218 research outputs found
Pattern formation during the evaporation of a colloidal nanoliter drop: a numerical and experimental study
An efficient way to precisely pattern particles on solid surfaces is to
dispense and evaporate colloidal drops, as for bioassays. The dried deposits
often exhibit complex structures exemplified by the coffee ring pattern, where
most particles have accumulated at the periphery of the deposit. In this work,
the formation of deposits during the drying of nanoliter colloidal drops on a
flat substrate is investigated numerically and experimentally. A finite-element
numerical model is developed that solves the Navier-Stokes, heat and mass
transport equations in a Lagrangian framework. The diffusion of vapor in the
atmosphere is solved numerically, providing an exact boundary condition for the
evaporative flux at the droplet-air interface. Laplace stresses and thermal
Marangoni stresses are accounted for. The particle concentration is tracked by
solving a continuum advection-diffusion equation. Wetting line motion and the
interaction of the free surface of the drop with the growing deposit are
modeled based on criteria on wetting angles. Numerical results for evaporation
times and flow field are in very good agreement with published experimental and
theoretical results. We also performed transient visualization experiments of
water and isopropanol drops loaded with polystyrene microsphere evaporating on
respectively glass and polydimethylsiloxane substrates. Measured evaporation
times, deposit shape and sizes, and flow fields are in very good agreement with
the numerical results. Different flow patterns caused by the competition of
Marangoni loops and radial flow are shown to determine the deposit shape to be
either a ring-like pattern or a homogeneous bump
Surface Engineering for Phase Change Heat Transfer: A Review
Among numerous challenges to meet the rising global energy demand in a
sustainable manner, improving phase change heat transfer has been at the
forefront of engineering research for decades. The high heat transfer rates
associated with phase change heat transfer are essential to energy and industry
applications; but phase change is also inherently associated with poor
thermodynamic efficiencies at low heat flux, and violent instabilities at high
heat flux. Engineers have tried since the 1930's to fabricate solid surfaces
that improve phase change heat transfer. The development of micro and
nanotechnologies has made feasible the high-resolution control of surface
texture and chemistry over length scales ranging from molecular levels to
centimeters. This paper reviews the fabrication techniques available for
metallic and silicon-based surfaces, considering sintered and polymeric
coatings. The influence of such surfaces in multiphase processes of high
practical interest, e.g., boiling, condensation, freezing, and the associated
physical phenomena are reviewed. The case is made that while engineers are in
principle able to manufacture surfaces with optimum nucleation or thermofluid
transport characteristics, more theoretical and experimental efforts are needed
to guide the design and cost-effective fabrication of surfaces that not only
satisfy the existing technological needs, but also catalyze new discoveries
Control and ultrasonic actuation of a gas-liquid interface in a microfluidic chip
This article describes the design and manufacturing of a microfluidic chip,
allowing for the actuation of a gas-liquid interface and of the neighboring
fluid. A first way to control the interface motion is to apply a pressure
difference across it. In this case, the efficiency of three different
micro-geometries at anchoring the interface is compared. Also, the critical
pressures needed to move the interface are measured and compared to theoretical
result. A second way to control the interface motion is by ultrasonic
excitation. When the excitation is weak, the interface exhibits traveling
waves, which follow a dispersion equation. At stronger ultrasonic levels,
standing waves appear on the interface, with frequencies that are half integer
multiple of the excitation frequency. An associated microstreaming flow field
observed in the vicinity of the interface is characterized. The meniscus and
associated streaming flow have the potential to transport particles and mix
reagents
Quantitative determination of the femoral offset templating error in total hip arthroplasty using a new geometric model.
AIMS
Traditionally, total hip arthroplasty (THA) templating has been performed on anteroposterior (AP) pelvis radiographs. Recently, additional AP hip radiographs have been recommended for accurate measurement of the femoral offset (FO). To verify this claim, this study aimed to establish quantitative data of the measurement error of the FO in relation to leg position and X-ray source position using a newly developed geometric model and clinical data.
METHODS
We analyzed the FOs measured on AP hip and pelvis radiographs in a prospective consecutive series of 55 patients undergoing unilateral primary THA for hip osteoarthritis. To determine sample size, a power analysis was performed. Patients' position and X-ray beam setting followed a standardized protocol to achieve reproducible projections. All images were calibrated with the KingMark calibration system. In addition, a geometric model was created to evaluate both the effects of leg position (rotation and abduction/adduction) and the effects of X-ray source position on FO measurement.
RESULTS
The mean FOs measured on AP hip and pelvis radiographs were 38.0 mm (SD 6.4) and 36.6 mm (SD 6.3) (p < 0.001), respectively. Radiological view had a smaller effect on FO measurement than inaccurate leg positioning. The model showed a non-linear relationship between projected FO and femoral neck orientation; at 30° external neck rotation (with reference to the detector plane), a true FO of 40 mm was underestimated by up to 20% (7.8 mm). With a neutral to mild external neck rotation (≤ 15°), the underestimation was less than 7% (2.7 mm). The effect of abduction and adduction was negligible.
CONCLUSION
For routine THA templating, an AP pelvis radiograph remains the gold standard. Only patients with femoral neck malrotation > 15° on the AP pelvis view, e.g. due to external rotation contracture, should receive further imaging. Options include an additional AP hip view with elevation of the entire affected hip to align the femoral neck more parallel to the detector, or a CT scan in more severe cases.Cite this article: Bone Jt Open 2022;3(10):795-803
Adapting response to a measles outbreak in a context of high vaccination and breakthrough cases: an example from Vaud, Switzerland, January to March 2024.
A measles outbreak with 51 cases occurred in the canton of Vaud, Switzerland, between January and March 2024. The outbreak was triggered by an imported case, and 37 (72.5%) subsequent cases were previously vaccinated individuals. Epidemiological investigations showed that vaccinated measles cases were symptomatic and infectious. In a highly vaccinated population, it is important to raise awareness among healthcare professionals to suspect and test for measles virus when an outbreak is declared, irrespective of the vaccination status of the patients
Changes in serum biomarker profiles after percutaneous mitral valve repair with the MitraClip system
BACKGROUND
Mitral regurgitation (MR) is one of the most common valvular diseases. Percu-taneous mitral valve repair with the MitraClipTM system is a novel percutaneous mitral valve repair (PMVR) technique for high-surgical-risk patients. However, the effect of PMVR on cir-culating cardiac or inflammatory biomarkers and their association with individual functional, echocardiographic and clinical outcomes is poorly investigated.
METHODS
A group of 144 patients with functional or degenerative MR (age, 75 ± 11 years; 41% females) underwent PMVR with the MitraClip system at the University Heart Center Zu-rich. Serum biomarkers as N-terminal pro-B-type natriuretic peptide (NT-proBNP), C-reactive protein (CRP) and creatinine were obtained from venous sampling at baseline and follow-up of 3-6 months.
RESULTS
Median NT-proBNP decreased insignificantly from 2,942 (IQR 1,596-5,722) to 2,739 (IQR 1,440-4,296) ng/L, p = 0.21. NT-proBNP changes did not correlate with baseline left ventricular (LV) ejection fraction or LV dimensions, with New York Heart Association class on follow-up, or with clinical events on follow-up. CRP levels reached a peak on the third postoperative day at 34.0 mg/L with a subsequent slow decrease over the ensuing days.
CONCLUSIONS
Despite successful PMVR, NT-proBNP remain fairly unchanged on follow-up and changes in NT-proBNP levels are poor predictors of functional improvement or clinical outcome after MitraClip treatment
Changes in serum biomarker profiles after percutaneous mitral valve repair with the MitraClip system
Background: Mitral regurgitation (MR) is one of the most common valvular diseases. Percutaneous mitral valve repair with the MitraClipTM system is a novel percutaneous mitral valve repair (PMVR) technique for high-surgical-risk patients. However, the effect of PMVR on circulating cardiac or inflammatory biomarkers and their association with individual functional, echocardiographic and clinical outcomes is poorly investigated.
Methods: A group of 144 patients with functional or degenerative MR (age, 75 ± 11 years; 41% females) underwent PMVR with the MitraClip system at the University Heart Center Zurich. Serum biomarkers as N-terminal pro-B-type natriuretic peptide (NT-proBNP), C-reactive protein (CRP) and creatinine were obtained from venous sampling at baseline and follow-up of 3–6 months.
Results: Median NT-proBNP decreased insignificantly from 2,942 (IQR 1,596–5,722) to 2,739 (IQR 1,440–4,296) ng/L, p = 0.21. NT-proBNP changes did not correlate with baseline left ventricular (LV) ejection fraction or LV dimensions, with New York Heart Association class on follow-up, or with clinical events on follow-up. CRP levels reached a peak on the third postoperative day at 34.0 mg/L with a subsequent slow decrease over the ensuing days.
Conclusions: Despite successful PMVR, NT-proBNP remain fairly unchanged on follow-up and changes in NT-proBNP levels are poor predictors of functional improvement or clinical outcome after MitraClip treatment
Guidelines for the treatment of diabetic ulcers
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72913/1/j.1524-475X.2006.00176.x.pd
Guidelines for the prevention of diabetic ulcers
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72321/1/j.1524-475X.2008.00357.x.pd
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