Proportionality Factor Research Articles

Study Explores Interaction Between Bit Whirl and High-Frequency Torsional Oscillations

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 23989, “The Nature of the Interaction Between Bit Whirl and High-Frequency Torsional Oscillations,” by Andreas Hohl, SPE, and Armin Kueck, Baker Hughes, and Vincent Kulke, TU Braunschweig, et al. The paper has not been peer reviewed. Copyright 2024 International Petroleum Technology Conference. _ Understanding the interaction of high-frequency torsional oscillations (HFTO) with other vibrational phenomena is essential to develop effective HFTO mitigation strategies. While coupling with axial vibrations and stick/slip already have been studied extensively, the interaction of HFTO with lateral vibrations has received less attention. The complete paper analyzes this interaction based on a bit/rock interaction model that accounts for the superimposed movement of whirl and HFTO at the bit. The new bit model provides a physics-based explanation of why bit backward whirl and torsional vibrations cannot be observed simultaneously. Introduction The torsional movement of HFTO is localized to the lower part of the bottomhole assembly (BHA). The amplitudes along the distance from the bit are scaled by complex mode shapes with a comparably small wavelength. This deflection of the BHA leads to high tangential acceleration and dynamic torsional torque loads. The self-excitation mechanism of HFTO can be modeled as a drilling torque that decreases when the bit rotary speed increases. The nonlinear drilling torque characteristic can be identified from field data. Because both stick/slip and HFTO correspond to a torsional movement of the drilling system, and both are excited by the rock-cutting process, they interact strongly. The mitigation strategies and optimal operational parameters to manage HFTO are, thus, strongly linked to the understanding of this interaction. In this work, the interaction of HFTO and bit backward whirl was analyzed and modeled to further interpret this observation. Bit backward whirl is a complex lateral movement of the bit. The understanding of the interaction between HFTO and backward whirl drives improvements of vibration-mitigation strategies and bit design to mitigate HFTO or bit backward whirl. Modeling of the Cutting Forces To study the interaction of whirl and HFTO in more detail, a simplified bit cutting-force model is needed. For a common polycrystalline-diamond-compact (PDC) bit, the cutting torque of the bit results from the rock-cutting process. The cutting process results in cutting forces on each individual cutter. For simpler modeling, the cutting forces are assumed to be proportional to the normal force on each cutter. The proportionality factor between the normal force and the cutting force at a cutter is called cutter aggressiveness and is dependent on the velocity of the cutter. The radial distance between the geometric center of the bit and a cutter, multiplied by the cutting force, results in the portion of the cutting torques of each cutter. These add up to the overall bit torque. The three central variables in the torque calculations are the normal force, cutting speed, and cutter aggressiveness.

Analysis for sparse channel representation based on dictionary learning in massive MIMO systems

AbstractThe accuracy analysis of dictionary sparse representation for channels in massive MIMO systems is a relatively unexplored field. Existing research has primarily focused on investigating the accuracy of dictionary sparse representation using simulation in massive MIMO systems, but has not provided quantitative accuracy analysis. To address this gap, the correlation numerical proportional factor is proposed to represent the accuracy performance of non‐zero elements in the coefficient matrix. Additionally, a qualitative analytical formula for dictionary sparse representation accuracy is provided and an optimal upper bound for the correlation numerical proportional factor is established. Furthermore, the innovation indicates that the accuracy of dictionary sparse representation is mainly influenced by the cross‐correlation between the pilots matrix and the dictionary matrix, as well as sparsity. The author has also developed a method for minimizing the correlation numerical proportional factor. In order to obtain an optimal sparse representation coefficient matrix, a cross‐correlation matrix is constructed and an analytical expression is derived for it as well as its use as an optimal hard decision threshold is determined. Finally, a sparse representation coefficient optimization algorithm is proposed using this optimal threshold. Simulation results demonstrate that this algorithm can significantly improve channel sparse dictionary representation accuracy.

Massive MIMO uplink and downlink joint representation based on couple dictionary learning

AbstractThe challenge of jointly representing both the uplink (UL) and downlink (DL) in massive multiple input multiple output (MIMO) systems have been tackled. Considering the angular reciprocity, a couple dictionary learning (CDL) support to enhance performance and address high complexity has been introduced. This approach minimizes the number of pilots and improves accuracy. Currently, accuracy analysis of UL/DL representation primarily relies on simulation. To bridge this gap, a proportion factor (PF) operator is proposed for CDL to assess accuracy. Specifically, a qualitative analysis formula is provided for accuracy and an optimal upper bound is established. Through theoretical proof, it is demonstrated that the accuracy of CDL for representation is mainly influenced by the cross‐correlation between the pilot matrix and the dictionary matrix. Inspired by PF operator, an optimal couple dictionary learning (OCDL) algorithm using singular value decomposition (SVD) is introduced to obtain dictionary updating, aiming at high‐precision representation. By establishing normalized mean squared error (NMSE), successful representation ratio, bit error rate (BER), and constellation performance, an OCDL algorithm that outperforms existing methods is showcased and channel representation accuracy is enhanced significantly.

Vorticity skewness of finite-amplitude rapidly rotating Rayleigh–Bénard convection

Rotating Rayleigh–Bénard convection denotes the convection between a warm plate and a cold plate in a rotating environment. It is a classic model for understanding convective vortices in the atmosphere and ocean. The influence of background rotation on fluid inertia breaks the symmetry between cyclones and anticyclones. Such a symmetry breaking could be represented by vorticity skewness, which still lacks a systematic theory. Rapidly rotating convection with stress-free boundaries and unit Prandtl number is a convenient starting point. The investigation starts from the convective onset stage, where the vortices grow stationarily. Asymptotic analysis shows that the volumetric vorticity skewness $S$ is produced by the interaction between the $n=0,1$ and $n=1,2$ vertical eigenmodes. The $n=0$ (barotropic) mode contributes positively to $S$ mainly by stretching the vertical relative vorticity, an ageostrophic effect. The $n=2$ mode makes a minor negative contribution to $S$ by preferentially intensifying the outflow over the inflow, a non-hydrostatic effect. The theory predicts $S$ to be proportional to the global Rossby number defined with the volumetric standard deviation of vorticity, ${Ro_g}$ . The proportional factor does not depend on the Rayleigh and Ekman numbers, agreeing with direct numerical simulations. Then the system enters the equilibrium stage. The stretching of vertical vorticity still contributes to $S$ dominantly. At ${Ro_g}\gtrsim 0.5$ , the emergent unsteady flow significantly suppresses the asymmetry between the inflow and outflow strength, and weakens its influence on $S$ .

Highest oxygen consumption prediction: introducing variable theoretical proportional factors for different sports.

The use of a fixed theoretical-proportional-factor (TPF15) is one of the indirect highest-oxygen-consumptions (HOC) assessment methods, but it may not accurately reflect the physiological differences across various sports (cycling-triathlon-running-football-multisport). The aim of this study is to evaluate the variability of TPF across different sports, proposing a series of sport-specific new TPF values for more accurate HOC estimation. A sample of 340 adults (26.01 ± 7.18years) performed a maximal-incremental-test using sport-specific-ergometers. HOC was considered for cycling , whereas for the other investigated sports it was considered . HOC was directly measured using a gas-analyzer, and TPF values were calculated using heart rate (HR): the ratio of HRmax/HRrest multiplied for the measured values of HOC. A one-way ANOVA was used to measure differences and Bland-Altman plots were constructed to compare predicted and actual / . Actual HOC was significantly greater than those predicted by the fixed TPF15 (P < 0.001). Sport-specific new TPF values ranged from 16.55 in multisport to 20.15 in cycling, consistently exceeding the old fixed TPF15, and predicting therefore better HOC. The new TPF exhibited a closer agreement with the directly measured / compared to the TPF15. Furthermore, the new TPF reduced the typical-measurement-error (14.94-17.78%) compared to TPF15 (15.63-24.13%). This study suggests that new TPF values predict / with higher accuracy compared to the traditional method. The use of HRmax and HRrest values allows to customize training programs for different athletes. Future research should focus on validating these findings across larger populations of athletes.

Prevalence and Associated Factors of Paroxysmal Atrial Fibrillation and Atrial Arrhythmias During Hospitalizations for Exacerbation of COPD.

This study aimed to investigate the proportion and risk factors of paroxysmal atrial fibrillation (AF) and atrial arrhythmias (AA) in patients hospitalized for acute exacerbation of chronic obstructive pulmonary disease (AECOPD) in Vietnam. A prospective observational study was conducted at two major hospitals in Hanoi, Vietnam, from January 2022 to January 2023. A total of 197 AECOPD patients were recruited. ECG and 24-hour Holter ECG were used to diagnose paroxysmal AF and AA. The prevalence of paroxysmal AF and AA were 15.2% and 72.6%, respectively. Factors associated with a higher likelihood of paroxysmal AF included aging 75 years old and above (aOR = 3.15; 95% CI: 1.28 to 8.48), Premature atrial complex (PAC) with 500 or more (aOR = 3.81; 95% CI: 1.48 to 10.97) and severity of COPD as group C and D (aOR = 3.41; 95% CI: 1.28 to 10.50). For AA, aging 75 years old and above (aOR = 2.25; 95% CI: 1.28 to 5.20), smoking (aOR = 2.10; 95% CI: 1.07 to 4.23) and P wave dispersion (PWD) with 40 milliseconds or more (aOR = 3.04; 95% CI: 1.54 to 6.19) were associated with a higher likelihood of AA. Overall, our findings highlight the associated factors with the paroxysmal AF and AA among AECOPD patients. This underscores the importance of a multifaceted approach to risk assessment and management in this vulnerable population, focusing not only on respiratory symptoms but also on comprehensive cardiovascular evaluation and intervention.

Relativistic generalized uncertainty principle for a test particle in four-dimensional spacetime

The generalized uncertainty principle provides a promising phenomenological approach to reconciling the fundamentals of general relativity with quantum mechanics. As a result, noncommutativity, measurement uncertainty, and the fundamental theory of quantum mechanics are subject to finite gravitational fields. The generalized uncertainty principle (RGUP) on curved spacetime allows for the imposition of quantum-induced elements on general relativity (GR) in four dimensions. In the relativistic regimes, the determination of a test particle’s spacetime coordinates, [Formula: see text], becomes uncertain. There exists a specific range of coordinates where the accessibility to [Formula: see text] is notably limited. Consequently, the spacetime coordinates lack both smoothness and continuity. The quantum-mechanical calculations of the spacetime coordinates are directly linked to their measurement through the expectation value [Formula: see text]. This expectation value is dependent on [Formula: see text], which is itself limited by a minimum measurable length [Formula: see text]. A crucial finding presented in this script is the existence of a lower bound for the Hamiltonian, which implies the stability of the quantum nature of spacetime. The direct correlation between [Formula: see text] and [Formula: see text] is a significant discovery, suggesting a proportional relationship. The conjecture is made that the primary metric g carries all essential information regarding spacetime curvature and serves a role akin to the Jacobian determinant in general relativity. Moreover, the linear relationship between [Formula: see text] and the Planck length [Formula: see text] is established with a proportionality factor of [Formula: see text], where [Formula: see text] denotes the RGUP parameter. The discretization of spacetime coordinates results in the discontinuity of the test particle’s wavefunction [Formula: see text], leading to an unrealistic [Formula: see text]. It is also noted that the lower limit of [Formula: see text] is directly proportional to the fundamental tensor.

The Effect of Cation Contamination on the Water Transport for PEM Water Electrolysis

Large-scale hydrogen production by PEM water electrolysis (PEMWE) in the energy sector requires a deep understanding of the system behaviour in failure cases and possible recovery procedures. This includes the purification of the anolyte feed water because the contamination with ions can cause the PEMWE stack to breakdown.[1] For instance, the presence of iron trace cations or other metal cations in the feed water leads to a performance loss due to higher ohmic resistance of the cell and higher iR-free voltages.[2] [3] Moreover, cation contamination might influence the water transport in a PEMWE cell. In principle, the transfer of the water molecules to the cathode is proportional to the proton flux from the cathode to the anode. The proportionality factor is defined as water transport coefficient and is also temperature dependent.[4] In case of the mono- and multivalent cations as trace elements in the feed water, the water loading of the membrane, which is expressed by water molecules per sulfonic acid group of the membrane, λ, decreases over time and leads to successive increase in the ohmic resistance. [5] However, the influence of cation contamination on the water transport in PEMWE is poorly understood to date.In this work, we investigated the effect of cation contamination in the anode feed water on the water crossover for PEMWE. Cation contamination experiments were carried out at a constant current density by adding different concentrations such as K2SO4, Na2SO4, etc. to the anode feed water. All electrochemical measurements were carried out in an in-house test bench equipped with a single cell of 5 cm2 geometric electrode area and potentiostat with booster. A commercially available catalyst coated perfluorosulfonic acid membranes (loading of 0.3 mg cm-2 geo Pt/C and 1 mgcm-2 geo IrOx) was used. The anode and cathode compartments were kept at atmospheric pressure and cell temperature of 80°C. To determine the water crossover from anode to cathode at different current densities, the cathode exhaust was cooled in a heat exchanger and measured by a gravimetric method. [4] Firstly, a conditioning procedure was performed with purified feed water until steady cell performance was achieved. The cell performance was evaluated using polarization curves, electrochemical impedance spectroscopy (EIS) and water crossover measurements. The last two are of particular interest, because they provide information about membrane humidification. The Tafel slope and mass transport overvoltage were established from the polarization curves and high frequency resistance (HFR). We observed a significant rise of the cell voltage by adding cations to the anode water feed within few hours. The analysis of Tafel slope and EIS data also reveal an increase of ohmic and mass transport resistances. In these experiments, we were able to correlate the HFR results with the water crossover as a function of the nature of the cation and its concentrations. Our data shows that the specific water crossover per current density decreases as a consequence of cation contamination. The switch back to purified feed water allows us to monitor the dynamics of the performance recovery process obtained from EIS and water crossover measurements. Additional measurements of the polarization curves and HFR were used to distinguish between reversible and irreversible degradation processes due to the cation contamination.Altogether, we present the effect of cation contamination on the water transport processes and provide deeper insights into the mass transport and performance losses for PEMWE.

Proportion and risk factors for hospital-acquired venous thromboembolism in children: a systematic review and meta-analysis of data from 20 million individuals in 22 countries

BackgroundHospital-acquired venous thromboembolism (HA-VTE) in children has been widely regarded. ObjectivesWe aimed to analyze the proportion and risk factors for HA-VTE in hospitalized children. MethodsWe conducted a comprehensive systematic search across 4 databases from 1990 to 2023. Cochran Q test was used to evaluate the heterogeneity of the effect sizes of study, and I2 statistic was used to quantify the heterogeneity. Pooled estimates were calculated by the inverse-variance weighted method in a fixed-effect model or a random-effect model when heterogeneity was low (I2 < 25%) or high (I2 > 25%), respectively. ResultsIn total, 105 original papers and 20,718,294 patients were included in the study, and the proportion of HA-VTE in children was 4.1% (95% CI, 2.9%-5.2%). Although the proportion of venous thromboembolism increased over the various research periods, the differences were not statistically significant. In the subgroup analysis based on country, the proportion of pediatric HA-VTE was lowest in the United Kingdom and highest in Spain, whereas when based on region, the proportion was lowest in Asia and highest in North America. Multiple HA-VTE risk factors were identified, including central venous catheter use, age of >10 years, surgery, injury, infection, obesity, mechanical ventilation, blood transfusion, malignancy, coagulation and hemorrhagic disorders, and length of hospital stay. ConclusionIn this study, we systematically analyzed the proportion and risk factors of HA-VTE in hospitalized children. Our findings provide valuable insights for the prevention and treatment of HA-VTE in pediatric patients.

Leaves to Measure Light Intensity.

Quantitative measurement of light intensity is a key step in ensuring the reliability and the reproducibility of scientific results in many fields of physics, biology, and chemistry. The protocols presented so far use various photoactive properties of manufactured materials. Here, leaves are introduced as an easily accessible green material to calibrate light intensity. The measurement protocol consists in monitoring the chlorophyll fluorescence of a leaf while it is exposed to a jump of constant light. The inverse of the characteristic time of the initial chlorophyll fluorescence rise is shown to be proportional to the light intensity received by the leaf over a wide range of wavelengths and intensities. Moreover, the proportionality factor is stable across a wide collection of plant species, which makes the measurement protocol accessible to users without prior calibration. This favorable feature is finally harnessed to calibrate a source of white light from exploiting simple leaves collected from agarden.

Permeability and Induced Polarization of Mudstones

AbstractElectrical measurements can be used to estimate hydraulic properties such as permeability (k) in sedimentary rocks. Previous work has focused on sandstones, siltstones, and carbonates, while investigations on mudstones have rarely been reported. In this study, we report on electrical geophysical measurements for 23 mudstone samples using an experimental approach designed to reliably saturate these low permeability mudstones. The modified Hagen‐Poiseuille model linking permeability to the formation factor (F) and an effective pore radius (r) provides an excellent fit to the data set with a near‐constant pore radius, indicating that the effective porosity (1/F) is the controlling factor on k. In these samples, the surface area normalized to pore volume (Spor), frequently used in permeability estimation models, varies by 1–2 orders of magnitude and is thus not a reliable proxy of the inverse effective hydraulic radius. The formation factor also exerts the primary control on induced polarization (IP) parameters, whereas Spor shows no relation to the IP parameters. A strong linear relationship is found between IP parameters (imaginary conductivity and normalized chargeability) and surface conductivity, although the proportionality factor is significantly lower than those observed in more permeable rocks and sediments. Apparent relationships between the polarization strength‐derived and time constant‐derived geophysical length scales and the effective hydraulic radius appear to be driven by variations in the electrochemical parameters (i.e., specific polarizability and diffusion coefficient). Overall, these findings emphasize that predicting hydraulic properties from electrical measurements in fine‐grained rocks remains challenging and requires further investigation into the electrochemical properties involved.

Proportion and risk factors of epiretinal membrane in residents of Brussels with versus without diabetes mellitus.

To compare the proportion of epiretinal membrane (ERM) between individuals with diabetes mellitus (DM) and without DM, who live in Brussels, to investigate possible risk factors for ERM formation and to compare the results with the ones of large population studies. Participants were divided into two groups; 99 patients with DM (group A) and 103 individuals without DM (group B). All participants underwent an undilated 7-field color fundus photography and a spectral domain optical coherence tomography (SD-OCT). Age, gender, race, type of diabetes, duration of medical treatment of diabetes, HbA1C rate, smoking, previous cataract surgery and educational level were investigated as possible risk factors. Epiretinal membrane was detected in 17.2% of group A and in 11.7% of group B participants. The difference is not statistically significant (χ2 (1) = 1.252, p = 0.263). The proportion of ERM was significantly associated with age in both groups (p = .009 and p < .001 respectively), as well as with smoking (p = .023) and previous cataract surgery (p = .028) in patients with DM. There is no statistically significant difference of ERM proportion between the two groups of the study. Age was recognized as a risk factor for both groups, while smoking and previous cataract surgery were identified as predictors only for diabetics.

A Novel Error-Based Adaptive Feedback Zeroing Neural Network for Solving Time-Varying Quadratic Programming Problems

This paper introduces a novel error-based adaptive feedback zeroing neural network (EAF-ZNN) to solve the time-varying quadratic programming (TVQP) problem. Compared to existing variable gain ZNNs, the EAF-ZNN dynamically adjusts the parameter to adaptively accelerate without increasing to very large values over time. Unlike adaptive fuzzy ZNN, which only considers the current convergence error, EAF-ZNN ensures regulation by introducing a feedback regulation mechanism between the current convergence error, the historical cumulative convergence error, the change rate of the convergence error, and the model gain parameter. This regulation mechanism promotes effective neural dynamic evolution, which results in high convergence rate and accuracy. This paper provides a detailed analysis of the convergence of the model, utilizing four distinct activation functions. Furthermore, the effect of changes in the proportional, integral, and derivative factors in the EAF-ZNN model on the rate of convergence is explored. To assess the superiority of EAF-ZNN in solving TVQP problems, a comparative evaluation with three existing ZNN models is performed. Simulation experiments demonstrate that the EAF-ZNN model exhibits a superior convergence rate. Finally, the EAF-ZNN model is compared with the other three models through the redundant robotic arms example, which achieves smaller position error.

Proportion and Potential Risk Factors of Poor Glycemic Control among Patients with Type 2 Diabetes Mellitus: Experience of a Tertiary Center in Baghdad, Iraq, 2020

Background: Diabetes Mellitus is the most prevalent metabolic disorder worldwide. Effective diabetes self-management and keeping the Glycosylated hemoglobin level within the normal range could decrease the burden on the health system by reducing hospital admissions and diabetic complications, lowering the financial strain on the health system. Objective: To recognize the potential risk factors of poor glycemic control in patients having type 2 Diabetes Mellitus in Baghdad, Iraq. Patients and Methods: This cross-sectional study was conducted in the Diabetes and Endocrine Center at Al-Kindy Teaching Hospital, Baghdad, Iraq, from June to November 2020. The total number of the study's participants was 234. Based on the cutoff point of glycosylated hemoglobin of 7, the patients with glycosylated hemoglobin of ≥7 were considered uncontrolled, and those with glycosylated hemoglobin of &lt;7 were considered controlled. Results: The proportion of cases with uncontrolled diabetes was 68.4% (160). The remaining 74 patients had controlled diabetes. Age, sex, marital status, and employment status were not significantly associated with the control status (P&gt;0.05). The binary analysis showed a significant association observed between the control status and level of education (P=0.001), income (P=0.001), presence of comorbidities (P=0.028), positive family history (P=0.03), dyslipidemia (P=0.001), cholesterol level (P=0.002), high triglyceride level (P=0.001), and low-density lipoprotein-cholesterol level (P=0.025). The smoking status, body mass index, and high-density lipoprotein-cholesterol level were not significantly associated with the control status (P&gt;0.05). The disease characteristics, including the disease duration, fasting blood glucose, type of medication, self-monitoring, healthy diet, physical activity, and medication adherence, were significant factors (P&lt;0.001). The multivariate regression method showed that dyslipidemia, FBS≥130, physical inactivity, and poor medication adherence were significant predictors for uncontrolled DM (P-value = 0.03, 0.001, 0.03, and 0.043, respectively). Conclusion: The most important potentially modifiable risk factors for poor diabetes control were dyslipidemia, physical inactivity, and poor adherence to the management protocol. Enhancing the education of patients and their healthcare providers on these factors is crucial to improving the patients’ control status.

Substantiation of the Use of a Flexible Chain-Type Subsoiler for Improving the Agrotechnological Properties of Soil

Technogenic influence on agricultural soils leads to the transformation of their morphological features, significantly worsens their agrochemical, physical, mechanical and agrotechnological properties, prevents the optimal use of potential soil fertility and, as a result, leads to a decrease in crop yield. Mechanical soil decompaction when using various types of subsoilers, including the flexible chain-type working body (the chain), is used to prevent the negative consequences of technogenic influence. According to the results of the analytical calculations, the proportionality factor of the chain length, which determines the ratio of the width of the plow grip to the chain length of a flexible subsoiler, was established. The specified coefficient is proportional and equals 2.4. The use of the specified coefficient allows us, at the stage of the development of the design and technological documentation, to determine the main design parameter of the flexible subsoiler, which is the length of the used chain depending on the width of the plow grip. The surface of the field cultivated with the experimental tillage tool meets the requirements for sowing the agricultural crops without performing additional technological operations.

A dose of nature to reduce sexual crimes in public outdoor spaces: Proposing the Landscape-Sexual Crime Model

Sexual crime is a critical global social problem. There remains a critical knowledge gap concerning whether and to what extent sexual crimes in public outdoor spaces can be influenced by landscape morphology of green spaces. This missing knowledge hinders the effective use of green spaces to reduce sexual crimes in these public settings. To address this issue, we collected a dataset comprising 5,155 cases of sexual crimes that occurred in public outdoor spaces in the United States from August 2021 to July 2022. A random forest model was employed to examine the statistical relationships between landscape morphology and sexual crimes. Additionally, we utilized the Shapley Additive Explanations (SHAP) model to quantify the interaction effects of landscape morphology with socioeconomic and demographic characteristics. This study yields three key findings: (1) Both the proportion and configuration factors of landscape morphology may significantly influence the sexual crime probability. (2) The relationships between landscape morphology and sexual crimes are nonlinear, and threshold values for the satisfactory dose and the preferred dose of green spaces can be identified. (3) There are significant interaction effects between landscape morphology with socioeconomic and demographic characteristics, emphasizing the importance of prioritizing green space interventions in socioeconomically disadvantaged areas. Lastly, through summarizing the findings of this study and previous research, we propose the Landscape-Sexual Crime Model (LSCM), which advocates for further research to explore effective strategies for using green spaces to reduce sexual crimes.

Beltrami fields with Morse proportionality factor

In this work we study Beltrami fields with non-constant proportionality factor on R3. More precisely, we analyze the existence of vector fields X satisfying the equations curl(X)=fX and div(X)=0 for a given f∈C∞(R3) in a neighborhood of a point p∈R3. Since the regular case has been treated previously, we focus on the case where p is a non-degenerate critical point of f. We prove that for a generic Morse function f, the only solution is the trivial one X≡0 (here generic refers to explicit arithmetic properties of the eigenvalues of the Hessian of f at p). Our results stem from the introduction of algebraic obstructions, which are discussed in detail throughout the paper.

Posttraumatic Hydrocephalus Following Decompressive Craniectomy in Traumatic Brain Injury: Proportion and Risk Factors

Abstract Background Posttraumatic hydrocephalus (PTH) is an important cause of morbidity after decompressive craniectomy (DC) following traumatic brain injury (TBI). Early diagnosis and treatment of PTH can prevent further neurological compromise in patients who are recovering from TBI. Objective The aim of this study was to assess the proportion of patients who develop hydrocephalus after undergoing DC and to identify the factors associated with PTH requiring surgical treatment in patients undergoing DC for TBI. Methods Data of patients undergoing DC for TBI in the Trauma Neurosurgery Unit, Medical College Hospital, Trivandrum, between June and December 2020 were collected prospectively. Results A total of 48 patients who underwent DC were studied. Six (12.5%) patients developed PTH. The patients were divided into two groups: PTH (patients who developed hydrocephalus) and non-PTH (patients who did not develop hydrocephalus). Age, sex, mode of injury, severity of injury, and preoperative radiological findings were not associated with the development of PTH. A distance of craniectomy margin from the midline of less than 2.5 cm was found to be statistically significant. No statistical difference was found in the outcome among the PTH and non-PTH groups. Conclusion Craniectomy with a superior limit too close to the midline can predispose patients undergoing DC to the development of hydrocephalus. We therefore suggest performing wide DCs with the superior limit greater than 25 mm from the midline.

Non-thyroidal Illness in Children with Congestive Heart Failure

To estimate the proportion and risk factors of non-thyroidal illness (NTI) in children with congenital heart disease (CHD) with congestive heart failure (CHF). This study enrolled children (6 weeks to 60 months age) with CHD and CHF. The clinical profile and disease severity, derived from the Pediatric Early Warning Score (PEWS) was recorded. Baseline blood samples were taken within 24 hours of hospitalization and evaluated for free tri-iodothyronine (fT3), free thyroxine (fT4), thyroid stimulating hormone (TSH), N-terminal pro-brain natriuretic peptide (NT pro-BNP) and reverse T3. A total of 80 (64 acyanotic CHD) children of median (interquartile range) age 5 (2.5, 8.0) months were enrolled. NTI was seen in 37 (46%) of whom 27 had low fT3 levels. The proportion of NTI was highest in children with severe disease (20/30), than moderate (4/9) or mild disease (13/41) (p=0.018). Ten (27%) patients with NTI died compared to 2 (4.7%) without NTI with unadjusted odds ratio (OR) [95% confidence interval (CI)] 7.593 (1.54, 37.38); p=0.006. After adjusting for NTI, shock and NT-pro-BNP levels, PEWS was the only significant predictor of mortality (OR: 1.41, 95% CI: 1.03, 1.92; p=0.032). Linear regression for fT3 identified a significant relationship with log NT-BNP [beta -3.541, (95% CI: -1.387, -0.388)] and with TSH [beta 2.652 (95% CI: 0.054, 0.383)]. The cutoff (area under the curve, 95% CI) that predicted mortality were fT4 <14.5 pmol/L (0.737, 0.60, 0.88), fT3/rT3 index <1.86 pg/ng (0.284, 0.129, 0.438) and NT pro-BNP >3725 pg/mL (0.702; 0.53, 0.88). NTI was present in a significant proportion of children with CHD and CHF. fT3 level was significantly associated with NTBNP levels and thus severity of CHF.

Optimizing Teamwork in the Operating Room: A Scoping Review of Actionable Teamwork Strategies.

Suboptimal teamwork in the operating room (OR) is a contributing factor in a significant proportion of preventable complications for surgical patients. Specifying behaviour is fundamental to closing evidence-practice gaps in healthcare. Current teamwork interventions, however, have yet to be synthesized in this way. This scoping review aimed to identify actionable strategies for use during surgery by mapping the existing literature according to the Action, Actor, Context, Target, Time (AACTT) framework. The databases MEDLINE (Medical Literature Analysis and Retrieval System Online), Embase, Cumulated Index to Nursing and Allied Health Literature (CINAHL),Education Resources Information Center (ERIC), Cochrane, Scopus, and PsycINFO were searched from inception to April 5, 2022. Screening and data extraction were conducted in duplicate by pairs of independent reviewers. The search identified 9,289 references after the removal of duplicates. Across 249 studies deemed eligible for inclusion, eight types of teamwork interventions could be mapped according to the AACTT framework: bundle/checklists, protocols, audit and feedback, clinical practice guidelines, environmental change, cognitive aid, education, and other), yet many were ambiguous regardingthe actors and actions involved. The 101 included protocol interventions appeared to be among the most actionable for the OR based on the clear specification of ACCTT elements, and their effectiveness should be evaluated and compared in future work.