall impacts at combustor-relevant ambient pressures

Liquid-fueled combustion systems demand optimal performance over a range of operating conditions—requiring predictable fuel injection events, spray breakup, and vaporization across a range of temperatures and pressures. In direct injection combustors, these sprays impinge directly on combustion chamber surfaces. Although the outcome of fuel droplets impacting a wall is primarily driven by the wall temperature and the Leidenfrost effect, the shifting liquid-vapor saturation point with pressure may influence the droplet-wall heat transfer rate and transition from nucleate to film boiling. In this paper, the role of ambient pressure on the droplet impact regimes, spreading rate, and droplet rebound velocity during impact are explored for representative low boiling point and high boiling point pure hydrocarbon liquids (n-heptane and n-decane). High-speed image sequences of the drop-wall impact were acquired for ambient pressures of 1–20 bar and wall temperatures ranging from 35–300 ∘C with a drop Weber number of ~ 50. Droplet impact sequences were recorded using a high-speed CMOS camera and were processed to measure the droplet spread, droplet rebound velocity and track the droplet centroid motion. The dynamics of the drop spreading and rebound show similar behavior across a range of ambient pressures with the largest differences observed for wetted versus non-wetted cases (above the Leidenfrost temperature). For both fluids, the onset of drop rebound remains bounded by the saturation temperature (shifting with ambient pressure) and the thermodynamic limit of liquid superheat. This leads to a decrease in the superheat temperature above the saturation point as the critical pressure is approached

Genome-Wide Association Analyses in 128,266 Individuals Identifies New Morningness and Sleep Duration Loci

Disrupted circadian rhythms and reduced sleep duration are associated with several human diseases, particularly obesity and type 2 diabetes, but until recently, little was known about the genetic factors influencing these heritable traits. We performed genome-wide association studies of self-reported chronotype (morning/evening person) and self-reported sleep duration in 128,266 white British individuals from the UK Biobank study. Sixteen variants were associated with chronotype (P<5x10(-8)), including variants near the known circadian rhythm genes RGS16 (1.21 odds of morningness, 95% CI [1.15, 1.27], P = 3x10(-12)) and PER2 (1.09 odds of morningness, 95% CI [1.06, 1.12], P = 4x10(-10)). The PER2 signal has previously been associated with iris function. We sought replication using self-reported data from 89,283 23andMe participants;thirteen of the chronotype signals remained associated at P<5x10(-8) on meta-analysis and eleven of these reached P< 0.05 in the same direction in the 23andMe study. We also replicated 9 additional variants identified when the 23andMe study was used as a discovery GWAS of chronotype (all P<0.05 and meta-analysis P<5x10(-8)). For sleep duration, we replicated one known signal in PAX8 (2.6 minutes per allele, 95% CI [1.9, 3.2], P = 5.7x10(-16)) and identified and replicated two novel associations at VRK2 (2.0 minutes per allele, 95% CI [1.3, 2.7], P = 1.2x10(-9);and 1.6 minutes per allele, 95% CI [1.1, 2.2], P = 7.6x10(-9)). Although we found genetic correlation between chronotype and BMI (rG = 0.056, P = 0.05);undersleeping and BMI (rG = 0.147, P = 1x10(-5)) and over-sleeping and BMI (rG = 0.097, P = 0.04), Mendelian Randomisation analyses, with limited power, provided no consistent evidence of causal associations between BMI or type 2 diabetes and chronotype or sleep duration. Our study brings the total number of loci associated with chronotype to 22 and with sleep duration to three, and provides new insights into the biology of sleep and circadian rhythms in humans

The p.M292T NDUFS2 mutation causes complex I-deficient Leigh syndrome in multiple families

Isolated complex I deficiency is the most frequently observed oxidative phosphorylation defect in children with mitochondrial disease, leading to a diverse range of clinical presentations, including Leigh syndrome. For most patients the genetic cause of the biochemical defect remains unknown due to incomplete understanding of the complex I assembly process. Nonetheless, a plethora of pathogenic mutations have been described to date in the seven mitochondrial-encoded subunits of complex I as well as in 12 of the nuclear-encoded subunits and in six assembly factors. Whilst several mitochondrial DNA mutations are recurrent, the majority of these mutations are reported in single families. We have sequenced core structural and functional nuclear-encoded subunits of complex I in a cohort of 34 paediatric patients with isolated complex I deficiency, identifying pathogenic mutations in 6 patients. These included a novel homozygous NDUFS1 mutation in an Asian child with Leigh syndrome, a previously identified NDUFS8 mutation (c.236C>T, p.P79L) in a second Asian child with Leigh-like syndrome and six novel, compound heterozygous NDUFS2 mutations in four white Caucasian patients with Leigh or Leigh-like syndrome. Three of these children harboured an identical NDUFS2 mutation (c.875T>C, p.M292T), which was also identified in conjunction with a novel NDUFS2 splice site mutation (c.866+4A>G) in a fourth Caucasian child who presented to a different diagnostic centre, with microsatellite and single nucleotide polymorphism analyses indicating that this was due to an ancient common founder event. Our results confirm that NDUFS2 is a mutational hotspot in Caucasian children with isolated complex I deficiency and recommend the routine diagnostic investigation of this gene in patients with Leigh or Leigh-like phenotypes

Rare germline variants are associated with rapid biochemical recurrence after radical prostate cancer treatment: a PPCG study

Background: Germline variants explain more than a third of prostate cancer (PrCa) risk, but very few associations have been identified between heritable factors and clinical progression.  Objective: To find rare germline variants that predict time to biochemical recurrence (BCR) after radical treatment in men with PrCa, and understand the genetic factors associated with such progression.  Design, Setting and Participants: Whole-genome sequencing data from blood DNA were analysed for 850 PrCa patients with radical treatment from the Pan Prostate Cancer Group (PPCG consortium) from UK, Canada, Germany, Australia and France. Findings were validated using 383 patients from The Cancer Genome Atlas (TCGA).  Outcome Measurements and Statistical analysis: 15,822 rare (MAF<1%) predicted-deleterious coding germline mutations were identified. Optimal multifactor and univariate Cox regression models were built to predict time to BCR after radical treatment, using germline variants grouped by functionally annotated gene-sets. Models were tested for robustness using bootstrap resampling.  Results: Optimal Cox regression multifactor models showed that rare predicted-deleterious germline variants in “Hallmark” gene-sets were consistently associated with altered time to BCR. Three gene-sets had a statistically significant association with risk-elevated outcome when modelling all samples: PI3K/AKT/mTOR, Inflammatory response and KRAS signalling (up). PI3K/AKT/mTOR and KRAS signalling (up) were also associated among patients with higher grade cancer, as were Pancreas-beta cells, TNFA signalling via NKFB and Hypoxia, the latter of which was validated in the independent TCGA dataset.  Conclusions: We demonstrate for the first time that rare deleterious coding germline variants robustly associate with time to BCR after radical treatment, including cohort-independent validation. Our findings suggest that germline testing at diagnosis could aid clinical decisions by stratifying patients for differential clinical management.  Patient summary: PrCa patients with particular genetic mutations have a higher chance of relapsing after initial radical treatment, potentially providing opportunities to identify which patients might need additional treatments earlier

Riociguat treatment in patients with chronic thromboembolic pulmonary hypertension: Final safety data from the EXPERT registry

Objective: The soluble guanylate cyclase stimulator riociguat is approved for the treatment of adult patients with pulmonary arterial hypertension (PAH) and inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH) following Phase

Multi-component fuel drop-wall interactions at high ambient pressures

In direct injection engines, multicomponent fuels are injected at high pressures—resulting in a finely atomized spray which impacts on the hot wall of the piston crown and cylinder liner. The variable operating load of typical combustors results in widely varying wall temperature and ambient pressures. For quantitative prediction of the combustion spray physics, detailed data is required for the impact of multicomponent fuel drops on these heated surfaces at combustor-relevant pressures. A series of experiments are presented for blends of n-heptane and n-decane, as well as a commercial gasoline blend impacting heated walls at ambient pressures in the range of 1–20 bar and wall temperatures up to 350 °C. Time-resolved image sequences for single drop impacts are used to classify the onset of Leidenfrost phenomena, nucleate boiling, and film spreading. Results are summarized by impact regime diagrams, and bi-component mixtures are found to replicate the systematic behavior observed for a gasoline drop with the higher volatility components controlling behavior at low pressure, and a decreasing effect at high pressure. These experiments establish a baseline for multicomponent drop-wall interactions at combustor-relevant pressure, and will aid in development of simulations incorporating relevant spray-wall physics in combustors.This article is published as Chausalkar, Abhijeet, Chol-Bum M. Kweon, and James B. Michael. "Multi-component fuel drop-wall interactions at high ambient pressures." Fuel 283: 119071. DOI: 10.1016/j.fuel.2020.119071.</p

Leidenfrost behavior in drop-wall impacts at combustor-relevant ambient pressures

Liquid-fueled combustion systems demand optimal performance over a range of operating conditions—requiring predictable fuel injection events, spray breakup, and vaporization across a range of temperatures and pressures. In direct injection combustors, these sprays impinge directly on combustion chamber surfaces. Although the outcome of fuel droplets impacting a wall is primarily driven by the wall temperature and the Leidenfrost effect, the shifting liquid-vapor saturation point with pressure may influence the droplet-wall heat transfer rate and transition from nucleate to film boiling. In this paper, the role of ambient pressure on the droplet impact regimes, spreading rate, and droplet rebound velocity during impact are explored for representative low boiling point and high boiling point pure hydrocarbon liquids (n-heptane and n-decane). High-speed image sequences of the drop-wall impact were acquired for ambient pressures of 1–20 bar and wall temperatures ranging from 35–300 ∘C with a drop Weber number of ~ 50. Droplet impact sequences were recorded using a high-speed CMOS camera and were processed to measure the droplet spread, droplet rebound velocity and track the droplet centroid motion. The dynamics of the drop spreading and rebound show similar behavior across a range of ambient pressures with the largest differences observed for wetted versus non-wetted cases (above the Leidenfrost temperature). For both fluids, the onset of drop rebound remains bounded by the saturation temperature (shifting with ambient pressure) and the thermodynamic limit of liquid superheat. This leads to a decrease in the superheat temperature above the saturation point as the critical pressure is approached.This article is published as Chausalkar, Abhijeet, Chol-Bum M. Kweon, Song-Charng Kong, and James B. Michael. "Leidenfrost behavior in drop-wall impacts at combustor-relevant ambient pressures." International Journal of Heat and Mass Transfer 153 (2020): 119571. DOI: 10.1016/j.ijheatmasstransfer.2020.119571.</p