Chondrocalcinosis is common in the absence of knee involvement

Introduction: We aimed to describe the distribution of radiographic chondrocalcinosis (CC) and to examine whether metacarpophalangeal joint (MCPJ) calcification and CC at other joints occurs in the absence of knee involvement. Methods: This was a cross-sectional study embedded in the Genetics of Osteoarthritis and Lifestyle study (GOAL). All participants (n = 3,170) had radiographs of the knees, hands, and pelvis. These were scored for radiographic changes of osteoarthritis (OA), for CC at knees, hips, symphysis pubis, and wrists, and for MCPJ calcification. The prevalence of MCPJ calcification and CC overall, at each joint, and in the presence or absence of knee involvement, was calculated. Results: The knee was the commonest site of CC, followed by wrists, hips, and symphysis pubis. CC was more likely to be bilateral at knees and wrists but unilateral at hips. MCPJ calcification was usually bilateral, and less common than CC at knees, hips, wrists, and symphysis pubis. Unlike that previously reported, CC commonly occurred without any knee involvement; 44.4% of wrist CC, 45.9% of hip CC, 45.5% of symphysis pubis CC, and 31.3% of MCPJ calcification occurred in patients without knee CC. Those with meniscal or hyaline articular cartilage CC had comparable ages (P = 0.21), and neither preferentially associated with fibrocartilage CC at distant joints. Conclusions: CC visualized on a plain radiograph commonly occurs at other joints in the absence of radiographic knee CC. Therefore, knee radiographs alone are an insufficient screening test for CC. This has significant implications for clinical practice, for epidemiologic and genetic studies of CC, and for the definition of OA patients with coexistent crystal deposition

Open Boundary Condition, Wilson Flow and the Scalar Glueball Mass

A major problem with periodic boundary condition on the gauge fields used in current lattice gauge theory simulations is the trapping of topological charge in a particular sector as the continuum limit is approached. To overcome this problem open boundary condition in the temporal direction has been proposed recently. One may ask whether open boundary condition can reproduce the observables calculated with periodic boundary condition. In this work we find that the extracted lowest glueball mass using open and periodic boundary conditions at the same lattice volume and lattice spacing agree for the range of lattice scales explored in the range 3 GeV $\leq$ 1/a $\leq$ 5 GeV. The problem of trapping is overcome to a large extent with open boundary and we are able to extract the glueball mass at even larger lattice scale $\approx$ 5.7 GeV. To smoothen the gauge fields and to reduce the cut off artifacts recently proposed Wilson flow is used. The extracted glueball mass shows remarkable insensitivity to the lattice spacings in the range explored in this work, 3 GeV $\leq$ 1/a $\leq$ 5.7 GeV.Comment: Replacement agrees with published versio

Tubing specifications selection and its effect on the results of hydraulic fracturing treatment in oil formations

Equipment specification, data collection and design process are critical factors for any hydraulic fracturing treatment success. This paper investigates tubing specifications selection and its effect on the results of hydraulic fracturing treatment in oil formations. Simulations were carried out on well E-45 owned by National Oil Corporation (NOC) of Libya using two main tools - Pumping Diagnostic Analysis Toolkit (PDAT) and Halliburton proprietary software package (FracPro) for analysing Mini-Frac pumping data. The initial modelling results using 3.5 inch tubing were compared with the experimental results obtained from the actual hydraulic fracturing tests carried out at the E45 by Halliburton as a sub-contractor for NOC. The simulation results showed good agreement with the experiments, validating the model. The model was then extended to explore alternate tubing diameters. This was implemented by introducing the relationship between the tub friction pressures and pumping rate (Friction Pressure vs. Pumping Rate) with the mentioned tube sizes. The results showed that in high stress rock formations, it is worthwhile to minimise the pipe friction by using higher tubing grade (4.5 inches) and burst pressure. A bigger tubing inner diameter can increase the allowable surface pumping rate and pressure

Two simple models of classical heat pumps

Motivated by recent studies on models of particle and heat quantum pumps, we study similar simple classical models and examine the possibility of heat pumping. Unlike many of the usual ratchet models of molecular engines, the models we study do not have particle transport. We consider a two-spin system and a coupled oscillator system which exchange heat with multiple heat reservoirs and which are acted upon by periodic forces. The simplicity of our models allows accurate numerical and exact solutions and unambiguous interpretation of results. We demonstrate that while both our models seem to be built on similar principles, one is able to function as a heat pump (or engine) while the other is not.Comment: 4 pages, 4 figure

Translocation through environments with time dependent mobility

We consider single particle and polymer translocation where the frictional properties experienced from the environment are changing in time. This work is motivated by the interesting frequency responsive behaviour observed when a polymer is passing through a pore with an oscillating width. In order to explain this better we construct general diffusive and non-diffusive frequency response of the gain in translocation time for a single particle in changing environments and look at some specific variations. For two state confinement, where the particle either has constant drift velocity or is stationary, we find exact expressions for both the diffusive and non-diffusive gain. We then apply this approach to polymer translocation under constant forcing through a pore with a sinusoidally varying width. We find good agreement for small polymers at low frequency oscillation with deviations occurring at longer lengths and higher frequencies. Unlike periodic forcing of a single particle at constant mobility, constant forcing with time dependent mobility is amenable to exact solution through manipulation of the Fokker-Planck equation.Comment: 9 pages, 5 figure